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Biomedical subjects

T Hoshi

Publications and source records attributed to T Hoshi.

At least 127 records · Page 7Linked to original sources
PubMed1992

MR imaging of chronic alcoholism.

We evaluated the brain lesions of patients with chronic alcoholism (n = 34) in comparison with age- and sex-matched controls (n = 40) by MR imaging. T1-weighted sagittal and axial images and T2-weighted axial images were obtained with a 0.5 T superconducting MR unit. Various brain measurements were then performed, and the presence of regions of abnormal signal intensity was also compared between the two groups. The brain measurements revealed significant cerebral atrophy (characterized by lateral and 3rd ventricular dilatation, and widening of the interhemispheric fissure) as well as significant cerebellar atrophy (represented by 4th ventricular dilatation) in the alcoholic group. These changes were more prominent in patients in their fifties and sixties than in those aged in the thirties and forties. Focal hypointense lesions were observed in 20.6% of the alcoholics and in 5% of the controls (p less than 0.01), while focal hyperintense lesions were observed in 61.8% of the alcoholics and in 20% of the controls (p less than 0.001). The severity of these MR findings correlated well with the age of the patients. These observations suggest that alcohol is an important promoter of brain aging.

Adult↗
PubMed1991

Simulated weightlessness and bone metabolism: impairment of glucose consumption in bone tissue.

The effect of simulated weightlessness on bone glucose consumption was investigated in skeletal unloading for up to 4 days. Skeletal unloading was designed using the model of hind-limb hang in rats. Femoral-diaphyseal fragments obtained from rats bred with skeletal unloading were cultured for 24 h at 37 degrees C in 5% CO2/95% air in Dulbecco's Modified Eagle Medium (high glucose, 4.5 g/dl). The consumption of medium glucose by bone tissues was significantly decreased by skeletal unloading for 2 and 4 days, while the production of lactic acid from bone tissues was not significantly altered. In addition, adenosine triphosphate (ATP) content in the cultured bone was significantly decreased by skeletal unloading. The presence of calcitonin (synthetic [Asu1,7] eel, 3 and 30 nM) fairly restored bone glucose consumption impaired by skeletal unloading. However, the effect of insulin (1 and 10 nM) on bone glucose consumption and ATP content was not seen in the bone tissues with skeletal unloading. These results suggest that the sensitivity of bone response for insulin action is reteriorated by skeletal unloading.

Adenosine Triphosphate↗
PubMed1991

Simulated weightlessness and bone metabolism: impairment of insulin effect on alkaline phosphatase activity in bone tissue.

The effect of simulated weightlessness on bone alkaline phosphatase was investigated after skeletal unloading for up to 4 days. The skeletal unloading was designed by using the model of hindlimb hang in rats. The femoral-diaphyseal fragments obtained from rats bred with skeletal unloading were cultured for 24 h at 37 degrees C in 5% CO2/95% air in Dulbecco's Modified Eagle Medium (high glucose). The bone alkaline and acid phosphatase activity were significantly decreased by skeletal unloading. When the bone tissue was cultured with synthetic [Asu1,7] eel calcitonin (3 and 30 nM), the hormone caused a significant increase of alkaline phosphatase activity in the bone tissues from rats with normal and skeletal-unloading. In culture with insulin (1.0 and 10 nM), skeletal unloading impaired the effect on insulin to increase bone alkaline phosphatase activity. Meanwhile, the culture with zinc sulfate (10 and 100 microM), which can increase bone protein synthesis, caused a remarkable elevation of alkaline phosphatase activity in the bone tissues form rats with normal and skeletal-unloading. Insulin (10 nM) did not alter the zinc effect. These findings suggest that the skeletal unloading with hindlimb hang causes the impairment of insulin's effect to increase alkaline phosphatase activity in the femoral diaphysis of rats, although the effects of calcitonin and zinc were not altered.

Alkaline Phosphatase↗
PubMed1991

Changes in hepatic metabolism through simulated weightlessness: decrease of glycogen and increase of lipids following prolonged immobilization in the rat.

The effect of simulated weightlessness on hepatic metabolisms of carbohydrates and lipids was investigated in rats that were chronically immobilized by means of a suspension harness. During the 10-day period of the suspension, the animals showed a substantial decrease in the hepatic glycogen content, whereas the content of hepatic total lipids was markedly elevated. Similar results were obtained when the "suspended" animals were provided with a regular amount of nutrients by a force-feeding procedure. In the suspended animals, hepatic parenchymal cells were filled with large fat droplets, and hepatic triglyceride contents were elevated. The prolonged immobilization led to a slight, but significant, increase in glucose-6-phosphatase activity in the liver, suggesting that an increased glycogen breakdown might have occurred in the suspended animals. However, it was unlikely that the increased amount of glucose produced by the glycogen breakdown was utilized as a substrate for the lipogenesis in the liver, because hepatic lipogenic enzyme activities were unaffected by the suspension. The results suggest that the hepatic lipids accumulate in animals exposed to a prolonged immobilization state, presumably due to a decreased lipolysis and/or a suppressed lipoprotein mobilization from the liver into the blood stream.

Adrenal Glands↗
PubMed1991

Simulated weightlessness and bone metabolism: evidence for direct gravitational effect and its related insulin action.

The effect of simulated weightlessness on bone metabolism was investigated in skeletal unloading for 4 days. Skeletal unloading was designed using the model of hind-limb hang in rats. In hypokinetic state, rats were fed while the right hind limb was weighed down and the left hind limb was unloaded (a state of weightlessness). Bone metabolism in normal rats did not vary significantly in the femoral diaphysis in right and left hind limb. Alkaline phosphatase activity and DNA content in the femoral diaphysis were not significantly altered by hypokinetic state without skeletal unloading, while the unloading caused an appreciable decrease in the enzyme activity and DNA content. However, femoral-diaphyseal zinc content and glucose consumption was significantly decreased by hypokinetic state with and without skeletal unloading. When femoral-diaphyseal tissues were cultured in the presence of insulin (10 nM), the hormone produced a significant increase of alkaline phosphatase activity and decrease of glucose consumption in the femoral-diaphyseal tissues obtained from normal and hypokinetic rats. This hormonal effect was not seen in bone tissues from hypokinetic rats with skeletal unloading. These results suggest that skeletal unloading-induced disorder of bone metabolism is directly related to gravitational effect and that gravitational stimulation may be involved in insulin action.

Alkaline Phosphatase↗
PubMed1991

Two types of inactivation in Shaker K+ channels: effects of alterations in the carboxy-terminal region.

Shaker potassium channels inactivate and recover from inactivation with multiple exponential components, suggesting the presence of multiple inactivation processes. We describe two different types of inactivation in Shaker potassium channels. N-type inactivation can occur as rapidly as a few milliseconds and has been shown to involve an intracellular region at the amino-terminal acting as a blocker of the pore. C-type inactivation is independent of voltage over a range of -25 to +50 mV. It does not require intact N-type inactivation, but is partially coupled to it. The kinetics of C-type inactivation are quite different for channels with different alternatively spliced carboxy-terminal regions. We have localized the differences in C-type inactivation between the ShB and ShA variants to a single amino acid in the sixth membrane-spanning region. N- and C-type inactivation occur by distinct molecular mechanisms.

Animals↗
PubMed1991

Oral administration of calcium hydroxide stimulates bone metabolism in the femoral diaphysis of rats with skeletal unloading.

The preventive effect of calcium hydroxide on the disorder of bone metabolism caused by skeletal unloading was investigated. Skeletal unloading was designed using the model of hindlimb hang in rats. Skeletal unloading for 7 d caused a significant decrease of inorganic phosphorus concentration in the serum and of alkaline phosphatase activity and deoxyribonucleic acid (DNA) content in the femoral diaphysis of rats. Oral administration of calcium hydroxide (16 and 24 mg Ca/kg) caused a significant increase in serum inorganic phosphorus concentration and femoral-diaphyseal calcium content and alkaline phosphatase activity of rats with skeletal unloading. Bone DNA content was significantly increased by the dose of 24 mg Ca/kg. These results clearly indicate that skeletal unloading-induced disorder of bone metabolism is partly prevented by oral administration of calcium hydroxide. Calcium ingestion may be useful as a therapeutic tool in the disorder of bone metabolism caused by skeletal unloading.

Animals↗
PubMed1991

Effects of various dietary protein contents on vitamin A status of rats exposed to prolonged immobilization through suspension.

The investigation was carried out to clarify the effects of various dietary protein contents on vitamin A status of rats exposed to prolonged immobilization through suspension. A rat wearing a special jacket to which metal chains were attached, was suspended for 10 days as an analogy of simulated weightlessness. Five groups of suspended rats were fed on the diets containing various amounts of casein (5, 10, 20, 40 and 60, w/w%), while control group received the 20% casein diet. Through suspending animals, a decrease in body weight gain and increase in adrenal weights occurred. Serum albumin concentration of the suspended rats fed on the 10, 20, 40 and 60% diets were the same as that of the control rats. The suspended rats showed lowered serum retinol concentrations and elevated hepatic retinyl palmitate contents without noticeable differences between the diets. The hepatic retinol levels were not clearly affected. In the suspended rats, testicular levels of retinyl palmitate and retinol significantly decreased as compared with the control. These parameters' alterations did not relate to serum albumin concentration and were independent of dietary protein levels. The results suggest that stress state may cause suppression of releasing hepatic vitamin A, resulting in a lowered serum retinol concentration, being independent of nutritional status of protein.

Adrenal Glands↗
PubMed1990

Biophysical and molecular mechanisms of Shaker potassium channel inactivation.

The potassium channels encoded by the Drosophila Shaker gene activate and inactivate rapidly when the membrane potential becomes more positive. Site-directed mutagenesis and single-channel patch-clamp recording were used to explore the molecular transitions that underlie inactivation in Shaker potassium channels expressed in Xenopus oocytes. A region near the amino terminus with an important role in inactivation has now been identified. The results suggest a model where this region forms a cytoplasmic domain that interacts with the open channel to cause inactivation.

Amino Acid Sequence↗
PubMed1990

Restoration of inactivation in mutants of Shaker potassium channels by a peptide derived from ShB.

Site-directed mutagenesis experiments have suggested a model for the inactivation mechanism of Shaker potassium channels from Drosophila melanogaster. In this model, the first 20 amino acids form a cytoplasmic domain that interacts with the open channel to cause inactivation. The model was tested by the internal application of a synthetic peptide, with the sequence of the first 20 residues of the ShB alternatively spliced variant, to noninactivating mutant channels expressed in Xenopus oocytes. The peptide restored inactivation in a concentration-dependent manner. Like normal inactivation, peptide-induced inactivation was not noticeably voltage-dependent. Trypsin-treated peptide and peptides with sequences derived from the first 20 residues of noninactivating mutants did not restore inactivation. These results support the proposal that inactivation occurs by a cytoplasmic domain that occludes the ion-conducting pore of the channel.

Amino Acid Sequence↗
PubMed1990

Beta-alanyl-L-histidinato zinc prevents skeletal unloading-induced disorder of bone metabolism in rats.

The effect of a new zinc compound beta-alanyl-L-histidinato zinc (AHZ) on the disorder of bone metabolism caused by skeletal unloading was investigated. Skeletal unloading was designed using the model of hind-limb hang in rats. Skeletal unloading for up to 4 days caused a remarkable decrease of zinc content, alkaline phosphatase activity, and DNA content in the femoral diaphysis of rats. Oral administration of AHZ (2.5, 5.0, and 10.0 mg/100 g) caused a significant increase in zinc, DNA, and calcium contents in the femoral diaphysis of rats with the skeletal unloading. Bone alkaline phosphatase activity was significantly increased by doses of 5.0 and 10.0 mg/100 g. These results clearly indicate that skeletal unloading-induced disorder of bone metabolism is prevented by the oral administration of AHZ. AHZ may be useful as a therapeutic tool in bone disorder.

Alkaline Phosphatase↗
PubMed1990

Effects of some autonomic drugs and neuropeptides on the mechanical activity of longitudinal and circular muscle strips isolated from the carp intestinal bulb (Cyprinus carpio).

1. The mechanical responses to some autonomic drugs and neuropeptides of longitudinal muscle (LM) and circular muscle (CM) strips isolated from the carp intestinal bulb were investigated in vitro. 2. Acetylcholine and carbamylcholine caused concentration-dependent transient contraction of both LM and CM strips. Tetrodotoxin had no effect, but atropine selectively decreased the contractile responses to acetylcholine and carbamylcholine. 3. Excitatory alpha-2 and inhibitory beta adrenoceptors were present in both LM and CM strips. 4. 5-Hydroxytryptamine (5-HT) caused concentration-dependent contraction of both LM and CM strips. Tetrodotoxin, atropine and methysergide decreased the contractile responses to 5-HT. 5. Some neuropeptides (angiotensin I, angiotensin II, bombesin, bradykinin, neurotensin, somatostatin and vasoactive intestinal polypeptide) did not cause any mechanical response (contraction or relaxation) in either smooth muscle strip. 6. Substance P (SP), neurokinin A (NKA) and neurokinin B (NKB) caused contraction of both LM and CM strips. However, the time course of the contraction in LM was different from that in CM. The order of potency was NKA greater than SP greater than NKB in LM strips and NKA greater than SP much greater than NKB in CM strips. In LM strips, the contractile responses to tachykinins were unaffected by spantide and methysergide, but partly decreased by tetrodotoxin and atropine. On the other hand, the contractile responses of CM strips were unaffected by tetrodotoxin, atropine, methysergide and spantide. 7. Dynorphin (1-13) (DYN), leucine-enkephalin (L-Enk) and methionine-enkephalin (M-Enk) caused concentration-dependent contraction of both LM and CM strips. The order of potency was DYN greater than M-Enk greater than L-Enk. Naloxone selectively decreased the responses to opiate peptides. 8. The present results indicate that acetylcholine, carbamylcholine, catecholamines, 5-HT, tachykinins (SP, NKA and NKB) and opiate peptides (DYN, L-Enk and M-Enk) affect the mechanical activity of LM and CM strips isolated from the carp intestinal bulb through their specific receptors.

Animals↗
PubMed1990

Uphill transport of beta-alanine in intestinal brush-border membrane vesicles.

The characteristics of beta-alaline uptake were studied in brush-border membrane vesicles isolated from the proximal small intestine of rabbits and were compared with those of L-alpha-alanine uptake. The uptake of beta-alanine as well as L-alpha-alanine was significantly stimulated by imposing an inwardly directed Na+ gradient. Studies on transstimulation and substrate specificity provide evidence that the transport system serving beta-alanine is distinct from the system serving alpha-alanine. The beta-system also accepts taurine as a substrate. The Na(+)-dependent uptakes of beta-alanine and L-alpha-alanine were differentially influenced by anions. The order in which anions supported uptake was Cl- = SCN- greater than F- greater than NO3- = SO2(-4) for beta-alanine, whereas it was SCN- greater than F- = Cl- = NO3- greater than SO2(-4) for L-alpha-alanine. Cl- appeared to be the preferred anion to support the uptake of beta-alanine. beta-Alanine uptake was greater in the presence of an inwardly directed Cl- gradient than in the presence of Cl- at equal concentrations on both sides of the membrane. The uptake was maximal when a Na+ gradient and a Cl- gradient were present simultaneously. The NaCl gradient-driven beta-alanine uptake was stimulated by an inside-negative K(+)-diffusion potential induced by valinomycin, showing that the uptake process is electrogenic. Stoichiometric analyses suggest that multiple Na+ and one Cl- are associated with the uptake of one beta-alanine molecule. The kinetic study shows that the transporter for beta-alanine is a high-affinity, low-capacity system (Kt = 46 +/- 1 microM; Vmax = 30 +/- 1 pmol.mg protein-1.15 s-1).

Alanine↗
PubMed1990

[The present states and considerations of orthognathic surgery in Japan. Questionnaire in department of orthodontics of university dental hospital, and department of oral surgery of university medical hospital].

To investigate the present state of orthognathic surgery, questionnaires were sent to 30 departments of orthodontics of university dental hospital and 60 departments of oral surgery of university medical hospital. 1. Orthognathic surgery was carried out in 100% of the departments of orthodontics and 91.8% of the departments of oral surgery examined. 2. There was a difference in the number of patients between individual hospitals. 3. Analyses of cephalogram were used in 96% of the departments of orthodontics and 93% of the departments of oral surgery. 4. Pre- and post-surgical orthodontic treatments were carried out in all of the departments of orthodontics. 5. Orthodontic appliances (83.9%) were used in the departments of orthodontics for intermaxillary fixation, while orthodontic appliances (47.8%) and wire splints (49.2%) were used in the departments of oral surgery. 6. It is pointed out that the criterion of orthognathic surgery, treatment objectives on soft and hard tissue, selection of surgical method, adaptability of soft tissue after surgery, relapse, treatment planning of two jaw surgery, and postoperative stability remain to be solved in future.

Humans↗
PubMed1990

Interaction of forskolin with voltage-gated K+ channels in PC12 cells.

Forskolin (FSK) directly blocks a distinct class of voltage-dependent K+ channels in pheochromocytoma cells. We have studied the biophysical mechanism of FSK action on these channels. The mean open duration decreased linearly with [FSK], indicating that a single molecule of FSK interacts with a single open K+ channel. FSK did not alter the voltage dependence of activation or the latency to first opening. Whole-cell currents in the presence of FSK did not show a rising phase in tail currents, suggesting that FSK-bound channels can close. We used a kinetic scheme in which FSK binds preferentially to the open state of the channel to describe its interaction with the K+ channel. This scheme is analogous to the modulated receptor hypothesis used to describe the interaction of local anesthetics with voltage-dependent Na+ channels.

Adrenal Gland Neoplasms↗