Search PubMed⌕ Search

Biomedical subjects

B Gordon

Publications and source records attributed to B Gordon.

At least 37 records · Page 2Linked to original sources
PubMed1992

Motor and sensory cortex in humans: topography studied with chronic subdural stimulation.

Classic neurosurgical teaching holds that once the Rolandic fissure (Rf) has been located, there are distinct differentiated primary motor and sensory functional units confined within a narrow cortical strip: Brodmann's Areas 4 and 6 for primary motor units in front of the Rf and 3, 1, and 2 for sensory units behind the Rf. To test this assumption, we examined in detail the records of cortical mapping done by electrical stimulation of the cerebral cortex via implanted subdural electrode grids in 35 patients with seizure disorders. Of 1381 stimulations of the electrode sites, 346 (25.1%) produced primary motor or motor-arrest and sensory responses in contralateral body parts: 56.8% were primary motor responses; 16.2% were motor-arrest; 22.5% were sensory; and the remaining 4.5% were mixed motor and sensory responses. Two-thirds (65.9%) of the primary motor responses were located within 10 mm of the Rf, and the remaining one-third (34.1%) were more than 10 mm anterior to the Rf or were posterior to the Rf. Furthermore, in the patient group with brain lesions, fewer than one-third (28.1%) of the responses were within the 10-mm narrow anterior strip. Our study reconfirmed that a significant number--at least one-third--of motor responses are distributed outside the classic narrow cortical strip. In patients with brain lesions, the motor representation is further displaced outside the narrow strip. This finding indicates that primary motor cortex may extend beyond the gyrus immediately anterior to the Rf.

Adolescent↗
PubMed1992

Evaluation of hemorheologic variables as implications for exercise-induced pulmonary hemorrhage in racing thoroughbreds.

Hematologic and rheologic changes were examined in 49 Thoroughbreds before and after competitive racing. Mean postrace values for RBC count, hemoglobin concentration, and PCV increased by 58 to 61%, whereas blood viscosity increased 2 to 3 times. Postrace echinocyte numbers were 162% greater than prerace values. Smaller, but statistically significant, changes were found for mean corpuscular hemoglobin concentration, red cell distribution width, plasma total protein concentration, total WBC count, neutrophil count, and lymphocyte count. Variables measured did not predict whether a horse was a bleeder not treated with furosemide, a bleeder treated with furosemide, or a nonbleeder.

Animals↗
PubMed1991

The effects of lipid lowering on diabetic retinopathy.

The effect of lipid lowering on hard exudates was determined in six consecutive patients with insulin-dependent diabetes mellitus. Diet and hypolipidemic drug therapy including the use of pravastatin, a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme-A reductase, were used to treat patients for one year. The total cholesterol concentration decreased from a mean baseline value of 231 mg/dl to a treatment mean value of 165 mg/dl. The mean low-density lipoprotein cholesterol concentration decreased from 157 mg/dl to 93 mg/dl. Masked grading of fundus photographs indicated an improvement in hard exudates in all six patients and a decrease in microaneurysms in four patients. Visual acuity improved in one patient and did not change (one line or less change) in five patients. No remarkable side effects resulting from treatment were observed. Our pilot study suggests that aggressive therapy of diabetic patients with hyperlipidemia may have a beneficial effect on background retinopathy.

Adult↗
PubMed1991

The effect of age on binding of MK-801 in the cat visual cortex.

We have examined the effect of age on the binding of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine maleate (MK-801) in the cat visual cortex. We hypothesized that this binding might change with age because: (1) MK-801 binds to a site associated with the N-methyl-D-aspartate (NMDA) receptor; (2) the NMDA receptor complex has been implicated in neural plasticity; (3) plasticity in the cat visual cortex is age dependent. We used standard receptor binding techniques to measure MK-801 binding in membrane homogenates in cats aged 7 days (d), 21 d, 43 d, 83 d, 7-8 months (mo) and over 2 years. Glutamate (100 microM), glycine (30 microM) and spermidine (20 microM) were used to enhance binding. We found that MK-801 binding is maximal at about 6 weeks of age, decreases slightly by 83 days and then decreases more dramatically in adults. Saturation analysis showed that the of binding with age resulted from variation in number of binding sites and not from variation in affinity. The ability of Mg2+ to inhibit MK-801 binding did not change with age. Dark rearing did not alter the development of MK-801 binding sites.

Aging↗
PubMed1991

Monitoring surface conditions of a Thoroughbred racetrack.

During a pilot study at a Thoroughbred racetrack, information was collected to include weather conditions and track surface properties (moisture content, composition, strength, and coefficient of friction between surface and hoof). Measured weather variables did not correlate to any pattern of horse injuries of breakdowns. Surface moisture content was variable, whereas the moisture content of the compacted cushion was constant. Track surfaces around the starting chutes were more compacted than were other areas of the track. Next to the rail, track surface was softer than the surface toward the middle of the track. The coefficient of friction between a hoof and the surface was not affected by location or surface moisture content.

Animals↗
PubMed1991

Dominant-side intracarotid amobarbital spares comprehension of word meaning.

Abolition of speech production after intracarotid amobarbital injection is generally considered evidence for language laterality. However, complex auditory comprehension may be preserved after injection of the dominant (left) side. The possibility that this sparing may be due to the intracarotid amobarbital injection not adequately deactivating some of the areas responsible for speech comprehension in the posterior part of the hemisphere was tested with a task known to be critically dependent on the left posterotemporal-inferoparietal region, one assessing visuo-verbal semantic relatedness. Even when the intracarotid injection of the left side produced marked deficits of speech production, comprehension of semantic relations was still intact in eight of 15 patients. Ten of these 15 patients also received right carotid injections, none of which affected comprehension of semantic relatedness. These data indicate that the intracarotid amobarbital injection cannot always specify the laterality of all language functions, an important concern when considering surgical procedures in the dominant posterotemporal-inferoparietal region.

Adolescent↗
PubMed1991

Verb effects during sentence processing.

We describe a study that explores how the properties of a verb's lexical entry contribute to on-line sentence processing. Schmauder (1991) has recently suggested that the verb-processing effects shown previously by Shapiro and his colleagues (Shapiro & Levine, 1990; Shapiro, Zurif, & Grimshaw, 1987; 1989) are not generalizable and may have been artifacts precipitated by experimental design factors. In this paper we logically analyze such a possibility and then present experiments that systematically investigate the design differences between the Shapiro et al. studies cited above and the Schmauder study. These analyses and experiments provide further evidence that verb effects during sentence processing are real, are to be expected given the architectures of recent parsing models, and are replicable using a dual task that is modified in reasonable ways.

Humans↗
PubMed1991

Limb apraxia without aphasia from a left sided lesion in a right handed patient.

A right handed man had a massive left middle cerebral artery stroke. CT and MRI revealed extensive destruction of both anterior and posterior areas typically associated with language. There was, however, no aphasia, but instead a marked limb apraxia, dyscalculia, dense right visual neglect, and anosognosia. These uncommon dissociations and associations support the hypothesis that cerebral control of motor function of the limbs is not fundamentally related to the motor control involved in speech, and the notion that handedness is related to laterality of motor control, and only accidentally to laterality of language control.

Aged↗
PubMed1991

Mapping the distribution of amobarbital sodium in the intracarotid Wada test by use of Tc-99m HMPAO with SPECT.

The intracarotid amobarbital sodium, or Wada, test has been used to localize speech and memory function prior to surgical treatment of temporal lobe seizures. The authors mixed technetium-99m hexamethyl-propyleneamine oxime (HMPAO) with amobarbital sodium and injected the mixture in 25 patients with epilepsy. Single photon emission computed tomography (SPECT) of the brain was then performed to determine intracerebral distribution of the amobarbital sodium. Results of SPECT were compared with those of conventional and digital subtraction angiography (DSA). The distribution of Tc-99m HMPAO and, presumably, amobarbital sodium varied from patient to patient. SPECT revealed a statistically different distribution from that predicted with conventional angiography. The distribution also often differed from that of DSA, although the difference was not significant. SPECT revealed infrequent delivery to mesial temporal lobe structures. This emphasizes the need for caution in the use of the intracarotid amobarbital sodium test to predict the outcome of removal of these areas.

Adolescent↗
PubMed1991

High frequency of antithrombin 3 and protein C deficiency following autologous bone marrow transplantation for lymphoma.

To investigate the possibility that a hypercoagulable state develops during autologous bone marrow transplantation (BMT), we measured levels of circulating natural anticoagulants and fibrinolytic proteins before and weekly during the hospital course of 18 patients undergoing autologous BMT for Hodgkin's and non-Hodgkin's lymphoma. Patients received either weekly (standard dose group) or daily (high dose group) vitamin K supplements with their total parenteral nutrition. By day 14 there had been a significant drop in protein C activity (mean of 95% of normal to 52%), protein C antigen (mean of 105% of normal to 70%), and antithrombin 3 activity (111% of normal to 83%), and an increase in fibrinogen (471-621 mg/dl) and tissue plasminogen activator (6.9-13.8 ng/ml). No changes were seen in free or total protein S, plasminogen activator inhibitor, prothrombin time or partial thromboplastin time. The decreases in protein C and antithrombin 3 persisted through day 28 after transplantation. The drop in protein C correlated strongly with decrease in serum albumin, suggesting impaired synthesis of these proteins by the liver. No differences were seen in any of these parameters between the standard and high dose groups. Deficiencies in anticoagulant proteins antithrombin 3 and protein C and a rise in fibrinogen without a concomitant improvement in fibrinolytic variables create a potentially hypercoagulable state which may contribute to the thrombotic complications of autologous BMT.

Adult↗
PubMed1990

Long-term cognitive sequelae of acyclovir-treated herpes simplex encephalitis.

Survival from untreated herpes simplex type 1 encephalitis is well known to be accompanied by severe cognitive impairments. Recently, acyclovir has been proven to be the most effective available treatment for this disease, with the expectation that it would appreciably reduce morbidity. We performed detailed assessments of four consecutive patients who received acyclovir in the early stages of biopsy-proven herpes encephalitis and who now have been followed up for 1.5 to 4 years. All four patients showed definite residual on either clinical or formal neuropsychological testing, most commonly dysnomia and impaired new learning for both verbal and visual material, even though three had normal performance on a standard clinical mental status test. All four patients were unable to function at their prior level of achievement. Therefore, despite early administration of acyclovir in herpes encephalitis, long-lasting neuropsychological residua are likely. Furthermore, cognitive deficits of prognostic importance may not be detected by clinical screening.

Acyclovir↗
PubMed1990

Delineation of single-word semantic comprehension deficits in aphasia, with anatomical correlation.

In 3 of 18 aphasic patients pure deficits in semantic comprehension at the single-word level were defined through a series of tasks that excluded possible confounding deficits in auditory perception, visual perception, or speech production. In these pure cases, deficits were found at the superordinate, equivalence, and subordinate levels of single-word semantic processing. Pure semantic deficits were found to be correlated with damage to the left posterior temporal and inferior parietal region; patients whose damage spared this area did not evince such deficits, and the converse was also true. This study confirms the existence of separable deficits in semantic comprehension and points conclusively to the left posterior temporal and inferior parietal region as being critical for semantic processing. This anatomical localization is in keeping with anatomical studies from nonhuman primates, suggesting that these regions may be concerned with multimodal processing and integration of language.

Aphasia↗
PubMed1990

Parameters for direct cortical electrical stimulation in the human: histopathologic confirmation.

Safe parameters for electrical cortical stimulation in humans are difficult to estimate from the animal experimental literature. We therefore examined the light microscopic histology at a total of 11 sites of direct subdural electrical stimulation, taken as part of anterior temporal lobectomies in 3 patients. Stimulations had been done through 3.175 mm diameter electrodes, with 0.3 msec square wave pulses of alternating polarity at 50 pulses/sec. In 2 patients, one site each had been used as a common reference for stimulation, receiving over 251 stimulation trials, most of 2-5 sec duration, at currents of 12.5-15.0 mA, 1 day prior to resection. The maximum charge per phase was 4.0-4.4 microC; the maximum charge density was 52-57 microC per geometric cm2 per pulse at the electrode surfaces. Comparison of hematoxylin and eosin, periodic acid-Schiff, and cresyl violet-stained material from the electrode sites with that from other regions did not show any histologic abnormalities attributable to the electrical stimulation. The relatively brief and intermittent periods utilized for human stimulation testing do not appear to cause structural damage at the light microscopic level at charge densities that exceed the threshold for damage established in animal studies with more continuous, chronic stimulation schedules.

Electric Stimulation↗
PubMed1990

The basis for choice reaction time slowing in Alzheimer's disease.

Slowed reaction time has been suggested as an early feature of Alzheimer's disease (AD), but the basis for this slowing has not been established. Patients with mild AD were compared with controls on a choice reaction time task, both cued (CCRT) and uncued (CRT). Initial and 1-year followup data were analyzed both as mean reaction times and as parameters of a fitted two-component quantitative model (the ex-Gaussian model). Slowing of CRT proved to be a sensitive test for AD. Slowing was due to changes in both the sensory/motor and the decisional components of the CRT model. However, these changes were found in both AD and slower, older controls. The modeling of CRT in AD is discussed.

Aged↗
PubMed1990

Evaluation of high performance liquid chromatography (HPLC), enzyme linked immunosorbent assay (ELISA) and particle concentration fluorescence immunoassay (PCFIA) methods for the screening, quantitation and pharmacokinetic study of furosemide in horses.

Equine plasma and urine samples were analyzed by using a high-performance liquid chromatography (HPLC), enzyme-linked immunosorbent assay (ELISA) and particle concentration fluorescence assay (PCFIA). Although ELISA and PCFIA were rapid, simple and sensitive for the screening of furosemide, they did not give reproducible quantitative results. The HPLC method, which required relatively longer analysis time, provided simple and reproducible quantitative analysis of furosemide in plasma and urine. The performance of the three methods was compared for the quantitation of furosemide in plasma obtained from thoroughbred mares dosed intravenously with furosemide (500 micrograms/kg (n = 7) and 1.0 mg/kg (n = 5)). Although the plasma furosemide profiles determined by ELISA, PCFIA and HPLC were similar, ELISA and PCFIA methods exhibited considerable variation in values. At high furosemide concentrations, the PCFIA method gave better quantitative values than ELISA. However, at trace furosemide concentrations the PCFIA method gave false positive values which were not confirmed by HPLC or ELISA. The pharmacokinetic values obtained from the HPLC data and the pharmacokinetic values obtained previously from the gas chromatographic data were comparable. The data obtained by ELISA and PCFIA were not suitable for the pharmacokinetic calculations.

Animals↗
PubMed1990

Early-onset dementia and extrapyramidal disease: clinicopathological variant of Gerstmann-Straussler-Scheinker or Alzheimer's disease?

A case of progressive dementia and extrapyramidal signs beginning at age 29, with a ten year course until death, is presented. Necropsy examination showed an assortment of plaque types (including striatal plaques), neurofibrillary tangles, granulovacuolar degeneration, and depigmentation of the substantia nigra and locus ceruleus. This case had pathological features found in both Gerstmann-Straussler-Scheinker disease and in Alzheimer's disease. While somewhat similar to several other cases with features of both diseases, it differs in the presence of dystonia and striatal plaques. Although such cases may be difficult to categorize at present, they must be considered in the differential diagnosis of early onset dementia.

Adult↗
PubMed1990

Lesions of nonvisual inputs affect plasticity, norepinephrine content, and acetylcholine content of visual cortex.

1. The depletion of both norepinephrine (NE) and acetylcholine (ACh) in the visual cortex can decrease plasticity. This decrease in plasticity, although dramatic under some circumstances, fails to occur under others. 2. We depleted cortical NE and ACh in 35- to 42-day-old kittens by making a lesion of the white matter behind the cingulate gyrus. One eye was sutured on the day of the lesion. We recorded from the visual cortex 7 days or 2-3 mo later and used the influence of the deprived eye on the cortical cells as a measure of plasticity. 3. We measured NE content by high-pressure liquid chromatography (HPLC) and inferred ACh depletion from depletion of choline acetyltransferase (ChAT) activity. NE depletion averaged 60% in the successfully depleted animals. Depletion of ChAT activity was consistent with NE depletion. 4. When recording occurred 7 days after the lesion and the sutured eye was contralateral to the lesion, plasticity was decreased on the side with the lesion; 70% of the cells were driven by the deprived eye. On the control, uninjured side only 15% of the cells were driven by the deprived eye. 5. In two circumstances the lesion did not cause a decrease in plasticity. In animals with suture ipsilateral to the lesion, the cortex remained plastic. In these animals only 26% of the cells in the hemisphere with the lesion were driven by the deprived eye. The cortex also retained its plasticity if the contralateral eye remained sutured for several months after the lesion, even though there was no recovery from NE and ACh depletion. 6. We conclude that depletion of NE and ACh does decrease plasticity; that is, it protects the deprived eye from losing its ability to drive cortical cells, at least for a short period of time. Depletion protects only the normally dominant contralateral pathway; the ipsilateral visual pathway remains plastic. 7. Perhaps the importance of the side of the deprived eye can be explained by assuming that depletion of NE and ACh removes facilitatory input. This would decrease the ability of cortical cells on the side with lesion to potentiate the input from the nondeprived eye relative to the deprived eye; that is, it would decrease the molecular deprivation (MD) effect. A removal of facilitation would also increase the visual input required to drive cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗