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Showing papers by "University of Oviedo published in 1998"


Journal ArticleDOI
TL;DR: The structural and thermodynamic properties of MgF2 have been investigated in a wide range of pressures and temperatures by coupling quantum-mechanical ab initio perturbed ion.
Abstract: The structural and thermodynamic properties of MgF2 have been investigated in a wide range of pressures (0−80 GPa) and temperatures (0−850 K) by coupling quantum-mechanical ab initio perturbed ion ...

395 citations


Journal ArticleDOI
TL;DR: Three strains of Lactobacillus, identified as L. acidophilus, L. gasseri, and L. jensenii, were selected from among 70 isolates from the vaginas of healthy premenopausal women for properties relevant to mucosal colonization or antagonism, and all self-aggregated and adhered to epithelial vaginal cells.
Abstract: Three strains of Lactobacillus, identified as Lactobacillus acidophilus, Lactobacillus gasseri, and Lactobacillus jensenii, were selected from among 70 isolates from the vaginas of healthy premenopausal women for properties relevant to mucosal colonization or antagonism. All three self-aggregated and adhered to epithelial vaginal cells, displacing well-known vaginal pathogens, such as G. vaginalis, and inhibiting the growth in vitro of Escherichia coli and Streptococcus agalactiae. The surface components involved in self-aggregation appeared to be proteins for L. gasseri and lipoproteins for L. acidophilus and L. jensenii, as judged by susceptibility to treatment with appropriate degrading enzymes. The factors responsible for adherence to epithelial vaginal cells seemed to be glycoproteins (L. acidophilus and L. gasseri) and carbohydrate (L. jensenii). The receptors of the vaginal cells were glycolipids, which presumably were the targets of the competition observed between the lactobacilli and the pathogenic microbes.

342 citations


Journal ArticleDOI
TL;DR: The lowest energy structures of nanoclusters were obtained by unconstrained dynamical and genetic-symbiotic optimization methods, using a Gupta $n$-body potential.
Abstract: The lowest energy structures of ${\mathrm{Au}}_{n}$ ( $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}38,55,75$) nanoclusters are obtained by unconstrained dynamical and genetic-symbiotic optimization methods, using a Gupta $n$-body potential. A set of amorphous structures, nearly degenerate in energy, are found as the most stable configurations. Some crystalline or quasicrystalline isomers are also minima of the cluster potential energy surface with similar energy. First principles calculations using density functional theory confirm these results and give different electronic properties for the ordered and disordered gold cluster isomers.

333 citations


Journal ArticleDOI
TL;DR: Melatonin increases gene expression for antioxidant enzymes in rat brain cortex in a manner similar to that found in humans, according to Munksgaard et al. (1998).
Abstract: During the last years several reports have demonstrated that melatonin is a efficient free radical scavenger and general antioxidant In addition, it has been shown that this neurohormone is able to increase the activity of glutathione peroxidase in rat brain cortex as well as the gene expression for some antioxidant enzymes in the Harderian gland of female Syrian hamster Also, it is well known that brain cells are particularly exposed to free radicals, with antioxidant enzymes as the major defense mechanism that the brain uses to neutralize reactive oxygen species The aim of the present study was to examine the influence of melatonin on gene expression for antioxidant enzymes in rat brain cortex Our results clearly demonstrate that exogenously administered melatonin increases the levels of mRNA for glutathione peroxidase, copper-zinc superoxide dismutase, and manganese superoxide dismutase in this tissue These stimulatory effects are observed after both acute and chronic treatment with this hormone, producing in the latter case the more marked increase We therefore conclude that melatonin exerts an important role in providing indirect protection against free radical injury by stimulating gene expression for antioxidant enzymes Consequently, melatonin could be considered as a potential therapeutic agent in some age-related neurodegenerative diseases where excessive free radical production has been implicated

314 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present predictions for the counts of extragalactic sources, the contributions to fluctuations and their angular power spectrum in each channel foreseen for the Planck Surveyor (formerly COBRAS/SAMBA) mission.
Abstract: We present predictions for the counts of extragalactic sources, the contributions to fluctuations and their angular power spectrum in each channel foreseen for the Planck Surveyor (formerly COBRAS/SAMBA) mission. The contribution to fluctuations owing to clustering of both radio and far-IR sources is found to be generally small in comparison with the Poisson term; however the relative importance of the clustering contribution increases and may eventually become dominant if sources are identified and subtracted down to faint flux limits. The central Planck frequency bands are expected to be ‘clean’: at high galactic latitude (|b| > 20°), where the reduced galactic noise does not prevent the detection of the extragalactic signal, only a tiny fraction of pixels is found to be contaminated by discrete extragalactic sources. Moreover, the ‘flat’ angular power spectrum of fluctuations resulting from extragalactic sources substantially differs from that of primordial fluctuations; therefore, the removal of contaminating signals is eased even at frequencies where point sources give a sizeable contribution to the foreground noise.

272 citations


Journal ArticleDOI
TL;DR: The data demonstrate that prudence should guide inferences about population structure and nucleotide divergence based on RAPD markers, and the nature of genetic variation uncovered by the RAPD method is unclear.
Abstract: Random amplified polymorphic DNA (RAPD) fragment reproducibility was assayed in three animal species: red deer (Cervus elaphus), wild boar (Sus scrofa) and fruit fly (Drosophila melanogaster). Ten 10-mer primers (Operon) were tested in two replicate reactions per individual under different stringency conditions (annealing temperatures of 35 degrees C or 45 degrees C). Two estimates were generated from the data: autosimilarity, which tests the reproducibility of overall banding patterns, and band repeatability, which tests the reproducibility of specific bands. Autosimilarity (the similarity of individuals with themselves) was lower than 1 for all three species ranging between values of 0.66 for Drosophila at 45 degrees C and 0.88 for wild boar at 35 degrees C. Band repeatability was estimated as the proportion of individuals showing homologous bands in both replicates. The fraction of repeatable bands was 23% for deer, 36% for boar and 26% for fruit fly, all at an annealing temperature of 35 degrees C. Raising the annealing temperature did not improve repeatability. Phage lambda DNA was subjected to amplification and the pattern of bands compared with theoretical expectations based on nucleotide sequence. Observed fragments could not be related to expected ones, even if a 2 bp mismatch is allowed. Therefore, the nature of genetic variation uncovered by the RAPD method is unclear. These data demonstrate that prudence should guide inferences about population structure and nucleotide divergence based on RAPD markers.

231 citations


Journal ArticleDOI
TL;DR: This study highlights the importance of knowing the carrier and removal status of canine coronavirus, as a source of infection for other animals, not necessarily belonging to the same breeds.
Abstract: I. Introduction II. Epidemiological Evidence Associating Breast and Prostate Cancer III. Incidence of Breast and Prostate Cancer in Different Countries: Dietary Factors IV. Genetic Abnormalities Common to Breast and Prostate Cancer A. AR alterations in prostate cancer B. AR alterations in breast cancer C. BRCA1 and BRCA2 alterations in breast cancer D. BRCA1 and BRCA2 alterations in prostate cancer E. Other genes associated with breast or prostate cancer V. Common Biochemical Features of Breast and Prostate Cancer A. Prostate-specific antigen (PSA) B. Apolipoprotein D (apoD) C. Zn-α2-gp D. Gross cystic disease fluid protein-15 E. Pepsinogen C F. Other proteins VI. Growth Factors in Breast and Prostate Cancer A. AIGF B. KGF VII. Theories of Breast and Prostate Cancer Development: Role of Steroid Hormones VIII. Conclusions

221 citations


Journal ArticleDOI
TL;DR: Analysis of the signal transduction mechanisms underlying the up-regulating effect of TGF-β1 on collagenase-3 expression demonstrated that this growth factor acts through a signaling pathway involving protein kinase C and tyrosine kinase activities.

202 citations


Journal ArticleDOI
TL;DR: It is proposed that the glycosyltransferases encoded by mtmGI and mtmGII are responsible for forming and transferring the disaccharide during mithramycin biosynthesis.
Abstract: Mithramycin is an antitumor polyketide drug produced by Streptomyces argillaceus that contains two deoxysugar chains, a disaccharide consisting of two d-olivoses and a trisaccharide consisting of a d-olivose, a d-oliose, and a d-mycarose. From a cosmid clone (cosAR3) which confers resistance to mithramycin in streptomycetes, a 3-kb PstI-XhoI fragment was sequenced, and two divergent genes (mtmGI and mtmGII) were identified. Comparison of the deduced products of both genes with proteins in databases showed similarities with glycosyltransferases and glucuronosyltransferases from different sources, including several glycosyltransferases involved in sugar transfer during antibiotic biosynthesis. Both genes were independently inactivated by gene replacement, and the mutants generated (M3G1 and M3G2) did not produce mithramycin. High-performance liquid chromatography analysis of ethyl acetate extracts of culture supernatants of both mutants showed the presence of several peaks with the characteristic spectra of mithramycin biosynthetic intermediates. Four compounds were isolated from both mutants by preparative high-performance liquid chromatography, and their structures were elucidated by physicochemical methods. The structures of these compounds were identical in both mutants, and the compounds are suggested to be glycosylated intermediates of mithramycin biosynthesis with different numbers of sugar moieties attached to C-12a-O of a tetracyclic mithramycin precursor and to C-2-O of mithramycinone: three tetracyclic intermediates containing one sugar (premithramycin A1), two sugars (premithramycin A2), or three sugars (premithramycin A3) and one tricyclic intermediate containing a trisaccharide chain (premithramycin A4). It is proposed that the glycosyltransferases encoded by mtmGI and mtmGII are responsible for forming and transferring the disaccharide during mithramycin biosynthesis. From the structures of the new metabolites, a new biosynthetic sequence regarding late steps of mithramycin biosynthesis can be suggested, a sequence which includes glycosyl transfer steps prior to the final shaping of the aglycone moiety of mithramycin.

192 citations


Journal ArticleDOI
TL;DR: A model is proposed integrating these and previously reported results for intracellular inactivation, secretion and extracellular reactivation of oleandomycin, with OleI being much more specific for ole fandomycin.
Abstract: A 5.2 kb region from the oleandomycin gene cluster in Streptomyces antibioticus located between the oleandomycin polyketide synthase gene and sugar biosynthetic genes was cloned. Sequence analysis revealed the presence of three open reading frames (designated oleI, oleN2 and oleR). The oleI gene product resembled glycosyltransferases involved in macrolide inactivation including the oleD product, a previously described glycosyltransferase from S. antibioticus. The oleN2 gene product showed similarities with different aminotransferases involved in the biosynthesis of 6-deoxyhexoses. The oleR gene product was similar to several glucosidases from different origins. The oleI, oleR and oleD genes were expressed in Streptomyces lividans. OleI and OleD intracellular proteins were partially purified by affinity chromatography in an UDP-glucuronic acid agarose column and OleR was detected as a major band from the culture supernatant. OleI and OleD showed oleandomycin glycosylating activity but they differ in the pattern of substrate specificity: OleI being much more specific for oleandomycin. OleR showed glycosidase activity converting glycosylated oleandomycin into active oleandomycin. A model is proposed integrating these and previously reported results for intracellular inactivation, secretion and extracellular reactivation of oleandomycin.

186 citations


Journal ArticleDOI
TL;DR: Concanavalin A treatment of SW1353 cells increased the amount of membrane-type-1 matrix metalloproteinase protein in the cell membranes, suggesting that this membrane-bound enzyme participates in an activation cascade involving collagenase 3 and the gelatinases.
Abstract: SW1353 chondrosarcoma cells cultured in the presence of interleukin-1, concanavalin A or PMA secreted procollagenase 3 (matrix metalloproteinase-13). The enzyme was detected in the culture medium by Western blotting using a specific polyclonal antibody raised against recombinant human procollagenase 3. Oncostatin M enhanced the interleukin-1-induced production of procollagenase 3, whereas interleukin-4 decreased procollagenase 3 synthesis. The enzyme was latent except when the cells had been treated with concanavalin A, when a processed form of 48 kDa, which corresponds to the active form, was found in the culture medium and collagenolytic activity was detected by degradation of 14C-labelled type I collagen. The concanavalin A-induced activation of procollagenase 3 coincided with the processing of progelatinase A (matrix metalloproteinase-2) by the cells, as measured by gelatin zymography. In addition, progelatinase B (matrix metalloproteinase-9) was activated when gelatinase A and collagenase 3 were in their active forms. Concanavalin A treatment of SW1353 cells increased the amount of membrane-type-1 matrix metalloproteinase protein in the cell membranes, suggesting that this membrane-bound enzyme participates in an activation cascade involving collagenase 3 and the gelatinases. This cascade was effectively inhibited by tissue inhibitors of metalloproteinases-2 and -3. Tissue inhibitor of metalloproteinases-1, which is a much weaker inhibitor of membrane-type 1 matrix metalloproteinase than tissue inhibitors of metalloproteinases-2 and -3 [Will, Atkinson, Butler, Smith and Murphy (1996) J. Biol. Chem. 271, 17119-17123], was a weaker inhibitor of the activation cascade.

Journal ArticleDOI
01 Nov 1998-Talanta
TL;DR: The different strategies for mercury species analysis in environmentally-related samples are reviewed and ranges of published detection limits achievable for such species determination by using hyphenated techniques between a chromatographic separation and a specific atomic detector are given.

Journal ArticleDOI
TL;DR: In this paper, the authors present a simulation model based on long-term field investigations on the western brown bear population in the Cordillera Cantabrica, including detailed life history data and information on environmental variations in food abundance.
Abstract: The status of the brown bear (Ursus arctos) in Spain has suffered a dramatic decline during the last centuries, both in area and numbers. Current relict populations are suspected to be under immediate risk of extinction. The aim of our model is to attain an understanding of the main processes and mechanisms determining population dynamics in the Cordillera Cantabrica. We compile the knowledge available about brown bears in the Cordillera Cantabrica, northern Spain, and perform a population viability analysis (PVA) to diagnose the current state of the population and to support current management. The specially constructed simulation model, based on long-term field investigations on the western brown bear population in the Cordillera Cantabrica, includes detailed life history data and information on environmental variations in food abundance. The method of individual-based modeling is employed to simulate the fate of individual bears. Reproduction, family breakup, and mortalities are modeled in annual time ...

Journal ArticleDOI
TL;DR: In this paper, the breaking of O/W emulsions of commercial soluble oils using CaCl 2 and AlCl 3 as coagulants is reported and the results show good agreement with the electric double layer theory and the Schulze-Hardy rule.

Journal ArticleDOI
TL;DR: In this article, the authors show how to classify singularities of vector fields up to codimension 4 for the notion of equivalence and show that a semianalytic stratification is not possible even for weak equivalence.
Abstract: In his well known paper `Singularities of vector fields', Takens made a topological classification of vector fields up to codimension 2 and introduced a semialgebraic stratification to distinguish the different cases; from dimensions he had to use the notion of `weak--equivalence'. In this paper we show how to classify singularities of vector fields on up to codimension 4 for the notion of equivalence. To separate the different cases we use a semianalytic stratification and show that a semialgebraic one is not possible, even for the notion of weak--equivalence. Up to codimension 3 the stratification is semialgebraic. We will always suppose that the vector fields are , although it will be clear that the results are valid for , with r sufficiently big. We provide a complete, but short, survey of the different techniques to be used, referring to the existing literature for precise calculations and pictures. We put much emphasis on the new results.

Journal Article
TL;DR: expression analysis of cathepsin L2 in human tumors revealed a widespread expression in colorectal and breast carcinomas but not in normal colon or mammary gland or in peritumoral tissues, opening the possibility that this novel enzyme may be involved in tumor processes, as already reported for other cysteine proteinases.
Abstract: We have identified and cloned a new member of the papain family of cysteine proteinases from a human brain cDNA library. The isolated cDNA codes for a polypeptide of 334 amino acids that exhibits all of the structural features characteristic of cysteine proteinases, including the active site cysteine residue essential for peptide hydrolysis. Pairwise comparisons of this amino acid sequence with the remaining human cysteine proteinases identified to date showed a high percentage of identity (78%) with cathepsin L; the percentage of identity with all other members of the family was much lower ( arin, which is commonly used as a substrate for cysteine proteinases. Cathepsin L2 proteolytic activity on this substrate was abolished by trans-epoxysuccinyl-l-leucylamido-(4-guanidino)butane, an inhibitor of cysteine proteinases, thus providing additional evidence that the isolated cDNA encodes a functional cysteine proteinase. Northern blot analysis of polyadenylated RNAs isolated from a variety of human tissues demonstrated that cathepsin L2 is predominantly expressed in the thymus and testis. This finding is in marked contrast with the wide tissue distribution of most cysteine proteinases characterized to date, including cathepsin L, and suggests that cathepsin L2 may play a specialized role in the thymus and testis. Expression analysis of cathepsin L2 in human tumors revealed a widespread expression in colorectal and breast carcinomas but not in normal colon or mammary gland or in peritumoral tissues. Cathepsin L2 was also expressed by colorectal and breast cancer cell lines as well as by some tumors of diverse origin, including ovarian and renal carcinomas. These results open the possibility that this novel enzyme may be involved in tumor processes, as already reported for other cysteine proteinases, including cathepsin L.

Journal ArticleDOI
TL;DR: Age-related secondary bilateral synchrony underlying ESES may be facilitated in multilobar polymicrogyria, and the good seizure outcome contrasts with that usually found in the presence of cortical malformations.
Abstract: Background and Objective: Patients with cortical malformations often have intractable seizures and are candidates for epilepsy surgery. Within an unselected series of patients with various forms of cortical malformation, nine patients with multilobar polymicrogyria had electrical status epilepticus during sleep (ESES) accompanied by infrequent focal motor seizures. Eight patients also had intractable atonic drop attack seizures. Because ESES usually is accompanied by a good long-term seizure prognosis, the objective of this study was to examine ESES outcome among patients with a structural lesion that is usually highly epileptogenic and has a low seizure remission trend. Methods: The nine patients had follow-up periods lasting 4 to 19 years. All underwent brain MRI, serial sleep EEG recordings, and cognitive testing during and after ESES. Results: ESES and drop attack seizures appeared between the ages of 2 and 5 years(mean, 4 years) and ceased between the ages of 5 and 12 years (mean, 8 years). At the last visit patients were 8 to 23 years of age (mean, 14.5 years) and were either seizure free or had very infrequent focal motor seizures during sleep. Three patients were free from antiepileptic drugs. In no patient was definite cognitive deterioration apparent after ESES in comparison with earlier evaluations. Conclusions: Age-related secondary bilateral synchrony underlying ESES may be facilitated in multilobar polymicrogyria. The good seizure outcome contrasts with that usually found in the presence of cortical malformations. For children with polymicrogyria and drop attack seizures, surgical treatment of the epilepsy should be considered cautiously, and sleep EEG recordings should be performed systematically.

Journal ArticleDOI
TL;DR: Melatonin is found to have a high clinical potential in the treatment of Parkinson's disease and possibly other neurodegenerative diseases, although more research on the mechanisms is yet to be done.
Abstract: It was recently reported that low doses of 6-hydroxydopamine (6-OHDA) induce apoptosis of naive (undifferentiated) and neuronal (differentiated) PC12 cells, and this system has been proposed as an adequate experimental model for the study of Parkinson's disease. The mechanism by which this neurotoxin damages cells is via the production of free radicals. Given that the neurohormone melatonin has been reported 1) to be a highly effective endogenous free radical scavenger, 2) to increase the mRNA levels and the activity of several antioxidant enzymes, and 3) to inhibit apoptosis in other tissues, we have studied the ability of melatonin to prevent the programmed cell death induced by 6-OHDA in PC12 cells. We found that melatonin prevents the apoptosis caused by 6-OHDA in naive and neuronal PC12 cells as estimated by 1) cell viability assays, 2) counting of the number of apoptotic cells, and 3) analysis and quantification of DNA fragmentation. Exploration of the mechanisms used by melatonin to reduce programmed cell death revealed that this chemical mediator prevents the 6-OHDA induced reduction of mRNAs for several antioxidant enzymes. The possibility that melatonin utilized additional mechanisms to prevent apoptosis of these cells is also discussed. Since this endogenous agent has no known side effects and readily crosses the blood-brain-barrier, we consider melatonin to have a high clinical potential in the treatment of Parkinson's disease and possibly other neurodegenerative diseases, although more research on the mechanisms is yet to be done.

Journal ArticleDOI
TL;DR: Cloned the murine homologue of human collagenase 2 and enzymatic analysis revealed that matrilysin, another MMP overexpressed in uterine tissue, is able to activate murine procollagenase 2, suggesting that both enzymes could form an activation cascade resulting in the generation of the collagenolytic activity required during the process of massive connective tissue resumption occurring in the involuting uterus.

Journal ArticleDOI
TL;DR: In this article, three different categories of analytical speciation of increasing analytical difficulty are proposed: computational approaches, direct species-specific and hybrid techniques, which are reviewed and critically assessed for biological materials.

Journal ArticleDOI
TL;DR: It is proposed that cathepsin Z may be the first representative of a novel subfamily of this class of proteolytic enzymes, including diverse peptide insertions and an unusual short propeptide, together with its unique chromosomal location among cysteine proteinases.

Journal ArticleDOI
TL;DR: The finding that bFGF was detected in all analyzed chondrosarcomas, together with the above in vitro studies on HCS-2/8 cells, suggest that this growth factor may be an in vivo modulator of collagenase-3 expression in these malignant tumors.
Abstract: Human collagenase-3 (MMP-13) is a member of the matrix metalloproteinase family of enzymes that was originally identified in breast carcinomas and subsequently detected during fetal ossification and in arthritic processes. In this work, we have found that collagenase-3 is produced by HCS-2/8 human chondrosarcoma cells. An analysis of the ability of different cytokines and growth factors to induce the expression of collagenase-3 in these cells revealed that basic fibroblast growth factor (bFGF or FGF-2) strongly up-regulated the expression of this gene. By contrast, other factors, including interleukin-1β and transforming growth factor-β, previously found to induce collagenase-3 expression in other cell types, did not exhibit any effect on the expression of this gene in chondrosarcoma cells. Further analysis of the bFGF-induced expression of collagenase-3 in human chondrosarcoma cells revealed that its effect was time and dose dependent, but independent of the de novo synthesis of proteins. Western blot analysis revealed that the up-regulatory effect of bFGF on collagenase-3 was also reflected at the protein level as demonstrated by the increase of immunoreactive protein in the conditioned medium of HCS-2/8 cells treated with bFGF. Immunohistochemical analysis of the presence of collagenase-3 in a series of 8 benign and 16 malignant cartilage-forming neoplasms revealed that all analyzed malignant chondrosarcomas stained positively for collagenase-3, whereas only 2 of 8 benign lesions produced this protease. In addition, the finding that bFGF was detected in all analyzed chondrosarcomas, together with the above in vitro studies on HCS-2/8 cells, suggest that this growth factor may be an in vivo modulator of collagenase-3 expression in these malignant tumors. These results extend the pattern of tumor types with ability to produce this matrix metalloproteinase and suggest that collagenase-3 up-regulation may contribute to the progression of human chondrosarcomas.

Journal ArticleDOI
TL;DR: In this article, a combined experimental and theoretical investigation on the stability and the volume behavior under hydrostatic pressure of the rocksalt $(B1)$ phase of ZnO is presented.
Abstract: We report the results of a combined experimental and theoretical investigation on the stability and the volume behavior under hydrostatic pressure of the rocksalt $(B1)$ phase of ZnO. Synchrotron-radiation x-ray powder-diffraction data are obtained from 0 to 30 GPa. Static simulations of the $\mathrm{ZnO} B1$ phase are performed using the ab initio perturbed ion method and the local and nonlocal approximations to the density-functional theory. After the pressure induced transition from the wurtzite phase, we have found that a large fraction of the $B1$ high-pressure phase is retained when pressure is released. The metastability of this ZnO polymorph is confirmed through the theoretical evaluation of the Hessian eigenvalues of a nine-parameter potential energy surface. This allows us to treat the experimental and theoretical pressure-volume data on an equal basis. In both cases, we have obtained values of the bulk modulus in the range of 160--194 GPa. For its zero-pressure first derivative, the experimental and theoretical data yield a value of $4.4\ifmmode\pm\else\textpm\fi{}1.0.$ Overall, our results show that the $\mathrm{ZnO} B1$ phase is slightly more compressible than previously reported.

Journal ArticleDOI
TL;DR: In this article, the mass transfer correlations have been obtained for the past eight decades by the Wilson-plot method which has proved to be suitable for systems operating in steady-state conditions and where the only variable is the fluid velocity.

Journal ArticleDOI
TL;DR: Sex ratio and sexual dimorphism in physiology and growth were studied in the dioecious tree Ilex aquifolium at two localities in northern Spain and efficiency of photosynthesis was significantly lower on fruiting branches of female plants than on nonfruiting branches.
Abstract: Sex ratio and sexual dimorphism in physiology and growth were studied in the dioecious tree Ilex aquifolium at two localities in northern Spain. Genet sex ratio was significantly male biased in one locality but not in the other. However, ramet and flowering ramet sex ratios were male biased at both study sites. Males had significantly thicker main trunks than females in one locality and produced more ramets in the other. Growth rate, estimated from mean width of annual rings, did not differ between localities, but males produced wider rings than females at both sites. Mean annual growth rates over the last 10, 20, and 30 yr were significantly higher for males. Measurements of chlorophyll fluorescence indicated that the efficiency of photosynthesis of leaves on nonfruiting branches of females was higher than for leaves on branches of male plants under low-light conditions, though not under saturating-light conditions. Efficiency of photosynthesis was significantly lower on fruiting branches of female plants than on nonfruiting branches. We discuss whether the observed between-sex differences are attributable to the higher cost of reproduction in females and/or to pollen competition.

Journal ArticleDOI
TL;DR: Examination of invertase activity in wild‐type and mutant cells expressing a truncated version of the HXk2 protein unable to enter the nucleus shows that a nuclear localisation of Hxk2 is necessary for glucose repression signalling of the SUC2 gene.

Journal ArticleDOI
TL;DR: Several cinoxacin (HCx) complexes with divalent metal ions have been prepared and characterized by spectroscopic techniques, showing activity similar to that of cinxacin.

Journal ArticleDOI
30 Sep 1998-Virology
TL;DR: It is concluded that transgenic plants expressing glycoprotein S polypeptides may possibly be used as a source of recombinant antigen for vaccine production.

Journal ArticleDOI
TL;DR: It is described here that the HXK2 gene product, isoenzyme PII of hexokinase, is located in both the nucleus and the cytoplasm of Saccharomyces cerevisiae cells.

01 Jan 1998
TL;DR: In this paper, the requirements of dynamically providing maximum torque under field-weakening operation were analyzed and three major issues are addressed: current regulator design, saturation techniques for current regulators, and flux regulator design to minimize transient errors when varying flux.
Abstract: Field-weakening techniques have been developed which provide maximum torque capability above rated speed. Un- fortunately, most of these techniques are valid only for steady-state operation and show significant sensitivity to dc-bus voltage and machine parameters. This paper analyzes the requirements of dynamically providing maximum torque under field-weakening operation. Three major issues are addressed: current regulator design, saturation techniques for current regulators in order to ensure best performance under voltage constraints, and flux regulator design to minimize transient errors when varying flux. Maximum dc-bus utilization through the proper use of saturation techniques, dynamic response, and reduced sensitivity are the advantages of the proposed solution.