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Biomedical subjects

R Balakrishnan

Publications and source records attributed to R Balakrishnan.

At least 19 recordsLinked to original sources
PubMed2002

Tracheo-innominate artery fistula: a rare complication in a laryngectomized patient.

A tracheo-innominate artery fistula is an uncommon but frequently fatal complication of tracheostomy. Rarely, it can also occur in laryngectomized patients. We report a post-laryngectomy, post-radiotherapy patient using a metal tracheostomy tube, who developed a tracheo-innominate artery fistula about two months after radiotherapy. To our knowledge this is only the second reported case in a laryngectomized patient. The computed tomography (CT) angiography findings helped confirm the diagnosis and the patient was successfully managed by surgical exploration and ligation of the innominate artery. Coagulase negative Staphylococcus aureus was cultured from a tracheal swab. The clinical features, CT angiography findings, management protocols and possible aetiological factors are discussed.

Brachiocephalic Trunk↗
PubMed2001

Reverse engineering the (beta/alpha )8 barrel fold.

The (beta/alpha)(8) barrel is the most commonly occurring fold among protein catalysts. To lay a groundwork for engineering novel barrel proteins, we investigated the amino acid sequence restrictions at 182 structural positions of the prototypical (beta/alpha)(8) barrel enzyme triosephosphate isomerase. Using combinatorial mutagenesis and functional selection, we find that turn sequences, alpha-helix capping and stop motifs, and residues that pack the interface between beta-strands and alpha-helices are highly mutable. Conversely, any mutation of residues in the central core of the beta-barrel, beta-strand stop motifs, and a single buried salt bridge between amino acids R189 and D227 substantially reduces catalytic activity. Four positions are effectively immutable: conservative single substitutions at these four positions prevent the mutant protein from complementing a triosephosphate isomerase knockout in Escherichia coli. At 142 of the 182 positions, mutation to at least one amino acid of a seven-letter amino acid alphabet produces a triosephosphate isomerase with wild-type activity. Consequently, it seems likely that (beta/alpha)(8) barrel structures can be encoded with a subset of the 20 amino acids. Such simplification would greatly decrease the computational burden of (beta/alpha)(8) barrel design.

Conserved Sequence↗
PubMed2001

Song pattern recognition in the grasshopper Chorthippus biguttulus: the mechanism of syllable onset and offset detection.

The male song of the duetting grasshopper Chorthippus biguttulus consists of syllables alternating with noisy pauses. The syllable-pause structure is important for song recognition by the female. Using playback experiments we investigated the mechanism by which intensity modulations within the song pattern are used to detect syllable onsets and offsets. We varied the relative onset level (level of the syllable beginning relative to the noisy pause) and the relative offset level (level of the noisy pause relative to the syllable end) independently in different experiments. For all females, an increase in intensity defining the syllable onset was necessary to evoke responses. Syllable offset cues were not always necessary: some females responded to continuous noise stimuli wherein only syllable onsets were marked by short pulses of high intensity. Those females that did not require syllable offset cues did not, however, lack a functional pause detection mechanism, since their responses to model songs containing silent pauses were restricted to a given range of pause durations. We propose that syllable-pause detection involves two independent processes: (1) syllable onset detection by a phasic neuronal unit that can be re-activated only after a short pause, and (2) the rejection of unacceptably long pauses by a second unit.

Acoustics↗
PubMed2001

Clear cell carcinoma of the larynx--a case report.

Clear cell carcinoma (CCC) of the larynx is extremely rare and to the best of our knowledge no such case has been reported in the paediatric age group. These tumours resemble the clear cell carcinoma of the major and minor salivary glands. We report such a lesion in a 15 years old boy presenting with hoarseness and an exophytic growth in the glottis. A frontolateral conservation laryngectomy with laryngoplasty was done and over 2 years follow-up has shown no evidence of loco-regional recurrence and he enjoys an acceptable voice.

Adenocarcinoma, Clear Cell↗
PubMed2001

LabVelocity: online tools for life science products, protocols, technical information, MEDLINE searches, and laboratory calculations.

As the pace of life science discovery increases, so do the demands on researchers. To remain competitive in the life science industry, researchers must use every tool at their disposal to keep up with new products, protocols, news, and literature in their field. While there are now myriad Web sites that assist researchers with this problem, many suffer from confusing user interfaces, poorly designed search engines, and a narrow information focus. Here, we present LabVelocity, a user-friendly Web site that provides a free multidisciplinary information-gathering service for the life science research community. Using LabVelocity, a researcher can quickly find the products, protocols, technical references, news, MEDLINE abstracts, and interactive software tools necessary for an experiment. This aggregation of information can streamline experimental planning and is especially useful when researchers want to set up a new laboratory or to venture outside their field of expertise.

Algorithms↗
PubMed2001

Endoscopic physiologic approach to allergy-associated chronic rhinosinusitis: a preliminary study.

Patients with allergy-associated chronic rhinosinusitis respond poorly to functional endoscopic sinus surgery (FESS), probably because of the altered nasosinus ventilatory physiology and the increased contamination of the nasosinus mucosa by the offending allergens. With this in mind, we describe the concept and technique of functional endoscopic nasosinus surgery (FENS) in such cases. The advantages of this technique are that it preserves the uncinate process, it limits ethmoidal exenteration via a transbullar approach, and it simultaneously corrects both septal and lateral wall pathologies. The aim of our randomized prospective study was to subjectively and objectively compare the efficacy of FESS and FENS in 64 patients with allergy-associated chronic rhinosinusitis. Subjective assessment was ascertained by visual analog scores, and objective assessment was made by nasal endoscopy. In this preliminary study, we found that FENS was superior to FESS in treating chronic sinusitis associated with nasal allergy.

Chronic Disease↗
PubMed2000

Paecilomyces fungus infection of the paranasal sinuses.

Fungal infections caused by Paecilomyces species are very rare and occur in adult patients with impaired host defences or following foreign body implants. They are found worldwide in soil and decaying vegetation. We describe a case of an 8 year old child who came with complaints of left sided nasal obstruction and discharge, telecanthus, diplopia and epiphora. On examination and investigation he had pansinusitis caused by P. lilacinus. An endoscopic sinus surgery was done and the patient was on oral Itraconazole for 6 months. To our knowledge, this is the first case reported in the paediatric age group.

Antifungal Agents↗
PubMed2000

Field-induced transitions and spatial chaos in the classical XY spin chain

We study the lowest-lying excitation of a classical ferromagnetic XY spin chain, in the presence of a symmetry breaking magnetic field. Extremizing the energy of this system leads to a two-dimensional nonlinear map, whose allowed phase space shrinks with increasing field in a nontrivial manner. The orbits of the map represent the set of extremum energy spin configurations. For each field, we compute the energy of the members of this set and find the lowest energy among them, excluding the obvious ground state configuration with all spins parallel along the field direction. This state turns out to be the unstable fixed point of the map. We show that up to a certain (primary) critical field, a separatrixlike 2pi soliton configuration is the lowest-energy excitation, with an energy very close to the ground state energy. For any field beyond this critical field, the soliton disappears and lowest excitation is a librational configuration corresponding to the outermost orbit in the phase plot at that field. Further, its energy is found to be much higher than the ground state energy, leading to a sharp jump in the difference in energy between the former and the latter at this field. With further increase in the field, sharp jumps in the excitation energy arise at certain secondary critical fields as well. We show that these appear when the corresponding spin configurations become commensurate. This complex behavior of the energy is interpreted and its effect on the magnetization and static susceptibility of the system is also studied.

Journal Article↗
PubMed2000

Rosai-Dorfman disease of the subglottis.

A case of subglottic narrowing caused by an extranodal deposit of sinus histiocytosis in a 29-year-old man is reported. The characteristic features of Rosai-Dorfman disease, such as massive painless cervical lymphadenopathy, fever, raised erythrocyte sedimentation rate and raised white cell count, were all found to be absent. However, typical histological features, such as diffuse lymphoplasmacytic infiltrate, Russel bodies, foamy histiocytes and histiocytes with emperipoiesis, confirmed the diagnosis. Rosai-Dorfman disease is an uncommon disorder and its presentation with progressive subglottic narrowing is extremely rare. Our experience in the management of this condition is reported and the review of literature is discussed.

Adult↗
PubMed1999

Parapharyngeal space mesenchymal chondrosarcoma in childhood.

A case of extra osseous mesenchymal chondrosarcoma occuring in the parapharyngeal space in a 7-year-old girl, is being presented for its rarity. It is a slow growing, locally aggressive tumour with a high incidence of local recurrence as well as distant metastasis. It is rare in the pediatric age group and rarer in the parapharyngeal space. It has a poor prognosis, the 5-year survival rate varies between 30 and 50%. Radical surgery is the treatment of choice. Radiotherapy and chemotherapy have an adjuvant role. More experience with this tumour is required to evaluate the most effective treatment. Current literature on this subject has been reviewed.

Child↗
PubMed1999

Extraskeletal Ewing's sarcoma in a kidney transplant patient.

Organ transplant recipients are prone to develop a variety of malignancies, most of which are encountered uncommonly in the general population. Approximately 5% to 7% of these malignancies are sarcomas, of which most are Kaposi's sarcomas. Ewing's sarcoma is an extremely uncommon tumor in organ transplant recipients, and only one case of skeletal Ewing's sarcoma has been reported in the transplant literature. We present a case of extraskeletal Ewing's sarcoma (EES) in a renal transplant patient.

Abdominal Muscles↗
PubMed1999

Solitary adult myofibroma of the pinna.

Solitary myofibroma is a recently described benign neoplasm of the skin or superficial soft tissue and it represents the adult counterpart of infantile myofibromatosis. This new clinicopathological entity is being recognized increasingly. A case of solitary myofibroma occurring in the pinna of a 50-year-old woman is presented. Such a lesion occurring in the pinna of an adult has not been reported in the literature.

Ear Neoplasms↗
PubMed1998

Prevention and management of synechia in pediatric endoscopic sinus surgery using dental wax plates.

Synechia formation is a very common complication of endoscopic sinus surgery (ESS). Inspite of meticulous post-operative care, synechia do form in quite a large number of patients. Moreover, frequent post-operative cleaning may not be possible without general anesthesia in non-compliant patients, especially children. This study compares the incidence of synechia following pediatric ESS with or without spacer/tamponade in the operated cavity. The authors have found dental wax plates to be equally effective and more economical spacers compared to Merocel tamponade, in prevention and management of synechia in the pediatric age group.

Case-Control Studies↗
PubMed1998

Endoscopic adenoidectomy in a case of Scheie syndrome (MPS I S).

The mucopolysaccharidoses (MPS) are a heterogeneous group of relatively rare, progressive, inherited lysosomal storage disorders, characterized by a deficiency of lysosomal enzymes which are responsible for the stepwise degradation of glycosaminoglycans. Their deficiency leads to the accumulation of glycosaminoglycans in various organs causing progressive disruption of cellular functions and multiple systemic effects including otolaryngological problems, upper airway obstructive disease being the most common. Scheie syndrome (MPS I S) is due to the deficient activity of alpha-L-iduronidase leading to the intralysosomal accumulation of dermatan sulfate and heparan sulfate. We present our experience in one such case occuring in a 6-year-old girl with ENT manifestations and who underwent a successful endoscopic adenoidectomy for symptomatic adenoid hypertrophy. This procedure was preferred over a conventional adenoidectomy in order to avoid complications associated with abnormal cervical vertebrae.

Adenoidectomy↗
PubMed1998

Dual ectopic thyroid: a report of two cases.

Ectopic thyroid is an uncommon embryological aberration characterized by the presence of thyroid tissue at a site other than in its usual pretracheal region. Usually it occurs along the path of descent of the developing thyroid primodium from the foramen caecum, commonest being lingual followed by sublingual and in the anterior midline of neck at, or below, the level of the hyoid bone. It is unusual for lingual thyroid to present simultaneously with another ectopic thyroid; reported here are two such cases.

Adolescent↗
PubMed1998

An endoscopic approach to the deviated nasal septum--a preliminary study.

The authors have used the nasal endoscope for the precise identification of pathological abnormalities of the nasal septum in relation to the lateral nasal wall including the osteo-metal complex and in its ultraconservative management. The aim of the study was to compare the efficacies of endoscope-aided septoplasty (EAS) over traditional septoplasty (TS) in treating the pathological septum and turbinates, performed in 30 cases each. The subjective assessment was carried out by visual analogue scores and objective assessment by nasal endoscopy. This study demonstrates the superiority and limitations of the endoscopic approach in managing a deviated nasal septum and the turbinates. The endoscope-aided technique was found to be more effective in relieving the contact areas and nasal obstruction (p = < or = 0.05). The authors advocate a combined approach--an endoscopic approach for inaccessible posterior deviation and the conservative traditional technique for accessible anterior deviation of the nasal septum.

Adolescent↗