Antibacterial activity of some α- substituted 2-Methyl-5-nitrofurans

The minimum inhibitory concentration values against Gram-negative and Gram-positive bacteria were determined and compared for a selected group of synthesized alpha-substituted 2-methyl-5-nitrofuran derivatives. In vitro oxidation of thiols to disulfides by 2-(iodomethyl)-5-nitrofuran indicated that oxidation of enzyme-thiol groups to disulfide bonds was a possible mode of action; but was discounted by noninhibition of thiol enzymes by these compounds. Electron-microscopic studies of the morphology of bacteria after treatment with these derivatives showed the formation of unusual elongation, branching and atypical rod shapes in E. coli, while S. aureus manifested multibud formation with some cytoplasmic protrusions. The possible mode of action of these compounds is discussed.     

Contrasting evolutionary histories among tightly linked HLA loci

Genes comprising the major histocompatibility complex (MHC) play a central role in governing the immune response of vertebrates. A great deal of information has been revealed on the molecular biology and physiology of these loci, but three features-the high polymorphism, tight linkage among the loci, and the nonrandom association of alleles-make the system of particular interest from the perspective of population genetics. Information on the dynamic evolutionary forces that have acted on a locus can be inferred from the number and distribution of alleles that it carries. Ten loci from the HLA region of the human MHC, each sampled from several different populations, have been examined for departures from the expected value of homozygosity under the condition of selective neutrality. The homozygosities of five class I and II loci that code for membrane glycoproteins, HLA-A, -B, -C, -DR, and -DQ, and of glyoxylase I (GLO) were significantly less than the neutrality expectations. This suggests the presence of some form of balancing selection. In spite of being closely linked, in fact, located between the class I and class II histocompatibility loci, the homozygosities of the four class III or complement loci C2, Bf, C4A, and C4B, which are detected by electrophoresis, were indistinguishable from, or exceeded, that expected under neutrality. Although this conforms to the suggestion that, in general, electrophoretic variants are neutral, because of the tight linkage to loci demonstrating a history of selection, it is possible that the mechanism for generating variation in the class III loci may be different from that of the class I and class II loci.     

Comparative studies of pollen and fluorescent dye transport by bumble bees visiting Erythronium grandiflorum

Summary In the Colorado Rocky Mountains the glacier lily Erythronium grandiflorum exhibits a striking dimorphism in pollen color and is commonly pollinated by the bumble bee Bombus occidentalis. We induced bees to visit sequences of flowers in a flight cage, and compared dispersal of distinctively-colored pollen and fluorescent pigment (dye) that the bee had picked up at a single donor flower. Nonparametric and parametric analyses showed that dispersal properties of pollen and dye differed; consistently less pollen was deposited and it was carried consistently shorter distances than dye. Dye thus does not provide an accurate means of assessing exacty where or how far pollen travels in this plant-pollinator system. On the other hand, both pollen and dye responded similarly to several experimental manipulations of donor and recipient flowers. Hence dye may well be of value for a qualitative investigation of how floral traits influence pollen dispersal.     

Cloning, nucleotide sequencing, and expression of tetanus toxin fragment C in Escherichia coli.

The amino acid sequence of the first 30 residues of fragment C of tetanus toxin was determined, and a mixture of 32 complementary oligonucleotides, each 17 bases long, was synthesized. A 2-kilobase (kb) EcoI fragment of Clostridium tetani DNA was identified by Southern blotting and was cloned into the Escherichia coli plasmid vector pAT153 with the 32P-labeled oligonucleotide mixture as a probe. A second 3.2-kb Bg/II fragment was identified and cloned with the 2-kb EcoRI fragment as a probe. The nucleotide sequence of 1.8 kb of this DNA was determined and was shown to encode the entire fragment C and a portion of fragment B of tetanus toxin. The tetanus DNA was expressed in E. coli with pWRL507, a plasmid vector containing the trp promoter and a portion of the trpE gene. The trpE-tetanus fusion proteins were visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and were shown to react with anti-fragment C antibody.     

The residual unilateral cleft lip nasal deformity: a three-phase correction technique

The author presents a three-phase correction technique for the residual unilateral cleft lip nasal deformity. This procedure involves a sculpting excision of the alar rim, use of this alar rim as an interpositional flap in lengthening the columella, and augmentation of the nasal tip and perialar sulcus with a free ear conchal cartilage graft. The concept has been incorporated in the revisionary surgery program of 74 patients over a period of 5 years with a minimal follow-up of 2 years. The majority of the patients are operated on between the ages of 5 and 7 years based on the concept of a need for a "tidy appearance" by first grade.     

Selenium-dependent and non-selenium-dependent glutathione peroxidase in human tissues of New Zealand residents

Glutathione peroxidase was assayed in human tissues of New Zealand residents by the coupled assay method. Total glutathione peroxidase was assayed using cumene hydroperoxide. The non-selenium-dependent activity was not detected with t-butyl hydroperoxide and thus was determined from the difference between total activity and the selenium-dependent activity using hydrogen peroxide or t-butyl hydroperoxide. Only selenium-dependent activity was found in whole blood, erythrocytes, platelets and biopsy skeletal muscle. A small non-selenium dependent activity was measured in plasma and a larger activity in biopsy liver supernatant and homogenate. Glutathione-S-transferase was detected in all tissues.     

The structure of the cytochrome a3-CuB site of mammalian cytochrome c oxidase as probed by MCD and EPR spectroscopy

The nature of the complexes formed between cytochrome c oxidase and the three inhibitory ligands N3-, CN-, and S2- have been investigated by a combination of MCD and EPR spectroscopy. CN- forms a linear bridge between the Fe III a3 and CuB II, suggesting that the distance between these centers in the oxidized enzyme is between 5 and 5.25 A. This distance is too short to permit N3- to form a linear bridge and the evidence suggests this to be bent. In contrast S2- or SH- is unable to form any bridge and it seems likely that two SH- ions are bound by the bimetallic site, one to Fe III a3 and the other to CuB I. The significance of the a3-CuB distance in terms of oxygen binding and reduction is discussed.     

The effect of methylene blue on the hepatocellular redox state and liver lipid content during chronic ethanol feeding in the rat.

Feeding of ethanol in a liquid diet to male Wistar rats caused decreases in the hepatic cytosolic and mitochondrial [NAD+]/[NADH] ratios. This redox-state change was attenuated after 16 days of feeding ethanol as 36% of the total energy intake. Supplementation of the ethanol-containing liquid diet with Methylene Blue largely prevented the ethanol-induced redox state changes, but did not significantly decrease the severity of the hepatic lipid accumulation that resulted from ethanol ingestion. Methylene Blue did not affect body-weight gain, ethanol intake or serum ethanol concentrations in ethanol-fed rats, nor did the compound influence the hepatic redox state or liver lipid content of appropriate pair-fed control animals. These findings suggest that the altered hepatic redox state that results from ethanol oxidation is not primarily responsible for the production of fatty liver after long-term ethanol feeding in the rat.     

Screening for antimalarial maculopathy in rheumatology clinics.

Ophthalmoscopy and three tests of visual function were undertaken in 39 patients with rheumatoid arthritis receiving treatment with antimalarial drugs and in a control group of 16 patients with rheumatoid arthritis who were not receiving such treatment. Visual contrast sensitivity, macular threshold to red light, and central visual fields to red targets were not significantly different in treated patients and controls. There were no abnormalities in visual acuity, but 11 of 76 eyes of treated patients showed minor macular abnormalities on ophthalmoscopy that were not seen in control patients, suggesting that ophthalmoscopy may be the most sensitive measure of early drug toxicity. Five rheumatologists were able to identify 52 of 65 minor changes detected by an ophthalmologist. These studies, and a critical review of published reports, suggest that in clinical practice antimalarial drugs can be administered safely to patients with rheumatoid arthritis without the need for repetitive routine examination by an ophthalmologist or the use of complicated physiological tests. Recording of visual acuity in each eye and ophthalmoscopy by the prescribing doctor may be all that are required to detect early antimalarial maculopathy.