The effect of static incubation on the yolk sac vasculature of the Japanese quail (Coturnix c. japonica)

Static incubation affects early embryonic development with, notably, a reduction area vasculosa expansion and diminished sub-embryonic fluid (SEF) volume, effects produced during a ‘critical’ period (3-7 days in the chick) (Baggott et al., 2002). Also, as noted by Babiker & Baggott (1992), SEF is produced in bulk only after the appearance of the yolk sac vasculature (YSV), which undergoes extensive proliferation before and during the critical period. Quantification of such changes in YSV requires estimates of both the quantity of vessels and the degree of branching. In the chick, total vessel length increased linearly up to 160h of incubation, whereas branching was maximal by about 96 h (Vico et al., 1998); so, by the critical period branching is complete yet vessel growth continues. It would seem likely, therefore, that a lack of turning would reduce both measures of YSV proliferation during the critical period. In quail the effect of static incubation seems not to be simply due to retardation of YSV proliferation, as vascular density index was reduced in unturned eggs in the middle of the critical period, only to increase again by 168 h. Also early in the critical period fractal dimension was 1.70 (as in the chick, Vico et al., 1998), yet then decreased in unturned eggs, although not significantly, and subsequently an increase occurred. Thus during the critical period static incubation specifically affects the structuring of the YSV but whether this is because of, or independent of, retardation of area vasculosa expansion is not known

Conductive elastomeric extensometer

Bridge circuit, in which conductive elastomeric material is the variable leg, precisely measures surface area changes in the human body. Circuits are used singularly, or in quantity by adding elements and amplifier circuits. Elastomeric strips can be located in a form-fitting garment

Connections of the corpus cerebelli in the green sunfish and the common goldfish

Examination of the connections of the corpus cerebelli in one perciform (Lepomis cyanellus) and one cypriniform teleost (Carassius auratus) reveal that ipsilateral afferent connections in both species arise from an anterior group of nuclei in the diencephalon and mesencephalon, and a posterior group of nuclei in the rhombencephalon. Some nuclei of the anterior group and all those of the posterior group have in addition a weaker, and the medial octavolateralis nucleus a stronger, contralateral component. The inferior olivary nucleus in both species projects solely contralaterally. Nucleus paracommissuralis, the ventral accessory optic nucleus and nucleus isthmi are minute in Carassius compared to Lepomis. The latter species has in addition a bilateral corpopetal projection (ipsilaterally stronger) from the lateral cuneate nucleus. Efferent fibers in both species reach the contralateral nucleus ruber, oculomotor nucleus, nucleus of the medial longitudinal fasciculus, torus semicircularis, ventromedial and ventrolateral thalamic nuclei, optic tectum and superior and inferior reticular formation. An additional weaker ipsilateral terminal field could be observed in all nuclei except in the ventrolateral and ventromedial thalamic nuclei, the dorsal periventricular pretectal nucleus and the optic tectum. Lepomis in addition has a bilateral terminal field in the ventral accessory optic nucleus (contralaterally stronger). In both species, stronger ipsilateral and weaker contralateral terminal fields were present in the torus Iongitudinalis and the valvula cerebelli. The two patterns of corpopetal connections in Lepomis and Carassius were used as models for perciforms and cypriniforms in the analysis of the existing information in the literature on teleosts. While most discrepancies in the literature on percomorphs and ostariophysines could be interpreted consistently, the available information on mormyrids revealed a very different pattern of corpopetal organization: presence of additional connections (from a division of the nucleus preglomerulosus) and absence of otherwise well-established corpopetal connections in teleosts. In a second step, a phyletic analysis of teleostean corpopetal organization revealed that while teleosts share with all other vertebrates a group of corpopetal connections from the rhombencephalon, they evolved many new, more anteriorly located afferent inputs to the corpus cerebelli. Furthermore, electroreceptive mormyrids in addition evolved newly at least one corpopetal connection and lost many others

Analysis of a model for the dynamics of prions II

A new mathematical model for the dynamics of prion proliferation involving an ordinary differential equation coupled with a partial integro-differential equation is analyzed, continuing earlier work. We show the well-posedness of this problem in a natural phase space, i.e. there is a unique global semiflow in the phase space associated to the problem. A theorem of threshold type is derived for this model which is typical for mathematical epidemics. If a certain combination of kinetic parameters is below or at the threshold, there is a unique steady state, the disease-free equilibrium, which is globally asymptotically stable; above the threshold it is unstable, and there is another unique steady state, the disease equilibrium, which inherits that property

Model-Independent Determinations of B -> D l nu , D* l nu Form Factors

We present nonperturbative, model-independent parametrizations of the individual QCD form factors relevant to B -> D* l nu and B -> D l nu decays. These results follow from dispersion relations and analyticity, without recourse to heavy quark symmetry. To describe a form factor with two percent accuracy, three parameters are necessary, one of which is its normalization at zero recoil, F(1). We combine the individual form factors using heavy quark symmetry to extract values for the product |V_{cb}| F(1) from B -> D* l nu data with negligible extrapolation uncertainty.Comment: uses harvmac and epsf, 22 pages, 3 eps figures include

GRANGER CAUSALITY AND U.S. CROP AND LIVESTOCK PRICES

Agricultural economists have recently been attracted to procedures suggested by Granger and others which allow observed data to reveal causal relationships. Results of this study indicate that "causality" tests can be ambiguous in identifying behavioral relationships between agricultural price variables. Caution is suggested when using such procedures for model choice.Demand and Price Analysis,

THE U.S. MEXICAN WINTER MARKET TRADE DISPUTE

On March 11, 1996, the Florida Fruit and Vegetable Association, the Florida Bell Pepper Growers Exchange, the Florida Farm Bureau, the Florida Department of Agriculture and Consumer Services and other U.S. tomato producers filed a petition with the International Trade Commission (ITC) for economic relief from the effects of increased tomato imports from Mexico under Section 202 (a) of the Trade Act of 1974. A second petition was filed with the U.S. Department of Commerce under Section 733 (a) of the U.S. Tariff Act of 1930, charging that Mexican tomatoes were being dumped on the U.S. market at prices less than fair market value (LTFV) and were the cause of material injury to the domestic industry. Florida growers blame their recent loss of market share and depressed prices during the 1995-96 winter season on NAFTA, the North American Free Trade Agreement. The reduction in trade barriers due to NAFTA allegedly resulted in a flood of Mexican tomato imports, which have depressed domestic prices and resulted in declining profits, employment and investments. These allegations constitute the legal criteria for a petition seeking economic relief from imports sold at less than fair market value. The ITC investigated the first petition and rejected it on July 2, 1996. The antidumping petition continued during the summer and fall, 1996, until trade negotiations resulted in a compromise agreement that suspended the investigation. On October 11, 1996, the U.S. and Mexican tomato growers reached an agreement suspending the dumping case and establishing a minimum import price for fresh tomatoes at $0.2068 per pound ($0.45/kg) or $5.17 per 25-pound box. The price floor appeared low enough to allow for competitive improvements and disposal of temporary oversupplies in the market. Thus the wholesale price of tomatoes from the two regions would be approximately equivalent, restoring a "level playing field."International Relations/Trade,