Renovascular disease: a review of diagnostic and therapeutic procedures

The clinical importance of renovascular disease, atherosclerotic or of other origin, arises from the fact, that renal artery stenosis (RAS), if hemodynamically significant (> 70% diameter reduction), induces arterial hypertension, renal insufficiency or both. The prevalence of RAS rises with increasing age and with the presence of atherosclerosis of the aorta, carotid, coronary and peripheral arteries. Typical clinical symptoms, as uncontrolled hypertension or renal dysfunction in the absence of pathological urinary findings, are helpful to select patients for further screening methods: We see a prominent role of color duplex sonography as a screening procedure. Intra-arterial angiography remains gold standard for the diagnosis of RAS. The major problem in daily clinical practice is the differentiation between patients in which hypertension and kidney function can be improved or normalized by removal of RAS and those with ''fixed'' hypertension and irreversible kidney dysfunction and therefore to decide if it is worth while to perform invasive treatment as angioplasty or surgery. In this setting, the proof of hemodynamic significance is essential and is indicated especially when the stenosis has a diameter reduction of < 50-70% only. Methods proving a critical stenosis are intra-arterial measurement of the pressure gradient, measurement of differential renal vein renin and duplex sonography. In addition, predictors of treatment outcome should be considered. Studies analyzing if patients improve with blood pressure and kidney function after removal of RAS have shown that high grade stenosis and/or very high blood pressure indicate a good outcome. Further prognostic factors are the absence of parenchymal disease and/or positive functional test. In the presence of a critical stenosis in a patient with a clear clinical problem with hypertension and/or renal dysfunction a positive effect of invasive treatment seems warranted despite the risks that must be considered as well in angioplasty as in surgery. The selection for the type of invasive treatment requires a clarification of the treatment goals in the individual patient, the evaluation of the morphology and localization of the stenosis as the presence of other vascular disease (aortic aneurysm, peripheral artery disease etc.) and the assessment of the risk according to the type of intervention.

A simple and sensitive method to study effects mediated by soluble lymphokines as demonstrated by the interaction of CD4+ and CD8+ cell subsets during T cell activation

A method is described for the study of lymphokine-mediated cellular interactions using triple wells, which permits co-culture of cell subpopulations without direct physical contact. The triple wells are constructed by slitting the walls to half height between three adjacent wells of a 96-well microtiter plate. The cells under study are positioned in the outer two wells, whereas the middle well serves to separate the cells. The half slits permit the wells to be treated independently before filling the triple well with the culture medium and prevents cell leakage thereafter. The feasibility of the method was established by studying the interaction of isolated CD4+ and CD8+ T cell subsets during T cell proliferation induced by immobilized anti-CD3 and anti-CD28 monoclonal antibodies.

CD30 induction and cytokine profiles in hepatitis C virus core-specific peripheral blood T lymphocytes

Since an efficient control of virus infections may depend on the appropriate lymphokine profile, we studied cytokine responses and CD30 induction, a recently proposed surrogate marker of type 2 cells, in 10 healthy anti-hepatitis C virus (HCV)-seropositive blood donors without viremia (group A) and in 15 patients with hepatitis C (group B). Intracytoplasmic IFN-gamma, IL-2, IL-4, and IL-10 were determined by triple-color flow cytometry in the CD3+ and CD3+/CD30+ lymphocyte subsets after stimulation of PBMC with rHCV core protein and five core-derived peptides corresponding to the four immunodominant Th epitopes C.T1 to C.T4. In group A, more type 1 cytokines were induced by the rHCV core protein and all immunodominant core peptides (p &lt; 0.05), whereas IL-10-producing T cells were found more frequently in group B. Induction of CD30+ T cells was found almost exclusively in group B (p &lt; 0.01). The difference in cytokine responses was due to the CD3+/CD30- T cell subset and not the CD3+/CD30+ subset, which predominantly produced both IL-10 and IFN-gamma, but only small amounts of IL-2 and IL-4. We conclude that immunodominant HCV core peptides induce preferentially type 1 cytokines in healthy anti-HCV-positive blood donors and CD30 expression in patients with chronic hepatitis C. However, in both groups, CD30+ T lymphocytes produce an intermediate Th0-like cytokine profile. Thus, chronicity in HCV infection may reflect a lack of type 1 cytokine production.

Anchor-linked intermediates in peptide amide synthesis are caused by dimeric anchors on the solid supports

Cleavage and kinetic studies have been carried out using commercially obtained H-Tyr(tBu)-5-(4'-aminomethyl-3',5'-dimethoxyphenoxy)valeric acid-TentaGelS (H-Tyr(tBu)-4-ADPV-TentaGelS) and H-Tyr (tBu)-4-ADPV-Ala-aminomethyl-resin (H-Tyr(tBu)-4-ADPV-AM-resin) prepared from commercially available resin and loaded with commercially available Fmoc-4-ADPV-OH amide anchor. Cleavage with pure trifluoroacetic acid (TFA) gave the intermediate H-Tyr-4-ADPV-NH2, which was then degraded to H-Tyr-NH2, and cleavage with TFA/dichloromethane (1:9) yielded H-Tyr-4-ADPV-NH2 which could be isolated in preparative amounts. Cleavage reactions with 15N-labelled H-Ala-4-ADPV-(15N)-Gly-AM-resin yielded the intermediate H-Ala-4-ADPV-NH2, which contained no 15N as demonstrated by 1H-NMR. The analysis of the commercial Fmoc-4-ADPV-OH amide anchor showed the presence of Fmoc-4-ADPV-4-ADPV-OH as an impurity in high amounts. This dimeric anchor molecule is the cause of formation of the anchor-linked peptide intermediate obtained during the cleavage from the resin. The particularly high acid-lability of the amide bond between the two ADPV moieties was utilized to synthesize sidechain and C-terminally 4-ADPV protected pentagastrin on a double-anchor resin, and to cleave it using 5% trifluoroacetic acid in dichloromethane. This method may offer a new way for the synthesis of protected peptide amides with improved solubility to be used in fragment condensation.

Molecular mechanisms of cytotoxicity: comparison of complement and killer lymphocytes

The membrane attack complex of complement is an amphiphilic fusion product of 5 glycoproteins, C5, C6, C7, C8 and C9. The membrane attack complex forms transmembrane channels that vary in size depending on the number of C9 molecules incorporated into the complex. The C5b-8 complex forms small channels and at high multiplicity can kill nucleated cells. At least 12 C9 molecules are required to form tubular poly C9 which evokes the ultrastructural image of the classical membrane lesion produced by complement. The membranes of erythrocytes and other blood cells contain a 70,000 dalton protein that can inhibit channel formation by the membrane attack complex. This protein is species specific and has been called homologous restriction factor. A cytotoxic protein immunochemically related to C9 was isolated from cytotoxic human large granular lymphocytes and from OKT3 activated human peripheral blood mononuclear cells. In the presence of Ca++, isolated C9 related protein (C9RP) formed circular structures that resembled poly C9. C9RP efficiently killed K562 cells, human melanoma cells, Raji cells and human large granular lymphocytes. The results suggest that the channel forming protein of cytotoxic lymphocytes and C9 of complement have a common evolutionary ancestry.

CTLs from lymphoid organs recognize an optimal HLA-A2-restricted and HLA-B52-restricted nonapeptide and several epitopes in the C-terminal region of HIV-1 Nef

In a previous analysis of HIV-1-specific CTLs in lymphoid organs from HIV-seropositive patients, we reported high frequencies of in vivo differentiated CTLs directed against two immunodominant regions in the central and in the C-terminal part of the HIV-1 Nef protein. The present study analyzes the epitopes recognized by CTLs in the carboxyl terminus of Nef (amino acids 182-205). In addition to several epitopes that are recognized in association with different HLA molecules (A1, A2, A25(10), B35, B52), we defined an optimal nonapeptide (190-198). This nonapeptide was recognized by CTLs down to nanomolar concentrations in the context of at least two HLA molecules, HLA-B52 and HLA-A2, including three HLA-A2 subtypes: HLA-A2.1, -A2.2, and -A2.4. We also determined the relative frequencies of effector CTLs directed against peptide 190-198 to be as high as 10(-4), as opposed to lower frequencies ranging between 5 x 10(-5) and 5 x 10(-6) observed for the other peptides recognized in the same region, thus confirming the optimal presentation of this nonapeptide in vivo. Molecular modeling of the interactions between HLA-A2.1 and Nef peptide 190-198 suggests the formation of a stable complex and allowed us to study sequence motifs that are important for the binding of the HIV-1 peptide in the pockets of the HLA-A2.1 molecule.

B-lymphocyte mitogenicity in vitro of a synthetic lipopeptide fragment derived from bacterial lipoprotein

Lipoprotein from the outer membrane of Escherichia coli is a potent mitogen towards lymphocytes of different species. A lipopeptide fragment corresponding to the N-terminal part of the lipoprotein was prepared by chemical synthesis. The mitogenicity of the compound was demonstrated by measuring the incorporation of both [3H]thymidine into DNA and [3H]uridine into RNA at various times after the addition of lipopeptide to mouse spleen cell cultures. The lipopeptide also activated B-lymphocyte development into immunoglobulin secreting cells, as shown by a hemolytic plaque assay. The mitogenicity of the synthetic compound was comparable to the activity of the B-lymphocyte mitogens lipoprotein and lipopolysaccharide. Thus, it was shown that a fragment of a bacterial surface component prepared by chemical synthesis, exhibits a marked biological activity.

[Pelvic vein thrombosis : Current treatment options and importance of recanalization procedures]

Venous thrombosis is a frequent disorder. A distinction is made between an acute phase of the disease and a chronic manifestation, the postthrombotic syndrome. In particular, proximal venous thrombosis/pelvic vein thrombosis can cause a life-threatening pulmonary embolism during the acute phase of the disease. The postthrombotic syndrome is characterized by the remodeling of the affected venous section, which is often caused by inflammation. Locally, the typical clinical finding is caused by scarred stricture of the vein with restricted drainage and peripheral venous hypertension. Acute thrombosis should be primarily treated by therapeutic anticoagulation and compression therapy of the affected extremity. The duration of these measures depends on clinical presentation, cause (provoked, unprovoked) and risk factors for venous thrombosis/recurrent thrombosis. Venous revascularization procedures are important both in the acute phase of the disease and in the treatment of postthrombotic syndrome. The recanalization treatment is mostly carried out as an endovascular or hybrid intervention and venous bypass procedures are reserved for special situations.

Analysis of allele-specific contact sites of natural HLA-DR17 ligands

The sequence motif of peptide ligands naturally associated with DR17 has indicated conserved residues at the relative positions P1-P4-P6-P 8.9 or 10. Eight naturally processed DR17 ligands were synthesized to study the role of conserved residues in DR17 binding. In their majority, they showed an excellent ability to bind to purified DR17 molecules. Binding experiments with variant peptides confirmed aspartate as the DR17-specific contact site at P4. In addition, hydrophobic or aromatic residues at P1 and P9, probably interacting with the NH2- and COOH-terminal pockets, and lysine or chemically related amino acids at P6 were important for binding. A core peptide of 10 amino acids, bordered by the terminal contact sites, is sufficient, although the ability to bind is reduced approximately 10-fold compared with the binding capacity of the natural ligand. Ala substitution of flanking stretches at either end completely restores the binding capacity to that of the natural ligand. This suggests that regions flanking the peptide core contribute to the binding strength nonspecifically, i.e., by forming H-bonds to MHC molecules. Natural DR1 and DR12 ligands like HLA-A2 (103-117) and transferrin receptor (140-156) failed to bind to DR17 molecules. However, substituting leucine for aspartate at P4 transformed DR1 and DR12 ligands into excellent DR17 binders. This conversion, enabled by a single amino acid substitution, emphasizes the importance of aspartate as the DR17-specific contact site and suggests that terminal contact residues are shared among DR1, DR12, and DR17 ligands. In contrast, additional aspartates introduced next to the contact site at P4 impaired the binding capacity. Regarding this specific role of asparate we expect that DR17-specific ligands will be rarely found among "promiscuous" peptides binding to several different DR molecules.

Rapid alterations in the plasma membrane structure of macrophages stimulated with bacterial lipopeptides

Synthetic lipopeptide analogues of the N-terminal region of bacterial lipoprotein are potent activators of macrophages. In a previous study we showed that within minutes after their addition to macrophage cultures, lipopeptides were found attached to the plasma membranes and within different compartments of the cells. Their rapid interaction with the plasma membrane is thought to occur via the insertion of their three fatty acids. We used the freeze-fracture technique to study the influence of lipopeptides on the architecture of plasma membranes. Fifteen to thirty seconds after addition of the lipopeptides, the freeze-fractured plasma membranes show a rapid decrease in the particle density. This effect is not due to a loss of proteins, but is caused by lateral diffusion of single particles, which subsequently aggregate. These alterations are transient, temperature-sensitive and disappear 20 min after stimulation. At 4 degrees C, no change is found in the architecture of the plasma membranes. Using electron energy loss spectroscopy (EELS), lipopeptides can neither be detected on the membrane nor within the cells when incubated at this temperature. Our findings suggest that membrane protein aggregation is involved in the rapid uptake of lipopeptides into macrophages after their interaction with the plasma membranes.