Denaturing HPLC for high-throughput screening of rifampicin-resistant Mycobacterium tuberculosis isolates

OBJECTIVE

To evaluate the use of denaturation high-performance liquid chromatography (dHPLC) as a rapid method to detect rifampicin (RMP) resistance based on mutations in the rpoB gene in a high-volume laboratory setting.

METHODS

A total of 132 RMP-resistant Mycobacterium tuberculosis strains with different rpoB mutation were used to optimise the running condition of dHPLC as a pilot study. A blind correlation study was subsequently done between dHPLC and in vitro RMP susceptibility tests on 3167 M. tuberculosis strains in a high-throughput clinical setting.

RESULTS

In the pilot study, rpoB mutation could be detected on 116/132 (87.9%) RMP-resistant strains by dHPLC. In the second phase of the study, 84/3107 (2.7%) clinical M. tuberculosis isolates were RMP-resistant. The sensitivity and specificity of dHPLC in the prediction of RMP resistance were 70/84 (83.3%) and 70/77 (91.0%), respectively. The specificity became 100% when 511 Leu to Pro mutation was excluded from the RMP resistance-related genetic changes.

CONCLUSION

In the detection of RMP resistance in a high-throughput laboratory setting, dHPLC has been demonstrated to be rapid, simple, workable, automatable and inexpensive in terms of running costs and the labour involved.

A next generation, pilot-scale continuous sterilization system for fermentation media

A new continuous sterilization system was designed, constructed, started up, and qualified for media sterilization for secondary metabolite cultivations, bioconversions, and enzyme production. An existing Honeywell Total Distributed Control 3000-based control system was extended using redundant High performance Process Manager controllers for 98 I/O (input/output) points. This new equipment was retrofitted into an industrial research fermentation pilot plant, designed and constructed in the early 1980s. Design strategies of this new continuous sterilizer system and the expanded control system are described and compared with the literature (including dairy and bio-waste inactivation applications) and the weaknesses of the prior installation for expected effectiveness. In addition, the reasoning behind selection of some of these improved features has been incorporated. Examples of enhancements adopted include sanitary heat exchanger (HEX) design, incorporation of a "flash" cooling HEX, on-line calculation of F(o) and R(o), and use of field I/O modules located near the vessel to permit low-cost addition of new instrumentation. Sterilizer performance also was characterized over the expected range of operating conditions. Differences between design and observed temperature, pressure, and other profiles were quantified and investigated.

Comparison of Luneau SA disposable and Goldmann applanation tonometer readings

PURPOSE

To test the agreement of intraocular pressure (IOP) measurements made with Luneau SA applanators and Goldmann applanator.

MATERIALS AND METHODS

A single-blind crossover trial. IOPs were measured in both eyes of subjects with both applanators. Type of applanator was alternated to eliminate systematic bias. Multiple observers were used. Observers were blind to the scale while performing measurements but not to the type of applanator used. The appearance of the meniscus was assessed semiquantitatively. All measurements were combined and presented in a Bland-Altman plot.

RESULTS

A total of 140 eyes of 79 subjects were tested by seven observers. The range of measurements was 6-45 mmHg (mean 17.8 mmHg) for the Goldmann applanator. On average, the Luneau SA applanator (range of measurements 4-36 mmHg) gave a measurement of 2.35 mmHg less than the Goldmann standard. The standard deviation of these differences was 2.13 mmHg, giving an upper 95% confidence limit of 6.53 mmHg and a lower 95% confidence limit of -1.83 mmHg. The measurements agreed in only 24 out of 140 instances. In 28 eyes, the disposable tonometer end point was difficult to assess owing to excessively thick rings. Linear extrapolation suggests an increase in difference with increasing IOP.

CONCLUSION

The inter-head inaccuracy, tendency to underestimate IOP, and lack of systematic inaccuracy make a corrective algorithm impossible to formulate. The range of variation between the Luneau SA disposable applanator and the Goldmann standard is sufficiently large to influence clinical management decisions. We speculate that one explanation is the interaction of the tonometer with the tear film, making end point determination difficult. Further research is being undertaken.

Secondary paracentral retinal holes following internal limiting membrane removal

AIM

To report on a new postoperative finding after delamination of the internal limiting membrane (ILM) for the treatment of different macular pathologies.

METHODS

Seven patients are described with paracentral retinal holes, all located temporally to the macula, which developed after pars plana vitrectomy and uncomplicated ILM removal for cystoid macular oedema (n = 3), macular pucker (n = 3), and macular hole (n = 1) with the use of indocyanine green (n = 4), trypan blue (n = 1), triamcinolone acetonide (n = 1), or without dye (n = 1).

CONCLUSION

The use of dyes has been incriminated in causing iatrogenic damage to the retina. In this series, the new observation of retinal holes in the macular area is thought to be related to the removal of the ILM itself. The authors speculate that ILM delamination may cause a retinal weakening by Müller cell damage; this may be followed by a structural breakdown and, consequently, hole formation.

Do antiviral CD8+ T cells select hepatitis C virus escape mutants? Analysis in diverse epitopes targeted by human intrahepatic CD8+ T lymphocytes

Hepatitis C virus (HCV) is a variable RNA virus that can readily establish persistent infection. Cellular immune responses are important in the early control of the virus. Evidence from animal models suggests that mutation in epitopes recognized by CD8+ T lymphocytes may play an important role in the establishment of persistence but in human persistent infection, equivalent evidence is lacking. We investigated this by analysing a unique resource: viruses from a set of chronically HCV-infected individuals in whom the CD8+ T-cell responses in liver had previously been accurately mapped. Virus was sequenced in seven individuals at 10 epitopes restricted by 10 human leucocyte antigen (HLA) molecules. Two main patterns emerged: in the majority of epitopes sequenced, no variation was seen. In three epitopes, mutations were identified which were compatible with immune escape as assessed using phylogenetic and/or functional studies. These data suggest that - even where specific intrahepatic T cells are detectable - many epitopes do not undergo mutation in chronic human infection. On the contrary, virus may escape from intrahepatic CD8+ T-cell responses in a 'patchy' manner in certain specific epitopes. Furthermore, longitudinal studies to identify the differences between 'selecting' and 'nonselecting' intrahepatic CD8+ T-cell responses are needed in HCV infection.

Visual loss following removal of intraocular silicone oil

AIM

To investigate the cause of visual loss following removal of intraocular silicone oil in patients who underwent vitrectomies for retinal detachment or giant retinal tear.

METHODS

The clinical records of three cases with visual loss following removal of silicone oil were reviewed. Investigations carried out included fundus fluorescein angiogram, optical coherence tomography, and electrophysiological studies.

RESULTS

Visual acuities dropped from 6/9 to 6/36 in two cases and 6/24 to 3/24 in the third. None of the three cases had macula detachment at any stage. Fundus fluorescein angiogram and optical coherence tomography were normal in all cases. Pattern electroretinogram showed reduced amplitudes of the P50 and N95 components. Multifocal electroretinogram indicated a selective damage to the central part of the macula.

CONCLUSIONS

The results suggest that the abnormality arises predominantly in the central part of the macula, especially the outer and middle layers. However, the exact mechanism still remains obscure.

A pilot study on the use of a perfluorohexyloctane/silicone oil solution as a heavier than water internal tamponade agent

AIMS

To report a prospective two centred non-comparative interventional pilot study of a solution of perfluorohexyloctane and silicone oil (Densiron-68) as a heavier than water internal tamponade.

METHODS

42 consecutive patients were recruited. The indications include proliferative vitreoretinopathy, retinal detachments arising from inferior retinal breaks, and inability to posture.

RESULTS

The success rate with one operation using Densiron was 81% and with further surgery 93%. At the end of the study all tamponade agents were removed in 90% of patients. Visual acuity improved from mean logMAR of 1.41 (SD 0.64) to 0.94 (SD 0.57), p = 0.001. There was little evidence of dispersion and excessive inflammation.

CONCLUSION

This new tamponade agent is being compared to conventional silicone oil in a prospective international randomised trial.

Variable assortative mating in replicate mating trials using Drosophila melanogaster populations derived from contrasting opposing slopes of 'Evolution Canyon', Israel

Significant assortative mating in laboratory studies has been previously shown between two populations of Drosophila melanogaster collected from micro-climactically contrasting and opposing slopes of 'Evolution Canyon' (Lower Nahal Oren, Israel; Korol et al., 2000). Coupled with evidence that the two populations are adapted to their respective environments, this has been suggested as a rare example of ongoing behaviourally mediated speciation occurring in the face of gene flow. Reproductive isolation between these populations, however, has never been confirmed by replicate experiments in an independent laboratory. For this reason, we tested recent collections of these populations for premating isolation in both the original (Haifa) and a new (Burnaby) laboratory under a variety of experimental protocols. Although non-random mating was found in the majority of trials conducted in Haifa, we were unable to replicate these strong results in Burnaby. Most notably, we failed to detect assortative mating in four separate double choice experiments. Significant non-random mating was detected, however, in three of six single choice experiments in Burnaby, suggesting that the populations are behaviourally differentiated in some manner. Why nonrandom mating was weaker in Burnaby than Haifa is not understood, but suggests that assortative mating may be sensitive to unknown environmental factors.

Optical coherence tomography in photodynamic therapy for subfoveal choroidal neovascularisation secondary to age related macular degeneration: a cross sectional study

AIMS

To introduce new terminology and validate its reliability for the analysis of optical coherence tomography (OCT) scans, compare clinical detection of cystoid macular oedema (CMO) and subretinal fluid (SRF) with OCT findings, and to study the effect of photodynamic therapy (PDT) on the foveal morphology.

METHODS

Patients with subfoveal, predominantly classic choroidal neovascularisation (CNV) secondary to age related macular degeneration (AMD) undergoing PDT were evaluated with refraction protocol best corrected logMAR visual acuity (VA), slit lamp biomicroscopy, stereoscopic fluorescein angiography (FFA), and OCT. New terminologies introduced to interpret the OCT scans were: neuroretinal foveal thickness (NFT), bilaminar foveal thickness (BFT), outer high reflectivity band thickness (OHRBT), intraretinal fluid (IRF), subretinal fluid (oSRF), and vitreomacular hyaloid attachment (VMHA).

RESULTS

Fifty six eyes of 53 patients were studied. VA was better in eyes with a thinner outer high reflectivity band (OHRBT) (p = 0.02) and BFT (p = 0.05). BFT was less in eyes that had undergone a greater number of PDT treatments (p = 0.04). There was poor agreement between OCT and clinical examination in the detection of CMO and subretinal fluid (kappa = 0.289 and kappa = 0.165 respectively). To validate the interpretation and measurements on OCT, two groups of 20 scans were analysed by two independent observers. There was good agreement between the observers in the detection of IRF, oSRF, and VMHA (p<0.001). Measurements of NFT and BFT had a high reproducibility, and of OHRBT reproducibility was low.

CONCLUSIONS

New terminology has been introduced and tested. OCT appears to be superior to clinical examination and FFA in the detection of CMO. In this study, better vision was associated with a thinner OHRBT and/or the absence of SRF giving insight into the biological effect of PDT.

Acute and reversible micrographia in a patient possibly due to cerebral ischaemia

We report a patient who developed acute and reversible micrographia, presumably due to cerebral ischaemia, on a background of mutism following a pharyngo-laryngectomy 10 years earlier. Magnetic resonance (MR) imaging showed chronic small vessel disease without evidence of an acute ischaemic lesion on diffusion-weighted sequences. Our patient's micrographia improved significantly within 12 days of symptom onset. The MR imaging was performed within 5 days of symptom onset, suggesting that the lesion was either too small for detection or had resolved on diffusion-weighted sequences.

Study of a chemically amplified resist for X-ray lithography by Fourier transform infrared spectroscopy

Future applications of microelectromechanical systems (MEMS) require lithographic performance of very high aspect ratio. Chemically amplified resists (CARs) such as the negative tone commercial SU-8 provide critical advantages in sensitivity, resolution, and process efficiency in deep ultraviolet, electron-beam, and X-ray lithographies (XRLs), which result in a very high aspect ratio. In this investigation, an SU-8 resist was characterized and optimized for X-ray lithographic applications by studying the cross-linking process of the resist under different conditions of resist thickness and X-ray exposure dose. The exposure dose of soft X-ray (SXR) irradiation at the average weighted wavelength of 1.20 nm from a plasma focus device ranges from 100 to 1600 mJ/cm(2) on the resist surface. Resist thickness varies from 3.5 to 15 mum. The cross-linking process of the resist during post-exposure bake (PEB) was accurately monitored using Fourier transform infrared (FT-IR) spectroscopy. The infrared absorption peaks at 862, 914, 972, and 1128 cm(-1) in the spectrum of the SU-8 resist were found to be useful indicators for the completion of cross-linking in the resist. Results of the experiments showed that the cross-linking of SU-8 was optimized at the exposure dose of 800 mJ/cm(2) for resist thicknesses of 3.5, 9.5, and 15 microm. PEB temperature was set at 95 degrees C and time at 3 min. The resist thickness was measured using interference patterns in the FT-IR spectra of the resist. Test structures with an aspect ratio 3:1 on 10 microm thick SU-8 resist film were obtained using scanning electron microscopy (SEM).

Amphetamines for schizophrenia

BACKGROUND

It is estimated that between 10% and 65% of people with schizophrenia use illicit drugs such as amphetamines. This group have an increased rate of hospitalisation, homelessness, unemployment and suicide compared with those with schizophrenia who do not abuse drugs.

OBJECTIVES

To evaluate the effects of amphetamines for people with schizophrenia in terms of clinically meaningful outcomes, cognitive functioning and physiological tests.

SEARCH STRATEGY

We searched the Cochrane Schizophrenia Group's Register (February 2002).

SELECTION CRITERIA

We included all randomised controlled trials investigating the effects of amphetamines on people with schizophrenia, compared with a placebo intervention.

DATA COLLECTION AND ANALYSIS

Working independently, we selected and critically appraised studies, extracted data and analysed on an intention-to-treat basis. Where possible and appropriate we calculated risk ratios (RR) and their 95% confidence intervals (CI), with the number needed to treat (NNT). For continuous data we calculated Weighted Mean Differences (WMD).

MAIN RESULTS

We included four short studies with a total of 83 participants. Data were few and poorly reported. The results indicated a reduction of negative symptoms for people allocated to amphetamines (n = 16, 1 RCT, WMD -3 CI -5.02 to -0.98). No such effect was found for positive symptom change (n = 16, 1 RCT, WMD 0 CI -4.46 to 4.46). Compared with placebo, amphetamines significantly increased metabolism in the left and right cerebellum (n = 23, 1 RCT, WMD 0.12 CI 0.06 to 0.18; n = 23 1 RCT, WMD 0.12 CI 0.06 to 0.18) and left striatum (n = 23, 1 RCT, WMD 0.14 CI 0.00 to 0.28) and also significantly decreased metabolism in the left dorsolateral prefrontal cortex (n = 23, 1 RCT, WMD -0.09 CI -0.17 to -0.01).

REVIEWERS' CONCLUSIONS

Understandably amphetamines are rarely formally evaluated in randomised studies and therefore unpublished work in this area is likely to exist. Addition of more studies may clarify reasons why people with schizophrenia persist in taking these harmful stimulants.

Iridescence of a shell of mollusk Haliotis Glabra

Pearls and shells of some mollusks are attractive inorganic materials primarily owing to the beauty of their natural lustrous and iridescent surface. The iridescent colors can be explained by diffraction or interference or both, depending on the microstructure of the surface. Strong iridescent colors are very evident on the polished shell of the mollusk Haliotis Glabra, commonly known as abalone. It would be interesting to study how these colors are produced on the surface of the shell. By using a scanning electron microscope (SEM), the surface of the shell is found to have a fine-scale diffraction grating structure, and stacks of thin crystalline nacreous layers or platelets are found below the surface. These observations suggest that the iridescent colors are caused by both diffraction and interference. From measurements done on the diffraction patterns that were obtained using a He-Ne laser illuminating the shell, the groove width of the grating structure was derived. Good agreement was found between the derived groove density by diffraction and that measured directly using the SEM. The crystalline structure of the nacreous layers of the shell is studied using Fourier transform infrared spectroscopy and SEM observations. The infrared absorption peaks of 700, 713, 862 and 1083 cm-1 confirmed that the nacre of the shell is basically aragonite. The strong iridescent colors of the shell are the result of high groove density on the surface which causes diffraction. The uniform stacking of layers of nacre below the surface of the shell also causes interference effects that contribute to the iridescent colors.