Genotoxicity and cell proliferative activity of omeprazole in rat stomach mucosa.

Induction of unscheduled DNA synthesis (UDS) as a marker of genotoxicity and induction of ornithine decarboxylase (ODC) activity as a marker of cell proliferative activity by omeprazole were determined in the glandular stomach mucosa of male F344 rats after oral administration. Commercial enteric-coated omeprazole (Losec) at doses of 30 and 100 mg/kg body weight induced a dose-dependent increase in UDS but not replicative DNA synthesis in the pyloric mucosa of rat stomach 4 h after its administration. Dose-dependent significant induction of ODC activity was observed in fundic and pyloric mucosa with a maximum 8 h after administration of omeprazole at doses of 37.5-100 mg/kg body weight. These results show that omeprazole has genotoxicity and cell proliferative activity in the rat glandular stomach mucosa.     

Antimutagenic Acitivity against Trp-P-1 of the Edible Thai Plant,Oroxylum indicum Vent.

A methanolic extract of Oroxylum indicum strongly inhibited the mutagenicity of Trp-P-1 in an Ames test. The major antimutagenic constituent was identified as baicalein with an IC₅₀ value of 2.78±0.15 μM. The potent antimutagenicity of the extract was correlated with the high content (3.95±0.43%, dry weight) of baicalein. Baicalein acted as a desmutagen since it inhibited the N-hydroxylation of Trp-P-2.     

Antimutagenic activity against trp-P-1 of the edible Thai plant, Oroxylum indicum vent.

A methanolic extract of Oroxylum indicum strongly inhibited the mutagenicity of Trp-P-1 in an Ames test. The major antimutagenic constituent was identified as baicalein with an IC50 value of 2.78+/-0.15 microM. The potent antimutagenicity of the extract was correlated with the high content (3.95+/-0.43%, dry weight) of baicalein. Baicalein acted as a desmutagen since it inhibited the N-hydroxylation of Trp-P-2.     

Mechanism of vasorelaxant activity of a fraction of root extract of Sesamum indicum Linn

The petroleum ether soluble fraction (SIPE) of the root extract of S. indicum was evaluated for the vasorelaxant activity using isolated rat aorta. SIPE up to 180 microg/ml concentration significantly inhibited phenylephrine- and KCl-induced contraction to the extent of 98.13 +/- 6.37 and 70.19 +/- 3.43% respectively in isolated rat aorta in a concentration dependent manner. The vasorelaxant activity was not blocked by propranolol (10 microM), atropine (1 microM) indomethacin (10 microM) and glibenclamide (10 microM). Influence of SIPE on phenylephrine-induced contractions in aortic preparations in absence of functional endothelium and on pre-incubating the tissue with L-NAME (300 microM) or methylene blue (10 microM) was also studied. SIPE at 180 microg/ml concentration could elicit partial relaxation in presence of L-NAME or methylene blue to the extent of 34.26 +/- 6.13 and 25.66 +/- 10.95% respectively. However, in absence of functional endothelium, SIPE exhibited little relaxation to the extent of 6.70 +/- 4.87%. These studies revealed that the vasorelaxant activity of SIPE was chiefly mediated through endothelium-dependent pathway.     

NuMA in rat testis--evidence for roles in proliferative activity and meiotic cell division

NuMA is a well-characterized organizer of the mitotic spindle, which is believed to play a structural role in interphase nucleus. We studied the expression of NuMA in rat seminiferous epithelium in detail. Different stages of the cycle of the seminiferous epithelium were identified using transillumination. Corresponding areas were microdissected and analysed using immunofluorescence, immunohistochemistry, or immunoblotting. NuMA was expressed in Sertoli cells, proliferating type A and B spermatogonia, and early spermatids but it was absent in late spermatids and mature spermatozoa. Interestingly, NuMA-positive primary spermatocytes lost their nuclear NuMA at the beginning of long-lasting prophase of the first meiotic division. A strong expression was again observed at the end of the prophase and finally, a redistribution of NuMA into pole regions of the meiotic spindle was observed in first and second meiotic divisions. In immunoblotting, a single 250-kDa protein present in all stages of the rat seminiferous epithelial cycle was detected. Our results show that NuMA is not essential for the organization of nuclear structure in all cell types and suggest that its presence is more likely connected to the proliferation phase of the cells. They also suggest that NuMA may play an important role in meiotic cell division.     

An autoradiographic investigation of the proliferative activity of pyloric caeca and gondas of Asterias rubens

The proliferative activity of the pyloric caeca of Asterias rubens was investigated. Autoradiographic experiments using intracoelomically injected (methyl-³H)-thymidine were performed throughout the year and incorporation into pyloric caeca and into gonads was studied. Tritiated thymidine was found to be incorporated mainly in the coelomic lining of both organs. Cell divisions in the coelomic lining may be necessary for the growth of these organs, for the production of coelomocytes or, in the case of the pyloric caeca, for growth of the digestive epithelium. Proliferative activity of the digestive epithelium of the pyloric caeca was only observed in the median duct. It is hypothesized that new cells, arising from mitosis, grow from the median duct to the side lobes and differentiate into storage cells, for example. The existence of a mitosis-inducing or mitosis-stimulating substance is discussed. In the ovaries follicle cells were found to incorporate (methyl-³H)-thymidine; in the testis, proliferation of the germinal epithelium occurred simultaneously in all spermatogenic columns. First, the spermatogonia and then later the spermatocytes became labeled. Absorption of substances from the coelomic fluid is discussed.     

Phosphatidohydrolase activity in a solubilized preparation from rat brain particulate fraction.

Phospholipase D activity (phosphatidylcholine phosphatidohydrolase, EC 3.1.4.4) was demonstrated in vitro in a solubilized preparation from rat brain particulate fraction which also possessed the transphosphatidylation activity. The preparation attacked a phosphatidylcholine microdispersion and cleaved the terminal phosphate diester bond of this phospholipid resulting in the formation of phosphatidic acid. The pH optimum for the phosphatidohydrolase activity was broad with an apparent peak aroung 6.0 whereas the transphosphatidylation showed a sharp pH optimum at 7.2 Ca²⁺ was not essential for the hydrolysis, but merely stimulated slightly with an optimum about 5 mm, however, it could be replaced by Mg²⁺. The hydrolysis of phosphatidylcholine by the enzyme was almost completely inhibited in the presence of either diethyl ether (20% by volume) or p-chloromercuriophenyl sulfonate (6 × 10 ^?5m). The latter inhibition was reduced by the addition of dithiothreitol (6 × 10^?4m). The result suggests an essential role of sulfhydryl group in the formation of the enzyme-substrate complex.The apparent K_m for phsophatidylcholine for the phosphatidohydrolase activity was about 8.3 × 10 ^?4m.     

NaCl induced ornithine decarboxylase and DNA synthesis in rat stomach mucosa

A sensitive method is described that detects an alteration in the structure of tRNA that is caused by cadmium but not by magnesium or zinc ions. The chromatographic system, RPC-5, separates Drosophila tyrosyl-tRNA into two fractions. These two isoacceptors differ by a single position in the anticodon where either a guanosine or queuine resides. Cadmium ions apparently interact with the tRNA and prevent the chromatographic separation. This is the first instance where cadmium is shown to cause a selective change in nucleic acid structure. The RPC-5 system seems to be uniquely useful in detecting such a change.     

Tritiated thymidine autoradiographic study of cell migration and renewal in the pyloric mucosa of golden hamsters

Summary The kinetics of cell proliferation, migration and renewal in the pyloric mucosa of golden hamsters were studied by flash, cumulative and pulse labelling autoradiography following ³H-thymidine injections.By flash labelling autoradiography, it was shown that the labelled epithelial cells are exclusively confined to a zone several cells wide in the region of the isthmus between the gastric pits and the pyloric glands. In the cumulative and pulse labelling experiments, this cell proliferation in the isthmus region was shown to be for replacement of both the surface epithelial and the glandular cells. The surface epithelial cells of the pyloric mucosa arising in the upper portion of the isthmus come to line the pits and the surface, and are sloughed off into the gastric lumen within a week. The mucin-containing glandular cells, which arise more deeply in the isthmus region, migrate downwards and are apparently lost at the deepest level of the glands. The life span of the mucin-containing glandular cells was estimated at about 14 days. This cell type appears to undergo renewal of the first produced, first lost pipe line variety. However, a small number of glandular cells was found to survive for more than 20 days (up to 30 days), suggesting the existence of a sub-population of cells with different kinetics in the pyloric glands.Supported by a Grant-in-Aid for Cancer Research from Ministry of Education, Science and Culture, Japan     

Productive HIV-1 infection of macrophages restricted to the cell fraction with proliferative capacity.

Retroviruses establish productive infection only in proliferating cells. Macrophages are often considered to be non-proliferating in vitro yet are susceptible to HIV-1 infection. This has led to the conclusion that HIV-1 can establish infection independent of host cell proliferation. We here report that a small proportion of macrophages does have proliferative capacity. A comparable small fraction of monocyte derived macrophages (MDM) supported productive HIV-1 infection as demonstrated in limiting dilution culture. Fluorescence activated cell sorting on the basis of incorporation of BrdUrd, a thymidine analog, and subsequent PCR analysis revealed the presence of proviral DNA only in the BrdUrd positive cell fraction with DNA synthesizing activity. To identify which phase of cell cycle is required for establishment of productive infection, growth arrest in G1 or G1/S phase prior to inoculation was performed. gamma-Irradiation, which arrests primary cells in G1, prevented both cell proliferation and establishment of productive infection in MDM. Treatment of MDM with aphidicolin, a specific inhibitor of DNA polymerase alpha and delta which arrests cells in G1/S phase of the cell cycle, also inhibited DNA synthesis but did not prevent establishment of productive infection which is completely analogous to observations in T cells. Our data thus indicate that not cell division itself but cellular conditions that coincide with cell proliferation are apparently indispensable for establishment of productive infection.     

Oroxylin A,a constituent of Oroxylum indicum inhibits adipogenesis and induces apoptosis in 3T3-L1 cells

Oroxylin A (OA) is a flavonoid found in Oroxylum indicum, a medicinal plant with multiple biological activities. This study was taken up to investigate the effect of OA, on adipogenesis, lipolysis and apoptosis in 3T3 L1 cells. Pre-adipocytes were treated with 10–40 μM OA on various days of adipogenesis treatment schedule. Mature adipocytes were treated with OA for lipolysis and apoptosis studies. In maturing pre-adipocytes, 10 μM OA suppressed intracellular lipid accumulation by 42.19% which was confirmed by lipidTox imaging of cells. In addition, OA decreased the nuclear translocation of PPARγ and mRNA expression of its downstream genes (FAS and LPL) along with adiponectin secretion. In mature adipocytes, 40 μM of OA decreased cell viability by 30% of control. Annexin V/PI staining showed induction of apoptosis which was further confirmed by enhanced levels of pro-apoptotic proteins Bax, cyt c, AIF and chromatin condensation. OA enhanced TNF-α secretion, lipolysis and decreased Akt phosphorylation in mature adipocytes. Findings suggest that OA possibly exerts its anti-obesity effect by affecting adipocyte life cycle at critical points of differentiation and maturity. When we compared the potency of OA with non-methoxylated flavonoids morin, naringenin and kaempferol on adipocyte life cycle OA was far more potent. Thus, study clearly indicates a new role for oroxylin A as regulator of adipocyte life cycle. In addition, study also suggested a specific role of methoxylated group in exerting lipolysis and cytotoxic effects in mature adipocytes.     

Electron microscopic observations on a new cell type in the fundus mucosa of the mouse stomach

Summary In the course of electron microscopic investigations of the fundus mucosa of the mouse stomach, a few cells of an unknown type were found by chance in the deep portions of the glands. These cells are characterized by two different kinds of specific granules in their cytoplasm, one of which being large and less dense, and the other one being small and dense. The large less dense granules resemble zymogen granules of the chief cell, which are formed by the rough endoplasmic reticulum and Golgi system. The small dense granules are quite similar to the secretory granules of the basal granulated cell, and are considered to be formed in the Golgi complex. Release figures of the small dense granule were not observed, numerous granules, however, were observed in close contact with the basal cell membrane. The occurrence of these two kinds of granules in one cell suggests that the basal granulated cell and the zymogenic cell originate from the same entodermal stem element.The author cordially thanks Professor Dr. Hisao Fujita, Department of Anatomy, Hiroshima University School of Medicine, for his kind advices and criticisms.     

Influence of age and gamma irradiation on the proliferative activity in regenerating rat liver.

The effect of aging (2-14 months) and total body irradiation (5.7 Gy of gamma radiation) on liver regeneration was investigated in rats 30 h after partial hepatectomy. Exposure of rats to irradiation 30 min before partial hepatectomy caused latent injury in the remaining liver cells. During the course of liver regeneration this became manifested as a delay in increasing the nucleic acid concentration and content and liver weight and, furthermore, as inhibition of the increase in the mitotic index and cellularity and pronounced increase in the frequency of chromosome aberrations in the postmetaphase. The pattern of age-related changes during liver regeneration was the same as that after irradiation, so that the differences between irradiated and nonirradiated animals became smaller with age.