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Biomedical subjects

K Nitta

Publications and source records attributed to K Nitta.

At least 235 records · Page 13Linked to original sources
PubMed1990

Renal and hemodynamic effects of endothelin in anesthetized dogs.

The effects of endothelin on systemic hemodynamics and renal functions were investigated in anesthetized dogs. Infusion of endothelin at a dose of 1 ng/kg/min decreased renal blood flow and increased renal vascular resistance and filtration fraction. Endothelin at doses higher than 10 ng/kg/min significantly decreased cardiac output, glomerular filtration rate, renal plasma flow, urine volume, and urinary sodium excretion. Mean arterial pressure showed a transient decrease at doses higher than 50 ng/kg/min. These results showed that endothelin in systemic administration has effects on renal functions as well as on systemic hemodynamics.

Anesthesia↗
PubMed1990

Amino acid sequence of a lectin from Japanese frog (Rana japonica) eggs.

The complete amino acid sequence and the location of disulfide bonds of a lectin from Japanese frog (Rana japonica) eggs, which specifically agglutinates transformed cells, are presented. The sequence was determined by analysis of peptides generated by digestion of the S-carboxyamidomethylated protein with Achromobacter protease I, or chymotrypsin, and by chemical cleavage with BNPS-skatole or cyanogen bromide. The lectin is a single-chain protein consisting of 111 residues, with a pyroglutamyl residue at the amino terminus. Four disulfide bonds link half-cystinyl residue 19 to 72, 34 to 82, 52 to 97, and 94 to 111. The sequence and the location of the disulfide bonds are highly homologous to those of bull frog (Rana catesbeiana) egg S-lectin. They are also homologous to human angiogenin, a tumor angiogenesis factor, and a family of pancreatic ribonucleases.

Amino Acid Sequence↗
PubMed1990

Lung lavage and surfactant replacement for hydrochloric acid aspiration in rabbits.

Hydrochloric acid (0.1 N, 5.0 ml.kg-1 in total) was administered intratracheally to 28 adult rabbits anesthetized with pentobarbital and mechanically ventilated with pure oxygen. When the PaO2 decreased to 14.1 +/- 2.8 kPa (mean +/- s.d.), the PaCO2 increased to 8.9 +/- 2.5 kPa, and the minute ventilation (VE) decreased to 51 +/- 8% of the baseline value, animals were divided into 4 groups. The deteriorated values did not improve in the non-treated (control) animals, whereas the animals treated with lung lavage and surfactant replacement showed a significant increase in PaO2 to 35.1 +/- 12.2 kPa, and maintained lower PaCO2 and larger VE than the controls. These parameters showed no significant improvement with surfactant replacement alone, and deteriorated further with lung lavage alone. The minimum surface tension (gamma min) of the edema fluid that accumulated in the airways after acid administration was 22.5 +/- 1.7 mN.m-1, and was not lowered by adding surfactant preparation (10 mg.ml-1) whose original gamma min was less than 2 mN.m-1. We concluded that surfactant inhibition by edema fluid was a cause of respiratory failure, and that lung lavage followed by surfactant replacement might be of therapeutic value for acid aspiration.

Animals↗
PubMed1990

Synthesis and antiviral activities of carbocyclic oxetanocin analogues.

9-Cyclobutyladenine (4a), cis- and trans-9-[3- (hydroxymethyl)cyclobutyl]adenine (4b) and 9-[3,3-bis(hydroxymethyl)cyclobutyl]adenine(4d) were prepared from the corresponding cyclobutylamine derivatives (1a, 1b and 1d). Guanine congeners (9a, cis- and trans-9b and 9d) and carbocyclic oxetanocin G (1',2'-trans-9f) were also prepared. Carbocyclic oxetanocin A(1',2'-trans-4f), the preparation of which we have already published, and G were found to be active against herpes simplex virus (type 1 and 2) in vitro, while cis-4b and cis-9b showed an in vitro antiretroviral activity against human immunodeficiency virus (type 1).

Adenine↗
PubMed1990

Inhibitory effects of flavonol glycosides on 12-O-tetradecanoylphorbol-13-acetate-induced tumor promotion.

The two-stage carcinogenesis by 7,12-dimethylbenz[a]anthracene and 12-O-tetradecanoylphorbol-13-acetate (TPA) in mice was inhibited by kaempferol and flavonol glycosides, whereas naringenin, a flavanone, had no effect. The induction of epidermal ornithine decarboxylase activity by TPA was also inhibited by kaempferol, whereas mauritianin, a kaempferol glycoside, failed to inhibit it. In addition, the effect of the flavonol glycosides on cell-mediated immunosuppression in the two-stage carcinogenesis, observed in terms of initiation after 14 weeks, was antagonized by mauritianin and myricitrin. Cell-mediated immunosuppression in the two-stage carcinogenesis was unaffected by kaempferol and naringenin. These results suggest that the inhibitory effects of flavonol glycosides may have been at least partly due to activation of immune responses against tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Comparative studies of carbohydrate-binding proteins from Xenopus laevis skin and eggs. Sugar-binding specificities and affinity purification.

Salt and detergent extracts of acetone-dried powder of Xenopus laevis skin and eggs were fractionated on sugar-Sepharose columns, to which lactose, melibiose, galactose, rhamnose and mannose had been covalently linked, by successive elution with chelating reagent and specific sugars, resulting in separation of the different Ca2(+)-dependent and Ca2(+)-independent carbohydrate-binding proteins. The skin of X. laevis contains a salt-extractable Ca2(+)-dependent lactose-binding lectin of 30 kilodalton (kDa) and the eggs a similar lectin of 43 kDa, but they both lack Ca2(+)-dependent galactose-binding lectins. The 30 kDa lactose-binding lectin which agglutinates human A erythrocytes was isolated by successive affinity chromatography on two linked sugar-Sepharose columns, i.e., a galactose-Sepharose-lactose-Sepharose (GL) column system. Since the 30 kDa lectin was not recovered in the Ca2(+)-dependent lactose-binding protein fraction from the GL column system under the dithiothreitol (DDT)-free conditions, it was concluded that the lectin requires the presence of DTT and calcium for binding to the lactose-Sepharose column.

Animals↗
PubMed1990

The anomaly of a non-bifurcating cervical carotid artery. Case report.

A case of a rare developmental anomaly of the cervical carotid artery is reported. In this patient the non-bifurcating carotid artery gave origin to all of the branches normally supplied by the external carotid artery and thereafter continued as the internal carotid artery. Embryological events responsible for this anomaly are briefly discussed.

Carotid Arteries↗
PubMed1990

Studies on new dehydropeptidase inhibitors. III. Biological properties of WS1358A1.

WS1358A1, a novel inhibitor of renal dehydropeptidase (DHP), augmented the urinary recovery of a carbapenem antibiotic imipenem and improved its protective effect in experimental infections when simultaneously administered to mice with the antibiotic. WS1358A1 was a competitive DHP inhibitor with a Ki value of 1.6 x 10(-7) M.

Animals↗
PubMed1990

[Why complete or partial response can not be achieved by immunotherapy].

It has been shown that shrinkage of tumor mass can hardly be achieved by immunotherapy. However, this does not appear to indicate that the immunotherapy is ineffective in cancer treatment. Although chemotherapy can reduce a tumor mass by means of fractional kill of tumor cells and, thereby assure complete and partial responses, the cytocidal action of immunotherapy seems to be effected through constant number cell kill. When residual tumor cells in patients who underwent radical surgery are considered from a microscopic standpoint, it is suggested from the disease-free survival curve that the tumor burden is surely reduced logarithmically even in each class of patients who failed to respond to adjuvant chemotherapy. Moreover, there is a great possibility that these residual tumor cells will acquire a drug resistance. Therefore, even if the degree of cell kill potential of immunotherapy is so low that complete or partial response cannot be achieved, the role of immunotherapy in combined modality for cancer treatment is inevitably important.

Cell Count↗
PubMed1990

[Tumor-regressing factor induced by antitumor polysaccharide in the serum of tumor-bearing mice].

A potent tumor-regressing activity was found in the serum of mice with S180 tumor undergoing rapid regression caused by antitumor polysaccharides. Beta (1-3) glucan including CM-TAK and lentinan and mannoglucan MGA induced such activity. It causes a rapid decrease in the number of tumor cells accompanied with a marked increase in neutrophiles in solid tumors. The entity of the activity was named as tumor-regressing factor (TRF) and was partially purified revealing a proteinaceous nature with an approximate molecular weight of 250,000. The factor was induced in a serum of tumor-bearing mice in various host-tumor combinations after the tumor growth had been established but only weakly in normal mice. The sensitivity of tumors to the factor was also dependent on the stage of tumor growth. The serum of normal mice or tumor-bearing mice without polysaccharide treatment exhibited similar activity as TRF after definite chromatographic step. The chromatographic behavior of the revealed activity was closely similar to that of the induced factor. It was postulated that a TRF-like activity exists in normal serum in a inactivated form being bound by antagonist(s) and the appropriate chromatography might remove the antagonist resulting in the active form of the factor. The concept was confirmed by reconstituting the chromatographic fractions, the revealed activity was again obscured after mixing with a certain fraction.

Animals↗
PubMed1990

Effects on herpes simplex virus type 1 of combined use of interferon-beta and anti-herpetic agents in vitro.

It has been shown that the use of interferon (IFN) alone has little or no therapeutic effect in the treatment of herpetic keratitis. However, IFN used in combination with anti-herpetic agents has high therapeutic efficacy. This interaction between IFN and anti-herpetic agents has not been elucidated clearly. In this study, the interaction between human fibroblast interferon (HuIFN-beta) and anti-herpetic agents, 5-iodo-2'-deoxyuridine (IDU), aciclovir (ACV) and 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG), was studied in vitro using VERO cells. After the formation of a monolayer of VERO cells, HuIFN-beta of various concentrations was added to the maintenance medium. After 24 hours incubation, the medium was removed and herpes simplex virus (HSV) type 1 was inoculated on the VERO cells. Then, anti-herpetic agents were added to the medium in various concentrations. After 48 hours incubation, plaques were counted and the reduction rate in numbers of plaque was calculated. It was found that the combination of HuIFN-beta with IDU, ACV or DHPG worked synergistically in the inhibition of HSV replication.

Acyclovir↗
PubMed1989

Effects of endothelin on renal regional blood flow in dogs.

The effects of intrarenal infusion of endothelin on renal blood flow were investigated in anesthetized dogs. Endothelin produced a biphasic change in the renal blood flow (RBF): an initial, transient increase followed by a marked, long-lasting decrease. The changes in the RBF were parallel to those in the renal cortical blood flow, whereas the changes in the medullary blood flow were less prominent. These results suggest that endothelin affects RBF, preferentially in the renal cortex.

Anesthesia↗
PubMed1989

The evolution of lysozyme and alpha-lactalbumin.

From the analysis of phylogenetic trees constructed from the amino acid sequences and metal-binding properties of various lysozymes c and alpha-lactalbumins, it was found that before the divergence of the lineages of birds and mammals, calcium-binding lysozyme diverged from non-calcium-binding lysozyme. alpha-Lactalbumin evolved from the calcium-binding lysozyme along the mammalian lineage after the divergence of birds and mammals. Rapid evolution took place, not in the process of acquisition of the activity of alpha-lactalbumin, but after the loss of lysozyme activity, due to the change in the distribution of selective pressure on each amino acid site. A general process for the change in function of a protein during evolution is suggested to be as follows: after duplication of the gene, one of their protein products acquires a new function, besides that already present; the old function is eventually lost.

Amino Acid Sequence↗
PubMed1989

Comparison of the binding of Ca2+ and Mn2+ to bovine alpha-lactalbumin and equine lysozyme.

The enthalpy change of the binding of Ca2+ and Mn2+ to equine lysozyme was measured at 25 degrees C and pH 7.5 by batch microcalorimetry: delta H degrees Ca2+ = -76 +/- 5 kJ mol-1, delta H degrees Mn2+ = -21 +/- 10 kJ mol-1. Binding constants, log KCa2+ = 6.5 +/- 0.2 and log KMn2+ = 4.1 +/- 0.5, were calculated from the calorimetric data. Therefore, delta S degrees Ca2+ = -131 +/- 20 JK-1 mol-1 and delta S degrees Mn2+ = 8 +/- 44 JK-1 mol-1. Removal of Ca2+ induces small but significant changes in the circular dichroism spectrum, indicating the existence of a partially unfolded apo-conformation, comparable with, but different from, the apo-conformation of bovine alpha-lactalbumin.

Animals↗
PubMed1989

Closed and continuous algae cultivation system for food production and gas exchange in CELSS.

In CELSS (Controlled Ecological Life Support System), utilization of photosynthetic algae is an effective means for obtaining food and oxygen at the same time. We have chosen Spirulina, a blue-green alga, and have studied possibilities of algae utilization. We have developed an advanced algae cultivation system, which is able to produce algae continuously in a closed condition. Major features of the new system are as follows. (1) In order to maintain homogeneous culture conditions, the cultivator was designed so as to cause a swirl on medium circulation. (2) Oxygen gas separation and carbon dioxide supply are conducted by a newly designed membrane module. (3) Algae mass and medium are separated by a specially designed harvester. (4) Cultivation conditions, such as pH, temperature, algae growth rate, light intensity and quantity of generated oxygen gas are controlled by a computer system and the data are automatically recorded. This equipment is a primary model for ground experiments in order to obtain some design data for space use. A feasibility of algae cultivation in a closed condition is discussed on the basis of data obtained by use of this new system.

Biomass↗
PubMed1989

Natriuretic and diuretic effects of endothelin in isolated perfused rat kidney.

In an attempt to clarify the pathophysiological role of endothelin (ET), a novel vasoconstrictor peptide, we administered this peptide into the medium of isolated perfused rat kidney (IPK). ET increased renal vascular resistance by 53%, and reduced inulin clearance by 29% in IPK at a higher concentration of 500 PM. However, fractional excretion of sodium and urine flow rate were increased by 160% and 109%, respectively. These findings suggest that ET modulates the tubular sodium reabsorption as well as the renal hemodynamics.

Animals↗
PubMed1989

MR imaging of experimental demyelination.

Seventeen rabbit sciatic nerves undergoing experimental demyelination and 17 control nerves were imaged in vivo with a 0.3-T MR imaging system using a silicone chamber wrapped around the nerves to isolate them from surrounding tissues. Three pulse sequences were used for each nerve: (1) spin-echo 500/28 (TR/TE), (2) spin-echo 2000/56, and (3) inversion recovery 1000/300/30 (TR/TI/TE). Image intensity data were acquired for each nerve by placing a region of interest over the nerve and measuring pixel brightness within the region of interest by means of a computer algorithm. The mean signal intensity of the experimental nerve was then compared with the mean signal intensity of the contralateral control nerve on the same image. Histologic sections of the nerves were stained with Loyez's stain for myelin and thionin for glial cells. MR findings were then compared with histopathologic data. Experimental nerves showed distinct stages of demyelination. Two fundamental observations were surmised from the data: (1) Perceptible MR signal changes are associated with early nerve degeneration, in which there is demyelination in the absence of glial cell proliferation; these changes are appreciated as increased intensity on heavily T2-weighted sequence. In these nerves no signal changes are seen on T1-weighted sequences. (2) Perceptible MR signal changes are associated with more advanced nerve degeneration, in which there is an increase in the number of glial cells in the absence of further demyelination; these changes are appreciated as decreased intensity on T1-weighted sequences and markedly increased intensity on T2-weighted sequences, respectively. The results show that MR can distinguish stages of demyelination in degenerating nerves, thereby providing a powerful method for the diagnosis and characterization of demyelinating disease.

Animals↗