A comparative study of the soil zinc fractions determined by chemical methods and electro-ultrafiltration (EUF) and their relations to zinc nutrition in rice

Rice (IR 42) was grown on two soils differing in zinc status for 30 days with and without Zn under submerged conditions in pots. The fate of soil zinc was characterized by extraction of the soil successively with copper acetate and sodium hypochlorite and by EUF extraction. Most of the applied zinc was extracted by copper acetate and represented as complexed fraction. There exists a close and significnat relation between Cu(OAc)₂-extractable zinc and Zn extracted by EUF for 5 minutes at 50 volts (r=0.98). The EUF-extractable zinc and Cu(OAc)₂-extractable zinc were significantly correlated with the zinc content in the plant (r=0.82). The data from this investigation suggest the possibility of Zn fractionation with the EUF technique and the fractions obtained agree closely to those determined by chemical methods. The results obtained indicate that Zn in soil is held by weak organic bonding and that the extractions by Cu(OAc)₂ and/or EUF-5 minutes serve as a useful basis for extimating zinc availability in rice soils.     

Variation in Male Fertilities and Pairwise Mating Probabilities in Picea glauca

Frequencies of multilocus male gametes in seeds collected from clones in several blocks of a white spruce seed orchard were analyzed as part of a 2-yr study of mating system variation in this species. Observed frequencies of male gamete types departed significantly from those expected assuming equal male fertilities among clones. Male gamete frequencies in seed crops were significantly heterogeneous among clones within blocks, and among blocks within clones. Clonal male fertilities were estimated from male gamete frequency data. These estimates were highly skewed, with a small proportion of the clones contributing male gametes to the majority of the seed. The estimates were significantly heterogeneous among clones within blocks, and among blocks within clones. Between-year variation in clonal male fertilities was also pronounced, with male fertilities of some clones changing by as much as three orders of magnitude. Clonal male fertility was significantly correlated with clonal male cone production in both years. These results are important with regard to assumptions made for the estimation of general combining ability, average genetic correlation among progeny from single parents, and expected response to selection in open-pollinated plant populations.     

Light and electron microscopical immunocytochemistry of 5'-nucleotidase in rat cerebellum

5'-Nucleotidase in nervous tissue has so far not been localised at the ultrastructural level using immunocytochemical techniques. We have now applied monoclonal antibodies and a polyclonal antiserum raised against this ecto-enzyme and describe the distribution of 5'-nucleotidase antigenicity in rat cerebellum both at the light and electron microscopic levels. Within all cerebellar layers, 5'-nucleotidase immunoreactivity was found on plasma membranes of glial elements, i.e. Bergmann glial cell processes crossing the molecular layer, astrocytic end-feet around blood vessels and glial cell extensions surrounding single Purkinje cells. In the granular layer, 5'-nucleotidase immunoreactivity was present on glial membranes interposed between granule cells. Neuronal cells or processes were devoid of immunoreactivity. The immunocytochemical results were compared with conventional 5'-nucleotidase histochemistry. Both techniques showed the same ecto-localisation of the enzyme and favour the view of 5'-nucleotidase being predominantly situated at glial plasma membranes.     

Acardiac fetus in a triplet pregnancy

The acardiac monster represents one of the most severe but rare congenital anomalies. It occurs only in multiple gestations associated with vascular anastomoses between the affected fetus and its co-twin. The prenatal diagnosis of an acardiac fetus must be suspected in any multiple gestation in which cardiac activity cannot be documented sonographically in a growing fetus. We report an acardiac fetus occurring in a spontaneously conceived triplet pregnancy. A review of the literature, including pathogenetic theories and sonographic reports, is discussed.     

A coordinate relationship between theGALK and theTK1 genes of the Chinese hamster

Chinese hamster cells in culture were treated with various concentrations of thymidine, 5-bromodeoxyuridine, trifluorothymidine, and 2-deoxy-D-galactose. Selection was made for deficiencies in the activities of galactokinase and thymidine kinase. Selection in the presence of thymidine, 5-bromodeoxyuridine, and trifluorothymidine was expected to produce clones deficient in thymidine kinase only, whereas those deficient in galactokinase were expected to be selected in the presence of 2-deoxy-D-galactose. However, it was found that clones growing in the presence of these inhibitors were frequently deficient in both enzymes. Or if a clone was deficient in only one, the deficiency frequently was not expected according to the selection procedure. This indicates some sort of coordinate relationship between the two gene loci, GALK and TK1, which specify galactokinase and thymidine kinase, respectively. GALK and TK1 are linked in all primates and rodents in which linkage determinations have been made. It is therefore probable that this linkage has been conserved for a long period of time. It is suggested that the apparent relationship between the two genes shown by the data presented here, as well as by others, supports the conclusion that linkage has been conserved by natural selection and is therefore not fortuitous.     

Current-voltage relations of the apical and basolateral membranes of the frog skin

We determined the current-voltage (I-V) relations of the apical and basolateral barriers of frog skins by impaling the cells with an intracellular microelectrode and assuming that the current across the cellular pathway was equal to the amiloride-inhibitable current. We found that: (a) The responses in transepithelial current and intracellular potential to square pulses of transepithelial potential (VT) varied markedly with time. (b) As a consequence of these transient responses, the basolateral I-V relation was markedly dependent on the time of sampling after the beginning of each pulse. The apical I-V plot was much less sensitive to the time of sampling within the pulse. (c) The I-V data for the apical barrier approximated the I-V relations calculated from the Goldman constant field equation over a relatively wide range of membrane potentials (+/- 100 mV). (d) A sudden reduction in apical bath [Na+] resulted in an increase in apical permeability and a shift in the apical barrier zero-current potential (Ea) toward less positive values. The shift in Ea was equivalent to a change of 45 mV for a 10-fold change in apical [Na+]. (e) The transient responses of the skin to square VT pulses were described by the sum of two exponentials with time constants of 114 and 1,563 ms, which are compatible with the time constants that would be produced by an RC circuit with capacitances of 65 and 1,718 microF. The larger capacitance is too large to identify it comfortably with a true dielectric membrane capacitance.     

The two-sex multiethnic stable population model

A two-sex multiethnic stable population is a model with fixed mortality and fertility parameters that explicitly recognizes the behavior of males and females in at least two distinct ethnic groups. The presence of intergroup fertility may allow the different ethnic groups to grow at a constant rate in a population with a fixed sex-ethnic composition. The present paper considers a variety of rules for determining the ethnicity of intergroup births based on the ethnicities of the mother and father, and examines the mathematical models implied by those rules. Numerical examples are presented for a two-ethnic-group population in cases where intergroup births are shared equally by the two groups, are all considered members of one particular group, and are all members of the father's group. A special case of a more general model, where sons become members of the father's group and daughters become members of the mother's group, is also considered. The results suggest that when intergroup fertility is not uncommon, how ethnicity is determined can substantially influence the ethnic composition of the population.     

Derivation and characterization of an efficiently myocarditic reovirus variant.

A reovirus variant, 8B, was isolated from a neonatal mouse which had been inoculated with a mixture of two reovirus strains: type 1 Lang (T1L) and type 3 Dearing (T3D) (E. A. Wenske, S.J. Chanock, L. Krata, and B. N. Fields, J. Virol. 56:613-616, 1985). 8B is a reassortant containing eight gene segments derived from the T1L parent and two gene segments derived from the T3D parent. Upon infection of neonatal mice, 8B produced a generalized infection characteristic of many reoviruses, but it also efficiently induced numerous macroscopic external cardiac lesions, unlike either of its parents. Microscopic examination of hearts from infected mice revealed myocarditis with necrotic myocytes and both polymorphonuclear and mononuclear cellular infiltration. Electron microscopy revealed viral arrays in necrotic myocytes and dystrophic calcification accompanying late lesions. Determination of viral titers in hearts from T1L-, T3D-, or 8B-infected mice indicated that growth was not the primary determinant of myocardial necrosis. Results from inoculations of athymic mice demonstrated that T cells were not a requirement for the 8B-induced myocarditis. Finally, 8B was more cytopathic than either of the parent viruses in cultured mouse L cells. Together, the data suggest that 8B-induced myocardial necrosis is due to a direct effect of reovirus on myocytes. Reovirus thus provides a useful model for the study of viral myocarditis.     

CORRELATED EVOLUTION OF SELF-FERTILIZATION AND INBREEDING DEPRESSION: AN EXPERIMENTAL STUDY OF NINE POPULATIONS OF AMSINCKIA (BORAGINACEAE)

The relation between inbreeding depression and rate of self-fertilization was studied in nine natural populations of the annual genus Amsinckia. The study included two clades (phylogenetic lineages) in which small-flowered, homostylous populations or species are believed to have evolved from large-flowered, heterostylous, self-compatible ones. In one lineage the small-flowered species is tetraploid with disomic inheritance. Rates of self-fertilization were 25% to 55% in the four large-flowered, heterostylous populations; 72% in a large-flowered but homostylous population; and greater than 99.5% in the four small-flowered, homostylous populations, which produce seed autonomously. When present, inbreeding depression occurred in the fertility but not the survival components of fitness. Using a cumulative fitness measure incorporating both survival and fertility (flower number), we found inbreeding depression to be lower in the four very highly self-fertilizing populations than in the five intermediate ones. The Spearman rank correlation between inbreeding depression and selfing rate for the nine populations was –0.50, but was not statistically significant (P = 0.12). Inbreeding depression was greater in the two tetraploid populations than in the very highly self-fertilizing, diploid ones. Phenotypic stability of progeny from self-fertilization tended to be higher in populations with lower inbreeding depression. We conclude that levels of self-fertilization and inbreeding depression in Amsinckia are determined more by other factors than by each other. Estimates of mutation rates and dominance coefficients of deleterious alleles, obtained from a companion study of the four highly self-fertilizing populations, suggest that a strong relationship may not be expected. We discuss the relationship of the present results to current theory of the coevolution of self-fertilization and inbreeding depression.