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N Chegini

Publications and source records attributed to N Chegini.

At least 91 records · Page 5Linked to original sources
PubMed1991

Role of luteal cell nucleus in the expression of gonadotropin action.

Gonadotropin receptors are not only present in cell membranes, but also in nuclei of bovine and human luteal cells. hCG/hLH can directly regulate several nuclear functions. To further investigate the role of luteal cell nucleus in the expression of gonadotropin action, the effect of enucleation of luteal cells on gonadotropin receptors and gonadotropin response was studied. Luteal cytoplasts were prepared by colchicine treatment of purified whole luteal cells followed by centrifugation at 37 C in a Percoll gradient. The cytoplasts were 85 to 90% pure with a recovery of about 57%. Cytoplasts were viable as determined by trypan blue exclusion (87%) and metabolically competent as determined by 3H-leucine incorporation into proteins. On the day of preparation, the viability and metabolic competency of cytoplasts were similar to control cells, i.e. untreated and colchicine treated whole luteal cells. In addition, cytoplasts and control cells showed a similar decline in number and viability during storage at 4 C. While control cells continue to be metabolically competent, cytoplasts showed a dramatic decline by 48 h of storage at 4 C. Neither the cytoplasts nor control cells degraded 125I-hCG. The kinetics of 125I-hCG association and dissociation, specificity and affinity of binding to cytoplasts were similar to control cells. However, the number of available gonadotropin receptors in cytoplasts was significantly lower than in control cells. Cytoplasts contained lower progesterone levels and more importantly, they could not be stimulated by 10 nM hCG or 10 mM dibutyryl cyclic AMP to produce more progesterone. Controls cells, on the other hand, contained higher progesterone levels and responded to hCG and dibutyryl cyclic AMP stimulation. In summary, removal of nuclei from luteal cells results in a partial loss of gonadotropin receptors and complete loss of steroidogenic response to hCG and dibutyryl cyclic AMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The presence of pregnancy-associated plasma protein-A in human corpora lutea: cellular and subcellular distribution and dependence on reproductive state.

Pregnancy-associated plasma protein-A (PAPP-A) is a high-molecular-weight glycoprotein primarily secreted by syncytiotrophoblasts of human placenta. It is not known, however, whether human CL of menstrual cycle or pregnancy also contain this protein. Therefore, light and electron microscope immunocytochemical studies were undertaken to investigate the presence, cellular and subcellular distribution, and dependence of luteal PAPP-A content on reproductive state. Human CL from early, mid, and late luteal phases and from term pregnancies immunostained specifically for PAPP-A. Immunostaining was found in large luteal cells (17-30 microns) but not in small luteal cells (7-16 microns) or in nonluteal cells in any of the reproductive states. Immunostaining was not found in negative control tissues, i.e. human liver or bovine CL of pregnancy. As expected however, term-pregnancy human placenta used for a positive control tissue immunostained intensely for PAPP-A. The luteal immunostaining was highest in early luteal phase, decreased progressively from early to mid and from mid to late luteal phases, and then disappeared in corpora albicantia. The relative intensity of immunostaining in early luteal phase human CL was similar to that in term-pregnancy human placenta and higher than in term-pregnancy human CL. The immunogold particles due to PAPP-A were primarily associated with secretory granules of large luteal cells. A small number of gold particles were also found in rough endoplasmic reticulum and cytoplasm. In conclusion, human CL contain immunoreactive PAPP-A. The luteal content varies with reproductive state, with the highest amount found in early luteal phase CL.(ABSTRACT TRUNCATED AT 250 WORDS)

Corpus Luteum↗
PubMed1991

Immunocytochemical localization of relaxin in human corpora lutea: cellular and subcellular distribution and dependence on reproductive state.

Relaxin is one of the hormones present during pregnancy and it is synthesized primarily by corpora lutea (CL). Other reproductive tissues including CL of the menstrual cycle may also synthesize this hormone. Very little is known, however, about the cellular and subcellular distribution of relaxin in human CL and dependence of luteal relaxin on the reproductive state. The light and electron microscope immunocytochemical studies described here were undertaken to obtain this information using antisera to porcine and human relaxin. Immunostaining was found in large luteal cells (17-30 microns) but not in small luteal cells (7-16 microns) or in nonluteal cells in any of the reproductive states or in human hepatocytes. Luteal immunostaining was low in early luteal phase; it increased progressively, reaching the highest level in late luteal phase, and then decreased greatly in corpora albicantia. Term pregnancy CL contained similar immunostaining as early luteal phase CL. Mid luteal phase CL contained more immunostained cells than late luteal phase CL, but the late luteal phase CL contained a greater amount of immunostaining per cell than mid luteal phase CL. The immunogold particles due to relaxin were primarily present in secretory granules and to a small extent in rough endoplasmic reticulum. Quantitation revealed that secretory granules contained a much higher number of gold particles than did rough endoplasmic reticulum. These two organelles from late luteal phase CL contained greater numbers of gold particles than those from mid luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Corpus Luteum↗
PubMed1991

Quantitative cell composition of human and bovine corpora lutea from various reproductive states.

The cell composition of human and bovine corpora lutea (CL) from various reproductive states was investigated by computerized video-based interactive Bioquant image analysis system IV and by light microscope immunocytochemistry. Human and bovine CL contained more nonluteal cells than luteal cells. Human CL contained a lower number of luteal and a greater number of nonluteal cells than bovine CL. Regardless of the reproductive state, human CL contained more small luteal cells than large luteal cells. In all reproductive states except in the late luteal phase, the bovine CL also contained more small luteal cells than large luteal cells. The average sizes of all the cells in human CL were smaller than in bovine CL. Human CL contained more vascular space than bovine CL during mid and late luteal phases. The number of luteal cells increased and nonluteal cells decreased from early to mid luteal phase, and then luteal cells decreased and nonluteal cells increased in late luteal phase and in degenerating human and bovine CL. While the change of number of small and large luteal cells first occurred from early to mid luteal phase in human CL, it did not take place until the late luteal phase in bovine CL. The average size of large luteal cells in humans and of small luteal cells in cattle did not change, whereas size of the other cells changed in different reproductive states in both human and bovine CL. The cell composition of term pregnancy human CL was similar to mid or late luteal phase, whereas the cell composition of early pregnancy bovine CL was similar to mid luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Cellular distribution and cycle phase dependency of gonadotropin and eicosanoid binding sites in bovine corpora lutea.

Bovine luteal functions are regulated by gonadotropins and eicosanoids. The specific binding sites that presumably mediate the actions of these regulatory agents have previously been characterized in bovine luteal tissue. However, the cellular distribution and/or the cycle phase dependency of these binding sites have never been investigated. In the present study, we investigated these parameters by using quantitative light microscope autoradiography. The results showed that both small and large luteal cells contained binding sites for LH/hCG, prostaglandin (PG)E2, PGF2 alpha, PGI2, and leukotriene (LT)C4. In addition, luteal blood vessels contained LH/hCG and LTC4 binding sites and luteal fibroblasts contained PGE2 binding sites. On a per cell basis, there were more binding sites for all ligands in large luteal cells as compared to small or nonluteal cells. After correction for the cellular area differences, small luteal cells contained more LH/hCG, PGE2, PGI2, and LTC4 binding sites, while large luteal cells contained more PGF2 alpha binding sites. The small and large luteal cell binding of hCG, PGE2, PGI2, and LTC4 increased from early to mid luteal phase, followed by a decline in the late luteal phase. PGF2 alpha binding, on the other hand, increased from early to late luteal phase. In contrast to luteal cells, binding of hCG and LTC4 to luteal blood vessels and binding of PGE2 to luteal fibroblasts did not change during the cycle. These results suggest that LH/hCG and eicosanoid regulation of luteal function is more complex than previously envisioned and it involves both small and large luteal cells and, in some cases, also nonluteal cells.

Animals↗
PubMed1991

Identification of epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor in surgically induced endometriosis in rats.

The present immunohistochemical studies used polyclonal antibodies specific to epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), and monoclonal antibodies to the extracellular binding domain of EGF receptor to elucidate their presence and cellular distribution in surgically induced endometriosis in the rat. Uterine segments were implanted in the mesenteric region adjacent to a blood vessel for a period of 4-6 weeks. During operative reexploration, the implanted tissues were intact, morphologically similar to the controls, and consisted of a cyst containing clear fluid and associated adhesion formation. All the uterine cell types immunostained with antibody to EGF. The highest immunostaining intensity was associated with inflammatory cells infiltrated among endometrial stromal cells, followed by luminal and glandular epithelial and stromal cells. The cysts consisted of an inner simple columnar epithelium, surrounded by several layers of smooth muscle and connective tissue. The cyst epithelial layer immunostained weakly, while the supporting wall stained moderately. The inflammatory cells found within the cyst cavity immunostained very intensely, comparable to those in the endometrium. The patterns of immunostaining for TGF-alpha and EGF receptor were similar to that observed for EGF. Myometrial smooth-muscle cells and endothelial and smooth-muscle cells of arterioles were also immunostained for EGF, TGF-alpha, and EGF receptor, but with lower intensity than that of the endometrium. These observations suggest that, like normal uterine tissue, endometrial implants produce EGF and TGF-alpha locally and contain receptors for EGF. These results imply a possible paracrine or autocrine role for growth factors in the establishment and/or maintenance of endometriotic tissue.

Animals↗
PubMed1990

Cellular distribution of prostacyclin synthase and specific prostacyclin binding sites in bovine corpora lutea of pregnancy.

The cellular distribution of prostacyclin (PGI2) synthase and specific PGI2 binding sites was investigated by light microscope immunocytochemistry and quantitative autoradiography. The immunostaining for the enzyme was found in small (15-18 microns) and large (18-45 microns) cells as well as in non-luteal cells, arteriole smooth muscle and endothelium. There was no consistent difference between small and large luteal cells and luteal vs. non-luteal cells in the immunostaining. Vascular smooth muscle and endothelial cells, on the other hand, contained less immunostaining than the other cells. Contrary to wide-spread distribution of PGI2 synthase, specific PGI2 binding sites were only found in the luteal cells. On a per cell basis, large luteal cells contained more sites than small luteal cells and vice versa when expressed per unit cell area. The [3H]PGI2 binding to the luteal cells was time and temperature dependent and was inhibited by excess unlabeled PGI2 but not by its metabolite, 6-keto-PGF1 alpha or other eicosanoids which bind to their own receptors. In conclusion, while PGI2 synthase is widely distributed among different cell types in bovine corpora lutea, specific binding sites which may mediate luteotropic actions of PGI2 are only present in small and large luteal cells.

Animals↗
PubMed1990

Tissue reactivity and degradation patterns of absorbable vascular ligating clips implanted in peritoneum and rectus fascia.

Absorbable vascular ligating clips are finding increasing use in intraabdominal surgery. We report the results of a light and scanning electron microscope investigation of the tissue reactivity and clip degradation patterns of two such materials, Absolok (polydioxanone) and Lactomer (copolymer of glycolic and lactic acid), implanted in the fascia and peritoneum of rabbits for intervals of 2 to 70 days. Cellular response to the clips, defined as the number of inflammatory cells/10(4) microns 2, was maximum at day 4 postimplantation, then gradually declined as the duration of implantation increased. This pattern, seen with both types of clips, was similar to that seen with polydioxanone (PDS) suture, but significantly greater than that associated with polypropylene (Prolene) suture. Although cellular response to the clips was greater in peritoneum than in fascia, especially on two occasions associated with adhesion formation, this was not statistically significant. Based on our morphological observations, the signs of clip degradation which were indicated by the appearance of surface crazing and cracks occurred earlier in peritoneum than in fascia.

Abdomen↗
PubMed1990

Light and electron microscope immunocytochemical localization of 5- and 12-lipoxygenases and cyclooxygenase enzymes in human granulosa cells from preovulatory follicles.

Cellular and subcellular distribution of 5- and 12-lipoxygenases and cyclooxygenase enzymes were investigated in human granulosa cells from preovulatory follicles using light and electron microscope immunocytochemistry. The results demonstrated that all three enzymes are present in granulosa cells but not in minor contaminating red blood cells. While the distribution of cyclooxygenase and 12-lipoxygenase was relatively uniform among the granulosa cells, 5-lipoxygenase was not uniformly distributed among these cells. All three enzymes are present in microvillus plasma membranes, rough endoplasmic reticulum, cytoplasm, nuclear membranes and chromatin. In summary, 5- and 12-lipoxygenases and cyclooxygenase enzymes, which catalyze the transformation of arachidonic acid into different eicosanoids, are present in several subcellular organelles including nuclei of granulosa cells from preovulatory follicles.

Arachidonate 12-Lipoxygenase↗
PubMed1990

The presence of gonadotropin receptors in nonpregnant human uterus, human placenta, fetal membranes, and decidua.

The possible presence of gonadotropin receptors in nonpregnant human uterus and human fetoplacental unit was investigated by light microscope immunocytochemistry using a monoclonal antibody to rat luteal hCG/LH receptors. The receptor antibody cross-reacted with human and bovine hCG/LH receptors and appears to be directed against the receptor rather than other proteins, including HLA class I antigens. Uterus and fetoplacental unit contained receptor antibody-binding sites, which indicates the presence of hCG/LH receptors. In the endometrium these receptors were present in glandular and luminal epithelial cells as well as in stromal cells. In the myometrium the receptors were detected in circular and elongated myometrial smooth muscle and vascular smooth muscle. Comparison of immunostaining intensities, which indicates the presence of different amounts of receptors, revealed that luminal and glandular epithelial cells contained more receptors than stromal cells. These cells, in turn, contained more receptors than myometrial and vascular smooth muscle. All cells in secretory phase uterine specimens contained more receptors than corresponding cells from the proliferative phase of the cycle. Midpregnancy placenta, amniotic epithelium, chorionic cytotrophoblasts, and decidual cells contained hCG/LH receptors. At term pregnancy, while receptors in fetal membranes and decidua continue to be detected, placental tissues did not show any detectable receptors unless the tissues were pretreated with neuraminidase. This indicated that term pregnancy placenta contain hCG/LH receptors masked by sialic acid residues. Comparison of immunostaining intensities suggested that syncytiotrophoblasts contained more receptors than cytotrophoblasts at midpregnancy; mesenchymal cells or blood vessels contained no detectable receptors. There were more receptors in decidua than in fetal membranes at mid- and term pregnancy. While the amniotic epithelial receptors decreased, the receptors in chorionic cytotrophoblasts and decidual cells increased from mid- to term pregnancy. In summary, hCG/LH receptors were demonstrated in the nonpregnant human uterus, human placenta, fetal membranes, and decidua. This indicates that hCG/LH may directly regulate functions of these tissues by endocrine, autocrine, or paracrine mechanisms.

Chorionic Gonadotropin↗
PubMed1990

In vivo and in vitro degradation of monofilament absorbable sutures, PDS and Maxon.

Two new absorbable monofilament suture materials polydioxanone and Maxon are being employed increasingly in abdominal surgery because of increased strength retention and decreased tissue reactivity compared with previously available materials. As part of our investigation of the behaviour of suture materials, 3-0 sutures of polydioxanone and Maxon were enclosed in nylon pouches, a technique developed for in vivo experiments to prevent cellular interaction with implanted devices. The pouched sutures were gas sterilized, then implanted in either the extrafascial space or peritoneal cavity for periods of 1-5 wk. Sterilized sutures were also incubated in Ringer's lactate at 37 degrees C. Tensile strength of the exposed sutures was measured. For a given suture material and duration of incubation, there was no significant difference in tensile strength degradation among the three test environments. Although the strength of unexposed Maxon is greater than that of polydioxanone, the residual strength of Maxon decreases more rapidly in use, so that, after 2 wk, the strength of polydioxanone is greater. Scanning electron microscope examination of the suture surfaces reveals that polydioxanone develops surface crazing with time, whereas the surface morphology of Maxon remains relatively unaltered.

Animals↗
PubMed1989

The presence of prostacyclin binding sites in nonpregnant bovine uterine tissue.

Myometrium of various animal species makes a considerable amount of prostacyclin (PGI2) which is a potent myometrial and uterine vascular smooth muscle relaxing agent. This action of PGI2 is perhaps mediated by binding to specific receptors, which have never been demonstrated in uterine tissue of any animal species until very recently. The quantitative light microscopic autoradiographic approach used in the present studies demonstrated that while bovine myometrial smooth muscle and uterine vascular smooth muscle contained PGI2 specific binding sites, endometrial and perimetrial cells contained few or no binding sites. The number of binding sites in circular and elongated myometrial smooth muscle and in arteriolar smooth muscle were similar (P greater than 0.05). The PGI2 binding to the uterine cells was greatly reduced (P less than 0.001) following coincubation with excess unlabeled PGI2, but not with its stable metabolite, 6-keto PGF1 alpha, PGE2, PGF2 alpha and leukotriene C4 which bind to nonpregnant bovine uterine tissue, also had no effect of PGI2 binding. In conclusion, nonpregnant bovine uterine tissue contain specific PGI2 binding sites which may mediate its potent relaxing effect on myometrium and uterine vasculature.

Animals↗
PubMed1989

Human chorionic gonadotropin increases chromatin solubility in isolated bovine and human luteal nuclei.

We have previously demonstrated that bovine and human luteal nuclei contain human chorionic gonadotropin/luteinizing hormone (hCG/LH) receptors and that these gonadotropins can directly stimulate nuclear membrane enzyme activity (nucleoside triphosphatase) involved in messenger ribonucleic acid (mRNA) transport from the nucleus to the cytoplasm. The present studies were undertaken to investigate the effect or hCG on chromatin solubility, reflecting perhaps synthesis and transport of RNA, in isolated bovine and human luteal nuclei. hCG increased chromatin solubility in a concentration-dependent manner. This hCG effect is either blocked or substantially reduced by the addition of hCG antiserum; denatured hCG had no effect and cyclic adenosine 3',5'-monophosphate could not mimic the hCG response. hCG had no effect on chromatin solubility in bovine liver or kidney nuclei and hormones other than hCG, human LH, or the beta subunit of hCG had no effect on chromatin solubility in bovine luteal nuclei, demonstrating the tissue and hormone specificity of the response. These findings further strengthen the concept of direct gonadotropin regulation of nuclear functions of luteal cells.

Animals↗
PubMed1988

A comparative scanning electron microscopic study on degradation of absorbable ligating clips in vivo and in vitro.

Using scanning electron microscopy, the degradation characteristics of two absorbable ligating clips, Absolok (polydioxanone) and Lactomer (poly-L-lactide-co-30%-glycolide) have been studied under in vivo and in vitro conditions. The rate of Absolok clip degradation was significantly greater than that of Lactomer clip degradation both in vitro and in vivo. The rate of degradation of Lactomer clips significantly increased and they showed a greater change in proportion of breakdown in vivo than in vitro compared to Absolok clips. The Absolok clip breakdown began with the formation of surface undulations which later developed into fissures. The undulations appeared on the clip surface as early as 7 days and by 2 weeks developed into fissures. The initial appearance of the fissures was at the edge of the clips particularly at the mating surface. The thickness of layers forming the fissures gradually decreased and by 15 weeks the layers appeared as very thin sheets of materials. The high energy areas (locking and molding points) were more resistant to breakdown and the remains of the clips were still present 25 weeks after initiation of the experiments. The Lactomer clips showed very little sign of degradation in vitro even after 10 weeks of incubation. However, in the in vivo experiments undulations formed on the clip surface as early as 2 weeks postimplantation. These clips also showed fissures similar to those observed on Absolok clips.

Animals↗
PubMed1988

Locking mechanism strength of absorbable ligating devices.

The locking mechanism strengths of the absorbable Absolok and Lactomer ligating clips and the absorbable Lactomer staple have been determined following implantation in an animal model. Three sizes of each type of clip and the single size of staple were enclosed in open mesh nylon pouches and implanted subcutaneously in rabbits for periods of 4, 7, 14, 21, and 28 days before tensile testing of the lock mechanisms. No change in the lock mechanism strength was detected for the Absolok clips before 21 days. The Lactomer clips and staples, however, showed significant decrease in lock mechanism strength within 7 days of implantation, this loss increasing with longer implantation times. A proportion of all the devices were found to have dissolved to an extent that precluded testing at 21 and 28 days. The findings indicate that the lock mechanisms of absorbable ligating clips differ significantly in their short-term (30 days) durability.

Animals↗
PubMed1988

Increase of nuclear bodies in bovine luteal cells after treatment with human chorionic gonadotropin.

Nuclear bodies, which are dynamic components of nuclei indicating the level of nuclear activation and cellular transcriptional and translational events, were found in small numbers (2 to 4 nuclear profiles per 150 examined) in control luteal tissue. The number of nuclear bodies, however, greatly increased after incubation with increasing concentrations of human chorionic gonadotropin (hCG). Either one simple or one complex, but very rarely two or more nuclear bodies per nuclear profile, were found in response to hCG. The nuclear bodies increased by 1 h of incubation with hCG at 38 degrees C (p less than 0.01), which further increased by 2 h, remained elevated until 8 h (p less than 0.01), and then returned to control levels by 12 h, Thirty to forty percent of the nuclear bodies that increased in response to hCG were complex nuclear bodies; these are larger than simple nuclear bodies, and contain a fibrillar capsule surrounding the electron-dense or granular core of tightly packed osmophilic material. While hCG increased the number of nuclear bodies similarly at 22 degrees C and 38 degrees C, it had no effect at 4 degrees C. hCG had no effect on nuclear bodies in luteal fibroblasts and endothelial cells or in bovine liver or kidney cells, suggesting that the effect of hCG was cell- and tissue-specific. High concentrations of human prolactin (hPRL), human follicle-stimulating hormone (hFSH), or prostaglandin (PG) E1 or PGF2 alpha had no effect on nuclear bodies in luteal cells, suggesting that the hCG effect was hormone-specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Alprostadil↗
PubMed1988

The presence of leukotriene C4-binding sites in bovine corpora lutea of pregnancy.

The presence of binding sites for [3H]leukotriene (LT) C4 in bovine corpora lutea of pregnancy was investigated with quantitative light microscopic autoradiography. Silver grains were found over small (15-20 microns) and large (20-50 microns) luteal cells and arteriolar smooth muscle. Vascular endothelial cells, erythrocytes in arteriolar lumen, and fibroblasts, on the other hand, contained very few or no net grains. The grain distribution over luteal cells and arteriolar smooth muscle was reduced (p less than 0.001) after coincubation with excess unlabeled LTC4 but not with excess unlabeled LTA4, LTB4, LTD4, LTE4, prostaglandin (PG)E2, PGF2 alpha or PGI2. The large luteal cells contained 16.1 net grains per cell, which was 6.4 and 7.0 times the number of specific grains as in small luteal and arteriolar smooth muscle cells, respectively (p less than 0.001). When the net grains were corrected for cell area differences, large luteal cells and arteriole smooth muscle cells contained a similar number of grains-which was two times as many as those found in small luteal cells. These findings suggest that LTC4 can potentially regulate functions of not only luteal cells but also luteal vasculature.

Animals↗