A modification of the Lowry procedure to simplify protein determination in membrane and lipoprotein samples

Identification of immunogenic outer membrane proteins of Haemophilus influenzae type b in the infant rat model system

Outer membrane proteins of Haemophilus influenzae type b which are immunogenic in infant rats were identified by a radioimmunoprecipitation method. Intact cells of H. influenzae type b were radioiodinated by a lactoperoxidase-catalyzed procedure, and an outer membrane-containing fraction was prepared from these cells. These radioiodinated outer membranes were mixed with sera obtained from rats convalescing from systemic H. influenzae type b disease induced at 6 days of age, and the resultant (antibody-outer membrane protein antigen) complexes were extracted from these membranes by treatment with nonionic detergent and ethylenediaminetetraacetic acid. These soluble antibody-antigen complexes were isolated by means of adsorption to protein A-bearing staphylococci, and the radioiodinated protein antigens were identified by gel electrophoresis followed by autoradiography. Infant rats were shown to mount a readily detectable antibody response to several different proteins present in the outer membrane of H. influenzae type b. Individual infant rats were found to vary both qualitatively and quantitatively in their immune response to these immunogenic outer membrane proteins.

Time course of capsaicin-induced functional impairments in comparison with changes in neuronal substance P content

1. Changes in the content of substance P (dorsal spinal cord, dorsal roots, dorsal root ganglia, saphenous nerve, skin) and functional changes (neurogenic plasma extravasation, chemosensitivity of the cornea) were measured in the rat from 10 min to 4 days after the s.c. injection of a single dose of 50 mg kg-1 capsaicin. 2. The substance P content in dorsal roots, saphenous nerve and hind paw skin progressively declined to about 60--70% of control 4 days after treatment, whereas that of the dorsal root ganglia rose, after an initial decline, to 140% after 1--4 days. 3. After denervation, impairment of neurogenic plasma extravasation could be observed not earlier than after one day, thus being comparable in time course to the depletion of substance P in the skin and saphenous nerve. 4. Neurogenic plasma extravasation and the chemosensitivity of the cornea were greatly diminished already 10 min after systemic capsaicin treatment, i.e. at a time when the substance P content of the peripheral nerve was still unchanged. These early effects of systemic capsaicin treatment are therefore caused by actions other than depletion of substance P.

Plasma lipoprotein induction and suppression of the generation of cellular procoagulant activity in vitro

Isolated human plasma very low density, intermediate density, and high density lipo-proteins at physiologic concentrations have been demonstrated in the preceding report to induce significant increases in the procoagulant activity of human peripheral blood mononuclear cells in vitro, whereas low density lipoprotein did not. The monocyte was identified in this study by cellular fractionation and by direct cytologic assays as the source of this inducible activity, thus identifying the procoagulant activity as a monokine. The generation of these lipoprotein-induced procoagulant monokines was entirely dependent upon the presence of lymphocytes. Isolated lymphocytes that had been exposed to the stimulatory lipoproteins could induce monocytes to produce the procoagulant activity, whereas neither the culture medium from lipoprotein-stimulated lymphocytes, homogenates of lymphocytes, nor other cells such as platelets could substitute for this requirement. The interaction of the stimulatory lipoproteins with lymphocytes was rapid, reaching completion within 30 min, and was equally effective at either 4 degrees or 37 degrees C. Low density lipoprotein did not stimulate lymphocytes to induce monocyte procoagulant activity, but did actively suppress the production of the procoagulant monokines induced by each of the stimulatory lipoproteins, as well as bacterial lipopolysaccharide. The monocyte was identified as the cell sensitive to low density lipoprotein suppression, and no suppression of lymphocyte triggering was observed. These observations on the interaction of plasma lipoproteins with lymphocytes and monocytes in vitro introduce two new regulatory events by which plasma lipoproteins influence the function of cells, and define a regulatory network by which certain lipoprotein classes trigger lymphocytes, which can in turn induce monocytes to express procoagulant activity. Only this latter phase is subject to lipoprotein suppression by physiologic concentrations of low density lipoprotein.

Plasma lipoprotein induction and suppression of the generation of cellular procoagulant activity in vitro: two procoagulant activities are produced by peripheral blood mononuclear cells

In the process of analyzing the effects of lipoproteins on functions of lymphoid cells, it was observed that physiological concentrations of isolated human plasma lipoproteins possess varying capacities to rapidly enhance the expression of procoagulant activity of human peripheral blood mononuclear cells in vitro. In a strict dose-dependent fashion, very low density lipoprotein, intermediate density lipoprotein, and high density lipoprotein enhanced both the surface expression by viable cells and the total cellular content of procoagulant activity during a 6-h incubation. Very low density lipoprotein induced a maximal 6.7-fold increase in the expression of a thromboplastin activity, which was consistent with tissue factor, in that it was dependent on Factors VII, X, and II. Both intermediate density lipoprotein and high density lipoprotein induced approximately a 12-fold increase of a different procoagulant activity which appears to be a direct prothrombin activator. This prothrombinase was calcium dependent and was inhibited by 2.5 mM diisopropylfluorophosphate, but was not neutralized by anti-Factor X antibodies or by inhibitors of Factor Xa. In contrast to the other lipoprotein density classes, low density lipoprotein did not stimulate procoagulant activity, but instead actively suppressed the generation of the two procoagulant activities induced by the stimulatory lipoproteins. Suppression by low density lipoprotein was clearly evident at molar ratios of low density lipoprotein to stimulatory lipoproteins of 1:3 or less. Reconstitution of all lipoproteins to physiological concentrations was not stimulatory as a consequence of the suppressive effects of low density lipoprotein. These data indicate that isolated plasma lipoproteins are capable of regulating the expression of two different procoagulant activities of peripheral blood mononuclear cells in vitro. The possibility that these interactions may be implicated in the association between certain types of hyperlipoproteinemias and thromboembolic disease merits study.

Factors controlling the proliferative rate, final cell density, and life span of bovine vascular smooth muscle cells in culture

Low density vascular smooth muscle (VSM) cell cultures maintained on extracellular-matrix(ECM)-coated dishes and plated in the presence of either plasma or serum will proliferate actively when serum-containing medium is replaced by a synthetic medium supplemented with three factors: high density lipoprotein (HDL, 250 micrograms protein/ml); insulin (2.5 micrograms/ml) or somatomedin C (10 ng/ml); and fibroblast growth factor (FGF, 100 ng/ml) or epidermal growth factor (EGF, 50 ng/ml). The omission of any of these three factors from the synthetic medium results in a lower growth rate of the cultures, as well as in a lower final cell density once cultures reach confluence. When cells are plated in the total absence of serum, transferrin (10 micrograms/ml) is also required to induce optimal cell growth. The effects of the substrate and medium supplements on the life span of VSM cultures have also been analyzed. Cultures maintained on plastic and exposed to medium supplemented with 5% bovine serum underwent 15 generations. However, when maintained on ECM-coated dishes the serum-fed cultures had a life span of at least 88 generations. Likewise, when cultures were maintained in a synthetic medium supplemented with HDL and either FGF or EGF, an effect on the tissue culture life span by the substrate was observed. Cultures maintained on plastic underwent 24 generations, whereas those maintained on ECM-coated dishes could be passaged repeatedly for 58 generations. These experiments demonstrate the influence of the ECM-substrate only in promoting cell growth but also in increasing the longevity of the cultures.

Human B lymphocytes form rosettes after insertion of T lymphocyte membrane constituents

Isolated plasma membranes from human thymocytes or peripheral T lymphocytes upon their reconstitution with envelope glycoproteins of Sendai virus, afforded membrane vesicles that fused efficiently with human peripheral B cells. The b cells thus obtained acquired the ability to form regular rosettes at 4 degrees C with sheep red blood cells. However, only B cells modified by fusion with thymocyte membranes formed stable rosettes at 37 degrees C, a property which distinguished thymocytes from peripheral T cells. Transfer of membrane components between human cells provides a new approach for the investigation of the sheep red blood cell receptor as well as the structure-function relationship of other lymphocyte membrane components.

Acetylcholine receptor from mammalian skeletal muscle. Oligomeric forms and their subunit structures

1. The acetylcholine receptor of cat denervated skeletal muscle was solubilised with Triton X-100 in the presence of protease inhibitors and was shown to have a sedimentation coefficient of about 9 S. This oligomer can be converted to a smaller, active 4-S species. 2. This 9-S glycoprotein was purified to homogeneity (showing pI = 5.0) by improved biospecific chromatography on alpha-neurotoxin and lectin affinity gels, and shown to bind specifically 10--11.5 mumoles [2,3-3H]propionyl-alpha-bungarotoxin/g protein. The association rate constant (3 x 10(5) M-1 s-1 at 25 degrees C) for this reaction was similar to that observed with membrane-bound or unpurified receptor; affinity constants for nicotinic ligands were also similar in all these cases. 3. By a variety of techniques, a major polypeptide of Mr about 43,000 was detected in the pure protein. Likewise, both 9-S and 4-S oligomers isolated in a pure state at high yield (approximately equal to 80%) by a novel technique using anti-toxin immunoglobulin, contained the same size of subunit. 4. Sub-synaptic and extra-synaptic forms of the receptor were alkylated specifically in the membrane-bound state with the affinity reagent bromo[3H]acetylcholine. As in the case of the pure receptor from denervated muscle, the same size polypeptide (Mr 43,000) was labelled. This was true, also, for both the 9-S and the 4-S oligomer of the denervated muscle receptor. 5. Proposed oligomeric structures of acetylcholine receptors containing single and multiple-size subunits are discussed.

Effect of various hepatic membrane fractions on microtubule assembly-with special emphasis on the role of membrane phospholipids

This report describes an interaction between rat brain microtubule protein and various hepatic fractions in vitro. Purified preparations of Golgi membranes, plasma membrane, rough and smooth endoplasmic reticulum, nuclear membranes, and mitochondria were obtained from the livers of 200-g rats. Several concentrations of fresh or sonicated frozen membranes were incubated with twice-cycled rat brain microtubule protein in a microtubule assembly buffer for 60 min at 30 degrees C. Changes in microtubule assembly were assessed either by quantitative electron microscopy on negatively stained samples or by spectrophotometric methods. The results show that all the tested membranes "bound" microtubule protein, preventing assembly: Golgi and plasma membranes, as well as mitochondria, were especially potent in this regard. To identify the membrane-associated components responsible for microtubule protein binding, the membranes were extracted with methanol-chloroform, and liposomes were prepared from the resulting lipids. Microtubule protein incubated with these liposomes showed a differential ability to assemble that was similar to the effect obtained with intact membranes. Membrane-extracted phospholipids were identified as the lipid component responsible for these changes, with the negatively charged phospholipids (cardiolipin and phosphatidylserine) being uniquely active. These findings indicate that hepatic membranes differentially interact with brain microtubule protein; this interaction may be dependent on membrane phospholipids.

Microvilli of the human term placenta. Isolation and subfractionation by centrifugation in sucrose density gradients

Human placental microvilli were isolated and separated into two fractions by centrifugation in sucrose density gradients. Electron-microscopic morphology and morphometry, the distribution of enzymic activities and the results of sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of proteins were used to assess the purity of the final preparations and to define their properties. The combined evidence strongly suggested that the preparations contained negligible material that was not plasma membrane. The two fractions of microvilli differed in buoyant density, protein composition, enzyme specific activities and microscopic appearance. Some of these differences were explained by the absence of internal structure in the microvilli of the lighter fraction.

Effect of inhibitors of GABA aminotransferase on the metabolism of GABA in brain tissue and synaptosomal fractions

Five inhibitors of the GABA degrading enzyme GABA-aminotransferase (GABA-T), viz., gabaculine, gamma-acetylenic GABA, gamma-vinyl GABA, ethanolamine O-sulphate, and aminooxyacetic acid, as well as GABA itself and the antiepileptic sodium valproate were administered to mice in doses equieffective to raise the electroconvulsive threshold by 30 V. The animals were killed at the time of maximal anticonvulsant effect of the respective drugs and GABA, GABA-T and glutamate decarboxylase (GAD) were determined in whole brain and synaptosomes, respectively. The synaptosomal fraction was prepared from brain by conventional ultracentrifugation procedures. All drugs studied brought about significant increases in both whole brain and synaptosomal GABA concentrations, and, except GABA itself, inhibited the activity of GABA-T. Furthermore, all drugs, except GABA and gamma-acetylenic GABA, activated GAD in the synaptosomal fraction. This was most pronounced with ethanolamine O-sulphate, which induced a twofold activation of this enzyme but exerted only a weak inhibitory effect on GABA-T. The results suggest that activation of GAD is an important factor in the mechanism by which several inhibitors of GABA-T and also valproate increase GABA concentrations in nerve terminals, at least in the relatively non-toxic doses as used in this study.

Solubilization of neuroleptic/dopamine receptors of human brain striatum

Dopaminergic neuroleptic receptors were solubilized by digitonin from post-mortem human brain putamen. The receptors were labelled by [3H]spiperone and separated from free [3H]spiperone by sephadex chromatography. Neuroleptics and neurotransmitters had similar inhibitory and stereoselective potencies on the solubilized and intact membrane receptors. The KD for [3H]spiperone was apparently high for the solubilized receptors. Unlike the rat striatum, therefore, the human putamen can be solubilized to release neuroleptic/dopamine receptors, permitting the future development of highly sensitive methods for detecting dopamine receptors.

Phorbol esters induce synthesis of thromboplastin activity in human monocytes

12-O-Tetradecanoylphorbol 13-acetate (TPA), phorbol 12,13-diacetate and phorbol 12,13-didecanoate were all potent inducers of thromboplastin activity in human monocytes in vitro, whereas 4 alpha-phorbol 12,13-didecanoate and 4 alpha-phorbol had no such effect. A concomitant increase in titrable apoprotein III antigen was found (apoprotein III is the protein component of thromboplastin). The increase was inhibited by cycloheximide and actinomycin D and partly by alpha-amanitin. The increase of thromboplastin activity was therefore most likely due to synthesis de novo of apoprotein III. The response was approximately halved in the absence of serum or Ca2+. Retinol had a weak inhibitory effect, and retinoic acid was inhibitory only at concentrations that also induced signs of cytotoxicity. TPA caused an initial rise in monocyte cyclic AMP concentration of about 90-120 min duration. No increase in 45Ca2+ influx was induced over 2 h. Good correlation exists between induction of apoprotein III synthesis in monocytes in vitro and mouse skin-tumour promotion in vivo by the various phorbol derivatives. Substances inactive in tumour promotion do not induce the synthesis of apoprotein III. General activating and cytotoxic effects of TPA were monitored by determining release of lysozyme, beta-glucuronidase and lactate dehydrogenase.

Canine transmissible venereal sarcoma: leukocyte adherence inhibition (LAI) reactivity of various lymphoid tissues of dogs with tumors at different stages of growth

Leukocyte adherence inhibition (LAI) reactivity of various lymphoid tissues of dogs with canine transmissible venereal sarcoma (CTVS) at different stages of growth was determined by the tube LAI test. Tumors were classified at the time of excision into progressor, steady state, and regressor stages of growth. The LAI reactivity to CTVS antigen extract of spleen, draining and non-draining lymph-node cells, and peripheral blood leukocytes of regressors (non-adherence index--NAI of 172.8 +/- 46.8, 148.1 +/- 64.7, 138.7 +/- 47.3, and 172.2 +/- 60.7, respectively) was significantly greater than that of progressors (46.1 +/- 20.0, 38.5 +/- 21.5, 50.2 +/- 30.0, 24,6 +/- 37.2, respectively, p less than 0.001) and normal dogs (47.5 +/- 22.8, 54.6 +/- 24.6, 26.7 +/- 14.0, 50.9 +/- 22.4, respectively, p less than 0.001). In contrast, LAI reactivity of progressor lymphoid tissues to CTVS antigen extract did not differ significantly from that of normal dogs. LAI reactivity of lymphoid tissues from steady state tumor bearers (97.9 +/- 39.2, 80.7 +/- 47.3, 87.1 +/- 40.0, 85.1 +/- 53,9, respectively) was intermediate between and significantly different from LAI reactivities of regressor (p less than 0.05) and progressor (p less than 0.01) lymphoid tissues. Significant LAI reactivity observed in regressors suggests the presence of a functional effector cell mechanism associated with spontaneous regression of CTVS. The three distinct patterns of LAI reactivity observed in tumor-bearing dogs appear to correlate with the clinical course of tumor growth.

Inheritance of the human platelet alloantigen, PlA1, in type I Glanzmann's thrombasthenia

The hereditary of the human platelet alloantigen, PlA1, has been studied in Glanzmann's thrombasthenia. The PlA1 content of platelets from three patients, 20 kindred of these patients, including parents and siblings, and 15 unrelated normal individuals was determined using immunologic techniques based on the release of 51Cr from labeled platelets. The amount of membrane glycoproteins (GP) IIb and IIIa in the platelets of these individuals was determined by quantitative crossed immunoelectrophoresis of Triton X-100 soluble proteins using a multispecific rabbit antibody raised against normal platelets. Platelets from the three thrombasthenic patients contained neither detectable GP IIb and GP IIIa nor detectable PlA1 antigen. Platelets from seven kindred with normal amounts of GP IIb and GP IIIa contained PlA1 antigen levels identical to those detected in platelets of normal individuals. Platelets from 13 kindred, including each parent studied, were shown to contain an amount of GP IIb and GP IIIa equivalent to 53% of that amount detected on normal platelets. Platelets from the same individuals expressed amounts of PlA1 antigen that were either 54.0 +/- 4.1 (mean +/- SD) or 28.0 +/- 2.7% of that present on platelets of normal individuals homozygous for the Al allele. The results presented in this report provide evidence that the expression of the thrombasthenic glycoprotein abnormality and the inheritance of PlA1 antigen are controlled by different genes. These results further suggest that lack of expression of the PlA1 antigen on thrombasthenic platelets results from the decrease or absence of the glycoprotein carrier of the PlA1 determinant, previously shown to be GP IIIa.

Lectin-induced inhibition of nerve growth factor binding by receptors of sympathetic ganglia

Nerve growth factor (NGF) initiates a pleiotypic response in numerous tissues derived from the neural crest by binding to specific plasma membrane receptors. In sympathetic ganglia this receptor has been characterized as a highly asymmetric, minimally hydrophobic, intrinsic membrane protein with a molecular weight of 135,000 (Costrini et al., 1979b). To further characterize this moiety we assessed the effects of lectins on 125I-NGF specific binding to preparations of particulate and nonionic detergent-extracted microsomal receptors of rabbit superior cervical ganglia (SCG). Concanavalin A (Con A) and wheat germ agglutinin (WGA), but not soybean agglutinin or Ulex europaeus 1, induced a concentration-related, carbohydrate-specific decrease in 125I-NGF binding. Following Con A exposure, 125I-NGF specific decrease in 125I-NGF binding. Following Con A exposure, 125I-NGF specific binding to particulate SCG receptors was maximally reduced to 23% of control values. WGA similarly reduced NGF binding to particulate microsomal receptors to 37% of control values. Scatchard analysis of growth factor binding following Con A exposure indicated that this lectin effect was principally due to a sixfold reduction in maximum receptor affinity. Lectin-associated impairment of NGF binding was also demonstrated by using a Triton X-100 solubilized receptor preparation. These results provide evidence that the high-affinity-state NGF receptor of SCG is a glycoprotein containing N-acetylglucosamine and alpha-D-mannopyranoside residues. These residues are probably located in close proximity to the growth factor binding region of the NGF receptor.

Acid glycohydrolase in Chinese hamster with spontaneous diabetes. VII. The lack of short-term glucose-effect in cultured kidney cells

An epithelial cell line, designated CHK-ACE, was established from the kidney of a spontaneously diabetic Chinese hamster from the highly inbred AC line. CHK-ACE was separated into two sublines, CHK-ACE-100 and CHK-ACE-400, by successive passages in 100 and 400 mg/dl glucose respectively. Extra- and intracellular activities of N-acetyl-beta-D-glucosaminidase and beta-D-galactosidase were measured in these cultures after exposure to varying concentrations of glucose (100, 200, 300 and 400 mg/dl) for one passage and 10% heated fetal calf serum for 6.5 h before enzyme measurements were taken; no apparent dependence on medium-glucose concentration was found. In serum-free medium, the time-dependent release of both N-acetyl-beta-D-glucosaminidase and beta-D-galactosidase was sustained for up to 24 h; no significant difference in their activities was found between CHK-ACE-100 cultures grown in 100 and 400 mg/dl glucose for one passage.

The activities of monoamine oxidase-A and -B, succinate dehydrogenase and acid phosphatase in the rat brain after hemitransection

The activities of monoamine oxidase-A and -B were determined in four brain regions (limbic system, occipito-temporal cortex, hemispheres and striatum) of the rat 0, 3, 6, 9 and 14 days after hemitransection of the left side. No larger or consistent change in the activity of monoamine oxidase-A towards 5-hydroxytryptamine was found for the left (hemitransected) side with respect to the right side for any of the rats. The monoamine oxidase-B activity towards beta-phenethylamine increased in the left side striatum to a significant level by 3 days, and in the hemispheres and occipito-temporal cortex on the left side, with respect to the right side by 9 days, but no significant changes were found for the limbic system. A small decrease in the activity of succinate dehydrogenase was found in the striatum on the left side by 9 days after hemitransection, but no change in the activity of acid phosphatase was found in this brain region.

Elevation of serum HDL and HDL cholesterol in cholesterol-fed male rabbits treated with estrogen

The effect of cholesterol feeding and estrogen administration on serum lipoproteins and lipoprotein lipid composition was investigated in male rabbits. The lipoprotein fractions were separated by preparative ultracentrifugation and the purity of each fraction was determined by polyacrylamide disc gel electrophoresis. The amount of cholesterol, cholesterol ester, triglycerides and phospholipids was determined in each of the lipoprotein fractions. It was found that treatment of the cholesterol-fed animals with estrogen resulted in an increase of their serum HDL, HDL cholesterol, HDL phospholipids and HDL triglycerides. This increase was accompanied by a decrease in serum VLDL, VLDL cholesterol and VLDL phospholipids. Since increased HDL and HDL cholesterol have been known to be associated with lower coronary heart disease, the increased serum HDL and HDL cholesterol resulting from estrogen treatment might account for the reported lower incidence of coronary heart disease in young women than in young men and the protective effect of estrogen against diet-induced and spontaneous atherosclerosis in animals.

The effect of different proportions of casein in semipurified diets on the concentration of serum cholesterol and the lipoprotein composition in rabbits

The effect of different proportions of casein in semipurified diets on the concentration of serum cholesterol and the lipoprotein composition was studied in rabbits. Low-casein diets (10% w/w) resulted in serum cholesterol levels and growth rates that were lower than high-casein diets (40%). An intermediate proportion of casein (20%) produced intermediate concentrations of serum cholesterol, but only minor differences in food intake and weight gain, compared with the high-casein group. In the animals with the highest values of total serum cholesterol (the 40% casein group), most of the serum cholesterol was transported in the very low density lipoproteins, whereas with moderate hypercholesterolemia (the 20% casein group), the low density lipoproteins were the main carriers of cholesterol. Elevation in lipoprotein cholesterol was associated in all groups with an increased ratio of cholesterol to protein, suggesting the formation of particles relatively rich in cholesterol. When the rabbits on the diet containing 10% casein were subsequently transferred to the 40% casein diet, a steep increase in the level of serum cholesterol occurred. Conversely, switching the rabbits on the 40% casein diet to the 10% casein diet resulted in a decrease in the level of serum cholesterol.

Extraction and partial purification of the nucleoside-transport system from human erythrocytes based on the assay of nitrobenzylthioinosine-binding activity

Nitrobenzylthioinosine, a potent nucleoside-transport inhibitor, binds to high-affinity sites on the human erythrocyte membrane. This binding is a specific interaction with functional nucleoside-transport sites. The protein(s) responsible for high-affinity nitrobenzylthioinosine binding was purified 13-fold by treatment of haemoglobin-free 'ghosts' with EDTA (pH 11.2) to remove extrinsic proteins, extraction of the protein-depleted membranes with Triton X-100 and passage of the soluble extract through a DEAE-cellulose column equilibrated with Triton X-100. Void-volume fractions were collected and treated with Bio-Beads SM-2 to remove detergent. These fractions contained 31% of the starting nitrobenzylthioinosine-binding activity. They also contained D-glucose-sensitive cytochalasin B-binding activity. Nitrobenzylthioinosine binding to the partially purified preparation was saturable (apparent Kd 1.6 nM) and inhibited by nitrobenzylthioguanosine, dipyridamole and uridine. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of pooled void-volume fractions revealed the presence of only two detectable protein bands, the broad zone 4.5 (containing glucose-transport protein) and a small amount of band 7.

Substance P in tumors: pheochromocytoma and carcinoid

Immunoreactive substance P (I-SP) was measured in two pheochromocytomas and a carcinoid of the caecum. The pheochromocytomas contained 1,5 and 50 pmol/g I-SP respectively. An HPLC analysis I-SP and catecholamines were enriched in the chromaffin granule fraction. The carcinoid contained 2900 pmol/g I-SP. About 40% of the immunoreactivity behaved like substance P on gel filtration, HPLC and in bioassays (fall in rabbit blood pressure and contraction of the guinea-pig ileum which was abolished by specific tachyphylaxis to substance P). These results indicate that authentic substance P is present in carcinoids and pheochromocytomas and that in the latter it is most likely stored in chromaffin granules.

Root-Associated N 2 Fixation (Acetylene Reduction) by Enterobacteriaceae and Azospirillum Strains in Cold-Climate Spodosols

N 2 fixation by bacteria in associative symbiosis with washed roots of 13 Poaceae and 8 other noncultivated plant species in Finland was demonstrated by the acetylene reduction method. The roots most active in C 2 H 2 reduction were those of Agrostis stolonifera, Calamagrostis lanceolata, Elytrigia repens , and Phalaris arundinacea , which produced 538 to 1,510 nmol of C 2 H 4 ·g −1 (dry weight)· h −1 when incubated at pO 2 0.04 with sucrose (pH 6.5), and 70 to 269 nmol of C 2 H 4 · g −1 (dry weight)·h −1 without an added energy source and unbuffered. Azospirillum lipferum, Enterobacter agglomerans, Klebsiella pneumoniae , and a Pseudomonas sp. were the acetylene-reducing organisms isolated. The results demonstrate the presence of N 2 -fixing organisms in associative symbiosis with plant roots found in a northern climatic region in acidic soils ranging down to pH 4.0.

Differential inhibition of ketogenesis by malonyl-CoA in mitochondria from fed and starved rats

Rates of ketogenesis in mitochondria from fed or starved rats were identical at optimal substrate concentrations, but responded differently to inhibition by malonyl-CoA. Kinetic data suggest that the K1 for malonyl-CoA is greater in the starved animal. These results indicate that, for the regulation of ketogenesis in the starved state, the lower sensitivity of carnitine palmitoyltransferase to inhibition by malonyl-CoA may be more important than the concentration of malonyl-CoA.

Inhibitory effects of tunicamycin and 2-deoxyglucose on thyroglobulin synthesis

The kinetic incorporation of labelled sugars and amino acids by rat thyroid hemilobes was measured in the presence of 2-deoxyglucose and tunicamycin, inhibitors of the glycosylation of glycoproteins. With either inhibitor the carbohydrate content of exocytosed thyroglobulin was only slightly decreased (less than 20% of control) whereas the rate of exocytosis was strongly inhibited (by 60-80%). As no intracellular accumulation or proteolysis of non-glycosylated molecules was detected, the reduced rate of thyroglobulin release seems essentially due to a decrease in protein synthesis. In a whole cell system (hemilobes), it is impossible to uncouple glycosylation and protein synthesis by incubation with tunicamycin; 50 micrograms/ml tunicamycin for 270 min inhibited total [3H]-glucosamine and 14C-labelled amino acid incorporation by 65% and 33% respectively. This can be contrasted with cell-free incubation of thyroid rough microsomes where glycosylation was blocked by the same tunicamycin concentration (90% inhibition of N-[3H]acetylglucosamine transfer from UDP-N-[3H]acetylglucosamine) whilst ongoing protein synthesis was not significantly modified (less than 4% inhibition). This clearly suggests that, in thyroid follicular cells, a regulatory link exists between the synthesis of the peptide moiety of a glycoprotein and its glycosylation.

Alteration of lymphocyte surface properties by insertion of foreign functional components of plasma membrane

We report the successful coreconstitution of solubilized lymphocyte plasma membranes and Sendai virus envelopes into membrane vesicles that possess the ability to fuse efficiently with mouse splenocytes of thymocytes to give fully viable cells with modified surface properties. Integration of donor membrane components into the acceptor cells was demonstrated by chemical, morphological, and immunological methods. Over 40% of the label from vesicles coreconstituted with radiolabeled (with 125I or 3H) lymphocyte membranes was incorporated into the fused cells. Insertion of biotin-labeled membrane components into the membranes of the acceptor cells was shown by electron microscopy with ferritin-conjugated avidin. Transfer of receptors to soybean agglutinin was also demonstrated. When vesicles from thymocyte membranes were fused with B splenocytes, over 50% of the cells were lysed with anti-theta antiserum and complement. Moreover, lymphocytes into which allogeneic membranes were incorporated triggered the autologous cells in the mixed lymphocyte reaction, indicating the functional transfer of major histocompatibility complex antigens. These findings strongly suggest that the transferred membranes were functionally incorporated into the acceptor cell membranes. The technique described opens new ways for elucidation of the role of the lymphocyte membrane in the immune response as well as for the understanding of the structure-function relationship of membrane components in other cells.