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S Guirguis

Publications and source records attributed to S Guirguis.

9 recordsLinked to original sources
PubMed2000

Characterization of thermosensitive chitosan gels for the sustained delivery of drugs.

The aim of this study was to investigate the physical properties of a chitosan/glycerophosphate (GP) thermosensitive solution which gels at 37 degrees C and evaluate the in vitro release profiles of different model compounds. The gelation rate was dependent on the temperature and on the chitosan deacetylation degree. The solution containing 84%-deacetylated chitosan could be stored 3 months at 4 degrees C without apparent change in viscosity. The in vitro release profiles of the model compounds depended on the presence of GP in the chitosan solution, on their molecular weight and on the presence of lysozyme in the release media. They were not affected by the electrostatic charge of the model compound when present at low concentrations. During the first 4 h, the release was accompanied by a substantial loss of the gel weight which was mainly attributed to the leaching of water and excess GP. Scanning electron micrographs revealed that the solutions yield gels with a highly porous structure after 24 h of exposure to a continuous flow of phosphate buffered saline. These results indicate that the chitosan/GP thermosensitive solutions gel rapidly at body temperature, can remain in the sol state at 4 degrees C and can sustain the delivery of macromolecules.

Chitin↗
PubMed1997

Neurobehavioral tests as a medical surveillance procedure: applying evaluative criteria.

Neurobehavioral impairment is among the earliest indicators of a toxic insult on the nervous system. Neurobehavioral tests measure behavior impairment by noninvasive procedures that assess various performance and personality changes. Neurobehavioral tests have been used on groups of workers included in epidemiologic research studies; however, their suitability for an ongoing medical surveillance program for workers exposed to neurotoxic agents has not been evaluated. In Ontario, Canada, a set of validity criteria must be met to determine whether a medical procedure may be prescribed for a specific medical surveillance program. The evaluative criteria are standards for judging the desirability of a procedure based on social values and scientific considerations. In this paper, various studies using neurobehavioral tests are reviewed, and the validity of using these procedures for medical surveillance is evaluated by applying the Ontario evaluation criteria. The conclusion is that neurobehavioral tests are useful for well-controlled, cross-sectional studies, but they do not yet meet the validity criteria for procedures prescribed in an ongoing medical surveillance program for workers exposed to neurotoxic agents.

Behavior↗
PubMed1994

New perspectives on use of thymic factors in immune deficiency.

Current knowledge on the role of thymic factors in the immune response is inadequate and remains relatively primitive when compared with present technical possibilities for assessing lymphocyte subsets or cytokine interaction. New studies support the potential importance of thymic factors as regulators of immune interactions. Indirect evidence supports the concept that thymic factors may work at the level of IL-2. The functional identity of cells responsive to thymic factors and the relation of observed effects to cytokine network interactions need to be established. The use of thymic factors in the future will depend on the development of criteria to identify appropriate settings in which to use such factors and the implementation of appropriate measures of immune functional response.

CD4-CD8 Ratio↗
PubMed1994

The capillary transport system for free fatty acids in the heart.

The nature of the process by which free fatty acids, which are tightly bound to albumin, traverse the endothelium of cardiac capillaries to reach the cardiac muscle cells, so that they are extracted to a net extent of approximately 40%, needs clarification. Previous studies have indicated that a membrane fatty acid-binding protein provides for carrier-mediated uptake of free fatty acids by isolated hepatocytes, cardiomyocytes, and jejunal mucosal cells. A monoclonal monospecific antibody was prepared against purified membrane fatty acid-binding protein from rat liver. Multiple-indicator dilution experiments were carried out in the isolated rat heart with labeled albumin, sucrose, and palmitate in the presence of control perfusate or perfusate containing either specific antibody or comparable nonspecific myeloma cell supernatant (each of the latter containing additional albumin, in identical concentrations). Analysis of the labeled-sucrose curves provided a permeability-surface area product for sucrose to which that for palmitate could be compared. In comparison with control supernatants, myeloma supernatant produced a minor inhibition of palmitate uptake, as a result of the increase in albumin concentration. The specific antibody, which contained identical albumin concentrations, produced a major inhibition of palmitate uptake, significantly greater than with the myeloma supernatant. The data indicate that the membrane fatty acid-binding protein mediates the transfer of free fatty acid across the endothelial cells of cardiac capillaries for presentation to heart muscle. Passive intramembrane lateral diffusion of palmitate could not provide an explanation for the findings.

Animals↗
PubMed1993

Pigmented villonodular synovitis in a child.

The authors present a case of pigmented villonodular synovitis (PVNS) in an adolescent with monarticular involvement of the ankle and without congenital anomalies or sibling involvement. Its rarity in the ankle and in childhood is discussed; a review of the clinical, radiological, and pathological features of PVNS is presented.

Ankle↗
PubMed1992

Flow-limited tracer oxygen distribution in the isolated perfused rat liver: effects of temperature and hematocrit.

We used the multiple-indicator dilution technique to examine the kinetics of tracer oxygen distribution and uptake in the rat liver perfused in a nonrecirculating fashion with blood. 51Cr-labeled 18O2-saturated erythrocytes, labeled albumin, sucrose and water (the tracers for oxygen and vascular, interstitial and cellular references) were injected simultaneously into the portal vein. Timed anaerobic samples were collected from the hepatic vein and analyzed by mass spectrometry for relative 18O2 enrichment and radioactivity. In a set of experiments performed at 32 degrees C, oxygen uptake was substantially diminished; tracer oxygen profiles approached those expected for a completely recovered, flow-limited substance. At 37 degrees C, much larger tracer oxygen sequestration occurred. Experiments were carried out at each temperature at higher and lower hematocrit, and oxygen consumption at each temperature was found to be independent of hematocrit. The tissue space of distribution for tracer oxygen relative to the total sinusoidal vascular content was influenced by the hematocrit: it was smaller at higher hematocrit and larger at lower hematocrit, as expected. The derived partition coefficient of oxygen for liver cells relative to plasma (expressed in terms of the liver and plasma water spaces) was, on average, 2.62 ml/ml; it was independent of the hematocrit. Analysis of the indicator dilution experiments indicates that the tracer oxygen is distributed into tissue in a flow-limited rather than a barrier-limited fashion, and that with this, an ongoing concomitant intracellular sequestration of tracer can be seen.

Animals↗
PubMed1984

Respiratory variables and exposure-effect relationships in isocyanate-exposed workers.

Respiratory variables in 95 isocyanate workers and 37 control workers were compared. The exposed workers had a slightly higher frequency of cough and shortness of breath than the controls and a significantly lower frequency of family history of asthma, hay fever, and bronchitis. The isocyanate workers had slightly lower baseline lung function than the control workers but demonstrated significantly larger declines in their pulmonary function over the work shift. Both groups showed some intraday and intraweek variation in lung function. The changes in lung function over the work shift varied with different job categories, the largest changes occurring in finishing-area workers. A gradation of response was observed when exposure was categorized as nil, low, or high, but no exposure-effect relationships could be demonstrated by regression analysis of either area or personal results.

Adult↗