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Biomedical subjects

B Gordon

Publications and source records attributed to B Gordon.

At least 55 records · Page 3Linked to original sources
PubMed1997

Galactosamine-induced fulminant hepatic necrosis in unanesthetized canines.

A large animal model of fulminant hepatic necrosis is necessary to test the efficacy of artificial liver support systems. A recent model was developed using D-galactosamine in anesthetized dogs. Because of the difficulties encountered with prolonged anesthesia, a similar protocol was used in 10 unanesthetized dogs. Intravenous infusions of D-galactosamine (1.0 to 1.5 gm/kg) did not result in uniform death of all animals at 72 hours or development of hypoglycemia. Severe hepatic necrosis was observed in all animals, but residual hepatocyte viability was evident in some. All animals developed severe consumption coagulopathy with histological evidence of disseminated intravascular coagulation (DIC) in four. A clinical picture characteristic of endotoxic shock was observed in most animals as a terminal event. The presence of endotoxin was confirmed in all dogs tested after 12 hours (7/10). The differences observed between this model and the anesthetized model are probably because of the toxic synergism between halothane and D-galactosamine. Neither model seems satisfactory for the testing of artificial liver support systems. The halothane model requires extremely long periods of anesthesia and mechanical ventilation. The present model does not cause uniform or universal death of the animals within 3 days. Foremost, both models result in DIC and endotoxic shock, neither of which is likely to respond to bioartificial liver support or treatment with conventional dialysis membranes.

Anesthesia↗
PubMed1997

Neuroperceptual differences in consonant and vowel discrimination: as revealed by direct cortical electrical interference.

The effects of direct cortical electrical interference on consonant and vowel discrimination were investigated in five patients with implanted subdural electrode arrays. Without electrical interference, patients performance discriminating consonants and vowels was intact. With electrical interference, consonant discrimination was impaired at one electrode site in each patient on the superior temporal gyrus of the lateral left perisylvian cortex. Conversely, vowel and tone discrimination remained relatively intact when tested with electrical interference at the same site. Analysis of patients' consonant discrimination errors revealed that neither differences in acoustic temporal structure nor syllable position fully account for the consonant-vowel perceptual dissociations elicited. Our data suggest that at the cortical level consonant and vowel perception are intrinsically distinct perceptual phenomena. The selective impairment of consonant, but not vowel, discrimination further suggests that consonant and vowel perception are distinguished by differences in relative dependence on the functional--perhaps integrative--resources of the left lateral superior temporal gyrus.

Adolescent↗
PubMed1997

Factors predicting morbidity following hematopoietic stem cell transplantation.

Circulating anticoagulants protein C (PC) and antithrombin III (AT) are markers of, and possibly involved in the pathogenesis of, significant organ dysfunction, in patients undergoing autologous peripheral blood stem cell (PSBC) or autologous bone marrow (BM) transplantation. The effect of the stem cell source, the use of hematopoietic growth factors (GFs), and the specific preparative regimen on the incidence of organ system dysfunction or on post-transplant levels of circulating anticoagulants has not been well studied. We analyzed 205 patients in an attempt to correlate organ dysfunction and AT and PC deficiencies with these transplant-specific factors (78 BMT with GM-CSF after transplant, 95 PBSCT without GM-CSF after transplant, and 32 PBSCT with GM-CSF after transplant). Patients transplanted with PBSC had a lower incidence of pulmonary dysfunction (20 vs 40%, P = 0.006) and liver dysfunction (4 vs 13%, P = 0.05) than patients receiving BM. The use of GF after transplant did not influence the development of subsequent organ dysfunction. In multivariate analysis, the stem cell source was again predictive of pulmonary dysfunction. In contrast, although patients transplanted with PBSC also had a lower incidence of PC deficiency (50 vs 81%, P < 0.01) and AT deficiency (20 vs 54%, P < 0.01) as compared with patients receiving BM, use of GM-CSF after transplant was a more significant risk factor for the development of anticoagulant deficiency (PBSC with GF vs PBSC without GF: PC deficiency 50 vs 78%, P = 0.007; AT deficiency 20 vs 47%, P = 0.005). In the multivariate analysis GM-CSF use was the only significant risk factor for development of anticoagulant deficiency. Since the clinical significance of anticoagulant deficiency has been well shown, further studies examining these effects of hematopoietic GFs appear warranted.

Antithrombin III Deficiency↗
PubMed1997

Neuropsychology and advances in memory function.

Recent developments in the functional and neural bases of several aspects of memory are described including long term cortical memory storage, the transition from immediate to permanent memory mediated by medial temporal structures, working memory, memory retrieval, and implicit memory. These are linked to current data on the nature of anterograde and retrograde amnesia in the degenerative diseases, and also to issues in the clinical diagnosis of memory impairments. Understanding the bases of memory can inform the diagnosis of memory impairments in degenerative diseases, and the patterns of impairment seen in the degenerative diseases can help contribute to knowledge of the mechanisms of normal memory.

Humans↗
PubMed1997

Neuronal generators of visual evoked potentials in humans: visual processing in the human cortex.

PURPOSE: We wished to define the localization of cortical generators of visual (pattern) evoked potentials (VEP) and the temporal sequence of activation in the occipital region. METHODS: In 4 candidates for epilepsy surgery, a large array of subdural electrodes was placed over occipital areas. Checkerboard pattern reversal stimuli were generated and the epileptogenic focus was localized and functionally mapped. Magnetic resonance imaging did not show any occipital lesions in any of the 4 patients. RESULTS: The area first activated was the lingual gyrus in the mesial occipital lobe (negative potential peaks at approximately 70 ms), followed by an area superior to the calcarine fissure (negative peaks at approximately 80 ms). Later (starting at approximately 90 ms), there were positive potentials over the occipital pole and lingual gyrus, followed by potentials at the lateral occipital lobe. CONCLUSIONS: These data support the idea that VEP are generated in the mesial and lateral occipital cortex by different circumscribed neuronal generators with different latencies of activation. The scalp-recorded N1 and P1 potential peaks most likely derive from the progressive activation of neuronal masses in different regions of the occipital lobe.

Brain Mapping↗
PubMed1997

Object shape processing in the visual system evaluated using functional MRI.

We used functional MRI (fMRI) to determine the cortical regions activated during processing of visual object shape in humans in six men and three women, using a paradigm with a baseline condition of simple shape detection and an activated condition of object/nonobject shape discrimination. Eight of the nine subjects studied showed significant signal changes. Seven of eight showed changes in the occipital lobes (five bilateral, two right only, one left only). All eight subjects with signal changes exhibited changes in the parietal lobes bilaterally. In the occipitotemporal gyri, there were signal changes bilaterally in seven subjects and unilaterally, on the right, in one. Activation-related fMRI signal increases were also present in the posterior superior and middle temporal gyri in seven of the subjects, with four showing bilateral signal changes, two showing signal changes on the left only, and one only on the right. The data strongly suggest that processing of object shape information in humans activates both the ventral and dorsal visual processing pathways ("what" and "where" pathways), described previously both in humans and in nonhuman primates.

Adult↗
PubMed1996

Brain metabolism patterns are sensitive to attentional effort associated with a tone recognition task.

Using positron emission tomography with the tracer 18-fluoro-D-deoxyglucose, we assessed regional cerebral glucose utilization patterns (rCMRglu) associated with three performance levels in a forced choice, tone recognition task. Four normal subjects responded with one hand when they heard a high-frequency tone (1500 Hz), and with the other hand when they recognized a low-frequency tone (750 Hz). The EASY (EAS) condition accuracy average was 96%, the INTERMEDIATE level accuracy averaged 89%, and the DIFFICULT (DIF) recognition task accuracy average was 77%. Statistical parametric mapping (SPM94) analysis revealed that the DIF minus EAS contrast is associated with a marked metabolic elevation in the right middle and inferior temporal gyri and the gyrus fusiformis. The EAS minus DIF contrast revealed greater rCMRglu in the right medial geniculate body. Enhanced activity in right temporal lobe structures may reflect a role in auditory memory and "image" visualization. The medial geniculate enhancement may reflect tone frequency assessment.

Adult↗
PubMed1996

Laminar distribution of MK-801, kainate, AMPA, and muscimol binding sites in cat visual cortex: a developmental study.

We used quantitative autoradiography to determine whether the development of glutamate receptors correlates with the sensitive period for monocular deprivation in the visual cortex. To study glutamate receptors, we incubated sections of cat visual cortex with tritiated (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10imin e-maleate (MK-801), tritiated kainate, and tritiated amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA). [3H]MK-801 is a noncompetitive ligand for the N-methyl-D-aspartate (NMDA) receptor. [3H]kainate and [3H]AMPA are competitive ligands for non-NMDA receptors. We used [3H]muscimol, which binds to GABAA receptors, so that we would have one control ligand that binds to a nonglutamate receptor. When all layers were combined, the results confirmed our previous studies with homogenate binding. [3H]MK-801 and [3H]kainate binding were significantly greater at 42 days than at earlier or later times. [3H]AMPA and [3H]muscimol binding did not show such a peak. This suggests that MK-801 and kainate binding sites are more likely to be involved in plasticity than are AMPA and muscimol binding sites. In layers 2/3, MK-801 had the greatest age-dependent changes; in layers 5 and 6, kainate binding changed most with age. This suggests that the mechanisms of plasticity may vary with cortical layer.

Animals↗
PubMed1996

Synchronous bilateral Wilms' tumor in a neonate.

OBJECTIVES: Wilms' tumor is the most common solid abdominal tumor of childhood. Wilms' tumor is extremely rare in the neonate, with less than 20 well-documented cases. No bilateral lesions in neonates have been described in the literature. METHODS: We report on a neonate who presented with synchronous bilateral Wilms' tumors. RESULTS: Child underwent bilateral partial nephrectomy, followed by standard chemotherapy, and is now well 2 years after completion of the therapy without any evidence for recurrent disease. CONCLUSIONS: Wilms' tumor should be included in the differential diagnosis of the solid renal mass in the neonate.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Conservative sharp wound debridement: state boards of nursing positions.

Nursing expertise in the area of wound care has expanded dramatically. Because of this rapid expansion, the scope of nursing practice is difficult to define and often creates practice overlaps with medicine. Conservative sharp wound debridement is an advanced-practice skill that falls into this practice overlap. Individual State Boards of Nursing were asked by questionnaire whether conservative sharp wound debridement was within registered nurse scope of practice in each state. Many replied affirmatively but outlined necessary requirements. Often education, competency validation, policy and procedures, and physician order were specified as necessary components of conservative sharp wound debridement performance by registered nurses. As experts in this field, it is our responsibility to ensure quality of wound care services and credibility of the practitioners who offer those services. To accomplish this, we must clearly define scope of practice. This definition should include an outline of the appropriate educational preparation and clinical practice necessary to ensure safe care. Policies, procedures, and protocols must be in place. Maintaining close working relationships with the individual State Boards of Nursing is important in this endeavor.

Clinical Competence↗
PubMed1996

Cognitive effects of resecting basal temporal language areas.

Electrical stimulation of the basal temporal region of the dominant hemisphere before partial temporal lobectomy for epilepsy sometimes produces temporary interruption of language function, but the significance of removal of this area is unknown. We evaluated the correlation between resection of the basal temporal language areas (BTLA) and certain types of postoperative language deficits. In a population of 25 patients, we mapped the inferolateral temporal lobe with cortical electrical stimulation, verifying the positions of the stimulating electrodes with three-dimensional computed tomography (CT). Eighty percent of the patients developed transient language deficits with stimulation, particularly with tests of confrontation naming and comprehension. BTLA was primarily located in the fusiform gyrus, from 1 to 9 cm from the temporal tip. At testing 6-12 months after operation, patients with BTLA resection performed worse (mean 9% decrease) than those with no BTLA resection (mean 4% improvement) on tests of confrontation naming (p = 0.03). Resection size accounted for less of the variance in decrease in confrontation naming than did resection of the BTLA. Tests of performance I.Q. (PIQ), verbal I.Q. (VIQ), or recognition memory for word and verbal learning showed no significant difference between these groups. Most patients do not have language decrease with removal of basal temporal lobe 5-6 cm from the tip, even with removal of BTLA. Some patients, however, have persistent decrease in naming.

Adolescent↗
PubMed1996

Does the central sulcus divide motor and sensory functions? Cortical mapping of human hand areas as revealed by electrical stimulation through subdural grid electrodes.

To clarify the exact anatomic relationship of electrically identified hand areas to the central sulcus, we constructed cortical surface renderings of magnetic resonance images (MRI) to locate the central sulcus accurately and measured the distances of stimulated points from the central sulcus and the Sylvian fissure. We obtained hand responses in 33 patients who underwent implantation of subdural grid electrodes for evaluation and surgical treatment of intractable epilepsy and analyzed these responses according to the presence of motor, sensory, mixed motor and sensory, and arrest responses. Hand motor responses occurred not only in the precentral gyrus but also in the postcentral gyrus, with great variability in superior-to-inferior distribution. Sensory responses also occurred in both the precentral and postcentral gyri with a distribution more ventral than that of motor responses. Mixed motor and sensory responses tended to be limited to the middle part of the central sulcus. Sites where electrical stimulation arrested simple hand repetitive voluntary movements occurred widely throughout the premotor and primary sensorimotor cortices. These data indicate a marked variability in the location of the human cortical hand area, and suggest that motor and sensory hand cortices overlap and are not divided in a simple manner by the central sulcus.

Brain Mapping↗
PubMed1996

Prolonged deficiency of protein C following hematopoietic stem cell transplantation.

Deficiencies in circulating anticoagulant protein C (PC) occur in patients undergoing hematopoietic stem cell transplantation. These deficiencies may predispose to thrombotic and other complications, and may contribute to the morbidity of transplantation. In most patients, PC reaches a nadir 14 days after the preparative regimen and then begins to increase toward normal. However, low PC has been seen months after transplantation. Neither the frequency of, nor risk factors for, this prolonged deficiency are known. We examined 71 adults undergoing stem cell transplantation and found low PC antigen and activity in 21% and 20% of patients, respectively. Low PC at day 100 correlated strongly with low PC pre-chemotherapy (PC antigen, r = 0.69, P < 0.001; PC activity, r = 0.59, P < 0.001). The incidence of deficiency of PC at day 100 was lower in patients undergoing peripheral stem cell transplantation compared with patients undergoing autologous BMT (12.5% vs 35%; P = 0.05), although several significant confounding variables exist. We conclude that deficiencies in protein C persist at least 100 days after stem cell transplantation in nearly one quarter of patients undergoing this procedure. Therefore, patients undergoing stem cell transplantation may be at prolonged risk of thrombotic and other complications. Further studies to determine the risk of prolonged deficiency based on stem cell source need to be performed.

Adult↗
PubMed1995

Tone discrimination performance in schizophrenic patients and normal volunteers: impact of stimulus presentation levels and frequency differences.

Psychophysical and cognitive studies carried out in schizophrenic patients show high within-group performance variance and sizable differences between patients and normal volunteers. Experimental manipulation of a target's signal-to-noise characteristics can, however, make a given task more or less difficult for a given subject. Such signal-to-noise manipulations can substantially reduce performance differences between individuals. Frequency and presentation level (volume) changes of an auditory tone can make a sound more or less difficult to recognize. This study determined how the discrimination accuracy of medicated schizophrenic patients and normal volunteers changed when the frequency difference between two tones (high frequency vs. low frequency) and the presentation levels of tones were systematically degraded. The investigators hypothesized that each group would become impaired in its discrimination accuracy when tone signals were degraded by making the frequencies more similar and the presentation levels lower. Schizophrenic patients were slower and less accurate than normal volunteers on tests using four tone levels and two frequency differences; the schizophrenic patient group showed a significant decrement in accuracy when the signal-to-noise characteristics of the target tones were degraded. The benefits of controlling stimulus discrimination difficulty in functional imaging paradigms are discussed.

Adult↗