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Biomedical subjects

S Nĕmecek

Publications and source records attributed to S Nĕmecek.

At least 19 recordsLinked to original sources
PubMed2000

[Evaluation of the results of surgery of intracranial supratentorial tumors in 363 children over the past 50 years (1948-1997)].

At the Department of Neurosurgery, Hradec Králové, in the course of 50 years (1948-1997) 363 children, 199 boys and 164 girls (1.2:1) aged under 18 years were operated on for intracranial supratentorial tumours. The average age in children at the time of first operation was 9.3 years; most frequently they participated those of 8 and 11 to 14 years of age. Children aged 1, 2 and 3 years constituted 4.7%, 4.4% and 5% of operations. The tumours were located in: cerebral hemispheres 123 (33.8%), lateral ventricles 17 (4.7%), IIIrd ventricle 5 (1.4%), hypothalamus 26 (7.2%), thalamus 19 (5.2%), basal ganglia 24 (6.6%), sellar region 86 (23.7%), chiasmatic region 38 (10.5%) and pineal region 19 (5.2%). 223 of tumours (61.4%) were located in the midline and 140 of them (38.6%) laterally (in hemispheres and lateral ventricles of the brain). 268 of tumours were histologically verified (73.8%) and 95 of cases were evaluated according to the neurosurgeon's point of view and/or to the clinical and CT controls (26.2%), because of the biopsy (especially in the pre-CT era) was highly riskfull. Histological typing of tumours was retrospectively reevaluated according to the present WHO classification. Summarized 53 types of tumours were differentiated. The most frequent lesions were various variants of astrocytic gliomas (135 = 37.2%). Further on the craniopharyngiomas dominated (73 = 20.1%). The tumours were operated on through craniotomies 299 times, by primarily drainage operations 52 times, functions 6 times, stereotactically 8 times and or by combination of these operations 82 times. Reoperation was needed for postoperative complications in 1.7% (6 times) and for delayed recurrence in 11.3% (41 times). The postoperative mortality (up to 1 month after initial surgery) was in 156 children operated on in pre-CT era (between 1948 and 1977), as compared with 207 children operated on in the era of CT (between 1978 and 1997) in astrocytomas 3.8:0%, pilocytic astrocytomas 6.5:2.8%, craniopharyngiomas 15.4:0% and in all tumours 12.2:2.9%. 16 children with orbital tumours (the average age 5.8 years) operated on with orbitofrontal approach were also evaluated. 14 of them survive for 5-37 years (on the average 16.6 years). The chronological development of diagnostic and operative processes of supratentorial tumours in children's care is discussed. The prognostic elements of present histobiological classification of tumours are positively evaluated.

Adolescent↗
PubMed1998

Immunohistochemical detection of intermediate filament nestin.

Using Rat-401 monoclonal antibody and peroxidase immunohistochemistry we have detected IF nestin in developing and adult rat tissues. Although epitope recognized by Rat-401 antibody is relatively resistant to aldehyde fixation and paraffin embedding, the embedding of tissue samples into polyester wax and microwave antigen retrieval of histological sections enabled us to enhance sensitivity of immunohistochemical detection and to identify cells expressing low levels of nestin. Our findings confirm that nestin is predominantly distributed in developing neural, myogenic and mesenchymal cells, i.e. cell types that have been previously described to express this intermediate filament. Furthermore, we made original findings on identification of nestin expression in additional cell types, e.g. newly formed endothelial cells of extra- and intraembryonic blood vessels, epithelial cells of the developing lens, and cells apposed to to hair follicles.

Animals↗
PubMed1997

Detailed evaluation of 2959 allogeneic and xenogeneic dense connective tissue grafts (fascia lata, pericardium, and dura mater) used in the course of 20 years for duraplasty in neurosurgery.

Surgical experience with 2959 allogeneic and xenogeneic dense connective tissue grafts (1767 of fascia lata, 909 of pericardium, and 283 of dura mater), used in 2665 neurosurgical operations performed in the course of 20 years (1976 to 1995) is reported. Duraplasty using either allogeneic or xenogeneic grafts has had a similar, and favourable clinical outcome. Nevertheless, the pliable deep frozen fascia lata grafts, which could be used in any location, have been reserved for sella turcica plugging, anterior cranial base plasty, aneurysmal wrapping, and surgery of lipomyelomeningocele. Pericardium and dura mater grafts were in the majority of cases used over the brain convexity and posterior cranial fossa. Ovine pericardium proved to be superior to bovine and allogeneic pericardia because of its workability, flexibility, reduced thickness, and better transparency. Postsurgical complications occurred in 7.3%, and they were: 1) cerebrospinal fluid fistulas in 2.8%; 2) meningites in 2.3% (aseptic 1.4%, bacterial 0.8%, and tumoural 0.1% meningites); 3) pseudomeningoceles in 2.2%; 4) wound infections in 0.6%; 5) malresorptive hydrocephalus in 0.5%; and 6) adhesions to nerve tissue in 0.5%. The majority of complications healed without surgery. Forty-eight grafts (1.6%) failed to fulfil the requirements of the surgeon, and 46 of them were re-operated upon. Though another thirty-nine grafts healed successfully, 39 shunts (1.5%) had to be performed for malresorptive hydrocephalus (0.9%), and/or for a big pseudomeningocele (0.6%). So, the pure complication rate in 2665 duraplasties was 3.1%. The complex evaluation of the allogeneic and xenogeneic grafts (fascia, pericardium, and dura mater), used for duraplasty in neurosurgery during the last 20 years proved them, as remarkably good, with a success rates of 96.9%.

Adult↗
PubMed1996

Allogeneic cartilage used for skull base plasty in children with primary intranasal encephalomeningocele associated with cerebrospinal fluid rhinorrhea.

Three children with primary intranasal encephalomeningocele associated with cerebrospinal fluid rhinorrhea were operated on at the Department of Neurosurgery, Hradec Králové. In two children, aged 4 and 9.5 years, freeze-dried allogeneic costal cartilage was glued into the skull base defect. This plugging was covered up with deep frozen allogeneic fascia lata. In the third child, an only 1-year-old boy, after transection of the neck of the encephalomeningocele freeze-dried allogeneic dura mater was glued on extradurally and deep-frozen allogeneic fascia lata applied intradurally. The cerebrospinal fluid rhinorrhea ceased immediately after surgery. Spontaneous atrophy of the intranasal portion of the encephalomeningocele was demonstrated respectively 11, 1, and 7 years postoperatively on computed tomography. To evaluate cartilage healing histologically, the extracted allogeneic cartilage used for orbital roof plasty after 4 months was examined. The extent of spotty regressions represented about 7% of the tissue volume. It is stressed that, once diagnosed, intranasal encephalomeningocele associated with cerebrospinal fluid rhinorrhea should be operated on for prevention of meningitis as soon as possible.

Brain↗
PubMed1996

Ovine pericardium: a new material for duraplasty.

The authors report on their 2 1/2-year clinical experience using a dural substitute, ovine pericardium, stabilized with 0.3% glutaraldehyde, flat freeze-dried, and sterilized with gamma-irradiation. Packaging of the ovine pericardium in double-plastic transparent bags allows simple storage in operating rooms and the opportunity for the surgeon to choose an ideal graft according to its shape, size, and plasticity. The ovine pericardia were examined histologically and by transmission and scanning electron microscopy in their native, freeze-dried, and irradiated forms. The final product is composed solely of pericardium fibrosum interwoven with artificially formed extracellular microcavities that serve as natural pores for the ingrowth of host tissue. The surfaces of the grafts appear smooth on the inner and rough on the outer sides. Sixteen grafts were examined macroscopically at autopsy and four of these were also examined histologically to illustrate their successful healing with no adhesion to the underlying brain. As a new dural substitute, ovine pericardium proved to be superior to bovine and allogeneic pericardia because of its workability, flexibility, and reduced thickness. In a study of 120 grafts, all but one healed without complications.

Adolescent↗
PubMed1996

Differentiation of epidermal growth factor-responsive neural precursor cells within neurospheres.

Genetically unmodified neural precursor cells (NPCs) derived from rate embryonic cortex were stimulated with Long-epidermal growth factor in vitro to form multicellular neurospheres. In our study, histology and transmission electron microscopy was for the first time utilized for analysis of three-dimensional neurospheres. Immunohistochemical phenotypization carried out on paraffin-embedded section revealed that most cells in the neurosphere expressed high levels of vimentin that is normally found in immature neural cells. Majority of glial cells expressed glial fibrillary acidic protein (GFAP) that is a specific marker for differentiated astrocytes. On the other hand, myelin basic protein (MBP), a marker of oligodendrocytes, was found only in a discrete subpopulation of glial cells. Similarly, electron microscopy recognized only rate myelin sheaths surrounding axons. Some cells displayed neuron-like morphology and were labelled with antibodies recognizing the neuronal antigens: 210 kDa neurofilaments (NF 210) and microtubule associated protein-2 (MAP-2). Surprisingly well-developed interneuronal synapses were found electronmicroscopically. The presence of synaptic vesicles was also confirmed by immunohistochemical detection of synaptophysin. Our results show that NPCs in neurospheres gradually differentiate into glial and neuronal cells.

Animals↗
PubMed1996

The beginnings and 50-year history of the Charles University Faculty of Medicine in Hradec Králové.

The Faculty of Medicine in Hradec Králové has some unique features that make it stand out from other similar faculties in this country: The school developed from regional traditions at the appropriate historic times, when due to closure of the universities during World War II. there was a serious death of physicians. The school was supported by the local governing organs, as well as by the generous financial assistance of citizens who identified with the idea of creating a university in Hradec Králové. An entirely new organizational form was utilized in the creation of the medical school: it was founded as a branch of the Faculty of Medicine at the Charles University in Prague. It was the first time that this form of organization in the history of our universities was used to prevent any legal delays during the postwar times when parliamentary legislation was not yet functional. It constitutes a synthesis of existing medical schools in Prague and Brno (Brünn): the first teachers were primarily equally recruited from both these universities. It had been connected almost from its beginning with the coexisting military medical school; at one time it represented this military medical training institution by itself. The school underwent so many transformations accompanied by the departure of a number of important professors that it was surprising that it was able to maintain its professional integrity. The answer to the question of why the first medical school in the postwar period was founded in Hradec Králové is not too difficult. The town was a metropolis of eastern Bohemia with an important cultural and political tradition; this eventually culminated in a targeted readiness of such institution.

Czech Republic↗
PubMed1995

Impedance monitoring in the stereotactic localization of intracranial structures.

Measurement of tissue impedance is a simple objective method for the localization of intracranial structures. Continuous bipolar impedance monitoring was performed during various CT-guided stereotactic procedures in 36 patients with brain pathology. The obtained values of the impedance profile along the trajectory were compared with the tissue density on CT scans or angled coronal and sagital CT reconstructions intraoperatively. The main goal was the selection of optimal biopsy targets and safe probe trajectory. Histologic findings of serial transtumoral biopsy were retrospectively correlated with both CT (or MRI) transposed data and patterns of tissue impedance. Intraoperative impedance monitoring enhanced the accuracy and safety of CT-guided procedures. The histologic examination of representative tissue samples avoids the risks of "blind" surgical or radiation management. This technique is reported with 6 illustrative cases.

Adult↗
PubMed1995

Cerebrospinal fluid dissemination of fetal neural isografts in brain of adult rats.

Our previous studies tend to document the temporary invasiveness of intraparenchymal fetal isografts. The present study exploits a model situation in which contacted host brain surface remains undamaged. We analyzed the behavior of transplant fragments that accidentally disseminated in cerebrospinal fluid pathways. The transplant seeding occurred in 7 cases out of 85 cases of healthy solid isografts taken from various parts of fetal brain. Fragments were found either as free (floating or simply lying close to the surface) or attached. Some attached fragments invasively penetrated the brain parenchyma. This speaks in favor of invasive properties of fetal neural transplants.

Animals↗
PubMed1995

Neural transplantation of the rat midgestation trophoblast.

The trophoblast may serve as an example of tissue that is endowed with invasive properties under physiological conditions. Invasiveness of the trophoblast is enabled by the secretion of various proteases capable of degrading extracellular matrix components. Trophoblast invasive behavior is strictly controlled by anti-invasive factors produced by uterine decidual cells. To assess invasive abilities of trophoblast cells we have transplanted E9 and E14 rat trophoblast (i.e. the trophoblast obtained on embryonic day 9 and 14) into the brain of adult rats. The brain parenchyma as an immunologically privileged site is suitable for acceptance of grafts of different tissues. Moreover, the trophoblast placed into the CNS lacks inhibitory influence of anti-invasive factors that normally regulate trophoblast invasivity in the course of intrauterine gestation. To visualize migration of grafted cells the nuclei of the trophoblast were labelled with bromodeoxyuridine prior to neural grafting. The transplant of E9 and E14 trophoblast cells obtained a blood nourishment from host vessels. A proper vascularization is necessary for a further transplant growth. The transplant contained labyrinthine trophoblast cells and giant cells that are typical for the rat placenta. Vital trophoblast cells were found in all grafts whose age did not exceed a lifespan of normal rat trophoblast cells i.e. 21-22 days. In the centre of the graft, no blood vessels were observed. Interstitial spaces of neighbouring trophoblast cells were filled with the host blood and morphology of these spaces mimicked lacunae of the placental trophoblast. E9 and E14 rat trophoblast continued to differentiate after transplantation into the CNS of adult rats. Histological structure of the grafts were compared with microscopical morphology of the normal rat placenta. E9 and E14 trophoblast is considerably differentiated and it does not invade a neighbouring tissue. Trophoblast cells located at t the graft periphery may migrate on free surfaces but they do not invade through the host parenchyma. Migration occurs at a limited distance from the transplant and the cells remain in a close contact with other trophoblast cells in the graft via their cytoplasmatic processes. The ability to lyse host blood vessels and form vascular lacunae is well preserved in E9 and E14 trophoblast after grafting into the CNS. This ability is necessary for a proper transport of nutrients from the host blood stream to fetal tissue that normally occurs in the placenta.

Animals↗
PubMed1995

Immunohistochemical detection of proliferative cells.

The cell proliferation represents one of the most relevant cellular functions. There are many approaches to assess the proliferative activity in tissues. Immunohistochemical methods offer a high sensitivity and specificity. They use monoclonal antibodies raised against specific antigens associated with the cell proliferation. Anti-BrdU immunohistochemistry detects bromodeoxyuridine (BrdU) which as an exogenous proliferation marker has been incorporated into the newly synthesized DNA of dividing cells. The best known endogenous proliferation markers are PCNA and Ki-67 that may be detected with specific commercially available antibodies. Here we describe our experience with an immunohistochemical detection of these proliferation markers. Anti-bromodeoxyuridine (BrdU) antibody binds BrdU that was exogenously introduced into the synthesizing DNA during the S-phase of the cell cycle. The precise timing and dosage of BrdU enable tissue kinetics studies. A long-time administration of BrdU may be used for labelling tissues with a low proliferative activity. BrdU incorporated into the cell nucleus is still a very stable antigen which gives a strong and reliable signal regardless the kind of fixation and further tissue processing. The proliferating cell nuclear antigen (PCNA) as an auxillary protein for DNA polymerase gamma is an evolutionarily conserved molecule that may be detected in human and animal frozen or paraffin-embedded tissues. In spite of the fact that anti-PCNA immunohistochemistry may weakly stain non-proliferating cells, PCNA is the most frequently detected proliferation marker. The staining intensity may be influenced by the kind of fixation and the length of microwave pretreatment. Ki-67 is another endogenous antigen detectable in proliferating cells. Its detection in paraffin-embedded sections requires also exposition to microwaves. Both Ki-67 and PCNA may be revealed in archival specimens that means these techniques do not require any prelabelling. Ki-67 labelling index (LI) correlates better with BrdU LI than PCNA LI as the Ki-67 antigen has a shorter half-life than PCNA.

Animals↗
PubMed1995

Cultivation of neural EGF-responsive precursor cells.

We demonstrated that proliferation of dissociated neural E14 and E19 rat precursor cells could be induced by Long-EGF. Dividing EGF-responsive neural progenitor cells stimulated by Long-EGF formed spherical multicellular clusters (neurospheres) which may reach macroscopical size. We have studied the inner organization of cells in semithin sections and revealed that the cell population within the neurosphere is not uniform. These are original findings as other researchers did not process neurospheres histologically. Cells located in a central area possessed neuron-like morphology whereas peripheral cells where differentiated to a lesser degree. Generally, we have observed several apoptotic cells or apoptotic bodies per section. Moreover, the central portion of the neurosphere contained degenerating cells that probably die from worsened nutrition conditions in the large neurosphere. After plating the neurosphere in serum-supplemented medium, cells began to migrate radially from the edge of the neurosphere and differentiate. The cells lying in the vicinity to the cluster mimicked radial glia whereas the cells located at the periphery of the colony took morphology of astroglial cells. These observations suggest EGF-responsive neural precursor cells retained their ability to produce both neuronal and glial phenotypes after prolonged cultivation period.

Animals↗
PubMed1995

Epilepsy associated with low-grade brain glial neoplasms.

In 1991-1993, 52 patients underwent surgery for low-grade supratentorial glioma. In 37 of them (astrocytoma 22, oligodentrocytoma 12, oligodendroglioma 2) seizures, often refractory to drug therapy, appeared as the first symptom. These cases were retrospectively analyzed. The patients had partial seizures: simple, complex, or secondarily generalized (preoperative duration: from 3 days to 17 years (mean 2 years); frequency: between 1 and 2/year and over 10/day). Neurological examination either revealed slight focal changes or was normal. Conventional craniotomy and resection of a tumor, without intraoperative electrocorticography, was performed. Partial resection was performed in 73%, subtotal in 5%, "total" in 22% of the cases. Postoperatively, 27 patients had focal radiotherapy, 3 of them in combination with chemotherapy. Two patients were reoperated. Out of 33 alive (89%), about two-thirds appear normal by neurological examination and are seizure-free at present (mean follow-up period 28 months). Most remain on antiepileptic drugs at lower doses. Histological and immunohistochemical analyses of resected tissue together suggest that the peripheral zone of cortical tumor infiltration may participate on epileptogenesis.

Adolescent↗
PubMed1994

Posterior fossa duraplasty in children: remarks on surgery and clinical and CT follow-up.

A series of 314 posterior fossa duraplasties in children were performed at the Department of Neurosurgery, Hradec Králové, over the past 33 years. Computed tomographic (CT) imaging was used to compare the healing of various kinds of collagenic dural substitutes--allogeneic fascia lata, allogeneic dura mater and xenogeneic pericardium. Early (8 days to 3 months following surgery) and late (1-18 years following surgery) axial CT scans with sagittal reconstruction for duraplasty in 55 children were evaluated. In early postoperative CT scans, epidural collections of cerebrospinal fluid, sanguinolent liquid or haematoma and/or pseudocysts or pseudomeningoceles appeared. In late CT follow-up, calcifications and ossifications in the "suboccipital coverings complex" (SCC) gradually developed and pseudocysts or pseudomeningoceles rarely persisted. It is concluded, on the basis of perioperative, clinical, and CT examinations, that posterior fossa duraplasties in children formed an important anatomical barrier and regardless of the type of graft had a favourable outcome; CT was shown to be a suitable method for the demonstration of dural grafts at the site of craniectomies.

Adolescent↗
PubMed1993

The possible use for immunohistochemical detection of cells in S-phase labeled by bromodeoxyuridine.

Experiences with the use of bromodeoxyuridine (BrdU) as a marker of cellular division were described within this paper. BrdU is incorporated in the course of S-phase of cell cycle into the arising DNA in place of thymidine. The presence of BrdU in cell nuclei of tested tissues was detected with a monoclonal antibody and immunoperoxidase method. It was found that: 1. In adult rats a total dose of 100 mg is sufficient for labeling nuclei in most tissues, however intensity of the staining varies. The largest amount of BrdU was revealed in enterocyte nuclei. Lower level of BrdU was detected in cells in the spleen and in the interalveolar septa (probably macrophages) and the lowest one was found in the liver (hepatocytes, Kupffer, and Ito cells); with the exception of individual astrocytes no labeling was revealed in the central nervous system. 2. ED14 (14 days old) rat embryo that had been exposed to BrdU in the mother body, revealed only a weak labeling because of the uptake of BrdU in the placenta. The highest level of BrdU was observed in mesenchymal cells surrounding primitive organs. 3. Explants of the cerebral rat ED14 cortex that had been exposed to BrdU during intrauterine development, remain to be BrdU positive even after their transplantation into the recipient's brain. Different intensity of cell nuclei labeling reflects the rate of mitoses from embryonic day 12 (ED12) to ED14 when BrdU had been administered.

Animals↗
PubMed1993

Inoculation of C6 cell suspension into the brain of adult rats: immunohistochemical study.

C6 glioma cell suspension has been inoculated into the brain of adult Long Evans rats. Animals were allowed to survive 2 to 60 days and then immunohistochemical detection of S100 protein and glial fibrillary acidic protein (GFAP) in tumors was carried out on paraffin-embedded sections. In our in vivo model the maximum positivity for both S 100 protein and GFAP was observed in C6 glial cells at 10 days after implantation. At that time increased levels of S 100 protein were expressed both in central areas containing more differentiated C6 glioma cells and in host reactive astrocytes at tumor boundary. Almost no S 100 protein was found in dividing and invading, i.e. less differentiated, C6 glioma cells at tumor periphery and in perivascular spaces of adjacent blood vessels. The distribution of GFAP positive cells followed a similar pattern as that of S 100 protein containing C6 cells. GFAP expressing cells were revealed in quiescent central tumor portions which were occupied by more differentiated cells. Tumors were surrounded by strongly GFAP positive host reactive astrocytes. Later on, when signs of tumor regression appeared there was a decrease in S 100 protein and GFAP immunoreactivity of C6 glioma cells. To summarize, we developed an in vivo model for observation of cell differentiation within a growing glioma. Less differentiated and more malignant glioma cells expressed almost no S 100 protein and GFAP in contradistinction to central and more quiescent tumor portions.

Animals↗
PubMed1992

Mature sacrococcygeal teratoma containing the lower half of a human body.

Twins were diagnosed by ultrasound in a 29-year-old woman. The cesarean delivery revealed at first a mature girl with a large benign sacrococcygeal teratoma and then a healthy boy. X-ray and CT examinations of the teratoma showed pelvic and lower limb bones. A mature teratoma-tridermoma (weight 475 g) containing the underdeveloped lower half of a human body was confirmed during surgery and verified morphologically. The fraternal twins, i.e., the girl operated upon and her brother, have been followed for 5 years and are without any complaints. They have normal neurological function.

Child, Preschool↗