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D Zivkovic

Publications and source records attributed to D Zivkovic.

At least 19 recordsLinked to original sources
PubMed2007

Acute scrotal pain in children--ten years' experience.

INTRODUCTION: Acute scrotal pain sometimes requires prompt surgical intervention and therefore accurate diagnosis of different etiologies of acute scrotal pain has great therapeutical and prognostic significance. The aim of this study was to analyze the incidence, symptomatology and results of treatment of acute scrotal pain in children. MATERIAL AND METHOD: The study included patients hospitalized at the Pediatric Surgery Clinic with a diagnosis of acute scrotal pain. We retrospectively analyzed anamnestic data (age of patient and duration of anamnesis prior to admission), clinical parameters obtained during physical examination, mode of treatment (operative or medical), intraoperative findings and (postoperative) treatment. RESULTS: The study included 256 patients with acute scrotal pain, aged from several hours up to 17 years of age (average 9.73 years). The average duration of symptoms prior to admission was 56.74 h. Acute epididymitis was diagnosed in 110 patients (43.0%), torsion of the testicular appendage in 104 patients (40.6%), torsion of the testis in 30 patients (11.7%) and other pathologies in another 12 patients. 166 patients (64.8%) underwent surgery, 42 patients with orchiepididymitis (38.2%), 92 patients with torsion of the testicular appendage (88.5%), and 16.6% of the patients with other pathologies. 22 patients with torsion of the testis underwent surgery (73.3%), while the rest of the 8 patients underwent manual detorquation of the testis. CONCLUSION: Regardless of the etiology of the acute scrotal pain, it is of great importance that the patient seeks medical assistance promptly. It is therefore important to educate the parents and patients about the problems related to acute scrotal pain.

Acute Disease↗
PubMed2006

Endoscopic correction of vesicoureteric reflux--our thirteen years' experience.

AIM OF THE STUDY: We review our thirteen years' experience with the endoscopic treatment of primary vesicoureteric reflux (VUR). METHODS: We retrospectively reviewed the charts of 81 patients with primary vesicoureteric reflux who were treated endoscopically. The study included 61 girls and 20 boys aged 3 - 15 years. Twenty-eight patients had unilateral reflux, and 53 patients had bilateral reflux. Endoscopic correction with Teflon paste was done in 64 patients, and endoscopic treatment with Deflux was done in 17 patients. A total of 134 ureters were treated. RESULTS AND CONCLUSION: Reflux was corrected in 87 ureters (64.9 %) after the first injection. The second injection resolved reflux in an additional 20 ureters (14.9 %). Reimplantation was necessary in 4 patients (4.9 %). Overall success rate of the endoscopic treatment was 85.0 %. Reflux was completely absent in 79.8 % of the treated patients, and 5.2 % of the patients had a decreased grade of reflux after the procedure. Treatment was unsuccessful in 3.0 % of the patients. In seven patients spontaneous resolution of the persisting reflux occurred. Endoscopic correction should be performed in all patients with grade two, three and four reflux. Grade one reflux should be treated conservatively, and grade five reflux should be treated surgically. Since Deflux is a biodegradable material, most of the patients should be treated bilaterally, even if they have only grade one reflux. Endoscopic correction of primary vesicoureteric reflux is an easy, simple, fast and safe procedure that, in most cases, prevents regurgitation of urine from the bladder to the upper parts of the urinary system.

Adolescent↗
PubMed2001

Ectopic Wnt signal determines the eyeless phenotype of zebrafish masterblind mutant.

masterblind (mbl) is a zebrafish mutation characterised by the absence or reduction in size of the telencephalon, optic vesicles and olfactory placodes. We show that inhibition of Gsk3beta in zebrafish embryos either by overexpression of dominant negative dn gsk3beta mRNA or by lithium treatment after the midblastula transition phenocopies mbl. The loss of anterior neural tissue in mbl and lithium-treated embryos is preceded by posteriorization of presumptive anterior neuroectoderm during gastrulation, which is evident from the anterior shift of marker genes Otx2 and Wnt1. Heterozygous mbl embryos showed increased sensitivity to inhibition of GSK3beta by lithium or dn Xgsk3beta that led to the loss of eyes. Overexpression of gsk3beta mRNA rescued eyes and the wild-type fgf8 expression of homozygous mbl embryos. emx1 that delineates the telencephalon is expanded and shifted ventroanteriorly in mbl embryos. In contrast to fgf8, the emx1 expression domain was not restored upon overexpression of gsk3beta mRNA. These experiments place mbl as an antagonist of the Wnt pathway in parallel or upstream of the complex consisting of Axin, APC and Gsk3beta that binds and phosphorylates beta-catenin, thereby destabilising it. mbl maps on LG 3 close to a candidate gene axin1. In mbl we detected a point mutation in the conserved minimal Gsk3beta-binding domain of axin1 leading to a leucine to glutamine substitution at position 399. Overexpression of wild-type axin1 mRNA rescued mbl completely, demonstrating that mutant axin1 is responsible for the mutant phenotype. Overexpression of mutant L399Q axin1 in wild-type embryos resulted in a dose-dependent dominant negative activity as demonstrated by the loss of telencephalon and eyes. We suggest that the function of Axin1/Mbl protein is to antagonise the Wnt signal and in doing so to establish and maintain the most anterior CNS. Our findings provide new insights into the mechanisms by which the Wnt pathway generates anteroposterior polarity of the neural plate.

Animals↗
PubMed2000

Vasa protein expression and localization in the zebrafish.

Primordial germ cell (PGC) development in the zebrafish is poorly understood. The expression of vasa RNA, the only molecular marker so far found to be expressed in fish PGCs, suggests its function in the establishment of the germline. The protein product of vasa is present throughout the life cycle in the germline of Drosophila, Caenorhabditis and Xenopus. The expression pattern of the Vasa protein in zebrafish, is still unresolved. We generated an anti-Vasa polyclonal antibody and show that it is maternally expressed initially throughout the embryo. Interestingly, from the two-cell- to the 1000-cell stage the protein is highly concentrated in two 'dots' near the center of the blastomeres and as such remains longest detectable in the animal pole blastomeres. The first distinct cell-specific expression occurs at 60% epiboly on one side of the blastoderm margin. The Vasa protein in the PGCs is organized in a subcellular granular-like conformation which is dynamic throughout development.

Animals↗
PubMed1999

Characterization of zebrafish primordial germ cells: morphology and early distribution of vasa RNA.

Research into germ line development is of conceptual and biotechnologic importance. In this study, we used morphology at the level of light and electron microscope to characterize the primordial germ cells (PGCs) of the zebrafish throughout embryonic and larval development. The study was complemented by the detailed analysis of mRNA expression of a putative germ line marker vasa. By morphology alone PGCs were identified at the earliest at the 5-somite stage in the peripheral endoderm in contact with the yolk syncytial layer. Subsequently, they move from lateral to medial positions into the median mesoderm and from there by means of the dorsal mesentery into the gonadal anlage at day 5 postfertilization (pf), to establish gonads with mesenchymal cells by day 9 pf. Ultrastructural analysis of the 4-day-old zebrafish larvae demonstrates the presence of the germ line-specific structures, nuage, and annulate lamellae. vasa RNA-positive cells can be followed during zebrafish embryogenesis from the 32-cell stage onward (Yoon et al., 1997). Upon completion of gastrulation, the RNA is exclusively present in the cells of the hypoblast, which as a consequence of convergence and extension movements first arrange themselves in a V-shaped string-like conformation to end up, by late somitogenesis, as a string of cells on each side of the midline. We show that the localization of maternal vasa RNA in the ovary changes from cytoplasmic, in the previtellogenic oocytes, to cortical in the vitellogenic oocytes, to concentrate at the boundary of the yolk and cytoplasm in the one cell stage zygote. These results demonstrate that the cortical vasa RNA localization precedes its cleavage furrow-associated localization in the embryos and is presumably cytoskeleton dependent. vasa RNA localization changes from asymmetric subcellular at the sphere stage, to become entirely cytoplasmic at the dome stage. These data suggest a close resemblance in modes of segregation of the germ plasma in the frog and vasa mRNA in the fish during cleavage stages. Based on the significantly larger size and the stereotype and similar position of morphologically distinct cells, presumed to be PGCs, and their vasa RNA-positive counterparts, we conclude that vasa RNA-positive cells are the PGCs and vasa RNA represents a definitive germ line marker in the fish. Dev Dyn 1999;216:153-167.

Animals↗
PubMed1999

Germ line development in fishes.

Classical work on germ cells in fishes has dealt with three main issues; their embryonic origin, the proliferation, and migration pathway during embryonic and larval development. Until recently, primordial germ cells (PGCs) have been studied in a number of fishes using morphological criteria only. The identification of the Drosophila vasa homolog gene of zebrafish now allows comparison of these morphological data with vasa RNA expression patterns in zebrafish. Teleost PGCs can be distinguished from somatic cells by their distinct morphology, at the earliest during gastrulation, and in most fishes their number varies between 10 and 30 during pregonial development. Mitosis is generally not observed in PGCs at extragonadal locations, whereas they are mitotically active once at the gonadal ridges. During gastrulation, PGCs appear to translocate from the epiblast to the hypoblast and during somitogenesis they are found associated with the most peripheral yolk syncitial layer (YSL). From the peripheral YSL they migrate through the median mesoderm into the dorsal mesoderm and then to the dorsal mesentery, where they establish the gonad primordia with mesenchymal cells. Vasa RNA positive cells, the PGCs of the zebrafish conform to these general observations. Interestingly, classical descriptive and experimental data can now be reevaluated using vasa as a molecular marker of the fish germ line. The power of zebrafish genetics together with possibilities of experimental embryology should accelerate research on aspects of vertebrate germ line development such as PGC migration, division and apoptosis, as well as (in) fertility. The present review summarizes some of the classical data on germ line development in fishes in relation to recent data on vasa expression in zebrafish and compares these findings, where appropriate, with those in other model organisms. Special emphasis is placed on vasa gene expression as a potential universal germ line marker and suggestions are made for novel, zebrafish specific approaches to investigate the vertebrate germ line.

Animals↗
PubMed1998

Comparison of sequence and function of the Oct-6 genes in zebrafish, chicken and mouse.

To examine the role of the Oct-6 gene in Schwann cell differentiation we have cloned and characterized the chicken and zebrafish homologues of the mouse Oct-6 gene. While highly homologous in the Pit1-Oct1/2-Unc86 (POU) domain, sequence similarities are limited outside this domain. Both genes are intronless and both proteins lack the amino acid repeats that are a characteristic feature of the mammalian Oct-6 proteins. However as in mammals, the aminoterminal parts of the chicken and zebrafish Oct-6 proteins are essential for transactivation of octamer containing promoters. By immunohistochemistry we have found that the chicken Oct-6 protein is expressed in late embryonic ensheathing Schwann cells of the sciatic nerve and is rapidly downregulated when myelination proceeds. This expression profile in glial cells is identical to that in the mouse and rat. Furthermore the zebrafish Oct-6 homolog is expressed in the posterior lateral nerve at a time when it contains actively myelinating Schwann cells. Thus despite extensive primary sequence divergence among the vertebrate Oct-6 proteins, the expression of the chicken and zebrafish Oct-6 proteins is consistent with the notion that Oct-6 functions as a 'competence factor' in promyelin cells to execute the myelination program.

Amino Acid Sequence↗
PubMed1998

Protein kinase A is involved in the induction of early mesodermal marker genes by activin.

In this study we have investigated the role of cAMP-dependent protein kinase A (PKA) in the induction of the early mesodermal marker genes goosecoid and no tail by activin in zebrafish embryos. We show that upon treatment with activin, zebrafish blastula cells exhibit a rapid and transient increase in PKA activity. In these cells, activin rapidly induces the expression of the immediate early response genes goosecoid and no tail. Stimulation and inhibition of PKA by activin, respectively, enhances and reduces the induction of goosecoid and no tail mRNA expression. Similar effects of PKA stimulation and inhibition on the induction by activin of a 1.8 kb zebrafish goosecoid promoter construct were observed. The induction by activin of a fragment of the zebrafish goosecoid promoter that mediates an immediate early response to activin is blocked by inhibition of PKA. Activation of PKA alone has no effect in these experiments. Finally, inhibition of PKA in whole embryos by overexpression of a dominant negative regulatory subunit of PKA reduces the expression of no tail and goosecoid, whereas the expression of even-skippedl remains unaltered. Overexpression of the catalytic subunit of PKA in embryos does not affect expression of goosecoid, no tail or even-skippedl. These data show that in dissociated blastulae, PKA is required, but not sufficient for activin signalling towards induction of goosecoid and no tail. In intact zebrafish embryos, PKA contributes to induction of goosecoid and no tail, although it is not required or sufficient.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1998

Hormone-inducible expression of secreted factors in zebrafish embryos.

The study of gene function at later stages of embryonic development by overexpression experiments is often complicated by genes exerting different functions at multiple stages of development, which renders analysis of stage-specific effects difficult. To address this problem an inducible expression system that supports timed expression of essentially any protein, including secreted proteins was designed. The system is based on a two step mechanism. A glucocorticoid inducible, Gal4-site binding chimeric transcription factor is expressed ubiquitously, whereas a gene of interest is placed under the control of a Gal4-site driven promoter. Treatment of zebrafish embryos injected with such constructs with the synthetic glucocorticoid dexamethasone results in readily detectable reporter activity within 3 h. The system was tested with induced expression of Xactivin(beta)B and X(wnt), which both were shown to induce morphological abnormalities, as well as alterations in the expression patterns of goosecoid and otx2, respectively. Coinjection of an inducible lacZ reporter vector served as an indicator for expressing cells in embryos. The present results demonstrate that this is a versatile inducible expression system for use in vertebrate embryos, that also supports expression of secreted proteins.

Activins↗
PubMed1997

Domains of retinoid signalling and neurectodermal expression of zebrafish otx1 and goosecoid are mutually exclusive.

Retinoid signalling plays an important role in embryonic pattern formation. Excess of retinoic acid during gastrulation results in axial defects in vertebrate embryos, suggesting that retinoids are involved in early anteroposterior patterning. To study retinoid signalling in zebrafish embryos, we developed a novel method to detect endogenous retinoids in situ in embryos, using a fusion protein of the ligand inducible transactivation domain of a retinoic acid receptor and a heterologous DNA binding domain. Using this method, we show that retinoid signalling is localized in zebrafish embryos in the region of the embryonic shield, and towards the end of gastrulation in a posterior dorsal domain. To investigate the relationships between the spatial distribution of retinoid signalling and the regulation of retinoid target genes, we studied the downregulation by retinoic acid of two genes expressed in anterior regions of the embryo, goosecoid and otx1. These experiments show that expression of both genes is strongly downregulated in the anterior neurectoderm of zebrafish embryos treated with retinoic acid, whereas mesendodermal expression is only mildly affected. Interestingly, a significant downregulation of goosecoid expression by retinoic acid was observed only during midgastrulation but not in earlier stages. In agreement with these results, spatial expression of goosecoid and otx1 does not overlap with the region of retinoid signalling in the late gastrula. Our data support the hypothesis that a localized retinoid signal is involved in axial patterning during early development, at least in part through the repression of anterior genes in posterior regions of the embryo. Furthermore, our data suggest that the action of retinoids is spatially as well as temporally regulated in the developing embryo.

Animals↗
PubMed1996

Active complex formation of type I and type II activin and TGF beta receptors in vivo as studied by overexpression in zebrafish embryos.

We have investigated the involvement of activin receptors and TGF beta type I receptor in zebrafish development. Overexpression of either full-length or a truncated form of mouse ActR-IIA interferes with the development. Different splice variants of mouse ActR-IIB have distinct effects; ActR-IIB4 induces abnormal embryos, whereas ActR-IIB2 does not. Activin and TGF beta type I receptors can induce axis duplications. Co-expression of ActR-IA or ActR-IB with the type II activin receptors results in a synergistic increase of the frequency of axis duplication. Moreover, ActR-IIB2 is synergistic with ActR-IA and ActR-IB, demonstrating that ActR-IIB2 can interact with the zebrafish ligand. Overexpression of TGF beta R-I with ActR-IIA or ActR IIB4 results in a synergistic increase in frequency of abnormal embryos, whereas in combination with ActR-IIB2 no such increase occurs.

Activins↗
PubMed1996

Regulation of the zebrafish goosecoid promoter by mesoderm inducing factors and Xwnt1.

Goosecoid is a homeobox gene that is expressed as an immediate early response to mesoderm induction by activin. We have investigated the induction of the zebrafish goosecoid promoter by the mesoderm inducing factors activin and basic fibroblast growth factor (bFGF) in dissociated zebrafish blastula cells, as well as by different wnts in intact embryos. Activin induces promoter activity, while bFGF shows a cooperative effect with activin. We have identified two enhancer elements that are functional in the induction of the goosecoid promoter. A distal element confers activin responsiveness to a heterologous promoter in the absence of de novo protein synthesis, whereas a proximal element responds only to a combination of activin and bFGF. Deletion experiments show that both elements are important for full induction by activin. Nuclear proteins that bind to these elements are expressed in blastula embryos, and competition experiments show that an octamer site in the activin responsive distal element is specifically bound, suggesting a role for an octamer binding factor in the regulation of goosecoid expression by activin. Experiments in intact embryos reveal that the proximal element contains sequences that respond to Xwnt1, but not to Xwnt5c. Furthermore, we show that the distal element is active in a confined dorsal domain in embryos and responds to overexpression of activin in vivo, as well as to dorsalization by lithium. The distal element is to our knowledge the first enhancer element identified that mediates the induction of a mesodermal gene by activin.

Activins↗
PubMed1995

Ionic responses to epidermal growth factor in zebrafish cells.

In mammalian cells the earliest cellular responses to epidermal growth factor (EGF) have been extensively characterized and include a number of ionic changes, such as a transient increase in calcium influx and a membrane hyperpolarization. The physiological significance of these ionic changes is uncertain. Therefore it is important to establish whether such ionic changes have been conserved during evolution, as this would point to an indispensable role for ionic signaling in growth factor action. We have isolated several embryonic zebrafish cell lines and studied the ionic events elicited by application of EGF to these cells. Using whole cell patch clamp recording, we show that activation of these receptors induces an outward current, which is dependent on the influx of extracellular calcium. The EGF-induced transmembrane currents were abolished by preincubation with different inhibitors of leukotriene synthesis, a feature of EGF-provoked ionic signaling which is also observed in mammalian cell lines. Therefore, these results demonstrate that ionic signaling, as well as the underlying second-messenger systems, is not restricted to mammalian cells, indicating that ionic signaling is of importance in growth factor action.

Animals↗
PubMed1994

Effects of retinoic acid on the expression of retinoic acid receptors during zebrafish embryogenesis.

The cDNAs encoding the zebrafish homologs of retinoic acid receptor alpha(zRAR alpha) and gamma (zRAR gamma) were isolated and their expression studied in normal and retinoic acid (RA) treated embryos. Expression boundaries in the central nervous system are clearly different from those observed in the mouse, which can only partly be explained by morphogenetic differences. Treatment of embryos with RA induces ectopic zRAR gamma expression in anterior brain structures and both zRAR alpha and zRAR gamma expression in the eyes. Furthermore, striking differences occur in the zRAR gamma expression pattern in pharyngeal arch mesenchyme. Since the development of all of these structures has been shown to be affected by exogenous RA, our data suggest a role for zRAR alpha and zRAR gamma in the establishment of the RA phenotype in zebrafish.

Amino Acid Sequence↗
PubMed1993

Polar ionic currents around embryos of Lymnaea stagnalis during gastrulation and organogenesis.

Embryos of Lymnaea stagnalis generate ionic currents which can be measured with the vibrating probe. Here we investigated the presence and origin of the currents during late embryonic development. During gastrulation the current pattern correlates with the animal-vegetal polarity and during organogenesis it is correlated to the newly formed antero-posterior axis. The origin of the ionic currents was studied by inhibition of the Na+/K(+)-pump with ouabain and by enzyme-cytochemical detection of the Ca(2+)-pump. Ouabain treatment resulted in a reduced current density around the embryo, indicating that the Na+/K(+)-pump contributes significantly to the net current. The Ca(2+)-pump was found to be localized in the vegetal blastomeres during gastrulation and in the larval kidney during organogenesis. It seems likely that this Ca(2+)-pump renders only a minor contribution to the net current in late embryonic development. Ionic currents have now been described in Lymnaea from the uncleaved egg up to the juvenile snail. During this period the overall current pattern changes only twice, demonstrating that the voltage gradient generated by the embryo remains stable during prolonged periods in development.

Animals↗
PubMed1993

[Tuberculosis of the tongue in chronic hematogenous lung tuberculosis].

According to epidemiological data pulmonary and extrapulmonary tuberculosis even today represents a significant socio-medical problem. Tongue tuberculosis is rare and has been described in single cases only. In our clinic a patient suffering from tongue tuberculosis and hematogenously spreading chronic pulmonary tuberculosis was treated for the first time. The diagnosis was made by means of biopsy and pathohistological examination. The tongue lesions on account of rich vascularisation reacted very quickly to the antituberculous therapy, and the pulmonary alterations regressed considerably so that the patient could be dismissed to policlinical treatment.

Antitubercular Agents↗
PubMed1989

Monitoring of naturally acquired and artificially induced immunity to Amblyomma variegatum and Rhipicephalus appendiculatus ticks under field and laboratory conditions.

The ability of rabbits, goats and cattle to acquire immunity to the ixodid ticks Amblyomma variegatum and Rhipicephalus appendiculatus was studied under laboratory and field conditions. Rabbits were successfully immunized with crude salivary gland extract (SGE) and midgut extract (ME) obtained from flat or partly fed female R. appendiculatus ticks. The lowest numbers of larvae were produced by females fed on rabbits immunized with unfed midgut extract. Similar reductions in larval production could be induced after three infestations of rabbits with adult R. appendiculatus. Also, successive feedings of nymphs of R. appendiculatus on rabbits resulted in significantly reduced engorgement weights. Skin testing with SGE induced delayed-type hypersensitivity reactions, which could be correlated with immunity to R. appendiculatus in rabbits. Moreover, circulating antibodies were detected in rabbits with an ELISA using SGE of R. appendiculatus. Immunity to A. variegatum nymphs could be induced in rabbits by repeated infestations, but this failed in goats. Immunization of goats with midgut extract from adult A. variegatum did not protect against subsequent nymphal challenge, but strong skin reactions were noticed when adults ticks fed on immunized goats. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of SGE and ME from A. variegatum revealed the presence of 48 protein bands in SGE and 29 bands in midgut extract. Western blotting employing serum from a rabbit immune to R. appendiculatus recognized a number of bands in SGE from R. appendiculatus, but also in SGE of A. variegatum. Immunity acquired by cattle to ixodid tick infestations under field conditions was monitored by skin testing with SGE and western blot analysis. In general, cattle with the lowest tick numbers manifested the strongest delayed-type hypersensitivity responses. Finally, western blot analysis employing sera from tick-infested and tick-naive cattle could not be related to actual immune status.

Animals↗