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Biomedical subjects

N N Youssef

Publications and source records attributed to N N Youssef.

At least 19 recordsLinked to original sources
PubMed2004

Effect of antioxidants and ACE inhibition on chemical modification of proteins and progression of nephropathy in the streptozotocin diabetic rat.

AIMS/HYPOTHESIS: This study was designed to determine whether inhibition of formation of AGE and advanced lipoxidation end-products (ALE) is a mechanism of action common to a diverse group of therapeutic agents that limit the progress of diabetic nephropathy. We compared the effects of the ACE inhibitor enalapril, the antioxidant vitamin E, the thiol compound lipoic acid, and the AGE/ALE inhibitor pyridoxamine on the formation of AGE/ALE and protection against nephropathy in streptozotocin diabetic rats. METHODS: Renal function and AGE/ALE formation were evaluated in rats treated with the agents listed above. Plasma was monitored monthly for triglycerides, cholesterol, creatinine and TNF-alpha, and 24-h urine samples were collected for measurement of albumin and total protein excretion. After 29 weeks, renal expression of mRNA for extracellular matrix proteins was measured, and AGE/ALE were quantified in skin and glomerular and tubular collagen. RESULTS: Diabetic animals were both hyperglycaemic and dyslipidaemic, and showed evidence of early nephropathy (albuminuria, creatinaemia). All interventions limited the progression of nephropathy, without affecting glycaemia. The order of efficacy was: pyridoxamine (650 mg.kg(-1).day(-1)) > vitamin E (200 mg.kg(-1).day(-1)) > lipoic acid (93 mg.kg(-1).day(-1)) approximately enalapril (35 mg.kg(-1).day(-1)). Pyridoxamine also significantly inhibited AGE/ALE accumulation in tissues; effects of other agents were mixed, but the degree of renoprotection was consistent with their effects on AGE/ALE formation. CONCLUSIONS/INTERPRETATION: All interventions inhibited the progression of nephropathy at the doses studied, but the maximal benefit was achieved with pyridoxamine, which also limited dyslipidaemia and AGE/ALE formation. These experiments indicate that the more effective the renoprotection, the greater the inhibition of AGE/ALE formation. For optimal protection of renal function, it would be beneficial to select drugs whose mechanism of action includes inhibition of AGE/ALE formation.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2003

Histologic study of head cartilage degeneration in rainbow trout (Oncorhynchus mykiss) infected with the parasite Myxobolus cerebralis.

A light microscopy study of head cartilage tissue in rainbow trout alevins (Oncorhynchus mykiss) infected with the parasite Myxobolus cerebralis showed that, regardless of the presence or absence of whirling disease symptoms such as black tail and whirling swimming due to altered tail and spine morphology, some fish presented large amounts of spores lodged in the head after three months of infection. The spores were located in regions where the cartilage was extensively destroyed.

Animals↗
PubMed2002

Study of the tail fin rays of rainbow trout (Oncorhynchus mykiss) infected with the parasite Myxobolus cerebralis.

A light, transmission and scanning microscope study of the rays (lepidotrichia) forming the tail fin of rainbow trout (Oncorhynchus mykiss) fingerlings infected with the parasite Myxobolus cerebralis showed that triactinomyxon adherence to the tail fin of host fingerlings occurred 10 min after infection. After 2 h of exposure, it was possible to observe triactinomyxon spores in the epidermis. Although the characteristic symptoms of the disease, such as a black tail and a change in tail morphology, were observed, there was no attack against the tissue forming the tail fin rays and triactinomyxon spores were not observed inside the leptotrichial matrix at any stage, indicating that the spores do not reach the rays or that their observation was not possible under the conditions of the present study.

Animals↗
PubMed2001

Clofazimine enteropathy in a pediatric bone marrow transplant recipient.

Clofazimine, previously used in the treatment of leprosy, is now used for treatment of Mycobacterium avium complex infection in patients with acquired immune deficiency syndrome, dermatologic disorders, and graft-versus-host disease. An 11-year-old boy developed a severe enteropathy 2 years after initiation of clofazimine treatment for graft-versus-host disease. Clofazimine enteropathy caused by crystal deposition can be life-threatening.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Visceral hyperalgesia in children with functional abdominal pain.

OBJECTIVE: Our purpose was to evaluate visceral sensitivity and psychologic profiles in children with functional gastrointestinal disorders. STUDY DESIGN: We measured visceral perception in the stomach and in the rectum by using an electronic barostat. Psychologic questionnaires were completed. Ten children with recurrent abdominal pain (RAP)(8 female, mean age 11.3 +/- 0.8 years), 10 children with irritable bowel syndrome (IBS) (8 female, mean age 13.0 +/- 0.9 years), and 15 control children (8 female, mean age 12.7 +/- 1.2 years) completed the study. RESULTS: Thresholds for visceral perception in the rectum were decreased in patients with IBS (P <.001 vs control patients) and in patients with RAP (P <.05 vs control patients). Children with IBS had lower thresholds than children with RAP (P <.01). In contrast, thresholds for perception were decreased in the stomach of children with RAP (P <.005 vs control patients) but not in children with IBS. There were elevated anxiety scores in 45% of patients. Duration of symptoms was associated with higher scores of anxiety (P <.001) and depression (P <.02). CONCLUSIONS: Hyperalgesia was demonstrated in children with RAP and IBS; sites of hyperalgesia appear to be associated with different symptom phenotypes; anxiety was common, and there was an association between the duration of symptoms and increased scores for both anxiety and depression.

Abdominal Pain↗
PubMed2001

Childhood constipation: evaluation and treatment.

Constipation is common in children. It is estimated that between 5% and 10% of pediatric patients have constipation and/or encopresis. Constipation is the second most referred condition in pediatric gastroenterology practices, accounting for up to 25% of all visits. In this article, a practical approach is laid out for those not familiar with constipation in children. Emphasis is placed on the evaluation and management options that are available to the treating practitioner. The diagnosis of constipation requires careful history taking and interpretation. Diagnostic tests are not often needed and are reserved for those who are severely affected. The daily bowel habits of children are extremely susceptible to any changes in routine environment. Constipation and subsequent fecal retention behavior often begins soon after a child has experienced a painful evacuation. Childhood constipation can be very difficult to treat. It often requires prolonged support by physicians and parents, explanation, medical treatment, and, most important, the child's cooperation.

Behavior Therapy↗
PubMed1996

Detection of Nosema locustae (Microsporidia:Nosematidae) in frozen grasshoppers (Orthoptera:Acrididae) by using monoclonal antibodies.

We developed several monoclonal antibodies that recognized germinated and nongerminated spores and other developmental stages of Nosema locustae, a pathogen of grasshoppers, by using spore homogenate as antigen. The hybridomas were produced with standard techniques. Indirect fluorescence assay demonstrated recognition by several antibodies to the spore and extruded polar filament. Monoclonal antibody D10-9-11 recognized the spore wall in smears and frozen sections of infected grasshopper fat body tissue, whereas monoclonal antibody D55-12 also labeled the extruded polar filament. Immunoelectron microscopy showed that monoclonal antibody D10-9-11 recognized the spore and several developmental stages. Enzyme-linked immunosorbent assay showed that monoclonal antibody D10-9-11 did not cross-react with immunogen prepared from other grasshopper pathogens, including Vairimorpha sp., Malameba locustae, and entomopox virus from migratory grasshoppers, Melanoplus sanguinipes (F.).

Animals↗
PubMed1993

Isolation and characterization of a linear plasmid from the entomopathogenic fungus Ascosphaera apis.

An extrachromosomal DNA plasmid was isolated from both mating types of the entomopathogenic fungus Ascosphaera apis and named pAaL. The subculture in which pAaL was first identified originated from mummified honey bee larvae from an apiary in Wyoming. Very similar, homologous plasmids were found in 9 out of 10 of isolates collected from diverse geographic locations. The plasmid is found inside the mitochondria, has the same buoyant density as mitochondrial DNA in bisbenzamide--CsCl gradients, and does not contain sequences homologous to either mitochondrial DNA or genomic DNA. The plasmid is linear, double-stranded, of 12 kilobase pair, and has a higher copy number than the mitochondrial DNA. Endonuclease and exonuclease digestions suggest that an inverted repeat is probably present at each terminus and that pAaL has two blocked 5' ends, probably due to the presence of terminal binding proteins. Restriction site data showed pAaL to be AT-rich. There were no apparent differences in the growth rate, culture appearance, and reproductive cycle of plasmid-bearing or plasmid-free A. apis isolates. pAaL was stably inherited in the plasmid-free strains, but it was lost in the progeny of crosses and reciprocal crosses between the plasmid-free strain and plasmid-bearing strains. The biological function of this plasmid has not yet been determined.

Ascomycota↗
PubMed1990

Esterase isozymes in a solitary bee, Megachile rotundata (Fab.): characterization, developmental multiplicity, and adult variability.

This study describes the biochemical characterization and genetic variation of cytosolic esterases in the alfalfa leafcutting bee, Megachile rotundata (Fab.). Esterase isozymes were separated by nondenaturing polyacrylamide gel electrophoresis and isoelectric focusing and characterized by inhibition with eserine sulfate, EDTA, paraoxon, and p-hydroxymercuribenzoate. Based on inhibition patterns and substrate specificity, there are major differences between adults and immature forms and more subtle differences between male and female adults. M. rotundata esterases are largely organophosphate sensitive and the two major adult allozymes were highly variable within the population examined. Differences in esterase expression between life stages with respect to niche and the occurrence of diploid males are discussed.

Animals↗
PubMed1987

Production of monoclonal antibodies specific for Eimeria tenella microgametocytes.

A panel of 4 monoclonal antibodies specific for Eimeria tenella, the causative agent of cecal coccidiosis of birds in the genus Gallus, was produced by standard techniques. The indirect fluorescent antibody (IFA) test demonstrated specificity of these 4 antibodies for the microgametocytes. Hybridoma TIA3B9 secreted a monoclonal antibody of subisotype IgG2b that was used throughout the course of this study. Immunologic potency of this antibody was demonstrated by in vitro experiments that revealed a greater than 50% reduction in oocyst production, indicating an apparent inhibition of fertilization.

Animals↗
PubMed1977

Development in cell cultures of Eimeria vermiformis Ernst, Chobotar and Hammond, 1971.

Development of Eimeria vermiformis from sporozoite to mature first-generation schizonts in cultured bovine kidney cells, Madin-Darby bovine kidney cells, and primary cultures of whole mouse embryos is described. Intracellular sporozoites were seen at 5 min, and for as long as 120 h after inoculation. Sporozoites were observed penetrating cells, with uninucleate trophozoites and immature schizonts with 2--6 nuclei first appearing 24 h after inoculation. Schizonts with 6 or more nuclei, as well as mature schizonts containing first-generation merozoites, were first seen between 36 and 48 h after inoculation of all 3 cell types used. The first indication of merozoite formation was determined by the appearance of small protuberances of cytoplasm at the periphery of schizonts. Merozoites began development at the periphery of schizonts and were later observed radiating from a central body of cytoplasm, 14--20 merozoites being formed. Some mature schizonts retained a small spherical residual body after merozoite formation was completed. After the rupture of schizonts, intracellular merozoites, which contained anterior and posterior refractile granules, were seen at 48, 72 and 96 h postinoculation. Merozoites were not seen entering or leaving cells. No further development was observed.

Animals↗
PubMed1975

The compound eye in the opaque-eye phenotype of Drosophilia melanogaster.

The compound eye of the opaque-eye mutant of Drosophila melanogaster was investigated by means of electron microscopy to determine the morphological and physical properties of ommatidial elements. These elements in the mutant were found to differ from those of the wild-type flies in the following ways: (1) The cuticular lens was thinner than that of the control and lacked the typical lamellar construction. (2) The Semper cells were irregular in shape and contained many membranous inclusions similar to those found in degenerating cells; also their nuclei contained virus-like particles. (3) The primary pigment cells contained an abundance of drosopterin-containing granules which were lacking in those of wild-type flies. (4) The superior and inferior central photoreceptor cells were misplaced and their rhabdomeres evidenced some degeneration. (5) The secondary pigment cells had only one type of pigment granules instead of the three types found in the control. These morphological changes in ommatidial elements induced physical abnormalities such as the apparent opaqueness of the eye, the lack of a pseudopupil, the probable disability of the photoreceptor cells to respond to light and the inability of the dioptric system to produce utilizable geometric images.

Animals↗