Nitrogen transformations in soil as affected by bacterial-microfaunal interactions

We investigated the effects of soil microfauna feeding on a soil bacterium (Pseudomonas cepacia) and the resultant influence on net N mineralization. As the bacterial biomass increased, it assimilated N from the soil. Later, only if this bacterial biomass decreased was N remineralized. Grazing by amoebae (Acanthamoeba polyphaga) always reduced bacterial biomass, increased respiration, and increased nitrogen mineralization. Grazing by nematodes (Mesodiplogaster lheritieri) always reduced bacterial numbers and increased respiration, but only increased N mineralization when nematode populations themselves declined from peak values.A N budget calculated for the populations indicated that the nematode biomass was not sufficient to account for the unmineralized N, so we postulate change in excretory pathways as the bacterial food becomes limiting. This budget further indicated that amoebal and bacterial biomass could account for all of the non-mineral N when only these two species were present.Our experiments showed that microfauna can play an important role in N mineralization in soil and that the mechanism for this role is more likely to be through direct excretion by the grazers than through indirect physiological effects on the bacteria.     

Subsonic jet aircraft and stratospheric pollution

A significant number of thepresent long-range subsonic jet aircraft flights are in the stratosphere. Based on fuel consumption, an equivalent of 107 SST aircraft (Concorde) have been flying in the stratosphere each year from 1960 to 1970 (620 equivalent SST in 1990). Subsonic jets in 1990 will burn about 1.6 times as much fuel in the stratosphere as SST aircraft. Based on a Concorde emission index of 12.5 for NO, the amount of NO_x emitted by subsonic jets in the stratosphere from 1960 to 1970 is equivalent to an average of 20 Concordes (444 Concordes in 1990). Available information concerning mixing and transport in the atmosphere indicates that both subsonic jets and the SST will fly in the same atmospheric environment in the upper troposphere and lower stratosphere insofar as dissipation of their exhaust pollutants is concerned. The tropopause is not an effective barrier to mixing of stratospheric and tropospheric air. Many processes contribute to mixing in the lower stratosphere where the residence time of contaminants is of the order of months instead of years.     

The effect of variation in egg numbers,body weight and egg weight upon shell thickness

It is expected that when birds consume a diet with a fixed calcium content variation in the rate of egg production, in body weight or in egg weight will lead to variation in calcium consumption. This analysis investigated whether, in a particular experiment, this also led to variation in egg shell thickness. Data from 67 birds over ten consecutive 28‐d periods were considered. Within birds and within periods it was found that the relationships between shell thickness and these production characters varied at different dietary calcium levels and in some cases the partial regression coefficients calculated were different in sign from those expected. However, only comparatively small amounts of variation in shell thickness could be ascribed to yariation in egg numbers, body weight or egg weight and, after regression, significant (P<0.001) differences still existed in shell thickness between birds. In this investigation there was little tendency for the egg shells to become thinner as the birds aged and hence the correlation coefficients between shell thickness and each of the three production characters due to common seasonal or ageing effects were small. The correlation between the angular transformation of the percentage cracked egg shells produced by each bird and its'mean shell thickness was — 0.357.     

Tooth root abscesses in llamas and alpacas: 123 cases (1994-2005)

OBJECTIVE: To determine features, outcome, and complications of surgical treatment of camelid tooth root abscesses. DESIGN: Retrospective case series. ANIMALS: 123 camelids with tooth root abscesses. PROCEDURES: Signalment, history, teeth involved, surgery performed, ancillary diagnostic tests, and short-term complications were recorded from each medical record. An owner questionnaire was used to obtain long-term (> 1 year) follow-up information. RESULTS: The most common surgical treatments included tooth extraction (n = 106) and apicoectomy (13). Owners provided follow-up information on 84 animals. Postoperative complications were reported in 42 of 84 animals. The most common complications included reinfection (n = 15), chronic draining tract (14), and osteomyelitis (14). Significantly more camelids that were in good or obese body condition at the time of surgery were alive at the time of follow-up, compared with those with thin body condition at the time of surgery. Camelids with 2 teeth extracted had significantly more complications than those with 1 tooth extracted. Thirty-four of 47 owners reported that they were completely satisfied with the outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Owners of camelids in poor body condition should be forewarned that such animals are at greater risk for complications following dental surgery. Clinicians should recognize that the number of teeth affected was not associated with a poorer outcome.     

Staphylococcal and micrococcal adherence to canine and feline corneocytes: quantification using a simple adhesion assay

In this paper a simple adhesion assay suitable for the assessment of bacterial adhesion to both canine and feline corneocytes is described. Using this assay Staphylococcus intermedius, Staphylococcus aureus and Staphylococcus chromogenes were shown to adhere well to both canine and feline corneocytes. The numbers of adherent bacteria were, however, generally lower for feline corneocytes. Both Staphylococcus hominis and a Micrococcus species adhered poorly to canine and feline corneocytes. This is the first report documenting bacterial adhesion to feline corneocytes.     

Identification and characterization of aquaporin-9 (AQP9) in porcine hepatic tissue and hepatocytes in monolayer culture

Aquaporins (AQPs) are members of a large family of integral membrane proteins involved in the rapid movement of water and neutral solutes across cell membranes. In this study, we have prepared an affinity-purified porcine-specific polyclonal antiserum to AQP9 and have investigated the distribution and expression of AQP9 in pig liver tissue and in hepatocytes in primary culture. Immunocytochemical analysis showed that AQP9 was primarily localized in the membrane structures of hepatocytes and was not associated with intrahepatic bile ducts or blood vessels. Western blot analysis indicated that AQP9 ranged in apparent molecular mass between 27 and 38 kD in whole liver and hepatocyte membrane fractions; minor components were also observed at approximately 34 kD in the cytosol compartment of hepatocytes, bile duct and gall bladder. A prominent immunoreactive band at 44 kD was shown to be an artifact of Western blot analysis. In primary cultures of porcine hepatocytes, glucagon enhanced absolute levels of AQP9 protein, while gene expression was enhanced by T3 and glucagon. Insulin alone had no discernable influence on AQP9 gene expression or its cellular protein levels. These data suggest that AQP9 is a major AQP in porcine hepatic tissue and appears to be primarily responsive to glucagon induction.