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A model of functional epistasis and linkage disequilibrium in populations with overlapping generations.

A model of functional epistasis is proposed in which it is assumed that coupling and repulsion genotypes differ in metabolic efficiency and thus in development time and net fecundity. The implications of this model are investigated for iteroparous populations with fluctuating rates of increase. It is found that the fluctuations in rate of increase can lead to large fluctuations in gamete frequency and D, the coefficient of linkage disequilibrium, but that D will almost always have a value of zero at some point during the populations' demographic cycle. Some of the model populations would be expected to be in a state of linkage disequilibrium only fleetingly: others would exhibit D-cycles interpretable as random fluctuation. Implications of the model for interpretations of existing data on linkage disequilibrium among enzyme loci in Drosophila are discussed.

Animals

Further characterization of Sendai virus DI-RNAs: a model for their generation.

Sendai virus DI-RNAs which contain complementary ends have been characterized as follows. First, the complementary ends of three DI-RNAs, although somewhat different in size (110-150 base pairs), contain sequences that are both identical to each other and to the 5' end of the nondefective (ND) genome. Second, almost all the sequences contained sequences that are both identical to each other and to the 5' end of the nondefective (ND) genome. Second, almost all the sequences contained in the DI-RNAs derive from sequences that are contiguous to the 5' end of the ND genome. The ND genome, on the other hand, does not contain any sequences that are complementary to its 5' end. A genetic map and a model for the generation of the Sendai DI-RNAs are presented.

Base Sequence

[Possibilities of the clinical comparison of diseases with a hereditary burden in the descendant generation using the model of "parents-children" ill with schizophrenia].

A special statistic method of confrontation of diseases with aggravation hereditary in the group "parents - children" is proposed. This method can be used under clinical formalization of the diseases. It is shown on a model group parents - children (118 pairs) suffering with schizophrenia, that statistical confrontation makes possible to work out group and individual prognoses in the descending generation. It is found that invariability in the descending generation is provided by a small number of stable indices, other symptoms being variable. Statistic description of the disease symptoms in the descending generation is of interest for planning genetic interpretation.

Adult

Bactericidal activity of a superoxide anion-generating system. A model for the polymorphonuclear leukocyte.

The acetaldehyde-xanthine oxidase system in the presence and absence of myeloperoxidase (MPO) and chloride has been employed as a model of the oxygen-dependent antimicrobial systems of the PMN. The unsupplemented xanthine oxidase system was bactericidal at relatively high acetaldehyde concentrations. The bactericidal activity was inhibited by superoxide dismutase (SOD), catalase, the hydroxyl radical (OH.) scavengers, mannitol and benzoate, the singlet oxygen (1O2) quenchers, azide, histidine, and 1,4-diazabicyclo[2,2,2]octane (DABCO) and by the purines, xanthine, hypoxanthine, and uric acid. The latter effect may account for the relatively weak bactericidal activity of the xanthine oxidase system when purines are employed as substrate. A white, carotenoid-negative mutant strain of Sarcina lutea was more susceptible to the acetaldehyde-xanthine oxidase system than was the yellow, carotenoid-positive parent strain. Carotenoid pigments are potent 1O2 quenchers. The xanthine oxidase system catalyzes the conversion of 2,5-diphenylfuran to cis-dibenzoylethylene, a reaction which can occur by a 1O2 mechanism. This conversion is inhibited by SOD, catalase, azide, histidine, DABCO, xanthine, hypoxanthine, and uric acid but is only slightly inhibited by mannitol and benzoate. The addition of MPO and chloride to the acetaldehyde-xanthine oxidase system greatly increases bactericidal activity; the minimal effective acetaldehyde concentration is decreased 100-fold and the rate and extent of bacterial killing is increased. The bactericidal activity of the MPO-supplemented system is inhibited by catalase, benzoate, azide, DABCO, and histidine but not by SOD or mannitol. Thus, the acetaldehyde-xanthine oxidase system which like phagocytosing PMNs generates superoxide (O.2-) and hydrogen peroxide, is bactericidal both in the presence and absence of MPO and chloride. The MPO-supplemented system is considerably more potent; however, when MPO is absent, bactericidal activity is observed which may be mediated by the interaction of H2O2 and O.2- to form OH. and 1O2.

Acetaldehyde

Sequential expression of immunoglobulin on developing mouse B lymphocytes: a systematic survey that suggests a model for the generation of immunoglobulin isotype diversity.

Paired immunofluorescent staining with antibodies specific for the major isotypes of mouse immunoglobulin was used to study the ontogenetic expression of diversity of cell surface immunoglobulin. The first B lymphocytes to emerge, derived from cytoplasmic IgM+ precursors, express sIgM exclusively. Between birth and 3 days of age separate populations of sIgM+ B lymphocyte acquire a second isotype: sIgD, one of the subclasses of sIgG, or sIgA. At 3 days, all splenic B lymphocytes that bear sIg or sIgA also express sIgM, but virtually none stain for sIgD. By 7 days, a substantial porportion of sIgG+ or sIgA+ lymphocytes in spleen and most of those in lymph node express both sIgM ans sIgD. Anti-mu antibody treatment from birth prevented development of B lymphocytes expressing any isotype. These observations suggest that the immature sIgM+ B lymphocyte is the pivotal cell in the generation of the different sublines of B cells and that sIgD ig or IgA. The frequency of lymphocytes bearing only sIgG or sIgA is higher in old than in young mice, suggesting that sIgD and sIgM may be lost after stimulation by antigens. The occurrence of a nearly identical distribution of sIg isotypes on B lymphocytes from athymic, pathogen-free mice suggests that primary expression of isotype diversity does not require T cells.

Aging

Generating synthetic genotypes using diffusion models.

SUMMARY: In this paper, we introduce the first diffusion model designed to generate complete synthetic human genotypes, which, by standard protocols, one can straightforwardly expand into full-length, DNA-level genomes. The synthetic genotypes mimic real human genotypes without just reproducing known genotypes, in terms of approved metrics. When training biomedically relevant classifiers with synthetic genotypes, accuracy is near-identical to the accuracy achieved when training classifiers with real data. We further demonstrate that augmenting small amounts of real with synthetically generated genotypes drastically improves performance rates. This addresses a significant challenge in translational human genetics: real human genotypes, although emerging in large volumes from genome wide association studies, are sensitive private data, which limits their public availability. Therefore, the integration of additional, insensitive data when striving for rapid sharing of biomedical knowledge of public interest appears imperative. AVAILABILITY AND IMPLEMENTATION: All non proprietary data and the code to replicate the experiments is available on Github.

Humans

Non-invasive strategy for gastric cancer detection: Integration of cell-free DNA fragmentomics and protein biomarkers.

Gastric cancer (GC) ranks as the fifth most common cancer worldwide, however, accurate and non-invasive diagnostic modalities for GC remain limited. Cell-free DNA (cfDNA) fragmentomics has emerged as a promising tool for cancer cell detection. Here we develop a gastric cancer detection model, named GaFraD model. The GaFraD model uses four cfDNA fragmentomics features, including fragment size ratio (FSR), copy number variation (CNV), 9-bp end motif (Motif), and fragment size at transcription start sites (TF). This model achieves an area under the receiver-operating characteristic curve (AUC) of 0.970 (95% CI: 0.944 - 0.990), a sensitivity of 95.0% and a specificity of 80.9%. By combining the GaFraD model and conventional protein biomarkers CA19-9 and PG-I/PG-II, the CONFIRM model was generated. The CONFIRM model attained an AUC of 0.986 (95% CI: 0.966 - 1.000), a sensitivity of 95.0% and a specificity of 95.6% in detecting GC. Moreover, the CONFIRM model achieved remarkable performance (AUC = 0.983, sensitivity 95.6%, specificity 94.2%) in distinguishing patients with early-stage GC from controls. Our work showed the high discriminatory power in distinguishing GC patients from controls, indicating the clinical potential of using cfDNA fragmentomics combined with protein biomarkers for non-invasive GC detection. The results of the study provide a new avenue for early, accurate, and non-invasive clinical diagnosis of GC.

Cell-free DNA

Artificial Intelligence for Natural Products Discovery and Development.

Natural products (NPs) remain a cornerstone of modern drug discovery, offering stereochemical complexity and diverse bioactivities that precisely modulate therapeutic targets, refined through billions of years of evolution. However, their research has long been hindered by inefficient, empirical workflows, high resource consumption, structural complexity, and the "multicomponent, multi-target" nature of their mechanisms. The exponential growth of genomic, metabolomic, and spectral data has overwhelmed conventional analytical methods, exposing critical bottlenecks in handling high-dimensional, heterogeneous datasets that exceed human interpretive capacity. Artificial intelligence (AI) is emerging as a transformative paradigm to address these challenges, integrating multi-omics and chemical data to shift NP research from fragmented empiricism toward mechanism-driven, precision-oriented development. By leveraging deep learning architectures- including graph neural networks, Transformers, and diffusion-based generative models-AI enables systematic decoding of NP biosynthesis, automated structure elucidation, rational target identification, knowledge extraction from vast unstructured scientific literature, and de novo molecular design. This review comprehensively surveys recent advances in AI applications across the full NP discovery and development pipeline, encompassing genome mining, structure-based and ligand-based virtual screening, multimodal structural characterization, lead optimization, and biosynthetic pathway engineering. We further examine the emerging roles of protein-centric, molecule- centric, and multimodal foundation models, as well as large language models, in bridging genotype-to-chemotype gaps and unlocking unstructured scientific knowledge. Finally, we discuss critical challenges including data scarcity, representational limitations for complex stereochemistry, physical plausibility in generative models, and the urgent need for experimental validation, while outlining future directions toward autonomous experimentation, closed-loop optimization, and human-AI collaborative discovery.

Artificial intelligence

An extended transition probability model of the variability of cell generation times.

The transition probability model of variability of cell generation times is extended so that the rate constant for the transition from the A-state to the B-phase of the cell cycle depends on on time which a particular all has already spent in the A-state. A specific time dependence of this rate constant is introduced. It is determined by the value of one constant which is then an additional parameter of the model. The corresponding cell population kinetics are calculated and compared to existing experimental evidence. The model accounts satisfactorily for the generation time distribution function and for the shortening of the G1 phase of binucleate cells. The time dependence of the transition probability is related to the cell kinetics of an hypothetical cell constituent. A possible relationship is proposed between the chemical parameters with the cell and the parameters of the cell population kinetics.

Animals

A model of quick phase generation in the vestibuloocular reflex.

The vestibuloocular relfex of the cat was studied during step and sinusoidal head velocity stimuli. A model is presented which simulates the observed slow phase and quick phase behavior. The model is constructed to be compatible with neurophysiological observations of the behavior of neurons in the pons. Emphasis is placed on the amplitude and timing of quick phases which are active orienting movements that drive the eyes into the direction of turning. It is proposed that quick phases, like saccades, are generated by a local feedback loop in the pons which rapidly drives the eyes to a point in the orbit specified by a vestibular signal. It is suggested that two internal signals specify the eye positions at which quick phases start and end. The statistics of the fluctuations of these signals was measured and correlation between them was discovered and incorporated in the model.

Animals

Influence of diastolic fibre orientation on the left ventricular power generation.

A mathematical model is described which in a simplified way, without directly taking into account the elastic properties of the heart wall, describes the EDV which corresponds to the experimental data. The model further describes the power generation of the left ventricle at high EDV. The volume density of power is expressed with a product of three factors (1) average density of the CE, (2) a factor which contains the inotropic properties of a single CE and (3) a form factor, which involves structural changes in the heart wall at various EDV.

Cardiac Volume

Biomarker-Based Nomogram to Predict Neoadjuvant Chemotherapy Response in Muscle-Invasive Bladder Cancer.

Background/Objectives: The aim of this study was to identify response prediction and prognostic biomarkers in muscle-invasive bladder cancer (MIBC) patients undergoing neoadjuvant chemotherapy (NAC). Methods: A retrospective multicentre study including 191 patients with MIBC who received NAC previous to radical cystectomy (RC) between 1996 and 2013. Gene expression patterns were analysed in 34 samples from transurethral resection of the bladder (TURB) using Illumina microarrays. The expression levels of 45 selected differentially expressed genes between responders and non-responders to NAC were validated by quantitative PCR in an independent cohort of 157 patients. Regression analysis was used to identify predictors of downstaging and relapse. A nomogram for predicting downstaging and relapse-including clinicopathological and gene expression variables-was developed. Results: The expression levels of 1352 transcripts differed between responders and non-responders to NAC. A nomogram based on the most predictive clinical variables (age, Tis (in situ), gender, history of NMIBC, and lymphadenopathy) and genes selected following the Akaike information criterion (AIC) (CBTB16, CHMP6, DDX54, CASP8, LOR, and PLEC) was then created. In addition, a three-gene expression prognostic model to predict tumour relapse was generated. This model was able to discriminate between two groups of patients with a significantly different probability of tumour relapse (HR: 2.11; CI: 1.16-3.83, p = 0.01). Conclusions: Our nomogram based on gene expression and clinical data is a useful tool to predict downstaging and tumour relapse after NAC in MIBC patients. Further validation is warranted.

bladder cancer

A second order model of the optic generator potential and its relation to Stevens' power function.

The component PIII of the electroretinogram representing the optic generator potential was recorded after stimulation with short stimuli with different light intensity. It is shown that the impulse response function of a linear second order model with intensity-dependent coefficients can be well fit to the recordings. Two of its parameters, after logarithmic transformations, are linearly dependent on the luminance while the third parameter varies only within a small interval. It is therefore possible to describe the relation between PIII and luminance in a linearized second order model. Furthermore, both the type of the function relating the gain of the model to the luminance and its exponent are nearly identical with the psychophysic function relating luminance to subjective brightness. Further physiological implications are also considered.

Animals

[Mechanism of early receptor potential generation and an electrical model of retinal rods in rats].

A passive electric model of the retinal rod can reproduce the changes of the ELP-waveform at temperatures within the range 10 degrees--45 degrees C. R2-component of the ERP is generated by the process with the time constant ca. 500 microseconds (37 degrees C) and activation energy 31 kcal/mol characteristic of metarhodopsin I--metarhodopsin II transition. R1 originates not later than at prelumirhodopsin--lumirhodopsin conversion. Charge displacements are 0.006 (R1) and 0.04 (R2) electronic charges per rhodopsin bleached. The model is used for determining membrane capacitance and resistance of the rat retinal rod.

Animals