SURVIVAL OF MANX SHEARWATERS PUFFINUS PUFFINUS

The breeding success of Manx Shearwaters at Skokholm Island, Pembrokeshire, was followed in study burrows, and data on survival of the young were augmented by ringing large numbers as they were about to leave the island and recapturing them in later years.
The weight of the young at fledging and the date at which they leave affect their chances of survival; overall, as many as 30% of the young birds may survive to reach breeding age, which is thought to be normally about 5–6 years. Adult mortality varies between wide limits of about 5 and 20%, but juvenile survival appears to be of about the right order to balance adult losses.
The significance of the one-egg clutch is discussed. At the normal time of laying the female may not be able to obtain sufficient food to form a second egg. A two-egg clutch, laid at a later date, would not produce more surviving young since these would fledge too late in the season to have a good chance of survival.
The advantage of leaving the island at a heavy weight is discussed, and it is concluded that the fat stores laid down give heavy young a greater chance than light young of migrating a long distance without food. It is possible that the young may even reach their winter quarters (off Brazil) without having to feed on passage if they depart with enough stored fat.     

Hepatic injury in chronic iron overload. Role of lipid peroxidation

In both hereditary hemochromatosis and in the various forms of secondary hemochromatosis, there is a pathologic expansion of body iron stores due mainly to an increase in absorption of dietary iron. Excess deposition of iron in the parenchymal tissues of several organs (e.g. liver, heart, pancreas, joints, endocrine glands) results in cell injury and functional insufficiency. In the liver, the major pathological manifestations of chronic iron overload are fibrosis and ultimately cirrhosis. Evidence for hepatotoxicity due to iron has been provided by several clinical studies, however the specific pathophysiologic mechanisms for hepatocellular injury and hepatic fibrosis in chronic iron overload are poorly understood. The postulated mechanisms of liver injury in chronic iron overload include (a) increased lysosomal membrane fragility, perhaps mediated by iron-induced lipid peroxidation, (b) peroxidative damage to mitochondria and microsomes resulting in organelle dysfunction, (c) a direct effect of iron on collagen biosynthesis and (d) a combination of all of the above.     

In vitro rates of oxidation and gluconeogenesis from L(+)- and D(-)lactate in bovine tissues

Slices of bovine kidney cortex, liver, heart and sternomandibularis muscle actively metabolized D- and L-lactate. Rates of D-lactate oxidation were greatest in kidney cortex followed by heart and liver with muscle exhibiting the lowest rates. L-lactate oxidation was greatest in kidney cortex followed by heart with liver and muscle exhibiting similar rates. Rates of oxidation of gluconeogenesis were similar for D- and L-lactate at 0.1 mm lactate but D utilization, as a percent of L, decreased as substrate concentrations increased to 50 mM. Bovine tissues appear to possess significant potential for D(-)lactate utilization. Estimates of this and possible interactions are discussed.     

Centrifugal waste disposal and the optimization of ant nest craters

We considered how ant, Tapinoma simrothi, colonies dispose of the material generated by their nest excavations in nest entrance craters. We developed a model for optimum crater formation on both flat and sloping ground (although we have not solved it in full generality for sloping ground). We found that the ants, when working on flat ground, show a close approximation to this least costly waste disposal. Craters on slopes may not be optimal even though they will be cheaper to make than ones of a similar volume on level ground. We further tested the model with a manipulative experiment, which also suggested the simple rule of thumb that ants might use. In response to having one-quarter of their crater removed, the ants focused most of their further waste disposal in that quarter. This suggests that their rule of thumb may be to deposit material at the nearest point with an angle of elevation less than that of the optimal angle. This should generate symmetrical craters on flat ground. The model also makes certain additional and testable predictions about the fine structure of craters.