Demographics and characteristics of leadership at allergy and immunology fellowships in the U.S. as of 2022.

Background: The subspecialty of allergy and immunology (AI) has grown tremendously since the first fellowship programs were developed nearly 80 years ago; however, there is little information with regard to the demographic characteristics and trends in training of fellowship directors (FDs). Objective: Our goal was to analyze the demographic characteristics and pathways in training that have led FDs to advance in the field and train the next generation of allergists and immunologists. Methods: We created a list of all current AI fellowship programs and FDs within the United States. Specific biographical, training, and research information was collected via an Internet search and questionnaire responses. The data were recorded and analyzed in a spreadsheet and unpaired t-tests were performed between male versus female groups for H - index comparison to establish if there was a statistically significant difference. Results: There were 84 total AI fellowship programs with 84 FDs. Forty-one FDs (48.8%) were men and 43 FDs (51.2%) were women; mean age was 51.1 years; and the average age at appointment for men was 45.7 years and for women was 41.4 years, with a statistically significant difference (p = 0.02). Self-reported race and ethnicity (77.4% response rate [n = 65]) were as follows: 55.4% white (n = 36), 23.1% Asian (n = 15), 6.2% biracial (n = 4), 7.7% Middle Eastern (n = 5), 4.6% Hispanic (n = 3), and 3.1% Black (n = 2). The average Hirsch-index (h-index) for FDs was 14.2, with an average of 42.1 publications and 1532.2 citations. The difference between the h-index for the men and for the women was statistically significant, being 17.8 and 11.2 respectively, with p = 0.0143. Conclusion: In AI FDs, women were adequately represented, and men and women were hired at similar ages. There was a statistically significant difference in research output (estimated by the h-index) between men and women. This suggests that research output did not limit women in being appointed as FDs.

Time from hospital presentation to head imaging in White, Black, and Hispanic geriatric trauma patients.

BACKGROUND: Health care disparities have been shown to negatively affect non-White people sustaining traumas, leading to increased morbidity and mortality. One possible explanation could be delays in emergent medical care. This study aims to assess if a disparity between races exists amongst acutely head-injured geriatric patients, as evidenced by the time it takes from emergency department (ED) presentation to performance of head computerized tomography (CT) imaging. METHODS: A prospective cohort study was conducted from August 15, 2019 to August 14, 2020 at the two trauma centers in a south Florida county covering 1.5 million residents. Patients aged ≥ 65 years who sustained a head injury were identified daily. Patients who had a head injury >24 h prior, sustained penetrating trauma, or were transferred from another hospital were excluded. The primary outcome was time measured between ED presentation and CT head performance. Patients were grouped by race as selected from White, Black, Hispanic, and other. Comparisons were made using ANOVA analysis. RESULTS: 4878 patients were included. 90% were White. The mean times to CT head were 90.3 min for White patients, 98.1 min for Black patients, and 86.6 min for Hispanic patients. There was a significant difference comparing time to CT between the three groups (F = 2.892, p = 0.034). Comparing each group to a combined others, there were no significant differences for White vs non-White (90.3 vs 91.3, F = 0.154, p = 0.695) or Hispanic vs non-Hispanic (86.6 vs 90.5, F = 0.918, p = 0.338); however Black vs non-Black (98.1 vs 89.9, F = 4.828, p = 0.028) was significant. CONCLUSIONS: Geriatric Black patients who sustained head trauma were found to have a longer time from ED presentation to performance of head CT than their non-Black counterparts.

Quimioterapia Neoadyuvante en Tumores Luminales Experiencia del Hospital Oncológico Marie Curie / Neoadjuvant Chemotherapy in Luminal Tumors Experience of the Marie Curie Cancer Hospital

Introducción La quimioterapia neoadyuvante (QTn) es una herramienta de uso cada vez más frecuente en el tratamiento del cáncer de mama. su repercusión es objetivada a partir de parámetros clínicos (examen físico y estudios por imagen) y parámetros anatomo-patológicos sobre la pieza quirúrgica. Existe variabilidad en el impacto de la Qt según el subtipo molecular. Este estudio evalúa el grado de respuesta (clínica y patológica) a la QTn de las pacientes con cáncer de mama subtipo luminal y la tasa de cirugías conservadoras en este subgrupo. Objetivo Describir la tasa de respuesta clínica y patológica obtenida en el subgrupo de pacientes luminales y evaluar la tasa de conversión a cirugía conservadora luego del tratamiento neoadyuvante. Material y método Se analizaron 220 historias clínicas pertenecientes a pacientes que realizaron neoadyuvancia en el periodo 2014-2017 en el Servicio de Patología Mamaria del Hospital Oncológico Marie Curie. Se incluyeron 78 pacientes con diagnóstico de carcinoma invasor subtipo luminal A y B, Her 2 negativas. Se evaluó la tasa de respuesta clínica, patológica y la tasa de cirugía conservadora. Resultados Se clasificaron como Luminal A el 26.9% (n=21) de las 78 pacientes, y Luminal B el 73.1% (n=57). La distribución por tamaño tumoral fue: T1 en el 1.25% (n= 1); T2 en 46.1% (n= 36); T3 en 37.2% (n=29) y T4 en el 15.4% (n=12) de los casos. No presentaban compromiso axilar (N0) el 24.3% de las pacientes (n=19), y se vio afectación ganglionar el 75.5 % (n= 59). El Estadio clínico más frecuente fue el III A (32% = 25 pacientes). El 60.3% (47 pacientes) de los casos tenía indicación de mastectomía de inicio y el 39.7% (41 pacientes) eran candidatas a cirugía conservadora. Posterior a la quimioterapia, se indicaron cirugías conservadoras en el 52.6 % (n=41) y mastectomía en el 47.4% (n=37), con una tasa de conversión a cirugía conservadora del 24.4%. La respuesta clínica completa fue del 28.2% (n=22) y la respuesta patológica completa del 16.6%. Conclusión Se observó una respuesta clínica y patológica acorde a la experiencia de otros centros, sobre todo en el subtipo luminal B, con una alta tasa de conversión a cirugía conservadora del 24.4%. Esto nos permite considerar la quimioterapia neoadyuvante como una opción de tratamiento válida para aquellas pacientes con cáncer de mama subtipo luminal B- Her 2 negativa.

Introduction Neoadjuvant chemotherapy (QTn) is a tool that is increasingly used in the treatment of breast cancer. its repercussion is objectified based on clinical parameters (physical examination and imaging studies) and anatomo-pathological parameters on the surgical specimen. There is variability in the impact of Qt according to the molecular subtype. This study evaluates the degree of response (clinical and pathological) to the QTn of patients with luminal subtype breast cancer and the rate of conservative surgeries in this subgroup. Objective To describe the clinical and pathological response rate in the subgroup of luminous patients and to evaluate the conversion rate in a conservative surgery after neoadjuvant treatment. Material and method We will analyze 220 clinical records belonging to patients that developed during the 2014-2017 period in the Breast Pathology Service of the Marie Curie Oncology Hospital. We included 78 patients with a diagnosis of invasive carcinoma luminal subtype A and B, their 2 negative. The clinical and pathological response rate and the rate of conservative surgery in each group were evaluated. Results Luminal A was classified as 26.9% (n = 21) of the 78 patients, and Luminal B was 73.1% (n = 57). The distribution by tumor size was: T1 at 1.25% (n = 1); T2 at 46.1% (n = 36); T3 in 37.2% (n = 29) and T4 in 15.4% (n = 12) of the cases. There is no axillary involvement (N0) in 24.3% of the patients (n = 19), and the ganglion was affected 75.5% (n = 59). The most frequent clinical stage was III A (32% = 25 patients). Sixty-three percent (47 patients) of the cases had an initial mastectomy indication and 39.7% (41 patients) were candidates for conservative surgery. After chemotherapy, conservative surgeries were indicated in 52.6% (n = 41) and mastectomy in 47.4% (n = 37), with a conversion rate to conservative surgery of 24.4%. The complete clinical response was 28.2% (n = 22) and the complete pathological response was 16.6%. Conclusion A clinical and pathological response was observed according to the experience of other centers, especially in luminal subtype B, with a high conversion rate to conservative surgery of 24.4%. This allows us to consider neoadjuvant chemotherapy as a valid treatment option for those patients with luminal B-Her 2 negative breast cancer.

The association of plasma fatty acids with prostate cancer risk in Nigerians.

PURPOSE: To investigate the role of fatty acids (FAs) in prostate cancer (PCa) risk in Nigeria, a country in transition to westernized diet high in animal fats, and currently experiencing rising rates of prostate cancer. METHODS: Men > or =40 years were recruited from surgery/urology clinics, University of Benin Teaching Hospital and from 2 rural and 2 urban communities. Personal information, urological symptom history and anthropometrics were recorded, digital rectal examination performed, and 30 mLs of fasting blood collected for prostatic specific antigen and fatty acid (FA) analysis. Odds ratio (OR) of PCa risk was determined by unconditional logistic regression with the plasma FA 1st quartile as reference, controlling for age, education, waist-to-hip ratio, and family history. RESULTS: Mean ages for 66 (22.6%) cases and 226 (77.4%) controls were 71.9+/-11.47 and 56.7+/-12.69 years, P<.001, and median (25th, 75th percentile) fasting plasma FA were 2,447 (2,087, 3,024) and 2,373 (2,014, 2,751) microg/mL, respectively. PCa risk trend was observed for total omega-6 FA, adjusted ORQ3vs.Q1 2.33 (95% CI, 0.77-7.07), P<0.05. Unadjusted ORQ4vs.Q1 for behenic and nervonic acids were 2.79 (95% CI, 1.27-6.10) and 2.40 (95% CI, 1.19-4.85), and unadjusted ORQ2vs.Q1 for erucic and arachidonic acids were 4.20 (95% CI, 1.79-9.82) and 3.81 (95% CI, 1.50-9.70) respectively. Unadjusted ORQ2vs.Q1 for omega-3 FAs eicosapentaenoic (EPA) and docosapentaenoic (DPA) were 0.39 (95% CI, 0.18-0.85) and 0.79 (95% CI, 0.35-1.79) respectively. CONCLUSIONS: In this population with high total plasma omega-3, we observed modest positive PCa risk trend with total plasma omega-6 (2.3), inverse risk reduction with EPA (0.4), and strong positive risk associations with behenic (2.8), erucic (4.2), and nervonic (2.4) acids. Total plasma omega-6 is highest in the educated high-income group. These findings should be confirmed in a larger study because of the potential serious implication of dietary transition particularly in a region designated as low-incidence for PCa.

Preoperative chemoradiation and flap reconstruction provide high local control and low wound complication rates for patients undergoing limb salvage surgery for upper extremity tumors.

BACKGROUND AND OBJECTIVES: Neoadjuvant protocols in the management of upper extremity sarcoma have improved local control rates but have been associated with high complication rates. We present a refinement of the Eilber protocol using judicious preoperative chemoradiation, limb salvage surgery, and flap coverage to achieve high local control rates with acceptable wound healing complications. METHODS: Patients presenting with upper extremity neoplasms from 1986 to 2002 were treated with a modified Eilber protocol, consisting of 3 days of adriamycin (30 mg/day) and sequential radiotherapy (300 cGy/day for 10 days). Limb salvage surgery with flap coverage where needed was performed 4-8 weeks later. Patients were followed prospectively for recurrence. RESULTS: Fifty-three consecutive patients with upper extremity tumors were treated and followed for a mean of 6.1 years. This cohort included 44 sarcomas and nine non-metastasizing, locally aggressive tumors. There were two local recurrences (3.8%). Limb salvage was achieved in all patients. Flaps were required in 43.4% of patients. Major complications occurred in 11%, were all flap related (partial flap loss, venous congestion), and went on to heal promptly with treatment. CONCLUSION: This modified Eilber protocol achieved 96% local control for upper extremity tumors with a wound complication rate of 11%. The liberal use of flaps of resulted in healed, stable wounds in all patients.

Clinical significance of the RT-PCR positive sentinel node in melanoma.

BACKGROUND: The clinical relevance of RT-PCR positivity for melanoma markers in the sentinel node remains controversial. Our purpose was to determine whether patients with a histologically negative but RT-PCR positive node were at an increased risk for recurrence than their RT-PCR negative counterparts. METHODS: Thirty-nine adult patients underwent sentinel node biopsies for melanoma between 1998 and 2000. Each sentinel node was bivalved. Half was serially sectioned and examined by routine hematoxylin and eosin (H&E) and immunohistochemistry (IHC; S100, HMB-45, melanA, and tyrosinase). The other half was analyzed by a nested RT-PCR assay for tyrosinase. RESULTS: Patients were followed for recurrence with a mean follow-up of 71.1 months. The odds ratio of recurrence for RT-PCR positive versus RT-PCR negative patients was 1.39 (0.34, 5.62; p = 0.73). Within the histology negative subgroups, the risk of recurrence in the RT-PCR positive group (26.7%) was not significantly different from the risk of recurrence in the RT-PCR negative group (22.2%) (p = 0.33 chi-squared). RT-PCR of the sentinel node was not a predictor for recurrence on multivariate analysis (p = 0.65). CONCLUSION: Sentinel node RT-PCR positivity did not risk stratify histologically negative melanoma patients beyond routine pathologic examination in this series.

Autologous diaphragm reconstruction with the pedicled latissimus dorsi flap.

The latissimus dorsi (LD) muscle has been previously described to repair diaphragmatic defects, but as a "reverse" flap, relying on secondary blood supply from the perforating lumbar vessels rather than primary inflow from the dominant thoracodorsal artery. We report resection of a retroperitoneal synovial sarcoma, with reconstruction of the hemidiaphragm using the LD rotated on its primary neurovascular bundle. By using the dominant pedicle, the vascularity of the flap is improved, minimizing the chance of flap tip loss. Maintaining an intact nerve supply prevents atrophy. As the distal origin of the LD is broad and flat, it is ideally suited for diaphragm repair. A latissimus-sparing thoracotomy incision is required to enable this method of diaphragm reconstruction.

Ever deeper and wider: incorporating sustainability into a practitioner oriented engineering curriculum.

Whilst valuable debates about how best to plan, promote, and evaluate sustainable futures for our communities are conducted by governments and NGOs at global gatherings, there is an equal, and possibly more pressing, need to inspire and equip engineering graduates with the means to design and implement the required solutions. However, incorporation of sustainability as a subject into existing syllabi is problematic, primarily because of the need for students to acquire both holistic and context specific skills. This contribution first considers the reasons why we should be concerned with the integration of sustainability concepts into graduate and post-graduate curricula. We then go on to discuss the significance of cross-disciplinary thinking and skills as a key element of sustainability relevant knowledge. Finally, we report the design and deployment, within a water engineering degree course, of a post-graduate module in "Process design for sustainability". The implications of our experiences for the theory and practice of engineering education are examined and suggestions made concerning best practice.

Lateralisation of language function in young adults born very preterm.

OBJECTIVE: To explore, using functional magnetic resonance imaging (MRI), the functional organisation of phonological processing in young adults born very preterm. SUBJECTS: Six right handed male subjects with radiological evidence of thinning of the corpus callosum were selected from a cohort of very preterm subjects. Six normal right handed male volunteers acted as controls. METHOD: Blood oxygenation level dependent contrast echoplanar images were acquired over five minutes at 1.5 T while subjects performed the tasks. During the ON condition, subjects were visually presented with pairs of non-words and asked to press a key when a pair of words rhymed (phonological processing). This task alternated with the OFF condition, which required subjects to make letter case judgments of visually presented pairs of consonant letter strings (orthographic processing). Generic brain activation maps were constructed from individual images by sinusoidal regression and non-parametric testing. Between group differences in the mean power of experimental response were identified on a voxel wise basis by analysis of variance. RESULTS: Compared with controls, the subjects with thinning of the corpus callosum showed significantly reduced power of response in the left hemisphere, including the peristriate cortex and the cerebellum, as well as in the right parietal association area. Significantly increased power of response was observed in the right precentral gyrus and the right supplementary motor area. CONCLUSIONS: The data show evidence of increased frontal and decreased occipital activation in male subjects with neurodevelopmental thinning of the corpus callosum, which may be due to the operation of developmental compensatory mechanisms.

Resistance to disruption and gapping of peripheral nerve repairs: an in vitro biomechanical assessment of techniques.

One potential cause of suboptimal results after nerve repair is disruption or gapping of the neurorrhaphy in the postoperative period. This study assesses the biomechanical strength of five nerve repair techniques: fibrin glue, simple epineurial sutures, and three other novel neurorrhaphy methods. Fifty rabbit sciatic nerve segments were divided and repaired utilizing one of five different methods, producing five groups of ten specimens. Fibrin glue and four epineurial suture techniques (simple, horizontal mattress, "Tajima," "Bunnell") were employed. Repaired nerve segments were ramp-loaded to failure on an Instron 8300 materials-testing machine at a displacement rate of 5 mm/min. Gapping at the repair site was captured using high-resolution video. Differences among the five groups were assessed for significance using ANOVA and Fisher's protected least squares differences post-hoc testing. The mean force to produce disruption was higher for mattress suture repairs relative to simple repairs, but not significantly so (p = 0.31). Both were significantly stronger than fibrin glue repairs (p < 0.0001). "Tajima" and "Bunnell" repairs were both statistically stronger than glue (p < 0.0001), simple (p < 0.0001), or mattress (p = 0.0004) repairs, but not significantly different from one another (p = 0.48). Data for gapping at the repair site were similar with all suture techniques outperforming fibrin glue (p = 0.003). "Bunnell" repairs demonstrated the most resistance to gapping, compared to glue (p < 0.0001), simple (p = 0.0001), mattress (p = 0.007) and "Tajima" repairs (p = 0.01). These data demonstrate that repairs done utilizing fibrin glue are significantly weaker than all types of suture repairs. Two novel techniques for nerve repair (epineurial "Tajima" and "Bunnell") are significantly more resistant to disruption and gapping. Further evaluation to assess the effect of these repair techniques on function is required.

Tensile strength of healing peripheral nerves.

Although the time required for a nerve to gain sufficient strength to withstand normal physiologic forces of joint motion is unknown, typically nerve repairs are protected up to 3 weeks postoperatively. The authors investigated the mechanical strength of a nerve repair as a function of time. Fifty adult Sprague-Dawley rats underwent sciatic nerve division and repair, and were sacrificed in groups of 10 at 0, 1, 2, 4, and 8 weeks. Repaired nerves were then mechanically loaded at 5 mm/min to failure. Gapping across the repair site was captured on high-resolution video. The contralateral sciatic nerve served as a control. A significant increase in tensile strength was gained between 0 and 1 week and between 2 and 4 weeks. Healing nerves achieved 63 percent of the strength of the control by 8 weeks. Controls showed no gain in strength over the testing period. Gapping occurred at lower forces at all time increments. From 0 to 1 week, a significant increase in load necessary to produce gapping was found, which did not increase significantly again until 8 weeks. These results may have implications for postoperative rehabilitation protocols in patients with nerve injuries.

Vacuum-assisted wound closure: a new approach to spinal wounds with exposed hardware.

STUDY DESIGN: The use of vacuum-assisted therapy to close upper thoracic and thoracolumbar spinal wounds was studied retrospectively. Two patients whose wounds failed conservative management were successfully treated by negative pressure therapy. OBJECTIVES: The authors evaluated the efficacy of applying vacuum therapy on patients with exposed spinal hardware and summarized current knowledge about this treatment. SUMMARY OF BACKGROUND DATA: Vacuum therapy was applied three times on two patients. METHODS: Success was defined as a stable, closed wound that required no future surgery and had no signs of chronic infection. RESULTS: Both patients' wounds were closed successfully and have received follow-up treatment for up to 10 months with no sign of recurrence. CONCLUSIONS: The cases illustrate the usefulness of vacuum-assisted therapy as an adjunct in closing complex back wounds with exposed spinal hardware. In the authors' experience, it helps establish a soft tissue envelope for wound healing and simplifies the need for future surgery.

Overwintering of codling moth (Lepidoptera: Tortricidae) larvae in apple harvest bins and subsequent moth emergence.

Codling moths, Cydia pomonella (L.), have long been suspected of emerging from stacks of harvest bins in the spring and causing damage to nearby apple and pear orchards. With increased use of mating disruption for codling moth control, outside sources of infestation have become more of a concern for growers using pheromone based mating disruption systems. Studies were designed to provide information on bins as a source of codling moth and the pattern of codling moth emergence from stacks of bins. In these studies, codling moth larvae colonized wood harvest bins at a much higher frequency than harvest bins made of injection molded plastic (189 moths emerged from wood compared with five from plastic). There was no statistical difference in the number of moths infesting bins that had been filled with infested fruit compared with bins left empty at harvest. This suggests that codling moth enter the bins during the time that the bins are in the orchard before harvest. Emergence of laboratory reared adult codling moth from wood bins placed in stacks was found to be prolonged compared with field populations. Temperature differences within the bin stacks accounted for this attenuated emergence pattern. Covering bin stacks with clear plastic accelerated codling moth development in the upper levels of the stack. Codling moth emergence patterns from plastic-covered stacks more closely coincided with male flight in field populations. This information could be important in developing a technique for neutralizing codling moth-infested bins, and in understanding how infested bins may influence pest management in fruit orchards that are located near bin piles. Implications for control of codling moth in conventional orchards and in those using mating disruption as the principal component of an integrated pest management system include increased numbers of treatments directed at areas affected by infested bins.

Sentinel node biopsy in melanoma using technetium-99m rhenium colloid: the London experience.

Nodal metastases in patients with melanoma identify a reduction of survival by 50%; however, elective lymph node dissection (ELND) has not been shown clearly to improve survival. Morton's technique of sentinel node biopsy, using preoperative lymphoscintigraphy and intraoperative blue dye, addresses elegantly the controversy regarding ELND. Sentinel node biopsy has been shown to stage the patient accurately because metastases from melanoma follow an orderly progression from the sentinel node to the remainder of the basin. Fifty-six consecutive patients with American Joint Committee on Cancer stage 1b or 2 melanoma seen at the London Health Sciences Center between July 1998 and January 2000 were enrolled prospectively to undergo sentinel node biopsy. Preoperative lymphoscintigraphy was conducted in the nuclear medicine department. A total of 10 to 15 MBq (0.27-0.41 mCi) of technetium 99m (99mTc) rhenium colloid or filtered sulfur colloid was injected intradermally around the biopsy scar. Images were obtained to localize all draining nodal basins. The location of the sentinel node was marked on the skin. The patient was taken to the operating room and anesthetized. Isosulfan blue dye was injected intradermally around the biopsy scar. A hand-held gamma probe was used intraoperatively as a guide to the first draining node. Blue-stained lymphatic channels aided in the dissection. Sentinel node localization was successful in 55 of 56 patients, for an overall success rate of 98%. Preoperative lymphoscintigraphy identified a sentinel node in an unpredictable location in 32% of patients. On average, 2.3 sentinel nodes per patient were identified on the initial scan, and 2.2 sentinel nodes per patient were recovered at surgery. Both 99mTc rhenium and filtered sulfur colloid showed no substantial differences in tracer uptake and retention in the sentinel node. Twelve patients had a positive sentinel node on routine histology, and 11 patients subsequently underwent completion lymphadenectomy. The mean thickness of the primary melanoma in the 12 patients with positive sentinel nodes was 3.7 mm compared with a mean tumor thickness of 1.8 mm in the remaining 41 patients with negative biopsies (p = 0.0003). Two patients experienced recurrence in a regional basin after negative pathological evaluation of the sentinel node. Reverse transcription-polymerase chain reaction analysis of both of these patients was positive. Two patients are alive with metastatic disease and 54 patients are alive without disease, with a mean follow-up of 1 year (range, 2-24 months). Complications occurred at a substantially higher rate (45%) after completion lymphadenectomy than after sentinel node biopsy alone (9%). Sentinel node biopsy is a feasible technique with a high success rate (98%), but it requires a multidisciplinary approach. This study validates the clinical usefulness of 99mTc rhenium colloid for lymphoscintigraphy.

The crystal structure of the Escherichia coli MobA protein provides insight into molybdopterin guanine dinucleotide biosynthesis.

The molybdenum cofactor (Moco) is found in a variety of enzymes present in all phyla and comprises a family of related molecules containing molybdopterin (MPT), a tricyclic pyranopterin with a cis-dithiolene group, as the invariant essential moiety. MPT biosynthesis involves a conserved pathway, but some organisms perform additional reactions that modify MPT. In eubacteria, the cofactor is often present in a dinucleotide form combining MPT and a purine or pyrimidine nucleotide via a pyrophosphate linkage. In Escherichia coli, the MobA protein links a guanosine 5'-phosphate to MPT forming molybdopterin guanine dinucleotide. This reaction requires GTP, MgCl(2), and the MPT form of the cofactor and can efficiently reconstitute Rhodobacter sphaeroides apo-DMSOR, an enzyme that requires molybdopterin guanine dinucleotide for activity. In this paper, we present the crystal structure of MobA, a protein containing 194 amino acids. The MobA monomer has an alpha/beta architecture in which the N-terminal half of the molecule adopts a Rossman fold. The structure of MobA has striking similarity to Bacillus subtilis SpsA, a nucleotide-diphospho-sugar transferase involved in sporulation. The cocrystal structure of MobA and GTP reveals that the GTP-binding site is located in the N-terminal half of the molecule. Conserved residues located primarily in three signature sequence motifs form crucial interactions with the bound nucleotide. The binding site for MPT is located adjacent to the GTP-binding site in the C-terminal half of the molecule, which contains another set of conserved residues presumably involved in MPT binding.

Mechanism of assembly of the Bis(Molybdopterin guanine dinucleotide)molybdenum cofactor in Rhodobacter sphaeroides dimethyl sulfoxide reductase.

A fully defined in vitro system has been developed for studying the mechanism of assembly of the bis(molybdopterin guanine dinucleotide)molybdenum cofactor in Rhodobacter sphaeroides dimethyl sulfoxide reductase (DMSOR). R. sphaeroides DMSOR expressed in a mobA(-) Escherichia coli strain lacks molybdopterin and molybdenum but contains a full complement of guanine in the form of GMP and GDP. Escherichia coli MobA, molybdopterin-Mo, GTP, and MgCl(2) are required and sufficient for the in vitro activation of purified DMSOR expressed in the absence of MobA. High levels of MobA inhibit the in vitro activation. A chaperone is not required for the in vitro activation process. The reconstituted DMSOR can exhibit up to 73% of the activity observed in recombinant DMSOR purified from a wild-type strain. The use of radiolabeled GTP has demonstrated incorporation of the guanine moiety from the GTP into the activated DMSOR. No role was observed for E. coli MobB in the in vitro activation of apo-DMSOR. This work also represents the first time that the MobA-mediated conversion of molybdopterin to molybdopterin guanine dinucleotide has been demonstrated directly without using the activation of a molybdoenzyme as an indicator for cofactor formation.

Pneumomediastinum after injection injury to the hand.

Pneumomediastinum as a consequence of injection injury to the hand has not been previously reported. We present a 22-year-old male who developed pneumomediastinum when a high pressure hose injected air into his hand. The anatomic continuity between peripheral ulnar neurovascular bundle and the hilar vessels provided the route for air entering the hypothenar eminence to penetrate the mediastinum. After ruling out life-threatening causes of pneumomediastinum such as esophageal perforation, his management included observation and serial radiographs. By one week there was complete resolution of the mediastinal air. This report demonstrates that pneumomediastinum may be associated with air injection injury of the hand, and that expectant management is appropriate.

Modified amino acids and peptides as substrates for the intestinal peptide transporter PepT1.

The binding affinities of a number of amino-acid and peptide derivatives by the mammalian intestinal peptide transporter PepT1 were investigated, using the Xenopus laevis expression system. A series of blocked amino acids, namely N-acetyl-Phe (Ac-Phe), phe-amide (Phe-NH2), N-acetyl-Phe-amide (Ac-Phe-NH2) and the parent compound Phe, was compared for efficacy in inhibiting the uptake of the peptide [3H]-D-Phe-L-Gln. In an equivalent set of experiments, the blocked peptides Ac-Phe-Tyr, Phe-Tyr-NH2 and Ac-Phe-Tyr-NH2 were compared with the parent compound Phe-Tyr. Comparing amino acids and derivatives, only Ac-Phe was an effective inhibitor of peptide uptake (Ki = 1.81+/- 0.37 mM). Ac-Phe-NH2 had a very weak interaction with PepT1 (Ki = 16.8+/-5.64 mM); neither Phe nor Phe-NH2 interacted with PepT1 with measurable affinity. With the dipeptide and derivatives, unsurprisingly the highest affinity interaction was with Phe-Tyr (Ki = 0.10+/-0.04 mM). The blocked C-terminal peptide Phe-Tyr-NH2 also interacted with PepT1 with a relatively high affinity (Ki = 0.94+/-0.38 mM). Both Ac-Phe-Tyr and Ac-Phe-Tyr-NH2 interacted weakly with PepT1 (Ki = 8.41+/-0.11 and 9.97+/-4.01 mM, respectively). The results suggest that the N-terminus is the primary binding site for both dipeptides and tripeptides. Additional experiments with four stereoisomers of Ala-Ala-Ala support this conclusion, and lead us to propose that a histidine residue is involved in binding the C-terminus of dipeptides. In addition, a substrate binding model for PepT1 is proposed.

Structure of the molybdenum site of Rhodobacter sphaeroides biotin sulfoxide reductase.

Conditions for heterologous expression of Rhodobacter sphaeroides biotin sulfoxide reductase in Escherichia coli were modified, resulting in a significant improvement in the yield of recombinant enzyme and enabling structural studies of the molybdenum center. Quantitation of the guanine and the molybdenum as compared to that found in R. sphaeroides DMSO reductase demonstrated the presence of the bis(MGD)molybdenum cofactor. UV-visible absorption spectra were obtained for the oxidized, NADPH-reduced, and dithionite-reduced enzyme. EPR spectra were obtained for the Mo(V) state of the enzyme. X-ray absorption spectroscopy at the molybdenum K-edge has been used to probe the molybdenum coordination of the enzyme. The molybdenum site of the oxidized protein possesses a Mo(VI) mono-oxo site (Mo=O at 1.70 A) with additional coordination by approximately four thiolate ligands at 2.41 A and probably one oxygen or nitrogen at 1.95 A. The NADPH- and dithionite-reduced Mo(IV) forms of the enzyme are des-oxo molybdenum sites with approximately four thiolates at 2.33 A and two different Mo-O/N ligands at 2.19 and 1.94 A.