Structures of Tyr188Leu mutant and wild-type HIV-1 reverse transcriptase complexed with the non-nucleoside inhibitor HBY 097: inhibitor flexibility is a useful design feature for reducing drug resistance.

The second generation Hoechst-Bayer non-nucleoside inhibitor, HBY 097 (S-4-isopropoxycarbonyl-6-methoxy-3-(methylthiomethyl)-3, 4-dihydroqui noxalin-2(1H)-thione), is an extremely potent inhibitor of HIV-1 reverse transcriptase (RT) and of HIV-1 infection in cell culture. HBY 097 selects for unusual drug-resistance mutations in HIV-1 RT (e.g. Gly190Glu) when compared with other non-nucleoside RT inhibitors (NNRTIs), such as nevirapine, alpha-APA and TIBO. We have determined the structure of HBY 097 complexed with wild-type HIV-1 RT at 3.1 A resolution. The HIV-1 RT/HBY 097 structure reveals an overall inhibitor geometry and binding mode differing significantly from RT/NNRTI structures reported earlier, in that HBY 097 does not adopt the usual butterfly-like shape. We have determined the structure of the Tyr188Leu HIV-1 RT drug-resistant mutant in complex with HBY 097 at 3.3 A resolution. HBY 097 binds to the mutant RT in a manner similar to that seen in the wild-type RT/HBY 097 complex, although there are some repositioning and conformational alterations of the inhibitor. Conformational changes of the structural elements forming the inhibitor-binding pocket, including the orientation of some side-chains, are observed. Reduction in the size of the 188 side-chain and repositioning of the Phe227 side-chain increases the volume of the binding cavity in the Tyr188Leu HIV-1 RT/HBY 097 complex. Loss of important protein-inhibitor interactions may account for the reduced potency of HBY 097 against the Tyr188Leu HIV-1 RT mutant. The loss of binding energy may be partially offset by additional contacts resulting from conformational changes of the inhibitor and nearby amino acid residues. This would suggest that inhibitor flexibility can help to minimize drug resistance.

Fat emulsion particle size: influence on the clearance rate and the tissue lipolytic activity.

In lipid emulsions for parenteral use the mean particle diameter of the droplets in the 20% emulsions is larger than in the 10% emulsions. In long-chain triglyceride emulsions it is greater than in medium-chain triglyceride emulsions. As the particle diameter decreases, the total interfacial area increases, as does the lipoprotein lipase (LPL) and hepatic lipase (HL) activity. For a given quantity of triglycerides and phospholipids the lipolytic activity is proportional to the total interfacial area. A doubling of the phospholipid concentration is accompanied by a small reduction in the activity of both enzymes. In going from long-chain to medium-chain triglycerides, there is an acceleration in the clearance rate of infused lipid. For a similar emulsion, the clearance rate decreases as the particle size decreases. It seems plausible that the larger the mean droplet diameter, the greater the participation of the reticuloendothelial system in the clearance.

Retention of marked sensitivity to (S)-4-isopropoxycarbonyl-6-methoxy-3-(methylthiomethyl)-3,4-di hydroquin oxaline-2(1H)-thione (HBY 097) by an azidothymidine (AZT)-resistant human immunodeficiency virus type 1 (HIV-1) strain subcultured in the combined presence of quinoxaline HBY 097 and 2',3'-dideoxy-3'-thiacytidine (lamivudine).

An azidothymidine (AZT)-resistant virus strain (HIV-1/AZT) (containing the 67 Asp --> Asn, 70 Lys --> Arg, 215 Thr --> Phe and 219 Lys --> Gln mutations into its reverse transcriptase) was grown in the combined presence of 2',3'-dideoxy-3'-thiacytidine (3TC, lamivudine) and the nonnucleoside reverse transcriptase inhibitor (S)-4-isopropoxycarbonyl-6-methoxy-3-(methylthiomethyl)-3,4-dih ydroquinoxaine-2(1H)-thione (quinoxaline HBY 097). Replication of HIV-1/AZT was inhibited to a significantly greater extent by the combination of 3TC and quinoxaline HBY 097 than by either drug alone. Virus breakthrough was markedly delayed in the combined presence of 3TC and HBY 097 at drug concentrations as low as 0.05 microg/mL and 0.0025 microg/mL, respectively. The virus that was recovered after exposure to the compounds (3TC and HBY 097) individually had acquired, in the genetic AZT-resistance background of HIV-1/AZT, 103 Lys --> Glu and 106 Val --> Ala mutations. The 103 Lys --> Glu mutation had not been observed before. However, both virus mutants retained marked sensitivity to HBY 097. In all cases, the genotypic AZT-resistance mutations were maintained in the mutant virus RT genomes, and the viruses also remained phenotypically resistant to AZT. Given the exquisite potency of a concomitant combination of 3TC and HBY 097 in suppressing virus replication, this drug combination should be further pursued in clinical trials in HIV-1-infected individuals.

Physico-chemical characterization, preparation and performance of poly (methylidene malonate 2.1.2) nanoparticles.

The present investigation confirms that initially implemented procedure to produce poly(methylidene malonate 2.1.2) (PMM 2.1.2) nanoparticles (Lescure et al. Pharm Res 1994;11:1270-77) lead to products mostly containing plasticizing oligomers which strongly lowered glass-transition temperature (Tg), dramatically reduced nanoparticle consistency and rendered them too sensitive to solubilization when diluted in an aqueous medium. From MALDI-TOF spectroscopy analysis, performed on intact colloids, emerged some structural information about these oligomeric species which could result from an intramolecular cyclization mechanism occurring soon in the course of the polymerization process. Thus, with the objective of overcoming these drawbacks, this contribution deals with the variations of manufacturing specifications such as pH and magnetic stirring speed to try and modulate molecular weight (MW) of nanoparticle constituents and reduce oligomer concentration. Although the analyses performed on these new nanoparticles were rather encouraging, the colloid formation yield became so low that it required the development of other methodologies, excluding a previous emulsion step, and allowing a controlled production of PMM 2.1.2-made nanoparticles having better physico-chemical characteristics while keeping good pharmaceutical capabilities.

Proteolytic enzymes from recombinant Streptomyces lividans TK24.

Different proteases from the culture fluids of recombinant Streptomyces lividans strains were isolated. Several individual proteases were separated and characterized. A chymotrypsin-chylike activity (CLA) was identified that specifically degrades a fusion protein between the alpha-amylase inhibitor from S. tendae (Tendamistat, HOE467) and proinsulin from the monkey Macaca fascicularis. The effective chemical inhibition of the degrading enzyme is demonstrated.

MSCT guided sizing of the Edwards Sapien XT TAVI device: impact of different degrees of oversizing on clinical outcome.

AIMS: Prospective data on the usage of 3-dimensional imaging based annulus sizing on the outcome of TAVI is not available yet and there is general uncertainty about the optimal degree of oversizing. In the current study we therefore assessed a 3-D MSCT guided over-sizing approach and evaluated the clinical outcome of different degrees of oversizing. METHODS: TAVI-size-selection was done using systolic MSCT-annulus cross-sectional-area (CSA) measurements in 107 patients with severe aortic stenosis with the goal to oversize the 3rd generation balloon expandable Edwards Sapien XT (ESTV) device in relation to the native aortic annulus CSA. RESULTS: Among different degrees of oversizing there were no differences in the occurrence of stroke, myocardial infarction and death. No aortic injuries were observed. The overall rate of >mild postprocedural aortic regurgitation (PAR) was 7.6%. Increasing oversizing ratios are associated with lower rates of >mild PAR (r = -0.236, p<0.02) with the lowest rate of >mild PAR in patients with area based oversizing ratios >25% and the highest rate in patients with oversizing ratios <15% (0% vs. 15.8%, p<0.02). The rate of postprocedural permanent pacemakers tended to be lower in patients with <15% oversizing compared to those with >25% oversizing (5.3 vs. 16.7%, p<0.23). CONCLUSIONS: MSCT guided ESTV-device sizing is safe and is associated with significantly lower than previously reported rates for PAR. A device/annulus oversizing ratio of 15-25% based on area and 7-12% based on mean diameter appears to provide the best risk-benefit ratio in terms of PAR reduction and conduction disorders.

[Principles of the TCP-implantation system after 2 years of clinical experience]. / Prinzipien des TCP-Implantationssystems nach zweijähriger klinischer Erfahrung.

The TCP implantation system is based on absorbable tricalcium phosphate ceramics which is used in different ways as porcelain-fused-to-metal material. The strict and complex application of preimplantologic and peri-implantologic principles, particularly the cleansing and preparation of the implant bed and of the bone tissue, as well as newly developed, internally cooled cutting and self-cleaning instructions are of special importance. The shape of the implant and the operative technique also play an important role in achieving a successful oral implant. The nonmetalic surface of the TCP implant has proved to be an important advantage. Since these implants induce a fusion with the bone tissue which does not include connective tissue, the use of elastic coupling elements that functionally imitate the periodontal tissue have proved to be an important factor in the primary and long-term success of the implant. The gnathologic formation of the chewing surfaces is just as important as the need for proper information, training, and supervision of the dentists as well as control of implants.

Spontaneous deletions of the chromosome-mobilizing plasmid R68.45 in Pseudomonas aeruginosa PAO.

In Pseudomonas aeruginosa strain PAO the chromosome-mobilizing IncP-1 plasmid R68.45 was unstable whereas the parent plasmid R68 was stable. The instability of R68.45 was observed in rec+ and rec strains within about 100 generations after conjugal transfer of the plasmid and, to a lesser extent, in established R68.45 donor strains. Two phenotypically distinct classes of R68.45 derivatives were obtained: (i) CbR (carbenicillin-resistant), TcR (tetracycline-resistant), KmR (kanamycin-resistant), Tra+ (transfer proficient), Cma- (chromosome-mobilizing ability), lacking the duplicated IS21 copy typical of R68.45 and indistinguishable from R68 by restriction enzyme analysis; (ii) CbR TcR KmS Tra- Cma-, due to deletion of one IS21 copy, the adjacent KmR gene, and a variable part of the Tra-1 region including, in most cases, the origin of transfer (oriT). Both types of deletion derivatives were stable. R68.45 derivatives lacking the Tra-2 region were not recovered spontaneously, but could be constructed in vitro and were stable in strain PAO. Deletion formation of type ii as well as Cma did not depend on homologous recombination and can be ascribed to functions of the duplicated IS21. Chromosome mobilization does not appear to require obligatory transfer of the entire R68.45 plasmid. Four ClaI restriction sites were mapped on R68 extracted from P. aeruginosa. One of these sites was cryptic, presumably because of methylation, when the plasmid was prepared from Escherichia coli (dam+).

A new implant philosophy.

This form of tooth implant appears to exhibit great potential since it eliminates the disorganized connective tissue layer present at the implant/bone interface of most other devices. Also, as established for other implants, as long as a tight cuff of relatively immovable tissue exists around the polished cervical collar of an implant, an effective seal against the ingress of oral fluid and toxic irritants appears to be maintained, although the nature of this seal has yet to be determined. In addition, the epimobile superstructure serves to dissipate occlusal stress on the "ankylosed" implant. The prognosis of an implant is determined in part by its associated superstructure. There is a need for research into the loading that can be accommodated by an implant. Further study is required to ascertain the full potential of this implant system.

Heterologous expression of the alpha-amylase inhibitor gene cloned from an amplified genomic sequence of Streptomyces tendae.

The coding region for a secreted proteinaceous inhibitor of the human alpha-amylase (tendamistat; HOE 467) was identified by using a synthetic oligonucleotide probe. The gene is part of a 37-kilobase amplified genomic sequence found in an overproducing mutant of Streptomyces tendae. After subcloning, sequence analysis revealed an open reading frame of 312 base pairs preceded by a putative ribosome-binding site. The reading frame is 30 codons longer than necessary for the mature protein. This sequence coded for an amino-terminal extension of tendamistat and shows typical features of a signal peptide. After being cloned into Streptomyces vector plasmids and transformed to the heterologous host, Streptomyces lividans TK24, the gene was expressed, and the alpha-amylase inhibitor was correctly processed and secreted into the culture medium. The amount of secreted protein was dependent on the gene dosage and on the promoter arrangement.

Analysis of IS21-mediated mobilization of plasmid pACYC184 by R68.45 in Escherichia coli.

Escherichia coli plasmids like pACYC184 or pBR325 can be mobilized by the P-type plasmid R68.45, which carries a tandem duplication of insertion element IS21, at a frequency of 10(-3)-10(-5) per donor cell. Analysis of exconjugant cells revealed that plasmid mobilization occurs via cointegrate formation involving transposition of IS21. No resolution of cointegrates of pACYC184 and the P-type plasmid could be found in recA recipient cells. In the cointegrate, the E. coli plasmid is flanked by single copies of IS21 in direct orientation. After resolution of the cointegrate in recA+ recipients, the mobilizing plasmid R68.45 lost one copy of IS21 becoming indistinguishable from plasmid R68. It was shown that during mobilization, insertion element IS21 transposes to the mobilized plasmid. Insertion sites and orientations of IS21 in 33 pACYC184::IS21 insertion mutants have been determined: IS21 was found to be integrated in plasmid pACYC184 in different regions but only in one orientation. The IS21 tandem structure of plasmid R68.45 and its role in the mobilization process is discussed.

Relationship of group P1 plasmids revealed by heteroduplex experiments: RP1, RP4, R68 and RK2 are identical.

The molecular relationships of the IncP1 plasmids RP1, RP4, R68 and RK2 were tested by electron microscopic examination of heteroduplexes. In several hybridization experiments molecules were detected which had a 7.8% portion of incomplete reannealing. This 'heterologous region' could be explained by the typical renaturation behaviour of the transposon Tn1. The identity of the Tn1 transposon present in RP1 and RP4 was proved by heteroduplex experiments with lambda phage DNA containing this transposon. These results indicated that the plasmids RP1 and RP4 are identical. Additional heteroduplex experiments between plasmids R68.45 and RP8 and between R68.45 and RK2 were performed. R68.45, a derivative of R68, has a small DNA insertion and RP8 can be regarded as a large insertion mutant of RP4; both insertions were used as single-stranded hybridization markers. From the hybrid molecules formed, it was deduced that R68 and RK2 are identical with RP1 and RP4 as far as molecular structure is revealed by the technique used.

Disulphide bridge formation of proinsulin fusion proteins during secretion in Streptomyces.

To study disulphide bridge formation by Streptomyces lividans TK 24 in secreted single chain precursors of insulin a fusion protein (PTF 1) was investigated consisting of monkey proinsulin and the aminoterminal sequence Asp1 to Gly43 of the alpha-amylase inhibitor tendamistat from Streptomyces tendae. The purified soluble protein PTF 1 has a molecular mass of 14.4 kDa. The primary structure was elucidated after digestion with lysyl endopeptidase and fragment analysis. In this system, disulphide bond formation occurs in a way that the first cysteine in proinsulin is linked to the next following cysteine in the amino-acid chain resulting in a non-natural folding of the insulin part of the fusion protein. Re-folding of PTF 1 by reduction and re-oxidation followed by proteolytic digestions led to insulins which are identical to authentic material. The ease of correct disulphide bond formation in solution and incorrect processing during secretion suggests involvement of yet unknown factors leading to an unfavourable folding of proinsulin.

Essentiality of histidine in adult mice.

The difficulty in demonstrating a histidine deficiency in adult animals may be due in part to the histidine reserve in skeletal muscle in the form of carnosine. Mice are unusual among vertebrates in that their muscle is free of carnosine and its methylated analogue, anserine. When mice were fed a histidine-free diet, weight loss was noticeable within 3 d and continued over a period of 18 d. At this point the animals had lost 25-30% of their original weight. These results are compatible with the view that a dietary histidine deficiency can be offset by carnosine. Mice, whose muscle contains no carnosine, show early signs of a deficiency when deprived of histidine.

In vitro activity of RU 29246, the active compound of the cephalosporin prodrug ester HR 916.

The in vitro activity of RU 29246 was compared with those of other agents against 536 recent clinical isolates. The MICs of RU 29246 for 90% of members of the family Enterobacteriaceae tested (MIC90s) were less than 2 micrograms/ml except those for Morganella spp. (16 micrograms/ml) and Proteus spp. (8 micrograms/ml). RU 29246 was active against Staphylococcus aureus (MIC90, < or = 8 micrograms/ml) and against Staphylococcus saprophyticus and coagulase-negative staphylococci (MIC90s, < or = 2 micrograms/ml). Streptococci and Neisseria gonorrhoeae were highly susceptible to RU 29246, and the activity of the agent against isolates of Streptococcus pneumoniae (MIC90, < or = 0.5 micrograms/ml), Haemophilus influenzae (MIC90, < or = 2 micrograms/ml), and Moraxella catarrhalis (MIC90, < or = 2 micrograms/ml) was comparable to those of the other cephalosporins tested. RU 29246 was insusceptible to hydrolysis by the common plasmid-mediated beta-lactamases (TEM-1 and SHV-1). However, hydrolysis by the new extended-spectrum beta-lactamases (TEM-3, TEM-5, and TEM-9) was detected. Results of the study suggested that RU 29246 should be investigated clinically for use in the treatment of a wide range of infections.

Laser versus laser plus afterloading with iridium-192 in the palliative treatment of malignant stenosis of the esophagus: a prospective, randomized, and controlled study.

Thirty-nine patients with malignant stenoses of the esophagus (22 adenocarcinomas, 17 squamous cell carcinomas) were treated either with Nd:YAG laser recanalization alone (N = 20) or with laser recanalization and subsequent endoluminal afterloading irradiation with iridium-192 at a dose of 3 x 7 Gy (6 x 7 Gy). Squamous cell carcinoma patients in the afterloading group showed a prolonged dysphagia-free first interval (65 vs. 30 days, p less than 0.03), while patients with an adenocarcinoma did not share this benefit, and had a need for more frequent endoscopic procedures (p less than 0.05). The complication of esophagitis was only seen following afterloading treatment (21%, N = 4). Re-stenosis occurred in all patients. Neither the duration of relative dysphagia nor survival time was prolonged after endoluminal irradiation in adenocarcinoma or squamous cell carcinoma patients. After prior laser recanalization, palliative afterloading treatment with iridium-192 would seem helpful only in cases of squamous cell carcinoma with a high performance status with the aim of prolonging the first dysphagia-free interval.

[Severe pancytopenia in old age after 12-month ACE inhibitor therapy]. / Schwere Panzytopenie im hohen Lebensalter nach zwölfmonatiger ACE-Hemmer-Therapie.

A sprightly 79-year-old woman was treated for high blood pressure with indapamide (2.5 mg/day) and the angiotensin converting enzyme (ACE) inhibitor lisinopril (5 mg/day). About 12 months after starting treatment a blood count carried out because of a syncopal attack revealed pancytopenia (haemoglobin 3.3 g/dl, erythrocytes 1.0 x 10(6)/microliters, leucocytes 1100/microliters, platelets 8000/microliters). Until then the blood count had been unremarkable. The bone marrow showed severe hypoplasia of all three cell lines with reactive plasmocytosis. Malignant cells were not present. The patient received a total of nine units of erythrocytes and seven units of platelets. Her care included reverse barrier nursing and antibiotic treatment. She was also given high dose steroid therapy (methylprednisone up to 150 mg/day) and granulocyte colony stimulating factor (filgrastim 300 micrograms/day subcutaneously for 25 days), and after a latent period of several weeks juvenile myeloid precursors reappeared in the blood. Before discharge from hospital the results rose to subnormal levels without further transfusions (haemoglobin 8.5/dl, erythrocytes 3.1 x 10(6)/microliters, leucocytes 3900/microliters, platelets 21.000/microliters). In the bone marrow, all three cell lines were beginning to recover. The final diagnosis was incompletely reversible pancytopenia resulting from secondary aplastic anaemia during ACE inhibitor therapy.