Serum concentration of VEGF, sFLT-1, and CD105 in patients with endometrial carcinoma

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Background: Preoperative evaluation of the risk for metastases in endometrial carcinoma is challenging. The aim of this study was to compare preoperative serum levels of angiogenetic markers VEGF, sFLT-1, and CD105 (endoglin) in predicting a metastasized disease. Methods: Preoperative sera from 100 consecutive patients diagnosed for endometrial carcinoma were collected. The serum concentrations of VEGF, sFLT-1, and CD105 were assessed by enzyme-linked immunosorbent assay (ELISA). The results were correlated to the presence of metastases, presence of deep (≥50%) myometrial invasion and histologic grade of the tumor. Cases with other than endometrioid histology were excluded from the study. Results: Eleven patients had a metastasized disease (≥Stage IIIA, FIGO 2009 classification). The serum concentration of VEGF was higher in the group with metastases (median [range] 394 pg/mL [31-1524 pg/mL] vs. 801 pg/mL [631-1183 pg/mL], p=0.001). The concentrations of sFLT-1 and CD105 did not show statistical difference between the two groups. In the multivariable analysis, the concentration of VEGF was the sole independent factor for the presence of metastases (OR 1.003, 95% CI 1.000-1.005, p=0.019). Conclusions: Preoperative serum VEGF concentration correlates with the presence of metastases in endometrioid endometrial carcinoma.

[Update on current care guidelines: ovarian cancer]

Ovarian cancer is the most lethal gynaecological cancer. It appears that seemingly ovarian or primary peritoneal carcinomas, in fact, originate from fimbriae. BRCA1/2 mutation carriers are recommended for the removal of ovaries and fimbriae, to reduce the risk of cancer. Treatment of epithelial ovarian cancer is based on the combination of surgery and chemotherapy. The residual tumour volume at the primary operation is the most important predictive factor of survival. The best response at the primary treatment is observed with combination chemotherapy with taxane and platinum. Adding bevacitzumab to first line chemotherapy may improve survival.

[Update on current care guidelines. Diagnosis, treatment and follow-up of cytological changes in the cervix, vagina and vulva]

Approximately 150 cervical cancer cases are diagnosed in Finland annually. Both incidence and mortality have decreased by 80% since organised screening began. Recently, screening based on primary HPV-testing with Pap-smear triage has been shown to be more sensitive and more specific among women over 35 years old in randomised studies and thus may be implemented in routine. Abnormal findings in Pap smears indicate management. Confirmed CIN1 lesions are followed up and CIN2 and worse lesions treated. Follow-up after treatment should be reliably arranged, because elevated risk of cancer remains over 20 years after treatment. Quality control is of utmost importance.

Ultrasonographic-guided pervaginal cul-de-sac cytology in the follow-up of ovarian carcinoma

The aim of this study was to compare, prospectively, traditional pervaginal cul-de-sac aspiration cytology with an ultrasonographic-guided aspirate in the detection of residual or recurrent ovarian carcinoma.

PATIENTS AND METHODS

Fifty-one patients with ovarian carcinoma were monitored during chemotherapy (21 patients) or follow-up (30 patients) after first-line treatment. All patients underwent both traditional blind pervaginal cul-de-sac aspiration cytology and an ultrasonographic-guided pervaginal aspirate. The samples were classified as class 0 or insufficient when no mesothelial cells were detected in the aspirate. The results of cytological classification of the aspirates were compared with each other according to sampling order.

RESULTS

Samples were classified as class 0 in 56% when the traditional cul-de-sac aspiration was taken first, and in 73% when ultrasonographic-guided aspiration was taken first (p = 0.249, Fisher's exact test). The number of class 0 samples was smaller among those taken second than among those taken first (22 (44%) vs. 33 (65%), p = 0.046). Four recurrences were detected during the mean follow-up of six months (range 2-11 months) in 30 patients who were followed-up after the first-line treatment. In one case, a positive cul-de-sac cytology was the first and only early indication of recurrence.

CONCLUSION

The use of ultrasonography did not improve the accuracy of the cul-de-sac aspiration. The greater amount of fluid in the cul-de-sac during the second sampling might contribute to achieving a better result.

A randomised phase III study comparing high-dose chemotherapy to conventionally dosed chemotherapy for stage III ovarian cancer: the Finnish Ovarian Cancer (FINOVA) study

Women with stage III ovarian cancer and with < or = 2 cm residual tumour were randomly assigned to receive either conventionally dosed chemotherapy (group A) or HDCT (group B). Patients allocated to group A received 6 cycles of paclitaxel (T) 135 mg/m2 and cisplatin (P) 75 mg/m2 every 3 weeks, and those allocated to HDCT received 3 TP cycles followed by peripheral blood stem cell mobilisation with cyclophosphamide (C) 3000 mg/m2 and T 175 mg/m2, and subsequently HDCT with carboplatin 1500 mg/m2, C 120 mg/kg, and mitoxantrone 75 mg/m2. The trial was closed early after 42 patients were entered due to slow accrual. The median follow-up time of patients who were alive was 81 months. The median progression-free survival time was 15.9 and 16.6 months (hazard ratio, HR 0.83; 95% CI 0.41-1.69, P = 0.61) and the median overall survival time was 43.7 and 64.3 months (HR, 0.74; 95% CI 0.34-1.61, P = 0.44) in groups A and B, respectively. Although one patient died of HDCT-related toxicity, the regimen was otherwise relatively well tolerated. We conclude that the HDCT regimen used was feasible, but did not result in significantly improved survival in this prematurely closed trial. A clinically important survival benefit cannot be excluded due to the small sample size.

Assembly of fluorescent chimeric virus-like particles of canine parvovirus in insect cells

Canine parvovirus (CPV) is a small non-enveloped ssDNA virus composed of the viral proteins VP1, VP2, and VP3 with a T=1 icosahedral symmetry. VP2 is nested in VP1 and the two proteins are produced by differential splicing of a primary transcript of the right ORF of the viral genome. The VP2 protein can be further proteolytically cleaved to form VP3. Previous studies have shown that VP1 and VP3 are unnecessary for capsid formation and consequently, that VP2 alone is sufficient for assembly. We have hypothesized that insertion of the enhanced green fluorescent protein (EGFP) at the N-terminus of VP2 could be carried out without altering assembly. To investigate the possibility to develop fluorescent virus-like particles (fVLPs) from such chimeric VP2 proteins, the corresponding fusion construct was abundantly expressed in insect cells. Confocal imaging indicated that the EGFP-VP2 fusion product was assembled to fluorescent capsid-like complexes. In addition, electron micrographs of purified EGFP-VP2 complexes showed that they displayed a very similar size and appearance when compared to VP2 VLPs. Further, immunolabelling of purified EGFP-VP2 VLPs showed the presence of EGFP within the structure. Fluorescence correlation spectroscopy (FCS) studies confirmed that fVLPs were very similar in size when compared to authentic CPV. Finally, feeding of mammalian cells susceptible to CPV infection with these fVLPs indicated that entry and intracellular trafficking could be observed. In summary, we have developed fluorescent virus-like nanoparticles carrying a heterologous entity that can be utilized as a visualization tool to elucidate events related to a canine parvovirus infection.

Ovarian manifestations in women with autosomal dominant polycystic kidney disease

BACKGROUND

Ovarian cysts are found in some premenopausal women with autosomal dominant polycystic kidney disease (ADPKD). Liver cysts are the major extrarenal manifestations, frequently found in postmenopausal women. Female steroid hormones may regulate hepatic cystogenesis, but ovarian manifestations in postmenopausal women are unknown. The aim of the present study is to investigate possible ovarian manifestations associated with ADPKD in premenopausal and postmenopausal women.

METHODS

The study group included 19 premenopausal or postmenopausal women with ADPKD and 19 age- and parity-matched control women with no history of renal disease. Ovarian structures and volumes were measured by means of transvaginal ultrasonography.

RESULTS

Three of 8 premenopausal and 1 of 11 postmenopausal women with ADPKD had a small unilateral single ovarian cyst; there were none in controls. Eight women with ADPKD and 8 controls of premenopausal age had similar ovarian volumes (4.92 +/- 2.97 versus 3.92 +/- 2.60 cm3). Eleven postmenopausal women with ADPKD had an increased mean ovarian volume compared with 11 postmenopausal controls (4.11 +/- 2.60 versus 1.66 +/- 0.96 cm3; P < 0.01). Ovarian volume was not associated with the use of hormonal replacement therapy or impaired renal function in postmenopausal women with ADPKD.

CONCLUSION

ADPKD is not associated with cystic ovaries, although single ovarian cysts are occasionally found. Equal ovarian volumes between premenopausal and postmenopausal women with ADPKD suggest a possible indirect effect of polycystic kidneys on gonads in aging women.

Intracellular route of canine parvovirus entry

The present study was designed to investigate the endocytic pathway involved in canine parvovirus (CPV) infection. Reduced temperature (18 degrees C) or the microtubule-depolymerizing drug nocodazole was found to inhibit productive infection of canine A72 cells by CPV and caused CPV to be retained in cytoplasmic vesicles as indicated by immunofluorescence microscopy. Consistent with previously published results, these data indicate that CPV enters a host cell via an endocytic route and further suggest that microtubule-dependent delivery of CPV to late endosomes is required for productive infection. Cytoplasmic microinjection of CPV particles was used to circumvent the endocytosis and membrane fusion steps in the entry process. Microinjection experiments showed that CPV particles which were injected directly into the cytoplasm, thus avoiding the endocytic pathway, were unable to initiate progeny virus production. CPV treated at pH 5.0 prior to microinjection was unable to initiate virus production, showing that factors of the endocytic route other than low pH are necessary for the initiation of infection by CPV.

Characterization of a nuclear localization signal of canine parvovirus capsid proteins

We investigated the abilities of synthetic peptides mimicking the potential nuclear localization signal of canine parvovirus (CPV) capsid proteins to translocate a carrier protein to the nucleus following microinjection into the cytoplasm of A72 cells. Possible nuclear localization sequences were chosen for synthesis from CPV capsid protein sequences (VP1, VP2) on the basis of the presence of clustered basic residues, which is a common theme in most of the previously identified targeting peptides. Nuclear targeting activity was found within the N-terminal residues 4-13 (PAKRARRGYK) of the VP1 capsid protein. While replacement of Arg10 with glycine did not affect the activity, replacement of Lys6, Arg7, or Arg9 with glycine abolished it. The targeting activity was found to residue in a cluster of basic residues, Lys5, Arg7, and Arg9. Nuclear import was saturated by excess of unlabelled peptide conjugates (showing that it was a receptor-mediated process). Transport into the nucleus was an energy-dependent and temperature-dependent process actively mediated by the nuclear pores and inhibited by wheat germ agglutinin.

Detection of canine parvovirus antigens with antibodies to synthetic peptides

Antibodies produced in rabbits against an 18-amino acid peptide (peptide 1, NSLPQSEGATNFGDIGVP) of capsid protein VP2/residues 292-309 of canine parvovirus (CPV) or against an 18-amino acid peptide (peptide 2, GKRNTVLFHGPASTKGKS) of nonstructural protein NS1/residues 391-409 of CPV identified, in immunofluorescence analysis, viral antigens in canine A 72 cells infected with CPV. Antibodies to peptide 2 also identified viral antigens in bovine cells infected with bovine parvovirus. In western blot analysis, antibodies to peptide 1 and peptide 2 also detected viral antigens derived from blue fox parvovirus, feline parvovirus, mink enteritis virus and raccoon dog parvovirus. The peptide antibodies could be used as convenient tools in diagnosis of infections caused by CPV or closely related viruses affecting cats, minks, blue foxes and raccoon dogs.

Purification and characterisation of a plasmin-sensitive surface protein of Staphylococcus aureus

Certain methicillin-resistant Staphylococcus aureus strains contain a 230-kDa cell-wall protein which is not present on the surface of other staphylococci. The presence of this 230-kDa protein is associated with a negative test result in commercial assays designed to detect fibrinogen-binding proteins and/or protein A on the staphylococcal surface. We have purified and partially characterised the 230-kDa protein from a lysostaphin digest of a non-agglutinating methicillin-resistant S. aureus strain. Partial amino acid sequence data obtained from the purified protein did not reveal any significant similarities to known proteins which indicates that the protein is novel. The 230-kDa protein was very sensitive to proteolysis; soluble plasmin, or plasmin formed on the bacterial-cell surface, rapidly degraded the 230-kDa protein to a 175-kDa form. The finding that the 230-kDa protein bound to lectins allowed its purification by affinity chromatography on immobilised wheat germ agglutinin. Furthermore, the degradation of the 230-kDa protein was associated with an increased adherence of non-agglutinating methicillin-resistant S. aureus cells to solid-phase fibronectin, fibrinogen or IgG.

Immunochromatographic assay for quantitation of milk progesterone

We describe a rapid immunochromatographic method for the quantitation of progesterone in bovine milk. The method is based on a 'competitive' assay format using the monoclonal antibody to progesterone and a progesterone-protein conjugate labelled with colloidal gold particles. The monoclonal antibody to progesterone is immobilized as a narrow detection zone on a porous membrane. The sample is mixed with colloidal gold particles coated with progesterone-protein conjugate, and the mixture is allowed to migrate past the detection zone. Migration is facilitated by capillary forces. The amount of labelled progesterone-protein conjugate bound to the detection zone, as detected by photometric scanning, is inversely proportional to the amount of progesterone present in the sample. Analysis is complete in less than 10 min. The method has a practical detection limit of 5 ng of progesterone per ml of bovine milk.

Affinity immunosensor for milk progesterone: identification of critical parameters

The effects of several experimental parameters on the performance characteristics of a competitive-type immunochromatographic assay of milk progesterone were studied. Increasing the size of the colloidal gold particles used as a label increased both maximal signal obtained and sensitivity of the assay measured as slope of the progesterone standard curve. The concentration of the antibody used to prepare the detection zone was found to be critical factor, in that low concentrations of antibody resulted in a poor sensitivity. The compatibilities of various buffer systems with the assay were studied. The assay worked well with buffers having a broad pH range of 4.5-8.5.

Rapid detection of methicillin-resistant Staphylococcus aureus strains not identified by slide agglutination tests

Seventy-nine methicillin-resistant Staphylococcus aureus (MRSA) strains, isolated during 1980 to 1990, were classified as MRSA Aggl- (14 strains) and MRSA Aggl+ (65 strains) strains on the basis of test results in slide agglutination assays designed to detect fibrinogen-binding protein (clumping factor) and protein A on the staphylococcal surface. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that lysostaphin digests of MRSA Aggl- strains contained a high-molecular-weight protein which was not detected in digests of MRSA Aggl+ strains. Immunization of rabbits with an MRSA Aggl- strain produced an antiserum which agglutinated all MRSA Aggl- strains and also 64 of 65 MRSA Aggl+ strains. Only 1 of 68 coagulase-negative staphylococci showed agglutination in this assay. The anti-MRSA Aggl- antiserum reacted mainly with a 230-kDa staphylococcal surface protein but also with a 175-kDa protein, probably formed by proteolysis of the former and a few slightly smaller proteins. These could not be immunologically detected in lysostaphin digests of MRSA Aggl+ strains. Purified antibodies reacting with the 230-kDa protein agglutinated all MRSA Aggl- strains, indicating that the protein is located on the surfaces of staphylococci. The results suggest a tentative role for the 230-kDa protein or its fragments as a novel target to develop more efficient rapid identification methods for S. aureus, including MRSA.

The risk of endometrial cancer in diabetic and hypertensive patients: a nationwide record-linkage study in Finland

The risk of endometrial cancer (EC) in diabetics and hypertensives was studied as part of the planning of a trial of the efficacy of screening for EC. Two nationwide registers, the Finnish Cancer Registry and the Social Insurance Institution's (SII) population register, were linked to obtain 1715 EC patients diagnosed during 1970-1974 with individually matched controls. Data on the right for state-reimbursed medication for diabetes or hypertension prior to the case's cancer diagnosis was obtained from the SII's population register and was used as indicator of the diseases in question. Diabetes was a strong and hypertension a relatively weak risk factor for EC. The relative risk for the association of EC with diabetes was 4.1 (95% confidence limits 2.7 and 6.9) and with hypertension 1.6 (95% confidence limits 1.3 and 2.1). Diabetics and hypertensives are identifiable risk groups for EC in Finland. Diabetics form a suitable target population for a trial of the efficacy of screening for EC.

Characterization of antigenic epitopes of potato virus Y

Immunochemical analysis of overlapping synthetic hexapeptides covering the entire length of the coat protein of potato virus Y (PVY) revealed immunodominant regions both at the N-terminal and at the C-terminal end of the coat protein. Immunization of rabbits with synthetic peptides representing N- and C-terminal regions of the coat protein resulted in production of antibodies that reacted with PVY. Antigenicity of PVY peptides was found to correlate with predicted beta turns, with hydrophilicity and with predicted chain flexibility. Characterization of the immunochemical properties of PVY will facilitate the development of detection methods for potyviruses.

Evaluation of three slide agglutination tests for rapid identification of Staphylococcus aureus

Three slide agglutination tests for identification of Staphylococcus aureus were compared. The agglutination tests used for evaluation were Staphaurex (Wellcome Diagnostics), Staphyslide-Test (BioMerieux), and ANI S. aureus TEST (Ani Biotech Oy). A total of 347 isolates were analyzed, including 288 strains of S. aureus, 49 of S. epidermis, 11 of S. intermedius, 12 strains of other staphylococci and 14 non-staphylococcal strains. One hundred of the S. aureus strains were isolates from cases of food poisoning, 129 from mastitis and 59 from other clinical cases. The sensitivities of the tests were also compared using diluted suspensions of S. aureus strains and with purified Protein A dilutions. The results showed that the sensitivities of the tests were 98.6%, 97.9% and 99.0% for Staphaurex, Staphyslide-test and ANI S. aureus TEST, respectively. The specificities were 100% for the Staphyslide test and 98.8% for both the ANI S. aureus TEST and the Staphaurex test. The sensitivities measured with diluted S. aureus strain suspensions and Protein A solutions were equal with the Staphaurex and ANI S. aureus TEST. All the agglutination tests studied proved to be practical, easy to use and accurate for the rapid identification of S. aureus strains from culture isolates.

Tumor-associated trypsin participates in cancer cell-mediated degradation of extracellular matrix

We have recently demonstrated that many cancer cell lines produce a novel trypsinogen isoenzyme called tumor-associated trypsinogen 2 (TAT-2). It was found during a search of the target protease for tumor-associated trypsin inhibitor (TATI). We now show that degradation of subendothelial cell extracellular matrix (ECM) by four different cell lines (COLO 205 colon carcinoma, K-562 erythroleukemia, CAPAN-1 pancreatic carcinoma, and HT 1080 fibrosarcoma) can be partially inhibited by TATI or neutralizing trypsin antibodies. When cells were cultured in serum-free medium on ECM, TATI and trypsin antibodies inhibited the release of immunoreactive fibronectin fragments from ECM by 47-54 and 40%, respectively. Degradation of isotopically labeled ([3H]serine, [3H]proline, and [35S]sulfate) ECM was also significantly prevented by TATI. At its maximum, it exerted a 57% inhibition on the degradation of [3H]serine-labeled ECM. Plasminogen added exogenously to the culture medium further potentiated the proteolysis of ECM. Interestingly, addition of enteropeptidase, an activator of TAT-2, also enhanced cell-mediated proteolysis as assessed by degradation of purified fibronectin coated onto the surface of wells. Immunoblot analysis showed that enteropeptidase-mediated proteolysis generated a pattern of fibronectin fragments similar to that obtained by digestion of purified fibronectin by TAT-2. These results demonstrate the existence of a proteolytic system in tumor cells which is dependent on the activation of TAT-2. We suggest that TAT-2 is involved in a protease cascade-stimulating tumor cell invasion and degradation of extracellular matrix.

Distribution of oral nimesulide in female genital tissues

Nimesulide is a non-steroidal anti-inflammatory agent which has proved to be effective in reducing menstrual discomfort in dysmenorrhoeaic women. To determine the concentrations of this drug in the uterus (fundus, cervix), oviduct, and ovaries and to correlate these findings with plasma concentrations, a single oral dose of 100 mg nimesulide was administered 1 to 6 h before surgery to 12 women undergoing hysterectomy and salpingo-oophorectomy, mainly for fibroids. Tissue samples were taken, concentration of nimesulide measured by HPLC, and findings compared with plasma concentrations. One patient not undergoing treatment served as control. Nimesulide concentration in the tissues studied was highest 3 h after administration, as expected from the drug's pharmacokinetic profile. The highest tissue/plasma ratio (0.5) was also found at that time. Average tissue concentrations at 1, 2, 3, and 6 h after drug intake ranged from 0.3 to 1.8 micrograms g-1, and plasma concentrations from 2.6 to 4.1 micrograms ml-1. Nimesulide was evenly distributed in the tissues studied.

Evaluation of three slide agglutination tests for rapid identification of Staphylococcus aureus

Three slide agglutination tests for identification of Staphylococcus aureus were compared. The agglutination tests used for evaluation were Staphaurex (Wellcome Diagnostics), Staphyslide-Test (BioMerieux), and ANI S. aureus TEST (Ani Biotech Oy). A total of 347 isolates were analyzed, including 288 strains of S. aureus, 49 of S. epidermis, 11 of S. intermedius, 12 strains of other staphylococci and 14 non-staphylococcal strains. One hundred of the S. aureus strains were isolates from cases of food poisoning, 129 from mastitis and 59 from other clinical cases. The sensitivities of the tests were also compared using diluted suspensions of S. aureus strains and with purified Protein A dilutions. The results showed that the sensitivities of the tests were 98.6%, 97.9% and 99.0% for Staphaurex, Staphyslide-test and ANI S. aureus TEST, respectively. The specificities were 100% for the Staphyslide test and 98.8% for both the ANI S. aureus TEST and the Staphaurex test. The sensitivities measured with diluted S. aureus strain suspensions and Protein A solutions were equal with the Staphaurex and ANI S. aureus TEST. All the agglutination tests studied proved to be practical, easy to use and accurate for the rapid identification of S. aureus strains from culture isolates.

Oral administration of the prostaglandin enisoprost induces uterine activity and softens the cervix during first trimester pregnancy

48 patients in the first trimester of pregnancy received a single oral dose of placebo or enisoprost (prostaglandin E1 analogue): 10, 25, 50, 100, 200 or 400 micrograms. Uterine activity was recorded for 1 h before and for 4 h after administration of the study drug with a Millar microtransducer. There was a dose-related increase in mean resting and active pressure, but not in frequency of pressure cycles. At the highest dose used, namely 400 micrograms, all 6 subjects bled. Enisoprost dilated the cervix and any further dilatation required was easy to accomplish.

Characterization of a tumor-associated serine protease

We have earlier identified and characterized a tumor-associated trypsin inhibitor (TATI) in the urine of patients with gynecological cancer. Elevated levels of TATI occur in urine and serum of cancer patients (Stenman, U. H., Huhtala, M. L., Koistinen, R. & Seppälä, M. (1982) Int. J. Cancer 30, 53-57). To explain the elevation of TATI in cancer, we have postulated the existence of a tumor-associated protease reacting with TATI. Such a protease, tentatively called protease T, was found in cyst fluid from mucinous ovarian tumors. The protease occurs in complex with TATI, and its protease activity can be measured only after dissociation of the complex. This is achieved by reversed phase chromatography at low pH and elution with an isopropyl alcohol gradient. Protease T is inhibited by phenylmethanesulphonyl fluoride indicating that it is a serine protease. Its optimum activity at pH 9.1 and molecular mass of 24 kDa in gel chromatography are similar to those of trypsin but the substrate specificity is not identical and its isoelectric point (pI) is about 4.0, which is lower than the corresponding values of both cationic (pI 9) and anionic trypsin (pI 5). Protease T could be associated with the elevation of TATI seen in certain tumor patients.

Fibronectin fragmentation induced by dental plaque and Bacteroides gingivalis

Degradation of fibronectin (FN) by subgingival and supragingival plaque and Bacteroides gingivalis (Bg) was studied in vitro. The degradation of FN by both types of plaque was relatively rapid, continuous but incomplete. Some differences were found between supra- and subgingival samples. Supragingival plaque extracts produced several FN fragments of 110-180 kd during short incubations of 15-60 min. The predominant fragment after overnight incubation was a 110 kd polypeptide. With subgingival plaque extract a more extensive degradation of FN was noted. The main degradation product was a 120 kd fragment after overnight incubation. Several peptide fragments were released from fibronectin by Bg extracts. Their molecular size was different from those produced by trypsin, elastase or dental plaque. When cell extracts of Bg were fractionated by high performance liquid chromatography, three separate peaks of fibronectin degrading activity were obtained. Two of those peaks also contained trypsin-like enzyme activity. The degradation of fibronectin and the subsequent formation of biologically active peptides may have many effects in periodontal pockets. These may include modifying effects on plaque growth and wound healing.

Solution structure of human plasma fibronectin using small-angle X-ray and neutron scattering at physiological pH and ionic strength

Human plasma fibronectin has been investigated at physiological pH and ionic strength, by using small-angle X-ray and neutron scattering techniques. The results indicate that the molecule is disc shaped with an axial ratio of about 1:10. In fact, an ellipsoid of revolution with semiaxes a = 1.44 nm and b = c = 13.8 nm is in agreement with the experimental scattering data, and can also fully explain the rather extreme hydrodynamic parameters reported for fibronectin. The X-ray data gave a radius of gyration of 8.9 nm and a molecular weight of 510,000, whereas the neutron data gave slightly larger values, 9.5 nm and 530,000, respectively. From the volume of the best fitting ellipsoid we obtain a degree of hydration of 0.61 g H2O/g protein (dry weight). Neutron data, recorded at different D2O concentrations in the solvent, gave a match point of 43% D2O, which indicates that approximately 80% of the hydrogens bound to oxygen and nitrogen are exchangeable.

Attachment of staphylococci and streptococci on fibronectin, fibronectin fragments, and fibrinogen bound to a solid phase

The attachment of Staphylococcus aureus (Cowan I) and two strains of group A and G streptococci on glass cover slips coated with fibronectin, fibronectin fragments, or fibrinogen was studied. The attachment was quantitated by counting the attached bacteria on glass surfaces coated with a similar molarity of the proteins. Fibronectin was a more effective attachment factor than fibrinogen for staphylococci, while group G streptococci attached better on fibrinogen- than on fibronectin-coated cover slips. In this system, group A streptococci bound almost exclusively to substrate-bound fibrinogen. Attachment experiments involving the use of staphylococci pretreated with soluble fibronectin or fibrinogen revealed that bacterium-bound fibronectin and fibrinogen were able to enhance the adherence on cover slips coated with fibronectin. The 30-kilodalton NH2-terminal and the 120- to 140-kilodalton COOH-terminal fragments of fibronectin, both of which contain bacterial binding sites, mediated the staphylococcal attachment, suggesting that both parts of the molecule are involved in the attachment mediated by fibronectin.

Secondary structure of human plasma fibronectin: conformational change induced by calf alveolar heparan sulfates

The quantitative analysis of circular dichroic spectra of native human plasma fibronectin according to the method of Provencher and Glöckner [Provencher, S. W., & Glöckner, J. (1981) Biochemistry 20, 33-37] indicated the presence of beta-sheet (79%), beta-turn (21%), but no alpha-helix or random coil in the secondary structure. The calf alveolar heparan sulfates induced a change in the conformation of fibronectin: the magnitude of the change depended on the molecular properties of the particular heparan sulfate preparations.

Binding sites for streptococci and staphylococci in fibronectin

Purified cathepsin G fragments of fibronectin were used to locate the binding sites for streptococci and staphylococci in the fibronectin molecule. The iodinated, NH2-terminal, 30-kilodalton (kd) fragment bound to group A and G streptococci and to Staphylococcus aureus. The 125I-labeled, COOH-terminal, 120- to 140-kd fragment bound weakly to group A streptococcus strain and to S. aureus when tested in a buffer of low ionic strength. The 30- and 120- to 140-kd fragments inhibited the binding of iodinated fragments to bacteria. The two fragments were, on a molar basis, equally effective, and they were more potent inhibitors than intact fibronectin. The gelatin-binding 40-kd fragment neither bound to any of the bacterial strains nor inhibited the binding of 125I-labeled 30-kd or 125I-labeled 120- to 140-kd fragments to bacteria. The results indicate that fibronectin has at least two separate binding sites for streptococci and staphylococci, one in the NH2-terminal region and another in the COOH-terminal region of the molecule, both capable of specific interaction with a complementary structure exposed on streptococcal and staphylococcal cell surfaces.

Characterization of fibronectin on human spermatozoa

Ejaculated human spermatozoa were shown to have fibronectin polypeptides on their surface. Immunofluorescence studies revealed fibronectin as a belt-like fluorescent band on the post-acrosomal area of sperm heads, whereas none was found in sperm tails. The location of the fluorescent band corresponded to the equatorial segment of the spermatozoon. Fibronectin polypeptides were heterogeneous with Mr ranging from 35000 to 210000, as revealed by immunoblotting and by immunoprecipitation of detergent extracts from surface-radioiodinated spermatozoa.

Identification of fibronectin fragments that bind to carboxy-group-modified proteins

Limited proteolysis of human plasma fibronectin with chymotrypsin, trypsin or thermolysin has been used to localize binding sites responsible for binding [Vuento, Korkolainen & Stenman (1982) Biochem. J. 205, 303-311] of fibronectin to carboxy-group-modified proteins. These bindings sites are different from those mediating binding of fibronectin to gelatin or heparin. They are located close to the C-terminus of the polypeptide chains of fibronectin, and apparently overlap with the C-terminal fibrin binding site.

Effect of chemical modification of arginine and lysine residues of fibronectin on its antigenic and gelatin-binding activity

The effect of chemical modification of arginine and lysine residues of fibronectin on its antigenic and gelatin-binding activity was studied by enzyme immunoassay techniques. Both modifications strongly reduced the gelatin-binding activity. Using conformation-specific antibodies it was shown that modification of lysines caused extensive conformational changes in the molecule. No such changes could be detected in arginine-modified fibronectin. The results suggest that arginine residues are directly involved in the binding of fibronectin to gelatin. Lysine residues seem to be important for maintaining a native conformation necessary for gelatin-binding.

Association of fibronectin with carboxy-group-modified proteins in vitro

Treatment of human immunoglobulin G, albumin and fibronectin with water-soluble carbodi-imide at pH4.75 in the presence of glycine ethyl ester resulted in an avid binding of (125)I-labelled native fibrinectin to the modified proteins. Succinoylation, reduction and alkylation or heat-denaturation had no such effect. In affinity chromatography under physiological conditions, serum was depleted of fibronectin when run through columns of the carbodi-imide-treated proteins coupled to agarose. Fractions eluted from such columns with urea were enriched in fibronectin. The binding of radiolabelled fibronectin to the carbodi-imide-treated proteins was inhibited by unlabelled fibronectin in relatively low concentrations, but also by albumin in higher concentrations. Heat-denatured albumin inhibited at concentrations approx. 10-30 times lower than native albumin. The binding reaction had a pH optimum of 6-8. It was inhibited at high ionic strength and in the presence of urea. Anionic detergents inhibited at millimolar concentrations, but non-ionic detergents did not inhibit the binding reaction. The results were interpreted as showing that: (1) fibronectin is capable of binding to itself, to immunoglobulin G and to albumin after a reduction of the negative surface charge of these proteins, and may have a general ability to bind such modified proteins; (2) this binding can take place under physiological conditions; (3) carboxy-group-modified proteins selectively bind fibronectin from serum. This novel binding phenomenon could be important in terms of the opsonin function of circulatory fibronectin. We propose that fibronectin may recognize modified (denatured) proteins and mediate their uptake by the reticuloendothelial system.

Essential charged amino acids in the binding of fibronectin to gelatin

The binding of fibronectin to gelatin-agarose was strictly dependent on pH, having a pH optimum of 7-9. The binding was strongly inhibited by increasing ionic strength. A chemical modification of lysyl and arginyl groups of fibronectin abolished the binding activity. The anionic detergents sodium dodecyl sulphate and sodium deoxycholate in concentrations of 10-100mM had the same effect. The binding was not affected by the non-ionic detergents Triton X-100, Tween 20 or Lubrol WX. The results demonstrate an important role of ionic interactions in the binding of fibronectin to gelatin. Absence of inhibition by non-ionic detergents suggests that hydrophobic interactions contribute relatively little to the binding of fibronectin to gelatin.

Effect of lectins and chemical modification on the hemagglutinin activity of human plasma fibronectin

Purified human plasma fibronectin has been shown to agglutinate protease-treated red cells [Vuento, Hoppe-Seyler's Z. Physiol. Chem. 360, 1327-1333, (1979)]. The present report shows that the activity is inhibited by low concentrations of lectins and by macromolecular serum factors. Chemical modification of carboxyl groups of fibronectin strongly inhibited the activity, but modification of amino groups of guanidinium groups had little effect on the activity. The results suggest that fibronectin receptors on erythrocyte surface are carbohydrate-containing molecules. Humoral macromolecular factors may control the interaction of fibronectin with cell surfaces. Chemical modification studies indicate that the parts of the fibronectin molecule responsible for the hemagglutinin activity are different from those mediating the binding of fibronectin to collagen.

Competitive enzyme immunoassay for human plasma fibronectin

A competitive enzyme immunoassay for the determination of fibronectin in plasma is described. An enzyme conjugate prepared by coupling alkaline phosphatase to rabbit anti-human fibronectin antibodies by glutaraldehyde was used as principal reagent. The assay was performed by coating polystyrene tubes with purified fibronectin and reacting these coated tubes with a mixture of sample and enzyme-labeled antibodies. After overnight incubation, the amount of enzyme activity associated with the tube was determined. An assay range of 0.5-20 microgram/ml of fibronectin was obtained. The mean concentration of plasma fibronectin in female patients was found to be 270 microgram/ml (standard deviation 50 microgram/ml, n = 22). Denatured fibronectin had low activity in the assay. The presence of cross-reacting antigens in rat and guinea pig plasma was demonstrated by the enzyme immunoassay technique.

Immunochemical characterization of human plasma fibronectin

Human plasma fibronectin has been purified by a non-denaturing affinity chromatography procedure [Vuento & Vaheri, (1979) Biochem.J. 183, 331--337], and antisera have been raised by immunizing rabbits with the native protein. The antisera reacted strongly with native fibronectin, but only weakly with reduced and alkylated fibronectin or with heat-denaturated fibronectin. Denaturation also affected the haemagglutinating and gelatin-binding activities of fibronectin and increased its susceptibility to proteolytic degradation. The antisera reacted with fragments of fibronectin obtained by proteolysis with plasmin. Large fragments (mol.wt. 180000--200000), lacking the region harbouring the interchain disulphide bridges but containing the sites responsible for gelatin-binding and haemagglutinating activity, showed as intense a reaction with the antisera as intact fibronectin. Smaller peptides showed a weaker reaction. All fragments tested showed sensitivity to denaturation in their reaction with the antisera. The results were interpreted as showing that: (1) native fibronectin has an ordered conformation that is easily perturbed by denaturation; (2) most of the antigenic determinants of the protein are dependent on conformation; (3) the region of the fibronectin molecule containing the interchain disulphide bridges has only few antigenic determinants; and (4) covalent interaction of the two subunits does not contribute to the antigenic structure recognized by rabbit antisera. The observed correlation between the antigenic activity and a structural and functional intactness of fibronectin suggests that the antibodies to native fibronectin could be used as a conformational probe in studies on this protein.

Spontaneous and polyamine-induced formation of filamentous polymers from soluble fibronectin

Fibronectin is a high-molecular-weight glycoprotein present in a soluble form in plasma and in other body fluids and as insoluble protein in connective tissue matrix. This study reports that soluble fibronectin is polymerized into filamentous structures and that polyamines stimulate this process and precipitate fibronectin. Fibronectin purified from human plasma under non-denaturing conditions appeared after negative staining as non-globular extended structures in the electron microscope. During storage of purified fibronectin at +4 degrees C, in particular a low ionic strength, increasing amounts of the protein appeared as protein filaments. These filaments had a diameter of 2--3 nm and a length of up to several micrometers. The filaments also formed bundles of variable thickness, apparently through lateral association. These structures could also be visualized by phase-contrast microscopy. Polyamines, at a concentration of 1--5 mM and at a low ionic strength, induced a rapid, extensive polymerization of fibronectin into filamentous structures. The effect increased in the order putrescine less than spermidine less than spermine. Polyamine-induced precipitation of fibronectin was reversible upon removal of the polyamine. Fibronectin secreted by normal and by malignant cells could be fairly selectively precipitated from the culture medium with polyamines. The observed filamentous polymers of soluble fibronectin resemble the filamentous fibronectin-containing pericellular structures in fibroblast cultures and may provide a model for studies on the deposition of fibronectin in matrix form.

Interaction of polyamines with proteins of human plasma: a preferential aggregation of fibrinogen and fibronectin (cold insoluble globulin)

The polyamines spermine and spermidine were found to aggregate proteins from human plasma and serum, apparently due to electrostatic interactions between these cations and anionic proteins. Fibrinogen and fibronectin (cold insoluble globulin) were identified as the major molecular components of aggregates, and fibronectin could be quantitatively removed from plasma by aggregation with spermine. The results indicate that fibrinogen and fibronectin have anionic groups which react with polyamines and which are essential for the solubility of these proteins.

Purification of fibronectin from human plasma by affinity chromatography under non-denaturing conditions

Fibronectin was purified from human plasma by affinity chromatography under nondenaturing conditions. The method was based on the previously known binding of fibronectin to gelatin. The novel features of our method are the use of arginine in the elution of fibronectin from immobilized gelatin [Vuento & Vaheri (1978) Biochem. J. 175, 333-336] and the use of arginine-agarose as second affinity step. The purified protein was homogeneous as judged by polyacrylamide-gel electrophoresis, analytical ultracentrifugation and two-dimensional immunoelectrophoresis. The yield was 60%. We propose that the method would be useful in preparation of fibronectin for studies on its biological activities, where it is important that the protein is obtained in a native state.

Hemagglutinin activity of human plasma fibronectin

Purified human plasma fibronectin at concentrations of about 30 microgram/ml was found to agglutinate trypsin-treated erythrocytes from certain species. The hemagglutination reaction was inhibited by specific antibodies to fibronectin, by relatively low concentrations of polyamines and by higher concentrations of basic amino acids and nonacetylated amino sugars. The divalent cations Ca2+ and Mg2+ and the chelating agent ethylenediaminetetraacetate did not affect the reaction. None of the neutral amino acids, neutral sugars or polyanions tested was inhibitory. The results imply that plasma fibronectin is capable of interacting with cell surfaces and support the idea of a similarity between cellular and plasma fibronectins.

Dissociation of fibronectin from gelatin-agarose by amino compounds

Soluble fibronectin of human plasma was specifically dissociated at neutral pH from gelatin-agarose by several cationic amino compounds, notably the polyamines spermine, spermidine and putrescine, the basic amino acid arginine, and amino sugars. The neutral and acidic amino acids and the N-acetylated derivatives of amino sugars tested were ineffective. Gel-filtration experiments demonstrated that [14C]spermidine bound to fibronectin but not to gelatin.