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Biomedical subjects

S Raza

Publications and source records attributed to S Raza.

At least 19 recordsLinked to original sources
PubMed2005

Calculation of immersion doses from external exposure to a plume of radioactive material.

The immersion doses from external exposure to a Gaussian plume of noble gases accidentally released into the atmosphere have been calculated. A numerical integration procedure employing Gauss-Legendre of 64th order has been used. The numerical procedure allows calculating the dose rate at any downwind horizontal or vertical distance. The dose rates were calculated using various forms of gamma dose build-up factors, including Linear, Berger and Geometric Progression (GP). The GP form, having an extraordinarily precise formulation, is a favored choice because the build-up factor levels off for large distances and does not increase exponentially as does the Berger form. The Linear form much under predicts the build-up and subsequently the dose rates for large distances from the source. The dose predictions using a simple uniform cloud model (that does not use any form of build-up factor) is also presented for comparison purposes. The comparison of dose rates with the already reported results indicated that the numerical procedure could be used for dose calculations from a Gaussian plume for all downwind and crosswind distances. The comparison of dose rates obtained using different forms of the build-up factors indicated that the Geometric Progression form was a favored choice and has a wider range of applicability as compared to the Linear or Berger form. The simple uniform cloud model for dose calculations is only suitable for plume centerline doses and should be used with caution for off-center distances.

Air Pollutants, Radioactive↗
PubMed2001

Tolerance of Bradyrhizobium sp. (Lupini) strains to salinity, pH, CaCO3 and antibiotics.

AIMS: Ten rhizobial isolates obtained from different locations in Egypt were examined for their ability to survive under stress conditions and their growth response to increasing levels of NaCl (1-8% w/v), pH (4-10), CaCO3 (1-10% w/v) and 12 antibiotics. METHODS AND RESULTS: All the rhizobial isolates tolerated a NaCl concentration up to 5% and were divided into two groups with respect to NaCl tolerance. The rhizobial isolates from group two showed significantly (P < 0.05) better survival under high NaCl concentration. All the tested isolates survived acidic (pH 4-5) and alkaline conditions (pH 9-10) and CaCO3 (up to 10% w/v) in liqued YEM medium. CONCLUSION: Antibiotic resistance patterns did not correlate to NaCl, pH or CaCO3 tolerance. Variations among different strains showed that there is potential to improve strain performance under stress conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The results suggest that selection of adapted strains under stress conditions is possible and can be used as inoculants for successful lupin growth.

Anti-Bacterial Agents↗
PubMed2001

A 3D Lagrangian particle model for direct plume gamma dose rate calculations.

A fully 3D Lagrangian particle model has been presented for calculating the direct gamma dose rates due to a radionuclide plume in the atmosphere. A continuous release of radionuclides into the atmosphere was simulated by liberating a series of puffs (each containing 100 Lagrangian particles). These puffs were released with a constant time lag between the successive puffs. The Lagrangian particle trajectories were tracked for about 25 h in a turbulent atmosphere, with a specified wind field. The atmosphere turbulent/stability characteristics like wind velocity fluctuations, eddy lifetime, etc, were obtained from the reported data in the published literature. For calculating the direct plume gamma dose rates, a point isotropic source formula has been used with appropriate attenuation and build-up factors for the air medium. Each Lagrangian particle represented a point source whose radioactive strength was calculated from the known release rate. The dose rates at ground due to the radionuclide plume were calculated by adding the contribution from each Lagrangian particle in the domain. The numerically calculated dose rates were compared with the numerical results reported in the literature. An excellent comparison was observed for downwind distances up to about 20 km. However, for distances exceeding 20 km, the numerical data were below the reported results for the Gaussian plume model. This discrepancy was due to the vertical wind shear. It is concluded that a Gaussian plume model can be used for the concentration calculations provided the lateral dispersion parameter, sigma(gamma), includes the effect of wind shear, for distances exceeding 20 km.

Air Movements↗
PubMed2001

Enantioselectivity in Candida antarctica lipase B: a molecular dynamics study.

A major problem in predicting the enantioselectivity of an enzyme toward substrate molecules is that even high selectivity toward one substrate enantiomer over the other corresponds to a very small difference in free energy. However, total free energies in enzyme-substrate systems are very large and fluctuate significantly because of general protein motion. Candida antarctica lipase B (CALB), a serine hydrolase, displays enantioselectivity toward secondary alcohols. Here, we present a modeling study where the aim has been to develop a molecular dynamics-based methodology for the prediction of enantioselectivity in CALB. The substrates modeled (seven in total) were 3-methyl-2-butanol with various aliphatic carboxylic acids and also 2-butanol, as well as 3,3-dimethyl-2-butanol with octanoic acid. The tetrahedral reaction intermediate was used as a model of the transition state. Investigative analyses were performed on ensembles of nonminimized structures and focused on the potential energies of a number of subsets within the modeled systems to determine which specific regions are important for the prediction of enantioselectivity. One category of subset was based on atoms that make up the core structural elements of the transition state. We considered that a more favorable energetic conformation of such a subset should relate to a greater likelihood for catalysis to occur, thus reflecting higher selectivity. The results of this study conveyed that the use of this type of subset was viable for the analysis of structural ensembles and yielded good predictions of enantioselectivity.

Butanols↗
PubMed2001

Patient expectations and costs of immediate reporting of screening mammography: talk isn't cheap.

OBJECTIVE: Our purpose was to determine whether patients prefer immediate or delayed results of screening mammography and to determine the cost of immediate reporting at our institution. MATERIALS AND METHODS: A survey was anonymously and randomly distributed to 129 women who were 35-70 years old during a visit to their primary care physician, asking the women's preference for receiving mammography results by one of two systems: by letter with a return visit for any additional tests; or by speaking at once with the radiologist, with the option of additional tests being performed during the same visit. Patients' willingness to pay for the latter service was also determined. A cost identification model was constructed using commercially available software. We considered the impact on radiologists' and technologists' time and the need for additional equipment and space, and we analyzed the effect on the cost of immediate reporting. RESULTS: One hundred twenty (93%) surveys were completed. Eighty women (67%) preferred immediate reporting, and 62 (78%) of these 80 patients would wait 30-60 min. The additional cost of immediate reporting is $28.22 per patient. Only 11% of patients were willing to pay this additional cost. When new equipment and space were not required, the cost would increase by $4.38. This cost was most influenced by the time required to give patients normal results. CONCLUSION: Most surveyed patients preferred speaking with a radiologist immediately but were unwilling to pay additional fees. Radiologists, hospital administrators, and health care planners must be aware of the costs of immediate reporting and must factor these costs into any change in hospital or national policy.

Adult↗
PubMed2000

NMDA receptor activation: critical role in oxidant tissue injury.

The excitatory amino acid glutamate serves important neurologic functions, but overactivation of its N-methyl-D-aspartate (NMDA) receptor is toxic to neurons (excitotoxicity). We report that NMDA receptor blocker MK-801 (dizocilpine maleate) attenuated oxidant injury induced by paraquat or by xanthine oxidase. We conclude that excitotoxicity may be a key factor in oxidant tissue injury.

Animals↗
PubMed2000

Use of Doppler ultrasound in the evaluation of breast carcinoma.

Ultrasound is an imaging modality commonly used to evaluate breast lesions in hopes to distinguish benign from malignant solid masses. Angiogenesis, defined as the emergence of new vessels to further the growth of tumor, has stimulated interest in the potential uses of Doppler ultrasound in patients with breast cancer. This article describes different forms of Doppler ultrasound, including color Doppler (CD), power Doppler (PD), and spectral Doppler (SD), as well as 3-dimensional (3D) ultrasound and ultrasound contrast media. We review the role of Doppler ultrasound in distinguishing benign from malignant solid breast masses. We also discuss the role of ultrasound in predicting tumor grade, histology, node status, and lymphatic vascular invasion, and in monitoring breast cancer treatment.

Breast↗
PubMed1999

Power Doppler sonography of breast cancer: does vascularity correlate with node status or lymphatic vascular invasion?

OBJECTIVE: The purpose of our study was to determine how breast cancer vascularity, as revealed by power Doppler sonography, correlates with lymph node involvement and lymphatic vascular invasion. MATERIALS AND METHODS: Breast sonograms obtained during a 2-year period were retrospectively reviewed. Patients who underwent power Doppler sonography of solid masses and had biopsy-proven carcinoma composed our study population. Power Doppler findings were categorized according to the presence or absence of vessels. Pathologic findings were reviewed for lymph node involvement and lymphatic vascular invasion. RESULTS: Of 176 patients with breast cancer, vessels were seen on power Doppler sonography in 128 (73%) and not seen in 48 (27%). Of 126 patients who underwent lymph node dissection, vessels were seen in 97 (77%) and not seen in 29 (23%). Lymph node involvement was seen in 42 (43%) of the 97 patients in whom vessels were seen and in three (10%) of the 29 in whom vessels were not seen. Of 150 patients examined for lymphatic vascular invasion, vessels were seen in 111 (74%) and not seen in 39 (26%). Lymphatic vascular invasion was seen in 47 (42%) of the 111 patients in whom vessels were seen and in five (13%) of the 39 in whom vessels were not seen. CONCLUSION: Tumor vascularity revealed by power Doppler sonography correlated strongly with detection of lymph node involvement and lymphatic vascular invasion, with sensitivities of 93% and 90%, respectively. However, the specificities were low, at 32% and 35%, respectively. More important, patients with breast cancer in whom vessels were not revealed by power Doppler sonography also were unlikely to have lymph node involvement and lymphatic vascular invasion: Negative predictive values were 90% and 87%, respectively.

Adult↗
PubMed1999

Assessment of pathologic prognostic factors in breast core needle biopsies.

BACKGROUND: Core needle biopsies (CNB) are being used increasingly as the initial diagnostic procedure in women with breast cancer. Many clinicians are interested in obtaining as much prognostic information as possible from these limited specimens. However, the accuracy of assessing pathologic prognostic factors in core biopsy material has not been studied in detail. DESIGN: We studied CNB and subsequent excision specimens from 79 women with invasive breast cancer. Slides from CNB and excision specimens were reviewed in a blinded fashion and each was assessed for histologic type, tumor size, histologic grade, lymphatic vessel invasion (LVI), and the presence of an extensive intraductal component (EIC). RESULTS: Among the 79 cancers, there were 58 invasive ductal carcinomas, six invasive lobular carcinomas, 13 invasive carcinomas with ductal and lobular features and two tubular carcinomas, based on examination of the excision specimens. Histologic type on CNB correlated with that on excision in 64 cases (81%). Although there was a significant correlation between tumor size on CNB and excision specimens (r2 = 0.30, P = 0.01), the pathologic T stage was underestimated on CNB in 79% of cases. Furthermore, T substage was underestimated on CNB in 71% of T1 lesions. There was concordance in histologic grade between CNB and excisions in 75% of cases. Among the 20 discordant cases, the grade was higher in the excision than in the CNB in 13 cases and lower in seven. However, all discrepancies were within one grade. None of the 17 cancers with LVI in the excision specimen showed LVI on the CNB. Among 14 cases with an EIC on the excision specimen, only four (29%) were scored as having an EIC on CNB. CONCLUSION: Histologic type can be accurately determined on CNB in most cases. While there was concordance in histologic grade between CNB and excision in the majority of cases, grade was discordant in a substantial minority (25%). The ability to accurately determine tumor size (pathologic T-stage), LVI, and EIC on CNB is severely limited.

Adenocarcinoma↗
PubMed1998

Glutamate toxicity in the lung and neuronal cells: prevention or attenuation by VIP and PACAP.

VIP, which has been demonstrated to reduce or prevent oxidant injury in the lungs and other organs, is shown here to protect against excitotoxic injury of the lung and excitotoxic death of cortical neuronal cells in primary culture. Glutamate killing of neuron-like PC-12 cells, attributable to oxidant stress rather that to excitotoxicity, is also reduced or prevented by VIP and by the closely related peptide PACAP. The exact mechanisms of this protection remain to be determined, but appear to include antioxidant and anti-apoptotic actions, and suppression of glutamate-induced upregulation of its own receptor. Both VIP and PACAP offer the promise of novel and nontoxic means of defending against NMDA and glutamate toxicity.

Animals↗
PubMed1998

Enhancement of systemic and pulmonary vasoconstriction by beta-amyloid peptides and its suppression by vasoactive intestinal peptide.

(1) A beta peptides potentiate vasoconstriction, caused by norepinephrine, and possibly other endogenous vasoconstrictors. If this potentiation occurs in the cerebral circulation, close to sites of A beta deposition in AD brains, the enhanced vasoconstriction could result in neuronal ischemia and death. (2) By neutralizing this deleterious effect of A beta, and through other neuroprotective mechanisms, VIP may provide an important defense against neuronal loss in AD.

Amyloid beta-Peptides↗
PubMed1998

Probing the stabilizing role of C-terminal residues in trimethylamine dehydrogenase.

In trimethylamine dehydrogenase, a homodimeric iron-sulfur flavoprotein, the C-terminal 17 residues of each subunit (residues 713-729) embrace residues on the other subunit. The role of this unusual mode of interaction at the subunit interface was probed by isolating three mutant forms of trimethylamine dehydrogenase in which the C-terminus of the enzyme was deleted by five residues [delta(725-729], 10 residues [delta(720-729)] and 17 residues [delta(713-729)]. The solution properties and conformational states of the three mutant enzymes were investigated using optical, fluorescence and circular dichroism spectroscopies, ANS binding and a novel and conformationally sensitive hydrodynamic method. The data reveal that sequential deletion of the C-terminus of trimethylamine dehydrogenase does not affect significantly dimer stability or the overall structural integrity of the enzyme. However, deletion of the C-terminus severely compromises, but does not abolish, the ability of the enzyme to become covalently coupled with the redox cofactor FMN in the active site, located over 20 A from the C-terminus. Hydrodynamic studies reveal minor conformational changes in the deletion mutants that lead to a more compact enzyme structure. These conformational changes are probably transmitted to the active site via altering the interaction of the C-terminus with the second helix in the beta/alpha barrel of trimethylamine dehydrogenase, leading to poor flavinylation during the folding of the enzyme and assembly with FMN.

Bacteria↗
PubMed1998

Columnar alteration with prominent apical snouts and secretions: a spectrum of changes frequently present in breast biopsies performed for microcalcifications.

We have noted in breast biopsies performed for microcalcifications a spectrum of lesions in the terminal duct lobular unit (TDLU) characterized by columnar epithelial cells with prominent apical cytoplasmic snouts, intraluminal secretions, and varying degrees of nuclear atypia and architectural complexity. The appearance of some of these lesions is worrisome, but diagnostic difficulties arise because the histologic features do not fulfill established criteria for the diagnosis of atypical ductal hyperplasia or ductal carcinoma in situ (DCIS). We have termed such lesions columnar alteration with prominent apical snouts and secretions (CAPSS). The purpose of this study was to define the pathologic spectrum and mammographic features of these lesions. We reviewed histologic sections and mammograms from 100 consecutive breast biopsies performed for microcalcifications. The prevalence and histologic features of CAPSS and the association with other histologic findings were recorded. CAPSS was identified in 42% of cases. At the lower end of the spectrum were lesions similar to columnar alteration of lobules but in which apical cytoplasmic secretion and nuclear stratification were more pronounced and cells with a hobnail configuration were common. More advanced lesions showed columnar epithelial cell tufts, bridges, and micropapillations with prominent apical cytoplasmic snouts and with greater degrees of nuclear stratification and atypia. At the upper end of the spectrum were lesions that could arguably be considered DCIS. Calcifications were present within CAPSS in 74% of cases, were frequently psammomatous, and were typically nonbranching and often round on mammography. Columnar alteration of lobules was more common in biopsies with than without CAPSS (74 versus 36%, p < 0.001). Ductal carcinoma in situ was seen with similar frequency in biopsies with and without CAPSS (38 versus 41%). However, DCIS in cases with CAPSS was more often of the low-grade micropapillary-cribriform type than in cases without CAPSS (56 versus 17%, p < 0.01), and CAPSS and DCIS commonly coexisted in the same or adjacent TDLUs. In conclusion, 1) CAPSS encompasses a spectrum of lesions bounded at the lower end by columnar alteration of lobules and at the upper end by low-grade DCIS. Lesions recently described by Page as "hypersecretory hyperplasia with atypia" fall within this spectrum. 2) Some CAPSS lesions present architectural or cytologic features that create diagnostic difficulties and raise the possibility of atypical ductal hyperplasia or DCIS; however, the level of cancer risk associated with CAPSS lesions that do not fulfill established criteria for atypical ductal hyperplasia or DCIS is unknown and requires evaluation in follow-up studies.

Biopsy↗