Impact of lower atmospheric carbon dioxide on tropical mountain ecosystems   总被引：1，自引：0，他引：1  

FA Street-Perrott  Y Huang  RA Perrott  G Eglinton  P Barker  LB Khelifa  DD Harkness  DO Olago 《Science (New York, N.Y.)》1997,278(5342):1422-1426

Carbon-isotope values of bulk organic matter from high-altitude lakes on Mount Kenya and Mount Elgon, East Africa, were 10 to 14 per mil higher during glacial times than they are today. Compound-specific isotope analyses of leaf waxes and algal biomarkers show that organisms possessing CO2-concentrating mechanisms, including C4 grasses and freshwater algae, were primarily responsible for this large increase. Carbon limitation due to lower ambient CO2 partial pressures had a significant impact on the distribution of forest on the tropical mountains, in addition to climate. Hence, tree line elevation should not be used to infer palaeotemperatures.  相似文献   

Ultrasound speed in the metacarpal cortex--a survey of 347 thoroughbreds in training.     

S H Buckingham  R N McCarthy  G A Anderson  R N McCartney  L B Jeffcott 《Equine veterinary journal》1992,24(3):191-195

Transmission ultrasound speed was determined in the third metacarpal bone of 347 Thoroughbred racehorses in training. In addition to direct measurement of apparent ultrasound speed and lateral bone diameter, several derived parameters were estimated (cortical ultrasound speed, corticomedullary ratio and cortical cross-sectional area). Multiple regression equations were developed for each ultrasound measurement using the explanatory variables: sex, age, duration and intensity of training, preparation number and previous shin soreness. The horses (114 females, 82 entire males and 151 geldings ranging in age from 20 to 116 months) had been in continuous training for an average of 10.0 weeks when measurements were made. All measurements except corticomedullary ratio were influenced by the sex of the horse. Geldings had significantly lower ultrasound transmission speed than entire males and females, reflecting a lower bone density. However, the geldings had larger cross-sectional areas (ie bone size). We suggest that the relationship between low ultrasound speed (ie low bone density) and large cross-sectional area maintains the overall mechanical integrity of the metacarpus. This relationship (high ultrasound speed and low cross-sectional area) was also found in each sex group. Ultrasound speed and corticomedullary ratio, but not cross-sectional area, were affected by age. Both duration and intensity of training influenced the ultrasound speed measurements. This study indicated that sex, age and state of training affect ultrasound results, but this explained only about 30% of the variance in the data. Other factors, ie genetic variation in bone density and size, differences in soft tissue thickness and distal limb temperature, presumably account for most of the variance.  相似文献   

Studies on equine prematurity 5: Histology of the adrenal cortex of the premature newborn foal     

P D Webb  D P Leadon  P D Rossdale  L B Jeffcott 《Equine veterinary journal》1984,16(4):297-299

The histology of the adrenal cortex of prematurely induced newborn pony foals in relation to their ability to survive the neonatal period is described.  相似文献   

Current concepts of hyperlipaemia in horses and ponies   总被引：2，自引：0，他引：2  

L B Jeffcott  J R Field 《The Veterinary record》1985,116(17):461-466

Hyperlipaemia is an important condition in ponies, not just because of the seriousness of the clinical signs and biochemical changes involved, but because of the distress it causes owners and breeders that have had animals suffer from it. Hyperlipaemia occurs most commonly in fat ponies in late pregnancy and is rarely seen in larger horses. The syndrome has similarities with conditions in other species but the definitive aetiologies are not yet known. The condition in ponies is undoubtedly related to stress. The biochemical mechanisms involved in equine hyperlipaemia are considered and an hypothesis of possible pathogenesis is put forward. This hypothesis is tested by presenting the results of a preliminary study to evaluate glucose and lipid metabolism in horses and ponies. It appears that the pony is markedly insensitive to insulin compared to larger horses which means that triglycerides are more readily mobilised and the animal is therefore susceptible to hyperlipaemia in a situation of negative energy balance. The effect of stress is to increase cortisol levels which only exacerbates the insulin insensitivity and so creates a vicious circle. The importance of an innate insulin insensitivity may also be important in the pathogenesis of such conditions as laminitis.  相似文献   

Sacroiliac Joint of the Horse 1. Gross morphology   总被引：1，自引：0，他引：1  

G. Dalin  L. B. Jeffcott 《Anatomia, histologia, embryologia》1986,15(1):80-85

A total of 22 morphological features were described in the sacroiliac joints of 41 horses which had no history of any low back condition. Some dramatic differences in both sacral and iliac aspects of joint shape and articular surfaces were seen according to age. These findings were thought to be due to progressive cartilaginous degeneration. Only minor significant differences were seen between left and right sacroiliac joints or between breeds and sex. The iliac surface was more prone to degenerative change. Ankylosis of the joints was not recorded and the incidence of articular or para-articular spur formation was low.  相似文献   

Problems encountered during induced foaling in pony mares.     

P D Rossdale  L B Jeffcott 《The Veterinary record》1975,97(19):371-372

  相似文献   

Effects of 25% propylene glycol hydrogel (Solugel) on second intention wound healing in horses     

Dart AJ  Cries L  Jeffcott LB  Hodgson DR  Rose RJ 《Veterinary surgery : VS》2002,31(4):309-313

OBJECTIVE: To evaluate the effect of a commercially available 25% propylene glycol hydrogel preparation (Solugel; Johnson and Johnson Medical, North Ryde, Australia) on healing of full-thickness skin wounds on the distal aspect of the limb in horses. STUDY DESIGN: Experimental. ANIMALS: Eight Standardbred horses. METHODS: Standardized (2.5 x 2.5 cm) full-thickness skin wounds were created over the mid-dorsomedial aspect of both metacarpi in 8 horses. One wound in each horse was dressed with saline solution (0.9% NaCl) soaked gauze, and one was treated with Solugel under dry regular gauze; wounds were then bandaged with gauze-coated cotton wool and elastic adhesive bandages. Wounds were videorecorded and rebandaged twice weekly until healed. Wound healing variables were measured from the videorecordings using a computer software package and analyzed as a randomized complete block design with repeated measures. Where necessary variables were made positive for analysis; significance was set at P <.05. RESULTS: The area of the wound at the first bandage change did not vary between treated and untreated wounds. Treatment had no effect on the total rate of healing, rate of healing during the retraction phase of healing, rate of healing after the retraction phase was complete, or the amount the wounds retracted. CONCLUSIONS: Using this model of wound healing, Solugel had no effect on second intention healing of distal limb wounds in horses. CLINICAL RELEVANCE: Solugel does not appear to have any beneficial effect on healing of small full-thickness skin wounds to the distal limb of horses.  相似文献   

Equine osteoclast-like cells generated in vitro demonstrate similar characteristics to directly isolated mature osteoclasts     

Gray AW  Davies ME  Jeffcott LB 《Research in veterinary science》2000,68(2):161-167

We report on novel methods to isolate osteoclasts (OC s) and generate osteoclast-like cells (OCL s) from the bone and bone marrow of the equine femur. OC s were successfully isolated from bone scrapings taken from the endosteal surface of the femurs of three horses. OCL s were generated from bone marrow cells taken from the same animals. The validity of using the formation of OCL s as a method for studying OC differentiation and activity was confirmed by the similar characteristics of these two cells. In particular, they both were multinuclear, expressed the enzyme tartrate resistant acid phosphatase and the vitronectin receptor. Most importantly, both were able to resorb bone as demonstrated by the formation of extensive resorption pits when cultured on dentine slices.The generation of OCL s from bone marrow obtained from the equine femur can therefore be used to study equine OC differentiation and for studies requiring the generation of large numbers of these cells. OC s isolated directly from the same bones may be used to examine the effect of a variety of factors on bone resorption in vitro and to continually reaffirm the validity of using OCL s for large-scale studies on OC biology. Such research is essential for improved understanding of bone turnover and endochondral ossification in the horse.  相似文献   

Single photon absorptiometry for the measurement of bone mineral content in horses   总被引：1，自引：0，他引：1  

L B Jeffcott  R N McCartney  V C Speirs 《The Veterinary record》1986,118(18):499-505

A safe, non-invasive method for the accurate measurement of bone mineral content in the third metacarpal bone of the horse is described. The technique involves scanning the bone with a single photon beam from an Americium-241 source. Data were obtained from the excised metacarpal bones from both forelimbs of 50 normal and seven lame horses. Measurements were made in vivo on eight normal and seven lame horses and on one experimental horse with osteopenia induced by partial weightlessness in a flotation tank. In the normal horses bone mineral content altered with age, particularly in the first six months of life. There were also differences according to the site of scanning on the metacarpus. The contribution of the splint bones to the total bone mineral content was less than 2 per cent distal to the mid-point of the metacarpus, but in the proximal shaft it increased to 12 per cent. No significant differences were noted either between right and left limbs, or between male and female animals. A reduction in bone mineral content was demonstrated in the affected leg of horses with chronic lameness and with osteopenia induced by weightlessness. The bone mineral content (g/cm) correlated well with the ash content (mg/100 mg dry bone weight), the specific gravity and the apparent transverse velocity of ultrasound (m/sec) through the bone. A measure of bone mineral density (g/cm3) was calculated from the bone mineral content and cross sectional area of the bone to overcome the individual differences in size of the metacarpus.  相似文献   

TECHNIQUE OF LINEAR TOMOGRAPHY FOR THE PELVIC REGION OF THE HORSE     

L. B. Jeffcott  BVetMed  PhD  FRCVS 《Veterinary radiology & ultrasound》1983,24(5):194-200

A method of linear tomography for the pelvic region of the horse is described. A custom-built unit was employed, and exposures of 140 kV and 400 mAs for three to four seconds were required in horses weighing approximately 450 kg. Animals were anesthetized and placed in lateral or dorsal recumbency. Radiographic quality of the lateral projection was considered unsatisfactory, but on ventrodorsal tomograms taken at an angle of swing of 10° or 20° most of the anatomic structures in the lumbar spine and pelvic girdle could be identified. The height of the plane of cut varied from 30 to 300 mm, according to anatomic location, but between animals the height of each structure was reasonably consistent.  相似文献