Use of chemostat for selection ofStreptomyces hygroscopicus mutants altered in regulation of maltose utilization

Summary Streptomyces hygroscopicus mutants showing altered fermentation kinetics were isolated using a selection procedure in a chemostat. Several mutants were obtained which differed in their capacity to produce the macrolide antibiotic turimycin.     

Activity of β-galactosidase in homogenates and isolated microvilli fraction of jejunal mucosa from suckling rats

1. beta-Galactosidase activity was studied in homogenates and isolated microvilli fraction of jejunal mucosa from 14-day-old suckling rats. o-Nitrophenyl beta-d-galactoside served as the substrate. 2. The microvilli fraction contains about one-third of the total activity of the original homogenate. 3. The pH optimum of the beta-galactosidase was 3.5 in the total homogenate and supernatant fraction, whereas in the microvilli fraction the maximum activity was at pH5.5. 4. This work gives further support to the view that two beta-galactosidases exist in the jejunal mucosa.     

The influence of postnatal nutrition on lipoprotein lipase activity and hormone sensitive lipolysis in vitro of rat adipose tissue

In rats grown up in small and large nests the lipolytic activity of adipose tissue was studied in vitro in dependence on age. Independent of age and sex a significantly higher lipoprotein lipase activity as well as a lower basal or norepinephrine stimulated lipolysis and reesterification (absolute) occurred in rats from small nests compared with rats from large nests. The calculated degree of reesterification was independent of the nest size, but decreased from 80% to 30% from one month to one year of age. The marked differences in the lipolytic activities of adipose tissue emphasize the distinct influence of the post-natal nutrition on metabolic functions in the later life and lead to the conclusion that the metabolism of adipose tissue of animals from small nests is directed towards a long-term increased storage of lipids.     

Robertsonian karyotype variation in wild house mice from Rhaeto-Lombardia

The European longtailed house mouse (M. m. brevirostris and domesticus) in the Rhaetian Alps and Lombardia presents a complex system of Robertsonian (Rb) variation and karyotype diversity, several adjoining populations homozygous for multiple Rb metacentric chromosomes, sites of coexistence of different Rb types, and zones of hybridization with non-Rb populations. The original "tobacco mouse" is just one of many local Rb variants, such as those from other Alpine areas (e.g., Orobian Alps) or from Central Lombardia, where a relatively large region within which the population is homogeneous for multi-Rb metacentrics is found. The present study is based strictly on material in which the chromosome arms were identified by G-banding, so that karyotypes within the areas under investigation could be compared. Altogether 111 mice were studied.     

Sex-chromosome aberrations in wood lemmings (Myopus schisticolor)

The wood lemming displays certain peculiar features: (1) The sex ratio shows a prevalence of females (FRANK, 1966; KALELA and OKSALA, 1966), and some females produce only female offspring (KALELA and OKSALA, 1966). (2) In a considerable proportion (in the present material, slightly less than half) of the females, an XY chromosome complement is found in the somatic tissues, but the Y is absent in the germ line of those studied (Fredga et al., 1976). Therefore, (3) a mechanism of double nondisjunction in early fetal life of XY females has to be postulated, which replaces the Y in the germ line by duplication of the X. It is assumed (4) that the X of XY females bears a sex-reversal factor that affects the male determining action of the Y (Fredga et al., 1977). There is (5) a strong presumption that in most cases the XY females are those that produce daughters only, but (6) a few exceptions may occur (FRANK, unpublished observations), suggesting that the regulation according to assumption 3 (perhaps also to 4) is incomplete in XY females. In the present report, four females are described with a 31,XO karyotype, two females with 33,XYY or 32,XY/33,XYY, respectively, two males with a 33,XXY, and one male with a 32,XX/33,XXY karyotype, as observed in a consecutive series of 502 wood lemmings. The incidence of sex-chromosome anomalies in liveborn and adult animals was 2.3%; the overall incidence, including embryos, was 1.79%. Neither the somatic XO constitution nor the existence of an extra Y in females precludes fertility. However, the XXY condition in the male results in sterility. There is certain evidence that an instability of the proposed mechanism for double mitotic nondisjunction of the sex chromosomes in oogonia accounts for the high rate of sex-chromosome aberrations in wood lemmings, at least when the mother is XY.     

The superficial cells of the transitional epithelium in the expanded and unexpanded rat urinary bladder. Transmission and scanning electron-microscopic study.

The superficial epithelial layer in the urinary bladder of adult rats was examined, in various states, using the transmission and scanning electron microscopes. A good agreement was obtained between the results of the two methods. When the urinary bladder is unexpanded, the superficial cells show marked bulges into the bladder lumen and the contacts between cells (mainly desmosomes) are displaced deep into the epithelium. The luminal surface is bizarrely bent and large parts of the membrane intrude into the cytoplasm, where they give the appearance of discoid and fusiform vesicles. Between neighboring cells, deep interdigitations are observed. In the scanning electron microscope, the surface of the epithelium appears cauliflower-like and has deep grooves, gullys and folds. When the bladder is expanded, the surface becomes smoother and the contacts between cells move to the surface. The stretched cells are angular in form (5-, 6- or 7-sided) and show great variations in surface area (150-500 mum2). The luminal cell membrane consists of an alternation of asymmetrical areas (120 A thick and 0.2-0.4 mum in length) with normal sections which are 80 A thick. In the scanning electron microscope, these thick areas appear as 4-, 5- or 6-sided plaques with a maximal diameter of 0.4 mum. The borders of the plaques are formed of portions of cell membrane which have a normal thickness and extrude as microcristae into the lumen. This produces a honeycomb appearance on the cell surface.