11C-methionine PET aids localization of microprolactinomas in patients with intolerance or resistance to dopamine agonist therapy

PURPOSE

To assess the potential for ¹¹C-methionine PET (Met-PET) coregistered with volumetric magnetic resonance imaging (Met-PET/MR^CR) to inform clinical decision making in patients with poorly visualized or occult microprolactinomas and dopamine agonist intolerance or resistance.

PATIENTS AND METHODS

Thirteen patients with pituitary microprolactinomas, and who were intolerant (n = 11) or resistant (n = 2) to dopamine agonist therapy, were referred to our specialist pituitary centre for Met-PET/MR^CR between 2016 and 2020. All patients had persistent hyperprolactinemia and were being considered for surgical intervention, but standard clinical MRI had shown either no visible adenoma or equivocal appearances.

RESULTS

In all 13 patients Met-PET/MR^CR demonstrated a single focus of avid tracer uptake. This was localized either to the right or left side of the sella in 12 subjects. In one patient, who had previously undergone surgery for a left-sided adenoma, recurrent tumor was unexpectedly identified in the left cavernous sinus. Five patients underwent endoscopic transsphenoidal selective adenomectomy, with subsequent complete remission of hyperprolactinaemia and normalization of other pituitary function; three patients are awaiting surgery. In the patient with inoperable cavernous sinus disease PET-guided stereotactic radiosurgery (SRS) was performed with subsequent near-normalization of serum prolactin. Two patients elected for a further trial of medical therapy, while two declined surgery or radiotherapy and chose to remain off medical treatment.

CONCLUSIONS

In patients with dopamine agonist intolerance or resistance, and indeterminate pituitary MRI, molecular (functional) imaging with Met-PET/MR^CR can allow precise localization of a microprolactinoma to facilitate selective surgical adenomectomy or SRS.

Systemic hemodynamics during cough induced and vasovagal syncope

Common faint and the so-called situational syncope are usually listed together in the category of “neurally mediated syncope”. Although vasovagal syncope has been subject of extensive research in the past years, its mechanism is not fully understood. Much less information is available about situational syncope. Numerous entities in this heterogeneous group are related to excessive straining (e.g. weight lifter's or trumpet player's syncope). Cough syncope is also associated with tremendous intrathoracic, intravascular, and even intracranial pressure fluctuations. Although reflex responses are certainly triggered during cough, their relative role, and their analogy with the classical vasovagal reaction are not clear. We report a case of vasovagal syncope and cough reaction occurring in the same subject during laboratory testing.

Evaluation of palatal saliva flow rate and oral manifestations in patients with Sjögren's syndrome

OBJECTIVE

The purpose of this study was to describe the oral properties of Sjögren's syndrome (SS), including the determination of palatal saliva (PS) flow rate.

SUBJECTS AND METHODS

Forty-nine SS patients and 43 healthy controls participated. Subjective symptoms were recorded and clinical assessments of the oral mucosal, dental and periodontal status were made. Unstimulated whole saliva (WS) and PS flow rates, the number of decayed, missing and filled teeth (DMF-T number), the gingival bleeding index (GBI) and the periodontal probing depth (PPD) were determined.

RESULTS

Despite the decrease in the flow rate of WS in SS patients, PS was not different from those of the controls (1.57 +/- 1.02 and 1.35 +/- 2.5 microl cm(-2) min(-1), respectively). GBI (20.0% vs. 10.5%, respectively), DMF-T (27.1 +/- 6.12 vs. 23.0 +/- 6.99, respectively) and PPD (2.28 +/- 1.09 mm vs. 1.82 +/- 0.73 mm, respectively) were higher in SS compared with the controls (P < 0.05). DMF-T and PPD showed a positive correlation with anti-SSA and/or anti-SSB antibody positivity in the serum (P < 0.05).

CONCLUSIONS

Data of the present study suggest that the subjective feeling of xerostomia in SS patients is the result of a decrease in the volume of the whole saliva, and not of the viscous PS. Correlation of DMF-T and PPD with autoantibody positivity reveals that the oral health status of SS patients may be associated with the general autoimmune process.

Induction of heat shock proteins fails to produce protection against trypsin-induced acute pancreatitis in rats

Heat shock proteins (HSPs) are necessary in the synthesis, degradation, folding, transport, and translocation of different proteins. It is well known that the increased expression of HSPs may have a protective effect against cerulein-induced pancreatitis in rats or against choline-deficient ethionine-supplemented diet model pancreatitis in mice. The aim of this study was to investigate the potential effects of HSP preinduction by cold or hot water immersion on trypsin-induced acute pancreatitis in rats. Trypsin was injected into the interlobular tissue of the duodenal part of the pancreas at the peak level of HSP synthesis, as determined by Western blot analysis. The rats were sacrificed by exsanguination through the abdominal aorta 6 h after the trypsin injection. The serum amylase activity, the tumor necrosis factor-alpha, interleukin-1, and interleukin-6 levels, the pancreatic weight/body weight ratio, and the pancreatic contents of DNA, protein, amylase, lipase, and trypsinogen were measured. A biopsy for histology was taken. Hot water immersion significantly elevated the HSP72 expression, while cold water immersion significantly increased the HSP60 expression. Cold water immersion pretreatment ameliorated the pancreatic edema in trypsin-induced pancreatitis, however this was not due to the HSP60. Hot water immersion pretreatment did not have any effect on the measured parameters in trypsin-induced pancreatitis. The findings suggest that the induction of HSP60 or HSP72 are not enough to protect rats against the early phase of this localized necrohemorrhagic pancreatitis model.

Water immersion pretreatment decreases pro-inflammatory cytokine production in cholecystokinin-octapeptide-induced acute pancreatitis in rats: possible role of HSP72

Heat shock proteins (HSPs) are cytoprotective proteins that are expressed constitutively and/or at elevated levels upon the exposure of cells to stress. The aim of this study was to investigate the potential effects of HSP preinduction by cold- (CWI) or hot-water immersion (HWI) on pro-inflammatory cytokine production (IL-1, IL-6, TNF-alpha) in cholecystokinin-octapeptide(CCK)-induced acute pancreatitis. Rats were injected with 3 x 75 microg/kg CCK subcutaneously at intervals of 2 h at the peak level of HSP synthesis, as determined by Western blot analysis. The animals were killed by exsanguination through the abdominal aorta 2 h after the last CCK injection. The serum IL-1, IL-6, TNF-alpha, and amylase levels, the pancreatic weight/body weight ratio, and the pancreatic contents of DNA, protein, amylase, lipase and trypsinogen were measured; biopsy for histology was taken. HWI significantly elevated the HSP72 expression, while CWI significantly increased the HSP60 expression. HWI pretreatment decreased all of the measured serum cytokine levels in this acute pancreatitis model. CWI and HWI pretreatment ameliorated most of the examined laboratory and morphological parameters of CCK-induced pancreatitis. The findings suggest the possible roles of HSP60 and HSP72 in the protection against CCK-induced pancreatitis. HSP72 might also participate in the reduction of pro-inflammatory cytokine synthesis.

Plasma renin activity, aldosterone and cortisol secretions after acute hemorrhage and supine to vertical postural change in dogs

Acute hemorrhage and horizontal to vertical postural change are accompanied by decrease in blood volume of cardiovascular central reflexogenic areas (CRA) and by central hypoxia, followed by pressor responses. In these both circumstances important reflexogenic and humoral pressor reactions occured, as cathecolamine, renin and aldosterone hypersecretions. Aldosterone hypersecretion is considered as produced by angiotensin II, by a complex renin-angiotensin(RA)-aldosterone system. The main purpose of this work was to clarify the presence of this RA-aldosterone system after acute hemorrhage and in head-up postural change. In this aim we studied on dogs renin, aldosterone and cortisol responses. We analysed in these two circumstances the correlation of plasma renin activity(PRA) and aldosterone plasma concentration(p.c.) in intact and bilaterally nephrectomised(BN) dogs. We also studied correlations between aldosterone and cortisol p.c., having in view that both are stimulated by ACTH, searching in this way another modality for aldosterone secretion.

Fluoride concentrations of unstimulated whole and labial gland saliva in young adults after fluoride intake with milk

Following a fluoride depletion period 6 subjects repeatedly rinsed with 30-ml volumes of milk with or without added fluoride (5 ppm). Rinsing time was timed according to the measurements on how long it took to drink 200 or 500 ml milk. Rinsing with fluoridated milk for a total interval of 20 and 60 s, respectively, did not influence significantly the fluoride concentration of unstimulated centrifuged whole saliva 45 min later. Neither the urinary fluoride concentration nor the fluoride excretion were significantly affected by rinsing with fluoridated milk during the first hour. However, intake of 1 or 2.5 mg of fluoride with 200 and 500 ml milk, respectively, resulted in significant elevations in whole saliva fluoride levels 45 min later. In addition, the fluoride excretions into urine produced during 60 min after the fluoride intakes were significantly elevated and those reflected the ingested dose of fluoride. The intake of either 1 or 2.5mg fluoride with milk did not significantly influence the fluoride level of unstimulated labial gland saliva collected simultaneously with whole saliva.

[The effect of a single-dose intravenous vinpocetine on brain metabolism in patients with ischemic stroke]

The effect of a single-dose i.v. infusion of vinpocetine on the cerebral blood flow (CBF) and glucose metabolism of post-stroke patients was studied by measuring the regional and global cerebral metabolic rates of glucose (CMRglu) and the corresponding kinetic constants before and after treatment. Transcranial Doppler (TCD) and single photon emission tomography (SPECT) measurements were also performed. The cerebral glucose metabolism was significantly higher in the contralateral hemisphere than in the affected one before therapy. In the affected hemisphere the regional glucose metabolism was inhomogenous: relatively low values were measured in the stroke region, whereas it was increased in the peristroke region. Although a single-dose vinpocetine treatment did not affect significantly the regional or global metabolic rates of glucose, the glucose transport (both intracellular up-take and release) was strongly affected in the whole brain, in the contralateral hemisphere and in the peri-infarct area of the symptomatic hemisphere. A slightly increased (not significant, N. S.) cerebral blood flow could be observed in the contralateral and a decreased flow (N. S.) in the symptomatic hemisphere.

The Ketel(D) dominant-negative mutations identify maternal function of the Drosophila importin-beta gene required for cleavage nuclei formation

The Ketel(D) dominant female-sterile mutations and their ketel(r) revertant alleles identify the Ketel gene, which encodes the importin-beta (karyopherin-beta) homologue of Drosophila melanogaster. Embryogenesis does not commence in the Ketel(D) eggs deposited by the Ketel(D)/+ females due to failure of cleavage nuclei formation. When injected into wild-type cleavage embryos, cytoplasm of the Ketel(D) eggs does not inhibit nuclear protein import but prevents cleavage nuclei formation following mitosis. The Ketel(+) transgenes slightly reduce effects of the Ketel(D) mutations. The paternally derived Ketel(D) alleles act as recessive zygotic lethal mutations: the Ketel(D)/- hemizygotes, like the ketel(r)/ketel(r) and the ketel(r)/- zygotes, perish during second larval instar. The Ketel maternal dowry supports their short life. The Ketel(D)-related defects originate most likely following association of the Ketel(D)-encoded mutant molecules with a maternally provided partner. As in the Ketel(D) eggs, embryogenesis does not commence in eggs of germline chimeras with ketel(r)/- germline cells and normal soma, underlining the dominant-negative nature of the Ketel(D) mutations. The ketel(r) homozygous clones are fully viable in the follicle epithelium in wings and tergites. The Ketel gene is not expressed in most larval tissues, as revealed by the expression pattern of a Ketel promoter-lacZ reporter gene.

The Ketel gene encodes a Drosophila homologue of importin-beta

The Drosophila melanogaster Ketel gene was identified via the Ketel(D) dominant female sterile mutations and their ketel(r) revertant alleles that are recessive zygotic lethals. The maternally acting Ketel(D) mutations inhibit cleavage nuclei formation. We cloned the Ketel gene on the basis of a common breakpoint in 38E1. 2-3 in four ketel(r) alleles. The Ketel(+) transgenes rescue ketel(r)-associated zygotic lethality and slightly reduce Ketel(D)-associated dominant female sterility. Ketel is a single copy gene. It is transcribed to a single 3.6-kb mRNA, predicted to encode the 97-kD Ketel protein. The 884-amino-acid sequence of Ketel is 60% identical and 78% similar to that of human importin-beta, the nuclear import receptor for proteins with a classical NLS. Indeed, Ketel supports import of appropriately designed substrates into nuclei of digitonin-permeabilized HeLa cells. As shown by a polyclonal anti-Ketel antibody, nurse cells synthesize and transfer Ketel protein into the oocyte cytoplasm from stage 11 of oogenesis. In cleavage embryos the Ketel protein is cytoplasmic. The Ketel gene appears to be ubiquitously expressed in embryonic cells. Western blot analysis revealed that the Ketel gene is not expressed in several larval cell types of late third instar larvae.

[Diffuse alveolar hemorrhage in systemic lupus erythematosus]

Of the 120 systemic lupus erythematosus (SLE) patients treated by the authors, two have developed diffuse alveolar haemorrhage. The authors' objective is to present this rare, but severe manifestation. Patients 1 and 2 were 66- and 22-year old women, respectively. Both had SLE with multi-organ involvements including diffuse proliferative lupus nephritis. Before the diagnosis of the disease, both patients had experienced pneumonitis that resolved on corticosteroid treatment. Soon after the diagnosis, respiratory failure, haemoptoea and acute anaemia developed, accompanied by a rapid deterioration in the general condition. Chest radiographs revealed bilateral, diffuse, alveolar infiltrates. The pulmonary haemorrhage temporarily ceased in response to corticosteroid treatment, but both patients later died in consequence of active SLE and mixed bacterial and fungal sepsis. Post mortem examination demonstrated fibrosing alveolitis and alveolar bleeding in Patient 1, and an immune complex deposition-induced alveolocapillary inflammation with alveolar haemorrhage in Patient 2. Diffuse alveolar haemorrhage is a life-threatening manifestation of SLE. Its onset may be preceded by episodes of pneumonitis resolving on corticosteroid treatment. An active diagnostic workup, intensive observation and aggressive immunosuppressive treatment are the cornerstones of the management. The early detection and the active treatment of secondary infections are obligatory. The authors consider the most difficult challenge to be the optimum coordination of the above treatment modalities.

Preparation and primary evaluation of [11C]CSC as a possible tracer for mapping adenosine A2A receptors by PET

A 11C labeled selective adenosine A2A antagonist, (E)-8-(3-chlorostyryl)-1,3-dimethyl-7-[11C]methylxanthine [11C]CSC) was prepared by the reaction of (E)-8-(3-chlorostyryl)-1,3-dimethylxanthine and [11C]methyl iodide. The decay-corrected radiochemical yield was 32.3% with a radiochemical purity of 99%, a specific activity of 1.85-5.55 GBq/mumol and a preparation time of 1 h. A primary evaluation of [11C]CSC as a potential tracer for mapping adenosine A2A receptors by positron emission tomography (PET) is also presented. Biodistribution and autoradiographic studies were carried out on Swiss mice and domestic rabbits. In mice the lung showed the highest uptake at 10 min after i.v. injection, followed by the liver, kidney, heart and brain. Inside the brain a high level of radioactivity accumulated in the striatum, in accordance with previous findings on the specific spatial distribution of A2A adenosine receptors and also in the medulla oblongata. Dynamic PET studies on rabbits showed a fast brain uptake of CSC, reaching a maximum in less then 2 min. On the basis of competition experiments with the unlabeled ligand [11C]CSC proves to bind specifically to the appropriate receptor.

Study of saliva secretion and the salivary fluoride concentration of the human minor labial glands by a new method

Unstimulated and stimulated flow rate from minor lower labial glands and the fluoride concentration of resting whole and labial saliva were measured over 15 min using a novel method avoiding eversion of the lips. Resting salivary flow rate was measured as 1.09+/-0.44 microl/min/cm2 and stimulated flow rate as 3.13+/-1.05 microl/min/cm2. Secretion rates were significantly (p<0.001) increased during periods of continuous speaking. The increase in secretion elicited by labial movements and speaking may result from mechanical stimulation and/or activity of myoepithelial cells. Fluoride concentrations in resting whole saliva and in unstimulated minor labial gland saliva were 0.066+/-0.048 and 0.181+/-0.073 parts/10(6), respectively. The secretory capacity of the minor labial glands and the high F concentration in their secretions suggests a significant contribution to the F content of whole saliva. Our non-invasive method permits collection from the minor labial glands of a volume large enough for chemical analysis. It should prove useful for studying the effects of different secretory stimuli.

Membrane stretch and salivary glands - facts and theories

Cell shape in salivary glands is affected by mechanical forces. In the acini and ducts cell shape is modified by the contractions of the myoepithelial cells in both the secretory and ductal portions of the glands. At the organ level shape changes are due to muscle contraction during mastication, food intake and speech. All these factors may cause some degree of stretching of salivary cell membranes. Recent studies suggest that physical forces influence signal transduction, gene expression, secretory function, cell differentiation and proliferation. Here we overview membrane stretch-activated cellular events. Evidence from a variety of tissues suggests that mechanical forces may alter the properties of acinar cells leading to cytoskeletal reorganisation, changes in ion fluxes, modulation of secretory activity and subsequent release of transmitters such as ATP. Transmitters released from acinar cells may modulate the secretory activity of salivary tissue, and interact with classical regulatory pathways.

An extended alpha-helix and specific amino acid residues opposite the DNA-binding surface of the cAMP response element binding protein basic domain are important for human T cell lymphotropic retrovirus type I Tax binding

The human T cell lymphotropic retrovirus type I (HTLV-I) trans-activator, Tax, interacts specifically with the basic-domain/leucine-zipper (bZip) protein, cAMP response element binding protein (CREB), bound to the viral Tax-responsive element consisting of three imperfect 21-base pair repeats, each with a cAMP response element core flanked by G/C-rich sequences. Here, the minimal CREB-bZip necessary for Tax binding is shown to be composed of amino acid residues 280-341. The Tax-CREB interaction involves an uninterrupted and extended alpha-helix in CREB that spans most of its basic domain to include amino acid residues localized to the NH2 terminus of the DNA binding region. Mutational analyses indicate that three residues, Arg284, Met291, and Glu299 unique to this region of the CREB/activating transcription factor-1 subfamily of bZip proteins, constitute the contact surface for Tax. Amino acid substitutions in these positions had little impact on CREB-bZip binding to DNA but abrogated its binding to Tax. Each of the contact residues for Tax are spaced approximately two helical turns apart on the side of the bZip helix directly opposite to that of the invariant DNA-binding residues. Molecular modeling reveals the Tax-contact residues to be near the minor groove of the G/C-rich DNA in the 21-base pair repeat. They most likely position Tax for minor groove contact with the G/C-rich sequences.

Cerebral effects of a single dose of intravenous vinpocetine in chronic stroke patients: a PET study

The effects of vinpocetine (Cavinton) on the cerebral glucose metabolism of chronic stroke patients are studied with positron emission tomography. The regional and global cerebral metabolic rates of glucose (CMRglu) and the kinetic constants related to them are quantified before and after single-dose intravenous vinpocetine treatment. These measurements are completed with transcranial Doppler sonography and single photon emission computed tomography to explore the possible mechanisms underlying the resulting changes in glucose uptake and metabolism in the brain. The authors' findings indicate that a single-dose vinpocetine treatment, although it does not affect significantly the regional or global metabolic rates of glucose, improves significantly the transport of glucose (both uptake and release) through the blood-brain barrier in the whole brain, the entire contralateral hemisphere, and in the brain tissue around the infarct area of the symptomatic hemisphere. These changes are in accord with increased blood flow in the entire contralateral hemisphere as well as decreased blood flow velocity and increased peripheral vessel resistance in the entire symptomatic hemisphere.

The Tomaj mutant alleles of alpha Tubulin67C reveal a requirement for the encoded maternal specific tubulin isoform in the sperm aster, the cleavage spindle apparatus and neurogenesis during embryonic development in Drosophila

The three dominant TomajD and their eleven revertant (TomajR) alleles have been localized to the alpha Tubulin67C gene of Drosophila melanogaster. Although the meiotic divisions are normally completed in eggs laid by TomajD/+, TomajD/-, TomajR/- females, embryogenesis arrests prior to the gonomeric division. The arrest is caused by: (1) the failure of prominent sperm aster formation; and (2) a consequent lack of female pronuclear migration towards the male pronucleus. Concomitant with the sperm aster defect, the four female meiotic products fuse (tetra-fusion), similar to what is seen in eggs of wild-type virgin females. In eggs of females heterozygous for weaker TomajR alleles, embryogenesis comes to a cessation before or shortly after cortical migration of cleavage nuclei. The apparent source of embryonic defect is the cleavage spindle apparatus. One of the three TomajD alleles is cold-sensitive and its cold-sensitive period coincides with the completion of female meiosis and pronuclear migration. Disorganized central and peripheral nervous systems are also characteristic of embryos derived from the temperature-sensitive TomajD/+ females. The Tomaj mutant phenotypes indicate an involvement of the normal alpha Tubulin67C gene product in: (1) the formation of the sperm aster; (2) cleavage spindle apparatus formation/function; and (3) the differentiation of the embryonic nervous system. The TomajD alleles encode a normal-sized alpha Tubulin67C isotype. Sequence analyses of the TomajD alleles revealed the replacement in different positions of a single negatively charged or neutral amino acid with a positively charged one. These residues presumably identify important functional sites.

Bimoclomol: a nontoxic, hydroxylamine derivative with stress protein-inducing activity and cytoprotective effects

Preservation of the chemical architecture of a cell or of an organism under changing and perhaps stressful conditions is termed homeostasis. An integral feature of homeostasis is the rapid expression of genes whose products are specifically dedicated to protect cellular functions against stress. One of the best known mechanisms protecting cells from various stresses is the heat-shock response which results in the induction of the synthesis of heat-shock proteins (HSPs or stress proteins). A large body of information supports that stress proteins--many of them molecular chaperones--are crucial for the maintenance of cell integrity during normal growth as well as during pathophysiological conditions, and thus can be considered "homeostatic proteins." Recently emphasis is being placed on the potential use of these proteins in preventing and/or treating diseases. Therefore, it would be of great therapeutic benefit to discover compounds that are clinically safe yet able to induce the accumulation of HSPs in patients with chronic disorders such as diabetes mellitus, heart disease or kidney failure. Here we show that a novel cytoprotective hydroxylamine derivative, [2-hydroxy-3-(1-piperidinyl) propoxy]-3-pyridinecarboximidoil-chloride maleate, Bimoclomol, facilitates the formation of chaperone molecules in eukaryotic cells by inducing or amplifying expression of heat-shock genes. The cytoprotective effects observed under several experimental conditions, including a murine model of ischemia and wound healing in the diabetic rat, are likely mediated by the coordinate expression of all major HSPs. This nontoxic drug, which is under Phase II clinical trials, has enormous potential therapeutic applications.

[Amiodarone-induced pulmonary fibrosis]

The most feared side-effect of long-term amiodarone therapy is progressive alveolitis/pneumonitis leading to pulmonary fibrosis. The case history of a patient is presented who received amiodarone unnecessarily in a high dose (600 mg/day) for 4 years: drug-induced dermatopathy, hypothyroidism and lung fibrosis developed. After cessation of amiodarone treatment the pulmonary complication did not disappear therefore glucocorticoid therapy was introduced. New-onset improductive cough, dyspnea, fever and/or enhanced erythrocyte sedimentation rate may suggest the presence of amiodarone pulmonary toxicity and may form the basis of indication of high-resolution computed tomography (HRCT). Amiodarone-induced pulmonary involvement can be shown by HRCT early, before the appearance of any considerable abnormality of chest radiography.

[Free radical reactions in juvenile rats treated with streptozotocin]

Male, weaned Wistar albino rats (n = 8) were treated by single dose of intravenous 50 mg/bodyweight-kg streptozotocin (STZ) injection. Changes in carbohydrate and lipid metabolism, and scavenger capacity of red blood cells and liver homogenates were evaluated and compared to the respective values of the control group (n = 9) after 3 weeks. HbAlc was significantly higher (p < 0.005) in the STZ treated group. Plasma triglyceride also showed a marked elevation compared to the control group (p < 0.05). Scavenger capacity in erythrocytes was significantly (p < 0.05) higher in treated animals while no change was observed in liver homogenates. No alteration was observed in the superoxide dismutase activity of treated animals, but catalase activity was weaker (p < 0.05). Thiobarbituric acid reactive substances were in higher concentration in plasma of STZ treated animals (p < 0.01) and were in comparable amount in homogenates. The results suggest that 3 weeks after STZ treatment of rats, alterations can be observed in the scavenger system and of the examined tissues changes are most prominent in erythrocytes.

Transcription factor AP-4 participates in activation of bovine leukemia virus long terminal repeat by p34 Tax

Three 21bp repeats can be found in the bovine leukemia virus long terminal repeat, which are crucial for the LTR directed gene expression by the trans activator protein Tax. Previous studies demonstrated that the major target of the Tax directed activation are the CRE-like elements in the center of these repeats. In this work we report that another motif of the 21bp repeats is also required for the Tax activation. Gel retardation--with the wild type or mutant 21bp repeats--revealed that cellular factors from HeLa cells were specifically bound to the center (CRE-like element) and the 3' region of the repeats, which contains a CAGCTG consensus AP-4 binding site. In vivo analysis using the synthetic 21bp repeats indicated that beyond the consensus CRE-like motif, the AP-4 site is also essential for Tax activation. To determine the role of AP-4 in BLV Tax trans activation, we used the AP-4 cDNA in antisense transient assays. In the in vivo experiments the antisense AP-4 RNA resulted in strongly decreased Tax activation. On the basis of these results we conclude that AP-4 is a good candidate of cellular factors involved in BLV Tax trans activation.

Substrate-dependent mechanisms in the catalysis of human immunodeficiency virus protease

The most preferred residue in the substrates of human immunodeficiency virus (HIV-1) protease is glutamic acid in the P2' position. The catalytic importance of this charged residue has been studied to obtain a detailed insight into the mechanism of action, which will promote drug design to combat the virus. To this end, we have synthesized Lys-Ala-Arg-Val-Leu*Phe(NO2)-Glu-Ala-Nle (substrate E) and its counterpart containing the neutral Gln (substrate Q) in place of Glu. Kinetic analyses have shown that the specificity rate constants (kcat/Km) display bell-shaped pH dependencies for both substrates, but the pH-independent limiting value is 35-40-fold higher with substrate E than with substrate Q. In contrast to the pH-rate profiles of kcat/Km, there is a striking difference between the pH dependencies of Km and kcat for the two substrates. This indicates different ground state and transition state stabilizations in the two reactions. Solvent kinetic deuterium isotope effects show that the rate-limiting step for the hydrolysis of substrate E is a chemical step coupled with proton transfer whereas with substrate Q it is a physical step, presumably a conformational change. Accordingly, the charged residue in P2' alters the rate-limiting step and the nature of the enzyme-substrate complex, resulting in different mechanisms for the two substrates.

Expansion of CREB's DNA recognition specificity by Tax results from interaction with Ala-Ala-Arg at positions 282-284 near the conserved DNA-binding domain of CREB

The transactivator protein of human T-lymphotropic virus type I (HTLV-I), Tax, forms multiprotein complexes with the ubiquitous transcription factor CREB and the CREB/ATF-1 heterodimer. The interaction between Tax and CREB is highly specific and results in increased binding of the Tax/CREB complexes to the HTLV-I 21-bp repeats. Despite the extensive sequence similarities between CREB and ATF-1, Tax interacts with ATF-1 only marginally. Compared with CREB, Tax/CREB exhibits greatly increased DNA recognition specificity and preferentially assembles on a consensus binding site, GGGGG(T/A)TGACG(T/C)(A/C)TA(T/C)C-CCCC, homologous to the HTLV-I 21-bp repeats. Here we report that Tax affects CREB binding to the Tax-inducible DNA elements by interacting with the basic-leucine zipper (bZip) domain of CREB. We show by domain switching that the basic region in CREB bZip can confer on c-Jun and ATF-1 leucine zippers the ability to interact with Tax in vitro. Mutational analyses further demonstrate that the amino acid residues of CREB critical for Tax/CREB interaction are Ala-Ala-Arg at positions 282-284 (AAR284), immediately upstream of the highly conserved DNA-binding domain (R/K)XX(R/K) N(R/K)XAAXX(S/C)RX(R/K)(K/R) characteristic of all bZip proteins. Specific amino acid substitutions in AAR284 of CREB weakened or abolished Tax/CREB interaction, whereas reciprocal changes in ATF-1 allowed it to interact with Tax. These results support a model in which the specific interaction between Tax and the AAR284 residues near the DNA-binding domain of CREB results in a multiprotein complex with altered DNA recognition property. This protein complex assembles selectively on the viral Tax-responsive 21-bp repeats to augment transcription.

Expression in Escherichia coli and in vitro processing of HIV-1 p24 fusion protein

Recombinant HIV-1 p24/p25 gag proteins were obtained from Escherichia coli using a cleavable fusion strategy. The fusion protein contains 280 amino acid residues of staphylococcal Protein A and 317 amino acid residues of p24/p25 flanking with the recognition/cleavage sequences for HIV protease. Fusion protein expressed under the control of lambda phage promoter PR was purified by IgG-Sepharose affinity chromatography. The p24/p25 part of the fusion protein was released by recombinant HIV protease in vitro. After a second IgG-Sepharose affinity chromatography, the purified p24/p25 proteins were obtained in milligram quantities. The HIV-1 p24/p25 protein displayed antigenicity similar to those of native counterparts confirmed by Western blot assays and the Abbott antigen test.

Member of the CREB/ATF protein family, but not CREB alpha plays an active role in BLV tax trans activation in vivo

The trans activator protein of Bovine Leukaemia Virus (tax) increases the rate of transcription from the virus promoter through 21 bp sequences located in three tandem copies in the virus LTR. Based on data obtained by three different experimental approaches we concluded that the central CRE-like motif found in each of the BLV 21 bp repeats plays an important and indispensable role in tax mediated trans activation. These include (i) in vivo analysis of the function of mutant 21 bp sequences in transient transfection, (ii) gel mobility shift assay to show that CREB binds to BLV 21 bp repeats in vitro and (iii) the demonstration that the production of antisense CREB mRNA inhibits tax trans activation. Further studies with different deletion mutant CREB proteins suggest that although CREB alpha can interact with factors involved in BLV trans activation, it does not promote transcription initiation; consequently some other member/s of the CREB/ATF family must be involved.

[The effect of H2-receptor blockers (cimetidine and ranitidin) on parotid gland secretion and salivary carbonic anhydrase activity in the rat]

It has been demonstrated, that the H2-receptor antagonists: cimetidine and ranitidine-administered in doses of the same order of magnitude as reported for the inhibition of rat gastric secretion and development of the experimentally induced gastric and duodenal ulcer-are capable of increasing significantly the parotid secretion evoked by the cholinergic stimulant bethanechol. The salivary carbonic anhydrase activity was also elevated after combined treatment of bethanechol(+)-cimetidine. The similar action of the two H2-antagonists appears to suggest that their effect on salivation is connected probably with the cholinergic activity and it is concluded that the combination of bethanechol with these blockers may improve the esophageal clearance, an action that may be beneficial in the treatment of the gastroesophageal reflux disease.

Mutational analysis of the HTLV-I trans-activator, Tax

The gene coding for the trans-activating factor (Tax) of the human T-cell leukemia virus, type I (HTLV-I) was mutagenized in vitro using oligonucleotide-directed mutagenesis and recombinant DNA techniques. All except one of the mutagenized tax constructs failed to trans-activate the HTLV-I LTR in a eukaryotic test system. Moreover, negative Tax mutant Arg-39----Gly was found to be trans-dominant. This observation suggests that Tax contains distinct functional domains mediating different interactions of the protein in the process of trans-activation.

Analysis of the complex transcription termination region of the Escherichia coli rrnB gene

The complex terminator region of the Escherichia coli rrnB gene was analyzed by subcloning the terminators T1 and T2 and the inverted repeats IR1 and IR2 individually, or in various combinations, in a normal or inverted orientation into a terminator probe vector. The in vivo terminating efficiency was assayed by measuring the galactokinase activity encoded by the downstream galK gene. Termination efficiencies of all fragments were compared in two constructs, differing in the presence or absence of readthrough translation over the investigated terminator signal. The following main conclusions were drawn. (a) T1 and T2 are both efficient terminators in isolated forms. (b) IR1 and IR2 have some terminating effect (much lower than the proper terminators), especially in the inverted orientation. Their presence modifies the effect of the proper terminators in a quite unpredictable way, especially if these regions are translated. (c) The terminators are not symmetrical; in the inverted orientation T1 is practically inactive and T2 termination is reduced. (d) Translation radically decreases the efficiency of the terminators. (e) Several sequences in the rrnB gene, upstream of the terminator region (one in the 16S RNA and one in the 5S RNA coding region), are very efficient in vivo terminators in the inverted orientation.

[Chromatographic study of salivary carbonic anhydrase isoenzymes in rats]

Authors could purify two isoenzymes (designated CA1 and CA2) from the submandibular gland but only one (CA1) from the submandibular saliva by gel filtration and affinity chromatography. They concluded, that CA1 is a high molecular weight (approximately 90 kD) membrane-bound glycoprotein and CA2 is a cytosolic isoenzyme with lower molecular weight (30 kD) comparing to CA1.

[Recurrent dissection of aortic aneurysm with pulmonary complications]

The authors demonstrate a case of aorta aneurysm. The patient had survived despite the relatively rare and unfavourable complications presented in the observed consecutive aortic dissections. Both dissections had led to severe complications of the respiratory tract, to hemothorax and to hemoptysis.

Indirect binding of human T-cell leukemia virus type I tax1 to a responsive element in the viral long terminal repeat

Several laboratories have demonstrated that tandem copies of the human T-cell leukemia virus type I 21-base-pair (bp) repeat cloned upstream of either a homologous or heterologous promoter increase transcription in the presence of tax1 protein. In this report, we provide evidence for a second tax1-responsive sequence in the viral long terminal repeat. Analysis of human T-cell leukemia virus type I promoter deletion mutants and plasmids containing cloned oligonucleotide motifs demonstrated that this 47-bp sequence, located between -117 and -163, confers responsiveness to tax1. We further demonstrated that proteins present in HeLa nuclear extracts bind specifically to this tax1-responsive sequence. Mutants that affected in vivo activity also decreased in vitro binding. Using an in vitro binding assay, we demonstrated that tax1 interacts indirectly with the 47-bp sequence, most likely through protein-protein interaction. Thus, while tax1 does not bind directly to DNA to enhance transcription, it may influence sequence-specific responses by interacting with the primary DNA-protein complex.

Characterization of cellular factors that interact with the human T-cell leukemia virus type I p40x-responsive 21-base-pair sequence

Transcriptional activation of the human T-cell leukemia virus type I (HTLV-I) long terminal repeat (LTR) by viral protein p40x requires a 21-base-pair (bp) sequence which is repeated three times within the LTR. This sequence contains a core octanucleotide (TGACGTCT) which has been attributed to be a cyclic-AMP (cAMP)-responsive element. We demonstrate here that the HTLV-I LTR can be specifically stimulated by cAMP regulators and have identified four proteins in HeLa cells that bind to the HTLV-I 21-bp sequence. We correlated the in vitro binding and transcriptional activity of one of these cellular factors (Mr, 180,000) to the trans-activation of the HTLV-I LTR by p40x. Point mutations were generated within the cAMP octanucleotide of the HTLV-I 21-bp sequence that simultaneously abolished biological responsiveness to trans-activation by p40x and to stimulation by cAMP. We found that these mutations also eliminated the binding of the 180-kilodalton HeLa factor to the HTLV-I 21-bp element. In the absence of a demonstrable DNA-binding property for p40x, we hypothesize that cellular proteins are involved, possibly through signal transduction pathways, in its trans-activation of responsive promoters.

In vivo and in vitro autoprocessing of human immunodeficiency virus protease expressed in Escherichia coli

The viral-specific protease of human immunodeficiency virus (HIV) has been expressed as a lacZ-protease fusion protein. This fusion protein contains protease cleavage sites at the gag/protease and protease/reverse transcriptase junctions and undergoes autoprocessing in vivo when expressed in Escherichia coli. The purified lacZ-protease fusion protein precursors also exhibit autoproteolytic activity in vitro. One cleavage product of the autoprocessing reactions is a 10-kDa protein that cross-reacts with peptide antisera prepared against the putative protease sequence. Consistent with the notion that HIV protease is an acid protease, its autoproteolytic activity is inhibited in alkaline buffers and by pepstatin A. The in vivo and in vitro autocleavage assays for HIV protease together with the overproduction of the protease should facilitate design and testing of therapeutic agents that inhibit gag-pol polyprotein processing and HIV virion maturation.

An Escherichia coli gene in search of a function

The rrnB gene of Escherichia coli is preceded by an open reading frame, which is cotranscribed with rrnB both in vivo and in vitro. It has earlier been shown that a 289 amino acid protein corresponding to this gene is actually synthesized in E. coli. In this paper we show that: (1.) The transcription of this gene diminishes the stringent response of the P1 promoter of the linked rrnB gene, but this is a cis effect and is not mediated by the protein product of the gene. (2.) The functional integrity of this gene seems to be essential, because efforts to replace it by a plasmid-coded copy mutagenized by Tn5 completely failed. (3.) The protein product of this gene was strongly overproduced by a recombinant plasmid, exploiting the principle of "translational coupling". This overproduction did not change the phenotype of the host cell significantly. The protein was purified to apparent electrophoretic homogeneity.

New regulatory features of the promoters of an Escherichia coli rRNA gene

Recombinant plasmids were constructed by fusing either promoter p1 or p2 or both promoters of the rrnB gene of Escherichia coli to a DNA fragment coding for the N-terminal alpha-peptide of beta-galactosidase. These plasmids contained various lengths of the 5'-leader region of rRNA as the 5'-terminal end of the alpha-peptide messenger. In some cases the entire 5'-terminal rRNA-coding sequence was removed, and alpha-peptide synthesis was governed by rac promoters formed by fusion of rrnBp2 and lac promoters. By measuring the level of alpha peptide, conclusions could be drawn about the activities of the promoters under various physiological conditions. It was found that the rate of transcription starting from promoter p1 or p2 might vary more than 10-fold during the growth cycle, showing a sharp maximum during outgrowth from the stationary phase into exponential growth or during nutritional shift-up. The target sequence of this regulation was localized to the leader region of the rrnB gene.

The role of upstream sequences in determining the strength of an rRNA promoter of E. coli

In vitro transcription experiments were carried out with recombinant plasmids containing the promoters of the rrnB gene of Escherichia coli, and with deletion mutants lacking various lengths of the AT-rich sequence upstream from the P1 promoter of that gene. The main conclusions are as follows: The in vitro transcriptional activity of the P1 and P2 promoters of the rrnB gene are an order of magnitude higher on closed-circular (supercoiled) templates than on linear DNA; the strong P1 and P2 promoters are heparin-sensitive on linear templates, and on circular DNA only P2 is heparin-resistant; removal of the upstream AT-rich region did not decrease the apparent in vitro strength of the P1 promoter under standard conditions (50 mM KCl, high RNA polymerase/DNA ratio); at higher salt concentrations, or with a lower RNA polymerase/DNA ratio, the deletion mutants displayed much lower in vitro transcriptional activity than the wild-type, and the apparent weakening of the P1 promoter was roughly proportional to the length of the deleted AT-rich sequence. The implications of these findings for the possible in vivo role of the AT-rich region are discussed.

Expression vectors based on the rac fusion promoter

The -35 region of the rrnB P2 promoter and the -10 region of the lacZpo promoter-operator were fused to form the strong and regulatable rac promoter. Vectors were constructed that allow the attachment of protein-coding sequences to the beta-galactosidase alpha-peptide (LacZ alpha) in any reading frame. By introducing a high-copy-number mutation, the synthesis of a LacZ alpha-chloramphenicol acetyltransferase fusion protein reached more than 60% of total cell protein in Escherichia coli.

High-copy-number derivatives of the plasmid cloning vector pBR322

A stable copy-number mutant of a pBR322-derived plasmid was isolated. The mutation was found to be a single G----T transversion located near the 3' end of a DNA segment coding for the regulatory RNA I. The resulting copy number for this plasmid is approx. 1000 per cell or 65% of total cellular DNA. Several cloning vectors have been constructed from this copy-number mutant and their practical application is discussed.