Identification of noncollagenous basement membrane glycopolypeptides synthesized by mouse parietal entoderm and an entodermal cell line

Using two-dimensional gel electrophoresis, we have identified two noncollagenous basement membrane (BM) glycopolypeptides which are synthesized by the mouse teratocarcinoma-derived parietal yolk sac (PYS) cell line. These glycopolypeptides have molecular weights of about 200,000 and isoelectric points of about 5.6. Polypeptides with identical parameters are synthesized by the parietal entodermal cells of mouse embryos and are found in Reichert's membrane. Pluripotent embryonal carcinoma cells (ECC) synthesize considerable amounts of the two polypeptides, whereas the yield from nullipotent ECC is negligible. The treatment of nullipotent F9 cells with retinoic acid, which induces entodermal differentiation, activates the synthesis of these polypeptides. These results indicate that the two polypeptides can be used as markers of parietal entoderm differentiation.     

Biochemical and genetic characterization of three hamster cell mutants resistant to diphtheria toxin

We describe here three different hamster cell mutants which are resistant to diphtheria toxin and which provide models for investigating some of the functions required by the toxin inactivates elongation factor 2 (EF-2). Cell-free extracts from mutants Dtx(r)-3 was codominant. The evidence suggests that the codominant phenotype is the result of a mutation in a gene coding for EF-2. The recessive phenotype might arise by alteration of an enzyme which modifies the structure of EF-2 so that it becomes a substrate for reaction with the toxin. Another mutant, Dtx(r)-2, contained EF-2 that was sensitive to the toxin and this phenotype was recessive. Pseudomonas aeruginosa exotoxin is known to inactivate EF-2 as does diphtheria toxin and we tested the mutants for cross-resistance to pseudomonas exotoxin. Dtx(r)-1 and Dtx(r)-3 were cross-resistant while Dtx(r)-2 was not. It is known that diphtheria toxin does not penetrate to the cytoplasm of mouse cells and that these cell have a naturally occurring phenotype of diphtheria toxin resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance of the hybrid cells to diphtheria toxin. Intraspecies hybrids containing the genome of mutants Dtx(r)-1 and Dtx(r)-3 had some resistance while those formed with Dtx(r)-2 were as sensitive as hybrids derived from fusions between wild-type hamster cells and mouse 3T3 cells.     

Protein intake regulation in the weanling rat: Effects of additions of lysine,arginine and ammonia on the selection of gluten and energy

The effects of adding lysine, arginine and ammonia to gluten on the self-selection of protein and energy by the weanling rat simultaneously offered a choice of two diets differing only in gluten concentration (15 and 55%) were tested. Previous studies have shown that while lysine (6 g/100 g) additions to gluten decreased the amount of gluten selected by the rat from 40 to 20 g per 100 g of food eaten, selection was not related to the nutritional quality of the gluten. When graded levels of arginine (1.8, 3.6 or 7.2 g/100 g) were added to the gluten with or without lysine (0 or 6 g/100 g) the dietary protein selection was unaffected. The addition of ammonia (1.4 g/100 g as NH₄Cl) to gluten had initially the same effect as lysine (6 g/100 g) but with time protein intake returned to control levels. This effect of ammonia was unaltered by arginine additions. It is concluded that the mechanisms which lead to decreases in gluten selection caused by lysine or ammonia are not similar, and that the effects of lysine on gluten selection are not caused by an increased arginine requirement for urea cycle activity.     

Application of CNDO2 theoretical calculations to interpretation of the chemical reactivity and biological activity of the syn and anti diolepoxides of benzo[a]pyrene

$\text{CNDO}\text{2}$ molecular orbital theoretical calculations performed on the anti and syn diolepoxides (1 and 2) of the potent carcinogen benzo[a]pyrene provide insight into the molecular structure and reactivity of these mutagenic and carcinogenic hydrocarbon metabolites. Hydrogen-bonded interaction between the 7-HO proton and the epoxide oxygen atom of 2 is shown to be absent in the normal semichair conformation of the tetrahydro ring, (H…O bond distance = 2.7 Å), but is energetically favored in a somewhat distorted puckered structure (H…O bond distance = 1.7 Å). Unexpectedly, internal H-bonding alters the relative electron density at C₉ and C₁₀, leading to prediction of the former as the more electrophilic center. Since all reactions of 2 take place exclusively at C₁₀, transannular H-bonding is concluded not to contribute significantly to the structure of 2. Diolepoxide reactions with both weak and strong nucleophiles and with DNA are discussed and the mechanisms interpreted in terms of molecular structure as determined by the theoretical calculations.     

Meningococcal Disease in California: Epidemiology and Management

Between 1969 and 1975 in California, 1,953 cases of meningococcal disease were reported. For cases reported in 1973, 1974 and 1975, detailed information about chemoprophylaxis of cases and contacts was obtained in addition to demographic and laboratory data. A review of data for the seven years showed a reduction in the case rate from 2.6 to 0.6 per 100,000 population, but this drop was due primarily to a very substantial decline in the military rate from 35.7 to 1.8 per 100,000 population. No reduction was apparent in the case fatality rate. Five groups of associated meningococcal disease cases were identified for a total of nine secondary or coprimary cases among 862 household contacts. Associated cases occurred in 10.4 per 1,000 household contacts—a rate several hundred times greater than that for the general population.The study findings indicate that many physicians are unaware of the following: (1) nonhousehold contacts are at little or no risk of contracting meningococcal disease; (2) prophylaxis should be offered only to household or intimate contacts immediately upon identification of an index case without waiting for test results for meningococcal carriage; (3) valid medical and epidemiologic indications exist for administering prophylaxis to household contacts who are culture negative as well as those who are culture positive; (4) the current drug of choice for prophylaxis is rifampin, but since no drug is completely effective, close medical observation remains the most important factor in the management of household or intimate contacts to meningococcal disease.     

Identification of detergents as components of wastewater sludge that modify the thermal stability of reovirus and enteroviruses.

The agent in wastewater sludge previously shown to reduce the heat required to inactivate reovirus (R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol. 34:681--688, 1977) was "separated" from other sludge components and analyzed by infrared spectroscopy. The infrared spectrum of this material was quite similar to the spectra of commercial anionic detergents, and subsequent analyses of the fractionated sludge samples revealed that anionic detergents in sludge were copurified with the virucidal activity. Further measurements on the virucidal activities of specific detergents revealed that ionic detergents reduce the heat required to inactivate reovirus, that cationic detergents are more active than anionic, and that nonionic detergents are inactive. Several detergents were also shown to protect poliovirus and other enteroviruses against inactivation by heat. These results indicate that ionic detergents are the major component in wastewater sludge that reduce the thermal stability of reovirus and, in addition, that detergents are able to protect enteroviruses against heat.     

Studies of the diphtheria toxin receptor on chinese hamster cells

Concanavalin A, wheat germ agglutinin and the ovalbumin glycopeptide are all inhibitors of the cytotoxic effect of diphtheria toxin on Chinese hamster cells. Ovalbumin glycopeptide loses its inhibitory property after treatment with β-N-acetylglucosaminidase. This demonstrates the importance of the glycopeptide structure for the mechanism of inhibition. The glycopeptide may be a toxin cell-surface receptor analogue. Diphtheria toxin-resistant mutants were isolated in order to search for cells that might have an altered toxin receptor. One mutant was 10-to 15-fold more resistant to diphtheria toxin than wild-type cells when protein synthesis was measured as a function of toxin concentration. However, when protein synthesis was measured as a function of time at a high toxin concentration, the time before onset of inhibition was identical in the mutant and wild-type cells. We present evidence indicating that the resistance of this mutant can be accounted for by a decreased affinity of toxin for a cell-surface receptor.     

Identification of the virucidal agent in wastewater sludge.

Anaerobically digested sludge contains an agent that causes irreversible inactivation of poliovirus. It has now been shown that the agent responsible for this activity is ammonia. The effect of ammonia on poliovirus appears to be typical for picornaviruses, but reovirus, an enteric virus of another group, is quite resistant to this compound. Because ammonia is not virucidal in its charged state, it expresses significant activity only at pH values greater than 8. Therefore, increasing the pH of sludge should cause rapid inactivation of indigenous picornaviruses.