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Biomedical subjects

R A Hodin

Publications and source records attributed to R A Hodin.

At least 19 recordsLinked to original sources
PubMed1997

Inhibition of inducible nitric oxide synthase ameliorates endotoxin-induced gut mucosal barrier dysfunction in rats.

BACKGROUND & AIMS: The permeability of intestinal epithelial monolayers increases after exposure to nitric oxide. The aim of this study was to investigate the role of excessive NO production on intestinal barrier function in rats injected with lipopolysaccharide (LPS). METHODS: Rats were injected with saline or LPS (5 mg/ kg). Bacterial translocation to mesenteric lymph nodes, liver, and spleen was assessed 24 hours after LPS injection. Mucosal permeability was determined by loading fluorescein-labeled dextran (mol wt, 4000 daltons) into an intestinal segment and measuring its appearance in plasma. Intestinal mucosal mitochondrial respiration was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. RESULTS: Intestinal tissue from LPS-challenged rats showed upregulation of inducible NO synthase (iNOS) messenger RNA expression and subsequent up-regulation of iNOS enzymatic activity. Plasma concentrations of nitrite plus nitrate (NO2-/NO3-) were increased for at least 24 hours after injection of LPS. Treatment with the selective iNOS inhibitor, aminoguanidine, inhibited iNOS enzymatic activity and overproduction of NO2-/NO3-. LPS-induced bacterial translocation was reduced by aminoguanidine. LPS-induced intestinal hyperpermeability was ameliorated by both aminoguanidine and another selective iNOS inhibitor, S-methylisothiourea. LPS depressed intestinal mucosal mitochondrial function, and this effect was ameliorated by aminoguanidine. CONCLUSIONS: Overproduction of NO may contribute to intestinal barrier dysfunction in LPS challenged rats, possibly by interfering with mitochondrial oxidative metabolism.

Animals↗
PubMed1997

Detection and management of parathyroid tumors.

Hyperparathyroidism is due to enlargement of one or more parathyroid glands and is most often treated by surgical resection. Recent advances have taken place in regard to preoperative localization and refinement of surgical technique. The underlying mechanisms of parathyroid tumorigenesis are just beginning to be unraveled. The management of asymptomatic hyperparathyroidism remains controversial, although a liberal approach to surgery has become more widely accepted.

Adenoma↗
PubMed1996

Thyroid hormone and the gut: selective transcriptional activation of a villus-enterocyte marker.

BACKGROUND: Thyroid hormone (T3) is an important regulator of gut mucosal growth, differentiation, and barrier function, but its mechanism of action in the gastrointestinal tract is largely unknown. The present studies were carried out to define the molecular mechanisms by which T3 alters gut gene expression. METHODS: In vivo: Adult, male, Sprague-Dawley rats were given three daily injections (intraperitoneal) of either saline solution or 30 micrograms/kg triiodothyronine. Small intestinal tissues were harvested, and Northern blot analyses were performed by using specific radiolabeled cDNA probes. In vitro: HT-29 cells were transfected with reporter plasmids and treated with or without T3, and chloramphenicol acetyltransferase activity was measured. RESULTS: The T3-induced changes in enterocyte gene expression occurred in villus enterocytes and not in crypt cells and were independent of food intake. Northern analyses with an intron-specific probe revealed that the T3 induction in intestinal alkaline phosphatase (IAP) expression occurs at the level of transcription. Transient transfection assays revealed no T3-induced changes under basal conditions but marked increases (sixfold, p < 0.001) when a T3-receptor (TR beta-1) plasmid was cotransfected. Furthermore, T3 was found to induce greater IAP reporter gene activity in differentiated (+ sodium butyrate) compared with undifferentiated HT-29 cells. CONCLUSIONS: T3 induces IAP expression at the level of gene transcription. Both in vivo and in vitro, IAP transcriptional activation occurs to a greater extent in differentiated enterocytes than in undifferentiated crypt cells. Transactivation of the IAP gene by T3 is mediated via a DNA cis-element(s) located within the 2.4 kb segment present in the reporter gene.

Animals↗
PubMed1996

Cellular growth state differentially regulates enterocyte gene expression in butyrate-treated HT-29 cells.

Enterocyte differentiation occurs at the crypt-villus junction through the transcriptional activation of cell-specific genes, including the brush-border enzyme intestinal alkaline phosphatase (IAP) and the microvillar structural protein, villin. Based upon previous in vivo studies demonstrating that IAP and villin are differentially affected by alterations in epithelial growth state, we examined the regulation of these two genes in an in vitro model of enterocyte differentiation. HT-29 cells were maintained in DMEM + 10% FCS and treated with sodium butyrate to induce enterocyte differentiation. Cell count and [3H]thymidine measurements confirm that sodium butyrate causes a marked decrease in cellular growth state, consistent with the differentiation process. Northern blot analyses revealed time- and dose-dependent increases (P < 0.001) in steady-state IAP and villin mRNA levels. The increases in both IAP and villin expression were dependent upon the presence of one or more newly synthesized proteins. Post-confluence and serum starvation were used to cause cell cycle withdrawal prior to the differentiation process. As predicted from our previous in vivo data, villin expression was unaffected by changes in cellular growth state, whereas IAP expression was dramatically diminished under hypoproliferative conditions. We conclude that early withdrawal from the cell cycle alters the course of enterocyte differentiation, specifically decreasing IAP expression.

Alkaline Phosphatase↗
PubMed1995

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)

Animals↗
PubMed1995

Outpatient thyroid and parathyroid surgery: a prospective study of feasibility, safety, and costs.

BACKGROUND: The purpose of this study was to determine feasibility, safety, and cost savings of outpatient thyroid and parathyroid surgery. METHODS: Consecutive unselected patients undergoing thyroid and parathyroid operations by two surgeons with a special interest in endocrine surgery were studied prospectively. RESULTS: One-hundred patients underwent operation, 61 as outpatients and 39 as inpatients. Outpatients included those undergoing thyroid lobectomy (39), total thyroidectomy (10), total thyroidectomy with parathyroidectomy (1), total thyroidectomy with modified neck dissection (1), and parathyroidectomy (10). Inpatients included those undergoing thyroid lobectomy (15), total thyroidectomy (8), total thyroidectomy with neck dissection (4), removal of substernal goiter (2), and parathyroidectomy (10). The average age of inpatients was slightly higher than that of outpatients (p < 0.05). Average hospital cost for outpatients was $1991 +/- $279 (range, $1594 to $2783) and for inpatients it was $2875 +/- 615 (range, $2031 to $4216), p < 0.001. Reasons for admission included extent of surgery (6), nausea (5), oversedation (4), urinary retention (2), inadequate home help (6), long travel time (2), patient preference (9), and medical reasons (5). No outpatients subsequently required admission. CONCLUSIONS: Outpatient thyroid and parathyroid surgery can be feasible and safe and resulted in a 30% savings in hospital costs. After extensive operations patients continue to require admission for postanesthetic complications, social reasons, or presence of serious comorbid disease.

Adult↗
PubMed1995

Small bowel adaptation: counterregulatory effects of epidermal growth factor and somatostatin on the program of early gene expression.

BACKGROUND: Small intestinal crypt cell proliferation is essential to the normal renewal of the epithelium, as well as the adaptive responses that follow resection or injury. The present studies were designed to elucidate the molecular mechanisms by which epidermal growth factor (EGF) and somatostatin interact to regulate crypt cell proliferation. METHODS: Rat crypt (IEC-6) cells were maintained in Dulbecco's modified Eagle's medium plus 10% fetal calf serum and treated with EGF (10 or 100 ng/ml) or somatostatin (0.5 microgram/ml). Cell counts were done to examine the effects on cellular growth, and Northern blot analyses were carried out by using complementary DNA probes corresponding to various protooncogenes. RESULTS: EGF caused a 41% increase in cellular growth, an effect that was almost completely blocked by pretreatment (30 minutes) with somatostatin. EGF led to dramatic increases in c-fos (greater than 20-fold), c-jun (2-fold), and jun B (3-fold) gene expression at 30 minutes, consistent with the previously characterized immediate-early gene response in IEC-6 cells. Somatostatin alone had no effects on protooncogene levels, but pretreatment with somatostatin resulted in a marked inhibition (80%, p < 0.001 in all cases) of the EGF-induced increases in protooncogene expression. CONCLUSIONS: Somatostatin inhibits the EGF-induced protooncogene expression in IEC-6 cells. The somatostatin inhibition of immediate-early gene expression lends support to its role as a negative growth regulator in intestinal epithelia and indicates that its effect occur at an upstream site in the cellular growth response.

Adaptation, Physiological↗
PubMed1995

Pattern of rat intestinal brush-border enzyme gene expression changes with epithelial growth state.

Enterocyte growth and differentiation occur simultaneously within the epithelium, but little is known regarding any relationship between these two processes. Four rat models of small intestinal epithelial hypo- and hyperplasia (neonatal ontogeny, fasting/refeeding, hypo-/hyperthyroidism, and bombesin treatment) were used to study the regulation of enterocyte gene expression in relation to epithelial growth state. Mucosal scrapings, as well as crypt and villus cell populations, were subjected to Northern blot analyses using radiolabeled cDNA probes corresponding to lactase, intestinal alkaline phosphatase, villin, ornithine decarboxylase (ODC), and the actin control. In all four models, the hypoplastic (atrophic) condition is characterized by high levels of lactase and low levels of the 3.0-kb intestinal alkaline phosphatase mRNA, whereas under hyperplastic conditions this pattern is reversed. The changes in intestinal alkaline phosphatase and lactase are qualitatively similar along the longitudinal axis of the intestine and are proportional to the degree of hyperplasia, as verified by ODC mRNA levels. Furthermore, the crypt-villus axis of differentiation is maintained regardless of epithelial growth state. In conclusion, the pattern of brush-border enzyme gene expression changes as a function of epithelial growth state, indicating a previously unrecognized degree of plasticity to the state of enterocyte differentiation.

Alkaline Phosphatase↗
PubMed1994

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)

Animals↗
PubMed1994

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.

Animals↗
PubMed1994

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.

Alkaline Phosphatase↗
PubMed1994

Fine-needle aspiration of normal thyroid tissue may result in the misdiagnosis of microfollicular lesions.

BACKGROUND: Inadvertent sampling of normal thyroid tissue surrounding a nodule may occur when clinically inexperienced personnel perform fine-needle aspiration (FNA) or when a nodule is small. Because the cytologic characteristics of normal thyroid tissue are not well known, we prospectively studied 42 patients undergoing thyroidectomy. METHODS: FNA was performed from the grossly normal contralateral lobe during thyroidectomy. Cytopathologists examined the slides without knowing the source of the tissue. RESULTS: FNA of grossly normal thyroid tissue was adequate for interpretation in 32 of 42 patients, and in nine of 42 cases it was interpreted as unremarkable. However, the remaining specimens were classified as microfollicular lesions (18), mixed macromicrofollicular lesions (three), Hürthle cell lesion (one), and papillary thyroid carcinoma (one). CONCLUSIONS: FNA of grossly normal thyroid tissue suggested a microfollicular lesion in 18 (56%) patients, a result that would raise the possibility of a follicular carcinoma and often lead to the recommendation for operation. When FNA is performed, normal thyroid tissue surrounding a nodule should be avoided, and the possibility of a sampling error should be considered when a microfollicular pattern is obtained in a patient with a small nodule.

Biopsy, Needle↗
PubMed1994

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.

Alkaline Phosphatase↗
PubMed1993

c-erb-A mRNA correlates with T3-receptor levels in liver and pituitary of tumor rats.

In the rat tumor model of the sick euthyroid syndrome, differential regulation of T3-induced cellular responses have been demonstrated in liver and anterior pituitary. These effects occur with a concomitant decrease in nuclear thyroid hormone receptor (TR) number as measured by the binding of 125I-labeled T3. To explore the possibility that these altered responses to T3 in tumor rats resulted from changes in the expression of different TR forms, we correlated the relative abundance of mRNAs encoding each receptor form with the concentration of TR measured by specific T3 binding. In anterior pituitary of tumor rats, TR beta-1 and beta-2 mRNA levels decreased to 51 and 45%, respectively, compared to controls; rat c-erb A alpha-2 mRNA, which encodes a TR-related DNA alpha-binding protein that does not bind T3, decreased to 46% of control. These findings correlate with a decrease in nuclear T3 binding capacity that has been shown to be 63% of control. The level of TR beta-1 mRNA, the only quantifiable TR form in liver, was decreased to 61% of control in the same hepatic tissue that revealed a 50% decrease in TR as measured by specific T3 binding. The coordinate down-regulation of all TR mRNA forms to a degree that parallels the decrease in TR number as measured by specific T3 binding suggests that the differential regulation of T3-mediated effects in illness is by a mechanism other than changing concentrations of specific receptor forms.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Thyroid hormone differentially regulates rat intestinal brush border enzyme gene expression.

Thyroid hormone [triiodothyronine (T3)] has been shown to play a critical role in the growth and maturation of the mammalian small intestine, but its mechanism of action has not been well studied. In the current study, an animal model of hypothyroidism and hyperthyroidism was used to study the effects of T3 on the small intestine. Adult rats were treated with propylthiouracil for a 6-week period and then given injections of either saline (hypothyroid) or 30 micrograms/100 g body wt of T3 (hyperthyroid). Northern blot analyses showed marked differential regulation of brush border enzyme gene expression. Lactase messenger RNA (mRNA) levels decreased approximately 75% along the length of the small intestine, whereas sucrase levels were unchanged. The intestinal alkaline phosphatase mRNA species were upregulated by T3, especially the 3-kilobase band, which increased most dramatically in jejunum. Further experiments showed significant levels of both the alpha-1 and beta-1 T3 receptor mRNAs within the small intestinal mucosa. Histological examination showed that T3 treatment causes marked villus hyperplasia throughout the length of the small intestine. These results provide insight into the mechanism by which T3 exerts its influence on the growth and differentiation of the intestinal epithelium.

Actins↗
PubMed1990

Gene expression from the c-erbA alpha/Rev-ErbA alpha genomic locus. Potential regulation of alternative splicing by opposite strand transcription.

Alternative splicing of the c-erbA alpha gene transcript generates mRNAs encoding a thyroid hormone (T3) receptor (alpha 1) and a non-T3-binding variant (alpha 2). Also encoded at this genomic locus is Rev-ErbA alpha (Rev), a non-T3-binding member of the T3/steroid hormone receptor family. The DNA strand coding for Rev is opposite of that encoding the c-erbA alpha proteins, such that bidirectional transcription is required to generate the Rev and alpha 2 mRNAs. We have used cycloheximide as a tool for studying the regulation of gene expression from this complex genomic locus. In 235-1 cells cycloheximide treatment increased Rev mRNA levels by 50-100-fold. The effect was detectable after a 1-2-h incubation with 20 micrograms/ml cycloheximide and maximal at 24 h. The cycloheximide-induced increase in Rev gene expression was due to inhibition of protein synthesis since anisomycin caused a similar induction of Rev mRNA. Nuclear run-on assays revealed an approximately 10-fold increase in the transcriptional rate of the Rev gene during cycloheximide treatment. In addition, cycloheximide stabilized the Rev mRNA, as evidenced by half-life determinations in the presence of actinomycin D (5 ng/ml). Thus, labile proteins repress basal Rev gene expression both transcriptionally and post-transcriptionally. Cycloheximide treatment also increased alpha 1 and decreased alpha 2 mRNA levels, with the alpha 1/alpha 2 ratio increasing approximately 10-fold. Interestingly, however, these effects appeared not to be due to changes in rates of transcription or degradation of either mRNA. A likely alternative, given the structure of the c-erbA alpha gene, is that inhibition of protein synthesis resulted in a change in the c-erbA alpha splicing pattern. We hypothesize that this may be causally related to the accumulation of Rev mRNA (or the nascent Rev gene transcript), which could inhibit splicing to alpha 2 by hybridizing to complementary sequences, favoring alpha 1 mRNA production. Since alpha 1 is a T3 receptor whereas alpha 2 is an inhibitor of T3 action, such changes could influence target cell responsiveness to T3.

Cell Line↗
PubMed1990

Differential and tissue-specific regulation of the multiple rat c-erbA messenger RNA species by thyroid hormone.

Thyroid hormone (T3) has been shown to regulate the level of its receptor in a number of tissues and cell lines. Recently, proteins encoded by the protooncogene c-erbA have been identified as T3 receptors. In the rat, four c-erbA gene products have been isolated, three of which, r-erbA alpha-1, r-erbA beta-1, and r-erbA beta-2, encode biologically active T3 receptors; the fourth, r-erbA alpha-2, may play an inhibitory role in T3 action. The present work examines the molecular nature of T3 receptor autoregulation using probes specific for each c-erbA mRNA. Rats were rendered hypothyroid with propylthiouracil and then treated with either saline or T3. Northern blot analyses reveal marked tissue-specific and differential regulation of the multiple c-erbA mRNAs by T3. In the pituitary the levels of r-erbA beta-1 mRNA increase, whereas the levels of the pituitary-specific r-erbA beta-2 mRNA decrease with T3 treatment. In heart, kidney, liver, and brain the levels of r-erbA beta-1 are unaffected by thyroidal status. The levels of both r-erbA alpha mRNAs decrease with T3 treatment in all tissues examined except for the brain, where there is no change. In addition, we find that changes in the mRNAs encoding specific subpopulations of T3 receptors do not always parallel changes in total nuclear T3 binding. Differential regulation of the specific c-erbA mRNA species could have important consequences for T3 action.

Animals↗