Beta receptor occupancy. Assessment in the intact animal

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Authors

Membrane Changes Associated with Platelet Activation: EXPOSURE OF ACTIN ON THE PLATELET SURFACE AFTER THROMBIN-INDUCED SECRETION

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The effect of aggregation and secretion on membrane proteins was studied in washed human platelets. Reversible aggregation without secretion was stimulated by ADP and secretion without aggregation was stimulated by thrombin in the presence of EDTA. No loss of platelet surface glycoproteins occurred during reversible ADP-induced platelet aggregation, as measured by quantitative polyacrylamide gel electrophoresis analysis of platelets that were labeled with 125I-diazotized diiodosulfanilic acid (DD125ISA) before ADP stimulation. Also, no new proteins became exposed on the platelet surface after ADP aggregation, as determined by DD125ISA labeling after stimulation. Thrombin-induced platelet secretion also caused no loss of platelet surface glycoproteins. However, after platelet secretion two new proteins were labeled by DD125ISA: (a) actin and (b) the 149,000-mol wt glycoprotein (termed GP-G), which is contained in platelet granules and secreted in response to thrombin. The identity of DD125ISA-labeled actin was confirmed by four criteria: (a) comigration with actin in three different sodium dodecyl sulfate-polyacrylamide gel electrophoresis systems, (b) elution from a particulate fraction in low ionic strength buffer, (c) co-migration with actin in isoelectric focusing, and (d) binding to DNase I. The identity of actin and its appearance on the platelet surface after thrombin-induced secretion was also demonstrated by the greater binding of an anti-actin antibody to thrombin-treated platelets, measured with 125I-staphylococcal protein A.

Authors

James N. George, Roger M. Lyons, Rebecca K. Morgan

Dopaminergic Inhibition of Metoclopramide-induced Aldosterone Secretion in Man: DISSOCIATION OF RESPONSES TO DOPAMINE AND BROMOCRIPTINE

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This study was designed to investigate the role of dopaminergic mechanisms in the control of aldosterone secretion in man. Five normal male subjects in metabolic balance at 150 meq sodium/d and 60 meq potassium/d constant intake received the specific dopamine antagonist, metoclopramide, 10 mg i.v. on 2 consecutive d. On the 1st d, the subjects received an infusion of 5% glucose solution (vehicle) from 60 min before to 60 min after metoclopramide administration; on the 2nd d, an infusion of dopamine 4 μg/kg per min was substituted for vehicle. Metoclopramide in the presence of vehicle increased plasma aldosterone concentrations from 2.4±1.1 to a maximum of 17.2±2.8 ng/100 ml (P < 0.01) and serum prolactin concentrations from 7.5±5.0 to a maximum of 82.2±8.7 ng/ml (P < 0.01). Dopamine 4 μg/kg per min did not alter basal plasma aldosterone concentrations, but blunted the aldosterone responses to metoclopramide significantly; in the presence of dopamine, plasma aldosterone concentrations increased from 3.1±0.5 to 6.2±1.4 ng/100 ml (P < 0.05) in response to metoclopramide. The incremental aldosterone responses to metoclopramide were significantly lower in the presence of dopamine than with vehicle. Dopamine 4 μg/kg per min suppressed basal prolactin to <3 ng/ml and inhibited the prolactin responses to metoclopramide; serum prolactin concentrations increased to a maximum of 8.5±2.3 ng/ml with metoclopramide in the presence of dopamine.

Authors

Robert M. Carey, Michael O. Thorner, Elizabeth M. Ortt

Effect of D-alanine methionine enkephalin amide on ion transport in rabbit ileum.

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The presence of enkephalins in the intestine and the use of opiates to treat diarrheal diseases suggests that enkephalins may affect intestinal ion transport. Using isolated rabbit ileal mucosa, we found that leucine enkephalin, methionine enkephalin, and D Ala2-methionine enkephalin amide (D Ala2-Met E) decreased the short circuit current (Isc) and potential difference although the effect of D Ala2-Met E was more pronounced and prolonged. D Ala2-Met E increased net sodium (+1.27 +/- 0.5 mu eq/cm2h), and chloride absorption (+2.33 +/- 0.4), and increased tissue conductance by 37%. Although the effect of enkaphalin on ion transport is opposite that of cyclic AMP, D-Ala2-Met had no effect on basal or vasoactive intestinal polypeptide-stimulated cyclic AMP levels. The effect of D-Ala2-Met E on Isc was blocked by naloxone, suggesting the involvement of specific opiate receptors. Tetrodotoxin completely blocked the decrease in Isc induced by D-Ala2-Met E but not by epinephrine, inferring that enkephalins are preganglionic neurotransmitters. The effect of D-Ala2-Met E on Isc was not blocked by phentolamine, haloperidol, or pretreatment of animals with 6-hydroxydopamine, suggesting that enkephalin does not affect the Isc by stimulating the release of alpha-adrenergic or dopaminergic agonists. D-Ala2-Met E also decreased the Isc in the presence of carbachol and bethanechol, indicating that enkephalin does not inhibit the release of acetylcholine. Further, up to 10 mu M atropine had no effect on the Isc. These studies demonstrate that enkephalins stimulate intestinal ion transport and may do so by stimulating (or inhibiting) the release of a nonadrenergic, noncholinergic neurotransmitter.

Authors

J Dobbins, L Racusen, H J Binder

Effects of aspirin and dipyridamole on the degradation of adenosine diphosphate by cultured cells derived from bovine pulmonary artery.

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To improve understanding of the mechanisms by which ADP is degraded during passage through the pulmonary vascular bed, we examined cultured endothelial and smooth muscle cells of bovine pulmonmary artery for their abilities to metabolize [8-14C]ADP. ADP is rapidly converted to AMP and then to adenosine, hypoxanthine, and inosine. Inosine is the major metabolite produced by endothelial cells. Radioactivity (5-10%) is accumulated intracellularly primarily as ATP. Medium containing 50 micro M ADP incubated with endothelial cells rapidly loses its ability to aggregate platelets and becomes antiaggregatory under conditions in which prostacyclin is absent. The antiaggregatory activity is probably the result of accumulated adenosine. 10 micro M dipyridamole inhibits cellular uptake of radioactivity by greater than 90%, and inosine in the medium is largely replaced by adenosine. This is accompanied by increased anti-aggregatory activity of conditioned medium, which can be matched by authentic adenosine at the same concentration. 1 mM aspirin had no effect on the metabolism of ADP by endothelial cells. Our results suggest: (a) Metabolism of ADP during passage through the lung is mainly the result of endothelial ADPase. (b) ADP released from aggregating platelets can be converted to the antiaggregatory substance, adenosine. Dipyridamole may exert some of its antithrombotic actions by preventing the intracellular uptake of adenosine, thereby increasing its concentration near the site of thrombus formation. (c) The ability of the vessel wall to degrade ADP should not be compromised by the use of aspirin as an antithrombotic drug. (d) Endothelium may retain some of its antithrombogenicity when prostacyclin generation is impaired.

Authors

D J Crutchley, U S Ryan, J W Ryan

Lamellar body depletion in dogs undergoing pulmonary artery occlusion.

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We have investigated the relationship between pulmonary artery occlusion (PAO) and the surfactant system of the lung by studying the ultrastructural responses of type II alveolar pneumocytes to PAO of 4-12 h duration in 16 mongrel dogs. In six of these animals, the occluded lung was allowed to reperfuse for 6 h before killing and in four animals subjected to PAO of 4 h duration, the occluded lung was ventilated with 5% CO2 balance air. PAO by itself resulted in a dramatic 80% reduction in the volumetric density of lamellar bodies (LB) in the type II cells. This resulted predominantly from a decrese in volume of the individual LB. Although reperfusion was associated with an increase in LB volume density toward normal, 6 h of reperfusion was insufficient to re-establish normal type II cellular morphology. Ventilation of the occluded lung with 5% CO2 prevented LB depletion indicating that alveolar CO2 tension may affect the release and/or synthesis of LB in type II pneumocytes.

Authors

J W Shepard Jr, D Hauer, K Miyai, K M Moser

Multiple Enzymatic Defects in Mitochondria in Hematological Cells of Patients with Primary Sideroblastic Anemia

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Activities of mitochondrial enzymes in blood cells from 69 patients with primary sideroblastic anemia were determined to elucidate the pathogenesis of the disease. In erythroblasts of patients with primary acquired type the activities of both δ-aminolevulinic acid synthetase and mitochondrial serine protease were inevitably decreased. The susceptibility to the protease of apo-δ-aminolevulinic acid synthetase prepared from erythroblasts of patients with this type was within the normal range, in contrast to that of pyridoxine-responsive anemia. The activities of mitochondrial enzymes such as cytochrome oxidase, serine protease, and oligomycin-sensitive ATPase, except citrate synthetase, were usually decreased in mature granulocytes of the patients. Patients with hereditary sideroblastic anemia also had decreased δ-aminolevulinic acid synthetase activity in erythroblasts, and decreased serine protease activity in both erythroblasts and mature granulocytes. Mature granulocytes obtained from patients with pyridoxine-responsive anemia before therapy had decreased cytochrome oxidase activity, however, the activity increased to a normal level when the patients were in remission. The activities of other mitochondrial enzymes in mature granulocytes were within normal range in these patients before pyridoxine therapy. The activities of these mitochondrial enzymes in lymphocytes were within normal range in all groups of patients with primary sideroblastic anemia.

Authors

Yosuke Aoki

Electron microsocpy of plasmic fragments of human fibrinogen as related to trinodular structure of the intact molecule.

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We have examined rotary shadowed, purified plasmic fragments of human fibrinogen with the electron microscope and have determined the relation of these fragments to the intact fibrinogen molecule. Both intact fibrinogen and its earliest cleavage product, fragment X, are trinodular. The next largest product, fragment Y, consists of two linked nodules. The two terminal products, fragments D and E, are single nodules. From measurements of simultaneously shadowed specimens of these different species, we conclude that the outer nodules of the trinodular fibrinogen molecule are the fragment D-containing regions and the central nodule is the fragment E-containing region.

Authors

W E Fowler, L J Fretto, H P Erickson, P A McKee

pathogenesis of the henny feathering trait in the Sebright bantam chicken. Increased conversion of androgen to estrogen in skin.

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In female chickens of all breeds development of female feathering pattern is mediated by estrogens, whereas normal males and castrated chickens of both sexes develop male feathering. Male chickens carrying the henny feathering trait (such as the Sebright bantam and golden Campine) develop a female feathering pattern but otherwise virilize normally. To examine the possibility that the henny feathering trait is the result of increased conversion of androgen to estrogen in skin, estrogen formation from [1,2,6,7-3H]testosterone was measured in tissue slices from control breeds and chickens with the henny feathering trait. Rates of estrogen formation were undetectable or low in all control tissues other than ovary, whereas rates were high in skin and skin appendages and detectable in many tissues from Sebright and Campine birds. The increased rate of estrogen formation in skin was demonstrable in Sebright chicks and in all areas of skin biopsied in the mature bird. Furthermore, plasma levels of 17 beta-estradiol were higher in Sebright and Campine than in control male cocks. Thus, increased formation of estrogen from androgen in the peripheral tissues probably explains the henny feathering trait.

Authors

F W George, J D Wilson

Diamine oxidase (histaminase). A circulating marker for rat intestinal mucosal maturation and integrity.

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Diamine oxidase (histaminase) is an enzyme found in high concentrations in the intestinal mucosa of humans and other mammalian species. We investigated whether plasma and mucosal levels of diamine oxidase activity reflect both the maturational status of the mucosa during its development in the newborn rate and the degree of mucosal damage during its injury in the adult rat. Litter mates were reared under identical conditions and killed at different ages from day 0 to day 40 after birth. Diamine oxidase in the small intestine was low at birth, increased gradually with age, reached a peak at 22 d, and then remained at normal adult levels, similar to the developmental patterns of maltase and sucrase. Plasma diamine oxidase rose in parallel with intestinal levels (n = 500, r = 0.84, P less than 0.001), reached a peak at 24 d, and then remained at normal adult levels. Diamine oxidase activity in 15 nonintestinal tissues was less than 5% of ileal mucosal activity, and no nonintestinal activities showed increase with age. Adult rat intestinal loops were perfused with hyperosmolar sodium sulfate solutions to produce selective damage to villus mucosa. With increasing mucosal damage, there was a progressive decrease in the enzyme activities studied; first, lactase levels fell, then maltase and sucrase, and finally mucosal and plasma diamine oxidase activity levels fell. The decrease in plasma diamine oxidase reflected the degree of mucosal damage (n = 29, P less than 0.04). Diamine oxidase activity is thus unique among intestinal mucosal enzymes studied to date in that circulating levels can serve as a marker of mucosal maturation and integrity.

Authors

G D Luk, T M Bayless, S B Baylin

Experimental Membranous Glomerulonephritis in Rats: QUANTITATIVE STUDIES OF GLOMERULAR IMMUNE DEPOSIT FORMATION IN ISOLATED GLOMERULI AND WHOLE ANIMALS

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Quantitation of immune deposit formation in glomeruli and correlation with immunohistologic and functional changes has been accomplished only in models of anti-glomerular basement membrane antibody-induced nephritis, or indirectly in immune complex disease by measuring radiolabeled antigen deposition. The kinetics of subepithelial immune deposit formation and the relationship between the quantity of antibody deposited and proteinuria are defined here for the first time in an established model of membranous immune complex nephritis (passive Heymann nephritis) induced by a single intravenous injection of 125I-labeled sheep immunoglobulin (Ig)G antibody to rat tubular brush border antigen (Fx1A). Measurement of antibody deposition in glomeruli (GAb) isolated from rats injected with 10 mg of anti-Fx1A demonstrated a mean of 12 μg GAb in 4 h, which increased linearly to 48 μg in 5 d. GAb represented only 20 and 44% of total kidney antibody binding at these times. Proteinuria occurred only after 4-5 d of antibody deposition in rats with total kidney antibody binding exceeding ∼200 μg/2 kidneys. Steroid treatment and vasoactive amine blockade did not significantly alter the quantity or localization of immune deposits. It was also demonstrated that isolated rat glomeruli specifically bound nephritogenic quantities of anti-Fx1A in vitro within hours. Analysis of the quantitative aspects of glomerular antibody deposition in vivo and glomerular antibody binding in vitro provides additional evidence that subepithelial immune deposits in passive Heymann nephritis may form in situ by reaction of free antibody with antigenic constitutents of the normal rat glomerulus. The observed kinetics of deposit formation differ markedly from those in anti-glomerular basement membrane disease and suggest a role for factors in addition to antigen-antibody interaction in determining this unique pattern of glomerular immune deposit formation.

Authors

David J. Salant, Christine Darby, William G. Couser

Danazol-induced Augmentation of Serum α1-Antitrypsin Levels in Individuals with Marked Deficiency of this Antiprotease

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Individuals with serum α1-antitrypsin levels below 80 mg/dl are clearly at risk for the development of accelerated panacinar emphysema. One possible approach to the therapy of this disorder would be to raise serum levels of this major antiprotease to establish protease-antiprotease homeostasis within the lung parenchyma. Because danazol, an impeded androgen, elevates levels of C1 inhibitor in patients deficient of that serum antiprotease, we hypothesized that this agent might also increase α1-antitrypsin levels in patients with α1-antitrypsin deficiency. To evaluate this concept, seven patients with severe emphysema associated with α1-antitrypsin deficiency (six PiZ and 1 MDuarteZ) and one asymptomatic individual (PiSZ) received 600 mg of danazol daily for 30 d. Five of the six PiZ patients responded to danazol therapy with significant increases in serum α1-antitrypsin levels (mean increase of 37%; P < 0.03). The two individuals who were heterozygous for the Z protein increased their serum levels by 85% (PiMDuarteZ) and 87% (PiSZ), respectively. These increases in serum α1-antitrypsin antigen were accompanied by commensurate increases in serum trypsin inhibition. Crossed immunoelectrophoresis showed no alterations of the microheterogeneity of the α1-antitrypsin or the presence of protease-antiprotease complexes in serum during danazol therapy. These data demonstrate that serum α1-antitrypsin levels can be augmented by danazol therapy in PiZ individuals as well as those heterozygotes with severe deficiency of α1-antitrypsin. The clinical relevance of these increases in serum α1-antitrypsin remains speculative, but these findings suggest that danazol may provide a means of improving the protease-antiprotease balance in these individuals and thus impede the progression of their lung disease.

Authors

James E. Gadek, Jack D. Fulmer, Jeffrey A. Gelfand, Michael M. Frank, Thomas L. Petty, Ronald G. Crystal

Branched Chain Amino Acid Oxidation in Cultured Rat Skeletal Muscle Cells: SELECTIVE INHIBITION BY CLOFIBRIC ACID

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Leucine metabolism in skeletal muscle is linked to protein turnover. Since clofibrate is known both to cause myopathy and to decrease muscle protein content, the present investigations were designed to examine the effects of acute clofibrate treatment on leucine oxidation. Rat skeletal muscle cells in tissue culture were used in these studies because cultivated skeletal muscle cells, like muscle in vivo, have been shown to actively utilize branched chain amino acids and to produce alanine. The conversion of [1-14C]leucine to 14CO2 or to the [1-14C]keto-acid of leucine (α-keto-isocaproate) was linear for at least 2 h of incubation; the production of 14CO2 from [1-14C]leucine was saturable with a Km = 6.3 mM and a maximum oxidation rate (Vmax) = 31 nmol/mg protein per 120 min. Clofibric acid selectively inhibited the oxidation of [1-14C]leucine (Ki = 0.85 mM) and [U-14C]isoleucine, but had no effect on the oxidation of [U-14C]glutamate, -alanine, -lactate, or -palmitate. The inhibition of [1-14C]leucine oxidation by clofibrate was also observed in the rat quarter-diaphragm preparation. Clofibrate primarily inhibited the production of 14CO2 and had relatively little effect on the production of [1-14C]keto-acid of leucine. A physiological concentration—3.0 g/100 ml—of albumin, which actively binds clofibric acid, inhibited but did not abolish the effects of a 2-mM concentration of clofibric acid on leucine oxidation. Clofibrate treatment stimulated the net consumption of pyruvate, and inhibited the net production of alanine. The drug also increased the cytosolic NADH/NAD+ ratio as reflected by an increase in the lactate/pyruvate ratio, in association with a decrease in cell aspartate levels. The changes in pyruvate metabolism and cell redox state induced by the drug were delayed compared with the nearly immediate inhibition of leucine oxidation. These studies suggest that clofibric acid, in concentrations that approximate high therapeutic levels of the drug, selectively inhibits branched chain amino acid oxidation, possibly at the level of the branched chain keto-acid dehydrogenase.

Authors

William M. Pardridge, Delia Casanello-Ertl, Luiza Duducgian-Vartavarian

Epinephrine plasma metabolic clearance rates and physiologic thresholds for metabolic and hemodynamic actions in man.

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To determine the plasma epinephrine thresholds for its metabolic and hemodynamic actions and plasma epinephrine metabolic clearance rates, 60-min intravenous epinephrine infusions at nominal rates of 0.1, 0.5, 1.0, 2.5, and 5.0 microgram/min were performed in each of six normal human subjects. These 30 infusions resulted in steady-state plasma epinephrine concentrations ranging from 24 to 1,020 pg/ml. Plasma epinephrine thresholds were 50-100 pg/ml for increments in heart rate, 75-125 pg/ml for increments in blood glycerol and systolic blood pressure, 150-200 pg/ml for increments in plasma glucose (the resultant of increments in glucose production and decrements in glucose clearance), blood lactate, blood beta-hydroxybutyrate, and diastolic blood pressure, and greater than 400 pg/ml for early decrements in plasma insulin. Changes in blood alanine, plasma glucagon, plasma growth hormone, and plasma cortisol were not detected. At steady-state plasma epinephrine concentrations of 24-74 pg/ml, values overlapping the basal normal range, the mean (+/-SE) plasma metabolic clearance rate of epinephrine was 52 +/- 4 ml x min-1 x kg-1; this value rose to 89 +/- 6 ml x min-1 x kg-1 (P less than 0.01) at steady-state epinephrine concentrations of 90-1,020 pg/ml. We conclude that in human subjects: (a) the plasma epinephrine thresholds for its hemodynamic and metabolic actions lie within the physiologic range, (b) epinephrine and norepinephrine accelerate their own metabolic clearance, and (c) epinephrine is 10 times more potent than norepinephrine.

Authors

W E Clutter, D M Bier, S D Shah, P E Cryer

Biochemical studies of two patients with the gray platelet syndrome. Selective deficiency of platelet alpha granules.

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The biochemistry of platelets from two unrelated patients with the gray platelet syndrome, a deficiency of platelet alpha-granules, has been evaluated. Ultrastructural studies of their platelets revealed the number of alpha-granules to be less than 15% of normal, whereas the number of dense bodies was within normal limits. Platelets from both patients had severe deficiencies of platelet factor 4 and beta-thromboglobulin (less than 10% of normal). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a marked deficiency of thrombin-sensitive protein in both patients. Analysis of the platelet-derived growth factor in one patient showed it was also markedly reduced. Levels of lysosomal enzymes, adenine nucleotides, serotonin, and catalase, and conversion of arachidonic acid by the lipoxygenase and cyclo-oxygenase enzymes, were within normal limits. The results provide important evidence to define the contents of alpha-granules and to differentiate these contents from the contents of lysosomal granules, dense bodies, and peroxisomes. Functional studies of these platelets showed deficiencies in ADP, thrombin, and collagen aggregation. The results suggest that alpha-granules or their contents make a contribution to normal platelet aggregation.

Authors

J M Gerrard, D R Phillips, G H Rao, E F Plow, D A Walz, R Ross, L A Harker, J G White

Cellular Action of Vasopressin in Medullary Tubules of Mice with Hereditary Nephrogenic Diabetes Insipidus

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Our previous studies (1974. J. Clin. Invest.54: 753-762.) suggested that impaired metabolism of cyclic AMP (cAMP) may be involved in the renal unresponsiveness to vasopressin (VP) in mice with hereditary nephrogenic diabetes insipidus (NDI). To localize such a defect to specific segments of the nephron, we studied the activities of VP-sensitive adenylate cyclase, cAMP phosphodiesterase (cAMP-PDIE), as well as accumulation of cAMP in medullary collecting tubules (MCT) and in medullary thick ascending limbs of Henle's loop (MAL) microdissected from control mice with normal concentrating ability and from mice with hereditary NDI.

Authors

Brian A. Jackson, Richard M. Edwards, Heinz Valtin, Thomas P. Dousa

Structure, Immunology, and Cell Reactivity of Low Density Lipoprotein from Umbilical Vein of a Newborn Type II Homozygote

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In this report we compare the cord blood lipoproteins of a newborn boy homozygote who has low density lipoprotein (LDL) receptor-defective familial hypercholesterolemia (FH) with the lipoproteins from cord blood of normal newborns. Plasma LDL-cholesterol and apoprotein (Apo)B were 612 and 233 mg/dl (vs. 31±16 and 24±12 mg/dl, respectively, for normals, n = 21). LDL-cholesterol/ApoB ratio was 2.6 vs. 1.4±0.5. Levels of ApoA-I, ApoA-II, and HDL-cholesterol were similar to normal cord plasma. Thus, the lipoprotein abnormality is apparent at birth and is definitely present in LDL. Abnormalities in other lipoprotein, lipid, and in plasma apoprotein levels were not detected. On zonal ultracentrifugation, FH LDL was comprised of two populations (LDLa and LDLb), both faster floating than normal cord LDL (LDLc). This difference was due to the larger diameters of the particles on electron microscopy (LDLa = 276ű32 and LDLb = 260ű38 vs. LDLc = 237ű26, n = 200 each, mean±1 SD), and their higher contents of lipids relative to protein (86 and 82% vs. 74%, LDLa, LDLb, and LDLc, respectively). More than 94% of the protein in both the FH and the normal preparations consisted of ApoB. FH LDL were more effective than control LDL in competing with 125I-LDL (adult) for limiting amounts of anti-LDL antibodies in radioimmunoassay. FH LDL also competed more effectively for binding to LDL receptors on cultured fibroblasts at 4°C, and FH LDL also delivered more cholesterol into the cells. Cells grown in lipoprotein-deficient serum contained 44±2 μg cholesterol/mg cell protein, incubation of cells for 18 h at 37°C in 5 μg/ml FH LDL (protein) or in normal LDL raised cellular cholesterol levels to 75±2 and 60±2 μg/mg, respectively.

Authors

Wolfgang Patsch, Joseph L. Witztum, Richard Ostlund, Gustav Schonfeld

Direct Demonstration of Separate Receptors for Growth and Metabolic Activities of Insulin and Multiplication-stimulating Activity (an Insulinlike Growth Factor) Using Antibodies to the Insulin Receptor

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Insulin and such insulinlike growth factors as multiplication stimulating activity (MSA) are related polypeptides that have common biological activities. Both insulin and MSA produce acute metabolic responses (stimulation of glucose oxidation in isolated fat cells) as well as growth effects (stimulation of [3H]thymidine incorporation into DNA in cultured fibroblasts). In addition, most cells have separate receptors for insulin and insulinlike growth factors, and both peptides have weaker affinity for each other's specific receptors than for their own. To determine, therefore, whether these effects are mediated by receptors for insulin, insulinlike growth factors, or both, we have selectively blocked insulin receptors with a specific antagonist, namely Fab fragments derived from naturally occurring antibodies to the insulin receptor.

Authors

George L. King, C. Ronald Kahn

Depressed primary in vitro antibody response in untreated systemic lupus erythematosus. T helper cell defect and lack of defective suppressor cell function.

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The in vitro antibody response of peripheral blood lymphocytes (PBL) from 19 patients with untreated systemic lupus erythematosus (SLE) was compared with that of 20 control patients and 44 normal subjects. Trinitrophenyl polyacrylamide beads (TNP-PAA) were used to induce IgM anti-TNP plaque-forming cells. SLE patients displayed a markedly depressed, and in most instances virtually absent, response. This was not due to an unusual kinetics of the response; nor could it be induced by preincubation of SLE patients' PBL. In co-cultures of SLE patients and normal PBL, the former, with few exceptions, did not exert a suppressive effect. In four patients the anti-TNP response of either unfractionated or T-depleted SLE PBL could be restored by T cells from a normal individual. Conversely in three of these patients, SLE T cells could not support the response of normal B cells, suggesting a T helper cell defect in SLE PBL. Concanavalin A (Con A)-induced suppressor cells of the antibody response could be assayed by two approaches: (a) in responder SLE patients, by the direct addition of Con A to TNP-PAA-stimulated cultures; (b) in seven patients by transfer of Con A-activated cells to the responding culture of a normal allogeneic donor. In both cases SLE PBL were able to exert a suppressive effect to the same extent as normal PBL.

Authors

J F Delfraissy, P Segond, P Galanaud, C Wallon, P Massias, J Dormont

Autologous Mixed Lymphocyte Reaction in Patients with Hodgkin's Disease: EVIDENCE FOR A T CELL DEFECT

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The proliferative response of T lymphocytes cultured with autologous non-T lymphocytes is known as the autologous mixed lymphocyte reaction (MLR). This reaction can be demonstrated reproducibly in healthy individuals and has been shown to generate specific cytotoxic T cells, as well as T cells that regulate antibody synthesis and cell-mediated immunity. In this study, we demonstrate that the autologous MLR is impaired or absent in most patients with Hodgkin's disease regardless of age, sex, pathologic stage, or histologic classification. In 64 patients, the mean autologous MLR was 3,084±1,878 cpm compared to 16,552±6,532 in 29 healthy donors. A defect in autologous MLR was observed in newly diagnosed patients before the initiation of therapy, but was also found in patients without evidence of recurrent disease up to 15 yr after treatment.

Authors

Edgar G. Engleman, Claudia J. Benike, Richard T. Hoppe, Henry S. Kaplan, F. Ralph Berberich

Elevated serum levels of pancreatic secretory proteins in cigarette smokers after secretin stimulation.

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The secretory pancreatic proteins in serum were analyzed in a group of cigarette smokers and a control group of nonsmokers before and after intravenous secretin stimulation. None of these persons had any signs of pancreatic disease. In the control group, serum total amylase activity, pancreatic isoamylase, cationic trypsinogen, and pancreatic secretory trypsin inhibitor concentrations varied within the normal range before and after secretin injection. In contrast, the concentrations of these pancreatic proteins in all the cigarette smokers elevated from normal to abnormally high serum concentrations after secretin stimulation. The results indicate a probable toxic effect of cigarette smoking on the exocrine pancreas.

Authors

G Balldin, A Borgström, A Eddeland, S Genell, L Hagberg, K Ohlsson