The synthesis of glucose and ammonia by kidney tubules isolated from suckling and early-weaned lambs

Glucose and ammonia production were examined in kidney tubules isolated from suckling and early-weaned lambs, on days 10-30 after birth, with abrupt weaning occurring at day 14. There were no differences in the rates of glucose or ammonia production for a given substrate by tubules isolated from any of the lambs, regardless of age or stage of weaning. The preferred substrates for gluconeogenesis were glycerol = lactate greater than propionate = pyruvate = fructose = proline greater than alanine greater than glutamate greater than glutamine greater than aspartate greater than glycine greater than serine, and for ammoniagenesis were glutamine much greater than alanine greater than aspartate much greater than serine greater than glycine = glutamate = proline.     

Differential regulation of hepatic carbonic anhydrase isozymes in the streptozotocin-diabetic rat

Most work with the male rat liver carbonic anhydrase isozymes in the past decade has centered on the cytosolic CA III and the mitochondrial CA V. This paper reports that the relative activity of both isozymes is altered in streptozotocin-diabetes. Carbonic anhydrase activity of perfused liver homogenates and disrupted, isolated mitochondria was measured by the mass spectrometric 18O decay technique at 37 degrees C. The contributions of the different isozymes were determined based on intracellular location and sensitivity to acetazolamide inhibition. Diabetes resulted in a twofold increase in the activity of CA V but a halving in the activity of CA III. This is the first time that liver CA V has been shown to be altered by physiological stress. The total carbonic anhydrase activity in the diabetic rat liver was unaltered compared with control rats; however, CA III never accounted for more than 50% of this activity. Since CA isozymes I, II, and IV together account for 30% of the CA activity in control rats and 70% in diabetic rats it is concluded that one or more of these isozymes is subject to regulation in the diabetic male rat. The increase in CA V during diabetes is in accord with this isozyme having an important function in provision of substrate for hepatic gluconeogenesis and ureagenesis.     

Identification of structures restricting tidal flow in New South Wales,Australia

New South Wales is the most populous state in Australia with 80% of its people living 100 km or less from the coast. One legacy of settlement has been the construction of structures that interrupt tidal flow to coastal wetlands. We initiated a four-phase operation to locate these structures. In the first phase, 148 1:25,000 scale topographic maps were examined for six types of structure with the potential to reduce tidal flow: bridges, causeways, culverts, floodgates, fords and weirs. In the second phase, anecdotal information on the presence, impact and suitability for modification of these structures was sought from commercial fishers, oyster farmers and district fisheries officers. In the third phase, field investigations were carried out to confirm the presence of the structures, gain a first-hand impression of rehabilitation potential, and gather site-specific information not available from the maps, such as the diameter of culverts. The fourth phase was a review of the anecdotal and field data by the commercial fishers and conservation managers working for NSW Fisheries. A database was constructed with catchment and sub-catchment data, type of habitat problem, rehabilitation potential and other relevant comments. Over 5,300 structures between mean sea level and the +10-m contour were located on the topographic maps; approximately 2,000 structures were not inspected (1,000 were above tidal limit and another 1,000 were inaccessible within the constraints of the project). Field inspections identified 500 structures that were incorrectly labeled. Another 1,000 structures were identified from sources other than the topographic maps, giving rise to a total of over 4,200 structures with potential for structural modification to rehabilitate estuarine habitat. Of these, 1,388, including 1,035 floodgates, 185 culverts, 91 weirs, 46 causeways, 26 bridges and 5 fords, were considered modifiable. Investigations are continuing to set up a ranking system by which to initiate rehabilitation activities. The results have relevance to habitat managers along the eastern seaboard and elsewhere in Australia, and the method by which the results were obtained may have application elsewhere.