Certainty of paternity and paternal effort in the collared flycatcher

Models of optimal parental investment predict that variationin certainty of paternity can affect the optimal level of paternalinvestment when a male's expected paternity in different nestingattempts is not fixed throughout his lifetime. Several attemptsto test this prediction experimentally in monogamous birds havefailed to induce a reduction in care by males. This may be becausethe method used, detaining males, is a poor model for what happenswhen a male's certainly of paternity is naturally reduced. Wecaught and detained female collared flycatchers Ficedula albicollisfor 1 h immediately after laying on one or two occasions inan attempt to induce variation in certainty of paternity forthe males they were mated to. By capturing females immediatelyafter laying we hoped to exploit the existence of an "inseminationwindow" since males should be very sensitive to female absenceduring this period. The general effect of the experimental manipulationwas consistent with reduced certainty of paternity: males respondedby reducing their level of paternal care to nestlings, and malesmated to females that had been caught on one morning fed nestlingssignificantly less often and made a smaller share of feedingvisits than males mated to control females. The effects of theexperiment were generally weak, however, and we argue that certaintyof paternity may be fixed well before egg laying, in which caseexperimental manipulations are unlikely to have large effects.It is difficult to predict die effects of natural variationin certainty of paternity on levels of male paternal care becausedifferential allocation by females mated to attractive malesmay act in the opposite direction     

Immersion heat treatments for inactivation of Salmonella enteritidis with intact eggs

The effects of water-bath immersion heat treatments on the inactivation of Salmonellaenteritidis within intact shell eggs were evaluated. Six pooled strains of Salm. enteritidis ( ca 3×10⁸ cfu, inoculated near the centre of the yolk) were completelyinactivated within 50–57·5 min at a bath temperature of 58°C and within 65–75min at 57°C (an 8·4 to 8·5- D process per egg). Following the initial 24 to35-min come-up period, semilogarithmic survivor curves obtained at 58 and 57°C yieldedapparent decimal reduction times ( D -values) of 4·5 and 6·0 min, respectively.Haugh unit values increased during heating, while yolk index and albumen pH values wereunaffected. Albumen clarity and functionality were affected by the thermal treatments; therefore,extended whip times would be required for meringue preparation using immersion-heated eggwhites. Immersion-heated shell eggs could provide Salmonella -free ingredients for thepreparation of a variety of minimally-cooked foods of interest to consumers and foodserviceoperators.     

Enzymatic epoxidation reactions

The oxygenases - enzymes which incorporate molecular oxygen directly into organic molecules - are ubiquitous and of high metabolic significance. These enzymes play crucial roles in the degradation of drugs and foreign substances and in the biosynthesis, interconversion and degradation of amino acids, lipids, porphyrins, vitamins and hormones. Thus, they are centrally involved in the mechanisms of cytotoxicity, mutagenicity, carcinogenicity and tissue necrosis. From the standpoint of enzyme technology, the ability of these enzymes to incorporate molecular oxygen into organic substrates efficiently and selectively is highly enticing, since such reactions are poorly accomplished using conventional chemistry. This review focuses on enzymatic epoxidation reactions, one example of the many chemical transformations catalysed by oxygenases. By way of introduction, an overview of the role of enzymatic epoxidation reactions in the metabolism of polycyclic aromatic hydrocarbons, in steroid biosynthesis and interconversion, and in various other pathways is presented. Following this, enzymatic epoxidation of simple olefins is considered in detail, with emphasis on bacterial systems and discussion of both enzymology and reactivity characteristics. Finally, a number of major issues which must be confronted if complex oxygenase systems are to be utilized in enzyme technology application are briefly discussed. Among these are specialized immobilization techniques, cofactor recycling, problems of enzyme stability, and the intriguing possibility of utilizing mechanistic information in the design of non-enzymatic, chemical model systems which mimic oxygenase catalysis.     

Incorporation of [14C]-2 deoxy-D-glucose into the lipids of normal cells as compared to virus-transformed cells

[¹⁴C]-2 deoxy-D-glucose is incorporated into the glycolipids of both normal and transformed cells. The chromatographic pattems of [¹⁴C]-2 deoxy-D-glucose labeled lipids differ markedly in oncornavirus and herpes simplex virus-transformed cells as compared to normal and virus-infected but not transformed cells. Deoxyglucoselabeled lipids with intermediate chromatographic mobility were enriched in normal and virus-infected but not transformed cells. Studies with a murine sarcoma virus-infected cell line which is temperature-sensitive for transformation indicated that the altered chromatographic pattern of [¹⁴C]-2 deoxy-D-glucose labeled lipids was related to the expression of the transformed phenotype.     

Contribution of the allelicMtz 3 andMtz 4 allotype genes to the formation of individual rabbit serum α2-macroglobulin molecules

The contribution of the allelicMtz ³ andMtz ⁴ genes to the formation of individual rabbit serum α₂-macroglobulin (α₂M) molecules was examined by precipitation of α₂M from rabbits of known genotype with antiallotype antisera. The α₂M was isolated fromz ³z³ andz ⁴z⁴ homozygous andz ³z⁴ heterozygous rabbits, iodinated with I¹²⁵ and precipitated by sequential reactions with antiallotype antiserum and goat anti-rabbit IgG. Purified unlabeled α₂M or α₂M in serum was used to inhibit competitively the reaction of antiallotype antiserum and labeled α₂M. Nearly all α₂M molecules have z3 or z4 antigenic determinants; approximately 50% of α₂M molecules in heterozygotes have both. Altogether, the z3, z3,4, and z4 molecules in heterozygotes have approximately 60% of the number of z3 and 40% of the number of z4 determinants as compared to the respective homozygotes. Unlike all other known allelic blood protein systems of rabbits, allelic exclusion does not occur in α₂M molecules of heterozygotes; rather, hybrid molecules are formed. Presented in part at the Fifty-fourth and Fifty-fifth Annual Meetings of the Federation of American Societies for Experimental Biology, Atlantic City, New Jersey, April 12–17, 1970, and Chicago, Illinois, April 12–17, 1971. This investigation was supported in part by U.S. Public Health Service Grants AI-09241 and AI-07043. B.H.B. performed this investigation in partial fulfillment of the requirements for the Doctor of Philosophy Degree in the Graduate College; he is supported by a postdoctoral fellowship from the Schweppe Foundation. K.L.K. is the recipient of U.S. Public Health Service Research Career Development Award AI-28687.     

Routes of administration and uptake of tritiated nucleotides

Summary The uptake, incorporation and distribution of tritiated thymidine and uridine into visceral organs of immature female and male rats was studied. Radioautographs of various organs were prepared 5, 15 and 30 min after intraperitoneal administration. The distribution of the radioactivity was compared with sections obtained 30 min after intravenous injection of the same amount of nucleotides.The intraperitoneal injection was performed by directing the needle toward the right side of the abdominal cavity. Visceral organs from the injected side contained consistently more silver grains than those from the opposite side. Sections of the abdominal organs showed a decreasing concentration gradient of reduced silver grains extending from the serosal part of the organ to the deeper layers. In addition, initial labeling was observed in sectors of organs which protruded into the peritoneal cavity. In contrast, following intravenous administration of nucleotides a concentration gradient was not observed in any of the visceral organs.The results of the present study suggest that nucleotides administered intraperitoneally may penetrate the abdominal organs directly via the serosal surface without prior entry into the general circulation.     

RESPONSE OF THE PREOSTEOBLAST AND STEM CELL OF RAT BONE MARROW TO A LETHAL DOSE OF X-IRRADIATION OR CYCLOPHOSPHAMIDE

Following syngeneic or autotransplantation of hemopoietic tissue to a heterotopic location, bone formation has been observed to occur in the implanted tissue. the characteristics of the cell residing in hemopoietic tissue with bone forming potential (preosteoblast) are unknown. to define some properties of this cell, its response to X-irradiation and cyclophosphamide (CTX) was compared to the response of the hemopoietic stem cell. Adult, male rats were exposed to 900 R whole body X-irradiation or 220 mg/kg of intraperitoneal CTX. With either treatment the dose was sufficient to kill the animals by bone marrow failure. At intervals following the X-irradiation or CTX, hemopoietic tissue was examined for the presence of viable hemopoietic stem cells and preosteoblasts. Following X-irradiation, viable hemopoietic stem cells and preosteoblasts could not be detected. Following CTX these cells could be detected. It is suggested that in the rat CTX at 220 mg/kg, although causing death by bone marrow failure, does not reduce the population of the preosteoblast or hemopoietic stem cell as effectively as 900 R X-irradiation.     

Replication of Mengovirus in HeLa Cells Preinfected with Nonreplicating Poliovirus

The replication of mengovirus in HeLa cells preinfected with poliovirus in the presence of 10(-3) M guanidine was investigated. Although host cell protein synthesis is inhibited by the presence of nonreplicating poliovirus, it is found that mengovirus ribonucleic acid (RNA) and protein synthesis proceed normally under the same conditions. Furthermore, no effects on mengovirus growth by poliovirus can be detected either when Mengo protein synthesis is interrupted by Acti-Dione or when its RNA synthesis is reduced by incubation at 28 C. It is suggested that the poliovirus inhibitory factor may be able to distinguish between an RNA element required in the protein-synthesizing apparatus of the host cell and a comparable element in that of the heterologous virus.