Search PubMed⌕ Search

Biomedical subjects

G Szekeres

Publications and source records attributed to G Szekeres.

At least 19 recordsLinked to original sources
PubMed2001

Immunohistochemical assessment and prognostic value of hepatitis B virus X protein in chronic hepatitis and primary hepatocellular carcinomas using anti-HBxAg monoclonal antibody.

Hepatitis B virus (HBV) is the most meaningful risk factor in chronic hepatitis, cirrhosis and primary hepatocellular carcinoma (PHC). The hepatitis B virus X protein (HBxAg) is a multifunctional protein with many important functions in hepatocellular carcinogenesis. A monoclonal anti-HBxAg antibody was developed in our laboratory and characterized by different methods. Using this antibody HBxAg was detected in formaldehyde fixed paraffin embedded tissue sections of 72 liver biopsies from patients with acute hepatitis, chronic hepatitis, cirrhosis and primary hepatocellular carcinoma. The co-expression of hepatitis B surface antigen (HBsAg), hepatitis B core antigen (HBcAg) and HBxAg was compared. The histological and cytological localization of the detected HBxAg showed a characteristic distribution in different stages of HBV infection. Strong and diffuse nuclear reaction was detected in PHC cases in contrast to the focal, cytoplasmic and nuclear labeling in the acute and chronic B hepatitis cases. Our antibody seems to be a suitable prognostic marker for routine pathohistological diagnosis and for comparative pathological and epidemiological research on the development of PHC.

Animals↗
PubMed2000

Visual information processing in patients with schizophrenia: evidence for the impairment of central mechanisms.

Patients with schizophrenia are especially impaired in the detection of spatial location if the briefly presented target stimulus is followed by a mask in a close temporal proximity (target location backward masking (BM) paradigm). It has been suggested that this phenomenon is related to the impairment of low spatial and high temporal frequency-sensitive transient (magnocellular) visual channels. To test this hypothesis, we measured target location BM and visual contrast sensitivity (CS) in clinically remitted patients with schizophrenia. In the BM task, subjects were asked to indicate the position of letters appearing at four possible spatial locations. In the CS test, a two-alternative forced choice method was used to measure the minimal contrast level required for the detection of horizontal gratings set at low spatial and high temporal frequencies (0.5 cycle/degree and 8 Hz, respectively). We found that the schizophrenia patients with normal CSs (spared transient channel functions) showed a marked deficit in the target location BM task. This suggests that the abnormality of subcortical transient channels does not explain some visual information processing dysfunctions in schizophrenia. Instead, deficient cortical interactions of rapidly changing environmental signals may be involved.

Adult↗
PubMed2000

Schizophrenics know more than they can tell: probabilistic classification learning in schizophrenia.

BACKGROUND: Previous studies have demonstrated impaired explicit and preserved implicit memory functions in schizophrenia. However, it is less clear whether schizophrenics can learn complex information (e.g. probabilistic stimulus response associations) with or without access for conscious recollection. In this study we applied a classification learning task to assess explicit and implicit processes concurrently. METHODS: Two test procedures were administered to 40 schizophrenic subjects and 20 healthy volunteers: a probabilistic classification learning (PCL) task to evaluate implicit memory functions; and a category cue recognition test to investigate the explicit memory system. The PCL task included feedback guided category learning of geometrical shapes. These shapes were called category cues, predicting class membership with certain probabilities. The gradual increase of categorization performance during the feedback learning was a potentially implicit process, whereas the subsequent recognition of category cues required explicit memory functions. RESULTS: The schizophrenic patients improved their categorization performance to a similar extent to the controls, but they failed to recognize the category cues. Memory performances were independent of the positive and negative symptoms. CONCLUSIONS: Patients with schizophrenia were able to establish representations of complex categories, but these remained unconscious. This is consistent with earlier reports, suggesting damaged explicit and spared implicit memory in schizophrenia.

Adult↗
PubMed1999

[Regional cerebral blood flow changes in schizophrenic patients detected by SPECT studies under resting and active conditions].

Brain SPECT studies in schizophrenia revealed changes in regional cerebral blood flow (rCBF). The rCBF changes can be detected more accurate by activating tests. The aim of this study was to assess rCBF changes under resting and activation condition by the Raven test. Four control patients (2 male, 2 female, average age 45 years, 26-57 years) and 11 chronic, treated schizophrenic patients (4 male, 7 female, average age: 46 years, 33-56 years) were studied in two HMPAO brain SPECT sessions, 48 hours apart, both resting and during activation task. The images were evaluated visually and semiquantitatively. Under resting condition in the control group, there were no significant rCBF changes. In the Raven activation test, a significantly higher blood flow in the prefrontal region was seen (p < 0.05). The schizophrenic group had a significantly lower rCBF in the temporal region under resting condition (p < 0.05): four patients displayed left, 4 right temporal hypoperfusion and 3 exhibited no rCBF abnormality. In the Raven activation tests 5 patients had prefrontal hyperperfusion, and the remaining 6 patients had no such activation answer. Five patients had hypoperfusion in the temporal region. In our sample, patients with chronic schizophrenia displayed significant temporal hypoperfusion. Moreover the chronic schizophrenic group exhibited a poor response to prefrontal activation compared to the control group.

Adult↗
PubMed1999

[Adenomyomatosis of the gallbladder].

A 64-year-old male patient was reported, surveying radiology and pathology of the adenomyomatosis. The authors emphasize the role of high resolution ultrasound and computer tomography in the diagnosis of gallbladder adenomyomatosis. Intramural cystic formation (anechoic diverticula) with echogenic foci and/or reverberation artifacts together with a full or a partial thickening of the gallbladder's wall was considered as the diagnostic criteria of the ultrasound examinations. They assist in finding the proper way among the difficulties of the different diagnosis, in the same time call the attention for the frequently misdiagnosed cases.

Adenomyoma↗
PubMed1999

Category learning and perceptual categorization in schizophrenia.

The aim of this study was to evaluate category learning in schizophrenia on tests of perceptual abstraction. Participants learned to categorize simple geometrical shapes. The categories were either well-defined (discrete categories, or DCs) or ill-defined (graded categories, or GCs). In DCs, the cues defining category membership can be verbalized in an all-or-none fashion, while in GCs they cannot be defined unambiguously. Three types of learning were used successively: serial presentation of category-exemplars, verbal description, and feedback. After the serial presentation, schizophrenia patients showed a deficit for GCs (p<0.005) but not for DCs (p = 0.98). After the verbal definition of GCs, the difference between schizophrenia patients and controls diminished (p = 0.09). Finally, after the feedback learning of GCs, a significant difference was observed again (p<0.0001), suggesting that schizophrenia patients were impaired in this learning paradigm. The GC-learning impairment after the serial presentation displayed a relationship with the score of the cognitive component assessed with the Positive and Negative Syndrome Scale (r = -0.66). In conclusion, these results suggest that the perceptual stage of abstraction is impaired in schizophrenia. This impairment can be partially compensated by instructions via top-down verbal processes.

Adult↗
PubMed1998

Abstraction is impaired at the perceptual level in schizophrenic patients.

This study investigates category learning in schizophrenia in order to evaluate abstraction abilities at the perceptual level. The participants learned about two categories of geometric shapes. The category exemplars were presented successively. In the case of schizophrenic patients, longer exposure time and more stimulus presentations were used to counterbalance attention impairments. In spite of this, the perceptual category learning was significantly impaired in the patient group. In contrast, when the training procedure involved verbal category definition and not perceptual learning, the performance of schizophrenics was similar to that of the healthy controls. These findings suggest that the perceptual learning of categories, but not free classification judgements are impaired in schizophrenia, and that this impairment is not due to pure attentional disturbances.

Adult↗
PubMed1998

[Testing basic visual functions in the evaluation of extrapyramidal side effects of antipsychotic agents].

One of the cornerstones of antipsychotic therapy is the evaluation of the effective dose that cause minimal extrapyramidal side effects. It is known that the visual system (e. g. the retina) contains dopaminergic cells similarly to the striatum where dopaminergic blockade is crucial in the induction of extrapyramidal symptoms. This rises the possibility that striatal functions can be tested by the evaluation of certain visual functions. This study compared the visual contrast-sensitivity of 20 schizophrenic patients on antipsychotic medication (9 patients were on risperidone, 9 on haloperidol, and 1-1 on zuclopenthixol and fluanxol treatment) to that of normal control subjects, and found significant impairment in the former group. The contrast-sensitivity impairments correlated with the severity of extrapyramidal symptoms. These results suggest that contrast-sensitivity measurements can be useful in the evaluation of neuroleptic threshold in the clinical practice.

Adult↗
PubMed1997

[Expression of macrophage markers in childhood and adult Langerhans histiocytosis (LCH)].

In the diagnosis of the Langerhans cell histiocytosis several monocyte and macrophag markers have been tested in the recent years. We compared the expression of macrophage and lymphoid markers in childhood and adult type Langerhans cell histiocytosis. Ten childhood and 11 adult cases were tested using paraffin sections of biopsy samples. We have examined 6 markers: the S-100, Lysozyme, CD68 macrophag and the CD1a, CD4, HLA-DR lymphoid markers. We have found that the CD68 marker was more frequently positive than the other examined macrophag markers, and proved to be almost as reliable as the recently discovered CD1a. The most interesting result was that the expression of the markers was different in the childhood and adult type of the disease. On the basis of our experience the possibility arise that the phenotype of the childhood and adult type of the Langerhans cell histiocytosis is different.

Adolescent↗
PubMed1997

[Prion dementias: nosology and diagnostic difficulties in the spectrum of Creutzfeld-Jakob encephalopathy].

Creutzfeldt-Jakob disease (CJD) is one form of subacute prion diseases with spongiform encephalopathy. Hereditary, infectious and sporadic types of the disorder can be distinguished. The abnormal transformation of the prion protein, relevant in the normal synaptic transmission is considered as an important factor in the development of this disease. Gerstmann-Sträussler-Scheinker syndrome (GSS) and familial fatal insomnia (FFI) are the other diseases belonging to the same disease spectrum. The common feature of these disorders is that the different mutation of the same prion protein could result in different phenotypes and symptoms. CJD is considered as a neurologic disorder but the clinical symptoms and differential diagnosis of the disease are also relevant problems in psychiatry. Because of the early onset of dementia and the psychotic and delusive symptoms, the patients with CJD are frequently admitted to psychiatric wards. Recently worldwide public interest has been focused on prion dementias because of the possible human transmission of bovine spongiform encephalopathy in the UK. The diagnostic problems of our seven CJD patients diagnosed since 1991 in the catchment area of Szeged city are discussed in the view of recent findings of molecular biology, nosology, diagnostic and therapeutic problems of this devastating disease.

Adult↗
PubMed1997

Model for quantitative immunohistochemical assessment of pulpal response to biomaterials.

The purpose of this study was to propose a new method for quantitative evaluation of the pulpal inflammation to restorative materials using immunohistochemistry and image analysis. Class V cavities were prepared and filled with different restorative materials in 20 healthy premolars to be extracted for orthodontic reasons. Teeth were extracted at different time intervals, fixed, demineralized, and embedded in paraffin. Six-micrometer-thick sections were cut serially and mounted on slides and every fifth section was stained using hematoxylin and eosin or Masson's trichrome, and served to localize the inflammatory reaction. The slides corresponding to the bulk of the inflammatory reaction were then used for immunohistochemical detection of the inflammatory cells using monoclonal antibodies: CD15 (granulocytes and histiocytes), CD45RO (T lymphocytes and monocytes), Pan-B cell (B lymphocytes, macrophages, and a subpopulation of T lymphocytes), CD45RA (B lymphocytes and monocytes), and EMA (plasma cells). The slides were observed and submitted to computerized image analysis using a SAMBA 2000 system for counting of the cells. The CD15, CD45RO, Pan-B-cell, and CD45RA antibodies positively stained the target cells, which could be counted with the computer. The EMA antibody did not permit staining of cells. These results indicate that polymorphonuclears, T lymphocytes, and B lymphocytes are present in inflamed human dental pulp. The immunologic detection of inflammatory cells followed by computerized image analysis allows an accurate characterization of pulpal pathology, and could be useful for the study of pulp reactions to restorative biomaterials.

Dental Materials↗
PubMed1995

Effect of ribonuclease A and deoxyribonuclease I on immunostaining of Ki-67 in fixed-embedded sections.

Immunostaining of the cell cycle-associated Ki-67 antigen was studied on routinely formalin-fixed and paraffin-embedded tissue sections, using the Ki-67-specific monoclonal antibody MIB-1. Immunomorphological analysis of the Ki-67 immunostaining pattern was carried out following tissue pre-treatments including combinations of microwave heating and trypsinization, as well as of ribonuclease and deoxyribonuclease pre-digestion of the sections. The nucleolar Ki-67 immunostaining after slide pre-treatment by microwave heating followed by trypsinization was reduced only by ribonuclease pre-digestion, if this latter was used before heating. Ki-67 immunostaining was not significantly reduced by deoxyribonuclease treatment. We conclude that Ki-67, located in the nucleoli, may be associated there with nucleolar RNA.

Deoxyribonuclease I↗
PubMed1994

Hapten-mediated identification of cell membrane antigens using an anti-FITC monoclonal antibody.

A monoclonal anti-FITC antibody (F4/1) was produced and demonstrated to be specific for both the free and protein-conjugated (either soluble or cell-bound) form of fluorescein, or carboxyfluorescein. When mouse thymocytes were labelled with a novel fluorescein derivative 5(6)-carboxyfluorescein succinimidyl ester (CFl-NSE), the incorporation of fluorescein was predominantly membrane-bound as demonstrated immunohistochemically. The coupling of CFl-NSE to cells displays a random distribution pattern as shown by immunoblotting of cell extracts prepared by detergent solubilization of CFl-NSE-labelled thymocytes. In addition, the Thy-1.2 antigen immunoprecipitated from a CFl-NSE-labelled thymocyte lysate with a rat monoclonal antibody (Mab) could be detected using the anti-FITC Mab. The molecular weight of the immunoprecipitated material could be estimated immediately by reference to the FITC-labelled molecular weight markers electrophoresed simultaneously.

Animals↗
PubMed1994

Bone marrow one step fixation-decalcification in Lowy FMA solution: an immunohistological and in situ hybridization study.

The immunoreactivity of paraffin embedded bone marrow biopsies (BMB) was studied following a one step 20-hour-fixation-decalcification in Lowy formalin mercuric chlorid acid solution which permits excellent histological stainings. Antibodies reactive with myeloid, megakaryocytic, erythroid cells, T and B lymphocytes, mastocytes and metastatic cells were compared. Nearly all antibodies working on paraffin sections were demonstrated on Lowy FMA fixed BMB. Special care was taken to define an optimal working dilution. Trypsinization was not necessary. A slide microwave pre-treatment appeared essential before testing CD20 L26, CD8, CD3, CD34, MB1 Kappa and Lambda antibodies. It was suitable for UCHL1, LN2, CD30 antibodies. The same fixative allowed an m RNA Kappa or Lambda in myeloma and EBER 1 EBV RNAs in HIV lymphoma visualization by in situ hybridization. The safety handling of the toxic mercuric chloride component is discussed.

Biopsy↗
PubMed1994

Ki-67 and p53 expression in cutaneous Bowen's disease: an immunohistochemical study of fixed-embedded tissue sections.

The monoclonal Ki-67-specific MIB-1 and p53 protein-specific DO-1 antibodies were used to identify proliferating cell fractions on microwave-pretreated paraffin sections of 7 cutaneous Bowen's disease specimens. A high Ki-67 score was characteristic of all cases examined, and significant p53-positivity was seen in 4 cases. In the peritumoral, histologically normal epidermis, Ki-67- and p53-positive cells were frequently present, in one case with very high scores (89% as well as 82%, respectively). These findings indicate an increase in the proliferative activity of the Bowen cells (high Ki-67 score) and that p53 mutations are frequently found in this disease. The p53 expression was not related to the Ki-67 score. The expression of Ki-67 and p53 in morphologically normal epidermal cells is also discussed. The histologically normal epidermal cells expressing p53 and Ki-67 antigens may correspond to pre-malignant clones.

Antigens, Neoplasm↗