Effect of luteinising hormone releasing hormone and its analogues on plasma luteinising hormone concentrations in incubating bantam hens

The ability of synthetic vertebrate luteinising hormone releasing hormones (LHRHs) and their long-acting analogues to maintain elevated plasma luteinising hormone (LH) concentrations and to stimulate ovarian growth was investigated in incubating bantam hens. Chicken LHRH-II (pGlu1-His2-Trp3-Ser4-His5-Gly6-Trp7-Tyr8-Pro9-G ly10-NH2) was more effective than chicken LHRH-I (pGlu1-His2-Trp3-Ser4-Tyr5-Gly6-Leu7-Gln8-Pro9-Gly10-N H2) or porcine LHRH (pGlu1-His2-Trp3-Ser4-Tyr5-Gly6-Leu7-Arg8-Pro9-Gly10-N H2) in stimulating the release of LH. Long-acting analogues of chicken LHRHs (chLHRHs) were created by substituting D-amino acids in position 6. An intravenous injection (10 micrograms/bird) of D-Arg6-chLHRH-II or of a long-acting mammalian analogue of LHRH (buserelin) resulted in a sustained release of LH for up to 8 h. Less sustained releases of LH were observed after the same doses of D-Ala6-chLHRH-I or of D-Trp6-chLHRH-I. Repeated subcutaneous injections of D-Arg6-chLHRH-II or buserelin at 7 to 9 h intervals for 9 d resulted in loss of pituitary gland responsiveness to these analogues. For this reason, the treatment failed to maintain elevated plasma LH concentrations and did not stimulate the growth of the ovary or oviduct.     

Comparing and modifying penaeid beam and otter trawls to improve ecological efficiencies

In an attempt to improve the selectivity and engineering performances of generic penaeid trawls, three established and one novel spreading‐mechanism configurations were assessed: otter boards attached (1) with and (2) without 3.15‐m sweeps to a 7.35‐m headline trawl, and a beam rigged directly to a 9.19‐m trawl (3) with and (4) without a horizontal wire and plastic streamers. Despite more surface area (7.5 vs 6.0 m²), both beam‐trawl configurations had significantly lower drag than the otter trawls (≤30%). When catches were standardised to per ha, the otter trawl with sweeps retained significantly more (1.3–2.4 times) school prawns, Metapenaeus macleayi (Haswell), than the other three configurations. Within systems, removing sweeps or adding a horizontal wire significantly reduced the unwanted catches of a key teleost (southern herring, Herklotsichthys castelnaui Ogilby) by 41 and 48%. The results illustrate the utility of simple anterior modifications for independently addressing penaeid‐trawling environmental issues.     

Acacia, cattle and migratory birds in southeastern Mexico

Acacia pennatula groves in mid-elevation valleys of southern Mexico supported both the highest density and diversity of migratory birds compared to other habitats in the region. In addition, we found the highest numbers for over half of the common migratory species. Despite the high degree of leaf loss during the late winter, acacia groves do not experience greater declines in insectivorous migratory bird populations than other local habitats. Color-marked individuals of canopy species had a strong tendency to remain resident within a single acacia grove throughout the winter. Management of native acacias on subtropical rangelands for wood products, fodder, and soil improvement would probably directly and indirectly benefit migratory song bird populations. Neotropical acacia woodland is primarily associated with grazing land for livestock which might discourage some from considering acacia management a viable option for migratory bird conservation. However, acacias were probably widespread in recent geologic time under drier conditions with heavy browsing and seed dispersal by a now extinct megafauna. Two observations suggest a foraging advantage for acacia use: the higher density of migratory birds in acacia is a result of higher numbers of canopy insectivores; and acacias are selected by migrants when they occur in mixed habitat. We hypothesize that plant investment in mechanical defenses (thorns) reduces energy available for chemical defenses effective against insect herbivores.     

Obituary

Extract

We called him Mac. In Scotland this is more than a convenient abbreviation for those claiming association with the clans of old. It carries a subtle implication of bestowed affection and acknowledged efficiency. On these terms, its application to James McGregor was peculiarly apt.     

A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs

It has generally been thought that the first dinosaurs quickly replaced more archaic Late Triassic faunas, either by outcompeting them or when the more archaic faunas suddenly became extinct. Fossils from the Hayden Quarry, in the Upper Triassic Chinle Formation of New Mexico, and an analysis of other regional Upper Triassic assemblages instead imply that the transition was gradual. Some dinosaur relatives preserved in this Chinle assemblage belong to groups previously known only from the Middle and lowermost Upper Triassic outside North America. Thus, the transition may have extended for 15 to 20 million years and was probably diachronous at different paleolatitudes.     

Plasma concentrations of luteinising hormone, follicle stimulating hormone, androgen, growth hormone, prolactin, thyroxine and triiodothyronine during growth and sexual development in the cockerel

Changes in concentrations of plasma luteinising hormone (LH), follicle stimulating hormone (FSH), androgen, growth hormone (GH), prolactin (Prl), thyroxine (T4) and triiodothyronine (T3) were measured during growth and sexual maturation in broiler cockerels reared in continuous light to 7 weeks and 14 h light/d thereafter. Concentrations of LH and FSH began to increase between 13 and 15 weeks, while those of androgens increased between 16 and 17 weeks. FSH concentration increased faster than that of LH. Concentrations of GH and Prl were high at 3 weeks; that of GH decreasing progressively between 3 and 14 weeks of age and thereafter remaining low, while that of Prl was low between 5 and 9 weeks, relatively high between 10 and 13 weeks, and then temporarily decreasing before increasing progressively during sexual maturation. Concentrations of T3 and T4 were higher in juvenile than in adult birds.     

Modelling root and stem lodging in sunflower

Stem and root lodging constitute significant adversities to sunflower (Helianthus annuus L.) cropping in Argentina. We have adapted previously developed models of the lodging process in cereals to the particularities of sunflower by using functions, developed using data obtained by mechanical lodging, for the [root failure moment/plant anchorage] and [stem failure moment/thickness of stem wall] relationships, and estimates of plant area loaded by wind gusts. The model uses this information to estimate wind failure speed (i.e., the wind speed at which lodging [stem or root, as appropriate] is expected to occur). The model was tested against information (plant and soil characteristics, measured wind gust velocity immediately preceding rainfall) obtained in 26 naturally lodged plots (6 stem-lodged, 20 root-lodged) which occurred across a network of trials (2 seasons, 4 sites, 3 hybrids, 4 crop population densities, all experiments fitted with automatic meteorological stations). Lodging events took place over a range of crop developmental stages between visible capitulum and harvest maturity. Lodging index (proportion of plants lodged) against the difference between observed and model-estimated wind failure speeds showed that the model had good predictive skill across the range of conditions explored in these experiments and was able to distinguish between hybrids of differential susceptibility to lodging within the same experiment. Sensitivity analyses showed that the principal determinants of lodging susceptibility were root plate diameter, stem wall thickness, and the area of the plant loaded by wind gusts. Within the observed ranges (almost twofold) of stem height and stem natural frequency, these two variables had little influence on lodging susceptibility. We conclude that the model, despite the simplifications incorporated into its structure, provides an effective and useful tool for the integration of the complex factors that determine lodging susceptibility in this species.     

Comparison of the fractionation and assay of domestic duck and fowl pituitary gonadotrophins

1. Pituitary glycoproteins from domestic ducks and fowls were fractionated to separate luteinising hormone (LH) and follicle stimulating hormone (FSH) activities using the same chromatographic steps. 2. Fractions were bioassayed for LH using the release of progesterone from fowl granulosa cells and for thyroid stimulating hormone (TSH) by measuring the release of thyroxine in 3-d-old chicks. Follicle stimulating hormone activity was measured either in a cockerel-testes radioreceptor assay or by the release of oestrogen from cultured rat Sertoli cells. 3. Fractions containing predominantly FSH or LH activity were isolated from the fowl glycoproteins. Duck gonadotrophin did not occur in fractions corresponding to those containing fowl FSH. 4. Duck gonadotrophin was found in a fraction corresponding with the most highly purified fowl LH fraction. A duck LH fraction was found with little FSH activity for which there was no corresponding fowl LH fraction. 5. It is concluded that domestic fowl and duck gonadotrophins have different chromatographic properties. Further study is required to determine whether the purified duck gonadotrophin preparation comprises proteins with similar physico-chemical properties but with separate FSH and LH biological activities.     

Endangered mammals of Chile: Status and conservation

The native mammalian fauna of Chile has suffered reductions in distribution and abundance. Of the 78 species of native mammals, 22 species plus 15 races of 5 additional species are of conservation concern. The status of each of these threatened taxons is given, using IUCN criteria, along with a discussion of the reasons for their status of concern. Exploitation for meat or pelts combined with habitat deterioration are the most prevalent reasons for the endangering of wildlife in Chile. Central Chile, the most developed and populated region, has the highest proportion of mammalian fauna of conservational concern, followed closely by arid northern Chile. Chilean authorities, with international assistance, have made progress in addressing these problems but much remains to be done that will require continued international assistance if many unique forms are to be preserved.