Physio-Morphological Changes in a Riboflavin Producer Eremothecium ashbyii DT1 and UV Mutants in Submerged Fermentation

Venugopal, Pujari,Chandra, T. S. 한국미생물 · 생명공학회 2001 Journal of microbiology and biotechnology Vol.11 No.4

By UV-irradiation of Eremothecium ashbyii DTl, a highly flavinogenic mutant (UV-18-57) and a nonflavinogenic mutant (UV-85) were obtained. The physio-morphological characteristics of these three strains were studied on glucose medium in submerged fermentation. Glucose utilization and mycelial growth occurred in 0-2 days of fermentation. By the third day, the biomass had declined. Extracellular riboflavin excretion was distinct from the second day, reaching a maximum rate by the fourth day. The hyphae of the highly flavinogenic mutant UV-18-57 were broader than DTI, while the nonflavinogenic UV-85 hyphae were very thin. Riboflavin accumulation was high in UV-18-57 (extracellular riboflavin, 825㎍/ml, and intracellular, 490㎍/ml) and caused the mycelia to swell into bulbous forms. Riboflavin accumulation was less in DTI (108㎍/ml extracellular and 24㎍/ml intracellular) and correspondingly its hyphae were thinner than those of UV-18-57 and swollen bulbous mycelia were not prominent. UV-85 was nonflavinogenic and, accordingly, its morphological characteristics included long thin filaments with no intracellular riboflavin accumulation. A large number of greenish fluorescence spores were seen in UV-18-57, whereas DTI had less spores and UV-85 was nonsporulating. Sporulation is correlated with riboflavin production. UV- 18-57 had better mycelial integrity and lysis started only by the seventh day, whereas DTI and UV-85 started to lyze earlier by 4-5 days. By the late stage of fermentation (eighth day), DT1 had a few long, thin filaments indicating some secondary growth, whereas UV-85 showed a compact pellet form of mycelia. Most mycelia of UV-18-57 still appeared intact.

Peripheral Blood As a Source of Stem Cells for Regenerative Medicine: Emphasis Towards Corneal Epithelial Reconstruction—An In Vitro Study

Venugopal Balu,Mohan Sumitha,Kumary T. V.,Anil Kumar P. R. 한국조직공학과 재생의학회 2020 조직공학과 재생의학 Vol.17 No.4

Background: Mesenchymal stem cell-based treatments are now emerging as a therapy for corneal epithelial damage. Although bone marrow, adipose tissue and umbilical cord blood are the main sources of mesenchymal stem cells (MSCs), other tissues like the peripheral blood also harbor mesenchymal-like stem cells called peripheral blood-derived mononuclear cells (PBMNCs). These blood derived stem cells gained a lot of attention due to its minimally invasive collection and ease of isolation. In this study, the feasibility of using PBMNCs as an alternative cell source to corneal limbal stem cells envisaging corneal epithelial regeneration was evaluated. Methods: Rabbit PBMNCs were isolated using density gradient centrifugation and was evaluated for mesenchymal cell properties including stemness. PBMNCs were differentiated to corneal epithelial lineage using rabbit limbal explant conditioned media and was evaluated by immuno-cytochemistry and gene expression analysis. Further, the differentiated PBMNCs were engineered into a cell sheet using an in-house developed thermo-responsive polymer. Results: These blood derived cells were demonstrated to have similar properties to mesenchymal stem cells. Corneal epithelial lineage commitment of PBMNCs was confirmed by the positive expression of CK3/12 marker thereby demonstrating the aptness as an alternative to limbal stem cells. These differentiated cells effectively generated an in vitro cell sheet that was then demonstrated for cell sheet transfer on an ex vivo excised rabbit eye. Conclusion: PBMNCs as an alternative autologous cell source for limbal stem cells is envisaged as an effective therapeutic strategy for corneal surface reconstruction especially for patients with bilateral limbal stem cell deficiency.

Investigation of transfer characteristics of high performance graphene flakes.

Venugopal, Gunasekaran,Krishnamoorthy, Karthikeyan,Kim, Sang-Jae American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.5

<P>In this article, we attempted a study on field effect transport characteristics of graphene flakes. These graphene flakes were exfoliated by mechanical peeling-off technique and the electrical contacts were patterned by photo-lithographic method. Graphene devices have shown better transfer characteristics which was obtained even in low-voltage (< 5 V). Back-gated graphene transistors were patterned on oxidized silicon wafers. A clear n-type to p-type transition at Dirac point and higher electron drain-current modulation in positive back-gate field with current minimum (the Dirac point) were observed at V(GS) = -1.7 V. The carrier mobility was determined from the measured transconductance. The transconductance of the graphene transistors was observed as high as 18.6 microS with a channel length of 68 microm. A maximum electron mobility of 1870 +/- 143 cm2/V x s and hole mobility of 1050 +/- 35 cm2/V x s were achieved at a drain bias 2.1 V which are comparatively higher values among reported for mechanically exfoliated graphene using lithographic method. The fabricated devices also sustained with high-current density for 40 hr in continuous operation without any change in device resistance, which could be applied for robust wiring applications.</P>

Fabrication and Characteristics of Submicron Stacked-Junctions on Thin Graphite Flakes

Venugopal, Gunasekaran,Kim, Sang-Jae American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.2

<P>We report on the fabrication and transport characteristics of submicron-size stacks along c-axis of thin graphite flakes. The stacks were fabricated using a three-dimensional focused-ion-beam (FIB) etching technique. The stack with in-plane area A of 0.5 microm2 showed nonlinear concave-like I-V characteristics even at 300 K; however the stack with A of > 0.5 microm2 were shown an ohmic-like I-V characteristic at 300 K for both low and high-current biasing. It turned into nonlinear characteristics when the temperature goes down. The in-plane area dependence of stack capacitance were discussed and the observed capacitance of stack with A of 0.5 microm2 is smaller than the capacitance of stack with A of 1 microm2 which causes the nonlinear I-V characteristics in stack with A of 0.5 microm2 even at 300 K.</P>

Self-assembled hollow mesoporous Co3O4 hybrid architectures: a facile synthesis and application in Li-ion batteries

Venugopal, N.,Lee, D. J.,Lee, Y.,Sun, Y. K. Royal Society of Chemistry 2013 Journal of materials chemistry. A, Materials for e Vol.1 No.42

Mechanically Relevant Anatomy of the Axis Vertebra and Its Relation to Hangman’s Fracture: An Illustrated Essay

Venugopal K. Menon 대한척추신경외과학회 2019 Neurospine Vol.16 No.2

patterns within the bone, and on that basis, to postulate its mechanism of injury, a literature review was conducted of the anatomy and biomechanics of Axis fractures. Two hypotheses have been presented: the internal gear hypothesis and the leaf spring hypothesis. Both are based on the trabecular anatomy of the vertebra and its load transmission patterns. The relationship of the Axis with Hangman’s injury is also discussed. According to the leaf spring hypothesis, the C2 pedicle corresponds to the shackle in the assembly and constitutes the weak link. The trabecular architecture of the Axis is such that the primary compression of the trabeculae is directed from the superior facet to the C2–3 endplate, with few trabeculae directed to the inferior facet. Along with the trabecular void in this area, this renders the isthmus vulnerable to trauma. The isthmus of the Axis is biomechanically susceptible to injury due to its unique anatomy in relation to the whole cervical spine and the internal load transmission patterns of the bone. The author suggests that in the flexion type of Hangman’s injury, the C1–2 posterior ligaments are disrupted and need to be addressed.

Fabrication of nanoscale three-dimensional graphite stacked-junctions by focused-ion-beam and observation of anomalous transport characteristics

Venugopal, Gunasekaran,Jung, Myung-Ho,Suemitsu, Maki,Kim, Sang-Jae Elsevier 2011 Carbon Vol.49 No.8

<P><B>Abstract</B></P><P>We report on the fabrication and transport characteristics of nanoscale stacked-junctions of thin graphite flake. The stacked-junctions were fabricated using a three-dimensional focused-ion-beam milling. By varying the effective in-plane area down to submicron scale, the stacked-junctions with in-plane area <I>A</I> (from 2 down to 0.25μm<SUP>2</SUP>) and stack height–length (from 300 to 100nm) along <I>c</I>-axis were fabricated. The nano-stack shows perfect <I>c</I>-axis transport characteristics in which we observed a semiconducting behavior for <I>T</I>>65K and metallic behavior for <I>T</I><65K. The obtained results were well fitted with the <I>c</I>-axis electrical conduction mechanism. The stack with in-plane area <I>A</I> of 0.25μm<SUP>2</SUP> showed nonlinear concave-like <I>I</I>–<I>V</I> characteristics even at 300K; however the stack with <I>A⩾</I>1μm<SUP>2</SUP> were shown an ohmic-like <I>I</I>–<I>V</I> characteristic at 300K for both low and high-current biasing. It turned into nonlinear characteristics when the temperature goes down. The observation of this anomalous transport characteristics were discussed in detail with stack capacitance calculations. The nonlinear characteristics observed at 300K for the stack with <I>A</I> of 0.25μm<SUP>2</SUP> were shown best fit with Fowler–Nordheim tunneling model.</P>

Comparative Effects of Curcumin and Its Analog on Alcohol- and Polyunsaturated Fatty Acid-Induced Alterations in Circulatory Lipid Profiles

Venugopal P. Menon,Kode Aruna,Penumathsa Suresh Varma,Kallikat Narayanan Rajasekaran,Rajagopalan Rukkumani 한국식품영양과학회 2005 Journal of medicinal food Vol.8 No.2

Excessive alcohol intake induces hyperlipidemia. Studies suggest that natural principles and their analogs are known to possess anti-hyperlipidemic properties. In the present work we tested the effect of curcumin, an active principle of turmeric (Curcuma longa), and a curcumin analog on alcohol- and thermally oxidized polyunsaturated fatty acid (PUFA)- induced hyperlipidemia. Male albino Wistar rats were used for the experimental study. Anti-hyperlipidemic activity of curcumin and curcumin analog was evaluated by analyzing the levels of cholesterol, triglycerides (TGs), phospholipids (PLs), and free fatty acids (FFAs). The results showed that the levels of cholesterol, TGs, PLs, and FFAs were increased significantly in alcohol-, PUFA-, and alcohol PUFA-treated groups, which were brought down significantly on treatment with either of the curcuminoids. Curcumin analog treatment was found to be more effective than curcumin treatment. From the results obtained, we conclude that both curcumin and its analog effectively protect the system against alcohol- and PUFA-induced hyperlipidemia and are possible candidates for the treatment of hyperlipidemia.

Effect of Photo-Irradiated Curcumin Treatment Against Oxidative Stress in Streptozotocin-Induced Diabetic Rats

Venugopal P. Menon,M. Sri Balasubashini,T. Mahesh 한국식품영양과학회 2005 Journal of medicinal food Vol.8 No.2

Increasing evidence in both experimental and clinical studies suggests that oxidative stress plays a major rolein the pathogenesis of diabetes mellitus. Although phenolic compounds attenuate oxidative stress-related damage, there areconcerns over toxicity of synthetic phenolic antioxidants, and this has considerably stimulated interest in investigating the roleof natural phenolics in medicinal application. In the present study, we examined the effect of photo-irradiated curcumin inexperimental diabetes to evaluate the anti-hyperglycemic properties of this compound on streptozotocin (40 mg/kg of bodyweight)-induced diabetes. Photo-irradiated curcumin was given at a dose of 10 or 30 mg/kg of body weight. The level ofblood glucose was elevated in diabetic animals. Circulatory lipid peroxidation, vitamin C, vitamin E, and enzymic antioxi-dants such as superoxide dismutase and catalase were analyzed. The antioxidant status decreased in diabetic animals. Oral ad-ministration of photo-irradiated curcumin for 45 days resulted in a significant decrease in the levels of blood glucose alongwith near-normalization of the enzymic activities and the levels of lipid peroxidative markers. The most effective results wereobtained on treatment with 30 mg/kg of body weight of photo-irradiated curcumin.

Modulatory Effects of Curcumin and Curcumin Analog on Circulatory Lipid Profiles During Nicotine-Induced Toxicity in Wistar Rats

Venugopal P. Menon,K.N. Rajasekharan,C. Kalpana 한국식품영양과학회 2005 Journal of medicinal food Vol.8 No.2

Nicotine, a major toxic component of cigarette smoke, plays a key role in the development of cardiovascular disease and lung cancer. In the present study, we have synthesized an analog of curcumin and biomonitored its influence over biochemical marker enzymes and lipid profiles on nicotine-induced toxicity in Wistar rats. The effects were compared with that of curcumin, a well-known antioxidant and anti-hyperlipidemic agent. Toxicity was induced by subcutaneous injection of nicotine at a dose of 2.5 mg/kg of body weight (5 days a week, for 22 weeks), and curcumin (80 mg/kg) was given simultaneously along with nicotine by intragastric intubation for 22 weeks. Measurements of activities of the biochemical marker enzymes aspartate transaminase, alanine transaminase, alkaline phosphatase, and lactate dehydrogenase and of plasma lipid profiles were used to monitor the anti-hyperlipidemic effects of curcuminoids. In nicotine-treated rats, enhanced plasma marker enzymes and lipid profiles were observed. Administration of curcumin or curcumin analog to nicotine-treated rats significantly reduced the activity of marker enzymes and plasma lipid levels. Thus, our findings suggest that curcumin and its analog exert an anti-hyperlipidemic effect against nicotine-induced lung toxicity and may be a promising agent for treatment of hyperlipidemia and atherosclerosis