Reduced GLP-1 and insulin responses and glucose intolerance after gastric glucose in GRP receptor-deleted mice

By applying a newly developed ELISA technique for determining biologically active intact glucagon-like peptide [GLP-1, GLP-1-(7-36)amide] in mouse, plasma baseline GLP-1 in normal NMRI mice was found to be normally distributed (4.5 +/- 0.3 pmol/l; n = 72). In anesthetized mice, gastric glucose (50 or 150 mg) increased plasma GLP-1 levels two- to threefold (P < 0.01). The simultaneous increase in plasma insulin correlated to the 10-min GLP-1 levels (r = 0.36, P < 0.001; n = 12). C57BL/6J mice deleted of the gastrin-releasing peptide (GRP) receptor by genetic targeting had impaired glucose tolerance (P = 0.030) and reduced early (10 min) insulin response (P = 0.044) to gastric glucose compared with wild-type controls. Also, the GLP-1 response to gastric glucose was significantly lower in the GRP receptor-deleted mice than in the controls (P = 0.045). In conclusion, this study has shown that 1) plasma levels of intact GLP-1 increase dose dependently on gastric glucose challenge in correlation with increased insulin levels in mice, and 2) intact GRP receptors are required for normal GLP-1 and insulin responses and glucose tolerance after gastric glucose in mice.     

Estimates of plasma, packed cell and total blood volume in tissues of the rainbow trout (Salmo gairdneri)

1. Total blood volume and relative blood volumes in selected tissues were determined in non-anesthetized, confined rainbow trout by using 51Cr-labelled trout erythrocytes as a vascular space marker. 2. Mean total blood volume was estimated to be 4.09 +/- 0.55 ml/100 g, or about 75% of that estimated with the commonly used plasma space marker Evans blue dye. 3. Relative tissue blood volumes were greatest in highly perfused tissues such as kidney, gills, brain and liver and least in mosaic muscle. 4. Estimates of tissue vascular spaces, made using radiolabelled erythrocytes, were only 25-50% of those based on plasma space markers. 5. The consistently smaller vascular volumes obtained with labelled erythrocytes could be explained by assuming that commonly used plasma space markers diffuse from the vascular compartment.     

Postcranial Functional Morphology of <Emphasis Type="Italic">Hyracotherium</Emphasis> (Equidae,Perissodactyla) and Locomotion in the Earliest Horses

A nearly complete skeleton of Hyracotherium grangeri is described from the early Wasatchian (early Eocene) of the Clarks Fork Basin in northwestern Wyoming. This specimen includes a virtually complete, well-preserved pre-caudal vertebral column allowing the first thorough investigation of the locomotory abilities of these early Eocene horses. The posterior thorax (T) and lumbus (L) are divided into a facultatively dorsostable region (T15-L3) and an obligately dorsostable region (L3-L7). The facultatively dorsostable region is characterized by robust, cranially-oriented neural spines and well-developed attachment sites for epaxial musculature, whereas the obligately dorsostable region is characterized by embracing zygapophyses and less developed spines and attachment sites. Limb morphology exhibits a mixture of primitive characters and derived features associated with cursoriality. As described by previous authors, limb mobility is restricted at the elbow and ankle due to interlocking humero-radial and tibio-astragalar articulations, respectively. In contrast, the presence of a rounded femoral head and well-developed pelvic and femoral attachment sites for hindlimb adductor muscles suggests a highly mobile hip joint. Limited inversion of the manus and pes may have been possible via differential movement between the proximal and distal carpal elements and at the transverse tarsal joint, respectively. The obligately dorsostable region of the vertebral column likely resisted variably-oriented torque applied by hip musculature, thereby preventing dislocation of the pelvis and lumbus. The facultatively dorsostable region would have facilitated dynamic positioning of the center of mass during rapid acceleration. Brief comparisons with Orohippus and Mesohippus postcrania are used to discuss the selective pressures imposed by changes in body mass and habitat on the postcranial evolution of Paleogene horses.     

Physiological disturbance and recovery dynamics of bonefish (Albula vulpes), a tropical marine fish, in response to variable exercise and exposure to air

Current understanding of the stress response in fishes has largely come from studies of freshwater-adapted salmonids, with proportionately few comparative studies having examined marine fishes. The current study sought to quantify the magnitude of physiological disturbances, recovery dynamics, and post-exercise behaviour in bonefish (Albula vulpes; a tropical marine fish) exposed to several different exercise and air exposure regimens. Results showed that metabolic disturbances (lactate production, hyperglycemia) increased following exercise and exposure to air, and that the magnitude of metabolic disturbance was proportional to the duration of the stressful event. Fish required between 2-4 h to return to resting values. Exercise and exposure to air also resulted in significant increases in plasma Ca2+, Cl- and Na+, but the magnitude of these ionic changes did not vary with exercise or exposure to air duration and required over 4-h to return to baseline levels. Mortality following exercise was observed only for fish that had been exposed to air for 3 min and not in fish that had been exposed to air for 1 min. Together, results from this study provide a physiological basis for management strategies that can improve the post-release survival of bonefish that have been caught during a catch-and-release angling event.     

Dentition ofSivaladapis nagrii (Adapidae) from the late Miocene of India

Two genera and three species of adapid primates are known from the middle and late Miocene of India and Pakistan. Most fossil specimens are fragmentary, but the best-known species, Sivaladapis nagrii,is now represented by enough specimens to permit composite reconstruction of much of the dentition. The incisors of Sivaladapishave spatulate crowns, and the canines are large, projecting teeth. Premolars and molars exhibit complex occlusion involving simultaneous approximation of pointed leading cusps on upper and lower molars, with linear trailing lophs. The premolar eruption sequence in Sivaladapisappears to be P ₂-P₄-P₃, as in most extant prosimians. Symphyseal fusion of the mandibular rami occurred early in ontogeny, before the eruption of any of the anterior permanent teeth. We interpret Sivaladapisto have been a specialized arboreal folivore that became extinct near the end of the Miocene, when the distribution of forests was increasingly restricted and colobine monkeys first invaded South Asia.     

Cranial morphology and adaptations in Eocene Adapidae. I. Sexual dimorphism in Adapis magnus and Adapis parisiensis

Adapis is one of the best known lemuriform fossil primates. Quantitative analysis of all well-preserved crania of Adapis magnus (n = 8) and Adapis parisiensis (n = 12) together with maxillary and mandibular dentitions preserving canines corroborates Stehlin's hypothesis that Adapis was sexually dimorphic. Males are from 13% to 16% larger than females in cranial length, corresponding to a weight dimorphism estimated at 44% to 56%, and have relatively broader skulls with more prominent sagittal and nuchal crests. Canine dimorphism ranges from 13% to 19%, which is equal to or only slightly greater than that expected as a result of body size dimorphism (i.e., relative canine dimorphism is slight or nonexistent). By comparison with living primates, the observed body size dimorphism in Adapis implies a polygynous breeding system. Cebus apella is a diurnal arboreal living primate with moderate body size dimorphism and slight relative canine dimorphism and one can speculate that Adapis lived in polygynous multimale troops of moderate size like those of C. appella. Adapis extends the geological history of sexual dimorphism and polygyny in primates back to the Eocene. Extant lemuriform primates are generally not dimorphic or polygynous and they clearly do not adequately represent the range of social adaptations present in Eocene primates. The evolutionary lineage from Adapis magnus to Adapis parisiensis exhibits reduction in body size and in relative canine size, and phyletic dwarfing in Adapis is possibly an adaptive response to increasing climatic seasonality and environmental instability in the late Eocene and early Oligocene.