The Valsalva manoeuvre--cardiovascular effects and performance technique: a critical review

Variations in the technique of the Valsalva manoeuvre (VM) have been shown to greatly influence the pattern of cardiovascular response (CVR) to the test. Intra-strain tachycardia, post-strain bradycardia, Valsalva ratio, and baroreflex sensitivity decrease in proportion to an increase in lung volume and a decrease in strain pressure at VM. In conditions of completely expanded lungs and low strain pressure many subjects reveal an intra-strain bradycardic response to VM instead of the usual tachycardic one. Intra-strain arterial hypotension and post-strain hypertension decrease with decrease in strain pressure. The changes in heart rate and blood pressure during an expiratory VM are greater than the responses observed during completition of an inspiratory VM. The rate of the deep inspiration prior to strain has an impact particularly on phase I of the VM. The magnitude of the CVR correlates with the strain duration, particularly at high levels of strain pressure, and depends on the baseline level of the cardiovascular parameters and their variations. The paper discusses the possible mechanisms of different CVRs to variations in the technique of the VM. Some practical recommendations are suggested.     

Differences in forebrain activation in two strains of rat at rest and after spinal cord injury

Forebrain activation patterns in normal and spinal-injured Sprague-Dawley (SD) rats were determined by measuring regional cerebral blood flow as an indicator of neuronal activity. Data are compared to our previously published findings from normal and spinal-injured Long-Evans (LE) rats and reveal a striking degree of overlap, as well as differences, between strains in the basal (unstimulated) forebrain activation in normal animals. Specifically, 81% of the structures sampled showed similar activation in both strains, suggesting a consistent and identifiable pattern of basal cerebral activation in the rat. LE controls showed significantly greater basal activation in the remaining structures compared to SD control group, including the anterior dorsal thalamus, basolateral amygdala, SII cortex, and the hypothalamic paraventricular nucleus. In contrast, spinal cord injury (SCI) resulted in strain-specific changes in forebrain activation categorized by structures that showed significant increases in: (1) only LE SCI rats (posterior, ventrolateral, and ventroposterolateral thalamic nuclei); (2) only SD SCI rats (anterior-dorsal and medial thalamus, basolateral amygdala, cingulate and retrosplenial cortex, habenula, interpeduncular nucleus, hypothalamic paraventricular nucleus, periaqueductal gray); or (3) both strains (arcuate nucleus, ventroposteromedial thalamus, SI and SII somatosensory cortex). These results provide information related to the remote, i.e. supraspinal, effects of spinal cord injury and suggest that genetic differences play an important part in the forebrain response to such injury. Brain activation studies therefore provide a useful tool in understanding the full extent of secondary consequences following spinal injury and for identifying potential central mechanism responsible for the development of pain.     

Biomechanical analysis and quantitative analysis of bone scintigraphy on thrust plate hip prosthesis

Introduction To study the load distribution of the thrust plate hip prosthesis (TPP, Sulzer Medica, Baar, Switzerland) on femoral bone, a TPP insertion group and intramedullary cemented stem insertion group were prepared with the use of embalmed femoral anatomic specimens, and strain on the femoral bone induced by loading was measured.Materials and methods Bone scintigraphy was performed in 26 joints which underwent total hip arthroplasty with the use of TPP, to enable quantitative evaluation of postoperative remodeling of the bone.Results In the TPP insertion group, the strain was almost equivalent to that in the untreated femoral control group. On the other hand, compared with the control group and TPP insertion group, strain in the proximal portion of the femoral bone (medial side of the femoral neck) was significantly smaller in the cemented stem group (control group versus cemented stem insertion group, p=0.0062; cemented stem insertion group versus TPP 130° insertion group, p=0.0005; cemented stem insertion group versus TPP 140° insertion group, p=0.0031). Bone scintigrams revealed decreased uptake at 12 weeks after operation compared with 6 weeks after operation, indicating that TPP allows earlier implant stabilization than the conventional stem.Conclusion Compared with the conventional stem, TPP is a prosthesis that can perform physiological load transmission.     

职业紧张、紧张反应、应对资源与工作能力的关系

目的　研究职业紧张、紧张反应、应对资源与工作能力的关系。方法　采用职业紧张量表 (OSI R)和工作能力指数法 (WAI)测试 2 2 70例不同职业类型者的职业紧张、紧张反应、应对资源和工作能力变化。结果　 ( 1)不同性别间工作能力差异无显著性 (P >0 0 5 )。职业紧张男性高于女性 (P <0 0 1) ,而应对资源女性高于男性 (P <0 0 5 )。≥ 5 0岁年龄段紧张程度较 <3 0岁年龄段得分高 ,而应对资源 <3 0岁年龄段均高于其他年龄段 (P <0 0 5 )。工作能力差异有显著性 (P <0 0 1) ,且随年龄增高呈下降趋势 (P <0 0 5 ) ,40～岁年龄段开始下降。 ( 2 )工作能力分级为好者 ,职业任务总均分及紧张反应得分显著降低 (P <0 0 5 ) ,而应对资源得分显著升高 (P <0 0 5 )。 ( 3 )工作能力与职业紧张、紧张反应总均分呈明显负相关 (P <0 0 1) ,而与应对资源呈正相关 (P <0 0 1) ;职业任务与紧张反应总均分呈正相关 ,二者与应对资源总均分呈负相关 (P <0 0 1)。 ( 4 )职业任务各子项与紧张反应各子项 (除工作环境子项与业务紧张反应外 )呈正相关 ;任务不适、任务模糊、任务冲突与应对资源各子项呈明显负相关 (P <0 0 5或P <0 0 1)。紧张反应各子项之间互为正相关 ,并与应对资源 (除人际关系与休闲外 )呈明显负     

Anxiolytic-like profile in Wistar, but not Sprague–Dawley rats in the social interaction test

Rationale The social interaction test is a valuable behavioural model for testing anxiolytic drugs in rodents, quantifying the level of social behaviour between pairs of rats.Objective The aim of the present study was to assess the appropriateness of the social interaction test for use with a Sprague–Dawley rat line, because of increasing use of this strain in targeted mutagenesis research.Methods Sprague–Dawley and Wistar rats received either diazepam or mCPP or were exposed to different environmental conditions (lighting, social isolation prior testing, habituation, testing-time). General anxiety-related parameters measured were: duration of active social contact, frequency of active social contact, latency to first contact. Different forms of active social contact were recorded: number of crawls, follows and sniffs. Secondly, aversion-induced hippocampal serotonin release and serotonin content in brain regions were measured.Results In Wistar rats habituation to the test substantially increased the time of social contact, an effect comparable with treatment with diazepam (1 mg/kg), whereas changes in the lighting level had less impact. Latency to the first contact increased under anxiety-reducing conditions, the frequency of contacts did not change consistently. Sprague–Dawley rats behaviour did not change under varying environmental conditions, and treatment with diazepam had only sedating effects at higher doses (5 mg/kg). Anxiogenic doses of mCPP caused reduced social interaction in both strains. Serotonin release and serotonin content were higher in the anxious Wistar rats.Conclusions Different rat strains as well as differing test conditions have a major impact on the outcome of this animal test for anxiety.     

Postnatal development of resistance to short-term high-dose toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in TCDD-resistant and -semiresistant rats

Despite great interspecies differences in adult 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) sensitivity, the toxic potency of TCDD is similar across species in fetal mortality. Han/Wistar (Kuopio; H/W) rats are exceptionally resistant to acute toxicity of TCDD, but show sensitivity to embryotoxicity and teratogenicity. The resistance of adult H/W rats to acute TCDD toxicity is based on a point mutation in the transactivation domain of the aryl hydrocarbon receptor (AHR) and to an unknown gene “B”. This study investigated the time course of postnatal development of resistance to TCDD and the significance of genotypic variation in resistance development. H/W, line A (a new line with the H/W-type mutated AHR), and line B rats (a line with normal AHR but moderately resistant because of gene “B”) were exposed to a single dose of TCDD 2-56 days after birth. H/W and line A rats received 1000 μg/kg; male and female B rats received 200 and 100 μg/kg, respectively. Survival was monitored for 42 days. Interestingly, although TCDD ceased growth and weight gain in all TCDD groups, the younger dosed animals did not seem to reach the body weight of the older dosed animals even in 100 days. The survival results after 42 days showed that line A rats are fairly resistant to TCDD immediately after birth, and their full TCDD resistance develops during the first week of life. The moderate resistance of line B rats develops approximately at the time of weaning. This difference in the time course of resistance development suggests that there are basic differences in pathways mediating resistance in lines A and B rats.     

Genetic identification and host range of the Spanish strains of Echinococcus granulosus

Three strains of Echinococcus granulosus have been previously identified in Spain (namely 'sheep', 'horse' and 'pig'), but these Spanish strains have not been properly genotyped yet. The aim of the present research was to identify the genotype to which they correspond to. Cyst isolates were obtained from different host species, and the strain to which each belonged was established by analysis of its random amplified polymorphic DNA (RAPD) banding patterns. These results were compared to those obtained with the analysis of two mitochondrial fragment sequences (cytochrome oxidase 1 (CO1) and NADH dehydrogenase 1 (ND1)) from each isolate. The Spanish 'sheep' strain corresponded with the genotype 1 (G1) of the parasite, infecting Spanish sheep, cattle, goat, pig, wild boar and human; the Spanish 'horse' strain corresponded with the genotype 4 (G4), only infecting Spanish horses; and the Spanish 'pig' strain corresponded with the genotype 7 (G7), infecting Spanish goat, pig and wild boar. Goat, pig and wild boar can be infected by two genotypes, G1 and G7. This circumstance, and especially the possibility of sylvatic intermediate hosts serving as reservoirs of the G1 genotype of the parasite, must be taken into consideration by authorities in order to develop and evaluate effective anti-hydatidosis programmes.     

In vivo anterior cruciate ligament strain behaviour during a rapid deceleration movement: case report

The mechanism of anterior cruciate ligament (ACL) injury is still unclear. To gain this insight, knowledge of the mechanical behaviour of the healthy ACL during activities that may stress the ligament must be investigated in vivo. The goal of this research was to measure ACL strain in vivo during rapid deceleration, a sport type movement that has been previously shown to precede injuries to the ACL in healthy subjects. A young male subject with no previous knee joint injuries volunteered after informed consent. The strain gauge device (DVRT) was calibrated and surgically implanted in the antero-medial band of the intact ACL. The subject was then transported to the lab for data collection. The zero strain position of the ACL was determined using the slack-taut technique. The subject hopped as quickly as possible from a distance of 1.5 m to the target, an X taped at the centre of a force plate, landing with the instrumented left leg and stopping in the landed position. The entire collection window was five seconds at 1000 Hz. A total of three rapid deceleration trials were collected and averaged over the hop cycle. The slack-taut test was then repeated to ensure proper operation of the DVRT and the reliability of the results. The results showed an average peak strain of the ACL during the instrumented Lachman test of 2.00±0.17%. The average peak strain of the ACL during the rapid deceleration task was 5.47±0.28%. The data indicate that the RD task caused an increase in peak ACL strain that is much higher than during the instrumented Lachman test, and that the strain begins to increase during the flight phase, prior to landing, and reaches a peak that corresponds to the peak ground reaction force. This technique may be used in further sport-specific movements to gain insight into movement patterns associated with ACL injury mechanisms.     

Central neurotensin receptor activation produces differential behavioral responses in Fischer and Lewis rats

Rationale Lewis (LEW) and Fischer (F344) rats exhibit marked differences in appetitive and consummatory responses to numerous drugs, including psychostimulants. Neurotensin (NT) produces psychostimulant-like actions, which sensitize with repeated exposure, and neuroleptic-like actions; effects that are dependent on the site of microinjection. The aim of the present experiments was to assess the behavioral sensitivity of these two strains of rats to NT receptor activation. Methods In expt 1, locomotor activity was assessed on alternate days following an ICV injection of NT, [d-Tyr¹¹]neurotensin (d-NT; 18 nmol/10 μl), or vehicle (days 1, 3, 5, and 7) in independent groups of LEW and F344 rats. On day 14, locomotor activity was assessed in all rats following an injection of d-amphetamine (1 mg/kg, IP). In expt 2, activity was assessed following injection into the ventral tegmental area of NT, or d-NT, (2.5 μg/hemisphere) or into the nucleus accumbens (2.5 and 5.0 μg/hemisphere). Results Repeated ICV injections of NT, or d-NT, produced differential behavioral effects in the two strains of rats on days 1–7; activity was initially suppressed in LEW, but less so in F344 rats, following NT. In F344, but not in LEW rats, d-NT produced a significant increase in activity. Neurotensin and d-NT sensitized LEW rats to amphetamine-induced ambulatory and non-ambulatory activity. Except for vertical activity, this effect was weaker or in the opposite direction in F344 rats. When injected into the ventral tegmental area, NT produced an increase in locomotor activity in both strains, an effect that was greater in F344 than LEW rats with d-NT. In the nucleus accumbens, NT marginally decreased activity in both strains, while d-NT produced a significant increase in F344 but not in LEW rats. Conclusions These results provide empirical evidence that endogenous NT neurotransmission within limbic circuitry differs in F344 and LEW rats.     

Dose-response analysis of short-term effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in three differentially susceptible rat lines

Line A, B, and C rats were selectively bred from TCDD-resistant Han/Wistar (Kuopio; H/W) and TCDD-sensitive Long-Evans (Turku/AB; L-E) rats. Line A rats are the most resistant to TCDD acute lethality followed by line B and line C rats. The resistance in line A rats is associated with a mutated H/W-type aryl hydrocarbon receptor (Ahr) allele (Ahr(hw)) and in line B rats the resistance is associated with an allele of an unknown gene B (B(hw)), while line C rats are almost as sensitive to TCDD as L-E rats. The dose-responses of characteristic short-term effects (day 8 postexposure) of TCDD were used to evaluate the efficacy (magnitude of effect) and potency relationships between these lines. Line A rats showed similar efficacies as line C (line A:line C efficacy ratio more than 0.7) for thymus weight, EROD activity, and incisor tooth defects. In contrast, efficacies in line A were decreased (efficacy ratios 0.19-0.37) for body weight change, serum bilirubin, and FFA levels, and serum ASAT activity. For most endpoints the efficacies in line B rats seem to be lower than in line C rats. The potencies were close to each other in line A and B rats, but somewhat lower than in line C rats. The results support our previous concept of two different AHR-mediated signaling pathways leading to dioxin type I and type II endpoints. Rats with the Ahr(hw/hw) genotype show a markedly decreased efficacy for type II endpoints, but B(hw) allele had only a minor effect on efficacies for most endpoints. Both H/W-type resistance alleles also decreased the potency of TCDD. However, the potency differences in short-term toxicity seem not to explain, at least alone, the differences seen in acute lethality among the rat lines.