Pharmacological properties of the hydroxylated histamine, (±)-4(5)-(2-amino-1-hydroxyethyl)-imidazole

The pharmacological effects of the -hydroxylated histamine, 4(5)-(2-amino-1-hydroxyethyl)-imidazole, on smooth muscle contraction of the ileum (H₁-receptor activity) and gastric acid secretion (H₂-receptor activity) of the guinea-pig were investigated and compared with those of histamine. Although -hydroxy histamine contracted the ileum with the same maximal response as hstamine, the concentration response curve was shifted to the right by approximately three orders of magnitude. At submaximal concentrations, co-administration of -hydroxy histamine with histamine revealed only additive effects. This H₁-activity was competitively inhibited by diphenhydramine. Similarly, the hydroxylated analogue also increased intracellular cyclic AMP level and [¹⁴C] aminopyrine accumulation as a marker of acid secretion in the parietal cells. However, the EC₅₀ was approximately ten fold that of histamine. This H₂-receptor activity was inhibited completely by cimetidine. These results suggest that -hydroxy histamine possesses nearly full intrinsic activities at both H₁ and H₂-receptors and that the introduction of a hydroxyl group at the -carbon reduces and dissociates these activities.     

The penetration of the salivary glands ofRhodnius prolixus byTrypanosoma rangeli

Ultrastructural studies of the mechanism of penetration of the salivary gland of the reduviid bugRhodnius prolixus byTrypanosoma rangeli showed that trypanosomes from the haemocoele penetrate the outer membranes of the gland flagellum foremost, disrupting the inner layers, to pass between the muscle cells to reach the gland cell basement membrane. This latter is also penetrated flagellum foremost, the parasite invaginating the gland cell plasmalemma beneath, to create a vacuole in which the trypanosome crosses the gland cells to reach the central lumen, often only losing its containing vacuole just before leaving the cell.The structure of the outer membranes surrounding the salivary gland appeared similar to, and often actually part of, the basement membrane of the gland cells. These outer membranes were found to enclose large numbers of multinuleate giant form trypanosomes, whose significance is as yet unknown, but could perhaps represent a stage in the life cycle of the parasite where genetic interchange could take place.     

A comparative immunohistological study of cerebellar enolases

Summary A comparative immunohistological study of the neurone-specific enolase and enolase, demonstrates the exclusive neuronal localization of enolase and its absence from glial cells. In contrast, enolase is located in astroglial cells. The validity of enolase as a neuronal marker and enolase as an astrocytic marker, is confirmed both by a double labelling technique, using antibodies to and to revealed with fluorescence or peroxidase in the same tissue sections, and by immunoelectronmicroscopy.     

Effects of vector cutting on its recombination with the chromosomal immunoglobulin gene in hybridoma cells

We have analyzed the effects of linearizing vector DNA on the frequency and pathway of its recombination with the homologous chromosomal gene. The pSV2neo vector bearing a 4.3-kb fragment encoding the mouse immunoglobulin heavy chain constant (C) region was cut either at sites within the C segment or outside C and then transferred to hybridoma cells bearing a mutant gene. The frequency of recombinant cells producing normal was then measured. For most cut sites, whether in regions of homology or of nonhomology, linearization of the transferred DNA enhanced the recombination frequency between the vector and chromosomal genes. When the vector was either uncut or cut at SacI in the region of homology, G418-resistant m⁺ recombinants were found to have integrated the vector by a single reciprocal homologous crossover; the enzyme site (SacI) used for cutting was present in the recombinants. By contrast, when the vector had been linearized at Pvul or SfiI in the region of nonhomology, vector integration involved nonhomologous crossovers, either between transferred DNA molecules or between transferred and chromosomal DNA, and the vector cut sites were absent in these recombinants. Some recombinants were found to have an unaltered as well as recombinant gene, suggesting that the nonhomologous recombination process might have involved sister chromatids.     

Altered synthesis of interferon-γ and expression of interferon-γ receptor by peripheral blood mononuclear cells from patients with IgA nephropathy and non-IgA proliferative glomerulonephritis

Previously we reported disease-specific interaction between interferon- (IFN-) and interleukin-4 (IL-4) in patients with IgA nephropathy (IgAN), suggesting the existence of unusual T cell behavior in this disease. In the present study, we investigated characteristic synthesis of interferon- (IFN-) and expression of IFN- receptor (IFN-R) in the peripheral blood mononuclear cells (PBMC) from patients with IgAN and other chronic proliferative glomerulonephritis (PGN). Heparinized peripheral blood samples were obtained from 38 patients with chronic mesangial proliferative glomerulonephritis (CGN; including 24 with IgA nephropathy) and 20 healthy controls. PBMC were isolated by gradient centrifugation and fragments were cultured in Iscove's modified Dulbecco's medium (IMDM) supplemented with 10% fetal calf serum (FCS) for 72 hr. IFN- concentrations in supernatants were evaluated by the enzyme-linked immunosorbent assay (ELISA). Other parts of PBMC pellets were reacted with anti-human IFN-R monoclonal antibody and FITC-labeled anti-mouse second antibody for analysis of IFN-R expression on these cells by FACScan. The remaining PBMC were fractionated into CD4⁺ T cells, CD8⁺ T cells, B cells, NK, cells and macrophages using the MACS cell sorting system. The isolated cells were evaluated for IFN- or IFN-R mRNA expression by the semiquantitative RT-PCR method.In vitro IFN- synthesis was enhanced in patients with CGN, and NK cells were revealed to be responsible for such enhancement. On the other hand, the expression of IFN-R on macrophages was suppressed in CGN patients. These results suggest that impairment of regulation of the IFN- system might be involved in the development of CGN.     

Pathogenesis of inflammatory edema in relation to the intensity of the thermal factor

Summary In inflammation developing in rabbits as a result of thermal burn at a temperature of 80–82°C additional globulins appear in the lymph flowing from the burned extremity; by their electrophoretic mobility these gobulins are referred as -globulins. This lymph injected intradermally to control animals disturbed the capillary permeability; this fact may be explained both by the presence of histamine in the lymph and by the appearance of additional -globulins.Following intradermal administration of lymph obtained 30 min after the burn at temperature of 50°, control rabbits exhibited a rise of the capillary permeability which may be attributed to the presence of histamine therein. In inflammation resulting from at 50°C, no -globulin fractions were found. Lymph obtained 24 h after the burn provoked no disturbance of the capillary permeability in rabbit skin. In burns caused by a moderate temperature (50°C) the leading role in the development of edema is evidently played by some other substances, not the additional -globulins. The data obtained point to differences in the pathogenesis of inflammatory edema depending on the intensity of action of the thermal factor.Presented by Active Member AMN SSSR, A. E. Braunshtein Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 1, pp. 32–36, January, 1964     

Histamine release in acute coronary occlusion-reperfusion in isolated guinea-pig heart

It has been shown that plasma histamine significantly increases during myocardial infarction in the dog. Histamine is also released when the isolated guinea-pig heart is reperfused after 30 minutes of low flow perfusion. The release of histamine and lactate dehydrogenase (LDH) after left anterior descending coronary artery ligation and release were investigated in the present study and related to the changes in electrocardiographic parameters and to a computer-aided analysis of left ventricular mast cell metachromasia.Spontaneous release of histamine was unchanged during ischemia and increased after the release of the ligature, while we observed a steady increase of LDH overflow. In parallel, a significant diminution of mast cell granule metachromasia was observed in left ventricular samples.The perfusion of the heart with FeCl₃/ADP (10 M/100M), a free radical-generating system, significantly enhanced both the basal and ischemic-reperfusion release of histamine, while perfusion with N-t-butyl-phenyl-nitrone (BPN/100 M) a spin-trapper molecule, significantly decreased histamine and LDH release and the loss in metachromasia of left ventricular mast cells induced by reperfusion. Inhibitors of xanthine oxidase (allopurinol, 10 M) and of calcium-activated proteases (leupeptin, 10 M) modified the kinetics of histamine and LDH release.     

Adrenaline-stimulated,aspirin-sensitive synthesis of histamine in the rat

The intravenous injection of 40 g/kg of adrenaline raised total rat lung histamine from 5.3±0.7 g, to 8.4±0.7 g and rat skin histamine from 624±51 g to 835±85 within 5 min. These changes were no longer apparent after 10 min. Stomach histamine was unaffected. Blood drawn 2 min after the injection of adrenaline failed to show an increased content of histamine. Rats given 1 mg/kg of compound 48/80, had greatly elevated levels of histamine in blood, but exhibited no increase in lung histamine. This result, as well as the extent of the increase of histamine observed in skin, which cannot be accounted for in any other way, point towards stepped-up local synthesis as the origin of the effect of adrenaline. Aspirin (20 mg/kg, intravenously 10 min prior to adrenaline), prevented increases of skin histamine. Evidence suggesting mast cells as the site of action of adrenaline, is discussed.     

Tedisamil blocks single large-conductance Ca2+-activated K+ channels in membrane patches from smooth muscle cells of the guinea-pig portal vein

Enzymatically dispersed smooth muscle cells of the guinea-pig portal vein were studied by the patch-clamp technique. They were found to have Ca²⁺-dependent K⁺ channels with the typical properties of the BK channel, i.e. a reversal potential at the calculated equilibrium potential for K⁺ ions, a striking voltage dependence, and a conductance of approximately 200 pS ([K⁺]₀ 50 mM, [K⁺]_i 150 mM, positive patch potentials). Tedisamil, a new bradycardic agent with an inhibitory action on K⁺ currents in heart muscle, reduced the open probability of the BK channels concentration-dependently (1–100 M) when applied at the cytosolic side of membrane inside-out patches. At 100 M [Ca²⁺]_i, the IC₅₀ of tedisamil was 13.8 M (¯x, n=5). Tedisamil increased the frequency of channel closures, and reduced the mean duration of openings from 8 ms to < 1 ms, while the mean duration of closures within bursts (1–2 ms) was not altered. Tedisamil did not affect long closures (> 160 ms) between bursts, either. The mean time of residence of tedisamil at the BK channel was estimated to be 1–2ms. Hence, tedisamil, in comparison to the slow blocker Ba²⁺ and the fast blocker tetraethylammonium, holds the position of an intermediate K⁺ channel blocker.Supported by the Deutsche Forschungsgemeinschaft     

Identification of c-Fos immunoreactive brainstem neurons activated during fictive mastication in the rabbit

In the present study we used the expression of the c-Fos-like protein as a functional marker to map populations of brainstem neurons involved in the generation of mastication. Experiments were conducted on urethane-anesthetized and paralyzed rabbits. In five animals (experimental group), rhythmical bouts of fictive masticatory-like motoneuron activity (cumulative duration 60–130 min) were induced by electrical stimulation of the left cortical masticatory area and recorded from the right digastric motoneuron pool. A control group of five animals (non-masticatory) were treated in the same way as the experimental animals with regard to surgical procedures, anesthesia, paralysis, and survival time. To detect the c-Fos-like protein, the animals were perfused, and the brainstems were cryosectioned and processed immunocytochemically. In the experimental group, the number of c-Fos-like immunoreactive neurons increased significantly in several brainstem areas. In rostral and lateral areas, increments occurred bilaterally in the borderzones surrounding the trigeminal motor nucleus (Regio h); the rostrodorsomedial half of the trigeminal main sensory nucleus; subnucleus oralis- of the spinal trigeminal tract; nuclei reticularis parvocellularis pars and nucleus reticularis pontis caudalis (RPc) pars . Further caudally-enhanced labeling occurred bilaterally in nucleus reticularis parvocellularis and nucleus reticularis gigantocellularis (Rgc) including its pars-. Our results provide a detailed anatomical record of neuronal populations that are correlated with the generation of the masticatory motor behavior.     

Interaction of G-actin with thymosin β4 and its variants thymosin β9 and thymosin β 9 met

Summary Thymosin ₄ is a major actin sequestering peptide in vertebrate cells and plays a role in the regulation of actin monomer/polymer ratio. Thymosin ₉ and thymosin ₉ ^met are minor variants of thymosin ₄. The possible function of these peptides has been investigated by comparing the actin binding properties of these -thymosins. Thymosin ₉ and thymosin ₉ ^met were found to inhibit polymerization of ATP-actin with identical K _d s of 0.7–0.8 M (as compared to 2±0.3 M for thymosin ₄); like thymosin ₄, they bound to ADP-G-actin with a 100-fold lower affinity than to ATP-G-actin. The interaction of thymosin ₄ and thymosin ₉ ^met with G-actin was weakened 20-fold upon oxidation of methionine-6 into methionine sulfoxide. Binding of thymosin ₄ to G-actin was accompanied by a 15% increase in the fluorescence intensity of actin tryptophans, and a 10 nm emission blue shift. Methionine-6 played an important role in this effect. The fluorescence change was used to monitor the kinetics of thymosin ₄ binding to G-actin in the stopped-flow. The reaction was bimolecular, with association and dissociation rate constants of 1.5 M^-1 s^-1 and 2s^-1 respectively, under physiological conditions. The possible physiological significances of methionine-6 oxidation and of the relatively slow binding kinetics in regulating thymosin ₄ function in vivo is discussed.     

γδ T Lymphocytosis Associated with Common Variable Immunodeficiency1

We present the case of a 28-year-old Caucasian female with common variable immunodeficiency (CVID) since age 5 who had a long history of hospitalizations for unexplained fevers and pulmonary infiltrates. The patient developed mild lymphocytosis 7 months prior to our evaluation. Flow cytometry of peripheral blood revealed an expansion of T lymphocytes, mild CD4 T lymphocytopenia, and a reduced CD4/CD8 ratio (0.2). Two subpopulations of T lymphocytes were found (CD3⁺/CD4^–/CD8⁺, 47%; CD3⁺/CD4^–/CD8^–, 53%), the vast majority of which expressed V-1. An infectious cause for the patient's T lymphocytosis could not be found. The sputum was chronically colonized with Staphylococcus aureus, and the organism produced TSST-1 in vitro. A bronchoalveolar lavage (BAL) revealed marked lymphocytosis, but T lymphocytes were not overrepresented in the BAL. Lymphocyte functional studies revealed poor proliferative responses to mitogens and staphylococcal superantigens and diminished cytokine production. V-1 T lymphocytes from the patient's blood were not expanded in vitro in response to staphylococcal superantigens. TCR gene rearrangement studies confirmed the presence of J and J1 clonal rearrangements accounting for only a small subpopulation of the T lymphocytes. These studies were repeated 5 months later and were unchanged. A bone marrow biopsy was negative for leukemia. Hence, the cause of the patient's T lymphocytosis could not be determined despite evaluation for underlying malignancy, occult infection, or superantigen-driven stimulation. The patient ultimately died of progressive respiratory insufficiency. The state of current knowledge regarding T lymphocytosis, decreased production of T lymphocytes, and a low CD4/CD8 ratio in association with CVID is discussed.     

Directional organization of eye movement and visual signals in the floccular lobe of the monkey cerebellum

The floccular lobe of the monkey is critical for the generation of visually-guided smooth eye movements. The present experiments reveal physiological correlates of the directional organization in the primate floccular lobe by examining the selectivity for direction of eye motion and visual stimulation in the firing of individual Purkinje cells (PCs) and mossy fibers. During tracking of sinusoidal target motion along different axes in the frontoparallel plane, PCs fell into two classes based on the axis that caused the largest modulation of simple-spike firing rate. For horizontal PCs, the response was maximal during horizontal eye movements, with increases in firing rate during pursuit toward the side of recording (ipsiversive). For vertical PCs, the response was maximal during eye movement along an axis just off pure vertical, with increases in firing rate during pursuit directed downward and slightly contraversive. During pursuit of target motion at constant velocity, PCs again fell into horizontal and vertical classes that matched the results from sinusoidal tracking. In addition, the directional tuning of the sustained eye velocity and transient visual components of the neural responses obtained during constant velocity tracking were very similar. PCs displayed very broad tuning approximating a cosine tuning curve; the mean half-maximum bandwidth of their tuning curves was 170–180 °. Other cerebellar elements, related purely to eye movement and presumed to be mossy fibers, exhibited tuning approximately 40 ° narrower than PCs and had best directions that clustered around the four cardinal directions. Our data indicate that the motion signals encoded by PCs in the monkey floccular lobe are segregated into channels that are consistent with a coordinate system defined by the vestibular apparatus and eye muscles. The differences between the tuning properties exhibited by PCs compared with mossy fibers indicate that a spatial transformation occurs within the floccular lobe.     

Enhancement of the immune response by immunization with L1210 cells preincubated in interferon

Mice were given a single intraperitoneal injection of L1210 cells preincubated either in interferon or in pseudointerferon. On the tenth day the mice were killed and the cytotoxicity of the sera against cells of leukemia L1210 was determined by the microcytotoxic test (a modification of Terasaki's method). Leukemic cells treated with interferon before immunization induced a more marked immune response than cells treated under the same conditions with pseudointerferon. The immune response, judging from the results of the cytotoxic test, was enhanced by two to four times.Laboratory of Immunology of Leukemias, Central Institute of Hematology and Blood Transfusion, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N.A. Fedorov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 6, pp. 706–707, June, 1976.     

Über heterogenetische Hämagglutinine bei Hepatitis

Zusammenfassung An Hand von 724 Titerbestimmungen der heterogenetischen Hämagglutinine bei Hepatitisseren, die 251 Erkrankten (Erwachsene) entstammten und von 479 gleichen Titerbestimmungen bei Normalseren wurden unterschiedliche Mittelwerte bezüglich der Titerhöhe bei beiden Kollektiven festgestellt. Es ergab sich eine Verschiebung der Titerhöhe der heterogenetischen Hämagglutinine bei Hepatitisseren gegenüber Normalseren nach den höheren Titerstufen hin, ohne daß jedoch der auch bei Normalseren festgestellte Höchsttiter von 1:128 bei den Hepatitisseren überschritten wurde. Die Differenz der Mittelwerte erwies sich als signifikant.Die Mittelwerte des heterogenetischen Hämagglutinintiters bei Hepatitisserem aus den Gesamtkollektiven der Patienten mit Spritzenanamnese (mögliche serogene Hepatitis) sowie mit Kontaktanamnese (wahrscheinliche epidemische Hepatitis) zeigten keine wesentlichen Unterschiede.Desgleichen verhielten sich die aus den Titerergebnissen von je 4 Wochen über eine Zeitspanne bis zu 20 Wochen errechneten Mittelwerte bei beiden Patientenkollektiven fast gleich. Dagegen zeigte das Verhalten der Titerwerte im Verlaufe der Krankheit bei beiden Patientenkollektiven Unterschiede. Bei der Patientengruppe mit Kontaktanamnese sinkt im Laufe eines Vierteljahres nach Krankheitsbeginn der prozentuale Anteil der niederen Titerstufen (<1:16) unter gleichzeitiger Zunahme des prozentualen Anteils der höheren Titerstufen (>1:16), während bei der Patientengruppe mit Spritzenanamnese der prozentuale Anteil der niederen Titerstufen (<1:16) nur geringe Schwankungen aufweist, der prozentuale Anteil der höheren Titerwerte (>1:16) aber nach vorübergehendem Ansteigen erheblich abnimmt.     

Effect of thyrotropin releasing hormone and thyroxine on cytochrome oxidase activity in the rat adenohypophysis

Thyrotropin releasing hormone (TRH), in a dose of 0.01 and 1.0 g/ml, sharply increased cytochrome oxidase activity in the adenohypophysis of rats fed for 6 weeks with methylthiouracil. This effect of TRH on enzyme activity was blocked by thyroxine (T₄), if added to the incubation medium in a concentration of 20 g/ml. Actinomycin D (20 g/ml) prevented the blocking of cytochrome oxidase by T₄. TRH in a concentration of 0.01 g/ml and T₄, in a dose of 2.0 g/ml, caused no change in cytochrome oxidase activity in the adenohypophysis of intact and partially thyroidectomized rats.Laboratory of Biological Standardization of Hormones, Institute of Experimental Endocrinology and Hormone Chemistry, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Yudaev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 11, pp. 559–562, November, 1977.     

Early recognition ofStreptococcus pneumoniae in patients with community-acquired pneumonia

The objective of this study was to assess the predictive value of signs, symptoms, and rapidly available laboratory parameters for pneumococci in community-acquired pneumonia (CAP). A prospective study on patients with CAP who were admitted to hospital was conducted. Clinical and laboratory data were collected according to a protocol. Two hundred sixty-eight patients aged 18 years or older, not living in a nursing home or not admitted to hospital within one week of this admission, with a new infiltrate on the chest radiograph consistent with pneumonia were included. According to microbiological and serological tests, patients were allocated to one of two aetiological groups,Streptococcus pneumoniae or other pathogens. Seventy-three variables were examined for a correlation with one of the aetiological categories by means of univariate and multivariate analysis. The resulting discriminant function was considered a clinical test for which posttest probabilities for pneumococcal pneumonia were calculated.Streptococcus pneumoniae was demonstrated in 79 patients and other pathogens in 83; no pathogens were detectable in 106 patients. The variables cardiovascular disease, acute onset, pleuritic pain, gram-positive bacteria in the sputum Gram stain, and leucocyte count correctly predicted the cause of CAP in 80% of all cases in both groups. Depending on the prevalence ofStreptococcus pneumoniae, posttest probabilities for pneumococcal pneumonia were up to 90%. It is concluded that data on history, together with the result of the Gram stain of sputum and the leucocyte count, can help to distinguishStreptococcus pneumoniae from other pathogens causing CAP.     

Evidence for direct reciprocal interactions between the central rhythm generators for spinal “respiratory” and locomotor activities in the rabbit

Summary 1. Rhythm generators for locomotion and respiration have been previously identified in the high spinal rabbit treated with nialamide and DOPA. In curarized preparations, with no sensory feedback, simultaneous recordings of motor commands from the nerves to the diaphragm and to several hindlimb nerves have demonstrated that central (intraspinal) interactions exist between these respiratory and locomotor activities. 2. The purpose of the present study was to investigate the nature of these interactions. Two main possibilities existed: (i) direct interactions taking place between the rhythm generators; (ii) the activity of one of the rhythm generators modifying the other generator's activity at its output (at the interneuronal or motoneuronal level). 3. The present analysis of the timing (and resetting) of activities in the phrenic, hindlimb extensor (gastrocnemius medialis) and flexor (tibialis anterior) nerves suggests a strong direct interaction between the two sets of rhythm generators. Each new locomotor cycle thus only begins at the termination of a long-lasting phrenic burst and a respiratory burst can only occur at certain parts of a locomotor cycle.Supported by the C.N.R.S. (ERA 411 and RCP 08.0803), the D.G.R.S.T. (DN 80-7-0252) and the INSERM (81-60-32)     

Cellular localization of inflammatory cytokines in human glomerulonephritis

We evaluated the expression of inflammatory cytokines in renal tissues obtained from 45 patients with several types of glomerulonephritis. Immunofluorescence studies with specific antibodies to interleukin (IL)-1, IL-1, IL-6, tumour necrosis factor (TNF)-, and TNF- showed intense cytoplasmic staining in the glomeruli and interstitium. Cells positive for these cytokines were found frequently in tissue from patients with lupus nephritis (WHO Class IV) and membranoproliferative glomerulonephritis, and, to a lesser extent, in tissue from patients with mesangial proliferative glomerulonephritis, Henoch-Schönlein purpura nephritis, and minimal change nephrotic syndrome. Most of these cells were dual-stained with a monoclonal antibody to monocytes-macrophages. In situ hybridization for cytokine mRNA, combined with immunoperoxidase staining for monocytes-macrophages, detected IL-1, IL-6, and TNF- mRNA in monocytes-macrophages infiltrating the glomeruli and interstitium. Occasionally, there was weak or moderate immunostaining for IL-1, IL-6, and TNF- in the glomerular mesangial and epithelial cells, but in situ hybridization signals were rarely found in these loci. These findings suggest that infiltrating monocytes-macrophages, rather than resident glomerular cells, are the major source of inflammatory cytokines in human glomerulonephritis.     

Participation of β-endorphin in the regulation of conditioned reflex activity of cats

The role of -endorphin in the regulation of conditioned instrumental food-procuring reactions and more complex forms of nervous activity such as reflexes of choice of the side of reinforcement was studied in cats. It was established that the subcutaneous injection of small doses of -endorphin (10 g/kg, 15 ·10^–6 g/kg) exerts a facilitatory nonspecialized effect on positive and negative food-procuring conditioned reflexes that has an overall adaptive character overall. The influence of the same doses of -endorphin on conditioned reflexes of choice is more complex in character, depending upon the initial level of conditioned reflex activity and on the typological features of the experimental animals. A possible mechanism of the influence of -endorphin on higher nervous activity is discUSSed.Deceased.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 76, No. 8, pp. 992–1000, August, 1990.