Effects of imidazoline antagonists of alpha 2-adrenoceptors on endogenous adrenaline-induced inhibition of insulin release

We studied the effects of adrenoceptor antagonists and imidazoline derivatives on endogenous adrenaline-induced inhibition of insulin release in anesthetized rats. The intracerebroventricular injection of neostigmine increased plasma levels of catecholamines and glucose but not insulin. Pretreatment with an i.p. injection with phentolamine caused a dose-dependent increase in insulin secretion. When atropine was coadministered with phentolamine, the phentolamine-induced increase in insulin secretion was inhibited. Neither phentolamine nor atropine affected plasma levels of catecholamine. Yohimbine and idazoxan, which are alpha 2-adrenoceptor antagonists, and tolazoline, a non-selective alpha-adrenoceptor antagonist, also reversed adrenaline-induced inhibition of insulin secretion. Phenoxybenzamine, prazosin, propranolol, and antazoline, an imidazoline without alpha 2-adrenoceptor activity, did not affect insulin levels. When agents were preinjected i.p. in rats that were given saline into the third cerebral ventricle, phentolamine and antazoline, but not yohimbine and idazoxan, increased plasma levels of insulin. The results suggest that the inhibition of insulin release induced by adrenaline was reversed by antagonism of alpha 2-adrenoceptors. Phentolamine and antazoline, both of which are imidazoline derivatives, induced insulin secretion independently of the adrenoceptors only under the resting conditions.

Ultrastructure of cardiac myocyte in the Asian elephant (Elephas maximus)

Cardiac myocytes of an Asian elephant (Elephas maximus) were observed by transmission electron microscopy. Typical ultrastructural features of cardiac myocytes are exhibited in the musculature of both the left and right atria, and left ventricle of the heart. Myofibrils, mitochondria, T-system and sarcoplasmic reticulum are well-developed within the cytoplasm. Many mitochondria are characteristically concentrated is some myocytes. Cardiac musculature is also distributed in the root of the caudal vena cava. Many atrial granules are detected not only in atrial myocytes, but also in the myocytes of the caudal vena cava. Atrial natriuretic polypeptide may be secreted from the caval venous wall in the elephant.

Histological and immunohistochemical analysis of lung development, with particular reference to lung hypoplasia

Using immunohistochemical (IH) staining for epithelial membrane antigen (EMA), keratin, Leu-7, Ca 19-9, secretory component (SC) and surfactant protein A (SPA) on formalin-fixed, paraffin-embedded autopsy cases of stillbirth and early neonatal death, the normal profile of IH-positive cells in the airway of the developing fetal lung was clarified. IH-positive cells first appeared in the proximal region of the lung, and then in the distal region. Keratin-positive cells and EMA-positive cells were abundant at the 10th gestational week (10 GW), the earliest stage observed in this study. Cells positive for Leu-7 and Ca 19-9 appeared during the time when bronchial branches developed, and were abundant at around 16 GW, the time of completion of bronchial branching. On the other hand, SPA- and SC-positive cells appeared after the completion of bronchial branching, and were abundant around 29 GW and 34 GW, respectively. Acinous structural development was observed in terms of radial alveolar count (RAC). Cases of lung hypoplasia defined as a lung weight to body weight ratio of under 0.012 at > or = 28 GW or under 0.015 at < 28 GW showed a rather high tendency of abnormalities of cellular differentiation revealed by IH staining.

Distribution of the DNA adducts of 2-amino-3-methylimidazo[4,5-f] quinoline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in the supF gene as determined by polymerase arrest assay

The distribution of the adducts of the cooked meat-derived heterocyclic amines 2-amino-3-methylimidazo[4,5-f] quinoline (IQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhlP) was examined in the supF gene of PSP189 by a polymerase-arrest assay using thermal-cycle sequencing. The reactive N-acetoxy metabolites of both compounds showed an overwhelming preference for reacting with guanine residues in the supF gene of the shuttle vector pSP189. The distribution of the IQ and PhlP guanine adducts was not random; instead, patterns of adduct hot-spots and cold-spots were observed. There was a striking similarity between both compounds in their preferred sites of adduct formation. The finding that IQ and PhlP adducted to guanine concurred with previous results showing that the target sites for IQ and PhlP mutations in supF were also at guanine. However, the adduct hot-spot sites were not predictive of the known sites of mutation hot-spots. In addition, despite the similarity in adduct hot-spots for IQ and PhlP, their reported mutation spectra in the supF gene were different. Factors in addition to adduct location therefore appear to play a role in the mutation spectra induced by the heterocyclic amines in the supF gene.

Spermidine-preferential uptake system in Escherichia coli. ATP hydrolysis by PotA protein and its association with membrane

PotA protein, one of the components of the spermidine-preferential uptake system in Escherichia coli, was purified to homogeneity, and some of its properties were examined. PotA protein showed Mg(2+)-and SH-dependent ATPase activity. The specific activity was approximately 400 nmol/min/mg of protein and the Km value for ATP was 385 microM. The nature of the ATP binding site was explored by identification of the amino acid residue photoaffinity-labeled with 8-azido-ATP. It was found that 8-azido-ATP was attached to cysteine 26. In the spermidine transport-deficient mutant E. coli NH1596, valine 135 of PotA protein, which is located between two consensus amino acid sequences for nucleotide binding (50-57 and 168-173), was replaced by methionine (Kashiwagi, K., Miyamoto, S., Nukui, E., Kobayashi, H., and Igarashi, K. (1993) J. Biol. Chem. 268, 19358-19363). This mutated PotA protein could be labeled with 8-azido-ATP, but showed very low ATPase activity. To identify which cysteine is involved in the function of potA protein, cysteines 26, 54, and 276 were replaced by alanine, threonine, and alanine, respectively. Among the three mutated PotA proteins, the mutated PotA protein C54T only lost both ATPase and spermidine uptake activities. The results taken together indicate that the adenine portion of ATP interacts with a domain close to the NH2-terminal end of PotA protein, and active centers of ATP hydrolysis are located both within and between the two consensus amino acid sequences for nucleotide binding. Association of PotA protein with membranes was strengthened by the existence of channel forming PotB and PotC proteins. ATPase of PotA protein was inhibited by spermidine, suggesting that uptake inhibition by spermidine may function during this process.

Cardiac musculature of the cranial vena cava in the common tree shrew (Tupaia glis)

Cardiac musculature of the cranial vena cava in the common tree shrew (Tupaia glis) was examined by light and transmission electron microscopy. The common tree shrew has well developed cardiac myocyte layers in the tunica media of the cranial vena cava, extending from the right atrium to the root of the subclavian vein. Because the common tree shrew belongs to a primitive group of mammals, the occurrence of cardiac musculature in the cranial vena cava may be a common feature in lower mammals. The development of this musculature indicates that active contraction of the cranial vena cava wall occurs in this species. Electron micrographs showed the typical ultrastructure of myocytes and nerve endings. These observations suggest that this musculature may serve as a regulatory pump for the return of venous blood to the right atrium and as a blood reservoir system under conditions of rapid heart rate. Additionally, the presence of atrial natriuretic polypeptide (ANP) was also demonstrated in the myocytes of the vena cava immunohistochemically. These findings show that the cardiac endocrine organ for ANP develops even in the principal veins including the cranial vena cava.

Gene of heat shock protein of sulfur-dependent archaeal hyperthermophile Desulfurococcus

To elucidate thermoresistance, a gene of a hyperthermophilic heat shock protein (HHSP) was isolated from the hyperthermophile Desulfurococcus strain SY which grows at 95 degrees C. The molecular weight of HHSP deduced from the open reading frame was 59,137 (545 amino acid residues). Sequence alignments of peptides reveal similarities (evolutionary distances) to the alpha (0.279) and beta (0.296) subunits of thermosome, TF55 (0.343) and human t-complex polypeptide 1. The structure of a thermophilic heat shock protein TGroEL (Tamada et al. (1991) Biochem, Biophys. Res. Commun. 179, 565) was quite different from that of HHSP. TGroEL and HSP60 have sequences identical to HHSP at its equatorial domain, while those identical to the alpha subunit of F-type ATPase are at its apical domain.

Immunocytochemical localization of the protein reactive to human beta-1, 4-galactosyltransferase antibodies during chick embryonic skin differentiation

BACKGROUND

beta-1, 4-Galactosyltransferase (GalTase) transfers galactose from UDP-galactose to terminal N-acetylglucosamine in glycoconjugates and is located both in the Golgi apparatus and in the plasma membrane. The cell surface GalTase is thought to be involved in cell-to-cell recognition and cell-to-extracellular matrix interaction.

METHODS

By the use of specific monoclonal antibodies against human GalTase, changes in cell surface localization of the protein reactive to the antibodies in chick embryonic skin during its differentiation in vivo and in vitro were detected immunohistochemically at both light- and electron microscopic levels. The distribution of glycoconjugates having terminal N-acetylglucosamine residues was detected by staining with succinylated wheat germ agglutinin (s-WGA).

RESULTS

Under the light microscope, intense immunostaining was observed in the keratinized epidermis, particularly in the intermediate layer. Marked changes in the localization of the staining were observed in vitamin A-induced mucus-secreting skin, in which keratinization was suppressed. The localization of the immunostaining was in parallel with that of glycoconjugates having terminal N-acetylglucosamine residues. Immunoelectron microscopically the immunostaining was located on the cell surface and in the intercellular space of the desmosomes in the intermediate cells of the keratinized epidermis. However, the staining was not present on the cell surface but was detected on the limiting membrane of the mucous granules, in the mucous metaplastic epidermis. In contrast, the staining was always found in the Golgi apparatus in all of the cells.

CONCLUSIONS

These results suggest that the protein reactive to human GalTase antibody may be involved in chick epidermal differentiation.

[Awareness and feelings of elderly patients and their families concerning disease during terminal hospitalization--malignancy versus non-malignancy]

We conducted a questionnaire survey on the awareness and feelings of elderly patients and their families concerning their diseases and prognosis during terminal hospitalization. Sixty-five families of 177 patients who died at our hospital in 1992 answered questions concerning estimation of the prognosis, understanding of the disease, satisfaction regarding explanation of the disease, wish to be informed of the diagnosis, feelings during hospitalization, and whether the family revealed the diagnosis to the patient. Patients with malignancy were not informed of the true diagnosis at this time. As to estimation of the prognosis, patients aged 70 or older who did not expect "cure" of their diseases at first were significantly fewer, and those anticipating "death" just before dying were significantly more frequent than those under age 70. In patients with malignancy, those aged 70 or older foresaw "incurability" at first significantly more frequently than those under age 70. Patients with malignancy knew the diagnosis in significantly fewer cases, believed the false diagnosis significantly more frequently, and showed dissatisfaction with the explanation of the disease significantly more frequently, than those with non-malignancy. Proportions of the family who told the diagnosis to the patient were 11.8% in malignancy and 38.8% in non-malignancy with statistical significance. These data indicate that medical care during terminal hospitalization should be modified principally based on informed consent, if that is the wish of the patient.

Mouse growth hormone-releasing factor secretion is activated by inhibin and inhibited by activin in placenta

We investigated the effects of activin and inhibin on the regulation of mouse growth hormone-releasing factor (mGHRF) secretion by primary placental cells harvested at Day 12 of pregnancy. Activin-A, an activator of FSH secretion, inhibited mGHRF secretion. In contrast, inhibin, an inhibitor of FSH secretion, activated mGHRF secretion. The lowest concentrations of activin-A and inhibin that significantly affected mGHRF secretion were 2 nM. Follistatin, a binding protein of activin, completely eliminated the ability of activin to inhibit mGHRF secretion. The steady-state level of mGHRF mRNA, as assessed by Northern analysis, was reduced by incubation of placental cells with activin-A. All activin and inhibin subunit mRNAs were expressed in mouse placenta, and their expressions increased during gestation. These findings suggest that activin and inhibin have opposite effects on mGHRF secretion as compared with FSH secretion and that they regulate mGHRF secretion in an autocrine or paracrine manner in the mouse placenta in vivo.

Microgravity generated by space flight has little effect on the growth and development of chick embryonic bone

Seven days' space flight of fertilized chicken eggs pre- incubated for 7 and 10 days on earth caused no differences in the morphology of osteoblasts, osteoclasts, and osteocytes of humerus and tibia from those of control embryos. Bone-resorbing and -forming activities of the femur were not different between control and flight groups. As a consequence, calcium and phosphorus contents of the femora between control and flight groups were not changed. Alkaline phosphatase activity of 3 different regions (resting cartilage, growth cartilage, and cortical bone) of tibia showed no significant difference between control and flight groups. No significant difference of gene expressions of hepatocyte growth factor and receptors of fibroblast growth factor was observed in perichondrium, trabecula, and skeletal muscles and tendons of hind limbs between control and flight groups. Unlike the results of previous space flight experiments in which young growing mammals were used, these morphological and biochemical results indicate that microgravity has little effect on bone metabolism of the chick embryo.

Ultrastructure of cardiac myocytes in the greater bandicoot rat (Bandicota indica)

Cardiac myocytes in the left ventricle and atrium of the greater bandicoot rat (Bandicota indica) were examined by transmission electron microscopy. The fine structure showed typical features of mammalian cardiac myocytes. In atrial myocytes, however, the areas occupied by mitochondria were much smaller than that filled with myofibrils. The decrease in mitochondria and the abundance of myofibrils are thought to be an ultrastructural adaptation to the large body size of this species. Many conducting myocytes were observed in both atrium and ventricle. The atrial conducting myocytes were ultrastructurally different from the Purkinje fibers of the ventricle. We suggest that the abundance and the ultrastructural variation of conducting myocytes are related to the physiological aspects, such as body size, of this animal.

Inhibition of growth hormone-releasing factor production in mouse placenta by cytokines using gp130 as a signal transducer

The aim of this study was to investigate whether mouse placenta produces mature mouse GHRF (mGHRF) and whether cytokines regulate placental mGHRF production. Using Sephadex G-50 gel filtration chromatography and reverse phase HPLC, we identified immunoreactive mGHRF in acid-ethanol extract of placental tissues, which had chromatographic characteristics identical to those of hypothalamic mature mGHRF peptide. The major peak of immunoreactive GHRF in the medium from cultured placental cells was resolved by HPLC at a fraction identical to hypothalamic mature mGHRF. Interleukin-6 (IL-6), IL-11, leukemia inhibitory factor (LIF), and oncostatin-M, which all use gp130 as a signal transducer, significantly inhibited mGHRF secretion by cultured placental cells. However, IL-1 alpha and tumor necrosis factor-alpha had no effect on mGHRF secretion. Antibodies to IL-6 or IL-6 receptor completely blocked the inhibitory effect of IL-6 on mGHRF secretion. Anti-LIF, and oncostatin-M inhibited the expression of mGHRF messenger RNA. These results suggest that mouse placenta produces and releases the mature mGHRF, which is indistinguishable by chromatographic criteria from that produced by the hypothalamus, and that signals through gp130 lead to the inhibition of mGHRF production and release in the mouse placenta.

Effects of KCA-012 on bone metabolism in organ culture

3,9-Dihydroxy-5H-benzofuro[3,2-c]quinoline-6-one (KCA-012), the chemical structure of which is closely similar to that of the phytoestrogen coumestrol, inhibited parathyroid hormone-, 1 alpha,25-dihydroxyvitamin D3- and prostaglandin E2-induced bone resorption of cultured fetal rat bones. KCA-012 also increased the calcium content of 9-day chick embryonic femur cultured in vitro. KCA-012 did not show any estrogenic activity as determined by an increase in the uterine weight of ovariectomized rats, whereas coumestrol did. These results indicate that KCA-012 has no estrogenic activity and has unique effects of inhibiting bone resorption and stimulating bone mineralization.

[Tension pneumocephalus in association with ventriculoperitoneal shunt and congenital bony defect in the mastoid tegmen]

The authors report a case of tension pneumocephalus in association with a congenital bony defect at the mastoid tegmen, and a ventriculoperitoneal (V-P) shunt for obstructive hydrocephalus, due to the presence of a posterior fossa meningioma. After multiple diagnosis and surgical procedures, congenital bony defect at the right mastoid tegmen demonstrated by a middle ear cavity computerized tomography (CT) scan, was identified as the source of entry of the air. The air must have penetrated the lateral ventricle through a porencephalic cyst in the right temporal lobe. Reconstruction of the bony defect in the mastoid tegmen successfully prevented further recurrence of tension pneumocephalus. We discussed the possible pathogenic mechanisms involved in this kind of tension pneumocephalus, and suggested that a middle ear cavity CT scan should be performed for tension pneumocephalus that has developed after V-P shunt.

Expression in Escherichia coli of a gene encoding a thermostable chitinase from Streptomyces thermoviolaceus OPC-520

An expression plasmid for a thermostable chitinase gene from S. thermoviolaceus OPC-520 in E. coli was constructed. A cloned chitinase (Chi40) was purified from the periplasmic space of E. coli harboring the expression plasmid. The N-terminal sequence of Chi40 was 11 amino acids longer than that of chitinase from S. thermovilaceus OPC-520 (ST chitinase), however, a loss or addition of the amino acid residues did not affect the enzymatic properties. The mutations of Asp-145 and Glu-147 drastically decreased the specific activity of chitinase from the wild type, indicating that both amino acid residues are the best candidates for the essential catalytic residues of Chi40.

A silencer element for the lipoprotein lipase gene promoter and cognate double- and single-stranded DNA-binding proteins

Transfection experiments with constructs containing various 5'-deleted fragments of the human lipoprotein lipase (LPL) promoter and the chloramphenicol acetyltransferase reporter gene revealed an LPL silencer element (LSE) in the region of nucleotides -225 to -81 of the LPL gene that functioned in Chinese hamster ovary (CHO) and HeLa cells. Gel retardation competition analysis showed the presence of a nuclear factor(s) capable of binding to the sequence of nucleotides -169 to -152 of LSE (LSE-6) in a single-stranded (opposite-strand) and double-stranded specific fashion, the binding affinity being almost the same in the two binding forms. Site-directed mutagenesis indicated that almost the entire sequence of LSE-6 was necessary to form the complexes and also critical for silencing activity in CHO cells. The amounts of this binding factor(s) in CHO and HeLa cells were closely associated with transcriptional silencing activity. Photochemical cross-linking experiments indicated that the single- and double-stranded elements recognized the same binding factor(s) with molecular masses of 54 to 63 kDa and 109 to 124 kDa. The 109- to 124-kDa DNA binding factor(s) was found to be a doublet of that of the 54- to 63-kDa factor by isoelectric focusing or by increasing the time of exposure to UV irradiation. When inserted upstream of another gene such as that of the simian virus 40 enhancer/promoter of pSV2CAT, the sequence of nucleotides -190 to -143 (LSE-1) also suppressed transcription of the reporter gene in CHO cells. These results strongly suggest that the LSE plays a role in regulation of LPL gene expression by suppressing its transcription.

Changes in expression of two endogenous beta-galactoside-binding isolectins in the dermis of chick embryonic skin during development in ovo and in vitro

In order to elucidate the roles of metal-independent animal lectins, we systematically investigated changes in expression of 2 kinds of beta-galactoside-binding isolectins (MW 14 and 16 kDa) in the dermis of chick embryonic tarsometatarsal skin during the course of development. These lectins were immunohistochemically located at different stages of development both in ovo and in vitro by light and electron microscopy. Light-microscopic observation showed that while positive staining for the 14-kDa lectin was weak at days 8 and 10 it became intense after day 13. In contrast, staining for the 16-kDa lectin was intense at days 8, 10, and 13, but it became weak after day 17 when keratinization of the epidermis was completed. Immuno-electron-microscopic observation revealed that both the 14 and 16-kDa lectins were located on the basement membrane, in the extracellular matrix, and in both the cytoplasm and the nucleus of dermal fibroblasts. Distribution of the 2 isolectins was also examined in cultured skin explants in vitro. The results were almost the same as those obtained in ovo when the skin explant was keratinized in the presence of hydrocortisone. However, in the skin explant where keratinization was prevented and mucous metaplasia was induced by the addition of vitamin A, the distribution of the 14-kDa lectin in the epidermis was significantly affected. These results indicate that (1) the expression of the 2 isolectins is differently regulated in both the dermis and epidermis, (2) the 16-kDa lectin is involved in the early stage of the formation of the dermis and the basement membrane and is replaced by the 14-kDa lectin as keratinization of the epidermis occurs, and (3) the expression of the 2 isolectins in the dermis is not significantly affected by the induction of mucous metaplasia, in contrast to their drastic changes in the epidermis.

Co-localization of placental lactogen-I, placental lactogen-II, and proliferin in the mouse placenta at midpregnancy

This study was undertaken to determine whether mouse placental lactogen (mPL)-I, mPL-II, and proliferin (PLF) are expressed by the same population of placental giant cells at midpregnancy. Tissue sections from Day 9 of pregnancy were analyzed by double immunofluorescence staining. Sections were stained for PLF by use of a rhodamine-conjugated second antibody, and for mPL-I or mPL-II by use of a fluorescein-conjugated second antibody. All three proteins were present in most of the same giant cells. The distribution of mPL-I and PLF among giant cells in vitro was also examined. When placental cells from Day 7 of pregnancy were cultured for 5 days, > 90% of the cells that immunostained for mPL-I also immunostained for PLF on the first 3 days of culture. Thereafter, the percentage of cells that contained both proteins declined rapidly while the percentage that contained only PLF increased, suggesting continued differentiation of the cells in vitro. These data demonstrate that the same trophoblast giant cells express mPL-I, mPL-II, and PLF simultaneously at midpregnancy, suggesting that their gestational profiles in maternal blood during this period result at least partly from changes in gene expression in one population of cells and not from differentiation of several subsets of giant cells, each expressing only one member of the gene family.

Mouse placental cells secrete immunoreactive growth hormone-releasing factor

The initial objective of this study was to establish a placental cell culture system in which the secretion of mouse growth hormone-releasing factor (mGHRF) could be examined during a several-day period. To determine when during pregnancy placental cells begin to express mGHRF, Northern blot analysis was carried out on total RNA from placentas collected on Days 6, 9, 11, 13, 15, 17, and 18 of pregnancy. Mouse GHRF mRNA could be detected as early as Day 11 of pregnancy. Its steady-state levels increased to maximum values on Days 15-17 and then declined slightly on Day 18. Placentas from Day 12 of pregnancy were selected for cell culture. The basal zone and labyrinth were dispersed in collagenase, and the cells were fractionated on a Percoll gradient. Two bands of cells were selected for further study. Both released significant amounts of immunoreactive mGHRF during a 5-day culture period. Effects of prolonged exposure of the cells to 8-bromo-cAMP and to agents that elevate intracellular cAMP concentration were then examined. Treatment of the cells with 0.5 mM 8-bromo-cAMP resulted in a significant decrease in the mGHRF concentration of the medium by the second day of culture. Mouse GHRF secretion was also inhibited by treatment of the cells with 100 ng/ml cholera toxin or 0.1 mM forskolin. The effect of 8-bromo-cAMP was concentration-dependent, with 0.1 mM being the lowest concentration that was active. 8-Bromo-cAMP treatment also reduced the steady-state level of mGHRF mRNA in the cells.(ABSTRACT TRUNCATED AT 250 WORDS)