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Biomedical subjects

L Edwards

Publications and source records attributed to L Edwards.

At least 109 records · Page 6Linked to original sources
PubMed1987

Scalp distribution of visual evoked potentials to foveal pattern and luminance stimuli.

Scalp potentials elicited by pattern reversal, pattern onset, and flash stimulation have been studied in normal subjects by means of a 16-channel brain mapping system. In two groups of experiments the topography of the major positive component in each response was compared with 4 degrees full- and lateral half-field stimuli and, for more detailed exploration of the pattern components by M-scaled stimuli selected to activate 1 cm2-patches of striate cortex and associated extrastriate re-projections. The 4 degrees stimuli were found to elicit scalp distributions for the pattern reversal P100 and the pattern onset C1 consistent with striate and extrastriate visual cortical origins respectively. Data on the flash P2 component suggest that stimulation was not localized accurately; this may have been due to lateral spread of neural activity in the retina. Predictably, the M-scaled stimuli showed extensive inter- and intraindividual variations depending on stimulus type and location relative to fixation. The manner in which, in some subjects, the region of maximal activity on the map appears to migrate with change of stimulus position possibly reflects local retinotopic order in visual evoked potential generator areas. However, data are neither extensive nor detailed enough to be conclusive.

Adult↗
PubMed1987

Orchiectomy versus long-acting D-Trp-6-LHRH in advanced prostatic cancer.

One hundred and four patients were randomised for the study. Fifty-five were entered into the D-Trp-6-LHRH group and 49 into the orchiectomy group. All pre-treatment patient characteristics were similar and testosterone levels at 1 month or later were in the castrate range in both groups. Forty-six patients (83%) in the D-Trp-6-LHRH group and 40 (82%) in the orchiectomy group had a partial remission or stable disease at 3 months or later. There was no significant difference between the groups for response or survival. Three patients in the D-Trp-6-LHRH group had a disease "flare" in the first 10 days of treatment. The flare symptoms resolved by the end of 4 to 8 weeks. The incidence of flushing, decreased libido and impotence was similar in both groups. Although there was less psychological morbidity in the D-Trp-6-LHRH group the difference did not reach statistical significance. Our results indicate that long-acting D-Trp-6-LHRH offers a safe and highly effective alternative to orchiectomy.

Clinical Trials as Topic↗
PubMed1987

Donor age-dependent decline in response of human red cell Ca2+-ATPase activity to thyroid hormone in vitro.

The effect of increasing donor age on the susceptibility of human red blood cell Ca2+-ATPase activity to stimulation in vitro by thyroid hormone was studied in 26 normal subjects, aged 15-81 yr. Basal enzyme activity (no added thyroid hormone) was unaffected by donor age. Group analysis, young (less than or equal to 50 yr) vs. elderly (greater than 60 yr old), revealed a 23% decrease in responsiveness of the enzyme to L-T4 (P less than 0.001). Regression analysis confirmed an age-dependent decline in thyroid hormone stimulability of Ca2+-ATPase [r = -0.42 (T4 effect) and -0.38 (T3 effect); P less than 0.01]. Red cell membrane Na,K-ATPase activity was not affected by donor age. Plasma T4 and T3 concentrations in these normal subjects also did not change with age. Possible contributions of the following mechanisms to this age-correlated change in enzyme activity were examined: altered responsiveness to calmodulin of membrane Ca2+-ATPase; membrane content of endogenous calmodulin, endogenous plasma T4 and T3 concentrations, and plasma glucose concentrations. Calmodulin responsiveness is required for iodothyronine action on the enzyme, but the calmodulin responsiveness of cells from elderly donors was not significantly different from that of cells from younger donors (P greater than 0.10). There was no relationship between membrane immunoassayable calmodulin and donor age or membrane calmodulin and Ca2+-ATPase activity. There were positive correlations between donor plasma T4 level and basal enzyme activity (P less than 0.05) and between donor plasma T3 concentration and hormone-responsive Ca2+-ATPase (P less than 0.01), but these did not contribute to the age effect. Plasma glucose previously was found to modulate red cell Ca2+-ATPase activity, but did not correlate with decreased hormone responsiveness of the enzyme in elderly donors. In conclusion, we found that the susceptibility of human red cell Ca2+-ATPase to in vitro thyroid hormone stimulation declined significantly with advancing donor age. Several possible calmodulin-dependent mechanisms for this age-dependent change were excluded, and thus, we postulate that the altered hormone sensitivity of the enzyme is membrane phospholipid mediated.

Adolescent↗
PubMed1987

Complementary components and local variations of the pattern electroretinogram.

Pattern electroretinograms have been presumed to arise from a combination of luminance and pattern detection activities. Since the responses at low spatial frequencies are linearly related to contrast and contain negligible pattern specific components, it is proposed that a retinal illuminance response for higher spatial frequencies can be computed from the optical transfer function of the eye. These computed responses are subtracted from pattern electroretinograms to reveal a pattern-specific response with a marked bandpass characteristic. The peak spatial frequency of the bandpass curve declines with increasing peripheral angle. For central vision, the peak amplitude of the pattern-specific response is larger than the retinal illuminance response, but, in the peripheral retina, the two responses are found to be almost equal. The possible origins of these signals are discussed, and it is concluded that the technique provides a method of obtaining separated illuminance and pattern responses from retinal regions having different properties of spatial selectivity.

Electroretinography↗
PubMed1986

Urinary diluting capacity in elderly diabetic subjects.

Urinary concentrating ability declines with normal human aging but diluting capacity has been less well studied as a function of age. We studied free water clearance (CH2O) in a group of Type II diabetic patients, aged 47 to 70 years. Conventional water load testing in sulfonylurea-treated diabetic patients revealed preservation of diluting capacity (ability to achieve Uosm less than 100 mOsm/kg) in subjects greater than 60 years of age. Tolazamide permitted expression of normal CH2O; chlorpropamide administration predictably reduced CH2O relative to tolazamide by 58% in subjects greater than 60 years. Free water clearance (CH2O) and glomerular filtration rate (GFR) were comparable in elderly subjects (greater than 60 years) and those less than or equal to 60 years. Normal CH2O in these diabetic patients was explained by persistently normal GFR in the study group. Osmolar clearance (Cosm) was insignificantly lower in diabetics greater than 60 years. Thus, a fall in CH2O in elderly diabetic patients is not a factor contributing to clinical hypoosmolar states encountered in this population.

Aged↗
PubMed1986

Role of topical tretinoin in melanoma and dysplastic nevi.

The retinoids have been investigated extensively as chemopreventive and therapeutic agents in a variety of neoplasms. They have been shown to inhibit the proliferation of transformed cell lines in vitro and transplanted tumors in vivo. In cultured murine melanoma cells, retinoids inhibit proliferation and induce differentiation. Human melanoma cell lines have shown a mixed response. The clinical experience with retinoids in melanoma has been limited. Previously we investigated the activity of topical B-all-trans-retinoic acid (Retin-A, vitamin A acid, retinoic acid, and tretinoin) against intracutaneous metastases from malignant melanoma. We saw complete remission of multiple lesions in one individual and regression of several lesions in a second patient. This experience led us to conduct the present pilot trial of topical tretinoin in dysplastic nevus syndrome. The latter is a precursor of malignant melanoma. We saw regression of some of the treated lesions to benign nevi showing minimal or no dysplasia. Thus topical tretinoin appears to possess some activity against melanoma and at least one of its precursor conditions. In view of these preliminary results, more extensive trials are warranted to better define the role of tretinoin in the chemoprevention of malignant melanoma in high-risk lesions.

Administration, Topical↗
PubMed1986

Effect of intralesional alpha 2-interferon on actinic keratoses.

The effect of intralesional alpha 2-interferon (IFN) on actinic keratoses was examined in this two-part study. In phase I, 11 of 12 lesions cleared following nine injections of IFN (5 X 10(5) IU per dose) compared with none of 12 keratoses injected with placebo. Smaller doses of IFN (1 X 10(5) IU and 1 X 10(4) IU per injection) produced clearing of 42% and 58% of lesions, respectively. The second phase, which was designed to investigate the optimum schedule for treatment with IFN, showed that a minimum of six injections of IFN (5 X 10(5) IU per injection) was necessary to clear 14 of 15 actinic keratoses. Although this mode of delivery is not practical for clinical use, intralesional alpha 2-IFN demonstrates biologic activity against actinic keratoses.

Adult↗
PubMed1985

Randomised controlled study of orchidectomy vs long-acting D-Trp-6-LHRH microcapsules in advanced prostatic carcinoma.

Safety and efficacy of a slow-release formulation of D-Trp-6-luteinising-hormone-releasing-hormone (D-Trp-6-LHRH) microcapsules were compared with orchidectomy in the initial treatment of advanced prostatic carcinoma. 41 patients were randomly assigned to D-Trp-6-LHRH and 38 to orchidectomy. Suppression of testosterone and reduction in prostatic acid phosphatase levels were similar in both groups. 87% of patients in the D-Trp-6-LHRH group and 81% in the orchidectomy group responded to treatment or showed no deterioration. Side-effects related to the decrease in testosterone were similar in both groups. 3 patients given D-Trp-6-LHRH had a disease "flare" in the first ten days of treatment which resolved completely when testosterone fell to castrate levels. Results of psychological assessment were similar in both groups before treatment, and on follow-up there was a weak trend towards decreased psychological morbidity in the hormone group. The slow-release preparation of D-Trp-6-LHRH microcapsules offers an important alternative in the management of advanced prostatic carcinoma.

Aged↗
PubMed1985

Source derivation of the brain-stem auditory evoked potential.

This study described the results of applying source derivation to the brain-stem auditory evoked potential. Unilateral stimulation gives rise to current sinks, associated with waves I and III, which are located in the vicinity of the ipsilateral mastoid. Waves II and V are associated with a pair of current sinks which appear bilaterally in the vicinity of each mastoid.

Adult↗