Biochemical and cellular changes occuring during conjugation in Hansenula wingei

Brock, Thomas D. (Indiana University, Bloomington). Biochemical and cellular changes occurring during conjugation in Hansenula wingei. J. Bacteriol. 90:1019-1025. 1954.-A technique has been devised for deagglutinating mixed populations of conjugating cells so as to be able to visualize microscopically early stages of the conjugation process. A cell can form a conjugation tube only when in contact with a cell of opposite mating type, but may do so even if the mate is unresponsive or ultraviolet-inactivated. Cell fusion occurs, however, only when both cells are able to form conjugation tubes in a region of contact. Fusion begins almost as soon as the two cells begin to form protuberances, and long before any dissolution of cell-wall material between the cells occurs. A cell which has conjugated in one region of its cell wall is still able to conjugate with another cell in another region, so that triply and quadruply conjugated cells are occasionally formed. There is no significant net increase in deoxyribonucleic acid, ribonucleic acid, protein, or carbohydrate which might be related to the conjugation process, because any minor changes that occur in these components are also detected when cells of only one mating type are incubated or when the conjugation process is inhibited with the antibiotic cycloheximide. Changes in activity of beta-1,3-glucanase (with laminarin as substrate) and beta-1,6-glucanase (with pustulan as substrate) have been measured during the conjugation process, in addition to changes in the activity of several control enzymes which would not be expected to be related to the conjugation process. Significant increases in invertase (sucrase), laminarinase, and pustulanase were detected, and minimal increases occurred in beta-glucosidase and acid phosphatase. However, these same increases were also observed in controls involving only one mating type; thus, these increases are probably not related to the conjugation process, but may be a result of other processes which probably occur during incubation in the conjugation medium.     

Impact of maternal serum alpha-fetoprotein screening on antenatal diagnosis.

An analysis has been made of indications for amniocentesis in the Edinburgh area from 1979 to 1981. About 5% of all mothers underwent the procedure. Among 2137 amniocenteses, 37% were performed on mothers 35 years old or more, and 30% on patients with raised serum alpha-fetoprotein. The total number of amniocenteses and the categories have been stable for the past three years. As a result of amniocentesis 104 pregnancies were terminated, 66 of which (63%) followed a raised maternal serum alpha-fetoprotein indication, while only 10 (9.6%) were in mothers aged 35 or more. There were a further 12 terminations based on raised serum alpha-fetoprotein but where no amniocentesis had been thought necessary. Even when figures for anencephaly are excluded from the analysis, maternal serum alpha-fetoprotein screening was responsible for detecting 35 out of 63 (56%) abnormal fetuses. This constitutes a strong case for the continuation of alpha-fetoprotein screening programmes.     

Evidence against a common subunit in adenylate kinase and pyruvate kinase

Summary A modified technique has been introduced which allows detection of PK in the presence of AK after starch-gel electrophoresis. It is shown that the PK isoenzyme patterns of different human tissues are independent of the AK phenotype of the person concerned. It is concluded that there is no basis for the previously held assumption that these two enzymes share a common polypeptide chain.This work was supported by a grant from the Scottish Hospital Endowments Research Trust (HERT 309).     

Characterization of Actinomyces israelii Serotypes 1 and 2

In a previous serological study, we compared 14 isolates of Actinomyces israelii serotype 2 with 13 serotype 1 cultures. The present study reports the morphological, physiological, and biochemical characteristics of these same 27 cultures. All of the isolates exhibited similar cellular morphology, and all but one produced the typical spider type microcolony on solid media. Twelve of 13 serotype 1 isolates produced the molar tooth type macrocolony, whereas only 2 of 14 serotype 2 cultures produced this type of rough colony. All of the serotype 1 isolates fermented arabinose with the production of acid; none of the serotype 2 cultures fermented this carbohydrate. All 27 cultures produced the greatest amount of growth when cultured under anaerobic conditions and grew poorly or not at all in air. Both groups of organisms produced similar reactions on other biochemical test media; these findings suggested that A. israelii serotype 2 should not be given a species designation.