Aldosterone does not stimulate the Na:K pump in isolated turtle colon

The study of the mechanisms by which mineralocorticoids stimulate sodium absorption across distal epithelia has focused on three possible sites of action: apical sodium permeability, the basolateral NaK pump, and the production of high-energy substrates. Recently we developed a method for direct measurement of the current generated by the basolateral NaK pump of the turtle colon [15]. In the presence of mucosal amphotericin-B and serosal barium the short-circuit current across the colon can be equated with the current produced by active electrogenic exchange of sodium for potassium across the basolateral membrane. This pump current is a measure of the transport capacity of the epithelial NaK pump that is uncomplicated by changes in apical membrane sodium permeability. Pump currents, thus defined, were compared in control tissues and tissues treated with aldosterone in vitro. After 9h Na absorption was increased 4-fold in the aldosterone-treated tissues but the values of the pump current were identical in the two groups. This result indicates that acute stimulation of sodium absorption by aldosterone does not occur by stimulating the NaK pump directly.     

Functional adaptation to high PCO2 of apically and basolaterally located Na+/H+ exchange activities in cultured renal cell lines

Cultured renal epithelial cells grown on filter support were examined for functional adaptation of Na⁺/H⁺ exchange activities to respiratory acidaemia, which was mimicked by increasing PCO₂ from 5% to 10% during 24 h or 48 h of cell culture. We have selected proximal tubular cell lines with either dual location of Na⁺/H⁺ exchange activities (MCT cells, RKPC-2 cells), apical location of Na⁺/H⁺ exchange activity (OK/ WOK cells) or a basolateral location of Na⁺/H⁺ exchange activities (LLC-PK₁/clone 4 cells, MDCK cells). Na⁺/H⁺ exchange activity was determined microspectrofluorometrically (using BCECF) in the absence of CO₂/HCO ₃ ^– . Respiratory acidaemia specifically increased apical Na⁺/H⁺ exchange activity (previously classified as amiloride-resistant) in MCT cells, in RKPC-2 cells and in WOK cells; it stimulated basolateral Na⁺/H⁺ exchange activity (previously shown to be amiloride-sensitive) in RKPC-2 cells, in LLC-PK₁/clone 4 cells and in MDCK cells, but did not affect basolateral Na⁺/H⁺ exchange activity in MCT cells. In MCT and in RKPC-2 cells the effect of high PCO₂ on apical Na⁺/H⁺ exchange was prevented by inhibition of protein kinase C. In RKPC-2 cells, activation of basolateral Na⁺/H⁺ exchange by high PCO₂ occurred also when protein kinase C was inhibited. In conclusion, these studies demonstrate stimulation of apical Na⁺/H⁺ exchange, but differential regulation of basolateral Na⁺/H⁺ exchange activities in response to a high-PCO₂-induced acid environment. Protein kinase C activation might be involved in mediating the effect of acidaemia on stimulation of apical Na⁺/H⁺ exchange activity (MCT and RKPC-2 cells).     

The isolated frog skin epithelium: Presence of α and β adrenergic receptors regulating active sodium transport and water permeability

Summary The effects of stimulation of and adrenergic receptors on short circuit current (S.C.C.), Na⁺ and Cl^– fluxes and osmotic water permeability were studied on isolated frog skin epithelial layers separated from the dermis.Low norepinephrine doses (final concentrations in the incubation medium ranging from 5×10^–9 to 10^–8 M) produced increased water permeability and S.C.C. The latter was entirely accounted for by an increase in the active Na⁺ influx. Na⁺ outflux and Cl^– fluxes were not modified. Both these effects disappeared after treatment with the blocking agent, Propranolol. Higher norepinephrine doses (final concentrations: 10^–7 to 10^–6 M) produced: 1. an increase in water permeability lower than that produced by low doses, the highest doses failing to increase water permeability, and 2. a triphasic change in S.C.C.: after an initial increase, S.C.C. dropped to its resting value and then rose again to a sustained value. Na⁺ and Cl^– flux measurements showed that the variation in S.C.C. reflected variations in active Na⁺ transport. When the same high norepinephrine doses were applied after treatment with the blocking agent Phentolamine, the effects observed were identical to those obtained with low doses.On blocked preparations, large doses of norepinephrine inhibited the water permeability and sodium transport increases induced by theophylline or oxytocin but did not modify those induced by 35-cyclic AMP. The inhibition was suppressed after blocking receptors.From the foregoing, it was concluded that both and adrenergic receptors are present in frog skin epithelial cells and are involved in the regulation of water and sodium permeability.It is suggested that the inhibitory effect of stimulation resulted from the inhibition of cyclic-AMP generating system, the activity of which is under the positive control effect of oxytocin and stimulation.     

Haemopathological responses to chronic inflammation in the houbara bustard (Chlamydotis undulata macqueenii)

Blood samples were collected from 12 clinically normal (CN) and 12 clinically abnormal (CA) captive houbara bustards (Chlamydotis undulata macqueenü). Total white blood cell counts for each group were carried out, followed by differential white cell and thrombocyte counts. One hundred thrombocytes from each bird were also measured using a micrometer eye piece and oil immersion light microscopy. The CA birds had significant increases both in the total white blood cell count and in the counts for heterophils, monocytes and basophils. This was associated with a significant thrombocytosis. The thrombocytes from the CA birds were also found to be significantly larger (mega thrombcytes) than those from the CN birds. These results suggest that the increase in the total white blood cell count in chronic inflammation in the houbara bustard is mainly due to an increase in the number of heterophils, monocytes and basophils. These results also suggest that both the thrombocyte count and the thrombocyte morphometrics may be important components of routine diagnostic haematological investigations in houbara bustards.     

A four-year study of α-fetoprotein in Vietnam (1969–1973)

By the method of double diffusion in gel -fetoprotein (-FP) was found in 66% of cases of hepatocellular carcinoma. When the more sensitive method of electroimmunodiffusion was used the frequency of positive findings was increased both in cases of hepatoma and other diseases. The results of quantitative estimation of -FP in patients after ligature of the hepatic artery indicate a decrease in the serum -FP concentration; this confirms the value of its determination for prognosis.Department of Pathological Physiology, Medical Institute, Hanoi, Vietnam. (Presented by Academician of the Academy of Medical Sciences of the USSR O. V. Baroyan.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 2, pp. 224–225, February, 1976.     

Control of metastatic properties of BL6 melanoma cells by H-2Kb gene: immunological and nonimmunological mechanisms

The effect of class I H-2 antigen expression on the metastatic properties of BL6 melanoma cells was investigated. The BL6-8 clone isolated from the highly metastatic BL6 melanoma did not express H-2K b gene. Following transfection with the H-2K^b gene, BL6-8 cells displayed a low metastatic potential in the immunocompetent as well as immunosuppressed (X-irradiated) or triple-immunodeficient mice with impaired T, B and natural killer (NK) cells function. The expression of H-2K^b gene and the low metastatic ability of transfected BL6 melanoma cells were associated with appearance of cell membrane soybean agglutinin (SBA) and Griffonia simplicifolia 1B₄ (GS1B₄) lectin-binding carbohydrataes. These alterations in cell surface carbohydrates were found to be a result of reduction in sialylation of SBA binding sites and upregulation of the 1.3 galactosyltransferase (1.3GT) gene. To assess the importance of H-2K^b-induced alterations in cell surface carbohydrates for metastasis formation, BL6-8 melanoma cells were transfected with H-2K^b gene without neo^r gene cotransfection and selected for adherence to SBA-lectin-conjugated agarose beads. The transfected clones that expressed SBA and GS1B₄ lectin-binding carbohydrates were low metastatic. Further analysis of these clones showed that presence of SBA and GS1B₄ lectin-binding carbohydrates rather than expression of H-2K^b molecules per se might be responsible for low metastatic potentials of H-2K^b-transfected cells in the immunocompromized mice. Studies of the possible mechanisms responsible for low metastatic ability of H-2K^b-transfected melanoma cells revealed that these cells displayed a reduced ability to adhere to murine pulmonary endothelial cells as well as to laminin and collagen IV. We hypothesized that the observed nonimmunological effects of H-2K^b gene in BL6 melanoma cells is a result of an interaction between the H-2K^b gene and B16 melanoma-specific ecotropic retrovirus. It results in inhibition of this retrovirus production with consecutive alteration in the expression of cellular genes controlling cell surface glycosylation and adhesion properties essential for the metastatic phenotype of BL6 melanoma.     

Preparation and molecular cytogenetic characterization of α-satellite DNA of human chromosome 6

Institute of Medical Genetics, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR, N. P. Bochkov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 107, No. 6, pp. 735–737, June, 1989.     

Localization of tissue transglutaminase and N (epsilon)-(gamma) -glutamyl lysine in duodenal cucosa during the development of mucosal atrophy in coeliac disease

Expression and transamidation activity of tissue transglutaminase (tTG) may be involved in the morphological modifications leading to the mucosal atrophy observed in coeliac disease (CD). We aimed to investigate the localization of tTG within the duodenal mucosa during the development of villous atrophy. The localization and level of expression of N-(-glutamyl) lysine isopeptides which could reflect the transamidation activity of tTG were also analyzed. tTG and N-(-glutamyl) lysine were localized using an immunohistochemical technique on duodenal biopsies obtained from 75 patients with CD and 51 subjects with normal mucosa (control group). The number of cases displaying tTG-expressing cells in the basement membrane and lamina propria was significantly higher in CD patients than in the control group. Moreover, the intensity of tTG staining in these areas was higher in CD. In contrast, the number of biopsies with tTG-expressing enterocytes was significantly lower in CD than in the control group. There was no difference in N-(-glutamyl) lysine between the two populations. Tissue transglutaminase was differently expressed in the various areas of the mucosa according to the stage of atrophy, whereas the localization and the intensity of the labelling of N-(-glutamyl) lysine isopeptides did not show any modification. The preferential localization in the basement membrane and lamina propria may reflect the involvement of tTG in the development of mucosal atrophy in CD.     

Peroxisome proliferator-activated receptor-α and liver cancer: where do we stand?

The peroxisome proliferator-activated receptor- (PPAR), first identified in 1990 as a member of the nuclear receptor superfamily, has a central role in the regulation of numerous target genes encoding proteins that modulate fatty acid transport and catabolism. PPAR is the molecular target for the widely prescribed lipid-lowering fibrate drugs and the diverse class of chemicals collectively referred to as peroxisome proliferators. The lipid-lowering function of PPAR occurs across a number of mammalian species, thus demonstrating the essential role of this nuclear receptor in lipid homeostasis. In contrast, prolonged administration of PPAR agonists causes hepatocarcinogenesis, specifically in rats and mice, indicating that PPAR also mediates this effect. There is no strong evidence that the low-affinity fibrate ligands are associated with cancer in humans, but it still remains a possibility that chronic activation with high-affinity ligands could be carcinogenic in humans. It is now established that the species difference between rodents and humans in response to peroxisome proliferators is due in part to PPAR. The cascade of molecular events leading to liver cancer in rodents involves hepatocyte proliferation and oxidative stress, but the PPAR target genes that mediate this response are unknown. This review focuses on the current understanding of the role of PPAR in hepatocarcinogenesis and identifies future research directions that should be taken to delineate the mechanisms underlying PPAR agonist-induced hepatocarcinogenesis.     

Role of adrenergic structures in functional control over the cerebral circulation

An investigation of the cerebral circulation by the thermoelectric method showed that stimulation of the cervical sympathetic nerve leads to considerable changes in the blood supply to the brain. The changes in blood flow are biphasic in character: An initial small increase is followed by a decrease below the original level. Pharmacological analysis with and adrenoblockers showed that the constrictor response of the cerebral vessels is due to excitation of -adrenergic structures and the dilator response to excitation of -adrenergic structures. A possible mechanism of these changes is postulated.Laboratory of Pathophysiology of Respiration, Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. M. Chernukh). Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 1, pp. 9–12, January, 1976.     

Human T-lymphocyte subset production of immune (γ) interferon

Human T, T, and T lymphocyte subpopulations have the capacity to respond to phytohemagglutinin (PHA)in vitro with proliferation and the production of a pH 2 and heat-labile interferon. This occurs both when the subsets are isolated by direct rosetting techniques or by negative selection. Macrophages enhance the production of the interferon by each lymphocyte subset and do not themselves produce interferon in response to products of PHA-activated lymphocyte subsets. Thus our studies indicate that subpopulations of T lymphocytes known to differ with regard to morphology, surface receptors, RNA content, response to corticosteroids and X-irradiation, and other functional capabilities do not differ with regard to their capacity to produce interferon.     

Human breast epithelium transplanted into nude mice

Summary Epithelial components of the normal human breast and their response to hormonal manipulation have been studied in the nude mouse. Six to eight week-old female athymic nude mice were used as the recipients of enzymatically prepared breast organoids, composed of ductal and lobuloalveolar structures. After 12 weeksin situ in the mouse mammary fat pad the human breast tissue retains its normal morphology as demonstrated by the presence of myosin positive myoepithelial cells and keratin positive luminal cells. Monoclonal antibodies M8 and M18 raised to components of the human milk fat globule membrane give a similar staining pattern in the xenografted organoids to that seen in the donor tissue. On mating the recipient female nude mice, the human breast tissue responds with both an increased³H-thymidine labeling index and -lactalbumin production. This model in conjunction with in vitro studies is, therefore, suitable for the study of extrinsic and intrinsic factors controlling differentiation and morphogenesis in the human breast.     

Functional reorganization of the noradrenergic system after partial fornix section: a behavioral and autoradiographic study

Previous experiments revealed that the cholinergic deficit in rats with a partial fornix section was accompanied by an increase in turnover of noradrenaline (NE) in the hippocampus. This noradrenergic hyperactivity contributed to the cognitive deficit in lesioned rats, probably by interaction with the cholinergic system. The present experiment examines the reorganization of the noradrenergic system after the damage induced by partial fornix section and attempts to determine if the increase in NE turnover is of locus coeruleus (LC) origin, or if it is a result of local regulation at the noradrenergic terminals. Rats were submitted to knife-cut section of the fornix, resulting in a decrease in choline acetyltransferase activity in the hippocampus, correlated with a significant behavioral deficit in a spatial memory task. Lesioned rats learned a nonspatial memory task normally. Sections of brains of these rats were submitted to quantitative autoradiography. [¹²⁵I]Iodopindolol binding was assessed in the dorsal and ventral hippocampus to determine availability of receptors. This was found to be significantly lower in lesioned rats. [¹²⁵I]Iodoclonidine was used to determine ₂ receptors binding in dorsal and ventral hippocampus and in LC. There was no difference in ₂ receptors in LC, a significant decrease in dorsal regions of the hippocampus, and a significant increase in ventral regions. Muscarinic M1 receptors in the hippocampus showed no changes after the lesion.     

Effect of triiodothyronine on system A amino acid transport in cells of rat submandibular gland

The effect ofL-3,5,3-triiodothyronine (T₃) on -aminoisobutyric acid (AIB) transport in isolated cell suspensions of rat submandibular gland was investigated. The uptake of ATB by these cells appeared to require extracellular Na⁺ and was inhibited by ouabain (10^–3 M). Cell suspensions from thyroidectomized rats which have been given three successive doses of T₃ on alternate days (50 g/100 g BW) showed a significant increase in AIB uptake compared with cells isolated from thyroidectomized rats treated with diluent. Efflux of AIB from the cell suspension was not affected by T₃. There was no significant changes in AIB uptake 12 h after a single injection of T₃ (50 g/100 g BW). However, there was a significant 49% and 65% increase in AIB net uptake at 24 and 48 h, respectively, after T₃ treatment. Under similar conditions, the cell suspension showed a 48% increase in NaK-ATPase activity at 12 h and to a peak of 61% at 24 h. Therefore, changes in NaK-ATPase activity preceded the changes in AIB net uptake upon treatment with T₃, implying that AIB uptake is probably mediated, at least in part, by the activity of NaK-ATPase.Abbreviations AIB -Aminoisobutyric acid - HBBS Hank's buffer salt solution - T₃ triiodothyronine This study was supported by NIH grant (AM 28590) and USUHS grant CO 7623