Increased thorn length in Acacia depranolobium —an induced response to browsing

Summary I report here longer thorns induced by large mammal herbivory on the tree Acacia depranolobium. I compared trees that had been browsed by domestic goats to trees protected from goat browsing. Thorns on browsed branches within the reach of goats (<125 cm above the ground) were significantly longer than thorns from higher branches on the same browsed trees, and significantly longer than branches at similar heights on unbrowsed trees. It appears that increased thorn length was an induced response to large mammal herbivory in Acacia depranolobium, both among and within individual trees.     

Characterization of capsid and noncapsid proteins of B19 parvovirus propagated in human erythroid bone marrow cell cultures.

The major capsid and noncapsid proteins of the pathogenic parvovirus B19, propagated in vitro, were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoprecipitation, and immunoblot of the erythroid fraction of infected human bone marrow cell cultures. There were two capsid proteins of 58 kilodaltons (kDa; the major species) and 84 kDa (the minor species). Newly synthesized capsid viral proteins were present in the supernatants of infected cultures. The major noncapsid protein of 77 kDa was localized to the nucleus.     

Control by insulin and insulin-related growth factor 1 of protein synthesis in a cell-free translational system from chick-embryo fibroblasts.

Insulin and insulin-related growth factor 1 (IGF-1) increase by 1.5-1.6-fold the rate of [3H]leucine incorporation into protein in primary monolayer cultures of chick-embryo fibroblasts (CEF); half-maximal hormone concentrations are 10 and 0.25 nM respectively. To investigate the mechanism of this effect, a rapid method is used to prepare a lysate from CEF which is active in protein synthesis. Lysate derived from cells treated for 30-150 min with insulin synthesized protein at 1.8-3.0-fold greater rate than did controls; the increased rate persisted for 20 min in vitro. Pactamycin (0.5 microM), an inhibitor of peptide-chain initiation, inhibited protein synthesis by 50% in lysates derived from insulin-treated and control cells. Thus insulin and IGF-1 cause an increase in the protein-synthesis rate in vivo, which persists in cell-free protein-synthesizing lysates of CEF.     

Retinoic acid induction of stress proteins in fetal mouse limb buds

Retinoic acid (RA) is teratogenic in rodent embryos. Several teratogens have been shown to induce the synthesis of a subset of heat shock proteins (stress proteins) in Drosophila. To determine if RA induces the synthesis of these proteins in rodent embryos, pregnant ICR mice were dosed with 100 mg/kg RA on Day 11 of gestation. Forelimb buds were removed from embryos 2.5 hr post-RA-treatment and nuclei were isolated, stained, and sorted from stages of the cell cycle. Nuclear proteins were extracted and analyzed by two-dimensional polyacrylamide gel electrophoresis. Nuclear proteins with molecular weights of approximately 84 and 25 kDa were synthesized in embryos in the G0 + G1 phase after pregnant dams were treated with RA. Isoelectric points, molecular weights, immunochemical blotting, and polypeptide mapping demonstrated that these proteins are indistinguishable from stress proteins isolated under a variety of conditions from rat submaxillary glands and mouse lymphoma cells. These results suggest that treatment with RA induces the synthesis of a subset of stress proteins; the role of these proteins in the teratogenic effects of RA is not known.     

Plasmodium falciparum: elicitation by peptides and recombinant circumsporozoite proteins of circulating mouse antibodies inhibiting sporozoite invasion of hepatoma cells

The immunodominant epitope region of the circumsporozoite protein of Plasmodium falciparum sporozoites contains 37 tandem repeats of the tetrapeptide Asn-Ala-Asn-Pro and 4 repeats of Asn-Val-Asp-Pro. Synthetic peptides and recombinant proteins of the repeat region were used to immunize mice using different doses and adjuvants. Antisera were tested for inhibition of sporozoite invasion of cultured human hepatoma cells. Synthetic peptides and recombinant proteins elicited high levels of antibodies that inhibited sporozoite invasion when emulsified with complete Freund's adjuvant. Since recombinant proteins with alum elicited a better antibody response to sporozoite invasion than they did without adjuvant, it may be that a recombinant protein containing 32 tandem copies of the tetrapeptide repeat combined with alum could be a candidate malarial vaccine suitable for human trials.     

Plasmodium falciparum: sporozoite boosting of immunity due to a T-cell epitope on a sporozoite vaccine

Plasmodium falciparum: Sporozoite boosting of immunity due to a T-cell epitope on a sporozoite vaccine. Experimental Parasitology 64, 64-70. The impact of a malaria sporozoite vaccine may be enhanced if protective immunity elicited by the vaccine is boosted by natural exposure to sporozoites. For this to occur, a helper T lymphocyte epitope present on the vaccine must be shared by sporozoites. These studies show that T cells from mice immunized with R32tet32, the Plasmodium falciparum sporozoite vaccine candidate, recognize an epitope of less than or equal to 7 amino acids derived from the circumsporozoite protein repeat region of R32tet32, as well as an epitope on the tet32 fusion protein tail of R32tet32. Exposure of R32tet32 immunized animals to P. falciparum sporozoites elicits a significant secondary antibody response which suggests that humans who are immunized and respond to this vaccine may be boosted by field exposure to sporozoite infected mosquitoes.     

Vasomotor control: functional hyperemia and beyond

Historically, functional hyperemia has been viewed largely as an interaction between a parenchymal cell and its associated microvasculature. Locally released metabolites have been thought to produce relaxation of the smooth muscle and a vasodilation that increases blood flow in proportion to metabolic need. This symposium report presents evidence from a variety of disciplines and a number of different types of biological preparations that demonstrates that functional hyperemia is a complex process involving several classes of microvessels including capillaries, arterioles, and small arteries. These vessels do not function independently but are coordinated by a complex set of interrelations involving at least three different modes of interaction between parenchymal cells and the various segments of the vascular bed. These are local metabolic effects, propagated effects extending over long segments of the vasculature, and flow-dependent vasodilation induced by local changes in blood flow. In addition to these acute responses to metabolic demand it appears that tissues may be capable of more long-term structural alterations of the arterial and arteriolar network in response to sustained changes in the relationship between supply and demand. The vascular bed appears to be able to adapt either by increasing the maximal anatomic diameter of the large arteries or by inserting new arterioles into the parenchyma. Thus, classical functional hyperemia appears to be but one manifestation of a multifaceted process leading to highly coordinated responses of many vascular elements, resulting finally in vascular patterns that are optimized to meet parenchymal cell demands.     

Post-translational processing of the porcine gastrin precursor by phosphorylation of the COOH-terminal fragment

The gene sequence encoding porcine preprogastrin is known; in order to clarify pathways of post-translational processing of the predicted precursor peptide we have characterized material reacting with antibodies to a synthetic peptide corresponding to the expected extreme COOH-terminal portion of the precursor. Radioimmunoassay was used to identify and monitor the purification of peptides in porcine antral mucosa. Two peptides (I and II) were isolated to homogeneity by steps involving gel filtration, ion exchange, and reversed-phase high performance liquid chromatography. The two co-eluted on gel filtration but were separated on anion-exchange chromatography. The more acidic peptide (II) was less hydrophobic on high performance liquid chromatography. Automated gas-phase microsequencing revealed the less acidic peptide (I) to have the sequence of porcine preprogastrin 96-104 (SAEEGDQRP); it would be produced by tryptic-like cleavage of Arg95-Ser96. The second peptide did not yield a phenylthiohydantoin-derivative on the first cycle but thereafter it sequenced as the first peptide (i.e. -AEEGDQRP). Incubation in alkali liberated almost equimolar amounts of phosphate from peptide II but not from I. In addition, alkaline phosphatase liberated phosphate and converted the acidic peptide to the less acidic one. The results suggest that serine in the first position is phosphorylated in peptide II but not I. The tripeptide -Ser(P)-Ala-Glu- also occurs in adrenocorticotropic hormone; this tripeptide is a substrate for physiological casein kinase. Potential phosphorylation sites occur at comparable positions in the precursors of a number of regulatory peptides.