Assay of plasma cannabidiol by capillary gas chromatography/ion trap mass spectroscopy following high-dose repeated daily oral administration in humans.

Plasma levels of cannabidiol (CBD) were ascertained weekly in 14 Huntington's disease patients undergoing a double-blind, placebo-controlled, crossover trial of oral CBD (10 mg/kg/day = about 700 mg/day) for 6 weeks. The assay procedure involved trimethylsilyl (TMS) derivatization of CBD and the internal standard delta-6-tetrahydrocannabinol (THC), capillary column gas chromatography, ion trap mass spectroscopy in positive ion chemical ionization mode using isobutane, and calculations of CBD levels based on peak ion intensity of the 387 M + H peak of delta-6-THC-TMS and the 459 M + H peak of CBD-2TMS. The sensitivity of the assay was about 500 pg/ml, and the precision was about 10-15%. Mean plasma levels of CBD ranged from 5.9-11.2 ng/ml over the 6 weeks of CBD administration. CBD levels averaged 1.5 ng/ml one week after CBD was discontinued, and were virtually undetectable thereafter. The elimination half-life of CBD was estimated to be about 2-5 days, and there were no differences between genders for half-life or CBD levels. Additionally, no plasma delta-1-THC, the major psychoactive cannabinoid of marijuana, was detected in any subject.     

Cisplatin and 5-fluorouracil for advanced locoregional and metastatic squamous cell carcinoma of the skin

Seven patients with advanced locoregional or metastatic squamous cell carcinoma of the skin were treated with cis-daimminedichloroplatin (cisplatin) and 5-fluorouracil (5-FU). Responses were seen in six of seven patients (three partial responses [PR] and three complete responses [CR]). One patient is alive and disease-free at 2 years. These results indicate that cisplatin and 5-FU is an effective combination regimen that should be used in future clinical trials in squamous cell carcinoma of the skin.     

A measure of independence. Teaching home blood pressure monitoring

Encouraging hypertensive pregnant women to take their own blood pressure produces reliable and consistent results. It has proved popular among women, enabling them to assess the fluctuations of their blood pressure at first hand and to maintain a sense of control.     

Racial identification in the context of prehistoric-historic biological continua: examples from South Asia.

The practice of 'racial palaeontology' disappeared 50 years ago with the fall of the biological race concept in systematics and population genetics. However, certain ethnic minorities claim close biological affinities with extinct (sometimes Pleistocene) populations. Forensic anthropologists may be involved in this issue through analyses of prehistoric and modern populations in circumstances where a biological continuum may exist. Skeletal evidence from South Asia is discussed.     

New insights on P2X purinoceptors

Significant advances in understanding of P_2X purinoceptor pharmacology have been made in the last few years. The limitations of nucleotide agonists as drug tools have now been amply demonstrated. Fortunately, inhibitors of the degrading ecto-ATPase enzymes are becoming available and it has become apparent that the complete removal of all divalent cations can be used experimentally in some systems to prevent nucleotide breakdown. Despite these issues, convincing evidence for P_2X receptor heterogeneity, from data with agonists, has recently been reported.A number of new antagonists at P_2X purinoceptors have also recently been described which to some degree appear to be more specific and useful than earlier antagonists like suramin. It is now apparent that suramin is a poor antagonist of ATP in many tissues because it potently inhibits ATPase activity at similar concentrations to those at which it blocks the P_2X purinoceptor.Advances in the use of radiolabelled nucleotides as radioligands for binding studies has allowed the demonstration of P_2X purinoceptors in a variety of tissues throughout the body including the brain. These studies have also provided evidence for receptor heterogeneity. Excitingly, two P_2X purinoceptor genes have been cloned but operational studies suggest that more than two types exist. The cloning studies have also demonstrated a unique structure for the P_2X purinoceptor which differentiates it from all other ligand-gated ion channel receptors. Further studies on P_2X purinoceptor operation and structure are needed to help resolve controversies alluded to regarding the characterization and classification of nucleotide receptors. Hopefully such studies will also lead to a better understanding of the physiological and pathological importance of ATP and its activation of P_2X purinoceptors. This will require the identification of better drug tools, in particular antagonists which may also provide the basis for novel therapeutic agents.     

A model for the prediction of osmolalities of modular formulas

A model is proposed for evaluation of osmolality of multicomponent formulas composed of modular ingredients. Nonlinear curve-fitting techniques applied to empirical data result in prediction of the osmolality of ingredients for any concentration desired. Osmolality of a multicomponent formula can be obtained by adding osmolalities of ingredients. Data handling is made possible by the use of simple microcomputer programs. The model is tested with products available for construction of amino acid-restricted diets.     

Calcium phosphate in catheter encrustation

Encrusted catheters from nine female patients were the source of samples of deposits which were examined by X-ray diffraction, atomic absorption spectroscopy, infra-red spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. In eight samples the only crystalline phase which could be clearly distinguished by X-ray diffraction was ammonium magnesium orthophosphate hexahydrate, NH4MgPO4 X 6H2O, which occurs naturally as the mineral struvite. However, atomic absorption spectroscopy revealed an appreciable concentration of calcium in all samples. Calcium phosphates have previously been detected in catheter deposits. Infra-red and EXAFS spectra were consistent with the calcium phosphate being present as a poorly crystalline hydroxyapatite. Thus the deposits appear to consist of a mixture of crystalline struvite and a form of hydroxyapatite which is not fully crystalline.