Some effects of bleomycin on the proliferation, maturation time and protein synthesis of hairless mouse epidermis.

Hairless mice were given 2 mg Bleomycin i.p. in 1-0 ml saline on two successive days. By a stathmokinetic method, by micro-flow fluorometry and by autoradiography certain kinetic parameters were measured during 10 days after the last injection. Cell counts were made and the turnover time of the differentiating cells estimated. Protein synthesis was estimated by the uptake of radioactive histidine, and dry cell mass measured by weighing. Bleomycin affected cell proliferation in the epidermis by depressing biphasically both the number of cells in, and the passage of cells through, the cell cycle phases: S, G2 and M, most probably by directly affecting late G1 cells and cells in mitosis. The time between the two minima of depressed DNA synthesis corresponded to the mean generation time of the basal cells. Histidine uptake and dry cell mass were slightly affected, but the turnover time of the differentiating cells was prolonged. Bleomycin thus had a strong long-lasting inhibitory effect on epidermal cell proliferation and a marked inhibitory effect on epidermal cell maturation in mice.     

Circadian variation in cell proliferation and maturation. A hypothesis for the growth regulation of the rat corneal epithelium.

The rat corneal epithelium has been chosen as a model for studying growth regulation. In this epithelium a large single cohort of cells enters the S phase during a fairly short time period once a day. The factor responsible for this wave of cell proliferation is unknown, but it may be a chemical signal from the central nervous system (the suprachiasmatic nucleus or the corpus pineale). The mature cell compartment of the corneal epithelium is assumed to produce a negative feedback factor (chalone), counteracting the effect of the circadian proliferative factor on the local cell proliferation. When no circadian factor is being produced, during most of the 24 h, the chalone seems to enhance the maturation process. During diminished chalone production (e.g. after cell injury and subsequent regeneration), we will get a more or less unrestricted cell proliferation in the tissue with a delayed maturation process prolonging the chalone depletion. This interaction between the circadian proliferative factor and the negative feedback factor for regulation of proliferation with its accompanying stimulatory effect on maturation, may represent a general mechanism in the regulation of cell proliferation in any tissue. Since in at least some organs virtually all cells entering the S phase do this as a single wave once a day, this mechanism may be enough to explain the regulation of cell proliferation during both normal and regenerative conditions.     

Characterization of Cronobacter recovered from dried milk and related products

Background  

Cronobacter is a recently proposed genus consisting of six genomospecies that encompass the organisms previously identified as Enterobacter sakazakii. Cronobacter are opportunistic pathogens and are known to cause serious infections in infants, particularly neonates. High case fatality rates have been associated with infections and acute sequelae can occur in survivors with severe ramifications on neurological development. Infant formula has been identified as one route of transmission for infection in infants. However, the primary reservoirs for subsequent contamination of foods with Cronobacter remain undefined due to the ubiquitous nature of these organisms. More recently, infections in adults have been reported, especially amongst the elderly and patients who are immunocompromised. To help prevent the transmission of infection, it is important to identify the main food sources for Cronobacter. The aim of this study was to identify and characterize Cronobacter isolated from dried-milk and related products available in an Egyptian food market.     

The impact of informal care-giving networks on adult children's care-giver burden

Previous research on the care-giver burden experienced by adult children has typically focused on the adult child and parent dyad. This study uses information on multiple informal care-givers and examines how characteristics of the informal care-giving network affect the adult child's care-giver burden. In 2007, 602 Dutch care-givers who were assisting their older parents reported on parental and personal characteristics, care activities, experienced burden and characteristics of other informal care-givers. A path model was applied to assess the relative impact of the informal care-giving network characteristics on the care-giver burden. An adult child experienced lower care-giver burden when the informal care-giving network size was larger, when more types of tasks were shared across the network, when care was shared for a longer period, and when the adult child had no disagreements with the other members of the network. Considering that the need for care of older parents is growing, being in an informal care-giving network will be of increasing benefit for adult children involved in long-term care. More care-givers will turn into managers of care, as they increasingly have to organise the sharing of care among informal helpers and cope with disagreements among the members of the network.