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Biomedical subjects

S Ashwal

Publications and source records attributed to S Ashwal.

At least 91 records · Page 5Linked to original sources
PubMed1988

Effect of nimodipine on newborn lamb cerebral blood flow.

The effects of nimodipine, on total and regional cerebral blood flow and cardiovascular function of the newborn chloralose-anesthetized lamb were investigated following intravenous bolus infusions (0.2, 0.6 and 2.0 micrograms/kg). At 2.0 micrograms/kg, the mean arterial blood pressure increased from 72.3 to 85.8 mm Hg. Total cerebral blood flow 45 min after infusion increased by 93%, as did regional flows to the gray (101%) and white (77%) matter and subcortex (108%). In a separate series of experiments we decreased arterial blood pressure from 71 to 40 mm Hg by phlebotomy. Nimodipine (30 micrograms/kg) bolus infusion significantly increased blood flow above control values to the total brain (41%), gray matter (53%), subcortex (76%) and brainstem (69%) 10 and 40 min later. However, no further increase in flow or decrease in cerebrovascular resistance was observed when compared to hypotension alone. Nimodipine appears to be well tolerated in the newborn lamb, and appears to increase cerebral flow during normotension. At the levels of hypotension used in the current experiments, nimodipine produced no further increases in cerebral blood flow.

Animals↗
PubMed1987

Nifedipine: effects on fetal and maternal hemodynamics in pregnant sheep.

We investigated the effects of nifedipine, a calcium entry blocker, on the fetal and maternal circulation. Nifedipine was administered intravenously for 30 minutes to chronically instrumented pregnant ewes. Infusion of 5 micrograms.kg-1.min-1 resulted in a 30% to 50% increase in total and regional fetal cerebral blood flow to the brain stem, watershed, and subcortical regions (p less than 0.05), without a significant change in fetal oxygenation or cardiac output. Infusion of 10 micrograms.kg-1.min-1 decreased uterine blood flow by 21% (p less than 0.001) and fetal arterial oxygen content by 15% (p less than 0.01), with no further increase in fetal cerebral blood flow. Maternal arterial pressure decreased and heart rate increased (p less than 0.001) without variation of arterial blood gases. Significant plasma levels of nifedipine were detected in the fetal and maternal circulations. In view of the potential adverse effects on the fetus, further studies are needed before nifedipine is considered for use in human pregnancy.

Animals↗
PubMed1987

Developmental changes in thickness, contractility, and hypoxic sensitivity of newborn lamb cerebral arteries.

The present studies were conducted to examine the possibility that the increased vulnerability of the newborn brain to hypoxia may be due to age-related differences in vascular thickness and contractility. Segments of rostral choroidal (RC), posterior communicating (PC), basilar (B), and common carotid (CC) arteries were taken from 3- to 7-day-old lambs (n = 11) and adult sheep (n = 8) and studied using standard in vitro techniques. In lamb cerebral arteries, maturation was associated with significant increases in vessel thickness and tension generation. Because the increases in tension generation (77, 90, and 135% in PC, B, and RC segments) were proportionately greater than the corresponding increases in thickness (45, 75, and 34% in PC, B, and RC), force per unit area increased with maturation in the cerebral arteries. In the CC segments, the age-related increases in thickness (117%) were greater than the increases in tension generation (30%), such that average force per unit area was actually greater in the lamb than in the sheep. In response to hypoxia (PO2 less than 15 torr), all vessels exhibited significant relaxation relative to normoxic controls, although the rates and magnitudes of relaxation varied considerably. In the sheep, the carotid exhibited rapid relaxation of small magnitude (21%), whereas the cerebral arteries relaxed more slowly and more completely (56, 52, and 45% in PC, B, and RC). In contrast, the lamb carotid segments relaxed more slowly than the cerebral arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Incontinentia pigmenti: association with anterior horn cell degeneration.

Incontinentia pigmenti (IP) has been associated with CNS involvement, including seizures, retardation, motor abnormalities, and malformations in greater than 30% of patients. Motor symptoms include spasticity and hyperreflexia; however, weakness and flaccidity have also been described. Peripheral nervous system neuropathology in patients with IP has not previously been reported. The infant with IP in this report showed generalized weakness due to anterior horn cell degeneration. The neuropathologic findings in both the central and peripheral nervous systems will be reviewed and contrasted to previous reports. Patients with IP and weakness should undergo neurodiagnostic evaluation of peripheral nervous system function.

Anterior Horn Cells↗
PubMed1986

Comparison of cerebral blood flow measurements by xenon computed tomography and dynamic brain scintigraphy in clinically brain dead children.

Because of the controversy over applying adult clinical and laboratory criteria to children suspected of brain death, xenon computed tomographic cerebral blood flow (XeCTCBF) and near simultaneous scintigraphy were studied in 10 children. Six met the clinical criteria, one of whom had three indeterminate scintigrams with only central flow on XeCTCBF. Another had considerable flow with scintigraphy and XeCTCBF. One with clinical and autopsy brainstem death but preserved cortical function also had flow on both. This preliminary study establishes that brain scintigraphy is occasionally hypersensitive to insufficient cerebral flow and promises more accurate early assessment with XeCTCBF. The expectation is that XeCTCBF can refine the criteria for the earlier establishment of brain death.

Brain↗
PubMed1986

Determination of cerebral death in the pediatric intensive care unit.

The clinical course, laboratory data, outcome, and autopsy findings in 61 pediatric patients with suspected brain death were reviewed. In 58% of patients, the initial EEG was isoelectric, and cerebral blood flow was absent. In six of nine children, the initial EEG, which showed activity, became isoelectric by 72 hours. In no child without demonstrable cerebral flow did flow resume in later studies. In four of five children who had initial EEG activity despite absent cerebral flow, an isoelectric EEG developed on repeated study. The average time from initial insult until clinically suspected brain death was 29.5 hours and 61.5 hours until brain death was confirmed. The time from confirmation of brain death until discontinuation of life support systems was 32 hours in the majority of patients. Our current protocol for evaluating pediatric patients with suspected brain death is reviewed with emphasis on the clinical examination, laboratory studies, and use of serial EEGs and radionuclide cerebral blood flow determinations.

Adolescent↗
PubMed1985

Rud syndrome revisited: ichthyosis, mental retardation, epilepsy and hypogonadism.

Rud syndrome is a rare disorder of childhood characterized by ichthyosis, mental retardation, epilepsy and hypogonadism. The authors report a family with this autosomal recessive disorder, review the clinical and dermatopathological findings, and contrast Rud syndrome with the other major neuro-ichthyosiform dermatoses.

Adolescent↗
PubMed1984

A new form of sea-blue histiocytosis associated with progressive anterior horn cell and axonal degeneration.

A 15-year-old girl evidenced a slowly progressive central nervous system degenerative disorder. The illness had begun and progressed between ages 1 and 12 years, with ataxia, spasticity, choreoathetosis, early-onset seizures (which later ceased), and mild retardation. At age 13 she had developed rapidly progressive generalized weakness and atrophy, indicating peripheral nervous system involvement. Laboratory investigation revealed the presence of sea-blue histiocytes in the bone marrow without evidence of a disorder of sphingolipid metabolism or neuronal ceroid lipofuscinosis. Muscle biopsy showed large- and small-group atrophy, and sural nerve biopsy demonstrated axonal degeneration. This patient's illness appears to be a hitherto undescribed form of "sea-blue histiocytosis" associated with neurological dysfunction in children.

Adolescent↗
PubMed1984

CNS primitive neuroectodermal tumors of childhood.

Primitive neuroectodermal tumors ( PNET ) of the central nervous system in children are rare, highly malignant, cystic, and sometimes calcific, and hemorrhagic tumors sharply demarcated from adjacent brain. Microscopically they consist of small predominantly undifferentiated dark cells with neuronal, glial, and mesenchymal elements. We have recently diagnosed and treated five children with PNET . We will review their case histories as well as summarize the previous 133 reported cases with reference to presenting complaints, tumor location, neurodiagnostic studies, and the retrospective results of four treatment programs: 1) surgery alone; 2) surgery and radiation therapy; 3) surgery, radiation therapy, and chemotherapy at time of recurrence; and 4) surgery, radiation therapy, and chemotherapy at onset.

Brain Neoplasms↗
PubMed1984

Brainstem auditory evoked responses in the newborn lamb. Studies during postnatal development and acute hypoxia.

Brainstem auditory evoked responses (BAER) have been studied in several species and have provided a neurophysiologic 'window' into brainstem function. We have pursued further studies in the newborn lamb and adult sheep. BAER amplitude increased as the stimulus intensity increased from 45 to 95 dB and as the click frequency decreased from 88.8 to 22.2 Hz. BAER latency increased as both the stimulus intensity decreased and the click frequency increased. Developmental studies were performed between the 2nd and 35th day of life in the newborn lamb. No significant change in either latency, amplitude, or wave morphology was noted in contrast to other species where developmental changes are prominent. This was due to both the prenatal maturation of the lamb's brain and to the relatively short interval of the postnatal studies. We also studied the effect of prolonged severe hypoxia and acidosis on the BAER in the newborn lamb and found no significant change in either the amplitude or latency of the response.

Acidosis↗
PubMed1984

Regional cerebral blood flow: studies in the fetal lamb during hypoxia, hypercapnia, acidosis, and hypotension.

In order to determine the relative roles of O2 tension and content, CO2 tension, hydrogen ion concentration, arterial blood pressure, and cardiac output in the regulation of fetal cerebral blood flow (CBF), we used radioactively labeled microspheres to measure flow to 20 major brain regions in 24 chronically catheterized fetal lambs. We continually monitored fetal heart rate and blood pressure, and periodically measured arterial PO2, PCO2, pH, and hematocrit. In addition to CBF measurements during control periods, we measured CBF during: 1) hypoxia (O2 content less than 6 ml X dl-1; O2 tension less than 15 torr) induced by having the ewe breathe a gas mixture with low O2 concentration, 2) hypercapnia (PCO2 greater than 50 torr) induced by increasing the maternal inspired CO2, 3) acidosis and alkalosis (7.60 greater than pH greater than 6.60) induced by infusing lactic acid or bicarbonate into the fetus, and 4) hypotension (blood pressure less than 35 mm Hg) and hypertension (blood pressure greater than 55 mm Hg) induced by rapidly phlebotomizing or transfusing the fetus. We used multiple regression analysis and analysis of covariance to examine the dependence of total cerebral blood flow on arterial O2 tension and content, CO2 tension, pH, blood pressure, and cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1983

Electrical injuries in children.

Electrical injuries in children continue to account for substantial morbidity and mortality. This review describes the responsible pathogenetic mechanisms and five separate types of injury. Multisystem complications are discussed as well as current concepts of patient management. We emphasize the importance of prevention and include a pediatrician's "reminder" list for parent education.

Burns, Electric↗
PubMed1983

Neuroradiology of primitive neuroectodermal tumors.

The neuroradiological findings in four cases of primitive neuroectodermal tumor of the cerebrum are described. These highly malignant neoplasms of childhood present as large, enhancing cerebral masses with extensive neovascularity. Cerebrospinal fluid seeding is common and distant extraneural metastases may occur.

Brain Neoplasms↗
PubMed1983

Acute flaccid neonatal paraplegia: a case report.

A 3-day-old neonate became acutely and irreversibly paraplegic below L1/L2 after umbilical artery catheterization. The paraplegia was attributed to infarction of the spinal cord because of thrombosis of the artery of Adamkievicz or injection of drugs through the catheter into the spinal cord circulation. Catheterization of a more peripheral artery or placement of the umbilical catheter tip at a lower level in the aorta may prevent similar complications.

Catheterization↗