Gut epithelial Interleukin-17 receptor A signaling can modulate distant tumors growth through microbial regulation

Microbes influence cancer initiation, progression and therapy responsiveness. IL-17 signaling contributes to gut barrier immunity by regulating microbes but also drives tumor growth. A knowledge gap remains regarding the influence of enteric IL-17-IL-17RA signaling and their microbial regulation on the behavior of distant tumors. We demonstrate that gut dysbiosis induced by systemic or gut epithelial deletion of IL-17RA induces growth of pancreatic and brain tumors due to excessive development of Th17, primary source of IL-17 in human and mouse pancreatic ductal adenocarcinoma, as well as B cells that circulate to distant tumors. Microbial dependent IL-17 signaling increases DUOX2 signaling in tumor cells. Inefficacy of pharmacological inhibition of IL-17RA is overcome with targeted microbial ablation that blocks the compensatory loop. These findings demonstrate the complexities of IL-17-IL-17RA signaling in different compartments and the relevance for accounting for its homeostatic host defense function during cancer therapy.

Microbial Regulation of Vitamin D Linked to Colorectal Cancer: A Sex Bias

In a recent issue of Cancer Cell, Li and colleagues revealed that Carnobacterium maltaromaticum (C. maltaromaticum) was significantly depleted in the stool samples of patients with colorectal cancer in a female-specific manner. C. maltaromaticum actively participated in the generation of vitamin D intermediary metabolites, which together with Faecalibacterium prausnitzii and Lachnispiraceae bacterium produce an active metabolite of vitamin D that protects against colorectal cancer development. C. maltaromaticum supplementation induced in a female-specific manner an increase in vitamin D levels that would activate its receptor in the colonic epithelium, protecting against the development of colorectal cancer.

The predicted relative risk of premature ovarian failure for three radiotherapy modalities in a girl receiving craniospinal irradiation

In girls and young women, irradiation of the ovaries can reduce the number of viable ovarian primordial follicles, which may lead to premature ovarian failure (POF) and subsequently to sterility. One strategy to minimize this late effect is to reduce the radiation dose to the ovaries. A primary means of reducing dose is to choose a radiotherapy technique that avoids irradiating nearby normal tissue; however, the relative risk of POF (RRPOF) due to the various therapeutic options has not been assessed. This study compared the predicted RRPOF after craniospinal proton radiotherapy, conventional photon radiotherapy (CRT) and intensity-modulated photon radiotherapy (IMRT). We calculated the equivalent dose delivered to the ovaries of an 11-year-old girl from therapeutic and stray radiation. We then predicted the percentage of ovarian primordial follicles killed by radiation and used this as a measure of the RRPOF; we also calculated the ratio of the relative risk of POF (RRRPOF) among the three radiotherapies. Proton radiotherapy had a lower RRPOF than either of the other two types. We also tested the sensitivity of the RRRPOF between photon and proton therapies to the anatomic position of the ovaries, i.e., proximity to the treatment field (2 ≤ RRRPOF ≤ 10). We found that CRT and IMRT have higher risks of POF than passive-scattering proton radiotherapy (PRT) does, regardless of uncertainties in the ovarian location. Overall, PRT represents a lower RRPOF over the two other modalities.

Calibration of a Bonner sphere extension (BSE) for high-energy neutron spectrometry

In a recent work, we constructed modular multisphere system which expands upon the design of an existing, commercially available Bonner sphere system by adding concentric shells of copper, tungsten, or lead. Our modular multisphere system is referred to as the Bonner Sphere Extension (BSE). The BSE was tested in a high energy neutron beam (thermal to 800 MeV) at Los Alamos Neutron Science Center and provided improvement in the measurement of the neutron spectrum in the energy regions above 20 MeV when compared to the standard BSS (Burgett, 2008 and Howell et al., 2009).However, when the initial test of the system was carried-out at LANSCE, the BSE had not yet been calibrated. Therefore the objective of the present study was to perform calibration measurements. These calibration measurements were carried out using monoenergetic neutron ISO 8529-1 reference beams at the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany. The following monoenergetic reference beams were used for these experiments: 14.8 MeV, 1.2 MeV, 565 keV, and 144 keV. Response functions for the BSE were calculated using the Monte Carlo N-Particle Code, eXtended (MCNPX). The percent difference between the measured and calculated responses was calculated for each sphere and energy. The difference between measured and calculated responses for individual spheres ranged between 7.9 % and 16.7 % and the arithmetic mean for all spheres was (10.9 ± 1.8) %. These sphere specific correction factors will be applied for all future measurements carried-out with the BSE.

Study of a gold-foil-based multisphere neutron spectrometer

Multisphere neutron spectrometers with active thermal neutron detectors cannot be used in high-intensity radiation fields due to pulse pile-up and dead-time effects. Thus, a multisphere spectrometer using a passive detection system, specifically gold foils, has been investigated in this work. The responses of a gold-foil-based Bonner sphere neutron spectrometer were studied for two different gold-foil holder designs; an aluminium-polyethylene holder and a polyethylene holder. The responses of the two designs were calculated for four incident neutron beam directions, namely, parallel, perpendicular and at +/-45 degrees relative to the flat surface of the foil. It was found that the use of polyethylene holder resulted in a more isotropic response to neutrons for the four incident directions considered. The computed responses were verified by measuring the neutron spectrum of a 252Cf source with known strength.

The socioeconomic impact of hepatitis E in Nepal

Hepatitis E disease is responsible for substantial morbidity in Nepal. A socioeconomic analysis was performed to describe the costs and the effects of hepatitis E disease (HE) on health status in a Nepalese population living in the Kathmandu Valley. A modified health status index was used to quantify healthy days lost associated with HE. One hundred thirty-four individuals recently recovered from HE were interviewed in June 1998. The median age was 22 years and 60% were female. Study participants were sick and bedridden for a median of 22 and 10 days, respectively. The median healthy days lost per individual was 35 (768,000 total per region). The median cost of illness per individual, including direct and indirect, was $37 ($1,238,676 total per region). The percentage of yearly income lost for wage earners totaled 19.4%. Hepatitis E disease is associated with significant costs and loss of healthy days in Nepal. Further research is warranted to understand and limit this common disease.

Expression of hsc 70, but not hsp 70, in human third molar dental pulp

The constitutive (hsc 70) and inducible (hsp 70) isoforms of heat shock protein 70 are important members of the superfamily of stress related proteins that protect and promote the recovery of cells from physiological and pathologic stress. The goal of this study was to define the baseline expression of hsc 70 and hsp 70 in disease-free, minimally stressed human dental pulp of the adult 3rd molar. Immunolocalization demonstrated moderate to heavy staining intensity for hsc 70 in both the cytoplasm and nucleus of odontoblasts and fibroblasts comprising the human pulp. Endothelial and smooth muscle cells displayed weak to moderate immunoreactivity for hsc 70 in both the cytoplasm and nucleus. Schwann cells demonstrated only weak nuclear staining for hsc 70. No immunoreactivity for hsp 70 was observed in any cell type in human pulp. Western, northern, and RT-PCR analysis of pulp preparations confirmed the expression of hsc 70 mRNA and protein within components of the pulp. These results demonstrate that cells of the human pulp express, under conditions of minimal stimulation, a key component of the stress response protein superfamily. The expression of hsc 70 under conditions of minimal stress may provide pulp components an advantage in resisting cell injury when stress occurs.

The physiology and technique of skin grafting

Skin grafting is one of the earliest described surgical procedures. In the age of microsurgery and free-tissue transfer, it remains a utilitarian means of achieving tissue coverage. This article discusses the physiology of skin grafting as well as current grafting techniques.

Expression of heat shock protein 27 in adult human third molar dental pulp

This study is the first to define the expression of hsp 27 in the pulp of the adult human third molar. Using a monoclonal antibody against human hsp 27, immunoreactivity was demonstrated in the odontoblasts, odontoblast processes, pulp fibroblasts, and smooth muscle and endothelial cells of vessel walls. Nerves were negative. Pulp fibroblasts were characterized by cytoplasmic staining and variable nuclear staining. Odontoblasts also displayed consistent cytoplasmic staining and variable nuclear staining. Western, Northern, and RT-PCR analysis confirmed the expression of hsp 27 mRNA and protein. Hsp 27 was also shown to be present in both the unphosphorylated and phosphorylated isoforms. In general, nuclear localization and phosphorylation of hsp 27 has been correlated with cells responding to stress or other stimuli. This study demonstrates that pulp from a single human third molar provides sufficient material to support a detailed molecular analysis of gene expression.

The chicken beta-globin gene promoter forms a novel "cinched" tetrahelical structure

We have previously shown that the G-rich sequence G16CG(GGT)2GG in the promoter region of the chicken beta-globin gene poses a formidable barrier to DNA synthesis in vitro (Woodford et al., 1994, J. Biol. Chem. 269, 27029-27035). The K+ requirement, template-strand specificity, template concentration independence, and involvement of Hoogsteen bonding suggested that the underlying basis of this new type of DNA synthesis arrest site might be an intrastrand tetrahelical structure. However, the arrest site lacks the four G-rich repeats that are a hallmark of previously described intramolecular tetraplexes and contains a number of noncanonical bases that would be expected to greatly destabilize such a structure. Here we report evidence for an unusual K+-dependent intrastrand "cinched" tetraplex. This structure has several unique features including the incorporation of bases other than guanine into the stem of the tetraplex, interaction between loop bases and bases in the flanking region, and base pairing between bases 3 and 5 of the tetrahelix-forming region to form a molecular "cinch." This finding extends the range of sequences capable of tetraplex formation as well as our appreciation of the conformational complexity of the chicken beta-globin promoter.

The effect of lipid peroxidation and lipolysis on the ability of lipoproteins to influence thromboplastin activity

High, low and very low density lipoproteins and lipoprotein (a) were prepared from porcine serum. The apolipoprotein components of the lipoproteins were then isolated and resuspended in soybean lecithin. Apolipoprotein B was also resuspended in lipids more representative of those found in LDL and VLDL. Lipid peroxidation was induced in samples of all the lipoproteins and reconstituted apolipoproteins by incubation with either Cu2+ ions or hedgehog 15-lipoxygenase. Furthermore, aliquots of the samples were incubated with a mixture of lipases. The effect of native preparations and the treated samples on the procoagulant activity of thromboplastin was examined. Native HDL, apo A-II, native LDL, reconstituted LDL and apo B inhibited thromboplastin activity, whereas native VLDL and reconstituted VLDL enhanced this activity. While the ability of HDL and apolipoprotein A-II to inhibit thromboplastin was unaltered by either Cu2+ oxidation, lipoxygenase oxidation or lipolysis, VLDL and particles resembling VLDL, which acted cooperatively with thromboplastin lost their activating potential. On the other hand, LDL and particles resembling LDL changed from being inhibitory to enhancing the thromboplastin activity following oxidation, but not after lipolysis. Apolipoprotein B fragments obtained by mild digestion of this protein, expressed an inhibitory effect towards thromboplastin, while extensive degradation of the protein reduced its inhibitory potential. It is suggested that modifications of lipoproteins in vivo can lead to a hypercoagulable state by modulation of the cofactor activity of thromboplastin to factor VII.

A novel K(+)-dependent DNA synthesis arrest site in a commonly occurring sequence motif in eukaryotes

We have found that a strong DNA synthesis arrest site forms in the chicken beta-globin promoter in vitro under physiological conditions. The arrest site is located in a G+C-rich region in which the guanines are located predominately on the top strand and the pyrimidines on the bottom strand. This region is non-palindromic and has no mirror symmetry. Arrest of DNA synthesis is only observed when the G-rich strand of the promoter is used as the template, and shows an absolute requirement for K+. The sequence G16CG(GGT)3 is necessary and sufficient to arrest DNA synthesis. This arrest is template concentration independent and is eliminated by blocking the N7 positions of the last 4 guanine residues in the arrest site. These observations suggest that the basis of the block to chain extension is the formation of an unusual tetraplex-like structure by the template strand. Sequences able to form intrastrand tetraplexes are ubiquitous in eukaryotes. We show that known intrastrand tetraplex-forming sequences arrest DNA synthesis in vitro, suggesting that this may be a general property of DNA tetraplexes. We suggest that the arrest of DNA synthesis by some of these structures may account for some of the high frequency of recombination associated with these loci, perhaps by promoting strand slippage or providing an opportunity for strand exchange.

The inhibition of thromboplastin by apolipoprotein-B and the effect of various associated lipids

Human apolipoprotein B was purified by barium sulphate adsorption, subsequent delipidation and gel filtration. The protein was then reconstituted in soya bean lecithin and its inhibitory effect towards thromboplastin was assayed by incubation with rabbit brain thromboplastin. The use of an antibody against human apolipoprotein B diminished this inhibition. The level of inhibition of thromboplastin by the reconstituted apolipoprotein was found to be dependent on the concentration of the phospholipids with which it was reconstituted, reaching a maximum inhibition at a lipid: protein ratio of 1:1 (w/w). However, higher phospholipid concentrations or inclusion of cholesterol esters or triglycerides diminished and at certain concentrations reversed the inhibitory effect of the apolipoprotein. These results point towards apolipoprotein B as an inhibitor whose activity towards thromboplastin could be dependent on the complexes it forms with the surrounding lipids.

Human immunodeficiency virus type 1 pol gene mutations which cause decreased susceptibility to 2',3'-dideoxycytidine

To investigate whether human immunodeficiency virus type 1 pol gene mutations are selected during prolonged 2',3'-dideoxycytidine (ddC) therapy, we used the polymerase chain reaction to amplify a portion of the reverse transcriptase segment of the pol gene from the peripheral blood mononuclear cell DNA of a patient with AIDS before and after an 80-week course of ddC therapy. The consensus sequence from the second sample contained a unique double mutation (ACT to GAT) in the codon for reverse transcriptase amino acid 69, causing substitution of aspartic acid (Asp) for the wild-type threonine (Thr). A mutation (ACA to ATA) also occurred in the codon for position 165, causing substitution of isoleucine (Ile) for Thr. The GAT (Asp) codon was introduced into the pol gene of a molecular clone of human immunodeficiency virus via site-directed mutagenesis. Following transfection, mutant and wild-type viruses were tested for susceptibility to ddC by a plaque reduction assay. The mutant virus was fivefold less susceptible to ddC than the wild type; cross-resistance to 3'-azido-3'-deoxythymidine or 2'3'-dideoxyinosine was not found. The Ile-165 mutation did not confer additional ddC resistance. The Asp-69 substitution may have contributed to the generation of resistant virus in this patient.

In vivo sequence variation of the human immunodeficiency virus type 1 env gene: evidence for recombination among variants found in a single individual

To assess in vivo sequence heterogeneity of the human immunodeficiency virus type 1 (HIV-1) env gene, we used the polymerase chain reaction to amplify proviral sequences present in peripheral blood mononuclear cell DNA of a patient with acquired immunodeficiency syndrome (AIDS). The amplified env gene fragment (575 bp) contains the first hypervariable region and part of the first conserved region. Eleven and twelve clones were sequenced, respectively, from specimens collected two months apart. Notable heterogeneity was observed among sequences recovered from both specimens. Also, the proviral population recovered from the first specimen varied significantly from that found in the second specimen. Both specimens contained forms with and without an 18 bp duplication. The presence or absence of this duplication, in addition to several point mutations, appear to define two molecular groups evolving in parallel within this patient. Several genotypes which had sequences characteristic of both groups occurred primarily in the second specimen; these can best be explained by multiple recombinational events between representatives of the two groups during reverse transcription. This study demonstrates that recombination may contribute significantly to the generation of diversity among HIV variants within a single individual.

In vivo prevalence of azidothymidine (AZT) resistance mutations in an AIDS patient before and after AZT therapy

In order to examine the in vivo prevalence of AZT resistance mutations in AID patients after long-term therapy we amplified, by polymerase chain reaction (PCR), a 654 bp pol gene fragment from peripheral blood mononuclear cell DNA samples from a patient before, and 19 months after, the start of AZT therapy. PCR products from each sample were cloned and 9 clones from each sample were sequenced. Seven of 9 clones from the post-AZT sample, but none from the pre-AZT sample, contained an amino acid substitution (Thr215 to Tyr) requiring two nucleotide changes within the same codon (ACC to TAC). This change had previously been shown by Larder and Kemp (Science, 246:1155-1158, 1989) to correlate with partial AZT resistance of virus isolates. In colony hybridizations using synthetic oligonucleotides corresponding to the mutant and wild-type sequences, 22 of 22 clones from the pre-AZT sample hybridized only to the wild-type probe while 21 of 26 clones from the post-AZT sample hybridized only to the mutant. Clinically, this patient remains well, indicating that while Tyr215 may be the first amino acid substitution leading to resistance, it alone does not appear to have significantly influenced the clinical status of this patient.

Maxillary metastasis of transitional cell carcinoma: report of a case

Metastases to the maxilla are extremely rare, and only 64 cases of histologically proven maxillary metastases can be found in the English-language literature. This article reports the first case of metastatic transitional cell carcinoma of the urinary bladder to the maxilla. The distribution of proven cases of maxillary metastasis and the possible anatomic pathways for this metastasis are discussed.

Nalbuphine sedation in a patient with long-term, high-dose chemotherapeutically controlled psychosis

Consideration of which pharmacologic agent to use when a patient requires sedation prior to an oral surgery procedure entails a number of factors, including past medical history, current medications and dose level, duration of administration, pharmacologic interactions, and the dental needs of the patient. The case described in this report illustrates the importance of consideration of these factors in a patient who required sedation prior to oral surgery while taking 800 mg chlorpromazine, 300 mg amantadine hydrochloride, and 900 mg of cimetidine daily. The possible pharmacologic interactions which could occur from concomitantly administering either diazepam or a narcotic in the presence of these agents are numerous and significant. The choice of sedative agent was further complicated by the fact that the patient was prescribed chlorpromazine and amantadine in doses which far exceeded the usual therapeutic levels and had been maintained for an extended period of time, over 8 months. Consequently, any adverse reactions that may have resulted when sedating a patient taking chlorapromazine and amantadine hydrochloride in lower doses for a shorter duration would be more likely to occur with greater speed and severity in a patient receiving such high-dose, long-term therapy. Also, unusual reactions which have not been reported with usual therapeutic dose levels might also occur since these high doses approach toxic levels for some patients. Additionally, a sedative agent had to be used which would not interfere with the antipsychotic effects of chlorpromazine since the patient's psychiatric condition required maintenance of these unusually high therapeutic levels. The following case report gives the rationale and outcome of utilizing nalbuphine for obtunding pain and producing sedation during an oral surgery procedure under such complex therapeutic conditions.

Early pulp changes after anterior maxillary osteotomy

For purposes of examining the pulpal reaction to segmental osteotomy, six adult female Macaca fascicularis monkeys received identical anterior maxillary osteotomies involving the incisors only. The mobilized segment was displaced distally a distance of approximately 2 mm, then splinted in place for a week. The healing and revascularization of the bone proceeded well, with no ischemic areas visible on the microangiograms other than in the animal examined immediately after operation. The osteotomy site was bridged with new bone at three months. The majority of the pulps of the mobilized segment and all teeth examined distal to the segment remained vital. No degenerative change other than the temporary disappearance of sensory nerves was observed in the vital pulps of the segments. By the six-month period, the sensory nerve supply to the dental pulp had regenerated completely.

Circular dichroic, infrared and other studies on the protein component of pig brain thromboplastin

1. A four-step procedure used to isolate the protein component (apoprotein III) of pig brain thromboplastin yielded approximately 25 mg from 500g of brain. 2. In the absence of detergent, apoprotein III had an apparent mol.wt. of 360 000 by gel-filtration, and, after electrophoresis on polyacrylamide gels in the presence of sodium docecyl sulphate, it appeared as a major protein band of mol.wt.59 000, suggesting the existence of polymeric and monomeric forms. 3. Chemical analyses of apoprotein III revealed that hydrophilic and hydrophobic amino acids were present in a ratio of 3:2, together with approx, 9% (w/w) of carbohydrate. 4. The far-u.v.c.d. and i.r. spectral data indicated that, like other membrane proteins, apoprotein III has a high percentage of unordered structure with lesser amounts of alpha and beta-forms. 5. Relipidation of apoprotein III to restore clotting activity caused no extensive alteration in the c.d. and i.r. spectra, indicating that the phospholipid associates with a comparatively small hydrophobic segment. The constrained unordered conformation, which makes the major contribution to the c.d. spectrum, probably forms a separate domain in the aqueous phase. The absence of any increase in the amplitude of both negative c.d. extrema, following relipidation, contrasted with the substantial increase observed in a helix-forming solvent and raises the possibility that the more stable polymeric form of apoprotein III is retained as the active form in the lipid phase. 6. We suggest that as a consequence of cell membrane damage, the recognition and activation of factor VII may involve minor changes of conformation that are dependent upon the flexibility inherent in an unordered secondary structure.

Aggressive ossifying fibroma of the maxilla: review of the literature and report of case

A case of a large aggressive ossifying fibroma of the maxilla has been presented. Review of the literature shows the literature shows the difficulty in establishing a definitive diagnosis through any single diagnostic modality. Much of this is due to the confusion surrounding classification of the tumor. Adjunctive radiographic and nuclear medicine diagnostic aids were utilized, as were clinical, laboratory, and histopathologic studies, in resolving the diagnostic questions posed by this large and aggressive tumor. Surgical intervention through conservative enucleation produced few operative or postoperative difficulties and minimal residual deformity. Differentiation of ossifying fibroma from other benigh and malignant neoplasms as well as fibrous dysplasia is important in the correct management of this lesion.

Malignant transformation of ameloblastic fibro-odontoma to ameloblastic fibrosarcoma

Two cases of malignant transformation of ameloblastic fibro-odontomas are presented, along with a review of the literature on ameloblastic fibrosarcomas. The occurrence of this malignant transformation of ameloblastic fibromas, ameloblastic odontomas, and ameloblastic fibro-odontomas appears to be more frequent than previously thought. This potential transformation alone does not justify radical treatment of all these benign lesions. If there is recurrence accompanied by a histologic pattern change toward a more unorganized fibrous stroma with displacement of the epithelial component, however, then more extensive treatment procedures appear to be indicated.

Scanning electron microscopic and electrophoretic studies on clotting factor adsorbents

Physical studies carried out on a range of protein and clotting factor adsorbents revealed marked morphological and charge differences. Their appearance in the scanning electron microscope could be used to classify the insoluble precipitates, calcijm phosphate, barium sulphate and citrate, as either amorphorous or crystalline. Surface charge is difficult to define but the present studies on the sparingly-soluble salts, based on calcium and barium, have revealed that they can be subdivided on the basis of the presence or absence of a charge reversal point in the pH-mobility curve. The anion component appeared to determine this characteristic; it was noted that phosphate and citrate ions had a marked effect and gave a biased negative potential at all pH values. We concluded that where a divalent cation is cohabiting with a trivalent anion, the greater potential-determining ability of the latter will dominate the overall charge at the surface of a particle, even below pH7 and the absence of a positive potential gives a monophasic pH-mobility curve. Differences in both the physical appearance and electrophoretic mobility of the adsorbents studied reflect the wide variation in their chemical composition, especially among the various forms of calcium phosphate which, unlike barium sulphate, can include substituted ions such as hydroxyl, in their crystal lattice. The definition of these characteristics allows their behaviour towards clotting factors to be more easily predicted.

Scanning electron microscopic and electrophoretic observations on barium sulphate used to absorb clotting factors

Electron microscopy and particle electrophoresis were found to be complementary techniques with which to complete the physical data from an earlier study on barium sulphates used to absorb clotting factors from serum. The differences revealed by scanning electron microscopy (S. E. M) in the physical shape of low and high density grades of barium sulphate particles appear to be of greater significance than charge as expressed by electrophoretic mobility, in determining whether or not precursor or performed factor Xa is eluted. This conclusion was based on the finding that at pH values close to 7, where the adsorption from serum occurs, all samples with the exception of natural barytes were uncharged. However as the high-density, or soil-grade, was found by S. E. M. to consist of large solid crystals it was suggested that this shape might induce activiation of factor X as a result of partial denaturation and consequent unfolding of the adsorbed protein. In contrast, uptake of protein into the centre of the porous aggregates revealed by S. E. M. pictures of low-density or X-ray grade barium sulphate may afford protection against denaturation and exposure of the enzyme site. The porous nature of particles of low-density barium sulphate compared with the solid crystalline forms of other grades accounts not only for its lower bulk density but also for its greater surface/gram ratio which is reflected by an ability to adsorb more protein from serum. Neither technique produced evidence from any of the samples to indicate the presence of stabilising agents sometimes used to coat particles in barium meals.

The purification and properties of factor X from pig serum and its role in hypercoagulability in vivo

The molecular weights or shapes of Factor X preparations determined by gel filtration were dependent on the density of the BaSO(4) used for the initial adsorption from serum. One form obtained with BaSO(4) of density 2g/ml behaved as if it had a molecular weight of 39000 and possessed preformed clotting activity (Factor Xa), whereas that of the form adsorbed with BaSO(4) of density 1g/ml had a molecular weight of 69000 and consisted of inactive Factor X precursor. Thus degradation accompanied by activation seems to occur as a result of surface adsorption on high-density BaSO(4) and is associated with an interchange of protein between the two bands observed electrophoretically. The clotting and esterase activities measurable in vitro after complete activation were not matched by a corresponding ability to induce thrombus formation and ;lethality' in vivo. The most effective preparations of Factor X in this respect possessed preformed activity, which was enhanced in the presence of phospholipid. Factor X lost activity more rapidly in dilute solution, and its concentration at the surface of phospholipid micelles probably decreases loss by dilution in circulating blood.

The role of digitonin in the activation of serum thrombotic accelerator

Digitonin in association with barium sulphate adsorbable protein solution may play more than one role in the induction of an experimental hypercoagulable state leading to intravascular coagulation. Firstly, it initiates a weak clotting stimulus in vivo; presumably by complexing with cholesterol it brings about the disruption of a lipoprotein complex and the exposure of an active enzyme site. Secondly, this study also demonstrated that digitonin is able to substitute for phospholipid in the acceleration of the clotting stimulus and emphasises the role of micelle-forming substances in the hypercoagulable state.