The exchange hypothesis for the formation of chromatid aberrations: an experimental test using bleomycin

The association between bleomycin-induced chromatid aberrations and BUdR-label exchange between sister chromatids was investigated in order to evaluate Revell's exchange hypothesis for the formation of chromatid aberrations. The results of this study indicate that a larger than expected proportion of chromatid breaks can be accounted for by the exchange hypothesis though not all breaks are the result of incomplete exchange.     

Unprocessed Bran in Treatment of Diverticular Disease of the Colon

Seventy patients with diverticular disease of the colon were treated with a high-residue, low-sugar diet including unprocessed bran. Follow-up for an average of 22 months showed marked relief of symptoms in 62 patients. Bowel habit was restored towards normal and abdominal discomfort relieved. Only seven patients were unable to give up the use of laxatives. Eight patients did not tolerate the bran diet, and one of these needed surgical treatment. None of the 62 patients who took the diet needed surgery.     

Isolation and Characterization of Temperature-Sensitive Mutants of Vesicular Stomatitis Virus, New Jersey Serotype

Forty-eight temperature-sensitive (ts) mutants have been isolated from a wild-type strain of the New Jersey serotype of vesicular stomatitis virus (VSV) after exposure to the base analogue mutagen 5-fluorouracil. Of these mutants, 47 have been classified into 6 nonoverlapping complementation groups containing 21, 17, 4, 3, 2, and 1 mutant, respectively (1 mutant remaining unallocated). The ribonucleic acid (RNA) phenotype of 23 of these mutants has been established. Four of the six groups contain one or more mutants unable to synthesize detectable amounts of viral RNA under restrictive conditions (39 C). No complementation was observed in mixed infection with ts mutants from the five established complementation groups of the Indiana serotype of VSV.     

Clonal Analysis of Cell Division in the Bacillus subtilis div IV-B1 Minicell-Producing Mutant

Spores of the Bacillus subtilis minicell-producing mutant div IV-B1 were germinated and grown to microcolonies in chambers which facilitate continuous observation of the developing clones with a phase-contrast microscope. Time lapse photographs were taken of 46 clones, covering the period from the beginning of outgrowth until at least two rounds of cell division had been completed. Cell lineages were constructed from contour length measurements of the photographs. These data include cell lengths, division site locations, and cell numbers in clones of various ages. From these data we have determined that the probability of a minicell being produced at any division by the div IV-B1 mutant is 0.31. The location of the abnormal division site which generates the first minicell produced in the outgrowing clone appears to be random with respect to the existing cell poles. In contrast, the location of the second abnormal division site, and hence the second minicell, is not random but rather occurs preferentially in proximity to the first minicell. This clustering of abnormal events suggests that division site location is related to pole age (generations), although other influences on minicell clustering cannot be ruled out at present.     

Substituted Sialic Acid Prosthetic Groups as Determinants of Viral Hemagglutination

Inhibitors of hemagglutination by type A2 influenza virus and a recently isolated strain of type B influenza virus were separated by sucrose density gradient centrifugation and agarose gel filtration from horse serum. Using selected reagents, it was demonstrated that the active substituent on the horse serum inhibitor of A2 influenza virus was 4-O-acetyl-N-acetylneuraminic acid; however, the active substituent on the inhibitor of the influenza B virus was shown to be N-acetylneuraminic acid (NANA). Sodium metaperiodate treatment of a component of horse serum resulted in a 10 to 15-fold enhancement of inhibitory activity against the type B virus, whereas the A2 inhibitor was completely destroyed. Since this enhancement did not occur with influenza B viruses isolated prior to 1965, it was considered that this sensitivity to an oxidized NANA glycoside may have been a reflection of an antigenic change which occurred at that time. The use of different virus strains and selected chemical reagents to define the important sialic acid prosthetic groups active in inhibition was described.     

The osmotic stability of lysosomes from adult and foetal guinea-pig liver tissue

1. Lysosome-rich fractions were obtained from foetal liver tissues as early as 35 days uterine age. Foetal lysosomes showed the same ;structure-linked latency' and acid hydrolytic potentiality characteristic of their adult counterparts. 2. The osmotic stability of lysosome-rich fraction from foetal guinea-pig liver tissue was greater than that of the corresponding adult lysosome fractions, p-nitrophenyl-phosphatase being used as marker enzyme. 3. The observation was confirmed by using beta-glycerophosphatase and phenolphthalein beta-glucuronidase as alternative marker enzymes. p-Nitrophenyl phosphate and beta-glycerophosphate appear to act as substrates for the same enzyme. 4. By using p-nitrophenylphosphatase activity measurements it was shown that the osmotic stability of foetal lysosomal fractions decreased with increasing foetal age, but at no time achieved the degree of osmotic instability characteristic of adult lysosomal fractions. 5. The correlation of these findings with the intracellular environment of lysosomes is discussed.     

Evidence implicating a membrane ATPase in the control of passive permeability of excitable cells

The temperature sensitivity of the ATPase enzyme systems in a muscle microsomal preparation from the crayfish, Astacus pallipes, was studied. Preincubation of the enzyme preparation in the range 33–36°C produced a marked inactivation of the ATPases; the Mg⁺⁺-dependent ATPase was very much more sensitive to this treatment than the Na⁺-K⁺-Mg⁺⁺-dependent ATPase. Thus, the Arrhenius μ for the inactivation of the Mg⁺⁺-dependent ATPase produced by eight minute preincubation is > 100 Kcals. These results are compared with the changes that are observed during the heat death of the whole animal, where exposure to 35°C produces a dramatic change in Na⁺ permeability within five minutes. Arrhenius μ for heat death is also > 100 Kcals and operates over the identical critical temperature range. It is suggested that the Mg⁺⁺-dependent ATPase controls passive permeability in these excitable cells and the results also confirm the view that Mg⁺⁺ and Na⁺-K⁺-Mg⁺⁺ ATPases are separate enzymes.     

ARAGONITE IN HALIMED A AND TYDEMANIA (ORDER SIPHON ALES)12

The mineral component of the marine green algal genus Halimeda is the orthorhombic calcium carbonate (aragonite); its presence appears to be a generic characteristic. Tydemania expeditionis also precipitates aragonite in contradistinction to species of the red alga Corallina wliich precipitate calcium carbonate of the hexagonal form (calcite). The analyses are based on x-ray diffraction methods. Although other inorganic substances arc present, the amounts are minor and probably represent contaminants. Specimens that are to be studied for mineral components should not be stored in formalin.