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Biomedical subjects

T Kumai

Publications and source records attributed to T Kumai.

101 records · Page 6Linked to original sources
PubMed1982

Gonadectomy-induced reduction of blood pressure in adult spontaneously hypertensive rats.

Adult male and female spontaneously hypertensive rats (SHR-Okamoto, Kyoto) were gonadectomized when they were 17 weeks old. Intact SHR showed a progressive increase of their blood pressure with growth, attaining systolic pressure levels of 194-208 in males and 163-173 mmHg in females when they were 29-30 weeks old. During this same period, the gonadectomized animals showed a significant reduction in blood pressure ranging from 168-175 in males and from 158-163 mmHg in females. These studies indicate that male and female SHR gonadectomized at 17 weeks of age do not show the progressive blood pressure rise that occurs in intact SHR. There was no change in heart rate in either sex. Corticosterone (B) levels in plasma were increased in the orchidectomized males, and 18-OH-DOC levels in plasma were increased in the adrenal glands of ovariectomized females indicating that these hormonal changes probably do not play a role in SHR hypertension. It appears that gonadal and other hormones are involved in the pathogenesis of SHR hypertension.

18-Hydroxydesoxycorticosterone↗
PubMed1981

Reflex discharge evoked by water stimulation on the frog tongue.

The frog tongue contains the chemoreceptor sensitive to water, the role of which has not been clarified. If the water on the tongue reflexly keeps the mouth closed as suggested by Zotterman, reflex discharges should be evoked in the nerve innervating the mandible elevator muscles. So far as we have studied, however, pronounced reflex discharges were evoked in the nerve innervating the submental and submaxillary muscles, but not in the nerves innervating the elevator muscles. This result suggests that the chemoreceptor sensitive to water in the frog tongue plays a role in the nostril closing mechanism.

Animals↗
PubMed1981

Reflex response of the hypoglossal nerve induced by chemical stimulation of the tongue and electrical stimulation of the glossopharyngeal nerve in the frog.

While applying solutions of 5 mM QHCl, 2 M NaCl and HCl at pH 3.0 to three different ipsilateral portions, root, middle and tip of the tongue surface of the frog, reflex discharges were recorded from three main branches of the hypoglossal nerve. Reflex discharges in the hypoglossal branch were elicited mainly when the caudal two-thirds of the tongue was stimulated with the chemicals, whereas those in the genioglossal branch occurred predominantly when the rostral two-thirds of the tongue was stimulated. The intrinsic branch responded reflexly to stimulation of any portion of the tongue. The hypoglossal branch was also highly sensitive to mechanical stimulation of the tip of the tongue. Action potentials reflexly elicited by electrical stimulation of medial and lateral branches of the glossopharyngeal nerve were recorded from the following two of the three efferent branches simultaneously. Then it was revealed that the activity of the hypoglossal branch was induced by sensory inputs from low threshold fibers in the medial branch, whereas that of the genioglossal branch was mainly by the lateral branch. Latencies between the electrical stimulation of the afferent branches and the potential in the hypoglossal branch produced by stimulation of the medial branch had the shortest latency. This reflex are may functionally play a role in retracting the tongue quickly after capturing a prey at the tip of the frog tongue.

Action Potentials↗
PubMed1981

[Dynamics of steroid hormones in hypercholesterolemic rats].

We evaluated the dynamics of endogeneous steroid hormones in hypercholesterolemic rats (HLR) F14, F10 in part, obtained by brother-sister mating of Sprague Dawley strain animals. Plasma free and total cholesterol levels in F14 and F10 were significantly high both in both sexes as compared with controls, however, hypertension did not always occur in the HLR; in one group the pressure was elevated but in another, it was normal. Weight of the ovaries was significantly higher than in the controls while weight of the uterus was significantly lower than in the controls. Progestin (progesterone, 20 alpha-OH-P) levels in the ovary were significantly higher (2-3 times) than in the controls, but the estradiol levels were significantly lower (1/2-1/3). Cyclic changes in vaginal smears were somewhat irregular and a continuous diestrus was infrequent. Weight of the testicles and the testosterone levels were significantly lower than in the controls while the estradiol level was somewhat higher. Weight of the prostate was normal. In both sexes, adrenal weights were significantly higher than in the controls. In female rats, adrenal corticosterone and 18-OH-DOC were significantly higher than in the controls, but such was not the case in the adrenals of male rats. All our results taken together, suggest that disturbance in hormonal regulation, particularly of the reproductive system in rats occurred in genetically induced hypercholesterolemia.

20-alpha-Dihydroprogesterone↗
PubMed1980

Effects of pH on frog gustatory responses to chloride salts of alkali-metal and alkali-earth-metal.

The pH effects on frog gustatory responses to alkali-metal and alkali-earth-metal chloride salts were examined using single fungi-form papilla preparations. Responses to 0.1-0.5 M NaCl were clearly dependent upon the pH of the stimulating solutions. The responses increased as the pH decreased from 6.5 to 4.5 and were almost completely suppressed at pH's above 6.5. There was no significant difference in the pH dependency of the response among alkali-metal chlorides. HCl solutions elicited only a poor response under conditions in which the water response was suppressed by the simultaneous presence of a low NaCl concentration. Responses to alkali-earth-metal chlorides varied in their pH dependency. Response to CaCl2 was slightly affected by pH changes from 4.5 to 9.0, response to SrCl2 was considerably suppressed in the alkaline region, and responses to BaCl2 and MgCl2 were strongly suppressed at pH's above 6.5. BeCl2 solutions showed less marked stimulating effects over the pH range tested. The differences in pH dependency described above suggest the existence of two kinds of receptor sites, one being pH-insensitive sites responsible for the calcium response and the other pH-sensitive sites responsible for the sodium response. A cross-adaptation test appeared to support this possibility. Assuming that the pH effect mentioned is related to changes in the state of ionization of the receptor molecule, the pKa of the ionizable group responsible for the sodium response was determined to be approximately 5.5.

Animals↗
PubMedDate not supplied

Impaired testicular function in rats with diet-induced hypercholesterolemia and/or streptozotocin-induced diabetes mellitus.

Hypercholesterolemia and diabetes mellitus are known to be accompanied by reproductive dysfunction. In this study, we investigated the effects of hypercholesterolemia, hyperglycemia, and these conditions combined, on testosterone (T) and testicular luteinizing hormone/human chorionic gonadotropin (LH/hCG) binding. Sprague-Dawley rats (8 weeks old) were divided into four groups: Group 1 was the control, group 2 was fed standard chow containing 2% cholesterol (C-diet), group 3 was administered streptozotocin (STZ, 65 mg/kg, i.p.), group 4 was treated with both the C-diet and STZ. After 4 weeks, rats were sacrificed. Serum glucose was significantly higher in the STZ group (304% that of controls) and the C-diet plus STZ group (345%), but there was no difference between the C-diet group (89%) and the control group. Serum cholesterol was significantly higher in the C-diet group (206% that of controls), the STZ group (452%) and the C-diet plus STZ group (2042%). Serum T, testicular T, and LH/hCG binding were significantly lower in the C-diet group (49%, 52%, and 81% that of controls, respectively), the STZ group (15%, 32%, and 72%) and the C-diet plus STZ group (8%, 21%, and 57%). These results suggest that hypercholesterolemia is an independent risk factor for testicular dysfunction and that the reduction of serum and testicular T levels is due at least in part to a reduction in testicular LH/hCG binding in rats with hypercholesterolemia, hyperglycemia, and these conditions combined. It is further suggested that the reduction in LH/hCG binding is mainly related to a rise in serum cholesterol levels.

Animals↗