Heritability of locomotor performance and its correlates in a natural population

Summary Locomotor capacities and their physiological bases are thought to be of considerable selective importance in natural populations. Within this functional complex, organismal performance traits (e.g., speed, stamina) are expected to be of more direct selective importance than their suborganismal determinants (e.g., heart size). Quantitative genetics theory predicts that traits of greater selective importance should generally have lower heritabilities at equilibrium. Contrary to these expectations, we report that organismal performance traits had the highest heritabilities in a natural population of garter snakes.     

Occurrence,distribution and nature of neuropeptide Y in the rat pancreas

Summary Significant quantities of a newly discovered peptide, neuropeptide Y, were found in the rat pancreas, where they were localized to nerves in the exocrine parenchyma and around arterial and ductal structures. Although unaffected by surgical parasympathectomy, the periarterial and periductal nerves were abolished by chemical sympathectomy, suggesting that NPY is partially costored with sympathetic transmitters in nerve fibers.     

Role of myelin P0 protein as a homophilic adhesion molecule.

Peripheral nervous system myelin is an extension of the Schwann cell's plasma membrane that tightly enwraps axons in many layers and permits nerve impulses to be rapidly conducted. It is not known how these multiple membrane layers are held together in this compact form. Here we present evidence supporting the hypothesis that the extracellular leaflets of myelin are held together by the most abundant protein of myelin of the peripheral nervous system, P0, by homophilic interaction of its extracellular domains. Transfected Chinese hamster ovary cells expressing P0 protein adhere to each other in suspension, to form large aggregates, whereas cells that are identical but which do not express P0 do not. We also show that this aggregation is mediated by homophilic binding between P0-expressing cells and that the apposing plasma membranes of these cells specifically form desmosomes, whereas control transfected cells do not. As the only difference between the two cell populations is the expression of P0, this protein is apparently responsible for the changes in morphology and adhesion in the cells that express it. The idea that P0 is a homophilic adhesion molecule is supported by its inclusion in the immunoglobulin supergene family, all members of which are involved in recognition and/or adhesion.     

Osmotic stress mimics effects of vasopressin on learned behaviour

It has been suggested that arginine vasopressin (AVP) is involved in the retention of learned responses, in addition to its classical physiological functions of water retention and modulation of blood pressure. AVP administered subcutaneously (s.c.), intraventricularly or intracerebrally can prolong extinction of active avoidance behaviour and can enhance retention in inhibitory (passive) avoidance. These effects have been interpreted as a direct action of AVP on the central nervous system to facilitate memory consolidation. AVP also has facilitatory effects on cognitive function in humans, and marked deficits in AVP function have been associated with certain types of psychopathology. Alternative hypotheses for the behavioural actions of AVP have involved motivational constructs such as arousal, and our recent work has focused on the role of arousal resulting from the activation of peripheral visceral signals in the behavioural effects of peripherally administered AVP. The development of a specific antagonist for AVP, 1-deaminopenicillamine-2-O-methyl tyrosine arginine vasopressin (dPTyr(Me)AVP), which can reverse the behavioural effects of exogenously administered AVP, has provided a powerful tool for examining the role of AVP in the behavioural responses produced by physiological challenges known to release vasopressin. However, the relationship between the behavioural effects of exogenously administered AVP and the behavioural function of endogenously released AVP has not been evaluated. We report here that a potent peripheral osmotic stimulus, the intraperitoneal (i.p.) injection of hypertonic saline, at doses known to release AVP both centrally and peripherally, will produce behavioural effects similar to those of exogenously administered AVP. Furthermore, the prolongation of active avoidance induced by this osmotic stimulus is reversed by pretreatment with dPTyr(Me)AVP, suggesting that endogenously released AVP may also produce behavioural effects.     

Genetic linkage studies suggest that Alzheimer's disease is not a single homogeneous disorder. FAD Collaborative Study Group

Alzheimer's disease, a fatal neurodegenerative disorder of unknown aetiology, is usually considered to be a single disorder because of the general uniformity of the disease phenotype. Two recent genetic linkage studies revealed co-segregation of familial Alzheimer disease with the D21S1/S11 and D21S16 loci on chromosome 21. But two other studies, one of predominantly multiplex kindreds with a late age-of-onset, the other of a cadre of kindreds with a unique Volga German ethnic origin, found absence of linkage at least to D21S1/S11. So far it has not been possible to discern whether these conflicting reports reflect aetiological heterogeneity, differences in methods of pedigree selection, effects of confounding variables in the analysis (for example, diagnostic errors, assortative matings), or true non-replication. To resolve this issue, we have now examined the inheritance of five polymorphic DNA markers from the proximal long arm of chromosome 21 in a large unselected series of pedigrees with familial Alzheimer's disease. Our data suggest that Alzheimer's disease is not a single entity, but rather results from genetic defects on chromosome 21 and from other genetic or nongenetic factors.