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Biomedical subjects

M Umezu

Publications and source records attributed to M Umezu.

At least 55 records · Page 3Linked to original sources
PubMed1991

[Pituitary and plasma levels of growth hormone (GH), follicle stimulating hormone (FSH) and luteinizing hormone (LH) in hereditary dwarf rats (rdw/rdw)].

Koto et al found a new hereditary dwarf mutation from breeding colony of Wistar-Imamichi rat and named 'rdw'. To characterize endocrinological functions in rdw rats, pituitary and plasma levels of pituitary hormones including growth hormone (GH), follicle stimulating hormone (FSH) and luteinizing hormone (LH) were compared between rdw and normal rats. The hormone levels were estimated with radioimmunoassay (RIA). It was found that pituitary and plasma levels of GH of rdw were drastically decreased and those of FSH and LH were inclined to decrease but not remarkable as compared with normal. Rats of rdw were, therefore, considered to be useful as a model animal for endocrinological defects.

Animals↗
PubMed1991

Mechanisms of hypertension induced by erythropoietin in patients on hemodialysis.

To investigate the mechanisms of hypertension induced by recombinant human erythropoietin (rHuEPO) in patients on hemodialysis (HD), mean blood pressure (MBP), plasma renin activity (PRA), whole blood viscosity, blood volume (BV), cardiac index (CI) and total peripheral resistance index (TPRI) were measured before and after treatment with rHuEPO for 3 months in 9 patients on HD. Pressor responsiveness to exogenous norepinephrine (NE) and angiotensin II (AII) were also compared before and after treatment. Four patients were 'responders' (R) whose MBP increased by more than 10 mmHg, and 5 patients were 'non-responders' (non-R) whose MBP was unchanged or increased by less than 10 mmHg. Initial PRA and TPRI were significantly higher and BV was significantly lower in R than in non-R. After treatment, TPRI was increased in both groups, but CI was decreased in non-R. There was a significant correlation between changes in MBP and blood viscosity to rHuEPO. Pressor responsiveness to NE and AII were significantly enhanced after rHuEPO treatment in responders. These results suggest that inappropriate cardiovascular responses to the correction of anemia, increased blood viscosity, and enhanced pressor responsiveness may participate in the development of rHuEPO-related hypertension.

Adult↗
PubMed1991

Echocardiographic findings in hemodialysis patients treated with recombinant human erythropoietin: proposal for a hematocrit most beneficial to hemodynamics.

We investigated the hemodynamic effects of the correction of anemia with recombinant human erythropoietin (rHuEPO) in 28 hemodialysis patients with severe anemia. Echocardiograms were recorded before the administration of rHuEPO (period I) with a hematocrit of 19.2 +/- 1.5% (mean +/- SD) and repeated twice (periods II and III) when the hematocrit was increased to 25.7 +/- 1.1% and to 30.0 +/- 1.0%. Left ventricular end-diastolic dimension (LVDd) decreased from 51.0 +/- 6.1 to 48.8 +/- 5.8 and to 48.3 +/- 7.1 mm, but no changes were observed in left ventricular end-systolic dimension. Cardiac output (CO) decreased from 5.89 +/- 1.46 to 5.00 +/- 1.44 and to 4.67 +/- 1.33 l/min. The thickness of the interventricular septum and the left ventricular posterior wall remained unchanged. Blood pressure was kept rather constant, although antihypertensive therapy needed to be adjusted to prevent the occurrence or aggravation of hypertension. Total peripheral resistance increased from 1481 +/- 359 to 1832 +/- 487 and to 1946 +/- 493 dynes.sec/cm5. The decreases in LVDd and CO were significant between periods I and II, without further changes between periods II and III. More antihypertensive therapy was needed in period III than in period II. Similar echocardiographic results were observed in 10 patients in whom antihypertensive therapy was not required throughout the study. In conclusion, an increase in hematocrit to 25% would be appropriate in order to obtain an effective hemodynamic improvement with rHuEPO therapy in dialysis patients although a higher hematocrit level might be desirable in order to improve working capacity.

Adult↗
PubMed1990

Cloning and sequence analysis of mink growth hormone cDNA.

A cDNA clone for mink growth hormone (GH) was isolated from a mink pituitary cDNA library, employing a part of rat growth hormone cDNA sequence as a probe. According to the nucleotide sequence, mature mink GH consists of 190 amino acids with a calculated molecular weight of 21,720. The amino acid sequence homology between the mature region of mink GH and those of pig GH, rat GH, bovine GH and human GH was 98.4%, 93.7%, 89.0% and 66.7%, respectively.

Amino Acid Sequence↗
PubMed1990

Regulatory mechanisms of erythropoietin levels in dialysis patients.

We described a radioimmunoassay system for measuring blood erythropoietin (Epo) levels using recombinant human Epo and evaluated the regulatory mechanisms of Epo in dialysis patients. A satisfactory dose-response relationship for Epo levels was observed within the wide range of 3-250 mU/ml with a sensitivity of approximately 5 mU/ml. The Epo levels were found to be 16.1 +/- 8.6 mU/ml (m +/- SD) in 422 uremic patients on maintenance dialysis and 17.1 +/- 7.2 mU/ml in 86 normal subjects. The Epo levels were not statistically different between the two groups, although the hematocrit was significantly lower in the dialysis patients. No correlation was observed between the Epo levels and hematocrit in the dialysis patients. Patients with polycystic kidneys had higher hematocrits and Epo levels than patients with chronic nephritis. No changes in Epo levels were observed with age and with the period of dialysis. Diurnal variations in the Epo levels revealed a significant increase after hemodialysis, and an acute reduction in hematocrit following massive hemorrhage raised the Epo levels up to 3,180 mU/ml. These findings indicate that the Epo levels in dialysis patients are inappropriately low for the severity of anemia and suggest that a negative feedback mechanism of the hematocrit on the Epo secretion may exist in uremic patients as well as in normal subjects and that the threshold for Epo secretion might be 'reset' at a low hematocrit level.

Erythropoietin↗
PubMed1989

Prerequisites to salvage profound biventricular failure patients with ventricular assist devices.

We conducted chronic experiments to determine how to treat profound biventricular failure systematically with ventricular assist devices (VADs) and to analyze the factors that affect prognoses for this condition. Anoxic arrest was induced in ten goats by aortic cross-clamping under normothermic conditions (38.5 degrees C) for 30 (n = 3), 45 (n = 1), and 60 (n = 6) minutes. A left ventricular assist device (LVAD) was implanted in eight animals, and a biventricular assist device (BVAD) was used in two. Three goats--two of which had undergone anoxic arrest for 30 minutes and one for 60 minutes--whose right atrial pressure (RAP) was approximately 18 mm Hg during the acute stage, recovered in two to three weeks, and the pumps were successfully removed. Pathological findings in these animals showed scattered areas of surviving myocardium, with connective tissue replacing the degenerated myocardium. The remaining five LVAD goats required higher RAPs to maintain circulation and died from various causes. Maintaining circulation without volume loading, even in the presence of arrhythmias, was easier with the BVAD. One BVAD animal that underwent 45 minutes of anoxic arrest recovered from right ventricular failure, and the right pump was removed. The second goat (anoxic arrest, 60 min) on the BVAD failed to recover. Autopsy of the myocardium revealed a thin ventricular wall. Our studies show that the use of VADs allows time for a failing heart to recover, but the potential for healing is affected by the severity of myocardial damage prior to VAD application.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Treatment of acute myocardial infarction with cardiogenic shock using left ventricular assist device.

We have treated ten cardiogenic shock patients after acute myocardial infarction (AMI) with a left ventricular assist device (LVAD). These patients were later divided into three groups: the first group with ventricular septal perforation, the second with aorto-coronary bypass grafting (ACBG) before LVAD implantation and the third group without ACBG. LVAD maintained the systemic circulation in each group, and cardiac function recovered enough to remove LVAD in 70% of the total patients. Two of three patients in the first group were discharged from hospital. Two weaned cases in the second group died of multiple organ failure and one was discharged, and hemorrhagic necrosis was seen in the bypassed area of the myocardium. One patient of the third group could not be weaned from LVAD because of respiratory failure though his heart function began to recover. Another case in the third group underwent bypass grafting after removal of LVAD. However ACBG surgery should be done very carefully because a patient in shock is occasionally intolerant to major surgery. In all groups, the major cause of death was multiple organ failure which was probably caused by the prolonged low output condition prior to LVAD application. In the light of this experience, it appears that LVAD should be applied before irreversible damage occurs to major organs, including the heart itself. To ensure the timely application of LVAD, some way must be found to introduce systematic application of LVAD into the normal course of AMI treatment.

Aged↗
PubMed1988

Endocrine profiles and embryo quality in superovulated Japanese Black cattle.

The relationships between plasma concentrations of progesterone (P4), estradiol-17beta (E2) and lutenizing hormone (LH) and embryo yield and quality were examined in 40 superovulated Japanese Black cattle. The results indicated that the ovarian function, especially the function of corpus luteum on the first treatment day, is an important factor for reliable superovulation in cattle. The levels of plasma E2 and LH at estrus were related to embryo yield and quality.

Journal Article↗
PubMed1988

Extrarenal role of aldosterone in the regulation of blood pressure.

To assess the hypothesis that aldosterone may have direct vasoconstrictive action, the acute effects of canrenoate potassium (Soldactone, S), an aldosterone antagonist, on hemodynamics and hormonal responses were determined before and after the intravenous administration of 2 mg/kg S in 11 patients with primary aldosteronism (PA), 9 patients with essential hypertension (EH), and 5 patients with renovascular hypertension (RVH). S caused a significant -12 +/- 2 mm Hg decrease in MBP in PA, -5 +/- 2 mm Hg in EH, and -4 +/- 1 mm Hg in RVH. Reduction in MBP was significantly higher in PA than in the others and there was a negative correlation between changes in MBP and basal PAC. The cardiac index did not change throughout the study in all groups, which led to a significant reduction in total peripheral resistance index (TPRI) in PA but not in the others. There was a significant correlation between changes in MBP and TPRI (r = 0.82, p less than 0.01). PRA did not change throughout the study, but PAC and cortisol were significantly elevated. There were no correlations between changes in MBP and hormonal responses. In conclusion, S resulted in a significant reduction of MBP mediated by a significant reduction of TPRI. These results suggest that aldosterone may have direct vasoconstrictive action and this extrarenal effect of aldosterone may be involved in the regulation of blood pressure.

Adult↗
PubMed1987

Seasonal changes in inhibin activity in seminal plasma and serum concentrations of FSH, LH and testosterone in the male goat (Capra hircus).

Inhibin activity in goat seminal plasma was measured by in vitro assay throughout successive 9 months and its relationship with the serum FSH, LH and testosterone concentrations was investigated. Total inhibin activity (TIA) in seminal plasma gradually increased from spring to summer, reduced in autumn (P<0.05) and recovered toward winter (P<0.05). Serum FSH and LH reached a peak in mid-summer (P<0.01) and returned to the low levels in autumn. Serum testosterone also increased in mid-summer and kept the high levels until the early winter (P<0.05). Some positive correlation was found in monthly levels between seminal TIA and serum FSH (r=0.305; P<0.05). Results suggest that the summer increase of inhibin activity in seminal plasma relates with the mid-summer rise of serum FSH levels in the male goat.

Journal Article↗
PubMed1985

Mechanical stability of elastomeric polymers for blood pump applications.

As a series of studies on the mechanical properties of materials used in cardiac prostheses, static and dynamic characteristics and stability of five kinds of elastomeric polymers have been studied by uniaxial tensile and fatigue tests in air at room temperature and in saline solution at 37 degrees C. Of all materials tested in this study, Texin MD85A, a segmented polyether polyurethane, has the lowest flexibility under static and dynamic conditions, with relatively high strength. Hexsyn, a polyolefin rubber, is highly flexible with little stress relaxation. However, this material has very low tensile strength and short elongation, and shows unstable change in the elastic modulus during cyclic deformation. Avcothane 51, a copolymer of polyurethane and silicon, has unstable mechanical properties and gradually stiffens upon cyclic deformation. On the other hand, Biomer, a segmented polyether polyurethane, has high flexibility and shows the most stable behavior during cyclic deformation regardless of test environment. Toyobo TM5, a similar segmented polyurethane to Biomer, has higher strength and ductility than Biomer, although its static and dynamic flexibility are slightly worse and less stable than those of Biomer. These results indicate that Biomer and Toyobo TM5 are more suitable for flexible components of cardiac prostheses.

Air↗
PubMed1985

Effects of implantation on the mechanical properties of the polyurethane diaphragm of left ventricular assist devices.

Tensile properties of blood pump diaphragms made from a segmented polyether polyurethane (Toyobo TM5) were studied after implanting in goats for variable periods of time up to 72 days. The implantation decreased the tensile strength and ultimate elongation at break, while the elastic modulus increased very slightly. These changes in the strength and ductility were primarily caused by the contact of material with blood rather than by the mechanical fatigue of material. Mechanical stability was greatly improved by removing residual oligomers from the material by a refining procedure. The refined polyurethane has characteristics favourable for blood pump applications.

Animals↗