Evolution ofMHC polymorphism: Extensive sharing of polymorphic sequence motifs between human and bovine DRB alleles

The evolution ofMHC polymorphism has been studied by comparing the amino acid and nucleotide sequences of 14 bovine and 32 humanDRB alleles. The comparison revealed an extensive sharing of polymorphic sequence motifs in the two species. Almost identical sets of residues were found at several highly polymorphic amino acid positions in the putative antigen recognition site. Consequently, certain bovine alleles were found to be more similar to certain human alleles than to other bovine alleles. In contrast, the frequencies of silent nucleotide substitutions were found to be much higher in comparisons between species than within species implying that none of the human or bovine DRB alleles originated before the divergence of these distantly related species. The results suggest that the observed similarity inDRB polymorphism is due to convergent evolution and possibly the sharing of short ancestral sequence motifs. However, the relative role of the latter mechanism is difficult to assess due to the biased base composition in the first domain exon of polymorphic class 11 genes. The frequency of silent substitutions betweenDRB alleles was markedly lower in cattle than in man suggesting that theDRB diversity has evolved more rapidly in the former species.     

Microwave irradiation increases recovery of neuropeptides from brain tissues

The effect of focused high energy microwave treatment (MW) on brain concentrations and molecular forms of substance P, neurokinin A, neuropeptide Y, neurotensin, galanin and calcitonin gene-related peptide was investigated. Groups of rats were treated as follows: 1) MW, storage for 60 min at 22°C, 2) Decapitation, storage for 60 min at 22°C, 3) Decapitation, storage for 60 min at 22°C, MW treatment, 4) MW, decapitation, storage for 2 min at 22°C and 5) Decapitation, storage for 2 min at 22°C. Peptide concentrations were in all instances highest in the MW sacrificed groups. MW increased the concentration of intact peptides by rapid inhibition of peptidase activity and increase in peptide solubility/extractability.     

Detyrosination of tubulin is not correlated to cold-adaptation of microtubules in cultured cells from the Atlantic cod (Gadus morhua)

Summary Isolated cod brain microtubules from the cold-adapted Atlantic cod (Gadus morhua) have previously been shown to be highly detyrosinated, a post-translational modification of tubulin usually found in stable subsets of microtubules. In this study we found this was not restricted only to isolated brain microtubules. Microtubules in primary cultures of brain and skin cells were composed of both tyrosinated (Tyr)- and detyrosinated (Glu)-tubulin seen by immunocytochemistry. Immunoelectron microscopy of isolated microtubules showed that individual microtubules were composed of a mixture of Tyr- and Glu-tubulin. Leukocytes with extending lamellopodia contained only microtubules stained with the antibody against Tyr-tubulin, and isolated heart tubulin lacked both Tyr- and Glu-tubulin, suggesting that a relative high level of detyrosination is a characteristic of most, but not all, cod microtubules. Brain cell microtubules were more resistant to mitotic inhibitors than skin cell microtubules, but this was not correlated to a difference in detyrosination. Brain and skin cell microtubules were only partially disassembled when incubated at 0°C. Upon reassembly of microtubules at 12°C, microtubules were still made of mixtures of Tyr- and Glu-tubulin, indicating that detyrosination of assembled microtubules is rapid and/or that in cod cells, in contrast to mammalian cells, Glu-tubulin can reassemble to microtubules. Our data show that most cod microtubules are highly detyrosinated, but this is not the cause of their cold adaptation or drug stability.     

Parasitoids in low-level populations ofLymantria dispar [Lep.: Lymantriidae] in different forest physiographic zones

A 2-year study was conducted on the distribution of parasitoids of gypsy moth,Lymantria dispar (L.) (Lep.: Lymantriidae), in mesic and adjacent higher elevation transition and xeric forest habitats in Vermont (U.S.A.). In both years, overall parasitism ranged from 12–18% in each habitat. When analyzed according to the life stage at which the host was collected, parasitism rates of greater than 40% were obtained among the late instars.Parasetigena silvestris (Robineau-Desvoidy) andPhobocampe disparis (Viereck) were recovered most commonly from the mesic habitat, andCotesia melanoscelus (Ratzeburg) andBlepharipa pratensis (= Sturmia scutellata) (Meigen) were most common in collections from the xeric area. Parasitism byCompsilura concinnata (Meigen) occurred at similar levels in all three habitats, and this species was responsible for the highest parasitism rates on the site, reaching 40% among the late instars in 1985. Percent parasitism byC. concinnata increased three-four-fold from 1984 to 1985, while parasitism by other species declined.     

Inhibition of ATP-regulated K+-channels by a photoactivatable ATP-analogue in mouse pancreatic β-cells

The effects of a photoactivatable (DMNPE-caged) ATP-analogue on ATP-regulated K⁺-channels (K_ATP-channel) in mouse pancreatic β-cells were investigated using the inside-out patch configuration of the patch-clamp technique. The caged precursor caused a concentration-dependent reduction of channel activity with a K_i of 17 μM; similar to the 11 μM obtained for standard Mg-ATP. The small difference in the blocking capacity between the precursor and ATP is probably the reason why no change in channel activity was observed upon photolysis of the caged molecule and liberation of ATP. It is suggested that the part of the ATP molecule involved in the blocking reaction of the K_ATP-channel is not sufficiently protected in DMNPE-caged ATP making this compound unsuitable for studying the rapid kinetics of ATP-induced K_ATP-channel inhibition.