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Biomedical subjects

P K Sehgal

Publications and source records attributed to P K Sehgal.

At least 19 recordsLinked to original sources
PubMed2006

A novel method to measure oxygen permeability and transmissibility of contact lenses.

PURPOSE: The present paper describes an accurate and cost-effective method requiring simple equipment to measure the oxygen permeability and transmissibility of contact lenses. METHOD: The method involves accurate measurement of oxygen across the material by allowing the gas (oxygen) to pass through the lens material in a specially fabricated lens mould. The expelled gas is collected by dissolution in ethanol and the oxygen is measured by titration of the solvent. RESULT: This method is suitable for the measurement of oxygen permeability and transmissibility of contact lenses of varying thickness and different radii of curvature. It can measure Dk and Dk/t of collagen bandage lenses in both wet and dry conditions. CONCLUSION: The oxygen permeability and transmissibility values obtained by this method were compared with the oxygen permeability standard values of commercially available contact lenses and the results are summarised.

Contact Lenses↗
PubMed2005

Evaluation of the inhibitory effect of triphala on PMN-type matrix metalloproteinase (MMP-9).

BACKGROUND: This study evaluated the inhibitory activity of triphala on PMN-type matrix metalloproteinase (MMP-9) expressed in adult periodontitis patients and compared its activity with another ayurvedic drug, kamillosan, and doxycycline, which has known inhibitory activity. METHODS: Matrix metalloproteinases (MMPs) were extracted from gingival tissue samples from 10 patients (six males, four females) with chronic periodontitis. Tissue extracts were treated with the drug solutions, the inhibition was analyzed by gelatin zymography, and the percentage of inhibition was determined by a gel documentation system. RESULTS: The activity of MMPs was significantly decreased with the use of the drugs. Triphala showed a 76.6% reduction of MMP-9 activity, whereas kamillosan showed a 46.36% reduction at a concentration of 1,500 microg/ml (crude extract) and doxycycline showed a 58.7% reduction at a concentration of 300 microg/ml (pure drug). CONCLUSION: The present study showed the strong inhibitory activity of triphala on PMN-type MMPs involved in the extracellular matrix (ECM) degradation during periodontitis.

Adult↗
PubMed2004

Alpha-crystallin-incorporated collagen matrices as an aid for dermal wound healing.

This study evaluated the effects of noncovalently incorporated crystallin into the collagen matrix for dermal wound-healing processes in rats. Crystallin-incorporated collagen matrix (CIC) showed better healing when compared to wounds treated with collagen matrix (CS) and without collagen (CR). Biochemical parameters and histological analysis revealed that increased wound contraction enhanced cell proliferation and efficient radical scavenging in the CIC group. The higher shrinkage temperature of CIC films when compared to CS groups suggested increased hydrothermal stability for the former material. An in vitro release study of CIC has showed sustained and time-dependent release of crystallin from the collagen matrix. These results demonstrate the possibility of using crystallin as therapeutic protein in the wound-healing process.

Animals↗
PubMed2004

Dermal wound healing processes with curcumin incorporated collagen films.

The wound healing process involves extensive oxidative stress to the system, which generally inhibits tissue remodeling. In the present study, an improvement in the quality of wound healing was attempted by slow delivery of antioxidants like curcumin from collagen, which also acts as a supportive matrix for the regenerative tissue. Curcumin incorporated collagen matrix (CICM) treated groups were compared with control and collagen treated rats. Biochemical parameters and histological analysis revealed that increased wound reduction, enhanced cell proliferation and efficient free radical scavenging in CICM group. The higher shrinkage temperature of CICM films suggests increased hydrothermal stability when compared to normal collagen films. Spectroscopic studies revealed that curcumin was bound to the collagen without affecting its triple helicity. Further we adopted the antioxidant assay using 2,2'-azobisisobutyronitrile to assess in vitro antioxidant activity of CICM. The antioxidant studies indicated that CICM quenches free radicals more efficiently. This study provides a rationale for the topical application of CICM as a feasible and productive approach to support dermal wound healing.

Animals↗
PubMed2003

Development of a novel non-human primate model for preclinical gene vector safety studies. Determining the effects of intracerebral HSV-1 inoculation in the common marmoset: a comparative study.

The owl monkey (Aotus trivirgatus) has served as the standard non-human primate model of herpes simplex virus-1 (HSV-1) infection because it is highly susceptible to HSV-1 encephalitis. Owl monkeys, however, are expensive, difficult to obtain, and difficult to maintain in captivity, thus greatly hampering the efficiency of preclinical gene therapy trials for brain tumors using HSV-1-based vectors. We have therefore compared the susceptibility of the common marmoset (Callithrix jacchus) with the owl monkey in a model of intracerebral inoculation of wildtype HSV-1 F-strain at increasing titers. The common marmosets consistently succumbed earlier to viral encephalitis than the owl monkeys. The histological evaluation of the common marmoset revealed extensive HSV-1 infection with a concomitant yet less marked inflammatory response compared to the owl monkeys. PCR for HSV-1 demonstrated a similar extra-CNS shedding route in both experimental models. Our findings show that the common marmoset is at least as susceptible to intracerebral HSV-infection as the owl monkey and that it can therefore serve as a valid and reliable experimental model for the important preclinical safety tests of HSV-based therapeutic viral vector constructs in the brain.

Animals↗
PubMed2000

Identifying the target cell in primary simian immunodeficiency virus (SIV) infection: highly activated memory CD4(+) T cells are rapidly eliminated in early SIV infection in vivo.

It has recently been shown that rapid and profound CD4(+) T-cell depletion occurs almost exclusively within the intestinal tract of simian immunodeficiency virus (SIV)-infected macaques within days of infection. Here we demonstrate (by three- and four-color flow cytometry) that this depletion is specific to a definable subset of CD4(+) T cells, namely, those having both a highly and/or acutely activated (CD69(+) CD38(+) HLA-DR(+)) and memory (CD45RA(-) Leu8(-)) phenotype. Moreover, we demonstrate that this subset of helper T cells is found primarily within the intestinal lamina propria. Viral tropism for this particular cell type (which has been previously suggested by various studies in vitro) could explain why profound CD4(+) T-cell depletion occurs in the intestine and not in peripheral lymphoid tissues in early SIV infection. Furthermore, we demonstrate that an acute loss of this specific subset of activated memory CD4(+) T cells may also be detected in peripheral blood and lymph nodes in early SIV infection. However, since this particular cell type is present in such small numbers in circulation, its loss does not significantly affect total CD4(+) T cell counts. This finding suggests that SIV and, presumably, human immunodeficiency virus specifically infect, replicate in, and eliminate definable subsets of CD4(+) T cells in vivo.

Animals↗
PubMed2000

Prolonged dominance of clonally restricted CD4(+) T cells in macaques infected with simian immunodeficiency viruses.

The repertoire of functional CD4(+) T lymphocytes in human immunodeficiency virus type 1-infected individuals remains poorly understood. To explore this issue, we have examined the clonality of CD4(+) T cells in simian immunodeficiency virus (SIV)-infected macaques by assessing T-cell receptor complementarity-determining region 3 (CDR3) profiles and sequences. A dominance of CD4(+) T cells expressing particular CDR3 sequences was identified within certain Vbeta-expressing peripheral blood lymphocyte subpopulations in the infected monkeys. Studies were then done to explore whether these dominant CD4(+) T cells represented expanded antigen-specific cell subpopulations or residual cells remaining in the course of virus-induced CD4(+) T-cell depletion. Sequence analysis revealed that these selected CDR3-bearing CD4(+) T-cell clones emerged soon after infection and dominated the CD4(+) T-cell repertoire for up to 14 months. Moreover, inoculation of chronically infected macaques with autologous SIV-infected cell lines to transiently increase plasma viral loads in the monkeys resulted in the dominance of these selected CDR3-bearing CD4(+) T cells. Both the temporal association of the detection of these clonal cell populations with infection and the dominance of these cell populations following superinfection with SIV suggest that these cells may be SIV specific. Finally, the inoculation of staphylococcal enterotoxin B superantigen into SIV-infected macaques uncovered a polyclonal background underlying the few dominant CDR3-bearing CD4(+) T cells, demonstrating that expandable polyclonal CD4(+) T-cell subpopulations persist in these animals. These results support the notions that a chronic AIDS virus infection can induce clonal expansion, in addition to depletion of CD4(+) T cells, and that some of these clones may be SIV specific.

Animals↗
PubMed1999

Mycobacterium bovis bacille Calmette-Guérin enhances pathogenicity of simian immunodeficiency virus infection and accelerates progression to AIDS in macaques: a role of persistent T cell activation in AIDS pathogenesis.

It has recently been proposed that Mycobacterium tuberculosis may enhance the pathogenicity of HIV infections and accelerate the course of HIV disease. This hypothesis has been tested in the present study using a simian immunodeficiency virus of macaques (SIVmac)/Mycobacterium bovis bacille Calmette-Guérin (BCG)-coinfected macaque model. Naive and chronically SIVmac-infected monkeys were evaluated. Following BCG inoculation, the SIVmac-infected monkeys exhibited the dominant responses of TCR-beta complementarity-determining region 3-restricted T cell subpopulations. This BCG-driven T cell activation correlated with a marked increase in viral loads in SIVmac-infected monkeys. Moreover, the prolonged T cell activation coincided with the enhanced decline of CD4+ PBL counts and the accelerated progression to clinical AIDS in the coinfected monkeys, suggesting that Mycobacterium-driven T cell activation may be the mechanism underlying the enhanced pathogenicity of AIDS virus infection in the coinfected individuals. Within 2 to 7 mo after BCG coinfection, all chronically SIVmac-infected monkeys died from SIV-induced AIDS including tuberculosis-like disease. Surprisingly, the naive monkeys manifested a T cell activation-related toxic shock syndrome and a profound depletion of CD4+ lymphocytes 2 wk after simultaneous SIVmac/BCG inoculation. These naive animals died 2 mo after SIVmac/BCG inoculation, with the evidence of the persistent SIV p27 antigenemia and SIVmac-induced disease. In contrast, the normal monkeys not infected with SIVmac survived BCG infection; the control SIVmac-infected animals showed a natural course of chronic SIV infection. Thus, results from this SIV/BCG coinfection model strongly support the hypothesis that active coinfection with HIV and Mycobacterium can impact remarkably on the AIDS virus-induced disease.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Cellular proliferation on desamidated collagen matrices.

The attachment and growth of human skin keratinocytes (KR) and fibroblasts (FB) on collagen modified by desamidation were investigated. Unlike type I native collagen, desamidated collagen has a sharp iso-ionic pH (5.1) thereby making available either negative or positively charged biomolecules as and when required for a specific bio-application. The cytocompatibility of desamidated collagen prepared from bovine achilles tendons (DCA) and hide trimmings (DCH) was compared with the bovine type I collagen (NC). KR or FB were seeded onto the wells of tissue culture plates coated with the collagen preparations (DCA, DCH and NC). Cellular proliferation on each of these substrates was monitored by reduction of MITT ([3-(4,5-dimethyl-2-thiazolyl)-2,5-dimethyltetrazolium bromide] and by determining the DNA synthesis with [3H]thymidine. In both cases cells proliferated well indicating that DCA and DCH serve as good substrata and are biocompatible. Cell growth occurred without any morphological changes in cell appearance as observed from the phase-contrast microscopy of the cultures, indicating no toxicity of the material during the period studied.

Adult↗
PubMed1998

In vivo effects of a bacterial superantigen on macaque TCR repertoires.

A macaque model was employed to explore staphylococcal enterotoxin B (SEB) superantigen-driven T lymphocyte responses. The SEB-reactive Vbeta+ cell subpopulations demonstrated a striking tri-phase response in rhesus monkeys following an SEB challenge in vivo. The hyperacute down-regulation, seen as early as 2 h through 2 days after SEB injection, was characterized by a disappearance of the reactive Vbeta-restricted PBL subpopulations from the circulation and decreased expression of these cell subpopulations in lymphoid tissues. Following this, a dominant expansion of reactive Vbeta-expressing CD4+ cell subpopulations occurred in lymph nodes and spleens, whereas in the peripheral blood a preferential expansion of reactive Vbeta-expressing CD8+ cell subpopulations was seen. An exhaustion of this response was then seen, with a prolonged decrease in the number of the reactive Vbeta+ CD4+ lymphocyte subpopulations. Interestingly, monoclonal or oligoclonal dominance was seen in the reactive Vbeta+ cell subpopulations in the period of the transition from the polyclonal cellular expansion to the exhaustion of the response, suggesting that some Vbeta+ cell clones may be more resistant than others to superantigen-mediated depletion. These results indicate that in vivo SEB superantigen-mediated effect on lymphocyte subpopulations in macaques is complex, suggesting that profound dynamics in the TCR repertoires may in part account for the susceptibility of higher primates to SEB-induced diseases.

Animals↗
PubMed1997

Studies on the desamidation of bovine collagen.

The most important reactive groups in collagen are amino, amido, guanidino, and carboxyl, all of which are present in comparatively large numbers. It is possible to modify amide groups present in the collagen of achilles tendons and hide trimmings by desamidation (DAM). DAM causes progressive hydrolysis of the amide groups of asparagine and glutamine side chains of collagen, thereby resulting in the reduction of the amide content of collagen. Loss of amide brings about an increase in the number of free carboxyl groups in the desamidated collagen, shown by reduction in its isoionic pH. The new modified collagen, like type I bovine collagen, has high viscosity and high hydroxyproline content. The fibril formation of the modified collagen showed slight variation, and polyacrylamide gel electrophoretic analysis indicated largely alpha components, indicating destruction of inter- and intramolecular crosslinks. The swelling behavior of the modified collagen is significantly higher compared to type I bovine collagen.

Amides↗
PubMed1996

In vitro T lymphopoiesis of human and rhesus CD34+ progenitor cells.

Differentiation of hematopoietic progenitor cells into T lymphocytes generally occurs in the unique environment of the thymus, a feature that has hindered efforts to model this process in the laboratory. We now report that thymic stromal cultures from rhesus macaques can support T-cell differentiation of human or rhesus CD34+ progenitor cells. Culture of rhesus or human CD34+ bone marrow-derived cells depleted of CD34+ lymphocytes on rhesus thymic stromal monolayers yielded CD3+CD4+CD8+, CD3+CD4+CD8-, and CD3+CD4-CD8+ cells after 10 to 14 days. In addition to classical T lymphocytes, a discrete population of CD3+CD8loCD16+CD56+ cells was detected after 14 days in cultures inoculated with rhesus CD34+ cells. CD3+ T cells arising from these cultures were not derived from contaminating T cells present in the CD34+ cells used to inoculate thymic stromal monolayers or from the thymic monolayers, as shown by labeling of cells with the lipophilic membrane dye PKH26. Expression of the recombinase activation gene RAG-2, which is selectively expressed in developing lymphocytes, was detectable in thymic cultures inoculated with CD34+ cells but not in CD34+ cells before thymic culture or in thymic stromal monolayers alone. Reverse transcriptase-polymerase chain reaction analysis of T cells derived from thymic stromal cultures of rhesus and human CD34+ cells showed a polyclonal T-cell receptor repertoire. T-cell progeny derived from rhesus CD34+ cells cultured on thymic stroma supported vigorous simian immunodeficiency virus replication in the absence of exogenous mitogenic stimuli. Rhesus thymic stromal cultures provide a convenient means to analyze T-cell differentiation in vitro and may be useful as a model of hematopoietic stem cell therapy for diseases of T cells, including acquired immunodeficiency syndrome.

Animals↗
PubMed1996

A prospective study of the epidemiology of colitis and colon cancer in cotton-top tamarins (Saguinus oedipus).

BACKGROUND & AIMS: Spontaneous colitis and colon cancer in the cotton-top tamarin have been shown to resemble human ulcerative colitis and its associated cancer. The effect of environment and diet on the evolution of the disease was studied in animals from birth to 5 years of age. METHODS: Newborn tamarins were assigned to three groups reared in (1) a colony in which colitis was highly prevalent and fed a standard diet; (2) an isolation unit and fed a standard diet or one of two semipurified diets; and (3) a multispecies nursery, returned to the colony, and fed the same semipurified diets. Mucosal biopsy specimens from the descending colon were taken at 4-month intervals. RESULTS: Acute colitis and chronic mucosal changes were significantly higher in the colony than in the isolation unit. Diet had no effect on acute colitis, but chronic mucosal changes were significantly higher in animals fed a standard diet than semipurified diets. CONCLUSIONS: Data suggest that acute colitis was associated with environment. Factors in the environment, including a transmissible agent, are discussed. Chronic mucosal changes were modified by diet. Cancer was associated with acute colitis and chronic changes and seems to be associated with diet.

Adenocarcinoma↗
PubMed1996

Induction of lymphocyte proliferation and severe gastrointestinal disease in macaques by a nef gene variant SIVmac239.

The molecularly cloned virus known as SIVmac239/YEnef causes extensive lymphocyte activation in unstimulated peripheral mononuclear cell cultures and induces an acute disease syndrome in macaque monkeys. Here we describe the histopathological and immunophenotypic changes and viral localization in peripheral lymph nodes, spleen, and gastrointestinal tract (including the gut-associated lymphoid tissue (GALT) in rhesus monkeys inoculated with SIVmac239/YEnet beginning at day 3 postinoculation (pi). The findings are compared with those of rhesus monkeys inoculated with the same dose of parental SIVmac239. Histopathological examination of peripheral lymphoid tissue and GALT demonstrated marked hyperplasia of T-cell-dependent regions and involution of germinal centers as early as day 7 pi. The most striking lesions were multifocal areas of lymphohistiocytic gastroenteritis and colitis. Cellular infiltrates peaked between day 7 and 14 pi and were composed primarily of CD3+ T lymphocytes and HAM-56+ monocyte/macrophages. Many of these inflammatory cells were also strongly immunoreactive for teh nuclear proliferation antigen Ki-67. Despite the presence of severe gastrointestinal pathology by day 7 pi, no significant difference in the numbers of virus-positive cells in the gastrointestinal tract was observed between these animals and SIVmac239-infected animals examined at the same time point. However, the distribution of virus in the gastrointestinal tract was markedly different, with virus localized to lymphoid nodules of GALT in SIVmac239-infected animals and restricted to areas of lymphohistiocytic gastroenteritis and colitis in animals infected with SIVmac239/YEnef. Our data indicate that the acute disease syndrome induced by SIVmac239/YEnef is not simply related to increased viral replication in the gastrointestinal tract but is likely due to inappropriate virus-induced T lymphocyte activation and proliferation in GALT and subsequent mucosal destruction.

Animals↗
PubMed1995

Progression to AIDS in the absence of a gene for vpr or vpx.

Rhesus monkeys (Macaca mulatta) were experimentally infected with strains of simian immunodeficiency virus (SIV) derived from SIVmac239 lacking vpr, vpx, or both vpr and vpx genes. These auxiliary genes are not required for virus replication in cultured cells but are consistently conserved within the SIVmac/human immunodeficiency virus type 2/SIVsm group of primate lentiviruses. All four rhesus monkeys infected with the vpr deletion mutant showed an early spike in plasma antigenemia, maintained high virus burdens, exhibited declines in CD4+ lymphocyte concentrations, and had significant changes in lymph node morphology, and two have died to date with AIDS. The behavior of the vpr deletion mutant was indistinguishable from that of the parental, wild-type virus. Rhesus monkeys infected with the vpx deletion mutant showed lower levels of plasma antigenemia, lower virus burdens, and delayed declines in CD4+ lymphocyte concentrations but nonetheless progressed with AIDS to a terminal stage. The vpr+vpx double mutant was severely attenuated, with much lower virus burdens and no evidence of disease progression. These and other results indicate that vpr provides only a slight facilitating advantage for wild-type SIVmac replication in vivo. Thus, progression to AIDS and death can occur in the absence of a gene for vpr or vpx.

Animals↗
PubMed1994

Macrophage function in simian AIDS. Killing defects in vivo are independent of macrophage infection, associated with alterations in Th phenotype, and reversible with IFN-gamma.

Infection of macrophages (M phi) in vitro with M phi-tropic isolates of simian immunodeficiency virus (SIV) did not affect killing of Cryptococcus neoformans up to 16 days after inoculation (p < 0.05). Conversely, alveolar M phi from animals with SIV-induced AIDS killed C. neoformans less efficiently (10.4 +/- 2.8% killing) and, when stimulated with phorbol myristate, produced less superoxide anion (O2-; 0.15 +/- 0.02 O2-/h/mg M phi protein) than M phi from uninfected monkeys (21.8 +/- 1.6% killing and 0.29 +/- 0.02 O2-/h/mg M phi protein). In contrast, killing and O2- release were accentuated in SIV+ asymptomatic animals (25.8 +/- 2.3% killing and 0.40 +/- 0.04 O2-/h/mg M phi protein; p < 0.05). M phi-mediated killing and O2- production could be restored by culturing the affected cells in supernatants derived from Con A-stimulated PBMC of uninfected or SIV+ asymptomatic monkeys. Supernatants with restorative properties had high IFN-gamma bioactivity (63.4 +/- 11.0 U/ml) and elevated IL-10 concentrations (75.3 +/- 10.4 pg/ml) as compared with PBMC supernatants derived from animals with AIDS (IFN-gamma, 9.7 +/- 4.9 U/ml; IL-10, 24.0 +/- 10.1 pg/ml). Functional restoration was found to be dependent, in part, on the presence of IFN-gamma, as neutralizing Abs to IFN-gamma significantly inhibited functional restoration in active supernatants. Moreover, the inactivity of supernatants from mitogen-stimulated PBMC cultures derived from animals with AIDS was not solely dependent upon the loss of CD4+ lymphocytes, inasmuch as purified pulmonary alveolar and peripheral blood CD4+ T cells from only uninfected and SIV+ asymptomatic animals, and not those from animals with AIDS, produced IFN-gamma upon mitogen stimulation. Collectively, these findings suggest that functional aberrations in alveolar M phi from animals with AIDS are not directly due to virus infection but likely result from changes in the pulmonary microenvironment in association with the multisystemic loss and dysfunction of CD4+ T cells.

Animals↗
PubMed1994

High-titer immune responses elicited by recombinant vaccinia virus priming and particle boosting are ineffective in preventing virulent SIV infection.

Eighteen rhesus monkeys were vaccinated with recombinant vaccinia viruses expressing SIVmac antigens in 3 separate rounds of experiments. Twelve of the monkeys were primed with a trivalent vaccinia virus recombinant expressing Gag, Pol, and Env polypeptides that can assemble into SIV pseudovirion particles and boosted with SIV particles in adjuvant. Four of the monkeys were primed with different vaccinia virus recombinants expressing env or gag+env followed by SIV particle boosts; two received vaccinia virus recombinants alone (env or env+gag). Despite the induction of vigorous immune responses, 17 of 18 rhesus monkeys became infected on challenge with a low dose of virulent SIVmac. The single protected animal was one of three challenged with homologous cloned SIV exactly matched to the clone used for construction of trivalent vaccinia virus recombinant and particles. Vaccination may have diminished SIV burdens and rates of CD4+ cell declines in some of the animals, but vaccinated/challenge/infected animals eventually developed fatal disease similar to control animals. These results highlight the extreme difficulty in achieving vaccine protection against virulent SIVmac infection even under idealized laboratory conditions.

Animals↗