THE GENETICS OF ALCOHOLISM: IS THERE AN INHERITED SUSCEPTIBILITY TO ALCOHOL-RELATED PROBLEMS?

Alcoholism and alcohol-related disorders have a pronounced familialtendency. There has been considerable debate over many yearsas to whether this represents transmission of genetic traitsor the influence of family environment on drinking behaviour.Studies of adopted children and of monozygotic compared withdizygotic twins show a modest but definite genetic influenceon drinking habits and, at least in men, on the occurrence ofpsychosocial problems related to alcohol abuse. There is evidencefor two types of alcoholism, one that is highly heritable andanother that shows a lesser degree of inheritance and requiresenvironmental stressors for it to be manifest. The mechanismsby which such genetic influences are expressed are unknown althoughthe metabolism of alcohol and many of its physiological effectsare partly genetically determined. No biological markers havebeen associated convincingly with a predisposition to alcoholismbut absence of an isoenzyme of aldehyde dehydrogenase, whichoccurs in 50% of Oriental populations, has been related to thealcohol-flush reaction which may have an aversive effect onalcohol consumption. This may explain the low incidence of alcoholproblems in Oriental countries. Genetic factors have long been thought to be responsible forthe variation in susceptibility to the physical sequelae ofchronic alcohol consumption such as cirrhosis and cardiomyopathy.Women develop many complications of alcoholism, especially liverdisease, after a shorter period of drinking and at a lower dailyalcohol intake than men, and this is partly related to differencesinbody size and composition and in hormonal status. Several hiitocompatibility(HLA) antigens have been linked to susceptibility to cirrhosis.The association for most is relatively weak but HLA-B8 and DR3are associated with accelerated development of cirrhosis, possiblyby stimulating cytotoxic immune reactions to alcohol-damagedliver cells. Little is known about what genetic factors mightpredispose to other alcohol-related diseases. Further work into the mechanisms by which genetic factors influencethe development of alcoholism and susceptibility to its complicationsmay help identify agents that interfere with these processes.Total abstinence from alcohol may be advisable for family membersof subjects with the highly heritable form of alcoholism. Untilmore is known about individual safe limits for drinking everyoneshould be advised to keep below 80g alcohol/day (for men) or40g/day (for women).     

Pilo-sebaceous duct physiology

We have used surface microscopy to measure the pil-sebaceous duct orifices at different sites in 150 subjects. Our data have shown that there are more pilo-sebaceous units on the face compared to the back and that these exists are smaller on the face. Despite the small exit the sebum excretion rate per gland on the forehead was not significantly different from that on the back. Thus the number of pilo-sebaceous duct units and the pilo-sebaceous canal exit size are possible factors in the localization of acne.     

Pseudomonas aeruginosa: Host defence in lung diseases

Lung infections caused by the opportunistic pathogen Pseudomonas aeruginosa can present as a spectrum of clinical entities from a rapidly fatal pneumonia in a neutropenic patient to a multi‐decade bronchitis in patients with cystic fibrosis. P. aeruginosa is ubiquitous in our environment, and one of the most versatile pathogens studied, capable of infecting a number of diverse life forms and surviving harsh environmental factors. It is also able to quickly adapt to new environments, including the lung, where it orchestrates virulence factors to acquire necessary nutrients, and if necessary, turn them off to prevent immune recognition. Despite these capabilities, P. aeruginosa rarely infects healthy human lungs. This is secondary to a highly evolved host defence mechanism that efficiently removes inhaled or aspirated pseudomonads. Many arms of the respiratory host defence have been elucidated using P. aeruginosa as a model pathogen. Human infections with P. aeruginosa have demonstrated the importance of the mechanical barrier functions including mucus clearance, and the innate immune system, including the critical role of the neutrophilic response. As more models of persistent or biofilm P. aeruginosa infections are developed, the role of the adaptive immune response will likely become more evident. Understanding the pathogenesis of P. aeruginosa, and the respiratory host defence response to it has, and will continue to, lead to novel therapeutic strategies to help patients.     

Lateral and anterior–posterior mandibular position discrimination by normal subjects

This study examined and compared lateral and anterior-posterior (A-P) mandibular position discrimination for a group of twenty normal subjects (mean age = 26 years). A specially designed and constructed sliding scale required subjects to position their mandible precisely in the horizontal plane and to try to discriminate differences in the control of their mandibular position. The results revealed that subjects are more sensitive in detecting changes in the lateral positioning of their mandible than in the A-P positions. Subjects' difference limen (DL) values (threshold of discrimination between two positions) in detecting changes in mandibular position to the right of centre was 1.59 mm, and to left of centre was 1.41 mm. Subjects' DL values obtained with the mandible forward, and back of, the reference position were 1.39 and 2.61 mm respectively.     

The air-powder dental abrasive unit—an evaluation using a model system

Air-powder abrasive systems are used in dentistry to remove dental plaque, calculus and stain from the surfaces of teeth. A model system consisting of a thin layer (14 micron) of vacuum-deposited aluminium was used to demonstrate the effectiveness of such a system. Photomicrographic analysis showed two distinct areas of removal: an inner area where removal of aluminium was complete, surrounded by an area where removal was incomplete. With the aid of a relocation pin attached to the nozzle of the instrument it was demonstrated that nozzle-target distance, the air pressure input, the flow of water and the time of operation were all factors which affected the clinical efficiency of the instrument.