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Biomedical subjects

L Pavlova

Publications and source records attributed to L Pavlova.

15 recordsLinked to original sources
PubMed2002

Hypercross-linked polystyrene and its potentials for liquid chromatography: a mini-review.

Hypercross-linked polymeric adsorbing materials are obtained under conditions that (i) their polymeric network is formed in the presence of large amounts of a thermodynamically good solvent (porogen) and (ii) the network is rigid. Hypercross-linked polystyrene is a transparent microporous low-density material with an apparent inner surface area of over 1,000 m2/g and an unprecedented adsorption capacity. To enhance the mass transfer, the adsorbent beads may be provided with large transport pores, in addition to the inherent micropores; these beads are opaque. Hypercross-linked polystyrene sorbents are widely used for large scale adsorption of organic compounds from aqueous and gaseous media and for solid-phase extraction of trace components. Novel perspective application areas of the materials are high-performance liquid chromatography column packings and blood purification. Present mini-review summarises basic principles of obtaining hypercross-linked materials, their structural peculiarities and distinguishing properties, as well as major application areas. Important new unpublished data are also included.

Adsorption↗
PubMed2001

Modeling cancer detection: tumor size as a source of information on unobservable stages of carcinogenesis.

This paper is concerned with modern approaches to mechanistic modeling of the process of cancer detection. Measurements of tumor size at diagnosis represent a valuable source of information to enrich statistical inference on the processes underlying tumor latency. One possible way of utilizing this information is to model cancer detection as a quantal response variable. In doing so, one relates the chance of detecting a tumor to its current size. We present various theoretical results emerging from this approach and illustrate their usefulness with numerical examples and analyses of epidemiological data. An alternative approach based on a threshold type mechanism of tumor detection is briefly described.

Computer Simulation↗
PubMed2000

Polymeric adsorbent for removing toxic proteins from blood of patients with kidney failure.

A hypercrosslinked styrenic polymer with an enhanced proportion of mesopores in the range 2-20 nm has been developed. The principle of the synthesis consists of the suspension polymerization of divinylbenzene (or copolymerization of styrene with divinylbenzene) in the presence of a porogen that is a theta-solvent for polystyrene. On the scale of thermodynamic affinity, theta-solvents occupy a border position between good solvents and precipitating media for the growing polymer chains. In this case, microphase separation takes place during the final stages of the polymerization process. The polymer was shown to adsorb 93-98% of beta2-microglobulin from the blood or plasma of patients with chronic kidney failure. At the same time, large essential proteins, like albumin, are not removed to a significant extent, obviously, due to the size-exclusion effect and the difference in the hydrophobicity of the proteins. By replacing surface exposed pendant vinyl groups of the polymer with hydrophilic functional groups, the material was made hemocompatible, according to the standard battery of biocompatibility tests required by ISO 10993 guidelines. No adverse effects such as fever or hypotension were noted in dogs in direct hemoperfusion experiments with the polymer.

Adsorption↗
PubMed2000

Antibodies against oncoproteins E6 and E7 of human papillomavirus types 16 and 18 in cervical-carcinoma patients from Russia.

Certain human papillomaviruses (HPV), mainly types 16 and 18, have been widely recognized as an essential etiologic factor for the development of carcinoma of the uterine cervix. The early HPV proteins E6 and E7 are consistently expressed in the tumor cells, and cervical-carcinoma patients can develop antibodies against these oncoproteins. For cervical-carcinoma patients from Eastern Europe and Russia, detailed information on HPV DNA prevalence and HPV-specific immune responses is limited. The presence of HPV DNA in 128 Russian cervical-carcinoma tissues was determined: HPV16 DNA was found in 78% of the cases, HPV18 DNA in 14%, and no HPV-DNA in 10%. Using 4 recently developed sensitive and highly specific second-generation enzyme-linked immunosorbent assays, we also analyzed the prevalence of antibodies against HPV16 and -18 E6 and E7 proteins in sera from 95 cervical-carcinoma patients, from 61 female patients with non-HPV-associated tumors and from 83 female healthy controls. The strong association of E6 and/or E7 antibodies with cervical carcinoma was confirmed, with 36% seropositives in this group against only 2% in the control groups. The detected antibodies are highly HPV-type-specific since all 26 HPV16-E6- or -E7-antibody-positive patients had HPV16 DNA in their tumor and 6 out of the 8 HPV18-antibody-positive patients had HPV18 DNA. Antibody responses to HPV16 E6 and E7 appear to be dependent on clinical stage of the disease, with 21% seropositives found in FIGO stage I, 42% in stage II and 53% in stage III. Antibody response to HPV16 E6 is more frequent than to E7, especially in early stages.

Adult↗
PubMed1997

Do cells repair precancerous lesions induced by radiation?

The most widely accepted point of view is that cells are endowed with the capacity to repair the primary lesions responsible for cancer induction. In radiobiology, this popular belief evolved from experiments of the same type as those that suggested the existence of sublethal radiation damage repair. The central problem with such data is that the cell-killing component of radiation damage may mask the effects associated with repair of precancerous lesions. The challenge is to separate the two processes that contribute to the observed tumor incidence after irradiation. using a recently developed stochastic model of radiation carcinogenesis allowing for cell death, we provide evidence that precancerous lesions are not subject to repair under certain experimental conditions.

Animals↗
PubMed1977

[Evoked hypercalcemia test and the pentagastrin test in assessing the functional state of the parafollicular apparatus of the thyroid in hyper- and hypothyroidism].

Calcium gluconate test (Ca ++ 10 mg/kg) was carried, for three hours, in 28 patients with thyrotoxicosis, 6--with hypothyroidism and 8 healthy subjects. Pentagastrin (Peptavlon)--2 microgram/kg/h was applied in 25 patients with thyrotoxicosis, 7 with hypothyroidism and 11 healthy subjects. A slowed down calcemia normalization was observed after calcium gluconate infusion in case of thyrotoxicosis and especially in hypothyroidism. Calcemia in the thyrotoxicosis, with pentagastrin test, is more decreased in thyrotoxicosis as compared with the healthy subjects, whereas in hypothyroidism the decrease is less or absent. In hypothyroidism, a deteriorated function of the parafollicular apparatus is thought to be involved, or a lack of sensitivity of the target cells of that hormone. Final conclusions are difficult to be drawn in hyperthyroidism because several explanations of the two positive test are possible.

Calcium↗
PubMed1977

[Studies of calcium-phosphorus metabolism in thyrotoxicosis].

Fifty eight patients with thyrotoxicosis were examined as well as 9 patients with hypothyroidism and 40 healthy subjects. A tendence towards hypercalcemia and hyperphosphatemia, hypercalciuria, hyperhydroxiprolinuria, elevated alkaline phosphatase were found in hyperthyroidism. In hypothyroidism--hypocalcemia, hypocalciuria, hypohydroxiprolinuria. The changes are associated with the direct effect of thyroid hormones upon bone system (intensified bone metabolism with predominance of destruction). Calciuria and HOP-uria in thyrotoxicosis depend on the severity of the disease. The elevated calcium excretion in thyrotoxicosis speaks for the presence of ostemalacic component. TRP, PEI, mean diametrically opposite in hyper- and hypothyroidism, support the hypothesis of the secondary hypoparathyroidism in thyrotoxicosis and hyperparathyroidism--in the hypothyroidism.

Adult↗
PubMedDate not supplied

High resolution mapping of chromosome 6 deletions in cervical cancer.

Chromosome 6 is frequently affected in different tumors. However, little information exists on chromosome 6 deletions in cervical cancer. We have studied loss of heterozygosity (LOH) and microsatellite instability (MIN) in 62 invasive squamous cell carcinomas of the cervix (CC) using 19 polymorphic microsatellite markers spanning both arms of chromosome 6 and one marker located at 5p15. We found that LOH at chromosome 6 is a common feature of cervical carcinomas: 90% (56/62) of CC had LOH at least at one locus and about 58% (36/62) had LOH on both arms of chromosome 6. The highest LOH incidence was shown in HLA region (6p21.3-6p21.1) with markers D6S273 and D6S276 in 52.7% and 45.2% of informative cases respectively. Frequent LOH on 6q was found at loci D6S311 (6q24-25. 1), D6S305 (6q26) and D6S281 (6q27-6qter) in 37.8%, 33.3% and 39.0% of informative cases respectively. There was no significant correlation observed between clinical parameters of cervical cancer (age, histologic grade, clinical stages and progression) and LOH frequency. Microsatellite instability was found in 3 out of 62 cases (4.8%) at three and more loci out of 20 tested. The study shows that several regions on 6p and 6q may harbour potential tumor-suppressor genes important for cervical cancer progression.

Carcinoma, Squamous Cell↗