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Biomedical subjects

R Balakrishnan

Publications and source records attributed to R Balakrishnan.

At least 19 recordsLinked to original sources
PubMed2004

The Gene Ontology (GO) database and informatics resource.

The Gene Ontology (GO) project (http://www. geneontology.org/) provides structured, controlled vocabularies and classifications that cover several domains of molecular and cellular biology and are freely available for community use in the annotation of genes, gene products and sequences. Many model organism databases and genome annotation groups use the GO and contribute their annotation sets to the GO resource. The GO database integrates the vocabularies and contributed annotations and provides full access to this information in several formats. Members of the GO Consortium continually work collectively, involving outside experts as needed, to expand and update the GO vocabularies. The GO Web resource also provides access to extensive documentation about the GO project and links to applications that use GO data for functional analyses.

Animals↗
PubMed2003

Allele and genotype frequency of CYP2C9 in Tamilnadu population.

OBJECTIVES: To identify the frequency of CYP2C9*1, *2 and *3 alleles and the genotype of CYP2C9 gene in the Tamilian population. METHODS: The study was conducted on 135 unrelated healthy human volunteers. DNA was extracted from the peripheral leukocytes samples and was analyzed using the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) protocol. The PCR products were digested with AvaII, KpnI or NsiI restriction enzymes. The digested products were separated using 8% polyacrylamide gel and stained by ethidium bromide. Genotyping of the subjects was done based on DNA fragment size. RESULTS: The frequencies of CYP2C9*1, *2 and *3 alleles in the Tamilian population were 0.907, 0.026 and 0.067, respectively. The distribution of CYP2C9*1/*1, *1/*2, *1/*3 and *2/*3 genotypes were 0.823, 0.044, 0.126 and 0.007, respectively. CONCLUSION: CYP2C9*3 is the most frequent mutant allele found in the Tamilian population. The distribution of this mutant allele in the Tamilian population was found to be lesser than in Caucasians but higher than in Chinese.

Adult↗
PubMed2002

Hyalinizing clear cell carcinoma of the base of the tongue.

Clear cell carcinoma of the salivary glands is a rare tumour that represents less than one per cent of all salivary tumours. They are divided into a biphasic, epithelial-myoepithelial carcinoma and a monophasic pattern which may be myoepithelial or ductal in origin. The latter is accompanied by prominent fibrohyaline stroma and has been described recently as hyalinizing clear cell carcinoma (HCCC). Most of the HCCC occur in the oral cavity, and are associated with minor salivary glands, unlike the biphasic pattern which is more common in the major salivary glands. In the oral cavity, the commonest site is the palate followed by the lips and the buccal mucosa. Its occurrence in the oropharynx and the larynx is extremely rare.

Adenocarcinoma, Clear Cell↗
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↗