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Biomedical subjects

H C Kwan

Publications and source records attributed to H C Kwan.

72 records · Page 4Linked to original sources
PubMed1976

Epstein-Barr-virus-specific IgA and IgG serum antibodies in nasopharyngeal carcinoma.

The sera of 73 patients with nasopharyngeal carcinoma (NPC), 28 patients with other carcinomas (OC) and 89 healthy subjects (HS) were tested for IgG and IgA antibodies to Epstein-Barr virus (EBV) viral capsid antigen (VCA). The majority of the NPC sera had IgG titres of 160 or above, whereas the majority of the other sera had titres below 160. For IgA reactivity to EBV-VCA, 68 of 73 (93-2%) NPC sera had titres of greater than or equal to 10. In contrast, only 6 of 28 (21-4%) OC sera and none of the HS sera had such titres. The mean serum concentrations of IgG, IgA, IgM and C3' were also determined in 55 NPC and 20 OC patients and 18 HS. They were all significantly higher in the NPC sera than in the HS. Although the concentrations of IgG and C3' were not significantly different in the two carcinoma groups, the concentrations of IgA and IgM were significantly higher in the NPC group than in OC. These findings appear to reflect the intensity of EBV-specific antigenic stimulation in NPC, and the EBV-specific serum IgA reactivity may be a sueful aid to the diagnosis of NPC, especially in cases with an occult primary tumour. It may be also of value as a screening test in people at high risk.

Antibodies, Viral↗
PubMed1975

Physiological basis of cerebellar dysmetria.

A primary control system for the arm position is formulated. The hypothesis that the cerebellum is a part of the system controller is checked by studying the nerve cells responses in the cerebellum, and motor cortex, to natural activation of muscular receptors. The results show that the cerebellum receives feedback information related to the speed of these receptors. The discussion concentrates on how the interruption of this feedback may result in excessive oscillations to instability. These observations are the base for evaluating how the cerebral lesions produce dismeasurements.

Animals↗
PubMed1975

Effect of succinylcholine on responses of neurons in the motor cortex to natural activation of muscle spindle primary endings.

In locally anesthetized cats, the effects of intravenous administration of succinylcholine (SCh) in sub-paralytic dosages on the responses of single neurons in motor cortex to small dynamic muscle stretches were studied. A large transient enhancement of these cortical responses with a time course corresponding to the peripheral action of SCh on muscle spindles was observed. This finding is discussed in terms of the hypothesis that muscle spindle primary endings may activate projections to motor cortex.

Animals↗
PubMed1975

Afferent-efferent linkages in motor cortex for single forelimb muscles.

1. In locally anesthetized cats, extracellular recordings were made from single neurons in the lateral cruciate gyrus of cerebral cortex. These neurons responded to natural activation of stretch receptors in single, contralateral, forelimb wrist muscles, typically with phasic excitation. Low-velocity stretches, which activate primary endings of muscle spindles, excited one set of neurons at a mean latency of 11 ms; high-velocity stretches, which principally activate Golgi tendon organs and/or secondary spindle endings, excited a second set at 18 ms. The cortical neurons showing threshold responses to low-velocity stretches were found exclusively within restricted columns, 0.5-2.0 mm in diameter, which were spatially separate for each muscle. Neurons exhibiting threshold responses to high-velocity stretches were present in high density within the same columns and were also distributed, although more sparsely, outside the columns. 2. These afferent columns were located in cytoarchitectonic area 4gamma, and were shown by intracortical microstimulation to coincide with the efferent columns for contraction of the same muscle from which in input rose. Discrete afferent columns were also found for single muscles in the peridimple region of sensory cortex (area 3a), spatially separate from the columns in motor cortex. The excitation of the columns in motor cortex by these inputs from muscle was independent of that in sensory cortex. 3. The role of the cerebellum in controlling these feedback systems to motor cortex was investigated by selective cooling of interpositus and dentate nucleus, respectively. Cooling of interpositus markedly reduced transmission in the high-threshold system; cooling of dentate had a similar effect on the low-threshold system. 4. The latency, threshold, and cooling data indicated that the low-threshold system to motor cortex utilizes extracerebellar pathways including medial lemniscus and is facilitated by dentate nucleus. The high-threshold system involves a transcerebellar pathway including interpositus nucleus. Both systems transmit velocity-related information, with each showing different and complementary sensitivity and dynamic range. 5. The results are discussed with reference to the cortical load-compensation mechanism postulated by Phillips (37-38).

Animals↗
PubMed1974

The variability in immunofluorescent viral capsid antigen antibody tests in population surveys of Epstein-Barr virus infections.

A comparative study of the extent of Epstein-Barr virus (EBV) infections in populations that differ with respect to the incidence of tumours associated with this virus is now in progress in different countries. In these surveys of antibody titres from the various study populations, it is of critical importance that strict comparability be maintained. Despite standardization of techniques and reagents in the cooperating laboratories, considerable variation in the results has remained. The components of the total variability in the results of the immunofluorescence test for estimating the antibody titres against viral capsid antigens (VCA) of the EBV have been investigated. With repeated tests on the same sera, four sources of variation were measured: the reading of the slides, the performance of the tests, the use of various batches of the same cell line as antigen, and the use of different cell lines. The greatest variations were due to the use of different cell lines and to differences in performing the test; the reading of the slides caused only minor variations. Both the systematic and unsystematic variations were measured. The systematic variation was great in tests between laboratories and when different cell lines were used as antigens. Most of the systematic variation resulting from the use of different cell batches from the same cell line could be accounted for by the differing proportions of brilliant fluorescent cells. Adjustments are possible to correct the systematic variation whenever this has been measured, but not the unsystematic "residual" variability, which presents the real obstacle to the comparison of results obtained in different laboratories or by different observers. To attain full comparability of VCA antibody tests the sera from the different surveys should all be tested in the same laboratory.

Analysis of Variance↗