Role of riverine colloids in macronutrient and metal partitioning and transport, along an upland-lowland land-use continuum, under low-flow conditions.

An assessment is made of the role of riverine colloids in macronutrient (nitrogen, phosphorus and carbon), metal and trace element partitioning and transport, for five rivers in the Ribble and Wyre catchments in north-western England, under baseflow/near-baseflow conditions. Cross-flow ultrafiltration was used to separate colloidal (<0.45 µm >1 kDa) and truly dissolved (<1 kDa) fractions from river water. Clear patterns were observed, along the upland-lowland land use continuum, in the partitioning and transport of macronutrients and metals between the colloidal, truly dissolved and acid-available particulate (>0.45 µm, suspended) fractions. Of these operationally-defined fractions measured, colloids were generally more important for both macronutrient and metal transport in the upland than in the lowland rivers. The results suggest that organic moieties in truly dissolved form from sewage effluent may have a greater capacity to chelate metals. Organic-rich colloids in the upland moorlands and metal oxide colloidal precipitates in the industrial rivers had a higher capacity for binding metals than the colloidal fractions in the urban and agricultural lowland rivers. Aggregation of these colloids may provide an important mechanism for formation of larger suspended particulates, accounting for a higher degree of metal enrichment in the acid-available particulate fractions of the upland moorland and lowland industrial rivers, than in the lowland agricultural and urban rivers. This mechanism of transfer of contaminants to larger aggregates via colloidal intermediates, known as 'colloidal pumping' may also provide a mechanism for particulate P formation and the high proportion of P being transported in the particulate fraction in the uplands. The cross-flow ultrafiltration data also allowed refinement of partition coefficients, by accounting for colloids within the solids phase and replacing the filtered (<0.45 µm) fraction with the truly dissolved (<1 kDa) concentrations. These provided a clearer description of the controls on metal and P partitioning along the upland-lowland continuum.

Vitamin D receptor polymorphisms are associated with altered prognosis in patients with malignant melanoma.

Calcitriol [1,25(OH)2D3], the hormonal derivative of vitamin D3, is an antiproliferative and prodifferentiation factor for several cell types, including cultured melanocytes and malignant melanoma (MM) cells. Several polymorphisms of the vitamin D receptor (VDR) gene have been described including a FokI RFLP in exon 2, BsmI, and ApaI polymorphisms in intron 8 and an adjacent TaqI RFLP in exon 9. Alterations in vitamin D/1,25(OH)2D3 levels and polymorphisms of the VDR have been shown to be associated with several systemic malignancies. We hypothesize that polymorphism in this gene may be associated with altered susceptibility and outcome in patients with MM. A hospital-based case-control study, using 316 MM cases and 108 controls, was used to assess associations with MM susceptibility. Breslow thickness, the most important single prognostic factor in MM, was used as the outcome measure. Polymorphisms at the FokI and TaqI restriction sites were determined using PCR-based methods. Polymorphism at the FokI, but not TaqI, RFLP was associated with an altered risk of MM (P = 0.014). More importantly, variant alleles were associated with increased Breslow thickness. Thus, homozygosity for variant alleles at both RFLP (ttff genotype combination) was significantly associated with thicker tumors. (> or = 3.5 mm; P = 0.001; odds ratio = 31.5). Thus, polymorphisms of the VDR gene, which would be expected to result in impaired function, are associated with susceptibility and prognosis in MM. These data suggest that 1,25(OH)2D3, the ligand of the VDR, may have a protective influence in MM, as has been proposed for other malignancies.

Ectopic pregnancy: incidence, presentation and management

A prospective study was performed to determine the incidence of ectopic pregnancy at San Fernando General Hospital, Trinidad, to identify risk factors and document the clinical presentation, diagnosis and treatment. All surgically diagnosed ectopic pregnancies presenting in 1994 at the Hospital were interviewed post-operatively, using a pre-formed questionnaire. Forty-six cases of ectopic pregnancy presented from January 1 to December 31, 1994. The ectopic pregnancy rate was 8.12 per 1000 deliveries and 6.65 per 1000 pregnancies. Twenty-four patients (53 percent) had a previous miscarriage but few women had recognised risk factors, the most common being PID in 5 (11 percent). All patients presented with abdominal pain, and other common symptoms were vaginal bleeding, 22 (49 percent), syncope, 22 (49 percent), and vomiting, 16 (36 percent). Sixteen patients (35 percent) presented in shock and 37 (80 percent) had an acute abdomen, with abdominal and pelvic tenderness being more than twice as commonly bilateral as unilateral. Thirty-three patients (72 percent) had surgery performed within 24 hours of admission because of their "acute" clinical presentation, and 14 of them also had a culdocentesis. For the other 13 patients (28 percent) the mean interval prior to surgery was 3.5 days. In this "subacute" group the main aid to diagnosis was ultrasound examination. Definitive treatment in all cases was total or partial salpingectomy. Rupture of the tubal pregnancy occurred in 43 (91 percent) of the women. Efforts to improve the early detection of ectopic pregnancy should focus on educating patients and increasing the index of suspicion among medical practitioners (AU)