Bioactive and immunoreactive concentrations of circulating luteinizing hormone during sexual maturation in the bovine.

The characteristics of circulating LH during sexual maturation in cattle were assessed by examining bioactive and immunoreactive LH concentrations, as well as their ratio (B/I ratio). Male and female intact control (CONT), gonadectomized (GNX; at 241 +/- 3 days of age, Day 0 of the study), and gonadectomized animals administered 17 beta-estradiol (GNXE) were evaluated. Serum samples were collected at 15-min intervals for 24 h at 1, 7, 13, 17, 21, 25, 29, 33, 37, and 43 wk subsequent to Day 0. Bioactive LH was assessed with an in vitro bioassay using mouse testicular interstitial cells. In initial experiments, immunoreactive LH was quantified in RIAs using three different antibodies. The two RIAs employing polyclonal antibodies overestimated low LH concentrations, but the absolute values obtained in each of the three assays were highly correlated. Hence, immunoreactive LH was measured in an RIA using monoclonal anti-bovine LH (bLH) (JR-518B7). No significant changes in the B/I ratios were observed during individual pulses of LH secretion. Accordingly, pools consisting of equal volumes of the serial blood samples collected during the 24-h period for each animal at each stage of maturation (pools) were compared. LH B/I ratios for GNX females increased significantly with time (p less than 0.01) and the B/I ratios for GNX males were significantly higher than for GNX females (p less than 0.05). Concentrations of LH in most of the pools for GNXE and CONT animals were extremely low or nondetectable until the later bleeding periods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Elevation and habitats: the potential of sites at different altitudes to provide refuges for phytophagous insects during climatic fluctuations

Uplands are expected to provide refuges for species subject to lowland habitat loss and projected climate changes. Here, we argue that upland populations also provide refuges when lowland sites are subject to climatic fluctuations and extreme events and that species with populations dispersed over adjoining uplands and lowlands spread their risk of extinction. A proviso is that development is sufficiently lagged with altitude but that development rates are compatible. Emergence patterns and development of the butterfly Anthocharis cardamines and its larval host plant Cardamine pratensis show these characteristics, and coupled with the butterfly’s capacity to migrate between isolated populations present a case where upland and lowland populations can act as sources when one or the other area is adversely affected by extreme events.     

Impact of node ablation on the morphogenesis of the body axis and the lateral asymmetry of the mouse embryo during early organogenesis.

The node of the mouse gastrula is the major source of the progenitor cells of the notochord, the floor plate, and the gut endoderm. The node may also play a morphogenetic role since it can induce a partial body axis following heterotopic transplantation. The impact of losing these progenitor cells and the morphogenetic activity on the development of the body axes was studied by the ablation of the node at late gastrulation. In the ablated embryo, an apparently intact anterior-posterior body axis with morphologically normal head folds, neural tube, and primitive streak developed during early organogenesis. Cell fate analysis revealed that the loss of the node elicits de novo recruitment of neural ectoderm and somitic mesoderm from the surrounding germ-layer tissues. This leads to the restoration of the neural tube and the paraxial mesoderm. However, the body axis of the embryo was foreshortened and somite formation was retarded. Histological and gene expression studies reveal that in most of the node-ablated embryos, the notochord in the trunk was either absent or interrupted, and the floor plate was absent in the ventral region of the reconstituted neural tube. The loss of the node did not affect the differentiation of the gut endoderm or the formation of the mid- and hindgut. In the node-ablated embryo, expression of the Pitx2 gene in the lateral plate mesoderm was no longer restricted to the left side but was found on both sides of the body or was completely absent from the lateral plate mesoderm. Therefore, the loss of the node results in the failure to delineate the laterality of the body axis. The node and its derivatives therefore play a critical role in the patterning of the ventral neural tube and lateral body axis but not of the anterior-posterior axis during early organogenesis.     

Proposed follow up programme after curative resection for lower third oesophageal cancer

Cyclins are indispensable elements of the cell cycle and derangement of their function can lead to cancer formation. Recent studies have also revealed more mechanisms through which cyclins can express their oncogenic potential. This review focuses on the aberrant expression of G1/S cyclins and especially cyclin D and cyclin E; the pathways through which they lead to tumour formation and their involvement in different types of cancer. These elements indicate the mechanisms that could act as targets for cancer therapy.