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Biomedical subjects

C Field

Publications and source records attributed to C Field.

At least 19 recordsLinked to original sources
PubMed2001

Observation of plasma focusing of a 28.5 GeV positron beam.

The observation of plasma focusing of a 28.5 GeV positron beam is reported. The plasma was formed by ionizing a nitrogen jet only 3 mm thick. Simultaneous focusing in both transverse dimensions was observed with effective focusing strengths of order tesla per micron. The minimum area of the beam spot was reduced by a factor of 2.0+/-0.3 by the plasma. The longitudinal beam envelope was measured and compared with numerical calculations.

Journal Article↗
PubMed2001

Observation of the Askaryan effect: coherent microwave Cherenkov emission from charge asymmetry in high-energy particle cascades.

We present the first direct experimental evidence for the charge excess in high-energy particle showers and corresponding radio emission predicted nearly 40 years ago by Askaryan. We directed picosecond pulses of GeV bremsstrahlung photons at the SLAC Final Focus Test Beam into a 3.5 ton silica sand target, producing electromagnetic showers several meters long. A series of antennas spanning 0.3 to 6 GHz detected strong, subnanosecond radio-frequency pulses produced by the showers. Measurements of the polarization, coherence, timing, field strength vs shower depth, and field strength vs frequency are completely consistent with predictions. These measurements thus provide strong support for experiments designed to detect high-energy cosmic rays such as neutrinos via coherent radio emission from their cascades.

Journal Article↗
PubMed2000

Lava lamp, a novel peripheral golgi protein, is required for Drosophila melanogaster cellularization.

Drosophila cellularization and animal cell cytokinesis rely on the coordinated functions of the microfilament and microtubule cytoskeletal systems. To identify new proteins involved in cellularization and cytokinesis, we have conducted a biochemical screen for microfilament/microtubule-associated proteins (MMAPs). 17 MMAPs were identified; seven have been previously implicated in cellularization and/or cytokinesis, including KLP3A, Anillin, Septins, and Dynamin. We now show that a novel MMAP, Lava Lamp (Lva), is also required for cellularization. Lva is a coiled-coil protein and, unlike other proteins previously implicated in cellularization or cytokinesis, it is Golgi associated. Our functional analysis shows that cellularization is dramatically inhibited upon injecting anti-Lva antibodies (IgG and Fab) into embryos. In addition, we show that brefeldin A, a potent inhibitor of membrane trafficking, also inhibits cellularization. Biochemical analysis demonstrates that Lva physically interacts with the MMAPs Spectrin and CLIP190. We suggest that Lva and Spectrin may form a Golgi-based scaffold that mediates the interaction of Golgi bodies with microtubules and facilitates Golgi-derived membrane secretion required for the formation of furrows during cellularization. Our results are consistent with the idea that animal cell cytokinesis depends on both actomyosin-based contraction and Golgi-derived membrane secretion.

Actins↗
PubMed2000

Progression of consequences among heavy-drinking college students.

Among a sample of 180 male and 226 female undergraduates, 84.2% reported a heavy drinking episode (5+ drinks for men, 4+ for women) within the previous 90 days. Principal-components analysis revealed 3 alcohol-related problem factors among the heavy drinkers (Careless Behavior, Risky/Reckless Behavior, and Authority Problems). Nearly all heavy drinkers experienced a careless behavior that was due to drinking (92.7%), and many reported a risky/reckless behavior (60.2%), yet only one third (33.9%) experienced an authority problem. Guttman scaling procedures revealed a progression from Careless Behavior to Reckless/Risky Behavior to an Authority Problem. Heavy drinkers with an authority problem drank more frequently, consumed more when drinking, endorsed more alcohol expectancies, and reported earlier ages of initial and regular drinking than other groups.

Adult↗
PubMed2000

Assessing coronary artery disease with thallium-201 rest and technetium-99m-sestamibi stress testing at two centers.

OBJECTIVE: In this study we assessed the specific location(s) of cardiac wall abnormalities in a population of patients referred for coronary artery disease and compared gender differences in the interpretation of nuclear medicine rest/stress results. METHODS: The study group consisted of 846 patients referred to 2 nuclear medicine outpatient cardiology centers for assessment between November 1998 and April 1999. All patients received dual-isotope perfusion 201Tl rest/99mTc-sestamibi stress tests. A retrospective analysis of patient results was performed. RESULTS: In both facilities the largest percentage of defects was identified in the inferior wall (35.5%), followed by the anterior wall (26.5%). Cardiac defects identified in 3 other walls were much lower: lateral wall (14.2%), septal (13.8%), and apical (9.5%). In both outpatient clinics the normalcy rate was much higher for women than men. The normalcy rate in men was 40%, whereas women demonstrated a normalcy rate of 60%. An analysis of treadmill stress versus pharmacologic stress did not illuminate the cause of this difference. CONCLUSION: The most common site of myocardial wall abnormalities occurred in the inferior wall followed by the anterior wall. A large disparity was identified between the results for men compared with those for women. Men had nearly twice the number of defects as women in this study.

Coronary Disease↗
PubMed1999

Cytokinesis in eukaryotes: a mechanistic comparison.

Cytokinesis is a crucial but poorly understood process of cell proliferation. Recently, molecular genetic analyses of fungal cytokinesis have led to an appreciation of contractile mechanisms in simple eukaryotes, and studies in animal and plant cells have led to new insights into the role of microtubules in the cleavage process. These findings suggest that fundamental mechanisms of cytokinesis may be highly conserved among eukaryotic organisms.

Actomyosin↗
PubMed1999

The economic burden of irritable bowel syndrome in Canada.

In the treatment of irritable bowel syndrome (IBS), medical practitioners and policymakers face the task of providing both high quality and cost effective medical care for a condition with no certain cure. To date, studies have examined only total medical costs to patients with symptoms consistent with an IBS diagnosis. However, these studies have not examined the direct and indirect costs incurred in the course of treatment for IBS, excluding the costs of unrelated medical conditions. Because patients with IBS have been shown to differ significantly from non-IBS patients in their desire to seek medical care, one cannot consider solely the cost differential in medical costs for IBS and non-IBS patients. The present study examines a set of patients who have been diagnosed with IBS and seek medical care for IBS.

Canada↗
PubMed1999

Therapy of metabolic disorders with intravenous (IV) access ports and long term intravenous L-carnitine therapy.

With the expansion of newborn screening to include many organic acidurias and fatty acid oxidation defects, effective therapies of these disorders will be needed. Currently severe disorders such as methylmalonic and propionic aciduria. conventional therapy with diet and oral L-camitine often prove ineffective in preventing failure to thrive and recurrent metabolic decompensations. L-carnitine provides a natural pathway for removal of the toxic metabolites in these disorders and is life saving therapy but, with poor oral absorption (25%), it is difficult to supply adequate carnitine to meet the metabolic needs of these patients. Long term intravenous L-carnitine therapy, administered through a subcutaneous venous access port in 5 patients with organic acidurias [propionic aciduria (2), methylmalonic aciduria (2), 3 methylglutaconic aciduria(1)] resulted in improved growth, lower frequency of metabolic decompensations and increased tolerance of natural protein in the diet. An added benefit was the ability to initiate fluid. electrolytes, and antibiotics during metabolic decompensations at home thus averting hospitalizations.

Carnitine↗
PubMed1998

Polymerization of purified yeast septins: evidence that organized filament arrays may not be required for septin function.

The septins are a family of proteins required for cytokinesis in a number of eukaryotic cell types. In budding yeast, these proteins are thought to be the structural components of a filament system present at the mother-bud neck, called the neck filaments. In this study, we report the isolation of a protein complex containing the yeast septins Cdc3p, Cdc10p, Cdc11p, and Cdc12p that is capable of forming long filaments in vitro. To investigate the relationship between these filaments and the neck filaments, we purified septin complexes from cells deleted for CDC10 or CDC11. These complexes were not capable of the polymerization exhibited by wild-type preparations, and analysis of the neck region by electron microscopy revealed that the cdc10Delta and cdc11Delta cells did not contain detectable neck filaments. These results strengthen the hypothesis that the septins are the major structural components of the neck filaments. Surprisingly, we found that septin dependent processes like cytokinesis and the localization of Bud4p to the neck still occurred in cdc10Delta cells. This suggests that the septins may be able to function in the absence of normal polymerization and the formation of a higher order filament structure.

Cell Cycle Proteins↗
PubMed1997

Isolation of actin-associated proteins from Caenorhabditis elegans oocytes and their localization in the early embryo.

The actin cytoskeleton plays an important, but poorly understood, role in the development of multicellular organisms. To help illuminate this role, we used actin filament affinity chromatography to isolate actin binding proteins from large quantities of Caenorhabditis elegans oocytes. To examine how these proteins might be involved in early development, we prepared antibodies against some of them and determined their distribution in fixed embryos. Three of these proteins co-localize with different subsets of the embryonic actin cytoskeleton. One co-localizes with actin to all cell cortices. The second oscillates between the nucleus and cortex in a cell-cycle-dependent manner. The third is asymmetrically enriched at the anterior cortex of one-cell embryos, showing a temporal and spatial localization suggestive of a function in generating developmental asymmetry. We conclude that biochemistry is a feasible and useful approach in the study of early C. elegans development, and that the embryonic actin cytoskeleton is regulated in a complex fashion in order to carry out multiple, simultaneous functions.

Actins↗
PubMed1997

Role and management of donkeys in Samburu and Turkana pastoralist societies in northern Kenya.

A survey was carried out in northern Kenya to obtain data on the role and management of donkeys in Samburu and Turkana pastoralist societies and to identify potential areas, if any, for interventions. Sixty-seven women owning or closely associated with 583 donkeys were surveyed during July/August 1994. The median donkey herd sizes in Samburu and Turkana societies were 4 and 10 respectively. Pack transport of water and domestic materials were the major reasons for keeping donkeys. Donkey milk, meat and blood were consumed widely by the Turkana but not by the Samburu. The major problems in donkey management were donkeys getting lost, being stolen, predation and being affected by diseases, in particular a disease condition involving unthriftiness, emaciation and slow growth. Traditional methods of treating donkey diseases were generally used. It was concluded that donkeys were an important component in the pastoralist societies surveyed although donkey numbers and transport capacity were not limiting factors in pastoralists activities. Potential areas for intervention were identified as disease investigation and stimulation of community based initiatives to tackle general management problems.

Animal Husbandry↗
PubMed1997

The effects of buspirone on perceived exertion and time to fatigue in man.

Male subjects exercised at 80% maximal rate of O2 uptake (VO2,max) following oral administration of either placebo or the partial 5-HT1A agonist buspirone (45 mg), using a paired design. Ratings of perceived exertion were higher following buspirone and time to volitional fatigue (median and inter-quartile range) fell significantly by approximately a third from 26 min (24-30 min) on placebo to 16 min (11-19 min) following buspirone. Serum prolactin was significantly elevated following buspirone administration, indicating increased hypothalamic 5-HT1A receptor stimulation. There were no significant differences in blood lactate or serum glucose between the trials. This study supports the possible central modulation of exercise tolerance by serotonergic pathways, although a role for dopamine cannot be excluded.

Adult↗
PubMed1995

Scintigraphic evaluation of the haemopoietic bone marrow using a 99mTc-anti-granulocyte antibody: a validation study with 52Fe.

To specify the validity of bone marrow scanning using a monoclonal anti-granulocyte antibody labelled with 99mTc (BW 250/183) for the functional assessment of haemopoiesis, we compared this method with 52Fe scan in 16 patients with haematological disorders. The examinations were performed using a rectilinear whole-body scanner and the distribution of the two tracers was assessed visually and quantitatively in anatomical bone marrow segments, the spleen and liver. Qualitative comparison showed concordance in the bone marrow distribution of the two tracers in 83% of the segments. Discrepancies were found in six patients with hypoplastic or aplastic marrow. The spleen was visualized in all cases with the 99mTc-Moab, including nine patients without splenic haemopoiesis (i.e. without spleen uptake of 52Fe). The uptake of the two tracers, quantified in bone marrow segments and the spleen, correlated well (P < 0.001), but not in the liver (NS). The correlation between the uptake values for each patient was excellent, except in cases of aplastic bone marrow. In conclusion, bone marrow scanning using a 99mTc labelled anti-granulocyte monoclonal antibody enables functional evaluation of the distribution of haemopoiesis. Limitations include the evaluation of bone marrow aplasia and identification of splenic haemopoiesis, for which 52Fe remains the tracer of choice.

Adolescent↗
PubMed1992

The incidence of total hip replacement in orthognathic surgery patients receiving short-term steroid therapy.

It is well known that long-term corticosteroid therapy can lead to avascular necrosis of the femoral head. There is suspicion among orthopedic surgeons that short-term, high-dose steroid use poses similar risks. The records of 2,773 patients (1,497 who had total hip replacement and 1,276 who had orthognathic surgery) were retrospectively reviewed. No hip replacements had been done in the orthognathic surgery group and none of the patients in the total hip replacement group had undergone orthognathic surgery. The use of short-course, systemic corticosteroids to reduce postoperative swelling in orthognathic surgery did not seem to cause avascular necrosis of the femoral head.

Adrenal Cortex Hormones↗