An investigation of factors affecting the accuracy of in vivo measurements of skin pigments by reflectance spectrophotometry.

Factors affecting the accuracy of the in vivo measurement of cutaneous pigments and blood oxygenation by reflectance spectrophotometry have been examined. It was found that stray light, the amounts of haemoglobin and melanin, and the level of blood oxygenation all contributed to the measured reflectance and had to be taken into account when calculating quantitative indices of skin pigments. Measurements on isolated sheets of epidermis demonstrated that over 50% of normally incident radiation is transmitted in a forward direction within 17 degrees of the incident direction and approximately 20% is backscattered between 90 degrees and 180 degrees out of the sample, approximately 6.0% of it by specular reflection at the surface. The effective optical pathlength in suspensions of whole red cells was found to be 7% greater than in simple solutions containing the same concentration of haemoglobin.

A portable scanning reflectance spectrophotometer using visible wavelengths for the rapid measurement of skin pigments.

A portable rapid scan reflectance spectrometer (400-700 nm in 2.8 s) has been developed for the measurement of cutaneous pigments. The instrument incorporates a tungsten halogen lamp light source, light transmission by fibre optics and wavelength selection by a circular variable wavelength interference filter. A microcomputer controls the instrument and processes the data. The performance of the instrument was evaluated by undertaking in vitro measurements of the reflectance spectra of blood. An index of the haemoglobin content of the sample based on the gradients of the log inverse reflectance spectrum between isobestic points at 527.5, 544 and 573 nm was devised and shown to be independent of the oxygenation of the haemoglobin. The haemoglobin index was combined with measurements at 558.5 nm, a wavelength at which absorbance is sensitive to the oxygenation of haemoglobin, to give a measure of oxygen saturation. The parameter was validated by determining the oxygen dissociation curve of red cells in plasma in vitro at pH 7.33, 37 degrees C and under a partial pressure of 40 mmHg of CO2.

Who gets committed: demographic and diagnostic data.

The study compares the sociodemographic and diagnostic characteristics of patients committed to psychiatric care in New Zealand in 1984 with total admissions and with the general population. Committed patients were significantly more likely to be aged 20-39 years, male, of Maori or Pacific Island ethnicity, and have a diagnosis of schizophrenia or affective disorder. These findings provide a baseline from which we may assess changes in the committed patient population following reform of the Mental Health Act.

Effects of oral ethinyl oestradiol and norethisterone on plasma copper and zinc complexes in post-menopausal women.

Orally administered ethinyl oestradiol increased the plasma total copper concentration and reduced the albumin concentration in post-menopausal women. Approximately 80% of the increase in copper was due to a rise in caeruloplasmin-bound copper and 20% to an increase in the amount of copper bound per gram of albumin. The plasma total zinc concentration was reduced, due partly to the decrease in albumin concentration and partly to a reduction in the amount of zinc bound per gram of albumin. Norethisterone had no significant effect on plasma copper but it reduced plasma zinc and albumin, though to a lesser extent than ethinyl oestradiol. When administered sequentially with ethinyl oestradiol, norethisterone diminished the effects of the former on plasma copper, zinc and albumin.

The usefulness of reflectance spectrophotometric measurements during psoralens and ultraviolet A therapy for psoriasis.

Reflectance spectrophotometry was used to obtain indices of the hemoglobin and melanin content of psoriatic lesions and adjacent clinically normal skin in thirteen patients undergoing photochemotherapy. The pretreatment lesional hemoglobin index was 2.8 times greater than that of adjacent uninvolved skin. With therapy, this index decreased rapidly initially, and during the second or third week approached that of the uninvolved skin. The ratio of lesional and uninvolved skin hemoglobin indices decreased to approximately 1.3, and continuation of PUVA treatment failed to reduce it further. Termination of treatment at this stage, which occurs before clinical resolution, resulted in subsequent clearance of psoriasis. The decrease in the lesional hemoglobin index and the clearance time appeared to be dose-dependent, and, indeed, a more aggressive regimen resulted in approximately 50% reduction in both the number of treatments and the cumulative dose required to achieve a stable hemoglobin index ratio and subsequent clinical clearance.

The stability and blanching efficacy of betamethasone-17-valerate in emulsifying ointment.

The bio-availability of betamethasone-17-valerate (Betnovate ointment) in emulsifying ointment (1 in 4 dilution) was investigated in ten subjects using a single-application vasoconstrictor assay; the blanching induced was measured using a skin reflectance spectrophotometer. The vasoconstrictor activity of the diluted preparations decreased with age. There was no significant difference between the vasoconstrictor activity of freshly made Betnovate 1 in 4 in emulsifying ointment and undiluted Betnovate ointment, and between 3-4 week old diluted Betnovate and emulsifying ointment base. Blanching induced by freshly prepared 4, 8 and 16-fold dilutions was not significantly different but a large reduction in blanching occurred on diluting 32-fold with emulsifying ointment. The degradation of betamethasone -17-valerate in emulsifying ointment was quantified by high performance liquid chromatography. More than 60% of the betamethasone -17-valerate underwent degradation within 6 h. There was a simultaneous increase in the concentration of betamethasone-21-valerate which peaked within 2 days and was followed by a slow degradation (half-life 8 days) to betamethasone free alcohol.

Reflectance spectrophotometric quantification of skin colour changes induced by topical corticosteroid preparations.

Reflectance spectrophotometry was used to observe the degree of vasoconstriction induced by topically applied corticosteroids. The average blanching effectiveness of the corticosteroid preparations as determined by this technique was the same as that found by other workers using subjective assessments. Reflectance spectrophotometry can be utilized to quantify the degree of vasoconstriction produced by local corticosteroids applied to the skin and is particularly suitable for measuring the response of individual subjects.

A theoretical and experimental study of light absorption and scattering by in vivo skin.

A theoretical treatment has been developed for the optical properties of a layered structure which absorbs and scatters light. This theory predicts that the logarithm of the inverse of reflectance (LIR) of the surface should be a useful parameter for the examination of that structure. This approach has been applied to a study of skin in vivo. An instrument was constructed for use in clinical situations to measure the LIR spectrum of skin over the visible region of the spectrum (450-760 nm). The contributions to the observed spectra made by pigments and the skin structure were deduced by reference to the theoretical model. Numerical indices were used to quantify the changes in skin haemoglobin content following the application of vasoconstricting preparations. The indices also provided a means of measuring erythema and melanin pigmentation induced in the skin by exposure to ultraviolet radiation. The assessments made using this instrument were more reproducible and sensitive than judgments made by eye.

Metal-androgen interrelationships in carcinoma and hyperplasia of the human prostate.

Zinc and cadmium concentrations were measured by atomic absorption spectroscopy in normal and pathological human prostates. Our studies confirm the values of zinc in normal tissue [6.84 +/- 1.21 (S.E.M.) mumol/g] and benign prostatic hypertrophy (BPH) (6.9 +/- 1.19 mumol/g) are similar, while in neoplastic tissues zinc concentrations were significantly lower (2.61 +/- 0.45 mumol/g). The Cd2+ levels in BPH (23.11 +/- 3.28 nmol/g) were, on the other hand, considerably higher than those found for normal tissues (5.15 +/- 0.62 nmol/g). In agreement with other published reports, Cd2+ concentrations were found to be markedly increased in carcinomatous tissue (129.79 +/- 22.22 nmol/g). No correlation was however established between the values for the two metals in either type of prostatic tissue. An established specific radioimmunoassay was used for the measurement of testosterone and dihydrotestoesterone (DHT) and a distinct pattern emerged upon comparing these results with those for the zinc and cadmium concentrations. It appears that the concentrations of DHT in benign hypertrophy and of testosterone and DHT in carcinoma were inversely proportional to the levels of Zn2+ in abnormal tissue. In contrast, the DHT levels in the hypertrophied and malignant tissue were proportional to the Cd2+ concentrations.