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Biomedical subjects

S I Shah

Publications and source records attributed to S I Shah.

At least 19 recordsLinked to original sources
PubMed2002

Study of Nd3+, Pd2+, Pt4+, and Fe3+ dopant effect on photoreactivity of TiO2 nanoparticles.

The metallorganic chemical vapor deposition method was successfully used to synthesize pure TiO(2) and Nd(3+)-, Pd(2+)-, Pt(4+)-, and Fe(3+)-doped TiO(2) nanoparticles. Polycrystalline TiO(2) structure was verified with x-ray diffraction, which showed typical characteristic anatase reflections without any separate dopant-related peaks. Transmission electron microscopy observations confirmed the existence of homogeneously distributed 22 +/- 3 nm TiO(2) nanoparticles. The particle size remained the same for the doped samples. The doping level of transition metals was kept at approximately 1 atomic percent, which was determined by x-ray photoelectron spectra and energy dispersive x-ray spectroscopy. The effects of different types of dopants on the photocatalytic activity were revealed by the degradation of 2-chlorophenols with an UV light source. The photocatalytic efficiency was remarkably enhanced by the introduction of Pd(2+) and Nd(3+). Nd(3+)-doped TiO(2) showed the largest enhancement. However, Pt(4+) changed the 2-chlorophenol degradation rate only slightly, and Fe(3+) was detrimental to this process. These effects were related to the position of the dopants in the nanoparticles and the difference in their ionic radii with respect to that of Ti(4+).

Journal Article↗
PubMed2001

Enhanced cationic liposome-mediated transfection using the DNA-binding peptide mu (mu) from the adenovirus core.

Promising advances in nonviral gene transfer have been made as a result of the production of cationic liposomes formulated with synthetic cationic lipids (cytofectins) that are able to transfect cells. However few cationic liposome systems have been examined for their ability to transfect CNS cells. Building upon our earlier use of cationic liposomes formulated from 3beta-[N-(N',N'-dimethylaminoethane)carbamoyl] cholesterol (DC-Chol) and dioleoyl-L-alpha-phosphatidyl-ethanolamine (DOPE), we describe studies using two cationic viral peptides, mu (mu) and Vp1, as potential enhancers for cationic liposome-mediated transfection. Mu is derived from the condensed core of the adenovirus and was selected to be a powerful nucleic acid charge neutralising and condensing agent. Vp1 derives from the polyomavirus and harbours a classical nuclear localisation signal (NLS). Vp1 proved disappointing but lipopolyplex mixtures formulated from pCMVbeta plasmid, mu peptide and DC-Chol/DOPE cationic liposomes were able to transfect an undifferentiated neuronal ND7 cell line with beta-galactosidase reporter gene five-fold more effectively than lipoplex mixtures prepared from pCMVbeta plasmid and DC-Chol/DOPE cationic liposomes. Mu was found to give an identical enhancement to cationic liposome-mediated transfection of ND7 cells as poly-L-lysine (pLL) or protamine sulfate (PA). The enhancing effects of mu were found to be even greater (six- to 10-fold) when differentiated ND7 cells were transfected with mu-containing lipopolyplex mixtures. Differentiated ND7 cells represent a simple ex vivo-like post-mitotic CNS cell system. Successful transfection of these cells bodes well for transfection of primary neurons and CNS cells in vivo. These findings have implications for experimental and therapeutic uses of cationic liposome-mediated delivery of nucleic acids to CNS cells.

Animals↗
PubMed2000

"Don't let go".

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Child↗
PubMed2000

Two distinct regions of loss on chromosome arm 4q in primary head and neck squamous cell carcinoma.

OBJECTIVE: To more clearly define the frequency and the regions of chromosome arm 4q loss in head and neck squamous cell carcinoma. DESIGN: A retrospective microsatellite analysis of DNA from previously microdissected primary tumor samples. SETTING: Academic medical center. PATIENTS AND METHODS: One hundred primary tumor samples from patients with head and neck squamous cell carcinoma were analyzed for loss of heterozygosity on the long arm of chromosome 4. The Kaplan-Meier method was used to estimate survival for 97 patients for whom clinical data were available. The Cox proportional hazards model was used to compare survival, and logistic regression was used to search for associations between clinical tumor characteristics and 4q status. RESULTS: Analysis of 33 polymorphic microsatellite markers identified 51 samples (51%) exhibiting loss of heterozygosity of 4q in at least 1 locus. Eighteen tumors revealed loss at all informative markers, indicating monosomy or complete deletion of 4q. Thirty-three tumors displayed partial loss of heterozygosity and delineated 2 minimal areas of loss at 4q2324 and 4q2829. Eleven tumors displayed loss solely at the 4q2324 region, 13 tumors displayed deletions confined to the 4q2829 region, and 9 tumors displayed selective loss at both regions. A separate analysis in a subset of 94 primary head and neck tumors was done to further delineate the minimal area of chromosomal loss at 4q2324. Analysis of 8 markers in this region allowed us to identify the smallest region of loss between markers D4S2986 and D4S1564 (a distance of 2 centimorgans). Review of the clinical records of 97 patients revealed no statistically significant association between 4q status and any clinical variable, including survival. CONCLUSION: These results confirm a high frequency of chromosome arm 4q loss in primary head and neck squamous cell carcinoma and might demarcate 2 novel putative suppressor loci involved in progression of this carcinoma.

Adult↗
PubMed2000

Enhancing the precision of ECG baseline correction: selective filtering and removal of residual error.

Reemergence of the problem of baseline correction is related to recent advancements in the electrocardiographic (ECG) analysis of beat-to-beat repolarization changes which play an important role in risk assessment and the prediction of sudden cardiac death. These alterations often have an amplitude of a few microvolts and duration of several milliseconds and their detection requires special accuracy of baseline estimation. Using detailed analysis of various types of residual errors we designed a two-step procedure for selective filtering of ECG and removal of residual error with minimal distortion of cardiac complexes and tested this approach on 100 simulated and 210 real ECG signals. Application of this procedure provided a twofold reduction in the error of baseline estimation and T-wave amplitude measurements compared to high-pass filtering. Selective application of this approach to the segments with low baseline drift allowed analysis of low-amplitude, beat-to-beat changes in repolarization during more than 70% of the recording time.

Algorithms↗
PubMed2000

Lung cancer after head and neck cancer: role of chest radiography.

OBJECTIVE: To examine whether screening chest radiographs lead to significantly longer life span in patients found to have pulmonary lesions than in those in whom lung cancer was detected after symptoms developed. STUDY DESIGN: A retrospective study. MATERIAL AND METHODS: Charts of 1,086 patients with squamous cell cancer of the head and neck treated for cure from January 1, 1974, to December 31, 1998, were analyzed. RESULTS: Pulmonary cancer developed in 62 patients. In 41 patients pulmonary malignancy was found because of patient symptoms. In 21 patients lung cancer was detected by routine annual chest radiography. Seventy-five percent of lung cancers were detected within 3 years of initial treatment of the head and neck cancer. CONCLUSION: Chest radiography is a poor screening tool, because it failed to find pulmonary lesions in more than 65% (41/62) of patients who were later found to have pulmonary cancer. Survival rate did not differ between patients in whom pulmonary cancer was found by screening chest radiography and those in whom symptoms prompted evaluation (P = .48). Using current treatment protocols, routine yearly chest radiography did not improve survival in patients with head and neck cancer. However, there maybe new therapeutic regimens under investigation that would benefit these patients if their lung cancers were found in early stages of disease. Future directives must include the establishment of an effective follow-up protocol for the early detection of lung malignancies in these patients.

Adult↗
PubMed1999

Changes in autonomic activity and ventricular repolarization.

An increase in sympathetic activity, manifested by shortening of RR intervals (RRi) and changes in RRi variability, precedes and possibly triggers ventricular tachyarrhythmias (VTAs) by altering repolarization. We examined the effects of autonomic activity on the projection of repolarization as detected by body surface potential maps (BSPMs). We recorded 32 lead/192-point BSPMs during passive head-up tilt, tilt + infusion of isoproterenol, rapid atrial pacing, and atrial pacing + infusion of isoproterenol. Changes in QT; recovery time; activation-recovery interval (ARi); T-wave amplitude; and QT, QRST, and ST integrals and their dispersion were analyzed. Autonomic effects on sinus node were inferred from the Fourier transform-derived low and high frequency powers of RRi variability. Patients were divided into those with (SHD) and without structural heart disease (NSHD). Heart rate increased, whereas QT interval and ARi declined with tilt in both groups. RRi variability indices of sympathetic activity increased in NSHD but did not change in SHD. T-wave amplitudes declined in NSHD but did not change in SHD, suggesting altered responsiveness of ventricular repolarization to autonomic stimulation. Tilt and rapid atrial pacing during infusion of isoproterenol resulted in a paradoxical increase in T-wave amplitudes in some patients, similar to that observed before the onset of spontaneous arrhythmias. We conclude that altering autonomic activity by head-up tilt and/or infusion of sympathomimetic agents results in significant changes in the body surface projection of cardiac repolarization, which differ in patients with SHD from those without SHD. Similar paradoxical changes in the T-wave amplitude have been observed before the onset of spontaneous VTA, suggesting that abnormal response of repolarization to autonomic stimulation predisposes to arrhythmogenesis.

Adult↗
PubMed1999

Comparative microsatellite analysis in discerning origin of disseminated tumor: the case of a patient with malignant ascites and a history of multiple tumors.

The origin of metastatic carcinoma is now always easily resolved on the basis of conventional dinical and pathological parameters, particularly in patients with more than 1 primary tumor. When 1 of the tumors is a renal cell carcinoma, the clinical picture is further confounded by the tendency of these tumors to be locally silent, to metastasize to unusual sites, and to disseminate long after removal of the primary tumor. We compared tumors for loss (ie, deletion) of loci on chromosomal arms 3p, 5q, 11q, and 18q in a patient with a malignant ascites fluid, a remote history of renal and colonic neoplasms, and a strong clinical suspicion of disseminated gastrointestinal adenocarcinoma. DNA from microdissected tumors and normal tissues was subjected to polymerase chain reaction-based microsatellite analysis. Even though the clinical picture suggested a gastrointestinal origin, comparison of genetic alterations clearly showed that the malignant ascites represented recurrence of the renal cell carcinoma. The malignant ascites and the primary renal cell carcinoma showed identical patterns of allelic loss at all loci tested. In contrast, the malignant ascites and colonic adenoma showed discordant patterns of allelic loss. Comparative microsatellite analysis provides a rapid genetic approach for discerning the origin of metastatic tumor spread. This may be a useful diagnostic adjunct when tumor origin is not clear on clinical or morphological grounds. In some instances, it may even provide a reasonable alternative to an extensive and costly conventional work-up.

Adenoma↗
PubMed1998

Keeping the faith.

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Clinical Clerkship↗
PubMed1997

Corneal topography of excimer laser photorefractive keratectomy using a 6-mm beam diameter. Summit PRK Topography Study Group.

OBJECTIVE: The purpose of the study is to define qualitative patterns of corneal topography after excimer laser photorefractive keratectomy (PRK) using a 6-mm beam diameter, investigate changes in patterns over time, and identify associations of topography patterns with clinical outcomes. DESIGN: Multicenter, prospective cohort study. PARTICIPANTS: Ninety-eight eyes of 90 patients with myopia who had undergone PRK using the Summit Technology, Inc., excimer laser with a 6-mm beam diameter. INTERVENTION: Computer-assisted videokeratography data were analyzed for eyes having undergone PRK. Topography patterns at 3, 6, and 12 months after surgery were classified and associations with clinical outcomes assessed. MAIN OUTCOMES MEASURED: Topography patterns after PRK were determined at 3, 6, and 12 months after surgery. Associations with preoperative characteristics of age and attempted correction, and postoperative outcomes of uncorrected and spectacle-corrected visual acuity, predictability, astigmatism, corneal haze, glare, halo, and patient satisfaction were analyzed. RESULTS: At 1 year, 21.4% of corneas showed a homogeneous topography, 27.6% showed a toric-with-axis configuration, 10.2% showed a toric-against-axis configuration, 7.1% showed an irregularly irregular topography, 24.5% showed a keyhole/semicircular pattern, and 9.2% showed focal topographic variants. From 3 to 6 months, 40.1% of maps changed; from 6 to 12 months, 53.1% of maps changed, generally to optically smoother, regular patterns. Older age and higher attempted correction were associated with the development of more irregular patterns. The irregular groups showed worse predictability than did the regular groups and a tendency for slight overcorrection. The average reported glare/halo of 1.33 (scale = 0 to 5) in this study was less than in a previous study of the 4.5- to 5-mm treatment zone. However, of six patients expressing dissatisfaction with the results of surgery, three ranked their glare or halo at the maximum level. CONCLUSIONS: Topography patterns using a 6-mm beam diameter are identifiable, improve with time, and may affect clinical outcomes after photorefractive keratectomy (PRK). The keyhole/semicircular pattern is more prevalent with a 6 mm treatment zone than with smaller treatment zones. Although optical side effects of glare and halo appear to be reduced with the 6-mm treatment, a small number of patients still report substantial glare or halo after the procedure.

Astigmatism↗
PubMed1996

Corneal optical irregularity after excimer laser photorefractive keratectomy. The Summit Photorefractive Keratectomy Topography Study Group.

PURPOSE: To assess the influence of corneal surface microirregularities on objective and subjective visual performance after photorefractive keratectomy (PRK). SETTING: Multicenter clinical trial. METHODS: The alpha version of the Potential Corneal Acuity (PCA) computer program, currently under development, was used to qualitatively and quantitatively analyze the corneal surface of 176 eyes of 176 patients 1 year after PRK. Color maps of corneal surface irregularities were reviewed and quantitative values (PCA) predicting best spectacle-corrected visual acuity (BSCVA) as limited by the cornea were evaluated for associations with qualitative topography patterns, optical zone decentration, and clinical outcomes of BSCVA, uncorrected visual acuity (UCVA), subjective patient satisfaction, and a subjective glare/halo index. RESULTS: Qualitatively, corneas after PRK were generally characterized by a ring of optical irregularity at the juncture of the ablation zone and untreated cornea. Standard corneal topography maps graded as irregular after PRK had a significantly higher PCA value than those graded as regular. There was a trend toward higher PCA values with greater optical zone decentration that was not statistically significant. Actual BSCVA was identical to that which the PCA value predicted in 32% of patients and was within one Snellen line in 71%, within two lines in 89%, and within three lines in 94%. The correlation between the PCA and the glare/halo index and with subjective patient satisfaction was statistically significant. The relationship between PCA and UCVA was not significant. CONCLUSIONS: A ring of optical microirregularity of the corneal surface can appear at the juncture of the treated and untreated cornea after PRK, indicating that the optical zone edge might affect objective and subjective postoperative visual outcomes. Further understanding of corneal surface topography and refinement of the PCA program should help explain visual outcome after PRK.

Adult↗
PubMed1996

Corneal asphericity following excimer laser photorefractive keratectomy. Summit PRK Topography Study Group.

BACKGROUND AND OBJECTIVE: To analyze corneal asphericity following excimer laser photorefractive keratectomy (PRK) and its influence on clinical outcomes. PATIENTS AND METHODS: A computer program (Holladay Diagnostic Summary, EyeSys Laboratories, Houston, TX) was used to qualitatively and quantitatively analyze the corneal asphericity of 132 patients 1 year following PRK for correction of myopia. Color maps depicting actual corneal asphericity as compared to the normal expected asphericity were reviewed, and quantitative values of asphericity were evaluated for associations with clinical outcomes of uncorrected visual acuity and spectacle corrected visual acuity, achieved refractive correction, a subjective glare/halo index, and subjective patient satisfaction, as well as standard corneal topography patterns and optical zone decentration following PRK. RESULTS: Following PRK, all corneas exhibited a positive central asphericity, changing from a prolate (negative asphericity) to an oblate optical contour. There was a trend toward higher positive asphericity measurements with improving spectacle corrected visual acuity which was not statistically significant; such a relationship was not found with uncorrected visual acuity. A significant association was found between greater achieved refractive correction and increased postoperative positive asphericity. No association was found between postoperative asphericity and the glare/halo index, subjective patient satisfaction, topography pattern, or optical zone decentration. CONCLUSION: Asphericity may be a useful quantitative descriptor of corneal optical contour following PRK. Greater positive central corneal asphericity is found with greater degrees of refractive correction. Further understanding of both the pre- and post-operative corneal contour and the consequent optical effects should aid in a better understanding of the optical outcomes of PRK.

Color↗
PubMed1987

Broviac catheter insertion: operating room or neonatal intensive care unit.

We reviewed the records of all infants hospitalized in the neonatal intensive care unit (NICU) who underwent insertion of a Broviac catheter from July 1, 1984 through August 30, 1985. Eighty-six catheters were inserted in 81 patients. Thirty-one catheters were inserted in the NICU and the remainder were inserted in the operating room (OR). The patient's average weight at the time of catheter insertion was the same in both groups. Fifty-two of the 55 OR catheters (95%) were inserted in the external or internal jugular vein while only 68% of the NICU catheters were placed in the jugular veins. Six of the NICU catheters (19%) and 11 of the OR catheters (20%) developed catheter-associated sepsis with positive blood cultures. The infection rate per catheter day was similar in both groups as was the incidence of catheter occlusion. The NICU catheters were in place for an average of 51 days, and there was an average 46 day lifespan for the OR inserted catheters. Broviac catheter insertion can safely be performed in the NICU without an increase in morbidity. Broviac catheter insertion in the NICU is less costly and saves transportation of the sick neonate to the operating room.

California↗