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J Malicki

Publications and source records attributed to J Malicki.

At least 19 recordsLinked to original sources
PubMed2001

Mutation of the zebrafish glass onion locus causes early cell-nonautonomous loss of neuroepithelial integrity followed by severe neuronal patterning defects in the retina.

Mutation of the glass onion locus causes drastic neuronal patterning defects in the zebrafish retina and brain. The precise stratified appearance of the wild-type retina is absent in the mutants. The glass onion phenotype is first visible shortly after the formation of optic primordia and is characterized by the rounding of cells and disruption of the ventricular surface in the eye and brain neuroepithelia. With exception of the dorsal- and ventral-most regions of the brain, neuroepithelial cells lose their integrity and begin to distribute ectopically. At later stages, the laminar patterning of retinal neurons is severely disrupted. Despite the lack of lamination, individual retinal cell classes differentiate in the glass onion retina. Mosaic analysis reveals that the glass onion mutation acts cell nonautonomously within the retina and brain, as neuroepithelial cell morphology and polarity in these tissues are normal when mutant cells develop in wild-type hosts. We conclude that the glass onion mutation affects cell-cell signaling event(s) involved in the maintenance of the neuroepithelial cell layer shortly after its formation. The disruption of neuroepithelial integrity may be the cause of the neuronal patterning defects following neurogenesis. In addition, the expression of the glass onion phenotype in a subset of neuroepithelial cells as well as its onset following the initial formation of the neuroepithelial sheets indicate the presence of genetically distinct temporal and spatial subdivisions in the development of this histologically uniform tissue.

Animals↗
PubMed2001

Improvement of counting helminth eggs with internal standard.

The sanitary regulations introduce a requirement for parasitological control of sewage water used for irrigation and fertilisation of crops. The existing methods of estimation of helminth eggs, based on the coproscopic method using sedimentation, desorption, centrifugation and flotation of the material, allow for only 30-75% efficiency. The aim of this paper is to present an improved quantitative estimation method. The proposed method is based on an internal standard. A predetermined number of eggs of Ascaris lumbricoides suis L is coloured with crystalline violet. These marked eggs are added to sample being examined. Counting the marked eggs in the sample and comparing them with their introduced number allows to estimate the efficiency of the procedure. This results in an increase in the efficiency of the method to 100%. It is possible to calculate the real number of helminth eggs in the sample on the basis of the estimated efficiency of the procedure. The sensitivity of the proposed method is at the level of about 0.4 ppm. The necessary number of replications in the method is about 10 times lower than that in the existing methods. The number of natural (not coloured) eggs does not influence the efficiency of the method with an internal standard.

Animals↗
PubMed2000

Genetically modified tumour vaccines (GMTV) in melanoma clinical trials.

Since melanoma is a model immunogenic malignancy incurable in the disseminated phase of its natural course different immunotherapeutic approaches are tested in clinical trials. A number of tumour vaccines genetically modified (GMTV), with various immunostimulatory factors, are tested in phase I/II clinical trials. These factors include cytokines, tumour antigens (TA), costimulatory molecules or HLA antigens. We have designed a novel, mixed auto/allogeneic cellular melanoma vaccine modified with the IL-6 and the sIL-6R genes. Preclinical studies in a mouse model demonstrated that the IL-6/sIL-6R based vaccine is able to elicit efficient anti-tumour responses, mediated by CD8+ and NK cells, which resulted in inhibition of the tumour growth, metastases formation and prolonged survival of the animals treated. Irradiation of vaccine cells does not only lead to their sterilisation but also causes increased secretion of exogenous IL-6 and sIL-6R. Since January 1996 we have vaccinated more than one hundred metastatic melanoma patients. Promising clinical results (22% CR+PR, 32% SD) and the evidence of immune responses in the vaccinated patients have prompted us to design a phase III clinical trial which is to be open in 2000.

Animals↗
PubMed2000

Harnessing the power of forward genetics--analysis of neuronal diversity and patterning in the zebrafish retina.

The seven major cell classes of the vertebrate retina are organized with remarkable precision into distinct layers. The appearance of this architecture during embryogenesis raises two questions of general importance. How do individual cell classes acquire their specialized structures and functions if they all originate from a morphologically uniform cell population? What mechanisms are responsible for the formation of such a complex and exact pattern? Recent advances present an opportunity to apply the tools of forward genetic analysis to identify mutations that affect these mechanisms in zebrafish. Molecular characterization will follow, providing insight into the basis of neuronal patterning in the vertebrate CNS.

Animals↗
PubMed2000

The zebrafish young mutation acts non-cell-autonomously to uncouple differentiation from specification for all retinal cells.

Embryos from mutagenized zebrafish were screened for disruptions in retinal lamination to identify factors involved in vertebrate retinal cell specification and differentiation. Two alleles of a recessive mutation, young, were isolated in which final differentiation and normal lamination of retinal cells were blocked. Early aspects of retinogenesis including the specification of cells along the inner optic cup as retinal tissue, polarity of the retinal neuroepithelium, and confinement of cell divisions to the apical pigmented epithelial boarder were normal in young mutants. BrdU incorporation experiments showed that the initiation and pattern of cell cycle withdrawal across the retina was comparable to wild-type siblings; however, this process took longer in the mutant. Analysis of early markers for cell type differentiation revealed that each of the major classes of retinal neurons, as well as non-neural Müller glial cells, are specified in young embryos. However, the retinal cells fail to elaborate morphological specializations, and analysis of late cell-type-specific markers suggests that the retinal cells were inhibited from fully differentiating. Other regions of the nervous system showed no obvious defects in young mutants. Mosaic analysis demonstrated that the young mutation acts non-cell-autonomously within the retina, as final morphological and molecular differentiation was rescued when genetically mutant cells were transplanted into wild-type hosts. Conversely, differentiation was prevented in wild-type cells when placed in young mutant retinas. Mosaic experiments also suggest that young functions at or near the cell surface and is not freely diffusible. We conclude that the young mutation disrupts the post-specification development of all retinal neurons and glia cells.

Animals↗
PubMed1999

The accuracy of dose determination during total body irradiation.

AIM: The aim of this work was to estimate the error in dose calculations, to check the agreement between the measured and calculated doses and to analyse dose discrepancies in the group of patients undergoing total body irradiation. PATIENTS AND METHODS: A combination of lateral and anterior-posterior fields was used in 8 fractions and on 4 consecutive days. Doses were preliminarily calculated and then measured in vivo by thermoluminescent, semiconductor and ionization dosimeters attached to the body in 10 representative transverse cross-sections. Calculations and measurements were carried out for the beam at the body entry and exit. The error in dose calculations was estimated for each reference point. Dose deviations between calculations and measurements were analysed using the Student's t-test. RESULTS: The error in preliminary dose calculations ranged from 3% to 15% (Table 1). Standard deviations of the measurements and percent deviations from the calculations exceeded 10% only for the lung and neck exits (Table 3). Average thermoluminescent readings were 6% higher than the corresponding semiconductor readings. The measured doses fitted the calculated values within the limit of error, except for the lung, head and neck exits for the whole group, depending on the type of fields used (Table 4).

Abdomen↗
PubMed1999

Development of the retina.

As in other vertebrate species, the zebrafish retina is simpler than other regions of the central nervous system. This relative simplicity along with rapid development, and accessibility to genetic analysis make the zebrafish retina an excellent model system for studies of neurogenesis in the vertebrate CNS. Several genetic screens have led to the isolation of an impressive collection of mutants affecting the retina and the retinotectal projections in zebrafish. A variety of techniques and markers are available to study the isolated mutants. These include several antigen- and transcript-detection methods, retrograde and anterograde labeling of neurons, blastomere transplantations, H3 labeling, and others. As past genetic screens have achieved a rather low level of saturation, the current collection of mutants can only grow in the future. Morphological and behavioral criteria have been successfully applied in zebrafish to search for defects in spinal development. In future genetic screens, progressively more sophisticated screening approaches will make it possible to detect very subtle changes in the retinal development. The remarkable evolutionary conservation of the vertebrate eye provides the basis for using the zebrafish as a model system for the detection and analysis of genetic defects potentially related to human eye disorders. Some of the genetic defects of the zebrafish retina indeed resemble human retinopathies. As the genetic analysis of the vertebrate visual system is far from being complete and new techniques are being introduced at a rapid pace, the zebrafish embryo will become increasingly useful as a model for studies of the vertebrate retina.

Animals↗
PubMed1999

oko meduzy mutations affect neuronal patterning in the zebrafish retina and reveal cell-cell interactions of the retinal neuroepithelial sheet.

Mutations of the oko meduzy (ome) locus cause drastic neuronal patterning defect in the zebrafish retina. The precise, stratified appearance of the wild-type retina is absent in the mutants. Despite the lack of lamination, at least seven retinal cell types differentiate in oko meduzy. The ome phenotype is already expressed in the retinal neuroepithelium affecting morphology of the neuroepithelial cells. Our experiments indicate that previously unknown cell-cell interactions are involved in development of the retinal neuroepithelial sheet. In genetically mosaic animals, cell-cell interactions are sufficient to rescue the phenotype of oko meduzy retinal neuroepithelial cells. These cell-cell interactions may play a critical role in the patterning events that lead to differentiation of distinct neuronal laminae in the vertebrate retina.

Animals↗
PubMed1998

Functional interactions of genes mediating convergent extension, knypek and trilobite, during the partitioning of the eye primordium in zebrafish.

Vertebrate eye development in the anterior region of the neural plate involves a series of inductive interactions dependent on the underlying prechordal plate and signals from the midline of the neural plate, including Hedgehog. The mechanisms controlling the spatiotemporal expression pattern of hedgehog genes are currently not understood. Cyclopia is observed in trilobite (tri) and knypek (kny) mutants with affected convergent extension of the embryonic axis during gastrulation. Here, we demonstrate that tri mutants show a high frequency of partial or complete cyclopia, kny mutants exhibit cyclopia infrequently, while knym119 trim209 double-mutant embryos have dramatically reduced convergent extension and are completely cyclopic. We analyzed the relationships between the convergent extension defect, the expression of hedgehog and prechordal plate genes, and the formation of cyclopia in knym119 and trim209 mutants. Our results correlate the cyclopia phenotype with the abnormal location of hh-expressing cells with respect to the optic primordium. We show that cyclopia in these mutants is not due to an incompetence of tri and kny cells to respond to Hedgehog signaling. Rather, it is a consequence of exceeding a critical distance (>40-50 micrometer) between hedgehog-expressing cells and the prospective eye field. We hypothesize that at this distance, midline cells are not in an appropriate position to physically separate the eye field and that HH and other signals do not reach the appropriate target cells. Furthermore, tri and kny have overlapping functions in establishing proper alignment of the anterior neural plate and midline cells expressing shh and twhh genes when the partitioning of the eye primordium takes place.

Animals↗
PubMed1998

Doses in critical organs during total body irradiation before bone marrow transplantation.

OBJECTIVES: Modification of the total body irradiation technique before bone marrow transplantation has been implemented to improve uniformity of the dose inside the irradiated body and to obtain appropriate reduction in doses in critical organs. METHODS: The total dose of 12.6 Gy was delivered with the use of a combination of the following fields: lateral, anterior-posterior, field to mediastinum, an electron field to the thorax wall and field to coxa. The doses were calculated for ten transverse body sections. Methods of dose reductions in critical regions by splitting different fields were proposed. RESULTS: The resulting dose deviations inside the body with the combination of all the implemented fields varied from 12.5 Gy to 13.6 Gy along the midline and from 12.4 Gy to 13.7 Gy outside the midline. Doses to the lungs were reduced to 8.6 Gy divided Gy 9.4 Gy, whereas those in the thorax wall and mediastinum were increased to 12.7 Gy divided by 13.5 Gy respectively. Doses to lenses were 12.9 Gy divided by 13.1 Gy.

Body Burden↗
PubMed1996

Mutations affecting development of the notochord in zebrafish.

The notochord is critical for the normal development of vertebrate embryos. It serves both as the major skeletal element of the embryo and as a signaling source for the establishment of pattern within the neurectoderm, the paraxial mesoderm and other tissues. In a large-scale systematic screen of mutations affecting embryogenesis in zebrafish we identified 65 mutations that fall into 29 complementation groups, each leading to a defect in the formation and/or maintenance of the notochord. These mutations produce phenotypic abnormalities at numerous stages of notochord development, thereby establishing a phenotypic pathway, which in turn suggests a genetic pathway for the development of the notochord. Perturbations within adjacent tissues in mutant embryos further indicate the importance of notochord-derived signals for patterning within the embryo and suggest that these mutations will yield additional insight into the cues that regulate these patterning processes.

Animals↗
PubMed1996

Mutations affecting the development of the embryonic zebrafish brain.

In a large scale mutagenesis screen for embryonic mutants in zebrafish, we have identified 63 mutations in 24 loci affecting the morphogenesis of the zebrafish brain. The expression of marker genes and the integrity of the axonal scaffold have been studied to investigate abnormalities in regionalization, neurogenesis and axonogenesis in the brain. Mutants can be broadly classified into two groups, one affecting regionalization along the anterior-posterior or dorsal-ventral axis, and the other affecting general features of brain morphology. The first group includes one locus that is required to generate the anlage of the midbrain-hindbrain boundary region at the beginning of somitogenesis. Four loci were identified that affect dorsal-ventral patterning of the brain, including the previously described cyclops locus. Mutant embryos of this class show a reduction of ventral neuroectodermal structures and variable fusion of the eyes. The second group includes a large class of mutations affecting the formation of brain ventricles. Analysis of this class reveals the requirement of a functional cardiovascular system for ventricle enlargement during embryogenesis. Mutations in one locus lead to the formation of supernumerary primary neurons, a phenotype reminiscent of neurogenic mutants in Drosophila. Other mutant phenotypes described here range from abnormalities in the fasciculation and outgrowth of axons to defects in the diameter of the neural tube. The identified loci establish the genetic foundation for a further analysis of the development of the zebrafish embryonic brain.

Animals↗
PubMed1996

Mutations affecting neural survival in the zebrafish Danio rerio.

Programmed cell death is a prominent feature of normal animal development. During neurogenesis, naturally occurring cell death is a mechanism to eliminate neurons that fail to make appropriate connections. To prevent accidental cell death, mechanisms that trigger programmed cell death, as well as the genetic components of the cell death program, are tightly controlled. In a large-scale mutagenesis screen for embryonic lethal mutations in zebrafish Danio rerio we have found 481 mutations with a neural degeneration phenotype. Here, we present 50 mutations that fall into two classes (termed spacehead and fala-like) that are characterized by two main features: first, they appear to affect cell survival primarily within the neuroectodermal lineages during somitogenesis, and second, they show an altered brain morphology at or before 28 hours of development. Evidence for the specificity of cell death within the central nervous system comes from visual inspection of dying cells and analysis of DNA fragmentation, a process associated with apoptotic cell death. In mutants, the level of dying cells is significantly increased in brain and spinal cord. Furthermore, at the end of somitogenesis, the cell count of radial glia and trigeminal neurons is reduced in some mutants of the spacehead class. A variety of neurodegenerative disorders in mouse and humans have been associated with abnormal levels of programmed cell death within the central nervous system. The mutations presented here might provide a genetic framework to aid in the understanding of the etiology of degenerative and physiological disorders within the CNS and the activation of inappropriate programmed cell death.

Animals↗
PubMed1996

Mutations affecting development of the zebrafish retina.

In a large scale screen for genetic defects in zebrafish embryogenesis we identified 49 mutations affecting development of the retina. Based on analysis of living embryos as well as histological sections, we grouped the isolated mutations into six phenotypic categories. (1) Mutations in three loci result in a loss of wild-type laminar pattern of the neural retina. (2) Defects in four loci lead to an abnormal specification of the eye anlagen. Only one eye frequently forms in this class of mutants. (3) Seven loci predominantly affect development of the outer retinal layers. Mutants in this category display cell loss mainly in the photoreceptor cell layer. (4) Nine mutations cause retardation of eye growth without any other obvious abnormalities in the retina. (5) A group of twelve mutations is characterized by nonspecific retinal degeneration. (6) Four mutations display retinal degeneration associated with a pigmentation defect. Finally, two mutations, one with absence of the ventral retina and one with an eye-specific pigmentation defect, are not classified in any of the above groups. The identified mutations affect numerous aspects of eye development, including: specification of the eye anlage, growth rate of the optic cup, establishment of retinal stratification, specification or differentiation of retinal neurons and formation of the dorsoventral axis in the developing eye.

Animals↗