α-MSH Stimulates Glucose Uptake in Mouse Muscle and Phosphorylates Rab-GTPase-Activating Protein TBC1D1 Independently of AMPK

The melanocortin system includes five G-protein coupled receptors (family A) defined as MC1R-MC5R, which are stimulated by endogenous agonists derived from proopiomelanocortin (POMC). The melanocortin system has been intensely studied for its central actions in body weight and energy expenditure regulation, which are mainly mediated by MC4R. The pituitary gland is the source of various POMC-derived hormones released to the circulation, which raises the possibility that there may be actions of the melanocortins on peripheral energy homeostasis. In this study, we examined the molecular signaling pathway involved in α-MSH-stimulated glucose uptake in differentiated L6 myotubes and mouse muscle explants. In order to examine the involvement of AMPK, we investigate α-MSH stimulation in both wild type and AMPK deficient mice. We found that α-MSH significantly induces phosphorylation of TBC1 domain (TBC1D) family member 1 (S237 and T596), which is independent of upstream PKA and AMPK. We find no evidence to support that α-MSH-stimulated glucose uptake involves TBC1D4 phosphorylation (T642 and S704) or GLUT4 translocation.     

Parasitoid pressure and the radiation of a gallforming group (Cecidomyiidae: Asphondylia spp.) on creosote bush (Larrea tridentata)

Summary We tested the Enemy Impact Hypothesis, which predicts that communities of one tropic level are organized by the tropic level above. In the case of gallforming insect communities, the hypothesis predicts that gall morphology will diverge, minimizing the number of parasitoids shared among species. We used the monophyletic group of gallforming cecidomyiids (Asphondylia spp.) on creosote bush (Larrea tridentata) to test this hypothesis, predicting that species with thicker gall walls should exclude species of parasitoids with shorter ovipositors and have lower levels of parasitism. Of 17 parasitoid species reared from Asphondylia galls on creosote bush, 9 accounted for over 98% of parasitism. Seven of these 9 species had ovipositors long enough to penetrate 10 of 13 gall morphs measured. There was no significant relationship between gall wall thickness and number of associated parasitoid species (r ²=0.01, P>0.05, n=13). There was no relationship between gall wall thickness and types of parasitoid species colonizing galls: parasitoids with the shortest ovipositors colonized all types of gall morphs and were dominant members of the parasitoid assemblages in galls with the thickest walls. Ultimately, there were no significant differences in percent parasitism among Asphondylia species, regardless of gall wall thickness. We found no difference in numbers of associated parasitoids or percent parasitism in galls with different textures (e.g. hairy versus smooth), different locations on the plant or different phenologies. Our results suggest that enemy impact has not influenced the diversity of this gall community. Gall wall thickness, phenology, location on the plant and surface structure do not appear to influence the distribution of parasitoid species. Other explanations are offered to account for diversity in gall morphology among these species.     

Consequences of host plant chemical and physical variability to an associated herbivore

The effects of watering and fertilizer treatments on the vigor and biochemistry of the willow,Salix lasiolepis, and subsequent colonization and survivorship of its gallforming herbivore,Euura lasiolepsis, were investigated in two field experiments. Some plants received low (LW), intermediate (MW) or high (HW) levels of water as treatments, while others received no (OF), low (LF) or high (HF) fertilizer levels. In the watering experiment, plant protein concentrations decreased, while growth rate and number of galls per plant increased with increased water treatments. Plant growth proved to be the best correlate of sawfly attack. Sawfly survivorship increased slightly with greater watering, and phenol concentrations showed no pattern among treatments. In the fertilization experiment, leaf protein increased with fertilization, although shoot length, number of galls and survivorship ofE. lasiolepis survivorship were greatest in intermediate treatment plants. In both experiments, plant growth, rather than protein or phenol levels, was the best predictor of sawfly attack and survivorship. In a natural experiment with galls on wild plants, galled tissue had significantly greater protein concentrations and lower phenol concentrations than did ungalled tissue. We suggest that gallformers modify host plant biochemistry within willow galls, which may explain why the chemical parameters of ambient plant quality we tested were less predictive than plant growth.     

Fetal cells in maternal blood: recovery by charge flow separation

Fetal blood cells can be recovered from the maternal circulation by charge flow separation (CFS), a method that obviates the risks associated with amniocentesis and chorionic villus sampling. By CFS, we processed blood samples from 13 women carrying male fetuses, 2 carrying fetuses with trisomy 21, and 1 who had delivered a stillborn infant with trisomy 18. On average more than 2000 fetal nucleated red blood cells were recovered per 20-ml sample of maternal blood. Recovery of fetal cells was confirmed by fluorescence in situ hybridization with probes for chromosomes Y, 18 and 21. After culturing of CFS-processed cells, amplification by the polymerase chain reaction revealed Y-chromosomal DNA in clones from four of six women bearing male fetuses, but not in clones from three women bearing female fetuses. Received: 8 January 1996 / Revised: 22 March 1996     

Altering Developmental Trajectories in Mice by Restricted Index Selection

A restricted index selection experiment on mice was carried out for 14 generations on rate of early postnatal development (growth rate from birth to 10 days of age) vs. rate of development much later in ontogeny (growth rate from 28 to 56 days of age). Early rate of development (E) approximates hyperplasia (changes in cell number) and later rate (L) reflects hypertropy (changes in cell size). The selection criteria were as follows: E+L0 was selected to increase early body weight gain while holding late body weight gain constant; E-L0 was selected to decrease early body gain while holding late gain constant; E0L+ was selected to increase late gain holding early gain constant; and E0L- was selected to decrease late gain holding early gain constant. After 14 generations of selection, significant divergence among lines has occurred and the changes in the growth trajectories are very close to expectation. The genetic and developmental bases of complex traits are discussed as well as the concept of developmental homoplasy.     

Cellular localisation of human epidermal growth factor receptor

We show here, using immunohistological techniques and a monoclonal antibody to the receptor for epidermal growth factor (EGFR) (Waterfield et al. 1982) that EGFR is present on a wide range of normal epithelial tissues and tumours arising from those sites. The distribution of the receptor suggests that EGF may be involved in the control of proliferation and possibly differentiation of surface epithelia. The strong tumour cell staining suggests an increased expression of the receptor in certain carcinomas.     

Lysosomal proliferation in rachitic avian intestinal absorptive cells following 1,25-Dihydroxycholecalciferol

Lysosomes in chick intestinal absorptive cells from rachitic (vitamin D-deficient) and vitamin D-replete animals were studied utilizing transmission electron microscopic histochemistry and ultrastructural morphometry. Absorptive cells from rachitic animals, serum calcium = 7.3±0.3 mg%, contained an average of 4.0±0.3 supranuclear lysosomes. In rachitic chicks sacrificed 9 hr post-injection of 1,25-dihydroxycholecalciferol, the active metabolite of vitamin D, the values for both serum calcium, 9.8 ± 0.2 mg%, and the number of apical absorptive cell lysosomes, 12.9±0.6, were increased over non-injected or vehicle-only injected animals. Lysosomes in vitamin D-replete absorptive cells were characterized by their intense staining with pyroantimonate, indicative of their high calcium content. The same organelles also produced a positive reaction for acid phosphatase. Rachitic lysosomes, also acid phosphatase positive, were only lightly stained with pyroantimonate. The lysosomal proliferation apparently induced by 1,25-dihydroxycholecalciferol may be a further indication that these organelles play a role in intestinal calcium transport and/or intracellular calcium homeostasis within the absorptive cell.