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Biomedical subjects

A Ghosh

Publications and source records attributed to A Ghosh.

At least 91 records · Page 5Linked to original sources
PubMed2001

Human immunodeficiency virus type 1 env sequences from Calcutta in eastern India: identification of features that distinguish subtype C sequences in India from other subtype C sequences.

India is experiencing a rapid spread of human immunodeficiency virus type 1 (HIV-1), primarily through heterosexual transmission of subtype C viruses. To delineate the molecular features of HIV-1 circulating in India, we sequenced the V3-V4 region of viral env from 21 individuals attending an HIV clinic in Calcutta, the most populous city in the eastern part of the country, and analyzed these and the other Indian sequences in the HIV database. Twenty individuals were infected with viruses having a subtype C env, and one had viruses with a subtype A env. Analyses of 192 subtype C sequences that included one sequence for each subject from this study and from the HIV database revealed that almost all sequences from India, along with a small number from other countries, form a phylogenetically distinct lineage within subtype C, which we designate C(IN). Overall, C(IN) lineage sequences were more closely related to each other (level of diversity, 10.2%) than to subtype C sequences from Botswana, Burundi, South Africa, Tanzania, and Zimbabwe (range, 15.3 to 20.7%). Of the three positions identified as signature amino acid substitution sites for C(IN) sequences (K340E, K350A, and G429E), 56% of the C(IN) sequences contained all three amino acids while 87% of the sequences contained at least two of these substitutions. Among the non-C(IN) sequences, all three amino acids were present in 2%, while 22% contained two or more of these amino acids. These results suggest that much of the current Indian epidemic is descended from a single introduction into the country. Identification of conserved signature amino acid positions could assist epidemiologic tracking and has implications for the development of a vaccine against subtype C HIV-1 in India.

Adult↗
PubMed2001

Sequential specification of neurons and glia by developmentally regulated extracellular factors.

Cortical progenitor cells give rise to neurons during embryonic development and to glia after birth. While lineage studies indicate that multipotent progenitor cells are capable of generating both neurons and glia, the role of extracellular signals in regulating the sequential differentiation of these cells is poorly understood. To investigate how factors in the developing cortex might influence cell fate, we developed a cortical slice overlay assay in which cortical progenitor cells are cultured over cortical slices from different developmental stages. We find that embryonic cortical progenitors cultured over embryonic cortical slices differentiate into neurons and those cultured over postnatal cortical slices differentiate into glia, suggesting that the fate of embryonic progenitors can be influenced by developmentally regulated signals. In contrast, postnatal progenitor cells differentiate into glial cells when cultured over either embryonic or postnatal cortical slices. Clonal analysis indicates that the postnatal cortex produces a diffusible factor that induces progenitor cells to adopt glial fates at the expense of neuronal fates. The effects of the postnatal cortical signals on glial cell differentiation are mimicked by FGF2 and CNTF, which induce glial fate specification and terminal glial differentiation respectively. These observations indicate that cell fate specification and terminal differentiation can be independently regulated and suggest that the sequential generation of neurons and glia in the cortex is regulated by a developmental increase in gliogenic signals.

Animals↗
PubMed2001

A unique experience with human pre-immune (12 weeks) and hypo-immune (16 weeks) fetal thymus transplant in a vascular subcutaneous axillary fold in patients with advanced cancer: a report of two cases.

BACKGROUND: The successful development of fetal cell/tissue transplantation in adults has resulted in the possibility of eventual therapeutic solutions with a variety of intractable diseases. Umbilical cord whole blood transplantation appears to be safe in the adult system. In severe forms of DiGeorge Syndrome, cultured thymus transplant can help in the reconstitution of the immune condition of the host. Successful fetal tissue transplant in adults has raised the hope of future effective gene transplant and its manipulation prospects to combat many diseases including hemopathies, inborn errors of metabolism, immunodeficiencies and even cancer and AIDS. MATERIALS AND METHOD: Two cases of advanced cancer were treated with fetal (pre-immune 12 weeks and hypo-immune 16 weeks) thymus transplants in subcutaneous vascular axillary folds, which were removed after one month. Thymuses were collected from consenting mothers undergoing hysterotomy and ligation. RESULTS AND ANALYSIS: Patient I was suffering from non-Hodgkins lymphoma (Ann Arbor Stage IV) and was receiving cyclophosphomide, doxorubicin, vincristine and prednisolone after a course of radiotherapy; she developed leucopenia (2.400/cmm), which improved after receiving a 16-week human fetal thymic graft. The leucopenia was eventually over-corrected and the leucocyte count reached 44,000/cmm within a month, which was reversed after the thymus was taken out. Histology of the excised thymic graft showed growth and proliferation without any graft vs. host (GVH) reaction. Patient 2 was suffering from breast duct carcinoma (T4, N2, M0,) with estrogen, progesterone, and epidermal growth factor negative status, and was treated with modified radical mastectomy and axillary clearance followed by chemotherapy with cyclophosphomide, methotrexate and 5-fluorouracil for six cycles. She also received a 12-week-old human fetal thymus at the contra-lateral axilla which was removed after one month. In this case the peripheral leucocyte count did not show appreciable variation as in the first case. However, histology of the excised thymic graft showed growth and proliferation with an appearance of Hassel's corpuscles. CONCLUSION: Pre-immune and hypo-immune human fetal thymic transplant is not rejected in patients suffering from advanced cancer within one month (observation period). Thymic lymphocyte shedding in the correction of leucopenia in the background of non-Hodgkin's lymphoma may have many therapeutic implications.

Adolescent↗
PubMed2001

In vitro susceptibility pattern of Sporothrix schenckii strains isolated from three centers in India.

BACKGROUND & OBJECTIVES: With the availability of more number of antifungal agents in recent years, drugs other than saturated solution of potassium iodide (SSKI) are being increasingly used to treat sporotrichosis. It was therefore considered pertinent to evaluate in vitro antifungal susceptibility pattern of Sporothrix schenckii strains isolated at three centers in India against five commonly used antifungal agents. METHODS: Agar dilution method was used to evaluate 50 clinical isolates (25 from north, 17 from east and 8 from south India) both in its yeast and mycelial forms against amphotericin-B, 5-fluorocytosine, ketoconazole, fluconazole and itraconazole. RESULTS: No resistance was observed in the yeast form of S. schenckii against amphotericin B and azoles. However, 54 per cent strains in the yeast form were resistant to 5-fluorocytosine. None of the strains was susceptible to amphotericin B and ketoconazole, 56 and 10 per cent strains in the mycelial form were susceptible to itraconazole and fluconazole respectively. No significant difference was observed in the antifungal susceptibility pattern among the strains isolated from these three regions in India. INTERPRETATION & CONCLUSION: Clinical isolates of S. schenckii from three regions of India had a more or less uniform antifungal susceptibility pattern. Itraconazole had the best in vitro susceptibility results against the clinical isolates of S. schenckii and has the potential to replace SSKI.

Antifungal Agents↗
PubMed2000

Immunization with recombinant LD1 antigens protects against experimental leishmaniasis.

The genes, ORFF and BT1 (previously ORFG), are part of the multigenic LD1 locus on chromosome 35 which is frequently amplified in Leishmania. BT1 encodes a biopterin transporter, while the function of the ORFF gene product is unknown, but it is localized to the nucleus. We show here that immunization of mice with recombinant ORFF and BT1 proteins, individually, or in combination, conferred partial protection against challenge with Leishmania donovani. Protection correlated with the production of antigen-specific antibodies and in vitro splenocyte proliferation. Thus, these antigens can be potential vaccine candidates against visceral leishmaniasis.

Animals↗
PubMed2000

Effect of vanillin on methylene blue plus light-induced single-strand breaks in plasmid pBR322 DNA.

The ability of vanillin (4-hydroxy-3-methoxybenzaldehyde), a naturally occurring food flavouring agent, in inhibiting photosensitization-induced single-strand breaks (ssbs) in plasmid pBR322 DNA has been examined in an in vitro system, independent of DNA repair/replication processes. Photosensitization of DNA with methylene blue, visible light and oxygen, induced ssbs resulting in the production of open circular form (OC form) in a concentration-dependent manner. The yield of OC form induced by photosensitization was increased several-fold by deuteration of the buffer and was found to be inhibited by sodium azide, a scavenger of singlet oxygen (1O(2)). Vanillin, per se, did not induce but inhibited photosensitization-induced ssbs in plasmid DNA, at millimolar concentrations. The inhibitory effect of vanillin was both concentration- and time-dependent. On a molar basis, vanillin was, however, less effective than trolox, a water-soluble analogue of alpha-tocopherol. Photosensitization by methylene blue system generates singlet oxygen, as one of the major components of ROS. Therefore, interaction of singlet oxygen with vanillin was investigated. The rate constant of vanillin with 1O(2) was estimated to be 5.93x10(7)M(-1)s(-1) and that of sodium azide as 2. 7x10(8)M(-1)s(-1). The present investigations show that vanillin can protect against photosensitization-induced ssbs in the plasmid pBR322 DNA, and this effect may partly be due to its ability to scavenge 1O(2).

Antioxidants↗