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Biomedical subjects

R M Harris

Publications and source records attributed to R M Harris.

At least 19 recordsLinked to original sources
PubMed1992

Collaboration as a strategy for acquired immunodeficiency syndrome prevention.

An eight-session training model used a social interactive framework to combine theoretical and methodological aspects of peer counseling, cross-cultural communication, and transcultural nursing, with a conviction that the participants (volunteers from an ongoing, urban methadone maintenance program) had significant strengths on which to build. The objective was to assist urban, drug dependent black women in taking control of their own lives through collaboration with health care professionals to develop and promote culturally acceptable behavioral alternatives related to reduction of risk for human immunodeficiency virus. The collaborative approach focused on rewards of behavioral change and minimized attention to prevention of negative behaviors, while openly valuing input from the women who are potential health promoters in their own communities. Evaluation of the Peer Counseling Leadership Training Program suggested that the approach facilitated personal risk-reducing behavioral change, improved self esteem, and successfully promoted involvement in community-based prevention efforts.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Strategies for AIDS prevention: leadership training and peer counseling for high-risk African-American women in the drug user community.

A culturally congruent training program to promote HIV risk-reduction behaviors was implemented in a convenient sample of 9 African-American women in an urban methadone treatment program. At each of eight peer counseling and leadership training (PCLT) program sessions, the transmission and prevention of AIDS were discussed while emphasizing enhancement of participants' self-esteem, confidence, and control over high-risk behaviors. The results indicate that support of the women helped develop their sense of purpose and self-worth, reduced sexual and drug use practices associated with risk for HIV and AIDS infection, and promoted assumption of leadership roles and dissemination of accurate AIDS-related information in their communities. It was apparent that knowledge alone does not change behavior if it conflicts with established norms, values, beliefs, and life-styles and that individuals who have a sense of personal control are more willing to explore alternative lower-risk behaviors.

Acquired Immunodeficiency Syndrome↗
PubMed1991

High-performance liquid chromatographic determination of 4,4'-methylenedianiline in human urine.

A method is described for the determination of urinary 4,4'-methylenedianiline (MDA) by high-performance liquid chromatography (HPLC). MDA was extracted from hydrolyzed urine using C18 solid-phase extraction columns. The extract was analyzed by reversed-phase HPLC with electrochemical detection at a cell potential of 0.8 V. The method was very sensitive (detection limit 2.5 micrograms/l) and quantitation using 4,4'-ethylenedianiline as an internal standard correlated well with results by gas chromatography-mas spectrometry. Run-to-run precision (n = 25) averaged 8.9%. In analysis of more than 160 potentially exposed workers, MDA was detected in less than 20% of the urines and concentrations ranged up to 210 micrograms MDA per g of creatinine.

Aniline Compounds↗
PubMed1991

Immobilization impairs recovery after spinal cord injury.

The effect of immobilization on motor recovery was studied in adult rats after subtotal spinal cord section. Anesthetized rats underwent three-quarter section of the cord, sparing the left lateral funiculus. After surgery, half the rats were placed in immobilization tubes for three to four weeks; the others were allowed free mobility. Hindlimb motor function was graded at various times in the two groups. In contrast to the marked recovery observed in mobile animals, the immobilized rats with similar cord lesions showed no significant motor recovery during the period of immobilization. Immobilized rats without cord lesions showed minimal transient deficits. In conclusion, hindlimb activity appears to be a necessary condition for motor recovery after subtotal spinal cord injury.

Animals↗
PubMed1989

Motor recovery in the absence of segmental afferents: a case study of incomplete spinal cord injury.

A 41-year-old male with a prior left L-5/S-1 radiculopathy developed complete quadriplegia following a gunshot wound to the left anterior neck. He subsequently recovered pinprick sensation over the left side of the trunk and lower extremity; and a right peroneal SEP, suggested sparing of long tracts on the right side. Voluntary motor strength gradually recovered more on the left than right for the L-5/S-1 segments, where tendon reflexes were absent. This unique case is discussed with respect to the effect of absent segmental afferents on suprasegmental recovery.

Adult↗
PubMed1989

Lipid content and lipid type as determinants of the epidermal permeability barrier.

During terminal differentiation, mammalian epidermal lipids undergo striking changes in both composition and distribution. Phospholipids and neutral lipids are replaced by a mixture of ceramides and neutral lipids organized in intercellular lamellar bilayers. Whether all of these lipids and/or whether specific lipid classes regulate permeability barrier function is not known. When hairless mice were treated with acetone, the degree of barrier perturbation (measured as transepidermal water loss, TEWL) increased linearly with the amount of lipid removed. Moreover, virtually all lipid species appeared to be removed by acetone treatment. In contrast, the nonpolar organic solvent, petroleum ether, while removing greater amounts of lipids, provoked lesser barrier abnormalities. As determined by both quantitative thin-layer chromatography and histochemistry, petroleum ether selectively extracted nonpolar lipids leaving sphingolipids and free sterols in place. In petroleum ether-treated animals, subsequent acetone treatment removed additional sphingolipids and produced a dramatic increase in TEWL. A linear relationship existed for the quantities of sphingolipid removed and degree of barrier disruption in acetone-treated, but not petroleum ether-treated animals. These results support a relationship between the total lipid content of the stratum corneum and barrier function. Secondly, although the results demonstrate the participation of the total lipid mixture in the barrier, removal of nonpolar species alone appears to cause only a modest level of barrier disruption, while removal of sphingolipids and free sterols leads to a more profound level of barrier perturbation.

Acetone↗
PubMed1988

Locomotor recovery following subtotal spinal cord lesions in a rat model.

Locomotor function is described over 4 weeks in adult rats recovering from mid-thoracic spinal cord lesions, sparing the left lateral and/or ventral funiculus. A composite locomotor score was developed to follow changes by grading the swing and stance phases of locomotion, hindleg struggling withdrawal, and hopping. Motor recovery was more rapid in left than right hindlegs, consistent with sparing of left supraspinal pathways. Two temporal phases of recovery were noted in some animals, perhaps arising from two different recovery mechanisms. Motor recovery in the right hindleg was similar whether a left lateral or ventral funiculus was spared.

Animals↗
PubMed1987

Axon collaterals in the thalamic reticular nucleus from thalamocortical neurons of the rat ventrobasal thalamus.

Thalamocortical relay neurons from the rat ventrobasal nucleus were identified physiologically and injected intracellularly with horseradish peroxidase. The axons of these cells were followed through serial sections in order to determine if collaterals were given off within the ventrobasal nucleus or the thalamic reticular nucleus. No local collaterals were seen in the ventrobasal nucleus, thus indicating that interactions between relay cells in this nucleus are minimal. Of axons that could be followed into the internal capsule, 76% gave off visible collaterals in the thalamic reticular nucleus. Half of these axons had collaterals showing extensive branching with the potential of innervating a large number of thalamic reticular neurons. The other half had short, simple branches of restricted extent. No correlations were found between the physiological properties of a cell and the existence or extent of axon collaterals. These results describe the anatomical basis for the initial part of a feedback loop through the thalamic reticular nucleus that provides the major inhibitory influence on rat ventrobasal neurons.

Animals↗
PubMed1987

Local circuit neurons in the rat ventrobasal thalamus--a GABA immunocytochemical study.

The ventrobasal thalamus of seven rats was processed for immunocytochemistry using antisera to glutamate decarboxylase or gamma-aminobutyrate (GABA). Glutamate decarboxylase-stained sections showed a network of stained fibers and terminals but no stained cell bodies. GABA-stained sections had fewer stained fibers and terminals but did show a few stained cell bodies. Cell bodies were especially apparent when carbazole was used for a chromogen for the peroxidase-antiperoxidase visualization. The GABA-stained cells were found to be distributed throughout the ventrobasal complex, to have smaller soma cross-sectional areas than most other cells (81 +/- 34 microns vs 105 +/- 36 microns for all cells) and to make up 0.4 +/- 0.3% of the neuronal population of the ventrobasal complex. Injections of horseradish peroxidase into the somatosensory cortex (SI) retrogradely filled many neurons in the ventrobasal thalamus, but none of these labeled neurons were double labeled with GABA. These results indicate that the GABA-labeled cells probably represent a small population of local circuit neurons in the rat ventrobasal thalamus.

Animals↗
PubMed1986

Morphology of physiologically identified thalamocortical relay neurons in the rat ventrobasal thalamus.

The anatomical structure of physiologically identified neurons of the rat ventrobasal thalamus was studied in order to determine if there are morphologically distinct subsets of neurons that correlate with the somatosensory submodalities processed by these cells. Intracellular recordings were used to determine the modality and receptive field of a neuron, after which horseradish peroxidase was iontophoretically injected into the cell, allowing it to be histologically visualized. Computer-assisted measurements of the labeled cells were made to quantitatively analyze the dendritic structure. Cells were divided into physiological groups stimulated by whiskers, glabrous skin, furry skin, noxious stimulation, or joint rotation. Qualitatively, all cells appeared similar, with the same types of branching patterns. Dendritic spines and long, sinuous appendages were found on all distal dendrites. Quantitatively, no statistically significant differences in dendritic structure were found between functionally defined groups with the aid of a number of parameters, including a fitted dendritic ellipse. There was a weak correlation between somal cross-sectional area and receptive field size, suggesting larger cells processed larger receptive fields. In summary, the ventrobasal thalamus of the rat, in contrast to that of higher mammals, appears to contain only one major cell type and to have a very simple neuronal circuitry.

Action Potentials↗
PubMed1985

Light microscopic depth measurements of thick sections.

Measurements of the thickness of a thick histological section or the depth of an object within the section, can be made most easily by reading differences in the setting of the fine focus knob of a compound light microscope. Two corrections must be made to such measurements: (1) when using a dry objective, a factor of 1.5 for the index of refraction of the specimen, and (2) a correction for the calibration of the fine focus itself. In addition, several precautions should be taken to minimize errors in the readings.

Histological Techniques↗
PubMed1985

The incidence of pine pollen reactivity in an allergic atopic population.

In the past there has been controversy concerning the allergenicity of pine pollen. Most reports have suggested that pine pollen has not been a significant allergen due to its low antigenicity and relatively large size. While little investigation has been done, there are some older studies supporting pine pollen as an allergen and its use in individual cases for immunotherapy. To our knowledge, no extended testing or screening had been done. A total of 200 patients presenting with symptoms during the pine pollen season were tested to Pinus radiata. Five (3.2%) of the 155 pollen-sensitive patients exhibited skin test sensitivity to Pinus radiata. Based on this data it is concluded that the incidence of skin test reactivity to pine pollen is low.

Humans↗