Therapy-related myelodysplastic syndrome in childhood: a retrospective study of 36 patients in Japan.

We report here a retrospective analysis of 36 children with therapy-related myelodysplastic syndrome (t-MDS) diagnosed between 1990 and 1999 in Japan. Their median age was 7.7 years and the median latency period for the development of t-MDS was 38.5 months. The primary tumors were hematologic in 15 of the cases and nonhematologic in 21. Chromosomal abnormalities were detected in 32/34(94%) patients: abnormalities of chromosomes 5and/or 7 in 41% and notably, 11q23 abnormalities in 31%. The prognosis of children with t-MDS was very poor as compared to children with primary MDS (5 year survival: 16% versus 54%, p<0.0001).

Reduction in hematopoietic stem cell numbers with in vivo drug selection can be partially abrogated by HOXB4 gene expression.

In vivo selection of hematopoietic stem cells (HSCs) offers an approach to enrichment of genetically modified blood cells in the context of gene therapy for blood disorders. We have previously demonstrated efficient HSC selection in mice using retroviral vectors expressing dihydrofolate reductase (DHFR) or methylguanine methyltransferase (MGMT) drug resistance genes. In this study, we examined whether drug selection was followed by subsequent HSC regeneration and, if not, whether regeneration could be augmented by enforced expression of HOXB4, which has previously been shown to enhance HSC regeneration after transplant. Using a murine competitive repopulation model, we found that selection using either the DHFR or the MGMT system was accompanied by a significant overall reduction in repopulating activity in secondary transplant assays, although hematopoiesis remained normal after recovery. Inclusion of a HOXB4 expression cassette in the DHFR vector resulted in a partial restoration of HSC numbers following selection and was associated with an increase in HSC selection efficiency. These results illustrate that while drug resistance vectors can protect transduced HSC from cytotoxic drugs, the self-renewal capacity of transduced HSCs is limited following in vivo selection. Strategies that increase self-renewal capacity could increase the efficiency and safety of in vivo selection.

Antitumour activity and adverse reactions of combined treatment with chitosan and doxorubicin in tumour-bearing mice.

We examined the antitumour activity and adverse reactions, such as myelotoxicity, gastrointestinal toxicity and body-weight loss,of the cancer chemotherapy drug doxorubicin when given with chitosan in sarcoma 180-bearing mice. Intraperitoneally administered doxorubicin (5 mg kg(-1)) given on days 1 and 8 with or without orally administered chitosan (200, 400 and 800 mg kg(-1) twice daily) inhibited tumour growth. The orally administered chitosan (400 and 800 mg kg(-1) twice daily) prevented doxorubicin-induced body-weight loss and small-intestinal mucosal injury. Similarly, the reduction of leucocyte number induced by the intraperitoneally administered doxorubicin was restored to normal by the oral administration of chitosan (400 and 800 mg kg(-1) twice daily). It seems likely that the mechanisms by which the orally administered chitosan protects against doxorubicin-induced gastrointestinal toxicity may be due to the formation of doxorubicin-chitosan complex in the small-intestinal mucosa through the diffusion of chitosan into the small-intestinal villi. In conclusion, our data suggest that the oral administration of chitosan prevents the gastrointestinal mucositis associated with doxorubicin therapy.

Protection and in vivo selection of hematopoietic stem cells using temozolomide, O6-benzylguanine, and an alkyltransferase-expressing retroviral vector.

Transfer of drug resistance genes to hematopoietic stem cells offers the potential to protect cancer patients from drug-induced myelosuppression and to increase the number of gene-modified cells by in vivo selection. In this study, a retroviral vector expressing both a P140K variant of human O6-methylguanine-DNA methyltransferase (MGMT) and an EGFP reporter gene was evaluated for stem cell protection in a murine transplant model. Mice transplanted with vector-transduced cells showed significant resistance to the myelosuppressive effects of temozolomide (TMZ), an orally administered DNA-methylating drug, and O6-benzylguanine (BG), a drug that depletes cells of wild-type MGMT activity. Following drug treatment, increases in EGFP(+) peripheral blood cells were seen in all peripheral blood lineages, and secondary transplant experiments proved that selection had occurred at the stem cell level. In a second set of experiments in which transduced cells were diluted with unmarked cells, efficient stem cell selection was noted together with progressive marrow protection with repeated treatment courses. Altogether, these results show that P140K MGMT gene transfer can protect stem cells against the toxic effects of TMZ and BG and that this vector/drug system may be useful for clinical myeloprotection and for in vivo selection of transduced stem cells.

Ataxin-3, the MJD1 gene product, interacts with the two human homologs of yeast DNA repair protein RAD23, HHR23A and HHR23B.

Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder caused by an expansion of the polyglutamine tract near the C-terminus of the MJD1 gene product, ataxin-3. The mutant ataxin-3 forms intranuclear inclusions in cultured cells as well as in diseased human brain and also causes cell death in transfected cells. However, the normal function of ataxin-3 remains unknown. To explore the function of ataxin-3, we used the two-hybrid system to screen for the protein(s) that interacts with ataxin-3. We found that ataxin-3 interacts with two human homologs of the yeast DNA repair protein RAD23, HHR23A and HHR23B. Furthermore, we confirmed that ataxin-3 interacts with the -ubiquitin-like domain at the N-terminus of the HHR23 proteins, which is important for nucleotide excision repair; however, ataxin-3 does not interact with -ubiquitin, implying that ataxin-3 might be functionally associated with the HHR23 proteins through this specific interaction. The normal and mutant ataxin-3 proteins show no difference in their ability to bind to the HHR23 proteins. However, in 293 cells HHR23A is recruited to intranuclear inclusions formed by the mutant ataxin-3 through its interaction with ataxin-3. These results suggest that this interaction is associated with the normal function of ataxin-3 and that some functional abnormality of the HHR23 proteins might exist in MJD.

Thrombopoietin enhances neutrophil production by bone marrow hematopoietic progenitors with the aid of stem cell factor in congenital neutropenia.

We examined the effects of granulocyte colony-stimulating factor (G-CSF), stem cell factor (SCF), and thrombopoietin (TPO), alone or in combination, on the generation of neutrophils by bone marrow (BM) cells from three patients with severe congenital neutropenia (SCN) through the use of a serum-deprived liquid culture system. Synergistic effects of G-CSF and SCF on the neutrophil production by BM CD34+CD38+c-kit+ cells were observed in SCN patients as well as in normal controls. The addition of TPO to the culture containing G-CSF and SCF further augmented the growth of neutrophils in the two groups. Single-cell culture experiments revealed that the three-factor combination caused increases in both the number and size of neutrophil colonies compared with G-CSF + SCF in normal BM cells, whereas only a significant increment in the colony size was observed in SCN patients. Even in the presence of SCF or SCF + TPO, the concentrations of G-CSF necessary for the substantial production of neutrophils by CD34+CD38+c-kit+ cells were higher in two patients compared with the levels obtained by normal control cells. In addition, TPO did not accelerate the maturation of neutrophilic cells supported by G-CSF + SCF. When BM CD34+CD38-c-kit+ cells were targeted, the addition of TPO to the culture containing G-CSF and SCF was required for significant neutrophil colony growth in the two groups. These results suggest that TPO enhances the G-CSF-dependent neutrophil production with the aid of SCF in this disorder.

Quantitative and qualitative differences in thrombopoietin-dependent hematopoietic progenitor development between cord blood and bone marrow.

BACKGROUND: To assess the clinical application of thrombopoietin (TPO) for thrombocytopenia of patients receiving cord blood (CB) or bone marrow (BM) transplants, we examined whether various types of hematopoietic progenitors including megakaryocyte (MK) progenitors from CB and BM exerted different proliferative and differentiative potential in the presence of TPO. METHODS: The development of MK, granulocyte-macrophage, and erythroid/mixed erythroid (E/Mix) progenitors in a serum-deprived liquid culture medium supplemented with TPO was compared between CD34+ CB and BM cells. RESULTS: The CD34+ CB cells generated 30-fold more MKs than the CD34+ BM cells, but the CB-derived MKs were more immature. A single-cell culture study showed that CB CD34+CD38- cells as well as CD34+CD38+ cells proliferated in response to TPO, whereas the two subpopulations of CD34+ BM cells showed little multiplication. In short-term liquid cultures containing CD34+ CB or BM cells, TPO significantly increased the absolute numbers of various types of colony-forming cells, compared with the input values. In particular, MK progenitors and E/Mix progenitors in CB were amplified to a substantially greater extent than in BM. The superior response of CD34+ CB cells to TPO observed in this study may be due in part to the use of cryopreserved cells. CONCLUSIONS: Our results suggest that TPO alone cannot only stimulate megakaryocytopoiesis but also increase the numbers of various types of hematopoietic progenitors, and that quantitative and qualitative differences in TPO-dependent hematopoietic progenitor development exist between CB and BM.

Retinoic acid is a negative regulator for the differentiation of cord blood-derived human mast cell progenitors.

We examined the effects of retinoids on the human mast cell development using a serum-deprived culture system. When 10-week cultured mast cells derived from CD34(+) cord blood cells were used as target cells, both all-trans retinoic acid (ATRA) and 9-cis RA inhibited the progeny generation under stimulation with stem cell factor (SCF) in a dose-dependent manner (the number of progeny grown by SCF plus RA at 10(-7) mol/L was one tenth of the value obtained by SCF alone). The early steps in mast cell development appear to be less sensitive to RA according to the single CD34(+)c-kit(+) cord blood cell culture study. The optimal concentration of RAs also reduced the histamine concentration in the cultured mast cells (3.00 +/- 0.47 pg per cell in SCF alone, 1.44 +/- 0.18 pg per cell in SCF+ATRA, and 1.41 +/- 0.10 pg per cell in SCF+9-cis RA). RT-PCR analyses showed the expression of RARalpha, RARbeta, RXRalpha, and RXRbeta messenger ribonucleic acid (mRNA) in 10-week cultured mast cells. The addition of an RAR-selective agonist at 10(-10) mol/L to 10(-7) mol/L decreased the number of mast cells grown in SCF, whereas an RXR-selective agonist at up to 10(-8) mol/L was inactive. Among RAR subtype selective retinoids used at 10(-9) mol/L to 10(-7) mol/L, only the RARalpha agonist was equivalent to ATRA at 10(-7) mol/L in its ability to inhibit mast cell growth. Conversely, the addition of excess concentrations of a RARalpha antagonist profoundly counteracted the retinoid-mediated suppressive effects. These results suggest that RA inhibits SCF-dependent differentiation of human mast cell progenitors through a specific receptor. (Blood. 2000;95:2821-2828)

Fiber connections of the corpus mamillare in a percomorph teleost, tilapia Oreochromis niloticus.

The hypothalamus and perhaps its function appear to be similar among vertebrates. Thus, studying the teleostean hypothalamus could be a good model for understanding common neural circuits and mechanisms retained through the vertebrates. However, connections of the inferior lobe, which is considered the hypothalamus in teleosts, is poorly known. The corpus mamillare (CM) is a nucleus of the inferior lobe named after the mammalian mamillary body based on similarities in external morphology. Afferent connections of the CM have been reported only in cypriniform teleosts. These include projections from the nucleus pretectalis superficialis pars magnocellularis, a nucleus lacking in percomorph teleosts, and projections from the secondary gustatory nucleus. Efferent connections of the CM have not been reported in teleosts. In the present study, the CM and its subdivisions and the connections of these subnuclei were identified in isolated and maintained brains of tilapia Oreochromis niloticus by local DiI and biocytin injection. Afferent connections confirmed by reciprocal injections were from the nucleus diffusus lobi inferioris (NDLI) and the nucleus diffusus tori lateralis (NDTL). Efferent connections of each CM subnuclei were also reciprocally confirmed. These connections were to the area dorsalis pars medialis of the telencephalon, the nucleus ventromedialis (NVM) of the thalamus, the tectum opticum (TO), and the nucleus posterioris periventricularis. Because the NDLI is known to receive gustatory information in tilapia, the CM could relay gustatory inputs to multisensory areas, the TO and NVM, for which there are no current reports regarding gustatory inputs.

Cytokine expression and production by purified Helicobacter pylori urease in human gastric epithelial cells.

Cytokines have been proposed to play an important role in Helicobacter pylori-associated gastroduodenal diseases, but the exact mechanism of the cytokine induction remains unclear. H. pylori urease, a major component of the soluble proteins extracted from bacterial cells, is considered to be one of the virulence factors for the inflammation in the gastric mucosa that is produced in H. pylori infection. However, the response of human gastric epithelial cells to the stimulation of urease has not been investigated. In the present study, we used human gastric epithelial cells in a primary culture system and examined whether H. pylori urease stimulates the gastric epithelial cells to induce proinflammatory cytokines by reverse transcription-PCR and enzyme-linked immunosorbent assay. First, by using peripheral blood mononuclear cells (PBMC) and a gastric cancer cell line (MKN-45 cells), we confirmed the ability of purified H. pylori urease to induce the production of proinflammatory cytokines. Furthermore, we demonstrated that the human gastric epithelial cells produced interleukin-6 (IL-6) and tumor necrosis factor alpha, but not IL-8, following stimulation with purified urease. The patterns of cytokine induction differed among human PBMC, MKN-45 cells, and human gastric epithelial cells. These results suggest that the human gastric epithelial cells contribute to the induction of proinflammatory cytokines by the stimulation of H. pylori urease, indicating that the epithelial cells were involved in the mucosal inflammation that accompanied H. pylori infection.

Comparison of PCR-restriction fragment length polymorphism analysis and PCR-direct sequencing methods for differentiating Helicobacter pylori ureB gene variants.

A method utilizing PCR-restriction fragment length polymorphism (RFLP) in the Helicobacter pylori genes is widely used to differentiate strains. However, with this typing method only a single base change at a specific restriction site can be detected. In addition, it is unclear whether the nucleotide base change recognized by RFLP is related to a substitution of encoded amino acid. To examine the validity of the PCR-RFLP method, 933-bp PCR products were obtained from 41 different clinical H. pylori isolates and were digested with Sau3A restriction endonuclease. Furthermore, the nucleotides of the same region in the ureB gene were directly sequenced and compared. PCR-RFLP confirmed that there was genetic diversity within the ureB gene with three distinct types, one being well conserved and the other two being variations. However, the direct sequencing method revealed that there was no difference at the nucleotide level among these RFLP types. Base substitutions recognized by Sau3A occurred in the third-base position and did not change the encoded amino acid. In addition, many nucleotide mutations, which could not be recognized by Sau3A, were frequently found. These results suggest that the PCR-RFLP method provides for an easy typing scheme of isolates, but does not reveal the true extent of genetic diversity. It is proposed that careful observation is required for the interpretation of results when clinical isolates are differentiated.

[Lymphocytic infundibuloneurohypophysitis during the first remission in acute lymphoblastic leukemia].

A 15-year-old girl developed acute lymphoblastic leukemia (ALL). The patient was treated according to the 13th protocol of the Tokyo Children's Cancer Study Group, and thereafter remained free of disease. However, at the age of 20, she complained of polyuria, polydipsia and amenorrhea. Hematological or meningeal relapse was ruled out on the basis of clinical and laboratory findings. The plasma concentrations of GH, TSH, LH, FSH, ACTH and ADH were low or below the detectable limits. There was no increase in urine osmolarity after water deprivation. Arginine, LH-RH, TRH and CRH tolerance tests revealed no or low responses of GH, LH/FSH, TSH, and ACTH/cortisol, respectively. Magnetic resonance imaging demonstrated thickening of the pituitary stalk, which was homogeneously enhanced by gadolinium administration. A biopsy specimen showed fibrosis and infiltration of CD8-positive T lymphocytes in a portion of the pituitary stalk, whereas the adenohypophysis was normal. In addition, no leukemic cells were observed in the samples. Thus, a diagnosis of lymphocytic infundibuloneurohyophysitis (LIN) was established. All the symptoms were improved by treatment with hydrocortisone, L-thyroxine, desamino-8-d-arginine vasopressin, estrogen and gestagen. This is the first reported case of ALL complicated by LIN.

[The value of intracellular CD41 antigen detection to the diagnosis of acute megakaryoblastic leukemia].

An 11-month-old boy was transferred to our hospital because of fever and bleeding tendency on March 13, 1998. Laboratory studies showed a white blood cell count of 43,360/microliter with 75% blasts, a hemoglobin concentration of 8.4 g/dl, and a platelet count of 23 x 10(3)/microliter. Surface marker analysis with a flow cytometer revealed that only 21% and 11% of the blasts, respectively, were positive for CD41 and CD42b. Treatment with a permeabilizing agent apparently increased the reactivity of the blasts with anti-CD41 monoclonal antibody (MoAb), which can recognize IIb independently of IIIa. However no significant differences were observed in reactivity with anti-CD41 MoAb (which recognizes the IIb/IIIa complex) anti-CD61 MoAb and anti-CD42b MoAb before or after fixation. Blasts positive for platelet peroxidase were observed by electron microscopy, thus confirming the diagnosis of acute megakaryoblastic leukemia. We concluded that the detection of intracellular antigens is useful for the quick diagnosis of acute megakaryoblastic leukemia characterized by low surface expression of megakaryocytic lineage antigens.

Interleukin-6 directly modulates stem cell factor-dependent development of human mast cells derived from CD34(+) cord blood cells.

In the present study, we attempted to clarify the effects of interleukin-6 (IL-6) on the growth and properties of human mast cells using cultured mast cells selectively generated by stem cell factor (SCF) from CD34(+) cord blood cells. The addition of IL-6 to cultures containing mast cells resulted in a substantial reduction of the number of progenies grown by SCF in the liquid culture. This IL-6-mediated inhibition of mast cell growth may be due in part to the suppression at the precursor level, according to the results of a clonal cell culture assay. Moreover, a flow cytometric analysis showed that the cultured mast cells grown in the presence of SCF+IL-6 had decreased c-kit expression. The exposure of cultured mast cells to SCF+IL-6 also caused substantial increases in the cell size, frequency of chymase-positive cells, and intracellular histamine level compared with the values obtained with SCF alone. The flow cytometric analysis showed low but significant levels of expression of IL-6 receptor (IL-6R) and gp130 on the cultured mast cells grown with SCF. The addition of either anti-IL-6R antibody or anti-gp130 antibody abrogated the biological functions of IL-6. Although IL-4 exerted an effect similar to that of IL-6 on the cultured mast cells under stimulation with SCF, the results of comparative experiments suggest that the two cytokines use different regulatory mechanisms. Taken together, the present findings suggest that IL-6 modulates SCF-dependent human mast cell development directly via an IL-6R-gp130 system.

Lupus nephritis in juvenile myelomonocytic leukemia.

A 13-year-old girl developed lupus nephritis and Hashimoto thyroiditis in the chronic phase of juvenile myelomonocytic leukemia (JMML). At age 7 months, she was diagnosed as having JMML based on the hepatosplenomegaly, leukocytosis, thrombocytopenia, increased levels of fetal hemoglobin, and spontaneous in vitro growth of granulocyte-macrophage progenitors. At the onset of JMML, she had hypergammaglobulinemia, antinuclear antibodies, rheumatoid factors and anti-smooth muscle antibody. She had been placed on oral 6-mercaptopurine for about 12 years, with clinical improvement. At age 13 years, she was found to have hematuria and proteinuria. She also developed arthritis and Raynaud's phenomenon as well. She had antinuclear antibodies, rheumatoid factors, LE phenomenon, beta-1C (C3) nephritic factor (C3NeF), antithyroid antibodies, and hypocomplementemia. The renal biopsy specimens revealed a diffuse increase in the mesangial cells and matrix by light microscopy, and intense staining of IgG, Clq and C3 by immunofluorescence microscopy. The hormonal study ultimately showed decreased thyroid functions. So she was diagnosed as lupus nephritis and Hashimoto thyroiditis. The patient is the first example to show close relationship between stem cell abnormalities in JMML and development of overt autoimmune disorders.

Thrombopoietin augments stem cell factor-dependent growth of human mast cells from bone marrow multipotential hematopoietic progenitors.

The effects of thrombopoietin (TPO) and/or stem cell factor (SCF) on the development of human mast cells from CD34(+) bone marrow (BM) cells were investigated using a serum-deprived liquid culture system. Mast cells were identified by measurement of intracellular histamine content, immunocytochemical staining, and flow cytometric analysis. Whereas SCF alone generated only a small number of tryptase+ cells, the addition of TPO to the culture containing SCF resulted in an apparent production of mast cells from 3 weeks until at least 15 weeks. Some of the cells reacted with an antichymase monoclonal antibody as well. Based on the effects of growth factor(s) on a later phase of the mast cell growth, TPO may stimulate an early stage of mast cell development in combination with SCF, whereas subsequent growth seems to be supported by SCF alone. Single-cell culture studies indicated that the CD34(+)CD38(-)c-kit+ cells and CD34(+)CD38(+)c-kit+ cells were responsible for the SCF + TPO-dependent mast cell production. Two-step culture assays clearly showed that mast cells originated from multilineage colony-forming cells that had potential to differentiate into neutrophil/mast cell lineages, neutrophil/macrophage/mast cell lineages, or neutrophil/macrophage/mast cell/erythroid lineages. These results suggest that TPO plays an important role in the development of human mast cells from CD34(+) BM cells in concert with SCF, and provide direct evidence of the differentiation into the mast cell lineage of human multipotential BM-derived progenitors.

Apoptosis of erythroid precursors under stimulation with thrombopoietin: contribution to megakaryocytic lineage choice.

Although the effect of thrombopoietin (TPO) on megakaryocyte production is well established, its role in the commitment of multipotential hematopoietic progenitors to the megakaryocytic lineage remains to be determined. In the present study, we attempted to clarify the determination process of megakaryocytic lineage as a terminal differentiation pathway under stimulation with TPO. Day 7 cultured cells grown by TPO derived from cord blood CD34+ cells were divided into four subpopulations on the basis of CD34 and CD41 expression. The CD34-/CD41- cells showed the labeling pattern of anti-CD42b and anti-CD9 antibodies closer to that of the CD34+/CD41- cells than the CD34+/CD41+ cells. Replating experiments revealed that approximately 40% of the CD34-/CD41- cells proliferated in response to a combination of growth factors, and more than 80% of them were pure erythroid precursors. However, this subpopulation failed to grow/survive and fell into apoptosis in the presence of TPO alone. In contrast, the CD34+/CD41+ cells, which predominantly contained megakaryocytic precursors, exerted a low but significant proliferative potential in the presence of TPO. The insufficient response to TPO of the CD34-/CD41- cells may result from the apparently low expression of c-MpI, as determined by flow cytometric analysis and reverse transcription-polymerase chain reaction analysis. Therefore, these results suggest that the apoptosis of hematopoietic precursors other than megakaryocytic precursors is related to the determination of the terminal differentiation under the influence of TPO.

Relationship between brain atrophy estimated by a longitudinal computed tomography study and blood pressure control in patients with essential hypertension.

To evaluate the relationship between blood pressure control and the progression of brain atrophy in the elderly, patients with essential hypertension and brain atrophy were longitudinally evaluated using computerized tomography (CT). The study evaluated 48 patients with essential hypertension aged 46-78 years, and 30 sex- and age-matched normotensive control subjects. The extent of brain atrophy as determined by caudate head index (CHI), the inverse cella media index (iCMI), and Evans' ratio (ER) was estimated twice at an interval of 5-9 years (mean, 6.9 years). The mean annual increases in CHI (deltaCHI), iCMI (delta iCMI), and ER (deltaER) were evaluated. Mean blood volume in the common carotid artery (BF) and the decrease in BF per year (deltaBF) were also determined. The deltaCHI, delta iCMI, and deltaER increased with age in the hypertensive subjects as well as the control group across all age groups evaluated. The deltaCHI, delta iCMI, and deltaER were significantly greater in the patients with essential hypertension in their 50 s as compared with the controls. In patients with essential hypertension aged 65 years or older, the deltaCHI, delta iCMI, and deltaER were significantly lower in the group in whom the blood pressure was controlled within the range of borderline hypertension than the groups in which it was controlled in the range of normal or mild hypertension. In the younger patients under the age of 65 with essential hypertension, blood pressure control did not affect the deltaCHI, delta iCMI, and deltaER. The deltaCHI, delta iCMI, and deltaER were significantly correlated with deltaBF in both groups. These findings indicate that control of systolic blood pressure within the range of borderline hypertension may delay the progression of brain atrophy in elderly patients with essential hypertension.

Tectal fiber connections in a non-teleost actinopterygian fish, the sturgeon Acipenser.

Tectal fiber connections were studied in members of an early branch of the actinopterygian lineage, the sturgeons Acipenser transmontanus and A. schrenkii, by means of biocytin, HRP, biotinylated dextran amine, and DiI tract tracing methods. The aim of this study is to elucidate the visual pathway via the optic tectum to the thalamus as a part of a series of studies on the visual pathways in sturgeons. After biocytin or biotinylated dextran amine injections to the optic tectum terminals are found bilaterally in the medial and lateral portions of both the dorsal thalamus and ventral thalamus. Ipsilateral projections are much more abundant. Tectal recipient areas in the thalamus overlap in part with the retinal recipient areas. After HRP or DiI injections to the dorsal or ventral thalamus, tectal neurons projecting to the thalamus were labeled in the ipsilateral or bilateral stratum periventriculare. Dendritic morphology of tectothalamic neurons suggests that they receive direct retinal input. These results suggest that visual information passes through the tectum to the thalamic areas which also receive direct retinal projections. In this regard, the visual system of Acipenser resembles that of chondrichthyans (sharks). Other fiber connections of the tectum are also described, which have not previously been studied by tracer methods in a sturgeon.

Visual thalamotelencephalic pathways in the sturgeon Acipenser, a non-teleost actinopterygian fish.

Terrestrial vertebrates (amphibians, reptiles, birds, and mammals) possess two visual systems, the geniculate and extrageniculate pathways to the telencephalon. In cartilaginous fishes (e.g. sharks) both retinal and tectal neurons project to neurons in the thalamus, which themselves project to a single area in the telencephalon. The condition in ray-finned fishes (Actinopterygii) is ambiguous. In many teleosts there is a well developed extrageniculate pathway but no obvious geniculate system. This study reports on the thalamotelencephalic projections of a sturgeon, a non-teleost ray-finned fish. Several tract tracing methods (e.g., HRP, WGA-HRP, biocytin, BDA, DiI) were employed in conjunction with normal techniques for identifying neural structures (e.g., Nissl, Golgi). After injections of tracer into retinal and tectal recipient areas of the thalamus, labeled terminals were observed in the ventrolateral region of the caudal telencephalon, an area referred to as the thalamic projection area. After injections of tracer into the telencephalon, populations of retrogradely filled neurons were located in both the dorsal and ventral thalamus. These data demonstrate that thalamic neurons in both retinal and tectal pathways project directly to the telencephalon. These results support the view that two visual pathways are a primitive feature of vertebrate brain organization. These results are also consistent with the hypothesis that the ancestor of Acipenser and Teleostei (Actinopteri) acquired a novel visual pathway to the telencephalon through the ventral portion of the thalamus.