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Biomedical subjects

J Gordon

Publications and source records attributed to J Gordon.

At least 613 records · Page 34Linked to original sources
PubMedDate not supplied

A dot-immunobinding assay for antimitochondrial antibodies.

A dot-immunobinding assay was established for the detection of antimitochondrial antibodies. Nitrocellulose strips were coated with sonicated rat liver mitochondria and incubated in the presence of human sera. The resulting immune complexes were visualized with an enzyme-linked second antibody. Antimitochondrial antibodies were found in the sera of 96% of patients with primary biliary cirrhosis, 17% of patients with autoimmune hepatitis and 4% of patients with progressive systemic sclerosis. Sera of patients with other liver diseases or with systemic lupus erythematosus, specimens positive for M1 and M3 mitochondrial antibodies and samples from normal controls were all negative. Antinuclear and other cytoplasmic antibodies were not detected in this assay. The dot-immunobinding assay for antimitochondrial antibodies is rapid and sensitive, and obviates the need for expensive equipment.

Animals↗
PubMedDate not supplied

In vivo validation of tissue segmentation based on a 3D feature map using both a hamster brain tumor model and stereotactically guided biopsy of brain tumors in man.

The purpose of this study was to validate our MR tissue segmentation technique using a hamster brain tumor model and malignant brain tumors in man. We used a multispectral tissue segmentation analysis. Three sets of MRI data were included: proton density, T2-weighted fast spin echo, and T1-weighted spin echo, as inputs. Three image preprocessing steps included correcting image nonuniformity, application of an anisotropic diffusion type filter, and data point selection by a qualified observer. We used the k-Nearest Neighbor segmentation algorithm, which does not require prior knowledge of the sample distribution. This choice allowed us to optimize the different tissue clusters present in three-dimensional (3D) feature space. In vivo validation of the technique was performed in hamsters harboring tumors induced with JC virus-transformed HJC-15 cells, as compared to three control animals. Human brain tumors obtained by stereotactically guided biopsy in six patients were also included in the study. Finally, brain tumors were removed from two patients who underwent conventional craniotomy using segmentation-derived images as a guide. In the hamsters, 10 tissues were correctly identified by segmentation and were confirmed histologically (P < .02). In the patients, there was also a strong correlation between our segmentation results and the tissue obtained by stereotactic biopsy (P < .01). In one of the two patients who underwent open craniotomy, segmentation images were useful in revealing tumor spread into vital areas of the brain (motor area). In conclusion, the results of segmentation correlate well with the tissues in vivo and thus warrant further clinical utilization and evaluation.

Adult↗
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Immortalized B lymphocytes produce B-cell growth factor.

The activation, clonal expansion and terminal differentiation of small resting B lymphocytes primed by an antigen (or antibodies to its receptors) appear to follow an orderly developmental sequence triggered at each stage by distinct soluble cytokines, primarily produced by T lymphocytes. For man, the only known B-cell mitogen independent of accessory cells for its action is the Epstein-Barr virus (EBV). Lymphocytes transformed by EBV are released from the usual constraints on B-cell growth, proliferating continuously in the absence of any exogenous cytokine. The resultant cell lines are of special interest as they possess certain features compatible with a preneoplastic state of Burkitt's lymphoma, one of two human cancers with which the virus is intimately associated. We report here that following EBV-transformation, B lymphoblasts release a soluble factor which mimics the B-cell stimulatory product(s) of mitogen-conditioned T lymphocytes. Furthermore, the virally-transformed cells utilize this activity to sustain their own growth. The ectopic production of an otherwise normal growth factor may represent a critical event in the malignant evolution of human lymphomas harbouring the EBV genome.

B-Lymphocytes↗
PubMedDate not supplied

Retinal light adaptation--evidence for a feedback mechanism.

Light adaptation is the adjustment of retinal response properties to variations in ambient illumination. It enables the encoding of visual information over a millionfold intensity range, from moonlight to broad daylight, despite the relatively small dynamic range of response of visual neurones. We have studied the effects of light adaptation on the dynamics and sensitivity of visual responses of neurones in the turtle retina, by measuring the responses of horizontal cells in the retina to light which was modulated with a sinusoidal time course around various mean levels. As a quantitative measure of the transduction from light to neural signals, we calculated the gain of response at each frequency. Gain is defined as the amplitude of the modulated response component divided by the amplitude of light modulation. We report here that the gain (mV photon-1) at low temporal frequencies decreased as the mean light level increased. Over a 2 log-unit range of mean light levels, low-frequency gain was inversely proportional to the mean light level, as in Weber's law. However, at high temporal frequencies, the gain was almost independent of mean light level. Our results are reminiscent of Kelly's results on human temporal-frequency sensitivity in various states of light adaptation. We found that a family of horizontal-cell temporal frequency responses, measured at various mean light levels, could be accounted for by a negative feedback model in which the feedback strength is proportional to mean light level.

Adaptation, Physiological↗
PubMedDate not supplied

Mechanism of antigen-driven selection in germinal centres.

The high affinity of antibodies produced during responses to T-cell-dependent antigens is associated with somatic mutation in the variable region of the immunoglobulin. Indirect evidence indicates that: (1) this arises by a process of hypermutation, acting selectively on rearranged immunoglobulin variable-region genes, which is activated in centroblasts within germinal centres; and (2) centrocytes, the progeny of centroblasts, undergo selection on the basis of their ability to receive a positive signal from antigen. We have now performed experiments analysing this selection process, and found that, on culture, centrocytes isolated from human tonsil kill themselves within a few hours by apoptosis. This is not a feature of other tonsillar B cells. Centrocytes can be prevented from entering apoptosis if they are activated both through their receptors for antigen and a surface glycoprotein recognized by CD40 antibodies.

Antibodies↗
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Changes in cerebral blood flow and recovery from acute stroke.

We prospectively studied 14 patients with acute cerebral infarctions using serial 133Xenon inhalation cerebral determination (133Xe-rCBF), scored neurological examinations, and neuropsychological testing. All patients underwent the same battery of tests at 3 days, 1 week, 2 weeks, and 4 weeks after cerebral infarction to determine the prognostic value of early rCBF studies and the chronological relationship of changes in rCBF to clinical status. Baseline rCBF within 3 days of symptoms of acute stroke did not correlate with clinical neurological outcome (r = -0.17, p less than 0.30; r = -0.18, p less than 0.28, for the two indices of rCBF used). Among the 11 patients demonstrating neurological recovery, 7 improved at 1 week, significantly before increases in rCBF (p less than 0.05). We conclude that early baseline rCBF does not predict clinical outcome in patients with acute cerebral infarctions and that return of neurological function precedes rather than follows increases in rCBF.

Aged↗
PubMedDate not supplied

Lowering the barriers.

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Persons with Disabilities↗
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Effect of interposition material on mechanical behavior in partial physeal resection: a canine model.

A canine model was used to investigate the mechanical properties of the partially resected physis and the role of load-sharing interposition material. Ten puppy knees were loaded axially, with strain gauges placed across the proximal tibial physis. After partial physeal resections, the knees were retested with and without polymethylmethacrylate (PMMA) in the resection gap. PMMA interposition moderated the change in physeal displacement noted with increasing areas of resection. The Heuter-Volkman law predicts decreased growth in response to increased physeal stress. We therefore recommend use of a load-sharing interposition material in resection of large physeal arrests in weightbearing areas.

Animals↗