CYTOCHROMES IN BRAIN MITOCHONDRIA FROM LAMBS WITH ENZOOTIC ATAXIA

Mitochondria from the cerebral cortex of untreated lambs from areas in which enzootic ataxia occurred showed a lower content of haem a (from cytochromes a and a 3) than mitochondria from control lambs with adequate copper but the haems of cytochromcs b2 c1 and c were not depleted. Cytochrome oxidase activity was closely correlated with the content of haem a (P<0.001) but there was no correlation with total mitochondrial copper which was always present in molar exccss of haem a. It is concluded that the lowered cytochrome oxidase activity in mitochondria from untreated lambs is immediately attributable to depletion of haem a. In clinically ataxic lambs that showed degradation of myelin in thc spinal cord, brain cytochrome oxidase was depressed by no more t han 60%. Arguments are advanced that this depletion was not sufficiently severe to have led to respiratory constraint     

4. UNUSUAL EXPERIENCES WITH BIRDS

Earlé, R. A. 1989. Breeding biology of the Redbreasted Swallow Hirundo semirufa. Ostrich 60: 13–21.

The two races of the Redbreasted Swallow Hirundo semirufa seem to have separate breeding seasons with the northern race H. s. gordoni breeding April-July, while most records for the nominate race fall in October-February. All nests studied were in concrete culverts less than 1 m high. Eggs laid in second clutches by individual females weighed significantly less than eggs laid in first clutches. Eggs hatched on average 16,2 days after incubation started or 18–21 days after the eggs were laid. Only females incubated. Chicks fledged 23–25 days after hatching and reached a maximum body mass of about 31,5 g on day 18 before a steady decline in mass until fledging. Most nesting failures resulted from infertile eggs or starvation of young in the nest (16,2% of all young starved). Overall breeding success was 60,6%. In all, 81,8% of first clutches produced fledglings but only 44,4% of second clutches. Over a three year period 4,9 young were produced per pair breeding in the area (1,6 young/pair/breeding season).