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Biomedical subjects

R L Nelson

Publications and source records attributed to R L Nelson.

At least 19 recordsLinked to original sources
PubMed2006

Free-air carbon dioxide enrichment of soybean: influence of crop variety on residue decomposition.

Elevated atmospheric CO2 can result in larger plants returning greater amounts of residue to the soil. However, the effects of elevated CO2 on carbon (C) and nitrogen (N) cycling for different soybean varieties have not been examined. Aboveground residue of eight soybean [Glycine max (L.) Merr.] varieties was collected from a field study where crops had been grown under two different atmospheric CO2 levels [370 micromol mol(-1) (ambient) and 550 micromol mol(-1) (free-air carbon dioxide enrichment, FACE)]. Senesced residue material was used in a 60-d laboratory incubation study to evaluate potential C and N mineralization. In addition to assessing the overall effects of CO2 level and variety, a few specific variety comparisons were also made. Across varieties, overall residue N concentration was increased by FACE, but residue C concentration was only slightly increased. Overall residue C to N ratio was lower under FACE and total mineralized N was increased by FACE, suggesting that increased N2 fixation impacted residue decomposition; total mineralized C was also slightly increased by FACE. Across CO2 levels, varietal differences were also observed with the oldest variety having the lowest residue N concentration and highest residue C to N ratio; mineralized N was lowest in the oldest variety, illustrating the influence of high residue C to N ratio. It appears (based on our few specific varietal comparisons) that the breeding selection process may have resulted in some varietal differences in residue quality which can result in increased N or C mineralization under elevated CO2 conditions. This limited number of varietal comparisons indicated that more work investigating varietal influences on soil C and N cycling under elevated CO2 conditions is required.

Agriculture↗
PubMed2001

The landing of the NEAR-Shoemaker spacecraft on asteroid 433 Eros.

The NEAR-Shoemaker spacecraft was designed to provide a comprehensive characterization of the S-type asteroid 433 Eros (refs 1,2,3), an irregularly shaped body with approximate dimensions of 34 x 13 x 13 km. Following the completion of its year-long investigation, the mission was terminated with a controlled descent to its surface, in order to provide extremely high resolution images. Here we report the results of the descent on 12 February 2001, during which 70 images were obtained. The landing area is marked by a paucity of small craters and an abundance of 'ejecta blocks'. The properties and distribution of ejecta blocks are discussed in a companion paper. The last sequence of images reveals a transition from the blocky surface to a smooth area, which we interpret as a 'pond'. Properties of the 'ponds' are discussed in a second companion paper. The closest image, from an altitude of 129 m, shows the interior of a 100-m-diameter crater at 1-cm resolution.

Journal Article↗
PubMed2001

Assessment of the usefulness of a diagnostic test: a survey of patient preference for diagnostic techniques in the evaluation of intestinal inflammation.

BACKGROUND: In order to assess the usefulness of radiolabeled white cell scanning in the diagnosis of intestinal inflammation, subjects were asked to rank several dimensions of preference for white cell scanning in relation to other diagnostic tests. Two groups were surveyed: one known to have inflammatory bowel disease and the second not familiar in most cases with the tests. Subjects were asked to rank preference for each of seven tests: radiolabeled white cell scan, colonoscopy, barium enema, sigmoidoscopy, enteroclysis, stool analysis and laparotomy for the diagnosis of IBD and impressions of discomfort, embarrassment, inconvenience and danger related to each test. Mean rank scores were calculated, test ranks compared within groups and significance determined by the Wilcoxon rank test. RESULTS: Significant differences were seen in overall preference for white cell scan over barium enema and colonoscopy (p < 0.01) in both survey groups. Perceived discomfort and embarrassment demonstrated similar rankings. CONCLUSION: This patient preference combined with the reported accuracy of white cell scanning further establishes the usefulness of this means of IBD diagnosis.

Adolescent↗
PubMed2001

Iron and colorectal cancer risk: human studies.

Some reports have associated iron with cancer risk, particularly of the colorectum. This review will focus on the human studies that have investigated this association. Comparative studies were sought in which people with and without colorectal neoplastic lesions, either cancers or adenomatous polyps, were assessed for iron exposure. Iron exposure variables included dietary iron intake, iron vitamin supplementation, body iron stores as measured by ferritin or transferrin saturation, and gene status for hereditary hemochromatosis. Medline was searched for published reports using the key words iron, cancer, colon, rectum, ferritin, transferrin, and hemochromatosis. In addition, the Cochrane Library was searched for relevant studies and several authors were contacted to investigate their awareness of unpublished studies. Studies were categorized by study design and ranked for quality of innovation in design, sample size, and thoroughness of iron status ascertainment. Thirty-three studies were reviewed in 26 publications. Of the larger studies, approximately three-quarters supported the association of iron, in all three strata of exposure, with colorectal neoplasia risk. Because iron is broadly supplemented in the American diet, the benefits of iron supplementation need to be measured against the long-term risks of increased iron exposure, one of which may be increased risk of colorectal cancer.

Colorectal Neoplasms↗
PubMed2001

Risk of disease in siblings of patients with hereditary hemochromatosis.

BACKGROUND: Parents of hereditary hemochromatosis (HH) homozygote patients, who are predominantly HH heterozygotes, have been found to have an increased risk of colonic neoplasia, diabetes, stroke death, stomach cancer and leukemia. The health histories of siblings of HH patients are reported. METHODS: Individuals homozygous for HH were mailed questionnaires concerning the health histories of their siblings. Spouses of the HH homozygotes were asked to complete accompanying questionnaires concerning their siblings. The frequencies of serious illness and, when specified, each reported disease were determined by zygosity, odds ratios and 95% confidence intervals estimated. RESULTS: Data were available for 279 siblings known to be HH homozygotes (HHs), and 1,265 other siblings of HH patients, who are predominantly hemochromatosis heterozygotes (HHhet). Controls consisted of 1,338 spouse siblings in whom only the general population prevalence of HH homozygosity and heterozygosity existed. Odds ratios comparing HH strata to controls were elevated for serious illness (1.12 in HHhet, 1.71 in HHs), diabetes (0.78, 2.45), arthritis (2.10, 1.69), and hepatoma (1.06, 11.96). CONCLUSIONS: There was a significant trend for increased risk of serious illness among siblings of HH patients with increasing exposure to the HH gene, especially for diabetes, arthritis and hepatoma.

Arthritis↗
PubMed2000

Repair of chronic anorectal fistulae using commercial fibrin sealant.

HYPOTHESIS: Commercially produced fibrin sealant can be used to completely close both simple and complex fistulae in ano. METHODS: A 29-patient prospective nonrandomized clinical trial was performed. In the operating room, the patient underwent an examination with anesthesia and the primary and secondary fistula tract openings were attempted to be identified. The fistula tract was curetted and fibrin sealant was injected into the secondary fistula tract opening until fibrin sealant was seen coming from the primary opening. A petroleum jelly gauze was then applied over the secondary opening and the patient was sent home. Follow-up visits were scheduled for 1 week, 1 month, 3 months, and 1 year later. RESULTS: Twenty-nine consecutive patients received fibrin sealant injections for their fistulae in ano, with a mean follow-up of 6 months. Two patients had a history of Crohn disease (regional enteritis) and 2 patients had human immunodeficiency virus infection. Overall, 17 (68%) of 25 patients have had successful closure of their fistula with 4 patients lost to follow-up. Two patients required reinjection with fibrin sealant, and neither of these subsequently had closure. One of the 2 patients with Crohn disease had closure, as well as 1 human immunodeficiency virus-positive patient. In addition, there has been no evidence of incontinence or complications related to the use of fibrin sealant in this procedure. CONCLUSIONS: Initial results in the treatment of chronic anorectal fistulae using commercial fibrin sealant are optimistic, but require further support through longer follow-up data. Fibrin sealant treatment of anorectal fistulae offers a unique mode of management which is safe, simple, and easy for the surgeon to perform. By using fibrin sealant, the patient avoids the risk of fecal incontinence and the discomfort of prolonged wound healing that may be associated with fistulotomy.

Adult↗
PubMed2000

Dermal island-flap anoplasty for transsphincteric fistula-in-ano: assessment of treatment failures.

PURPOSE: The aim of this study was to assess the treatment failures of island-flap anoplasty for fistula-in-ano, a procedure designed to treat fistula without sphincter division. METHODS: Data concerning all patients having dermal island-flap anoplasty for the treatment of transsphincteric fistula were reviewed. Variables assessed were age, gender, radial fistula location, cause, Crohn's disease, previous fistula operations, other complicating illnesses, internal sphincter closure, simultaneous use of fibrin adhesive injection, and use of combined dermal and rectal flap for large fistulas. Postoperative data collected included persistence of the distal tract, recurrence of the fistula, and treatment of the recurrence. Recurrence (or persistence) of the fistula was the dependant variable and each risk factor for recurrence was assessed using chi-squared analyses. RESULTS: Seventy-three flaps were performed in 65 individuals. Recurrence developed 17 times in 13 individuals. Recurrence was more likely to occur in males, patients who have had previous treatment of fistulas, patients with large fistulas requiring combined flaps, and patients who had simultaneous fibrin glue injection. Patients with Crohn's disease and individuals having internal sphincter closure had fewer recurrences. Factors reaching statistical significance included closure of the internal sphincter, the use of fibrin glue, and cause of the fistula. CONCLUSION: No specific anatomic or demographic characteristic is sufficiently associated with failure to exclude any patient from the operation. Closure of the internal sphincter should be done as part of the procedure and fibrin glue injection should not be done simultaneously.

Anal Canal↗
PubMed2000

Repair of fistulas-in-ano using fibrin adhesive: long-term follow-up.

PURPOSE: Fibrin adhesive has been successfully used to treat fistulas-in-ano, but long-term data have been lacking. We report the results of our 18-month study examining the repair of fistulas-in-ano using autologous and commercial fibrin adhesive. METHODS: A 79-patient, prospective, non-randomized clinical trial was performed in which fibrin adhesive was used to repair fistulas-in-ano. Twenty-six patients were treated with autologous fibrin tissue adhesive made from their own blood, and 53 patients were treated with commercial fibrin sealant. In the operating room the patient underwent an examination under anesthesia, with an attempt to identify the primary and secondary fistula tract openings. The fistula tract was then curetted. Fibrin adhesive was injected into the secondary fistula tract opening until adhesive was seen coming from the primary opening. A petroleum jelly gauze was then applied over both the primary and secondary openings, and the patient was sent home. Follow-up visits occurred one week, one month, three months, and one year later. RESULTS: Fourteen of 26 (54 percent) patients treated with autologous fibrin tissue adhesive made from their own blood had complete closure of their fistulas after a one-year follow-up, whereas 34 of 53 (64 percent) patients treated with commercial fibrin sealant had closure of their fistulas. Most treatment failures occurred within the first 3 months, but late failures were seen as far as 11 months postoperative. CONCLUSIONS: Fibrin tissue adhesive offers a unique mode of managing fistulas-in-ano, which is surgically less invasive, but recurrences up to one year later are being seen. Longer follow-up and further research is recommended for improvement.

Adult↗
PubMed2000

Evidence that a dodecamer duplication in the gene HOPA in Xq13 is not associated with mental retardation.

A recent study suggested that a dodecamer duplication in exon 42 of the HOPA gene in Xq13 may be a significant factor in the etiology of X-linked mental retardation. In an effort to investigate this possibility, we determined the incidence of the dodecamer duplication in cohorts of non-fragile X males with mental retardation from three countries, cohorts of fragile X males from two countries, 43 probands from families with X-linked mental retardation and control cohorts from three countries. The duplication was found in 3.6-4.0% of male patients from two non-fragile X groups (Italy and South Carolina), in 1.2% from another non-fragile X group (South Africa), but in no male patients from families with X-linked mental retardation (South Carolina). The dodecamer duplication was also found in several white males with fragile X syndrome from France (5%) and South Africa (22.2%). Additionally, the duplication was found in 1.5% of South Carolinian newborn males, 2.5% South Carolinian male college students, 5% Italian male controls and 4.5% of the white South African controls. None of the black South African non-fragile X individuals with mental retardation, the fragile X or the control samples tested carried the duplication, suggesting that the duplication is rare in the black South African population. The incidence of the duplication was not significantly different between any of the groups in the study. Therefore, results of our studies in four different populations do not corroborate the findings of the previous study, and indicate that the HOPA dodecamer duplication does not convey an increased susceptibility to mental retardation.

Adult↗
PubMed1999

Carcinoma in situ of the colorectum: SEER trends by race, gender, and total colorectal cancer.

BACKGROUND AND OBJECTIVES: To determine if Americans of African origin (blacks) have less access to colonoscopic polypectomy than Americans of European origin (whites), the rate of carcinoma in situ of the colorectum (CIS), a disease more similar to benign adenoma of the colorectum than invasive cancer in its symptomatology, discovery, and treatment, was determined in the United States from 1973 to 1994. The hypothesis being tested is that CIS will be far less common in blacks than in whites and that rates of CIS should be increasing in whites from 1973 to 1994. METHODS: CIS and invasive carcinoma of the colorectum incidence data were obtained from Surveillance, Epidemiology, and End Results (SEER) Public Use Files from 1973 through 1994. Rates were age adjusted and proportions determined by division of CIS rates for each subsite by total carcinoma rates, for each year, race, and gender. The colorectum was divided anatomically in this analysis at the junction of the descending and sigmoid colon. RESULTS: The relationships between male/female and black/white CIS incidence rates were broadly similar to invasive cancer rates over the 21 years of SEER, demonstrating a white male predominance for distal disease, a black male predominance for proximal disease, and a decline in incidence since 1988. CIS as a proportion of total colorectal cancer increased in all races and genders from 1973 to 1987, but then declined in all groups. CONCLUSIONS: The majority of CIS is excised by endoscopic resection. Therefore, this might be considered a surrogate population for those individuals who have colonoscopic resection of benign adenomas. It is this latter treatment that has been hypothesized to be the cause for the declining incidence of invasive colorectal cancer. However, data presented herein do not support this hypothesis.

Black People↗
PubMed1999

Repair of fistulas-in-ano using autologous fibrin tissue adhesive.

PURPOSE: Our goal was to determine if autologous fibrin tissue adhesive derived from the precipitation of fibrinogen using a combination of ethanol and freezing, could be used to completely close both simple and complex fistulas-in-ano. METHODS: A 26-patient pilot study was performed in which 100 ml of a patient's blood was drawn 90 minutes before surgery. Autologous fibrin tissue adhesive was prepared. In the operating room the patient underwent an examination under anesthesia, and the primary and secondary fistula tract openings were attempted to be identified. The fistula tract was curetted, and autologous fibrin tissue adhesive was injected into the secondary fistula tract opening until fibrin glue was seen coming from the primary opening. A petroleum jelly gauze was then applied over the secondary opening, and the patient was sent home. Follow-up visits were scheduled for one week, one month, three months, and one year later. RESULTS: Twenty-six patients received autologous fibrin tissue adhesive fistula injections, with a mean follow-up of 3.5 months. Initial results were encouraging. Twenty-one of 26 patients (81 percent) had successful initial closure of their fistulas. Two of five failures were injected a second time, and one closed, giving an overall successful closure rate of 85 percent (22/26 patients). Of five patients who failed, mean time to failure was 3.8 weeks. In addition, there was no evidence of infection or complications related to the procedure. CONCLUSION: Our initial results are optimistic and require further support through longer follow-up data. Fibrin glue treatment of anorectal fistulas offers a unique mode of management that is safe, simple, and easy for the surgeon to perform. By using autologous fibrin tissue adhesive the patient avoids the risk of anal incontinence and the discomfort of prolonged wound healing which may be associated with fistulotomy.

Adult↗
PubMed1999

Technical manual for manufacturing autologous fibrin tissue adhesive.

PURPOSE: The aim of this article is to provide a concise and simple technical manual for manufacturing autologous fibrin tissue adhesive derived from the precipitation of fibrinogen using a combination of ethanol and freezing for surgery. METHODS: All materials and equipment needed to manufacture ethanol-based autologous fibrin tissue adhesive are listed. In addition, step-by-step instructions are provided to allow for easy and rapid fibrin adhesive production. RESULTS: Ethanol-based autologous fibrin tissue adhesive can be manufactured in under 60 minutes. Furthermore, at our institution the startup cost for manufacturing ethanol-based autologous fibrin tissue adhesive was under $2,500.00. CONCLUSION: Ethanol-based autologous fibrin tissue adhesive is a safe, reliable, and easily manufactured autologous fibrin tissue adhesive that can be made by a trained technician in any blood bank, pharmacy, or surgical laboratory.

Ethanol↗
PubMed1999

Meta-analysis of operative techniques for fissure-in-ano.

PURPOSE: Operative techniques commonly used for fissure-in-ano include anal stretch, open lateral sphincterotomy, closed lateral sphincterotomy, posterior midline sphincterotomy, and to a lesser extent dermal flap coverage of the fissure. Reports of direct comparisons among these techniques are variable in their results and for the most part underpowered. A rigorous analysis of the combined reports was therefore undertaken to determine whether a preferred technique for fissure surgery can be elucidated. METHODS: MEDLINE was searched for all published reports using the key words "surgery" and "anal fissure." All reports in which there was a direct comparison between at least two operative techniques were reviewed, and when more than one report existed for any given pair, that report was included in the meta-analysis. If crude data were not presented in the report, the authors were contacted, and crude data were obtained. The two most commonly used end points in these reports were persistence of the fissure and postoperative incontinence of flatus. These are the only two end points included in the meta-analysis. The meta-analysis was performed using Epi-Info software obtained from the Centers for Disease Control and Prevention (www.cdc.gov). RESULTS: Seventeen publications fulfilled the criteria of the study, encompassing 2,727 patients. Significant differences were found for both persistence and incontinence to flatus when comparing anal stretch to all forms of sphincterotomy. No significant difference was found comparing open to closed lateral internal sphincterotomy for persistence or incontinence. Posterior midline sphincterotomy was not significantly different from lateral sphincterotomy related to persistence or incontinence. CONCLUSION: Internal anal sphincterotomy is superior to anal stretch and should probably be performed in the lateral location, although both the open and closed techniques seem equally efficacious.

Databases, Factual↗