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Biomedical subjects

C Scott

Publications and source records attributed to C Scott.

At least 199 records · Page 11Linked to original sources
PubMed1991

Construction of synthetic genes using PCR after automated DNA synthesis of their entire top and bottom strands.

A new method is described for the direct construction of synthetic genes by applying a modified version of the polymerase chain reaction (PCR) to crude oligonucleotide mixtures made by automated solid phase DNA synthesis. Construction of the HIV-1 393 bp rev gene and the 655 bp nef gene by this method is illustrated. The sequences for the entire top and bottom strands of rev were each programmed into an automated DNA synthesizer. Following DNA synthesis, the two crude oligonucleotide solutions were mixed together, specific primers were added, and the target gene was amplified by a modified PCR technique. Although the longer (greater than 200 bases) strands comprise a very small percentage of the total DNA after solid phase synthesis, this method uses PCR to 'find' and amplify such strands to create the target gene. The rev gene constructed by this method was found to contain 4 sequence errors, which were subsequently corrected by site-directed mutagenesis. In order to evaluate the source of sequence errors, several nef genes were made from the top and bottom strand DNA synthesis solutions using independent PCR's. Results suggest that sequence errors arose from both DNA synthesis and PCR. The utility of this method in producing a functional gene is demonstrated by expression of rev in E.coli.

Base Sequence↗
PubMed1991

Corneal ulcer and adverse reaction rates in premarket contact lens studies.

We analyzed clinical data on 22,739 contact lens wearers who were studied and whose lenses were approved under 48 manufacturer-sponsored studies for the Food and Drug Administration between 1980 and 1988. The incidence of corneal ulcers was low in the cosmetic (nontherapeutic) daily-wear soft and rigid gas-permeable lens wearers (1/1,923 and 1/1,471 patient-years, respectively). Corneal ulcers and severe adverse reactions occurred two to four times more frequently in extended-wear cosmetic soft and rigid gas-permeable lens wearers than in cosmetic daily-wear lens wearers. Aphakic extended-wear soft lens users were nine times more likely to develop a corneal ulcer when compared to the soft daily-wear cosmetic group. Corneal abrasions and keratitis accounted for 81 of 159 severe adverse reactions, whereas corneal ulcers accounted for 28 of 159 adverse reactions. The data indicate that overnight extended wear of contact lenses is associated with a greater risk of serious, sight-threatening complications than daily wear.

Aphakia↗
PubMed1991

The relationship of nasopharyngeal carcinomas and second independent malignancies based on the Radiation Therapy Oncology Group experience.

The authors sought to learn if the incidence of second independent malignancies after the irradiation of carcinomas of the nasopharynx is similar to that observed after treatment of tumors arising in other head and neck sites. One hundred twenty-one patients who had primary carcinomas of the nasopharynx who were treated solely by ionizing radiation (according to the specifications of a Radiation Therapy Oncology Group protocol) were identified and their subsequent well-being was reviewed. Overall there was a 4.1% incidence of second malignancies (2% after 3 years, 5% after 5 years, and 8% after 8 years) with most arising in the upper aerodigestive tract. This rate is significantly less than the rate associated with other head and neck sites. It is not significantly different from the rate of first malignancies observed in an age-matched and sex-matched population. When only those patients who were free of all evidence of neoplastic disease 6 months after the completion of radiotherapy are considered, similar analysis leads to similar outcomes. The authors conclude that the risk of second malignancies after the successful irradiation of carcinomas of the nasopharynx is substantially less than after treatment of tumors at other head and neck sites.

Adolescent↗
PubMed1991

Phase I/II study, combination of radiotherapy and hyperthermia in patients with deep-seated malignant tumors: report of a pilot study by the Radiation Therapy Oncology Group.

This is a report of a Phase I/II study activated in March 1984 and completed in October 1988 by the Radiation Therapy Oncology Group on the feasibility/toxicity of hyperthermia in patients with deep-seated malignant tumors. The main objective of this study was to evaluate the morbidity of regional hyperthermia (systemic and regional, acute and late effects); a secondary objective was to evaluate tumor response to combined irradiation and regional hyperthermia. A total of 54 patients with locally advanced abdominal or pelvic malignancy were accrued to this study; 42% were male and 58% female. Seventy-five of the patients had pelvic tumors and 25% abdominal tumors. Acute toxicities included grade 4 in three patients (1 cutaneous, 1 infection and 1 chemical peritonitis) one grade 3 (skin), and 12 grade 2 toxicities (6 skin and 6 gastrointestinal). With regard to late toxicities, grade 4 was noted in one patient (skin), grade 3 (GI) in one, and grade 2 (skin, peripheral neuropathy) in six patients. The prescribed course of hyperthermia was completed in 17 (32%) of patients. In 36 patients (68%) the course of hyperthermia was terminated, primarily because of patient discomfort. Tumor response was assessed by physical examination or radiological studies. Of 44 patients evaluable for response, there were 17 (39%) complete responses and 6 (14%) partial responders. Significant technical problems in heat delivery and thermometry remain.

Abdominal Neoplasms↗
PubMed1990

Community hospital carotid endarterectomy in patients over age 75.

We compared the prevalence of stroke and death in 133 patients aged 75 and older in whom 170 carotid endarterectomies were performed with that in 501 patients less than age 75 in whom 640 carotid endarterectomies were performed. There were three strokes (2%) in patients aged 75 and older and nine strokes (1%) in younger patients (p = 0.7). There were 8 deaths (5%) in patients aged 75 and older and 14 deaths (2%) in younger patients (p = 0.1). After controlling for the possible confounding effects of diabetes, prior stroke, history of angina, prior carotid artery disease, previous vascular surgery, history of myocardial infarction, preoperative hypertension requiring medication, and female gender, a logistic regression model showed that patients aged 75 and older were no more likely to have a stroke or death than patients under age 75. We conclude that age alone is not a contraindication to the safe performance of carotid endarterectomy in the community hospital.

Age Factors↗
PubMed1989

The role of hemoglobin concentration in the outcome of misonidazole-sensitized radiotherapy of head and neck cancers: based on RTOG trial #79-15.

Recent data from the DAHANCA (Danish Head and Neck Cancer) 2 study implies a positive effect of high hemoglobin concentration in concert with misonidazole for the treatment of head and neck cancers by radiotherapy. We have therefore reviewed and updated our analysis of RTOG protocol 79-15, which included the effect of misonidazole plus radiotherapy in a presumably similar population. Despite additional follow-up and more sophisticated analysis, our analysis does not demonstrate an influence of hemoglobin concentration on any of the outcome measures we examined. Possible explanations for the difference in findings of RTOG 79-15 and DAHANCA 2 are discussed. Radiation therapy of head and neck squamous cancers, Hypoxia and hemoglobin conc. in head and neck cancers, Oral cavity cancer, Effect of radiation therapy, Oropharynx cancer, Hemoglobin and radiotherapy, Hemoglobin concentration, Effect upon radiotherapy, Irradiation of oropharynx cancer, Hgb effect.

Carcinoma, Squamous Cell↗
PubMed1989

Union election activity in the hospital industry.

In the past five years, there has been a dramatic decrease in the number of representation elections in the hospital industry. Once a union is in place, however, decertification is less likely to occur than in other industries.

Collective Bargaining↗
PubMed1988

Remote viewing.

Remote viewing is the supposed faculty which enables a percipient, sited in a closed room, to describe the perceptions of a remote agent visiting an unknown target site. To provide convincing demonstration of such a faculty poses a range of experimental and practical problems, especially if feedback to the percipient is allowed after each trial. The precautions needed are elaborate and troublesome; many potential loopholes have to be plugged and there will be strong temptations to relax standards, requiring exceptional discipline and dedication by the experimenters. Most reports of remote viewing experiments are rather superficial and do not permit assessment of the experimental procedures with confidence; in many cases there is clear evidence of particular loopholes left unclosed. Any serious appraisal of the evidence would have to go beyond the reports. Meanwhile the published evidence is far from compelling, and certainly insufficient to justify overthrow of well-established scientific principles.

Data Collection↗
PubMed1988

High-density lipoprotein subclass distribution in premature newborns before and after the onset of enteral feeding.

Changes in high-density lipoprotein (HDL) subclass distribution were evaluated in a group of premature infants during the early postnatal period to ascertain whether enteral feeding brought about a rapid shift from neonatal to adult-like distributions. All infants were fed a combination of breast milk and formula. Cord blood of premature infants had a predominance of large, less dense (HDL2b)gge and a paucity of intermediate-sized (HDL3a)gge particles. Lack of a peak in the (HDL3a)gge is a characteristic feature for cord blood, whereas a prominent (HDL3a)gge peak is characteristic of adult plasma. After the start of enteral feeding, blood was obtained at two time-points: 6-14 days (sample A) and 17-32 days (sample B) postdelivery. With the onset of feeding, triglyceride increased significantly from an average of 34 mg/dl in cord blood to 120 mg/dl in sample B, and cholesterol increased from 86 to 112 mg/dl in the same period. Increases in plasma lipid concentrations were paralleled by a redistribution of subclasses such that three components of almost equal intensity were evident in sample B; these consisted of (HDL2b)gge, (HDL2a2)gge, and (HDL3b)gge. A paucity of (HDL3a)gge particles persisted even after onset of enteral feeding; thus, increases in plasma triglyceride and cholesterol per se are not sufficient to induce the adult-like distribution. It is suggested that development of the normal adult HDL subclass pattern is complex and is probably related to the development and interaction of several factors, including plasma enzymes involved in lipid hydrolysis and esterification, lipid exchange proteins, and hormonal status.

Age Factors↗
PubMed1988

Early gastric cancer in clinical practice.

A description of four patients with early gastric cancer diagnosed by endoscopy is reported. All patients presented with type III (excavated or ulcerative) early gastric cancer. Early gastric cancer appeared to be slow growing in three patients, and was difficult to diagnose in two cases, especially when associated with large gastric ulcers. Endoscopic biopsy of nonhealing or recurrent gastric ulcers and endoscopic follow-up to complete ulcer healing are recommended.

Adult↗
PubMed1987

Predicting the pharmacodynamics of heparin: a clinical evaluation of the Hepcon System 4.

The magnitude of the anticoagulation response to heparin (heparin responsiveness) varies substantially from patient to patient. Identifying extremes of sensitivity and resistance prior to intravenous administration of heparin would facilitate anticoagulation for cardiopulmonary bypass (CPB). The performance of the Hepcon System 4 (HemoTec, Inc, Englewood, CO), an instrument designed for that purpose, was tested. Using nonheparinized blood samples from 157 patients scheduled for surgery requiring CPB, this device performed activated coagulation times (ACT) with three different concentrations of in vitro heparin. After determining each patient's in vitro heparin response, the heparin dose predicted to produce ACT values of 480 seconds (group 1, N = 77) or 600 seconds (group 2, N = 80) was administered. Five minutes later each patient's ACT was determined with the Hemochron method (International Technidyne, Inc, Edison, NJ). Simultaneously, several other variables that might predict heparin responsiveness were investigated. When compared with the observed ACT, the Hepcon System 4 inadequately predicted the response. There was considerable scatter in this comparison, but most frequently the in vitro method substantially underestimated the in vivo heparin dose requirement. Heparin responsiveness decreased significantly with high platelet counts and advanced age, but was unaffected by the initial hematocrit, ACT, partial thromboplastin time, or preoperative heparin therapy. Previous investigations have not identified a relationship between advanced age and reduced heparin responsiveness. Combining the Hepcon heparin dose-response in vitro method with the other parameters evaluated, stepwise regression could only account for 39% of the observed variability in heparin responsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1987

Mutually independent effects of adrenocorticotropin on luteinizing hormone and testosterone secretion.

In this study, we examined the effect of ACTH on the sensitivity of the testes to gonadotropin and determined the role of the testosterone (T) negative feedback system in mediating the inhibitory effect of ACTH on LH secretion in adult male rats. ACTH infusion for 3 days reduced basal levels of serum T and the T response to GnRH, but did not alter basal levels of serum LH (immunoreactive) or the LH response to GnRH. These effects required the presence of the adrenal glands. Infusion of corticosterone (B) at a dose that increased serum B concentrations 9-fold had an effect similar to that of ACTH on basal serum T levels and the serum T response to GnRH. Basal levels of serum LH and the serum LH response to GnRH were not affected by B administration. These data suggest that ACTH administration reduces the sensitivity of the testes to LH, resulting in a lower basal level of T and a reduced T response to GnRH. This effect was independent of basal serum LH levels or the LH response to GnRH. It appears that B mediates the effect of ACTH on testicular sensitivity to gonadotropin. In another experiment, ACTH administration for 4 days did not alter serum LH values, but reduced serum T levels in sham-castrated male rats. In contrast, ACTH treatment blunted the increase in serum LH after castration by day 2 of treatment, despite the absence of detectable levels of serum T within 6 h after castration. These data suggest that T is not essential for the inhibitory effect of ACTH on LH secretion to occur. They do not support the hypothesis that ACTH enhances the sensitivity of the hypothalamus and/or pituitary to the negative feedback effects of T.

Adrenalectomy↗
PubMed1985

Genetic polymorphism at the kappa chain locus in mice: comparisons of restriction enzyme hybridization fragments of variable and constant region genes.

Variable (V kappa) and constant (C kappa) region genes of the mouse kappa light chain have been compared in inbred strains and in geographically isolated or genetically separated populations of mice by Southern blot analysis of endonuclease-restricted germline DNA. In most cases, the C kappa gene is found on a single restriction fragment while the V kappa genes of the V kappa 19 and V kappa 21 groups are each found on several (6-18) fragments. The restriction fragment (RF) patterns of V kappa 19 and V kappa 21 groups are both polymorphic when compared among inbred mouse strains. Southern blot patterns of V kappa 21 and V kappa 19 of inbred strains are also found among some geographically isolated populations of mice, suggesting that inbred strains acquired kappa loci from different subspecies. Some populations of geographical isolates show V kappa 21, V kappa 19, and C kappa contexts similar to inbred mice while more distantly related species within the genus Mus and laboratory rats show no apparent similarity in context to inbred strains. Variable region genes determining the RF patterns of V kappa 19 and V kappa 21 appear to be linked to each other and to the C kappa and Lyt-3 loci.

Animals↗