Effects of CD28 blockade on subsets of naïve T cells in cats

OBJECTIVE: To determine whether human CTLA4-Ig ([hu]CTLA4-Ig) inhibits costimulation-dependent lymphocyte proliferation in vitro, compare the effects of (hu)CTLA4-Ig with cyclosporine and steroids on CD4+ and CD8+ T-cell lymphocyte proliferation, and determine whether memory T-cell function remains intact in the presence of (hu)CTLA4-Ig. ANIMALS: 29 cats. PROCEDURE: Peripheral blood mononuclear cells (PBMCs) were stimulated with concanavalin A (costimulation-dependent mitogen) or phorbol 12-myristate 13-acetate and ionomycin (costimulation independent mitogens) alone or in the presence of (hu)CTLA4-Ig, cyclosporine, or dexamethasone; effects of these treatments on lymphocyte proliferation were assessed by incorporation of thymidine labeled with tritium or flow cytometry. Antigen-specific proliferation was determined by stimulating PBMCs from 2 healthy cats seropositive for Toxoplasma gondii with soluble Toxoplasma antigen alone or in the presence of (hu)CTLA4-Ig or cyclosporine. RESULTS: (hu)CTLA4-Ig inhibited costimulation-dependent lymphocyte proliferation in vitro but had no effect on costimulation-independent lymphocyte proliferation. Compared with mitogen alone, (hu)CTLA4-Ig caused a significant decrease in responder frequency and proliferative capacity of CD4+ T cells; however, the effect on CD8+ T cells was not significant. Cyclosporine alone or with dexamethasone had a significantly greater suppressive effect on responder frequency and proliferative capacity of CD4+ and CD8+ T cells, compared with (hu)CTLA4-Ig. Compared with cyclosporine, (hu)CTLA4-Ig appeared to have a sparing effect on antigen-specific proliferation of memory CD4+ and CD8+ T cells. CONCLUSIONS AND CLINICAL RELEVANCE: (hu)CTLA4-Ig selectively inhibited costimulation-dependent proliferation of lymphocytes in vitro and had a sparing effect on antigen-specific proliferation of memory cells. The specificity of its mechanism of action suggests that (hu)CTLA4-Ig may prevent allograft rejection but leave memory responses to previously encountered antigens intact.     

Influence of D-lactate on metabolic acidosis and on prognosis in neonatal calves with diarrhoea

Three hundred bucket-fed diarrhoeic calves up to the age of 21 days were used to investigate the degree in which D-lactic acid contributes to metabolic acidosis in bucket-fed calves with naturally acquired neonatal diarrhoea. Fifty-five percent of all diarrhoeic calves had serum D-lactate concentrations higher than 3 mmol/l. Mean (+/-SD) D-lactate values were 5.7 mmol/l (+/-5.3, median: 4.1 mmol/l). D-lactate values were distributed over the entire range of detected values from 0 to 17.8 mmol/l in calves with base excess of -10 to -25 mmol/l. Serum D-lactate concentration was higher in patients with ruminal acidosis (6.6 +/- 5.2 mmol/l; median: 5.9 mmol/l) than in those with physiological rumen pH (5.3 +/- 5.4 mmol/l; median: 3.7 mmol/l). There was no evidence of a correlation (r = 0.051) between the serum levels of D-lactate and creatinine (as an indicator of dehydration). D-lactate was correlated significantly with both base excess (r = -0.685) and anion gap (r = 0.647). The proportion of cured patients was not significantly different between the groups with elevated (>3 mmol/l) and normal serum D-lactate concentrations. This study shows that hyper-D-lactataemia occurs frequently in diarrhoeic calves, has no impact on prognosis but may contribute to the clinical picture associated with metabolic acidosis in these animals.     

D-Lactic acidosis in calves as a consequence of experimentally induced ruminal acidosis

In order to test the hypothesis that ruminal drinking in calves can lead to D-lactic metabolic acidosis, ruminal acidosis was induced in nine calves by intraruminal application of untreated whole milk via a stomach tube. The amount of the daily force-fed liquid was 3 x 1 l. The experimental design called for an end of intraruminal applications if two or more of the following signs were observed: severe depression, estimated degree of dehydration >10%, absence of sucking reflex, lack of appetite for two consecutive feedings, severe metabolic acidosis with calculated Actual Base Excess (ABE) <-15 mmol/l. The procedure was scheduled to be discontinued on the 17th day of experiment. The onset of ruminal acidification occurred rapidly, and mean pH value fell from 6.70 (+/-0.48) to 4.90 (+/-0.38) after the first application. The following days the pH values varied between 4 and 5. Rumen acidity was characterized biochemically by a significant increase in both isomers of lactic acid. The effects of the intraruminal administration on the calves were detrimental; eight of nine calves showed an acute disease process. According to the pre-established clinical standard, seven of nine calves were removed from the intraruminal feeding schedule. All but one of the calves developed severe systemic acidosis. The increase in anion gap demonstrated the net acid load. In all the calves D-lactate levels were found to show a significant and rapid increase. On the contrary, L-lactate never deviated from physiological levels. These observations confirm that, in young calves as in adult cattle, ruminal acidosis may lead to a clinically manifested D-lactic metabolic acidosis.     

Survey of the large-animal diplomates of the American College of Veterinary Internal Medicine regarding knowledge and clinical use of polymerase chain reaction: implications for veterinary education

A questionnaire was developed to document the knowledge base of large-animal diplomates of the American College of Veterinary Internal Medicine (ACVIM) regarding polymerase chain reaction (PCR) technology and to identify the common use of this technology in equine practice. Ninety-three of the 278 mailed questionnaires were returned, for an overall response rate of 33.4%. Ninety respondents (99%) reported being familiar with the general principles of nucleic acid probe technology; however, only 52 (57%) knew the difference between conventional (traditional) and real-time (second-generation) PCR. The majority of the respondents (88%) emphasized the need for continuing education on molecular diagnostics. Eighty-four (92%) of the respondents regularly use PCR (conventional and/or real-time) for the detection of equine pathogens, and 80 (88%) commonly submit their samples to university/state veterinary laboratories. Blood, nasal swabs, and feces are the three equine specimens most commonly submitted for PCR analysis of Streptococcus equi, Lawsonia intracellularis, Neorickettsia risticii, equine herpesvirus 1/4, Rhodococcus equi, Sarcocystis neurona, and equine influenza virus. Diplomates reported costs associated with molecular diagnostics and unreliability of PCR as the most common limitations of PCR. Didactic training in veterinary curricula and during continuing-education opportunities continues to be necessary to produce veterinarians who have an understanding of the clinical applications of molecular diagnostics.     

Impacts of biodiversity loss on ocean ecosystem services

Human-dominated marine ecosystems are experiencing accelerating loss of populations and species, with largely unknown consequences. We analyzed local experiments, long-term regional time series, and global fisheries data to test how biodiversity loss affects marine ecosystem services across temporal and spatial scales. Overall, rates of resource collapse increased and recovery potential, stability, and water quality decreased exponentially with declining diversity. Restoration of biodiversity, in contrast, increased productivity fourfold and decreased variability by 21%, on average. We conclude that marine biodiversity loss is increasingly impairing the ocean's capacity to provide food, maintain water quality, and recover from perturbations. Yet available data suggest that at this point, these trends are still reversible.     

Phylogeny, diversity, and species delimitation in some species of the Xiphinema americanum-group complex (Nematoda: Longidoridae), as inferred from nuclear and mitochondrial DNA sequences and morphology

During nematode surveys in southern Spain and Italy 14 populations of Xiphinema species tentatively identified as Xiphinema americanum-group were detected. Morphological and morphometrical studies identified three new species and six known Xiphinema americanum-group species, viz.: Xiphinema parabrevicolle n. sp., Xiphinema parapachydermum n. sp., Xiphinema paratenuicutis n. sp., Xiphinema duriense, Xiphinema incertum, Xiphinema opisthohysterum, Xiphinema pachtaicum, Xiphinema rivesi, and Xiphinema santos. The Xiphinema americanum-group is the most difficult Xiphinema species group for diagnosis since the morphology is very conservative and morphometric characters often overlap. This group includes vectors of several important plant pathogenic viruses that cause significant damage to a wide range of agricultural crops. Molecular characterisation of these species using D2-D3 expansion regions of 28S rRNA, 18S rRNA, ITS1-rRNA and the protein-coding mitochondrial gene, cytochrome oxidase c subunit 1 was carried out and maximum likelihood and Bayesian inference analysis were used to reconstruct phylogenetic relationships among these species and with other Xiphinema americanum-group species.