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Biomedical subjects

R Gross

Publications and source records attributed to R Gross.

At least 19 recordsLinked to original sources
PubMed2006

Laser microscopy of tunneling magnetoresistance in manganite grain-boundary junctions.

Using low-temperature scanning laser microscopy we directly image electric transport in a magnetoresistive element, a manganite thin film intersected by a grain boundary (GB). Imaging at variable temperature allows reconstruction and comparison of the local resistance versus temperature for both the manganite film and the GB. Imaging at low temperature also shows that the GB switches between different resistive states due to the formation and growth of magnetic domains along the GB. We observe different types of domain wall growth; in most cases a domain wall nucleates at one edge of the bridge and then proceeds towards the other edge.

Journal Article↗
PubMed2006

Patient information on cognitive symptoms in multiple sclerosis - acceptability in relation to disease duration.

OBJECTIVE: Recently, regular cognitive screening assessments have been advised in multiple sclerosis (MS). No studies have been carried out yet on the acceptability of information on cognitive deficits among MS patients. MATERIALS AND METHODS: Translation of an information booklet developed by a working group of European MS Rehabilitation Centers. Distribution of the booklet among 133 MS patients of two rehabilitation units and one outpatient clinic together with a one-page questionnaire. RESULTS: The booklet was highly understandable and rated to give moderate new information. Overall, the brochure was perceived as encouraging but significantly less so (P = 0.014) in recently diagnosed patients. Patients with subjectively perceived deficits considered the brochure to be significantly more relevant (P = 0.002). CONCLUSION: Information on cognitive deficits does not increase fears even in recently diagnosed MS patients. Patients with perceived deficits found the information more relevant than others and also less familiar. Thus, it seems appropriate to offer information about cognitive impairments to MS patients.

Adult↗
PubMed2005

Autonomic function after botulinum toxin type A or B: a double-blind, randomized trial.

To compare autonomic effects of botulinum toxin (BTX), we randomized patients with cervical dystonia to receive either BTX-A or BTX-B in a double-blind manner. Efficacy and physiologic questionnaire measures of autonomic function were assessed at baseline and 2 weeks after injection. Patients treated with BTX-B had less saliva production (p < 0.01) and greater severity of constipation (p = 0.037) than those treated with BTX-A, but did not differ in other tests of autonomic functions.

Adolescent↗
PubMed2005

Medication refill logistics and refill adherence in HIV.

PURPOSE: Strict adherence to antiretroviral therapy is instrumental in viral suppression and treatment success. The relation between pharmacy-based factors and treatment adherence has been under-explored. We aimed to determine whether different medication refill mechanisms were associated with differences in antiretroviral refill adherence. METHODS: We conducted a retrospective cohort study of 110 HIV-infected subjects on standard antiretroviral regimens for >or=3 months cared for at the Philadelphia Veterans' Affairs Medical Center HIV clinic. The primary outcome was a pharmacy-based measure of antiretroviral refill adherence over the 3 months of treatment immediately prior to the study date. RESULTS: The group obtaining refills at the pharmacy had lower adherence [80% (interquartile range (IQR), 69-99%)] than the group obtaining refills via pill organizers dispensed by a pharmacist [99% (IQR, 97-100%), p=0.003] and the group obtaining refills via mail order [91% (IQR, 79-100%); p=0.04]. CONCLUSIONS: Mail ordering and pharmacists dispensing refills in pill organizers may each be effective strategies for improving medication adherence, although they target different barriers and differ in their degree of intensity. Each should be considered for adherence interventions in HIV and further studied in other disease and treatment settings.

Adult↗
PubMed2005

Extensive immigration from compensatory hatchery releases into wild Atlantic salmon population in the Baltic sea: spatio-temporal analysis over 18 years.

Genetic homogenization has been recognized as a serious threat in an increasing number of species, including many salmonid fishes. We assessed the rate and impact of immigration from the main hatchery stocks of Atlantic salmon in the Gulf of Bothnia into one of the largest wild salmon populations in the Baltic Sea, the River Vindelälven, within a temporal framework of 18 years (from 1985-2003). We provide genetic evidence based on mtDNA and microsatellite markers, using mixed-stock analysis, that a large proportion (66%) of fin-damaged spawners (n=181) caught in the Ume/Vindelälven during 1997-2003 originated from the hatcheries in the Rivers Angermanälven, Luleälven and Ljusnan. The maximum-likelihood estimate of immigration rate from these hatcheries into the wild Vindelälven population was 0.068 (95% CI 0.021-0.128) over the studied time period (1985-2003) and reached up to a quarter (m=0.249, 95% CI 0.106-0.419) of the total population during 1993-2000. This resulted in significant (P<0.01) genetic homogenization trend between the wild Vindelälven population and hatchery stocks of the Angermanälven and Luleälven. Our results demonstrate extensive straying from geographically distant hatchery releases into wild salmon population and emphasize the genetic risks associated with current large-scale stocking practices in the Baltic Sea.

Animals↗
PubMed2005

Mitochondrial and nuclear DNA phylogeography of European grayling (Thymallus thymallus): evidence for secondary contact zones in central Europe.

Mitochondrial and microsatellite DNA markers were applied to infer the phylogeography, intraspecific diversity and dynamics of the distributional history of European grayling (Thymallus thymallus) with focus on its central and northern European distribution range. Phylogenetic and nested clade analyses revealed at least four major mtDNA lineages, which evolved in geographical isolation during the Pleistocene. These lineages should be recognized as the basic evolutionary significant units (ESUs) for grayling in central and northern Europe. In addition, and in contrast to previous work on grayling, the results of Bayesian analysis of individual admixture coefficients, two-dimensional scaling analysis and spatial analysis of molecular variance provided evidence for a high level of admixture among major lineages in contact zones between drainages (e.g. the low mountain range of Germany), most likely resulting from glacial perturbations and ancient river connections between drainages during the Pleistocene glaciations. Even within river systems, a high level of differentiation among populations was revealed as indicated by the microsatellite data. Grayling sampled from 29 sites displayed high levels of differentiation (overall F(ST) = 0.367), a high number of private alleles and high bootstrap support for the genetic distance-based population clusters across 12 loci. We specifically discuss our results in context of phylogeograpic studies on other European freshwater fish species with habitat preferences similar to those of grayling. Our study shows that both large-scale phylogeographical and detailed genetic analyses on a fine scale are mandatory for developing appropriate conservation guidelines of endangered species.

Animals↗
PubMed2004

Alteration of beta-cell constitutive NO synthase activity is involved in the abnormal insulin response to arginine in a new rat model of type 2 diabetes.

We have previously obtained a new type 2 diabetic syndrome in adult rats given streptozotocin and nicotinamide, characterized by reduced beta-cell mass, partially preserved insulin response to glucose and tolbutamide and excessive responsiveness to arginine. We have also established that the neuronal isoform of constitutive NO synthase (nNOS) is expressed in beta-cells and modulates insulin secretion. In this study, we explored the kinetics of glucose- and arginine-stimulated insulin release in perifused isolated islets as well as the effect of N-omega-nitro-L-arginine methyl ester (L-NAME), a NOS inhibitor, to get insight into the possible mechanisms responsible for the arginine hypersensitivity observed in vitro in this and other models of type 2 diabetes. A reduced first phase and a blunted second phase of insulin secretion were observed upon glucose stimulation of diabetic islets, confirming previous data in the isolated perfused rat pancreas. Exposure of diabetic islets to 10 mM arginine, in the presence of 2.8 mM glucose, elicited a remarkable monophasic increment in insulin release, which peaked at 639 +/- 31 pg/islet/min as compared to 49 +/- 18 pg/islet/min in control islets (P << 0.01). The addition of L-NAME to control islets markedly enhanced the insulin response to arginine, as expected from the documented inhibitory effect exerted by nNOS activity in normal beta-cells, whereas it did not further modify the insulin secretion in diabetic islets, thus implying the occurrence of a defective nNOS activity in these islets. A reduced expression of nNOS mRNA was found in the majority but not in all diabetic islet preparations and therefore cannot totally account for the absence of L-NAME effect, that might also be ascribed to post-transcriptional mechanisms impairing nNOS catalytic activity. In conclusion, our results provide for the first time evidence that functional abnormalities of type 2 experimental diabetes, such as the insulin hyper-responsiveness to arginine, could be due to an impairment of nNOS expression and/or activity in beta-cells.

Animals↗
PubMed2004

The role of group C and group G streptococci in acute pharyngitis in children.

Group C streptococci (GCS) and group G beta-haemolytic streptococci (GGS) have caused well-documented epidemics of acute pharyngitis in children, but the importance of these organisms in causing endemic or sporadic pharyngitis is uncertain. The heterogeneity of GCS and GGS may obscure the role of certain subtypes, such as the large-colony-forming strains of group C (Streptococcus dysgalactiae subsp. equisimilis) or group G, in endemic pharyngitis. For a 1-year period, children (aged 6 months to 18 years) (n = 2085) who presented with pharyngitis to the children's hospital emergency department and two outpatient offices were enrolled in a cross-sectional study to ascertain the role of large-colony-forming GCS and GGS in acute pharyngitis. Control patients (n = 194) were children who presented to the same locations during the same time period with non-respiratory tract symptoms or to the orthopaedic cast clinic. Throat cultures were obtained by a standard reference method, and swabs were plated on Strep-Selective Agar. Lancefield grouping and species identification was performed on all beta-haemolytic isolates. In total, 65 (3%) large-colony-forming GCS and GGS strains were obtained from pharyngitis patients, and three (1.5%) were obtained from the control group (odds ratio 2.0; 95% confidence interval 0.6-6.1). The low isolation rate of large-colony-forming strains of GCS and GGS indicates that even if these organisms are associated with acute, sporadic pharyngitis in paediatric patients, they represent an unusual pathogen.

Acute Disease↗
PubMed2004

P2Y purinergic potentiation of glucose-induced insulin secretion and pancreatic beta-cell metabolism.

Purine nucleotides and their analogs increase insulin secretion through activation of pancreatic beta-cell P2Y receptors. The present study aimed at determining the role of glucose metabolism in the response to P2Y agonists and whether ATP-activated K+ channels (KATP channels) are involved in this response. The experiments were performed in the rat isolated pancreas, perfused with a Krebs-bicarbonate buffer supplemented with 2 g/l bovine serum albumin under dynamic glucose conditions from 5 mmol/l baseline to 11 mmol/l. ADPbetaS (0.5 micromol/l) was selected as a stable and selective P2Y agonist. This compound, ineffective on the 5 mmol/l glucose background, induced a significant threefold increase in insulin release triggered by the glucose challenge. The effect of ADPbetaS was markedly reduced (P <0.001) in the presence of an inhibitor of glucose metabolism. In addition to glucose, the ADP analog also amplified the beta-cell insulin response to 15 mmol/l methyl pyruvate (P <0.05), but it was ineffective on the insulin response to 2.5 mmol/l methyl succinate. A nonmetabolic stimulus was applied using tolbutamide (185 micromol/l). Insulin secretion induced by the KATP channel blocker was strongly reinforced by ADPbetaS (P <0.001), which prompted us to check a possible interplay of KATP channels in the effect of ADPbetaS. In the presence of diazoxide 250 micromol/l and 21 mmol/l KCl, ADPbetaS still amplified the second phase of glucose-induced insulin secretion (P <0.001). We conclude that P2Y receptor activation is able to promote insulin secretion through a mechanism, involving beta-cell metabolism and a rise in intracellular calcium; this effect does not result from a direct inhibitory effect on KATP channels.

Adenosine Diphosphate↗
PubMed2003

A hidden pseudogap under the 'dome' of superconductivity in electron-doped high-temperature superconductors.

The ground state of superconductors is characterized by the long-range order of condensed Cooper pairs: this is the only order present in conventional superconductors. The high-transition-temperature (high-T(c)) superconductors, in contrast, exhibit more complex phase behaviour, which might indicate the presence of other competing ground states. For example, the pseudogap--a suppression of the accessible electronic states at the Fermi level in the normal state of high-T(c) superconductors-has been interpreted as either a precursor to superconductivity or as tracer of a nearby ground state that can be separated from the superconducting state by a quantum critical point. Here we report the existence of a second order parameter hidden within the superconducting phase of the underdoped (electron-doped) high-T(c) superconductor Pr2-xCe(x)CuO4-y and the newly synthesized electron-doped material La2-xCe(x)CuO4-y (ref. 8). The existence of a pseudogap when superconductivity is suppressed excludes precursor superconductivity as its origin. Our observation is consistent with the presence of a (quantum) phase transition at T = 0, which may be a key to understanding high-T(c) superconductivity. This supports the picture that the physics of high-T(c) superconductors is determined by the interplay between competing and coexisting ground states.

Journal Article↗
PubMed2003

Mood changes with deep brain stimulation of STN and GPi: results of a pilot study.

The results of this study suggest that there are mood changes associated with deep brain stimulation of the subthalamic nucleus (STN) and the globus pallidus interna (GPi). Further, optimal placement of electrodes in both STN and GPi seems to result in overall improvement in mood and is associated with a lower incidence of adverse mood effects than stimulation outside the optimal site. Preliminary data from this study, however, suggest that slight movement dorsal or ventral to the site of optimal motor performance may be associated with more adverse changes in mood with STN stimulation than with GPi stimulation.

Aged↗
PubMed2002

Identification and genomic organization of gene loci negatively controlled by the virulence regulatory BvgAS two-component system in Bordetella bronchiseptica.

The two-component system BvgAS positively controls transcription of the virulence genes of Bordetella pertussis and B. bronchiseptica, which include several genes for toxins and adhesins. On the other hand, the BvgAS system negatively controls the expression of a poorly characterized set of genes, the so-called virulence repressed ( vrg) genes. To investigate the function of this group of genes and their relationship to virulence, we identified several novel vrg genes of B. bronchiseptica via the generation of transcriptional fusions with gfp (the ORF encoding Green Fluorescent Protein) by transposon mutagenesis. Expression of all of the vrg genes was enhanced under phenotype-modulating growth conditions and in phase variants, demonstrating that their transcription is indeed controlled by the BvgAS system. In addition, transcription of most of these new vrg genes was found to be affected by the growth phase of the bacteria, with maximal expression being observed in the late logarithmic or stationary phase. The majority of these genes encode putative metabolic functions involved in redox reactions and amino acid transport. Interestingly, several vrg genes of B. bronchiseptica are not expressed or have been lost in B. pertussis, indicating that, possibly as a consequence of its adaptation to a single host organism, many vrg genes of B. pertussis are gradually decaying.

Animals↗
PubMed2002

Determinants of weight and length of Indonesian neonates.

OBJECTIVE: To investigate the determinants of neonatal weight and length. DESIGN: From 16-20 week of pregnancy, 366 mothers of the neonates had participated in the community-based study to investigate the effect of weekly supplementation during pregnancy with iron and vitamin A on infant growth. Women from five villages were allocated randomly to receive two tablets each containing 60 mg iron as ferrous sulphate and 250 micro g folic acid (n=121) or two tablets each containing 2400 RE vitamin A in addition to the same amount of ferrous sulphate and folic acid (n=122). A third ('daily') group (n=123) participating in the national iron supplementation programme was recruited from four neighbouring villages. RESULTS: Neonatal weight and length did not differ between the two weekly groups and between the weekly iron group and the 'daily' group. Iron and vitamin A status during pregnancy did not influence neonatal weight and length significantly. Boys were 100 g heavier and 0.53 cm longer than girls (P<0.05). First born neonates were lighter (P<0.01) and tended to be shorter (P=0.070) than neonates of higher birth order. Maternal age and education as well as other socioeconomic determinants were not associated with neonatal weight and length. Neonatal weight was 32% explained by gestational age, maternal weight, postnatal measurement, gender and parity, while neonatal length was 28% explained by gestational age, maternal weight, postnatal measurement, gender and maternal height. CONCLUSIONS: Gestational age, maternal weight at second trimester and infant gender were the main predictors of neonatal weight and length. SPONSORSHIP: The study was supported by The Netherlands Organization for Scientific Research-Netherlands Foundation for the Advancement of Tropical Research (NWO-WOTRO; WV 93-280) and Neys-van Hoogstraten Foundation (IN 114), The Netherlands, and German Agency for Technical Cooperation (GTZ)/South East Asian Ministers of Education Organization (SEAMEO), Indonesia.

Adolescent↗
PubMed2002

Modulation of A(beta) peptides by estrogen in mouse models.

Clinical studies have shown that estrogen deprivation through menopause is a risk factor in both the initiation and progression of Alzheimer's disease (AD) and that estrogen replacement therapy may be protective. One of the major pathological features in the human AD brain is the senile plaque, a proteinaceous structure composed mainly of heterogeneous peptides collectively known as A-beta (A(beta)). In vitro studies have linked estrogen with A(beta) modulation, suggesting that one-way that estrogen depletion at menopause may exacerbate the features of AD is through A(beta) accumulation. To test this, two studies were performed on transgenic models of amyloidosis. Firstly, transgenic mice without detectable amyloid aggregates were subjected to ovariectomy and estradiol supplementation, and A(beta) levels were assessed. Secondly, the effects of estrogen modulation were assessed in mice at an age when plaques would be forming initially. Overall, A(beta) levels were higher in estrogen-deprived mice than intact mice, and this effect could be reversed through the administration of estradiol. These data suggest that, in vivo, estrogen depletion leads to the accumulation of A(beta) in the CNS, which can be reversed through replacement of estradiol. These results provide evidence that post-menopausal estrogen depletion may be linked to an increased risk of AD through A(beta) modulation.

Amyloid beta-Peptides↗
PubMed2002

Population genetics of shortnose sturgeon Acipenser brevirostrum based on mitochondrial DNA control region sequences.

Shortnose sturgeon is an anadromous North American acipenserid that since 1973 has been designated as federally endangered in US waters. Historically, shortnose sturgeon occurred in as many as 19 rivers from the St. John River, NB, to the St. Johns River, FL, and these populations ranged in census size from 10(1) to 10(4), but little is known of their population structure or levels of gene flow. We used the polymerase chain reaction (PCR) and direct sequence analysis of a 440 bp portion of the mitochondrial DNA (mtDNA) control region to address these issues and to compare haplotype diversity with population size. Twenty-nine mtDNA nucleotide-substitution haplotypes were revealed among 275 specimens from 11 rivers and estuaries. Additionally, mtDNA length variation (6 haplotypes) and heteroplasmy (2-5 haplotypes for some individuals) were found. Significant genetic differentiation (P < 0.05) of mtDNA nucleotide-substitution haplotypes and length-variant haplotypes was observed among populations from all rivers and estuaries surveyed with the exception of the Delaware River and Chesapeake Bay collections. Significant haplotype differentiation was even observed between samples from two rivers (Kennebec and Androscoggin) within the Kennebec River drainage. The absence of haplotype frequency differences between samples from the Delaware River and Chesapeake Bay reflects a probable current absence of spawning within the Chesapeake Bay system and immigration of fish from the adjoining Delaware River. Haplotypic diversity indices ranged between 0.817 and 0.641; no relationship (P > 0.05) was found between haplotype diversity and census size. Gene flow estimates among populations were often low (< 2.0), but were generally higher at the latitudinal extremes of their distribution. A moderate level of haplotype diversity and a high percentage (37.9%) of haplotypes unique to the northern, once-glaciated region suggests that northern populations survived the Pleistocene in a northern refugium. Analysis of molecular variance best supported a five-region hierarchical grouping of populations, but our results indicate that in almost all cases populations of shortnose sturgeon should be managed as separate units.

Animals↗
PubMed2002

Nitric oxide participates in the intestinal pathology associated with murine syngeneic graft-versus-host disease.

Syngeneic graft-versus-host disease (SGVHD) develops following lethal irradiation, reconstitution with syngeneic bone marrow, and treatment with a short course of cyclosporin A (CsA) therapy. The disease is characterized by the development of a T helper cell type 1-like cytokine response [interleukin (IL)-12, interferon-gamma (IFN-gamma), and tumor necrosis factor alpha], and macrophage activation is central to development of the syndrome. It has been shown that nitric oxide (NO) participates significantly in the development of allogeneic GVHD. Studies were initiated to determine if NO participates in the pathology associated with SGVHD. Significant increases in inducible NO synthase (iNOS) mRNA and circulating NO were found in the tissues of SGVHD versus control animals. Treatment of SGVHD animals with the iNOS inhibitor aminoguanidine (AG) reversed the pathology associated with this disease. Furthermore, AG treatment reduced the production of IL-12 and IFN-gamma mRNA in the colons of CsA-treated mice. These studies demonstrate that NO participates in the pathological processes that are associated with the development of murine SGVHD.

Animals↗
PubMed2001

Genome interdependence in insect-bacterium symbioses.

Symbioses between unicellular and multicellular organisms have contributed significantly to the evolution of life on Earth. As exemplified by several studies of bacterium-insect symbioses, modern genomic techniques are providing exciting new information about the molecular basis and the biological roles of these complex relationships, revealing for instance that symbionts have lost many genes for functions that are provided by the host, but that they can provide amino acids that the host cannot synthesize.

Animals↗