Murumuru (Astrocaryum murumuru) meal as an additive to elephant grass silage / Torta de murumuru (Astrocaryum murumuru) como aditivo en el ensilado de pasto elefante / Torta de murumuru (Astrocaryum murumuru) como aditivo em silagens de capim elefante

Abstract Background: Tropical grasses, such as elephant grass, have high moisture content during its ideal phenological state for silage. High moisture content hinders proper preservation and reduces the nutritive value of silage due to secondary fermentation and production of effluents. Adding feed materials with high dry matter content, such as murumuru (Astrocaryum murumuru) meal, is a potential alternative to improve silage yield. Objective: To determine the effects of including murumuru meal (0, 7, 14, 21, and 28%) on the fermentative characteristics, microbiological activity, aerobic stability, and chemical composition of elephant grass silages. Methods: A completely randomized design with five treatments and five replicates was used. Elephant grass was collected at 60 d of age, minced, and homogenized with murumuru meal. The mass was placed in experimental 15-L silos. The silos were collected and analyzed 45 d later. Results: Effluent production decreased (p<0.05) as the proportions of murumuru meal in silage increased. A quadratic effect (p<0.05) was observed on dry matter recovery. An increase (p<0.05) was observed in dry matter content, a decrease (p<0.05) in the neutral detergent fiber content, and an increase (p<0.05) in the non-fibrous carbohydrate content with the inclusion of murumuru meal. Conclusions: Addition of murumuru meal improves chemical composition and does not affect the fermentative characteristics of elephant grass silage, while it reduces effluent losses. Nevertheless, the inclusion of murumuru meal in the elephant grass silage decreased the time of aerobic stability.

Resumen Antecedentes: los pastos tropicales, tales como el pasto elefante, tienen alto contenido de humedad cuando están en su estado fenológico ideal para ensilar. Esto dificulta su adecuada preservación en el silo, reduciendo el valor nutritivo del ensilaje debido a fermentaciones secundarias y generación de efluentes. Una posible solución sería incluir materiales con alto contenido de materia seca, tales como la torta de murumuru (Astrocaryum murumuru). Objetivo: determinar el efecto de la inclusión de torta de murumuru (0; 7; 14; 21 y 28%) sobre las características fermentativas, microbiológicas, estabilidad aeróbica y composición química de los ensilajes de pasto elefante. Métodos: se utilizó un diseño completamente al azar, con cinco tratamientos y cinco repeticiones. El pasto elefante fue colectado a los 60 días de edad, luego picado y homogeneizado con la torta de murumuru. La masa fue colocada en silos experimentales con capacidad de 15 L. Luego de 45 días de ensilado, los silos fueron abiertos y las muestras fueron colectadas para su posterior análisis. Resultados: hubo reducción (p<0,05) en la producción de efluentes a medida que se incrementó la proporción de torta de murumuru en el ensilado. Se observó un efecto cuadrático (p<0,05) en la recuperación de materia seca. Hubo aumento (p<0,05) en los contenidos de materia seca con la adición de torta de murumuru. Se observó disminución (p<0,05) en el contenido de fibra detergente neutra y aumento (p<0,05) de carbohidratos no fibrosos. Conclusión: La adición de torta de murumuru mejora la composición química, reduce las perdidas por efluentes y no afecta las características fermentativas de ensilado de pasto elefante. Sin embargo, la inclusión de la torta de murumuru en el ensilado de pasto elefante disminuye el tiempo en estabilidad aeróbica.

Resumo Antecedentes: capins tropicais, como por exemplo o capim-elefante apresentam alto teor de umidade quando possuem produtividade compatível e estão no estádio fenológico adequado para ensilagem. Isso dificulta a adequada preservação no silo, ocasionando a redução do valor nutritivo da silagem devido a fermentações secundárias e a produção de efluentes. Uma possível solução seria o uso de aditivos com alto teor de matéria seca, como bolo de murumuru (Astrocaryum murumuru). Objetivo: determinar o efeito da inclusão da torta de murumuru (0; 7; 14; 21 e 28%) na ensilagem de capim-elefante sobre as características fermentativas, microbiológicas, estabilidade aeróbia e a composição química das silagens. Métodos: utilizou- se um delineamento inteiramente casualizado, com cinco tratamentos e cinco repetições. O capim-elefante foi colhido aos 60 dias de idade, o mesmo foi picado e homogeneizado à torta de murumuru. A massa foi ensilada em silos experimentais com capacidade de 15 L. Após 45 dias de ensilagem, os silos foram abertos e amostras foram coletadas para posteriores análises laboratoriais. Resultados: houve redução (p<0,05) na produção de efluentes à medida que se elevaram as proporções da torta de murumuru na ensilagem. Observou-se efeito quadrático (p<0,05) na recuperação de matéria seca. Houve aumento (p<0,05) nos teores de matéria seca com a adição da torta murumuru. Observou-se diminuição (p<0,05) nos teores de fibra em detergente neutro e aumento (p<0,05) nos teores de carboidratos não fibrosos. Conclusão: torta de murumuru como aditivo melhora a composição química, reduz perdas principalmente por efluente e não afeta as características fermentativas de silagens de capim- elefante. Entretanto, a inclusão da torta de murumuru na ensilagem de capim-elefante diminui o tempo em estabilidade aeróbia.

The use of a computer-based decision support system facilitates primary care physicians' management of chronic pain.

We tested whether computer-based decision support (CBDS) could enhance the ability of primary care physicians (PCPs) to manage chronic pain. Structured summaries were generated for 50 chronic pain patients referred by PCPs to a pain clinic. A pain specialist used a decision support system to determine appropriate pain therapy and sent letters to the referring physicians outlining these recommendations. Separately, five board-certified PCPs used a CBDS system to "treat" the 50 cases. A successful outcome was defined as one in which new or adjusted therapies recommended by the software were acceptable to the PCPs (i.e., they would have prescribed it to the patient in actual practice). Two pain specialists reviewed the PCPs' outcomes and assigned medical appropriateness scores (0 = totally inappropriate to 10 = totally appropriate). One year later, the hospital database provided information on how the actual patients' pain was managed and the number of patients re-referred by their PCP to the pain clinic. On the basis of CBDS recommendations, the PCP subjects "prescribed" additional pain therapy in 213 of 250 evaluations (85%), with a medical appropriateness score of 5.5 +/- 0.1. Only 25% of these chronic pain patients were subsequently re-referred to the pain clinic within 1 yr. The use of a CBDS system may improve the ability of PCPs to manage chronic pain and may also facilitate screening of consults to optimize specialist utilization.

The role of topical antibiotic prophylaxis in patients undergoing contaminated head and neck surgery with flap reconstruction.

OBJECTIVES/HYPOTHESIS: Patients undergoing contaminated head and neck surgery with flap reconstruction have wound infection rates of 20% to 25% with parenteral antibiotic prophylaxis. Studies suggest that perioperative antimicrobial mouthwash reduces oropharyngeal flora and may prevent wound infections. We hypothesized that the addition of topical antibiotics to a parenteral prophylactic regimen would reduce the incidence of wound infection in these high-risk patients. STUDY DESIGN: We performed a randomized, prospective clinical trial. METHODS: Patients received either 1) parenteral piperacillin/tazobactam (3.375 g every 6 hours for 48 h) or 2) parenteral piperacillin/tazobactam plus topical piperacillin/tazobactam administered as a mouthwash immediately before surgery and once a day for 2 days postoperatively, with piperacillin/tazobactam added to the intraoperative irrigation solution. The wounds of all patients were evaluated daily using predefined objective criteria. RESULTS: Sixty-two patients met inclusion criteria and were enrolled in the study. The overall wound infection rate was 8.1% (95% confidence interval [CI], 2.7%-17.8%). Two of 31 patients (6.4%) who received parenteral antibiotics alone developed a wound infection compared with 3 of 31 patients (9.7%) randomly assigned to receive topical plus parenteral antibiotics. This difference was not statistically significant (P = >.05). Infection rate was not associated with flap type (rotational vs. free tissue transfer), mandibular reconstruction, age, gender, tumor site, stage, surgical duration, or blood loss. CONCLUSIONS: These results suggest that piperacillin/tazobactam is a highly effective antibiotic for prevention of wound infection in patients undergoing flap reconstruction following contaminated head and neck surgery. However, the addition of topical piperacillin/tazobactam does not appear to enhance the prophylactic benefit of parenteral antibiotics alone.

Hormone selectivity in thyroid hormone receptors.

Separate genes encode thyroid hormone receptor subtypes TRalpha (NR1A1) and TRbeta (NR1A2). Products from each of these contribute to hormone action, but the subtypes differ in tissue distribution and physiological response. Compounds that discriminate between these subtypes in vivo may be useful in treating important medical problems such as obesity and hypercholesterolemia. We previously determined the crystal structure of the rat (r) TRalpha ligand-binding domain (LBD). In the present study, we determined the crystal structure of the rTRalpha LBD in a complex with an additional ligand, Triac (3,5, 3'-triiodothyroacetic acid), and two crystal structures of the human (h) TRbeta receptor LBD in a complex with either Triac or a TRbeta-selective compound, GC-1 [3,5-dimethyl-4-(4'-hydroy-3'-isopropylbenzyl)-phenoxy acetic acid]. The rTRalpha and hTRbeta LBDs show close structural similarity. However, the hTRbeta structures extend into the DNA-binding domain and allow definition of a structural "hinge" region of only three amino acids. The two TR subtypes differ in the loop between helices 1 and 3, which could affect both ligand recognition and the effects of ligand in binding coactivators and corepressors. The two subtypes also differ in a single amino acid residue in the hormone-binding pocket, Asn (TRbeta) for Ser (TRalpha). Studies here with TRs in which the subtype-specific residue is exchanged suggest that most of the selectivity in binding derives from this amino acid difference. The flexibility of the polar region in the TRbeta receptor, combined with differential recognition of the chemical group at the 1-carbon position, seems to stabilize the complex with GC-1 and contribute to its beta-selectivity. These results suggest a strategy for development of subtype-specific compounds involving modifications of the ligand at the 1-position.

Definition of the surface in the thyroid hormone receptor ligand binding domain for association as homodimers and heterodimers with retinoid X receptor.

Thyroid hormone receptors (TRs) bind as homodimers or heterodimers with retinoid X receptors (RXRs) to DNA elements with diverse orientations of AGGTCA half-sites. We performed a comprehensive x-ray crystal structure-guided mutation analysis of the TR ligand binding domain (TR LBD) surface to map the functional interface for TR homodimers and heterodimers with RXR in the absence and/or in the presence of DNA. We also identified the molecular contacts in TR LBDs crystallized as dimers. The results show that crystal dimer contacts differ from those found in the functional studies. We found that identical TR LBD residues found in helices 10 and 11 are involved in TR homodimerization and heterodimerization with RXR. Moreover, the same TR LBD surface is operative for dimerization with direct repeats spaced by 4 base pairs (DR-4) and with the inverted palindrome spaced by 6 base pairs (F2), but not with TREpal (unspaced palindrome), where homodimers appear to be simply two monomers binding independently to DNA. We also demonstrate that interactions between the TR and RXR DNA binding domains stabilize TR-RXR heterodimers on DR-4. The dimer interface can be functional in the cell, because disruption of key residues impairs transcriptional activity of TRs mediated through association with RXR LBD linked to GAL4 DNA-binding domain.

Maternal cytokine levels during pregnancy and adult psychosis.

We investigated levels of maternal cytokines in late pregnancy in relation to the subsequent development of adult schizophrenia and other psychoses in their offspring. The sample included the mothers of 27 adults with schizophrenia and other psychotic illnesses and 50 matched unaffected controls from the Providence cohort of the Collaborative Perinatal Project. Serum samples were analyzed for interleukin 1 beta (IL-1-beta), interleukin 2 (IL-2), interleukin 6 (IL-6), interleukin 8 (IL-8), and tumor necrosis factor alpha (TNF-alpha) by enzyme immunoassay. Maternal levels of TNF-alpha were significantly elevated among the case series (t = 2.22, p =.04), with evidence of increasing odds of psychosis in relation to higher cytokine levels. We did not find significant differences between case and control mothers in the serum levels of IL-1, IL-2, IL-6, or IL-8. These data support previous clinical investigations reporting maternal infections during pregnancy as a potential risk factor for psychotic illness among offspring.

Chemoradiation for metastatic SCCA: role of comorbidity.

OBJECTIVES: A previous study of 371 patients with extracapsular spread (ECS) of cervical metastases from squamous cell carcinoma (SCCA) of the head and neck revealed a survival advantage for patients treated with adjuvant chemoradiation, compared with those treated with surgery and radiation or surgery alone. While all patients in the study were offered adjuvant chemotherapy, only 35% selected this option. Comorbidity was identified as a reason for declining chemotherapy. Recently, Piccirillo demonstrated that the Modified Medical Comorbidity Index (MMCI) is a valid instrument to classify and quantify severity of comorbidity. We applied this instrument to previously reported patients with ECS to determine 1) how comorbidity affected treatment selection, 2) whether the survival advantage of adjuvant chemoradiation persisted after controlling for comorbidity, and 3) the impact of comorbidity on outcome. STUDY DESIGN: This was a nonrandomized, retrospective study. METHODS: Patients in the initial study underwent resection of the primary tumor and neck dissection. Eligible patients elected to receive chemoradiation, radiation, or no further treatment. Comorbidity scores were assigned according to the MMCI. Data were analyzed according to disease-specific survival and overall survival. RESULTS: The study population consisted of 330 patients. More severe comorbidity was related to higher overall mortality rates after controlling for treatment. Adjuvant chemoradiation resulted in improved disease-specific and overall survival compared with adjuvant radiation after adjusting for severity of comorbidity. CONCLUSIONS: These results substantiate the benefits of adjuvant chemoradiation for patients with SCCA of the head and neck. Furthermore, these results reinforce the importance of comorbidity as a prognostic indicator for this population of patients.

Cancer of the tongue in patients less than forty.

INTRODUCTION: It is the opinion of many surgeons that the biologic potential of cancer that develops in young people is different compared with older patients. Prior reports on small series of patients addressing this issue have inadequate statistical power to resolve the question. METHODS: By use of the techniques of meta-analysis, patients less than 40 years old who had undergone treatment of squamous cell carcinoma (SCC) of the oral tongue were examined. Twenty-eight patients who were encountered in the Department of Otolaryngology, University of Pittsburgh School of Medicine, and 94 patients were identified in the literature for a total of 122 patients <40 years old. A control group of 150 patients, aged 40 years and older treated for SCC of the oral tongue between 1982 and 1994 was identified. RESULTS: Three-year disease-free survival in the group of patients aged less than 40 was 53.3% compared with 3-year disease free survivorship of 55.0% in the older cohort of patients. CONCLUSION: These data strongly suggest that the outcomes of treatment for SCC of the oral tongue in young patients are similar compared with patients older than 40 with similar extent of disease.

Mastocytosis: diverse presentations and outcomes.

Within the general category of mastocytosis lies an array of clinical presentations with differing prognostic implications. We report 3 cases of systemic mastocytosis distinguished by novel aspects of the disease. Case 1 documents the first successful orthotopic liver transplantation in a patient with mastocytosis; case 2 depicts a potential hereditary component of mastocytosis; and case 3 documents the progression of mastocytosis with hematologic abnormality to mast cell leukemia. Future investigations, such as the early definition of c-kit receptor mutations, may provide additional insight as to the molecular basis for this heterogeneous disease and guidance for prognostic implications and targeted therapies.

Structure and specificity of nuclear receptor-coactivator interactions.

Combinatorial regulation of transcription implies flexible yet precise assembly of multiprotein regulatory complexes in response to signals. Biochemical and crystallographic analyses revealed that hormone binding leads to the formation of a hydrophobic groove within the ligand binding domain (LBD) of the thyroid hormone receptor that interacts with an LxxLL motif-containing alpha-helix from GRIP1, a coactivator. Residues immediately adjacent to the motif modulate the affinity of the interaction; the motif and the adjacent sequences are employed to different extents in binding to different receptors. Such interactions of amphipathic alpha-helices with hydrophobic grooves define protein interfaces in other regulatory complexes as well. We suggest that these common structural elements impart flexibility to combinatorial regulation, whereas side chains at the interface impart specificity.

Molecular and structural biology of thyroid hormone receptors.

1. Thyroid hormone receptors (TR) are expressed from two separate genes (alpha and beta) and belong to the nuclear receptor superfamily, which also contains receptors for steroids, vitamins and prostaglandins. 2. Unliganded TR are bound to DNA thyroid hormone response elements (TRE) predominantly as homodimers, or as heterodimers with retinoid X-receptors (RXR), and are associated with a complex of proteins containing corepressor proteins. Ligand binding promotes corepressor dissociation and binding of a coactivator. 3. Recent studies from our group have focused on the acquisition and use of X-ray crystallographic structures of ligand-binding domains (LBD) of both the rat (r) TR alpha and the human (h) TR beta bound to several different ligands. We have also developed ligands that bind selectively to the TR beta, which may provide ways to explore the differential functions of TR alpha compared with TR beta isoforms. 4. The LBD is comprised mostly of alpha-helices. The ligand is completely buried in the receptor and forms part of its hydrophobic core. Kinetic studies suggest that the limiting step in formation of high-affinity ligand-receptor complexes is the rate of folding of the receptor around the ligand. Ligands can be fitted tightly in the ligand-binding pocket and small differences in this fitting may explain many structure-activity relationships. Interestingly, analysis of the structures of antagonists suggests that they have chemical groups, 'extensions', that could impair receptor folding around them and, thus, prevent the agonist-induced conformation changes in the receptor. 5. The TR structures allowed us to see that the mutations that occur in the syndrome of generalized resistance to thyroid hormone are located in the vicinity of the ligand-binding pocket. 6. X-ray structure of the TR has also been used to guide construction of mutations in the TR surface that block binding of various proteins important for receptor function. Studies with these TR mutants reveal that the interfaces for homo- and heterodimerization map to similar residues in helix 10 and 11 and also allow the definition of the surface for binding of coactivators, which appears to be general for nuclear receptors. Formation of this surface, which involves packing of helix 12 of the TR into a scaffold formed by helices 3 and 5, appears to be the major change in the receptor structure induced by hormone occupancy.

Mechanisms of thyroid hormone action: insights from X-ray crystallographic and functional studies.

This review summarizes the studies conducted in our laboratory on the mechanisms of thyroid hormone action over the past two decades. We have attempted to place our studies on thyroid hormone receptors (TRs) in perspective with the work conducted by other investigators that established their nuclear localization, DNA-binding properties, DNA response elements, and the role of other proteins involved in TR-mediated regulation of gene transcription. Recently, our crystallographic studies of the TR ligand binding domain (LBD) revealed that the ligand has a structural role in the folding of the receptor's hydrophobic core. The analysis of the structure led to biochemical and genetic studies that have defined the surfaces on the TR LBD required for dimerization and binding of coactivator proteins. Placement of the mutations found in patients with the syndrome of generalized resistance to thyroid hormone on the TR LBD revealed that they were restricted to amino acids in the vicinity of the binding pocket for thyroid hormone. The insights gained from the elucidation of the TR LBD structure will provide the basis for the design of compounds with selective agonistic or antagonistic activities.

X-ray crystallographic and functional studies of thyroid hormone receptor.

We have solved several X-ray crystallographic structures of TR ligand-binding domains (LBDs), including the rat (r) TR alpha and the human (h) TR beta bound to diverse ligands. The TR-LBD folding, comprised mostly of alpha-helices, is likely to be general for the superfamily. The ligand, buried in the receptor, forms part of its hydrophobic core. Tight fitting of ligand into the receptor explains its high affinity for the TR, although the structure suggests that ligands with even higher affinities might be generated. The kinetics of 3,5,3'-triiodo-L-thyronine (T3) and 3,5,3',5'-tetraiodo-L-thyronine (T4) binding suggest that folding around the ligand, rather than receptor opening, is rate-limiting for high affinity binding. TR beta mutations in patients with resistance to T3 cluster around the ligand; these different locations could differentially affect on other receptor functions and explain the syndrome's clinical diversity. Guided by the structure, mutations have been placed on the TR surface to define interactions with other proteins. They suggest that a similar surface in the LBD is utilized for homo- or heterodimerization on direct repeats and inverted palindromes but not on palindromes. Coactivator proteins that mediate TR transcriptional activation bind to a small surface comprised of residues on four helices with a well-defined hydrophobic cleft, which may be a target for pharmaceuticals. The coactivator-binding surface appears to form upon ligand-binding by the folding of helix 12 into the scaffold formed by helices 3, 4 and 5. The analysis of most currently used antagonists suggest that although they probably fit into the ligand-binding pocket, they possess a group that may alter proper folding of the receptor, with disruption of the coactivator-binding surface (the 'extension model').

Lymphatic mapping with isosulfan blue dye in squamous cell carcinoma of the head and neck.

OBJECTIVE: To determine whether intraoperative lymphatic mapping with isosulfan blue dye and sentinel lymph node biopsy accurately demonstrates the pathway of regional metastases from mucosal sites in squamous cell carcinoma of the head and neck. DESIGN: A prospective clinical study of intraoperative lymphatic mapping. SETTING: An academic tertiary referral center. PATIENTS: Patients with previously untreated squamous cell carcinoma of the head and neck whose surgical treatment included neck dissection. INTERVENTION: Injection of isosulfan blue dye into the mucosa surrounding squamous cell carcinomas of the upper aerodigestive tract during cervical lymphadenectomy. OUTCOME MEASURES: Correlation of the pathologic findings in the blue sentinel lymph node with those in the remaining cervical lymphatics. RESULTS: No blue-stained cervical lymphatics were identified after injection of the mucosa surrounding the primary squamous cell carcinoma with isosulfan dye. CONCLUSION: The technique of intraoperative lymphatic mapping with isosulfan blue dye requires further study before it can be used for the detection of occult cervical metastases in squamous cell carcinoma of the head and neck.

DAX1 mutations map to putative structural domains in a deduced three-dimensional model.

The DAX1 protein is an orphan nuclear hormone receptor based on sequence similarity in the putative ligand-binding domain (LBD). DAX1 mutations result in X-linked adrenal hypoplasia congenita (AHC). Our objective was to identify DAX1 mutations in a series of families, to determine the types of mutations resulting in AHC and to locate single-amino-acid changes in a DAX1 structural model. The 14 new mutations identified among our 17 families with AHC brought the total number of families with AHC to 48 and the number of reported mutations to 42; 1 family showed gonadal mosaicism. These mutations included 23 frameshift, 12 nonsense, and six missense mutations and one single-codon deletion. We mapped the seven single-amino-acid changes to a homology model constructed by use of the three-dimensional crystal structures of the thyroid-hormone receptor and retinoid X receptor alpha. All single-amino-acid changes mapped to the C-terminal half of the DAX1 protein, in the conserved hydrophobic core of the putative LBD, and none affected residues expected to interact directly with a ligand. We conclude that most genetic alterations in DAX1 are frameshift or nonsense mutations and speculate that the codon deletion and missense mutations give insight into the structure and function of DAX1.

Hormone-dependent coactivator binding to a hydrophobic cleft on nuclear receptors.

The ligand-binding domain of nuclear receptors contains a transcriptional activation function (AF-2) that mediates hormone-dependent binding of coactivator proteins. Scanning surface mutagenesis on the human thyroid hormone receptor was performed to define the site that binds the coactivators, glucocorticoid receptor-interacting protein 1 (GRIP1) and steroid receptor coactivator 1 (SRC-1). The residues involved encircle a small surface that contains a hydrophobic cleft. Ligand activation of transcription involves formation of this surface by folding the carboxyl-terminal alpha helix against a scaffold of three other helices. These features may represent general ones for nuclear receptors.

Implications of cartilage invasion in surgically treated laryngeal carcinoma.

BACKGROUND: Cartilage invasion adversely affects the outcome of laryngeal carcinoma treated with radiotherapy. The UICC and American Joint Committee on Cancer (AJCC) classify laryngeal carcinoma with cartilage invasion as T4 or stage IV. METHODS: This study examines the prognostic significance of cartilage involvement in T3,4 N0,1 glottic carcinoma treated with total laryngectomy. Patients with tumor extension to pharynx, tongue, and thyroid gland, extracapsular spread, positive resection margins, and less than 2 years' follow-up were excluded. RESULTS: Sixty-seven pT3 (cartilage free of tumor) and 37 pT4 (cartilage invaded by tumor) cases were studied. The difference between the pT3 and pT4 groups in terms of local or regional recurrence, distant metastasis, and determinate survival was not significant. CONCLUSIONS: The results of this study question the use of cartilage invasion as a staging parameter for surgically treated laryngeal carcinoma. However, further studies with larger sample sizes are required to fully elucidate the prognostic significance, if any, of cartilage invasion in surgically treated cancer of the larynx.

A novel TR beta mutation (R383H) in resistance to thyroid hormone syndrome predominantly impairs corepressor release and negative transcriptional regulation.

Resistance to thyroid hormone (RTH) is characterized by elevated serum thyroid hormones, failure to suppress pituitary TSH secretion, and variable T3 responsiveness in peripheral tissues. The disorder is associated with diverse mutations that cluster within three areas of the thyroid hormone beta(TR beta) receptor. Here, we report a novel RTH mutation (R383H), which is located in a region not known to harbor naturally occurring mutations. Although the R383H mutant receptor activated positively regulated genes to an extent comparable to wild-type (WT), negative transcriptional regulation of human TSH alpha and TRH promoters was impaired in either TR beta 1 or TR beta 2 contexts, and WT receptor function was dominantly inhibited. T3-dependent changes in basal transcription with R383H were also impaired: on the TRH promoter, basal activation by unliganded R383H was not reversed by T3 to the same extent as WT; similarly transcriptional silencing by an unliganded Gal4-R383H fusion was not relieved at a T3 concentration that derepressed WT. In keeping with this, ligand-dependent corepressor release by R383H, either in a protein-protein interaction assay or as a DNA-bound heterodimer with retinoid X receptor on either positive or negative thyroid hormone response elements, was disproportionately impaired relative to its ligand-binding affinity, whereas its T3-dependent recruitment of coactivator was unimpaired. These properties were shared by another previously described RTH mutant (R429Q), and in the crystal structure of TR alpha the homologous residues interact in a polar invagination. Our data indicate a role for these residues in mediating negative transcriptional regulation and facilitating corepressor release and suggest that predominant impairment of these functions may be the minimal requirements for causation of RTH.

Comparison of ampicillin/sulbactam versus clindamycin in the prevention of infection in patients undergoing head and neck surgery.

BACKGROUND: Patients requiring major oncologic head and neck surgery are at high risk for postoperative wound infection when the surgical site is contaminated by secretions from the upper aerodigestive tract. Studies to identify agents active in the prevention of postoperative wound infection may serve to reduce patient morbidity. METHODS: Patients scheduled for a major contaminated head and neck surgical procedure were randomly assigned to receive either ampicillin/sulbactam or clindamycin. Medication was administered 1 to 2 hours prior to surgery and every 6 hours, for a total of five doses. Postoperatively, patients were followed daily for the development of wound infection or other septic complication. RESULTS: A total of 242 patients were enrolled in the study; 119 received ampicillin/sulbactam, and 123 received clindamycin. A total of 169 patients were considered evaluable. Of the evaluable patients, 14% in each group developed a postoperative wound infection. There were no statistically significant differences between the number of days to onset of wound infection, nor was there a statistically significant difference in the rate of non-wound infections in the two groups. There were no statistically significant differences between the intent to treat group and the evaluable group of patients. CONCLUSION: It is concluded that ampicillin/sulbactam is as safe and effective as clindamycin in preventing postoperative wound infection following major head and neck surgery.