Prognosis and clinicopathologic features in patients with gastric stump cancer after curative surgery.

Background: Gastric stump ("remnant") cancer is the development of a malignancy related to previous gastric surgery. Prognosis in gastric stump cancer, compared with that in primary gastric cancer, is still controversial. Methods: From January 1988 to December 2012 at a single medical centre in Taiwan, 105 patients with gastric stump cancer, including 85 with previous peptic ulcer disease and 20 with previous gastric cancer, were analyzed for clinicopathologic characteristics and overall survival (os). Results: The 5-year os rates for patients with gastric stump cancer and with primary gastric cancer were 51.2% and 54.5% respectively (p = 0.035). Analysis of clinicopathologic characteristics indicated that, compared with patients having primary gastric cancer, those with gastric stump cancer had more lymph node metastasis (p < 0.001) and had been diagnosed at a more advanced stage (p = 0.047). Multivariate analysis with os as an endpoint showed that age [p = 0.015; hazard ratio (hr): 2.300; 95% confidence interval (ci): 1.173 to 4.509], tumour size (p = 0.037; hr: 1.700; 95% ci: 1.031 to 2.801), stromal reaction (p = 0.021; hr: 1.802; 95% ci: 1.094 to 2.969), and pathologic N category (p = 0.001; hr: 1.449; 95% ci: 1.161 to 1.807) were independent predictors in gastric stump cancer. The os rates for patients with gastric stump cancer who previously had gastric cancer or peptic ulcer disease were 72.9% and 50.0% respectively (p = 0.019). The Borrmann classification was more superficial (p = 0.005), lymph node metastases were fewer (p = 0.004), and staging was less advanced (p = 0.025) in patients with gastric stump cancer who previously had gastric cancer than in their counterparts who previously had peptic ulcer disease. Conclusions: Survival is poorer in patients with gastric stump cancer who previously had peptic ulcer disease than in those who previously had primary gastric cancer. Patients with gastric stump cancer who previously had gastric cancer and could receive curative gastrectomy tended to have a better prognosis because of a more superficial Borrmann classification. Regular follow-up in patients who have undergone gastric surgery is recommended for the early detection of gastric stump cancer.

Development of multiple complications in type 2 diabetes is associated with the increase of multiple markers of chronic inflammation.

Patients with type 2 diabetes (T2DM) are known at risk for developing cardiovascular disease (CVD), nephropathy, and cancer. We were interested to find out whether multiple markers associated with chronic inflammation are detectable in patients with T2DM and are increased in patients with T2DM who developed additional clinical complications. A sequence of multiple risk markers for atherogenesis, associated with chronic inflammation, was measured in patients with T2DM before and after the development of clinical complications. We found that multiple clinical complications frequently developed simultaneously in patients with T2DM. At the early stage of T2DM, only low levels and low percent elevations of multiple risk markers were detected. However, both the level and the percent elevation of these markers were found to increase with disease progression and the development of clinical complications. We believe that chronic inflammation not only contributes to the pathogenesis of T2DM but also continues to increase in T2DM patients who are developing additional clinical complications. It appears that these multiple markers are potentially useful not only for monitoring the progression of T2DM but also predicting the risk of developing macro- and microvascular disease, nephropathy, and cancer.

Characteristics of primary rhegmatogenous retinal detachment in Taiwan.

PURPOSE: To investigate the epidemiological characteristics and related risk factors for primary rhegmatogenous retinal detachment (RRD) in Taiwan. METHODS: The case-control study was based on retrospective chart review of hospital patients treated for primary RRD from 1995 to 2001, inclusively. The preoperative fundus findings and refractive status were collected for each patient. Controls were selected from a nationwide survey of visual impairment in the adult population during the same period. Risk factors for RRD were analysed by logistic regression. A total of 1032 RRD cases and 3537 controls were enrolled for the study. RESULTS: A pronounced bipeak pattern was evident in the age distribution for primary RRD in the third and sixth decades of life. Atrophic hole with lattice degeneration was preferential to younger (20-30 years) and highly myopic individuals (-7.4+/-5 D), whereas the flap tear tended to occur in middle-aged individuals (50-60 years) and those with moderate myopia (-4.1+/-5 D). The odds ratio for primary RRD with myopia, male gender, and older age (>40 years) were 1.33/D, 2.15, and 1.69, respectively. CONCLUSIONS: Myopia is an important RRD risk factor for young Taiwanese. The increasing prevalence of myopia has predisposed the young population to RRD.

Evidence that involucrin, a marker for differentiation, is oxygen regulated in human squamous cell carcinomas.

The majority of hypoxic cells in squamous cell carcinomas of the head and neck and cervix express involucrin, a molecular marker for differentiation. This raises the question of whether involucrin is an oxygen-regulated protein and, if so, whether it could serve as an endogenous marker for tumour hypoxia. Consistent with oxygen regulation, involucrin protein was found to increase with increasing hypoxia in confluent cultures of moderately differentiated human SCC9 cells. Cells harvested at the point of confluence and exposed to graded concentrations of oxygen revealed a K(m) of approximately 15 mmHg for involucrin induction. This is similar to K(m)s for HIF-1alpha, CAIX and VEGF. Involucrin induction showed a steep dependence on pO(2) with a transition from minimum to maximum expression occurring over less than an order of magnitude change in pO(2). In contrast to SCC9 cells, involucrin was not induced by hypoxia in poorly differentiated SCC4 cells. It is concluded that involucrin is an oxygen-regulated protein, but that differentiation modulates its transcription status with respect to hypoxia induction.

Measuring resident satisfaction in residential aged care.

PURPOSE: The aims of this study were to assess the factor structure, reliability, and validity of an existing Resident Satisfaction Questionnaire (RSQ) and to develop a short-form RSQ for regular use in residential aged care settings. DESIGN AND METHODS: A cross-sectional survey design was adopted to collect the required information, with facilities being selected using stratified random sampling. Both exploratory and confirmatory factor analyses were conducted on a sample of 1,146 residents in 70 residential aged care facilities in Western Australia. RESULTS: The RSQ is confirmed to be a reliable, valid, context-relevant, and easy-to-use instrument for assessing residents' satisfaction with their residential aged care facilities. Resident satisfaction, as assessed via the RSQ, was found to be a multidimensional construct comprising six factors-Room, Home, Social Interaction, Meals Service, Staff Care, and Involvement. IMPLICATIONS: A 24-item short version of the RSQ can be constructed based on the six-factor resident satisfaction measurement model and used as a regular monitoring tool of resident satisfaction for quality improvement purposes.

Semiquantitative immunohistochemical analysis for hypoxia in human tumors.

OBJECTIVE: The goal of this study was to develop a semiquantitative scoring system for measuring hypoxia in human tumors by an immunohistochemical marker approach. METHODS AND MATERIALS: Eighteen patients diagnosed with squamous cell carcinoma of the uterine cervix or head and neck were infused intravenously with a solution of pimonidazole hydrochloride at a dose of 0.5 gm/m2. Twenty-four hours later, four biopsies on average from each tumor were fixed in formalin, processed into paraffin blocks, and sectioned. Tissue sections were immunostained for the presence of pimonidazole adducts. Microscopic images (x200) of immunostaining were captured and quantitated by standard image analysis. Images with known amounts of hypoxia spanning ranges of > 0% to 5%, > 5% to 15%, > 15% to 30%, and >30% were assigned scores of +1, +2, +3, and +4, respectively. Three observers then used this calibrated scoring system to analyze hypoxia in tumor sections in a blinded fashion. RESULTS: Excellent interobserver reproducibility was obtained with the calibrated, semiquantitative, immunohistochemical assay for hypoxia in squamous cell carcinomas. CONCLUSION: The calibrated, semiquantitative assay shows promise as an approach to simplifying the quantitation of human tumor hypoxia by immunohistochemical techniques.

Invasive oxygen measurements and pimonidazole labeling in human cervix carcinoma.

PURPOSE: This study was designed to compare tumor hypoxia assessed by invasive O2 sensitive electrodes and pimonidazole labeling in primary human cervix carcinomas. METHODS AND MATERIALS: Twenty-eight patients with primary cervix carcinomas (FIGO Stage Ib-IVa) were investigated. Both invasive pO2 measurements and pimonidazole labeling were obtained in all patients. Before treatment, patients were given pimonidazole as a single injection (0.5 g/m2 i.v.). Ten to 24 h later, oxygenation measurements were done by Eppendorf histography, and after this procedure biopsies were taken for pimonidazole-binding analysis. Tumor oxygen partial pressure (pO2) was evaluated as the median tumor pO2 and the fraction of pO2 values < or = 10 mmHg (HF10). Biopsies were formalin fixed and paraffin embedded, and hypoxia was detected by immunohistochemistry using monoclonal antibodies directed against reductively activated pimonidazole. Pimonidazole binding was evaluated by a semiquantitative scoring system. RESULTS: Both Eppendorf measurements and pimonidazole binding showed large intra-and intertumor variability. A comparison between pimonidazole binding expressed as the fraction of fields at the highest score and HF10 showed a trend for the most well-oxygenated tumors having a low fraction of fields; however, the correlation did not reach statistical significance (p = 0.43, r = 0.165; Spearman's rank correlation test). CONCLUSION: Hypoxia measured in human uterine cervix carcinomas is heterogeneously expressed both within and between tumors when assessed by either invasive pO2 measurements or pimonidazole binding. Despite a trend that tumors with high pO2 values expressed less pimonidazole binding, no correlation was seen between the two assays in this preliminary report.

Long-term effects of ketoconazole in the treatment of residual or recurrent Cushing's disease.

Ketoconazole is an imidazole derivative used to treat systemic and superficial mycoses by inhibiting sterol synthesis in fungi. The drug impairs steroid hormone synthesis by blocking mitochondrial P450-dependent enzyme systems. Because of its potent inhibitory effects on adrenal steroidogenesis, ketoconazole is valuable in controlling hypercortisolism. We investigated the effects of long-term treatment of this drug on three patients who had residual or recurrent Cushing's disease after surgical treatment. Ketoconazole was administered orally and adjusted according to individual response and 24-hour urinary free cortisol excretion levels. All three patients had good clinical and biochemical responses to ketoconazole therapy without adverse effects. The 24-hour urinary free cortisol levels were kept around 114.8+/-52.4 microg/24 h, 143.0+/-59.9 microg/24 h, and 122.9+/-79.9 microg/24 h, respectively (reference range, 35 to 120 microg/24 h). All three patients had follow-up magnetic resonance imaging or computed tomography of the pituitary gland, which revealed no significant changes in the sellar region. Daily ketoconazole doses ranged from 200 to 1200 mg per day. Follow-up periods were 65, 86, and 83 months, respectively. In conclusion, ketoconazole is valuable in the long-term treatment of residual or recurrent Cushing's disease when surgical treatment is contraindicated or unsuccessful.

The effects of glurenorm on plasma glucose and lipids in patients with type 2 diabetes mellitus.

BACKGROUND: The effects of sulfonylureas on plasma glucose, lipids, and macrovascular complications are of interest. This study was designed to investigate the effects of glurenorm on plasma glucose and lipids in patients with type 2 diabetes mellitus. METHODS: Nineteen patients, 15 men and 4 women, with an age range of 38-69 years, and with type 2 diabetes mellitus, were studied. Plasma glucose, glycated hemoglobin, and lipids were compared before and 3 months after glurenorm treatment. RESULTS: Fasting and postprandial plasma glucose, and HbA1c significantly improved after 3 months of glurenorm treatment. The mean (+/- SD) triglyceride level of 10 patients with mild to moderate hypertriglyceridemia decreased from 279 +/- 66 to 219 +/- 100 mg/dl (p = 0.054). The total cholesterol, low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) of 14 hypercholesterolemic patients did not change significantly. Their mean body weight increased significantly from 65.7 +/- 9.6 to 67.2 +/- 9.9 kg (p = 0.002). CONCLUSION: Glurenorm was effective for glycemic control but caused weight gain in type 2 diabetic patients. Triglycerides in hypertriglyceridemic patients, and total cholesterol, LDL-C, and HDL-C in hypercholesterolemic patients did not improve after glurenorm treatment.

Familial defective apolipoprotein B-100: detection and haplotype analysis of the Arg(3500)-->Gln mutation in hyperlipidemic Chinese.

Familial defective apolipoprotein (apo) B-100 (FDB) is caused by R3500Q mutation of the apo B gene resulting in decreased binding of LDL to the LDL receptor. Two other apo B mutations, R3500W and R3531C, affecting binding are known to date. We screened the apo B gene segment around codon 3500 by heteroduplex analysis and single strand conformation polymorphism (SSCP) analysis in a total of 373 hyperlipidemic individuals. Two single-base mutations were detected and confirmed by DNA sequencing. One mutation, ACA(3528)-->ACG change, resulted in degenerate codon with no amino acid substitution. The other mutation, CGG(3500)-->CAG mutation, resulted in an Arg(3500)-->Gln substitution (R3500Q). The prevalence of heterozygote in this selected population was 0.3% (95% confidence interval, 0.01-1.5%) for the R3500Q mutation, and 2.4% (95% confidence interval, 1.1-4.5%) for the previously described R3500W mutation. The results suggest that the R3500Q mutation is not a significant factor contributing to moderate hypercholesterolemia in Chinese (P=0.027). Family studies of the R3500Q carrier revealed a further two individuals heterozygous for the mutation, both of whom were hypercholesterolemic. Analysis of the R3500Q allele using six diallelic markers and the 3'HVR marker revealed a haplotype which was the same as that reported in a Chinese American but differed from that reported in a Chinese Canadian. Our data support limited multiple recurrent origins for R3500Q in Chinese population.

A clinical study of hypoxia and metallothionein protein expression in squamous cell carcinomas.

The objective was to discover whether the oxygen-regulated protein, metallothionein, is expressed in the hypoxic cells of squamous cell carcinomas. Twenty patients with squamous cell carcinoma of the uterine cervix or head and neck were infused with a solution of the hypoxia marker, pimonidazole hydrochloride, at a dose of 0.5 g/m2. The following day, biopsies were collected, formalin fixed, paraffin embedded, and sectioned at 4 microm. Sections from each biopsy were immunostained for pimonidazole binding, metallothioneins I and II, involucrin, and proliferating cell nuclear antigen. A total of 84 biopsies were analyzed. Sixty-four of 84 biopsy sections contained hypoxia. Of the hypoxia-containing sections, 43 of 64 or 67% showed no microregional overlap between hypoxia and metallothionein; 7 of 64 showed overlap; and 14 of 64 showed a combination of overlap and no overlap. On a tumor-by-tumor basis, 5 of 7 head and neck and 7 of 13 cervix tumors showed no overlap between metallothionein and hypoxia at the microregional level. Ranges for the percentage of the area of hypoxia in head and neck (<0.9 to 17%) and cervix (<0.1 to 14%) tumors were similar. In the hypoxia-containing sections, immunostaining for involucrin, a molecular marker for differentiation, overlapped with that for hypoxia in 82% of the cases. The majority of hypoxic cells in squamous cell carcinomas do not express metallothionein protein, although metallothionein is induced by hypoxia in human tumor cells in vitro. Hypoxic cells in human tumors tend to be in regions immunostaining for involucrin, and it seems possible that differentiation of hypoxic cells in squamous cell carcinomas might affect metallothionein I and II expression.

Patient perceived quality-of-care in hospital in the context of clinical pathways: development of an approach.

Clinical pathways have been introduced in many hospitals with the aims of improving efficiency, reducing costs, and improving the quality and outcomes of care. However, there is a shortage of research evidence regarding the extent to which they do in fact achieve such aims. This paper describes the development and testing of a patient-perceived quality-of-care questionnaire for use in relation to the assessment of clinical pathways. Issues of validity and reliability are addressed and illustrative examples of results for two pilot hospitals are presented.

Binge drinking disturbs hepatic microcirculation after transplantation: prevention with free radical scavengers.

Disturbances in hepatic microcirculation increase graft injury and failure; therefore, this study evaluates the effects of ethanol on microcirculation after liver transplantation. Donor rats were given one dose of ethanol (5 g/kg) by gavage 20 h before explantation, and grafts were stored in University of Wisconsin solution for 24 h before implantation. Acute ethanol treatment decreased 7-day survival of grafts from about 90 to 30%, increased transaminase release nearly 4-fold, and decreased bile production by 60%. Moreover, portal pressure increased significantly and liver surface oxygen tension decreased about 50%, indicating that ethanol disturbs hepatic microcirculation. Pimonidazole, a 2-nitroimidazole hypoxia marker, was given i.v. to recipients 30 min after implantation, and grafts were harvested 1 h later. Ethanol increased hepatic pimonidazole binding about 3-fold, indicating that ethanol led to hypoxia in fatty grafts. Ethanol also significantly increased free radicals in bile. Catechin (30 mg/kg i.v. upon reperfusion), a free radical scavenger, and Carolina Rinse solution, which contains several agents that inhibit free radical formation, minimized disturbances in microcirculation and prevented pimonidazole adduct formation significantly. These treatments also blunted increases in transaminase release and improved survival of fatty grafts. Destruction of Kupffer cells with GdCl(3) (20 mg/kg i.v. 24 h before explantation) or inhibition of formation of leukotrienes with MK-886 (50 microM in University of Wisconsin or rinse solution) also minimized hypoxia and improved survival after transplantation. Taken together, these results demonstrate that ethanol disturbs hepatic microcirculation, leading to graft hypoxia after transplantation, most likely by activating Kupffer cells and increasing free radical production.

Comparisons among pimonidazole binding, oxygen electrode measurements, and radiation response in C3H mouse tumors.

Pimonidazole binding was compared with oxygen electrode measurements and with measurements of the radiobiologically hypoxic fraction in C3H mammary tumors in which oxygenation was manipulated by means of subjecting tumor-bearing CDF1 mice to air breathing, carbogen breathing, oxygen breathing, hydralazine injection or tumor clamping. Hypoxia measured by pimonidazole binding could be correlated with both pO2 (r2 = 0.81) and radiobiologically hypoxic fraction (r2 = 0.85) in this system. The scope and limitation of pimonidazole as an immunohistochemical marker for tumor hypoxia is discussed.

Preliminary studies on target antigens for the diagnosis of Trichomonas vaginalis infection.

Trichomonas vaginalis, a parasitic protozoa residing in the human urogenital tract, causes one of the most common sexually transmitted diseases, trichomoniasis. Clinical diagnosis of T. vaginalis infection mainly involves a wet-mount microscopic examination, and a culture method, and both of which are either laborious or time-consuming. An immunodiagnostic strategy is under development, which is based on the fact that T. vaginalis releases various protein factors, notably proteinases, into the culture medium, some of which can also be detected in vaginal washes. These factors are closely related to the clinical presentation of trichomonad vaginitis, and thusly may serve as potential earmarks for diagnosis. We have attempted to identify the most appropriate target antigen(s) by screening and analyzing the profile of T. vaginalis antigens existing in patient's vaginal secretion, using the antiserum raised against the total secretory antigens from T. vaginalis cultures. Two T. vaginalis antigens with molecular weights near 110 KDa have been demonstrated to be useful antigens as the diagnostic markers.

Effects of prolonged ACTH-stimulation on adrenocortical accumulation of lipofuscin granules in aged rats.

Subcellular deposition of lipofuscin granules is a marker of aging. Human and rodent adrenal cortices accumulate lipofuscin granules with age, but the mechanism that leads to the accumulation is not known. The ultrastructural appearance of lipofuscin granules resembles that of secondary lysosomes. Since adrenocortical subcellular events are predominantly influenced by ACTH action, we therefore studied the effect of prolonged ACTH-stimulation on adrenocortical accumulation of secondary lysosome-like granules, designated herein as lipofuscin granules. Using aged Fischer 344 male rats as a model, we found that a 7 day ACTH stimulation exerts a reducing effect on adrenocortical lipofuscin accumulation. Thus, adrenocortical accumulation of lipofuscin granules with age in vivo may not be an irreversible process.

Relationship of hypoxia to metallothionein expression in murine tumors.

PURPOSE: To investigate if metallothionein, an endogenous chemo- and radioprotectant, is expressed in hypoxic cells in mouse C3H mammary carcinomas and if that expression responds to acute changes in tumor hypoxia. METHODS AND MATERIALS: C3H mammary tumors were established in the hind legs of female CDF1 mice. The mice were then subjected to air breathing (chronic hypoxia), carbogen breathing (acute decrease in hypoxia), or hydralazine injection (acute increase in hypoxia). Ninety minutes after the start of the experiment, tumors were excised, fixed in formalin, and sectioned. Hypoxic cells and metallothionein-containing cells were quantitated by image analysis. Pimonidazole hydrochloride and an IgG1 mouse monoclonal antibody were used to detect hypoxia, and a mouse antimetallothionein monoclonal antibody (DAKO) was used to detect Type I and II metallothionein in sets of contiguous tissue sections. RESULTS: The distribution of immunostaining intensity for metallothionein was the same in all three groups-heavy in hypoxic cells and light in other regions of the tumors. The acute increase in hypoxia caused by hydralazine injection was accompanied by an increase in metallothionein expression (p = 0.04). Carbogen breathing largely eliminated pimonidazole binding, but metallothionein expression persisted in the tumors of carbogen-breathing mice. CONCLUSIONS: Hypoxic cells in C3H mammary carcinomas strongly express metallothionein. Metallothionein expression is responsive to acute increases in hypoxia brought about by hydralazine injection. The effectiveness of hydralazine in enhancing the activation of bioreductive cytotoxins might be offset by the increased expression of metallothionein. The persistence of metallothionein in tumors of carbogen-breathing mice might contribute to a residual radioresistance in the tumors.

Effects of prolonged ACTH-stimulation on adrenocortical cholesterol reserve and apolipoprotein E concentration in young and aged Fischer 344 male rats.

Changes in the morphology of rat adrenal cortex with age include increased accumulations of lipid droplets and lipofuscin granules. Because glandular concentrations of cholesteryl esters (CE) and apolipoprotein (apo) E are also increased in parallel, the utilization or metabolism of lipid-droplet stored CE for steroidogenesis might be altered in aging cells. To explore this possibility, adrenocortical cholesterol storage and utilization were studied in 3-6 months-old (mo) (Y) rats and 20-23 mo (O) Fischer 344 male rats. Both groups received either adrenocorticotropin (ACTH1-39, Acthar gel) or gelatin alone daily for seven consecutive days. We found that: (a) the CE concentration in O rats, but not Y animals, was diminished by ACTH. The depleted CE in stimulated-O rats was replenished within five days post stimulation. Failure to deplete CE in stimulated-Y rats was not associated with an insufficient dose of the hormone, since stimulation of Y animals with higher doses of ACTH actually increased the CE concentration. In contrast, adrenocortical free cholesterol concentration remained constant during stimulation regardless of age. (b) The depleted CE in stimulated-O rats was principally comprised of cholesteryl adrenate, cholesteryl arachidonate and cholesteryl cervonate. The accumulated CE in stimulated-Y animals was primarily comprised of cholesteryl adrenate, cholesteryl arachidonate and cholesteryl oleate. (c) Whereas in stimulated-Y rats adrenal apoE concentration declined, the concentration in stimulated O animals was well maintained. (d) In vitro, adrenal homogenate or cytosolic fraction from stimulated-O rats displayed a higher capacity to hydrolyze exogenous CE than its Y counterpart. However, cholesterol esterification with external fatty acid substrates in adrenal homogenate or microsomal fraction was comparable in the two age-groups. Our findings revealed altered adrenocortical cholesterol reserve in O rats to cope with prolonged ACTH-stimulation. Changes in apoE levels and CE hydrolysis activity may be factors associated with this alteration. Depletion and accumulation of adrenocortical CE are reflected in parallel changes in cholesteryl adrenate and cholesteryl arachidonate, suggesting physiologic importance of these polyunsaturated fatty acids during sustained steroidogenesis.

Anterior chamber angles shallowing and intraocular pressure after topical pilocarpine.

Pilocarpine has been well recognized as the drug of choice for acute angle-closure glaucoma. The purpose of this study is to clarify quantitatively the change of anterior chamber angle and depth with the passage of time after pilocarpine drop administration. Chamber angles of the four quadrants and chamber depths were measured in 18 normal subjects by Scheimpflug Video Image prior to and 30, 60, and 180 minutes after administration of one drop of 4% pilocarpine in one eye, while the opposite eye served as control. The anterior chamber angle and depth showed a significant shallowing at 30, 60 and 180 minutes after 4% pilocarpine administration with a maximal effect of -3.61 degrees and -0.15 mm at 30 minutes, respectively, while the reduction of intraocular pressure reached its maximal effect at 180 minutes. These facts should be well understood in the treatment of angle-closure glaucoma.

Marking hypoxic cells for complement and cytotoxic T lymphocyte-mediated lysis: using pimonidazole.

Artificial antigens are created when 2-nitroimidazoles bind to hypoxic cells. These antigens have been used in the immunodetection of tumour hypoxia but they might also serve to stimulate immune lysis of hypoxic tumour cells by complement- and cell-mediated processes. In order to test this hypothesis, lymphocytes isolated from the spleens of C3H/HeN mice that had been immunised with pimonidazole-labelled 3152-PRO cells were subcultured and tested for their ability to lyse chromium-51 loaded, pimonidazole-labelled 3152-PRO cells in an in vitro assay. In a parallel study, commercially available, rabbit complement was tested for its ability to lyse pimonidazole-labelled V79-4 cells in the presence of monoclonal antibodies which recognise protein adducts of reductively activated pimonidazole. Complement-mediated cell lysis was measured by means of an MTT assay. Complement-mediated and cell-mediated lysis was observed at pimonidazole concentrations which, in themselves, do not produce cell killing.