John P. Seery

Asymmetric stem-cell divisions define the architecture of human oesophageal epithelium

In spite of its clinical importance, little is known about the stem-cell compartment of the human oesophageal epithelium [1,2]. The epithelial basal layer consists of two distinct zones, one overlying the papillae of the supporting connective tissue (PBL) and the other covering the interpapillary zone (IBL) [3]. In examining the oesophageal basal layer, we found that proliferating cells were rare in the IBL and a high proportion of mitoses were asymmetrical, giving rise to one basal daughter and one suprabasal, differentiating daughter. In the PBL, mitoses were more frequent and predominantly symmetrical. The IBL was characterised by low expression of ?1 integrins and high expression of the beta2 laminin chain. By combining fluorescence-activated cell sorting (FACS) with in vitro clonal analysis, we obtained evidence that the IBL is enriched for stem cells. A normal oesophageal epithelium with asymmetric divisions was reconstituted on denuded oesophageal connective tissue. In contrast, asymmetric divisions were not sustained on skin connective tissue, and the epithelium formed resembled epidermis. We propose that stem cells located in the IBL give rise to differentiating daughters through asymmetric divisions in response to cues from the underlying basement membrane. Until now, stem-cell fate in stratified squamous epithelia was believed to be achieved largely through populational asymmetry [4-6].

A Proton Magnetic Resonance Spectroscopy Study of the Striatum and Cerebral Cortex in Parkinson's Disease

Animal studies have suggested an increased striatal glutamate activity in Parkinsons disease models, although this has not been substantiated in magnetic resonance spectroscopy studies in patients. Our initial aim was to assess glutamate and glutamine levels in the striatum of patients with idiopathic Parkinsons disease, using multivoxel proton magnetic resonance spectroscopy techniques. Since data were collected from other areas of the brain without a priori selection, information on the cortex was also obtained. Twelve healthy volunteers, seven dyskinetic and five non-dyskinetic patients were studied. Peak area ratios of choline-containing compounds (Cho), glutamine and glutamate (Glx) and N-acetyl moieties including N-acetylaspartate (NAx), relative to creatine (Cr) were calculated. Spectra were analysed from the corpus striatum, the occipital cortex and the temporo-parietal cortex. The median Glx/Cr ratio was unaltered in the striatal spectra of Parkinsons disease patients compared to healthy controls. However, the more severely affected patients had significantly reduced NAx/Cr ratios in spectra localised to the temporo-parietal cortex, compared to healthy controls. Furthermore, the entire patient population had significantly reduced Cho/Cr ratios in spectra from the temporo-parietal cortex, compared to the reference population. We found no evidence of increased striatal glutamate in either dyskinetic or non-dyskinetic Parkinsons disease. However, the low NAx/Cr and Cho/Cr ratios in the temporo-parietal cortex may indicate the presence of subclinical cortical dysfunction.

MR imaging and spectroscopy of the basal ganglia in chronic liver disease: Correlation of T1-weighted contrast measurements with abnormalities in proton and phosphorus-31 MR spectra

The purpose of this study was to correlate the hyperintensity in the globus pallidus seen on T1-weighted magnetic resonance imaging (MRI) of the brain in chronic liver disease with changes in metabolite ratios measured from both proton and phosphorus-31 magnetic resonance spectroscopy (MRS) localised to the basal ganglia. T1-weighted spin echo (T1 WSE) images were obtained in 21 patients with biopsy-proven cirrhosis (nine Childs grade A, eight Childs grade B and four Childs grade C). Four subjects showed no evidence of neuropsychiatric impairment on clinical, psychometric and electrophysiological testing, four showed evidence of subclinical hepatic encephalopathy and 13 had overt hepatic encephalopathy. Signal intensities of the globus pallidus and adjacent brain parenchyma were measured and contrast calculated, which correlated with the severity of the underlying liver disease, when graded according to the Pughs score (p<0.05). Proton MRS of the basal ganglia was performed in 12 patients and 14 healthy volunteers. Peak area ratios of choline (Cho), glutamine and glutamate (Glx) and N-acetylaspartate relative to creatine (Cr) were measured. Significant reductions in mean Cho/Cr and elevations in mean Glx/Cr ratios were observed in the patient population. Phosphorus-31 MRS of the basal ganglia was performed in the remaining nine patients and in 15 healthy volunteers. Peak area ratios of phosphomonoesters (PME), inorganic phosphate, phosphodiesters (PDE) and phosphocreatine relative to BATP (ATP) were then measured. Mean values of PME/ATP and PDE/ATP were significantly lower in the patient population. No correlation was found between the T1WSE MRI contrast measurements of the globus pallidus and the abnormalities in the metabolite ratios measured from either proton or phosphorus-31 MR spectra. Our results suggest that pallidal hyperintensity seen on T1WSE MR imaging of patients with chronic liver disease is not related to the functional abnormalities of the brain observed in hepatic encephalopathy.

PA-FABP, a novel marker of human epidermal transit amplifying cells revealed by 2D protein gel electrophoresis and cDNA array hybridisation

Human epidermal stem cells express higher levels of β1 integrins than their more differentiated daughters, transit amplifying cells. In a search for additional stem and transit cell markers we used proteomics and differential cDNA hybridisation to compare keratinocytes fractionated on the basis of β1 integrin expression. There were remarkably few differences between the two populations and none of the RNAs differed in abundance by more than 2‐fold. Nevertheless, proteomics revealed upregulated expression of epidermal fatty acid binding protein (PA‐FABP, also known as E‐FABP), Annexin II and two keratin related proteins in the transit population. An unknown high molecular mass protein was upregulated in the stem cell population. The upregulation of PA‐FABP was confirmed by Northern blotting and conventional and whole mount labelling of human epidermis. We conclude that PA‐FABP is a novel marker of epidermal transit amplifying cells.

Pathogenesis and treatment of chronic hepatic encephalopathy

The various treatment strategies for hepatic encephalopathy are compared in the light of the available body of scientific work on the pathogenesis of the syndrome. Data on animal models of hepatic encephalopathy and in vitro studies on brain slices are discussed. Difficulties in extrapolating the results obtained to the human situation are highlighted, while results of human positron emission tomography and magnetic resonance spectroscopy studies are outlined on the background of the potential weaknesses of these non‐invasive techniques.

Abnormal expression of the E-cadherin-catenin complex in dysplastic Barrett's oesophagus.

It is now accepted that altered E-cadherin-catenin complex expression in oesophageal cancer correlates with clinical and pathological parameters, while abnormal E-cadherin expression occurs early in Barretts oesophagus. We evaluated immunohistochemically the expression and cellular localization of alpha-, beta-, and gamma-catenin, and E-cadherin in 5 dysplastic and 26 non-dysplastic cases of Barretts oesophagus. Usually all three catenins were localized at the cell membrane, as was E-cadherin. A similar staining pattern for E-cadherin and the catenins was observed in all cases of non-dysplastic Barretts syndrome. However, 60% (3/5) of cases with dysplasia showed loss of membranous beta-catenin staining and diffuse cytoplasmic distribution, with predominantly nuclear localization in two cases. Membranous staining and concomitant cytoplasmic localization of E-cadherin, alpha-catenin and gamma-catenin were seen in one case with abnormal beta-catenin immunoreactivity. Our results indicate that altered subcellular distribution of beta-catenin occurs frequently in dysplastic Barretts oesophagus and possibly reflects the signalling function of this molecule.

IFN-gamma transgenic mice: clues to the pathogenesis of systemic lupus erythematosus?

Transgenic mice overexpressing IFN-γ in the epidermis develop an inflammatory skin disease resembling cutaneous lupus erythematosus shortly after birth. By 3 months of age, most female transgenics develop a lupus-like syndrome characterised by production of IgG anti-dsDNA, antihistone and antinucleosome autoantibodies. The autoantibodies are nephritogenic, with one-third of females developing a severe immune complex mediated glomerulonephritis. Analysis of these transgenics suggests that pathogenic autoantibodies arise via an antigen-driven T-cell-dependent mechanism with apoptotic keratinocytes acting as a potential source of autoantigen. The mechanism of autoantibody production in IFN-γ transgenics may be relevant to human lupus and is consistent with a central role for cutaneous T cells in the pathogenesis of systemic lupus erythematosus in man.

The application of magnetic resonance spectroscopy to the study of hepatic encephalopathy

H EPATIC encephalopathy occurs in two distinct forms. In acute liver failure, the condition progresses rapidly, over a period of days or even hours, and has a high associated mortality if left untreated (1). The predominant neuropathological picture is of cerebral oedema, due to increased permeability of the blood brain barrier (2). Death may result from cerebral coning with herniation of the brain through the basilar foramena, as a result of increased intracranial pressure from the development of cerebral oedema (2). The neuropsychiatric abnormalities affecting patients with chronic liver disease are termed portal-systemic encephalopathy (PSE) or chronic hepatic encephalopathy (CHE). This condition results from either the development of hepatocellular failure or a portasystemic collateral circulation in patients with chronic liver disease. This may arise as a complication of portal hypertension or from the surgical placement of a portasystemic shunt, usually for the management of uncontrolled variceal bleeding (3). Such shunts may be performed by standard surgical techniques or else by using transjugular intrahepatic portasystemic stent shunts (TIPSS), which are placed under radiological guidance. In most patients, encephalopathy results from a combination of these factors. CHE is usually subclinical, affecting reaction times in activities of daily living such as driving and operating machinery (4). It is usually detected in slowing of the electroencephalographic (EEG) frequency or as impairment of psychometric performance (5-7). However in about 30% of patients with chronic liver disease, the syndrome may become clinically overt with alterations in behaviour, mood, personality and disturbances in consciousness (5). The condition is usually characterised by remissions and relapses, although in some pa-

Circadian Rhythm of Cutaneous Hypersensitivity Reactions in Nocturnal Asthma

BACKGROUND Diurnal variation in mast cell discharge may play a central role in the early morning fall in peak expiratory flow rate (PEFR) in nocturnal asthmatic patients. METHODS We tested the hypothesis that there is a circadian rhythm in mast cell response to allergen in 15 patients with nocturnal asthma by measuring the magnitude of cutaneous hypersensitivity reactions at 0600, 1200, 1800, and 2400 hours. Pre-admission, prick skin testing on the ventral aspect of the forearm to various allergens was performed. The allergen producing the largest wheal was tested at six sites on one forearm. Response was quantified after 20 minutes by measuring the area of the wheal produced using planimetry. Every six hours the skin testing was repeated at six new sites on alternating forearms. The average area of the six wheals was calculated and recorded at each time. The prick skin technique was used at all times. RESULTS Maximal reactions occurred in 10 of the 15 patients at noon (P = .031, Friedmans two way analysis of variance). In these 10 patients wheal area at the time of maximum reactivity was on average 3.3-fold higher than at the time of minimum reactivity. The mean wheal areas for all 15 patients at 0600, 1200, 1800, and 2400 hours were 34 mm2, 42 mm2, 34 mm2, and 35 mm2 respectively. CONCLUSIONS These observations support the concept of a circadian rhythm in mast cell activity in patients with severe nocturnal asthma.

A reinterpretation of the events in gastric carcinogenesis

It is proposed here that the initial events in gastric carcinogenesis occur at the junction of the oxyntic and antral mucosae. Intestinal metaplasia represents an adaptive counter-response to early neoplastic change at this site. Chronic gastric ulceration may arise due to the elimination of overtly dedifferentiated cells at a later stage in the evolution of the neoplastic process. Intestinal type gastric carcinoma possibly represents breakthrough past these mechanisms.