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Biomedical subjects

T Mikami

Publications and source records attributed to T Mikami.

At least 721 records · Page 40Linked to original sources
PubMed1979

Factors affecting frequency dependence of resistance observed in healthy lungs.

The frequency dependence of effective resistance of the respiratory system was studied in seated and supine healthy subjects by use of a forced oscillation technique for the purpose of estimating the distribution of regional ventilation. Effective resistance determined at respective FRC levels of both these body postures fell with an increase in the breathing frequency, although the frequency dependence of resistance delta R/delta f was more dominant in the supine posture than when seated. The delta R/delta f increased to an appreciable extent by reducing the lung volume in the seated posture, while in the supine position the value was relatively insensitive to the volume change. The chest wall vibration measured during the forced oscillation was found to be larger in amplitude in the basilar than in the apical regions, and the regional difference became less dominant by postural change from seated to supine. Transthoracic electrical impedance change measured during voluntary ventilations with different frequencies gave a slight frequency dependence when measured in the basilar region either in the seated or supine posture. The above results lead to the conclusion that an inhomogeneous distribution of time constants independent of gravity appears between the apex and the base, and the gravity-independent distribution of time constants, either interlobular or intralobular, would be a prime determinant of the frequency-dependent resistance.

Humans↗
PubMed1979

Inhibitory effects of macrophages against Marek's disease virus plaque formation in chicken kidney cell cultures.

Inhibition of plaque formation by Marek's disease virus (MDV) in chicken kidney cell cultures was investigated with the use of peritoneal exudate cells (PEC) from chickens. PEC from MDV-infected White Leghorn chickens inhibited the formation of MDV plaques, whereas the inhibitory effect of PEC from chickens vaccinated with herpesvirus of turkey (HVT) or PEC from normal chickens was very weak. However, PEC from either normal chickens or HVT-vaccinated chickens inhibited the MDV plaque formation in the presence of serum from MDV-infected chickens but not from normal or HVT-vaccinated chickens. The capacity of PEC to inhibit plaque formation was significantly reduced when PEC was treated with carrageenan but not with antithymus or antibursa cell serum. These results indicate that macrophages may have a role in protection against Marek's disease by reducing the number of MDV-infected cells and thereby decreasing the spread of the virus in vivo.

Animals↗
PubMed1978

Induction of C-type virus in cell lines derived from calf form bovine lymphosarcoma.

For attempt to detect an etiological agent, cultures from bovine lymphosarcoma cases (adult form (ALS), calf form (CLS), and thymic form (TLS) were maintained in vitro for over a 18 month period. In two cultures from ALS, bovine leukemia virus (BLV) antigen was constantly detected. On the other hand, BLV antigen remained negative in cultures from two CLS and one TLS cases up to 40 passages. The RNA dependent DNA polymerase activities in these cultures were also negative. Treatment of a culture from CLS (3178) originated from liver tumor with 5'-iodo-2'-deoxyuridine (IdU) and dexamethasone (DXM) resulted in production of an agent serologically and morphologically similar to BLV and in alteration of cell morphology. No virus was detected in culture from TLS after treatment with IdU and DXM.

Animals↗
PubMed1978

Intranasal tumor of the ethmoid olfactory mucosa in sheep.

Intranasal tumors (papillary adenomas or adenocarcinomas) of the ethmoid olfactory mucosa of sheep were investigated by light and electron microscopy. The fine structure of the tumor cells was characterized by the presence of numerous secretory granules. Viral particles, which were morphologically similar to a visna-maedi virus, were detected in all tumor tissues and in 3 of 4 cultures examined. The particles (about 97 nm) had an eccentrically located electron-dense core and numerous spikes on their surfaces. The RNA-dependent DNA polymerase activities in the tumor cells or the cultured cell from the tumor were greater than those in the normal intranasal tissues or the cultured cells from the choroid plexus. Viral particles similar to herpesvirus were also detected in 1 culture.

Adenocarcinoma↗
PubMed1977

Preparation and antitumor activity of o-palmitoyldextran phosphates, o-palmitoyldextrans, and dextran phosphate.

Dextran was modified by introduction of palmitoly and phosphate groups. The derivatives were analyzed by sequential periodate oxidation-sodium borohydride reduction. Only one of these derivatives showed a significant growth-inhibitory effect when administered alone, while a second derivative showed, in combination therapy with an ineffective dose of Mitomycin C, a marked synergistic effect.

Animals↗
PubMed1977

Studies on salivary gland ribonucleases. II. Purification of ribonucleases from bovine submaxillary gland and the effects of polyamines on their activities.

Four alkaline ribonucleases [EC 3.1.4.22] were purified 2,050- to 3,460-fold from bovine submaxillary gland by repeated CM-Sephadex C-25 chromatography and Sephadex G-50 gel filtration, with a total recovery of about 13%. These were designated as RNase BS1, BS2, BS3, and BS4, based on their order of elution from a CM-Sephadex C-25 column. The molecular weights of these enzymes were estimated by gel filtration to be 19,000, 17,500, 17,000, and 12,000, 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 RNase BS4 greater than BS3 greater than BS2 greater than BS1. The stimulation by spermine is due to the increased cleavage of C5'-O-P linkages adjacent to cytosine nucleotide. The reason for the differences in the degree of spermine stimulation of these enzymes is discussed.

Animals↗
PubMed1977

Gelation of Limulus lysate by synthetic dextran derivatives.

The Limulus test has been considered specific for the presence of bacterial endotoxins. To synthesize a simple model of endotoxin, palmitoyldextran phosphate was prepared by modification of dextran by palmitoylation and phosphorylation. The present studies indicated that a variety of polysaccharide derivatives, such as palmitoyldextran phosphate, palmitoyldextran, and dextran phosphate, give a positive Limulus test and show pyrogenic activity, except for low molecular dextran derivatives. On the other hand, polysaccharides, such as dextran, starch (soluble-, chitosan, xylan, and lentinan, were negative in these assays. The gelation reaction of Limulus lysate by modified dextran derivatives may depend on the molecular weight or modification of polysaccharides by palmitoylation and/or phosphorylation to a great extent.

Chemical Phenomena↗