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Place-of-birth-by-residence data, tabulated by age and sex for the same areal units in two successive censuses, have been used to estimate intercensal net migration flows. However, a fuller use of the same data permits the estimation of place-to-place flows. This paper describes a method for estimating intercensal migration streams from place-of-birth- by-residence data and illustrates its application with data on the white female native population of the United States. [ABSTRACT FROM AUTHOR]

New procedures are developed in this article for estimating parameters of the Pearsonian Type I curve which are particularly adaptive to factors influencing the pattern of age-specific fertility rates. It is shown that with this model the number of parameters required for the graduation and simulation of these rates can be reduced to only three--total fertility rate, mean and modal ages of fertility. The reduction in the number of fertility parameters offers considerable operational and analytical advantages, and makes the Pearsonian Type I curve particularly appropriate for the construction of a parametric model for fertility projections. In light of the results of empirical tests based on fertility data for Canada, the model's potential for birth projections appears quite promising. [ABSTRACT FROM AUTHOR]

We have determined unidirectional influxes by measuring rate of uptake between 0.5 and 1.0 min of incubation in 5 mm galactose.H-inulin was used to correct for galactose in residual mucosal solution. Influx was greatly depressed by removing Na from or adding 10 m phlorizin to the incubation medium. Influx was also greatly depressed by making the mucosal solution anaerobic during a 10-min preincubation period. The same severe inhibition of galactose influx by mucosal anaerobiosis also occurrend under conditions in which the epithelial cells did not gain Na. After taking into account the effect of the mucosal unstirred water layer, influxes could be normalized to a concentration of 1.0 mm at the membrane surface. It was estimated that at 1.0 mm the phlorizin-sensitive component of galactose influx was reduced 93% by 10 min of mucosal anaerobiosis. Unidirectional effluxes were estimated by subtracting steady-state downhill mucosal-to-serosal flux from influx. The ease of efflux was apparently augmented 2.8-fold by mucosal anaerobiosis. After 10 min of mucosal anaerobiosis, there was no longer any directional preference for movement of galactose across the brush border and there was no uphill transport, in spite of the persistence of a large Na gradient. These results provide strong evidence against the theory that ion gradients provide the major source of energy for directional preference and uphill transport. [ABSTRACT FROM AUTHOR]

Ionophoric material isolated by tryptic digestion of (Na+K)-ATPase containing electroplax membranes shows fluctuating discrete current levels in oxidized cholesterol membranes with conductance amplitudes ranging from 10 to 10 mhos, suggesting pore formation. The rate of pore formation is dependent on the imposed voltage. If the voltage is maintained for a short time (5 to 10 sec), pore formation is reversible, whereas permanent pores are formed when the voltage is maintained for more than 10 sec. At pH=7 the permeability ratio for sodium versus chloride is 5 and for potassium versus sodium, 1.7. The permeability of the ionophoric material is dependent on pH. At pH=6 a conversion takes place from more cation-permeable to more anionpermeable pores, suggesting that histidine plays a role in the permeation mechanism. A model is proposed to account for the observed ionophoric properties. [ABSTRACT FROM AUTHOR]

The partition of alkali cations and anions between an aqueous and an immiscible organic phase has been studied in the absence and presence of neutral and carboxylic ionophores of the valinomycin and nigericin types, respectively. Cation extraction into the organic phase was augmented considerably by the ionophores, and a cation specificity of K≧Rb>Cs≫Na was found for all the neutral ionophores tested. Evidence is given that the actual values of ion specificity are a function of the solvent polarity, especially for valinomycin where an inversion of the K/Rb specificity was observed. The ionophores examined have the following rank order of effectiveness for K extraction into a standard organic phase consisting of 70% toluene-30% n-butanol: valinomycin>18-crown-6≫trinactin>enniatin B≈dinactin>monactin>nonactin. The ion affinity and selectivity data thus obtained have been compared with data previously reported. In a toluene-butanol solvent, extraction of cations in the absence of ionophores occurs as ion pairs. On the other hand, the neutral ionophores extract the cations by the mechanism of complexation, with the lipophilic anions coextracted as free gegenionic species at lower ionophore complex concentrations. When the concentration of extracted cations exceeds 1×10 m, ion pairing between the ionophore complex and the anion occurs, and this tendency increases with increasing concentration and decreasing polarity of the organic phase. Anion pairing with the complexed cations is much less than for the free cations and this effect appears to be due to the larger distance of closest approach of the anion for the complexed cation. [ABSTRACT FROM AUTHOR]

The cation selectivity and its relation to the inward-going rectification of the immature egg cell membrane of a starfish, Nordora punctiformis, were studied and the following results were obtained. (1) When the external saline contains usual ion species the cell membrane at rest is predominantly permeable to K ions. The K chord conductance g depends on the electrochemical potential of K ions, Δ V=V−E and the external K concentration [K] by $$(\Delta V_h \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ \doteq } - 15mV,\upsilon \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ \doteq } 7mV)$$ . (2) The permeability sequence of monovalent cations and the permeability ratios P/P of the cell membrane at rest obtained with membrane tpotential measurements are, T1 (1.5)>K(1.0)>Rb(0.3 to 0.4)>NH(0.03 to 0.04)>Na, Cs. (3) Current-voltage relations obtained when the external solution contains Rb, Cs or T1 in addition to K show: (a) Rb and Cs decrease the K conductance and the rate of decrease becomes greater with an increasing hyperpolarization, thereby the inward-going rectification is reduced; (b) the membrane conductance shows an 'anomalous mole fraction dependence' in Tl-K media, i.e., the conductance becomes minimum at a certain mole fraction; and (c) the current-voltage relation often shows a transitiontype behavior suggesting that the membrane undergoes metastable states during an ncrease of hyperpolarization. [ABSTRACT FROM AUTHOR]

The operation of a seven-compartment model is described with respect to flows of Na within and across this system, simulating published results obtained on frog skin. The seven compartments represent: one outside and one inside solution compartment; the subcorneal space; the first reacting cell layer (1. RCL); the remaining cell compartment; the non-, or slowly exchangeable Na compartment; the extracellular space. Assuming reasonable volumes for the epidermal compartments and further chosing, by trial and error, appropriate rate constants, a set of seven simultaneous linear differential equations was solved by the application of the Continuous System Modeling Program (CSMP), using an IBM 1130 computer. Initial conditions for influx, backflux and net flux were taken which correspond to [Na]; [Na]=115 mm. Print-out data were obtained at 0.5-min intervals for 30 min, when steady states were obtained in 13 models studied, varying certain k's thus simulating actions of chemical agents (hormones; drugs). Simulation was achieved with regard to rate of influx, backflux and net flux, steady-state time (30 min), and electrical potentials. In addition, this approach gave detailed information on Na pool sizes and their variations with changes in k's. These results are compared to published data on frog skin and good agreement between operation of skin epidermis and model was found. [ABSTRACT FROM AUTHOR]