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Biomedical subjects

M R Nelson

Publications and source records attributed to M R Nelson.

108 records · Page 6Linked to original sources
PubMedDate not supplied

Measurement and classification of retinal vascular tortuosity.

Automatic measurement of blood vessel tortuosity is a useful capability for automatic ophthalmological diagnostic tools. We describe a suite of automated tortuosity measures for blood vessel segments extracted from RGB retinal images. The tortuosity measures were evaluated in two classification tasks: (1) classifying the tortuosity of blood vessel segments and (2) classifying the tortuosity of blood vessel networks. These tortuosity measures were able to achieve a classification rate of 91% for the first problem and 95% on the second problem, which confirms that they capture much of the ophthalmologists' notion of tortuosity. Finally, we discuss how the accuracy of these measures can be influence by the method used to extract the blood vessel segments.

Diagnosis, Computer-Assisted↗
PubMedDate not supplied

Augmented sensory nerve action potentials during distant muscle contraction.

We previously reported that the median sensory nerve action potentials (SNAP) increased in amplitude during ipsilateral abductor pollicis brevis contraction. The objectives of the present project were to study the timing and origin of this phenomenon and to eliminate the possibility of local artifact. Ten normal subjects were recruited. The baseline was established using ten threshold stimuli, which were delivered to the median nerve at the wrist at 0.2 Hz. Using the same stimulus strength, the SNAP was recorded while the tibialis anterior was contracted at 25, 50, 75, and 100% of maximum force. Responses were signal-averaged. Results showed an increase in ipsilateral SNAP amplitude between baseline and maximum contraction of 6 +/- 2 microV (standard error, P = 0.004) and contralateral amplitude of 8 +/- 2 microV (standard error, P = 0.01). Statistical analysis was performed with analysis of variance for repeated measures and paired t test. The effect peaked between 0 and 10 min after contraction and lasted from 1.5 to more than 20 min after muscle relaxation. In conclusion, SNAP appear to be enhanced during and after muscle contraction. Theories concerning underlying causes for this event are discussed.

Adult↗
PubMedDate not supplied

Effect of isometric contraction on threshold somatosensory evoked potentials.

We previously described the augmentation of sensory nerve action potential amplitudes after near and remote isometric muscle contraction. In this study, we wished to determine if the sensory cortex was involved in this process. In this prospective, intrinsically controlled study, we studied threshold somatosensory evoked potentials in 12 normal subjects with stimulation of the median nerve at 5.1 Hz. The subjects were tested during the following conditions: baseline, 25%, and 75% maximum isometric abductor digiti minimi contraction for 4 min. Each of these conditions was recorded before, during, and 4 min and 8 min after contraction. Results showed that at 25% contraction, there was a significant temporal increase in N9 amplitude (2.1-2.6 microV; P = 0.05, analysis of variance, repeated measures) and a decrease in N20 amplitude with 75% contraction (1.9-1.6 microV; P = 0.03, analysis of variance, repeated measure). No significant changes were noted in the spinal cord or brainstem recordings. In conclusion, it appears that augmentation of the brachial plexus peripheral nervous system recording occurs concurrently with central inhibitory gating. The possibility of peripheral nervous system adaptability will be discussed.

Adult↗
PubMedDate not supplied

Sexual behaviour amongst travellers: a study of genitourinary medicine clinic attenders.

Two hundred and fifty attendees at two London genitourinary medicine clinics were asked to complete an anonymous self-administered questionnaire, enquiring about sexual behaviour whilst abroad. Two hundred and forty-three questionnaires were evaluable. In the study group there were 116 women, and 127 men (62 heterosexuals and 65 homosexuals). Ninety women, 53 heterosexual men and 53 homosexual men had travelled abroad over the preceding 6 months. Of these 18 (20%) of women, 26 (51%) of heterosexual men and 19 (36%) of homosexual men had sex with a local foreign contact on holiday. Although both heterosexual and homosexual men were statistically more likely to have sex abroad with a local inhabitant, women were more likely to have unprotected sexual intercourse with a local partner. This has important implications for the spread of sexually transmitted disease including hepatitis B and HIV.

Adolescent↗
PubMedDate not supplied

Screening for lower genital tract infections in women presenting for termination of pregnancy.

Over a four-month study period, 87 patients requesting termination of pregnancy at a gynaecology clinic were offered screening for sexually transmitted diseases, of whom 63 accepted. A total of 41 infections were found in 34 women, the commonest being vaginal candidiasis and bacterial vaginosis. Chlamydia was found in six patients. Although HIV antibody testing was offered to every patient, all declined this test.

Abortion, Induced↗
PubMedDate not supplied

Intralesional interferon for the treatment of recalcitrant molluscum contagiosum in HIV antibody positive individuals--a preliminary report.

Molluscum contagiosum is common in HIV disease and available therapies have a poor success rate and require frequent clinic visits. Interferon alpha has been used to treat recalcitrant condylomata acuminata and this study was undertaken to assess the use of this treatment in unresponsive molluscum contagiosum. A total of 30 molluscum contagiosum were injected with one megaunit of interferon alpha weekly for 4 weeks; 11 molluscum contagiosum completely cleared and 18 reduced in size by over 50%. Molluscum less than 0.5 cm in diameter, and those in patients without AIDS were more likely to respond. No surrounding lesions changed in size.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Efficacy of a nelfinavir- and nevirapine-containing salvage regimen.

PURPOSE: In this study, our purpose was to assess the efficacy of nelfinavir- and nevirapine-containing salvage regimens in nonnucleoside reverse transcriptase inhibitor (NNRTI)-naive patients virologically failing a protease inhibitor (PI)-based combination. METHOD: A retrospective case note review of all patients virologically failing their PI-based combination who were switched to a regimen containing both nelfinavir (1 g t.d.s.) and nevirapine (200 mg b.d.). CD4 cell counts and viral loads were monitored. Genotypic analysis was performed using RT-PCR sequencing. RESULTS: Nineteen patients commenced a salvage regimen containing nelfinavir and nevirapine. Five patients also changed at least one nucleoside reverse transcriptase inhibitor (NRTI), although in one case this represented recycling. Thirty-eight percent (6/16) of patients achieved a viral load below the level of detection (BLD; <200 copies/mL; complete responders [CR]), 3 achieved <20 copies/mL. Five patients achieved > or =1 log drop (partial responders [PR]) that was not sustained over follow-up, and five failed to respond to therapy (nonresponders [NR]). CRs tended to have wild-type NNRTI and PI sequences relative to PRs and NRs. CONCLUSION: In heavily pretreated patients, a nelfinavir-and nevirapine-containing salvage regimen resulted in a virological response in 38% of patients that was sustained in 31% over 63 weeks.

Adult↗
PubMedDate not supplied

Maternal pregravid weight, age, and smoking status as risk factors for low birth weight births.

The Illinois Department of Public Health, in cooperation with the Centers for Disease Control (CDC), monitors trends in the prevalence of prenatal risk factors that are major predictors of infant mortality and low birth weight (LBW). Analyzed data from CDC are available to the department annually. During 1988, a total of 26,767 records of Illinois women giving birth were submitted to CDC. These surveillance data support the fact that women older than 30 years who smoke and enter pregnancy underweight are at greatest risk of delivering LBW babies. Overall, 13.9 percent of underweight smokers had LBW infants compared with 8 percent of underweight nonsmokers. Prevalence of LBW among underweight and smoking women older than 34 years was much higher (29.6 percent) than among those between ages 30 and 34 (15.2 percent). The prevalence of LBW decreased as the pregravid weight increased among normal weight smokers (10 percent) and overweight smokers (8.6 percent).

Adolescent↗