Investigating the Correlation between Proliferative Diabetic Retinopathy (PDR) and the duration of diabetes mellitus

The objective of this study is to determine the correlation between proliferative diabetic and duration retinopathy and duration of diabetes mellitus. This study was conducted using a total of one hundred (100) diabetic patients from Trinidad Eye Hospital Diabetic Retinopathy Screening Program (DESP). An efficient screening along with fundus photographs was done prior to collection of data. All data received from TEH database were entered into IBM SPSS statistical software (version 6). Tests such as One-Way ANOVA as well as Chi square test was used to determine the correlation between duration of diabetes and progression of diabetic retinopathy through grading of photographs. From the results obtained in this study, there was a correlation between duration of diabetic retinopathy and the grade obtained therefore the objective of the study was answered. In conclusion, it can be stated that a longer duration of diabetes mellitus relates to an increase in the progression of diabetic retinopathy. Additionally, there was no associated correlation between ethnicity and the progression of diabetic retinopathy indicating that ethnicity is not a definite risk factor for the progression of the condition.

Comparing the expected refractive status from immersion biometry and the achieved refractive status post-cataract surgery

Objective: To investigate the accuracy of Immersion A-Scan Biometry by comparing the relationship between the predicted refractive status from the biometric data with the achieved refractive status determined from objective/subjective refraction. Design and Methodology: Sixty patients were recruited from the Trinidad Eye Hospital (TEH) who was scheduled to undergo cataract surgery. The method of ocular biometry measurement used in this study was Immersion A-scan Biometry using the Aviso: The Ultrasound Platform. The biometric data was then recorded along with the expected refractive status based on the SRK-T formula used to calculate the power of the intra-occular lens (IOL) to be implanted. Results: Out of the 60 patients used, phacoemulsification surgery was performed on 33 right eyes and 27 left eyes. The goal of emmetropia after surgery was achieved in 32 patients among the 60 patients. The 28 patients that were unable to achieve emmetropia brought awareness to the assumptions of errors within the biometric data. The visual acuity was improved significantly in all patients after the phacoemulsification surgery. Conclusion: The study confirmed that there is no significant difference between the refractive status predicted from Immersion A-scan biometry with the refractive status achieved post cataract surgery.

Characterization of the ABCA4 gene in Stargardt's Disease in Trinidad and Tobago

Objectives: Stargardt's disease is an autosomal recessive macular dystrophy caused by mutations in the photoreceptor cell-specific ATP-binding cassette sub-family A member 4, transporter (ABCA4) gene. We studied (i) the predicted effects of mutations on the function of the ABCA4 transporter and (ii) the existence of four common mutations in local Stargardt patients. Design and Methodology: (i) The freeware PROVEAN (Protein VariationEffect Analyzer; J. Craig Venter Institute, CA,USA) was used to predict the deleterious effect257 mutations in the ABCA4 gene. PROVEANscores below -2.5 were considered deleterious.One-way ANOVAs were used to detect anysignificant differences in mean (±SE) PROVEANscores among mutation types or protein domains I,II, III or IV. (ii) Using saliva, DNA was isolated from three Stargardt patients. Chromosomal regions were amplified by PCR, sequenced (Macrogen Inc., Seoul, Korea) and sequence alignment (NCBI, MD, USA) used to detect the presence of four mutations; c.768G>T (p.Val256=), c.4469G>A (p.Cys1490Tyr), c.6079C>T (p.Leu2027Phe) and c.1804C>T (p.Arg602Trp). Results: (i) Sixty-three percent of mutations predicted deleterious effects. There were no significant (p<0.05) differences between mean PROVEAN scores among mutation types (substitutions, - 4.49±0.20; deletions/insertions, -6.35±0.67) or protein domains (domain I, -4.79 ± 0.39; domain II, -4.65 ± 0.36; domain III, -5.48 ± 0.51; domain IV, -4.39 ± 0.34). (ii) These mutations were not detected in Stargardt's patients. Conclusion: (i) Functionality of the ABCA4 protein is affected by multiple mutations. (ii) Novel mutations are present in local patients. Currently, we seek to profile novel mutations in six families using molecular inversion probes.

The LysR-like regulator LeuO in Escherichia coli is involved in the translational regulation of rpoS by affecting the expression of the small regulatory DsrA-RNA.

The translation of rpoS, which encodes the general stress sigma factor, sigmaS, in Escherichia coli, is stimulated by various stress conditions. Regulatory factors involved in this control are the RNA-binding Hfq (HF-I) protein, the histone-like protein H-NS and the small regulatory DsrA-RNA (with the last being specifically required for increased rpoS translation at low temperature). Here, we report the characterization of a transposon insertion mutant (Tn10-8) with reduced sigmaS levels that led to the identification of an additional factor involved in the regulation of rpoS translation, the LysR-like regulator LeuO. Tn10-8 decreases rpoS translation predominantly at low growth temperature. The mutation results in similarly strongly reduced DsrA-RNA expression and does not affect rpoS expression in a dsrA null mutant background, indicating that it affects rpoS translation via DsrA-RNA. Tn10-8 is inserted 26bp upstream of the leuO open reading frame, which encodes a putative LysR-like regulator of unknown function. Instead of being a leuO null mutation, Tn10-8 activates leuO expression as a result of the p(out) promoter on IS10L reading into leuO, indicating that LeuO represses dsrA and thereby reduces rpoS translation at low temperature. LeuO does not contribute to temperature regulation of dsrA since its own expression is rather low and not temperature dependent. In a mutant deficient for H-NS, however, leuO is strongly derepressed. We conclude that rpoS translation is controlled by a regulatory network that includes Hfq, H-NS, LeuO and DsrA-RNA. In this network, H-NS plays a dual role by interfering with rpoS translation in general and, via LeuO, influencing the synthesis of its own low-temperature antagonist, DsrA-RNA.

Characterization of Bacterial Communities from Activated Sludge: Culture-Dependent Numerical Identification Versus In Situ Identification Using Group- and Genus-Specific rRNA-Targeted Oligonucleotide Probes

The structures of bacterial communities were studied in activated sludge samples obtained from the aerobic and anaerobic zones of a wastewater treatment plant showing enhanced phosphorous removal. Samples were analyzed by in situ hybridization with oligonucleotide probes complementary to selected regions of the 16S and 23S ribosomal RNA (rRNA) characteristic for defined phylogenetic entities (genera and larger groups). The microbial community structures revealed by molecular techniques were compared with the compositions of culturable bacterial communities, obtained from the characterization of 255 isolates from tryptone-soy (TS) agar and R2A agar. These isolates were characterized by 89 physiological tests and their cellular fatty acid patterns, and identified. Culture-dependent techniques indicated the following distribution: different Aeromonas spp. (2.7-8.3% on R2A agar; 45.0-63.7% on TS agar), Acinetobacter spp. (5.4-9.0% on R2A agar; 5.0-9.1% on TS agar), Pseudomonas spp. (up to 10% on R2A agar) and Shewanella putrefaciens (up to 3.0% on R2A agar), all members of the gamma subclass of Proteobacteria, were isolated most frequently. The relatively rare isolates of the beta subclass were identified as Acidovorax spp., Alcaligenes spp., and Comamonas spp.. The Gram-positive bacteria (high DNA G+C) were assigned mainly to Arthrobacter spp., Microbacterium spp., and Mycobacterium phlei. In order to assess the in situ abundance of the most frequently isolated genus, Aeromonas, two rRNA-targeted oligonucleotide probes were developed. The two gamma proteobacterial genera Aeromonas and Acinetobacter constituted less than 5% of all bacteria. In situ, Proteobacteria belonging to the beta subclass and high G+C Gram-positive bacteria were dominant. From filamentous bacteria, Sphaerotilus spp. and Leptothrix spp. could be detected occasionally. In addition, one sample contained a high proportion of the morphologically distinct filaments of Microthrix parvicella.

UDP-glucose is a potential intracellular signal molecule in the control of expression of sigma S and sigma S-dependent genes in Escherichia coli.

The sigma S subunit of RNA polymerase is the master regulator of a regulatory network that controls stationary-phase induction as well as osmotic regulation of many genes in Escherichia coli. In an attempt to identify additional regulatory components in this network, we have isolated Tn10 insertion mutations that in trans alter the expression of osmY and other sigma S-dependent genes. One of these mutations conferred glucose sensitivity and was localized in pgi (encoding phosphoglucose isomerase). pgi::Tn10 strains exhibit increased basal levels of expression of osmY and otsBA in exponentially growing cells and reduced osmotic inducibility of these genes. A similar phenotype was also observed for pgm and galU mutants, which are deficient in phosphoglucomutase and UDP-glucose pyrophosphorylase, respectively. This indicates that the observed effects on gene expression are related to the lack of UDP-glucose (or a derivative thereof), which is common to all three mutants. Mutants deficient in UDP-galactose epimerase (galE mutants) and trehalose-6-phosphate synthase (otsA mutants) do not exhibit such an effect on gene expression, and an mdoA mutant that is deficient in the first step of the synthesis of membrane-derived oligosaccharides, shows only a partial increase in the expression of osmY. We therefore propose that the cellular content of UDP-glucose serves as an internal signal that controls expression of osmY and other sigma S-dependent genes. In addition, we demonstrate that pgi, pgm, and galU mutants contain increased levels of sigma S during steady-state growth, indicating that UDP-glucose interferes with the expression of sigma S itself.