Age and pasture effects on vernal transition in mares

The objectives of the present study were to determine if follicular activity was less in old than in young mares during the spring transition and if green pasture would hasten onset of the ovulatory season. Experiments were conducted over 2 sequential years using young mares (3 to 7 yr) and old mares (> or =14 yr). In Experiment 1, growth of the largest and second-largest follicles were compared for young mares (5 to 7 yr) and old mares (> or =14 yr) for 21 d prior to the first ovulation of the year. More follicular activity was noted in young than in old mares. Main effect of age was significant for diameter of the largest follicle, and interaction of day-by-age was significant for diameter of the second-largest follicle. Prior to the beginning of the breeding season, the mares were randomly divided into dry-lot and pasture groups. The interval from May 2 to ovulation was shorter (P < 0.005) for mares put on pasture on May 2 than for mares kept in dry lot (means +/- SEM, 14.5 +/- 2.7 and 21.3 +/- 3.2 d, respectively). In Experiment 2, follicular activity was compared among 3 age groups (3 to 7, 17 to 19, and > or =20 yr). The total number of follicles > or =10 mm was higher (P < 0.05) for young mares and lower (P < 0.05) for old mares than for mares of an intermediate age. Main effect of age and interaction of day-by-age were significant for diameter of largest and second-largest follicles, being smaller for mares > or =20 yr than for younger mares. The interval from development of a follicle > or =30 mm to ovulation was shorter (P < 0.05) for mares placed on pasture when a > or =30 mm follicle developed than the interval for mares kept in dry lot (5.7 +/- 0.7 and 8.2 +/- 0.9 d, respectively). In summary, less follicular activity occurred in old than in young mares during the transitional period, and mares pastured on green grass ovulated sooner in the spring than mares housed on dry lot and fed hay.     

Determination of argininosuccinate lyase and arginase activities with an amino acid analyzer

The measurement of argininosuccinate lyase (ASase) and arginase, both in liver and erythrocytes, was developed by using a commercial amino acid analyzer. The method is based upon the use of two different substrates, argininosuccinate and arginine for ASase and arginase, respectively, and the measurement of only one final metabolite: ornithine. The use of ornithine as a marker of biological activity of ASase is related to the fact that in the urea cycle, the specific activity of arginase is much higher than that of ASase; thus, during in vitro determinations, arginine, which is the product of ASase, is rapidly converted to ornithine. The sensitivity of the methods is very high since we were able to detect both activities using very diluted rat liver homogenates (0.10 mg protein/ml) or few microliters of human blood. In rat liver the Vmax for ASase and arginase were respectively 0.54 and 140 mumol/h/mg protein; the apparent Km values 1.25 and 13.5 mM. In human erythrocytes the Vmax for the same enzymes were 7.2 and 170 nmol/h/mg Hb and the apparent Km values were 0.66 and 9.5 mM. In 10 healthy volunteers the specific activity of ASase and arginase determined in blood were respectively 8.60 +/- 0.46 and 124.1 +/- 14.5 nmol/h/mg Hb. The results obtained from 2 patients suffering from argininosuccinic aciduria were also reported. In these latter cases while ASase was not detectable in blood, arginase activity was at the lowest end of the confidence limits determined in healthy volunteers.     

Plant communities and phytogeographical position of a large depression in the Great Chaco,Argentina

A survey is presented of the vegetation of the central region of the Santafesinian Chaco (Argentina), a scarcely populated flat area of 20 000 km², with seasonal flooding. Soils have a strong halo-hydromorphic character and vegetation is basically halophilous. Trees are scarce and most communities are savannas, grasslands or swampy vegetation. Twenty-three communities are described, some of them with several variants. The most widespread communities areSpartina argentinensis grasslands,Elyonurus muticus savannas and a complex of hygrophilous communities. The most important communities are distributed in relation to a topographical gradient, and their structure is shaped by recurrent flooding and fire disturbance. Most of the area is virgin land with very little human interference. The phytogeographical position of the area is discussed. Nomenclature: Burkart, A. 1969, 1974, 1979. Flora ilustrada de Entre Rios, INTA, Buenos Aires, and Cabrera, 1963, 1965a, b, 1967, 1968, 1970. Flora de la Provincia de Buenos Aires, INTA, Buenos Aires.     

Left handed �� helix models for mammalian prion fibrils

We propose models for in vitro grown mammalian prion protein fibrils based upon left handed beta helices formed both from the N-terminal and C-terminal regions of the proteinase resistant infectious prion core. The C-terminal threading onto a β-helical structure is almost uniquely determined by fixing the cysteine disulfide bond on a helix corner. In comparison to known left handed helical peptides, the resulting model structures have similar stability attributes including relatively low root mean square deviations in all atom molecular dynamics, substantial side-chain-to-side-chain hydrogen bonding, good volume packing fraction, and low hydrophilic/hydrophobic frustration. For the N-terminus, we propose a new threading of slightly more than two turns, which improves upon the above characteristics relative to existing three turn β-helical models. The N-terminal and C-terminal beta helices can be assembled into eight candidate models for the fibril repeat units, held together by large hinge (order 30 residues) domain swapping, with three amenable to fibril promoting domain swapping via a small (five residue) hinge on the N-terminal side. Small concentrations of the metastable C-terminal β helix in vivo might play a significant role in templating the infectious conformation and in enhancing conversion kinetics for inherited forms of the disease and explain resistance (for canines) involving hypothesized coupling to the methionine 129 sulfur known to play a role in human disease.Key words: prion, amyloid fibril, domain swap, beta helix, computational biology     

Correspondences between low-energy modes in enzymes: dynamics-based alignment of enzymatic functional families

Proteins that show similarity in their equilibrium dynamics can be aligned by identifying regions that undergo similar concerted movements. These movements are computed from protein native structures using coarse-grained elastic network models. We show the existence of common large-scale movements in enzymes selected from the main functional and structural classes. Alignment via dynamics does not require prior detection of sequence or structural correspondence. Indeed, a third of the statistically significant dynamics-based alignments involve enzymes that lack substantial global or local structural similarities. The analysis of specific residue-residue correspondences of these structurally dissimilar enzymes in some cases suggests a functional relationship of the detected common dynamic features. Including dynamics-based criteria in protein alignment thus provides a promising avenue for relating and grouping enzymes in terms of dynamic aspects that often, though not always, assist or accompany biological function.     

transAlign: using amino acids to facilitate the multiple alignment of protein-coding DNA sequences

Background  

Alignments of homologous DNA sequences are crucial for comparative genomics and phylogenetic analysis. However, multiple alignment represents a computationally difficult problem. For protein-coding DNA sequences, it is more advantageous in terms of both speed and accuracy to align the amino-acid sequences specified by the DNA sequences rather than the DNA sequences themselves. Many implementations making use of this concept of "translated alignments" are incomplete in the sense that they require the user to manually translate the DNA sequences and to perform the amino-acid alignment. As such, they are not well suited to large-scale automated alignments of large and/or numerous DNA data sets.     

Platelet activation in patients with colorectal cancer

Aspirin may reduce the risk of colorectal neoplasia at doses similar to those recommended for the prevention of cardiovascular disease. Thus, we aimed to address whether enhanced platelet activation, as assessed by the measurement of the urinary excretion of 11-dehydro-TXB(2) (a major enzymatic metabolite of TXB(2)), occurs in patients with colorectal cancer. In 10 patients with colorectal cancer, the urinary excretion of 11-dehydro-TXB(2) was significantly higher than in 10 controls, matched for sex, age and cardiovascular risk factors [1001(205-5571) versus 409(113-984) pg/mg creatinine, respectively, median (range), P<0.05]. The administration of aspirin 50 mg daily for 5 consecutive days to colorectal cancer patients caused a cumulative inhibition of platelet cyclooxygenase (COX)-1 activity either ex vivo, as assessed by the measurement of serum TXB(2) levels, or in vivo, as assessed by urinary 11-dehydro-TXB(2) excretion. In conclusion, enhanced platelet activation occurs in colorectal cancer patients. Permanent inactivation of platelet COX-1 by low-dose aspirin might restore anti-tumor reactivity.     

Gene therapy by adenovirus-mediated vascular endothelial growth factor and angiopoietin-1 promotes perfusion of muscle flaps

An experimental study was conducted to investigate the potential use of intravascular gene therapy with adenovirus-mediated (Ad) vascular endothelial growth factor (VEGF) or angiopoietin-1 (Ang-1) for the enhancement of muscle flap perfusion and to evaluate the effect of therapy on microcirculatory hemodynamics and microvascular permeability in vivo by using a cremaster muscle flap model in the rat. The cremaster tube flap was left intact after isolation of the pudo-epigastric pedicle. A total of 90 male Sprague-Dawley rats were divided into five groups of 18 each, according to the type of intraarterial treatment. Control flaps received phosphate-buffered saline. Group 2 (the control gene encoding green fluorescent protein, Ad-GFP) served as the adenovirus control. In Groups 3, 4, and 5, flaps were pretreated with Ad-VEGF, Ad-Ang-1, and Ad-Ang-1 + Ad-VEGF, respectively. Flaps were preserved in a subcutaneous pocket in the hindlimb for evaluation of functional capillary density and microvascular permeability indices at 3, 7, and 14 days by intravital microscopy system. At day 7 and 14, Ad-VEGF, Ad-Ang-1, and combined treatment groups showed significantly higher numbers of capillary densities when compared with control and Ad-GFP groups (p < 0.05). At day 14, Ad-VEGF was the superior treatment group compared with Ad-Ang-1 and Ad-VEGF + Ad-Ang-1 (p < 0.05). Overall, there was a linear increase in the number of functional capillaries in all treatment groups (p < 0.05). At day 3 after Ad-Ang-1 therapy, a significantly lower permeability index was found when compared with Ad-VEGF + Ad-Ang-1 and Ad-VEGF alone treatment (p < 0.05). At day 7, the Ad-VEGF group had the highest score of permeability index compared with control, combined, and Ad-Ang-1 groups (p < 0.05). Histologic evaluation of muscle flaps demonstrated mild focal inflammation. There was evidence of mild vasculitis in all flaps except control muscles. Intravascular angiogenic therapy with Ad-VEGF or Ad-Ang-1 was technically feasible, as demonstrated by expression of the control gene, GFP, along the vascular tree. All treatment groups increased perfusion of the muscle flap over a period of 14 days, indicating a long-lasting effect of gene therapy. Ang-1 alone or in combination with VEGF was as effective as VEGF alone in augmenting muscle perfusion with more stable vessels 1 week after gene therapy.     

Removal of deslorelin (Ovuplant) implant 48 h after administration results in normal interovulatory intervals in mares

Deslorelin implants, approved for use in inducing ovulation in mares, have been associated with prolonged interovulatory intervals in some mares. Administration of prostaglandins in the diestrous period, following a deslorelin-induced ovulation, has been reported to increase the incidence of delayed ovulations. The goals of the present study were: (1) to determine the percentage of mares given deslorelin that experience delayed ovulations with or without subsequent prostaglandin treatment, and (2) to determine if removal of the implant 48 h after administration would effect the interval to subsequent ovulation. We considered interovulatory intervals to be prolonged if they were greater than the mean +/- 2 standard deviation (S.D.) of the control group in study 1 and the hCG group in study 2. In study 1, we retrospectively reviewed reproduction records for 278 mares. We either allowed the mare to ovulate spontaneously or induced ovulation using deslorelin acetate implants or hCG. We administered prostaglandin intramuscularly, 5-9 days after ovulation in selected mares in each group. A higher percentage of mares which were induced to ovulate with deslorelin and given prostaglandins had a prolonged interovulatory interval (23.5%; n = 16), as compared to deslorelin-treated mares that did not receive prostaglandins (11.1%; n = 5). In study 2, we induced ovulation in mares with hCG (n = 47), a subcutaneous deslorelin implant via an implanting device provided by the manufacturer (n = 28), or a deslorelin implant via an incision in the neck (n = 43) and we removed the implant 48 h after administration. We administered prostaglandin to all mares 5-9 days after ovulation. In study 2, mares from which the implant was removed had a normal ovulation rate and none had a prolonged interval to ovulation. Administration of prostaglandin after deslorelin treatment was associated with a longer interval from luteolysis to ovulation than that found in mares not treated with deslorelin. Prostaglandin administration during diestrus may have exacerbated the increased interval to ovulation in deslorelin-treated mares. We hypothesize that prolonged secretion of deslorelin from the implant was responsible for the extended interovulatory intervals.