Differential cloning of novel intestine-specific genes whose expression is altered under conditions of villus atrophy

Atrophy of the small intestinal villi occurs in a variety of disease states and is associated with diarrhea, malabsorption, and impaired barrier function. We have previously demonstrated that villus atrophy is associated with an increase in lactase and a decrease in intestinal alkaline phosphatase gene expression. Given these changes in enterocyte phenotype with villus atrophy, we speculated that there may be other intestine-specific genes whose expression is altered as a function of epithelial growth state. We have employed two molecular techniques in order to identify and clone complementary DNAs (cDNA) which are differentially expressed in atrophic compared to normal small intestinal mucosa. In differential cDNA library (+/-) screening, duplicate filters of a normal jejunal cDNA library are hybridized with radiolabeled cDNA probes from either atrophic or control tissues. Comparisons of the intensities of hybridized clones allows for the identification of differentially expressed gene products. In the mRNA differential display system, RT-PCR is used to randomly amplify mRNA species. Similar to cDNA library screening, comparisons of radiolabeled bands on a polyacrylamide sequencing gel allow for the identification of differentially expressed genes. Using these methods, we have identified a novel cDNA, called D9, which appears to be expressed exclusively in the intestinal mucosa. Northern analyses have confirmed that the expression of the D9 mRNA is dramatically decreased under conditions of villus atrophy, suggesting an underlying relationship with epithelial growth state. DNA sequence analysis (GenBank) reveals no identity to previously cloned genes.(ABSTRACT TRUNCATED AT 250 WORDS)

[The diagnosis and treatment of insulinoma: an analysis on 20 cases]

From 1967 to 1994, a total of 20 pathologically proved benign insulinoma cases were treated in our hospital. Tumors were solitary in 19 cases, and multiple in 1, with diameter ranging from 0.5 to 3.0 cm. Diagnosis was made by autopsy in one and by laparotomy in 19. All 18 cases except for the one dying of pancreatic fistula postoperatively during the same hospitalization were followed up for 1 to 18 years without recurrence. The authors recommended calcium infusion test as the standard method of diagnosis, analysed the false diagnosis in one patient, and discussed operative experience on tumors deeply buried in the head of the pancreas.

Thyroid hormone responsiveness is developmentally regulated in the rat small intestine: a possible role for the alpha-2 receptor variant

Thyroid hormone (T3) alters gene expression through binding to a receptor protein located within the nucleus of target cells. Multiple forms of the T3 receptor (TR) have been identified and are encoded by the alpha and beta c-erbA genes. We have previously found that TR beta-1 is the major receptor form expressed in the adult rat small intestine, although there are also moderate levels of c-erbA alpha-2, a nonhormone-binding variant that is thought to inhibit T3 action. In developing rats, we studied the regulation of two small intestinal enterocyte genes previously shown to be T3 responsive, lactase and 3.0-kilobase intestinal alkaline phosphatase (IAP). Animals were treated with six daily ip injections of either saline (control) or 30 micrograms/100 g BW T3 (T3 group) and killed at 10 and 25 days of age. Northern analyses of RNA derived from intestinal tissues showed that the magnitude of the T3-induced changes in lactase and IAP gene expression increased with development. Jejunal 3.0-kilobase IAP messenger RNA (mRNA) levels were unaffected by T3 at 10 days, but increased by 15-fold at 25 days. Similarly, jejunal lactase mRNA levels were unchanged by T3 at 10 days, but decreased by 75% at 25 days. Qualitatively similar results were seen in the duodenum and ileum. Studies of TR expression revealed that TR beta-1 mRNA levels were unchanged during the developmental period, whereas the levels of c-erbA alpha-2 decreased by 90% between 5-25 days after birth. These results indicate that the rat small intestine becomes increasingly T3 responsive during postnatal development. These changes occur in parallel with a decline in c-erbA alpha-2 levels, suggesting that this T3 receptor variant may play a role in this hormonal responsiveness.

Bombesin maintains enterocyte phenotype in fasted rats

BACKGROUND

Previous studies have suggested a relationship between enterocyte phenotype and the growth state of the epithelium; under atrophic conditions, lactase gene expression is high, whereas intestinal alkaline phosphatase (IAP) expression is low, and vice versa. On the basis of this model, we hypothesized that the intestinal trophic factor bombesin would alter brush-border enzyme gene expression in a predictable way.

METHODS

Adult rats were fasted for 48 hours and treated (intraperitoneally) with either 10 micrograms/kg bombesin or the saline control every 8 hours. Small intestinal mucosal scrapings were taken, total RNA purified, and Northern blot analyses performed with radiolabeled cDNA probes corresponding to lactase, IAP, villin, and actin. Tissue samples were also taken for measurement of mucosal thickness.

RESULTS

Bombesin administration caused an increase in jejunal mucosal thickness, thereby confirming its trophic effects. Bombesin resulted in a decrease in lactase mRNA levels and an increase in IAP mRNA levels along the length of the small intestine. No changes occurred in the expression of either villin or actin. The pattern of enterocyte gene expression in the bombesin-treated animals was similar to that in control-fed rats.

CONCLUSIONS

Bombesin differentially regulates rat enterocyte gene expression, decreasing lactase and increasing IAP mRNA levels. These results lend further support to the hypothesis that a close relationship exists between enterocyte phenotype and epithelial growth state.

Immediate-early gene expression in EGF-stimulated intestinal epithelial cells

The mammalian small intestinal epithelium is a continuously renewable population of cells which arise from a proliferative zone of undifferentiated stem cells within the crypts. Epidermal growth factor (EGF) is thought to play a role in the maintenance and proliferative response of the intestinal epithelium. In order to investigate the early changes in intestinal gene expression which occur in response to a mitogenic stimulus, we performed studies in two different cell lines (IEC-6 and HT-29), both of which have characteristics of intestinal crypt cells. Cells were grown in DMEM + 10% FCS at 37 degrees C/5% CO2 and treated with either EGF (10 ng/ml) and/or cycloheximide (CHx) (10 micrograms/ml) for various times. Northern blot analyses were performed on total RNA using 32P-labeled cDNA probes corresponding to various protooncogenes. Our results showed that EGF treatment caused rapid increases in c-fos, c-jun, and junB expression (P < 0.001) in both cell lines. c-fos and c-jun followed similar time courses, peaking at 30 min, whereas junB levels plateaued at 1 hr. The magnitude and time course of protooncogene induction by EGF were similar in the two cell lines. A dose-response experiment indicated peak EGF effects at 10 ng/ml. CHx treatment resulted in greater and more prolonged increases in protooncogene expression when compared to EGF alone, indicating that protein synthesis is not required for protooncogene induction.(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal pattern of rat small intestinal gene expression with refeeding

Studies were carried out to elucidate the molecular mechanisms underlying small intestinal epithelial growth. Adult rats were fasted for 4 days and then refed a chow diet for up to 48 h. Histological examination confirmed the sequential occurrence of mucosal atrophy and hyperplasia. Northern blot analyses of RNA derived from small intestinal mucosal scrapings revealed a striking pattern of alterations in the expression of two different categories of genes. There were very early increases in the expression of c-fos and c-jun, reflecting the mitogenic response to refeeding that occurs within the crypt compartment. Studies using the protein synthesis inhibitor cycloheximide suggest that c-fos and c-jun are part of the "immediate-early" response of the small intestine. At later time points after the refeeding stimulus, differential changes occurred in the expression of the brush-border enzymes, lactase, and intestinal alkaline phosphatase (IAP). Refeeding caused a decrease in lactase gene expression and an increase in the expression of the 3.0-kb IAP mRNA species, reflecting a return of the villus phenotype to the normal fed state. Thus we have demonstrated a complex and temporally related pattern of gene expression within the small intestinal epithelium upon refeeding. The results provide insight into the relationship between the processes of intestinal growth and differentiation.

[Experimental and epidemiological studies on the interrelationship of thiocyanate and thyroid function]

The testing of a SCN- dose (32 mg NaSCN/kg oral 21 d long) which is about 100 fold above the alimentary SCN(-)-uptake on guinea pig has shown neither histologic/morphometrical nor clinical clue to thyrostatic effect. In 6 regions of the GDR (1,349 persons) has not been secured epidemiologically any relationship between SCN- serum level as well as SCN- urine level and goiter. The partly in the tendency low increase of SCN- level by patients with bland goiter was always under the levels of smokers without goiter, exceeded indeed the threshold of significance in the area of Werdau. In the industrial agglomeration areas the I(-)-SCN(-)-quotient at the most unfavourable cases ran to 3.5 (Halle, smoker, struma), was consequently close to the critical level of the goiter risk.

[TSH receptor antibody determination using the TSH radioreceptor antibody assay in clinical practice]

We tested the clinical valency of the TSH-receptor antibody (TBIAb) determination (TRAK assay, Fa. Henning) for the differential diagnostics of various diseases of the thyroid gland (n = 259), particularly of the hyperthyroidism. In 110 out of 114 basedowians TBAIAb could be proved (sensitivity 96%). The specifity to healthy persons (n = 20) was 100%, to the disseminated autonomy (n = 61) 92%. In 43 bland strumas and 22 cases of primary hypothyroidisms no circulating TBIAb were found. Of 40 cases of Basedow's hyperthyroidism the TBIAb titres were pursued during a 12-month methimazol therapy. In these cases was shown that negative antibody titres at the end of the treatment were connected with an essentially lower rate of early relapses than positive ones. Moreover, a highly dosed application of methimazol revealed a more favourable tendency than a low dosed one. From this we conclude that the TBIAb measurement with a commercial kit is a sensitive, sufficiently specific and practicable method for the differential diagnostics of hyperthyroidism and that to a certain degree it allows conclusions on the course of Basedow's disease after thyrostatic long-term therapy.

N-acetylator phenotypes in hyperthyroidism

Acetylator phenotypes were determined with sulfamethazine in 114 healthy volunteers, 87 patients with immunogenic hyperthyroidism (Graves' disease) and 38 patients with disseminated thyroid autonomies. About 90% of the patients were females. No significant differences of acetylator phenotypes were observed between female volunteers and hyperthyreotic patients younger than 50 years. The proportion of slow acetylators was higher in older patients. Early and late relapses did not depend on acetylator status.

[Results of thyroid hormone therapy in bland struma]

2,191 patients with bland struma were treated with tri-iodothyronine and a mixed preparation (thyreotom) for at least 2 years. Several clinical criteria were used for judgement. A good result could be obtained in 78.3 to 51.2% depending on the size of the struma (I-III). While in diffuse strumata good results were obtained in 87.8 to 69.0%, in nodular goitres we were successful only in 52.0-32.9%. The therapy may be successful at every age. Since with growing age the nodular goitres prevail, the chances of success become smaller. For the same reason there is a close correlation between age of the goitre and the therapeutic effect. The rate of success continuously decreases with growing age of the goitre. From this results that the therapy in goitre must begin early, before nodular and regressive changes, respectively, render the treatment difficult or render an acceptable result difficult.

[Problems of treatment with thyroid hormones. Thyroxin monotherapy or a T3/T4 combination preparation?]

At the instance of T3- and T4-measurements of the daily profile in the serum after the application of triiodothyronine and the usual T3/T4-combination preparations is referred to the unphysiologically high T3-peaks 2 to 4 hours after the application depending on the proportion of triiodothyronine. The three distributed all over the day doses of e.g. thyreotom do not sufficiently smooth such undulations. The lacking triiodothyronine serum peaks after application of pure thyroxin as a bolus confirm the demand of a thyroxin monotherapy. Nevertheless, for answering the question of the "physiologic thyroid hormone therapy" some problems remain open which are discussed. Taking into consideration these facts (particularly conversation and extrathyroid influence of the thyroid hormone metabolism) a combination of T3 to T4 in the ratio 1:10 is recommended.