The effects of indomethacin and verapamil on the shape changes of vascular endothelial cells resulting from exposure to various inflammatory agents

Histamine (300 M), bradykinin (2 M), prostaglandin E₂ (PGE₂) (30 M), or the leukotrienes (LT) C₄ and E₄ (1 M) but not D₄ (1 M) appliedin vitro have been shown to change the shape of endothelial cells lining the guinea pig isolated thoracic inferior vena cava. All caused the formation of inter-endothelial cell gaps. Pre-treatment with either indomethacin (100 M) or verapamil (20 M) reduced the effects of these compounds. It is suggested that indomethacin and verapamil act by reducing the amount of intracellular calcium available for the shortening of contractile protein filaments within endothelial cells.     

On the regulation of the expressed L-type calcium channel by cAMP-dependent phosphorylation

The Ca²⁺ channel subunits _1C-a and _1C-b were stably expressed in Chinese hamster ovary (CHO) and human embryonic kidney (HEK) 293 cells. The peak Ba²⁺ current (I _Ba) of these cells was not affected significantly by internal dialysis with 0.1 mM cAMP-dependent protein kinase inhibitor peptide (mPKI), 25 M cAMP-dependent protein kinase catalytic subunit (PKA), or a combination of 25 M PKA and 1 M okadaic acid. The activity of the _1C-b channel subunit expressed stably in HEK 293 cells was depressed by 1 M H 89 and was not increased by superfusion with 5 M forskolin plus 20 M isobutylmethylxanthine (IBMX). The _1C-a·₂·₂/ complex was transiently expressed in HEK 293 cells; it was inhibited by internal dialysis of the cells with 1 M H 89, but was not affected by internal dialysis with mPKI, PKA or microcystin. Internal dialysis of cells expressing the _1C-a·₂·₂/ channel with 10 M PKA did not induce facilitation after a 150-ms prepulse to +50 mV. The Ca²⁺ current (I _Ca) of cardiac myocytes increased threefold during internal dialysis with 5 M PKA or 25 M microcystin and during external superfusion with 0.1 M isoproterenol or 5 M forskolin plus 50 M IBMX. These results indicate that the L-type Ca²⁺ channel expressed is not modulated by cAMP-dependent phosphorylation to the same extent as in native cardiac myocytes.     

Efficient selection of μ m − mutants from μm-expressing myeloma cells by treatment with ricin A-conjugated anti-μ antibody

We have developed an efficient system for obtaining myeloma mutants defective intrans-acting factors required for immunoglobulin (Ig) gene expression. The system consists of a myeloma cell line designed for this purpose and an efficient method for selecting mutants from it. The cell line is X63.653 transfected with the gene, whose tailpiece sequence was replaced with the transmembrane sequence of human EGF receptor to hold on the cell surface and whose CH1 sequence was removed to prevent from being retained in the endoplasmic reticulum. It efficiently and stably expressed chains of IgM on the cell surface ( _m ⁺ ) without light chains. To obtain mutants lacking _m ( _m ^– ) from the _m ⁺ cell line by selectively killing _m ⁺ cells, a method with ricin A-conjugated anti- antibody was more reliable than complement lysis mediated by anti- antibody. Applying the system, we obtained a variety of _m ^– mutants.     

The effects of intraportl infusions of glucagon on the hepatic arterial and portal venous vascular beds of the dog: Inhibition of hepatic arterial vasoconstrictor responses to noradrenaline

The sympathetically-innervated hepatic arterial and portal venous vascular beds of the dog were perfused simultaneously in situ. Glucagon was infused into the hepatic portal vein (1–10 g/min); it caused increases in hepatic portal vascular resistance and tended to reduce the hepatic arterial vascular resistance. Extrahepatic effects of intraportal infusions of glucagon included increases in superior mesenteric blood flow and heart rate and falls in systemic arterial pressure.A test dose of noradrenaline (10 g) injected into either the hepatic artery or the portal vein caused both hepatic arterial and portal venous vasoconstriction. The hepatic arterial constrictor responses to noradrenaline were antagonized intraportal infusions of glucagon. In contrast, intraportal glucagon did not antagonize the portal constrictor responses to intraarterial or intraportal noradrenaline.Elevated portal blood glucagon concentrations may protect the hepatic arterial blood flow from vasoconstriction due to elevated systemic levels of vasoactive substances including catecholamines.     

Comparison of disk diffusion,the E test,and detection ofmecA for determination of methicillin resistance in coagulase-negative staphylococci

The aim of this study was to find a reliable, fast, and simple alternative to the methicillin disk method for determination of methicillin resistance in coagulase-negative staphylococci, since results of this method are often difficult to read due to growth within the zone of inhibition. The sensitivity of 319 strains of coagulase-negative Staphylococci to a 5 g methicillin disk on Mueller-Hinton agar using an incubation period of 48 h was compared with that of 1 (1 g and 5 g oxacillin disks on Mueller-Hinton agar with or without 2% NaCl, using an incubation period of 24 h. The detection ofmecA (MecAgen) by the polymerase chain reaction was used as a standard. Minimum inhibitory concentrations were determined by means of the E test. Of the 225mecA-positive strains, 190, 215, and 193 were resistant to 5 g methicillin, 1 g oxacillin and 5 g oxacillin disks on Mueller-Hinton agar, respectively, and 216, 218, and 223 were resistant on Mueller-Hinton agar with 2% NaCl. Of the 94mecA-negative strains, 89, 93, and 94 were susceptible to 5 g methicillin, 1 g oxacillin, and 5 g oxacillin disks on Mueller-Hinton agar, respectively, and 92, 93, and 94 were susceptible on Mueller-Hinton agar with 2% NaCl. Using breakpoints of 2 g/ml for oxacillin resistance and 8 g/ml for methicillin resistance, the E test yielded sensitivities of 99.6 and 99.1% and specificities of 97.9 and 98.9% after 48 h of incubation. The 5 g oxacillin disk was faster and easier to read than the methicillin disk and correlated better with detection ofmecA than the methicillin disk or the 1 g oxacillin disk.     

Lack of additive effect between mechanisms of resistance to carbapenems and other beta-lactam agents inPseudomonas aeruginosa

Eighty-nine clinical isolates resistant (n=61) or susceptible (n=28) to imipenem and exhibiting the main patterns of susceptibility to other -lactam agents (wild type pattern, penicillinase pattern, constitutive cephalosporinase pattern) were studied in order to investigate (i) the mechanism of resistance involved and (ii) whether resistance to carbapenems affects the level of resistance to other -lactam agents and, conversely, if resistance to other -lactam agents affects the level of resistance to carbapenems. For this purpose, the presence of OprD protein in the cell wall was detected by Western blot and -lactamase activity by spectrophotometric assay and isoelectric focusing. OprD expression was not detectable in the imipenem-resistant (MIC16 g/ml) strains. It was decreased in half the strains for which MICs of imipenem were 2 to 8 g/ml and was close to a normal level in the most susceptible strains (MIC 1 g/ml), thus demonstrating a direct correlation between the level of susceptibility to imipenem and the level of OprD expression. No imipenemase activity was detected in imipenem-resistant strains. Synergy between imipenem or meropenem and BRL42715 was observed for all of the strains, demonstrating the role of cephalosporinase in carbapenem resistance. Within each pattern of susceptibility, the mean MICs of -lactam agents other than carbapenems were similar, whether the strains were susceptible or resistant to imipenem. Conversely, the mean MICs of imipenem or meropenem for either the imipenem-resistant or the imipenem-susceptible strains were similar, regardless of the susceptibility of these strains to the other -lactam agents. Thus, when several mechanisms of resistance to -lactam agents are present in the same strain ofPseudomonas aeruginosa, there is no additive effect between these mechanisms.     

Effects of inhibitors and ion substitutions on oscillations of cell membrane potential in cells expressing the RAS oncogene

Previous studies revealed that in NIH fibroblasts expressing the ras oncogene but not in other NIH fibroblasts, bradykinin leads to sustained, calcium dependent oscillations of cell membrane potential by repetitive activation of calcium-sensitive K⁺ channels. The present study has been performed to test for ion and inhibitor sensitivity of these oscillations. Both, Lys-bradykinin (kallidin) and bradykinin, but not any shorter peptide tested, maintained the oscillations. The oscillations are abolished in the presence of the K⁺ channel blocker barium (10 nmol/l). The amplitude but not the frequency of the oscillations is dependent on the extracellular potassium concentration. The oscillations are not dependent on the presence of extracellular sodium, bicarbonate or chloride. The oscillations are abolished in the absence of extracellular calcium and their frequency is significantly decreased at reduced extracellular calcium (to 0.2 mmol/l). The oscillations are not inhibited by acute administration of ouabain (0.1 mmol/l), by dimethylamiloride (100 mol/l), furosemide (1 mmol/l) and hydrochlorothiazide (100 mol/l), by cobalt (100 mol/l), zinc (100 mol/l), gadolinium (100 mol/l), verapamil (10 mol/l) and diltiazem (10 mol/l), but are abolished in the presence of 100 mol/l lanthanum, 1 mmol/l cadmium, 10 mol/l nifedipine, 25 mol/l SK & F 96365 and 200 mol/l TMB-8. Stimulation of calcium entry by 10 mol/l ionomycin is frequently followed by oscillations of cell membrane potential even in the absence of bradykinin. In conclusion, in cells expressing the ras oncogene bradykinin leads to sustained activation of calcium channels at the cell membrane, which cause oscillations of the cell membrane potential by triggering intracellular calcium release.     

Pyramidal tract of the cat: axon size and morphology

Summary The purpose of this work was to determine the number and morphology of pyramidal tract (PT) axons in the cat, using electron microscopy, modern methods of fixation, and computer-assisted morphometric analysis. Sections taken at the level of the medullary pyramids in three animals were fixed and magnified up to 10,000 x to produce photomicrographs. Morphological data were entered into computer files for analysis by tracing axon perimeters on micrographs mounted on a digitizer tablet. The number of axons per PT averaged 415,000, of which 88% were myelinated and 12% were unmyelinated. 90% of the myelinated axons fell in the diameter range 0.5–4.5 m. Axons larger than 9 m diameter accounted for 1% of the total; the largest were 20–23 m. Myelinated axon mean diameter was 1.98 m; because of the skewed distribution, with many small axons and a few very large axons, median diameter was 1.60 m. Size distribution was relatively uniform throughout the PT cross section, with all sizes represented in all regions. However, the more medial regions had a higher proportion of small fibers than the more lateral regions: mean medial diameter was 1.85 m while mean lateral diameter was 2.09 m. Myelin sheath thickness averaged 7.9% of fiber diameter for axons up to 11 m, but was constant at 0.9 m for larger fibers. Myelinated fibers were distorted from the circular shape in cross section, with a mean circularity index (or form factor) of 0.85, which implies that the fibers could swell about 15% without rupture of the cell membrane. Unmyelinated fibers averaged 0.18 m diameter (range 0.05–0.6 m); the largest unmyelinated axons were larger than the smallest myelinated axons. It is concluded that previous work greatly underestimated the number of axons in the cat pyramidal tract.     

Effects of tyramine and calcium on the kinetics of secretion in intact and electroporated chromaffin cells superfused at high speed

Fast superfusion of electroporated bovine adrenal chromaffin cells with a K⁺ glutamate-based solution containing 50 nM free Ca²⁺ and 2 mM adenosine 5-triphosphate, dipotassium salt (K₂ATP), produced a steady-state low catecholamine secretion, measured on-line with an electrochemical detector (about 20 nA). Rapid switching to electroporation solutions containing increasing Ca²⁺ concentrations ([Ca²⁺]) produced a rapid increase in the rate and peak secretion, followed by a decline. At intermediate [Ca²⁺] (3–100 M), a fast peak and a slow secretory plateau were distinguished. The fast secretory peak identifies a readily releasable catecholamine pool consisting of about 200–400 vesicles per cell. Pretreatment of cells with tyramine (10 M for 4 min before electroporation) supressed the initial fast secretory peak, leaving intact the slower phase of secretion. With [Ca²⁺] in the range of 0.1–3 M, the activation rate of secretion increased from 2.3 to 35.3 nA · s^–1, reached a plateau between 3–30 M and rose again from 100 to 1000 M [Ca²⁺] to a maximum of 91.9 nA · s^–1. In contrast, total secretion first increased (0.1–1 M Ca²⁺), then plateaud (1–100 M Ca²⁺) and subsequently decreased (100–1000 M Ca²⁺). At 30 and 1000 M extracellular [Ca²⁺] or [Ca²⁺]_o, the activation rates of secretion from intact cells depolarised with 70 mM K⁺were close to those obtained in electroporated cells. However, secretion peaks were much lower in intact (93 nA at 30 M Ca²⁺) than in electroporated cells (385 nA). On the other hand, inactivation of secretion was much faster in intact than in electroporated cells; as a consequence, total secretion in a 5-min period was considerably smaller in intact (10.6 A · s at 1000 M Ca²⁺) than in electroporated cells (42.4 A,s at 1 M Ca²⁺). Separation of the time-courses of changes in intracellular [Ca²⁺] or [Ca²⁺]_i and secretion in intact chromaffin cells depolarised with 70 mM K⁺was demonstrated at different [Ca²⁺]_o. The increase in the rate of catecholamine release was substantially higher than the increase of the average [Ca²⁺]_i. In contrast, the decline of secretion was faster than the decline of the peak [Ca²⁺]_i. The results are compatible with the idea that the peak and the amount of catecholamine released from depolarised intact cells is determined essentially by plasmalemmal factors, rather than by vesicle supply from reserve pools. These plasmalemmal factors limit the supply of Ca²⁺ by the rates of opening and closing of voltage-dependent Ca²⁺ channels of the L-and Q-subtypes, which control the local [Ca²⁺]_i near to exocytotic sites.     

Tension development and calcium sensitivity in skinned muscle fibres of the frog

Calcium activated isometric tension development was measured in single skinned muscle fibres of the ileofibularis muscle of the frog. The experiments were carried out at 5°C, pH=6.9, 1 mM free Mg²⁺ and an ionic strength of 160 mM. A Hill curve was fitted to the isometrically developed tension at different Ca²⁺ concentrations by means of a non-linear least mean square approximation. At a sarcomere length of 2.15 m, the Ca²⁺ concentration for half maximum tension (K) was 1.6 M. This Ca²⁺ concentration decreased with increasing sarcomere length; at 2.7 m, K was 1.1 M and at 3.1 m, K was 0.9 M. Therefore, Ca sensitivity is increased at larger sarcomere lengths. Consequently, the optimal sarcomere length for tension development shifted to larger values when the Ca²⁺ concentration was lowered. Osmotic compression of the fibre at 2.15 m by means of 5% Dextran also caused an increase in Ca sensitivity (K was 1.0 M). At 2.7 m, addition of 5% Dextran hardly affected the Ca sensitivity. The possible role of the interfilament spacing in the explanation of these results discussed.     

Phosphorylation-regulated low-conductance Cl− channels in a human pancreatic duct cell line

A low-conductance Cl^– channel has been identified in the apical membrane of the human pancreatic duct cell Capan-1 using patch-clamp techniques. Cell-attached channels were activated by the vasoactive intestinal polypeptide (VIP, 0.1 mol/l), dibutyryl-adenosine 3,5-cyclic monophosphate (db-cAMP, 1 mmol/l), 8-bromo adenosine 3,5-cyclic monophosphate (8-BrcAMP, 1 mmol/l), 3-isobutyl-1-methyl-xanthine (IBMX, 100 mol/l) and forskolin (10 mol/l). No channel activity was observed in non-stimulated control cells. In both cell-attached and excised inside-out patches, the channel had a linear current/voltage relationship and a unitary conductance of 9 pS at 23°C and 12 pS at 37°C. Its opening probability was not voltage dependent although pronounced flickering was induced at negative potentials. Anionic substitution led to the selectivity sequence Cl^–>I^–>HCO₃ ^–>gluconate. In insideout excised patches, the channel activity declined spontaneously within a few minutes. Reactivation of silent excised channels was achieved by adding protein kinase A (PKA, in the presence of ATP, cAMP and Mg²⁺). Conversely, active channels were silenced in the presence of alkaline phosphatase. The PKA-activated Cl^– channel was 4,4-diisothiocyanatostilbene-2,2-disulphonic acid (DIDS, 100 mol/l) and 4-acetamido-4-isothiocyanatostilbene-2, 2-disulphonic acid (SITS, 100 mol/l) insensitive, but was blocked by diphenylamine-2-carboxylic acid (DPC, 100 mol/l). These results demonstrate that the apical low-conductance Cl^– channel in Capan-1 is regulated on-cell by VIP receptors via cAMP and off-cell by PKA and phosphatases. They provide evidence that this channel is closely related to the cystic fibrosis transmembrane conductance regulator (CFTR) Cl^– channel.     

Transformation of Saccharomyces cerevisiae with plasmids containing fragments of yeast 2 μ DNA and a suppressor tRNA gene

Hybrid plasmids have been constructed containing segments of the yeast plasmid 2 DNA, the yeast ochre-suppressing SUP4.0 gene and the bacterial plasmid pBR322. Yeast transformation is detected with a host containing multiple ochre auxotrophic mutations. The transformed SUP4.0 gene is active and can promote growth in the absence of all the requirements. Plasmids containing different fragments of 2 DNA all appear to be active in high frequency transformation of yeast containing 2 DNA, except those containing the HindlII-D fragment. The transforming plasmids undergo recombination with the indigenous 2 DNA. Integration of the transforming plasmid into the host chromosome has been detected by hybridization of restriction enzyme cleaved DNA with labelled pBR322. The plasmids contain restriction enzyme sites which can be used for cloning other genes into yeast.Abbreviations kb kilobase pair - 2 the yeast plasmid of 6.2 kb size     

Catecholamine excretion by the healthy adult human

Summary During the past few years much progress has been made concerning the development of accurate chemical methods for the determination of adrenaline, noradrenaline, and hydroxy-methoxy mandelic acid in urine and blood plasma. The problem of establishing standard values for the healthy average adult human of both sexes has thus become more urgent. We determined creatinine, adrenaline and noradrenaline (trihydroxyindole method) as well as hydroxy-methoxy mandelic acid (HMMA) in 16 men and 11 women. The daily excretion of creatinine remained to within 5% in 12 of the 27 subjects but varied by more than 5% to over 20% in the remaining 15 subjects. The mean values of the 24 hr urinary catecholamine excretion were: for men: noradrenaline = 24.3±6.9 g, adrenaline = 7.1±2.9 g, the NA/A ratio = 4.1±2.3, HMMA=6.9±2.1 mg; for women: noradrenaline = 23.1±7.1 g, adrenaline = 5.6±2.4 g, ratio = 5.1±3.6, HMMA=6.2±2.5 mg. A study of the diurnal variation showed that adrenaline and noradrenaline excretion was highest during the period from 7–15 hr, decreased from 15–23 hr by 20% for noradrenaline and by 30% for adrenaline, and further decreased during the time from 23–7 hr by 45% for noradrenaline and 75% for adrenaline; the excretion of HMMA was the same during the two day-time periods and was 35% lower during the night. The resting plasma levels were: for men: noradrenaline = 0.12 g/l and adrenaline = 0.23 g/l; for women: noradrenaline = 0.11 g/l and adrenaline =0.21 g/l. The values reported here agreed well with data obtained by Kärki (1956) from bioassay and were of the same order of magnitude as those collected by Brunjes (1964) using a different version of the trihydroxyidole method. The discrepancies with some other studies were critically reviewed.     

Molecular size-dependent leakage of intracellular molecules from frog skeletal muscle fibers permeabilized with β-escin

The permeability of -escin-treated cell membrane was characterized in terms of the permeant molecular size, by monitoring the leak of cytoplasmic molecules in frog skeletal muscle fibers. With a low concentration of -escin (5 M), most of the cellular ATP was lost within 30–40 min (as revealed by rigor force generation), whereas a fluorescence-labeled dextran injected into the cytoplasm (10 kDa) and cytoplasmic proteins (14–80 kDa) slowly leaked out of the cell. A high concentration of -escin (50–100 M) accelerated the leak of large molecules. Therefore, low concentrations of -escin may be used as a means of permeabilizing the cell membrane to relatively small molecules, while retaining a major fraction of the cellular macromolecules.Abbreviations MOPS 3-[N-morpholino]propanesulfonic acid - KMS potassium methanesulphonate - PIPES piperazine-N,N-bis[2-ethanesulfonic acid] - EGTA ethylene glycol-bis( -amino-ethyl ether)N,N,N,N-tetraacetic acid - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis     

Inhibition of14C-Aminopyrine accumulation in isolated rabbit gastric glands by the H2-receptor antagonist HOE 760 (TZU-0460)

Acid secretion in isolated rabbit gastric glands was measured by means of the¹⁴C-aminopyrine accumulation technique. Hoe 760 (TZU-0460) and Hoe 062, the desacetylated compound of Hoe 760, caused a concentration-dependent reduction of histamine (100 M) induced aminopyrine-accumulation. The IC₅₀-values were 3.16±0.84 M (n=5) and 1.58±0.6 M (n=6) for Hoe 760 and Hoe 062, respectively. In comparison an IC₅₀ of 9.0±0.72 M (n=6) was obtained for cimetidine and 3.3±1.4 M (n=5) for ranitidine. The IC₅₀-values of ranitidine, Hoe 760 and Hoe 062 were significantly different (p<0.05) from cimetidine. The addition of increasing concentrations of Hoe 760 to the histamine concentration-response curve caused a parallel rightward shift. The transformation of these concentration-response curves according to Arunlakshana and Schild indicated that this inhibition was caused by a competitive antagonism of the histamine receptor on the parietal cell. In agreement with these findings the dbc-AMP stimulated aminopyrine accumulation remained unaffected by the H₂-receptor antagonists.     

Role of the GTP-binding protein Gs in the β-adrenergic modulation of cardiac Ca channels

In the heart, the guanosine 5-triphosphate (GTP)-binding protein G_s is activated by hormone binding to -adrenergic receptors and stimulates the intracellular cyclic adenosine 3,5-monophosphate (cAMP) pathway that leads to phosphorylation of L-type Ca channels by the cAMP-dependent protein kinase A [28]. Additionally, G_s can modulate cardiac Ca channels directly in cell-free systems [57]. In order to examine the question of whether these pathways could be separated functionally and whether they act independently or synergistically on L-type Ca channels in intact cells, the whole-cell Ca current (I _Ca) and the respective current density were measured in guinea-pig ventricular myocytes at 0 mV. The following results were obtained.First, typically, the I _Ca density increased from 12 to 40 A/cm² following application of 1 M isoproterenol (ISP) to myocytes bathed in solutions containing 1.8 mM CaCl₂. However, 1 M ISP enhanced I _Ca only from 9 to 17 A/cm² after inhibition of the protein kinase A by dialysis of 0.5 mM Rp-cAMPS (the Rp-isomer of adenosine 3,5-monophosphorothioate) in the presence of 0.5 mM GTP. Withdrawal of GTP from the dialysate attenuated the effects of ISP on I _Ca. Thus, Rpc-AMPS unmasks a GTP-dependent component of the -adrenergic stimulation of I _Ca, which probably reflects the direct stimulation of Ca channels by G_s under block of cAMP-dependent phosphorylation.Second, in cells under dialysis with 100 or 200 M cAMP, bath application of 20–40 M 3-isobutyl-1-methylxanthine (IBMX) enhanced the I _Ca density to about 41 A/cm² indicating saturation of the cAMP pathway. Under this condition, 1 M ISP was without significant effect on I _Ca. This result may suggests that direct G_s stimulation is rather ineffective on Ca channels after maximal cAMP-dependent phosphorylation. Alternatively, maximal stimulation of the cAMP pathway may also interfere with the activation of the G_s pathway in intact myocytes.Third, simultaneous application of 1 M ISP and 40 M IBMX enhanced I _Ca up to densities of around 75 A/cm² during cell dialysis with 100 M cAMP, an effect much stronger than that exerted by IBMX alone under similar conditions. Since it seems likely that G_s is activated more quickly, than the cAMP pathway during application of the ISP/IBMX mixture, the latter result suggests that a direct effect of G_s may act to prime L-type Ca channels for cAMP-dependent phosphorylation during -adrenergic stimulation of cardiac myocytes.     

Effect of natural inhibitors of free radical reactions on adrenalin autoxidation

Water-soluble antioxidants (1 M reduced glutathione, 3 M cysteine, 1 M ascorbate), in the presence of EDTA, inhibit the adrenalin autoxidation reaction at pH 10.2, whereas their oxidized forms, and also -tocopherol (40 M), have no such effect. The inhibiting power of superoxide dismutase is many times greater than that of the substances tested. Adrenochrome formation during free-radical oxidation of adrenalin takes place without the participation of the hydroxyl radical.Department of Biochemistry, Second Moscow Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR V. N. Orekhovich.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 1, pp. 33–35, January, 1976.     

The effect of hyperosmotic challenge upon ion transport in cultured renal epithelial layers (MDCK)

Exposure of the basal-lateral surfaces of MDCK epithelia, mounted in Ussing chambers, to medium made hyperosmotic by the non-electrolyte mannitol, resulted in a marked inhibition of the adrenalinestimulated inward short-circuit current (Cl^– secretion). This inhibition was unaccompanied by a reversal of the adrenaline-stimulated increment in tissue conductance, indicating that the inhibition was due to modulation of ion transport at the basal-lateral membranes. Loop-diuretic-sensitive ⁸⁶Rb(K⁺) efflux mediated by the Na⁺-K⁺ — 2 Cl^– cotransporter at the basal-lateral membranes was markedly stimulated by hypertonic exposure. A diuretic-sensitive K⁺ (Cl^–) loss was observed in shrunken cells upon prolonged exposure (20 min), showing that the net direction of cotransport flux was outward. ⁸⁶Rb(K⁺) efflux stimulated by adrenaline (100 M), exogenous ATP (100 M) and A23187 (10 M) was attenuated in shrunken cells, suggesting that basal-lateral K⁺ conductance is reduced in hyperosmotic media. Cotransport stimulation by hyperosmotic medium was asymmetric, apical bathing hypertonicity being ineffective. These data are consistent with a low hydraulic permeability of the apical membranes.     

Mechanical properties of mammalian single smooth muscle cells I. A low cost large range microforce transducer

Summary A transducer has been developed for measuring the minute forces generated during isometric contractions (1.0–10.0N) of single smooth muscle cells from the pig urinary bladder and the human uterus. In addition to its high sensitivity, resolution and stability (100 mVN^–1, <0.1N and <2.0N h^–1), the transducer features a very wide range (100–140N) with good linearity, enabling measurement of contractions as well as passive force-length characteristics within one uninterrupted measurement session. Since the transducer features an independent and interchangeable force to displacement conversion system, different force ranges can be realized by inserting force conversion systems with different compliances.     

Fine structural survey of Gudden's tegmental nuclei in the rat: cytology and axosomatic synapses

Summary The fine structure of neuronal somata and axosomatic synapses in each subnucleus of Gudden's tegmental nuclei was studied by use of electron microscopy. The pars principalis of the ventral tegmental nucleus of Gudden (TVP) is composed of oblong or triangular, medium sized neurons (11.8x22.6 m, 211.4 m²) containing many mitochondria, lysosomes, Golgi apparatus, and rough endoplasmic reticulum composing Nissl bodies. The light oval nucleus with a prominent nucleolus is centrally situated, and indentations of its nuclear envelope are recognized in all neurons. The neuron in the pars ventralis of the dorsal tegmental nucleus of Gudden (TDV) is similar to that in the TVP, but its average size is significantly smaller (10.0x18.8 m, 151.4 m²), and its organelles are also less well developed. The pars dorsalis of the dorsal tegmental nucleus of Gudden (TDD) is composed of spindle shaped, small neurons (6.9x16.2 m, 85.1 m²) characterized by their irregular shaped nucleus with its invaginated envelope. These neurons have a thin rim of cytoplasm, poorly developed organelles and no Nissl bodies. The average number of axosomatic terminals in a sectional plane is 9.9 in the TVP, 9.6 in the TDV and 2.6 in the TDD, and the bouton covering ratio is 24.3% in the TVP, 26.5% in the TDV and 7.4% in the TDD. The respective percentages of round, flat and pleomorphic type axosomatic terminals were estimated, and the flat type terminals were found to be dominant in the TVP, the pleomorphic type terminals in the TDV, and the round type terminals in the TDD.