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Biomedical subjects

C Mitchell

Publications and source records attributed to C Mitchell.

At least 73 records · Page 4Linked to original sources
PubMed1983

The masking of tinnitus with pure tones.

The tinnitus of 32 subjects was studied. The tinnitus in each subject was matched to tones and bands of noise. Tones were then used to determine masking curves. Four types of masking curves were found. These types are similar to those previously reported. The findings also supported previous studies where tinnitus masking curves were found to differ significantly from conventional masking curves. Audiometric curves were grouped according to severity of hearing loss in order to determine whether subjects with similar threshold curves had similar masking curves. Similarities were noted in only one group: those with the least hearing loss. The relation between masking curves and the success of masking therapy is discussed.

Audiometry↗
PubMed1983

Management of the acute asthma attack at home.

Asthma is a disease of remission and exacerbation but the combination of optimal interval therapy with early aggressive self initiated medication during deterioration (particularly oral corticosteroids) should prevent the crises which require emergency intervention. The first and last words in acute asthma management must be prevention and prevention.

Acute Disease↗
PubMed1982

Metabolism of immunoglobulin A in lactating mice: origins of immunoglobulin A in milk.

The metabolism of albumin and IgA was studied in normal and lactationg mice. Lactation resulted in significant changes in the metabolism of these proteins. The serum albumin concentration was lowered from 47 mg/ml in normals to 24 mg/ml in lactating mice. However, only a slight decrease in the serum concentration of IgA was observed during lactation. The proportion of polymeric and monomeric IgA in serum and milk was evaluated by gel exclusion chromatography. The onset of lactatin led to a rise in the proportion of polymeric IgA (P-IgA) in serum from 37% to 51%. The proportion of P-IgA in milk was 65% and remained constant throughout lactation. P-IgA and albumin were shown to be efficiently transferred from the serum of lactating mice into their milk. Serum decay studies were performed to evaluate the turnover of the serum pools during lactation. The rates of disappearance from the serum of isotopically labeled albumin and P-IgA were observed to increase dramatically during lactation, suggesting that both of these two mild proteins might be derived at least in part from the serum. The sites of synthesis of mild IgA (local vs. extra-mammary gland) were evaluated by determining the extent of dilution of isotopically labeled serum IgA during transport through the mammary gland into the milk. Early in lactation, the majority of the IgA in mouse milk appeared to be derived from distant sites and transferred via the blood to the mammary gland. However, by day 8 of lactation, the isotopically labeled P-IgA in milk was significantly diluted by the IgA synthesized in the mammary gland. Albumin and IgG were not diluted by local synthesis indicating that these proteins were exclusively serum-derived.

Animals↗
PubMed1982

Postoperative respiratory morbidity: identification and risk factors.

Two hundred consecutive patients admitted for general surgery were studied prospectively to evaluate the contribution of risk factors to postoperative respiratory morbidity (PORM). PORM was expressed both in terms of individual clinical features present on the second postoperative day (when the incidence was greatest), and as an aggregate score incorporating many clinical features. The importance of recognised risk factors, such as previous respiratory disease, cigarette smoking, upper abdominal procedures and the duration of surgery was confirmed, in that these factors were associated with some of the individual clinical features of PORM. The relative importance and independent contribution of these risk factors were assessed by their association with the aggregate score. A naso-gastric tube (NGT) present for 24 hours postoperatively was the factor more associated with PORM. The NGT identified patients at risk more clearly than, and independently of, the next most important factor, upper abdominal surgery. The duration of surgery did not contribute to PORM after the influence of NGT and site of surgery had been considered. Previous respiratory disease predisposed to PORM, and was best identified by, in order of importance, an observed productive cough, a reduced one second forced expiratory volume, and purulent sputum. After the incidence of these factors had been considered, cigarette smoking and a history of a chronic productive cough did not contribute further to PORM.

Abdomen↗
PubMed1981

Prevalence of respiratory morbidity in Brisbane waterside workers. A study of possible asbestos-related disease.

Ninety-eight Brisbane waterside workers who had been exposed to several dusts, particularly that of asbestos fibre, were studied. Forty-nine subjects complained of dyspnoea while walking uphill, 46 had basal endinspiratory crepitations, and chest X-ray films showed small irregular opacities in 41 subjects and pleural abnormalities in 27 subjects. Internal comparisons showed that ventilatory function was correlated significantly with duration of employment on the wharves, independently of the effect of age and total cigarette consumption. Forced vital capacity decreased by 20 mL/year on wharves, and one-second forced expiratory volume by 34 mL/year, in excess of the age-related decrease. These findings suggest that these workers have developed parenchymal lung disease probably related to asbestos-dust exposure on the wharves.

Adult↗
PubMed1981

DNA modification in rat lungs following intratracheal or subcutaneous administration of 4-nitroquinoline-1-oxide, benzo[a]pyrene or 2-aminoanthracene.

Benzo[a]pyrene (BP)-, 2-aminoanthracene (2AA)- and 4-nitroquinoline-1-oxide (4NQO)-mediated DNA modification were investigated in rat lungs by using alkaline sucrose gradient sedimentation. The exposure-route, the physicochemical nature of the administered compound and the number of treatments were all important in determining the extent of DNA modification. 4NQO produced qualitatively similar modification whether instilled intratracheally (i.t.) as a suspension or injected subcutaneously (s.c.) in a soluble form. BP and 2AA produced no DNA alteration when injected s.c; they did, however, modify DNA sedimentation when instilled as a suspension, but not until 24 h after treatment. Furthermore, BP caused no DNA modification at any sampling time when instilled in a lipid solvent. In contrast to the DNA modification observed at 24 h after a single i.t. treatment with a BP suspension, no such alteration was detected 12 or 24 h after the last of 5 similar daily treatments. These results are discussed with respect to mechanisms of differential transport, clearance and metabolism of administered carcinogens.

4-Nitroquinoline-1-oxide↗
PubMed1980

Selected events following insertion of the Progestasert system.

The incidences of selected events were analyzed following insertion of the PROGESTASERT intrauterine progesterone contraceptive system (IPCS) and following its reinsertion after one year of use. Reinsertion did not interrupt the stabilizing or declining trends in incidences of P.I.D., removals for bleeding/pain, removals for other medical reasons, unplanned pregnancies, moderate/severe menstrual cramps and bleeding, and premenstrual/intermenstrual cramps. Comparison of the incidence of P.I.D. in the U.S. population with postinsertion incidence of P.I.D. in IPCS users indicates that the IPCS does not increase the likelihood that a woman will have P.I.D. over the likelihood that she would have it without use of the IPCS. The incidences of expulsions and intermenstrual spotting and bleeding rose temporarily after reinsertion to about half their previous peaks and then diminished markedly within two months, reverting to the levels and favorable patterns of change established during the first year.

Female↗
PubMed1980

Tuning curves of cochlear and brainstem responses in the guinea pig.

A tone-on-tone masking paradigm was used to determine tuning curves of cochlear and brainstem responses in the guinea pig. The tuning curves are considered to be a measure of the frequency specificity of these potentials. Calculated Q10 values are used in an indicator of the sharpness of tuning of these potentials. The tuning curves of cochlear and brainstem responses were found to be similar with both showing considerable frequency specificity.

Animals↗
PubMed1979

Reflection-impulsivity and the evaluation process.

The relationship between reflection-impulsivity, hypothese generation and testing, and evaluation of the quality of one's own solutions was explored in the framework of Kagan's theory. The Matching Familiar Figures test (MFF) and a pattern-matching task were administered to 94 children from 8-0 to 11-11 years. Multiple regression analyses and analyses of variance showed that children who were inaccurate on the MFF were more likely to offer a solution on the pattern-matching task before they had sufficient information to guarantee a correct solution and to make errors despite sufficient information to have avoided those errors. Thus reflection-impulsivity as measured by the MFF were related to 2 other measures of the evaluation process on another visual match-to-sample task. Only 1 of 3 hypothesis-testing variables was significantly related to MFF performance, and that relationship was rather small.

Child↗