Depression of nuclear transcription and extension of mRNA half-life under anoxia in Artemia franciscana embryos

Transcriptional activity, as assessed by nuclear run-on assays, was constant during 10 h of normoxic development for embryos of the brine shrimp Artemia franciscana. Exposure of embryos to only 4 h of anoxia resulted in a 79.3+/−1 % decrease in levels of in-vivo-initiated transcripts, and transcription was depressed by 88. 2+/−0.7 % compared with normoxic controls after 24 h of anoxia (means +/− s.e.m., N=3). Initiation of transcription was fully restored after 1 h of normoxic recovery. Artificially lowering the intracellular pH of aerobic embryos to the value reflective of anoxia (pH 6.7) showed that acidification alone explained over half the transcriptional arrest. Initiation of transcription was not rescued by application of 80 % carbon monoxide under anoxia, which suggests that heme-based oxygen sensing is not involved in this global arrest. When these transcriptional data are combined with the finding that mRNA levels are unchanged for at least 6 h of anoxia, it is clear that the half-life of mRNA is extended at least 8.5-fold compared with that in aerobic embryos. In contrast to the activation of compensatory mechanisms to cope with anoxia that occurs in mammalian cells, A. franciscana embryos enter a metabolically depressed state in which gene expression and mRNA turnover are cellular costs apparently not compatible with survival and in which extended tolerance supercedes the requirement for continued metabolic function.

N-terminal proatrial natriuretic peptide correlates with systolic dysfunction and left ventricular filling pattern in patients with idiopathic dilated cardiomyopathy

OBJECTIVE

To investigate the diastolic Doppler filling pattern in patients with idiopathic dilated cardiomyopathy and its relation to N-terminal pro-atrial natriuretic peptide (NT-pro-ANP).

METHODS

32 patients (26 male, six female) with idiopathic dilated cardiomyopathy were investigated. All were in sinus rhythm. Conventional M mode echocardiography and Doppler echocardiography was done in each patient. Pulsed wave Doppler inflow signals were obtained and the following variables were measured: maximum E wave, maximum A wave, E/A ratio, E wave deceleration time, A wave deceleration time. NT-pro-ANP was measured using radioimmunoassay.

RESULTS

Mean (SD) left ventricular ejection fraction was 34 (7)% and mean left ventricular end diastolic diameter on M mode echocardiography was 69 (7) mm. Left ventricular filling indices were as follows: maximum E wave velocity, 0.86 (0.22) m/s; maximum A wave velocity, 0.71 (0.24) m/s; E/A ratio, 1.41 (0.65). Mean E wave deceleration time was 140 (50) ms; mean A wave deceleration time was 100 (20) ms. In a stepwise forward regression model, NT-pro-ANP correlated significantly with left atrial diameter (r = 0.603; p < 0. 001), left ventricular ejection fraction (r = -0.758; p < 0.001), and Doppler derived E/A ratio (r = 0.740; p < 0.001).

CONCLUSIONS

In patients with idiopathic dilated cardiomyopathy there is a relation between NT-pro-ANP and both systolic and diastolic variables. In a multivariate model NT-pro-ANP correlated with left atrial diameter, left ventricular ejection fraction, and Doppler derived E/A ratio on transmitral inflow.

Natriuretic peptides in patients with diastolic dysfunction due to idiopathic dilated cardiomyopathy

AIMS

The degree of systolic dysfunction does not always correlate with functional impairment in patients with congestive heart failure. In contrast, diastolic dysfunction correlates well with functional impairment. In heart failure, both elevation of N-terminal proatrial natriuretic peptide and B-type natriuretic peptide are markers of a poor prognosis.

METHODS

We investigated 32 patients (26 male, 6 female; mean age 55+/-2 years) with dilated cardiomyopathy and sinus rhythm. M-mode echocardiography and 2D-echocardiography were carried out in each patient. Pulsed-wave Doppler inflow signals were obtained and the following parameters were measured: maximal E wave and maximal A wave velocity, E/A ratio, E wave deceleration time, A wave deceleration time. Immediately after echocardiography blood samples were collected from patients in the supine position. N-terminal proANP and brain natriuretic peptide were measured using a radioimmuno assay.

RESULTS

The left ventricular ejection fraction was 34+/-1%, the left ventricular end-diastolic diameter on M-mode echocardiography was 68+/-1 mm, while left atrial diameter was 45+/-1 mm. Univariate analysis revealed a significant correlation between both left atrial diameter and ejection fraction and N-terminal proANP and brain natriuretic peptide. All transmitral Doppler parameters showed a significant correlation with N-terminal proANP and brain natriuretic peptide. On forward stepwise regression analysis, left atrial diameter and ejection fraction were able to predict both N-terminal proANP and brain natriuretic peptide. However, of the diastolic parameters only the E/A ratio remained significant. Mildly symptomatic patients differed significantly from severely symptomatic patients in all Doppler parameters. Mildly symptomatic patients had significantly lower levels of N-terminal proANP (0.571+/-0.079 vs 2.282+/-0.340 nmol. l(-1);P<0.001) and brain natriuretic peptide (51+/-14.8 vs 474.2+/- 86.8 pg. ml(-1);P<0. 001).

CONCLUSION

There is a close relationship between natriuretic peptides and diastolic Doppler parameters of left ventricular filling in patients with dilated cardiomyopathy. There is also a significant difference between patients with mild and severe functional impairment regarding both natriuretic peptides and transmitral Doppler parameters.

Determination of cardiac output by the Fick method, thermodilution, and acetylene rebreathing in pulmonary hypertension

Assessment of cardiac output is an important part of the management of patients with pulmonary hypertension. The accuracy of the thermodilution technique in patients with low cardiac output or severe tricuspid regurgitation has been questioned. To address this issue, we simultaneously compared 105 cardiac output measurements by the Fick method and thermodilution in 35 patients with pulmonary hypertension. Moreover, we evaluated the acetylene rebreathing technique, a noninvasive method of determining cardiac output. The mean difference +/- 95% limit of agreement between thermodilution and the Fick method was +0.01 +/- 1.1 L/min. The mean difference +/- 95% limit of agreement between acetylene rebreathing and the Fick method was -0.23 +/- 1.14 L/min. Neither the mean agreement nor the 95% limits of agreement of both thermodilution and acetylene rebreathing with the Fick method were affected by the presence of low cardiac output or severe tricuspid regurgitation. We conclude that thermodilution and acetylene rebreathing are useful tools for assessing cardiac output in patients with pulmonary hypertension, even in the presence of low cardiac output or severe tricuspid regurgitation.

Signaling in human osteoblasts by extracellular nucleotides. Their weak induction of the c-fos proto-oncogene via Ca2+ mobilization is strongly potentiated by a parathyroid hormone/cAMP-dependent protein kinase pathway independently of mitogen-activated protein kinase

Extracellular nucleotides acting through specific P2 receptors activate intracellular signaling cascades. Consistent with the expression of G protein-coupled P2Y receptors in skeletal tissue, the human osteosarcoma cell line SaOS-2 and primary osteoblasts express P2Y1 and P2Y2 receptors, respectively. Their activation by nucleotide agonists (ADP and ATP for P2Y1; ATP and UTP for P2Y2) elevates [Ca2+]i and moderately induces expression of the c-fos proto-oncogene. A synergistic effect on c-fos induction is observed by combining ATP and parathyroid hormone, a key bone cell regulator. Parathyroid hormone elevates intracellular cAMP levels and correspondingly activates a stably integrated reporter gene driven by the Ca2+/cAMP-responsive element of the human c-fos promoter. Nucleotides have little effect on either cAMP levels or this reporter, instead activating luciferase controlled by the full c-fos promoter. This induction is reproduced by a stably integrated serum response element reporter independently of mitogen-activated protein kinase activation and ternary complex factor phosphorylation. This novel example of synergy between the cAMP-dependent protein kinase/CaCRE signaling module and a non-mitogen-activated protein kinase/ternary complex factor pathway that targets the serum response element shows that extracellular ATP, via P2Y receptors, can potentiate strong responses to ubiquitous growth and differentiative factors.

Influence of beta-blockers on melatonin release

OBJECTIVE

Melatonin is a mediator in the establishment of the circadian rhythm of biological processes. It is produced in the pineal gland mainly during the night by stimulation of adrenergic beta1- and alpha1-receptors. Sleep disturbances are common side-effects of beta-blockers. The influence of specific beta-blockade as well as that of combined alpha-and beta-blockade on melatonin production has not been investigated in humans before.

METHODS

We performed a randomized, double-blind, placebo-controlled, cross-over study in 15 healthy volunteers. Subjects received single oral doses of 40 mg (R)-propranolol, 40 mg (S)-propranolol, 50 mg (R)-atenolol, 50 mg (S)-atenolol, 25 mg (R,S)-carvedilol, 120 mg (R,S)-verapamil or placebo at 1800 hours. Urine was collected between 2200 hours and 0600 hours, and 6-sulfatoxy-melatonin (aMT6s), the main metabolite of melatonin which is almost completely eliminated in urine, was determined by radioimmunoassay (RIA).

RESULTS

Mean nocturnal excretion of aMT6s in urine after intake of the drugs was as follows (in microg): placebo 26; (R)-propranolol 24 (-7%, NS); (S)-propranolol 5 (-80%, P < 0.001); (R)-atenolol 27 (+7%, NS); (S)-atenolol 4 (-86%, P < 0.01); (R,S)-carvedilol 23 (-10%, NS); (R,S)-verapamil 29 (+14%, NS). These data show that only the specifically beta-blocking (S)-enantiomers of propranolol and atenolol decrease the nocturnal production of melatonin whereas the non-beta-blocking (R)-enantiomers have no effect. Unexpectedly, (R,S)-carvedilol which inhibits both alpha- and beta-adrenoceptors does not decrease melatonin production.

CONCLUSION

These findings indicate that beta-blockers decrease melatonin release via specific inhibition of adrenergic beta1-receptors. Since lower nocturnal melatonin levels might be the reason for sleep disturbances, further clinical studies should investigate whether or not oral administration of melatonin might avoid this well-known side-effect of beta-blockers. The reason why (R,S)-carvedilol does not influence melatonin production remains to be determined.

Results of spinal cord decompression and thoracolumbar pedicle stabilisation in relation to the time of operation

Short-segment pedicle stabilisation, transpedicular disc resection and autologous cancellous bone grafting is performed in trauma patients being transferred to our trauma centre with thoracolumbar fracture/dislocations. A follow-up examination of 88 patients, who were operated during the years of 1985-1992, took place after an average time of 5.6 years. Our results suggest that the earlier operative decompression and spine stabilisation takes place, the better is the recovery rate in patients with neurologic deficits. The highest neurologic recovery rates were found in patients operated within 8 h after the initial trauma. High remission rates were still found, if the patients had been operated within 48 h. After this time there was no significant difference in the neurologic outcome compared to the time of operation.

P2Y receptor subtypes differentially couple to inwardly-rectifying potassium channels

Subtypes of P2Y receptors are well characterized with respect to their agonist profile but little is known about differences in their intracellular signalling properties. When expressed in Xenopus oocytes, both P2Y2 and P2Y6 receptors effectively couple to endogenous Ca2+-dependent Cl--channels. However, only P2Y2 receptors increased currents mediated by inward-rectifier K+ channels of the Kir3.0 subfamily. This increase in Kir-current was sensitive to pertussis toxin, while activation of Ca2+-dependent Cl--channels was not. In contrast, suramin, a P2 receptor antagonist, inhibited activation of both channels. These observations suggest that, in contrast to P2Y6, P2Y2 receptors couple to two different classes of G proteins.

Local and systemic delivery of low molecular weight heparin following PTCA: acute results and 6-month follow-up of the initial clinical experience with the porous balloon (PILOT-study). Preliminary Investigation of Local Therapy Using Porous PTCA Balloons

The purpose of this study was to assess safety and feasibility of intracoronary delivery of reviparin using a porous balloon following percutaneous transluminal coronary angioplasty. The 2.7 mm porous balloon used in this study had 35 holes arranged in a spiral pattern. Eighteen patients (male n = 10, female n = 8, age 63 +/- 9 years) undergoing successful PTCA in coronary arteries with a vessel diameter of 2.5 to 3.0 mm determined by online QCA (LAD = 11, RCX = 3, RCA = 4) were included. They received a bolus of 7,000 anti-Xa-IU reviparin followed by local delivery of 1,500 anti-Xa-IU in 4 ml with an injection pressure of 2 atm. The patients received additionally 10500 anti-Xa-units intravenously during the following 24 hours and a daily dose of 7000 anti-Xa-units reviparin subcutaneously for the following 28 days. Angiograms were obtained before and after PTCA, directly after local delivery, at 24 hours postintervention and after 6 months. The primary success rate was 100%. Quantitative coronary angiography showed a minimum luminal diameter of 0.42 +/- 0.14 mm before PTCA, 1.87 +/- 0.45 after PTCA, 1.67 +/- 0.43 after LDD, 1.63 +/- 0.46 after 24 hours, and 1.06 +/- 0.6 after 6 months. Angiographic follow-up was obtained in all patients. No major complications occurred during the 6-month follow-up period. The angiographic restenosis rate was 28% (5/18) at follow-up. This study demonstrates safety and feasibility of local intracoronary delivery of reviparin with a porous balloon following PTCA even in smaller diameter coronary arteries.

Viscosupplementation with hylan G-F 20: a 26-week controlled trial of efficacy and safety in the osteoarthritic knee

Hylan G-F 20, which is derived from hyaluronan, is a highly purified, elastoviscous fluid with rheologic properties similar to those of synovial fluid in the knee joints of healthy young persons. The efficacy and safety of viscosupplementation with hylan G-F 20 were evaluated in a multicenter, double-masked clinical study in patients with chronic idiopathic osteoarthritis (OA) of the knee of 1 to 30 years' duration. Three intra-articular injections of 2 mL hylan G-F 20 were administered 1 week apart to 57 knees. The control group (60 knees) received 2 mL of physiologic buffered saline solution at the same intervals. Patients were predominantly female (65%), with a mean age of 62 years and mean weight of 76 kg. Using a visual analogue scale, patients assessed the following clinical variables: pain during weight-bearing, pain at rest during the night, reduction of pain during the most painful movement of the knee, and treatment success. Evaluators also assessed patients' loss of activity while performing difficult daily tasks and treatment success. There was dramatic early improvement in all six variables with hylan G-F 20 beginning after the first injection; the improvement continued through the study end points. The differences between hylan G-F 20 and saline treatment were statistically significant for all outcome measures. In the hylan G-F 20 group, 39% to 56% of patients were free or nearly free of weight-bearing pain 10 to 24 weeks after the last injection. Treatment with saline was less effective, with fewer than 13% of patients free or nearly free of weight-bearing pain. Use of rescue therapy was significantly greater in the saline group than in the hylan G-F 20 group. No adverse events were observed in the injected joint after hylan G-F 20 treatment. These results demonstrate that hylan G-F 20 is effective and well tolerated in the management of chronic idiopathic OA.

Cloning of P2Y6 cDNAs and identification of a pseudogene: comparison of P2Y receptor subtype expression in bone and brain tissues

Cellular responses to ATP/UTP and analogs are mediated by G-protein coupled P2Y receptors and have been proposed to play a role in the regulation of bone metabolism. Using a degenerate PCR approach on MG-63 cell cDNA we found PCR fragments coding for human P2Y1 and a new receptor, P2Y6. cDNA cloning of the P2Y6 receptor identified three of cDNA isoforms. Two contained the same contiguous ORFs but differed in their 5 UTRs and may therefore originate by alternative splicing whereas the third represents a pseudogene. Analysis of P2Y receptor subtype expression in human bone and the osteoblastic cell lines OHS-4 and MG-63 by RT-PCR showed that all known human P2Y receptor subtypes (P2Y1, P2Y2, P2Y4, P2Y6, and P2Y7) were expressed. In contrast, analysis of brain-derived cell lines suggests that a selective expression of P2Y receptor subtypes occurs in brain tissue.

Long-term results of pedicle stabilized thoracolumbar fractures in relation to the neurological deficit

88 patients with thoracolumbar fractures and short-segment (mono or two segment) pedicle instrumentation from the years 1985-92 had a follow-up examination after an average time of 5.6 years. The 56 men and 32 women had an average age of 32.6 years at the time of injury, 24 patients primarily had a complete and 43 patients an incomplete paraplegia, 21 patients showed no neurological deficits. The operative decompression of the spinal cord and stabilization of the injured spine by short segment pedicle instrumentation led to a complete or partial remission of the neurological deficits in 93% of the patients with incomplete paraplegia. Operative stabilization allowed an early mobilization and rehabilitation of these patients. We found no tendency to an increased complication rate in patients with neurological deficits compared to patients without neurological deficits. Patients with initially incomplete paraplegia complained more often about pain than all the other patients. Despite intensive rehabilitation and retraining programs handicapped patients had obvious disadvantages regarding their further careers.

Cloning of P2Y6 cDNAs and identification of a pseudogene: comparison of P2Y receptor subtype expression in bone and brain tissues

Cellular responses to ATP/UTP and analogs are mediated by G-protein coupled P2Y receptors and have been proposed to play a role in the regulation of bone metabolism. Using a degenerate PCR approach on MG-63 cell cDNA we found PCR fragments coding for human P2Y1 and a new receptor, P2Y6. cDNA cloning of the P2Y6 receptor identified three cDNA isoforms. Two contained the same contiguous ORFs but differed in their 5' UTRs and may therefore originate by alternative splicing whereas the third represents a pseudogene. Analysis of P2Y receptor subtype expression in human bone and the osteoblastic cell lines OHS-4 and MG-63 by RT-PCR showed that all known human P2Y receptor subtypes (P2Y1, P2Y2, P2Y4, P2Y6, and P2Y7) were expressed. In contrast, analysis of brain-derived cell lines suggests that a selective expression of P2Y receptor subtypes occurs in brain tissue.

Effects of a novel 2,3-oxidosqualene cyclase inhibitor on cholesterol biosynthesis and lipid metabolism in vivo

BIBB 515 (1-(4-chlorobenzoyl)-4-((4-(2-oxazolin-2-yl) benzylidene))piperidine) is a potent and selective inhibitor of 2,3-oxidosqualene cyclase (OSC) [EC 5.4.99.7]. In rats and mice BIBB 515 inhibited OSC in vivo in a dose-dependent manner after 1, 3, and 5 h with ED50 values from 0.2 to 0.5 mg/kg (1 to 5 h) in rats and 0.36 (1 h) to 15.5 (3 h) and 33.3 (5 h) mg/kg in mice. Inhibition of [14C]acetate incorporation into sterols was found to parallel the effects on OSC when measured after 1 h (mice) or 3 h (rats). ED50 calculated were 0.9 mg/kg (mice) and 0.1 mg/kg (rats). Dose-dependent lipid-lowering activity was seen in normolipemic hamsters after 11 days treatment (-19% for total cholesterol and -32% for VLDL + LDL cholesterol at 55 mg/kg BIBB 515 per day) and in hyperlipemic hamsters after 25 days (-25% for total cholesterol and -59% for LDL-cholesterol at 148 mg/kg BIBB 515 per day). Calculation of kinetic parameters revealed no relevant differences between control and treatment groups in LDL clearance or fractional catabolic rates, but significant reductions of LDL production rates (-30% to -54%). Liver LDL receptor mRNA of the treated animals was not or only slightly increased. Liver VLDL secretion as measured by the Triton WR1339 method was reduced after BIBB 515 in rats and hamsters. It is concluded that the lipid-lowering effect of BIBB 515 is mainly the result of an inhibition of LDL production rather than due to an increase in LDL catabolism. OSC inhibitors may offer a novel approach for lipid-lowering therapy.

[The Schnitzler syndrome as a cause of recurrent fever of unknown origin]

HISTORY AND CLINICAL FINDINGS

For 4 years a 56-year-old woman had been suffering from chronic urticaria. In the past two years she had developed recurrent fever, each 1-3 days in duration. In the last 6 to 8 months she also had severe aching in the legs. There were no significant findings on physical examination other than non-itching urticarial rash over trunk and limbs.

INVESTIGATIONS

Blood sedimentation rate was increased (maximum 88/110 mm), as were WBC count (16,200/microliter, 83% neutrophils) and the activity of alkaline leucocyte phosphatase (225 U/l). Monoclonal IgM gammopathy type kappa and circulating IgM immune complex (15.4 mg/dl) were demonstrated in serum. Skin biopsy of a new urticarial lesion revealed vasculitis. Iliac crest biopsy was unremarkable and showed no lymphoid cell infiltration. Bone scintigraphy revealed bilaterally increased storage in femur and tibia. Magnetic resonance imaging demonstrated marrow infiltration without space-occupying features in the affected femur and tibia.

TREATMENT AND COURSE

Conjunction of fever, generalised urticaria, joint/bone pain and monoclonal gammopathy of kappa type having established the diagnosis of Schnitzler's syndrome, treatment with ibuprofen was started (initially 1,200 mg daily by mouth, followed by reduction to 600 mg daily). All symptoms rapidly improved and the bone changes regressed, but not the monoclonal gammopathy. But when the ibuprofen dosage had been decreased to 600 mg daily, the urticaria recurred, though in milder form.

CONCLUSION

This case demonstrates the efficacy of ibuprofen in the treatment of the Schnitzler's syndrome. Furthermore reversibility of scintigraphic bone lesions could be demonstrated under ibuprofen treatment.

TSG-6 expression in human articular chondrocytes. Possible implications in joint inflammation and cartilage degradation

OBJECTIVE

The hyaluronan-binding protein TSG-6 (tumor necrosis factor-stimulated gene 6) forms a stable complex with the serine protease inhibitor, inter-alpha-inhibitor, potentiates the inhibition of plasmin activity, and has antiinflammatory effects in vivo. This study examines the expression of TSG-6 in human articular chondrocytes and cartilage.

METHODS

Human articular chondrocytes and cartilage explants were stimulated with cytokines, growth factors, and other agents. TSG-6 expression was analyzed by imaging-assisted Northern and Western blotting.

RESULT

TSG-6 messenger RNA (mRNA) expression was upregulated by cytokines and growth factors, predominantly interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), platelet-derived growth factor AA (PDGF-AA), and transforming growth factor beta 1 (TGF beta 1). TSG-6 mRNA induction by TGF beta 1 was delayed as compared with IL-1beta. Treatment of the cells with the glucocorticoid dexamethasone neither induced TSG-6 mRNA nor did it affect IL-1 beta-induced transcript levels. TSG-6 mRNA induction may involve several signal transduction pathways. The strong transcriptional stimulation by phorbol myristate acetate suggests protein kinase C (PKC)-mediated signaling. In contrast, PKA- and Ca- dependent signals are only marginally involved as messengers leading to increased TSG-6 levels after IL-1beta and TNF alpha treatment. In chondrocyte and cartilage organ cultures, both free TSG-6 (35 kd) and the complex with inter-alpha-inhibitor (120 kd) were present and upregulated by IL-1 beta, TNF alpha, or TGF beta 1.

CONCLUSION

Chondrocytes are a source of TSG-6 which may play a role in cartilage remodeling and joint inflammation.

Evidence for the presence of NK1 and NK3 receptors on cholinergic neurones in the guinea-pig ileum

In a guinea-pig ileum longitudinal muscle preparation, substance P (SP) (> or = 6 nM) caused an initial contraction followed by a sustained plateau contraction of about 20-50% of the initial response. This plateau contraction is caused by the SP-induced activation of cholinergic motoneurones which contract the smooth muscles by the released acetylcholine (ACh). We investigated the contribution of neurokinin NK1 and NK3 receptors during this 'plateau phase' of contraction. The plateau contraction induced by SP (60 nM) was significantly reduced by the NK1 receptor antagonist CP-96,345 (200 nM) added 5 min after SP, but was not affected by its inactive enantiomer CP-96,344 (200 nM). The NK1 receptor antagonist CP-99,994 (100 nM) significantly reduced the plateau contraction induced by SP (60 nM and 600 nM) and that induced by the NK1 receptor agonist substance P-O-methylester (SPOMe; 100 nM). CP-99,994 (100 nM), however did not affect the plateau contraction induced by the NK3 receptor agonist [Asp5,6, MePhe8]-SP(5-11) (100 nM). The plateau contraction induced by SP (600 nM) was not affected by the NK3 receptor antagonist SR-142,801 (100 nM), added 5 min after SP. Pre-incubation of the ileum with SR-142,801 (100 nM) 30 min prior to the addition of SP (600 nM) also had no significant effect on the plateau contraction. However, it significantly reduced the ileal contraction in the first minutes after the initial spasmogenic contraction. We suggest that SP induces the plateau contraction of the guinea-pig ileum longitudinal muscle mainly by the activation of NK1 receptors on cholinergic neurones.

Effects of a novel 2,3-oxidosqualene cyclase inhibitor on the regulation of cholesterol biosynthesis in HepG2 cells

Within the cholesterol biosynthesis cascade, the enzyme 2,3-oxidosqualene cyclase [EC 5.4.99.7] is of special interest due to its dual function: cyclization of 2,3-monoepoxysqualene to lanosterol and 2,3;22,23-diepoxysqualene to oxylanosterol. Further determination of the significance of this enzyme for the intracellular cholesterol homeostasis was done with BIBX 79, a new potent, specific inhibitor of this enzyme. In HepG2 cells the effects of BIBX 79 on cholesterol biosynthesis, 2,3-oxidosqualene cyclase as well as HMG-CoA reductase activities were studied. BIBX 79 is a potent inhibitor of sterol biosynthesis in HepG2 cells (IC50 4 x 10(-9) M). No other enzyme within the cholesterol biosynthesis cascade was significantly inhibited as was evidenced by a radio HPLC detection system. In contrast to simvastatin, no direct interaction with HMG-CoA reductase was observed. When incubating HepG2 cells for 16 h with the HMG-CoA reductase inhibitor simvastatin (10(-6)-10(-10) M) HMG-CoA reductase activity was increased up to 180%. BIBX 79 did also affect HMG-CoA reductase activity under these conditions: in concentrations of BIBX 79 "> or =" 10(-9) "< or =" 10(-7) M, where a partial inhibition of 2,3-oxidosqualene cyclase is observed, HMG-CoA reductase activity was decreased. However, higher concentrations of BIBX 79 that totally blocked 2,3-oxidosqualene cyclase led to an increase in HMG-CoA reductase activity. This effect of BIBX 79 on HMG-CoA reductase is thought to be mainly mediated by oxysterols that are formed by the cyclization of 2,3;22,23-diepoxysqualene. 2,3;22,23-Diepoxysqualene is preferentially cyclized by the 2,3-oxidosqualene cyclase and, consequently, only high inhibitor concentrations will also block 2,3;22,23-diepoxysqualene cyclization. Thus, by partial blockade of this enzyme, both an inhibition of lanosterol and subsequently cholesterol formation as well as a concomitant effect on HMG-CoA reductase can be achieved. Both effects complement each other and lead to an effective control of cholesterol biosynthesis. It is therefore concluded that 2,3-oxidosqualene cyclase plays a crucial role in the regulation of intracellular cholesterol homeostasis. 2,3-Oxidosqualene cyclase inhibitors offer an attractive approach for novel lipid-lowering agents.

[Studies of the time structure of pathologic speech production. Presenting a screening method for evaluating expressive speech performance]

A simple screening method is presented, which was designed to help evaluate speech disorders. An algorithm norms the digitalized speech signals by time and measures the duration of the pause intervals. With this method the classification of speech performance is possible.