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Biomedical subjects

G Krishnan

Publications and source records attributed to G Krishnan.

At least 19 recordsLinked to original sources
PubMed2002

Endonasal endoscopic dacryocystorhinostomy.

A review of endoscopic dacryocystorhinostomy (EDCR) performed in University Hospital from 1998 till early 2001 were carried out. They were reviewed for indication, functional results, complications and other associated factors. Eleven patients (6 female and 5 male) were reviewed. All had unilateral nasolacrimal duct (NLD) obstruction (6 right, 5 left). Their ages range from 6 to 73 years. All 11 had persistent epiphora while 4 had concurrent recurrent dacryocystitis with purulent discharge. Two patients had history of lacrimal sac abscess that needed drainage. Ten patients had the procedure performed successfully. Functional results were excellent in 8 patients (80%) while two patients still had occasional epiphora although markedly reduced. Complications include synachae (1 patient), premature dislodgement of Jones tube (1 patient) and impacted tube in a child. Our experience with EDCR concludes it to be an easy, efficient treatment for nasolacrimal duct obstruction with minimal complications.

Adolescent↗
PubMed2001

A quorum sensing-associated virulence gene of Pseudomonas aeruginosa encodes a LysR-like transcription regulator with a unique self-regulatory mechanism.

The human opportunistic pathogen Pseudomonas aeruginosa strain PA14 infects both plants and animals. Previously, using plants to screen directly for P. aeruginosa virulence-attenuated mutants, we identified a locus, pho34B12, relevant in mammalian pathogenesis. Here, nonsense point mutations in the two opposing ORFs identified in the pho34B12 locus revealed that one of them, mvfR (multiple virulence factor Regulator), is able to control all of the phenotypes that mutant phoA34B12 displays. Both genetic and biochemical evidence demonstrate that the mvfR gene encodes a LysR-like transcriptional factor that positively regulates the production of elastase, phospholipase, and of the autoinducers, 3oxo-dodecanoyl homoserine lactone (PAI I) and 2-heptyl-3-hydroxy-4-quinolone (PQS), as well as the expression of the phnAB operon, involved in phenazine biosynthesis. We demonstrate that the MvfR protein is membrane-associated and acts as a transcriptional activator until cells reach stationary phase, when a unique negative feedback mechanism is activated to signal the down-regulation of the MvfR protein. This work reveals an unprecedented virulence mechanism of P. aeruginosa and identifies a unique indispensable player in the P. aeruginosa quorum-sensing cascade.

Animals↗
PubMed2001

Cervical intraepithelial changes & HIV infection in women attending sexually transmitted disease clinics in Pune, India.

BACKGROUND & OBJECTIVES: Cervical cancer is the most important cause of malignancy associated deaths among women in India. Western studies have reported higher risk of abnormal Pap smears in HIV infected women. A large burden of HIV infection and increasing HIV epidemic in India threatens to exacerbate incidence of cervical cancer. The objective of this study was to assess the frequency of Pap smear abnormalities and its association with HIV infection in women attending sexually transmitted disease (STD) clinics and to identify associated risk factors. METHODS: Between June 1996 and September 1999, women attending two STD clinics in Pune were screened for HIV infection, offered STD laboratory diagnosis and treatment and their Pap smears were evaluated. RESULTS: Squamous cell abnormality was detected in 10 per cent of HIV sero negative women attending STD clinics. This proportion was nearly double (19.2%) (Odds ratio = 2.14, 95% C.I. 1.03-4.48, P = 0.04) in HIV seropositive women. Having more than one life time partners and presence of STDs were also significantly associated with Pap smear abnormality in univariate analysis. In multivariate analysis, women presenting with STD and HIV infection both, were 2.8 times more likely to have inflammatory Pap smear and 3.5 times more likely to have abnormal Pap smear compared to HIV seronegative women presenting without STDs. INTERPRETATION & CONCLUSION: Pap smear abnormalities were common in women attending STD clinics in Pune. Presence of HIV infection further increased the risk two-folds. Therefore, women suffering from STDs should undergo periodic Pap smear screening for early detection of cervical abnormalities and should receive appropriate management to reduce morbidity and mortality.

Ambulatory Care Facilities↗
PubMed2000

Saxiphilin, a saxitoxin-binding protein with two thyroglobulin type 1 domains, is an inhibitor of papain-like cysteine proteinases.

The type 1 domain of thyroglobulin is a protein module (Thyr-1) that occurs in a variety of secreted and membrane proteins. Several examples of Thyr-1 modules have been previously identified as inhibitors of the papain family of cysteine proteinases. Saxiphilin is a neurotoxin-binding protein from bullfrog and a homolog of transferrin with a pair of such Thyr-1 modules located in the N-lobe. Saxiphilin is now characterized as a potent inhibitor of three cysteine proteinases as follows: papain, human cathepsin B, and cathepsin L. The stoichiometry of enzyme inhibition reveals that both Thyr-1 domains of saxiphilin inhibit papain (apparent K(i) = 1. 72 nm), but only one of these domains inhibits cathepsin B (K(i) = 1. 67 nm) and cathepsin L (K(i) = 0.02 nm). Physical association of saxiphilin and papain blocked from turnover at the active-site cysteine residue can be detected by cross-linking with glutaraldehyde. The rate of association of saxiphilin and cathepsin B is strongly pH-dependent with an optimum at pH 5.2, reflecting control by at least two H(+)-titratable groups. These results further demonstrate that various Thyr-1 domains are selective inhibitors of cysteine proteinases with utility in the study of protein interactions and degradation.

Amino Acid Sequence↗
PubMed2000

Growth and development of smooth bromegrass and tall fescue in TNT-contaminated soil.

Plants can be used for effective and economical remediation of soil provided they are tolerant or resistant to contaminants. This study was conducted to determine effects of 2,4,6-trinitrotoluene (TNT) on growth and development of smooth bromegrass and tall fescue. Seeds of both species were grown in contaminated and non-contaminated soil mixed at ratios to obtain a range of concentrations and also in non-contaminated soil underlain by contaminated and non-contaminated soil mix. Germination, shoot and root dry weight, root length and area were measured. Germination and height of both species decreased with increasing TNT concentration. Shoot dry weight from tall fescue was 50% greater than smooth bromegrass at a given TNT concentration. Root length, area and dry weight of both species decreased with increasing TNT concentration. Root area and dry weight were greater for smooth bromegrass compared to tall fescue. This research indicates tall fescue and smooth bromegrass can germinate and grow in soils with concentrations less than 31 and 24 mg TNT l(-1), respectively.

Journal Article↗
PubMed1999

Insights into linear and nonlinear cochlear transduction: application of a new system-identification procedure on transient-evoked otoacoustic emissions data.

Transient-evoked otoacoustic emissions (TEOAE) were used to characterize linear and nonlinear cochlear transduction using a new system-identification procedure. In this technique, a computational model of the system is first developed. From the measured stimulus and response records, spectral-density functions and multiple coherence functions are calculated. The coherence functions allow the characterization of linear/nonlinear processes as a function of frequency. Summations of linear and nonlinear coherences provide a goodness-of-fit of the chosen model. Finite impulse response pulses with a bandwidth of 1-8 kHz were used to evoke otoacoustic emissions. Eleven adults with normal hearing served as subjects. Third- and fifth-order polynomial models were used to model the data, and the results indicate that the fifth-order model is a better fit to the TEOAE data. The results of this study suggest that this system-identification procedure can be successfully applied to model cochlear transduction using a broadband stimulus. Most importantly, coherence functions provide useful insights into linear and nonlinear cochlear processes and have the potential to be developed as a clinical measure for monitoring changes in cochlear status.

Acoustic Stimulation↗
PubMed1996

The effects of subcortical lesions on evoked potentials and spontaneous high frequency (gamma-band) oscillating potentials in rat auditory cortex.

Functional subdivisions of auditory cortex in the rat were identified based on the distribution of temporal components of the mid-latency auditory evoked potential (MAEP) recorded with a multichannel epipial electrode array. Spontaneous data collected from the same location exhibited spindle-shaped bursts of oscillations in the gamma-band (20-40 Hz) whose location and spatial distribution were similar to that of the MAEP complex in that the bursts were localized to primary and secondary auditory cortex, the principle targets of thalamocortical projections. This suggested that the neural generators of these electrophysiological events may be similar. However, ablation of the medial geniculate nucleus (MG) of the thalamus revealed that while this nucleus is required for the generation of MAEPs, it is not required for the generation of spontaneous gamma-band oscillations. Ablation of subcortical cholinergic nuclei revealed that cholinergic input via the thalamus or the basal forebrain is not necessary for the generation of either MAEPs or spontaneous gamma-band oscillations recorded in this study. These results indicated that there may be networks of cells in sensory cortical areas endowed with an intrinsic capacity to oscillate independently of sensory or cholinergic input, but that may be modulated by this input.

Acoustic Stimulation↗
PubMed1996

Frontoethmoid mucocele: one-year follow-up after endoscopic frontoethmoidectomy.

Endoscopic sinus surgery for frontal sinus mucocele is gaining popularity. A case study, and the CT scan of a large frontal mucocele with 1-year follow up is presented showing the lining of the sinus cavity well healed and the frontal sinus ostium as patent. Endoscopic sinus surgery, therefore, is a potentially useful method for treating large frontal mucoceles.

Endoscopy↗
PubMed1994

Characterization of apocytochrome C binding to human erythrocytes.

The binding of 125I-labeled apocytochrome c to human erythrocytes was determined for free apocytochrome c concentrations at 10(-10)-10(-6) M. At about 2 x 10(-9) M, maximum cell association of apocytochrome c occurs at 50 mM NaCl and at 22 degrees C. Intact erythrocytes at 22 degrees C have three classes of apocytochrome c binding sites: one high-affinity noncooperative site (n1 = 728 per cell, Kd1 = 1.5 x 10(-9) M) and two positively cooperative sites (n2 = 3.7 x 10(4) per cell, Kd2 = 1.2 x 10(-7) M, alpha 2 = 2.0, and n3 = 2.5 x 10(5) per cell, Kd3 = 7.1 x 10(-7) M, alpha 3 = 12). Erythrocytes at 37 degrees C, and erythrocyte ghosts at 22 degrees C, also have three classes of apocytochrome c binding sites, and most sites are positively cooperative.

Apoproteins↗
PubMed1994

A review of the management of 107 dizzy patients at the university hospital.

The common investigations done were pure tone audiometry, electronystagmography, X-ray of the internal auditory meatus, CT-scan of the internal auditory meatus and X-ray of the cervical spine. After the examinations and investigations only 52 patients out of the 107 could be given any diagnosis. The most common diagnosis for the vertigo was Meniere's disease.

Adolescent↗
PubMed1994

Nasal scarring by joss stick burns.

Vasomotor rhinitis is a common condition in Malaysia. Patients' dissatisfaction with medical treatment of this recurring condition leads them to seek other forms of traditional cures. This paper highlights the complications in such patients who seek traditional cures for their chronic condition.

Adult↗
PubMed1994

Migrating foreign body--an unusual presentation.

A case report of an ingested fish bone migrating to the subcutaneous tissue in the neck is presented. During its course of migration there was no significant morbidity. The usual management is to locate the foreign body and remove it. A review of the literature indicates that this is evidently a rare case.

Esophageal Perforation↗
PubMed1993

Halophilic class I aldolase and glyceraldehyde-3-phosphate dehydrogenase: some salt-dependent structural features.

Aldolase and glyceraldehyde-3-phosphate dehydrogenase from the extremely halophilic archaebacterium Haloarcula vallismortis are stable only in high concentrations of KCl present within the physiological environment. Data concerning the structural changes in the two enzymes as a result of lowering of salt concentration and changes in pH were obtained by monitoring the intrinsic protein fluorescence in the presence of quenchers. When the KCl concentrations were lowered below 2 M or in the presence of 6 M guanidine hydrochloride, the emission maximum shifted to a longer wavelength, indicating enhanced exposure of tryptophyl residues to the solvent. The spectral characteristics of the two proteins in guanidine hydrochloride and 0.4 M KCl were identical. However, these denatured states appear to be different than those observed after acid denaturation. Further perturbation of fluorescence was observed due to I-, and application of the Stern-Volmer law showed that the total fluorescence was available to the quenchers only in 0.4 M KCl solutions. The unfolding of proteins in 0.4 M KCl was a gradual process which was accompanied by a time-dependent loss in enzyme activity. The activity loss was complete within 30 min for aldolase whereas in the case of GAPDH nearly 3 h was required for the destruction of activity. For both enzymes, inactivation and protein denaturation were strongly correlated. The data on activity and thermostability measurements of the two enzymes in varying concentrations of KCl and potassium phosphate revealed that though both proteins are halophilic, the forces in the maintenance of their stability could be different.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylamide↗
PubMed1992

Comparative study of plain-film radiographs of maxillary sinuses between radiologists and clinicians.

Maxillary sinuses plain film radiographs of 59 patients were reviewed and reported by both clinicians or Radiologists at the University Hospital, Kuala Lumpur. There was agreement in 52 reports of the plain film radiographs however there was partial differences in about seven cases. This gave an impression that the ENT specialist and the Radiologist were both capable of reporting plain film radiographs of maxillary sinuses, even though the radiologist has no opportunity of doing detail clinical examination of the patient.

Adolescent↗
PubMed1991

An unusual class I (Schiff base) fructose-1,6-bisphosphate aldolase from the halophilic archaebacterium Haloarcula vallismortis.

An electrophoretically homogeneous class I (Schiff base) alsolase has been isolated for the first time from the archaebacterial halophile Haloarcula (Halobacterium) vallismortis. The aldolase was characterized with respect to its molecular mass, amino acid composition, salt dependency, immunological cross-reactivity and kinetic properties. The subunit mass of aldolase is 27 kDa, which is much smaller than other class I aldolases. By the gel filtration method, the molecular mass of the halobacterial enzyme was estimated as 280 +/- 10 kDa, suggesting a decameric nature. In contrast to many halobacterial proteins, the H. vallismortis aldolase, though a halophilic enzyme, did not show an excess of acidic residues. Unlike the eukaryotic aldolases, the activity of the halobacterial enzyme was not affected by carboxypeptidase digestion. The general catalytic features of the enzyme were similar to its counterparts from other sources. No antigenic similarity could be detected between the H. vallismortis aldolase and class I aldolase from eubacteria and eukaryotes or class II halobacterial aldolases.

Amino Acids↗