Chymotryptic-like hydrolysis of luliberin (LH-RF) by an adenohypophyseal enzyme of high molecular weight

An enzyme that hydrolyzes the fluorogenic chymotrypsin substrate glutaryl-Gly-Gly-Phe-β-naphthylamide has been partially purified from extracts of bovine anterior pituitaries. Like chymotrypsin, this enzyme hydrolyzes the neuropeptide Luliberin (LH-RF, <Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂) at the carboxyl-side of Trp and Tyr, but it differs from the pancreatic protease by its high molecular weight, insensitivity towards OH-reactive agents and other enzymechemical parameters. It seems, however, to be identical to the “cation-sensitive neutral endopeptidase”. In the course of this study evidence has also been obtained that LH-RF is not degraded by the cystinyl-arylamidase.     

Role of luteinizing hormone-releasing factor (LH-RF) and LH on maintenance of early gestation in rats.

The role of luteinizing hormone (LH) and LH-releasing hormone (LH-RH) in the maintenance of early pregnancy in rats was studied. Serum levels of progesterone (P) and LH were measured daily in untreated pregnant rats from Day 4 through parturition. Serum levels of P and LH were determined on Days 11 and 15 of pregnancy in animals treated with antisera to LH (LH-A/S) and to LH-RH (LH-RH-A/S) on Days 8-10. Serum levels of P peaked on Days 7 and 16 in untreated animals, after which they declined sharply just before delivery. Serum LH fluctuated between 30-160 ng/ml during pregnancy but did not exhibit any distinctive peaks. Treatment with .2 ml LH-A/S on Days 8-10 reduced serum P to virtually undetectable levels on Day 11, and only a slight recovery was evident on Day 15. Lower doses of LH-A/S had no effect. Administration of 1.3 ml LH-RH-A/S had no effect on serum levels of P or LH, and did not impede fetal development. The results indicate that LH is essential to the luteotropic complex of early pregnancy in the rat, and also that LH-RH-A/S can maintain to some extent basal levels of P and LH during early pregnancy.     

The influence of foraging benefits on association of cattle egrets (Bubulcus ibis) with cattle

Summary The degree of association between cattle egrets (Bubulcus ibis) and cattle was studied during one summer on Saint Catherines Island, Georgia, USA. Previous work by Grubb (1976) and others indicated that cattle egrets foraging with cattle require fewer steps and less time to catch prey than egrets foraging without cattle and single egrets catch prey at a higher rate than egrets foraging in groups of two or more with cattle. Accordingly, we predicted that when given a choice egrets should forage with cattle rather than alone, egrets should prefer to associate with standing rather than sitting cattle, and single egrets associated with cattle should be more common than expected by chance.In excess of two-thirds of the egrets accompanied cattle. Neither time of day nor month influenced the degree of association, but egrets in forest were more likely to be associated with cattle than egrets in pasture. Standing cattle were more likely to be accompanied by egrets than were sitting cattle. Single egrets occurred more frequently than expected by chance when accompanying standing cattle but not when associated with sitting cattle. Thus, cattle egrets usually distributed themselves among cattle in the way predicted by optimal foraging theory.We dedicate this paper to the memory of Michael D. Sabath     

Environmental temperature and lactation (with special reference to cattle)

The majority of fundamental information on temperature effects on lactation is on cattle. The yield and composition of milk are affected by the temperature of the environment or the animal's body temperature. Environmental temperatures lower and higher than the comfort zone temperatures, diminish yield and alter many of the components of milk. Concepts as to the possible manner in which temperature may alter the synthesis of milk and the role of the neuro-endocrine and environmental physiological funtions in the maintenance of lactation were presented. The elucidation of many of these postulated mechanisms of temperature effect on lactation merely awaits the application of available modern endocrine, physiological, and biochemical techniques utilizing chromatography, tracer, fluorometric, manometric, and other procedures.

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Zusammenfassung Der Hauptteil der grundsÄtzlichen Kenntnisse über Einflüsse der Temperatur auf die Milcherzeugung betrifft Rinder. Die Milchleistung und Zusammensetzung der Milch werden von der Temperatur der Umgebung sowie im Tier beeinflusst. Temperaturen der Umgebung, die höher oder tiefer sind als die des normalen körperlichen Wohlbefindens, verringern die Michleistung und verÄndern die Zusammensetzung der Milch. Die verschiedenen Arten der VerÄnderung der Milchsynthese durch Temperaturunterschiede und die Rolle der neuro-endokrinen und anderen physiologischen Funktionen zur Unterstützung der Milcherzeugung werden dargestellt-Die AufklÄrung vieler dieser angenommenen Mechanismen des Temperatureinflusses auf die Milchproduktion verlangt lediglich die Anwendung der üblichen modernen Methoden der Hormonforschung, der Physiologie und Biochemie.

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Resume La majeure partie des recherches faites sur l'influence exercée par la température sur la lactation concerne les bovidés. La quantité et la composition du lait son influencées par la température ambiante ou par celle du corps de l'animal. Des températures extérieures supérieures ou inférieures à celles limitant la zone de confort diminuent les quantités de lait sécrété et modifient plusieurs de ses composants. On indique ici les différentes possibilités d'action de la température sur la sythèse du lait et le rÔle que jouent les fonctions physiologiques, en particulier neuroendocrines sur le maintient de la lactation. L'établissement de bien des mecanismes supposés de l'influence de la température sur la production laitière nécessite l'utilisation des techniques modernes en physiologie et en biochimie ainsi que dans la recherche des hormones. Il s'agit en particulier de la Chromatographie,de la chimie, de la mesure de la fluorescence, des mesures de pression, etc.

     

Studies on hemoglobin variants in Korean cattle

814 hemoglobin samples from Korean cattle were investigated by starch gel electrophoresis for the detection of hemoglobin variants. A new variant of cattle hemoglobin, called Hb, H, was recognized. It has a slower rate of migration than Hb A.
Hemoglobin types from 814 Korean cattle were as follows: 652 of Hb AA type (80.1 %), 133 of Hb AB (16.4 %), 12 of Hb AC (1.5 %), 9 of Hb BB (1.1 %), 2 of Hb BC (0.2 %), 4 of Hb AH (0.5 %), 1 of Hb CH (0.1 %), 1 of Hb HH (0.1 %). These figures correspond to the frequencies: Hb^A = 0.893, Hb^B = 0.093, Hb^c =0.009, Hb^H = 0.004.
Gene frequencies at the Hb locus in Korean cattle were compared among six population from different provinces. Generally, high frequencies of Hb^A were observed in each province.     

Two-step freezing of cattle blastocysts with dimethylsulfoxyde (DMSO) or glycerol

Sixty five cattle blastocysts were frozen by the so-called two-step freezing method: The samples were seeded at -7 degrees C and then directly brought at -30 degrees C for 30 minutes before being taken into liquid nitrogen. Results in terms of survival rates at thawing and after short term cultures were compared to two controlled linear cooling rate procedures (i.e. 0.3 degrees C/min and 1.3 degrees C/min). The results demonstrate that: 1) two-step freezing yielded approximately the same survival rate as the two others techniques and 2) Glycerol yielded better survival rates than DMSO treatments (56 vs 31% after 24 hours in culture).     

Association of BoLA-DRB3.2 alleles with tick (Boophilus microplus) resistance in cattle

Losses caused by bovine tick burdens in tropical countries have a tremendous economic impact on production systems. Besides reducing production, this parasite can cause death in the most susceptible animals. The use of commercial acaricides has been the major method of control, but their misuse has led to tick resistance to many chemicals. More recently, vaccines have been used in some countries without solving the problem completely. An alternative could be the development of resistant animals and the use of genetic markers and candidate genes that could help with the enormous task of selecting resistant animals. The bovine lymphocyte antigen genes (BoLA) have been shown to be associated with some parasitic infestations and disease incidence. Thus, the objective of the present study was to determine the association of BoLA-DRB3.2 alleles with tick resistance in cattle. The study was conducted on 231 F2 (Gyr x Holstein) animals that were artificially infested with 10,000 tick larvae. Log of tick count +1 was used as the dependent variable in a mixed animal model with allele substitution effects in addition to fixed effects of year and season at tick count, sex of calves, age of animal at tick count, hair type (short-straight, short-curl, long-straight, and long-curl), coat color (white, >75% white, 50- 75% white, and 25-50% white), and additive genetic, permanent environmental and residual effects as random. Females showed fewer ticks than males. Animals with short-straight hair were more resistant to tick infestation than animals with long-curl hair, and animals with whiter coat color also had fewer ticks. An association between BoLA alleles and lower tick number was found for alleles DRB3.2 *18, *20 and *27 at the 5% significance level. Also, one allele (DRB3.2*16) showed an association at the 10% level. Allele *27 was the most frequent in the population (30.7%), followed by alleles *16 (10.8%), *20 (8.7%) and *18 (2.4%). These results suggest that BoLA-DRB3.2 alleles could be used to help in the selection of animals resistant to tick infestation. However, further studies involving a larger population of cattle in combination with other BoLA genes may help to understand the mechanisms of resistance to parasites.