[Immune-related genes and their determined immune cell microenvironment to predict the prognosis of gastric adenocarcinoma].

Objective: Through bioinformatics analysis to screen key immune-related genes (IRGs) and cancer-related pathways in gastric adenocarcinoma (GAC) therapy, combining immune cell microenvironment to predict the prognosis of GAC. Methods: RNA sequencing and clinical data were obtained from public databases. Differentially expressed IRGs between GAC and normal tissues were identified by integrated bioinformatics analysis. Univariate and multivariate Cox regression analyses were applied to screen survival-associated IRGs. Then, we established the risk signature model and found another database for external validation. In addition, we explored the relationship with the immune cell microenvironment in each GAC sample using CIBERSORT algorithms. Results: A total of 78 differentially expressed IRGs were screened, including 47 up-regulated and 31 down-regulated genes. Subsequently, a five-IRGs signature (BMP8A、MMP12、NRG4、S100A9 and TUBB3) was significantly associated with the overall survival of GAC patients. Survival analysis indicated that patients in the high-risk group have a poor prognosis. The results of the multivariate analysis revealed that the risk score was an independent prognostic factor. Further analysis showed that the prognostic model had excellent predictive performance in both TCGA and GEO validated cohorts. Besides, the results of tumor-infiltrating immune cell analysis indicated that the risk score could reflect the status of the tumor immune microenvironment. Conclusion: BMP8A, MMP12, NRG4, S100A9 and TUBB3 with the risk signature model are associated with prognosis in patients with GAC, combined with tumor-infiltrating immune cells to provide new markers for immunotherapy in GAC.

[Establishment of a nomogram model for predicting lymph node metastasis in patients with cN0 gastric cancer based on combination of preoperative C-reactive protein/albumin ratio].

Objective: To investigate the relationship between systemic inflammatory markers such as neutrophil/lymphocyte ratio (NLR) and C-reactive protein/albumin ratio (CAR), and lymph node metastasis in patients with cN0 gastric cancer. To establish a nomogram model to predict the risk of lymph node metastasis in patients with cN0 gastric cancer. Methods: The preoperative systemic inflammatory markers and clinical data of 134 patients with cN0 gastric cancer were retrospectively analyzed, and these markers of patients with negative (pN0) or positive (pN+ ) lymph node metastasis in postoperative pathological diagnosis were compared. The receiver operating characteristic (ROC) curve was used to evaluate the predictive effect of preoperative systemic inflammatory markers on lymph node metastasis. The influencing factors for lymph node metastasis were assessed by univariate analysis and multivariate logistic regression analysis. A nomogram subsequently established by R software was validated by Bootstrap resampling as internal validation. Results: Compared with pN0 group, NE (P=0.022), CRP (P<0.001), NLR (P<0.001), PLR (P=0.003) and CAR (P<0.001) were higher, LY (P=0.003) and Alb (P=0.042) were lower in pN+ group. ROC curve analysis showed that the area under the curve (AUC) of postoperative pathological lymph node metastasis in patients with cN0 gastric cancer diagnosed by NLR, PLR and CAR were 0.687, 0.651 and 0.694, respectively, and the best cutoff values were 2.12, 113.59 and 0.02, respectively. The corresponding sensitivity and specificity were 62.9% and 72.2%, 77.4% and 48.6%, 74.2% and 58.3%, respectively. Univariate analysis showed that tumor size, depth of invasion, NLR, PLR and CAR were associated with lymph node metastasis in cN0 gastric cancer patients (all P<0.05). Multivariate analysis showed that depth of invasion, NLR and CAR were independent influencing factors of lymph node metastasis in patients with cN0 gastric cancer. OR were 8.084, 3.540 and 3.092, respectively (all P<0.05). The C-index of the nomogram model was 0.847 (95% CI: 0.782-0.915). The predicting calibration curve was properly fit with the ideal curve in calibration chart. Conclusion: Combination of NLR and CAR to establish a nomogram model has a good consistency and can accurately predict the risk of lymph node metastasis in patients with cN0 gastric cancer.

Aconitine induces cell apoptosis in human pancreatic cancer via NF-κB signaling pathway.

OBJECTIVE: Pancreatic cancer is one of the leading causes of death from cancer in European countries and the United States. This study sought to investigate the effects of aconitine, a well-known aconitum plant-produced toxin, on pancreatic cancer cell growth and apoptosis and to explore the potential mechanisms. MATERIALS AND METHODS: In this study, pancreatic cancer cell lines Miacapa-2 and PANC-1 were cultured, and cell viability was examined in these two cells treated with different doses of aconitine. Moreover, cell apoptosis was also analyzed upon aconitine treatment, and the specific mechanism was examined by Western blot assay and caspase activity detection. RESULTS: The results showed that aconitine inhibited pancreatic cancer cell growth in a dose- and time-dependent manner. The administration of aconitine in Miapaca-2 and PANC-1 cells also induced cell apoptosis by upregulating the expression of pro-apoptotic factors Bax, cl-caspase-3, cl-caspase-9, and cleaved poly (ADP-ribose) polymerase 1 (PARP1), and by decreasing the anti-apoptotic Bcl-2 expression. More importantly, NF-κB was also decreased upon aconitine treatment. In a xenograft mouse model of pancreatic cancer, aconitine suppressed tumor growth and increased cell apoptosis. CONCLUSIONS: This study is the first report on the effects of aconitine on pancreatic cancer, and it reveals that aconitine may serve as a potent therapeutic strategy for clinical treatment of pancreatic cancer.

First Report of Powdery Mildew (Pseudoidium neolycopersici) on Croton (Codiaeum variegatum var. pictum) in China.

Croton (Codiaeum variegatum (Linn.) var. pictum (Lodd.)) is an ornamental plant commonly grown in southern China. In March 2014, severe powdery mildew infections were observed on crotons in gardens of Hainan University (20.1°N and 110.3°E), Haikou, Hainan province. Disease incidence was estimated in a random batch of 100 plants in three replicates, with the average value approaching 80%. Symptoms first appeared as white circular patches on the adaxial surface and expanded to the abaxial surface, petioles, and stems. The top leaves were the most affected. Upper surfaces of the infected leaves were covered by white, dense mycelia. As the disease progressed, infected leaves turned purple on the lower surfaces and curly before becoming necrotic and abscising from the plant. Powdery mildew was more severe in shaded environments, especially during rainy or foggy weather in early spring. Two hundred conidiophores and conidia were observed microscopically. The conidiophores were straight or occasionally flexuous, 62.3 to 127.6 × 6.2 to 10.2 µm, consisting of two to three straight cells. Conidia were born in solitary on the top of conidiophores. Conidia were hyaline, ellipsoidal, 26.4 to 42.2 × 11.7 to 23.4 µm (average 32.5 × 16.5 µm), contained no distinct fibrosin bodies, and produced a subterminal germ tube. The wrinkling pattern of the outer walls of older conidia was angular or reticulated. Appressoria were single and multilobed. Cleistothecia were not observed. Based on morphological characteristics, the fungus was identified as Oidium neolycopersici (2), which was recently renamed Pseudoidium neolycopersici (L. Kiss) (3). The identity was confirmed by sequence analysis. Genomic DNA was extracted from the foliar powdery mildew colonies using Chelex-100 (Bio-Rad, Shanghai, China). The rDNA internal transcribed spacer (ITS) region was amplified with primers ITS1 and ITS4 (5). The ITS sequence of the representative isolates C01 (GenBank Accession No. KJ890378.1) and four other powdery mildew samples collected from crotons in Hainan University was 100% identical to that of P. neolycopersici isolates from tomato plants such as JQ972700 and AB163927. Inoculations were made by gently pressing diseased leaves onto leaves of five healthy plants of croton and tomato ('Money maker'). Five non-inoculated croton and tomato plants served as controls. Inoculated and non-inoculated plants were maintained in an incubator at 25°C with a 12-h photoperiod. After eight days, typical powdery mildew symptoms developed on 93% of the inoculated plants, while no symptom developed on the non-inoculated plants. The pathogenicity tests were repeated three times. The same fungus was always re-isolated from the diseased tissue according to Koch's postulates. The pathogenicity tests further confirmed that the pathogen from crotons is P. neolycopersici (Basionym. Oidium neolycopersici (KJ890378.1)), which is commonly known as the tomato powdery mildew. P. neolycopersici is also a pathogen of Normania triphylla (1) and papaya (4). To our knowledge, this is the first report of P. neolycopersici infecting croton. The avenue of this pathogen entering gardens of Hainan University remains unknown. The gardens are located far away from tomato farms. Also no symptom of powdery mildew on croton was observed during surveys in other locations in Haikou. The origin of the pathogen warrants additional research. References: (1) D. Delmail et al. Mycotaxon 113:269, 2010. (2) L. Kiss et al. Mycol. Res. 105:684, 2001. (3) L. Kiss et al. Mycol. Res. 115:612, 2011. (4) J. G. Tsay et al. Plant Dis. 95:1188, 2011. (5) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

CTC1 increases the radioresistance of human melanoma cells by inhibiting telomere shortening and apoptosis.

Melanoma has traditionally been viewed as a radioresistant cancer. However, recent studies suggest that under certain clinical circumstances, radiotherapy may play a significant role in the treatment of melanoma. Previous studies have demonstrated that telomere length is a hallmark of radiosensitivity. The newly discovered mammalian CTC1­STN1-TEN1 (CST) complex has been demonstrated to be an important telomere maintenance factor. In this study, by establishing a radiosensitive/radioresistant human melanoma cell model, MDA-MB-435/MDA-MB­435R, we aimed to investigate the association of CTC1 expression with radiosensitivity in human melanoma cell lines, and to elucidate the possible underlying mechanisms. We found that CTC1 mRNA and protein levels were markedly increased in the MDA-MB­435R cells compared with the MDA-MB­435 cells. Moreover, the downregulation of CTC1 enhanced radiosensitivity, induced DNA damage and promoted telomere shortening and apoptosis in both cell lines. Taken together, our findings suggest that CTC1 increases the radioresistance of human melanoma cells by inhibiting telomere shortening and apoptosis. Thus, CTC1 may be an attractive target gene for the treatment of human melanoma.

Enhanced radiosensitivity of SW480 cells via TRAIL up-regulation mediated by Egr-1 promoter.

Radiosensitization of cancer cells to irradiation could improve the efficacy of radiotherapy. The early transcriptional factor (Egr-1) promoter induced expression of downstream genes after irradiation. TNF-related apoptosis-inducing ligand (TRAIL) is known to induce apoptosis in malignant cells, but displayed little or no toxicity on normal cells. In this study, we constructed pcDNA3.1-Egr-1-TRAIL (pEgr.1-TRAIL) recombinant plasmid and evaluated its effect on human colon cancer cell line SW480. pEgr.1-TRAIL transfection combined with radiotherapy caused dramatically elevation of TRAIL expression both in mRNA and protein levels, much lower radiobiological parameters in clonogenic assays, accompanied by remarkably increase in apoptosis ratio. Furthermore, pEgr.1-TRAIL transfected cells displayed higher proportion in G0/G1 phase. Our results suggested that pEgr.1-TRAIL can sensitize SW480 cells to radiation, and the radiosensitization is related to cell cycle changes and apoptosis mediated by up-regulation of TRAIL expression. These findings support the potential future application of genetic radiotherapy against carcinoma.

Cytotoxicity and radiosensitization effect of TRA-8 on radioresistant human larynx squamous carcinoma cells.

TRAIL induces apoptosis in a variety of tumorigenic and transformed cell lines, but not in many normal cells. Recent studies have demonstrated that death receptor 5 (DR5), one of the two death receptors bound by TRAIL, showed expression in most malignantly transformed cells. This study evaluated effects of a monoclonal antibody (TRA-8) to human death receptor 5, combined with ionizing radiation, on radioresistant human larynx squamous carcinoma cell line (Hep-2R). Cells were treated with TRA-8 alone or in combination with radiation, cell viability inhibition was measured by MTT assay, and the induction of apoptosis was determined by Annexin V staining. Radionsensitivity of Hep-2R cells treated with TRA-8 were investigated with long-term clonogenic assays. Regulation of DR5 expression in cells after radiation was analyzed by indirect immunofluorescence using murine TRA-8 in combination with flow cytometry. The results suggested that TRA-8 enhanced radionsensitivity of Hep-2R cells, and that TRA-8 regulated Hep-2R cell cycle arrest at G2/M phase. Irradiation up-regulated the expression of DR5, and when combined with TRA-8 yielded optimal survival benefit. Therefore, TRA-8 can be used in combination with irradiation in radioresistant human larynx squamous carcinoma cells. Monoclonal antibodies such as TRA-8 may play an important role in the development of an effective treatment strategy for patients with radioresistant cancers.

Polar residues drive association of polyleucine transmembrane helices.

Although many polar residues are directly involved in transmembrane protein functions, the extent to which they contribute to more general structural features is still unclear. Previous studies have demonstrated that asparagine residues can drive transmembrane helix association through interhelical hydrogen bonding [Choma, C., Gratkowski, H., Lear, J. D. & DeGrado, W. F. (2000) Nat. Struct. Biol. 7, 161-166; and Zhou, F. X., Cocco, M. J., Russ, W. P., Brunger, A. T. & Engelman, D. M. (2000) Nat. Struct. Biol. 7, 154-160]. We have studied the ability of other polar residues to promote helix association in detergent micelles and in biological membranes. Our results show that polyleucine sequences with Asn, Asp, Gln, Glu, and His, residues capable of being simultaneously hydrogen bond donors and acceptors, form homo- or heterooligomers. In contrast, polyleucine sequences with Ser, Thr, and Tyr do not associate more than the polyleucine sequence alone. The results therefore provide experimental evidence that interactions between polar residues in the helices of transmembrane proteins may serve to provide structural stability and oligomerization specificity. Furthermore, such interactions can allow structural flexibility required for the function of some membrane proteins.

Interhelical hydrogen bonding drives strong interactions in membrane proteins.

Polar residues in transmembrane alpha-helices may strongly influence the folding or association of integral membrane proteins. To test whether a motif that promotes helix association in a soluble protein could do the same within a membrane, we designed a model transmembrane helix based on the GCN4 leucine zipper. We found in both detergent micelles and biological membranes that helix association is driven strongly by asparagine, independent of the rest of the hydrophobic leucine and/or valine sequence. Hydrogen bonding between membrane helices gives stronger associations than the packing of surfaces in glycophorin A helices, creating an opportunity to stabilize structures, but also implying a danger that non-specific interactions might occur. Thus, membrane proteins may fold to avoid exposure of strongly hydrogen bonding groups at their lipid exposed surfaces.

Hyperalgesia due to nerve damage: role of nerve growth factor.

The hypothesis that nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) contribute to hyperalgesia resulting from nerve damage was tested in rats in which the sciatic nerve was partially transected on one side. Administration of antisera raised against NGF and BDNF relieved mechanical and thermal hyperalgesia in these animals. It has been suggested that NGF may elicit hyperalgesia by inducing mast cells to release algesic agents such as serotonin (5-HT). We found that degranulation of mast cells with compound 48/80 relieved mechanical and thermal hyperalgesia produced by nerve damage. We also found that local injection of the 5-HT2A and 5-HT3 receptor antagonists ketanserin and ICS 205-930 into the affected hind paw relieved mechanical hyperalgesia in a dose-dependent fashion. These findings support the idea that in this rat model of hyperalgesia due to peripheral nerve damage, NGF acts on mast cells to induce release of 5-HT, which sensitizes nociceptors. Hyperalgesia due to nerve injury and hyperalgesia due to inflammation may share some common features.

An O(2n) volume molecular algorithm for Hamiltonian path.

We design volume-efficient molecular algorithms for all problems in #P, using only reasonable biological operations. In particular, we give a polynomial-time 0(2(n)n2log2n)-volume algorithm to compute the number of Hamiltonian paths in an n-node graph. This improves Adleman's celebrated n!-volume algorithm for finding a single Hamiltonian path.

Structure of DNA-porphyrin complex.

We report the 2.4 A resolution X-ray structure of a complex in which a small molecule flips a base out of a DNA helical stack. The small molecule is a metalloporphyrin, CuTMPyP4 [copper(II) meso-tetra(N-methyl-4-pyridyl)porphyrin], and the DNA is a hexamer duplex, [d(CGATCG)]2. The porphyrin system, with the copper atom near the helical axis, is located within the helical stack. The porphyrin binds by normal intercalation between the C and G of 5' TCG 3' and by extruding the C of 5' CGA 3'. The DNA forms a distorted right-handed helix with only four normal cross-strand Watson-Crick base pairs. Two pyridyl rings are located in each groove of the DNA. The complex appears to be extensively stabilized by electrostatic interactions between positively charged nitrogen atoms of the pyridyl rings and negatively charged phosphate oxygen atoms of the DNA. Favorable electrostatic interactions appear to draw the porphyrin into the duplex interior, offsetting unfavorable steric clashes between the pyridyl rings and the DNA backbone. These pyridyl-backbone clashes extend the DNA along its axis and preclude formation of van der Waals stacking contacts in the interior of the complex. Stacking contacts are the primary contributor to stability of DNA. The unusual lack of van der Waals stacking contacts in the porphyrin complex destabilizes the DNA duplex and decreases the energetic cost of local melting. Thus extrusion of a base appears to be facilitated by pyridyl-DNA steric clashes.

Clathrate hydrates are poor models of biomolecule hydration.

Clathrate hydrates form the basis of a general model of biomolecule hydration. In clathrate hydrate crystal structures, the size of hydrogen-bonded water rings is highly constrained to five members. The clathrate hydrate model predicts that the size of water rings near biomolecule surfaces is similarly constrained to five members. This report describes a test of this model of biomolecule hydration. We have demonstrated that five-membered water rings are not a general feature of protein or nucleic acid hydration. The clathrate hydrate model appears to be inappropriate for soluble biomolecules.

Solid-phase derivatization reactions for biomedical liquid chromatography.

Polymeric reagents have been developed for performing off- and on-line derivatizations of numerous organic analytes in HPLC-detection modes. Such reagents utilize ionic or covalent attachment of labile tags that possess specific detector enhancement properties: ultraviolet, electrochemical, fluorescence, and so forth. Specific synthetic procedures have evolved to generate various linkages of the tag to the underlying, polymeric support, usually involving activated ester connections (leashes). The polymer itself may play a number of roles in the nature of the overall reactions, such as hydrophobic-hydrophillic exclusion, pore size restriction, stabilization of the attachment leashes, and protection of the tags from hydrolysis in aqueous media. The basic, underlying chemistry of polymeric reagents has evolved to the point where it is possible to engineer the polymer support itself, the attachment leash, and the various tags that are then transferred to the analyte molecules. These procedures have now reached the stage of commercialization and practical applicability for real-world drugs and bioorganics in complex biofluid type samples. Polymer supported reagents can now be used for direct injection of biofluids with solid-phase (hydrophobic) extraction of the analytes of interest, followed by sample cleanup, derivatization, elution onto the HPLC column, peak compression, gradient HPLC elution, multiple detection, and final data interpretation with quantitation. This review summarizes much or most of what has been described in the scientific literature over the past decade in the various areas where polymeric reagents are being used for derivatization in HPLC and in capillary electrophoresis as well.

Water ring structure at DNA interfaces: hydration and dynamics of DNA-anthracycline complexes.

In crystallographic structures of biological macromolecules, one can observe many hydration rings that originate at one water molecule, pass via hydrogen bonds through several others, and return to the original water molecule. Five-membered water rings have been thought to occur with greater frequency than other ring sizes. We describe a quantitative assessment of relationships between water ring size and frequency of occurrence in the vicinity of nucleic acid interfaces. This report focuses on low-temperature X-ray crystallographic structures of two anthracyclines, adriamycin (ADRI) and daunomycin (DAUN), bound to d(CGATCG) and on several DNA structures published previously by others. We have obtained excellent low-temperature (-160 degrees C, LT) X-ray intensity data for d(CGATCG)-adriamycin and d(CGATCG)-daunomycin with a multiwire area detector. The LTX-ray data sets contain 20% (daunomycin, LT-DAUN) and 35% (adriamycin, LT-ADRI) more reflections than were used to derive the original room-temperature (15 degrees C) structures [Frederick, C.A., Williams, L.D., Ughetto, G., van der Marel, G. A., van Boom, J.H., Rich, A., & Wang, A.H.-J. (1990) Biochemistry 29, 2538-2549]. The results show that five-membered water rings are not preferred over other ring sizes. This assessment is consistent with our observation of broad dispersion W-W-W angles (sigma = 20 degrees). In addition, we report that the thermal mobility, distinct from the static disorder, of the amino sugar of daunomycin and adriamycin is significantly greater than that of the rest of the complex. This mobility implies that if the central AT base pair is switched to a CG base pair, there should be a low energy cost in avoiding the guanine amino group. The energy difference (for the sugar-binding preference) between d(CGTACG) and d(CGCGCG) could be considerably less than 20 kcal/mol, a value proposed previously from computation.

Direct determination of adamantanamine in plasma and urine with automated solid phase derivatization.

A simple, highly sensitive and selective method is described for adamantanamine determination in plasma and urine by high-performance liquid chromatography with fluorescence detection. The method involved a simultaneous extraction and derivatization of biological fluids with a 9-fluoreneacetate (9-FA) solid-phase derivatization reagent. This approach eliminated tedious sample preparation steps and provided automatic derivatization with selective and efficient sample clean-up for direct injection of biological fluids. Derivatized adamantanamine was separated under conventional reversed-phase conditions and determined by fluorescence detection. The optimization and validation of the derivatization method with the 9-FA solid-phase reagent is described.

9-Fluoreneacetyl-tagged, solid-phase reagent for derivatization in direct plasma injection.

We describe here a resin-based derivatization reagent, containing a 9-fluoreneacetyl tag on a controlled-pore substrate, for direct injection analysis of amphetamine in plasma. On-line, pre-column derivatization was performed by direction injection of diluted plasma sample into an sodium dodecyl sulfate-containing mobile phase. Amphetamine was trapped in the hydrophobic derivatization column and derivatized at elevated temperature by the activated solid-phase reagent. The derivatized 9-fluoreneacetyl amphetamide was separated by reversed-phase high-performance liquid chromatography with a step gradient and determined by fluorescence detection. The synthesis scheme, characterization, and optimization of the derivatization conditions for the solid-phase reagent are described. The method was evaluated by reproducibility tests and single blind spiking analysis. This solid-phase reagent combined with a surfactant containing mobile phase provided a sensitive and simple procedure for on-line derivatization in direct injection analysis of biological fluids.

Comparison of 9-fluorenylmethoxycarbonyl and 9-fluoreneacetyl-tagged silica-based derivatization reagents in high-performance liquid chromatography.

Two silica reagents based on a 4-hydroxy-3-nitrobenzoyl backbone were synthesized and characterized with 9-fluorenylmethoxycarbonyl (FMOC) and 9-fluoreneacetyl (FA) tags. These reagents were tested by derivatization of primary and secondary amines. Derivatization conditions such as temperature, time and triethylamine catalyst were tested. The FA-tagged silica reagent showed better performance than the FMOC-tagged silica reagent by a comparison of derivatization efficiencies, stabilities of reagents, and blank reagent interferences with derivatization. Finally, cadaverine and an aliphatic amine mixture were analysed using the FA-tagged reagent by pre-column, off-line derivatization and fluorescence detection.

Plasmin-induced platelet aggregation is accompanied by cleavage of aggregin and indirectly mediated by calpain.

We recently reported that thrombin-induced platelet aggregation 1) is accompanied by cleavage of aggregin, a 100-kDa membrane protein and a putative ADP receptor, 2) is indirectly mediated by intracellularly activated calpain, and 3) requires the occupancy of high-affinity thrombin receptors. Because of the similarities between responses after platelet activation induced by thrombin and plasmin (greater than or equal to 1.0 casein unit/ml), we investigated whether or not plasmin-induced platelet aggregation proceeds by the same mechanism that underlies thrombin-induced platelet aggregation. We found that the rate of plasmin-induced aggregation of washed intact platelets and that of platelets modified by 5'-p-fluorosulfonylbenzoyladenosine (FSBA, an affinity analogue of ADP, which covalently modifies aggregin) were similar, indicating that the aggregation is independent of the ADP effect. Plasmin completely cleaved [3H]FSBA-labeled aggregin in intact platelets. A mixture of metabolic inhibitors (2-deoxy-D-glucose, gluconolactone, and antimycin A) completely inhibited plasmin-induced platelet aggregation and plasmin-induced cleavage of aggregin, demonstrating that an energy-requiring step is involved in the reaction. The synthetic hexapeptide affinity reagent Phe-Gln-Val-Val-Cys(NpyS)-Gly-NH2 (NpyS = 3-nitro-2-thiopyridine), a potent and specific inhibitor of thrombin-induced platelet aggregation and platelet calpain, completely inhibited plasmin-induced platelet aggregation and plasmin-induced cleavage of aggregin. These results suggest that, like thrombin, plasmin-induced platelet aggregation is accompanied by the cleavage of aggregin and these responses are indirectly mediated by the intracellularly activated calpain.(ABSTRACT TRUNCATED AT 250 WORDS)