Search PubMed⌕ Search

Biomedical subjects

C D Nelson

Publications and source records attributed to C D Nelson.

11 recordsLinked to original sources
PubMed2001

Brief exposure to -Gz reduces cerebral perfusion pressure during subsequent +Gz stress in rats.

INTRODUCTION: In humans, +Gz exposure immediately preceded by exposure to zero or -Gz can result in unexpected incapacitation ("push-pull" effect). Our goals were to establish whether this phenomenon exists in rats and to evaluate the importance of varying the duration of -Gz exposure on magnitude of the push-pull effect on cerebral perfusion pressure. METHODS: Eight conscious male rats were studied in the transition from +5 Gz to +10 Gz imposed by centrifugation. This was done with (push-pull) or without (control) 2 s exposure to -5 Gz applied using a counterbalanced design. Seven isoflurane anesthetized rats were studied in the transition from 0Gz (+1Gy) to + 1Gz imposed by tilting. This was done with (push-pull) or without (control) 0.5, 1, 3, or 9 s exposure to -1Gz imposed immediately prior to the transition applied using a counterbalanced designed. RESULTS: Exposure to 2 s of -5 Gz significantly (p < 0.01) reduced carotid artery pressure in the 4th through 8th s of exposure to +10 Gz by an average of 15 mmHg compared with control. In the tilt experiments, a push-pull effect was found with mild Gz exposure (+/-1Gz) with as little as 0.5 s -Gz exposure. Varying the head-down dwell time did not alter the magnitude of the exaggerated hypotension induced by "push-pull" (p = 0.90). CONCLUSIONS: We conclude that rats express a "push-pull" effect similar to that observed in humans but that altering the duration of exposure to -Gz does not influence the magnitude of the "push-pull" effect.

Animals↗
PubMed2001

Manual medicine diversity: research pitfalls and the emerging medical paradigm.

Recent studies published in leading medical journals have concluded that chiropractic treatment is not particularly helpful for relieving asthma and migraine symptoms because even though study participants showed notable improvement in symptoms, those subjects who received sham manual medicine treatments also showed improvement. Yet the sham treatment received by control groups in these studies is reminiscent in many ways of traditional osteopathic manipulation. This seems to represent not only a failure to recognize the value of many manual medicine techniques but also an ignorance of the broad spectrum of manual medicine techniques used by various practitioners, from osteopathic physicians to chiropractors to physical therapists. Such blind spots compromise research methodology with regard to manual medicine studies, which could, in turn, diminish the role of manual medicine in clinical practice. Osteopathic manipulative treatment provides an excellent model for recognizing and integrating the full range of manual medicine techniques into research and clinical applications because of the wide range of techniques employed. The potential exists for these techniques to contribute much to medical research and clinical practice--provided that osteopathic physicians and other manual medicine practitioners work to alleviate ignorance about the efficacy of various forms of manipulation.

Asthma↗
PubMed2000

Does autonomic blockade reveal a potent contribution of nitric oxide to locomotion-induced vasodilation?

We sought to test the role of nitric oxide (NO) in governing skeletal muscle (iliac) vascular conductance during treadmill locomotion in dogs (n = 6; 3.2 and 6.4 km/h at 0% grade, and 6.4 km/h at 10% grade). As seen previously, the increase in muscle vascular conductance accompanying treadmill locomotion was little influenced by NO synthase inhibition alone with N(omega)-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg iv), but the absolute value of conductance achieved during locomotion was reduced. Such ambiguous results provide an unclear picture regarding the importance of NO during locomotion. However, muscle vasodilation is normally restrained by the sympathetic system during locomotion. Thus a significant contribution by NO to the increase in vascular conductance that accompanies locomotion could be masked by partial withdrawal of the competing influence of sympathetic vasoconstrictor nerve activity secondary to the rise in arterial pressure following systemic L-NAME administration. To test this possibility, we compared the rise in muscle vascular conductance before and after L-NAME treatment while ganglionic transmission was blocked by hexamethonium. Under these conditions, L-NAME significantly reduced both the rise in vascular conductance (by 32%, P < 0.001) and the absolute level of vascular conductance (by 30%, P < 0.001) achieved during locomotion with no effect on blood flow. Thus augmented NO production normally provides a significant drive to relax vascular smooth muscle in active skeletal muscle during locomotion. Potential deficits stemming from the absence of NO following L-NAME treatment are masked by less intense sympathetic restraint when autonomic function is intact.

Animals↗
PubMed2000

Automated image analysis of live/dead staining of the fungus Aureobasidium pullulans on microscope slides and leaf surfaces.

An image analysis program and protocol for the identification and enumeration of live versus dead cells of the yeast-like fungus Aureobasidium pullulans was developed for both populations on microscope slides and leaf surfaces. Live cells took up CellTracker Blue, while nonviable cells stained with DEAD Red. Image analysis macro programs running under Optimas software were used to acquire images and to differentiate and enumerate viable from nonviable cells. The software was capable of discriminating green as a third parameter for identification and quantification of green fluorescent protein-expressing cells in a wild-type population.

Green Fluorescent Proteins↗
PubMed1999

The abdominal brain and enteric nervous system.

Conventional medical treatment for neurologic disorders such as epilepsy, migraine, and autism focuses on the brain. Although standard medical treatment is often helpful, the underlying causes of these disorders are not well understood. Furthermore, some individuals respond poorly or not at all to regular medicine. Evidence is accumulating in the medical literature that the enteric nervous system (ENS)-that part of the nervous system associated with the alimentary canal-also plays a role in these disorders. Historically, the concept of an autonomous abdominal nervous system was advocated by Byron Robinson, Johannis Langley, and Edgar Cayce. The work of these three prominent historical figures is considered along with modem view-points on the abdominal nervous system. Complementary therapies that address the nervous system of the abdomen have potential as useful adjuncts to conventional treatment for certain neurologic disorders.

Abdomen↗
PubMed1991

Verbal dyspraxia in treated galactosemia.

Galactosemia is an inborn error of metabolism that causes life-threatening illness a few days after galactose-containing milk is fed to a newborn. Early treatment with a strict lactose-free diet results in rapid improvement, and, until recently, it was thought that the long-term prognosis in such infants was usually good. The speech characteristics of 24 patients treated for galactosemia were examined. Fifty-four percent had the specific speech disorder, verbal dyspraxia. This finding was not related to age at diagnosis, severity of symptoms in the newborn period, or to biochemical control. There may be, however, a relation between dyspraxia and diminished IQ scores observed in the group of patients with dyspraxia judged as "severe." The findings indicate the association of a specific and unusual speech defect with a specific and rare metabolic disorder.

Adolescent↗
PubMedDate not supplied

On the number of genes controlling the grass stage in longleaf pine.

The grass stage is an inherent and distinctive developmental trait of longleaf pine (Pinus palustris), in which height growth in the first few years after germination is suppressed. In operational forestry practice the grass stage extends for two to several years and often plays a role in planting failures and decisions to plant alternative species. Interspecies hybrids involving loblolly (P. taeda) and slash (P. elliottii var. elliottii) pines have been investigated as a means to produce planting stock with improved early height growth and to develop backcross populations for advanced generation breeding. We have reevaluated data from several interspecies populations, with the objective of estimating the number of genes contributing to the difference in first-year height growth between longleaf and loblolly pines. Estimates based on means and variances of parental and interspecies hybrid and backcross families suggest a minimum of 4 to 10 genes with standard errors less than half the estimates. These results suggest that the grass stage has evolved through the accumulation of alleles at several loci, each with small effects on various components of first-year height growth. Given the complexity of the grass-stage trait, tree breeders may need to combine genetic marker analysis with recurrent backcross breeding to efficiently develop longleaf pine planting stock for improved reforestation.

Analysis of Variance↗