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Biomedical subjects

C H Ramirez-Ronda

Publications and source records attributed to C H Ramirez-Ronda.

22 records · Page 2Linked to original sources
PubMed1975

Effects of divalent cations on binding of aminoglycoside antibiotics to human serum proteins and to bacteria.

Binding of gentamicin and related deoxystreptamine-containing aminoglycoside antibiotics to proteins in human serum can vary significantly with changes in experimental conditions. The concentrations of divalent cations are important variables, and binding increases progressively as the concentrations of calcium and magnesium decrease. Maximal binding of deoxystreptamine-containing aminoglycosides to human serum is approximately 70% in the absence of divalent cations. The binding of (3)H-labeled gentamicin to Pseudomonas aeruginosa increases and its bactericidal activity against P. aeruginosa is enhanced in the absence of divalent cations. In contrast, binding of (3)H-labeled gentamicin to Escherichia coli and bactericidal activity against E. coli do not vary significantly in the presence and in the absence of divalent cations. Interference with uptake of gentamicin provides a plausible explanation for the observation that the minimal inhibitory concentration of gentamicin for P. aeruginosa increases as the concentration of calcium or magnesium in bacteriological media increases. Although significant binding of deoxystreptamine-containing aminoglycosides to plasma proteins does not occur under normal physiological conditions in man, the possibility remains that variations in protein binding of these aminoglycosides might be significant under pathological conditions.

Aminoglycosides↗
PubMed1975

Adherence of bacteria to heart valves in vitro.

The abilities of 14 strains of aerobic gram-positive cocci and gram-negative bacilli to adhere in vitro to human or canine aortic valve leaflets were compared. 2-mm sections of excised valve leaflets were obtained by punch biopsy and were incubated under standardized conditions in suspensions of bacteria. Valve sections were subsequently washed and homogenized, and quantitative techniques were used to determine the proportions of bacteria from the initial suspensions that had adhered to the valve sections. Comparable results were obtained when these adherence ratios were determined by two independent methods based either on measurements of bacterial viability or of radioactivity in 51Cr-labeled bacteria. For each bacterial strain, the adherence ratio was constant over a wide range of concentrations of bacteria in the incubation medium. Strains of enterococci, viridans streptococci, coagulase-positive and coagulase-negative staphylococci and Pseudomonas aeruginosa (adherence ratios 0.003-0.017) were found to adhere more readily to valve sections than strains of Escherichia coli and Klebsiella pneumoniae (adherence ratios 0.00002-0.00004). The organisms that most frequently cause bacterial endocarditis were found to adhere best to heart valves in vitro, suggesting that the ability to adhere to valvular endothelium may be an important or essential charcteristic of bacteria that cause endocarditis in man.

Animals↗
PubMedDate not supplied

Granulomatous hepatitis.

According to the literature on the subject, hepatic granulomas are present in 2.4%-10% of the liver tissue specimens examined in general hospitals. The pathogenesis and pathological importance of these lesions remain unclear in many cases. Hepatic granulomas have been associated with a wide variety of diseases, among which sarcoidosis, followed by tuberculosis, figure most prominently. The etiology remains undetermined in less than or equal to 36% of reported cases. In some instances the lesions are found by chance, and in other cases they are associated with a prolonged course of fever of undetermined origin, which may or may not resolve spontaneously. In the present article, the histopathogenesis and appearance of these lesions are described; the associated diseases are reviewed with detailed emphasis on the clinical manifestations, pathology, and diagnosis of those diseases most commonly responsible for the lesions; and, finally, some comments are offered on the diagnostic work-up and controversial management of undiagnosed cases.

Bacterial Infections↗