Biomedical subjects

M H Wilson

Publications and source records attributed to M H Wilson.

At least 19 recordsLinked to original sources

PubMed2005

Increased and decreased activity elicits specific morphological adaptations of the neuromuscular junction.

The objective of this investigation was to compare the effects of decreased vs. increased activity on the neuromuscular system. Twenty-four young adult (7 weeks old) Sprague-Dawley rats were randomly assigned to three treatment groups (N=8/group). Increased activity was achieved by treadmill running for up to 1 h/day. Decreased activity was induced by muscle unloading via the hindlimb suspension model. Control animals engaged in normal weight bearing and ambulatory activity. At the end of the 10 week intervention period, animals were killed and soleus muscles were removed, quickly frozen, and examined using cytofluorescent (neuromuscular junctions) and histochemical (myofibers) procedures. Pre-synaptic morphology was quantified by measuring nerve terminal branching, and post-synaptic assessment was conducted by staining acetylcholine receptors at the endplate. Myofiber profiles of solei were compiled by determining fiber size (cross-sectional area) and fiber type composition. Results show that exercise training significantly (P<or=0.05) enhanced nerve terminal branching without modifying endplate size. In contrast, muscle unloading failed to influence nerve terminal branching, but significantly reduced endplate dimensions. Likely, the diminution of endplate size among unloaded myofibers was caused by the dramatic loss of size (approximately 60%) observed among those fibers. Both increased and decreased activity evoked reductions in the ratio of endplate area to length of nerve terminal branches, thus altering the pre- to post-synaptic relationship of neuromuscular junctions. In conclusion, the present data demonstrate that both increased and decreased activity significantly remodels the neuromuscular junction, but the locus (pre- vs. post-synaptic) and nature (expansion vs. reduction) of that remodeling are specific to the form of the alteration in activity.

Animals↗

PubMed2001

Factors preventing gun acquisition and carrying among incarcerated adolescent males.

CONTEXT: Despite the wide availability of guns in the United States, not all delinquent adolescents own guns and not all adolescent gun owners carry them at all times. Research about the factors that prevent high-risk youth from acquiring and carrying guns is limited. OBJECTIVE: To determine, from the perspective of incarcerated adolescent males, factors that prevent acquiring or carrying guns, either on a temporary or permanent basis. DESIGN AND SETTING: In-depth, semistructured interviews were conducted with randomly selected incarcerated adolescent males at a residential juvenile justice facility from January to May 1998. Transcribed interviews were examined for recurrent themes. PARTICIPANTS: Forty-five incarcerated adolescent males. MAIN OUTCOME MEASURES: Reported factors limiting gun acquisition and carrying. RESULTS: Seventy-one percent of the sample had either owned or carried a gun out of their home. We identified 6 recurring themes that, at least on occasion, prevented or delayed delinquent youth from acquiring or carrying guns. The most commonly cited factors were fear of being arrested and incarcerated and lack of perceived need for a gun. Other themes included not wanting to hurt oneself or others, respect for the opinions of others, inability to find a source for a desired gun, and lack of money to acquire a desired gun. CONCLUSIONS: We identified 6 factors that limited gun acquisition and carrying among a sample of incarcerated male adolescents. Knowledge of these factors should inform intervention efforts to reduce youth gun acquisition and carrying.

Adolescent↗

PubMed2001

The role of a conserved inter-transmembrane domain interface in regulating alpha(2a)-adrenergic receptor conformational stability and cell-surface turnover.

Functional and structural data from G protein-coupled receptors (GPCR) predict that transmembrane-domain (TM)2 is adjacent to TM7 within the GPCR structure, and that within this interface a conserved aspartate in TM2 and a conserved asparagine in TM7 exist in close proximity. Mutation at this D79(TM2)-N422(TM7) interface in the alpha(2A)-adrenergic receptor (alpha(2A)AR) affects not only receptor activation but also cell-surface residence time and conformational stability. Mutation at TM2(D79N) reduces allosteric modulation by Na(+) and receptor activation more dramatically than affecting cell-surface receptor turnover and conformational stability, whereas mutation at TM7(N422D) creates profound conformational instability and more rapid degradation of receptor from the surface of cells despite receptor activation and allosteric modulation properties that mirror a wild-type receptor. Double mutation of TM2 and 7(D79N/N422D) reveals phenotypes for receptor activation and conformational stability intermediate between the wild-type and singly mutated alpha(2A)AR. Additionally, the structural placement of a negative charge at this TM2/TM7 interface is necessary but not sufficient for receptor structural stability, because mislocalization of the negative charge in either the D79E alpha(2A)AR (which extends the charge out one methylene group) or the D79N/N422D alpha(2A)AR (placing the charge in TM7 instead of TM2) results in conformational lability in detergent solution and more rapid cell-surface receptor clearance. These studies suggest that this interface is important in regulating receptor cell-surface residence time and conformational stability in addition to its previously recognized role in receptor activation.

Allosteric Regulation↗

PubMed2000

Mechanisms regulating the cell surface residence time of the alpha 2A-adrenergic receptor.

Despite considerable insights concerning the mechanisms regulating short-term agonist-mediated G protein-coupled receptor (GPCR) internalization, little is known about the mechanisms regulating GPCR surface residence over long periods of time. Herein, we experimentally evaluated mechanisms regulating the surface t(1/2) of various alpha(2A)-adrenergic receptor (alpha(2A)AR) structures. The Delta 3i alpha(2A)AR (lacking the third intracellular loop), D79N alpha(2A)AR (impaired G protein coupling), and CAM alpha(2A)AR (enhanced G protein coupling) all exhibited a cell surface alpha(2A)AR turnover in Chinese hamster ovary cells that was faster than that of the wild type (WT). Cell surface receptor turnover could be slowed with ligand occupancy of D79N alpha(2A)AR (agonist or antagonist) and CAM alpha(2A)AR (antagonist only) but not the Delta 3i- or WT alpha(2A)AR. This selective ligand-induced surface stabilization was paralleled by a dramatic ligand-dependent receptor density upregulation for D79N- and CAM alpha(2A)AR structures. Receptors which exhibited surface turnover and density that could be modulated by ligand (D79N and CAM) also demonstrated structural instability, measured by a loss of radioligand binding capacity in detergent solution over time without parallel changes in receptor protein content. In contrast, the shorter surface t(1/2) of the Delta 3i alpha(2A)AR, whose cell surface t(1/2) and steady state density were not altered by ligand occupancy, occurred in the context of a structurally stable receptor in detergent solution. These results demonstrate that changes in receptor structure which alter receptor-G protein coupling (either an increase or decrease) are paralleled by structural instability and ligand-induced surface stabilization. These studies also provide criteria for assessing the structural instability of the alpha(2A)AR that can likely be generalized to all GPCRs.

Adrenergic alpha-2 Receptor Agonists↗

PubMed2000

Glutathione S-transferase M1 null genotype is associated with a decreased risk of myocardial infarction.

Tobacco smoke is a major cause of both cancer and vascular disease. Although its carcinogenic role via induction of DNA damage and mutation is well established, the mechanisms involved in vascular disease remain unclear. One possibility is that DNA damage causes smooth muscle cell proliferation in the intima of arteries, thereby contributing to atherothrombotic processes. The binding of chemicals to DNA is modulated by detoxification enzymes, including glutathione S-transferases (GST) and microsomal epoxide hydrolase (EPXH). We therefore examined whether polymorphisms in these genes influence risk of cardiovascular disease. Blood was obtained from 398 patients admitted for angiographic investigation of chest pain and 196 age- and sex-matched controls. Patients were subdivided into those with and without previous acute myocardial infarction (AMI). DNA was analyzed for deletions in the GSTM1 and T1 genes and for substitutions in EPXH and GSTP1 genes. The GSTM1 null genotype occurred at a significantly lower frequency in the AMI patient group (48%) compared both to patients with no history of AMI (59%) and to the control group (57.2%). When subjects were stratified for smoking status, a significant association was observed only in smokers, suggesting the polymorphism is more important in the presence of tobacco smoke exposure. The association remained significant after adjusting for age, sex, and stenosis (presence or absence). No significant associations were observed between the other genotypes and cardiovascular disease (chi(2) test; P>0.1). The results of this study indicate that the GSTM1 null genotype is protective against AMI, an effect that is more marked in smokers. However, further study is required in order to elucidate the as yet unexplained, mechanisms underlying this association.

Base Sequence↗

PubMed2000

Screening for iron deficiency anemia by dietary history in a high-risk population.

BACKGROUND: Iron deficiency anemia (IDA) in young children is important to identify because of its adverse effects on behavior and development. Because of costs and inconvenience associated with blood test screening and the decline in prevalence of IDA, the Institute of Medicine and the Centers for Disease Control and Prevention recommend that blood test screening for IDA be targeted to children first identified by dietary and health history. OBJECTIVE: To evaluate a parent-completed dietary and health history as the first stage of 2-stage screening for IDA. DESIGN AND METHODS: A cross-sectional study was conducted in inner-city clinics in children 9 to 30 months old having routine anemia screening as part of a scheduled visit. Parents completed a questionnaire and children had venous blood sampling for complete blood count and ferritin. Anemia was defined as Hb <11.0 g/dL. Iron deficiency (ID) was defined as ferritin <10 microg/L or mean corpuscular volume <70 fL and red cell distribution width >14.5%. Children were categorized into 1 of 4 groups: iron-sufficient, not anemic (ISNA); iron-sufficient, anemic (ISA); iron-deficient, not anemic (IDNA); and iron-deficient anemic (IDA). The questionnaire consisted of 15 dietary items in domains of infant diet, intake of solid food, intake of beverages, and participation in the Special Supplemental Nutrition Program for Women, Infants, and Children together with 14 historical items in domains of birth history, recent illness, chronic medical conditions, history of anemia, and maternal history. Analysis was performed on individual items, domains, and combinations of selected items. RESULTS: In the 282 study subjects, the prevalence of anemia (35%), IDNA (7%), and IDA (8%) did not vary significantly by age. Among individual historical and dietary questions, maternal history of anemia and drinking >2 glasses of juice per day identified the highest proportion of children with IDA: 50% sensitivity (95% confidence interval [CI]: 16,81) and 77% sensitivity (95% CI: 54,89), respectively. However, specificities for these questions were 60% (95% CI: 55,65) and 22% (95% CI: 17,27), respectively. Domains of questions with the highest sensitivity for IDA were beverage intake (91%; 95% CI: 68,99) and intake of solid food (91%; 95% CI: 68,99). However, specificities of the domains were only 14% (95% CI: 10,18) and 29% (95% CI: 24,35), respectively. The dietary items used by Boutry and Needlman were 95% (95% CI: 77, 99) sensitive but only 15% (95% CI: 11,19) specific for IDA. The recommendations of the Centers for Disease Control and Prevention for health and dietary screening were 73% (95% CI: 56,92) sensitive and 29% (95% CI: 24,35) specific for IDA. The individual questions, domains of questions, and interdomain groups of questions had similar sensitivity and specificity for anemia and ID (IDA + IDNA). CONCLUSION: In this high-risk population, neither individual nor combinations of parental answers to dietary and health questions were able to predict IDA, anemia, or ID well enough to serve as a first-stage screening test.

Anemia, Iron-Deficiency↗

PubMed1999

Why don't physicians follow clinical practice guidelines? A framework for improvement.

CONTEXT: Despite wide promulgation, clinical practice guidelines have had limited effect on changing physician behavior. Little is known about the process and factors involved in changing physician practices in response to guidelines. OBJECTIVE: To review barriers to physician adherence to clinical practice guidelines. DATA SOURCES: We searched the MEDLINE, Educational Resources Information Center (ERIC), and HealthSTAR databases (January 1966 to January 1998); bibliographies; textbooks on health behavior or public health; and references supplied by experts to find English-language article titles that describe barriers to guideline adherence. STUDY SELECTION: Of 5658 articles initially identified, we selected 76 published studies describing at least 1 barrier to adherence to clinical practice guidelines, practice parameters, clinical policies, or national consensus statements. One investigator screened titles to identify candidate articles, then 2 investigators independently reviewed the texts to exclude articles that did not match the criteria. Differences were resolved by consensus with a third investigator. DATA EXTRACTION: Two investigators organized barriers to adherence into a framework according to their effect on physician knowledge, attitudes, or behavior. This organization was validated by 3 additional investigators. DATA SYNTHESIS: The 76 articles included 120 different surveys investigating 293 potential barriers to physician guideline adherence, including awareness (n = 46), familiarity(n = 31), agreement (n = 33), self-efficacy (n = 19), outcome expectancy (n = 8), ability to overcome the inertia of previous practice (n = 14), and absence of external barriers to perform recommendations (n = 34). The majority of surveys (70 [58%] of 120) examined only 1 type of barrier. CONCLUSIONS: Studies on improving physician guideline adherence may not be generalizable, since barriers in one setting may not be present in another. Our review offers a differential diagnosis for why physicians do not follow practice guidelines, as well as a rational approach toward improving guideline adherence and a framework for future research.

Attitude of Health Personnel↗

PubMed1999

Use of social services by pregnant Medicaid eligible women in Baltimore.

OBJECTIVES: To use linked health and social service databases to determine differences in the use of social services by pregnant women in different managed care systems. METHODS: Comparison of service use by women enrolled in a fee-for-service primary care case management program (Maryland Access to Care or MAC), in a capitated health maintenance organization (HMO), or not assigned to managed care using six state databases. Participants included 5181 women receiving Medical Assistance (MA) and delivering in Baltimore City in 1993. Outcome measures were receipt of WIC, AFDC, and Food Stamps. RESULTS: The overall proportions of women receiving WIC, AFDC, and Food Stamps at delivery were 52.7%, 89.2%, and 62.7%, respectively. Women enrolled in an HMO at delivery were less likely to be receiving WIC (adjusted odds ratios, 0.8, 95% CI, 0.69 to 0.93), AFDC (OR, 0.20; CI, 0.03 to 0.43 for women with prior children and OR 0.13; CI, 0.09 to 0.20 for women without prior children), and Food Stamps (OR 0.77; CI, 0.59 to 0.95 for women with prior children and OR, 0.49; CI, 0.35 to 0.67 for women without prior children) than their MAC counterparts. Women not assigned to managed care also generally were less likely than their MAC counterparts to receive WIC (OR 0.55; CI, 0.46, 0.66), AFDC (OR 1.07; CI 0.83, 1.30 for women with prior children and OR 0.24; CI 0.18, 0.34 for women without prior children), and Food Stamps (OR 0.31; CI 0.08, 0.55 for women with prior children and OR 0.31; CI 0.23, 0.41 for women without prior children). CONCLUSIONS: Although many low-income pregnant women qualify for select social services, receipt of WIC and Food Stamps was low. Increasing efforts are needed by managed care systems and public health agencies to ensure delivery of appropriate services for women.

Adolescent↗

PubMed1999

Relationship between primary care practices in medical school admission and the matriculation of underrepresented-minority and female applicants.

PURPOSE: To determine whether primary care-oriented (generalist) admission practices at U.S. medical schools address physician workforce diversity issues by resulting in the admission of more members of underrepresented-minority populations or more women. METHOD: The authors performed cross-sectional, secondary analyses of databases from the Association of American Medical Colleges (AAMC). The independent variables were four generalist admission practices: generalist admission committee chair, greater representation of generalists on admission committee, offering preferential admission to likely generalists, and having a premedical recruitment activity targeting likely generalists. The control variable was public/private school ownership. The dependent variables were the mean ages of the matriculating classes and the proportions of students at each school who were African American, (total) underrepresented minorities, women, and married. RESULTS: Ninety-five percent of medical schools completed the AAMC's Survey of Generalist Physician Initiatives in either 1993 and 1994; 94% of matriculants replied to the AAMC's 1994 Matriculating Student Questionnaire. In multivariable analyses, no admission practice was associated with percentages of African Americans, total underrepresented minorities, or women. CONCLUSIONS: Schools with primary care-oriented admission practices did not admit greater percentages of underrepresented-minority students or women. Additional efforts may be required to attract and admit minority and female applicants.

Black or African American↗

PubMed1998

Associations between primary care-oriented practices in medical school admission and the practice intentions of matriculants.

PURPOSE: To assess associations of primary-care-oriented medical school admission practices with matriculants practice intentions. METHOD: The authors performed cross-sectional, secondary analyses of databases from the Association of American Medical Colleges (AAMC). The independent variables were four medical school admission practices. The control variable was school ownership (public vs private). The dependent variables were the proportions of matriculants at each school interested in generalism, rural practice, and locating in a socioeconomically deprived area. RESULTS: One hundred and twenty medical schools (95%) completed the AAMC's Survey of Generalist Physician Initiatives in either 1993 or 1994; 94% of matriculants replied to the AAMC's 1994 Matriculating Student Questionnaire. Twenty-five percent of the schools had admission committee chairs who were generalists, half had over 25% generalists on their admission committees, 64% gave admission preference to students likely to become generalists, and 33% reported premedical recruitment efforts that targeted applicants likely to become generalists. In multivariable analyses, premedical recruitment efforts and public school ownership (all p < .01) were associated with greater interest of matriculants in both generalism and rural practice. CONCLUSIONS: Public medical schools and schools with premedical recruitment activities targeting future generalists admitted greater proportions of students interested in primary care and rural practice.

Career Choice↗

PubMed1998

Evaluation of the alpha(2A)-adrenergic receptor gene in a heritable form of temporal lobe epilepsy.

An autosomal dominant form of human temporal lobe epilepsy (TLE) has been mapped to a region of chromosome 10q that contains the intronless alpha(2A)-adrenergic receptor (alpha(2A)AR) gene. Because mutation of the alpha(2A)AR gene in the mouse fosters epileptogenesis, we developed methods for analysis of the alpha(2A)AR coding region applicable to any pathophysiologic state in which the alpha(2A)AR could be implicated in the disease mechanism. This study rules out mutations in the alpha(2A)AR coding region as causal for this form of autosomal dominant TLE.

Animals↗

PubMed1996

Effective immunization with live attenuated influenza A virus can be achieved in early infancy. Pediatric Care Center.

The immunogenicity of vaccines can be modified in infancy by maternal antibodies and other immunizations. Hence, the safety and immunogenicity of two doses of 10(7) TCID50 of live, attenuated cold-adapted (ca) influenza A/Kawasaki/86 (H1N1) reassortant virus vaccine given with or apart from childhood immunizations were evaluated in infants, starting at 2, 4, or > 6 months of age, in randomized, double-blind trials. The ca vaccine was safe and did not significantly reduce the immunogenicity of the childhood vaccines in these infants. Infectivity of ca virus (virus shedding, > or = 4-fold rise in serum hemagglutination inhibition antibody titer, or both) was affected by age, quantity of ca virus given, and prior ca virus infection. Two doses of 10(7) TCID50 of ca influenza virus infected all infants, indicating that both doses are probably needed to achieve immunity against influenza in infants < 6 months of age.

Antibodies, Viral↗

PubMed1996

Evaluation of a live attenuated bovine parainfluenza type 3 vaccine in two- to six-month-old infants.

BACKGROUND: A safe and effective parainfluenza type 3 (PIV-3) virus vaccine is needed to prevent serious PIV-3-associated illness in infants younger than 6 months of age. In previous studies a live bovine PIV-3 (BPIV-3) vaccine, which was developed to prevent human PIV-3 (HPIV-3) disease, was shown to be safe, infectious, immunogenic and phenotypically stable in 6- to 36-month-old infants and children. METHODS: The safety, infectivity and immunogenicity of a single dose of the BPIV-3 vaccine was evaluated in a randomized, placebo-controlled, double blinded trial in 19 infants 2 to 5.9 months of age and in 11 additional 6- to 36-month-old subjects. RESULTS: The BPIV-3 vaccine was well-tolerated in both age groups and infected 92% of those younger than 6 months and 89% of those older than 6 months of age. Serum hemagglutination-inhibition (HAI) antibody responses to HPIV-3 and to BPIV-3, respectively, were detected in 42 and 67% of the younger infants, compared with 70 and 85% of the older subjects. In the younger infants we analyzed the rate of antibody response by titer of maternally acquired antibodies; low titer was defined as a preimmunization serum HAI titer < 1:8 and high titer was defined as a preimmunization serum HAI titer > or = 1:8. Young infants with a low titer of maternally acquired antibodies were significantly more likely to respond to the BPIV-3 vaccine that those with a high titer (89% vs. none for serum HAI response to BPIV-3; P = 0.02, Fisher's exact test). CONCLUSIONS: This study demonstrated that the BPIV-3 vaccine was safe and infectious in infants younger than 6 months of age and was also immunogenic in the majority of these young infants. Additional studies are needed to determine whether two or more doses will enhance the immunogenicity of the BPIV-3 vaccine in young infants and to assess its safety and immunogenicity when given simultaneously with routine childhood immunizations.

Antibodies, Viral↗

PubMed1995

A live attenuated bovine parainfluenza virus type 3 vaccine is safe, infectious, immunogenic, and phenotypically stable in infants and children.

The safety, infectivity, immunogenicity, transmissibility, and phenotypic stability of an intranasal bovine parainfluenza virus type 3 (BPIV-3) candidate vaccine was evaluated in a randomized, double-blind, placebo-controlled trial. Of human parainfluenza virus type 3 (HPIV-3)-seronegative children, 92% were infected, and 92% developed a serum hemagglutination-inhibiting (HAI) antibody response to BPIV-3 and 61% to HPIV-3. Geometric mean HAI titers were 1:40 to BPIV-3 and 1:16 to HPIV-3. In studies to evaluate vaccine transmissibility, none of 14 placebo recipients in close contact with 14 vaccinees shed BPIV-3. BPIV-3 isolates from seronegative vaccinees retained the attenuation phenotype when tested in rhesus monkeys. Although it is difficult to evaluate the safety and immunogenicity of such a vaccine in an open population of children who frequently become infected with HPIV-3, it appears that the live BPIV-3 vaccine is attenuated, infectious, immunogenic, poorly transmissible, and phenotypically stable and warrants further evaluation as a candidate vaccine in infants and children.

Animals↗

PubMed1995

A live human parainfluenza type 3 virus vaccine is attenuated and immunogenic in healthy infants and children.

The safety, infectivity, immunogenicity, and phenotypic stability of the cold-passaged (cp) candidate vaccine cp-45, a cold-adapted (ca), temperature-sensitive (ts) mutant of the JS strain of human parainfluenza virus type 3 (HPIV-3), was evaluated in 114 children 6 months to 10 years old in a randomized, placebo-controlled, double-blind trial. The cp-45 vaccine was well tolerated when given intranasally to parainfluenza virus type 3 (PIV-3)-seropositive and -seronegative children. With 10(4) or 10(5) TCID50 of cp-45 vaccine, 86% of seronegative vaccines were infected, 83% of whom shed virus at a mean peak titer of 10(22) pfu/mL. Virus present in respiratory specimens retained the ts phenotype, and each of 86 PIV-3 isolates tested retained both the ca and ts phenotypes. One dose of 10(5) TCID50 of vaccine induced a serum hemagglutination-inhibiting antibody response in 81% of vaccinees; the geometric mean titer was 1:32. These studies indicate that the cp-45 HPIV-3 vaccine is satisfactorily attenuated, infectious, immunogenic, and phenotypically stable and merits further evaluation in infants and young children.

Antibodies, Viral↗

PubMed1995

Safety and immunogenicity of a cold-adapted influenza A (H1N1) reassortant virus vaccine administered to infants less than six months of age.

A safe and effective influenza vaccine is needed to prevent serious influenza illness in infants younger than 6 months of age. The purpose of this study was to determine whether two doses of the cold-adapted (ca) influenza A reassortant vaccine would be safe and immunogenic in this age group. In the first part of this study, infants received two doses of 10(5) or 10(6) 50% tissue culture-infectious dose (TCID50) of the ca influenza vaccine separately from routine immunizations. In the second part of this study two 10(6) TCID50 doses of the ca influenza vaccine were given with routine immunizations at 2 and 4 or 2 and 6 months of age. The ca influenza vaccine was well-tolerated by participants in both parts of this study. Two doses of the ca influenza vaccine were immunogenic in infants who received them separately from routine immunizations; 83% of vaccinees developed protective titers of serum hemagglutination-inhibition (HAI) antibody. In contrast, when the ca vaccine was administered with routine immunizations, protective HAI antibody titers were induced in only 20% of those immunized at 2 and 4 months of age and 50% of those immunized at 2 and 6 months of age. There were no statistically significant associations between HAI antibody response to ca influenza vaccination and dose schedule, presence of passively acquired maternal HAI antibody, ethnic group or breast-feeding status. Young age at the time of first immunization, however, appeared to correlate with decreased response to the hemagglutinin antigen of the influenza A virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1995

Ultrasound measurement of transcranial distance during head-down tilt.

Exposure to microgravity elevates blood pressure and flow in the head, which may increase intracranial volume (ICV) and intracranial pressure (ICP). Rhesus monkeys exposed to simulated microgravity in the form of 6 degrees head-down tilt (HDT) experience elevated ICP. With humans, twenty-four hours of 6 degrees HDT bed rest increases cerebral blood flow velocity relative to pre-HDT upright posture. Humans exposed to acute 6 degrees HDT experience increased ICP, measured with the tympanic membrane displacement (TMD) technique. Other studies suggest that increased ICP in humans and cats causes measurable cranial bone movement across the sagittal suture. Due to the slightly compliant nature of the cranium, elevation of ICP will increase ICV and transcranial distance. Currently, several non-invasive approaches to monitor ICP are being investigated. Such techniques include TMD and modal analysis of the skull. TMD may not be reliable over a large range of ICP and neither method is capable of measuring the small changes in intracranial volume that accompany changes in pressure. Ultrasound, however, may reliably measure small distance changes that accompany ICP fluctuations. The purpose of our study was to develop and evaluate an ultrasound technique to measure transcranial distance changes during HDT.

Adult↗

PubMed1993

Preventing motor vehicle-occupant and pedestrian injuries in children and adolescents.

Injuries to young motor vehicle occupants and pedestrians continue to be a leading cause of childhood and adolescent mortality and morbidity. Recent articles relevant to childhood traffic injuries are reviewed here. Topics include infant passengers traveling on lap, effectiveness of seat belts for 4 to 14 year olds, passengers riding in the back of pickup trucks, and characteristics of young drivers. Socioecologic and geographic factors in pedestrian injuries are also discussed, along with parents' expectations of their children's street-crossing skills, the efficacy of a school-based pedestrian training program, and children's abilities to estimate safe intervals between traffic when crossing streets.

Accident Prevention↗