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Biomedical subjects

R Niki

Publications and source records attributed to R Niki.

At least 37 records · Page 2Linked to original sources
PubMed1985

The wide distribution of CT scanners in Japan.

Computerized tomography (CT) scanners have been widely distributed throughout Japan since 1975, with the total number reaching 2120 in December 1982. This figure is larger than that of all European countries. Furthermore, the number of CT scanners per million population, Japan exceeds the United States. An investigation to explain the reasons for this rapid increase of CT in Japan with comparisons between Japan and the United States is presented. Uniquely 'Japanese' characteristics may explain the diffusion of CT as follows: the government has no explicit policy to control the adoption of CT. CT has been widely distributed, not only to the large public hospitals, but also, to smaller private hospitals. CT is frequently adopted without assigning additional skilled personnel. Japanese manufacturers have produced low-price CT in addition to developing an active marketing campaign.

Hospital Bed Capacity↗
PubMed1985

[An outbreak of staphylococcal dermatitis in laboratory mice].

An epizootic of dermatitis with erosion, ulcer and crust broke out in an experimental colony of JCL-ICR mouse over a period from December 1975 to June 1976. The disease was detected in 592 of a total of 1831 mice of 3-24 months old, especially in males of 7-24 months old (517/821). At the beginning of December 1975, only a few males of 12 months old were found to have the lesion on the back skin, and thereafter the dermatitis prevailed gradually among the mice. Histopathologic examinations showed the loss of the epidermis, necrosis and/or collapse of the corium, accumulation of serous exudate with neutrophilic cell infiltration and a few cocci scattered on the surface. In chronic cases, fibrous granulation tissues with neutrophilic cell infiltration were formed in the corium. Staphylococcus aureus was isolated in pure culture from the skin lesions in all of the mice examined. Skin disease similar to that of the field case was reproduced in mice inoculated subcutaneously with 10(7) viable organisms of the fresh isolate. By giving chlortetracycline in drinking water for 7 days, treatment of the affected mice was efficacious in mild cases, but not in severe cases.

Aging↗
PubMed1985

[Biological properties, phage typing and antimicrobial susceptibility of Staphylococcus aureus isolated from dermatitis in laboratory mice].

The characteristics of 167 isolates of S. aureus from 106 mice suffering dermatitis were examined. All 167 isolates coagulated both rabbit and human plasmas and 161 of them also coagulated bovine plasma. All the isolates produced heat-stable and heat-labile DNase, phosphatase and yellow pigment, reduced nitrate, hydrolysed egg yolk, Tween 80, and hippurate, and grew on crystal violet agar in colonies of the negative type C and on medium with 10% NaCl. The majority of them produced fibrinolysin, protease and acetoin. Fifty-three percent were gelatinase positive. In hemolysis tests, 25, 57 and 45 isolates showed alpha-, beta-, alpha beta-hemolysis, respectively. Forty isolates did not produce hemolysins in the rabbit and sheep blood agar. All of 75 isolates tested produced acid from fructose, galactose, glucose, glycerol and mannose, but did not from arabinose, dextrin, inulin, raffinose, salicin, sorbitol and xylose. Most of these isolates produced acid from lactose, mannitol, sucrose and trehalose. All of the 75 isolates were highly sensitive to penicillin, methylphenylisoxazolyl penicillin, erythromycin, spiramycin, lincomycin, chloramphenicol, tetracycline, kanamycin, gentamicin and cephaloridine, but were resistant to sulfisoxazole. With phages of human set, all 167 isolates were typable at 100 X RTD. All but one of the typable isolates belonged to mixed lytic groups. These were I + III (35 isolates), I + M (1), I + III + M (124) and I + II + III + M (6), with long phage patterns. When the 167 isolates were biotyped as described by Hájek and Marsálek [7, 8], 5 belonged to biotype A, 1 to biotype B and 60 to biotype C.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Dynamic mechanical properties of milk and milk gel.

The dynamic mechanical properties of milk and milk gel were examined as functions of frequency, temperature, and concentration. The real and imaginary parts of the complex rigidity G' and G" measured at various frequencies were found to be superimposable onto a single set of master relaxation curves by performing the horizontal shift along the logarithmic frequency axis except for milk gel which were prepared at different temperatures. The results show that the rigidity of milk gel depends on the concentration of milk C in such a way that G* alpha C2. It was found that G' depends on the temperature as G' alpha T. It was also found that the complex rigidity of skim milk solution depends on the angular frequency omega in such a way that G* alpha omega 1/2. The dependence of G* on frequency seems to indicate the formation of structure by casein micelle in solution.

Animals↗
PubMed1982

Dynamic viscoelastic studies on the mechanism of milk clotting process.

The reaction order of the clotting process of milk-rennet system was determined by an analysis of clotting curves obtained from the measurement of the complex rigidity at various concentrations of milk and rennet under the conditions of fixed weight ratio of rennet to milk. The results obtained show that the clotting process of milk-rennet system after gelation begins is described by a single first order reaction. At constant weight ratio of rennet to skim milk, it was found that G'00 increases almost linearly with increasing temperature. Under the conditions of a constant milk concentration and temperature, the latent period is inversly proportional to the enzyme concentration and the rate constant of gelation is proportional to the enzyme concentration. These results were discussed in terms of Payens' theory of enzymatic clotting processes and Ziff's theory of the kinetics of polymer gelation.

Animals↗
PubMed1982

Application of the theory of gelation to enzymatic clotting process of casein micelle solution.

Dynamic mechanical measurements were carried out to clarify the mechanism of the clotting process of casein micelle solution. It was found that the clotting process of casein micelle solution was formally expressed by a first order reaction. The enzyme concentration dependence of the latent time tL and the rate constant of gelation Kg were found to be tL alpha [E]-1.1, and Kg alpha [E]1.0, respectively. These results were intrepreted on the basis of the theory of gelation. The results obtained here were found to agree with the theoretical conjectures. The casein micelle concentration dependence of the complex rigidity was also studied.

Animals↗
PubMed1981

[Pathological studies on spontaneous tumors in mice (author's transl)].

The incidence and histopathology of the spontaneous tumors in over 2-year-old ddY strain mice, an outbred widely used in Japan, are described. The incidences of the total spontaneous tumors were 47.5% in males and 66.7% in females in actual numbers. These, however, could be corrected to 64.4% and 80.0%, respectively, when the accidental death are omitted from the results. The incidences of the pulmonary tumors were very high; 39.2% in males and 26.7% in females of the total spontaneous tumors, respectively. Other tumors which showed high incidences were, lymphoid tumors; 17.5% in males and 19.2% in females and mammary tumors; 26.7% exclusively in females. However, no strain-specific tumors were observed which are common in inbred strains such as leukemia in AKR or mammary tumors in C3H strains, partly suggesting broad genetic variation of the strains. Histopathological examination revealed prevailing types of the tumors to be papillary adenoma of pulmonary tumors, simple adenoma of mammary tumors and poorly differentiated lymphosarcoma of lymphatic tissues.

Animals↗
PubMed1980

A sedimentation equilibrium study of the temperature-dependent association of bovine beta-casein.

The temperature-dependent association of beta-casein was studied by the sedimentation equilibrium method. The weight-average molecular weight of the protein was determined in 0.2 M sodium phosphate buffer (pH 6.7) at 20, 15, 10 and 2 degrees C, and was found to be dependent markedly on both temperature and protein concentration. The data were well fitted by a monomer-n-mer association scheme, and the values of n, the second viral coefficient, and the free energy change for the association (association constant) were evaluated. The results show that temperature not only shifts the equilibrium but alters the polymer size: the values of n are 49, 22, and 12 at 20, 15, and 10 degrees C, respectively; the free energy change per monomer becomes more negative with increasing temperature, indicating that the attraction between the monomers in a polymer is stronger at higher temperature. This effect of temperature is in contrast to that of ionic strength which affects mainly the equilibrium. The enthalpy change, entropy change, and heat capacity change for the association were also estimated and were indicative of the formation of a considerable amount of hydrophobic bonds upon association.

Caseins↗
PubMed1980

Osseous changes and abnormalities of mineral metabolism in rats with glycopeptide-induced nephritis.

A laboratory model of renal osteodystrophy was developed in rats by a single injection of glycopeptide isolated from renal cortical tissues of rats according to the method used by Shibata et al. to induce glomerulonephritis. Approximately 60-70 days after injection, severe proteinuria appeared and continued for at least 170 days at a rate of more than 1 g/day. Morphological changes in the kidney were typical of chronic glomerulonephritis. The plasma calcium concentration was lowered transiently by the 96th day after injection, but was restored to the normal range thereafter. Plasma parathyroid hormone levels, however, continued to rise in parallel with the degree of proteinuria. Marked secondary hyperparathyroidism was induced which led to severe bone atrophy. Histological examinations showed a marked increase of resorbing cavities, with a quantitatively larger number of osteoclasts in cortical bone tissues compared with the control animals. No spontaneous remission was observed. It is emphasized that all of the biochemical and morphological changes reported here were induced by a single injection of homologous renal glycopeptide, and they were highly reproducible.

Animals↗
PubMed1980

Comparative therapeutic effects of vitamin D3 and its derivatives on experimental renal osteodystrophy.

The comparative effectiveness of vitamin D3 and its derivatives in curing hyperparathyroidism and osteodystrophic bone lesions was examined in a laboratory model of renal osteodystrophy associated with marked secondary hyperparathyroidism in rats. The experimental model was prepared by a single injection of homologous glycopeptide. Plasma levels of 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] appeared to decrease in the rats receiving glycopeptide. Various doses of vitamin D3 derivatives [2 or 10 microgram/kg D3, 2 microgram/kg 25-hydroxyvitamin D3 (25OHD3), 0.1 microgram/kg 1 alpha,25(OH)2D3, and 0.1 or 0.2 microgram/kg 1 alpha-hydroxyvitamin D3 (1 alpha OHD3)] were daily administered orally to the nephritic rats for 23 days before sacrifice. 1 alpha,25(OH)2D3 and 1 alpha OHD3 were much more potent than 25OHD3 and D3 in reducing the hyperplasia of parathyroir glands. The potency of 1 alpha OHD3 in curing the histological changes of osteodystrophy appeared to be greater than that of 1 alpha,25(OH)2D3. The same dose level of 1 alpha OHD3 was more effective than 1 alpha,25(OH)2D3 in enhancing plasma 1 alpha,25(OH)2D3 levels.

Animals↗
PubMed1980

Vascularly perfused rat small intestine: a research model for drug absorption.

Rat isolated small intestine was perfused at a fixed flow rate through the superior mesenteric artery with whole rat blood recycled from a devised oxygenator-reservoir. As indicated by perfusion pressure, tissue glucose and oxygen consumption, and histological studies, the perfused intestine remained in a viable state over the perfusion period of 2 hr. Rapid absorption of glucose from the intestinal tract was observed after the intraduodenal injection. When single doses of acetaminophen were injected into the duodenal lumen or poured over the perfused intestine, the absorption was rapid and dose-dependent. Shortly after single intraduodenal injections of salicylamide, salicylamide in free and conjugated forms (sulfate and glucuronide) appeared in the circulating blood. These results indicate that the vascularly perfused intestinal preparation has wide applications in biochemical experimental fields.

Acetaminophen↗
PubMed1979

Structure of beta-casein.

The temperature and concentration dependent association of beta-casein was studied by means of viscometry, gel filtration chromatography, electron microscopy, analytical ultracentrifugation and UV difference spectrophotometry. Degrees of polymerization of 12, 22 and 49 and free energies of association of -21, -23 and -25kJ/mole monomer were found at temperatures of 10, 15 and 20 degrees C respectively in 0.2 M Na phosphate buffer pH 6.7. Monomeric beta-casein was not a completely random coil but became more compact with increasing temperature, due to hydrophobic interactions.

Calorimetry↗
PubMed1977

Interaction of sodium dodecyl sulfate and of non-ionic detergents with S-carboxyamidomethyl-k-casein.

Sodium dodecyl sulfate binds to S-carboxyamidomethyl-k-casein in a highly cooperative manner at a concentration near the critical micelle concentration, showing a strong dependence on ionic strength. The maximum number of sodium dodecyl sulfate molecules bound is attained above the critical micelle concentration, and is very close to the micelle aggregation number in the absence of protein. The binding sites on the protein for sodium dodecyl sulfate are localized mainly on para-k-casein part, which is a hydrophobic fragment of k-casein produced by rennin attack. The mode of the action of sodium dodecyl sulfate on S-carboxyamidomethyl-k-casein resembles that of several integral membrane proteins, rather than of water soluble proteins. On considering possible situations, it is suggested that the unusual interaction of S-carboxyamidomethyl-k-casein with sodium dodecyl sulfate is responsible for an anomalous migration of reduced k-casein observed in sodium dodecyl sulfate polyacrylamide gel electrophoresis. Further, the suggestion was made by the binding studies of sodium dodecyl sulfate and non-ionic detergents that the sites which were involved in self-association of S-carboxyamidomethyl-k-casein participated in the binding sites of detergents.

Caseins↗