Function and interactions of integrins

Integrins are heterodimeric cell adhesion molecules that link the extracellular matrix to the cytoskeleton. The integrin family in man comprises 24 members, which are the result of different combinations of 1 of 18 alpha- and 1 of 8 beta-subunits. Alternative splicing of mRNA of some alpha- and beta-subunits and postranslational modifications of integrin subunits further increase the diversity of the integrin family. In their capacity as adhesion receptors that organize the cytoskeleton, integrins play an important role in controlling various steps in the signaling pathways that regulate processes as diverse as proliferation, differentiation, apoptosis, and cell migration. The intracellular signals that lead to these effects may be transduced via cytoplasmic components, which have been identified as integrin-binding proteins in yeast two-hybrid screens and which could mediate the coupling of integrins to intracellular signaling pathways. In this review an overview is given of the function and ligand-binding properties of integrins as well as of proteins that associate with integrins and may play a role in their signaling function.

Survival and causes of death in cirrhotic and in noncirrhotic patients with primary hemochromatosis

We analyzed survival and causes of death among 163 patients with primary hemochromatosis diagnosed between 1959 and 1983. The mean follow-up period was 10.5 +/- 5.6 years (+/- S.D.). Cumulative survival was 92 per cent at 5 years, 76 per cent at 10 years, 59 per cent at 15 years, and 49 per cent at 20 years. Life expectancy was reduced in patients with cirrhosis of the liver as compared with those without cirrhosis (P less than or equal to 0.05), in patients with diabetes mellitus as compared with those without diabetes (P less than or equal to 0.002), and in patients who could not be depleted of iron during the first 18 months of venesection therapy as compared with those who could be depleted (P less than or equal to 0.001). Prognosis was not influenced by sex (P less than or equal to 0.5). Patients without cirrhosis had a life expectancy that was not different from that expected in an age- and sex-matched normal population. Analysis of the causes of death in 53 patients, as compared with the normal population, showed that liver cancer was 219 times more frequent among the patients (16 patients), cardiomyopathy was 306 times more frequent (3 patients), liver cirrhosis was 13 times more frequent (10 patients), and diabetes mellitus was 7 times more frequent (3 patients). Death rates for other causes, including extrahepatic carcinomas (seven patients), were not different from the rates expected. We conclude that patients with hemochromatosis diagnosed in the precirrhotic stage and treated by venesection have a normal life expectancy, whereas cirrhotic patients have a shortened life expectancy and a high risk of liver cancer even when complete iron depletion has been achieved.

Prevention of colorectal cancer by flexible endoscopy and polypectomy. A case-control study of 32,702 veterans

OBJECTIVE

To determine whether patients with colorectal cancer are less likely than unaffected controls to have had one or more endoscopic procedures (flexible sigmoidoscopy, colonoscopy, or polypectomy) before being diagnosed with cancer.

DESIGN

Case-control study.

SETTING

Hospitals of the Department of Veterans Affairs.

PATIENTS

8722 and 7629 case-patients with colon and rectal cancer, respectively, and age-, sex-, race-matched controls who were discharged at the same time as the corresponding case-patients.

MEASUREMENTS

Number and type of endoscopic procedures of the large bowel done from 1981 until the development of colorectal cancer in each case-patient. The influence of endoscopic procedures on the development of colorectal cancer was tested by conditional multiple logistic regression analysis.

RESULTS

Compared with controls, patients with colorectal cancer were less likely to have had an endoscopic procedure of the large bowel before being diagnosed with cancer (odds ratio for colon cancer, 0.51 [95% CI, 0.44 to 0.58]; odds ratio for rectal cancer, 0.55 [CI, 0.47 to 0.64]). In patients who had flexible sigmoidoscopy, colonoscopy, and polypectomy, the odds ratios were even smaller. When analyzed by separate 1-year intervals, patients with cancer had significantly fewer procedures during periods of up to 6 years before their onset of their cancer. Similarly, fewer inpatient and outpatient procedures were done in patients than in controls.

CONCLUSIONS

Endoscopic procedures of the large bowel reduce the risk for developing colon and rectal cancer by 50%, their protective influence lasting 6 years.

Integrin alpha 6/beta 4 complex is located in hemidesmosomes, suggesting a major role in epidermal cell-basement membrane adhesion

The alpha 6/beta 4 complex is a member of the integrin family of adhesion receptors. It is found on a variety of epithelial cell types, but is most strongly expressed on stratified squamous epithelia. Fluorescent antibody staining of human epidermis suggests that the beta 4 subunit is strongly localized to the basal region showing a similar distribution to that of the 230-kD bullous pemphigoid antigen. The alpha 6 subunit is also strongly localized to the basal region but in addition is present over the entire surfaces of basal cells and some cells in the immediate suprabasal region. By contrast staining for beta 1, alpha 2, and alpha 3 subunits was very weak basally, but strong on all other surfaces of basal epidermal cells. These results suggest that different integrin complexes play differing roles in cell-cell and cell-matrix adhesion in the epidermis. Immunoelectron microscopy showed that the alpha 6/beta 4 complex at the basal epidermal surface is strongly localized to hemidesmosomes. This result provides the first well-characterized monoclonal antibody markers for hemidesmosomes and suggests that the alpha 6/beta 4 complex plays a major role in epidermal cell-basement membrane adhesion. We suggest that the cytoplasmic domains of these transmembrane glycoproteins may contribute to the structure of hemidesmosomal plaques. Immunoultrastructural localization of the BP antigen suggests that it may be involved in bridging between hemidesmosomal plaques and keratin intermediate filaments of the cytoskeleton.

Structure and function of hemidesmosomes: more than simple adhesion complexes

The attachment of cells to the extracellular matrix is of crucial importance in the maintenance of tissue structure and integrity. In stratified epithelia such as in skin as well as in other complex epithelia multiprotein complexes called hemidesmosomes are involved in promoting the adhesion of epithelial cells to the underlying basement membrane. In the past few years our understanding of the role of hemidesmosomes has improved considerably. Their importance has become apparent in clinical conditions, in which absence or defects of hemidesmosomal proteins result in devastating blistering diseases of the skin. Molecular genetic studies have increased our knowledge of the function of the various components of hemidesmosomes and enabled the characterization of protein-protein interactions involved in their assembly. It has become clear that the alpha6beta4 integrin, a major component of hemidesmosomes, is able to transduce signals from the extracellular matrix to the interior of the cell, that critically modulate the organization of the cytoskeleton, proliferation, apoptosis, and differentiation. Nevertheless, our knowledge of the mechanisms regulating the functional state of hemidesmosomes and, hence, the dynamics of cell adhesion, a process of crucial importance in development, wound healing or tumor invasion, remains limited. The aims of this review are to highlight the recent progresses of our knowledge on the organization and assembly of hemidesmosomes, their involvement in signaling pathways as well as their participation in clinical pathologic conditions.

Mouse egg integrin alpha 6 beta 1 functions as a sperm receptor

Binding between sperm and egg plasma membranes is an essential step in fertilization. Whereas fertilin, a mammalian sperm surface protein, is involved in this crucial interaction, sperm receptors on the egg plasma membrane have not been identified. Because fertilin contains a predicted integrin ligand domain, we investigated the expression and function of integrin subunits in unfertilized mouse eggs. Polymerase chain reactions detected mRNAs for alpha 5, alpha 6, alpha v, beta 1, beta 3, and beta 5. Immunofluorescence revealed alpha 6 beta 1 and alpha v beta 3 on the plasma membrane. GoH3, a function-blocking anti-alpha 6 monoclonal antibody, abolished sperm binding, but a nonfunction-blocking anti-alpha 6 monoclonal antibody, a function-blocking anti-alpha v beta 3 polyclonal antibody, and an RGD peptide had no effect. Somatic cells bound sperm avidly, but only if they expressed alpha 6 beta 1. A peptide analog of the fertilin integrin ligand domain inhibited sperm binding to eggs and alpha 6 beta 1+ cells and diminished GoH3 staining of eggs. Our results indicate a novel role for the integrin alpha 6 beta 1 as a cell-cell adhesion receptor that mediates sperm-egg binding.

Long-term nonsurgical management of Barrett's esophagus with high-grade dysplasia

BACKGROUND & AIMS

Surgical resection of the esophagus is frequently recommended for Barrett's high-grade dysplasia (HGD) without cancer.

METHODS

During a 20-year period, patients were diagnosed and observed through an organized surveillance program at the Hines Veterans Affairs Hospital. The program was supported by Hines VA and organized and managed by 2 endoscopists using preestablished endoscopic criteria.

RESULTS

Barrett's esophagus was diagnosed in 1099 patients, and 36,251 esophageal mucosal specimens were reviewed. Seventy-nine of 1099 patients (7.2%) initially had HGD (34 prevalent) or subsequently developed HGD (45 incident) without evidence of cancer. Of the 75 HGD patients who remained without detectable cancer after the 1 year of intensive searching, 12 developed cancer (16%) during a mean 7.3-year surveillance period: 11 of the 12 who were compliant were considered cured with surgical or ablation therapy. Cancer did not develop in the remaining 63 HGD patients during the surveillance period.

CONCLUSIONS

HGD without cancer in Barrett's esophagus follows a relatively benign course in the majority of patients. In the patients who eventually progress to cancer during regular surveillance, surgical resection is curative. Surveillance endoscopies with biopsy is a valid and safe follow-up strategy for Barrett's patients who have HGD without cancer.

Episialin (MUC1) overexpression inhibits integrin-mediated cell adhesion to extracellular matrix components

Episialin (MUC1) is a transmembrane molecule with a large mucin-like extracellular domain protruding high above the cell surface. The molecule is located at the apical side of most glandular epithelial cells, whereas in carcinoma cells it is often present at the entire surface and it is frequently expressed in abnormally large quantities. We have previously shown that overexpression of episialin reduces cell-cell interactions. Here we show that the integrin-mediated adhesion to extracellular matrix of transfectants of a melanoma cell line (A375), a transformed epithelial cell line (MDCK-ras-e) and a human breast epithelial cell line (HBL-100) is reduced by high levels of episialin. This reduction can be reversed by inducing high avidity of the beta 1 integrins by mAb TS2/16 (at least for beta 1-mediated adhesion). The adhesion can also be restored by redistribution of episialin on the cell surface by monoclonal antibodies into patches or caps. Similarly, capping of episialin on ZR-75-1 breast carcinoma cells, growing in suspension, caused adherence and spreading of these cells. We propose that there is a delicate balance between adhesion and anti-adhesion forces in episialin expressing cells, which can be shifted towards adhesion by strengthening the integrin-mediated adhesion, or towards anti-adhesion by increasing the level of expression of episialin.

Integrin recognition of different cell-binding fragments of laminin (P1, E3, E8) and evidence that alpha 6 beta 1 but not alpha 6 beta 4 functions as a major receptor for fragment E8

The involvement of integrins in mediating interaction of cells to well-characterized proteolytic fragments (P1, E3, and E8) of laminin was assessed by antibody blocking studies. Cell adhesion to fragment P1 was affected by mAbs against the integrin beta 1 and beta 3 subunits and furthermore could be prevented completely by a synthetic peptide containing the Arg-Gly-Asp sequence. Because the beta 3 antibody-sensitive cell lines expressed the vitronectin receptor (alpha v beta 3) at high levels, the involvement of this receptor in cell adhesion to P1 is strongly suggested. Integrin-mediated cell adhesion to E3 is of low affinity and was inhibited by antibodies against the integrin beta 1 subunit. In contrast, adhesion of some cell types to E3 was not or only partially sensitive to inhibition by anti-integrin subunit antibodies. Cell adhesion to E8 was blocked completed by integrin alpha 6 or beta 1 antibodies. The alpha 6-specific antibody did not inhibit cell adhesion to E3 or P1. Furthermore, the antibody only blocked adhesion to laminin of those cells that adhered exclusively to the E8 fragment. In addition, expression of alpha 6 beta 1 was closely correlated with the ability of cells to bind to the E8 fragment of laminin. These results indicate that the alpha 6 beta 1 integrin is a specific receptor for the E8 fragment of laminin. Many cell types expressed, instead of or in addition to alpha 6 beta 1 the recently described integrin alpha 6 beta 4. Although the ligand of alpha 6 beta 4 was not identified, it must be different from that of alpha 6 beta 1, because cells that express alpha 6 beta 4, but not alpha 6 beta 1, do not adhere to E8, and cell adhesion to E8 was specifically blocked by beta 1 specific antibodies. In conclusion, the data indicate that distinct integrin receptors belonging to the beta 1 or beta 3 subfamily are involved in adhesion of cells to the various laminin fragments. Adhesion to E3 may also be brought about by other receptor molecules, possibly proteoglycans, not belonging to the integrin family.

Epithelial detachment due to absence of hemidesmosomes in integrin beta 4 null mice

Integrins are heterodimeric transmembrane glycoproteins which are engaged in a variety of cellular functions, such as adhesion, migration and differentiation1. The integrin alpha 6 beta 4 is expressed on squamous epithelia, on subsets of endothelial cells, immature thymocytes and on Schwann cells and fibroblasts in the peripheral nervous system. In stratified epithelia, alpha 6 beta 4 is concentrated in specialised adhesion structures, called hemidesmosomes, which are implicated in the stable attachment of the basal cells to the underlying basement membrane by connecting the intermediate filaments with the extracellular matrix. The nature of the interactions between the various hemidesmosomal proteins, that lead to the formation of hemidesmosome is poorly understood. To study the contribution of the integrin alpha 6 beta 4 in hemidesmosome formation and their anchoring properties, we inactivated the beta 4 gene in mice by targeted gene disruption. Homozygous beta 4 null mice died shortly after birth and displayed extensive detachment of the epidermis and other squamous epithelia. The dramatically reduced adhesive properties of the skin was accompanied by the absence of hemidesmosomes at the basal surface of keratinocytes. No evidence was found for impaired T-cell development, nor for defects in myelination in the peripheral nervous system.

The alpha 1/beta 1 and alpha 6/beta 1 integrin heterodimers mediate cell attachment to distinct sites on laminin

This study was undertaken to determine the roles of individual alpha/beta 1 integrin heterodimers in promoting cellular interactions with the different attachment-promoting domains of laminin (LN). To do this, antibodies to the integrin beta 1 subunit or to specific integrin alpha subunits were tested for effects on cell attachment to LN, to elastase fragments E1-4 and E1, derived from the short arms and core of LN's cruciform structure, and to fragment E8 derived from the long arm of this structure. The human JAR choriocarcinoma cells used in this study attached to LN and to fragments E1 and E8. Attachment to E1-4 required a much higher substrate coating concentration, suggesting that it is a poor substrate for JAR cell attachment. The ability of cells to attach to different LN domains suggested the presence of more than one LN receptor. These multiple LN receptors were shown to be beta 1 integrin heterodimers because antibodies to the integrin beta 1 subunit inhibited attachment of JAR cells to LN and its three fragments. To identify the individual integrin alpha/beta 1 heterodimers that mediate interactions with these LN domains, mAbs specific for individual beta 1 heterodimers in human cells were used to study JAR cell interactions with LN and its fragments. An anti-alpha 6/beta 1-specific mAb, GoH3, virtually eliminated cell attachment to E8 and partially inhibited attachment to E1 and intact LN. Thus the major alpha 6/beta 1 attachment domain is present in fragment E8. An alpha 1/beta 1-specific mAb (S2G3) strongly inhibited cell attachment to collagen IV and partially inhibited JAR attachment to LN fragment E1. Thus, the alpha 1/beta 1 heterodimer is a dual receptor for collagen IV and LN, interacting with LN at a site in fragment E1. In combination, the anti-alpha 1- and anti-alpha 6-specific antibodies completely inhibited JAR cell attachment to LN and fragment E1. Thus, the alpha 1/beta 1 and alpha 6/beta 1 integrin heterodimers each function as LN receptors and act together to mediate the interactions of human JAR choriocarcinoma cells with LN.

Cost-effectiveness of colonoscopy in screening for colorectal cancer

BACKGROUND

Fecal occult blood testing, flexible sigmoidoscopy, and colonoscopy are used to screen patients for colorectal cancer.

OBJECTIVE

To compare the cost-effectiveness of fecal occult blood testing, flexible sigmoidoscopy, and colonoscopy.

DESIGN

The cost-effectiveness of the three screening strategies was compared by using computer models of a Markov process. In the model, a hypothetical population of 100 000 persons 50 years of age undergoes annual fecal occult blood testing, sigmoidoscopy every 5 years, or colonoscopy every 10 years. Positive results on fecal occult blood testing or adenomatous polyps found during sigmoidoscopy are worked up by using colonoscopy. After polypectomy, colonoscopy is repeated every 3 years until no polyps are found.

DATA SOURCES

Transition rates were estimated from U.S. vital statistics and cancer statistics and from published data on the sensitivity, specificity, and efficacy of various screening techniques. Costs of screening and cancer care were estimated from Medicare reimbursement data.

TARGET POPULATION

Persons 50 years of age in the general population.

TIME HORIZON

The study population was followed annually until death.

PERSPECTIVE

Third-party payer.

OUTCOME MEASURE

Incremental cost-effectiveness ratio.

RESULTS OF BASE-CASE ANALYSIS

Compared with colonoscopy, annual screening with fecal occult blood testing costs less but saves fewer life-years. A screening strategy based on flexible sigmoidoscopy every 5 or 10 years is less cost-effective than the other two screening methods.

RESULTS OF SENSITIVITY ANALYSIS

Screening with fecal occult blood testing is more sensitive to changes in compliance rates, and it becomes easily dominated by colonoscopy under most conditions assuming less than perfect compliance. Other assumptions about the sensitivity and specificity of fecal occult blood testing, screening frequency, efficacy of colonoscopy in preventing cancer, and polyp incidence have a lesser influence on the differences in cost-effectiveness between colonoscopy and fecal occult blood testing.

CONCLUSIONS

Colonoscopy represents a cost-effective means of screening for colorectal cancer because it reduces mortality at relatively low incremental costs. Low compliance rates render colonoscopy every 10 years the most cost-effective primary screening strategy for colorectal cancer.

Structural and functional aspects of filamins

Filamins are a family of high molecular mass cytoskeletal proteins that organize filamentous actin in networks and stress fibers. Over the past few years it has become clear that filamins anchor various transmembrane proteins to the actin cytoskeleton and provide a scaffold for a wide range of cytoplasmic signaling proteins. The recent cloning of three human filamins and studies on filamin orthologues from chicken and Drosophila revealed unexpected complexity of the filamin family, the biological implications of which have just started to be addressed. Expression of dysfunctional filamin-A leads to the genetic disorder of ventricular heterotopia and gives reason to expect that abnormalities in the other isogenes may also be connected with human disease. In this review aspects of filamin structure, its splice variants, binding partners and biological function will be discussed.

The prevalence of hemorrhoids and chronic constipation. An epidemiologic study

Hemorrhoids are a frequently occurring disorder widely believed to be caused by chronic constipation. In the present study, the epidemiology of hemorrhoids was evaluated and compared with the epidemiology of constipation. The analysis was based on 4 data sources: from the United States, the National Health Interview Survey, the National Hospital Discharge Survey, and the National Disease and Therapeutic Index; from England and Wales, the Morbidity Statistics from General Practice. Results showed that 10 million people in the United States complained of hemorrhoids, corresponding to a prevalence rate of 4.4%. In both sexes, a peak in prevalence was noted from age 45-65 yr, with a subsequent decrease after age 65 yr. The development of hemorrhoids before age 20 yr was unusual. Whites were affected more frequently than blacks, and increased prevalence rates were associated with higher socioeconomic status. This was in contrast to the epidemiology of constipation, which demonstrated an exponential increase in prevalence after age 65 yr and was more common in blacks and in families with low incomes or low social status. The data presented illustrate differences in the epidemiologic behavior of hemorrhoids and constipation, calling the presumption of causality between constipation and hemorrhoids into question.

Monoclonal antibodies against human milk-fat globule membranes detecting differentiation antigens of the mammary gland and its tumors

Mouse monoclonal antibodies have been raised against human milk-fat globule membranes (HMFGM) to obtain reagents for mammary tumor diagnosis. A panel of 17 anti-HMFGM antibodies was selected for further investigation. Antibody-blocking studies indicated that with these antibodies at least nine different non-overlapping epitopes could be distinguished on six different molecules, MAM-1 to MAM-6. Electron microscopic studies of the cellular localization of the antigens detected by some of these antibodies revealed that they were present on the cell membrane mainly, on the microvilli, lining intercellular and intracytoplasmic lumina. The reactivity of the antibodies was studied on normal and tumor tissues and on in vitro cell lines. All antibodies reacted with the resting mammary gland while eight antibodies also bound to breast tumors. None of the antibodies was specific for the mammary gland or its tumors only, but most antibodies also reacted with other epithelial cells, especially of secretory tissues. When tested on a variety of cell lines a distribution reflecting the tissue distribution could be demonstrated. One of the antibodies reacted with nearly all carcinomas and their metastases and did not react with lymphomas, sarcomas, neuroblastomas, melanomas or nervous system tumors. The specificity of the antibodies, tested individually, was not sufficient for further differential diagnosis of the carcinomas, but when some of these antibodies were used in a panel they contribute to an important improvement of the diagnosis.

The alpha 6 beta 4 integrin is a receptor for both laminin and kalinin

Previously, we have establish K562 transfectants that express either alpha 6A beta 1 or alpha 6B beta 1 (K alpha 6A or K alpha 6B) on their surface. Both cell lines bind to laminin and kalinin after treatment with the beta 1-stimulatory antibody TS2/16. Here we introduce the full-length beta 4 cDNA into the alpha 6A- and alpha 6B-expressing K562 cells and selected stably transfected cells. The beta 4 subunit was expressed on the surface of both transfectants and it formed dimers with the alpha 6A or alpha 6B subunits. Immunoprecipitation and preclearing analyses revealed that both transfectants expressed alpha 6 beta 1, in addition to alpha 6 beta 4. While K alpha 6A and K alpha 6B cells required TS2/16 stimulation for binding to laminin or kalinin, adhesion of the unstimulated beta 4-transfected K alpha 6A and K alpha 6B cells to these matrix components was already substantial. This adhesion was mediated by both alpha 6 beta 1 and alpha 6 beta 4 since it was completely blocked by an alpha 6-specific antibody or by a combination of anti-beta 1 and anti-beta 4 antibodies, but only partially by either of these latter two antibodies alone. Adhesion to laminin was completely blocked by an antiserum to laminin fragment E8 as was the adhesion to kalinin by an antibody to kalinin, demonstrating the specificity of adhesion. Both transfectants always adhered more strongly to kalinin than to laminin. Furthermore, binding to kalinin was less well blocked by antibodies to beta 4 than binding to laminin, indicating that the affinity of alpha 6 beta 4 for kalinin is higher than that for laminin. The fact that alpha 6 beta 1 mediated adhesion without TS2/16 stimulation on the beta 4-transfected K alpha 6A and K alpha 6B cells suggests that some activation of alpha 6 beta 1 had occurred in these cells, even though binding was increased when they were actively stimulated by the antibody TS2/16. Finally, we show that Mn2+ induced binding of solubilized alpha 6 beta 4 to matrix containing kalinin, deposited by the murine cell line RAC-11P/SD. This binding was inhibited by the anti-alpha 6 mAb GoH3. Together, these results indicate that both alpha 6 beta 1 and alpha 6 beta 4 are receptors for laminin and kalinin and that there are no differences in ligand specificity between the A and B variants of the alpha 6 subunit when associated with either beta 1 or beta 4.

Opposing time trends of peptic ulcer and reflux disease

BACKGROUND

Gastritis associated hypochlorhydria may be protective against gastro-oesophageal reflux disease. It was hypothesised that the historic decline in Helicobacter pylori infection resulted in a decline in peptic ulcer and a concomitant risk in reflux disease.

AIMS

To study the time trends of peptic ulcer and reflux disease.

METHODS

Hospitalisation rates were analysed using the computerised database of the US Department of Veterans Affairs from 1970 until 1995. Death rates were calculated from the Vital Statistics of the United States.

RESULTS

From 1970 to 1995, hospitalisation rates for gastric and duodenal ulcer, as well as gastric cancer fell, while the hospitalisation rates for gastro-oesophageal reflux disease and those for oesophageal adenocarcinoma rose significantly. Similar time trends were observed with respect to the death rates. There were notable ethnic differences. White subjects incurred higher rates of reflux disease and oesophageal adenocarcinoma and lower rates of gastric ulcer or cancer compared with non-whites.

CONCLUSIONS

The ethnic variations and the opposing time trends of gastroduodenal versus oesophageal disease are consistent with the hypothesis that the declining infection rates of H pylori in the general population have led to a rise in the occurrence of gastro-oesophageal reflux disease and associated oesophageal adenocarcinoma.

The stomach in health and disease

The stomach is traditionally regarded as a hollow muscular sac that initiates the second phase of digestion. Yet this simple view ignores the fact that it is the most sophisticated endocrine organ with unique physiology, biochemistry, immunology and microbiology. All ingested materials, including our nutrition, have to negotiate this organ first, and as such, the stomach is arguably the most important segment within the GI tract. The unique biological function of gastric acid secretion not only initiates the digestive process but also acts as a first line of defence against food-borne microbes. Normal gastric physiology and morphology may be disrupted by Helicobacter pylori infection, the most common chronic bacterial infection in the world and the aetiological agent for most peptic ulcers and gastric cancer. In this state-of-the-art review, the most relevant new aspects of the stomach in health and disease are addressed. Topics include gastric physiology and the role of gastric dysmotility in dyspepsia and gastroparesis; the stomach in appetite control and obesity; there is an update on the immunology of the stomach and the emerging field of the gastric microbiome. H. pylori-induced gastritis and its associated diseases including peptic ulcers and gastric cancer are addressed together with advances in diagnosis. The conclusions provide a future approach to gastric diseases underpinned by the concept that a healthy stomach is the gateway to a healthy and balanced host. This philosophy should reinforce any public health efforts designed to eradicate major gastric diseases, including stomach cancer.

Protection by endoscopy against death from colorectal cancer. A case-control study among veterans

BACKGROUND

Although several clinical and epidemiologic studies suggest that timely diagnostic procedures of the large bowel may reduce mortality from colorectal cancer, the evidence for this relationship is primarily circumstantial.

METHODS

A case-control study was conducted among hospitalized US military veterans to investigate whether diagnostic procedures of the large bowel were performed in the period preceding the diagnosis of colorectal cancer less frequently in patients dying of colorectal cancer than in control patients. Data files of a total of 4411 veterans dying of colorectal cancer between 1988 and 1992 were extracted from the records of the US Department of Veterans Affairs, Washington, DC. Data of four living control patients and four dead control patients without colorectal cancer were matched by age, sex, and race to each case patient. The case and the two control populations were compared by conditional logistic regression, calculating odds ratios, and their 95% confidence interval.

RESULTS

Diagnostic procedures of the large bowel reduced mortality from colorectal cancer, the odds ratio being 0.41 (range, 0.33 to 0.50) for the comparison with living control patients. The protective effects of proctosigmoidoscopy, colonoscopy, and polypectomy lasted for 5 years. The procedures were protective against death from cancer of the colon, as well as cancer of the rectum. The most protective influence was associated with removal of tissue through biopsy, fulguration, and polypectomy. Similar influences were found comparing case patients with dead control patients.

CONCLUSION

Removal of tissue represents the most effective means to reduce mortality from cancers of the large bowel. It retains its efficacy over a time period of 5 years.

Physician visits in the United States for constipation: 1958 to 1986

Since 1958, the National Disease and Therapeutic Index (NDTI) has provided annual statistics summarizing the frequency physicians throughout the United States are visited for different disease conditions. In our present study, these data were used to examine the epidemiology of constipation. Since NDTI statistics are available for a longer time period than other U.S. statistics, they might confirm or disprove the relevance of recent environmental changes on the occurrence of this disorder. The average number of physician visits for constipation in the United States was 2.5 million per year, corresponding to a prevalence of 1.2%. The largest number of these patients (31%) was seen by general and family practitioners, followed in declining order by internists (20%) and pediatricians (15%). Only 4% of all these patients was seen by gastroenterologists. Eight-five percent of these patients received a prescription for medication, with laxatives and cathartics being the most frequently prescribed drugs. Among physician visits for constipation, female prevalence was 1.6% compared with 0.8% for males (P less than 0.001). In both sexes, there was a significant age-related increase in the rate of physician visits, with the steepest rise from 1.3% to 4.1% occurring between the age groups 60-64 and over 65. From 1958 to 1986, the rate of all physician visits for constipation remained unchanged. However, during this time period, there was a twofold rise in physician visits for those patients ages 0-9 years, while a smooth decline occurred in all of the older age groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Recognition of the laminin E8 cell-binding site by an integrin possessing the alpha 6 subunit is essential for epithelial polarization in developing kidney tubules

It has been previously shown that A-chain and domain(E8)-specific antibodies to laminin that inhibit cell adhesion also interfere with the establishment of epithelial cell polarity during kidney tubule development (Klein, G., M. Langegger, R. Timpl, and P. Ekblom. 1988. Cell. 55:331-341). A monoclonal antibody specific for the integrin alpha 6 subunit, which selectively blocks cell binding to E8, was used to study the receptors involved. Immunofluorescence staining of embryonic kidneys and of organ cultures of metanephric mesenchyme demonstrated coappearance of the integrin alpha 6 subunit and the laminin A-chain in regions where nonpolarized mesenchymal cells convert into polarized epithelial cells. Both epitopes showed marked colocalization in basal areas of tubules, while an exclusive immunostaining for alpha 6 was observed in lateral and apical cell surfaces of the tubular epithelial cells. Organ culture studies demonstrated a consistent inhibition of kidney epithelium development by antibodies against the alpha 6 subunit. The data suggest that the recognition of E8 cell-binding site of laminin by a specific integrin is crucial for the formation of kidney tubule epithelium from undifferentiated mesenchymal stem cells. In some other cell types (endothelium, some ureter cells) an exclusive expression of alpha 6 with no apparent colocalization of laminin A-chain in the corresponding basement membrane was seen. Thus, in these cells, integrins possessing the alpha 6 subunit may bind to laminin isoforms that differ from those synthesized by developing tubules.

Geographic variation of inflammatory bowel disease within the United States

One approach to learn about possible environmental risks in inflammatory bowel disease relates to studying its geographic pattern of occurrence. The geographic variation of inflammatory bowel disease within the United States was analyzed using the accumulated 17.5 million hospital discharges of all U.S. Medicare beneficiaries during two consecutive years. To validate the geographic pattern shown by the Medicare data, hospitalization was compared with mortality from inflammatory bowel disease among different states. Mortality and hospitalization statistics both suggested that the occurrence of inflammatory bowel disease was determined by environmental factors that had a marked geographic variation within the United States. Both Crohn's disease and ulcerative colitis appeared to be more frequent in northern parts of the United States than in southern and in urban more than rural parts. These trends were observed for men and women and for blacks and whites alike. Similar geographic patterns of Crohn's disease and ulcerative colitis suggested the influence of one or more identical risk factors for both diseases.

Comorbid occurrence of laryngeal or pulmonary disease with esophagitis in United States military veterans

BACKGROUND & AIMS

It has been speculated that gastroesophageal reflux disease (GERD) represents a risk factor for the occurrence of extraesophageal complications. The aim of this study was to compare the comorbid occurrence of sinus, laryngeal, and pulmonary diseases in case subjects with and control subjects without reflux esophagitis.

METHODS

The case population consisted of all patients with erosive esophagitis (International Classification of Diseases code 530.1) or esophageal stricture (ICD code 530.3) who were discharged from hospitals of the Department of Veteran Affairs between 1981 and 1994. In multivariate logistic regressions, the occurrence of sinus, pharyngeal, laryngeal, or pulmonary disease was compared between cases with and an equal number of controls without esophagitis or stricture.

RESULTS

A total of 101,366 case subjects was analyzed. Erosive esophagitis and esophageal stricture were associated with sinusitis (odds ratio, 1.60; 95% confidence interval, 1.51-1.70), pharyngitis (1.48; 1.15-1.89), aphonia (1.81; 1.18-2.80), laryngitis (2.01; 1.53-2.63), laryngeal stenosis (2.02; 1.12-3.65), chronic bronchitis (1.28; 1.22-1.34), asthma (1.51; 1.43-1.59), chronic obstructive pulmonary disease (1.22; 1.16-1.27), pulmonary fibrosis (1.36; 1.25-1.48), bronchiectasis (1.26; 1.09-1.47), pulmonary collapse (1.31; 1.23-1.40), and pneumonia (1.15; 1.12-1.18).

CONCLUSIONS

Patients with reflux esophagitis are at an increased risk of harboring a large variety of sinus, pharyngeal, laryngeal, and pulmonary diseases.