Time-Resolved Photoluminescence in Antimonide and Dilute Nitride Quantum Well Structures

This Master's thesis is devoted to semiconductor samples study using time-resolved photoluminescence. This method allows investigating recombination in semiconductor samples in order to develop quality of optoelectronic device. An additional goal was the method accommodation for low-energy-gap materials. The first chapter gives a brief intercourse into the basis of semiconductor physics. The key features of the investigated structures are noted. The usage area of the results covers saturable semiconductor absorber mirrors, disk lasers and vertical-external-cavity surface-emittinglasers. The experiment set-up is described in the second chapter. It is based on up-conversion procedure using a nonlinear crystal and involving the photoluminescent emission and the gate pulses. The limitation of the method was estimated. The first series of studied samples were grown at various temperatures and they suffered rapid thermal annealing. Further, a latticematched and metamorphically grown samples were compared. Time-resolved photoluminescence method was adapted for wavelengths up to 1.5 µm. The results allowed to specify the optimal substrate temperature for MBE process. It was found that the lattice-matched sample and the metamorphically grown sample had similar characteristics.

Functional studies on bacterial nucleotide-regulated inorganic pyrophosphatases

CBS domains are ~60 amino acid tandemly repeated regulatory modules forming a widely distributed domain superfamily. Found in thousands of proteins from all kingdoms of life, CBS domains have adopted a variety of functions during evolution, one of which is regulation of enzyme activity through binding of adenylate-containing compounds in a hydrophobic cavity. Mutations in human CBS domain-containing proteins cause hereditary diseases. Inorganic pyrophosphatases (PPases) are ubiquitous enzymes, which pull pyrophosphate (PPi) producing reactions forward by hydrolyzing PPi into phosphate. Of the two nonhomologous soluble PPases, dimeric family II PPases, belonging to the DHH family of phosphoesterases, require a transition metal and magnesium for maximal activity. A quarter of the almost 500 family II PPases, found in bacteria and archaea, contain a 120-250 amino acid N-terminal insertion, comprised of two CBS domains separated in sequence by a DRTGG domain. These enzymes are thus named CBS-PPases. The function of the DRTGG domain in proteins is unknown. The aim of this PhD thesis was to elucidate the structural and functional differences of CBS-PPases in comparison to family II PPases lacking the regulatory insert. To this end, we expressed, purified and characterized the CBS-PPases from Clostridium perfringens (cpCBS-PPase) and Moorella thermoacetica (mtCBS-PPase), the latter lacking a DRTGG domain. Both enzymes are homodimers in solution and display maximal activity against PPi in the presence of Co2+ and Mg2+. Uniquely, the DRTGG domain was found to enable tripolyphosphate hydrolysis at rates similar to that of PPi. Additionally, we found that AMP and ADP inhibit, while ATP and AP4A activate CBSPPases, thus enabling regulation in response to changes in cellular energy status. We then observed substrate- and nucleotide-induced conformational transitions in mtCBS-PPase and found that the enzyme exists in two differentially active conformations, interconverted through substrate binding and resulting in a 2.5-fold enzyme activation. AMP binding was shown to produce an alternate conformation, which is reached through a different pathway than the substrate-induced conformation. We solved the structure of the regulatory insert from cpCBS-PPase in complex with AMP and AP4A and proposed that conformational changes in the loops connecting the catalytic and regulatory domains enable activity regulation. We examined the effects of mutations in the CBS domains of mtCBS-PPase on catalytic activity, as well as, nucleotide binding and inhibition.

Novel CO2 Regulated Proteins in Synechocystis PCC 6803

The large biodiversity of cyanobacteria together with the increasing genomics and proteomics metadata provide novel information for finding new commercially valuable metabolites. With the advent of global warming, there is growing interest in the processes that results in efficient CO2 capture through the use of photosynthetic microorganisms such as cyanobacteria. This requires a detailed knowledge of how cyanobacteria respond to the ambient CO2. My study was aimed at understanding the changes in the protein profile of the model organism, Synechocystis PCC 6803 towards the varying CO₂ level. In order to achieve this goal I have employed modern proteomics tools such as iTRAQ and DIGE, recombinant DNA techniques to construct different mutants in cyanobacteria and biophysical methods to study the photosynthetic properties. The proteomics study revealed several novel proteins, apart from the well characterized proteins involved in carbon concentrating mechanisms (CCMs), that were upregulated upon shift of the cells from high CO₂ concentration (3%) to that in air level (0.039%). The unknown proteins, Slr0006 and flavodiiron proteins (FDPs) Sll0217-Flv4 and Sll0219-Flv2, were selected for further characterization. Although slr0006 was substantially upregulated under C_i limiting conditions, inactivation of the gene did not result in any visual phenotype under various environmental conditions indicating that this protein is not essential for cell survival. However, quantitative proteomics showed the induction of novel plasmid and chromosome encoded proteins in deltaslr0006 under air level CO₂ conditions. The expression of the slr0006 gene was found to be strictly dependent on active photosynthetic electron transfer. Slr0006 contains conserved dsRNA binding domain that belongs to the Sua5/YrdC/YciO protein family. Structural modelling of Slr0006 showed an alpha/beta twisted open-sheet structure and a positively charged cavity, indicating a possible binding site for RNA. The 3D model and the co-localization of Slr0006 with ribosomal subunits suggest that it might play a role in translation or ribosome biogenesis. On the other hand, deletions in the sll0217-sll218- sll0219 operon resulted in enhanced photodamage of PSII and distorted energy transfer from phycobilisome (PBS) to PSII, suggesting a dynamic photoprotection role of the operon. Constructed homology models also suggest efficient electron transfer in heterodimeric Flv2/Flv4, apparently involved in PSII photoprotection. Both Slr0006 and FDPs exhibited several common features, including negative regulation by NdhR and ambiguous cellular localization when subjected to different concentrations of divalent ions. This strong association with the membranes remained undisturbed even in the presence of detergent or high salt. My finding brings ample information on three novel proteins and their functions towards carbon limitation. Nevertheless, many pathways and related proteins remain unexplored. The comprehensive understanding of the acclimation processes in cyanobacteria towards varying environmental CO₂ levels will help to uncover adaptive mechanisms in other organisms, including higher plants.

Peritonite por bário

We report a case of a 49 years-old man who underwent a barium meal examination for an epigastric pain. A perforated gastric ulcer with barium extravasation into peritoneal cavity was seen on X-rays. During an emergency laparotomy, a perforated pyloric ulcer was noted, along with barium contamination in the peritoneal cavity. The ulcer was closed with an omental patch and an extensive peritoneal lavage with saline was performed. During the postoperative period, the patient developed signs of peritonitis and underwent a new laparotomy was at the 9th day showing a subfrenic abscess with a large barium contamination. The patient presented septic shock and multiple organ failure. dying on the 21th day.

Pseudomixoma peritoneal: abordagem cirúrgica em dois casos

The authors report the surgical procedure in two patients with pseudomyxoma peritonei, histologically considered as mucinous adenocarcinoma. In both patients, intestinal loops and other visceras were blocked and it was not possible to localize the tumor's origin. There was, in both cases, a great volume of mucinous ascitis. In the first patient a laparotomy was performed and a drainage by a five centimeters peritoneostomy in the abdominal upper left quadrant. In the second just a peritoneostomy was performed in the same location. The sequential irrigation of the abdominal cavity controlled the ascitis in a few days. Certainly this approach avoided a second procedure to clean the mucinous ascitis.

Abscesso intrabdominal tardio pós colecistectomia laparoscópica

Perforation of the gallbladder during laparoscopic cholecystectomy may be associated with intraperitoneal gallstone spillage. Several complications secondary to lost gallstones in the abdominal cavity have been described. We report a rare complication of abdominal abscess secondary to two gallstones left in the abdominal cavity. A 75-year-old female presented with spontaneous drainage of pus through the umbilicus five years after laparoscopic cholecystectomy. An ultrasonographic evaluation of the abdomen revealed a solid mass of 56x26 mm of diameter, with acoustic shadow, localized distal to the umbilicus. At laparotomy, an abscess with two biliary calculi was drained. The patient had good recovery, with no complication.

Corpo estranho retido na cavidade abdominal durante onze anos

A retained foreign body in the abdominal cavity following surgery is a continuing problem. Despite precautions, the incidence is grossly underestimated. Presentation is possible as a pseudotumour, occlusive, or septic syndrome. We describe a case of retained surgical sponge that remained asymptomatic for eleven years.

Megacólon chagásico associado a pneumatose cística difusa do delgado e úlcera péptica duodenal

Diffuse intestinal pneumatosis appears as gaseous cysts in the intestinal wall in the submucosal layer or, more frequently, sub-serous layer. It affects more the jejunum than the ileum, can be diffuse and may extend into the colon. It's diagnosis is established during a small bowel transit examination, necropsy examination or during surgical exploration of the peritoneal cavity.

Hérnia de Morgagni simulando lipoma torácico

The Morgagni hernia is the rarest kind of diaphragmatic hernia , occurring in 3% of all cases. It consists of the protrusion of the abdominal content into the thoracic cavity including omentum and transverse colon, among others. It is more common in the right side and appears more frequently after 40 years of age or after a raise in the intra-abdominal pressure. Patients with Morgagni hernia are usually asymptomatic. In the X-ray it appears like an opaque image in the cardiophrenic angle.Surgical correction is the treatment of choice for this conditions. We present one case of Morgagni hernia successfully treated.

Corpos estranhos provenientes de acessos cirúrgicos à cavidade abdominal: aspectos fisiopatológicos e implicações médico legais

There is no large series about retained foreign bodies in abdominal cavity. In fact data are underestimated because of the lack of reports considering its serious medicolegal implications. An inflammatory fibrotic process inside the peritoneal cavity, a virtual discharge of inorganic material through the surgical incision and also a slow process of transmural migration into the intestinal lumen are the most frequent pathophysiologic situations. It is not uncommon the incidental diagnosis of foreign body and radiographic studies may be particularly helpful to elucidate the etiology. An early recognition minimizes the surgical risks and contributes to avoid severe complications. The best approach is to adopt preventive measures. Careful peroperative materials vigilance and instrumentation and also a meticulous check at the end of operations are essential to avoid such legal responsibility.

Cirurgia endoscópica transluminal por orifícios naturais: realidade atual

Natural orifice transluminal endoscopic surgery (NOTES) is an emerging experimental alternative to conventional surgery that eliminates abdominal incisions and incision-related complications by combining endoscopic and laparoscopic techniques to diagnose and treat abdominal pathology. Natural orifice transluminal endoscopic surgery refers to the method of accessing the abdominal cavity through a natural orifice under endoscopic visualization. Since its introduction in 2004, numerous reports have been published describing different surgical interventions. Recently, a group of expert laparoscopic surgeons and endoscopists outlined the limitations of this approach and issued recommendations for progress toward human trials. Transluminal surgery is a new method for accessing the abdomen under direct endoscopic visualization. Preliminary studies have demonstrated the feasibility of this technique in animal models; however, further research is warranted to validate its safety in humans.

The Roots of Neurofibromas in Neurofibromatosis 1 — A Question of Multipotency, Differentiation and Hiding

Neurofibromatosis type 1 (NF1) is an autosomal dominant cancer predisposition syndrome that affects about 1 in 3500 individuals worldwide. NF1 is caused by mutations in the NF1 gene that encodes the tumor suppressor protein neurofibromin, an inactivator of the Ras oncogene. The hallmarks of NF1 include pigmentary lesions of the skin, Lisch nodules of the iris and cutaneous neurofibromas. Cutaneous neurofibromas are benign tumors composed of all the cell types of normal peripheral nerve. The traditional view of neurofibroma development has been that cutaneous neurofibromas arise from the disruption of the small nerve tributaries of the skin and subsequent proliferation of the resident cells. The second hit mutation in the NF1 gene has been considered as a prerequisite for neurofibroma development. The second hit is detectable in a subpopulation of primary Schwann cells cultured from neurofibromas. This thesis challenges the traditional concept of neurofibroma development. The results show that cutaneous neurofibromas are intimately associated with hair follicular structures and contain multipotent precursor cells (NFPs), suggesting that neurofibromas may arise from the multipotent cells which reside in hair follicles. Furthermore, this study presents that neurofibroma-derived Schwann cells that harbor bi-allelic inactivation in the NF1 gene express HLA class II genes and may act as nonprofessional antigen presenting cells. The CD4- and FoxP3-positive cells detected in cutaneous neurofibromas suggest that these cells may represent regulatory T cells (Tregs) which interact with HLA II –positive cells and aid the tumor cells in hiding from the immune system and are thus mediators of immune tolerance. This thesis also investigated neurofibroma development in the oral cavity and the use of different biomarkers to characterize cellular differentiation in neurofibromas. The results revealed that oral neurofibromas are not rare, but they usually appear as solitary lesions contrary to multiple cutaneous neurofibromas and present high heterogeneity within and between tumors. The use of class III beta-tubulin as a marker for neuronal differentiation led to an unexpected finding showing that multiple cell types express class III beta-tubulin during mitosis. The increased understanding of the multipotency of tumor cells, cellular differentiation and ability to hide from immune system will aid in the development of future treatments. Specifically, targeting Tregs in NF1 patients could provide a novel therapeutic approach to interfere with the development of neurofibromas.

Management of stab wounds to the anterior abdominal wall

The meeting of the Publication "Evidence Based Telemedicine - Trauma and Emergency Surgery" (TBE-CiTE), through literature review, selected three recent articles on the treatment of victims stab wounds to the abdominal wall. The first study looked at the role of computed tomography (CT) in the treatment of patients with stab wounds to the abdominal wall. The second examined the use of laparoscopy over serial physical examinations to evaluate patients in need of laparotomy. The third did a review of surgical exploration of the abdominal wound, use of diagnostic peritoneal lavage and CT for the early identification of significant lesions and the best time for intervention. There was consensus to laparotomy in the presence of hemodynamic instability or signs of peritonitis, or evisceration. The wound should be explored under local anesthesia and if there is no injury to the aponeurosis the patient can be discharged. In the presence of penetration into the abdominal cavity, serial abdominal examinations are safe without CT. Laparoscopy is well indicated when there is doubt about any intracavitary lesion, in centers experienced in this method.

Complex pulmonary aspergilloma treated by cavernostomy

Objective: To evaluate the effectiveness of cavernostomy in patients with complex fungal balls.Methods: We analyzed the medical records of patients undergoing cavernostomy between January 2005 and May 2013, evaluating: age, gender, preoperative signs and symptoms, predisposing disease, preoperative tests, location of the aspergilloma, etiologic agent, cavernostomy indication, postoperative outcome.Results: Ten patients were male. The mean age was 42.9 years (34-56). The most frequent symptom was repeated pulmonary bleeding. Cavernostomy was proposed for patients at high risk for lung resection. It was performed in 17 patients and all of them had pulmonary tuberculosis sequelae, with cavitations. The indication in all cases was hemoptysis and elimination of phlegm. The cavernostomies were performed in a single surgical procedure. In all 17 patients the cavity was left open after the withdrawal of the mycetoma. In all patients hemoptysis ceased immediately. Operative mortality was 9.5% (1).Conclusion: cavernostomy is an effective treatment alternative in patients at high risk. It may be useful in some patients with complex aspergilloma, irrespective of lung function or bilateral disease. It is technically easy, has low-risk, saves parenchyma, and may be performed in a single operative time.

Correlation between the oropharyngo-laryngoscopic findings and the severity of obstructive sleep apnea

Objective: To correlate anatomical and functional changes of the oral cavity, pharynx and larynx to the severity of obstructive sleep apnea syndrome (OSAS). Methods : We conducted a cross-sectional study of 66 patients of both genders, aged between 21 and 59 years old with complaints of snoring and / or apnea. All underwent full clinical evaluation, including physical examination, nasolarybgoscopy and polisonography. We classified individuals into groups by the value of the apnea-hypopnea index (AHI), calculated measures of association and analyzed differences by the Kruskal-Wallis and chi-square tests. Results : all patients with obesity type 2 had OSAS. We found a relationship between the uvula projection during nasoendoscopy and OSAS (OR: 4.9; p-value: 0.008; CI: 1.25-22.9). In addition, there was a major strength of association between the circular shape of the pharynx and the presence of moderate or severe OSAS (OR: 9.4, p-value: 0.002), although the CI was wide (1.80-53.13). The septal deviation and lower turbinate hypertrophy were the most frequent nasal alterations, however unrelated to gravity. Nasal obstruction was four times more common in patients without daytime sleepiness. The other craniofacial anatomical changes were not predictors for the occurrence of OSAS. Conclusion : oral, pharyngeal and laryngeal disorders participate in the pathophysiology of OSAS. The completion of the endoscopic examination is of great value to the evaluation of these patients.