Effect of lead on blood protoporphyrin levels of a group of ring teal ducks (Callonetta leucophrys)

This research determined the relationships between blood lead level and zinc protoporphyrin (ZnPROTO), protoporphyrin IX (PROTO), and free erythrocyte protoporphyrin (FEP) levels in a group of 18 ring teal ducks. Blood samples were drawn from two groups of ring teal ducks as part of the routine health maintenance program of the New York Zoological Park. One group of six teals had been exposed to what is believed to be lead-contaminated dust, while the second group of twelve teals was unexposed. Blood samples were analyzed for lead by flameless atomic absorption and for protoporphyrins by fluorescence. Blood lead level and log blood lead level had positive correlations with each of the protoporphyrins: the logarithmic correlations were better than the nonlogarithmic correlations, and PROTO correlated better than ZnPROTO. With one exception, PROTO levels were higher than ZnPROTO levels. The results suggest that PROTO, FEP, or ZnPROTO could serve as a biological indicator of lead poisoning in ring teal ducks.     

A rapid posttranslational myristylation of a 68-kD protein in D. discoideum

Cells incubated with [3H]myristate were shown to rapidly and specifically acylate a 68-kD protein, p68, in a developmentally-regulated manner. The fatty acid incorporated into p68 was identified as myristate, and is linked to the protein via an amide bond, apparently to an NH2-terminal glycine. The acylation of p68 in D. discoideum displays some unusual properties. Unexpectedly, myristylation of p68 is a posttranslational event and occurs in the presence of inhibitors of protein synthesis. Another unusual finding was that although p68 is a stable protein, the acyl moiety is removed with a half time of approximately 15 min.     

Analysis of Adenosine Immunoreactivity, Uptake, and Release in Purified Cultures of Developing Chick Embryo Retinal Neurons and Photoreceptors

We have investigated the presence of endogenous adenosine and of mechanisms for adenosine uptake and release in chick embryo retinal neurons and photoreceptors grown in purified cultures in the absence of glial cells. Simultaneous autoradiographic and immunocytochemical analysis showed that endogenous adenosine and the uptake mechanism for this nucleoside colocalize in practically all the photoreceptors, but only in approximately 20% of the neurons. Approximately 25% of the neurons showed either immunocytochemical labeling or autoradiographic labeling, while greater than 50% of the neurons were unlabeled with both techniques. [3H]Adenosine uptake was saturable and could be inhibited by nitrobenzylthioinosine and dipyridamole and by pretreatment of the [3H]adenosine with adenosine deaminase. Although these observations indicate that the uptake is specific for adenosine, only 35% of accumulated radioactivity was associated with adenosine, with the remaining 65% representing inosine, hypoxanthine, and nucleotides plus uric acid. Adenosine as well as several of its metabolites were released by the cells under basal as well as K(+)-stimulated conditions. Potassium-enhanced release was blocked by 10 mM CoCl2 or in Ca2(+)-free, Mg2(+)-rich solutions. The results indicate that retinal cells that synthesize, store, and release adenosine differentiate early during embryogenesis and are therefore consistent with a hypothetical role for adenosine in retinal development.     

Through-bond electron-transfer interaction in proteins

A model for the through-bond electronic interaction between electron donor and acceptor in proteins is developed. We use a one-electron Hamiltonian, write the Dyson's equation in site representation and solve it by using a Green's function formalism with some renormalization ideas. An expression for Tab which describes the exponential decay with distance bond per bond is obtained. Covalent, non-covalent and convergent pathways are considered and no periodic approximation is needed.     

The relationship of conceptus number and fetal sex to maternal serum testosterone concentration in the rat

On Day 8 of pregnancy, the number of implantation sites in pregnant rats was adjusted to 1, 2, 4, 6, or greater than 10. Blood was collected on Days 11, 12, 15, 18, and 20 for the determination of serum testosterone, progesterone, and androstenedione. Serum testosterone levels exhibited a direct linear relationship with implantation number, increasing from 1 through greater than 10 implants. This linear relationship was particularly evident at Days 12, 15, and 18 of pregnancy. Serum progesterone levels increased from one to four conceptuses and plateaued above this number. There was no apparent relationship between the number of conceptuses and serum androstenedione levels, which may reflect the multiple origins of this steroid in the pregnant rat. In a separate group of rats in which the number of conceptuses was adjusted to three on Day 8 of pregnancy, blood was collected on Days 11, 12, 15, 18, and 20. Fetal sex was determined between the last bleeding and the day of parturition. Serum testosterone was determined and results were examined with regard to the number of male/female fetuses in the litter of three. There was no relationship between maternal serum testosterone levels and the number of male fetuses, indicating that the fetal testis does not make a significant contribution to circulating maternal testosterone levels.     

Serine/threonine protein phosphatases in Dictyostelium discoideum: no evidence for type I activity.

Extracts from Dictyostelium discoideum contain type 2A and 2C serine/threonine-specific protein phosphatases with properties very similar to those from mammals according to their sensitivity to okadaic acid and to their dependence for divalent cations. In contrast, no type 1 protein phosphatase is found at any time of development, neither in the cytosolic nor in the particulate fraction, using glycogen phosphorylase a, casein, histone or the non-proteinous 4-Methylumbelliferyl phosphate as substrates. Both type 2A and 2C protein phosphatase activities remain constant throughout the development cycle.     

Genetic elements involved in Tn21 site-specific integration, a novel mechanism for the dissemination of antibiotic resistance genes.

Transposon Tn21 codes for a site-specific integration system, which is probably a novel recombination mechanism, responsible for the acquisition of resistance genes in this widespread family of transposons. Using insertion and deletion mutagenesis we have identified the genetic loci of the various recombination hot-spots (RHS) and of the gene product (the integrase) that catalyses the reaction. The site of recombination has been localized in two of the RHSs to the DNA sequence GTTAG, which is present at the 3' termini of a loosely conserved palindromic sequence of approximately 59 bp. This 59 bp sequence, which flanks the inserted genes in a number of naturally occurring transposons, is the only element required in cis for the recombination reaction.