Biomedical subjects

M L Dao

Publications and source records attributed to M L Dao.

9 recordsLinked to original sources

PubMed1990

Calorie consumption level influences development of C3H/Ou breast adenocarcinoma with indifference to calorie source.

To analyze simultaneously the influence attributable to calorie consumption level and percentage of dietary fat on the spontaneous development of mammary adenocarcinoma, virgin female C3H/Ou mice were separated into five dietary groups. Four groups of mice were fed purified diets either ad libitum (16-18 kcal/mouse/day) or restricted 40% in calorie consumption (10-11 kcal/mouse/day), and diets contained either 4.5%, 7.5%, 67%, or 68% calories from fat. Mice that consumed isocaloric diets developed breast malignancy at a comparable pace. Consuming a diet in which fats were present only at levels sufficient to satisfy the threshold requirement of essential fatty acids, 4.5-7.5% of the total calories, or alternatively where dietary fat represented greater than 67% of the total calories consumed, did not significantly alter the tendency for breast tumor development. The pace and frequency with which tumors occurred reflected the host's level of calorie consumption. Mice consuming a high caloric diet, low or high in fat, tended to have a shortened latency to breast tumor formation, an increased incidence of breast tumors, elevated serum prolactin levels, elevated levels of antibodies to mouse mammary tumor virus, and elevated circulating immune complex levels.

Adenocarcinoma↗

PubMed1990

Dietary manipulation of mammary tumor development in adult C3H/Bi mice.

Chronic energy intake restriction (CEIR) in virgin female mice is one of the most effective ways of reducing significantly mammary adenocarcinoma in C3H/Bi mice, a strain which develops mammary adenocarcinoma associated with the murine mammary tumor virus spontaneously and at high incidence. In this study, the influence of chronic energy intake restriction imposed on fully mature (4- to 5-month-old), breeding female C3H/Bi mice was addressed, and the influence of energy intake where energy was derived largely from fat versus diets in which energy was derived largely from carbohydrates on tumor development and survival rate was investigated. The results show that chronic energy intake restriction can be delayed until full maturation and successful reproduction and still reduce significantly the incidence of mammary tumor development in this relatively short-lived strain of mice. Our findings demonstrate that the overriding dietary factor controlling mammary tumor development in these experiments in C3H/Bi mice was the level of energy intake, regardless of the primary source of energy (fat or carbohydrates).

Adenocarcinoma↗

PubMed1989

Decrease by chronic energy intake restriction of cellular proliferation in the intestinal epithelium and lymphoid organs in autoimmunity-prone mice.

In previous studies we demonstrated that chronic energy intake restriction (CEIR) by a diet relatively low in fat, relatively high in carbohydrate, and reduced 40% in total calories extends life span and delays development of autoimmune disease in autoimmunity-prone mice. To investigate a possible cellular basis for this dramatic action of CEIR, we analyzed the rate of incorporation of [3H]thymidine by cells of the intestinal epithelium, thymus, spleen, and mesenteric lymph nodes in ad libitum-fed mice vs. CEIR mice of three autoimmunity-prone strains. In New Zealand Black (NZB), MRL/MP-lpr/lpr (MRL/lpr), and BXSB mice, CEIR slowed the rate of uptake of [3H]thymidine and, by inference, the rate of cellular proliferation among epithelial cells along the entire length of the gastrointestinal tract. Furthermore, CEIR decreased the apparent proliferative rate of lymphoid cells of the thymus, spleen, and mesenteric lymph nodes. This action by CEIR on the proliferative rate of cells of these rapidly replicating cell populations may point to an important mechanism by which calorie restriction inhibits the development of autoimmune disease and extends longevity in autoimmunity-prone mice.

Animals↗

PubMed1989

Influence of chronic energy intake restriction on intestinal alkaline phosphatase in C3H/Bi mice and autoimmune-prone MRL/lpr,lpr mice.

The influence of chronic energy intake restriction (CEIR) on the level and activity of intestinal alkaline phosphatase was investigated in mice of the autoimmune-prone MRL/lpr,lpr strain and in mice of the autoimmune-resistant C3H/Bi strain. In both strains of mice, CEIR of 40% resulted in a significant increase in intestinal alkaline phosphatase (IAP) specific activity in MRL/lpr,lpr mice after 10 wk of feeding, and in C3H/Bi mice after 6 wk of feeding. An increase in the amount of immunoreactive alkaline phosphatase antigen was also found to be associated with the increased enzyme activity in CEIR mice. These results suggest that a specific induction of an intestinal enzyme occurs or, alternatively, that there is a specific relative decrease in synthesis of intestinal proteins other than IAP as a function of CEIR. Thus, CEIR appears to regulate the expression of proteins in the small intestine in a specific manner.

Alkaline Phosphatase↗

PubMed1989

Sequence analysis of the wall-associated protein precursor of Streptococcus mutans antigen A.

The nucleotide sequence has been determined for the Streptococcus mutans wall-associated protein A (wapA) gene from serotype c strains Ingbritt and GS5. The nucleotide sequence for each wapA gene was virtually identical, although the gene from strain GS5 contained a 24 base pair deletion. A 29 amino acid signal peptide was specified by each wapA gene with a mature protein of 424 amino acids (Mr, 45,276) for strain Ingbritt and 416 amino acids (Mr, 44,846) for strain GS5. In the C-terminal region of the wall-associated protein A, considerable sequence similarity was found with the membrane anchor region of proteins from other Gram-positive organisms such as the group A streptococcal M protein and the group G streptococcal IgG binding protein. Adjacent to the proposed membrane anchor is a highly hydrophilic region which may span the cell wall; both sequence data and experimental evidence indicate the existence of a region immediately outside the wall at which proteolytic cleavage occurs to release antigen A of Mr 29,000 into the culture supernatant. Thus, the wall-associated protein A is a precursor of the 29,000 Mr antigen A.

Amino Acid Sequence↗

PubMed1989

Molecular cloning of the Streptococcus mutans gene specifying antigen A.

A gene encoding a Streptococcus mutans surface protein antigen has been isolated from a strain GS-5 gene bank constructed via the Streptococcus-Escherichia coli shuttle vector pSA3. This E. coli recombinant clone, designated 4B2, expressed S. mutans proteins, as shown by Western immunoblot analysis with a specific rabbit antibody to S. mutans surface antigens. Three bands were observed, including a 52-kilodalton (kDa) protein (pI 5.7), a 29-kDa protein (pI 4.2), and a 20-kDa protein usually present in lower amounts. The 52- and 29-kDa proteins both reacted with a monoclonal antibody to S. mutans antigen A, a 29-kDa protein which has been characterized and used as a vaccine for the prevention of induced caries in rodents and monkeys. The 52-kDa protein, but not the 29-kDa protein, showed a capacity to bind to a broad number of carbohydrate polymers. The results from this study suggest that the recombinant 4B2 clone specifies a 52-kDa protein which is a precursor to the 29-kDa antigen A.

Antibodies, Bacterial↗

PubMed1985

An improved method of antigen detection on nitrocellulose: in situ staining of alkaline phosphatase conjugated antibody.

A biological stain for alkaline phosphatase was applied to detect immune complexes immobilized on nitrocellulose. This method was sensitive and useful for in situ staining of antigens, in dot-immunobinding assays and immunoblots. In addition to its sensitivity, the staining of alkaline phosphatase conjugated antibody was also highly stable, and allowed a permanent record of original immunochemical data. A rapid and simple method is also described using this technique for screening translation products of recombinant clones.

Alkaline Phosphatase↗

PubMed1985

Streptococcus-Escherichia coli shuttle vector pSA3 and its use in the cloning of streptococcal genes.

A shuttle vector that can replicate in both Streptococcus spp. and Escherichia coli has been constructed by joining the E. coli plasmid pACYC184 (chloramphenicol and tetracycline resistance) to the streptococcal plasmid pGB305 (erythromycin resistance). The resulting chimeric plasmid is designated pSA3 (chloramphenicol, erythromycin, and tetracycline resistance) and has seven unique restriction sites: EcoRI, EcoRV, BamHI, SalI, XbaI, NruI, and SphI. Molecular cloning into the EcoRI or EcoRV site results in inactivation of chloramphenicol resistance, and cloning into the BamHI, SalI, or SphI site results in inactivation of tetracycline resistance in E. coli. pSA3 was transformed and was stable in Streptococcus sanguis and Streptococcus mutans in the presence of erythromycin. We have used pSA3 to construct a library of the S. mutans GS5 genome in E. coli, and expression of surface antigens in this heterologous host has been confirmed with S. mutans antiserum. A previously cloned determinant that specifies streptokinase was subcloned into pSA3, and this recombinant plasmid was stable in the presence of a selective pressure and expressed streptokinase activity in E. coli, S. sanguis (Challis), and S. mutans.

Chloramphenicol↗

PubMed1979

Purification of a new high activity form of glucose-6-phosphate dehydrogenase from rat liver and the effect of enzyme inactivation on its immunochemical reactivity.

A new form of cytoplasmic glucose-6-phosphate dehydrogenase (E.C.1.1.1.49) was purified from rat liver by protamine sulfate precipitation, ammonium sulfate fractionation, ion exchange chromatography with diethylaminoethyl cellulose, and affinity chromatography with Cibacron blue agarose and NADP agarose. This form of the enzyme has a specific activity of over 600 units/mg of protein and gives essentially a single band by polyacrylamide gel electrophoresis. The form of the enzyme isolated by this purification method is 3 times more active than the form purified from liver by previously reported procedures. The relative mass of this pure glucose-6-phosphate dehydrogenase enzyme was determined by disc gel electrophoresis to be 269,000. This high activity glucose-6-phosphate dehydrogenase enzyme, after inactivation by reaction with palmityl-CoA, was no longer precipitated by specific rabbit and goat antisera to this purified enzyme. Thus, the possibility still exists that starved fat-refed animals contain glucose-6-phosphate dehydrogenase (G6PD) enzyme protein in an inactivated form no longer detectable by either enzyme activity or immunoprecipitation.

Animals↗