julilili42/papers huggingface dataset:
Heterogeneity of fish taste bud ultrastructure as demonstrated in the holosteans Amia calva and Lepisosteus oculatus
2000-09-29

Taste buds are the peripheral sensory organs of the gustatory system. They occur in all taxa of vertebrates and are pear–shaped intra–epithelial organs of about 80 μm height and 50 μm width. Taste buds mainly consist of specialized epithelial cells, which synapse at their bases and therefore are secondary sensory cells. Taste buds have been described based on studies of teleostean species, but it turned out that the ultrastructure of teleostean taste buds may differ between distinct systematic groups and that this description is not representative of those taste buds in other main taxa of fishes, such as selachians, holosteans and dipnoans. Furthermore, it is not known how variable the micromorphologies of non–teleostean taste buds are. For this reason the taste buds of two holosteans, Lepisosteus oculatus and Amia calva , were investigated and compared. While in both species the taste buds are of the same shapes and sizes, the cellular components of their sensory epithelia differ: in Lepisosteus taste buds comprise two types of elongated light cells and one type of dark cells. In contrast, Amia taste buds contain only one type of light, but two types of dark elongated cells. Afferent synapses are common in the buds of both species, efferent synapses occur only in Lepisosteus taste buds. These differences show that even in the small group of holostean fishes the taste buds are differently organized. Consequently, a representative type of fish taste buds does not exist.
Global existence for a non-local mean curvature flow as a limit of a parabolic-elliptic phase transition model
2000-09-30

We consider a free boundary problem where the velocity depends on the mean curvature and on some non-local term. This problem arises as the singular limit of a reaction-diffusion system which describes the microphase separation of diblock copolymers. The interface may present singularities in finite time. This leads us to consider weak solutions on an arbitrary time interval and to prove the global-in-time convergence of solutions of the reaction-diffusion system.
The d -Alanine Residues of Staphylococcus aureus Teichoic Acids Alter the Susceptibility to Vancomycin and the Activity of Autolytic Enzymes
2000-10-01

ABSTRACT Recently, Staphylococcus aureus strains with intermediate resistance to vancomycin, the antibiotic of last resort, have been described. Multiple changes in peptidoglycan turnover and structure contribute to the resistance phenotype. Here, we describe that structural changes of teichoic acids in the cell envelope have a considerable influence on the susceptibility to vancomycin and other glycopeptides. S. aureus cells lacking d -alanine esters in teichoic acids exhibited an at least threefold-increased sensitivity to glycopeptide antibiotics. Furthermore, the autolytic activity of the d -alanine mutant was reduced compared to the wild-type, and the mutant was more susceptible to the staphylolytic enzyme lysostaphin. Vancomycin inhibited autolysis at very high concentrations but neither in the wild-type nor in the mutant was the autolytic activity influenced in the range of the MIC. Mutant cells had a considerably higher capacity to bind vancomycin.
G‐protein mediated gating of inward‐rectifier K+ channels
2000-10-01

G‐protein regulated inward‐rectifier potassium channels (GIRK) are part of a superfamily of inward‐rectifier K + channels which includes seven family members. To date four GIRK subunits, designated GIRK1–4 (also designated K ir 3.1–4), have been identified in mammals, and GIRK5 has been found in Xenopus oocytes. GIRK channels exist in vivo both as homotetramers and heterotetramers. In contrast to the other mammalian GIRK family members, GIRK1 can not form functional channels by itself and has to assemble with GIRK2, 3 or 4. As the name implies, GIRK channels are modulated by G‐proteins; they are also modulated by phosphatidylinositol 4,5‐bisphosphate, intracellular sodium, ethanol and mechanical stretch. Recently a family of GTPase activating proteins known as regulators of G‐protein signaling were shown to be the missing link for the fast deactivation kinetics of GIRK channels in native cells, which contrast with the slow kinetics observed in heterologously expressed channels. GIRK1, 2 and 3 are highly abundant in brain, while GIRK4 has limited distribution. Here, GIRK1/2 seems to be the predominant heterotetramer. In general, neuronal GIRK channels are involved in the regulation of the excitability of neurons and may contribute to the resting potential. Interestingly, only the GIRK1 and 4 subunits are distributed in the atrial and sinoatrial node cells of the heart and are involved in the regulation of cardiac rate. Our main objective of this review is to assess the current understanding of the G‐protein modulation of GIRK channels and their physiological importance in mammals.
Characterization of Reutericyclin Produced by Lactobacillus reuteri LTH2584
2000-10-01

ABSTRACT Lactobacillus reuteri LTH2584 exhibits antimicrobial activity that can be attributed neither to bacteriocins nor to the production of reuterin or organic acids. We have purified the active compound, named reutericyclin, to homogeneity and characterized its antimicrobial activity. Reutericyclin exhibited a broad inhibitory spectrum including Lactobacillus spp., Bacillus subtilis , B. cereus , Enterococcus faecalis , Staphylococcus aureus , and Listeria innocua . It did not affect the growth of gram-negative bacteria; however, the growth of lipopolysaccharide mutant strains of Escherichia coli was inhibited. Reutericyclin exhibited a bactericidal mode of action against Lactobacillus sanfranciscensis , Staphylococcus aureus , and B. subtilis and triggered the lysis of cells of L. sanfranciscensis in a dose-dependent manner. Germination of spores of B. subtilis was inhibited, but the spores remained unaffected under conditions that do not permit germination. The fatty acid supply of the growth media had a strong effect on reutericyclin production and its distribution between producer cells and the culture supernatant. Reutericyclin was purified from cell extracts and culture supernatant of L. reuteri LTH2584 cultures grown in mMRS by solvent extraction, gel filtration, RP-C 8 chromatography, and anion-exchange chromatography, followed by rechromatography by reversed-phase high-pressure liquid chromatography. Reutericyclin was characterized as a negatively charged, highly hydrophobic molecule with a molecular mass of 349 Da. Structural characterization (A. Höltzel, M. G. Gänzle, G. J. Nicholson, W. P. Hammes, and G. Jung, Angew. Chem. Int. Ed. 39:2766–2768, 2000) revealed that reutericyclin is a novel tetramic acid derivative. The inhibitory activity of culture supernatant of L. reuteri LTH2584 corresponded to that of purified as well as synthetic reutericyclin.
Comparison between Plasma and Whole Blood Specimens for Detection of Aspergillus DNA by PCR
2000-10-01

ABSTRACT Ninety-six plasma and whole blood specimens from nine selected patients were analyzed for the presence of Aspergillus DNA. Nineteen specimens from three patients with proven aspergillosis were PCR positive in both materials, whereas an additional 22 were PCR positive in whole blood only. All 36 samples from six patients without signs of aspergillosis were negative in both assays. We conclude that although plasma and whole blood spiked with Aspergillus conidia showed an identical lower detection limit (10 CFU), the sensitivity of plasma PCR was lower than that of PCR performed on whole blood samples.
Induction of Apoptosis by Glyoxal in Human Embryonic Lung Epithelial Cell Line L132
2000-10-01

Oxidative stress has been suggested to play a central role in the pathogenesis of lung fibrosis and lung epithelial cell apoptosis is considered to be a key event during fibrogenesis. Studies from various laboratories have indicated that metabolic conditions may initiate oxidative stress, thereby contributing to epithelial cell death. This study was designed to test the hypothesis that glyoxal, an intermediate product in the glycation reaction leading to advanced glycation end products (AGEs), may induce lung epithelial cell apoptosis. We investigated the in vitro effects of glyoxal on fetal human lung epithelial L132 cells. Immunocytochemical analysis of paraffin-embedded cells and fluorescence-activated cell sorter analysis revealed a dose-dependent accumulation of the glycoxidation product (epsilon)N-carboxymethyllysine (CML) in all compartments of the cell. It has been shown that CML modification of proteins may serve as an indicator for oxidative stress. To examine the role of apoptosis in epithelial lung cells we investigated glyoxal-dependent changes in pro- and antiapoptotic mediators bax and activated caspase-3, and galectin-3 and bcl-2, respectively. Increasing concentrations of glyoxal (50 to 400 microM) induced an increase in the number of apoptotic cells. The apoptotic changes were confirmed by transmission electron microscopy. Immunocytochemical analysis of treated cells revealed the presence of other AGEs such as pentosidine as well as products of lipid peroxidation.
Phantom limb pain: cortical plasticity and novel therapeutic approaches
2000-10-01

Phantom limb pain is still a very frequent consequence of peripheral deafferentation or amputation of a limb. Recent findings from animal and neuroimaging studies suggest that phantom limb pain might be a central phenomenon, related to changes in the cortical, thalamic and spinal representation of the painful limb, and might be a type of somatosensory pain memory. Based on these assumptions, new treatment approaches focus on sensory discrimination training or motor cortex stimulation in an effort to influence cortical reorganization. Prevention of perpetuation of a somatosensory pain memory might also be possible through pharmacological agents such as N-methyl-D-aspartate antagonists and gamma-aminobutyric acid agonists, substances that have been shown to influence and prevent cortical reorganization.
Physiology of apoptosis
2000-10-01

Ion fluxes and volume changes of the whole cell as well as of organelles belong to the hallmarks of apoptosis; however, the molecular mechanism regulating these changes is only poorly characterized. Several ion channels in the plasma membrane, in particular the N-type K + channel, the chloride channel cystic fibrosis conductance regulator, and an outward rectifying chloride channel, as well as the mitochondrial permeability transition pore, have been implicated to be involved in signal transduction cascades regulating apoptosis. Furthermore, Bcl-2-like proteins have been suggested to function, at least in part, as ion channels, because they display some homology to bacterial pore-forming toxins. In contrast to the demonstration of the involvement of these different ion channels in apoptosis, the molecular consequences regulated by these ion channels, and finally triggering apoptosis, are almost completely unknown.
Molecular Characterization of Lantibiotic-synthesizing Enzyme EpiD Reveals a Function for Bacterial Dfp Proteins in Coenzyme A Biosynthesis
2000-10-01

The lantibiotic-synthesizing flavoprotein EpiD catalyzes the oxidative decarboxylation of peptidylcysteines to peptidyl-aminoenethiols. The sequence motif responsible for flavin coenzyme binding and enzyme activity is conserved in different proteins from all kingdoms of life. Dfp proteins of eubacteria and archaebacteria and salt tolerance proteins of yeasts and plants belong to this new family of flavoproteins. The enzymatic function of all these proteins was not known, but our experiments suggested that they catalyze a similar reaction like EpiD and/or may have similar substrates and are homododecameric flavoproteins. We demonstrate that the N-terminal domain of the Escherichia coli Dfp protein catalyzes the decarboxylation of (R)-4'-phospho-N-pantothenoylcysteine to 4'-phosphopantetheine. This reaction is essential for coenzyme A biosynthesis.
Polyamines as gating molecules of inward‐rectifier K+ channels
2000-10-01

Inward‐rectifier potassium (K ir ) channels comprise a superfamily of potassium (K + ) channels with unique structural and functional properties. Expressed in virtually all types of cells they are responsible for setting the resting membrane potential, controlling the excitation threshold and secreting K + ions. All K ir channels present an inwardly rectifying current–voltage relation, meaning that at any given driving force the inward flow of K + ions exceeds the outward flow for the opposite driving force. This inward‐rectification is due to a voltage‐dependent block of the channel pore by intracellular polyamines and magnesium. The present molecular–biophysical understanding of inward‐rectification and its physiological consequences is the topic of this review. In addition to polyamines, K ir channels are gated by intracellular protons, G‐proteins, ATP and phospholipids depending on the respective K ir subfamily as detailed in the following review articles.
KATP channels gated by intracellular nucleotides and phospholipids
2000-10-01

The K ATP channel is a heterooctamer composed of two different subunits, four inwardly rectifying K + channel subunits, either K ir 6.1 or K ir 6.2, and four sulfonylurea receptors (SUR), which belong to the family of ABC transporters. This unusual molecular architecture is related to the complex gating behaviour of these channels. Intracellular ATP inhibits K ATP channels by binding to the K ir 6.x subunits, whereas Mg‐ADP increases channel activity by a hydrolysis reaction at the SUR. This ATP/ADP dependence allows K ATP channels to link metabolism to excitability, which is important for many physiological functions, such as insulin secretion and cell protection during periods of ischemic stress. Recent work has uncovered a new class of regulatory molecules for K ATP channel gating. Membrane phospholipids such as phosphoinositol 4,5‐bisphosphate and phosphatidylinositiol 4‐monophosphate were found to interact with K ATP channels resulting in increased open probability and markedly reduced ATP sensitivity. The membrane concentration of these phospholipids is regulated by a set of enzymes comprising phospholipases, phospholipid phosphatases and phospholipid kinases providing a possible mechanism for control of cell excitability through signal transduction pathways that modulate activity of these enzymes. This review discusses the mechanisms and molecular determinants that underlie gating of K ATP channel by nucleotides and phospholipids and their physiological implications.
Suppression of Systemic, Intramuscular, and Subcutaneous Adipose Tissue Lipolysis by Insulin in Humans1
2000-10-01

In addition to sc and visceral fat deposits, muscle has been shown to contain relevant amounts of lipids whose breakdown is subject to hormonal regulation. The aim of the present study was to determine insulin dose-response characteristics of systemic, sc adipose tissue and muscle lipolysis in humans. We used a combination of isotopic (primed continuous infusion of [d5]glycerol) and microdialysis techniques (catheters placed in the anterior tibial muscle and sc abdominal adipose tissue) during a three-step hyperinsulinemic-euglycemic clamp (insulin infusion, 0.1, 0.25, 1.0 mU/kg x min) in 13 lean, healthy volunteers. The glycerol rate of appearance was used as the index for systemic lipolysis; interstitial glycerol concentrations were used as the index for muscle and sc adipose tissue lipolysis. The insulin concentrations resulting in a half-maximal suppression (EC50) of systemic lipolysis, adipose tissue, and muscle lipolysis were 51, 68, and 44 pmol/L, respectively (between one another, P < 0.001). For each compartment there were significant correlations between the EC50 and the insulin sensitivity index for glucose disposal (r > 0.67; P < 0.05). However, lipolysis (as percent of baseline) was similar during the first two insulin infusion steps, but was significantly lower in adipose (22+/-2%) than in muscle (53+/-4%; P < 0.001) during step 3. Although we have no direct measurement of interstitial insulin concentrations, we conclude that based on the EC50 values, muscle is more sensitive with respect to the net effect of circulating insulin (transendothelial transport plus intracellular action) on lipolysis than sc adipose tissue in terms of exerting its full suppression within the physiological insulin range. This could be important in muscle for switching from preferential utilization of free fatty acids to glucose in the postprandial state. Inadequate suppression of im lipolysis resulting in excessive local availability of free fatty acids may represent a novel mechanism contributing to the pathogenesis of impaired glucose disposal, i.e. insulin resistance, in muscle.
Role of hydrodynamic processes in the pathogenesis of peritumoral brain edema in meningiomas
2000-10-01

Object. In a prospective study, 28 patients with 32 intracranial meningiomas were examined to determine the role of hydrodynamic interaction between tumor and surrounding brain tissue in the pathogenesis of peritumoral brain edema. Methods. Gadolinium—diethylenetriamine pentaacetic acid (Gd-DPTA), an extracellular contrast agent used for routine clinical imaging, remains strictly extracellular without crossing an intact blood—brain barrier. Therefore, it is well suited for investigations of hydrodynamic extracellular mechanisms in the development of brain edema. Spin-echo T 1 -weighted magnetic resonance images were acquired before and after intravenous administration of 0.2 mmol/kg Gd-DPTA. Additional T 1 -weighted imaging was performed 0.6, 3.5, and 6.5 hours later. No significant Gd-DPTA diffused from tumor into peritumoral brain tissue in 12 meningiomas without surrounding brain edema. In contrast, in 17 of 20 meningiomas with surrounding edema, contrast agent in peritumoral brain tissue was detectable after 3.5 hours and 6.5 hours. In three of 20 meningiomas with minimum surrounding edema (&lt; 5 cm 3 ), contrast agent effusion was absent. After 3.5 hours and 6.5 hours strong correlations of edema volume and the maximum distance of contrast spread from the tumor margin into adjacent brain parenchyma (r = 0.84 and r = 0.87, respectively, p &lt; 0.0001) indicated faster effusion in larger areas of edema. Conclusions. The results of this study show that significant contrast agent effusion from the extracellular space of the tumor into the interstitium of the peritumoral brain tissue is only found in meningiomas with surrounding edema. This supports the hypothesis that hydrodynamic processes play an essential role in the pathogenesis of peritumoral brain edema in meningiomas.
Extracting regions of interest applying a local watershed transformation
2000-10-01

We present a new technique for extracting regions of interest (ROI) applying a local watershed transformation. The proposed strategy for computing catchment basins in a given region of interest is based on a rain-falling simulation. Unlike the standard watershed algorithms, which flood the complete (gradient magnitude of an) image, the proposed approach allows us to perform this task locally. Thus, a controlled region growth is performed, saving time and reducing the memory requirement especially when applied on volume data. A second problem arising from the standard watershed transformation is the over-segmented result and the lack of sound criteria for merging the computed basins. For overcoming this drawback, we present a basin-merging strategy introducing four criteria for merging adjacent basins. The threshold values applied in this strategy are derived from the user input and match rather the attributes of the selected object than of all objects in the image. In doing so, the user is not required to adjust abstract numbers, but to simply select a coarse region of interest. Moreover, the proposed algorithm is not limited to the 2D case. As we show in this work, it is suitable for volume data processing as well. Finally, we present the results of applying the proposed approach on several example images and volume data sets.
Normalization of elevated CD4?/CD8? (double-negative) T cells after thymectomy parallels clinical remission in myasthenia gravis associated with thymic hyperplasia but not thymoma
2000-10-01

T-cell-dependent B-cell help is likely to be of major importance in the pathogenesis of myasthenia gravis, but mechanisms provoking a pathological anti-acetylcholine receptor (AChR) response are poorly understood. We report on the dysregulation of recently identified CD4-/CD8- (double-negative) T cells (DN T cells), which have been shown to participate in immunoregulation and antibody augmentation. Compared with healthy controls, significantly increased frequencies of DN T cells were found in the blood of myasthenia gravis patients with lymphofollicular hyperplasia. After thymectomy, however, normalization in the number of these cells was seen in parallel with clinical improvement and reduction in anti-AChR antibody titers. The effect of thymectomy was observed irrespective of adjuvant treatment and held true for up to 4 years of follow-up. In marked contrast, frequencies similar to control values were found in myasthenia gravis patients with thymoma, with thymectomy having no further reducing effect. These data indicate that CD4-/CD8- T cells not only participate in the pathogenesis of myasthenia gravis but also correlate with disease activity and histological findings.
Significance of serum protein S100 levels in screening for melanoma metastasis: does protein S100 enable early detection of melanoma recurrence?
2000-10-01

A number of recent reports suggest serum protein S100 as a prognostic parameter in patients with metastatic melanoma. In the present study, serum protein S100 was investigated as a tumour marker for screening for melanoma metastasis in patients attending regular follow-up examinations. During the period from September 1997 to December 1998, serum protein S100 levels were measured by an immunoluminometric assay in 411 consecutive high risk melanoma patients (666 samples) and in 120 control subjects. Melanoma patients with resected primary tumours with a tumour thickness of 1.5 mm or more with resected metastasis were included in the study. Overall, 41 of the 411 patients developed metastasis during the period of observation. According to the distribution of protein S100 levels, the following different cut-off values were examined: 0.08 μg/l (95 percentile of the control group) and 0.13 μg/l (95 percentile of the group of melanoma patients without metastasis). The test efficiency for protein S100 as a diagnostic test for the detection of metastasis was highest for the cut-off value of 0.13 μg/l. In eight of the 41 patients (19.5%), elevation of protein S100 was the first sign of recurrence. Of the 41 patients with metastatic disease, 13 had elevated protein S100, giving a sensitivity of 0.32. The specificity for the detection of metastasis was 0.96. In eight of the 14 patients (57%) who developed distant metastasis, elevated S100 values were the first sign of tumour progression. In conclusion, determination of serum protein S100 levels enables earlier detection of distant metastasis in patients at high risk for metastasis. The impact on survival time needs to be investigated in follow-up studies.