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PubMed2000

Collective response of an array of rotating particles to fluctuating confining forces

We study the influence of fluctuations of confining forces on the rotation patterns in a dense array of cylinders. Our theoretical studies are motivated by new results from detailed time-resolved experimental measurements. In order to calculate the system's evolution in time at each moment, a molecular-dynamics code adapted to the system is developed. The numerical procedure is tested by a comparison with rigorous predictions derived analytically. The chain's reaction on oscillating confining forces is analyzed numerically for different typical cases. Our theoretical results reproduce the striking features of the experimental data. A quantitative analysis of the experimental data is performed by a computation of their power spectrum and of spatial and temporal correlation functions. From our comparison of the theoretical and experimental results we conclude that the experimental rotation patterns result of random superpositions of different steady-state patterns ("collective random walk").

Journal Article↗
PubMed1990

Chemical evolution and the origin of life: cumulative keyword subject index 1970-1986.

This cumulative subject index encompasses the subject indexes of the bibliographies on Chemical Evolution and the Origin of Life that were first published in 1970 and have continued through publication of the 1986 bibliography supplement. Early bibliographies focused on experimental and theoretical material dealing directly with the concepts of chemical evolution and the origin of life, excluding the broader areas of exobiology, biological evolution, and geochemistry. In recent years, these broader subject areas have also been incorporated as they appear in literature searches relating to chemical evolution and the origin of life, although direct attempts have not been made to compile all of the citations in these broad areas. The keyword subject indexes have also undergone an analogous change in scope. Compilers of earlier bibliographies used the most specific term available in producing the subject index. Compilers of recent bibliographies have used a number of broad terms relating to the overall subject content of each citation and specific terms where appropriate. The subject indexes of these 17 bibliographies have, in general, been cumulatively compiled exactly as they originally appeared. However, some changes have been made in an attempt to correct errors, combine terms, and provide more meaningful terms.

Exobiology↗
PubMedDate not supplied

Experimental investigations in prolonged myocardial ischaemia. Note I. Biology of the myocardial fiber after transient myocardial fiber after transient myocardial ischaemia.

The first ten days' evolution of post-ischaemic lesions of the premonitory or angina pectoris syndrome type was experimentally studied by the challenge of a short-term (10 and 15 min) ischaemia, of an adaptation to ischaemia and an adaptation followed by prolonged ischaemia (20 and 35 min). Worthy of note was the persistence of reversible lesions after short-term ischaemia and adaptation, and the progressive evolution towards cytolysis and cicatrization of some pancicellular foci after adaptation followed by prolonged ischaemia. The role of mitochondrial lesions, of lysosomal hydrolases, the inefficiency of renewed circulation, as well as problems of diagnosis are discussed.

Angina Pectoris↗
PubMed1998

Stochastic processes strongly influence HIV-1 evolution during suboptimal protease-inhibitor therapy.

It has long been assumed that HIV-1 evolution is best described by deterministic evolutionary models because of the large population size. Recently, however, it was suggested that the effective population size (Ne) may be rather small, thereby allowing chance to influence evolution, a situation best described by a stochastic evolutionary model. To gain experimental evidence supporting one of the evolutionary models, we investigated whether the development of resistance to the protease inhibitor ritonavir affected the evolution of the env gene. Sequential serum samples from five patients treated with ritonavir were used for analysis of the protease gene and the V3 domain of the env gene. Multiple reverse transcription-PCR products were cloned, sequenced, and used to construct phylogenetic trees and to calculate the genetic variation and Ne. Genotypic resistance to ritonavir developed in all five patients, but each patient displayed a unique combination of mutations, indicating a stochastic element in the development of ritonavir resistance. Furthermore, development of resistance induced clear bottleneck effects in the env gene. The mean intrasample genetic variation, which ranged from 1.2% to 5.7% before treatment, decreased significantly (P < 0.025) during treatment. In agreement with these findings, Ne was estimated to be very small (500-15,000) compared with the total HIV-1 RNA copy number. This study combines three independent observations, strong population bottlenecking, small Ne, and selection of different combinations of protease-resistance mutations, all of which indicate that HIV-1 evolution is best described by a stochastic evolutionary model.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Infant mouse model of E. coli diarrhoea: clinical protection induced by vaccination of the mothers.

Protection of infant mice against experimental E. coli B41 diarrhoea by immunization of the mothers with homologous E. coli strain was studied. The influence of the number, dose, route and moment of vaccination(s) on protection, measured by the reduced mortality rate of infant mice during the 15 days following oral challenge, was tested. The highest dose of vaccine, namely 10(8) formalin-killed E. coli by parenteral routes or 3 X 10(9) live E. coli by peroral (p.o.) route resulted in the best effect, whatever the immunization procedure used. A single vaccination of the mothers mainly delayed death without marked reduction of the mortality rate. Subcutaneous (s.c.) immunization with 10(8) formalin-killed E. coli was nevertheless more efficient than p.o. vaccination with 3 X 10(8) live E. coli. Equal levels of protection were observed when the above s.c. vaccination occurred either 15 days before the onset of gestation or on the 8th day or 15th day. In contrast, the p.o. immunization resulted in no effect when done on the 15th day of gestation. Great improvement in protection was obtained with two vaccinations, when priming occurred 15 days before the onset of gestation and boosting on the 8th day, except with two combined p.o. vaccinations with 3 X 10(8) live E. coli. Both dosages of priming and boosting seemed to matter. Peroral, subcutaneous or intraperitoneal priming with about 10(8) E. coli resulted in nearly equal effects, when boosting occurred subcutaneously with 10(8) killed E. coli. However, i.p. priming probably resulted in some non-specific effect, as shown by the slower clinical evolution of the controls. A tenfold dosage increase in p.o. priming alone led to the best protective effect observed when boosting was done three weeks after priming. The occurrence of s.c. boosting one week later, namely four weeks after priming, markedly improved protection with every route tested, and more particularly with the s.c. one. However, complete protection was never obtained. Protective effect was mostly transmitted after birth by the colostrum and the milk of the immune mothers, as demonstrated by cross-fostering experiments. Using the best immunization procedures, variability of the model was studied, by repeating experiments several times. Clinical evolution of the controls was very similar from one experiment to another, whatever the route and the moment of immunizations. In contrast, vaccinated groups showed variations which increased with time, especially on and after seven days following inoculation. Clinical evolution of individual litters belonging to the same experimental group indicated that each mother did not equally respond to the vaccination.

Animals↗
PubMed1999

Structure, evolution, and liver-specific expression of sterol 12alpha-hydroxylase P450 (CYP8B).

The rat CYP8B cDNA encoding sterol 12alpha-hydroxylase was cloned and sequenced. The amino acid sequence of the heme-binding region of CYP8B was close to those of CYP7A (cholesterol 7alpha-hydroxylase) and CYP7B (oxysterol 7alpha-hydroxylase). Molecular phylogenetic analysis suggests that CYP8B and the CYP7 family derive from a common ancestor. The P450s of the CYP7 and CYP8 families, except for CYP8A (prostacyclin synthase), catalyze the oxygenation of sterols from an alpha surface in the middle of the steroid skeleton. These facts suggest that CYP8B is a P450 closely linked to those of the CYP7 family. CYP8B was expressed specifically in liver. Hepatic CYP8B mRNA level and the 12alpha-hydroxylase activity were altered by cholestyramine feeding, starvation, streptozotocin-induced diabetes mellitus, and administration of clofibrate, dexamethasone or thyroxin, indicating the pretranslational regulation of CYP8B expression. The enhanced CYP8B mRNA expression in streptozotocin-induced diabetic rats was significantly decreased by insulin within 3 h of its administration. These facts demonstrate a regulatory role of insulin in CYP8B expression as a suppressor.

Amino Acid Sequence↗
PubMed1988

Experimental autoimmune arthritis in mice. II. Early events in the elicitation of the autoimmune phenomenon induced by homologous type II collagen.

Intradermal injection of 100 micrograms of native homologous type II collagen (CII) into DBA/1-susceptible mice induced a progressive and chronic polyarthritis. This experimental autoimmune arthritis (EAA) closely mimicked the clinical evolution of human rheumatoid arthritis (RA) except for the sex linkage. Males were highly susceptible to EAA induction even when the amount of autoantigen injected was reduced to 25 micrograms. Conversely, females remained resistant to the disease even when a booster injection of 50 micrograms was administered. With regard to age, no major difference in the incidence was observed, although younger males developed a more severe arthritis than older ones. Anti-CII autoantibodies were detected in all immunized animals, regardless of the presence or absence of joint pathology. However, in arthritic mice, the onset of the disease was associated with a predominance of IgG2a autoantibodies. Kinetic studies revealed that females as well as males exhibited early histological lesions and detectable humoral responses toward mouse CII as of the second week postimmunization. Moreover, a specific cellular autoreactivity to homologous CII occurred in different lymphoid organs with a higher intensity in females than in males. Taken together, these findings suggest that homologous CII injection induces an early subclinical arthritis that develops progressively in all immunized mice, but would be down-regulated several weeks after priming, exclusively in females.

Animals↗
PubMed1984

Self-sequencing of amino acids and origins of polyfunctional protocells.

The primal role of the origins of proteins in molecular evolution is discussed. On the basis of this premise, the significance of the experimentally established self-sequencing of amino acids under simulated geological conditions is explained as due to the fact that the products are highly nonrandom and accordingly contain many kinds of information. When such thermal proteins are aggregated into laboratory protocells, an action that occurs readily, the resultant protocells also contain many kinds of information. Residue-by-residue order, enzymic activities, and lipid quality accordingly occur within each preparation of proteinoid (thermal protein). In this paper are reviewed briefly the phenomenon of self-sequencing of amino acids, its relationship to evolutionary processes, other significance of such self-ordering, and the experimental evidence for original polyfunctional protocells.

Amino Acid Sequence↗
PubMed1999

[Supporting experimental animals rights in medicine].

The paper outlines the history of experiments on animals in medicine and biology. It also presents the sources of the notion and its evolution along with the roles played by Silesian Medical Academy representative in supporting experimental animals rights.

Animal Rights↗
PubMed1994

Sequential study of an experimental model of graft vs. host disease (GvHD) in non-immunosuppressed F1 (CBA/J x C57BL/6) mice.

In order to determine the optimal day for the evaluation of an experimental model of GvHD in F1 mice and the histopathologic evolution of the lesions in different organs, we studied 10-day-old F1 (CBA/J x C57BL/6) mice inoculated with splenic lymphoid cells of the male parental CBA/J strain (n = 42) that were sacrificed between 1 and 14 days postinoculation. The evolution of the relative spleen index (RSI) and the histopathologic lesions in different organs were also determined. F1 mice inoculated with Medium 199 were used as controls. Significant RSI increases (p < 0.0001) were found in the experimental group between 2 and 14 days postinoculation, with a peak at the eighth day, associated with the most severe histopathologic lesions in the organs studied. We suggest the eighth day as the optimal time for evaluation of this experimental model.

Animals↗
PubMed2003

Enhanced peroxynitrite decomposition protects against experimental obliterative bronchiolitis.

Obliterative bronchiolitis (OB) affects over half of all survivors following lung or heart-lung transplantation. Respiratory epithelial cell injury, peribronchial inflammation, and proliferation of fibrovascular tissue causing airway occlusion characterize the lesion. While peroxynitrite is known to participate in other models of acute lung injury, its role in the evolution of OB is unclear. Using a rat model of experimental OB, tracheas from Brown-Norway or Lewis rats were transplanted into Lewis recipients. Treated animals received FP-15, a peroxynitrite decomposition catalyst, at 1 mg/kg/day intraperitoneal for 14 days. Luminal obstruction, epithelial loss, and inflammatory infiltrate were examined, as was nitrotyrosine staining by immunohistochemistry in explanted tracheas. By postoperative day 14, control allografts demonstrated marked peribronchial inflammation, near complete loss of respiratory epithelium and extensive intraluminal proliferation of fibrovascular connective tissue, with a mean 83% reduction in airway cross-sectional area. Allograft recipients treated with FP-15 showed reduced nitrotyrosine formation, preservation of respiratory epithelium, limited peribronchial inflammation, and only 14% (P <.001) reduction in airway cross-sectional area. Peroxynitrite therefore appears to play a role in the development of obliterative bronchiolitis in rats. The peroxynitrite decomposition catalyst, FP-15, is protective when administered daily and warrants investigation into its potential clinical utility.

Animals↗
PubMed2003

Dynamics of DNA in vitro evolution with Mnt-repressor: simulations and analysis.

The dynamics of DNA in vitro evolution with Mnt-repressor has been studied numerically and analytically. Based on experimental data and realistic energy landscape for DNA-Mnt-repressor interaction, we investigated the dynamics of DNA in vitro evolution using stochastic simulations. The binding energy of DNA to Mnt-repressor was considered to consist of two parts: the DNA sequence specific and nonspecific. The crossover observed in real experiments is numerically recovered. We demonstrate that the evolution trajectories are drastically dispersed and no typical evolution passage exists during the evolution. Particularly, Fisher's theorem of natural selection is verified. A theoretical analysis for the evolution is also included.

DNA↗
PubMed2001

Saccharomyces cerevisiae as a starter culture in Mycella.

The potential use of Saccharomyces cerevisiae FB7 as an additional starter culture for the production of Mycella, a Danish Gorgonzola type cheese, was investigated. Two dairy productions of Mycella, each containing batches of experimental cheeses with S. cerevisiae added and reference cheeses without yeast added were carried out. For both experimental and reference cheeses, chemical analysis (pH, a(w), NaCl, water and fat content) were carried out during the ripening period, but no significant differences were found. The evolution of lactic acid bacteria was almost identical in both the experimental and reference cheeses and similar results were found for the number of yeast. S. cerevisiae FB7 was found to be predominant in the core of the experimental cheeses throughout the ripening period, while Debaryomyces hansenii dominated in the reference cheese and on the surface of the experimental cheeses. In the cheeses with S. cerevisiae FB7, an earlier sporulation and an improved growth of Penicillium roqueforti was observed compared to the reference cheeses. Furthermore, in the experimental cheese, synergistic interactions were also found in the aroma analysis, the degradation of casein and by the sensory analysis. The observed differences indicate a positive contribution to the overall quality of Mycella by S. cerevisiae FB7.

Caseins↗
PubMed2003

Chaotic synchronization and evolution of optical phase in a bidirectional solid-state ring laser.

We present results on experimental and theoretical studies of chaos in a solid-state ring laser with periodic pump modulation. We show that the synchronized chaos in the counter-propagating waves is observed for the values of pump modulation frequency fp satisfying the inequality f1 < fp < f2. The boundaries of this region, f1 and f2, depend on the pump-modulation depth. Inside the region of synchronized chaos we study not only dynamics of amplitudes of the counter-propagating waves but also the optical phases of them by mixing the fields of the counter-propagating waves and recording the intensity of the mixed signal. We demonstrate experimentally that in the regime of synchronized chaos the regular phase jumps appear during intervals between adjacent chaotic pulses. We improve the standard semi-classical model of a SSRL and consider an effect of spontaneous emission noise on the temporal evolution of intensities and phase dynamics in the regime of synchronized chaos. It is shown that at the parameters of the experimentally studied laser the noise strongly affects the temporal dependence of amplitudes of the counter-propagating waves.

Lasers↗
PubMed1992

Karyotypic evolution of a murine mammary adenocarcinoma in vitro and during progression from primary to metastatic growth in vivo.

We have previously described a murine mammary tumor cell line (SP1) that metastasizes when transplanted into the mammary gland, but not when injected into the subcutaneous site. We used cytogenetic markers to assess genetic heterogeneity, and to monitor the selection and evolution of karyotypically distinct cell types during primary tumor growth and in metastases. The SP1 tumor cells are hypotetraploid (mean chromosome number = 72), and have at least four karyotypically distinct cell types. We found no consistent pattern of selection of tumor cell types in primary tumors. However, metastases were derived from a cell type that was present in the corresponding primary tumor. In addition, novel, karyotypically distinct cell types also appeared in the metastatic nodules. Markers that appeared in metastases included two translocations, t(10;18) and t(1;19). By injecting a mixture of cells from a metastatic nodule with a non-metastatic clone into mice, we showed that the new cell types in metastases displayed a stable increased growth and metastatic potential when compared to the non-metastatic clone, or when compared to the initial cell type from which the metastases derived. These results indicate that metastases are derived from a distinct cell type in the primary tumor, but that additional chromosome and cell evolution occurs, resulting in new cell types that are selected in metastases.

Adenocarcinoma↗
PubMed1993

The proton NMR spectrum in acute EAE: the significance of the change in the Cho:Cr ratio.

We have studied by nuclear magnetic resonance spectroscopy the evolution of the proton spectral changes in acute experimental allergic encephalomyelitis. We found an in vivo elevation in the ratio between the peaks assigned to "choline containing compounds" (Cho) and creatine plus phosphocreatine (Cr). This was associated with an increase in choline, betaine, and phosphorylcholine (PC) as well as a reduction in N-acetylaspartate (NAA), aspartate, N-acetylaspartatylglutamate and inositol in vitro. Histological examination revealed inflammation with no evidence of demyelination or neuronal loss. We conclude that the increase in the ratio of Cho:Cr was due to an increase in the concentrations of PC, betaine, and choline in association with inflammation, and not as others have suggested, with demyelination. The reported reduction in NAA may be due to dysfunction of neurones rather than their loss.

Animals↗
PubMedDate not supplied

Influence of confounding factors on designs for dose-effect relationship estimates.

Three types of designs can be used to estimate the drug dose-effect relationship during phase II clinical trials: parallel-dose designs (parallel); cross-over designs (X), and dose-escalation designs ([symbol: see text]). Despite the use of non-linear mixed effect models, the potential influence of confounding factors on [symbol: see text] designs has not been previously fully elucidated; we undertook simulations to investigate this for all three experimental designs. We found that: (i) monotonic spontaneous evolution of the effect (EV) did not affect the maximum effect estimation (Emax) and the dose giving 50 per cent of this (ED50); (ii) EV similar to a regression to the mean gave rise to biases for [symbol: see text] designs; (iii) the introduction of a pharmacodynamic carry-over generates important biases and imprecision for [symbol: see text] designs, even when the carry-over is adjusted for; (iv) the introduction of non-responders resulted in bias and imprecision for both Emax and ED50 in all three designs.

Antihypertensive Agents↗