Biomedical subjects

G Cheung

Publications and source records attributed to G Cheung.

10 recordsLinked to original sources

PubMed1991

MRI of the normal hippocampus.

Before it is possible to use MR imaging to investigate changes in the hippocampus in disease processes such as epilepsy and memory disorders, it is imperative that normal variations are defined. Using specific anatomic locations, we evaluated the hippocampi of 29 normal volunteers with coronal MR studies. Mild variations occur with regard to hippocampal size and shape, and hippocampal fissure visualization. Hippocampal signal intensity is isointense to cortical gray matter. Recognition of normally occurring variations should help prevent over-interpretation of hippocampal changes in pathologic disorders.

Amygdala↗

PubMed1991

MRI of the temporal lobe: normal variations, with special reference toward epilepsy.

Recent investigations of epilepsy, Alzheimer's disease, amnesia, and schizophrenia have used magnetic resonance imaging (MRI) to evaluate changes in temporal lobe structures. Normal variations in these structures need to be defined before one can use these structures to describe abnormal conditions. Twenty-nine normal volunteers were studied by coronal MRI. Frequent findings include notching of the uncus by the tentorium or adjacent vessels (22/29) and asymmetry of the temporal horns (20/29). This finding of uncal notching strengthens the evidence against "incisural sclerosis" as the basis for hippocampal sclerosis. Temporal horn dilatation occurred in four. However, mild asymmetry of the temporal horn was seen frequently at its anterior tip (16/29) and may be related to head rotation. Asymmetry of the choroidal fissure was never marked. Mild asymmetry was common at the hippocampal head (pes). Mild enlargement of the right temporal lobe by visual inspection is not uncommon. Subtle asymmetry of the white matter between the hippocampus and the collateral sulcus occurred in six. The collateral sulcus does not always point to the temporal horn. The occipitotemporal sulcus may point to the temporal horn. Asymmetric uncal protrusion (0/29) and Sylvian fissure dilatation (4/29) occur rarely.

Cerebral Ventricles↗

PubMed1991

Relationship of hippocampus and amygdala to coronal MRI landmarks.

Magnetic resonance imaging is playing an increasingly important role in the evaluation of the hippocampus, particularly in epilepsy, schizophrenia, and Alzheimer's dementia. Because of the complex configuration of the hippocampus, it is difficult to compare from patient to patient. We developed a system to allow comparison of the hippocampus on coronal images. We performed 34 magnetic resonance studies on 29 normal subjects. Ten anatomic landmarks were identified. These landmarks have a consistent 5-mm periodicity regardless of usual head flexion. In the second phase of our investigation, we showed that the amygdala, hippocampal head, hippocampal body, and hippocampal tail have a consistent relationship to the coronal magnetic resonance imaging landmarks.

Adolescent↗

PubMed1990

Omeprazole.

Omeprazole is the first acid-pump inhibitor. With its unique mechanism of action, it represents a new class of drugs in treatment of GERD, reflux esophagitis, and hypersecretory conditions. Overall, its adverse effects are mild and transient and found to be well-tolerated. Thus, omeprazole will serve as an important new agent in the management of some gastrointestinal disorders.

Esophagitis, Peptic↗

PubMed1979

Purification and properties of the hemagglutinin from Wistaria floribunda seeds.

Extracts of Wistaria floribunda seeds contain separable erythroagglutinating and lymphocyte mitogenic activities. We wish to report the purification and characterization of the erythroagglutinating lectin of these seeds. A phosphate-buffered saline (PBS) extract of the ground seeds was made to 50% ethanol and the precipitate, which contained both the agglutinin and mitogen, was dissolved in PBS. The erythroagglutinating activity was adsorbed onto insoluble polyleycyl derivatized A + H active hog gastric mucin. After desorption with 0.2 M D-galactose and removal of the sugar by dialysis, the eluate displayed three protein bands on polyacrylamide gel electrophoresis. The major component represented 85% of the mixture. Immunoelectrophoresis of the mixture demonstrated immunochemical identity among the proteins. Gel filtration through Sephadex G-200 resulted in purification of the major component. Based upon the composition and subunit molecular weight, it was concluded that the three components represent a dimer, tetramer, and octamer of a single glycopolypeptide chain of 28 000. The erythroagglutinin has a pI at pH 5.4 and one cystine per dimeric unit.

Agglutinins↗

PubMed1979

Orbital measurements in the presence of epicanthi in healthy North American Caucasians.

Anthropometric examination of 1,312 healthy North American Caucasians (654 boys, 658 girls) aged 6-18 years revealed epicanthus in 387 subjects (29.5%, 198 boys and 189 girls). Significantly more epicanthi were minor (232, 59.9%) than major, i.e., moderate or marked (155, 40.1%; SED = 3.5, diff. = 19.8). Only one quarter of major epicanthi were marked, i.e., covered the inner canthus (39, 3% of entire sample population). The prevalence of major epicanthi decreased significantly with age in both sexes. Surface measurements did not confirm the visual illusion that the interocular distance is wide in subjects with epicanthus. The nasal root was on average shallower and the eye fissure shorter and more tilted in subjects with major epicanthus than in those without. Though minor epicanthus in Caucasians is a statistical variation of normal eye lid structure, major epicanthus persisting in adulthood may indicate developmental disturbance. Anthropometry provides accurate measurements of orbital dimensions necessary to identify such developmental disturbances.

Adolescent↗

PubMed1977

Immunological specificity and memory in a scleractinian coral.

Tissue transplantation immunity with a specific memory component is demonstrated in populations of Montipora. This highly discriminating immunoreactivity derives from extensive allogeneic polymorphism of histocompatibility (H) markers. An H system of immunorecognition is postulated to have originated in multicellular invertebrates probably beginning with coelenterates.

Animals↗

PubMed1976

Brain glucose utilization in undernourished rats.

The in vivo incorporation of radioactivity from [U-14C]glucose was reduced in undernourished rat pups at ages 6, 10, and 17 days for brain lipids, and at age 10 days for brain amino acids. Brain glucose concentrations were lower at age 20 days (controls 1.58 +/- 0.26 vs. test 1.14 +/- 0.07 mumol/g) but other alterations in brain glucose, glycogen, ATP, or phosphocreatine concentrations were not found. Brain mitochondrial glutamate dehydrogenase activity was 21% and 30% lower in undernourished animals at ages 10 and 20 days, respectively. Brain mitochondrial and supernatant isocitrate dehydrogenase activities and pyruvate kinase activity were similar for undernourished and control animals. Brain glycogen levels were 2-4 times higher in late fetal and newborn control animals (13.6 and 15.3 mumol/g) than in older animals (4.2-5.7 mumol/g). Brain glucose, ATP, and phosphocreatine levels increased from the 15-day fetus to the newborn, but thereafter showed no further increase.

Adenosine Triphosphate↗

PubMedDate not supplied

Evidence for formaldehyde antibodies and altered cellular immunity in subjects exposed to formaldehyde in mobile homes.

Eight symptomatic individuals chronically exposed to indoor formaldehyde (HCHO) at low concentrations (0.07-0.55 ppm) were compared to 8 nonexposed subjects with respect to: (1) presence of IgG and IgE antibodies to HCHO conjugated to human serum albumin (F-HSA); (2) the percentage of venous blood T and B cells by E and EAC-rosetting; and (3) the ability of T and B cells to undergo mitogen (PHA, PWM) stimulated blastogenesis as measured by the incorporation of tritiated thymidine. Anti-F-HSA IgG, but no IgE, antibodies were detected in the sera of the 8 exposed subjects; none were found in 7 of the unexposed controls. T lymphocytes were decreased in the exposed (48 +/- 11.5%) compared to the control (65.9 +/- 4.97%) subjects (p greater than .001 less than .01). B cells were 12.6 +/- 1.6% (HCHO group) and 14.75 +/- 2.1% (controls) (p greater than .02 less than .05). The incorporation of labeled thymidine by T cells (PHA) was decreased: 17,882 +/- 2,293 cpm (HCHO group) and 28,576 +/- 3,807 cpm (p greater than .001 less than .01). T and B cell blastogenesis (PWM) was 9,698 +/- 1,441 cpm (HCHO group) and 11,279 +/- 1,711 (controls) (p greater than .05 less than .1). Exposure to HCHO appears to stimulate IgG antibodies to F-HSA and decrease the proportion of peripheral T cells.

Adult↗

PubMedDate not supplied

Imaging findings in hippocampal sclerosis: correlation with pathology.

We evaluated the ability of preoperative radiologic imaging to detect hippocampal sclerosis in 31 patients who underwent surgery for intractable epilepsy. Hippocampal sclerosis is commonly associated with surgically treatable temporal lobe epilepsy. It is pathologically described as neuronal cell loss with associated gliosis in the hippocampus. While previous reports have correlated imaging results with clinical or qualitative histologic findings, this study used quantitative pathologic criteria (neuronal cell density) to diagnosis hippocampal sclerosis. We focused our study on the 11 patients with cryptogenic temporal lobe epilepsy. Of these, nine had hippocampal sclerosis by pathologic criteria. MR findings included unilateral hippocampal atrophy, an increased signal in the hippocampus on long TR scans, and atrophy in the adjacent white matter and temporal lobe. Hippocampal atrophy was most frequently seen in the red nucleus plane on coronal scans, corresponding to the body of the hippocampus. We also compared hippocampal size on MR with neuronal density in surgical specimens of the 11 patients with cryptogenic temporal lobe epilepsy. A statistically significant correlation was found between MR size and neuronal density in CA3 and CA4 of the cornu ammonis and the granular cell layer of the hippocampus. Since temporal lobectomy eliminated seizures in seven of nine patients with hippocampal sclerosis, preoperative diagnosis by MR has important therapeutic consequences.

Adolescent↗