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At least 19 recordsLinked to original sources
PubMedDate not supplied

Total cerebral ischemia: a new model system for the study of post-cardiac arrest brain damage.

The pathophysiology of post-cardiac arrest brain damage is not well understood. Many of the model systems presently used to study global ischemia have serious limitations. A new model system for total cerebral ischemia (TCI), using aortic and inferior vena caval occlusion balloons, is described. This model system produces verifiable TCI and avoids surgical invasion of the thorax or the use of vasoactive drugs. It does not impede cerebral venous return and protects the cardiopulmonary system from damage. This model system can be used to study the efficacy of various therapeutic interventions following a standardized CNS global ischemic insult.

Animals↗
PubMed1978

Thermometric enzyme linked immunosorbent assay in continuous flow system: optimization and evaluation using human serum albumin as a model system.

Thermometric enzyme-linked immunosorbent assay (TELISA) is described. After the procedure of optimization, human serum albumin was assayed using anti-human serum albumin bound to Sepharose CL 4-B in the enzyme thermistor unit and catalase as label on the free antigen. The model system was used for assays down to 10(-13)M and the preparation of immobilized antibodies was used repeatedly up to 100 times. Comparative studies of the TELISA technique with bromocresol green, immunoturbidimetric and rocket immunoelectrophoretic methods were carried out and showed that TELISA could be used as an alternative method.

Catalase↗
PubMed1975

An interpretation of the three line EPR spectrum of nitric oxide hemeproteins and related model systems: the effect of the heme environment.

The EPR spectra of the nitric oxide (NO) derivatives of structurally perturbed Fe (II) hemeproteins show various patterns, all of which are characterized by the conspicuous three-line hyperfine splitting due to 14NO, in contrast to that of the native proteins. For the purpose of obtaining structural information from these three line spectra, the model systems were studied, which consist of NO, heme (or TPP-Fe(II), where TTP means alpha, beta, gamma, delta-tetraphenylporphine) and the nitrogenous base, pyridine or quinoline, which, respectively, give the native type or the three line (perturbed type) EPR spectrum. The ring proton paramagnetic shift of quinoline in this system shows that it is not coordinated to NO-TPP-Fe(II) as a normal axial ligand, in contrast to pyridine which gives the shift pattern of the ordinary axial ligation. This observation suggests that in the NO-hemeproteins some perturbations of the protein structure cause the rupture or distortion of the bond between the imidazole nitrogen on the fifth coordination site and the heme iron, resulting in the three line spectrum. The EPR study of the model systems, the pentacoordinated complex, NO-heme and NO-TPP-Fe(II), in various media revealed that the pentacoordinated species indeed exhibits, depending upon its environment, a variety of spectra, which closely reproduce the three line patterns observed in the perturbed proteins and some related model systems. Such spectral variation can be attributed to the difference in the degree of quenching the internal motion and/or the structural heterogeneity caused by molecular environment.

Electron Spin Resonance Spectroscopy↗
PubMed1979

Plasmodium fragile and Macaca mulatta monkeys as a model system for the study of malaria vaccines.

Pladmodium fragile and the Macaca mulatta monkey are presented as a model system for the study of malarial vaccines. Four animals were immunized with culture-grown P. fragile merozoites and subsequently challenged with culture-produced parasites. One animal failed to develop a detectable parasitemia following primary challenge. Two other immunized animals had primary infections which were short-term. the parasitemias in these three monkeys following secondary challenge were short-term and the immunity was apparently sterilizing. The fourth immunized monkeys had recrudescences of the primary and secondary infection but differed markedly from the four control animals. Indirect fluorescent antibody titers increased as a result of the immunization and were indicative of the level of immunity. Because of the many similarities to the human-P. falciparum model system, the P. fragile-M. mulatta system appears to be particularly well suited for a number of malaria vaccine studies.

Animals↗
PubMed1978

Stereological model system for free cells and base-line data for human peripheral blood-derived small T-lymphocytes.

T-lymphocytes derived from human peripheral blood and passed through a nylon-wool column, were employed to develop and test a new stereological model system for free spherical cells, allowing a quantitative characterization of the cell and its components at the ultrastructural level. Electron micrographs were recorded in a hierarchical manner at three different levels of magnification and subjected to point counting procedures. The resulting parameters were expressed in relation to various reference compartments, both absolute and relative. Results indicated that the average volume of a small, non-activated T-lymphocyte was 103.8 micron3, the nuclear volume 47.5 micron3 and the cytoplasmic volume 55.9 micron3. On the average, the cytoplasm contained 30 mitochondria, 0.7 micron3 RER-cisternae, 0.2 micron3 cisternae and vesicles of the Golgi apparatus and about 231,000 free ribosomes (most of them single). The ratio of eu- to heterochromatin volume was 0.5. The design and application of the stereological model system are discussed with regard to dynamic studies of a variety of free cells, such as macrophages, neutrophilic granulocytes and various lymphocytes.

Adult↗
PubMed2026

Nurse-led attribution remodeling training based on the Neuman systems model to enhance resilience, adaptive coping, and attributional style in women newly diagnosed with breast cancer: A randomized controlled trial.

BACKGROUND: Psychological interventions for patients with breast cancer often overlook the critical role of maladaptive attributional style in shaping their adjustment. Therefore, the need for theory-driven, scalable interventions that target cognitive restructuring, particularly during the vulnerable post-diagnosis period, is clear. OBJECTIVE: To evaluate the effectiveness of a nurse-led attribution remodeling training intervention grounded in the Neuman systems model for improving resilience, adaptive coping, and attributional style among women newly diagnosed with breast cancer. DESIGN: A randomized controlled trial. SETTING: A tertiary general hospital. PARTICIPANTS: A total of 130 eligible women newly diagnosed with breast cancer were recruited between March and November 2024. METHODS: A two-arm parallel-group randomized controlled trial was conducted. Participants were randomly assigned to receive either attribution remodeling training plus routine nursing (n = 65) or routine nursing only (n = 65). The nurse-led attribution remodeling training intervention, delivered via a blended model of in-person sessions and continued support through the WeChat mobile platform, was designed to systematically reshape maladaptive attributions into more adaptive ones. Resilience (primary indicator), coping strategy (i.e., confrontation, avoidance, resignation), and attributional style (secondary indicators) were assessed at baseline and at 1, 3, and 6 months post-baseline. A linear mixed model was used to analyze the effects of group, time, and group-by-time interactions. Effect sizes (Cohen's D) were calculated based on the means and standard deviations. RESULTS: At the 6-month follow-up, the intervention group had better outcomes than the control group in terms of resilience (mean difference: 1.49, 95% confidence interval: 0.37, 2.61), confrontation coping (3.35 [2.33, 4.37]), and adaptive attributional style (4.16 [3.87, 4.45]). Avoidance coping showed a small increase (0.82 [0.22, 1.42]), whereas resignation coping decreased (-1.66 [-2.49, -0.83]). Group effects and group-by-time interactions were statistically significant for all outcomes. Effect sizes at 6 months ranged from small for resilience (D = 0.28) and avoidance coping (D = 0.26) to moderate for confrontation coping (D = 0.60) and resignation coping reduction (D = -0.51), and large for attributional style (D = 0.94). CONCLUSIONS: Attribution remodeling training is a promising and effective theory-based intervention that can enhance psychological adaptation in women newly diagnosed with breast cancer. By strengthening key defense mechanisms, as conceptualized by the Neuman systems model, the program is effective, scalable, and nurse-deliverable for psycho-oncology care, bridging a critical gap in supportive cancer care and empowering nurses as primary psychological support providers. REGISTRATION: ChiCTR2000031827, registered prospectively on April 11, 2020, www.Chictr.or.cn.

Humans↗
PubMed1975

Murexide for determination of free and protein-bound calcium in model systems.

The determination with murexide of free and protein-bound calcium in model systems of known composition, ionic strength, and pH was investigated. The spectra of calcium murexide in the presence of varying amounts of calcium ions indicated that the absorption maximum fo calcium murexide complex occurs at 480 nm while that of murexide ion is at 520 nm. The absorbance at 509 nm is independent of calcium ion concentration and, therefore, could be used to measure the total dye. The spectra are pH dependent but constant in the range 6.5 to 7.0. The apparent dissociation constant of calcium murexide is dependent upon ionic environment, ionic strength, and free calcium ion concentration. The relationship between the apparent dissociation constant and free calcium concentration was established. Whole casein had no effect on the absorption spectra of calcium murexide and no affinity for calcium murexide complex or murexide ion. Beta-casein, at the concentrations employed, did not influence the dissociation fo calcium murexide. At pH 7.0, ionic strength .1, and 2 C, Beta-casein bound calcium as if there were 8.65 binding sites per molecule, each of pK 2.23, corresponding to an intrinsic association constant of 168.9 liters per mole.

Barbiturates↗
PubMed1978

Transformation by viruses: simian virus 40 as a model system.

Simian virus 40 (SV40), a DNA-containing tumor virus in the papovavirus group, represents an ideal model system for the analysis of the mechanism of viral-induced tumorigenesis because of the small size of its genome and its broad range of oncogenic potential. Viral genes persist and are expressed in SV40-transformed cells. Temperature-sensitive (ts) mutants of the virus have proved to be valuable tools for the identification and analysis of viral gene expression in transformed cells. Through the use of such mutants, it has been determined that a specific gene product (A-protein) is required to initiate cellular transformation. The role of virus genes in the maintenance of the transformed state was determined by transformation of the cells of mouse, hamster, and human origin by ts virus containing A-gene mutations. These cells were then examined under permissive and nonpermissive conditions for the presence of a variety of intracellular and surface alterations commonly associated with neoplastic transformation. From the results of such experiments, it has been concluded that an SV40-specific function is also necessary for the maintenance of at least some of the phenotypic properties of the transformed state. Indirect evidence, derived from a comparison of the biological and biochemical properties of the SV40-induced tumor (T) antigen and the gene A-protein, supports the idea that T-antigen is a product of the A-gene. One model devised to explain the mechanism by which the gene A-protein might function as an effector of transformation is presented.

Animals↗
PubMed1978

Model systems for cardiotoxic effects of anthracyclines.

The use of anthracycline antibiotics in cancer chemotherapy is limited by their cardiotoxic qualities. For the evaluation of new derivatives animal model systems are required. Cardiomyopathy can be induced in rabbits and monkeys, but these models are too expensive for screening purposes. In rats, anthracycline antibiotics cause morphologic lesions of the heart muscle, but these are more difficult to demonstrate than in larger animals. However, significant changes of the heart function (electrocardiogram (ECG), cardiac output), the function of heart mitochondria (inhibition of electron transfer, uncoupling of oxidative phosphorylation and inhibition of Ca translocation) occur in a dose-related manner. Intraventricular conduction defect demonstrated in the ECG is one of the earliest and most consistent expressions of the cardiotoxic properties of anthracyclines. It was therefore used as primary screening parameter. The results of the screening of over 50 new anthracyclines has shown that the cardiotoxic properties vary considerably and that they are not closely related to the chemotherapeutic and the hematotoxic properties. Interesting structure-activity relationships were observed in a series of rubidazone derivatives substituted at the benzhydrazone part of the molecule.

Animals↗
PubMed1975

Study of the mechanism of thyroid hormone secretion in an in vitro model system: indirect evidence for fusion of lysosomes with thyroglobulin liposomes.

The interaction between [131I]-thyroglobulin liposomes and thyroidal lysosomes was used as an in vitro model system for analyzing the relation of colloid droplets to lysosomes in follicular cells. The rates of hydrolysis of [131I]-thyroglobulin in a liposome-lysosome system (Lipo-Lyso system) and a thyroglobulin-lysosome system (TG-Lyso system) were compared. Hydrolysis of thyroglobulin in the Lipo-Lyso system increased hyperbolically and was greater than that in the TG-Lyso system for about 10 h. Liposomal thyroglobulin was not degraded by the 20,000 X g supernatant obtained on disruption of the lysosomal fraction. On varying the pH of the incubation medium, the highest activity was observed under acidic conditions in both systems. Under neutral or weakly alkaline conditions, the Lipo-Lyso system still showed 50% of the maximal hydrolytic activity, while the TG-Lyso system showed no activity. ATP and anaerobic conditions had no effect on either system. Cysteine (5 X 10-2M) and p-chloromercuribenzene sulfonic acid (PCMBS, 10-3 M) had not influence on hydrolysis in the Lipo-Lyso system, but in the TG-Lyso system cysteine greatly increased, and PCMBS significantly reduced the rate of hydrolysis. Dibutyryl cyclic AMP had no effect. Chlorpromazine (Cpz) decreased liposomal thyroglobulin hydrolysis in a concentration-dependent manner. In the TG-Lyso system, concentrations of 10-4M Cpz had no effect. These results strongly suggest that liposomes rapidly fused with lysosomes, providing optimal conditions for hydrolysis of thyroglobulin.

Adenosine Triphosphate↗
PubMed1979

A new dynamic model system for the study of capture reactions for diffusable compounds in cytochemistry. II. Effect of the composition of the incubation medium on the trapping of phosphate ions in acid phosphatase cytochemistry.

A model system developed for the study of the dynamics of capture reactions for diffusable compounds in cytochemistry served as a basis for the experiments reported in the present paper. The model was used to study the effect of the composition of the cytochemical medium on the trapping of phosphate ions by lead (II) ions in acid phosphatase cytochemistry. In this system a phosphate-containing solution and a lead-containing solution (cytochemical medium) are pumped along opposite sides of a polyacrylamide film. The phosphate concentration at which measurable precipitation starts in the film (critical phosphate concentration) was taken as a measure of the trapping efficiency of the cytochemical medium. The addition of beta-glycerophosphate and cytidine-5'-monophosphate to a buffered lead-containing solution resulted in a higher critical phosphate. The addition of chloride ions and acetone, as well as decreasing the molarity of the acetate buffer of the cytochemical medium, were found to lower the critical phosphate concentration, whereas the addition of fluoride ions, glucose, and sucrose had no effect. From the effect of variations in the composition of the cytochemical medium on the trapping efficiency and the turnover number of acid phosphatase in the medium, it was possible to predict which cytochemical medium would be the most suitable for the demonstration of acid phosphatase activity in guinea-pig peritoneal exudate cells. The results were in accordance with the localization of acid phosphatase activity: the higher the trapping efficiency and the turnover number, the higher the amount of precipitate and the number of positive enzymatic sites. In this way an improved cytochemical medium for acid phosphatase was developed.

Acetone↗
PubMed1979

Hybridoma antibody immunoassays for the detection of parasitic infection: development of a model system using a larval cestode infection in mice.

A prototype immunodiagnostic assay has been developed using chronic infection with the larval cestode, Mesocestoides corti, as a model system in mice. The assay is highly sensitive, it appears to be absolutely specific for M. corti infection, and is based on the inhibition of binding (by sera from infected mice) of a radiolabelled anti-M. corti hybridoma antibody to a crude M. corti antigen extract. The hybridoma antibody binds to living M. corti larvae and is an IgG1 protein. In large scale experiments no false positives were detected and the only M. corti-infected mice not detected by the assay were hypothymic nude (nu/nu) mice. Only limited success has been achieved in attempts to convert the assay to one not requiring parasite antigen and based on the inhibition of binding of radiolabelled anti-parasite hybridoma antibody and a large pool of anti-idiotype antiserum. Monoclonal antibodies derived from anti-parasite antibody-secreting hybridoma cell lines will be of particular use in the development of new, highly specific, immunodiagnostic reagents for the detection of parasite infection, exposure and disease.

Animals↗
PubMed1977

The starfish (Patiria and Pisaster) oocyte: a model system for the study of hormone-surface interaction in oogenesis.

Studies were made to determine if the starfish (Patiria and Pisaster) oocyte could serve as a model system for investigations of hormone-surface interactions in eucaryotic cells. Treatment of starfisch oocytes with maturation inducing hormone, 1-methyladenine, was observed by scanning electron microscopy to induce surface alteration. The action of the hormone was dependent on the presence of the cation Ca++. Although caffeine, theophylline, and theobromine supposedly inhibit maturation of oocytes, studies using the starfish oocyte showed that theobromine does not inhibit maturation and the inhibition caused by caffeine and theophylline is reversible. Other studies using the starfish oocyte and tritiated 1-methyladenine showed that the hormone does not dissociate from the oocyte once bound, and that the oocyte surface may have multiple receptors for 1-methyladenine. From these studies it was concluded that the starfish oocyte is a useful model for studies of hormone-surface interactions in eucaryotic cells.

Adenine↗
PubMed1979

The effect of long-term exposure to cigarette smoke on the height and specificity of the secondary immune response to influenza virus in a murine model system.

The effect of long-term exposure to cigarette smoke on the height and specificity of the secondary humoral immune response to influenza was investigated in a murine model system. It was shown that if mice were pre-immunized with a sub-lethal infection of influenza virus and then exposed to cigarette smoke daily for 36 weeks, they were able to mount a secondary immune response of normal height on subsequent challenge with the homologous virus strain. The response however, was less specific than that elicited in control mice, with high titres of cross-reacting antibody by haemagglutination-inhibition to the following strain in the same antigenic series. Recall of antibody to the previous strain in the antigenic series was not observed in either control or smoke-exposed animals. These results serve to correct an earlier discrepancy between the murine system and human studies in which the response to influenza infection in mice was depressed by prolonged exposure to cigarette smoke, whereas in man the response of smokers did not differ significantly from that of non-smokers. This apparent discrepancy had been caused by a lack of previous experience of influenza in the mice, which had therefore mounted a primary response, compared with the secondary response observed in the human studies.

Animals↗
PubMed1976

Isolated cortical granules: a model system for studying membrane fusion and calcium-mediated exocytosis.

Cortical granules are secretory vesicles bound to the inner surface of the plasma membrane of sea urchin eggs. Intact granules can be isolated by shearing away the cytoplasm of eggs which have been bonded to a protamine-coated surface. When Ca2+ is added to preparations of isolated granules the granules fuse with each other and release their contents. It is believed that isolated cortical granules may be an excellent model system for the biochemical study of exocytosis.

Animals↗
PubMedDate not supplied

[Experimental teratocarcinoma in mice: a model system for the study of the relationship between cellular surface antigens and embryonic differentiation].

Several cell lines (either of embryonal carcinoma or of differentiated cells derived from teratomas) have been established in vitro from transplantable testicular teratomas. Primitive cell lines, propagated in vitro as embryonal carcinoma have retained the ability of the original tumor to differentiate in vivo or in vitro into must embryonic cell types. Features of this model system for study of early embryogenesis are described. Emphasis is placed on the description of the cell surface antigens of several cell lines. Syngeneic antisera raised against two primitive lines (F9 and PCC4) and against a differentiated one (Endo) have allowed the detection of three groups of cell surface antigens, present on teratoma cells, tumor cells and embryonic cells. The F9 antigen appears to be specific to be specific of the very early steps of egg development (morula and blastocyst). After egg implantation, it keeps expressed on the cells of the male germ line. The PCC4 antigen has a similar cell type distribution but appears to be more specific of multipotential cells. The Endo antigen is essentially specific of endodermal derivatives. The F9 antigen is probably specified by the wild type allele (+ tl2) of the tl2 gene at the T-Locus of the mouse, a gene which plays some critical role in early development. The molecular structure of this antigen, as determined from immunoprecipitates is very similar to that of H-2 antigens. In addition, a cross-reacting material is found in Man, with a tissue distribution identical to that found in the mouse.

Alleles↗
PubMed1978

Asymmetric budding of viruses in epithelial monlayers: a model system for study of epithelial polarity.

Infection of two different lines of polarized epithelial cells grown as monolayers with several types of enveloped viruses results, for each virus type, in a characteristic asymmetric budding of virions. Influenza virus (WSN strain), simian virus 5, and Sendai virus bud exclusively from the free (apical) surface of the cells, while vesicular stomatitis virus acquires its envelope only from the basolateral plasma membrane. Because different viruses select specific domains of plasma membrane in the same cell type, virus-infected epithelial monolayers can provide an excellent model system for studies of the mechanisms that generate regional differences in the distribution of plasma membrane components of epithelial cells.

Cell Line↗
PubMed1979

Lipophilicity and biological acitivity. Drug transport and drug distribution in model systems and in biological systems.

Different equilibrium and non-equilibrium models are used to simulate drug transport and drug distribution. The percentage of absorbed drug, the rate constants of drug absorption and the drug concentrations in the different compartments of the models can be described quantitatively by the bilinear model, e.g., log ci = a log P-b log (betaP + 1) + c. A nearly perfect fit is obtained for the simulated data from this model. Drug absorption and distribution in biological systems can be explained and described by the model-derived equations. Examples from the literature include buccal absorption, gastric and intestinal in situ and in vitro absorption, colonic absorption, renal clearance, and absorption through the skin and the blood-brain barrier; in all those cases the bilinear model gives an excellent fit of the experimental data. Combination of the pH-partition theory with the bilinear model leads to a simple quantitative model for the precise description of the relationships between lipophilicity, degree of ionization, and absorption, distribution and biological activity of drugs.

Absorption↗