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Biomedical subjects

N Brown

Publications and source records attributed to N Brown.

At least 55 records · Page 3Linked to original sources
PubMed2001

Comparative analysis of pharmacologic and/or genetic disruption of cyclooxygenase-1 and cyclooxygenase-2 function in female reproduction in mice.

Cyclooxygenase (COX)-derived prostaglandins are critical in female reproduction. Gene targeting studies show that ovulation, fertilization, implantation, and decidualization are defective in COX-2 deficient mice. We used genetic and pharmacologic approaches to perturb COX function and examine the differential and synergistic effects of inhibition of COX-1, COX-2, or of both isoforms on reproductive outcomes during early pregnancy in mice. The results demonstrate that simultaneous inhibition of COX-1 and COX-2 produces more severe effects on early pregnancy events than inhibition of either isoform alone. The effects of pharmacological inhibition of COX-2 on female reproductive functions were less severe than the null mutation of the COX-2 gene. A combined approach showed that COX-2 inhibition in COX-1(-/-) mice induced complete reproductive failure, suggesting a lack of alternative sources of prostaglandin synthesis. This investigation raises caution regarding the indiscriminate use of COX inhibitors and shows for the first time the distinct and overlapping pathways of the cyclooxygenase systems in female reproduction.

Animals↗
PubMed2001

trans-dominant inhibition of connexin-43 by mutant connexin-26: implications for dominant connexin disorders affecting epidermal differentiation.

Dominant mutations of GJB2-encoding connexin-26 (Cx26) have pleiotropic effects, causing either hearing impairment (HI) alone or in association with palmoplantar keratoderma (PPK/HI). We examined a British family with the latter phenotype and identified a new dominant GJB2 mutation predicted to eliminate the amino acid residue E42 (DeltaE42) in Cx26. To dissect the pathomechanisms that result in diverse phenotypes of dominant GJB2 mutations, we studied the effect of three Cx26 mutants (DeltaE42, D66H and R75W) identified in individuals with PPK/HI, and another (W44C) present in individuals with non-syndromic HI on gap junctional intercellular communication. We expressed mutant Cx26 alone and together with the epidermal connexins Cx26, Cx37 and Cx43 in paired Xenopus oocytes, and measured the intercellular coupling by dual voltage clamping. Homotypic expression of each connexin as well as co-expression of wild-type (wt) Cx26/wtCx43 and wtCx26/wtCx37 yielded variable, yet robust, levels of channel activity. However, all four Cx26 mutants were functionally impaired and failed to induce intercellular coupling. When co-expressed with wtCx26, all four mutants suppressed the wtCx26 channel activity consistent with a dominant inhibitory effect. However, only those Cx26 mutants associated with a skin phenotype also significantly (P<0.05) inhibited intercellular conductance of co-expressed wtCx43, indicating a direct interaction of mutant Cx26 units with wtCx43. These results demonstrate, for the first time, a trans-dominant negative effect of Cx26 mutants in vitro. Furthermore, they support a novel concept suggesting that the principal mechanism for manifestation of dominant GJB2 mutations in the skin is their dominant interference with the function of wtCx43. This assumption is further corroborated by our finding that Cx26 and Cx43 focally colocalize at gap junctional plaques in affected skin tissue of two carriers of DeltaE42.

Adolescent↗
PubMed2001

The history of photodetection and photodynamic therapy.

Light has been employed in the treatment of disease since antiquity. Many ancient civilizations utilized phototherapy, but it was not until early last century that this form of therapy reappeared. Following the scientific discoveries by early pioneers such as Finsen, Raab and Von Tappeiner, the combination of light and drug administration led to the emergence of photochemotherapy as a therapeutic tool. The isolation of porphyrins and the subsequent discovery of their tumor-localizing properties and phototoxic effects on tumor tissue led to the development of modern photodetection (PD) and photodynamic therapy (PDT). This review traces the origins and development of PD and PDT from antiquity to the present day.

Aminolevulinic Acid↗
PubMed2000

Coordinated regulation of fetal and maternal prostaglandins directs successful birth and postnatal adaptation in the mouse.

Cyclooxygenase (COX)-derived prostaglandins (PGs) regulate numerous maternal-fetal interactions during pregnancy. PGs stimulate uterine contractions and prepare the cervix for parturition, whereas in the fetus, PGs maintain patency of the ductus arteriosus (DA), a vascular shunt that transmits oxygenated placental blood to the fetal systemic circulation. However, the origin and site of action of these PGs remain undefined. To address this, we analyzed mice lacking COX-1 (null mutation) or COX-2 (pharmacologic inhibition) or pups with a double null mutation. Our results show that COX-1 in the uterine epithelium is the major source of PGs during labor and that COX-1(-/-) females experience parturition failure that is reversible by exogenous PGs. Using embryo transfer experiments, we also show that successful delivery occurs in COX-1(-/-) recipient mothers carrying wild-type pups, establishing the sufficiency of fetal PGs for parturition. Although patency of the DA is PG dependent, neither COX-1 nor COX-2 expression was detected in the fetal or postnatal DA, and offspring with a double null mutation died shortly after birth with open DAs. These results suggest that DA patency depends on circulating PGs acting on specific PG receptors within the DA. Collectively, these findings demonstrate the coordinated regulation of fetal and maternal PGs at the time of birth but raise concern regarding the use of selective COX inhibitors for the management of preterm labor.

Adaptation, Physiological↗
PubMed2000

An investigation of the rigor of interpretation rules for STRs derived from less than 100 pg of DNA.

By increasing the PCR amplification regime to 34 cycles, we have demonstrated that it is possible routinely to analyse <100 pg DNA. The success rate was not improved (without impairing quality) by increasing cycle number further. Compared to amplification of 1 ng DNA at 28 cycles, it was shown that increased imbalance of heterozygotes occurred, along with an increase in the size (peak area) of stutters. The analysis of mixtures by peak area measurement becomes increasingly difficult as the sample size is reduced. Laboratory-based contamination cannot be completely avoided, even when analysis is carried out under stringent conditions of cleanliness. A set of guidelines that utilises duplication of results to interpret profiles originating from picogram levels of DNA is introduced. We demonstrate that the duplication guideline is robust by applying a statistical theory that models three key parameters - namely the incidence of allele drop-out, laboratory contamination and stutter. The advantage of the model is that the critical levels for each parameter can be calculated. This information may be used (for example) to determine levels of contamination that can be tolerated within the strategy employed. In addition we demonstrate that interpreting one banded loci, where allele dropout could have occurred, using LR=1/2f(a) was conservative provided that the band was low in peak area. Furthermore, we demonstrate that an apparent mis-match between crime-stain and a suspect DNA profile does not necessarily result in an exclusion. The method used is complex, yet can be converted into an expert system. We envisage this to be the next step.

Alleles↗
PubMed2000

Suppression of atrial myosin gene expression occurs independently in the left and right ventricles of the developing mouse heart.

Many cardiac genes are broadly expressed in the early heart and become restricted to the atria or ventricles as development proceeds. Additional transcriptional differences between left and right compartments of the embryonic heart have been described recently, in particular for a number of transgenes containing cardiac regulatory elements. We now demonstrate that three myosin genes which become transcriptionally restricted to the atria between embryonic day (E) 12.5 and birth, alpha-myosin heavy chain (MHC), myosin light chain (MLC) 1A and MLC2A, are coordinately downregulated in the compact myocardium of the left ventricle before that of the right ventricle. alpha-MHC protein also accumulates in the right, but not left, compact ventricular myocardium during this period, suggesting that this transient regionalization contributes to fktal heart function. dHAND and eHAND, basic helix-loop-helix transcription factors known to be expressed in the right and left ventricles respectively at E10. 5, remain regionalized between E12.5 and E14.5. Downregulation of alpha-MHC, MLC1A, and MLC2A in iv/iv embryos, which have defective left/right patterning, initiates in the morphological left (systemic) ventricle regardless of its anatomical position on the right or left hand side of the heart. This points to the importance of left/right ventricular differences in sarcomeric gene expression patterns during fktal cardiogenesis and indicates that these differences originate in the embryo in response to anterior-posterior patterning of the heart tube rather than as a result of cardiac looping. Dev Dyn 2000;217:75-85.

Animals↗
PubMed2000

Fatal Mycobacterium bovis BCG infection in TNF-LT-alpha-deficient mice.

Neutralization of TNF or disruption of TNF-R1 leads to fatal Mycobacterium bovis BCG infection. Here we used TNF-LT-alpha-deficient mice to test whether a complete disruption of TNF and LT-alpha reduces further host resistance to BCG infection. The bacterial burden especially in the lungs of TNF-LT-alpha-deficient mice was significantly increased and the mice succumbed to infection between 8 and 10 weeks. In the absence of TNF-LT-alpha the granulomatous response was severely impaired and delayed. The cells in the granulomas of TNF-LT-alpha-deficient mice expressed low levels of MHC class II and ICAM-1. They contained a few T cells and F4/80-positive macrophages expressing little iNOS and acid phosphatase activity. By contrast, the lethal action of endotoxin was dramatically reduced in BCG-infected TNF-LT-alpha-deficient mice. In summary, in the absence of TNF-LT-alpha the recruitment and activation of mononuclear cells in response to BCG infection were significantly delayed and reduced resulting in immature granulomas allowing uncontrolled fatal infection.

Animals↗
PubMed2000

Oral uracil and Ftorafur plus leucovorin: pharmacokinetics and toxicity in patients with metastatic cancer.

PURPOSE: To assess the pharmacokinetics of Ftorafur (tegafur, FT), 5-fluorouracil (5-FU), and uracil in 31 cancer patients who were enrolled in phase I studies of oral uracil and FT (UFT). The correlation between pharmacokinetic parameters and toxic effects of UFT was evaluated. METHODS: Uracil and FT were orally administered in a 4:1 molar ratio at FT doses of 200-400 mg/m2 per day. Patients also received leucovorin at 150 mg/day. Daily doses were divided into three doses and administered at 8-h intervals for 28 consecutive days. Plasma FT concentrations were measured by high-performance liquid chromatography, and plasma 5-FU and uracil concentrations were determined using gas chromatography-mass spectrometry. National Institutes of Health Common Toxicity Criteria were used for assessment of toxicity. RESULTS: The concentrations of FT, 5-FU, and uracil showed wide interpatient variations. Maximum plasma concentrations (Cp(max)) of all three compounds were achieved in 0.3 to 4.0 h. At the various study doses, the terminal half-life (t 1/2beta) of FT ranged from 3.9 to 5.9 h, the area under the concentration-versus-time curve (AUC0-6h) ranged from 16,220 to 52,446 (ng/ml)h, the total clearance (ClT) ranged from 100 to 175 ml/min, and the steady-state volume of distribution (Vd(ss)) ranged from 18.3 to 28.7 l. The 5-FU generated from FT had an apparent distribution half-life (t 1/2alpha) and an apparent elimination half-life (t 1/2beta) of 0.3-1.3 h and 4.9-7.0 h, respectively. The AUC0-6h of 5-FU ranged from 120 to 325 (ng/ml)h. Uracil had a t 1/2alpha of 0.2-0.5 h and the level quickly returned to the endogenous level. The AUC0-6h for uracil ranged from 605 to 3764 (ng/ml)h, the ClT ranged from 3225 to 7748 ml/min, and the Vd(ss) ranged from 341 to 1354 l. The Cp(max) and AUC0-6h of both FT and uracil were significantly correlated with FT doses (P-values of 0.0244 and 0.0112) and with uracil doses (P-values of 0.0346 and 0.0083), respectively. In addition to interpatient variations, intrapatient variations were also observed in six patients who had pharmacology studies done on days 1 and 26+/-2 at the same study dose. We found that the repeated treatment with UFT caused cumulative increases in the values of Cp(max), Ctrough, and AUC0-6h of FT and 5-FU. The major toxic effects observed were diarrhea and nausea and vomiting. The occurrence of these toxic effects correlated significantly with the Cp(max) and AUC0-6h of 5-FU. CONCLUSIONS: The pharmacology studies showed that FT and uracil were readily absorbed orally and that FT was rapidly converted to 5-FU. The preliminary findings suggest that determination of plasma levels of 5-FU after oral administration of UFT may help predict subsequent toxic effects.

Tegafur↗
PubMed2000

The spectrum of mutations in erythrokeratodermias--novel and de novo mutations in GJB3.

Intercellular channels in skin are a complex and functionally diverse system formed by at least eight connexins (Cx). Our recent molecular studies implicating Cx defects in inherited skin disorders emphasize the critical role of this signaling pathway in epidermal differentiation. Erythrokeratodermia variabilis (EKV) is an autosomal dominant genodermatosis with a striking phenotype characterized by the independent occurrence of transient localized erythema and hyperkeratosis. The disease maps to 1p34-p35, and recently we identified the causative gene GJB3 encoding Cx31. We have now investigated GJB3 in two families and three sporadic cases with EKV, and report three new heterozygous mutations. In a sporadic case, we detected a mutation leading to substitution of a conserved phenylalanine (F137L) in the third transmembrane domain, which likely interferes with the proper assembly or gating properties of connexons. In another family, all three affected individuals carried two distinct mutations on the same GJB3 allele. However, only a de novo heterozygous missense mutation replacing arginine 42 with proline (R42P) co-segregated with the disease, while a 12 bp deletion predicted to eliminate four amino acid residues in the variable carboxy terminal domain of Cx31 was also found in clinically unaffected relatives but not in 90 unaffected controls. Including the previously published mutations, in toto, five different missense mutations have now been detected in 6 out of 17 families investigated by our laboratory, all of which presumably affect the cytoplasmic amino terminal and transmembrane domains of Cx31. In contrast, two mutations linked to progressive high-tone hearing impairment were located in the second extracellular domain, suggesting that the character and position of Cx mutations determine their phenotypic expression in different tissues. However, the phenotypic spectrum of GJB3 mutations seems not to include progressive symmetric erythrokeratodermia, another dominant genodermatosis with overlapping features, since no mutations were found in six unrelated families tested.

Connexins↗
PubMed2000

The bottom line: the effect of written expert witness statements on juror verdicts and information processing.

Mock jurors recruited from jury rolls were either not given written statements of expert witnesses' direct testimony or were provided with such statements before or after the presentation of that testimony. Presentation of the statements before the testimony and cross-examination provided jurors with a schema that allowed them to distinguish more effectively among the claims of four differentially worthy plaintiffs because they processed more probative evidence than other jurors. Jurors in receipt of written statements before the testimony found the evidence to be more comprehensible than other jurors. Jurors provided with written statements following testimony and cross-examination were able to differentiate between the most and least severely injured plaintiffs, whereas jurors not in receipt of any written statements were unable to differentiate among any of the differentially worthy claimants. The limitations of this case management technique and of the study are discussed.

Adult↗
PubMed2000

Sedative but not anxiolytic properties of benzodiazepines are mediated by the GABA(A) receptor alpha1 subtype.

Inhibitory neurotransmission in the brain is largely mediated by GABA(A) receptors. Potentiation of GABA receptor activation through an allosteric benzodiazepine (BZ) site produces the sedative, anxiolytic, muscle relaxant, anticonvulsant and cognition-impairing effects of clinically used BZs such as diazepam. We created genetically modified mice (alpha1 H101R) with a diazepam-insensitive alpha1 subtype and a selective BZ site ligand, L-838,417, to explore GABA(A) receptor subtypes mediating specific physiological effects. These two complimentary approaches revealed that the alpha1 subtype mediated the sedative, but not the anxiolytic effects of benzodiazepines. This finding suggests ways to improve anxiolytics and to develop drugs for other neurological disorders based on their specificity for GABA(A) receptor subtypes in distinct neuronal circuits.

Allosteric Site↗
PubMed2000

Genome-wide analysis of single-nucleotide polymorphisms in human expressed sequences.

Single-nucleotide polymorphisms (SNPs) have been explored as a high-resolution marker set for accelerating the mapping of disease genes. Here we report 48,196 candidate SNPs detected by statistical analysis of human expressed sequence tags (ESTs), associated primarily with coding regions of genes. We used Bayesian inference to weigh evidence for true polymorphism versus sequencing error, misalignment or ambiguity, misclustering or chimaeric EST sequences, assessing data such as raw chromatogram height, sharpness, overlap and spacing, sequencing error rates, context-sensitivity and cDNA library origin. Three separate validations-comparison with 54 genes screened for SNPs independently, verification of HLA-A polymorphisms and restriction fragment length polymorphism (RFLP) testing-verified 70%, 89% and 71% of our predicted SNPs, respectively. Our method detects tenfold more true HLA-A SNPs than previous analyses of the EST data. We found SNPs in a large fraction of known disease genes, including some disease-causing mutations (for example, the HbS sickle-cell mutation). Our comprehensive analysis of human coding region polymorphism provides a public resource for mapping of disease genes (available at http://www.bioinformatics.ucla.edu/snp).

Base Sequence↗
PubMed2000

Correction of defective host response to Mycobacterium bovis BCG infection in TNF-deficient mice by bone marrow transplantation.

Tumour necrosis factor-alpha (TNF) plays a central role in the recruitment and activation of mononuclear cells in mycobacterial infection. In the absence of type 1 TNF receptor, Mycobacterium bovis Bacillus Calmette-Guerin (BCG) infection of mice is not contained, leading to fatal disease. Because type 1 TNF receptor binds both TNF and lymphotoxin-a, we used TNF-deficient mice to determine the specific role of TNF in the host resistance to BCG infection. The bacterial burden of the lungs of TNF-deficient mice was substantially increased and the mice succumbed to pneumonia between 8 and 12 weeks with a defective granuloma response. Atypical granulomas developed by 4 weeks expressing low levels of MHC class II, intracellular adhesion molecule (ICAM-1), CD11b and CD11c. Macrophages showed little signs of activation and had low levels of acid phosphatase activity and inducible nitric oxide synthase (INOS) expression. Despite the defective cellular recruitment, the chemokines, monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1 (MIP-1alpha), were increased in broncho-alveolar lavage fluid of TNF-deficient mice. The defective host response was corrected by the transplantation of normal bone marrow cells into irradiated TNF-deficient mice. These results demonstrate that TNF derived from hemopoietic cells rather than from mesenchymal origin are essential for a normal host response to BCG infection. Furthermore, TNF dependent expression of adhesion molecules may be essential for the recruitment of mononuclear cells for the formation of bactericidal BCG granulomas.

Acid Phosphatase↗
PubMed2000

Increased resistance to mycobacterial infection in the absence of interleukin-10.

Interleukin-10 (IL-10) down-regulates T helper type 1 cell and macrophage functions. As IL-10 is induced along with tumour necrosis factor (TNF) and IL-12 in mycobacterial infection, we asked whether endogenous IL-10 plays a role in the antimycobacterial response. We demonstrate here that IL-10-deficient mice eliminate Mycobacterium bovis Calmette-Guérin bacillus faster than wild-type mice. Granulomas are significantly larger, containing more CD-11b- and CD11c-positive antigen-presenting cells and T cells, and the expression of major histocompatibility complex class II and intracellular adhesion molecule-1 is increased. Macrophages in granulomas of IL-10-deficient mice express high levels of TNF, acid phosphatase and inducible nitric oxide synthase (iNOS). Finally, an increased cutaneous delayed-type hypersensitivity reaction to mycobacterial proteins is further evidence of an augmented cell-mediated immune response. In conclusion, the cell-mediated immunity is enhanced in the absence of IL-10, resulting in a robust granuloma response, which accelerates the clearance of mycobacteria. Therefore, endogenous IL-10 attenuates mycobacterial immunity.

Animals↗
PubMed2000

Mental health service user involvement in nurse education: exploring the issues.

This paper reports on findings and issues arising from a study designed to promote mental health service users' involvement in a preregistration nursing curriculum. Users' views about the knowledge, skills and attributes required by mental health nurses were explored to inform the curriculum design. Strategies that would facilitate long term, active user involvement in the design and delivery of the curriculum were also explored. Findings are presented with concurrent discussion of issues arising from the research process in relation to user involvement in education. The issue of 'conflict' explores findings relating to users' views of a 'good' mental health nurse and inherent conflicts between user and professional views are highlighted. The representativeness of the research participants is explored and debated in relation to service user involvement in nurse education. Finally, the concepts of 'involvement' and 'tokenism' are discussed and recommendations made about how active user involvement in nurse education can be achieved.

Curriculum↗
PubMed2000

What are the criteria that mentors use to make judgements on the clinical performance of student mental health nurses? An exploratory study of the formal written communication at the end of clinical nursing practice modules.

Issues concerning the assessment of student nurse performance in clinical practice have pre-occupied nurse educationalists for some time and continue to pose problems. The debate in the nursing literature tends to revolve around two seemingly mutually exclusive positions related to competence vs. learning outcomes. These are views that seem to be held by academics with little reference to clinical nurses who have responsibility for the assessment of student performance in clinical practice. This paper adds to the wider debate on clinical assessment by reporting on a small research study that explored the written comments that 150 mentors made in relation to the performance of student mental health nurses following periods of clinical practice. An extensive literature review is provided in order to place the debate in context, followed by a brief outline of the research study, its findings, discussion and conclusion. This analysis of findings demonstrates that student learning is of major concern to mentors, and that the assessment of student performance in clinical practice is not restricted by pre-determined behavioural learning outcomes. Personal characteristics of students exert a great influence on judgements about clinical performance. This paper does not offer solutions to the search for the perfect clinical assessment, but it does call for an increased dialogue between educationalists and mentors to discuss the implications of this research for the development of an appropriate clinical assessment tool.

Adult↗