Is the neuropathology of new variant Creutzfeldt-Jakob disease and kuru similar?
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Brain↗
Biomedical subjects
J Beck
Publications and source records attributed to J Beck.
Binding of dipalmitoyl-phosphatidylcholine liposomes to lung epithelial type II cells and other surfaces.
To better understand the interaction of phosphatidylcholine liposomes with lung type II cells, their association with rat type II pneumocytes in primary culture was investigated. With a filtration assay technique free and cellularly bound liposomes were separated and an apparent binding site with a Bmax of 171 nmol/mg protein and a Kd of 470 nmol/l was detected. Bound liposomes were displacable by an excess of unlabelled liposomes, were sensitive to EDTA and trypsin treatment and were not significantly competed with by dioleyl-phosphatidylcholine liposomes. However, a site with identical characteristics was demonstrated in experiments performed with blanc dishes in the absence of cells. This site was generated by liposomes bound to the blanc culture dish, which could not be removed by extensive washing, but which were released by EDTA and trypsin and were trapped during filtration. These problems were overcome by a centrifugation assay technique. Then non-specific binding was less than 1% and cellular binding was inhibited dose-dependently by liposomes made from various phospholipids. These studies may facilitate attempts to direct liposomes as carriers to specific cellular targets in the lungs.
1,2-Dipalmitoylphosphatidylcholine↗
Experimental confirmation of a hepatitis B virus (HBV) epsilon-like bulge-and-loop structure in avian HBV RNA encapsidation signals.
Hepatitis B viruses replicate via reverse transcription of an RNA intermediate. This RNA pregenome serves as mRNA and is packaged into capsids and reverse transcribed. Both processes require the interaction of the viral reverse transcriptase, P protein, with the 5'-proximal epsilon-signals on the pregenome. For epsilon of human hepatitis B virus (HBV), the presence of a functionally important stem-loop structure with a central bulge, part of which acts as template for a short primer of first-strand DNA synthesis, has been experimentally confirmed. Based on phylogeny and its functional similarities to epsilon, the D epsilon-signal of duck hepatitis B virus (DHBV) had been proposed to have a similar structure which does not, however, correspond to the most stable computer prediction. We have therefore experimentally determined the secondary structures of D epsilon and of the H epsilon-signal of heron hepatitis B virus which differs considerably from D epsilon in primary sequence yet interacts productively with DHBV P protein. Our data support an HBV epsilon-like structure for both D epsilon and H epsilon; in particular the bulge is highly conserved, in accord with its special function in replication. However, the apical loop in H epsilon is much enlarged suggesting that, by an induced-fit mechanism, both RNAs may adopt a new, probably similar conformation in the complex with P protein.
Animals↗
Study of respirator effect on nasal-oral flow partition.
Factors affecting worker tolerance of respiratory personal protective devices are inadequately understood. This study evaluates whether respirator-type loads affected the switch from nasal to oral breathing. Eleven healthy subjects were studied under progressive exercise conditions, using a respirator full-face mask with inspiratory resistance (I), pressure breathing (P) (10 cm H2O end-expiratory pressure), or no load (N). A rapid-response thermistor was used to determine whether flow was predominantly oral or nasal. Both P and I increased the percentage of time that breathing was predominantly oral. The effect was most pronounced at higher exercise levels. The percentage of mouth breathing appeared to be closely related to the expiratory time. This study suggests that nasal-oral flow partitioning should be considered as a possible determinant of respirator tolerance.
Adult↗
Anterior ischemic optic neuropathy following neck dissection.
BACKGROUND: Ischemic optic neuropathy (ION) is a rare but devastating complication of surgery. It has traditionally been associated with intraoperative hypotension in patients with underlying arteriosclerosis. METHODS: We present a case of ION following bilateral neck dissections in which there was minimal intraoperative hypotension and preservation of both internal jugular veins. The potential etiology of this disease is discussed along with a review of the literature. RESULTS: Five cases of ION following neck dissection have been documented. This complication is associated with the combination of intraoperative hypotension and anemia in the setting of prolonged bilateral neck dissection. Treatment is supportive, and final visual prognosis is variable. CONCLUSIONS: Ischemic optic neuropathy following neck dissection is best avoided by intraoperative blood pressure and anemia management. When it does occur, supportive therapy must be given. Final visual outcome is variable.
Carcinoma, Squamous Cell↗
Leukocyte-endothelium interactions in global cerebral ischemia.
A closed cranial window was implanted in male Mongolian Gerbils to investigate leukocyte-endothelium interactions (LEI) at the brain surface in global cerebral ischemia (GCI) by intravital fluorescence microscopy. Four days after 15 min of bilateral common carotid artery occlusion the ischemic tissue damage was histologically analysed in selectively vulnerable areas of the brain. The frequency of Rhodamine 6G labeled leukocytes rolling along ("roller") and firmly attached ("sticker") to postcapillary endothelium was assessed before and up to 180 min after GCI. As compared to the sham operated control animals induction of LEI was found in animals with GCI, following a steady increase up to a significant level attained at 60 min (rollers) or at 120 min of reperfusion (sticker), respectively (p < 0.05). In animals with cerebral ischemia histological assessment revealed a significant decrease of viable neurons in the CA1-sector of hippocampus (neurons/mm2 +/- SEM: 1308 +/- 71 vs. 829 +/- 106), in parietal neocortex (727 +/- 17 vs. 542 +/- 49), and in striatum (547 +/- 26 vs. 352 +/- 49; p < 0.01), respectively. A significant correlation between the extent of irreversible neuronal damage and the frequency of leukocyte adherence to the endothelium could not be established. Nevertheless a direct correlation between the number of surviving neurons and of rolling leukocytes was observed, which may be suggestive of a protective potential of leukocyte rolling.
Animals↗
A novel method for direct and fluorescence independent determination of drug efflux out of leukemic blast cells.
Multi drug resistance (MDR) is often due to an increased efflux of anti cancer drugs out of leukemic blast cells. Efflux assays are used to get an impression of functional resistance in those cells. Dyes like rhodamine 123 or 3'3'-diethyloxocarbocyanine iodide are commonly used for this purpose. A major known disadvantage is that dyes do not behave like cytotoxic drugs in efflux experiments. Assays using the self fluorescence of drugs like anthracyclines can not reveal a real impression of intracellular or effluxed drug due to quenching of the drug fluorescence in the nuclei of the cells. We have developed a reproducible and sensitive assay for direct and quantitative determination of drug efflux out of blast cells. This was done by a novel double radioactive labelling using a 3H-labelled drug and 14C-labelled sucrose as extracellular marker. So this assay can be applied to every drug of interest. Quenching of fluorescence is also by-passed with this technique as well as protracting washing or silicon oil procedures. As a model system we used the T-lymphoblastoid cell line CCRF CEM and its resistant sublines vincristine 100 and adriamycin 5000. The results were also transferable to clinical specimens of leukemic patients. In conclusion our assay may be used for precise and direct efflux measurement of a broad range of anti-cancer drugs in clinical MDR evaluation.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Provocative motor nerve conduction testing in presumptive carpal tunnel syndrome unconfirmed by traditional electrodiagnostic testing.
In this controlled prospective study, 22 consecutive surgical candidates with clinically diagnosed CTS and negative findings on median nerve-sensory and motor-conduction velocity tests in both hands were reexamined with a protocol incorporating 5 specific positions of the wrist. Four of the 5 positions represented maximum physiologic ranges of motion for the patient. These positions were neutral (unstressed), extension, flexion, radial deviation, and ulnar deviation. Motor latency was recorded in each of the 5 positions using otherwise standard technique. The least latency value in the test sequence was subtracted from the greatest to yield a value called differential latency. Thirty-two control studies were obtained on both hands of 16 normal volunteers and were used to establish a control differential latency, which was seen to have a mean of .13 ms. A 2 standard deviation z value of .11 ms was calculated, giving an upper limit of normal (control) differential latency of .24 ms. Preoperative studies yielded an average differential latency of .44 ms, with 20 of 22 patients having differential latency values of greater than .24 ms. Evaluations of these same patients 3 months after surgery showed differential latency values within the same range as those of the control group. Simple modification of standard nerve testing techniques to include positional variation increased the yield of positive test results in 20 of 22 patients with CTS whose electrodiagnostic tests otherwise produced negative findings.
Adult↗
Detection of neuroblastoma cells in CD34+ selected peripheral stem cells using a combination of tyrosine hydroxylase nested RT-PCR and anti-ganglioside GD2 immunocytochemistry.
A sensitive assay was developed for the detection of neuroblastoma cell contamination in CD34+ selected and unseparated peripheral blood stem cells (PBSC) used for autologous transplantation in stage 4 neuroblastoma patients. Specifically, we established a non-radioactive nested cDNA-PCR (nPCR) for detection of tyrosine hydroxylase (TH) gene expression combined with anti-disialoganglioside GD2 immunocytochemistry with the murine monoclonal antibody (MAb) 14G2a. Sensitivities of TH nPCR determined with a number of neuroblastoma cell lines and PBSCs correlated to cell line dependent basal TH gene expression levels and ranged from 1:10(4) to 1:10(6). The sensitivity obtained by immunocytochemistry was 1:10(5). We observed the highest PBSC contamination rate of 47% (18/38) among 38 PBSC specimens exclusively obtained from stage 4 neuroblastoma patients by using TH nPCR and GD2 immunocytochemistry in combination. Furthermore, a clinically applied purging method, CD34+ selection by immunoabsorption (CD34+ purity 42.4%), was used on 16 PBSCs. 10/16 (63%) preparations were contaminated prior to CD34+ selection and 56% (9/16) remained contaminated. A significant reduction of neuroblastoma cell contamination by CD34+ selection was not detectable, but the absolute amount of re-infused tumour cells was decreased due to 100-fold smaller cell counts of CD34+ selected grafts used for transplantation. 22 PBSC preparations were used for transplantation. A Kaplan-Meier analysis showed an event-free survival probability of 0.56 +/- 0.22 (n = 9) in the group with contaminated PBSCs versus 0.88 +/- 0.12 (n = 8) with no detectable neuroblastoma-cell contamination. Our data suggest that the combined use of TH nPCR and GD2 immunocytochemistry is optimal to detect contamination and monitor purging strategies.
Antigens, CD34↗
Mixed hematopoietic chimerism after allogeneic bone marrow transplantation: the impact of quantitative PCR analysis for prediction of relapse and graft rejection in children.
It still remains unclear whether patients with mixed hematopoietic chimerism (MC) after allogeneic bone marrow transplantation (allo-BMT) have an increased risk of developing relapse or graft failure. To address this question, we monitored the individual dynamics of chimerism after allo-BMT in pediatric patients within a prospective case control study. The individual ratio of donor to recipient peripheral white cells was determined by quantification of genomic variable number of tandem repeats (VNTRs) with a polymerase chain reaction (PCR) approach. Within the study period from 1 January 1994 until 1 July 1996 we investigated 50 sequences of 46 pediatric patients after allo-BMT (32 with malignant, 18 with nonmalignant diseases). We found complete chimerism (CC) in 34/50 cases, MC in 12/50 follow-ups and 4/50 patients revealed autologous recovery (AC). Eight of 12 patients with MC showed increasing autologous patterns and subsequently relapsed or rejected their graft, 3/12 decreasing amounts of recipient DNA and turned to CC upon further follow-up. One patient of 12 who had severe combined immunodeficiency (SCID), attained engraftment with a stable MC pattern. Three patients of 34 with CC relapsed lacking a transitional MC interval. However, the time span between last CC confirmation and relapse in each of these three patients was 6 months or longer. We suggest that these patients also developed a stage of transitional MC but that the critical timepoint of molecular confirmation by PCR was missed as time intervals in the individual follow-up of these three patients were too long (> or = 6 months). In summary, the results demonstrate that the individual risk of developing relapse or graft failure is significantly enhanced in the MC situation (P < 0.0005). Therefore the quantitative analysis of MC at short time intervals might be of great value to identify high risk patients which will have a significantly/enhanced risk for relapse or graft rejection.
Adolescent↗
Additional immunotherapy on the basis of increasing mixed hematopoietic chimerism after allogeneic BMT in children with acute leukemia: is there an option to prevent relapse?
The success of allogeneic BMT (allo-BMT) in children with acute leukemias is mainly affected by relapse. There is evidence that these patients have only a little or no benefit from additional immunotherapy if the treatment is started in frank hematological relapse. Recently we were able to demonstrate that pediatric patients with acute leukemias and increasing mixed chimerism (MC) post-transplant have a significantly enhanced risk of developing relapse. We asked whether there is a possibility of preventing relapse, eg by withdrawal of post-transplant immunosuppression or by administration of donor lymphocytes in an early phase of the development of relapse. We present the case reports of two children (MDS and AML) with rapidly increasing MC in whom withdrawal of post-transplant immunosuppression or donor lymphocyte infusion (DLI) did prevent relapse.
Acute Disease↗
Statistical strategies for event rate comparisons in dental studies.
Dental researchers are interested in measures of association between explanatory variables and various disease indicators, where both can be measured at the tooth or surface level. The usual chi-square tests for event rate comparisons are inadequate to analyze such data since teeth within the same individual are correlated with one another. This situation may become further complicated when stratification adjustment is of interest, particularly when the stratification factor is also at the tooth or surface level, such as tooth type or presence of previous disease for the tooth. Consequently, statistical methods are needed to control for the correlation of sites in the mouth. A survey sampling approach is suggested; with this method, the sample is managed as a one stage cluster sample of patients to obtain the design base covariance matrix for the cell counts in a contingency table. The covariance matrix for the cell counts can be obtained from statistical software used to analyze data from large sample surveys. Approximate estimates for variance for various measures of association can then be obtained by Taylor series methods. Event rate comparisons through the odds ratio, relative risk, risk difference as well as other measures of association can be made with adjustments for the intra-patient correlation. Methods for summary measures of association across strata are considered as well.
Dental Research↗
Sequence- and structure-specific determinants in the interaction between the RNA encapsidation signal and reverse transcriptase of avian hepatitis B viruses.
Hepatitis B viruses (HBVs) replicate by reverse transcription of an RNA intermediate. Packaging of this RNA pregenome into nucleocapsids and replication initiation depend crucially on the interaction of the reverse transcriptase, P protein, with the cis-acting, 5' end-proximal encapsidation signal epsilon. The overall secondary structure is similar in all of the hepadnaviral epsilon signals, with a lower and an upper stem, separated by a bulge, and an apical loop. However, while epsilon is almost perfectly conserved in all mammalian viruses, the epsilon signals of duck HBV (DHBV) and heron HBV (D epsilon and H epsilon, respectively) differ substantially in their upper stem regions, both in primary sequence and in secondary structure; nonetheless, H epsilon interacts productively with DHBV P protein, as shown by its ability to stimulate priming, i.e., the covalent attachment of a deoxynucleoside monophosphate to the protein. In this study, we extensively mutated the variable and the conserved positions in the upper stem of D epsilon and correlated the functional activities of the variant RNAs in a priming assay with secondary structure and physical P protein binding. These data revealed a proper overall structure, with the bulge and certain key residues, e.g., in the loop, being important constraints in protein binding. Many mutations at the evolutionarily variable positions complied with these criteria and yielded priming-competent RNAs. However, most mutants at the conserved positions outside the loop were defective in priming even though they had epsilon-like structures and bound to P protein; conversely, one point mutant in the loop with an apical structure different from those of D epsilon and H epsilon was priming competent. These results suggest that P protein binding can induce differently structured epsilon RNAs to adopt a new, common conformation, and they support an induced-fit model of the epsilon-P interaction in which both components undergo extensive structural alterations during formation of a priming-competent ribonucleoprotein complex.
Animals↗
Diaphragm interference pattern EMG and compound muscle action potentials: effects of chest wall configuration.
The effect of chest wall configuration on the diaphragm electromyogram (EMGdi) was evaluated in five healthy subjects with an esophageal electrode for both interference pattern EMGdi (voluntary contractions) and electrically evoked diaphragm compound muscle action potentials (CMAPs). Diaphragm CMAPs (both unilateral and bilateral) were evaluated for the baseline-to-peak amplitude (Ampl), the time from the onset of the CMAP to first peak (T1), root mean square (RMS), and center frequency (CF) values of the CMAP power spectrum. CF values from the interference pattern EMGdi power spectrum were also calculated. For CMAPs obtained at an electrode position least influenced by variations induced by electrode positioning, Ampl increased with diaphragm shortening from functional residual capacity (FRC) to total lung capacity (TLC) by 101 and 98% (unilateral and bilateral, respectively). Bilateral CMAP RMS values increased 116% from FRC to TLC. CMAP T1 values decreased with diaphragm shortening from FRC to TLC by 1.1 and 2.1 ms for the unilateral and bilateral stimulations, respectively, and CF increased for the bilateral diaphragm CMAPs with diaphragm shortening. CF values from the interference pattern EMGdi did not show any consistent change with chest wall configuration. Thus CF values of the interference pattern EMGdi obtained with an esophageal electrode can be considered reliable for physiological interpretation, at any diaphragm length (if electrode positioning and signal contamination are controlled for), contrary to the diaphragm CMAPs, which are sensitive to changes in chest wall configuration. It is speculated that the different results (over the effects of chest wall configuration on interference pattern EMGdi and diaphragm CMAPs) amy be because of summation properties of the signals and how these influence the EMG power spectrum.
Action Potentials↗
Measuring of the postcopulatory departure in male rats.
Spontaneous departure from the female was observed in male rats during testing of instrumental sexual responses. Male rats were tested in an apparatus consisting of two compartments connected by a runway composed of four parallel corridors. The final corridor of the runway and the goal compartment as well as the goal compartment and the start compartment were connected by one-way doors enabling the male to run only in one direction. An incentive female was tethered in the goal compartment. After contact with the female, lasting up to the end of a mount bout, or after exploration of the goal compartment, if the copulatory behaviour was not displayed, the male spontaneously passed to the start compartment and a new run started thereafter. The male thus performed the runs through the apparatus without any intervention from the experimenter.
Animals↗
Improved set of short-tandem-repeat polymorphisms for screening the human genome.
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Chromosome Mapping↗
Hepatitis G virus (HGV)--association with graft failure after hematopoietic stem cell transplantation?
A group of 28 children was investigated after hematopoietic stem cell transplantation for evidence of hepatitis G virus (HGV) infection. HGV RNA was detected in 14 of the 28 patients (50%) and persisted in 9 of 11 patients with follow-up samples for up to 32 months. Whereas thrombopoiesis was delayed in 2 of the 14 HGV-RNA-negative patients (14.3%), 6 out of 14 (42.9%) patients in the HGV-RNA-positive group had a delayed thrombopoiesis and 2 of the latter group had to be retransplanted because of complete graft failure. These were the only cases with hepatitis C virus (HCV) coinfection. Significant liver diseases were also found only in these 2 patients with HGV and HCV coinfection. These results suggest that HGV infection may significantly influence the engraftment in patients after hematopoietic stem cell transplantation, particularly if coinfection with HCV occurs.
Adolescent↗
A sensitive procedure for mapping the boundaries of RNA elements binding in vitro translated proteins defines a minimal hepatitis B virus encapsidation signal.
Using the structured RNA encapsidation signal (D(epsilon)) and the reverse transcriptase (P protein) of duck hepatitis B virus (DHBV) as an example, we devised a sensitive mapping procedure that yields accurate information on the minimal RNA sequence required for interaction with a few nanograms of an RNA-binding protein. RNAs from pools of end-labeled, partially hydrolyzed transcripts that bound to in vitro translated His-tagged P protein were isolated using immobilized Ni2+-ions. Size analysis by PAGE is consistent with a gradual gain in binding-competence from a minimum of 5 to a maximum of 8 base pairs in the basal stem of D(epsilon). The procedure should be generally applicable to the convenient and precise fine mapping of RNA-protein interactions.
Hepatitis B Virus, Duck↗