Molecular characterization of Echinococcus granulosus strains in Sardinia.

Investigations were undertaken to determine the genotypes of the parasite Echinococcus granulosus that were present in livestock animals on the island of Sardinia. Liver, lung, and spleen samples were obtained from 770 sheep, 229 cattle, and 277 pigs slaughtered in Sardinia between January 2003 and April 2005, and the number and fertility of hydatid cysts were determined. Protoscoleces and/or germinal layer were collected from individual cysts, DNA was extracted from 91 samples, and polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (RFLP) methods were used for identification of the strain genotype for each sample (G1, G5, G6/G7). Fragments of the mitochondrial cytochrome c oxidase subunit 1 and NADH dehydrogenase I were sequenced. Hydatid disease prevalence of 75.3, 41.5, and 9.4% were found in the organs collected from sheep, cattle, and pigs, respectively. Molecular analysis showed that 89 of 91 ovine, bovine, and swine cysts belonged to the G1 genotype (common sheep strain) of E. granulosus. Parasite isolates from two pigs were identified to belong to the G7 genotype (pig strain). Our results confirm the high prevalence of E. granulosus infection in livestock animals in Sardinia and reveal the presence of at least two parasite genotypes in Sardinia.

Predisposition to repeat breeding in UK cattle and success of artificial insemination alone or in combination with embryo transfer.

To investigate whether there was a subpopulation of repeat breeders (cows or heifers that returned to oestrus after three inseminations) that were less fertile after a fourth artificial insemination (AI) with or without additional embryo transfer, and to estimate the efficacy of AI plus embryo transfer to overcome repeat breeding problems, a two-part investigation was carried out. Part 1 involved 85 repeat breeders and 85 controls subjected to AI alone. In part 2, 128 repeat breeders received AI on day 0 plus an embryo transfer seven days later, while controls received embryo transfer alone on day 7. In repeat breeders, the interval between calving and pregnancy was 80 days longer than in the controls (P=0.01), irrespective of previous fertility treatment which had mainly focused on the ovaries. The incidence of dystocia was similar in repeat breeders and in controls, but repeat breeders had a higher previous incidence of moderate uterine infection compared with controls (P=0.04). In repeat breeder cows, pregnancy rates for AI alone were 30 per cent after the fourth AI (controls: 45 to 64 per cent after one to three inseminations) compared with 52.6 per cent after a fourth AI with embryo transfer (controls with embryo transfer alone: 49 per cent). Successful pregnancies after a fourth AI plus embryo transfer produced a 6.25 per cent incidence of twins.

Molecular characterization of Echinococcus granulosus in sheep and goats of Peloponnesus, Greece.

Although cystic echinococcosis (CE) has been a recognized public health problem in Greece, molecular data are lacking regarding the types and prevalences of infecting strains of the etiological agent Echinococcus granulosus. Therefore, we investigated the prevalence of CE and determined the infecting genotypes in sheep and goats in Peloponnesus, a large region of southern Greece. Liver and lung samples were obtained from 210 sheep and 190 goats slaughtered between January and December 2005, and the number, morphology, and fertility of hydatid cysts were determined. Protoscoleces or germinal layers were collected from individual cysts (20 sheep and 20 goats), and DNA was extracted. A polymerase chain reaction (PCR)/seminested PCR system was used to distinguish the G1, G5, and G6/G7 strains, and a specific molecular diagnosis was obtained by sequencing PCR-amplified mitochondrial DNA encoding cytochrome c oxidase subunit 1 and NADH dehydrogenase I genes. The prevalence of CE was 30.4% in sheep and 14.7% in goats; fertile cysts were found in 16.2 and 7.4%, respectively. Overall, 18 of 20 sheep harbored the G1 genotype (common sheep strain), while the remaining two animals had the G3 (buffalo) strain. All 20 goats were infected with the G7 (pig) strain. These results document the prevalence of E. granulosus infection in food animals in this geographical area and reveal for the first time the presence of, at least, three parasite genotypes.

Genetic variation within Taenia multiceps in Sardinia, Western Mediterranean (Italy).

Investigations were undertaken on Taenia multiceps to determine if genetic variation was present within the parasites of Sardinia (Italy). Forty samples were obtained from various locations of Sardinia and deoxyribonucleic acid (DNA) was extracted. Polymerase chain reaction (PCR) was performed on NADH dehydrogenase I (ND1) and cytochrome c subunit 1 (CO1) mitochondrial genes and amplicons were then sequenced and aligned with Bioedit software. Pairwise comparison between the ND1 sequences of the T. multiceps isolates showed differences ranging from 1.27 to 2.54% using an isolate obtained from Wales as an outgroup, while COI sequences showed within the samples coming from Sardinia a lesser degree of variability, ranging from 0.22 to 0.67%. Considering the two genes, it was possible to define at least three specific genetic variants in Sardinian samples, which we have termed Tm1, Tm2, and Tm3. This is the first description of genetic variability in T. multiceps. Further investigations will be required to understand to what extent the genetic variability described in this paper would be reflected also in phenotypic differences.

Bistability and irreversible transitions in a simple substrate cycle.

The dynamic properties of a simple substrate cycle involving two antagonist enzymes are investigated. One of these enzymes exhibits a non-linearity through inhibition by excess substrate. Depending either on the interconverted substrate pool concentration or the maximal activity of the non-inhibited enzyme, monostability, bistability and irreversible transitions may occur. A reversible bistable cycle is shown to present interesting features for regulatory purposes as it can respond to external (and/or internal) modulations in two different ways: A buffering effect by efficient stabilization of the steady-states, or, an increase in sensitivity by switching the system from one regime to the opposite one. The plausible biochemical and biological implications of irreversible transitions are discussed and emphasized in terms of "metabolic transitions".

Effects of various direct or indirect dopamine agonists on the latency of the acoustic startle response in rats.

The effects of dopamine agonists were investigated on the latency of the acoustic startle response in male Wistar rats. Four indirect dopamine agonist were tested: GBR 12783 (5-20 mg/kg), BTCP (5-20 mg/kg), dexamphetamine (3-6 mg/kg) and L-DOPA 100 mg/kg associated with benserazide 25 mg/kg; they induced an increase in startle latency. Apomorphine at a dose (50 micrograms/kg) known to decrease dopaminergic transmissions, was ineffective on the startle response. On the contrary, at 0.6 or 2 mg/kg, apomorphine induced an increase in the startle latency. A similar effect was observed with bromocriptine at 10 mg/kg from the 10th min up to at least the 9th hour after treatment. The specific agonist of D2 receptors Ru 24926 (0.45 mg/kg) enhanced the startle latency as well as the specific agonist of D1 receptors SKF 38393 (10 mg/kg). The association of these drugs resulted in an apparent additivity of their individual effects. The effect of apomorphine (0.6 mg/kg) was only partially reduced by a high dose of the specific D2 antagonist amisulpride (80 mg/kg) and more clearly antagonized by the specific D1 antagonist SCH 23390 (50 micrograms/kg). It is concluded that D2 and D1 receptors contribute to the increase in startle latency elicited by direct or indirect dopamine agonists.

Hysteresis phenomena between periodic and stationary solutions in a model of pacemaker and nonpacemaker coupled cardiac cells.

We were interested in investigating the behaviour of a cardiac electrophysiological model including coupled pacemaker (PM) and nonpacemaker (NPM) cells. To this aim, a modified version of the model of Van Capelle and Durrer was used. First, few discrete values were assigned to coupling resistance (CR) and respective cell sizes and numerical simulations versus time showed three possible kinds of response pattern: sustained rhythmic activity, subthreshold oscillations, and complete inhibition. Then, after setting a fixed value to PM cell size, we undertake a thorough study of the system by using bifurcation-continuation techniques and CR was chosen as the continuation parameter. On the maximum action potential--CR plane representation, we could describe five behavioural zones: complete inhibition, coexistence of complete inhibition and NPM large oscillations, NPM large oscillations, coexistence of NPM large oscillations and subthreshold oscillations, subthreshold oscillations. Within the zones of qualitatively different coexisting solutions, a detailed exploration clearly demonstrated the presence of hysteresis cycles. Indeed, the status of the system depended on its immediate previous story within narrow ranges of CR values. Such a coexistence of stable solutions for identical values of CR may suggest an explanation of the intermittant activity elicited from abnormal ectopic foci observed in certain ventricular rhythm disturbances. In addition, a Hopf bifurcation point, from which emerged stationary and periodic solutions, was followed on the PM cell size--CR plane and from this representation we could deduce that the smaller the PM cell, the higher the CR must be for the PM cell to escape from the NPM cell inhibition.