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Biomedical subjects

Y Shigematsu

Publications and source records attributed to Y Shigematsu.

At least 163 records · Page 9Linked to original sources
PubMed1989

Branched-chain alpha-ketoacids and related acids in thiamin-deprived rats.

We showed elevated plasma levels of branched-chain amino acids, alpha-ketoacids, alpha-hydroxyacids in thiamin-deprived rats, which had decreased liver thiamin levels (2.4% of control) after 4 weeks of feeding of thiamin-deficient diet. The ratios of mean levels of these acids in thiamin-deficient rats to those in control rats were as follows: total branched-chain amino acids 1.6; total branched-chain alpha-ketoacids 2.7; total branched-chain alpha-hydroxyacids 3.6; pyruvic acid 1.6. The plasma level of total branched-chain alpha-hydroxyacids was correlated to liver thiamin concentration (r = -0.67, p less than 0.01), but those of the other two acids were not correlated. Although the increased levels of branched-chain acids in thiamin-deprived rats were less remarkable than those of ill patients with maple syrup urine disease, they reflect the reportedly decreased branched-chain alpha-ketoacid dehydrogenase activities (about 40% of control), and we discussed whether the toxic effects of individual branched-chain acid could be demonstrated by its administration to the thiamin-deprived rats.

Amino Acids, Branched-Chain↗
PubMed1989

[Development of a system for monitoring the production of leukotriene B4, C4, D4 and E4 in whole blood of pediatric asthmatic patients].

We have developed a new method using a computerized photodiode-array spectrophotometer (CPAS), to characterize the biosynthesis and the inhibition of leukotriene (LT) B4, C4, D4 and E4 in calcium ionophore (Ca-I)-stimulated whole blood. The results obtained were as follows: 1. The use of CPAS enabled us to identify and measure LTs from 2 ml volume of Ca-I stimulated whole blood as well as to check the purity of LTs, without any use of radioimmunoassay or bioassay. 2. LTC4 produced in whole blood was almost completely converted to LTE4 after 80 min incubation, and at this time both the production of LTE4 and LTB4 reached a plateau and remained constant thereafter. 3. Azelastine added in vitro caused a dose-dependent inhibition of Ca-I stimulated LTB4 and LTE4 production with an IC50 of 10 microM.

Adolescent↗
PubMed1988

Selection of an atrazine-resistant tobacco cell line having a mutant psbA gene.

A mutant cell line that shows high resistance to the photosynthesis-inhibiting herbicide atrazine was selected from cultured photomixotrophic Nicotiana tabacum cv. Samsun NN cells by repeated exposure to toxic levels of the herbicide. This resistance was confirmed by measurements of Hill reaction activity in isolated thylakoid membranes. Nucleotide sequencing revealed that the resistant cell line had a point mutation in its chloroplast psbA gene. The 264th codon, AGT (serine) was changed to ACT (threonine) in this mutant. This new type of mutation also conferred moderate cross-resistance to diuron and subsequently was stable in the absence of continued selection pressure.

Amino Acid Sequence↗
PubMed1988

Significance of systolic time intervals in predicting prognosis of primary pulmonary hypertension.

To elucidate the characteristics of left ventricular (LV) function and LV shape in primary pulmonary hypertension (PPH), systolic time intervals (STIs) and two-dimensional echocardiograms in seven patients with PPH were studied and compared with those of 12 normal controls. Serial changes in STIs were also analyzed as to clinical outcomes. All patients were females and aged from 14 to 53 years. The follow-up period was 50 +/- 30 months, and five patients died of cardiac causes during the study period. The patients with PPH had a significantly prolonged pre-ejection period (PEP) and PEP index. Left ventricular ejection time (LVET) and the LVET index in the PPH group, at the time of diagnosis, showed no statistical differences compared with those of the controls, but three patients with PPH showed a marked shortening of LVET. A significant decrease in the LVET/PEP ratio was observed in patients with PPH. Left ventricular end-diastolic dimension (EDD) and end-systolic dimension (ESD) were significantly less in patients with PPH than in the controls. No difference in percent fractional shortening of the left ventricle and the mean velocity of circumferential fiber shortening was observed. The degree of LVET shortening correlated with the decrease in EDD (r = 0.97). During follow-up, marked shortening of the LVET index, below approximately 350 msec, was observed immediately before death or clinical deterioration. From these results, we conclude that in PPH, (1) left ventricular function is impaired due to reduced volume of the left ventricle during diastole, reflecting a shortening of LVET and the LVET index, and (2) analysis of serial LVET indexes is useful for predicting the prognosis.

Adolescent↗
PubMed1987

Enhanced blood pressure response to isometric handgrip exercise in patients with essential hypertension: effects of propranolol and prazosin.

To elucidate whether a difference exists in blood pressure (BP) elevation during isometric handgrip exercise (IHG) between essential hypertensives (EHT) and normotensives (NT), IHG was carried out in 12 NT and 46 EHT under constant sodium intake using a new instrument. The acute effects of propranolol and prazosin on IHG were also examined in EHT. The change in systolic BP (delta SBP) during IHG in EHT, delta SBP = 61 +/- 21 mmHg, was markedly greater than that in NT, delta SBP = 28 +/- 4 mmHg. Among EHT, delta BP increased with increasing severity of hypertension. Neither the changes in plasma norepinephrine nor in epinephrine during IHG showed significant differences between EHT and NT. The pressor response during IHG could not be suppressed by propranolol, but about 30% suppression of BP was observed during IHG with prazosin. It is concluded from these findings that EHT have an exaggerated BP response to IHG that is due to increased post-junctional alpha 1-adrenoceptors.

Adult↗
PubMed1987

Failure to induce puberty in a man with X-linked congenital adrenal hypoplasia and hypogonadotropic hypogonadism by pulsatile administration of low-dose gonadotropin-releasing hormone.

To elucidate the mechanism of hypogonadotropic hypogonadism in a patient with X-linked congenital adrenal hypoplasia, we studied the effects on serum LH and FSH of repeated iv administration of GnRH (400 micrograms, over 2 h, once a day, for 14 consecutive days), pulsatile sc administration of GnRH (5 micrograms every 90 min during days 1 approximately 56, 10 micrograms every 90 min during days 57 approximately 91) and an iv bolus injection of 10 mg of naloxone. The repeated administration of GnRH restored the hyporesponsiveness of serum FSH and increased serum testosterone level from less than 1.0 to 1.7 nmol/l, but the impaired LH response to the standard GnRH test was not improved. The pulsatile administration of GnRH for 91 consecutive days did not induce a clinical or a biochemical change of puberty. Serum testosterone remained undetectable less than 1.0 nmol/l, the hyporesponsiveness of serum LH was not improved, but basal FSH level was significantly increased and the impaired FSH response to the standard GnRH test was slightly improved. Naloxone had no effect on serum LH or FSH before or during the pulsatile administration. We conclude that hypogonadotropic hypogonadism in our patient is due to the pituitary dysfunction and that the endogenous opioid peptides may not play a role in the mechanism of inhibited gonadotropin secretions.

Adolescent↗
PubMed1986

Leukotriene B4 and 20-OH-LTB4 in purulent peritoneal exudates demonstrated by GC-MS.

Inflammatory peritoneal exudates from 11 patients with purulent peritonitis or non-perforative appendicitis were analyzed by gas chromatography mass spectrometry (GC-MS) for their content of 5S, 12R-dihydroxy-6,14-cis-8,10-trans-eicosatetraenoic acid (LTB4) and its omega-oxidized catabolite, 5S,12R,20-trihydroxy-6,8,10,14-eicosatetraenoic acid (20-OH-LTB4). Eleven samples of peritoneal exudates were examined. LTB4 and 20-OH-LTB4 were demonstrated only in the samples from patients with purulent peritonitis. LTB4 was detected in 4 samples, and 20-OH-LTB4 was detected in 6 samples by GC-MS with selected ion monitoring. In addition, a nearly full spectrum corresponding to that of synthetic 20-OH-LTB4 was obtained with 3 samples. Neither LTB4 nor 20-OH-LTB4 were detected in samples from patients with non-perforative appendicitis. LTB4 or 20-OH-LTB4 may be related to the pathophysiological mechanism of purulent inflammations.

Appendicitis↗
PubMed1986

Leukotriene B4 biosynthesis in polymorphonuclear leukocytes from blood of umbilical cord, infants, children, and adults.

The biosynthesis of 5(S), 12(R)-dihydroxy-6,14-cis-8,10-trans-eicosatetraenoic acid, leukotriene B4, by human polymorphonuclear leukocytes was examined in relation to age. The leukotriene B4 production by polymorphonuclear leukocytes from umbilical cords, infants, and adults was assayed using high pressure liquid chromatography. The specificity of the leukotriene B4 assay was examined by gas chromatography mass spectrometry. Polymorphonuclear leukocytes from 10 umbilical cords, 24 infants and children, and 10 adults were examined for their ability to synthesize leukotriene B4, in vitro after stimulation by the ionophore A23187 or platelet-activating factor. Among the infants and children, there was a slight age-dependent increase of leukotriene B4 production by polymorphonuclear leukocytes in response to ionophore A23187, but it was not statistically significant. Leukotriene B4 production by polymorphonuclear leukocytes in the umbilical cords and infants was not significantly lower than that of polymorphonuclear leukocytes in adults in response to both ionophore A23187 and platelet-activating factor under our experimental conditions.

Adolescent↗
PubMed1985

Latency of horizontal cell response in the carp retina.

The response latency of horizontal cells in the carp retina was investigated by means of the stimulus-response crosscorrelation using a randomly modulated light of various wavelengths. R/G type cells produced two response components with some difference in latency; short-latency hyperpolarising response to green light and long-latency depolarising one to red light. The latency difference could not be made smaller than 14 ms by increasing the intensity of test light. These results were reconciled with similar measurements under selective chromatic adaptation. The latency difference revealed here supports the current view of neural circuitry that accounts for spectral response characteristics of horizontal cell subtypes.

Adaptation, Ocular↗
PubMed1985

Difference in myocardial characteristics between hypertrophic cardiomyopathy and myocardial hypertrophy due to essential hypertension.

To investigate the qualitative difference in myocardial hypertrophy that exists between hypertrophic cardiomyopathy (HCM) and essential hypertension (HT), we measured the mean wall thickness (MWT), the early diastolic time intervals (IIA-MVO time: from the second heart sound to the point of mitral valve opening, MVO-O time: from MVO to the O point of apexcardiogram) and the MVO-O/IIA-MVO ratio. The MWT in HCM and HT was measured by biventriculogram and echocardiogram, respectively. The MWT showed no significant difference between HT (13.1 +/- 3.0 mm) and non-obstructive type of HCM (14.8 +/- 3.7), but the MWT in obstructive type (1.08 +/- 0.24) was significantly thinner than that in HT. As the MWT increased, both IIA-MVO and MVO-O time were prolonged in both groups. But the mode of prolongation was quite different. In HT, the prolongation of the IIA-MVO time was almost always greater than that of the MVO-O time. In HCM, the prolongation of the latter was greater than that of the former. The MVO-O/IIA-MVO ratio in HT was significantly less than that in normal subjects, but those in HCM were significantly greater. These findings suggest that the differences in the early diastolic time intervals between HCM and HT are not due to the magnitude of the left ventricular hypertrophy, but due to myocardial characteristics.

Adult↗
PubMed1985

The analysis of systolic and diastolic time intervals: a more sensitive non-invasive method in the assessment of left ventricular dysfunction in the patients with essential hypertension.

Time indices and volumetric parameters were investigated in patients with essential hypertension subdivided into three groups according to the WHO stage classification. The ratio of ejection time (ET) and pre-ejection period (PEP), ET/PEP remained within normal range in WHO-I but decreased significantly in WHO-II and reached extremely low values in WHO-III. ET did not change in WHO-I and WHO-II but became significantly reduced in WHO-III. Prolongation of PEP in WHO-II and WHO-III increased with progression of hypertensive stage. Isovolumic relaxation time (IRT) showed the same pattern as the prolongation of PEP; positive correlation between PEP and IRT was observed (r=0.55). On the other hand, significant changes of volumetric parameters were only observed in WHO-III. These results indicated that the time indices were a more sensitive parameter than the volumetric ones in the assessment of left ventricular dysfunction in the patients with essential hypertension.

Adult↗