Marriage and the parenting alliance: longitudinal prediction of change in parenting perceptions and behaviors

The study evaluates how marriage and the parenting alliance affect parenting experiences over time. Couples (N = 79) with school-age children who have mental retardation completed self-report and observational measures of marriage, the parenting alliance, and parenting attitudes and behaviors at 2 periods, 18-24 months apart. Longitudinal structural equation modeling demonstrated significant effects of marital quality on changes over time in self-reports of perceived parenting competence for both the mothers and the fathers, and in observed negative mother-child interactions. Also, in all cases, the parenting alliance mediated the effects of marriage on parenting experiences. There was little evidence of reciprocal causation in which parenting variables predicted change in the quality of marriage and the parenting alliance. Interactions involving child age suggested that teenagers as opposed to younger children were more reactive to negative features of their parents' marital functioning and parenting alliance. Implications are discussed regarding stable but negative marital functioning and regarding possible differences in mothers' and fathers' parenting in the context of marital distress.     

Computerized tomographic assessment of the composition of gallstones

We present the results of an in vitro study of biliary lithiasis (n = 106) with computerized tomography (CT). We analyzed the correlation between composition of gallstones (crystallographic analysis of thin sections and atomic absorption spectrophotometric analysis of total calcium content) with CT patterns (densitometry) and their corresponding attenuations. Six main CT patterns were distinguished: hypodense (homogeneous and heterogeneous), dense, homogeneous hyperdense, ringed hyperdense and irregular hyperdense. Statistically significant differences (p < 0.05) were found between attenuations for cholesterol (mixed and pure) and pigmentary stones. We found a good inverse correlation between attenuations and cholesterol content; the contents of pigment, inorganic calcic salts and total calcium content also showed significant direct correlations (p < or = 0.01). Of the samples classified as pure cholesterol type stones, 86.4% showed hypodense patterns, and the remaining 13.6% showed irregular hyperdense patterns. Of the pigmentary stones, 80% showed homogeneous hyperdense images. All stones that contained more than 3% calcium produced hyperdense patterns, whereas 72.4% of the stones that contained less calcium produced hypodense images. Tomodensitometric measurements provided more information than simple radiography, and made it possible to distinguish a greater variety of gallstone types based on structural complexity.     

Evidence that the mediobasal hypothalamus is the primary site of action of estradiol in inducing the preovulatory gonadotropin releasing hormone surge in the ewe

Although a neural site of action for estradiol in inducing a LH surge via a surge of GnRH is now well established in sheep, the precise target(s) for estrogen within the brain is unknown. To address this issue, two experiments were conducted during the breeding season using an artificial model of the follicular phase. In the first experiment, bilateral 17beta-estradiol microimplants were positioned in either the medial preoptic area (MPOA) or the mediobasal hypothalamus (MBH), and LH secretion was monitored. An initial negative feedback inhibition of LH secretion was observed in ewes that had estradiol microimplants located in the MPOA (6 of 6 ewes) or caudal MBH in the vicinity of the arcuate nucleus (4 of 4). In contrast, a normal LH surge was only found in animals bearing estradiol microimplants in the MBH (5 of 10). Detailed analysis of estradiol microimplant location with respect to the estrogen receptor-alpha-immunoreactive cells of the hypothalamus revealed that 4 of the 5 ewes exhibiting a LH surge had microimplants located bilaterally within or adjacent to the area of estrogen receptor-expressing cells of the ventromedial nucleus. Two of these ewes exhibited a LH surge without showing any form of estrogen negative feedback. In the second experiment, we used the technique of hypophyseal portal blood collection to monitor GnRH secretion directly at the time of the LH surge induced by estradiol delivered either centrally or peripherally. Central estradiol implants induced the GnRH surge. The duration and mean plasma concentration of GnRH during the surge were not different between animals given peripheral or central MBH estradiol implants. Cholesterol-filled MBH microimplants did not evoke a GnRH surge. We conclude that the ventromedial nucleus is the primary site of action for estradiol in stimulating the preovulatory GnRH surge of the ewe, whereas the MPOA and possibly the caudal MBH are sites at which estrogen can act to inhibit LH secretion. These data provide evidence for the sites within the ovine hypothalamus responsible for mediating the bimodal influence of estradiol on GnRH secretion and suggest that different, and possibly independent, neuronal cell populations are responsible for the negative and positive feedback actions of estradiol.     

Interaction of the two proteins of the methoxylation system involved in cephamycin C biosynthesis. Immunoaffinity, protein cross-linking, and fluorescence spectroscopy studies

Cephamycin C-producing microorganisms contain a two-protein enzyme system that converts cephalosporins to 7-methoxycephalosporins. Interaction between the two component proteins P7 (Mr 27,000) and P8 (Mr 32,000) has been studied by immunoaffinity chromatography using anti-P7 and anti-P8 antibodies, cross-linking with glutaraldehyde, and fluorescence spectroscopy analysis. Co-renaturation of the P7 and P8 polypeptides resulted in the formation of a protein complex with a molecular mass of 59 kDa, which corresponds to a heterodimer of P7 and P8. Glutaraldehyde cross-linking of the polypeptides after assembly of the protein complex showed the presence of a single heterodimer form that reacted with antibodies against P7 and P8. Each separate protein did not associate with itself into multimers. The P7.P8 complex co-purified by immunoaffinity chromatography from extracts of Nocardia lactamdurans and Streptomyces clavuligerus, suggesting that both proteins are present as an aggregate in vivo. Fluorescence spectroscopy studies of 5-methylaminonaphthalene-1-sulfonyl-P7 in response to increasing concentrations of P8 showed a blue shift in the fluorophore emission, indicating a conformational change of P7 in response to the interaction of P8 with an apparent dissociation constant of 47 microM. NADH showed affinity for the P7 component. The P7.P8 complex interacted strongly with the substrates S-adenosylmethionine and cephalosporin C, differently from that occurring with the separate P7 or P8 components, resulting in a strong blue shift in the fluorescence emission spectra of the complex.     

Reproducibility of fluorine-18-6-fluorodopa positron emission tomography in normal human subjects

We calculated the mean energy required to produce an ion pair (W) in methane-, propane- and butane-based tissue-equivalent (TE) gas mixtures from W values in pure constituent gases according to various models for energy partition among gas components. We found an agreement between the experimental and calculated W values in the methane-based TE gas regardless of the model concept. In contrast, only those models which take into account differences in the stopping powers, total ionization cross sections and model constants of gas components give acceptable results for the propane-based TE gas. The calculated W value for high-energy electrons in the isobutane-based TE gas mixture is 25.2 eV for high-energy electrons and 28.0 eV for approximately 5 MeV alpha particles.     

Fabrication of low defect density 3C-SiC on SiO2 structures using wafer bonding techniques

This paper reports on a process to fabricate single-crystal 3C-SiC on SiO₂ structures using a wafer bonding technique. The process uses the bonding of two polished polysilicon surfaces as a means to transfer a heteroepitaxial 3C-SiC film grown on a Si wafer to a thermally oxidized Si wafer. Transfer yields of up to 80% for 4 inch diameter 3C-SiC films have been achieved. Homoepitaxial 3C-SiC films grown on the 3C-SiC on SiO₂ structures have a much lower defect density than conventional 3C-SiC on Si films.     

Apomorphine modifies the visual responses of cells in the rabbit's lateral geniculate nucleus

It has been shown that enhancing or reducing dopaminergic activity in the retina modifies the balance between center and surround responses of retinal neurons such as ganglion cells. We investigated how these changes are reflected in the dorsal lateral geniculate nucleus (dLGN) by studying the effects of injections of apomorphine, a mixed D1 and D2 agonist of dopamine, on the visual responses of geniculate cells. Experiments were carried out on anesthetized adult pigmented rabbits. A varnished tungsten microelectrode was used to record single-unit activity in the dLGN. The flash electroretinogram was also recorded to monitor retinal changes and to confirm the success of the injections. Apomorphine was injected intravitreally or intravenously. The results can be summarized as follows. Apomorphine decreased the amplitude of the b-wave of the electroretinogram. For most dLGN cells, apomorphine produced a strong reduction in response amplitude evoked by sine-wave grating stimuli, presented at various spatial frequencies. Responses to flashing spots were also reduced but to a much lesser extent than those to gratings. In addition, the balance between the responses to small and large spots changed in favor of large stimuli. Consequently, after injection of apomorphine, the geniculate cells were preferentially activated by large-sized flashing stimuli. These data suggest that apomorphine can reduce the spatial contrast sensitivity of cells in the dLGN. This effect could be mediated by the reduction of the strength of lateral inhibition at the retinal level.