Publications by authors named "Virendra K Tiwari"

Background: Standard neoadjuvant chemotherapy for locally advanced esophageal or gastroesophageal junction squamous cancer, 5-fluorouracil plus platinum, is toxic and logistically challenging; alternative regimens are needed.

Methods: This was a phase III randomized open-label noninferiority trial at Tata Memorial Center, India, in resectable locally advanced esophageal or gastroesophageal junction squamous cancer. Patients were randomly assigned 1:1 to 3 cycles of 3-weekly platinum (cisplatin 75 mg/m2 or carboplatin area under the curve 6) with paclitaxel 175 mg/m2 (day 1) or 5-fluorouracil 1000 mg/m2 continuous infusion (days 1-4), followed by surgery.

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The utilization of a radical robotic thymectomy, with clearance of the mediastinal tissue between the two phrenic nerves for a thymoma, is well established. The complex mediastinal anatomy, limited space and the location of the heart introduce a distinctive challenge, particularly when adopting a right-sided approach to identify and dissect along the left phrenic nerve. We present our technique for performing a robotic radical thymectomy from a right-sided approach, tailored for a localized thymoma.

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Article Synopsis
  • Enzymes like isocyanide hydratase (ICH) have complex structures that make it hard to study how they catalyze reactions, but researchers used advanced techniques to observe these processes in real-time.* -
  • The active site of ICH has various shapes, and during the reaction, the formation of specific intermediates helps stabilize the configurations necessary for catalysis.* -
  • The study shows that the ionization of a specific amino acid (aspartate) during the reaction triggers structural changes in the enzyme, influencing how it functions—this reveals how electrostatic interactions control enzyme behavior.*
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Purpose: Esophageal cancer is among the leading causes of cancer-related mortality worldwide. Patients presenting with localized and loco-regionally advanced cancer without distant metastases have reasonable survival with multimodality management. Adequate and comprehensive staging is the backbone for proper selection of patients fit for curative treatment.

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Purpose: Febrile neutropenia (FN) is a serious complication in hematologic malignancies, and lung infiltrates (LIs) remain a significant concern. An accurate microbiological diagnosis is crucial but difficult to establish. To address this, we analyzed the utility of a standardized method for performing bronchoalveolar lavage (BAL) along with a two-step strategy for the analysis of BAL fluid.

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  • Insulin-like growth factors (IGFs) are crucial for growth in vertebrates, and the GH-IGF axis can be used to monitor fish growth performance, particularly in butter catfish (Ompok bimaculatus).
  • The study examines the molecular characteristics and expression levels of igf-1 and igf-2 in the liver and muscle of fish under varying stocking densities over a 180-day culture period, revealing that igf-1 expression decreases at higher densities while igf-2 remains stable.
  • The research finds that igf-1 is a better growth regulator related to culture density, with potential implications for improving harvest scheduling and optimizing culture practices in aquaculture.
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Enzymes populate ensembles of structures with intrinsically different catalytic proficiencies that are difficult to experimentally characterize. We use time-resolved mix-and-inject serial crystallography (MISC) at an X-ray free electron laser (XFEL) to observe catalysis in a designed mutant (G150T) isocyanide hydratase (ICH) enzyme that enhances sampling of important minor conformations. The active site exists in a mixture of conformations and formation of the thioimidate catalytic intermediate selects for catalytically competent substates.

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The standard of care for esophageal malignancies has evolved over the years from open transthoracic esophagectomy to a minimally invasive approach due to the reduction in surgical trauma and significant impact on postoperative outcomes. Minimally invasive approaches include video-assisted thoracoscopic surgery and robot-assisted thoracoscopic surgery. These minimally invasive approaches have an attendant learning curve that early-career surgeons are required to negotiate before achieving proficiency in the procedure.

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Reaction discovery and catalyst screening lie at the heart of synthetic organic chemistry. While there are efforts at catalyst design using computation/artificial intelligence, at its core, synthetic chemistry is an experimental science. This review overviews biomacromolecule-assisted screening methods and the follow-on elaboration of chemistry so discovered.

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This video tutorial describes a left lower lobectomy performed by the uniportal approach. A single 2-cm incision in the lateral chest wall is used as the utility port. The procedure begins with division of the inferior pulmonary ligament and isolation of the inferior pulmonary vein.

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Mediastinal staging in potentially resectable non-small cell lung cancer is of paramount importance since it impacts the survival of the patient. With increasing nodal stage, survival was noted to precipitously decline. Nodal status also determined the use of neoadjuvant/adjuvant therapy and other treatment modalities.

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Article Synopsis
  • An experiment was carried out for 180 days to analyze how environmental conditions and stocking density affect the growth, survival, feed utilization, and economic viability of butter catfish in floating cages in India.
  • The study found that a lower stocking density of 15 fingerlings per meter resulted in significantly better growth metrics, survival rates, and feed efficiency compared to higher densities, particularly at 35 fingerlings per meter.
  • The research concluded that maintaining lower stocking densities (15-25 fingerlings per meter) not only enhances fish growth and survival but also yields better economic returns, with the best benefit-cost ratio observed at the lowest density.
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A formal synthesis of the antiviral drug (-)-oseltamivir (Tamiflu) has been accomplished starting from -anisic acid via a dissolving metal or electrochemical Birch reduction. The correct absolute stereochemistry is efficiently set through enzyme-catalyzed carbonyl reduction on the resultant racemic α,β-unsaturated ketone. A screen of a broad ketoreductase (KRED) library identified several that deliver the desired allylic alcohol with nearly perfect facial selectivity at the new center for each antipodal substrate, indicating that the enzyme also is able to completely override inherent diastereomeric bias in the substrate.

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How changes in enzyme structure and dynamics facilitate passage along the reaction coordinate is a fundamental unanswered question. Here, we use time-resolved mix-and-inject serial crystallography (MISC) at an X-ray free electron laser (XFEL), ambient-temperature X-ray crystallography, computer simulations, and enzyme kinetics to characterize how covalent catalysis modulates isocyanide hydratase (ICH) conformational dynamics throughout its catalytic cycle. We visualize this previously hypothetical reaction mechanism, directly observing formation of a thioimidate covalent intermediate in ICH microcrystals during catalysis.

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C-H bonds are ubiquitous in organic molecules and typically these bonds are chemically indistinct from each other and it would be highly advantageous for a synthetic chemist to have the ability to choose which C-H bond is functionalized in a given molecule. A controlled and positional-selective C-H bond functionalization is still a prominent goal in this area. With recent developments in transition metal-catalyzed regiodivergent C-H functionalizations, a switch in regioselectivity between two reactive sites within a given substrate is possible under catalytic control, and has profoundly impacted synthetic strategies.

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A prospective observational study was done at the Regional Cancer Centre, Thiruvananthapuram, a tertiary referral center for cancer care in India with an aim to assess the surgical outcomes of CO laser resection of oral lesions in terms of operative time, blood loss, hospital stay, postoperative pain, time to re-epithelization, pathological margins achieved and the postoperative scar. The excision was performed in 30 patients with a diagnosis of either potentially malignant lesions (leucoplakia, erythroplakia) or early cancers, i.e.

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A unique site-selectivity switch has been achieved in the ruthenium-catalyzed C-H arylation reaction of N-acetyl-1,2-dihydroisoquinolines. This metal-mediated switch is antipodal to the previous report on the palladium-mediated C-4 C-H arylation on the same substrate. Mechanistic details reveal interesting aspects of the reaction pathway, and kinetic studies bring out the difference in the modes of C-H activation adopted by the two catalytic systems.

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Gossypiboma is a mass formed around cotton material acting as foreign body in visceral cavity. In our study, we present a case of gossypiboma following open cholecystectomy. A surgical sponge left in the peritoneal cavity following cholecystectomy, caused inflammatory reaction, perforation and intraluminal migration.

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The Indian hill trout cyprinid, Barilius bendelisis is a member of family Cyprinidae that dwells in shallow, cold, and clear water. In this study, growth parameters and reproductive biology of Indian hill trout, Barilius bendelisis from river Gaula, Central Himalaya region, India, were studied. The length-frequency data were grouped sex wise and were analyzed to determine the growth and mortality parameters using the computer software programme, FAO-ICLARM Stock Assessment Tool (FISAT II).

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A highly site-selective, heteroatom-guided, palladium-catalyzed direct arylation of 4H-chromenes is reported. The C-H functionalization is driven not only by the substituents and structure of the substrate but also by the coupling partner being used. The diastereoselective assembly of the core structure of Myristinin B has been achieved by using a dual C-H functionalization strategy for regioselective direct arylation.

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A new approach to C-2 arylated indoles has been developed by utilizing a ruthenium-catalyzed, heteroatom-directed regioselective C-H arylation. The reaction is highly site-selective and results in very good yields. The highlight of the work is the use of a removable directing group and compatibility of the catalytic system with halogen functional groups in the substrates.

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The circulatory protein, human serum albumin (HSA), is known to have two melting point temperatures, 56 and 62 °C. In this present manuscript, we investigate the interaction of HSA with a synthesized bioactive molecule 3-pyrazolyl 2-pyrazoline (PZ). The sole tryptophan amino acid residue (Trp214) of HSA and PZ forms an excellent FRET pair and has been used to monitor the conformational dynamics in HSA as a function of temperature.

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A new approach for the functionalization of C-4 of isoquinolines is reported. The method utilizes palladium catalyzed, hetero-atom guided (or electrophilic metalation) direct arylation via regioselective C-H functionalization of dihydroisoquinolines.

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A new approach for the regioselective functionalization of the C-3-position of quinolines is described. The method utilizes heteroatom guided regioselective C-3 palladation followed by arylation via transmetalation with aryl boronic acids to yield 3-aryl-N-acyl-1,2-dihydroquinolines. In a one-pot sequence, N-deacylation followed by aromatization leads to important 3-arylquinolines in good yields.

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One species of each of five genera of Harpellales--Gauthieromyces, Harpella, Legeriomyces, Stachylina and Zygopolaris--are reported for the first time from India. Gauthieromyces indicus is described from the hindguts of Baetis sp. nymphs.

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