Pharmacological effects of GR138950, a novel angiotensin AT1 receptor antagonist

The antagonist activity of GR138950 (1-[[3-bromo-2-[2-[[(trifluoromethyl)sulphonyl]amino]phenyl]-5- benzofuranyl]methyl]-4-cyclopropyl-2-ethyl-1H-imidazole-5-carboxamide) was investigated at angiotensin AT1 receptors and AT2 receptors in vitro and on blood pressure in conscious rats. GR138950 suppressed and displaced angiotensin II (AII) concentration-effect curves in the rabbit isolated aorta (pKb approximately 9.0-9.7) but had no effect against phenylephrine or serotonin induced-contractions. GR138950 competed with [3H]-AII for angiotensin AT1 receptors in rat liver membranes (pKi = 9.09). GR138950 had no apparent affinity for angiotensin AT2 receptors (bovine cerebellum; pKi < 6.0). GR138950 (1 mg/kg i.a. and p.o.) inhibited pressor responses to AII, but not phenylephrine, in conscious normotensive rats. Parallel displacements in AII dose-response curves occurred without any reduction in the maximum response to AII. The antagonist activity of GR138950 lasted for up to 24 h. GR138950 (> 0.03 mg/kg i.a., > 0.3 mg/kg p.o.) significantly reduced diastolic blood pressure (DBP) in renal artery ligated hypertensive rats. DBP was reduced maximally, 5 to 7 h after administration and the antihypertensive effect of GR138950 lasted for up to 48 h. Daily administration (5 days) of GR138950 to renal artery ligated hypertensive rats produced a sustained reduction in DBP. Acute administration of GR138950 (1 mg/kg i.a.) also significantly reduced DBP in spontaneously hypertensive rats but not in normotensive rats. Heart rate was little changed in renal artery ligated hypertensive rats, normotensive rats and spontaneously hypertensive rats. These experiments demonstrate that GR138950 is a potent, selective and specific angiotensin AT1 receptor antagonist that is orally active and reduces DBP in conscious hypertensive rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic differentiation of Candida albicans strains by mixed-linker polymerase chain reaction

Restriction fragment length polymorphisms (RFLPs) of C. albicans were visualized using a mixed-linker polymerase chain reaction (PCR) and a C. albicans-specific primer (C. albicans 1059-bp species-specific repeat sequence). The method produced 10-14 bands of between 200 and 1400 bp on agarose gel electrophoresis and ethidium bromide staining. It gave comparable results to Southern blot hybridization with good reproducibility and the time required for the production of typing profiles was reduced to less than 2 days.

Lymphoproliferative disease of donor origin arising in patients after orthotopic liver transplantation

BACKGROUND

Lymphoproliferative disease is a well recognized complication of organ transplantation and in many cases is associated with Epstein-Barr virus (EBV) infection. It is widely though that posttransplantation lymphoproliferative disease (PTLPD) arises from recipient lymphoid cells. However, solid organ allografts are likely to include donor lymphoid tissue around or within the transplanted organ. Therefore, it is possible that transplanted donor lymphocytes may proliferate to form PTLPD:

METHODS

The genetic origin of tumor cells was determined by microsatellite DNA fingerprinting using the polymerase chain reaction (PCR). Their EBV association and clonality were established by PCR amplification of DNA extracted from formalin fixed, paraffin embedded tissue using primers to conserved regions of the EBV genome and the immunoglobulin heavy chain gene, respectively.

RESULTS

The authors have demonstrated two cases of lymphoproliferative disease that were derived from donor lymphocytes in orthotopic liver transplant recipients. In both cases, the proliferating cells were EBV DNA positive. Furthermore, the PTLPD was restricted to allograft tissue around the porta hepatis. However, the two cases differed in their clonal properties and response to treatment: one case was oligoclonal and regressed after antiviral therapy and a modest reduction of immunosuppression, whereas the other contained two clonal populations and was controlled only after treatment with antineoplastic chemotherapy.

CONCLUSION

This study has demonstrated two cases of PTLPD that were derived from donor lymphoid tissue. Although both cases were associated with EBV and remained localized to allograft tissue, their clonality and response to therapy differed.

The diagnostic use of the polymerase chain reaction for the detection of Mycobacterium tuberculosis

Detection of Mycobacterium tuberculosis by microscopy is difficult in specimens containing fewer than 10(4) bacteria/mL and growth in culture can take up to 6 wks. In this study the Polymerase Chain Reaction (PCR) was investigated as a rapid diagnostic technique for the detection of M. tuberculosis. The presence of DNA polymerase inhibitors in sputum specimens poses a potentially serious problem as false negative results can occur. In this study polymerase inhibitors were detected by inclusion of an internal plasmid control in each test. DNA from specimens in which the internal control failed to amplify was purified with a DNA binding matrix before retesting by PCR. A total of 169 sputum specimens were examined and 4 were found to have inhibitors. The correlation between detection of M. tuberculosis by PCR with a combination of culture, Ziehl-Neelsen (ZN) staining and patient history was 97.6%. This study confirms that PCR offers a more sensitive and rapid alternative for the detection of M. tuberculosis to ZN staining and culture, with results being available within 24 hrs of a specimen being received in the laboratory.

Bromobenzofuran-based non-peptide antagonists of angiotensin II: GR138950, a potent antihypertensive agent with high oral bioavailability

We have identified GR138950, a potent antagonist of the angiotensin II receptor with high oral bioavailability, as our second drug candidate to GR117289. Using GR117289, a compound with moderate bioavailability (20%) in man as a lead, we pursued a strategy aimed at enhancing bioavailability. The strategy was based on SAR established around the diacid GR117289, and from this, it was proposed that a monoacid, in particular a trifluoromethanesulfonamide, should be better absorbed after oral administration and have enhanced oral bioavailability. This led to the identification of GR138950, a potent antihypertensive agent in the renal hypertensive rat, causing sustained falls in blood pressure after oral administration. Oral bioavailability of GR138950 in rats and dogs is high, confirming that GR138950 is well absorbed after oral administration. Moreover, the low plasma clearance and long plasma half-life suggest that this compound will be suitable for once a day administration. Furthermore, the preliminary data indicate that the high bioavailability of GR138950 seen in rats and dogs translates to man. These results demonstrate clearly that GR138950 has the potential to be a clinically effective antihypertensive agent. Further studies are in progress to evaluate GR138950 in the treatment of hypertension.

Genotype and phenotype of oral Candida albicans from patients infected with the human immunodeficiency virus

Candida albicans has been shown to vary in its phenotypic expression with the progression of human immunodeficiency virus (HIV) infection. Isolates of C. albicans were obtained from 45 patients with HIV infection during the progression of their disease and differentiated using two methods. The first utilized the morphological characteristics of colonies, and the second method utilized a small portion of C. albicans DNA as a probe on Southern-transferred, EcoRI-digested C. albicans genomic DNA. In 67% of the patients a single strain of C. albicans, as determined by the DNA analysis, was isolated from each individual. The phenotypic expression of the genetically identical strains varied considerably over the experimental period with one morphotype being predominant. These results showed that the genotype of C. albicans persisted in the majority of HIV-infected individuals, but that the phenotypical expression of this strain changed. A novel finding in this study was that 18 strains of C. albicans had DNA which did not hybridize to the probe used.

Comparison of Pneumocystis carinii detection by toluidine blue O staining, direct immunofluorescence and DNA amplification in sputum specimens from HIV positive patients

Pneumocystis carinii pneumonia (PCP) is the commonest opportunistic infection in AIDS patients. By using the polymerase chain reaction (PCR), specific DNA sequences can be amplified and used in diagnosis of infections such as PCP where the causative pathogen is both difficult to grow and present in low numbers. Twenty HIV positive patients were investigated for PCP. Twenty sputa (15 induced and 5 expectorated) had toluidine blue O staining, direct immunofluorescence and PCR performed for Pneumocystis carinii in a blinded fashion. PCR was performed using primers pAZ102-E 5' GATGGCTGTTTCCAAGCCCA 3' and pAZ102-H 5' GTGTACGTTGCAAAGTACTC 3' from the gene coding for Pneumocystis carinii mitochondrial ribosomal RNA with a specific 346 base-pair sequence being amplified from positive specimens. Ten of the patients had Pneumocystis carinii shown by conventional tests and PCR. Another 3 patients were positive only by PCR, all had evidence of infection with Pneumocystis carinii; the first was positive by subsequent conventional stains, the second was treated for bacterial bronchitis but had a non-resolving chest infection with PCP found on postmortem after 4 mths, the third had a typical interstitial infiltrate on CXR and responded to empiric PCP treatment. PCR is more sensitive than toluidine blue O staining and direct immunofluorescence in detecting Pneumocystis carinii in sputum from HIV patients and may become the diagnostic method of choice for PCP.

Cardiovascular effects of GR117289, a novel angiotensin AT1 receptor antagonist

1. The effect of GR117289, an angiotensin AT1 receptor antagonist, on diastolic blood pressure (DBP) was determined in angiotensin-dependent and angiotensin-independent models of hypertension in rats. In addition, the antagonist profile of GR117289 at angiotensin AT1 receptors was determined in conscious renal hypertensive rats and conscious normotensive rats, dogs and marmosets. 2. Intra-arterial and oral administration of GR117289 (0.3-3 mg kg-1, i.a.; 1-10 mg kg-1, p.o.) to 6-day left renal artery ligated hypertensive (RALH) rats (DBP > 140 mmHg) produced significant, dose-related reductions in DBP with little apparent effect on heart rate (< 15%). The antihypertensive effect of GR117289 developed progressively over several hours and with some doses persisted for 24-48 h after administration. 3. Administration of GR117289 (1 mg kg-1, i.a.) on 5 consecutive days to RALH rats reduced DBP on each day. The antihypertensive effect of GR117289 was not cumulative as DBP had almost returned to base-line values, 24 h after administration of each dose. 4. A dose of GR117289 (3 mg kg-1, i.a.), which produced a substantial reduction in DBP (about 70 mmHg) in RALH rats, was administered to rats in which blood pressure was elevated either by unilateral renal artery clipping, sustained infusion of angiotensin II (AII), DOCA-salt administration or genetic inbreeding. GR117289 reduced DBP in rats in which the renin-angiotensin system was activated by renal artery clipping or AII infusion but had little effect in normotensive rats, DOCA-salt rats and SHR. 5. Systemic administration of All to RALH rats and to normotensive rats, dogs and marmosets elicited reproducible pressor responses in all species. Systemic or oral administration of GR1 17289 (3 mg kg-1)inhibited the pressor responses produced by All, resulting in parallel, rightward displacements of All dose-response curves.6. Maximal displacements of All dose-response curves occurred 1 h and 1-7 h after systemic and oral administration, respectively. GR1 17289 produced a 32-246 fold displacement after systemic administration and a 4-12 fold displacement after oral administration. The effect in dogs was short lasting after systemic administration but the effect of GRI17289 lasted for up to 24 h in rats and marmosets and for up to 24 h after oral administration in all species. The antagonist activity appeared specific for angiotensin receptors as GRi17289 did not inhibit pressor responses to phenylephrine or vasopressin.7. These experiments demonstrate that GRI 17289 reduces blood pressure in conscious hypertensive rats after both systemic and oral administration, and is an effective antagonist at angiotensin AT1 receptors in conscious rats, dogs and marmosets.

Inhibitors of cholesterol biosynthesis. 2. 3,5-Dihydroxy-7-(N-pyrrolyl)-6-heptenoates, a novel series of HMG-CoA reductase inhibitors

A series of 7-[2,3-diaryl-5-(1-methylethyl)-1H-pyrrol-1-yl]-3,5- dihydroxy-6-heptenoates was prepared and evaluated for its ability to inhibit the enzyme HMG-CoA reductase in vitro. Maintaining a 5-(1-methylethyl) substituent found to be optimal in related studies, structure-activity relationships were established for compounds modified at positions 2, 3, and 4 of the pyrrole ring. The 4-fluorophenyl group was preferred at the pyrrole 2-position, while incorporation of a range of substituted phenyl groups and pyridyl substituents at the 3-position provided compounds with equivalent enzyme inhibitory activities and widely different lipophilicities. Pentasubstituted pyrrole 3h was found to have a 10-fold greater potency than lovastatin.

Isolation of a DNA probe for identification of Mycobacterium kansasii, including the genetic subgroup

In order to develop a DNA-based assay to identify all Mycobacterium kansasii clinical isolates, a specific DNA probe was isolated in plasmid p6123. A total of 145 M. kansasii clinical isolates were collected from several countries and were examined with three probes by DNA hybridization. Of the 145 isolates, 115 (79%) were positive with the previously described probe pMK1-9 (Z. H. Huang, B. C. Ross, and B. Dwyer, J. Clin. Microbiol. 29:2125-2129, 1991), 129 (88%) were positive with the commercial Accu-probe assay (Gen-Probe), and 145 (100%) were positive with the p6123 probe. Southern blot analysis of EcoRI-digested M. kansasii chromosomal DNA with p6123 revealed that all Accu-probe-positive M. kansasii strains exhibited a 3-kb fragment, whereas all Accu-probe-negative M. kansasii strains displayed DNA fragments of variable molecular sizes. These results indicate that, unlike the previously described probes for M. kansasii, the fragment cloned into p6123 identified all 145 biochemically typical strains tested and provides an ideal target for future DNA-based speciation assays.

Use of a repetitive element isolated from Mycobacterium tuberculosis in hybridization studies with Mycobacterium bovis: a new tool for epidemiological studies of bovine tuberculosis

Typing of M. bovis isolates for epidemiological purposes is possible using restriction endonuclease analysis (REA). However, the DNA fragment patterns obtained are complex and difficult to analyse due to the large number of bands produced. In an attempt to develop a less complicated typing scheme two DNA probes were used in hybridization studies to detect restriction fragment length polymorphisms (RFLP) in M. bovis. An oligonucleotide probe which matches part of the insertion sequence IS6110 produced few bands and failed to discriminate between bovine isolates of M. bovis. A probe prepared from a highly repeated DNA sequence, cloned from M. tuberculosis when used on southern blots of AluI digested M. bovis DNA, resulted in a discriminating typing scheme which was easier to perform and analyse than the REA. The RFLP typing scheme identified 27 different strains from a total of 36 isolates of M. bovis and 7 reference strains from the M. tuberculosis complex. Using REA, 24 types were identified using BclI and PvuII digests and 23 different types using BstEII digests. When results of all 3 enzyme digests were combined, the REA identified 27 types from the same strains. Ten isolates of M. bovis from 5 properties involved in an outbreak of bovine tuberculosis were all identified as the same type with both techniques.

Identification of an insertion sequence-like element in a subspecies of Mycobacterium kansasii

Analysis of a genomic DNA clone library of a strain from the genetic subspecies of Mycobacterium kansasii determined the existence of a repetitive insertion sequence-like element. The element is 947 bp long and is present in a minimum of 1 to 11 copies per genome. Similar to insertion sequences, it contains a 3-bp (TAG) direct repeat at its extremities and a transcription promoter-like sequence. In addition, for one of the clones sequenced, a potential cointegrate formation, a characteristic frequently observed with insertion sequences, was revealed. This insertion sequence does not contain short inverted repeats near the ends or a large open reading frame to code for a transposase enzyme. Its host range is restricted to a previously described genetic subspecies of M. kansasii and is not present in typical M. kansasii or other mycobacterial species. When used as a probe for Southern blot hybridization, significant heterogeneity between different isolates of the M. kansasii subspecies was observed. This repeated element will be useful in further studies on the characterization, diagnosis, and epidemiology of M. kansasii.

Characterization of Mycobacterium tuberculosis strains from Vietnamese patients by Southern blot hybridization

A total of 41 Mycobacterium tuberculosis strains from patients of Vietnamese origin were analyzed by Southern blot hybridization with two different probes, IS6110 (Otal, I., et al., J. Clin. Microbiol. 29:1252-1254, 1991; Ross, B. C., et al., J. Clin. Microbiol. 30:942-946, 1992; Thierry, D., et al., J. Clin. Microbiol. 28:2668-2673, 1990; van Soolingen, D., et al., J. Clin. Microbiol. 29:2578-2586, 1991) and pTBN12 (Ross, B. C., et al., J. Clin. Microbiol. 30:942-946, 1992). The restriction fragment patterns of nine of these strains were virtually identical when the pTBN12 probe was used; five strains had a single copy of IS6110, and four strains failed to hybridize with the IS6110 probe. This relatively high frequency of strains with no or one copy of IS6110 suggests that the usefulness of IS6110 for epidemiological study may be limited in certain populations.

Emergence during unsuccessful chemotherapy of multiple drug resistance in a strain of Mycobacterium tuberculosis

Serial isolates of Mycobacterium tuberculosis were cultured from a patient who failed to respond to standard antituberculous chemotherapy. Isolates were cultured in March 1989, July 1989, December 1989 and May 1990. Each successive isolate was found to be resistant to a wider range of antituberculous drugs than its predecessors. The initial isolate was resistant to isoniazid and rifampin, the second isolate was also resistant to ethambutol, the third was also resistant to pyrazinamide, ansamycin (= rifabutin) and ofloxacin and the last isolate was also resistant to ciprofloxacin and sparfloxacin. All four isolates' bacteriophage typing profiles and DNA restriction fragment patterns determined by Southern blot hybridization using the IS6110/IS986 probes and the new probe pTBN12 were concordant. It was concluded that this patient was persistently infected with a single strain of Mycobacterium tuberculosis which developed resistance to a number of families of drugs but did not show any significant change in typing patterns. The problem of acquired multiple drug resistance, particularly to fluoroquinolones and rifamycins, represents a new challenge in tuberculosis therapy.

Rapid, simple method for typing isolates of Mycobacterium tuberculosis by using the polymerase chain reaction

To develop a molecular typing method for Mycobacterium tuberculosis based on the polymerase chain reaction, oligonucleotide primers were designed to the ends of the insertion sequence IS6110 in an attempt to amplify DNA between clusters of this element on the genome. Although in many strains the copy number of this element is low and is distributed throughout the genome, most strains examined produced a banding pattern which varied between isolates including strains with one copy of IS6110. With strains isolated from patients in epidemiologic clusters of tuberculosis, the banding patterns were similar within each cluster but distinct from those in strains from different clusters. Similarly, multiple isolates from the same patient yielded a consistent banding pattern. Sequencing of four polymerase chain reaction products revealed that amplification was occurring between copies of IS6110 in two of the products and from a single copy of IS6110 to a nonspecific priming site in the other two. This technique provides a rapid and simple means of typing M. tuberculosis isolates for epidemiologic studies.

Pharmacological profile of GR117289 in vitro: a novel, potent and specific non-peptide angiotensin AT1 receptor antagonist

1. This paper describes the effects of GR117289 (1-[[3-bromo-2-[2-(1H-tetrazol-5-yl)phenyl]-5-benzo-furanyl]methyl ]-2-butyl-4-chloro-1H-imidazole-5-carboxylic acid) at angiotensin receptors and binding sites in rabbit aorta, rat liver and bovine cerebellum preparations in vitro. 2. In rabbit isolated aortic strips, GR117289 (0.3, 1 and 3 nM) caused a concentration-related, insurmountable suppression of the concentration-response curve to angiotensin II (AII). When the contact time was increased, a greater degree of antagonism of AII was observed, suggesting that GR117289 is slow to reach equilibrium. A pKB of 9.8 +/- 0.1 was calculated for GR117289 after 3 h incubation. GR117289 (1 microM) did not affect contractile responses to phenylephrine or 5-hydroxytryptamine (5-HT) in the rabbit aorta. 3. GR117289 (1 nM) alone caused a marked suppression and a slight rightward displacement of the AII concentration-response curve. Co-incubation with the competitive, surmountable AT1 receptor antagonist, losartan (10 nM, 100 nM and 1 microM), resulted in a concentration-related upward and rightward displacement of the concentration-response curve to subsequently administered AII. In separate experiments in which preparations were pre-incubated with GR117289 (1 nM), subsequent addition of losartan (1 microM) for 2, 15 or 45 min caused a further, but similar, rightward displacement of the concentration-response curve to subsequently administered AII with a time-dependent increase in the maximum response.4. Suppression of All-induced contractile responses, caused by superfusion with GRI17289 (0.3, 1 or 3 nM) was not reversed by continuously washing the tissues for 3 h; in fact, the potency of GRI 17289 was slightly enhanced after this period.5. In rat liver membranes, GRI17289 was a potent competitor with [3H]-AII for AT, binding sites(pKi = 8.7 +/- 0.1) but in bovine cerebellum membranes, it was a very weak competitor for AT2 binding sites (pKi<6). Pre-incubation of rat liver membranes with GRI17289 had little effect on its affinity(pKi = 9.1 +/- 0.21), but increasing the concentration of bovine serum albumen in the assay buffer from 0.001% to 0.1% w/v decreased affinity (pKi= 7.5 +/- 0.1).6. In saturation binding experiments in rat liver membranes, GRI 17289 (12 nM) increased the Kd of[3H]-AII from 0.28 +/- 0.06 nM to 0.37 +/- 0.02 nM, and decreased Bm. from 10.0 +/- 0.1 to 5.6 +/-0.3 fmol mg' tissue. In other experiments, GR1 17289 (1 jIM) did not alter the rate of dissociation of[3H]-AII from AT1 binding sites, following addition of excess unlabelled All.7. In rabbit aorta vascular smooth muscle membranes, GR1 17289 competed with ['25I]-Sar'1le8 All for binding to AT, binding sites. In the presence of 0.1% w/v bovine serum albumen, a pIC50 of 7.6 +/- 0.1 was calculated. Under the same conditions, but with rat liver membranes, a pIC50 of 7.8 +/- 0.1 was determined.8. Taken together, these results show that GRI17289 is a potent, specific, selective and insurmountable antagonist at angiotensin AT, receptors. Its profile in the rabbit aorta is consistent with the proposalthat GRI17289 is a slowly reversible (pseudo-irreversible) antagonist at these receptors.

Characterization and comparison of Australian human spotted fever group rickettsiae

The microbiological and molecular characteristics of the rickettsiae isolated from humans with Queensland tick typhus (QTT) caused by Rickettsia australis and the recently described Flinders Island spotted fever (FISF) were compared. Clinically and serologically, the diseases are similar. Cell culture reveals differences in the plaque-forming abilities of the isolates. Characterization of the gene encoding the genus-specific 17-kDa antigen of R. australis revealed a unique nucleotide sequence unlike those of the FISF isolate and Rickettsia rickettsii. Southern blot analysis of rickettsial DNA from the isolates with a 17-kDa-antigen gene probe revealed the presence of this gene in all isolates but no difference in banding patterns. When a probe for the rRNA genes was used, clear differences in banding patterns of isolates from patients with QTT and FISF were revealed. Thus, the rickettsiae isolated from patients with FISF differ from those from patients with QTT and may represent a new rickettsial species.

Identification of a genetically distinct subspecies of Mycobacterium kansasii

To assess the usefulness of a specific DNA probe for Mycobacterium kansasii, 105 isolates from Australia, Belgium, Japan, South Africa, and Switzerland were collected and analyzed. Twenty of these isolates were probe negative, of which 18 were from Belgium and Switzerland. Analysis of all isolates by Southern blot hybridization indicated a lack of variability among probe-positive isolates, while probe-negative isolates were clearly distinct and showed greater diversity. Sequence analysis of the 250 nucleotides at the 5' end of the 16S rRNA gene revealed that 19 of the 20 probe-negative isolates had a sequence different from that of M. kansasii. A total of five nucleotide differences were present in a cluster consisting of two nucleotide deletions and three nucleotide substitutions. These results suggest the existence of a genetic subspecies of M. kansasii.

Isolation of a fastidious Mycobacterium species from two AIDS patients

Two strains of fastidious mycobacteria were isolated from two patients with AIDS and clinical disease suggestive of Mycobacterium avium complex infection. Acid-fast bacilli were isolated from blood and bone marrow of both patients in BACTEC 12B and/or 13A media. The acid-fast bacilli failed to grow on subculture to routine Löwenstein-Jensen medium containing pyruvate and egg yolk agar. After several attempts, the strain from one patient was finally cultured on Middlebrook 7H9 medium with agar, charcoal, and yeast extract 13 months after the initial specimens were received in the laboratory. The second patient's strain was cultured on the same medium 6 weeks postinoculation with fresh BACTEC fluid and 5 months after specimen collection. Routine biochemical and growth tests were performed on these isolates but failed to give definitive identifications. 16S rRNA gene sequencing suggested that the organisms share at least 98.9% homology with M. simiae. Even greater homology (99.86%) was found with the recently described species "M. genavense." Recognition of the fastidious nature of some mycobacteria that infect AIDS patients is important in the treatment of infections in these patients and in understanding the epidemiology of atypical mycobacterial infections. It is suggested that a liquid culture medium such as BACTEC be employed for primary isolation of mycobacteria from AIDS patients and that subculture to the charcoal medium described here be carried out for those organisms that fail to grow on subculture to routine media.

Conformationally constrained tachykinin analogues: potent and highly selective neurokinin NK-2 receptor agonists

The design and synthesis of potent and selective neurokinin NK-2 receptor agonists 12 (GR64349) and 31 are described, together with structure-activity relationships for related analogues. Compound 12 (EC50 = 3.7 nM at NK-2 receptors in the rat colon; selectivity > 1000- and > 300-fold with respect to NK-1 and NK-3 receptors, respectively) was derived by incorporation of a Gly-Leu gamma-lactam conformational constraint into the C-terminal region of the neurokinin A octapeptide analogue [Lys3]-NKA(3-10). Compound 31 (EC50 = 15 nM in rat colon) contains a novel fused-bicyclic constraint at the corresponding site in the substance P hexapeptide analogue [Ava6]-SP(6-11).

Highly potent and selective heptapeptide antagonists of the neurokinin NK-2 receptor

Incorporation of D-Pro9 into substance P related peptides is known to enhance neurokinin NK-2 receptor agonist potency and selectivity with respect to other neurokinin receptors. We now report that replacement of D-Trp9 by D-Pro9 in the nonselective neurokinin antagonist [Arg5,D-Trp7,9, Nle11]-SP(5-11) gave a partial agonist with NK-2 receptor selectivity. Further incorporation of Pro10 provided the weak but selective NK-2 antagonist Arg-Ala-D-Trp-Phe-D-Pro-Pro-Nle-NH2 (compound 4; NK-2 pKB = 5.9; NK-1 pKB = 4.7; NK-3 pKB less than 4.6). Addition of a suitable lipophilic N-terminal substituent (e.g. Boc, PhCO, cyclohexylcarbonyl) to this compound greatly enhanced NK-2 antagonist activity (compound 10, GR 83074; NK-2 pKB = 8.2), and combined with further optimization of the N-terminal amino acids, provided the extremely potent and selective NK-2 antagonist PhCO-Ala-Ala-D-Trp-Phe-D-Pro-Pro-Nle-NH2 (compound 34, GR 94800; NK-2 pKB = 9.6; NK-1 pKB = 6.4; NK-3 pKB = 6.0). Compounds of this class produced a potent inhibition of NK-2 agonist-induced bronchoconstriction in the anaesthetized guinea-pig.

Squalestatin 1, a potent inhibitor of squalene synthase, which lowers serum cholesterol in vivo

Squalestatin 1 is a member of a novel family of fermentation products isolated from a previously unknown Phoma species (Coelomycetes). Squalestatin 1 is a potent, selective inhibitor of squalene synthase, a key enzyme in cholesterol biosynthesis; in vitro, 50% inhibition of enzyme activity is observed at a concentration of 12 +/- 5 nM (range of 4-22 nM). Squalestatin 1 inhibits cholesterol biosynthesis from [14C]acetate by isolated rat hepatocytes (50% inhibition at 39 nM) and by rat liver in vivo. In marmosets, a species with a lipoprotein profile similar to that of man, squalestatin 1 lowers serum cholesterol by up to 75%. This compound will allow further investigation of the control of the sterol biosynthesis pathway and could also lead to the development of new therapies for elevated serum cholesterol.

Ribotyping of Helicobacter pylori from clinical specimens

Ribotyping is a method used to type strains of bacteria by analyzing the restriction enzyme digestion patterns of the rRNA genes. This method was applied to 126 strains of Helicobacter pylori from 100 unrelated symptomatic patients who had endoscopies done and to 15 strains from 15 infected subjects from seven families. Analysis of the rRNA gene patterns revealed 77 distinct ribotypes from the 100 patients. From 15 of these subjects, isolates were recovered from antral mucosal biopsies at follow-up endoscopy. All follow-up isolates from the same patient, with one exception, yielded identical digest patterns. This patient had strains with two distinct digest patterns obtained from a set of three isolates cultured from biopsy specimens taken at different times. Five patients who had isolates recovered from different sites in the stomach (antrum, gastric body, duodenum, and pyloric channel) showed ribotyping patterns which were identical for each patient yet distinct between patients. In seven family groups studied, identical digest patterns were detected in members of two families, with variability in strains detected among members of the remaining families. This study demonstrates that ribotyping provides a useful, reliable, reproducible, and highly discriminatory typing scheme for the study of H. pylori infection.