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Biomedical subjects

T Maki

Publications and source records attributed to T Maki.

At least 217 records · Page 12Linked to original sources
PubMed1985

Multiple factors in the prediction of risk of proliferative diabetic retinopathy.

To identify risk factors for the development of proliferative diabetic retinopathy, we compared 111 patients with longstanding insulin-dependent diabetes who had proliferative retinopathy (cases) with 81 patients with diabetes of similar duration (an average of 26 years) who did not have proliferative diabetic retinopathy (controls). The cases had diabetes that was more difficult to manage, as evidenced by their more frequent blood sugar levels above 200 mg per deciliter (11 mmol per liter) on routine clinic visits (odds ratio, 1.6 for each increment of 10 per cent in the relative frequency), and they expended less effort in managing their diabetes, as indicated by their less frequent testing of urine for sugar (odds ratio, 0.3). Among those who did not have myopia, the cases also had an excess of the HLA-DR phenotypes 4/0, 3/0, or X/X (odds ratio, 10.0). Among those with myopia, these phenotypes did not carry an increased risk of proliferative retinopathy. These results support a multifactorial model for the development of proliferative diabetic retinopathy; however, the mechanisms of action of the identified factors remain unknown.

Adolescent↗
PubMed1985

Nerve and muscle vulnerability to ischemia.

Nerve and muscle vulnerability to structural damage during ischemia was examined in the hind legs of 50 cats after transient simultaneous clamping of the aorta and femoral artery for 1 to 10 h. Not until 5 h of ischemia were mild necrotic changes noted in nerves. Moderate to severe changes occurred after 8 h of ischemia. Contrariwise, mild muscle necrotic changes developed after 2-3 h, and moderate to severe changes after 5-7 h. The anterior tibialis muscle was usually more severely damaged than the gastrocnemius and soleus muscles. These studies demonstrate that: Longer periods of ischemia are required to produce nerve damage than suggested by previous tourniquet compression experiments. Longer periods of ischemia are necessary to produce necrosis in the posterior than anterior and lateral compartment muscles of the leg. Muscle is more vulnerable than nerve to ischemia.

Animals↗
PubMed1985

Induction of graft-versus-host disease by small intestinal allotransplantation in rats.

Adult male (LewisXBrown Norway) F1 (LBNF1) rats received heterotopic small intestinal transplants from Lewis donors. Lewis-to-Lewis and LBNF1-to-LBNF1 isografts served as controls. All of the allograft recipients died after a median survival time of 16.2 days, but all isografted rats survived indefinitely. During the period of deterioration, allografted rats developed marked cutaneous erythema and became increasingly weak and cachectic. Histological changes of the skin, spleen, and grafts were characteristic of graft-versus-host disease (GVHD). There was a marked degree of relative splenomegaly. Injection of spleen cells obtained from LBNF1 rats with clinical GVHD into the foot-pad of syngeneic LBNF1 rats resulted in significant enlargement of the ipsilateral popliteal lymph node. The degree of lymph node enlargement was comparable to that induced in LBNF1 rats by injection of normal Lewis spleen cells. These results clearly demonstrate the ability of the small intestinal allograft to cause rapid and fatal GVHD in rats that are incapable of graft rejection.

Animals↗
PubMed1985

Redifferentiation of cancer cells: bestatin, estradiol, and prostaglandin D2.

The induction of redifferentiation of cancer cells was studied. This was achievable with bestatin, especially in combination with sex hormones or prostaglandin D2, in murine undifferentiated mammary adenocarcinoma cells in vitro. Prostaglandin D2 also exerted a similar redifferentiating effect on M1 murine leukemia cells and a consecutive bestatin-hormone regimen was effective in endocrine tumors in man. Cancer redifferentiation may one day be developed into a clinical technique.

Animals↗
PubMed1985

[Radioactive and stable cobalt concentrations in mussel in Kyushu islands, Japan].

Two kinds of mussel, Septifer virgatus and Mytilus edulis, were collected from Kyushu island, Japan, in order to elucidate a background level of 60Co, which is one of the most significant radionuclide for environmental monitoring around a nuclear power plant. The mussels were collected from 7 locations in 1983 and classified 2 or 3 groups depending on their shell size at each location. Activities of 60Co were measured by a low-background beta counter after purified by means of chemical separation and electrodeposition. Stable cobalt concentrations were determined by colorimetric method. The concentrations of cobalt in Septifer virgatus are one order higher level than that in Mytilus edulis. There are not so large difference in cobalt content depending on shell size so long as comparing them at the same location. The radioactivities in mussels show the same trend as stable cobalt. It has become apparent that Septifer virgatus has a tendency to concentrate cobalt with growing but Mytilus edulis is opposite. The cobalt-60 introduced to sea from nuclear explosions seems to be relatively constant in coastal seawater since specific activities are distributed in a narrow range in spite of kind, shell size and location.

Animals↗
PubMed1984

In flight negative pion assessments using time-of-flight technique.

Time-of-flight measurement was applied to obtain the energy spectra of the neutron emitted from tissue-equivalent plastic (TEP) exposed by pi- mesons. The separation of electrons and muons in beams was attempted. Neutrons from TEP exposed by pi- mesons at P pi = 500 MeV/c were separated from gamma-rays by the NE 213 liquid scintillator and the pulse-height analyzer. The double differential cross sections for neutron energy are obtained. The cross sections of the neutron energy distributions show a preponderance of low energy neutrons and a high energy tail extending to approximately 100 MeV.

Electrons↗
PubMed1984

[The applicability of pions to cancer radiotherapy. III. Measurement of x-ray and gamma-rays by NaI detector for the determination of the peak-region in pi- meson exposure].

A method of externally observing the stop-region of pi- meson for monitoring during exposure to a patient is discussed. Negative pi mesic X-rarys, gamma-rays and neutrons are emitted from the region where pi- mesons stop and produce stars. These radiations can be detected outside the exposed patient. Water phantom as normal tissue equivalent material was exposed by pi- mesons at various depths. The resulting gamma-ray yields were determined by counting the gamma-rays in coincidence with incident pi- mesons using a sodium iodide (NaI) detector. This type of gamma-ray measuring system is useful to make sure that the peak position of the depth-dose distribution in the patient is exactly situated at the desired one during exposure. It is suggested that the scintillation camera with a multiholecollimator is a powerful and convenient tool for the two dimensional peak positioning.

Gamma Rays↗
PubMed1984

Prolactin has a direct effect on adrenal androgen secretion.

The role of PRL in the secretion of androgens by the adrenal glands was investigated in vivo and in vitro. In women with hyperprolactinemia whose pituitary-adrenal function was normal, there was significant correlation between serum PRL and dehydroepiandrosterone sulfate [(DHEA-S) gamma = 0.48, P less than 0.05, n = 34] and DHEA (gamma = 0.50, P less than 0.05, n = 34), but not with androstenedione. Long term administration of sulpiride to normal women increased both serum PRL and DHEA-S, whereas acute elevation of PRL after a single iv dose of domperidone had no influence on the serum DHEA-S levels. Monolayer cultures of human adrenal cells were used in order to study the direct effect of PRL on adrenal androgen secretion. The daily secretion of DHEA-S, DHEA, androstenedione, and cortisol was determined. In the absence of ACTH, PRL had no effect on steroid secretion in a 7-day culture period. In the presence of ACTH, there was a daily increase in the secretion of steroids. PRL, when added in combination with ACTH, potentiated the effect of ACTH on DHEA-S and DHEA but not on androstenedione and cortisol secretion on the seventh day in culture. These results indicate that PRL has a direct synergistic effect with ACTH on adrenal cells to increase adrenal androgen release. Increases in DHEA-S and DHEA but not androstenedione in vitro and correlation between serum PRL and DHEA-S and DHEA but not androstenedione in women with hyperprolactinemia suggest that the synergistic effect of PRL on adrenal androgen secretion may result from partial inhibition of adrenal 3 beta-hydroxysteroid dehydrogenase.

Adrenal Glands↗
PubMed1984

Effect of angiotensin II on secretion of adrenal androgens.

To assess the effect of angiotensin II (A II) on the secretion of human adrenal androgens (AA), plasma dehydroepiandrosterone (DHEA), DHEA sulfate (DS) and delta 4-androstenedione (delta 4-A) were measured in eight normal men 60 and 120 min after stimulation of endogenous A II by a bolus injection of 40 mg frusemide, and the direct effect of A II on the secretion of adrenal androgens was examined in cultured human adrenocortical cells in the presence of a low concentration of ACTH. The administration of frusemide led to a significant increase in the plasma DHEA and DS concentration as well as plasma renin activity (PRA) and aldosterone concentration (PAC), but did not change plasma cortisol and delta 4-A. In the culture of human adrenocortical cells, 10(-9)-10(-5) M A II or 10(-13) M ACTH alone did not stimulate the secretion of DHEA, DS and delta 4-A, while 10(-7) and 10(-5) M A II in the presence of 10(-13) M ACTH caused a significant increase in DHEA and DS secretion with no change in delta 4-A. These results suggest that the activated renin-angiotensin system stimulates the secretion of adrenal androgens by a direct effect of A II on adrenal cortical cells.

Adrenal Cortex↗
PubMed1983

[The applicability of pions to cancer radiotherapy. I. Experimental measurements of the capture and absorption of pions in polymer].

A future application of negative pions to radiotherapy has arrived at a promising stage. Negative pions, in addition to their good localization characteristics, offer an advantage of favorably influencing biological factors because of differences in the quality of radiation given to a) the treatment volume and b) the intervening normal tissue. By utilizing dose fractionation, the low dose to intervening normal tissue with its low LET allows these tissues to recover better than cells in the treatment volume. In this study the lucite phantom was bombarded with 150 MeV/c and 173 MeV/c negative pions and 173 MeV/c positive pions, respectively, by using the 12 GeV proton synchrotron of the National Laboratory for High Energy Physics (KEK). Range-energy relations in the lucite and the remaining curves of pions were observed. The observed range of pions in lucite agreed well with the theoretical prediction. The remaining curves show the different structures for pi+ and pi- mesons. Peak to plateau ratio is ten times.

Elementary Particles↗