Lytic and mechanical stability of clots composed of fibrin and blood vessel wall components

BACKGROUND

Proteases expressed in atherosclerotic plaque lesions generate collagen fragments, release glycosaminoglycans (chondroitin sulfate [CS] and dermatan sulfate [DS]) and expose extracellular matrix (ECM) proteins (e.g. decorin) at sites of fibrin formation.

OBJECTIVE

Here we address the effect of these vessel wall components on the lysis of fibrin by the tissue plasminogen activator (tPA)/plasminogen system and on the mechanical stability of clots.

METHODS AND RESULTS

MMP-8-digested collagen fragments, isolated CS, DS, glycosylated decorin and its core protein were used to prepare mixed matrices with fibrin (additives present at a 50-fold lower mass concentration than fibrinogen). Scanning electron microscopy (SEM) showed that the presence of ECM components resulted in a coarse fibrin structure, most pronounced for glycosylated decorin causing an increase in the median fiber diameter from 85 to 187 nm. Rheological measurements indicated that these structural alterations were coupled to decreased shear resistance (1.8-fold lower shear stress needed for gel/fluid transition of the clots containing glycosylated decorin) and rigidity (reduction of the storage modulus from 54.3 to 33.2 Pa). The lytic susceptibility of the modified fibrin structures was increased. The time to 50% lysis by plasmin was reduced approximately 2-fold for all investigated ECM components (apart from the core protein of decorin which produced a moderate reduction of the lysis time by 25%), whereas fibrin-dependent plasminogen activation by tPA was inhibited by up to 30%.

CONCLUSION

ECM components compromise the chemical and mechanical stability of fibrin as a result of changes in its ultrastructure.

Mutational spectrum of smith-lemli-opitz syndrome patients in hungary

Smith-Lemli-Opitz (SLO) syndrome is an autosomal recessive disorder characterized by multiple congenital abnormalities and mental retardation. The condition is caused by the deficiency of 7-dehydrocholesterol reductase (DHCR7) which catalyzes the final step in cholesterol biosynthesis. Biochemical diagnosis is based on increased concentration of 7-dehydrocholesterol (7-DHC) in the patient serum. Both life expectancy and quality of life are severely affected by the disease. The estimated prevalence of SLO syndrome ranges between 1:20,000 and 1:40,000 among Caucasians. Although the mutational spectrum of the disease is wide, approximately 10 mutations are responsible for more than 80% of the cases. These mutations show a large interethnic variability. There are no mutation distribution data from Hungary to date. Thirteen patients were diagnosed with SLO syndrome in our laboratory. As first-line tests, serum 7-DHC and total cholesterol were measured and, in positive cases, molecular genetic analysis of the DHCR7 gene was performed. Complete genetic background of the disease could be identified in 12 cases. In 1 case only 1 mutation was detected in a heterozygote form. One patient was homozygous for the common splice site mutation c.964-1G>C, while all other patients were compound heterozygotes. One novel missense mutation, c.374A>G (p.Tyr125Cys) was identified.

Insertion/deletion polymorphism of the angiotensin-converting enzyme predicts left ventricular hypertrophy after renal transplantation

BACKGROUND

Kidney transplant recipients show a higher risk for cardiovascular complications, such as left ventricular hypertrophy and heart failure, leading to the premature death in many cases.

METHODS

We investigated the contribution of angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism to the development of left ventricular hypertrophy (LVH), an indicator of heart disease progression among kidney transplant recipients.

RESULTS

We observed a significant correlation between graft function and left ventricular mass index. The occurrence of LVH or severe LVH was significantly greater among patients with at least one D-allele (ID or DD).

CONCLUSION

The use of ACE inhibitors or angiotensin receptor blockers seemed to be advantageous for patients with the ID and especially, the DD genotype.

Hindered dissolution of fibrin formed under mechanical stress

BACKGROUND

Recent data indicate that stretching forces cause a dramatic decrease in clot volume accompanied by gross conformational changes of fibrin structure.

OBJECTIVE

The present study attempts to characterize the lytic susceptibility of fibrin exposed to mechanical stress as a model for fibrin structures observed in vivo.

METHODS AND RESULTS

The relevance of stretched fibrin models was substantiated by scanning electron microscopic (SEM) evaluation of human thrombi removed during surgery, where surface fibrin fibers were observed to be oriented in the direction of shear forces, whereas interior fibers formed a random spatial meshwork. These structural variations were modeled in vitro with fibrin exposed to adjustable mechanical stress. After two- and three-fold longitudinal stretching (2 × S, 3 × S) the median fiber diameter and pore area in SEM images of fibrin decreased two- to three-fold. Application of tissue plasminogen activator (tPA) to the surface of model clots, which contained plasminogen, resulted in plasmin generation which was measured in the fluid phase. After 30-min activation 12.6 ± 0.46 pmol mm(-2) plasmin was released from the non-stretched clot (NS), 5.5 ± 1.11 pmol mm(-2) from 2 × S and 2.3 ± 0.36 pmol mm(-2) from 3 × S clot and this hampered plasmin generation was accompanied by decreased release of fibrin degradation products from stretched fibrins. Confocal microscopic images showed that a green fluorescent protein-fusion variant of tPA accumulated in the superficial layer of NS, but not in stretched fibrin.

CONCLUSION

Mechanical stress confers proteolytic resistance to fibrin, which is a result of impaired plasminogen activation coupled to lower plasmin sensitivity of the denser fibrin network.

End-of-life decisions in Hungarian intensive care units

The awareness of local practice of end-of-life decisions in accordance with the law and ethical principles is essential for intensive care physicians in all countries. The first step for the required social dialogue is to investigate local practice. We performed the first Hungarian survey with the aim of better understanding local practice in end-of-life decisions in intensive care units. Questionnaires were sent out electronically to 743 members of the Hungarian Society of Anaesthesiology and Intensive Care. Respecting anonymity, we have statistically evaluated 103 replies (response rate 13.8%) and compared the results to data from other European countries. The results show that the practice of intensive care physicians in Hungary is rather paternalistic. Intensive care physicians generally make their decisions alone (3.75/5 points) without considering the opinion of the patient (2.57/5 points), the relatives (2.14/5 points) or other medical staff (2.37/5 points). Furthermore, they prefer not to start a form of treatment rather than to withdraw an ongoing one. Nevertheless, the frequency of end-of-life decisions (3 to 9% of intensive care unit patients) made in Hungarian intensive care units is less than in other European countries. End-of-life decisions are part of medical practice. Since the legal and ethical framework is unclear practice varies between locations and mostly depends on individual decisions rather than established protocols or guidance. For end-of-life decisions, self-determination must be supported and a dialogue must be established between lawmakers and physicians.

Insertion/Deletion polymorphism of Angiotensin-converting enzyme as a risk factor for chronic allograft nephropathy

Angiotensin-converting enzyme (ACE) inhibitor therapy is widely used to treat chronic allograft nephropathy (CAN), which suggests a possible role of the renin-angiotensin system in the pathologic mechanism of the disease. The objective of this study was to investigate the possible link between CAN and ACE. The ACE insertion/deletion polymorphism and the amount and activity of ACE were determined in cadaver kidney recipients with CAN (n = 38) or normal renal function (n = 34). The DD genotype was observed significantly more frequently in the CAN group compared with the group with normal renal function. Moreover, the DD genotype was associated with a higher serum ACE concentration and greater serum ACE activity, compared with II genotype homozygotes. The insertion/deletion polymorphism of ACE affects ACE expression and activity in serum, and, therefore, may have an important role in the pathogenesis of CAN. These findings suggest that determination of the ACE genotype may be useful in identifying patients at high risk. In particular, the DD genotype may be considered an indication for ACE inhibitor therapy.

Neutrophil granulocyte-dependent proteolysis enhances platelet adhesion to the arterial wall under high-shear flow

SUMMARY BACKGROUND

Under high shear stress platelets adhere preferentially to the adventitia layer of the arterial vessel wall in a von Willebrand factor (VWF)-dependent manner.

OBJECTIVE

The present study was undertaken in an attempt to characterize the structural background of the relative thromboresistance of the media and the impact of neutrophil leukocyte-derived proteases (matrix metalloproteinases, neutrophil elastase) on platelet adhesion in this layer of the arteries.

METHODS AND RESULTS

Platelet adhesion to cross-sections of the human iliac artery was monitored by indirect immunofluorescent detection of GpIIb/IIIa antigen. Exposure of the vessel wall to activated neutrophils or neutrophil-derived proteases increased platelet adhesion to the media about tenfold over the control level at 3350 s(-1) surface shear rate. In parallel with this enhanced thrombogenicity morphological changes in the media were evidenced by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The fine proteoglycan meshwork seen with Cupromeronic Blue enhancement of the SEM images was removed by the proteolytic treatment and the typical collagen fiber structure was exposed on the AFM images of the media.

CONCLUSION

Through their proteases activated neutrophils degrade proteoglycans, unmask VWF binding sites and thus abolish the thromboresistance of the media in human arteries.

Renal artery aneurysm at the anastomosis after kidney transplantation

Vascular complications represent serious problems after kidney transplantation. An aneurysm of the transplanted renal artery is an extremely rare but potentially devastating complication that which occurs in fewer than 1% of recipients. It can cause hypertension, functional impairment, and even graft loss. A 49-year-old man was admitted 6 months after his second renal transplantation. Duplex ultrasonography demonstrated an aneurysm at the anastomosis of the transplanted renal artery. The patient has not had any complaints. The function of the graft was stable. A computed tomography scan confirmed the diagnosis. Because of the high risk of rupture we decided upon surgical repair. During the operation, blood flow to the kidney was occluded; the graft was cooled with Euro-Collin's solution and ice-cold saline. After the resection there was enough usable arterial wall to construct a new anastomosis. The patient had an uneventful postoperative period, the serum creatinine decreased to the preoperative level, and the function of the graft was stable. Renal artery aneurysms represent high-risk complications. We decided on surgical repair, which was performed with simultaneous perfusion and cooling of the graft. There are only a few similar cases in the literature; it was the first operation using this method in our practice. Surgical reconstruction of a renal artery aneurysm, if feasible, is a safe procedure that prevents aneurysm rupture and saves the graft.

Feeding habits and trophic niche overlap between sympatric golden jackal (Canis aureus) and red fox (Vulpes vulpes) in the Pannonian ecoregion (Hungary)

The feeding ecology of the golden jackal ( Canis aureus L., 1758) and its interspecific trophic relationship with the sympatric red fox (Vulpes vulpes (L., 1758)) was investigated in an area of recent range expansion of the golden jackal in Hungary, central Europe. Diet composition was determined by scat analysis (over 4 years: jackal 814 scats; fox 894 scats). Compared with jackals, foxes consumed more small mammals (mean biomass consumed: jackal 77%; fox 68%) and to a lesser extent plant matter (6% and 18%, respectively). The importance of other prey, such as wild boar ( Sus scrofa L., 1758), cervids, brown hare ( Lepus europaeus Pallas, 1778), birds, reptiles, fish, invertebrates, and domestic animals, was minimal. Both mesocarnivores consumed primarily small animals (<50 g: 92% and 87%, respectively); this implies a typical searching and solitary hunting strategy. The trophic niche breadth of both species was very narrow and the fox proved to be more of a generalist. The food overlap index between the two canids was high (mean, 73%) and varied with the decreasing availability and consumption of small mammals. Based on prey remains found in scats, small-mammal specialization over a 2-year period and seasonal predation upon wild boar piglets (mainly by the jackal), seasonal fruit eating (mainly by the fox), and scavenging on wild or domestic ungulates (both predators) were found.

Laparoscopic resection of a bleeding meckel s diverticulum: a case report and review of the literature

The preoperative diagnosis of Meckel's diverticulum in adults is uncommon, and even more infrequent is the presentation of a bleeding Meckel's diverticulum after childhood. The case of a 22-year old, otherwise healthy male is presented here. The diagnosis was made by barium examination of small bowel and confirmed by diagnostic laparoscopy, followed by complete laparoscopic resection using an Endo-GIA Stapler (United States Surgical Corp., Norwalk, Conn.]. Histopathological examination of the specimen showed inflammed ileal mucosa with hemorrhages in several foci. The literature of Meckel's diverticula and its complications are reviewed here. Based on data from the reviewed literature and our own experience, we suggest that laparoscopic resection is the treatment of choice for Meckel's diverticulum, if it is diagnosed preoperatively or during diagnostic laparoscopy. The procedure allows for a smooth postoperative course, early discharge from the hospital, and arapid return to normal activity.

Double-stranded rna elements and virus-like particles in Aspergilli

Mycoviruses with double-stranded RNA (dsRNA) genomes are frequently encountered in Aspergillus isolates. A detailed study of such dsRNA elements in black Aspergillus isolates collected worldwide was carried out, and the data were analysed. The results indicate that about 10% of black Aspergilli are infected. However, the geographic distribution of infected isolates exhibits large variations; 3-13% of the isolates collected from different continents were found to carry dsRNA elements. Hybridization experiments indicated that electrophoretic banding patterns are not reliable tools for estimating the diversity of these mycovirus genomes. Among strains representing other Aspergillus sections, dsRNA segments indicative of mycovirus infection were observed for the first time in 4 species (A. leporis, A. petrakii, A. fumigatus and A. primulinus). The latter species is able to reproduce sexually. This is the second report on the detection of naturally-occurring dsRNAs in sexually reproducing Aspergillus species. The presence of virus-like particles in these and other Aspergilli was also examined by electron microscopy. Most infected Aspergillus isolates examined were found to carry virus-like particles in the size range 36-40 nm.

Surface structures of new and lesser known species of thermobifida as revealed by scanning electron microscopy

Surface structures of representatives of the genus Thermobifida were examined by scanning electron microscopy. Spores formed at the tips of multibranched sporophores initially resembled short sausages; then, upon maturation, they gradually built up their typical ovoid shape. Characteristic differences were observed between T. cellulolytica strain TB108 and T. fusca strains TM51. The spores of TB108 were larger (0.8x 1.3 microm) than those of TM51 (0.6 x 1.1 microm) in consequence of the more thickened outer squamous layer. When Thermobifida strains were grown on cellulose as sole carbon source, the mycelium was found to coil around the cellulose crystals and multiple protuberances emerged, resulting in a scabrous appearance to the mycelial surface. The presence of these cellulosome-like structures yielded a 24.5% surface enlargement of the scabrous mycelium as compared with the smooth one. The cellulosome emergence pattern paralleled the proportional increase in free endoglucanase activity measured during the culturing of these actinomycetes in the presence of cellulose.

Synthesis of vinca alkaloids and related compounds, Part XCVI. Nitration study of vinblastine-type bisindole alkaloids

The bisindole alkaloids vinblastine, vincristine, and N-formyl-leurosine were nitrated and subsequently converted to amino derivatives. In the case of compounds 5e and 5b cytotoxic activity has been found for non-small cell lung cancer and breast cancer in the concentration range tested (10(-5)-10(-9) M). 5b also showed potency in the screen for colon cancer and leukemia.

Role of hydrogen bonding in the interaction between a xylan binding module and xylan

NMR studies of the internal family 2b carbohydrate binding module (CBM2b-1) of Cellulomonas fimi xylanase 11A have identified six polar residues and two aromatic residues that interact with its target ligand, xylan. To investigate the importance of the various interactions, free energy and enthalpy changes have been measured for the binding of xylan to native and mutant forms of CBM2b-1. The data show that the two aromatic residues, Trp 259 and Trp 291, play a critical role in the binding, and similarly that mutants N264A and T316A have no affinity for the xylose polymer. Interestingly, mutations E257A, Q288A, N292A, E257A/Q288A, E257A/N292A, and E257A/N292A/Q288A do not significantly diminish the affinity of CBM2b-1 for the xylose polymers, but do influence the thermodynamics driving the protein-carbohydrate interactions. These thermodynamic parameters have been interpreted in light of a fresh understanding of enthalpy-entropy compensation and show the following. (1) For proteins whose ligands are bound on an exposed surface, hydrogen bonding confers little specificity or affinity. It also displays little cooperativity. Most specificity and affinity derive from binding between the face of sugar rings and aromatic rings. (2) Loss of hydrogen bonding interactions leads to a redistribution of the remaining bonding interactions such that the entropic mobility of the ligand is maximized, at the expense (if necessary) of enthalpically favorable bonds. (3) Changes in entropy and enthalpy in the binding between polysaccharide and a range of mutants can be interpreted by considering changes in binding and flexibility, without any need to consider solvent reorganization.