Biregular classification of Fano 3-folds and Fano manifolds of coindex 3

The Fano 3-folds and their higher dimensional analogues are classified over an arbitrary field k [unk] C by applying the theory of vector bundles (in the case B(2) = 1) and the theory of extremal rays (in the case B(2) >/= 2). An n-dimensional smooth projective variety X over k is a Fano manifold if its first Chern class c(1)(X) epsilon H(2)(X, Z) is positive in the sense of Kodaira [Kodaira, K. (1954) Ann. Math. 60, 28-48] (or ample). If n = 3 and c(1)(X) generates H(2)(X, Z), then either (i) X is a complete intersection in a Grassmann variety G with respect to a homogeneous vector bundle E on G: the rank of E is equal to codim(G)X and X is isomorphic to the zero locus of a global section of E, (ii) X is a linear section of a 10-dimensional spinor variety X(12) (10) [unk] P(k) (15), or (iii) X is isomorphic to a double cover of P(k) (3), a 3-dimensional quadric Q(k) (3), or a quintic del Pezzo 3-fold V(5) [unk] P(k) (6). If n = 4 and c(1)(X) is divisible by 2, then X [unk] C is isomorphic to (a) a complete intersection in a homogeneous space or its double cover, (b) a product of P(1) and a Fano 3-fold, (c) the blow-up of Q(4) [unk] P(5) along a line or along a conic, or (d) a P(1)-bundle compactifying a line bundle on P(3) or on Q(3) [unk] P(4).     

Mode of action of neuropeptides from the adipokinetic hormone family

Neuropeptides of the adipokinetic hormone (AKH) family regulate inter alia mobilisation of various substrates from stores in the fat body of insects during episodes of flight. How is this achieved? In insects which exclusively oxidise carbohydrates for flight (cockroaches), or which oxidise carbohydrates in conjunction with lipids (locusts) or proline (a number of beetles), the endogenous AKHs bind to a G(q)-protein-coupled receptor, activate a phospholipase C and the resulting inositol trisphosphate releases Ca(2+) from internal stores. In addition, influx of extracellular Ca(2+) is increased and, via a kinase cascade, glycogen phosphorylase is activated, glucose-1-phosphate produced, and transformed to trehalose, which is released into the haemolymph. In locusts, additionally, adenylate cyclase is activated and cyclic AMP is synthesised. In insects which use lipids for sustained flight (locust, tobacco hornworm moth) or proline for flight (certain beetles), adenylate cyclase is activated after the AKHs bind to their respective G(s)-protein-coupled receptor. The resulting cyclic AMP, together with the messengers intra- and extracellular Ca(2+), activate a triacylglycerol lipase, which results in the production of 1,2 diacylglycerols (in locusts, moths) or (hypothetically) free fatty acids (fruit beetle).     

Tubular presentations pi of subsets of manifolds

In this note the Weierstrass integral J is taken as L, the Riemann integral of length. Here M(n), n > 1, is a compact, connected manifold of class C(infinity) with a positive definite Riemann structure. Presentations (phi, U(phi)) in M(n) and geodesics (with the aid of the Euler-Riemann equations) are defined in Morse, M. (1976) "Global variational analysis: Weierstrass integrals on a Riemannian Manifold," Mathematical Notes (Princeton University Press, Princeton, NJ). Christoffel terminology is not suitable for our purposes. Conjugate points on a geodesic need a definition that does not distinguish between simple and nonsimple geodesics. Tubular presentations pi of an open neighborhood of a geodesic lead to such a definition. These presentations are locally biunique and "compatible" with the earlier biunique presentations in M(n). We shall use a presentation pi in proving Theorem A below. Theorem A is essential in computing the Fréchet numbers of product manifolds as we shall show in a later paper.     

Amelioration of the diagnostic possibilities of irrigraphy by a new index, I0

Irrigraphie (segmental impedance plethysmography) is a reliable non invasive method for the positive and topographic diagnosis of arterial occlusive disease and for its prognosis (5, 8, 9, 12, 13). The method is based on pulse volume recordings at six different positions of the leg (from 1 = proximal to 6 = distal). The amplitude of the signal is related to heart rate and to the basic impedance of the segment of the leg. The diagnosis of aorto-iliac disease is proposed when the upper extremity index (I1MS) over the lower extremity proximal index (I1) ratio (ITA) is increased (greater than 1.4), or when the I1 value is lower than 1.9. The diagnosis of femoro-popliteal disease is proposed when there is a significant drop between I1 and the above knee index I3. However in a recent study we found that I1 value drops when there is a severe femoro-popliteal lesion. In this case, irrigraphie proposes erroneously the diagnosis of aorto-iliac and femoro-popliteal diseases. In order to improve the method, we thought that a new electrod position (I0) over the iliac region would give to irrigraphie a more reliable topography diagnosis possibility. In this study 32 patients were analysed with angiography and irrigraphy, and divided into 3 groups: group I = isolated iliac disease (19); group F = isolated femoral diseases (22); group IF = ilio-femoral diseases (12). We observe from the ROC analysis, that I0 has a sensitivity of 84% and a specificity of 86%, when the iliac lesions are isolated whereas I1 and ITA give a lower specificity (52%). However, when aorto-iliac lesions are combined with femoro-popliteal lesions the irrigraphie is a little less sensitive (71%). In conclusion I0 index is more reliable for the topographical diagnosis of obstructive disease of the iliac artery than I1 index and we suggest to replace I1 by I0 whenever it is possible.     

Theory of the dependence of population levels on environmental history for semelparous species with short reproductive seasons

A population that is strongly self-regulating through density-dependent effects is expected to be such that, if many generations have elapsed since its establishment, its present size should not be sensitive to its initial size but should instead be determined by the history of the variables that describe the influence of the environment on fecundity, mortality, and dispersal. Here we discuss the dependence of abundance on environmental history for a semelparous population in which reproduction is synchronous. It is assumed that at each instant t: (i) the rate of loss of members of age a by mortality and dispersal is given by a function rho of t, a, and the present number x = x(a,t) of such members; and (ii) the number x(0,t) of members born in the population is given by a function F of t and the number of x(a(f),t) at a specified age a(f) of fecundity. It is further assumed that the functions rho and F have the forms rho(x,a,t) = pi(1)(a,t)x + pi(2)(a,t)x(2) and F(x(a(f),t),t) = nu(t)x(a(f),t). For such a population, a change in the environment is significant only if it results in a change in nu(t) pi(1)(a,t), or pi(2)(a,t), and, hence, the history of the environment up to time t is described by giving nu(tau), pi(1)(a,tau), and pi(2)(a,tau) for each tau 相似文献   

Important role of carotid chemoreceptor afferents in control of breathing of adult and neonatal mammals

This review provides a summary and prospective on the importance of carotid/peripheral chemoreceptors to the control of breathing during physiologic conditions. For several days after carotid body denervation (CBD), adult mammals hypoventilate (+10 mmHg increase in Pa(CO(2))) at rest and during exercise and CO(2) sensitivity is attenuated by about 60%. In addition, if the rostral ventrolateral medulla is cooled during NREM sleep after CBD, a sustained apnea is observed. Eventually, days or weeks after CBD, a peripheral ventilatory chemoreflex redevelops and there is a normalization of breathing (rest and exercise) and CO(2) sensitivity. The site (s) of the regained chemosensitivity has not been established. This plasticity/redundancy after CBD appears greater in neonates than in adult mammals. These data suggest the carotid and other peripheral chemoreceptors provide an important excitatory input to medullary respiratory neurons that is essential for breathing when wakeful stimuli and central chemoreceptors are absent.     

Electrophysiological study of the action of angiotensin II on the rat myometrium.

Angiotensin II (A II) produces a contraction of visceral and vascular smooth muscles of different species. The accompanying electrophysiological changes were measured on strips of rat myometrium at 35 degrees C using the double sucrose-gap technique. A II at concentrations from 5 x 10(-10) to 10(-6)M produces a depolarization and an increase in membrane conductance. This increase in membrane conductance is not membrane potential dependent since it is observed even when the membrane potential is maintained at the resting level. When all Na + in the test solution is replaced by either Li + or Mg (2+), the depolarizing effect of 10(-6)M A II is either markedly reduced or abolished. Under these conditions, A II produces a small initial hyperpolarization, which is modified by external potassium concentration changes and abolished by tetraethylammonium chloride. When all Cl- is replaced by either NO (-3) or cyclohexanesulfamate, A II (10(-6) M) still produces a 20-m V depolarization. The removal of extracellular Ca (2+) or K+ does not have any effect on the depolarizing action of A II, which also is not changed by 10(-3) M ouabain. In conclusion, A II produces a depolarization of the uterine smooth muscle membrane through an increase in the membrane conductance to Na+. The membrane conductance to potassium is increased simultaneously. The contraction induced by A II shows two components: a phasic component triggered by the Ca (2+) entry associated with spike production and a tonic component due to the release of Ca(2+) from intracellular stores.     

Mechanism of the myosin catalyzed hydrolysis of ATP as rationalized by molecular modeling

The intrinsic chemical reaction of adenosine triphosphate (ATP) hydrolysis catalyzed by myosin is modeled by using a combined quantum mechanics and molecular mechanics (QM/MM) methodology that achieves a near ab initio representation of the entire model. Starting with coordinates derived from the heavy atoms of the crystal structure (Protein Data Bank ID code 1VOM) in which myosin is bound to the ATP analog ADP.VO(4)(-), a minimum-energy path is found for the transformation ATP + H(2)O --> ADP + P(i) that is characterized by two distinct events: (i) a low activation-energy cleavage of the P(gamma) O(betagamma) bond and separation of the gamma-phosphate from ADP and (ii) the formation of the inorganic phosphate as a consequence of proton transfers mediated by two water molecules and assisted by the Glu-459-Arg-238 salt bridge of the protein. The minimum-energy model of the enzyme-substrate complex features a stable hydrogen-bonding network in which the lytic water is positioned favorably for a nucleophilic attack of the ATP gamma-phosphate and for the transfer of a proton to stably bound second water. In addition, the P(gamma) O(betagamma) bond has become significantly longer than in the unbound state of the ATP and thus is predisposed to cleavage. The modeled transformation is viewed as the part of the overall hydrolysis reaction occurring in the closed enzyme pocket after ATP is bound tightly to myosin and before conformational changes preceding release of inorganic phosphate.     

Independent control of grafting density and conformation of single-stranded DNA brushes

We describe self-assembly of ssDNA brushes that exploits the intrinsic affinity of adenine nucleotides (dA) for gold surfaces. The grafting density and conformation of these brushes is deterministically controlled by the length of the anchoring dA sequences, even in the presence of thymine nucleotides (dT). We produce and characterize brushes of model block-oligonucleotides, d(T(m)-A(n)), with systematically varied lengths m and n of the thymine and adenine blocks [denoted d(T(m)) and d(A(n)), respectively]. The hairpin conformation, dominant for self-complementary d(T(m)-A(n)) oligos in solution, is disrupted by the high preferential affinity of dA for gold surfaces. As a result, the d(T(m)-A(n)) oligos adsorb as a brush of d(T) strands immobilized via the d(A) blocks. Quantitative analysis by FTIR spectroscopy and x-ray photoelectron spectroscopy (XPS) reveals a unique feature of DNA immobilization via d(A) blocks: The surface density of dA nucleotides is close to saturation and is nearly independent of d(A) block length. Accordingly, the lateral spacing (grafting density) of the d(T) blocks is determined by the length of the d(A) blocks. The d(T) blocks extend away from the surface in a brush-like conformation at a lateral spacing 2-3 times larger (a grafting density 5-10 times lower) than in analogous films immobilized via standard thiol linkers. This combination of brush-like conformation and low saturation grafting density is expected to increase the efficiency of DNA hybridization at surfaces. Therefore, immobilization via d(A) blocks offers a method of producing DNA brushes with controlled properties for applications in biotechnology and nanotechnology.     

Prevalence of Coeliac Disease in the General Population of Northern Spain: Strategies of Serologic Screening

Background: Coeliac disease (CD) is common in Western countries. In Spain, however, no studies exist on its prevalence. The best method for serologic screening is also unknown. Methods. We determined the IgA and IgG antigliadin antibodies (AGA) and IgA antiendomysium antibodies (AEA) in a sample of 1170 randomly selected subjects from a health area in northern Spain. The prevalence of CD was calculated with a two-step serologic screening method (first IgA and IgG AGA and then AEA in those positive for AGA) or with only one step with AEA determination. Diagnosis was confirmed by small-intestinal biopsy. Results: When using a two-step strategy, we found 174 (15%) subjects with AGA. Only one of these was confirmed by means of AEA (prevalence of CD = 0.9/1000). Two subjects were found to be positive when a one-step strategy was used (prevalence of CD = 1.7/1000). This yielded an economic saving of 19% with regard to the use of a two-step strategy. One new case of CD in a seronegative subject was diagnosed during the study (real prevalence of CD = 2.6/1000; 95% confidence interval = 0.7-8.2). Conclusions: The prevalence of CD in Northern Spain is 2.6/1000 (1:389). One-step serologic screening (AEA) is both more economical and more sensitive than the two-step procedure (first AGA and then AEA if AGA is positive).     

Crystal structure of tetrameric form of human lysyl-tRNA synthetase: Implications for multisynthetase complex formation

In mammals, many aminoacyl-tRNA synthetases are bound together in a multisynthetase complex (MSC) as a reservoir of procytokines and regulation molecules for functions beyond aminoacylation. The alpha(2) homodimeric lysyl-tRNA synthetase (LysRS) is tightly bound in the MSC and, under specific conditions, is secreted to trigger a proinflammatory response. Results by others suggest that alpha(2) LysRS is tightly bound into the core of the MSC with homodimeric beta(2) p38, a scaffolding protein that itself is multifunctional. Not understood is how the two dimeric proteins combine to make a presumptive alpha(2)beta(2) heterotetramer and, in particular, the location of the surfaces on LysRS that would accommodate the p38 interactions. Here we present a 2.3-A crystal structure of a tetrameric form of human LysRS. The relatively loose (as seen in solution) tetramer interface is assembled from two eukaryote-specific sequences, one in the catalytic- and another in the anticodon-binding domain. This same interface is predicted to provide unique determinants for interaction with p38. The analyses suggest how the core of the MSC is assembled and, more generally, that interactions and functions of synthetases can be built and regulated through dynamic protein-protein interfaces. These interfaces are created from small adaptations to what is otherwise a highly conserved (through evolution) polypeptide sequence.     

Model for regulation of the histidine operon of Salmonella.

A model is proposed that accounts for regulation of the histidine operon by a mechanism involving alternative configuration of mRNA secondary structure (the alternative stem model). New evidence for the model includes sequence data on three regulatory mutations. The first (hisO1242) is a mutation that deletes sequences needed to form the attenuator mRNA stem and causes constitutive operon expression. The second mutation (hisO9654) is a His- ochre (UAA) mutation in the leader peptide gene; the existence of this mutation constitutes evidence that the leader peptide gene is translated. The third mutation (hisO9663) is remarkable. It neither generates a nonsense codon nor affects a translated sequence; yet, it is suppressible by amber suppressors. We believe this mutation causes a His- phenotype by interfering with mRNA secondary structure. The suppressibility of the mutation is probably due to disruption of the attenuator stem by ribosomes that read through the terminator codon of the leader peptide gene. This explanation is supported by the observation of derepression of a wild-type control region in the presence of an amber suppressor. Evidence is presented that hisT mutants (which lack pseudouridine in the anticodon arm of histidine tRNA) may cause derepression of the his operon by slowing protein synthesis in the leader peptide gene.     

急性胆管炎的诊断与非手术治疗进展

急性胆管炎是细菌感染引起的胆道系统的急性炎症。依据其对初期内科治疗的反应情况及是否伴发器官功能障碍,分为轻中重三型。及时行胆道减压是治疗此病的关键。内镜下胆道引流具有恢复快、疗效好、并发症少、费用低等特点,目前已广泛应用于临床。     

Predictors of atherosclerosis

It is herein discussed what should be measured as predictors of atherosclerosis, to increase the predictive power of coronary risk evaluation in clinical practice. Plasma apolipoprotein (apo)B and apoAI have been reported to be stronger predictors of coronary artery disease (CAD) than plasma low-density lipoprotein (LDL)-cholesterol (C) and high-density lipoprotein (HDL)-C. The estimation of plasma levels of remnants of TG-rich lipoproteins is also important for coronary risk evaluation. An increase in plasma small, dense LDL is a risk factor for CAD. It is not practical to measure plasma small, dense LDL as a routine clinical examination. We should estimate the plasma levels of small, dense LDL by plasma triglyceride (TG), apoB, and HDL-C levels. Oxidized LDL (ox-LDL) plays an important role in atherosclerosis. Further large-scale, prospective studies are necessary to determine whether the measurement of plasma ox-LDL and autoantibodies against ox-LDL is an essential predictor of atherosclerosis. High plasma levels of Lp(a) are a risk factor for atherosclerotic vascular diseases in subjects with high plasma LDL-C levels and multiple coronary risk factors. Metabolic syndrome (MS) has been recognized recently as a predictor of CAD. As a result, it should be elucidated whether MS must be involved in the coronary risk evaluation score because all components of MS are involved in the score. A high plasma level of high-sensitivity C-reactive protein (hs-CRP) is an important predictor of atherosclerotic diseases. Whether it is essential to measure the plasma levels of atherosclerosis surrogate markers in clinical practice remains to be elucidated. It is concluded that plasma levels of apoB, apoAI, remnant-like particle (RLP)-C, lipoprotein (a) [Lp(a)], and hs-CRP in addition to those of lipids should be measured as predictors of atherosclerosis in clinical practice. We need to establish a new atherosclerosis risk evaluation scoring system involving the above factors, based on large-scale, prospective studies, to prevent atherosclerotic vascular diseases. In Japan, plasma levels of Lp(a), RLP-C, and hs-CRP are routinely measured in clinical practice. As a result, it would be rather easy to establish a new atherosclerosis risk evaluation scoring system in Japan.     

Efficiency of the CO2-concentrating mechanism of diatoms

Diatoms are responsible for a large fraction of CO(2) export to deep seawater, a process responsible for low modern-day CO(2) concentrations in surface seawater and the atmosphere. Like other photosynthetic organisms, diatoms have adapted to these low ambient concentrations by operating a CO(2) concentrating mechanism (CCM) to elevate the concentration of CO(2) at the site of fixation. We used mass spectrometric measurements of passive and active cellular carbon fluxes and model simulations of these fluxes to better understand the stoichiometric and energetic efficiency and the physiological architecture of the diatom CCM. The membranes of diatoms are highly permeable to CO(2), resulting in a large diffusive exchange of CO(2) between the cell and external milieu. An active transport of carbon from the cytoplasm into the chloroplast is the main driver of the diatom CCM. Only one-third of this carbon flux is fixed photosynthetically, and the rest is lost by CO(2) diffusion back to the cytoplasm. Both the passive influx of CO(2) from the external medium and the recycling of the CO(2) leaking out of the chloroplast are achieved by the activity of a carbonic anhydrase enzyme combined with the maintenance of a low concentration of HCO(3)(-) in the cytoplasm. To achieve the CO(2) concentration necessary to saturate carbon fixation, the CO(2) is most likely concentrated within the pyrenoid, an organelle within the chloroplast where the CO(2)-fixating enzyme is located.     

Effect of phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 on the function of reversing factor in the initiation of protein synthesis.

The reticulocyte reversing factor (RF) isolated as a complex with eukaryotic initiation factor 2 (eIF-2) acts catalytically in restoring protein synthesis in reticulocyte lysates inhibited by heme deficiency. In reconstituted in vitro assay mixtures containing Mg2+ (0.25-0.5 mM), RF catalyzes the formation of the binary complex (eIF-2-GDP) but this effect is inhibited when eIF-2 is phosphorylated by the heme-regulated kinase for the alpha-subunit of eIF-2 (HRI). More significantly, RF catalyzes the rapid dissociation of (eIF-2-GDP), which permits the exchange of GTP for GDP and, in the presence of Met-tRNAf, promotes the formation of the ternary complex (eIF-2-Met-tRNAf X GTP). However, phosphorylation of the binary complex by HRI prevents its dissociation by RF and, as a consequence, ternary complex formation is inhibited. Our results indicate that phosphorylated binary complex [eIF-2(alpha P).GDP] interacts with RF to form a [RF . eIF-2(alpha P)] that is not readily dissociable. This binding of RF renders it unavailable to catalyze the dissociation of unphosphorylated binary complex, thereby blocking the recycling of eIF-2. Since RF is present in lysates at a limited concentration relative to that of eIF-2, the sequestering of RF in this manner could account for the observation that the phosphorylation of a small proportion of eIF-2 in heme-deficient lysates is sufficient to inhibit protein synthesis.     

Analysis of segmental kinetics of the left ventricle after intravenous administration of urokinase in the acute phase of myocardial infarction

From 1982 to 1984 included, 31 patients under 70 years of age were admitted during the first three hours of a primary myocardial infarction (MI) and are the subject of a randomized prospective study. 16 patients are treated with 5,000 U of heparin given in intravenous bolus, followed with 150,000 IU of urokinase (UK) in intravenous bolus, then 12,000 IU of UK/min for 90 min or a total dose of 1,230,000 IU. 15 patients are treated with heparin alone (intravenous bolus of 5,000 U). Repeated titrations of creatine phosphokinase (CPK) and the coagulation parameters are performed during the first 24 hours. A coronary angiography with ventriculography (RAO 30 degrees) is performed on the 1st day (D1) and the 3rd week (W3). Study of the left ventricular kinetics (LV) is carried out according to the Stanford method. At D1, the rate of coronary patency is 56 p cent (n = 9) in the UK (A) group and 53 p. cent (n = 8) in the control group B (heparin alone). The percentage of late re-thrombosis is 0 p. cent in group A and 12.5 p. cent in group B (heparin alone). 1 patient died in each group. The CPK peak is less high in case of coronary patency in group A than in case of thrombosis (1,444 +/- 413 vs 1,710 +/- 120 U -heparin alone) and occurs earlier (16 +/- 2 h vs 21 +/- 1 h). In group A a significant decrease of fibrinogen (p. 0.01) as well as plasminogen and alpha-2-antiplasmins (p less than 0.001), is noted. No severe haemorrhagic complications nor sustained rhythm disorders are noted.(ABSTRACT TRUNCATED AT 250 WORDS)     

Permeability of a Macro-Cracked Concrete Effect of Confining Pressure and Modelling

The effects of confining pressure are investigated for two samples of a macro-cracked concrete. Samples are first macro-cracked with a splitting tensile strength test (Brazilian) technique. Gas permeability is continually measured under increasing (or decreasing) confining pressure, whereas crack closure (or opening) is recorded with an LVDT (Linear Variable Differential Transformer) device. Despite a mechanical closure of the macro-crack, identified at around 20 MPa confining pressure, gas permeability continues to decrease as confinement is increased. This means that a model of the macro-crack by two parallel planes (using Poiseuille law) cannot be used to represent permeability variations during closure (or opening) of cracks. As a consequence, a physical model is designed in order to simulate with a better consistency the real behaviour of the macro-crack. This simple modelling allows both behaviours, mechanical and hydraulic, under confining pressure, to be simulated with the same set of parameters.