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Biomedical subjects

C S Brown

Publications and source records attributed to C S Brown.

At least 37 records · Page 2Linked to original sources
PubMed1999

Ground-based studies and space experiment with potato leaf explants.

This article details the extensive preflight research required to make a plant experiment conform to the constraints imposed by the spaceflight system. Potato explants, each consisting of a leaf, an axillary bud, and small stem section, were flown on USML-2 in the ASTROCULTURE (TM) flight hardware to study tuber formation from the axillary bud during the 16 days of flight. To obtain acceptable explant materials: 1) parent plants had to be grown under reduced light (150 micromoles m-2 s-1 PPF) to ensure uniform bud and tuber development, 2) leaves had to be trimmed to fit the small size of the flight growth chamber, and 3) only young, fully expanded leaves from plants 5-7 weeks old could be used. After six scrubs, the experiment was flown successfully October 20 to November 5 and produced tubers and accumulated starch similar to that produced on ground controls.

Culture Techniques↗
PubMed1999

Electron-cytochemical study of Ca2+ in cotyledon cells of soybean seedlings grown in microgravity.

Microgravity and horizontal clinorotation are known to cause the rearrangement of the structural-functional organization of plant cells, leading to accelerated aging. Altered gravity conditions resulted in an increase in the droplets volume in cells and the destruction of chloroplast structure in Arabidopsis thaliana plants, an enhancement of cytosolic autophagaous processes, an increase in the respiration rate and a greater number of multimolecular forms of succinate- and malate dehydrogenases in cells of the Funaria hygrometrica protonema and Chlorella vulgaris, and changes in calcium balance of cells. Because ethylene is known to be involved in cell aging and microgravity appears to speed the process, and because soybean seedlings grown in space produce higher ethylene levels we asked: 1) does an acceleration of soybean cotyledon cell development and aging occur in microgravity? 2) what roles do Ca2+ ions and the enhanced ethylene level play in these events? Therefore, the goal of our investigation was to examine of the interaction of microgravity and ethylene on the localization of Ca2+ in cotyledon mesophyll of soybean seedlings.

Calcium↗
PubMed1999

Ultrastructural organization of cells in soybean root tips in microgravity.

Root apex cells of higher plants have unique structure and functions. In particular, the central cells of root cap are considered as the site of gravity perception in roots and are characterised by structural polarity, including directional sedimentation of amyloplasts with to gravity. Past studies have shown that root growth, structural organisation of the cells, and structural polarity of statocytes were affected in microgravity. Microgravity-grown plants also exhibited enhanced production of ethylene and decreased production of starch relative to ground controls. In this paper, the effects of microgravity and ethylene on ultrastructural organisation of the cells in soybean root apices are presented.

Microscopy, Electron↗
PubMed1998

Changes in Arabidopsis leaf ultrastructure, chlorophyll and carbohydrate content during spaceflight depend on ventilation.

Leaf structure and function under spaceflight conditions have received little study despite their important implications for biological life support systems using plants. Previous reports described disruption of the membrane apparatus for photosynthesis and a general decrease in carbohydrate content in foliage. During a series of three short-duration experiments (Chromex-03, -04, -05) on the US space shuttle (STS-54, STS-51, STS-68), we examined Arabidopsis thaliana leaves. The plants were at the rosette stage at the time of loading onto the space shuttle, and received the same light, temperature, carbon dioxide and humidity regimes in the orbiter as in ground controls. The experiments differed according to the regime provided in the headspace around the plants: this was either sealed (on mission STS-54); sealed with high levels of carbon dioxide (on mission STS-51) or vented to the cabin air through a filtration system (on mission STS-68). Immediately post-flight, leaf materials were fixed for microscopy or frozen in liquid nitrogen for subsequent analyses of chlorophyll and foliar carbohydrates. At the ultrastructural level, no aberrations in membrane structure were observed in any of the experiments. When air-flow was provided, plastids developed large starch grains in both spaceflight and ground controls. In the experiments with sealed chambers, spaceflight plants differed from ground controls with regard to measured concentrations of carbohydrate and chlorophyll, but the addition of airflow eliminated these differences. The results point to the crucial importance of consideration of the foliage microenvironment when spaceflight effects on leaf structure and metabolism are studied.

Arabidopsis↗
PubMed1998

Peripartum cardiomyopathy: a comprehensive review.

The objective of this article is to review the etiology, diagnosis, treatment, prognosis, and natural history of peripartum cardiomyopathy. The English language medical literature was accessed though MEDLINE from 1966 to the present; additional sources were obtained by cross-referencing. Because of the limited number of studies and patients, metaanalysis could not be performed; however, the existing data regarding the etiology, diagnosis, treatment, and prognosis of peripartum cardiomyopathy are presented. Approximately 1000 U.S. women will have peripartum cardiomyopathy this year, and for many it will be fatal. The etiology of this disease remains uncertain, but current evidence suggests myocarditis of viral, autoimmune, or idiopathic origin. The utility of immunosuppressive therapy remains ambiguous; however, other advances in medical therapy for dilated cardiomyopathy and cardiac transplantation have significantly improved quality of life and survival for patients. As the initial patient contact, obstetricians and family practitioners must recognize this malady early and rapidly institute the proper medical therapy directed toward the congestive state.

Cardiomyopathy, Dilated↗
PubMed1998

Development and growth of potato tubers in microgravity.

A potato explant consisting of a leaf, its axillary bud, and a small segment of stem will develop a tuber in 10-14 days when grown on earth. The tubers develop from the axillary buds and accumulate starch derived from sugars produced through photosynthesis and/or mobilized from leaf tissue. Potato explants were harvested and maintained in the Astroculture (TM) unit, a plant growth chamber designed for spaceflight. The unit provides an environment with controlled temperature, humidity, CO2 level, light intensity, and a nutrient delivery system. The hardware was loaded onto the space shuttle Columbia 24 hours prior to the launch of the STS-73 mission. Explant leaf tissue appeared turgid and green for the first 11 days of flight, but then became chlorotic and eventually necrotic by the end of the mission. The same events occurred to ground control explants with approximately the same timing. At the end of the 16-day mission, tubers were present on each explant. The size and shape of the space-grown tubers were similar to the ground-control tubers. The arrangement of cells in the tuber interior and at the exterior in the periderm was similar in both environments. Starch and protein were present in the tubers grown in space and on the ground. The range in starch grain size was similar in tubers from both environments, but the distribution of grains into size classes differed somewhat, with the space-grown tubers having more small grains than the ground control tubers. Proteinaceous crystals were found in tubers formed in each condition.

Environment, Controlled↗
PubMed1998

Management of SSRI-induced sexual dysfunction.

OBJECTIVE: To describe the occurrence and management of sexual dysfunction induced by selective serotonin-reuptake inhibitors (SSRIs), to provide an overview of sexual dysfunction, reports of SSRI-induced sexual dysfunction, and management strategies. DATA SOURCES: Information was retrieved from a MEDLINE English-literature search from January 1986 to July 1998 and by review of references. Indexing terms included sexual dysfunction, antidepressants, selective serotonergic reuptake inhibitors, fluoxetine, sertraline, paroxetine, fluvoxamine, clomipramine, buspirone, nefazodone, bupropion, cyproheptadine, amantadine, yohimbine, and central nervous system stimulants. STUDY SELECTION: There are no controlled studies describing SSRI-induced sexual dysfunction or its management. Twenty-one studies are presented, including 2 open-label studies, 12 case series, and 7 case reports. SSRI-induced sexual dysfunction is described with fluoxetine, paroxetine, sertraline, and fluvoxamine for 3-24 weeks of therapy. DATA SYNTHESIS: Data were organized according to the pharmacologic agent used in the management of SSRI dysfunction, target population, SSRI implicated, type of sexual dysfunction, experimental design, and treatment response. Data were extracted from methodology and results sections of reports. Methodologic flaws included failure to account for gender differences, omission of SSRI dose and duration, and use of concomitant drugs. CONCLUSIONS: The frequency of reports suggests that SSRI-induced dysfunction is a common adverse effect; controlled studies are necessary to determine prevalence. Most reports have occurred with fluoxetine, but this phenomenon may be related to its widespread use. Further study is needed to evaluate baseline sexual function, to define target populations, and to compare SSRIs in inducing sexual dysfunction. Serotonin antagonists and dopamine agonists have been used most often to treat SSRI-induced dysfunction and have generally been effective, but controlled studies are also needed.

Adrenergic alpha-Antagonists↗
PubMed1998

Current drug therapy recommendations for the treatment of attention deficit hyperactivity disorder.

Attention deficit hyperactivity disorder (ADHD) is characterised by symptoms of inattentiveness and/or hyperactivity-impulsivity which are not appropriate to the child's age. This disorder usually manifests by age 3 and affects up to 5% of school-age children. Although the aetiology is unknown, ADHD appears to have a strong genetic component and to involve dysregulation of the CNS dopaminergic system. Psychostimulants are the mainstay of therapy. The majority of patients will respond to an adequate trial of one of the 3 available stimulants, methylphenidate, dexamphetamine or pemoline. Use of the tricyclic antidepressants as second-line agents is supported by substantial literature. Third-line agents include amfebutamone (bupropion) and clonidine. Other modalities have been studied, but sufficient research is not available to recommend their use over the abovementioned treatments. Assessment of response is best achieved by objective rating scales which allow for input from various environments.

Antidepressive Agents, Tricyclic↗
PubMed1998

Blue light requirements for crop plants used in bioregenerative life support systems.

As part of NASA's Advanced Life Support Program, the Breadboard Project at Kennedy Space Center is investigating the feasibility of using crop plants in bioregenerative life support systems (BLSS) for long-duration space missions. Several types of electric lamps have been tested to provide radiant energy for plants in a BLSS. These lamps vary greatly in terms of spectral quality resulting in differences in growth and morphology of the plants tested. Broad spectrum or "white" light sources (e.g., metal halide and fluorescent lamps) provide an adequate spectrum for normal growth and morphology; however, they are not as electrically efficient as are low-pressure sodium (LPS) or high-pressure sodium (HPS) lamps. Although LPS and HPS, as well as the newly tested red light-emitting diodes (LEDs), have good photosynthetically active radiation (PAR) efficiencies, they are deficient in blue light. Results with several of the crops tested for BLSS (wheat, potato, soybean, lettuce, and radish) have shown a minimum amount of blue light (approximately 30 micromoles m-2 s-1) is necessary for normal growth and development. For example, the lack of sufficient blue light in these lamps has resulted in increased stem elongation and significant reductions in photosynthesis and yield. To avoid problems with blue-deficient lamps and maximize yield, sufficient intensity of HPS or blue light supplementation with red LEDs or LPS lamps is required to meet spectral requirements of crops for BLSS.

Biomass↗
PubMed1998

Life cycle experiments with Arabidopsis grown under red light-emitting diodes (LEDs).

Light-emitting diodes (LEDS) are a potential lighting source for space-based plant growth systems because of their small mass, operational longevity, and spectral quality. However, the vegetative and reproductive growth and development of plants grown under narrow spectrum LEDs must be characterized before acceptance of LEDS as an alternative light source for growing plants. The objectives of this study were 1) to determine the feasibility of using red LEDS for growing Arabidopsis thaliana L. through a full seed-bearing generation, and 2) to determine if supplemental blue radiation is necessary for growth and seed production. Arabidopsis grown under red LEDS alone produced viable seed, but these plants had abnormal leaf morphology and delayed flowering in comparison to control plants grown under broad spectrum white light or red LEDS supplemented with blue light.

Arabidopsis↗
PubMed1997

Anatomical features of pepper plants (Capsicum annuum L.) grown under red light-emitting diodes supplemented with blue or far-red light.

Pepper plants (Capsicum annuum L. cv., Hungarian Wax) were grown under metal halide (MH) lamps or light-emitting diode (LED) arrays with different spectra to determine the effects of light quality on plant anatomy of leaves and stems. One LED (660) array supplied 90% red light at 660 nm (25nm band-width at half-peak height) and 1% far-red light between 700-800nm. A second LED (660/735) array supplied 83% red light at 660nm and 17% far-red light at 735nm (25nm band-width at half-peak height). A third LED (660/blue) array supplied 98% red light at 660nm, 1% blue light between 350-550nm, and 1% far-red light between 700-800nm. Control plants were grown under broad spectrum metal halide lamps. Plants were gron at a mean photon flux (300-800nm) of 330 micromol m-2 s-1 under a 12 h day-night photoperiod. Significant anatomical changes in stem and leaf morphologies were observed in plants grown under the LED arrays compared to plants grown under the broad-spectrum MH lamp. Cross-sectional areas of pepper stems, thickness of secondary xylem, numbers of intraxylary phloem bundles in the periphery of stem pith tissues, leaf thickness, numbers of choloplasts per palisade mesophyll cell, and thickness of palisade and spongy mesophyll tissues were greatest in peppers grown under MH lamps, intermediate in plants grown under the 660/blue LED array, and lowest in peppers grown under the 660 or 660/735 LED arrays. Most anatomical features of pepper stems and leaves were similar among plants grown under 660 or 660/735 LED arrays. The effects of spectral quality on anatomical changes in stem and leaf tissues of peppers generally correlate to the amount of blue light present in the primary light source.

Calcium Oxalate↗
PubMed1997

Induction of atrioventricular node reentrant tachycardia with adenosine: differential effect of adenosine on fast and slow atrioventricular node pathways.

OBJECTIVES: This study sought to evaluate the sensitivity of fast and slow atrioventricular (AV) node pathways to incremental doses of adenosine in patients with typical AV node reentrant tachycardia. BACKGROUND: Although adenosine is known to depress conduction through the AV node, the relative sensitivity to adenosine of the anterograde fast and slow pathways in patients with dual AV node pathways and typical AV node reentrant tachycardia has not previously been studied. METHODS: Sixteen patients with dual AV node physiology and typical AV node reentrant tachycardia and 10 control patients were given incremental doses of adenosine during atrial pacing. RESULTS: In 14 of 16 patients with dual-AV node physiology, administration of small doses of adenosine during atrial pacing led consistently to transient block of impulse conduction in the fast pathway before block in the slow pathway, resulting in abrupt prolongation of the AH interval with continued 1:1 AV conduction. The mean (+/- SD) doses of adenosine required to cause conduction block in the fast and slow pathways were 2.7 +/- 3.0 and 7.2 +/- 4.7 mg, respectively (p = 0.004). In 9 of 16 patients, administration of low dose adenosine led to initiation of AV node reentrant tachycardia. The control patients showed no abrupt increases in AH interval with administration of adenosine during atrial pacing. CONCLUSIONS: In most patients with dual AV node pathways and typical AV node reentrant tachycardia, the fast pathway is more sensitive than the slow pathway to the effects of adenosine.

Adenosine↗
PubMed1997

Factors influencing the efficiency of cationic liposome-mediated intravenous gene delivery.

We have characterized the relationships between the design of cationic liposomes as a gene transfer vehicle, their resulting biodistribution and processing in animals, and the level and sites of gene expression they produce. By redesigning conventional cationic liposomes, incorporating cholesterol (chol) as the neutral lipid and preparing them as multilamellar vesicles (MLV), we increased the efficiency of cationic liposome:DNA complex (CLDC)-mediated gene delivery. Expression of the luciferase gene increased up to 1,740-fold and of the human granulocyte-colony stimulating factor (hG-CSF) gene up to 569-fold due to prolonged circulation time of injected CLDC, and increased uptake and retention in tissues. The level of gene expression per microgram of DNA taken up per tissue was 1,000-fold higher in lung than in liver, indicating that in addition to issues of delivery and retention of injected DNA, tissue-specific host factors also play a central role in determining the efficiency of expression. Vascular endothelial cells, monocytes, and macrophages are the cell types most commonly transfected by intravenous injection of CLDC.

Animals↗
PubMed1997

Structure of potato tubers formed during spaceflight.

Potato (Solanum tuberosum L. cv. Norland) explants, consisting of a leaf, axillary bud, and small stem segment, were used as a model system to study the influence of spaceflight on the formation of sessile tubers from axillary buds. The explants were flown on the space shuttle Columbia (STS-73, 20 October to 5 November 1995) in the ASTROCULTURE (TM) flight package, which provided a controlled environment for plant growth. Light and scanning electron microscopy were used to compare the precisely ordered tissues of tubers formed on Earth with those formed during spaceflight. The structure of tubers produced during spaceflight was similar to that of tubers produced in a control experiment. The size and shape of tubers, the geometry of tuber tissues, and the distribution of starch grains and proteinaceous crystals were comparable in tubers formed in both environments. The shape, surface texture, and size range of starch grains from both environments were similar, but a greater percentage of smaller starch grains formed in spaceflight than on Earth. Since explant leaves must be of given developmental age before tubers form, instructions regarding the regular shape and ordered tissue geometry of tubers may have been provided in the presence of gravity. Regardless of when the signalling occurred, gravity was not required to produce a tuber of typical structure.

Culture Techniques↗
PubMed1997

Photomorphogenesis, photosynthesis, and seed yield of wheat plants grown under red light-emitting diodes (LEDs) with and without supplemental blue lighting.

Red light-emitting diodes (LEDs) are a potential light source for growing plants in spaceflight systems because of their safety, small mass and volume, wavelength specificity, and longevity. Despite these attractive features, red LEDs must satisfy requirements for plant photosynthesis and photomorphogenesis for successful growth and seed yield. To determine the influence of gallium aluminium arsenide (GaAlAs) red LEDs on wheat photomorphogenesis, photosynthesis, and seed yield, wheat (Triticum aestivum L., cv. 'USU-Super Dwarf') plants were grown under red LEDs and compared to plants grown under daylight fluorescent (white) lamps and red LEDs supplemented with either 1% or 10% blue light from blue fluorescent (BF) lamps. Compared to white light-grown plants, wheat grown under red LEDs alone demonstrated less main culm development during vegetative growth through preanthesis, while showing a longer flag leaf at 40 DAP and greater main culm length at final harvest (70 DAP). As supplemental BF light was increased with red LEDs, shoot dry matter and net leaf photosynthesis rate increased. At final harvest, wheat grown under red LEDs alone displayed fewer subtillers and a lower seed yield compared to plants grown under white light. Wheat grown under red LEDs+10% BF light had comparable shoot dry matter accumulation and seed yield relative to wheat grown under white light. These results indicate that wheat can complete its life cycle under red LEDs alone, but larger plants and greater amounts of seed are produced in the presence of red LEDs supplemented with a quantity of blue light.

Biomass↗