Ultrastructural changes in Blastomyces dermatitidis after in vitro exposure to lidocaine

Electron microscopic examination of yeasts of Blastomyces dermatitidis, exposed in vitro to concentrations of lidocaine that occur when the drug is used for topical anesthesia, showed that lidocaine rapidly damaged intracellular structures. The extent of damage was dependent on the concentration of drug and length of exposure. The observed ultrastructural changes were very similar to those reported for other drugs that directly damage membranes. This relationship suggests that the antifungal effect of lidocaine is the result of direct membrane damage.     

CG dinucleotide clusters in MHC genes and in 5'' demethylated genes

In the DNA of higher vertebrates the dinucleotide CG is unique in two respects: it occurs far less frequently than would be expected on the basis of the content of cytosine and guanine in a given DNA segment ("CG suppression") and it contains predominantly 5-methyl-cytosine, the only modified nucleotide common in vertebrate DNA. Here we point out the existence of CG clusters, i.e. localized lapses in the usual CG suppression, in two categories of DNA segments from vertebrates: around the polymorphic exons of major histocompatibility complex (MHC) genes and in the 5' regions of certain other genes. These observations contradict the recent suggestion that CG frequency is uniform over long contiguous segments of DNA containing several genes. A model for the origin of these CG clusters as a consequence of regional demethylation of germline DNA is supported by analysis of other sequence features of these regions as well as by previously published data on the methylation status in sperm DNA of two of these CG-rich regions.     

Genetics of Ia-like alloantigens in chickens and linkage withB major histocompatibility complex

Two sets of backcross matings were performed to test for linkage between genes coding for the Ia-like antigens (Ia) and the B erythrocyte antigens (Ea-B) of the chicken. Evidence is presented which indicates that the la antigens are determined by a single codominant locus and that theEa-B and Ia loci are on the same chromosome. Failure to detect a single recombinant between theEa-B and Ia loci out of 208 progeny suggests close linkage of the two genes with a map distance of up to about 2 centimorgans. The Ia genes are thus included in theB major histocompatibility complex of the chicken.     

Biology of Azospirillum-Sugarcane Association: Enhancement of Nitrogenase Activity

Azospirillum brasilense was reisolated from associations with callus tissue cultures of sugarcane and compared with stock cultures of the inoculated bacterium and related strains. Although the reisolate had a growth rate similar to stock cultures, it exhibited a severalfold increase in maximum specific activity of nitrogenase. The reisolate and the parent culture had similar ultrastructure. The general ultrastructure of Azospirillum is described. The bacterium was capsulated when grown on nitrogen-free nutrient agar plates and on callus, but was not capsulated when growing in a subsurface zone in N-free semisolid nutrient agar, except rarely in aging cultures. Capsulation may be a protective mechanism against unfavorable pO₂ under dinitrogen-fixing conditions. Pleomorphism occurred in capsulated forms, and the ultrastructure of these forms is described.     

The effect of ionic strength on the entropy-driven polymerization of tobacco mosaic virus protein: Contributions of electrical work and salting-out

The entropy-driven polymerization of tobacco mosaic virus protein is favored by an increase in ionic strength, μ, and by a decrease in pH. The effect of ionic strength is interpreted in terms of salting-out and electrical work, a function of charge and, therefore, of pH as well as of μ. The extent of polymerization is measured in terms of a characteristic temperature, $\text{T}{}^1$, corresponding to a characteristic value of the equilibrium constant, $\text{K}{}_{\mathrm{<mtext>c</mtext>}}{}^{\mathrm{T1}}$ is measured at an early stage in the polymerization process where the optical density increment from light scatter is 0.01. The theory developed encompassing both salting-out and electrical work terms relates $\text{1}\text{T}{}^1$ to μ approximately according to the equation, $\text{1}\text{T}{}^1\text{= C + Bμ ?}\text{A}\text{μ}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, where C is the ratio of entropy to enthalpy, B is proportional to the salting-out constant divided by enthalpy, and $\text{A}\text{μ}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ depends upon the square of the charge and is proportional to the electrical work contribution divided by the enthalpy. Data in which μ varied from 0.025 to 0.150 at three pH values, 5.95, 6.35, and 6.50, were fitted to this equation and the parameters C, B, and A were evaluated. Experiments were also carried out at a constant μ of 0.10 at pH values in increments of 0.1 between 5.9 and 6.8. The theory predicts that, at constant μ, $\text{1}\text{T}{}^1$, corrected for the electrical work contribution, is a linear function of pH with a negative slope proportional to the number of hydrogen ions bound per protein unit during polymerization, divided by the enthalpy. The data obtained fit two straight lines with different slopes above and below pH 6.3. Independent experiments carried out by the method of Stevens and Loga show that the number of hydrogen ions bound per protein unit also differs above and below pH 6.3 and the ratio of these is the same as the ratio of the above mentioned slopes. The data, therefore, make it possible to evaluate the enthalpy to be 24.8 kcal/mol of associating A protein and, with this value, the parameters C, B, and A can be interpreted. Standard entropies range from 86 e.u. at pH 6.5 to 88.5 at pH 5.95 and the salting-out constant, K_S^′, is 2.2 at all pH values studied. At μ = 0.10, the values of the electrical work contribution at pH 5.95, 6.35, and 6.50 are +0.298, +0.455, and +0.534 kcal/mol, respectively. Theoretical calculations from models predict values in agreement within a factor of less than two.     

Comparison of isolated peanut agglutinin receptor glycoproteins from human,bovine and porcine erythrocyte membranes

Affinity chromatography has been used to isolate and compare the peanut agglutinin receptors from neuraminidase-treated human, bovine and porcine erythrocyte membranes. Passage of Triton X-100-solubilised membrane material through either Sepharose- or acrylamide-based affinity columns resulted in the reversible binding of receptor molecules to the immobilised lectin. Elution with 0.2M galactose released specifically bound glycoprotein fractions, the composition and molecular weights of which were determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate.Carbohydrate analysis by gas chromatography identified these bound glycoprotein fractions as the major sources of the $\text{O-}\text{glycosidic-linked}$ disaccharide $\text{galactosyl}\text{-β-(1 → 3)-N-}\text{acetylgalactosamine}$ in these membranes. It is suggested that these isolated fractions represent a discrete population of glycoproteins within the membranes studied, which possess both $\text{O-}\text{glycosidic}$- and $\text{N-}\text{glycosidic-linked}$ carbohydrates.     

Altered surface glycoproteins in melanoma cell variants with reduced metastasizing capacity selected for resistance to wheat germ agglutinin

Variants of B 16-F 1 mouse melanoma cells selected for resistance to wheat germ agglutinin (WGA) toxicity $\text{in}\text{vitro}$ were found to have undergone a stable surface change correlated both to lectin resistance and reduced metastasizing potential. The surface alteration, as indicated by the increased electrophoretic mobilities of several lactoperoxidase-iodinated cell surface proteins in SDS-PAGE, was restricted to polypeptides able to interact with WGA. The availability of lectin-resistant melanoma cell variants having altered metastasizing behavior provides a promising approach to studies of the role of specific cell surface components in the metastasizing process.     

A newborn child with karyotype 47,XX,+der(12) (12pter→12q12::8q24→8qter),t(8;12) (q24;q12) pat

Summary A case of Meckel or Gruber syndrome is reported, together with a survey of the relevant literature of recent years (1971–1977), in reference to a probably autosomal recessive inheritance of this malformation.