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Biomedical subjects

M Hamada

Publications and source records attributed to M Hamada.

At least 613 records · Page 34Linked to original sources
PubMed1981

The screening of beta-lactamase inhibitors: inhibition by fatty acids produced by bacteria.

An active principle inhibiting beta-lactamases, which was found in the culture of a bacillus strain was a mixture of known C14-C17 fatty acids. The mixture was separated into five components by high-performance liquid chromatography. Among these components, 12-methyltetradecanoic acid showed the strongest activity (I50: 20-146 microM). The anteiso fatty acids having the 1-methylpropyl group exhibited an interesting activity inhibiting beta-lactamases.

Bacillus↗
PubMed1981

Modification of protective mechanisms against Listeria monocytogenes during pregnancy.

Protective mechanisms against Listeria monocytogenes were examined at different stages of pregnancy in C3H/He mice. Bacterial growth at an early phase of infection was depressed from day 10 of gestation to day 5 postpartum, whereas bacterial growth at a late phase of infection was enhanced on day 10 of gestation. Spleen cells from nonimmunized mice on day 10 of gestation suppressed the expression of acquired resistance to infection in immunized mice. We conclude that the augmented resistance during pregnancy at an early phase of primary infection is due to the activation of nonimmune macrophages, which compensates for the depressed cell-mediated immunity at a late phase of infection that may be due to the function of nonspecific suppressor cells detectable in the spleen of the pregnant mice.

Animals↗
PubMed1981

Oxanosine, a novel nucleoside from actinomycetes.

Oxanosine, a novel nucleoside, has been isolated from the culture filtrate of a strain of Streptomyces. The structure was determined to be 5-amino-3-beta-D-ribofuranosyl-3H-imidazo [4,5-d] [1,3]oxazin-7-one by X-ray crystallographic analysis and chemical studies. Oxanosine showed weak antibacterial activity on peptone agar; for example, Escherichia coli K-12 (MIC 12.5 mcg/ml). The antibacterial activity was antagonized by addition of guanine, guanosine and 5'-guanylic acid. Oxanosine inhibited the growth of HeLa cells in vitro (IC50 32 mcg/ml) and suppressed the growth of L-1210 leukemia in mice. The primary action of oxanosine appears to be inhibition of GMP-synthetase. Intravenous injection of 4 mg of oxanosine to mice does not show any toxic sign.

Cell Division↗
PubMed1981

[The echocardiographic study in 13 cases with infective endocarditis (author's transl)].

The echocardiographic study was performed in 13 cases with infective endocarditis including one case with annular subvalvular left ventricular (LV) aneurysm. The echocardiographic findings were compared with clinical as well as anatomical findings obtained by surgery or autopsy. The valvular vegetations were visualized echocardiographically in 6 cases (46%); 2 cases in aortic valve (AV), 2 in mitral valve (MV) and 2 in both valves. In 3 out of 4 cases with AV vegetation, the abnormal echo was seen in the LV outflow tract. Two out of these 3 cases indicated "flail aortic leaflet" with early closure of the MV, and immediate aortic valve replacement was performed. Unfortunately, one died 4 weeks after operation. The echocardiographic findings showed good correlation with anatomical findings in 4 cases with valve replacement. Out of 4 cases with MV vegetation, one developed the progressive growth with subsequent rupture of the chordae tendinae to the anterior mitral leaflet, which paralleled to the clinical deterioration. In another one case, the echocardiographic size of vegetation in the MV reduced significantly shortly after the episode of cerebral embolism. In a case of annular subvalvular LV aneurysm possibly due to infective endocarditis, echo free space was visualized in the interventricular septum, coinciding well with postmortem anatomical findings. It seemed to be reasonable to indicate surgical repair in cases with evident vegetation and considerable destruction of AV, in which congestive heart failure inevitably develops and the prognosis is poor.

Adult↗
PubMed1980

Clinical evaluation of biventriculo-cineangiographic findings in hypertensive left ventricular hypertrophy.

In the present study, we demonstrated that hypertensive left ventricular hypertrophy can be divided angiographically into symmetrical (SH) and asymmetrical septal hypertrophy (ASH) groups. In the SH group, the dynamics of the septal wall and the free wall were almost the same as those of the control group. On the other hand, the ASH group rather resembled the HCM group in the thickness and dynamics of the septal wall and the free wall as well as in the septal configuration. The most characteristic difference of the ASH and HCM groups from the SH group was in the significantly greater thickness of the septal wall at end diastole. However, in view of the developmental mechanism of hypertensive heart, it is interesting to note that the more the septal-free wall ratio increases, the more the thickness of the septal wall increases in the SH group.

Adult↗
PubMed1980

Studies on new aminoglycoside antibiotics, istamycins, from an actinomycete isolated from a marine environment. III. Nutritional effects on istamycin production and additional chemical and biological properties of istamycins.

Streptomyces tenjimariensis SS-939 produced istamycins in a medium containing starch as the carbon source and soy bean meal as the nitrogen source. Istamycin production decreased substantially when starch was substituted with mono- or di- saccharides such as glucose, glycerol and maltose. A marked decrease of istamycin production was also observed when a rapidly used nitrogen source such as yeast extract, peptone or casamino acid was employed instead of soy bean meal. Addition of palmitate at a concentration of 0.2% doubled istamycin production. Istamycins A and B were found to be as active as fortimicin A and sporaricin A against Gram-positive and Gram-negative bacteria including aminoglycoside-resistant strains.

Aminoglycosides↗