Comparing means based on generalized matched sampling.
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Clinical Trials as Topic↗
Biomedical subjects
L Wilkens
Publications and source records attributed to L Wilkens.
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↗
A STIMULUS PARADIGM FOR ANALYSIS OF NEAR-FIELD HYDRODYNAMIC SENSITIVITY IN CRUSTACEANS
We present several relatively simple procedures for studying the physiology of near-field mechanoreceptors in crustaceans which extend previous measures of sensitivity. The advantages include the quantitative analysis of range fractionation and directionality of receptors and interneurons in the sensory hierarchy of the central nervous system (CNS), based on a stimulus paradigm that is reproducible and easy to use. The technical considerations for quantitative fluid-coupled stimulation addressed by this paper are the complexity of dipole flow fields, reflected interference from traveling waves, and the underlying stimulus wave form. The techniques described here offer corresponding advantages for physiological experiments using other aquatic organisms. In electrophysiological experiments, crustacean preparations are typically placed in an experimental chamber filled with water or saline solution. For studies on near-field sensory receptors, i.e. those responding to flow fields in the aquatic medium, a dipole or vibrating sphere is frequently used to generate stimulus waves (Tautz et al. 1981; Wiese and Wollnik, 1983; Ebina and Wiese, 1984; Hatt, 1986; Heinisch and Wiese, 1987; Tautz, 1987; Wiese and Marschall, 1990; Killian and Page, 1992b). A dipole stimulator is easily constructed by attaching a spherical probe to an electromechanical device such as a loudspeaker, pen motor or piezo crystal. A periodic signal fed to the transducer generates the oscillating dipole movements. With the sphere immersed in the bathing medium, dipole flow fields are generated (see Kalmijn, 1988, for further discussion of dipole sources), whereas dipole oscillations introduced at the air­saline interface generate traveling surface waves. Numerous additional devices and techniques have been used to stimulate crustacean receptors. Several involve wave motion introduced from one end of the chamber by diaphragms or paddles (Laverack, 1962b, 1963; Flood and Wilkens, 1978), by cylindrical dippers (Wilkens and Larimer, 1972; Wiese et al. 1976; Wiese and Schultz, 1982; Reichert et al. 1983) or by water drops (Laverack, 1962b; Strandburg and Krasne, 1985). Another form of fluid-coupled stimulation involves small jets of saline (Laverack, 1963; Tautz, 1990; Schmitz, 1992). In other studies, receptor hairs have been stimulated directly by using a stylus in place of the dipole, e.g. a needle or glass capillary in contact with the hair (Laverack, 1962a; Killian and Page, 1992a; Yen et al. 1992; Nagayama and Sato, 1993) or a miniature wire loop or capillary tube placed over the hair shaft (Mellon, 1963; Wiese, 1976; Tautz et al. 1981; Killian and Page, 1992b).
Journal Article↗
[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↗
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↗
[Detection of bcl-2/JH gene rearrangements in non-Hodgkin's lymphomas and chronic tonsillitis, but not in Hodgkin's lymphomas. Molecular genetic and immunohistochemical study].
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DNA, Neoplasm↗
[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↗
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↗
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↗
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↗
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↗
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↗
Rare events associated with tubal sterilizations: an international experience.
The results from previous analyses of an international data set collected by Family Health International are reviewed in relation to the incidence, severity, risk factors, and outcomes of rare events associated with tubal sterilization. The rare events included for review, by sequence of their relationship to the tubal sterilization procedure are: luteal phase pregnancy, intraoperative complications (uterine perforation, unintended laparotomy required for completion of the laparoscopic procedure, and technical failure in tubal ring sterilization), deaths, early readmission following laparoscopic sterilization, hysterectomy after laparoscopic sterilization, and pregnancy (intrauterine and ectopic) conceived after tubal sterilization. The widespread use of this method of contraception has important public health implications, and awareness of these events will help clinicians minimize such incidences and better deal with them when they arise.
Female↗
Delivery type and neonatal mortality among 10,749 breeches.
Data on 10,749 breech presentations were analyzed for the effect of delivery type on neonatal mortality. Most of the data are from developing countries, and most of the hospitals have higher mortality than is found in Europe or the United States. The simultaneous effect of type of hospital where the delivery occurred, type of breech, birthweight, and parity were examined. The benefit of cesarean delivery was greater for nulliparae than multiparae, greater for footlings than for frank or complete breeches, and greater for larger babies than smaller ones. This last finding probably reflects the quality of neonatal care in developing country hospitals rather than the value of cesarean section. Maternal mortality and morbidity was higher among women delivered abdominally than among those delivered vaginally.
Adult↗
Interval tubal sterilization in obese women--an assessment of risks.
Obesity is considered to be a complicating factor in most surgical procedures, but very few studies have investigated whether this is true for tubal sterilization. We used a large international data set to investigate the effect of obesity on tubal sterilization. Each of the 159 women delineated as obese (greater than 50% above the mean ideal weight) was matched with a woman of normal weight on important provider variables such as center, operator, and type of surgical procedure. Incidences of anesthesic, surgical, and early postsurgical complications were comparably low and of a mild nature for both the obese and the nonobese groups. Incidence of surgical difficulties was higher, and as a result, the technical failure rate was also higher and the surgical time longer for obese women than for nonobese women. However, none of these surgical difficulties or technical failures led to serious consequences. The difference in surgical times was small and is probably of little practical significance. It appears that the surgical difficulties of tubal sterilization in moderately obese women can be easily overcome.
Anesthesia↗
Expulsions in immediate postpartum insertions of Lippes Loop D and Copper T IUDs and their counterpart Delta devices--an epidemiological analysis.
In this paper, an epidemiological analysis was performed, using an international data set, exclusively on the expulsion problem associated with postpartum IUD insertions. The inserter's experience in postplacental insertions is probably an important determining factor for IUD expulsions. Immediate insertions (within 10 minutes after placental delivery) are possibly associated with lower expulsion rates than later insertions (eg. two to 72 hours after placental delivery) during the woman's postpartum hospitalization. No significant differences were detected between the standard Lippes Loop D and Copper T IUDs and their counterpart Delta devices specifically designed for postpartum use, between the two types of Delta device or between the hand and inserter methods. A case-control analysis also did not detect any significant association between IUD expulsions and mild complications occurring or management performed during the third stage of labor and delivery. The practical implications of these findings, the methodologic problems of this analysis and future research strategies are also discussed.
Adult↗
Interphase cytogenetics in pathology: principles, methods, and applications of fluorescence in situ hybridization (FISH).
Characteristic chromosome aberrations have been identified in various tumors. Fluorescence in situ hybridization (FISH) using specific probes that are generated by vector cloning or in vitro amplification and labeled with fluorescent dyes allow for the detection of these genetic changes in interphase cells. This technique, that is also referred to as "interphase cytogenetics", can be performed in cytological preparations as well as in sections of routinely formaldehyde-fixed and paraffin-embedded tissue. In cancer research and diagnostics, interphase cytogenetics by FISH is used to detect numerical chromosome changes and structural aberrations, e.g., translocations, deletions, or amplifications. In this technical overview, we explain the principles of the FISH method and provide protocols for FISH in cytological preparations and paraffin sections. Moreover, possible applications of FISH are discussed.
Cytological Techniques↗
Single- and double-color oligonucleotide primed in situ labeling (PRINS): applications in pathology.
Molecular cytogenetics is mostly performed by fluorescence in situ hybridization using long DNA probes that are generated by vector cloning. Oligonucleotide primed in situ labeling (PRINS) is a recent method that has been established for the detection of the centromeric or telomeric region in metaphase chromosomes. In this overview, we demonstrate the possible applications of PRINS and provide elaborated protocols for its use in intact interphase cells of routine cytological preparations, e.g., cell smears, touch preparations, and cytospins of non-neoplastic and neoplastic tissues. Moreover, the various modifications of the PRINS method, such as multi-color PRINS for targeting different chromosomes within one cell or the enzymatic detection of the PRINS product instead of the more commonly used fluorochromes, are discussed.
Centromere↗