Biology subjects

Aravind, S.

Publications and source records attributed to Aravind, S..

4 recordsLinked to original sources

bioRxiv2025

Sustained Isobutene Production by Synechocystis Entrapped in Polyvinyl Alcohol Hydrogel Beads

Cyanobacteria convert CO2 into valuable compounds using solar energy, making them ideal for sustainable isobutene production, a key precursor for fuels and chemicals. This study aimed to enhance isobutene production in engineered Synechocystis sp. PCC 6803 strains: Syn- RnKICD, producing isobutene from -ketoisocaproate (KIC) via Rattus norvegicus - ketoisocaproate dioxygenase (RnKICD), and Syn-F336V, expressing a mutant variant of RnKICD with improved KIC specificity. We investigated the effects of varying culture conditions, including light intensity, inorganic carbon, and nitrogen on isobutene production. Nitrogen limitation emerged as a critical factor, improving yields by reducing growth. This likely occurred due to decreased competition from branched-chain amino acid (BCAA) biosynthesis, redirecting carbon toward isobutene synthesis. However, prolonged nitrogen limitation ultimately reduced productivity due to impaired metabolic functions. To address this limitation, we employed a polyvinyl alcohol-sodium alginate (PVA-SA) hydrogel, crosslinked with B(OH)- and Ca{superscript 2}, to entrap cells. This approach restricted growth while maintaining cell viability and isobutene productivity. Optimizing crosslinking parameters such as time, pH, and the hydrogel-to-cell mass ratio improved bead stability under bicarbonate and nitrate supply. This strategy extended cell viability and isobutene productivity in Syn-RnKICD and Syn- F336V by nearly a month, increasing yields by 60% and 80%, respectively, compared to suspension cells, achieving a maximum yield of 94 mg/g DW. This study underscores the importance of optimizing environmental conditions for isobutene production in Synechocystis and highlights the effectiveness of PVA-SA cell entrapment as a biocatalyst platform for sustained chemical production. HighlightsO_LIOptimized light, carbon, and nitrogen sources enhanced isobutene production. C_LIO_LIRate of isobutene production increased 10-fold compared to our previous report. C_LIO_LINitrogen limitation improved isobutene yield by redirecting carbon from growth. C_LIO_LIPVA-entrapped cells sustained isobutene productivity for nearly 31 days. C_LI

microbiology↗

bioRxiv2020

The effect of pre-resection obesity on post-resection body composition after 75% small bowel resection in rats

BackgroundIn patients with short bowel syndrome, an elevated pre-resection Body Mass Index may be protective of post-resection body composition. We hypothesized that rats with diet-induced obesity would lose less lean body mass after undergoing massive small bowel resection compared to non-obese rats. MethodsRats (CD(R)IGS; age = 2 mo; N = 80) were randomly assigned to either a high-fat (obese rats) or a low-fat diet (non-obese rats), and fed ad lib for six months. Each diet group then was randomized to either underwent a 75% distal small bowel resection (massive resection) or small bowel transection with re-anastomosis (sham resection). All rats then were fed ad lib with an intermediate-fat diet (25% of total calories) for two months. Body weight and quantitative magnetic resonance-determined body composition were monitored. ResultsPreoperative body weight was 884 {+/-} 95 vs. 741 {+/-} 75 g, and preoperative percent body fat was 35.8 {+/-} 3.9 vs. 24.9 {+/-} 4.6%; high-fat vs. low fat diet, respectively (p < 0.0001); preoperative diet type had no effect on lean mass. Regarding total body weight, massive resection produced an 18% vs. 5% decrease in high-fat vs. low-fat rats respectively, while sham resection produced a 2% decrease vs. a 7% increase, respectively (p < 0.0001, preoperative vs. necropsy data). Sham resection had no effect on lean mass; after massive resection, both high-fat and low-fat rats lost lean mass, but these changes were not different between the latter two rat groups. ConclusionThe high-fat diet and low-fat diet induced obesity and marginal obesity, respectively. The massive resection produced greater weight loss in high-fat rats compared to low-fat rats. The type of dietary preconditioning had no effect on lean mass loss after massive resection. A protective effect of pre-existing obesity on lean mass after massive intestinal resection was not demonstrated.

physiology↗

bioRxiv2018

Collateral development and arteriogenesis in hindlimbs of domestic swine after ligation of arterial inflow

IntroductionThe development of collateral vasculature is a key mechanism compensating for arterial occlusions in patients with peripheral artery disease (PAD). We aimed to examine the development of collateral pathways after ligation of native vessels in a porcine model of PAD. MethodsRight hindlimb Ischemia was induced in domestic swine (N=11, male, kg) using two different versions of arterial ligation. Version 1 (N=6) consisted of ligation/division of the right external iliac, profunda femoral (RPFA) and superficial femoral arteries (RSFA). Version 2 (N=5) consisted of the ligation of Version 1 with additional ligation/division of the right internal iliac artery (RIIA). Development of collateral pathways was evaluated with standard angiography at baseline (prior to arterial ligation) and at termination (4-8 weeks later). Relative luminal diameter of the arteries supplying the ischemic right hindlimb were determined by 2D angiography, as percent of the size of the distal aortic diameter. ResultsThe dominant collateral pathway that developed after version 1 ligation connected the RIIA to the RPFA and RSFA/popliteal artery. Mean luminal diameter ({+/-} standard error) of the RIIA at termination increased by 38% (P<0.05) compared to baseline. Two co-dominant collateral pathways developed in version: (i) from the common internal iliac trunk and left internal iliac artery to the reconstituted RIIA, which then supplied the RPFA and RSFA/popliteal arteries; and (ii) from left profunda artery to the reconstituted RPFA. Mean diameter of the common internal iliac trunk and left profunda artery both increased at termination in the range of 20% (p < 0.05). ConclusionTwo versions of hindlimb ischemia induction (right ilio-femoral artery ligation with and without right internal iliac artery ligation in swine produced differing collateral pathways, along with changes to the diameter of the inflow vessels (i.e., arteriogenesis). Radiographic and anatomical data of the collateral formation in this porcine model should have value in investigation of the pathophysiology of hindlimb ischemia, and assessment of angiogenic therapies as potential treatments for PAD.

physiology↗

bioRxiv2018

Generation of tumorigenic porcine pancreatic ductal epithelial cells: toward a large animal model of pancreatic cancer

Background. A large animal model of pancreatic cancer would permit development of diagnostic and interventional technologies not possible in murine models, and also would provide a more biologically-relevant platform for penultimate testing of novel therapies, prior to human testing. Here, we describe our initial studies in the development of an autochthonous, genetically-defined, large animal model of pancreatic cancer, using immunocompetent pigs.\n\nMethods. Primary pancreatic epithelial cells were isolated from pancreatic duct of domestic pigs; epithelial origin was confirmed with immunohistochemistry. Three transformed cell lines subsequently were generated from these primary cells using expression of oncogenic KRAS and dominant negative p53, with/without knockdown of p16 and SMAD4. We tested these cell lines using in vitro and in vivo assays of transformation and tumorigenesis.\n\nResults. The transformed cell lines outperformed the primary cells in terms proliferation, population doubling time, soft agar growth, 2D migration, and Matrigel invasion, with the greatest differences observed when all four genes (KRAS, p53, p16, and SMAD4) were targeted. All three transformed cell lines grew tumors when injected subcutaneously in nude mice, demonstrating undifferentiated morphology, mild desmoplasia, and staining for both epithelial and mesenchymal markers. Injection into the pancreas of nude mice resulted in distant metastases, particularly when all four genes were targeted.\n\nConclusions. Tumorigenic porcine pancreatic cell lines were generated. Inclusion of four genetic \"hits\" (KRAS, p53, p16, and SMAD4) appeared to produce the best results in our in vitro and in vivo assays. The next step will be to perform autologous or syngeneic implantation of these cell lines into the pancreas of immunocompetent pigs. We believe that the resultant large animal model of pancreatic cancer could supplement existing murine models, thus improving preclinical research on diagnostic, interventional, and therapeutic technologies.

cancer biology↗