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Biomedical subjects

L Mackenzie

Publications and source records attributed to L Mackenzie.

At least 19 recordsLinked to original sources
PubMed1996

Pentobarbitone induces Fos in astrocytes: increased expression following picrotoxin and seizures.

Fos immunoreactivity was observed in astrocytes identified by immunoreactivity to glial fibrillary acidic protein, 1.5 h following intravenous pentobarbitone anesthesia (20-30 mg/kg). Fos-positive astrocytes were seen only in the hilus of the hippocampus. Pentobarbitone administered after picrotoxin but without seizures resulted in an increase in both the intensity of Fos labeling and areal distribution of Fos-positive hilar astrocytes. Pentobarbitone administered after single picrotoxin-induced seizures resulted in an increased number of Fos immunoreactive astrocytes in the hilus and other hippocampal regions and their presence in the upper layers of Fr1, Fr2, cingulate, visual, and perirhinal cortex. Our observations that Fos is expressed in astrocytes following pentobarbitone, provides support for the current view that glial cell processes can be activated by pentobarbitone stimulation of GABAa receptor-chloride channels.

Animals↗
PubMed1996

Frontal cortex leads other brain structures in generalised spike-and-wave spindles and seizure spikes induced by picrotoxin.

Generaliszed spike-and-wave (SW) spindles (5-7 Hz) associated with myoclonic jerks precede the occurrence of regular spikes (2-3 Hz) associated with convulsive seizure induced by picrotoxin. SW spindles occur spontaneously in rodent and cat under some experimental conditions and are considered to be models of human generalised epilepsy. These spindles have been proposed as being led by a thalamic pacemaker. To examine this possibility in picrotoxin-induced SW spindles and seizure spikes, we recorded EEG using chronically implant unipolar electrodes during intravenous picrotoxin infusion in freely behaving rat. The 6 EEG signals were digitally sampled at 1000 Hz. Linear correlation, spectral, coherence and phase analyses were undertaken to determine time differences (TDs) between EEG channels and the brain structure leading seizure activity. One frontal cortex led all other structures during SW spindles. TD between SW spindles in the leading frontal cortex (Fr1) and the contralateral Fr1 was 3.6 + / - 0.5 msec. All ipsilateral structures (hippocampus, thalamus, amygdala, caudate nucleus and occipital cortex) were delayed by more than 3 msec from Fr1 (intralaminar thalamic nuclei - by 6.3 + / - 0.9 msec). TDs of SW spindles between subcortical regions were less than 1.5 msec. Similar relationships with slightly smaller TDs were found with spikes during convulsive seizure except TDs between frontal cortices did not significantly differ from zero. We suggest that seizure activity induced by picrotoxin is led by one Fr1 during SW spindles and by both frontal cortices working as one system during convulsive seizure.

Animals↗
PubMed1995

Distribution of Fos-positive neurons in cortical and subcortical structures after picrotoxin-induced convulsions varies with seizure type.

The distribution of Fos protein was mapped in rat brain following a single non-focal convulsive seizure. Single seizures were induced with intravenous picrotoxin in unhandled animals housed in isolation. Different convulsive behaviours occurred unpredictably. The least severe seizures were predominantly localised to the face, head and forelimbs, without loss of posture control (restricted seizures). The most extensive seizures affected all limbs and trunk, sometimes with falling (generalised seizures). There was a correlation between seizure behaviour and distribution of Fos induction. After restricted seizures, Fos was induced at highest levels in neocortex and piriform cortex and was prominent in entorhinal cortex, caudal-ventral caudate-putamen and amygdala. Regions of thalamus were consistently and lightly labelled, but Fos induction did not occur in hippocampus. After generalised seizures, there was Fos induction in cortex but less than after restricted seizures and, in three of four animals, also in dentate gyrus, hippocampus and subiculum. There was occasional or variable labelling of thalamus, basolateral amygdala and caudate-putamen. One animal with generalised seizures showed no hippocampal Fos induction. The findings indicate that picrotoxin induces seizures with at least two different patterns of neuronal involvement. The cortex, part of the caudate-putamen, amygdala and thalamus are involved in restricted seizures while the hippocampus, cortex and thalamus are involved in generalised seizures. The results do not support the view that generalised seizures are a progression from restricted forms. Cortical Fos involvement is entirely consistent with the participation of cortex in non-focal epilepsy. In these non-focal seizures, the dentate-hippocampus may be a source of excitation to cortex in the generalised group while the cortex appears to be the predominant site of excitation in the restricted group.

Animals↗
PubMed1993

Non convulsive spike-wave discharges do not induce Fos in cerebro-cortical neurons.

Immunohistochemical localisation of Fos was used as a marker of neuronal activity to demonstrate neurons active during non-convulsive spike-wave epilepsy. Fos-positive neurons in cortex and several subcortical areas were counted. In undisturbed animals. Fos counts were not related to spike-wave in any region. With the electroencephalographic (EEG) recording procedure. Fos induction occurred in all regions, even after habituation. However, in central cortex, counts were found to be inversely related to spike-wave duration. This suggests that neuronal activity is not increased during spike-wave and that the central cortex in these animals is less responsive to arousal than in non-epileptic animals.

Animals↗
PubMed1992

Cell-free CD5 in patients with rheumatic diseases.

Since an increased frequency of CD5+ B cells has been reported in rheumatoid arthritis (RA) and primary Sjögren's syndrome (SS), and the expression of the molecule was reduced on the T cells of some SS patients, we hypothesised that there would be an accelerated turnover of CD5 in these disorders. We describe a novel enzyme-linked immunosorbent assay for measuring cell-free (CF) CD5, using rabbit F(ab')2 anti-CD5 antibody as capture agent and monoclonal anti-CD5 antibody as revealing agent. It was established that CF-CD5 was detectable in RA and SS sera, as opposed to sera from patients with ankylosing spondylitis and normal controls. The level of CF-CD5 did not correlate with rheumatoid factor in RA patients but was significantly higher (P less than 0.05) in SS patients with extraglandular manifestations than in those with glandular disease. Three of the latter patients with significantly increased levels of CD5-negative T cells did not have a particularly high proportion of CF-CD5 in these sera.

Antigens, CD↗
PubMed1992

Nonconvulsive electrocorticographic paroxysms (absence epilepsy) in rat strains.

Rat strains were screened for evidence of unresponsive periods associated with high-voltage spike and wave paroxysms on electroencephalography--a rodent model of human absence epilepsy. Five commonly used strains were newly noted to express the spike and wave phenomenon. Only an inbred Sprague Dawley rat strain did not exhibit such episodes. The existence of the phenomenon in many and unrelated inbred rat strains suggests that both genetic and environmental factors are causal.

Animals↗
PubMed1991

Sequence analysis and idiotypic relationships of BEG-2, a human fetal antibody reactive with DNA.

Monoclonal antibody (mAb) BEG-2 is a dsDNA binding IgM lambda derived from a 12-week human fetus. Two binding site idiotypes (BEG-2 Id alpha and BEG-2 Id beta) have been defined with the use of polyclonal rabbit anti-idiotypic anti-serum. BEG-2 Id alpha is located on the lambda light chain and has been described previously. The BEG-2 Id beta is present on the mu heavy chain. By means of a direct binding ELISA, BEG-2 Id beta has been identified on EBV-derived mAbs from human fetal liver or spleen (5%), human cord blood (2.7%) and adult peripheral blood (1%). In addition, the Id is present on 8.5% of adult spleen-derived hybridoma antibodies and 6% of RA synovium-derived hybridoma antibodies. In all populations the presence of the Id is strongly associated with binding to DNA and other polyanions. Competition assays indicated that the Id was located at or near the antigen-binding site on these molecules. To explore the structural basis of this binding, a major part of the BEG-2 heavy chain was sequenced and found to be encoded by a member of the VH4 family joined to a variant of JH5 by a very short Diversity or N region. Of the BEG-2 Id beta positive mAbs for which the VH family has been determined, five are encoded by VH4 and two are encoded by VH6, but none is encoded by other families. Thus, the BEG-2 Id beta identifies a set of polyreactive antibodies that are common in fetal life, persist into adulthood and are encoded by VH6 and, a subset of VH4 genes.

Amino Acid Sequence↗
PubMed1990

The relationship between CD5-expressing B lymphocytes and serologic abnormalities in rheumatoid arthritis patients and their relatives.

The influence of genetic factors on the expression of CD5+ B lymphocytes and their relationship to a broad spectrum of autoantibodies was investigated in a study of 12 patients with rheumatoid arthritis (RA) and 52 of their healthy first-degree relatives. The proportion of CD5+ B cells was significantly higher in RA patients (mean +/- SEM 23.9 +/- 2.7%) compared with that in their relatives (18.3 +/- 1.1%, P less than 0.05) and compared with that in a group of healthy control subjects (16.1 +/- 1.8%; P less than 0.05). Much more striking, however, were the high levels of CD5+ B cells found in the patients and their relatives in 5 of the families studied. Increases in total immunoglobulin levels and autoantibody levels were frequently observed in RA patients (approximately 20-40%) and their relatives (approximately 10-20%). Furthermore, a statistically significant correlation (P less than 0.01) between IgM rheumatoid factor and the percentage of B lymphocytes expressing CD5 was observed.

Adult↗
PubMed1990

The antibody repertoire of early human B cells. I. High frequency of autoreactivity and polyreactivity.

Cord blood and fetal liver B cells were immortalized using Epstein-Barr virus, and IgM antibodies from the resulting lines and clones were examined for their binding to a variety of auto-antigens and micro-organisms by ELISA and fluorescence assays. Auto-antigens tested included Fc of IgG, ssDNA and dsDNA, cardiolipin, histones 1-4, collagens type I and II, thyroglobulin, cytoskeletal components, and a tissue section screen. Of 71 cell lines tested, all but 19 showed some autoreactivity. All 32 fetal liver lines reacted to some self-antigens. In cord blood clones, 16 out of 26 bound to auto-antigens. Many of the clones reacted with more than one auto-antigen and were 'polyreactive'. Some of the cord blood clones bound to extracts of micro-organisms, showing specificity for both endogenous and exogenous antigens. The high frequency of CD5+ B cells in the cord blood (greater than 50%) and fetal liver (greater than 70%) argues for many of these clones being derived from this subset. Therefore, our data support the concept that many 'early' B cells produce polyreactive IgM which can bind to a variety of different auto-antigens and micro-organisms. These IgM antibodies are similar to those described by others as 'natural antibodies'.

Antibody Specificity↗
PubMed1990

CD5 mRNA expression and auto-antibody production in early human B cells immortalized by EBV.

A number of studies have suggested that lymphocytes producing polyreactive antibodies belong to the CD5+ B-cell subset. In this study we have examined CD5 at the cell surface and mRNA levels in EBV-driven cord blood and fetal liver clones previously characterized in terms of their antibody specificities. We show that EBV-immortalized cells can express surface CD5, and that some of the clones not expressing surface CD5 express it at the mRNA level. The complete absence of CD5 mRNA in some polyreactive clones is consistent with the proposition that the production of auto-antibodies and multispecific antibodies is not restricted to the CD5+ B-cell subset.

Antigens, CD↗
PubMed1990

T gamma delta cells and their subsets in blood and synovial tissue from rheumatoid arthritis patients.

We have examined the frequencies of T gamma delta cells in blood, synovial fluids, and synovial membranes of patients with rheumatoid arthritis (RA) and in blood from age-matched controls. Immunocytochemical and immunohistochemical techniques were used with monoclonal antibodies BB3 and A13 to define a major and minor blood subset of T gamma delta cells respectively. Together, these antibodies identify the majority (if not all) of the peripheral blood T gamma delta cells. Significantly lower levels of T gamma delta cells were found in the blood of RA patients compared with controls, whilst higher but not significant numbers were found in the synovial fluids of paired samples. Scattered T gamma delta cells were found only in some synovial membranes with a distribution similar to the T alpha beta cells. Analysis of the two different T gamma delta-cell subsets indicated a ratio of BB3 to A13 of about 5:1 in control and RA blood. However, this ratio was less than 1:1 in the RA synovial fluids and membranes. The migratory nature of the A13+ cells could account for their predominance in these sites. The possible pathological significance of these cells in the rheumatoid synovial fluid and synovial membranes is discussed.

Adult↗
PubMed1988

CD5-expressing B lymphocytes in the blood and salivary glands of patients with primary Sjögren's syndrome.

CD5, the human counterpart of Ly-1 molecules in the mouse, are detectable but weakly expressed on a minute fraction of circulating B cells. The number of CD5 + B cells in the blood of patients with Sjögren's syndrome was slightly higher than in control blood, but it became statistically significant after treatment of the cells with phorbol myristic acetate. These numbers were even higher in patients with homogeneous serum bands than in the others. A few scattered cells were stained with anti-human IgM antibody on salivary gland sections, and among them 5-10% were found to be positive for anti-CD5.

Adult↗
PubMed1988

Chronic lymphocytic leukemic (CLL) cells secrete multispecific autoantibodies.

A subset of B cells expressing the CD5 marker, a 67 KD molecule, has been implicated in the pathogenesis of autoimmune disease. To study the immunoglobulin repertoire of CD5+ B cells we investigated chronic lymphocytic leukemic (CLL) cells, since the majority of the malignant clones express CD5. CLL were induced to secrete their IgM in vitro by phorbol 12-myristate 13-acetate (PMA) and the supernatants screened for binding to a panel of autoantigens. Twelve out of 14 CLL clones were autoreactive, binding to Fc of IgG, ssDNA, dsDNA, histones, cardiolipin, or cytoskeletal components. Many also bound to more than one antigen tested for, showing multispecificity. Our data suggest that a high proportion of CD5+ B cells are programmed to secrete multispecific autoantibodies.

Antibodies, Neoplasm↗
PubMed1988

The importance of CD5-positive B cells in nonorgan-specific autoimmune diseases.

CD5, the human counterpart of Ly-1 molecules in the mouse, are detectable but weakly expressed on a minute fraction of circulating B cells. The number of CD5-expressing B cells is increased in patients with rheumatoid arthritis or primary Sjögren's syndrome. These cells are similar to those leading to chronic lymphocytic leukemia (they may be induced to produce multispecific autoantibodies). Multispecific autoantibodies have also been described in the early B cell repertoire.

Animals↗
PubMed1987

Reduced B-cell galactosyltransferase activity in rheumatoid arthritis.

Autosensitisation to IgG may be important in the pathogenesis of rheumatoid arthritis and could be related to reduced glycosylation of the oligosaccharides in the C gamma 2 region of serum IgG. The activity of galactosyltransferase, the enzyme that catalyses the addition of galactose to the oligosaccharide chains, was measured in the circulating B cells of seventeen patients with classic rheumatoid arthritis. It was significantly lower than that of a group of eleven controls (p less than 0.001) or of nine age-matched controls (p less than 0.001). In contrast, the enzyme activity of the T cells was within the range of that in nine age-matched controls, and enzyme activity in monocyte-rich mononuclear-cell populations was higher than in controls, possibly reflecting stimulation of the monocytes in rheumatoid arthritis. These findings suggest that galactosyltransferase may regulate the degree of glycosylation during IgG synthesis and could therefore be implicated in the rheumatoid inflammatory process.

Adult↗
PubMed1987

Pharmacological modulation of photodynamic therapy with hematoporphyrin derivative and light.

The interactions between photodynamic therapy (PDT) with hemotoporphyrin derivative (HPD) and treatment with cytotoxic drugs have been examined using both an in vitro tissue culture assay and an in vivo transplantable mouse tumor assay. Adriamycin (0.5-4.0 mg/kg) administered with HPD and at the time of irradiation potentiated the photodynamic effect, doubling the duration of tumor control. Adriamycin administered after PDT was not as effective. Methotrexate (0.2 mg/kg) also potentiated the tumor response to PDT. The other cytotoxic agents tested, cyclophosphamide, thiotepa, vincristine, and 5-fluorouracil, did not result in significant increases in tumor responses at the doses tested. In contrast to the effects observed in vivo, Adriamycin inhibited the photodynamic destruction of Raji or Lewis lung carcinoma cells in vitro, in part by reducing the uptake of HPD. Methotrexate had no effect on either the uptake of HPD or the efficacy of photodynamic destruction of Raji cells in vitro. The discrepancy between the in vitro and in vivo results implies that the interaction between PDT and other pharmacological agents cannot be assessed in vitro.

Animals↗
PubMed1987

CD5 positive B cells in patients with rheumatoid arthritis: phorbol ester mediated enhancement of detection.

CD5 molecules present on human T cells are detectable but weakly expressed on some human B cells. We have increased the sensitivity of their detection by treating the B enriched cells with phorbol myristic acetate (PMA), a tumour promoting agent. The numbers of CD5+ B cells in the blood of patients with rheumatoid arthritis (RA) were higher than in control blood, and after PMA treatment this was statistically significant. CD5+ B cells were also increased in tonsils, lymph nodes, and spleens after PMA activation. There were no significant differences between the percentages of B cells carrying chi or lambda light chains in their expression of CD5 molecules in patients with RA.

Adult↗