Retinoic acids and thyroid hormone act synergistically with dexamethasone to increase growth hormone-releasing hormone receptor messenger ribonucleic acid expression

The effects of all-trans-retinoic acid (RA), 9-cis-retinoic acid (9cRA), and thyroid hormone (T3) on GH-releasing hormone receptor (GHRH-R) messenger RNA (mRNA) expression were studied using ribonuclease protection assay in the fetal rat pituitary gland and in MtT/S cells, a clonal GH cell line derived from an estrogen-induced somatotropic tumor in the rat. Although RA (1 microM), 9cRA (1 microM), or T3 (1 nM) alone showed little effect on GHRH-R mRNA expression in the MtT/S cells, each of these substances was found to act synergistically with dexamethasone (DEX; 500 nM) to increase GHRH-R mRNA expression. The effects of RAs and T3 were dose dependent, with maximum effects observed at 1 microM and 1 nM, respectively. The maximum effect of RAs or T3 was not further augmented by the addition of T3 or RAs, respectively. No apparent differences were observed in this study between the actions of RA and 9cRA. The Northern analyses showed that MtT/S cells express retinoic acid receptor alpha2 mRNA and thyroid hormone receptor beta2 mRNA, and DEX did not affect the levels of these mRNAs. This suggests that the role of DEX in enabling RAs or T3 to up-regulate GHRH-R mRNA levels is not an induction of the expression of each specific receptor for RAs and T3. The similar enhancement of DEX induction of GHRH-R mRNA by RAs or T3 was also observed in the fetal rat pituitary gland in culture, suggesting that RA and/or T3 is involved in the mechanisms responsible for the developmentally regulated expression of GHRH-R mRNA.

Regional expression of a gene encoding a neuron-specific Na(+)-dependent inorganic phosphate cotransporter (DNPI) in the rat forebrain

We have analyzed expression of a gene encoding a brain-specific Na(+)-dependent inorganic phosphate cotransporter (DNPI), which was recently cloned from human brain, in rat forebrain using in situ hybridization. The expression of DNPI mRNA showed a widespread but highly heterogeneous pattern of distribution in the forebrain, where hybridization signals were observed in neurons but not in any other types of cells. Neurons expressing the mRNA were far more numerous in the diencephalon than in the telencephalon. In the thalamus, a number of neurons with high levels of signals were localized to all nuclei of the dorsal thalamus, habenular nuclei and subthalamic nucleus, but not the reticular nucleus and zona incerta. Moderate signal levels were seen in many neurons throughout the hypothalamus, particularly the ventromedial, paraventricular, supraoptic and arcuate nuclei, lateral hypothalamic area and mammillary complex. In contrast, expression of DNPI mRNA in the telencephalon was generally at a low level and occurred locally in some restricted regions within the neocortex, retrosplenial cortex, piriform cortex, olfactory regions, hippocampal formation and medial amygdaloid nucleus. The present results suggest that DNPI functions in heterogeneous neuron populations as a neuron-specific Na(+)-dependent inorganic phosphate cotransport system predominantly expressed in the diencephalon of the rat.

A RUNX2/PEBP2alpha A/CBFA1 mutation displaying impaired transactivation and Smad interaction in cleidocranial dysplasia

Cleidocranial dysplasia (CCD), an autosomal-dominant human bone disease, is thought to be caused by heterozygous mutations in runt-related gene 2 (RUNX2)/polyomavirus enhancer binding protein 2alphaA (PEBP2alphaA)/core-binding factor A1 (CBFA1). To understand the mechanism underlying the pathogenesis of CCD, we studied a novel mutant of RUNX2, CCDalphaA376, originally identified in a CCD patient. The nonsense mutation, which resulted in a truncated RUNX2 protein, severely impaired RUNX2 transactivation activity. We show that signal transducers of transforming growth factor beta superfamily receptors, Smads, interact with RUNX2 in vivo and in vitro and enhance the transactivation ability of this factor. The truncated RUNX2 protein failed to interact with and respond to Smads and was unable to induce the osteoblast-like phenotype in C2C12 myoblasts on stimulation by bone morphogenetic protein. Therefore, the pathogenesis of CCD may be related to the impaired Smad signaling of transforming growth factor beta/bone morphogenetic protein pathways that target the activity of RUNX2 during bone formation.

[The relationship between stages and biochemical markers of smoking. Workplace-based cross-sectional and longitudinal studies]

In order to clarify smokers' characteristics by "Stages of Change" based on Prochaska's transtheoretical model, we conducted cross-sectional and logitudinal studies with biochemical markers of smoking and smoking habits. In a workplace-based sample of 277 male smokers, we examined cross-sectionally the relationships between stages and biochemical markers of smoking which include expired carbon monoxide concentrations and urinary nicotine metabolite concentrations, and smoking habits which include the number of cigarettes smoked per day, yields of cigarettes, inhalation patterns, time to first morning cigarette, and quit attempts in the past. Additionally we examined longitudinally the relationship between stages and expired carbon monoxide concentrations, the number of cigarettes, and yields of cigarettes. In the cross-sectional study there were significant differences among stages on expired carbon monoxide concentrations (P = 0.006), urinary nicotine metabolite concentrations (P = 0.049), the number of cigarettes smoked per day (P = 0.001), and yields of cigarettes (P = 0.042) using analyses of variance. There were also significant differences among stages on time to first morning cigarette (P = 0.018) and quit attempts in the past (P < 0.001) using chi-square tests. In the longitudinal study for each level of elevation in stage during a one-year period, expired carbon monoxide concentrations decreased on an average of 2.3 ppm (P = 0.125) and the number of cigarettes smoked per day decreased on an average of 2.8 cigarettes per day (P = 0.07). However, the yields of cigarettes did not change during the one-year period.

Neutrophil elastase inhibitor, ONO-5046 suppresses ozone-induced airway mucus hypersecretion in guinea pigs

To investigate the role of neutrophil elastase in ozone-induced airway hypersecretion, we measured goblet cell secretion by using a semiquantitative morphometric technique in guinea pigs. The magnitude of mucus discharge was estimated from the mucus score, which is inversely related to the degree of mucus discharge in histological sections of trachea stained for mucus glycoprotein with periodic acid Schiff/Alcian blue. Mucus hypersecretion of goblet cells was induced by ozone exposure and persisted for up to 5 h after exposure. Pretreatment with N-[2-¿4-(2,2-dimethyl-propionyloxy) phenyl-sulfonylamino¿ benzoyl] aminoacetic acid (ONO-5046), a specific neutrophil elastase inhibitor (200 mg/kg, intraperitoneally), significantly inhibited goblet cell hypersecretion both just after and 5 h after ozone-exposure, but the latter inhibition was not complete. In bronchoalveolar lavage fluid, ozone exposure significantly increased the number of neutrophils just after and 5 h after exposure, while ONO-5046 significantly inhibited the increase in neutrophils only 5 h after ozone-exposure. These results indicate that neutrophil elastase may play an important role in the ozone-induced tracheal goblet cell hypersecretion and influx of neutrophils.

PEBP2alphaA/CBFA1 mutations in Japanese cleidocranial dysplasia patients

Cleidocranial dysplasia (CCD) is an autosomal dominant human bone disease whose genetic locus has been located on chromosome 6p21, where the PEBP2alphaA/CBFA1 gene essential for osteogenesis also maps. Previously, several heterozygous mutations in PEBP2alphaA/CBFA1 were found in CCD patients. In this study, we identified six different types of mutations in PEBP2alphaA/CBFA1 in Japanese CCD patients. Four cases were similar to those reported previously: two were nonsense mutations in the Runt domain, one was a hemizygous deletion, and the other was a missense mutation in the Runt domain which abolished the DNA-binding activity of Runx2/PEBP2alphaA/CBFA1. The remaining two mutations were novel: one had a heterozygous gt-to-tt mutation at the splice donor site (gt) between the exon3-intron junction, which resulted in abnormal exon3 skipping, and the other had a mutation in exon7, which led to the introduction of a translational stop codon in the middle of the transactivation domain. Thus, defects in either the DNA-binding domain or transactivation domain of Runx2/PEBP2alphaA/CBFA1 can cause CCD. The results not only provide a strong genetic evidence that mutations involving in PEBP2alphaA/CBFA1 contribute to CCD, but also provide a useful tool to study how Runx2/PEBP2alphaA/CBFA1 plays its pivotal role during osteoblastic differentiation.

Congenital balloon digits in two neonates caused by constriction rings

Balloon digits were found in two neonates with congenital constriction ring syndrome. The affected digits were the right long finger and right great toe. They were surgically treated at the age of 10 and 9 days, respectively. Morphologic improvement was dramatic after surgery. In cases with extensive enlargement, severe cyanosis, redness, and no subsidence of edema within several days after birth, early operative treatment may be necessary to maintain digit viability and prevent autoamputation due to circulatory embarrassment. It can also be helpful to prevent fibrosis of the subcutaneous tissue. Pathologic examination revealed marked proliferation of fibrous tissue and lymphatic vessels.

Regulation of growth hormone-releasing hormone receptor messenger ribonucleic acid expression by glucocorticoids in MtT-S cells and in the pituitary gland of fetal rats

Regulation of GH-releasing hormone receptor (GHRH-R) messenger RNA (mRNA) expression was studied, with the ribonuclease protection assay, in the fetal rat pituitary gland and in MtT-S clonal cells. GHRH-R mRNA was first detected on embryonic day (E)19 and increased rapidly thereafter, to reach a maximum at E21. Incubation of E17 or E18 pituitaries with 50 nM dexamethasone (DEX), a synthetic glucocorticoid, induced GHRH-R mRNA expression, suggesting that glucocorticoids play a pivotal role in the developmental expression of this mRNA. In E19 pituitaries, 24 h treatment with DEX increased GHRH-R mRNA by 60%, and GH mRNA by 76%, but did not affect pit-1 mRNA level, suggesting that the effect of DEX is specific for expressions of GH mRNA and GHRH-R mRNA. The accumulation of GHRH-R mRNA by DEX was time dependent, and it was slightly enhanced by the protein synthesis inhibitor, puromycin (100 microM). In MtT-S cells (a pituitary cell line established from an estrogen-induced tumor), DEX induced GHRH-R mRNA expression within 2 h in a dose-dependent manner. This induction was augmented by puromycin (100 microM) or cycloheximide (3.5 microM). However, the RNA synthesis inhibitor Actinomycin D (1 microM) completely inhibited GHRH-R mRNA accumulation in response to either DEX or DEX plus puromycin, suggesting that glucocorticoids induce GHRH-R mRNA mainly through stimulation of mRNA transcription. These results suggest: that GHRH-R mRNA accumulation in the fetal pituitary gland of rats normally occurs at E19, probably because of the direct action of glucocorticoids on the pituitary gland, to stimulate GHRH-R mRNA transcription; and that the expression of glucocorticoid receptors is an important event in GH cell development in rats. Accordingly, immunocytochemical results suggest an increase in glucocorticoid receptors in immature GH cells between E17 and E18. The present results also imply that MtT-S cells may be a good model in which to further study the molecular mechanisms of the regulation of GHRH-R gene expression.

A simple bone cyst containing secretory cells in its lining membrane in a patient with polyostotic fibrous dysplasia

An 11-year-old boy, severely affected with polyostotic fibrous dysplasia, showed radiographically rapid expansion of a cystic lesion in his right humerus. At biopsy, there was an extraordinarily thin shell of bone and a cavity encapsulated by a hypertrophic fibrous membrane and filled with yellow serous fluid. Histologically, in addition to typical features of fibrous dysplasia, the fibrous capsule membrane was composed of proliferated mesenchymal cells characteristic of the affected bone. Ultrastructurally, many secretory granules were observed in numerous cytoplasmic vacuoles in the capsular cells as well as in the cultured cells isolated from the evacuated fluid.

Differential effect of nephrectomy on renal expressions of IGF-I and IGFBPs mRNA in selective growth hormone-deficient rats

It is known that growth hormone (GH) contributes to glomerulosclerosis and that this probably occurs via insulin-like growth factor-I (IGF-I). However, the manner by which GH and nephrectomy (Nx) alter IGF-binding protein (IGFBP) mRNA in the kidney has not been fully explained. The effects of GH on renal IGF-I and IGFBP-1, 2, 3, 4, and 5 following Nx were examined in spontaneous dwarf rats (SDRs) which have a complete and specific lack of GH among pituitary hormones. In normal Sprague-Dawley rats (SDs), Nx resulted in significant decreases in levels of IGFBP-1 mRNA and IGFBP-5 mRNA to 62.7 +/- 4.9 and 56.5 +/- 5.0% those of sham-operated kidneys, respectively. Nx did not alter the IGF-I mRNA level in SDs. The levels of IGFBP-2, IGFBP-3, and IGFBP-4 mRNAs were likewise unchanged following nephrectomy. In SDRs, Nx significantly decreased the levels of IGFBP-1, IGFBP-4, and IGFBP-5 mRNA, to 57 +/- 2.6, 46 +/- 12, and 64 +/- 8.1% of sham-operated animals. However, Nx did not alter the levels of IGF-I, IGFBP-2, and IGFBP-3 mRNA. GH injections of nephrectomized SDRs fully normalized the decreased IGFBP-4 mRNA levels, whereas levels of IGFBP-1 and IGFBP-5 mRNA were not reversed. The altered expression of IGFBP-4 mRNA following Nx of SDRs compared to that of SDs appears highly significant since it is known that, unlike SDs, glomerulosclerosis does not fully develop in SDRs following renal ablation. The change in the IGFBP-4 mRNA level might be related to the development of glomerulosclerosis in SDs.

Effect of nitric oxide synthase inhibitor on allergen- and hyperventilation-induced bronchoconstriction in guinea-pigs

To elucidate the role of endogenous nitric oxide (NO) in allergen- (AIB) and hyperventilation-induced bronchoconstriction (HIB), the effects of an NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), on AIB and HIB were studied in guinea-pigs. In the AIB group, 21 anaesthetized guinea-pigs, actively sensitized with 1% ovalbumin, were challenged with aerosolized 0.1% ovalbumin solution under mechanical ventilation. In the HIB group, 14 guinea-pigs were challenged with hyperventilation (tidal volume of 12 mL x kg(-1) at 150 breaths x min(-1) with 21% O2 and 5% CO2 dry gas) for 5 min. In both groups, lung resistance (RL) was measured using a pressure-volume-sensitive body plethysmograph, with or without L-NAME pretreatment (8 mg x kg(-1) i.v. followed by 2 mg x kg(-1) x min(-1) i.v.). The NO precursor, L-arginine was injected at a rate of 15 mg x kg(-1) x min(-1) after L-NAME injection (10 mg x kg(-1)) in the AIB group. The results were as follows. In the AIB group, the maximal RL change was significantly potentiated by pretreatment with L-NAME. This potentiating effect of L-NAME was reversed by L-arginine. In the HIB group, the pretreatment with L-NAME had no effect on increases in RL. These findings suggest that endogenous nitric oxide may play an important role in the modulation of allergen-, but not hyperventilation-induced bronchoconstriction in guinea-pigs.

Bradycardia induced by irinotecan: a case report

Irinotecan chloride (CPT-11) is a new semi-synthetic camptothecin analogue which has encouraging antitumor activity against various malignancies. The major and unique toxicity of CPT-11 is diarrhea. Cardiovascular toxicity is rare and has not been found in clinical trials performed in Japan except for a very few cases of insignificant tachycardiac arrhythmia. We report a case of a 69-year-old man with recurrent colon cancer who suffered from bradycardia induced by infusion of CPT-11. Other toxicities including hematological toxicity and diarrhea were mild. Pharmacokinetic analysis using a limited sampling model revealed that the occurrence of bradycardia did not correlate with the excess of drug exposure. Although all of the cholinergic actions reported in the literature were mild, cardiotoxicity may come to be a clinically significant problem. If the events were examined more thoroughly, the cholinergic effect may be discovered more frequently. To administer CPT-11 safely needs meticulous monitoring not only for hematological toxicity and diarrhea but also for other cholinergic actions including bradycardia.

The influence of relative body weight on toxicity of combination chemotherapy with cisplatin and etoposide

PURPOSE

This study was conducted to determine whether there was any relationship between the adverse toxicity of combination chemotherapy and clinical values including age, sex, creatinine clearance (Ccr), body surface area and relative body weight.

METHODS

Cisplatin at a dose of 80 mg/m2 on day 1 and etoposide at a dose of 100 mg/m2 on days 1, 2 and 3 were given to 42 consecutive patients with solid tumors. All patients had normal major organ function and received uniform hydration therapy.

RESULTS

Body Mass Index as a measure of relative body weight was inversely correlated with the percentage decrease in white blood cells (P = 0.0681) and platelet count (P = 0.0115). Body surface area was also inversely correlated with leukopenia (P = 0.0171) and thrombocytopenia (P = 0.0058). In contrast, age, sex and Ccr had no significant relationship with adverse toxicity.

CONCLUSIONS

It is concluded that dose adjustment of combination chemotherapy with cisplatin and etoposide according to age or ideal body weight is not appropriate and that a conventional dose modification method based solely on body surface area is probably not sufficient to reduce interpatient variability of cancer chemotherapy. A pharmacokinetic and pharmacodynamic study of combination chemotherapy is warranted to establish the ideal dose modification method.

Score-dependent fertility model for the evolution of cooperation in a lattice

The evolution of cooperation is studied in a lattice-structured population, in which each individual plays the iterated Prisoner's Dilemma game with its neighbors. The population includes Tit-for-Tat (TFT, a cooperative strategy) and All Defect (AD, a selfish strategy) distributed over the lattice points. An individual dies randomly, and the vacant site is filled immediately by a copy of one of the neighbors in which the probability of colonization success by a particular neighbor is proportional to its score accumulated in the game. This "score-dependent fertility model" (or fertility model) behaves very differently from score-dependent viability model (viability model) studied in a previous paper. The model on a one-dimensional lattice is a analysed by invasion probability analysis, pair-edge method mean-field approximation, pair approximation, and computer simulation. Results are: (1) TFT players come to form tight clusters. When the probability of iteration w is large, initially rare TFT can invade and spread in a population dominated by AD, unlike in the complete mixing model. The condition for the increase of TFT is accurately predicted by all the techniques except mean-field approximation; (2) fertility model is much more favorable for the spread of TFT than the corresponding viability model, because spiteful killing of neighbors is favored in the viability model but not in the fertility model; (3) eight lattice games on two-dimensional lattice with different assumptions are examined. Cooperation and defects can coexist in the models of deterministic state change but not in the models of stochastic state change.

[A case of neurologic type of Wilson's disease with increased aluminum in liver: comparative study with histological findings to metal contents in the liver]

Histological findings and metal contents in the liver were studied in a patient with neurologic type of Wilson's disease. Copper and aluminum contents in the biopsied liver of the patient with Wilson's disease were measured simultaneously by neutron activation analysis at Research Reactor Institute, Kyoto University. Four cases of adult cirrhosis were selected as the control for cirrhosis and five cases of adult liver as the control for neurologically normal. The biopsied liver showed markedly increase in the copper content (814.4 micrograms/g: dry weight) and extremely high content of aluminum (479.4 micrograms/g: dry weight), compared to those of the controls. On the other hand, macroscopically no cirrhosis was observed and the characteristic appearances of macronodular cirrhosis failed to detect histologically. Interestingly the fibrosis or inflammation of the liver was seen faintly. It is likely that toxic metals in the liver such as aluminum, copper and manganese might be implicated in the pathogenesis of neurologic type of Wilson's disease.

Congenital anterolateral bowing of the tibia with ipsilateral polydactyly of the great toe

We report on two cases of congenital unilateral anterolateral bowing and focal defect of the tibia associated with ipsilateral polydactyly of the great toe. Computed tomographic examination showed an unusual partial cleft of the tibia at the site of bowing. A long follow-up of one patient showed spontaneous resolution of the bowing without progression to pseudoarthrosis. These anomalies should be considered as a new entity related to the tibial developmental field.

Sp1 protein contributes to airway-specific rat MUC 2 mucin gene transcription

We have shown increases in the abundance of airway mucin mRNA during the pathogenesis of chronic obstructive pulmonary disease in rat models (Jany et al., 1991) and now seek to determine the underlying mechanisms. As transcriptional modulation may be involved, we provide here a functional analysis of the 5' flanking region of a rat mucin gene (MUC 2). Using deletion mutants to bp -859, we constructed expression cassettes in CAT vectors and transfected them into two MUC 2-expressing cell lines, SPOC 1, a rat airway epithelial cell line and IEC-6, a rat intestinal epithelial cell line, and into one MUC 2 non-expressing cell line, FR, a rat skin fibroblast cell line. Results indicated that nucleotides -59 to -40 mediated high level expression in SPOC 1, but not in the other cells. Used as a probe in gel shift assays, fragment -59/-40 formed complexes of differing mobilities when incubated with nuclear protein extracts from the three cell types. Mutation of the putative Sp1 binding site in the probe sequence interfered with protein binding in all three cell types, but anti-Sp1 antibody supershifted a band formed only by airway cell extracts. A model of airway cell-specific MUC 2 transcription is proposed.

Involvement of glucocorticoid-induced factor(s) in the stimulation of growth hormone expression in the fetal rat pituitary gland in vitro

The mechanism by which glucocorticoids induce GH expression between embryonic days 18 and 19 (E18-19) in the fetal rat pituitary gland was examined with an in vitro organ culture system. Twenty-four hour incubation of E18 pituitary glands in serum-free medium containing either dexamethasone (DEX, 5-50 nM) or corticosterone (0.55 microM) resulted in a conspicuous accumulation of GH messenger RNA (mRNA), whereas no spontaneous expression of GH mRNA was noted without glucocorticoid. Triiodothyronine (1 nM) alone weakly induced GH mRNA but increased the effect of DEX 2-fold. The GH mRNA accumulation was not observed after 5 or 10 h incubation with DEX. However, a 10-h incubation with DEX followed by 14 h chase incubation without DEX resulted in apparent induction of GH mRNA. The induction of GH mRNA by DEX was completely inhibited by puromycin. These data, taken as a whole, suggest that the induction of GH mRNA by DEX in the fetal pituitary gland is not a direct effect of DEX on the GH gene but is mediated by a factor that is synthesized in the pituitary gland in response to DEX. Both immunoblot and RNase protection assays suggested that this factor is not pit-1, which is known to be required for GH mRNA expression.

Role of tachykinins in bronchoconstriction induced by intravenous administration of bradykinin in guinea-pigs

To elucidate the role of tachykinins in bronchoconstriction induced by intravenous administration of bradykinin (Bk), we studied the effects of FK224, a neurokinin-1 (NK1) and neurokinin-2 (NK2) receptor antagonist, on the bronchoconstriction induced by intravenous (i.v.) administration of Bk (5-100 micrograms.kg-1) in guinea-pigs. Total pulmonary resistance -(RL) was measured using a pressure-volume sensitive body plethysmograph in anaesthetized artificially ventilated guinea-pigs pretreated with atropine (1 mg.kg-1) and propranolol (1 mg.kg-1). In the control group, i.v. administration of Bk produced a dose-dependent increase in RL. In animals pretreated with FK224, bronchoconstriction induced by higher doses of Bk (10, 50 and 100 micrograms.kg-1) was significantly reduced, whilst the bronchoconstriction caused by lower doses of Bk (5 and 7.5 micrograms.kg-1) was not. Pretreatment with a combination of FK224 and indomethacin markedly inhibited the bronchoconstriction induced by each dose of Bk compared with the groups pretreated with FK224 alone. Although pretreatment with indomethacin alone significantly reduced RL at a high dose of Bk (50 micrograms.kg-1), the reduction was significantly lower than that produced by a combination of FK224 and indomethacin. These results suggest that intravenous administration of a high dose of bradykinin causes bronchoconstriction both by cyclo-oxygenase products and by release of tachykinins.

Antley-Bixler syndrome: a disorder characterized by congenital synostosis of the elbow joint and the cranial suture

The Antley-Bixler syndrome is a rare disorder characterized by craniosynostosis, midface hypoplasia, radiohumeral synostosis, joint contractures, arachnodactyly, and femoral bowing and fractures. We report four cases with this disorder, all of which had craniosynostosis, midface hypoplasia with characteristic facial appearance, and contractures of bilateral elbow joints. However, femoral bowing, fractures, and arachnodactyly were not seen in our patients. In addition, proximal phalanges of the thumb and the great toe showed deformity of the delta phalanx in two cases. Characteristic features in these cases were the synostotic deformity of the elbow joint; three had radioulnahumeral synostosis, and one had radioulnar synostosis. Therefore, our cases indicated that various synostotic patterns of the elbow joints may exist in this syndrome. It is reasonable to propose that characteristic craniofacial appearance associated with the synostosis of the elbow joints of various forms should be considered minimal diagnostic criteria of the Antley-Bixler syndrome.

[Mucin gene--regulation of the expression of MUC2 and MUC3 mucin gene in the airway]

Mucus hypersecretion is a characteristic feature of several human airway diseases, including chronic bronchitis, cystic fibrosis and asthma. Analysis of rat disease models has suggested that mucin synthesis is up-regulated as part of the disease process. To understand the primary structure of secretory mucins, several cDNAs encoding airway mucin have been isolated. In most cases, full-length sequences have not been obtained. In this review, we focused on the MUC2 and MUC3 mucin gene. MUC2 mucin has been reported to be expressed in the human lung with airway disease and in the rat lung with infection and exposure to irritant such as SO2. MUC3 is also expressed in the bronchus. Less is known about the structure and the expression pattern of the MUC3 mucin gene. Recent findings show that the expression pattern of the MUC2 and MUC3 mucin genes differ strikingly, suggesting that they play distinct functional roles in the airway and intestine. Functional analysis of mucin gene promoter will provide better understanding of the regulation of its expression in the airway under both normal and pathological conditions.

BAY u3405, a thromboxane A2 antagonist, reduces bronchial hyperresponsiveness in asthmatics

OBJECTIVE

Thromboxane A2 (TXA2) is reported to induce bronchial hyperresponsiveness along with the well-documented bronchoconstrictor action on smooth muscles. We examined the effect of the TXA2 antagonist, BAY u3405, on bronchial hyperresponsiveness to methacholine (MCh) in asthmatics.

PATIENTS

Twelve adult asthmatics were studied in a randomized, double-blind, placebo-controlled, crossover fashion.

DESIGN

Following a 2-week run-in period, the subjects were administered 75 mg of BAY u3405 or placebo orally, twice a day for 2 weeks each in a crossover design, interposing a 2-week washout period. Bronchial hyperresponsiveness was measured by the astograph method. Briefly, the respiratory resistance (Rrs) was measured by the forced oscillation method during continuous inhalation of MCh in stepwise incremental concentrations, until Rrs reached twice the baseline value. Bronchial hyperresponsiveness was evaluated as the minimum cumulative dose (Dmin) of MCh that induced an increase in Rrs. Dmin was calculated so that 1 U of Dmin equals to 1 min of inhalation of aerosol solution at 1.0 mg/mL during quiet breathing.

RESULTS

Three subjects were withdrawn from the evaluation because they had asthmatic attacks or wheezing during the study. The Dmin value of 0.533 U (GSEM 1.675) after the BAY u3405 treatment was significantly greater than that of 0.135 U (GSEM 1.969) after the placebo treatment (p = 0.0139). There were no safety concerns in either treatment group.

CONCLUSION

We conclude that BAY u3405 may be a useful drug for attenuating bronchial hyperresponsiveness in bronchial asthma.

Immunoreactive luteinizing hormone (ir-LH) cells in the lung and stomach of chick embryos

Luteinizing hormone (LH) immunoreactivity was detected in the lung and stomach of chick embryos by the immunoperoxidase staining technique using specific antiserum to chicken LH. Immunoreactive LH (ir-LH) cells first appeared in the primordial cells of the epithelial layer of lung bud and foregut as well as of Rathke s pouch in the 3-day-old embryo, Hamburger and Hamilton stage 21. Ir-LH cells increased in number with advancing age of embryos in the lung, stomach, and pituitary gland. In the lung of 7-day-old embryos, stage 31, the ir-LH cells were distributed in the epithelium of primary, secondary, and tertiary bronchi, and their shapes were pseudostratified columnar, simple columnar, and simple cuboidal, depending on their sites in the intrapulmonary airway. Ir-LH cells were more numerous in the median part than in the lateral part of the lung, and the population in the epithelial layer of entobronchi of the secondary bronchi was 4 times higher than that in ectobronchi and laterobronchi of the secondary bronchi and in the primary bronchi. The immunoreactive products were found, either in the entire cell or in the apical part, facing the lumina of bronchi. In the stomach, ir-LH cells were found in the epithelial layer of gastric glands. No ir-LH cells were observed in interstitial regions, which consisted of mesenchymal cells and blood vessels, in the lung and stomach tissues. With advancing age, ir-LH cells changed their shapes to flat or squamous, coincident with the formation of parabronchi. Other pituitary hormones were not observed immunohistochemically in either the lung or stomach before hatching. Preabsorption of the antiserum against avian LH with the purified chicken LH or the extract of pituitaries from 10-day-old embryos completely destroyed the immunoreactivity to the cells in the lung and the pituitary. A single band of the immunoreaction products, whose molecular weight was around 25 K daltons, was shown by the immunostaining of nitrocellulose membrane transblotted after sodium dodecylsulphate-polyacrylamide gel electrophoresis of the purified pituitary LH, extracts of pituitaries from 10-day-old embryos, and the extracts of lungs from 7-, 10-, and 14-day-old chick embryos. These results demonstrated that ir-LH cells are present in extrapituitary tissues, and may play an important role during the development of chick embryonic lung and stomach.