In vivo localization of DNA sequences and visualization of large-scale chromatin organization using lac operator/repressor recognition

We report a new method for in situ localization of DNA sequences that allows excellent preservation of nuclear and chromosomal ultrastructure and direct, in vivo observations. 256 direct repeats of the lac operator were added to vector constructs used for transfection and served as a tag for labeling by lac repressor. This system was first characterized by visualization of chromosome homogeneously staining regions (HSRs) produced by gene amplification using a dihydrofolate reductase (DHFR) expression vector with methotrexate selection. Using electron microscopy, most HSRs showed approximately 100-nm fibers, as described previously for the bulk, large-scale chromatin organization in these cells, and by light microscopy, distinct, large-scale chromatin fibers could be traced in vivo up to 5 microns in length. Subsequent experiments demonstrated the potential for more general applications of this labeling technology. Single and multiple copies of the integrated vector could be detected in living CHO cells before gene amplification, and detection of a single 256 lac operator repeat and its stability during mitosis was demonstrated by its targeted insertion into budding yeast cells by homologous recombination. In both CHO cells and yeast, use of the green fluorescent protein-lac repressor protein allowed extended, in vivo observations of the operator-tagged chromosomal DNA. Future applications of this technology should facilitate structural, functional, and genetic analysis of chromatin organization, chromosome dynamics, and nuclear architecture.

Mitochondrial transmission during mating in Saccharomyces cerevisiae is determined by mitochondrial fusion and fission and the intramitochondrial segregation of mitochondrial DNA

To gain insight into the process of mitochondrial transmission in yeast, we directly labeled mitochondrial proteins and mitochondrial DNA (mtDNA) and observed their fate after the fusion of two cells. To this end, mitochondrial proteins in haploid cells of opposite mating type were labeled with different fluorescent dyes and observed by fluorescence microscopy after mating of the cells. Parental mitochondrial protein markers rapidly redistributed and colocalized throughout zygotes, indicating that during mating, parental mitochondria fuse and their protein contents intermix, consistent with results previously obtained with a single parentally derived protein marker. Analysis of the three-dimensional structure and dynamics of mitochondria in living cells with wide-field fluorescence microscopy indicated that mitochondria form a single dynamic network, whose continuity is maintained by a balanced frequency of fission and fusion events. Thus, the complete mixing of mitochondrial proteins can be explained by the formation of one continuous mitochondrial compartment after mating. In marked contrast to the mixing of parental mitochondrial proteins after fusion, mtDNA (labeled with the thymidine analogue 5-bromodeoxyuridine) remained distinctly localized to one half of the zygotic cell. This observation provides a direct explanation for the genetically observed nonrandom patterns of mtDNA transmission. We propose that anchoring of mtDNA within the organelle is linked to an active segregation mechanism that ensures accurate inheritance of mtDNA along with the organelle.

Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes

Ketosis, the metabolic response to energy crisis, is a mechanism to sustain life by altering oxidative fuel selection. Often overlooked for its metabolic potential, ketosis is poorly understood outside of starvation or diabetic crisis. Thus, we studied the biochemical advantages of ketosis in humans using a ketone ester-based form of nutrition without the unwanted milieu of endogenous ketone body production by caloric or carbohydrate restriction. In five separate studies of 39 high-performance athletes, we show how this unique metabolic state improves physical endurance by altering fuel competition for oxidative respiration. Ketosis decreased muscle glycolysis and plasma lactate concentrations, while providing an alternative substrate for oxidative phosphorylation. Ketosis increased intramuscular triacylglycerol oxidation during exercise, even in the presence of normal muscle glycogen, co-ingested carbohydrate and elevated insulin. These findings may hold clues to greater human potential and a better understanding of fuel metabolism in health and disease.

Adefovir dipivoxil for the treatment of lamivudine-resistant hepatitis B mutants

Lamivudine has been shown to be an effective therapy for chronic hepatitis B, but resistance to this nucleoside agent is common after prolonged use. Five patients with chronic hepatitis B virus (HBV) infection developed resistance to lamivudine after 9 to 19 months of treatment. In 4 patients this occurred after liver transplantation and the remaining individual had stable cirrhosis. In each case, resistance was confirmed to be caused by one or more mutations in the HBV-DNA polymerase gene and was associated with active underlying liver disease. The patients were treated with adefovir dipivoxil in a dose of 5 to 30 mg daily. Two to 4 log(10) reductions in HBV-DNA levels were observed in 4 cases, and the fifth patient became negative by quantitative polymerase chain reaction (PCR) after retransplantation in conjunction with hepatitis B immunoglobulin (HBIg). Virologic improvement was associated with stable or declining serum alanine transaminase levels in 4 patients. HBV-DNA suppression has been sustained during a mean treatment period of 13 months (range 11 to 15 months), including 1 patient in whom lamivudine has been discontinued. Mild changes in renal function were observed during treatment in most cases but did not require early discontinuation of the drug. This study provides evidence that adefovir dipivoxil can be an effective treatment for lamivudine-resistant HBV mutants as well as wild-type HBV.

Studies on intercellular LETS glycoprotein matrices

Intercellular matrices secreted by chick embryo fibroblasts in culture were studied by scanning electron microscopy. Cell-cell contact is a prerequisite for the expression of such matrices. The smallest fiber detected by transmission electron microscopy is 5--10 nm in diameter. These matrix fibers tend to cluster to form bundles. Immunofluorescence and immunoferritin procedures reveal that LETS protein is one of the components of the matrices. The matrices are isolated from other cellular organelles by detergent treatment. More than 90% of the proteins in cell-free matrices are LETS protein, suggesting that the matrices are probably made of only one component--LETS protein. Since the solubilization of matrices requires beta-mercaptoethanol, LETS protein matrices may be the first known polymer system in nature to use disulfide linkage as an intermolecular polymerization vehicle. Collagen does not appear to be involved in such matrices. The LETS protein matrix supports the morphological conversion of rounded cells into spindle-shaped, and also promotes myoblast fusion. It does not, however, exert an effect upon cell growth, the rate of glucose uptake or protease production.

Immediate heart-rate response to standing: simple test for autonomic neuropathy in diabetes

The immediate heart-rate response to standing was measured in 22 normal controls and 25 patients with diabetes, 15 of whom had autonomic neuropathy. The response in the controls and patients without autonomic neuropathy was characteristic and consistent, with tachycardia maximal at around the 15th beat and relative bradycardia maximal at around the 30th beat. The diabetics with autonomic neuropathy, however, showed a flat response. In three controls the response was abolished with intravenous atropine but not with propranolol, showing that it is mediated through the vagus. A simplified test using routine ECGs and measuring the R-R interval at beats 15 and 30 with a ruler is easily performed as an outpatient procedure and may be used as a measure of autonomic function in diabetes.

Pharmacological PKA inhibition: all may not be what it seems

Signaling through the cyclic adenosine monophosphate-dependent protein kinase [protein kinase A (PKA)] is an important and widely studied area of signal transduction research. This signaling pathway is commonly investigated through the use of the pharmacological PKA inhibitors H89 and KT 5720. Both of these compounds are thought to block PKA actions through competitive inhibition of the adenosine triphosphate site on the PKA catalytic subunit. Recently, a number of studies have identified actions of H89 and KT 5720 that are independent of their effects on PKA. These nonspecific effects are widespread; they include actions on other protein kinases and signaling molecules and also on basic cellular functions, such as transcription. Here, I summarize the nonspecific effects of these two compounds and compare their actions with those of other PKA inhibitors.

Dynamics of centromeres during metaphase-anaphase transition in fission yeast: Dis1 is implicated in force balance in metaphase bipolar spindle

In higher eukaryotic cells, the spindle forms along with chromosome condensation in mitotic prophase. In metaphase, chromosomes are aligned on the spindle with sister kinetochores facing toward the opposite poles. In anaphase A, sister chromatids separate from each other without spindle extension, whereas spindle elongation takes place during anaphase B. We have critically examined whether such mitotic stages also occur in a lower eukaryote, Schizosaccharomyces pombe. Using the green fluorescent protein tagging technique, early mitotic to late anaphase events were observed in living fission yeast cells. S. pombe has three phases in spindle dynamics, spindle formation (phase 1), constant spindle length (phase 2), and spindle extension (phase 3). Sister centromere separation (anaphase A) rapidly occurred at the end of phase 2. The centromere showed dynamic movements throughout phase 2 as it moved back and forth and was transiently split in two before its separation, suggesting that the centromere was positioned in a bioriented manner toward the poles at metaphase. Microtubule-associating Dis1 was required for the occurrence of constant spindle length and centromere movement in phase 2. Normal transition from phase 2 to 3 needed DNA topoisomerase II and Cut1 but not Cut14. The duration of each phase was highly dependent on temperature.

Dendritic cells from patients with myeloma are numerically normal but functionally defective as they fail to up-regulate CD80 (B7-1) expression after huCD40LT stimulation because of inhibition by transforming growth factor-beta1 and interleukin-10

Limited response to idiotype vaccination in patients with myeloma suggests that there is a need to develop better immunotherapy strategies. It has been determined that the number of high-potency CMRF44+CD14-CD19- dendritic cells (DCs) in the blood of patients with myeloma (range, 0.03%-0.8% of mononuclear cells [MNCs]; n = 26) was not significantly different from that in controls (range, 0.05%-0.8% of MNCs; n = 13). Expression of the costimulatory molecules CD80 and CD86 on DCs from these patients (mean, 29%+/-17% of MNCs and 85%+/-10% of MNCs, respectively) was also normal (mean, 29%+/-17% and 86%+/-16% of MNCs, respectively). Up-regulation of CD80 expression in response to stimulation by human huCD40LT + interleukin (IL)-2 was significantly reduced on the DCs of patients with myeloma during stable disease (n = 9) and was absent during progressive stages (n = 7) of disease. Similar effects were seen on B cells but not on monocytes of the same group of patients. CD86 expression on DCs was high before (86%) and after (89%) stimulation. Inhibition of CD80 up-regulation was neutralized by either anti-transforming growth factor (TGF)-beta1 or anti-IL-10. Up-regulation of CD80 on DCs of controls was inhibited by rTGF-beta1 in a dose-dependent manner. Serum TGF-beta1 and IL-10 levels were normal in most patients studied. Cytoplasmic TGF-beta1 was increased in plasma cells during progressive disease. Thus patients with myeloma have normal numbers of DCs, but CD80 expression may fail to be up-regulated in the presence of huCD40LT because of tumor-derived TGF-beta1 or IL-10. Autologous high-potency DCs may have to be tested for CD80 up-regulation and biologically modified ex vivo before idiotype priming for immunotherapy.

Human papillomavirus type 16 DNA cooperates with activated ras in transforming primary cells

The close association of human papillomavirus type 16 DNA with a majority of cervical carcinomas implies some role for the virus in this type of cancer. To define the transforming properties of HPV-16 DNA in vitro we have now performed transfection experiments on baby rat kidney cells using HPV-16 DNA in conjunction with an activated ras gene. We have demonstrated that a 6.6-kb DNA fragment, containing the early genes of HPV-16 under the control of Moloney murine leukaemia virus long terminal repeats (MoMuLV-LTRs), cooperates with EJ-ras in transforming these cells. Both DNAs are required and neither alone is effective. The cooperating activity appears to reside in a protein or proteins derived from the E6/E7 region of the HPV-16 genome.

Neuronal programming by microbiota regulates intestinal physiology

Neural control of the function of visceral organs is essential for homeostasis and health. Intestinal peristalsis is critical for digestive physiology and host defence, and is often dysregulated in gastrointestinal disorders¹. Luminal factors, such as diet and microbiota, regulate neurogenic programs of gut motility^2-5, but the underlying molecular mechanisms remain unclear. Here we show that the transcription factor aryl hydrocarbon receptor (AHR) functions as a biosensor in intestinal neural circuits, linking their functional output to the microbial environment of the gut lumen. Using nuclear RNA sequencing of mouse enteric neurons that represent distinct intestinal segments and microbiota states, we demonstrate that the intrinsic neural networks of the colon exhibit unique transcriptional profiles that are controlled by the combined effects of host genetic programs and microbial colonization. Microbiota-induced expression of AHR in neurons of the distal gastrointestinal tract enables these neurons to respond to the luminal environment and to induce expression of neuron-specific effector mechanisms. Neuron-specific deletion of Ahr, or constitutive overexpression of its negative feedback regulator CYP1A1, results in reduced peristaltic activity of the colon, similar to that observed in microbiota-depleted mice. Finally, expression of Ahr in the enteric neurons of mice treated with antibiotics partially restores intestinal motility. Together, our experiments identify AHR signalling in enteric neurons as a regulatory node that integrates the luminal environment with the physiological output of intestinal neural circuits to maintain gut homeostasis and health.

Risk of recurrence of bipolar disorder in pregnant and nonpregnant women after discontinuing lithium maintenance

OBJECTIVE

Pregnancy poses major challenges for the treatment of bipolar disorder, and information to guide clinical care remains very sparse. The authors sought to determine the illness recurrence risk for women with bipolar disorder who discontinue lithium maintenance during pregnancy.

METHOD

The authors retrospectively compared recurrence rates and survival functions for 101 women with DSM-IV bipolar disorder (68 type I, 33 type II) during pregnancy and postpartum (N=42) or during equivalent periods (weeks 1-40 and 41-64) for age-matched nonpregnant subjects (N=59) after either rapid (1-14 days) or gradual (15-30 days) discontinuation of lithium. Recurrence rates also were obtained for the year before discontinuing lithium.

RESULTS

Rates of recurrence during the first 40 weeks after lithium discontinuation were similar for pregnant (52%) and nonpregnant women (58%) but had been much lower for both in the year before treatment was discontinued (21%). Among subjects who remained stable over the first 40 weeks after lithium discontinuation, postpartum recurrences were 2.9 times more frequent than recurrences in nonpregnant women during weeks 41-64 (70% versus 24%). Depressive or dysphoric-mixed episodes were more prevalent in pregnant than nonpregnant women (63% versus 38% of recurrences). Recurrence risk was greater after rapid than after gradual discontinuation, and for patients with more prior affective episodes, but was similar for diagnostic types I and II.

CONCLUSIONS

Rates of recurrence during the first 40 weeks after lithium discontinuation were similar for pregnant and nonpregnant women but then sharply increased postpartum. Risk was much lower during preceding treatment and less with gradual discontinuation. Treatment planning for potentially pregnant women with bipolar disorder should consider the relative risks of fetal exposure to mood stabilizers versus the high recurrence risks after discontinuing lithium.

Systematic comparison of different algorithms for apnoea detection based on electrocardiogram recordings

Sleep apnoea is a common disorder that is usually diagnosed through expensive studies conducted in sleep laboratories. Sleep apnoea is accompanied by a characteristic cyclic variation in heart rate or other changes in the waveform of the electrocardiogram (ECG). If sleep apnoea could be diagnosed using only the ECG, it could be possible to diagnose sleep apnoea automatically and inexpensively from ECG recordings acquired in the patient's home. This study had two parts. The first was to assess the ability of an overnight ECG recording to distinguish between patients with and without apnoea. The second was to assess whether the ECG could detect apnoea during each minute of the recording. An expert, who used additional physiological signals, assessed each of the recordings for apnoea. Research groups were invited to access data via the world-wide web and submit algorithm results to an international challenge linked to a conference. A training set of 35 recordings was made available for algorithm development, and results from a test set of 35 different recordings were made available for independent scoring. Thirteen algorithms were compared. The best algorithms made use of frequency-domain features to estimate changes in heart rate and the effect of respiration on the ECG waveform. Four of these algorithms achieved perfect scores of 100% in the first part of the study, and two achieved an accuracy of over 90% in the second part of the study.

Autoantibodies in breast cancer: their use as an aid to early diagnosis

BACKGROUND

There is increasing evidence that the immune system produces a humoral response to cancer-derived antigens. This study assessed the diagnostic potential of autoantibodies to multiple known tumour-associated proteins.

PATIENTS AND METHODS

Sera from normal controls (n = 94), primary breast cancer patients (n = 97) and patients with ductal carcinoma in situ (DCIS) (n = 40) were investigated for the presence of autoantibodies to p53, c-myc, HER2, NY-ESO-1, BRCA1, BRCA2 and MUC1 antigens by enzyme-linked immunosorbent assay.

RESULTS

Reproducibly elevated levels of autoantibodies were seen in at least one of the six antigens in 64% of primary breast cancer patient sera and 45% of patients with DCIS at a specificity of 85%. No significant differences were seen when patients were subdivided by age, tumour size, histological grade, lymph node status or detection methodology.

CONCLUSIONS

Autoantibodies against one or more of these tumour-associated antigens appears to indicate the presence of early-stage breast cancers. Autoantibody assays against a panel of antigens could be used as an aid to mammography in the detection and diagnosis of early primary breast cancer, especially in younger women at increased risk of breast cancer where mammography is known to have reduced sensitivity and specificity.

Uncoupling proteins in human heart

Abnormal energetic activity in heart failure correlates inversely with plasma free-fatty-acid concentrations. However, the link between energetic and metabolic abnormalities is unknown. To investigate this association, we obtained blood samples from 39 patients undergoing coronary artery bypass graft surgery. Patients fasted overnight before samples were taken. When plasma free-fatty-acid concentrations were raised, cardiac mitochondrial uncoupling proteins (UCP) increased (isoform UCP2, p<0.0001; isoform UCP3, p=0.0036) and those of glucose transporter (GLUT4) protein decreased (cardiac, p=0.0001; skeletal muscle, p=0.0006). Consequently, energy deficiency in heart failure might result from increased mitochondrial UCPs (ie, less efficient ATP synthesis) and depleted GLUT4 (ie, reduced glucose uptake). New treatment to correct these energy defects would be to simultaneously lower plasma free fatty acids and provide an alternative energy source.

Rabies Virus CVS-N2c(ΔG) Strain Enhances Retrograde Synaptic Transfer and Neuronal Viability

Virally based transsynaptic tracing technologies are powerful experimental tools for neuronal circuit mapping. The glycoprotein-deletion variant of the SAD-B19 vaccine strain rabies virus (RABV) has been the reagent of choice in monosynaptic tracing, since it permits the mapping of synaptic inputs to genetically marked neurons. Since its introduction, new helper viruses and reagents that facilitate complementation have enhanced the efficiency of SAD-B19(ΔG) transsynaptic transfer, but there has been little focus on improvements to the core RABV strain. Here we generate a new deletion mutant strain, CVS-N2c(ΔG), and examine its neuronal toxicity and efficiency in directing retrograde transsynaptic transfer. We find that by comparison with SAD-B19(ΔG), the CVS-N2c(ΔG) strain exhibits a reduction in neuronal toxicity and a marked enhancement in transsynaptic neuronal transfer. We conclude that the CVS-N2c(ΔG) strain provides a more effective means of mapping neuronal circuitry and of monitoring and manipulating neuronal activity in vivo in the mammalian CNS.

Comparison of the in vitro transforming activities of human papillomavirus types

The association of certain human papillomavirus (HPV) types with the majority of human cervical carcinomas suggests a role for the virus in the development of this type of cancer. In this paper, we have examined the transforming properties of several HPV types where the early region genes of the virus are under the control of a strong heterologous promoter and show that major differences exist between the HPV types in their ability to transform primary rat kidney epithelial cells in conjunction with an activated ras oncogene. Those HPV types most commonly found in carcinomas--types 16, 18, 31 and 33--are capable of co-operating with ras to transform primary cells, but those types most commonly found in benign lesions--types 6 and 11--are not. We further demonstrate that the E7 gene of HPV16 by itself is sufficient to co-operate with activated ras to produce transformed cells which are tumorigenic in immunocompetent animals.

Autoantibodies in lung cancer: possibilities for early detection and subsequent cure

BACKGROUND

People with lung cancer usually present at a late stage in the course of their disease when their chances of long-term survival are low. At present there is little to offer for early diagnosis, even in those at high risk of developing the disease. Autoantibodies have been shown to be present in the circulation of people with various forms of solid tumour before cancer-associated antigens can be detected, and these molecules can be measured up to 5 years before symptomatic disease.

OBJECTIVE

To assess the potential of a panel of tumour-associated autoantibody profiles as an aid to other lung cancer screening modalities.

METHODS

Plasma from normal controls (n = 50), patients with non-small cell lung cancer (n = 82) and patients with small cell lung cancer (n = 22) were investigated for the presence of autoantibodies to p53, c-myc, HER2, NY-ESO-1, CAGE, MUC1 and GBU4-5 by enzyme-linked immunosorbent assay.

RESULTS

Raised levels of autoantibodies were seen to at least 1/7 antigens in 76% of all the patients with lung cancer plasma tested, and 89% of node-negative patients, with a specificity of 92%. There was no significant difference between the detection rates in the lung cancer subgroups, although more patients with squamous cell carcinomas (92%) could be identified.

CONCLUSION

Measurement of an autoantibody response to one or more tumour-associated antigens in an optimised panel assay may provide a sensitive and specific blood test to aid the early detection of lung cancer.

Clinical validation of an autoantibody test for lung cancer

Background: Autoantibodies may be present in a variety of underlying cancers several years before tumours can be detected and testing for their presence may allow earlier diagnosis. We report the clinical validation of an autoantibody panel in newly diagnosed patients with lung cancer (LC).

Patients and methods: Three cohorts of patients with newly diagnosed LC were identified: group 1 (n = 145), group 2 (n = 241) and group 3 (n = 269). Patients were individually matched by gender, age and smoking history to a control individual with no history of malignant disease. Serum samples were obtained after diagnosis but before any anticancer treatment. Autoantibody levels were measured against a panel of six tumour-related antigens (p53, NY-ESO-1, CAGE, GBU4-5, Annexin 1 and SOX2). Assay sensitivity was tested in relation to demographic variables and cancer type/stage.

Results: The autoantibody panel demonstrated a sensitivity/specificity of 36%/91%, 39%/89% and 37%/90% in groups 1, 2 and 3, respectively, with good reproducibility. There was no significant difference between different LC stages, indicating that the antigens included covered the different types of LC well.

Conclusion: This assay confirms the value of an autoantibody panel as a diagnostic tool and offers a potential system for monitoring patients at high risk of LC.

Molecular and phylogenetic characterisation of Cryptosporidium from birds

Avian isolates of Cryptosporidium species from different geographic locations were sequenced at two loci, the 18S rRNA gene and the heat shock gene (HSP-70). Phylogenetic analysis of the sequence data provided support for the existence of a new avian species of Cryptosporidium infecting finches and a second species infecting a black duck. The identity of Cryptosporidium baileyi and Cryptosporidium meleagridis as valid species was confirmed. Also, C. baileyi was identified in a number of isolates from the brown quail extending the host range of this species.

Autonomic dysfunction in dementia

BACKGROUND

There are no studies of autonomic function comparing Alzheimer's disease (AD), vascular dementia (VAD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD).

AIMS

To assess cardiovascular autonomic function in 39 patients with AD, 30 with VAD, 30 with DLB, 40 with PDD and 38 elderly controls by Ewing's battery of autonomic function tests and power spectral analysis of heart rate variability. To determine the prevalence of orthostatic hypotension and autonomic neuropathies by Ewing's classification.

RESULTS

There were significant differences in severity of cardiovascular autonomic dysfunction between the four types of dementia. PDD and DLB had considerable dysfunction. VAD showed limited evidence of autonomic dysfunction and in AD, apart from orthostatic hypotension, autonomic functions were relatively unimpaired. PDD showed consistent impairment of both parasympathetic and sympathetic function tests in comparison with controls (all p<0.001) and AD (all p<0.03). DLB showed impairment of parasympathetic function (all p<0.05) and one of the sympathetic tests in comparison with controls (orthostasis; p = 0.02). PDD had significantly more impairment than DLB in some autonomic parameters (Valsalva ratio: p = 0.024; response to isometric exercise: p = 0.002). Patients with VAD showed impairment in two parasympathetic tests (orthostasis: p = 0.02; Valsalva ratio: p = 0.08) and one sympathetic test (orthostasis: p = 0.04). These results were in contrast with AD patients who only showed impairment in one sympathetic response (orthostasis: p = 0.004). The prevalence of orthostatic hypotension and autonomic neuropathies was higher in all dementias than in controls (all p<0.05).

CONCLUSION

Autonomic dysfunction occurs in all common dementias but is especially prominent in PDD with important treatment implications.

Summary report on the ISOBM TD-4 Workshop: analysis of 56 monoclonal antibodies against the MUC1 mucin. San Diego, Calif., November 17-23, 1996

Sixteen research groups participated in the ISOBM TD-4 Workshop in which the reactivity and specificity of 56 monoclonal antibodies against the MUC1 mucin was investigated using a diverse panel of target antigens and MUC1 mucin-related synthetic peptides and glycopeptides. The majority of antibodies (34/56) defined epitopes located within the 20-amino acid tandem repeat sequence of the MUC1 mucin protein core. Of the remaining 22 antibodies, there was evidence for the involvement of carbohydrate residues in the epitopes for 16 antibodies. There was no obvious relationship between the type of immunogen and the specificity of each antibody. Synthetic peptides and glycopeptides were analyzed for their reactivity with each antibody either by assay of direct binding (e.g. by ELISA or BiaCore) or by determining the capacity of synthetic ligands to inhibit antibody binding interactions. There was good concordance between the research groups in identifying antibodies reactive with peptide epitopes within the MUC1 protein core. Epitope mapping tests were performed using the Pepscan analysis for antibody reactivity against overlapping synthetic peptides, and results were largely consistent between research groups. The dominant feature of epitopes within the MUC1 protein core was the presence, in full or part, of the hydrophilic sequence of PDTRAPAP. Carbohydrate epitopes were less easily characterized and the most useful reagents in this respect were defined oligosaccharides, rather than purified mucin preparations enriched in particular carbohydrate moieties. It was evident that carbohydrate residues were involved in many epitopes, by regulating epitope accessibility or masking determinants, or by stabilizing preferred conformations of peptide epitopes within the MUC1 protein core. Overall, the studies, highlight concordance between groups rather than exposing inconsistencies which gives added confidence to the results of analyses of the specificity of antimucin monoclonal antibodies.