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Biomedical subjects

J Jancar

Publications and source records attributed to J Jancar.

At least 19 recordsLinked to original sources
PubMed2004

Large-scale methacrylate monolithic columns: design and properties.

Monoliths represent a special class of chromatographic supports. In contrast to other stationary phases, they consist of a single piece of highly porous material through which a sample is mainly transported by convection. As a consequence, monoliths enable fast separations and exhibit flow-unaffected properties, which make them attractive for purification of macromolecules like proteins or DNA. In this work, methacrylate-based monolithic columns with the bed volume up to 8000 ml are characterized. They perform high-resolution separations of several hundreds of grams of proteins per hour by utilizing liter per minute flow rates. They are incompressible under these operating conditions and resistant to strong alkaline conditions.

Animals↗
PubMed2003

Transfer of gradient chromatographic methods for protein separation to Convective Interaction Media monolithic columns.

Convective Interaction Media (CIM) columns are monolithic columns optimized for the separation of macromolecules. Some of them operate in the axial mode while others operate in the radial mode depending on the column size. In this work we tested the approach suggested by Yamamoto [Biotechnol. Bioeng., 48 (1995) 444] for transfer of gradient methods between columns of different size. A simplified equation for transfer was derived together with a criterion for its application. Separation was evaluated for a standard protein mixture and peroxidase enzymes present in fermentation broth. Salt and pH gradients were applied. Similar resolutions were obtained for each sample on all columns which demonstrates that the proposed approach can be successfully used for method scale-up on this type of column.

Chromatography, Ion Exchange↗
PubMed2000

On the heterogeneous structure of thermally cured bis-GMA/TEGDMA resins.

In this paper we report on the morphogenesis of dental resins formed by a thermally initiated radical cross-linking copolymerization of model dental resins. These systems were considered reasonable model simplifications of the actual resins used in commercial filling composites, veneers, etc. Effect of bis-GMA content varying from 0 to 100% on the degree of conversion and morphology of the cured resin was investigated. Dynamic scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical thermal analysis (DMTA) and high temperature solvent extraction experiments were performed in order to determine the nature and location of unreacted unsaturations in relation to bis-GMA concentration. The interval of cure temperatures, ranging from 23 to 250 degrees C, may seem irrelevant from the clinical point of view but is instrumental for an understanding of the processes involved. Single glass transition temperature (Tg) found in DMTA experiments showed that the copolymerization process between bis-GMA and TEGDMA is random in nature, however, the overall cure reaction is inhomogeneous and this inhomogeneity is increasing with increasing bis-GMA molar fraction. Heterogeneous character of the cure was reflected into the network morphogenesis characterized by microgellation preceded by cyclization and, following connection of microgels. These cure kinetics resulted in a heterogeneous morphology of the cured resin. Moreover, it was shown that the cure kinetics controls to a great extent the degree of conversion of the reactive vinylidene C=C bonds in a fully cured resin. A decrease in bis-GMA concentration in the resin mixture led to a higher degree of conversion, however, even a neat TEGDMA homopolymer did not exhibit C=C conversion greater than 65-70% under the cure conditions used. Leaching out tests, consisting of an extraction of unreacted monomer from a finely ground cured resin in boiling cyclohexanone at 160 degrees C over a period of 5 d, revealed total weight loss of the order of 3.2-5.6 wt % regardless of the total conversion. No uncured monomer was detected in the extract solution using FTIR spectroscopy, however, the method used is not sensitive to the presence of oligomers. It was concluded that the remaining unreacted double bonds are the inevitable result of the diffusion controlled heterogeneous cure reaction. The low rate of diffusion in the resin beyond its gel point is controlled by high monomer rigidity, low mobility and radius of gyration of the monomers. The unreacted C=C bonds exist in the form of pendant, side groups chemically attached to the network. In addition, a hypothesis has been proposed that for concentrations of rigid bis-GMA monomers above 50 wt %, preferably only one methacrylate group of its molecule has reacted on the time span of the experiment performed and has been incorporated in the cured network. Hence, a substantial part of unsaturation exists in the solid polymer in the form of pendant groups formed by mechanically ineffective bis-GMA monomers. The results are in good qualitative agreement with computer simulations based on the kinetic gelation model.

Journal Article↗
PubMed2000

Progress in the classification of hematological neoplasms. From REAL to WHO concept

Recent advances in immunology, molecular biology and cytogenetics as well as the development of new diagnostic techniques set out the necessity for the redefinition and reclassification of hematological malignancies. Therefore, WHO in 1995 assigned the Society of Hematopathology and European Association for Hematopathology to create a new classification of these neoplasms. The result of collaborative efforts of leading hematopathologists from both organizations is the World Health Organisation (WHO) classification of hematological neoplasms. WHO classification adopted basic concepts, defined criteria introduced by REAL classification of lymphoid neoplasms and extended them to myeloid, histiocytic and mastocytic neoplasms. WHO classification of hematological neoplasms is represented by a list of disease entities and its variants, opened for inclusion of new entities, updating of diagnostic criteria and changes of nomenclature. The clinical relevance of the proposed entities has been evaluated by the clinicians, members of Clinical Advisory Committee. The proposed classification is a challenge to the clinicians to create new treatment strategy, directed towards particular disease entities. The presentation of WHO classification in our review is limited to myeloid and lymphoid neoplasms.

Journal Article↗
PubMed1998

Increased life expectancy in people with untreated phenylketonuria.

The records of 17 people with intellectual disability and untreated phenylketonuria (12 females and five males), who were resident in the Stoke Park Group of Hospitals, Bristol, England, 25 years ago, were re-examined for life expectancy. Six subjects had died (five females and one male). The oldest deceased female was 69 years of age. The average age at death was 55.8 years. Eleven subjects were still alive (seven females and four males). The oldest living male was 79 years of age. The average age of the survivors was 55.7 years.

Adult↗
PubMed1998

Age-related fractures in people with intellectual disability and epilepsy.

The present paper describes age-related fractures in 68 people with intellectual disability and epilepsy (39 females and 29 males). A higher incidence of fractures in epileptic subjects (26%) was noted when they were compared with non-epileptic patients (15%). In the sample of 263 epileptics (121 females and 142 males), a higher number of females (32%) sustained fractures than their male counterparts (20%). The peak period of all fractures is between 40 and 49 years of age. The highest incidence of fractures in females occurred during the periods from 10 to 19 and 40 to 49 years, while the peak was between 30 and 39 years for males. The causes of fractures and preventative measures are discussed, and further avenues for research are indicated.

Adolescent↗
PubMed1996

Life expectancy of mentally retarded hemiplegics.

Sixty-four mentally retarded people with hemiplegia (35 females and 29 males), first recorded in 1963, were re-examined 30 years later for life expectancy. Detailed physical and mental states, lengths of hospital stays and other information were noted. Recent advances in diagnosis and prognosis of hemiplegics were included. The results of the study indicate that, with special provisions available, people with hemiplegia have the prospect of reaching pensionable age and beyond: the oldest female is 85 and the oldest male 76 years of age.

Adult↗
PubMed1994

Screening of matrices and fibers for reinforced thermoplastics intended for dental applications.

Plastics reinforced with continuous fibers (FRC) are being developed for dental applications, such as prosthodontic frameworks and orthodontic retainers. Flexure properties, stress relaxation and hydrolytic stability of FRC based on six thermoplastic matrices, three types of fibers, and three fiber volume fractions were evaluated. Samples with clinically relevant dimensions were tested. Polycarbonate was the preferred matrix material. Polycarbonate reinforced with 42 volume percent glass fibers exhibited the highest combination of flexure modulus (17.9 +/- 2.6 GPa), flexure strength (426 +/- 40 MPa), reinforcing efficiency (0.79), and resistance to stress relaxation. No statistically significant difference was observed between E and S2 glass reinforced composites under the experimental conditions used. Kevlar reinforced materials exhibited a low flexure modulus and strength. The apparent flexure moduli of all composites decreased with span length in the range of clinical interest. Generally, the prevalent mode of failure for all FRC investigated was brittle failure under flexure loading. Relatively large sample-to-sample variation in both composition and properties indicated that improved fabrication methods will be needed in future studies. The combination of good flexure properties, formability, and translucency suggests that novel appliance designs for dentistry are feasible with FRC, but further studies of its properties and particularly the effects of fiber/matrix interfacial quality are needed.

Dental Materials↗
PubMed1994

Mental and physical health and ageing in mental handicap: a review.

With some exceptions, the mental and physical health problems of elderly mentally handicapped people are similar to those of the elderly population as a whole. Psychiatric disorder is more common due to a higher frequency of behaviour disorders. Increased longevity has been accompanied by a progressive increase in deaths from age-related conditions and in individuals with Down's syndrome exposed a predisposition to premature senility and dementia. Service issues include general health care, preventive measures, provision for those with psychiatric and age-related problems, and staff training.

Adult↗
PubMed1994

Fatal intestinal obstruction in the mentally handicapped.

In a retrospective study of hospital records over a 50-year period, data on 32 patients who died as a result of intestinal obstruction are presented and compared with comparison groups and national mortality statistics. There was a higher incidence and lower mean age at death of fatal intestinal obstruction compared with the total national population. The mean age at death significantly increased over the study period. Intestinal volvulus was a common cause of obstruction particularly in those with cerebral palsy. There was a high prevalence of chronic constipation and megacolon. Foreign-body obstruction was de facto related to pica, but overall, there was a low prevalence of pica. Overall, mean IQ was low, but only significantly so in the male subjects. The length of acute illness was short; in 22 patients it was less than 24 h. Vomiting and abdominal distension were often absent and abdominal signs were recorded only in five patients. Pain or distress was recorded in only nine patients. Only eight patients were correctly diagnosed before death and only two had surgery. The results suggest that fatal intestinal obstruction is more common in mentally handicapped people and chronic constipation and megacolon are risk factors. Intestinal obstruction in mentally handicapped people can present late and with deceptively minimal signs and symptoms.

Adolescent↗
PubMed1994

Dysthymia and mental handicap.

Two cases of dysthymia in mentally handicapped patients are described. The absence of publications on dysthymia in the mentally handicapped is noted. The importance of early diagnosis and treatment with advanced antidepressants and psychotherapy is emphasised.

Adult↗
PubMed1994

Electric treatment of human melanoma skin lesions with low level direct electric current: an assessment of clinical experience following a preliminary study in five patients.

In this study we have investigated the effects of negative low level direct electric current electrotherapy (current: 1 milliampere; treatment time: 30 minutes) in metastatic or primary melanoma skin lesions. After 12 applications in five patients, tumour regression was observed in all evaluable melanoma skin lesions; four of them were classified as partial responses. This study shows that locally applied electrotherapy with a negative low level direct electric current is an effective treatment that results in reduction of tumour mass of human melanoma skin lesions, and it is possible that it has a positive influence on the course of the metastatically disseminated melanoma. No serious side effects were observed.

Adult↗
PubMed1992

Sclerosing inflammatory pseudotumor of the urinary bladder in a child.

A case of inflammatory pseudotumor of the urinary bladder in a 2-year-old child is presented. It was characterized by nodular intravesical growth and massive infiltration of the bladder wall. Microscopically, the lesion showed in its largest part a relatively paucicellular spindle cell growth and a sclerotic appearance with a thin superficial cellular zone resembling granulation tissue. Another morphological characteristic was a marked capillary proliferation revealed by immunohistochemical reactions to factor VIII-associated protein, laminin, and collagen IV. The last feature appears to be an integral part of the process, which most closely resembled fibromatosis of the adult type, a rare pattern of growth in inflammatory pseudotumor.

Child, Preschool↗