Distribution of Alginate Lyase Activity among Strains of Bacillus circulans

Strains from four different DNA relatedness groups of Bacillus circulans showed apparent alginate lyase activity; the activity of three strains examined had mannuronidase specificity. A representative strain of group 4 also produced apparent inducible unsulfated chrondroitin lyase activity.     

Untargeted mutagenesis induced by UV in the lacI gene of Escherichia coli

Summary Using a nonselective method, we have estimated the proportion of untargeted mutations in the lacI gene of E. coli by transferring either irradiated or unirradiated F pro lac plasmids from an excision deficient donor to an excision deficient pro lac deleted recipient that had been irradiated and allowed to induce recA dependent functions for 30 min. We find that about 10 percent of the mutations induced by either 3.5 Jm^-2 or 7 Jm^-2 UV are untargeted.     

Transforming growth factors--an overview

Transforming Growth Factors (TGFs) are a sub-group of a larger family of protein hormones. Two major types of TGF are currently known, alpha-TGF and beta-TGF. Biologically their most important property is to act synergistically to induce anchorage-independent growth of target cells otherwise incapable of such growth. Since this growth parameter is well correlated with tumorigenicity in vivo, these factors may play a role in cancer development. Biochemically both alpha-TGF and beta-TGF have been well characterised in some types of cells and tissues. Their role in normal and neoplastic growth is actively studied.     

Mice coisogenically immunized against H-2 class I antigens on transfected l cells reject transplanted embryonal carcinoma cells

Evidence is presented of the ability of H-2 class I antigens to function as teratocarcinoma transplantation (Gt) antigens. Coisogenic immunization against H-2 class I antigens expressed on transfected L cells is shown to induce resistance to embryonic carcinoma (EC) cell allografts. The K^b, D^b, D^d, and, in appropriate recipients, L^d antigens can function as Gt antigens. The protocol presented may be useful for the molecular identification of other genes encoding histocompatibility antigens.     

Histochemical and immunohistochemical localization of hexokinase isoenzymes in normal rat liver

Summary Histochemical and immunohistochemical procedures have been used to examine the localization of three of the four hexokinase isoenzymes present in the liver of fed female Wistar rats. Distinctive distribution patterns were found for hexokinase type I and glucokinase but hexokinase type II was not detectable. Hexokinase type I was identified in sinusoidal cells and in bile duct epithelia, nerves and arteries in the portal triad. Glucokinase, the major isoenzyme, was confined to parenchymal cells where it was present in much higher amounts in perivenous compared with periportal hepatocytes. Staining within these two zones was not homogeneous and each had a mosaic appearance caused by the presence of a few hepatocytes containing little or no glucokinase amongst the majority of darkly stained cells in perivenous areas and a few darkly stained cells amongst the majority of unstained cells in periportal areas. Hence, hepatocytesin situ are a strikingly heterogeneous population of cells. Their metabolic status cannot be controlled simply by the differential supply of oxygen, substrates and hormones to different regions of the liver acini as proposed in the metabolic zonation model. Phenotypic differences may exist between cells within a given metabolic zone which influence their ability to respond to different environmental conditions.     

The organization of immunoglobulin variable kappa chain genes on mouse chromosome 6

One mouse with a known recombination (NAK) at the Igk locus on chromosome 6 and two new recombinants [B6.PL (7 NS) and B6.PL (85NS)] were examined using a series of probes, each of which is specific for a set of immunoglobulin (Ig) Vk genes. Under high stringency conditions, each probe detects from 1 to 19 Bam HI restriction endonuclease fragments (REFs) in genomic DNA by Southern transfer hybridization techniques. Analysis of the REF patterns indicate that the NAK recombination event occurred within the variable region of Igk. The REF patterns of the two B6.PL congenic mice provided two additional recombination events which could be examined. Although some of the REFs had shared mobility among the parental strains, at least 1 and up to 13 polymorphic REFs were present for a given probe among the NZB and AKR parental strains. The results from the NAK mouse indicate that at least some members of Vk4, Vk8, Vk10, and Vk21 were on one side of the recombination event linked to the Lyt-2 ^a and Igk-Efl ^a alleles of AKR, while the Vk9, Vk11, and Vk24 REF patterns came from the NZB parental strain linked to the Igk-Ef2 ^b (Vk1) allele. The two B6.PL congenics produced a refined map on the Lyt-2, Lyt-3 side of the Vk region. The B6.PL (85NS) mice retained the Vk21 REF pattern of the Lyt-2 ^a, Lyt-3 ^a donor strain PL/J, while displaying the C57BL/6 REF pattern for the other Vk gene groups tested. The B6.PL (75NS) mice retained the REF patterns of PL/J for Vk21 and Ef-1, indicating a third recombination. This indicates the Vk gene order is (Lyt-2; Vk21); Ef-1; (Vk4; Vk8; Vk10); and (Vk9; Vk11; Vk24; Ef-2).     

The effect of sub-lethal doses of dieldrin on resting and active metabolism in two species of shrimps

The effects of dieldrin on the active (VaO2) and resting (VrO2) oxygen consumption rates of the shrimps Macrobrachium faustinum (De Sassure) and Macrobrachium amazonicum (Heller) were studied during exposure for 4 days at 0.01 p.p.b. and 7 days at 0.0002 p.p.b., respectively. The VrO2 of M. faustinum increased significantly (P less than 0.01) by 48% but the VaO2 decreased by 13%. The VrO2 and VaO2 decreased by 43 and 70%, respectively, in M. amazonicum. Thus, in both species the aerobic metabolic scope for activity decreased. The increased resting metabolic rate of the indigenous M. faustinum is ascribed to energy consuming responses which allow compensation for the effects of the stressor. The stressor may be said to have moved this species into a metabolic "zone of compensation". The decreased resting metabolic rate of the pond-cultured M. amazonicum is ascribed to greater susceptibility, more extensive metabolic breakdown and failure of compensatory responses. This species might be said to have been forced by the stressor into a metabolic "zone of collapse".     

A comparison of the fecundities of two species of toad (Bufo bufo and B. calamita) from different habitat types in Britain

The fecundities of Natterjack toads, Bufo calamita , on a Cumbrian dune system and a relict heathland site in Hampshire were compared and contrasted with the fecundity of Common toads, B. bufo , on the Cumbrian dunes. For both species, fecundity was positively correlated with length, while in B. calamita length was also correlated with size of eggs produced, and age of the female. Bufo calamita was found to invest more energy exponentially in egg production with increasing length, and therefore age. This species also laid more than twice as many eggs as comparably-sized female B. bufo , and some probably produced two clutches of spawn per year in southern England. The enhanced fecundity of the species was believed to be an adaptation to living in areas with unpredictable spawning sites. Small female B. bufo on the dunes appeared to put more energy into egg production when small than individuals of the same species on other habitat types in Britain, possibly as a result of reduced life expectancy on the dune habitat. There was a link between old age and the production of non-viable spawn in B. calamita , and males of this species which spawned at the end of the prolonged breeding season were found to have reduced fertilization efficiency when spawning on consecutive evenings.     

Ecdysteroids regulate the release and action of eclosion hormone in the tobacco hornworm, Manduca sexta (L.)

The relationship between the ecdysteroid titre and eclosion hormone was explored for the pupal and adult ecdyses of Manduca sexta. Ecdysteroid treatment late during either moult caused a dosedependant delay in the time of ecdysis. Sensitivity to exogenous steroid treatment dropped off as the respective moults neared completion and in both cases coincided with the time of the low point in the endogenous ecdysteroid titre. It was concluded that an ecdysteroid decline is a normal prerequisite for the ecdyses of both stages. The steroid drop is important for two aspects of the eclosion hormone system: it causes target tissues to become sensitive to the peptide and it is a prerequisite for the subsequent release of eclosion hormone itself. Thus, the dual action of the declining ecdysteroid titre insures that when eclosion hormone is released, the tissues will be competent to respond to it.     

Mechanical Method of Inoculating Plates for Antibiotic Sensitivity Testing

A mechanical method of inoculating culture plates for antibiotic sensitivity testing is described. This method, which involves the use of a modified laboratory centrifuge, is rapid and provides a homogeneous distribution of organisms.