Search PubMed⌕ Search

Biomedical subjects

A Hill

Publications and source records attributed to A Hill.

At least 217 records · Page 12Linked to original sources
PubMed1989

Neurosonographic features of Aicardi's syndrome.

Aicardi's syndrome occurs in females and is associated with profound mental retardation, agenesis of the corpus callosum, chorioretinal lacunae, and infantile spasms. We report a distinctive combination of abnormalities which was observed on real-time cranial ultrasound scans of two infants with Aicardi's syndrome. These abnormalities include bilateral prominent cysts in the choroid plexus in conjunction with agenesis of the corpus callosum. Recognition of these radiologic findings may suggest the diagnosis of Aicardi's syndrome in early infancy even prior to the onset of seizures or visualization of chorioretinal lacunae.

Agenesis of Corpus Callosum↗
PubMed1989

MR imaging of periventricular leukomalacia in childhood.

Eight children with clinical and radiologic abnormalities consistent with periventricular leukomalacia were investigated with MR imaging of the brain that employed both inversion-recovery and T2-weighted spin-echo imaging sequences. The more precise delineation of white and gray matter on inversion-recovery images as compared with CT allows a detailed demonstration of the anatomic features of periventricular leukomalacia; specifically, a reduced quantity of white matter in the periventricular region and centrum semiovale and, in more severe cases, cavitated infarcts that replace the immediate periventricular white matter. The T2-weighted spin-echo and short inversion time inversion-recovery images demonstrated abnormally increased signal in white matter that appeared normal on CT scans and only minimally abnormal on conventional inversion-recovery images. These abnormalities most probably represent white matter gliosis that extends beyond the immediate periventricular regions. MR recognition of cerebral white matter abnormalities associated with periventricular leukomalacia may confirm the clinical suspicion of this diagnosis in children with spastic diplegia or quadriplegia.

Adolescent↗
PubMed1989

Assessment of the fetus: relevance to brain injury.

This article reviews recent advances in the antepartum and intrapartum assessment of the fetus and their relationship to brain injury in the newborn. The antepartum assessment involves observation of fetal body and eye movements, the nonstress and contraction stress tests, measurement of amniotic fluid volume, the fetal biophysical score and measurement of fetoplacental blood physiology. There is evidence to suggest that seizures may either be epileptic in origin or initiated and mediated by nonepileptic mechanisms. Therapeutic decisions may be based on bedside assessment of the pathophysiology of observed seizures. Although EEG/video monitoring plays a role in the management of neonatal seizures, clinical evaluation of the seizures may provide initial data critical to decisions concerning immediate management.

Embryonic and Fetal Development↗
PubMed1989

Perinatal asphyxia: clinical aspects.

This article reviews the significance of hypoxic-ischemic encephalopathy and the associated patterns of cerebral injury in the context of the most probable timing of the insult and prognosis. The evolution of the clinical features of significant hypoxic-ischemic encephalopathy, and the diagnostic value of imaging and electrophysiologic and metabolic studies are discussed. Current approaches to management are outlined.

Asphyxia Neonatorum↗
PubMed1988

Notification of mumps.

Explore the source record for details and available documents.

Communicable Disease Control↗
PubMed1988

Amaurosis fugax in teenagers. A migraine variant.

Sudden, transient loss of vision in one eye (amaurosis fugax) is associated frequently with atherosclerosis of the internal carotid artery in adults and may herald a stroke. Thus, cerebral angiography is often performed. Amaurosis fugax in children is uncommon and an underlying cause is rarely demonstrated. Recurrent episodes of amaurosis fugax occurred in five adolescents. A characteristic evolution and pattern of visual loss, consistent with choroidal ischemia as the underlying mechanism, was described by four of them. Although none of the episodes were accompanied by headache, four patients had a history of common migraine at other times or a family history of migraine. These episodes of visual loss may represent a migraine variant, and cerebral angiography is not indicated in adolescents with such a history.

Adolescent↗
PubMed1988

Reduced platelet count as a risk factor for intraventricular hemorrhage.

The role of thrombocytopenia as a risk factor for intraventricular hemorrhage in infants of very low birth weight is unclear. This study investigates the relationship between the lowest platelet count and the occurrence of intraventricular hemorrhage in 302 consecutively admitted infants with birth weights under 1500 g. Intraventricular hemorrhage, which occurred in 90 infants (29.8%), was correlated with the lowest platelet count obtained during the first 4 days of life. In 27 infants with intraventricular hemorrhage, the lowest platelet count was less than 100 X 10(9)/L. Statistical analysis of the data demonstrated that reduced platelet count was not associated significantly with intraventricular hemorrhage. Similarly, the severity of intraventricular hemorrhage did not correlate with the lowest platelet count. These data suggest that a reduced platelet count does not play a major role in the pathogenesis of intraventricular hemorrhage in infants of very low birth weight.

Asphyxia Neonatorum↗
PubMed1988

Selective brainstem injury in an asphyxiated newborn.

We report the clinical, radiological, and neuropathological features of selective brainstem injury in an asphyxiated term infant. Disproportionate injury to thalamus, basal ganglia, and brainstem with relative sparing of cortex and subcortical white matter is observed occasionally after acute total asphyxia. Although this entity has been well documented neuropathologically, the specific computed tomographic findings have not been reported previously to our knowledge, and the clinical correlation is recognized rarely.

Asphyxia Neonatorum↗
PubMed1988

Neuronal migration abnormalities can still be diagnosed by computed tomography!

Magnetic resonance imaging is presently the best modality for evaluating gray/white matter anatomy. However, this modality is expensive and not yet readily available in all countries. Most neuronal migration abnormalities can be accurately diagnosed by computed tomography (CT) provided excellent scanning technique is used. Abnormalities of neuronal migration were identified with CT brain scans in 68 children and were categorized as focal heterotopias (11 patients), multifocal heterotopias (19 patients) of diffuse migration disorders (38 patients). The principal indications for imaging were correlated to the radiological features. Neuropathological confirmation of the migration abnormality was obtained in 8 patients. An increased awareness by both clinicians and radiologists together with optimal CT technique are essential for the accurate diagnosis of migration disorders in children.

Brain↗
PubMed1988

Absorption of 'non-absorbable' markers and an improved method for determining cholesterol absorption rates.

The determination of uptake rates for lipids across absorptive epithelia, using radiolabelled compounds has normally used non-absorbable volume markers to correct gross tissue counts for contamination by adherent mucosal fluid. There is evidence however to indicate that the macromolecules traditionally used as non-absorbable markers are in fact absorbed. This may result in an overestimate of the apparent adherent mucosal fluid with consequent errors in the calculation of lipid uptake. An in-vitro method was used to assess cholesterol absorption by human gallbladder from artificial bile, containing 3H-dextran 70,000 as a 'non-absorbable' volume marker. Both cholesterol and dextran were transported through the mucosa and appeared on the serosal side of the gallbladder. Confirmation of dextran absorption was obtained by electron microscopic examination of the gallbladder epithelium. By using the serosal appearance of dextran as a guide to the amount of absorbed (intracellular) dextran in the tissue samples, we have derived a formula to calculate tissue dextran absorption and, from the revised adherent mucosal volume, have consequently obtained more realistic estimates of tissue lipid uptake. In this study, comparison made between the previous estimate of lipid uptake compared to this new calculation, showed that the previous technique significantly underestimated true lipid uptake.

Absorption↗
PubMed1988

Brain swelling in the asphyxiated term newborn: pathogenesis and outcome.

The role of brain swelling following acute hypoxic-ischemic insult in the genesis of brain injury in the term newborn is controversial. Recent experimental animal studies suggest that it may result from prior irreversible cerebral necrosis and therefore represents a consequence as opposed to a cause of major brain injury. In this study, 32 asphyxiated term newborns were studied during the first week of life with serial intracranial pressure measurements. A total of 26 infants had CT scans during the first five days of life. Seven patients had two CT scans within this period. These investigations were correlated with outcome at 18 months of age. Seven infants had increased intracranial pressure (greater than 10 mm Hg) that reached a maximum between 36 and 72 hours of age. Cerebral perfusion pressures remained normal, which makes ongoing ischemic injury unlikely as a cause. The seven patients with increased intracranial pressure had decreased attenuation on CT that was generalized in six infants and patchy in one infant. Of the infants with increased intracranial pressure and severe CT abnormalities, three died and four had severe neurologic sequelae. In seven infants, a second CT scan at three to four days of life demonstrated progression of the decrease in tissue attenuation. Most of the infants with normal intracranial pressure (23/25) had no or had only minor neurologic abnormalities at follow-up. These data suggest that brain swelling is relatively uncommon in the asphyxiated term newborn.(ABSTRACT TRUNCATED AT 250 WORDS)

Asphyxia Neonatorum↗
PubMed1987

Pliocene hominid partial mandible from Tabarin, Baringo, Kenya.

Sediments in the Tugen Hills, west of Lake Baringo, Kenya, form one of the best fossiliferous successions known in Africa spanning the period from 14 my to less than 4 my. Hominoid fossils have previously been recovered from a number of localities in the region. We describe here a new hominid mandible (KNM-TH 13150) from the site of Tabarin, in the Chemeron Formation. Isotopic determinations on a tuff below the fossiliferous horizon gives dates of 4.96 my and 5.25 my. The associated fauna is consistent with these results and independently suggests a minimum age for the specimen of 4.15 my. Although fragmentary, the preserved morphology of the Tabarin mandible is consistent with the diagnosis of the Pliocene hominid Australopithecus afarensis. It can be distinguished from all other currently recognized hominoid taxa.

Animals↗
PubMed1987

Quantitative considerations of T-cell activation and self tolerance.

We have reviewed evidence for the hypothesis that T-cell activation by antigen is an all or none process which is triggered when signal strength exceeds a certain threshold. Signal is generated by multivalent interaction between T-cell antigen receptors (TCR) and antigenic epitopes on the surface of antigen-presenting cells (APC) or target cells. Therefore total signal strength (Stot) will depend upon the concentration of TCR (and other accessory molecules that bind to cell surface ligands, e.g. CD4 and CD8) on T cells, the concentration of antigen on APC or targets and the affinity of interaction between receptors (a broad term incorporating TCR plus CD4 and CD8) and antigen. This hypothesis means that T-cell self tolerance is quantitatively determined by self-antigen concentrations on cell surfaces. Implications for a variety of immunological phenomenona are reviewed.

Animals↗
PubMed1987

Genetic manipulation of centromere function.

A conditional centromere was constructed in Saccharomyces cerevisiae by placing the centromere of chromosome III immediately downstream from the inducible GAL1 promoter from S. cerevisiae. By utilizing growth conditions that favor either transcriptional induction (galactose-carbon source) or repression (glucose-carbon source) from the GAL1 promoter, centromere function can be switched off or on, respectively. With the conditional centromere we were able to radically alter the mitotic transmission pattern of both monocentric and dicentric plasmids. Moreover, it was possible to selectively induce the loss of a single chromosome from a mitotically dividing population of cells. We observed that the induction of chromosome III aneuploidy resulted in a dramatic change in cell morphology. The construction of a conditional centromere represents a novel way to create conditional mutations of cis-acting DNA elements and will be useful for further analysis of this important stabilizing element.

Centromere↗
PubMed1987

Periventricular leukomalacia: radiologic diagnosis.

Fifteen infants and children with clinical evidence of periventricular leukomalacia (i.e., spastic diplegia or quadriplegia and premature birth) were studied. Computed tomography (CT) scans of the brain demonstrated the following characteristic abnormalities: reduction in quantity of periventricular white matter, particularly at the trigone, deep and prominent sulci that abutted the ventricles without interposed white matter, and ventriculomegaly with irregular outline of the lateral ventricles. The location and severity of abnormalities on CT scans correlated well with the neurologic abnormalities observed at follow-up and the known anatomic location of periventricular leukomalacia. These observations demonstrate the diagnostic value of CT scanning for periventricular leukomalacia during late infancy and childhood. Although serial ultrasonography during the first weeks of life may be diagnostic of periventricular leukomalacia, it is of less value later. In contrast, CT scans obtained beyond 6 months of age can demonstrate a characteristic pattern of abnormalities that may be considered diagnostic of periventricular leukomalacia.

Encephalomalacia↗