Photocurrent-driven transient symmetry breaking in the Weyl semimetal TaAs

Symmetry plays a central role in conventional and topological phases of matter, making the ability to optically drive symmetry changes a critical step in developing future technologies that rely on such control. Topological materials, like topological semimetals, are particularly sensitive to a breaking or restoring of time-reversal and crystalline symmetries, which affect both bulk and surface electronic states. While previous studies have focused on controlling symmetry via coupling to the crystal lattice, we demonstrate here an all-electronic mechanism based on photocurrent generation. Using second harmonic generation spectroscopy as a sensitive probe of symmetry changes, we observe an ultrafast breaking of time-reversal and spatial symmetries following femtosecond optical excitation in the prototypical type-I Weyl semimetal TaAs. Our results show that optically driven photocurrents can be tailored to explicitly break electronic symmetry in a generic fashion, opening up the possibility of driving phase transitions between symmetry-protected states on ultrafast timescales.

Comparative evaluation of qualitative and quantitative remineralization potential of four different remineralizing agents in enamel using energy-dispersive X-ray: An in vitro study

Background:

The principles of minimally invasive dentistry clearly tells us the need for clinically effective measures to remineralize the early enamel caries lesions.

Aims and Objectives:

The aim of this study was to evaluate the remineralisation potential of four different remineralisation agents used quantitatively by surface microhardness and qualitatively by energy dispersive X ray analysis.

Materials and Methods:

Artificial enamel lesions were created on the buccal surfaces of 60 extracted mandibular second premolar. Specimens were randomly assigned to four groups (n=15) according to the remineralisation agents used: Group 1-Nano Hydroxyapatite, Group 2-Fluoride, Group 3-CPP ACP, Group 4-Chitosan 5mg. All products were applied according to the manufacturer's instructions and specimens were stored in daily renewed artificial saliva. Surface microhardness was assessed using Rockwell hardness test and change in mineral content was evaluated using Energy Dispersive X ray analysis.

Statistical Analysis:

One way analysis of Variance test and post-hoc Tukey test were conducted for multiple group comparison.

Results:

There was remarkable remineralisation in Hydroxyapatite treated comparatively to the other three groups.

Conclusion:

All remineralising agents showed improved surface remineralisation. However complete remineralisation did not occur within 7 days. Nanohydroxyapatite showed the highest potential for remineralisation followed by CPP-ACP, Chitosan and Fluoride.

Optically Driven Collective Spin Excitations and Magnetization Dynamics in the Néel-type Skyrmion Host GaV_{4}S_{8}

GaV_{4}S_{8} is a multiferroic semiconductor hosting magnetic cycloid (Cyc) and Néel-type skyrmion lattice (SkL) phases with a broad region of thermal and magnetic stability. Here, we use time-resolved magneto-optical Kerr spectroscopy to show the coherent generation of collective spin excitations in the Cyc and SkL phases. Our micromagnetic simulations reveal that these are driven by an optically induced modulation of uniaxial anisotropy. Our results shed light on spin dynamics in anisotropic materials hosting skyrmions and pave a new pathway for the optical manipulation of their magnetic order.

Abstract P3-03-14: Clinical utility of one-step nucleic acid amplification (OSNA) in axillary surgery after neoadjuvant chemotherapy (NAC)

Introduction

NAC has been used for downsizing of the tumour in breast and axilla to allow more conservative surgery. In the NAC setting, intraoperative assessment of sentinel lymph node(s) (SLN) is still considered necessary1. Current awareness of the prognostic value for axillary nodal down-staging has renewed interest in analysis of SLN post-NAC.

In this study we want to examine the clinical utility of OSNA (based on CK19 mRNA detection) as a method of intra-operative analysis of SLN to assist real-time decision-making for axillary surgery post-NAC in early breast cancer (EBC).

Methods

Retrospective analysis of prospective data on 399 consecutive patients with EBC who received NAC followed by breast surgery with SLN biopsy (408 axillae) and assessment by OSNA, from September 2011 to January 2018 at the Royal Marsden Hospital (UK). OSNA readouts from the Sysmex RD-100i were collected separate to and blinded from clinico-pathological data. A negative or benign pre-treatment axillary ultrasound scan or indeterminate ultrasound with negative or benign axillary cytology/histology prior to NAC was considered cN0. Univariate analysis (significance at p<0.05) was used to identify risk of recurrence. Patients had a median (mean) follow up of 32.5 (36) months.

Results

The median age at diagnosis was 49 years, median BMI 26, 41 EBC (10%) were screen-detected, 292 (72%) were grade 3 and the most frequent phenotype was receptor triple negative (n=132, 32%).

Of 408 axillae, 248 (60%) were initially cN0, of which 113 (46%) had a pathological complete response (pCR) in the breast. SLN in 54 (22%) cN0 patients were positive on OSNA, of which only 6 (9%) had further involved axillary nodes all 6 of which were ER+ Her2-.

The remaining 160 (40%) axillae were cN1 of which 87 (54%) had conversion to ypN0 including 55 (34%) with both ypT0ypN0.

Axillary lymphadenectomy (AL) was performed in 79 (19%) patients overall, of which n=22 (28%) were cN0 and 57 (72%) were cN1. Of these, 30 (53%) of the cN1 and 6 of 22 (45%) of cN0 had at least 1 additional positive AL node.

Overall 59 (14.4%) patients relapsed. A significantly worse rate of relapse was observed in cN1 compared to cN0 patients (37/159 (23.3%) versus 22/244 (9%), p<0.001). Combined pCR of both breast and axilla (in cN1, n=54) was associated with a significantly reduced risk of relapse and death (p<0.001) compared to those without pCR of either breast or axilla (n=62). Of the latter 18 (29%) relapsed (including 10 deaths).

The mean of both the single highest node tumour load (and total nodal tumour load), as measured by CK19mRNA copies/ul on OSNA, were significantly higher at 90,000 (98,300) for those who relapsed versus 23,100 (25,100) for those without relapse (p=0.027).

Conclusions

The OSNA assay is an accurate tool for axillary SLN analysis in patients after NAC and was helpful in intra-operative axillary management. OSNA reduces the need for a second surgery for AL in 20% of breast cancer patients with a positive-SLN after NAC and might offer additional prognostic value.

Reference

1. NCCN. National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology Breast Cancer.2016.Version 2.2016.

Citation Format: Muscara F, Christaki G, Richardson C, O'Connell R, Padmanabhan P, Warwick J, Lee Y, Smith I, Nerurkar A, Osin P, Krupa K, Rusby J, Roche N, Gui G, MacNeil F, Barry P. Clinical utility of one-step nucleic acid amplification (OSNA) in axillary surgery after neoadjuvant chemotherapy (NAC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-14.

A tunable time-resolved spontaneous Raman spectroscopy setup for probing ultrafast collective excitation and quasiparticle dynamics in quantum materials

We present a flexible and efficient ultrafast time-resolved spontaneous Raman spectroscopy setup to study collective excitation and quasi-particle dynamics in quantum materials. The setup has a broad energy tuning range extending from the visible to near infrared spectral regions for both the pump excitation and Raman probe pulses. Additionally, the balance between energy and time-resolution can be controlled. A high light collecting efficiency is realized by high numerical aperture collection optics and a high-throughput flexible spectrometer. We demonstrate the functionality of the setup with a study of the zone-center longitudinal optical phonon and hole continuum dynamics in silicon and discuss the role of the Raman tensor in time-resolved Raman scattering. In addition, we show an evidence for unequal phonon softening rates at different high symmetry points in the Brillouin zone of silicon by means of detecting pump-induced changes in the two-phonon overtone spectrum. Demagnetization dynamics in the helimagnet Cu2OSeO3 is studied by observing softening and broadening of a magnon after photo-excitation, underlining the unique power of measuring transient dynamics in the frequency domain, and the feasibility to study phase transitions in quantum materials.

Comparative evaluation of apical microleakage in immediate and delayed postspace preparation using four different root canal sealers: An in vitro study

BACKGROUND

Endodontically treated teeth often lack sufficient support for a permanent restoration. During post space preparation, it is important not to disturb the integrity of the apical seal.

AIM

This study compared the effect of immediate versus delayed post space preparation on the apical seal using four different sealers.

MATERIALS AND METHODS

One hundred and thirty single rooted teeth were biomechanically prepared and obturated with single cone gutta-percha and 4 sealers: Endoflas FS, AH Plus, Gutta flow and MTA. Teeth were divided randomly into eight groups, post spaces were prepared using Gates Glidden drills immediately for group I, III, IV and VII. For groups II, IV, VI and VIII prepared after storage of the specimens in 100% humidity for one week. The samples were kept in methylene blue dye, centrifuged at 3000 rpm for 3 min sectioned and then measured under stereomicroscope for apical leakage.

STATISTICAL ANALYSIS

The data was analysed using one way ANOVA and post hoc Tukey test.

RESULTS

All the specimens showed dye leakage, and a statistically significant difference was seen among all the groups (P > 0.05) except Gutta flow.

CONCLUSION

Less leakage is seen when post space is prepared immediately.

Three-dimensional evaluation of surface roughness of resin composites after finishing and polishing

Aim:

This study aims to investigate the effects of finishing and polishing procedures on four novel resin composites using three-dimensional optical profilometer.

Materials and Methods:

Four composites classified according to their filler size, were selected: Filtek™ Z350 XT/Nanofill (3M™ ESPE™), Esthet-X HD/Hybrid (Dentsply Caulk), Te Econom/Microfill (Ivoclar Vivadent^®), Tetric EvoCeram^® /Nanohybrid (Ivoclar Vivadent^®). Composite specimens were made in Plexiglass mold and polished with Soflex (3M ESPE), Enhance + Pogo (Dentsply Caulk). Both the systems were used according to the manufacturers’ instructions, and the polished surfaces were assessed with an optical profilometer.

Statistical Analysis Used:

Kruskal-Wallis test and further pairwise comparison were performed by Mann-Whitney test.

Results:

The smoothest surfaces for all the resin composites tested were obtained from the Mylar strip; statistically significant differences were observed among them (P = 0.001). The order of composites was ranked from the lowest to highest surface roughness; Filtek Z350 XT < Te Econom < Tetric EvoCeram < Esthet XHD. Pairwise multiple comparison with Mann-Whitney test showed Filtek Z350 to have the smoothest surface and the least with Teric EvoCeram. Among the polishing systems, Soflex showed the smoothest surface and was significantly different from Pogo (P = 0.046).

Conclusions:

The effectiveness of the polishing systems seems to be dependent on the material used, treatment modality and also on the filler particle size.

Identification of pheromone-carrying protein in the preorbital gland post in the endangered Indian male Blackbuck Antelope cervicapra L

In mammals, a low molecular mass protein (17-20 KDa) reported from the pheromone sources such as urine, saliva, glandular secretion, etc., as ligand-carrier (pheromone carrier) has been associated with chemo-communication. Since the preorbital gland post is one of the major pheromone sources in Indian Blackbuck, an endangered species, we assumed that it possibly contains low molecular mass protein for chemical communication. Hence, we investigated the preorbital gland post in territorial and non-territorial male blackbucks for such low molecular mass proteins adopting SDS-PAGE and LC-MS/MS analysis. The total content of protein was higher in the post of territorial males than non-territorial males of adult and sub-adult. In fact, the protein profiles such as 17, 21, 25, 42 and 61 kDa were noted in the gland secretion of territorial and non-territorial males. The intensity of the 17 kDa protein band was higher in territorial males than non-territorial males. In-gel trypsin digestion of the 17 kDa band was processed and subjected to LC-MS/MS and SEQUEST analyses. The results of LC-MS/MS and SEQUEST search showed the presence of α(2u)-globulin in the 17 kDa band. In addition, the identified α(2u)-globulin sequence possessed GDW residues, which are the characteristic signature for lipocalin family. Since the α(2u)-globulin has been reported from the pheromone-carrying proteins in some mammals, this protein may carry the volatiles (pheromone compounds) in male Blackbucks preorbital gland to evoke the scent marking for maintaining territoriality (home range) and attraction towards female, through the secretion of glandular protein.

Modeling Suggests a Mechanism of Synergy Between Hepatitis C Virus Entry Inhibitors and Drugs of Other Classes

Hepatitis C virus (HCV) entry inhibitors (EIs) act synergistically with drugs targeting other stages of the HCV lifecycle. The origin of this synergy remains unknown. Here, we argue that the synergy may arise from the complementary activities of the drugs across cell subpopulations expressing different levels of HCV entry receptors. We employ mathematical modeling of viral kinetics in vitro, where cells with a distribution of entry receptor expression levels are exposed to HCV with or without drugs. The drugs act independently in each cell, as expected in the absence of underlying interactions. Yet, at the cell population level our model predicts that the drugs exhibit synergy. EIs effectively block infection of cells with low receptor levels. With high receptor levels, where EIs are compromised, other drugs are potent. This novel mechanism of synergy, arising at the cell population level may facilitate interpretation of drug activity and treatment optimization.

Urinary incontinence in women: a comprehensive review of the pathophysiology, diagnosis and treatment

Urinary incontinence (UI) or involuntary leakage of urine is a distressing and serious health problem. It has a significant psychosocial and economic burden leading to significant quality of life issues. UI is more prevalent than most chronic diseases yet largely underreported. Aging and age-related changes in the bladder play a significant role in the development of UI. This in combination with cognitive dysfunction, functional impairment, pharmacotherapy, smoking, childbearing, obesity and coexisiting comorbidities worsen the condition. Due to the burden UI places on the individual, their family and society, it is important for providers to diagnose and have ready treatment options available. The three most common types of UI are stress urinary incontinence (SUI), urge urinary incontinence (UUI), or a combination of both, mixed urinary incontinence (MUI). This review describes the pathophysiology of incontinence; and diagnosis and treatment (conservative, pharmacological, and surgical therapies) of incontinence in women.

Phase behaviour of PMMA-b-PHEMA with solvents methanol and THF: modelling and comparison to the experiment

Self-consistent field theory is used to model the self-assembly of a symmetric PMMA-block-PHEMA in the presence of two solvents, methanol and tetrahydrofuran (THF). The model predictions are compared to our experimental results of solvent-vapour annealing of thin polymer films, where the sequence of cylinder to gyroid (or micelles) to lamellar phases was found upon increasing the methanol-THF ratio and for particular extents of film swelling. The Hansen solubility parameters are used to estimate the Flory-Huggins interaction parameters (χ) needed in the theoretical model. However, because enacting the experimental range of high (χ)N values is computationally prohibitive, the use of moderate (χ)N values is compensated by employing larger values of the solvent-to-polymer size ratio (α). This approach is validated by showing that the predicted phase diagrams exhibit qualitatively similar trends whether (χ)N or α is increased. Using such an approach, the theory predicts a cylinder to gyroid to lamellar transition on increasing the THF-methanol ratio, a trend consistent with that observed in the experiments.

Observation of standing waves of electron-hole sound in a photoexcited semiconductor

Three-dimensional multicomponent plasmas composed of species with very different masses support a new branch of charge-density fluctuations known as acoustic plasmons. Here, we report on an ultrafast optical method to generate and probe coherent states of acoustic plasmons in a slab of GaAs, which relies on strong photoexcitation to create a large population of light electrons and heavy holes. Consistent with the random-phase-approximation theory, the data reveal standing plasma waves confined to these slabs, similar to those of conventional sound but with associated velocities that are significantly larger.

Hepatoprotective Activity of Herbal Preparation (Hp-4) against Alcohol Induced Hepatotoxicity in Mice

Free radicals include both Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS).When free radicals are produced in a regulated manner in a healthy human body it is scavenged efficiently by antioxidant defense system. But excess generation of pro-oxidants by continuous chain reaction in the form of ROS and RNS cause several human diseases. The shift of the balance in the favour of pro-oxidants results in a condition called “oxidative stress”. Alcohol is primarily metabolized in the liver to generate ROS and RNS, leading to diseases such as cirrhosis, fatty liver and chronic hepatitis. Alcohol induced damage is associated with oxidative stress. The excess generation of prooxidants and reduced antioxidant levels provide an effective model of Hepatotoxicity which is noteworthy. Recent trend is to discover polyherbal formulation of medicinal plants which have hepatoprotective function. In the present study 80% alcoholic extract of leaves of Aloe vera, Bacopa monniera, Moringa oleifera and rhizome of Zingiber officinale were utilized to prepare Herbal Preparation or HP-4.Further the hepatoprotective effects of HP-4 was tested in alcohol induced Hepatotoxicity in mice. Silymarin is a well known hepatoprotective drug was used as a standard for comparison. Biochemical and histopathological studies provided ample evidence that HP-4 provided a hepatoprotective role in alcohol induced hepatotoxicity which was comparable to drug Silymarin. The presence of phytochemicals in HP-4 provided a synergistic, supra-additive and co-operative effects in the hepatoprotective function in alcohol induced hepatotoxicity mice model. DOI: http://dx.doi.org/10.3126/ijasbt.v2i1.9346 Int J Appl Sci Biotechnol, Vol 2(1): 50-58

A comparative evaluation of the fracture resistance of three different pre-fabricated posts in endodontically treated teeth: An in vitro study

Aims:

To compare the fracture resistance and primary mode of failure of three different pre- fabricated posts like stainless steel, carbon fiber and ceramic posts in endodontically treated crowned permanent maxillary central incisors.

Materials and Methods:

Root canal treatment was performed on all 30 maxillary central incisors. Post space was prepared and samples were divided into three groups of 10 each. The teeth were inserted with pre-fabricated stainless steel, carbon fiber and ceramic post and cemented using adhesive resins, core fabricated and crowns placed. Mode of failure was carried out by immersing the teeth in black ink for 12 h and then sectioning them mesio-distally. Fracture above the embedded resin was considered favorable and fracture below the resin level was considered unfavorable.

Statistical Analysis:

Fracture strength was measured using a universal testing machine. Data were evaluated statistically using the Kruskal Wallis test and the Mann Whitney “U”-test. Mode of failure was evaluated statistically using the chi-square test.

Results:

There was a statistically significant difference showing that the stainless steel post had a better fracture resistance when compared with the other two posts and the carbon fiber showed a statistically more favorable fracture when compared with the other two posts.

Conclusions:

Within the limitations of this study, it can be concluded that the pre-fabricated stainless steel post exhibited a significantly higher fracture resistance at failure when compared with the carbon fiber post and the ceramic post. The mode of failure of the carbon fiber post was more favorable to the remaining tooth structure when compared with the pre-fabricated stainless steel post and the ceramic post.

Indirect imaging of cardiac-specific transgene expression using a bidirectional two-step transcriptional amplification strategy

Transcriptional targeting for cardiac gene therapy is limited by the relatively weak activity of most cardiac-specific promoters. We have developed a bidirectional plasmid vector, which uses a two-step transcriptional amplification (TSTA) strategy to enhance the expression of two optical reporter genes, firefly luciferase (fluc) and Renilla luciferase (hrluc), driven by the cardiac troponin T (cTnT) promoter. The vector was characterized in vitro and in living mice using luminometry and bioluminescence imaging to assess its ability to mediate strong, correlated reporter gene expression in a cardiac cell line and the myocardium, while minimizing expression in non-cardiac cell lines and the liver. In vitro, the TSTA system significantly enhanced cTnT-mediated reporter gene expression with moderate preservation of cardiac specificity. After intramyocardial and hydrodynamic tail vein delivery of an hrluc-enhanced variant of the vector, long-term fluc expression was observed in the heart, but not in the liver. In both the cardiac cell line and the myocardium, fluc expression correlated well with hrluc expression. These results show the vector's ability to effectively amplify and couple transgene expression in a cardiac-specific manner. Further replacement of either reporter gene with a therapeutic gene should allow non-invasive imaging of targeted gene therapy in living subjects.

Going to scale with professional skilled care

Because most women prefer professionally provided maternity care when they have access to it, and since the needed clinical interventions are well known, we discuss in their paper what is needed to move forward from apparent global stagnation in provision and use of maternal health care where maternal mortality is high. The main obstacles to the expansion of care are the dire scarcity of skilled providers and health-system infrastructure, substandard quality of care, and women's reluctance to use maternity care where there are high costs and poorly attuned services. To increase the supply of professional skilled birthing care, strategic decisions must be made in three areas: training, deployment, and retention of health workers. Based on results from simulations, teams of midwives and midwife assistants working in facilities could increase coverage of maternity care by up to 40% by 2015. Teams of providers are the efficient option, creating the possibility of scaling up as much as 10 times more quickly than would be the case with deployment of solo health workers in home deliveries with dedicated or multipurpose workers.

Study on Staphylococcus aureus strain HPC-250 for associated antibacterial property

We isolated a Staphylococcus aureus strain HPC-250 producing antibacterial agent against Paenibacillus strain HPC-251. Both strains were isolated from the same environmental niche. The bacteria were identified using the partial sequencing of their TA-cloned 16S rDNA. Spectrum of the antibacterial agent was also tested against routine observed bacteria with drinking water contamination such as Escherichia coli, Salmonella, Pseudomonas, and Vibrio and these were found to be sensitive. Bacteria like Acinetobacter and Burkholderia were found to be resistant. The differential antibacterial activity of the HPC-250 was observed for the genus Bacillus where B. subtilis remained resistant although B. sphaericus was sensitive.

Tin foil as bolus material for therapeutic electron beams from the Varian Clinac 2100C/D

Tin foils of sub-millimetre thickness have been investigated as bolus material for therapeutic electron beams from the Varian Clinac 2100C/D linear accelerator. Measurements with ionisation chamber and radiographic film in Plastic Water or water were performed under tin foil bolus to determine surface dose, therapeutic ranges, output factor correction, penumbra and dose outside the field edge. Appropriate thicknesses of tin foil for 90% dose at the surface were found to be approximately 0.3 mm for 6 MeV, and 0.4 mm for 9 MeV and 12 MeV. Enhanced therapeutic interval with tin foil bolus over water-equivalent bolus has previously been reported, but was found not to be evident for 12 MeV and for a small (4 x 4 cm2) 9 MeV field. The penumbra width of fields with tin foil and water-equivalent bolus were found to be within 2 mm, while the doses at 1 cm outside the field edge were within 1.5% of peak dose. Output factor corrections for fields with tin foil were measured as within 2% of unity. Air gaps between the tin foil and phantom surface up to 5 mm were observed to have minimal effect on output correction factor, relative surface dose, and therapeutic range.

Discovery of a bacterium, with distinctive dioxygenase, that is responsible for in situ biodegradation in contaminated sediment

Microorganisms maintain the biosphere by catalyzing biogeochemical processes, including biodegradation of organic chemical pollutants. Yet seldom have the responsible agents and their respective genes been identified. Here we used field-based stable isotopic probing (SIP) to discover a group of bacteria responsible for in situ metabolism of an environmental pollutant, naphthalene. We released 13C-labeled naphthalene in a contaminated study site to trace the flow of pollutant carbon into the naturally occurring microbial community. Using GC/MS, molecular biology, and classical microbiological techniques we documented 13CO2 evolution (2.3% of the dose in 8 h), created a library of 16S rRNA gene clones from 13C labeled sediment DNA, identified a taxonomic cluster (92 of 95 clones) from the microbial community involved in metabolism of the added naphthalene, and isolated a previously undescribed bacterium (strain CJ2) from site sediment whose 16S rRNA gene matched that of the dominant member (48%) of the clone library. Strain CJ2 is a beta proteobacterium closely related to Polaromonas vacuolata. Moreover, strain CJ2 hosts the sequence of a naphthalene dioxygenase gene, prevalent in site sediment, detected before only in environmental DNA. This investigative strategy may have general application for elucidating the bases of many biogeochemical processes, hence for advancing knowledge and management of ecological and industrial systems that rely on microorganisms.

Respiration of 13C-labeled substrates added to soil in the field and subsequent 16S rRNA gene analysis of 13C-labeled soil DNA

Our goal was to develop a field soil biodegradation assay using (13)C-labeled compounds and identify the active microorganisms by analyzing 16S rRNA genes in soil-derived (13)C-labeled DNA. Our biodegradation approach sought to minimize microbiological artifacts caused by physical and/or nutritional disturbance of soil associated with sampling and laboratory incubation. The new field-based assay involved the release of (13)C-labeled compounds (glucose, phenol, caffeine, and naphthalene) to soil plots, installation of open-bottom glass chambers that covered the soil, and analysis of samples of headspace gases for (13)CO(2) respiration by gas chromatography/mass spectrometry (GC/MS). We verified that the GC/MS procedure was capable of assessing respiration of the four substrates added (50 ppm) to 5 g of soil in sealed laboratory incubations. Next, we determined background levels of (13)CO(2) emitted from naturally occurring soil organic matter to chambers inserted into our field soil test plots. We found that the conservative tracer, SF(6), that was injected into the headspace rapidly diffused out of the soil chamber and thus would be of little value for computing the efficiency of retaining respired (13)CO(2). Field respiration assays using all four compounds were completed. Background respiration from soil organic matter interfered with the documentation of in situ respiration of the slowly metabolized (caffeine) and sparingly soluble (naphthalene) compounds. Nonetheless, transient peaks of (13)CO(2) released in excess of background were found in glucose- and phenol-treated soil within 8 h. Cesium-chloride separation of (13)C-labeled soil DNA was followed by PCR amplification and sequencing of 16S rRNA genes from microbial populations involved with (13)C-substrate metabolism. A total of 29 full sequences revealed that active populations included relatives of Arthrobacter, Pseudomonas, Acinetobacter, Massilia, Flavobacterium, and Pedobacter spp. for glucose; Pseudomonas, Pantoea, Acinetobacter, Enterobacter, Stenotrophomonas, and Alcaligenes spp. for phenol; Pseudomonas, Acinetobacter, and Variovorax spp. for naphthalene; and Acinetobacter, Enterobacter, Stenotrophomonas, and Pantoea spp. for caffeine.

Geochemical and physiological evidence for mixed aerobic and anaerobic field biodegradation of coal tar waste by subsurface microbial communities

We used geochemical analyses of groundwater and laboratory-incubated microcosms to investigate the physiological responses of naturally occurring microorganisms to coal-tar-waste constituents in a contaminated aquifer. Waters were sampled from wells along a natural hydrologic gradient extending from uncontaminated (1 well) into contaminated (3 wells) zones. Groundwater analyses determined the concentrations of carbon and energy sources (pollutants or total organic carbon), final electron acceptors (oxygen, nitrate, sulfate), and metabolic byproducts (dissolved inorganic carbon [DIC], alkalinity, methane, ferrous iron, sulfide, Mn2+). In the contaminated zone of the study site, concentrations of methane, hydrogen, alkalinity, and DIC were enhanced, while dissolved oxygen and nitrate were depleted. Field-initiated biodegradation assays using headspace-free serum bottle microcosms filled with groundwater examined metabolism of the ambient organic contaminants (naphthalene, 2-methylnaphthalene, benzothiophene, and indene) by the native microbial communities. Unamended microcosms from the contaminated zone demonstrated the simultaneous degradation of several coal-tar-waste constituents at the in situ temperature (10 degrees C). Lag phases prior to the onset of biodegradation indicated the prevalence of both aerobic and anaerobic conditions in situ. Electron acceptor-amended microcosms from the most contaminated well waters demonstrated only aerobic naphthalene degradation. Collectively, the geochemical and microbial evidence show that biodegradation of coal-tar-waste constituents occurs via both aerobic and anaerobic terminal electron accepting processes at this site.

Corneal topography and Schirmer testing in eyes with the Hudson-Stahli line

PURPOSE

To evaluate corneal topographic features and tear secretion in eyes with the Hudson-Stahli line.

METHODS

Keratometry, computerized videokeratography and Schirmer testing were performed in 50 cases with bilateral Hudson-Stahli line, and 55 controls without the Hudson-Stahli line. Similar tests were performed in 21 subjects with unilateral Hudson-Stahli line.

RESULTS

Corneal topographic features and keratometry in the horizontal meridian were similar in cases and controls, and in fellow eyes of subjects with unilateral Hudson-Stahli line. Keratometry in the vertical meridian in cases (43.01 +/- 2.01) was significantly lesser than in controls (43.94 +/- 1.77) (P = 0.01). This value was not different in fellow eyes of patients with unilateral Hudson-Stahli line. Schirmer testing revealed significantly greater tear secretion in cases (16.72 +/- 4.99 mm) compared to controls (12.57 +/- 3.62 mm) (P < 0.01). In subjects with unilateral Hudson-Stahli line, mean Schirmer values in the eye with the line (17.52 +/- 6.86 mm) were significantly greater than in eyes without (13.67 +/- 4.64 mm) (P = 0.04).

CONCLUSION

Formation of the Hudson-Stahli line may be dependent on the presence of normal tear secretion in the eye.

Interface fluid after laser in situ keratomileusis

We report a case in which raised intraocular pressure (IOP) was associated with interface fluid after uneventful bilateral laser in situ keratomileusis (LASIK). The patient presented with diffuse lamellar keratitis in both eyes 3 weeks postoperatively that was treated aggressively with topical corticosteroids. A steroid-induced rise in IOP resulted in interface fluid accumulation and microcystic edema. Measurements with the Goldmann tonometer revealed an IOP of 3.0 mm Hg in both eyes. However, Schiotz tonometry recorded a pressure of 54.7 mm Hg in both eyes. Reduction in the dosage of topical corticosteroid and medical treatment of the raised IOP resulted in resolution of the microcystic edema and interface fluid accumulation. This case highlights the inaccuracies of IOP measurement after LASIK and the resulting complications.

Bilateral penetrating keratoplasty--indications, results and review of literature

PURPOSE

To analyze the indications, functional results, and rates of graft rejection and failure after bilateral penetrating keratoplasty (PK) in a major eye care hospital and research center in India.

METHODS

Retrospective review of the case records of 38 patients who underwent bilateral PK and had at least 6 months follow-up after corneal transplantation in the second eye.

RESULTS

The mean age of the 38 patients (20 M, 18 F) was 35 +/- 25 years (range, 0.5 to 79 years). Mean follow-up was 49 +/- 23 months (range, 13.4 to 116.4 months) after surgery in the first eye and 31 +/- 22 months (range, 6.6 to 103.6 months) after surgery in the second eye. The average time interval between surgery in the first and second eye was 18 +/- 10 months (range, 0 to 38 months). The commonest indications for surgery were corneal dystrophies (50%), aphakic bullous keratopathy (21%), and keratoconus (11%). Postoperatively, secondary glaucoma occurred in 2 first and 3 second eyes. Best-corrected visual acuity at last follow-up was > 6/12 in 34% of first eyes and 50% of second eyes, and was < 6/60 in 26% and 18% of first and second eyes respectively. Allograft rejection occurred in 4 of the first eyes and 3 of the second eyes. The two-year graft survival rate in first eyes was 70% and in second eyes was 83%. Worse outcomes were noted in grafts performed for secondary endothelial failure. Earlier graft failure occurred in first eyes (54 +/- 5 months) compared to second eyes (79 +/- 10 months) (Logrank Test p = 0.2311).

CONCLUSIONS

Bilateral penetrating keratoplasty has reasonable success in selected patients. Corneal transplantation in the second eye does not seem to increase the risk of graft rejection in either eye.

Duplex RT-PCR for simultaneous detection of hepatitis A and hepatitis E virus isolated from drinking water samples

A duplex reverse transcription polymerase chain reaction (RT-PCR) protocol for simultaneous detection of hepatitis A virus (HAV) and hepatitis E virus (HEV) in water samples has been developed and demonstrated. Both HAV and HEV were concentrated from drinking water samples through a one-step concentration protocol. Different cDNA could be produced in the RT step carried out with a random primer in a single reaction tube. Two different sets of primers specific for HAV-cDNA and HEV-cDNA were used for PCR amplification. Amplified DNA products representing HAV and HEV were identified by gel electrophoresis at 247 and 327 bp (base pair) sequences, respectively. Specific sets of primers amplified a single type of virus and no cross-reactivity of the primers was noticed in duplex RT-PCR. The protocol was used for direct isolation and detection of HAV and HEV from 23 water samples in urban areas of Chennai city. Out of these, nine water samples were positive for HAV, and three for HEV. All three samples positive for HEV were also positive for HAV. The test provides a rapid and economical means of water quality surveillance to specifically detect HAV and HEV.

Corneal endothelial cell density and morphology in normal Indian eyes

PURPOSE

To describe corneal endothelial cell density and morphology in the Indian population and to compare endothelial cell characteristics in the Indian population with data available in literature for American and Japanese populations.

METHODS

Specular microscopy and corneal pachymetry were performed in both eyes of 537 normal Indian volunteers, aged 20-87 years. Parameters studied included endothelial cell density, cell area, coefficient of variation (CV) in cell area and hexagonality.

RESULTS

Mean endothelial cell density in the study population was 2,525 +/- 337 cells/mm2. There was a statistically significant decrease in endothelial cell density with age (p < 0.001, correlation -0.387) and the rate of cell loss was 0.3% per year. There was also a statistically significant increase in mean cell area (p < 0.001, correlation 0.362) and CV (p = 0.02, correlation 0.096), and decrease in percentage of hexagonal cells (p = 0.01, correlation -0.127) with increasing age. There was no significant difference in these parameters between fellow eyes of subjects. In all age groups, the mean endothelial cell density was significantly lower than values reported previously in the Japanese population. The values were less than those described in the American population, but the differences were statistically significant only in the 20-30 and 41-50 year age groups.

CONCLUSION

Normative data for the endothelium in the Indian population are reported. Endothelial cell density in Indian eyes is less than the values described in the Japanese and American populations.

Corneal autografting: a systematic approach

OBJECTIVE

To describe a systematic approach to corneal autografting.

PATIENTS AND METHODS

Retrospective review of case records of 3 patients who underwent this procedure.

RESULTS

All patients achieved satisfactory visual recovery. Oversized grafts of 0.5 mm had less post-operative complications in the recipient eye. A phakic blind eye that received a 0.5 mm undersized graft had a temporary ocular hypertensive phase.

CONCLUSIONS

Corneal autografting is a safe and effective technique in selected patients. The preferred surgical technique consists of surgery first on the blind eye, excision of a 0.5 mm oversized donor graft, cataract extraction if the eye is phakic, and use of an appropriate temporary keratoprosthesis to maintain donor eye integrity until autografting is completed in the eye with visual potential.

Partial flap during laser in-situ keratomileusis: pathogenesis and timing of retreatment

PURPOSE

To report the timing of retreatment and clinical outcomes in patients with a partial corneal flap during laser in-situ keratomileusis (LASIK), and to describe the causes of this complication.

METHODS

Retrospective review of case records of four patients (4 eyes) who had a partial corneal flap during LASIK.

RESULTS

The mean age of the four patients was 23 +/- 4.7 years, and mean preoperative spherical equivalent (SE) refraction was -9.1 +/- 3.1 D (range, -5.5 to -13 D). A 160 microns corneal flap was attempted during the initial treatment. Retreatment with a 180 microns corneal flap was performed at a mean of 5.1 +/- 1.6 weeks (range, 4 to 7.5 weeks) after the initial procedure. There were no intraoperative complications during retreatment. Post-LASIK mean SE refraction was -1.0 +/- 1.1 D (range, +0.38 to -2.0 D), after a mean follow up of 19 +/- 15.7 weeks (range, 7 to 42 weeks). Best spectacle-corrected visual acuity decreased in one eye from 6/5 to 6/6 and was maintained in the others.

CONCLUSION

LASIK retreatment can be performed as early as one month after a partial flap, if the refraction is stable and a thicker corneal flap is created.

Nocardia Asteroides keratitis: report of seven patients and literature review

PURPOSE

To describe clinical features and treatment outcomes in patients with advanced Nocardia asteroides keratitis.

METHODS

Retrospective review of case records of 7 patients with culture-proven Nocardia keratitis.

RESULTS

Corneal infection occurred after corneal trauma in two patients, cataract surgery in three patients, penetrating keratoplasty in one patient and was associated with a silicone buckle element infection in one patient. Mean duration of infection at presentation was 33.4 days (7-75 days), and five patients had received prior treatment with corticosteroids. Six of seven patients had deep corneal suppuration at the time of presentation, clinically suggestive of mycotic keratitis. In two patients who had received prolonged corticosteroid therapy (> or = 45 days), the eyes could not be salvaged. Complete resolution of infection was achieved in all 4 eyes treated with topical fortified cefazolin eye drops (50 mg/ml).

Understanding corneal topography

With the increase in corneal laser refractive surgery, there is a greater need for precise evaluation of the corneal surface. Articles published in the past year have reported possible use of confocal scanning laser technology-based devices to image the cornea. Other studies have compared existing instruments and software in an effort to determine if data from different instruments are comparable. Topographic evaluation also has served to highlight long-term complications of procedures like radial keratotomy and the promise of newer surgical procedures like the intrastromal corneal ring segments. Studies of the corneal surface have helped refine surgical procedures like photorefractive keratectomy, laser in situ keratomileusis, penetrating keratoplasty, and cataract surgery. Topographic measures that serve as direct correlates of ocular visual performance, however, still remain elusive. Studies in the past year have confirmed that corneal topographic evaluation may be a powerful tool in the search for a genetic basis of keratoconus. Important areas for future research include precise determination of the power of the postrefractive surgery cornea to allow precise estimation of intraocular lens power in these eyes. Detecting the presence of past corneal refractive surgery in donor eyes also is likely to be a challenge. Despite the numerous advances in the field of corneal topography in the past year, there is still a need to present the data in a standardized format that is universal to all instruments and technologies.

Fellow eye treatment in excimer photo refractive keratectomy

PURPOSE

To describe symmetry of response in fellow eyes of patients undergoing photorefractive keratectomy (PRK) for myopia, analyse the risk factors leading to asymmetry in response and to determine if delayed treatment of the second eye increases safety and predictability of PRK.

METHODS

Retrospective review of case records of 133 patients who underwent bilateral myopic PRK and had a minimum follow up of 6 months in both eyes.

RESULTS

Postoperative uncorrected visual acuity, spherical equivalent (SE) refraction within +/- 1 D of emmetropia, best-corrected visual acuity (BCVA) and corneal haze were not significantly different in fellow eyes of patients undergoing PRK for myopia. Of 87 eyes in group 1 (myopia < 6 D), 96.6% had uncorrected visual acuity > or = 6/12, 89.7% were within +/- 1 D of emmetropia, none lost > or = 1 line BCVA, and none had haze > or = grade 3. Similar results for 98 eyes in group II (myopia 6 to 9.9 D) were 75.6%, 55.1%, 2.0% and 2.0% respectively. For 81 eyes in group III (myopia > or = 10 D) the results were 42.7%, 33.3%, 8.6%, and 4.9% respectively. Among 84 patients with similar preoperative myopia in both eyes, 54 (64.3%) patients had a postoperative SE difference < or = 1 D in fellow eyes. Risk factors for asymmetric response among fellow eyes included increasing preoperative myopia (p < 0.001) and dissimilar treatment technique in the two eyes (p = 0.03). Corneal haze did not increase significantly after the third postoperative month.

CONCLUSION

This study demonstrates that considerable symmetry of response exists in fellow eyes of patients undergoing myopic PRK. Early PRK in the fellow eye of patients with < 6 D myopia is safe and allows quick visual rehabilitation of the patient. In patients with myopia > or = 6 D, a 3-month interval before treating the second eye may improve the safety of the procedure.

Ligneous conjunctivitis: a clinicopathologic study of 3 cases

The clinical, histopathologic features, and treatment outcomes in 3 patients with ligneous conjunctivitis are described. Bilateral, idiopathic membranes occurred in the palpebral conjunctiva in 2 patients. In 1 patient, unilateral conjunctival changes occurred in the bulbar conjunctiva, at the site of pterygium excision. Treatment included topical hyaluronidase, chymotrypsin, heparin, and cyclosporine and surgical excision with limited or no success. In one patient, conjunctival autografting from the normal fellow eye resulted in pseudomembrane formation at the donor site in the previously unaffected eye. Histopathological evaluation of excised membranes revealed the presence of amorphous eosinophilic hyaline material and chronic inflammatory cells. Immunohistochemical study revealed a predominance of T-lymphocytes. This case series confirms the recalcitrant clinical course of ligneous conjunctivitis. Conventional treatment modalities described in literature were not useful in the management of this condition. Surgical manipulation of the unaffected fellow eye in patients with unilateral disease can result in pathologic conjunctival changes, and is best avoided.

Bilateral corneal infiltrates after excimer laser photorefractive keratectomy

A 26-year-old man developed painless inferior subepithelial infiltrates away from the site of ablation in both eyes after excimer laser photorefractive keratectomy (PRK) for myopia. Clinical characteristics of the corneal infiltrates resembled staphylococcal-immune infiltrates. The condition responded to treatment with topical diluted steroids and antibiotics. There was no residual corneal scarring. The infiltrates did not affect the refractive outcome of the surgery. Recognition of this rare entity will help clinicians avoid aggressive investigative and treatment modalities that can affect the results of PRK.

In situ tumbling of the AcrySof intraocular lens

The small incision through which foldable acrylic intraocular lenses (IOLs) are implanted does not allow easy explantation of the lens in the event of intraoperative complications. Reversal of the IOL optic during insertion, although rare, can predispose to postoperative complications such as pupillary capture of the IOL, capsule bag distension syndrome, and refractive problems. Explanting the IOL can damage it, the cataract wound, or both. We describe a technique of in situ tumbling of the AcrySof IOL to correct reversed-optic implantation that preserves the integrity of the IOL and anterior segment structures.

Excimer laser phototherapeutic keratectomy: indications, results and its role in the Indian scenario

PURPOSE

To report indications, technique, and results of excimer phototherapeutic keratectomy (PTK), and describe possible reasons for the small numbers of such procedures performed in a referral institute in India.

METHODS

Retrospective review of case records of 10 patients (11 eyes) who underwent excimer PTK at our institute between February 1994 and September 1997.

RESULTS

Corneal scars were the most common indication for treatment. Best-corrected visual acuity (BCVA) improved in 6 eyes (mean: 2 lines of Snellen acuity). All eyes had BCVA > or = 6/12 after treatment. None of the patients experienced loss of BCVA after treatment. Unaided visual acuity improved in 3 eyes and decreased in 2 eyes. Change in spherical equivalent refraction > or = 1 diopter occurred in 77.8% of eyes after treatment. Treating central corneal scars resulted in a significant hyperopic shift in refraction.

CONCLUSIONS

Excimer PTK is a safe and effective procedure for the treatment of superficial corneal opacities. Post-treatment ametropia may require further correction with optical aids. Inappropriate referrals, deep corneal scars, and cost of the procedure could have contributed to the small numbers of PTK performed at our institute. Improved understanding of procedural strengths and limitations could lead to increased use of this procedure, with satisfying results in selected patients.

Explantation of silicone plate haptic intraocular lenses

The stress on small self-sealing incisions in cataract surgery has resulted in the increased use of foldable intraocular lenses (IOL). Plate haptic silicone IOLs implanted with the help of an injector require extremely small incision lengths and are extensively used. The authors discuss difficulties in explanting such lenses, especially in inflamed eyes. Two patients who underwent plate-haptic silicone IOL explantation for postoperative bacterial endophthalmitis are described. Plate haptic IOLs have a tendency to dislocate posteriorly because of poor capsular fixation and increased posterior bowing. Enlarging a small rhexis prior to attempting explantation of these lenses reduces this complication. Difficulties inherent in explanting plate haptic silicone IOLs in inflamed eyes are discussed, along with suggestions to overcome them.

Combined phacoemulsification and penetrating keratoplasty

To highlight indications, technique, and advantages of closed-chamber phacoemulsification and intraocular lens (IOL) implantation during penetrating keratoplasty for corneal opacities. Case reports of 2 patients who underwent combined phacoemulsification, IOL implantation and penetrating keratoplasty. The technique described allowed controlled capsulorrhexis, cataract removal and in-the-bag IOL implantation. Complications due to increased posterior pressure during open-sky extracapsular cataract were not encountered. The surgical technique described in this report can only be used in selected patients undergoing combined corneal transplant and cataract surgery. In this group of patients, however, the technique offers many intra- and postoperative advantages.

Corneal topography in atypical pellucid marginal degeneration

PURPOSE

Pellucid marginal degeneration (PMD) is commonly described as a noninflammatory corneal ectasia typically involving the inferior cornea. Although reports of superior corneal changes in PMD exist, the topographic patterns of these PMD variants are not well characterized. We describe corneal topographic alterations seen in eyes with atypical PMD.

METHODS

Computer-assisted videokeratography was performed in 10 eyes of five patients with PMD.

RESULTS

Eight of the eyes studied had changes involving the superior cornea, with or without changes in the inferior cornea. Atypical presentations of PMD included extension of inferior peripheral thinning above the horizontal meridian and occurrence of superior corneal thinning and ectasia with or without typical inferior changes. Atypical PMD reveals topographic patterns similar to classic PMD, but corneal changes also involve the nasal, temporal, or superior quadrants or a combination of these. The topographic maps reflect the location of peripheral corneal thinning and extent of corneal protrusion.

CONCLUSIONS

Corneal topographic changes in atypical PMD are similar to those seen in typical PMD but can involve the superior cornea.