Maintenance of the cellobiose utilization genes of Escherichia coli in a cryptic state

The genes for cellobiose utilization are normally cryptic in Escherichia coli. The cellobiose system was used as a model to understand the process by which silent genes are maintained in microbial populations. Previously reported was (1) the isolation of a mutant strain that expresses the cellobiose-utilization (Cel) genes and (2) that expression of those genes allows utilization of three beta- glucoside sugars: cellobiose, arbutin, and salicin. The Cel gene cluster has now been cloned from that mutant strain. In the course of locating the Cel genes within the cloned DNA segment, it was discovered that inactivation of the Cel-encoded hydrolase rendered the host strain sensitive to all three beta-glucosides as potent inhibitors. This sensitivity arises from the accumulation of the phosphorylated beta- glucosides. Because even the fully active genes conferred some degree of beta-glucoside sensitivity, the effects of cellobiose on a series of five Cel+ mutants of independent origin were investigated. Although each of those strains utilizes cellobiose as a sole carbon and energy source, cellobiose also acts as a potent inhibitor that reduces the growth rate on glycerol 2.5-16.5-fold. On the other hand, wild-type strains that cannot utilize cellobiose are not inhibited. The observation that the same compound can serve either as a nutrient or as an inhibitor suggests that, under most conditions in which cellobiose will be present together with other resources, there is a strong selective advantage to having the cryptic (Cel0) allele. In those environments in which cellobiose is the sole, or the best, resource, mutants that express the genes (Cel+) will have a strong selective advantage. It is suggested that temporal alternation between these two conditions is a major factor in the maintenance of these genes in E. coli populations. This alternation of environments and fitnesses was predicted by the model for cryptic-gene maintenance that was previously published.      

Isolation of arboviruses from insects collected at Beatrice Hill, Northern Territory of Australia, 1974-1976

Between October 1974 and May 1976, 57 596 mosquitoes, 169 957 Culicoides, 5923 Lasiohelea and 1043 phlebotomines were collected for virus isolation at Beatrice Hill (lat. 12 degrees 39'S.,long. 131 degrees 20'E.) in the Northern Territory of Australia. A total of 94 viruses belonging to 22 different serological groupings was isolated. The following species of insect yielded viruses which were identified and those viruses marked with an asterisk represent a new record of insect host: Culex annulirostris: Ross River, Kokobera, Barmah Forest, Corriparta, Eubenangee*, Wongorr; Anopheles amictus: Mapputta*; An bancroftii: bovine ephemeral fever*; An farauti: Eubenangee*; An annulipes: Mapputta; Culicoides marksi: Barmah Forest*, Belmont, Eubenangee*, Wallal, Warrego, Leanyer*, Parker's Farm*, Humpty Doo*; C. peregrinus: Beatrice Hill*; C. oxystoma: Bunyip Creek*, Marrakai*; C. pallidothorax: Wongorr*; C. histrio: Thimiri*; Lasiohelea spp.: Humpty Doo*. Pools of mixed species of Culicoides yielded bluetongue, Belmont, CSIRO Village, Warrego and Facey's Paddock viruses. Filter-passing agents not yet identified, were isolated from Cx annulirostris and An bancroftii. As well as providing new locality records for all but one of the 22 viruses isolated, the study yielded five new viruses (bluetongue serotype 20, CSIRO Village, Marrakai, Beatrice Hill and Humpty Doo viruses) and a new record for Thimiri virus which had not been recorded previously in Australia nor had it been isolated from an arthropod. Nine of the viruses isolated occur in more than one family of Diptera.     

Onchocerca sweetae (Nematoda: Filarioidea): notes on the intermediate host.

Microfilariae of Onchocerca sweetae are broadly distributed in the superficial layers of the dermis of the water buffalo (Bubalus bubalis). A total of 2855 insects representing 20 species were collected from O. sweetae-infected bait buffaloes. Only one species, Culicoides sp. "M", ingested microfilariae from buffalo skin. Larval development of O. sweetae was observed in the thorax of this species. Atotal of 829 insects, representing 7 species and including 749 parous Culicoides spp. were collected from light and Manitoba traps. Developing filarioid larvae were observed only in Culicoides sp. "M". It is concluded that Culicoides sp. "M" is a natural intermediate host of O. sweetae in the Northern Territory of Australia.     

All‐trans retinoic acid exposure increases connexin 43 expression in cumulus cells and improves embryo development in bovine oocytes

In developing follicles, cellular coupling within cumulus–oocyte complexes (COCs) creates a functional syncytium allowing for the passage of small molecules. In many species, intercellular coupling between granulosa cells results from the expression of connexin 43 (CX43 or Gja1) and the formation of gap junctional plaques. Previously, our lab has shown that oocytes with a higher developmental potential had higher CX43 expression in their cumulus cells compared with developmentally incompetent oocytes. All‐trans retinoic acid (ATRA) has been shown to increase CX43 expression in several different cell types. In this study we investigated the effect of ATRA treatment, during maturation, on CX43 expression and localization in cumulus cells and the developmental competence of bovine oocytes. COCs and granulosa cells exposed to ATRA during maturation had significantly higher CX43 expression and increased gap junctional coupling, respectively. In addition, there was a significant increase in the maturation, cleavage, and blastocyst rates in ATRA treated COCs. Data from these studies suggest that not only can CX43 be used as a biomarker for oocyte health, it can also potentially be manipulated using ATRA to increase the number of oocytes achieving developmental competence.     

Fracture prevention in COPD patients; a clinical 5-step approach

Although osteoporosis and its related fractures are common in patients with COPD, patients at high risk of fracture are poorly identified, and consequently, undertreated. Since there are no fracture prevention guidelines available that focus on COPD patients, we developed a clinical approach to improve the identification and treatment of COPD patients at high risk of fracture. We organised a round-table discussion with 8 clinical experts in the field of COPD and fracture prevention in the Netherlands in December 2013. The clinical experts presented a review of the literature on COPD, osteoporosis and fracture prevention. Based on the Dutch fracture prevention guideline, they developed a 5-step clinical approach for fracture prevention in COPD. Thereby, they took into account both classical risk factors for fracture (low body mass index, older age, personal and family history of fracture, immobility, smoking, alcohol intake, use of glucocorticoids and increased fall risk) and COPD-specific risk factors for fracture (severe airflow obstruction, pulmonary exacerbations and oxygen therapy). Severe COPD (defined as postbronchodilator FEV₁ < 50% predicted) was added as COPD-specific risk factor to the list of classical risk factors for fracture. The 5-step clinical approach starts with case finding using clinical risk factors, followed by risk evaluation (dual energy X-ray absorptiometry and imaging of the spine), differential diagnosis, treatment and follow-up. This systematic clinical approach, which is evidence-based and easy-to-use in daily practice by pulmonologists, should contribute to optimise fracture prevention in COPD patients at high risk of fracture.     

In vitro germline potential of stem cells derived from fetal porcine skin

Two of the unanswered questions in mammalian developmental biology are when and where the fate of the germ cell is specified. Here, we report that stem cells isolated from the skin of porcine fetuses have the intrinsic ability to differentiate into oocyte-like cells. When differentiation was induced, a subpopulation of these cells expressed markers such as Oct4, Growth differentiation factor 9b (GDF9b), the Deleted in Azoospermia-like (DAZL) gene and Vasa - all consistent with germ-cell formation. On further differentiation, these cells formed follicle-like aggregates that secreted oestradiol and progesterone and responded to gonadotropin stimulation. Some of these aggregates extruded large oocyte-like cells that expressed oocyte markers, such as zona pellucida, and the meiosis marker, synaptonemal complex protein 3 (SCP3). Some of these oocyte-like cells spontaneously developed into parthenogenetic embryo-like structures. The ability to generate oocyte-like cells from skin-derived cells may offer new possibilities for tissue therapy and provide a new in vitro model to study germ-cell formation and oogenesis.