Renoprotective effects of telmisartan on renal injury in obese Zucker rats.

The purpose of the present study was to investigate the renoprotective effect of telmisartan, an angiotensin II receptor antagonist, on the early stages of diabetic nephropathy in obese Zucker rats, which is a type 2-related diabetes mellitus model. Telmisartan 1, 3 or 10 mg/kg/day was orally administered to 7-week-old rats that demonstrated glucose tolerance without albuminuria or proteinuria, for 24 consecutive weeks (Experiment A). In another experiment (Experiment B), oral administration of telmisartan 10 mg/kg/day was initiated at the age of 16 weeks after the rats demonstrated marked proteinuria, and continued for 24 weeks. Telmisartan inhibited the increase in proteinuria and albuminuria in a dose-dependent manner, and the inhibition for all telmisartan groups was statistically significant by the completion of administration (Experiment A). Telmisartan also displayed similar inhibitory effects on proteinuria and albuminuria in Experiment B. Histologically, telmisartan [3 and 10 mg/kg/day] was associated with a significant decrease in the progression of glomerulosclerosis, and significantly improved interstitial cell infiltration, interstitial fibrosis and dilation and atrophy of renal tubules. Furthermore, telmisartan treatment was associated with a tendency towards normalized plasma lipids (total cholesterol and triglyceride). Our results suggest that telmisartan has a definite renoprotective effect against renal injury in type II diabetic nephropathy.

Three-dimensional angioarchitecture in transplantable rat fibrosarcomas.

Three-dimensional angioarchitecture in a transplantable fibrosarcoma (SS) in F344 rats was investigated by scanning electron microscopy (SEM) of vascular corrosion casts. Tumours were produced in syngeneic rats by implantation of a tumour fragment from another SS tumour. Viable SS tumours, observed up to post-implantation (PI) week 5, showed a high degree of vascularization, consisting of arterioles and veins, and intertwining capillaries branching from such vessels. The capillaries showed numerous finger-like outgrowths, indicating active sprouting of endothelial cells and contributing to tumour growth. In contrast, SS tumours in rats given a single dose (4 mg/kg/bodyweight) of cisplatin at PI week 1 were reduced in volume, lacking in capillary outgrowths, and of low vascular density. Necrotic areas in SS tumours were surrounded by capillaries with sharp tips and wrinkled surfaces. Thus, the findings indicated differences in three-dimensional angioarchitecture between vigorously developing tumours and (1) tumours degenerating as the result of treatment with an anti-cancer drug, or (2) necrotic tumour tissues. SEM of vascular corrosion casts may prove useful for the evaluation of neovascularization in mesenchymal tumours.

Expressions of vascular endothelial growth factor and basic fibroblast growth factor in tumors induced by two different cloned cell lines established from transplantable rat malignant fibrous histiocytoma.

In order to establish base-line data on angiogenic factors in development of mesenchymal tumors, expressions of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in implanted MT-8 and MT-9 tumors, both derived from a transplantable malignant fibrous histiocytoma (MFH) in the F344 rat, were investigated by immunohistochemistry and Western blotting method. MT-8 and MT-9 tumors were developed in syngeneic rats by implant of a tumor tissue fragment. MT-8 tumors were examined on post-implantation (PI) days 3, 6, 9 and 17, and MT-9 tumors were on PI days 9, 14, 17 and 23. The growth of MT-8 tumors was faster than that of MT-9 tumors. Histologically, MT-8 tumors were features of undifferentiated sarcomas, whereas MT-9 tumors exhibited a typical storiform growth pattern of MFH. Immunohistochemically, all cells constituting MT-8 and MT-9 tumors reacted with antibodies to VEGF and bFGF, indicating production of these factors by mesenchymal neoplastic cells. However, there were no marked differences in these immunoreactions between tumors examined. Thus, the bands obtained in the Western blotting methods were densitometrically scanned. The expression levels of VEGF and bFGF gradually increased PI day 3 to 9 in MT-8 tumors and PI day 9 to 17 in MT-9 tumors. On last examination day, the levels of bFGF in both tumors and of VEGF in MT-9 tumors decreased, but the VEGF expression level in MT-8 tumors was still increased. These findings indicated that VEGF and bFGF may contribute cooperatively to angiogenesis in an early growth of mesenchymal tumor development.

Collaborative work to evaluate toxicity on male reproductive organs by repeated dose studies in rats 10). Testicular toxicity of adriamycin observed 2 and 4 weeks after a single intravenous administration.

The present study was performed to clarify whether toxic effects of the antitumor drug, adriamycin (ADR) on the male genital organ can be adequately detected 2 and 4 weeks after a single intravenous administration in the rat. ADR was intravenously administered once to 10 Crj:CD (SD) male rats/group aged 6 weeks (4-week group) and 8 weeks (2-week group) at doses of 0, 2 and 6 mg/kg. The rats were sacrificed at the age of 10 weeks. For comparison 10 rats/group were killed 2 weeks after a single intravenous administration at the age of 4 weeks (immature group). Saline was administered to control rats. Histopathological examination and a quantitative morphometry were carried out after measurement of testes weights at necropsy. In rats of the 4-week and 2-week groups, mean absolute testicular weight in all groups was significantly decreased. However, changes in mean relative weight were not evident in the 2-week group. Disappearance of seminiferous epithelial cells was observed histopathologically in rats dosed with 2 and 6 mg/kg in the 2-week group. The change was more severe in the 4-week group, when reduction of spermatogenesis and giant cells were also observed at 6 mg/kg. The quantitative morphometry in the 2-week group showed decreases in the numbers of spermatogonia and spermatocytes in stages X and XII at 2 mg/kg, and in the numbers of spermatogonia in all stages and spermatocytes in all stages except stage V at 6 mg/kg. Moreover, the numbers of spermatogonia and spermatocytes in all stages and spermatids in stages II-III and V were decreased with dose related manner in the 4-week group. In contrast, no obvious change in testes weights was apparent in the immature group. However, the numbers of spermatogonia and spermatocytes in all stages were decreased at 6 mg/kg. In conclusion, testicular toxicity of ADR could be detected 2 weeks after a single administration. Susceptibility of the testes of immature rats to ADR might be less than that of older animals.

Poorly differentiated carcinoma of the parotid gland in a six-week-old Sprague-Dawley rat.

A poorly differentiated spontaneous tumor was found in the parotid gland region of a 6-wk-old female Sprague-Dawley rat. The tumor consisted of undifferentiated cells forming dense clusters, well-defined nests, or compact sheets. In some areas, spindle-shaped cells were arranged in a fascicular fashion. Neither ductular nor acinar structures were seen. No keratinization was observed, either. Mitotic figures were frequent. All neoplastic cells were immunoreactive for pankeratin but negative for vimentin, alpha-smooth muscle actin and S-100 protein. Ultrastructurally, the tumor cells were characterized by desmosome-like junctional complexes, poorly developed cytoplasmic organelles, and microvilli-like cytoplasmic processes. Based on these findings and its anatomical location, the present tumor was diagnosed as a poorly differentiated carcinoma of the parotid gland.

Localization of a G-protein-coupled inwardly rectifying K+ channel, CIR, in the rat brain.

The cellular localization of a G-protein-coupled K+ channel, CIR, in the rat brain has been demonstrated using a CIR-specific antibody, in combination with in situ hybridization. The CIR protein and messenger RNA were found in the cerebellar cortex, hippocampal formation, olfactory system, cerebral cortex, basal ganglia, several nuclei of the lower brain stem and the choroid plexus. In contrast to the messenger RNA, which was concentrated in the cell soma, the CIR protein was found in a subset of nerve fibers and, in other cases, in axon terminals. In the cerebellar cortex and hippocampus, the CIR protein was concentrated in the axon terminals of basket cells which are known to be GABAergic interneurons. This discrepancy between the distribution of protein and messenger RNA was observed in the substantia nigra, the interpeduncular, trigeminal, hypoglossal, oculomotor and red nuclei of the lower brain stem, and the tufted and mitral cells of the olfactory bulb. These observations suggested the translocation of the CIR protein into the nerve fibers following synthesis in the cell soma. Furthermore, its specific neuronal localization, especially in GABAergic interneurons, suggested the importance of CIR in synaptic transmission in neuronal systems.

Characteristics of a rat fibrosarcoma-derived transplantable tumour line (SS) and cultured cell lines (SS-P and SS-A3-1) showing myofibroblastic and histiocytic phenotypes.

A transplantable tumour line (SS) was established in syngeneic rats from a spontaneous fibrosarcoma that had arisen in the submandibular salivary gland of a 24-month-old male F344 rat. A cell line (SS-P) was induced from SS, and a cloned cell line (SS-A3-1) was isolated from SS-P. The primary tumour consisted of oval to spindle-shaped cells arranged in bundles with abundant collagen fibres; ultrastructurally, neoplastic cells exhibited fusiform morphology with prominent rough endoplasmic reticulum. SS tumours showed marked interlacing fascicle and herring-bone growth patterns. SS-P and SS-A3-1 were similar morphologically to each other, consisting of oval, spindle or polygonal cells and occasional multinucleated giant cells. Tumours induced by SS-P and SS-A3-1 were histologically similar to SS tumours. Immunohistochemically, all cells in the primary tumour, SS tumours and tumours induced both by SS-P and SS-A3-1 and by SS-P and SS-A3-1 cultures gave a positive reaction to vimentin. Interestingly, neoplastic cells reacting to ED1 (rat macrophage/histiocyte-specific antibody) and alpha-smooth muscle actin (alpha-SMA) appeared in SS tumours and tumours induced by SS-P and SS-A3-1 and by SS-P and SS-A3-1 cultures. Cells with histiocytic fine structures and myofibroblastic cells with cytoplasmic actin-like microfilaments were also observed by electron microscopy. The present rat fibrosarcoma-derived transplantable tumour line (SS) and cell lines (SS-P and SS-A3-1) might express myofibroblastic and histiocytic phenotypes, probably depending on the surrounding conditions. These cell lines may prove useful for studying the mechanisms of phenotypic plasticity in neoplastic fibroblasts.

Functional characterization and localization of a cardiac-type inwardly rectifying K+ channel.

We cloned inwardly rectifying K+ channel cDNAs from porcine, rat and human, which were structurally almost identical with recently reported CIR(cKATP-1). The expression of CIR alone was low and unstable in Xenopus oocytes. The CIR/GIRK1 co-expression showed an increased current amplitude. Both the CIR and CIR/GIRK1 currents increased by coexpressing G beta gamma. The CIR and CIR/GIRK1 currents displayed two qualitative differences. (1) The conductance of the CIR channel did not saturate, but that of the CIR/GIRK1 channel showed saturation at hyperpolarized potential. (2) The CIR current showed instantaneous activation upon hyperpolarization, whereas the CIR/GIRK1 current exhibited slow activation, which was fitted by the sum of two exponentials. The CIR/GIRK1 current was also different from the GIRK1 current. The activation of the CIR/GIRK1 current was approximately ten times faster than that of the GIRK1 current. The increase in current amplitude and the qualitative differences imply the formation of functional heteromultimer. The CIR/GIRK1 channel showed differences from the native muscarinic K+ channel in that the basal level before m2 receptor activation is significantly large, and that the activation kinetics are much faster. Using anti-CIR antiserum, the CIR was detected in myocardial cells of the atrium and the ventricular subendocardial layer, and in the cardiac ganglion.

[Cushion-like structure in coronary arteries of rats].

The vascular architecture in the rat heart was investigated with SEM using a corrosion cast and light microscopy of paraffin sections stained with Hematoxylin-Eosin and Elastica-Domagk methods. In corrosion cast models of the left and right descending coronary arteries, Y- and T-type branching patterns were distinguished. The Y-type bifurcations were found at branching sites of the larger vessels and precapillary arterioles in the myocardium, whereas the T-type bifurcations were found at branching sites of the smaller vessels. On the surface of the corrosion cast of the T-type bifurcation symmetrical shallow depressions were observed at an orifice of a daughter vessel. The depression was confirmed to be produced by protrusions consisting of smooth muscles and elastic fibers of the vascular wall. The structure is presumed to be an arterial cushion which plays some role in avoiding plasm skimming and regulating blood flow.

Developmental and regressive changes in the testes of the Himalayan rabbit.

The testes of 81 Himalayan rabbits, controls in toxicity studies, and 113 purpose-bred rabbits of various age groups from birth to 2 years were studied. In mature male rabbits, regressive changes in the seminiferous tubules including the multinucleated spermatid giant cells were common and showed a tendency for age-related and seasonal differences. The finding is considered as a remnant of the previous seasonal and possibly also social testicular regression in wild living animals. The giant cells develop from the syncytium of the germinative epithelium and have parallels in phylogenesis.