Silver nitrate prophylaxis.

In many countries the statutory use of silver nitrate prophylaxis as soon as possible after birth has recently been reviewed from both a human rights and a medical standpoint. It has been argued that silver nitrate does not prevent all cases of gonococcal ophthalmia neonatorum (GON) and that it causes chemical conjunctivitis, pain and visual impairment, which may interfere with parent-infant bonding. Furthermore, the low incidence of GON, better methods of prenatal diagnosis, and the availability of suitable alternative prophylactic medication and of effective methods of treatment of GON have prompted recommendations that alternative prophylaxis be legally allowed or that mandatory prophylaxis be eliminated altogether. This paper reviews the situation and provides updated recommendations.     

Antimicrobial action of silver nitrate

Silver nitrate 3 mug/ml prevented the separation into two daughter cells of sensitive dividing cells of Pseudomonas aeruginosa growing in nutrient broth plus the chemical. Cell size of sensitive cells was increased and the cytoplasmic contents, cytoplasmic membrane and external cell envelope structures were all abnormal. P. aeruginosa cells grown in the presence of silver nitrate 9 mug/ml showed all these changes to a marked degree except inhibition of cell division was not observed. Silver nitrate (1.5 mug/ml) in distilled water inactivated bacteriophage T2 particles as determined by their infectivity to Escherichia coli B cultures. Lysozyme (50 mug/ml) reduced, and sodium chloride (0.9%) blocked this activity.     

Inhibition of microalgal growth by silver nitrate

AgNO₃ (0.1 mg l^–1) inhibits the growth of the microalgae, Chlorella vulgaris and ChlorellaVT-1. Glutathione at 0.1 mm added to AgNO₃-treated cells eliminated inhibition of growth whereas a glutathione synthesis inhibitor l-S,R-buthionine sulfoximine, failed to affect growth.     

Reduction of silver nitrate by cystoliths ofFicus elastica

Summary The cystoliths ofFicus elastica turn dark when a 2 per cent solution of silver nitrate is applied to the leaf sections. The cystoliths appear as if they reduce the silver ions and impregnate themselves with metallic silver. The reducing activity is, however, accounted for by ascorbic acid, and not by the cystoliths in themselves. The darkening reaction takes place in the presence of ascorbic acid either natively contained in fresh leaves or exogenously replenished after killing of the leaf sections. The cystoliths can react, however, only when they maintain the calcareous cortex intact. The reaction no longer occurs even in the presence of ascorbic acid when the cystoliths have been deprived of the cortex by exposure to Na₂-EDTA.     

Quenching of the fluorescence of proteins by silver nitrate

The mechanisms by which Ag⁺ may quench protein tryptophanyl fluorescence have been studied. A 1:1 Ag⁺-tryptophan complex was detected spectrophotometrically and shown to have a k_a = 6.5 × 10³ M^?1. The complex was nonfluorescent. Ag⁺ and NO₃^? each caused collisional quenching which proceeded at nearly diffusion-controlled rates in a series of indole-containing compounds. Analysis of the rates by means of Stern-Volmer plots and lifetime measurements showed also that charge and the presence of salt influence the quenching rate constants.The fluorescence of nonsulfhydryl proteins was quenched by AgNO₃ only in concentrations needed for Stern-Volmer quenching of simple indole model compounds. However, the plots for protein quenching were generally nonlinear, a reflection of the heterogeneity of tryptophanyl residues. AgNO₃ quenching increased the polarization of protein fluorescence and decreased the lifetime. Rotational relaxation times were determined from Perrin plots of reciprocal polarization vs fluorescence intensity in the presence of various amounts of AgNO₃.The fluorescence of the sulfhydryl proteins ovalbumin, yeast, and equine liver alcohol dehydrogenases was strongly quenched by AgNO₃ in parallel with the formation of Ag⁺-mercaptide bonds. The quenching of fluorescence of sulfhydryl proteins was exhibited even in 8 m urea, thus ruling out conformational change as a major basis for the quenching. It was found that Ag⁺ mercaptide bond formation was accompanied by development of an ultraviolet absorption band. The reaction of Ag⁺ with cysteine, for example, could be followed spectrophotometrically. The uv absorption of different silver mercaptides varied with the compound and pH.Since the uv absorption of Ag⁺-mercaptides extended up to 340 nm, and was also found in Ag⁺-treated sulfhydryl proteins, energy transfer from excited tryptophans seemed a reasonable basis for the observed fluorescence quenching. This possibility was confirmed by calculation of Förster critical transfer distances for a variety of donor-acceptor (Ag⁺-mercaptide) pairs.The lifetime of sulfhydryl protein fluorescence was decreased by AgNO₃, but the emission spectrum was relatively little affected, in contrast to previously reported quenching by Hg²⁺. Additional mechanisms of fluorescence alteration by Ag⁺ in proteins (e.g., “heavy atom” effect, conformational changes, enhancement of sulfhydryl quenching) are also considered.The spectral effects of Ag⁺ interaction with proteins have the following practical applications:determination of —SH groups; probe of accessibility of binding sites and tryptophan-sulfhydryl distances; determination of rotational relaxation times by Perrin plots of reciprocal polarization vs lifetime; kinetic studies of Ag⁺ interaction with proteins.     

硝酸银对常见呼吸道病原体的抑制作用

目的证实硝酸银对常见呼吸道病原体具有抑制作用。方法采用血凝试验和鸡胚培养法观察硝酸银对副流感病毒的抑制作用;采用细胞培养法观察硝酸银对腺病毒的抑制作用;采用细菌培养法观察硝酸银对肺炎链球菌和乙型溶血型链球菌的抑制作用。结果硝酸银对副流感病毒和腺病毒有明显的抑制作用,对肺炎链球菌和乙型溶血型链球菌有极强的杀菌作用。结论硝酸银对常见呼吸道病原体有明显的抑制作用。     

Enhanced shoot regeneration from Brassica campestris by silver nitrate

Summary The morphogenetic response of Brassica campestris genotype R500 to inhibitors of ethylene biosynthesis and action was investigated. A medium containing 1.0 mg.l^–1 NAA, 2.0 mg.l^–1 BAP, and 30 or 60 M AgNO₃ significantly enhanced both the percentage shoot regeneration and the number of shoots per cotyledon expiant. Although callus proliferation occurred on hypocotyl segments, no shoots were formed in response to AgNO₃ with expiants older than five days. Cotyledons older than six days formed shoots only with AgNO₃. Cobalt chloride at 20 and 30 M increased cotyledon shoot regeneration but was inferior to AgNO₃. Hypocotyl segments were unresponsive. Salicylic acid at 25 and 50 M prevented both shoot regeneration and callusing without any obvious toxic effects. Removal of expiants from AgNO₃ after 12 days did not alter the percentage of shoot regeneration but increased the number of shoots per expiant. This response was dependent on the level of BAP. Percentage shoot regeneration and number of shoots per cotyledon explant were not affected by removal of CoCl₂. These results indicate that the poor regenerative capacity of this genotype may be related to ethylene biosynthesis or metabolism.Abbreviations NAA Naphthalene Acetic Acid - BAP 6-Benzylamino Purine - MS Murashige and Skoog Medium     

Susceptibility of multidrug-resistant isolates ofKlebsiella pneumoniae to silver nitrate

Multidrug-resistant (MDR) clinical isolates ofKlebsiella pneumoniae were checked for their sensitivity toward silver nitrate by the tube-dilution method. Nearly 75% of MDR strains clould be successfully inhibited by 5 mg/L of silver nitrate. A significant correlation was observed between incidence of silver and trimoxazole resistance and silver and kanamycin resistance in these isolates. The genetic linkage of these two properties could not be proved since simultaneous curing and co-transfer studies gave negative results.     

Mode of bactericidal action of silver zeolite and its comparison with that of silver nitrate

The properties of the bactericidal action of silver zeolite as affected by inorganic salts and ion chelators were similar to those of silver nitrate. The results suggest that the contact of the bacterial cell with silver zeolite, the consequent transfer of silver ion to the cell, and the generation of reactive oxygen species in the cell are involved in the bactericidal activity of silver zeolite.     

Mass spectrometry of the silver nitrate derivatives of cyclopropenoid compounds

1,2-dihexylcyclopropene, 1,2-diheptylcyclopropene, 1,2-dioctylcyclopropene, methyl malvalate, and methyl sterculate have been reacted with silver nitrate in methanol to form the corresponding methoxy and ketone derivatives. GLC, IR, and MS data are presented. The mass spectra and a possible method for determining the cyclopropene ring position are discussed.