Shabtay Dikstein

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.

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.

Stimulability, adenosine triphosphatases and their control by cellular redox processes

This review suggests that oxidation of reduced glutathione in the cell has a profound effect on active and passive cation permeability as well as on the chemical stimulaiion of excitable cells. Since permeabilities are presumably regulated by ATP-ases, it is speculated that the pentose shunt, glutathione, and the lipid environment, regulate the activity of different ATP-ases, and hence the permeability and chemical stimulability of cells. A hypothesis of this type might provide a link between the metabolic state of the cell and certain functions of the cell membrane.

The influence of eyelid temperature on the delivery of meibomian oil.

The aim of this study is to establish the effect of heating and cooling of the eyelid on the delivery of oil from the meibomian glands, as indicated by the extent of re-establishment of the reservoir of meibomian oil on the human eyelid margin, resulting from 10 conscious blinks, following pre-cleaning by a hexane swab. A standard handling sequence was followed. Step 1. Both upper and lower eyelids of both eyes of human volunteers were cleaned by a hexane swab and measured by a Meibometer to show satisfactory removal of the pre-existing oil (initial reading less than 60 instrumental units (IU)). The volunteers were then asked to blink 10 times at their normal rate. Then the eyelid was re-measured by the Meibometer. Step 2. The closed eyelids were heated for 5 min by a 250 W infrared lamp from a distance of 50 cm. The eyelid temperature was measured by an infrared thermometer, then Step 1 was repeated. Step 3. The eyelids were cooled for 5 min by an ice-pack (crushed ice in a towel). The eyelid temperature was measured, then Step 1 was repeated. Both eyes of 20 female subjects, aged 68 +/- 3 S.E.M. (range 52-84) years were examined. The mean instrumental reading (IU +/- S.E.M.) after 10 blinks at 33.4 +/- 0.1 degrees C was 154 +/- 12. On increasing the eyelid surface temperature by 4.9 +/- 0.3 degrees C we obtained an increase of 49 +/- 9 IU. On decreasing it by 7.6 +/- 0.4 degrees C we obtained a decrease of 46 +/- 9 IU. We conclude that temperature significantly influences the delivery of the meibomian gland secretion. Our results are in agreement with the 10-blink recovery value of 191 +/- 9.3 IU previously reported. They also agree with the reported benefit of warm compresses to improve delivery from dysfunctional glands. The most likely explanation for our findings is a change in the viscosity of the meibomian oil.

ATP DETERMINATION WITH THE TRICARB SCINTILLATION COUNTER

Die Arbeit beschreibt eine neue Technik zur Bestimmung geringster Mengen von ATP (10–11 Mol und weniger) mit der Luciferin-Luciferase-Methode. Die dabei erzeugten Impulse werden mit einem Scintillationszähler gemessen.

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.

Efficiency and survival of the corneal endothelial pump

Abstract In this article the state of knowledge on the biochemical requirements of the corneal endothelial fluid pump is summarized. This pump is a general interest for the study of transport mechanisms. It is a single layer of homogenous cells, very actively transporting fluid out of the cornea (25–40 μl/cm 2 /hr). The transmembrane potential, if there is any, is less than 1 mV. Its regulatory role is largely responsible for the maintenance of corneal thickness in vivo; changing the fluid composition on the epithelial side in vitro has no effect on the course of deturgescence. From the histological, biochemical and biophysical viewpoints, the corneal endothelium seems to be a simpler system for the study of active transcellular water and salt movement than accepted models.

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.

On the Therapeutic Possibilities of Some Cannabinoids

Cannabis has been used as a therapeutic agent since ancient times. Li (1974) and Rosenthal (1971) have described its use by the ancient Chinese and in medieval Arab society. Walton (1938) and more recently Mikuriya (1973) have summarized the medical use of cannabis in Europe during the nineteenth and early twentieth century. In spite of the very promising and rather non-toxic effects of the drug, its use rapidly declined due to the notorious variability of crude cannabis preparations. The advances made since the determination of the structure of cannabidiol in 1963, the isolation in pure form and structure elucidation of delta-1-THC in 1964, and the development of various synthetic routes during the middle sixties (Mechoulam, 1973) have clarified the chemistry and pharmacology of the cannabinoids and have made possible initiation of research into the use of pure natural or synthetic cannabinoids as drugs.

The involvement of the intracellular redox state and pH in the metabolic control of stimulus-response coupling

Publisher Summary This chapter discusses the consecutive stages involved in the operation of the stimulus–response–recovery (SRR) cycle. When a pharmacological agonist interacts with a receptor, usually situated on the outer cell membrane, it sets in motion a chain of events known as the “SRR” cycle. The cycle starts with a “receptor mechanism”; it consists of those signaling processes that translate the receptor–agonist interaction into a change in the intracellular concentration of the second messenger. The chapter discusses the question of whether the redox state controlling enzymes and their products are themselves obligatory parts of a receptor mechanism or whether they act in a regulatory manner by inhibiting or stimulating part of the receptor mechanism. The chapter focuses on response systems activated by pharmacomechanic coupling rather than those occurring by electromechanic coupling. The difference lies in the fact that electromechanic coupling occurs via a change in potential across the plasma membrane, whereas pharmacomechanic coupling does not.