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Biomedical subjects

A Subramanian

Publications and source records attributed to A Subramanian.

61 records · Page 4Linked to original sources
PubMed1987

Highly toxic coplanar PCBs: occurrence, source, persistency and toxic implications to wildlife and humans.

Isomer-specific determinations of PCB congeners in a wide variety of animal species such as fish, marine mammals (whale, dolphin and porpoise) and terrestrial mammals (dog, cat and human) revealed the environmental occurrence of highly toxic coplanar 3,3',4,4'-tetrachlorobiphenyl (T(4)CB), 3,3',4,4',5-pentachlorobiphenyl (P(5)CB) and 3,3',4,4',5,5'-hexachlorobiphenyl (H(6)CB) within a range of few pg g(-1) to several ten ng g(-1) in fat tissues (except fish) on a wet weight basis. Detection of these toxic residues in wild specimens collected from remote areas such as the North Pacific suggests the already widespread distribution of coplanar PCBs as in the case of general PCB pollution. The clear positive correlations between concentrations of total PCBs and each of the three coplanar PCBs obtained in all mammals analysed suggest that the sources of coplanar PCB contamination to the environment are mainly commercial PCB preparations. Comparison of the composition of three toxic coplanar PCBs in commercial PCB mixtures and in the various animals indicates the relative metabolisability of these congeners as follows: 3,3',4,4'-T4CB>3,3',4,4',5-P5CB>3,3',4,4',5,5'-H6CB. Moreover, marine mammals seem to have lower potency to metabolise the coplanar PCBs in comparison with terrestrial mammals. In human adipose tissues, the concentrations of coplanar PCBs were found to be much higher than 2,3,7,8-tetrachlorodibenzo-p-dioxin (T(4)CDD), 2,3,4,7,8-pentachlorodibenzofuran (P(5)CDF) and other toxic congeners. 'T(4)CDD-equivalent' analysis based on the enzyme induction potencies and the residues of these toxic chemicals indicates that 3,3',4,4',5-P(5)CB may impose a greater toxic threat than dioxins and furans to the humans and probably to wildlife also.

Journal Article↗
PubMed1979

Salinity adaptation in the snake eel Pisoodonophis boro (Ham-buch).

The snake eel Pisoodonophis Boro (Family Ophichthidae) burrows, causing leaks in the bunds and damaging the salterns and paddy fields adjoining estuaries. The animal's capability to withstand brine in salterns and fresh water in paddy fields was determined from laboratory experiments. The eel tolerated salinities ranging from deionized water to 75%. Adaptation to fresh water as well as full strength seawater was completed within 24 h. The concentration of sodium and chloride in the blood varied by 10--20% on transfer from seawater to fresh water. P. boro can survive in paddy fields but not in salterns. However, their occurrence in both is described as a rare phenomenon and not obligatory.

Adaptation, Physiological↗
PubMedDate not supplied

Effect of antibody orientation on immunosorbent performance.

The impact of antibody orientation on immunosorbent efficiency was quantitatively assessed. A pH-dependent murine monoclonal antibody (Mab) against human protein C (hPC), recombinant hPC (rhPC) and two different immobilization chemistries and matrices were used as model systems. The lysyl groups of the rhPC were covalently modified with an acetic acid ester of N-hydroxysuccinimide and this modified rhPC was used as a Fab masking agent (FMA). The FMA was used to mask the antigen binding regions (Fab) of the Mab prior to and during covalent immobilization. Thereafter, the residual active sites of the support were inactivated and the FMA was removed. Mab was immobilizeed at low bead-averaged densities of about 0.4-1.1 mg Mab/mL matrix to minimize local density effects. Immunosorbents made using masked Mab (oriented coupling) gave antigen binding efficiencies (nAg) of 42-48% compared with 18-22% for those made by random coupling. The amount of (Fab)2 released from pepsin digestion of immunosorbents was about 3-4-fold higher for matrices having been made with FMA-masked Mab relative to unmasked Mab. Thus, the (Fab)2 accessibility to pepsin correlates well with higher functional efficiency (nAg) and serves as a measure of orientation. In summary, at low Mab density and a 2:1 molar rhPC to Mab binding stoichiometry, about 80% or more of the Mab randomly coupled through amino moieties was improperly oriented relative to oriented coupled Mab, which correlated with about 50% of lost Mab functionality upon immobilization.

Amines↗
PubMedDate not supplied

Bioactivities of a tumour necrosis-like factor released by chicken macrophages.

To test for tumour necrosis-like factor (TNF) of chickens, supernatants of a lipopolysaccharide (LPS)-stimulated chicken macrophage cell line MQ-NCSU were analysed. A sequence of ion-exchange and gel-permeation chromatography was utilised to isolate TNF-like activity from the culture supernatant. The peak of TNF-like cytotoxic activity corresponded to the fractions with a molecular weight of 81 kDa or higher. Polyclonal anti-human TNF-alpha antiserum cross-reacted by Western blotting with a 17 kDa protein in the TNF-containing fraction under denaturing conditions. This result indicated that chicken TNF-like factor in the biologically active form may be a protein multimer of monomers of about 17 kDa. The molecular weight of these monomers is similar to the molecular weight of mammalian TNF-alpha. Chicken TNF-like factor stimulated macrophages by inducing morphological changes, enhancing Ia-expression, nitric oxide (NO) production and by synergising with interferon (IFN)-gamma in the induction of NO release from macrophages. The biological activities were not neutralised by anti-human TNF antiserum. These data suggest that LPS-stimulated chicken macrophages produced a functional homologue to mammalian TNF-alpha. This may be structurally quite different from the mammalian TNF molecule. Other factors may have been co-purified with the chicken TNF-like factor having overlapping functions and molecular weight. However, co-purification of chemokines and interleukin-1, major macrophage derived factors, with the chicken TNF-like factor can be excluded based on the purification strategies.

Animals↗