Biomedical subjects

G Lang

Publications and source records attributed to G Lang.

At least 19 recordsLinked to original sources

PubMed2006

NMR study of the magnetic and metal-insulator transitions in Na0.5CoO2: a nesting scenario.

Co and Na NMR are used to probe the local susceptibility and charge state of the two Co sites of the Na-ordered orthorhombic Na(0.5)CoO(2). Above T(N) = 86 K, both sites display a similar T dependence of the spin shift, suggesting that there is no charge segregation into Co(3+) and Co(4+) sites. Below T(N), the magnetic long range commensurate order found is only slightly affected by the metal-insulator transition at T(MIT) = 51 K. Furthermore, the electric field gradient at the Co site does not change at these transitions, indicating the absence of charge ordering. All these observations can be explained by successive spin-density wave induced by two nestings of the Fermi surface specific to the x = 0.5 Na ordering.

Journal Article↗

PubMed2004

Lung transplantation for end-stage primary pulmonary hypertension.

Developments in transplant techniques, peri-operative management and medical therapy have changed the place of transplantation in the treatment armamentarium available for PPH. The aim of this article is therefore, to describe the current knowledge of transplantation for PPH, and to define its place in view of the recent advances in medical therapy.

Echocardiography↗

PubMed2003

Low content of the natural ocular anti-angiogenic agent pigment epithelium-derived factor (PEDF) in aqueous humor predicts progression of diabetic retinopathy.

AIMS/HYPOTHESIS: Retinopathy is the most common microvascular complication of diabetes. Our aim was to address the predictive value of pro-angiogenic and anti-angiogenic markers for progression of retinopathy. METHODS: Aqueous humor was collected at cataract surgery from 32 diabetic patients who had no or very mild retinopathy (ETDRS stage </=20) and 33 normoglycaemic control subjects. Content of pro-angiogenic vascular endothelial growth factor and angiogenic inhibitor pigment epithelium-derived factor were determined. ANGIOGENIC activity was quantified by measuring its effect on the migration of capillary endothelial cells. The predictive value of the initial level of these markers for progression of retinopathy was studied by following the probands for a maximum of 75 months. RESULTS: In the aqueous fluid content of vascular endothelial growth factor was increased in diabetic patients (mean values 492 versus 292 pg/ml; p=0.0052), and pigment epithelium-derived factor values were decreased (mean values 1740 versus 3680 ng/ml; p=0.0058) compared to control subjects. Of the diabetic patients ten progressed during follow-up (ETDRS stage >47B). This subgroup showed lower pigment epithelium-derived factor content when compared to non-progressors and control subjects. Migratory activity in samples of patients from the control group and in diabetic patients without progression was generally inhibitory due to pigment epithelium-derived factor. Inhibition was blocked by neutralizing antibodies to pigment epithelium-derived factor. In diabetic patients initial angiogenic activity was higher in those who later developed retinopathy (vs. controls p=0.00005; vs. no progressors p=0.0003). Both pigment epithelium-derived factor and migratory response predicted progression. CONCLUSION/INTERPRETATION: Pigment epithelium-derived factor is an important negative regulator of angiogenic activity of aqueous humor. Its content in the aqueous humor of diabetic patients strongly predicts who among them will develop progression of retinopathy.

Aged↗

PubMed2003

Full absolute stereostructures of natural products directly from crude extracts: The HPLC-MS/ MS-NMR-CD 'triad'.

This chapter deals with an efficient methodology available in our Center of Excellence, BIOTECmarin: the novel analytical 'triad' HPLC-MS/MS-NMR-CD. By this method, which was, in this complemented form, first introduced into phytochemical research by our group, we can not only rapidly identify known structures, but can also investigate new metabolites and establish their full absolute stereostructures online, directly from crude extracts, without the necessity of first isolating the compounds. The LC-CD option, which we have been using for the first time in natural products analysis, becomes even more valuable by the possibility of interpreting the online CD spectra by their simulation or prediction through quantum chemical calculation, thus avoiding the usual, often risky, empirical comparison with the CD spectra of (sometimes not so related) compounds of known absolute stereostructure or the application of (sometimes not really applicable) likewise empirical CD rules. The hyphenated analytical methods are additionally complemented by our synthetic expertise, again involving new concepts and strategies developed in our group. The methods and their application will first be explained and exemplified for plant-derived ('terrestrial') natural products, for which they were initially developed, and will then be applied to the online structural elucidation of novel natural products from marine organisms.

Alkaloids↗

PubMed2003

Sorbicillactone A: a structurally unprecedented bioactive novel-type alkaloid from a sponge-derived fungus.

This chapter deals with the discovery of sorbicillactone A, as an illustrative example of the fruitful cooperation within BIOTECmarin--its isolation and chemical characterization, and its biological activities. Sorbicillactone A was isolated from a strain of Penicillium chrysogenum cultured from a sample of the Mediterranean sponge Ircinia fasciculata; it possesses a unique bicyclic lactone structure, seemingly derived from sorbicillin. Among the numerous known sorbicillin-derived structures, it is the first found to contain nitrogen and thus the first representative of a novel type of 'sorbicillin alkaloids', apparently originating from a likewise remarkable biosynthesis. Furthermore, the compound exhibits promising activities in several mammalian and viral test systems, in particular a highly selective cytostatic activity against murine leukemic lymphoblasts (L5178y) and the ability to protect human T cells against the cytopathic effects of HIV-1. These properties qualify sorbicillactone A or one of its derivatives for animal and (hopefully) also future therapeutic human trials.

Alkaloids↗

PubMed2003

Proliferative diabetic retinopathy is associated with a low level of the natural ocular anti-angiogenic agent pigment epithelium-derived factor (PEDF) in aqueous humor. a pilot study.

Retinopathy is the most common microvascular diabetes complication and represents a major threat to the eyesight. The aim of this study was to address the role of pro- and anti-angiogenic molecules in diabetic retinopathy in the aqueous humor of the eye. Aqueous humor was collected at cataract surgery from 19 diabetic patients and from 13 age- and sex-matched normoglycemic controls. Levels of pro-angiogenic vascular endothelial growth factor (VEGF) and angiogenic inhibitor pigment epithelium-derived factor (PEDF) were determined. Angiogenic activity of the aqueous humor was quantified by measuring its effect on the migration of capillary endothelial cells. In the aqueous fluid, VEGF levels were increased in diabetics (mean values: 501 vs. 367 pg/ml; p = 0.05), compared to controls. PEDF was found to be decreased in diabetics (mean values: 2080 vs. 5780 ng/ml; p = 0.04) compared to controls. In seven diabetic patients with proliferative retinopathy, the most profound finding was a significant decrease of the PEDF level (mean value: 237 ng/ml), whereas VEGF levels were comparable to diabetic patients without proliferation (mean value: 3153; p = 0.003). Angiogenic activity in samples of patients from the control group was generally inhibitory due to PEDF, and inhibition was blocked by neutralizing antibodies to PEDF. Likewise, in diabetics without proliferation, angiogenic activity was also blocked by antibodies to PEDF. We will demonstrate here that the level of the natural ocular anti-angiogenic agent PEDF is inversely associated with proliferative retinopathy. PEDF is an important negative regulator of angiogenic activity of aqueous humor. Our data may have implications for the development of novel regimens for diabetic retinopathy.

Aged↗

PubMed2002

[What is the cost of vascular operations? A prospective cost analysis of conventional and combined endovascular interventions].

Current and future legislation demand improved efficiency in the medical services. The aim of this study was to analyse the costs of vascular surgery in order to reveal potential ways of reducing expense. Taking into account the staff, equipment and operating theatre supplies, we analyzed 58 elective operations comprising 47 conventional and 11 combined endovascular procedures. The mean overall costs calculated for the different operations were: 5.269 DM for a transfemoral embolectomy (n = 3), 8.504 DM for a patchplasik of the profunda arteria (n = 8), 10.265 DM for a femoro-popliteal bypass with a prosthesis (n = 6)--13.180 DM with a vein (n = 2), 9.864 DM for conventional iliac artery reconstruction (n = 7)--iliac endovascular combined procedure (n = 4) 14.494 DM, 14.951 DM for a Y-prosthesis in case of stenosis (n = 3)--13.288 DM in case of infrarenal aortic aneurysm (IAA, n = 4), 11.954 DM for a tube prosthesis in case of IAA (n = 3), 23.571 DMY-stent prothesis for IAA (n = 5), 19.914 DM stent for a thoracic aneurysm (n = 2), 7.153 DM a carotid thrombendarterectomy (n = 6), 5.503 DM for varicosis surgery (n = 5). Because of the high cost of materials, the total outlay for combined endovascular procedures appeared to be high when compared to conventional vascular surgery. Substantial savings concerning the operation may only be achieved if facility structure and qualification of staff meets the particular requirements.

Adult↗

PubMed2001

Magnetoencephalography and stereopsis: rhythmic cortical activity in humans recorded over the parieto-occipital cortex.

We have studied human stereopsis by analysing magnetoencephalographic signals during the presentation of stereograms using frequency analysis. The study of synchronised firing of cortical neurones is a new way of understanding information processing in the brain and it is hypothesised that frequencies greater than 35 Hz are used for higher-order processing. We report the response of cortical neurones involved in stereopsis recorded from over the occipital and parietal cortices using a single channel axial superconducting quantum interference device neuromagnetometer. Our main result was increased cortical activity in the gamma-band at frequencies apparently related to stereopsis and the perception of depth. Our results are consistent with reports in the literature that suggest that frequencies above 40 Hz are involved in attention, pattern recognition and higher order visual activity.

Adult↗

PubMed2001

Non-toxic pyrrolizidine alkaloids from Eupatorium semialatum.

The leaves of Eupatorium semialatum were investigated for the occurrence of pyrrolizidine alkaloids. Although this type of alkaloids generally occurs in the Eupatorieae, only unusual non-toxic pyrrolizidines of the tussilagin type were identified. All compounds are methyl esters of the corresponding beta-amino acids.

Journal Article↗

PubMed2001

[Repeat rupture of covered rupture of non-anastomotic false aneurysm after femoropopliteal bypass].

For arterial reconstructions veins or alloplastic vascular prostheses are used. Nonanastomotic pseudoaneurysms of vascular protheses are a rare event. Breaks of the suture material, structural defects of the transplant fabric or degenerative modifications in the recipient vessel can cause nonanastomotic or anastomotic pseudoaneurysms. Such pseudoaneurysms are known from early clinical application of ePTFE grafts. In the case presented a nonanastomotic rupture of a ePTFE graft is described with partial repair of the rupture site by fibroblasts and connective tissue, which prevented bleeding.

Anastomosis, Surgical↗

PubMed2001

Isolation and characterization of glyoxal-arginine modifications.

5-(4,5-Dihydroxy-2-imino-1-imidazolidinyl)norvaline (1) was identified as the only product of the early reaction of arginine with glyoxal, which was slowly degraded to N(5)-[[(carboxymethyl)amino](imino)methyl]ornithine (3, N(7)-carboxymethylarginine). No other structures could be detected within a range of pH 4-8 and 20-50 degrees C in reaction conditions. The rates of formation for both products increased with pH and temperature. In equilibrium, the vincinal diol groups of 1 were 86% trans configured. The formation of 1 was reversible, as could be shown by cis-trans isomerization of the separated isomers and by regeneration of arginine in the presence of the alpha-dicarbonyl trapping reagents, o-phenylenediamine and aminoguanidine. Both 1 and 3 were converted to 5-(2-imino-5-oxo-1-imidazolidinyl)norvaline (2) only under strong acidic conditions.

Arginine↗

PubMed2001

Acute hemodynamic effects and angina improvement with enhanced external counterpulsation.

Enhanced external counterpulsation (EECP) is an effective noninvasive treatment for coronary artery disease. The mechanism of action is felt to be hemodynamic. The complex hemodynamic effects have been simply quantified by calculating a previously described effectiveness ratio (ER). The EECP Clinical Consortium, a clinical registry of 37 centers, prospectively enrolled 395 chronic stable angina patients (79 women, 316 men, mean age 66 years) to examine the relation of the ER to posttreatment improvement in Canadian Cardiovascular Society angina class (CCS). Women and the elderly underwent planned subgroup analysis. The ER was calculated during the first and last hours of a 35-hour course of EECP treatment. After EECP, CCS improved by at least 1 class in 88% of patients, 87% of men and 92% of women (p = NS), and in 89% of patients < or = 66 years and 88% of patients > 66 years old (p = NS). The initial and final ER were similar in patients with and without improvement in CCS. Significant first-hour ER differences were seen between men and women (0.96 +/- 0.03 vs 0.76 +/- 0.04, p<0.005), and between ages < or = 66 and > 66 years old (1.04 +/- 0.04 vs 0.81 +/- 0.03, p<0.0001). However, all subgroups responded equally well to EECP treatment. EECP is effective in improving CCS in chronic stable angina patients; it has comparable effects in men and women and across a broad range of ages. The hemodynamic effect of EECP (ER) does not predict improvement in CCS and may indicate that other factors, such as neurohormonal changes, may have a significant role in mediating the observed EECP benefits.

Adult↗

PubMed2000

[Domestic orchids].

Explore the source record for details and available documents.

Plants, Medicinal↗

PubMed2000

C-methyl-flavonoids from the leaf waxes of some Myrtaceae.

The thin waxy coatings on leaves of nine species of Callistemon, two of Melaleuca and one species of Metrosideros, have been studied for the occurrence of leaf surface flavonoids. The Callistemon species and Metrosideros robusta exhibit only C-methylated flavonoids, while O-methyl flavonoids were detected in Melaleuca huegelii. The new natural C-methyl flavonol, 5,7-dihydroxy-3,8,4'-trimethoxy-6-C-methylflavone, was isolated from Metrosideros robusta. The leaf wax of Callistemon coccineus contains the novel C-methylflavonoid, 5,4'-dihydroxy-8-C-methyl-7-methoxy flavanone.

Flavanones↗

PubMed2000

Anti-ICAM-1 blockade reduces postsinusoidal WBC adherence following cold ischemia and reperfusion, but does not improve early graft function in rat liver transplantation.

BACKGROUND/AIM: The present in vivo study investigated the impact of a monoclonal antibody directed against the intercellular adhesion molecule-1 (ICAM-1) on initial microvascular reperfusion injury after liver transplantation. METHODS: Orthotopic, syngeneic liver transplantation including arterial reconstruction was performed in male Lewis rats after 24 h graft storage in University of Wisconsin (UW) solution at 4 degrees C. Animals received either an anti-ICAM-1 antibody (n=7), an IgG1 control antibody (n=8) or saline only (n=7). Hepatic microvascular alterations during the initial 90 min of reperfusion were assessed using intravital fluorescence microscopy. Early graft dysfunction was determined by analysis of bile flow. RESULTS: After treatment with anti-ICAM-1 mAb, hepatic microvascular perfusion was found improved when compared with that of IgG1- and saline-treated controls. In addition, anti-ICAM-1 mAb effectively reduced the number of permanently adherent white blood cells in postsinusoidal venules (284.4+/-59.1 mm(-2) vs IgG1: 371.9+/-26.7 mm(-2) and saline: 431.8+/-46.4 mm(-2); p<0.05). In contrast, the number of stagnant white blood cells in sinusoids was higher (p<0.05) in liver grafts with blocked ICAM-1 (320.6+/-17.2 mm(-2)) compared with that of IgG1- (215.2+/-11.1 mm(-2)) and saline-treated controls (226.4+/-14.0 mm(-2)). Measurement of hepatic uptake of fluorescent-labeled latex particles did not reveal significant differences in phagocytic activity. Finally, bile flow also did not differ between the three groups studied. CONCLUSION: Together these results indicate that ICAM-1 is involved in the process that mediates white blood cells adherence in postsinusoidal venules, whereas in hepatic sinusoids other mechanisms apart from ICAM-1-mediated white blood cells adherence seem to be fundamental for posttransplant white blood cells accumulation. Our data further suggest that white blood cells adherence in postsinusoidal venules via ICAM-1 does not make a major contribution to the pathogenesis of early cold ischemia/reperfusion injury after liver transplantation.

Animals↗

PubMed2000

Use of clinical guidelines for treatment of anemia among hemodialysis patients.

Changing financial incentives have strongly influenced dosing patterns of recombinant human erythropoietin (rHuEPO) since its introduction in 1989. Although guidelines for prescribing rHuEPO exist, the extent to which they are adhered to is unknown. Using a retrospective cohort observational study design, the factors influencing the initial dosing of rHuEPO prescribed to 413 hemodialysis patients in 1994 were examined. Patient weight, the only recommended guideline, was not found to be a significant predictor of dosing of rHuEPO after controlling for selected patient demographic and clinical characteristics. The strongest predictor for initial rHuEPO dosing was hematocrit followed by White race (p < 0.05). Finally, each subsequent month was associated with a significantly larger initial rHuEPO dose, reflecting the general trend in increasing dose since 1991 (p < 0.001). In conclusion, despite the recent DOQI guidelines for treatment of anemia among persons with chronic renal failure, providers are not using patient weight as an independent criterion for determining dosing of rHuEPO.

Adolescent↗

PubMed2000

Treatment benefit in the enhanced external counterpulsation consortium.

The present study utilized a cohort of 2,289 consecutive patients enrolled in the Enhanced External Counterpulsation (EECP) Consortium to evaluate whether results of university studies showing EECP safety and effectiveness in treating angina can be generalized. EECP was found to be safe and well tolerated with a 4.0% rate of adverse experiences. Angina class improved in 74% of patients with limiting angina (Canadian Cardiovascular Society, CCS, functional class II-IV), with patients most impaired at baseline demonstrating the greatest improvement (39.5% of patients in CCS III and IV improved 2 or more classes). Efficacy was independent of provider setting or experience, women responded as well as men, and although younger patients demonstrated a greater likelihood of improvement, EECP was effective in patients ranging from 19 to 97 years. Extending the benefit of EECP treatment to a wider range of patients may be indicated based on these findings.

Adult↗

PubMed2000

[Results of lumbar and lumbosacral fusion: clinical and radiological correlations in 113 cases reviewed at 3.8 years].

PURPOSE OF THE STUDY: Spinal fusion requires the use of hardware for reduction and stabilization. We present the clinical and radiological behavior of a population of patients with lumbar and lumbosacral spinal fusion. MATERIALS AND METHODS: Between 1990 and 1992, 113 patients were operated for lumbar and lumbosacral fusion. Mean age of the population was 43 years and mean follow-up was 3.8 years. Most of the fusions were L4-S1 fusions. 56% of the patients had a previous surgery. Thirteen patients in the series were reoperated and analyzed separately. In the majority of the cases, the indication for surgery was back pain with or without leg pain. Diagnoses were: spondylolisthesis, discopathy, scoliosis, and pseudoarthrosis. The spine was fused and reduced using two lordotic rods. Peroperative and postoperative lordosis were calculated on X-rays. Clinical results were analyzed with the Beaujon-Lassale score. RESULTS: Mean improvement was significantly better for spondylolisthesis than for other pathologies (85.6% versus 77.1%). Returning to work was possible for 85.5% of those with improvement and was not possible for 69.8%. The gain achieved in lordosis at surgery was lost at last follow-up. The lordosis of the construct appeared to protect against the development of discopathies above and below the construct. Discopathis led to a poor score. The rate of non-union was 7.9%, the rate of repeated surgery 6.1% and the rate of hardware removal 23.8%. At last follow-up, improvement was achieved in 45.6% of the 13 patients of the series who had repeat surgery. DISCUSSION: The results in our series are similar to those reported by others. Lumbar lordosis is an important factor: if lost, more interbody fusions may be subsequently required. Diagnosis of non-union is difficult and reoperation is the only sure manner to prove it by applying distraction-compression manoeuvres on the screws. All non-unions presented were symptomatic; incidence in the series was thus probably higher. Non-union and reoperation with a longer fusion are perhaps correlated with insufficient elasticity in the osteosynthesis. Optimal rod elasticity is a factor which remains to be defined. CONCLUSION: Clinical results of lumbar and lumbosacral fusions are not unsatisfactory, but in our series almost one patient out of three had to be reoperated. One of the reasons for so many reoperations is certainly hardware rigidity. Hardware was not removed without testing the fusion as this is the only means of sure diagnosis of non-union. Reoperation should not be considered a failure in this difficult surgery of back pain which requires long-term surgical follow-up.

Adolescent↗