PubMed Health⌕ Search

Biomedical subjects

C R Lyttle

Publications and source records attributed to C R Lyttle.

82 records · Page 5Linked to original sources
PubMed1977

Pyruvate dehydrogenase complex from higher plant mitochondria and proplastids: regulation.

The activity of the pyruvate dehydrogenase complex from pea (Pisum sativum L.) mitochondria is inhibited when MgATP is added to the reaction mixture; 50% inhibition occurs at 4 mm ATP. The inhibition does not increase with time and is higher in the more highly purified preparations. Crude preparations of the complex show a time-dependent inactivation when incubated with 7.5 mm MgATP alone but this is not found with the more highly purified complex. This inactivation does not occur at 0 C. The complex could not be reactivated by high concentrations of Mg(2+). It is suggested that a phosphorylation-dephosphorylation mechanism may occur in plants, but the phosphatase and kinase are not tightly bound to the complex and are lost on isolation. The complex does not respond in a significant manner to energy charge. The NAD(+) to NADH ratio is the principal means of regulation of the complex, NADH being competitive with NAD(+) for the dihydrolipoamide component. The CoA to acetyl-CoA ratio is not important in regulation.The castor bean (Ricinus communis L.) proplastid complex is inhibited by the addition of 2 mm MgATP to the assay mixture. The inhibition is immediate, suggesting that phosphorylation of the enzyme is not involved or must be very rapid. Incubation of the complex with 20 mm MgCl(2) causes an activation of the complex. Maximum activity is not expressed in this case for 30 minutes. A similar activation can be achieved by preincubating the complex with 1 mm pyruvate. These data suggest that the complex is not fully activated on isolation.

Journal Article↗
PubMed1976

Subcellular localization of oestrogen-induced uterine peroxidase.

The distribution of oestrogen-induced peroxidase in the resuspended 8000g pellet of rat uterine homogenates was examined by centrifugation in a sucrose density gradient. Within 10h of treatment with oestradiol, peroxidase activity was found in a region devoid of catalase or urate oxidase (peroxisomal markers) which did not overlap the fractions containing succinate dehydrogenase (mitochondrial marker) or acid phosphatase (lysosomal marker). The induced uterine enzyme was localized in reticular membrane-bound vesicles with isopycnic density of 1.28g/ml from which it could be released by treatment with detergent.

Animals↗
PubMed1972

Metabolism of (4- 14 C)oestradiol by oestrogen-induced uterine peroxidase.

1. An enzyme that catalyses the metabolism and binding of [4-(14)C]oestradiol to protein and to other high-molecular-weight substances in the presence of H(2)O(2) was shown to be absent from the uteri of immature rats and to be induced by physiological doses of oestrogen or pregnant-mare-serum gonadotrophin. 2. The pH optimum, stability to heat and other characteristics of the uterine enzyme system as well as its subcellular distribution were determined. 3. The increase in the ability of uterine preparations to convert [4-(14)C]oestradiol into water-soluble products as a result of oestrogen treatment was accompanied by an increase in peroxidase and NADH oxidase activities and was inhibited by actinomycin D and cycloheximide. 4. The results support the proposal that the increase in peroxidase activity after oestrogen treatment might be part of an adaptive response of the uterus permitting it to bind and inactivate oestrogens and thus limit the duration of their effect upon this target tissue.

Albumins↗
PubMedDate not supplied

Mouse ascites golgi (MAG) mucin expression and regulation by progesterone in the rat uterus.

OBJECTIVE: To study the regulation of the blood group A-related high-molecular weight mucin glycoprotein epitope (mouse ascites golgi, MAG)-a menstrual cycle-dependent marker of endometrial receptivity-in a non-human endometrium model. METHODS: Immature Sprague-Dawley rats were injected with 1 microg of estradiol, 100 microg of testosterone, 100 microg of dexamethasone, 2.5 mg of progesterone (P), 0.325 mg of RU486, P and RU486, 100 microg of tamoxifen, or vehicle for 3 days, sacrificed, and the uteri were stained for MAG. Immunohistochemistry and blood analysis were the measurements used to compare the specimens from the exogenous hormonal and endogenous hormonal groups. Electron microscopy was used to locate the MAG epitope in one pseudopregnant adult Sprague-Dawley rat. RESULTS: The MAG epitope was present in endometrial glands of Sprague-Dawley rats, with maximal expression during proestrus and diestrus. Electron microscopy confirmed the Golgi location of this MAG epitope. In the untreated group, less than 0.5% of endometrial glands stained for MAG. The MAG was seen only in the glands of the P-treated rats and RU486 blunted this stimulatory effect by more than 95%. As little as 0.1 mg of P promoted MAG expression, with maximal response at 2.5 mg. Staining was seen 24 hours after P treatment, peaked at 72 hours, then declined. Induction of endogenous P by superovulation with pregnant mare serum gonadotropin (PMSG) and hCG (pseudopregnancy) also resulted in strong MAG glandular staining. CONCLUSION: Our results suggest that the MAG epitope is cyclically expressed and induced by P in rat endometrial glands.

ABO Blood-Group System↗
PubMedDate not supplied

Hormonal regulation of complement factor B in human endometrium.

PROBLEM: Recent investigations have demonstrated the presence of complement components in human endometrium in a cycle-specific manner. Luteal phase endometrium has been shown to synthesize complement C3 de novo, whereas proliferative endometrium produces little or no C3. Likewise factor B, which is critical to the activation of the alternative pathway of complement, has been shown to be present only in the glandular epithelium of luteal phase endometrium. This investigation was designed to determine if factor B is present in the endometrium in a high progesterone state such as pregnancy or with exogenous progesterone treatment. METHOD: Endometrial biopsies were obtained from patients on progesterone therapy. The endometrium of early pregnancy was evaluated by obtaining biopsies from patients with ectopic pregnancies as well as from patients undergoing therapeutic termination. Immunohistochemistry was performed on each biopsy using monoclonal antibodies to factor B. RESULTS: Our results demonstrate the presence of factor B in the glandular epithelial cells of the endometrium of patients treated with exogenous progesterone therapy. Additionally, factor B was localized to the glandular compartment of the endometrium from patients with ectopic gestations. Interestingly, the evaluation of an implantation site from an early gestation demonstrated factor B in the maternal decidua only; trophoblast did not exhibit the presence of factor B. CONCLUSION: Factor B exists in the endometrium in a hormone-dependent manner and is not expressed in fetal tissue in early gestation.

Complement Factor B↗