Biomedical subjects

S He

Publications and source records attributed to S He.

At least 37 records · Page 2Linked to original sources

PubMed2002

Novel growth factors involved in the pathogenesis of proliferative vitreoretinopathy.

AIMS: To determine whether hepatocyte growth factor (HGF) and connective tissue growth factor (CTGF) are expressed in human specimens of proliferative vitreoretinopathy (PVR) and to propose a model of PVR pathogenesis based upon the known activities of these growth factors. Methods Immunohistochemical methods (ABC Elite) were used to demonstrate the presence of HGF and CTGF in cryostat sections of five human PVR membranes. RESULTS: In each of the five PVR membranes, stromal cells were immunohistochemically positive for both HGF and CTGF. Based upon this information and the known actions of these growth factors, a model of PVR pathogenesis was developed. In this model, injury of the retina induces an inflammatory response that upregulates HGF expression inducing the formation of multilayered groups of migratory retinal pigment epithelial cells (RPE). These RPE, present in a provisional extracellular matrix, come in contact with vitreous containing TGF-beta. The TGF-beta is activated, upregulating expression of CTGF. Under the influence of TGF-beta and CTGF, RPE become myofibroblastic and fibrosis ensues. Retinal traction induces further detachment continuing the cycle of retinal injury. CONCLUSIONS: HGF and CTGF are expressed in PVR membranes and may play important roles in the pathogenesis of PVR. The expression and function of these growth factors should be critically examined in human PVR specimens, in in vitro cultures of RPE, and in animal models of PVR.

Connective Tissue Growth Factor↗

PubMed2002

Overall haemostatic potential can be used for estimation of thrombin-activatable fibrinolysis inhibitor-dependent fibrinolysis in vivo and for possible follow-up of recombinant factor VIIa treatment in patients with inhibitors to factor VIII.

Thrombin generation induced by recombinant factor VIIa (rFVIIa) in patients with haemophilia and/or inhibitors to factor VIII/IX could enhance generation of thrombin-activatable fibrinolysis inhibitor (TAFI), a recently described link between coagulation and fibrinolysis. TAFI is unstable and it is not easy to measure its active form in vivo. Overall haemostatic potential (OHP) is a novel method for haemostasis estimation, based on determination of the fibrin aggregation curve in which tiny amounts of thrombin are used for activation of clotting. We measured OHP in six patients with inhibitors to factor VIII before injection of rFVIIa and 10 and 120 min thereafter. Overall fibrinolytic potential (OFP) and clot lysis time (CLT) analysed by this method could be used for indirect estimation of TAFI generation. We found no change in pro-TAFI and total TAFI antigen before and after treatment with rFVIIa. OHP was almost undetectable before treatment but increased into the range of normal pooled plasma 10 and 120 min after rFVIIa treatment, as did CLT. However, after addition of potato tuber carboxypeptidase inhibitor, a specific inhibitor of TAFI, the shortening of CLT was lower than that in NPP. OFP was increased in patient plasma both 10 and 120 min after treatment compared with NPP. There was a strong positive correlation between pro-TAFI concentration and shortening of CLT after PTCI addition and a negative correlation between pro-TAFI concentration and OFP 10 min after rFVIIa injection. Thus, rFVIIa normalizes OHP and CLT 10 min after injection. While this improvement slightly decreases, but still exists after 2 hours, it suggests efficacy in bleeding prevention using a protocol based on rFVIIa administration every 2 hours.

Carboxypeptidase B2↗

PubMed2002

The assay of overall haemostasis potential used to monitor the low molecular mass (weight) heparin, dalteparin, treatment in pregnant women with previous thromboembolism.

The present study aimed to assess whether the determination of overall haemostasis potential (OHP) in plasma is powerful enough to monitor the prophylactic effect of low molecular mass heparin (dalteparin, Fragmin) in patients with increased risk of thromboembolitic events. In five pregnant women who had a history of deep venous thrombosis, OHPs were kinetically investigated in gestation weeks 32-35 twice during 24 h (before injection and after 1, 2, 4, 6, 8, 10, 12, 14, 16 and 24 h). Levels of anti-activated factor X (anti-FXa), reflecting dalteparin activity, as well as prothrombin fragments 1 + 2 (F1 + 2) and soluble fibrin, were also measured. In converse relation to changes of anti-FXa, OHPs decreased reaching the lowest level between 2 and 8 h after the injection, and then rose again, returning to the levels around those before the administration. There were no significant variations in concentrations of F1 + 2 and soluble fibrin during the observation course. These findings indicate that the OHP assay can monitor the alteration of haemostatic balance under the dalteparin influence while anti-FXa only shows the activity of the drug present in plasma. Additionally, analyses of thrombin generation markers are not useful to screen immediate changes in the haemostatic system after dalteparin injection.

Adult↗

PubMed2001

[Diagnostic value of tau in cerebrospinal fluid in alzheimer disease].

OBJECTIVE: To search for reliable and quantitative biochemical marker for diagnosis of Alzheimer disease. METHODS: ELISA-double enzyme amplification assay was used to detect the total tau and abnormally hyperphosphorylated (p-tau) in cerebrospinal fluid specimens of patients with Alzheimer disease (AD, N = 52, 30 from the Netherlands and 22 from Wuhan and Haikou, China), vascular dementia (VD, N = 46, 18 from the Netherlands and 28 from Haikou), and non-neurological disease (N = 37, 13 from the Netherlands and 24 from Haikou) and of normal elderly controls (N = 56, 26 from the Netherlands, and 30 from Wuan and Haikou). RESULTS: The measurement of CSF specimens from Netherlands Brain Bank showed that the levels of total tau and p-tau in CSF specimens of AD patients were significantly higher than those in CSF of patients with VD and non-dementia neurological disorders, and of age-matched non-neurological normal controls. With CSF tau > or = 370 pg/ml as the marker for diagnosis of AD, the sensitivity, specificity, reliability as well as differentiation rate of AD from VD were 90.0%, 79.0%, 82.8% and 66.7%, respectively. With CSF p-tau > or = 120 pg/ml as the marker for diagnosis of AD, the sensitivity, specificity, reliability as well as differentiation rate of AD from VD were 93.3%, 89.5%, 90.8%, and 83.3% respectively. The measurement of total and phosphorylated taus in CSF specimens of AD and non-AD patients and normal controls collected in China showed the similar results; and the sensitivity, specificity, reliability as well as differentiation rate of AD from VD were 77.3%, 85.4%, 83.7% and 71.4% with CSF tau > or = 120 pg/ml as the marker for diagnosis of AD. There was no correlation between CSF tau and p-tau and age, sex, and seriousness of disease. CONCLUSION: Increased phosphorylated tau in human cerebrospinal fluid is a reliable biomarker for diagnosis of Alzheimer disease.

Aged↗

PubMed2001

Identification of the catalytic nucleophile of the Family 31 alpha-glucosidase from Aspergillus niger via trapping of a 5-fluoroglycosyl-enzyme intermediate.

The mechanism-based reagent 5-fluoro-alpha-d-glucopyranosyl fluoride (5F alpha GlcF) was used to trap a glycosyl-enzyme intermediate and identify the catalytic nucleophile at the active site of Aspergillus niger alpha-glucosidase (Family 31). Incubation of the enzyme with 5F alpha GlcF, followed by peptic proteolysis and comparative liquid chromatography/MS mapping allowed the isolation of a labelled peptide. Fragmentation analysis of this peptide by tandem MS yielded the sequence WYDMSE, with the label located on the aspartic acid residue (D). Comparison with the known protein sequence identified the labelled amino acid as Asp-224 of the P2 subunit.

Amino Acid Sequence↗

PubMed2001

A simple and rapid laboratory method for determination of haemostasis potential in plasma. II. Modifications for use in routine laboratories and research work.

To offer a suitable method for use in routine laboratories and research work, some modifications were made in the assay of overall haemostatsis potential (OHP) we developed earlier. Thrombin in a decreased dose with or without tissue-type plasminogen activator was added to plasma for initiation of fibrinogen clotting. Areas under two fibrin-aggregation curves i.e., above-mentioned OHP and overall coagulation potential (OCP) were thus created. A difference between the two parameters reflects the overall fibrinolysis potential (OFP), calculated by ((OCP-OHP)/OCP) x 100%. To obtain reference ranges, investigations were performed in 142 healthy adults of different ages and in 29 healthy women with a normal pregnancy. In 16 patients suffering from coronary heart disease (CHD), OCPs and OHPs increased but OFPs decreased. In 10 pre-eclamptic women with moderate enhancement of OCP, the OHPs became noticeably higher in most while the OFPs lower. Extremely low or undetectable levels of OHP and OCP were shown in samples of Factors VIII-, IX-, VII-, V-, X- or II-deficient plasma. In 13 healthy volunteers treated with acetylsalicylic acid (ASA), OHPs expectedly declined during the administration and rose again after withdrawal. The above findings demonstrate that the modifications in the present study have rendered the method more effective for detecting haemostatic changes and relevant for monitoring treatments.

Adult↗

PubMed2001

Are increased levels of von Willebrand factor in chronic coronary heart disease caused by decrease in von Willebrand factor cleaving protease activity? A study by an immunoassay with antibody against intact bond 842Tyr-843Met of the von Willebrand factor protein.

Low levels of von Willebrand factor (VWF) in von Willebrand's disease type 2A (VWD 2A) result from increased cleavage of the bond 842Tyr-843Met in the VWF protein by VWF cleaving protease. On the other hand, decreased levels of this protease result in unusually large VWF in thrombotic thrombcytopenic purpura with thrombotic complications. In the present study, we designed an enzyme-liked immunosorbent assay of VWF cleaving protease activity to be used to assess whether the high levels of VWF in coronary heart disease (CHD) relate to a deficiency of this protease. Plasma samples with added Pefabloc and CaCl(2) were incubated with purified VWF coated on a microtiter plate. The remaining undigested multimers were quantified by an antibody directed against the intact 842Tyr-843Met bond of the VWF protein. Phosphate-buffered saline (PBS), instead of plasma, was used to obtain the initial level of coated undigested VWF. The reduction in absorbance at 492 nm between PBS and the unknown sample was taken as a measure of the protease activity. The assay was applied to plasma samples from 21 senior women with chronic CHD (cases) and 34 age-matched controls, as well as to samples from three patients with VWD 2A. The protease activity was similar in the two women groups (P>.05), although the VWF antigen levels were higher in the cases (P<.01). The VWD 2A patients had similar plasma levels of the protease to that in normal pooled plasma (NPP). In the senior controls, the protease activity correlated with the subject age (r's=-.61, P<.01, n=34). In conclusion, the developed method is specific for evaluating the protease function on VWF cleavage. The moderate increase of VWF antigen in chronic CHD may not depend on the protease activity. The age influence on the protease levels supports earlier findings of higher VWF levels in healthy older subjects. A high sensitivity of the mutated protein of VWF for the protease effect rather than increases in activity or quantity of the enzyme is probably involved in the pathogenesis of VWD 2A.

ABO Blood-Group System↗

PubMed2001

Evolution and transmission of stable CTL escape mutations in HIV infection.

Increasing evidence indicates that potent anti-HIV-1 activity is mediated by cytotoxic T lymphocytes (CTLs); however, the effects of this immune pressure on viral transmission and evolution have not been determined. Here we investigate mother-child transmission in the setting of human leukocyte antigen (HLA)-B27 expression, selected for analysis because it is associated with prolonged immune containment in adult infection. In adults, mutations in a dominant and highly conserved B27-restricted Gag CTL epitope lead to loss of recognition and disease progression. In mothers expressing HLA-B27 who transmit HIV-1 perinatally, we document transmission of viruses encoding CTL escape variants in this dominant Gag epitope that no longer bind to B27. Their infected infants target an otherwise subdominant B27-restricted epitope and fail to contain HIV replication. These CTL escape variants remain stable without reversion in the absence of the evolutionary pressure that originally selected the mutation. These data suggest that CTL escape mutations in epitopes associated with suppression of viraemia will accumulate as the epidemic progresses, and therefore have important implications for vaccine design.

Adult↗

PubMed2001

The identification of the catalytic nucleophiles of two beta-galactosidases from glycoside hydrolase family 35.

The beta-galactosidases from Xanthomonas manihotis (beta-Gal Xmn) and Bacillus circulans (beta-Gal-3 Bcir) are retaining glycosidases that hydrolyze glycosidic bonds through a double displacement mechanism involving a covalent glycosyl-enzyme intermediate. The mechanism-based inactivator 2,4-dinitrophenyl 2-deoxy-2-fluoro-beta-D-galactopyranoside was shown to inactivate beta-Gal Xmn and beta-Gal-3 Bcir through the accumulation of 2-deoxy-2-fluorogalactosyl enzyme intermediates with half lives of 40 and 625 h, respectively. Peptic digestion of these labeled enzymes and analysis by LC-MS identified Glu(260) and Glu(233) as the catalytic nucleophiles involved in the formation of the glycosyl-enzyme intermediate during catalysis by beta-Gal Xmn and beta-Gal-3 Bcir, respectively. These findings confirm the previous prediction of the position of these residues based on primary sequence similarities to other members of the glycoside hydrolase family 35.

Amino Acid Sequence↗

PubMed2001

Orientation-selective adaptation and tilt after-effect from invisible patterns.

Exposure to visual patterns of high contrast (for example, gratings formed by alternating white and black bars) creates after-effects in perception. We become temporarily insensitive to faint test patterns that resemble the pre-exposed pattern (such as gratings of the same orientation), and we require more contrast to detect them. Moreover, if the test pattern is slightly tilted relative to the pre-exposed one, this tilt may be perceptually exaggerated: we experience a tilt after-effect. Here we show that these visual after-effects occur even if the pre-exposed grating is too fine to be perceptually resolved. After looking at a very fine grating, so high in spatial frequency that it was perceptually indistinguishable from a uniform field, observers required more contrast to detect a test grating presented at the same orientation than one presented at the orthogonal orientation. They also experienced a tilt after-effect that depended on the relation of the test pattern's tilt to the unseen orientation of the pre-exposed pattern. Because these after-effects are due to changes in orientation-sensitive mechanisms in visual cortex, our observations imply that extremely fine details, even those too fine to be seen, can penetrate the visual system as far as the cortex, where they are represented neurally without conscious awareness.

Adaptation, Physiological↗

PubMed2001

The activation of synovial mast cells: modulation of histamine release by tryptase and chymase and their inhibitors.

Mast cells have been implicated as having pivotal roles in arthritis, but little is known of the processes leading to the activation of synovial mast cells or their potential for pharmacological control. We have investigated the ability of tryptase and chymase, and inhibitors of these major mast cell proteases to modulate the activation of mast cells from human synovial tissue. The tryptase inhibitor drug N-(1-hydroxy-2-naphthoyl)-L-arginyl-L-prolinamide hydrochloride (APC366) inhibited immunoglobulin E (IgE)-dependent histamine release in a dose-dependent manner, with about 70% inhibition being achieved at a dose of 300 microM. Histamine release stimulated by calcium ionophore A23187 was also inhibited by this compound. The chymase inhibitor chymostatin inhibited IgE-dependent histamine release by approximately 60% at 1 microg/ml. Tryptase at concentrations of 3.0 microg/ml and greater stimulated histamine release from synovial cells, which was dependent on catalytic activity, whereas chymase had little effect on these cells. The activation of mast cells by tryptase may represent an amplification process in the synovium. The mast cell stabilising properties of inhibitors of tryptase and chymase could be of therapeutic value in arthritis.

Calcimycin↗

PubMed2001

Substantial differences in specificity of HIV-specific cytotoxic T cells in acute and chronic HIV infection.

Cytotoxic T lymphocytes (CTLs) play a vital part in controlling viral replication during human viral infections. Most studies in human infections have focused on CTL specificities in chronic infection and few data exist regarding the specificity of the initial CTL response induced in acute infection. In this study, HIV-1 infection in persons expressing human histocompatibility leukocyte antigen (HLA)-A*0201 was used as a means of addressing this issue. In chronic infection, the dominant HLA-A*0201-restricted CTL response is directed towards the epitope SLYNTVATL ("SL9") in p17 Gag (residues 77-85). This epitope is targeted by 75% of HLA-A*0201-positive adults, and the magnitude of this A*0201-SL9 response shows a strong negative association with viral load in progressive infection. Despite using the highly sensitive peptide-major histocompatibility complex tetramer and intracellular cytokine assays, responses to the SL9 epitope were not detectable in any of 11 HLA-A*0201-positive subjects with acute HIV-1 infection (P = 2 x 10(-6)), even when assays were repeated using the SL9 peptide variant that was encoded by their autologous virus. In contrast, multiple responses (median 3) to other epitopes were evident in 7 of the 11 A*0201-positive subjects. Longitudinal study of two subjects confirmed that the A*0201-SL9 response emerged later than other CTL responses, and after viral set point had been reached. Together, these data show that the CTL responses that are present and that even may dominate in chronic infection may differ substantially from those that constitute the initial antiviral CTL response. This finding is an important consideration in vaccine design and in the evaluation of vaccine candidates.

Acute Disease↗

PubMed2001

1,2,5-Thiadiazolidin-3-one 1,1 dioxide: a powerful scaffold for probing the S' subsites of (chymo)trypsin-like serine proteases.

The 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold (I) embodies a motif that allows it to dock to the active site of (chymo)trypsin-like proteases in a predictable and substrate-like fashion. Consequently, inhibitors derived from this heterocyclic scaffold interact with both the S and S' subsites of an enzyme. Exploitation of binding interactions with both the S and S' subsites of a target enzyme may lead to compounds with greatly enhanced enzyme selectivity and inhibitory potency. This preliminary report describes the use of a series of compounds having the heterocyclic scaffold linked to various amino acids to probe the S' subsites of human leukocyte elastase (HLE), proteinase 3 (PR 3), and cathepsin G (Cat G). For comparative purposes, a series of compounds derived from a related scaffold, isothiazolidin-3-one 1,1 dioxide (II), was also generated. Several of the compounds were found to be highly potent and selective time-dependent inhibitors of HLE, PR 3, and Cat G.

Cathepsin G↗

PubMed2001

Fast method for the localisation of current dipoles in the human brain.

A fast algorithm for localising multiple current dipoles in the human brain by measuring the external magnetic field is presented. A genetic algorithm is used first for rough estimate of locations. To speed up the global optimisation algorithm, an explicit solution for a spherical head model is used for the rough estimation. This rough estimate is then used as a start for a fine search using a gradient-based algorithm, in which a boundary element solution for a realistic brain-shaped head model is used. Numerical simulation indicates that the present algorithm converges three-four times faster than an algorithm using a brain-shaped head model in all the steps.

Algorithms↗

PubMed2001

Visual motion and the human brain: what has neuroimaging told us?

Recently, neuroimaging techniques have been applied to the study of human motion perception, complementing established techniques such as psychophysics, neurophysiology and neuropsychology. Because vision, particularly motion perception, has been studied relatively extensively, it provides an interesting case study to examine the contributions and limitations of neuroimaging to cognitive neuroscience. We suggest that in the domain of motion perception neuroimaging has: (1) revealed an extensive network of motion areas throughout the human brain, in addition to the well-studied motion complex (MT+); (2) verified and extended findings from other techniques; (3) suggested extensive top-down influences on motion perception; and (4) allowed experimenters to examine the neural correlates of awareness. We discuss these contributions, along with limitations and future directions for the neuroimaging of motion.

Attention↗

PubMed2001

Filling-in at the natural blind spot contributes to binocular rivalry.

The human natural blind spot is usually filled in based on the contextual information. When two sufficiently different images are presented to the two eyes, observers typically perceive an alternation between the two images (binocular rivalry). Both the filling-in process and binocular rivalry have been the subject of considerable research. This study investigates whether filled information in one eye's natural blind spot can contribute to binocular rivalry. A radial grating (D=12 degrees ) was presented to one eye, centered on the natural blind spot. Observers perceived a complete figure in monocular view; the blind spot area was filled-in based on the surrounding information. Simultaneously, a circular grating smaller than the blind spot (D=4 degrees ), was presented to the fellow eye in the region corresponding to the other eye's blind spot. The amount of rivalry as indexed by how often the smaller circular grating remained visible was measured. The results suggest that the filled information in the area of the blind spot does contribute to the rivalry process.

Humans↗

PubMed2001

Inhibition of serine proteases by functionalized sulfonamides coupled to the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold.

A challenge associated with drug design is the development of selective inhibitors of proteases (serine or cysteine) that exhibit the same primary substrate specificity, that is, show a preference for the same P(1) residue. While these proteases have similar active sites, nevertheless there are subtle differences in their S and S' subsites which can be exploited. We describe herein for the first time the use of functionalized sulfonamides as a design and diversity element which, when coupled to the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold yields potent, time-dependent inhibitors of the serine proteases human leukocyte elastase (HLE), proteinase 3 (PR 3) and cathepsin G(Cat G). Our preliminary findings suggest that (a) appending to the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold recognition and diversity elements that interact with both the S and S' subsites of a target protease may result in optimal enzyme selectivity and potency and, (b) functionalized sulfonamides constitute a powerful design and diversity element with low intrinsic chemical reactivity and potentially wide applicability.

Cathepsin G↗

PubMed2001

Medial axis reformation: a new visualization method for CT angiography.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate a new method (medial axis reformation [MAR]) for visualizing three-dimensional vascular data at electron-beam computed tomographic (CT) angiography. MATERIALS AND METHODS: MAR was performed automatically with a personal computer-based workstation. After the region of interest was edited, voxels were divided into groups according to their path lengths. Centroids of groups were connected to form the medial axis. Then, the medial axis was refined with multiscale medial response. Bifurcations were also detected and refined. Finally, curved sections were generated through the branches and laid out onto a single image by using a splitting method. The authors performed MAR during electron-beam CT angiography of coronary arteries, common carotid arteries, and iliac arteries. RESULTS: MAR displayed curved sections of branched vessels on one image, cut through the axis of vessels to show the vessel diameter objectively, and allowed the viewing direction to be altered arbitrarily. CONCLUSION: Results of preliminary applications demonstrate that MAR is a valuable new visualization method for CT angiography.

Adult↗