抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

CA : A Cancer Journal for Clinicians

admission. This proportion could already be greater in some parts of the country and may increase if referrals of cases of self-poisoning increase faster than the facilities for their assessment and management. The provision of social work and psychiatric expertise in casualty departments may be one means of preventing unnecessary medical admissions without risk to the patients. Dr Blake's and Dr Bramble's figures do not demonstrate, however, that any advantage would attach to medical teams taking over assessment from psychiatrists except that, by implication, assessments would be completed sooner by staff working on the ward full time. What the figures actually suggest is that if assessment of overdoses were left to house doctors there would be an increase in admissions to psychiatric units (by 19°U), outpatients (by 5O°'), and referrals to social services (by 140o). So for house doctors to assess overdoses would provide no economy for the psychiatric or social services. The study does not tell us what the consequences would have been for the six patients who the psychiatrists would have admitted but to whom the house doctors would have offered outpatient appointments. E J SALTER

Vitamin D deficiency.

[Crohn's disease].

Glucose-6-phosphate dehydrogenase deficiency

Background Thymoquinone is the major active principle of Nigella sativa (N. sativa) and constitutes about 30% of its volatile oil or ether extract. N. sativa oil and seed are commonly used as a natural remedy for many ailments. Using modern scientific techniques, a number of pharmacological actions of N. sativa have been investigated including immunostimulant, anti-inflammatory, anticancer, antioxidant, antihistaminic, antiasthmatic, hypoglycemic, antimicrobial and antiparasitic. There are only few reports regarding the toxicity of thymoquinone. Methods The present study was carried out to determine LD50 of thymoquinone both in mice and rats, orally as well as intraperitoneall, by the method of Miller and Tainter. Autopsy and histopathology of liver, kidney, heart and lungs were also determined. Results The LD50 in mice after intraperitoneal injection was determined to be 104.7 mg/kg (89.7-119.7, 95% confidence interval) and after oral ingestion was 870.9 mg/kg (647.1-1094.8, 95% confidence interval). Whereas, LD50 in rats after intraperitoneal injection was determined to be 57.5 mg/kg (45.6-69.4, 95% confidence intervals) and after oral ingestion was 794.3 mg/kg (469.8-1118.8, 95% confidence intervals). The LD50 values presented here after intraperitoneal injection and oral gavages are 10-15 times and 100-150 times greater than doses of thymoquinone reported for its anti-inflammatory, anti-oxidant and anti-cancer effects. Conclusion Thymoquinone is a relatively safe compound, particularly when given orally to experimental animals.

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Oral and intraperitoneal LD50 of thymoquinone, an active principle of Nigella sativa, in mice and rats.

A common glucose-6-phosphate dehydrogenase (G6PD) variant characterized by severe enzyme deficiency and B-like electrophoretic mobility is called "G6PD-Mediterranean" because it is found in different populations around the Mediterranean Sea. Sequence analysis of Italian subjects has revealed that the molecular basis of G6PD-Mediterranean is a single C-T transition at nucleotide position 563, causing a serine phenylalanine replacement at amino acid position 188. Most G6PD-Mediterranean subjects also have a silent C-T transition (without amino acid replacement) at nucleotide position 1311. Twenty-one unrelated individuals from Saudi Arabia, Iraq, Iran, Jordan, Lebanon, and Israel with both severe G6PD deficiency and B-like electrophoretic mobility were tested for both mutations by using amplification followed by digestion with appropriate restriction enzymes. All but one had the 563 mutation, and, of these, all but one had the 1311 mutation. Another 24 unrelated Middle Eastern individuals with normal G6PD activity or not known to be G6PD deficient were similarly tested. Four had the silent mutation at position 1311 in the absence of the deficiency mutation at position 563. We conclude that (1) the large majority of Middle Eastern subjects with the G6PD-Mediterranean phenotype have the same mutation found in Italy, (2) the silent mutation is an independent polymorphism in the Middle East, with a frequency of about .13, and (3) the mutation leading to the G6PD-Mediterranean deficiency has probably arisen on a chromosome that already carried the silent mutation.

Origin and spread of the glucose-6-phosphate dehydrogenase variant (G6PD-Mediterranean) in the Middle East.

OBJECTIVES 
To assess the serum level of 25 hydroxyvitamin D 25OHD among healthy Saudi Arabian women living in the eastern province.
 METHODS 
A cross-sectional randomized study was conducted between February 1st 2008 and May 31st 2008 at the King Fahd University Hospital, Al-Khobar, Kingdom of Saudi Arabia in 200 Saudi women between 25-35 years group 1 and women of > or =50 years group 2. Clinical examination, laboratory tests, a complete blood picture, serum calcium, phosphorous, alkaline phosphatase, parathormone, and the serum levels of 25OHD levels were carried out. Data on lifestyle, dietary, and demographic questionnaires were collected. Vitamin D was defined as deficient with serum level <50 nmol/L, insufficient between 52-72 nmol/L, and normal as 75nmol/L.
 RESULTS 
In group 1, 70% of women had normal 25OHD, and in women of group 2, 45% had normal levels of 25OHD. Alkaline phosphatase and parathormone levels were significantly higher in women with low vitamin D levels. Sun exposure and consumption of dairy products were minimal.
 CONCLUSIONS 
Vitamin D deficiency among healthy young Saudi women of 25-35 years was 30% and 55% in women of > or =50 years. This study indicates that hypovitaminosis D is common in young and postmenopausal women. Efforts are require to augment and encouraged women for adequate exposure to sunlight and increased intake of fortified vitamin D products to maintain skeletal health.

25-Hydoxyvitamin D levels among healthy Saudi Arabian women.

BACKGROUND: Studies in 1980s and 1990s indicated that vitamin D levels in the ethnic Saudi Arabian population were low but no studies since that time have evaluated vitamin D levels among healthy y...

Vitamin D levels in healthy men in eastern Saudi Arabia.

BACKGROUND AND OBJECTIVES: The effects of vitamin D on bone mass remain to be understood. This study was conducted with the objective of evaluating the influence of 25-hydroxyvitamin D (25OHD) leve...

Amein K. Al-Ali

Papers

Oral and intraperitoneal LD50 of thymoquinone, an active principle of Nigella sativa, in mice and rats.

Origin and spread of the glucose-6-phosphate dehydrogenase variant (G6PD-Mediterranean) in the Middle East.

25-Hydoxyvitamin D levels among healthy Saudi Arabian women.

Vitamin D levels in healthy men in eastern Saudi Arabia.

Influence of vitamin D levels on bone mineral density and osteoporosis.