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A Bosma

Publications and source records attributed to A Bosma.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effect of adrenalectomy in kindled rats.

It has previously been observed that adrenalectomy (ADX) increases the amplitude of transient Ca currents in CA1 hippocampal neurons. In the present study, the effect of ADX on cellular properties of CA1 neurons was investigated under conditions that challenge the CA1 network, i.e. in fully kindled rats, 5-6 weeks after the last kindling session. At this time, adrenally intact kindled rats showed, in comparison to non-kindled controls, a reduced population spike amplitude evoked in the CA1 area by Schaffer/commissural fiber stimulation, an increased amplitude of low-threshold, transient Ca currents and a decrease of the high-threshold, sustained Ca currents. As observed before, ADX in non-kindled rats increased the amplitude of transient Ca currents while sustained Ca currents were not affected. In kindled rats, ADX did not increase the transient Ca current amplitude beyond the level reached by kindling alone. The kindling-induced reduction of the sustained Ca current was partly normalized after ADX. Field responses of kindled rats were not affected by ADX. These data support the view that lack of adrenal hormones does not exacerbate but, to some extent, normalizes the kindling-induced changes in cellular properties and network function of the CA1 area. The hormonal effects on kindling may be reciprocal in nature, since kindling, in turn, was found to affect the stress response and the corticosteroid receptor mRNA expression in the hippocampus.

Adrenal Glands↗
PubMed1996

Corticosteroid actions on the expression of kainate receptor subunit mRNAs in rat hippocampus.

Previous studies have shown that corticosteroid hormones affect kainate-induced excitotoxic processes in the rat hippocampus. In the present study we employed in situ hybridization to examine the effect of adrenalectomy, and subsequent treatment with a low or a high lose of corticosterone on the mRNA levels for kainate receptor subunits in the hippocampus. We observed that adrenalectomy by itself does not affect the expression pattern for the GluR6, GluR7, KAR1 and KAR2 subunits. However, treatment of the adrenalectomized animals with a low dose of corticosterone (3 micrograms/100 g bodyweight) resulted in an enhanced expression of the KAR1, KAR2 and GluR6 subunit mRNAs, when compared to the expression levels in the untreated rats or the sham operated controls. Treatment with a high dose of corticosterone (1 mg/100 g bodyweight) yielded expression levels which were significantly lower than those observed in animals treated with a low corticosterone dose, for the KAR1, KAR2 and GluR7 subunit mRNAs; the levels did not differ from those in untreated rats or in the sham group. We conclude that changes in corticosteroid receptor occupancy, which may occur daily due to circadian or stress-induced variations in the circulating corticosterone level, potentially regulate high affinity kainate receptor activation and the processes in which these receptors are involved.

Adrenal Cortex Hormones↗
PubMed1995

Risk of residual rectal mucosa after proctocolectomy and ileal pouch-anal reconstruction with the double-stapling technique. Postoperative endoscopic follow-up study.

PURPOSE: This study was designed to assess the risk of retained rectal mucosa after proctocolectomy and ileal pouch-anal anastomosis with the double-stapling technique. METHODS: A total of 113 patients underwent proctocolectomy with an ileal pouch-anal reconstruction. In 57 patients the anastomosis between pouch and proximal anal canal was performed using the double-stapling technique. In 26 patients the procedure was carried out without a protecting ileostomy. Of the remaining 31 patients with a proximal ileostomy, 15 underwent endoscopy six weeks postoperatively. Circular biopsies were taken just distal from the pouch-anal anastomosis. RESULTS: Histologic examination revealed rectal mucosa in at least one biopsy in 7 of 15 patients. At follow-up (mean 18 months) no (distal) pouchitis was clinically noticed. In one patient with familial polyposis, a few polyps, distal of the anastomosis, had to be endoscopically removed. CONCLUSIONS: Double-stapled ileal pouch-anal anastomosis has a considerable risk of residual rectal mucosa, because of combined linear transection and circular stapling with bilateral dog-ear formation of rectal mucosa. Residual rectal mucosa did not seem to influence clinical results at follow-up.

Adenomatous Polyposis Coli↗
PubMed1995

Role of vitamin A in liver fibrosis.

The relationship between vitamin A and liver fibrosis was studied with a CCl4-induced fibrosis model in rats. Depending on the time of administration, vitamin A can potentiate or reduce fibrosis: when present during CCl4-treatment parenchymal cell damage and fibrosis were enhanced, whereas vitamin A post-treatment strongly reduced fibrosis. Enhanced fibrosis was also found in rats with low hepatic retinoid levels. Administration of beta-carotene during CCl4-treatment reduced several signs of fibrosis. The notion that liver retinoids play an important role in hepatic fibrogenesis is discussed.

Animals↗
PubMed1995

Beta-carotene (provitamin A) decreases the severity of CCl4-induced hepatic inflammation and fibrosis in rats.

Earlier data from experiments in rats have shown that administration of retinyl esters (vitamin A) strongly influences the effects of CCl4 on the liver. The accumulation of collagen was inhibited, but an increase in CCl4-toxicity with high mortality was observed. The present study was conducted to examine the effects of beta-carotene (provitamin A) on CCl4-related general and hepatic toxicity in rats. Oral administration of beta-carotene during CCl4-treatment resulted, biochemically, in a significantly lower increase in the hydroxyproline liver content and, histopathologically, in less severe liver fibrosis as compared with the liver of rats not treated with beta-carotene. The study also showed that beta-carotene administration could prevent the long-term loss of retinoids from the CCl4-injured liver. No significant toxic effects of beta-carotene, as previously found with retinyl esters (vitamin A), were observed. This experimental study suggests that beta-carotene has the therapeutic potential to decrease the severity of liver fibrosis without marked toxicity.

Animals↗
PubMed1994

Experimental colitis in rats induces low-grade endotoxinemia without hepatobiliary abnormalities.

In three experimental models in rats, surgical construction of a self-filling blind loop (SFBL), trinitrobenzene sulfonic acid (TNB) -induced colitis, and the combination of SFBL and TNB, the hypothesis was studied that intestine-derived endotoxins play a role in the pathogenesis of hepatobiliary disorders in chronic inflammatory bowel disease (CIBD). After eight weeks of treatment, a mild increase in portal and systemic endotoxin levels and interleukin-6 concentrations was observed and the serum levels of alkaline phosphatase, bilirubin, and ALAT were only mildly increased in SFBL plus TNB rats. Histopathological examination of the liver showed hardly any abnormalities in all three rat models. These results show that low-grade portal and systemic endotoxinemia in rats, induced by bacterial overgrowth and/or chemical colitis, is not able to induce hepatobiliary alterations. To exclude definitively a possible role for portal endotoxinemia in the pathogenesis of CIBD-associated hepatobiliary abnormalities, however, an adequate animal model for CIBD is urgently needed.

Alanine Transaminase↗
PubMed1994

Alcohol in combination with malnutrition causes increased liver fibrosis in rats.

Rats were malnourished for 12 months with a highly inadequate fat-rich, calorie-sufficient but otherwise poly-deficient liquid diet composed of mashed potatoes with mayonnaise, comparable with the nutritional intake of many chronic alcoholics. When alcohol was incorporated into this diet, administered as whisky in drinking water available ad libitum, the livers of all eight rats showed increased fibrosis and cirrhosis as compared to the livers of the eight non-alcohol-treated, isocalorically fed, paired control rats. Alcohol-treated rats developed fibrosis and cirrhosis on a dietary fat content of 38% of total caloric intake and low blood alcohol levels, ranging from 50 to 126 mg/dl, due to gradual intake over the day and to low absolute intake (mean 11.9 +/- 0.6 g/kg per day). None of the rats died spontaneously. Malnutrition is likely to be an important factor in the development of the fibrosis of alcoholic liver disease, and this rat model may be used to study aspects of the pathogenesis.

Alanine Transaminase↗
PubMed1994

Assessment of tumor infiltration depth in rectal cancer with transrectal sonography: caution is necessary.

PURPOSE: To assess the depth of infiltration of rectal cancer with transrectal ultrasound (US) (TRUS) and analyze interpretation errors. MATERIALS AND METHODS: Fifty-five consecutive patients with rectal cancer who underwent TRUS were prospectively studied. The effect of different patient inclusion criteria and US criteria was evaluated retrospectively. RESULTS: Extensive overstaging of T2 tumors, partially caused by inflammatory (desmoplastic) reaction or retraction of the muscularis propria, resulted in a specificity of only 24% for detection of perirectal infiltration. Sensitivity was 97%, and accuracy was 64%. Considerable variation in staging accuracy was observed when different patient selection criteria were used. Variation of US criteria improved differentiation between T2 and T3 tumors only slightly. CONCLUSION: The effect of different US criteria on differentiation of T2 and T3 tumors is limited. Spontaneous or iatrogenic inflammation is a major limiting factor. The accuracy of TRUS in staging rectal cancer is affected by patient inclusion criteria.

Aged↗
PubMed1994

Effects of biliary endoprostheses on the extrahepatic bile ducts in relation to subsequent operation of the biliary tract.

Despite the widespread use of transpapillary biliary endoprostheses, little is known about their effect on the extrahepatic bile ducts. In an experimental study in dogs, we induced inflammatory changes in the bile ducts by stent insertion and studied the reversibility of these changes after stent removal. In addition, the consequences of a period of preoperative stenting for subsequent operation of the biliary tract and the eventual detrimental effects of stenting on the histologic factors of the liver were studied. Twenty-six mongrel dogs were randomly divided into four groups: group 1, stenting during four weeks; group 2, after four weeks stenting, construction of a hepaticojejunostomy; group 3, four days of common bile duct (CBD) ligation, four weeks stenting and hepaticojejunostomy, and group 4, four days of CBD ligation and hepaticojejunostomy. All dogs were sacrificed two months after the last procedure. Hepatic biopsies were obtained during each procedure and bile duct biopsies during hepaticojejunostomy and upon sacrifice. Four weeks of stenting of a normal or obstructed CBD resulted in fibrosed bile ducts, showing severe chronic inflammation with papillary hyperplasia of the epithelium. All bile cultures grew fecal bacteria. Two months after stent removal, inflammation was still present, albeit less severe. Stenting and subsequent surgical treatment resulted in a higher incidence of postoperative complications (54 percent) compared with the control group (14 percent), although this did not reach statistical significance. Hepatic histologic factors were not markedly changed after transpapillary endoprosthesis placement, but after hepaticojejunostomy cholangiolitis was observed. Whenever transpapillary biliary endoprostheses are used, the local effects on the extrahepatic bile ducts and the subsequent bacterial contamination of the bile should be considered.

Anastomosis, Surgical↗
PubMed1994

Prognostic significance of tumor DNA content in carcinoma of the hepatic duct confluence.

BACKGROUND: In an attempt to identify prognostic factors in carcinoma of the hepatic duct confluence, the value of tumor DNA content was studied in 58 patients with this type of malignancy. METHODS: Of 58 patients (ages 26 to 74 years) surgically treated for carcinoma of the hepatic duct confluence, tumor DNA content was assessed in relationship to clinical-pathologic characteristics and patient survival. Thirty-three patients underwent additive radiotherapy. Nuclear DNA content was analyzed by flow cytometry. RESULTS: Resection was radical in only three patients with negative surgical resection margins and dissection (cleavage) margins. Twenty-eight patients (48%) had diploid tumors, and 30 patients (52%) had aneuploid tumors. No significant correlation was found between tumor DNA ploidy, degree of tumor differentiation, lymph node status, and hepatic infiltration. Aneuploid tumors were significantly associated with neural invasion. The median overall survival was 18 months. The survival period of patients with diploid tumors was significantly (p < 0.0003) longer than the survival period of those with aneuploid tumors (median survival, 26 months and 11 months, respectively). Additive radiotherapy improved survival significantly only in patients with aneuploid tumors. When tested by univariate survival analysis, DNA ploidy, additive radiotherapy, and the state of the surgical resection margins were significant prognostic factors. With multivariate survival analysis, only DNA ploidy, age, hepatic infiltration, and lymph node status were significantly related to prognosis. CONCLUSIONS: This survival analysis shows that DNA ploidy is a powerful prognostic determinant of carcinoma of the hepatic duct confluence.

Adult↗
PubMed1994

Fat-storing cells and myofibroblasts are involved in the initial phase of carbon tetrachloride-induced hepatic fibrosis in BN/BiRij rats.

This study on the appearance, distribution and kinetics of fibroblast-like cells (fat-storing cells, transitional cells, myofibroblasts and fibroblasts) after CCl4-treatment was undertaken to delineate further the respective roles of these cell types in liver fibrogenesis. The different cell types were distinguished on the basis of their immunophenotypic pattern with a combination of marker antibodies and on the basis of ultrastructural characteristics. Combined staining for alpha-smooth muscle actin (sma) and desmin (Des) revealed perisinusoidal fat-storing cells (FSC) as d+ sma- and myofibroblasts around the central veins of the normal rat liver as d+ sma+. During the initial phase of CCl4-induced hepatic fibrosis (week 1 and 2), the number of d+ sma+ cells increased in the degenerating area around the central veins and d+ sma+ cells appeared in the very thin fibrotic septa at week 2. Ultrastructural examination of the affected central areas showed the presence of myofibroblasts. These sma+ cells proliferated, as shown by double staining for bromodeoxyuridine (BrdU) and sma. In degenerating parenchymal areas, d+ sma- FSC were present. The FSC in the perisinusoidal space of areas which were not affected by CCl4 intoxification, remained d+ sma-. These immunostaining findings support the electron microscopical results, which show the presence of cells with the typical ultrastructural characteristics of FSC in both the degenerating areas and the perisinusoidal space of unaffected areas. After one week of CCl4-treatment, enhanced deposition of procollagen type III was observed around the central veins. Enhanced deposition of collagen type IV was seen subendothelially along the sinusoids, notably in degenerating parenchymal areas where the septa were later formed. FSC appear to be the principal source of collagen type IV during fibrogenesis. These observations further support and specify the role of FSC in early fibrogenesis. With the progression of the CCl4-induced fibrosis, d+ sma+ myofibroblasts remained localized in the fibrotic septa, but now along their outer edge. The majority of the cells in the septa were formed by d- sma- cells indicating a prominent role of fibroblasts in the septal formation. Septal fibroblasts are not only likely to produce matrix components, but also were shown to degrade collagen, as evidenced by the increased number of collagen-containing vacuoles during the course of fibrosis. In conclusion, myofibroblasts and FSC appear to be the main cell types involved in the initial phase of liver fibrogenesis induced by CCl4. Both myofibroblasts and FSC divide and transform.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Vitamin A deficiency potentiates carbon tetrachloride-induced liver fibrosis in rats.

Earlier studies have shown that retinoid administration suppresses the generation of hepatic fibrosis and stimulates its regression in normal (i.e., vitamin A-sufficient) carbon tetrachloride-treated rats. This study focuses on the possible role of a marginal or deficient vitamin A status on carbon tetrachloride-induced fibrosis. This experimental study in rats shows that vitamin A status, reflected by hepatic retinoid content (retinol and retinyl esters), modulates the development of hepatic fibrosis induced by carbon tetrachloride. In rats with low hepatic retinoid levels (12 +/- 0.9 micrograms/gm liver), carbon tetrachloride-induced liver fibrosis was more pronounced than in rats with sufficient hepatic retinoid levels (1,065 +/- 327 micrograms/gm liver). Enhanced liver fibrogenesis was confirmed both morphologically and by a higher hydroxyproline content of the liver. It was associated with a reduced liver weight and the development of parenchymal regeneration nodules. Furthermore, carbon tetrachloride treatment itself reduced the hepatic retinoid content in rats independently of the liver vitamin A status before treatment and increased serum retinol levels in vitamin A-sufficient rats. The results show that the vitamin A status of the liver plays an important role in hepatic fibrogenesis. Low hepatic vitamin A levels, which can be the result not only of low dietary intake but also of interference with vitamin A metabolism by agents such as ethanol and carbon tetrachloride, may be a risk factor for the development of liver fibrosis. We suggest that retinoids modulate collagen synthesis and deposition irrespective of the degree of hepatocellular necrosis induced by carbon tetrachloride.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Preservation of canine liver grafts using HTK solution.

HTK (histidine-tryptophane-ketoglutarate) organ preservation solution has been shown to be effective in human kidney transplantation, but the efficacy of HTK for extended liver preservation has not been determined. In this study, canine livers were preserved in HTK and compared with livers preserved in University of Wisconsin solution. First, the right and left liver lobes in dogs were flushed separately with cold HTK and UW, respectively, according to a double-flush method. After splitting the liver, the right and left lobes were stored at 4 degrees C in either solution for 24 hr and 48 hr and assessed microscopically for parenchymal cell swelling, and enzyme histochemically for 5'-nucleotidase (5'-NT) as a marker of ischemic liver injury. Unlike livers preserved in UW (n = 5), HTK-preserved livers (n = 5) showed progressive parenchymal cell swelling after 24-hr and 48-hr storage. The 5'-NT scores in HTK livers were lower than in UW livers, indicating increased storage injury (0-5% and 66-85% in HTK- and UW-preserved livers, respectively, after 48-hr storage). Second, graft function was tested in an orthotopic liver transplantation model in the dog. Whole livers were flushed in situ with cold HTK or UW and stored at 4 degrees C for 24 hr or 48 hr. Liver grafts stored in HTK were not washed out prior to reflow in the recipient, in contrast to grafts stored in UW. Livers preserved for 24 hr using HTK showed life-supporting function after transplantation (n = 5, survival 12 hr-8 days). All grafts preserved for 48 hr in HTK did not function (n = 5, survival < 10 hr). UW-preserved grafts all functioned after 24-hr storage (n = 5, survival > 6 days), as well as after 48-hr storage (n = 6, survival > 6 days). Peak serum glutamic oxaloacetic transaminase (SGOT) values after transplantation of 24-hr and 48-hr HTK-preserved livers did not differ from peak SGOT values of UW-preserved livers after similar preservation times. In conclusion, UW solution is more effective than HTK solution in extended preservation of canine liver grafts: 24-hr storage of livers preserved with HTK solution is feasible, whereas 48-hr storage results in a nonfunctioning graft.

5'-Nucleotidase↗
PubMed1993

Colorectal adenomas: inflammatory changes that simulate malignancy after laser coagulation--evaluation with transrectal US.

To evaluate the assumption that inflammatory changes in the rectal wall after treatment of colorectal adenoma with photocoagulation may simulate malignant infiltration, the findings were reviewed in 23 follow-up examinations performed with transrectal ultrasound (TRUS) in 17 patients with benign adenoma. Special attention was given to the appearance of the wall layers underneath the adenoma. After partial coagulation, changes in the colorectal wall were usually seen on TRUS scans obtained early in follow-up; sometimes the thickened muscle layer had an irregular outer margin. In three of the 13 early examinations, lesions mimicked malignancy. To correlate these findings with histologic proof, an experimental study was performed: Colorectal specimens from pigs were examined with ultrasound (US) and microscopy. The abnormal sonographic appearance of specimens on US scans was caused by an inflammatory reaction in the deep wall layers; concomitant serositis appeared to be responsible for the malignancy-mimicking irregular outer margin. In screening for malignancy in colorectal adenoma, TRUS may cause overstaging during the first 6 weeks after polypectomy or after a session of laser treatment and should be avoided.

Adenoma↗
PubMed1993

Role of Helicobacter pylori in the pathogenesis of complications of Meckel's diverticula.

OBJECTIVE: To assess the possible role of colonisation of ectopic gastric mucosa in Meckel's diverticula by Helicobacter pylori in causing inflammation, ulceration, perforation and bleeding. DESIGN: Retrospective study. SETTING: Three hospitals in Amsterdam, The Netherlands. MATERIAL: Specimens of 65 diverticula, 49 of which had been resected incidentally, and 16 of which had been thought to be the presenting feature. MAIN OUTCOME MEASURE: The presence of H. pylori in gastric mucosa. RESULTS: 19 Diverticula contained ectopic tissue, 18 gastric and one pancreatic tissue. Gastric tissue was found in 10 of the diverticula removed incidentally, and 8 of those that were thought to be symptomatic. In 5 of the 8 there were signs of complications that might have been related directly to the presence of gastric tissue (perforation--n = 3; bleeding--n = 1; and peptic stenosis--n = 1), and none contained H. pylori. H. pylori was found in only one of the 18 diverticula, in which there were also signs of gastritis. CONCLUSION: H. pylori has no role in the pathogenesis of the complications of Meckel's diverticula.

Adolescent↗
PubMed1992

Perirectal lymph nodes in rectal cancer: in vitro correlation of sonographic parameters and histopathologic findings.

Preoperative staging of lymph nodes in patients with rectal cancer is essential for selecting the most appropriate therapy. To determine the discriminating value of all ultrasound parameters described in the literature, the authors obtained high-frequency sonograms of 43 lymph nodes in 21 resected rectal specimens, thereby simulating the in vivo situation. Univariate analysis revealed that inhomogeneity (P less than .0005), short axis diameter (P less than .005), and hilar reflection (P less than .01) were helpful in differentiating between metastatically involved and noninvolved lymph nodes. A prognostic trend was seen for long-axis diameter (P = .05), roundness index (P = .09), and echogenicity (P = .05). With stepwise logistic regression analysis, inhomogeneity and hilar reflection were selected as being independently discriminative. Inhomogeneity is a parameter with a high specificity; hilar reflection is particularly sensitive. No clear differentiation could be made, however, in a sizable proportion of lymph nodes (60%). The prospective use of especially these significant parameters in vivo is recommended to determine their ultimate value in preoperative staging.

Humans↗