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Biomedical subjects

M Umemoto

Publications and source records attributed to M Umemoto.

125 records · Page 7Linked to original sources
PubMed1984

In vitro study on contribution of oxidative metabolism of isolated rabbit heart mitochondria to myocardial reperfusion injury.

The present study was performed to clarify oxygen-induced damage following myocardial reperfusion, using three mitochondrial preparations from isolated rabbit hearts (nonischemic hearts and those subjected to 40 and 90 minutes of normothermic global ischemia). The viability of mitochondria was evaluated by adenosine triphosphate generation. The extent of mitochondrial injury produced by reactive oxygen metabolism was assessed by the intensity of hydroxyl radical signal detected with electron spin resonance spectroscopy and the reduction of coenzyme Q10 level. The greatest oxygen-induced injury was observed in 40-minute ischemic mitochondria exposed to pure oxygen. The use of superoxide dismutase and catalase satisfactorily prevented the oxygen-induced injury. Moreover, the net adenosine triphosphate generation of the 40-minute ischemic mitochondria was comparable to that of the nonischemic mitochondria without the enzymes. These results suggest that reperfusion of the ischemic myocardium with viable mitochondria is deleterious, because mitochondria are susceptible to injury resulting from oxidative metabolism, and that the use of superoxide dismutase, together with catalase, is beneficial for the restoration of cardiac function after ischemia.

Adenosine Triphosphate↗
PubMed1983

Studies on salivary gland ribonucleases. III. Purification and properties of three ribonucleases from bovine parotid gland.

Three alkaline ribonucleases [EC 3.1.4.22] were purified 4,500- to 7,850-fold from bovine parotid gland by repeated CM-Sephadex C-25 chromatography and Sephadex G-50 gel filtration, with a total recovery of about 33%. They were designated as RNase BP1, BP2, and BP3, based on their order of elution from a CM-Sephadex C-25 column. The molecular weights of these enzymes were estimated by gel electrophoresis to be 18,500, 18,000, and 14,000, respectively. These enzymes are very similar to RNase A in that they are inhibited by heparin, show preferential hydrolysis of C5'-O-P linkages adjacent to a cytosine nucleotide rather than a uracil nucleotide, and in their antigenic properties. Spermine was found to stimulate the activities of these enzymes; the degree of stimulation was in the order of RNase BP3 greater than BP2 greater than BP1. The stimulation by spermine is mainly due to the increased cleavage of C5'-O-P linkages adjacent to cytosine nucleotides. From the results of amino acid analysis, glycosidase digestion and amino-terminal sequencing, it was suggested that the differences in molecular weights of RNase BP1, BP2, and BP3 are due to the differences in carbohydrate contents. In addition, it was suggested that RNase BP3 is identical with RNase A.

Animals↗
PubMed1983

Immunopharmacologic studies of D-penicillamine-L-cysteine disulfide.

Effects of D-penicillamine-L-cysteine disulfide (P-C) on some immunological parameters were examined in normal and immunity-impaired mice and rats. P-C enhanced the DNA synthesis in concanavalin A-stimulated mouse spleen cell cultures in vitro. In vivo, administration of P-C produced either enhancement or depression of plaque forming cell (PFC) response and delayed type hypersensitivity (DTH) to sheep red blood cells (SRBC) in low responder mice to SRBC, depending on the dose of P-C. P-C restored the impaired PFC response in hydrocortisone-pretreated mice. The enhancing effect of P-C was not shown in high responder mice to SRBC, but an inhibiting effect was observed. P-C inhibited the suppressor cell induction on PFC response in mice immunized with a supraoptimum dose of antigen. In adjuvant arthritic rats, P-C induced severe arthritis by eliminating the suppressor cells regulating this disease process. The relevance of these findings and mode of action of D-penicillamine in rheumatoid arthritis is discussed.

Animals↗
PubMed1983

[Echocardiographic findings in 3 cases of mucopolysaccharidosis].

Mucopolysaccharidosis (MPS) has been shown to cause cardiac involvements. However, echocardiographic features of MPS were not well understood. We examined echocardiographic findings in three adult patients with MPS. The diagnosis was confirmed by measuring urinary acid mucopolysaccharide and alpha-L-iduronidase activity in the white blood cell and skin fibroblast. The age ranged from 29 to 54 years. Two patients were Scheie syndrome (MPS I-S) and one was suspected to be Maroteaux-Lamy syndrome (MPS VI). All patients had a systolic heart murmur suggestive of aortic stenosis, and one had an additional apical systolic murmur consistent with mitral regurgitation. The echocardiogram revealed the following findings; 1) an abnormal thickening of all aortic leaflets with reduced valve opening in all cases, 2) diffuse and marked thickening of the mitral leaflets, chordae and papillary muscles, no upward motion of the posterior mitral leaflet in spite of reduced E-F slope (13, 23 and 17 mm/sec, respectively), and slight narrowing of the mitral orifice, and 3) a slightly thickened and dilated left ventricle (IVS: 11, PW: 12, EDd: 58, and ESd 44 mm) in the case with Maroteaux-Lamy syndrome. The last finding was probably due to deposition of mucopolysaccharide in the myocardium, because the coronary arteriogram in this case did not demonstrate any significant lesions. The echocardiographic characteristics in our adult MPS cases were similar to those reported in infant or juvenile cases with Hurler syndrome (MPS 1-H) or Hunter syndrome (MPS II). However, our Maroteaux-Lamy patient may be the first case, in which myocardial involvement by mucopolysaccharide was suggested echocardiographically.

Adult↗
PubMed1981

Presynaptic alpha-adrenergic mediation of self-stimulation in locus coeruleus in rats treated neonatally with 6-hydroxydopamine.

Rats self-stimulating in the region of the locus coeruleus and treated neonatally with 6-hydroxydopamine (6-OHDA) injected bilaterally in the same region were tested for effects of adrenergic receptor blockers on a lever-pressing behavior to obtain the brain reward. The neonatally treated animals (16 microgram total dose, 8 microgram X 2) self-stimulated at abnormally high rates compared with controls. Yohimbine (5 mg/kg i.p.) and phentolamine (5 mg/kg) suppressed self-stimulation in controls and treated subjects. Phenoxybenzamine (10 mg/kg) reduced the response rate for the brain reward but did not abolish the behavior in the 6-OHDA-treated animals and had minor effects in controls. Propranolol (10 mg/kg) had no effects. The 6-OHDA subjects tested for the effects of D-amphetamine and L-amphetamine (0.5 mg/kg) showed facilitation of responding after the former but not after the latter. Self-stimulation in the 6-OHDA subjects was suppressed by treatment with alpha-methyl-p-tyrosine and pimozide. The significance of these findings is discussed in terms of the use of alpha-adrenoreceptor antagonists to separate the pre- from the post-synaptic action of released norepinephrine and in terms of the norepinephrine hypothesis of rewarding effects of brain stimulation in the dorsal pons.

Animals↗
PubMedDate not supplied

Regeneration of adult budgerigar's hair cells following acoustic trauma.

The functional and structural changes of hair cells of the adult budgerigar following acoustic trauma were examined using auditory brainstem response (ABR), and both scanning and transmission electron microscopy. Just after exposure to a 1,500-Hz pure tone at 120 dBSPL for 98 h, severe damages and disappearance of short hair cells were observed in the middle region of the basilar papilla. Fourteen days after the exposure, the threshold of ABR recovered to the level before the exposure, and normal short hair cells, which have synapses with nerve endings, were rearranged all over the damaged region of the basilar papilla. These results indicate that the hair cells of the adult budgerigar have capability to regenerate, and to restore the auditory perceptive function following acoustic trauma.

Animals↗
PubMedDate not supplied

Development of melanosomes and cytochemical observation of tyrosinase activity in the inner ear.

The ultrastructure and tyrosinase activity of melanocytes in the inner ear of pigmented guinea pigs were observed. Melanocytes/melanocyte-like cells were seen in the stria vascularis, the vestibular dark cell area and the endolymphatic sac. In the stria vascularis, melanosomes in several stages of maturation were seen in the cytoplasm of the intermediate cells and melanin-laden endosomes existed in the basal cells. Only the intermediate cells contained tyrosinase-positive cytoorganelles; Golgi sacs and neighboring small vesicles. Numerous melanocytes containing many melanosomes were observed under the epithelium of the vestibular dark cell area, and they showed tyrosinase activity. Melanocytes were seen in the endolymphatic sac, and they also showed tyrosinase activity. However, the epithelial cells of the endolymphatic sac, which had vacuoles containing melanin, did not show tyrosinase activity. Based on these findings, it can be said that (1) most of the intermediate cells of the stria vascularis must be melanocytes, (2) melanogenesis is vigorous in melanocytes of the inner ear, and (3) melanin in the epithelial cells of the endolymphatic sac is transferred in from melanocytes and is never synthesized in the epithelial cells.

Animals↗