The periodic loss of metabolically unstable DNA during replication of chromosomal DNA of CHO cells

The fate of ³H-thymidine incorporated into newly synthesized DNA of CHO cells was analyzed by either the estimation of the incorporated radioactivity per cell or sedimentation in alkaline sucrose gradient. Under conditions in which DNA synthesis proceeded continuously, of incorporated radioactivity was periodically lost and regained during a 90 min chase, corresponding to a cyclic change in the sedimentation profiles. When DNA synthesis was inhibited by hydroxyurea no cyclic change of the incorporated radioactivity was observed. The cyclic changes were regarded as the result of an actual metabolic change in³H-labelled DNA probaly joining to one of the newly formed sister strands of DNA and the loss of radioactivity seems to require active continued DNA synthesis.     

Effect of TNF-alpha on prolactin secretion from rat anterior pituitary and dopamine release from the hypothalamus: comparison with the effect of interleukin-1 beta.

The effects of human recombinant interleukin-1 beta and -6 and tumor necrosis factor-alpha (TNF-alpha) on the releases of PRL and dopamine were examined using monolayer cultures of rat pituitary cells and hypothalamic cells. The release of PRL from rat pituitary cells in 30 min was increased about 2-fold (p less than 0.05) by 10(5) U/l interleukin-1 beta, 10(5) U/l interleukin-6 or 100 micrograms/l TNF-alpha. TNF-alpha at 100 micrograms/l significantly increased PRL release within 5 min incubation and this effect continued throughout the next 30 min of incubation. Incubation for 5 min with TNF-alpha caused dose-dependent stimulation of PRL release. These cytokines did not modulate [3H]-dopamine release from primary cultures of hypothalamic cells. These results suggest that these cytokines stimulate PRL release directly at the pituitary gland, without modifying the release of dopamine from the hypothalamus.     

Prostaglandin E2 Activates Ca2+ Channels in Bovine Adrenal Chromaffin Cells

We have demonstrated that prostaglandin E2 (PGE2) treatment of bovine adrenal chromaffin cells results in a sustained elevation of intracellular Ca2+ concentration ([Ca2+]i) in these cells. Because the continued elevation of [Ca2+]i was dependent on extracellular Ca2+ concentration, it can be assumed that the PGE2-induced [Ca2+]i increase is due, at least in part, to an opening of membrane Ca2+ channels. In this study, we used electrophysiological methods to examine the mechanism of the PGE2-induced [Ca2+]i increase directly. Puff application of PGE2 to the external medium resulted in a prolonged depolarization in about half of the chromaffin cells examined. In whole-cell voltage-clamp recordings, an increase in inward current was observed over a 6-7 min period following bath application of PGE2 (greater than or equal to 10 microM), even in the absence of external Na+. This inward current was abolished when the recordings were made with the cells in a Ca2(+)-free medium, but it was not inhibited by Mn2+, a blocker of voltage-dependent Ca2+ channels. In cell-attached patch-clamp configuration, PGE2 produced an increase in the opening frequency of inward currents. The reversal potential of the PGE2-induced currents was about +40 mV, which is close to the reversal potential of the Ca2+ channel. The opening frequency was not affected by membrane potential changes. In inside-out patch-clamp configuration, inositol 1,4,5-trisphosphate (2 microM) added to the cytoplasmic side activated the Ca2(+)-channel currents, but PGE2 was ineffective when applied to the cytoplasmic side. These results suggest that PGE2 activates voltage-independent Ca2+ channels in chromaffin cells through a diffusible second messenger, possibly inositol 1,4,5-trisphosphate.     

A second gene for the African green monkey poliovirus receptor that has no putative N-glycosylation site in the functional N-terminal immunoglobulin-like domain.

Using cDNA of the human poliovirus receptor (PVR) as a probe, two types of cDNA clones of the monkey homologs were isolated from a cDNA library prepared from an African green monkey kidney cell line. Either type of cDNA clone rendered mouse L cells permissive for poliovirus infection. Homologies of the amino acid sequences deduced from these cDNA sequences with that of human PVR were 90.2 and 86.4%, respectively. These two monkey PVRs were found to be encoded in two different loci of the genome. Evolutionary analysis suggested that duplication of the PVR gene in the monkey genome had occurred after the species differentiation between humans and monkeys. The NH2-terminal immunoglobulin-like domain, domain 1, of the second monkey PVR, which lacks a putative N-glycosylation site, mediated poliovirus infection. In addition, a human PVR mutant without N-glycosylation sites in domain 1 also promoted viral infection. These results suggest that domain 1 of the monkey receptor also harbors the binding site for poliovirus and that sugar moieties possibly attached to this domain of human PVR are dispensable for the virus-receptor interaction.     

Goblet-like cells in atrophic vaginal smears and their histologic correlation. Possible confusion with endocervical cells.

The occurrence and origin of goblet-like cells seen between clusters of parabasal cells in atrophic vaginal smears were investigated. The goblet-like cells were cytologically identified in the vaginal smears from 23 (19.2%) of 120 patients whose smears showed an atrophic pattern, but without any inflammatory, dysplastic or malignant changes. Histologically, these cells were found in sections from 6 (18.8%) of 32 elderly women with atrophic vaginal epithelium. The goblet-like cells were situated among the squamous cells of the upper layer of the atrophic squamous epithelium from the vagina to the portio. These goblet-like cells in atrophic smears were initially misinterpreted as endocervical cells, which are regarded as a marker of smear adequacy in the cytologic screening for cancer of the uterine cervix. The correct interpretation of these goblet-like cells in smears from postmenopausal and elderly women is thus obviously important in assessing the adequacy of the sample for the detection of abnormal cells.     

Denitrification and Ammonia Formation in Anaerobic Coastal Sediments

Simultaneous determinations of nitrogen gas production, ammonia, and particulate organic nitrogen formation in the coastal sediments of Mangoku-Ura, Simoda Bay, and Tokyo Bay were made by using the ¹⁵N-label tracer method. The rate of nitrogen gas production in the sediment surface layer was about 10⁻² μg atom of N per g per h, irrespective of the location of the sediments examined. [¹⁵N]ammonia and -particulate organic nitrogen accounted for 20 to 70% of the three products, and after several hours of incubation, the major fraction of nondenitrified ¹⁵N in Mangoku-Ura and Simoda Bay sediments was recovered as ammonia. In Tokyo Bay sediments, particulate organic nitrogen was produced at a greater rate than was ammonia. The reduction rate data suggest that the pathway of nitrate reduction to ammonia is important in coastal sediments.     

Neurite formation and membrane changes of mouse neuroblastoma cells induced by valinomycin

A clonal cell line of mouse neuroblastoma cells was found to undergo morphological differentiation in the presence of a K⁺ ionophore, valinomycin, in the assay medium. This effect was blocked by increasing the concentration of KCl of the medium, suggesting that the changes in resting membrane potential and ion fluxes may be involved in the mechanism of the formation of neurites. No enhancement of the neurite formation was observed in salines containing high concentrations of KCl in the absence of valinomycin. Depolarizing agents including veratridine, gramicidin and ouabain did not stimulate the outgrowth of neurites. Neither electrophoretic mobility of the cells nor molecular anisotropy of fluorescence probes in the membranes was modified by the treatment of valinomycin. Instead, it modified the slow binding phase in kinetics of the interaction of 1-anilinonaphthalene-8-sulfonate (ANS) with the cells, which is related to the penetration process of the probe into membranes. Valinomycin also enhanced the fluorescence intensity of ANS by increasing the binding sites in neuroblastoma cells.     

A change in membrane microviscosity of mouse neuroblastoma cells in association with morphological differentiation

Changes in membrane microviscosity as well as in membrane constituents of mouse neuroblastoma clone N-18 were studied in association with neurite formation. The membrane microviscosity studied by fluorescence technique increased with the formation of neurites. The concomitant increase increase in the ratio of cholesterol to phospholipids was also observed.     

Chondroitinase-Producing Bacteria in Natural Habitats

A search was undertaken for bacteria which degrade chondroitin sulfate in nature and to find bacteria with a usefully high rate of chondroitinase (ChSase) productivity. First, 253 ChSase-producing bacteria were obtained from aquatic and land environments in Japan by aerobic and anaerobic screening methods. Identification according to Bergey's Manual of Determinative Bacteriology or Bain and Shewan (1968) permitted assignment of the majority of the isolates to seven genera, Aeromonas, Vibrio, Flavobacterium, Beneckea, Proteus, Micrococcus, and Arthrobacter. Next, ChSase productivities of all the isolates were compared with those of two established ChSase-producing stock strains, Proteus vulgaris NCTC 4636 and Flavobacterium heparinum ATCC 13125. As a result, special attention was given to production by a strain of Aeromonas sp. of large quantities of extracellular ChSase-AC. None of the isolates from the current study displayed significant ChSase-ABC productivity. Finally, ChSase-AC was prepared from the culture fluid of the Aeromonas strain by fractional precipitation with ammonium sulfate, chromatography on phospho-cellulose and diethylaminoethyl-cellulose, and gel filtration on Sephadex G-200. It was concluded that the Aeromonas strain may represent a profitable source of the enzyme ChSase-AC.