Muscle architecture and out‐force potential of the thoracic limb in the eastern mole (Scalopus aquaticus)

Moles have modified thoracic limbs with hypertrophied pectoral girdle muscles that allow them to apply remarkably high lateral out‐forces during the power stroke when burrowing. To further understand the high force capabilities of mole forelimbs, architectural properties of the thoracic limb muscles were quantified in the Eastern mole (Scalopus aquaticus). Architectural properties measured included muscle mass, moment arm, belly length, fascicle length, and pennation angle, and these were used to provide estimates of maximum isometric force, joint torque, and power. Measurements of muscle moment arms and limb lever lengths were additionally used to analyze the out‐force contributions of the major pectoral girdle muscles. Most muscles have relatively long fascicles and little‐to‐no pennation. The humeral abductor/rotators as a functional group are massive and are capable of relatively high force, power, and joint torque. Of this group, the bipennate m. teres major is the most massive and has the capacity to produce the highest force and joint torque to abduct and axially rotate the humerus. In general, the distal limb muscles are relatively small, but have the capacity for high force and mechanical work by fascicle shortening. The muscle architectural properties of the elbow extensors (e.g., m. triceps brachii) and carpal flexors (e.g., m. palmaris longus) are consistent with the function of these muscles to augment lateral out‐force application. The humeral abductor/rotators m. latissimus dorsi, m. teres major, m. pectoralis, and m. subscapularis are calculated to contribute 13.9 N to out‐force during the power stroke, and this force is applied in a ‘frontal’ plane causing abduction of the humerus about the sternoclavicular joint. Moles have several specializations of their digging apparatus that greatly enhance the application of out‐force, and these morphological features suggest convergence on limb form and burrowing function between New and Old World moles. J. Morphol. 274:1277–1287, 2013. © 2013 Wiley Periodicals, Inc.     

The combined effect of environmental factors and neighbouring populations on the distribution and abundance of Arvicola terrestris. An approach using rule-based models

We investigated how the interplay between environmental factors and presence of neighbouring populations determines the distribution and abundance of a small, endangered rodent, the water vole ( Arvicola terrestris ). We studied thriving and non-fragmented populations of water voles in the absence of their main predator, the introduced American mink ( Mustela vison ). A low degree of population fragmentation, such as the one characterizing the studied populations, was probably typical of water voles before their decline started. We found that under these conditions water voles' distribution is mainly determined by three environmental factors: presence of freshwater, adequate food, and cover. Variance in other factors is well tolerated by water voles. We obtained this result by the use of rule-based models in two separate areas. The two models correctly classified 81% and 83% of the observed cases, respectively. When optimised on one area and cross-validated on the other area the performance of the models was still high (73% and 79%) indicating that the models were robust and generalizable. We also found that the density of animals was lower in sub-optimal than in optimal habitat. We then tested the hypothesis that the number of neighbouring colonies determines the probability of finding voles in a given section. We found that the presence of nearby colonies was an important factor in determining the presence of water voles in sub-optimal habitat, while isolated patches of suitable habitat were less likely to host water voles. These observations suggest the possible presence of a source-sink dynamic, where an optimal habitat acts as a source for populating sub-optimal habitats that may be considered a sink habitat. These findings are discussed in the context of water vole conservation.     

Range expansion and potential dispersal mechanisms of the exotic cladoceran Daphnia lumholtzi

. Recently the exotic cladoceran Daphnia lumholtzi has invadedfreshwater systems throughout the southern and midwestern UnitedStates. We conducted regional surveys of eastern Kansas reservoirsto document the range expansion of D.lumholtzi. Daphnia lumholtziwas found in five of 35 reservoirs sampled in 1994, and 11 ofthe 35 reservoirs when re-sampled in 1997. In addition, we sampled40 small ponds inaccessible to recreational boats, within thewatershed of an invaded reservoir. We did not find D.lumholtziin any of these ponds, suggesting that non-human dispersal mechanismsplay an insignificant role in the range expansion of D.lumholtzithroughout the United States. Further experimentation, however,is needed to determine if the absence of D.lumholtzi from thesesmall ponds is due to insufficient dispersal mechanisms or theinability of this invader to successfully colonize followingarrival. Daphnia lumholtzi has broad limnological tolerances.However, invaded reservoirs tend to be larger in area, havehigher Secchi disk depths, and lower total phosphorus, totalnitrogen and chlorophyll a levels relative to non-invaded reservoirs.Analyses of pre-invasion zooplankton communities indicate thatD.lumholtzi may be invading reservoirs in which native Daphniaspecies are rare. While the long-term effects of the invasionof D.lumholtzi are unknown, it has the potential to dominatelate summer zooplankton communities in eastern Kansas reservoirs.Therefore, we need to continue to survey and monitor invadedreservoirs to document the range expansion of D.lumholtzi anddetermine the long-term implications of the introduction ofthis invader.     

Inhibition of Nitric Oxide Synthase Blocks N-Methyl-D-Aspartate-, Quisqualate-, Kainate-, Harmaline-, and Pentylenetetrazole-Dependent Increases in Cerebellar Cyclic GMP In Vivo

The synthesis of nitric oxide by brain slices has been demonstrated in several laboratories. In addition, in vitro studies have demonstrated stimulation of nitric oxide synthesis by excitatory amino acid receptor agonists. These data have led to the hypothesis that this readily diffusible "intercellular messenger molecule" acts to generate a cascade effect by activating guanylate cyclase in several cell types and thereby augment levels of the second messenger cyclic GMP (cGMP). Therefore, we evaluated this hypothesis in vivo, by testing the actions of the nitric oxide synthase inhibitor N-mono-methyl-L-arginine (NMMA) on elevations in level of mouse cerebellar cGMP generated by excitatory amino acid receptor agonists. The stimulatory effects of D-serine, quisqualate, and kainate were all found to be antagonized by this enzyme inhibitor. In addition, NMMA antagonized the increases in cerebellar cGMP level elicited by harmaline and pentylenetetrazole, pharmacological agents that augment endogenous excitatory amino acid transmission. Our data are, therefore, the first in vivo demonstration that nitric oxide is an important "messenger molecule" in the cerebellum, mediating the actions of kainate, quisqualate, and N-methyl-D-aspartate receptor agonists on guanylate cyclase. These data are consistent with previous in vitro findings with kainate and N-methyl-D-aspartate.     

An investigation of the role of circulating catecholamines in the control of ventilation during acute moderate hypoxia in rainbow trout (Oncorhynchus mykiss)

Summary Gill ventilation volume ( w), arterial blood oxygen tension (PaO₂) and arterial blood oxygen content (CaO₂) of rainbow trout (Oncorhyncus mykiss) were monitored during normoxia [waterPO₂ (PwO₂) 155 Torr], hypoxia (PwO₂=72±5.8 Torr), or hyperoxia (PwO₂=643±32 Torr). Fish hyperventilated during acute (30 min) hypoxia and hypoventilagted during acute hyperoxia. Plasma catecholamine levels were unchanged after 30 min of hypoxia or hyperoxia. In addition, selective adrenoceptor blockade with either propranolol (-adrenoceptor antagonist) or phentolamine (-adrenoceptor antagonist) did not modify the hyperventilatory response during hypoxia. These results indicate that circulating catecholamines are not involved in the control of ventilation in moderately hypoxic rainbow trout. In the summer, intra-arterial infusion of catecholamine in normoxic trout caused transient (adrenaline) or persistent (noradrenaline) hypoventilation. These observations also do not support a role for catecholamines in the stimulation of ventilation.During hypoxia,PwO₂,PaO₂ andCaO₂ were depressed whereas during hyperoxia, onlyPwO₂ andPaO₂ was elevated significantly. Thus, it is suggested that the hypoventilatory response to hyperoxia is mediated by a direct effect of elevatedPwO₂/PaO₂, whereas the hyperventilatory response to hypoxia is mediated by changes inPwO₂/PaO₂, and/orCaO₂.     

Combined use of in situ hybridisation and immunocytochemistry for the investigation of prolactin gene expression in immature,pubertal, pregnant,lactating and ovariectomised rats

Summary We have investigated the use of in situ hybridisation together with immunocytochemistry for the study of endocrine cell function, using as an example the expression of prolactin messenger RNA (mRNA) in pituitaries of rats under various endocrinological conditions. In situ hybridisation using a ³²P-labelled cRNA probe for rat prolactin was carried out on sections of 4% paraformaldehyde-fixed pituitaries from prepubertal, pubertal, pregnant, lactating and ovariectomised rats and adjacent sections were immunostained for prolactin. Northern gel analysis was performed on total RNA extracts of pregnant, lactating and control pituitaries. While in ovariectomised rat pituitaries both prolactin immunoreactivity and prolactin mRNA were decreased, no differences in prolactin immunostaining were seen between prepubertal, pubertal, pregnant or lactating rats and controls, even when the supra-optimal dilution technique was used. However, using in situ hybridisation, prolactin mRNA signal was increased in prepubertal rats, and with hybridisation and northern gel analysis the signal was reduced in pregnant rats and markedly increased in lactating rats. The combined use of in situ hybridisation and immunocytochemistry provides morphological information concerning endocrine gene expression and protein synthesis in the pituitary gland.     

N α -Dimethylcoprogens Three novel trihydroxamate siderophores from pathogenic fungi

Summary Three novel siderophores have been isolated from a highly pathogenic strain ofAlternaria longipes (ATCC 26293). The compounds are N -dimethylated analogs of coprogen, neocoprogen I and isoneocoprogen I. Structures of the compounds have been determined by¹H- and¹³C-NMR, fast-atom-bombardment (FAB) mass spectroscopy and partial hydrolysis. One of the new compounds, N -dimethylcoprogen, is also produced, as the major siderophore, in another fungus,Fusarium dimerum.     

The fate of ‘biodegradable’ plastics in municipal leaf compost

Summary Blends of starch with polypropylene, starch with polyethylene, polycaprolactone with polyethylene, and a copolymer of -hydroxybutyrate and -hydroxyvalerate (PHB/V) were exposed to degrading leaves in a municipal leaf composting operation. Every month for 6 months, duplicate samples were analyzed for changes in weight and tensile properties, and many of these samples were further analyzed for changes in molecular weight and surface morphology. All results were compared to controls which were incubated for 6 months in moist, sterile leaves at a leaf compost temperature. Very little change was noted for any of the polyolefin blends over the 6-month period. In contrast, PHB/V samples showed massive deterioration with substantial weight loss. Although there was a decrease in molecular weight and a loss of tensile properties in leaf-exposed PHB/V films, the sterile control films also showed similar changes, but without weight loss. Of the microbial isolates from film surfaces, only fungi possessed PHB/V depolymerase activity.