Gas Exchange during Xylazine–ketamine Anesthesia in Neonatal Calves

Ten neonatal calves were anesthetized with xylazine and ketamine intramuscularly and breathed air spontaneously. Drug injection was repeated after 45 minutes. Each injection resulted in a rapid and sustained increase in respiratory rate, but arterial carbon dioxide tension (PaCO2) increased, indicating hypoventilation. Arterial hypoxemia, primarily caused by hypoventilation, developed within 15 minutes of each injection, but gradually disappeared. Acidemia was primarily respiratory in origin. Heart rate and arterial blood pressure decreased for the duration of anesthesia (90 minutes). This form of anesthesia is a satisfactory alternative to inhalation anesthesia of neonatal calves.     

Infrared spectroscopy of comet 81P/Wild 2 samples returned by Stardust

Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust.     

Organics captured from comet 81P/Wild 2 by the Stardust spacecraft

Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.     

Impact features on Stardust: implications for comet 81P/Wild 2 dust

Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse features were created by particles varying from dense mineral grains to loosely bound, polymineralic aggregates ranging from tens of nanometers to hundreds of micrometers in size. The cumulative size distribution of Wild 2 dust is shallower than that of comet Halley, yet steeper than that of comet Grigg-Skjellerup.     

Hyperactivated Sperm Motility: Are Equine Sperm Different?

A recent study has suggested a central role for hyperactivated sperm motility in successful equine in vitro fertilization, as the highest apparent fertilization rates reported yet were obtained using exogenous stimulation of hyperactivated motility in sperm that had been incubated for capacitation. Hyperactivated motility has been studied intensively in other species, but little data are available in this area in the horse. Hyperactivated motility is associated with an influx of calcium from the extracellular space, and in other species this occurs because of an increase in intracellular pH during capacitation. Influx of calcium seems to trigger changes in flagellar function through calcium–calmodulin–calmodulin kinase-related effects on dynein function, but the exact mechanisms resulting in hyperactivated motility are still unclear. We have been exploring the physiology of hyperactivated motility in stallion spermatozoa and have found many of the mechanisms present in other species to be in place in the stallion. Further research is needed to determine why stallion spermatozoa seem to fail to undergo hyperactivation in response to capacitating environments that support this activity in other species.     

Characterization of age- and location-associated variations in the composition of articular cartilage from the equine metacarpophalangeal joint

Objective: To characterize the impact of age, gender, location and individual animal variation on the composition of articular cartilage from the metacarpophalangeal joint of horses. Design: Cartilage specimens were obtained from the metacarpophalangeal joints of 28 male, female and castrated male horses ranging in age from one day to 27 years of age. Cartilage samples from the distal metacarpus, proximal first phalanx and proximal sesamoids were analyzed separately. Chondrocyte number, DNA content, proteoglycan concentration and total collagen content were determined for each animal and joint location. Results: Age and joint location had a significant effect on chondrocyte number and DNA content with higher cell counts and DNA content detected in cartilage from the youngest age groups and in cartilage from the metacarpus and proximal sesamoids. The influence of age on chondrocyte numbers was not significant in horses over two years of age. Both age and joint location also influenced total proteoglycan and collagen content. Lower proteoglycan and collagen concentrations were detected in younger horses, and cartilage from the metacarpus had lower proteoglycan and collagen concentrations than that from other joint locations. Gender did not appear to influence chondrocyte number or matrix content of equine articular cartilage. However, there was significant residual variation in cellularity, proteoglycan levels and collagen content between individual animals that could not be explained by the signalment factors considered in this study. Conclusions: Future studies examining equine articular cartilage should avoid direct morphologic comparisons between animals of different ages, and any comparisons made between individuals should be interpreted cautiously. In addition, in vitro tissue culture models should avoid the use of cartilage pooled from different animals or from different locations within the same joint.