Renal function in children treated for central nervous system malignancies.

AIM: The aim of the study was to evaluate renal function and to assess the usefulness of the following nephrotoxicity markers: cystatin C (CYS C), beta-2 microglobulin (B2MG) and neutrophil gelatinase-associated lipocalin (NGAL) in 38 (18 girls, 20 boys) children previously treated for central nervous system malignancy. MATERIAL: Median age at evaluation was 13.7 years (range 2.1-22 years). The mean follow-up time after the completion of chemotherapy was 3.2 years (range 0.16-6.5 years). RESULTS: Subclinical chronic kidney disease (estimated glomerular filtration rate: eGFR 90-60 ml/min/1.73 m(2)) was found in 22 patients (58 %), while renal insufficiency (eGFR 30-60 ml/min/1.73 m(2)) was found in six children (16 %). It has been demonstrated statistically significant negative correlation between the eGFR and cystatin C concentration (p < 0.0001) and eGFR and beta-2 microglobulin concentration (p < 0.02). Conversely, there was no correlation between eGFR and NGAL. Thirteen children (34 %) developed drug-induced tubulopathy: decreased tubular reabsorption of phosphate (TRP) and renal tubular threshold for phosphate (Tmp/GFR). CONCLUSION: Children treated for CNS tumours often develop drug-induced chronic renal disease, involving the glomeruli and/or renal tubules. Cystatin C and beta-2 microglobulin seemed to be good markers for chronic kidney damage in these patients, which is probably not true for NGAL.

A novel recyclable hemoperfusion adsorbent based on TiO2 nanotube arrays for the selective removal of ß2-microglobulin.

Prolonged and excessive accumulation of ß2-microglobulin (ß2m) in the blood can lead to various kidney-related and other diseases. Currently, the most effective method of removing ß2m from the blood is hemoperfusion. Although some traditional hemoperfusion adsorbents such as cellulose and polystyrene microspheres have been used for the removal of ß2m, their selectivity still needs improvement. Immunosorbents have been developed to address this issue, but high cost and limited application are concerns. TiO2 nanotube arrays (TNTAs) have shown great potential in adsorption-related biomedical applications. In this study, we designed and developed a novel TNTA-based hemoperfusion adsorbent for the removal of ß2m, which has demonstrated good biocompatibility, selectivity, and reusability. We investigated the ß2m adsorption capacities of TNTAs with different pore sizes. The results indicate that TNTAs with a pore size matching the size of ß2m exhibit higher adsorption capacity while also having lower adsorption capacity for albumin, showing the importance of pore size on the selectivity of adsorbents. Additionally, green regeneration of TNTAs is achieved via the photocatalytic activity originating from TiO2. Even after five cycles, the adsorption capacity of TNTAs remained above 70%. Our work demonstrates that inorganic materials with ordered pores are capable to be candidates for hemoperfusion, possessing advantages over traditional organic materials such as high stability, security, and low cost.

Absence of altered expression of optineurin in primary open angle glaucoma patients.

PURPOSE: To investigate the expression level of the optineurin gene (OPTN) in the blood of primary open angle glaucoma (POAG) patients to determine if altered expression is playing a role in primary open angle glaucoma systemically. METHODS: Patients (n=47) were eligible for inclusion if they met standard clinical criteria for POAG, including age greater than 40 years, intraocular pressure ≥21 mmHg in at least one eye before treatment, normal-appearing anterior chamber angles bilaterally on gonioscopy, and optic nerve injury characteristic of POAG. Control subjects (n=27) were recruited who were free from glaucoma by examination. DNA from patient was sequenced to look for possible mutations in the coding region of OPTN or its promoter. RNA was extracted from leukocytes of patients and controls and converted to cDNA by reverse transcriptase enzyme, and quantitative PCR was used to assess expression levels of OPTN and the ß-globulin gene. The ratio of OPTN expression to ß-globulin gene expression for POAG patients was compared to that of controls and to clinical characteristics of POAG patients. RESULTS: No mutation(s) were detected in any of the patients after sequencing the full OPTN gene and its promoter region. Mean OPTN (p≤0.35), and ß-globulin (p≤0.48) gene expression values were statistically similar in POAG patients and controls. OPTN/ß-globulin (p≤0.83) ratios were also indistinguishable between POAG patients and controls. OPTN/ß-globulin ratios were not significantly associated with age, sex, or ethnicity of patients within the POAG group. Similarly, OPTN/ß-globulin ratios were not significantly affected by ethnicity or clinical parameters related to POAG severity including maximum intraocular pressure, vertical cup-to-disk ratio, static perimetry mean deviation, or static perimetry pattern standard deviation. CONCLUSIONS: OPTN expression is not altered in the blood of POAG patients, suggesting that OPTN expression is not changed systemically and implying that other mechanisms are involved in POAG pathogenesis.

Unaltered myocilin expression in the blood of primary open angle glaucoma patients.

PURPOSE: To investigate the expression of the myocilin gene (MYOC) in the blood of primary open angle glaucoma (POAG) patients to determine if altered systemic expression is playing a role. METHODS: Patients (n=47) were eligible for inclusion if they met standard clinical criteria for POAG. Control subjects (n=27) were recruited who were free from glaucoma by examination. RNA was extracted from leukocytes of patients and controls and converted to cDNA by reverse transcriptase enzyme, and quantitative PCR was used to assess expression levels of MYOC and the house keeping gene ß-globulin (HBB). The ratio of MYOC expression to HBB expression for POAG patients was compared to that of controls and to clinical characteristics of POAG patients. RESULTS: Mean gene expression values were statistically similar in POAG patients and controls for both MYOC (p≤0.55) and HBB (p≤0.48). MYOC/HBB ratios were also statistically indistinguishable between POAG patients and controls (p≤0.90). MYOC/HBB ratios were not significantly associated with age, sex, or ethnicity of patients within the POAG group. Similarly, MYOC/HBB ratios were not significantly associated with clinical parameters related to POAG severity, including maximum intraocular pressure, vertical cup-to-disk ratio, static perimetry mean deviation, or static perimetry pattern standard deviation. CONCLUSIONS: MYOC expression is not altered in the blood of POAG patients, unlike MYOC expression in trabecular meshwork (TM) cultures. These results suggests that MYOC expression is not altered systemically but rather that MYOC expression may contribute to POAG pathogenesis in specific tissues such as TM.

Prototypic chromatin insulator cHS4 protects retroviral transgene from silencing in Schistosoma mansoni.

Vesicular stomatitis virus glycoprotein (VSVG) pseudotyped murine leukemia virus (MLV) virions can transduce schistosomes, leading to chromosomal integration of reporter transgenes. To develop VSVG-MLV for functional genomics in schistosomes, the influence of the chicken ß-globin cHS4 element, a prototypic chromatin insulator, on transgene expression was examined. Plasmid pLNHX encoding the MLV 5'- and 3'-Long Terminal Repeats flanking the neomycin phosphotransferase gene (neo) was modified to include, within the U3 region of the 3'-LTR, active components of cHS4 insulator, the 250 bp core fused to the 400 bp 3'-region. Cultured larvae of Schistosoma mansoni were transduced with virions from producer cells transfected with control or cHS4-bearing plasmids. Schistosomules transduced with cHS4 virions expressed 2-20 times higher levels of neo than controls, while carrying comparable numbers of integrated proviral transgenes. The findings not only demonstrated that cHS4 was active in schistosomes but also they represent the first report of activity of cHS4 in any Lophotrochozoan species, which has significant implications for evolutionary conservation of heterochromatin regulation. The findings advance prospects for transgenesis in functional genomics of the schistosome genome to discover intervention targets because they provide the means to enhance and extend transgene activity including for vector based RNA interference.

Electrophoretic serum protein fraction profile during the different physiological phases in Comisana ewes.

The aim of this study was to evaluate the influence of different physiological phases on serum total proteins and their fractions of ten Comisana ewes housed in Mediterranean area. From each animal, blood samples were collected at different physiological phases: late pregnancy, post-partum, early, mid-, end lactation and dry period. On all samples serum total proteins were determined by the biuret method, and albumin, α-globulins, ß(1) -globulins, ß(2) -globulins and γ-globulins concentrations were assessed using an automated system. One-way repeated measures analysis of variance was applied to determine the significant effect of different physiological phases on the parameters studied. During the late pregnancy and post-partum, total proteins, ß1- and ß2-globulins and γ-globulins showed the highest values. Starting from post-partum, α-globulins increased to reach their peaks in mid-lactation. Early lactation was characterized by low γ-globulins values. The increase in serum albumin concentration and the drop in some globulin fractions determined the significant increase in albumin/globulin ratio. The obtained results contributed to improve the knowledge on electrophoretic profile during the different physiological phases in ewes, confirming that pregnancy and lactation periods affect the protein metabolism. Particularly, serum protein fractions pattern could give information about dehydration, plasma volume expansion and hepatic function, which occur during the different physiological phases. Dynamics of the protein profile - from pregnancy to dry period - which are provided by our results, could be considered as guidelines for the management strategies to guarantee the nutritional needs of these animals during the different physiological phases and to avoid a decline of productive performance and consequently an economic loss.

Measuring the level of agreement in hematologic and biochemical values between blood sampling sites in leatherback sea turtles (Dermochelys coriacea).

Conservation programs to protect endangered sea turtles are being instituted worldwide. A common practice in these programs is to collect blood to evaluate the health of the turtles. Several different venipuncture sites are used to collect blood from sea turtles for hematologic and biochemistry tests, depending on the species. To date, it is unknown what affect venipuncture site may have on sample results. The purpose of this study was to measure the level of agreement between hematologic and biochemistry values collected from the dorsal cervical sinus and the interdigital vein of leatherback (Dermochelys coriacea) sea turtles. Paired heparinized blood samples were obtained from the dorsal cervical sinus and the interdigital vein of 12 adult female nesting leatherback sea turtles on Keys Beach, St. Kitts, West Indies. Even though the sample population was small, the data for each chemistry were normally distributed, except for creatine kinase (CK). There was no significant difference when comparing biochemistry or hematologic values by venipuncture site, except for CK (P = 0.02). The level of agreement between sampling sites was considered good for albumin, calcium, globulin, glucose, packed cell volume, phosphorus, potassium, sodium, total protein, total solids, uric acid, white blood cell count, and all of the individual white cell types, while the level of agreement for aspartate aminotransferase and CK were considered poor. This information, coupled with the fact that the interdigital vein affords a less-invasive procedure, demonstrates that the interdigital vein is an appropriate location to use when establishing a hematologic and biochemical profile for leatherback sea turtles.

[Effects of modified liangge powder contained serum on LPS stimulated TLR4 expression and release of cytokines in mouse platelets].

OBJECTIVE: To observe the effects of Modified Liangge Powder (MLP) on the expressions of platelet toll like receptor 4 (TLR4) and the release of platelet-derived cytokines interleukin 8 (IL-8), beta platelet globulin (beta-TG), soluble CD40 ligand (sCD40L). METHODS: The modulating effects on the release of cytokines from mice platelets by TLR4 ligand through monoclonal antibody blocking TLR4 on platelet were compared. The stimulated platelet by LPS was incubated with low (0.94 g/mL), medium (1.89 g/mL), and high (2.84 g/mL) dose of MLP contained serum. The changes of the platelet TLR4 expression and platelet-derived cytokines were observed. RESULTS: The positive expression rate of platelet TLR4 obviously decreased (P < 0.01) and the release of sCD40L and beta-TG from platelets significantly increased (P < 0.01) after stimulated by LPS. However, the release of sCD40L and beta-TG from platelets obviously decreased by TLR4 monoclonal antibody (P < 0.05, P < 0.01). There was no statistical difference in IL-8 between before and after LPS stimulation (P > 0.05). Platelet TLR4 positive expression rate was significantly higher after incubated by medium and high doses of MLP contained serum (P < 0.01), and the releasing of sCD40L and beta-TG was lower in the serum contained groups. The inhibitory effects were enhanced in a dose-dependent manner. CONCLUSIONS: LPS induced platelet activation by TLR4 and released sCD40L and beta-TG, while the release of platelet IL-8 was not dependent on platelet TLR4-LPS pathway. MLP could inhibit LPS-stimulated sCD40L and beta-TG, inhibit the binding of platelet TLR4 and LPS in a dose-dependent manner, thus reducing the release of platelet cytokines.

[Assessment of the effect of selected mixture of food additives on the protein metabolism--model studies]. / Ocena wplywu mieszaniny wybranych dodatków do zywnosci na wskazniki metabolizmu bialkowego--badania modelowe.

BACKGROUND: Contemporarily, food production without food additives is very rare. Increasingly often, however, scientific works report on adverse effects of specified, single food additives on the body. Data is, in turn, lacking on the synergistic effect of a mixture of different food additives on body functions and its main metabolic pathways. OBJECTIVE: The objective of this study, an animal model, was to evaluate if and in what way the compound of chosen and most frequently used and consumed food additives, along with the change of diet composition to processed, purified, influence the selected markers of protein metabolism. MATERIAL AND METHODS: The animals were divided into four groups, which were fed with compound of feed pellets: group I and II with basic compound, group III and IV with modified compound in which part of the full grain was replaced by isocalorie wheat flour type 500 and saccharose. Animals from groups I and III received tap water, which was standing for some time, to drink. Animals from groups II and IV received solution of chosen additives to food and next they were given water to drink. The amount of given food additives was evaluated by taking into consideration their consumption by people recalculated to 1 kg of their body mass. The experiment spanned for 7 weeks. RESULTS: It was ascertained that the applied additives caused significant changes in total protein concentration and its fractions: albumin, alpha1-globulin, alpha2-globulin, beta-globulin and gamma-globulin in the blood serum of the animals under research, which can indicate and contribute to disclosure of creation of undesirable food reaction, especially when recommended levels of consumption of those additives are being exceeded. The organism response to the applied additives and accompanying it change of diet was essentially connected to sex of the animals. Undesirable character of changes taking place under the influence of applied additives, was observed both in animals fed with basic feed and modified feed with various intensity according to the parameter under research. CONCLUSIONS: The analysis of the results achieved enabled concluding that the applied mixture of food additives caused significant changes in the concentration of total protein and its fractions: albumins, alphal-, alpha2-, beta- and gamma-globulins in blood serum of the investigated animals. These changes may indicate but also may contribute to the development or manifestation of undesirable nutritional responses, especially when recommended dietary allowances are exceeded. The body's response to the applied additives and concomitant modification of diet composition was significantly correlated with sex of the animals. The unfavorable character of changes following the administration of additives was observed in both the animals on the basal diet and these fed the modified feed mixture, yet with a different intensity that was found to depend not on the feeding group but on the parameter examined.

Down-regulation of OPA1 in patients with primary open angle glaucoma.

PURPOSE: Heterozygous optic atrophy type1 (OPA1) mutations are responsible for dominant optic atrophy, and the down regulation of OPA1 expression in patients with Leber hereditary optic neuropathy may imply that Opa1 protein levels in mitochondria play a role in other spontaneous optic neuropathies as well. Mitochondrial and metabolic abnormalities may put the optic nerve at risk in primary open angle glaucoma (POAG), and this preliminary study was designed to investigate whether altered OPA1 expression might be present in the progressive optic neuropathy of POAG. METHODS: Patients were eligible for inclusion if they met standard clinical criteria for POAG, including age greater than 40 years, intraocular pressure ≥ 21 mmHg in at least one eye before treatment, normal-appearing anterior chamber angles bilaterally on gonioscopy, and optic nerve injury characteristic of POAG. RNA was extracted from leukocytes and converted to cDNA by reverse transcriptase enzyme, and real time PCR was used to assess expression levels of OPA1 and the ß-globulin (HBB) housekeeping gene. The ratio of OPA1 expression to HBB expression (OPA1/HBB) for POAG patients was compared to that of controls and to clinical characteristics of POAG patients. RESULTS: Forty-three POAG patients and 27 controls were completely phenotyped with a full ophthalmologic examination and static perimetry. Mean age (POAG 67.9 years; controls 61.8 years) and sex (POAG 26 males/17 females; controls 11/16) were similar for the two groups. Mean OPA1/HBB of POAG patients (1.16, SD 0.26) was 18% lower than controls (1.41, SD 0.50), and this difference was statistically significant (p≤0.021). OPA1 expression differed between the groups (p≤0.037), but HBB expression did not differ (p≤0.24). OPA1/HBB was not correlated with any clinical feature of POAG patients. CONCLUSIONS: Transcriptional analysis of peripheral blood leucocytes is a limited model system for studying the consequences of mitochondrial abnormalities in the optic nerve. Nevertheless, OPA1 is known to affect mitochondrial stability and has now been implicated in several spontaneous optic neuropathies. Decreased OPA1 expression in POAG patients is another indication that mitochondrial function, and possibly mitochondrially-induced apoptosis, may play a role in the development of POAG.

Pattern of serum protein fractions in dairy cows during different stages of gestation and lactation.

In dairy cows the period of transition from late gestation to early lactation is recognized as inducing considerable metabolic adaptation. The aim of this study was to analyse modifications in serum protein values occurring during the dry and the transition period and during lactation in a group of five Holstein cows of high average milk production. For all subjects, selected on the basis of their pregnancy status, blood samples were collected at different physiological phases: dry period (-60, -30 d to calving), transition period (almost 7 d to calving, 7 d after calving), and lactation (weeks 2, 5 and 15 after calving), for a total of eight blood samples for each cow. On each blood sample total proteins and electrophoresis analysis were performed. On the data obtained, normally distributed (P<0·05, Kolmogorov-Smirnov's test), one-way Repeated Measure Analysis of Variance (ANOVA), was applied to evaluate the influence of different stages of gestation and lactation on the considered parameters. Results showed a significant effect on total proteins, α1-globulins, ß-globulins, γ-globulins and albumin/globulin ratio. Most of the detected modifications were related to the transition from gestation to lactation, indicating that it is a period of great metabolic stress for cows. On the basis of the obtained results we can affirm that the pattern of serum protein fraction rn could give information about dehydration, plasma volume expansion and hepatic function occurring during the peripartum period in dairy cows.

Modulation of the alternative complement pathways by beta 1 H globulin.

C3b inactivator accelerator (A-C3bINA) was isolated from human plasma. An antiserum produced against the purified protein gave a reaction of identity with beta 1 H, a well-documented contaminant of C3 preparations. Beta 1 H appears to be composed of a single polypeptide chain containing a significant quantity of carbohydrate, and having a sedimentation coefficient of 5.6 on analytical, and 6.4 on sucrose density gradient ultracentrifugation. Its mol wt based on SDS polyacrylamide gel electrophoresis and equilibrium sedimentation is approximately 150,000, whereas it elutes from Sephadex G200 with an apparent mol wt of 300,000, suggesting that beta 1 H is an asymmetric molecule. Beta 1 H potentiates the inactivation of C3b by C3b inactivator, binds to EAC43 to limit the formation of EAC43bB and EAC43bBP, and in contrast to C3b inactivator, it increases the rate of loss of hemolytic sites from EAC43bB and EAC43bBP. For the C3b inactivator-potentiating effect, beta 1 H and C3b inactivator must necessarily be simultaneously present. The kinetics of inactivation of C3b by C3b inactivator and beta 1 H are first order, suggesting that potentiation is not a multistep process. The mechanisms of binding to C3b and inhibition of the alternative pathway convertases C3bB and C3bBP are currently unknown.

The reaction mechanism of beta-1C-globulin (C'3) in immune hemolysis.

During immune hemolysis by human complement, C'3 (beta(1C)-globulin) becomes physically attached to the erythrocyte membrane. Binding of C'3 was found to be mediated by cell-bound, activated C'2 and to have the characteristics of an enzymatic reaction. A single C'4,2a site on the cell surface effected the binding of several hundred molecules of C'3 if the latter was provided in excess. The accumulation of hemolytically inactive, physicochemically altered C'3 in the fluid phase was found to be an inherent feature of the process of C'3 binding. It is postulated that C'4,2a activates C'3 for its subsequent reaction with cell membrane receptors. Antierythrocyte antibody did not play an essential role in C'3 uptake; C'3 could be bound to erythrocyte-C'4,2a complexes which were entirely devoid of antibody. Cell-bound C'3 proved hemolytically active, the degree of hemolysis being proportional to the number of C'3 molecules per cell. Binding of a large number of C'3 molecules per cell was found to be a prerequisite for the production of the immune adherence phenomenon and for immune hemolysis.

Expression of HLA-A, -B, and -C and beta 2-microglobulin antigens in human choriocarcinoma cell lines.

Immunoprecipitation of [35S]methionine-labeled cell extracts and analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that cells from two human choriocarcinomas JaR and BeWo contained beta 2-microglobulin. The JaR cells, and one subline of BeWo, did not express surface HLA-A, -B, and -C (HLA-ABC) antigens, nor did JaR contain the antigens when cell-free extracts were measured in a sensitive radioimmunoassay. It may be concluded that the lack of expression of HLA-ABC antigens in choriocarcinoma (and in the trophoblast) is not a result of lack of beta 2-microglobulin, as is the case for the Burkitt's lymphoma cell line, Daudi.

Isolation and analysis of the mechanism of action of an inactivator of C4b in normal human serum.

A complement regulatory principle, C4b inactivator, was isolated in a partially purified form from normal human serum. The C4b inactivator, a beta1-globulin with an approximate mol wt of 88,000 daltons, and which may be identical to C3b inactivator, cleaved C4b in free solution or on the surface of cells and rendered it unable to participate in hemolytic reactions or to interact with cells, having receptors for C4b. C/b inactivator functioned by cleaving the alpha-polypeptide chain of C4b at a single site which was sufficient to dissociate the molecule into two fragments, C4c and C4d, and to inactivate it biological function. Certain structural correlates of C4 functions deriving from these studies are discussed and a model for C4 structure based on these findings is presented.

Relationship between HL-A antigens and beta-2-microglobulin as studied by immunofluorescence on the lymphocyte membrane.

The antibody-induced redistribution of beta2-microglobulin (beta2-micro) and HL-A antigens on the surface of living lymphocytes was studied by immunofluorescence. When all beta2-micro was redistributed on the lymphocyte membrane by specific rabbit antibodies and goat antirabbit Ig conjugates, the HL-A antigens were no more detectable with anti-HL-A conjugates outside the beta2-micro caps already formed. However, the redistribution of HL-A antigens fails to provoke the redistribution of all detectable beta2-micro molecules. These results suggest that HL-A antigens may be associated with beta2-micro at the cell surface, but that all beta2-micro molecules are not bound to HL-A antigens.

The relationship between 2 -microglobulin and immunoglobulin in cultured human lymphoid cell lines.

beta(2)-microglobulin was detected on the cell surface and in the medium of human lymphoid cells established in long-term culture. The secretion of beta(2)-microglobulin was relatively uniform when different cell lines were compared, whereas IgG production varied widely. kappa- and micro-membrane antigens were modulated by specific antibody; beta(2)-microglobulin was not modulated. Anti-kappa and anti-micro antisera had no effect on the expression of membrane beta(2)-microglobulin, nor had anti-beta(2)-microglobulin antiserum any effect on the expression of kappa- and micro-membrane antigens.

Beta 2-microglobulin is selectively associated with H-2 and TL alloantigens on murine lymphoid cells.

We have used a rabbit antiserum prepared against purified rat beta2-microglobulin to immunoprecipitate molecules from lysates of radioiodinated murine thymocytes and splenocytes. All the molecules that are reactive with this serum have subunits of 44,000 and 12,000 and can be identified as H-2 and TL antigens. Thus, the anti-beta2mu serum can deplete lysates of the majority of the TL and H-2 atigens which can be subsequently recognized by alloantisera. If TL and H-2 are precipitated from the lysates before the addition of anti-beta2mu, no beta2mu-reactive molecules remain. Our results indicate that Ia antigens cannot be depleted from the lysates with anti-beta2mu. The studies also suggest that TL and H-2 heavy chains can exist as both monomers and dimers. These observations are discussed with regard to previous studies concerning the native structure of H-2 and TL antigens.

The first component of the kinin-forming system in human and rabbit plasma. Its relationship to clotting factor XII (Hageman Factor).

The isolation and characterization of the first component of the kinin-forming system in human and rabbit plasma are presented. Functionally, the molecule is the precursor of the activator of prekallikrein (Pre-PKA) and evidence is presented that it is identical with Hageman factor (clotting factor XII). The component from each plasma possessed similar characteristics. This molecule was found to have a mol wt of 110,000 and sedimentation rate of 4.6S. It migrated in electrophoresis as a beta-globulin, having an isoelectric point of 6.1. Upon activation with glass, kaolin, diatomaceous earth, ellagic acid, or trypsin, the activated molecule converted purified prekallikrein (prokininogenase) to the active enzyme. Clot-promoting activity was associated with the capacity to activate prekallikrein through each procedure of isolation. The clot-promoting factor was in precursor form, requiring treatment with kaolin or trypsin to gain activity. Evidence indicated that the protein was Hageman factor (factor XII): it promoted clotting of factor XII-deficient, but not Factor XI- or IX-deficient plasma, and did not convert fibrinogen to fibrin it bound to and was activated by kaolin or other negatively charged particles in the presence of chelating agents; the activation by kaolin could be prevented by pretreating the kaolin with hexadimethrine bromide (H Br); prekallikrein-activating and clot-promoting activities were identical in their physical properties; and the prekallikrein activator could not be detected in Hageman factor-deficient plasma. Activation of Hageman factor was accompanied by cleavage of the molecule into several fragments, one of which possessed prekallikrein-activating (PKA) and clot-promoting properties. The PKA fragment sedimented at 2.6S and by gel filtration was found to have a molecular weight of 32,000. The PKA possessed only 1/50 the clot-promoting capacity of the freshly activated native molecule.