The effects of a novel histamine-3 receptor inverse agonist on essential tremor in comparison to stable levels of alcohol

Essential tremor (ET) is a common movement disorder. Animal studies show that histaminergic modulation may affect the pathological processes involved in the generation of ET. Histamine-3 receptor inverse agonists (H3RIA) have demonstrated attenuating effects on ET in the harmaline rat model. In this double-blind, three-way cross-over, single-dose, double-dummy study the effects of 25 mg of a novel H3RIA (MK-0249) and a stable alcohol level (0.6 g L(-1)) were compared with placebo, in 18 patients with ET. Tremor was evaluated using laboratory tremorography, portable tremorography and a clinical rating scale. The Leeds Sleep Evaluation Questionnaire (LSEQ) and a choice reaction time (CRT) test were performed to evaluate potential effects on sleep and attention, respectively. A steady state of alcohol significantly diminished tremor as assessed by laboratory tremorography, portable tremorography and clinical ratings compared with placebo. A high single MK-0249 dose was not effective in reducing tremor, but caused significant effects on the LSEQ and the CRT test. These results suggest that treatment with a single dose of MK-0249 does not improve tremor in alcohol-responsive patients with ET, whereas stable levels of alcohol as a positive control reproduced the commonly reported tremor-diminishing effects of alcohol.

Effect of the cathepsin K inhibitor odanacatib on bone resorption biomarkers in healthy postmenopausal women: two double-blind, randomized, placebo-controlled phase I studies

Inhibition of cathepsin K (CatK) is a potential new treatment for osteoporosis. In two double-blind, randomized, placebo-controlled phase I studies, postmenopausal female subjects received odanacatib (ODN), an orally active, potent, and selective CatK inhibitor, once weekly for 3 weeks or once daily for 21 days. Bone turnover biomarkers, safety monitoring, and plasma ODN concentrations were assessed. These studies showed ODN to be well tolerated. Pharmacokinetic (PK) analysis revealed a long half-life (t(1/2); 66-93 h) consistent with once-weekly dosing. Pronounced reductions in C-terminal telopeptide of type I collagen (approximately 62%) and N-terminal telopeptide of type I collagen normalized to creatinine (NTx/Cr) (approximately 62%) at trough (C(168 h)) were seen following weekly administration. Robust reductions in CTx (up to 81%) and NTx/Cr (up to 81%) were seen following daily administration. ODN exhibits robust and sustained suppression of bone resorption biomarkers (CTx and NTx/Cr) at weekly doses > or = 25 mg and daily doses > or = 2.5 mg.

Suppression of Niacin-induced Vasodilation with an Antagonist to Prostaglandin D2 Receptor Subtype 1

Niacin (nicotinic acid) reduces cardiovascular events in patients with dyslipidemia. However, symptoms associated with niacin-induced vasodilation (e.g., flushing) have limited its use. Laropiprant is a selective antagonist of the prostaglandin D(2) receptor subtype 1 (DP1), which may mediate niacin-induced vasodilation. The aim of this proof-of-concept study was to evaluate the effects of laropiprant (vs placebo) on niacin-induced cutaneous vasodilation. Coadministration of laropiprant 30, 100, and 300 mg with extended-release (ER) niacin significantly lowered flushing symptom scores (by approximately 50% or more) and also significantly reduced malar skin blood flow measured by laser Doppler perfusion imaging. Laropiprant was effective after multiple doses in reducing symptoms of flushing and attenuating the increased malar skin blood flow induced by ER niacin. In conclusion, the DP1 receptor antagonist laropiprant was effective in suppressing both subjective and objective manifestations of niacin-induced vasodilation.

Bioequivalence of an ezetimibe/simvastatin combination tablet and coadministration of ezetimibe and simvastatin as separate tablets in healthy subjects

OBJECTIVE

To assess the bioequivalence of an ezetimibe/simvastatin (EZE/SIMVA) combination tablet compared to the coadministration of ezetimibe and simvastatin as separate tablets (EZE + SIMVA).

METHODS

In this open-label, randomized, 2-part, 2-period crossover study, 96 healthy subjects were randomly assigned to participate in each part of the study (Part I or II), with each part consisting of 2 single-dose treatment periods separated by a 14-day washout. Part I consisted of Treatments A (EZE 10 mg + SIMVA 10 mg) and B (EZE/SIMVA 10/10 mg/mg) and Part II consisted of Treatments C (EZE 10 mg + SIMVA 80 mg) and D (EZE/SIMVA 10/80 mg/mg). Blood samples were collected up to 96 hours post-dose for determination of ezetimibe, total ezetimibe (ezetimibe + ezetimibe glucuronide), simvastatin and simvastatin acid (the most prevalent active metabolite of simvastatin) concentrations. Ezetimibe and simvastatin acid AUC(0-last) were predefined as primary endpoints and ezetimibe and simvastatin acid Cmax were secondary endpoints. Bioequivalence was achieved if 90% confidence intervals (CI) for the geometric mean ratios (GMR) (single tablet/coadministration) of AUC(0-last) and Cmax fell within prespecified bounds of (0.80, 1.25).

RESULTS

The GMRs of the AUC(0-last) and Cmax for ezetimibe and simvastatin acid fell within the bioequivalence limits (0.80, 1.25). EZE/ SIMVA and EZE + SIMVA were generally well tolerated.

CONCLUSIONS

The lowest and highest dosage strengths of EZE/SIMVA tablet were bioequivalent to the individual drug components administered together. Given the exact weight multiples of the EZE/SIMVA tablet and linear pharmacokinetics of simvastatin across the marketed dose range, bioequivalence of the intermediate tablet strengths (EZE/SIMVA 10/20 mg/mg and EZE/SIMVA 10/40 mg/mg) was inferred, although these dosages were not tested directly. These results indicate that the safety and efficacy profile of EZE + SIMVA coadministration therapy can be applied to treatment with the EZE/SIMVA tablet across the clinical dose range.

Effects of lorazepam on fear-potentiated startle responses in man

Sudden intense sensory stimuli elicit a cascade of involuntary responses, including a short-latency skeletal muscular response ('eyeblink startle response') and longer-latency autonomic responses. These responses are enhanced when subjects anticipate an aversive event compared to periods when subjects are resting ('fear potentiation'). It has been reported previously that the anxiolytic diazepam can suppress fear-potentiation of the eyeblink startle response in human volunteers. The present experiment aimed to confirm and extend these observations by examining the effect of another benzodiazepine, lorazepam, on the eyeblink and skin conductance components of the acoustic startle, and on fear-potentiation of these responses. Eighteen male volunteers participated in three weekly sessions in which they received oral treatment with placebo, lorazepam (1 mg) and lorazepam (2 mg), according to a balanced three-period, crossover, double-blind design. Two hours after ingestion of the treatments, electromyographic responses of the orbicularis oculi muscle and skin conductance responses were evoked by sound pulses during alternating periods in which the threat of an electric shock (electrodes attached to the subject's wrist) was present (THREAT) and absent (SAFE). The THREAT condition was associated with significant increase in the amplitude of the electromyographic (EMG) and skin conductance responses; there were also increases in baseline skin conductance, the number and amplitude of 'spontaneous' skin conductance fluctuations and self-rated anxiety. Lorazepam attenuated the effect of THREAT on self-rated anxiety and on the amplitude of the EMG response, but had no significant effect on fear-potentiation of the skin conductance responses. These results extend previous findings of the effect of diazepam on the fear-potentiated eyeblink startle response to lorazepam, and suggest that fear-potentiation of the later autonomic component of the startle response may be less sensitive to benzodiazepines than the fear-potentiated eyeblink response and self-rated anxiety.

Effect of L-000845704, an alphaVbeta3 integrin antagonist, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women

The alphaVbeta3 integrin (vitronectin receptor) plays a pivotal role in bone resorption. We hypothesized that L-000845704, an alphaVbeta3 integrin antagonist, would potently inhibit bone resorption, thereby increasing bone mass as assessed by bone mineral density (BMD) in women with postmenopausal osteoporosis. In a multicenter, randomized, double-blind, placebo-controlled, 12-month study, 227 women (average 63 yr) with low lumbar spine or femoral neck BMD were randomly assigned to receive 100 or 400 mg L-000845704 once daily (qd), 200 mg L-000845704 twice daily (bid), or placebo. L-000845704 increased lumbar spine BMD (2.1, 3.1, and 3.5% for the 100-mg-qd, 400-mg-qd, and 200-mg-bid treatment groups, respectively, vs. -0.1% for placebo; P < 0.01 all treatments vs. placebo). Only 200 mg L-000845704 bid significantly increased BMD at the hip (1.7 vs. 0.3% for placebo; P < 0.03) and femoral neck (2.4 vs. 0.7% for placebo; P < 0.05). No L-000845704 group increased total body BMD. All doses of L-000845704 resulted in a similar approximately 42% decrease from baseline of N-telopeptide cross-links (P < 0.001 vs. placebo). L-000845704 was generally well tolerated; adverse events resulting in discontinuation from the study were relatively infrequent. In conclusion, the antiresorptive effect of the alphaVbeta3 integrin antagonist L-000845704 translated into significant increases in lumbar spine BMD. Furthermore, 200 mg L-000845704 bid provided efficacy at the hip sites. These data suggest that the alphaVbeta3 integrin antagonist L-000845704 could be developed as an effective therapeutic agent for osteoporosis.

Results of a randomized, dose-ranging trial of etoricoxib in patients with osteoarthritis

OBJECTIVES

To evaluate the clinical efficacy and tolerability of etoricoxib in the treatment of osteoarthritis (OA) of the knee and define the clinically active dose range for further clinical trials.

METHODS

This two-part, randomized, double-blind, placebo- and active comparator-controlled trial was conducted in 617 adults with knee OA. In Part 1 (6 weeks), patients received placebo, etoricoxib 5, 10, 30, 60 or 90 mg q.d. In Part 2 (8 weeks), patients received etoricoxib 30, 60 or 90 mg q.d. or diclofenac 50 mg t.i.d., predetermined at Part 1 allocation. Efficacy and safety were evaluated. Primary efficacy end-points were the Western Ontario and McMaster's University Osteoarthritis Index (WOMAC) Pain subscale, Patient Global Assessment of Response to Therapy, and Investigator Global Assessment of Disease Status.

RESULTS

At 6 weeks, etoricoxib 5, 10, 30, 60 and 90 mg each demonstrated clinical efficacy superior to placebo. Maximal efficacy was seen with 60 mg. In Part 2, etoricoxib 30, 60 and 90 mg were generally similar to diclofenac. Patients receiving etoricoxib 30, 60 or 90 mg in Parts I and II had sustained effects over 14 weeks. All treatments were well tolerated.

CONCLUSIONS

Etoricoxib 60 mg once daily showed maximal efficacy in treating OA in this study. Etoricoxib 5-90 mg once daily was generally well tolerated in OA patients for up to 14 weeks.

Effects of enteric-coated, low-dose aspirin on parameters of platelet function

BACKGROUND

Aspirin is widely used as an anti-thrombotic drug; however, it has been suggested that enteric-coated formulations of aspirin may be less bioavailable and less effective as anti-thrombotic agents.

AIM

To assess the effect of a formulation of enteric-coated, low-dose (81 mg) aspirin on serum generated thromboxane B2 and platelet aggregation in healthy subjects.

METHODS

Twenty-four subjects participated in a double-blind, randomized, placebo-controlled, parallel-group, multiple-dose study. Twelve subjects in each of two groups received a daily oral dose of enteric-coated aspirin (81 mg) or matching placebo for 7 days. Serum thromboxane B2 and platelet aggregation (using 1 mm arachidonic acid and 1 microg/mL collagen as agonists) were measured 1-3 days prior to day 1, on day 1 (prior to therapy) and 4 h after the last dose on day 7.

RESULTS

After seven daily doses of enteric-coated aspirin, the mean percentage inhibition from baseline of ex vivo generated serum thromboxane B2 was 97.4%, compared with a 7.8% increase after placebo treatment. The mean percentage inhibition of arachidonic acid- and collagen-induced platelet aggregation was 97.9% and 70.9%, respectively, following enteric-coated aspirin, compared with - 1.0% and 2.7%, respectively, after placebo.

CONCLUSIONS

The anti-platelet effects of multiple, daily, low-dose aspirin (as assessed by inhibition of serum thromboxane B2 and platelet aggregation) are not adversely affected by enteric coating.

Liquid chromatographic-tandem mass spectrometric urine assay for a highly metabolized cyclic ureidobenzenesulfonamide: issues concerning assay specificity and quality control preparation

An LC-MS-MS method was validated for the quantitation of a beta(3) agonist (A) in human urine to support Phase I studies. A was designed to accelerate metabolism for weight reduction. During assay development a significant loss of A was apparent from frozen urine quality control samples. The addition of 0.75% bovine serum albumin (BSA) in urine (v/v) was required to maximize the recovery of A from urine. Urine samples were basified and extracted into methyl t-butyl ether-isopropyl alcohol (90:10, v/v). The organic layer was washed, evaporated, reconstituted, and injected onto a 5 cm, C8 HPLC column prior to MS-MS analysis. The standard curve was linear from 5 to 500 ng/ml. Intraday precision for peak area ratios from BSA urine samples at seven separate concentrations over a range of 5-500 ng/ml (n=5) was <4.0% and calculated concentrations were within 91-115% of nominal concentrations. Interday precision for BSA urine quality control (QC) samples at four separate concentrations (n=10 of each) was <5.0% and individual calculated concentrations were within 90-111% of nominal concentrations. This work emphasizes that potential metabolites and quality control standards should be prepared and assayed as early as possible in method development, especially before the sample collection section of the clinical protocol is prepared. The methods described here have wide utility to other compounds containing basic benzene sulfonamides and to beta3 agonist candidates.

Rofecoxib, a COX-2 inhibitor, does not inhibit human gastric mucosal prostaglandin production

BACKGROUND & AIMS

Rofecoxib, an inhibitor of the inducible cyclooxygenase (COX)-2 enzyme, appears not to cause acute gastroduodenal injury or chronic ulceration. To attribute this to COX-2 selectivity with sparing of gastric mucosal prostaglandin synthesis requires direct proof.

METHODS

Twenty-four healthy, nonsmoking Helicobacter pylori-negative volunteers were randomized to 1 of 2 separate concurrent blinded crossover studies. Sixteen volunteers received rofecoxib, 50 mg once daily, for 5 days in one treatment period and placebo in the other. Eight volunteers similarly received naproxen, 500 mg twice daily, and placebo. On day 5 of each period, antral mucosal prostaglandin E2 (PGE2) synthesis was measured by radioimmunoassay after vortexing for 3 minutes. Whole blood COX-1 activity was measured as serum thromboxane (TXB)2- and COX-2 activity as lipopolysaccharide (LPS)-induced PGE2.

RESULTS

Naproxen decreased gastric mucosal PGE2 synthesis by 65% (90% confidence interval [CI], 53%-74%; P = 0.001 vs. placebo) in contrast to an 18% increase after rofecoxib (90% CI, -11% to 57%; P = 0.313 vs. placebo). Naproxen also significantly inhibited both serum TXB2 by 94% and LPS-induced PGE2 production by 77% (both P < or = 0.002 vs. placebo), but rofecoxib only inhibited COX-2-dependent LPS-induced PGE(2) (by 79%; P < 0.001 vs. placebo).

CONCLUSIONS

Rofecoxib (50 mg) lacked naproxen's ability to reduce the availability of gastroprotective prostaglandins.

A new cyclooxygenase-2 inhibitor, rofecoxib (VIOXX), did not alter the antiplatelet effects of low-dose aspirin in healthy volunteers

The present study examined whether rofecoxib (VIOXX), a new specific inhibitor of cyclooxygenase-2 (COX-2), would interfere with the desired antiplatelet effects of aspirin. Thus, the effects of rofecoxib on inhibition of ex vivo serum-generated thromboxane B2 (TXB2) and platelet aggregation by low doses (81 mg) of aspirin were examined in healthy volunteers. This was a double-blind, randomized, placebo-controlled, parallel study of two treatment groups (n = 12 per group) in which subjects received 50 mg of rofecoxib or placebo for 10 days in a blinded fashion. Subjects also received 81 mg aspirin once on each of days 4 through 10 in an open-label fashion. Blood for measurement of serum TXB2 production and platelet aggregation studies was collected on day 1 (prior to rofecoxib/placebo), on day 4 (prior to aspirin), and on day 10 (before and 4 hours following the seventh dose of aspirin). Platelet-derived serum TXB2 (COX-1 assay) was measured in blood clotted for 1 hour at 37 degrees C. Platelet aggregation was independently induced employing 1 mM arachidonic acid and 1 microgram/mL collagen as agonists. Rofecoxib administered alone had no significant effect on serum TXB2 production or platelet aggregation (day 4). TXB2 production was inhibited 98.4% by aspirin coadministered with either rofecoxib or placebo (day 10). Similarly, platelet aggregation induced by arachidonic acid was inhibited 93.7% and 93.5% by aspirin coadministered with either rofecoxib or placebo, respectively (day 10). The comparable values for inhibition of collagen-induced platelet aggregation were 86.8% and 90.8%, respectively. No important clinical or laboratory adverse experiences were observed. In conclusion, rofecoxib alone (50 mg QD for 4 days) did not inhibit serum TXB2 production or platelet aggregation. In addition, rofecoxib (50 mg QD for 10 days) did not alter the antiplatelet effects of low-dose aspirin (inhibition of platelet aggregation and TXB2 production). Rofecoxib was generally well tolerated when administered alone or in combination with low-dose aspirin.

Single dose methodology to assess the influence of an alpha1-adrenoceptor antagonist on uroflowmetric parameters in patients with benign prostatic hyperplasia

AIMS

To establish methodology which rapidly and reliably assesses the effect of an alpha1-adrenoceptor antagonist on peak urine flow rates in men with benign prostatic hyperplasia (BPH). This methodology could then be applied to screening new drugs to treat BPH.

METHODS

Twenty-five patients with BPH enrolled in a double-blind, placebo-controlled, two-period crossover study. Patients were either withdrawn from their current alpha1-adrenoceptor antagonist therapy (n = 22) or were untreated prestudy (n = 3) and all met prespecified uroflowmetric criteria including: (1) a peak urine flow rate (Qmax) < 12 ml s-1 off therapy (or < 10 ml s-1 if untreated prestudy) and (2) a decrease in peak urine flow rate (Qmax) of > 2 ml s-1 after withdrawal from therapy. Study treatment consisted of tamsulosin 0.4 mg (or matching placebo) once daily for 8 days in a two-period crossover. Uroflowmetry was performed predose and once postdose (4.5-5.5 h postdose) on day 1, and once postdose (4.5-5.5 h postdose) on day 8 of each treatment period.

RESULTS

After a single dose of tamsulosin, the least-square mean difference between tamsulosin and placebo in the change from baseline Qmax was 2.8 ml s-1 (P = 0.017 vs placebo). After 8 days dosing of tamsulosin, the least-square mean difference between tamsulosin and placebo in the change from baseline Qmax was also 2.8 ml s-1 (P = 0.044 vs placebo). Additionally, there was no significant difference observed between the single and multiple dose results (P > 0.200 for between group difference).

CONCLUSIONS

Both single and multiple doses of tamsulosin 0.4 mg increased Qmax in men with BPH. A single dose produced a comparable response to multiple dose administration. The magnitude of the effect was greater than the effect generally seen in longer term clinical trials, but this difference may be explained by the patient population in this study which was preselected for 'responsiveness' to an alpha1-adrenoceptor antagonist. These results support the utility of single dose uroflowmetric measurements in rapidly providing preliminary data on new investigational agents, specifically agents which act to increase urine flow in men with BPH. However, clinical efficacy would still need to be confirmed with longer term clinical trials.

Efficacy and tolerability of the specific cyclooxygenase-2 inhibitor DFP compared with naproxen sodium in patients with postoperative dental pain

DFP [3-(2-propyloxy)-(4-methyl-sulfonylphenyl)-(5,5-dimethyl)-fu ranone] is a highly specific cyclooxygenase-2 inhibitor (>2500-fold selective in transfected Chinese hamster ovary cell assays) that has demonstrated efficacy in preclinical models of pain and inflammation. The present single-dose, randomized, double-masked, double-dummy, placebo-controlled, parallel-group study was undertaken to compare DFP 5, 25, and 50 mg with naproxen sodium 550 mg and with placebo in 196 patients (mean age, 25.8 years; 187 [95.4%] males) who experienced moderate-to-severe pain after surgical removal of > or =2 third molars. Overall analgesic effect, duration of effect, time to onset of analgesic effect, peak analgesic effect, and tolerability were assessed over a 24-hour postdose period. Both DFP 25 and 50 mg, as well as the active comparator, naproxen sodium 550 mg, were significantly more effective than placebo. The onset of analgesic effect in the DFP 25-mg, DFP 50-mg, and naproxen sodium 550-mg groups did not differ significantly. DFP was generally well tolerated in single doses up to 50 mg. DFP 50 mg was efficacious in the treatment of postoperative dental pain and was indistinguishable from the active comparator, naproxen sodium 550 mg.

Acute effect of ephedrine on 24-h energy balance

Ephedrine is used to help achieve weight control. Data on its true efficacy and mechanisms in altering energy balance in human subjects are limited. We aimed to determine the acute effect of ephedrine on 24-h energy expenditure, mechanical work and urinary catecholamines in a double-blind, randomized, placebo-controlled, two-period crossover study. Ten healthy volunteers were given ephedrine (50 mg) or placebo thrice daily during each of two 24-h periods (ephedrine and placebo) in a whole-room indirect calorimeter, which accurately measures minute-by-minute energy expenditure and mechanical work. Measurements were taken of 24-h energy expenditure, mechanical work, urinary catecholamines and binding of (+/-)ephedrine in vitro to human beta1-, beta2- and beta3-adrenoreceptors. Twenty-four-hour energy expenditure was 3.6% greater (8965+/-1301 versus 8648+/-1347 kJ, P<0.05) with ephedrine than with placebo, but mechanical work was not different between the ephedrine and placebo periods. Noradrenaline excretion was lower with ephedrine (0.032+/-0.011 microg/mg creatinine) compared with placebo (0.044+/-0.012 microg/mg creatinine) (P<0.05). (+/-)Ephedrine is a relatively weak partial agonist of human beta1- and beta2-adrenoreceptors, and had no detectable activity at human beta3-adrenoreceptors. Ephedrine (50 mg thrice daily) modestly increases energy expenditure in normal human subjects. A lack of binding of ephedrine to beta3-adrenoreceptors and the observed decrease in urinary noradrenaline during ephedrine treatment suggest that the thermogenic effect of ephedrine results from direct beta1-/beta2-adrenoreceptor agonism. An indirect beta3-adrenergic effect through the release of noradrenaline seems unlikely as urinary noradrenaline decreased significantly with ephedrine.

Predicted amino acid sequence and genomic organization of Trypanosoma cruzi hsp 60 genes

We describe the isolation of a Trypanosoma cruzi protein-coding gene that exhibited about 50% identity with members of the family of heat shock protein (hsp) 60 genes. Since this homology extended for most of the predicted 562 amino acid open reading frame and was comparable to the level of sequence identity between the individual hsp 60 genes from diverged species, we conclude that we have isolated and characterized a T. cruzi hsp 60 gene. The T. cruzi hsp 60 genes are arranged in tandem arrays, and the presence of restriction fragment length polymorphisms (RFLPs) among the different hsp 60 genes suggests the presence of several separate gene arrays encoding hsp 60 members.

Antigenic variation in African trypanosomes

African trypanosomes evade the humoral immune response by periodically changing the antigenic identity of their variant cell-surface glycoprotein (VSG) coat. Antigenic variation relies on DNA rearrangement events that can translocate a silent VSG gene to a telomerically located VSG gene expression site. Antigenic switches can also be brought about by the differential transcriptional control of the expression sites, only one of which is transcribed at any time.

Allelic polymorphism of the Trypanosoma brucei polyubiquitin gene

We have characterized a second T. brucei polyubiquitin gene (UbB) that is highly similar in the coding and flanking regions to a previously described T. brucei polyubiquitin gene (UbA). However, UbB differs from UbA in 2 respects: (1) the predicted carboxy-terminal amino acid of UbB is methionine, as opposed to leucine in UbA, and (2) UbB contains approximately 13 ubiquitin repeats, as opposed to approximately 30 repeats in UbA. In Southern blots of intact T. brucei DNA separated by pulsed field gel electrophoresis, the polyubiquitin sequences have been shown to reside on band 19, which may contain 3 chromosomes. Three experiments that target a neomycin-resistance gene to the polyubiquitin locus demonstrate a one-to-one ratio of polyubiquitin 3-flanking sequences, which suggests that UbA and UbB are alleles rather than duplications. Four additional strains of T. brucei and one strain of T. equiperdum show variation in their polyubiquitin gene size, suggesting that this is a common polymorphism.

Characterization of VSG gene expression site promoters and promoter-associated DNA rearrangement events

The expressed variant cell surface glycoprotein (VSG) gene of Trypanosoma brucei is located at the 3' end of a large, telomeric, polycistronic transcription unit or expression site. We show that the region 45 kb upstream of the VSG gene, in the expression site on a 1.5-Mb chromosome, contains at least two promoters that are arranged in tandem, directing the transcription of the expression site. DNA rearrangement events occur specifically, at inactivation of the expression site, and these events delete the most upstream transcribed region and replace it with a large array of simple-sequence DNA, leaving the downstream promoter intact. Because of the placement of simple-sequence DNA, the remaining downstream promoter now becomes structurally identical to previously described VSG promoters. The downstream promoter is repetitive in the genome, since it is present at several different expression sites. Restriction fragment length polymorphism mapping allows grouping of the expression sites into two families, those with and those without an upstream transcription unit, and the DNA rearrangement events convert the expression sites from one type to the other. Deletion of the upstream transcription unit also leads to the loss of several steady-state RNAs. The findings may indicate a role for promoter-associated DNA rearrangement events, and/or interactions between tandemly arranged promoters, in expression site transcriptional control.

Chromosome organization of the protozoan Trypanosoma brucei

The genome of the protozoan Trypanosoma brucei is known to be diploid. Karyotype analysis has, however, failed to identify homologous chromosomes. Having refined the technique for separating trypanosome chromosomes (L. H. T. Van der Ploeg, C. L. Smith, R. I. Polvere, and K. Gottesdiener, Nucleic Acids Res. 17:3217-3227, 1989), we can now provide evidence for the presence of homologous chromosomes. By determining the chromosomal location of different genetic markers, most of the chromosomes (14, excluding the minichromosomes), could be organized into seven chromosome pairs. In most instances, the putative homologs of a pair differed in size by about 20%. Restriction enzyme analysis of chromosome-sized DNA showed that these chromosome pairs contained large stretches of homologous DNA sequences. From these data, we infer that the chromosome pairs represent homologs. The identification of homologous chromosomes gives valuable insight into the organization of the trypanosome genome, will facilitate the genetic analysis of T. brucei, and suggests the presence of haploid gametes.

Alpha-amanitin resistant transcription of protein coding genes in insect and bloodstream form Trypanosoma brucei

The variant cell surface glycoprotein (VSG) gene expression sites of the protozoan Trypanosoma brucei are transcribed by an unusual alpha-amanitin resistant RNA polymerase. All other protein coding genes of T.brucei examined to date are transcribed by an alpha-amanitin sensitive RNA polymerase, presumably RNA polymerase II. We now show that transcription of protein coding genes by alpha-amanitin resistant RNA polymerases is not unique to the bloodstream form expressed VSG gene expression sites, but also occurs in insect form trypanosomes, which do not express VSG genes. In insect form trypanosomes transcription of the procyclin or PARP genes is resistant to alpha-amanitin to a degree comparable with that of VSG and ribosomal RNA (rRNA) genes. Comparison of the alpha-amanitin resistantly transcribed PARP and VSG gene families shows that they both produce one of the most abundant mRNAs [1-3% of poly(A)+] and they both encode the major cell surface proteins of their respective life cycle stages. Transcription of a subset of functionally comparable protein coding genes is thus mediated by an RNA polymerase which differs from the regular RNA polymerase II.

Progressive adrenal failure in polyglandular autoimmune disease

We describe the clinical course of a boy who developed progressive adrenal failure, beginning with failure of the zona glomerulosa, as part of polyglandular autoimmune disease. Initially the patient presented with hypoparathyroidism and mucocutaneous candidiasis. ACTH tests at ages 8 and 11 yr resulted in a normal response of both mineralo- and glucocorticoids. The constellation of hyponatremia , hyperkalemia, and growth failure at age 14 yr prompted a reevaluation. A repeat ACTH test, assessing individual contributions of zone fasciculata and glomerulosa, showed normal plasma cortisol, desoxycorticosterone, and corticosterone responses and a normal urinary response of 18-hydroxydeoxycorticosterone and tetrahydrodeoxycorticosterone. Urinary 18-hydroxycorticosterone and urinary as well as plasma aldosterone were undetectable. PRA was markedly elevated. The ACTH response of adrenal androgens, presumably metabolic products of the zona reticularis, was also deficient. Antiadrenal antibodies against all three layers of the adrenal cortex were present. Mineralocorticoid therapy resulted not only in normalization of electrolytes and PRA but also in catch-up growth. Repeat testing of fasciculata function at age 19 yr now shows that the patient's cortisol response to ACTH response in abnormal. The course of this patient suggest that in addition to monitoring the electrolyte status, periodic tests for both mineralo- and glucocorticoid synthesis should be performed in children with polyglandular autoimmune disease because progressive adrenal insufficiency may go unrecognized.

Aldosterone response to prolonged ACTH infusion in juvenile hypertension

The effects of a continuous 5-day ACTH infusion (40 units/24 hr) on plasma aldosterone (aldo) concentration and urinary excretion of aldosterone pH 1 conjugate, tetrahydroaldosterone and free aldo were investigated in 6 normotensive children, and 7 children with hypertension of unknown origin. In both groups, an initial rise of plasma aldo and all urinary aldo metabolites and a subsequent fall were observed during the ACTH test. The decline in plasma aldo correlated significantly with a decrease in plasma renin activity and serum K+. There was, however, evidence for another regulatory factor of aldo secretion during ACTH infusion because on a low salt diet. ACTH produced a similar aldo pattern which could not be attributed to the changes in plasma renin activity or serum K+. Urinary excretion of both free aldo and tetrahydroaldosterone, a metabolite formed in the liver, showed a slower decrease during ACTH infusion than aldosterone pH 1 conjugate, which is of renal origin. The change in pattern of urinary aldo metabolites may be caused by a relative increase of the free, nonprotein bound plasma fraction of aldo and an enhanced metabolism of aldo in the liver during ACTH infusion. Neither in the baseline state nor during the ACTH test was there a difference between the normotensive and the hypertensive group in any of the aldo parameters.

New studies of the 11 beta-hydroxylase and 18-hydroxylase enzymes in the hypertensive form of congenital adrenal hyperplasia

Studies in four children with congenital adrenal hyperplasia due to 11 beta-hydroxylase deficiency provide evidence for two separate 11 beta-hydroxylating systems in the adrenal zona fasciculata and zona glomerulosa. In addition, these studies support the proposal that the adrenal 11 beta- and 18-hydroxylating activities are related and may involve the same enzyme protein and catalytic site. In the untreated or poorly treated state, despite elevation of deoxycorticosterone (DOC) and tetrahydrodeoxycorticosterone, urinary free 18-hydroxy-DOC was in the low normal range and did not increase normally with ACTH. PRA and urinary free 18-hydroxycorticosterone (18-OHB), tetrahydroaldosterone (TH Aldo), and pH 1 aldosterone were suppressed in the untreated and ACTH periods. Glucocorticoid administration suppressed plasma ACTH, and urinary tetrahydro-DOC and free DOC excretion decreased to the normal range. Concomitantly, there was a rise in PRA accompanied by parallel increase in urinary 18-OHB, urinary TH Aldo, and pH 1 aldosterone. While on dexamethasone, a low sodium diet (10 meq/day) resulted in prompt sodium retention, with a further rise in PRA and urinary 18-OHB, TH Aldo, and pH 1 aldosterone. These studies indicate the presence of both an 11 beta- and an 18-hydroxylase deficiency in the zona fasciculata and normal 11 beta- and 18-hydroxylase function in the zona glomerulosa, suggesting that these two enzymatic functions are related and that separate enzyme systems are present in the two zones.

Adrenocortical function, electrolyte metabolism, and blood pressure during prolonged adrenocorticotropin infusion in juvenile hypertension

The effect of a continuous 5-day ACTH infusion (40 U/24 h) on adrenocorticoid function, electrolyte metabolism, and blood pressure was investigated in eight normotensive children and eight patients with hypertension of unknown origin. There was a continuous rise of plasma cortisol and deoxycorticosterone in all patients. Plasma aldosterone rose transiently in the normotensive and the hypertensive group. A transient kaliuresis and a continuous fall in serum K+ were observed in all patients. ACTH induced sodium retention and weight gain. The observed increase in systolic blood pressure correlated significantly with the cumulative sodium retention in the normotensive and the hypertensive groups. No correlation between sodium retention and diastolic pressure was found. ACTH on a low salt diet (10 meq/24 h) produced a blood pressure rise which was smaller than that on regular salt. The blood pressure rise did not correlate with any of the hormones measured. This study provides evidence for an unidentified ACTH-stimulable adrenal factor capable of raising blood pressure in normotensive children and patients with juvenile hypertension. The ACTH-induced blood pressure rise is only partly salt dependent and the mechanism of the rise remains unclear.

6 beta-Hydroxycortisol excretion in hypercortisolemic states

Urinary 6beta-hydroxycortisol (6betaOHF) excretion was measured and compared with free cortisol and 17-hydroxycorticosteroid (17OH) excretion in normal children, patients with Cushing's syndrome or disease (CSD), and patients during cortisol therapy. Normal 6betaOHF excretion in children was 0.23 +/- 0.03 mg/m2/24 h (mean +/- SE). No sex difference was found. ACTH infusion (40 U/day for 5 days) and high dose cortisol altered the 6 betaOHF:17OH ratio so that it was indistinguishable from the ratio seen in CSD. The fact that both Cushing's disease and high dose cortisol therapy caused the same change in the 6 betaOHF:17OH ratio suggests that cortisol and not ACTH induced 6beta-hydroxylase in hypercortisolemic subjects. Since the 6betaOHF:17OH ratio in CSD patients was always well above the normal range, measurement of 6betaOHF excretion was a better and more rapid test for chronic hypercortisolemia than urinary 17OH or free cortisol. Thus, measurement of urinary 6betaOHF is suggested as a good diagnostic test for hypercortisolemic states.

Mineralocorticoids, salt balance and blood pressure after prolonged ACTH administration in juvenile hypertension

The effect of a 5 day ACTH test (40 U/24 h) on plasma aldosterone (aldo), deoxycorticosterone (DOC), plasma renin activity (PRA) and urinary excretion of aldosterone-pH1-conjugate (pH-1-aldo) and tetrahydro-DOC (TH-DOC) was investigated in 8 normotensive children (group I), 8 patients with hypertension of unknown origin (group II), and 4 hypertensive children with dexamethasone suppressible hyperaldosteronism (DSH) (group III). Changes in blood pressure and sodium balance were studied in all groups. Under baseline conditions there was no hormonal difference between group I and II. In contrast, the children in group III had a suppressed PRA and a 1.5--2 fold elevation of aldo and DOC. Plasma DOC and urinary THDOC increased continuously 10--50 fold in all groups during the ACTH test. Aldo rose transiently 2--4 fold on the first day of ACTH and fell subsequently below baseline levels in group I and II. The children with DSH (group III), however, showed an unusual, sustained aldo stimulation with ACTH. PRA decreased significantly after ACTH in group I and II. Sodium retention aTH administration. The highest blood pressure rise was observed in group III (from 124/72 to 139/90 mm Hg). The blood pressure response to ACTH was partly sodium dependent. Although aldo and DOC and sodium retention may contribute to the ACTH induced blood pressure elevation, other factors must play a role.