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Biomedical subjects

S Cortez

Publications and source records attributed to S Cortez.

12 recordsLinked to original sources
PubMed2006

Utilisation of controlled pore topology for the separation of bioparticles in a mixed-glass beads column.

To study the flow of shaped particles in porous media, elution of spherical and rod-like micro-organisms was performed through beds of spherical glass beads. A 0.04 cm/s constant flow rate was used with 5 microm yeast suspensions, 1 microm latex micro-spheres and rod-like bacilli Lactobacillus bulgaricus 6 microm long and 0.5 microm in diameter. Yeast cells' diameter is close to the bacilli length and micro-spheres have the same diameter as bacilli. All particle types have similar density. To make the different packing beds, 1.125 mm coarse beads and 0.1115 mm fine beads were used. Experiments were carried out using a column loaded with the binary packing (volume fraction of coarse particles in the mixture 0.7) or a monosize packing with the same amount of coarse or fine particles as used in the binary packing. Analysis of experimental results was based on two models: pure exclusion effect and hydrodynamic separation model [hydrodynamic chromatography (HDC)]. Results for spheres show that the classic HDC model fits to the experimental data whenever the ratio of particle size to the pathway bend scale is high ( approximately 1/100, micro-spheres). However, if this ratio increases and becomes approximately 1/20, the HDC model needs to be corrected due to the effect of channel wall curvature on exclusion. This led to a modified HDC equation of the form R=B/(1+2lambda-2.8lambda(2)), where R is the retention, lambda is the aspect ratio and constant B>or=1. Bacillus separation follows an exclusion mechanism, since pore topology is important in the separation of shaped particles when the aspect ratio approaches lambda=0.1. In the case of a binary packing bed, rod-like particles display a different behaviour than the one exhibited by the spherical particles of the same scale as bacilli, either in length or in diameter. This may be explained by the interaction between rod-like bacilli and the bed's pore topology. A generalised exclusion model for particles was proposed to be R=A/(1-lambda)(z), where A is the coefficient proportional to the tortuosity and the parameter z=1, 2 or 3 depends mainly on pore shape. Controlled pore topology opens interesting applications for bio-separation (in porous micro-fluidic devices, deep bed filtration) and might be especially important for macromolecules and micro-organisms separation with different shapes.

Bacillus↗
PubMed2002

Optically driven spin memory in n-doped InAs-GaAs quantum dots.

We show that the spin state of the resident electron in an n-doped self-assembled InAs-GaAs quantum dot can be written and read using nonresonant, circularly polarized optical pumping. A simple theoretical model is presented and accounts for the remarkable dynamics producing counterpolarized photoluminescence.

Journal Article↗
PubMed1998

Histologic evidence of a radiosensitizing effect of Taxol in patients with astrocytomas.

The new anticancer agent Taxol appears to potentiate the effects of radiation on brain tumor cell lines in vitro and was recently evaluated by our group as a radiosensitizer in a phase I study for primary brain tumors. In that study, we administered Taxol as a three-hour IV infusion repeated every week for six weeks and gave daily cranial irradiation concurrently for a total of 6000 rads. We reviewed the charts of the 60 patients who participated in the study, and identified twelve patients who underwent a second surgery after treatment because of progressive symptoms and an enlarging intracranial mass on MRI. Pathologically, each patient showed prominent radionecrosis, and other evidence of accelerated radiation changes (confluent areas of coagulative necrosis, bizarre nuclei, marked thickening and fibrinoid changes in multiple blood vessels). These changes were noted many weeks earlier than would be expected after radiation therapy alone and were independent of age, and tumor histology. We postulate that the accelerated radiation changes may be due to the radiation sensitizing effects of Taxol. We also noted a change of the pattern of tumor recurrence, compared to historic reports, and a dose-necrosis relationship where the resected tumor is formed completely of necrotic tissue in patients who received 150 mg/m2 or higher dose of Taxol. These observations may be of significance for future study design.

Adult↗
PubMed1998

The temporal profile and morphologic features of neuronal death in human stroke resemble those observed in experimental forebrain ischemia: the potential role of apoptosis.

Although neuronal death has been studied in experimental models of ischemia, the precise mechanisms regulating cell death remain unclear. Furthermore, the timing and pattern of neuronal death in human stroke has not been extensively studied. To further our understanding of ischemia-induced neuronal death, we examined the temporal profile of histochemical and morphologic characteristics of hippocampal neuronal death following experimental forebrain ischemia and compared these findings to human brain specimens obtained from subjects suffering cerebral infarction. Transient forebrain ischemia (TFI) was induced in normothermic adult rats by bilateral carotid artery occlusion combined with hypotension. Animals were sacrificed at 6, 12, 18, 24, 48, and 72 h and 7, 14, and 28 days following ischemia (n = 4 at each time point). Experimental tissue was analyzed using light and electron microscopy as well as TUNEL histochemistry. A total of 27 human brain specimens with neuropathological confirmation of ischemic damage and appropriate controls were also examined using light microscopy and TUNEL histochemistry. Dense TUNEL staining in hippocampal CA-1 neurons was present at 48 and 72 h following experimental ischemia. Prior to these times, little or no nuclear staining was noted and after 72 h nuclear staining diminished rapidly. Ultrastructural findings at these time points demonstrated many features similar to those seen in cells undergoing apoptosis, such as cell shrinkage with increased electron density, chromatin condensation with formation of heterochromatin, intact plasma membranes, and intact intracellular organelles. In a similar fashion, human stroke specimens during the subacute period showed dense nuclear TUNEL staining in penumbral neurons, whereas in the acute or chronic stages little or no staining was noted. Our results demonstrate that the timing of morphologic changes and TUNEL histochemistry following human stroke resembles that observed in experimental TFI. Furthermore, neuronal death in both experimental ischemia and human stroke share several features characteristic of apoptotic cell death.

Adolescent↗
PubMed1994

Spinal subdural abscess: successful treatment with limited drainage and antibiotics in a patient with AIDS.

The authors present a case of Staphylococcus aureus spinal subdural abscess in a patient with AIDS. Although complete surgical drainage has been strongly advocated in the literature, this patient made a complete neurologic and symptomatic recovery and radiographically demonstrated resolution of the abscess with only limited surgical drainage and parenteral antibiotics. Magnetic resonance imaging findings of this unusual lesion are discussed. Relevant literature in the management of spinal subdural abscesses is reviewed.

AIDS-Related Opportunistic Infections↗
PubMed1991

Cardiomyopathy and myocyte intranuclear inclusions in neuronal intranuclear inclusion disease: a case report.

Neuronal intranuclear inclusion disease (NIID) is a progressive, usually fatal degenerative neurologic condition characterized by eosinophilic, intranuclear inclusions in neurons of the central and peripheral nervous system. We report a boy with onset of disease manifestations at age 3 and death at age 9, who showed clinical and pathologic findings characteristic of NIID. The case is unique because of cardiomyopathy manifested 1 year prior to death. Postmortem findings confirmed the presence of cardiomyopathy and revealed intranuclear inclusions in myocytes. Neither nuclear inclusions in the myocardium nor cardiac involvement have previously been reported in NIID.

Cardiomyopathies↗
PubMed1991

A novel metalloproteinase present in freshly isolated rat glomeruli.

We have utilized [3H] gelatin to document high activity of a metalloproteinase present in freshly isolated rat glomeruli. [3H] gelatin degradation by glomeruli was markedly inhibited by EDTA (10 mM: -89 +/- 2.3%) and o-phenanthroline (2 mM: -72 +/- 0.1%), inhibitors of metalloproteinases. No significant inhibition of [3H]gelatin degradation was observed with inhibitors of serine or cysteine proteinases. Most (greater than 80%) of the glomerular metalloproteinase (GLOMP) activity was associated with the pellet after centrifugation of sonicated glomeruli at 100,000 g for 90 min. The pH optimum for gelatin degradation by sonicated glomeruli was approximately pH 8.5. Sodium dodecyl sulfate substrate (gelatin)-polyacrylamide gel electrophoresis revealed a single major band of EDTA-inhibitable gelatin-degrading activity with a molecular mass of approximately 116-125 kDa. The GLOMP activity was not inhibited by tissue inhibitors of metalloproteinases, did not appear to be latent, and was not activated by organomercurial activators of several latent metalloproteinases. GLOMP activity was increased 3.4-fold after incubation with trypsin (20 micrograms/ml, 25 min, 22 degrees C). These data indicate that GLOMP is distinct from the previously described matrix metalloproteinases, as well as other metalloproteinases present in the kidney, including the gelatinase secreted by cultured mesangial cells, Meprin, and endopeptidase 24.11 (enkephalinase, EC 3.4.24.11).

Animals↗
PubMed1991

[Sulfonamide and toltrazuril therapy of experimental turkey coccidiosis].

Following experimental infection of caged turkeys with a mixed oocyst suspension of E. meleagrimitis, E. adenoeides and E. gallopavonis, the efficacy of sulfachlorpyrazine, sulfaquinoxaline + pyrimethamine, sulfaquinoxaline + diaveridine, and toltrazuril was investigated based on clinical and parasitological parameters. Infected turkeys developed severe clinical symptoms. Only weak symptoms were observed in those groups which were treated with the sulfa- and sulfa-DHFR-inhibitors. The toltrazuril-treated group remained free of clinical symptoms. At the 8th day after infection, the clinical lesions coincided with the intensity of the gut lesions together with parasitological findings based on microscopical examination of mucosal smears. The same coincidence was observed for parameters such as oocyst excretion and body weight development.

Animals↗
PubMed1982

Liquid formula diet for human metabolic studies.

A liquid formula diet for use in studies with human subjects has been developed. All of the components can be obtained readily from commercial sources. For preparation of the diet, only equipment that customarily is found in institutional kitchens is needed. Acceptability over periods of several months is manifested by a large number of patients who consumed the liquid formula diet as their sole source of food.

Adult↗