Apparent confined placental mosaicism of trisomy 16 and multiple fetal anomalies: case report

Trisomy 16 is frequently found confined to the placenta (confined placental mosaicism (CPM)), with a structurally normal fetus. In some cases of trisomy 16, the fetus has uniparental disomy for chromosome 16 (UPD16) which is associated with intrauterine growth restriction (IUGR) and fetal anomalies. We report a case of apparent confined placental mosaicism for trisomy 16, using standard cytogenetic techniques, but with multiple fetal abnormalities including congenital diaphragmatic hernia in which there was no evidence of UPD in the disomic tissues examined. Subsequent examination of fetal tissues using fluorescent in situ hybridization (FISH) demonstrated low levels of mosaicism for trisomy 16 in all the tissues examined. The use of FISH permits identification of mosaicism which conventional techniques may not identify.

Middle cerebral artery peak systolic velocity in the prediction of fetal anemia

OBJECTIVE

The fetal middle cerebral artery peak systolic velocity (MCA PSV) has been suggested as a potential test to predict the fetal hematocrit level. We tested the hypothesis that a low fetal hematocrit is associated with an increase in MCA PSV in a prospective study of normal and alloimmunized pregnancies.

METHODS

Fetal hematocrit and MCA PSV were obtained in 26 alloimmunized fetuses, immediately before their first fetal blood transfusions between 15 and 35 weeks. Results were compared with the MCA PSVs from 170 control fetuses not at risk of alloimmune anemia between 13 and 37 weeks.

RESULTS

In control fetuses, PSV varied with gestation (PSV = 0.56 - 0.032 GA + 0.00086 GA2, where GA is gestational age; R2 = 0.41). The correlation between PSV and hematocrit Z scores (Pearson correlation coefficient r = -0.69) was highly significant (P = 0.0001). Using a PSV > 1 SD, the sensitivity of the test in predicting a fetal hematocrit < 2 SD below the mean was only 64% but the specificity was 100%. However, the sensitivity of the test in predicting a fetal hematocrit < 3 SD and < 4 SD rose to 73% and 83%, while the specificity was still good (93% and 80% respectively).

CONCLUSIONS

MCA PSV and fetal hematocrit are highly significantly correlated. The sensitivity of the test was good and the high positive predictive value indicates that the presence of a raised PSV (defined as > 1 SD) is a strong indicator of fetal anemia. In conclusion, MCA PSV is a useful test in clinical practice for the detection of fetal anemia.

Transgenic expression of green fluorescent protein in mouse oxytocin neurones

Routine targeting of neurones for expression of exogenous genes would facilitate our ability to manipulate their internal milieu or functions, providing insight into physiology of neurones. The magnocellular neurones of the paraventricular and supraoptic nuclei of the hypothalamus have been the objects of limited success by this approach. Here we report on the placement of the enhanced green fluorescent protein (eGFP) coding sequence at various locations within an oxytocin transgene. Placement within the first exon yielded little to no expression, whereas placement in the third exon (as an in-frame fusion with the carboxyl terminus of the oxytocin preprohormone) resulted in cell-specific expression of eGFP in oxytocin neurones. Furthermore, placement of the eGFP sequence downstream of a picornavirus internal ribosomal entry site (IRES), also in the third exon, allowed expression of the eGFP as a separate protein. Other coding sequences should now be amenable to expression within oxytocin neurones to study their physiology.

Fetal brain activity demonstrated by functional magnetic resonance imaging

Functional magnetic resonance imaging was used to study fetal brain activity. This activity was in response to an auditory stimulus.

The impact of genomics on the search for novel tuberculosis drugs

The emergence of multidrug-resistant strains of Mycobacterium tuberculosis has highlighted the need for new drugs to treat tuberculosis. Drugs that either shorten the overall duration of therapy or that simplify the regimen would significantly improve compliance and hence reduce treatment failure rates. The drug development process begins with identification and validation of specific targets. These may be relevant for inhibiting growth of the bacterium in vitro, and hence yield novel bactericidal agents, or they may be required at other stages of growth, such as survival in host macrophages. With the availability of the complete genome sequence of M. tuberculosis, the primary sequence of every drug target in the pathogen is known. A combination of approaches is being employed to exploit the information contained in the genome and thereafter to identify lead compounds that may yield new drugs.

Radiopharmaceuticals in PET imaging

OBJECTIVE

PET isotopes are being used more commonly in nuclear medicine. This paper introduces the nuclear medicine technologist to the use of PET imaging. The major focus of this article is on the isotopes that are used in this modality and how they differ from traditional isotopes. The nuclear medicine technologist will become familiar with PET isotopes by reading about PET history, the production and availability of PET isotopes, and the use of this modality in a traditional hospital setting.

Creating clinical opportunities in a managed care environment

The Continuum of Care clinical experience was developed to provide future nurses with practice in a managed care environment. Students see how the critical care patient's needs change during the recovery process and assist the patient with the transition to self-care at home. Patient and student evaluations indicate the experience increases students' understanding of the role of the nurse in managed care while facilitating patients' transition to the self-care environment.

Biosynthetic origin of mycobacterial cell wall galactofuranosyl residues

SETTING

Mycobacterial galactofuran is essential to the linking of the peptidoglycan and mycolic acid cell wall layers. Galactofuran biosynthesis should thus be essential for viability.

OBJECTIVE

The objective was to determine the pathway of galactofuranosyl biosynthesis and to clone a gene encoding an essential enzyme necessary for its formation.

DESIGN

Specific enzymatic conversions involved in formation of galactopyranose and galactofuranose residues in other bacteria were tested for in Mycobacterium smegmatis. M. tuberculosis deoxyribonucleic acid (DNA) was identified by homology.

RESULTS

It was shown that the de novo synthesis of the galactose carbon skeleton occurred in M. smegmatis by the transformation of UDP-glucopyranose to UDP-galactopyranose via the enzyme UDP-glucose 4-epimerase (E.C. 5.1.3.2). The N-terminal sequence of this enzyme was obtained after purification. The galactose salvage pathway enzyme, UDP-glucose-galactose-1-phosphate uridylyltransferase (E.C. 2.7.7.12), was also shown to be present. The critical biosynthetic transformation of the galactopyranose to galactofuranose ring form was shown to occur at the sugar nucleotide level via the enzyme UDP-galactopyranose mutase (E.C. 5.4.99.9). The M. tuberculosis DNA encoding this enzyme was sequenced, the gene expressed in Escherichia coli, and the expected enzymatic activity demonstrated.

CONCLUSION

Galactofuranose biosynthesis can now be pursued as a potential drug target in M. tuberculosis.

Improved fluorometric and chromatographic methods for the quantification of fumonisins B(1), B(2) and B(3)

Fumonisins pose serious health risks to humans and livestock, making their detection imperative in foods and feedstuffs. This detection can be accomplished quickly, precisely and accurately in a two-step chromatographic process. In the first step, fumonisins are extracted from a sample and isolated on an immunoaffinity column. In the second step, fumonisins are converted to fluorescent derivatives and quantified either through high-performance liquid chromatography (HPLC) or by fluorometer. These methods offer significant improvements in performance compared to earlier technology: limits of detection as low as 0.016 micrograms/g with HPLC-based detection and 0.25 micrograms/g for fluorometer-based detection; greater assay linearity (with HPLC, r = 0.997; with fluorometer, r = 0.998); larger immunoaffinity column capacity (77% recovery at 12.5 micrograms) and extended assay range (0-10 micrograms/g) for methods. The percentage recovery of fumonisins over the entire assay range averaged 83% for both the fluorometer and HPLC methods. Precision studies were performed for both the fluorometer and the HPLC methods. The average coefficient of variation was 14% for the fluorometer method and 8.3% for the HPLC method. As a result of the efficient separation, the improved HPLC method offers the advantage of precise individual quantification of FB1, FB2 and FB3. The two methods were compared using 33 naturally or artificially contaminated corn samples. Linear regression analysis demonstrated an excellent correlation (r = 0.996) between the two techniques. Higher recoveries of fumonisins were obtained using this HPLC method than with the official AOAC method.

Cutaneous T-cell lymphoma: centuries of controversy

Two hundred years have passed since the description of mycosis fungoides by Alibert. During this time, the disease has been the focus of intense controversy and research, with these two intimately intertwined. In this article, the major components of the controversies surrounding cutaneous T-cell lymphoma are examined. The next millenium will see the resolution of these controversies and the fruition of continued research into this condition.

Stereochemical course of enzymatic enolpyruvyl transfer and catalytic conformation of the active site revealed by the crystal structure of the fluorinated analogue of the reaction tetrahedral intermediate bound to the active site of the C115A mutant of MurA

MurA (UDP-GlcNAc enolpyruvyl transferase), the first enzyme in bacterial peptidoglycan biosynthesis, catalyzes the enolpyruvyl transfer from phosphoenolpyruvate (PEP) to the 3'-OH of UDP-GlcNAc by an addition-elimination mechanism that proceeds through a tetrahedral ketal intermediate. The crystal structure of the Cys115-to-Ala (C115A) mutant of Escherichia coli MurA complexed with a fluoro analogue of the tetrahedral intermediate revealed the absolute configuration of the adduct and the stereochemical course of the reaction. The fluorinated adduct was generated in a preincubation of wild-type MurA with (Z)-3-fluorophosphoenolpyruvate (FPEP) and UDP-GlcNAc and purified after enzyme denaturation. The fluorine substituent stabilizes the tetrahedral intermediate toward decomposition by a factor of 10(4)-10(6), facilitating manipulation of the adduct. The C115A mutant of MurA was utilized to avoid the microheterogeneity that arises in the wild-type MurA from the attack of Cys115 on C-2 of FPEP in competition with the formation of the fluorinated adduct. The crystal structure of the complex was determined to 2.8 A resolution, and the absolute configuration at C-2 of the adduct was found to be 2R. Thus, addition of the 3'-OH of UDP-GlcNAc is to the 2-si face of FPEP, corresponding to the 2-re face of PEP. Given the previous observation that, in D2O, the addition of D+ to C-3 of PEP proceeds from the 2-si face [Kim, D. H., Lees, W. J., and Walsh, C. T. (1995) J. Am. Chem. Soc. 117, 6380-6381], the addition across the double bond of PEP is anti. Also, because the overall stereochemical course has been shown to be either anti/syn or syn/anti [Lees, W. J., and Walsh, C. T. (1995) J. Am. Chem. Soc. 117, 7329-7337], it now follows that the stereochemistry of elimination of H+ from C-3 and Pi from C-2 of the tetrahedral intermediate of the reaction is syn.

The provision of enabling services to higher-risk pregnant women and children in Medicaid managed care

As managed care organizations become the major payer model for the higher-need, higher-risk population of Aid to Families with Dependent Children women and children, they would benefit from looking at lessons learned during the past decade as policy makers and providers struggled to identify less costly, but effective strategies to reduce morbidity and mortality associated with poor birth outcomes. This article discusses the experience of one community in providing enabling services, the opportunity for new partnerships, measuring the outcomes, and the financing of enabling services in a managed care model.

Student Pre-entry Experience and First Year of Employment

BACKGROUND

Student clinical and work-related experiences are available at many healthcare organizations, but little is known about how these experiences contribute to the employer/nurse work relationship that begins after graduation. This study examined the relationship of senior BSN students' past employer experience in describing first-year employer commitment and turnover.

METHODS

The sample was 63 senior BSN students. Experience factors measured included job selection factors, pre- and one-year commitment, organizational climate, employer support, and first-year turnover.

RESULTS

Organizational climate was the experience-related factor most important in explaining first-year commitment.

CONCLUSION

Findings suggest the importance of supportive work environments to new nurses both before and after accepting the first graduate nurse position.

Running exercise may reduce risk for lung and liver cancer by inducing activity of antioxidant and phase II enzymes

The effects of exercise, ethanol, and exercise plus ethanol-treatments on activity of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and UDP-glucuronosyl transferase (UDP-GT) in lung and liver were investigated. All treatments induced SOD and CAT activity in the lung while CAT activity was enhanced only by the combined treatments in the liver. Ethanol reduced hepatic SOD activity, while with the combined treatment SOD was normal. Exercise enhanced UDP-GT activity in liver and lung while ethanol had no effect and GST activity was induced in the liver by the combined treatment. Thus exercise may reduce risk for lung and hepatic cancer and prevent an ethanol-induced increase in risk for hepatic cancer by enhancing activity of antioxidant and phase II enzymes.

Managed bioremediation of soil contaminated with crude oil soil chemistry and microbial ecology three years later

Analysis of samples taken from three experimental soil lysimeters demonstrated marked long-term effects of managed bioremediation on soil chemistry and on bacterial and fungal communities 3 yr after the application of crude oil or crude oil and fertilizer. The lysimeters were originally used to evaluate the short-term effectiveness of managed (application of fertilizer and water, one lysimeter) vs unmanaged bioremediation (one lysimeter) of Michigan Silurian crude oil compared to one uncontaminated control lysimeter. Three years following the original experiment, five 2-ft-long soil cores were extracted from each lysimeter, each divided into three sections, and the like sections mixed together to form composited soil samples. All subsequent chemical and microbiological analyses were performed on these nine composited samples. Substantial variation was found among the lysimeters for certain soil chemical characteristics (% moisture, pH, total Kjeldahl nitrogen [TKN], ammonia nitrogen [NH4-N], phosphate phosphorous [PO4-P], and sulfate [SO4 (-2)]). The managed lysimeter had 10% the level of total petroleum hydrocarbons (TPH-IR) found in the unmanaged lysimeter. Assessment of the microbial community was performed for heterotropic bacteria, fungi, and aromatic hydrocarbon-degrading bacteria (toluene, naphthalene, and phenanthrene) by dilution onto solid media. There was little difference in the number of heterotrophic bacteria, in contrast to counts of fungi, which were markedly higher in the contaminated lysimeters. Hydrocarbon-degrading bacteria were elevated in both oil-contaminated lysimeters. In terms of particular hydrocarbons as substrates, phenanthrene degraders were greater in number than naphthalene degraders, which outnumbered toluene degraders. Levels of sulfate-reducing bacteria seem to have been stimulated by hydrocarbon degradation.

Structure of UDP-N-acetylglucosamine enolpyruvyl transferase, an enzyme essential for the synthesis of bacterial peptidoglycan, complexed with substrate UDP-N-acetylglucosamine and the drug fosfomycin

BACKGROUND

UDP-N-acetylglucosamine enolpyruvyl transferase (MurA), catalyses the first committed step of bacterial cell wall biosynthesis and is a target for the antibiotic fosfomycin. The only other known enolpyruvyl transferase is 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase, an enzyme involved in the shikimic acid pathway and the target for the herbicide glyphosate. Inhibitors of enolpyruvyl transferases are of biotechnological interest as MurA and EPSP synthase are found exclusively in plants and microbes.

RESULTS

The crystal structure of Escherichia coli MurA complexed with UDP-N-acetylglucosamine (UDP-GlcNAc) and fosfomycin has been determined at 1.8 A resolution. The structure consists of two domains with the active site located between them. The domains have a very similar secondary structure, and the overall protein architecture is similar to that of EPSP synthase. The fosfomycin molecule is covalently bound to the cysteine residue Cys115, whereas UDP-GlcNAc makes several hydrogen-bonding interactions with residues from both domains.

CONCLUSIONS

The present structure reveals the mode of binding of the natural substrate UDP-GlcNAc and of the drug fosfomycin, and provides information on the residues involved in catalysis. These results should aid the design of inhibitors which would interfere with enzyme-catalyzed reactions in the early stage of the bacterial cell wall biosynthesis. Furthermore, the crystal structure of MurA provides a model for predicting active-site residues in EPSP synthase that may be involved in catalysis and substrate binding.

Enzymatic synthesis of UDP-galactofuranose and an assay for UDP-galactopyranose mutase based on high-performance liquid chromatography

A method to prepare UDP-galactofuranose (UDP-Galf) free of UDP-galactopyranose (UDP-Galp) is described. The UDP-Galf is synthesized enzymatically from UDP-Galp using the enzyme UDP-galactopyranose mutase. Treatment of UDP-Galp with the enzyme yields an equilibrium mixture of UDP-Galp and UDP-Galf in which UDP-Galf is approximately 7%. In spite of its low yield, the UDP-Galf is readily purified from starting UDP-Galp using a Dionex PA-100 ion exchange HPLC column. The purified UDP-Galf was characterized by chemical degradations, by electrospray mass spectrometry, and by several nuclear magnetic resonance techniques. In addition, an HPLC assay for the enzyme UDP-galactopyranose mutase is presented that requires 0.5 microgram of UDP-Galf per assay and can be used for both qualitative and quantitative measurements of the enzyme activity. These procedures should thus aid in the characterization of the enzymes involved in galactofuranosyl biosynthesis for the cell walls of Mycobacteria, for the lipophosphoglycan of Leishmania, and for other microorganisms where galactofuranosyl residues are found.

Transposition and fusion in the primary dentition: report of case

A case is reported of the fusion and transposition of the maxillary right central and lateral primary incisors. The unerupted permanent successors exhibit anomalies as detailed previously in this paper.

Characterization of a Cys115 to Asp substitution in the Escherichia coli cell wall biosynthetic enzyme UDP-GlcNAc enolpyruvyl transferase (MurA) that confers resistance to inactivation by the antibiotic fosfomycin

The antibiotic fosfomycin inhibits bacterial cell wall biosynthesis by inactivation of UDP-GlcNAc enolpyruvyl tranferase (MurA). Prior work has established that Cys115 of Escherichia coli and Enterobacter cloacae MurA is the active site nucleophile alkylated by fosfomycin and implicated this residue in the formation of a covalent phospholactyl-enzyme adduct derived from substrate, phosphoenolpyruvate (PEP). On the basis of sequencing information from putative MurA homolog from Mycobacterium tuberculosis, we generated a C115D mutant of E. coli MurA that was highly active but fully resistant to time-dependent inhibition by fosfomycin. Fosfomycin still bound to the active site of C115D MurA, as established by the observed reversible competitive inhibition by fosfomycin. Fosfomycin still bound to the active site of C115D MurA, as established by the observed reversible competitive inhibition vs PEP. In contrast to the broad pH-independent behavior of wild-type (WT) MurA, C115D mutant activity titrated across the pH range examined (pH 5.5-9) with an apparent pKa approximately 6, with kcatC115D ranging from approximately 10kcatWT at pH 5.5 to <0.1kcatWT at pH9.0. Km(PEP)115D was relatively constant in the pH range examined and increased approximately 100-fold relative to Km(PEP)WT. A fosfomycin-resistant C115E mutant with -1% activity of the C115D mutant was found to follow a pH dependence similar to that observed for C115D MurA. The contrasting pH dependences of WT and C115D MurA was also observed in the reaction with the pseudosubstrate, (Z)-3-fluorophosphoenolpyruvate, strongly suggesting a role for Cys/Asp115 as the general acid in the protonation of C-3 of PEP during MurA-catalyzed enol ether transfer. The difference in nucleophilicity between the carboxylate side chains of Asp115 and Glu115 and the thiolate group of Cys115 suggests that covalent enzyme adduct formation is not required for catalytic turnover and, furthermore, provides a chemical rationale for the resistance of the C115D and C115E mutants to fosfomycin inactivation.