Biological and DNA evidence of two dissimilar populations of the Rhipicephalus sanguineus tick group (Acari: Ixodidae) in South America

In this work, the biology, mitochondrial DNA and fertility of hybrids from two strains of Rhipicephalus sanguineus, from Brazil and Argentina, were compared. Engorged larvae, nymphs and adults from Argentina weighed more and the engorgement period of adult females was significantly longer than those of their Brazilian counterparts, whereas adult female tick yield rate was higher for the Brazilian strain. High intraspecific divergence of mitochondrial DNA was detected between R. sanguineus from Brazil and Argentina. On the other hand, a strong genetic relationship was detected between European and Argentinean R. sanguineus populations while the Brazilian population appeared to be related to the African Rhipicephalus turanicus. Adult hybrid females laid eggs, which were mostly unviable, whereas a mean of more than 1400 larvae hatched per egg mass from pure Brazilian and Argentinean strains. These results showed that differences between these strains are greater than previously assumed and that the biosystematic status of R. sanguineus ticks from South America should be re-evaluated. Wide variations, such as these might account for the reported worldwide differences in biology and vector capacity of this species.     

Effect of early gestational undernutrition on angiogenic factor expression and vascularity in the bovine placentome

The effect of early gestation maternal undernutrition followed by realimentation on placentomal vascular growth and angiogenic factor expression was determined in multiparous beef cows bred to the same bull. Cows gestating only female fetuses (n = 30) were fed in equal numbers to meet the NRC requirements (control) or were fed below the NRC requirements to lose BW (nutrient restricted; NR) from d 30 to 125 of gestation. After slaughter on d 125 of gestation, 10 control and 10 NR cows were necropsied. The remaining NR cows (n = 5) were then fed to achieve a BCS equal to their control group contemporaries (n = 5) by d 220 of gestation. All cows were fed the control diet from d 220 until 250 of gestation, when the remaining control and NR cows were slaughtered and necropsied. At necropsy, placentomes were fixed via perfusion of the caruncular and cotyledonary arteries to determine capillary vascular density. Cotyledonary (fetal placental) and caruncular (maternal placental) tissues also were snap-frozen in liquid nitrogen, and mRNA concentrations of vascular endothelial growth factor and its 2 specific receptors, fms-like tyrosine kinase and kinase insert domain containing receptor, as well as placental growth factor, were determined. There was no effect of diet or day of gestation on the percentage of proliferating caruncular cells. Although diet did not impact cotyledonary cellular proliferation, there was an increase (P < 0.05) in the percentage of proliferating cells on d 250 compared with d 125 of gestation. Nutrient restriction from d 30 to 125 increased (P < or = 0.10) placental mRNA concentrations of placental growth factor and fms-like tyrosine kinase; however, there was no alteration in vascularity. By d 250 of gestation, NR cows had increased (P < 0.05) caruncular capillary surface density and decreased (P < 0.05) cotyledonary capillary area density, capillary number density, and capillary surface density compared with control cows. Although nutrient restriction had little effect on placental vascularity by d 125, upon realimentation, alterations in vascularity became apparent by d 250 of gestation, suggesting a placental programming effect.     

Comparison of estimates of hip dysplasia genetic parameters in Estrela Mountain Dog using linear and threshold models

Genetic parameters, breeding values, and genetic trends of hip dysplasia in Estrela Mountain Dogs were estimated using a linear model (LM) and a threshold model (TM). A database with 313 animals was used. Right and left hip joints were individually scored, according to the Fédération Cynologic Internationale grading rules of the canine hip dysplasia system, as normal (1), borderline (2), slight (3), moderate (4), and severe (5 and 6). The estimate of repeatability was lower in LM (0.86) than in TM (0.90). The same tendency was verified with the heritability because its estimate in LM was 0.38 and in TM was 0.43. However, these results did not establish any statistical differences between the models. The genetic trend of canine hip dysplasia for LM and TM showed a similarity in shape, but considerable individual differences were found in the EBV ranking lists. Therefore, the selection of breeding animals would not be the same with the 2 methodologies. To select the best method for genetic evaluation of hip dysplasia, further studies using more data and other dog breeds are required.     

Failure mode and bending moment of canine pancarpal arthrodesis constructs stabilized with two different implant systems

Objective— To compare failure mode and bending moment of a canine pancarpal arthrodesis construct using either a 2.7 mm/3.5 mm hybrid dynamic compression plate (HDCP) or a 3.5 mm dynamic compression plate (DCP).
Study Design— Paired in vitro biomechanical testing of canine pancarpal arthrodesis constructs stabilized with either a 2.7/3.5 HDCP or 3.5 DCP.
Sample Population— Paired cadaveric canine antebrachii (n=5).
Methods— Pancarpal arthrodesis constructs were loaded to failure (point of maximum load) in 4-point bending using a materials-testing machine. Using this point of failure, bending moments were calculated from system variables for each construct and the 2 plating systems compared using a paired t-test. To examine the relationship between metacarpal diameter and screw diameter failure loads, linear regression was used and Pearson' correlation coefficient was calculated. Significance was set at P <.05.
Results— HDCP failed at higher loads than DCP for 9 of 10 constructs. The absolute difference in failure rates between the 2 plates was 0.552±0.182 N m, P =.0144 (95% confidence interval: −0.58 to 1.68). This is an 8.1% mean difference in bending strength. There was a significant linear correlation r=0.74 ( P -slope=.014) and 0.8 ( P -slope=.006) between metacarpal diameter and failure loads for the HDCP and 3.5 DCP, respectively.
Conclusion— There was a small but significant difference between bending moment at failure between 2.7/3.5 HDCP and 3.5 DCP constructs; however, the difference may not be clinically evident in all patients.
Clinical Relevance— The 2.7/3.5 HDCP has physical and mechanical properties making it a more desirable plate for pancarpal arthrodesis.     

Assessment of stiffness and strength of 4 different implants available for equine fracture treatment: a study on a 20 degrees oblique long-bone fracture model using a bone substitute

OBJECTIVE: To compare the mechanical properties of 4 stabilization methods for equine long-bone fractures: dynamic compression plate (DCP), limited contact-DCPlate (LC-DCP), locking compression plate (LCP), and the clamp-rod internal fixator (CRIF--formerly VetFix). STUDY DESIGN: In vitro mechanical study. SAMPLE POPULATION: Bone substitute material (24 tubes) was cut at 20 degrees to the long axis of the tube to simulate an oblique mid-shaft fracture. METHODS: Tubes were divided into 4 groups (n=6) and double plated in an orthogonal configuration, with 1 screw of 1 implant being inserted in lag fashion through the "fracture". Thus, the groups were: (1) 2 DCP implants (4.5, broad, 10 holes); (2) 2 LC-DCP implants (5.5, broad, 10 holes); (3) 2 LCP implants (4.5/5.0, broad, 10 holes) and 4 head locking screws/plate; and (4) 2 CRIF (4.5/5.0) and 10 clamps in alternating position left and right of the rod. All constructs were tested in 4-point bending with a quasi-static load until failure. The implant with the interfragmentary screw was always positioned on the tension side of the construct. Force, displacement, and angular displacement at the "fracture" line were determined. Construct stiffness under low and high loads, yield strength, ultimate strength, and maximum angular displacement were determined. RESULTS: None of the implants failed; the strength of the bone substitute was the limiting factor. At low loads, no differences in stiffness were found among groups, but LCP constructs were stiffer than other constructs under high loads (P=.004). Ultimate strength was lowest in the LCP group (P=.01), whereas yield strength was highest for LCP constructs (409 N m, P=.004). CRIF had the lowest yield strength (117 N m, P=.004); no differences in yield strength (250 N m) were found between DCP and LC-DCP constructs. Differences were found for maximum angular displacement at the "fracture" line, between groups: LPC相似文献   

Prediction of accuracy of estimated Mendelian sampling terms

This study describes a general framework for predicting the accuracy of Mendelian sampling terms when truncation selection is applied on best linear unbiased prediction (BLUP) estimated breeding values. A selection index approach is followed. The pseudo‐BLUP index is extended to include terms related to the Mendelian sampling term. Predicted accuracies are compared with those obtained through stochastic computer simulation. Good predictions for the accuracy of the Mendelian sampling term were obtained both at selection time and at convergence of long‐term contributions of selected candidates for a range of heritabilities and population structures. The prediction approach developed provides a key tool for obtaining predictions of genetic response from quadratic optimization that maximizes the rate of genetic progress while restricting the rate of inbreeding.     

Vascular-targeted photodynamic therapy (VTP) of a canine-transmissible venereal tumour in a murine model with Pd-bacteriopheophorbide (WST09)

Treatment of canine‐transmissible venereal tumour (CTVT) with local vascular‐targeted photodynamic therapy (VTP) using Pd‐bacteriopheophorbide (WST09) as a drug is suggested as an alternative to conventional chemotherapy. Male CD1 nude mice were subcutaneously grafted with the xenograft‐transmissible canine venereal tumour (XTVT). The VTP protocol delivered once consisted of intravenous administration of WST09 (10 mg kg^?1) followed by immediate local illumination with a diode laser (763 nm). Controls included animals treated with light or WST09 alone. Macroscopic and microscopic evaluations of tumour response were conducted 10, 24 and 48 h after treatment. Upon VTP, tumours underwent necrosis that lasted 8–10 days and exhibited complete healing by 25–35 days, reaching an overall long‐term cure rate (83%) by 90 days after treatment. This study suggests that VTP with WST09 can efficiently treat CTVT in a single session, as compared with 4–6 sessions of chemotherapy and thus may be feasible for common veterinary practice, particularly under ambulatory conditions.