Actin-containing cables within anchorage-dependent rat embryo cells are dissociated by plasmin and trypsin

The distribution of intracellular actin has been examined by specific immunofluorescence in a series of normal and SV40-transformed cell lines of rat origin. A consistent correlation was found between the presence of large thick sheathes of actin-containing material and anchorage-dependent growth control. Anchorage-independent growth by these cells has been shown to be associated with the production and secretion of a plasminogen activator, and dependent upon the presence of the active protease plasmin. We have found that these phenomena can be linked as follows. First, treatment with plasmin, but not urokinase or plasminogen, reversibly removes the actin-containing cables from normal rat embryo fibroblasts, and similar results are obtained with trypsin. Thrombin and chymotrypsin are relatively ineffective in causing the disappearance of the cables. Second, sera such as dog or monkey, which permit high levels of plasmin formation and activity, support cell growth in semi-solid media better than sera in which plasminogen is activated poorly or that are plasminogen-deficient; concomitantly, cables disappear in the former but not in the latter sera. The addition of a plasmin inhibitor prevents the disappearance of actin-containing cables.     

Carbon dioxide induces endotrophic germ tube formation in Candida albicans

Candida albicans formed germ tubes when exposed to air containing 5 to 15% carbon dioxide (CO2). The CO2-mediated germ tube formation occurred optimally at 37 degrees C in a pH range of 5.5 to 6.5. No germ tubes were produced at 25 degrees C, even when the optimal concentration of CO2 (10%) was present in the environment. The requirement of CO2 for germ tube formation could be partially substituted by sodium bicarbonate but not by N2. Carbon dioxide was required to be present throughout the entire course of germ tube emergence suggesting that its role is not limited to an initial triggering of morphogenic change. We suggest that carbon dioxide may be a common effector responsible for the germ tube promoting activity of certain chemical inducers for C. albicans.     

The requirements for bicarbonate and metabolism of the inducer during germ tube formation by Candida albicans

Factors affecting germ tube formation in Candida albicans at suboptimal temperatures were investigated. Candida albicans formed germ tubes between 22 and 30 degrees C in solution when incubated without shaking, in the presence of bicarbonate (2 mg mL-1). Other conditions depended on the inducer used. Proline could induce germ tube formation optimally only when its concentration was between 200 and 400 mM. A concentration of 0.05 mM N-acetylglucosamine was sufficient to induce germ tube formation. N-Acetylglucosamine could induce germ tube formation at 30 but not at 25 degrees C. N-Acetylglucosamine induced germ tube formation was most reproducible when the cells were first starved by incubation in water for 16-24 h at 20 degrees C. Germ tubes induced by proline could be formed at pH values between 3.8 and 9.0 at 30 degrees C, but only between 7.0 and 7.5 at 25 degrees C. The addition of 0.05 to 5 mM glucose to a 5 mM proline induction solution allowed germ tube formation at 30 but not at 25 degrees C. Glucose (400 mM) did not suppress germ tube formation at 30 degrees C but only 5 mM was sufficient to cause a 65% suppression at 25 degrees C. The results show the importance of CO2 and (or) bicarbonate to the induction of germ tube formation and are consistent with the metabolism of the inducer.     

Cholestatic jaundice caused by cloxacillin: macrophage inhibition factor test in preventing rechallenge with hepatotoxic drugs.

Severe intrahepatic cholestasis occurred in a patient after taking nitrofurantoin, ampicillin, and cloxacillin. As only nitrofurantoin was known to cause cholestasis she was given cloxacillin again two years later. The cholestasis reappeared at once. A macrophage inhibition factor test confirmed that cloxacillin was the offending drug. Cloxacillin should be added to the growing list of drugs causing cholestasis. Inadvertent rechallenge with hepatototoxic drugs might be prevented by routine use of the macrophage inhibition factor test.     

Immature red cells have ferritin receptors

Ferritin binds to immature red cells. The binding appears to be specific: (1) It is abolished by a large competing dose of nonradioactive ferritin. (2) There is little binding of ferritin to mature red cells. (3) Other high molecular weight proteins (gamma globulin and thyroglobulin) are not bound.     

An active-site-directed irreversible inhibitor of delta 5-3-ketosteroid isomerase

The α and β isomers of spiro-3-oxiranyl-5α-androstan-17β-ol were tested as possible inhibitors of Δ⁵-3-ketosteroid isomerase of $\text{Pseudomonas}\text{testosteroni}$. The β-oxirane causes a first-order irreversible inactivation of the enzyme and shows saturation kinetics (K_I, 17 μM). Protection against inactivation is exhibited by 19-nortestosterone, a competitive inhibitor of the isomerase. Although the α-oxirane was found to be a good reversible inhibitor (K_i, 21 μM), prolonged incubation with it failed to produce any inactivation of the isomerase. The results obtained are consistent with the presence of a nucleophilic group situated near the 3-keto group of the substrate in the enzyme-steroid complex.     

Heterogeneous biofilm activity in a segregated anaerobic fluidized bed bioreactor

Bed segregation in a fluidized bed bioreactor profoundly influenced biofilm thickness and microbial activities of the biofilm along the bed height. Bioparticles coated with a thin biofilm, observed at the bottom of the reactor, had a higher specific activity in propylene glycol and n-propanol degradation than in thick biofilms developed at the top of the reactor. Although no significant difference was observed in specific activity for propionate and acetate along the reactor flow axis, more total propionate and acetate conversion occurred in regions of thicker biofilm accumulation.