Sequential aspects of spontaneous abortion: maternal age, parity, and pregnancy compensation artifact

At least 3 hypotheses predict that spontaneous abortion risk differs during reporductive history: genuine maternal age effects change individual risks; genuine birth order effects change individual risks; and variant individual risks, which are really independent of both age and parity, produce an artifactual association of risk with age in populations of women. The availability of large numbers of reproductive histories recorded on magnetic tape by the Collaborative Study on Cerebral Palsy provides an opportunity to weigh these hypotheses. Information was gathered between mid-1959 and mid-1966 by 13 hospitals, mostly east of the Mississippi. Random samples of essentially all women registering in the obstetric clinics of the collaborating institutions entered the study. Generally, these women came from poorer urban areas. Data are taken from the interviews at 1st registrations only. At this time, women had prior reproductive histories of varying lengths. The data are analyzed to yield broad comparative evaluations of the maternal age, parity, and artifact hypotheses. When the logit transforms of abortion risks were regressed on maternal age, the linear component was positive and significant at the 1% level in every ethnic group. In all categories except blacks, the fit to such a simple model was quite adequate. Fit in the case of the blacks was disturbed by the high rate among 13-year olds and the low rate among 37-year olds. The 37-year old black sample was the only one to depart markedly from the trend of increased risk at high age. Primary analysis of birth order defects used Slater's (1962) rank order statistic on a group of histories. In every ethnic category the observed mean value of Slater's statistic exceeds its expected value of 0.5; every standardized deviation has a negligibly small probability when tested against the normal distribution. The conclusin is that spontaneous abortions tend to come late in a reproductive history. The white data showed a definite trend contrary to expectation under the pregnancy compensation hypothesis. Although not significant in the "o" (liveborn) versus "x" (abortion) contrast, the lowering trent in maternal age with prior abortion experience was signifixant for the longer histories. Equally surprising was the apparent positive finding in the black data. In sum, the data clearly showed that among women with histories mixing spontaneous abortions and live births, risk of abortion was greater at higher parity. Although the women sampled tended to be young, and increase of risk with age was demonstrated in the white sample. These effects were not because of sample biases. Black age effects were possibly confounded with pregnancy compensation artifact which can mimic aging influence in unselected samples.     

Effect of valinomycin and gramicidin d on the reflection coefficient of soybean root systems

Valinomycin and gramicidin D were used to test the hypothesis that a lipoprotein membrane is the osmotic barrier in mature root systems. Hydroponically grown soybean (var. Ranson) root systems were pressurized in steps between 0.2 and 5.0 bars at 25 C. Steady-state flow rates and exudate osmotic potentials were measured at each pressure. Valinomycin or gramicidin D to a final concentration of 2.6 or 5.0 micromolar, respectively, was injected into the nutrient solution, and steady-state values were again measured between 0.2 and 5.0 bars. Both ionophores reduced the x intercept of the straight line portion of the flux rate versus pressure curve, and increased the exudate osmotic potential at infinite flow rate. Valinomycin lowered the reflection coefficient from 0.91 to 0.76, whereas gramicidin D lowered the reflection coefficient from 0.86 to 0.81. The results support the hypothesis that one or more lipoprotein membranes in the root system function in regulation of ion movement from the ambient solution to the stele during high transpiration rates.     

Studies on the Fine Structure of Microorganisms : V. Morphogenesis of Nuclear and Membrane Structures during Ascospore Formation in Yeast

The fine structure of cells of Saccharomyces cerevisiae engaged in the formation of ascospores was studied in electron micrographs of ultrathin sections. Although the mode of the first reduction division could not be clearly determined, the second nuclear division appeared to proceed in a manner similar to that observed previously during vegetative division. That is, division by constriction of the existing nucleus occurs without dissolution of the nuclear membrane and without involvement of discrete chromosomes. Variously shaped areas of low electron density were discerned within the nucleoplasm; these had not been previously seen in the vegetative nucleus. The significance of this nuclear differentiation and its possible similarity to nuclear structures reported in bacteria and an imperfect fungus are discussed. The cytoplasmic membrane appears first in the developing ascospore. The formation of an outer coat and an inner coat then follows. The cytoplasmic vacuole was observed not to be incorporated into the spore. An unusual intracytoplasmic membrane was observed in the spore and appeared to be at least temporarily continuous with the nuclear membrane.     

Mapping of the Gene Encoding the Regulatory Subunit RIIα of cAMP-Dependent Protein Kinase (Locus PRKAR2A) to Human Chromosome Region 3p21.3–p21.2

We have determined the chromosomal localization of the gene for the regulatory subunit RIIα of cAMP-dependent protein kinase (locus PRKAR2A) to human chromosome 3 using polymerase chain reaction (PCR) and Southern blot analysis of two different somatic cell hybrid mapping panels. Furthermore, PCR analysis of a chromosome 3 mapping panel revealed the presence of a human RIIα-specific amplification product only in cell lines containing the region 3p21.3–p21.2. The localization of PRKAR2A was confirmed by PCR mapping using the Stanford G3 Radiation Hybrid Panel as template. The results from this analysis demonstrated that PRKAR2A is most closely linked to D3S3334 (lod score 12.5) and flanked by D3S1322E and D3S1581.     

Human beta3 adrenergic receptor agonists containing imidazolidinone and imidazolone benzenesulfonamides

The cyclopentylpropylimidazolidinone L-766,892 is a potent beta3 AR agonist (EC50 5.7 nM, 64% activation) with 420- and 130-fold selectivity over binding to the beta1 and beta2 ARs, respectively. In anesthetized rhesus monkeys, L-766,892 elicited dose-dependent hyperglycerolemia (ED50 0.1 mg/kg) with minimal effects on heart rate.     

Inhibition of the rumen anaerobic fungus Neocallimastix frontalis by fermentation products

The effects of bacterial fermentation products on cellulose degradation by the rumen fungus Neocallimastix frontalis have been investigated. H₂, formate, lactate and ethanol were strong inhibitors, particularly at high concentrations. Acetate and malate also inhibited, whereas succinate had a variable effect. Butyrate and propionate had no inhibitory effects.     

Effect of Methanobrevibacter smithii on Xylanolytic Activity of Anaerobic Ruminal Fungi

Three different ruminal anaerobic fungi, Neocallimastix frontalis PNK2, Sphaeromonas communis B7, and Piromonas communis B19, were grown axenically or in coculture with Methanobrevibacter smithii on xylan. N. frontalis and S. communis in monoculture and coculture accumulated xylobiose, xylose, and arabinose in the growth medium; arabinose was not metabolized, but xylobiose and xylose were subsequently used. The transient accumulation of xylose was much less evident in cocultures. Both the rate and extent of xylan utilization were increased by coculturing, and metabolite profiles became acetogenic as a result of interspecies hydrogen transfer; more acetate and less lactate were formed, while formate and hydrogen did not accumulate. For each of the three fungi, there were marked increases in the specific activities of extracellular xylanase (up to fivefold), alpha-l-arabinofuranosidase (up to fivefold), and beta-d-xylosidase (up to sevenfold) upon coculturing. The stimulating effect on fungal enzymes from coculturing with M. smithii was independent of the growth substrate, and the magnitude of the stimulation varied according to the enzymes and the incubation time. For an N. frontalis-M. smithii coculture, the positive stimulation was maintained during an extended (18-day) incubation period, and this affected not only hemicellulolytic enzymes but also polysaccharidase and glycoside hydrolase enzymes that were not involved in xylan breakdown. The specific activity of cell-bound endopeptidase was not increased under the coculture conditions used in this study. The higher enzyme activities in cocultures are discussed in relation to catabolite repression.