Western hegemony over african agriculture in Southern Rhodesia and its continuing threat to food security in independent zimbabwe

Zimbabwe's communal farmers are now less food secure than they were two generations ago. The roots of this decline lie not only in the confinement of Africans to marginal land but also in the historic forced replacement of their sustainable, indigenous farming system with one whose productivity now relies on the use of large amounts of expensive chemical inputs. Environmentally-friendly, traditional farming practices such as pyro-culture, minimum tillage, mixed cropping, and bush fallowing were completely wiped out and replaced with a highly technical western or ganic farming system based on plough cultivation and continuous monocultures of commodity crops, that were supposed to be sustained by liberal amounts of green and animal manures. This gave rise to an effective agricultural hegemony that was due, mainly, to the zealous dedication of an American Mormon missionary whose motives were evangelical rather than scientific.     

Duplication, deletion, and polymorphism in the sex-determining region of the mouse Y chromosome

The ZFY gene in the sex-determining region of the human Y chromosome encodes a "zinc-finger" protein that may be the testis-determining factor, TDF. Although the Y chromosomes of most placental mammals carry a single homolog of ZFY, the mouse Y chromosome has two homologs, both in the sex-determining (Sxr) region. Zfy-1 alone may suffice to determine maleness; Zfy-2 is dispensable, as it was deleted in an Sxr variant that retains sex-determining function but has lost other genes. Both loci mapped near the centromere of the mouse Y chromosome. The Y chromosomes of the subspecies Mus musculus musculus and M. m. domesticus were distinguishable by a Zfy-1 restriction fragment polymorphism, which can be used to study their differing interactions with autosomal sex-determining genes.     

Neurogenic Component of Chronic Renal Hypertension

Infusion of angiotensin or renin in small quantities affects the sympathetic nervous system so that responses are increased to either drugs or reflexes that cause release of norepinephrine at nerve endings. Response to injected norepinephrine is relatively unchanged. This action of angiotensin is dependent upon an intact sympathetic nervous system. The direct vasoconstrictor action of angiotensin is not an essential part of the enhanced response. The phenomenon was shown to have relevance to acute and chronic experimental renal hypertension in dogs by the fact that in both the pressor response to tyramine was enhanced. We believe that the ability of angiotensin to intensify the effect of normal neurogenic vasomotor activity, along with an upward reset of the carotid sinus buffer mechanism, might account importantly for the neurogenic component of renal hypertension.     

Wolves, moose, and the allometry of population cycles

After a decade of dramatic population fluctuations, protected populations of wolves and moose in Isle Royale National Park in Lake Superior returned in 1983 to the levels observed in the 1950's. Inherent lags in this predator-prey system and the strong recovery of the moose population following a wolf population crash suggest that these populations may continue to cycle with a period length of about 38 (95 percent confidence interval, +/-13) years. Such a long-term cycle is consistent with the proposal that period length of herbivore population cycles will characteristically scale according to the fourth root of body mass, a basic allometric relation linking physiological cycles to population processes.     

Increased cardiovascular reactivity to agiotensin caused by renin

After a short period of tachyphylaxis, there is a marked and sustained enhancement of pressor re sponses to renin and angiotensin during chronic administration of renin.