Search PubMed⌕ Search

Biomedical subjects

L Wilkens

Publications and source records attributed to L Wilkens.

At least 19 recordsLinked to original sources
PubMed1996

Detection of numerical karyotype changes in the giant cells of Hodgkin's lymphomas by a combination of FISH and immunohistochemistry applied to paraffin sections.

Conventional karyotyping of Hodgkin's disease (HD) has until now yielded only limited insight into karyotypic characteristics of this disease. For this reason, fluorescence in situ hybridization (FISH) using alpha-satellite chromosome-specific probes was applied to paraffin sections of HD tumors in order to verify numerical aberrations suggested to be specific for HD in the literature. The FISH technique was combined with immunohistochemical detection of the CD30 antigen to allow easier identification of the Reed-Sternberg and Hodgkin (RS&H) cells. The number of specific FISH signals per nucleus was determined both in CD30-positive RS&H cells as well as in non-malignant "bystander" cells in order to assess differences in the signal distribution. Contrasted with normal lymphoid cells, the tumor cells in HD were found to be polysomic for at least one of the chromosomes analyzed (1,2,4, and 8). The technique described is a reliable method for confirmation of results obtained from conventional cytogenetics, which is especially suited for archival material or samples not containing dividing cells.

Antigens↗
PubMed1996

Microwave pretreatment improves RNA-ISH in various formalin-fixed tissues using a uniform protocol.

RNA is situ hybridization technique (RNA-ISH) is hampered by formalin fixation of tissues. This necessitates a pretreatment step of enzymatic digestion. However, to achieve the best results, digestion times and concentrations of enzymes have to be adapted for every specimen in a cumbersome procedure. Microwave pretreatment (MP) of formalin-fixed tissues has developed to become a powerful tool in immunohistochemistry (IHC) in recent years. To evaluate whether MP could also be helpful for RNA-ISH, we compared MP and conventional enzymatic pretreatment systematically using different tissues and various fixation times. As a model for RNA-ISH we chose the detection of kappa/lambda light chain mRNA in tonsils and lymph nodes with follicular hyperplasia and lymph nodes of patients with lymphocyte predominant Hodgkin's Disease (LPHD). Signal intensity obtained after MP was at least as good or dramatically enhanced as that obtained with optimized, single case adapted conventional pretreatment, the morphology being much better preserved after MP. These results confirm MP as a suitable method to unify the staining protocols in RNA-ISH, regardless of the duration of formalin fixation. Based on our results we recommend MP as a reliable and inexpensive method to enhance, standardized and simplify RNA-ISH.

Formaldehyde↗
PubMed1996

Fluorescence in situ hybridization (FISH) is a reliable diagnostic tool for detection of the 9;22 translocation.

The fluorescence in situ hybridization (FISH) technique for detection of the 9;22 translocation was compared with the "gold standard" of conventional cytogenetics. For this purpose, both methods were applied to 81 bone marrow aspirates and/or peripheral blood specimens comprising 50 CML cases and controls from 31 patients without CML. Independently, core biopsies of these 81 patients were investigated by three histopathologists. Conventional karyotype analysis from unstimulated bone marrow cells was successful in 71/81 cases and demonstrated the Ph-chromosome in 42/46 CML patients. With FISH, results were obtained in all 81 cases investigated, confirming fusion of the ber and abl genes in all cytogenetically Ph-positive patients. Among the five Ph-chromosome-negative specimens bcr/abl fusions were detected in only one patient. The percentage of cells found to be Ph-positive by both methods was correlated, but in individual cases considerable differences in the numbers of Ph-positive cells were observed. Different results may be due to selection of cells after in vitro cultivation predominantly. FISH proved to be a very reliable technique for specimens that do not contain dividing cells. With FISH, large numbers of cells can easily be scored which is an advantage compared to conventional cytogenetics. Therefore, this method is particularly suitable for those whose therapy is being monitored or a relapse is suspected. However, the FISH results should be evaluated critically with respect to the practical limit of sensitivity since non-specific fusion signals can also be observed in a small percentage of cells in non-CML cases. It is suggested that each laboratory define its own threshold of bcr/abl fusion signals for diagnosing Ph-positive CML by FISH.

Adolescent↗
PubMed1996

Light-chain mRNA in lymphocyte-predominant and mixed-cellularity Hodgkin's disease.

There is growing evidence for a B-cell lineage of lymphocyte-predominant Hodgkin's disease (1). To support this assumption, in situ hybridization techniques were used to detect immunoglobulin light-chain mRNA in 44 formalin-fixed specimens of Hodgkin's lymphoma (22 of lymphocyte-predominant Hodgkin's disease; 22 of mixed-cellularity Hodgkin's disease). In addition, immunoglobulin light chains were evaluated by polyclonal antisera. All specimens had been unequivocally diagnosed histologically by the referees of the German Hodgkin Trial and been immunophenotyped by monoclonal antibodies against CD15, CD20, CD30, and CD45. Light-chain mRNA coding either for kappa or for lambda could be detected by an enhanced in situ hybridization protocol using microwave heating in the lymphocytic and histiocytic cells of 14 (64%) of 22 specimens of lymphocyte-predominant Hodgkin's disease tested. None of the specimens, however, belonging to one of the classic subtypes of Hodgkin's disease (mixed-cellularity Hodgkin's disease) showed positivity for mRNA in the giant tumor cells. Our results support the idea that lymphocyte-predominant Hodgkin's disease represents a B-cell malignancy that is a entity separate from classic Hodgkin's disease. Diverging results of former studies in assessing light-chain mRNA in lymphocytic and histiocytic cells probably reflect problems with the detection threshold, i.e., the sensitivity of the techniques applied.

Hodgkin Disease↗
PubMed1995

The bcl-2/JH gene rearrangement is undetectable in Hodgkin's lymphomas: results from the German Hodgkin trial.

Ninety-one Hodgkin's lymphomas (HD), 52 non-Hodgkin lymphomas (NHL) and 33 specimens of non-neoplastic lymphatic tissues were investigated by polymerase chain reaction (PCR) for the presence of the bcl-2/JH gene rearrangement. The majority of the HD cases were drawn from the files of the German Hodgkin trial where diagnoses are established by a panel of four independent histopathologists. Using the very sensitive PCR method which detected 1 positive among 10000 negative cells, the bcl-2/JH gene rearrangement was found in 7/52 NHL and 3/16 tonsils with follicular hyperplasia, but in none of the 91 HD. The bcl-2 protein, however, was expressed by malignant cells of B and T cell lymphomas and by the giant tumour cells in 2/13 HD lymphocyte predominant, 11/28 HD nodular sclerosing I, 14/17 HD nodular sclerosing II, 10/27 HD mixed cellularity and 3/3 HD lymphocyte depleted. The bcl-2/JH rearrangement is thus independent of protein over-expression, the latter being found in all types of lymphomas. Our results do not confirm the findings of others who have detected the bcl-2/JH rearrangement in HD. These discrepancies may be explained by differences in choice of material, the gene rearrangement actually occurring in bystander cells but not in Reed-Sternberg or Hodgkin cells, or by contamination.

Chromosomes, Human, Pair 18↗
PubMed1995

Demonstration of the Philadelphia translocation by fluorescence in situ hybridization (FISH) in paraffin sections and identification of aberrant cells by a combined FISH/immunophenotyping approach.

The Philadelphia translocation was demonstrated by two-colour fluorescence in situ hybridization (FISH) in decalcified paraffin sections of bone marrow from patients with chronic myelogenous leukaemia. FISH was combined with immunocytochemical detection of different membrane-bound or cytoplasmic antigens. With this new technique, the cells bearing the 9:22 translocation can be identified morphologically, as well as immunocytochemically, in tissue sections.

Antigens, CD↗
PubMed1994

Effects of antigen retrieval by microwave heating in formalin-fixed tissue sections on a broad panel of antibodies.

Formaldehyde fixation of biopsy specimens for routine purposes has often been held responsible for the poor reproducibility of immunohistochemical studies. Recently, antigen retrieval (AGR) using microwave irradiation was described as a potential tool to enhance immunostaining. A comparison of conventional staining and staining after microwave heating was performed for 52 markers, using tissues fixed in formaldehyde for 24 h, 1 to 6 weeks and 3 years respectively, as well as consultant case material. After adequate duration of fixation (24 h), only a few markers (17%) showed better results after AGR, but this percentage was increased to 50% when tissues were fixed for longer periods. Maximal enhancement was obtained in the group of consultant cases (58% of tested markers demonstrated better staining results), in which the period of fixation and tissue processing was unknown. To achieve reliable enhancement with AGR, continuous heating (100 degrees C) should not be shorter than 20 min. In conclusion, AGR may become the most important tool to simplify and equalize immunohistochemical techniques, if critically evaluated.

Antibodies, Monoclonal↗
PubMed1994

Influence of formalin fixation on the detection of cytomegalovirus by polymerase chain reaction in immunocompromised patients and correlation to in situ hybridization, immunohistochemistry, and serological data.

The possibility of detecting cytomegalovirus (CMV) in formalin-fixed tissues by polymerase chain reaction (PCR) was evaluated in necroposies from lung tissues in a total of 24 patients who either had received organ transplants or were immunocompromised. PCR using two different pairs of primers for amplification of the major immediate early antigen of CMV was performed on fresh tissues and tissues fixed for 24, 48, and 72 h in neutral buffered formalin and compared to immunohistochemistry (IHC) and in situ hybridization (ISH). The fresh tissues of nine patients with serological evidence for acute CMV infection were all positive for CMV by PCR. After formalin fixation, the majority of the patients failed to show distinct signals with one or both pairs of primers as measured by densitometry. In contrast to this, fresh tissues of 15 patients without signs of an acute CMV infection were found either negative or weakly positive by PCR. Using IHC or ISH, positive results were observed only in five of nine and four of nine patients with acute CMV infection, respectively. These data demonstrate that, if only formalin-fixed tissue is available, PCR for CMV detection should be performed using two pairs of primers and should be supported by IHC.

Adolescent↗
PubMed1994

[Hodgkin lymphomas ar negative with regard to bcl-2/JH gene rearrangement, but partly express BCL-2 protein: analysis of 83 cases from the German Hodgkin Trial].

Conflicting data on the presence of bcl-2/JH gene rearrangement and BCL-2 protein expression in Hodgkin's disease (HD) have been reported. To find out the reason for these differences, well characterized cases from the German National Trial were examined by PCR for the bcl-2 gene rearrangement and immunohistochemically for BCL-2 protein expression. No bcl-2/JH rearrangement could be detected among the HD analyzed from paraffin sections, as well as another 24 cases of HD investigated in fresh tissue. Contrasted with this, immunohistochemistry demonstrated BCL-2 protein expression in all types of HD. In conclusion, our results suggest that the bcl-2/JH gene rearrangement does not play a role in HD, but BCL-2 protein is frequently expressed by RS/H cells of non-lymphocyte predominance subtypes.

Antigens, CD↗
PubMed1993

Noise enhancement of information transfer in crayfish mechanoreceptors by stochastic resonance.

In linear information theory, electrical engineering and neurobiology, random noise has traditionally been viewed as a detriment to information transmission. Stochastic resonance (SR) is a nonlinear, statistical dynamics whereby information flow in a multi-state system is enhanced by the presence of optimized, random noise. A major consequence of SR for signal reception is that it makes possible substantial improvements in the detection of weak periodic signals. Although SR has recently been demonstrated in several artificial physical systems, it may also occur naturally, and an intriguing possibility is that biological systems have evolved the capability to exploit SR by optimizing endogenous sources of noise. Sensory systems are an obvious place to look for SR, as they excel at detecting weak signals in a noisy environment. Here we demonstrate SR using external noise applied to crayfish mechanoreceptor cells. Our results show that individual neurons can provide a physiological substrate for SR in sensory systems.

Action Potentials↗
PubMed1993

[Isolated late pulmonary metastasis of adenoid cystic carcinoma of the parotid gland].

Eight years after removal of an adenoid cystic carcinoma (ACC = cylindroma) of the parotid gland, a female patient of 41 years of age developed isolated multiple lung metastases. She died three years later in the course of a respiratory insufficiency. Basing on this typical case record, the very rare ACC is presented, which has a tendency to pulmonary metastasising. The pathology, course of the disease, treatment and indication for performing a lung transplant in similar cases are discussed.

Adult↗
PubMed1992

Covariance adjustment of survival curves based on Cox's proportional hazards regression model.

Cox's proportional hazards regression model is a useful statistical tool for the analysis of 'survival data' from longitudinal studies. This multivariate method compares the 'survival experience' between two or more exposure groups while allowing for simultaneous adjustment of confounding due to one or more covariates. In addition to the summary regression statistics, further insight on the exposure--response relationship can be gained by visually examining the covariates-adjusted survival curves in the respective comparison groups. Covariates-adjusted survival curves are usually computed by the 'average covariate method'. This method is, however, subject to potential drawbacks. A method that avoids these drawbacks is to estimate adjusted survival curves by the corrected group prognostic curves approach. We have written a computer program to construct survival curves by the latter method. The program is coded in the Interactive Matrix Language of SAS.

Humans↗
PubMed1989

Differentiation between papillary and nonpapillary renal cell carcinomas by DNA analysis.

Recent studies have shown that the deletion of chromosome 3p or the loss of DNA sequences at 3p is generally associated with the development of renal cell carcinoma (RCC). However, chromosome analysis of some papillary RCCs suggested that this type of tumor differs genotypically from the most common nonpapillary RCCs. Therefore, by using cytogenetic and molecular genetic approaches, we examined human papillary and nonpapillary RCCs for the loss of heterozygosity or homozygosity at the short arm of chromosome 3. The constitutional heterozygosity for the DNF15S2 locus and for one allele of the c-erbA beta and the c-raf-1 proto-oncogenes was lost in nonpapillary RCCs, whereas both alleles were retained in each papillary RCC analyzed. We conclude that the loss of DNA sequences at the chromosome 3p region is a genomic change occurring consistently in nonpapillary RCCs, but never occurring in papillary RCCs.

Carcinoma, Renal Cell↗
PubMed1989

Renal oncocytoma. A phenotypic and genotypic entity of renal parenchymal tumors.

The light and electron microscopic morphology of two renal parenchymal tumors was consistent with the diagnosis of renal oncocytoma. Both tumors had a mosaic chromosome pattern of cells with normal and abnormal karyotypes. No recurrent chromosome aberration and also no rearrangement of chromosome 3p was found. Restriction analysis of the mitochondrial DNA revealed a new autoradiographic band at about 50 basepairs in size occurring exclusively in oncocytomas. The possible use of these findings in the diagnosis of renal oncocytomas is discussed.

Adenoma↗
PubMed1988

Nondisjunction reduplication of chromosome 3 is not a common mechanism in the development of human renal cell tumors.

Because of the recurrent loss of regions of the chromosome 3 short arm in renal cell carcinomas, a chromosomal mechanism for the expression of recessive cancer genes has been implicated in the development of this type of tumor. Nondisjunction and subsequent reduplication of a mutant chromosome is one of the presumed mitotic mechanisms leading to the expression of recessive cancer genes. Using variant fluorescence at the centromeric region of chromosome 3 and a restriction fragment length polymorphism on chromosome 3p, we found chromosome 3 heteromorphism in the constitutional cells of 14 of 15 patients with renal tumors showing two normal chromosomes 3. This heteromorphism was maintained in each tumor. Therefore, the mechanism of nondisjunction and reduplication in the development of homozygosity for a mutant chromosome 3 in renal tumors remains questionable.

Chromosomes, Human, Pair 3↗
PubMed1986

In-hospital maternal mortality risk by cesarean and vaginal deliveries in two less developed countries--a descriptive study.

Cesarean deliveries are increasing in both developed countries and less developed countries (LDCs). Recent studies in the U.S. have revealed a significantly higher mortality risk for women who delivered abdominally than for those who delivered vaginally, even when the effect of the conditions which necessitated cesarean delivery was taken into account. We chose for study from an international maternity monitoring network, five centers from two LDCs that reported an in-hospital maternal mortality rate (MMR) of around 10 per 1000 parturient women. The pooled data revealed an MMR of 5.1 per 1000 women with vaginal deliveries. For women with cesarean delivery, the total MMR was 36.2 and the MMR attributable to cesarean section was estimated to be 12.8; both rates were per 1000 procedures. The leading cause of death was eclampsia for the vaginal deliveries and sepsis for the cesarean deliveries. The risk of maternal mortality inherent with the cesarean section procedure per se (not counting the risk associated with the labor and delivery complications that necessitated cesarean section) as well as the practical avoidability of maternal deaths for either mode of delivery in these LDC hospitals are discussed.

Anesthesia, Obstetrical↗