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At least 1,189 records · Page 66Linked to original sources
PubMed1992

Construction of a human chromosome 4 YAC pool and analysis of artificial chromosome stability.

In order to construct a human chromosome 4-specific YAC library, we have utilized pYAC4 and a mouse/human hybrid cell line HA(4)A in which the only human chromosome present is chromosome 4. From this cell line, approximately 8Mb of chromosome 4 have been cloned. The library includes 65 human-specific clones that range in size from 30kb to 290kb, the average size being 108kb. In order to optimize the manipulation of YAC libraries, we have begun to investigate the stability of YACs containing human DNA in yeast cells; these studies will also determine if there are intrinsic differences in the properties of chromosomes containing higher eukaryotic DNAs. We are examining two kinds of stability: 1] mitotic stability, the ability of the YAC to replicate and segregate properly during mitosis, and 2] structural stability, the tendency of the YAC to rearrange. We have found that the majority of YACs examined are one to two orders of magnitude less stable than authentic yeast chromosomes. Interestingly, the largest YAC analyzed displayed a loss rate typical for natural yeast chromosomes. Our results also suggest that increasing the length of an artificial chromosome improves its mitotic stability. One YAC that showed a very high frequency of rearrangement by mitotic recombination proved to be a mouse/human chimera. In contrast to studies using total human DNA, the frequency of chimeras (i.e., mouse/human) in the YAC pool appeared to be low.

Blotting, Southern↗
PubMed1989

Construction of a chimeric series of Bacillus cyclomaltodextrin glucanotransferases and analysis of the thermal stabilities and pH optima of the enzymes.

The cyclomaltodextrin glucanotransferase (CGTase, EC 2.4.1.19) gene from the alkalophilic Bacillus sp. strain no. 17-1 was cloned in Escherichia coli. The cloned CGTase gene consisted of a single open reading frame which would encode a polypeptide of 713 amino acids, and the first 27 amino acid residues comprised a signal peptide. The nucleotide sequence and the amino acid sequence of this CGTase (CGTase 17-1) gene had strong homology with those of the CGTase (CGTase 38-2) gene previously cloned in our laboratory from the alkalophilic Bacillus sp. strain no. 38-2, although the enzymic properties of the CGTase 17-1 were distinct from those of the CGTase 38-2. To analyse those enzymic properties further, we constructed 12 chimeric CGTases using three restriction nuclease sites and compared the enzymic properties of the chimeric CGTases. The N-terminal part of the enzyme was important for heat stability, and the pH-activity profile was influenced by both the N- and the C-terminal parts. A third segment was less important for enzymic properties.

Amino Acid Sequence↗
PubMed2006

Expression of botulinum neurotoxins A and E, and associated non-toxin genes, during the transition phase and stability at high temperature: analysis by quantitative reverse transcription-PCR.

Production of botulinum neurotoxin A (BoNT/A) and associated non-toxic proteins (ANTPs), which include a non-toxic non-haemagglutinin (NTNH/A) as well as haemagglutinins (HAs), was found previously to be dependent upon an RNA polymerase alternative sigma factor (BotR/A). Expression of the botR/A, bont/A and antp genes, monitored by reverse transcription and real-time PCR analysis, occurred concomitantly at the transition between the exponential and stationary growth phases of Clostridium botulinum A. The botR/A expression level was about 100-fold less than those of the bont/A and antp genes. Therefore, BotR/A is an alternative sigma factor controlling the botulinum A locus genes during the transition phase. The highest toxin concentration was released into the culture supernatant 12 h after maximum expression of the botR/A, bont/A and antp genes, without any apparent bacterial lysis. Toxin levels were then stable over 5 days in cultures at 37 degrees C, whereas a dramatic decrease in lethal activity was observed between 24 and 48 h in cultures at 44 degrees C. High temperature did inhibit transcription, since expression levels of the botR/A, bont/A and antp genes were similar in cultures at 37 and 44 degrees C. However, incubation at 44 degrees C triggered a calcium-dependent protease that degraded BoNT/A and NTNH/A, but not HAs. In C. botulinum E, which contains no gene related to botR, the bont/E and p47 genes were also expressed during the transition phase, and no protease activation at 44 degrees C was evident.

Bacterial Proteins↗
PubMed2001

Tibiotalocalcaneal arthrodesis: a biomechanical analysis of the rotational stability of the Biomet Ankle Arthrodesis Nail.

We hypothesized that the posterior-to-anterior (PA) calcaneal interlocking screw of the Biomet Ankle Arthrodesis Nail would increase rotational stability secondary to increased bone purchase compared with the standard lateral-to-medial (transverse) screw. Each of 10 fresh human cadaver lower limbs (five matched pairs) were stabilized with a nail inserted retrograde through the calcaneus, talus, and tibia according to standard technique. One limb of each pair was fixed with a transverse calcaneal screw; the contralateral limb, with a PA calcaneal screw. Each limb was then subjected to torsional testing on an MTS Mini Bionix load frame. The PA screw construct was significantly stiffer than the transverse screw construct: 1.96 and 1.41 Nm/E, respectively (P < 0.036).

Ankle Joint↗
PubMed1998

An electromyographical analysis of the scapular stabilizing synergists during a push-up progression.

Current literature recommends incorporating push-up progressions into upper extremity rehabilitation for advanced training of the scapular stabilizers. No documentation exists to demonstrate changes in the level of muscle activation when push-up progressions are performed. The purpose of this study was to determine the effect of difficulty level for push-ups on electrical activity of the scapular stabilizing synergists. Sixteen subjects performed five repetitions for each of the three conditions in a push-up progression. Electromyographic data collected on the serratus anterior, upper trapezius, and lower trapezius revealed a statistically significant interaction effect between the serratus anterior and upper trapezius and push-up condition when the feet were elevated. No significant interaction was found between push-up condition and the lower trapezius. This study supports the clinical use of push-up progressions to facilitate activation of the serratus anterior and the upper trapezius during upper extremity rehabilitation.

Adolescent↗
PubMedDate not supplied

[Letter: Analysis of the lateral stability of the protofibril lattice in the a-disk of striated muscle].

The stability of a long cylinder system in electrolytic solution is calculated numericaly, suggesting that the equibrium arises from the balance between electrostatic and disperion forces. The influence of such parameters as Hammakker's constant, ionic strength and surface potential are considered. Our results show a much better agreement with X-ray difrecation experimental data, than the results of approximate calculation do.

Electrolytes↗
PubMed1975

Some aspects of specimen collection and stability in trace element analysis of body fluids.

Analyses for trace elements in biological fluids are uniquely susceptible to extreme errors unless special precautions are taken during collection, storage, and analysis. The integrity of the specimen may be compromised before it is analyzed, by contamination during collection and processing or by attenuation of the analyte concentration during storage. If this happens, determined values are not valid even though the method of analysis is extremely sensitive and highly accurate. Obstacles to obtaining precise and accurate analytical data arising from these factors are discussed. We consider control procedures applicable at all stages for ascertaining the sources of error and eliminating them.

Body Fluids↗
PubMedDate not supplied

[A comparative analysis of the functional stability (based on electrophysiological criteria) of slices of the suslik and guinea pig brains maintained under deep hypothermia].

The effect of prolonged deep cooling has been investigated in hippocampal and septal slices from the brain of hibernating and active ground squirrels, as well as of the guinea pigs. The slices were kept at low temperatures (2-4 degrees C) for various periods of time (from several hours to 6 days) and were periodically tested in a warm (31 degrees C) incubation medium. Hippocampal field potentials (mainly of the field CA1) and spontaneous activity of single neurones of the medial septum were recorded. Significant differences were observed in the recovery of functional activity of the slices after their preparation as well as after cooling between experimental groups of animals. Slices from hibernating ground squirrels retained their activity for 7-9 days, those from active ones--for 6-7 days, whereas slices from guinea pigs did not recover their functional activity after cooling for more than 1-2 days.

Animals↗
PubMed1991

A mathematical model for the interaction between cytotoxic T lymphocytes and tumour cells. Analysis of the growth, stabilization, and regression of a B-cell lymphoma in mice chimeric with respect to the major histocompatibility complex.

A mathematical model of the response of cytotoxic T lymphocytes (CTL) to the nonexponential growth of an immunogenic tumour is presented. The model describes satisfactorily the kinetics of growth and regression of the B lymphoma BCL1 in the spleen of mice chimeric with respect to the major histocompatibility complex (H-2b----H-2d). Numerical estimations of the parameters describing processes that cannot be measured in vivo have been derived. It is predicted that the development of the tumour and its clinical manifestation have a recurrent profile with a cycle of three to four months. According to the model the limited growth of the BCL1 tumour and its transition into the dormant state are associated with a high rate of accumulation of CTL in the tumour, rapid lysis of lymphoma cells, and the inability of tumour cells to suppress the affector functions of cytotoxic lymphocytes. The model is also capable of representing the phenomenon of tumours 'sneaking through' and the immunostimulation of tumour growth.

Animals↗
PubMed1991

[Analysis of occlusion and stability in complete dentures].

The prosthetic treatment of edentulous patients must be carried out with the dual objective of preserving the residual ridges and re-establishing the functional activities of the masticatory system. The authors propose to investigate the subjective efficiency of the prosthesis by an interview of the patients, and the objective efficiency by clinical testing, after one year of use. In this study, a group of 41 patients, males and females, are supplied with bimaxillary full dentures according to GERBER's technique. Special attention is given to the teeth position in relation to the base stabilisation surface. The teeth likely to unbalance the prostheses were not mounted. The inter-maxillary relationship at the horizontal level was obtained by using a gothic arch recording. After one year of use, the following results were obtained: patients very satisfied with their upper denture: 43.9%; patients very satisfied with their lower denture: 39%; satisfied: 51% for the upper denture; satisfied: 56.1% for the lower denture; not satisfied: 4.9% for the two dentures. Only 12 patients (29.2%) had all of their posterior teeth put in. The decrease in the number of teeth did not reveal any significant decrease in the mastication efficiency, according to the patients opinion (2.4%). The original occlusion was restored in 78% of the cases. The authors emphasized the importance of the occlusal relationship and of the posterior teeth for stability and efficiency in the treatment of edentulous patients.

Adult↗