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Biomedical subjects

S Dikstein

Publications and source records attributed to S Dikstein.

At least 19 recordsLinked to original sources
PubMed2001

The efficiency of humectants as skin moisturizers in the presence of oil.

BACKGROUND/AIMS: The research on the treatment of "dry skin syndrome" is hampered by the lack of a suitable animal model. Formerly, we developed a validated guinea pig in vivo model in which the dry skin syndrome persists at least for 1 week. We can, therefore, compare the pharmacological effectiveness of known and potential moisturizers for the treatment of dry skin syndrome. Our aim is to study whether the moisturizing efficiency of humectants depends on the solvents in which they are dissolved. METHODS: "Dry skin syndrome" was induced on the shaved skin on one side of guinea pigs by daily application of 2% sodium lauryl sulphate in deionized water (SLS) for 3 days. The other shaved side was used as control. After ascertaining skin dryness, that side was treated for 6 days with glycerol or 1,2-hexanediol in different solvents: water, or medium chain triglycerides (MCT) or mixtures of MCT with isopropyl alcohol in different proportions. Measurement of the in vivo moisturizing effect was carried out by a Comeometer CM 825; erythema was measured by a Mexameter MX 16. RESULTS: Treatments with glycerol (1M) in water reversed the skin dryness shown by both instruments. When dissolving glycerol in MCT, no moisturizing effect was found, probably because glycerol does not dissolve in the oil. No moisturizing effect was found with different combinations of glycerol in the mixtures of MCT and isopropyl alcohol. No moisturizing effect was found using another polyol moisturizer: 1,2 hexanediol (1M) dissolved in MCT oil. Glycerol or 1,2-hexanediol abolished the erythema only when they were dissolved in water alone. CONCLUSION: Polyol moisturizers such as glycerol or 1,2-hexanediol do not act in the presence of oils against the sodium lauryl sulphate-induced dry skin in our guinea pig model. Since in an oil-in-water (O/W) emulsion, the water evaporates within several minutes, one has to question the ability of moisturizing emulsions to treat dry skin. In such instances, one cannot draw conclusions about the moisturizing efficiency of the preparation merely from the presence of the humectant. One has to study the effect of the finished preparation.

Animals↗
PubMed2001

Differences in corneocyte surface area in pre- and post-menopausal women. Assessment with the noninvasive videomicroscopic imaging of corneocytes method (VIC) under basal conditions.

The differences between pre- and postmenopausal women and men on corneocyte surface area were investigated by a noninvasive exfoliation method. Surface corneocytes were collected with a modified detergent scrub technique. Separated corneocytes were analyzed by videomicroscopy and image analyses (NIH Image 1.59). Additionally transepidermal water loss (TEWL) and stratum corneum hydration, water-holding capacity and moisture accumulation velocity were measured. 21 postmenopausal females without hormonal substitution (age 50.6 years), 33 premenopausal women (age 41.0 years) and 25 men matched for age (age 44.0 years) were included in this study. The smallest corneocyte surface area was seen in premenopausal women (368.0 pixels). For postmenopausal women and the male control population almost equal values could be detected (postmenopausal women 401.1 pixels; men 401.8 pixels). Significant differences were calculated with the ANOVA test (p = 0.0050) and post-hoc analyses (Dunn test); premenopausal vs. postmenopausal women (p < 0.05) and premenopausal women vs. men (p < 0.05), but not postmenopausal women vs. men (p > 0.05). No statistically significant differences could be detected for TEWL, stratum corneum hydration parameters. No correlation could be found between the corneocyte surface area and barrier or hydration parameters. The detected differences support the hypothesis that sexual hormones have an impact on corneocyte surface area, because sex hormone levels are higher in premenopausal women than in non-hormone-substituted postmenopausal women or men.

Adult↗
PubMed1994

Measurement of skin pH.

The knowledge of the skin surface pH-acid mantle is updated. The conviction that chronic alkalinization is damaging has been strengthened. Extensive skin surface pH data on the skin of non-white people are still missing. In the case of any measurement, the need for extensive infrastructural research and evaluation by non-parametric methods is emphasized. Infrastructural studies evaluate the range and change of the measured parameters for each test method according to sex, age and body area, as well as the sensitivity of the method to pharmacological influences. A detailed knowledge of the normal-representative range would make it possible to select those individuals whose measured parameter is outside the main 95% of the population; a detailed study of such individuals would be a very effective method of understanding the basic regulatory mechanism of the measured parameter.

Adolescent↗
PubMed1993

Influence of ageing on the in vivo mechanics of the skin.

The response of the skin to common in vivo tests (in-plane uniaxial stretch, torsion, indentation and levarometry) is analyzed in terms of their suitability for ageing studies. The analysis suggests that low-load indentation and small deformation levarometry are well suited for ageing studies since the skin response under these tests can be directly related to its structure and constituent properties (known to be affected by ageing). The measured forehead skin response under these tests in 'young' (20-26 years) and 'old' (64-80 years) subjects is presented and compared with predictions of corresponding models. The results show that levarometry is more sensitive to ageing than indentometry.

Adult↗
PubMed1993

An instrument for quantifying meibomian lipid on the lid margin: the Meibometer.

An instrument, the Meibometer, is described for estimating the casual level of meibomian lipid on the human eyelid margins, adapted from a commercially-available instrument used for measurement of skin surface lipid. A loop of plastic tape is pressed onto the everted lower lid margin to lift off a blot of lipid. The resultant change in light transmission of the tape is read by a photometer. Readings are not affected by side (R or L), time of day or lid surface temperature. After cleaning lipid from the lid margins with hexane, the rate of recovery per 10 blinks, as a percentage of the pre-cleaned level, was measured as 33.7 +/- 5.8 (mean +/- SE). This rate of delivery appears to provide enough lipid for complete resurfacing of the preocular tear film with every blink. Over short periods no detectable lipid was delivered in the absence of blinking.

Adult↗
PubMed1993

The casual level of meibomian lipids in humans.

Using a modified skin surface lipid measuring instrument, the Meibometer, the amounts of meibomian lipid on the lid margins (the casual levels) of 421 subjects aged 1 to 94 years were measured. The lowest levels were found in children younger than 14 years (means +/- S.E.: males = 1.48 +/- 0.17, females = 1.53 +/- 0.17 micrograms lipid/mm2 lid margin surface) and rose with age, the highest levels being found in males aged 60-69 years (mean +/- S.E. = 3.26 +/- 0.18 micrograms lipid/mm2 lid margin surface). Male levels were higher than females in the 20-29 years age group but male and female levels became indistinguishable above the age of 50. These age- and sex-related changes differed markedly from those seen in skin surface lipid levels. The age-related changes in the casual levels of lid lipids remain unexplained although an endocrinological mechanism modified by morphological factors is considered.

Adolescent↗
PubMed1991

Sebum measurements for rapid identification of hyperandrogenism due to an ovarian Leydig cell tumor.

Direct measurements of sebum with the Sebumeter were used in a patient with a benign androgen-producing tumor of the ovary. Androgen levels fell immediately after surgery, whereas the markedly elevated sebum levels found preoperatively dropped to normal after a delay of more than 2 weeks. Therefore, the Subumeter, due to its simplicity, may be useful for the preliminary screening and follow-up of patients with hyperandrogenic states.

Aged↗
PubMed1990

In-vivo indentation of human skin.

Indentation tests were carried out on the forehead skin of volunteers under loading pressures of 0-5 KPa. The indentation was found to increase asymptomatically with loading pressure. In an attempt to develop a quantitative index for aging of the skin, its response to indentation loading was analyzed in reference to its glycosaminoglycan (GAG) containing ground substance and fibers' network microstructure. An analytic model that considers the skin as an incompressible solid-fluid mixture was developed and utilized to simulate the skin's indentation response. Following parameter fitting, the predicted results are in close agreement with the data. The model can thus serve as a tool for evaluating the effect of changes in the dermis components which accompany aging.

Adult↗
PubMed1988

Study of skin ageing as a function of social and professional conditions: modification of the rheological parameters measured with a noninvasive method--indentometry.

Skin ageing was studied with a noninvasive method: indentometry. We measured two rheological parameters: resistance to pressure, indentation, under the pressure of 10 g/cm2, and elastic rebound, elasticity, after the removal of the pressure. We studied three different populations: cloistered nuns, white collar and blue collar workers. We found in all populations a steady decrease in elasticity as a function of age; this effect was always steeper in females. The working women lost their elasticity more rapidly than the nuns, and the male blue collar workers lost their elasticity more rapidly than the male white collar workers. The development of indentation as a function of age is somewhat different. The white collar males showed a steady loss of resistance to pressure with age much more rapidly than their blue collar counterparts. The females showed either a biphasic change (the nuns), no change at all (the white collar workers) or a loss of resistance to pressure (the blue collar workers). These results show that professional as well as social factors may influence skin ageing.

Adult↗
PubMed1981

The Pharmacology of the hypotensive action of N,N-dimethyl para-methoxyphenylethylamine in rats.

N,N-dimethyl para-methoxyphenylethylamine prevents hypertension and reverses existing high blood pressure in DOCA-saline treated rats. Indomethacin prevents its hypotensive effect, therefore the suggested mechanism is increase in prostaglandin(s) synthesis. The effect of the usual receptor antagonists on the hypotensive effect of the title compound can also be fitted into the framework of this hypothesis.

Adrenergic alpha-Antagonists↗