Biomedical subjects

S Youssef

Publications and source records attributed to S Youssef.

At least 37 records · Page 2Linked to original sources

PubMed1999

Expansion of neonatal tolerance to self in adult life: I. The role of a bacterial adjuvant in tolerance spread.

T cell neonatal tolerance to self evolves perturbation of the Th1/Th2 balance towards Th2-type self-specific T cells. In the current study we have demonstrated that a tolerant state could be extended to another encephalitogenic determinant only if the neonatally tolerizing determinant was co-administered in adult life with an emulsion of Mycobacterium tuberculosis (i.e. complete Freund's adjuvant). The mechanisms underlying tolerance elicitation and expansion were then explored by an in vitro system in which indirect suppression could be measured. Addition of a tolerizing epitope to splenic T cells from neonatally tolerized animals induced a marked suppression of the anti-MT response. This response could be restored by neutralizing antibodies to IL-4. In contrast, the neutralizing antibodies to IL-4 had no affect on the response of these cells to the tolerizing determinant. These findings are highly significant not only because they explore the important role of microbial antigens in neonatal tolerance, but also because they distinguish, for the first time, between tolerizing and tolerized T cells.

Aging↗

PubMed1999

Increased renal expression of vascular endothelial growth factor (VEGF) and its receptor VEGFR-2 in experimental diabetes.

It has been suggested that the cytokine vascular endothelial growth factor (VEGF) has an important role in the pathogenesis of diabetic retinopathy, but its role in nephropathy has not been clearly demonstrated. Assessment of VEGF, 125I-VEGF binding, and vascular endothelial growth factor receptor-2 (VEGFR-2) in the kidney was performed after 3 and 32 weeks of streptozotocin-induced diabetes. Gene expression of both VEGF and VEGFR-2 was assessed by Northern blot analysis and the localization of the ligand and receptor was examined by in situ hybridization. VEGF and VEGFR-2 protein were also evaluated by immunohistochemistry. Binding of the radioligand 125I-VEGF was evaluated by in vitro and in vivo autoradiography. Diabetes was associated with increased renal VEGF gene expression. VEGF mRNA and protein were localized to the visceral epithelial cells of the glomerulus and to distal tubules and collecting ducts in both diabetic and nondiabetic rats. Renal VEGFR-2 mRNA was increased after 3 weeks of diabetes but not in long-term diabetes. In situ hybridization and immunohistochemical studies revealed that glomerular endothelial cells were the major site of VEGFR-2 expression. In addition, VEGFR-2 gene expression was detected in cortical and renomedullary interstitial cells and on endothelial cells of peritubular capillaries. There was an increase in 125I-VEGF binding sites after 3 but not 32 weeks of diabetes. The major VEGF binding sites were in the glomeruli. 125I-VEGF binding was also observed in medullary rays and in the renal papillae. These studies indicate an early and persistent increase in renal VEGF gene expression in association with experimental diabetes. In addition, an early and transient increase in renal VEGF receptors was also observed in diabetic rats. These findings are consistent with a role for VEGF in mediating some of the changes observed in the diabetic kidney.

Animals↗

PubMed1998

Neutralizing antibodies to IFN-gamma-inducing factor prevent experimental autoimmune encephalomyelitis.

Specific oligonucleotide primers were used to identify and isolate IFN-gamma-inducing factor (IGIF) from the brain of rats with developing experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune disease of the central nervous system that serves as a model for multiple sclerosis. IGIF was highly transcribed in the brain at the onset and during the course of active EAE. PCR products encoding rat IGIF were used to generate the recombinant protein that was used to induce anti-IGIF neutralizing Abs. These Abs significantly reduced the production of IFN-gamma by primed T cells proliferating in response to their target myelin basic protein epitope and by Con A-activated T cells from naive donors. When administered to rats during the development of either active or transferred EAE, these Abs significantly blocked the development of disease. Splenic T cells from protected rats were cultured with the encephalitogenic myelin basic protein epitope and evaluated for production of IL-4 and IFN-gamma. These cells, which proliferated, exhibited a profound increase in IL-4 production that was accompanied by a significant decrease in IFN-gamma and TNF-alpha production. Thus, we suggest that perturbation of the Th1/Th2 balance toward Th2 cells is the mechanism underlying EAE blockade by anti-IGIF immunotherapy.

Adoptive Transfer↗

PubMed1998

Long-lasting protective immunity to experimental autoimmune encephalomyelitis following vaccination with naked DNA encoding C-C chemokines.

DNA vaccination represents a novel means of expressing Ag in vivo for the generation of both humoral and cellular immune responses. The current study uses this technology to elicit protective immunity against experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune disease of the central nervous system that serves as an experimental model for multiple sclerosis. RT-PCR verified by Southern blotting and sequencing of PCR products of four different C-C chemokines, macrophage-inflammatory protein-1alpha (MIP-1alpha), monocyte-chemotactic protein-1 (MCP-1), MIP-1beta, and RANTES, were performed on brain samples from EAE rats to evaluate mRNA transcription at different stages of disease. Each PCR product was then used as a construct for naked DNA vaccination. The subsequent in vivo immune response to MIP-1alpha or MCP-1 DNA vaccines prevented EAE, even if disease was induced 2 mo after administration of naked DNA vaccines. In contrast, administration of the MIP-1beta naked DNA significantly aggravated the disease. Generation of in vivo immune response to RANTES naked DNA had no notable effect on EAE. MIP-1alpha, MCP-1, and MIP-1beta mRNA transcription in EAE brains peaked at the onset of disease and declined during its remission, whereas RANTES transcription increased in EAE brains only following recovery. Immunization of CFA without the encephalitogenic epitope did not elicit the anti-C-C chemokine regulatory response in DNA-vaccinated rats. Thus, modulation of EAE with C-C chemokine DNA vaccines is dependent on targeting chemokines that are highly transcribed at the site of inflammation at the onset of disease.

Amino Acid Sequence↗

PubMed1998

The natural history of sacrococcygeal teratomas diagnosed through routine obstetric sonogram: a single institution experience.

BACKGROUND/PURPOSE: The antenatal diagnosis of sacrococcygeal teratoma (SCT) is increasingly being made with fetal sonography. However, the natural history of SCT detected on routine obstetric sonogram is not well defined. METHODS: A retrospective chart review of 21 fetal SCT diagnosed on routine sonography at Hospital Sainte-Justine between 1980 and 1997 were performed. The patients' clinical and sonographic characteristics, prenatal, and perinatal outcomes were examined. Prognostic criteria were identified by correlating patients' characteristics with outcome. RESULTS: In utero mortality rate was 19% and perinatal mortality rate was 14%. The incidence of premature labor was 50%. Of the various criteria examined as an independent variable, the presence of a solid tumor was found to be a important negative prognostic factor with a 67% incidence of death in utero and an overall mortality rate of 100%. Patients with new onset polyhydramnios were at significant risks for premature labor (100%). All of the perinatal deaths were attributable to tumor rupture. CONCLUSIONS: The course of sacrococcygeal teratoma diagnosed on routine sonograms is associated with a higher-than-expected incidence of prenatal and perinatal complications. Close antenatal follow-up for new onset polyhydramnios and the presence of a completely solid tumor will help optimize patient counseling and treatment.

Female↗

PubMed1998

Hepatic advanced glycation endproduct binding is increased in experimental diabetes.

Advanced glycation endproducts (AGEs) have been implicated in the pathogenesis of diabetic complications. However, clearance pathways for these products have not been fully delineated. This study investigates changes in AGE binding in the liver in association with experimental diabetes using in vitro and in vivo radioautography techniques. Male Sprague-Dawley rats were randomised into control and diabetic rats and sacrificed after 3 weeks. Frozen liver sections (20 microm) were incubated with 125I-AGE-BSA. To further localise the AGE binding site, in vivo radioautography was performed by injection of 15 microCi of 125I-AGE-BSA into the abdominal aorta of the rat. Specific binding sites for AGEs were detected in the liver by in vitro radioautography. There was a significant increase in 125I-AGE binding in the liver of diabetic rats. Emulsion radioautography revealed that binding was localised primarily in Küpffer and liver endothelial cells. AGE binding sites were increased in the liver after 3 weeks of experimental diabetes. It remains speculative as to whether these binding sites represent AGE clearance receptors.

Animals↗

PubMed1997

Vascular hypertrophy in experimental diabetes. Role of advanced glycation end products.

The accelerated formation of advanced glycation end products (AGEs) and the overexpression of transforming growth factor beta (TGF-beta) have both been implicated in the pathogenesis of diabetic microvascular and macrovascular complications. Previous studies in our laboratory have demonstrated that the vascular changes in diabetes include hypertrophy of the mesenteric vasculature. To examine the role of AGEs in this process, streptozotocin-induced diabetic rats and control animals were randomized to receive aminoguanidine, an inhibitor of AGE formation, or no treatment. Animals were studied at 7 d, 3 wk, and 8 mo after induction of diabetes. When compared with control animals, diabetes was associated with an increase in mesenteric vascular weight and an increase in media wall/lumen area. By Northern analysis, TGF-beta1 gene expression was increased 100-150% (P < 0.01) and alpha1 (IV) collagen gene expression was similarly elevated to 30-110% compared to controls (P < 0.05). AGEs and extracellular matrix were present in abundance in diabetic but not in control vessels. Treatment of diabetic rats with aminoguanidine resulted in significant amelioration of the described pathological changes including overexpression of TGF-beta1 and alpha1 (IV) collagen. These data implicate the formation of AGEs in TGF-beta overexpression and tissue changes which accompany the diabetic state.

Animals↗

PubMed1997

Advanced glycation end products and their receptors co-localise in rat organs susceptible to diabetic microvascular injury.

Advanced glycation end products (AGEs) are believed to play an important role in the development of diabetic complications. AGEs are increased in experimental diabetes and treatment with the inhibitor of advanced glycation end products, aminoguanidine, has been shown to attenuate the level of these products in tissues undergoing complications. Recently, an AGE-binding protein has been isolated from bovine lung endothelial cells and termed the receptor for advanced glycated end products (RAGE). The present study sought to determine the distribution of AGE and RAGE in tissues susceptible to the long-term complications of diabetes including the kidney, eye, nerve, arteries as well as in a tissue resistant to such complications, the lung. Using polyclonal antisera both AGE and RAGE were found to co-localize in the renal glomerulus. AGE staining was clearly increased with age and was further increased by diabetes. Aminoguanidine treatment reduced AGE accumulation in the kidney. Co-localisation of AGE and RAGE was demonstrated in the inner plexiform layer and the inner limiting membrane of the retina and in nerve bundles from mesenteric arteries. In the aorta, both AGE and RAGE were found in the intima, media and adventitia. Medial staining was increased in diabetes and was reduced by aminoguanidine treatment. A similar pattern was observed for RAGE in the aorta. In the lung, RAGE was found widely distributed throughout the lung whereas the distribution of AGE staining was more limited, primarily localising to macrophages. The co-localisation of AGEs and RAGE in sites of diabetic microvascular injury suggests that this ligand-receptor interaction may represent an important mechanism in the genesis of diabetic complications.

Animals↗

PubMed1997

Intrahepatic biliary-enteric bypass for complete extrahepatic biliary obstruction in children.

Intrahepatic biliary-enteric anastomosis is rarely practiced in pediatric surgery. The authors report on two children who have been successfully treated using this method. First described by Longmire and Sandford in 1948, intrahepatic biliary-enteric anastomosis is possible in children. This procedure is only indicated as a last recourse for circumstances in which the extrahepatic biliary tree is completely obstructed.

Anastomosis, Roux-en-Y↗

PubMed1997

Role of angiotensin II and bradykinin in experimental diabetic nephropathy. Functional and structural studies.

We explored the relative roles of the suppression of angiotensin II and the prevention of bradykinin degradation in mediating the renoprotective effects of ACE inhibitors in experimental diabetic nephropathy. Over a 24-week period, we studied male Sprague-Dawley diabetic and control rats and Sprague-Dawley diabetic rats treated with the ACE inhibitor ramipril, the angiotensin II-AT1 receptor antagonist valsartan, the bradykinin-B2 receptor antagonist HOE 140 (icatibant), and a combination of ramipril and icatibant. Serial measurements of urinary albumin excretion, blood pressure, and glycated hemoglobin were performed monthly. After 6 months, the animals were killed for the measurement of kidney weight and the assessment of glomerular ultrastructure. Over 24 weeks, urinary albumin excretion showed a continuous rise in the untreated diabetic rats. Both ramipril and valsartan, which were equihypotensive, prevented the increase in urinary albumin excretion over the whole study period. Icatibant therapy did not attenuate the antialbuminuric effect of the ACE inhibitor, nor did it have any effect as the sole therapy. Diabetes was associated with increased glomerular basement membrane thickness, glomerular volume, and total mesangial volume. Both ACE inhibition and angiotensin II receptor antagonism attenuated the glomerular ultrastructural changes to a similar degree. Icatibant did not attenuate the effects of ramipril on glomerular morphology. ACE inhibitors and angiotensin II-AT1 receptor blockers appear to confer similar benefits in experimental diabetic nephropathy, and bradykinin-B2 receptor blockers do not influence this effect. These findings suggest that the blockade of angiotensin II is the major pathway responsible for renoprotection afforded by ACE inhibition in experimental diabetic nephropathy.

Albuminuria↗

PubMed1995

Repair of congenital diaphragmatic hernia after weaning from extracorporeal membrane oxygenation.

Stabilization and delayed operation for patients with congenital diaphragmatic hernia (CDH) is now widely accepted. When preoperative extracorporeal membrane oxygenation (ECMO) is needed, most centers have CDH repaired on ECMO to minimize the risk of postoperative deterioration. The authors adopted a policy of weaning from ECMO before repair in an effort to avoid hemorrhagic risks. They reviewed their experience with CDH patients who required ECMO for stabilization before repair but for whom post-ECMO repair was planned. The records of all high-risk CDH patients with a gestational age of at least 34 weeks were reviewed. Eighteen patients were identified. None of the eight who were stabilized and operated on without ECMO required bypass postoperatively; all survived. Ten were placed on bypass, nine for stabilization before repair. Of the nine, seven (78%) were weaned from ECMO to conventional ventilation. Repair of the diaphragmatic defect was performed an average of 3.8 days later; none of these patients had severe pulmonary hypertension postoperatively, and all survived. Two could not be weaned before repair, one of whom had a complex congenital heart defect. This patient died. The other patient had repair on ECMO because of intrathoracic gastric volvulus. Severe blood loss prompted decannulation, and the patient died. One patient who was placed on bypass was transferred 10 days after having had repair elsewhere (at 4 hours of age). Pulmonary hypertension did not resolve, and the postmortem examination showed alveolar capillary dysplasia, with focal misalignment of the pulmonary vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracorporeal Membrane Oxygenation↗

PubMed1995

Protective effect of the serotonin receptor antagonist cinanserin in two canine models of pacing-induced myocardial ischemia.

Previous studies have indicated that structurally dissimilar serotonin2 (5HT2) antagonists can protect globally ischemic/reperfused reperfused rat hearts. We therefore determined if the 5HT2 antagonist cinanserin can protect the ischemic myocardium in two models of pacing-induced ischemia in anesthetized dogs. In one model, dogs were subjected to repeated 5-min episodes of pacing superimposed upon left anterior descending coronary artery stenosis such that an ST segment elevation of 10-11 mV was obtained and upon cessation of pacing, a return of ST segment elevation to baseline. In vehicle-treated animals, this ST segment elevation to baseline. In vehicle-treated animals, this ST segment elevation was constant for all pacing-induced ischemic episodes. After infusion of 20 micrograms/kg/min cinanserin (intracoronary, i.c.), ST segment elevation was significantly reduced during pacing-induced ischemia at all times measured postdrug. In the second model, animals were subjected to pacing-induced ischemia for 15 min such that segmental shortening was reduced to zero. Upon cessation of pacing-induced ischemia, recovery of shortening was assessed. In vehicle-treated dogs, function recovered to only 40% of baseline at 3 h into recovery. Pretreatment with 5 micrograms/kg/min cinanserin i.c. significantly improved recovery of postischemic function. In both protocols, cinanserin had no effect on ischemic regional blood flow or peripheral hemodynamics. Thus, cinanserin appears to exert profound protective effects in two models of effort-induced ischemia.

Analysis of Variance↗

PubMed1994

Aortoesophageal fistula: congenital and acquired causes.

Aortoesophageal fistula (AEF) is a rare but frequently lethal cause of upper gastrointestinal bleeding. This is a report of the authors' experience with four cases--two from congenital and two from acquired causes. A review of the pediatric cases reported in the literature is included. The mortality from AEF is high, and can be decreased in two ways. AEF can be prevented by avoiding prolonged nasogastric intubation in patients with known vascular rings, and by promptly removing esophageal foreign bodies and promptly treating periesophageal abscesses. Once an AEF occurs, it presents with typical large-herald upper gastrointestinal bleeding of bright red blood, and cardiovascular collapse. Recognition of this pattern, with vigorous resuscitation and aggressive surgical management, will improve the survival rate.

Aortic Diseases↗

PubMed1994

Minimally conjoined omphalopagi: a consistent spectrum of anomalies.

Omphalapagus twins constitute less than one third of all siamese twins. Most omphalopagi are attached by a skin bridge that often contains hepatic tissue. Only four cases of omphalopagi attached by an intestinal bridge have been reported. The authors present two additional cases of conjoined twins minimally attached by a small bowel and bladder bridge. In both instances, the spectrum of anomalies included a ruptured omphalocele and imperforate anus with cloacal anomalies. The attachment consisted of an open urachal remnant joining the two bladders, and the short small bowel of twin A attached to the terminal ileum of twin B. Separation was uneventful. For one set of twins, the case part of the proximal colon of twin B was used to lengthen the bowel of twin A. Three of the twins survived and underwent additional procedures for repair of the cloacal anomalies. All four previously reported cases of minimally conjoined omphalopagi presented with a remarkably similar spectrum of anomalies. All had ruptured omphaloceles, imperforate anus with cloacal anomalies, and urachal anomalies. Intestinal connection was consistently at a point corresponding to the Meckel diverticulum site of twin B, with blood supply to the small bowel of twin A, probably via the vitelline artery. The consistent spectrum of anomalies encountered with minimally conjoined omphalopagi allows planning of separation. Caution is required to avoid overlooking the patent urachus, and intestinal lengthening procedures based on the vitelline artery become an important consideration.

Anus, Imperforate↗

PubMed1993

Childhood primary pulmonary neoplasms.

Nine children (6 boys, 3 girls) were diagnosed with a primary endobronchial or pulmonary parenchymal neoplasm. The average age at diagnosis was 9 years. Presenting complaints included cough (7), fever (5), pulmonary infection (3), respiratory distress (3), weight loss (2), pain (2), and hemoptysis (1). Pulmonary x-rays showed persistent atelectasis, pneumonic infiltrates or mass lesions. A computed tomography scan was performed in 8. Five of six endobronchial tumors were diagnosed with bronchoscopy and biopsy. Treatment consisted of thoracotomy and pulmonary resection in 7 cases and laser resection in 2. The pathologic diagnoses were bronchial carcinoid (3), bronchial mucoepidermoid carcinoma (1), inflammatory pseudotumor (plasma cell granuloma) of the bronchus (2) and of the lung parenchyma (1), fibrosarcoma (1), and rhabdomyosarcoma (1). Postoperative chemotherapy was given only to the patient with pulmonary rhabdomyosarcoma; this child died. One child has developed a local recurrence while 7 children are alive and free of disease at an average of 2.4 years postresection. Pulmonary neoplasms are unusual in the pediatric age group and represent a wide spectrum of pathology. Including the present series, 383 tumors have been described. Seventy-six percent were malignant. Early investigation and surgical intervention are essential in children with persistent pulmonary symptoms or x-ray abnormalities. In most cases, the prognosis is excellent with complete surgical resection; however, malignancies other than bronchial adenoma are associated with significantly mortality.

Bronchial Neoplasms↗

PubMed1993

Superior activity of a thromboxane receptor antagonist as compared with aspirin in rat models of arterial and venous thrombosis.

We determined the effects of aspirin and a novel thromboxane A2/prostaglandin endoperoxide (TP)-receptor antagonist, BMS-180291, on thrombosis and bleeding times in skin and mesenteric arteries. In anesthetized rats, occlusive thrombosis was induced in the carotid artery by topical application of ferrous chloride and in the vena cava by blood flow stasis combined with either infusion of thromboplastin or hypotonic saline. Aspirin (1, 10, and 50 mg/kg) did not reduce arterial or venous thrombus weight significantly. BMS 180,291 (150 micrograms/kg/min) decreased arterial thrombus weight and hypotonic saline-induced caval thrombus weight by 58 and 57%, respectively. BMS-180291 lacked antithrombotic activity at a lower dose (50 micrograms/kg/min) and failed to inhibit thromboplastin-induced caval thrombosis. BMS-180291 (150 micrograms/kg/min) significantly reduced arterial thrombus weight by 40% when plasma epinephrine concentration was increased to 5 ng/ml. BMS-180291 and aspirin produced increases of only < or = 30% in bleeding times. These results demonstrate that BMS-180291 has antithrombotic activity in experimental aspirin-resistant arterial and venous thrombosis. Both aspirin and BMS-180291 have only modest effects on small artery hemostasis in rats.

Animals↗

PubMed1992

Cholelithiasis in newborns and infants.

Cholelithiasis in infants is rare, and has usually been associated with hemolysis, ileal disease, congenital anomalies of the biliary tree, hyperalimentation, and prolonged fasting. With the increased use of abdominal ultrasonography (US), more cases of cholelithiasis are being discovered. We report our experience with 13 infants diagnosed on abdominal US to have gallstones. There were 9 boys and 4 girls with an average age at diagnosis of 2.6 months (range, 0 to 9 months). Predisposing factors could be identified in only 6 of the 13 patients. Two patients with obstructive jaundice underwent cholecystectomy and common bile duct exploration. One patient with choledocolithiasis and common bile duct dilatation was observed. His stone passed spontaneously, with resolution of symptoms. Ten patients without cholestasis remained asymptomatic, with disappearance of lithiasis in five of them. Neonatal cholelithiasis is more common than previously suspected; it seems to affect males more often than females and is usually not associated with known predisposing factors. It appears to be a temporary, self-limiting phenomenon, and an aggressive approach is not warranted in the asymptomatic infant. Surgical or radiological intervention should be reserved for the symptomatic patients or those with underlying lithogenic disorders.

Cholecystectomy↗

PubMed1992

Neonatal gastrointestinal perforations.

Neonatal gastrointestinal perforation has been associated with mortality rates of 40% to 70%. Over the past 20 years, 81 infants (46 boys and 35 girls) were treated for a gastrointestinal perforation at this institution. Perforation occurred from birth to 50 days (average, 8.2 days). Etiologies included necrotizing enterocolitis (NEC) (68%), meconium ileus (10%), and idiopathic gastric perforation (7%). Seventy-six infants underwent surgical exploration and five infants, considered too small or too sick to withstand a laparotomy, were treated with peritoneal lavage only. There were 29 deaths, an overall mortality of 36%. Ninety percent of the death occurred in patients with NEC, while all patients with gastric perforations survived. There has not been a significant improvement in survival in recent years, partly because of an increase in the proportion of NEC-related perforations. However, there is a narrowing of the mortality gap between low birth weight and normal weight infants. As the risk inherent to laparotomy in neonates is decreasing, other factors, such as the underlying etiology or the site of perforation, play a more important prognostic role.

Enterocolitis, Pseudomembranous↗