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Biomedical subjects

A M Smith

Publications and source records attributed to A M Smith.

At least 163 records · Page 9Linked to original sources
PubMed1997

Scopolamine increases prehensile force during object manipulation by reducing palmar sweating and decreasing skin friction.

The aim of this study was to determine whether relatively long-term changes in skin friction induced by a pharmacological blockade of sweat excretion would alter the grip forces applied to objects of a variety of different surface textures and frictions. Five men and three women were asked to lift the vertically mounted armature of a linear motor between the thumb and index finger and to hold it against an opposing force for 2 s. A 1.0-kHz tone indicated to the subject that the manipulandum had been correctly positioned between the upper and lower position limits. The linear motor generated a 2.5-N force tangential to the skin surface simulating an object weighing approximately 250 g. Three different polyamide plastic surfaces (either smooth or etched with 1.0 mm high Braille beads evenly spaced at 2- or 3-mm intervals) contacted the fingers in these experiments. Subjects lifted and held in a precision grip one of the three surfaces for blocks of ten consecutive trials, but the order of presentation of the three different textures was varied to offset the effect of expectancy. On a second block of ten trials the subjects were requested to release the object slowly to measure the ratio of the grip force normal to the grasped surface to the tangential load force at the moment of slip. This ratio or its inverse provided the coefficient of friction or the slip ratio for a particular subject and surface condition. Twelve hours prior to a second recording session all subjects placed transdermal patches of 1.5 mg scopolamine behind each ear to reduce palmar sweating by blocking the muscarinic receptors of exocrine sweat glands. The subjects were re-tested following procedures that were identical to the first session. Scopolamine significantly reduced the friction of the skin on the smooth and 2-mm beaded surfaces, but the friction of the 3-mm beaded texture was unaffected. Scopolamine also caused subjects to increase both the peak and static grip forces for all the textures including the 3-mm beaded surface, suggesting that for two of the three surfaces they were responding to the increased slipperiness of the skin due to reduced sweat production.

Adult↗
PubMed1997

Spatial transformation during 3D reconstruction in positron emission tomography.

Spatial transformations of positron emission tomographic data for aligning images or transforming to standard anatomical space are usually performed with reconstructed images. However, they can also be performed during the reconstruction process, thereby interpolating the raw data fewer times. We investigated the performance of spatial transformations during reconstruction, implemented it in a standard 3D reconstruction algorithm, and tested it on phantom and patient H215O activation studies for the application of aligning both transmission and emission scans. Performing the transformations during reconstruction was shown to be equivalent to performing the transformations with reconstructed images for this particular application.

Algorithms↗
PubMed1997

Carotid artery and jugular vein ligation with and without hypoxia in the rat.

A continuing concern about the use of extracorporeal membrane oxygenation (ECMO) is the cannulation of the common carotid artery or the internal jugular vein. The authors investigated the changes that might occur in the brain with neck vessel ligation in the normal and the hypoxic rat. Two groups of 60 rats each were studied. The first group was divided into three subgroups of 20 animals each. Subgroup 1 (HH) was hypoxic both 24 hours before and 24 hours after operation. Subgroup 2 (HN) (the ECMO model) was hypoxic before operation and recovered for 24 hours in room air. Subgroup 3 (NN) underwent the entire procedure in room air. For each oxygen environment, four different operations were performed: carotid artery ligation, jugular vein ligation, carotid artery and jugular vein ligation, and dissection of the vessels without ligation (sham). Thus each subgroup was further divided into four sub-subgroups based on the operation performed. Rats were again anesthetized after a 24-hour recovery period and killed using low, blunt cervical dislocation. In the first group of 60 rats, the skull was opened and the brain was carefully removed from the cranial vault and placed in a fixative. The brains were placed in a small magnetic resonance imaging (MRI) head coil in groups of five and scans were obtained to provide T1 and T2 images that correlated with histological sections. MRI scans were reviewed in random, blinded fashion by an imager unaware of how these animals had been treated. The brains were then sectioned coronally at six corresponding levels: frontal, mid and posterior cerebrum, midbrain, pons, and medulla. Histological examination was performed in blinded fashion. The number of lesions (usually ischemic as noted by a decrease in the number of neurons) was totaled for each area of the brain. There were no differences that were consistent or statistically significant in the MR images of brains removed from the head, although it would appear that rats with jugular vein and carotid artery ligation were relatively protected. In the HN group jugular vein ligation was worst, and adding carotid artery ligation was best. In the histological studies the NN group had significantly more lesions than the HH group (P < .01). The second group of 60 rats was divided and treated as the first group in all respects except that MRI was conducted immediately after death on intact heads, and no histological studies were performed. This was done to control for lesions that might have been produced by removal of the brains from the skulls. In this group all findings were right sided. One animal in the HN group showed midcerebral white matter edema after jugular and carotid ligation. Focal anterior cerebral edema was seen in another animal (HH) after isolated carotid ligation. An occipital infarct was found in one animal (HH) after both carotid and jugular ligation. The authors conclude that neck vessel ligation in the hypoxic or normoxic rat causes only occasional and sporadic brain injury much as is seen clinically in newborn ECMO patients.

Animals↗
PubMed1997

Patterns of smoking among inner-city teenagers: smoking has a pediatric age of onset.

OBJECTIVES: (1) To test the hypothesis that the prevalence of smoking among African-American teenagers is lower than among whites and Hispanic inner-city senior high school students; (2) to assess the patterns of smoking among inner-city teenagers; and (3) to ascertain the relationship between smoking status and their knowledge, attitudes, beliefs, and behaviors. METHODS: All students attending inner-city senior high schools in two cities in New Jersey were included in the survey (n = 8,900). Response Rate was 85%; 89% of respondents were minority teenagers. RESULTS: The overall point prevalence rate of cigarette smoking was 9%. Almost all smoking began before the age of 16 years. The factors that significantly (p < .001) contributed to the initiation of cigarette smoking were: peer influence, self-initiation, and the influence of relatives' cigarette smoking. The factors that were stated to play a major role in progression to regular smoking were: perceptions that smoking relieves stress and feelings of induced pleasure while smoking. In addition, smokers were significantly (p < .0005) less knowledgeable about smoke-related diseases than exsmokers or nonsmokers. Over two-thirds of smokers and exsmokers believed that it is the physician's responsibility to advise patients to quit smoking and the majority of the current smokers contemplated quitting smoking. The data support the hypothesis that smoking prevalence among African-American teenagers is significantly lower than among white and Hispanic teenagers who attended the senior high school and resided in the inner city. CONCLUSION: These data suggest that multidimensional antismoking strategies are needed to address the smoking among predominately minority teenagers. This includes supportive messages from physicians, relatives, friends along with public policy to act as motivating factors to discourage early smoking.

Adult↗
PubMed1997

Three predominant clones identified within penicillin-resistant South African isolates of Streptococcus pneumoniae.

The worldwide spread of antibiotic-resistant pneumococcal clones is cause for concern. In South Africa, penicillin-resistant pneumococci are mostly associated with serogroups 6 and 19, therefore, we have analyzed the clonal relationships between resistant isolates of these two serogroups. DNA fingerprinting of penicillin-binding protein genes and arbitrarily-primed PCR, have identified two penicillin-resistant pneumococcal clones of serotype 19A and serotype 6B, and a third multi-resistant serotype 19A clone, of which all three clones are predominant within South Africa's penicillin-resistant pneumococcal population. These clones are represented by strains isolated from hospitals that are widely separated in South Africa. Further studies are required to establish whether these clones have expanded in the rest of Africa or spread to other continents.

Cloning, Molecular↗
PubMed1997

Localization of antigenic sites on Der p 2 using oligonucleotide-directed mutagenesis targeted to predicted surface residues.

BACKGROUND: Understanding the molecular nature of allergen-antibody interactions is important to understanding the mechanism of conventional immunotherapy as well as to designing alternative immunotherapeutic strategies. Many important allergens have been cloned and expressed, making it possible to apply recombinant DNA techniques to dissect antigenic determinants. OBJECTIVE: The aim of this study was to use predictive algorithms and site-directed mutagenesis to investigate monoclonal antibody and IgE antibody epitopes of the major house dust mite allergen Der p 2. METHODS: Computer algorithms were used to assess the primary amino acid sequence of Der p 2 and to identify regions of hydrophilic and flexible sequence. Subsequently, site-directed mutagenesis was used to generate amino acid substitutions at hydrophilic residues at positions 44-46 and at position 100. The variants were tested in a competitive inhibition ELISA with four group 2-specific murine monoclonal antibodies and with human IgE antibody from mite allergic patients. RESULTS: Conservative amino acid substitutions at position 44-46 did not distinguish IgE antibody epitopes, but did suggest that these residues are involved in the epitope defined by one monoclonal antibody, 15E11. Non-conservative substitution of proline at this position reduced binding to all four monoclonal antibodies, as well as IgE antibody, by 50-80%. Point mutants at position 100 mapped the epitopes of two monoclonal antibodies, 7A1 and 13A4, previously shown to bind the same region of Der p 2. In addition, the two variants tested at this position showed distinct inhibition curves with these two monoclonal antibodies indicating differences in fine specificity. CONCLUSIONS: Using predictive algorithms, in the absence of tertiary structural information, we have been able to localize important B cell determinants on Der p 2. The results suggest that it is possible to modulate antibody recognition of allergens using site-directed mutagenesis and that this approach may provide a new strategy for allergen specific immunotherapy.

Antibodies, Monoclonal↗
PubMed1997

Recombinant mite allergens. New technologies for the management of patients with asthma.

The introduction of molecular cloning techniques has led to advances in allergen identification and sequencing, production of recombinant allergens, identification of B-cell and T-cell epitopes, and tertiary structural analysis of allergen molecules. Over 10 groups of mite allergens have been cloned from Dermatophagoides spp., as well as several homologous allergens from Euroglyphus maynei, Lepidoglyphus destructor, and Blomia tropicalis. The availability of these allergens has made it feasible to consider their use for both diagnostic and therapeutic purposes. Several recombinant Dermatophagoides allergens show comparable reactivity on skin testing and in serologic assays to natural allergens, and cocktails of the recombinant proteins could be used as diagnostic reagents. New technologies have been developed for detection of allergen-specific IgE and for environmental allergen detection using rapid diagnostic tests. Novel approaches to immunotherapy are also being investigated, including T-cell-peptide based vaccines, allergen variants which lack IgE reactivity, and naked DNA vaccines. The application of allergen biotechnology should lead to improvements in the management of mite-allergic patients with asthma and represents a logical step toward reducing asthma mortality and morbidity.

Allergens↗
PubMed1997

Sex, alcohol and drugs? Young people's experience of Schoolies Week.

The 'Schoolies Week' phenomenon attracts more than 10,000 school leavers to Surfers Paradise in November and December each year. In a survey of these young people (N = 1796), from Queensland, New South Wales (NSW), and Victoria, about two-thirds of the young men and one-third of the young women expected to have sexual intercourse while in Surfers Paradise. Of these, about 80 per cent expected to use condoms. Most expected to be drunk most nights or every night of their holidays and 27 per cent of young men and 17 per cent of young women expected to be 'stoned' most nights or every night. Most young men and a significant proportion of young women achieved these expectations, with respondents from NSW and Victoria being more likely to do so than Queensland residents. Over one-third of the sample had engaged in sexual intercourse prior to interview, and of these, two-thirds of young men and over half the young women always used condoms with casual partners. The rates for sexual intercourse with regular partners were slightly lower. Those who were inconsistent condom users on holiday were likely to have a history of inconsistent condom use and to have multiple casual partners and/or regular partners in addition to casual partners. It is recommended that the NSW and Victorian governments accept some responsibility for the behaviour of young people attending Schoolies Week. A coordinated intervention strategy is required because there are significant prior indicators of young people's risk practices in Surfers Paradise during Schoolies Week.

Adolescent↗
PubMed1997

Gene targeting and the biology of learning and memory.

The general goal of genetic studies of learning and memory is to develop and test theories that explain the animal's behavior in neuroanatomical, neurophysiological, cellular, and molecular terms. In this review we describe the role that gene targeting and other transgenic techniques have had in the study of mammalian learning and memory. We focus especially on the hippocampus, a brain structure that is thought to be central to the processing and temporary storage of complex information. We also discuss the main issues that confront this young field, as well as our vision for its future.

Animals↗
PubMed1997

Comparison of the neuronal activity in the SMA and the ventral cingulate cortex during prehension in the monkey.

Two monkeys were trained to use the thumb and forefinger to lift and hold an instrumented apparatus within a narrow position window for 1 s. The device was equipped to measure the position and the grip and lifting forces exerted by the animal. On blocks of trials the weight and surface texture could be varied or a force-pulse perturbation could be systematically delivered 750 ms after the object entered the window. If unopposed, the perturbation would displace the hand from the position window, and in preparation for this perturbation the monkeys either increased their grip force before the perturbation or raised the object higher within the position window. Two clearly separated clusters of cells in the medial wall of the frontal lobe were found to be active in relation to the task. One group of cells (n = 115) was located in the caudal and medial part of area 6, in the supplementary motor area (SMA), and the other (n = 92) was located in the ventral bank of the cingulate sulcus (CMAv), in area 23c. In each area, neurons were characterized by their sensorimotor features clearly related to the hand in addition to their modulated activity in the task. In the SMA, 71% (42 of 59) of the neurons tested for receptive fields responded to peripheral and mainly proprioceptive stimulation, and 71% of them (30 of 42) received inputs from the hand. In the CMAv, 77% (48 of 62) of the neurons responded to peripheral proprioceptive stimulation, and 77% (37 of 48) exhibited receptive fields originating from the hand. Intracortical microstimulation applied to 43 sites in the SMA evoked discrete hand movements at 12 loci, whereas in the CMAv hand movements were observed at 8 of 27 sites tested with an average threshold of > 15 microA. A strong similarity was observed between the SMA and CMAv neurons in their sensorimotor features as well as the modulation of their activity in relation to the prehension task. In both areas the activity was poorly related to grip force and significant correlation with peak grip force was observed for only 9 and 7% of the CMAv and SMA neurons, respectively. In the SMA only five cells exhibited increased activity before the perturbation and in the CMAv no changes in activity were found despite the presence of clear preparatory increases in grip force in anticipation of the perturbation. The perturbation evoked reflexlike excitation of 38% (25 of 65) of the neurons in the CMAv and 28% (20 of 71) of the cells in the SMA; these cells were similar in magnitude and latency (approximately 50 ms) in both areas. In both the SMA and CMAv, most of the neurons increased their firing rate < 200 ms before the grip force onset and the overlap in the distribution of neuronal response times suggests a parallel activation of the SMA and CMAv neurons during the prehension task.

Animals↗
PubMed1997

Hospice and palliative care in the UK 1994-5, including a summary of trends 1990-5.

A survey of hospice and specialist palliative care services in the UK in the year 1994-5 was undertaken, enquiring about inpatient, home care and day care services. Over 500 questionnaires were sent out in June 1995 and replies were analysed by the Hospice Information Service. Details of admissions, deaths, discharges and length of patient care are given, as well as an analysis of ethnic grouping, diagnosis, age and sex of patients. The response rates to various parts of the questionnaire are tabulated and national estimates are made of the numbers of patients receiving palliative care from specialist providers. The survey is one in a series of annual surveys and the development of specialist palliative care services over the last five years is discussed.

Age Distribution↗
PubMed1997

An actual use comparison of condoms meeting Australian and Swiss standards: results of a double-blind crossover trial.

The performance of condoms in actual use has been poorly researched in the past, especially in comparing condoms that met different quality control standards as indicated by laboratory testing. The present study used a double-blind crossover design to compare the performance of 2 types of condoms in actual use; one that met the Australian and International Organization for Standardization (ISO) standards for condom quality and one that met the more stringent Swiss Quality Seal requirements. Ninety-two men recruited from Metropolitan Melbourne completed a self-report diary sheet after each condom was used which assessed the performance of the condom and the conditions under which it was used. From a total of 1917 condom uses, there was an overall breakage risk of 2.7%. The breakage risk ratio (Australian/ISO:Swiss) for all types of use was 1.16 (95% confidence interval 0.68-1.99). When subanalyses by method of entry were performed, the condoms meeting the Swiss standard appeared to fare better than the Australian/ ISO standards for anal sex (RR = 4.84, 95% CI 1.07-21.8, P = 0.022), while the opposite was the case for vaginal sex (RR = 0.74, 95% CI 0.35-1.53, P = 0.41). The result for anal use was statistically significant at the 5% level, despite being based on fewer condom trials than that for vaginal use, but this result needs to be replicated. Although the participants appeared representative of the general male population in Melbourne in the age bracket 18-46 years, there was a significant history of condom usage reported. This may have influenced the risk of breakage.

Adult↗
PubMed1997

A Rorschach comparison of psychopathic and nonpsychopathic conduct disordered adolescents.

Forty-eight male subjects who met the DSM-IV (APA, 1994) criteria for conduct disorder (CD) were assessed for psychopathy level using a modified version of the Psychopathy Checklist-Revised (PCL-R, Forth, Hart, & Hare, 1990). Rorschach variables associated with self-perception, affects, and object relations, early behavioral problems and history of violence were compared between psychopathic and nonpsychopathic CD adolescents. Psychopathic CD subjects were significantly more self-centered and violent than nonpsychopathic CD subjects. Decreased attachment and anxiety were found in both CD groups. Our study adds empirical support to the heterogeneity noted among CD adolescents (PCL-R), supports the utility of the Rorschach for detecting individual differences among CD subjects, and extends the empirical work of Gacono and Meloy (1994) to adolescent psychopathy.

Adolescent↗
PubMed1997

Beyond autonomy.

Explore the source record for details and available documents.

Adolescent↗
PubMed1996

Linkage analyses of schizophrenia to chromosome 6p24-p22: an attempt to replicate.

The present study evaluates evidence for linkage of schizophrenia to chromosome 6p24-p22. An independent sample of 211 families ascertained on the basis of having an affected sib-pair diagnosed with schizophrenia or schizoaffective disorder was assessed with seventeen polymorphic markers spanning a 37cM region. Linkage analysis was performed with parametric and non-parametric methods to test for cosegregation using 4 models of inheritance. Neither two-point nor multipoint non-parametric analyses reached significance at a level less than 0.01 for any markers examined in the region and lod score analyses were not suggestive of linkage. Based on initial findings in the present data set and recently published linkage results, two specific areas were densely covered with markers and tested for linkage disequilibrium. After correcting for multiple comparisons within each locus, no significant deviation from expected allele transmission ratios was observed. The present findings together with the published literature fail to find consistent evidence of a linkage for schizophrenia to a single locus on chromosome 6.

Adult↗