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Biomedical subjects

R M Marshall

Publications and source records attributed to R M Marshall.

At least 19 recordsLinked to original sources
PubMed2001

The architecture of active zone material at the frog's neuromuscular junction.

Active zone material at the nervous system's synapses is situated next to synaptic vesicles that are docked at the presynaptic plasma membrane, and calcium channels that are anchored in the membrane. Here we use electron microscope tomography to show the arrangement and associations of structural components of this compact organelle at a model synapse, the frog's neuromuscular junction. Our findings indicate that the active zone material helps to dock the vesicles and anchor the channels, and that its architecture provides both a particular spatial relationship and a structural linkage between them. The structural linkage may include proteins that mediate the calcium-triggered exocytosis of neurotransmitter by the synaptic vesicles during synaptic transmission.

Animals↗
PubMed2000

Prolonged cyclooxygenase-2 induction in neurons and glia following traumatic brain injury in the rat.

Cyclooxygenase-2 (COX2) is a primary inflammatory mediator that converts arachidonic acid into precursors of vasoactive prostaglandins, producing reactive oxygen species in the process. Under normal conditions COX2 is not detectable, except at low abundance in the brain. This study demonstrates a distinctive pattern of COX2 increases in the brain over time following traumatic brain injury (TBI). Quantitative lysate ribonuclease protection assays indicate acute and sustained increases in COX2 mRNA in two rat models of TBI. In the lateral fluid percussion model, COX2 mRNA is significantly elevated (>twofold, p < 0.05, Dunnett) at 1 day postinjury in the injured cortex and bilaterally in the hippocampus, compared to sham-injured controls. In the lateral cortical impact model (LCI), COX2 mRNA peaks around 6 h postinjury in the ipsilateral cerebral cortex (fivefold induction, p < 0.05, Dunnett) and in the ipsilateral and contralateral hippocampus (two- and six-fold induction, respectively, p < 0.05, Dunnett). Increases are sustained out to 3 days postinjury in the injured cortex in both models. Further analyses use the LCI model to evaluate COX2 induction. Immunoblot analyses confirm increased levels of COX2 protein in the cortex and hippocampus. Profound increases in COX2 protein are observed in the cortex at 1-3 days, that return to sham levels by 7 days postinjury (p < 0.05, Dunnett). The cellular pattern of COX2 induction following TBI has been characterized using immunohistochemistry. COX2-immunoreactivity (-ir) rises acutely (cell numbers and intensity) and remains elevated for several days following TBI. Increases in COX2-ir colocalize with neurons (MAP2-ir) and glia (GFAP-ir). Increases in COX2-ir are observed in cerebral cortex and hippocampus, ipsilateral and contralateral to injury as early as 2 h postinjury. Neurons in the ipsilateral parietal, perirhinal and piriform cortex become intensely COX2-ir from 2 h to at least 3 days postinjury. In agreement with the mRNA and immunoblot results, COX2-ir appears greatest in the contralateral hippocampus. Hippocampal COX2-ir progresses from the pyramidal cell layer of the CA1 and CA2 region at 2 h, to the CA3 pyramidal cells and dentate polymorphic and granule cell layers by 24 h postinjury. These increases are distinct from those observed following inflammatory challenge, and correspond to brain areas previously identified with the neurological and cognitive deficits associated with TBI. While COX2 induction following TBI may result in selective beneficial responses, chronic COX2 production may contribute to free radical mediated cellular damage, vascular dysfunction, and alterations in cellular metabolism. These may cause secondary injuries to the brain that promote neuropathology and worsen behavioral outcome.

Animals↗
PubMed2000

Reference group data for the Reitan-Indiana Neuropsychological Test Battery for Young Children.

This study presents a data set for a reference group on the Reitan-Indiana Neuropsychological Test Battery for Young Children. The data set is based on a sample of 224 children, ages 5 to 8 years, referred to a special services cooperative for academic or behavioral concerns during the years 1980 through 1993. Data are presented in terms of sample size, means, standard deviations, diagnostic classifications, and population characteristics. Previously published data sets are reviewed in comparison to this newly acquired data set. Potential advantages of this data set include the larger sample, contemporary data collection, and a sample drawn from a United States school-referred population.

Child↗
PubMed1999

Automatic acquisition of fiducial markers and alignment of images in tilt series for electron tomography.

Three-dimensional reconstruction of a section of biological tissue by electron tomography requires precise alignment of a series of two-dimensional images of the section made at numerous successive tilt angles. Gold beads on or in the section serve as fiducial markers. A scheme is described that automatically detects the position of these markers and indexes them from image to image. The resulting set of position vectors are arranged in a matrix representation of the tilt geometry and, by inversion, alignment information is obtained. The scheme is convenient, requires little operator time and provides an accuracy of < 2 pixels RMS. A tilt series of 60-70 images can be aligned in approximately 30 min on any modern desktop computer.

Algorithms↗
PubMed1999

Diabetes risk factors in low-income Mexican-American children.

OBJECTIVE: To learn if Mexican-American children from low income neighborhoods have excess diabetes risk factors. RESEARCH DESIGN AND METHODS: The study involved 173 Mexican-American children aged 9 years. This is the age before type 2 diabetes usually develops in youths and where the disparity in body fat between Mexican-American and non-Hispanic white children is evident. The study also targets poor children because diabetes and being overweight are more common in Mexican-American adults from a lower than from a higher socioeconomic status. The diabetes risk factors measured were percent body fat, dietary fat intake, daily fruit and vegetable intake, and physical fitness. Body fat was measured by bioelectric impedance, dietary intake was measured by three 24-h dietary recalls, and physical fitness was measured by a modified Harvard step test. RESULTS: According to self-reported dietary recalls, Mexican-American children ate higher than recommended fat servings and had higher percent energy from fat and saturated fat. On the other hand, their reported daily fruit and vegetable intake was half of that recommended by national dietary guidelines. A large percentage of these children were at unacceptable physical fitness levels. Percent body fat was higher in these Mexican-American children than that reported for non-Hispanic white children. Finally, 60% of the children had a first- or second-degree relative with diabetes. CONCLUSIONS: Because diabetes is highly prevalent in Mexican-American adults, type 2 diabetes in increasing in Mexican-American youths, and diabetes risk factors are more common in Mexican-American children, a prudent measure would be to explore early-age diabetes risk factor prevention programs in this population.

Adolescent↗
PubMed1998

Dissection of active zones at the neuromuscular junction by EM tomography.

We used EM tomography to examine the fine structure of the apparently amorphous electron dense material that is seen at active zones of axon terminals when viewed by conventional 2D electron microscopy. Serial 1-nm optical slices from 3D reconstructions of individual thin tissue sections reveal that the material is composed of an interconnecting network of elongate components directly linked to synaptic vesicles and the presynaptic membrane. Each vesicle at the active zone that lies adjacent to the presynaptic plasma membrane has several such connections. Information provided by reconstruction data may be useful in generating experiments aimed at understanding the mechanisms involved in the docking of synaptic vesicles and their exocytosis during synaptic transmission.

Animals↗
PubMed1996

Use of the long vs short form of the speech sounds perception test in a school-age population.

A sample of 645 school-age children, ages 9 to 14 years, were administered independent forms of the Speech Sounds Perception Test for older children. 328 subjects took the complete test (SSPT-60) and 317 were administered only the first 30 items (SSPT-30). Comparison of mean errors indicated that significantly more errors were made by subjects given the SSPT-30. Decisions regarding the use of each form for school-age children are discussed.

Affective Symptoms↗
PubMed1990

How to improve allocation of support service costs.

Better accounting for support service costs at outpatient facilities involves distinguishing between fixed and variable expenses, then creating separate budgets for them. To simplify this step, financial managers can create a surrogate, such as the number of patient visits, to represent service activity. Once this is completed, separated costs are allocated by using criteria that recognize short-term and long-term service use.

Budgets↗
PubMed1987

Physician/school teacher collaboration. Some practical considerations.

Physician/school teacher collaboration is crucial if exceptional students are to receive appropriate educational services mandated by Public Law 94-142 and Public Law 99-457. There is little in the professional literature to guide physicians who may be interested in working more closely with school personnel. The present article provides specific suggestions and recommendations to private practitioners for initiating and managing interprofessional collaboration with school personnel.

Child↗
PubMed1986

Epilepsy and education: the pediatrician's expanding role.

School systems, teachers, health systems, and physicians are striving to assist students to reach their full potential. Physicians have an understanding of seizures and medications that should be shared with teachers. In turn, teachers know what parts of students' learning seem to be affected by their epilepsy; they also work with students every day and this gives them a unique perspective of changes in the patient's status. Epilepsy can profoundly affect the student-patient, the school, and the home. Pediatricians are in the unique position to share medical information with teachers and parents. By sharing this information, physicians encourage collaboration. Increased collaboration, in turn, helps to reduce the myths and fears surrounding epilepsy. It provides teachers with the information they use to plan instructional programs, and it improves physicians' decisions regarding diagnosis and treatment. Physician/teacher collaboration is generally advocated for patients-students in the "devastated" and the "compromised" groups. Collaboration is not necessary in patients without problems and it is probably preferable not to risk stigmatizing otherwise intact children by attaching the label "epilepsy" to them. When collaboration is indicated, teachers will need some way of organizing information about students' seizure, educational, medical, and psychosocial background. The appendix contains a list of questions grouped according to these categories. If teachers can answer these questions they will be well on the way to resolving the problems confronting the student with epilepsy. It is hoped that physicians will be available and willing to assist teachers and that teachers will seek their assistance.

Child↗
PubMed1985

Medical and educational literature on physician/teacher collaboration.

Recent changes in the education of exceptional children are placing new demands on physicians and teachers to work together. This article reviews the published educational and medical literature on physician/teacher collaboration. Articles from both fields contend that collaboration is necessary, desirable, and possible. As expected, all articles favor increased collaboration, however, specific guidelines to improve collaboration are surprisingly scarce. Suggestions to improve collaboration are provided.

Child↗
PubMed1984

Improving physician/teacher collaboration.

This paper describes a three-phase project designed to improve physician/teacher collaboration with exceptional school children. In phase 1, the school district's 54 special education personnel completed a 24-item questionnaire designed to identify communication and role-expectancy problems. Phase 2 consisted of a series of workshops in which physicians explained their evaluations and and treatments of exceptional children. In phase 3 a collaboration model linking the school district and a university-based medical center was developed and implemented. Questionnaire data, the collaboration model, and suggestions for other models are presented.

Child↗
PubMed1977

The prevalence of calcified upper urinary tract stone disease in a random population--Cumbernauld Health Survey.

It is difficult to obtain the true prevalence of stone disease in community. A proper random sample of a population has been studied and a figure of 3.83% of calcified stones have been found in 2,000 subjects. The significance of biochemical, bacteriological, skeletal and other surgical abnormalities is discussed. It is now possible to study individual groups within the population with respect to stone disease.

Adolescent↗