Notes: Three kinds of coherent phonons (0.30, 1.90, and 3.75 THz) have been observed in silver nanoparticles embedded in BaO thin films by means of the femtosecond time-resolved pump-probe technique. The generation of 0.3 THz coherent phonons is attributed to the resonant excitation of localized surface plasmon of silver nanopaticles, and the resonant impulsive stimulated Raman scattering in silver aggregates is responsible for the generation of 1.90 and 3.75 THz coherent phonons. © 1999 American Institute of Physics.

Notes: The binding energies and configurations for single Si adatoms on the Si(100) surface are investigated theoretically. Detailed comparisons between previously published and new calculations using classical potentials, semiempirical formulations, and density functional theory (DFT) are made. The DFT calculations used both the plane-wave-pseudopotential approach in a periodic slab geometry and the Gaussian-orbital based all-electron approach employing cluster geometries. In the local-density approximation excellent agreement between the cluster and slab results was obtained. Inclusion of gradient corrections to the exchange-correlation energy significantly improves absolute binding energies and changes relative energies by as much as 0.3–0.5 eV depending on the particular exchange-correlation functional used. Binding energies and relative energies obtained using the classical potentials disagree with the gradient corrected DFT energies at about the 0.6–0.9 eV level, and most find qualitatively different local minima from those found in the DFT calculations. The semiempirical approaches give results intermediate in quality between those of the classical potentials and the ab initio calculations. Analysis of the energies and binding site geometries provides insight into the shortcomings of some of the classical potentials. © 1995 American Institute of Physics.

Notes: Reproductive aging in the Brown Norway rat occurs because of testicular as well as hypothalamic-pituitary dysfunction. Excitatory amino acids (EAA) participate in the regulation of pulsatile secretion of hypothalamic GnRH and pituitary LH. In the present study, we studied the EAA-GnRH-LH axis for possible age-related alterations in prepubertal (35 days), young (3–4 months), middle-aged (12–13 months) and old (21–23 months) rats. In the first experiment, an intra-atrial cannula was implanted in rats of different ages to evaluate the pituitary response to small, physiological intravenous bolus administration of GnRH (0.5 or 1.0 nmol/100 g body weight). The results showed no age-related significant differences in in-vivo serum LH or FSH responsiveness to GnRH. In a second experiment, blood samples for the gonadotropins were withdrawn immediately before and 10 min after an iv injection of the glutamate receptor agonist N-methyl- d-aspartate (NMDA; 5 mg/kg, a dose that induces a physiological LH pulse in young rats). Administration of NMDA induced significant increases in LH and prolactin in all groups of animals (P〈0.05) and a significant FSH response in young and middle-aged but not old rats. NMDA-induced LH, FSH and prolactin release was higher (P〈0.05) in prepubertal rats than in all other age groups. Compared with young rats, NMDA-induced increase in plasma LH and prolactin was lower (P〈0.05) in old rats. In the third experiment, to ascertain whether this reduced LH response to NMDA in old rats was exerted at the hypothalamic level, the effects of NMDA on GnRH release in vitro from preoptic area-medial basal hypothalamus (POA-MBH) fragments were compared among rats of different ages. GnRH efflux in response to NMDA was significantly attenuated with increasing age. GnRH release in vitro was higher in prepubertal and lower in old than in young rats (P〈0.05). Lastly, we measured amino acid concentrations in hypothalamic tissue (POA-MBH fragments). Prepubertal rats had higher levels of glutamate and taurine than young rats. Significant reductions in glutamate and γ-aminobutyric acid (GABA) levels were found in old compared to young rats. In conclusion, these results showed that the hypothalamic NMDA-GnRH-LH axis was altered in old rats. The decreased hypothalamic content of some of the EAA and the reduced responsiveness of GnRH neurons to NMDA (both in vivo and in vitro) may contribute to an altered LH pulsatile secretion observed in old rats.

Notes: The acid invertase (β-fructosidase, EC 3·2·1·26) was localized at subcellular level via immunogold electron microscopy in the phloem-unloading zone of developing apple fruit. The enzyme (immunogold particles) was found to reside predominantly in the cell walls of the sieve element/companion cell (SE/CC) complex, phloem parenchyma cells and other parenchyma cells. There was almost no gold particle found in cytoplasm and vacuole. This distribution pattern remained unchanged throughout the growing season, but the enzyme numbers varied. The density of immunogold particles increased during fruit development. The immunoblotting of soluble and insoluble acid invertases provided a supporting proof for the assays of immunolocalization. The biochemical analysis showed a predominantly cell-wall-distributed activity of acid invertase that corresponds essentially with its amount distribution. The ultrastructural observations showed that there were numerous plasmodesmata between the parenchyma cells, but almost no plasmodesmium between the SE/CC complex and its surrounding parenchyma cells, practically resulting in the symplasmic isolation of the SE/CC complex. It is therefore suggested that the unloading pathway of sucrose from the SE/CC complex may be predominantly apoplasmic in the developing apple fruit, and that the unloaded sucrose may be hydrolysed by the functional acid invertase localized in the cell wall before it is loaded in sink cells.

Notes: The size at maturity in many male poeciliid fish is believed to be controlled by ‘social control mechanism’, and post-maturation growth is insignificant. In the Clear Creek gambusia, Gambusia heterochir. post-maturation growth in male fish is limited. Male G. heterochir matures at a fixed size, and age of maturation is dependent on environmental factors (e.g. temperature). In the presence of an adult male, the maturation size of a young male is largely determined by genetic factors rather than ‘social control’ factors. A male can switch its status as a ‘dominant’ or ‘subordinate’ male, depending on the relative size of rival males in mating competition. Mating success of a large (dominant) male reduces as the number of competing small (subordinate) males increases. These unique reproductive tactics may explain in part why ‘social control mechanism’ does not play a key role in determining the maturation size of male G. heterochir.

Notes: : Natural vitamin E was extracted by supercritical fluid extraction of carbon dioxide (SFE-CO2) from wheat germ. Several SFE-CO2 parameters, such as extracting pressure, extracting temperature, and flow rate of carbon dioxide were examined as the independent variables of central composite rotate design (CCRD). Through the response surface methodology (RSM), the optimal processing conditions were determined and the quadratic response surfaces were drawn from the mathematical models. The results demonstrated that the extracting pressure, temperature, pressure × temperature interaction, and flow rate of CO2 significantly affected the yield of the natural Vitamin E's extraction, while two interactions containing the flow rate of CO2 had no significant effect on the yield of natural vitamin E. The optimal processing conditions of the extraction of natural vitamin E in wheat germ by SFE-CO2 were: extracting pressure 5000 PSI, extracting temperature 316 K, and flow rate of carbon dioxide 1.7 ml/min. Optimum value predicted by RSM for the concentration of natural vitamin E was 2307 mg/100g. Close agreement between experimental and predicted values was obtained.

Notes: Pedunculated peritoneal surface polyps in pseudomyxoma peritonei syndrome Aims: Pseudomyxoma peritonei syndrome is a rare disease that originates from an adenomatous lesion of the appendix that, from pressure, perforates to gain access to the free peritoneal cavity. The relative sparing of the small bowel surfaces allows for complete cytoreduction even though many kilograms of mucinous tumour exist at other sites within the abdomen and pelvis. The purpose of this study was to examine the mechanism whereby the small bowel remains free of gross tumour and peritoneal surface polyps form. Methods and results: Peritoneal surface polyps were harvested and examined grossly and histologically. A hypothesis for their formation on small bowel and small bowel mesentery was proposed. Polyps are known to be associated with repeated motion of enteric contents moving past adenomatous tissue so that, over time, an elongated stalk is created. We have repeatedly observed pedunculated polyps on the peritoneal surface of the small bowel in patients with pseudomyxoma peritonei syndrome. No other site within the peritoneal cavity has had a pseudomyxoma polyp located upon its surface. Conclusions: The peristaltic motion of the small bowel causes adherent adenomatous tissue to develop a stalk on the peritoneal surface. Motion not only creates polypoid lesions but also repeatedly clears mucinous tumour cells from the small bowel surface. With pseudomyxoma peritonei and with other types of cancerous dissemination, prevention of adherence by motion may interfere with the implantation of malignant cells.

Notes: [Auszug] The technique of conversion provides several advantages for gene mapping projects of complex diseases such as cancer. The approach takes advantage of selective retention of a subset of human chromosomes within somatic cell hybrids, isolating single copies of all desired human chromosome pairs. This ...

Notes: [Auszug] Conversion provides several advantages for gene mapping projects of complex diseases such as cancer. The approach takes advantage of selective retention of a subset of human chromosomes within somatic cell hybrids, isolating single copies of all desired human chromosome pairs. This strategy ...