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Results for “systems drift”

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At least 19 recordsLinked to original sources
PubMed2026

Hologenomic interactions promote the higher-order evolvability of phenotypic complexity.

Current models for evolvability and complexity generally focus on mutational and regulatory processes in the host genome alone, limiting their ability to explain the origin, inheritance, and dynamics of many phenotypes. We describe a framework treating multigenome interactions in the holobiont as a central process that impacts the genotype-phenotype map, expanding the dimensionality of mechanisms producing heritable variation, generating novel traits, and exploring adaptive trajectories. These mechanisms can promote both complex phenotypic innovation and evolutionary systems drift. Many evolutionary pathways and novelties cannot be fully understood from host data alone but require consideration of hologenomic targets of selection. We outline hypotheses and methods to quantify and evaluate their impacts as a fundamental macroevolutionary process.

cellular innovation↗
PubMed1976

A pressure- and flow-insensitive reference electrode liquid junction.

The design and construction of a pressure- and flow-insensitive reference liquid junction for use in ion concentration electrode measuring systems is described. The junction is inexpensive, is very easily and rapidly constructed, is rugged, and is adaptable to various applications. When used in a pH-measuring system, drift, pressure artifacts, and flow artifacts are negligible. The response time of the system appears to be less than 10 ms. Using the pH electrode device as described, the dissociation reaction rate constant of H2CO3 at 24 degrees C was determined to be 22 s-1.

Electrodes↗
PubMed1979

Primary position vertical nystagmus: 'directional preponderance' of the pusuit system?

The essential disturbance in five patients with vertical nystagmus was an inability to generate smooth pursuit eye movements in the direction of the quick phase of their nystagmus. As the cause of this behavior, the authors suggest an asymmetric impairment of the visual input to the pursuit system. This defect causes a 'directional preponderance' of the pursuit system detectable as a continuous drift off target. The drift is interrupted by refoveating saccades, thus resulting in a vertical nystagmus.

Adult↗
PubMed2026

Repair and regeneration across the lifespan: an ontogenetic perspective.

The capacity for tissue repair and regeneration undergoes a profound and progressive decline across the human lifespan, representing a fundamental driver of aging and chronic disease. This review establishes a comprehensive ontogenetic framework by mapping the continuous biological transition from the flawless, scarless regenerative plasticity of embryonic development to the irreversible fibrotic scarring and organ failure characteristic of senescence. We synthesize the hierarchical collapse of reparative networks across multiple biological scales. Importantly, this ontogenetic decline should not be interpreted as a purely degenerative trajectory but rather as a dynamic systems-level reprogramming in which evolutionary trade-offs prioritize tumor suppression, immune surveillance, and reproductive fitness over long-term regenerative fidelity. Recognizing this adaptive reallocation of biological resources reframes aging not simply as failure but as a predictable recalibration of repair hierarchies. At the molecular and cellular levels, the accumulation of genomic instability, unresolvable DNA damage, and mitochondrial dysfunction gradually overwhelms intracellular quality-control mechanisms. Concurrently, epigenetic drift and chronic, low-grade systemic inflammation ("inflammaging") dismantle the stem cell niche, driving adult stem cell exhaustion and shifting wound healing away from functional tissue replacement toward maladaptive fibrosis. Furthermore, we examine divergent, organ-specific repair trajectories. By contrasting the severe regenerative restrictions of the adult central nervous system and myocardium with the persistent, yet exhaustible, resilience of the liver, we elucidate the unique intrinsic and microenvironmental barriers that impede structural and functional recovery. Finally, we evaluate the clinical paradigm shift from passive management of age-related degeneration to active restoration of tissue integrity. By integrating systemic geroscience-which addresses the global hallmarks of aging-with targeted bioengineering and in vivo epigenetic modulation, contemporary regenerative medicine seeks to recreate permissive, youthful microenvironments. Ultimately, mastering these ontogenetic principles holds unprecedented potential to reactivate endogenous repair pathways, mitigate multi-organ collapse, and significantly extend human functional healthspan.

DNA repair↗
PubMed1977

Chimeric drift in allophenic mice.

The composition of the immune system of 33 allophenic mice of four different types [C57BL/6 in equilibrium DBA/1, C57BL/6 in equilibrium (CBA X CBA/H-T6), C57BL/6 in equilibrium (A X SJL), DBA/1 in equilibrium (CBA X CBA/H-T6)] was studied. It was found that the parental composition of the peripheral white blood cells changed significantly during a two-month interval in 11/33 or 33% of the mice studied. This phenomenon has been termed chimeric drift. The animals were sacrificed between 9 and 16 months of age, and the parental composition of the peripheral white blood cells, spleen white blood cells, and thymocytes was determined on the day of sacrifice. It was foound that the peripheral white blood cell and spleen white blood cell compositions showed a high degree of correlation. However 8/33 or 24% of the mice studied showed discordance of the spleen and thymocyte cell populations. Seven of the 8 mice which showed spleen-thymocyte discordance, had also shown evidence of chimeric drift earlier in their lives. We suggest that this is evidence that chimeric drift may have an immunological basis.

Animals↗
PubMed1977

Two-stage operation for anatomical correction of transposition of the great arteries with intact interventricular septum.

To allow redevelopment of the posterior ventricle in an infant with transposition of the great arteries and intact interventricular septum, at the age of 4 weeks the pulmonary artery was banded, an aortopulmonary shunt was fashioned proximal to the band, and atrial septectomy was performed. Peak systolic posterior ventricular pressure immediately rose to systemic level (70 mm Hg.) During the next 4 months the pressure drifted back to 55 mm Hg but rose to 72 mm Hg after angiography without a rise in end-diastolic pressure. When the child was six months old anatomical correction of the transposition was successfully performed, the aorta, pulmonary, and coronary arteries being reattached to the appropriate ventricles. Debanding was performed at the same time. For the first 48 hours after operation phenoxybenzamine was given to reduce overload. At 6-month follow-up the child remained symptomless and was not on any cardiac drugs; left-ventricular function was good. This two-stage technique should widen the application of anatomical correction from a small selected group with additional defects to include most patients with transposition of the great arteries.

Aorta↗
PubMed1977

An automatically balancing isolation amplifier for the decoupling of measuring systems with high impedances.

It is theoretically shown that different conditions of coupling and grounding cause error voltages with the simultaneous use of two high-impedance measuring systems (e.g. pH electrodes). By the use of special amplifiers using optical transmission systems these error voltages are prevented. The transmission characteristics of the couplers are sensitive to changes in temperature due to the incorporation of infrared emitters in the system. An amplifying equipment with high d. c. stability was developed. The temperature drift was suppressed by the use of a special chopper stabilisation.

Electric Conductivity↗
PubMed2026

AI-driven snapshot hyperspectral imaging for on-line sorting systems in food industry: From real-time sensing to intelligent decision-making.

High-throughput food sorting requires rapid, non-destructive detection of external defects, foreign materials, and internal quality attributes in heterogeneous food matrices. Conventional scanning hyperspectral imaging may suffer from motion-induced spatial-spectral mismatches, whereas snapshot hyperspectral imaging (S-HSI) captures spectral images within a single integration time. However, its advantage is limited by trade-offs in resolution, signal-to-noise ratio (SNR), reconstruction uncertainty, and calibration stability, which are further amplified by variable tissue structure, surface reflection, moisture, and fat distribution in foods. This review critically examines artificial intelligence (AI)-driven S-HSI for on-line food sorting within a sensing-representation-decision-execution framework. Compact architectures are compared according to their physical constraints, food-sorting suitability, and ability to support mapping between spectral responses and physicochemical quality attributes. AI strategies are reviewed for spectral reconstruction, image restoration, spatial-spectral representation, band selection, uncertainty-aware decision-making, and edge implementation. AI can partially compensate for snapshot-specific limitations, but current evidence remains largely limited to laboratory or prototype studies. Future work should link system performance to food safety and quality outcomes by reporting throughput, decision latency, calibration drift, missed-detection risk, false-rejection cost, and closed-loop sorting success.

Hyperspectral Imaging↗
PubMed1976

Pathogenesis of visna. I. Sequential virologic, serologic, and pathologic studies.

A total of 56 Icelandic sheep were infected with visna virus by intracerebral injection of strain 1514 and the course of infection was followed for 12 months. Virus was isolated from more than 90 per cent of the animals, primarily from central nervous system and lymphoid tissues. However, titers of free infectious virus were minimal and virus isolation often required the use of tissue explants. All sheep raised serum-neutralizing and complement-fixing antibodies beginning 1 to 3 months after infection. Differences in neutralization titers against the infecting strain (1514) and a reference strain (796) suggested that antigenic drift might occur during prolonged infection. High cerebrospinal fluid neutralization titers in the spinal fluid indicated local antibody production in the central nervous system. Although the incidence of clinical disease during the 1st year of infection was less that 10 per cent, approximately 80 per cent of the sheep examined had central nervous system histologic lesions of variable severity, which were marked 1 month after infection with little progression during the subsequent year. There was a striking correlation between the severity of central nervous system lesions and the frequency of virus isolations from all tissues. These observations provide detailed base line data on visna infection, suggest some of the mechanisms responsible for the persistence of infection and for the slowness and irregularity of disease occurrence, and form the basis for further experiments on the role of immunologic mechanisms in the pathogenesis of this slow infection.

Animals↗
PubMed1976

Antigenic variants of influenza A virus obtained in vitro.

The aim of this study was to investigate antigenic "drift" in the haemagglutinin and neuraminidase antigens of influenza A virus in vitro under immunological pressure. Variants of the "Asian" influenza strains A/England/12/64 (H2N2) and A/Tokyo/3/67 (H2N2) were isolated in the allantois-on-shell system in the presence of homologous postinfection ferret sera. For each of these two viruses three generations of variants were isolated and characterized. It was found that the successive antigenic variants of A/Eng/12/64 did not resemble A/Tokyo/3/67. Thus it is probable that the pathway of antigenic drift in vitro was not the same as that which occurred in nature during the evolution of A/Tokyo/3/67 from A/Eng/12/64. In addition, A/Tokyo/3/67, which was the last strain to be prevalent before the A/Hong Kong subtype appeared, underwent significant antigenic drift from "junior" to "senior" variants. This finding did not support the concept that, when antigenic drift occurs, resulting in the appearence of viruses with new haemagglutinin antigen subtypes, the previously prevalent strain has no capacity for further antigenic drift. The study did not result in the production of strains that were identifiable as "bridging" viruses between the H2 and H3 haemagglutinin subtypes. The present paper includes the first report of antigenic variation in the neuraminidase antigens of influenza A viruses occurring in vitro under immunological pressure.

Antigens, Viral↗
PubMed1976

Picture quality of computed tomography.

Some limitations that impair the picture quality of computed tomography are presented. Picture grain is analyzed in detail and its relationship to different matrix sizes is demonstrated. The choices of matrix size for viewing various parts of the body are defined, and the need for higher resolution in the future is debated. Comparison is made between two scanning systems: the moving fan beam with rotation and the simple rotating fan beam. Possible artifacts in the picture caused by drift and delay in dector response are discussed.

Computers↗
PubMed1977

An improved technique for the rapid continuous measurement of whole blood glucose, suitable for clinical application in an artificial endocrine pancreas.

An improved bedside technique for the continuous monitoring of glycemia is described. A linear relationship results between whole blood glucose concentration and plasma glucose levels, and allows the calibration of the system in terms of plasma glucose levels. In operation venous blood is withdrawn at a steady rate using a double-lumen catheter and directed to a continuous-flow laboratory analyzer, where glucose analysis is carried out using a modified glucose oxidase-peroxidase methodology. The improvements in this technique include: i) a reduction in the delay of the analyzer to 90 s, making it suitable for application in a system for blood glucose regulation, ii) a minimal blood requirement of 3 ml/h, permitting long-term monitoring, iii) elimination of the need for systemic anticoagulation, iv) an excellent correlation (r = 0.993) between the measured whole blood glucose and the actual plasma glucose concentration, v) an average baseline drift of +0.5 mg%/h, vi) a sensitivity loss of less than 0.1%/h, and vii) a reasonable operating cost. This technique was implemented as part of a clinical apparatus known as an artificial endocrine pancreas which has been reliably applied in clinical and animal studies.

Adult↗
PubMed1979

pH gradient electrophoresis and isoelectric focusing of lipoproteins on agarose bead thin layers.

A new method of isoelectric focusing (IEF) and pH gradient electrophoresis, using thin layers of agarose gel beads, was devised to investigate chylomicrons and very low density lipoproteins (VLDL). pH gradient stability and cathodal gradient drift were similar to those of polyacrylamide gel IEF, and linearity of gradients was maintained for 23 hr. Chylomicrons and VLDL were detectable without staining. Chylomicrons from human serum and from rat lymph migrated in this system. Rat lymph chylomicrons, obtained by ultracentrifugation, migrated in several discrete bands, and this heterogeneity or rat chylomicrons was confirmed by electron microscopic demonstration of chylomicrons in each band. This new technique has permitted the first measurement of isoelectric points of some lipoproteins in the ultracentrifuged fraction of human serum chylomicrons and the first separation of multiple discrete fractions of ultracentrifuged lymph chylomicrons.

Animals↗
PubMed1977

Circadian rhythm of synaptic excitability in rat and monkey central nervous system.

Synaptic responses in hippocampal granule cells to stimulation of their afferent fibers from the entorhinal cortex fluctuate with a 24-hour period. The phase of this cycle for rats and monkeys depends on whether the animal is naturally nocturnal or diurnal. In a rat blinded by enucleation, the rhythm persists but drifts out of phase with the rhythm of sighted controls.

Action Potentials↗
PubMed1977

An implantable semiconductor beta-radiation detector.

An implantable beta-radiation detector suitable for the measurement of reginal blood flow in the experimental animal by the indicator clearance principle is described. A lithium-drifted silicon diode encapsulated in a stainless steel case is sutured over the site of interest. A suitable beta-emitting isotope, such as 85Kr in saline solution, is injected into the arterial supply and its calibrated against a mechanical system and showed excellent agreement up to 600 ml/100 g per min. At very high rates beyond the physiological range, flow was underestimated by a maximum of 10%. In vivo comparisons of myocardial blood flow assessed by the beta detector did not agree well with estimates of flow from a precordial counter or by the microsphere technique. Possible reasons are spatial heterogeneity of regional myocardial blood flow, the greatly different masses of tissue involved, or our inability to achieve sufficient numbers of spheres for accuracy in a 50-mg mass of tissue. The unit was still functional after 50 days in a chronic animal.

Animals↗
PubMed1978

Antigenic drift in influenza A viruses. I. Selection and characterization of antigenic variants of A/PR/8/34 (HON1) influenza virus with monoclonal antibodies.

Antigenic variants of A/PR/8/34 [HON1] influenza virus were selected after a single passage of the parent virus in embryonated chicken eggs in the presence of monoclonal antibodies to this virus. The monoclonal antibodies were produced by a hybridoma and were specific for an antigenic determinant on the HA molecule of the parent virus. Seven antigenic variants were analyzed with 95 monoclonal anti-HA antibodies prepared in vitro in the splenic fragment culture system. Three subgroups of antigenic variants were distinguished. The antigenic changes were primarily recognized by monoclonal antibodies to the strain- specific determinants of the parental hemagglutinin (HA) molecule. Monoclonal antibodies to HA determinants shared (in an identical or cross-reactive form) by parental virus and more than three heterologous viruses of the HON1 and H1N1 subtypes were unable to recognize the antigenic change on the variants. Similarly, heterogeneous antibody preparations could not differentiate between parental and variant viruses. The results are compatible with the idea that the HA of PR8 has available a large repertoire of antigenic modifications that may result from single amino acid substitutions, and that antigenic changes can occur in the strain- specific determinants on the HA molecule in the absence of concomitant changes in the cross-reactive HA determinants. The findings suggest that antigenic drift, in order to be epidemiologically significant, probably requires a series of amino acid substitutions in, or close to, the antigenic area on the HA molecule.

Antibodies, Viral↗
PubMed1975

Nuclear protein changes in rat hepatomas correlating with growth rate.

The nature of nuclear proteins that are soluble in 8 M urea-50 mM phosphate, pH 7.6, was compared in rat liver and Morris hepatomas, Isoelectric focusing, using carrier ampholytes for a pH gradient of 3.5 to 10, indicated that with increasing growth rate of the hepatomas there was a progressive tendency for a decrease in nonhistone nuclear proteins with isoelectric points in the range 7.5 to 8.9 and an increase in the range 5.1 to 6.7. Studies on the influence of time on the pH gradient revealed that a nonuniform drift provided a better resolution of the pH range 7.5 to 8.9 at 7 hr than at 24 hr, while the latter time for electrofocusing gave an improved resolution of the pH range 5.1 to 6.7 Polyarcylamide gel electrophoresis in a urea-acetic acid system showed that 8 M urea-50 mM phosphate; pH 7.6 extracted a small part of the histones from nuclei of both liver and hepatomas. There was less extraction of histones from the hepatoma nuclei, especially in two rapidly growing hepatomas with the most notable difference being seen in the lysine-rich H1 histone. The results suggested that in addition to qualitative or quantitative changes in nonhistone nuclear proteins in liver cancer there are alterations in the binding of histones to chromatin.

Acetates↗
PubMed1976

Development of a probe for endoureteral investigation of peristalsis by flow velocity and cross section area measurement.

A probe system for measurement of ureteric flow velocity and ureter cross section area is described. The flow velocity transducer is placed at the tip of a conventional 4-F ureteric catheter. The cross section transducer consists of two circular electrodes at an interval of 4 mm, mounted on the catheter just behind the flow velocity transducer. In vitro calibration established voltage as a function of flow velocity according to Kings law. Stability was excellent (0-point drift less than 1%/hour). Response time for flow rise was 0.02 second, and for flow fall 1.0 second. Variations of the ambient temperature at constant flow showed a margin of error in flow determination of 10 to 15%/1 degrees C temperature variation. In vitro calibration of the cross section transducer established linear correlation between voltage and tube diameter, but limited by the actual interelectrode interval. Probe displacement from tube axis gave an error of up to 10%. In vivo studies were made in anaesthetized pigs. The probe did not affect ureter peristalsis. Flow velocities ranged from 0 to 5 cm/second and ureter cross sectional areas between 0 and 0.2 cm2. Further developments in the measuring system are discussed.

Animals↗