Biomedical subjects

J ten Kate

Publications and source records attributed to J ten Kate.

At least 19 recordsLinked to original sources

PubMed2006

Tibolone and metabolites induce prolactin production in human endometrial stromal cells in vitro: evidence for cell-specific metabolism.

In this study, we assessed the effects of tibolone and its metabolites on the production of a progesterone sensitive parameter, prolactin, in human endometrium stroma cells in vitro. In addition, the metabolism of the compounds by isolated stromal and epithelial cells was evaluated. The reference compounds, progesterone, Org 2058, and DHT all induced prolactin production. Oestradiol also slightly induced prolactin production and enhanced the response to Org 2058. Tibolone and Delta4-tibolone were similar with regard to potency to induce prolactin levels in the culture supernatant. Their potency was lower than that of Org 2058, similar to that of progesterone and higher than that of DHT. The efficacies of tibolone, Delta4-tibolone and Org 2058 were similar (approximately 200-fold induction). The estrogenic tibolone metabolites 3alpha- and 3beta-OH tibolone also significantly stimulated prolactin production. Their potency, however, was low since significance was reached only at the highest concentrations tested. The PR antagonist Org 31710 inhibited both tibolone- and Delta4-tibolone-induced prolactin production. The responses of tibolone and Delta4-tibolone were not affected by co-incubation with the androgen receptor antagonist OH-flutamide. The effect of tibolone, but not Delta4-tibolone, was antagonized approximately 50% in combination with the highest dose (1 microM) estrogen receptor antagonist, ICI 164384. The induction of prolactin by 3alpha- and 3beta-OH tibolone was antagonized most potently by Org 31710, but also by ICI 164384 and OH-flutamide. Tibolone is metabolized differently in epithelial and stromal cells of the human endometrium. The epithelial cells mostly produce the progestagenic/androgenic Delta4-tibolone. The stromal cells produce predominantly the 3beta-OH tibolone, and some Delta4-tibolone, but the net effect observed with regard to prolactin production is progestagenic. When the metabolites 3alpha-OH, 3beta-OH, and Delta4-tibolone were added to the cultures no conversions were observed. The HPLC analyses showed no evidence for the production of sulfated metabolites. In conclusion, the net effects on endometrial stromal cells are predominantly progestagenic. Tibolone is converted by epithelial cells into Delta4-tibolone which displays progestagenic and androgenic activities, whereas in stromal cells also the estrogenic metabolites 3alpha- and 3beta-OH tibolone are formed.

Cells, Cultured↗

PubMed2001

Intestinal permeability in newborns with necrotizing enterocolitis and controls: Does the sugar absorption test provide guidelines for the time to (re-)introduce enteral nutrition?

BACKGROUND: In necrotizing enterocolitis (NEC), (sub)mucosal edema, hemorrhage, ulceration, or necrosis will disturb intestinal integrity, as reflected by an increased intestinal permeability. Enteral substrate is therefore withheld for a variable period up to 3 weeks (in many clinics). The authors used the sugar absorption test to measure intestinal permeability changes in surgically treated necrotizing enterocolitis patients and surgical controls to evaluate the usefulness of this test in timing the (re-)introduction of enteral feeding in NEC patients as intestinal integrity recovers. METHODS: Changes in intestinal permeability to lactulose and rhamnose were evaluated prospectively in 13 children with NEC and 10 operated control patients. The patients were given 1 mL/kg body weight lactulose/rhamnose solution at different time intervals after admission. The lactulose to rhamnose (L/R) ratio was determined by gaschromatography in 4-hour urine samples. RESULTS: The L/R ratios in NEC patients were increased for prolonged periods of time with a tendency to decrease in the third week after the start of NEC. However, in some cases, the increased L/R ratios even exceeded the 3-week period of starvation. High peaks in the L/R ratio were seen in patients suffering from bowel perforation or sepsis. Compared with necrotizing enterocolitis patients, L/R ratios of control patients were increased only in the first days after surgery and normalized more rapidly. The results of the L/R tests in this study corroborated the clinical condition of the patients. CONCLUSIONS: The sugar absorption test shows an individual variability in the recovery of intestinal permeability in a group of seriously ill newborns with advanced stages of NEC. An individual approach in restarting enteral nutrition seems to be justified; however, the optimal time-point to restart enteral nutrition cannot be determined by the sugar absorption test alone. Combining parameters of intestinal integrity and function could enable a more accurate determination of this optimal timepoint. J Pediatr Surg 36:587-592.

Capillary Permeability↗

PubMed2001

Iron saturation of serum ferritin in patients with adult onset Still's disease.

OBJECTIVE: Patients with Still's disease show a prominent acute phase reaction. Our hypothesis is that under these circumstances the iron uptake of ferritin will not keep pace with its synthesis, and is therefore not a valid reflection of the iron status in these patients. METHODS: Previously we developed a method to measure the iron content of ferritin; we investigated the usefulness of this method to establish the iron status of patients with anemia of inflammation. RESULTS: In 9 patients with adult onset Still's disease (AOSD) we observed high ferritin concentrations and measured the iron saturation of ferritin. The mean value of saturation was 9.1%, while saturation in the healthy control group was 17.8%, a statistically significant difference (p < 0.005). Soluble transferrin receptor concentrations indicated a functional iron deficiency. CONCLUSION: We conclude that the acute phase ferritin in patients with AOSD contains less iron in comparison to ferritin in healthy controls. We suggest that soluble transferrin receptor is the method of choice in estimating the iron status of patients with an acute phase reaction.

Acute-Phase Reaction↗

PubMed1999

Iron saturation of ferritin in the course of phlebotomy treatment in patients with haemochromatosis.

This paper describes the iron saturation of ferritin in haemochromatosis patients during phlebotomy therapy. The iron saturation of ferritin does not change during therapy and cannot be used as a parameter to follow therapy. Furthermore, the iron saturation seems to be a constant characteristic of a given person. It does not vary with the body iron stores in patients with haemochromatosis.

Adult↗

PubMed1998

Expression of a marker for colonic crypt base cells is correlated with poor prognosis in human colorectal cancer.

BACKGROUND: There is a need for markers in colorectal cancer which will allow subclassification of stage groups into subgroups with high versus low risk of recurrent disease. AIMS: To develop monoclonal antibodies that recognise antigens or immature crypt base cells, on the assumption that in a neoplasm undifferentiated but not the terminally differentiated cells will be responsible for tumour progression. METHODS: Colon crypt cells which were isolated from human colonic mucosa by EDTA/EGTA incubation were studied. By stepwise harvesting, crypt base cell enriched fractions were obtained, and after incubation with antibodies against dominant antigens, used as immunogens. RESULTS: Of one crypt base cell specific antibody (5E9), the reactive epitope appeared to be a non-terminal carbohydrate in the mucin O-glycans of the colon. The epitope did not seem to be colon specific, but was expressed in a variety of other tissues. In colorectal carcinomas, 5E9 immunoreactivity identified a subgroup of patients with a tendency for worse prognosis. CONCLUSION: A mucin associated maturation epitope was identified in colonic crypt base cells, the expression of which in Dukes' stage B3 colorectal carcinoma may be associated with poor prognosis.

Adenocarcinoma↗

PubMed1997

The iron content of serum ferritin: physiological importance and diagnostic value.

In this paper we present a method for determining the iron saturation of ferritin as a possible independent predictor of iron stores. Serum ferritin was purified by immunochemical precipitation, and could be completely recovered from serum without any contamination from transferrin. The iron content of the precipitated ferritin was determined by flameless atomic absorption spectrophotometry (FAAS) and the ferritin-iron saturation was calculated using the original serum ferritin concentration. The intra- and inter-assay variation coefficients were 4.2% and 13.4% respectively. The first results with this assay indicate that serum ferritin contains a considerable amount of iron. Furthermore the results show that the iron saturation of ferritin in patients with acute phase response is significantly lower than the saturation found in healthy volunteers (19.3% and 24.3% respectively). These results suggest a possible role for the ferritin-iron saturation in the assessment of iron stores in patients suffering from acute phase response. In addition, the considerable amount of iron in ferritin suggests the need to revise the physiological role of this substance in relation to the serum iron homeostasis.

Acute-Phase Reaction↗

PubMed1996

p21ras in carcinogenesis.

The activation of p21ras proteins is required in signal transduction pathways that lead to cell proliferation. More recently, a role for p21ras proteins has also been suggested in pathways to apoptosis and in the regulation of the cell cycle. Pointmutated p21ras oncogenes code for constitutively activated p21ras proteins, which disturb the balance between cell growth and cell death in favour of cell growth. In this way, p21ras oncoproteins may contribute to carcinogenesis. The binding of growth factors to their receptors triggers a cascade of protein interactions, including activation of the p21ras proteins. In turn, p21ras proteins set the machinery for cell division in motion by stimulating different effector proteins which regulate the morphological alterations, the nutritional requirements, and the changes in gene expression necessary for cell division. The presence of p21ras oncoproteins constitutively stimulate proliferation, whilst the apoptotic pathway is suppressed along with the loss of cell cycle regulation. This review describes the function of the p21ras proteins in signal transduction pathways that control proliferation and apoptosis, and regulate the cell cycle. The dysregulation of these signal transduction pathways due to the presence of p21ras oncoproteins is discussed in the context of early carcinogenesis.

Animals↗

PubMed1995

In vivo and in vitro invasion in relation to phenotypic characteristics of human colorectal carcinoma cells.

In this study we investigated the tumorigenicity, growth pattern and spontaneous metastatic ability of a series of nine human colorectal carcinoma cell lines after subcutaneous and intracaecal xenografting in nude mice. CaCo2 cells were found to be poorly tumorigenic to non-tumorigenic in either site; the other cell lines were tumorigenic in both sites. SW1116, SW480 and SW620 did not show local invasive in the NCI-H716 and LS174T cells were both invasive in the caecum, but only NCI-H716 was invasive in the subcutis. HT29 and 5583 (S and E) cells were invasive in the caecum and from that site metastatic to the lungs and/or the liver. HT29 and 5583S cells were both invasive in the subcutis, but 5583E cells were not. Of each category of in vivo behaviour in the caecum, one cell line was further investigated with regard to invasion in vitro (into embryonic chick heart fragments), E-cadherin expression in vivo and in vitro and in vitro production of u-PA and t-PA. These parameters were chosen in view of their purported role in extracellular matrix degradation and intercellular adhesion, which are all involved in the invasive and metastatic cascade. Invasion in vitro was not predictive for invasion or metastasis in vivo. In the cell line which showed invasion in embryonic chick heart tissue, heterogeneous E-cadherin expression was observed in vitro together with a relatively high production of u-PA. The non-invasive cell lines showed in vitro homogeneous expression of E-cadherin with a relatively low production of u-PA. In vivo expression of E-cadherin was either absent or heterogeneous. We conclude that: (1) colorectal carcinoma xenografts show site-specific modification of in vivo invasive and metastatic behaviour; (2) invasion in vitro does not correlate with invasion and metastasis in vivo; (3) in vitro non-invasion might be associated with homogeneous E-cadherin expression and low production of u-PA; (4) E-cadherin expression in vitro differs from E-cadherin expression in vivo. The results support the notion that the microenvironment in which cancer cells grow is one of the factors involved in the regulation of invasive and metastatic behaviour.

Animals↗

PubMed1994

Type and number of Ki-ras point mutations relate to stage of human colorectal cancer.

Point mutations in the Ki-ras gene belong to the genetic key events in tumorigenesis of colorectal cancer. The type and number of point mutations were detected in specimens from patients with colorectal carcinomas stages as Dukes B and C using single-stranded conformational polymorphism analysis and sequencing. G-A transitions in codon 12 were exclusively found in Dukes B tumors, G-T transversions mainly in Dukes C, and G-C transversions only in Dukes C tumors. Apparently, the G-T and G-C transversions are associated with metastatic behavior of colorectal carcinomas, while G-A transitions are not. In several samples, multiple point mutations could be detected in codon 12, the frequency of multiple mutations increasing with the stage of the tumor.

Base Sequence↗

PubMed1994

L-CAM expression in lymph node and liver metastases of colorectal carcinomas.

L-CAM, also known as E-cadherin, is a cell adhesion molecule expressed on the plasma membranes of epithelial cells at the intercellular interface. From in vitro gene transfection experiments the idea has been conceived that loss of L-CAM expression might be related to the invasive capacity as well as metastatic potential of tumour cells. In several tumours a relation between the grade of differentiation and L-CAM expression has been noticed: loss of differentiation appears to be associated with loss of L-CAM immunoreactivity. Also, in lymph node metastases of poorly differentiated carcinomas loss of L-CAM expression was demonstrated. In this study we describe L-CAM expression in lymphogenous and haematogenous metastases of large bowel adenocarcinomas, using an indirect immunoperoxidase method with the monoclonal anti-L-CAM antibody 6F9. All the metastases studied--lymphogenous as well as haematogenous--demonstrated L-CAM immunoreactivity in a pattern comparable to that of primary tumours. Intratumour heterogeneity in expression was noted, with normal intercellular, apical (non-functional), and focally negative areas in the same tumour. The data indicate that primary tumours and their metastases do not differ strikingly in their pattern of L-CAM expression. This would be consistent with transient rather than constitutive down-regulation of L-CAM in invasive and metastatic cancer cells.

Cadherins↗

PubMed1993

Transfected c-Ha-ras oncogene enhances karyotypic instability and integrates predominantly in aberrant chromosomes.

A human colon tumor cell line, SW480, was transfected with the c-Ha-ras oncogene, the wild type c-Ha-ras gene, or the pSV2neo plasmid. Cytogenetic analysis and localization of chromosome integration sites were combined in an attempt to analyze the effects of transfection with the c-Ha-ras oncogene on the karyotype. All transfected cell lines showed new clonal chromosome abnormalities present in all cells, ranging from three new aberrations in pSV2neo-transfected SW480 cell lines to eight in c-Ha-ras oncogene-transfected SW480 cell lines. The level of expression of c-Ha-ras mRNA after transfection with the c-Ha-ras oncogene was positively correlated with increased genetic instability, reflected in enhanced karyotypic instability. A combination of banding and fluorescence in situ hybridization (FISH) was used to identify chromosome integration sites. Plasmids containing ras integrated predominantly in new structurally rearranged chromosomes (five of eight). Three of five integration sites in new structurally rearranged chromosomes were localized at or near translocation breakpoints situated in telomeric regions. Specific chromosomes were not involved in the chromosome rearrangements. The results indicate that 1) enhanced expression of c-Ha-ras mRNA correlates with an increase in genetic instability in c-Ha-ras oncogene-transfected SW480 cell lines, and 2) that no specific integration site was observed but ras-containing plasmids were located predominantly in aberrant chromosomes near or at translocation breakpoints involving telomeric bands.

Chromosome Aberrations↗

PubMed1993

Human Caco-2 cells transfected with c-Ha-Ras as a model for endocrine differentiation in the large intestine.

Endocrine cells occur in approximately 30% of all colorectal adenocarcinomas, and this feature appears to correlate with a relatively poor prognosis. To study the factors regulating endocrine differentiation in colorectal cancer, which may bear resemblance to the regulation of endocrine differentiation in normal intestinal mucosa, models in which differentiation can be manipulated are essential. However, endocrine features in colorectal cancer cell lines are scarce and are almost exclusively observed in xenografts, presumably as a result of differentiation induction by stromal components. We attempted to demonstrate endocrine differentiation in the colonic adenocarcinoma cell line Caco-2, which is frequently used as a model for enterocytic differentiation. In vitro endocrine tumor cells were not encountered. In vivo studies were cumbersome, because of the low take rate of Caco-2 cells. We did manage to establish nude mouse xenografts of Caco-2 cells by inoculating cells in collagen gel and by suppressing natural killer cell activity. In an attempt to induce a better take rate and to investigate the effect of Ras oncoprotein overexpression on endocrine differentiation, Caco-2 cells were transfected with a point-mutated c-Ha-Ras gene. The cell line Caco-2 EJ6, generated from these experiments, could be xenografted in nude mice with a high take rate, yielding a moderately well differentiated adenocarcinoma, morphologically identical to the tumors derived from untransfected Caco-2 cells. The xenografts displayed goblet cell, enterocytic, Paneth cell and endocrine differentiation. In vitro endocrine differentiation was observed neither under standard conditions nor with extracellular matrix components as differentiation inducers. We conclude that the Caco-2 cell line and its c-Ha-Ras transfected subline Caco-2 EJ6 in vivo display endocrine differentiation. Ras overexpression does not enhance endocrine differentiation. Due to its favorable growth properties in vivo, Caco-2 EJ6 is a suitable model for studies on endocrine differentiation in colorectal cancer.

Animals↗

PubMed1993

Epithelial-stromal interactions in colon cancer.

In this paper investigations concerning the interactions at the interface between tumor cells and tumor stroma are reviewed. As a model for tumor cell-extracellular matrix interaction human colorectal carcinoma cell lines, in vitro and in vivo, in nude mouse xenografts, were chosen. Based on the available data and on a review of the literature the following conclusions can be drawn. Most malignant epithelial neoplasms at the site of tumor cell invasion display defects in the epithelial basement membrane. This is not merely the result of enzymatic dissolution but rather reflects a shift in basement membrane turnover towards degradation. Elsewhere in the same primary tumor or in a metastasis the balance might be shifted more towards basement membrane deposition. The tendency of a tumor to deposit basement membranes reflects the biological potential of the neoplasm. Basement membranes are deposited by stromal cells or by a concerted action of tumor and stromal cells. Differentiation in a carcinoma is modulated by factors in the extracellular matrix. Endocrine differentiation can be induced in vitro by native basement membranes but also by direct contact of the tumor cells with fibroblasts. Basic FGF is one of the extracellular matrix factors with differentiation inducing capacity. Expression of cell adhesion molecules and integrin receptors tends to be down-regulated in carcinoma cells. Alterations in the expression of these proteins might not be constitutive but rather modulated by the direct environment of the tumor cell and might not only include quantitative alterations but also changes in their cell surface distribution, causing or following loss of cell polarity.

Basement Membrane↗

PubMed1992

L-CAM expression in normal, premalignant, and malignant colon mucosa.

L-CAM is a cell adhesion molecule which is expressed at the intercellular borders of most epithelial cells. L-CAM has been demonstrated to act as an invasion suppressor in carcinoma cell lines. In order to determine whether or not L-CAM expression might distinguish between invasive and non-invasive or metastatic and non-metastatic colon neoplasms, we studied L-CAM expression in normal colon mucosa, colon adenomas with various degrees of dysplasia, and colon carcinomas by immunohistochemistry, using the 6F9 monoclonal anti-L-CAM antibody. Normal mucosa showed evenly distributed distinct L-CAM immunoreactivity along intercellular borders. In adenomas and carcinomas, a similar though weaker expression was observed. This pattern showed a tendency to decrease in parallel with decreasing differentiation. However, no correlation was found with Dukes stage or area within the tumour. In some carcinomas, L-CAM was expressed at the luminal surface of the cells. In others, L-CAM expression was not found. These results suggest that L-CAM expression is disregulated or lost as an early event in the development of colon neoplasia and indicate that L-CAM expression does not correlate with invasive or metastatic potential.

Adenoma↗

PubMed1992

Does ex vivo labelling of proliferating cells in colonic and vaginal mucosa reflect the S-phase fraction in vivo?

The ex vivo labelling of DNA-synthesizing epithelial cells in colonic and vaginal mucosa was compared with in vivo labelling. For this purpose, in vivo S-phase cells were labelled with [3H]thymidine (Tdr) and ex vivo labelling was continued by culturing tissue specimens in bromodeoxyuridine (BrdU). Various methods of tissue culture were employed in order to improve diffusion of medium (and BrdU) in the tissue. BrdU and 3H-TdR labelling were evaluated by immunohistochemistry and autoradiography respectively. Ex vivo labelling resulted in a patchy distribution of labelled cells, which did not correspond with the 3H-TdR labelling pattern obtained in vivo. Under the described conditions ex vivo labelling does not appear to be a reliable for estimation of the proliferative activities in vivo.

Animals↗

PubMed1992

Bromodeoxyuridine (BrdU) immunocytochemistry by exonuclease III (Exo III) digestion.

A new procedure is described to generate single-stranded DNA by exonuclease III (Exo III) digestion for bromodeoxyuridine (BrdU) immunocytochemistry on tissue sections. We compared this procedure with the most widely used procedure of DNA denaturation with 2 N HCl. In vivo and in vitro pulse and continuous labelling of tissues and cells were used. The specimens were fixed in formalin, ethanol, glutaraldehyde, Carnoy's, Bouin's or Zamboni's fixative and embedded in paraffin or used unfixed as cryostat sections or cytospin preparations. After Exo III digestion, BrdU substituted DNA was detected irrespective of the fixation procedure applied. The optimal protocol for nuclease digestion appeared to be simultaneous incubation, of 10 Units Exo III per ml EcoRI buffer and anti-BrdU monoclonal antibody at 37 degrees C. The advantages of Exo III digestion for BrdU immunocytochemistry compared to acid denaturation were: less non-specific nuclear background reactivity, no DNA renaturation, less DNA loss, optimal nuclear morphology, increase in antibody efficiency and the possibility for simultaneous detection of acid-sensitive tissue constituents. Disadvantages of the Exo III digestion are decreased sensitivity and the need for more rigorous pepsin pretreatment. We conclude that Exo III digestion of DNA is an appropriate alternative for acid denaturation for BrdU immunocytochemistry on sections of pulse-labelled specimens.

Animals↗

PubMed1990

Colonic mucosal changes in nude mice associated with orthotopic xenografts of human colon cancer cells.

We used the nude mouse tumour xenograft model to study the pathogenesis of mucosa alterations in the large bowel surrounding a carcinoma. In mouse colonic mucosa overlying HT-29 colonic carcinoma xenografts in the caecum, the crypts were elongated in comparison with those in distant mucosa and also frequently showed a shift towards sialomucin production. These features, which are comparable with socalled transitional mucosa (TM) in man, were absent in control animals inoculated with Indian Ink instead of HT-29 cells. Although the localization of the proliferative cell compartment in mouse colonic mucosa overlying HT-29 xenografts appeared to be confined to the lower half of the crypt as in normal mucosa, the relative length of the DNA synthesizing cell compartment along the crypts was slightly elongated. These data strongly suggest that TM should be regarded as a secondary phenomenon rather than a premalignant change in large intestinal epithelium and that higher proliferative activity of epithelial cells contributes little to the elongation of crypts in TM.

Animals↗

PubMed1990

Southern and dot blot analysis of DNA from formalin-fixed, paraffin-embedded tissue samples from colonic carcinomas.

Two extraction methods for the isolation of DNA from formalin-fixed, paraffin-embedded tissue samples from colonic carcinomas were compared. The processed DNAs were compared with DNAs from fresh specimens of the same tumors. The two extraction methods gave similar results. Formalin-fixation and paraffin-embedding irreversibly denatured DNA and consequently decreased the extraction yield and interfered with the quantitative measurement of DNA. Southern blot and dot blot analysis of processed and native DNA was performed using a c-myc and an actin probe. The results show that for Southern analysis processed DNA can be used but, due to the generation of random breaks, the restriction fragments have to be small. Furthermore, the fixation-induced crosslinking of DNA appears to hamper hybridization. For these reasons processed DNA can be analyzed better by dot blot rather than Southern blot hybridization.

Blotting, Southern↗