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G J Mizejewski

Publications and source records attributed to G J Mizejewski.

At least 55 records · Page 3Linked to original sources
PubMed1981

Development of estradiol-positive feedback on luteinizing hormone release in the female rat: a quantitative study.

Experiments were conducted to study, in a quantitative manner, the development of estradiol (E2)-positive feedback on LH release in the female rat. A Silastic capsule (20 mm in length/100 g BW) containing E2 dissolved in corn oil (400 micrograms/ml) reproduced first proestrous levels of serum E2 when implanted sc in juvenile rats of different ages (days 20-32). When similar capsules were implanted in infantile rats (days 10-18), serum E2, measured 2 days later, was found to be extremely elevated in 12- and 14-day-old rats (4-6 times higher than first proestrous levels), declining thereafter so that in 16- to 20-day-old rats the levels were only 2-fold greater than proestrous values. Serum levels of alpha-fetoprotein decreased markedly between days 12-28, and both normal and implant-produced serum E2 levels paralleled the decline in the protein titers. However, calculation of the total E2 binding capacity of alpha-fetoprotein indicated that in addition to binding to this protein, there are additional factors responsible for the persistence of E2 in the serum of infantile rats. A LH surge could not be induced in 12- or 14-day-old rats by a 48-h E2 pulse, despite the presence of substantial amounts of free E2, which exerted profound negative feedback effects. Between days 16-20, only E2 levels that were at least 2-fold higher than first proestrous values were effective in inducing a LH surge. Between days 22-34, a LH surge was elicited by serum E2 levels very similar to those seen during the first proestrus. By days 26-28, the profile of the LH surge was indistinguishable from that of the first preovulatory surge. Starting on day 26, and in addition to the LH surge elicited by the 48-h E2 pulse, an earlier surge occurred on the next day after E2 implantation. By day 30, the early LH surge became firmly established, and the late surge was no longer apparent. It is suggested that in the female rat, the development of E2-positive feedback comprises four phases: phase I, before day 16, in which the surge mechanism of the LH-releasing system is not developed; phase II, between days 16-20, in which E2 levels twice as high as those of first proestrus are necessary to activate the LH surge mechanism; phase III, which is initiated at the beginning of the juvenile period (approximately days 20-22) and in which the LH surge mechanism responds to E2 levels of preovulatory magnitude; and mechanism responds to E2 levels of preovulatory magnitude; and phase IV, which begins around days 26-28 and in which a 24-h exposure to E2 levels of preovulatory magnitude is sufficient to elicit a LH surge.

Aging↗
PubMed1980

Estradiol affinity chromatography: application to purification of murine alpha-fetoprotein.

A one-step batch procedure is described for purification of murine alpha-fetoprotein (AFP) by estradiol affinity chromatography. Various ratios of carbodiimide (C), diaminononame (D) and estradiol hemisuccinate (E) were tested to determine optimal conditions for AFP purification. Although yields of AFP ranged from 15 to 44% depending on the reagent ratio employed, AFP isolates free of other protein contaminants were achieved at C:D:E ratios of 10:10:1 with a 29% yield. Both estrone and estradiol proved efficient as elution agents to free AFP bound to the estradiol-Sepharose beads, but higher yields were produced with estrone. After isolation the estrogen-eluted AFP preparations were analyzed by (1) estradiol-binding assays, (2) third-party radiocoprecipitation, (3) inhibition of radioimmunoassay for estrone and estradiol and (4) exchange of unlabeled for radiolabeled estradiol. These results indicated that the steroid remained attached to the eluted AFP molecule.

Animals↗
PubMed1979

Purification of alpha-fetoprotein from mouse amniotic fluid by gel-entrapped antibody filtration.

A one-step immunospecific affinity chromatographic method for purification of mouse alpha-fetoprotein (AFP) directly from amniotic fluid is described. The procedure employed a rabbit anti-AFP immunoglobulin-G entrapped in a polyacrylamide gel matrix prepared as a gel slurry. The presence of impurities could not be demonstrated in the eluted fraction and the recovery of AFP was approximately 26%. Sufficient quantities of AFP were readily purified for raising antibodies and for purity studies.

Albumins↗
PubMed1979

Characterization of murine hepatoma BW7756. I. Selected biochemical properties of liver and hepatoma.

Selected biochemical properties, based on hepatocellular function, were assessed in the mouse hepatoma BW7756 and host and/or normal mouse liver. These biochemical properties included (a) alpha-fetoprotein (AFP) production, (b) lipid composition, (c) isozyme patterns and enzyme activities, and (d) cyclic AMP levels. The tumor evidenced an exponential growth phase and vigorous production of AFP in the first 3 weeks following transplant. The concentration of AFP in the sera of tumor-bearing mice increases roughly with the growth of the hepatoma. The percentage of total lipid in the hepatoma was greater than in either normal or host liver; however, the liver displayed more phospholipid than the tumor, while more triglyceride was demonstrable in the hepatoma. Of the 17 isozyme patterns analyzed, seven--acid phosphatase, malate dehydrogenase, aspartate amino-transferase, glucose-6-phosphate dehydrogenase, esterase, lactate dehydrogenase, and xanthine dehydrogenase--were different in the liver and the tumor. The cyclic AMP levels decreased in the tumor and the host spleen from day 10 to day 21; however, slight increases were noted in the tumor and host spleen and liver at day 28. These studies suggested 2--3 weeks posttransplantation as the optimal time for investigational use of this hepatoma.

Animals↗
PubMed1979

alpha-Foetoprotein:immunoreactivity of the major oestrogen-binding component in mouse amniotic fluid.

Competitive protein binding studies, using oestrone as the inhibitor, demonstrated that mouse amniotic fluid contains a high affinity oestradiol-binding component precipitable by monospecific rabbit anti-alpha-foetoprotein (AFP) in a double-antibody radio-immunoassay. On disc gel radio-electrophoresis the oestrogen-binding entity migrated as an alpha-1 protein which was immunoreactive to anti-AFP serum. Immunoprecipitation of protein-bound [3H]-oestradiol from solution was proportional to anti-AFP immunoglobulin G concentration. Rabbit antisera directed against other major proteins in amniotic fluid did not produce significant precipitation of radioactivity. Only when anti-AFP antiserum was the complexing protein and AFP, either crude or purified, was the binding protein did a substantial [3H]-oestradiol precipitate form. Our data suggest that oestradiol and anti-AFP do not bind at the same sites on the AFP molecule and that estradiol does not serve as a hapten in the production of anti-AFP serum in rabbits.

Amniotic Fluid↗
PubMed1979

Immunobiologic studies in hepatoma-bearing mice passively immunized to alpha-fetoprotein.

Mice bearing the BW7756 hepatoma were passively immunized using rabbit antiserum to murine alpha-fetoprotein (AFP) administered in constant or increasing doses. Control tumor-bearing mice were inoculated with saline or nonimmune rabbit serum (NRS) (constant or increasing doses), or were left untreated. The tumor growth curves from mice receiving constant or increasing doses of anti-AFP or constant doses of NRS showed suppression of hepatoma growth; but in both groups of anti-AFP-treated mice this was accompanied by gross anatomical changes, including necrosis, more extensive than in the NRS-treated or other control mice. AFP blood levels roughly paralleled the tumor growth responses. Since an immunological response against the rabbit serum was elicited in the host, it is possible that circulating immune complexes play some role in tumor suppression. Changes observed in liver- and spleen-to-body weight ratios may also reflect a response to circulating immune complexes.

Animals↗
PubMed1978

Studies of autoimmune induction in the rat lacrimal gland.

Induction of autoimmunity in the rat lacrimal gland was presently assessed. Antibodies to lacrimal gland extract were detectable in 58% of the immunized rats. Skin tests were positive at 4 week postimmunization in 70% of the animals. Histological observations revealed the presence of mononuclear cell infiltrates surrounding the ductal and acinar epithelium at 2--6 weeks.

Animals↗
PubMed1977

Isolation and characterization of alpha-fetoprotein from the mouse hepatoma BW7756.

Purification of alpha-fetoprotein from mouse hepatoma BW7756 extracts was performed using ammonium sulfate precipitations, gel filtration, ion-exchange chromatography and isoelectric focusing. These procedures produced a 5.6% yield of alpha-fetoprotein with 96% purity. Polyacrylamide slab gel electrophoresis, extended agarose electrophoresis and immunoelectrophoresis demonstrated that mouse hepatoma alpha-fetoprotein migrated at pH 8.6 as a rapid alpha1, or postalbumin globulin. Crossed antibody electrophoresis of the agarose zone containing alpha-fetoprotein failed to demonstrate microheterogeneity. Molecular weight analysis of the mouse hepatoma alpha-fetoprotein on a calibrated Sephadex G-200 column yielded a value of 72 000-73 000 for the native protein. Sodium dodecyl sulfate gel electrophoresis subsequently demonstrated a single polypeptide chain with a molecular weight of 72 000. Amino acid analysis showed the alpha-fetoprotein to be an acidic protein dominated by hydrophobic residues. The total carbohydrate content was 5.5%, and 3 mol of sialic acid were detected per mol of alpha-fetoprotein. Although neutral sugars were the principal class present, galactosamine was the most abundant single sugar detected.

Amino Acids↗
PubMed1976

Studies of human chorionic gonadotrophin in steroid-primed hypophysectomized rats.

The uptake of [125I]HCG was studied in the ovaries of intact and hypophysectomized (Hypox) Sprague-Dawley rats. The [125I]HCG localized specifically in the ovary of the intact rat, and to a lesser extent, in the ovary of the hypox rat. The concentration of HCG in all other tissues and organs of either sex was negligible. However, the localization of [125I]HCG in the hypox rat was enhanced by the presence of exogenous steroids. The greatest increase in HCG uptake was observed in the rats primed with androgen; while a lesser enhancement was demonstrated in the oestrogen treated rats. Comparison of the ovary-to-body weight ratios revealed that a greater amount of HCG localized in the androgen-primed rats than in the oestrogen treated animals even though the ovaries of the former were smaller. These findings suggest that the hypox rat ovary primed with androgen could provide a highly sensitive animal model for further studies of the HCG cell receptor site in animals free of pituitary influence.

Animals↗
PubMed1975

Alpha fetoprotein: effect of heterologous antiserum on hepatoma cells in vitro.

Hepatoma cells derived from The Jackson Laboratory mouse hepatoma BW7756 synthesized alpha fetoprotein (AFP) in vitro. The AFP was immunologically identical to that circulating in the sera of hepatoma-bearing mice. An in vitro cytotoxic effect of rabbit antiserum to AFP was studied in hepatoma cells obtained both from fresh cell suspensions and short-term cell culture. The use of intact and/or inactivated anti-AFP serum inhibited the growth of the AFP-producing cells. The cytotoxic effects of the antiserum depended on exposure time and serum concentration. The cytotoxicity was complement independent, as demonstrated by studies with heat-deactivated serum devoid of extrinsic complement. The control target cells included fresh cell suspensions of normal mouse liver and mouse muscle fibroblasts grown in short-term culture. Specificity of the antisera for the target cells was demonstrated by absorption with purified mouse AFP. The results could be explained by the presence of AFP on the hepatoma cell surface.

Animals↗