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Biomedical subjects

K Sakai

Publications and source records attributed to K Sakai.

At least 703 records · Page 39Linked to original sources
PubMed1993

Factor in urinary extracts from pregnant women that inhibit mouse oocyte maturation in vitro.

Mouse oocyte maturation inhibitory factors, on the basis of inhibitory activity of spontaneous germinal vesicle breakdown (GVBD) of denuded mouse oocytes in culture, were extracted and partially purified by reversed-phase resin adsorption and Sephadex G-100 and G-50 column chromatographies from the urine of pregnant women. Denuded oocytes obtained from ovaries of ICR mice underwent spontaneous GVBD by cultivation for 3 h in modified Krebs-Ringer's buffered solution, while this spontaneous GVBD was found to be inhibited by adding the final preparation (U-D-4) of urine. The inhibition was dose dependent, ranging from 0.6 to 10 micrograms protein/ml medium. Oocytes treated with U-D-4 and resuspended in control medium resumed GVBD. The molecular mass of U-D-4 was estimated to be less than 2,000 Da with gel filtration. Ether treatment failed to extract inhibitory factor(s) from U-D-4 and pepsin treatment inactivated U-D-4, indicating that inhibitory factor(s) in U-D-4 are peptide-like substances. The inhibitory effect of U-D-4 on spontaneous GVBD was partially reversed in the presence of naloxone, a potent opioid antagonist. U-D-4s obtained from urine samples of pregnant women, nonpregnant women, and men showed the inhibitory effect on spontaneous GVBD; however, the activity of U-D-4 obtained from pregnancy urine was significantly more potent than those of the other urine samples.

Animals↗
PubMed1993

Inhibition of glucose absorption by phlorizin affects intestinal functions in rats.

BACKGROUND: To investigate the mechanism of regulation of intestinal disaccharidase activity and glucose absorption, the effect of dietary intake of phlorizin, a potent and specific inhibitor of intestinal glucose transport, on intestinal disaccharidase activity and Na(+)-dependent glucose transporter was examined in rats. METHODS: Jejunal disaccharidase activity and the number of Na(+)-dependent glucose transporters were determined in rats maintained on a low-starch diet, a high-starch diet, or low-starch diets containing various amounts of phlorizin (0.1%-0.9% wt/wt). RESULTS: Jejunal disaccharidase activity increased in a dose- and time-dependent manner. Stimulation of jejunal disaccharidase activity only occurred when phlorizin was added to starch-containing diets, not when it was added to a carbohydrate-free diet. Addition of the same amount of phloretin and glucose (constituents of phlorizin), to the diet failed to increase disaccharidase activity. The maximum binding of phlorizin to brush border membrane vesicles was increased in the rats fed phlorizin, whereas the dissociation constant remained unchanged, suggesting an increase of glucose transporter expression. CONCLUSIONS: Dietary phlorizin increased the jejunal disaccharidase activity and Na(+)-dependent glucose transporter expression. The trigger for these changes may have been due to an increased luminal glucose content.

Administration, Oral↗
PubMed1993

Memory and imagery in the temporal lobe.

Experimental and clinical studies in primates indicate that visual information is stored and retrieved by interactions between the temporal association area and the medial temporal lobe structures. Recent findings from single-neuron recordings have provided new evidence that perceptual aspects of the temporal neocortex are closely related to its memory function based on association. They further suggest that imagery is also implemented by the same neural mechanism that subserves memory retrieval.

Animals↗
PubMed1993

SPECT imaging in a case of primary respiratory tract amyloidosis.

SPECT findings in a very rare case of primary amyloidosis localized in the laryngotracheobronchial area are reported. SPECT using Tc-99m PYP revealed widespread uptake in the larynx and the entire tracheobronchial tree up to the subsegmental divisions; the areas corresponded to diffuse thickening and calcification of the walls on CT. SPECT using Ga-67 citrate also showed marked uptake in the same area, consistent with the findings shown by SPECT using Tc-99m PYP.

Adult↗
PubMed1993

Vascularized osteochondral allografts in an immunosuppressed rat model: graft modulation and host immune tolerance.

The effects of 4 weeks of cyclosporin A (7 mg/kg per day) (CyA) on the survival of vascularized osteochondral grafts between rat strains [DA (donor) and Lewis (recipient)] and the presence and significance of host immune tolerance and graft antigen modulation after cessation of immunosuppression have been examined. Isografts (n = 12) survived without apparent abnormality for 8 weeks but showed signs of wasting after longer periods; unprotected allografts (n = 5) were rejected within 2 weeks. After 4 weeks of CyA, allografts remained healthy for at least 12 weeks but then deteriorated (n = 40). Antigen modulation was examined by graft removal at various intervals after cessation of CyA and reimplantation into a naive recipient (n = 14). All were rejected rapidly. Host tolerance was examined by graft removal at various periods after cessation of CyA and reimplantation of a fresh allograft (n = 15). Some of the second grafts survived at least 4 weeks without immunosuppression. The findings indicate development of incomplete host tolerance but no antigenic modulation of the graft.

Animals↗
PubMed1993

Reinnervated free muscle transplantation for extremity reconstruction.

Reinnervated free muscle transplantation was used to rehabilitate severely impaired extremities in patients with brachial plexus palsy and for functional limb salvage in cases of traumatic muscle loss or radical excision of a malignant soft-tissue tumor. Fifty-eight reinnervated free muscle transplantations were implanted in 46 patients. Twenty-four patients had simultaneous reconstruction of two functions, such as finger and elbow flexion lost to brachial plexus palsy; 12 patients underwent double muscle transplantation; 15 patients received free muscle transplants for limb salvage after tumor excision in an extremity; 6 transplants replaced traumatic muscle loss; and 1 was used for reconstruction of finger flexion after poliomyelitis. Twenty-six latissimus dorsi, 25 gracilis, and 7 rectus femoris muscles were used as donors. All muscles survived. The postoperative follow-up ranged from 18 months to 4 years. The speed and extent of reinnervation of the transplanted muscle depended on the choice of recipient nerve, the patient's age, and the occurrence of postoperative vascular complications. Neurotization by the spinal accessory nerve or the posterior interosseous nerve resulted in the most rapid recovery. The administration of postoperative chemotherapy did not delay recovery of function. Free muscle transplantation is consistently successful and provides a functional extremity in severely handicapped patients.

Adolescent↗
PubMed1993

Xylosylation of Phenolic Hydroxyl Groups of the Monomeric Lignin Model Compounds 4-Methylguaiacol and Vanillyl Alcohol by Coriolus versicolor.

When 4-methylguaiacol (MeG), a phenolic lignin model compound, was added to a culture that was inoculated with Coriolus versicolor, it was bioconverted into 2-methoxy-4-methylphenyl beta-d-xyloside (MeG-Xyl). The phenolic hydroxyl group of vanillyl alcohol was much more extensively xylosylated than the alcoholic hydroxyl group. When a mixture of MeG and commercial UDP-xylose was incubated with cell extracts of mycelia, transformation of UDP-xylose into MeG-Xyl was observed. This result suggested that UDP-xylosyltransferase was involved in the xylosylation of phenolic hydroxyl groups of lignin model compounds.

Journal Article↗
PubMed1993

Neuropathological studies of the spinal cord in early stage HTLV-I-associated myelopathy (HAM).

Necropsy findings for a patient with HTLV-I-associated myelopathy (HAM) of 9 months clinical duration are reported. Loss of myelin sheaths and axons together with perivascular lymphocytic infiltration was seen in the lateral and posterior columns of the spinal cord from the cervical to the lumbar region where vacuolar changes caused by the splitting of myelin sheaths were prominent. Immunohistochemical analyses revealed CD8+ cytotoxic T cell infiltration predominated in the absence of HTLV-I core protein antigen bearing-cells in the brain and spinal cord. Myelin sheath damage and predominant CD8+ cytotoxic T cell infiltration are thought to be the main neuropathological findings in the spinal cord in early stage HAM.

Aged↗
PubMed1993

The interval between the positive peak of premyoclonus spike and the onset of myoclonus is shorter than the cortical latency in cortical myoclonus.

In 6 patients with cortical myoclonus, the intervals between the positive peak of the premyoclonus cortical spike and the onset of the myoclonic jerk [interval (Sp-Mcl)] were precisely measured by the computer-assisted jerk-locked averaging method. The intervals (Sp-Mcl) were 13.0-15.8 ms for the abductor pollicis brevis, 8.0-10.4 ms for the extensor digitorum communis and 5.5 ms for the biceps brachii, respectively. These were apparently shorter than the normal latencies of the responses elicited by transcranial cortical stimulation. The difference between the interval (Sp-Mcl) and the spinal latency was -0.8 to 3.5 ms, which was not long enough for the time required for the descending volleys going down from the cortex to the spinal cord. We have concluded that the motor cortex is activated before the positive peak of the premyoclonus spike in cortical myoclonus.

Adult↗
PubMed1993

Intra-arterial infusion of insulin attenuates vasoreactivity in human forearm.

Hyperinsulinemia may contribute to the development of hypertension. The aim of the present study was to determine whether hyperinsulinemia modulates vascular reactivity to phenylephrine or angiotensin II. In 10 young, healthy volunteers, the left brachial artery was cannulated for drug infusion and direct measurements of arterial pressure. We measured forearm blood flow by a strain-gauge plethysmograph while infusing phenylephrine (0.2, 0.8, and 2.4 micrograms/min) and angiotensin II (5, 10, and 20 ng/min) locally into the brachial artery before and during simultaneous intra-arterial infusion of insulin (0.15 mU/kg per minute). Forearm vascular resistance was calculated from directly measured arterial pressure and forearm blood flow. Intra-arterial infusion of insulin raised the local plasma insulin level from 10.3 +/- 1.4 to 133.3 +/- 21.1 microU/mL (P < .01) and did not change blood glucose level in the venous effluents of the forearm. Insulin infusion slightly but not significantly increased basal forearm blood flow (4.6 +/- 1.5 to 5.5 +/- 0.9 mL/min per 100 milliliters, NS) and decreased forearm vascular resistance (22.1 +/- 2.1 to 20.3 +/- 2.8 U, NS). Phenylephrine and angiotensin II increased forearm vascular resistance dose dependently before and during simultaneous insulin infusion (P < .01 for both). Intra-arterial infusion of insulin attenuated vascular reactivity to phenylephrine (P < .01) and angiotensin II (P < .01). None of these drugs changed blood pressure or heart rate. Our results suggest that hyperinsulinemia attenuates vascular reactivity in the forearm resistance vessels in healthy humans.

Adult↗
PubMed1993

Regional cerebral blood flow measured with N-isopropyl-p-[123I]iodoamphetamine and its redistribution in ischemic cerebrovascular disease.

BACKGROUND AND PURPOSE: The relation between the redistribution phenomenon and regional cerebral blood flow and its clinical significance were investigated in stroke patients. METHODS: Single-photon emission computed tomography studies using N-isopropyl-p-[123I]iodoamphetamine were performed on 16 patients (26 to 77 years old) with chronic infarction and 10 age-matched normal control subjects. Regional cerebral blood flow was quantitatively measured by a microsphere model, and the redistribution on delayed images was analyzed in ischemic lesions. RESULTS: Supratentorial mean cerebral blood flow and the ratio of gray matter to white matter in normal subjects were 52.7 +/- 5.0 mL/100 g per minute and 2.34, respectively. Low-activity areas of ischemic lesions on early images were classified into two abnormal zones, an infarct area and a peri-infarct area. These regions were characterized by regional blood flow averaging 9 to 20 mL/100 g per minute and 22 to 41 mL/100 g per minute, respectively. Redistribution, which was minimally present in the infarct area, was markedly enhanced in the peri-infarct area. After bypass surgery, we observed a significant increase of blood flow (+22%) in the peri-infarct area. CONCLUSIONS: The data indicate that the redistribution phenomenon depends on the maintenance of a minimal blood flow that would sustain cellular function and that this phenomenon is useful to evaluate bypass surgery in patients with chronic infarction.

Adult↗
PubMed1993

Swelling controlled zero order and sigmoidal drug release from thermo-responsive poly(N-isopropylacrylamide-co-butyl methacrylate) hydrogel.

Thermo-responsive hydrogels of poly(N-isopropylacrylamide-co-butyl methacrylate) (poly-(IPAAm-co-BMA)) are capable of swelling-deswelling changes in response to external temperature. As poly(IPAAm-co-BMA) gels swell larger at a lower temperature, the degree and rate of the swelling could be controlled by temperature without altering the chemical structure. Therefore, drug release profiles were remarkably changed by alternation of temperature. The release profiles of indomethacin from poly(IPAAm-co-BMA) were observed to be zero-order at 20 degrees C. This release profile was explained in terms of a Case-II diffusion mechanism; which indicates relaxation of polymer chains with swelling was rate-determining. In the case of 10 degrees C, release demonstrated a sigmoidal profile. The acceleration of drug release was due to a rapid increase in swelling with disappearance of the glassy core which had constrained swelling. The regulation of the water-uptake process by changing external temperature remarkably affected drug release and resulted in several different release profiles.

Acrylic Resins↗
PubMed1993

Electron immunohistochemical localization in rat bronchiolar epithelial cells of tryptase Clara, which determines the pneumotropism and pathogenicity of Sendai virus and influenza virus.

The intracellular localization in rat bronchiolar epithelial cells of a novel trypsin-like protease named tryptase Clara, a possible activator of inactive viral fusion glycoprotein of influenza A and wild-type Sendai virus in the respiratory tract, was examined by electron microscopy. In thin sections embedded in LR White, gold particles indicating immunoreactivity of tryptase Clara were detected specifically in secretory granules of Clara cells. No immunoreactivity was detected in bronchiolar ciliated cells, alveolar cells including epithelial Type I and II cells, or alveolar macrophages. Some granules enveloped in a thin membrane and labeled intensely with immunogold particles were seen protruding from peripheral and submembrane regions and a few were observed free in the airway lumen. Scanning electron microscopy also revealed smooth droplets along the main body of Clara cells. These data suggest that tryptase Clara is secreted into the bronchiolar lumen. These findings are the first to show the subcellular localization of tryptase Clara in rat bronchioles and suggest the site of proteolytic activation of the progeny of enveloped pneumotropic viruses, such as Sendai virus and influenza virus.

Animals↗
PubMed1993

Desmoyokin, a 680 kDa keratinocyte plasma membrane-associated protein, is homologous to the protein encoded by human gene AHNAK.

We have obtained a monoclonal antibody (33A-3D) that specifically recognize desmoyokin, a 680 kDa desmosomal plaque protein that is well characterized in bovine muzzle epidermis. A cDNA clone (DY6, 3693 bp) was isolated by immunoscreening a mouse keratinocyte expression library with 33A-3D, and it was confirmed that DY6 has a partial coding sequence for desmoyokin. DY6 consists of highly homologous repeats about 128 residues long. Furthermore, the 128-residue repeats exhibit a quasi seven-residue substructure, which we believe will adopt an antiparallel beta-sheet structure. Surprisingly, the amino acid sequence showed a significant homology with AHNAK, a newly identified human gene encoding a 700 kDa protein, which was suggested to be down-regulated in neuroblastoma. From its extensive homology, the similarity in both size and structure, and the identical patterns on Southern blot analysis of genomic DNAs, desmoyokin and AHNAK protein are thought to be identical. Although the desmoyokin/AHNAK protein is detected in a variety of cell types at both protein and mRNA levels, its distribution in keratinocytes (associated closely with cell membrane) is quite different from that in cells other than keratinocytes (distributed diffusely in the cytoplasm). These findings suggest that the desmoyokin/AHNAK protein is a ubiquitous molecule with a unique structure and appears to have different distributions (and probably different functions) among different cells.

Amino Acid Sequence↗
PubMed1993

Alteration of hepatic DNA synthesis in rats treated with N-nitrosodimethylamine during early stages of copper deficiency.

The main aim of this research was to clarify that nutritional dietary copper may participate in the protective action against hepatocarcinogenesis in rats by N-nitrosodimethylamine (NDMA). The copper concentrations in serum and liver from 2 to 8d after rats were first fed a copper deficient diet (copper, 0.6 ppm) decreased significantly compared to those of pair-fed rats (copper in a control diet, 7 ppm). The subcellular distribution of copper in the liver at 5d after feeding of a copper deficient diet began was measured and the copper concentrations in soluble and nuclear fractions decreased at a similar rate in copper deficient rats treated with or without NDMA, compared to those of pair-fed rats. The incorporation of [3H]thymidine into rat liver DNA at 48 h after treatment with NDMA markedly increased under the experimental conditions used. By giving rats a copper deficient diet for a few days the increased incorporation of [3H]thymidine into liver DNA of rats treated with NDMA was enhanced compared to that of pair-fed rats treated with NDMA. The activity of thymidine kinase in liver of copper deficient rats treated with NDMA was also found to increase significantly compared to that of pair-fed rats treated with NDMA.

Animals↗
PubMed1993

Purification and characterization of novel N-acyl-D-aspartate amidohydrolase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6.

Alcaligenes xylosoxydans subsp. xylosoxydans A-6 (Alcaligenes A-6) produced N-acyl-D-aspartate amidohydrolase (D-AAase) in the presence of N-acetyl-D-aspartate as an inducer. The enzyme was purified to homogeneity. The enzyme had a molecular mass of 56 kDa and was shown by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) to be a monomer. The isoelectric point was 4.8. The enzyme had maximal activity at pH 7.5 to 8.0 and 50 degrees C, and was stable at pH 8.0 and up to 45 degrees C. N-Formyl (Km = 12.5 mM), N-acetyl (Km = 2.52 mM), N-propionyl (Km = 0.194 mM), N-butyryl (Km = 0.033 mM), and N-glycyl (Km = 1.11 mM) derivatives of D-aspartate were hydrolyzed, but N-carbobenzoyl-D-aspartate, N-acetyl-L-aspartate, and N-acetyl-D-glutamate were not substrates. The enzyme was inhibited by both divalent cations (Hg2+, Ni2+, Cu2+) and thiol reagents (N-ethylmaleimide, iodoacetic acid, dithiothreitol, and p-chloromercuribenzoic acid). The N-terminal amino acid sequence and amino acid composition were analyzed.

Alcaligenes↗
PubMed1993

Production, purification, and characterization of D-aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6.

The best inducers for D-aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6 (Alcaligenes A-6) were a poor substrate, N-acetyl-gamma-methyl-D-leucine, and an inhibitor, N-acetyl-D-alloisoleucine. The enzyme has been homogeneously purified. The molecular weight of the native enzyme was estimated to be 58,000 by gel filtration. A subunit molecular weight of 52,000 was measured by SDS-PAGE, indicating that the native protein is a monomer. The isoelectric point was 5.2. The enzyme was specific to the D-isomer and hydrolyzed N-acetyl derivatives of D-leucine, D-phenylalanine, D-norleucine, D-methionine, and D-valine, and also N-formyl, N-butyryl, and N-propionyl derivatives of D-leucine. The Km for N-acetyl-D-leucine was 9.8 mM. The optimum pH and temperature were 7.0 and 50 degrees C, respectively. The stabilities of pH and temperature were 8.1 and 40 degrees C. D-Aminoacylases from three species of the genus Alcaligenes differ in inducer and substrate specificities, but are similar with respect to molecular weight and N-terminal amino acid sequence.

Alcaligenes↗