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Biomedical subjects

H Shimada

Publications and source records attributed to H Shimada.

At least 901 records · Page 50Linked to original sources
PubMed1983

Stimulatory and inhibitory effects of guanine nucleotides on arginine-vasotocin-sensitive adenylate cyclase in the epithelial cell membranes of the bullfrog bladder.

The effects of arginine-vasotocin and nucleotides on the steady-state kinetics of the adenylate cyclase activity in the epithelial cell membranes of the bullfrog (Rana catesbiana) bladder were studied. Arginine-vasotocin stimulated adenylate cyclase more effectively than oxytocin or arginine-vasopressin, with respect to both the maximal hormonal activation ratio relative to basal, and the hormone concentration yielding a half-maximal response (apparent Km). Arginine-vasotocin, GTP and its analogue guanyl-5'-yl imidodiphosphate (Gpp(NH)p) increased the Vmax of the basal adenylate cyclase activity, but showed no effect of the apparent Km of the system for ATP. In addition, Gpp(NH)p enhanced the arginine-vasotocin-stimulated adenylate cyclase activity, further increasing the Vmax, while GTP showed no statistically significant effect. Dual effects of GDP were apparent: it was stimulatory at 1 x 10(-5) mol/l and inhibitory at 1 x 10(-3) mol/l, on both the basal and the arginine-vasotocin-stimulated adenylate cyclase activity. Guanosine 5'-monophosphate, CTP, UTP and ITP showed no apparent effect on the enzyme activity. Sodium fluoride acted in the same manner as GTP on the adenylate cyclase system, increasing only basal activity. Adenylate cyclase activities exhibited pH optima that were less distinct in the presence than in the absence of Gpp(NH)p. The Arrhenius plot of the temperature experiment showed that a high-energy step was involved for activation by Gpp(NH)p or arginine-vasotocin. When the relative activation ratios by arginine-vasotocin at different ATP concentrations were studied, a distinct activation optimum was shown at 2.5 x 10(-4) mol ATP/l, either in the absence or presence of Gpp(NH)p. The possibility that GTP, GDP nd ATP play a regulatory role in the epithelial cells of the bullfrog bladder by adjusting the responsiveness of the system to a natural hormone, arginine-vasotocin, is discussed.

Adenosine Triphosphate↗
PubMed1982

Dynamic protein structures. Effects of pH on conformer stabilities at the ligand-binding site of bovine heart myoglobin carbonyl.

The single ligand-binding site of bovine myoglobin carbonyl exists in four discrete conformations as shown by four C--O stretch bands for the carbonyl ligand. Both this infrared spectrum and the visible spectrum are altered by changes in pH from 4.7 to 8.2 at 20 degrees C. The spectral changes can be related to monoprotonation or monodeprotonation at a protein residue with a pKa = 6.0 +/- 0.2. Below pH 5.5, an additional proton-coupled infrared spectral change is evident. Histidine is an appropriate site for pKa approximately 6; there are 13 histidines in the protein. However, the nature of the pH effects on infrared spectra indicates that neither the proximal nor the distal histidine is a likely site. The state of protonation of the protein has a marked effect on the relative stabilities of the four conformers but appears to have little effect on the discrete conformer structures per se in that C--O stretch band frequencies and shapes are nearly insensitive to changes in pH. The sum of the four integrated infrared band intensities is similarly insensitive. These findings provide strong support for the presence of four conformers of significantly different structure at the heme ligand-binding site and for rapid interconversions among these structures.

Animals↗
PubMed1982

Transmission and scanning electron microscopic studies on the tumors of neuroblastoma group.

Ultrastructural study of neuroblastoma group tumors including 7 neuroblastomas, 4 ganglioneuroblastomas, and 2 ganglioneuromas was performed by using both TEM and SEM. Tumor cells showed a wide variation comparable to the developmental stages of nerve cells and were classified into four types according to the neuritic process projections; namely apolar, monopolar, bipolar, and multipolar. Neuroblastoma was composed of small cells of apolar, monopolar, and bipolar types with few multipolar cells. Tumor cells ganglioneuroblastoma and ganglioneuroma were multipolar type. SEM observation demonstrated characteristic varicosities in the elongated neuritis processes, and by TEM examination the dilated portions of these varicosities revealed disruption or disappearance of parallel runnings of the microtubules and microfilaments. TEM examination demonstrated presence of Schwann cells in ganglioneuroblastoma and ganglioneuroma, and satellite cells and perineurial cells in ganglioneuroma. The hitherto undescribed cells with caveolar structure which are thought to be a precursor of these stromal elements were disclosed in ganglioneuroblastoma. In order to evaluate the maturation and prognosis of tumors of this group, stromal differentiation seems to be equally important as ganglionic differentiation because both stromal elements and tumor cells have a common origin of neural crest.

Child↗
PubMed1982

Cloverleaf skull syndrome. An autopsy case and review of literature.

An autopsy case of cloverleaf skull deformity associated with hydrocephalus, systemic skeletal malformation including facial dysostosis, fused elbow, syndactyly of the toes, odd digits and striking anomaly of tracheal cartilage is presented. Extra-skeletal abnormalities included covered anus, dermal sinus and the absence of corpus callosum and the septum pellucidum. Several basal skull deformity appeared to be a primary morphologic alteration associated with premature closure of the specific sutures, which terminally resulted in life-threatening hydrocephalus. Histological investigation showed the abnormalities of endochondral ossification in the cartilage at the epi- and meta-physis of the fused elbows. In addition, electron microscopical study revealed unusual fat droplet-containing chondrocytes even in the resting and multiplicative phase. Association of the tracheal anomaly with this syndrome was disclosed in this case. Generalized bone and cartilage abnormalities not only in the skeletal system but also in the internal organs strongly suggest that this disorder involves generalized osteocartilagenous system. The present case makes a total of 14 cases of the cloverleaf skull syndrome reported in the Japanese literatures to date. Major clinical and pathologic findings of these cases were summerized.

Abnormalities, Multiple↗
PubMed1982

Amyloid deposits in the aged tongue: a postmortem study of 107 individuals over 60 years of age.

The incidence and distribution of amyloid deposits in aged tongues obtained from 107 necropsies over 60 years of age were examined. Thirty-nine tongues were affected with amyloid deposits and the overall incidence was 36.4%. The incidence increased with each advancing decade, and the group over 90 years old showed the highest incidence of 59.6%. Although the amount of amyloid deposits differed in each case, severely affected cases were most frequently found in the advanced decades. Amyloid deposits were almost always confined to blood vessels, especially arterioles and arteries. They occasionally occupied the entire wall and occluded the lumen. Blood vessels affected with amyloid were usually located in the muscle layers of the tongue. Vessels in the subepithelial layer and lingual glands were, however, sometimes affected. Amyloid deposits were resistant to Congo red staining with the potassium permangante method, and stained positively with DMAB. The present study suggested that the tongue is an important organ as to the appearance of amyloid deposits in elderly persons.

Age Factors↗
PubMed1982

Effects of diazoxide and hydrochlorothiazide on water permeability and sodium transport in the frog bladder.

The effects of diazoxide and hydrochlorothiazide on vasopressin-induced increments in osmotic water flow and sodium transport across the frog bladder were studied. Diazoxide enhanced the vasopressin-induced osmotic water flow of the bladder, but did not affect the cyclic AMP- or theophylline-induced water flow. Hydrochlorothiazide did not affect the vasopressin-induced water flow. Our results suggest that diazoxide increased the water flow by inhibiting the activity of phosphodiesterase in bladder epithelial cells, whereas hydrochlorothiazide did not. On the other hand, both drugs suppressed the short-circuit current of the bladder membrane and inhibited the Na,K-dependent ATPase activity of the kidney cells. These results suggest that both drugs decreased sodium transport in the bladder by inhibiting Na,K-dependent ATPase activity.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1982

Distribution of gamma-glutamyl transpeptidase and glutaminase isoenzymes in the rabbit single nephron.

"Phosphate-independent maleate-stimulated glutaminase" was investigated as a function of gamma-glutamyl transpeptidase (gamma-GTP). The activity of gamma-GTP in brush border membranes was found to be four times higher than that in the microsomal fraction of the renal cortex. This gamma-GTP activity was exclusively located in the proximal tubule of isolated single nephrons. Specific activity of gamma-GTP was 105 U/g protein (19.8 microU/mm length) in the first 2 mm portion of the proximal tubule and 1352 U/g protein (209 microU/mm) in the last 2 mm portion of the proximal straight tubule. Activity of phosphate independent glutaminase (PIG) was distributed in the same patterns as those of gamma-GTP, not only in the subcellular fractions, but also in the isolated nephron segments. On the other hand, phosphate dependent glutaminase (PDG) was distributed highly in the papillary mitochondrial fraction and in the distal tubule. Observations on the effect of pH on the enzyme activities of gamma-GTP and PDG showed that these enzyme activities were decreased significantly when the pH of the assay mixture was lowered. In the case of PIG, however, the effect of pH was just reversed. From these findings, it may be possible to interpret that gamma-GTP may play an important role in ammonia production in the brush border membrane of the proximal tubule as a function of glutaminase.

Animals↗
PubMed1982

[A progesterone-dependent step in HCG-induced ovulation in immature rats (author's transl)].

The effect of antiserum to progesterone on follicular rupture during the ovulatory process was studied. Mean number of ova shed following treatment of immature rats sequentially with PMS and hCG was reduced in a dose-dependent manner by simultaneous injection with increasing doses of antiserum to progesterone. When the animal received 1.2 ml of the antiserum, hCG-induced ovulation was blocked completely. To be effective, antiserum treatment had to be within 6 h of hCG treatment; antiserum given 9 h after hCG was ineffective. Progesterone restored' the antiserum blocked ovulation completely or incompletely when administered intravenously within 6 h of treatment with hCG. The first 6 h was shown to be a progesterone-dependent step in the ovulatory process in this experimental system.

Animals↗