bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular cytogenetic discrimination and reaction to wheat streak mosaic virus and the wheat curl mite in Zhong series of wheat  Thinopyrum intermedium partial amphiploids
Authors: Chen Qin , Conner R L , Li H J , Sun S C , Ahmad F , Laroche A , Graf R J
Published: February 2003

Thinopyrum intermedium (2n = 6x = 42, JJJsJsSS) is potentially a useful source of resistance to wheat streak mosaic virus (WSMV) and its vector, the wheat curl mite (WCM). Five partial amphiploids, namely Zhong 1, Zhong 2, Zhong 3, Zhong 4, and Zhong 5, derived from Triticum aestivum × Thinopyrum intermedium crosses produced in China, were screened for WSMV and WCM resistance. Zhong 1 and Zhong 2 had high levels of resistance to WSMV and WCM. The other three partial amphiploids, Zhong 3, 4, and 5, were resistant to WSMV, but were susceptible to WCM. Genomic in situ hybridization (GISH) using a genomic DNA probe from Pseudoroegneria strigosa (SS, 2n = 14) demonstrated that two partial amphiploids, Zhong 1 and Zhong 2, have almost the identical 10 Th. intermedium chromosomes, including four Js, four J, and two S genome chromosomes. Both of them carry two pairs of J and a pair of Js genome chromosomes and two different translocations that were not observed in the other three Zhong lines. The partial amphiploids Zhong 3, 4, and 5 have another type of basic genomic composition, which is similar to a reconstituted alien genome consisting of four S and four Js genome chromosomes of Th. intermedium (Zhong 5 has two Js chromosomes plus two JsW translocations) with six translocated chromosomes between S and Js or J genomes. All three lines carry a specific SSJs translocated chromosome, which might confer resistance to barley yellow dwarf virus (BYDV-PAV). The present study identified a specific Js2 chromosome present in all five of the Zhong lines, confirming that a Js chromosome carries WSMV resistance. Resistance to WCM may be linked with J or Js chromosomes. The discovery of high levels of resistance to both WSMV and WCM in Zhong 1 and Zhong 2 offers a useful source of resistance to both the virus and its vector for wheat breeding programs.Key words: GISH, genomic composition, J, Js and S genomes, Thinopyrum intermedium, partial amphiploid, WSMV, WCM resistance.
The cytogenetics of thelytoky in a predominantly asexual parasitoid wasp with covert sex
Authors: Belshaw Robert , Quicke Donald L.J
Published: February 2003

Asexual lineages in the parasitoid wasp Lysiphlebus fabarum (Hymenoptera: Braconidae: Aphidiinae) have previously been shown to have occasionally undergone sexual reproduction and recombination with males from related sexual populations. In the present study, the cytogenetic system of asexual females in this species is shown by 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) staining to be central fusion automixis. This system has the potential to allow occasional sex and recombination without leading to an elevation of ploidy and with the maintenance of at least some heterozygosity. No evidence of the bacterial symbiont Wolbachia was found, and the observed system was compared with that in parasitoid wasps where asexuality is the result of Wolbachia infection.Key words: Lysiphlebus, Aphidiinae, amphimixis, parthenogenesis, arrhenotoky.
Mapping quantitative trait loci for bean traits and ovule number inTheobroma cacaoL.
Authors: Clement D , Risterucci A M , Motamayor J C , N'Goran J , Lanaud C
Published: February 2003

Quantitative trait loci (QTL) mapping for bean traits and the number of ovules per ovary was carried out in cocoa (Theobroma cacao L.) using three test-cross progenies derived from crosses between a lower Amazon Forastero male parent (Catongo) and three female parents: one upper Amazon Forastero (IMC78) and two Trinitario (DR1 and S52). RFLP (restriction fragment length polymorphism), microsatellite, and AFLP (amplified fragment length polymorphism) markers were used for mapping. Between one and six QTL for bean traits (length, weight, and shape index) and one and four QTL for the number of ovules per ovary were detected using composite interval mapping (CIM). Individual QTL explained between 5 and 24% of the phenotypic variation. QTL clusters were identified on several chromosomes, but particularly on chromosome 4. QTL related to bean traits were detected in the same region in both Trinitario parents and in a close region in the upper Amazon Forastero parent. In reference to a previous diversity study where alleles specific to Criollo and Forastero genotypes were identified, it was possible to speculate on the putative origin (Criollo or Forastero) of favorable QTL alleles segregating in both Trinitario studied.Key words: Theobroma cacao, bean traits, quantitative trait loci (QTL).
High-speed jet flows over spillway aerators
Authors: Kökpınar Mehmet Ali , Göğüş Mustafa
Published: February 2003

The characteristics of high-speed air-entrained jet flow over a spillway aerator were investigated using experimental data. Three different ramp designs (as well as the case of no ramp) were tested in a channel where the bed slope was adjusted to 0, 0.17, and 0.57, respectively. The effects of aerator geometry and flow condition on the air-entrainment process within the water jet and on the pressure fluctuations in the impact region are the main focus of the investigation. An extensive data analysis was performed for data obtained from this study and from a similar laboratory study conducted by another investigator. Experimental relations were derived for nondimensional parameters of jet length, aerator cavity subpressure number, and aeration rates through the lower and upper nappes of the water jet. Scale effects for lower nappe aeration and aerator cavity subpressure number were considered and a good correlation was determined with prototype aerator measurements of Emborcaçao, Foz do Areia, and Keban dams for lower nappe aeration and Guri Dam for aerator cavity subpressure numbers. An aerator without a ramp may be subjected to excessive pressure fluctuations at the impact region due to insufficient air entrainment. Key words: air entrainment, aerator, scale effect, jet length, cavity subpressure.
Multiple phytoplasmas associated with potato diseases in Mexico
Authors: Leyva-López Norma Elena , Ochoa-Sánchez Juan Carlos , Leal-Klevezas Diana Sara , Martínez-Soriano Juan Pablo
Published: February 2003

In recent years, the potato crop in Mexico has been notably affected by diseases recognized as potato purple top (PPT) in foliage and potato hair sprouts (PHS) in germinating tubers. In both cases, these syndromes reduce production by affecting viability of the tubers used as seeds. There is evidence indicating that phytoplasmas are associated with these syndromes. This study presents data on the molecular detection, characterization, and ecology of the pathogens related to PPT and PHS. Restriction fragment length polymorphism (RFLP) and sequence analysis indicated that PPT phytoplasma belongs to the 16SrI group and PHS phytoplasma fits in the 16SrII group. In this paper, we report that the two different phytoplasmas have been found coexisting in the same potato plant, which demonstrates the presence of mixed infection in the field. These phytoplasmas were also detected in weeds surrounding potato fields; therefore they should be considered as alternative hosts or natural reservoirs of PPT and PHS phytoplasmas.Key Words: mycoplasma-like organisms, witches' broom, purple top, fine sprouts, alternate hosts.
Enzymatic activity of endophytic fungi of six native seedling species from Doi Suthep-Pui National Park, Thailand
Authors: Lumyong Saisamorn , Lumyong Pipob , McKenzie Eric H.C , Hyde Kevin D
Published: February 2003

Endophytic fungi were isolated from the stems, petioles, midribs, and leaves of seedlings of six native tree species collected from Doi Suthep-Pui National Park, Thailand. Endophytes were isolated from all tissue samples investigated, and taxa included five ascomycetes, eight anamorphic taxa, and numerous sterile mycelia. Twenty-six strains were tested for their ability to produce cellulase, mannanase, proteinase, and xylanase. The ability to produce these enzymes was distributed amongst the strains tested. Rainforest seedlings supported a diverse array of endophytes that have a wide range of enzymatic activities. The implication of enzyme production in relation to lifestyle abilities of the endophytes is discussed.Key words: cellulase, hydrolytic enzyme, mannanase, protease, xylanase.
A role of xylanase, α-L-arabinofuranosidase, and xylosidase in xylan degradation
Authors: Rahman A.K.M Shofiqur , Sugitani Naoyasu , Hatsu Masahiro , Takamizawa Kazuhiro
Published: February 2003

Renewable natural resources such as xylans are abundant in many agricultural wastes. Penicillium sp. AHT-1 is a strong producer of xylanolytic enzymes. The sequential activities of its xylanase, α-L-arabinofuranosidase, and β-xylosidase on model hemicellulose oatspelt xylan was investigated. Optimum production of the enzymes was found in culture containing oatspelt xylan at 30°C and initial pH 7.0 after 6 days. The enzymes were partially purified by ammonium sulphate fractionation and anion-exchange chromatography on DEAE-Toyopearl 650 S. The apparent molecular mass was 21 kDa, and the protein displayed an "endo" mode of action. The xylanase exhibited glycotransferase activity. It synthesized higher oligosaccharides from the initial substrates, and xylotriose was the shortest unit of substrate transglycosylated. Xylanolytic enzymes (enzyme mixture) produced by this Penicillium sp. interacted cooperatively and sequentially in the hydrolysis of oatspelt xylan in the following order: α-L-arabinofuranosidase [Formula: see text] xylanase [Formula: see text] β-xylosidase. All three enzymes exhibited optimal activity under the same conditions (temperature, pH, cultivation), indicating that they alone are sufficient to completely depolymerize the test xylan. Results indicate that the xylanolytic enzyme mixture of Penicillium sp. AHT-1 could be useful for bioconversion of xylan-rich plant wastes to value-added products.Key words: xylanase, enzyme purification, enzymatic hydrolysis, Penicillium sp. AHT-1.
Reductive dechlorination of weathered Aroclor 1260 during anaerobic biotreatment of Arctic soils
Authors: Kuipers Bianca , Cullen William R , Mohn William W
Published: February 2003

We investigated the microbial reductive dechlorination of both weathered (aged) and nonweathered (freshly added) Aroclor 1260 in aerobic soil from Resolution Island, Nunavut, Canada. Initial polychlorinated biphenyl (PCB) concentrations were 106 and 100 ppm, respectively. The aerobic soil samples were inoculated with anaerobic sediment, incubated at 30°C until methanogenic, inoculated with a dechlorinating enrichment culture, and incubated a further 8 weeks. The average number of chlorine substituents per biphenyl molecule was biologically reduced from 6.6 to 5.1 and from 6.2 to 4.5 for weathered and nonweathered Aroclor 1260, respectively. Removal of hexa- and heptachlorobiphenyls (CBs), the major homolog groups present, was significantly greater for nonweathered than for weathered Aroclor 1260. Formation of dechlorination products, primarily 2,2',4,4'- and 2,2',4,6'-tetraCBs, was also significantly greater for nonweathered than for weathered Aroclor 1260. We additionally compared the dechlorination at 21°C of weathered Aroclor 1260 in soils from Resolution Island and Saglek, Labrador, Canada. The average number of chlorine substituents per biphenyl molecule was biologically reduced from 6.7 to 5.1 and from 6.5 to 4.6, respectively. This study demonstrated the potential for bioremediation of aerobic soil contaminated with Aroclor 1260 and showed that weathering may limit such treatment to an extent variable among different soils.Key words: biodegradation, PCB, polychlorinated biphenyl, bioremediation.
Thyroid-hormone-induced phosphate absorption inAplysia californicagut is mediated through protein synthesis
Authors: Gerencser George A , Cornette Kuuleialoha M , Zhang Jianliang
Published: February 2003

The mucosal membranes of Aplysia californica forgut epithelia contain a sodiumphosphate symporter that is stimulated by triiodothyronine. Actinomycin D, puromycin, or cycloheximide inhibited the triiodothyronine-stimulated phosphate absorption. It appears that thyroid hormone manifests its effects on phosphate absorption in the A. californica gut through protein synthesis.Key words: phosphate absorption, sodiumphosphate symporter, protein synthesis.
Cyclic nucleotide phosphodiesterase isozymes expressed in mouse skeletal muscle
Authors: Bloom Timothy J
Published: February 2003

To understand changes in cyclic nucleotide metabolism in muscle disease states, the expression of phosphodiesterase (PDE) isozymes in normal mouse leg muscle was examined. Four subcellular fractions were generated by differential centrifugation at 10 000 × g and 100 000 × g. cAMP PDE activity was found predominately in the soluble fractions, while cGMP PDE activity was more evenly distributed amongst soluble and particulate fractions. Pharmacological inhibitors demonstrate that PDE4 represents the major cAMP hydrolyzing activity and PDE2 represents the major cGMP hydrolyzing activity in mouse leg muscle. PDE1 is expressed at low levels, while PDE3 and PDE5 are intermediate. Between 20 and 40% of total PDE activity remained in the presence of inhibitors for PDE1PDE5, indicating that other PDE families contribute to the total PDE pool. Reverse-transcription PCR with family-specific primers showed expression of mRNA for PDE7PDE9, supporting this conclusion. Total PDE activity was found to be elevated in tissue extracts from a mouse model of Duchenne's muscular dystrophy.Key words: cyclic nucleotide, phosphodiesterase, skeletal muscle, pharmacological inhibitors, muscular dystrophy.
Models of depressed hepatic mrp2 activity reveal bromosulphophthalein-sensitive passive K+flux
Authors: Li Qin , Briggs M Martha , Folkens Doris , Hill Ceredwyn E
Published: February 2003

Bile acid independent flow composes up to 40% of hepatic bile secretory capacity. Apical (canalicular) efflux of non-bile-acid organic anions provides the major osmotic driving force for bile acid independent flow. Organic anion accumulation in the hepatocyte is accompanied by increases in both K+conductance in isolated hepatocytes and passive K+flux in the perfused rat liver, which are indicative of K+channel activation. We used two models of disrupted canalicular anion transport to test whether organic anion stimulated K+efflux occurs independently of anion excretion. In both wild type (wt) and mrp2 mutant (transport minus, tr) rat liver, bromosulfophthalein (BSP; 0.5mM) caused a reversible increase in K+flux that (i) was outwardly directed with low external K+and (ii) depended upon the electrochemical potential for K+. K+efflux from wt livers of both sexes was about 1.5 times larger than that from trlivers. Further, K+release from female rat livers was about three times higher than that from male livers, independent of phenotype. Two transcripts of the rat hepatocyte K+channel (Kir4.2) were expressed in hepatocytes of all rats. The results demonstrate that BSP stimulates basolateral (sinusoidal) K+channels independently of its canalicular excretion, revealing an early event in BAIF and suggesting that Kir4.2 may mediate BSP-sensitive K+flux.Key words: liver, GY, gender-specific, male, female, transport minus, Kir4.2.
Antioxidative and free radical scavenging effects of ecdysteroids fromSerratula strangulata
Authors: Cai Yu-Jun , Dai Jin-Qiu , Fang Jian-Guo , Ma Lan-Ping , Hou Li-Fen , Yang Li , Liu Zhong-Li
Published: February 2003

The antioxidative and free radical scavenging effects of four ecdysteroids, 20-hydroxyecdysone (E1), 25-deoxy-11,20-dihydroxyecdysone (E2), 24-(2-hydroxyethyl)-20-hydroxyecdysone (E3), and 20-hydroxyecdysone-20,22-monoacetonide (E4), isolated from the Chinese herbSerratula strangulata have been investigated in vitro. These ecdysteroids could protect human erythrocytes against oxidative hemolysis induced by a water-soluble azo initiator 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH). They could also inhibit the peroxidation of rat liver microsomes induced by hydroxyl radicals, as monitored by the formation of thiobarbituric acid reactive substances (TBARS), and prevent radical-induced decrease of membrane fluidity as determined by fluorescence polarization. They reacted with galvinoxyl radicals in homogeneous solution, and the pseudo-first-order rate constants were determined spectrophotometrically by following the disappearance of galvinoxyl radicals. Compounds E1 and (or) E3 were the most active in both antioxidative and radical-scavenging reactions.Key words: ecdysteroid, Serratula strangulata, free radical, erythrocyte, lipid peroxidation, antioxidant.
Angiotensin-II-induced enhanced expression of Gi proteins is attenuated by losartan in A10 vascular smooth muscle cells: role of AT1receptors
Authors: Anand-Srivastava Madhu B , Palaparti Anuradha
Published: February 2003

We have previously shown that treatment of A10 vascular smooth muscle cells (VSMCs) with angiotensin II (Ang II) enhanced the expression of inhibitory guanine nucleotide regulatory proteins (Giα2and Giα3). In the present studies, we have investigated the role of type 1 angiotensin receptors (AT1) in the Ang-II-induced enhanced expression of Giα proteins and their functions in A10 SMCs. Ang II enhanced the levels of Giα2and Giα3proteins and their mRNA, as determined by Western and Northern blot analysis, respectively; losartan treatment attenuated the enhanced expression of Giα2and Giα3proteins and their mRNA in a concentration-dependent manner. In addition, the inhibition of adenylyl cyclase induced by Ang II and des(Glu18,Ser19,Glu20,Leu21,Gly22)ANP423-NH2(C-ANP423), which was attenuated by Ang-II treatment, was partially restored by losartan treatment. Similarly, losartan was also able to restore the Ang-II-induced stimulatory responses of isoproterenol and N-ethylcarboxamide adenosine (NECA) on adenylyl cyclase activity. These results suggest a role for AT1receptors in Ang-II-evoked increases in Giα protein expression and Gs-mediated stimulation in VSMCs.Key words: angiotensin II, AT1receptor, Gi proteins, adenylyl cyclase, losartan, A10 smooth muscle cells.
Effect of antihypertensive treatment on small artery remodeling in hypertension
Authors: Schiffrin Ernesto L
Published: February 2003

Blood vessels are remodeled in hypertension both structurally and functionally. The changes that occur in their structure, mechanical properties, and function contribute to blood pressure elevation and to complications of hypertension. We studied the remodeling of small arteries in experimental animals and humans. Smooth muscle cells of small arteries are restructured around a smaller lumen, with significant remodeling of the extracellular matrix and collagen and fibronectin deposition. Interestingly, there is no evidence of net growth of the vascular wall (which results in so-called eutrophic remodeling), particularly in the milder forms of human essential hypertension. Hypertrophic remodeling and increased small artery stiffness may be found in more severe forms of hypertension. Almost all hypertensive patients have vascular structural remodeling. However, only some exhibit endothelial dysfunction. This is particularly true in mild hypertension, in which endothelial dysfunction is less common. A 1-year treatment of hypertensive patients with angiotensin converting enzyme inhibitors, angiotensin AT1 receptor antagonists, and long acting calcium channel blockers corrected small artery structure and, to variable degrees depending on the agents used, impaired endothelial function. In contrast, beta blockers did not improve structure, function, or mechanics of vessels. When beta-blocker-treated patients were switched to an AT1 receptor antagonist, small artery structure and impaired endothelial function were corrected. The vascular protective action of some antihypertensive agents may contribute to improve outcome for hypertensive patients, although this is presently unproven.Key words: resistance arteries, smooth muscle, hypertrophy, endothelium, angiotensin converting enzyme inhibitors, AT1 receptor antagonists, calcium channel blockers, beta blockers.
Prevention of myosin-induced autoimmune myocarditis in mice by anti-L3T4monoclonal antibody
Authors: Yuan Hai-Tao , Liao Yu-Hua , Wang Zhaohui , Dong Ji-Hua , Cao Lin-Sheng , Wang Zhao-Hui , Wang Jin-Ping , Fu Michael L.X
Published: February 2003

This study was aimed at studying the effect of the induction of immune tolerance to swine cardiac myosin from anti-L3T4monoclonal antibody injection and whether the immune tolerance could protect mice with myosin-induced myocarditis from myocardial injury. Twenty-four Balb/c mice were divided into two groups at random. All of the mice were immunized with swine cardiac myosin on the 1st day, 14th, 28th, 42nd, and 52nd day. Immune tolerance was induced by triplicate injections of 400 μg anti-L3T4McAb on the 0 day (intravenous), 1st day, and 2nd day (intraperitoneal) in McAb-treated group. In the saline-treated group, saline of the same volume as anti-L3T4monoclonal antibody was used as a control. The sera and hearts biopsies of all mice were collected on the 58th day. The anti-cardiac myosin antibody was examined with ELISA, and pathological changes of heart were observed by light microscope. It was shown that mice immunized with swine cardiac myosin could produce anti-myosin antibody and the anti-cardiac myosin antibody was positive in most of the saline-treated group but negative in the McAb-treated group. Morphologically, myocardial degeneration, necrosis, and infiltration of inflammatory cells were found in the saline-treated group but not in the McAb-treated group. In conclusion, this study indicated that the immune tolerance to cardiac myosin was induced by the anti-L3T4monoclonal antibody, and accordingly myocardial injury could be prevented by induction of immune tolerance.Key words: anti-L3T4monoclonal antibody, myosin, immune tolerance, myocarditis.
Agonistic autoantibodies directed against the angiotensin II AT1receptor in patients with preeclampsia
Authors: Wallukat Gerd , Neichel Dajana , Nissen Eberhard , Homuth Volker , Luft Friedrich C
Published: February 2003

We showed that sera from patients with preeclampsia contain autoantibodies directed against the angiotensin II AT1receptor. The antibodies recognize an epitope on the second extracellular loop of the receptor and are immuno globulins of the IgG3 subclass. The antibodies accelerate the beating rate of neonatal rat cardiomyocytes. The agonistic effect can be blocked with the AT1receptor blocker losartan and can be neutralized by a peptide corresponding to the AT1receptor's second extracellular loop. In further studies we shown that the autoantibodies recognize a specific conformation of the AT1receptor. Cleavage of the external disulfide bond with dithiothreitol caused an inactivation of the receptor when stimulated either with Ang II or the autoantibodies in a system of cultured neonatal rat cardiomyocytes. Long-term stimulation of the AT1receptor with either agonists down-regulated the AT1receptor-mediated response to a second Ang II stimulation. These observations show that the agonistic autoantibodies behave pharmacologically in a similar fashion to Ang II. We have found the autoantibodies in all women meeting the clinical criteria of preeclampsia and suggest that they may be important to the pathogenesis of the disease.Key words: angiotensin II, preeclampsia, autoantibodies, IgG subclasses, dithiotrietol, AT1receptor.
Nuclear prostaglandin signaling system: biogenesis and actions via heptahelical receptors
Authors: Gobeil, Jr. Fernand , Vazquez-Tello Alejandro , Marrache Anne Marilise , Bhattacharya Mosumi , Checchin Daniella , Bkaily Ghassan , Lachapelle Pierre , Ribeiro-Da-Silva Alfredo , Chemtob Sylvain
Published: February 2003

Prostaglandins are ubiquitous lipid mediators that play pivotal roles in cardiovascular homeostasis, reproduction, and inflammation, as well as in many important cellular processes including gene expression and cell proliferation. The mechanism of action of these lipid messengers is thought to be primarily dependent on their interaction with specific cell surface receptors that belong to the heptahelical transmembrane spanning G protein-coupled receptor superfamily. Accumulating evidence suggests that these receptors may co-localize at the cell nucleus where they can modulate gene expression through a series of biochemical events. In this context, we have recently demonstrated that prostaglandin E2-EP3receptors display an atypical nuclear compartmentalization in cerebral microvascular endothelial cells. Stimulation of these nuclear EP3receptors leads to an increase of eNOS RNA in a cell-free isolated nuclear system. This review will emphasize these findings and describe how nuclear prostaglandin receptors, notably EP3receptors, may affect gene expression, specifically of eNOS, by identifying putative transducing elements located within this organelle. The potential sources of lipid ligand activators for these intracellular sites will also be addressed. The expressional control of G-protein-coupled receptors located at the perinuclear envelope constitutes a novel and distinctive mode of gene regulation.Key words: PGE2, EP receptors, cell nucleus, signal transduction, gene transcription.
Effect of human urotensin-II infusion on hemodynamics and cardiac function
Authors: Hassan Ghada S , Chouiali Fazila , Saito Takayuki , Hu Fu , Douglas Stephen A , Ao Zhaohui , Willette Robert N , Ohlstein Eliot H , Giaid Adel
Published: February 2003

Recent studies have shown that the vasoactive peptide urotensin-II (U-II) exerts a wide range of action on the cardiovascular system of various species. In the present study, we determined the in vivo effects of U-II on basal hemodynamics and cardiac function in the anesthetized intact rat. Intravenous bolus injection of human U-II resulted in a dose-dependent decrease in mean arterial pressure and left ventricular systolic pressure. Cardiac contractility represented by ±dP/dt was decreased after injection of U-II. However, there was no significant change in heart rate or diastolic pressure. The present study suggests that upregulation of myocardial U-II may contribute to impaired myocardial function in disease conditions such as congestive heart failure.Key words: urotensin-II, rat, infusion, heart.
Preischemic administration of ribose to delay the onset of irreversible ischemic injury and improve function: studies in normal and hypertrophied hearts
Authors: Wallen W Jack , Belanger Michael P , Wittnich Carin
Published: February 2003

Compared with normal hearts, those with pathology (hypertrophy) are less tolerant of metabolic stresses such as ischemia. Pharmacologic intervention administered prior to such stress could provide significant protection. This study determined, firstly, whether the pentose sugar ribose, previously shown to improve postischemic recovery of energy stores and function, protects against ischemia when administered as a pretreatment. Secondly, the efficacy of this same pretreatment protocol was determined in hearts with pathology (hypertrophy). For study 1, SpragueDawley rats received equal volumes of either vehicle (bolus i.v. saline) or ribose (100 mg/kg) before global myocardial ischemia. In study 2, spontaneously hypertensive rats (SHR; blood pressure [Formula: see text] 200/130) with myocardial hypertrophy underwent the same treatment protocol and assessments. In vivo left ventricular function was measured and myocardial metabolites and tolerance to ischemia were assessed. In normal hearts, ribose pretreatment significantly elevated the heart's energy stores (glycogen), and delayed the onset of irreversible ischemic injury by 25%. However, in vivo ventricular relaxation was reduced by 41% in the ribose group. In SHR, ribose pretreatment did not produce significant elevations in the heart's energy or improvements in tolerance to global ischemia, but significantly improved ventricular function (maximal rate of pressure rise (+dP/dtmax), 25%; normalized contractility ((+dP/dt)/P), 13%) despite no change in hemody na mics. Thus, administration of ribose in advance of global myocardial ischemia does provide metabolic benefit in normal hearts. However, in hypertrophied hearts, ribose did not affect ischemic tolerance but improved ventricular function.Key words: ribose, SHR, ischemia, ventricular function, metabolism.
Propagation of action potentials between parallel chains of cardiac muscle cells in PSpice simulation
Authors: Sperelakis Nicholas
Published: February 2003

Propagation of action potentials between parallel chains of cardiac muscle cells was simulated using the PSpice program. Excitation was transmitted from cell to cell along a strand of three or four cells not connected by low-resistance tunnels (gap-junction connexons) in parallel with one or two similar strands. Thus, two models were used: a 2 × 3 model (two parallel chains of three cells each) and a 3 × 4 model (three parallel chains of four cells each). The entire surface membrane of each cell fired nearly simultaneously, and nearly all the propagation time was spent at the cell junctions, thus giving a staircase-shaped propagation profile. The junctional delay time between contiguous cells in a chain was about 0.20.5 ms. A significant negative cleft potential develops in the narrow junctional clefts, whose magnitude depends on several factors, including the radial cleft resistance (Rjc). The cleft potential (Vjc) depolarizes the postjunctional membrane to threshold by a patch-clamp action. Therefore, one mechanism for the transfer of excitation from one cell to the next is by the electric field (EF) that is generated in the junctional cleft when the prejunctional membrane fires. Propagation velocity increased with elevation of Rjc. With electrical stimulation of the first cell of the first strand (cell A1), propagation rapidly spread down that chain and then jumped to the second strand (B chain), followed by jumping to the third strand (C chain) when present. The rapidity by which the parallel chains became activated depended on the longitudinal resistance of the narrow extracellular cleft between the parallel strands (Rol2). The higher the Rol2 resistance, the faster the propagation (lower propagation time) over the cardiac muscle sheet (2-dimensional). The transverse resistance of the cleft had no effect. When the first cell of the second strand (cell B1) was stimulated, propagation spread down the B chain and jumped to the other two strands (A and C) nearly simultaneously. When cell C1 was stimulated, propagation traveled down the C chain and jumped to the B chain, followed by excitation of the A chain. Thus, there was transverse propagation of excitation as longitudinal propagation was occurring. Therefore, transmission of excitation by the EF mechanism can occur between myocardial cells lying closely parallel to one another without the requirement of a specialized junction.Key words: propagation in cardiac muscle, transverse propagation between myocardial cells, PSpice simulations, electric field in junctional cleft.
The influence of resource seasonality on the breeding patterns of the Eurasian otter (Lutra lutra) in Mediterranean habitats
Authors: Ruiz-Olmo Jordi , Olmo-Vidal Josep Maria , Mañas Sisco , Batet Antoni
Published: February 2003

Litters of small Eurasian otter (Lutra lutra) cubs ranged from one to four, with those of one and two accounting for 95%. Significant variations were found between locations and according to the main diet (average ranging between 1.1 and 2.4 cubs/female). We found a seasonal pattern in otter breeding in some areas, being different in each. In the Prepyrenees, most births took place between March and June (85%). In Mediterranean rivers of the Ebro basin, most births occurred between December and February (57%). In both, the small cubs were found outside the dens just 23 months after the time of birth. Fish and crayfish exhibited a seasonal fluctuation, with a maximum density of biomass between the end of spring and the end of summer and minimum densities in winter. Water was always flowing in the Pyrenees and Prepyrenees rivers; however, in Mediterranean rivers, important periods of drought were observed, concentrated especially in summer and some winters. Timing of birds corresponded to variation in abundance of food (energy needs) and water resources in space and time. The presence of adequate prey species for the cubs (Ebro's barbel (Barbus graellsii and Barbus haasi) and American crayfish (Procambarus clarkii) in our study area) plays an important role. Interannual variations in food can affect the otter's reproductive cycle and breeding success.
Tests of emigration in small mammals under experimental conditions
Authors: Nelson A R , Johnson C L , Matter W J , Mannan R W
Published: February 2003

Holding animals in enclosures that block emigration causes demographic abnormalities called "fence effects." Experimenters have built exits that require animals to move through unfavorable conditions to leave enclosures. There are doubts about whether individuals that cross these challenging exits are true emigrants. We tested whether an exit that required house mice (Mus musculus) to swim through a water-filled trough was used only by mice triggered to emigrate from an experimental enclosure. Also, we examined the responses of mice to the availability of resources and the presence of conspecific adult animals in a small enclosure with an exit and in an enclosure made by joining two single enclosures. All mice left a barren enclosure within 12 h but no mice left during 7-day trials in a resource-rich enclosure during spring and summer. At the end of trials with repeated introduction of pairs of mice, about 85% of resident mice were the first mice added. Nearly all mice added later left the enclosure. A relatively constant number of mice became residents in small enclosures and about 2.3 times as many mice resided in double enclosures. Mice readily found and used exits when motivated to leave and did not accidentally pass through exits during routine exploration. Thus, mice that stayed in enclosures were not "fenced in" by the water-filled exit and exhibited residency as in nature. Tests of exits should give ecologists confidence that animals can display normal residency and emigration behaviors in experimental settings. The defense of resources by residents and the emigration of excess animals resulted in a consistent limit to the number of animals able to reside in enclosures.
Molecular systematics of some North American species of Diplostomum (Digenea) based on rDNA-sequence data and comparisons with European congeners
Authors: Galazzo Daniel E , Dayanandan Selvadurai , Marcogliese David J , McLaughlin J Daniel
Published: February 2003

The systematics of Diplostomum species, common intestinal parasites of piscivorous birds, has long been problematic, owing to phenotypic plasticity and the paucity of morphological features that are often subject to age- and host-induced variation. We sequenced the ITS15.8SITS2 regions of the rDNA from adult Diplostomum huronense, Diplostomum indistinctum, and Diplostomum baeri obtained from experimentally infected ring-bill gulls (Larus delawarensis) and compared them with partial ITS1 sequences from several species of Diplostomum in GenBank. The three North American species were distinguishable on the basis of ITS sequences. Sequences from D. huronense differed from those of D. indistinctum at 12 sites in ITS1 and 4 sites in ITS2, supporting morphological and morphometric data that indicate the two are distinct species. Sequences of D. huronense and D. indistinctum differed from those of D. baeri at 27 and 24 sites, respectively, in ITS1 and 15 and 12 sites, respectively, in ITS2. Phylogenetic analysis of partial ITS1 sequences revealed that the North American and European species of Diplostomum formed separate groups, with the former being basal to the latter. The results indicated that D. huronense and D. indistinctum from North America are distinct from Diplostomum spathaceum and other similar species from Europe. Furthermore, sequences from specimens identified as D. baeri from North America differed from those of D. baeri from Europe by 3.8% in ITS1 (23 sites). While morphologically similar, the two are not conspecific. Sequences of the North American species have been deposited in GenBank (AY 123042123044).
Pivotal temperature for loggerhead turtles (Caretta caretta) from Kyparissia Bay, Greece
Authors: Mrosovsky N , Kamel Stephanie , Rees Alan F , Margaritoulis D
Published: February 2003

Pivotal temperature (the constant temperature giving 50% of each sex) for two clutches of loggerhead sea turtles (Caretta caretta) from Kyparissia Bay, Greece, was 29.3°C. Pivotal incubation duration (the time from laying to hatching giving 50% of each sex) was 52.6 days. These values are close to those obtained for this species in Brazil and the United States, providing further evidence that these characteristics are relatively conservative in different populations. Methodological differences between different experiments and limitations on accuracy of equipment make the detection of small differences problematic. Comparison of incubation durations in the field with the pivotal durations obtained here suggest that hatchling sex ratio on some Mediterranean beaches is female biased but probably varies considerably within this region.
Relationship between predation-risk factors and sexual segregation in Dall's sheep (Ovis dalli dalli)
Authors: Corti Paulo , Shackleton David M
Published: February 2003

Using a population of Dall's sheep (Ovis dalli dalli), we examined two of the four main sexual-segregation hypotheses proposed: (1) the reproductive-strategy hypothesis, which proposes that males feed in the best foraging areas to enhance their reproductive fitness and females use areas with lower predation risk to raise offspring; and (2) the sexual dimorphism  body size hypothesis, which proposes that females use the areas with best forage to satisfy the nutritional demands of gestation and lactation, and that males, owing to their larger body size, have greater absolute metabolic requirements and therefore have to feed on forages which are more abundant but of lower quality. In our study, males were found farther from cover, in gentle terrain, and at lower altitude than were female groups, which were near cliffs or talus at higher altitudes. Female groups without lambs left cover, but were always active (feeding or moving). Forage density index values were higher in areas used by males than in areas used by female groups. Nutritional components were generally similar, but fibre content was higher in male areas. Signs of wolves (Canis lupus) and predation on Dall's sheep were recorded only at male areas. The results support the reproductive-strategy hypothesis, indicating that predation plays a key role in the development of sexual segregation in Dall's sheep.
Aspects of lymph-heart function inRana catesbeiana
Authors: Esbaugh A J , Hazel M , Toews D P
Published: February 2003

The effect of voluntary dives on the posterior lymph heart rate of the bullfrog, Rana catesbeiana, was tested and compared with the blood-heart rate (n = 6). This was performed by cannulating the posterior lymph heart and femoral artery simultaneously. Blood-heart rates during submergence were significantly lower (α = 0.05) then pre-submergence rates at all sampling times. In contrast, the lymph hearts showed significantly lower rates only during the first and last submergence intervals. It is believed that the lymph-heart bradycardia found during these intervals is due in part to the physiological "preparations" for diving by the frog. Further information regarding posterior lymph heart contractions was gained by cannulating two posterior lymph hearts on one side of the frog (n = 5). It was found that these hearts beat within 100 ms of each other between 66 and 97% of the time (α = 0.05). The combined contraction of the three posterior lymph hearts could facilitate the movement of lymph through the outflow valve and into the venous circulation. This study represents the first time the axial coordination of homolateral lymph hearts has been shown to extend to the multiple posterior lymph hearts.
Clearcut logging restricts the movements of terrestrial Pacific giant salamanders (Dicamptodon tenebrosus Good)
Authors: Johnston Barbara , Frid Leonardo
Published: February 2003

Pacific giant salamanders (Dicamptodon tenebrosus Good) in the Chilliwack River valley of southwestern British Columbia are at the periphery of their range, and therefore of conservation concern. Although logging is a potential threat to the species, no studies have examined how clear-cutting affects its terrestrial stage. We used radio telemetry to compare the movements of 35 terrestrial Pacific giant salamanders at sites with three different logging histories: forested, clearcut to the stream margin, and clearcut with riparian buffer strips. The results demonstrate that logging affected movements of the salamanders. Salamanders in clearcuts remained significantly closer to the stream, spent more time in subterranean refuges, and had smaller home ranges than those at forested sites. During a dry year, salamanders in clearcuts were significantly more dependent on precipitation for their movement than salamanders in forested habitats. Salamander movement behavior in riparian buffer strips was not significantly different from that at forested sites but was significantly different from that at clearcut sites. Riparian buffer strips appear to mitigate some of the negative effects of clearcuts on salamander movement.
Host specificity and colonization by Zachvatkinia caspica, an analgoid feather mite of Caspian Terns
Authors: Bridge Eli S
Published: February 2003

The relationships between feather mites and their avian hosts have great potential as subjects for studies of evolution and ecology. However, we must first achieve a better understanding of the ecological roles of feather mites (mutualistic versus parasitic) as well as their degree of host specificity before we can search for broad generalities at work in bird/feather-mite systems. I investigated host switching and feeding ecology in Zachvatkinia caspica, an analgoid feather mite that lives among the feathers of Caspian Terns (Sterna caspia). My approach involved imping (i.e., transplanting) mite-free feathers from California Gulls (Larus californicus) and Caspian Terns onto mite-infested Caspian Tern wings and quantifying the extent to which mites colonized the newly introduced feathers. This approach allowed me to expose the mites to both host and non-host feathers as well as to the presence or absence of preen oils collected from the two bird species. Mites "incubated" on tern wings showed no obvious avoidance of gull feathers or preen oil. This colonization of gull feathers suggests that some mite species have the potential to occupy a number of host species and that host switching in nature may be limited by infrequent opportunities to colonize nontraditional hosts.
Effect of operational sex ratio on femalefemale versus malemale competitive aggression
Authors: Grant James W.A , Foam Patricia E
Published: February 2003

We compared the patterns of femalefemale and malemale competition in Japanese medaka (Oryzias latipes) in response to changes in the operational sex ratio (OSR), the ratio of sexually active members of one sex to sexually active members of the opposite sex. As expected, courtship behaviour and intrasexual aggression were more frequent in males than in females. However, the overall patterns of femalefemale and malemale aggression were similar: intrasexual aggression increased with the OSR (female/male OSR for females and male/female OSR for males), consistent with predictions of mating-systems theory. A comparative analysis of our data and those from three other studies indicated that the rate of intrasexual aggression was greater in males than in females, but the patterns of intrasexual aggression were similar: the rate increased linearly and with a common slope with increasing OSR over a range of 0.43.
Synchrony in Svalbard reindeer population dynamics
Authors: Aanes Ronny , Sæther Bernt-Erik , Solberg Erling J , Aanes Sondre , Strand Olav , Øritsland Nils Are
Published: February 2003

We examined potential synchrony in the growth rates of three Svalbard reindeer (Rangifer tarandus platyrhynchus) populations and tested whether this pattern may result from correlated environmental variation. Two neighbouring populations had synchronized dynamics during the study period, while a more distant population showed different temporal variation. Climatic forcing (the Moran effect) was a likely synchronizing mechanism in combination with contrasting density-dependence patterns between the synchronous and asynchronous populations. Local climate was a more important synchronizing agent than a regional climate index (the Arctic Oscillation). Nevertheless, our results also suggest that variation in climate at a large scale may be important. Based on indirect measurements of dispersal/migration, our findings indicate that this factor does not play a key role in the spatial synchrony of Svalbard reindeer population dynamics.
Morphological and molecular identification of Saccoglossus species (Hemichordata: Harrimaniidae) in the Pacific Northwest
Authors: Smith Shannon E , Douglas Rob , Silva Karen Burke da , Swalla Billie J
Published: February 2003

Hemichordates, especially enteropneust worms, have become increasingly important in phylogenetic studies to test theories of chordate evolution. However, there are many populations of enteropneusts along the Pacific Northwest coast of North America that have not been identified. Here we show that two common Pacific Northwest enteropneust species, Saccoglossus pusillus and Saccoglossus bromophenolosus, can be distinguished by both morphological and molecular characters, and we identify several populations of both species. We compare them with a closely related species, Saccoglossus kowalevskii, from the Atlantic coast of North America. We compile the morphological characters used to distinguish harrimaniid enteropneusts, and we describe a new staining method to examine the gill bars and proboscis skeleton of enteropneusts to aid in identification. Using 18S and 16S ribosomal DNA sequences, we determine that the range of S. pusillus extends from southern California, where the worm was first identified, to southern Canada. This previously unknown large range shows a dramatic geographic cline in adult body size, with the smallest populations found in the south and the largest adults near Vancouver Island. In contrast, S. bromophenolosus may be a Pacific Northwest species that was relatively recently introduced from the Atlantic Ocean.