Staphylococcal penicillinase was inactivated by treatment with a relatively low concentration of methyldichlorophenyl-isoxazolyl penicillin (dicloxacillin). Inactivated enzyme was isolated by gel-filtration and reactivated by incubation at 37°C. It is suggested that the inactivated enzyme is penicilloyl enzyme which is readily hydrolyzed to active enzyme.

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6-MFA, a new antiviral agent isolated from Aspergillus flavus, strain 6-MFA, showed significant protection rates in mice against fatal Semliki Forest Virus (SFV) challenge. Major antiviral activity resided intracellularly in fungal mycelia. Maximum (100%) antiviral activity could be achieved after 5 days of incubation of the fungus under stationary conditions in SHOPE'S medium. ED₅₀ of crude 6-MFA is around 36 mg/kg body weight and the maximum tolerated dose, over 300 mg/kg body weight in mice. Mice protected by 6-MFA against initial SFV challenge remained refractory to subsequent challenge. No direct virucidal action of 6-MFA was observed.

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Studies on the physico-chemical characteristics of a new antiviral agent designated 6-MFA obtained from Aspergillus flavus, in culture show that 6-MFA is a thermolabile, non-dialyzable, Seitz-filterable and high molecular substance and can be withstand freezedrying. Biosynthesis of 6-MFA is favored at pH 6. 6-MFA is more stable in vitro at pH 6 and 7. Virus-like particles are associated with preparations of 6-MFA.

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Investigations on the anti-Semliki Forest virus activity of a new antiviral agent (designated 6-MFA) obtained from fungus Aspergillus flavus, strain 6-MFA, show that when low doses of 6-MFA, having alone little effect, are suitably combined with cycloheximide, antiviral activity in mice may be enhanced 9- to 10-fold.

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(1) Treatment with doxycyline substantially reduces the acute toxicity of daunomycin to the mouse. Treatment with doxycycline alters the distribution of daunomycin amongst the body tissues of the mouse. The ability of the isolated kidney to bind the daunomycin is enhanced by pretreatment with doxycycline. This observation is in agreement with the phenomenon noted in vivo with the same organ.
(2) The antineoplastic activity of daunomycin, tested in vivo in mice bearing Sarcoma 180 is not modified by treatment with doxycyctine, nor does doxycycline modify the inhibition of DNA synthesis in isolated Sarcoma 180 cells by daunomycin.
(3) The experiments carried out on isolated cell, namely: (a) lack of interactions between daunomycin and doxycycline on the incorporation of thymidine into DNA, (b) no modifications in the uptake and retention of daunomycin by cells pretreated with doxycyline, suggest the hypothesis that the similar pharmacological behavior of the two molecules with regard to the tumor is due to 2 kinds of receptors that are affected differently by the two drugs.
(4) The decrease in the acute toxicity of the antibiastic drug might be due to an interaction between doxycycline and those receptors of the toxic effect which are normally affected by daunomycin in the animals not treated with doxycycline.

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Actinotiocin is a new sulfur-con tainig peptide antibiotic obtained from the cultured broth and the mycelium of Actinomadura pusilla A-118 (S₂-118). It is extracted with ethyl acetate and purified by silica gel chromatography. It forms colorless columnar crystals, melts at 247-249°C, and gives [α]²⁰_D+164° (c0.77, dioxane). C₄₉H_53-55N₁₃O₁₀S₅ was suggested for its molecular formula by elemental analysis. On acidic hydrolysis of actinotiocin, a new large molecular amino acid (III, C₂₈H₁₈N₆O₆S₄) having some heteroaromatic rings, serine, proline, glycine and unidentified amino acids were obtained. The partial structure of the amino acid (III) was deduced from the chemical reaction and spectral data. Actinotiocin showed strong antibacterial activity against gram-positive bacteria and no cross resistance with commercial antibiotics. The administration of 1, 000mg/kg of this antibiotic into mice by intraperitoneal and oral routes did not result in any toxic symptoms.

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In the course of our search for new antibiotics, a strain of Bacillus circulans No. YQW-B6 was isolated from a soil sample collected in Taiwan. This organism produced a complex of aminoglycoside antibiotics designated Bu-1709, and the two major components, A₁ and A₂, were identified as butirosins A (I) and B (II)^2-4), respectively. This paper reports the bioactive degradation products from butirosins and the semi-synthesis of butirosin analogs.

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Cholesterol and lecithin can antagonize growth inhibition of Aspergillus niger by mycobacillin only if added at the same time as the antibiotic. Experiments with different derivatives of cholesterol and components of lecithin indicate that the 3-β-hydroxyl group of the former and the oleic acid component of the latter are responsible for antagonistic action.

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