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Biomedical subjects

L Whitaker

Publications and source records attributed to L Whitaker.

At least 37 records · Page 2Linked to original sources
PubMed1994

Raynaud's syndrome: diagnosis and treatment.

Patient care and research in clinical vascular surgery have traditionally and appropriately focused on the complications of atherosclerosis. Without question, however, the clinical field of vascular surgery encompasses a number of areas other than clinical vasospasm as exemplified by Raynaud's syndrome. At the Clinical Research Center at the Oregon Health Sciences University, during the past 20 years the vascular surgery unit has maintained an active research program in Raynaud's syndrome and to date has enrolled and longitudinally followed more than 1000 patients with this affliction. There has been an opportunity to participate in the long-term management of this large population with emphasis both on natural history and vascular laboratory diagnosis and treatment. Raynaud's syndrome is a condition characterized by episodic digital ischemia in response to cold or emotional stimuli. The incidence is greater in women, and it is more frequent in areas with a cool, damp climate. Raynaud's usually affects the hands and fingers, but it may affect the feet and toes as well. The classical Raynaud's attack is tricolor and consists of blanching of the digits resulting from cessation of arterial flow, then cyanosis upon rewarming. This is followed by reactive hyperemia, which causes the digits to turn red. Raynaud's syndrome is classified into two groups: vasospastic or obstructive. Vasospastic Raynaud's is generally cold-induced. Nicotine, stress, and caffeine are associated with vasospasm. Obstructive Raynaud's is observed in association with other diseases such as connective tissue disorders, atherosclerosis, traumatic occlusion, Buerger's disease, and occupational related disorders. The diagnosis of Raynaud's is based on differentiating between vasospasm and obstruction and detecting the presence of associated disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1993

On the plausibility of the clonal expansion theory of the immune system in terms of the combinatorial possibilities of amino-acids in antigen and self-tolerance.

The clonal expansion theory of the immune system was first proposed over 30 years age (Jerne, 1955; Burnet, 1959). It still forms the basis of current thinking about the immune system. It was not obvious to the authors of this paper that the combinatorial possibilities of the 20 available amino acids in antigen peptides could result in a system that could distinguish successfully between self and foreign antigen, utilizing only the trial and error method proposed by the clonal expansion theory. In this paper it is demonstrated that the theory is credible on this issue, at least with respect to major histocompatibility complex (MHC) restricted antigen recognition, and that the very high proportion of immature lymphocytes that die in the thymus is consistent with the theory.

Amino Acids↗
PubMed1993

Prostitution and risk of HIV: female prostitutes in London.

OBJECTIVE: To measure the prevalence of HIV and to describe established risk factors in female prostitutes. DESIGN: A cross sectional survey. SETTING: A genitourinary medicine clinic, streets, and magistrates' courts in London. SUBJECTS: 280 female prostitutes recruited between April 1989 and August 1991. MAIN OUTCOME MEASURES: Infection with HIV-1, reported risk behaviours, and prevalence of sexually transmitted infections. RESULTS: 228 of the women had HIV tests, and two (0.9% (95% confidence interval 0% to 2.1%)) were infected with HIV-1. Reported use of condoms was high for commercial clients and low for non-paying partners: 98% (251/255) of women used condoms with all clients and 12% (25/207) with non-paying partners for vaginal intercourse. Twenty two women were current or past injecting drug users. Of the 193 women examined for sexually transmitted infections, 27 had an acute infection (gonorrhoea, chlamydia, trichomonas, or primary genital herpes) at the time of interview. Infection was associated with younger age and increasing numbers of non-paying sexual partners, but not with duration of prostitution, numbers of clients, or reports of condom failures. When age and numbers of non-paying partners were analysed by logistic regression they remained significantly associated with sexually transmitted infections. CONCLUSIONS: A large and diverse sample of prostitutes had a low prevalence of infection with HIV and high levels of use of condoms in commercial sex. There was a significant risk of other sexually transmitted infections associated with prostitutes' non-commercial sexual relationships, in which unprotected sex is common. Interventions to reduce the risk of sexually transmitted infections in prostitutes should address both commercial and non-commercial sexual partnerships.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Neisseria gonorrhoeae isolated at St. Mary's Hospital London, 1980-91.

OBJECTIVE: To describe and discuss the trends in the isolation of Neisseria gonorrhoeae from patients attending the Genitourinary Medicine Clinic at St. Mary's Hospital, Paddington, London between 1980 and 1991. DESIGN: A retrospective study of the total number of gonococci isolated over an eleven year period was performed. In addition, for the years 1988-1991 the number of isolates from homosexual men was analysed by age of the patient, site of infection and HIV antibody status of the patient. RESULTS: The total number of N. gonorrhoeae isolates identified declined markedly between 1980 and 1989 from 3670 to 750 isolates. Over the same time period the number of specimens screened for N. gonorrhoeae fell by 50%. In 1990 there was an increase in N. gonorrhoeae isolates but this was not maintained, and in 1991 the number of N. gonorrhoeae fell to its lowest level of 638 isolates. The decrease since 1980 occurred in both men and women although the number of rectal isolates from men showed a steeper decline reaching its lowest level of 24 isolates in 1988. The number of rectal isolates from homosexual men has since increased with a peak in 1990. Many of the infections among homosexual men occurred in older men and included insignificant number of patients who were HIV positive. CONCLUSION: Gonorrhoea among attenders at St. Mary's Hospital has declined dramatically since 1980 following trends reported from much of Europe. The increase in gonococcal isolates since 1989 and the peak in 1990 are unexplained but are coincident with a higher number of isolates from homosexual men.

Adult↗
PubMed1993

Late functional results after surgical closure of acquired ventricular septal defect.

To assess the longer term outlook for patients who have undergone surgery for acquired (postinfarction) ventricular septal defect, we interviewed and studied 60 survivors from a single regional cardiac center between 3 and 144 months after the operation. Including the patients who died within 1 month of the operation, the 5-, 10-, and 14-year survivals (with standard errors) were 69% (65% to 74%), 50% (44% to 57%), and 37% (27% to 46%). Eighty-two percent of patients were in New York Heart Association class I or II. Ten patients (17%) had a persisting but not hemodynamically significant ventricular septal defect. Mean left ventricular ejection fraction was reduced at 0.39 (standard deviation 0.15), but this did not correlate with either New York Heart Association class or exercise tolerance. Twenty-eight patients (47%) had asymptomatic arrhythmias (17 with ventricular premature beats). Angina and other medical problems were not prevalent.

Aged↗
PubMed1992

A theoretical problem of interpreting the recently reported increase in homosexual gonorrhoea.

There has been considerable interest recently in using the occurrence of gonorrhoea infection as an indicator of sexual behaviour relevant to the transmission of human immunodeficiency virus. Mathematical models of gonorrhoea transmission can predict increasing incidence with decreasing sexual activity in the population, due to a resultant concentration of sexual activity in an active 'core' group. Increases in the incidence of gonorrhoea reported recently should therefore be interpreted with caution.

Gonorrhea↗
PubMed1992

Concordance of auxotype/serovar classes of Neisseria gonorrhoeae between sexual contacts.

One hundred and three known sexual-contact pairs of patients with culture-proven gonorrhoea who attended St Mary's Hospital, London between May 1989 and February 1991 were identified. All isolates from these patients were serotyped and auxotyped and compared for type concordance within sexual-contact pairs. Serotype was concordant in 80 (78%) of 103 sexual-contact pairs, auxotype in 88 (85%) and auxotype/serovar (A/S) class in 66 (64%) on the first screening. All pairs of isolates showed concordance in both serotype and auxotype when typing was repeated using a single set of serotyping reagents and of auxotyping media. Seventeen serovars, 9 auxotypes and 36 A/S classes were found in this population. Our results suggest that both serotyping and auxotyping may be used as markers to allow tracing of sexual-contact pairs, but that a single set of reagents should be used to ensure maximum reliability.

Contact Tracing↗
PubMed1992

Soft-tissue reconstruction of the face: a comparison of dermal-fat grafting and vascularized tissue transfer.

Eight patients treated with dermal-fat grafts and 8 patients treated with vascularized tissue transfer were retrospectively reviewed to determine the efficacy of the two methods in the treatment of the soft-tissue defects in Romberg's disease, clefting syndromes including hemifacial microsomia, and traumatic defects. Follow-up averaged 4 years and ranged from 1 to 9 years for the vascularized transfers and 1.5 to 11 years for the dermal-fat grafts. Both techniques were able to provide enduring augmentation. The vascularized transfers were able to provide a greater amount of augmentation. We conclude that dermal-fat grafting is a satisfactory technique for mild to moderate defects, but that vascularized transfers are required for moderate to severe defects.

Adolescent↗
PubMed1987

Diagnosis of gestational diabetes by capillary blood samples and a portable reflectance meter: derivation of threshold values and prospective validation.

Paired capillary-venous samples were obtained from 255 women undergoing a glucose challenge test and 116 women undergoing an oral glucose tolerance test. The capillary equivalents for the venous threshold values were calculated by regression analysis. The glucose challenge test predictions of either normal or abnormal agreed in 82%. The sensitivity, specificity, and positive and negative predictive values for the capillary oral glucose tolerance test were 89%, 90%, 62%, and 98%, respectively. These capillary equivalents were then applied prospectively to 147 women undergoing a glucose challenge test and 141 women undergoing an oral glucose tolerance test. The concurrence rate of the glucose challenge test in the prospective group was 90%. The sensitivity, specificity, and positive and negative predictive values for the capillary oral glucose tolerance test were 64%, 95%, 75%, and 92%. When the venous threshold recommendations of the American Diabetes Association were used instead of those standard at our institution, these values increased to 75%, 98%, 83%, and 96%, respectively. The recommended capillary values of the American Diabetes Association were 100% sensitive but had a positive predictive value of only 20%. Based on the prospective group, the cost per case of gestational diabetes identified would decline 63% if both a capillary glucose challenge test and an oral glucose tolerance test were used and 25% if the capillary glucose challenge test and venous oral glucose tolerance test were used. Combining the data set for new regression equations, the following venous-capillary threshold sets emerged: glucose challenge test, 140 mg/dl/150 mg/dl; fasting oral glucose tolerance test, 105 mg/dl/114 mg/dl; 1 hour, 190 mg/dl/211 mg/dl; 2 hours, 165 mg/dl/183 mg/dl; 3 hours, 145 mg/dl/157 mg/dl. The sensitivity, specificity, and negative predictive values for the capillary oral glucose tolerance test with these thresholds were 80%, 97%, 80%, and 97%. In conclusion, capillary glucose testing for diabetes during pregnancy is feasible and cost-effective.

Blood Glucose↗
PubMed1986

The relationship between capillary and venous glucose concentration during pregnancy.

Previous attempts to construct capillary equivalents of venous glucose values for prognostic purposes have failed. We examined the relationship between capillary and venous glucose concentration during pregnancy in 258 women who had samples taken at four different time intervals in relation to two different standardized meals. Capillary glucose concentration was determined with the Chemstrips bG and an Accu-Chek reflectance colorimeter and venous plasma glucose concentration was measured by the hexose kinase technique on an AutoAnalyzer. The capillary: venous relationship was constant over time for a given meal but the magnitude of the difference was affected by time. The capillary: venous relationship differed significantly between the two standard meals. The findings indicate that meal size and sampling time must be controlled for when one is attempting to construct capillary equivalents for venous derived norms. The failure of previous studies to control for these variables may explain their inability to construct useful capillary equivalents for venous glucose values. Our findings also indicate that attainment of venous norms with capillary specimens represent, in reality, tighter control.

Blood Glucose↗
PubMed1984

Ocular motility in craniofacial reconstruction.

Of 140 children undergoing major craniofacial reconstruction at The Children's Hospital of Philadelphia and examined preoperatively and postoperatively by the Ophthalmology Division, only 10 had surgically induced alteration in primary position horizontal alignment, 4 greater than 10 prism diopters. Only 2 patients had a new strabismus in primary position created by craniofacial surgery, both cranial nerve palsies. We believe early strabismus surgery is advantageous for attainment of binocularity and ease of tissue manipulation. Of 44 patients with craniofacial dysostosis (Crouzon), 20 had preoperative strabismus, and 12 required extraocular muscle surgery. Five of 12 had anomalies of extraocular muscle number and structure, usually involving the superior rectus muscle.

Adolescent↗