Effect of metal complexation on the bioavailability of nitrilotriacetic acid to Chelatobacter heintzii ATCC 29600.

Many polluted sites contain a mixture of organics and heavy metals. Nitrilotriacetic acid has been chosen as a model organic compound to study the effect of metal binding on organic bioavailability and degradation of organics. The effect of varying the ratio of metal to nitrilotriacetic acid on its utilisation has been examined using the gram-negative bacterium Chelatobacter heintzii ATCC 29600. The following parameters of substrate utilisation were examined: growth, degradation, respiration, mineralisation and nitrilotriacetic acid uptake. Complexation of nitrilotriacetic acid by Cu(II), Ni(II), Co(II) and Zn(II) prevented utilisation of nitrilotriacetic acid by C. heintzii; complexation to Fe(III) or Mn(II) did not. The pattern of inhibition was consistent with a 1:1 stoichiometry of metal binding to nitrilotriacetic acid. Inhibition was not due to metal ion toxicity, but was a result of metal-nitrilotriacetic acid complexes being recalcitrant to degradation. In addition, the effect of complexing (phosphate) and non-complexing (PIPES) buffers on bioavailability was examined: Co and Zn prevented degradation of nitrilotriacetic acid in PIPES buffer, but not in phosphate buffer. This was due to the removal of Co and Zn from solution by phosphate precipitation, leaving nitrilotriacetic acid uncomplexed. The results demonstrated that metal-organic complexation can alter the bioavailability of organic pollutants and may also modulate the toxicity of heavy metals.

Use of unopposed estrogen in women with uteri: prevalence, clinical implications, and economic consequence.

OBJECTIVE: Hormone replacement therapy with estrogen/progestin is the treatment of choice for relieving postmenopausal vasomotor symptoms and preventing urogenital atrophy and osteoporosis in women with intact uteri. However, despite the known increased incidence of endometrial hyperplasia when unopposed estrogen is used in such women, this progestin regimen has not been universally adopted. DESIGN: This study was conducted in a managed care organization to determine the extent of the use of unopposed estrogen in women with intact uteri. Pharmacy claims data for all women 55 years or older with claims for estrogen only from September 1, 1996, to December 31, 1996, were reviewed. A total of 5,209 records were identified, from which 480 were randomly selected. A survey of the members' physicians was then carried out to determine hysterectomy status and was confirmed by chart audit. RESULTS: Thirty-three (11%) of the members identified had not undergone hysterectomy. Follow-up physician contact revealed that five women did not have a uterus. Use of estrogen without opposing progestin was documented in a substantial percentage of files reviewed. It is of concern that with the documentation of the risks of endometrial hyperplasia and carcinoma in the intact uterus, unopposed therapy still occurs. In addition to the clinical costs, there are economic consequences to this practice. An economic model of unopposed estrogen use was created. A management cost of $1,504 for 3 years was estimated. CONCLUSIONS: Further educational efforts are needed to ensure the use of opposed estrogen in the woman with an intact uterus.

Cell ashing for trace element analysis: A new approach based on ultraviolet/ozone.

We studied a new approach to cell ashing based on illuminating the specimens with a low-pressure mercury discharge lamp. We analyzed with synchrotron spectromicroscopy its effects on different physiological elements in neurobiological specimens. Our results demonstrate that carbon is removed, whereas phosphorus, calcium, potassium, and sulfur are retained and their relative concentrations are enhanced. Applied to trace elements, this technique will enhance their practical detectability.

Comparison of two isotope dilution/mass spectrometric methods for determination of total serum cholesterol.

Isotope dilution/mass spectrometric methods for total serum cholesterol, developed separately at the Karolinska Institutet (KI) and the National Bureau of Standards (NBS), were compared by applying them to a common set of serum pools. A search for the cause of a systematic difference of a few percent in results from the two methods revealed that the KI cholesterol standard contained lathosterol, which interfered with the calibration of the method. With NBS Standard Reference Material cholesterol used for new analyses at the KI, the average difference in mean values dropped to 0.2%. The NBS results are more precise. This is attributed to the protocols NBS used for sample preparation and mass spectrometry. However, these protocols make the NBS method more complex and time-consuming. A recent critical article on the use of this technique for total cholesterol is also examined.