Difference in arginine vasopressin responsive cAMP production between apical and basolateral membrane of cultured renal epithelial cells (MDCK)

It has been reported that vasopressin (AVP)-sensitive renal epithelial cell line (MDCK) forms morphologically polarized monolayers when cultured on plates. We studied whether the AVP-responsive cAMP production system would be located solely on the basolateral surface of these cells as has already been shown on the renal tubules. We used two methods to overcome the inaccessibility to the basolateral surface of the cultured cell layer and to study the apical and basolateral surfaces separately. One was culture on collagen sheet and the other was on Millipore filters. Our experiments showed that MDCK cell increased adenosine 3':5'-cyclic monophosphate (cAMP) content prominently only when vasopressin was accessible to the basolateral surface. Accordingly, MDCK cells were shown to have the AVP-responsive cAMP production system predominantly on the basolateral surface of the cell membrane.     

Stimulatory effect of epidermal growth factor on prostaglandin E2 production in mouse fibrosarcoma cell line (HSDM1 C1)

Using HSDM1 C1 cell line derived from the mouse fibrosarcoma which synthesizes and secretes prostaglandin (PG) E2, specific binding sites for epidermal growth factor (EGF), a potent growth stimulator of many tissues, and its effect on PGE2 production by cultured tumor cells were studied. HSDM1 C1 cell line possessed specific, high-affinity receptors for EGF: Kd (5.5 X 10(-10 M) and binding capacity (17,650 sites/cell). EGF significantly stimulated PGE2 production in HSDM1 C1 line cultured in serum-free medium for 24 h in a dose-dependent manner; a 2.5-fold increase over control was induced by as little as 0.1 ng/ml and the maximal effect (3.5-fold increase) by 1 ng/ml. Its stimulatory effect on PGE2 production was completely blocked by indomethacin, an inhibitor of PG biosynthesis. These data suggest that EGF may be involved in modulation of synthesis and/or secretion of PGE2, a potent bone-resorbing factor, by the tumors which may partly contribute to hypercalcemia in certain types of neoplasms.     

Concomitant suppression of plasma ACTH- and beta-endorphin-like immunoreactivity by cyproheptadine, naloxone, and somatostatin in the ectopic ACTH syndrome

Release of plasma ACTH- and beta-endorphin (beta-EP)-like immunoreactivity (LI) was studied in vivo in a patient with an ectopic ACTH-producing malignant thymoma. Administration of lysin vasopressin stimulated concomitant release of plasma ACTH- and beta-EP-LI. Administration of cyproheptadine, naloxone, and somatostatin significantly suppressed plasma levels of ACTH- and beta-EP-LI, while saline infusion did not. Gel exclusion chromatography of the plasma extracts revealed that ACTH-LI consisted of two components, large and small molecular weight form, while beta-EP-LI consisted of three components, large molecular weight, beta-lipotropin-, and beta-EP-sized form; each of these components was incompletely suppressed by somatostatin infusion. It is suggested that certain tumors may have acquired aberrant multiple receptors during malignant transformation which may lead to the paradoxical hormone response as demonstrated in this case.     

Effect of various catecholamine antagonists on prolactin secretion in conscious male rabbits

To clarify physiological roles of catecholaminergic systems in the control of rabbit prolactin (PRL) release, the effect of various catecholamine receptor antagonists on plasma PRL levels was examined in conscious, freely moving male rabbits. An intravenous (iv) injection of yohimbin (2.5 mg/kg body wt), an alpha 2-adrenoreceptor antagonist, but not prazosin (2 mg/kg body wt), an alpha 1-adrenergic receptor antagonist, resulted in a significant elevation of plasma PRL. Conversely, propranolol (2.5 mg/kg body wt, iv), a nonselective beta-adrenoreceptor antagonist, and metoprolol (2.6 mg/kg body wt, iv), a beta 1-adrenergic antagonist, slightly but significantly suppressed basal levels of plasma PRL. On the other hand, haloperidol (0.5 mg/kg body wt, iv), pimozide (0.3 mg/kg body wt, iv), sulpiride (5 mg/kg body wt, iv), chlorpromazine (3 mg/kg body wt, iv), and YM-09151-2 (0.2 mg/kg body wt, iv), all dopamine receptor antagonists caused a significant increase in plasma PRL. These results suggest that dopaminergic and alpha 2-adrenergic mechanisms exert a tonic inhibitory role and beta-adrenergic mechanisms, probably beta 1, a tonic stimulatory role in the regulation of PRL release in the rabbit.     

Selective enhancement in striatal [H]nitrendipine binding following chronic treatment with morphine

Two parameters of Ca²⁺ dynamics in brain preparations (⁴⁵Ca-uptake to slices and [³H]nitrendipine binding to membrane fractions) were measured in naive and chronic morphine-administered rats. While morphine did not have any effect on ⁴⁵Ca-uptake to striatal slices in normal Krebs-Ringer solution, it inhibited K⁺-stimulated ⁴⁵Ca-uptake to slices. Furthermore, the effect of morphine was antagonized by naloxone. Inhibition of K⁺-stimulated ⁴⁵Ca-uptake to striatal slices by morphine was not observed in preparations obtained from chronic morphine-administered rats (6 mg/kg/b.i.d./7 days). In membrane fractions, [³H]nitrendipine binding increased by 34% in striatum following chronic morphine treatment, whereas no change was observed in the cortex and hippocampus. The results will be discussed in relation to the phenomena underlying chronic morphine administration.     

Accumulation of ornithine decarboxylase-antizyme complex in HMOA cells.

A new method was developed for the assay of ornithine decarboxylase (ODC)-antizyme complex, in which alpha-difluoromethylornithine (DFMO)-inactivated ODC was used to release active ODC competitively from the complex. ODC-antizyme complex was present in the extracts of hepatoma tissue-culture (HTC) cells and of ODC-stabilized variant HMOA cells, in much larger amounts in the latter. Cellular amounts of the complex fluctuated after a change of medium in a similar manner in HTC and HMOA cells, increasing during the period of ODC decay. After treatment with cycloheximide, the decay of ODC-antizyme complex in HMOA cells was more rapid than the decay of free ODC, but it was much slower than the decay of free ODC or complexed ODC in HTC cells. Administration of putrescine caused a rapid increase in the amount of ODC-antizyme complex in both HTC and HMOA cells, but nevertheless the decay of total ODC (free ODC plus ODC-antizyme complex) was more rapid with putrescine than with cycloheximide. These results suggested the possibility that ODC is degraded through complex-formation with antizyme. In contrast with complexed antizyme, free antizyme was not stabilized in HMOA cells.     

Human cellular src gene: nucleotide sequence and derived amino acid sequence of the region coding for the carboxy-terminal two-thirds of pp60c-src.

The nucleotide sequence of the 3' two-thirds of a highly conserved, molecularly cloned human cellular src gene (c-src) has been determined. This region of the c-src gene encodes the tyrosine kinase domain of the cellular src protein (pp60c-src) and corresponds to exons 6 through 12 of the chicken c-src gene, as well as nucleotides 545 to 1542 of the Rous sarcoma virus src gene (v-src). The human c-src sequence is very strongly conserved with respect to both the chicken c-src and the Rous sarcoma virus v-src genes, with nearly 90% nucleotide homology observed in this region. Amino acid sequence conservation in this region is even greater; 98% of the amino acids are conserved between human and chicken c-src. Furthermore, the exon sizes and the locations of the exon-intron boundaries are identical in the human and chicken c-src genes. However, sequences within the introns have not been conserved, and the introns within the human c-src gene are significantly larger than the corresponding introns within the chicken c-src gene. The strong amino acid conservation between the carboxy-terminal two-thirds of pp60c-src of species as divergent as humans and chickens suggests that this portion of the pp60c-src protein specifies one or more functional domains that are of great importance to some aspect of normal cellular growth or differentiation.     

Electrophoretic variants of blood proteins in Japanese. IV. Prevalence and enzymologic characteristics of glucose-6-phosphate dehydrogenase variants in Hiroshima and Nagasaki

Summary Electrophoretic screening of glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6PD) was conducted one sample of 9,260 children born to the atomic bomb survivors in Hiroshima (Honshu) and Nagasaki (Kyushu). The prevalence of electrophoretic variants was 0.11% in males and 0.42% in females in Hiroshima, and 0.16% in males and 0.31% in females in Nagasaki. Enzymologic characteristics of 10 variants obtained from three males and seven hemizygous fathers of heterozygous females were examined. As a result, three new types of G6PD variants were identified among five variants detected in Hiroshima, and three new types among five variants in Nagasaki. All the variants except one belonged to Class 3, as defined by Yoshida et al. (1971).     

Morphological aspects on pancreatic islets of non-obese diabetic (NOD) mice

The pancreatic islets of female non-obese diabetic (NOD) mice (a model of insulin-dependent diabetes mellitus), have been examined by both light and electron microscopy. At about the age of 2 weeks, mononuclear cells began to infiltrate in or near the islets and some of these cells were in contact with the islet cells. Following this degeneration of islet B-cells took place, the process occurring in two ways. In many cells numerous secretory granules with extremely dense cores occupied the cytoplasm. Other cells, however, were filled with low-density secretory granules and the nuclei of these cells became pycnotic. After degeneration of B-cells, the islets were effaced by numerous mononuclear cells. With the onset of the diabetic state these mononuclear cells gradually disappeared, and thereafter small islets remained. By electron microscopy, retrovirus-like particles were observed in cisternae of the rough endoplasmic reticulum in islet B-cells at all stages. With an anti-retrovirus serum (goat anti-KiMSV-NIHxeno serum), positive immunofluorescence was observed in some pancreatic islet cells of NOD mice aged 1 day and 4, 6, 8, 9, 10 and 14 weeks. It is suggested that these virus particles may be intimately related to the inflammatory reaction occurring in the islets and to the development of diabetes mellitus.