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Biomedical subjects

R G Feldman

Publications and source records attributed to R G Feldman.

At least 55 records · Page 3Linked to original sources
PubMed1993

Magnetic resonance imaging (MRI), neurobehavioral testing, and toxic encephalopathy: two cases.

The objective of this investigation was to examine cerebral magnetic resonance imaging (MRI) pathology and functional deficits demonstrated by neuropsychological testing in cases of toxic encephalopathy. Two subjects, occupationally exposed to toxic chemicals, were studied. As part of their neurological assessment, MRI was done and each underwent a neuropsychological battery for patients with toxic exposures (White et al. Clin. Neuropharmacol. 13(5), 392-412, 1990). In Case 1, who was exposed to inorganic mercury, MRI showed mild central and cortical atrophy. Punctiform foci (T2) were noted in both frontal regions underlying the precentral gyri and in the subcortical myelin. Neuropsychological testing showed problems in cognitive flexibility, cognitive tracking, inhibiting perseveration, fine manual motor coordination, visuospatial analysis and organization, memory, and affect and personality. In Case 2, who was exposed to 2.6-dimethyl-4-heptanone, MRI showed multiple small foci in the white matter and pons. Neuropsychological testing indicated affective changes, deficits in manual motor speed, verbal fluency, visuospatial organization, and short-term memory. Lack of aphasia in patients with toxic encephalopathy indicates that neurotoxins probably affect subcortical and mesial temporal structures more than cortical gray matter. These MRI studies show subcortical sites of pathology.

Behavior↗
PubMed1993

Human B lymphocyte in vitro response to the group B streptococcal type III capsular carbohydrate.

Anti-group B streptococcal type III polysaccharide-specific human B cells from the peripheral circulation can be activated and detected in an in vitro culture system. It is possible to detect both IgM- and IgG- producing cells from both seropositive and seronegative donors. The specificity of the response was demonstrated by inhibition with excess liquid phase antigen and the use of related but antigenically distinct control antigens. The response was absent without the addition of T cells, optimal at 10% and 25% T cells respectively for IgM- and IgG-secreting cells, and undetectable using 50% T cells. The optimal antigen concentration for in vitro B-cell activation is 2.5 x 10(-4) micrograms/ml. Cells from 5 of 6 seropositive donors and 3 of 7 seronegative donors produced specific IgM antibody after culture with antigen. We conclude that the control of the human antibody response to the group B streptococcal type III polysaccharide is influenced by T cells. The response seen in the culture system may be of value in assessing future vaccine candidates designed to prevent neonatal infections.

Antibodies, Bacterial↗
PubMed1993

Age influences magnitude but not duration of response to levodopa.

Following an all-night fast, 45 patients with Parkinson's disease were examined using certain motor items present in the United Parkinson's Disease Rating Scale. All were given a single tablet of carbidopa 25 mg and levodopa 250 mg and re-examined 90 minutes later. In addition to this evaluation, 23 of these patients underwent further scoring over a 4-hour period. A significant negative correlation was found between age and one important aspect of drug-derived benefit: magnitude of response. In contrast, age had no apparent influence on duration of benefit from the drug. Although baseline (fasting) scores were predictably correlated with duration of disease, magnitude of response was not adversely influenced by this variable. Not all Parkinsonian signs were equally influenced by age. Whereas the poor response of gait and bradykinesia appeared to be dependent on age, no such effect was noted on rest tremor scores. The data indicate that in patients with Parkinson's disease treated long term, factors associated with age rather than duration of disease may have a stronger adverse influence on magnitude of response to levodopa.

Adult↗
PubMed1992

Blink reflex measurement of effects of trichloroethylene exposure on the trigeminal nerve.

Trichloroethylene (TCE) exposure is known to have specific toxic effects on cranial nerves, the trigeminal nerve (V) in particular. The electrophysiological measurement of the blink reflex (BR) can quantify latency changes in the Vth and VIIth cranial nerve reflex arc. Prior study looked at the blink reflex measurement in a community group exposed to TCE in their drinking water. This study evaluated the use of the electrophysiologic blink reflex as an indicator of neurotoxic effects of TCE in occupationally exposed workers. The BR was tested in individual cases with documented histories of exposure to known chemical neurotoxins including TCE (n = 18). When compared with the nonexposed laboratory control values (n = 30), the subjects with a significant history of TCE exposure demonstrated the most prolonged latencies (greater than or equal to 3.0 SD above the nonexposed group mean) in the R1 component of the blink reflex measurement. The electrophysiological study of the blink reflex has application in assessing TCE exposure and in documenting the neurotoxic effects of that exposure on trigeminal nerve functions in humans.

Adult↗
PubMed1992

A perceived cluster of amyotrophic lateral sclerosis cases in a Massachusetts community.

We investigated a report of a perceived cluster of amyotrophic lateral sclerosis (ALS) in Middleborough, Mass. Although an increase in ALS incidence was observed [2.51 deaths/100,000 person-years (p-y)], relative to the statewide rate over the years 1969-1985 (1.26/100,000 p-y), it was not statistically significant at the 95% confidence level. Problems in evaluating possible neurological disease clusters and their association with environmental exposures are presented.

Adult↗
PubMed1992

Lead neurotoxicity and disorders of learning.

Preventable and treatable causes of disorders of learning caused by lead exposure can be recognized by heightened awareness of this potential hazard. The Centers for Disease Control using data from many studies of neurobehavioral effects of lead in children and animals, has redefined the lead exposure threshold for clinical and social intervention from 25 micrograms/dL to 10 micrograms/dL. This article reviews the pertinent studies that provide evidence of the effects of lead exposure on development of the nervous system, effects on neural structures involved in memory and learning, and the impact of early lead encephalopathy on adolescent and adult learning skills and cognitive performance. Physicians, teachers, and child care personnel are responsible for identifying children with behavioral signs of subclinical lead intoxication as early as possible. Screening programs and preventive strategies, such as the multitier Centers for Disease Control approach referred to in this article, are necessary. It is no longer reasonable to assume that lead-exposure children not demonstrating severe encephalopathy will recover completely, without residual brain damage after removal from exposure. Sufficient evidence now exists to clearly demonstrate measurable effects of low levels of lead body burden on behavioral and intellectual performance, resulting in learning disorders.

Child↗
PubMed1992

Abnormalities in color vision and contrast sensitivity in Parkinson's disease.

Dopamine is a neurotransmitter found in the retina. Delays in the visual evoked responses and abnormalities in contrast sensitivity occur in patients with Parkinson's disease. Improvement in the P100 has followed L-dopa therapy. Suspected abnormalities at the retinal level in Parkinson's disease are observed in reductions in photopic, scotopic, and pattern-derived electroretinograms. We studied 35 patients with Parkinson's disease and 26 controls of comparable age and visual acuities using visual evoked responses, color vision, and contrast sensitivity testing. Contrast sensitivity thresholds were significantly different at most frequencies tested, using both stationary and temporally modulated sinusoidal gratings. The total error score of the Farnsworth-Munsell 100 Hue Test revealed significant differences between the patients and controls. The contrast thresholds derived from certain spatial frequencies and the total error in color score were significantly related to the duration of disease. A stepwise discriminant analysis correctly identified 94% of the patients and 94% of the controls. The significant error in chromatic discrimination observed in Parkinson's disease patients may be due to altered intraretinal dopaminergic synaptic activity in these patients.

Color Perception↗
PubMed1991

Hippocampal lesions in dominantly inherited Alzheimer's disease.

We compared hippocampal lesions in three pedigrees of Familial Alzheimer's Disease (FAD). In these pedigrees, the disease is inherited as an autosomal dominant disorder and has been linked to DNA markers on chromosome 21. In eight cases of FAD (four from one pedigree and two each from two others) we quantified neurofibrillary tangles (NFT) and senile plaques (SP) in hippocampal subdivision CA1-4, subiculum, presubiculum, and dentate gyrus. We observed consistent patterns of the distribution of lesions: The highest density of NFT and SP was present in CA1-2; virtually no SP or NFT were present in presubiculum; SP diameter was consistently greatest in CA4. We found no overall differences among pedigrees in total densities of NFT and SP, but statistical analyses disclosed that an uncommon type of SP was disproportionately present in two pedigrees. This type of SP was usually restricted to CA4, had a marked amyloid core devoid of argyrophilic neurites. These studies also disclosed inter- and intrafamilial heterogeneity of lesion distribution (including congophilic angiopathy and cerebellar plaques) in these three pedigrees.

Alzheimer Disease↗
PubMed1990

Relation of distribution of conduction velocities to nerve biopsy findings in n-hexane poisoning.

Distribution of conduction velocities (DCV) of sensory fibers in sural nerve was investigated in three patients with n-hexane poisoning. Measurements were made at 1-2 months, 4-9 months, and at 11, 23, and 36 months after ending exposure. A sural nerve biopsy was obtained from one of the patients. The results indicated the characteristic changes of n-hexane toxicity: myelinated nerve fiber degeneration and paranodal swelling, resulting in changes in the fiber diameter distribution. The DCV documented these changes. After removal from toxic exposure, varying degrees of recovery were studied clinically and evaluated with nerve conduction parameters. The DCV reflects the pathological changes in nerve in toxic neuropathy due to n-hexane.

Adult↗
PubMed1990

Immunoglobulin prophylaxis for infants exposed to varicella in a neonatal unit.

The investigation and prophylaxis with anti-varicella-zoster immunoglobulin (ZIG) of 15 preterm infants (24-33 weeks gestation and 1-300 days postnatal age) exposed to varicella on a neonatal intensive care unit are described. Varicella-zoster virus (VZV) IgG was detectable in 13 infants (24-28 weeks gestation) less than 105 days of age and born to seropositive mothers. Current guidelines recommend ZIG for all preterm infants of less than 28 weeks gestation following exposure to VZV. Our findings suggest that ZIG need be given only to seronegative infants or infants of seronegative mothers and to those over 60 days postnatal age.

Antibodies, Viral↗
PubMed1990

Environmentally related disorders of the nervous system.

Specific physical and chemical agents found in the workplace and in the general environment are responsible for characteristic pathologic processes within the nervous system. It has been shown that many neurotoxic agents produce a dose-related spectrum of impairment ranging from mild slowing of nerve conducting velocity or prolongation in reaction time to neuropathy and frank encephalopathy. Clinical manifestations are determined by the agent involved, by the dose of exposure, the vulnerability of the cellular target, the ability of the organism to metabolize and excrete the agent, and the ability to repair damage. An occupational history, including evaluation of evidence of specific agents and job history, is a critical component in the clinical management of individuals with suspect neurotoxic disease. Environmentally-induced disorders can be prevented by appropriate environmental controls. Prevention of neurotoxic disease is a complex process requiring continuous involvement of public health agencies and strong scientific research.

Central Nervous System Diseases↗
PubMed1990

Prevalence of anti-group B streptococcal type III capsular IgG antibodies in the United Kingdom and an analysis of their specific IgG subclasses.

Neonatal infection due to group B streptococcus (GBS) has a higher incidence in the USA than in the United Kingdom. A British population was investigated to ascertain the proportion of women who have protective anti-GBS type III IgG levels. Thirty-one (34%) of 90 pregnant women, 10 (43%) of 23 nonpregnant women, and 5 (50%) of 10 mothers of healthy colonized infants had anti-type III IgG greater than or equal to 2 micrograms/ml. Of 19 mothers who had infants infected with GBS type III, 17 (89%) had low specific IgG levels; of the other 2, the infants themselves had low IgG levels. The proportion of women in the UK with protective antibody levels is higher than in the USA. Sera (12) were assayed for anti-type III IgG isotypes; all contained IgG2, 6 had detectable IgG1, and 1 had IgG4.

Antibodies, Bacterial↗