Flecainide exerts paradoxical effects on sodium currents and atrial arrhythmia in murine RyR2-P2328S hearts

Aims

Cardiac ryanodine receptor mutations are associated with catecholaminergic polymorphic ventricular tachycardia (CPVT), and some, including RyR2-P2328S, also predispose to atrial fibrillation. Recent work associates reduced atrial Na_v1.5 currents in homozygous RyR2-P2328S (RyR2^S/S) mice with slowed conduction and increased arrhythmogenicity. Yet clinically, and in murine models, the Na_v1.5 blocker flecainide reduces ventricular arrhythmogenicity in CPVT. We aimed to determine whether, and how, flecainide influences atrial arrhythmogenicity in RyR2^S/S mice and their wild-type (WT) littermates.

Methods

We explored effects of 1 μm flecainide on WT and RyR2^S/S atria. Arrhythmic incidence, action potential (AP) conduction velocity (CV), atrial effective refractory period (AERP) and AP wavelength (λ = CV × AERP) were measured using multi-electrode array recordings in Langendorff-perfused hearts; Na⁺ currents (I_Na) were recorded using loose patch clamping of superfused atria.

Results

RyR2^S/S showed more frequent atrial arrhythmias, slower CV, reduced I_Na and unchanged AERP compared to WT. Flecainide was anti-arrhythmic in RyR2^S/S but pro-arrhythmic in WT. It increased I_Na in RyR2^S/S atria, whereas it reduced I_Na as expected in WT. It increased AERP while sparing CV in RyR2^S/S, but reduced CV while sparing AERP in WT. Thus, RyR2^S/S hearts have low λ relative to WT; flecainide then increases λ in RyR2^S/S but decreases λ in WT.

Conclusions

Flecainide (1 μm) rescues the RyR2-P2328S atrial arrhythmogenic phenotype by restoring compromised I_Na and λ, changes recently attributed to increased sarcoplasmic reticular Ca²⁺ release. This contrasts with the increased arrhythmic incidence and reduced I_Na and λ with flecainide in WT.

The lowry method for protein quantitation

The most accurate method of determining protein concentration is probably acid hydrolysis followed by amino acid analysis. Most other methods are sensitive to the amino acid composition of the protein and absolute concentrations cannot be obtained. The procedure of Lowry et al. (1) is no exception, but its sensitivity is moderately constant from protein to protein, and it has been so widely used that Lowry protein estimations are a completely acceptable alternative to a rigorous absolute determination in almost all circumstances where protein mixtures or crude extracts are involved.

Radiology of acute thoracic and lumbar spine injuries

Thoracolumbar vertebral fractures typically involve high velocity trauma such as road traffic collisions, falls from height or sporting accidents, and are a major cause of spinal injury. Plain radiographs remain the first-line investigation, but interpretation can be difficult because of the variety of injury patterns and sometimes subtle radiographic signs. This article reviews the normal anatomy, systematic interpretation of thoracic and lumbar radiographs and typical injury patterns.

Tumour heterogeneity: a problem in biopsy assessment of the proliferation index of oesophageal adenocarcinomas

Tumour heterogeneity may pose a problem when biopsy specimens are taken to measure proliferation (for example, in assessing response to therapy). Two "biopsy specimens" were taken from the centre and two from the edge of the luminal surface of 20 resected oesophageal adenocarcinomas. The proliferation index for each "biopsy specimen" was measured by counting Ki67 labelled nuclei in histological sections. The proliferation index was not associated with tumour differentiation or stage. There was site specific heterogeneity with a significant difference in proliferation index between the central (mean (SD) 36.4 (9.7)) and edge "biopsy specimens" (39.3 (9.9)). There was, however, a wide range of differences between pairs of "biopsy specimens" from both sites. In conclusion, if a tumour is to be sampled for measurement of the proliferation index before and after treatment, then the sequential biopsy specimens (preferably duplicated on each occasion) should be taken consistently from a leading edge of the lesion.

Simultaneous recording of receptor current and intraciliary Ca2+ concentration in salamander olfactory receptor cells

1. The suction pipette technique was combined with laser spot fluorescence microscopy to record simultaneously odour-induced current responses and intraciliary Ca2+ concentration from isolated salamander olfactory receptor cells loaded with the fluorescent Ca2+ indicator fluo-3. 2. When exposed for 1 s to increasing odour concentrations both the suction pipette current and fluo-3 fluorescence increased dynamically, rising with a similar time course. Thereafter, the fluorescence signal decayed more slowly, outlasting the current response by 0.56 +/- 0.12 s. 3. The fluo-3 fluorescence evoked by progressively increasing odour concentrations varied in an approximately linear manner with the magnitude of the suction pipette current. 4. Prolonged odour stimulation evoked synchronous oscillations in both suction pipette current and intraciliary calcium concentration with a mean period of 4.5 +/- 0.3 s. 5. When external Na+ was omitted from the stimulating solution the oscillation period for both the current and fluorescence signals was lengthened by a factor of 1.9 +/- 0.2 in comparison with the oscillation period when stimulated in Ringer solution. 6. These results support the currently accepted mechanism for Ca2+ homeostasis within the olfactory cilia, and are consistent with the notion that the oscillations induced by prolonged odour exposure represent the coupled oscillation of Ca2+ and cyclic nucleotide concentrations.

Responses to prolonged odour stimulation in frog olfactory receptor cells

1. The suction pipette technique was used to record receptor current and spiking responses from isolated frog olfactory receptor cells during prolonged odour stimuli. 2. The majority (70 %) of cells displayed 'oscillatory' responses, consisting of repeated bursts of spikes accompanied by regular increases in receptor current. The period of this oscillation varied from 3.5 to 12 s in different cells. The remaining cells responded either with a 'transient' burst of spikes at the onset of stimulation (10 %), or by 'sustained' firing throughout the odour stimulus (20 %). 3. In cells with oscillatory responses, the Ca(2+)-activated Cl(-) channel blocker niflumic acid prolonged the period of oscillation only slightly, despite a 3.8-fold decrease in the receptor current. A 3-fold reduction in the external Cl(-) concentration nearly doubled the receptor current, but had little effect on the oscillation period. These results imply that the majority of the receptor current underlying these oscillatory responses is carried by the Ca(2+)-activated Cl(-) conductance, suggesting that the intracellular Ca(2+) concentration oscillates also. 4. In cells with oscillatory responses, the period of oscillation was prolonged 1.5-fold when stimulated in a low-Na(+) solution designed to incapacitate Na(+)-Ca(2+) exchange, irrespective of whether Na(+) was replaced by permeant Li(+) or impermeant choline. The dependence of the oscillation period upon external Na(+) suggests that it may be governed by the dynamics of Ca(2+) extrusion via Na(+)-Ca(2+) exchange. 5. Exposure to the membrane-permeable cyclic nucleotide analogue CPT-cAMP evoked a sustained rather than an oscillatory response even in cells with oscillatory responses to odour. The inability of CPT-cAMP to evoke an oscillatory response suggests that the cAMP concentration is likely to oscillate also. 6. Perforated-patch recordings revealed that oscillatory responses could only be evoked when the membrane potential was free to change, but not when it was clamped near the resting potential. Since substantial changes in Ca(2+)-activated Cl(-) current, and hence odour-induced depolarisation, had little effect upon the period of oscillation, changes in membrane potential are suggested to play only a permissive role in these oscillatory responses. 7. These results are interpreted in terms of the coupled oscillation of Ca(2+) and cyclic nucleotide concentrations within the olfactory cilia during prolonged odour stimulation.

A light-dependent increase in free Ca2+ concentration in the salamander rod outer segment

1. The Ca(2+) indicator dye fluo-5F was excited by an argon ion laser to measure changes in free Ca(2+) concentration ([Ca2+]i) in the outer segments of isolated salamander rods rapidly exposed to a 0 Ca(2+), 0 Na(+) solution designed to minimise surface membrane Ca(2+) fluxes. Over 30-60 s of laser illumination, the fluorescence first increased rapidly and then declined at a rate that was much slower than in Ringer solution and consistent with previous physiological evidence that 0 Ca(2+), 0 Na(+) solution greatly retards light-induced changes in [Ca(2+)]i. 2. The initial increase in fluorescence was investigated with a sequence of 100 ms laser flashes presented at 5 s intervals. The fluorescence evoked by the second laser flash was on average 30 % larger than the first, and subsequent responses exhibited a slow decline like that measured with continuous laser exposures. The initial increase in fluorescence did not depend upon the timing of exposure to 0 Ca(2+), 0 Na(+) solution but appeared to be evoked by exposure to the laser light. 3. Both the increase and subsequent decline in fluorescence measured with brief laser flashes could be reduced by incorporation of the Ca(2+) chelator BAPTA. This and other results indicate that the fluorescence increase was unlikely to have been caused by a change in the affinity of fluo-5F for Ca(2+) or an increase in the quantity of incorporated dye available to bind Ca(2+) but reflects an actual release of intracellular Ca(2+) within the outer segment. 4. The pool of Ca(2+) available to be released could be decreased if, before the first laser flash, the rod was exposed to light bright enough to bleach a substantial fraction of the photopigment. The releasable pool could also be depleted by exposure to saturating light of much lower intensity if delivered in Ringer solution but not if delivered in 0 Ca(2+), 0 Na(+) solution. We conclude that Ca(2+) can be released within the outer segment both by the bleaching of rhodopsin and by the reduction in [Ca(2+)]i which normally accompanies illumination in Ringer solution. 5. The activation of rhodopsin appears somehow to induce the release of Ca(2+) from a binding site or store within the outer segment. Substantial release, however, required stimulating light of an intensity sufficient to bleach a considerable fraction of the visual pigment. It therefore seems unlikely that such release contributes to the normal Ca(2+)-mediated modulation of transduction during light adaptation. The mechanism and physiological function of light-induced Ca(2+) release are unknown.

Regulation of Staphylococcus aureus pathogenesis via target of RNAIII-activating Protein (TRAP)

Staphylococcus aureus can cause disease through the production of toxins. Toxin production is autoinduced by the protein RNAIII-activating protein (RAP) and by the autoinducing peptide (AIP), and is inhibited by RNAIII-inhibiting peptide (RIP) and by inhibitory AIPs. RAP has been shown to be a useful vaccine target site, and RIP and inhibitory AIPs as therapeutic molecules to prevent and suppress S. aureus infections. Development of therapeutic strategies based on these molecules has been hindered by a lack of knowledge of the molecular mechanisms by which they activate or inhibit virulence. Here, we show that RAP specifically induces the phosphorylation of a novel 21-kDa protein, whereas RIP inhibits its phosphorylation. This protein was termed target of RAP (TRAP). The synthesis of the virulence regulatory molecule, RNAIII, is not activated by RAP in the trap mutant strain, suggesting that RAP activates RNAIII synthesis via TRAP. Phosphoamino acid analysis shows that TRAP is histidine-phosphorylated, suggesting that TRAP may be a sensor of RAP. AIPs up-regulate the synthesis of RNAIII also in trap mutant strains, suggesting that TRAP and AIPs activate RNAIII synthesis via distinct signal transduction pathways. Furthermore, TRAP phosphorylation is down-regulated in the presence of AIP, suggesting that a network of signal transduction pathways regulate S. aureus pathogenesis.

Response properties of isolated mouse olfactory receptor cells

Response properties of isolated mouse olfactory receptor cells were investigated using the suction pipette technique. Cells were exposed to the odour cineole or to solutions of modified ionic content by rapidly changing the solution superfusing the cilia. All experiments were performed at 37 degrees C. Mouse olfactory receptor cells displayed a steep dependence of action potential frequency on stimulus concentration, a 3-fold increase in stimulus concentration often saturating the firing frequency at 200-300 Hz. The receptor current increased more gradually with increasing cineole concentration and did not saturate within the 100-fold range of cineole concentrations applied. When stimulated for 30 s with a low odour concentration, cells responded with sporadic spike firing. Higher concentrations led to the generation of a large receptor current at the onset of stimulation which returned to baseline levels within a few seconds, accompanied during its rising phase by a short burst of action potentials. Thereafter an oscillating response pattern was observed during the remainder of the stimulus, consisting of repetitive increases in receptor current of around 1 s duration accompanied by short bursts of action potentials. Olfactory adaptation was studied by comparing the responses to two closely spaced odour stimuli. The response to the second odour stimulus recovered to 80% of its original magnitude when the cell was superfused with Ringer solution during the 5 s interval between odour exposures. In contrast, exposure to a choline-substituted low Na+ solution between odour stimuli had two effects. First, the receptor current response to the first odour stimulus did not terminate as quickly as in the presence of Na+, suggesting the presence of a Na+ -Ca2+ exchanger. Second, the response to the second stimulus only recovered to 55% of its original magnitude, demonstrating the involvement of Na+-Ca2+ exchange in the recovery of sensitivity in mouse olfactory receptor cells following stimulation.

Adaptation in vertebrate photoreceptors

When light is absorbed within the outer segment of a vertebrate photoreceptor, the conformation of the photopigment rhodopsin is altered to produce an activated photoproduct called metarhodopsin II or Rh(*). Rh(*) initiates a transduction cascade similar to that for metabotropic synaptic receptors and many hormones; the Rh(*) activates a heterotrimeric G protein, which in turn stimulates an effector enzyme, a cyclic nucleotide phosphodiesterase. The phosphodiesterase then hydrolyzes cGMP, and the decrease in the concentration of free cGMP reduces the probability of opening of channels in the outer segment plasma membrane, producing the electrical response of the cell. Photoreceptor transduction can be modulated by changes in the mean light level. This process, called light adaptation (or background adaptation), maintains the working range of the transduction cascade within a physiologically useful region of light intensities. There is increasing evidence that the second messenger responsible for the modulation of the transduction cascade during background adaptation is primarily, if not exclusively, Ca(2+), whose intracellular free concentration is decreased by illumination. The change in free Ca(2+) is believed to have a variety of effects on the transduction mechanism, including modulation of the rate of the guanylyl cyclase and rhodopsin kinase, alteration of the gain of the transduction cascade, and regulation of the affinity of the outer segment channels for cGMP. The sensitivity of the photoreceptor is also reduced by previous exposure to light bright enough to bleach a substantial fraction of the photopigment in the outer segment. This form of desensitization, called bleaching adaptation (the recovery from which is known as dark adaptation), seems largely to be due to an activation of the transduction cascade by some form of bleached pigment. The bleached pigment appears to activate the G protein transducin directly, although with a gain less than Rh(*). The resulting decrease in intracellular Ca(2+) then modulates the transduction cascade, by a mechanism very similar to the one responsible for altering sensitivity during background adaptation.

Adaptation-induced changes in sensitivity in frog olfactory receptor cells

The suction pipette technique was used to study simultaneously the odour-induced action potential and receptor current responses in frog olfactory receptor cells, which were exposed to the odour cineole for 1 s by rapidly exchanging the solution bathing their cilia. The frequency of action potential firing increased as the odour concentration was raised and saturated within a 15-fold elevation above the odour threshold, while the number of spikes fired initially grew at low-to-intermediate concentrations but then declined at higher concentrations. The receptor current response rose steadily and showed no clear sign of saturation over the 300-fold range of cineole concentration employed. The effect of adaptation on the sensitivity of olfactory receptor cells was investigated by first exposing the cell for 4 s to an adapting pre-pulse and then stimulating with a 1 s test pulse. As the pre-pulse concentration was increased, adaptation led to a progressive shift of the dose-response relationships towards higher test pulse concentrations. This resulted in a steep decline in the sensitivity of the receptor current response, combined with an even more dramatic fall in the sensitivity of the spiking responses, since the higher pre-pulse concentrations prevented the generation of action potentials at test pulse concentrations which still evoked a receptor current response.

Adaptation of the odour-induced response in frog olfactory receptor cells

1. Receptor current and spiking responses were recorded simultaneously from isolated frog olfactory receptor cells using the suction pipette technique. Cells were stimulated with the odour cineole by rapid exchange of the solution bathing the olfactory cilia. 2. The receptor current response to a 1 s odour stimulus increased in a graded manner over a 300-fold range of odour concentration without clear saturation, and was accompanied by a train of action potentials. As the concentration of the odour stimulus increased, the frequency of firing increased also, until it saturated at the highest concentrations. The number of spikes evoked by the stimulus first increased and then decreased with increasing concentration, reaching a maximum at intermediate odour concentrations. The dose-response relation for spike firing rose at lower odour concentrations than the dose-response relation for the receptor current response. 3. Adaptation to steady odour stimuli was investigated by exposing the cilia to a 4 s odour pre-pulse and then to a 1 s odour test pulse. As the pre-pulse concentration was increased the dose-response relations derived from the receptor current and spiking responses shifted to higher absolute test pulse concentrations. However the number of spikes fired in response to a given test pulse was little affected by the pre-pulse until, at the highest pre-pulse concentrations spike firing was abolished despite the continued presence of a receptor current response. 4. The sensitivity of the receptor-current response to incremental stimuli fell with increasing pre-pulse concentration, declining with a limiting slope of 2.4 in double logarithmic co-ordinates. The sensitivity determined from the spiking responses declined to zero at a lower pre-pulse concentration, reflecting the abolition of spike firing at pre-pulse concentrations which still evoked a graded receptor-current response.

Expression, characterization, and mutagenesis of the Yersinia pestis murine toxin, a phospholipase D superfamily member

A phospholipase D (PLD) superfamily was recently identified that contains proteins of highly diverse functions with the conserved motif HXKX4DX6G(G/S). The superfamily includes a bacterial nuclease, human and plant PLD enzymes, cardiolipin synthases, phosphatidylserine synthases, and the murine toxin from Yersinia pestis (Ymt). Ymt is particularly effective as a prototype for family members containing two conserved motifs, because it is smaller than many other two-domain superfamily enzymes, and it can be overexpressed. Large quantities of pure recombinant Ymt allowed the formation of diffraction-quality crystals for x-ray structure determination. Dimeric Ymt was shown to have PLD-like activity as demonstrated by the hydrolysis of phosphatidylcholine. Ymt also used bis(para-nitrophenol) phosphate as a substrate. Using these substrates, the amino acids essential for Ymt function were determined. Specifically, substitution of histidine or lysine in the conserved motifs reduced the turnover rate of bis(para-nitrophenol) phosphate by a factor of 10(4) and phospholipid turnover to an undetectable level. The role of the conserved residues in catalysis was further defined by the isolation of a radiolabeled phosphoenzyme intermediate, which identified a conserved histidine residue as the nucleophile in the catalytic reaction. Based on these data, a unifying two-step catalytic mechanism is proposed for this diverse family of enzymes.

Light-dependent changes in outer segment free-Ca2+ concentration in salamander cone photoreceptors

Simultaneous measurements of photocurrent and outer segment Ca2+ were made from isolated salamander cone photoreceptors. While recording the photocurrent from the inner segment, which was drawn into a suction pipette, a laser spot confocal technique was employed to evoke fluorescence from the outer segment of a cone loaded with the Ca2+ indicator fluo-3. When a dark-adapted cone was exposed to the intense illumination of the laser, the circulating current was completely suppressed and fluo-3 fluorescence rapidly declined. In the more numerous red-sensitive cones this light-induced decay in fluo-3 fluorescence was best fitted as the sum of two decaying exponentials with time constants of 43 +/- 2.4 and 640 +/- 55 ms (mean +/- SEM, n = 25) and unequal amplitudes: the faster component was 1.7-fold larger than the slower. In blue-sensitive cones, the decay in fluorescence was slower, with time constants of 140 +/- 30 and 1,400 +/- 300 ms, and nearly equal amplitudes. Calibration of fluo-3 fluorescence in situ from red-sensitive cones allowed the calculation of the free-Ca2+ concentration, yielding values of 410 +/- 37 nM in the dark-adapted outer segment and 5.5 +/- 2.4 nM after saturating illumination (mean +/- SEM, n = 8). Photopigment bleaching by the laser resulted in a considerable reduction in light sensitivity and a maintained decrease in outer segment Ca2+ concentration. When the photopigment was regenerated by applying exogenous 11-cis-retinal, both the light sensitivity and fluo-3 fluorescence recovered rapidly to near dark-adapted levels. Regeneration of the photopigment allowed repeated measurements of fluo-3 fluorescence to be made from a single red-sensitive cone during adaptation to steady light over a range of intensities. These measurements demonstrated that the outer segment Ca2+ concentration declines in a graded manner during adaptation to background light, varying linearly with the magnitude of the circulating current.

Na+-dependent Ca2+ extrusion governs response recovery in frog olfactory receptor cells

To study the mechanism by which Ca2+, which enters during the odor response, is extruded during response recovery, recordings were made from isolated frog olfactory receptor cells using the suction pipette technique, while superfusing the olfactory cilia with solutions of modified ionic composition. When external Na+ was substituted with another cation, the response to odor was greatly prolonged. This prolongation of the response was similar irrespective of whether Na+ was replaced with Li+, which permeates the cyclic nucleotide-gated conductance, or choline, which does not. The prolonged current was greatly reduced by exposure to 300 microM niflumic acid, a blocker of the calcium-activated chloride channel, indicating that it is carried by this conductance, and abolished if Ca2+ was omitted from the external solution, demonstrating that Ca2+ influx is required for its generation. When the cilia were exposed to Na+-free solution after odor stimulation, the recovery of the response to a second stimulus from the adaptation induced by the first was greatly reduced. We conclude that a Na+-dependent Ca2+ extrusion mechanism is present in frog olfactory cilia and that it serves as the main mechanism that returns cytoplasmic Ca2+ concentration to basal levels after stimulation and mediates the normally rapid recovery of the odor response and the restoration of sensitivity after adaptation.

A phase II trial of cisplatin and 5-fluorouracil in adenocarcinoma of the oesophagus

The effect of brief neoadjuvant chemotherapy in patients with apparently operable adenocarcinoma of the oesophagus has been investigated. Two courses of cisplatin and 5-fluorouracil (CFu) were given, followed by evaluation of the response by barium swallow. Twenty-one of 23 patients completed both courses. Two showed a complete response and five a partial response. In only one patient was there a pathological complete response. Toxicity was mild and consisted principally of nausea and vomiting. All patients underwent surgical exploration; resection was completed in 17. There were three hospital deaths (18%). Although CFu has produced two complete responses (on barium swallow) and one complete pathological clearance of tumour, the disappointing total response rate of 7/21 (33%; 95% CI 13-53) or 7/23 (30%; 95% CI 12-49) leads us to believe that further Phase II trials are needed to identify more efficacious agents and regimens.

A phase II trial of four courses of preoperative chemotherapy in squamous or anaplastic carcinoma of the oesophagus

We have reported the results of a previous Phase II trial of two courses of neoadjuvant mitomycin (6 mg/m2), ifosfamide (3 g/m2) and cisplatin (50 mg/m2) (MIC) in squamous or anaplastic carcinoma of the oesophagus. In this current study, we have investigated whether there was any clinical benefit in extending the preoperative treatment to four courses for patients who responded after two courses. Response was assessed by barium swallow, which was compared with previous barium swallows performed prior to any treatment and after the second course of MIC. Of an initial 43 patients, 27 (63%) were assessed as responders after two courses of MIC. Twenty of these 27 patients were entered into the study with a view to receiving two further courses of MIC prior to surgery. Seventeen completed four courses. Five patients were complete responders after two courses and remained complete responders after four courses. Twelve patients were partial responders after two courses; six of these became complete responders after four courses, five remained partial responders, and one showed progression. Haematological toxicity and alopecia were increased after extending the number of courses beyond two. On pathological assessment, three patients with a complete response after four courses, and one with a complete response after three courses, had microscopic clearance of tumour. Extension beyond two courses of neoadjuvant MIC gives an improvement in response, as judged by barium assessment, but increases toxicity, cost of treatment and delay before surgery. Although the numbers are small, the results suggest that a worthwhile improvement in the radiological response of squamous or anaplastic oesophageal tumours may be gained by proceeding beyond two courses of MIC. A randomized trial, with larger numbers of patients, is needed to show whether there is any improvement in radiological and pathological response rates and in survival to be gained by the extension of treatment beyond two courses.

Catalytic mechanism of the phospholipase D superfamily proceeds via a covalent phosphohistidine intermediate

The phospholipase D (PLD) superfamily includes enzymes of phospholipid metabolism, nucleases, as well as ORFs of unknown function in viruses and pathogenic bacteria. These enzymes are characterized by the invariant sequence motif, H(X)K(X)4D. The endonuclease member Nuc of the PLD family was over-expressed in bacteria and purified to homogeneity. Mutation of the conserved histidine to an asparagine in the endonuclease reduced the kcat for hydrolysis by a factor of 10(5), suggesting that the histidine residue plays a key role in catalysis. In addition to catalyzing hydrolysis, a number of phosphohydrolases will catalyze a phosphate (oxygen)-water exchange reaction. We have taken advantage of this observation and demonstrate that a 32P-labeled protein could be trapped when the enzyme was incubated with 32P-labeled inorganic phosphate. The phosphoenzyme intermediate was stable in 1 M NaOH and labile in 1 M HCl and 1 M hydroxylamine, suggesting that the enzyme forms a phosphohistidine intermediate. The pH-stability profile of the phosphoenzyme intermediate was consistent with phosphohistidine and the only radioactive amino acid found after alkaline hydrolysis was phosphohistidine. These results suggest that the enzymes in the PLD superfamily use the conserved histidine for nucleophilic attack on the substrate phosphorus atom and most likely proceed via a common two-step catalytic mechanism.

Bleached pigment produces a maintained decrease in outer segment Ca2+ in salamander rods

A spot confocal microscope based on an argon ion laser was used to make measurements of cytoplasmic calcium concentration (Ca2+i) from the outer segment of an isolated rod loaded with the fluorescent calcium indicator fluo-3 during simultaneous suction pipette recording of the photoresponse. The decline in fluo-3 fluorescence from a rod exposed to saturating illumination was best fitted by two exponentials of approximately equal amplitude with time constants of 260 and 2,200 ms. Calibration of fluo-3 fluorescence in situ yielded Ca2+i estimates of 670 +/- 250 nM in a dark-adapted rod and 30 +/- 10 nM during response saturation after exposure to bright light (mean +/- SD). The resting level of Ca2+i was significantly reduced after bleaching by the laser spot, peak fluo-3 fluorescence falling to 56 +/- 5% (SEM, n = 9) of its value in the dark-adapted rod. Regeneration of the photopigment with exogenous 11-cis-retinal restored peak fluo-3 fluorescence to a value not significantly different from that originally measured in darkness, indicating restoration of the dark-adapted level of Ca2+i. These results are consistent with the notion that sustained activation of the transduction cascade by bleached pigment produces a sustained decrease in rod outer segment Ca2+i, which may be responsible for the bleach-induced adaptation of the kinetics and sensitivity of the photoresponse.

Expression of E-cadherin in oesophageal carcinomas from the UK and China: disparities in prognostic significance

AIMS

To study the expression and prognostic significance of the cell adhesion molecule E-cadherin in oesophageal tumours from the UK (low risk area) and China (high risk area).

METHODS

E-cadherin expression was measured immunohistochemically in resected tumours from 17 patients in the UK with adenocarcinoma, 23 patients from the UK with squamous carcinoma, and 30 patients from China with squamous carcinomas who survived for five years postoperatively and compared with similar tumours from patients in the same regions who did not survive (140 tumours in all).

RESULTS

Normal squamous epithelial cells and well differentiated areas of tumours showed membranous staining for E-cadherin expression. Cytoplasmic staining, heterogeneous staining, or an absence of staining was seen in dysplastic epithelium and in less well differentiated areas of tumours. Only one of 140 primary tumours had homogeneous membranous expression. In tumours from UK patients with adenocarcinoma (p = 1.00) and from Chinese patients with squamous carcinomas (p = 0.06) there was no correlation between E-cadherin absence and non-survival. In tumours from UK patients with squamous carcinomas there was a significant correlation between absence of E-cadherin and non-survival (p = 0.009). Tumours from UK patients with squamous carcinoma who survived were significantly less likely to be E-cadherin absent than those from Chinese patients with squamous carcinomas who survived (p = 0.007). Multivariate analysis (n = 37 UK, paired data) showed that absence of E-cadherin in the primary tumour was a weak independent prognostic factor for non-survival (30% significance level; p = 0.26; odds ratio = 3.56). In UK nodal metastases there was no correlation between E-cadherin expression and survival.

CONCLUSIONS

Squamous carcinomas from UK patients differed from both adenocarcinomas from UK patients and carcinomas from Chinese patients with respect to E-cadherin expression and prognostic significance. In tumours from UK patients, E-cadherin absence in the primary carcinoma (a weak independent prognostic factor) but not metastases correlated with non-survival.

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.

Voltage-dependent block by L- cis -diltiazem of the cyclic GMP-activated conductance of salamander rods

Block by L-cis-diltiazem of the cyclic GMP-activated conductance was studied in excised inside-out patches from the salamander rod outer segment. When L-cis-diltiazem was applied from the cytoplasmic face of the patch, current suppression increased monotonically with membrane depolarization, the ratio of blocked to unblocked current varying e-fold in 50 mV. This suggests that L-cis-diltiazem interacts with a binding site located about half-way across the membrane field, and is unable to fully traverse the cyclic GMP-activated channel. The kinetics of block were accelerated by increasing L-cis-diltiazem concentration and by depolarization. These results can be fitted by a single barrier model in which the barrier peak is located about a third of the way across the membrane field from the cytoplasmic face. Application of L-cis-diltiazem from the extracellular face of the patch also resulted in an enhancement of block with membrane depolarization. Indirect evidence supports the notion that this block resulted from partition of the unchanged form of the blocker across the membrane, and its subsequent interaction with the cytoplasmic face of the conductance.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Effects of chemotherapy on ultrastructure of oesophageal squamous cell carcinoma

Seven oesophageal squamous carcinomas, treated with pre-operative chemotherapy (mitomycin-C, ifosfamide and cisplatin-MIC), with a course finishing 21 days prior to resection, were examined by electronmicroscopy. In one treated case detailed light microscopy failed to reveal any tumour. Five of the remaining six tumours showed cytotoxic damage in that apoptosis and unusual necrotic changes were observed in almost all the neoplastic cells. These features were not seen in untreated cases. In four additional cases, who received one pulse of MIC followed by biopsy or resection within 3-6 days, apoptotic changes were very pronounced and extensive and most neoplastic cells presented unusual degeneration with characteristic derangement of the cytoskeleton, destruction of organelles and accumulation of glycogen. The ultrastructural appearance of 18 untreated resected oesophageal squamous carcinomas was studied for comparison with the treated tumours. The study has demonstrated ultrastructural changes resulting from chemotherapy. Results suggest that the regimen is more effective against squamous carcinomas than against adenocarcinomas of the oesophagus, as judged by comparison with the results of a previous study.

Expression of p53 protein in oesophageal carcinoma: clinicopathological correlation and prognostic significance

Correlation of p53 expression with 5-year survival and histopathological parameters was examined immunohistochemically in two groups of 30 patients with oesophageal carcinoma (5-year survivors versus non-survivors). Tumour type, sex, operative procedure and age were matched. Some 64 per cent of squamous carcinomas and 79 per cent of adenocarcinomas were p53 positive. Normal squamous, normal glandular and metaplastic glandular epithelia were negative. Dysplastic squamous and glandular epithelium adjacent to tumours was positive when the tumour was positive and negative when it was not. Univariate analysis showed that nodal status (P = 0.001), and grade and depth of invasion (both P = 0.01) correlated with outcome. Correlation of tumour grade with outcome, when the most poorly differentiated area is used, is a novel finding for oesophageal carcinoma. The p53 status was not significantly associated with survival or any of these parameters.