Properties of heart fibroblasts of adult rats in culture

Summary In the heart of the adult rat, fibroblasts are mainly responsible for the synthesis and deposition of the collagenous matrix. Because these cells in vitro may serve as an important model system for studies of collagen metabolism in heart tissue, we have cultured and characterized rat-heart fibroblasts from young adult and old animals. Conditions included use of media of different compositions with and without addition of ascorbate. Cell used were either cultured directly from fresh tissues or thawed previously frozen cells. Cultured cells were studied with respect to growth properties, morphology and ultrastructure and patterns of collagen. Heart fibroblasts generally resembled fibroblasts cultured from other tissues, but were more like skeletal muscle fibroblasts in that they deposited, in addition to type I collagen, type IV collagen and laminin. The fibroblasts showed a typical appearance in phase-contrast microscopy and electron microscopy. In the case of cells grown with added ascorbate, aligned collagen fibrils in the extracellular matrix showed a periodicity typical of type I collagen. The deposition of type I collagen occurred only in medium supplemented with ascorbate, and in that circumstance increased as a function of time past confluence; this was independent of the age of the animal from which the cells were obtained or of other changes of medium composition studied. Immunofluorescence studies with specific antibodies revealed that the cells deposited types I and IV collagens, laminin and fibronectin. In contrast to the case of type I collagen, the deposition of type IV collagen occurred in cells grown either with or without ascorbate. Direct observation of type IV collagen is consistent with the previous finding of type IV mRNA in cardiac fibroblasts in situ and in freshly isolated populations of these cells.     

Resistance of Pseudomonas to Quaternary Ammonium Compounds: II. Cross-Resistance Characteristics of a Mutant of Pseudomonas aeruginosa

Tube dilution experiments showed that benzalkonium chloride (BC)-resistant mutants of Pseudomonas aeruginosa grown in the presence of 1,000 mug of BC per ml were at least 20 times more sensitive to polymyxin B and colistin sulfate than the BC-sensitive (BCS) parent strain. BCS cells selected for resistance to 500 mug of polymyxin B per ml remained sensitive to BC. There was little difference in the amount of carbenicillin, gentamicin sulfate, or rifampin needed to prevent growth of either the BCS or BC-resistant (BCR) strains. Growth of BCR cells was inhibited by ethylenediaminetetraacetate at a concentration of 400 mug/ml or less, whereas the BCS strain grew at ethylenediaminetetraacetate levels of 10,000 mug/ml. Phenylmercuric acetate and thimerosal inhibited growth of BCR and BCS cells at concentrations of 10 mug/ml or less. BCR cells were cross-resistant to >1,000 mug/ml concentrations of five other quaternary ammonium compounds, including three with C(16) alkyls and two with alkyl groups of shorter length. The BCS strain was also resistant to >1,000 mug/ml concentrations of the three quaternary ammonium compounds with C(16) alkyl groups but, in addition to BC, was inhibited by 200 mug/ml levels or less of the two quaternary ammonium compounds containing alkyl groups of less than 16 carbon atoms.     

Chemical Detection of Microbial Prey by Bacterial Predators

A motile, predacious bacterium which degraded Pythium debaryanum was strongly attracted to substances released into the medium by the fungus. A nonpredacious bacterium was not attracted to these substances. The predator bacterium was specifically attracted to cellulose and its oligomers which are known to be components of the cell wall of Pythium. Ethanol inhibited chemotaxis of the bacterium without affecting either its motility or its ability to degrade cellulose. A second predacious bacterium was isolated for the alga, Skeletonema costatum. The role of chemoreception in the detection of microbial prey by bacterial predators in natural habitats is discussed.     

Human placental cathepsin B1. Isolation and some physical properties

A reproducible procedure for the isolation, from human placenta, of a cathepsin B1 in a homogeneous state, demonstrated by electrophoretic, ultracentrifugal and enzymic criteria, was carried out. The pH optimum was near pH5.5. The placental enzyme catalysed the release of acid-soluble u.v.-dense products from haemoglobin and myoglobin. It was inhibited by heavy metals and several compounds which react with the thiol groups. The optimum temperature was between 37° and 42°C. The molecular weight of the enzyme was calculated to be 24250.     

Skin Collagen and Thickness in Women with Hirsuties

Total skin collagen is greatly increased in women with hirsuties. This is presumably due to androgen, whether locally produced or circulating.     

Effect of Pregnancy on Sebum Excretion

Sebum excretion rates from forehead skin were measured serially during and after pregnancy in 10 normal women. Only minor fluctuations occurred during the middle and last trimesters of pregnancy, but there was a pronounced decrease in the postpartum period. Probably a powerful sebotrophic factor is present in pregnancy, but its nature is conjectural.     

Chronic Obstructive Pulmonary Emphysema—Is Exercise Beneficial?

Following a six-week program of training in a series of exercises, a significant number of patients with chronic obstructive pulmonary emphysema showed decided improvement in functional activity. Subjective improvement also was noted and kept the patient motivation high.Preliminary observations indicated that the improvement could be maintained long after the end of the training period.     

Mechanism of cadmium uptake by activated sludge

Summary The significance of metabolic activity in cadmium uptake by unacclimated activated sludge was studied. Below 30 mg/l cadmium in solution, biosorption was found to follow the Freundlich isotherm, which is the most common pattern for physico-chemical adsorption. More than 95% of total cadmium uptake was achieved within 5 min metal-sludge contact time. Biosorption increased strongly when the initial cadmium concentration in solution was raised from 10 to 100 mg/l, whereas in the same concentration range the metabolic activity of the sludge, as measured by respiratory activity and extracellular protein production, was very significantly inhibited. The addition of nutrients at low but significant levels failed to increase cadmium uptake in 2 h contact time, while in 24 h the addition of nutrients caused the biosorption to increase by only 5–10% without any significant growth of the biomass. Biosorption was found to increase with temperature between 5° C and 40° C, in correlation with an increase in the metabolic activity of the sludge. Pretreatment of the sludge with metabolic inhibitors (NaN₃ and UV rays) appeared to cause only a very slight decrease (5–10%) of biosorption. These results suggest that metabolic uptake of cadmium was low and that adsorption to the surface of the cells was the major mechanism of uptake.Offprint requests to: S. S. Sofer