Biomedical subjects

A Subramanian

Publications and source records attributed to A Subramanian.

At least 19 recordsLinked to original sources

PubMed2006

Human blood monitoring program in Japan: contamination and bioaccumulation of persistent organochlorines in Japanese residents.

Concentrations of persistent organochlorines (OCs)-such as polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs), hexachlorobenzene, and tris(4-chlorophenyl)methane [TCPMe]-were determined in plasma samples from residents of three sub-metropolitan locations in Japan (Miyako, Saku, and Tottori) for the purpose of studying the geographic variation and specific accumulation of OCs. Residue concentrations of PCBs and DDTs were the highest in samples collected in Saku (400 and 370 ng/g lipid wt, respectively) whereas samples from Miyako contained greater CHL residues (70 ng/g lipid wt) than those from the other two locations. This contamination pattern reflects the historic use of OCs in each area. For the first time, tris (4-chlorophenyl) methane (TCPMe) concentrations were detected in most of the plasma sample analyzed. Concentrations of TCPMe which ranged from <0.1 to 8.1 ng/g lipid wt eight, were lower than those previouly reported in other human tissue. Larger geographic differences in OC accumulation were observed for PCBs and CHLs, whereas DDTs and HCHs exhibited little variability. PCB concentrations in samples from Saku residents were higher than those from residents of countries in the circumpolar Arctic region but lower than those reported for some populations in the United States and Western European countries. Interestingly, CHL residue concentrations in human blood from Japan are among the highest values reported for the countries examined, suggesting continued increased exposure to CHLs of the Japanese population. Time-trend analysis of CHLs in human blood samples from Miyako (Okinawa prefecture) showed that CHL residues have decreased substantially during the last decade, indicating the effect of the official ban of CHLs in 1986 in Japan. Isomer-specific analysis of PCBs revealed lower proportions of higher chlorinated congeners such as hepta- and octachlorobiphenyls in women than in men, suggesting the possibility of preferential elimination of higher chlorinated biphenyls in women. The difference in sex-dependent accumulation of OC compounds in healthy and ill persons was suggested. To our knowledge, this is the first report on the specific accumulation of persistent QCs, including TCPMe, in human blood samples from Japan.

Adult↗

PubMed2006

Contamination by persistent organic pollutants in dumping sites of Asian developing countries: implication of emerging pollution sources.

In Asian developing countries, large amounts of municipal wastes are dumped daily in open dumping sites without proper management. This practice may cause several adverse environmental consequences and increased health risk to local communities. To elucidate contamination by persistent organic pollutants (POPs)--including dichloro-diphenyl-trichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), chlordanes, hexachlorobenzene (HCB), and polychlorinated biphenyls (PCBs)--in such dumping sites, soil samples were collected from open dumping sites and respective control sites in Cambodia, India, and Vietnam from 1999 through 2001. Our results demonstrated that DDTs, PCBs, and HCHs were dominant contaminants in the dumping sites. However, the contamination pattern was not consistent, showing higher HCHs in India than in Cambodia and Vietnam. Interestingly, in all of the countries, extremely higher levels of POPs were observed in the dumping sites compared with those in the respective control sites, suggesting significant amplification of POP contamination in the dumping sites of Asian developing countries. Mean concentrations of DDTs and PCBs were 350 and 140 ng/g dry weight, respectively, in the dumping sites of Cambodia and 26 and 210 ng/g, respectively, in India. These residue levels were hundreds to thousands times higher than those in general soils, implying possible risk to human health of the local communities, especially to the rag pickers, including children who work in these sites to collect recyclable materials. Composition of DDT compounds suggested their recent use in populated areas, which in turn might have caused increased levels of DDTs in the open dumping sites. In addition, composition of HCH isomers revealed their different use pattern in different countries.

Asia↗

PubMed2006

Changing trends in US injury profiles: revisiting non-fatal occupational injury statistics.

The purpose of this paper is to review the current trends in non-fatal injury profiles of workers in the United States. It is generally accepted that occupational injury and illness rates are affected by many factors, such as the amount and quality of training, employee turnover rates, work experience, extent of mechanization and automation, job-related parameters, and worker gender. In the last decade, not only have the technologies used in the workplace changed significantly, there has been a greater awareness among employers and employees as to the importance of containing work injuries. Additionally, the extent of outsourcing for labor-intensive jobs has increased dramatically owing to cheaper labor costs in places such as China and Mexico. These changes have affected the manufacturing sector of US industry more than any other sector. How these changes have influenced the injury and illness profiles of the American worker is of considerable interest given the increased attention paid to work-workplace design, injury hazard control, and ergonomics in general. In this paper, we compare the injury and illness profiles of US workers separated by nearly a decade. The trends from early 1990s are compared to those from early 2000s. Data from the Bureau of Labor Statistics were used to compile the injury statistics. The results of our comparison show that while the absolute numbers of work-related injuries and illnesses have declined over the last 10 years, the basic trends associated with different factors remain almost unchanged. The reasons for this decline are discussed in this paper.

Back Injuries↗

PubMed2006

Somatic cell nuclear transfer in buffalos: effect of the fusion and activation protocols and embryo culture system on preimplantation embryo development.

The present study was conducted primarily to evaluate several factors that affect the nuclear transfer programme in water buffalos, in which relatively few studies have been performed. Embryos reconstructed with quiescent fetal fibroblasts and metaphase II cytoplasts were matured for 24 h, and activation was found to be comparatively better than in those matured for 30 h. A significantly higher proportion of embryos fused (52.0 +/- 1.9) and cleaved (51.2 +/- 1.7) when the couplets were fused 4-6 h before activation than when fused and activated simultaneously (46.5 +/- 1.6 and 44.5 +/- 2.0, respectively). Development of nuclear transfer embryos to the blastocyst stage (4.8 +/- 2.2) was supported by a commercially available sequential medium, and cleavage (76.5 +/- 2.8) was significantly higher in this medium compared with cleavage in TCM-199 with oviduct epithelial cell coculture (45.6 +/- 1.5) and synthetic oviduct fluid (21.8 +/- 6.6). Of the 16 cloned embryos transferred, none resulted in pregnancy. The present study demonstrates that optimal numbers of cloned buffalo blastocysts can be obtained from oocytes matured for 24 h, fused 3-4 h before activation and cultured in a commercially available sequential media (G1/G2), thus providing further information to enable successful nuclear transfer in buffalos.

Animals↗

PubMed2005

Infrared optical properties and AFM of spin-cast chitosan films chemically modified with 1,2 Epoxy-3-phenoxy-propane.

Chemical modification of spin-cast chitosan films has been performed. This modification involves the attachment of 1,2 Epoxy-3-phenoxy-propane, commonly known as glycidyl phenyl ether (GPE), to the amine group of the chitosan molecule. Optical properties of modified films have been determined in the infrared region of the spectrum using spectroscopic ellipsometry, and are reported in this paper. Special attention is paid to the infrared region where the index of refraction and extinction coefficients from 750 to 4000 cm(-1) were determined. Difference plots of IR optical data before and after chemical modification were generated to confirm that modification had occurred. Optical modeling of infrared spectroscopic ellipsometry (IRSE) data with respect to chemical bond vibrations has also been performed. This modeling involved curve fitting of resonant chemical bond absorptions using Lorentz oscillators. These oscillator models allow for comparison of modified chitosan to unmodified chitosan. The purpose of this research was to determine infrared optical constants of chemically modified chitosan films This work shows that surface chemistry of biomaterials can be studied quite sensitively with spectroscopy ellipsometry, detecting as little as 100 ng/cm(2) of GPE.

Adsorption↗

PubMed2005

UV-vis-infrared optical and AFM study of spin-cast chitosan films.

Optical properties of spin-cast chitosan films have been determined in the infrared, visible, and ultraviolet region of the spectrum using spectroscopic ellipsometry. Optical constants for the UV-vis-near IR spectra from 130 to 1700 nm were determined using Cauchy dispersion forms combined with Lorentzian oscillator models in the absorptive shorter wavelength regions. Infrared index of refraction and extinction coefficients from 750 to 4000 cm(-1) were determined using ellipsometric data fits to dispersion models based on harmonic oscillators. This modeling determined that optical anisotropy was present and measurable over all wavelength regions of ellipsometric data. To obtain information on the micro- and nano-scale surface structure, tapping mode atomic force microscopy (AFM) imaging was employed to determine morphology and roughness information of dry spin-cast chitosan films.

Algorithms↗

PubMed2005

An investigation into the effect of axillary surgery on ipsilateral axillary sweating--a pleasing 'complication' or a potential treatment for hyperhidrosis?

Although there had not been complaints of excessive sweating pre-operatively, it was noticed incidentally that a large proportion of patients who had undergone axillary lymph node sampling or clearance for breast carcinoma seemed to report ipsilateral sweat loss as a pleasing 'complication'. We interviewed 65 consecutive patients who had all had axillary dissections performed by the same surgeon's technique; the interviews were held 2-102 months after their operations. In 36 cases, patients reported no change in axillary sweating (mean 35 months), whereas 29 patients reported a decrease (mean 50 months). This result was statistically significant at the 95% confidence interval (p=0.022).

Adult↗

PubMed2005

Organochlorine residues in odontocete species from the southeast coast of India.

Blubber from bottle-nose dolphins, spinner dolphins, humpback dolphin (Tursiops truncatus, Stenella longirostris and Sousa chinensis) were collected from the Bay of Bengal (southeast coast of India) and analyzed for the organochlorine pesticides hexachlorocyclohexane (HCHs), p,p'-dichlorodiphenyl trichloroethane (DDTs), and polychlorinated biphenyls (PCBs). All nine specimens analyzed contained considerable levels of all the three chemical classes where DDT was in the range of 3330-23330 ng/g; HCHs in the range of 95-765 ng/g; and PCBs in the range of 210-1220 ng/g (wet weight basis). The reasons for this and the variations in the isomer pattern of HCHs and DDT and its metabolites in marine mammal tissues are discussed.

Adipose Tissue↗

PubMed2005

Improvement of glucose tolerance in Zucker diabetic fatty rats by long-term treatment with the dipeptidyl peptidase inhibitor P32/98: comparison with and combination with rosiglitazone.

AIM: The aim of this study was to investigate the effect of long-term treatment with the dipeptidyl peptidase inhibitor P32/98 and its combination with rosiglitazone on blood glucose control and islet of Langerhans histology in male Zucker diabetic fatty (ZDF) rats, when treatment begins before or after the development of overt diabetes. METHODS: ZDF rats were treated with P32/98 from the age of 9, 12 or 15 weeks. Rosiglitazone maleate was given to a separate group from the age of 13 weeks. P32/98 was given to all of these rosiglitazone-treated rats from 16 weeks of age. Rosiglitazone maleate was also given from 16 weeks of age to half the rats that were given P32/98 from 9 weeks of age. The compounds were given by oral gavage until the rats were 14 weeks old and then in the diet. The experiment was terminated at the age of 20-21 weeks. Blood glucose, plasma insulin and oral glucose tolerance were measured at intervals; islet histology was assessed terminally. RESULTS: P32/98 improved glucose tolerance after both single and multiple doses when treatment started at 9 weeks of age, also after the third week of treatment when treatment began at 12 or 15 weeks of age. P32/98 reduced daytime blood glucose when treatment began at 12 weeks. Treatment with rosiglitazone increased food intake and body weight, and after 2 weeks, reduced daytime blood glucose, water intake and the area under the glucose tolerance curve. A single dose of P32/98 markedly improved glucose tolerance in rosiglitazone-treated rats. When treatment had begun at 9 weeks of age, P32/98 stimulated insulin secretion in some glucose tolerance tests. Neither P32/98 nor rosiglitazone affected pancreatic insulin content, nor did they have clear effects on islet histology. CONCLUSION: P32/98 elicited a sustained improvement in glucose tolerance in both prediabetic and diabetic ZDF rats. The effects of P32/98 on glucose and insulin were similar to those of rosiglitazone, and in contrast to rosiglitazone, P32/98 did not increase food intake or body weight. However, neither compound was especially effective at improving diabetes in ZDF rats when treatment began at 9, 12 or 15 (P32/98) or 13 (rosiglitazone) weeks of age.

Animals↗

PubMed2004

Direct observation of charge transfer at a MgO(111) surface.

Transmission electron diffraction (TED) combined with direct methods have been used to study the sqrt[3]xsqrt[3]R30 degrees reconstruction on the polar (111) surface of MgO and refine the valence charge distribution. The surface is nonstoichiometric and is terminated by a single magnesium atom. A charge-compensating electron hole is localized in the next oxygen layer and there is a nominal charge transfer from the oxygen atoms to the top magnesium atom. The partial charges that we obtain for the surface atoms are in reasonable agreement with empirical bond-valence estimations.

Journal Article↗

PubMed2004

Dioxins and related compounds in human breast milk collected around open dumping sites in Asian developing countries: bovine milk as a potential source.

In this study, concentrations of dioxins and related compounds (DRCs)--such as polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls--were found in human breast milk from women living near dumping sites of municipal waste and reference sites in India, Cambodia, Vietnam, and the Philippines during 1999 to 2000. DRCs were detected in all human breast milk samples analyzed, demonstrating that residents in these Asian developing countries have been exposed to these contaminants. In India, the concentrations of DRCs in human breast milk from women living near the investigated dumping site were notably higher than those from women living near reference sites and from women in other Asian developing countries. Toxic equivalent quantity (TEQ) levels of DRCs were comparable with or higher than those reported in the general populations of developed countries since 1990. In contrast, levels of these contaminants in human breast milk in women from Cambodia and Vietnam were not significantly different between milk from women living near the dumping and reference sites. These results indicate that significant pollution sources for DRCs are present in Indian dumping sites and that residents there have been exposed to relatively higher levels of these contaminants. TEQ levels in human breast milk from the dumping site in India tended to decrease with an increase in the number of previous deliveries by mothers, whereas no significant relationship was observed in Cambodia, Vietnam, or the Philippines. This suggests that mothers who have been exposed to relatively high levels of DRCs transfer greater amounts of these contaminants to the first infant than later ones through breast-feeding, which in turn implies that the first children of these mothers might be at higher risk from DRCs. When the residue levels of DRCs in bovine milk collected from the Indian dumping site and reference sites were examined, TEQ levels in bovine milk from the dumping site were higher than those from reference sites. This result suggests that bovine milk is a potential source of DRCs for residents living near the dumping site in India. To our knowledge, this is the first comprehensive study on exposure to DRCs of residents living in proximity to open dumping sites of municipal waste in Asian developing countries.

Adolescent↗

PubMed2004

Coronary subclavian steal syndrome.

Inappropriate alterations in flow in the form of steal syndromes are a well recognised phenomenon. In the subclavian steal syndrome a proximal subclavian artery stenosis is responsible for reversal of flow in the vertebral artery and symptoms of vertebrobasilar ischaemia occur with arm movement. After internal mammary artery grafting to the coronary circulation, during coronary artery bypass surgery (CABG), coronary subclavian steal can occur. Retrograde flow occurs from the myocardium through the internal mammary graft to the subclavian artery secondary to a proximal subclavian stenosis. It is a rare but important cause of recurrent chest pain after coronary surgery.

Aged↗

PubMed2004

Surface crystallography via electron microscopy.

The study of atomic structure of surfaces is fundamental to the understanding of electronic, chemical and mechanical properties of surfaces and numerous techniques have been developed to this end. Transmission Electron Microscopy techniques, namely transmission electron imaging (TEM) and diffraction (TED), due to their ability to provide structural information at very high resolutions, have emerged as powerful tools for the study of surface structure. In this article we review the experimental method alongside the various post-processing routines that are necessary to extract vital structural information from experimental data.

Journal Article↗

PubMed2004

Intravenous administration of an AAV-2 vector for the expression of factor IX in mice and a dog model of hemophilia B.

Previous experiments have demonstrated the stable expression of factor IX (FIX) protein in mice and canine models of hemophilia B following portal vein gene transfer with a recombinant adeno-associated virus (rAAV) vector encoding FIX. Here, we present the results of studies that further optimized the rAAV vector transgene cassette used to express FIX and explored the use of the less-invasive intravenous (i.v.) route of vector administration for the treatment of hemophilia B. First, a liver-specific promoter was evaluated in conjunction with cis-acting regulatory elements in mice. Constructs that included both the beta-globin intron and the woodchuck hepatitis virus post-transcriptional regulatory element resulted in the highest level of FIX expression in vivo. Using this optimized vector, we demonstrate that i.v. injection was feasible for hepatic gene transfer in mice, achieving 70-80% of portal vein expression levels of FIX. In further studies using the Chapel Hill strain of hemophilia B dogs, we demonstrate for the first time FIX expression and partial correction of the bleeding disorder following i.v. administration of an AAV vector.

Animals↗

PubMed2004

Comparison of different fabrication techniques used for processing 3-dimensional, porous, biodegradable scaffolds from modified starch for bone tissue engineering.

3 dimensional, porous, biodegradable scaffolds were fabricated using modified starch of varying degree of substitution (DS) by extrusion processing. Freeze drying/lyophilization was also employed to fabricate scaffolds from modified starch. The research efforts have been focused on the comparison of the above-mentioned techniques by comparing the properties of the fabricated scaffolds in the paradigm of bone tissue engineering. The physicomechanical properties like porosity, compressive strength and modulus, pore size and microstructure were tested and analyzed by liquid replacement, mechanical testing and scanning electron microscopy respectively. The biodegradability of scaffolds was evaluated by soaking the samples in aqueous medium and Hank's balanced salt solution at 37-degree invitro. The cytotoxicity studies on these scaffolds were also conducted. The scaffolds have a 3D structure consisting of interconnected pores with good porosity, pore size, adequate compressive strength and modulus and exhibit good biodegradability as well as biocompatibility. After further optimization in the processing conditions and parameters they could be made useful for bone tissue engineering.

Absorbable Implants↗

PubMed2003

Family physicians are an important source of mental health care.

While comprising about 15 percent of the physician workforce, family physicians provided approximately 20 percent of physician office-based mental health visits in the United States between 1980 and 1999. This proportion has remained stable over the past two decades despite a decline in many other types of office visits to family physicians. Family physicians remain an important source of mental health care for Americans.

Humans↗

PubMed2003

Congener-specific patterns and toxic assessment of polychlorinated biphenyls in resident and migratory birds from Southern India and Lake Baikal in Russia.

Concentrations of polychlorinated biphenyls (PCBs), including non-, mono-, and di-ortho congeners, were determined in migratory and resident birds collected from India and Lake Baikal in Russia. In the 11 different species examined, total PCBs concentrations were in the range of 11-4500 ng/g (wet wt). IUPAC 105, 118, 138, 153, and 180 were the predominant congeners in almost all the birds. White-cheeked tern collected from India and common tern collected from Lake Baikal showed high PCBs concentrations of 4400 ng/g (wet wt) and 4500 ng/g (wet wt), respectively, and accumulated relatively high ratios of penta-CBs (IUPAC 118, 105, 99). Toxic equivalents (TEQs) of non- and mono-ortho PCB congeners in birds collected from India and Lake Baikal were in the range of 1.5-56 and 2.8-370 pg/g wet wt, respectively. Toxic assessment results led by calculated TEQs of the transfer to eggs from female birds revealed that TEQs in most of migratory and resident birds were comparable to the lowest observable effect level (LOAEL) of chicken which is a highly sensitive species against dioxin-like compounds. Calculated transfer TEQs to eggs of common tern collected from Lake Baikal in autumn, however, exceeded the LOAEL of CYP1A induction in bald eagle embryos and ED50 of that in pheasant embryos, suggesting that embryo toxicity by coplanar PCBs in some avian species breeding in Lake Baikal is possible.

Animals↗

PubMed2002

Metastasis to and from the central nervous system--the 'relatively protected site'.

The brain has long been recognised as a site with a very low rate of metastases, despite the potential for cancers to be extremely locally aggressive. This feature contrasts with most of the rest of the body, where metastatic spread is much more common. The pathological behaviour of any tumour is governed by both its inherent composition and the composition of the matrix in which it is sited. Much work has been done in recent years to elucidate the factors within the central nervous system (CNS) that give the brain its unique properties. Tumour interactions with the blood-brain barrier, microglia, and various matrix proteins, cytokines, and growth factors have a central role. This review concentrates mainly on the process of tumour spread from the CNS and explores how the brain is a protected site. CNS metastases from extraneural sites are also briefly covered.

Animals↗