Isoflurane post-conditioning influences myocardial infarct healing in rats.

Isoflurane post-conditioning causes an early increase in cardiac progenitor cells; however, during the chronic phase of infarct healing, the number was smaller compared to control, which suggests a positive effect on infarct scar maturity. Myofibroblasts participate in early phase infarct contraction, but their number is small in a mature scar. We investigated whether isoflurane post-conditioning stimulates differentiation of progenitor cells to myofibroblasts and to verify our hypothesis that isoflurane post-conditioning improves maturation of a myocardial scar. Ischemia was induced for 30 min in female rats. From the last 5 min of ischemia until 10 min into reperfusion, the isoflurane group received 1.5% isoflurane, while the control group received only an air-oxygen mixture. Infarct area was analyzed using immunohistochemistry. During the subacute phase of infarct healing, the number of myofibroblasts was greater in isoflurane-treated animals than in the control group. During the chronic phase of infarct healing, post-conditioned animals exhibited fewer myofibroblasts compared to control animals, even those derived from progenitor cells, i.e., α-smooth actin-nestin positive cells. In addition, isoflurane post-conditioning resulted in higher percentage of mature blood vessels compared to control animals. The myocardium of the isoflurane treated animals exhibited more myofibroblasts in granulation tissue compared to control animals. The smaller number of myofibroblasts together with the greater number of mature blood vessels during the chronic phase of healing demonstrated faster healing of the infarct area of isoflurane-treated animals compared to control animals.

Apoptotic pathways and stemness in the colorectal epithelium and lamina propria mucosae during the human embryogenesis and carcinogenesis.

AIM: Programmed cell death is essential both during normal organ development and carcinogenesis. In this study we immunohistochemically analyzed different pathways of cell death in 11 human conceptuses 5th-10th-weeks old, 10 low and high grade colorectal carcinomas (CRC), and 10 normal colon samples by using markers for apoptosis (caspase-3, AIF, TUNEL), proliferation (Ki-67) and stemness (Oct-4). RESULTS: Between the 5th and 10th week of development, caspase-3 and AIF showed moderate-to-strong expression in the developing gut wall. During development, number of caspase-3-reactive cells decreased, while AIF increased. While healthy colorectal control and low grade CRC showed moderate expression of caspase-3 and AIF, in high grade CRC their expression was strong. Tumor tissues displayed significantly higher number of positive cells than controls. Occasionally, co-expressing of both markers characterized dying cells. In developing colon, Oct-4 and Ki-67 showed moderate-to-strong expression, while some cells co-expressed both markers. Their number decreased in the epithelium and increased in the connective tissue in later development. Healthy colorectal control displayed moderate Ki-67 and mild Oct-4 reactivity. While in low-grade CRC expression Oct-4 and Ki-67 was moderate, in high-grade CRC their expression was strong. Although Oct-4 and TUNEL occasionally co-expressed in all samples, both grades of CRC contained cells that were Oct-4 positive only. CONCLUSION: Our study revealed two different parallel pathways of cell death, with characteristic increase of AIF-mediated apoptosis when compared to caspase-3, and presence of stemness cells both during colon development and carcinogenesis. These finding might be considered as important diagnostic, survival and CRC therapy predictors.

Expression pattern of PAX3 and PAX6 genes during human embryogenesis.

The expression of human PAX6 and PAX3 genes was investigated in 6 human 6-9 week old conceptuses by in situ hybridization. During human embryonic development (6-8 developmental weeks), PAX6 was expressed in the ventricular zone of telencephalon and diencephalon, and in the ventricular and ventral intermediate zones of medulla oblongata and spinal cord. PAX6 expression was detected in both layers of the optic cup, optic stalk and prospective corneal epithelium. Infundibulum and Rathke's pouch of the pituitary gland showed hybridization signal as well. In the early fetal period (9 developmental weeks) PAX6 expression increased in the spinal cord. In the eye, hybridization signal characterized the corneal and lens epithelium, pigmented and neural retina, while it was missing in the optic disc and nerve. In a 6-week human embryo, transcripts of PAX3 gene were observed in the ventricular zone at the mesencephalic-rhombencephalic border, and in the dorsal part of the ventricular zone and the roof plate of the medulla oblongata and the spinal cord. In the 8-9-week fetus, PAX3 expression increased in dorsal parts of the spinal cord. PAX3 characterized ectomesenchyme of the upper and lower jaw, and tongue. During early human development, PAX6 and PAX3 genes seem to be involved in the brain regionalization and establishment of dorso-ventral polarity of the spinal cord. Additionally, PAX6 participates in organogenesis of the eye and the pituitary gland, and PAX3 in the development of face and neck mesenchyme.

Expression of PAX2 gene during human development.

The expression of human paired-box-containing PAX2 gene was examined in 7 human conceptuses 6 to 9 weeks old by in situ hybridization. The embryos were collected after legal abortions, embedded in paraffin, serially cut in transversal direction and treated with S35 labeled probe for PAX2. In the neural tube of 6-week embryos, PAX2 was expressed in the outer part of the ventricular zone on both sides of the sulcus limitans. At later stages, it was expressed in the intermediate zone of the spinal cord, both in alar and basal plates except in the region of motor neuroblasts. In the brain, expression of PAX2 extended from mesencephalic-rhombencephalic border along the entire rhombencephalon in a manner similar to that described for the spinal cord. Expression of PAX2 gene in the eye was seen in the optic cup and stalk, and later in the optic disc and nerve. In the ear, expression was restricted to the part of the otic vesicle flanking the neural tube and later to the utricle and cochlea. Expression of PAX2 was observed in developing kidneys as well. During human development PAX2 has a spatially restricted expression along the compartmental boundaries of the neural tube, and within developing eye, ear and kidneys. Differentiation of those organs seems to be mediated by PAX2 gene at the defined stages of human development.

Effect of maternal hyperoxygenation on experimentally produced uteroplacental insufficiency in the rat.

The paper examines the effects of maternal hyperoxygenation on uteroplacental insufficiency produced by ligation of the uterine artery. Maternal hyperoxygenation did not significantly affect experimentally produced growth retardation or survival of the fetuses from the ligated horn. Analysis of the vascular anatomy revealed that additional oxygen improves the survival of fetuses compromised by uteroplacental insufficiency only in the presence of anastomosis between the uterine and ovarian arteries. The study demonstrated the importance of that anastomosis in evaluating the results obtained by this experimental model.

Morphological and immunohistochemical characteristics of axial structures in the transitory human tail.

Ultrastructural relationships between the notochord and neighboring spinal cord were examined during the regression of the human tail. Also, the presence of certain extracellular matrix components in the notochord was immuno-histochemically analysed in the 4th to 12th week old embryos. At the early stages, a close apposition of the notochord to the spinal cord exists in the entire tail region. The external surface of both structures is covered with a continuous basal lamina. The narrow tissue interspace contains interdigitating cell processes and both amorphous and fibrillar extracellular matrix material. With advancing embryonic age, separation of the two structures occurs in craniocaudal direction and the widening interspace becomes occupied by mesenchymal cells. During tail regression and spinal cord retraction, the appearance of large intercellular spaces and cell degeneration takes place in both tissues. With age, the extracellular matrix of the notochord, predominantly the perinotochordal sheath, increases in amount and antigenic complexity. While the intensity of laminin, collagen type IV and type III expression rises continuously during the period examined, the expression of fibronectin begins first at later stages, after the separation of the notochord from the spinal cord. The possible developmental significance of the described phenomena in the regression of the posterior end of the human tail remains to be elucidated.

Morphological diversity of dying cells during regression of the human tail.

During normal human development a number of transient structures form and subsequently regress completely. One of the most prominent structures that regress during development is the human tail. We report here a histological and ultrastructural study of cell death in the cranial and caudal (tail) parts of the neural tube in 4 to 6-week-old human embryos. Initially, the human tail is composed of tail bud mesenchyme which differentiates into caudal somites, secondary neural tube, notochord and tail gut. Later on, these structures gradually regress by cell death. During the investigated period, we observed two morphologically distinct types of dying cells. The well-described apoptotic type of cell death was observed only in the cranial neural tube that forms during primary neurulation. The other type of cell death characterized by necrotic morphology was observed in the tail mesenchyme and in the caudal neural tube that forms during secondary neurulation. This morphological diversity suggests that besides differences in origin and fate there are different mechanisms of developmental cell death between two parts of the human neural tube. We can speculate that the apoptotic type of cell death is associated with the precise control of cell numbers and that the other morphologically distinct type of cell death is responsible for the massive removal of transitory structures.

A nephron-sparing surgical procedure for Fraley's syndrome. A case report.

A 14.5-year-old girl with Fraley's syndrome, which caused left flank pain and massive haematuria with anaemia underwent left renal surgery. The infundibulum for the left upper calyx group was entrapped between the lower segmental renal artery and one branch of the renal vein. Despite other known surgical procedures, the surgeon explored the area around the entrapped infundibulum and resected the vein. Impression of the infundibulum disappeared, the dilatation of the upper calyces diminished, the pain was immediately relieved, and the haematuria stopped. In the two-year follow-up period the patient remained healthy, without haematuria or a subjective feeling of illness. The surgical treatment performed was successful, and it is also one of the most nephron-sparing procedures available.

Expression of cytokeratin 8, vimentin, syndecan-1 and Ki-67 during human tooth development.

Spatio-temporal immunolocalizations of cytokeratin 8 (CK8), vimentin, syndecan-1 and Ki-67 were analyzed in ten human incisors and canine tooth germs between the 7th and 20th developmental weeks. CK8 expression was mild to moderate in the epithelial tooth parts, while it shifted from absent or mild in its mesenchymal parts, but few cells, sparsely distributed throughout the tooth germ, strongly expressed CK8. As development progressed, CK8 expression increased to strong in preameloblasts, while expression of vimentin increased to moderate in the epithelial and mesenchymal tooth parts, particularly in the dental papilla and sac. Co-expression of CK8 and vimentin was observed in some parts of the tooth germ, and was increasing in the differentiating preameloblasts and preodontoblasts. Syndecan-1 showed characteristic shift of expression from epithelial to mesenchymal tooth parts, being particularly strong in dental papilla, sac and cervical loops, while co-expression of Ki-67/syndecan-1 was strong in the dental papilla. Our study demonstrated spatio-temporal expression and restricted co-expression of the investigated markers, indicating participation of CK8 and vimentin in cell proliferation and migration, and differentiation of preodontoblasts and preameloblasts. Our data also suggest involvement of syndecan-1 in morphogenesis of the developing tooth crown and cervical loops, and together with CK8 and vimentin in differentiation of preameloblasts and preodontoblasts.

The involvement of proliferation and apoptosis in the early human gonad development.

Distributions of the Ki-67, TP53, caspase-3 and AIFM1 markers were histologically investigated in the 5th to 9th week developing gonads of 12 human conceptuses using immunohistochemical and immunofluorescence methods. Between the 5th and 8th developmental week, proliferation gradually increased in the surface gonad epithelium (26-52 %) and stroma (19-42 %), but then slightly decreased in the surface epithelium (35 %) during the early foetal period. In medulla, low proliferation activity decreased from 15 to 12 % between the 7th and 9th week. At earliest stages of gonadal development, primordial germ cells (PGC) were only rarely TP53 positive. In the 7th and 8th week, almost all PGC-s displayed TP53 positivity, while their number decreased in early fetal period. During the investigated period, caspase-3 reactivity gradually decreased in surface epithelium, while it increased in PGC and medulla of developing gonad AIFM1-positivity first appeared in surface gonad epithelium and then predominantly in PCG-s while caspase-3 characterized different cell populations within the developing gonad. AIFM1 and caspase-3 co-localized only during the migration of PCG-s. The number and distribution of Ki-67, TP53, caspase-3 and AIFM1 reacting cells changed coincidently with development end regression of the sex cords in indifferent and early fetal gonad. Our results indicate that the number of PGC might be controlled by balance of TP53 and AIFM1, leading to caspase-3 independent cell death. Other cell populations are probably eliminated by caspase-3-dependent cell death. Both pathways of cell death seem to operate during early human gonad development, while their intensity varies depending on the cell type and developmental period analysed.

Involvement of pro-apoptotic and anti-apoptotic factors in the early development of the human pituitary gland.

The spatial and temporal pattern of appearance of pro-apoptotic caspase-3 and p53 proteins, and anti-apoptotic bcl-2 protein was investigated in the developing pituitary gland of 6 human embryos 5-8-weeks old, using morphological and immunohistochemical techniques. Their dynamic appearance was analyzed in the Rathke's pouch (future adenohypophysis), mesenchyme, and in the developing neurohypophysis. In the 5th and 6th week, caspase-3 positive cells appeared in the Rathke's pouch (5%) and stalk (11%), in the mesenchyme, but not in the neurohypophysis. In the 6th and 7th week, apoptotic cells were more numerous in the caudal part of the Rathke's pouch due to its separation from the oral epithelium. Pro-apoptotic p53 protein was detected in all parts of the pituitary gland throughout the investigated period. Nuclear condensations characterized cells positive to caspase-3 and p53 proteins. Apoptotic cells displayed condensations of nuclear chromatin on an ultrastructural level as well. While caspase-3 dependent pathway of cell death participated in morphogenesis of the adenohypophysis and associated connective tissue, p53-mediated apoptosis most likely participates in morphogenesis of all parts of the gland, including neurohypophysis. The anti-apoptotic bcl-2 protein was also detected in all parts of the developing gland. With advancing development, the positivity to bcl-2 protein increased in the cells of the adenohypophysis, while it decreased in the neurohypophysis. Bcl-2 protein probably prevented cell death in all parts of the gland and enhanced cell differentiation. The described pattern of appearance of the investigated pro-apoptotic and anti-apoptotic factors might be important for normal morphogenesis and function of the pituitary gland.

Role of the notochord in the development of cephalic structures in normal and anencephalic human fetuses.

Normal and anencephalic human conceptuses were analysed histologically to investigate the role of differentiation of the intracranial notochord and its relation to the formation of the basichondrocranium. We have examined 16 normal embryos and fetuses and 4 anencephalic fetuses. Each developmental stage of formation of the normal basichondrocranium presented specific morphological changes during the course of notochord depletion. In contrast with normal specimens, anencephalic fetuses presented malformations of the basichondrocranium which were always related to an abnormal position of the notochord. Macroscopical differences between craniorachischisis and cranioschisis in fetuses with anencephaly correlated with the existence of two histologically different degrees of malformation. In fetuses with craniorachischisis we found severe disturbances in the shape, position and ossification of the basichondrocranium and in the course of the intracranial notochord. In fetuses with cranioschisis the described disturbances of the basichondrocranium and intracranial notochord were mild. In addition, marked differences in affection of the central nervous system and the hypophysis were observed. These findings suggest different periods of dysmorphogenesis. Our results underline the importance of the chordal mesoderm in the differentiation for the formation of cephalic structures in Man.

Histological features of axial structures during embryonic and fetal stages of human craniorachischisis.

Histological characteristics of developing axial structures in human conceptuses with craniorachischisis were investigated during the embryonic and fetal periods and compared with normal samples. The morphological relationship of the notochord to the axial skeleton and neural tube was analyzed along cervical and thoracic vertebral segments using serial paraffin sections. The embryonic stage of malformed conceptuses disclosed a correlated affection of the notochord and vertebral column, as well as the overlying central nervous system. The degree of histological changes within the spinal cord depended on the level of the vertebral axis examined: completely unorganized nervous tissue was overlying cervical and upper thoracic vertebrae, while more caudally it resembled a normal spinal cord. During the fetal period the histological disturbances of all axial structures were more pronounced. Extensive notochordal branching was associated with the malformed formation and ossification of the vertebral column. At this stage we found no correlation of histological changes between the spinal cord and the mesodermally derived structures (notochord, vertebral column) along the cranio-caudal body extent, as neural tissue had completely transformed into area cerebrovasculosa. We speculate that our histological observations could be the result of primary affection of mesodermal structures during very early stages of development. Divergence in histological findings within axial structures between the embryonic and fetal periods support recent mutational investigations on animals.

Spinal cord-notochord relationship in normal human embryos and in a human embryo with double spinal cord.

Spinal cord-notochord relationship was analyzed histologically and immunohistochemically in normal human conceptuses between the 4-8 developmental weeks and in a 8-week embryo with double spinal cord. In the early 4-week embryo, the gradual closure of the neural tube along the cranio-caudal body axis was paralleled by the differentiation of the median hindge point cells at the ventral midline of the tube and by its temporary close association with the notochord. During the 5th-8th developmental weeks, the neuroepithelium differentiating into three distinct layers was accompanied by a solid, ventromedially positioned notochord. In the abnormal 8-week embryo, the additional spinal cord was located ventrolaterally from the vertebral column. Both spinal cords appeared bilaterally asymmetric, with their floor and roof plates irregularly formed. An abnormally enhanced pattern of neuroepithelial differentiation characterized their dorsal parts. Furthermore, additional spinal nerves and ganglia and an abnormal bony structure were associated with the spinal cord positioned outside the vertebral column. The underlying vertebral bodies were misshaped and contained scattered supernumerary groups of notochord cells. Our investigation underlines the importance of the notochord-neural tube relationship in the morphogenesis of the spinal cord. We suggest that the double spinal cord was induced by the split notochord.

Effects of hyperbaric oxygen on rat embryos.

The aim of the study was to investigate the toxic effects of hyperbaric oxygen (HBO) on rat embryos. Two groups of Fischer pregnant rats were exposed to oxygen at pressures of 324 and 426 kPa for 90 min per day for 5 consecutive days (8-12 days of gestation). The third group was exposed to normobaric oxygen for 12 h on the eighth day of gestation. Two control groups were used; the first was comprised of intact and the second of sham-treated animals. The HBO treatment did not significantly affect maternal weight gain or reduce litter size, nor did it induce any embryonic abnormalities. However, the fetal body weight was reduced and the placental weight increased in the groups exposed to HBO at pressures of 324 and 426 kPa. When female fetuses which had been exposed to oxygen at 324 or 426 kPa were compared to the intact control group, a reduction in wet weights of 9.2 (p < 0.05) and 12.1% (p < 0.01), respectively, was noted. Male fetuses exposed to oxygen at 324 and 426 kPa displayed a reduced body weight of 11.7 (p < 0.01) and 16.6% (p < 0.01), respectively. Placental weight was increased by 18.9 (p < 0.01) and 23.6% (p < 0.01) in the groups exposed to oxygen at 324 and 426 kPa, respectively. These data suggest that HBO, either at 324 or 426 kPa, is not potent at inducing malformations and that the largest embryotoxic effects are upon fetal body weight and placental weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Variations in the formation of the human caudal spinal cord.

Collection of 15 human embryos between 4-8 developmental weeks was used to histologically investigate variations in the development of the caudal part of the spinal cord and the neighboring axial organs (notochord and vertebral column). In the 4-week embryo, two types of neurulation were parallelly observed along the anteroposterior body axis: primary in the areas cranial to the neuroporus caudalis and secondary in the more caudal tail regions. In the 5-week embryos, both parts of the neural tube fused, forming only one continuous lumen in the developing spinal cord. In the three examined embryos we found anomalous pattern of spinal cord formation. Caudal parts of these spinal cords displayed division of their central canal into two or three separate lumina, each surrounded by neuroepithelial layer. In the caudal area of the spinal cord, derived by secondary neurulation, formation of separate lumina was neither connected to any anomalous notochord or vertebral column formation, nor the appearance of any major axial disturbances. We suggest that development of the caudal part of the spinal cord differs from its cranial region not only in the type of neurulation, but also in the destiny of its derivatives and possible modes of abnormality formation.

Changes in the expression of intermediate filaments and desmoplakins during development of human notochord.

Indirect immunofluorescence was used to study the expression of desmosomal and intermediate filament (IF) proteins in the human notochord between the 4th and 12th weeks of embryonic development. Towards the end of this period, the development of the notochord is characterized by its gradual physiological atrophy and disappearance inside the vertebral bodies. In all of our embryos, the notochord cells expressed cytokeratin and vimentin but not desmin, neurofilament protein or glial fibrillary acidic protein. Throughout the stages studied, the expression of cytokeratin was strong. Vimentin expression, on the other hand, changed during the stages studied. In our youngest embryos, vimentin could be detected only in the peripheral cells of the notochord. During development, a distinct increase occurred in vimentin expression, and in the oldest embryos, all notochord cells showed bright vimentin-specific fluorescence. Simultaneously with this modification, a change occurred in the expression of desmosomal proteins: The notochord cells expressed desmoplakins abundantly during early stages, but weakly or not at all during later stages. Correspondingly, electron microscopy of the same stages showed a striking decrease in the number of desmosomes between notochord cells. Our results confirm that, during early development, the notochord displays features specific for epithelial cells. This accords with the view that notochord is of epithelial origin. The modifications observed in the expression of IF and desmosomal proteins were temporally correlated with developmentally regulated atrophy of the notochord. The programmed regression of the notochord cells is thus associated with a switch from a predominantly epithelial phenotype to a more mesenchymal one.

Differences in origin and fate between the cranial and caudal spinal cord during normal and disturbed human development.

Differences in histological appearance between the cranial and caudal parts of the spinal cord and associated axial organs were analyzed in 9- and 15-week-old human dysraphic fetuses and compared with normal fetuses. In human development the cranial part of the neural tube down to the lumbosacral level forms during primary neurulation, while its caudal part results from secondary neurulation. In the 9-week fetus with cervical spina bifida, the cranial spinal cord displayed a variety of morphological changes along the cranio-caudal axis. Spinal cord in the upper cervical region transformed into the area cerebrovasculosa, while the lower cervical and thoracic levels showed only disturbed differentiation of the cell layers and roof plate. The degree of the cranial spinal cord dysmorphogenesis correlated with anomalies of the underlying notochord and vertebral column. The caudal to lumbosacral region of the spinal cord appeared normal. In the case of the 15-week-old fetus with complete dysraphia, the area cerebrovasculosa was found along the whole extent of the cranial spinal cord, while more caudally, all axial organs showed a normal histological structure. Our findings confirmed a different origin for the cranial and caudal parts of the human spinal cord. The appearance of dysraphic disorders corresponded to the time of primary neurulation; therefore, they resulted in the faulty formation of the cranial spinal cord. Normally formed caudal spinal cord appears during secondary neurulation at later developmental stages.

Fibronectin expression in the developing human spinal cord, nerves, and ganglia.

AIM: Analysis of developmental role of fibronectin during differentiation of the human spinal cord, nerves, and ganglia. METHODS: Seven normal human embryos and fetuses between the 7th and 9th developmental week and a 9-week fetus with cervical spina bifida were histologically examined on hematoxylin and eosin stained serial paraffin sections of thoracic axial segments. Monoclonal antibody to the human cell fibronectin fragment was used for immunohistochemical detection of fibronectin. RESULTS: In the 7th and 8th week of development, fibronectin was weakly expressed in the ventricular and intermediate zones of the spinal cord. Intense fibrillar expression was found in the marginal zone of the spinal cord - first over the ventral gray horns and later over the lateral and dorsal gray horns, and along the pathways of ventral and dorsal roots of the spinal nerves and in the spinal ganglia. At 9th week, fibronectin expression disappeared in the ventricular and intermediate zones a nd became weak and granular in the marginal zone of the spinal cord. In the spinal cord of a 9-week malformed fetus with cervical spina bifida, fibronectin expression was completely absent. Fibronectin was expressed in the nerves and ganglia throughout the investigated period, both in normal and malformed human conceptuses. CONCLUSION: Transient expression of fibronectin in the human spinal cord coincided with the most intense neuronal differentiation. Temporal and spatial expression of fibronectin during normal development, and its absence in a malformed human fetus suggests developmental role of fibronectin for the normal formation of the spinal cord.

Identification of two Ikaros-like transcription factors in lamprey.

The jawless Agnatha (lampreys and hagfishes) represent the phylogenetically oldest order of vertebrates that are believed to lack the adaptive immune system of jawed vertebrates. In order to search for molecular markers specific for cellular components of the adaptive immune system in lampreys, we used the polymerase chain reaction (PCR) to identify genes for transcription factors of the Ikaros family in genomic DNA and cDNA libraries from two species of lampreys, Petromyzon marinus and Lampetra fluviatilis. The mammalian Ikaros-like family of transcription factors consists of five members, Ikaros, Helios, Aiolos, Eos and Pegasus, of which the first three appear to be essential for lymphocyte development. Two different Ikaros-like genes, named IKLF1 and IKLF2, were identified in lamprey. They both have the conserved exon-intron structure of seven exons and show alternative splicing like their counterparts in jawed vertebrates. The genes code for predicted proteins of 589 and 513 amino acid residues, respectively. The proteins contain six highly conserved zinc finger motifs that are 83-91% identical to the mammalian members of the Ikaros-like family. The remaining parts of the sequences are, however, mostly unalignable. Phylogenetic analysis based on the alignable segments of the sequences does not identify the orthologous gene in jawed vertebrates but rather shows equidistance of the lamprey Ikaros-like factors to each other and to Ikaros, Helios, Aiolos and Eos. Expression studies by reverse transcription (RT)-PCR and in situ hybridization (ISH), however, provide evidence for moderate expression in presumed lymphoid tissues like the gut epithelium and for high levels of expression in the gonads, especially in the ovary.