Sensitivity of boreal forest carbon balance to soil thaw

We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; and laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 +/- 0.5 metric ton of carbon per hectare per year (ton C ha-1 year-1) from 1994 to 1997, with a gain of 0.6 +/- 0.2 ton C ha-1 year-1 in moss and wood offset by a loss of 0.8 +/- 0.5 ton C ha-1 year-1 from the soil. The soil remained frozen most of the year, and the decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool ( approximately 150 tons C ha-1) appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of carbon dioxide from the site.     

Shear-wave splitting and implications for mantle flow beneath the MELT region of the east pacific rise

Shear-wave splitting across the fast-spreading East Pacific Rise has been measured from records of SKS and SKKS phases on the ocean-bottom seismometers of the Mantle Electromagnetic and Tomography (MELT) Experiment. The direction of fast shear-wave polarization is aligned parallel to the spreading direction. Delay times between fast and slow shear waves are asymmetric across the rise, and off-axis values on the Pacific Plate are twice those on the Nazca Plate. Splitting on the Pacific Plate may reflect anisotropy associated with spreading-induced flow above a depth of about 100 km, as well as a deeper contribution from warm asthenospheric return flow from the Pacific Superswell region.     

CLINICAL AND PATHOLOGICAL STUDIES OF BORDER LEICESTER RAMS NATURALLY INFECTED WITH ACTINOBACILLVS SEMINIS

Clinical examination of 31 rams with evidence of Actinobacillus seminis infection revealed 15 cases with marked lesions of the scrotal contents, two cases with very mild lesions, one with testicular atrophy but no abnormality of the epididymides, and another 13 without any palpable abnormalities of the genitalia. The rams were from a Border Leicester flock and included 27 un-mated rams from 6 to 12 months old. Histological examinations of affected epididymides showed a mixed purulent and non-purulent inflammation, with cystic hyperplasia of the ductus epididymis. Interstitial fibrosis and spermatic granulomas were seen in chronic lesions. Bilateral testicular atrophy and seminal degeneration were found in the nine rams that were autopsied. The clinical and pathological features of the disease are similar to those of ovine brucellosis. A pyelonephritis of unknown significance was found in four of the nine rams examined.     

OBSERVATIONS ON THE EPIDEMIOLOGY OF PORCINE PARVOVIRUS

Evidence presented suggests that porcine parvovirus is highly stable and infective. Introduction of virus to susceptible herds results in 100% infection rate within the following 3 months. Active immunity is associated with high persistent levels of haemagglutination-inhibitating (HI) antibody (> 256), piglets suckling immune sows acquiring HI titres between 10,000 and 40,000. Loss of passive immunity, measured by HI, occurs in a majority of pigs between 14 and 26 weeks of age (mean 21 weeks), whilst an average of 25% (2–47%) of pigs lose HI titres between 26 and 36 weeks of age. Susceptibility to challenge with virus does not occur until 3–5 weeks following loss of HI titres. In endemically infected herds 98–100% of adult pigs show serological evidence of active immunity.
A significant proportion of gilts may not be actively immune to porcine parvovirus at the time of first service, and subsequent infection may occur while these gilts are pregnant.     

RANULA IN THE DOG–A SURGICAL TREATMENT

A surgical treatment of ranula in the dog is described. The main features is the insertion of a stainless steel wire loop in a drainage incision. A permanent sinus or artificial puncta is hereby produced. The adaptability of this technique is illustrated in the two unusual cases presented.     

Equine anhidrosis: A review of pathophysiologic mechanisms

Anhidrosis is loss of the ability to sweat. The problem is seen in horses kept in a hot humid climate, and it may cause severe impairment of thermoregulation in the equine athlete. British Thoroughbreds imported to her tropical colonies are the earliest recorded cases, and since then the syndrome has come to be described as one of Thoroughbreds, usually performance athletes, undergoing acclimatization to heat and humidity. A recent epidemiologic study of cases in Florida has shown, however, that many different breeds, and long time inhabitants of a hot climate, may be affected. Equine sweat glands are of the apocrine type, and sweating is stimulated by direct local release of epinephrine from adrenergic nerve endings and by circulating epinephrine. Lack of sweating could be due to a number of possible flaws in a sequence from central nervous stimulation through sweat stimulation and secretion to delivery of sweat to the skin surface. The most likely possibilities are inadequate sweat gland response due to habituation of receptors to a high circulating level of epinephrine and occlusion of the sweat ducts by keratin plugs. Hormonal or metabolic imbalance may play a role both in the onset and secondary signs associated with anhidrosis.