RESUMO
The acute and chronic toxicities of streptomycin sulfate (SS) and of the streptomycin hydrochloride-calcium chloride complex (SCC) were compared. The LD50 determined in mice was significantly higher for SCC than for SS. Chronic toxicity was evaluated by recording the nystagmus induced by damped torsion pendulum in rabbits. SS and SCC treatments (200 mg/kg intramuscularly of absolute streptomycin base) decreased the duration, the maximal frequency, and the total number of beats of nystagmus. However, SCC-induced changes were significantly lower than SS-induced ones. The extent of the lesion in the crista ampullaris was evaluated by light and electron microscopy and was correlated with the electrophysiological findings. Because the authors also demonstrated that there are no differences in the antibacterial effects of these salts, SCC may have a place in long-term streptomycin treatment.
Assuntos
Cloreto de Cálcio/toxicidade , Otopatias/induzido quimicamente , Otopatias/prevenção & controle , Infecções/tratamento farmacológico , Nistagmo Fisiológico/efeitos dos fármacos , Estreptomicina/toxicidade , Vestíbulo do Labirinto/efeitos dos fármacos , Doença Aguda , Animais , Cloreto de Cálcio/antagonistas & inibidores , Doença Crônica , Combinação de Medicamentos , Otopatias/patologia , Otopatias/fisiopatologia , Eletronistagmografia/efeitos dos fármacos , Feminino , Dose Letal Mediana , Masculino , Camundongos , Modelos Biológicos , Nistagmo Fisiológico/fisiologia , Coelhos , Estreptomicina/antagonistas & inibidores , Estreptomicina/uso terapêutico , Vestíbulo do Labirinto/patologia , Vestíbulo do Labirinto/fisiologiaRESUMO
The neuromuscular blockade produced by the amino-glycosidic-aminocyclitolic antibiotics streptomycin and kanamycin and its reversal by calcium was quantitatively studied in the isolated phrenic nerve-diaphragm preparation of the rat. The low dose-response curves obtained presenting no significant deviation from parallelism are highly suggestive of a competitive type of antagonism between those substances. The streptidinic moiety of streptomycin showed the same properties as the original antibiotic. Streptomycin and kanamycin decreased the amplitude of intracellularly recorded e.p.p.'s of the toad sartorius muscle in a manner quite similar to that described for magnesium ions which suggests an interference of the antibiotics with the cooperative interaction of calcium ions with specific receptive sites at the presynaptic membrane of the neuromuscular junction.
Assuntos
Cálcio/farmacologia , Canamicina/farmacologia , Junção Neuromuscular/efeitos dos fármacos , Estreptomicina/farmacologia , Animais , Anuros , Cálcio/antagonistas & inibidores , Potenciais Evocados/efeitos dos fármacos , Técnicas In Vitro , Canamicina/antagonistas & inibidores , Placa Motora/efeitos dos fármacos , Contração Muscular/efeitos dos fármacos , Ratos , Estreptomicina/antagonistas & inibidoresRESUMO
A line-frequency sine-wave stimulator of solid-state construction is described. Switching transients are avoided by starting and stopping the stimulating trains at exactly zero volts. Train repetition frequency and duration are controllable, the latter down to one-half cycle. External control of both frequency and duration is possible.
