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PubMed1999

Development of erythroid and myeloid progenitors in the yolk sac and embryo proper of the mouse.

In this study, we have mapped the onset of hematopoietic development in the mouse embryo using colony-forming progenitor assays and PCR-based gene expression analysis. With this approach, we demonstrate that commitment of embryonic cells to hematopoietic fates begins in proximal regions of the egg cylinder at the mid-primitive streak stage (E7.0) with the simultaneous appearance of primitive erythroid and macrophage progenitors. Development of these progenitors was associated with the expression of SCL/tal-1 and GATA-1, genes known to be involved in the development and maturation of the hematopoietic system. Kinetic analysis revealed the transient nature of the primitive erythroid lineage, as progenitors increased in number in the developing yolk sac until early somite-pair stages of development (E8.25) and then declined sharply to undetectable levels by 20 somite pairs (E9.0). Primitive erythroid progenitors were not detected in any other tissue at any stage of embryonic development. The early wave of primitive erythropoiesis was followed by the appearance of definitive erythroid progenitors (BFU-E) that were first detectable at 1-7 somite pairs (E8.25) exclusively within the yolk sac. The appearance of BFU-E was followed by the development of later stage definitive erythroid (CFU-E), mast cell and bipotential granulocyte/macrophage progenitors in the yolk sac. C-myb, a gene essential for definitive hematopoiesis, was expressed at low levels in the yolk sac just prior to and during the early development of these definitive erythroid progenitors. All hematopoietic activity was localized to the yolk sac until circulation was established (E8.5) at which time progenitors from all lineages were detected in the bloodstream and subsequently in the fetal liver following its development. This pattern of development suggests that definitive hematopoietic progenitors arise in the yolk sac, migrate through the bloodstream and seed the fetal liver to rapidly initiate the first phase of intraembryonic hematopoiesis. Together, these findings demonstrate that commitment to hematopoietic fates begins in early gastrulation, that the yolk sac is the only site of primitive erythropoiesis and that the yolk sac serves as the first source of definitive hematopoietic progenitors during embryonic development.

Animals↗

PubMed2001

The influence of locomotion on air-sac pressures in little penguins.

Air-sac pressures have been reported to oscillate with wing beat in flying magpies and with foot paddling in diving ducks. We sought to determine the impact on air-sac pressure of wing beats during swimming and of the step cycle during walking in little penguins (Eudyptula minor). Fluctuations averaged 0.16+/-0.06 kPa in the interclavicular air sacs, but only 0.06+/-0.04 kPa in the posterior thoracic sac, generating a small differential pressure between sacs of 0.06+/-0.02 kPa (means +/- S.E.M., N=4). These fluctuations occurred at approximately 3 Hz and corresponded to wing beats during swimming, indicated by electromyograms from the pectoralis and supracoracoideus muscles. There was no abdominal muscle activity associated with swimming or exhalation, but the abdominal muscles were active with the step cycle in walking penguins, and oscillations in posterior air-sac pressure (0.08+/-0.038 kPa) occurred with steps. We conclude that high-frequency oscillations in differential air-sac pressure enhance access to and utilization of the O(2) stores in the air sacs during a dive.

Abdominal Muscles↗

PubMed2006

Gross morphological features of the lung and air sac in the Japanese quail.

This study was conducted to reveal the morphological characteristics of the lung and air sacs in Coturnix coturnix japonica (Japanese quails). Ten quails were allocated into two groups. Tracheas of 5 quails with neoprene latex and 5 quails with methylmetacrylate were injected to fill the trachea and air sacs. Latex embalmed animals were stored in 10% formaldehyde solution for two months. Animals given methylmetacrylate were maserated in 30% potassium hydroxide at 40 degrees C for two days. Lungs were located in the dorsal part of the thorax and very close to the thoracic vertebrae and ribs. Shorter than the dorsal border, the ventral border lied between the 3rd and 6th ribs. Cervical, clavicular, cranial thoracic, caudal thoracic and abdominal sacs were identified. These sacs had connection with the 3rd, 4th and 5th lateroventral and 4th mediolateral bronchi. Saccus cervicalis was located on the left and right portions of the vertebrae cervicales et thoraricae with a pronounced communication ventromedially. However, the cervical sac aeration of only all cervical vertebrae was present in this study. Humerus was a non-aerated bone. Pneumatic foramen was absent and did not aerate the sternum. Cranial thoracic sac connected to the 1st, 2nd and 4th medioventral bronchi and gave no diverticulum for aeration. Cranial thoracic sac received air through the 4th medioventral and the 1st and 2nd lateroventral bronchi. Left and right abdominal air sacs paramedially produced diverticulum femorale, but this diverticulum did not enter the femur.

Air Sacs↗

PubMedDate not supplied

The development of the endolymphatic duct and sac. A light microscopical study.

The development and maturation of the endolymphatic sac were studied in the CBA/CBA mouse. The otocyst is developed at gestational day 10 and the primitive endolymphatic sac is present as a large slit-like appendage at day 12 of gestation. At day 18 the endolymphatic sac is clearly detached from the rest of the otocyst, forming a true sac. The epithelial lining consists of only one layer of immature cells containing large vesicles. The endolymphatic sac is surrounded by a rich network of vessels. One day before birth, the epithelial lining is uneven and the first signs of differentiation into light and dark cells is visible. This situation is more pronounced 2 days post partum when the sac also seems to be filled with a stainable material. At day 6 post partum the otic capsule fuses around the sac, forming the vestibular aqueduct. At 14 days post partum the sac is mature, with clearly developed light and dark cells and widened lateral intercellular spaces, constituting the rugose epithelium. The lumen is filled with a stainable precipitate and a few free-floating cells.

Animals↗

PubMed1995

Using the number of yolk sacs to determine amnionicity in early first trimester monochorionic twins.

The purpose of this study was to evaluate the relationship between the number of yolk sacs and amnionicity in monochorionic twin pregnancies scanned early in the first trimester. We retrospectively reviewed images of all monochorionic twins scanned between 6 and 9.5 weeks' gestation and with pathologic or sonographic confirmation of chorionicity-amnionicity. Each film was reviewed for the number of yolk sacs present, as well as for the gestational age at which the amniotic membrane was first visualized. Twenty monochorionic-diamniotic pregnancies and two monochorionic-monoamniotic pregnancies met the criteria for inclusion in the study. In diamniotic pregnancies scanned at less than 8 weeks' gestation, only the yolk sacs were identified; none of the dividing amniotic membranes were detected. Two yolk sacs were identified in all but one case. In this case, although one yolk sac was seen at 6 weeks, follow-up scanning at 8 weeks revealed two yolk sacs. In each of the monochorionic-monoamniotic twin pregnancies, one yolk sac was seen at 9 weeks and a single amnion encircled both embryos. We conclude that the sonographic identification of two yolk scas in monochorionic twins enables us to make the diagnosis of diamniotic twins early in the first trimester, before the amniotic membrane can be imaged. The presence of one yolk sac should prompt a follow-up ultrasonogram to assign amnionicity definitively.

Adult↗

PubMed1983

Evidence that protein ingested by the rat visceral yolk sac yields amino acids for synthesis of embryonic protein.

[3H]Leucine-labelled haemoglobin was prepared from rat reticulocytes incubated in the presence of [3H]leucine. Conceptuses from 9-5-day pregnant rats were incubated in vitro tox 48 h, with [3H]leucine-labelled haemoglobin present for the final 12, 8, 4, 2 or 0.5 hours. Radioactivity accumulated in visceral yolk sac and in embryonic tissue. When exposure to labelled haemoglobin was for only a short period before harvesting, all the radioactivity found in the embryo and most of that found in the visceral yolk sac trichloroacetic acid-soluble (i.e. associated with free amino acid rather than with protein). After longer exposures the proportion of radioactivity that was acid-soluble decreased to minimum values of about 20%. SDS-polyacrylamide gel electrophoresis of the protein-associated radioactivity in visceral yolk sac and embryo was performed. After exposure to labelled haemoglobin for 1 h only prior to harvesting, the yolk sac contained a single peak of radioactivity coincident in mobility with haemoglobin. The embryo contained no protein-associated radioactivity. After exposure to labelled haemoglobin for 12h, many protein bands in both yolk sac and embryo were radiolabelled. Thus a single radiolabelled protein pinocytically captured by the visceral yolk sac can give rise to the presence of many labelled proteins in embryo and visceral yolk sac. These results indicate that the source protein underwent proteolytic digestion and that the amino acids generated were re-utilized for protein synthesis in both embryonic and visceral yolk-sac cells.

Amino Acids↗

PubMed1993

Intracellular and extracellular elemental composition of the endolymphatic sac studied by X-ray microanalysis.

X-ray microanalysis was performed along with light microscopy (LM) on rapidly frozen and cryo-sectioned endolymphatic sac tissues of adult guinea pigs, to determine the elemental composition of the different cell types in this tissue as well as the content of the sac lumen. The morphological preservation and spatial resolution of cryo-sectioned endolymphatic sac was found adequate for the identification of the different cell types of the sac in the transmission electron microscope. Further cell type identification was performed by comparing scanning transmission electron microscopy images with LM images on adjacent serial sections. X-ray microanalysis demonstrated differences between epithelial and sub-epithelial cells in the intracellular concentrations of sodium, chlorine, potassium, calcium, phosphorus and sulphur. Measurements performed in the lumen of the endolymphatic sac showed elevated sodium and decreased potassium levels as compared with the known levels of these elements in cochlear or vestibular endolymph. High phosphorus and sulphur levels were also found in the endolymph of the sac. Other morphological and analytical findings on the luminal content point out that otoconial destruction and cleaning of the endolymph from the cell debris and other products such as lipids and proteins take place in the endolymphatic sac. Our results suggest that the endolymphatic sac participates in fluid absorption (osmoregulation), ion transport and otoconial destruction. The data support the longitudinal flow theory of the endolymph.

Animals↗

PubMed1996

Developmental expression and vitamin D regulation of calbindin-D28K in chick embryonic yolk sac endoderm.

The yolk is an important calcium source for the developing chick embryo. The epithelial yolk sac endodermal cells lie in direct contact with the yolk and are the principal nutrient-transporting cell type. We previously reported that vitamin D treatment stimulated yolk calcium mobilization and that the vitamin D-dependent Ca2+-binding protein, calbindin-D28K, is present in the yolk sac. We report here the developmental expression and regulation of calbindin-D28K in the yolk sac. Calbindin-D28K is expressed as early as incubation d 3 and is found exclusively within the cytoplasm of endodermal cells. Comparative protein and mRNA analyses of yolk sac and dissociated yolk sac endodermal cells as a function of development and treatment with calcitriol (1,25-dihydroxyvitamin D3) in vitro and in vivo showed a development-specific and vitamin D-inducible expression of calbindin-D28K. Northern analysis revealed the expression of vitamin D receptor mRNA in the yolk sac, beginning as early as d 3, strongly indicating that the extraembryonic yolk sac is an early vitamin D target tissue. Cultured yolk sac endodermal cells should serve as a useful in vitro cell model for analyzing the cellular and molecular mechanisms of vitamin D action.

Animals↗

PubMed2000

Comparative morphology of the marrow sac.

Electron microscopic techniques have been used to profile the morphologies of marrow sacs in different laboratory species. These structures all comprise a condensed layer of overlapping fibroblast-like stromal cells and apparently confine the medullary and endosteal osteoblast/lining cells to separate histiotypic compartments. There were some variations in the morphology of the sac cells in the different species. In rats, cats, and sheep, scanning electron microscopy (SEM) showed a seamless arrangement of marrow sac cells which resembled a thin, flat simple squamous epithelium; they displayed few intercellular cytoplasmic processes. In the rabbit and pigeon, the sac comprised a more woven, multilayered fabric of broadly elongate flat fibroblast-like cells which displayed numerous intercellular processes. Transmission electron microscopy (TEM) showed that all marrow sac cells were attenuated with elongated nuclei, a few small round mitochondria, and a sparse rough endoplasmic reticulum. In the majority of animals, the sac was one to two cell layers thick. The rabbit and pigeon sacs were multilayered, and never less than three to four cells deep. The cell layers were not closely apposed. Tight or gap junctions were absent at the points of intercellular contact. These morphological results suggest that marrow sacs are common elements of the vertebrate skeleton with species specific morphologies.

Animals↗

PubMed2003

Sonography of pregnancies with first-trimester bleeding and a small intrauterine gestational sac without a demonstrable embryo.

OBJECTIVE: This was a prospective observational cohort study to evaluate the outcome and prognostic criteria of pregnancies with first-trimester bleeding and a gestational sac <or=16 mm without a demonstrable embryo. METHODS: Criteria for admission into the study included: (1) first-trimester bleeding; (2) a transvaginal scan performed upon admission demonstrating a single intrauterine gestational sac with a mean diameter <or=16 mm and without a demonstrable embryo. The outcome variable was miscarriage, defined as pregnancy loss prior to 22 weeks. The following explanatory variables were considered: maternal age, menstrual age, size of the gestational sac, presence or absence of the yolk sac and subchorionic hematoma, and beta-human chorionic gonadotropin levels. The relationship of these variables with pregnancy failure was analyzed by stepwise logistic regression. RESULTS: Of 50 patients, 32 (64%) underwent miscarriage. The receiver-operating characteristics (ROC) curve of the size of the gestational sac demonstrated a high level of statistical significance (area under the ROC curve 0.9080, P < 0.000001) and stepwise logistic regression revealed that this was the only variable independently correlated with the subsequent occurrence of miscarriage. DISCUSSION: It is commonly accepted that in pregnant patients with first-trimester bleeding, demonstration by transvaginal ultrasound of an intrauterine gestational sac <or=16 mm without an embryo may be compatible with a viable pregnancy. Our results suggest that in general this finding is associated with a poor outcome, with miscarriage occurring in two-thirds of patients. When the sac is small for gestational age, the risk of miscarriage is greatly increased. In the present series, a gestational sac diameter less than -1.34 standard deviations of the mean was associated with pregnancy failure in over 90% of cases.

Adult↗

PubMed1997

The apoptosis and proliferation of SAC-activated B cells by IL-10 are associated with changes in Bcl-2, Bcl-xL, and Mcl-1 expression.

Interleukin-10 (IL-10), a cytokine from mouse Th2 cells and macrophage that inhibits IL-2 and IFN-gamma production by Th1 cells, has been reported to stimulate growth and differentiation of B cells activated by CD40 or antigen receptor crosslinking. Our early observation revealed that IL-10 had B cell growth factor (BCGF) activity in human B cells preactivated with SAC or anti-Ig. The responsiveness of the preactivated B cells to IL-10 greatly increased when B cells were activated in the presence of IL-2, whereas IL-10 has no BCGF activity when added at the initiation of activation by SAC. To investigate the dual effects (proliferation and apoptosis) of IL-10 on B cells, the expression of a panel of bcl-2 protoncogene family members, bcl-2, bcl-x, mcl-1, and bax, was analyzed when B cells were activated by SAC. Bcl-xL protein was not expressed in the small resting B cells but was induced by SAC stimulation, reaching its peak at 48 hr. The addition of IL-2 further augmented the Bcl-xL expression with the same kinetics, whereas Bcl-2 and Mcl-1 were expressed by resting B cells and enhanced by SAC stimulation. However, the addition of IL-10 at the initiation of activation down-regulated Bcl-xL, Bcl-2, and Mcl-1 expression. At the same time, B cell proliferation was inhibited and apoptotic cell number increased, suggesting the growth arrest and/or apoptosis of B cells. The apoptosis of SAC-activated B cells by IL-10 was further confirmed by propidium iodide-staining and Annexin V-FITC-staining methods. In contrast, IL-10 failed to down-regulate the Bcl-xL and Bcl-2 expression but rather augmented the expression of Mcl-1 of B cells after preactivation for 48 hr with SAC and IL-2. Under this culture condition, B cells responded to IL-10 to proliferate and differentiate, while IL-2 and IL-10 had an additive or synergistic effect. Taken together, our data suggest that IL-10 acts on the induction stage of Bcl-xL expression and regulates the apoptosis and proliferation of SAC-activated B cells through their bcl-2 family gene expression.

Animals↗

PubMed1988

Proliferation of leukemic B cells in response to SAC and anti-mu. Evidence for different modes of action and comparison to proliferation and differentiation induced by conditioned medium.

We investigated the proliferative responses and immunoglobulin production of highly purified E-rosette negative largely leukemic B cells from patients with CLL to Staphylococcus aureus Cowan I (SAC) or to SAC in combination with anti-mu or conditioned medium (CM). The latter was derived by stimulating human peripheral blood mononuclear leukocytes with PHA. We observed: (1) that purified E-rosette negative largely leukemic B cells from 25% (five out of 20) of the patients exhibited proliferative responses to SAC; (2) inhibition of SAC-induced proliferation by anti-mu in certain patients, whereas synergism between SAC and anti-mu in inducing proliferative responses in others; (3) the lack of synergism between SAC and CM in inducing proliferative responses, which is in contrast to the strong synergism that was observed between anti-mu and CM in inducing proliferation; and (4) induction or enhancement by SAC alone of Ig production by largely leukemic B-cell populations from few patients with CLL and purified tonsillar B lymphocytes, but not peripheral blood B cells from normal donors. These results suggest that SAC and anti-mu induce proliferation of B cells by different mechanisms and that B-cell proliferation and differentiation is dependent not only on the mitogen but also on the activation state of the cells.

Adjuvants, Immunologic↗

PubMed2004

Symptomatic sac enlargement and rupture due to seroma after open abdominal aortic aneurysm repair with polytetrafluoroethylene graft: Implications for endovascular repair and endotension.

OBJECTIVE: We report 5 patients in whom a symptomatic perigraft seroma developed within the aortic sac, without vascular endoleak, after open repair of an abdominal aortic aneurysm (AAA) with a polytetrafluoroethylene (PTFE) graft. We also discuss possible relationships of this phenomenon to endovascular repair of AAAs. PATIENTS AND METHODS: Over 18 years, 1156 patients underwent repair of an AAA by one of the authors (B.M.B.). Of these, 1084 underwent open repair, 256 with PTFE grafts. Five patients in the PTFE group (2.3%) returned at a mean of 4.5 years with acute abdominal or back pain and enlargement of the aortic sac. Mean diameter of the aneurysms was 5.9 cm preoperatively and 8.1 cm at readmission. There was no evidence of vascular endoleak on computed tomography scans, but 1 patient had a retroperitoneal hematoma. RESULTS: Laparotomy in 4 patients disclosed a seroma containing firm rubbery gelatinous material under tension, histologically identified as amorphous eosinophilic material containing thrombus and degenerate blood cells in all cases. Rupture of the sac was confirmed in the patient with a retroperitoneal hematoma. The sac contents were evacuated and the integrity of the underlying grafts and anastomoses was confirmed before sac reduction, with imbricating sutures, and closure was performed. One patient died at 8 months of an unrelated cause; the other 3 patients remain well at mean follow-up of 12 months. The fifth patient received conservative treatment and remains asymptomatic 3 years after acute presentation. CONCLUSIONS: These findings of sac enlargement without vascular endoleak after open AAA repair are reminiscent of sac enlargement in the absence of endoleak after endovascular AAA repair. This has been referred to as endotension. The comparatively benign outcome in 5 patients with symptomatic sac enlargement, including 2 patients with rupture, after open AAA repair provides data to support a circumspect approach to endotension, especially in patients with asymptomatic disease, which has been reported as occurring in almost half of patients who received a PTFE Excluder endograft.

Aged↗

PubMedDate not supplied

Lectin cytochemistry of the lacrimal sac epithelium in experimental dacryocystitis.

PURPOSE: To study the glycoconjugates in the lacrimal sac epithelium of Japanese white rabbits with experimentally induced chronic dacryocystitis. METHODS: Chronic dacryocystitis was induced by a subcutaneous injection of albumin followed by an injection of Staphylococcus aureus into the lacrimal sac. The histological appearance of the lacrimal sac was studied using the alcian blue-periodic acid-Schiff sequence. In addition, the specific binding to the lacrimal sac epithelium of Ulex europaeus agglutinin 1, Ricinus communis agglutinin 1, peanut agglutinin, and soybean agglutinin was also studied. RESULTS: Staining with alcian blue-periodic acid-Schiff sequence showed hyperplasia of the goblet cells in the inflamed lacrimal sac epithelium. Lectin cytochemistry revealed specific binding of Ulex europaeus agglutinin 1, Ricinus communis agglutinin 1, peanut agglutinin, and soybean agglutinin to the lacrimal sac epithelium. CONCLUSIONS: These results indicated that the composition of glycoconjugates in the lacrimal sac epithelium is markedly changed in dacryocystitis. There seems to be a fundamental abnormality in glycoconjugate synthesis in the chronically inflamed lacrimal sac epithelium.

Animals↗

PubMed1993

Dacryocystitis associated with malignant lymphoma of the lacrimal sac.

BACKGROUND: Tumors of the lacrimal sac are unusual, and lymphomas of the lacrimal sac are quite rare. Four patients with a history of well-differentiated, small cell lymphoma or chronic lymphocytic leukemia presented with either acute or chronic dacryocystitis and epiphora due to lymphomatous infiltration of the lacrimal sac. METHODS: All four patients underwent dacryocystorhinostomy with lacrimal sac biopsy. All tissues underwent complete histopathologic evaluation including immunohistochemical studies for cell surface markers and, in addition, were compared with previous biopsies performed for the initial diagnosis of lymphoma. FINDINGS: All biopsies demonstrated small cell well-differentiated lymphoma on histologic and immunofluorescent examination. No patient demonstrated orbital involvement on computed tomography. One patient had previously diagnosed chronic lymphocytic leukemia and one patient demonstrated diffuse lymph node involvement on postoperative systemic evaluation. All four patients underwent additional chemotherapy. No recurrence of dacryocystitis or epiphora occurred. CONCLUSION: Four patients presented with dacryocystitis secondary to lacrimal sac lymphoma. Lymphomatous lacrimal sac infiltration is an unusual cause of dacryocystitis. Biopsy of the lacrimal sac plays a diagnostically important role in dacryocystorhinostomy even in the absence of obvious tumorous involvement of the lacrimal sac mucosa.

Acute Disease↗

PubMed2002

Intra-aneurysm sac pressure--the holy grail of endoluminal grafting of AAA.

OBJECTIVES: To relate intra-aneurysm sac pressure during endoluminal AAA repair to early and late endoleak, as well as to the aneurysm size upon follow-up. DESIGN: Prospective clinical investigation. METHODS AND PATIENTS: In 46 patients who had their AAAs treated by a stent graft (group I), intra-operative pressure measurement was performed (aorta uni-iliac stent grafts: 25 cases, bifurcated stent grafts: 21 cases). In 18 patients with open repair (group II) flow in the inferior mesenteric artery, and the pressure in the aneurysm sac was measured, before and after aortic and iliac cross clamping. Values are given in median with range. RESULTS: In group I, complete exclusion of AAA (no endoleak on intra-operative control angiogram) resulted in a statistically significant decrease in mean sac pressure from 74 (55-101) to 47 (4-104) mmHg. Pulse pressure reduced from 67 (34-103) to 8 (0-74) mmHg. In 11 patients a proximal type I endoleak was sealed by balloon modeling, after which the mean sac pressure reduced from 63 (14-91) to 52 (4-74) mmHg (n.s. versus patients with primary seal). Intra-operative pressure did not correlate with change in AAA diameter during twelve months follow-up. In group II, cross clamping of the proximal aorta significantly reduced mean sac pressure to 32 (21-55) mmHg, and the pulse pressure to 0 (0-13) mmHg (p < 0.05). Subsequent cross clamping of the iliac arteries did not significantly change the pressures. CONCLUSIONS: Measurement of intra-aneurysm sac pressure can help to detect and treat endoleaks during endoluminal grafting. However, the intra-operative sac pressure did not predict the fate of aneurysm during follow up. Compared to open repair of AAA, the sac pressure after endoluminal grafting remains significantly higher, in relation to pulse pressure.

Aged↗

PubMed2005

Polar distribution dynamics of Con A binding sites in embryo sacs is temporally coupled by the fertilization process.

The binding site distribution of concanavalin agglutinin (Con A) and wheat germ agglutinin (WGA) on embryo sacs at various developmental stages of Torenia fournieri L was studied by using a cooled Charge Coupled Device (CCD) and fluorescent Con A and WGA probes. The distribution patterns of Con A and WGA binding sites on embryo sacs changed during the fertilization process. The fluorescent signal indicating Con A binding sites was distributed evenly on the surface of the embryo sac wall before anthesis, was much denser on the micropylar end of the embryo sac wall and looked like a corona on the day of anthesis. After pollination, stronger fluorescence was present on the micropylar end of the embryo sac wall and the filiform apparatus (FA), showing an obvious polar distribution. When the pollen tube entered the embryo sac and reached a synergid, the fluorescence was still concentrated on the micropylar end and FA, and started to appear on the synergid. After fertilization, the polar distribution of the fluorescence gradually disappeared and an even distribution pattern was observed again on the embryo sac wall. These results revealed that the dynamic distribution of Con A binding sites was temporally coupled with the process of fertilization. WGA binding site distribution on the embryo sac was also investigated and showed a simple pattern but also regularly changed during the process of fertilization. The variation of these lectin binding sites during the fertilization process suggests that lectin binding site interactions may play a role in the process.

Binding Sites↗

PubMed1975

Prolactin binding activity on the crop sacs of juvenile, mature, parent and prolactin-injected pigeons.

Specific prolactin (PRL) binding activity of lactoperoxidase catalyzed 125I-labeled ovine-PRL was determined in a membrane-rich particulate fraction of pigeon crop sacs. Levels of TSH, LH or FSH as high as 1000 ng each were unable to displace the 125I-o-PRL bound to 600 mug of crop sac microsomal protein, whereas competitive displacement was achieved with as little as 0.5 ng unlabeled PRL. Ovine GH exhibited some cross reactivity when incubated in amounts greater than 500 ng, but this could be accounted for by its stated PRL contamination. Specific PRL binding activities were determined in juvenile and mature pigeons with unstimulated crop sacs, and parent pigeons with 'crop milk' and mature birds injected with PRL for 4 days. Crop sacs from juvenile birds contained approximately twice as much binding activity as crop sacs from mature pigeons. Parent and PRL injected pigeons, each with proliferated crop sac epithelium, exhibited 4-5 times as much specific PRL binding as the non-proliferated crops from juvenile or mature birds. These results show that the pigeon crop sac contains specific binding sites for PRL, and that the crop sac response to PRL is associated with an increase in PRL binding activity.

Age Factors↗