Pronase reduces intramembranous particle density in uterine epithelial cells in vivo

The proteolytic enzyme, pronase, was injected into the uterine lumen of rats. This treatment removed half the intramembranous particles (IMPs) from the apical plasma membrane of the uterine epithelial cells but tight junctions of these cells were unaffected. We conclude that at least some of the IMPs are proteinaceous in nature and suggest that IMPs not affected by pronase may be deeply embedded in the lipid bilayer.     

Thermal inhibition of repair of methylmethane sulfonate-damaged DNA in chick embryo fibroblasts

Chick embryo fibroblasts were treated with the monofunctional alkylating agent methylmethane sulfonate at various concentrations for 1 h at 42°C, rinsed and then incubated post-treatment at various temperatures at which the kinetics of alkali-labile bond disappearance was followed. Growth experiments showed that these cells grew similarly at temperatures of either 37°C or 42°C. Repair as assessed by removal of alkali-labile bond was also similar for postincubation in the temperature range 37–42°C for damage due to methylmethane sulfonate treatment at concentrations less than 1.5 mM. When the postincubation temperature was raised higher than 42.5–43°C, this type of repair was stopped. The normal internal body temperature of adult chickens is about 41.6°C. Hence the present finding indicates that chick cells are much more severely restricted in DNA repair at temperatures above normal than are mammalian cells, which can function in this respect for several deg. C above 37°C.     

Effect of change in particle number on pulmonary clearance of aerosolized 99mTc-DTPA

Pulmonary clearance (PCl) of inhaled aerosolized 99mTc-diethylenetriamine pentaacetic acid (DTPA) across the alveolocapillary membrane is diffusion limited. Therefore, if the mixing of the 99mTc-DTPA in the aqueous hypophase underlying surfactant is slow or incomplete or if there were no hypophase, an increase in the alveolar surface area occupied by 99mTc-DTPA particles would increase the absorption rate. The aim of this study was to examine whether there is an effect on PCl of changing the number of inhaled particles. The change in particle number was accomplished by a setup of four parallel jet nebulizers feeding a central delivery chamber of 400 cm3. We performed two kinds of experiments in eight healthy nonsmokers between 28 and 52 yr of age. In the first experiment, 99mTc-DTPA in saline was nebulized in one nebulizer, while saline was nebulized in the other three. In the second experiment the number of inhaled particles containing 99mTc-DTPA was increased by a factor of four by nebulizing 99mTc-DTPA in saline in all four nebulizers simultaneously. Increasing the number of inhaled 99mTc-DTPA particles caused an increase in PCl of 24.2% (P less than 0.01). We conclude that there is a slight but significant effect of changing the number of DTPA particles on PCl and that this is probably due to an uneven mixing of the 99mTc-DTPA in the aqueous hypophase underlying the surfactant lining and the alveoli.     

A decade of diabetes: keeping children out of hospital.

OBJECTIVES--To document the number of children aged less than 15 years who developed diabetes and were managed within one large health district, and to evaluate the outcome of those children managed without hospital admission at diagnosis. DESIGN--A retrospective study over 1979-88, when a paediatrician and a physician with special interests in childhood diabetes initiated joint clinics. Data collected from the district diabetes register and files of consultants and health visitors specialising in diabetes. SETTING--Referral of children to consultants in Leicestershire (total population 863,000). MAIN OUTCOME MEASURES--The proportion of children managed without hospital admission, comparison of readmission rates and glycated haemoglobin concentrations between children admitted and those not admitted. RESULTS--Over 10 years 236 children aged 10-14 years developed diabetes (annual incidence rate 12.8/100,000 child population (95% confidence interval 11.3 to 14.7)). In total 138 were not admitted to hospital but received supervised management based at home. Admitted children were younger or acidotic or their family doctors did not contact the diabetes team. Duration of admission declined from seven days in 1979-80 to three days in 1987-8. Ninety two were not admitted to hospital during the 10 years for any reason. Significantly fewer children who received management at home were readmitted for reasons related to diabetes than the group treated in hospital (30 (22%) v 40 (41%); p = 0.004). Concentrations of glycated haemoglobin were no different between the two groups. CONCLUSIONS--Children with newly diagnosed diabetes may be safely and effectively managed out of hospital. Domiciliary or community based management depends on the commitment of consultants specialising in diabetes working in close cooperation with general practitioners, specialist nurses in diabetes, and dietitians.     

Clutch size relative to tree cavity size in Northern Flickers

We analysed clutch size versus nest size in 153 broods of the Northern Flicker Colaptes auratus , a woodpecker using natural cavities in British Columbia, Canada. Larger volume cavities were less susceptible to predation and cavity size was positively associated with the age and body size of males and with the body condition of female parents. Although clutches varied between 4 and 11 eggs, and the floor area of cavities varied about 5-fold, we found no relationship between clutch size and floor area or cavity volume. To see if there were fitness consequences to clutch size relative to nest size, we examined hatching success and nestling mortality in flicker broods. Hatching success was not related to cavity size, but crowding slightly reduced nestling survival even when clutch size was controlled statistically. However, there was no effect of cavity size on the total number of nestlings fledged. Newly excavated flicker cavities were smaller than reused cavities suggesting a cost to excavation. This cost, coupled with the minimal fitness consequences of overcrowding, may explain why flickers do not adjust clutch size to cavity size.     

Repair of benzo[a]pyrene-initiated DNA damage in human cells requires activation of DNA polymerase alpha

Normal human fibroblasts treated with r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) yielded DNA polymerase alpha with elevated levels of activity, incorporated [3H]thymidine as a function of unscheduled DNA synthesis, and exhibited restoration of normal DNA-strand length as a function of unscheduled DNA synthesis. Lipoprotein-deficient fibroblasts treated with BPDE did not show elevated levels of DNA polymerase alpha activity, exhibited minimal [3H]thymidine incorporation, and had fragmented DNA after 24 h of repair in the absence of lipoprotein or phosphatidylinositol supplementation. When DNA polymerase beta activity was inhibited, cells with normal lipoprotein uptake exhibited [3H]thymidine incorporation into BPDE-damaged DNA but did not show an increase in DNA-strand length. DNA polymerase alpha activity and [3H]thymidine incorporation in lipoprotein-deficient fibroblasts increased to normal levels when the cells were permeabilized and low-density lipoproteins or phosphatidylinositol were introduced into the cells. DNA polymerase alpha isolated from normal human fibroblasts, but not from lipoprotein-deficient fibroblasts, showed increased specific activity after the cells were treated with BPDE. When BPDE-treated lipoprotein-deficient fibroblasts were permeabilized and 32P-ATP was introduced into the cells along with lipoproteins, 32P-labeled DNA polymerase alpha with significantly increased specific activity was isolated from the cells. These data suggest that treatment of human fibroblasts with BPDE initiates unscheduled DNA synthesis, as a function of DNA excision repair, which is correlated with increased activity of DNA polymerase alpha, and that increased DNA polymerase alpha activity may be correlated with phosphorylation of the enzyme in a reaction that is stimulated by low-density lipoprotein or by the lipoprotein component, phosphatidylinositol.