Small Sample Distribution and Power of the Binomial Index of Dispersion and Log Likelihood Ratio Tests

This paper considers the exact distribution of the X² index of dispersion and -2 log (likelihood ratio) tests for the hypothesis of homogeneity of c independent samples from a common binomial population. The exact significance levels and power of these tests under ‘logit’ alternatives are compared numerically for the cases: c = 3, 4, 5 and various sample sizes. n₁ = 5,10 for i = 1,…, c.     

15N-nmr spectroscopy. 33. Assignments of isotactic and syndiotactic sequences in poly(D,L-amino acids)

¹⁵N-enriched (D ,L -Leu)_n, (γ-OMe-D ,L -Glu)_n, (D ,L -Val)_n, and (D ,L -Phe)_n were prepared, 40.55-MHz ¹⁵N-nmr spectra were measured in various solvents. The signal patterns depend strongly on the nature of the solvent, yet in most cases at least four signals are resolved, representing the four enantiomeric pairs of triads L -L -L (D -D -D ), L -D -L (D -L -D ), L -L -D (D -D -L ), and D -L -L (L -D -D ). Numerous copolypeptides of the general structure (A)_n-B*-(A)_m (the asterisk denotes 40–50% ¹⁵N enrichment) were synthesized and measured as models for syndiotactic sequences in the spectra of poly(D ,L -amino acids). In this way unambiguous assignments for both isotactic and syndiotactic trials were obtained. A spectroscopic rule was established: “isotactic sequences absorb downfield of syndiotactic ones.” Furthermore, the spectra of various types of stereocopolypeptides such as (L -Leu/L -Val)_n and (L -Leu/D -Val)_n were investigated, including the ternary systems (L -Leu/L -Ala/D -Ala)_n (L -Leu/L -Ala/Gly)_n, (L -Leu/D -Ala/Gly)_n, (L -Val/L -Ala/Gly)_n, and (L -Val/D -Ala/Gly)_n. All copolymerization of D - and L -amino acid NCAs investigated in this work showed a low degree of stereoselectivity.     

Formation and stability of helical poly(N epsilon,N epsilon,N epsilon-trimethyl-L-lysine) in sodium perchlorate solution

Poly(trimethyl-L-lysine), [Lys(Me₃)]_n, is converted from random coil to α-helix at about 1/30 of the NaClO₄ concentration required by poly(L-lysine), (Lys)_n. NaClO₄ generates turbidity in [Lys(Me)₃]_n at concentrations above that required for helix formation, and decreases turbidity above lM NaClO₄. The turbidity runs parallel to enhanced, and then decreased, fluorescence of a dansyl label. Helix formation per se does not induce enhanced fluorescence. Increasing NaClO₄ concentration increases T_m linearly with log[NaClO₄] for both (Lys)_n and [Lys(Me₃)]_n until the denaturing effect of high NaClO₄ sets in. Increasing NaClO₄ also increases the breadth of the transition. Heating helical [Lys(Me₃)]_n or (Lys)_n does not produce a CD spectrum resembling that of “random-coil” (Lys)_n, except for [Lys(Me₃)]_n at relatively low NaClO₄ concentration.     

A systematic search for the structures,stabilities, and electronic properties of bimetallic Ca<Subscript>2</Subscript>-doped gold clusters: comparison with pure gold clusters

The local meta-GGA exchange correlation density functional (TPSS) with a relativistic effective core potential was employed to systematically investigate the geometric structures, stabilities, and electronic properties of bimetallic Ca₂Au _n (n = 1–9) and pure gold Au _n (n ≤ 11) clusters. The optimized geometries show that the most stable isomers for Ca₂Au _n clusters have 3D structure when n > 2, and that one Au atom capping the Ca₂Au _n−1 structure for different-sized Ca₂Au _n (n = 1–9) clusters is the dominant growth pattern. The average atomic binding energies and second-order difference in energies show that the Ca₂Au₄ isomer is the most stable among the Ca₂Au _n clusters. The same pronounced even–odd alternations are found in the HOMO–LUMO gaps, VIPs, and hardnesses. The polarizabilities of the Ca₂Au _n clusters show an obvious local minimum at n = 4. Moreover, the inverse corrections to the polarizabilities versus the ionization potential and hardness were found for the gold clusters.     

Polymorphic microsatellite DNA markers for the white‐breasted thrasher,Ramphocinclus brachyurus

We isolated and characterized six polymorphic microsatellite markers for the white‐breasted thrasher from genomic libraries enriched for (AC)_n, (GT)_n, (CAAA)_n, (TTTC)_n, (GAC)_n, (CT)_n and (TTTG)_n microsatellites. The number of alleles per locus ranged from two to seven. Observed heterozygosity (H_O) ranged from 0.30 to 0.85.     

Genetic differentiation among coastal and offshore common bottlenose dolphins,Tursiops truncatus,in the eastern North Pacific Ocean

Common bottlenose dolphins (Tursiops truncatus) are found worldwide in temperate and tropical regions, often occurring as distinct coastal and offshore ecotypes. Along the west coast of the United States, two stocks are recognized for management based on morphological and photo‐identification studies: a California coastal stock, estimated at 450–500 individuals, and a California/Oregon/Washington offshore stock of about 1,000 animals. This study is the first to analyze genetic differentiation between these stocks. We examined both the hypervariable portion of the mitochondrial DNA (mtDNA) control region and fifteen microsatellite markers for coastal (n = 64) and offshore (n = 69) dolphins. Significant genetic differentiation was found between the two stocks for mtDNA (Φ_ST = 0.30, P < 0.001; F_ST = 0.14, P < 0.001) and microsatellite loci (F_ST = 0.19, P < 0.001). Coastal dolphins had less genetic diversity than offshore dolphins. Further substructuring within the offshore stock was not detected. The level of genetic differentiation between the coastal and offshore dolphins is consistent with long‐term separation and reinforces recognizing them as separate stocks. These findings are particularly important for management of the smaller, less genetically diverse, coastal stock that is vulnerable to a variety of anthropogenic threats.     

Block copolymers of amino acids. I. Synthesis and structure of copolymers of L-alanine or L-phenylalanine with D,L-lysine-d7 or D,L-lysine

Water-soluble block copolymers of the type (A)_m-(B)_n-(A)_p, where (A)_m,p was either poly(D ,L -lysine-α,β,β,γ,γ,δ,δ-d₇) or poly(D ,L -lysine) and (B)_n was either poly(L -alanine) or poly(L -phenylalanine), were synthesized for conformational studies by proton magnetic resonance spectroscopy. Analytical determination of the amount of the initiator fragment (n-hexylamine) at the C-terminus of the copolymers was used to obtain the number-average degrees of polymerization, DP _n, and thereby, together with the amino acid composition, to establish the covalent structures of the polymers. The values of DP _n were found to be much lower than those deduced from sedimentation equilibrium or form viscosity measurements. These deviations, which also are thought to have arisen in similar studies reported in the literature, are attributable to intermolecular aggregation; the relation of such aggregation to covalent structure (and its effect on the polymerization reaction) is discussed in terms of the conditions and mechanism of synthesis of block copolymers of amino acids.     

拔节期干旱和复水对春玉米物候的影响及其生理生态机制

物候不仅是气候变化的指示指标,也是作物模型的关键参数。现有研究主要关注物候变化与气候环境因子的关系,关于植物物候变化的生理生态机制研究很少。基于春玉米拔节期干旱与不同时间(抽雄期和吐丝期)复水的田间模拟试验分析表明:(1)不同时间复水均使灌浆期延长,乳熟期推迟(9d),表明物候对前期水分胁迫存在记忆。(2)干旱条件下叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)和相对叶绿素含量(SPAD)均随物候进程呈先降后升再降趋势,且均在抽雄期达到极小值;不同时间复水均使P_n、T_r和G_s在吐丝期达到极大值,而SPAD则在灌浆期达到极大值;叶水势(LWP)随干旱进程整体呈下降趋势,不同时间复水均只是减缓了其下降速度,表明LWP可用于描述物候对前期水分胁迫的记忆。(3)通径分析和决策系数分析表明,P_n是最主要的物候影响因子,而影响LWP的土壤相对湿度(RSWC)则是物候的主要控制因子,物候的变化是由P_n的累积变化引起,表明存在P_n的物候触发阈值。研究结果为春玉米物候变化的准确预测提供了依据。     

Circulation,metabolic rate,and body size in mammals

Summary This paper attempts to explain Kleiber's rule, which relates metabolic rate of mammals to their body mass, from the structure and function of the blood circulation system.Abbreviations a scaling factor - fractal dimension - hydrodynamic conductivity - l _n length of an arterial blood vessel at bifurcation level n - M body mass - N maximal number of bifurcation levels - p pressure - Q flow - r size of Bohr effect - r _n radius of an arterial blood vessel at bifurcation level n - V volume - VO ₂ rate of oxygen unloading - Z _n number of arterial blood vessels at bifurcation level n     

Characterization of highly variable (GA/CT) n microsatellites in the bur oak,Quercus macrocarpa

The objective of this study was to ascertain the usefulness of polymerase chain reaction (PCR)-based microsatellite analysis for studying pollination and parentage in a wind-pollinated temperate tree. A small insert genomic library of the bur oak (Quercus macrocarpa) was constructed and screened for the presence of (CA/GT) _n and (GA/CT) _n repeats. The proportion of positive clones yielded estimates of 3×10⁵ such dinucleotide repeats per genome, roughly comparable to abundances reported in other eukaryotic genomes. Thirteen positive clones were sequenced. In contrast to mammalian genomes, the (GA/CT) _n motif was more abundant than the (CA/GT) _n motif in these clones. The (GA/CT) _n repeats also showed longer average repeat length (mean n=16.2 versus 7.3), suggesting that they are better candidates for yielding polymorphic genetic markers in oak genomes. Indeed, a survey of adult bur oaks and offspring in a small stand in northern Illinois at 3 of these (GA/CT) _n microsatellite loci revealed Mendelian inheritance and extremely high levels of polymorphism, with the number of alleles at each locus ranging from 11–20 and heterozygosity ranging from 0.66 to 0.75. These results, indicating that (GA/CT) _n microsatellites are both abundant and highly polymorphic in the bur oak genome, suggest that such genetic markers have tremendous potential for applications for studies of parentage, pollination and dispersal in temperate trees.     

Conformational analysis of polytripeptides (Gly-Pro-Ala)n, (Gly-Ala-Hyp)n,and (Gly-Ala-Ala)n in connection with the problem of collagen structure

Conformational analysis of triple helics of a type of collagen was performed with typical collagen tripeptide sequences based on Gly-Pro-Ala, Gly-Ala-Hyp, and Gly-Ala-Ala. During energy minimization, the possibility of continual deformation of the pyrrolidine cycle was taken into account in order to achieve better accuracy in the resulting structure. The (Gly-Pro-Ala)_n structure is almost isomorphic to the (Gly-Pro-Hyp)_n structure obtained in the previous work [Tumanyan, V. G. & Esipova, N.G. (1982) Biopolymers 21 , 475–497]. For a collagen-type structure, the optimal conformation of (Gly-Ala-Hyp)_n tends to have a decreased unit twist (t = 15°), although the energy advantage with respect to the conformation with t = 45° is not so significant. A similar situation is observed for (Gly-Ala-Ala)_n. In this case, the energy decrease during unwinding to t = 15° from t = 45° is quite small. The conformations of (Gly-Ala-Hyp)_n and (Gly-Ala-Ala)_n with t = 15° exhibit a similarity with a triple complex of polyproline II helices—a noncoiled coil such as (Gly-Pro-Hyp)_n and (Gly-Pro-Ala)_n. A similar structure may be postulated for subcomponent cq1 of the first component of a human complement containing substantial Gly-X-Pro and Gly-X-Y tripeptide derivatives in the primary structure (X, Y = any amino acid). The results suggest that the observed helical symmetry of collagen (t = 36°) is a consequence of superposition of diffraction patterns (for sufficiently long segments) from various helices (t varies from ～15° for Gly-X-Hyp and Gly-X-Y to ～56° for Gly-Pro-Ala). For short alternating segments, some unification of different helical structures is possible.     

Advanced glycation end products and antioxidant status in nondiabetic and streptozotocin induced diabetic rats: effects of copper treatment

The effects of Cu(II) supplementation on glycemic parameters, advanced glycation end products (AGEs), antioxidant status (glutathione; GSH and total antioxidant capacity; TAOC) and lipid peroxidative damage (thiobarbituric acid-reactive substances, TBARS) were investigated in streptozotocin (STZ) induced diabetic rats. The study was carried out on Wistar albino rats grouped as control (n = 10), CuCl₂ treated (n = 9), STZ (n = 10) and STZ,CuCl₂ treated (n = 9). STZ was administered intraperitoneally at a single dose of 65 mg/kg and CuCl₂, 4 mg copper/kg, subcutaneously, every 2 days for 60 days. At the end of this period, glucose(mg/dl), Cu(μg/dl), TBARS(μmol/l), TAOC(mmol/l) were measured in plasma, GSH(mg/gHb) in erythrocytes and glycated hemoglobin (GHb)(%) in blood. Plasma AGE-peptides(%) were measured by HPLC flow system with spectrofluorimetric and spectrophotometric detectors connected on-line. Data were analyzed by the non-parametric Kruskal–Wallis and Mann–Whitney U test. In the STZ group glucose, GHb and AGE-peptide levels were all significantly higher than the control group (P < 0.01, P < 0.05, and P < 0.01, respectively). CuCl₂ treated group had significantly lower glucose but significantly higher GHb, TAOC and TBARS levels than the control group (P < 0.05, P < 0.001, P < 0.05 and P < 0.001, respectively). STZ,CuCl₂ treated group had significantly higher GHb, TAOC and TBARS levels compared with the control group (P < 0.001, P < 0.05 and P < 0.05, respectively); but only TAOC level was significantly higher than the STZ group (P < 0.01). This experimental study provides evidence that copper intake increases total antioxidant capacity in both nondiabetic and diabetic states. However despite the potentiated antioxidant defence, lipid peroxidation and glycation enhancing effects of CuCl₂ are evident under nondiabetic conditions.     

Hormonal stimulation of avian embryonic cartilage growth in vitro: Histologic and ultrastructural features

Summary We studied the histologic and ultrastructural features of embryonic chick cartilage after the cartilage had been incubated in serum-free medium that contained hormones and growth factors known to stimulate in vitro cartilage growth. Pelvic cartilages from 9 d chick embryos were incubated in BGJ_b (Fitton-Jackson modification) medium alone (control) or medium containing one of the following:N ⁶ monobutyryl cyclic AMP 0.5 mM, forskolin 100 μM, triiodothyronine (T₃) 10 nM, insulin 45 nM, or somatomedin C 0.67 nM. At the end of 3 d of incubation the cartilages were fixed in buffered formalin. Significant growth (increases in size, wet and dry weight) was seen with each treatment group. N⁶-Monobutyryl cAMP treated cartilage had an increased number of flattened immature chondrocytes with large nuclei and prominent nucleoli. The histologic and ultrastructural features of forskolin treated cartilage were indistinguishable from N⁶-monobutyryl cAMP treatment. The T₃ treated cartilage contained large hypertrophic chondrocytes with prominent lacunar typical of mature cartilage. T₃ Treated cartilage had considerable vacuole formation and dilated endoplasmic reticulum. Insulin and somatomedin treated cartilage had histologic appearance similar to control cartilage. Thus, the effects of various hormones on embryonic cartilage growth in vitro can be separated as to whether growth is the result of chondrocytic hyperplasia (cyclic AMP mediated), chondrocytic hypertrophy with maturation (T₃), or a combination of both hyperplasia and hypertrophy (insulin and somatomedin-C). This study was supported by a grant (K08 AM 01021-01) from the National Institute of Arthritis, Metabolism, Diabetes, and Kidney Diseases, Bethesda, MD, and a Basil O'Connor Starter Grant (0-400) from the March of Dimes.     

Helix coil transitions of d (A)n·d(T)n,d(A-T)n·d(A-T)n,and d(A-A-T)n·d(A-T-T)n; evaluation of parameters governing DNA stability

The thermally induced helix-coil transitions of three A-T DNAs, d(A)_n·d(T)_n, d(A-T)_n·d(A-T)_n, and d(A-A-T)_n·d(A-T-T)_n, were studied. Experimental transition curves of the DNAs were analyzed using the loop entropy model of DNA melting. The calculation of the melting curve of d(A-A-T)_n·d(A-T-T)_n is presented using the integral equation formalism of Goel and Montroll. The aim of this work was to evaluate thermodynamic parameters which govern DNA stability and to test the theoretical model employed in the analysis. Our results show (1) an excellent over-all agreement between theory and experiment, (2) a loop entropy exponent k = 1.55 ± 0.05 provided the best fit to all the polymer transition curves, (3) the evaluated stacking free energies reflect the relative stability of the DNAs, and (4) the stacking energies of the ApA·TpT dimer evaluated from d(A)_n·d(T)_n and d(A-A-T)_n·d(A-T-T)_n differ. The last result is consistent with different conformations for the dimer in these two polymers.     

Identification of microsatellite loci in lake sturgeon,Acipenser fulvescens,and their variability in green sturgeon,A. medirostris

From (CATC)_n, (GATA)_n, (AAAC)_n, and (CA)_n–enriched libraries for the lake sturgeon Acipenser fulvescens, 254 primer pairs were developed. These primer pairs resulted in the identification of 128 microsatellite loci in either A. fulvescens or A. medirostris. Polymorphic loci were identified in both sturgeon species for 48 of the primer pairs and 14 of the primer pairs amplified polymorphic loci only in A. medirostris. Most of the identified loci appear to be tetrasomic (79.1% in A. fulvescens and 64.5% in A. medirostris). These results offer estimates of the degree of diploidization in each of these species.     

Tightly linked di- and tri-nucleotide microsatellites do not evolve in complete independence: evidence from linked (TA)n and (TAA)n microsatellites of chickpea (Cicer arietinum L.)

In order to understand the dynamics of microsatellite evolution, we have studied allelic variation at a closely linked (TA) _n and (TAA) _n microsatellite loci in 114 land races of chickpea (Cicer arietinum L.), sampled worldwide. These two loci are separated by 27 bp. The two loci showed a very high degree of polymorphism and hence the combined length with the genetic diversity of 0.93, 0.90 and 0.98 for (TAA) _n , (TA) _n and the combined length, respectively. Using the variation data at the linked loci, a standardized index of linkage disequilibrium was also computed (I ^S _A =0.092), which tests the null hypothesis of no linkage and was significant, indicating the presence of linkage disequilibrium. Furthermore, the dynamics of allelic variation showed that there is a threshold combined length, below which both (TAA) _n and (TA) _n loci evolve independently, and above which, if one locus increase in size, the other closely linked locus has a tendency to decrease its size and vice versa, without change in the overall ratio of (TAA) _n and (TA) _n allele sizes at the region. This result indicates that there are processes in the cell, which read the combined size of the two loci both for proportion and length and determine the direction of tightly linked di- and tri-nucleotide repeat evolution.Communicated by R. Hagemann     

Genetic control of two independently segregating loci in mice to the sequential polypeptide (Tyr-Ala-Glu-Gly)n

Immune responses to the sequential helical polypeptide (Tyr-Ala-Glu-Gly)_n [(T-A-G-Gly)_n] in mice is under the control of at least two separate genes. One gene,Ir-(T-A-G-Gly)-1, which is linked, toH-2 haplotypesb, f, andr, controls the ability to respond and maps to theIA subregion. A non-H-2-linked locus,Ir-(T-A-G-Gly)-2. is responsible for the magnitude of the antibody response, which is expressed as a high, intermediate, or low level of antibody production. The antibody produced is of the IgG class, and does not crossreact even with the closely related sequential helical polymer (Tyr-Glu-Ala-Gly)_n [(T-G-A-Gly)_n]. Immune responsiveness is a dominant trait,i.e., the F₁ generations of responder x nonresponder crosses are responders. However, the data obtained with both backcross populations are not easily interpretable. The contribution of the B-cell mitogenic activity of the sequential polymer to activation of suppressor T cells is considered as a possible explanation for the backcross results. The possible role of the Ia. W29 specificity present in the mouse strains responding to both (T-A-G-Gly)_n and calf skin collagen type I in modulating responses to the polymers is discussed.     

NMR-based metabonomic evaluation of livers from rats chronically treated with tamoxifen,mestranol, and phenobarbital

In this study, we look at the metabolic effects of long-term dosing with tamoxifen, mestranol or phenobarbital on the liver. Tamoxifen, mestranol and phenobarbital have all been reported to act as promoters of hepatic tumors. While tamoxifen and mestranol are known to have estrogenic activity, in the liver phenobarbital is a non-estrogenic compound. Aqueous and lipophilic liver extracts from control and chronically treated Fisher 344 rats were evaluated by nuclear magnetic resonance spectroscopy (NMR). In both the aqueous and lipophilic sample sets, the estrogenic action of mestranol appears to be responsible for the clustering of these samples with those animals treated with tamoxifen. Phenobarbital does not have estrogenic activity and, therefore, clusters away from the estrogenic and control groups. In the lipophilic samples, the fatty acid peak (CH₂)_n was higher in tamoxifen-treated rats than in control, phenobarbital- or mestranol-treated rats. In the aqueous samples, serine and choline levels were higher in phenobarbital-treated rats than controls, which may be an indication that the folate–homocysteine metabolic pathways were altered.     

The cytokinin activities of 6-α-alkylbenzyloxypurines

The homologous series of 6-α-n-alkylbenzyloxypurines with alkyl groups (—(CH₂)_nCH₃) from n = 0 to n = 11 have been prepared and examined in three tests for cytokinin activity. The parent benzyloxypurine was also included in the tests. Substituting methyl (n = 0) into the methylene group of 6-benzyloxypurine removed activity almost completely; thereafter, increasing the size of the alkyl group (n = 1–5) gave compounds which were active in all tests, the butyl (n = 3) and pentyl (n = 4) derivatives being more active than 6-benzyloxypurine itself. Activity then fell as the series was ascended; the higher homologues (n = 8–11) being completely inactive. The results are discussed in relation to steric and other considerations.     

The curative activity of non-ionic surface-active agents against some powdery mildew diseases

Eight non-ionic surfactants of the general formula RO(C₂H₄O)_nH were examined as fungicides for the control of various powdery mildew diseases. Those based on the condensation products of cetyl and oleyl alcohol with ethylene oxide were effective only as curative fungicides, having very little protective potential. This activity was greatest in products with n= 6–10. The most effective derivative, having eight ethylene oxide units, was particularly active in greenhouse tests against Sphaerotheca fuliginea on cucumber, S. pannosa on roses, and Podosphaera leucotricha on apples at concentrations which were not damaging to these crops. Although this compound caused damage to apples in the field it was effective against rose mildew and apple mildew, and its purely curative action gave a level of control equal to the standard dinitro compounds, which are capable of acting as either protectant or curative fungicides. This suggests that the dinitro-compounds also probably act mainly in a curative fashion against these diseases in the field.