Biology subjects

Joseph, J.

Publications and source records attributed to Joseph, J..

5 recordsLinked to original sources

bioRxiv2018

Evolutionarily conserved anatomical and physiological properties of olfactory pathway till fourth order neurons in a species of grasshopper (Hieroglyphus banian)

Olfactory systems of different species show variations in structure and physiology despite some conserved characteristics. We characterized the olfactory circuit of the grasshopper Hieroglyphus banian of family Acrididae (subfamily: Hemiacridinae) and compared it to a well-studied species of locust, Schistocerca americana (subfamily: Cyrtacanthacridinae), also belonging to family Acrididae. We used in vivo electrophysiological, immunohistochemical and anatomical (bulk tract tracing) methods to elucidate the olfactory pathway from the second order neurons in antennal lobe to the fourth order neurons in {beta}-lobe of H. banian.\n\nWe observe highly conserved anatomical and physiological characteristics till the fourth order neurons in the olfactory circuit of H. banian and S. americana, though they are evolutionarily divergent (~57 million years ago). However, we found one major difference between the two species-there are four antennal lobe tracts in H. banian while only one is reported in S. americana. Besides, we are reporting for the first time, a new class of bilateral neurons which respond weakly to olfactory stimuli even though they innervate densely downstream of Kenyon cells.

neuroscience↗

bioRxiv2018

Characterization of the olfactory system in Apis dorsata, an Asian honey bee

The European honeybee, Apis mellifera is the most common insect model system for studying learning and memory. We establish that the olfactory system of Apis dorsata, an Asian species of honeybee as an equivalent model to Apis mellifera to study physiology underlying learning and memory. We created an Atlas of the antennal lobe and counted the number of glomeruli in the antennal lobe of Apis dorsata to be around 165 which is similar to the number in the other honey bee species Apis mellifera and Apis florea. Apis dorsata was found to have five antenno-cerebral tracts namely mACT, lACT and 3 mlACTS which appear identical to Apis mellifera. Intracellular recording showed that the antennal lobe interneurons exhibit temporally patterned odor-cell specific responses. The neuritis of Kenyon cells with cell bodies located in a neighborhood in calyx retain their relative neighborhoods in the peduncle and alpha lobe forming a columnar organization in the mushroom body. Alpha lobe and the calyx of the mushroom body were innervated by extrinsic neurons with cell bodies in the lateral protocerebrum. A set of GABA positive cells in the lateral protocerebrum send their neurites towards alpha-lobe. Apis dorsata was amenable to olfactory conditioning and showed good learning and memory retention at 24 hours. They were amenable to massed and spaced conditioning and could distinguish trained odor from an untrained novel odor.

neuroscience↗

bioRxiv2018

Azithromycin reduces systemic inflammation and provides survival benefit in murine model of polymicrobial sepsis

Sepsis is a life threatening systemic inflammatory condition triggered as a result of excessive host immune response to infection. In the past, drugs modulating immune reactions have demonstrated protective effect in sepsis. Azithromycin (macrolide antibiotic) with immunomodulatory activity was therefore evaluated in combination with ceftriaxone in a more clinically relevant murine model of sepsis induced by caecal ligation and puncture (CLP). First, mice underwent CLP and 3 h later were administered with vehicle, sub-effective dose of ceftriaxone (100 mg/kg, subcutaneous) alone or in combination with immunomodulatory dose of azithromycin (100 mg/kg, intraperitoneal). Survival was then monitored for 5 days. Parameters like body temperature, blood glucose, total white blood cell count, plasma glutathione (GSH), plasma and lung myeloperoxidase (MPO) as well as cytokine (interleukin IL-6, IL-1{beta}, tumor necrosis factor-) levels along with bacterial load in blood, peritoneal fluid and lung homogenate were measured 18 h after CLP challenge. Combination group significantly improved the survival of CLP mice. It attenuated the elevated levels of inflammatory cytokines and MPO in plasma and lung tissue and increased the body temperature, blood glucose and GSH which were otherwise markedly decreased in CLP mice. Ceftriaxone exhibited significant reduction of bacterial count in blood, peritoneal fluid and lung homogenate, while co-administration of azithromycin did not further reduce it. This confirms that survival benefit by azithromycin was due to immunomodulation and not by its antibacterial action. Findings of this study indicate that azithromycin in combination with ceftriaxone could exhibit clinical benefit in sepsis.

pharmacology and toxicology↗

bioRxiv2017

Cytoskeletal mechanisms of axonal contractility

Mechanotransduction is likely to be an important mechanism of signalling in thin, elongated cells like neurons. Maintenance of pre-stress or rest tension may facilitate mechanotransduction in these cells. In recent years, functional roles for mechanical tension in neuronal development and physiology are beginning to emerge but the cellular mechanisms regulating neurite tension remain poorly understood. Active contraction of neurites is a potential mechanism of tension regulation. In this study, we have explored cytoskeletal mechanisms mediating active contractility of neuronal axons. We have developed a simple assay where we evaluate contraction of curved axons upon trypsin-mediated detachment. We show that curved axons undergo contraction and straighten upon de-adhesion. Axonal straightening was found to be actively driven by actomyosin contractility, while microtubules may subserve a secondary role. We find that while axons show a monotonous decrease in length upon contraction, subcellularly, the cytoskeleton shows a heterogeneous contractile response. Further, using an assay for spontaneous development of tension without trypsin-induced de-adhesion, we show that axons are intrinsically contractile. These experiments, using novel experimental approaches, implicate the axonal cytoskeleton in tension homeostasis. Our data suggest that while globally the axon behaves as a mechanical continuum, locally the cytoskeleton is remodelled heterogeneously.

biophysics↗

bioRxiv2017

Photoacoustic molecular rulers based on DNA nanostructures

Molecular rulers that rely on the Forster resonance energy transfer (FRET) mechanism are widely used to investigate dynamic molecular processes that occur on the nanometer scale. However, the capabilities of these fluorescence molecular rulers are fundamentally limited to shallow imaging depths by light scattering in biological samples. Photoacoustic tomography (PAT) has recently emerged as a high resolution modality for in vivo imaging, coupling optical excitation with ultrasound detection. In this paper, we report the capability of PAT to probe distance-dependent FRET at centimeter depths. Using DNA nanotechnology we created several nanostructures with precisely positioned fluorophore-quencher pairs over a range of nanoscale separation distances. PAT of the DNA nanostructures showed distance-dependent photoacoustic signal generation and experimentally demonstrated the ability of PAT to reveal the FRET process deep within tissue mimicking phantoms. Further, we experimentally validated these DNA nanostructures as providing a novel and biocompatible strategy to augment the intrinsic photoacoustic signal generation capabilities of small molecule fluorescent dyes.

bioengineering↗