PubMed Health⌕ Search

Biomedical subjects

R Nowak

Publications and source records attributed to R Nowak.

At least 37 records · Page 2Linked to original sources
PubMed2001

A first step in prediction of the nanoscale structure of porous silicon from processing parameters.

The present work addresses the formation of porous silicon layers by means of anodic dissolution of p- and p(+)-type boron-doped (100) silicon wafers in 15, 25, and 35 vol% HF-ethanol solutions. The study concerned the dependence of the porous silicon layer growth rate dh/dt on electric current density i as well as on HF concentration. The formation of a porous silicon layer was found to follow a generic linear relationship, in(dh/dt)--in(i), which holds irrespective of the processing conditions. The combination of two equations, experimental and theoretical, derived from Faraday's equation, allowed us to reach conclusions on the relationship between the growth rate dh/dt and the degree of porosity, constituting a first step in prediction of the nanoporous structure of silicon based on processing parameters. This electrochemical approach complements physical models of silicon pore formation.

Computer Simulation↗
PubMed2001

[Assessment of quadriceps muscle isometric strength following operative treatment of femoral shaft fractures].

The authors investigated quadriceps muscle strength following operative treatment of femoral shaft fractures in 135 patients. Patients were categorized according to the kind of procedure performed: open Kuntscher intramedullary nailing--30 cases; Zespol--30 cases; AO plate osteosynthesis--47 cases and closed intramedullary nailing 28 cases. Two groups of patients were formed according to surgical technique: open method--107 cases and closed method--28 cases. 39 patients treated with an open method required re-operation. The best results were obtained in cases treated with closed technique--79.6%. The worst results were noted in the group requiring re-operation: 56.7%. The worst results were found in cases with comminuted fractures, and those located in the distal third of the femoral shaft.

Adolescent↗
PubMed2000

Germ cell-like telomeric length homeostasis in nonseminomatous testicular germ cell tumors.

Telomere maintenance plays an important role in cell proliferation and tumor survival. Human male germ cells, which carry long telomeres and express telomerase, give rise to a highly heterogeneous group of malignant tumors. We compared telomeric length and telomerase activity between two major histological types of primary testicular germ cell tumors. Fifteen out of 16 seminoma samples revealed telomeric restriction fragment (TRF) length below 13 kb; the remaining seminoma showed a major TRF fraction of 18 kb and a distinct minor fraction of above 23 kb length. In contrast, all 13 samples from nonseminomas showed TRF length >/=23 kb, which is similar to that reported in human sperm. Nine out of 11 seminoma specimens and six out of seven nonseminomas studied showed moderate to high telomerase activity, the only telomerase-negative nonseminoma being pure mature teratoma. These results indicate to a major difference in telomeric length between seminomas and nonseminomas, which is apparently unrelated to the presence of telomerase activity, and suggest a germline-like homeostasis of telomeric length is preserved in human nonseminomas. Oncogene (2000) 19, 4075 - 4078.

Adult↗
PubMed2000

Shift of aberrant antigen expression at relapse or at treatment failure in acute leukemia.

The flow cytometric detection of aberrant antigen expression is one method proposed for the quantification of minimal residual disease (MRD) in acute leukemias. The present study was designed to investigate the stability of the aberrant antigen expression at relapse or at treatment failure of initial chemotherapy. For this purpose, multiparameter immunophenotyping with a panel of 15 monoclonal antibodies was used at diagnosis as well as at relapse (43 patients with overall 65 aberrations) and at treatment failure (35 patients with overall 66 aberrations). There was a significant decrease in the percentage of the initially described aberrant antigen expression on leukemia blasts at relapse (P = 0.001; n = 65) as well as at treatment failure (P = 0.0001; n = 66) considering all aberrations in the whole leukemia population. Concerning only patients with acute myelogenous leukemia (AML), significant decreases in the aberrant expression could be detected at relapse (P = 0.031; n = 42) and at treatment failure (P = 0.0001; n = 52). The changes in patients with acute lymphoblastic leukemia (ALL) were significant only at relapse (P = 0.006; n = 23). Initially, the most informative aberration was not detectable in four patients at relapse and in seven patients at treatment failure. A decrease of under 50% of the initial value was observed in another 8 patients at relapse and in 10 patients at treatment failure. In further studies assessing the detection of aberrant antigen expression for MRD, quantification of the relapses should be explicitly analyzed regarding the persistence of the initially described aberrant antigen expression.

Adult↗
PubMed2000

2-NAP, a peripheral CCK-A receptor antagonist, modulates the development of a preference for the mother by the newborn lamb.

The aim of this study was to investigate the effect of devazepide (DEV), a cholecystokinin (CCK)-A receptor antagonist, which crosses the blood-brain barrier (BBB) and prevents the development of a preferential relationship with the dam, and compare it to that of 2-NAP, which acts peripherally. At birth, lambs received either an intraperitoneal injection of saline (CTL), DEV (0.1 mg/kg), or 2-NAP (0.01, 0.1, or 1 mg/kg). No major side effects were observed after the injection, however, there was a trend for lambs receiving CCK-A antagonists to be more vocal in the first 2 h and to loose more weight between birth and 3 h. When tested in a two-choice test situations at 24 h of age, the latency to reach a ewe and the total time spent next to them were not affected by the treatments. On the other hand, unlike CTLs, lambs receiving DEV or 0.1 mg of 2-NAP did not spend significantly more time near their dam than near the alien ewe. 2-NAP had no effect at 0.01 mg/kg, but at 1 mg/kg, it improved the preference score. There was no relationship between preference scores and the variations in weight recorded during the neonatal period. The effects of DEV, but not those of 2-NAP, persisted at 48 h of age. Thus, these results support the hypothesis that peripheral CCK receptors are involved in the development of a preference for the mother, but the effects differ according to the amount of 2-NAP that the lambs receive.

Animals↗
PubMed2000

Hancokinol from Vincetoxicum officinale.

Hancokinol (1), a member of migrated lupane triterpenoids, was isolated from the aerial parts of Vincetoxicum officinale, along with known plant sterols and long chain alkanols.

Humans↗
PubMed2000

Long-term cultured IL-2-dependent T cell lines demonstrate p16(INK4a) overexpression, normal pRb/p53, and upregulation of cyclins E or D2.

Acquisition of an immortal phenotype by circumvention of the normal senescence program can be an important step in tumor development and progression. The regulation of life-span checkpoints is complex and abrogation of these processes can occur at different levels. To better understand these mechanisms in long-term cultured lymphocytes we have characterized two human long-term cultured IL-2-dependent T cell lines regarding telomere length, telomerase activity, and the expression of selected cell cycle regulators (pRb, p53, cyclin E, cyclin D1, cyclin D2, cyclin D3, cdk4, p16(INK4a), p21(WAF1), p27(KIP1), c-myc, bcl-2, and NPAT). We compared these cell lines with a primary T lymphoblast population with a limited life span from the same donor. Both T cell lines with extraordinary growth capacity showed telomere length stabilization, high telomerase activity and demonstrated wild-type pattern of pRb and p53 but strong p16(INK4a) protein expression. The growth inhibitory activity of p16(INK4a) seemed to be abrogated by enhanced expression of cyclin D2, cdk4, and c-myc in one T cell line and overexpression of cyclin E in the second T cell line.

Cell Culture Techniques↗
PubMed2000

Efficacy of the nicotine patch for relief of craving and withdrawal 7-10 weeks after cessation.

The objective of this study was to test the efficacy of the nicotine patch for relief of craving and withdrawal beyond 6 weeks (during weeks 7-10), among heavy, dependent smokers, using a multicenter, randomized, double-blind, placebo-controlled trial. The subjects were 421 nicotine-dependent smokers who had quit smoking with the NicoDerm CQ nicotine patch, recruited from among enrollees in the NicoDerm CQ Committed Quitters behavioral program. Following 6 weeks of 21-mg active patch use, participants who had not relapsed were randomized to receive either active or placebo patches for an additional 4 weeks with tapering (14-mg patch in weeks 7-8 and 7-mg patch in weeks 9-10). Craving and withdrawal symptoms were assessed daily by phone interview during weeks 7-10 following cessation. The active patch group reported significantly lower craving and withdrawal, and higher positive mood scores in weeks 7-8 (p < 0.001, 0.001, and 0.03, respectively) and weeks 9-10 (p < 0.02, 0.01, and 0.02, respectively) compared to the placebo group. It was concluded that some smokers may be best served by 10 weeks of patch treatment. This study demonstrated the utility of continuing patch treatment for symptom relief in weeks 7-10 of abstinence. Future research should examine the optimal duration of treatment, which may vary across different classes of smokers.

Administration, Cutaneous↗
PubMed2000

Role of mother-young interactions in the survival of offspring in domestic mammals.

The defining characteristic of mammals is that females nurse and care for their young; without this, the neonate has no chance to survive. Studies on wild and domestic species show that the neonatal period is the most critical step in the lifetime of a mammal. This review compares three well-studied species (the rabbit, pig and sheep) that differ in their parental strategies and in the problems that neonates have to overcome. As a general trend, mother-young interactions vary according to the maturity of the newborn, and the size of the litter. Neonatal survival relies to a great extent on an environment that is ecologically appropriate for the developmental stage of the neonate, and on optimum interactions with the mother. Adaptive maternal care supposes that the mother provides the basic needs of the neonate: warmth (in pigs and rabbits) or shelter, food, water and immunological protection (via colostrum) and, in some instances, protection from predators and other conspecifics. A major risk facing all neonates, other than the birth process itself, is inadequate colostrum intake owing to delayed suckling or competition with siblings, which leads to starvation, hypothermia or even crushing, as has been observed in pigs.

Animals↗
PubMed2000

[The us of video-EEG in the diagnosis of epilepsy syndromes in the developmental age].

In the Department of Developmental Neurology, K. Marcinkowski University of Medical Sciences in Poznań 120 video-EEG were performed in 1997-1998. Video-EEG monitoring was executed by means of computer electroencephalograph "Ceegraph" (Biologic--USA). A group of 20 patients between the age of 20 months up to 19 years, whose video-EEG was analysed, was hospitalised because of diagnostic doubtful seizures. Stimultaneous EEG and clinical events recordings were evaluated with the use of videotape at all children. In the investigated group, 13 patients with epileptic seizures (5 with nonepileptic seizures, 1 patient with choreatic movements and 1 with nocturnal myoclonus) were recorded. There were 3 children classified with generalised absence seizures, 3 with partial seizures and 1 patient with myoclonic seizure among the children with epilepsy. Moreover, there were several different cases diagnosed: 3 patients presented Lennox-Gastaut syndrome, 1 was classified with West's syndrome, 1 patient was characterised by Alpers syndrome and 1 with tuberous sclerosis. Psychogenic pseudoepileptic seizures were classified in 5 patients, in 3 of them both epileptic and nonepileptic events occurred. Utility of video-EEG monitoring allows to differentiate and classify seizures and epileptic syndromes in childhood, especially absence seizures and psychogenic pseudoepileptic seizures. Its use makes the introduction of appropriate treatment possible.

Adolescent↗
PubMed2000

[The use of EEG polarization in the localization of epilepsy focus].

Multiple spatio dipole structure of brain cortex has been developed to transform the traditional scalp EEG into an image of source activities. Computer use of complex calculation algorythms identify those brain regions which are active and contribute to the epileptiform discharges. The Chair and Department of Developmental Neurology at University of Medical Sciences in Poznań received a new imaging technique Focus (Megis, Germany) for testing, which allows to obtain maps of topographic EEG distribution at the instant chosen in time. Our research was based on 32-channel EEG files recorded on Ceegraph SE (Bio-Logic, USA). The purpose of the study was the comparison of traditional EEG evaluation and automatic analysis made by computer programm "FOCUS". EEG records in patients with simple partial and complex seizure were marked by a physician, electroencephalographer. Digital EEG records were also analysed by a source imaging Focus software. The best localisation of epileptic focus has been obtained in baso-mesial temporal lobe. The new technique of dipole automatic analysis is a non-invasive method providing information about seizure localisation.

Brain Mapping↗
PubMed2000

[P300 event-related potential in epileptic children and adolescents].

P300 is a manifestation of activity in a limited capacity system "whose use in the service of different tasks is under relative control by instruction". It is accepted as an objective correlate of mental processing involved in the allocation of attentional resources when immediate memory is engaged. The aim of this study was to evaluate cognitive function in epileptic children and adolescents. We applied the "auditory oddball" paradigm to elicit event-related potentials (ERPs) according to the IFCN recommendation standards. ERPs were studied in fifteen patients with generalized epileptic seizures at matched age (8-18 years) (mean 13.8 +/- 2.4 y). 50 neurologically normal children were used as a control group. ERP were averaged with a Multiliner (Toennies, Germany) equipment. The method included two different tones for frequent and for rare stimuli generated at random. The tones were presented binaurally through headphones. ERPs were recorded at Fz, Cz and Pz according to the International 10-20 system. ERPs for target and non-target stimuli were averaged separately. The major positive peak between 250 and 500 ms for the rare tones was regarded as the cognitive evoked potential (P300). Latency values were obtained from the intersection of extrapolated lines from the ascending and descending slopes of each peak. The latencies of the N1, P2, N2 and P300 waves were determined for each subject, as well as peak to peak amplitudes of N1-P2, P2-N2, N2-P300. Auditory event related potential may be helpful procedures used in objective evaluation of cognitive function in patients with epilepsy.

Adolescent↗
PubMed2000

Different treatment modalities of tinnitus at the EuromedClinic.

A retrospective study at the ear, nose, and throat department of the EuromedClinic showed considerable improvements immediately after the end of the treatments for acute and for chronic tinnitus. Eighty percent of our patients suffering from acute tinnitus showed an improvement with intravenous medication without hyperbaric oxygen treatment, and 65.7% showed improvement with infusion therapy and hyperbaric oxygen. However, at 3 months and then later (long-term results), the figures decreased to 67% and 46%, respectively. In the chronic tinnitus group, the therapeutic effect dropped from 66.7% to 34% (with only intravenous medication) and from 60% to 28% (with combined therapy). These facts can explain the importance of beginning the treatment of patients suffering from tinnitus as early as possible (i.e., acute stage).

Acute Disease↗
PubMed1999

Colostrum mediates the development of mother preference by newborn lambs.

The first sucking bouts have strong rewarding properties in the establishment of a preference for the mother by newborn lambs. In this study we designed an artificial teat (Experiment 1) and a method of tube feeding (Experiment 2) to investigate the role of nonnutritive sucking and colostrum intake as reinforcers in the development of this relationship (Experiment 3). In this third experiment, lambs of the control group (n=10) had free access to the udder. In the other groups they were prevented from sucking between birth and 6 h by covering the ewe's udder while lambs received one of the following treatments: access to nonnutritive teats fitted onto the mother's udder (n=12), tube fed with colostrum (n=11), or fully deprived (n=10). When tested in a two-choice test at 24 h of age, controls and lambs receiving colostrum spent significantly more time near their mother than near the alien ewe. By contrast, deprived lambs did not. Half of the lambs having access to nonnutritive teats displayed a preference for their mother; the other half chose the alien ewe. However, most lambs that were affected by the treatments displayed a preference for their mother when a second test was performed at 48 h. In conclusion, these results demonstrate that a neonatal nasogastric infusion of colostrum has the same rewarding properties as a complete sucking bout. They also provide evidence for the first time that a relationship with the dam can be established via a nutritional signal originating from the gastrointestinal sphere.

Animals↗
PubMed1999

Detection of residual aneuploid leukemic cells by "continuous gating".

BACKGROUND: A new method for the detection of residual aneuploid leukemic cells in bone marrow by flow cytometry is described. This method is based on the analysis of FCM derived list-mode-datasets with a new software called "Continuous Gating". The program is able to decrease the detection level of aneuploid tumor cells by analyzing groups of cells with comparable antigen density and scatter properties. METHODS: Aneuploid acute lymphocytic leukemia cells with a known CD34 expression were diluted with diploid bone marrow cells to a concentration of 10, 1, 0.1, 0.05, and 0.01%. Each sample was measured in a FACScan flow cytometer, after staining with CD34 Moab and propidium iodide. Listmode-data were analyzed with the new "Windows"-based "Continuous Gating" software. A gate was set in the DNA parameter, defining the channels in which the aneuploid G0/G1-peak of possible residual tumor-cells should be found. Ten thousand overlapping gates of size 200 x 200 channels (out of 1,023 x 1,023 channels) were set automatically by the program into the side-scatter (SSC)/CD34 dot-plot, calculating the percentage of aneuploid G0/G1-phase cells for every specific gate. RESULTS: The results are plotted in a contour-plot. In dot-plot gates with less than 20 cells, the calculation of the percentage of aneuploid cells was declared invalid and the area in the contour-plot was marked. Detection of residual aneuploid cells, based on a defined expression of CD34 and granularity (SSC), was possible down to a contamination of 0.1%. CONCLUSIONS: The new "Continuous Gating" software can be used for the automated detection of aneuploid leukemic cells, if the density of a certain surface-marker is slightly different from normal cells.

Adult↗