Biomedical subjects
Publications and source records attributed to J J Hicks.
In order that blastocyst implantation occurs in mammals, it is required the synthesis and secretion of several substances including steroid hormones by the preimplanted embryo. In this paper, we analyze the embryo endocrine capacity for biosynthesis and secretion of progesterone and several progestines.
Uterine contraction is essential for genital tract functioning among mammal females. For women, the main interest are the possible alterations, and the ability to manage them with drug use. Due to the fact that contraction regulation is multifactorial, several medications are used in basic and clinical research, both to know contraction mechanisms, and to interfere with its alterations. This review considers contraction mechanism at molecular-cellular level, and the different molecules regulating it; as well as the effects that different medications produce upon such mechanism.
In order that blastocyst implantation occurs in mammals, it is required the synthesis and secretion of several substances including steroid hormones by the preimplanted embryo. In this paper, we analyze the embryo endocrine capacity for biosynthesis and secretion of progesterone and several progestines.
Establishment of pregnancy in mammals is a process resulting of closely concerted events. The participation of the embryo through its development and secretory activity on the one hand, and on the other, the oviductal and endometrial tissues, by means of their secretions, give the optimal conditions to let the embryo establish creating a proper milieu for its nutrition and development. In this review, we analyze the influence of the oviductal and uterine secretions upon early embryonic development and differentiation and some transport systems of nutritional elements required in the early stages of the blastogenesis.
The metabolic adaptability of Taenia solium cysticerci was studied in vitro, by measuring their respiratory rate before, during, and after trypsin-induced evagination. Under aerobic conditions, the oxygen consumption increased about 40% during evagination of the cysticeri and returned to basal rates after the process was completed. The percentage of evagination induced by trypsin was not affected under anaerobic conditions or in the presence of respiratory poisons such as cyanide and carbon monoxide. These data indicate that cysticerci use either aerobic or anaerobic pathways according to oxygen availability in the environment. Results from experiments of irreversible respiratory poisoning using cyanide suggest the presence of an alternative respiratory chain. Proteolytic action of trypsin on a fibrous layer surrounding the invaginated larvae is suggested by histological evidence.
The properties of type I and occupied and unoccupied type II cytosolic estrogen binding sites in the rat endometrium were analyzed on day five of pregnancy; the samples studied correspond to blastocyst receptive endometrium (implantation sites), nonreceptive endometrium and ovariectomized uterine horn endometrium, from the same pregnancy rats. The occupied binding site type II was analyzed by exchange assays. Dissociation constant obtained from experiments carried out at 4 or 25 degrees C are similar for each one of the binding site at the three different endometrium samples; the binding capacity (femtomoles/mg protein) from the sites type I and type II and the ratio between occupied (by endogenous estradiol) and unoccupied site type II, seems to be characteristic for each one of the three analyzed endometrium.
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The presence of polyamines (putrescine, spermidine and spermine) and the enzymatic activity of extrahepatic arginase (E.C. 3.5.3.1) which catalizes the hydrolysis of L-arginine into L-ornithine and urea have been related with cellular growth and development in several tissues. The enzymatic activity of arginase in rat implantation sites and its participation in reproductive process is demonstrated. Long-Evans adult rats during the 4th or 5th days of pregnancy were utilized. Arginase activity is higher in non-decidualized tissue (86.1 +/- 33 nmoles of urea/mg protein/min-1) when was compared with implantation sites (61.7 +/- 17). Intrauterine administration of several concentrations of a new synthetic L-ornithine analogue, AIAVA (2-amine-5-iodoacetamide valeric acid), produced embryonic growth arrest concomitant with arginase inhibition but not ornithine decarboxylase. From our results it is possible to stress the metabolic importance of uterine arginase in reproductive process.
Experiments were undertaken to investigate whether ultrastructural changes could be visualized in the endometrial epithelial linings brought about by the presence of spermatozoa. Female rabbits were inseminated with intact spermatozoa in one uterine horn, and the other horn was injected with inactive (dead) spermatozoa, which served as the control. Ruthenium red was used to enhance contrast of glycoproteins of epithelial plasma membranes. There was a decrease in the number and height of microvilli of epithelial cells in those horns injected with intact spermatozoa along with a decrease of ruthenium red deposits. In contrast, microvilli were numerous in those horns injected with inactive spermatozoa, and ruthenium red deposits also were numerous. This marker was not seen between neighboring epithelial cells in any of the injected horns. Control virgin animals, however, disclosed ruthenium red deposits in luminal plasma membranes and along the junctional complexes of epithelial cells. Intact spermatozoa could modify the synthesis or turnover of glycoproteins of outer coats owing to a possible cell-to-cell interaction between spermatozoa and endometrium. The lack of ruthenium red deposits in junctional complexes in the injected animals and their presence in the virgin control rabbits suggest the opening of communicating channels in the two former groups due possibly to the PMSG priming not present in the virgin control animals.
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Decarboxylation of L-ornithine by L-ornithine decarboxylase (ODC; E.C.4.1.1.17.) is the initial step in the biosynthesis of putrescine, ODC activity is generally low in most tissues, marked increases are associated with rapid tissue growth and particularly with mammalian embryogenesis. 0.5 mg/kg of DL-alpha-difluoromethylornithine (DFMO) (irreversible inhibitor of ODC) was administered to uterine horns of Long-Evans adult rats during the 4th day of pregnancy. As control material, saline (0.15 M) was administered to contralateral uterine horn. The animals were sacrificed on different days, the uterine horns were removed and the number of implant of implanted embryos were counted. DNA, RNA, protein and dry weight content in implantation sites (5th day of pregnancy) indicated that decidualization following DFMO took place normally but that embryonic growth was arrested in the treated horn. When 100 micrograms of putrescine were added together with DFMO, the embryotoxic effect was absent.
3H-sialyl residues transfer by subcellular epididymal fractions [plasma membrane (PM), microsomes (MI), and mitochondria (MT)] to both endogenous and exogenous acceptors was studied. Their fraction purity was valued (5' nucleotidase and glucose 6-phosphatase activities). The glycoprotein or glycolipid N-acetyl neuraminyl transferase activity in microsomes were 5 times higher in caput than in cauda (624 to 125 pmoles/30 min/mg protein). PM activity also was higher in caput. In MT fraction, the activity was smaller. Two mechanisms related to spermatozoa glycoprotein changes during maturation are proposed: secretion to the lumen of molecules previously glycosilated in microsomes and transialylation to spermatozoa from membranal ectoenzymes localized on the surface of the epididymal epithelium.
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Phospholipases A2 and C (93 and 500 mU) were administered to uterine horns of Long-Evans adult rats during the first five days of pregnancy. As control material, saline (0.15 M) was administered to contralateral uterine horns. The animals were sacrificed on the ninth day of pregnancy, the uterine horns were removed and the number of implanted embryos were counted. Both horns were examined with light and electron microscopes. For electron microscopy, Ruthenium red was used to visualize possible changes of the outer coat (glycocalix) of the plasma membrane of endometrial epithelial cells. Implantation was inhibited when phospholipases A2 and C were administered during the first three days of pregnancy. Ultrastructural modifications included decrease of glycoproteins as demonstrated by diminution of the Ruthenium red staining that may indicate a decrease in the negative surface charges of endometrial surface epithelium.
Endometrial differentiation of the implantation site (IS) is regulated by hormonal and local influences (egg). To better understand the possible participation of cyclic nucleotides in this process, we measured cAMP and cGMP by RIA in IS of the rat on day 6 of pregnancy. IS showed an increase of both nucleotides (3.54 and 0.57 pmoles/mg DNA) when compared with the remaining endometrium (NIS) (2.70 and 0.30). The cAMP/cGMP ratio did not change significantly. We also found an increase in the proteins/mg DNA ratio (12.04 in IS vs 10.63 in NIS) and in the hydration of IS. Our hypothesis is that together these two nucleotides function as a monodirectional system in which they act cooperatively as positive effectors of different sequential steps in the overall process of implantation.
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