Eyelid closure causes myopia in humans

Humans with unilateral ptosis are more myopic in the closed eye than in the normal eye. The effect seems unrelated to visual loss. In pairs of humans ranked for sleep and myopia, the more myopic tends to sleep the more. We conclude that eyelid closure causes myopia.     

Chronobiology of sleep in humans

Periodic circadian (24-h) cycles play an important role in daily hormonal and behavioural rhythms. Usually our sleep/wake cycle, temperature and melatonin rhythms are internally synchronized with a stable phase relationship. When there is a desynchrony between the sleep/wake cycle and circadian rhythm, sleep disorders such as advanced and delayed sleep phase syndrome can arise as well as transient chronobiologic disturbances, for example from jet lag and shift work. Appropriately timed bright light is effective in re-timing the circadian rhythm and sleep pattern to a more desired time, ameliorating these disturbances. Other less potent retiming effects may also be obtained from the judicious use of melatonin and exercise.     

Natriuretic potency of hydrochlorothiazide in humans

Zusammenfassung Hydrochlorothiazide, ein oral verabreichbares Diuretikum, führt beim Menschen in Dosen von 25 bis 75 mg zu einer exponentiellen Zunahme der Natriumausscheidung. Eine maximale Diurese wird mit 75–100 mg erreicht. Das neue Pharmakon ist 20mal aktiver als Chlorothiazide.

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Hydrochlorothiazide is the generic name of a new diuretic agent manufactured by CIBA under the trade mark ESIDREX.     

On maximal oxygen consumption in hypoxic humans

The present paper discusses the factors affecting maximal O2 consumption (VO2max) in hypoxia (4300 m above sea level) along the following lines: 1) In acute hypoxia, the fractional limitation to VO2max imposed by circulatory O2 transport (FQ') is 50%, instead of 70% as in normoxia. This is due to the increase in the blood O2 transport coefficient (beta b) as PO2 decreases, as a consequence of the sigmoidal shape of the O2 dissociation curve of hemoglobin. The remaining 50% is assumed to be equally partitioned between tissue O2 transfer (Ft') and mitochondria O2 utilization (Fm'). 2) In chronic hypoxia, FQ' = 0.45, Ft' = 0.20 and Fm' = 0.35, as a consequence of reduced muscle fiber size and muscle mitochondrial density following acclimatization. 3) The relationship between VO2max and PIO2 in both acute and chronic hypoxia reflects the O2 dissociation curve. 4) Acclimatization to chronic hypoxia does not have the function of preserving VO2max.     

Molecular basis of homocysteine toxicity in humans

Because of its similarity to the protein amino acid methionine, homocysteine (Hcy) can enter the protein biosynthetic apparatus. However, Hcy cannot complete the protein biosynthetic pathway and is edited by the conversion to Hcy-thiolactone, a reaction catalyzed by methionyl-transfer RNA synthetase in all organisms investigated, including human. Nitrosylation converts Hcy into a methionine analogue, S-nitroso-Hcy, which can substitute for methionine in protein synthesis in biological systems, including cultured human endothelial cells. In humans, Hcy-thiolactone modifies proteins posttranslationally by forming adducts in which Hcy is linked by amide bonds to -amino group of protein lysine residues (Hcy-N-Lys-protein). Levels of Hcy bound by amide or peptide linkages (Hcy-N-protein) in human plasma proteins are directly related to plasma total Hcy levels. Hcy-N-hemoglobin and Hcy-N-albumin constitute a major pool of Hcy in human blood, larger than total Hcy pool. Hcy-thiolactone and Hcy-thiolactone-hydrolyzing enzyme, a product of the PON1 gene, are present in human plasma. Modification with Hcy-thiolactone leads to protein damage and induces immune response. Autoantibodies that specifically recognize the Hcy-N-Lys-epitope on Hcy-thiolactone-modified proteins occur in humans. The ability of Hcy to interfere with protein biosynthesis, which causes protein damage, induces cell death and elicits immune response, is likely to contribute to the pathology of human disease.Received 30 May 2003; received after revision 21 July 2003; accepted 15 August 2003     

Biological effectiveness of solar UV radiation in humans

Solar UVB radiation is prejudicial to the health of humans in a number of ways. Erythema and photodermatoses are acute reactions of the skin; keratitis and conjunctivitis are acute reactions of the eye. Various types of skin cancer, accelerated aging of the skin, and cataract formation in the crystalline lens are reactions that appear with great latency. UV radiation can also cause damage to the immune system and DNA. For the period 1981–1991, an increase in erythemal effective UVB radiation of +(7±4)% per decade was measured in a non-pulluted high mountain area (Jungfraujoch, 3576m a.s.l., Switzerland). This increase is related to a decrease in stratospheric ozone. The effects on human health are discussed. A 10% ozone reduction increases non-melanoma skin cancer by 26% and cataract by 6 to 8%.     

The causes of Charcot-Marie-Tooth disease

Charcot-Marie-Tooth (CMT) disease serves as the summary term for the most frequent forms of inherited peripheral neuropathies that affect motor and sensory nerves. In the last 12 years, 14 genes have been identified that cause different CMT subforms. The genes found initially are predominantly responsible for demyelinating and dysmyelinating neuropathies. Genes affected in axonal and rare forms of CMT have only recently been identified. In this review, we will focus on the currently known genes that are associated with CMT syndromes with regards to their genetics and function.Received 5 April 2003; received after revision 20 May 2003; accepted 23 May 2003     

Avian influenza viruses infecting humans

Avian species, particularly waterfowl, are the natural hosts of influenza A viruses. Influenza viruses bearing each of the 15 hemagglutinin and nine neuraminidase subtypes infect birds and serve as a reservoir from which influenza viruses or genes are introduced into the human population. Viruses with novel hemagglutinin genes derived from avian influenza viruses, with or without other accompanying avian influenza virus genes, have the potential for pandemic spread when the human population lacks protective immunity against the new hemagglutinin. Avian influenza viruses were thought to be limited in their ability to directly infect humans until 1997, when 18 human infections with avian influenza H5N1 viruses occurred in Hong Kong. In 1999, two human infections with avian influenza H9N2 viruses were also identified in Hong Kong. These events established that avian viruses could infect humans without acquiring human influenza genes by reassortment in an intermediate host and highlighted challenges associated with the detection of human immune responses to avian influenza viruses and the development of appropriate vaccines.     

Glutamate dehydrogenase activity in normal and tumoural skin in humans

Résumé Les auteurs ont étudié l'activité de la glutamate déhydrogénase dans la peau normale et dans les épithéliomes de la peau chez l'homme. Ils ont observé que l'enzyme est dans les tumeurs beaucoup plus active que dans la peau normale. De même, dans l'épithéliome, l'inhibition par le Zn⁺⁺ et la O-phénantroline necessite de plus hautes concentrations que pour la peau normale. Les modifications constatées pourraient servir au diagnostic différentiel des tumeurs de la peau chez l'homme.     

Substance P-induced fibrinolysis in the forearm of healthy humans

Physiological saline with or without substance P (50 ng/ml) was infused into the humeral artery in 6 healthy males. Indices of fibrinolytic activity (whole blood diluted lysis time, euglobulin lysis time, lysis areas in non-heated fibrin plates produced by plasma or euglobulin precipitate, plasminogen plasma levels, ₂-macroglobulin, Cl-inhibitor, and ₂-antiplasmin) were evaluated in the homolateral antecubital vein before and after 5 min of substance P or saline infusion. After substance P the fibrinolytic activity increased, as can be seen from the shortening of lysis times (p<0.01) and enlargement of the lysis areas (p<0.01). A reduction of plasminogen plasma levels (p<0.01), associated with a decrease in ₂-anitplasmin (p<0.01), was also found. Alpha₂-macroglobulin and Cl-inhibitor were instead unaltered by the peptide. The saline infusion, on the other hand, was unable to modify any of the examined indices. We concluded that exogenous substance P given intra-arterially increases fibrinolytic activity in locally-sampled venous blood through a mechanism which remains to be elucidated.     

Suppressed collagenolytic activity in polymorphonuclear leucocytes from diabetic humans

Summary Extracts of polymorphonuclear leucocytes (PMNL) from diabetic human exhibited less collagenolytic activity than extracts from normoglycemic control subjects. Partially purified control extracts produced ^A and ^B collagen breakdown products of the type generated by mammalian collagenase; the diabetic preparation produced decreased amounts of the same products. The diabetic PMNLs may synthesize abnormally low levels of collagenase or contain inactive forms of this enzyme.Supported by a grant (No. DE-03987) from the National Institute of Dental Research (N.I.H.), USA. This study forms part of the Ph.D. thesis of G.A. Nicoll.Acknowledgments. The authors wish to thank Ms Salema Karim and Mr F.R. Singh for excellent technical assistance.     

The count of blood platelets and sex in humans

Summary It has been shown that there is a higher count of blood platelets and thrombopoietic activity of plasma in women than men.     

Excess bioavailability of zinc may cause obesity in humans

The body weight or body weight/height ratio exhibits a positive linear correlation to hair zinc (Zn) concentration which is more strongly positive in men than in women. The obese of both sexes possess higher Zn concentrations in their hair than those with normal body weight/height. The degree of obesity increases with the increase in the hair Zn concentration.