[Effect of phentolamine on portal pressure in cirrhotic patients with portal hypertension]

Changes of hepatic venous wedge pressure (WHVP) and portal venous pressure (PVP) in fourteen patients with postnecrotic cirrhosis proved pathologically and seven patients with colon carcinoma without hepatopathy were observed before and after the infusion of alpha-adrenergic receptor antagonist phentolamine from peripheral venous. The results indicate that phentolamine can reduce WHVP and PVP of cirrhotic patients with portal hypertension efficiently (0.56-0.63 kPa, 0.42-0.50 kPa, respectively, P < 0.01), but it effects arterial diastolic pressure and heart rate simultaneously (arterial diastolic pressure reduced by 0.94-10.7 kPa, while heart rate increased by 8.67-10.67 per minute). Phentolamine doec not reduce portal pressure on patients without portal hypertension.

Isolation of an amino-terminal region of bovine papillomavirus type 1 E1 protein that retains origin binding and E2 interaction capacity

In vitro DNA binding results from a series of E1 proteins containing amino-terminal or carboxy-terminal truncations indicated that sequences between amino acids 121 and 284 were critical for origin binding. Additional binding experiments with E1 proteins containing internal, in-frame insertions or deletions confirmed the importance of the region defined by truncated E1 proteins and also demonstrated that downstream sequences were not required for binding activity in the context of the full-length E1 protein. On the basis of mapping results from the E1 mutants, a clone (pE1(121-311)) was constructed that expressed E1 amino acids within the approximate boundaries of the critical sequences for DNA binding. The E1(121-311) protein retained origin-specific DNA binding, confirming that this region was not only necessary but was also sufficient for origin recognition. In addition to origin binding, E1(121-311) bound E2 protein in a cold-sensitive manner. Therefore, DNA binding and E2 binding activities colocalize to a 191-amino-acid functional domain derived from the amino-terminal half of the E1 protein. Finally, three E1 proteins with mutations in this region all lacked DNA binding activity and were all defective for in vivo replication. Two of these E1 mutants retained E2 binding capability, demonstrating that origin recognition by E1 is critical for replication and cannot necessarily be rescued by an interaction with E2 protein.

Mammalian p50Cdc37 is a protein kinase-targeting subunit of Hsp90 that binds and stabilizes Cdk4

CDC37, an essential gene in Saccharomyces cerevisiae, interacts genetically with multiple protein kinases and is required for production of Cdc28p/cyclin complexes through an unknown mechanism. We have identified mammalian p50Cdc37 as a protein kinase-targeting subunit of the molecular chaperone Hsp90. Previously, p50 was observed in complexes with pp60v-src and Raf-1, but its identity and function have remained elusive. In mouse fibroblasts, a primary target of Cdc37 is Cdk4. This kinase is activated by D-type cyclins and functions in passage through G1. In insect cells, Cdc37 is sufficient to target Hsp90 to Cdk4 and both in vitro and in vivo, Cdc37/Hsp90 associates preferentially with the fraction of Cdk4 not bound to D-type cyclins. Cdc37 is coexpressed with cyclin Dl in cells undergoing programmed proliferation in vivo, consistent with a positive role in cell cycle progression. Pharmacological inactivation of Cdc37/Hsp90 function decreases the half-life of newly synthesized Cdk4, indicating a role for Cdc37/Hsp90 in Cdk4 stabilization. This study suggests a general role for p50Cdc37 in signaling pathways dependent on intrinsically unstable protein kinases and reveals a previously unrecognized chaperone-dependent step in the production of Cdk4/cyclin D complexes.

Molecular mechanisms of COUP-TF-mediated transcriptional repression: evidence for transrepression and active repression

COUP-TF, an orphan member of the nuclear receptor superfamily, has been proposed to play a key role in regulating organogenesis, neurogenesis, and cellular differentiation during embryonic development. Since heterodimierization is a common theme within the nuclear receptor superfamily and has been demonstrated to modulate transcriptional properties of heterodimeric partners via allosteric interactions, we have devised a strategy to examine the silencing function of COUP-TF in a heterodimeric context. We find that the intrinsic active repression function of COUP-TF is not affected by heterodimerization. Moreover, COUP-TF can transrepress the ligand-dependent activation of its heterodimeric partners without its own DNA binding site. Using receptor deletion mutants in transfection assays, we show that the region necessary for COUP-TF silencing function is not sufficient for its transrepression activity. Furthermore, our studies indicate that in addition to its active repression function, COUP-TF can repress several different types of activator-dependent transactivation. However, this active repression function of COUP-TF may be differentially regulated by some other activator(s). These studies provide new insights into the molecular mechanism(s) of COUP-TF-mediated repression.

[Serum adrenaline and noradrenaline levels in cirrhosis patients with portal hypertension]

High Pressure Liquid chromatography was used to measure serum adrenaline (E) and noradrenaline (NE) concentrations in 38 portal hypertensive patients, 28 idiopathic hypertensive patients, and 34 controls, respectively. It was found that peripheral E in portal hypertensive patients and controls was 57.5 +/- 37.4 pg/ml and 23.5 +/- 11.2 pg/ml respectively (P < 0.01), and peripheral NE was 451.1 +/- 381.2 pg/ml and 183.0 +/- 83.3 pg/ml (P < 0.01). Compared with controls, peripheral E and NE in idiopathic hypertensive patients were also significantly increased (54.9 +/- 39.9 pg/ml vs. 23.6 +/- 11.2 pg/ml, P < 0.01, and 524.3 +/- 219.9 pg/ml vs. 183.0 +/- 83.3 pg/ml, P < 0.01). E and NE in superior vena cava (SVC), portal vein, and peripheral artery in portal hypertensive patients were also increased, but only the elevation of E in SVC was significant (207.2 +/- 55.4 pg/ml vs. 83.7 +/- 46.7 pg/ml, P < 0.05). Our results reveal significant metabolic disorders of E and NE in portal hypertensive patients, which may play an important role in the pathogenesis of portal hypertension.

[An autoradiographic study of alpha 1-adrenoceptors in hepatic tissues in cirrhotic patients with portal hypertension]

We studied hepatic alpha 1-adrenoceptors of 8 hepatitis virus B-related cirrhotic patients with portal hypertension and 8 control surgical patients without liver disease by light radioautography. The density of alpha 1-adrenoceptors in various hepatic structures ("healthy" control vs. patients, per 10,000 microns 2) was as follows: on hypatocytes 1255.07 +/- 151.44/583.37 +/- 47.64 (P < 0.01); on intrahepatic artery walls 705.06 +/- 188.68/183.54 +/- 46.77 (P < 0.01); on intrahepatic portal walls 409.98 +/- 88.73/154.02 +/- 20.65 (P < 0.01); on hepatic venule walls 339.29 +/- 94.85/.... The decrease of density of alpha 1-adrenoceptors in cirrhotic liver tissues may be a result of the destruction of nomal hepatic structure by hepatitis virus B and the down-regulation of alpha 1-adrenoceptors.

Differentiation of Cryptosporidium parvum, C. muris, and C. baileyi by PCR-RFLP analysis of the 18S rRNA gene

We have developed a combined polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assay for the detection and differentiation of Cryptosporidium parvum, Cryptosporidium muris, and Cryptosporidium baileyi. The assay utilizes PCR to amplify an approximately 1750 basepair product of the Cryptosporidium 18S rRNA gene. Following double digestion with restriction endonucleases Dral and Vsp1, this PCR product yields DNA fragments that can be resolved electrophoretically into RFLP profiles that are distinct for C. parvum, C. muris, and C. baileyi. Previous PCR-restriction analyses could not simultaneously differentiate all three species. Future application of this technique could include predicting the disease-causing potential of oocyst-contaminated environmental specimens and helping to determine the source of oocyst contamination.

[Changes of histamine receptors in the liver of the rat during the development of experimental cirrhosis]

It remains unknown whether changes of histamine H1 and H2 recepters in the liver occur during the development of cirrhosis. 48 male Wistar rats were divided, equally and randomly, into experiment and control groups, and the rats in the experiment group were induced by CCl4 to form experimental cirrhosis models. Then, at different stages during the development of experimental cirrhosis, the maximal binding capacity (Bmax), dissociation constants (Kd), and binding ability (BA = Bmax/Kd) of histamine H1 and H2 receptors in the livers of the two groups were analysed by radioligand binding assay. At early stage of the development of experimental cirrhosis, the Bmax of H2 receptor in the rat liver was not statistically different from that of normal control; at middle and advanced stages of the course, the Bmax of H2 recepter were significantly lower than normal. The Bmax of H1 receptor was obviously lower than normal at each stage. At middle stage, the Kd of H1 receptor was significantly higher than normal, whereas the Kd of H1 receptor at the other two stages and the Kd of H2 receptor at each stage were not remarkably different from those of the controls. At each stage of the development of experimental cirrhosis, the BA of H1 and H2 receptor was all significantly lower than that of the normal controls. It was concluded that the "down-regulation" of the receptors may be an important factor for the reduction of Bmax and BA of the two histamine receptors, and these changes of the receptors may possibly led to metabolic disorder of carbohydrates and phospholipid in the liver and lower the liver's ability to inactivate histamine.

Simplified method for recovery and PCR detection of Cryptosporidium DNA from bovine feces

An assay to identify Cryptosporidium DNA in bovine feces has been developed emphasizing standardization of sample preparation and simplification of the DNA recovery process for PCR amplification and DNA hybridization detection. The Cryptosporidium DNA recovery-PCR detection procedure (CR-PCR) can recover DNA suitable for PCR amplification without using or generating hazardous chemicals or wastes. In comparisons with a commercial enzyme-linked immunoassay (Color Vue-Cryptosporidium; Seradyn, Indianapolis, Ind.), the CR-PCR could detect 10(3) to 10(4) times fewer purified oocysts diluted in solution (water or buffered saline) and 10(2) times fewer oocysts from diarrheic feces and showed earlier detectability from solid, nondiarrheic feces in an experimental infection. This assay may prove useful for detecting Cryptosporidium oocysts in feces and in clarifying the role of livestock in waterborne outbreaks of cryptosporidiosis.

[A quantitative study on alpha-1 adrenergic receptor in the liver of Wistar rats during the process of CCl4-induced hepatic cirrhosis]

In this study, radioligand binding analysis was used to quantitatively measure the concentration and affinity of alpha-1 adrenergic receptor in the liver of Wistar rats during the process of CCl4-induced liver cirrhosis. It was found that compared with normal controls, the maximal binding capacity (Bmax) of alpha-1 adrenergic receptor in the liver of 13 pre-cirrhotic rats decreased from 132.8 +/- 25.0fmol/mg to 96.9 +/-20.8fmol/mg of protein (P < 0.01) with increased dissociation constant (Kd, from 0.1633 +/- 0.0322nM to 0.3079 +/- 0.0786nM, P < 0.01). The Bmax in 20 cirrhotic rats decreased significantly from 132.8 +/- 25.0fmol/mg to 71.9 +/- 17.7fmol/mg of protein (P < 0.01), while Kd values increased from 0.1633 +/- 0.0322nM to 0.4012 +/- 0.0965nM (P < 0.01). These findings indicate that the decrease of binding capacity and affinity of alpha adrenergic receptor may play a role in the disturbances of metabolism of catecholamine often seen in some cirrhotic patients and have implications in the pathogenesis of portal hypertension.

[Plasma prostacyclin (PGI2) levels in peripheral venous, arterial and portal venous blood in cirrhotic patients with portal hypertension and their clinical implication]

Plasma levels of PGI2 were measured by radioimmunoassay in 20 consecutively admitted cirrhotic patients with portal hypertension from Aug. 1993 to Aug. 1994. It was found that cirrhotic patients with portal hypertension had much higher portal venous PGI2 levels than controls (528.25 +/- 205.48ng/L vs. 235.73 +/- 49.36ng/L, P < 0.001). Portal venous PGI2 levels in patients with cirrhosis and portal hypertension correlated significantly with portal venous pressure (r = 0.60, P < 0.05). The results indicate that increased portal venous PGI2 levels may have a role in maintenance of established portal hypertensive state in cirrhotic patients with portal hypertension.

[Computed sonography observation on the effects of cimetidine on the liver blood flow in cirrhotic patients with portal hypertension]

The effects of cimetidine on the hepatic and portal vein blood flow were investigated in 20 cirrhotic patients with portal hypertension by computed sonography. Cimetidine given intravenously at a dose of 0.4g significantly increased the hepatic vein blood flow (60.2% +/- 63.6%, P < 0.01), at the same time its calculated cross section area increased by 40.2% +/- 81.3% (P < 0.01). The portal vein blood flow increased by 53.2% +/- 52.3% (P < 0.01). While its cross section area was 16.8% +/- 17.3% (P < 0.01). These results showed that the histamine H2-receptor antagonist cimetidine may dilate liver vascular bed and reduce portal blood flow resistance in cirrhotic patients with portal hypertension.

[The level of serum gastrin and ulceration in cirrhotic patients with portal hypertension]

A higher incidence of gastric and duodenum ulcer was well recognized in patients with liver cirrhosis, but the mechanism has not been fully identified. In this study, serum gastrin, free portal pressure (FPP) were measured in 24 consecutively admitted cirrhotic portal hypertensive patients, and preoperative basic acid output (BAO) was measured in 13 randomized patients. Among the 24 patients, concomitant duodenal ulcers were found in 3 by both gastroduodenoscopy and barium series, and gastritis was found in all patients. It was found that most patients (71%) with liver cirrhosis have a elevated level in serum gastrin, whereas BAO is lower than normal in all patients, and the higher the FPP, the lower the BAO is. We believe that the congestive gastroduodenal mucosal lesion was underlying the ulceration most often seen in patients with portal hypertension.

Mouse retinoid X receptor contains a separable ligand-binding and transactivation domain in its E region

Steroid, thyroid, and retinoid hormones exert their biological functions by interacting with their cognate nuclear receptors. Upon binding receptors, hormones induce a protease-resistant structural change in the receptor ligand-binding domain and subsequently activate the receptors. Utilizing partial proteolysis, we have been able to delineate a region in the mouse retinoid X receptor beta (mRXR beta) required for ligand binding. A separable activation domain within the mRXR beta E region has been identified. The activation domain, which is 21 amino acids in length, is located at the extreme C terminus of mRXR beta. This domain is not required for ligand binding since removal of this sequence neither eliminates the ligand-induced, protease-resistant conformational change nor alters the ligand-enhanced DNA binding. Furthermore, deletion of this activation domain converts the receptor into a transcriptional silencer. Finally, a further truncation of 9 amino acids (for a total of 30 amino acids) from the C terminus results in a mutant which does not undergo the protease-resistant conformational change and cannot bind DNA as a homodimer. Nevertheless, this mutant is still able to form a heterodimer with the thyroid hormone receptor. Therefore, homodimerization and heterodimerization can be distinguished by this nine-amino-acid sequence.

The tau 4 activation domain of the thyroid hormone receptor is required for release of a putative corepressor(s) necessary for transcriptional silencing

The C terminus of nuclear hormone receptors is a complex structure that contains multiple functions. We are interested in the mechanism by which thyroid hormone converts its receptor from a transcriptional silencer to an activator of transcription. Both regulatory functions are localized in the ligand binding domain of this receptor superfamily member. In this study, we have identified and characterized several functional domains within the ligand binding domain of the human thyroid hormone receptor (TR beta) conferring transactivation. Interestingly, these domains are localized adjacent to hormone binding sites. One activation domain, designated tau 4, is only 17 amino acids in length and is localized at the extreme C terminus of TR. Deletion of six amino acids of tau 4 resulted in a receptor that could still bind hormone but acted as a constitutive silencer, indicating that tau 4 is required for both transactivation and relief of the silencing functions. In addition, we performed in vivo competition experiments, the results of which suggest that in the absence of tau 4 or hormone, TR is bound by a corepressor protein(s) and that one role of hormone is to release corepressor from the receptor. We propose a general model in which the role of hormone is to induce a conformational change in the receptor that subsequently affects the action of tau 4, leading to both relief of silencing and transcriptional activation.

Mechanisms for synergistic activation of thyroid hormone receptor and retinoid X receptor on different response elements

The thyroid hormone receptors (TR) form heterodimers with the retinoid X receptors (RXR) and activate target genes through thyroid-responsive elements (TRE). Heterodimerization elevates the DNA binding efficiency and thus can result in functional synergism between TR and RXR. Here we demonstrate that DNA sequences dictate the cooperative activation between TR and RXR despite the high affinity binding of the heterodimer to those TREs. We provide evidence that the C-terminal activation domain of RXR can modulate the triiodothyronine (T3) responsiveness of TR/RXR heterodimers on reporter genes without altering the DNA binding properties of the heterodimers. The modulation function of this relatively small region is under the control of specific TRE sequences and promoter context. These data indicate that this C-terminal region of RXR is likely involved in receptor-cellular factor(s) interactions. Finally, we propose that the synergistic activation by TR and RXR is achieved through elevated DNA binding and, dependent on the DNA sequence, the interaction of RXR with other transcription factors.

Genetically defined nuclear localization signal sequence of bovine papillomavirus E1 protein is necessary and sufficient for the nuclear localization of E1-beta-galactosidase fusion proteins

The 605 amino acid E1 protein of bovine papillomavirus type 1 (BPV-1) is a multifunctional nuclear protein required for viral DNA replication. A nuclear localization signal (NLS) sequence was previously defined by point mutations in three short adjacent clusters of basic amino acids located in the amino-terminal region of the E1 protein. In this study, we used a fusion protein approach to evaluate the contribution of other regions of the E1 protein to nuclear transport. The nearly full-length E1 gene and six non-overlapping subfragments were each fused in-frame with the lacZ gene in a eukaryotic expression vector. Each clone was electroporated into COS-1 cells, and the intracellular location of the E1-beta-galactosidase fusion proteins was determined by immunofluorescence. Only the constructs containing the full-length E1 or a single subregion (E1-259; amino acids 84 to 166) produced fusion proteins that entered the nucleus. Point mutations in the NLS sequences of the E1-259-lacZ construct prevented nuclear translocation of the corresponding fusion protein. This confirms the previous result that the cluster of basic amino acids is critical for nuclear transport. Furthermore, the data obtained in this investigation indicated that the region of E1 containing the NLS sequence was not only necessary, but was also sufficient for nuclear localization. No other region of E1 contained independent nuclear localization activity.

Ligand-dependent conformational changes in thyroid hormone and retinoic acid receptors are potentially enhanced by heterodimerization with retinoic X receptor

Recently, many lines of evidence have been accumulated indicating that thyroid hormone receptor (TR) and retinoic acid receptor (RAR) undergo a ligand-dependent conformation change. Since most of these results were obtained by either gel-shift assay or circular dichroism spectroscopic studies, it was not clear which part of the receptor bore the major conformational change. Moreover, it is not clear whether the formation of heterodimer between TR or RAR and retinoic X receptor (RXR) has any effects on this structural change. Utilizing partial proteolytic analysis, we demonstrated that thyroid hormone and retinoic acid induce a specific protease-resistant conformation to their cognate receptors. Studies of various deletion mutants reveal that the entire ligand binding domain of these receptors is involved in this change, and suggest that ligand may induce a more compact structure in its binding domain. Evidence from native gel electrophoresis supports this notion. This conformational change occurs in the absence of DNA and occurs independently of other domains in the receptor. Heterodimerization between TR or RAR and the RXR has little effect on receptor conformation in the absence of hormone but does enhance the ligand-dependent structural change. Interestingly, dual hormone treatment, i.e. thyroid hormone and 9-cis RA, intensifies this enhancement. We suggest that the observed protease-resistant conformation may introduce a different configuration to the receptor and therefore may affect the receptor in various ways, but most likely is involved in converting the receptor from a negative regulator to a positive activator.

Multiple mechanisms of chicken ovalbumin upstream promoter transcription factor-dependent repression of transactivation by the vitamin D, thyroid hormone, and retinoic acid receptors

The chicken ovalbumin upstream promoter transcription factor (COUP-TF) is a member of the steroid/thyroid hormone receptor superfamily about which little is known of its functional role in the cell. However, it is able to repress hormonal induction of target genes by vitamin D3 receptor (VDR), thyroid hormone receptor (TR), and retinoic acid receptor (RAR). We have shown previously that COUP-TF can bind a wide variety of A/GGGTCA repeats. This promiscuous recognition of response elements correlates with the ability of COUP-TF I to repress other receptors that bind to A/GGGTCA repeats with different spacings between the half-sites. Here we show that repression of transactivation by these receptors is a general phenomenon for the COUP-TF subfamily, as inhibition is also observed with COUP-TF II. This repression is also dose-dependent on COUP-TF. Inhibition of VDR, TR, and RAR activities also occurs through natural physiological response elements found in the osteocalcin, myosin heavy chain, and beta RAR promoters, respectively. In search of the mechanisms of repression by COUP-TF we show that it does not involve the formation of detectable functionally inactive heterodimers between COUP-TF and VDR, TR, and RAR. Instead, we show that the mechanism of repression could occur at three different levels: (a) active silencing of transcription and dual competition for; (b) occupancy of DNA binding sites; and (c), heterodimer formation with retinoid X receptor, the coregulator of VDR, TR, and RAR. The silencing activity was localized to the putative ligand binding domain of COUP-TF. We postulate that COUP-TF may play a master role in regulating transactivation by VDR, TR, and RAR.

Hormone and antihormone induce distinct conformational changes which are central to steroid receptor activation

Antihormones are potent antagonists of hormone action in vivo, but the mechanism underlying this antagonism is not understood. Several steroid hormones transform (activate) their receptors from a cytosolic, non-DNA binding 8 S sedimentation form to a nuclear, DNA binding 4 S form. Transformation is accompanied by the loss of associated heat shock proteins. We have previously demonstrated that an additional hormone-dependent step, separate from heat shock protein removal, is required for activation of the human progesterone receptor. We have devised an assay in which the human progesterone receptor translated in vitro binds to its specific response element in a hormone-dependent manner. As assessed by limited proteolytic digestion, hormone treatment of the nascent receptor induces a dramatic conformational change within the protein. The conformational change occurs in the absence of DNA and renders the entire ligand binding domain resistant to digestion by proteases. A number of antiprogestins, including RU486, induce an equally dramatic, but distinct, structural alteration of the ligand binding domain. The distinction centers upon the final 30 to 40 amino acids at the carboxyl terminus. The conformational change can be induced by ligand prior to dissociation of the 8 S complex and is not induced by heat shock protein removal in the absence of hormone. Remarkably, virtually identical hormone-induced conformational changes were detected following proteolytic analysis of in vitro translated retinoic acid receptors. Our data indicate that the sole necessary event in the activation of steroid receptors is conformational modification by the ligand. Furthermore, we conclude that transcriptional inactivation of steroid receptors by antihormones involves the induction of an inappropriate structural conformation at the extreme carboxyl terminus of the ligand binding domain.

A double-blind trial of oral immunotherapy for Artemisia pollen asthma with evaluation of bronchial response to the pollen allergen and serum-specific IgE antibody

Eighteen asymptomatic Artemisia pollen asthma patients with normal pulmonary function were selected for a double-blind trial of oral immunotherapy. Each patient had a positive skin test to Artemisia pollen extract and also a positive bronchial challenge response to the same extract. The patients were randomly assigned to active treatment or placebo group and received intensive oral administration of Artemisia pollen extract over a 50-day course. The nine patients who received the active treatment ingested a cumulative dose of 396,652 PNU and showed a significant decrease in serum-specific IgE antibodies (P less than .05) and a significant reduction in bronchial sensitivity to the same extract (P less than .01). The changes in these two variables correlated well (r = .8787, P less than .01). The nine patients who received the placebo showed no significant changes in serum-specific IgE or bronchial sensitivity to Artemisia pollen extract. Follow-up of two cases with the same extract showed that the reductions in serum-specific IgE as well as bronchial sensitivity induced by oral immunotherapy were maintained for 3 months.