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Biomedical subjects

B Gordon

Publications and source records attributed to B Gordon.

At least 73 records · Page 4Linked to original sources
PubMed1995

Auditory speech processing in the left temporal lobe: an electrical interference study.

Auditory syllable discrimination, identification, and comprehension were investigated by direct cortical electrical interference in three patients with indwelling subdural electrode arrays. Without electrical interference, patients performed similarly to matched normal subjects. With electrical interference, selective deficits were observed in the posterior superior temporal (PST) lobes of all three patients. At specific PST sites, only comprehension was impaired, while at proximal sites comprehension and identification were impaired, but discrimination remained intact. At a single PST site, all three auditory speech functions were impaired. These findings suggest that lower-level auditory speech functions can operate independent of higher-level processes, as claimed by traditional hierarchical models. However, analysis of discrimination errors revealed lexical-semantic and phonological effects, suggesting that higher-level functions also influence lower-level processing. These data can be explained by a bidirectional processing model, with differentially weighted connections.

Adolescent↗
PubMed1995

Lipopolysaccharide priming of superoxide release by human neutrophils: role of membrane CD14 and serum LPS binding protein.

Previous studies have suggested that lipopolysaccharide (LPS) interactions with neutrophils and monocytes are mediated via the CD14 receptor, in the presence of serum factors such as LPS-binding protein (LBP) and septin. The present study was designed to test if CD14-mediated LPS priming of human neutrophils is dependent upon the presence of serum proteins and to evaluate the contribution of serum factors in LPS-neutrophil interactions. The results demonstrate that CD14 mediates the priming of neutrophil superoxide release by LPS both in the presence and in the absence of serum. However, priming by LPS is greatly enhanced in the presence of human serum, and the factor responsible for this phenomenon is LBP and not heat-sensitive proteins, such as septin.

Acute-Phase Proteins↗
PubMed1995

Distributed representations of semantic knowledge in the brain.

Category-specific language impairments have been postulated to require the existence of an explicit category organization within semantic memory. However, it may be possible to demonstrate analytically that this is not necessary. We hypothesize that category-specific organization can emerge from perceptual, functional, and associative feature information about objects that is maintained in order to process language. In this paper, we conduct several experiments to test the computational validity of this hypothesis. Physical objects were encoded in terms of semantic features, based on basic perceptual and motor modalities and higher level knowledge of function, for use in artificial neural networks. Mathematical methods were used to analyse the encodings and the neural networks. The results demonstrate the emergence of semantic categories in the networks, although such information was not preprogrammed. We conclude that category-specific language organization can emerge from the inherent nature of semantic features themselves, and does not require special internal categorical organization of semantic memory.

Brain↗
PubMed1995

Clinical spectrum of adrenal myelolipoma: analysis of 8 tumors in 7 patients.

Adrenal myelolipoma is a rare, benign, and biochemically nonfunctioning tumor. Most patients with adrenal myelolipoma are asymptomatic and the condition is discovered incidentally at autopsy. Review of the literature reveals 70 patients with surgically documented adrenal myelolipoma. We report 7 additional patients with 8 adrenal myelolipomas, of whom 5 underwent surgical removal because of tumor size, unusual imaging features or symptomatology. Of our patients 4 had symptomatic lesions requiring surgical removal, while 1 had an adrenal myelolipoma that was discovered intraoperatively. Of the remaining 2 patients 1 had a small (3 cm.) lesion discovered incidentally on excretory urography and 1 had bilateral adrenal myelolipoma discovered incidentally on computerized tomography.

Adrenal Gland Neoplasms↗
PubMed1994

Prospective study of central nervous system function in amateur boxers in the United States.

Active amateur boxers from six US cities were studied in 1986-1990 to determine whether changes in central nervous system function over a 2-year interval (as evaluated by tests of perceptual/motor function, attention/concentration, psychomotor speed, memory, visuoconstructional ability, and mental control, measures of ataxia and brain-stem auditory evoked potentials, and electroencephalography) were associated with degree of participation in amateur boxing. A total of 484 participants were examined at baseline; 393 (81.2%) were examined 2 years later. At baseline, 22% of the participants had not yet competed in a bout; 9% had never competed in a bout by the second examination. Exposure was defined by number bouts, sparring-years, and sparring with a professional boxer. Very few statistically significant odds ratios were found between exposure and change in function. Significant tests of trend were found between the total number of bouts incurred before the baseline examination and changes in memory, visuoconstructional ability, and perceptual/motor ability. The significant trends for change in function in the latter two domains were primarily due to performance on the Block Design test, which was common to both test domains. No statistically significant associations were found between more recent bouts (after the baseline visit) and any functional domains, nor between bouts or sparring and any other outcome measures. The significant trends with past bouts, but not more recent bouts, may reflect the need for a long latency period before effects are manifest. Alternatively, given changes in safety practices, the observed association may be related to more severe exposure from bouts that occurred before 1986, when new safety measures were imposed.

Adolescent↗
PubMed1994

Rater agreement for the Rey-Osterrieth Complex Figure Test.

This report assesses the intrarater and interrater reliability of quantitatively scoring the Rey-Osterrieth Complex Figure Test (RCF). The intrarater correlation coefficients were .96, .99, and .96, and the interrater correlation coefficients were .88, .97, and .96 for the Copy, Immediate Recall, and Delayed Recall, respectively. However, statistically significant mean differences in score were found between raters on the Copy, Immediate, and Delayed Recall. Though the majority of structural units within the RCF are reliably scored, several units had a greater magnitude of observed scoring differences compared to the other units after adjusting for expected differences. Overall, reliability estimates demonstrate high intrarater reliability and acceptable interrater reliability except for the potential for systematic scoring differences.

Adolescent↗
PubMed1994

Cortical tongue area studied by chronically implanted subdural electrodes--with special reference to parietal motor and frontal sensory responses.

Motor and sensory cortical tongue representations were examined in 40 patients with intractable seizures who underwent chronic subdural electrode grid implantation. Tongue responses were observed in a wide area 4.5 cm anterior and 3 cm posterior to the central sulcus. The distribution of the responses was not influenced by whether the responses were unilateral or bilateral. In patients with fronto-parietal lesions, the tongue motor area was located significantly more superior to the Sylvian fissure and more anterior to the central sulcus than was the tongue motor area of patients without organic lesion. Both motor and sensory responses were found outside of the classic precentral or postcentral area on the lateral surface of the cortex. Motor responses ('parietal motor responses') could occur posterior to the central sulcus and, rarely, sensory responses ('frontal sensory responses') were identified anterior to the central sulcus. These paradoxical parietal motor and frontal sensory responses were seen in 17 out of 40 (42.5%) patients. Nine of these 17 patients had no organic brain lesion on MRI. Clinical factors, such as patient's age, duration of seizures and cognitive functions (IQ, word fluency score), did not influence the frequency of the paradoxical responses. However, patients with brain lesions showed a tendency to have associated paradoxical responses (P < 0.05). In conclusion, paradoxical responses are not uncommon in epilepsy patients, particularly in those with organic lesions. The physiological and clinical implications of the paradoxical responses are discussed.

Adolescent↗
PubMed1994

Electrical stimulation and language.

Electrical stimulation has been used for over half a century in clinical settings to facilitate the surgical treatment of patients with intractable seizures and cortical structural lesions. It should be employed as the final result of a stepwise process in patient management but, when called for, can be very accurate in localizing critical functional areas. We discuss the use of this technique in patient evaluation, with an emphasis on the evaluation of patients with seizure disorders.

Cerebral Cortex↗
PubMed1994

Effect of granulocyte-macrophage colony-stimulating factor on oral mucositis after hematopoietic stem-cell transplantation.

PURPOSE: Oral mucositis following high-dose chemotherapy may result in systemic infection and airway compromise, and the severity of oral mucositis may be dose-limiting. Here we investigate the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF), which significantly shortens duration of neutropenia after hematopoietic stem-cell transplantation (HSCT) on oral mucositis. PATIENTS AND METHODS: Thirteen children undergoing HSCT were prepared with etoposide (VP-16), thiotepa (TT), and total-body irradiation (TBI), and 13 with VP-16, TT, and cyclophosphamide (CPM). Following transplantation, 14 patients received GM-CSF at a dose of 125 micrograms/m2/d by continuous intravenous infusion (six prepared with VP-16, TT, and TBI, and eight prepared with VP-16, TT, and CPM), and 12 patients received no growth factor. RESULTS: Mucositis was more severe and persisted longer in patients prepared with the TBI-containing regimen. For this regimen, the duration of severe oral mucositis was shortened by the administration of GM-CSF, although the severity of mucositis was unaffected. No statistically significant effect of GM-CSF could be shown in patients who received VP-16, TT, and CPM. The incidence of positive fungal oral or blood cultures did not appear different whether patients received GM-CSF or not. CONCLUSION: For patients undergoing stomatotoxic HSCT regimens, GM-CSF may reduce the duration of oral mucositis, but is unlikely to effect the severity of oral mucositis or risk of airway compromise, and the severity of mucositis is likely to remain dose-limiting.

Adolescent↗
PubMed1994

Priming effect of Porphyromonas gingivalis lipopolysaccharide on superoxide production by neutrophils from healthy and rapidly progressive periodontitis subjects.

Pre-incubation of neutrophils from rapidly progressive periodontitis (RPP) patients with lipopolysaccharide (LPS) extracted from Porphyromonas gingivalis was found to prime the neutrophils for enhanced FMLP-stimulated superoxide production in a dose-dependent manner. The priming effect of P. gingivalis LPS on neutrophils from control subjects was scanty or without effect at all. Inclusion of human serum in the experimental priming conditions increased the control and RPP neutrophil response by 2 to 3 fold. Blocking of the CD14 receptor on the neutrophil surface with monoclonal antibody eliminated the priming effect. Furthermore, incubation of control neutrophils with P. gingivalis LPS in the presence of serum from RPP patients generated a higher response as compared to incubation with control serum. The data suggest that neutrophil priming described in RPP patients is dependent on a serum factor which alters the neutrophil response to priming agents such as LPS.

Aggressive Periodontitis↗
PubMed1993

Anatomic correlates of memory from intracarotid amobarbital injections with technetium Tc 99m hexamethylpropyleneamine oxime SPECT.

OBJECTIVE: To better identify regions of the brain affected by intracarotid amobarbital injections and to more precisely predict whether resections of specific brain regions will cause postoperative memory deficits. DESIGN: We modified the standard intracarotid amobarbital procedure by adding a radioactive tracer to the amobarbital injection, thereby providing better correlation between behavior and deactivated brain region. SETTING: Tertiary-care hospital center with a dedicated program for medical and surgical treatment of epilepsy. PATIENTS: We studied 39 patients with medically intractable epilepsy drawn from a regional referral base. INTERVENTION: Intracarotid injection of 125 mg of sodium amobarbital with 37 MBq of technetium Tc 99m hexamethylpropyleneamine oxime (HMPAO), followed by language and memory testing. MAIN OUTCOME MEASURES: The distribution of amobarbital as measured by single photon emission computed tomographic imaging of HMPAO and patient performance on memory tasks. RESULTS: Medial temporal regions were irrigated by the amobarbital in only 28% of the injections. Overall, findings suggest that medial temporal and lateral neotemporal cortex play a role in memory. CONCLUSIONS: The regions involved in memory function vary by individual, as does the distribution of amobarbital. Thus, the most accurate method of determining correlation of brain region with memory function during intracarotid amobarbital injection involves the use of a tracer such as HMPAO.

Adolescent↗
PubMed1993

Verb-argument structure processing in complex sentences in Broca's and Wernicke's aphasia.

We describe three experiments that explore the real-time access of verb-argument structures in a group of normal control subjects, a group of Broca's aphasic patients, and a group of Wernicke's aphasic patients. Specifically, we examine whether our subjects exhaustively access the thematic representations of verbs in active, passive, cleft-subject, and cleft-object sentences. We find that our normal control subjects and Broca's aphasic patients are sensitive to the thematic properties of verbs, regardless of sentence type. Our Wernicke's aphasic patients do not show on-line sensitivity to this lexical property. We discuss these results in terms of multiple resources dedicated to specific sentence processing devices, a possible semantic deficit in Wernicke's aphasia, and a double-dissociation between the operation of accessing a verb's thematic properties and the operation of computing the trace-antecedent relation.

Aged↗
PubMed1993

Phase I pharmacokinetics study of high-dose fotemustine and its metabolite 2-chloroethanol in patients with high-grade gliomas.

The pharmacokinetics of high-dose fotemustine followed by autologous bone-marrow transplantation during a phase I-II clinical trial in 24 patients with glioblastoma or astrocytoma (grade III-IV) was investigated. Plasma levels of fotemustine were determined by high-performance liquid chromatography (HPLC) and UV detection. The metabolite, 2-chloroethanol, was simultaneously followed in six patients by gag liquid chromatography and electron capture detection (GLC-ECD) assay. The drug was given as a 1-h infusion on 2 consecutive days. In all, 40 pharmacokinetic determinations of fotemustine were made at dose levels ranging from 2 x 300 to 2 x 500 mg/m2. Plasma drug elimination was best described by a bi-exponential model, with short distribution and elimination half-lives of 4.15 +/- 2.57 and 28.8 +/- 12.1 min being observed, respectively. No significant difference in half-lives or clearance was seen between the first and the second administration. During dose escalation, the mean area under the concentrationtime curve (AUC) increased from 5.96 +/- 2.89 to 12.22 +/- 3.95 mg l-1 h. Drug clearance was independent of the dose given and equal to 109 +/- 65 l/h, indicating no possible saturation of metabolism and elimination mechanisms at these high-dose levels. The metabolite 2-chloroethanol appeared very early in plasma samples. Its elimination was rapid and rate-limited by the kinetics of the parent compound, giving the same apparent terminal half-life. A close relationship between AUC and C45 values was evidenced (r = 0.890). Associated with the stability of fotemustine kinetic parameters, this could be used in future studies for individual dose adjustment, particularly for high-dose fractionated regimens.

Adult↗
PubMed1993

Determination of current density distributions generated by electrical stimulation of the human cerebral cortex.

With the use of a 3-dimensional finite element model of the human brain based on structural data from MRI scans, we simulated patterns of current flow in the cerebral hemisphere with different types of electrical stimulation. Five different tissue types were incorporated into the model based on conductivities taken from the literature. The boundary value problem derived from Laplace's equation was solved with a quasi-static approximation. Transcranial electrical stimulation with scalp electrodes was poorly focussed and required high levels of current for stimulation of the cortex. Direct cortical stimulation with bipolar (adjacent) electrodes was found to be very effective in producing localized current flows. Unipolar cortical stimulation (with a more distant reference electrode) produced higher current densities at the same stimulating current as did bipolar stimulation, but stimulated a larger region of the cortex. With the simulated electrodes resting on the pia-arachnoid, as usually occurs clinically, there was significant shunting of the current (7/8 of the total current) through the CSF. Possible changes in electrodes and stimulation parameters that might improve stimulation procedures are considered.

Cerebral Cortex↗
PubMed1993

Functional significance of the mu rhythm of human cortex: an electrophysiologic study with subdural electrodes.

The existence of the mu rhythm and its general anatomical and physiological relationships are well known. There are few data, however, regarding the details of its anatomical and physiological specificity. We implanted fronto-temporal subdural electrode grids in 9 patients with intractable epilepsy to facilitate their surgical management. A 7-11 Hz cortical mu rhythm was observed in 5-16 electrodes located over the sensorimotor cortex as mapped by electrical stimulation. The mu rhythm was blocked by contralateral face and arm movements, passive movements of contralateral arm, and by ipsilateral arm movements. There was correspondence between the body area movement of which blocked the mu at a given site and the body region that was affected by stimulation at the same site. Power spectral analysis showed an overall decrease in power in all frequency bands. This was less prominent in the 14-100 Hz band resulting in a relative increase in high frequency power in association with movement. We conclude that both the presence and blocking of mu rhythm are specific to the somatic representation of the cortex from which it is recorded. Its functional significance may be similar to other sensory rhythms like the occipital alpha rhythm.

Adolescent↗
PubMed1993

Mirth, laughter and gelastic seizures.

Little is known about what pathways subserve mirth and its expression laughter. We present three patients with gelastic seizures and laughter elicited by electrical stimulation of the cortex who provide some insight into the mechanisms of laughter and its emotional concomitants. The first patient had seizures manifested by laughter without a subjective feeling of mirth. Magnetic resonance imaging showed a cavernous haemangioma in the left superior mesial frontal region. Ictal subdural electrode recording showed the seizure onset to be in the left anterior cingulate gyrus. Removal of the lesion and of the seizure focus rendered the patient virtually seizure free over 16 months of follow-up. The other two patients had complex partial seizures of temporal lobe origin. Electrical stimulation of the fusiform gyrus and parahippocampal gyrus produced bursts of laughter accompanied by a feeling of mirth. These cases reveal a high likelihood of cingulate and basal temporal cortex contribution to laughter and mirth in humans, and suggest the possibility that the anterior cingulate region is involved in the motor act of laughter, while the basal temporal cortex is involved in processing of laughter's emotional content in man.

Adult↗
PubMed1993

High-dose chemotherapy and autologous hematopoietic stem-cell transplantation for aggressive non-Hodgkin's lymphoma.

PURPOSE: To evaluate clinical and tumor characteristics in patients receiving high-dose chemotherapy and autologous peripheral stem-cell transplantation (PSCT) or bone marrow transplantation (ABMT) for relapsed or primary refractory non-Hodgkin's lymphoma (NHL). PATIENTS AND METHODS: One hundred fifty-eight patients with NHL received high-dose chemotherapy and ABMT or PSCT. A multivariate analysis of characteristics was performed for comparison of the long-term failure-free survival (FFS) rate. RESULTS: Using a multivariate analysis, a prognostic model was constructed with patients in the good-prognosis group being those without a mass > or = 10 cm at the time of transplant, and no more than one of the following characteristics: three or more prior chemotherapy regimens, lactate dehydrogenase (LDH) level above normal, and chemotherapy resistance. Patients in the poor-prognosis group had a mass > or = 10 cm, or two of the other characteristics noted. The poor-prognosis group had a 3-year FFS rate of 10%, compared with a 45% 3-year FFS in the good-prognosis group (P < .001). Within the prognostic groups, there was no difference in the 3-year FFS rate of the poor-prognosis patients who received ABMT versus PSCT (10% v 12%; not significant). However, in the good-prognosis group, patients who received ABMT had a 3-year FFS rate of 32%, compared with 70% for those who received PSCT (P < .008). CONCLUSION: This prognostic model can identify patients with good and poor prognoses following high-dose chemotherapy and ABMT or PSCT for aggressive NHL. In good-prognosis patients, those who received PSCT had a superior FFS rate.

Adolescent↗