Role of habitat and landscape in structuring small mammal assemblages in hedgerow networks of contrasted farming landscapes in Brittany,France

In this study, we investigated the environmental factors driving small mammal (rodents and shrews) assemblages in permanent habitat patches in response to a gradient of agricultural intensification. Small mammals were sampled using a trapping standard method in the hedgerow networks of three contrasted landscapes differing by their level of land-use intensity and hedgerow network density (BOC1: slightly intensified; BOC2: moderately intensified and POL: highly intensified). We hypothesized that habitat and landscape characteristics have to be considered to understand the structure of local community. In that way, we carried out a multi-scale study using environmental variables ranging from local habitat (structure and composition of the hedgerows) to hedgerows neighbourhoods in a radius of 300 m (land cover and connectivity around hedges) and to landscape units (three sites). During 1 year, 24 hedgerows were sampled seven times, representing a total of 1,379 captures (86% of rodents and 14% of shrews) and eight species, dominated by the wood mouse (Apodemus sylvaticus) and the bank vole (Clethrionomys glareolus). Inter-site variability was significant and accounted for 18% of total variation in small mammal species abundances. But intra-site variability was also highlighted: species abundance profiles may differ greatly among hedgerows within a site. The more explanatory variables were identified at the different scales of the study: the landscape unit POL was shown to be an important factor in structuring the community, but the predominant factors explaining differences of abundances among hedgerows were about local habitat. In fact, the width of hedges and the tree species richness appeared to be significant and explaining the greatest part of the total variation of the small mammal community composition.     

Doxorubicin and BAY 12-9566 for the treatment of osteosarcoma in dogs: a randomized, double-blind, placebo-controlled study

BACKGROUND: This study was designed to assess the efficacy of a matrix metalloproteinase inhibitor in prolonging posttreatment survival for dogs with appendicular osteosarcoma after treatment with amputation and doxorubicin chemotherapy. HYPOTHESIS: Survival will be prolonged in dogs receiving BAY 12-9566. ANIMALS: The study included 303 dogs with appendicular osteosarcoma. METHODS: Dogs were treated with doxorubicin (30 mg/m2) every 2 weeks for 5 treatments starting 2 weeks after amputation. Dogs were randomly allocated to receive a novel nonpeptidic biphenyl inhibitor of matrix metalloproteinases (MMPs, BAY 12-9566; 4-[4-4-(chlorophenyl)phenyl]-4-oxo-2S-(phenylthiomethyl) butanoic acid) or placebo after doxorubicin chemotherapy. RESULTS: Median survival for all 303 dogs was 8 months; and 1-year, 2-year, and 3-year survival rates were 35%, 17%, and 9%, respectively. Treatment with BAY 12-9566 did not influence survival. Multivariate analysis revealed that increasing age (P = .004), increasing weight (P = .006), high serum alkaline phosphatase (ALP) (P = .012) and high bone ALP (P < .001) were independently associated with shorter median survival times. Additional analyses on available data indicated that as the number of mitotic figures in the biopsy increased (P = .013), and as plasma active MMP-2 concentrations increased (P = .027), the risk of dying increased. CONCLUSIONS AND CLINICAL IMPORTANCE: Doxorubicin is an effective adjuvant to amputation in prolonging survival for dogs with appendicular osteosarcoma.     

Vertical Flux of Biogenic Carbon in the Ocean: Is There Food Web Control?

Models of biogenic carbon (BC) flux assume that short herbivorous food chains lead to high export, whereas complex microbial or omnivorous food webs lead to recycling and low export, and that export of BC from the euphotic zone equals new production (NP). In the Gulf of St. Lawrence, particulate organic carbon fluxes were similar during the spring phytoplankton bloom, when herbivory dominated, and during nonbloom conditions, when microbial and omnivorous food webs dominated. In contrast, NP was 1.2 to 161 times greater during the bloom than after it. Thus, neither food web structure nor NP can predict the magnitude or patterns of BC export, particularly on time scales over which the ocean is in nonequilibrium conditions.     

The Induction of a Secondary Corpus Luteum on Day 12 Post‐Ovulation can Delay the Time of Luteolysis in High‐Producing Holstein Cows

Luteolysis before the time of maternal recognition of pregnancy is one cause of low fertility in high‐producing dairy cows. The objective of this study was to assess whether induction of a secondary corpus luteum (CL) late in the luteal phase would delay the time of luteolysis. Twenty high‐producing Holstein cows were synchronized to ovulation (Day 0) with the Ovsynch protocol and received hCG (1500 IU im) on Day 12. Corpora lutea formation (as evaluated by ultrasonography) and plasma P4 concentrations were monitored from Days 4 to 36. hCG treatment induced the formation of one secondary CL (CL2) in 11 of 20 cows (55%) from the dominant follicle (mean diameter: 14.2 ± 0.9 mm) of two‐wave (3/11) and three‐wave (8/11) cycles. The maximal diameter of the CL2 (23.3 ± 1.9 mm) was reached approximately 6 days after hCG treatment and was correlated with its structural lifespan (p < 0.01). Cows that formed a CL2 after hCG had higher mean plasma P4 concentrations on Day 14 (+4.5 ng/ml) and Day 18 (+3.0 ng/ml) compared with cows without CL2 (p < 0.05). The structural regression of CL2 begun approximately 8 days after that of the CL1, and the median time at which the first drop in circulating P4 levels occurred was later in cows that formed a CL2 than in those that did not (Day 26 vs Day 18; p < 0.01). Thus, the induction of a CL2 by hCG on Day 12 might reduce the risk of premature luteolysis in high‐producing dairy cows after insemination.     

Effects of storage and incubation temperature on the viability of eggs, embryos and larvae in two strains of an African catfish, Heterobranchus longifilis (Siluriformes, Clariidae)

Two experiments, dealing with short‐term storage of ova and thermal conditions to optimize gamete and eggs management in hatcheries of the African catfish, Heterobranchus longifilis, were carried out. In the first experiment, ova collected by stripping from two strains of H. longifilis were stored for intervals up to 8 h at two temperature regimes: in a domestic refrigerator (3–5°C) and at ambient room temperature (20.5–22°C). In the second experiment, eggs were incubated from fertilization to hatching at different experimental temperatures (21, 25, 29, 32 and 35°C) to determine the effects of temperature on the kinetics of white egg appearance, hatching times and hatching quality. Gamete storage at warmer temperatures significantly prolonged viability irrespective of the strain used. In fact, the hatching rate for ova stored at 20.5–22 and 3–5°C for 5 h ranged between 75.2–79.3% and 6.5–9.4% respectively. Loss of viability was most noticeable after 6 h storage at ambient room temperature. Post‐storage viability significantly declined after 2 h exposure to the domestic refrigerator temperature. No hatching of normal larvae took place after 8 h post‐storage time. Results from the second experiment showed that time to maximum whitening of eggs was both strain‐ and temperature‐dependent. The time to maximum mortality of eggs was shorter in the Layo strain (LS) than in the Noun strain (NS), regardless of incubation temperature. The appearance of white eggs was shorter with increasing incubation temperatures. Hatching times decreased with increasing temperature, regardless of strain. Hatching took place from 21 to 27 h and 19 to 24 h after fertilization at temperature of 29°C, respectively, for NS and LS. The length of the hatching period was remarkably shorter for LS than NS at any tested incubation temperature, except 35°C. No hatching took place at 21°C. The highest proportion of normal larvae occurred at 25 and 29°C, respectively, for NS and LS. Hatching rate was highest at 25 and 29°C, respectively, for NS and LS. There was a significantly higher proportion of deformed larvae at 35°C regardless of the strain.     

Acquired myasthenia gravis associated with oral sarcoma in a dog

Acquired myasthenia gravis is a common neuromuscular disorder resulting from autoantibody directed against the post-synaptic acetylcholine nicotinic receptors in skeletal muscle. Myasthenia gravis has been reported previously as a paraneoplastic syndrome. This case report presents myasthenia gravis secondary to an oral sarcoma in a juvenile Mastiffdog.     

Myofibrillar proteins in white muscle of the developing African catfish Heterobranchus longifilis (Siluriforms, Clariidae)

Developmental changes in myofibrillar protein composition were investigated in the myotomal muscle of the African catfish, Heterobranchus longifilis (Clariidae), by several electrophoretic techniques. The main muscle fibres of larvae and the fast-white muscle fibres of juvenile and adult fish were found to express distinct myosin heavy chain and myosin light chain 2 (LC2) isoforms. Three myosin LC2 chains were successively detected, differing by their isoelectric points. In contrast, the alkali light chains remained qualitatively and quantitatively unchanged during fish growth. Actin, -tropomyosin, and troponin-C (TN-C) were also similar in larval, juvenile, and adult white muscle, but an additional larval tropomyosin isoform was found in the first developmental stages. Two isoforms of troponin-T (TN-T) and troponin-I (TN-I) were synthesised in the course of fish growth. Transition from the larval to the adult isoform was much faster for TN-T than for TN-I. Slow-red muscle myofibrils from adult H. longifilis showed no common component (except actin) with larval, juvenile, or adult fast-white muscle myofibrils. Red myofibrils displayed a single TN-T and a single TN-I isoform, but two isoforms of TN-C. The myofibrillar protein isoforms synthesised at any given developmental stage almost certainly reflect changes in the functional requirements of swimming muscles in the course of fish development.