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Biomedical subjects

Alok Sharma

Publications and source records attributed to Alok Sharma.

At least 19 recordsLinked to original sources

CRISPR-Enabled functional genomics in hPSCs-derived neural models for autism spectrum disorder.

Autism Spectrum Disorder (ASD) is a genetically heterogeneous neurodevelopmental condition in which hundreds of individually rare risk variants converge on a small number of shared biological pathways, including synaptic scaffolding, chromatin remodeling, excitation-inhibition balance, and cellular energy metabolism. Translating this genetic heterogeneity into mechanistic insight requires experimental systems capable of interrogating individual gene functions in human-relevant neural contexts at scale. CRISPR-enabled functional genomics in human pluripotent stem cell (hPSC)-derived neural models, spanning neural progenitors, cortical and inhibitory neurons, astrocytes, microglia, and brain organoids, provides precisely this capability. By integrating pooled perturbation screens with multimodal readouts including single-cell and spatial transcriptomics, chromatin accessibility profiling, proximity labeling proteomics, multi-electrode array electrophysiology, and metabolic flux analysis, these platforms enable systematic, causal mapping of ASD gene function at system resolution. Early applications have already revealed convergent mechanisms: BAF complex disruption expands the ventral progenitor pool and biases its fate toward oligodendrocyte and interneuron lineages; ADNP loss impairs microglial synaptic pruning through altered endocytic trafficking; and mTOR pathway dysregulation in PTEN- and TSC2-perturbed models links genetic risk directly to metabolic and mitochondrial dysfunction. Computational frameworks including MIMOSCA and SCEPTRE enable causal network reconstruction and pseudotime inference from these datasets, moving the field from gene lists toward pathway-level models of ASD pathobiology. Translational applications leverage isogenic iPSC panels and variant-level base and prime editing to stratify ASD variants by functional impact, informing gene therapy design for haploinsufficient targets such as CHD8 and SCN2A via AAV or antisense oligonucleotide delivery. Remaining challenges, including model developmental immaturity, batch variability, and the difficulty of modeling polygenic risk, are addressed by a roadmap integrating spatial perturbomics, AI-driven causal inference, and population-scale standardized biobanks. This review synthesizes the current state of CRISPR-based functional genomics in human stem cell neural models as a coherent experimental framework for converting ASD genetic associations into mechanistic understanding and therapeutic opportunity.

Humans↗

Rhizosphere Pseudomonas sp. strains reduce occurrence of pre- and post-emergence damping-off in chile and tomato in Central Himalayan region.

Based on in vitro screening for PGP and anti-mycelial activity against three zoosporic pathogenic oomycetes, Pythium aphanidermatum 123, P. aphanidermatum 4746, and Phytophthora nicotianae 4747, seven bacterial isolates were selected for field trials on tomato and chile to test for plant growth promotion under natural and artificial disease-infested field sites in both winter and wet seasons. The effectiveness of isolates in the field trials correlated with the in vitro antagonism screening data. Pseudomonas sp. FQP PB-3, FQA PB-3 and GRP(3) showed substantial beneficial effects on plant growth promotion and lowered considerably the incidence of pre- and post-emergence damping-off in both the crops under various disease scenarios. For example, seed bacterization with these bacterial strains reduced pre-emergence-damping off by ca. 60-70% in the two natural sites, with and without histories of fungicide use in the winter season, and to a lesser extent, ca. 20-40%, in the warmer wet (high humidity; 85-92%) season. The suppression efficacy for post-emergence damping-off was less compared to pre-emergence damping-off although still significant (P > 0.05). Our data unambiguously show that screening of a large number of bacterial pool identifies promising isolates that show beneficial effects on all stages of plant growth in natural oomycete-infested regimes.

Antibiosis↗

Structural characterization and oligomerization of PB1-F2, a proapoptotic influenza A virus protein.

Recently, a novel 87-amino acid influenza A virus protein with proapoptotic properties, PB1-F2, has been reported that originates from an alternative reading frame in the PB1 polymerase gene and is encoded in most known human influenza A virus isolates. Here we characterize the molecular structure of a biologically active synthetic version of the protein (sPB1-F2). Western blot analysis, chemical cross-linking, and NMR spectroscopy afforded direct evidence of the inherent tendency of sPB1-F2 to undergo oligomerization mediated by two distinct domains located in the N and C termini, respectively. CD and (1)H NMR spectroscopic analyses indicate that the stability of structured regions in the molecule clearly depends upon the hydrophobicity of the solvent. In aqueous solutions, the behavior of sPB1-F2 is typical of a largely random coil peptide that, however, adopts alpha-helical structure upon the addition of membrane mimetics. (1)H NMR analysis of three overlapping peptides afforded, for the first time, direct experimental evidence of the presence of a C-terminal region with strong alpha-helical propensity comprising amino acid residues Ile(55)-Lys(85) connected via an essentially random coil structure to a much weaker helix-like region, located in the N terminus between residues Trp(9) and Lys(20). The C-terminal helix is not a true amphipathic helix and is more compact than previously predicted. It corresponds to a positively charged region previously shown to include the mitochondrial targeting sequence of PB1-F2. The consequences of the strong oligomerization and helical propensities of the molecule are discussed and used to formulate a hypothetical model of its interaction with the mitochondrial membrane.

Amino Acid Sequence↗

Cytodiagnosis of multiple myeloma presenting as orbital involvement: a case report.

BACKGROUND: Plasma cell neoplasms represent autonomous proliferations of plasma cells and can manifest as diffuse myeloma with systemic involvement (plasma cell myeloma or multiple myeloma), monoclonal gammopathy of undetermined significance (MGUS), or as variants of plasma cell myeloma such as indolent myeloma, smoldering myeloma, osteosclerotic myeloma, plasma cell leukaemia and non-secretory myeloma. Localized neoplastic proliferation of plasma cells presents as solitary plasmacytoma of bone or extramedullary plasmacytoma. Involvement of orbit can occur as a solitary plasmacytoma, or as part of systemic involvement in multiple myeloma, the clinical outcome being significantly worse in the latter setting. Orbital involvement in multiple myeloma is very rare with less than 50 cases reported in the literature. Early cytological diagnosis of such lesions is vital for timely institution of appropriate therapy. As far as we are aware only six previous cases of cytological diagnosis of multiple myeloma involving the orbit are on record. CASE PRESENTATION: A 37 year old male presented with low grade fever showing evening rise, headache, diplopia and swelling in the right periorbital and temporal region. Imaging studies revealed destructive lesion of sphenoid, frontal bone and zygomatic arch with soft tissue component extending to infratemporal fossa and orbit. A fine needle aspirate from the temporal region swelling showed features of a plasmacytoma, and subsequent workup confirmed the presence of systemic disease. A final diagnosis of multiple myeloma with orbital involvement at presentation was made. CONCLUSION: Present case describes the extremely rare presentation of multiple myeloma with orbital involvement and highlights the utility of cytology in such lesions. Fine needle aspiration diagnosis of plasmacytoma at extramedullary sites offers an opportunity for non-invasive verification of systemic involvement, and thus plays a major role in early diagnosis and management of these patients.

Journal Article↗

Suggestive evidence for the involvement of the second calcium and surface loop in interfacial binding: monoclinic and trigonal crystal structures of a quadruple mutant of phospholipase A2.

The crystal structures of the monoclinic and trigonal forms of the quadruple mutant K53,56,120,121M of recombinant bovine pancreatic phospholipase A2 (PLA2) have been solved and refined at 1.9 and 1.1 A resolution, respectively. Interestingly, the monoclinic form reveals the presence of the second calcium ion. Furthermore, the surface-loop residues are ordered and the conformation of residues 62-66 is similar to that observed in other structures containing the second calcium ion. On the other hand, in the trigonal form the surface loop is disordered and the second calcium is absent. Docking studies suggest that the second calcium and residues Lys62 and Asp66 from the surface loop could be involved in the interaction with the polar head group of the membrane phospholipid. It is hypothesized that the two structures of the quadruple mutant, monoclinic and trigonal, represent the conformations of PLA2 at the lipid interface and in solution, respectively. A docked structure with a phospholipid molecule and with a transition-state analogue bound, one at the active site coordinating to the catalytic calcium and the other at the second calcium site, but both at the i-face, is presented.

Animals↗

Plant growth-promoting Pseudomonas sp. Strains reduce natural occurrence of anthracnose in soybean (Glycine max L.) in central Himalayan region.

Biological control is an accepted important component of current plant disease management strategies. Introduction of bacterized seeds carrying bacterial isolates with proven growth-promotion capabilities and antagonistic characteristics offer a valid alternative to chemical protectants. Root colonization of disease-susceptible (PS 1024) and moderately resistant (PS1042) varieties of soyabean (Glycine Max L) by fluorescent pseudomonad (FLPs) strains GRP3, PEn-4, PRS1, and WRS-24 was studied in relation to natural occurrence of anthracnose caused by Colletotrichum dematium (Pers Ex Fr.) Grove. Rhizoplane population of FLPs was maintained at a critical level (5.3 cfu) up to 30 days of plant growth, followed by a steep decline. Indigenous FLPs population, however, remained nearly unchanged (3.0 to 2.4 log g(-1) root) between 30 days and 75 days of plant growth. The relative FLPs population in rhizosphere was lower than that in rhizoplane. Although intervarietal difference was observed, the root/shoot length remained unaffected. Compared to nonbacterized control, dry root weight was improved by FLPs treatment. Severity of foliar anthracnose was reduced significantly after FLPs treatment in the variety PS 1042. Because the point of FLPs treatment (seed bacterization) was away from the site of disease appearance (leaf), operation of induced systemic resistance in strains PEn-4 and GRP3 appears imminent.

Colletotrichum↗

X-ray studies of crystalline complexes involving amino acids and peptides. XLIII. Adipic acid complexes of L- and DL-lysine.

The asymmetric unit of the DL-lysine complex of adipic acid [bis(DL-lysinium) adipate], 2C6H15N2O2+.C6H8O(4)2-, contains a zwitterionic singly charged lysinium cation and half a doubly charged adipate anion (the complete anion has inversion symmetry). That of the L-lysine complex (lysinium hydrogen adipate), C6H15N2O2+.C6H9O4-, consists of a lysinium cation and a singly charged hydrogen adipate anion. In both structures, the lysinium cations organize into layers interconnected by adipate or hydrogen adipate anions. However, the arrangement of the molecular ions in the layer is profoundly different in the DL- and L-lysine complexes. The hydrogen adipate anions in the L-lysine complex form linear arrays in which adjacent ions are interconnected by a symmetric O...H...O hydrogen bond.

Adipates↗

A comparison of diagnostic protocols for interpretation of frequency doubling perimetry visual fields in glaucoma.

BACKGROUND: Frequency doubling perimetry (FDP) shows good correlation with achromatic automated perimetry in the assessment of glaucoma. However, many recommended protocols lead to a significant number of false positives and negatives. Therefore, it may be difficult to identify visual field loss owing to glaucoma. We investigated the accuracy of a diagnostic protocol that only considered either temporal wedge, arcuate, or nasal step field loss on an FDP field as significant. METHODS: Sixty-eight subjects who were glaucoma suspects, glaucoma patients or normal controls were recruited selectively. After achromatic automated perimetry and FDP visual field testing, results were compared between a conventional protocol and ones that took into account the position of FDP visual field loss. RESULTS: If an FDP field was considered abnormal only when either a temporal wedge, an arcuate or a nasal step defect was present, the presence of a nasal step yielded the most accurate results with the least false positives (kappa coefficient=0.76) and with only minimal increase in false negatives, compared with a conventional FDP protocol (kappa coefficient=0.70). CONCLUSIONS: Although, not statistically significant in this case, our results suggested a trend that a diagnostic protocol which considers nasal step FDP field loss significant may have a greater degree of accuracy when compared with conventional protocols and may facilitate interpretation in a clinical setting.

Female↗

Desmoplastic infantile ganglioglioma with calcification.

Desmoplastic infantile gangliogliomas (DIGs) are rare intracranial, cystic tumors, usually detected within the first 2 years of life. Histologically, these tumors are characterized by intense desmoplasia and a divergent astrocytic and neuronal differentiation. Less than 60 well-documented cases of this extremely rare tumor are reported in the literature. We present the case of a 10-month-old male child presenting with a large, cystic, intracranial lesion and having the characteristic histological features of a DIG. In addition, the lesion also showed focal areas of calcification within the tumor, not usually considered a feature of this entity. The present case extends the reported spectrum of this rare entity and describes the unusual occurrence of calcification within the lesion.

Brain Neoplasms↗

Primary squamous cell carcinoma of the renal pelvis masquerading as pyonephrosis: a case report.

Squamous cell carcinoma of the renal pelvis is a rare tumor, which is usually associated with nephrolithiasis. It is rarely associated with pyonephrosis. We report the case of a 69-year-old man who presented with features of pyonephrosis and underwent nephrectomy. The postoperative histological evaluation revealed an unsuspected squamous cell carcinoma of renal pelvis with a concomitant pyonephrosis. The rarity of this tumor in the absence of renal calculi and its association with pyonephrosis is highlighted.

Aged↗

Transnasal flexible laryngo-oesophagoscopy: an evaluation of the patient's experience.

The aim of this study was to evaluate the patient's experience of transnasal flexible laryngo-oesophagoscopy under local anaesthetic in an out-patient setting. This was a clinical observational study using a patient questionnaire and visual analogue score. Subjects were 50 patients seen in the hospital's ENT outpatient clinic between March and August 2004 in whom transnasal flexible laryngo-oesophagoscopy was performed and who completed pain discomfort questionnaires. Any patient undergoing transnasal flexible laryngo-oesophagoscopy, for either diagnostic or therapeutic purposes, was included in the study. Patients in whom transnasal flexible laryngo-oesophagoscopy was not necessary as part of their investigation or treatment were excluded. Patients completed a questionnaire, providing a simple visual analogue score for discomfort during the procedure. Any operative complications were noted by the surgeon. All patients completed transnasal flexible laryngo-oesophagoscopy, and the upper aerodigestive tract was clearly visualized. The procedure is well tolerated, with mean score of <1 out of 10 for all forms of discomfort. There was a complication rate of 2 per cent (one patient with epistaxis); no other complications occurred. Transnasal flexible laryngo-oesophagoscopy is a new diagnostic and therapeutic technique which is well tolerated by patients. It compares favourably with other flexible endoscopic techniques. This report documents for the first time a detailed description of patients' experience of this technique.

Chest Pain↗

A FRET-based probe for epidermal growth factor receptor bound non-covalently to a pair of synthetic amphipathic helixes.

Epidermal growth factor (EGF) receptor plays a pivotal role in a variety of cellular functions, such as proliferation, differentiation, and migration. To monitor the EGF receptor (EGFR) activity in living cells, we developed a probe for EGFR activity based on the principle of fluorescence resonance energy transfer (FRET). Previously, we developed a probe designated as Picchu (Phosphorylation indicator of the CrkII chimeric unit), which detects the tyrosine phosphorylation of the CrkII adaptor protein. We used a pair of synthetic amphipathic helixes, WinZipA2 and WinZipB1, to bind Picchu non-covalently to the carboxyl-terminus of the EGFR. Using this modified probe named Picchu-Z, the activity of EGFR was followed in EGF-stimulated Cos7 cells. We found that a high level of tyrosine phosphorylation of Picchu-Z probe remained after endocytosis until the point when the EGFR was translocated to the perinuclear region. These findings are in agreement with the previously reported "signaling endosome" model. Furthermore, by pulse stimulation with EGF and by acute ablation of EGFR activity with AG1478, it was suggested that the phosphorylation of Picchu-Z probe, and probably the phosphorylation of EGFR also, underwent a rapid equilibrium (tau(1/2) < 2 min) between the phosphorylated and dephosphorylated states in the presence of EGF.

Animals↗

Spinal intramedullary arachnoid cyst in a 4-year-old girl: a rare cause of treatable acute quadriparesis: case report.

The authors report their experience in successfully treating a 4-year-old girl who presented with sudden onset of quadriparesis that lasted for 20 days. Magnetic resonance (MR) imaging of the spine revealed an intramedullary cystic lesion extending from C-4 to C-6. A C4-6 laminectomy was performed followed by a median myelotomy. The cyst was decompressed and most of the cyst wall was excised. The histopathological findings were consistent with those of an arachnoid cyst. By postoperative Day 3, power had gradually returned to normal in all her limbs. On follow-up reviews at 2 and 17 months, the results of her neurological examinations remained normal. Follow-up MR imaging of the spine at 17 months revealed an intramedullary residual cystic lesion extending from C-5 to C-6, without any mass effect. An intramedullary arachnoid cyst should be considered in the differential diagnosis of an intramedullary cystic lesion.

Arachnoid Cysts↗

Anterior instrumentation for cervical spine tuberculosis: an analysis of surgical experience with 61 cases.

OBJECTIVE: To evaluate the efficacy of anterior instrumentation in patients with subaxial and cervicodorsal spinal tuberculosis in reconstruction of the spine, providing pain relief, neurological recovery and prevention of deformity. MATERIALS AND METHODS: The records of 61 consecutive patients, of surgically treated spinal tuberculosis affecting C3 to D2 region, in our neuro and spinal surgery unit over a five-year period were retrospectively reviewed. Patients with involvement of the C3-C6 vertebrae underwent excision of the involved vertebrae and intervertebral discs followed by reconstruction with titanium implants by anterior approach. A transclavicular approach was used for patients with involvement of the C7-D2 vertebrae. A five-drug antituberculous regimen was administered for a period of one year. The follow-up ranged from 24 to 84 months (mean 38 months). Clinical and radiological assessment using flexion and extension radiographs was performed at 24 months for all cases. RESULTS: The neck pain score based on a visual analog scale (1-10) changed from a pre-operative average of 7 to 2 at follow-up after 4 months. Fifty-two patients (85%) had complete relief of pain while 16 patients who had Grade III to IV muscle strength regained complete power. The asymmetric wasting in patients with involvement of the cervicodorsal region did not recover completely. Flexion-extension radiographs at 24 months did not show any evidence of instability or nonunion. CONCLUSIONS: Anterior reconstruction using titanium plates and locking screws for stabilization of the subaxial and cervicodorsal region tuberculosis is a useful adjunct in preventing kyphotic deformity. A satisfactory segmental stability and fusion is achieved by this technique.

Adolescent↗

Angiosarcoma of scalp: a case report.

Cutaneous angiosarcomas are rare and constitute less than 1% of all malignant mesenchymal tumours. Most angiosarcomas of skin arise in the following clinical settings: 1. face and scalp of elderly 2. following lymphoedema and 3. post radiation. We present a case of an elderly man presenting with scalp lesion of 18 months duration. Histological examination of the biopsy revealed features of an angiosarcoma, which showed imunohistochemical positivity for factor VIII related antigen.

Aged↗

Maroteaux-Lamy syndrome.

Mucopolysaccharidoses are a type of lysosomal storage disorders characterized by defect in the degradation of Mucopolysaccharides due to deficiency of specific lysosomal enzymes leading to their accumulation in various tissues. MPS -VI (Maroteaux-Lamy Syndrome) is an autosomal recessive syndrome due to deficiency of enzyme Aryl- Sulfatase -B, and is characterized by characteristic facies, normal intelligence, Dysostosis multiplex, organomegaly, joint stiffness, corneal clouding and striking inclusions in peripheral blood leucocytes. We present an 8-year-old male child with MPS-VI syndrome, confirmed by enzyme assay.

Abnormalities, Multiple↗