Biomedical subjects

H R Matthews

Publications and source records attributed to H R Matthews.

At least 19 recordsLinked to original sources

PubMed1997

Five newly established oesophageal carcinoma cell lines: phenotypic and immunological characterization.

The derivation of permanent cell lines from 40 resected oesophageal carcinomas has been attempted. Five long-term lines have been established from three adenocarcinomas, one mixed carcinoma and one squamous carcinoma. Molecular and cellular analyses have been carried out on the lines and clones derived from them. Karyotype analysis indicates genetic variation among the clones. HLA-A, -B and -C is expressed constitutively, but not HLA-DR. ICAM-1-expressing phenotypes may have arisen during adaptation to long-term culture. All lines are capable of response to interferon-gamma (IFN-gamma) and all produce transforming growth factor beta 1 (TGF-beta 1). Two lines are resistant to the inhibitory growth effects of the latter, possibly contributing to malignancy. It is anticipated that these lines, originating from histologically different carcinomas, will provide a valuable, continuous resource for the investigation and treatment of these aggressive tumours.

Animals↗

PubMed1997

Actions of Ca2+ on an early stage in phototransduction revealed by the dynamic fall in Ca2+ concentration during the bright flash response.

To study the actions of Ca2+ on "early" stages of the transduction cascade, changes in cytoplasmic calcium concentration (Ca2+i) were opposed by manipulating Ca2+ fluxes across the rod outer segment membrane immediately following a bright flash. If the outer segment was exposed to 0 Ca2+/0 Na+ solution for a brief period immediately after the flash, then the period of response saturation was prolonged in comparison with that in Ringer solution. But if the exposure to 0 Ca2+/0Na+ solution instead came before or was delayed until 1 s after the flash then it had little effect. The degree of response prolongation increased with the duration of the exposure to 0 Ca2+/0 Na+ solution, revealing a time constant of 0.49 +/- 0.03 s. By the time the response begins to recover from saturation, Ca2+i seems likely to have fallen to a similar level in each case. Therefore the prolongation of the response when Ca2+i was prevented from changing immediately after the flash seems likely to reflect the abolition of actions of the usual dynamic fall in Ca2+i on an early stage in the transduction cascade at a site which is available for only a brief period after the flash. One possibility is that the observed time constant corresponds to the phosphorylation of photoisomerized rhodopsin.

Ambystoma↗

PubMed1996

Role of cytoplasmic calcium concentration in the bleaching adaptation of salamander cone photoreceptors.

1. In order to study the possible involvement of Ca2+ in the bleaching adaptation of cones isolated from the retina of the salamander Ambystoma tigrinum, changes in cytoplasmic calcium concentration ([Ca2+]i were opposed by exposing the outer segment to a low-Ca(2+)-O Na+ solution designed to minimize Ca2+ fluxes across the outer segment membrane. 2. When a cone was exposed in normal Ringer solution to bright light bleaching a significant fraction of the photopigment, the circulating current was initially suppressed completely and then recovered to a maintained value less than the value in darkness before the bleach. When the outer segment of the cone was stepped to low-Ca(2+)-O Na+ solution before the bleach was delivered, the circulating current recovered more slowly or (for large bleaches) remained completely suppressed for the duration of the solution exposure. 3. If, during the period for which the current was suppressed in low-Ca(2+)-O Na+ solution, the cone outer segment was exposed to the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), the circulating current was restored. The dim flash response recorded under these conditions exhibited kinetics and integration times similar to those recorded in low-Ca(2+)-O Na+ solution in darkness before the bleach. If, instead, the outer segment was returned to Ringer solution after the bleach, thereby allowing [Ca2+]i to fall from its dark-adapted level to the appropriate bleach-adapted level, the kinetics of the response in low-Ca(2+)-O Na+ solution were greatly accelerated, and the integration time considerably reduced. This was true regardless of whether or not the low-Ca(2+)-O Na+ solution included IBMX. 4. The role of Ca2+ in bleaching adaptation appeared to resemble its role in background adaptation, since in both cases exposure to low-Ca(2+)-O Na+ solution suppressed the acceleration of response kinetics. Responses recorded from cones in low-Ca(2+)-O Na+ solution were nearly identical in waveform and sensitivity during background light or after bleaches, provided that IBMX was used to restore sufficient photocurrent so that responses to flashes could be recorded, and sensitivity was corrected for loss in quantum catch. 5. These results indicate that the fall in [Ca2+]i in cones after a bleach is necessary both for the acceleration of the flash response and the adaptational decrease in sensitivity, as is the case for adaptation by background light.

1-Methyl-3-isobutylxanthine↗

PubMed1996

Static and dynamic actions of cytoplasmic Ca2+ in the adaptation of responses to saturating flashes in salamander rods.

1. In order to study the relative contribution to light adaptation of the various actions of Ca2+ in rod photoreceptors, changes in cytoplasmic calcium concentration ([Ca2+]i) were opposed by manipulating the calcium fluxes across the outer segment membrane at different times during the response to a bright flash. 2. When the outer segment was superfused with 0 Ca2+, 0 Mg2+,0 Na+ solution just before a bright flash, the period of response saturation was greatly prolonged. But if instead the solution change was made at progressively increasing times after the flash, the delay before the response recovered from saturation declined exponentially towards its value in Ringer solution with a time constant of around 1 s. In contrast, recovery time was little affected by stepping to 0 Ca+,0 Mg2+,0 Na+ solution before the flash and returning to Ringer solution shortly before the normal time of recovery from saturation. 3. When a bright flash was delivered just before the extinction of steady light, the response recovered from saturation progressively earlier as this steady intensity was increased. If, instead, the outer segment was transferred to 0 Ca2+,0 Mg2+,0 Na+ solution just before the bright flash then the time spent in saturation by the response was prolonged in darkness, but this additional delay progressively decreased as the steady intensity increased. 4. These results are consistent with the notion that the light-induced reduction of the time spent in saturation by the bright flash response in Ringer solution resulted from the static decrease in [Ca2+]i induced by the background, while the additional delay in the recovery from saturation when further changes in [Ca2+]i were prevented stemmed from the abolition of the dynamic fall in [Ca2+]i during the flash response. 5. Analysis of the effects of steady light on the time spent in saturation by the bright flash response under these conditions suggests that actions of [Ca2+]i at, or soon after, the time of the flash are largely responsible for the graded changes which take place in the bright flash response during light adaptation, while rapid actions of [Ca2+]i at the time of response recovery also play a role in the adaptation of the steady response to background light itself. 6. These data have been interpreted in terms of differential actions of [Ca2+]i on 'early' stages (e.g. events leading to phosphodiesterase activation) and 'late' stages (e.g. guanylyl cyclase) in the transduction mechanism. A quantitative model is presented which suggests that actions of [Ca2+]i on 'late' stages play a proportinately larger role in background adaptation than actions on 'early' stages.

Animals↗

PubMed1996

Phase II study of mitomycin, ifosfamide and cisplatin in adenocarcinoma of the oesophagus.

We evaluated the effect of brief neoadjuvant chemotherapy in patients with apparently operable adenocarcinoma of the oesophagus. Two courses of mitomycin (6 mg/m2), ifosfamide (3 g/m2) and cisplatin (50 mg/m2;MIC) were given followed by evaluation of response by barium swallow and computed tomography scan. Of 20 patients, 17 completed both courses and 4 (20%) showed a partial response. Toxicity was generally mild and consisted principally of nausea and vomiting. Altogether, 15 patients were surgically explored; resection was completed in 12 patients, 3 of whom died in hospital (25%). Neoadjuvant therapy with MIC offers no advantage over surgery alone.

Adenocarcinoma↗

PubMed1996

Dark adaptation in vertebrate photoreceptors.

Exposure of the eye to bright light bleaches a significant fraction of the photopigment in rods and cones and produces a prolonged decrease in the sensitivity of vision, which recovers slowly as the photopigment is regenerated. This sensitivity decrease is larger than would be expected merely from the decrease in the concentration of the pigment. Recent experiments have shown that the decrease in sensitivity is produced largely by an excitation of the phototransduction cascade by bleached pigment; even in darkness, it produces an equivalent background similar to that produced by real steady background illumination. Thus, excitation produced by a form of rhodopsin thought previously to be inactive has a profound effect on the physiology of the photoreceptor. This raises the possibility that forms of other G protein-coupled receptors thought to be inactive might also play an important role in signal transduction and disease.

Adaptation, Physiological↗

PubMed1996

Persistent activation of transducin by bleached rhodopsin in salamander rods.

The hydrolysis-resistant GTP analogue GTP-gamma-S was introduced into rods isolated from the retina of the salamander Ambystoma tigrinum to study the origin of the persistent excitation induced by intense bleaching illumination. Dialysis of a dark-adapted rod with a whole-cell patch pipette containing 2 mM GTP-gamma-S resulted in a gradual decrease in circulating current. If the rod was first bleached and its sensitivity allowed to stabilize for at least 30 min, then dialysis with GTP-gamma-S produced a much faster current decay. The circulating current could be restored by superfusion with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, suggesting that the decay in current originated from persistent excitation of the phosphodiesterase by transducin bound to GTP-gamma-S. We conclude that the persistent excitation which follows bleaching is likely to involve the GTP-binding protein transducin, which mediates the normal photoresponse. This observation suggests that a form of rhodopsin which persists long after bleaching can activate transducin much as does photoisomerized rhodopsin, although with considerably lower gain.

1-Methyl-3-isobutylxanthine↗

PubMed1996

Lymphocyte infiltration in oesophageal carcinoma: lack of correlation with MHC antigens, ICAM-1, and tumour stage and grade.

Infiltration by T lymphocytes into oesophageal carcinomas was assessed immunohistochemically, total T lymphocyte numbers by staining for CD3 and activated T lymphocytes by staining for CD25. Five squamous carcinomas and seven adenocarcinomas, resected without neoadjuvant treatment, were studied. Computer aided quantitation showed that total numbers of tumour infiltrating CD3 positive cells were highly variable (range 48-1673 cells/mm2). They were located largely in the stromal (87.9-99.2%) rather than intratumoral regions. Up to 84% of tumour infiltrating T lymphocytes were CD25 positive, although the median figure was 33%. There was no correlation between T lymphocyte infiltration or activation and expression of class I and II histocompatibility antigens, intercellular adhesion molecule-1, tumour stage or grade. These results imply that the local inflammatory response in oesophageal carcinomas is deregulated, which may be a factor contributing to the aggressive nature of the tumours.

Adenocarcinoma↗

PubMed1995

Removal of phosphate from phosphohistidine in proteins.

Kinetic constants of KM = 0.8 microM, 3 microM and 1.6 microM, and kcat = 9 s-1, 7 s-1 or 9 s-1 were determined for histidine dephosphorylation by protein phosphatases 1, 2A and 2C respectively. IC50 values were determined for the inhibition of protein phosphatase 1 by inhibitor 1 (IC50 = 1 nM), inhibitor-2 (IC50 = 3 nM) and okadaic acid (IC50 = 30 nM) and for the inhibition of protein phosphatase 2A by okadaic acid (IC50 = 0.02 nM) and microcystin-LR (IC50 = 1 nM). Inhibitor-1 (Ki = 0.7 nM) and okadaic acid (Ki = 32 nM) are noncompetitive with protein phosphatase 1. Some of the IC50 values were low enough to violate the assumptions of the usual inhibition equations and a more general approach to the analysis of the data was used. On the basis of these kinetic parameters and the presence of phosphohistidine, the major cellular protein serine/threonine phosphatases are likely to act as protein histidine phosphatases in the cell.

Animals↗

PubMed1995

Protein histidine phosphatase activity in rat liver and spinach leaves.

Whole cell extracts from rat liver or spinach leaves contain divalent ion-independent protein histidine phosphatase activity due to phosphatases of the PP1/PP2A family. In the rat liver extract, almost all the activity was found in the PP1, PP2A1 and PP2A2 peaks. In the spinach leaf extract, four phosphorylase phosphatase activity peaks were resolved--three containing PP1 and one containing PP2A--and all showed histidine phosphatase activity. Thus, protein histidine phosphatase activity is expressed in the cytosolic forms of protein phosphatases of the PP1/PP2A family in mammalian and plant cells.

Animals↗

PubMed1995

Effects of lowered cytoplasmic calcium concentration and light on the responses of salamander rod photoreceptors.

1. In order to study the interactions between cytoplasmic calcium concentration ([Ca2+]i) and light in modulating the responses of rod photoreceptors, [Ca2+]i was held at different levels by manipulating Ca2+ fluxes across the outer segment membrane. 2. If [Ca2+]i was reduced by the removal of external Ca2+ in the continued presence of Na+, and then held near this reduced level by exposure to 0 Ca(2+)-0 Na+ solution, the onset of the recovery phase of the response to a bright flash delivered just before the return to Ringer solution was accelerated, much as is the case during light adaptation, provided that precautions were taken to minimize Na+ influx. 3. If the rod was first allowed to adapt to steady light, [Ca2+]i held near the appropriate light-adapted level by superfusion with 0 Ca(2+)-0 Mg(2+)-0 Na+ solution and the light extinguished, the onset of the recovery phase of the bright flash response varied with the original background intensity in the same way as in the continued presence of steady light. These results indicate that reduction of [Ca2+]i is sufficient to induce this manifestation of light adaptation in darkness. 4. When [Ca2+]i was held at a reduced level in darkness, not only was the sensitivity to dim flashes reduced, but the response rising phase was also delayed and its amplitude increased supralinearly with flash intensity, neither of which changes is seen during light adaptation. However, similar changes in response kinetics resulted when [Ca2+]i was held near its normal dark level and the phosphodiesterase was partially inhibited by 3-isobuty-1-methylxanthine (IBMX), suggesting that they arose indirectly from an elevated cyclic GMP concentration rather than from a direct effect of Ca2+. 5. If [Ca2+]i was held near the normal dark level and bright steady light presented, the circulating current was completely suppressed. Partial inhibition of the phosphodiesterase by superfusion with 0 Ca(2+)-0 Na+ solution including IBMX resulted in restoration of the circulating current. Dim flash responses recorded under these conditions exhibited kinetics similar to those recorded in 0 Ca(2+)-0 Na+ solution in darkness, in contrast to the response acceleration seen when [Ca2+]i was held near the appropriate light-adapted level. These results indicate that the kinetics of the flash response depend on [Ca2+]i rather than on the steady light intensity.

1-Methyl-3-isobutylxanthine↗

PubMed1995

Prospective audit of perforation rates following upper gastrointestinal endoscopy in two regions of England.

After cardiopulmonary complications, perforation is the second most important cause of complications following flexible upper gastrointestinal endoscopy. A recent audit of 14,149 procedures detected a perforation rate of 0.05 per cent (overall mortality rate 0.008 per cent) during diagnostic endoscopy, and a perforation rate of 2.6 per cent (overall mortality rate 1.0 per cent) following oesophageal intubation or dilatation. The incidence of perforation following both diagnostic and therapeutic upper gastrointestinal endoscopy has not changed over the past 10 years. The risk factors are numerous but this audit demonstrated that inexperience increases the likelihood of perforation.

Aged↗

PubMed1995

Protein kinases and phosphatases that act on histidine, lysine, or arginine residues in eukaryotic proteins: a possible regulator of the mitogen-activated protein kinase cascade.

Phosphohistidine goes undetected in conventional studies of protein phosphorylation, although it may account for 6% of total protein phosphorylation in eukaryotes. Procedures for studying protein N- kinases are described. Genes whose products are putative protein histidine kinases occur in a yeast and a plant. In rat liver plasma membranes, activation of the small G-protein, Ras, causes protein histidine phosphorylation. Cellular phosphatases dephosphorylate phosphohistidine. One eukaryotic protein histidine kinase has been purified, and specific proteins phosphorylated on histidine have been observed. There is a protein arginine kinase in mouse and protein lysine kinases in rat. Protein phosphohistidine may regulate the mitogen-activated protein kinase cascade.

Animals↗

PubMed1995

Weight gain as an indicator of response to chemotherapy for oesophageal carcinoma.

Patients with oesophageal carcinoma commonly present with dysphagia and weight loss, which may be related to the tumour burden and/or the physical obstruction to the passage of food. In this study we have examined the relationship between weight change and response to chemotherapy in 28 patients undergoing neo-adjuvant chemotherapy for squamous or anaplastic carcinoma. Two pulses of mitomycin, ifosfamide and cisplatin were given 3 weeks apart. Body weights were measured prior to the first pulse and 3 weeks after the second. Patients underwent oesophageal dilatation routinely at diagnostic endoscopy prior to chemotherapy, in order to permit oral nutrition. No dietary modifications were made. Tumour response was assessed on a barium swallow. Patients had a normal spread of weights on presentation. In the non-responding group (n = 9), eight patients lost weight and one gained weight. Of the partial responders (> 50% tumour shrinkage; n = 11), five gained weight, five lost weight and one remained constant. In the complete response group (n = 8), six gained weight and two lost weight. Statistical analysis showed a significant difference (F = 4.61; P = 0.02) between change in weight expressed as a percentage of ideal weight in nonresponders (mean -5.3%) versus partial responders (mean +2.4%), and in non-responders versus complete responders (mean +1.1%). Weight gain during chemotherapy is a good indication of response, although its absence does not preclude a response. In the majority of patients who respond to chemotherapy there will be an increase in weight with improvement in their general condition prior to operation.

Adult↗

PubMed1995

Bleached pigment activates transduction in salamander cones.

We have used suction electrode recording together with rapid steps into 0.5 mM IBMX solution to investigate changes in guanylyl cyclase velocity produced by pigment bleaching in isolated cones of the salamander Ambystoma tigrinum. Both backgrounds and bleaches accelerate the time course of current increase during steps into IBMX. We interpret this as evidence that the velocity of the guanylyl cyclase is increased in background light or after bleaching. Our results indicate that cyclase velocity increases nearly linearly with increasing percent pigment bleached but nonlinearly (and may saturate) with increasing back-ground intensity. In cones (as previously demonstrated for rods), light-activated pigment and bleached pigment appear to have somewhat different effects on the transduction cascade. The effect of bleaching on cyclase rate is maintained for at least 15-20 min after the light is removed, much longer than is required after a bleach for circulating current and sensitivity to stabilize in an isolated cone. The effect on the cyclase rate can be completely reversed by treatment with liposomes containing 11-cis retinal. The effects of bleaching can also be partially reversed by beta-ionone, an analogue of the chromophore 11-cis-retinal which does not form a covalent attachment to opsin. Perfusion of a bleached cone with beta-ionone produces a rapid increase in circulating current and sensitivity, which rapidly reverses when the beta-ionone is removed. Perfusion with beta-ionone also causes a partial reversal of the bleach-induced acceleration of cyclase velocity. We conclude that bleaching produces an "equivalent background" excitation of the transduction cascade in cones, perhaps by a mechanism similar to that in rods.

1-Methyl-3-isobutylxanthine↗

PubMed1995

Lack of correlation of P-glycoprotein expression with response to MIC chemotherapy in oesophageal cancer.

The multidrug resistance gene product P-glycoprotein (P-GP) was assessed immunohistochemically (by antibody JSB-1) in biopsy specimens from 27 oesophageal squamous carcinomas and 10 adenocarcinomas before treatment with mitomycin, ifosfamide and cisplatin (MIC). Tumours were assessed following treatment and correlation with response sought. Of the squamous carcinomas, 74% (20/27) responded to MIC but only one expressed P-GP before and after treatment. Of the adenocarcinomas, 30% (three of 10) responded. Seven of the 10 adenocarcinomas expressed P-GP before treatment but all 10 were P-GP positive after chemotherapy. The difference in prevalence and induction of P-GP between the histological types was highly significant and may correlate with the greater response to MIC seen in squamous carcinomas compared with adenocarcinomas. P-GP cannot be used as a predictive marker of response as tumours express it inconsistently with response to MIC. Resistance to MIC may be due to other mechanisms.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Expression of HLA-ABC, HLA-DR and intercellular adhesion molecule-1 in oesophageal carcinoma.

AIM: To examine the expression of HLA-ABC and HLA-DR major histocompatibility (MHC) antigens and intercellular adhesion molecule (ICAM)-1 in normal, inflamed, metaplastic, and neoplastic oesophageal tissue and in freshly disaggregated tumours. METHODS: Sequential sections of frozen tissue and cytospins of freshly disaggregated tumour were stained using the ABC peroxidase system and monoclonal antibodies specific for HLA-ABC, HLA-DR and ICAM-1. RESULTS: Normal oesophageal tissue showed positive staining for HLA-ABC in the basal layers of the oesophageal squamous epithelium and on the epithelial cells of the submucosal oesophageal glands. HLA-DR and ICAM-1 were not detected in either of these cell types. In 20 of 37 (54%) carcinomas HLA-ABC was expressed weakly, with heterogeneous expression in nine (24%). Two tumours showed strong expression of HLA-ABC, but 15 of 37 (41%) were negative. HLA-DR and ICAM-1 were expressed weakly in six of 37 (16%) carcinomas without correlation with each other or with the expression of HLA-ABC. CONCLUSIONS: HLA-ABC is absent from a high proportion of oesophageal carcinomas (41%) and is otherwise variably and weakly expressed with strong expression in only a small fraction (3%). In other carcinomas there is a higher level of HLA-ABC expression. This discrepancy may partly explain the aggressive nature of oesophageal carcinomas. HLA-DR and ICAM-1 are not normally expressed on those cells from which oesophageal carcinomas are thought to arise. The limited expression found here could suggest a partial or inhibited immune response against oesophageal carcinoma. In vivo repressive factors may be involved.

Adenocarcinoma↗

PubMed1994

The effect of pH on the block by L-cis-diltiazem and amiloride of the cyclic GMP-activated conductance of salamander rods.

Block by L-cis-diltiazem and amiloride of the cyclic GMP-activated conductance was studied in inside-out patches excised from the salamander rod outer segment. When cytoplasmic pH was varied, the steady-state level of block by L-cis-diltiazem changed in the way that would be predicted if it were the protonated ammonium group that is responsible for effecting block. This is in contrast to the recent results of Haynes (J. gen. Physiol. 100, 783 (1992)) in catfish cones, where no such change was seen. Amiloride was found to block the conductance with a similar voltage dependence to that of L-cis-diltiazem. The dependence of amiloride block on cytoplasmic pH was found to be shifted relative to that of L-cis-diltiazem, consistent with the 1 pH-unit higher pKa value of amiloride and the idea that it is only the charged form of amiloride which can effect block. This suggests that the results seen with L-cis-diltiazem were indeed due to changes in the proportion of blocker in the protonated form, and not to effects of protons on the channel.

Ambystoma↗