The effects of thiamine inhibition on ruminal fermentation: a preliminary study

Inhibition of methanogenesis in ruminal cultures was attempted by hindering thiamine availability through its degradation by ‘polyphenols’ and competition for active sites on enzymes and transporters using thiamine structural analogs. Effects on fermentation were small and not consistently reversed by adding thiamine. Lack of major effects of the compounds evaluated could be due to intracellular synthesis of thiamine covering most requirements.     

The occurrence and distribution of certain polypeptides within the human carotid body

Summary Both carotid bodies from 26 patients coming to necropsy were fixed in 10% neutral buffered formalin and sections 4 m thick were stained for various peptides by use of the immunogold technique. The results show that the human carotid body contains met- and leu-enkephalin, substance P, vasoactive intestinal peptide (VIP), neurotensin and bombesin. The distribution of these six peptides within the carotid body differs. Thus met- and leu-enkephalin are both present predominantly within glomic chief cells but with a marked tendency to favour the dark variant of these cells. Substance P and VIP both show a weak immunoreactivity in comparison to the enkephalins and are present in all three variants of chief cell. Neurotensin shows the weakest immunoreactivity of all and is restricted to a few glomic chief cells in a minority of cases. Bombesin also shows a weak immunoreactivity in glomic chief cells but a strong reaction in glomic arteries and arterioles. In these vessels bombesin appears to be confined to smooth muscle cells in the media but we cannot say whether it is secreted by them or merely bound to receptor sites on their membranes. These findings are related to quantitative data on the concentration of peptides in the human carotid body from a previous paper with which we were associated.     

Production of Highly Labeled Adenoviruses

A method is described for increasing the incorporation of radioactive thymidine into adenovirus deoxyribonucleic acid by the use of amethopterin. In addition, a modified procedure is presented for the preparation of highly purified adenoviruses. This procedure, which employs enzymatic digestion of cellular debris, obviates the necessity for fluorocarbon treatment of crude virus suspensions, and routinely provides excellent recovery of virus.     

Difference imaging of adenovirus: bridging the resolution gap between X-ray crystallography and electron microscopy.

While X-ray crystallography provides atomic resolution structures of proteins and small viruses, electron microscopy provides complementary structural information on the organization of larger assemblies at lower resolution. A novel combination of these two techniques has bridged this resolution gap and revealed the various structural components forming the capsid of human type 2 adenovirus. An image reconstruction of the intact virus, derived from cryo-electron micrographs, was deconvolved with an approximate contrast transfer function to mitigate microscope distortions. A model capsid was calculated from 240 copies of the crystallographic structure of the major capsid protein and filtered to the correct resolution. Subtraction of the calculated capsid from the corrected reconstruction gave a three-dimensional difference map revealing the minor proteins that stabilize the virion. Elongated density penetrating the hexon capsid at the facet edges was ascribed to polypeptide IIIa, a component required for virion assembly. Density on the inner surface of the capsid, connecting the ring of peripentonal hexons, was assigned as polypeptide VI, a component that binds DNA. Identification of the regions of hexon that contact the penton base suggests a structural mechanism for previously proposed events during cell entry.     

Exercise,agonistic behaviour and food acquisition in Arctic charr,Salvelinus alpinus

Synopsis Although swimming is energetically costly, a number of studies on salmonid species have demonstrated increased growth rates in fishes forced to swim for prolonged periods at moderate speeds (typically 1–2 body lengths per sec). This suggests that additional energetic costs of swimming are more than met by alternative compensatory gains. The mechanisms underlying such effects are not fully understood. In this paper, we describe an experiment designed to examine one possible mechanism, namely a swimming-induced inhibition of aggression, with consequent beneficial effects on growth. The study used Arctic charr,Salvelinus alpinus, a species for which a positive relationship between exercise and growth has been clearly established. Using direct behavioural observations on small groups, we demonstrate that individuals displaying high levels of aggressive behaviour are able to monopolise access to food and that enforced swimming at a moderate speed (1 body length per sec) reduces the incidence of aggression although not the degree of monopolisation of food shown by aggressive individuals. These results suggest that the enhanced growth rates accompanying enforced swimming may reflect lower energetic costs of reduced aggressive activity rather than improved access to food by subordinates.     

Sesquiterpene lactones of Vernonia — influence of glaucolide-A on the growth rate and survival of Lepidopterous larvae

Summary Sesquiterpene lactone glaucolide-A from Vernonia, incorporated in the rearing diets of five species of Lepidoptera, significantly reduced the rate of growth of larvae of the southern armyworm, Spodoptera eridania; fall armyworm, S. frugiperda; and yellowstriped armyworm, S. ornithogalli. Quantitative feeding tests demonstrated that decreased feeding levels and reduced growth resulted from ingestion of a sesquiterpene lactone. Ingestion of glaucolide-A increased the number of days to pupation in four of the species. In the southern armyworm, it significantly reduced pupal weight. Glaucolide-A decidedly reduced percentage of survival of southern and fall armyworms. Yellow woollybear, Diacrisia virginica, and cabbage looper, Trichoplusia ni, larvae were essentially uneffected by the ingestion of the sesquiterpene lactone. Sesquiterpene lactones adversely affect growth rate and survival of certain insects that feed upon plants containing them. They apparently function as defensive products, screening out a portion of the potential herbivores.Vernonieae: Compositae     

Distribution and complementarity of hydropathy in multisubunit proteins

A survey of 40 multisubunit proteins and 2 protein-protein complexes was performed to assay quantitatively the distribution of hydropathy among the exterior surface, interior, contact surface, and noncontact exterior surface of the isolated subunits. We suggest a useful way to present this distribution by using a "hydropathy level diagram." Additionally, we have devised a function called "hydropathy complementarity" to quantitate the degree to which interacting surfaces have matching hydropathy distributions. Our survey revealed the following patterns: (1) The difference in hydropathy between the interior and exterior of subunits is a fairly invariant quantity. (2) On average, the hydropathy of the contact surface is higher than that of the exterior surface, but is not greater than that of the protein as a whole. There was variation, however, among the proteins. In some instances, the contact surface was more hydrophilic than the noncontact exterior, and in a few cases the contact surface was as hydrophobic as the protein interior. (3) The average interface manifests significant hydropathy complementarity, signifying that proteins interact by placing hydrophobic centers of one surface against hydrophobic centers of the other surface, and by similarly matching hydrophilic centers. As a measure of recognition and specificity, hydropathy complementarity could be a useful tool for predicting correct docking of interacting proteins. We suggest that high hydropathy complementarity is associated with static inflexible interactions. (4) We have found that some subunits that bind predominantly through hydrophilic forces, such as hydrogen bonds, ionic pairs, and water and metal bridges, are involved in dynamic quaternary organization and allostery.     

Peromyscus alcohol dehydrogenase: Lack of cross-reacting material in enzyme-negative animals

Two forms of alcohol dehydrogenase (ADH), coded by allelic genes, have been purified to homogeneity from Peromyscus. Monospecific antisera to the purified enzymes have been raised in rabbits. These antisera fail to detect cross-reacting material in the liver of ADH-negative animals on Ouchterlony plates. Immuno-titration of anti-ADH antiserum with ADH in liver extracts from AdhS/AdhS and AdhS/AdhN animals results in identical equivalence points, again suggesting the absence of cross-reacting material coded by the AdhN allele. Over a wide range of anti-ADH antiserum dilutions, radiolabeled protein was not immunoprecipitable from liver extracts of AdhN/AdhN animals. These immunochemical tests, in conjunction with previous studies, suggest that the AdhN allele in Peromyscus does not produce inactive polypeptide in normal levels that bears immunological determinants similar to those of the fast and slow ADH isozymes.