Estrogen receptor and progesterone receptor genes are expressed differentially in mouse embryos during preimplantation development

Estrogen and progesterone play an important role in the development and implantation of preimplantation embryos. However, it is controversial whether these hormones act directly on the embryos. The effects of these hormones depend on the existence of their specific receptors. To determine whether estrogen receptor (ER) and progesterone receptor genes are expressed in mouse preimplantation embryos, we examined RNA from embryos at different stages of preimplantation development by reverse transcription-polymerase chain reaction techniques. ER mRNA was found in oocytes and fertilized eggs. The message level began to decline at the two-cell stage and reached its lowest level at the five- to eight-cell stage. ER mRNA was not detectable at the morula stage but reappeared at the blastocyst stage. Progesterone receptor mRNA was not detectable until the blastocyst stage. The embryonic expression of ER and progesterone receptor genes in the blastocyst suggests a possible functional requirement for ER and progesterone receptor at this stage of development. These results provide a basis for determining the direct role of estrogen and progesterone in preimplantation embryos.

Clinical and Imaging Characteristics of Arteriopathy Subtypes in Children with Arterial Ischemic Stroke: Results of the VIPS Study

BACKGROUND AND PURPOSE

Childhood arteriopathies are rare but heterogenous, and difficult to diagnose and classify, especially by nonexperts. We quantified clinical and imaging characteristics associated with childhood arteriopathy subtypes to facilitate their diagnosis and classification in research and clinical settings.

MATERIALS AND METHODS

The Vascular Effects of Infection in Pediatric Stroke (VIPS) study prospectively enrolled 355 children with arterial ischemic stroke (2010-2014). A central team of experts reviewed all data to diagnose childhood arteriopathy and classify subtypes, including arterial dissection and focal cerebral arteriopathy-inflammatory type, which includes transient cerebral arteriopathy, Moyamoya disease, and diffuse/multifocal vasculitis. Only children whose stroke etiology could be conclusively diagnosed were included in these analyses. We constructed logistic regression models to identify characteristics associated with each arteriopathy subtype.

RESULTS

Among 127 children with definite arteriopathy, the arteriopathy subtype could not be classified in 18 (14%). Moyamoya disease (n = 34) occurred mostly in children younger than 8 years of age; focal cerebral arteriopathy-inflammatory type (n = 25), in children 8-15 years of age; and dissection (n = 26), at all ages. Vertigo at stroke presentation was common in dissection. Dissection affected the cervical arteries, while Moyamoya disease involved the supraclinoid internal carotid arteries. A banded appearance of the M1 segment of the middle cerebral artery was pathognomonic of focal cerebral arteriopathy-inflammatory type but was present in <25% of patients with focal cerebral arteriopathy-inflammatory type; a small lenticulostriate distribution infarct was a more common predictor of focal cerebral arteriopathy-inflammatory type, present in 76%. It remained difficult to distinguish focal cerebral arteriopathy-inflammatory type from intracranial dissection of the anterior circulation. We observed only secondary forms of diffuse/multifocal vasculitis, mostly due to meningitis.

CONCLUSIONS

Childhood arteriopathy subtypes have some typical features that aid diagnosis. Better imaging methods, including vessel wall imaging, are needed for improved classification of focal cerebral arteriopathy of childhood.

Granzyme K cleaves the nucleosome assembly protein SET to induce single-stranded DNA nicks of target cells

Although granzymes (Gzms) A- and B-induced cell death pathways have been defined, little is known about how other orphan Gzms function in CTL-mediated cytotoxicity. GzmK and A are tryptases among all the Gzms of humans and they are closely linked on the same chromosome. In this study, we showed that GzmK can be efficiently delivered into target cells with a cationic lipid protein transfection reagent Pro-Ject. We found human GzmK triggers rapid cell death independently of caspase activation. The features of death are characterized by rapid externalization of phosphatidylserine, nuclear morphological changes and single-stranded DNA nicks. GzmK hydrolyzes the nucleosome assembly protein SET in its recombinant and native forms or in intact cells. Cleavage of SET by GzmK abrogates its nucleosome assembly activity. After GzmK loading, SET and DNase NM23H1 rapidly translocate into the nucleus and SET is cleaved, where the nuclease activity of NM23H1 is activated to nick chromosomal DNA.

Immunolocalization of estrogen receptor protein in the mouse blastocyst during normal and delayed implantation

We previously showed that estrogen receptor (ER) mRNA is present in preimplantation mouse embryos. The apparent synthesis of ER mRNA by the blastocyst at the time of implantation when estrogen is required was of special interest. A demonstration of the presence of ER protein would support the idea that estrogen can act directly on the embryo. The mouse embryo at the blastocyst stage is differentiated into two cell types, the trophectoderm and the inner cell mass. To determine whether ER mRNA is translated into ER protein and its cell-specific distribution, immunocytochemical analyses were performed in mouse blastocysts. ER protein was detected in all cell types of the normal, dormant, or activated blastocyst. To trace the fate of ER in these cell types, immunocytochemistry was performed in implanting blastocysts and early egg cylinder stage embryos developed in culture. Again, ER was detected in all cells of the implanting blastocyst. At the early egg cylinder stage, continued expression of ER was observed in cells derived from the inner cell mass or the trophoblast. In trophoblast giant cells, ER was concentrated in small regions of the nucleus, possibly the nucleoli, which was similar to that observed in dormant and activated blastocysts. The embryonic expression of ER at such early stages in a broad array of cells suggests that ER may have a general role during early development.

Evolution and heterogeneity of non-hereditary colorectal cancer revealed by single-cell exome sequencing

Recently single-cell whole-exome sequencing (scWES) has deeply expanded and sharpened our knowledge of cancer evolution and subclonality. Herein, with scWES and matched bulk whole-exome sequencing (bulk WES) on two colorectal cancer (CRC) patients with normal or adenomatous polyps, we found that both the adenoma and cancer were of monoclonal origin, and both shared partial mutations in the same signaling pathways, but each showed a specific spectrum of heterogeneous somatic mutations. In addition, the adenoma and cancer further developed intratumor heterogeneity with the accumulation of nonrandom somatic mutations specifically in GPCR, PI3K-Akt and FGFR signaling pathways. We identified novel driver mutations that developed during adenoma and cancer evolution, particularly in OR1B1 (GPCR signaling pathway) for adenoma evolution, and LAMA1 (PI3K-Akt signaling pathway) and ADCY3 (FGFR signaling pathway) for CRC evolution. In summary, we demonstrated that both colorectal adenoma and CRC are monoclonal in origin, and the CRCs further diversified into different subclones with heterogeneous mutation profiles accumulating in GPCR, PI3K-Akt and FGFR signaling pathways. ScWES provides evidence for the importance of mutations in certain pathways that would not be as apparent from bulk sequencing of tumors, and can potentially establish whether specific mutations are mutually exclusive or occur sequentially in the same subclone of cells.

Association between changes in symptoms and gastric emptying in gastroparetic patients treated with gastric electrical stimulation

To investigate whether there is an association between gastric emptying rate and symptom improvement in gastroparetic patients treated with gastric electrical stimulation (GES), we retrospectively reviewed 63 gastroparetic patients who received GES therapy for at least 1 year. Patient characteristics, seven upper gastrointestinal (GI) symptoms and 4-h standardized gastric emptying test (GET) were evaluated at baseline and at 1 year of GES. All symptoms were significantly reduced (P < 0.001). Mean gastric retention was reduced by 7% (P = 0.102) for measurement at 4 h. Of the 63 patients, 14 had their GET normalized and 49 remained delayed after 1 year. Normalized GET patients had a similar symptom improvement as those whose GET remained delayed. Of all upper GI symptoms, the improvements in vomiting (P = 0.04), nausea (P = 0.002) and epigastric pain (P = 0.001) were significantly correlated with reduction in 4-h gastric retention between baseline and 12 months of GES therapy for patients with normalized gastric emptying but there were no correlations with any symptoms and change in gastric emptying for those patients who remained delayed. In summary, overall gastric emptying is not significantly accelerated at 4 h after successful symptomatic improvement with GES but nausea, vomiting and epigastric pain can be correlated with normalization of GET in a subset of patients.

Apoptosis modulatory activities of transiently expressed Bcl-2: roles in cytochrome C release and Bax regulation

Bcl-2 and Bcl-X(L) are pro-survival members of the Bcl-2 family. These proteins have been shown to antagonize the pro-apoptotic activity of Bax and promote cell survival through blocking Bax translocation from the cytosol to mitochondria and by preventing the release of cytochrome c. However, it has been recently reported that transiently expressed Bcl-2 unexpectedly leads to significant cell toxicity. To study this intriguing phenomenon, we have carried out further analyses into the properties of transiently expressed Bcl-2. We found that various isoforms of human and different species of Bcl-2 were equally capable of inducing apoptosis. In addition, we discovered that transient expression of Bcl-2, unlike its pro-survival homolog Bcl-X(L), can lead to the release of cytochrome c from mitochondria and that the resulting cell death can be inhibited by caspase and calpain inhibitors. Moreover, we have shown that unlike the pro-apoptotic protein Bid, the toxicity associated with the transient expression of Bcl-2 occurs independent of the activity of the endogenous Bax. Finally, we found that in spite of its intrinsic toxicity, transiently expressed Bcl-2 is fully capable of blocking the ectopically expressed Bax from localizing to mitochondria. Taken together, these studies demonstrate that transiently expressed Bcl-2 displays opposing functional properties.

Some features of intestinal absorption of intact fibrinolytic enzyme III-1 from Lumbricus rubellus

In order to investigate whether earthworm fibrinolytic enzyme III-1 (EFE-III-1) isolated from Lumbricus rubellus is capable of transporting into blood through intestinal epithelium and keeping its biological function in circulation, we have raised an antibody against EFE-III-1. The immunological results showed that 10-15% of intact EFE-III-1 was absorbed by the intestinal epithelium with the incubation chamber method [Vilhardt and Lundin, Acta Physiol. Scand. 126 (1986) 601-607]. The enzyme could be detected in the intestinal epithelial cells by immunohistochemistry. Furthermore, immunoreactive intact EFE-III-1 was found in serum or plasma after intraperitoneal injection of rats. Approx. 10% of the full-size enzyme could transport through the intestinal epithelium. The maximum remaining activity in blood could be assayed around 60 min after the intraperitoneal injection.

Embryonic estrogen receptors: do they have a physiological function?

In normal estrogen target tissues, estrogen action is mediated through a specific nuclear transcription factor, the estrogen receptor (ER). The site of estrogen action in the developing organism is therefore determined by cells that contain ER and other necessary tissue and gene-specific components for estrogen-mediated transcription. Immunocytochemical methods were used to determine the cellular localization and tissue distribution of ERs in reproductive tracts of mouse fetuses. Nuclear staining for ER was observed in reproductive tracts at fetal days 13 to 15. ERs were present in the precursors of both male and female reproductive tracts at these early developmental stages, which may be attributable to their similar embryonic origins. However, as the tissues undergo sexual differentiation at later fetal and early neonatal ages, ER increases in the female reproductive tracts as compared with the male. ER was detected by immunoblotting on fetal day 10 (before sexual differentiation) in extracts of whole mouse embryos. To determine whether ER and progesterone receptor genes are expressed earlier in development, we examined RNA from preimplantation mouse embryos using reverse transcriptase-polymerase chain reaction techniques. ER mRNA was found in oocytes and fertilized eggs. Message concentration declined at the 2-cell stage and reached its lowest level at the 5- to 8-cell stage. ER mRNA was not detectable at the morula stage but reappeared at the blastocyst stage. Progesterone receptor mRNA was not detectable until the blastocyst stage. The embryonic expression of ER and progesterone receptor genes in the blastocyst suggests a possible functional requirement for estrogen and progesterone receptors in preimplantation embryos.

Association of the status of interstitial cells of Cajal and electrogastrogram parameters, gastric emptying and symptoms in patients with gastroparesis

Our goal was to investigate associations between the status of interstitial cells of Cajal (ICC) and electrogastrogram (EGG) parameters, gastric emptying and symptoms in a large cohort of patients with gastroparesis. Forty-one patients with refractory gastroparesis who were referred for gastric electrical stimulation (GES) underwent full thickness gastric (antrum) biopsy during the surgery to place the GES device. The biopsy samples were stained with c-kit and scored for the presence of ICC based on criteria obtained from 10 controls. All patients underwent EGG recordings, a 4-h standardized scintigraphic gastric emptying study and symptom assessment prior to the surgery. Based on antral biopsy, 15 patients (36%) had almost no ICC (ICC- group) and 26 patients had adequate cell numbers (ICC+ group). EGG recordings in the ICC- group displayed significantly less normal slow waves than in the ICC+ group both in the fasting and fed states. Tachygastria in the ICC- group was significantly more than in the ICC+ group both in the fasting (32 +/- 8%vs 11 +/- 2%) and fed states (27 +/- 9%vs 12 +/- 2%). There was no statistical difference in gastric emptying, symptom severity of gastroparesis, aetiology, age and gender between the two groups. Severely depleted ICC occurs in up to 36% of gastroparetic patients and significantly correlates with an abnormal EGG. Severely depleted ICC does not correlate with the severity of gastroparesis as assessed by gastric emptying or symptom status but did result in a poorer symptomatic response to GES. These data suggest that the EGG may have a role for predicting ICC status during clinical evaluation of gastroparetic patients.

GADD45B mediates podocyte injury in zebrafish by activating the ROS-GADD45B-p38 pathway

GADD45 gene has been implicated in cell cycle arrest, cell survival or apoptosis in a cell type specific and context-dependent manner. Members of GADD45 gene family have been found differentially expressed in several podocyte injury models, but their roles in podocytes are unclear. Using an in vivo zebrafish model of inducible podocyte injury that we have previously established, we found that zebrafish orthologs of gadd45b were induced upon the induction of podocyte injury. Podocyte-specific overexpression of zebrafish gadd45b exacerbated edema, proteinuria and foot-process effacement, whereas knockdown of gadd45b by morpholino-oligos in zebrafish larvae ameliorated podocyte injury. We then explored the role of GADD45B induction in podocyte injury using in vitro podocyte culture. We confirmed that GADD45B was significantly upregulated during the early phase of podocyte injury in cultured human podocytes and that podocyte apoptosis induced by TGF-β and puromycin aminonucleoside (PAN) was aggravated by GADD45B overexpression but ameliorated by shRNA-mediated GADD45B knockdown. We also showed that ROS inhibitor NAC suppressed PAN-induced GADD45B expression and subsequent activation of p38 MAPK pathway in podocytes and that inhibition of GADD45B diminished PAN-induced p38 MAPK activation. Taken together, our findings demonstrated that GADD45B has an important role in podocyte injury and may be a therapeutic target for the management of podocyte injury in glomerular diseases.

The impact of oral consumption of Lactobacillus plantarum P-8 on faecal bacteria revealed by pyrosequencing

Lactobacillus plantarum P-8 (Lp-8) is a novel probiotic bacterium showing beneficial effects in human. The current study is a follow-up work of a previous clinical trial, and it aimed at understanding the mechanism of the observed desirable effects by evaluating the change in faecal bacterial structure at phylogenetic level. The genomic DNAs used for 16S rRNA polymerase chain reaction (PCR)-pyrosequencing were obtained from the previous clinical trial. Briefly, 33 recruited subjects were given a single daily oral dose of Lp-8 (6×1010 cfu) for 4 weeks. Faecal genomic DNAs were extracted from samples collected before (day 0) and after (day 28) Lp-8 consumption from the subjects. Our results show that the consumption of Lp-8 did not result in major change in the faecal bacterial structure by principal coordinate analysis. However, multivariate analysis of variance and analysis of UniFrac metric distances at day 0 and day 28 revealed significant difference in the faecal bacterial structure upon Lp-8 treatment. Thus, the difference lied on the less abundant rather than the predominant lineages. At genus level, the relative abundance of 5 Firmicutes genera (Leuconostoc, Lactobacillus, Sporacetigenium, Blautia and Staphylococcus) significantly increased after Lp-8 consumption, whereas 3 Proteobacteria genera (Shigella, Escherichia and Enterobacter) decreased (P<0.05). 60 key responding lineages could be identified at operational taxonomic unit (OTU) level by redundancy analysis. Among them, the abundance of 18 OTUs showed significant difference (P<0.05), while 12 OTUs exhibited modest change (0.05<P<0.01) upon treatment. Our study identified a shift in the faecal bacterial structure upon Lp-8 administration, which may explain some of the previously observed beneficial effects.

Reduction of Lactobacillus in the milks of cows with subclinical mastitis

Clinical and subclinical bovine mastitis are the most frequent diseases encountered on dairy farms worldwide, which cause significant economic loss and veterinary cost. The mastitic disease status is associated with increases in both milk bacterial pathogens and somatic cell count (SCC). Although it is well established that the mastitic pathogens generally correlate with the milk SCC, to our knowledge, the correlation between the probiotic genus, Lactobacillus, and the mastitic causative bacteria and SCC have not been determined previously. Thus, in this study, milk samples from 12 mild and 28 severe subclinical mastitic dairy cows were collected from the same farm. The overall milk bacterial load was quantified with the total plate count method. The Lactobacillus genus and 4 common clinical and subclinical mastitic pathogens (Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, and Trueperella pyogenes) in the sampled milk were enumerated by quantitative PCR. Mild and severe subclinical mastitic samples were distinctly separated on the principal component analysis score plot generated based on the quantities of these 5 target bacteria, suggesting that clear differences existed in the microbiological composition between the two sample groups. Based on comparison with the pairwise Mann-Whitney test, the mild subclinical mastitic dairy cows had a significantly higher amounts of lactobacilli (P=0.0175), but lower E. coli (P=0.0002), S. aureus (P<0.0001), S. agalactiae (P=0.0001) and T. pyogenes (P=0.0044) quantities, while an opposite trend occurred in the severe subclinical mastitic group. The negative correlation between Lactobacillus and the pathogenic bacteria, as well as the SCC, was confirmed with Spearman correlation analysis. Data generated from the current study may hint to a close relationship between Lactobacillus and the health of bovine udder.

Sulfatide-tenascin interaction mediates binding to the extracellular matrix and endocytic uptake of liposomes in glioma cells

Tenascin-C is an extracellular matrix glycoprotein, whose expression is highly restricted in normal adult tissues, but markedly up-regulated in a range of tumors, and therefore serves as a potential receptor for targeted anticancer drug or gene delivery. We describe here a liposomal carrier system in which the targeting ligand is sulfatide. Experiments with tenascin-C-expressing glioma cells demonstrated that binding of liposomes to the extracellular matrix relied essentially on the sulfatide-tenascin-C interaction. Following binding to the extracellular matrix, the sulfatide-containing liposomes were internalized via both caveolae/lipid raft- and clathrin-dependent pathways, which would ensure direct cytoplasmic release of the cargoes carried in the liposomes. Such natural lipid-guided intracellular delivery targeting at the extracellular matrix glycoproteins of tumor cells thus opens a new direction for development of more effective anticancer chemotherapeutics in future.

Complete activation of Bax by a single site mutation

Bax translocation from the cytosol to mitochondria culminates a key step by which this protein mediates cell death. Here, we identified two amino acids, L70 and D71, within the BH3 domain of Bax that play a critical role in regulating Bax's cytosolic vs mitochondrial distribution. Individual substitution of these amino acids with alanine resulted in Bax conformational change, oligomerization, localization to mitochondria and cell death. Further mutational analysis indicated that L70 interacts with T174, V177 and A178 of Bax's C-terminal hydrophobic segment, while the negative charge of D71 is required for maintaining Bax in its soluble monomeric state. In summary, we have identified a new regulatory site that controls Bax's subcellular distribution and activation.

The effect of contact lens induced oedema on the accuracy of Goldmann tonometry in a mature population

AIM

To determine the effect of contact lens induced oedema on the accuracy of Goldmann tonometry measurements of intraocular pressure (IOP) in mature subjects.

METHODS

22 healthy subjects aged between 50 and 60 years were recruited. Corneal curvature, IOP, and central corneal thickness (CCT) were measured before and after two hours of monocular closed eye wear of a thick hydroxyethyl methacrylate (HEMA) contact lens. Measurements were then repeated at 20 minute intervals for one hour after lens removal.

RESULTS

Both CCT (+54.1 mum) and IOP (+2.7 mm Hg) increased significantly after lens wear (p<0.001, paired t test with Bonferroni correction). For the hour following lens removal, the measured IOP was correlated to the increase in CCT (r = 0.84, p<0.001), at a rate of 1.0 mm Hg/10 mum (95% confidence interval, 0.8 to 1.2 mm Hg/10 mum, linear mixed model analysis).

CONCLUSIONS

A relatively small increase in CCT from contact lens induced corneal oedema caused an overestimation error in Goldmann tonometry measurements of IOP in healthy mature subjects.

An evaluation of resident exposure to respirable particulate matter and health economic loss in Beijing during Beijing 2008 Olympic Games

Previous epidemiological studies showed that air pollutants, especially respirable particulate matter, including PM(10), could impose harmful effects on human health. The assessment of the effects of PM(10) on mortality and morbidity makes an important basis for enhancing pollution control efforts, and for protecting public health. In this study, we measured the levels of Beijing residents' exposure to PM(10) during three different time periods around the Beijing Olympic Games held in 2008, and calculated the economic cost associated with human health. A comparative analysis of human exposure to PM(10) and associated health economics was also made to see the difference between 2005 and 2008. GIS technology was employed to interpolate the distribution of population and PM(10) data collected by 27 stations at a scale of 1kmx1km. Study results show that Beijing's population is distributed in a highly inhomogeneous manner, with the majority of people dwelling in the city proper. During the Olympic Games, population-weighted PM(10) exposure came down by 46% and 19% respectively, compared with the pre-OG and the post-OG periods. Consequently, the economic cost associated with human health during the Games came down by 38% and 16% respectively, compared with the pre-OG and the post-OG periods. Comparative analysis shows that during the Olympic Games, both PM(10) and the economic cost associated with health as a proportion of GDP sat at the bottom of the 4-year statistics, indicating that in addition to favorable weather conditions, enhanced traffic and emission control policies and measures have produced a noticeable effect on PM(10) reduction.

Is symptom relief associated with reduction in gastric retention after gastric electrical stimulation treatment in patients with gastroparesis? A sensitivity analysis with logistic regression models

BACKGROUND

Enterra gastric electrical stimulation (GES) is an alternative treatment for gastroparesis (GP) when standard medical therapy fails. The aims of this study were to evaluate the association between total symptom score (TSS) and reduction in gastric retention (GR) after GES by GP etiology and to examine the sensitivity of the association to varying cutpoints used to define GR and TSS improvement.

METHODS

Gastric retention assessed with a standardized (99m) Tc radio-labeled egg meal and TSS measured by a five-point Likert scale in 221 GP patients treated with Enterra GES therapy for at least 1 year were analyzed. Bivariate chi-square test and multivariable logistic regression with all possible cutpoints were used to assess the consistency of association and quantitate the relationship across three GP etiologies.

KEY RESULTS

Symptom relief in diabetic GP was more likely attributable to GR reduction as indicated by the consistently significant odds ratios (P < 0.01) across all cutpoints. The association in idiopathic GP was inconclusive because odds ratios were sensitive to cutpoints with P-values ranging from 0.01 to 0.47. No association was found for patients with post surgical gastroparesis (P > 0.1 for all cutpoints). Patient age, gender, baseline TSS and baseline GR had no significant effect at 5% level on clinical improvement regardless of cutpoints for GR.

CONCLUSIONS & INFERENCES

Association between clinical improvements and GR reduction following GES treatment depends on patient etiology and was able to be demonstrated in diabetic GP. The association for idiopathic GP was inconclusive and no such association was found for post surgical GP across all possible cutpoint combinations.

Molecular dynamics used in radiation therapy

In this Letter, classical molecular dynamics is used to deal with optimization problems occurring in intensity modulated radiation therapy. By introducing the concepts of virtual atom and virtual cluster, the optimization process in this kind of therapy can be considered as an analogy to finding the equilibrium configuration of a cluster. This viewpoint gives great insight into the optimization problems. To show how the idea works, a dose-based objective function is adopted to obtain the optimized intensity profiles. The results and high computational efficiency show that molecular dynamics is applicable clinically for this therapy. The idea presented here also could be inspiring to other fields where optimization problems exist.

Reversible exposure of human platelet fibrinogen receptors by antiplatelet tetraspanin monoclonal antibodies via induction of a conformational change in membrane glycoprotein IIb/IIIa complex

Antihuman platelet tetraspanin (CD9 antigen) monoclonal antibodies, HI117 and SJ9A4, can induce human platelet aggregation and secretion. As platelet aggregation is mediated by fibrinogen binding to its receptors exposed on platelet glycoprotein IIb/IIIa complex, we, therefore, investigated the induction of platelet fibrinogen receptors by HI117 and SJ9A4. It was found that HI117 and SJ9A4 induced specific fibrinogen binding to human platelets, suggesting that the two monoclonal antibodies evoked obvious exposure of fibrinogen receptors on human platelets. But in the absence of fibrinogen, the monoclonal antibody-exposed fibrinogen receptors gradually lost their capacity to bind fibrinogen and closed. Our results also showed that HI117 and SJ9A4, when activating platelets, caused a conformational change in glycoprotein IIb/IIIa complex, which must contribute to the exposure of functional fibrinogen receptors on this integrin. The effect of HI117 and SJ9A4 on glycoprotein IIb/IIIa complex seems, however, to be indirect, because the HI1117 and SJ9A4-induced fibrinogen binding was reduced by pretreatment of platelets with sphingosine, aspirin, apyrase, and/or PGI2. Taken together, we conclude that the antihuman platelet tetraspanin monoclonal antibodies, HI117 and SJ9A4, reversibly expose platelet fibrinogen receptors via inducing a conformational change in glycoprotein IIb/IlIa complex. Three signaling pathways, that is, thromboxane, secreted ADP, and cAMP pathways may be involved in this process, while protein kinase C activation seems to be the final common step of the three pathways.