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Biomedical subjects

H Mikami

Publications and source records attributed to H Mikami.

At least 199 records · Page 11Linked to original sources
PubMed1989

A case of acute tubulointerstitial nephritis and uveitis syndrome with a dramatic response to corticosteroid therapy.

A 23-year-old female with acute renal failure associated with acute tubulointerstitial nephritis and uveitis is reported. Renal tubular acidosis and inflammatory reactions consisting of markedly increased erythrocyte sedimentation rate and high serum immunoglobulin levels were seen on admission. Light microscopy revealed infiltration of mononuclear cells in the interstitium. Immunofluorescence of renal tissues was negative in staining for immunoglobulins, fibrinogen, and complement components. Bone marrow specimens did not show any granulomatous lesions. The etiology of this tubulointerstitial nephritis and uveitis syndrome was not clear. Immunological evaluation showed a slight decrease of the OKT4/OKT8 ratio in the peripheral blood. OKT8- and OKM1-positive cells had infiltrated diffusely into the renal interstitium. Acute tubulointerstitial nephritis and uveitis responded dramatically to steroid therapy. It was suggested that immunological factors might correlate with the onset and/or development of this syndrome. It is indicated that high-dose steroid therapy might be useful for patients with acute interstitial nephritis and uveitis.

Adult↗
PubMed1989

Contribution of the baroreflex afferent nerves to the production of vasoconstricted hypertension in volume-expanded dogs.

Dextran in lactated Ringer's solution (20 ml/kg) was infused for 1 hour into anesthetized dogs with sinoaortic denervation and vagotomy (deafferentation; n = 10) and dogs treated with hexamethonium (de-efferentation; n = 13) to compare with our previous observation in dogs with an intact autonomic nervous system (control, n = 34). During the infusion, increase in blood pressure associated with increase in cardiac output was observed in all three groups. The increases in blood pressure were larger in the two groups with an impaired autonomic nervous system. In the recovery period, the control dogs and the hexamethonium-treated dogs showed gradual increases in total peripheral resistance and in vasoconstricted hypertension 3 hours after stopping the infusion. In contrast, the dogs with sinoaortic denervation and vagotomy did not show any increase in total peripheral resistance. The vasoconstricted groups showed peaks of natriuresis soon after the infusion, not 3 hours after the infusion when vasoconstriction was observed, although the dogs with deafferentation did not show a significant increase in natriuresis. Norepinephrine (0.5 micrograms/kg) was administered intravenously before and after volume expansion, and the pressor responses in the three groups after volume expansion were enhanced similarly (143%, 128%, and 136%, respectively). These results indicate that the afferent signals from peripheral vessels to the brain contribute to the production of vasoconstricted hypertension after acute volume expansion and that the vasoconstriction is independent of pressor hypersensitivity and is dissociated in time from the natriuresis.

Afferent Pathways↗
PubMed1989

Changes in plasma renin activity and aldosterone concentration in response to endothelin injection in dogs.

The effects of endothelin on the renin-aldosterone system were examined by injecting it intravenously at low (40 pmol/kg) and high (400 pmol/kg) doses into pentobarbital-anesthetized dogs. Plasma renin activity and aldosterone concentration together with hemodynamic parameters were measured before and 60 min after endothelin injection. The lower dose of endothelin induced no significant increase in mean blood pressure or total peripheral resistance. It caused a slight decrease of plasma renin activity from 10.3 +/- 1.6 to 5.9 +/- 1.3 micrograms.l-1.h-1 (p less than 0.1) and a decrease of aldosterone concentration from 364 +/- 68 to 231 +/- 58 ng/l (p less than 0.05) with an increase in total peripheral resistance (p less than 0.05), but it did not cause any clear change in the plasma renin activity or aldosterone concentration. Thus, endothelin increases the blood pressure mainly by vasoconstriction. The finding of a slight decrease in the plasma renin activity after the lower dose of endothelin, together with our previous finding that endothelin inhibits renin release from isolated rat glomeruli, suggests that endothelin inhibits renin release in vivo. With the higher dose of endothelin, stimulation of renin release secondary to renal vasoconstriction might have counteracted the direct inhibitory action of endothelin. The decrease in aldosterone concentration may have been due to the direct inhibitory action of endothelin on aldosterone release or it may be a secondary effect induced by suppression of plasma renin activity.

Aldosterone↗
PubMed1989

Bronchial reactivities in guinea pigs to acetylcholine or histamine exposure.

The bronchial reactivities in Hartley guinea pigs to acetylcholine (ACh) or histamine (Hist) were investigated, and the following results obtained; 1. Eight-week-old animals were exposed to ACh and Hist. A significant relationship was observed between the concentrations of the chemicals and the time needed to produce falling down (TNPFD) due to the asthmatic reaction to ACh and Hist. 2. Eight-week-old animals were exposed to 0.1% ACh and 0.05% Hist, for which the mean TNPFD +/- standard error were 377 +/- 33 sec and 122 +/- 5 sec respectivity. However, no difference in reactivity between male and female animals was noted. 3. Eight- and 9-week-old animals were exposed to 0.01% ACh and 0.025% Hist. A positive correlation was observed (r = 0.736, p less than 0.01) between the TNPFD for ACh and that for Hist. 4. Growing animals from 2 weeks to 20 weeks old were exposed to 0.08% ACh and 0.025% Hist. After inhalation of both chemicals, 6-week-old animals showed the greatest prolongation of mean TNPFD (lowest sensitivity). 5. Eight-week-old animals were exposed to 0.08% ACh and 0.025% Hist. With both of these chemicals, a positive correlation was observed between TNPFD and dose threshold (ACh r = 0.886, p less than 0.001; Hist r = 0.891, p less than 0.001).

Acetylcholine↗
PubMed1989

Trial of IgG therapy for lupus nephritis--report of two cases with a successful response.

Two cases with systemic lupus erythematosus (SLE) were treated with high-dose intravenous IgG. In patient 1, the IgG therapy dramatically improved both the lupus nephritis and serological titers for SLE. In patient 2, intravenous IgG yielded a partial remission in the lupus nephritis as well as a satisfactory decrease in proteinuria and disappearance of the skin rash characteristic of SLE. IgG therapy is suggested as possibly beneficial for the treatment of SLE based on different mechanisms from those of corticosteroid action. Further studies are needed to determine the detailed efficacy of IgG therapy for SLE.

Adult↗
PubMed1989

Direct vascular effects of 19-hydroxyandrostenedione.

A C19 steroid, 19-hydroxyandrostenedione (19-OHAD), an amplifier of the mineralocorticoid effects of aldosterone, is known to cause hypertension in rats during chronic administration. In the present study we examined the direct vasoconstrictive effects of 19-OHAD and aldosterone in vitro as a possible mechanism of their hypertensinogenic effects. Contractile responses of central ear arteries from normal male rabbits to either 19-OHAD or aldosterone were examined in Krebs' bicarbonate buffer. When given alone, neither 19-OHAD nor aldosterone consistently caused contraction of the arteries, nor did 19-OHAD amplify the contractile action of aldosterone to a detectable range. Pretreatment of the ear arteries with desipramine, an inhibitor of neuronal uptake (uptake 1) of norepinephrine (NE), resulted in significant concentration-dependent contraction by each steroid. This contraction was markedly attenuated by prazosin but not by yohimbine. Both steroids significantly potentiated the contractile reaction of the ear arteries to exogenous NE in a dose-related manner without pretreatment with desipramine, suggesting that 19-OHAD may increase vascular resistance through the inhibition of extraneuronal NE uptake (uptake 2). These results suggest that 19-OHAD is not an amplifier of aldosterone at the vascular site.

Aldosterone↗
PubMed1988

Potentiation of the pressor effect of angiotensin II by intraventricular infusion of hypertonic saline.

The effect of selective NaCl loading to the brain on the blood pressure regulation was examined in male Wistar rats. Hypertonic NaCl (0.8M, 1 microL/h) was infused for 7 days into the lateral ventricle (ICV) along with intravenous (IV) infusion of angiotensin II (AII) at a dose of 5.4 pmol/kg per minute. Although neither ICV hypertonic NaCl or IV AII infusion alone had any substantial pressor effect, concomitant administration of these resulted in a consistent and significant increase in the blood pressure on day 7 over the baseline value, amounting to 29 +/- 5 mm Hg (n = 9; P less than 0.001). Inasmuch as the increase in the BP was totally prevented by intraperitoneal injection of guanethidine (40 mg/day), hyperactivity of the sympathetic nervous system appears, at least in part, responsible for the BP elevation caused by the combination of ICV hypertonic NaCl and IV subpressor AII infusion.

Angiotensin II↗
PubMed1988

Purification and characterization of human renal dehydropeptidase I.

Dehydropeptidase I from human kidney was purified over 100-fold. The purified enzyme had an isoelectric point of 4.75, apparent molecular weights of 135,000 by gel filtration and of 66,500 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and an optimal pH of 7.4. Human renal dehydropeptidase I hydrolyzed imipenem, carpetimycins A and B, and Sch 29,482.

Anti-Bacterial Agents↗
PubMed1988

Albumin gene transcription is enhanced in liver of nephrotic rats.

The level of albumin mRNA and the transcription rate of the albumin gene were studied in the liver of control rats and rats with nephrosis induced by injection of the aminonucleoside of puromycin. Total RNA was extracted from liver by the guanidium thiocyanate method. The albumin mRNA level was measured by cDNA-RNA dot-blot hybridization, and the transcription rate of the albumin gene was measured by the "run-on" transcription assay using isolated nuclei. Urinary protein excretion in nephrotic rats was significantly higher than in control rats (258 +/- 132 vs. 12 +/- 2 mg/day), and the serum albumin concentration in nephrotic rats was significantly lower. There was no difference in body weight, liver weight, serum creatinine, or urea nitrogen between the two groups. Both the level of albumin mRNA and the transcription rate of the albumin gene in the nephrotic liver were about twice as high as those in the control liver. There was no difference in the level of beta-actin mRNA between the two groups. Northern blot analysis showed that both putative precursor RNA and the mature form of albumin mRNA were increased in nephrotic rats. We conclude that albumin synthesis is increased in the liver of nephrotic rats and a transcriptional process is responsible for this increase.

Actins↗
PubMed1988

Vasoconstriction and hypersensitivity to vasoactive substances after acute volume expansion in dogs.

In a search for factors contributing to the sustained blood pressure (BP) elevation in acutely volume-loaded animals, dextran dissolved in lactated Ringer's solution (20 ml/kg) was infused into 34 mongrel dogs over a period of 1 hour under pentobarbital anesthesia and changes in hemodynamic and humoral variables were monitored during its infusion and for 3 hours after its infusion. BP elevation during volume loading (from 114 +/- 3 to 128 +/- 3 [SEM] mm Hg) was attributed to an increase in cardiac output. After volume loading, some dogs maintained BP elevation whereas others did not. The former group showed an increase in total peripheral resistance, demonstrating a transformation of cardiac output to total peripheral resistance as a responsible factor in maintenance of the elevated BP. The plasma levels of norepinephrine, vasopressin, and plasma renin activity were not elevated, indicating that these vasoactive factors were not responsible for elevation of the BP or total peripheral resistance. The changes in the hematocrit, atrial natriuretic factor, urine volume, and urinary sodium excretion were identical in the two groups, and natriuresis was not prominent when total peripheral resistance was high. Pressor responses to norepinephrine and angiotensin II were potentiated 3 hours after stopping infusion in both groups, but this potentiation was not correlated with the increase in total peripheral resistance or mean BP. Thus, acute volume expansion produced resistance-dependent hypertension following the initial volume-dependent hypertension. It is unlikely that a vascular sensitizing natriuretic factor plays a role in the resistance-dependent BP elevation. The mechanism and physiological importance of hypersensitivity to vasoactive substances remain to be elucidated.

Aldosterone↗
PubMed1988

Chimeric heterosis in mandibular size in mice.

Morphometrical observations were carried out on the mandibles of chimeras made from the embryos of C57BL/6 and BALB/c mice to compare with the two strains and their reciprocal F1 crosses. The results of the principal component analysis indicate that the first principal component (PC1) and the second principal component (PC2) extracted might be acceptable as size and shape factors, respectively. Variations of both PC1 and PC2 were generally larger in the chimeras than in the two component strains and their F1 crosses. The mean PC1 value of the chimeras was larger than that of the two component inbred strains, and it was similar to that of F1 crosses, or slightly larger. The overall size of the mandible represented by PC1 tended to be larger in the chimeras consisting of two component cells that were approximately equivalent than in those that shifted to either cell population. The above trend was observed in both sexes. These results indicate that chimeric heterosis due to the interaction between genetically different cells (C57BL/6 and BALB/c) has some relation to mandible size. The mean PC2 value, which was accepted as shape factor, was intermediate between the two inbred strains. The mandible size (PC1) and shape (PC2) were bilaterally symmetrical, except for the shape in the female chimeras and in (C57BL/6 x BALB/c)F1.

Animals↗
PubMed1988

Appearance of interfrontal bone in chimeric mouse.

The incidence of the interfrontal bone in mice differs between strains, being high in C57BL/6 and low in BALB/c. In the present study, aggregation chimeras (C57BL----BALB) were examined to reveal whether or not genetically different cells interact in the morphogenesis of the interfrontal bone. In C57BL/6 mice, large interfrontal bones appeared in almost all animals, whereas in BALB/c and reciprocal F1 crosses (C57 BL x BALB, BALB x C57BL), large bones were seldom observed while tiny bones at the inside of the skull appeared at a low incidence. In contrast, chimeras frequently had large interfrontal bones, the size of which varied considerably. Based on the degree of chimerism as determined by coat color mosaicism and glucose phosphate isomerase (G PI) analysis of tissues, the chimeric mice containing a dominant population of C57BL cells had large interfrontal bones, while those with a predominance of BALB cells had no bone or had tiny ones. The results indicated that the appearance of the interfrontal bone corresponded with the population of the C57BL cells occupying the skeletal rudiment, and that there was no interaction between C57BL cells and BALB cells in the morphogenesis of the interfrontal bone.

Animals↗
PubMed1988

[Reaction of various experimental animals to exposure to acetylcholine or histamine, and morphological observations of bronchial smooth muscle].

We investigated the sensitivity of the airway of various experimental animals to acetylcholine (ACh) and histamine (Hist). The experimental animals were exposed to 0.1% ACh or 0.05% Hist. Guinea pigs and rabbits exhibited an asthmatic reaction to both chemicals, but rabbits seemed to have a milder reaction than guinea pigs to both chemicals. Mice, rats and hamsters showed no reaction. We then performed a morphological study of the airways of 5 species in order to clarify the reason for their different reactivities to ACh and Hist. In the morphological study, abundant smooth muscle could be seen in the terminal bronchioles and respiratory bronchioles of guinea pigs and rabbits. In contrast, animals of other species had little smooth muscle in either site. Mice had no respiratory bronchioles. Consequently, we concluded that there is a high correlation between sensitivity to ACh and Hist and the extent of smooth muscle distribution around the airway.

Acetylcholine↗
PubMed1988

Central sodium loading modifies norepinephrine content in the ventrolateral medulla and blood pressure in rats.

We evaluated the effects of intracerebroventricular (ICV) infusion of hypertonic NaCl on blood pressure (BP) control as well as on NE content in the ventrolateral medulla (VLM). Nine groups of Wistar rats received 10 day's ICV infusion of NaCl solutions containing either norepinephrine (NE, 1.3 micrograms/min) or a synthetic NE precursor, 1-threo-3,4-dihydroxyphenylserine (1-DOPS, 17 micrograms/min) for 3 concentrations (0.15M, 0.8M or 1.5M) of NaCl. On day 9, only the group on ICV infusion of 1.5M NaCl alone had a significant rise in BP (133 +/- 3 mmHg, P less than 0.05 vs control) while other groups remained normotensive. The ICV infusion of 1.5M NaCl reduced NE content, determined by a microdialysis method, in the VLM while the concomitant ICV infusion of NE or 1-DOPS restored it suggesting that the decrease in NE content in the VLM may be a contributing factor in the BP elevation by the central salt loading.

Animals↗