A first order experimental design to assess soluble proteins released by a new keratinase from Doratomyces microsporus on human substrates

The influence of temperature, pH, keratinase concentration, substrate concentration and incubation time on the soluble proteins released by a new keratinase from Doratomyces microsporus was studied with an experimental design assisted by a simplex method. Only 16 spectrophotometric analyses were required. This study was carried out by measuring, according to Smith's method, the concentration of soluble proteins released by the enzyme on two human substrates: stratum corneum and nails. Results give optimum conditions for the keratinase to release the soluble proteins: Temperature, 28 degrees C; pH, 9.5; keratinase concentration, 0.94% (weight of keratinase lyophilisat/final volume), substrate concentration, 4.9% (weight of skin powder/final volume); and a 5 h 50 min incubation for the stratum corneum. Temperature, 37 degrees C; pH, 9.2, keratinase concentration, 0.11% (weight of keratinase lyophilisat/final volume); substrate concentration, 4.9% (weight of nail powder/final volume) and a 6 h 10 min incubation time for nails.

Further studies on the mechanism for the antithrombotic effects of naroparcil, an orally active thiozyloside compound

The antithrombotic beta-D-xyloside, naroparcil, has previously been shown to induce a dose-related increase of circulating glycosaminoglycans (GAGs) together with an antithrombin activity (anti-IIa) via heparin cofactor II (HCII) in the rabbit. In order to go further in the mechanisms, the relationship between the antithrombotic activity, the HCII-mediated anti-IIa activity and the plasma GAG content was investigated. We showed that the in vitro specific activity on the inhibition of thrombin by HCII of the plasma GAG extract from naroparcil-treated rabbits was increased by a factor of 60 when compared to controls. In addition, the fractionation of the plasma GAG extract by affinity chromatography on immobilized HCII led to a more potent material whereas the low-affinity fraction was shown to be inactive in thrombin inhibition by HCII. The qualitative analysis of GAGs showed the presence of the deltaDi-4S DS disaccharide, undetectable in control, which accounted for 22% in the unfractionated GAG extract and for 60% in the high affinity fraction. In vitro experiments using immuno-depleted plasma in antithrombin III (ATIII), HCII or both, indicated that the anti-IIa activity of the plasma GAG extract from naroparcil-treated rabbits was mainly due to HCII potentialisation. The unfractionated GAG extract and the high affinity fraction were shown to be antithrombotic in a Wessler-based model in the rat, giving ED80 values of 610 UA/kg and 56 UA/kg respectively whereas the low-affinity fraction was devoid of any antithrombotic activity. These results show that the antithrombotic activity of naroparcil is dependent on modification in the plasma GAG profile which inactivates thrombin via the HCII.

[The activation patterns during atrial fibrillation in an experimental model]

INTRODUCTION AND OBJECTIVES

In atrial fibrillation, along with the mechanisms of complete reentry and random activation focal activation patterns have been described which have been attributed both to propagation from the endocardium and to the existence of zones with automatic activity. The objectives of present study are to analyze and quantify the atrial activation patterns in an experimental model of atrial fibrillation.

MATERIAL AND METHODS

In 11 Langendorff-perfused rabbit hearts atrial fibrillation was induced by atrial burst pacing after right atrial dilatation with an intra-atrial balloon. A multiple electrode consisting of 121 electrodes and positioned in the right atrial free wall was used to construct the activation maps corresponding to 10 segments of 100 ms in 11 different episodes of sustained atrial fibrillation (one per experiment).

RESULTS

Of the 110 segments analyzed, 44 (40%) corresponded to random activation patterns. Fifteen segments (14%) corresponded to complete reentry, and in these cases the number of consecutive rotations ranged from 1 to 2.25 (mean 1.4 +/- 0.4). In 49 segments (44%) a single activation front was seen to pass through the recording area without block; alternatively, two simultaneous fronts were recorded that did not re-excite the zone activated by the other. In two segments (2%) there was a focal activation pattern without evidence of propagation from the epicardium surrounding the activated zone.

CONCLUSIONS

a) in the experimental atrial fibrillation model used, random activation patterns are more frequent than complete reentry patterns; b) complete reentry can occur in areas smaller than 1 cm2, and c) focal activation during atrial fibrillation is rare.

Antithrombotic and anticoagulant activities of a low molecular weight fucoidan by the subcutaneous route

Fucoidans (high-molecular-weight sulfated polysaccharides extracted from brown seaweeds) have anticoagulant and antithrombotic effects. They inhibit thrombin by catalyzing both serpins (antithrombin and heparin cofactor II) according to their chemical structures and origins. In this study, a low-molecular-weight (LMW) fucoidan of 8 kDa was obtained by chemical degradation of a high-molecular-weight fraction. The antithrombotic and anticoagulant activities of this new compound were compared to those of a low-molecular-weight heparin (LMWH), dalteparin, following subcutaneous administration to rabbits. This LMW fucoidan exhibited dose-related venous antithrombotic activity, with an ED80 of about 20 mg/kg, 2 h after a single subcutaneous injection. Its activity was comparable to that of dalteparin (close to 200 anti-Xa IU/kg) and was maximal 30 min after a single subcutaneous injection. The activity remained stable (about 70%) from 1 to 4 h after injection, but disappeared by 8 h. The antithrombotic activity was not associated with either a prolongation of the thrombin clotting time (TCT) or an increase in anti-Xa activity, contrary to dalteparin. A slight prolongation of APTT occurred with both compounds. This venous antithrombotic activity was associated with a decrease in ex vivo thrombin generation and with a significant increase in the lag phase in a thrombin generation test. LMW fucoidan thus has potent antithrombotic activity and a potentially weaker haemorrhagic effect (i.e. a smaller effect on coagulation tests and a smaller prolongation of the bleeding time) than dalteparin.

The beneficial effect of a beta-D-xyloside, Iliparcil, in the prevention of postthrombolytic rethrombosis in the rat

The effect of Iliparcil, a new orally active beta-D-xyloside venous antithrombotic, was studied on the rethrombosis following thrombolytic therapy in rats, using a modified Umetsu model. The drug was administered by oral route prior to thrombolytic therapy, which consisted of administering a combination of heparin and urokinase (H/U) at 37.5 and 70,000 IU/kg, respectively. Time to reocclusion increased from 3.9 min with saline to 10.5 min following H/U injection. When Iliparcil (30 mg/kg, oral route) was administered 4 h before H/U injection, the time to reocclusion was increased by 250% compared with H/U alone (p < 0.001). Similarly, dermatan sulfate (DS), administered intravenously (3 mg/kg) 5 min before thrombus induction, also increased the time to reocclusion (300% compared with H/U alone; p < 0.001). It was also shown that times to reocclusion following Iliparcil or DS treatments were still increased even when heparin dosage was decreased. These results suggest that an antithrombotic product derived from the beta-D-xyloside family could be advantageously used in combination with thrombolytic treatment instead of heparin, which causes complications and side effects.

Carbaxylosides of 4-ethyl-2-oxo-2H-benzopyran-7-yl as non-hydrolyzable, orally active venous antithrombotic agents

A (-)-conduritol F derivative was condensed with 4-ethyl-7-hydroxy-2H-1-benzopyran-2-one and converted into (+)-4-ethyl-7-[(1'R,2'S,3'S,4'R)-2',3',4'- trihydroxycyclohexyloxy]-2H-1-benzopyran-2-one ((+)-2). Enantiomer (-)-2 was obtained from a (+)-conduritol F derivative. The carbaxyloside (-)-2 with the L-xylose configuration was more active than (+)-2 in the Wessler's model.

Spectrofluorimetric determination of 5-methoxypsoralen pharmacokinetic in patients' serum

In medicine, psoriasis and vitiligo are most often treated with PUVA therapy (psoralen plus ultraviolet A). The determination of psoralen in patients' blood is necessary, as it is admitted that the therapeutic efficiency depends on drug concentration in patients' serum. The amount of UVA to administer is inversely proportional to serum peak concentration. High-performance liquid chromatography (HPLC) and gas chromatography are the most employed methods for determining psoralens in patients' serum. The 2 techniques are precise and very sensitive, but time consuming. The aim of this paper is to propose a suitable method which is rapid and simple. It is a spectrofluorimetric technique for 5-methoxypsoralen (5-MOP) determination in the serum of patients treated with PUVA therapy. 5-MOP extraction was carried out with an heptane/dichloromethane mixture (4/1; v/v), according to the Stolk method (1980). A calibration curve (CC) was plotted from 5-MOP concentrations (range 50, 100, 200, 300, 400, 500 ng/ml). The CC was linear with a good coefficient of correlation: r = 0.9971, and a suitable coefficient of variation (CV) of 7.0%. The recovery of the method ranged from 85.3 +/- 4.2 to 108 +/- 4.1%. The assay precision gave a CV ranging from 0.10 to 6.90%, with an error inferior to +/-10%. The method did not reveal any interference from serum components on the 5-MOP emission wavelength. The limit of detection of 5-MOP was 15 ng/ml. The proposed procedure was proved to be appropriate for a rapid determination of 5-MOP in patients' serum. This technique could also be employed for other psoralens used in PUVA therapy (e.g., 8-methoxypsoralen).

Psoralens percutaneous permeation across the human whole skin and the epidermis in respect to their polarity (in vitro study)

8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP) and 4,5',8-trimethylpsoralen (TMP) are commonly used in PUVA therapy [psoralen (P) + ultraviolet light A (UVA) irradiation] to treat skin diseases such as psoriasis and vitiligo. In order to predict the choice of the suitable drug(s) for topical applications, with appropriate dosage, percutaneous permeation of the psoralens, in connection with their solubilities and partition coefficients in an octanol/water system, were investigated. The percutaneous penetration experiments were accomplished by the deposit of ethanolic psoralen solution onto human skin and epidermis fragments mounted on Franz cells. Six cells were employed for each psoralen solution and for the whole skin layer as well as for the epidermis. The diffused psoralens in the receptor solution (1.4%, of human serum albumin) were quantified by using high performance liquid chromatography. The solubilities and the partition coefficients (PC) were carried out in an octanol/water system, in triplicate by using spectrofluorimetry. The results demonstrated that cumulated permeated quantities (ng/cm2) over 24 h, across the whole skin and the epidermis were in the following order for the three psoralens: 8-MOP > 5-MOP > TMP. The lipophilicity, expressed via the log PC, was as follows: 1.93 +/- 0.01 (8-MOP), 2.00 +/- 0.01 (5-MOP) and 3.14 +/- 0.01 (TMP). It was inversely correlated with cumulated penetrated amounts over 24 h in both whole skin and epidermis. From these results, TMP could be predicted as the most convenient psoralen for topical applications, because of its weak penetrability. Considering the relationship between psoralens lipophilicity and permeation, only 5-MOP and 8-MOP could be used, topically or orally, especially in the case of generalised skin disorders.

The antithrombotic potential of dalteparin in man assessed indirectly by Wessler's technique

The aim of this study was to demonstrate the effectiveness of a new experimental approach for assessing the antithrombotic potential of low molecular weight heparins (LMWH) such as dalteparin. In this approach, sera obtained from healthy volunteers treated with various i.v. doses of dalteparin (30, 60 or 120 anti-Xa IU/kg) or placebo (physiological saline) were used as the thrombogenic challenge in a Wessler's stasis model of experimental venous thrombosis in the rat. Sera from placebo-treated volunteers showed a stable thrombogenic activity (0.25 ml/kg of serum producing thrombi of about 50 mg wet weight). Sera from healthy volunteers having previously received dalteparin however demonstrated dose- and time-related reductions in their thrombogenic activity. Half-lives of these effects were 300. 444 and > 480 min for 30, 60 and 120 anti-Xa IU/kg dalteparin respectively. These values were significantly higher than the corresponding anti-Xa and anti-IIa half-lives.

The arterial antithrombotic activity of thioxylosides in a rat model of laser-induced thrombosis

beta-D xylosides have been shown to have venous antithrombotic properties after simple oral administration. Therefore, the arterial antithrombotic effect of these compounds was investigated in vivo, using the experimental thrombosis model induced by laser injury. The products tested were administered orally, 4 h before the thrombosis induction. Two beta-D xylosides were tested (LF 09-0055 and LP 05-0030), either after a simple oral administration at 50, 100, 200, and 400 mg/kg, or after repetitive oral administration at 200 mg/kg twice daily during 5 days. These compounds increased significantly the number of laser shots required to induce arterial thrombosis and decreased the number of emboli and the duration of embolization. At single-dose or repeated administrations, these xylosides did not affect diluted thrombin time in platelet-poor plasma collected after thrombosis inductions. They induced a dermatan sulfate-like activity in the plasma of treated rats, as measured by heparin cofactor II-mediated thrombin inhibition assay. These data suggest that these xylosides are potent arterial antithrombotic agents after single or repetitive oral administrations. beta-D xylosides constitute a very promising therapeutic class of orally active antithrombotic drugs.

Pharmacologic and biochemical profiles of new venous antithrombotic beta-D-xyloside derivatives: potential antiathero/thrombotic drugs

Following a screening program for orally active antithrombotic drugs, it was found that a series of thioxyloside compounds presented with good venous antithrombotic properties. Of more than 500 compounds, LF 09-0055, LF 04-0212, and LF 05-0030 were the most active at inhibiting venous thrombus formation in the rat and rabbit Wessler model after intravenous and oral dosing. LF 05-0030 showed the greatest activity with an ED80 value of 6 mg/kg on oral administration in rats. This activity was maintained in several different models of venous thrombosis and shown to be devoid of anticoagulant effects or hemorrhage. Kinetic studies have demonstrated that maximal levels of activity, following either intravenous or oral dosing, occurred between 2 and 4 hours after administration. This may reflect the type of mechanism involved, since it has been well documented in the literature that xylosides are capable of initiating glycosaminoglycan (GAG) synthesis. Moreover, in vitro galactosyltransferase 1 (the second enzyme involved in GAG polymerization) enzymic assays showed that these thioxyloside derivatives were good acceptors for galactose transfer and therefore at initiating GAG formation. Further in vivo experimentation demonstrated that after treatment by these molecules an important elevation in circulating GAG occurred, with LF 05-0030 presenting the greatest activity, being five times higher than control levels. In addition it was found that dermatan sulfate levels, expressed as antithrombin activity by heparin cofactor II, were significantly increased over control values. As such, this dermatan sulfate moiety is believed to support the antithrombotic activity observed. Studies are underway to investigate the activity of these interesting molecules in atherosclerosis and other vessel wall diseases.

Lipophilicity determination of psoralens used in therapy through solubility and partitioning: comparison of theoretical and experimental approaches

The aim of this study was to determine and to compare experimental and theoretical solubilities (S) as well as partition coefficients (PC) in an octanol/water system of psoralen (P), 8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP) and 4,5',8-trimethylpsoralen (TMP). For each psoralen, experimental results were performed in triplicate with a spectrofluorimetric technique. The measurements were achieved 10 times for each solution. The obtained order of the solubilities in pure octanol was 5-MOP approximately TMP > P > 8-MOP, while in water-saturated octanol it was expressed as follows: TMP approximately 5-MOP > P > 8-MOP. However, the following order was found for hydrophobicity: TMP > 5-MOP > 8-MOP > P. The solubility ratios (SR) in pure octanol and water were assessed (mean +/- SD): 3.13 +/- 0.01 (P), 2.60 +/- 0.01 (8-MOP), 3.75 +/- 0.01 (5-MOP), and 5.11 +/- 0.01 (TMP). In saturated phases, they were 3.27 +/- 0.01, 2.63 +/- 0.01, 3.85 +/- 0.01, and 5.32 +/- 0.01, respectively. The PCs were determined with low concentrations according to the Dearden and Bresnen32 method and they were 1.67 +/- 0.01, 1.93 +/- 0.01, 2.00 +/- 0.01, and 3.14 +/- 0.01, respectively. Solubility parameters (delta), in Hildebrand unit (H) or in (cal/cm3)1/2, were evaluated. They confirmed the polarity of psoralens, previously expressed through the PC, although the positional isomers (5-MOP and 8-MOP) revealed no difference. Hildebrand's approach to the solubility of regular solutions and Yalkowsky's concept of the solubility of nonelectrolytes and weak electrolytes in an octanol/water system permitted a comparison of the theoretical and experimental results. The perspective of this work is to use the physicochemical properties of the psoralens in practice for insuring convenient experimental assays and the prediction, in vitro, of the percutaneous absorption of these compounds.

Experimental venous thrombosis induced by homologous serum in the rat

To investigate the effects of new drugs on the prevention of venous thrombosis, the Wessler stasis model is extensively employed usually in the rabbit. In this model, a hypercoagulable state is achieved by the administration of either heterologous serum (often human serum) or an activated coagulation factor followed by total stasis of the vein in which the thrombus is to be formed. Although classically the stasis model is performed in rabbits, it is possible to induce experimental venous thrombosis in a number of animal species, including rats. However, the use of homologous serum as the activating or thrombogenic agent has been previously described only in the dog and in the rabbit. The purpose of the present study was to compare the activities of heterologous and homologous serum as hypercoagulating agents in a rat stasis model of venous thrombosis using Wessler's technique. Heparin was employed as a reference antithrombotic compound in order to compare the two thrombogenic challenges.

In vitro study of percutaneous absorption, cutaneous bioavailability and bioequivalence of zinc and copper from five topical formulations

Percutaneous absorption and cutaneous bioavailability of zinc and copper from zinc 2-pyrrolidone 5-carboxylate (ZnPC), zinc oxide (ZnO), zinc sulfate (ZnSO4), copper 2-pyrrolidone 5-carboxylate (CuPC) and copper sulfate (CuSO4) were compared using 5 formulations (3 emulsions and 2 ointments) that were applied topically on human skin in vitro. After application for 72 h, percutaneous absorption of zinc from ointments containing ZnO and ZnSO4 was found to be lower than that from a ZnPC-containing emulsion (0.36 and 0.34 versus 1.60% of applied dose). In the case of copper, the flux after a 72-hour treatment period showed that there had been minimal release from CuPC- and CuSO4-containing formulations (approximately 5 ng/cm2/h). All formulations used in this study effected an increase in zinc and copper concentrations in whole skin and epidermis. Bioequivalence of the 5 formulations based on pharmacokinetic results was assessed, and salt and vehicle effects were discussed.

Venous antithrombotic and anticoagulant activities of a fucoïdan fraction

Fucoïdans catalyse thrombin inhibition by antithrombin (AT) and heparin cofactor II (HCII); their affinity for each serpin varies according to the seaweed species from which they are extracted, as well as their chemical composition and molecular weight. We extracted a homogeneous fucoïdan fraction from Ascophyllum nodosum, a brown seaweed, and tested its anticoagulant and antithrombotic activities. At a fucoïdan concentration of 3.75 micrograms/ml, thrombin inhibition mediated by AT showed an apparent second-order rate constant (kapp) of 2 x 10(8) M-1 min-1, compared to 1.5 x 10(6) M-1 min-1 for the uncatalyzed reaction. The kapp value of thrombin inhibition via HCII was 1.17 x 10(9) M-1 min-1 at a fucoïdan concentration of 50 micrograms/ml, compared to 1.72 x 10(5) M-1 min-1 for the uncatalyzed reaction. In a Wessler model of venous thrombosis, the fucoïdan fraction, injected intravenously to rabbits 10 min before thrombosis induction, exhibited antithrombotic activity: 1.8 mg/kg was the dose which inhibited F Xa-induced thrombus formation by 80% (ED80), compared to a heparin ED80 of 0.1 mg/kg. At this ED80 the antithrombotic effect of the fucoïdan persisted longer than that of heparin (30 min versus 15 min). The thrombin clotting time (TCT) was significantly prolonged (73 s versus control 29 s, compared to 53 s with heparin) 10 min after a fucoïdan bolus infusion giving a plasma fucoïdan concentration of 14.6 +/- 2.7 micrograms/ml. The bleeding time was slightly increased after fucoïdan infusion at the ED80. Fucoïdan extracted from marine flora thus shows promise as an antithrombotic drug.

A mutant of Azospirillum brasilense Sp7 impaired in flocculation with a modified colonization pattern and superior nitrogen fixation in association with wheat

We report here significant phenotypic and genetic differences between Azospirillum brasilense Sp7 and spontaneous mutant Sp7-S and their related properties in association with wheat. In contrast to the wild-type strain of Sp7, colonies of Sp7-S stained weakly with Congo red when grown on agar media containing the dye and did not flocculate in the presence of fructose and nitrate. Scanning and transmission electron micrographs showed clearly that the Sp7-S strain lacked surface materials present as a thick layer on the surface of the wild-type Sp7 strain. Different patterns of colonization on wheat roots between Sp7 and Sp7-S, revealed by in situ studies using nifA-lacZ as a reporter gene, were related to a large increase in nitrogenase activity (acetylene reduction) with Sp7-S in association with normal and 2,4-dichlorophenoxyacetic acid-treated wheat for assays conducted under conditions in which the nitrogenase activity of free-living Azospirillum organisms was inhibited by an excess of oxygen. Randomly amplified polymorphic DNA analysis indicated the close genetic relationship of Sp7-S to several other sources of Sp7, by comparison to other recognized strains of A. brasilense. Genetic complementation of Sp7-S was achieved with a 9.4-kb fragment of DNA cloned from wild-type Sp7, restoring Congo red staining and flocculation.

The effect of the beta-D-xyloside naroparcil on circulating plasma glycosaminoglycans. An explanation for its known antithrombotic activity in the rabbit

Beta-D-Xylosides are known to initiate or prime free glycosaminoglycan (GAG) chain synthesis in cell and tissue culture. As such, the effect of the venous antithrombotic beta-D-xyloside, naroparcil, was investigated on the plasma GAG profile in the rabbit after oral administration. Using dose-response experiments, we showed that antithrombin activity via antithrombin III and heparin cofactor II was increased in parallel with GAG plasma levels compared to control. A more detailed qualitative examination of plasma GAGs by cellulose acetate electrophoresis and ion-exchange chromatography, following oral administration of naroparcil at 400 mg/kg, revealed the presence of higher density charged molecules compared to control. The extracted GAGs were found to activate inhibition of thrombin by heparin cofactor II and contained approximately 25% of a dermatan sulfate-like compound (undetectable in control), which could be responsible for the antithrombotic effect. Using radiolabeled naroparcil, we found radiolabeled GAG fractions and the fact that naroparcil was a substrate for galactosyltransferase I, the second enzyme responsible for GAG chain polymerization, suggested that the compound could initiate in vivo the biosynthesis of antithrombotic free GAG chains. This is, to our knowledge, the first description of the in vivo effect of a beta-D-xyloside on GAG biosynthesis; furthermore, this is correlated with an antithrombotic action.

The venous antithrombotic profile of naroparcil in the rabbit

The venous antithrombotic profile of naroparcil or (4-[4-cyanobenzoyl]-phenyl)-1.5-dithio-beta-D-xylopyranoside was investigated in the rabbit following single i.v. and oral administration. Naroparcil attenuated thrombus development in a Wessler stasis model of venous thrombosis (jugular vein) employing bovine factor Xa as a thrombogenic stimulus giving ED50 values of 21.9 mg/kg and 36.0 mg/kg after respectively i.v. and oral administration. Venous antithrombotic activity was maximal 2-3 h after i.v. administration and 4-8 h after oral administration. Four hours after the oral administration of maximal antithrombotic (Wessler model, factor Xa) doses (100 and 400 mg/kg), naroparcil had no significant effect on bleeding time. In platelet poor plasma obtained from animals treated 4 h previously with various doses (25 to 400 mg/kg) of naroparcil, there was no detectable anti-factor Xa nor antithrombin activity. Similarly, naroparcil had no effect on APTT nor on thrombin time. A sensitized thrombin time (to about 35 s) was modestly but significantly increased following oral administration of the compound at 400 mg/kg. However, thrombin generation by the intrinsic pathway was reduced in a dose-related manner, maximal reduction being 65% at 400 mg/kg. The same dose of naroparcil enhanced the formation of thrombin/heparin cofactor II complexes at the expense of thrombin/antithrombin III complexes in plasma incubated with (125I)-human alpha-thrombin and induced the appearance of dermatan sulfate-like material in the plasma of treated rabbits, as measured by a heparin cofactor II-mediated thrombin inhibition assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycosylated derivatives of benzophenone, benzhydrol, and benzhydril as potential venous antithrombotic agents

A series of glycosylated derivatives of benzophenone, benzhydrol, and benzhydril has been synthesized and evaluated for potential activity as venous antithrombotic agents. Studies on structure-activity relationships revealed that compounds having an electron-withdrawing group in the benzhydril or benzhydrol moiety, and specifically those having the beta-D-xylopyranosyl structure in the sugar moiety, were good antithrombotic agents in a rat model of venous thrombosis.

Cellulose degradation by Clostridium thermocellum: from manure to molecular biology

Clostridium thermocellum, a Gram-positive, thermophilic anaerobe produces a highly active cellulase system. This system, termed the cellulosome, is a complex composed of at least 14-18 different types of components organized around a large, cellulose-binding protein. Combining recombinant DNA technology and protein biochemistry has proved to be a successful approach in unravelling some important features of the system.