julilili42/papers huggingface dataset:
Apoptosis in yeast – a monocellular organism exhibits altruistic behaviour
2000-05-01

Apoptosis is a highly regulated form of programmed cell death crucial for life and health in metazoan animals. Apoptosis is defined by a set of cytological alterations. The recent discovery of these markers in yeast indicates the presence of the basic mechanisms of apoptosis already in unicellular eukaryotes. Oxygen radicals regulate both mammalian and yeast apoptosis. We suggest that apoptosis originated in unicellular organisms as an altruistic response to severe oxidative damage. Later, cells developed mechanisms to purposely produce reactive oxygen species as a regulator of apoptosis. Yeast may become an important model to investigate the conserved steps of apoptosis.
Identification of the Novobiocin Biosynthetic Gene Cluster of Streptomyces spheroides NCIB 11891
2000-05-01

ABSTRACT The novobiocin biosynthetic gene cluster from Streptomyces spheroides NCIB 11891 was cloned by using homologous deoxynucleoside diphosphate (dNDP)-glucose 4,6-dehydratase gene fragments as probes. Double-stranded sequencing of 25.6 kb revealed the presence of 23 putative open reading frames (ORFs), including the gene for novobiocin resistance, gyrB r , and at least 11 further ORFs to which a possible role in novobiocin biosynthesis could be assigned. An insertional inactivation experiment with a dNDP-glucose 4,6-dehydratase fragment resulted in abolishment of novobiocin production, since biosynthesis of the deoxysugar moiety of novobiocin was blocked. Heterologous expression of a key enzyme of novobiocin biosynthesis, i.e., novobiocic acid synthetase, in Streptomyces lividans TK24 further confirmed the involvement of the analyzed genes in the biosynthesis of the antibiotic.
Ectopic Expression of the Neuropeptide Pigment-Dispersing Factor Alters Behavioral Rhythms inDrosophila melanogaster
2000-05-01

To study the function of the neuropeptide pigment-dispersing factor (PDF) in the circadian system of Drosophila , we misexpressed the pdf gene from the grasshopper Romalea in the CNS of Drosophila and investigated the effect of this on behavioral rhythmicity. pdf was either ectopically expressed in different numbers of neurons in the brain or the thoracical nervous system or overexpressed in the pacemaker neurons alone. We found severe alterations in the activity and eclosion rhythm of several but not all lines with ectopic pdf expression. Only ectopic pdf expression in neurons that projected into the dorsal central brain severely influenced activity rhythms. Therefore, we conclude that PDF acts as a neuromodulator in the dorsal central brain that is involved in the rhythmic control of behavior. Overexpression of pdf in the pacemaker neurons alone or in the other neurons that express the clock genes period ( per ) and timeless ( tim ) did not disturb the activity rhythm. Such flies still showed a rhythm in PDF accumulation in the central brain terminals. This rhythm was absent in the terminals of neurons that expressed PDF ectopically. Probably, PDF is rhythmically processed, transported, or secreted in neurons expressing per and tim , and additional PDF expression in these cells does not influence this rhythmic process. In neurons lacking per and tim , PDF appears to be continuously processed, leading to a constant PDF secretion at their nerve terminals. This may lead to conflicting signals in the rhythmic output pathway and result in a severely altered rhythmic behavior.
Blood Group A Antigen Is a Coreceptor in Plasmodium falciparum Rosetting
2000-05-01

ABSTRACT The malaria parasite Plasmodium falciparum utilizes molecules present on the surface of uninfected red blood cells (RBC) for rosette formation, and a dependency on ABO antigens has been previously shown. In this study, the antirosetting effect of immune sera was related to the blood group of the infected human host. Sera from malaria-immune blood group A (or B) individuals were less prone to disrupt rosettes from clinical isolates of blood group A (or B) patients than to disrupt rosettes from isolates of blood group O patients. All fresh clinical isolates and laboratory strains exhibited distinct ABO blood group preferences, indicating that utilization of blood group antigens is a general feature of P. falciparum rosetting. Soluble A antigen strongly inhibited rosette formation when the parasite was cultivated in A RBC, while inhibition by glycosaminoglycans decreased. Furthermore, a soluble A antigen conjugate bound to the cell surface of parasitized RBC. Selective enzymatic digestion of blood group A antigen from the uninfected RBC surfaces totally abolished the preference of the parasite to form rosettes with these RBC, but rosettes could still form. Altogether, present data suggest an important role for A and B antigens as coreceptors in P. falciparum rosetting.
Topical application of St John’s wort (Hypericum perforatum L.) and of its metabolite hyperforin inhibits the allostimulatory capacity of epidermal cells
2000-05-01

St John's wort (Hypericum perforatum) is a traditional herbal medicine that is used for the topical treatment of superficial wounds, burns and dermatitis. The characteristic metabolites of St John's wort are the photodynamic active plant pigment hypericin and the phloroglucin-derivative hyperforin. To date, no studies on immunomodulatory properties of topical preparations of St John's wort have been performed. Here, we investigated the alloantigen presenting function of human epidermal cells (EC) exposed to Hypericum ointment in vivo in a mixed EC lymphocyte reaction (MECLR). The effect of Hypericum ointment was compared with the immunosuppressive effect of solar-simulated radiation (SSR). Subsequently, we tested purified hyperforin in vivo and in vitro in a MECLR to evaluate its possible contribution to the effect of the Hypericum ointment. Furthermore, we assessed the effect of hyperforin on the proliferation of peripheral blood mononuclear cells (PBMC) in vitro. Compared with untreated skin, treatment with Hypericum ointment resulted in a significant suppression of the MECLR (P </= 0.001) that was similar to the effect of SSR. The combination of Hypericum ointment plus SSR was not significantly different from either treatment alone. EC isolated from skin treated with the hyperforin containing ointment also showed a reduced capacity to stimulate the proliferation of allogeneic T cells (P </= 0.001). Similarly, in vitro incubation of EC with hyperforin suppressed the proliferation of alloreactive T cells (P </= 0.001). Furthermore, hyperforin inhibited the proliferation of PBMC in a dose-dependent manner, without displaying pronounced toxic effects as determined by Trypan blue staining. The results demonstrate an inhibitory effect of Hypericum extract and of its metabolite hyperforin on the MECLR and on the proliferation of T lymphocytes that may provide a rationale for the traditional treatment of inflammatory skin disorders with Hypericum extracts.
Differential Diagenesis of Rhythmic Limestone Alternations Supported by Palynological Evidence
2000-05-01

Alternating cemented and uncemented, fine-grained layers from Pliocene periplatform carbonates of the Great Bahama Bank have fundamentally different diagenetic features. The cemented layers consist predominantly of microspar, interpreted as an early marine, shallow-burial cement. The intercalated, uncemented, softer layers are devoid of microspar cement and exhibit signs of mechanical compac-tion. Precursor sediments of both cemented and uncemented layers apparently consisted largely of aragonite needles. The needles in the compacted layers show signs of dissolution, suggesting that the calcium carbonate required for cementation of the uncompacted layers was provided by aragonite dissolution within the compacted layers. The lack of compaction in the cemented layers shows that cementation, and hence aragonite dissolution in the adjacent compacted layers, took place in the shallow-burial realm. The dissolved carbonate was trans-ported by diffusion to adjacent layers and reprecipitated as calcite cement, thereby preventing significant compaction of these layers. These processes are not yet complete in the material examined, and some aragonite remains in the compacted layers. The sedimentary composition of the two rock types (compacted and uncompacted) is similar, indicating a similar precursor sediment for both. Between 1.5 and 7 times the concentration of palynomorphs oc-curs in the compacted layers, apparently the result of passive diage-netic enrichment. Although the trigger for diagenetic differentiation has not been determined, the pure limestone succession studied here appears to serve as a clay-free analog to limestone–marl alternations.
A preliminary study of spatial distribution and mating system of pygmy mouse lemurs (Microcebus cf myoxinus)
2000-05-01

According to current hypotheses on the evolution of life history traits and social systems of Malagasy lemurs, nocturnality is associated with a solitary lifestyle and a polygynous or promiscuous mating system. Recent studies, however, have indicated that this may not be true of all lemurs. The goal of this study was to investigate the sociality and the mating system of pygmy mouse lemurs (Microcebus cf myoxinus), which are the smallest known primates, and which retain characteristics of the most primitive primates. I compared my findings with data on the sympatric Microcebus murinus and Cheirogaleus medius. Observational, morphometric and spatial distribution data were obtained by a radiotracking study in 1994, and from a capture-recapture study conducted during 1995/96. Pygmy mouse lemurs usually slept alone in a tangle of vegetation. During the mating season, sleeping sites of males were distributed over a much broader area than were female sites, indicating that male home ranges are larger than those of females. The home ranges of males overlapped during the mating season, and males occasionally roamed over long distances during a single night. Pygmy mouse lemurs forage primarily alone. Analysis of estrus stages indicate that female cycles are unsynchronized during the mating season. There was a lack of sexual dimorphism in body size but not in body mass. Males were heavier than females during the reproductive season but lighter than females the rest of the year. Testes of males varied in size seasonally and enlarged significantly during the mating season. The presence of a vaginal sperm plug in a female indicated the importance of preventing additional matings in this species. Thus pygmy mouse lemurs follow the predictions derived from sexual selection theory for multi-male mating systems with promiscuous matings and male sperm competition.
Intestinal ultrasonography in children and young adults: bowel wall thickness is age dependent.
2000-05-01

The purpose of this study was to investigate bowel wall thickness in children, adolescents, and young adults as measured by ultrasonography. Ultrasonographic evaluation of the small bowel and the colon was performed in 128 subjects (age range, 3 days to 40 years). Bowel wall thickness increased significantly (P < 0.0001) increased with age, reaching a maximum colon wall thickness of 2.0 mm at the age range of 20 to 29 years. In the ileum, maximum wall thickness reached 1.5 mm at the age range of 10 to 14 years. The findings emphasize the need for age-specific normal values for bowel wall thickness measured by ultrasonography.
Dynamic MR imaging of liver metastases with Gd-EOB-DTPA
2000-05-01

Purpose: To assess liver and lesion enhancements by dynamic MR imaging after bolus injection of the hepatobiliary contrast agent gadolinium ethoxybenzyldiethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) in patients with liver metastases and to compare the effect of different doses. Material and Methods: A randomized double-blinded trial with doses of 12.5, 25 and 50 μmol/kg Gd-EOB-DTPA was performed in 35 patients with liver metastases. Liver enhancement, tumor enhancement and liver lesion contrast-to-noise (C/N) ratios were calculated from breath-hold gradient echo images (100/5/80°) recorded precontrast and at different times up to 10 min postcontrast. Results: Normal liver showed a characteristic enhancement pattern, with a rapid enhancement in the first 45 s postcontrast and a slight but significant further increase up to 600 s. The initial enhancement in the lesions was also pronounced, but the enhancement was slightly decreased after 240 s postcontrast. At dose levels of 12.5 and 25 μmol/kg Gd-EOB-DTPA, C/N ratios significantly increased compared to baseline from 90 to 600 s. Postcontrast C/N-values obtained using 50 μmol/kg Gd-EOB-DTPA were not significantly increased, except for the examinations 480 s postcontrast. Conclusion: In liver metastases, C/N ratios obtained with doses of 12.5 and 25 μmol/kg Gd-EOB-DTPA were slightly superior to 50 μmol/kg Gd-EOB-DTPA. This finding is probably due to a more pronounced extracellular effect of the contrast medium at higher doses.
A novel hyperglycaemic clamp for characterization of islet function in humans: assessment of three different secretagogues, maximal insulin response and reproducibility
2000-05-01

Background Characterization of beta‐cell function in humans is essential for identifying genetic defects involved in abnormal insulin secretion and the pathogenesis of type 2 diabetes. Materials and methods We designed a novel test assessing plasma insulin and C‐peptide in response to 3 different secretagogues. Seven lean, healthy volunteers twice underwent a 200 min hyperglycaemic clamp (10 mmol L −1 ) with administration of GLP‐1 (1.5 pmol . kg −1 . min −1 ) starting at 120 min and an arginine bolus at 180 min. We determined glucose‐induced first and second‐phase insulin secretion, GLP‐1‐stimulated insulin secretion, arginine‐stimulated insulin response (increase above prestimulus, ΔI arg ) and the maximal, i.e. highest absolute, insulin concentration (I max ). Insulin sensitivity was assessed during second‐phase hyperglycaemia. On a third occasion 6 subjects additionally received an arginine bolus at &gt; 25 m m blood glucose, a test hitherto claimed to provoke maximal insulin secretion. Results Insulin levels increased from 46 ± 11 p m to 566 ± 202 p m at 120 min, to 5104 ± 1179 p m at 180 min and to maximally 8361 ± 1368 p m after arginine (all P &lt; 0.001). The within subject coefficients of variation of the different secretion parameters ranged from 10 ± 3% to 16 ± 6%. Except for second‐phase which failed to correlate significantly with ΔI arg ( r = 0.52, P = 0.23) and I max ( r = 0.75, P = 0.053) all phases of insulin secretion correlated with one another. The insulin concentration after the arginine bolus at &gt; 25 m m glucose ( n = 6) was 2773 ± 855 p m vs. 7562 ± 1168 p m for I max ( P = 0.003). Conclusion This novel insulin secretion test elicits a distinct pattern of plasma insulin concentrations in response to the secretagogues glucose, GLP‐1 and arginine and is highly reproducible and can be used for differential characterization of islet function.
Early Detection ofAspergillusInfection after Allogeneic Stem Cell Transplantation by Polymerase Chain Reaction Screening
2000-05-01

Invasive aspergillosis (IA) has become a major cause of mortality in patients after allogeneic stem cell transplantation. To assess the potential of prospective polymerase chain reaction (PCR) screening for early diagnosis of IA, 84 recipients of an allogeneic stem cell transplant were analyzed with the investigators blinded to clinical and microbiologic data. Of 1193 blood samples analyzed, 169 (14.2%) were positive by PCR. In patients with newly diagnosed IA (n=7), PCR positivity preceded the first clinical signs by a median of 2 days (range, 1-23 days) and preceded clinical diagnosis of IA by a median of 9 days (range, 2-34 days). Pretransplantation IA (relative risk [RR], 2.37), acute graft-versus-host disease (RR, 2.75), and corticosteroid treatment (RR, 6.5) were associated with PCR positivity. The PCR assay revealed a sensitivity of 100% (95% confidence interval [CI], 48%-100%) and a specificity of 65% (95% CI, 53%-75%). None of the PCR-negative patients developed IA during the study period. Thus, prospective PCR screening allows for identification of patients at high risk for subsequent onset of IA.
Activation of Group II Metabotropic Glutamate Receptors Inhibits Synaptic Excitation of the Substantia Nigra Pars Reticulata
2000-05-01

Loss of nigrostriatal dopaminergic neurons in Parkinson's disease (PD) leads to increased activity of glutamatergic neurons in the subthalamic nucleus (STN). Recent studies reveal that the resultant increase in STN-induced excitation of basal ganglia output nuclei is responsible for the disabling motor impairment characteristic of PD. On the basis of this, it is possible that any manipulation that reduces activity at excitatory STN synapses onto basal ganglia output nuclei could be useful in the treatment of PD. We now report that group II metabotropic glutamate receptors (mGluRs) are presynaptically localized on STN terminals and that activation of these receptors inhibits excitatory transmission at STN synapses. In agreement with the hypothesis that this could provide a therapeutic benefit in PD, a selective agonist of group II mGluRs induces a dramatic reversal of catalepsy in a rat model of PD. These results raise the exciting possibility that selective agonists of group II mGluRs could provide an entirely new approach to the treatment of PD. These novel therapeutic agents would provide a noninvasive pharmacological treatment that does not involve the manipulation of dopaminergic systems, thus avoiding the problems associated with current therapies.
Identification and substrate specificity of a ferrichrome-type siderophore transporter (Arn1p) in Saccharomyces cerevisiae
2000-05-01

Genes encoding transporters for heterologous siderophores have been identified in Saccharomyces cerevisiae, of which SIT1, TAF1, and ENB1 encode the transporters for ferrioxamines, ferric triacetylfusarinine C and ferric enterobactin, respectively. In the present communication we have shown that a further gene encoding a member of the major facilitator superfamily, ARN1 (YHL040c), is involved in the transport of a specific class of ferrichromes, possessing anhydromevalonyl residues linked to N(delta)-ornithine (ARN). Ferrirubin and ferrirhodin, which both are produced by filamentous fungi, are the most common representatives of this class of ferrichromes. A strain possessing a disruption in the ARN1 gene was unable to transport ferrirubin, ferrirhodin and also ferrichrome A, indicating that the encoded transporter recognizes anhydromevalonyl and the structurally-related methylglutaconyl side-chains surrounding the iron center. Ferrichromes possessing short-chain ornithine-N(delta)-acetyl residues such as ferrichrome, ferricrocin and ferrichrysin, were excluded by the Arn1 transporter. Substitution of the iron-surrounding N-acyl chains of ferrichromes by propionyl residues had no effect, whereas substitution by butyryl residues led to recognition by the Arn1 transporter. This would indicate that a chain length of four C-atoms is sufficient to allow binding. Using different asperchromes (B1, D1) we also found that a minimal number of two anhydromevalonyl residues is sufficient for recognition by Arn1p. Contrary to the iron-surrounding N-acyl residues, the peptide backbone of ferrichromes was not an important determinant for the Arn1 transporter.
A Schläfli differential formula for simplices in semi-riemannian hyperquadrics, Gauss-Bonnet formulas for simplices in the de Sitter sphere and the dual volume of a hyperbolic simplex
2000-05-01

In this paper we prove a Schläfli differential formula for the volume of simplices in central unit hyperquadrics of semi-Euclidean space R n+1 q .Then we apply this result to obtain Gauss-Bonnet formulas for simplices with riemannian faces in the de Sitter sphere, and to generalize a formula of L. Santaló relating the volume of a hyperbolic simplex with the measure of the set of hyperbolic hyperplanes intersecting it.
Three-Dimensional Computer Morphometry of the Maxilla and Face in Infants with Pierre Robin Sequence-A Comparative Study
2000-05-01

Objective To analyze the morphology of the maxillary crest in infants with Pierre Robin sequence using an anthropometric coordinate system and to compare the data with those of healthy infants. Setting The study was performed at a craniofacial center servicing a large geographic area. Participants The study involved eight infants aged 1–28 days (average, 7 days) with an established diagnosis of Pierre Robin sequence and six healthy infants aged 1–43 days (average, 22 days). Main outcome Measures Physical models of the maxilla and face obtained by alginate replication were analyzed by computer morphometry yielding the three-dimensional topology of the maxillary crest. Results The maxillary crest of children with Pierre Robin sequence shows an increased inclination relative to the transverse plane (30 ± 3.9 degrees) as compared with that of healthy infants (20 ± 2.9 degrees). The maxillary crest of the patients is shortened in the sagittal direction by comparison with healthy controls. Conclusions The increased inclination of the maxilla in infants with Pierre Robin sequence may aggravate the retroposition of the mandible and may thus be a pathogenetic factor contributing to the severe respiratory problems.
A preliminary study of spatial distribution and mating system of pygmy mouse lemurs (Microcebus cf myoxinus)
2000-05-01

According to current hypotheses on the evolution of life history traits and social systems of Malagasy lemurs, nocturnality is associated with a solitary lifestyle and a polygynous or promiscuous mating system. Recent studies, however, have indicated that this may not be true of all lemurs. The goal of this study was to investigate the sociality and the mating system of pygmy mouse lemurs (Microcebus cf myoxinus), which are the smallest known primates, and which retain characteristics of the most primitive primates. I compared my findings with data on the sympatric Microcebus murinus and Cheirogaleus medius. Observational, morphometric and spatial distribution data were obtained by a radiotracking study in 1994, and from a capture–recapture study conducted during 1995/96. Pygmy mouse lemurs usually slept alone in a tangle of vegetation. During the mating season, sleeping sites of males were distributed over a much broader area than were female sites, indicating that male home ranges are larger than those of females. The home ranges of males overlapped during the mating season, and males occasionally roamed over long distances during a single night. Pygmy mouse lemurs forage primarily alone. Analysis of estrus stages indicate that female cycles are unsynchronized during the mating season. There was a lack of sexual dimorphism in body size but not in body mass. Males were heavier than females during the reproductive season but lighter than females the rest of the year. Testes of males varied in size seasonally and enlarged significantly during the mating season. The presence of a vaginal sperm plug in a female indicated the importance of preventing additional matings in this species. Thus pygmy mouse lemurs follow the predictions derived from sexual selection theory for multi-male mating systems with promiscuous matings and male sperm competition. Am. J. Primatol. 51:41–60, 2000. © 2000 Wiley-Liss, Inc.