Biomedical subjects

B Devaraj

Publications and source records attributed to B Devaraj.

7 recordsLinked to original sources

PubMed1997

Coherent detection techniques in optical imaging of tissues.

To form optical images from the transmitted or reflected light that is multiply scattered inside biological tissue, several detection techniques that extract the least-scattered photons or path-resolved photons have been developed. This paper reviews the coherent detection techniques. Emphasis is put on coherent detection imaging methods based on optical heterodyning, whose attractive features include quantum-noise-limited sensitivity, wide dynamic range, and excellent directionality and selectivity. Coherent detection methods have been implemented to achieve laser computed tomography and micrometre-resolution cross-sectional images in both in vivo and in vitro biological systems. Imaging works by ourselves and others are described, and an experimental study on coherent photon migration through highly scattering media is described to aid the understanding of the coherent detection method in selectively detecting the signal-carrying photons.

Diagnostic Imaging↗

PubMed1996

Development and applications of new technology for two-dimensional space-time characterization and correlation analysis of ultraweak biophoton information.

We describe the spatial distribution and temporal correlation analysis of ultraweak biophoton emission based on photoelectron pulse time series and position measurement techniques. Experimental results on the spatio-temporal variation of biophoton emission from soybean seedlings after physical and chemical stimulation to the root tip are analyzed. Our results suggest the potential usefulness of this technique to quantify the transmission mechanisms of biological signals in the living system by measuring the biophoton emission.

Photons↗

PubMed1995

Ultraweak biophoton emission imaging of transplanted bladder cancer.

Biophoton emission or spontaneous ultraweak light emission has been observed from almost all living organisms, with intensities ranging from 10(-19) to 10(-16) W/cm2. The measurement of biophoton emission offers the attractive possibility of noninvasive monitoring of the underlying physiological function of a living system. In the present study, ultraweak biophoton emission from mice with transplanted bladder cancer was detected by a two-dimensional photon-counting system. Photon counts were observed to be 1.51-4.73 times higher from the regions of untreated tumor than from normal regions. Our study suggests that this novel technique may be applicable to the diagnosis of superficial tumors.

Animals↗

PubMed1991

Monitoring a mammalian nuclear membrane phase transition by intrinsic ultraweak light emission.

The first thermodynamic measurements of the intensity of light emission associated with native lipid peroxidation in a biological membrane are described. Kinetics of the radical chain reaction are shown to be sensitive to membrane structural phase and lipid dynamics. This is demonstrated by a novel measurement of a phase transition in the membrane of the intact mammalian nucleus. The apparent activation energies of lipid peroxidation in this system are also obtained for the first time. We suggest that this measurement may be more generally applicable as a method for monitoring membrane phase transitions.

Animals↗

PubMed1991

Ultraweak light emission from rat liver nuclei.

An extremely weak native light emission from rat liver nuclei was detected and studied using a highly sensitive single photon counting system. This emission is oxygen dependent and we attribute it to (per) oxidative processes. The effects of deuterium oxide and 1,4-diazabicyclo-[2.2.2] octane on the light emission suggests the possible involvement of singlet oxygen. The kinetic features of the underlying reactions including biphasic response to both oxygen and temperature changes, could be clearly discerned. Further study of this light emission can serve as a useful adjunct to biochemical investigations of oxidative processes which play an important role in mutation, carcinogenesis and aging.

Animals↗

PubMed1987

Clinical application of Percoll gradient-separated bone marrow.

We have evaluated the transplantation potential of bone marrow stem cell concentrates isolated from the 40/60% interface of discontinuous Percoll gradients. This mononuclear fraction is free from platelets and depleted of granulocytes, and contains the majority of granulocyte-macrophage colony-forming cells (GM-CFC), erythroid burst-forming units (BFU-E), and granulocyte, erythroid, macrophage, megakaryocyte colony-forming cells (GEMM-CFC) in less than 10% of the cell number of the original buffy coat. This preparation allows further manipulation without the clumping and cell loss associated with buffy coat cell preparations. Cells isolated by this technique were evaluated for hematopoietic restoration potential in 14 patients who received allogeneic bone marrow transplants as supportive therapy after high dose cytoreduction to treat leukemias or lymphoma. The number of nucleated cells infused varied from 1.6-5.5 X 10(7)/kg, and the number of GM-CFC infused ranged from 0.4 to 3.7 X 10(5)/kg. There was an inverse relationship between the time to recovery of granulocytes and platelets and the number of GM-CFC infused when fewer than 10(5) GM-CFC/kg were transplanted. Above this dose, there was recovery within 10-15 days after transplantation. The stem cell-enriched fraction contained 30-40% of the original number of T lymphocytes, and acute graft-versus-host disease was observed in seven of these patients.

Adolescent↗

PubMed1987

Limiting-dilution analysis of the effects of colony-stimulating factors, phytohemagglutinin, and hydrocortisone on hematopoietic progenitor cell growth.

The effects of colony-stimulating factors (CSFs), phytohemagglutinin (PHA), and hydrocortisone on the growth of human bone marrow hematopoietic progenitor cells (granulocyte-macrophage; GM) were analyzed in a limiting-dilution assay (LDA). Both low-density bone marrow cells separated by discontinuous Percoll gradients and a T cell-depleted and progenitor-enriched cell fraction obtained by the combination of counterflow elutriation centrifugation and Percoll gradients were examined in LDA. GCT (monocytoid cell line-conditioned medium containing GM-CSF), human placenta-conditioned medium, bladder carcinoma cell line 5637-conditioned medium (containing GM- and G-CSF), and recombinant CSF (G-CSF) directly induced proliferation of progenitors with single-hit kinetics. In some instances, however, PHA-stimulated lymphocyte-conditioned medium (containing G- and GM-CSF) showed deviation from single-hit kinetics, which demonstrated the presence of factor(s) suppressive to progenitor growth. In a T cell-depleted, progenitor-enriched fraction, PHA alone was found to suppress progenitor growth at a level as low as 100 ng/mL. The addition of hydrocortisone (10(-6) mol/L) increased the progenitor frequency but suppressed progenitor growth at 10(-4) mol/L. LDA appears to be a valuable method for exploring mechanisms of factors regulating hematopoietic cell growth.

Bone Marrow Cells↗