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Biomedical subjects

C Chen

Publications and source records attributed to C Chen.

At least 1,243 records · Page 69Linked to original sources
PubMed1985

Erythrocyte differentiation of naturally occurring isotopic lithium abundances.

Lithium is effective in the treatment of mania. There are two naturally occurring stable lithium isotopes, Li-7 (92.6%) and Li-6 (7.4%). Usually there is little differentiation between isotopes of an element, but chemical and behavioural data suggest dissimilarities exist between lithium isotopes. Results are now reported indicating that a group of manic patients given lithium chloride were able to differentiate Li-6 from Li-7 at the membrane level. Blood samples were drawn, erythrocytes separated from plasma and the isotopic abundances of Li-6 and Li-7 determined by atomic absorption spectrophotometry. The ratio of abundances of Li-6 in the erythrocyte and plasma was 1.274 indicating the erythrocyte membrane had the in vivo capability of isotope fractionation.

Adult↗
PubMed1985

Broiler aflatoxicosis with recovery after replacement of the contaminated diet.

Broiler chickens were fed a diet containing 2057 and 1323 micrograms/kg feed of aflatoxins B1 and B2, respectively, for 35 d. Effects of aflatoxins on growth, food consumption, efficiency of food utilisation and manifestations of aflatoxicosis were compared with control birds at the end of the feeding trial and at 1, 2, 4, 8 and 16 d after replacing the contaminated feed. No difference in food consumption was observed between the controls and the aflatoxin-fed chickens, but efficiency of food utilisation was decreased from 2.2 for the controls to 2.4 g food/g gain for the group fed aflatoxins. Aflatoxins caused depressed growth and enlargement of the kidney, liver, heart and gall bladder. Haemorrhagic spots were present on the surface of the muscles and some of the livers. Most livers from aflatoxin-fed birds were pale and infiltrated with lipid. After withdrawal of the food containing aflatoxins, all apparent gross lesions of aflatoxicosis disappeared, with no evidence of any lesions 8 d after removal of the contaminated diet.

Aflatoxin B1↗
PubMed1985

Acupuncture therapy in acute abdomen.

Acupuncture as a therapeutic measure for abdominal pain was early recorded in Huangdi Neijing ("Yellow Emperor's Canon of Medicine"). Fruitful experiences have been accumulated in the practice of the long historical years. Nowadays acupuncture therapy has become one of the main therapeutic methods in surgical acute abdomen and is widely used clinically.

Abdomen, Acute↗
PubMed1985

The T lymphocyte response to cytochrome c. V. Determination of the minimal peptide size required for stimulation of T cell clones and assessment of the contribution of each residue beyond this size to antigenic potency.

The B10.A T cell proliferative response to pigeon cytochrome c is mainly directed against a single antigenic determinant located at the carboxy-terminal end of the molecule. In the present experiments, we used synthetic peptide analogs of the carboxy-terminal sequence of moth cytochrome c to explore the structural requirements for antigenic potency. The minimum-sized peptide capable of stimulating a full response varied with the T cell clone, but within the limits of the biological systems studied, was shown to be moth fragment 97-103. Addition of more amino acids at the amino terminal end increased the antigenic potency in uneven increments, with a large contribution being made at residue 95. Analysis of amino acid substitutions at this position provided no evidence that it contained a residue that directly contacted the T cell receptor. Instead, good agreement with an analysis that made use of helix-coil transition theory suggested that this residue, as well as others, increased antigenic potency by contributing to the stabilization of the secondary structure of the molecule in an alpha-helical configuration. The maximum effect of chain length on antigenic potency appeared to stop at residue 93, in agreement with the theoretical analysis. However, addition of several more amino-terminal residues to residue 93 showed one additional significant increment of increased potency. This was almost entirely accounted for by a single lysine located four amino acids beyond the glutamic acid at residue 93 (approximately one turn of an alpha-helix away). To experimentally test whether alpha-helix-forming tendencies could account for the increased potency of the larger analogs, the degree of helix formation in trifluoroethanol was assessed by circular dichroism measurements. A good correlation was found between antigenic potency and percentage of alpha-helix for peptides of increasing chain length from moth 95-103 up to moth 86-90; 94-103. These results suggest that secondary structure may play an important role in determining the potency of antigenic determinants involved in the activation of T lymphocytes.

Animals↗
PubMed1984

Modified rosette inhibition test with mouse lymphocytes for detection of early pregnancy factor in human pregnancy serum.

The rosette inhibition test has been modified so that early pregnancy factor (EPF) in human pregnancy serum can be detected with mouse lymphocytes. Interference with the assay, which would result from incubation of lymphocytes with heterologous serum proteins, is prevented by the introduction of an ion exchange chromatography step. This provides a simple and rapid method for separating EPF from interfering serum proteins. Human pregnancy and non-pregnancy sera were assayed for EPF with human lymphocytes and results compared with those obtained with DEAE-Sephacel fractions of the same sera tested with mouse lymphocytes. The 2 systems showed good agreement but the mouse assay gave greater differentiation between positive and negative results. When monoclonal anti-T cell antibodies, Hu Ly-m1 and anti-Ly-1.1, were substituted for anti-lymphocyte sera in the human and mouse assay systems respectively, similar results were obtained. The mouse assay system has several advantages over the human assay, including stability of the anti-mouse lymphocyte serum and the ready availability of mouse lymphocytes. Moreover the modified method may be applied not only to the assay of human EPF, but also to the assay of EPF from other species. This would be of value if several species were being studied in 1 laboratory, or if sufficient quantities of lymphocytes from a particular species were not available.

Animals↗
PubMed1984

Immunochemical characterization of the androgen-dependent spermine-binding protein of the rat ventral prostate.

A solid-phase radioimmunoassay was developed to measure the level of the androgen-dependent spermine-binding protein (SBP) in the cytosol fraction of the rat ventral prostate during endocrine manipulation. The concentration of SBP and immunologically cross-reacting material (CRM) in the ventral prostate was at least 5000 times higher than the level of CRM detected in rat serum or cytosol from other rat tissues. Cytosol from the ventral prostate of intact rats was separated by DEAE-cellulose chromatography into three major fractions of CRM. One of these fractions corresponded to the elution position of SBP. Cytosol prepared from rats 48 h after castration lacked SBP and one of the two other fractions of CRM. This loss coincided with an increase in CRM in the remaining fraction. No significant difference was detected in the total level of CRM when intact and 48 h-castrated rats were compared. Injection of rats with 5 alpha-dihydrotestosterone (DHT) immediately after castration prevented these changes in the profile of CRM. Several proteins cross-reacting with antibodies to purified SBP were detected in cytosol by using an immunoblot procedure. The highest-Mr band corresponded to SBP. The effect of short- and long-term castration and subsequent DHT treatment on CRM was studied by using the immunoblot technique. Short-term castration (2 days) led to the disappearance of CRM coinciding with SBP (Mr 35 000-38 000) and an increase in smaller forms of CRM (Mr 24 000 and 22 000). Injection of rats with DHT 2 days after castration led to the reappearance of CRM corresponding to SBP, which returned to normal levels within 4 to 5 days of treatment. Long-term castration (up to 14 days) led to a gradual disappearance of all CRM; subsequent DHT treatment led to the reappearance of all forms of CRM and normal levels were attained within 5 days. We have identified SBP and the various forms of CRM as a secretory product of the rat ventral prostate by immunohistochemical staining and by DEAE-cellulose fractionation of prostatic fluid. Prostatic fluid is rich in proteolytic activity and these proteinases may be responsible for processing SBP to small forms of CRM.

Animals↗
PubMed1984

Tissue deposition and clearance of aflatoxins from broiler chickens fed a contaminated diet.

A study was conducted to determine aflatoxin levels in the tissues of broiler chickens that had been fed a diet containing 2057 micrograms aflatoxin B1 and 1323 micrograms aflatoxin B2/kg for 35 days. Results showed that aflatoxins were deposited in all tissues. The highest levels of aflatoxins were present in the gizzards, livers and kidneys. There was evidence that the high levels of aflatoxins B1 and B2 in the gizzards might have been caused by contamination by the gizzard contents during the slaughtering process. After feeding the aflatoxin-contaminated diet for 35 days, mean values for the combined aflatoxins were less than 3 micrograms/kg of tissue. Four days after withdrawal of the aflatoxin-contaminated ration, there were no detectable amounts of aflatoxins in any of the tissues. The results indicate that broiler chickens rapidly clear aflatoxins from their tissues once they are transferred to an aflatoxin-free diet.

Aflatoxins↗
PubMed1984

Positive regulatory interactions of the HIS4 gene of Saccharomyces cerevisiae.

The role of cis- and trans-acting elements in the expression of HIS4 has been examined by using HIS4-lacZ fusions in which lacZ expression is dependent upon the HIS4 5' noncoding region. The cis-acting sequences involved in regulation were defined by studying the effects of the wild-type and various deletions and their revertants on regulation via the general control of amino acid biosynthesis. The role of trans-acting genes was analyzed by studying the regulation of the HIS4-lacZ fusions in strains carrying mutations in the GCN (AAS) or GCD (TRA) genes and in strains carrying the GCN genes on high-copy-number plasmids. These studies have led to the following conclusions. (i) HIS4 is positively regulated by the general control. (ii) At least one copy of the 5'TGACTC3' repeat at -136 is required in cis for this regulation. (iii) Both the GCN4 gene and at least one copy of the repeated sequence are required for expression at the repressed level. (iv) The open reading frames in the 5' noncoding region are not required in either cis or trans for the regulation of HIS4.

Chromosome Deletion↗