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Biomedical subjects

R Arora

Publications and source records attributed to R Arora.

At least 91 records · Page 5Linked to original sources
PubMed1998

Structural plasticity in RNA and its role in the regulation of protein translation in coliphage Q beta.

We have analyzed both conformational and functional changes caused by two large cis-acting deletions (delta 159 and delta 549) located within the read-through domain, a 850 nucleotide hairpin, in coliphage Q beta genomic RNA. Studies in vivo show that co-translational regulation of the viral coat and replicase genes has been uncoupled in viral genomes carrying deletion delta 159. Translational regulation is restored in deletion delta 549, a naturally evolved pseudorevertant. Structural analysis by computer modeling shows that structural features within the read-through domain of delta 159 RNA are less well determined than they are in the read-through domain of wild-type RNA, whereas predicted structure in the read-through domain of evolved pseudorevertant delta 549 is unusually well determined. Structural analysis by electron microscopy of the genomic RNAs shows that several long range helices at the base of the read-through domain, that suppress translational initiation of the viral replicase gene in the wild-type genome, have been destabilized in delta 159 RNA. In addition, the structure of local hairpins within the read-through region is more variable in delta 159 RNA than in wild-type RNA. Stable RNA secondary structure is restored in the read-through domain of delta 549 RNA. Our analyses suggest that structure throughout the read-through domain affects the regulation of viral replicase expression by altering the likelihood that long-range interactions at the base of the domain will form. We discuss possible kinetic and equilibrium models that can explain this effect, and argue that observed changes in structural plasticity within the read-through domain of the mutant genomes are key in understanding the process. During the course of these studies, we became aware of the importance of the information contained in the energy dot plot produced by the RNA secondary structure prediction program mfold. As a result, we have improved the graphical representation of this information through the use of color annotation in the predicted optimal folding. The method is presented here for the first time.

Allolevivirus↗
PubMed1998

Shear bond strength of resin-modified restorative glass-ionomer cements to dentin--an in vitro study.

An in vitro study was carried out on 40 periodontally involved, caries free human maxillary and mandibular molars to evaluate shear bond strength of resin- modified restorative glass-ionomer cements to dentin. Teeth were divided into four groups, Group I--Fuji II (Conventional glass ionomer) Group II (Fuji II LC), Group III (Vitremer), Group IV (Geristore). Shear bond strength was tested using a transaxial testing machine. Results showed that shear bond strength of all resin-modified restorative glass-ionomer cements was higher than conventional glass ionomer (Fuji II) tested. No statistical difference was found between Fuji II LC and Geristore. However, bond strength of Vitremer was lower than Fuji II LC and Geristore but higher than Fuji II.

Chemical Phenomena↗
PubMed1998

Senior-Loken syndrome with unusual manifestations.

The Senior-Loken syndrome, also called Hereditary Renal Retinal Dystrophy is a rare disorder that combines a juvenile nephronophthisis-like disease with tapetoretinal degeneration. We are reporting a family in which two, possibly three siblings are affected by this disorder. In addition to these two documented components of the disease, our patients also have unusual manifestations: short stature; skeletal abnormalities in the form of kyphoscoliosis, short metacarpals; and cutis laxa-unreported so far.

Adult↗
PubMed1998

An alternative approach to bandage contact lenses.

PURPOSE: Therapeutic bandage contact lenses have been used in the management of a variety of corneal and anterior segment disorders. However, clinical experience with the therapeutic use of disposable contact lenses is limited. The present study was designed to evaluate the efficacy of disposable contact lenses as bandage lenses in anterior segment disorders. METHODS: We fit 45 patients who had various corneal and anterior segment disorders with disposable contact lenses (42% etafilcon A and 58% water content). We used this lens as a healing and surgical adjunct and for structural support and symptomatic relief. Patients were followed for a minimum period of 3 months. Therapeutic efficacy and complications were evaluated. RESULTS: Eighty-two percent of patients were fit successfully. Ninety-one percent of the successfully fit patients were therapeutic successes. Disposable lenses were found to be very useful in the management of epithelial abnormalities and as surgical adjuncts. Dry eye was the most frequent cause of contact lens associated therapeutic failure. Complications included contact lens deposits, lens loss, and corneal neovascularization. CONCLUSIONS: The use of disposable lenses was most effective in conditions requiring short-term lens use where one to two lens applications were sufficient to allow healing, making disposable lenses a very convenient and cost-effective alternative to conventional therapeutic bandage contact lenses. For reasons of cost, disposable lenses were not a viable alternative in conditions requiring therapeutic lens use for long periods of time.

Adult↗
PubMed1998

Ectopic pregnancy--changing trends.

This study is an attempt to have an overall view of the changing trends in the clinical presentation, diagnostic modalities and management of ectopic pregnancy over a period of three and a half decades. The incidence of ectopic pregnancy was one in 368 during the 15-year period from 1959-1973 (group A) and has increased to one in 160 during the latter part of the study period from 1988-1993 (group B). Medical termination of pregnancy, abortion, intra-uterine contraceptive device and previous tubal ligation were the important risk factors recently (group B). Unruptured tubal pregnancy was diagnosed in 9.8% (group B) as compared to only 3% in group A. However, as most of the patients came to the hospital with disturbed pregnancy, the use of ultrasonography and urine gravindex test was helpful in only 14% in the latter part of the study. The characteristic clinical features like pain abdomen with amenorrhoea, vaginal bleeding and positive culdocentesis were the most reliable diagnostic criteria in both the groups. There is an increasing trend towards conserving the tubes and methotrexate use recently.

Adult↗
PubMed1997

Effects of atrial fibrillation on left ventricular function and geometry in mitral stenosis.

This study shows that patients with mitral stenosis have depressed left ventricular ejection performance and spherical remodeling of the left ventricular cavity, which is more marked in those with atrial fibrillation. These changes have important clinical implications regarding treatment strategy in patients with mitral stenosis and chronic atrial fibrillation.

Atrial Fibrillation↗
PubMed1997

Translational activation in coliphage Qbeta: on a polycistronic messenger RNA, repression of one gene can activate translation of another.

We present evidence for translational activation of the Qbeta coliphage maturation cistron, mediated by the presence of Qbeta replicase. This activation does not require RNA replication, translation of a second gene, or any direct protein-RNA binding at the maturation gene initiation site. Our data support a model in which the Qbeta maturation gene remains translationally "off" by two means: (1) the thermodynamic stability of an RNA structure that greatly discourages, but does not eliminate, ribosome access at the maturation start site; and (2) the presence of the stronger, proximal coat gene ribosome binding site. Moreover, maturation gene expression is switched "on" when ribosome entry at the coat initiation site, present on the same polycistronic RNA molecule, is repressed by Qbeta replicase, thereby allowing ribosomes to compete for the weaker, upstream maturation start site.

Allolevivirus↗
PubMed1997

Prediction of pKa values of phenolic and nitrogen-containing compounds by computational chemical analysis compared to those measured by liquid chromatography.

The pKa values of 64 phenolic and 50 nitrogen-containing compounds were obtained by reversed-phase liquid chromatography and computational chemical calculation. The chromatographically obtained values of phenolic compounds were equal to pKa values from references and Hammett's equation, and those of nitrogen-containing compounds were lower than the reference values. It appeared difficult to calculate the properties of the ortho effect and nitro group by the computational calculation method. However, the calculation was simpler than selecting different constants of Hammett's equation for a variety of compounds.

Computer Simulation↗
PubMed1997

Evaluation of neuropathy in patients on suramin treatment.

Suramin, a promising chemotherapeutic agent, causes a dose-limiting sensorimotor polyneuropathy. We undertook a phase 1 study of suramin that included serial neurologic and electrophysiologic examinations as part of the safety evaluation. We found that 6 of 41 (15%) patients developed suramin-induced demyelinating neuropathy which resembled Guillain-Barre syndrome clinically. There was 1 asymptomatic patient with electrophysiologic abnormalities suggestive of a demyelinating neuropathy. In addition, 1 patient with mild axonal neuropathy at baseline had deterioration of his symptoms during suramin treatment. Four asymptomatic patients developed electrophysiologic findings suggestive of a mild axonal neuropathy. We conclude that: (1) serial electrophysiologic monitoring is helpful for early detection of suramin-induced neuropathy; and (2) fixed dosing schedule of suramin without adaptive control does not lead to an increased incidence of demyelinating neuropathy when compared to adaptively controlled dosing schedules.

Adult↗
PubMed1997

Percutaneous transluminal angioplasty for renovascular hypertension in children: initial and long-term results.

OBJECTIVE: To evaluate the efficacy and safety of percutaneous transluminal renal angioplasty (PTRA) in children. METHODS: We performed aortography and attempted PTRA in 35 consecutive children (age 5 to 14 years, mean 10.8 +/- 2.5 years) with severe hypertension having > or = 75% renal artery stenosis (RAS). RESULTS: The stenosis was caused by aortoarteritis in 31 (88.6%) cases and by juvenile idiopathic fibromuscular disease (FMD) in four (11.4%) cases. Twenty-seven (77.1%) patients, including three having RAS of solitary functioning kidney with total occlusion of contralateral renal artery, had bilateral RAS and eight (22.9%) had unilateral RAS. PTRA was technically successful in 54 (91.5%) of 59 stenotic lesions in 31 (88.6%) of 35 patients. Both aortoarteritis and FMD patients had significant decrease in RAS after PTRA. One patient had acute reocclusion of one renal artery after bilateral PTRA, which could be successfully opened by reangioplasty. Postangioplasty angiographic restudy performed in 18 patients at 4 to 72 months (mean 23.1 +/- 27.9 months) after successful angioplasty showed restenosis in 8 (25.8%) of 31 lesions initially dilated and de novo lesions of aorta in two patients. All seven restenotic renal artery lesions attempted and both stenosis of aorta were successfully dilated. Twenty-nine of 31 patients with successful PTRA have been followed up from 4 to 108 months (mean 41.0 +/- 29.3 months). Mean systolic blood pressure decreased from 185.1 +/- 27.4 to 120.6 +/- 19.2 mm Hg and mean diastolic blood pressure decreased from 118.4 +/- 13.2 to 84.6 +/- 10.4 mm Hg after PTRA. Twenty seven (93.1%) of these 29 patients had benefical blood pressure response. Seventeen (58.6%) patients improved, 10 (34.5%) were cured, although 2 (6.9%) patients failed to respond to PTRA. Blood pressure response was better in FMD as compared to aortoarteritis group. Patients with unilateral RAS, discrete stenosis, and post-PTRA stenosis < or = 20% also identified good blood pressure response. CONCLUSION: Aortoarteritis is the most common cause of renovascular hypertension in South Asian children. PTRA is safe and highly effective and therefore should be the treatment of choice in pediatric renovascular hypertension.

Adolescent↗
PubMed1997

Retinoblastoma--a histologic and immunohistologic study.

Histopathology and various immunohistochemical markers were studied in 40 cases of human retinoblastoma. In histopathology, tumour type, extent and invasion were studied. In immunohistochemistry, both glial and neural markers were used to know the histogenesis of this tumour. The glial markers, glial fibrillary acidic protein and vimentin, were detected in retinal astrocytes and Muller's cells in normal retina and perivascular glia in retinoblastoma. The neural marker, neurone-specific enolase stained neurones in outer and inner nuclear layers in normal retina, Flexner-Wintersteiner rosettes in retinoblastoma and tumour cells is differentiated retinoblastoma. Another neural marker, neurofilament triplet polypeptide stained neurones in inner nuclear layer of normal retina and Flexner-Wintersteiner rosettes in well-differentiated retinoblastoma. These results support the view that retinoblastoma has predominantly neuronal origin.

Biomarkers, Tumor↗
PubMed1997

Black corneal ulcer.

PURPOSE: To discuss the etiology of an unusual finding of black color in a corneal ulcer. METHODS: Smear examination and culture of the corneal scraping were undertaken. RESULTS: The causative organism was found to be Aspergillus ruger. CONCLUSION: Black color in the corneal ulcer is attributed to Aspergillus niger.

Administration, Topical↗
PubMed1997

Impact of mode of delivery on maternal mortality in eclampsia.

Determinants of maternal mortality and causes of death pertaining to mode of delivery have been discussed. There were 23 deaths (case fatality rate of 7.2%) and maximum deaths occurred in intrapartum eclampsia (12 ie, 52.17%). Caesarean section was performed in 92 cases (28.7%) of which 4 women died (4.3%). Maternal mortality in cases who delivered vaginally was 7.1% (16 out of 225) and 3 cases died undelivered. Authors feel that at the referral centres early caesarean section in eclampsia may help in reducing maternal mortality.

Adult↗
PubMed1996

cis-acting elements within an RNA coliphage genome: fold as you please, but fold you must!!

Using an in vivo complementation system, we conducted a mutational analysis of the bacteriophage Q beta readthrough cistron. In the Q beta cDNA-containing plasmid, pQ beta m100, we constructed six defined Q beta deletion cDNA genomes, each missing between 86 and 447 nucleotides from within the readthrough cistron. These deletion plasmids were introduced into host cells that are constitutively supplied with Q beta readthrough protein from the plasmid pQ beta RT. Under these conditions, all six deletion genomes spontaneously generated phage particles, each exhibiting a characteristic plaque phenotype and virus forming potential. Isolated readthrough-defective phage particles were subsequently used to infect host cells that carried helper readthrough protein. Passaged viruses yielded both larger plaques and higher titers, compared with those of the parent phages. Sequence analysis revealed that the genomes of the passaged viruses had deleted additional regions of readthrough RNA sequence. We discuss the possibilities that (1) the disruption of a well-defined structural domain in Q beta RNA was selectively disadvantageous to phage infection, and that (2) the evolved viral populations were selected by virtue of their ability to restore critical integrity of short and/or long-range nucleotide interactions within this region of Q beta RNA.

Base Sequence↗