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Biomedical subjects

M Ahdab-Barmada

Publications and source records attributed to M Ahdab-Barmada.

At least 19 recordsLinked to original sources
PubMed2001

P-glycoprotein and bilirubin disposition.

P-glycoprotein (Pgp), an ATP-dependent plasma membrane efflux pump, is expressed in abundance on the luminal aspect of brain capillary endothelial cells and astrocytes of the blood-brain barrier where it limits the passage of a variety of lipophilic substrates into the central nervous system. This review summarizes current evidence characterizing (1) unconjugated bilirubin as a potential substrate for Pgp and (2) the ontogeny of Pgp expression at the blood-brain barrier and apical brush border epithelium of the gastrointestinal tract, findings that may provide insights regarding the disposition of bilirubin in immature subjects.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Sudden death in an adolescent boy due to a colloid cyst of the third ventricle.

A 13-year-old boy died suddenly at night while asleep. A colloid cyst filled the third ventricle, obstructed the flow of cerebral spinal fluid, and led to prominent hydrocephalus. Acute ventricular distension with brain herniation resulted in death, whereas repeated previous episodes had led to cerebral compression and edema. Complaints included only episodic headache in the month prior to death. His pediatrician prescribed a course of Imitrex (sumatriptan) because of lack of neurologic signs or other symptoms and a family history of migraine headaches. The headaches persisted, however, and within 1 month the patient died. The difficulty of accurate clinical diagnosis in this case is common. Subtle signs or even lack of symptoms of increased intracranial pressure may prevent a timely diagnosis before the occurrence of deadly complications. This case report helps to remind both forensic medical examiners and clinicians that this entity, although rare, should remain in the differential diagnosis of headache in children and young adults and of hydrocephalus at autopsy. Timely diagnosis of this benign lesion can lead to a surgical cure.

Adolescent↗
PubMed1997

A rat model of leptomeningeal human neoplastic xenografts.

Leptomeningeal (LM) cancer spread from either a primary brain tumor or a systemic cancer is rapidly fatal. Current therapies are ineffective and highly toxic to normal nervous system tissues. A xenograft model of LM neoplasia in nude rats using a diversity of tumor cell types was established in order to evaluate new treatment strategies and to study the pharmacokinetics and biological effects of treatments administered into the subarachnoid space. Consistent leptomeningeal engraftment and progressive tumor growth was seen after intrathecal injection of 9 of 13 tumor cells lines, including 2 melanomas, 2 neuroblastomas, 2 medulloblastomas, 2 gliomas, and 1 breast cancer. Clinical signs ranged from steady weight loss commencing from the day after tumor implantation to absence of any signs for three weeks until the sudden occurrence of major neurological deficits or death. Pathologic examination showed only leptomeningeal tumor growth with some cell lines and severe parenchymal invasion with others. CSF cytology consistently demonstrated tumor cells in animals with LM disease. Cranial magnetic resonance (MR) following intravenous (i.v.) administration of a contrast agent revealed enhancing lesions one week following melanoma tumor implantation. Reliable ventricular puncture was demonstrated by radiography following intraventricular (IVent) injection of an iodinated contrast material. IVent instillation of saline, albumin, or antibodies did not provoke clinical toxicity or an inflammatory response.

Animals↗
PubMed1995

Ectopic posterior pituitary tissue and paracentric inversion of the short arm of chromosome 1 in twins.

Twin boys with hypopituitarism, hypoplasia of the anterior pituitary gland. ectopic posterior pituitary tissue and paracentric inversion of the short arm of chromosome 1 are described. The smooth appearance at the base of the median eminence and the absence of a pituitary stalk at autopsy in these boys implies that the hypopituitarism resulted from a developmental aberration. It remains to be determined if there is a casual relationship between the chromosome 1 anomaly and hypopituitarism.

Choristoma↗
PubMed1994

Cerebrovascular lesions in infants and children dying after extracorporeal membrane oxygenation.

The neuropathologic autopsy findings of a group of infants and children at Children's Hospital of Pittsburgh who died after treatment with extracorporeal membrane oxygenation (ECMO) were reviewed and tabulated. The study surveyed an 11-year period (February, 1980 to May, 1991); of 268 children receiving ECMO therapy for severe cardiopulmonary failure, 94 patients died, 70 of whom were autopsied and permission for brain examination was granted in only 44. The frequency of ischemic neuronal necrosis (50%), focal cerebral infarcts (50%), intracerebral hemorrhages (52%), and periventricular leukomalacia (41%) was higher in this group of ECMO-treated patients than that observed in the general autopsy population from which the study patients were selected. The frequency of ischemic and hemorrhagic brain lesions was similar among neonates and older infants and children. This documentation of cerebrovascular lesions in children dying after ECMO may provide a better understanding of potential brain damage in the larger population of infants and children who survive this invasive procedure.

Brain↗
PubMed1994

Intracranial infantile myofibromatosis.

Infantile myofibromatosis is a proliferative disorder of infancy and early childhood characterized by nodular or diffuse growth of lesions that are comprised of a mixture of mesenchymal elements within the skin, subcutaneous tissues, skeletal muscle, bone, and/or visceral organs. Although these pseudotumors are considered to be the most common fibrous "neoplasm" of infancy, central nervous system involvement is reportedly rare. During the last 7 years, the authors have treated three children with intracranial myofibromas who presented at 6 weeks, 7 months, and 3 3/4 years of age, respectively. Each child had a large calvarial mass that produced significant brain compression despite a paucity of neurological signs. On computerized tomography, these tumors were isodense to brain tissue, enhanced strongly with intravenous contrast material, and showed smoothly marginated bone erosion without surrounding sclerosis. On magnetic resonance imaging, the tumors were hypointense on T1-weighted images, with dense enhancement following the administration of intravenous contrast medium, and hyperintense on T2-weighted images. At operation, the tumors were highly vascular and appeared to arise from within the leaves of the dura, eroding through the overlying bone, but not violating the galeal or arachnoidal layers. Two of the lesions were adherent to major dural venous sinuses. Both of these lesions were completely resected in continuity with the involved dura, and have not recurred 6 years and 1 year, respectively, postoperatively. However, in one patient in whom the involved dura was not resected at the initial procedure, the tumor recurred rapidly. A complete excision of the tumor and involved dura was then performed and the patient is now recurrence-free, 5 1/2 years after the second surgical resection. All patients tolerated resection well, but two have required cranioplasty for persistent calvarial defects. The surgical experience with these lesions is reviewed and the distinctive features of their clinical presentation, radiographic appearance, operative management, and outcome are discussed.

Brain Neoplasms↗
PubMed1993

Substantia nigra damage after fluorothyl-induced seizures in rats worsens after post-seizure recovery: no exacerbation with hyperglycaemia.

The substantia nigra pars reticularis (SNPR) of rats is highly susceptible to both seizure- and ischaemia-mediated damage. Hyperglycaemic exacerbation of brain damage similar to that observed after global brain ischaemia may also occur in rats with status epilepticus. We tested the hypotheses that hyperglycaemia exacerbates seizure-induced SNPR damage in rats and that SNPR lesions develop rapidly post-seizure. Halothane-anaesthetized, paralysed, and mechanically ventilated rats were prepared for haemodynamic and EEG monitoring. Halothane was discontinued, and mechanical ventilation on 30% oxygen/70% nitrous oxide was continued for 1 h. Three treatment groups (20 rats each) were studied: (1) control, lactated Ringer's solution; (2) equiosmolar control, 40% mannitol; and (3) hyperglycaemia, 50% dextrose. Infusions were started 5 min before seizures were induced with flurothyl 3% administered for either 45 (n = 10) or 75 (n = 10) min. Immediately after seizures, half of the animals underwent cerebral perfusion-fixation with formalin and half were allowed to recover for 2 h post-seizure and then perfused. Brain histology was assessed by light microscopy and scored 0-5 (0 = no damage) for the percentage of eosinophilic neurons and vacuolation in the SNPR. Glucose administration decreased the severity of SNPR damage in rats subjected to 75 min of seizures and 2 h recovery (pathology scores: control, eosinophilic neurons = 3.6, vacuolation = 4.0; hyperglycaemia, eosinophilic neurons = 3.0, vacuolation = 2.75; p < 0.05). SNPR damage was worse after 2 h of recovery (pathology scores: 0 h recovery, eosinophilic neurons = 0.9, vacuolation = 0.1; 2 h recovery, eosinophilic neurons = 3.9, vacuolation = 3.8; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Lactic↗
PubMed1993

The neuropathology of liver transplantation: comparison of main complications in children and adults.

Neurologic complications remain important factors in mortality and morbidity of liver transplant patients, despite 5-yr survival rates of nearly 75% achieved with improved surgical and anesthetic techniques, better selection of recipients and donors, and immunosuppression. In order to analyze and compare the occurrence of neuropathologic complications in children with that in adults, we reviewed all complete autopsies done on liver transplant patients at the University of Pittsburgh from March 1, 1981 until December 31, 1990. A retrospective study of all neuropathologic lesions in 68 children and 132 adults indicated a higher occurrence of cerebrovascular lesions in children than in adults. Intracranial hemorrhages occurred in 27% of the children and in 20% of adults; cerebral ischemic lesions showed even a higher prevalence in children than in adults: focal infarcts occurred in 32% of children and 18% of adults, and global brain ischemia was observed in 49% of children and 20% of adults. Intracranial aspergillosis was the most common fungal infection in both children and adults (4% children, 10% adults). Systemic posttransplant lymphoproliferative disorders were more frequent in children and occurred in nine children and four adults. CNS lymphoma occurred in two children and one adult. Progressive multifocal leukoencephalopathy was seen in one adult only.

Adolescent↗
PubMed1992

Fatty liver, encephalopathy, and sudden unexpected death in early childhood due to medium-chain acyl-coenzyme A dehydrogenase deficiency.

A case of sudden death associated with fatty liver and encephalopathy is described in a 4-year old white boy with medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency. The death was caused by hypoglycemia triggered by fasting and vomiting associated with a minor viral infection. The differential diagnosis of the hepatoencephalopathy is discussed in relation to other conditions, especially Reye's syndrome. The forensic pathologist should be familiar with MCAD and other deficiencies of beta-oxidation of fatty acids as a cause of sudden unexpected death in children in order to advise parents in genetic counseling to prevent disability or death of other affected, but still asymptomatic siblings.

Brain Diseases↗
PubMed1991

Brain glutamine synthetase activity and hyperoxia in neonatal rats.

We have previously shown that exposure to 100% oxygen for 2 h results in a two-fold decrease in the brain glutamine synthetase activity of neonatal rats. The present study examines whether this decrement in enzyme activity leads to a global accumulation of glutamate, an excitotoxin which is a substrate for this enzyme. Despite a demonstrable decrement in whole brain glutamine synthetase activity, whole brain glutamate content is unaltered in animals exposed to 100% oxygen for 2 h. Furthermore, despite a persistent two-fold decrement in glutamine synthetase activity in animals exposed to 100% oxygen for 6 h, there remained no significant difference in glutamate content or in the glutamate/glutamine ratio between these animals and animals similarly exposed to room air. These results imply that the observed decrease in glutamine synthetase activity does not globally influence the glutamate content of the brain.

Animals↗
PubMed1991

Risk factors associated with kernicterus in the newborn infant: importance of benzyl alcohol exposure.

The prevalence of kernicterus in our neonatal intensive care unit (NICU) decreased from more than 2/1000 live births in 1980 to none in 1984. To clarify predictors of kernicterus, we examined the medical records of infants born during that time who died between 2 and 28 days of age. Infants were divided into three groups: those with kernicterus, all born before June 10, 1982 (n = 29); contemporaneous controls (n = 28); and infants born after June 10, 1982 (n = 32). Benzyl alcohol was not used after June 10, 1982. Kernicteric infants were more likely than contemporaneous controls to have seizures (p less than 0.001). Indices of pulmonary disease, arterial partial pressure of carbon dioxide and end-expiratory pressure on the ventilator were higher after 1982. However, exposure to benzyl alcohol was not different in kernicteric infants and contemporaneous controls, suggesting that benzyl alcohol exposure was not the explanation for the decrease in the prevalence of kernicterus in our NICU.

Analysis of Variance↗
PubMed1991

Cerebellar glutamine synthetase in children after hypoxia or ischemia.

BACKGROUND: Glutamate has been implicated in the pathophysiology of acute hypoxic-ischemic encephalopathy. Glutamine synthetase is an enzyme found in astrocytes that converts glutamate to its nontoxic analogue, glutamine. The present study tests the hypothesis that brain glutamine synthetase activity increases in response to acute hypoxic-ischemic insults and not in response to chronic hypoxia-ischemia or non-hypoxic-ischemic neurological disease. SUMMARY OF REPORT: Frozen sections of cerebellum from children who died with acute or chronic hypoxic-ischemic insults or chronic non-hypoxic-ischemic neurological disease were spectrophotometrically assayed for glutamine synthetase activity by an observer who was blinded to the clinical group assignment of each specimen. Enzyme activity was elevated in specimens from children with acute hypoxic-ischemic insults (mean 6.5; range 5.4-7.2 units/g wet tissue wt) as compared with those from patients with chronic hypoxia-ischemia (mean 2.8; range 0.7-10.2 units/g wet tissue wt) or with non-hypoxic-ischemic neurological disease (mean 2.6; range 1.3-3.9 units/g wet tissue wt). This difference was not due to differences in the degree of histological astrocytosis or edema among the specimens. Statistical analysis by the Kruskal-Wallis one-way analysis of variance by ranks test indicates that the three data groups do not come from one population (p less than 0.05). CONCLUSIONS: These results support the notion that glutamine synthetase activity increases in response to acute hypoxic-ischemic nervous system injury in children and that other compensatory mechanisms prevail in the case of chronic hypoxic-ischemic insults.

Analysis of Variance↗
PubMed1990

A distinctive triad of malformations of the central nervous system in the Meckel-Gruber syndrome.

A distinct triad of central nervous system (CNS) malformations (prosencephalic dysgenesis, occipital exencephalocele and rhombic roof dysgenesis) was present in seven cases of the Meckel-Gruber syndrome examined at autopsy. We compared our findings with those previously described. Microcephaly, sloping forehead, posterior occipital exencephalocele, cerebellar hypoplasia, Chiari malformation, hydrocephalus, polymicrogyria, arhinencephaly, holoprosencephaly and anencephaly constituted a broad spectrum of the reported CNS anomalies. Few reports contained a comprehensive description of the observed CNS malformations. In those reports, and in our cases, features of prosencephalic dysgenesis included agenesis of olfactory bulbs and tracts (arhinencephaly), hypoplasia of optic nerves and chiasm, agenesis of corpus callosum, fused thalami or complete holoprosencephaly. The occipital encephalocele has consisted of a displacement of rhombic roof elements, including caudal third ventricle, cerebellar vermis and fourth ventricle, extruded through an enlarged posterior fontanelle rather than through an occipital cranium bifidum and is thus more precisely labeled an exencephalocele. Different degrees of dysgenesis of posterior fossa structures, described by some as a variant of Dandy-Walker cyst with features of a Chiari malformation, were often associated with this occipital exencephalocele. This pattern of CNS anomalies represents a triad of malformations probably associated with defective ventral induction of the developing CNS by the prechordal mesoderm.

Abnormalities, Multiple↗
PubMed1989

Central pontine myelinolysis after liver transplantation.

Eight adults and 3 children out of 85 patients who had neuropathologic examination after death following orthotopic liver transplantation showed central pontine myelinolysis (CPM). Four patients also had extrapontine myelinolysis. Eight patients had significant serum sodium changes. In 5, the fluctuation occurred perioperatively and 4 had a clinical picture consistent with CPM, although no patient had this as an antemortem diagnosis. We emphasize the role of hepatic dysfunction as a cause of CPM and recommend careful monitoring of electrolytes in the perioperative period of patients undergoing liver transplantation.

Adult↗
PubMed1986

Hyperoxemic retinal neuronal necrosis in the premature neonate.

A cytologically distinctive type of acute hyperoxemic injury of retinal neurons occurs in premature neonates. Ganglion cells in the central well-vascularized neonate retina are susceptible to excessive oxygen and this is expressed morphologically by karyorrhexis of their nuclei. We observed retinal neuronal necrosis in neonates who had hyperoxemia of greater than 150 torr for two hours or longer in the first week of life. Neuronal necrosis was strikingly associated with immaturity as determined by gestational age and birth weight: of 30 involved neonates, all were below 2,000 g; of 47 autopsied premature infants with birth weights under 1,500 g who survived for at least two days, 26 (55%) had acute retinal necrosis. When gestational age was used as a measure of prematurity, the highest incidence occurred in the 24- to 27-week group where 13 of 21 (62%) were involved. Hyperoxemic karyorrhectic changes, most prominent in the ganglion cells of the macula, are distinct from the classic peripheral mesenchymal vascular abnormalities of retinopathy of prematurity.

Birth Weight↗