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Biomedical subjects

R Dell

Publications and source records attributed to R Dell.

At least 19 recordsLinked to original sources
PubMed2001

Cyclodextrin-modified biosensors: comparision of cyclodextrin-linked ferrocenes as mediators in sol-gel and screen-printed formats for sensing acetylcholine.

This work reports the comparison of a sol-gel and a screen-printed biosensor format using new mediators and a sensitive thin-film (ref. 1: P. Kataky and D. Parker, Analyst, 1996, 121, 1829) to enhance the sensitivity and stability of biosensors. The new mediators were per-alkylated cyclodextrin linked ferrocenes and a control, ferrocene aminocarboxylic acid. The thin film comprised a cocktail with polyurethane, plasticiser, lipophilic anion and a perethylated beta-CD. The analyte targeted was acetylcholine using the established horseradish peroxidase-choline-oxidase-acetylcholine esterase relay. The screen-printed electrode format showed a marked decrease in oxidation potential, the magnitude of the shift depended on the structure of the mediator and the membrane covering. Although lower oxidation-potentials were observed with the sol-gel format sensors, their response was more akin to aqueous solution behaviour. Electrocatalytic currents were observed suggesting a highly efficient electron transfer process.

Journal Article↗
PubMed1999

Anaesthesia for strabismus surgery: a regional survey.

An increase in the demand by local surgeons for neuromuscular block during strabismus surgery, and the forced duction test in particular, led us to review the literature and conduct a regional survey of anaesthetic techniques used. A questionnaire was distributed to 379 anaesthetists in the region and 264 responses were received. The results demonstrated that 55% of paediatric patients and 66% of adult patients may have been operated on under suboptimal conditions; residual tone may have been present in the extraocular muscles during forced duction testing and strabismus correction.

Adolescent↗
PubMed1995

Comparison of HIV+ and HIV- adolescents: risk factors and psychosocial determinants.

According to the World Health Organization, half of the 14 million people with human immunodeficiency virus (HIV) worldwide were infected between the ages of 15 and 24 years. However, details about HIV-positive (HIV+) youths' risk-related behavior and social context have not been previously reported. OBJECTIVES. To outline detailed sexual and drug use practices, social and psychological status of HIV+ youth compared with a cohort of HIV-negative (HIV-) youth; and to examine the ability of the health belief and risk-taking models to predict sexual and drug use acts of HIV+ youth. METHODS. HIV testing was conducted on and a 207-item structured interview covering HIV risk-related acts, protective factors and background information was administered to 72 HIV+ and 1142 HIV- adolescents aged 13 through 21 years receiving care in an adolescent clinical care unit of a large medical center in New York City. Data were analyzed for adolescents reporting sexual intercourse (71 HIV+ and 722 HIV-) by logistic regression analysis of five domains to identify variables significantly associated with HIV seropositivity. RESULTS. Logistic regressions indicated significant differences in sexual risk acts based on serostatus and gender. Anonymous, blinded seroprevalence testing identified 11% more HIV+ adolescents than would have been identified by current counseling and testing practices. HIV+ adolescents were significantly more likely to be sexually abused (33 vs 21%, P < .05), engage in anal sex and survival sex (32 vs 4%, P < .01), unprotected sex with casual partners (42 vs 23%, P < .05), have had sex under the influence of drugs (52 vs 27%, P < .01), have a sexually transmitted disease (59 vs 28%, P < .01), use multiple drugs (43 vs 9%, P < .01) and engage in multiple problem behaviors (72 vs 30%, P < .01) than HIV- young people. HIV+ females reported more oral (69 vs 45%, P < .01) and/or anal (42 vs 12%, P < .01) intercourse compared to HIV- females. HIV+ males reported significantly higher rates of both insertive (82 vs 46%, P < .05) and receptive (51 vs 4%, P < .01) oral and anal (53 vs 13%, P < .01) intercourse than HIV- males. Protective factors were not significantly different for HIV+ and HIV- young people. CONCLUSIONS. Routine, confidential HIV counseling and testing should be considered for adolescents having unprotected sexual intercourse when age-specific services are available for HIV+ youth. Prevention programs should consider adolescents' history of abuse, homelessness, and other social as well as psychological dimensions in designing comprehensive care strategies to address HIV+ adolescents' multiple problem behaviors and living situations. Current theoretical models of health behaviors should be reconsidered, given the lack of their association to HIV risk acts of HIV+ youth. Age-specific services and interventions for HIV+ youth are urgently needed as HIV is spreading among youth worldwide.

Acquired Immunodeficiency Syndrome↗
PubMed1994

cDNA sequences of Schistosoma japonicum coding for two cathepsin B-like proteins and Sj32.

Sequences of three cDNAs of Schistosoma japonicum are presented. Two of them code for the antigens Sj32 (hemoglobinase) and cathepsin B. The third clone represents a mutant derivative of the cathepsin B gene. The DNA and amino acid sequences are compared to their homologues from S. mansoni. The mutant cathepsin B, in which the Cys29 in the active center is replaced by Ser, is discussed with respect to a possible function.

Amino Acid Sequence↗
PubMed1993

The evaluation of targeted outreach in an adolescent HIV/AIDS program.

PURPOSE: Most HIV infected youth are unaware of their serostatus. Among adolescents who know they are HIV positive, only a small percentage are currently receiving care in age-specific programs. Establishing effective links between prevention and service programs is critical in reaching this group of young people. METHODS: A specific outreach strategy was designed to develop more referrals from a wider variety of agencies to better serve youth at risk for HIV. A needs assessment of community-based agencies was the basis for: 1. overcoming barriers to care, 2. specifying the target population, 3. assessing existing referrals, and 4. selecting agencies for different levels of intensity of outreach. RESULTS: Six barriers faced by potential referring agencies were identified and corresponding solutions created which were incorporated into the outreach strategy. A comparison was made of referrals in the years before, during and after the outreach strategy was instituted. A significant difference by (chi 2 analysis) was noted in the number of agencies (p < 0.05), number of individuals (p < 0.01), number of appointments kept (p < 0.01), and the number of HIV+ youth enrolled (p < 0.01) during the year when the plan was fully implemented compared to previous and subsequent years. CONCLUSIONS: Systematic targeted outreach programs are an efficient way to maximize the time and effort of outreach staff. The result was an increase in the number and diversifity of referrals. This strategy could be used by groups caring for adults or younger children who want to expand services to include adolescents or by groups providing HIV/AIDS care who want to specifically serve adolescents.

Adolescent↗
PubMed1993

Human immunodeficiency virus-infected adolescents: the first 50 patients in a New York City program.

To address the unique manifestations of human immunodeficiency virus (HIV) among adolescents aged 13 through 21 years, a comprehensive evaluation and treatment program for high-risk and HIV-positive adolescents was developed in New York City in 1987. Among HIV-infected youth, mean age of testing was 18.2 years. One third of the HIV-positive patients were female and four fifths were African-American or Hispanic. No significant differences were found between HIV-positive (n = 50) and HIV-negative (n = 43) patients for age at first intercourse, injecting or other illicit drug use, history of sexually transmitted diseases, or survival sex (exchange of sex for money or drugs). HIV-positive males were more likely than HIV-negative males to have engaged in anal intercourse and to report a history of sexual abuse. Among infected females, 82% acquired HIV through heterosexual intercourse. Almost half (48%) of HIV-positive adolescents had significant immune dysfunction at the time of their initial visit (CD4 < 500/mm3) and were eligible for zidovudine. Many HIV-positive adolescents continued high-risk behaviors such as intercourse without condoms, particularly those with ongoing dependence on drugs or alcohol. With the epidemic of HIV infection increasing nationwide among adolescents, specialized, comprehensive programs are needed to counsel and treat HIV-infected adolescents and youth in high-risk situations.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Theophylline disposition in adolescents with asthma.

Adolescents frequently require medication for acute and chronic illnesses. A proper dosage schedule is needed to achieve efficacy without toxicity during adolescence when there are marked changes in body size and organ function. Theophylline disposition was studied in 70 asthmatic adolescents, ages 8-18 years, to determine if pubertal changes in body size, composition, and organ function are associated with changes in drug disposition. Forty-eight youngsters were studied as outpatients and 22 while hospitalized. Half-life (t1/2) was computed for all patients. Volume of distribution and clearance were determined for inpatients only. Chronological age and anthropometric growth parameters were measured. Lean body mass (LBM) was derived from anthropometric measurements. Half-life was significantly correlated with developmental stage (Tanner r = 0.42, age r = 0.33, p less than 0.01), and body size (height r = 0.39, LBM r = 0.33, weight r = 0.33, p less than 0.01). LBM (kg/kg) was significantly correlated with volume of distribution (L/kg) (r = 0.59, p less than 0.01). Best-fits for t1/2 contained two variables: t1/2 = -4.57 + 1.31 (sex) + 0.0687 (height) (r = 0.48) and t1/2 = -3.54 + 1.32 (sex) + 0.0725 (LBM) (r = 0.43). Chronological age alone is not a useful basis for determining medication dosages due to the heterogeneity in rates of development and body size among adolescents. Half-life increases with increasing height or LBM. Although compliance is clearly an important factor in achieving optimal control of symptoms, this study demonstrates that dose adjustment during times of rapid growth during puberty is equally important.

Adolescent↗
PubMed1991

Schistosoma mansoni and S. japonicum: decline of antibodies against diagnostic adult worm antigens (Sm31/32) following praziquantel treatment of mice.

Mice were infected with 10, 100 or 200 cercariae of Schistosoma mansoni or S. japonicum and treated between one and two months later with two doses of praziquantel. At this time, the animals had high levels of antibodies against the adult worm proteins Sm31/32 (schistosome cathepsin B and haemoglobinase). Antibody levels were followed up for about one more year by Western blots and ELISA using purified Sm31/32. Among the 34 surviving mice perfused at the end of the experiments, 14 had between 1 and 4 and one mouse had 8 residual stunted worms. In most mice without detectable worms, anti-Sm31/32 antibodies started to drop within a few months after therapy. In other animals of this group and in those harbouring residual worms, the decrease in titers was not observed or less pronounced. Thus, the presence of even one stunted worm was sufficient to induce continued high titres of antibodies. Decreasing levels of antibody against Sm31/32, however, reflected complete elimination of schistosomes.

Animals↗
PubMed1991

Changes in nurse cell nuclei during synchronous infection with Trichinella spiralis.

The rate of enlargement of nuclei was determined on 4-microns-thick sections of synchronously infected mouse thigh muscle. Normal muscle nuclei had a geometric mean volume of 84 microns and a range of 42-170 microns 3. At days 5, 6, 7, 8, and 10 and 6 mo after infection, mean nuclear volume was 177 (100-315) microns 3, 254 (140-462) microns 3, 278 (172-447) microns 3, 681 (407-1,138) microns 3, 512 (326-804) microns 3, and 509 (298-870) microns 3, respectively. Size of nuclei for any given day followed a log normal distribution. On days 7 and 8 after infection, 31% of enlarged nuclei had 2 nucleoli, whereas only 15% had 2 nucleoli on day 10. One percent of enlarged nuclei in 6-mo-old nurse cells had double nucleoli. The number of enlarged nuclei in 6-mo-old nurse cells was determined from serial sections of infected tongue muscle. Each nurse cell contained an average of 40 enlarged nuclei. Sixty-four percent of nurse cells examined (n = 55) had between 30 and 60 enlarged nuclei. However, there was great variation in the range (7-142). These results are discussed in relation to the development of the nurse cell.

Animals↗
PubMed1986

An analysis of the variability in estimates of bioenergetic variables in preterm infants.

Estimates of average daily energy expenditure and minimal observed oxygen consumption are commonly used to characterize the energy metabolism of neonates. Yet, the errors inherent in these estimates have not been defined. Using measurements of oxygen consumption and carbon dioxide production made in healthy growing low birth weight infants during eight consecutive 3-h interfeeding epochs, we have determined the variability in the mean oxygen consumption, carbon dioxide production, respiratory quotient, total daily energy expenditure, and the minimal observed oxygen consumption among the feeding epochs. The coefficient of variation for oxygen consumption ranged from 3.1 to 9.1%, for minimal observed oxygen consumption from 3.7 to 16.7%, for carbon dioxide production from 3.3 to 7.4%, and for total daily energy expenditure from 2.9 to 7.6%. The SDs for respiratory quotient ranged from 0.008 to 0.066. From these 24-h data we have calculated the error in predicting daily estimates of the mean values for these variables if observations are made for less than 24 h. As expected, this error decreases with increasing duration of observation. These data should prove useful in the design and interpretation of investigations of neonatal energy expenditure.

Carbon Dioxide↗
PubMed1982

Self-detection of a breast mass in adolescent females.

The frequency of self-discovered breast masses in adolescent females has not previously been described. The histologic diagnosis rather than the means of detection has been the focus of previous surveys. Seven characteristics of 95 patients admitted from 1968-1979 for the evaluation of a breast mass were delineated. The mean age at hospitalization was 15.9 years (range 12-20). The delay from detection to hospitalization was 7.2 months (range 0.5-72). In 77 cases the mass was detected by the patient; 11 were found during a physician examination, 4 by a family member, and 3 by an unrecorded source. Diagnoses were fibroadenoma (71), abscess (11), cyst (9), lipoma (2), and cystosarcoma phyllodes (2). The median length of the masses was 2.6 cm, width 2.3 cm, with a median mass area (diameter x length) of 6 cm2. When patients were compared for age, delay in hospitalization, means of detection, family history, and mass size, the girls with abscesses were younger and had a shorter time delay before hospitalization. Self-discovery was the means of detection in 77 of 95 (81%). The means of detection is an important factor to consider in weighing the merits of teaching breast self-examination procedures to adolescent females.

Abscess↗
PubMed1981

Spontaneous variability in minute ventilation oxygen consumption and heart rate of low birth weight infants.

Continuous measurements of minute ventilation (VI), oxygen consumption (VO2), heart rate (HR), activity, and temperature were made in eleven low birth weight infants during the interval between feedings. Significant increases in VI, VO2, and HR were noted between quiet and active sleep. (VI Active - VI Quiet/VI Quiet) X 100 = 18.4% VO2 Active - VO2 Quiet/VO2 Quiet) X 100 = 10.1% and HR Active - HR Quiet/HR Quiet) X 100 = 6.4%. Significant differences were also noted within epochs of the same state of sleep: mean slope VI versus time in epoch (t) = -156 ml/kg . min/hr, VO2 versus t. = 1.49 ml/kg . min/hr and HR versus t = -15.0 beats/min/hr. Differences between successive epochs of the same state of sleep were also observed: VI, +5.9 to 46.6%; VO2, 4.7 to 24.6%; HR, 1.0 to 9.7%. These differences were related to the length of time after feeding. These data indicate that steady state conditions do not occur in growing low birth weight infants and that the design of studies of respiration and metabolism in these infants should include continuous assessment of the state of sleep or activity and time after feeding to ensure that experimental and control periods are truly comparable.

Heart Rate↗