Differential food utilization of benthic amphipods of a tropical estuary: a stable isotopic (δ13C and δ15N) investigation

Globally, stable isotopic methods are rapidly being employed in food web studies to quantify the relative proportions of diverse primary carbon sources in an animal diet. Tropical estuarine ecosystems, one of the vital marine habitats, harbor complex food webs due to the multiplicity of habitats and resources. The complex system of inputs and exchanges of organic matter sometimes complicate identification of the carbon sources that support the higher trophic levels. To assess the primary food sources of four abundant amphipod species in the anthropogenically influenced upper Vashishti estuary, Carbon and Nitrogen stable isotopes were employed. Seasonal variations were significant for δ13C and δ15N of suspended particulate organic matter (SPOM) and also for δ13C of sediment organic matter (SOM), but not for the isotopic values of individual amphipod species. Significant variations in the δ13C and δ15N values between amphipods suggested species-specific diets. Mixing model output indicated discrepancies in seasonal variations of food preferences between species. Trophic level values of all amphipod species indicated seasonality with lower values during post-monsoon. The low δ15N values of SPOM, SOM, and amphipod species were possibly due to the anthropogenic input of nitrogen in the estuary.

Refractive outcomes following yttrium aluminum garnet laser (532 nm green laser) in severe retinopathy of prematurity

PURPOSE

To assess the refractive outcomes in eyes with severe Retinopathy of prematurity (ROP) after treatment with the frequency-doubled neodymium-doped yttrium aluminum garnet (Nd-YAG) laser 532 nm (green laser) at 1-2 years of age and compare with eyes that underwent spontaneous regression of ROP and to identify the risk factors associated with the refractive outcomes in laser-treated eyes with severe ROP.

METHODOLOGY

Infants who underwent laser treatment with green laser were enrolled in Group 1 and those who had spontaneous regression of ROP were enrolled in Group 2. All these children underwent a visual assessment, refraction using 1% cyclopentolate eye drops and indirect ophthalmoscopy at 1-2 years of age. Data regarding the gestational age, sex, birth weight, inborn (born in our institution) or outborn (born outside and referred to us), stage and zone of ROP and laser spots given were obtained from the treatment records. Data were analyzed using SSPS 19.0 software for Windows (SSPS Inc., Chicago, Illinois, USA).

RESULTS

A total of 102 infants were enrolled, 51 in each group. Visual acuity ranged from 0.25-1 cycles per cm in both groups. Spherical equivalent (SE) ranged from - 8.25 D to + 5.50 D in Group 1 and -1.00D to +4.00D in Group 2. Group 1 had an incidence of 23.5% Myopia and 33.4% Astigmatism which was significantly more than Group 2. The linear regression model predicted a decrease in the SE by 0.658D if the number of laser spots increased by 1000 (P < 0.001). No other risk factors (gestational age/birth weight) were found to have a significant association with refractive errors in the lasered ROP group.

CONCLUSIONS

Eyes with laser-treated severe ROP are frequently associated with myopia and astigmatism when compared to spontaneously regressed ROP. The number of laser spots delivered has a direct association with the amount of refractive error.

Assessment of circulating fibrotic proteins (periostin and tenascin -C) In Type 2 diabetes mellitus patients with and without retinopathy

PURPOSE

Diabetic retinopathy is a leading cause of vision impairment. Surging diabetic population and poor visual care raises the need for better diagnostic tools. Hence, it is worthwhile to look for biomarkers associated with the disease pathogenesis. Periostin and tenascin-C are matricellular proteins mediating fibrillogenesis in retinopathy. Their serum levels and association with the presence and severity of retinopathy in diabetics is of importance to be explored.

METHODS

The study involved two groups of type 2 diabetes patients, 38 controls without retinopathy and 38 cases with retinopathy. We obtained serum sample and performed biochemical autoanalysis for routine parameters. Special parameters periostin, tenascin-C, and C-peptide were estimated by ELISA.

RESULTS

Periostin and tenascin-C were significantly elevated in the retinopathy group. Periostin progressively increased among subgroups. C-peptide decreased significantly in retinopathy group and had a negative correlation with duration of DM, duration of retinopathy, HbA1c and tenascin-C. We observed a positive correlation for periostin and tenascin-C with duration of diabetes. The AUC for C-peptide was the highest (0.750) amongst our parameters. HOMA 2 (%B) index was significantly lower in retinopathy group.

CONCLUSIONS

Serum Levels of PO and TnC increased in retinopathy. As the disease advances, periostin level increases, indicating continuing fibrosis and fibrovascular membrane formation. Periostin and tenascin-C increase with duration of retinopathy whereas levels of C-peptide decrease. C-peptide has a better differentiating potential for DR from DM. Reduced insulin production as indicated by declined HOMA 2-%BETA in retinopathy favors hyperglycemia and chronic inflammatory state for the disease progression.

Association of serum omentin-1, apelin and chemerin concentrations with the presence and severity of diabetic retinopathy in type 2 diabetes mellitus patients

Omentin-1 is a novel adipokine with anti-inflammatory functions. Apelin is associated with hyperinsulinemia and pathological angiogenesis. Chemerin has both pro- and anti-inflammatory actions and implicated in insulin resistance and metabolic syndrome. The aim of this study was to assess serum omentin-1, apelin and chemerin concentrations and to investigate their association with the presence and severity of DR in T2DM patients. Serum omentin-1, apelin and chemerin were measured in 112 patients with DR and 56 patients without DR. Bivariate analysis showed omentin-1 correlated negatively with hsCRP and TyG index; while apelin correlated positively with chemerin. Linear regression data showed that apelin and chemerin were independent predictors of DR severity. ROC curve revealed that omentin-1 was the best discriminant for DR while apelin was the best discriminant for vision threatening retinopathy. Serum omentin-1 concentration correlates negatively, while serum apelin and chemerin concentrations correlate positively with DR presence and severity in T2DM patients.

Efficacy of Mobile Phone Technology for Managing Side Effects Associated with Chemotherapy among Cancer Patients: A Systematic Review and Meta-Analysis

Background To establish the evidence related to the efficacy of mobile phone technology for managing side effects of chemotherapy and improved quality of life among patients with cancer.

Methods Articles published in peer-reviewed journals were included in this review. Randomized control trials (RCTs) and non-randomized control trials (non-RCTs) consisting of mobile-based interventions (mobile application, smart phone App-based interventions or guidelines to manage side-effects of chemotherapy or mobile health services), and adult cancer patients (aged 18 or above years) as participants who were undergoing chemotherapy and received mobile phone-based interventions as an interventional group versus control/comparator group who were getting routine or usual care were included in this systematic review. Databases such as Scopus, Science Direct, Cochrane library, PubMed, and Google Scholar were systematically searched between 2007 and 2020. Using the Cochrane risk of bias tool, the methodological quality of the included studies was evaluated by two independent authors.

Results We included 10 trials, involving 1467 cancer patients and the number of participants ranged from 50 to 457. All trials measured the side effects of chemotherapy as the main outcome and three trials measured the quality of life as the main outcome.

Ten trials included for narrative synthesis showed a significant decrease in chemotherapy side effects and considerable improvement in the quality of life in the interventional group than in the comparison group. Meta-analysis of four RCTs containing 803 subjects concluded a significant improvement (p < 0.0001) in the quality of life.

A significant improvement in the quality of life was revealed by random effects model (SMD = 0.31, 95% CI: 0.17, −0.46) and a significant difference (Z = 4.37, p < 0.001) was identified between experimental and control groups.

Conclusion Current review strengthens the evidence that utilizing mobile-phone based technology has favorable effects on improving the quality of life by minimizing side-effects associated with chemotherapy among cancer patients.

Burkholderia cenocepacia keratitis

Case report: A 33-year-old lady with history of failed keratoplasty for decompensated cornea due to childhood trauma and secondary glaucoma, post glaucoma drainage implant, with pseudophakia in the right eye, developed bacterial keratitis following foreign body trauma to corneal graft. Corneal cultures yielded Burkholderia cenocepacia identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF- MS, bioMerieux, France). She healed with topical antibiotics (moxifloxacin 0.5%) in 1 month. Ours is the first report of ocular Burkholderia cenocepacia infection, possibly an under reported, aerobic, organism.

Circulating adropin and vascular endothelial growth factor receptor-2 levels in age-related macular degeneration and T2DM patients-A cross-sectional study

Background:

Macular drusen formation and angiogenesis are the two chief processes associated with age-related macular degeneration. Adropin and vascular endothelial growth factor receptor-2 (VEGFR-2) may be involved in these pathologies. By altering lipid metabolism, adropin may contribute in the early stages of age-related macular degeneration (AMD). VEGFR-2 may participate in the later form of AMD, by promoting angiogenesis. This study compared the circulatory levels of adropin and VEGFR-2 in AMD and patients without AMD and assessed their association with disease severity, to understand their possible role in AMD.

Objectives:

This study aimed to assess and compare the serum levels of adropin and VEGFR-2 in patients with AMD and type 2 diabetes patients without AMD, and, to investigate the correlation between these two parameters with disease severity.

Methods:

Our study involves two groups of 39 each. Group A (age-related macular degeneration) and Group B (diabetes patients without age-related macular degeneration). Routine parameters fasting blood sugar (FBS), lipid profile, and liver function tests (LFT) were estimated by using autoanalyzer. Serum adropin and VEGFR-2 were assessed by ELISA.

Results:

Among the basic parameters, systolic blood pressure and fasting blood glucose alone were significantly different across the groups. We did not find significant alterations in adropin and VEGFR-2 levels between the study groups. Our lipid profile parameters (triglycerides and total cholesterol) have significant positive association. VEGFR-2 showed a positive correlation with the severity of AMD. Adropin did not exhibit any correlation with disease severity and with VEGFR-2.

Conclusion:

We could not find any observable alterations of statistical significance, in adropin and VEGFR-2 levels. VEGFR-2's correlation with disease severity could be important. Adropin might have subtler roles in AMD, though not evident from our study, and requires a deeper observation at the molecular level to elucidate its function.

Gd2Te3: an antiferromagnetic semimetal

We report high-precision magnetization ([Formula: see text]), magnetic susceptibility ([Formula: see text]), specific heat (C _p(T, H)) and 'zero-field' electrical resistivity, [Formula: see text], data taken on Gd₂Te₃ single crystal over wide ranges of temperature and magnetic field (H), with either [Formula: see text]-axis or [Formula: see text]-plane. [Formula: see text] and [Formula: see text] unambiguously establish that the b-axis is the easy direction of magnetization whereas any direction in the ac-plane is a hard direction. The [Formula: see text]-type anomaly in 'zero-field' specific heat, C _p(T, H  =  0), and an abrupt drop in [Formula: see text] (characteristic of the paramagnetic (PM) - antiferromagnetic (AFM) phase transition) are observed at the Néel temperature, [Formula: see text] K. [Formula: see text] and C _p(T,H) clearly demonstrate that [Formula: see text] shifts to lower temperatures with increasing H irrespective of whether H points in the easy or hard direction. When [Formula: see text], the [Formula: see text] isotherms at temperatures in the range 2.5 K [Formula: see text] [Formula: see text] K reveal the existence of a field-induced spin-flop (SF) transition at fields 4.0 T [Formula: see text] [Formula: see text] [Formula: see text] 4.5 T. The first principles electronic band structure and density of states calculations, based on the density functional theory, correctly predict an AFM ground state (stabilized primarily by the 4f  Gd³⁺ - 5p  Te^2-- 4f  Gd³⁺ superexchange interactions) and the observed semi-metallic behavior for the Gd₂Te₃ compound. Moreover, these calculations yield the values [Formula: see text] [Formula: see text] for the ordered magnetic moment per Gd atom at T  =  0, [Formula: see text] mJ mol^-1 K^-2 for the Sommerfeld coefficient for the electronic specific heat contribution and [Formula: see text] K for the Curie-Weiss temperature, respectively. These theoretical estimates conform well with the corresponding experimental values [Formula: see text] [Formula: see text], [Formula: see text] mJ mol^-1 K^-2 and [Formula: see text] K.

Risk factors for endothelial cell damage in diabetics after phacoemulsification

BACKGROUND

To assess the corneal endothelium, central corneal thickness and the factors associated with endothelial cell damage after phacoemulsification in diabetics in comparison with non-diabetics.

METHODS

It was a case control study with 80 eyes each in the diabetic group and the control group. Intraoperative mydriasis, effective phaco time (EPT) and postoperative inflammation were measured. Preoperative, 1^st week, 6^th week and 3^rd month postoperative endothelial cell density (ECD), coefficient of variation (CV), hexagonality and central corneal thickness (CCT) were also measured using Konan noncon robo specular microscope (Model - NSP 9900).

RESULTS

In the control group, patients in the age group of 60-69 years were 3.8 times more at risk of ECL compared to patients in the age group of 50-59 years. Patients in whom EPT was ≥0.50 min, were 8.8 times more at risk of ECL when compared to patients in whom EPT <0.25 min. In the diabetic group, patients who had an inflammatory score of 1+ in the first postoperative week; also had 5.7 times more risk of ECL when compared to patients in whom the inflammatory score was 0.5+ in the first postoperative week. There was a significant increase in CV (p-0.03) and CCT (p-0.03), significant decrease in the hexagonality (p-0.01) and no statistically significant difference in the endothelial cell loss (ECL) (p-0.34) in diabetics after phacoemulsification when compared to controls.

CONCLUSION

The present study reveals postoperative inflammation as a risk factor for ECL in diabetics and not intraoperative mydriasis and EPT.

Circulating matrix modulators (MMP-9 and TIMP-1) and their association with severity of diabetic retinopathy

AIMS

Diabetic Retinopathy (DR) is the leading cause of vision loss in the working age population. Matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1), are molecules involved in extracellular tissue matrix remodelling. They are implicated in the loss of retinal tissue integrity, a major cause of DR, that leads to retinal tissue degradation and apoptosis. This study is therefore, conducted to compare the serum levels of MMP-9 and TIMP-1 in T2DM patients without and with retinopathy, and to evaluate their association with the severity of DR.

MATERIALS AND METHODS

Our study comprised of 2 groups of 41 each. Group A (cases) included T2DM patients with retinopathy and Group B (controls) included T2DM patients without retinopathy. Routine parameters, mainly, fasting blood glucose, and lipid profile were measured using autoanalyzer. Serum MMP-9, TIMP-1, and insulin levels were assessed using ELISA method.

RESULTS AND CONCLUSION

Statistically significant increase in the levels of MMP-9, insulin, fasting blood glucose and lipid profile were observed in the serum of T2DM patients with retinopathy, as compared with those without retinopathy. These results help to conclude that rise in MMP-9, and associated serum markers promote disease progress in DR. These findings suggest that the elevations of our study markers in the serum of the type 2 diabetic patients with retinopathy, as compared to those without retinopathy, play important roles in aggravating tissue matrix degradation, supporting DR disease progression.

Sequential development of non-arteritic anterior ischemic optic neuropathy in a patient on hemodialysis

Purpose: Non-arteritic anterior ischemic optic neuropathy (NA-AION) is typically a disorder of patients 50 years and older predisposed to the vascular and structural optic disc risk factors. We present an interesting case of sequential development of NA-AION in a 45-year-old patient with end-stage renal disease undergoing hemodialysis.

Methods: Observational case report.

Results: A 45-year-old female on hemodialysis for chronic renal failure complained of sequential acute onset sudden painless gross diminution of vision in right eye followed by the left eye. At presentation, fundus examination revealed secondary optic atrophy and a pallid disc edema with few hemorrhage in the right and left eye, respectively. Ambulatory blood pressure recorded nocturnal dips of diastolic blood pressure. Fundus fluorescein angiography showed hypoperfusion of the left optic disc, confirming the diagnosis of NA-AION. She was treated with oral steroids, but with no improvement.

Conclusion: Both treating nephrologist and ophthalmologist should be aware of this uncommon but potentially blinding complication, to permit its early recognition and prevent the occurrence in the fellow eye. Also, care should be taken to prevent and treat any hypotensive episodes during and following dialysis therapy in such high-risk patients.

Epidemiological and diagnostic studies of microfilariasis in buffaloes

A study was conducted to determine the prevalence of microfilariasis and analysis of diagnostic methods in buffaloes at Veterinary Poly Clinic, Gudiwada with relation to season, age and breed for a period of 1 year (March 2011-February 2012).Out of 1,222 blood smears examination, only 123 samples were found positive for microfilariasis with a prevalence rate of 10.06 %. Highest prevalence was observed in monsoon (12.54 %) followed by summer (9.18 %) and least in winter (7.05 %). Buffaloes above 9 years age were at high risk with a prevalence rate of 12.5 %, followed by 3-9 years (10.7 %) and below 3 years age (6.09 %) respectively. Breed wise prevalence of microfilariasis was higher in graded murrah buffaloes 10.87 % compared to non-descripts (6.19 %). Three commonly used diagnostic techniques viz. Modified Knott's Technique, thick blood smear examination and wet film examination were done to evaluate comparative sensitivity/efficacy. Among these techniques, 100 % efficacy was observed in Modified Knott's Technique and 86.99 % in thick blood smear examination followed wet film examination 78.04 % respectively.

Awareness and practices on eye effects among people with diabetes in rural Tamil Nadu, India

BACKGROUND

Recently eye effects of Diabetes Mellitus (DM) are an important concern due to increase in its trend especially in developing countries.

OBJECTIVES

To assess the awareness related to eye effects of DM and its prevention practices among people with diabetes.

METHODS

This cross sectional study was conducted from January 2013 to April 2013 in Villupuram district of Tamil Nadu, India. All 105 people with diabetes from the service area of two sub-centres were included. Data on socio demographic details, history of DM, awareness on systemic complications of DM, effects of DM on eyes, practice on regular blood check-up, eye examination and source of information were collected by interview technique using a structured questionnaire. Univariate and multiple logistic regression analysis were done to assess the association of awareness of eye examination with socio-demographic variables.

RESULTS

Mean age of the study population was 56.7 years. About 93 people with diabetes (88.6%) tested their blood sugar at least once in every 3 months. About 80 people with diabetes (76.2%) were aware of at least one systemic complication of DM. Although 78 (74.3%) people with diabetes were aware that DM could affect the eyes, majority of this group (68, 87.2%) did not know the specific effects of DM on eyes. In this group, about 28(35.9%) people with diabetes were not aware of the reasons for eye effects, while others mentioned that persistent high blood sugar level (n=26, 33.3%), longer duration of DM (n=14, 17.9%) and lifestyle (n=10, 12.8%) were the reasons for the eye effects of DM. Only 31 (29.5%) of them knew that their eyes must be regularly examined. People with diabetes who had post-secondary and above (>10th standard) level of education had significantly higher awareness on examination of eye (Adjusted OR=19.63).

CONCLUSION

Although awareness of people with diabetes on systemic effects of DM was more, their awareness on specific eye effects and need for regular screening was low. Systematic efforts are required to increase awareness on eye effects and importance of regular screening in this population.

Density functional study of electronic structure, elastic and optical properties of MNH2 (M=Li, Na, K, Rb)

We report a systematic first principles density functional study on the electronic structure, elastic and optical properties of nitrogen based solid hydrogen storage materials LiNH2, NaNH2, KNH2, and RbNH2. The ground state structural properties are calculated by using standard density functional theory, and also dispersion corrected density functional theory. We find that van der Waals interactions are dominant in LiNH2 whereas they are relatively weak in other alkali metal amides. The calculated elastic constants show that all the compounds are mechanically stable and LiNH2 is found to be a stiffer material among the alkali metal amides. The melting temperatures are calculated and follow the order RbNH2 < KNH2 < NaNH2 < LiNH2. The electronic band structure is calculated by using the Tran–Blaha modified Becke–Johnson potential and found that all the compounds are insulators, with a considerable band gap. The [NH2]− derived states completely dominate in the entire valence band region while the metal atom states occupy the conduction band. The calculated band structure is used to analyze the different interband optical transitions occurring between valence and conduction bands. Our calculations show that these materials have considerable optical anisotropy.

Synthesis of oleic acid functionalized Fe3O4 magnetic nanoparticles and studying their interaction with tumor cells for potential hyperthermia applications

In the present study, oleic acid (OA) functionalized Fe3O4 magnetic nanoparticles (MN) were synthesized following modified wet method of MN synthesis. The optimum amount of OA required for capping of MN and the amount of bound and unbound/free OA was determined by thermogravimetric analysis (TGA). Further, we have studied the effect of water molecules, associated with MN, on the variation in their induction heating ability under alternating current (AC) magnetic field conditions. We have employed a new approach to achieve dispersion of OA functionalized MN (MN-OA) in aqueous medium using sodium carbonate, which improves their biological applicability. Interactions amongst MN, OA and sodium carbonate were studied by Fourier transform infrared spectroscopy (FT-IR). Intracellular localization of MN-OA was studied in mouse fibrosarcoma cells (WEHI-164) by prussian blue staining and confocal laser scanning microscopy (CLSM) using nile blue A as a fluorescent probe. Results showed MN-OA to be interacting mainly with the cell membrane. Their hyperthermic killing ability was evaluated in WEHI-164 cells by trypan blue method. Cells treated with MN-OA in combination with induction heating showed decreased viability as compared to respective induction heating controls. These results were supported by altered cellular morphology after treatment of MN-OA in combination with induction heating. Further, the magnitude of apoptosis was found to be ~5 folds higher in cells treated with MN-OA in combination with induction heating as compared to untreated control. These results suggest the efficacy of MN-OA in killing of tumor cells by cellular hyperthermia.

Clear lens extraction in Alport syndrome with combined anterior and posterior lenticonus or ruptured anterior lens capsule

We describe the results of clear lens extraction in 7 eyes of 4 Alport-syndrome patients. Three patients (6 eyes) had both anterior and posterior lenticonus; the fourth patient had spontaneous rupture of the anterior lens capsule, resulting in an acute drop in vision. Clear lens extraction was an effective method for visual rehabilitation in Alport syndrome patients.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Primary stromal iris cysts treated successfully with ab externo laser Nd:YAG photocoagulation

Two boys presented with primary solitary stromal iris cyst in the inferior quadrant. Both patients were treated with Nd:YAG laser puncturing the cyst wall. The cyst wall collapsed and fluid leaked out in the anterior chamber. No complication was noted. The cyst recurred in the first child at 2 months of follow-up and was re-treated with laser. There was no further recurrence after 12 months of follow-up in case 1 or after 10 months of follow-up in case 2. To the authors' knowledge, this is the first documented report of Nd:YAG treatment of primary stromal cyst.

Comparison of the clinical presentation and visual outcome in open globe injuries in adults and children over 30 months

PURPOSE

To compare the clinical presentation and final visual outcome of open globe injuries in children and adults in a referral hospital over a 30-month period.

METHODS

This is an institutional-based prospective study of open globe injuries cases presenting in the emergency department between July 2003 and December 2005. Patients were divided in 2 groups: group 1, children (2-15 years), and group 2, adults (>15 years). All the patients were admitted and emergency surgical interventions were undertaken. The clinical features at presentation and the final visual acuity are compared. Chi-square and Fisher exact tests were used for statistical analysis.

RESULTS

Ninety and 84 patients were included in group 1 and group 2, respectively. The most common places of injuries were home or while playing outdoor games in group 1 (67%) and workplace in group 2 (53.5%). The presenting features were significantly more grave in group 2. These included poor presenting visual acuity (p=0.012), vitreous prolapse (p=0.002), presence of relative afferent pupillary defect (p=0.001), and incidence of endophthalmitis (p=0.004). Time interval between injury and surgical intervention (p=0.018) was better in group 2. Other features, such as presence of hyphema, uveal tissue prolapse, cataract, intraocular foreign body, and length or location of laceration were similar in both groups. The final visual outcome was similar in the groups (p = 0.21), with approximately half of the patients achieving vision of 20/60 or better in each group.

CONCLUSIONS

The majority of injuries in children and adults occurred in their homes or workplaces, respectively. Although the clinical presentations of open globe injuries were significantly more grave in adults than in children, the final visual outcomes were similar.

Lenz microphthalmic syndrome in an Indian patient

A case of Lenz microphthalmia syndrome in a seven-month-old male child having features of unilateral anophthalmia, microcephaly, external ear and finger abnormalities, hydrocele and hypospadias is being reported. The unilateral involvement and anophthalmia is rare in Lenz syndrome. The manifestation of hydrocele in association with this syndrome has not been seen in earlier cases. This is the first documented case from India.

Regulation of phototransduction in short-wavelength cone visual pigments via the retinylidene Schiff base counterion

Short-wavelength visual pigments (SWS1) have lambda(max) values that range from the ultraviolet to the blue. Like all visual pigments, this class has an 11-cis-retinal chromophore attached through a Schiff base linkage to a lysine residue of opsin apoprotein. We have characterized a series of site-specific mutants at a conserved acidic residue in transmembrane helix 3 in the Xenopus short-wavelength sensitive cone opsin (VCOP, lambda(max) approximately 427 nm). We report the identification of D108 as the counterion to the protonated retinylidene Schiff base. This residue regulates the pK(a) of the Schiff base and, neutralizing this charge, converts the violet sensitive pigment into one that absorbs maximally in the ultraviolet region. Changes to this position cause the pigment to exhibit two chromophore absorbance bands, a major band with a lambda(max) of approximately 352-372 nm and a minor, broad shoulder centered around 480 nm. The behavior of these two absorbance bands suggests that these represent unprotonated and protonated Schiff base forms of the pigment. The D108A mutant does not activate bovine rod transducin in the dark but has a significantly prolonged lifetime of the active MetaII state. The data suggest that in short-wavelength sensitive cone visual pigments, the counterion is necessary for the characteristic rapid production and decay of the active MetaII state.

The photobleaching sequence of a short-wavelength visual pigment

The photobleaching pathway of a short-wavelength cone opsin purified in delipidated form (lambda(max) = 425 nm) is reported. The batho intermediate of the violet cone opsin generated at 45 K has an absorption maximum at 450 nm. The batho intermediate thermally decays to the lumi intermediate (lambda(max) = 435 nm) at 200 K. The lumi intermediate decays to the meta I (lambda(max) = 420 nm) and meta II (lambda(max) = 388 nm) intermediates at 258 and 263 K, respectively. The meta II intermediate decays to free retinal and opsin at >270 K. At 45, 75, and 140 K, the photochemical excitation of the violet cone opsin at 425 nm generates the batho intermediate at high concentrations under moderate illumination. The batho intermediate spectra, generated via decomposing the photostationary state spectra at 45 and 140 K, are identical and have properties typical of batho intermediates of other visual pigments. Extended illumination of the violet cone opsin at 75 K, however, generates a red-shifted photostationary state (relative to both the dark and the batho intermediates) that has as absorption maximum at approximately 470 nm, and thermally reverts to form the normal batho intermediate when warmed to 140 K. We conclude that this red-shifted photostationary state is a metastable state, characterized by a higher-energy protein conformation that allows relaxation of the all-trans chromophore into a more planar conformation. FTIR spectroscopy of violet cone opsin indicates conclusively that the chromophore is protonated. A similar transformation of the rhodopsin binding site generates a model for the VCOP binding site that predicts roughly 75% of the observed blue shift of the violet cone pigment relative to rhodopsin. MNDO-PSDCI calculations indicate that secondary interactions involving the binding site residues are as important as the first-order chromophore protein interactions in mediating the wavelength maximum.

The methanol-induced conformational transitions of beta-lactoglobulin, cytochrome c, and ubiquitin at low pH: a study by electrospray ionization mass spectrometry

The methanol-induced conformational transitions under acidic conditions for beta-lactoglobulin, cytochrome c, and ubiquitin, representing three different classes of proteins with beta-sheets, alpha-helices, and both alpha-helices and beta-sheets, respectively, are studied under equilibrium conditions by electrospray ionization mass spectrometry (ESI-MS). The folding states of proteins in solution are monitored by the charge state distributions that they produce during ESI and by hydrogen/deuterium (H/D) exchange followed by ESI-MS. The changes in charge state distributions are correlated with earlier studies by optical and other methods which have shown that, in methanol, these proteins form partially unfolded intermediates with induced alpha-helix structure. Intermediate states formed at about 35% methanol concentration are found to give bimodal charge state distributions. The same rate of H/D exchange is shown by the two contributions to the bimodal distributions. This suggests the intermediates are highly flexible and may consist of a mixture of two or more rapidly interconverting conformers. H/D exchange of proteins followed by ESI-MS shows that helical denatured states, populated at around 50% methanol concentration, transform into more protected structures with further increases in methanol concentration, consistent with previous circular dicroism studies. These more protected structures still produce high charge states in ESI, similar to those of the fully denatured proteins.

Methanol-induced conformations of myoglobin at pH 4.0

The equilibrium methanol-induced conformation changes of holomyoglobin (hMb) at pH 4.0 have been studied by circular dichroism, tryptophan fluorescence, and Soret band absorption and by electrospray ionization mass spectrometry (ESI-MS). Optical spectra show the following: (1) In 35-40% (v/v) methanol/water, the native-like secondary structure remains, the tertiary structure is lost, the heme protein interactions are decreased, and a folding intermediate is formed. (2) In 50% methanol, heme is lost from the protein, and there is a small decrease in helicity together with a loss of tertiary structure. (3) At >60% methanol, the helicity increases and the apoprotein goes into a helical denatured state. The conformations are also probed by the charge states produced in ESI-MS and by hydrogen/deuterium (H/D) exchange with mass measurement by ESI-MS. At 0-30% methanol, native hMb produces relatively low charge states (9(+)-13(+)) in ESI-MS and exchanges relatively few hydrogens. In 35-40% methanol, at which an intermediate is formed, there is a bimodal distribution of hMb ions with both low (9(+)-13(+)) and high (14(+)-23(+)) charge states and also a high charge state distribution (12(+)-26(+)) of apomyoglobin (aMb) ions. Low and high charge states of hMb and a high charge state of aMb all show the same H/D exchange rate, indicating that an unfolded hMb intermediate interconverts between folded hMb and unfolded aMb. The charge state distribution for the unfolded hMb intermediate observed here is similar to that of the recently reported transient intermediate formed during the acid denaturation of hMb. At 50% alcohol the protein produces predominantly high charge states of aMb ions and shows H/D exchange rates close to those of the acid-denatured protein. H/D exchange of the helical denatured protein at alcohol concentrations >60%, at which high charge states of aMb are produced, shows that the protein structure is more protected than at approximately 50% methanol.

Production of interferon-alpha in high cell density cultures of recombinant Escherichia coli and its single step purification from refolded inclusion body proteins

Escherichia coli TG1 transformed with a temperature-regulated interferon-alpha expression vector was grown to high cell density in defined medium containing glucose as the sole carbon and energy source, utilizing a simple fed-batch process. Feeding was carried out to achieve an exponential increase in biomass at growth rates which minimized acetate production. Thermal induction of such high cell density cultures resulted in the production of approximately 4 g interferon-alpha/l culture broth. Interferon-alpha was produced exclusively in the form of insoluble inclusion bodies and was solubilized under denaturing conditions, refolded in the presence of arginine and purified to near homogeneity, utilizing single-step ion-exchange chromatography on Q-Sepharose. The yield of purified interferon-alpha was approximately 300 mg/l with respect to the original high cell density culture broth (overall yield of approximately 7.5% active interferon-alpha). The purified recombinant interferon-alpha was found by different criteria to be predominantly monomeric and possessed a specific bioactivity of approximately 2.5 x 10(8) IU/mg based on viral cytopathic assay.

A single-step purification of assembled insulin on a resource RPC column

We have designed an efficient single step purification process using Resource RPC column in conjunction with triethyl amine/acetonitrile solvent system at similar pH at which the in vitro assembly of insulin is carried out from its two chains. The conditions have been optimized to separate native insulin from its single chain precursors as well as from other by-products. This method obviates the need of acidification, centrifugation, gel filtration, and concentration steps before HPLC purification of insulin from assembly mixture. The system offers wide pH stability, rapid regenerability, excellent pressure/flow characteristics, and high loading capacity. The authenticity and purity of human insulin purified by this procedure was evaluated by analytical reverse phase HPLC, peptide mapping, and isoelectric focusing.

Temperature-induced production of recombinant human insulin in high-cell density cultures of recombinant Escherichia coli

The construction of expression vectors encoding either the human insulin A- or B-chains fused to a synthetic peptide and the temperature-induced expression of the recombinant genes in Escherichia coli are reported. Using this two-chain approach we also describe the separate isolation of the insulin A- and B-chains from inclusion bodies and their subsequent assembly into native human insulin. The production of the insulin fusion proteins were carried out in high-cell density fed-batch cultures using a synthetic medium with glucose as sole carbon and energy source. The expression of the recombinant genes by temperature-shift in high-cell density cultures of recombinant E. coli resulted in product yields of grams per litre of culture broth, e.g. 4.5 g of insulin B-chain fusion protein per litre of culture broth. This translates into an expression yield of about 800 mg of the insulin B-chain per litre of culture. Under similar cultivation conditions the expression yield of the insulin A-chain corresponds to approximately 600 mg per litre of culture. The metabolic burden imposed on the recombinant cells during temperature-induced production of insulin fusion proteins in high-cell density cultures is reflected in an increased respiratory activity and a reduction of the biomass yield coefficient with respect to glucose.

Alkaline unfolding and salt-induced folding of bovine liver catalase at high pH

We have studied the alkaline unfolding of bovine liver catalase and its dependence on ionic strength by enzymic activity measurements and a combination of optical methods like circular dichroism, fluorescence and absorption spectroscopies. Under conditions of high pH (11.5) and low ionic strength, the native tetrameric enzyme dissociates into monomers with complete loss of enzymic activity and a significant loss of alpha-helical content. Increase in ionic strength by addition of salts like potassium chloride and sodium sulphate resulted in folding of alkaline-unfolded enzyme by association of monomers to tetramer but with significantly different structural properties compared to native enzyme. The salt-induced tetrameric intermediate is characterized by a significant exposure of the buried hydrophobic clusters and significantly reduced alpha-helical content compared to the native enzyme. The refolding/reconstitution studies showed that the salt-induced partially folded tetrameric intermediate shows significantly higher efficiency of refolding/reconstitution as compared to alkaline-denatured catalase in the absence of salts. These studies suggest that folding of multimeric enzymes proceeds probably through the hydrophobic collapse of partially folded multimeric intermediate with exposed hydrophobic clusters.

Physico-chemical characterization of grain dust in storage air of Bangalore

An Anderson personal cascade impactor was used to study the particle mass size distribution in the storage air of two major grain storage centers in Bangalore. Dust levels in storage air as well as the personal exposures of workers were determined along with a detailed study on the particle size distribution. Protein and carbohydrate content of the dust were also determined respectively in the phosphate buffer saline (PBS) and water extracts by using the standard analytical techniques. Personal exposures in both of the grain storage centers have been found to be much above the limit prescribed by ACGIH (1995-96). But the results of particle size analysis showed a higher particle mass distribution in the non-respirable size range. The mass median diameters (MMD) of the storage air particulate of both the centers were found to be beyond the respirable range. Presence of protein and carbohydrate in the storage air dust is indicative of the existence of glyco-proteins, mostly of membrane origin.

Ionic-strength-dependent transition of hen egg-white lysozyme at low pH to a compact state and its aggregation on thermal denaturation

Equilibrium acid-induced unfolding of hen egg-white lysozyme has been investigated by a combination of optical methods, size-exclusion chromatography, and differential scanning calorimetry. The results showed the presence of a partially folded state of hen egg-white lysozyme at pH 1.5, characterized by a substantial secondary structure, a large solvent exposure of non-polar clusters, and significantly disrupted tertiary structure. A large enthalpy was also associated with the conversion of the acid-unfolded state to a fully unfolded state. Size-exclusion chromatography and 8-anilino-1-naphthalenesulphonic acid-binding studies showed an ionic-strength-induced transition of the partially folded state to a compact conformation. Furthermore, an ionic-strength-dependent aggregation on thermal unfolding of the partially folded intermediate was also observed. These observations provide insights into the possible features responsible for the stabilization of intermediates in the folding of hen egg-white lysozyme.