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J Fleming

Publications and source records attributed to J Fleming.

At least 55 records · Page 3Linked to original sources
PubMed1998

Shaker-1 mutations reveal roles for myosin VIIA in both development and function of cochlear hair cells.

The mouse shaker-1 locus, Myo7a, encodes myosin VIIA and mutations in the orthologous gene in humans cause Usher syndrome type 1B or non-syndromic deafness. Myo7a is expressed very early in sensory hair cell development in the inner ear. We describe the effects of three mutations on cochlear hair cell development and function. In the Myo7a816SB and Myo7a6J mutants, stereocilia grow and form rows of graded heights as normal, but the bundles become progressively more disorganised. Most of these mutants show no gross electrophysiological responses, but some did show evidence of hair cell depolarisation despite the disorganisation of their bundles. In contrast, the original shaker-1 mutants, Myo7ash1, had normal early development of stereocilia bundles, but still showed abnormal cochlear responses. These findings suggest that myosin VIIA is required for normal stereocilia bundle organisation and has a role in the function of cochlear hair cells.

Animals↗
PubMed1997

Myosin VIIA is required for aminoglycoside accumulation in cochlear hair cells.

Myosin VIIA is expressed by sensory hair cells and has a primary structure predicting a role in membrane trafficking and turnover, processes that may underlie the susceptibility of hair cells to aminoglycoside antibiotics. [3H]Gentamicin accumulation and the effects of aminoglycosides were therefore examined in cochlear cultures of mice with different missense mutations in the myosin VIIA gene, Myo7a, to see whether myosin VIIA plays a role in aminoglycoside ototoxicity. Hair cells from homozygous mutant Myo7ash1 mice, with a mutation in a nonconserved region of the myosin VIIA head, respond rapidly to aminoglycoside treatment and accumulate high levels of gentamicin. Hair cells from homozygous mutant Myo7a6J mice, with a mutation at a highly conserved residue close to the ATP binding site of the myosin VIIA head, do not accumulate [3H]gentamicin and are protected from aminoglycoside ototoxicity. Hair cells from heterozygotes of both alleles accumulate [3H]gentamicin and respond to aminoglycosides. Although aminoglycoside uptake is thought to be via apical surface-associated endocytosis, coated pit numbers on the apical membrane of heterozygous and homozygous Myo7a6J hair cells are similar. Pulse-chase experiments with cationic ferritin confirm that the apical endocytotic pathway is functional in homozygous Myo7a6J hair cells. Transduction currents can be recorded from both heterozygous and homozygous Myo7a6J hair cells, suggesting it is unlikely that the drug enters via diffusion through the mechanotransducer channel. The results show that myosin VIIA is required for aminoglycoside accumulation in hair cells. Myosin VIIA may transport a putative aminoglycoside receptor to the hair cell surface, indirectly translocate it to sites of membrane retrieval, or retain it in the endocytotic pathway.

Adenosine Triphosphate↗
PubMed1997

Combined diesel exhaust particulate and ragweed allergen challenge markedly enhances human in vivo nasal ragweed-specific IgE and skews cytokine production to a T helper cell 2-type pattern.

We have previously shown that in vivo nasal challenge with diesel exhaust particles (DEP) induces both quantitative and qualitative changes in local IgE production and stimulates generalized local cytokine production. We have now investigated the combined effects of intranasal challenge with DEP plus ragweed allergen on local humoral immune responses. We collected nasal lavages from ragweed sensitized subjects at different times after nasal challenge. As compared with challenge with ragweed alone, challenge with both DEP and ragweed induced markedly higher ragweed-specific IgE but not total IgE levels or IgE-secreting cell numbers. Total and specific IgG4 levels also were enhanced, while total IgG levels were not. Synergy was also observed between the DEP and ragweed in altering the profile of epsilon mRNAs generated by alternative splicing, mRNAs that code for different expressed IgE proteins. Intranasal challenge with ragweed alone induced inconsistent and low levels of mucosal cytokine mRNAs. In contrast, challenge with both ragweed plus DEP resulted in decreased expression for Th1-type cytokines (IFN-gamma and IL-2) but elevated expression of mRNA for other cytokines (IL-4, -5, IL-6, IL-10, IL-13). This synergy between DEP and natural allergen exposure is suggested as a key feature in increasing allergen-induced respiratory allergic disease.

Adult↗
PubMed1997

A study of potential risk factors for sexual abuse in childhood.

Research aimed at identifying risk factors for childhood sexual abuse (CSA) is crucial for the development of preventative strategies. This study examined the relationship between a number of possible risk factors and CSA in a community sample of women using multivariate analysis and carefully operationalized variables. The variables significantly associated with CSA were physical abuse, having a mother who was mentally ill, not having someone to confide in, and being socially isolated. With the exception of physical abuse, different predictors emerged for abuse before and after age 12. Social isolation and experiencing the death of a mother were significant predictors for abuse before age 12, while the predictors of CSA after age 12 were physical abuse and a mentally ill mother. For abuse perpetrated by a family member, the significant predictors of CSA were physical abuse, having no one to confide in, having no caring female adult, and having an alcoholic father. For girls abused by someone outside of the family, the significant predictors were physical abuse, social isolation, mother's death, and having an alcoholic mother. While CSA can happen to any child, this study highlights circumstances that may increase the chances of abuse and should form the basis of prevention and intervention strategies.

Adolescent↗
PubMed1997

Comparison of Fy(b) status as determined serologically and genetically.

Comparison of the serologically determined phenotype and the genotype of samples as defined by PCR-RFLP indicated a significant percentage of discrepancies on analysis of serologically defined Fy(a + b-) samples. An investigation of these discrepancies has shown that the serologically determined phenotype of the samples varies with respect to the reagent used but that the PCR-RFLP assay gives reliable results for all the samples investigated. The samples which yielded the discrepant results were further investigated and the results indicated weakened expression of the Fyb antigen. This may arise by a method similar to the expression of Fyx although we found the incidence of these samples to be much higher than that reported for Fyx. These results may have important implications for the routine testing of blood donations, particularly in situations where the unit is to be transfused to a patient who has previously formed an anti-Fyb.

Duffy Blood-Group System↗
PubMed1997

Decreased digital flow persists after the abatement of cocaine-induced hemodynamic stimulation.

This study determined whether the development of delayed ischemic sequelae due to cocaine use--after the return of arterial blood pressure (BP) and heart rate to near-baseline values--may be attributable to regional vasoconstriction which persists beyond the acute systemic hemodynamic response. Five cocaine-using volunteers received intravenous infusions of saline placebo and cocaine 0.50 mg/kg several days apart in a double-blinded cross-over design. The intensity and duration of the cocaine-induced decrease in peripheral blood flow (as documented by laser Doppler flowmetry of the finger) were compared to the increases in BP (obtained with a Dinamap) and heart rate using paired t-test and repeated-measures analysis of variance. A significant increase in BP and a significant decrease in finger flow were noted by the first time point (5 min). Within 15 min, cocaine induced a 36% +/- 5% increase in BP and a 73% +/- 18% decline in finger flow (P < 0.05 for difference between percent change in BP and percent change in flow). Dinamap(systolic) and Dinamap(diastolic) returned to within 15% of baseline within 30 min, while finger flow remained more than 50% below baseline for the remainder of the 60-min study period (P < 0.05). Changes in heart rate paralleled those in BP. Except for isolated cases of documented coronary vasoconstriction in patients presenting with complications after cocaine use, this study is the first to document the persistence of cocaine-induced vasoconstriction of a sensitive vascular bed beyond the hypertensive response. It thus helps to explain the development of ischemic injury after cocaine use despite a stable rate-pressure product.

Adult↗
PubMed1997

Teaching physiology and the World Wide Web: electrochemistry and electrophysiology on the Internet.

Students seek active learning experiences that can rapidly impart relevant information in the most convenient way possible. Computer-assisted education can now use the resources of the World Wide Web to convey the important characteristics of events as elemental as the physical properties of osmotically active particles in the cell and as complex as the nerve action potential or the integrative behavior of the intact organism. We have designed laboratory exercises that introduce first-year medical students to membrane and action potentials, as well as the more complex example of integrative physiology, using the dynamic properties of computer simulations. Two specific examples are presented. The first presents the physical laws that apply to osmotic, chemical, and electrical gradients, leading to the development of the concept of membrane potentials; this module concludes with the simulation of the ability of the sodium-potassium pump to establish chemical gradients and maintain cell volume. The second module simulates the action potential according to the Hodgkin-Huxley model, illustrating the concepts of threshold, inactivation, refractory period, and accommodation. Students can access these resources during the scheduled laboratories or on their own time via our Web site on the Internet (http./(/)phys-main.umsmed.edu) by using the World Wide Web protocol. Accurate version control is possible because one valid, but easily edited, copy of the labs exists at the Web site. A common graphical interface is possible through the use of the Hypertext mark-up language. Platform independence is possible through the logical and arithmetic calculations inherent to graphical browsers and the Javascript computer language. The initial success of this program indicates that medical education can be very effective both by the use of accurate simulations and by the existence of a universally accessible Internet resource.

Computer Communication Networks↗
PubMed1997

Unravelling the genetics of deafness.

Hearing-impaired mouse mutants not only are good models for human hereditary deafness, but also are extremely useful for understanding the molecular basis of the cochlear defect. We describe here how we identified the gene responsible for the deafness and vestibular defects in the shaker-1 mouse mutant as a myosin VII gene. Three different mutations, all causing the same phenotype in different lines of mouse, were found, providing good evidence that we had, indeed, found the correct gene. The same gene was subsequently found to be involved in Usher's syndrome type 1B, which features deafness, vestibular dysfunction, and progressive retinitis pigmentosa. The myosin VII gene is expressed in sensory hair cells, but not in supporting cells or neurons. We are investigating the role of myosin VII in hair cell development and function. Analysis of the different mutant stocks suggests it has at least two functions. First it is involved in the development and maintenance of the stereocilia bundle. Second, it has a role in inner hair cell function. No evidence of retinal degeneration like that in Usher's syndrome has been found in the shaker-1 mutants so far studied. The benefits of understanding the function of the gene for families with Usher's type 1B are discussed. This gene is the first to be identified as causing the most common type of disorder in human hearing impairment, neuroepithelial abnormalities, and suggests a new class of candidate genes for involvement in such defects.

Animals↗
PubMed1997

Chemopreventive and growth inhibitory effects of selenium.

There is very convincing evidence that a high dietary level of selenium substantially reduces the incidence of a wide variety of animal cancers. The human epidemiological evidence is less clear cut, but overall suggests that selenium may be protective: the evidence is strongest in men in relation to gastro-intestinal cancers. There is evidence that dietary selenium compounds reduce the formation of DNA adducts by carcinogens. Selenium compounds also inhibit growth in vitro and induce apoptosis. In general, there is a good correlation between the effectiveness of selenium compounds in chemoprevention and growth inhibition, implying that the mechanisms of growth inhibition and chemoprevention may be similar and that a major factor in the chemopreventive effects of selenium compounds in vivo is their ability to retard outgrowth of pre-malignant cells. Various hypotheses have been advanced as to how selenium compounds might prevent tumour cell growth. One is that they cause apoptosis by inducing oxidative stress. However, we have shown that the most potent selenium compound, selenodiglutathione (SDG), a natural metabolite of selenite, does not induce oxidative stress, at least not in the same way as other oxidants such as H2O2 and diamide. Firstly, a partially selenium-resistant variant cell line does not show increased resistance to H2O2. Moreover, SDG does not induce widespread tyrosine phosphorylation, including MAP and SAP kinases, like other oxidants such as H2O2 and diamide and its effects are not reversed by pretreatment with the tyrosine kinase inhibitor, herbimycin. Our experiments with the selenium-resistant variant suggest that a novel selenium-binding protein may be involved in growth inhibition by selenium.

Anticarcinogenic Agents↗
PubMed1996

The Sp4H deletion may contain a new locus essential for postimplantation development.

Sp4H is a semi-dominant mutation that maps to mouse chromosome 1. Heterozygous mice exhibit white spotting of the belly, whereas the fate of the homozygous embryos is unknown. We have previously shown that the entire coding region of the Pax3 gene is deleted in the Sp4H mutant. In this study, we have analyzed the fate of the Sp4H homozygous embryos. No Sp4H homozygotes were detected by Southern blot or PCR analysis in 82 E9-E13-day embryos. We have also documented a significant increase in the number of resorption sites in Sp4H heterozygous matings compared to control litters. Sections of the resorption sites (moles) suggest that postimplantation development is arrested prior to gastrulation. We have mapped the extent of the deletion to a maximum of 1.53 +/- 0.6 cM using markers flanking the Pax3 locus. Four anonymous markers, D1Mit215, D1Mit253, D1Mit332, and D1McG156, have been shown to be deleted in the Sp4H mutation. Further nondeleted markers have been used to extend the linkage map of this region. A total of 22 loci were analyzed in a Splotch intraspecific backcross. Using these data and deletion mapping data, we predict the following order of markers: (D1Mit46, Vil)-(D1Mit79)-(D1Mit132, D1McG153)-(D1Mit332)-(D1-McG156, D1Mit253, D1Mit215, Pax3)-(D1Mit134)-(D1Mit8, D1Mit9, D1Mit44, D1Ler3, D1Mit183)-(D1Mit53, D1Mit82, D1Mit182)-(Bcl2). As the deletion is large enough to include other genes, and it seems that deletion of Pax3 is not likely to account for the early death of the embryos, we suggest that another developmentally important gene may be deleted in the Sp4H mouse mutant and that this may be responsible for the early death of the homozygous mutant embryos.

Alleles↗
PubMed1996

Repeat pediatric visits to a general emergency department.

STUDY OBJECTIVE: To determine the rate of repeat visits among children cared for in a general emergency department and associated demographic and clinical variables. METHODS: We carried out a chart review of patients seen in the ED of a general hospital serving both inner-city and suburban populations. Our subjects were all children younger than 18 years seen in the study ED between July 1, 1992, and June 30, 1993 (N = 4,276). RESULTS: We found 291 repeat visits (defined as a subsequent visit within 14 days) n 245 children. Among the 242 repeat visits for related complaints, 200 were unanticipated and most without a clear medical need. Mantel-Haenszel adjusted odds ratios (MHORs) showed a significantly increased risk of repeat visit with public insurance (controlled for age: MHOR, 2.57, and 95% confidence interval [CI], 1.93 to 3.43; controlled for race: MHOR, 2.70, and 95% CI, 1.99 to 3.66) and age younger than 2 years (controlled for insurance MHOR, 1.67, and 95% CI, 1.27 to 2.19; controlled for race: MHOR, 1.89, and 95% CI, 1.47 to 2.47. CONCLUSION: Repeat visits were more likely for respiratory diagnoses and less likely for minor trauma. Both visits and repeat visits were more likely in patients from poorer census tracts than in those from equidistant, more affluent ones.

Adolescent↗
PubMed1996

The epidemiology of alcohol use in Australian women: findings from a national survey of women's drinking.

This is the first study of alcohol use, alcohol problems and alcohol dependence in a general population sample of Australian women using a standardized screening instrument developed by the World Health Organization, the Alcohol Use Disorders Identification Test (AUDIT). Sixty-six percent of a sample of 6000 women randomly selected from the electoral rolls responded to the questionnaire. The majority of women (87%) had drunk alcohol at some time in their lives, while 82% had consumed alcohol within the past 12 months. Of the women who currently drank alcohol, 34% were classified as hazardous drinkers, 4% as harmful drinkers and 1% as dependent according to AUDIT definitions. Using a cut-off score of 8 for the AUDIT, 8% of women were classified as currently having a drinking pattern of hazardous or harmful alcohol consumption. These women were more likely to be younger (17-44 years), single, or living in a de facto relationship. The results of this survey provide important data which can be used as a bench-mark to measure changes in women's drinking behaviour and drinking related problems.

Adolescent↗
PubMed1996

Home assessment of sleep disorders by portable monitoring.

Ambulatory home monitoring has been employed for a number of applications. Portable sleep/wake recorders are useful for assessment of the hypersomnias, circadian sleep/wake disorders, parasomnias, and periodic movements in sleep. Wrist actigraphy can usefully approximate sleep versus wake state during 24 h and has been used for monitoring insomnia, circadian sleep/wake disturbances, and periodic limb movement disorder. Home monitoring of cardiopulmonary parameters can be employed for detection and follow-up of sleep-disordered breathing (sleep apnea, upper airway resistance syndrome). The techniques available for portable monitoring, although valuable, do not replace traditional in-laboratory polysomnography for full assessment of a sleep disorder.

Ambulatory Care↗