Mechanism of DmS-II-mediated pause suppression by Drosophila RNA polymerase II

Transcription elongation factor S-II mediates nascent transcript cleavage by RNA polymerase II (Reines, D. (1992) J. Biol. Chem. 267, 3795-3800). We have examined the mechanism of action of the Drosophila S-II analog, DmS-II, in a defined transcription system. Our results show that DmS-II is necessary and sufficient to activate nascent transcript cleavage by RNA polymerase II during transcription of a dC-tailed template. The pattern of transcripts resulting from prolonged action by DmS-II indicates that there are kinetic barriers to transcript shortening. During the cleavage reaction, the polymerase remains in register with the template strand and generates mainly nucleotide dimers. The ability of DmS-II to mediate transcript shortening resides in the carboxyl-terminal half of the protein. Our results support a model for pause suppression in which DmS-II binds to the paused polymerase, causes one cleavage event and is then released from the complex. Elongation by the polymerase then allows a second encounter with the pause site and a second chance of passing the site. Complete pause suppression may require multiple transcript shortening events for some polymerase molecules.

Phosphorylation and activation of protamine kinase by two forms of a myelin basic protein kinase from extracts of bovine kidney cortex

Two myelin basic protein kinases designated MBPK-1 and MBPK-2 were purified to apparent homogeneity from extracts of bovine kidney cortex. The purified preparations exhibited an apparent M(r) approximately 40,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and approximately 42,000 (MBPK-1) and 45,000 (MBPK-2) by gel permeation chromatography. Up to 0.4 and 1.8 mol of phosphoryl groups were incorporated per mol of MBPK-1 and MBPK-2, respectively, on threonines following incubation with ATP. Autophosphorylation, incubation with protein phosphatase 2A2 (PP2A2), CD45, or T-cell protein tyrosine phosphatase did not affect MBPK-1 activity. Autophosphorylation increased by about 3-fold MBPK-2 activity. This autophosphorylation and activation was reversed by PP2A2 but not by CD45 or T-cell protein tyrosine phosphatase. MBPK-1 and MBPK-2 displayed a positive reaction with an antibody to mitogen-activated protein kinase. Purified preparations of protamine kinase were activated by about 1.5-6-fold and, after inactivation with PP2A2, were reactivated by about 30% by MBPK-1 and MBPK-2. Activation and reactivation correlated with the incorporation, respectively, of 0.1-0.5 and 0.5 mol of phosphoryl groups/mol of the protamine kinase on serines. The results show that MBPK-1 and MBPK-2 are protamine kinase-activating kinases and suggest that MBPK-1 and MBPK-2 may be related to mitogen-activated protein kinase.

Purification and characterization of an autophosphorylation-activated protein serine threonine kinase that phosphorylates and inactivates protein phosphatase 2A

Protein phosphatase 2A2 is inactivated by phosphorylation following incubation with purified preparations of an autophosphorylation-activated protein kinase (Hong Guo and Zahi Damuni (1992) Proc. Natl. Acad. Sci. U.S.A. 90, 2500-2504). This protein kinase was purified about 250,000-fold from extracts of bovine kidney to apparent homogeneity. The purified preparations exhibited a single polypeptide of apparent M(r) approximately 36,000. Up to 1 mol of phosphoryl groups was incorporated per mol of the purified kinase following incubation with ATP. This autophosphorylation reaction (t1/2 approximately 0.5-1 min) was accompanied by a approximately 10-fold activation of the kinase. Autophosphorylation and activation were reversed by protein phosphatase 2A2 or the catalytic subunit of protein phosphatase 1. Phosphoamino acid analysis indicated that the kinase underwent autophosphorylation on threonines. The rate of autophosphorylation was independent of the concentration of the enzyme and a slope of 0.97 (gamma = 0.998) was obtained by van't Hoff's plot indicating that autoposphorylation was intramolecular. Relative to myelin basic protein, the enzyme exhibited about 8, 62, 130, 33, 5, and < 0.1% activity with histones H1, H2A, H2B, H3, and H4 and with glycogen synthase alpha, respectively. Heparin inhibited the activity of the enzyme half-maximally at about 20 micrograms/ml. The results indicate that this autophosphorylation-activated kinase is a new protein kinase.

Hypothermia blunts acetylcholine increase in CSF of traumatically brain injured rats

Activation of muscarinic acetylcholine (ACh) receptors contributes to the pathophysiological consequences of moderate experimental traumatic brain injury (TBI). Hypothermia (30 degrees C) provides protection in experimental TBI. We measured ACh levels in CSF and plasma 5 min after moderate fluid percussion TBI under normothermic or hypothermic conditions, because ACh in the CSF has been correlated with the severity of behavioral deficits after TBI. Three groups were examined: TBI with hypothermic brain (30 degrees C), TBI with normothermic brain (37 degrees C), or sham TBI with normothermic brain (37 degrees C). ACh concentrations in CSF were significantly higher in 37 degrees C TBI rats, but not in 30 degrees C TBI rats compared to shams. ACh concentrations in plasma did not differ between groups. These results suggest that a contributing factor to the neuroprotective effects of moderate hypothermia in TBI may be related to the reduction of excessive ACh levels in the central nervous system following injury.

Autophosphorylation-activated protein kinase phosphorylates and inactivates protein phosphatase 2A

Purified preparations of a distinct autophosphorylation-activated protein kinase from bovine kidney phosphorylated and inactivated purified preparations of protein phosphatase 2A2 (PP2A2) by about 80% with the autophosphorylation-activated protein kinase, protamine kinase, and 32P-labeled myelin basic protein as substrates. Analysis of incubations performed in the presence of 0.2 mM [gamma-32P]ATP by autoradiography following SDS/PAGE and by FPLC gel permeation chromatography on Superose 12 demonstrated that the catalytic subunit of PP2A2 was phosphorylated in the incubation mixtures containing the kinase and phosphatase. Up to 0.3 mol of phosphate groups was incorporated per mol of the catalytic subunit of PP2A2 following incubation with the kinase. This phosphorylation was enhanced about 5-fold in the presence of 0.4 microM microcystin-LR. In addition, up to 1 mol of phosphate groups was incorporated per mol of the PP2A2 subunit of apparent M(r) approximately 60,000 when microcystin-LR was included. Analysis by thin-layer chromatography indicated that PP2A2 catalyzed an autodephosphorylation reaction which was inhibited by microcystin-LR. Phospho amino acid analysis showed that the catalytic subunit of PP2A2 was phosphorylated on threonine residues by the autophosphorylation-activated protein kinase. Together with previous observations, the results suggest that inactivation of PP2A by phosphorylation catalyzed by the autophosphorylation-activated protein kinase could contribute to the marked increase in the phosphorylation of cellular proteins in response to insulin and other mitogens.

Effect of catecholamines on intracellular pH in sheep cardiac Purkinje fibres

1. It has been reported that catecholamines affect intracellular pH (pHi) in a number of tissues, generally by altering the kinetics of the Na(+)-H+ exchanger. We postulated that catecholamines might affect pHi in cardiac tissue. We tested this in resting sheep cardiac Purkinje fibres by measuring transmembrane potential and pHi with standard and H(+)-sensitive microelectrodes. 2. Adrenaline and the beta-adrenergic agonist isoprenaline, both 5.0 x 10(-6) M, resulted in depolarization and intracellular acidification (adrenaline, 0.03 +/- 0.01 pH units, n = 8, P = 0.005; isoprenaline, 0.08 +/- 0.01 pH units, n = 17, P = 0.0001). The alpha-adrenergic agonist phenylephrine, at concentrations up to 200 microM, had no significant effect on membrane potential or pHi. 3. Isoprenaline significantly attenuated the half-time (t0.5) for pHi recovery from intracellular acidification induced via the NH4Cl pulse technique. Isoprenaline also attenuated the hyperpolarization that is normally seen at the onset of pHi recovery. Phenylephrine slightly reduced the t0.5 for recovery, although the reduction did not reach statistical significance. 4. Forskolin, 7.5-10 x 10(-5) M, an agent that raises intracellular cyclic adenosine 3',5'-monophosphate (cyclic AMP), also induced depolarization and acidification, similar to that induced by adrenaline and isoprenaline. 5. In the presence of the Na(+)-H+ exchange blocker 5-dimethyl amiloride, 2-6 x 10(-5) M, isoprenaline-induced acidification was blunted but not abolished. When administered in Na(+)-free Tyrode solution, isoprenaline-induced acidification was also not abolished. Buffering power, tested using the NH4Cl method, was not decreased by isoprenaline, but rather, was slightly increased. Reversal of H+ driving force across the cell membrane from the normally inward direction to outward (achieved by increasing pHo to 8.3-8.5 and depolarizing the membrane with 10 mM K+ solutions) did not prevent intracellular acidification from occurring in the presence of isoprenaline. When glycolysis was inhibited by a 60 min exposure to glucose-free solution containing 5.5 mM 2-deoxyglucose, acidification by isoprenaline was nearly abolished. 6. We conclude that, in resting sheep Purkinje fibres, beta- but not alpha-adrenergic stimulation results in intracellular acidification and depolarization, probably mediated via an increase in cyclic AMP. beta- but not alpha-adrenergic stimulation slows the rate of recovery from intracellular acidification and blunts the hyperpolarization associated with this recovery. 7. The intracellular acidification appears to be due both to partial inhibition of Na(+)-H+ exchange and to stimulation of glycolysis by beta-adrenergic agents.

[Application of electron microscopy in the diagnosis of neoplasms]

The majority of neoplasms can be diagnosed by light microscopy, but in some cases the diagnosis remains ambiguous due to poor differentiation, even though special stainings have been employed. This paper presents 34 cases of neoplasms in which the tumors were diagnosed by electron microscopy. This includes distinguishing (1) anaplastic carcinoma from lymphoma; (2) anaplastic carcinoma from amelanotic melanoma; (3) APUDoma from other tumors; (4) different mesenchymal tumors. The diagnoses of 4 cases of malignant melanoma, 11 cases of APUDoma, 7 cases of poorly differentiated carcinoma or anaplastic carcinoma, 2 cases of non-Hodgkin's lymphoma, 9 cases of mesenchymal tumors and 1 cases of other tumors have been resolved by electron microscopy. It is obvious that in some cases, electron microscopy can be of help in establishing a correct diagnosis.

Gap-junctional protein connexin 43 is expressed in dermis and epidermis of human skin: differential modulation by retinoids

Retinoids are effective modulators of proliferation and differentiation of keratinocytes in vivo and in vitro. In mouse 10T1/2 cells, retinoid action on proliferation and neoplastic transformation is correlated with the upregulation of gap-junctional communication and expression of connexin 43 (Cx43). In the present study we have determined if retinoids induce similar effects on gene expression in human skin. Studies were conducted in intact skin and on cultured keratinocytes and dermal fibroblasts. In a clinical study, 2 weeks of treatment with 0.05% all-trans retinoic acid resulted in increased expression of Cx43 mRNA and protein in epidermis. Expression occurred predominantly in the suprabasal layer. Cultured cells exhibited a differential response to retinoic acid. In keratinocytes, increased expression of Cx43 occurred at low (10(-11) M) concentrations, whereas inhibition occurred at high (10(-7) M) concentrations; however, junctional communication, measured by dye transfer, was not altered over this concentration range. Dermal fibroblasts, in contrast, exhibited a dose-dependent increased expression of Cx43 at concentrations up to 10(-7) M retinoic acid and proportionately increased their junctional communication over this dose range. These data indicate that control of Cx43 gene expression by retinoids in human skin cells is complex. The production of gradients of junctional channels could play a role in the control of growth and differentiation in epidermis.

Posterior chamber IOL implantation in traumatic cataract with injured complications

Twenty-five cases of posterior chamber IOL implantation in traumatic cataract with complications associated with primary injury were reported. The operating methods were described and the post-operative complications were discussed. Seventy-two percent of patients have the correct vision over 20/40. It is suggested that the posterior chamber IOL can be implanted in traumatic cataract with some injured complications.

Comparative studies of the carbohydrate of human gamma-crystallins from fetal and adult lenses with agglutinins

Using gel chromatography of Sephadex G-75 superfine connected with Sephadex G-50 fine column, three human gamma-crystallins (gamma 1, gamma 2, gamma 3) could be obtained. Seven agglutinins (LCA, SBA, DBA, PNA, BSL, RCA and UEA) were used to detect the sugar of sub-gamma-crystallins, which had been transferred to nitrocellulose membrane and finally stained with ABC reagents and the substrate of HPR. These results suggested that gamma 2- and gamma 3-crystallins contain sugar, but gamma 1-crystallin has no sugar. There is a decrease of carbohydrate of gamma 2 and gamma 3 as the development of the lens (esp. the former). It was postulated that in gamma-crystallins (gamma 2, gamma 3) the sugar components helped stabilizing the molecular structure (folding polypeptide, prevent protein breaking). The sugar components decreased with age by the post-translation modification.

Cytoarchitectonic abnormalities in hippocampal formation and cerebellum of dreher mutant mouse

The laminated structures in the hippocampal formation and cerebellum of homozygous dreher mice were compared to their littermates and to C57BL/6J mice in Nissl- and myelin-stained preparations. In the dreher dentate gyrus, ectopic granule cells were situated in the molecular layer, and frequently there was either partial or complete absence of the infrapyramidal limb of the granule cell layer. In the dreher hippocampus, the cells of the pyramidal cell layer in area CA3 formed widely dispersed arrangements, and there were ectopically situated pyramidal cells in the stratum radiatum and stratum oriens. In the dreher cerebellum, 3 abnormal patterns were observed: (1) disruptions of foliation with normal cytoarchitectonic structure, (2) foliation with a mixture of normal laminated structure and abnormal laminated structure, and (3) almost complete absence of the cerebellum. In abnormal folia exhibiting the second or third pattern, islands consisting of agglomerations of both granule cells and Purkinje cells or just granule cells were observed. The neuronal heterotopias and cytoarchitectonic disorganization observed in the present study are apparently secondary to disruption of cell proliferation and neuronal migration produced directly or indirectly by the dreher mutation. In addition, the fact that the phenotypic abnormalities in homozygous dreher mice produces different abnormal morphologies in different specimens may be useful for analyzing the development of the hippocampal formation and cerebellum.

Cytoarchitectonic abnormalities in cerebellum and hippocampal formation of beige mutant mouse

Abnormalities in the cerebellum and hippocampal formation of the beige mouse were revealed by histological and immunohistochemical examination. In the cerebellum, Purkinje cells and clusters of granule cells, plus an occasional Bergmann glia cell, were located ectopically in the molecular layer. In the hippocampus, ectopically situated pyramidal cell were found in the stratum oriens of area CA3. The infrapyramidal mossy fiber layer (IPMFL) was formed by fiber bundles emerging from two districtly separated areas of the dentate gyrus. The IMPFL was not compact, but appeared as clumps of scattered fiber bundles. The neuronal heterotopias and cytoarchitectonic disorganization observed in the beige mutant mouse cerebellum and hippocampus may prove to be very useful parameters in analyzing the relationship between the immune system and the development of the central nervous system.

Anisodamine antagonizes acetylcholine-induced inhibition of adrenergic neurotransmission in the canine saphenous vein

The effect of anisodamine, an alkaloid structurally related to atropine and isolated from a Chinese herb, on adrenergic neurotransmission was studied using isolated canine saphenous veins. Helical strips of vein were incubated in modified physiological salt solution containing L-(7- 3H)-norepinephrine (3 x 10(-7) mol/L) for two hours and then mounted for isometric tension recording and superfusion. Increases in isometric tension and efflux of total tritiated compounds and 3H-norepinephrine evoked by electrical stimulation were inhibited by acetylcholine (10(-6) mol/L). This effect of acetylcholine was antagonized to comparable levels by anisodamine (10(-6) mol/L) or atropine (10(-6) mol/L). The results demonstrate that anisodamine blocks prejunctional muscarinic receptors.

Recombinant monocyte-derived interleukin-1 receptor antagonist reverses inhibitory effects of interleukin-1 on Leydig cell steroidogenesis

Previously we have reported that interleukin-1 (IL-1) is a potent inhibitor of Leydig cell function. Most recently, IL-1 receptor antagonist (IL-1ra) has been purified, sequenced and cloned. In the present study, we evaluated the recombinant monocyte-derived IL-1ra on the inhibitory effects of IL-1. The addition of recombinant human IL-1ra up to 1000 ng/ml has no discernible effects on human chorionic gonadotropin (hCG)-stimulated testosterone formation in primary cultures of rat Leydig cells. Similar to that reported previously, IL-1 beta caused a dose-dependent inhibition of hCG-induced testosterone. The inhibitory effect of IL-1 beta could be reversed by the concomitant addition of IL-1ra. The amounts of IL-1ra required to reverse the effect of IL-1 were 25-fold higher. Our results suggest that IL-1 is important in modulating Leydig cell function and its effect most likely is mediated by specific IL-1 receptors.

Drosophila RNA polymerase II elongation factor DmS-II has homology to mouse S-II and sequence similarity to yeast PPR2

DmSII is a Drosophila RNA polymerase II elongation factor which suppresses pausing by RNA polymerase II at specific sites on double stranded templates. Using antibodies produced against the purified protein, a Drosophila cDNA expression library was screened and a cDNA was isolated which encoded a portion of DmSII. When this cDNA was used to probe Kc cell mRNA the predominant species was found to be 1.4 kb in length. The original cDNA was used to screen a Drosophila Kc cell cDNA library resulting in the isolation of a 1.4 kb cDNA which was then sequenced. The deduced protein sequence for DmSII exhibited high similarity to mouse SII protein sequence. In addition, significant sequence similarity was found with the protein encoded by the yeast gene PPR2, which is involved in regulation of URA4 gene expression. The comparison of amino acid sequences suggests that DmSII is comprised of two domains homologous to mouse SII separated by a flexible, serine rich region of low homology. The shorter yeast protein has sequence similarity only to the carboxy terminal domain.

Regulation of insulin-like growth factor-I messenger ribonucleic acid expression in Leydig cells

In the present study, we evaluated insulin-like growth factor-I (IGF-I) messenger RNA expression in the rat testis. Crude interstitial cells were separated into three distinct bands on 15-60% Percoll density gradients. IGF-I mRNA was mainly localized in the Leydig cell-enriched fraction (band 3), while band 1 and band 2 cells did not contain significant amounts of IGF-I mRNA. Leydig cell IGF-I mRNA consisted of multiple species varying from 0.8 to 7.5 kb and was present in rat Leydig cells all ages examined, from 25 to 55 days old. To further document that IGF-I mRNAs are present in Leydig cells, the method of Klinefelter et al. (Biol. Reprod. (1987) 36, 769-783) was used to isolate highly purified (greater than 98% pure) Leydig cells. Most of the IGF-I mRNA was localized in these Leydig cells, while there was no detectable IGF-I mRNA in the whole testis or other interstitial cells. Furthermore, IGF-I mRNA in Leydig cells was increased more than 2-fold by growth hormone (GH) administration in vivo. This suggests that IGF-I mRNA in Leydig cells is also GH dependent. Interstitial IGF-I produced in Leydig cells may have both autocrine and paracrine effects in the testis.

Interleukin-2 is a potent inhibitor of Leydig cell steroidogenesis

Interstitial tissue of the testis consists of Leydig cells, macrophages, lymphocytes, plasma cells, mast cells and fibroblasts. Previously we have reported that interleukin-1 (IL-1) inhibits Leydig cell androgen production. In the present study, the effect of IL-2 was investigated. Leydig cells (10(5) cells/ml) from adult Sprague-Dawley rats were cultured with or without IL-2 for 24 h. After medium changes, human CG (hCG), 8-bromo-cAMP, or forskolin was added with or without IL-2. Cultures were continued for an additional 24 h, and testosterone and cAMP levels were measured. IL-2 up to 100 U/ml had no effect on basal testosterone production. hCG-stimulated testosterone formation was inhibited in a dose-dependent manner by the addition of IL-2. IL-2 in a concentration of 100 U/ml decreased hCG-induced testosterone formation from 49.6 +/- 3.6 ng/ml (mean +/- SE) to 8.5 +/- 4.2 ng/ml. The hCG dose-response curve was shifted to the right by the addition of IL-2. Maximal testosterone production in response to hCG was reduced 40% in the presence of IL-2 (50 U/ml) without alteration of median effective dose (ED50). IL-2 also inhibited hCG-induced cAMP formation and 8-bromo cAMP- and forskolin-stimulated testosterone production. However, IL-2 did not alter the binding of [125I]hCG to purified Leydig cells. Furthermore, IL-2 significantly inhibited the conversion of 20-OH-cholesterol, 22-OH-cholesterol, pregnenolone, progesterone, 17 alpha-hydroxypregnenolone, and 17 alpha-hydroxyprogesterone to testosterone but did not alter the conversion of dehydroepiandrosterone and androstenedione to testosterone. Our results suggest that a T cell growth factor, IL-2, is a potent inhibitor of steroidogenesis. IL-2 may play a paracrine role in modulating Leydig cell function.

The thiomethyl anion: Formation, reactivity, and thermodynamic properties

The thiomethyl anion (1) has been generated by fluorodesilylation of trimethylsilylmethanethiol in a variable-temperature flowing afterglow device. The proton affinity (1649 ± 12 kJ mol(-1)) and electron affinity (0.67 ± .13 eV) were determined and compared to a previously reported molecular orbital calculation. Isomerization via a 1,2-proton shift does not take place between -40° and 100°C despite a 156 kJ mol(-1) driving force. Ion-molecule reactions of 1 were examined with a number of reagents including N20, O2, CS2, COS, and CO2, Hydride ion transfer was observed in every case, along with other products, and thermodynamic information has been derived.

Differential effects of recombinant interleukin-1 alpha and beta on Leydig cell function

Previously we have reported that human chorionic gonadotropin(hCG)-stimulated testosterone biosynthesis was markedly inhibited by purified natural human interleukin-1 (IL-1). In the present study we evaluated the effects of human and murine recombinant IL-1 (rIL-1) on Leydig cell steroidogenesis in primary culture. Human rIL-1 beta caused a dose-dependent inhibition of hCG-, 8-bromo cyclic AMP-, and forskolin-induced testosterone formation. In contrast, human rIL-1 alpha was considerably less potent. When the effects of the cytokines were corrected for their biological potencies, human rIL-1 beta and murine rIL-1 alpha were still more effective than human rIL-1 alpha in inhibiting testosterone production (at least 100-fold more potent). Thus, even though IL-1 alpha and IL-1 beta bind to the same receptors on T cells, Leydig cells exhibit differential sensitivity in response to rIL-1 alpha and rIL-1 beta which is partly species dependent.

Tumor necrosis factor-alpha enhances inhibitory effects of interleukin-1 beta on Leydig cell steroidogenesis

Human recombinant tumor necrosis factor-alpha (rTNF alpha) alone (up to 1000 units/ml) did not alter either basal or human chorionic gonadotropin (hCG)-induced testosterone formation in primary culture of rat Leydig cells. However, concomitant addition of rTNF alpha with human recombinant interleukin-1 beta (rIL-1 beta) enhanced the inhibitory effects of rIL-1 beta. The rIL-1 beta dose response curve was shifted to the left (IC50 changed from 1 ng/ml to 0.3 ng/ml). Even though rTNF alpha had no effect on testosterone formation, hCG-stimulated cyclic AMP formation was inhibited by rTNF alpha in a dose dependent manner. In the presence of both rTNF alpha and rIL-1 beta, hCG-induced cyclic AMP formation and binding of [125I]-hCG to Leydig cells were further inhibited. Testicular macrophages represent about 20% of the interstitial cells. TNF alpha and IL-1 may be produced locally by interstitial macrophages and have paracrine effects on Leydig cell function.