Age and day-night changes in clonidine-induced analgesia in mice

Administrations of clonidine hydrochloride (0.1, 1.0 mg/kg) to young, mature, and old mice influenced their response time on a thermally aversive surface (50 degrees C) in an age-dependent manner. This analgesic effect was of short duration. During daytime measurement periods, young and mature mice showed significantly greater analgesic responses than did the old animals. Although all animals were able to perform the appropriate paw-licking response, the old mice displayed tremors and locomotor disturbances after receiving clonidine. These effects were not seen in the younger groups. Both the young and mature animals showed a substantial enhancement of their analgesic responses after receiving clonidine at night, whereas a significant but much reduced nighttime increase in antinociceptive effect was seen in old animals. Yohimbine, but not prazosin, inhibited clonidine-induced analgesia in young animals. Old mice given combinations of clonidine and these adrenergic antagonists showed elevations in response times, accompanied by severe behavioural changes.     

Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses

Background

L-theanine, an amino acid contained in green tea leaves, is known to block the binding of L-glutamic acid to glutamate receptors in the brain, and has been considered to cause anti-stress effects by inhibiting cortical neuron excitation. Both L-theanine and caffeine, which green tea contains, have been highlighted for their beneficial effects on cognition and mood.

Methods

In this study, we investigated the effects of orally administered L-theanine or caffeine on mental task performance and physiological activities under conditions of physical or psychological stress in humans. Fourteen participants each underwent three separate trials, in which they orally took either L-theanine + placebo, caffeine + placebo, or placebo only.

Results

The results after the mental tasks showed that L-theanine significantly inhibited the blood-pressure increases in a high-response group, which consisted of participants whose blood pressure increased more than average by a performance of a mental task after placebo intake. Caffeine tended to have a similar but smaller inhibition of the blood-pressure increases caused by the mental tasks. The result of the Profile of Mood States after the mental tasks also showed that L-theanine reduced the Tension-Anxiety scores as compared with placebo intake.

Conclusions

The findings above denote that L-theanine not only reduces anxiety but also attenuates the blood-pressure increase in high-stress-response adults.     

Effects of elements on blood pressure

This article presents a comprehensive review of all known elements involved in blood pressure control. Data source was by computerized literature searches. A total of 28 elements have been documented as being involved in blood pressure control. The individual elements react directly and indirectly in a variety of metabolic and structural activities known to participate in blood pressure regulation. Reports from both experimental animal and human subjects are presented. The role of certain elements in blood pressure control is controversial. Conversely, important established functions of dosage, absorption, storage, and excretion of individual elements are known and are described in relation to blood pressure control. Some elements are pressor, whereas others are depressor in action, and this article demonstrates the important role elements play in the control of blood pressure.     

Periodic fluctuations of the blood pressure and heart contraction rate in premature newborn infants

To study the postnatal development of circadian rhythm of the blood pressure and the heart rate these parameters were monitored automatically during 24-72 hours at 5h intervals. Fifty infants were investigated at the age 1, 2, 3, and 4 weeks. The results were compared with the cosine curves of different periods (1-48 h) by the IBM PC XT. The fluctuations with all mentioned periods including circadian could be determined in each infant, dominating period being of any duration. In traditional approach the expressiveness of periodical fluctuations is evaluated by the amplitude of cosine curve. Application of the criterion has shown that only amplitude values exceeding 8 mm Hg should be taken into account. Hence, the analysis of BP and HR time series has demonstrated that about 45-50% of the infants have noncircadian rhythms, 20-20% have no significant periodical fluctuations and only 25-30% have circadian rhythm.     

Effects of climatic fluctuations and land-use changes on the hydrology of temperate fluviogenous mire

The upper part of the Narew River valley (NE Poland) belongs to the last extensive undrained, non-reclaimed valley wetlands in Central Europe. However, in recent decades, the fluviogenous mire has experienced a significant change in water resources which may be linked to climatic fluctuations and changes in vegetation. In NE Poland during the last three decades, a clear trend toward milder and drier climate has been observed that has resulted in lower river discharge. Reduction in surface water inflow into the mire, diminished duration and degree of flooding, decrease in summer rainfall and increase in evapotranspiration have led to the substantial fall of the groundwater table in the valley and a decrease in volume of water stored in organic sediments. A comparison of water table measurements made in the 1970s with contemporary observations showed that presently, summer minimum groundwater levels are as much as 60 cm lower than in the past. A significant drop of water table elevation might be additionally attributed to increased ET caused by cessation in agricultural use of the mire and expansion of Phragmites. Between the 1970s and 2002, the total amount of water lost by ET increased by 42%, whereas ET_o rose by 7% only. We found that patches of common reed rushes were hot spots for ET across the Narew wetland landscape. The evaluation of the effectiveness of restoration measures aimed at restoration of the water conditions in the Narew mire led us to the conclusion that raising the river water level by use of in-stream structures may be not adequate to make up the summer moisture deficit and ensure a sufficiently high groundwater level in the adjacent wetland. The restoration goal may be partly achieved by large vegetation manipulation in the form of mowing or grazing. Vegetation management could reduce ET by 170 mm m⁻² year⁻¹, potentially minimizing the extent and the duration of groundwater drawdowns.     

Effects of chronic insulin treatment on blood pressure in rats

There is an evident epidemiological association between plasma insulin levels and blood pressure. The mechanism that relates insulin to blood pressure and the role of insulin in the pathogenesis of arterial hypertension have not been clearly defined. The present study was designed to examine the effects of chronic hyperinsulinism on blood pressure and to determine different related morphological variables. WistarKyoto rats were subcutaneously injected with insulin (25 UI/Kg of weight) daily during the eight weeks of the experiment. Data were collected on systolic and diastolic arterial pressures and heart rate by plethysmography and direct recording (in the last week), and on morphological variables. A statistically significant elevation of systolic arterial pressure was produced after the sixth week of hyperinsulinaemia. At the end of the treatment, the systolic arterial pressure was 173.7 +/- 26.1 in the hyperinsulinaemic rats versus 153.09 +/- 21.7 in the control group. The values obtained by direct recording and by plethysmography did not differ. These results indicate that chronic hyperinsulinism produces a significant elevation in systolic blood pressure levels in the rats studied.     

Clinical relevance of about-yearly changes in blood pressure and the environment

Changes identified by inferential statistics from summer to winter of high to low arterial blood pressures (BP) have been quantified as a large predictable about-yearly BP swing. This condition of a large annualBP amplitude (LABPA) raises concern about hypotension as well as hypertension and raises new questions regarding appropriate guidelines for diagnosis and treatment. Recommendations made in the fall on the basis of data collected in the summer may be totally inadequate in dealing with the patient's condition in the winter. In order to avoid such mistakes, it is imperative to implement a systematic surveillance of BP in the light of current chronobiological limits. Patients with a large circannual BP amplitude are particularly suited for a study of the underlying hormonal mechanisms. The longitudinal monitoring of their BP is also amenable to the study of environmental influences from near and far.Dedicated to the memory of Agostino Carandente, MD, who until his death on 26 August 1996 used the resources available to him as manager of a major pharmaceutical company in a nearly fulltime endeavor to foster chronobiology, and published the journalChronobiologia, which for 21 years was a leading medium for the dissemination of chronobiologic research worldwide. Agostino Carandente also inspired his children to follow the trail he helped blaze and contributed his familial, intellectual and financial means to the science of the body's time structure. Agostino's love for Latin prompts the following motto of this paper: Quæcumque vera sunt — tam physicalia, emotionalia, ac intellectualia, quam diagnostica, præventiva, curativaque — cognoscunt ante et supra ceteros chronobiologi et chronobiologæ (whatever truths there are — whether physical, emotional and intellectual, or diagnostic, preventive and curative — before and above all others, chronobiologist understand them).     

淫羊藿总黄酮对大鼠动脉血压影响及其机制的实验研究

目的：观察淫羊藿（HE）对大鼠动脉血压的影响。方法：在大鼠侧脑室注射（icv）淫羊藿总黄酮（TFE）观察其对股动脉血压（ABP）的影响。结果：淫羊藿总黄酮对正常和应激高血压（SIH）大鼠平均动脉血压（MAP）有降低作用,用荷包牡丹碱（Bic）影响TFE的降压效应。结论：TFE具有降压效应,其机制可能与GABAA受体相关．     

Effects of elements in human blood pressure control

This review enumerates and discusses the elements involved in the control of human blood pressure via a historical evolutionary form. The older and most recent element literature presentations were researched using MEDLINE and a manual review of documents cited. Independent data extraction and cross-referencing was performed. Of the 28 known elements that can influence blood pressure, 15 were found to be involved in human blood pressure regulation. The elements were divided into four groups: electrolyte, composed of sodium, potassium, calcium, and magnesium; metal, which included zinc, copper, and iron; toxic, made up of lead, mercury, cadmium, barium, thallium, arsenic; miscellaneous (lithium and selenium). Evolutionary historical data, possible mechanisms of actions, and interactions between elements that have been shown to influence blood pressure are discussed. Controversy exists over the therapeutic use of elements to alter blood pressure but is absent in the case of the toxic group where preventive control is a proven public health matter. The significance of these 15 elements in the regulation of human blood pressure has been established and ongoing studies will continue to reinforce their influence and importance.     

Analysis of bronchovascular downstream blood pressure changes in exercising sheep

The relative roles of neural and pressure gradient factors, causing a fall or maintenance of bronchial blood flow in exercising sheep, are unknown. These were examined in sheep prepared under thiopentone/isoflurane general anaesthesia with a pulsed Doppler probe mounted on the bronchial artery, and aortic pressure (Pa) catheter in superficial cervical artery. After recovery, Swan-Ganz catheters were inserted under local anaesthesia into the pulmonary artery. Bronchial flow and conductance (Qbr, Cbr), and pressure gradients (Pg; i.e. aortic minus right atrial, Pg_RAP; pulmonary artery, Pg_Ppa; and, left atrial (wedge) Pg_LAP) were derived from continuous records, after switching between downstream sites during and after moderately severe treadmill exercise (3.8 km.h(-1), for 1.7 min, 6 min recovery). The protocol was repeated after combined alpha1,alpha2-adrenoceptor/cholinoceptor blockade using phentolamine methanesulfonate and methscopolamine bromide. Bronchial flow fell in both receptor intact (INT) and (BL) blocked state. Pa rose in INT, but downstream pressures rose only 3.7 (RAP), 2.8 (Ppa) and 2.0 (LAP) mmHg (P for each < 0.05) in both INT and BL. Pg_RAP and Pg_Ppa did not rise, but Pg_LAP rose 4.0 mmHg (P < 0.05). In BL, Pa fell, as did Pg_RAP (7.0 mmHg, P < 0.05), Pg_Ppa (8.9 mmHg, P < 0.001), but Pg_LAP did not change. Thus, downstream pressures change by small amounts, and pressure gradients to RAP and Ppa sites do not change during moderately severe exercise in normal sheep. The fall in Qbr in INT is due to neural factors, but in BL is due to a fall in Pg. The relative rise in Pg_LAP in both INT and BL favours redistribution within total Qbr to the pulmonary capillary/vein/left atrium site.     

Effects of chronic baroreceptor unloading on blood pressure in the dog

We have developed a new model of chronic baroreceptor unloading (CBU) in the dog. Initial characterization of the model indicated that CBU increased mean arterial pressure (MAP) by an average of 22 mmHg for 7 days. The goal of the present study was to replicate the previous study using telemetry to record MAP continuously and to determine the effects of CBU (n = 7) on chronic regulation of MAP. We also prepared a group of dogs with sinoaortic denervation (SAD, n = 6) to compare the time course of changes in MAP in the two models. Control levels (7 day average +/- SE) of MAP in the CBU and SAD groups were 94 +/- 2 and 94 +/- 1 mmHg, respectively. MAP averaged 124 +/- 8 and 103 +/- 4 mmHg during the first and second weeks after SAD (both P < 0.05) and then declined to levels not different from control during weeks 3-5. In the CBU group, MAP averaged 120 +/- 4 mmHg during the first week, declined to 111 +/- 4 mmHg during the second week, and stabilized at 104 mmHg during weeks 3-5 (all P < 0.05 compared with control). Plasma norepinephrine levels were increased significantly for the first week after SAD and for 2 wk after CBU but were not different from control for the remainder of the study. These results indicate that the initial increase in MAP after CBU is not sustained but declines to a level that is modestly higher than control. However, because MAP did not fall to control levels, the results are compatible with the hypothesis that baroreceptor input can influence the long-term level of MAP.