Modulation of pulmonary neuroendocrine cells in idiopathic interstitial pneumonia

In order to reveal modulation of the number of pulmonary neuroendocrine cells (PNEC) in interstitial lung diseases and to clarify significance of cell proliferation activity in occurrence of PNEC, we counted airway PNEC of the patients of idiopathic interstitial pneumonia, secondary interstitial pneumonia and control lungs, and compared the number of PNEC with airway Ki-67 labeling. The lung tissue samples were obtained by video-assisted thoracoscopic surgery from 22 patients with usual interstitial pneumonia (UIP), 7 with non-specific interstitial pneumonia (NSIP), 8 with chronic hypersensitivity pneumonia (CHP), 13 with collagen vascular disease (CVD), and were compared with age-matched control lungs. The tissues were immunostained for chromogranin A and for Ki-67. Average incidence of bronchiolar PNEC in normal, UIP, NSIP, CHP, CVD lungs was 0.169%, 0.348%, 0.326%, 0.175% and 0.201%, respectively, and average Ki-67 labeling index in them was 0.241%, 1.186%, 1.605%, 1.058%, and 2.353%, respectively. And, in UIP lungs, PNEC incidence or Ki-67 labeling index was different according to pathological lesions. Thus, PNEC increase in the bronchiole of UIP, and the incidence of PNEC varies according to degree of activity of epithelial cell proliferation probably related to epithelial cell injury. Moreover, enhanced expression of human homolog of achaete-scute complex (hASH1) mRNA in UIP lungs suggests that hASH1 could play roles in the regulation of PNEC.

Functional analysis and the molecular dissection of zinc-fingers and homeoboxes 1 (ZHX1)

Zinc-fingers and homeoboxes 1 (ZHX1) is a protein that interacts with the activation domain of the A subunit of nuclear factor-Y. The function of ZHX1, as a transcription factor, was characterized and their domains were mapped. To determine the nuclear localization signal, expression vectors, in which various truncated forms of ZHX1 were fused to the C-terminal of green fluorescence protein (GFP), were transfected into human embryonic kidney (HEK) 293 cells. All GFP-ZHX1 fusion proteins including an arginine-rich region that corresponds to the amino acid sequence between 734 and 768 were localized in the nuclei. A dimerization domain of the ZHX1 was also mapped using protein-protein interaction assays. The homeodomain (HD) 1 consisting of the amino acid sequence between 272 and 432 of ZHX1 was necessary and sufficient for dimerization. Lastly, the transcriptional activity of ZHX1 was examined using a mammalian one-hybrid system. ZHX1, fused to the C-terminal of the GAL4 DNA-binding domain, was co-transfected with luciferase reporter plasmids with or without five copies of the GAL4-binding site into HEK293 cells. The luciferase activity was decreased in both concentration- and GAL4-binding site-dependent manner. The acidic region corresponding to the amino acid sequence between 831 and 873 was a repressor domain and dimerization was prerequisited for full repressor activity.

Early growth response gene-1 regulates the expression of the rat luteinizing hormone receptor gene

LH receptor gene expression is primarily regulated via specific interactions of trans-acting proteins and cis-acting DNA sequences in the upstream region of the gene. In this study, we report, using luciferase assays, that the region between -171 and -137 base pairs (bp) is essential for basal expression of the rat LH receptor gene. To identify factors that interact with the region between -171 and -137 bp and regulate expression of the gene, a rat granulosa cell cDNA library was screened using a yeast one-hybrid system. A positive clone, isolated by the screening, encodes a transcription factor early growth response gene-1 (Egr-1). To determine the sequence to which Egr-1 protein binds, electrophoretic mobility shift assay (EMSA) was employed. The Egr-1 protein was produced by an in vitro transcription/translation system using a full-length rat Egr-1 cDNA. The upstream region between -171 and -137 bp contains 2 overlapping Egr-1 consensus sequences. The EMSA revealed that Egr-1 binds independently to both sites. The overexpression of Egr-1 in MA-10 cells caused an approximately 2-fold increase in reporter luciferase activity. However, no induction of the luciferase activity was observed when luciferase constructs that lacked or had mutations in either or both of the Egr-1 sites were used, indicating that Egr-1 positively regulates LH receptor gene expression. In differentiated granulosa cells that had been pretreated with FSH for 48 h, the levels of both mRNA and Egr-1 protein were induced by hCG or cAMP, reaching maximal levels approximately 1.5 h after treatment and then returning to basal levels 8 h thereafter. No Egr-1 mRNA or protein was detected in undifferentiated granulosa cells, even after stimulation with 8-bromoadenosine-cAMP. These results suggest that Egr-1 functions only in luteinized granulosa cells after stimulation with hCG or cAMP. In conclusion, the findings demonstrate that Egr-1 actually binds to the regulatory upstream region of the LH receptor gene and positively regulates receptor gene expression. In addition, Egr-1 expression was observed only in luteinized granulosa cells after stimulation with hCG or cAMP. The present study provides further support to the hypothesis that Egr-1 plays important roles in the pituitary-gonadal axis.

Rat zinc-fingers and homeoboxes 1 (ZHX1), a nuclear factor-YA-interacting nuclear protein, forms a homodimer

Zinc-fingers and homeoboxes 1 (ZHX1) is a protein which interacts with the activation domain of the A subunit of nuclear factor-Y. To analyze the physiological role(s) of ZHX1, we searched ZHX1-interacting protein(s) using a yeast two-hybrid system. The rat counterpart of ZHX1 cDNAs was cloned from an ovarian granulosa cell complementary DNA (cDNA) library, indicating that ZHX1 is able to form a homodimer. An analysis of the nucleotide sequence and its deduced amino acid sequence show that rat ZHX1 consists of 873 amino acid residues. Northern blot analysis shows that ZHX1 messenger RNA is expressed ubiquitously and that the level in the ovary are not regulated by gonadotropins. Furthermore, transfection experiments with green fluorescence protein (GFP) expression vectors into human embryonic kidney HEK293 cells reveal that full-length ZHX1 fused to the GFP is localized in the nuclei. Thus, we report on the molecular cloning, expression and characterization of full-length rat ZHX1 cDNA.

Excitation-contraction coupling in cardiac muscle of lobster (Homarus americanus); the role of the sarcolemma and sarcoplasmic reticulum

The T-tubules and sarcoplasmic reticulum (SR) serving excitation-contraction (EC) coupling in lobster (Homarus americanus) cardiac muscle are similar to those in mammalian myocardium. Tetanic contraction is elicited by a burst of action potentials from the cardiac ganglion. In this study we evaluated the roles of the sarcolemma and SR in EC coupling of the ostial valve muscle (orbicularis ostii m. or OOM) of lobster heart. The OOM was mounted in a bath with saline on a microscope stage; force was measured by strain gauge. [Ca2+]i was measured using iontophoretically micro-injected fura-2 salt. Peak [Ca+]i, peak tetanic force and time to peak [Ca2+]i increased with that of stimulus train duration (TD), to a maximum at a TD of 500 ms. Force increased with [Ca2+]. Cd2+ reduced force by 90%; ryanodine and caffeine reduced tetanic [Ca2+]i transients by 80% and 70%, and force by 90% and 80%, respectively. Ryanodine, caffeine and cyclopiazonic acid slowed the decline of [Ca2+]i and force during relaxation. Relaxation required [Na+]o. The rate of decline of [Ca2+]i appeared to be a sigmoidal function of the [Ca2+]i and increased for any [Ca2+]i with TD. Inactivity slowed relaxation of force; stimulation accelerated relaxation. These data suggest important contributions of Ca2+ transport both across the sarcolemma and across the SR membrane during EC-coupling of lobster cardiac muscle, while average cytosolic [Ca2+]i regulates the rate of [Ca2+]i elimination during relaxation.

Follicle-stimulating hormone is indispensable for the last spermatogonial mitosis preceding meiosis initiation in newts (Cynops pyrrhogaster)

We previously reported that mammalian FSH induced differentiation of secondary spermatogonia into primary spermatocytes in organ culture of newt testicular fragments, whereas in medium lacking FSH primary spermatocytes never appeared. Here, we investigated why spermatogonia fail to form primary spermatocytes in the absence of FSH. Spermatogonia maintained proliferative activity and viability at about half the level of those cultured in the presence of FSH, progressed into the seventh generation, but became moribund during the G2/M phase. Thus, the eighth generation of spermatogonia never appeared, suggesting that cell death is the chief reason why primary spermatocytes fail to form in the absence of FSH. The presence of Dmc1, a molecular marker for the spermatocyte stage, confirmed our microscopic observations that spermatogonia differentiated into primary spermatocytes in the presence of FSH. Thus, FSH is indispensable for the completion of the last spermatogonial mitosis, a prerequisite for the conversion of germ cells from mitosis to meiosis. Because prolactin induced apoptosis in spermatogonia during the seventh generation, we propose that a checkpoint exists for the initiation of meiosis in the seventh generation whereby spermatogonia enter meiosis when the concentration ratio of FSH to prolactin is high but fail to do so when the ratio is low.

Modulation of the expression of the Cip/Kip family of cyclin-dependent kinase inhibitors in foetal developing lungs of hamsters

We examine the cell proliferation activity and expression of cyclin-dependent kinase inhibitors of the Cip/Kip family, p21Cip1, p27Kip1 and p57Kip2, in foetal hamster lungs to determine the expression patterns of the cyclin-dependent kinase inhibitors and to clarify the relationship between expression of the cyclin-dependent kinase inhibitors and lung development. Foetal hamster lungs on gestational days 12.5-16 (the day of birth) and adult lungs were fixed in 4% paraformaldehyde. Frozen sections were immunostained for the cyclin-dependent kinase inhibitors, and examined by immunostaining for Ki-67 and bromodeoxyuridine to determine the proliferation activity of the foetal lungs. During the foetal period, cell proliferation activity, as analysed by Ki-67 or bromodeoxyuridine labelling, decreased with development of the lung. In contrast to the gradual decrease of cell proliferation activity, cells with p27Kip1 immunoreactivity increased with development. On the other hand, p21Cip1-positive cells were most prominent around gestational day 14.5, while after birth positive cells decreased markedly. A few p57Kip2-positive cells were detected in the bronchiolar epithelium on gestational day 14.5. Western blotting analyses confirmed these immunostaining patterns. Thus, the levels of the cyclin-dependent kinase inhibitors of the Cip/Kip family are modulated in the lungs during the foetal period, and each shows a unique expression pattern. The cyclin-dependent kinase inhibitors may play roles not only in regulating cell proliferation activity but also in regulating other functions such as differentiation in the lung during the foetal period.

Spontaneous and repetitive cardiac slowdown in the freely moving spiny lobster, Panulirus japonicus

The fluctuation of heartbeat interval was investigated to assess cardio-regulatory nervous function in freely moving spiny lobsters. This was performed by time series analysis of the heartbeat interval recorded from restrained animals, freely moving animals, and isolated hearts. The heart rate of freely moving animals exhibited on/off switching: i.e., an elevated and maintained rate was repetitively interrupted by periods of decreased rate. Each period was initiated by a sudden decrease in rate and was terminated by an exponential return to normal activity. In order to explain this characteristic change in heart rate, we have constructed a neurotransmitter release-reuptake model for such bi-stable activity of cardio-regulatory nerves. The model was successful in reproducing the characteristic observed fluctuation. In freely moving animals, the brain seems to regulate the heart through the inhibitory nerve in an "on/off" manner. In the hearts of restrained animals and isolated hearts, the heart rate exhibited white-noise like fluctuation. This implies that stress impairs the normal bi-stable regulatory mode.

A silver-containing halogen-free inorganic photochromic glass

A halogen-free inorganic photochromic soda-lime silicate glass containing silver ions has been developed; reversible change between colorless and yellow color in this glass is achieved through combined 193 nm excimer laser irradiation and heat treatment.

High cyclin E and low p27/Kip1 expressions are potentially poor prognostic factors in lung adenocarcinoma patients

Cyclin E is an important regulator of entry into the S phase of the cell cycle. p27/Kip1 (p27) binds to cyclin E/Cdk2 complex and negatively regulates cell proliferation. We immunohistochemically examined the expression of cyclin E and p27 in 98 cases of resected lung adenocarcinoma to evaluate the prognostic significance of cyclin E and p27. Cyclin E was expressed in 16 cases (16%), and p27 was expressed in 41 cases (42%). Using Kaplan-Meier survival analysis, patients with cyclin E positive (P=0.0017) and p27 negative (P=0.011), both individually and in combination (P<0.0001), had a worse prognosis. We also analyzed the relationship of these findings to clinicopathological parameters, which revealed that cyclin E-positive, p27-negative cases had a higher Ki67 expression (P=0.012) and a higher rate of lymph node metastasis (P=0.0078) than other groups. Our results suggested that cyclin E over expression, in association with p27 reduction in particular, may potentially be a poor prognostic factor in lung adenocarcinoma patients. However, to verify the prognostic significance of these factors, a multivariate analysis of a larger number of patients should be undertaken.

Cloning and characterization of gonadotropin-inducible ovarian transcription factors (GIOT1 and -2) that are novel members of the (Cys)(2)-(His)(2)-type zinc finger protein family

Gonadotropins are essential for ovarian follicular development and differentiation. To identify genes that are rapidly induced by gonadotropin in the immature rat ovary, ovarian genes were screened by a subtraction cloning procedure. cDNA clones encoding novel members of the (Cys)(2)-(His)(2)-type zinc finger protein family GIOT1 and -2 (gonadotropin-inducible transcription factor 1 and 2), were identified. Two isoforms of GIOT2 (GIOT2 alpha and 2 beta), which are probably produced by alternative splicing, also exist. Nucleotide sequence analysis revealed that GIOT1, but not GIOT2, contains the krüppel-associated box-A domain at the NH(2) terminus. RNA analyses revealed that these mRNAs were rapidly and temporarily induced by gonadotropins in the rat testis as well as in the ovary. In situ hybridization study revealed that expression of GIOT1 was induced in theca interna cells in the ovary and Leydig cells in the testis. Interestingly, the gene expression of GIOT1 is restricted to the pituitary, adrenal, testis, and ovary, while GIOT2 gene is expressed ubiquitously. A functional analysis of GIOT1 and -2 by a GAL4-based mammalian one-hybrid system revealed that GIOT1, but not GIOT2, is a transcriptional repressor and that the krüppel-associated box-A domain of GIOT1 is responsible for the transcriptional repressor activity. A GAL4-based yeast two-hybrid system was also used to identify proteins that interact with the rat GIOT1. We cloned genes encoding rat homologs of human I-mfa domain containing protein and transcriptional intermediary factor 1 beta, both of which are transcription-regulatory proteins. Interaction of these proteins with GIOT1 was directly demonstrated by GST pull-down assay. Our data strongly suggest that GIOT1 may function as a novel transcriptional repressor by working with rat homologs of human I-mfa domain containing protein and transcriptional intermediary factor 1 beta proteins and may play a significant role at the transcription level in the folliculogenesis.

Molecular cloning of natriuretic peptide receptor A from bullfrog (Rana catesbeiana) brain and its functional expression

A comparative study of natriuretic peptide receptor (NPR) was performed by cloning the NPR-A receptor subtype from the bullfrog (Rana catesbeiana) brain and analyzing its functional expression. Like other mammalian NPR-A receptors, the bullfrog NPR-A receptor consists of an extracellular ligand binding domain, a hydrophobic transmembrane domain, a kinase-like domain and a guanylate cyclase domain. Sequence comparison among the bullfrog and mammalian receptors revealed a relatively low ( approximately 45%) similarity in the extracellular domain compared to a very high similarity ( approximately 92%) in the cytoplasmic regulatory and catalytic domains. Expression of NPR-A mRNA was detected in various bullfrog tissues including the brain, heart, lung, kidney and liver; highest levels were observed in lung. Functional expression of the receptor in COS-7 cells revealed that frog atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) elicited cyclic guanosine 3'5'-monophosphate production by stimulating the receptor in a dose-dependent manner from 10(-10) M concentrations. Rat ANP was also effective in stimulating the frog receptor whereas rat BNP and porcine BNP were less responsive to the receptor. On the other hand, frog C-type natriuretic peptide (CNP) as well as porcine CNP stimulated the receptor only at high concentrations (10(-7) M). This clearly indicates that the bullfrog receptor is a counterpart of mammalian NPR-A, and is specific for ANP or BNP but not for CNP.

Molecular cloning and heterologous expression of novel glucosyltransferases from tobacco cultured cells that have broad substrate specificity and are induced by salicylic acid and auxin

Scopoletin is one of the phytoalexins in tobacco. Cells of the T-13 cell line (Nicotiana tabacum L. Bright Yellow) accumulate a large amount of scopoletin, also known as 7-hydroxy-6-methoxycoumarin, as a glucoconjugate, scopolin, in vacuoles. We report here the molecular cloning of glucosyltransferases that can catalyze the glucosylation of many kinds of secondary metabolites including scopoletin. Two cDNAs encoding glucosyltransferase (NtGT1a and NtGT1b) were isolated from a cDNA library derived from the tobacco T-13 cell line by screening with heterologous cDNAs as a probe. The deduced amino-acid sequences of NtGT1a and NtGT1b exhibited 92% identity with each other, approximately 20-50% identities with other reported glucosyltransferases. Heterologous expression of these genes in Escherichia coli showed that the recombinant enzymes had glucosylation activity against both flavonoids and coumarins. They also strongly reacted with 2-naphthol as a substrate. These recombinant enzymes can utilize UDP-glucose as the sugar donor, but they can also utilize UDP-xylose as a weak donor. RNA blot analysis showed that these genes are induced by salicylic acid and auxin, but the time course of the expression was different. This result is similar to the changes in scopoletin glucosylation activity in these tobacco cells after addition of these plant growth regulators. These results might suggest that one of the roles of the products of these genes is scopoletin glucosylation, in response to salicylic acid and/or auxin, together with the other glucosyltransferases in tobacco cells.

The role of preoptic area and anterior hypothalamus and median raphe nucleus on thermoregulatory system in freely moving rats

To clarify the role of the preoptic area and anterior hypothalamus (PO/AH) on thermoregulatory system and the effects of serotonergic innervation from the median raphe nucleus (MRN) on body temperature (Tb), we perfused tetrodotoxin (TTX) solution into the PO/AH or MRN by using a microdialysis technique at different ambient temperatures (5, 23 and 35 degrees C) in freely moving rats. Tb was continuously monitored by using a telemetry system. In the MRN, perfusion of TTX solution induced significant hypothermia in the normal environment, a greater decrease in Tb during cold exposure and had no effect on Tb during heat exposure. In the PO/AH, perfusion of TTX solution induced significant hyperthermia in normal environment, a greater increase in Tb during heat exposure and had no effect on Tb during cold exposure. Our results indicate that the PO/AH regulates mainly heat loss or inhibits the loci regulating heat production. Furthermore, heat production appears to be regulated by other loci receiving serotonergic innervation from the MRN.

Cold suppression of follicle-stimulating hormone activity on proliferation and survival of newt spermatogonia

In newts elevated titers of plasma prolactin (PRL), induced by low temperature, cause apoptosis in the penultimatemitotic stage of spermatogonia, and this cell death is suppressed by antiserum against newt PRL, but only during the initial 3 days of exposure (Yazawa et al., 1999). Thus, factors other than PRL must be involved in spermatogonial death. Follicle-stimulating hormone (FSH) may be a plausible candidate. Accordingly, the current study examined the activityof FSH on the proliferation and survival of spermatogonia at low temperatures in vivo and in vitro. Porcine FSH (pFSH) administration in vivo inhibited spermatogonial death induced at 12 degrees C, but failed to do so at8 degrees C. Also pFSH promoted in vitro the proliferation of spermatogonia at 12 degrees C, but not at 8 degrees C. Furthermore,dibutyryl cyclic AMP stimulated in vitro DNA synthesis of secondary spermatogonia at 12 degrees C, but not at 8 degrees C. These different responses to temperatures were not caused by different levels of mRNA for the receptor of follicle-stimulating hormone, the numberof FSH binding sites, or FSH binding affinity to its receptors in the testicular cells. Thus, the results indicate that a temperature-sensitive period exists duringthe postreceptor process and is responsible for thelack of response of newt testis to FSH at 8 degrees C.

Caspase activity in newt spermatogonial apoptosis induced by prolactin and cycloheximide

We previously showed in vivo and in vitro, that among the spermatogenic stages of the newt, prolactin (PRL) induces apoptosis specifically in the penultimate stage of secondary spermatogonia. In the current report, we demonstrate in vitro that cycloheximide (CHX), an inhibitor of protein synthesis, induces morphological apoptotic changes similar to those caused by PRL, such as chromatin condensation and apoptotic body formation. Next, we found that Z-VAD-fmk, an inhibitor of various caspases, suppressed the apoptosis induced by PRL and CHX, but ICE inhibitor Ac-YVAD-CHO or caspase-3 inhibitor Ac-DEVD-CHO did not. As high caspase activity was present in extracts of testes treated with CHX, we suggest that an unidentified caspase induces the morphological changes of apoptosis in newt spermatogonia.

Cloning and functional expression of an E box-binding protein from rat granulosa cells

Ovarian granulosa cells undergo cell growth and cytodifferentiation during follicular maturation. In a number of tissues, the gene expression that is responsible for the cytodifferentiation is largely dependent on E box(es) located upstream of the responsible genes. In this study, we report on the cloning of cDNA(s) encoding E box (5'-CACGTG-3')-binding protein from a rat granulosa cell cDNA library using a yeast one-hybrid system. When multiple E box sequences were used as target, we obtained a positive clone that encodes the rat homologue of upstream stimulatory factor 2 (USF2). An analysis of the nucleotide sequence and its deduced amino acid sequence reveals that rat USF2 protein consists of 346 amino acid residues and belongs to the basic helix-loop-helix/leucine zipper protein family. Northern blot analysis shows that rat USF2 mRNA exists as multiple forms between 1.6 and 2.2 kilobases. The size of the cloned insert was identical to that of the transcript of maximal length. Electrophoretic mobility shift assays showed that in vitro-translated rat USF2 specifically binds to the E box. In addition, cotransfection experiments with luciferase-reporter constructs in HepG2 cells reveal that the overexpression of rat USF2 leads to an increase of luciferase activity in the E box sequence-dependent manner. Thus, we report molecular cloning, expression, and functional characterization of full-length rat USF2 cDNA.

Expression of cyclin-dependent kinase inhibitors in taste buds of mouse and hamster

Taste buds are specialized epithelial cell clusters in the oral squamous cell epithelium. Although taste buds have been reported to renew rapidly, the mechanism of cell cycle control in these specialized structures remains unresolved. To clarify the cell cycle status and role of cyclin-dependent kinase inhibitors (CDKI) for cell cycle control in the taste buds, we analyzed cell proliferation activity using bromodeoxyuridine (BrdU) and Ki-67 immunostainings and the expression of the Cip/Kip family of CDKI (p21Cip1, p27Kip1, and p57Kip2) in the circumvallate papillae of mouse and hamster. BrdU-positive cells were detected in the basal layer of the oral epithelium. In the taste buds, Ki-67-positive cells were seen in the basal area, with only a very few positive cells in the taste buds. Both p21Cip1 and p27Kip1 positive cells were seen in the suprabasal layer of the non-gustatory oral epithelium. In the taste buds, stronger p27Kip1 staining was detected than in the non-gustatory epithelium. Western blotting analysis revealed that p27Kip1 was abundant in the mucosal tissues from circumvallate papillae. Thus, our study suggests that the taste bud cells except for basal cells are post-mitotic cells and that the cell cycle arrest associated with taste bud cell differentiation could be regulated predominantly by p27Kip1.

Significance of proneural basic helix-loop-helix transcription factors in neuroendocrine differentiation of fetal lung epithelial cells and lung carcinoma cells

In this brief review article, we describe how cell fate determination by which the airway epithelial cells become neuroendocrine or non-neuroendocrine is regulated by a network of basic helix-loop-helix transcription (bHLH) factors in a similar manner to neuronal differentiation, and how this system could work to determine cell differentiation of human lung carcinomas. Immunohistochemical studies reveal that mammalina achaete-scute complex homologue (Mash)1 is expressed in pulmonary neuroendocrine cells (PNEC), while hairy and Enhancer of split (Hes)1 is expressed in pulmonary non-neuroendocrine cells (non-PNEC). Studies using gene-deficient mice for the bHLH factors revealed that in Mash1 homozygous null mice no PNEC are detected, while PNEC increase markedly in Hes1 homozygous null mice. These observations suggest that Mash1 is an essential positive factor for neuroendocrine differentiation of lung epithelium, and that Hes1 is one of the repressive factors for neuroendocrine differentiation. Moreover, immunohistochemical studies revealed that Notch receptors are detected in non-PNEC, and thus the Notch signalling pathway could play a role in the determination of airway epithelial cell differentiation. In human lung carcinomas, a similar bHLH network should operate to determine cell differentiation phenotypes. Generally, expression of the human homologue of Mash1 (HASH1) is detected in small cell carcinoma and carcinoids, while Hes1 seems to be expressed mainly in non-small cell carcinoma. Thus, proneuronal bHLH factors may play roles in cell fate determination of the airway epithelial system, and may regulate human airway epithelial cells in diseased conditions.

Conversion from mitosis to meiosis: morphology and expression of proliferating cell nuclear antigen (PCNA) and Dmc1 during newt spermatogenesis

The conversion from mitosis to meiosis is a phenomenon specific to the cellular progenitors of gametes; however, the mechanism or mechanisms responsible for this conversion are poorly understood. To this end, some morphological and molecular changes that occur during the initiation of meiosis in newt spermatogenesis are reported in the present paper. In situ morphologic studies revealed that spermatogonial stages comprise two phases: early mitotic generations (G1-G4) and late mitotic generations (G5-G8). Morphologic conversion from secondary spermatogonia to primary spermatocytes occurred during the intermediate stage of premeiotic DNA replication. The expression of proliferating cell nuclear antigen (PCNA), a DNA polymerase-delta auxiliary protein, in spermatogonia was weak in G1, highest during DNA synthesis (S), decreased in G2 and was not detectable in dividing cells. Complementary DNA for newt homologs of DMC1 (disrupted meiotic cDNA), which is an Escherichia coli RecA-like protein specifically active during meiosis, were isolated. The newt Dmc1 mRNA was first expressed significantly during the preleptotene stage and this continued into the spermatid stage. These observations present a basis for investigating the mechanism(s) controlling the conversion of newt spermatogonial cells from mitosis to meiosis.

Newt prolactin and its involvement in reproduction

The amino acid sequence of newt (Cynops pyrrhogaster) prolactin deduced from the nucleotide sequence of its cDNA showed a relatively high homology with sequences of chicken and sea turtle prolactins as well as with those of anuran prolactins. Cynops prolactin receptor transcripts were detected in various tissues and organs, suggesting that prolactin plays multiple roles in urodeles. Urodele prolactin was purified from the pituitaries of C. pyrrhogaster. Antiserum against this prolactin was used for radioimmunoassay of plasma prolactin and immunoneutralization experiments. Endogenous prolactin was shown to induce migration to water, courtship behavior, and cessation of spermatocytogenesis in the Cynops newt. The hormone was found to be involved in the development of cloacal glands such as the lateral and abdominal glands, growth of the tail and Mauthner neurons, secretion of oviducal jelly, and enhanced synthesis of a female attracting pheromone (sodefrin), and responsiveness of the olfactory epithelium to sodefrin. In most of these cases, prolactin was found to act synergistically or antagonistically with sex steroids. We also discovered that hypersecretion of prolactin in the newts subjected to cold temperature was induced by hypothalamic stimulation rather than release from hypothalamic inhibition.Key words: prolactin, newts, reproduction.

Newt prolactin and its involvement in reproduction

The amino acid sequence of newt (Cynops pyrrhogaster) prolactin deduced from the nucleotide sequence of its cDNA showed a relatively high homology with sequences of chicken and sea turtle prolactins as well as with those of anuran prolactins. Cynops prolactin receptor transcripts were detected in various tissues and organs, suggesting that prolactin plays multiple roles in urodeles. Urodele prolactin was purified from the pituitaries of C. pyrrhogaster. Antiserum against this prolactin was used for radioimmunoassay of plasma prolactin and immunoneutralization experiments. Endogenous prolactin was shown to induce migration to water, courtship behavior, and cessation of spermatocytogenesis in the Cynops newt. The hormone was found to be involved in the development of cloacal glands such as the lateral and abdominal glands, growth of the tail and Mauthner neurons, secretion of oviducal jelly, and enhanced synthesis of a female attracting pheromone (sodefrin), and responsiveness of the olfactory epithelium to sodefrin. In most of these cases, prolactin was found to act synergistically or antagonistically with sex steroids. We also discovered that hypersecretion of prolactin in the newts subjected to cold temperature was induced by hypothalamic stimulation rather than release from hypothalamic inhibition.