Motile response patterns and ultrastructural observations of the isolated outer hair cell

The tonotopic organization of the mammalian cochlea is accompanied by structural gradients which include the somatic lengths of outer hair cells (OHCs). These receptors rest upon the vibrating portion of the basilar membrane and have been reported to exhibit motile responses following chemical and electrical stimulation. These movements were examined in detail in this dissertation. It was found that isolated OHCs cultured in vitro respond to chemical depolarization with slow tonic movements, and to electrical waveforms with bi-directional, frequency following movements extending from DC to at least 10 kHz.^ Slow contractions were also elicited following electrical stimulation, bath incubation in carbachol (a cholinergic agonist), and increases in extracellular K+ concentration as little as 50 mM.^ Isolated OHCs display anatomical features which are remarkable when contrasted with those prepared from intact receptor organs. A complex structure located between the cuticular plate and the nuclear membrane was consistently observed and was examined by serial cross-sections which revealed a network of non-membrane bound densities. This corresponded to a granular complex seen at the light microscope level. The complex was composed of dense regions of organelles, striated structures embedded within the core, and a circumferential network of microtubules residing in the peri-nuclear portion of the cell. In cells which had lost their nuclear attachment to the terminal synaptic body, the granular complex could be made to contract without effecting any change in cellular length, implying that the complex may be the driving force behind certain aspects of the motile response.^ Most cells displayed movements which revealed asymmetries analogous to those reported for OHC receptor potentials in vivo. The contraction phase (for longer cells) was shown to have a small time constant (approximately 400 microseconds) and saturated with limited displacements. The expansion phase had time constants as large as 1.3 milliseconds but yielded displacements as much as 60 percent larger than those seen for contractions.^ Additional waveform characteristics seen in the in vivo response could be emulated either by biasing the cell's resting length with either direct current, triggering contractions via large electrical displacements, or incubation with depolarizing compounds.^ Alternatively, short (20-30 um) cells revealed more linear response characteristics to the probe stimulus. Partial saturation was achieved and revealed a DC component which was opposite in polarity to that seen in longer cells. (Abstract shortened with permission of author.) ^

Prevalence and risk factors for Helicobacter pylori in the Ysleta del Sur Pueblo population

Background: Helicobacter pylori infection among Native Americans is more prevalent than any other minority group in the United States. Few studies involving Helicobacter pylori have been conducted on Native Americans and no previous studies have been conducted in the Ysleta del Sur Pueblo population. Therefore we wanted to explore the prevalence and risk factors of Helicobacter pylori within this community. We also explored whether household transmission is occurring. ^ Materials and Methods: We conducted a cross-section study on the prevalence of Helicobacter pylori in the Ysleta del Sur Pueblo community. Main household caregivers were interviewed on household conditions, hygiene practices, and household sociodemographics. All household members were tested for IgG urine antibodies against Helicobacter pylori using RAPIRUN test kits. 13C urea breath testing using BREATHTEK kits was provided to study participants that had positive antibody results and utilized as confirmatory results of infection. ^ Results: Prevalence of Ysleta del Sur Pueblo was determined to be 27.4%. When comparing for ethnicity, Native Americans had increased prevalence of infection then Mexican-Americans living on the Pueblo. That prevalence increased from 1.6 to 3.3 when taking account only United States born study participants. The household secondary prevalence rate was found to be 23.8%. Helicobacter pylori infection rates increased with increasing age and decreasing income. ^ Conclusions: Native Americans had an increased risk of infection. As expected risk factors for Helicobacter pylori correlated with previous studies, but we found evidence of limited current transmission within households. However, due to the limited sample size (n=62) and power, we were not able to find statistical significance for some risk factors. A statistical association was found with age where increasing prevalence corresponded with increasing age suggesting that the birth cohort may be in effect within this population.^

Poverty, Educational Attainment and Health Among America’s Children: Current and Future Effects of Population Diversification and Associated Socioeconomic Change

A complex of interrelated factors including minority status, poverty, education, health status, and other factors determine the general welfare of children in America, particularly in heavily diverse states such as Texas. Although racial/ethnic status is clearly only a concomitant factor in that determination it is a factor for which future projections are available and for which the relationships with the other factors in the complex can be assessed. After examining the nature of the interrelationships between these factors we utilize direct standardization techniques to examine how the future diversification of the United States and Texas will affect the number of children in poverty, the educational status of the householders in households in which children in poverty live and the health status of children in 2040 assuming that the current relationships between minority status and these socioeconomic factors continue into the future. In the results of the analyses, data are compared with the total population of the United States and Texas in 2040 assumed in the first simulation scenario, to have the race/ethnicity characteristics of 2008 and in the second those projected for 2040 by the U.S. Census Bureau for the nation and by the Texas State Data Center for Texas in 2040. The results show that the diversification of the population could increase the number of children in poverty in the United States by nearly 1.8 million more than would occur with the lower levels of diversification evident in 2008. In addition, poverty would become increasingly concentrated among minority children with minority children accounting for 76.2 percent of all children in poverty by 2040 and with Hispanic children accounting for nearly half of the children in poverty by 2040. Results for educational attainment show an increasing concentration of minority children in households with householders with very low levels of education such that by 2040, 85.2 percent of the increase in the number of children in poverty would be in households with a householder with less than a high school level of education. Finally, the results related to several health status factors show that children in poverty will have a higher prevalence of nearly all health conditions. For example, the number of children with untreated dental conditions could increase to more than 4 million in the United States and to nearly 500,000 in Texas. The results clearly show that improving the welfare of children in America will require concerted efforts to change the poverty, educational, and health status characteristics associated with minority status and particularly Hispanic status. Failing to do so will lead to a future in which America’s children are increasingly impoverished, more poorly educated, and less healthy and which, as a result, is an America with a more tentative future.

A costing exercise of provision of prevention of HIV transmission from mother to child services in Vietnam

Objectives. This dissertation focuses on estimating the cost of providing a minimum package of prevention of mother-to-child HIV transmission (PMTCT) in Vietnam from a societal perspective and discussing the issues of scaling-up the minimum package nationwide. ^ Methods. Through collection of cost-related data of PMTCT services at 22 PMTCT sites in 5 provinces (Hanoi, Quang Ninh, Thai Nguyen, Hochiminh City, and An Giang) in Vietnam, the research investigates the item cost of each service in minimum PMTCT packages and the actual cost per PMTCT site at different organizational levels including central, provincial, and district. Next, the actual cost per site at each organizational level is standardized by adjusting for HIV prevalence rate to arrive at standardized costs per site. This study then uses the standardized costs per site to project, by different scenarios, the total cost to scale-up the PMTCT program in Vietnam. ^ Results. The cost for HIV tests, infant formula, and salary of health workers are consistently found to be the biggest expenditures in the PMTCT minimum package program across all organizational levels. Annual cost for drugs for prophylaxis treatment, operating and capital, and training costs are not substantial (less than 5% of total costs at all levels). The actual annual estimated cost for a PMTCT site at the central level is nearly VND 1.9 billion or US$ 107,650 (exchange rate US$ 1 = VND 17,500) while the annual cost for a provincial site is VND 375 million or US$ 21,400. The annual cost for a district site is VND 139 million (∼US$ 8,000). ^ The estimated total annual cost to roll out the PMTCT minimum package to the 5 studied provinces is approximately US$ 1.1 million. If the PMTCT program is to be scaled-up to 14 provinces until 2008 and up to 40 provinces through the end of 2010 as planned by the Ministry of Health, it would cost the health system an approximate annual amount of US$ 2.1 million and US$ 5.04 million, respectively. The annual cost for scaling-up the PMTCT minimum package nationwide is around US$ 7.6 million. Meanwhile, the total annual cost to implement PMTCT minimum packages to achieve PMTCT national targets in 2010 (providing counseling service to 90% of all pregnant women; 60% of them will receive HIV tests and 100% of HIV (+) mother and their newborn will receive prophylaxis treatment) would be US$ 6.1 million. ^ Recommendations. This study recommends: (1) the Ministry of Health of Vietnam should adjust its short-term national targets to a more feasible and achievable level given the current level of available resources; (2) a detailed budget for scaling-up the PMTCT program should be developed together with the national PMTCT action plan; (3) the PMTCT scaling-up plan developed by the Ministry of Health should focus on coverage of high prevalence population and quality of services provided rather than number of physical provinces reached; (4) exclusive breastfeeding strategy should be promoted as part of the PMTCT program; and (5) for a smooth and effective rolling out of PMTCT services nationwide, development of a national training plan and execution of this plan must precede any other initiations of the PMTCT scaling-up plan. ^

Systematic literature review on internet-based interventions to prevent HIV transmission

Objective. To perform a systematic review of the internet based HIV prevention interventions.^ Data Source. Data resources including Ovid Medline, CINAHL (EBSCOhost and Psycinfo) were searched for the relevant articles. Study Selection: Studies were selected if the entire article was in English, Randomized control trial performed after 1998 till current, internet based aimed towards HIV/AIDS prevention. ^ Data Extraction. Each relevant article was coded using a code sheet which consisted of background information, study characteristics, study population information, program details, intervention and results. Data Synthesis: Total of seven relevant articles were coded and the information obtained was incorporated into the evidence tables for comparison.^ Conclusion. Overall the internet based HIV prevention studies have been very successful in recruiting large number of people but has not been able to show effective results due to high attrition. More research needs to be done in the area.^

Dengue transmission risk maps of the continental United States

Dengue fever is a strictly human and non-human primate disease characterized by a high fever, thrombocytopenia, retro-orbital pain, and severe joint and muscle pain. Over 40% of the world population is at risk. Recent re-emergence of dengue outbreaks in Texas and Florida following the re-introduction of competent Aedes mosquito vectors in the United States have raised growing concerns about the potential for increased occurrences of dengue fever outbreaks throughout the southern United States. Current deficiencies in vector control, active surveillance and awareness among medical practitioners may contribute to a delay in recognizing and controlling a dengue virus outbreak. Previous studies have shown links between low-income census tracts, high population density, and dengue fever within the United States. Areas of low-income and high population density that correlate with the distribution of Aedes mosquitoes result in higher potential for outbreaks. In this retrospective ecologic study, nine maps were generated to model U.S. census tracts’ potential to sustain dengue virus transmission if the virus was introduced into the area. Variables in the model included presence of a competent vector in the county and census tract percent poverty and population density. Thirty states, 1,188 counties, and 34,705 census tracts were included in the analysis. Among counties with Aedes mosquito infestation, the census tracts were ranked high, medium, and low risk potential for sustained transmission of the virus. High risk census tracts were identified as areas having the vector, ≥20% poverty, and ≥500 persons per square mile. Census tracts with either ≥20% poverty or ≥500 persons per square mile and have the vector present are considered moderate risk. Census tracts that have the vector present but have <20% poverty and <500 persons per square mile are considered low risk. Furthermore, counties were characterized as moderate risk if 50% or more of the census tracts in that county were rated high or moderate risk, and high risk if 25% or greater were rated high risk. Extreme risk counties, which were primarily concentrated in Texas and Mississippi, were considered having 50% or greater of the census tracts ranked as high risk. Mapping of geographic areas with potential to sustain dengue virus transmission will support surveillance efforts and assist medical personnel in recognizing potential cases. ^