Porcine big gastrin: Sequence,synthesis, and immunochemical studies

The synthesis of the tetracontapeptide corresponding to a revised sequence for porcine big gastrin is described. Both the synthetic and natural material were identical by radioimmunoassay using L33 antiserum, which is specific for the N-terminal region of the sequence.     

Expression and function of transplantation antigens with altered or deleted cytoplasmic domains

Two mutants of the class I gene encoding the H-2L^d transplantation antigen have been constructed. In one mutant the cytoplasmic domain of the class I molecule has been altered by deletion of 24 of the 31 C-terminal residues, and in the second the C-terminal 25 residues of the cytoplasmic domain have been replaced with a unique sequence of 19 amino acids. These mutant class I genes have been transferred into mouse L cells by DNA-mediated gene transfer. Both mutant genes are expressed at normal levels on the cell surface, and they have charge properties and sizes consistent with the introduced alterations. These mutant L^d molecules can serve as target antigens for allogeneic cytotoxic T cells and as restricting elements for virus-specific cytotoxic T cells. These results show that the 24 residues replaced or deleted from the carboxy terminus of the class I molecule are not required for its transport to or integration in the plasma membrane, nor for its function as a target antigen or a restricting element during T-cell-mediated cytotoxicity.     

Effect of nitrogen starvation on the level of adenosine 3′,5′-monophosphate in Anabaena variabilis

Low levels of adenosine 3′,5′-monophosphate (cyclic AMP) were detected in the cyanobacterium Anabaena variabilis using a protein binding assay and two radioisotopic labelling methods. The basal concentration of intracellular cyclic AMP ranged from 0.27 pmol/mg protein in A. variabilis Kutz grown under heterotrophic conditions to 1.0–2.7 pmol/mg protein in A. variabilis strain 377 grown autotrophically. Extracellular cyclic AMP was found to comprise as much as 90% of the total cyclic AMP in rapidly growing cultures. When A. variabilis strain 377 was starved of nitrogen, a 3–4-fold increase in intracellular cyclic AMP was observed during the 24 h period coincident with early heterocyst development.     

Automated DNA sequencing and analysis of the human genome

In the past few years, striking advances have been made in automating DNA sequence analysis. Currently, efforts are underway to automate and improve DNA purification, mapping, and data processing procedures. The predictable advances in these technologies should soon place us in a position to sequence the entire human genome. The information derived from this project will have profound implications for basic biology and clinical medicine alike.     

N omega-nitro-L-arginine methyl ester selectively inhibits pulmonary vasodilator responses to acetylcholine and bradykinin.

The effects of N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of endothelium-derived relaxing factor (EDRF) production, on vascular tone and responses were investigated in the pulmonary vascular bed of the intact-chest cat under conditions of controlled blood flow and constant left atrial pressure. When pulmonary vascular tone was elevated with U-46619, intralobar injections of acetylcholine, bradykinin, sodium nitroprusside, isoproterenol, prostaglandin E1 (PGE1), lemakalim, and 8-bromo-guanosine 3',5'-cyclic monophosphate (8-bromo-cGMP) dilated the pulmonary vascular bed. Intravenous administration of L-NAME elevated lobar arterial and systemic arterial pressures without altering left atrial pressure. When U-46619 was infused after L-NAME to raise lobar arterial pressure to levels similar to those attained during the control period, vasodilator responses to acetylcholine and bradykinin were reduced significantly, whereas responses to PGE1, lemakalim, and 8-bromo-cGMP were not altered, and responses to nitroprusside were increased. There was a small effect on the response to the highest dose of isoproterenol, and pressor responses to BAY K 8644 and angiotensin II were not altered. These results are consistent with the hypothesis that EDRF production may involve the formation of nitric oxide or a nitroso compound from L-arginine and that EDRF production may have a role in the regulation of tone and in the mediation of responses to acetylcholine and bradykinin in the pulmonary vascular bed of the cat.     

Contrasting responses of black fly species (Diptera: Simuliidae) to experimental whole-stream warming

1. As global temperatures continue to rise, assessment of how species within ecological communities respond to shifts in temperature has become increasingly important. However, such assessments require detailed long-term observations or ecosystem-level manipulations that allow for interactions among species and the potential for species dispersal and exchange with the regional species pool.
2. We examined the effects of experimental whole-stream warming on a larval black fly assemblage in southwest Iceland. We used a paired-catchment design, in which we studied the warmed stream and a nearby reference stream for 1 year prior to warming and 2 years during warming and estimated population abundance, biomass, secondary production, and growth rates for larvae of three black fly species.
3. Experimental warming by 3.8°C had contrasting effects on the three black fly species in the assemblage. The abundance, biomass, growth, and production of Prosimulium ursinum decreased in the experimental stream during the warming manipulation. Despite increasing in the reference stream, the abundance, biomass, and production of another species, Simulium vernum, decreased in the experimental stream during warming.
4. In contrast, warming had an overall positive effect on Simulium vittatum. While warming had little effect on the growth of overwintering cohorts of S. vittatum, warming led to an additional cohort during the summer months and increased its abundance, biomass, and production. Overall, family-level production was enhanced by warming, despite variation in species-level responses.
5. Our study illustrates that the effects of climate warming are likely to differ even among closely related species. Moreover, our study highlights the need for further investigation into the uneven effects of warming on individual species and how those variable effects influence food web dynamics and ecosystem function.