Warfarin, not direct oral anticoagulants nor antiplatelet therapy, is associated with increased bleeding risk in emergency general surgery patients: implications in this new era of novel anticoagulants: An EAST Multicenter study

INTRODUCTION

To assess perioperative bleeding complications & in-hospital mortality in patients requiring emergency general surgery (EGS) presenting with a history of antiplatelet (AP) vs. direct oral anticoagulant (DOAC) vs warfarin use.

METHODS

Prospective observational study across 21 centers between 2019-2022. Inclusion criteria were age ≥ 18 years, & DOAC, warfarin or AP use within 24 hours of an EGSP. Outcomes included perioperative bleeding and in-hospital mortality. The study was conducted using ANOVA, Chi-square, and multivariable regression models.

RESULTS

Of the 413 patients, 221 (53.5%) reported AP use, 152 (36.8%) DOAC use, & 40 (9.7%) warfarin use. Most common indications for surgery were obstruction (23% (AP), 45% (DOAC), 28% (warfarin)), intestinal ischemia (13%, 17%, 23%), & diverticulitis/peptic ulcers (7%, 7%, 15%). Compared to DOAC use, warfarin use was associated with significantly higher perioperative bleeding complication (OR 4.4 [2.0, 9.9]). There was no significant difference in perioperative bleeding complication between DOAC & AP use (OR 0.7 [0.4, 1.1]). Compared to DOAC use, there was no significant difference in mortality between warfarin use (0.7 [0.2, 2.5]) or AP use (OR 0.5 [0.2, 1.2]). After adjusting for confounders, warfarin use (OR 6.3 [2.8, 13.9]), medical history and operative indication were associated with an increase in perioperative bleeding complications. However, warfarin was not independently associated with risk of mortality (OR 1.3 [0.39, 4.7]), whereas intraoperative vasopressor use (OR 4.7 [1.7, 12.8)), medical history & postoperative bleeding (OR 5.5 [2.4, 12.8]) were.

CONCLUSIONS

Despite ongoing concerns about the increase in DOAC use & lack of readily available reversal agents, this study suggests that warfarin, rather than DOACs, is associated with higher perioperative bleeding complications. However, that risk does not result in an increase in mortality, suggesting that perioperative decisions should be dictated by patient disease & comorbidities rather than type of antiplatelet or anticoagulant use.

Anticoagulation in emergency general surgery: Who bleeds more? The EAST multicenter trials ACES study

BACKGROUND

While direct oral anticoagulant (DOAC) use is increasing in the Emergency General Surgery (EGS) patient population, our understanding of their bleeding risk in the acute setting remains limited. Therefore, the objective of this study was to determine the prevalence of perioperative bleeding complications in patients using DOACs versus warfarin and AP therapy requiring urgent/emergent EGS procedures (EGSPs).

METHODS

This was a prospective observational trial, conducted between 2019 and 2022, across 21 centers. Inclusion criteria were 18 years or older, DOAC, warfarin/AP use within 24 hours of requiring an urgent/emergent EGSP. Demographics, preoperative, intraoperative, and postoperative data were collected. ANOVA, χ 2 , and multivariable regression models were used to conduct the analysis.

RESULTS

Of the 413 patients enrolled in the study, 261 (63%) reported warfarin/AP use and 152 (37%) reported DOAC use. Appendicitis and cholecystitis were the most frequent indication for operative intervention in the warfarin/AP group (43.4% vs. 25%, p = 0.001). Small bowel obstruction/abdominal wall hernias were the main indication for operative intervention in the DOAC group (44.7% vs. 23.8%, p = 0.001). Intraoperative, postoperative, and perioperative bleeding complications and in-hospital mortality were similar between the two groups. After adjusting for confounders, a history of chemotherapy (odds ratio [OR], 4.3; p = 0.015) and indication for operative intervention including occlusive mesenteric ischemia (OR, 4.27; p = 0.016), nonocclusive mesenteric ischemia (OR, 3.13; p = 0.001), and diverticulitis (OR, 3.72; p = 0.019) were associated with increased perioperative bleeding complications. The need for an intraoperative transfusion (OR, 4.87; p < 0.001), and intraoperative vasopressors (OR, 4.35; p = 0.003) were associated with increased in-hospital mortality.

CONCLUSION

Perioperative bleeding complications and mortality are impacted by the indication for EGSPs and patient's severity of illness rather than a history of DOAC or warfarin/AP use. Therefore, perioperative management should be guided by patient physiology and indication for surgery rather than the concern for recent antiplatelet or anticoagulant use.

LEVEL OF EVIDENCE

Prognostic and Epidemiologic; Level III.

Early cognitive impairment is common in pediatric patients following mild traumatic brain injury

INTRODUCTION

The incidence and factors related to early cognitive impairment (ECI) after mild traumatic brain injury (mTBI) in pediatric trauma patients (PTPs) are unknown. Prior data in the adult population demonstrated an ECI incidence of 51% after mTBI and strong correlation with initial Glasgow Coma Scale (GCS) and Brain Injury Guidelines (BIG) category. Therefore, we hypothesized that ECI is common after mTBI in PTPs and associated with initial GCS and BIG category.

METHODS

A single-center, retrospective review of PTPs (age, 8-17 years) from 2015 to 2019 with intracranial hemorrhage and mTBI (GCS score, 13-15) was performed. Primary outcome was ECI, defined as Ranchos Los Amigos score less than 8. Comparisons between ECI and non-ECI groups regarding Injury Severity Score (ISS), demographics, and cognitive and clinical outcomes were evaluated using χ2 statistics and Wilcoxon rank sum tests. Odds of ECI were evaluated using multivariable logistic regression.

RESULTS

From 47 PTPs with mTBI, 18 (38.3%) had ECI. Early cognitive impairment patients had a higher ISS than non-ECI patients (19.7 vs. 12.6, p = 0.003). Injuries involving motor vehicles were more often related to ECI than non-auto-involved mechanisms (55% vs. 15%, p = 0.005). Lower GCS score (odds ratio [OR], 6.60; 95% confidence interval [CI], 1.34-32.51, p = 0.02), higher ISS (OR, 1.12; 95% CI, 1.01-1.24; p = 0.030), and auto-involved injuries (OR, 6.06; 95% CI, 1.15-31.94; p = 0.030) were all associated with increased risk of ECI. There was no association between BIG category and risk of ECI (p > 0.05).

CONCLUSION

Nearly 40% of PTPs with mTBI suffer from ECI. Lower initial GCS score, higher ISS, and autoinvolved mechanism of injury were associated with increased risk of ECI. Brain Injury Guidelines category was not associated with ECI in pediatric patients.

LEVEL OF EVIDENCE

Prognostic study, Level III.

Nerve monitoring decreases recurrent laryngeal nerve injury risk for neoplasm-related thyroidectomy

OBJECTIVE

Conflicting reports exist regarding the benefit of intraoperative neuromonitoring (INM) for patients undergoing thyroidectomy. We hypothesized that in a national sample, the risk of mild and severe RLNi is decreased for patients undergoing neoplasm-related disease (NRD) thyroidectomy with INM compared to patients without INM.

METHODS

The database was queried for patients that underwent total thyroidectomy for NRD with and without INM. A multivariable logistic regression model was used to determine the associated odds of RLNi.

RESULTS

From 6942 patients, 4269 (61.5%) had INM during thyroidectomy. Patients with INM had a similar rate of overall RLNi compared to patients without INM (5.7% vs. 6.6%, p = 0.118). After adjusting for covariates, INM was associated with decreased odds of severe-RLNi (OR 0.23, p = 0.036) but not mild-RLNi (p = 0.16).

CONCLUSION

INM is associated with a nearly 80% decreased associated odds of severe RLNi during thyroidectomy for NRD. Future prospective confirmation is needed, and if confirmed, patients undergoing thyroidectomy for NRD should have INM to reduce the risk of RLNi and its associated morbidity.

An interview study with medical scribes on how their work may alleviate clinician burnout through delegated health IT tasks

OBJECTIVES

To understand how medical scribes' work may contribute to alleviating clinician burnout attributable directly or indirectly to the use of health IT.

MATERIALS AND METHODS

Qualitative analysis of semistructured interviews with 32 participants who had scribing experience in a variety of clinical settings.

RESULTS

We identified 7 categories of clinical tasks that clinicians commonly choose to offload to medical scribes, many of which involve delegated use of health IT. These range from notes-taking and computerized data entry to foraging, assembling, and tracking information scattered across multiple clinical information systems. Some common characteristics shared among these tasks include: (1) time-consuming to perform; (2) difficult to remember or keep track of; (3) disruptive to clinical workflow, clinicians' cognitive processes, or patient-provider interactions; (4) perceived to be low-skill "clerical" work; and (5) deemed as adding no value to direct patient care.

DISCUSSION

The fact that clinicians opt to "outsource" certain clinical tasks to medical scribes is a strong indication that performing these tasks is not perceived to be the best use of their time. Given that a vast majority of healthcare practices in the US do not have the luxury of affording medical scribes, the burden would inevitably fall onto clinicians' shoulders, which could be a major source for clinician burnout.

CONCLUSIONS

Medical scribes help to offload a substantial amount of burden from clinicians-particularly with tasks that involve onerous interactions with health IT. Developing a better understanding of medical scribes' work provides useful insights into the sources of clinician burnout and potential solutions to it.

A national analysis of pediatric firearm violence and the effects of race and insurance status on risk of mortality

OBJECTIVES

To perform a national analysis of pediatric firearm violence (PFV), hypothesizing that black and uninsured patients would have higher risk of mortality.

METHODS

The Trauma Quality Improvement Program (2014-2016) was queried for PFV patients ≤16 years-old. Multivariable logistic regression models on all patients and a subset excluding severe brain injuries were performed.

RESULTS

The PFV mortality rate was 11.2%. 66.5% of PFV patients were black (p < 0.001). Deceased patients were more likely to be uninsured (14.5% vs. 5.3%, p < 0.001). Black race was an associated risk factor for mortality in patients without severe brain injury (OR 5.26, CI 1.00-27.47, p = 0.049) but not for the overall population (OR 1.32, CI 0.68-2.56, p = 0.39).

CONCLUSION

Nearly two-thirds of PFV patients were black. Contrary to previous studies, black and uninsured pediatric patients did not have an increased risk of mortality overall. However, in a subset of patients without severe brain injury, black race was associated with increased mortality risk.

SUMMARY

Between 2014 and 2016 the mortality rate for pediatric firearm violence (PFV) in children 16 years and younger was 11.2%. Although two-thirds of PFV patients were black, black race and lack of insurance were not risk factors of mortality for the overall population. Once patients with severe brain injury were excluded, black race and became associated with an increased risk of mortality.

[Reduced availability of potential cornea donors: reasons and suggestions]

AIM

The purpose of the study was to analyse the number of potential cornea donors in relationship to the number of actual donors. Furthermore, the reasons for the discrepancy between the number of the potential and actual donors were analysed.

METHODS

Over a period of 6 months data were collected from 6 hospitals and the institute for forensic medicine of the university hospital. The reasons why only a few actual donors from a big pool of potential donors remain for transplantation were investigated.

RESULTS

Circumstances related to the medical staff were causal for refusal in 37 % of the cases. In 23 % the cause for refusal was related to the relatives (23 %). Furthermore, in 16 organisational problems caused a failure in cornea donation. 18 % were excluded due to contraindications. A total rate of 6 % actual donors was achieved.

CONCLUSIONS

The final consent rate was only 6 % out of all potential donors. Organisational failure was only 16 % in contrast to 60 % refusal due to causes relating to medical staff and relatives. Therefore, further education of physicians and the public is needed.

Einflussfaktoren auf das Hornhautendothel in Organkultur w�hrend des Transports

PURPOSE

Experiments were performed to evaluate to what extent low temperature and mechanical shock are tolerated by the endothelium of corneal grafts in organ culture.

METHODS

A total of 40 paired corneal grafts were kept in organ culture for 7-28 days at 34.5 degrees C. After this period, the grafts were divided into 8 groups: (A(1)) organ culture at 20 degrees C for 12 h, thereafter organ culture at 34.5 degrees C for 7 days: (A(2)) control for group A(1) maintained at 34.5 degrees C over the whole culture period: (B(1)) organ culture at 10 degrees C for 12 h, thereafter organ culture at 34.5 degrees C for 7 days: (B(2)) control for group B(1) maintained at 34.5 degrees C over the whole culture period: (C(1)) mechanical shock exerted 100 times (>100 g), thereafter organ culture at 34.5 degrees C for 7 days: (C(2)) control for group C(1) maintained at 34.5 degrees C over the whole culture period with no mechanical shock: (D(1)) organ culture at 10 degrees C for 12 h, mechanical shock exerted 100 times (>100 g) and then organ culture at 34.5 degrees C for 7 days: (D(2)) control for group D(1) maintained at 34.5 degrees C over the whole culture period with no mechanical shock. Endothelial evaluation was performed immediately before and at the end of the final culture period.

RESULTS

The following values for loss of endothelial cells were obtained: A(1) 5.7%+/-6.9, A(2) 4.3%+/-15.9, B(1) 10.4%+/-14.4, B(2) 7.2%+/-14.0, C(1) 7.2%+/-6.3, C(2) 0.7%+/-13.4, D(1) 3.7%+/-7.6, D(2) 1.1%+/-7.4.

CONCLUSIONS

According to these experiments, lowering the temperature to 10 degrees C over a period of 12 h and/or mechanical shock above 100 g exerted 100 times did not seem to affect the endothelium of corneal grafts in organ culture.

On the iron-sulfur clusters in the complex redox enzyme dihydropyrimidine dehydrogenase

Porcine liver dihydropyrimidine dehydrogenase is a homodimeric iron-sulfur flavoenzyme that catalyses the first and rate-limiting step of pyrimidine catabolism. The enzyme subunit contains 16 atoms each of nonheme iron and acid-labile sulfur, which are most likely arranged into four [4Fe-4S] clusters. However, the presence and role of such Fe-S clusters in dihydropyrimidine dehydrogenase is enigmatic, because they all appeared to be redox-inactive during absorbance-monitored titrations of the enzyme with its physiological substrates. In order to obtain evidence for the presence and properties of the postulated four [4Fe-4S] clusters of dihydropyrimidine dehydrogenase, a series of EPR-monitored redox titrations of the enzyme under a variety of conditions was carried out. No EPR-active species was present in the enzyme 'as isolated'. In full agreement with absorbance-monitored experiments, only a small amount of neutral flavin radical was detected when the enzyme was incubated with excess NADPH or dihydrouracil under anaerobic conditions. Reductive titrations of dihydropyrimidine dehydrogenase with dithionite at pH 9.5 and photochemical reduction at pH 7.5 and 9.5 in the presence of deazaflavin and EDTA led to the conclusion that the enzyme contains two [4Fe-4S]2+,1+ clusters, which both exhibit a midpoint potential of approximately -0.44 V (pH 9.5). The two clusters are most likely close in space, as demonstrated by the EPR signals which are consistent with dipolar interaction of two S = 1/2 species including a half-field signal around g approximately 3.9. Under no circumstances could the other two postulated Fe-S centres be detected by EPR spectroscopy. It is concluded that dihydropyrimidine dehydrogenase contains two [4Fe-4S] clusters, presumably determined by the C-terminal eight-iron ferredoxin-like module of the protein, whose participation in the enzyme-catalysed redox reaction is unlikely in light of the low midpoint potential measured. The presence of two additional [4Fe-4S] clusters in dihydropyrimidine dehydrogenase is proposed based on thorough chemical analyses on various batches of the enzyme and sequence analyses. The N-terminal region of dihydropyrimidine dehydrogenase is similar to the glutamate synthase beta subunit, which has been proposed to contain most, if not all, the cysteinyl ligands that participate in the formation of the [4Fe-4S] clusters of the glutamate synthase holoenzyme. It is proposed that the motif formed by the Cys residues at the N-terminus of the glutamate synthase beta subunit, which are conserved in dihydropyrimidine dehydrogenase and in several beta-subunit-like proteins or protein domains, corresponds to a novel fingerprint that allows the formation of [4Fe-4S] clusters of low to very low midpoint potential.

Exclusion of the branchio-oto-renal syndrome locus (EYA1) from patients with branchio-oculo-facial syndrome

In addition to craniofacial, auricular, ophthalmologic, and oral anomalies, the distinctive phenotype of the branchio-oculo-facial (BOF) syndrome (MIM 113620) includes skin defects in the neck or infra/supra-auricular region. These unusual areas of thin, erythematous wrinkled skin differ from the discrete cervical pits, cysts, and fistulas of the branchio-oto-renal (BOR) syndrome (MIM 113650). Although the BOF and BOR syndromes are sufficiently distinctive that they should not be confused, both can be associated with nasolacrimal duct stenosis, deafness, prehelical pits, malformed pinna, and renal anomalies. Furthermore, a reported father and son [Legius et al., 1990, Clin Genet 37:347-500] had features of both conditions. It was not clear whether they had an atypical presentation of either BOR or BOF syndrome, or represented a private syndrome. In light of these issues, we selected the BOR locus (EYA1) as a possible gene mutation for the BOF syndrome. In five BOF patients, there were no mutations detected in the EYA1 gene, suggesting that it is not allelic to the BOR syndrome.

Time-dependent variation in weight and body composition in healthy adults

OBJECTIVES

To define the limits of change in body weight and body composition after different time intervals in healthy, normal adults.

METHODS

Prospective and retrospective analyses of paired body composition studies in a total of 326 healthy adults, ages 18 to 97. Measurements included body weight, fat and fat-free mass (FFM) by dual x-ray absorptiometry (DXA) and bioimpedance analysis (BIA), plus body cell mass (BCM) by whole-body counting of 40K and BIA.

RESULTS

Time interval between studies was a significant predictor of the differences in paired studies. The 95% confidence intervals for percent difference were lowest for body weight, intermediate for BCM and FFM, and highest for fat, in part because of the differences in sizes of these body compartments. There were significant associations among the changes in body composition by BIA and by criterion methods, suggesting that the observed changes are real.

CONCLUSIONS

The normal variation in body weight and body composition increases over time. Time-dependent criteria may increase the sensitivity in diagnosing malnutrition. Interpreting changes in body compartments requires consideration of the size of each compartment.

Detection of chromosomal aberrations by a whole-genome microsatellite screen

Chromosomal aberrations are a common cause of multiple anomaly syndromes that include developmental and growth retardation. Current microscopic techniques are useful for the detection of such aberrations but have a limit of resolution that is above the threshold for phenotypic effect. We hypothesized that a genomewide microsatellite screen could detect chromosomal aberrations that were not detected by standard cytogenetic techniques in a portion of these individuals. To test this hypothesis, we performed a genomewide microsatellite screen of patients, by use of a currently available genetic-marker panel that was originally designed for meiotic mapping of Mendelian traits. We genotyped approximately 400 markers on 17 pairs of parents and their children who had normal karyotypes. By using this approach, we detected and confirmed two cases of segmental aneusomy among 11 children with multiple congenital anomalies. These data demonstrate that a genomewide microsatellite scan can be used to detect chromosomal aberrations that are not detected by microscopic techniques.

Validation of bioimpedance analysis as a measure of change in body cell mass as estimated by whole-body counting of potassium in adults

BACKGROUND

The body cell mass (BCM) is an important measure of macronutrient status, but measurements are difficult to obtain outside of sophisticated research laboratories. Bioimpedance analysis (BIA) is a simple technique that holds promise as a means of estimating body composition. The purpose of this study was to evaluate the ability of BIA to estimate changes in BCM as measured by whole body counting of 40K (TBK).

METHODS

Paired studies of BCM, including both TBK and BIA, were compared in 87 human immunodeficiency virus-positive subjects and in 62 healthy, weight-stable control adults. Potential errors in the predictions were examined.

RESULTS

BCM change by TBK and BIA correlated closely (r = .755). After accounting for errors related to repeat measures of TBK, the correlation coefficient was .784, with a standard error of the estimate of 1.24 kg. The differences between predicted and measured BCM change were consistent with a normal distribution. However, there was a systematic error in prediction, with BIA underpredicting the magnitudes of both gains and losses in BCM by TBK.

CONCLUSIONS

BIA is a useful surrogate for measuring changes in BCM in clinical circumstances. Because TBK assesses only intracellular potassium, whereas BIA reflects all intracellular cations, the underprediction of BCM change by BIA compared with TBK could be related to changes in intracellular potassium concentration as a result of malnutrition or its treatment.

Studies of body composition and fat distribution in HIV-infected and control subjects

OBJECTIVE

Recent studies have documented alterations in body fat distribution that have been associated with protease inhibitor therapy. We compared body composition, including measurements of fat distribution, in 96 HIV-infected subjects studied since January 1996 (current HIV), subjects seen prior to January 1996 (previous HIV), and healthy controls.

DESIGN

Retrospective cross-sectional studies of subjects matched by gender, race, age, and height.

METHODS

Body weight, height, body cell mass by whole-body counting of 40K plus fat, fat-free mass, and body fat distribution by anthropometry were measured.

RESULTS

Current HIV men weighed more (p = .025) and had more body cell mass than previous HIV men, but less than controls (p < .001). In women, the between group differences in fat were greater than the differences in body cell mass. Current and previous HIV study subjects had lower indices of subcutaneous and higher indices of visceral fat than controls. In current HIV subjects, body fat distribution was significantly associated with log plasma HIV RNA content but not with antiretroviral or protease inhibitor usage, nor with CD4+ lymphocyte counts. In 7 of 9 current HIV subjects studied, 24-hour urinary free cortisol excretion was abnormally high.

CONCLUSIONS

Alterations in body fat distribution are a characteristic feature in HIV infection. The occurrence of increased visceral fat content and decreased subcutaneous fat content preceded the era of combination antiretroviral therapy. The alteration in fat distribution may be affected by plasma HIV RNA content rather than antiretroviral or protease-inhibitor therapy. The body composition alterations might be associated with endogenous hypercortisolism.

Porcine recombinant dihydropyrimidine dehydrogenase: comparison of the spectroscopic and catalytic properties of the wild-type and C671A mutant enzymes

Dihydropyrimidine dehydrogenase catalyzes, in the rate-limiting step of the pyrimidine degradation pathway, the NADPH-dependent reduction of uracil and thymine to dihydrouracil and dihydrothymine, respectively. The porcine enzyme is a homodimeric iron-sulfur flavoprotein (2 x 111 kDa). C671, the residue postulated to be in the uracil binding site and to act as the catalytically essential acidic residue of the enzyme oxidative half-reaction, was replaced by an alanyl residue. The mutant enzyme was overproduced in Escherichia coli DH5alpha cells, purified to homogeneity, and characterized in comparison with the wild-type species. An extinction coefficient of 74 mM-1 cm-1 was determined at 450 nm for the wild-type and mutant enzymes. Chemical analyses of the flavin, iron, and acid-labile sulfur content of the enzyme subunits revealed similar stoichiometries for wild-type and C671A dihydropyrimidine dehydrogenases. One FAD and one FMN per enzyme subunit were found. Approximately 16 iron atoms and 16 acid-labile sulfur atoms were found per wild-type and mutant enzyme subunit. The C671A dihydropyrimidine dehydrogenase mutant exhibited approximately 1% of the activity of the wild-type enzyme, thus preventing its steady-state kinetic analysis. Therefore, the ability of the C671A mutant and, for comparison, of the wild-type enzyme species to interact with reaction substrates, products, or their analogues were studied by absorption spectroscopy. Both enzyme forms did not react with sulfite. The wild-type and mutant enzymes were very similar to each other with respect to the spectral changes induced by binding of the reaction product NADP+ or of its nonreducible analogue 3-aminopyridine dinucleotide phosphate. Uracil also induced qualitatively and quantitatively similar absorbance changes in the visible region of the absorbance spectrum of the two enzyme forms. However, the calculated Kd of the enzyme-uracil complex was significantly higher for the C671A mutant (9.1 +/- 0.7 microM) than for the wild-type dihydropyrimidine dehydrogenase (0.7 +/- 0.09 microM). In line with these observations, the two enzyme forms behaved in a similar way when titrated anaerobically with a NADPH solution. Addition of an up to 10-fold excess of NADPH to both dihydropyrimidine dehydrogenase forms led to absorbance changes consistent with reduction of approximately 0.5 flavin per subunit, with no indication of reduction of the enzyme iron-sulfur clusters. Absorbance changes consistent with reduction of both enzyme flavins were obtained by removing NADP+ with a NADPH-regenerating system. On the contrary, the two enzyme species differed significantly with respect to their reactivity with dihydrouracil. Addition of dihydrouracil to the wild-type enzyme species, under anaerobic conditions, led to absorbance changes that could be interpreted to result from both partial flavin reduction and the formation of a complex between the enzyme and (dihydro)uracil. In contrast, only spectral changes consistent with formation of a complex between the oxidized enzyme and dihydrouracil were observed when a C671A mutant enzyme solution was titrated with this compound. Furthermore, enzyme-monitored turnover experiments were carried out anaerobically in the presence of a limiting amount of NADPH and excess uracil with the two enzyme forms in a stopped-flow apparatus. These experiments directly demonstrated that the substitution of an alanyl residue for C671 in dihydropyrimidine dehydrogenase specifically prevents enzyme-catalyzed reduction of uracil. Finally, sequence analysis of dihydropyrimidine dehydrogenase revealed that it exhibits a modular structure; the N-terminal region, similar to the beta subunit of bacterial glutamate synthases, is proposed to be responsible for NADPH binding and oxidation with reduction of the FAD cofactor of dihydropyrimidine dehydrogenase. The central region, similar to the FMN subunit of dihydroorotate dehydrogenases, is likely to harbor the site o

Secondary tritium and solvent deuterium isotope effects as a probe of the reaction catalyzed by porcine recombinant dihydropyrimidine dehydrogenase

Dihydropyrimidine dehydrogenase catalyzes the rate-limiting step in the degradation of pyrimidines in mammals, the reduction of uracil or thymine to their 5,6-dihydro derivatives. The reduction of uracil by enzyme-bound reduced flavin involves both proton and hydride transfer. In order to determine whether hydride and proton transfer occur in a concerted or stepwise fashion, and to determine the nature of the transition state for the reduction, secondary tritium kinetic isotope effects were measured in H2O and D2O. The tritium isotope effect using 5-3H-uracil is 0.90 +/- 0.03 in H2O and becomes more inverse, 0.85 +/- 0.04, in D2O. Data are interpreted in terms of a stepwise reduction at C-6 followed by protonation at C-5. A late transition state is proposed for the proton transfer at C-5 of uracil.

Purification, characterization, and kinetics of porcine recombinant dihydropyrimidine dehydrogenase

Porcine recombinant dihydropyrimidine dehydrogenase was purified from Escherichia coli cells using cell disruption, ammonium sulfate fractionation, and chromatography on DEAE-cellulose and 2',5'-ADP-Sepharose. The yield was 60% with a specific activity of 14 units/mg protein. On SDS/PAGE the purified dehydrogenase exhibits a single band, indicating that no proteolytic degradation was taking place during purification. In agreement with the native enzyme, all cofactors, FMN, FAD, NADPH, and two iron-sulfur clusters, have been found. EPR spectra of the reduced dehydrogenase obtained at pH 9.5 are characteristic for two [4Fe-4S]1+ cubanes in dipolar interaction. Quantification of the observed signals indicated 0.95 spins per subunit, showing only partially reduced iron-sulfur clusters. The kinetic parameters of the porcine recombinant enzyme are very similar to those of the native enzyme. Thus, it can be concluded that the porcine recombinant enzyme behaves like the native dehydrogenase.

Purification and characterization of dihydropyrimidine dehydrogenase from Alcaligenes eutrophus

Dihydropyrimidine dehydrogenase from Alcaligenes eutrophus was purified to homogeneity using ammonium sulfate fractionation and chromatography on phenyl-Sepharose, MonoQ-Sepharose, and 2,5-ADP-Sepharose. The enzyme is a homotetramer with a subunit molecular mass of 52 kDa. The absorption spectrum of the bacterial dihydropyrimidine dehydrogenase has maxima in the 300- and 400-nm region, suggesting a flavoprotein. The enzyme contains 4 mol FMN, about 24 mol iron and acidlabile sulfide per mole of protein, implying a flavoprotein with FeS centers. The bacterial dehydrogenase is NADPH dependent with B-side stereospecificity. The initial velocity patterns of the bacterial dehydrogenase together with isotope exchange at equilibrium and a quantitative analysis of the product and dead-end inhibition data suggest a rapid equilibrium random kinetic mechanism, which is in contrast to results obtained for dihydropyrimidine dehydrogenase from pig liver. The pig liver enzyme adheres to a nonclassical two-site ping-pong kinetic mechanism [B. Podschun, P. F. Cook, and K. D. Schnackerz (1990) J. Biol. Chem. 265, 12966-12972], whereas for the bovine enzyme a rapid equilibrium random kinetic mechanism was proposed based on steady-state kinetic data [D. J. T. Porter and T. Spector (1993) J. Biol. Chem. 268, 19321-19327].

Detection of a subtle rearrangement of chromosome 22 using molecular techniques

Conventional cytogenetics is a useful clinical tool that has a lower limit of sensitivity of 2-5 Mb for detection of duplications or deletions. Because the threshold of clinically significant aneusomy is below this range, there is a need for approaches to improve the sensitivity of the detection of aneusomy. We have implemented a system of screening for subtle unbalanced translocations in children with multiple congenital anomalies of unknown cause. Our approach uses subtelomeric microsatellite markers to detect small areas of segmental aneusomy due to unbalanced translocations. Herein we report a patient with severe multiple congenital anomalies and a normal karyotype who was diagnosed by this approach. Microsatellite markers from 41 telomeres were analyzed and were normal with the exception of those on distal chromosome 22. Further analysis with additional microsatellites and fluorescent in situ hybridization confirmed duplication of 22q13.2-qter. We conclude that microsatellite screening can detect subtle unbalanced translocations in children with severe anomalies.

Further delineation of the branchio-oculo-facial syndrome

We review 43 patients (15 new, 28 literature) with the branchio-oculo-facial (BOF) syndrome, which has a distinctive phenotype ranging from mild to severe forms, consisting of eye, ear, oral, and craniofacial anomalies. Virtually ubiquitous and possibly pathognomonic are the cervical/infra-auricular skin defects. Much less common are supra-auricular defects occurring as isolated anomalies or with cervical defects. Regardless of location, these lesions may have aplastic, "hemangiomatous," or otherwise abnormal overlying skin, and draining sinus fistulae. Renal malformations are frequent, but congenital heart and central nervous system defects are rare. Psychomotor performance is usually normal, but development delays, hypotonia, and visual, hearing, and speech problems are common. Autosomal dominant inheritance seems likely. Overlap between the BOF and branchio-otorenal syndromes has been observed, but elucidation of its molecular basis is not yet available. This article also discusses 5 patients with atypical manifestations considered to be possibly affected or probably unaffected, who are sufficiently unusual to be excluded from the final data analysis.

Prenatal diagnosis of Pallister-Killian syndrome: resolution of cytogenetic ambiguity by use of fluorescent in situ hybridization

We report a case of Pallister-Killian syndrome initially diagnosed prenatally as tetrasomy 21. A 33-year-old primiparous woman was noted at 24 weeks' gestation to have moderate polyhydramnios. Ultrasonography showed diminished fetal stomach filling, hydronephrosis, and prominence of the cisterna magna. Cytogenetic analysis of cultured amniocytes was initially interpreted as mosaic tetrasomy 21: 46,XX/47,XX,+i(21q). The patient was then referred to our centre for genetic counselling. At 34 weeks' gestation, a dysmorphic infant was delivered and died within 30 min. Physical features were consistent with the Pallister-Killian syndrome. Renal, gastrointestinal, and central nervous system anomalies were found at post-mortem examination. Analysis of peripheral lymphocytes revealed 5 per cent of cells with a marker chromosome, while 92 per cent of cultured fibroblasts had this same marker. Fluorescent in situ hybridization (FISH) using an alpha-satellite probe for chromosomes 13 and 21 failed to hybridize to the marker, while a chromosome 12 centromeric probe unequivocally identified it as an i(12p). Use of FISH can provide rapid, specific prenatal diagnosis of ambiguous marker chromosomes and improve prenatal counselling.

Psychiatric disability associated with the fragile X chromosome

Fragile X (or Martin-Bell) syndrome, a common, genetic, mental retardation disorder is increasingly being recognized as a major cause of cognitive disability and psychiatric illness in boys. Here, we present a study in which relatives in 4 generations of a large family with the fra(X) chromosome were given comprehensive psychiatric evaluations in order to further describe the psychopathology associated with this condition. Three of 4 males with the fra(X) chromosome were found to have autistic behavior. An adult fra(X) male had a chronic schizoaffective disorder and mental retardation. In female relatives, a relationship was found between the fra(X) carrier status and psychopathology including schizoaffective and major affective disorders.