bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing Predictors of Willingness to Treat HIV+ Patients for New York City Male and Female General Practice Dentists 50 Years of Age or Younger
Authors: Kunzel Carol , Sadowsky Donald , Tseng Chin‐Lin
Published: April 2007

Objectives: This article develops and compares gender‐specific predictive models for willingness to treat HIV‐infected patients (PHIV+) for male and female private general practice dentists (GPDs). Methods: Based on mail survey data collected in Manhattan and Queens, New York City (73.3% response rate), hierarchical multiple regression analyses were conducted for male and female dentists 50 years of age or younger (n=763) and for those in solo practice. Results: The gender‐specific predictive models (R2s=0.72) do not differ, except for the influence of practice viability, a moderately strong, statistically significant predictor for men, while the least powerful, statistically nonsignificant predictor for women. This distinction remains for solo male and female practitioners. Informal/formal collegial norms are more influential predictors within the solo female model than within the solo male model. Conclusion: Findings are encouraging for further work in developing predictive models for clinician subpopulations, with an eye toward developing intervention strategies that reflect key predictive factors for each group.
The Relationship Between the Number of Sound, Decayed, and Filled Permanent Tooth Surfaces and the Number of Sealed Surfaces in Children and Adolescents
Authors: Clark D. Christopher , Berkowitz Jonathan
Published: April 2007

Objectives: The purpose of this investigation was to determine the prevalence of sound, decayed, filled, and sealed permanent tooth surfaces for children and adolescents from three fluoridated communities in British Columbia and to develop a predictive model of sealant use that included the dental caries status of tooth surfaces. Methods: Children in grades 2 and 3 (n=2,715) and adolescents in grades 8 and 9 (3,317) were surveyed to determine the prevalence of sound, decayed, filled, and sealed permanent tooth surfaces. The DMFS index, modified to include incipient (D1) and cavitated (D2) lesions, was used to measure the status of all tooth surfaces. The prevalence of D1D2MF and sealed tooth surfaces was estimated by age group and tooth type. Logistic regression models were developed to analyze the association between a number of independent variables and sealant use. Results: About 60 percent of surveyed students had one or more sealants present, with a mean of 3.2 sealants per subject. Of all pit and fissure surfaces on permanent first molars, 23.4 percent and 20.1 percent were sealed for the 11 years and younger and 12 years and older age groups, respectively. For these same two age groups, the percentages of pit and fissure surfaces that were decayed and filled were 6.7 percent and 19.7 percent, respectively. For both age groups combined, 10.8 percent and 23.7 percent of all pit and fissure surfaces on second molars and premolars, respectively, were sealed. The prevalence of decayed and filled pit and fissure surfaces was 5.6 percent and 1.8 percent, respectively, for second molars and premolars. Premolars were being sealed at a rate of 13 to 1 compared to the number of decayed and filled surfaces. Logistic regression failed to identify meaningful predictors of sealant use. Conclusion: Results from this study found an increase in the prevalence of sealants in the three communities surveyed, yet failed to identify criteria used by dentists or auxiliaries when making decisions about sealant placement. Professional education in the appropriate use of sealants may be necessary.
Effect of an Amine Fluoride Dentifrice on Dental Caries Used in a Community‐based Oral Health Education Program
Authors: Pakhomov Guennadi N. , Moller Ingolf J. , Atanassov Nicola P. , Kabackchieva Rositza I. , Sharkov Nikolai I.
Published: April 2007

Objectives: The purpose of this study was to investigate the caries‐reducing effect of an amine fluoride toothpaste when used under real‐life conditions in a community preventive program. Methods: Approximately 12,500 children 3–12 years of age were provided with toothpaste (four tubes or 360 grams annually during three years) to be used in kindergartens or schools and once a day at home. The teachers supervised daily toothbrushing sessions. Random samples of children in each of the ages 3, 6, 9, and 12 years were selected from the intervention and the reference communities at both the start of the study and after three years, and examined for dental caries experience. Results: Amine fluoride dentifrice seemed to provide a reduction in dental caries prevalence compatible to the most commonly used fluoride dentifrice compounds. Conclusion: The implemented fluoride toothpaste program is a feasible and practical method of improving the oral health status of children.
A 24‐month Study Comparing Sealant and Fluoride Varnish in Caries Reduction on Different Permanent First Molar Surfaces
Authors: Bravo Manuel , Baca Pilar , Llodra Juan Carlos , Osorio Estrella
Published: April 2007

Objective: The aim of this study was to determine the separate effects of dental sealants and fluoride varnish on dental caries in fissured and nonfissured surfaces of permanent first molars. Methods: A clinical trial was conducted with three groups of 6‐ to 8‐year‐old schoolchildren: a sealant group (n=100), in which Delton was applied to first molars; a varnish group (n=98), in which Duraphat was applied to first molars; and a control group (n=116), which had no intervention as part of the study. Absolute and percent caries reductions were compared at 24 months. Results: Compared to the controls, sealants resulted in a 68 percent and 87 percent reduction on fissured and nonfissured surfaces, respectively. The corresponding figures for varnish were 38 percent and 66 percent. Conclusion: Sealant and fluoride varnish are effective in preventing caries in both fissured and nonfissured surface.
Establishing Maternal and Child Health Data Collection Priorities for State and Local Oral Health Programs
Authors: Kuthy Raymond A. , Siegal Mark D. , Wulf Colleen A.
Published: April 2007

Objective: This paper identifies specific data items for use by state and local agencies in a maternal and child oral health needs assessment model. Methods: A modified Delphi approach was used to develop consensus on items for inclusion in the data set and their relative importance. Initially, 31 data items were chosen from several national sources. All state dental directors, along with other selected administrators and advisory committee members for this process, were asked to categorize each of the data items as core (essential), important but optional, or of lesser importance. Short comments about each data item were accepted, as were additions to the list of data items. Two rounds of comments were held. Results: Eleven data items/types of information were selected as core items to be included in all needs assessments. All but one of these items were determined by the scores of the respondents. The advisory committee strongly recommended that at least one core item relate to the public's perception of oral health. Some differences in perceived importance of several items existed among the state dental directors, local dental directors, and the advisory committee. Twenty‐one items were identified as being important, but optional, and seven were considered less than important and not included in the model data set. Conclusions: A modified Delphi approach facilitated the development of core and optional data items for a model oral health needs assessment. This model has potential for a common reporting mechanism so that states and local dental programs can share data.
Taking Dental Self‐care to the Extreme: 24‐month Incidence of Dental Self‐extractions in the Florida Dental Care Study
Authors: Gilbert Gregg H. , Duncan R. Paul , Earls Janet L.
Published: April 2007

Objective: A common response to health‐related symptoms is to treat oneself in lieu of or prior to seeking formal health care. Among the more extreme forms of dental self‐care is dental self‐extraction. To our knowledge, no study of the incidence of this behavior has been conducted. The objective of this study was to determine if one form of dental self‐care, dental self‐extraction, is a real phenomenon, and if so, to determine its incidence. Methods: The Florida Dental Care Study is a longitudinal study of changes in oral health, whose subjects participated for an interview and clinical examination at baseline and 24 months after baseline. Results: Of the 739 persons who participated through 24 months, 176 lost one or more teeth. Of these 176 persons, 13 (7%) extracted one or more of their own teeth. The clinical status at baseline of the self‐extracted teeth was consistent with the ability to self‐extract. Conclusion: The phenomenon of dental self‐extraction is real and is not limited to residents of developing nations or geographically isolated areas. Because of the potential for prolonged bleeding or bacterial endocarditis in certain population groups, community health clinicians and officials should be cognizant of this behavior.
Residency Training in Dental Public Health: Assessment of Status, Needs, and Issues
Authors: Wotman Stephen , Pyle Marsha , Duffy Rosemary
Published: April 2007

The opportunities for public health training have declined over the years while the need for public health skills is likely to increase. This paper reports the results of a project, sponsored by the Health Resources and Services Administration, which answers the question of “how best to invest in the dental public health education system so as to fulfill the profession's responsibilities to protect and improve the oral health of individuals and society.’’ An information base on dental public health education, practice, and specialization was developed from an extensive review of the literature and a survey of dentists concerning employment and practice requirements for public health dentists. An advisory group considered this information, met to discuss the issues involved in dental public health training, and provided advice to the project staff. Based on the information gathered as part of the project, recommendations were made to: (1) develop a grant program to support advanced education in dental public health; (2) increase the competencies of dentists who are working in public health positions and not eligible for board certification via off‐site residencies; (3) develop model programs in areas of great need, such as general public health, management, policy, prevention, environmental health and research, that in conjunction with a basic public health core, could satisfy the eligibility requirements of the American Board of Dental Public Health; (4) develop student loan forgiveness programs for dentists and dental hygienists working in public health; and (5) develop additional credential recognition programs for dental public health workers.
The Development of Competencies for Specialists in Dental Public Health
Authors: Weintraub Jane A.
Published: April 2007

This paper describes the process of developing new competency statements and performance indicators for the specialty of dental public health. These competencies help define the specialty and provide a base for educational curricula and the specialty board examination. The process included a survey of four target groups: all board members, all directors or co‐directors of advanced education programs in dental public health, people who had become diplomates in the last three years, and all students currently enrolled in dental public health programs. Many constituencies were represented at the workshop, conducted in May 1997, to develop the competency document. After the workshop, the document underwent a series of review activities.
Prevention of Early Childhood Caries—Results of a Fluoride Toothpaste Demonstration Trial on Chinese Preschool Children after Three Years
Authors: Schwarz Eli , Lo Edward C. M. , Wong May C. M.
Published: April 2007

Objectives: This field demonstration trial evaluates the long‐term effects of introducing daily toothbrushing with fluoride toothpaste in a Chinese kindergarten (test group) compared to caries development in children who had no organized preventive program (control group). Methods: In the test group teacher‐supervised toothbrushing was initiated with 1,000 ppm MFP toothpaste in addition to oral health education activities. Test and control children were examined at baseline (n=289, aged 3 years) and annually thereafter. Results: After three years, 251 children (87%) were still in the trial. Caries development (dmfs) calculation included only those children who were present at both baseline and subsequent annual examinations. At baseline the mean dmfs was 4.8 in the test group and 6.5 in the control group (NS). After three years the caries increment was 6.2 and 8.4 in the test group and the control group, respectively (P<.05). Adjusting for reversals, the net caries increment was 3.6 and 6.3, respectively (P<.01). Additionally, multiple linear regression analysis indicated that both baseline dmfs, the program and plaque level had a significant effect on the net caries increment. The use of hierarchical caries severity zones was useful for the identification of those children most at risk for further caries development. Conclusion: We conclude that a daily toothbrushing with limited involvement of professional staff was feasible in a Chinese kindergarten and that caries development was significantly slowed in the test children. Caries severity zones may possibly assist in determining levels of intervention.
Dental Utilization by Low‐income Mothers
Authors: Kuthy Raymond A. , Odom John G. , Salsberry Pamela J. , Nickel Jennie L. , Polivka Barbara J.
Published: April 2007

Objective: This study examines the influence of predisposing, enabling, and need variables on whether low‐income mothers sought dental care during the past year. This report is a substudy of mothers and children on their self‐reported health status, utilization, access, and satisfaction with health care in general. Methods: A convenience sample of 502 mothers and youngest child younger than 6 years old was administered a face‐to‐face questionnaire in four Ohio counties. Information was collected at county human services offices and WIC clinics between November 1995 and July 1996. Using whether or not the mother sought dental care as the dependent variable, logistic regression models were created for the variables within the predisposing, enabling, and need characteristics separately and together. Results: Fewer than one‐half of the mothers sought dental care during the past year. Variables associated with the predisposing characteristic explained little about who sought care. Those mothers who have Medicaid coverage are 2.7 times more likely to have a dental visit than those without insurance. Moreover, those mothers who perceive any dental need are several times less likely to have received dental care than those who have no perceived need. Conclusion: Even among a somewhat homogeneous population of low‐income women, source of payment for dental services and perceived need for dental care are discriminating variables in determining who seeks dental care.
The Efficiency of Semiannual Silane Fluoride Varnish Applications: a Two‐year Clinical Study in Preschool Children
Authors: Petersson Lars G. , Twetman Svante , Pakhomov Gennady N.
Published: April 2007

Objective: The aim of this two‐year community demonstration trial was to study the caries inhibitory effects of semiannual applications of a fluoride varnish in preschool children. Methods: Twenty‐four public dental health clinics in the county of Halland, Sweden, with 5,137 preschool children, 4 and 5 years of age, were matched and equally allocated to a fluoride varnish group (n=2,535) and a reference group (n=2,602). The children in the fluoride varnish group were treated every six months with topical applications of a silane fluoride varnish, Fluor Protector (0.1% F), while no fluoride varnish was used in the reference group. Both groups received a basic preventive program at annual checkups consisting of dietary counseling and instructions to parents to brush their children's teeth at least once daily with fluoridated dentifrice. Caries data were collected by clinical examinations at baseline and after one and two years. Results: Caries prevalence at baseline did not differ significantly between the groups. After two years, the mean caries incidence was low and no statistical difference was found in the total number of carious and filled surfaces (dfs) between the two groups. However, the incidence of approximal lesions (dfsa) was significantly lower (P<.05) in the fluoride varnish group than the reference group. Children in the fluoride varnish group with dfs scores of 1–4 and ≥5 at the start of the study exhibited a statistically significant (P<.05) reduction in approximal caries incidence of 19 percent and 25 percent, respectively, when compared with the reference group. Conclusion: Preschool children 4 and 5 years of age with clinical caries who receive semiannual applications of a silane fluoride varnish containing 0.1 percent F experience a reduced incidence of approximal caries over two years.
Determinants for Dental Visit Behavior among Hong Kong Chinese in a Longitudinal Study
Authors: Lo Edward C. M. , Schwarz Eli
Published: April 2007

Objectives: The aim of this research was to study the major determinants for dental services utilization among middle‐aged Hong Kong Chinese in a longitudinal study using an expanded Andersen and Newman model as the theoretical framework. Methods: A random sample of 372 middle‐aged Hong Kong Chinese were interviewed and clinically examined in an oral health survey. The findings were explained to the subjects and they were advised to seek care from their own dentist as appropriate. Results: A total of 322 subjects were interviewed over the telephone after 12 months. About half had visited a dentist within the study period. Results of the bivariate analysis showed that proportionally more subjects who had dental benefit coverage, had prevention‐oriented attitudes, were regular users of dental services, had received counseling from a dentist, or had more filled teeth at the baseline examination had visited a dentist within the study period. Logistic regression analysis produced a final model consisting of seven factors and three interaction terms that was able to classify 68 percent of the subjects into the correct user category. Conclusion: The expanded Andersen and Newman model was useful as a theoretical framework in studying the dental services utilization behaviors of the Hong Kong adults.
Patterns of Dietary Fluoride Supplement Use During Infancy
Authors: Levy Steven M. , Kiritsy Mary C. , Slager Susan L. , Warren John J.
Published: April 2007

Objectives: This paper reports on patterns of dietary fluoride supplement use during infancy. Methods: Data were collected by mail for a birth cohort (n=1,072) studied at 6 weeks and 3, 6, 9, and 12 months of age. Results: Percentages using supplements were 13.7 at 6 weeks, 13.4 at 3 months, 16.5 at 6 months, 13.0 at 9 months, and 12.1 at 12 months. Among those receiving supplements, mean proportions of weeks that supplements were received during the different time periods varied from 0.59 to 0.80. Number of days per week receiving supplements averaged 4.8 to 5.0. Mean fluoride dosages when supplements were received were 0.22 mg to 0.24 mg. Estimated average daily fluoride ingestion per day (among those receiving supplements during that time period and factoring in those days and weeks that supplements were not received) was 0.11 mg at 6 weeks, 0.15 mg at 3 months, 0.12 mg at 6 months, 0.11 mg at 9 months, and 0.14 mg at 12 months. Among the subset of 129 children with complete data at all time points who used supplements sometime during their first year of life, mean annual daily supplement dosage was 0.07 mg fluoride, with 75 percent having less than or equal to 0.10 mg. Those infants with mothers and fathers with more education were more likely to receive supplements. Conclusion: Group average use of fluoride supplements was fairly consistent over the 12 months; however, individual patterns varied substantially. Estimated actual mean daily fluoride intake when including days that supplements were not received was substantially less than the recommended 0.25 mg per day.
Preventive Oral Health Behaviors among African‐Americans and Whites in Detroit
Authors: Ronis David L. , Lang W. Paul , Antonakos Cathy L. , Borgnakke Wenche S.
Published: April 2007

Objective: This study compared the preventive oral health behaviors of African‐Americans and whites. Methods: Face‐to‐face interviews were conducted with a probability sample of 384 African‐American and 358 white adults living in the greater Detroit area. Questions focused on brushing, flossing, and dental visits. Results: More than 95 percent of both groups reported brushing daily; however, whites were more likely to brush all teeth, including parts that do not show. Frequency of flossing did not differ between groups. African‐Americans, however, were less likely to floss all of their teeth. Whites were more likely than African‐Americans to get dental check‐ups at least once a year and much less likely to indicate they had never had a dental check‐up. African‐Americans tended to have less education and lower family income than whites and were more likely than whites to have Medicaid. Race differences in brushing thoroughness and annual check‐ups were greatly reduced when income, education, and insurance were controlled statistically. Conclusion: African‐Americans are less likely than whites to brush thoroughly, floss thoroughly, and get dental check‐ups. These differences are partly traceable to differences in socioeconomic status and access to professional oral health care.
Coverage and Quality of Oral Cancer Information in the Popular Press: 1987–98
Authors: Canto Maria T. , Kawaguchi Yoko , Horowitz Alice M.
Published: April 2007

Objectives: National data show a lack of knowledge and misinformation about oral cancer and its early detection among the general public. A major source of health information is the popular press. For that reason this study reviewed coverage and quality of news items on the topic of oral cancer in the popular press. In addition, the number and types of tobacco advertisements in women and men's magazines were recorded for a one‐year period. Methods: Articles from magazines and newspapers were retrieved from the Magazine Index (1987 to April 1998), Newspaper Abstract (1989 to April 1998) and the Health & Wellness (1987 to April 1998) databases. The articles were analyzed both for adequacy of content and information. Results: A total of 50 articles and news items including oral cancer were identified and analyzed, 18 from newspapers and 32 from magazines. Ninety‐four percent of the articles mentioned at least one risk factor for oral cancer. More than half of the articles (56%) identified spit tobacco (chewing tobacco or snuff) as the major risk factor for oral cancer, while far fewer mentioned either cigarettes (32%) or cigars (12%). Over 50 percent of the articles did not mention warning signs for oral cancers. Fourteen percent suggested clinical oral cancer examinations by a health professional; only 8 percent advised the use of self‐examination. A total of 417 tobacco advertisements (482 pages) were found among 22 magazines for the one‐year period. They included 410 cigarette ads, seven cigar ads, and no spit tobacco ads. Conclusion: This study demonstrates the lack of coverage about oral cancer in the popular press in the past decade and provides a partial explanation of the public's lack of knowledge and misinformation about oral cancers.
Changes in Dental Health and Dental Health Habits from 3 to 5 Years of Age
Authors: Mattila Marja‐Leena , Paunio Päivi , Rautava Päivi , Ojanlatva Ansa , Sillanpää Matti
Published: April 2007

Objectives: This study sought to determine how dental health and dental health habits change from 3 to 5 years of age and to consider whether preventive dental health care helped in preventing or halting caries in children. Methods: The study included 67 maternity health care clinics, 72 well‐baby clinics, and 69 dental health care clinics. Of the 1,292 newborn children, 1,003 (90.8%) were included in this study. Results: Preventive dental health care contributed to dental caries being halted in only 13.2 percent of those children who had enamel caries at 3 years of age. The dmft index did not increase in 22.6 percent of those children who had dentinal caries at 3 years of age. For all others, the disease became more severe. Toothbrushing habits of 3‐year‐old children were very consistent over the two years studied. Children were at a risk for caries when their mothers had nine years of basic education, when they already had plaque and caries at 3 years of age, and when the frequency of eating sweets increased the most during the two‐year study period. Conclusion: Among 3‐year‐old children, plaque is an indicator of caries risk and therefore should be a key element in health education. Those children who already have evidence of caries at 3 years of age should be the target of preventive dental services because of their increased risk.
Components of Self‐reported Oral Health and General Health in Racial and Ethnic Groups
Authors: Atchison Kathryn A. , Der‐Martirosian Claudia , Gift Helen C.
Published: April 2007

Objective: The objective of this study is to investigate the validity of the General Oral Health Assessment Index (GOHAI), a self‐reported oral health measure, when used in an all‐age adult sample of Hispanics and African‐Americans. Methods: The study groups were 506 disadvantaged Hispanic and African‐American adults who were recruited at low‐cost medical and dental clinics. To explore the validity of the GOHAI in an all‐age, ethnically diverse sample, principal component and principal factor analyses were conducted on the 12 items of the GOHAI and the 14 items constituting the MOS physical/social and mental health components. Results: Four factors accounted for 40 percent of the total variance of health as measured by the MOS and GOHAI items: general health, physical/worry oral health, mental health, and social oral health. An association between socioeconomic variables and each subscale was found to be significant except for the physical/worry oral health subscale. Conclusion: This study confirms that the GOHAI is valid when used in younger and ethnically diverse samples. The findings also emphasize that oral health is distinct from general health and that the use of generic self‐reported measures of health may miss important aspects of oral health that are valuable for dental health professionals.
Oral/Pharyngeal, Laryngeal, and Lung Cancer Discharge Trends in Department of Veterans Affairs Hospitals
Authors: Fedele Denise J. , Jones Judith A. , Niessen Linda C. , Guo Ingrid Y. , Harrison Kathleen
Published: April 2007

Objective: This paper describes trends in oral and pharyngeal (O/P) cancer diagnoses in Department of Veterans Affairs (VA) hospitals from 1983 to 1993 and compares these trends to those of laryngeal and lung cancers. Methods: The VA patient treatment file was used to identify unique hospital discharges from 1983 to 1993 having ICD‐9‐CM codes for O/P, laryngeal, and lung cancers. Descriptive statistics were tabulated to determine prevalence and distribution. Trends of change over time were analyzed using regression analyses of the percent rate on year. Results: Between 1983 and 1993 the annual number of O/P cases among users of VA hospitals decreased from 4,983 to 3,298. Despite overall declines in O/P cancer discharges in VA, cancer of the pharynx, tongue, and salivary gland continues to increase. O/P cancer in younger persons also continues to increase in VA. Overall, laryngeal cancers significantly increased, while no significant change was associated with lung cancer. Conclusion: VA needs to evaluate the changes in the patterns of O/P cancer to ascertain whether this represents a shift in care from inpatient to outpatient care. VA should seek further information regarding these trends to better plan, implement, and evaluate programs to provide early diagnosis and treatment targeted to veterans.
The up and down bobbing of human walking: a compromise between muscle work and efficiency
Authors: Massaad Firas , Lejeune Thierry M. , Detrembleur Christine
Published: April 2007

Human walking has a peculiar straight‐legged style. Consequently, the body's centre of mass (CM) moves up and down with each step, which is noticeable in their up and down head bobbing while walking. This vertical CM movement enables humans to save energy via a pendulum‐like mechanism but is probably a relatively recent locomotor innovation insofar as earliest bipeds may have walked flexed and flat. We investigated the mechanics, energetics, muscle efficiency and optimization of human walking by decreasing and increasing the vertical CM displacement (flat and bouncy walking) in comparison to normal walking at six speeds (1–6 km h−1). In both flat and bouncy walking, the pendular mechanism was reduced and the energy cost was increased. However, this increase was unexpectedly much sharper in flat walking where muscles provided normal mechanical work but with a decrease in muscle efficiency. In bouncy walking, muscles provided extra mechanical work in an efficient way. Our results showed that not only do humans bob up and down in normal walking to save energy via a pendulum‐like mechanism but also to make their muscles work efficiently. Actually, walking flat makes the muscles work in unfavourable conditions that waste energy. Furthermore, we are still close to a flat CM displacement relative to our current ability to change this displacement, which suggests that reducing vertical CM displacement is indeed important but only to certain limits. Evolution may ultimately have chosen the best compromise between flat locomotion that requires little work to move and bouncy locomotion that improves muscle efficiency to minimize energy consumption.
Mammalian target of rapamycin in the human placenta regulates leucine transport and is down‐regulated in restricted fetal growth
Authors: Roos Sara , Jansson Nina , Palmberg Isabelle , Säljö Karin , Powell Theresa L. , Jansson Thomas
Published: April 2007

Pathological fetal growth is associated with perinatal morbidity and the development of diabetes and cardiovascular disease later in life. Placental nutrient transport is a primary determinant of fetal growth. In human intrauterine growth restriction (IUGR) the activity of key placental amino acid transporters, such as systems A and L, is decreased. However the mechanisms regulating placental nutrient transporters are poorly understood. We tested the hypothesis that the mammalian target of rapamycin (mTOR) signalling pathway regulates amino acid transport in the human placenta and that the activity of the placental mTOR pathway is reduced in IUGR. Using immunohistochemistry and culture of trophoblast cells, we show for the first time that the mTOR protein is expressed in the transporting epithelium of the human placenta. We further demonstrate that placental mTOR regulates activity of the l‐amino acid transporter, but not system A or taurine transporters, by determining the mediated uptake of isotope‐labelled leucine, methylaminoisobutyric acid and taurine in primary villous fragments after inhibition of mTOR using rapamycin. The protein expression of placental phospho‐S6K1 (Thr‐389), a measure of the activity of the mTOR signalling pathway, was markedly reduced in placentas obtained from pregnancies complicated by IUGR. These data identify mTOR as an important regulator of placental amino acid transport, and provide a mechanism for the changes in placental leucine transport in IUGR previously demonstrated in humans. We propose that mTOR functions as a placental nutrient sensor, matching fetal growth with maternal nutrient availability by regulating placental nutrient transport.
Effective release rates at single rat Schaffer collateral–CA1 synapses during sustained theta‐burst activity revealed by optical imaging
Authors: Awatramani G. B. , Boyd J. D. , Delaney K. R. , Murphy T. H.
Published: April 2007

To understand how information is coded at single hippocampal synapses during high‐frequency activity, we imaged NMDA receptor‐mediated Ca2+ responses in spines of CA1 neurons using two‐photon microscopy. Although discrete quantal events were not readily apparent during continuous theta‐burst stimulation (TBS), we found that the steady‐state dendritic Ca2+ response was spatially restricted (half‐width < 1 μm), voltage dependent and sensitive to MK‐801, indicating that that it was mediated by activation of NMDA receptors at single synapses. Partial antagonism of NMDA receptors caused a similar reduction of NMDA EPSCs (measured at the soma) and local dendritic Ca2+ signals, suggesting that, like EPSCs, the steady‐state Ca2+ signal was made up of a linear addition of quantal events. Statistical analyses of the steady‐response suggested that the quantal size did not change dramatically during TBS. Deconvolution of TBS‐evoked Ca2+ responses revealed a heterogeneous population of synapses differing in their capacity to signal high‐frequency information, with an average effective steady‐state release rate of ∼2.6 vesicles synapse−1 s−1. To assess how the optically determined release rates compare with population measures we analysed the rate of decay of peak EPSCs during train stimulation. From these studies, we estimated a unitary vesicular replenishment rate of 0.02 s−1, which corresponds to an average release rate of ∼0.8–2 vesicles s−1 at individual synapses. Additionally, extracellular recordings from single Schaffer collaterals revealed that spikes propagate reliably during TBS. Hence, during high‐frequency activity, Schaffer collaterals conduct spikes with high fidelity, but release quanta with relatively lower efficiency, leaving NMDA receptor function largely intact and synapse specific. Heterogeneity in release rates between synapses suggests that similar patterns of presynaptic action potentials could trigger different forms of plasticity at individual synapses.
Three distinct muscarinic signalling pathways for cationic channel activation in mouse gut smooth muscle cells
Authors: Sakamoto Takashi , Unno Toshihiro , Kitazawa Takio , Taneike Tetsuro , Yamada Masahisa , Wess Jürgen , Nishimura Masakazu , Komori Seiichi
Published: April 2007

Using mutant mice genetically lacking certain subtypes of muscarinic receptor, we have studied muscarinic signal pathways mediating cationic channel activation in intestinal smooth muscle cells. In cells from M2subtype‐knockout (M2‐KO) or M3‐KO mice, carbachol (100 μm) evoked a muscarinic cationic current (mICat) as small as ∼10% of mICatin wild‐type (WT) cells. No appreciable current was evoked in M2/M3double‐KO cells. All mutant type cells preserved normal G‐protein–cationic channel coupling. The M3‐KO and WT mICateach showed a U‐shaped current–voltage (I–V) relationship, whereas the M2‐KO mICatdisplayed a linearI–Vrelationship. Channel analysis in outside‐out patches recognized 70‐pS and 120‐pS channels as the major muscarinic cationic channels. Active patches of M2‐KO cells exhibited both 70‐pS and 120‐pS channel activity usually together, either of which consisted of brief openings (the respective mean open times Oτ= 0.55 and 0.23 ms). In contrast, active M3‐KO patches showed only 70‐pS channel activity, which had three open states (Oτ= 0.55, 3.1 and 17.4 ms). In WT patches, besides the M2‐KO and M3‐KO types, another type of channel activity was also observed that consisted of 70‐pS channel openings with four open states (Oτ= 0.62, 2.7, 16.9 and 121.1 ms), and patch current of this channel activity showed a U‐shapedI–Vcurve similar to the WT mICat. The present results demonstrate that intestinal myocytes are endowed with three distinct muscarinic pathways mediating cationic channel activation and that the M2/M3pathway targeting 70‐pS channels, serves as the major contributor to mICatgeneration. The delineation of this pathway is consistent with the formation of a functional unit by the M2‐Goprotein and the M3‐PLC systems predicted to control cationic channels.
Heterogeneity of firing properties among rat thalamic reticular nucleus neurons
Authors: Lee Sang‐Hun , Govindaiah G. , Cox Charles L.
Published: April 2007

The thalamic reticular nucleus (TRN) provides inhibitory innervation to most thalamic relay nuclei and receives excitatory innervation from both cortical and thalamic neurons. Ultimately, information transfer through the thalamus to the neocortex is strongly influenced by TRN. In addition, the reciprocal synaptic connectivity between TRN with associated thalamic relay nuclei is critical in generating intrathalamic rhythmic activities that occur during certain arousal states and pathophysiological conditions. Despite evidence suggesting morphological heterogeneity amongst TRN neurons, the heterogeneity of intrinsic properties of TRN neurons has not been systematically examined. One key characteristic of virtually all thalamic neurons is the ability to produce action potentials in two distinct modes: burst and tonic. In this study, we have examined the prevalence of burst discharge within TRN neurons. Our intracellular recordings revealed that TRN neurons can be differentiated by their action potential discharge modes. The majority of neurons in the dorsal TRN (56%) lack burst discharge, and the remaining neurons (35%) show an atypical burst that consists of an initial action potential followed by small amplitude, long duration depolarizations. In contrast, most neurons in ventral TRN (82%) display a stereotypical burst discharge consisting of a transient, high frequency discharge of multiple action potentials. TRN neurons that lack burst discharge typically did not produce low threshold calcium spikes or produced a significantly reduced transient depolarization. Our findings clearly indicate that TRN neurons can be differentiated by differences in their spike discharge properties and these subtypes are not uniformly distributed within TRN. The functional consequences of such intrinsic differences may play an important role in modality‐specific thalamocortical information transfer as well as overall circuit level activities.
Preparation of Ni Nanoparticles and Evaluation of Their Tribological Performance as Potential Additives in Oils
Authors: Qiu Sunqing , Zhou Zhongrong , Dong Junxiu , Chen Guoxu
Published: April 2007

The application of nanoparticles in tribology has received considerable attention in recent years. In this paper, we described the preparation of Ni nanoparticles in microemulsions of sodium dodecyl sulphate (SDS)/isopentanol/cyclohexane/water and their tribological performance as additives in oils. The size of these nanoparticles is about 10 nm, and their shape is spherical. The four-ball test results indicate that Ni nanoparticles are potential additives for lubricating oils, and the tribological performance of lubricating oils can be improved significantly by dispersing Ni nanoparticles in oils. The maximum non-seizure load (PB) has been increased by 67 percent as compared with background oil. The wear scar diameter has been reduced from 0.71 mm to 0.49 mm. The relative percentage in friction coefficient has decreased 26 percent. The tribological mechanism is that a deposit film in the contacting regions was formed, which prevented the direct contact of rubbing surfaces and greatly reduced the frictional force between the contacting surfaces.
The Effect of Shear Flow and Dissolved Gas Diffusion on the Cavitation in a Submerged Journal Bearing
Authors: Groper M. , Etsion I.
Published: April 2007

Two possible, long standing speculated mechanisms are theoretically investigated in an attempt to understand previous experimental observations of pressure build up in the cavitation zone of a submerged journal bearing. These mechanisms are (1) the shear of the cavity gas bubble by a thin lubricant film dragged through the cavitation zone by the rotating shaft and (2) the mass transfer mechanism which dictates the rate of diffusion of dissolved gas out of and back into the lubricant. A comparison with available experimental results reveals that while the cavitation shape is fairly well predicted by the “shear” mechanism, this mechanism is incapable of generating the level of the experimentally measured pressures, particularly towards the end of the cavitation zone. The “mass transport” mechanism is found inadequate to explain the experimental observations. The effect of this mechanism on the pressure build up in the cavitation zone can be completely ignored.
Spreading Mechanism of PFPE Lubricant on the Magnetic Disks
Authors: Tani Hiroshi , Matsumoto Hiroyuki
Published: April 2007

The lubrication mechanism when the magnetic head is sliding on the magnetic disk in the drag test with cyclic interval rest periods, is discussed. A long rest period decreased the wear of disks and friction force. This result indicated that the reflow of lubricant into the contact areas decreased the wear of texture asperities. Next, the molecular spreading behavior of a lubricant film was calculated by Monte Carlo method to estimate the effect of lubricant recovering velocities. The lubricant replenishment into a thinner lubricant area made by an etching technique was measured. The measured profiles of lubricant replenishment were approximately agreed with the calculated profiles using a spreading model. It was clearly estimated that the reflow velocities changed in various cases of the environmental temperature, the radius of removal lubricant area, and the thickness of the lubricant films. Experimentally, the dependencies of temperature, the radius of removal lubricant area, and the lubricant thickness were measured in the drag test. This lubricant-spreading model adequately explained these results.
Slider Vibration Analysis at Contact Using Time-Frequency Analysis and Wavelet Transforms
Authors: Knigge Bernhard , Talke Frank E.
Published: April 2007

Time-frequency analysis and wavelet transforms are employed to investigate transient contact dynamics at the head/disk interface of computer hard drives. Wavelet transforms are used to resolve multiple short consecutive contacts at high time resolution at high frequencies. The reassignment method is applied to the time-frequency distribution to enhance the time-frequency resolution, thereby allowing to resolve air-bearing and slider body frequencies simultaneously. The results indicate that strong impacts between slider and disk can lead to excitations of slider body and suspension vibrations. Finite element modal analysis of nano and pico glide sliders is found to be in good agreement with experimentally measured frequencies.
The Effect of Porosity on the Head-Media Interface
Authors: Knudsen James K. , Palmquist Kenneth E.
Published: April 2007

A lubrication model for the head-media interface is presented which includes the effect of porosity in the media coating. Experimental data is shown which illustrates the reduction in head-media spacing as porosity is increased. A modified Reynolds equation is derived to account for the effects of coating porosity. Other authors have considered a very thin porous layer to simulate a liquid lubricant or surface microstructure on a nonporous substrate. This study considers a porous layer that can be much larger than the bearing clearance. Darcy’s law is used in the porous layer. Velocity-slip effects, resulting both from rarefaction and the porous boundary, are considered. The modified Reynolds equation is applied to a simple capillary model of a porous layer as an illustrative example. The modified Reynolds equation was incorporated into a finite-element model for the head-media interface. Computations show reduced head-media clearance as porosity and permeability are increased in agreement with experimental data.
Head-Disk Dynamics in the Flying, Near Contact, and Contact Regimes
Authors: Wang Run-Han , Nayak Vasant , Huang Fu-Ying , Tang Wade , Lee Francis
Published: April 2007

To achieve an areal density approaching 50 Gb/in.2 for the magnetic storage of data in hard disk drives requires reduced mechanical and magnetic spacing. Off-track jitter caused by airflow or contact can cause track misregistration on the order of 20–70 nm which may be excessive for adequate servo performance. The magnetic signal can be used to identify both the vertical spacing modulation due to the air bearing modes and off-track jitter due to suspension modes with nanometer resolution. We find that the off-track jitter in the flying regime is driven by airflow and is a strong function of the disk velocity and the suspension type. In the contact regime, the vertical spacing modulation and off-track jitter increase due to contact. Using a laser Doppler vibrometer we identified the leading contribution to the off-track jitter to be primarily the first torsional mode (T1) and to a lesser extent the first bending mode (B1) of the suspension.
Thermal Features of Compliant Foil Bearings—Theory and Experiments
Authors: Salehi Mohsen , Swanson Erik , Heshmat Hooshang
Published: April 2007

The paper presents an analytical and experimental investigation aimed at eliciting the thermal characteristics of air lubricated compliant foil bearings. A Couette Approximation to the energy equation is used in conjunction with the compressible Reynolds equation to obtain a theoretical temperature distribution in the air used as a lubricant. The effect of temperature on the thermal properties of the working fluid is included. In parallel, an experimental program was run on a 100 mm diameter foil bearing operating at speeds up to 30,000 rpm employing cooling air across the bearing. The temperature rise of the cooling air provided an indication of the amount of heat energy conducted across the top foil of the bearing from the hydrodynamic film. The temperatures resulted from some tests are compared with the temperatures predicted by the analysis, and maximum over-prediction of about 19 percent was obtained. This simplified approach provides us with reasonably predicted temperatures. By comparing the theoretical heat dissipation obtained from the analytical predicted temperatures with the amount of heat carried away by the cooling air it was possible to arrive at the relative quantities of heat transferred from the bearing by convection via side leakage and by conduction via the top foil. From these comparisons it was deduced that about an average of 80 percent of the heat energy is carried away by conduction. The transient temperatures of the foil bearing in conducted tests for various speeds and loads are also presented.
Steady State Performance Characteristics of a Tilting Pad Thrust Bearing
Authors: Glavatskikh Sergei B.
Published: April 2007

The paper reports results of the experimental investigation into the steady state performance characteristics of a tilting pad thrust bearing typical of design in general use. Simultaneous measurements are taken of the pad and collar temperatures, the pressure distributions, oil film thickness, and power loss as a function of shaft speed, bearing load, and supplied oil temperature. The effect of operating conditions on bearing performance is discussed. A small radial temperature variation is observed in the collar. A reduction in minimum oil film thickness with load is approximately proportional to p−0.6, where p is an average bearing pressure. It has also been found that the oil film pressure profiles change not only due to the average bearing load but also with an increase in shaft speed and temperature of the supplied oil.