Biomedical subjects

D J Simon

Publications and source records attributed to D J Simon.

9 recordsLinked to original sources

PubMed2003

Associations of lead biomarkers with renal function in Korean lead workers.

AIMS: To compare associations of lead biomarkers with renal function in current and former lead workers. METHODS: Cross sectional analysis of first year results from a longitudinal study of 803 lead workers and 135 controls in South Korea. Clinical renal function was assessed by blood urea nitrogen (BUN), serum creatinine, and measured and calculated creatinine clearance. Urinary N-acetyl-beta-D-glucosaminidase (NAG) and retinol-binding protein were also measured. RESULTS: Mean (SD) tibia lead, blood lead, and DMSA chelatable lead levels in lead workers were 37.2 (40.4) micro g/g bone mineral, 32.0 (15.0) micro g/dl, and 767.8 (862.1) micro g/g creatinine, respectively. Higher lead measures were associated with worse renal function in 16/42 models. When influential outliers were removed, higher lead measures remained associated with worse renal function in nine models. An additional five associations were in the opposite direction. Effect modification by age was observed. In 3/16 models, associations between higher lead measures and worse clinical renal function in participants in the oldest age tertile were significantly different from associations in those in the youngest age tertile which were in the opposite direction. Mean urinary cadmium (CdU) was 1.1 micro g/g creatinine (n = 191). Higher CdU levels were associated with higher NAG. CONCLUSIONS: These data suggest that lead has an adverse effect on renal function in the moderate dose range, particularly in older workers. Associations between higher lead measures and lower BUN and serum creatinine and higher creatinine clearances may represent lead induced hyperfiltration. Environmental cadmium may also have an adverse renal impact, at least on NAG.

Adolescent↗

PubMed2001

GABA enhances transmission at an excitatory glutamatergic synapse.

GABA mediates both presynaptic and postsynaptic inhibition at many synapses. In contrast, we show that GABA enhances transmission at excitatory synapses between the lateral gastric and medial gastric motor neurons and the gastric mill 6a and 9 (gm6a, gm9) muscles and between the lateral pyloric motor neuron and pyloric 1 (p1) muscles in the stomach of the lobster Homarus americanus. Two-electrode current-clamp or voltage-clamp techniques were used to record from muscle fibers. The innervating nerves were stimulated to evoke excitatory junctional potentials (EJPs) or excitatory junctional currents. Bath application of GABA first decreased the amplitude of evoked EJPs in gm6a and gm9 muscles, but not the p1 muscle, by activating a postjunctional conductance increase that was blocked by picrotoxin. After longer GABA applications (5-15 min), the amplitudes of evoked EJPs increased in all three muscles. This increase persisted in the presence of picrotoxin. beta-(Aminomethyl)-4-chlorobenzenepropanoic acid (baclofen) was an effective agonist for the GABA-evoked enhancement but did not increase the postjunctional conductance. Muscimol activated a rapid postsynaptic conductance but did not enhance the amplitude of the nerve-evoked EJPs. GABA had no effect on iontophoretic responses to glutamate and decreased the coefficient of variation of nerve-evoked EJPs. In the presence or absence of tetrodotoxin, GABA increased the frequency but not the amplitude of miniature endplate potentials. These data suggest that GABA acts presynaptically via a GABA(B)-like receptor to increase the release of neurotransmitter.

Animals↗

PubMed2001

Neuro-ophthalmic manifestations of head trauma.

OBJECTIVE: To describe the neuro-ophthalmic findings in a group of patients with head trauma. MATERIALS AND METHODS: A retrospective chart review of all patients given a diagnosis code of head trauma in the neuroophthalmology unit at Emory University between 1991 and 1999. RESULTS: A total of 326 consecutive patients were reviewed (203 [63%] men and 123 [37.0%] women). Age ranged from 2 to 86 years, with a mean of 30 years. Motor vehicle accident was the most common cause of head trauma, occurring in 195 (59.8%) patients. An abnormal neuro-ophthalmic examination was noted in 185 of 326 patients (56.7%). Loss of consciousness was not associated with any outcome, but the presence of a neuroimaging abnormality, particularly intracranial hemorrhage, was significantly associated with specific neuroophthalmic deficits. CONCLUSIONS: Head trauma causes a number of neuroophthalmic manifestations. The afferent and efferent pathways are vulnerable to traumatic injury, although the efferent system is more commonly affected. Loss of consciousness may not be a reliable predictor of specific neuro-ophthalmic outcomes, but neuroimaging abnormalities may.

Adolescent↗

PubMed2000

GP73, a novel Golgi-localized protein upregulated by viral infection.

We report the isolation and characterization of GP73, a novel 73kDa human Golgi protein. The GP73 cDNA was cloned by differential screening of a cDNA library derived from the liver of a patient with adult giant-cell hepatitis (GCH), a rare form of hepatitis with presumed viral etiology. In vitro transcription-translation studies indicate that GP73 is an integral membrane protein, and immunolocalization experiments using epitope-tagged GP73 demonstrate that the protein is localized to the Golgi apparatus. Northern blot analysis of RNA from multiple human tissues reveals a single GP73 mRNA transcript with a size of approximately 3.0kb. Immunohistochemical studies using rabbit polyclonal antisera directed against recombinant GP73 demonstrate that the protein is preferentially expressed by epithelial cells in many human tissues. In normal livers, GP73 is consistently present in biliary epithelial cells, whereas hepatocytes show little or no signal. In contrast, livers of patients with GCH display strong GP73 immunoreactivity in multinucleated hepatocytes. GP73 mRNA and protein are expressed in highly differentiated HepG2 hepatoma cells after infection with adenovirus in vitro. We conclude that GP73 represents a novel, epithelial cell-specific integral membrane Golgi protein that can be upregulated in response to viral infection.

Adult↗

PubMed1998

The ophthalmology of intracranial vascular abnormalities.

PURPOSE: To provide a practical review of the ophthalmologic manifestations of intracranial vascular abnormalities. METHODS: We reviewed ocular manifestations of the most common intracranial vascular abnormalities: intracranial aneurysms, carotid-cavernous fistulas, arteriovenous malformations, and cavernous malformations. RESULTS: Unruptured aneurysms can compress the third cranial nerve and the anterior visual pathways. Ruptured aneurysms and subarachnoid hemorrhage can result in Terson syndrome and papilledema. Direct and indirect carotid-cavernous fistulas most commonly cause the classic triad of proptosis, conjunctival chemosis, and cranial bruit but can masquerade as chronic conjunctivitis. Arteriovenous malformations, with or without hemorrhage, may compress portions of the retrochiasmal pathways, causing visual field loss. Cavernous malformations, when in the brainstem, commonly cause abnormalities of supranuclear, nuclear, and fascicular ocular motility. CONCLUSIONS: The ophthalmologist may be the first physician to encounter clinical manifestations of intracranial vascular abnormalities that may herald devastating neurologic complications. Prompt diagnosis facilitates appropriate management and therapy.

Adult↗

PubMed1998

Migraine and reduced work performance: a population-based diary study.

OBJECTIVE: This article estimates lost work days and lost work day equivalents in a population sample of migraineurs, differentiating work loss due to headache episodes that met criteria for migraine from migrainous headaches not meeting full criteria and nonmigrainous headaches. METHODS: A random digit dialing survey of 5,071 adults identified 800 subjects with migraine headaches. By clinical examination, a subsample of 225 met migraine diagnostic criteria; 174 of these patients completed at least 11 weeks of daily diaries. This report concerns the subgroup of 122 individuals with regular paid employment. Subjects completed a daily diary over a 3-month period to assess the occurrence of headaches and International Headache Society (IHS) criteria for each headache occurrence. We report estimates of lost work days and lost work day equivalents by type of headache. RESULTS: Participants reported headaches on 8.1 work days, of which 2.2 headache days met criteria for migraine (IHS 1.1, 1.2), and an additional 2.1 headache days were migrainous without meeting full migraine criteria (IHS 1.7). On average, migraineurs missed 1.1 days of work due to headache in 3 months, of which 0.7 lost work days were due to migraine and 0.3 were due to migrainous headaches. When at work with headache, work effectiveness was reduced 41% for migraine headaches, 28% for migrainous headaches, and 24% for other headaches. Over 3 months, migraineurs experienced an average of 3.0 lost work day equivalents, of which 1.4 were due to migraine and an additional 0.7 were due to migrainous headaches. The most disabled 20% of the participants accounted for 77% of the lost work days; 40% of subjects accounted for 75% of the lost work day equivalents. CONCLUSIONS: Employed migraine sufferers experienced considerable work loss and reduced work performance due to headache. The most severely affected migraineurs accounted for most of the reduced work performance. Targeting the most severely affected persons may be necessary to reduce work loss among migraineurs substantially.

Absenteeism↗

PubMed1992

Self-perception, social skills, adjustment, and inhibition in young adolescents with craniofacial anomalies.

This study examines the relationships between self-perception, social skills, overall adjustment, and social inhibition in 45 young adolescents with craniofacial anomalies (CFA). Self-perception, social skills, and inhibition scores are within the normal range while the average adjustment is 1.5 SD below the average. Regression analyses were conducted. Social skills and athletic competence are the best predictors of adjustment and accounted for 73.5% of the variance in adjustment. Adjustment of adolescents is associated with degree of inhibition, with more poorly adjusted adolescents displaying greater inhibition. Self-esteem did not predict to adjustment. The theoretical and clinical implications of these findings are discussed.

Adolescent↗

PubMed1987

cDNA cloning and characterization of vinculin mRNA.

Vinculin and meta-vinculin are related proteins that localize to adherens junctions. To facilitate studies on the biology of these proteins cDNA clones were isolated from a chick embryonic library made in lambda gt 11. Three clones, accounting for 1/2 of the vinculin message, were identified by immunological analyses of fusion proteins and by hybrid-arrested translation. Sequence analyses of the 3' ends of these clones reveal allelic variants. Northern blot analyses suggests the presence of multiple vinculin messages, the most prominent one at 6.2 kb, almost twice the size needed to encode vinculin.

Animals↗

PubMed1981

Coins in the esophagus: two for the price of one.

A case of coin obstruction of the esophagus is presented. A seven-year-old child presented with a history of accidental coin ingestion. Radiographs displayed a coin impacted in the esophagus at the thoracic inlet. After endoscopic removal, a follow-up film demonstrated a second coin in the same location, which had been exactly superimposed over the first.

Child↗