Stiff, and sticky in the right places: the dramatic influence of preorganizing guest binding sites on the hydrogen bond-directed assembly of rotaxanes.

Structural rigidity and the preorganization of thread binding sites are shown to have a major influence on template efficiency in the synthesis of hydrogen bond-assembled rotaxanes. Preorganization is so effective, in fact, that with good hydrogen bond acceptors (amides) a "world record" yield of 97% for a [2]rotaxane is obtained. The truly remarkable feature of this efficient template, however, is that it allows even poor hydrogen bond acceptors (esters) to be used to prepare hydrogen bond-assembled rotaxanes, despite the presence of competing hydrogen bonding groups (anions) which bind the key intermediates at least 10000x more strongly than single, unorganized, ester groups! The structures of the rotaxanes are established unambiguously in solution by (1)H NMR spectroscopy and in the solid state by X-ray crystallography. As a series they provide unique experimental information regarding the nature of amide-ester hydrogen bonding interactions; in particular they suggest that in CDCl(3), amide-ester NH...O=C hydrogen bonds are approximately 1 kcal mol(-)(1) weaker than the corresponding amide-amide interactions.

A quantum-mechanical description of macrocyclic ring rotation in benzylic amide.

Catenanes can undergo rotation of one ring through the cavity of the other. Since macroscopic and molecular properties must clearly vary with the relative positions and orientations of the interlocked components, a complete understanding of the way that the rings rotate is of considerable importance. Here we show that low-dimensional quantum-mechanical modeling can yield rate constants and barriers similar to those obtained by temperature-dependent nuclear magnetic resonance experiments. Data from both non-hydrogen bond disrupting (e.g. CDCl3) and hydrogen bond disrupting (e.g. [D6]DMSO) solvents are well reproduced demonstrating the validity of the model. The successful simulation of the rates of circumrotations by entirely harmonic transition state theory originates from the description of the anharmonic levels of the systems through an effective harmonic frequency, not very different from twice the zero point energy. The nature of the model makes it extendable, in principle, to the calculation of properties dependent upon circumrotational activity.

Photoinduction of fast, reversible translational motion in a hydrogen-bonded molecular shuttle.

A rotaxane is described in which a macrocycle moves reversibly between two hydrogen-bonding stations after a nanosecond laser pulse. Observation of transient changes in the optical absorption spectrum after photoexcitation allows direct quantitative monitoring of the submolecular translational process. The rate of shuttling was determined and the influence of the surrounding medium was studied: At room temperature in acetonitrile, the photoinduced movement of the macrocycle to the second station takes about 1 microsecond and, after charge recombination (about 100 microseconds), the macrocycle shuttles back to its original position. The process is reversible and cyclable and has properties characteristic of an energy-driven piston.

Allelic losses in carcinoma in situ and testicular germ cell tumours of adolescents and adults: evidence suggestive of the linear progression model.

Testicular germ cell tumours (TGCTs) may arise through a process of multi-step carcinogenesis, and loss of heterozygosity (LOH) at specific loci is likely to be an important early event, although this has not been studied in detail. In order to explore the pathogenetic relationships among TGCTs, we investigated the genetic changes in testicular tumours that exhibit a disease continuum through the precursor carcinoma in situ (CIS) to either seminoma (SE) and/or non-seminomatous germ cell tumour (NSGCT). Universal amplification has been performed on 87 TGCT specimens and 36 samples of CIS cells microdissected from single paraffin-embedded tumour sections from 40 patients, including multiple specimens of CIS and TGCT cells of varied histology microdissected from 24 individual patients. Seventy-seven microsatellite markers were used to assay these samples for LOH at candidate regions selected from the literature, mapping to 3q, 5q, 9p, 11p, 11q, 12q, 17p and 18q. Construction of deletion maps for each of these regions identified common sites of deletion at 3q27-q28, 5q31, 5q34-q35, 9p22-p21 and 12q22, which correlate with allelic losses we have also observed in the precursor CIS cells. Evidence for allelic loss at 3q27-q28 was observed in all of the embryonal carcinoma samples analysed. We conclude that inactivation of gene(s) within these regions are likely to be early events in the development and progression of TGCTs. These results also provide molecular evidence in support of the hypothesis that SE is an intermediate stage of development within a single neoplastic pathway of progression from CIS precursor cells to NSGCT.

Genetic diversity at the FMR1 locus in the Indonesian population.

We report an analysis of allelic diversity at short tandem repeat polymorphisms within the fragile XA locus in 1069 male volunteers from twelve Indonesian sub-populations. An odd numbered allele of DXS548 was found at high frequency in all Indonesian populations. Greater allelic diversity was identified at the loci under study than has been previously reported for an Asian population. These differences distinguish the Indonesian population from all previously reported Asian, European and African populations. A high frequency of small premutation alleles, 4/120 (3.3%, 95% CI 0.9-8.3%), was identified in the Moluccan population of Hiri Island.

Microsatellite genome screening: rapid non-denaturing, non-isotopic dinucleotide repeat analysis.

The study of reverse genetics has made it possible for scientists to isolate and identify the genes responsible for such human diseases as cystic fibrosis and Duchenne- and Becker-type muscular dystrophy. The expensive and time-consuming process of detecting restriction fragment length polymorphisms by Southern blotting was the only method available to localize these genes. With the discovery of polymorphic microsatellite sequences in the human genome, the speed and ease of which a genome screening can be performed has increased dramatically. This paper reports on advanced methods for detection of microsatellite-repeated sequences making the task of mapping human genes simpler, safer and more economical.

Carrier detection in X-linked retinitis pigmentosa.

X-linked retinitis pigmentosa (XLRP) is manifested in affected males in their first decade and results in blindness by the third or fourth decade. Carrier detection is difficult since most carrier females show no or only equivocal signs well into or beyond their reproductive years. The genes, or the mutations causing RP have not been identified but at least two have been localised to the short arm of the X chromosome provisionally named RP2 and RP3. Identifying inheritance of one or other of these genes must be done by linkage in families using close, informative DNA markers. Here we report the localisation of a highly informative polymerase chain reaction (PCR) detectable microsatellite marker DXS538 using a previously studied family with X-linked RP3 in which recombination had occurred in the region of importance. The DXS538 dinucleotide repeat locus was previously localised to Xp21.1-p11.21 to study RP3 in one XLRP family. Using published RFLP data we narrowed the localisation of DXS538 to the region Xp21.1-p11.23. Thus DXS538 is now a convenient diagnostic tool, aiding carrier detection of XLRP in females, as shown in the family presented here.

Prostatitis--an increasing clinical problem for diagnosis and management.

Prostatitis remains a challenging condition. The clinical features are often nonspecific while the aetiology and pathogenesis can be diverse and includes inflammatory, obstructive, and/or chemical causes and may also be related to calculi. Four categories are recognized: acute bacterial prostatitis, chronic bacterial prostatitis, non-bacterial prostatitis and prostatodynia. The diagnosis of prostatitis was advanced substantially by the introduction of sequential sampling of urine aliquots following prostatic massage. Bacterial prostatitis is largely associated with the Enterobacteriaceae although Pseudomonas spp., enterococci and Staphylococcus aureus may also be isolated. In chronic bacterial prostatitis a variety of streptococci and anaerobic bacteria may be isolated. Treatment is difficult largely owing to the limited range of agents able to achieve therapeutic concentrations within prostatic fluid, which has a pH lower than that of plasma. Trimethroprim, co-trimoxazole and the tetracyclines have been widely used. The quinolones have recently been shown to diffuse readily into the prostate; ofloxacin and temafloxacin have produced the highest concentrations in prostatic fluid. Antibiotic treatment requires prolonged high dosage and careful monitoring to ensure that bacterial eradication has occurred. Other forms of management have included the judicious use of anti-inflammatory agents and analgesics. In some patients zinc sulphate has proved to be of symptomatic benefit.

Treatment of familial staphylococcal infection--comparison of mupirocin nasal ointment and chlorhexidine/neomycin (Naseptin) cream in eradication of nasal carriage.

Twenty-six families with recurrent staphylococcal infections were treated with either mupirocin nasal ointment (group M) or chlorhexidine neomycin (Naseptin) cream (group N) to the anterior nares, each combined with chlorhexidine soap for washing and chlorhexidine powder applied to other possible carriage sites. Patients receiving mupirocin following failure with chlorhexidine/neomycin (group M/N) were also treated. Treatment was given for seven days to 99 patients, 32 index (infected) patients and 67 family members. Follow-up swabs were collected by a study nurse 8, 14, 28, and 91 days after starting treatment. The carriage of Staphylococcus aureus in the anterior nares was 67%, in the axillae 22%, in the groin 23%, and perianal 19%. The carriage rates in the index patients was higher than family members, in all sites. The eradication of S. aureus from the nasal carriage site after therapy at 8 days was 95% in group M, 85% in group M/N and 61% in group N. Recolonization during the follow-up period was much less in those treated with mupirocin: 57% of patients in group M and 42% in group M/N were not carriers at 91 days, whereas 89% of patients group N were again colonized. Assessment clinically and in terms of prevention of further infective lesions showed that there was a higher response to mupirocin than to chlorhexidine/neomycin. Mupirocin nasal is a successful therapy for removing nasal carriage of S. aureus and has a prolonged effect on recolonization.

The rapid analysis of dystrophin gene deletions shows variable electrophoretic mobility.

The introduction of PCR technology to the molecular diagnosis of genetic diseases has increased the speed and range of DNA tests available. Previous analyses of dystrophin gene mutations were time consuming, taking weeks to complete, and used radioisotopic methods. Further developments in DNA amplification and post-amplification techniques have made conventional tube PCR redundant. The rapid methodologies described enable the efficient screening of large populations for genetic disorders, although precautions must be taken when analysing the PCR products.

An 11-month incidence study of infections in wards of a district general hospital.

Between March 1988 and January 1989, an incidence study of infections in patients occupying 122 beds in a district general hospital was undertaken. Nursing notes, medical notes, temperature charts, drug prescription charts and laboratory information were reviewed three times a week to determine if patients had infection which met strict case definitions. In addition, the surveyor consulted with ward nursing and medical staff for clarification of symptoms and signs indicative of infection. During the study, 668 infections were identified amongst 3326 patients. Three hundred and thirty-eight (51%) were community-acquired infections (CAI) and 330 hospital-acquired infections (HAI). Excluding 24 HAI acquired in other hospitals, the incidence rates were 9.2 HAI per 100 discharges, and 1.1 HAI per 100 patient days. The common types of CAI were pneumonia, abdominal infection and urinary tract infection. The main types of HAI were urinary tract infection, surgical wound infection and pneumonia. The microorganisms most frequently associated with CAI and HAI were Gram-negative bacilli.

An investigation into Clostridium perfringens enterotoxin-associated diarrhoea.

An investigation was carried out to establish the incidence of diarrhoea associated with the presence of enterotoxigenic Clostridium perfringens. The results indicate a high risk group, namely elderly hospitalized patients, who should be investigated for this organism in a similar way to Clostridium difficile if symptoms occur. The significance of antibiotic association is suggested and cross-infection was shown to be a possibility. Detection of the enterotoxin was accompanied in all cases by the presence of high faecal counts of enterotoxigenic strains of C. perfringens.

Antibacterial activity of lomefloxacin.

Lomefloxacin has marked activity against Gram-negative bacilli including Enterobacteriaceae, non-fermenting strains and Haemophilus influenzae with 98% of all isolates tested having MICs of 0.25 mg/l or less. Sixty-eight per cent of Pseudomonas aeruginosa strains were sensitive to 1 mg/l with a few strains resistant to 8 or 16 mg/l. Gram-positive cocci were more resistant, particularly streptococci, where the MICs vary between 1 and 8 mg/l. Bactericidal activity was similar to inhibitory activity and the effect of increasing serum concentrations and bacterial inocula was minimal. The MIC and MBC were increased in the presence of urine, particularly at an acid pH 5. Comparative MICs showed that lomefloxacin was more active than ofloxacin and pefloxacin, similar to norfloxacin but less active than ciprofloxacin for Gram-negative bacteria but not for Gram-positive cocci. Comparative studies with sensitivity disc concentrations showed that a 5 micrograms disc was more satisfactory than the 10 micrograms disc as the zone sizes were more suitable for routine testing. Solutions of lomefloxacin showed instability in bright sunlight when 52% of activity was lost in 1 h. Similar instability was shown in impregnated discs which lost up to 40% activity in 6 h exposure. Lomefloxacin showed a wide range of activity against Gram-negative bacteria including multiresistant strains and Pseudomonas spp. Gram-positive bacteria were less susceptible, with streptococci more resistant than staphylococci. Lomefloxacin is well absorbed after oral administration giving high blood and urine concentrations and its prolonged half-life means once daily dosing in the treatment of many types of bacterial infection may be possible.