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Biomedical subjects

A Timmer

Publications and source records attributed to A Timmer.

At least 19 recordsLinked to original sources
PubMed2006

Expression and cellular localisation of chloride intracellular channel 3 in human placenta and fetal membranes.

Chloride channels regulate the movement of a major cellular anion and are involved in fundamental processes that are critical for cell viability. Regulation of intracellular chloride is achieved by multiple classes of channel proteins. One class of putative channels are the chloride intracellular channel (CLIC) family. Evidence suggests that several CLICs are expressed in human placenta, although their roles in this tissue are not certain. Northern blot analysis has shown that CLIC3 is highly expressed in placenta relative to other human tissues; however, its cellular distribution is not known. This study used microarray expression profiling to clarify which CLICs are expressed in human placenta and RT-PCR, Western blot and immunohistochemistry to determine the expression pattern of CLIC3 in human placenta and fetal membranes. Placentas and fetal membranes were obtained from term pregnancies after delivery and placental tissue was obtained from first trimester following either chorionic villous sampling or elective pregnancy termination. Trophoblast cells were isolated from first trimester and term placentas and placental endothelial cells were isolated from term placentas. Microarray expression profiling identified high expression of mRNA for CLICs 1, 3 and 4 in the isolated first trimester and term trophoblast cells. High mRNA expression in the isolated endothelial cells was also found for CLICs 1 and 4, but not CLIC3. Low expression was found for CLIC5 in all three types of isolated cells. RT-PCR confirmed that CLIC3 mRNA was expressed in trophoblast cells at both gestational ages, but was not present in endothelial cells. CLIC3 mRNA was also identified in whole placental extracts at both gestational ages and in term amnion and choriodecidua. Immunohistochemistry using a chicken anti-human CLIC3 antibody localised strong CLIC3-specific staining to the syncytiotrophoblast and villous cytotrophoblast cells in both first trimester and term placentas, and weaker staining in extravillous trophoblast cells in first trimester. In fetal membranes at term strong CLIC3-specific staining was localised to chorionic trophoblast cells, with weaker staining in amniotic epithelial and decidual cells. It was previously shown that chloride uptake was increased into cells that had been transfected with CLIC3. CLIC3 may facilitate chloride ion movement and the regulation of cellular processes associated with the movement of chloride in the placental and fetal membrane cells in which it is expressed.

Chloride Channels↗
PubMed2006

ADAM19 expression in human nephrogenesis and renal disease: associations with clinical and structural deterioration.

ADAM19, an enzyme from the ADAM (a disintegrin and metalloproteinase) family, is involved in various cell-cell and cell-matrix interactions. It can cleave epidermal growth factor (EGF)-like growth factors, such as heparin-binding (HB)-EGF and neuregulin (NRG), from the cell membrane. ADAM-mediated EGF receptor activation is crucial in the development of renal pathology. Based on these data, we studied ADAM19 in human nephrogenesis and renal disease. We collected 20 fetal kidneys and 56 biopsies from patients with various renal diseases. The unaffected part of kidneys from eight patients with renal cell carcinoma served as control. RNA in situ hybridization revealed widespread ADAM19 mRNA expression in the nephrogenic zone of human fetal kidneys. Normal human kidneys showed constitutive ADAM19 expression in distal tubules and endothelial cells, whereas proximal tubules were negative. In renal disease, ADAM19 was de novo expressed in proximal tubules and glomerular mesangium and upregulated in distal tubules and endothelial cells. ADAM19 colocalized with tubular and interstitial NRG, however, not with HB-EGF. Independent of renal disorder, mesangial ADAM19 expression was associated with glomerular damage as assessed by mesangial matrix expansion, focal glomerulosclerosis, and glomerular macrophage influx (all P<0.001). ADAM19 in proximal tubules and in peritubular capillaries was associated with interstitial fibrosis (P<0.05). Finally, increasing tubular ADAM19 was associated with declining renal function (P<0.05). The abundant ADAM19 expression during nephrogenesis points to a role in growth promotion and regulation. The high ADAM19 expression in renal disease suggests involvement in profibrotic and proinflammatory processes leading to renal deterioration.

ADAM Proteins↗
PubMed2006

Fatal illness associated with pulmonary hypertension in a neonate caused by intrauterine echovirus 11 infection.

Nonpolio enterovirus (NPEV) infections are known to cause a wide range of illnesses in the neonatal period. In most cases, NPEV is presumed to be contracted during birth. Intrauterine NPEV infections occur infrequently. A case of intrauterine echovirus 11 infection with pneumonia, persistent pulmonary hypertension of the newborn, and purpura fulminans is presented.

Echovirus Infections↗
PubMed2006

The Tulip classification of perinatal mortality: introduction and multidisciplinary inter-rater agreement.

OBJECTIVE: To introduce the pathophysiological Tulip classification system for underlying cause and mechanism of perinatal mortality based on clinical and pathological findings for the purpose of counselling and prevention. DESIGN: Descriptive. SETTING: Tertiary referral teaching hospital. POPULATION: Perinatally related deaths. METHODS: A classification consisting of groups of cause and mechanism of death was drawn up by a panel through the causal analysis of the events related to death. Individual classification of cause and mechanism was performed by assessors. Panel discussions were held for cases without consensus. MAIN OUTCOME MEASURES: Inter-rater agreement for cause and mechanism of death. RESULTS: The classification consists of six main causes with subclassifications: (1) congenital anomaly (chromosomal, syndrome and single- or multiple-organ system), (2) placenta (placental bed, placental pathology, umbilical cord complication and not otherwise specified [NOS]), (3) prematurity (preterm prelabour rupture of membranes, preterm labour, cervical dysfunction, iatrogenous and NOS), (4) infection (transplacental, ascending, neonatal and NOS), (5) other (fetal hydrops of unknown origin, maternal disease, trauma and out of the ordinary) and (6) unknown. Overall kappa coefficient for agreement for cause was 0.81 (95% CI 0.80-0.83). Six mechanisms were drawn up: cardio/circulatory insufficiency, multi-organ failure, respiratory insufficiency, cerebral insufficiency, placental insufficiency and unknown. Overall kappa for mechanism was 0.72 (95% CI 0.70-0.74). CONCLUSIONS: Classifying perinatal mortality to compare performance over time and between centres is useful and necessary. Interpretation of classifications demands consistency. The Tulip classification allows unambiguous classification of underlying cause and mechanism of perinatal mortality, gives a good inter-rater agreement, with a low percentage of unknown causes, and is easily applicable in a team of clinicians when guidelines are followed.

Cause of Death↗
PubMed2004

Matrix-metalloproteinase activity in first trimester placental bed biopsies in further complicated and uncomplicated pregnancies.

UNLABELLED: Trophoblast invasion is partly regulated by matrix-metalloproteinases (MMPs). Aberrations in MMP-activity in early pregnancy are thought to play a role in the pathophysiology of pregnancy associated conditions like pre-eclampsia and intra-uterine growth restriction (IUGR). A direct relation however, has not been published. We tested the hypothesis that MMP activity in the decidua is compromised in the first trimester of pregnancies, which are complicated by hypertensive disorders or IUGR in later pregnancy. During chorionic villus biopsy, decidua is microscopically separated from the villi and stored. A selection of pregnancies complicated by pre-eclampsia or HELLP-syndrome or IUGR was made, with two matched controls each. Zymography was performed to identify the presence of MMPs, and subsequently immunohistochemistry for MMP-2 and -9 and cytokeratin 7 to examine differences between cases and controls. Next, a specific immuno-capture assay was used to determine the activity of MMP-1, -2, -3, -8, -9, and 13, total as well as active. Although presence of MMP-2 and MMP-9 was found, which corresponded with the immunohistochemistry, no significant differences could be demonstrated between activity of total MMP-2 and total MMP-9 in complicated and uncomplicated pregnancies. Activity of MMP-1, -3, -8 and -13 could not be detected. IN CONCLUSION: our study confirms the presence of MMP-2 and -9 in first trimester placental bed biopsies, but does not support the current concept of deranged MMP-activity in early pregnancy in further complicated pregnancies.

Adult↗
PubMed2004

Fetal thrombotic vasculopathy in the placenta: a thrombophilic connection between pregnancy complications and neonatal thrombosis?

OBJECTIVE: Fetal thrombotic vasculopathy (FTV) has been related to pregnancy complications and neonatal thrombosis separately. We assessed whether a relationship existed in our population of women with neonates who were admitted to our Neonatal Intensive Care Unit (NICU). In addition, the presence of thrombophilic factors in children and parents was investigated. METHODS: Two groups were detected by a search of the departmental databases. Group A was a cohort of 5000 neonates admitted to our NICU (1992-2002). Infants who developed thrombotic complications were selected. Group B was a cohort of placentae from our institution (2000, n = 141). Those with a diagnosis of FTV were selected. Case-notes and laboratory results were obtained through the hospital information system. RESULTS: Of Group A, thrombosis was reported in 55 children. Of these, 20 matching placentae were available. Eight placentae showed FTV (40 per cent). Of the eight corresponding pregnancies, seven were complicated by pre-eclampsia and/or intra uterine growth restriction (IUGR). Of the 12 placentae without FTV, five of the pregnancies had pre-eclampsia and/or IUGR (odds ratio for relation FTV-Complications: 9.8, 95 per cent CI = 0.9-107). In Group B, nine placentae showed FTV (6.4 per cent). Of these nine, six of the pregnancies were complicated by pre-eclampsia and/or IUGR. None of the neonates developed thrombosis. CONCLUSION: Pre-eclampsia and/or IUGR as well as neonatal thrombosis are both associated with fetal thrombotic vasculopathy in the placenta. However, in our selected-tertiary centre-population, FTV did not predict neonatal thrombosis. The thrombophilic investigations of parents and children were incomplete. A standard approach for evaluating parents at risk for FTV and evaluating neonates at risk for thrombosis should be developed.

Adult↗
PubMed2003

Morphology of testicular parenchyma adjacent to germ cell tumours. An interim report.

A comparative morphological analysis of parenchyma adjacent to testicular germ cell tumours (TGCT) was performed in a series of 181 orchidectomy specimens: 86 with seminomas (Se), 72 with nonseminomatous germ cell tumours (NS) and 23 with combined tumours (CT, which have a Se and a NS component). The following morphological features were semiquantitatively scored: spermatogenesis (modified Johnsen score); amount of tubular atrophy; amount of carcinoma in situ (CIS); amount of intertubular tissue. Absence and presence was scored for the following features: lymphocytic infiltrate surrounding and invading CIS; intratubular seminoma (ISe); intratubular nonseminoma (INS); microlithiasis; diffuse and nodular hyperplasia of Leydig cells; angioinvasiveness; testicular angiopathy. Using non-parametric statistics these features were correlated with each other and with tumour type, tumour size and age of the patient. Se-patients presented at significantly higher age than NS-patients (36 vs 29 years, p=0.001). The age of patients with CT (32 years) was in between that of Se- and NS-patients. No correlation was found between patient age and tumour size. Parenchyma adjacent to Se, compared to parenchyma adjacent to NS had the following significant differences: a lower Johnsen score (5.6 vs 7.2, p=0.005); less frequent (85% vs 97% of specimens, p=0.016) and a lesser amount of CIS (26% vs 32% of tubules, p=0.015); more frequent peri- (80% vs 60% of specimens, p=0.001) and intratubular (68% vs 30% of specimens, p=0.001) lymphocytic infiltrates; more extensive tubular atrophy (36% vs 15% of tubules, p=0.001); and a larger area of intertubular tissue (42% vs 34% of parenchyma area, p=0.016). The pooled Se and CT had a significantly higher frequency of ISe than the NS (31% vs 17% of specimens, p=0.036). With one exception INS was only found adjacent to NS or CT, with a frequency of 16%, and 20% of the specimens, respectively. It was significantly associated with angio-invasiveness. In specimens lacking angio-invasion the frequency of INS was 6%. The correlation of INS with tumour size and patient age was studied in a series of 145 NS and CT (95 from the original series supplemented by 50 newer cases). In this series INS was significantly associated with smaller tumours and younger patients. Extensive tubular atrophy was significantly correlated with higher age, the diagnosis of Se, a low Johnsen score, and the presence of angiopathy. The more tubular atrophy, the less CIS (both in incidence and amount). Inversely, a higher Johnsen score is associated with smaller tumours, the diagnosis of NS or CT, a higher incidence and a larger amount of CIS, and little tubular atrophy. Tubules with mature spermatogenesis were found in 42% of the specimens regardless of tumour type. We conclude that ISe and INS are probably frequent intermediate stages between CIS and Se and NS, respectively. The features of parenchyma adjacent to Se are probably due to the host response elicited by the invasive Se, which secondarily also affects CIS. The long time to clinical presentation allows the host to eradicate most of the CIS by the time the tumour is surgically removed. The much less extensive morphological features of a host response in parenchyma adjacent to NS support the contention that NS originates as INS, behind the blood/testis barrier, without exposure of the host to tumour cells with a seminomatous phenotype (CIS- or Se cells). Microlithiasis and testicular angiopathy are frequent, but not specific findings in parenchyma next to TGCT. Their relationship with the development with TGCT is unexplained.

Adult↗
PubMed2003

GLUT12 expression in human placenta in first trimester and term.

The aim of this study was to characterize the expression of a novel glucose transporter protein GLUT12 in human placenta. GLUT12 mRNA expression was identified by RT-PCR in extracts from five normal term placentae and in extracts from cultured cells of the JAR, JEG-3 and HTR-8Svneo cell lines. In further studies, paraffin sections of first trimester tissue from chorionic villus sampling and term tissue obtained after delivery were analysed by immunohistology with a GLUT12 specific polyclonal antibody. GLUT12 immunoreactivity was expressed predominantly in the syncytiotrophoblast and in extra-villous trophoblast cells in first trimester tissues at 10, 11 and 12 weeks' gestation. In term tissue, however, GLUT12 staining was not detected in syncytiotrophoblast and was found predominantly in villous vascular smooth muscle cells and villous stromal cells. These results suggest that there is a dynamic spatial and temporal expression pattern for the novel glucose transporter GLUT12 in human placenta.

Adult↗
PubMed2001

Determinants of abstract acceptance for the Digestive Diseases Week--a cross sectional study.

BACKGROUND: The Digestive Diseases Week (DDW) is the major meeting for presentation of research in gastroenterology. The acceptance of an abstract for presentation at this meeting is the most important determinant of subsequent full publication. We wished to examine the determinants of abstract acceptance for this meeting. METHODS: A cross-sectional study was performed, based on abstracts submitted to the DDW. All 17,205 abstracts submitted from 1992 to 1995 were reviewed for acceptance, country of origin and research type (controlled clinical trials (CCT), other clinical research (OCR), basic science (BSS)). A random sub-sample (n = 1,000) was further evaluated for formal abstract quality, statistical significance of study results and sample size. RESULTS: 326 CCT, 455 OCR and 219 BSS abstracts were evaluated in detail. Abstracts from N/W Europe (OR 0.4, 95% CI 0.3-0.6), S/E Europe (OR 0.4, 95% CI 0.2-0.6) and non-Western countries (OR 0.3, 95% CI 0.2-0.5) were less likely to be accepted than North-American contributions when controlling for research type. In addition, the OR for the acceptance for studies with negative results as compared to those with positive results was 0.4 (95% CI 0.3-0.7). A high abstract quality score was also weakly associated with acceptance rates (OR 1.4, 95% CI 1.0-2.0). CONCLUSIONS: North-American contributions and reports with statistically positive results have higher acceptance rates at the AGA. Formal abstract quality was also predictive for acceptance.

Abstracting and Indexing↗
PubMed2001

Uterine artery Doppler flow and uteroplacental vascular pathology in normal pregnancies and pregnancies complicated by pre-eclampsia and small for gestational age fetuses.

This study was conducted to investigate the association between uterine artery Doppler flow patterns and uteroplacental vascular pathology in normal and complicated pregnancies in view of the recently described concept of heterogeneous causes of hypertensive pregnancy complications. Forty-three women whose pregnancies were complicated by pre-eclampsia, the HELLP (Haemolysis, Elevated Liver enzymes, Low Platelets) syndrome and/or small for gestational age (SGA) fetuses and 27 women with normal pregnancies undergoing elective caesarean section were included. We obtained uterine artery Doppler waveforms at a mean of 4 days before delivery. Placental bed biopsies were obtained at caesarean section and analysed for physiological changes and pathological changes. We found that abnormal uterine artery Doppler flow was strongly associated with pregnancy complications. Absence of physiological changes was seen in 58 per cent of complicated pregnancies and 40 per cent of normal pregnancies. Pathological changes were seen in 58 per cent of complicated pregnancies and 53 per cent of normal pregnancies; they occurred in spiral arteries with and without physiological changes, and there was no significant correlation to Doppler results. In conclusion, absence of physiological changes is associated with abnormal uterine artery Doppler flow and pregnancy complications. However, there is a gradient in the severity of uteroplacental vascular pathology and the correlation with pregnancy complications is not as strong as previously thought. There is also a significant degree of uteroplacental vascular pathology in normal pregnancies with normal uterine artery Doppler flow. This variation may be partly due to sampling error, as a typical biopsy contains only one or two spiral arteries. We hypothesize that additional factors might be necessary to induce the clinical syndrome of pre-eclampsia.

Arteries↗
PubMed2001

Publication rates following pancreas meetings.

Publication rates and determinants of publication were studied based on abstracts presented at pancreatic meetings. All abstracts presented at the 1994 and 1995 annual meetings of the European Pancreatic Club (EPC) and the American Pancreatic Association (APA) were followed up by searching MEDLINE. Publication rates were compared using log-rank tests and multiple logistic regression. The prestige of the publishing journals was compared using Kruskal-Wallis tests on scientific impact factors (SIF). Overall, 340 abstracts were presented at the EPC, and 254 were presented at the APA. Of these, 203 (59.7%, EPC) and 138 (54.3%, APA) were later published in peer-reviewed journals. Publication rates did not differ by study type or country region of origin. In addition, median SIFs were similar by conference (APA vs. EPC) and research type (basic science vs. clinical studies) (overall, 1.7). However, North American and North/West European articles were published in higher impact journals as compared with those from other countries. Publication rates and median journal SIFs in pancreas research are similar to those reported from other medical specialty meetings. There is no difference by conference, type of research, or origin (North American vs. European).

Abstracting and Indexing↗
PubMed2000

[Risk factors and surgery rates in gallstones. Results of a population-based study].

STUDY OBJECTIVE: The prevalence of gallstone disease, time trends in the frequency of cholecystectomies and risk factors for the occurrence of cholelithiasis were examined in a cross-sectional population study. METHODS: The survey was based on a random sample from the populations of 4 regions in Germany, stratified by region, age and sex. Information on the frequency of gallstone disease and on potential risk factors were collected by standardized interviews. For the statistical analysis, multiple logistic regression was used. RESULTS: Overall, 1,085 persons were interviewed. The age-standardized prevalence of known gallstones was 4.2% for men and 14.5% for women. The frequency of cholecystectomy almost tripled in women from 1985 to 1994 as compared to 1975 to 1984 despite a decreasing trend in gallstone diagnoses in the same time period. No such trend was apparent in men. In men, age, body weight, changes in body weight, diabetes and use of corticosteroids were identified as risk factors for gallstone disease. In women, gallstone disease was also associated with body weight, changes in body weight and age, and, in addition, the number of births. An inverse association with gallstone disease was found for use of oral contraceptives and level of education in women.

Adolescent↗
PubMed2000

Non-enzymatic triggering of the ceramide signalling cascade by solar UVA radiation.

Ceramide is a key component of intracellular stress responses. Evidence is provided for a novel mechanism of ceramide formation that mediates solar ultraviolet (UV) A radiation-induced expression of the intercellular adhesion molecule (ICAM)-1. Similarly to UVA radiation, ceramide stimulation of human keratinocytes induced ICAM-1 mRNA expression and activated the ICAM-1 promoter through transcription factor AP-2. Ceramide-activated AP-2 and ceramide-induced ICAM-1 reporter gene activation were abrogated through deletion of the AP-2 binding site. UVA radiation increased the level of ceramide in keratinocytes and inhibition of sphingomyelin synthesis prevented UVA radiation-induced ICAM-1 expression. Hitherto, two pathways have been identified for ceramide accumulation: hydrolysis from sphingomyelin through neutral and acid sphingomyelinases, and de novo synthesis by ceramide synthase. UVA radiation did not activate any of these enzymes. Ceramide generation in UVA-irradiated cells, however, was inhibited by singlet oxygen quenchers and mimicked in unirradiated cells by a singlet oxygen-generating system. In addition, UVA radiation and singlet oxygen both generated ceramide in protein-free, sphingomyelin-containing liposomes. This study indicates that singlet oxygen triggers a third, non-enzymatic mechanism of ceramide formation.

Base Sequence↗
PubMed2000

Role of metallothionein in cisplatin sensitivity of germ-cell tumours.

Cisplatin (CDDP) is an extremely active drug in the treatment of germ-cell tumours. Earlier, we found an unexpected inverse correlation between the total amount of sulfhydryl groups and CDDP sensitivity in a panel of 3 human germ-cell-tumour and 3 colon-carcinoma cell lines. Major components of the sulfhydryl groups are glutathione and metallothionein (MT). We further investigated a possible role of MT in the CDDP sensitivity of germ-cell tumours. MT levels and functionality of the germ-cell-tumour and colon-carcinoma cell lines were found to be inversely correlated with CDDP sensitivity. No difference in sub-cellular localization of MT could be observed among the types of cell lines. In agreement with the in vitro data, immunohistochemical detection of MT was high in 11/14 primary human germ-cell tumours and low in 7/7 human colon carcinomas. MT-protein expression in primary germ-cell tumours did not discriminate between responding and non-responding patients. As compared with the primary tumours, MT-protein expression decreased in 5/7 post-chemotherapy residual vital tumours or remained undetectable (2/7). MT-protein expression in the germ-cell tumours was not related to total p53-protein expression. In summary, over-expression of MT was found in germ-cell tumours, both in cell lines and in human tumours. Although MT-protein over-expression seems to be associated with the CDDP sensitivity of germ-cell tumours, MT-protein expression in primary germ-cell tumours did not differ between responding and non-responding patients and therefore cannot be used to predict response to chemotherapy.

Antineoplastic Agents↗