Assessment of energy requirement for the retinal arterial network in normal and hypertensive subjects

The retinal arterial network structure can be altered by systemic diseases such as hypertension and diabetes. In order to compare the energy requirement for maintaining retinal blood flow and vessel wall metabolism between normal and hypertensive subjects, 3D hypothetical models of a representative retinal arterial bifurcation were constructed based on topological features derived from retinal images. Computational analysis of blood flow was performed, which accounted for the non-Newtonian rheological properties of blood and peripheral vessel resistance. The results suggested that the rate of energy required to maintain the blood flow and wall metabolism is much lower for normal subjects than for hypertensives, with the latter requiring 49.2% more energy for an entire retinal arteriolar tree. Among the several morphological factors, length-to-diameter ratio was found to have the most significant influence on the overall energy requirement.     

High frequency characteristics of the arterial system

Pressure, flow and diameter were measured in the abdominal aorta of five anesthetized dogs during normal heart beats and heart beats with a superimposed impulse (generated by rapidly injecting a small volume of saline into the system). From Fourier analysis it was found that the impulse enhanced the amplitudes of the higher harmonics so that frequencies up to 80 Hz could be studied. Both the input impedance and apparent phase velocity above 20 Hz were independent of frequency and their average values were designated as characteristic impedance and true phase velocity. Average characteristic impedance for all five animals was 2.0 +/- 0.1 X 10(8) Nsm-5 and average phase velocity was 8.3 +/- 0.6 ms-1. Phase velocities calculated from characteristic impedance (1.76-2.39 X 10(8) Nsm-5) and from the slope of the pressure-diameter relation (0.102-0.25 X 10(-8) Nm-3) were similar to the true phase velocity as defined above (6.79-9.85 ms-1). It may be concluded that the input impedance converges to characteristic impedance and apparent phase velocity converges to phase velocity for high frequencies.     

Age-related characteristics of the organic angioarchitectonics of normal rats and in arterial hypertension

Architectonics of intraorganic arterial vessels in the cervical cortex, heart, kidneys and spleen have been investigated in 40 normotensive and spontaneously hypertensive rats, 6 months and 1 year old. In all the organs studied a direct dependence has been revealed between the degree of changes in the intraorganic arteries and relative content of the arterial vessels in the tissue organs. Functional changes of the arterial vessels in the organs studied observed during the hypertensive phase, transfer into the organic ones, as a result of prolonged adaptation, when the stage of a stable hypertension takes place.     

Effect of brain serotonin on the arterial pressure and plasma renin in normal and hypertensive rats]

The effects of changes in brain serotonin content after injections of p-chlorophenylalanine (p-CPA), L-5-hydroxytryptophan (L-5HTP) and 5-6-dihydroxytryptamine (5-6DHT) on the mean arterial pressure (MAP), plasma renin activity (PRA) and peripheral levels of atrial natriuretic peptide (ANP) have been studied in normal and hypertensive (2K:1C model) male Wistar rats. The p-CPA (250 mg/kg) and L-5HTP (200 mg/kg) were injected i.p., while 5-6 DHT (15 micrograms/animal in 10 mu/animal vehicle) was injected into lateral brain ventricles. The effects were studied 24 h after the p-CPA injection, 2 h after L-5HTP and 10 or 20 days after 5-6DHT administration. The fall in brain serotonin produced by p-CPA and 5-6DHT did not modify the MAP values in the normal and hypertensive rat model, whereas the increase induced after L-5HTP injection only caused a slight decrease in arterial pressure in normotensive animals. The ARP experimented remarkable rises in the normal and hypertensive rats, these values increasing after L-5HTP and falling after p-CPA and 5-6 DHT injections. Similar changes are detected in the normal group after administration of these substances related to serotoninergic brain activity. The ANP levels rose after renal artery constriction, and they are not affected by the above mentioned substances. Only p-CPA and 5-6DHT reduced a low decrease in the ANP levels 10 days after their administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Physical performance and skeletal muscle characteristics after 2-week hind-limb unweighting

It is well-known that 2 weeks of hind-limb suspension or space flight induce the sufficient decrease of the physical performance and simultaneously changes of muscle contractile properties and fiber size. However, the data on enzyme activities changes at present are contradictory. Numerous authors have pointed to the increase, reduction of its activity as well as its stability after experiments of the similar design. In previous studies it was shown that beta-GPA (beta-guanidino-propionic acid) administration increased the oxidative enzyme activities in the skeletal muscles and improved their contractile properties in hind-limb suspended rats. The aim of our study is to clear out what determines changes of the physical performance after 2 weeks of hind-limb suspension and beta-GPA administration.     

Large signal,low frequency characteristics of the systemic arterial system

A 4-parameter model to represent the relationship between slowly changing arterial inflow and the resulting pressure change was proposed. In order to determine values for the parameters and test the model in a wide range of pressure and flow, two experimental procedures were used. Firstly, slow oscillations in aortic pressure (period, 4 sec) were produced by means of an external pump connected to the aorta, and secondly, cardiac arrest was induced for about 2–3 sec by stimulating the right vagus. It was shown mathematically that the pressure and pump displacement information obtained in these experiments could be related to the model parameters. Values for the model parameters were obtained in 6 anesthetized dogs using a least squares adjustment procedure. Using aX ²-test, it was concluded that the model represented the arterial system for each animal well.     

Carnitine ester hydrolysis in arteries from normal and cholesterol-fed rabbits and the effects of carnitine esters on arterial microsomal ACAT

• 1.1. Carnitine ester hydrolysis was observed in homogenates of normal rabbit (Oryctolagus cuniculus) aortas and in intact aortas from normal and cholesterol-fed rabbits using [¹⁴C]palmitoylcarnitine as a substrate.
• 2.2. Hydrolytic activity was decreased approximately 50% in arterial tissue from cholesterol-fed rabbits and may account for the observation that carnitine esters accumulate in arteries of animals fed atherogenic diets.
• 3.3. Long-chain acylcarnitines (C₁₄–C₁₈) were found to be moderate inhibitors of microsomal acylCoA:cholesterol acyltransferase (ACAT, EC 2.3.1.26); short-chain acylcarnitine (C₂–C₁₀) and carnitine itself were not inhibitors.
• 4.4. The data suggest that the increase in activity of arterial ACAT that characteristically parallels the development of atherosclerosis does not occur as a result of carnitine ester accumulation.

     

Systemic arterial pressure and characteristics of its changes in response to hypertensive agents in tumor-bearing animals

Arterial pressure (in the carotid artery determined by electromanometry) and total peripheral resistance (changes in the clear space of resistive arteries of the mesenterium, skeletal muscles and mammary glands measured by biotelemicroscopy) were studied in tumor-bearing animals (random bred, BALB/c and CBA mice with Ehrlich carcinoma). With the growth of hypodermic injected tumor, it has been shown that the arterial pressure first dropped and then there was a tendency towards normalization, but the pressure never reached the initial level. At the same time arterial dilatation took place, especially at the first stage of tumor growth. This shows the dependence of changes in arterial pressure on the clear space of resistive arteries. It was also revealed that changes in the vascular tone were connected with the functional disturbances of adrenoactive structures but not with reduced myocyte contractility.     

Ultrastructural characteristics of branch sphincters and precortical arteries in the rabbit pial arterial system

Structural peculiarities of pial arteries and their active microvascular segments-sphincters in offshoots and precortical arteries have been investigated, using electron and light microscopy. Our studies have revealed that these vascular segments, which can independently change their lumen, possess multiple myoendothelial junctions, as well as neuro-muscular contacts. This gives evidence of their independent responses that might be determined by structural peculiarities and innervation of their walls.     

去负荷小鼠比目鱼肌收缩特性和纤维类型转化

目的:探讨去负荷后小鼠比目鱼肌的收缩特性与骨骼肌纤维类型转化之间的关系。方法:采用离体肌肉灌流技术和电刺激方法,在小鼠后肢去负荷28 d引起骨骼肌萎缩后,观察比目鱼肌单收缩、强直收缩能力和肌疲劳指标等收缩特性的改变,同时利用组织免疫荧光染色和实时定量聚合酶链式反应(real-time PCR)等技术检测去负荷后比目鱼肌快慢肌纤维组成和纤维类型转化的变化。结果:去负荷28 d后,小鼠比目鱼肌单收缩力、强直收缩能力和疲劳指数(fatigue index)均有显著性下降,同时伴有快肌纤维亚型的增加和慢肌纤维亚型的减少。结论:去负荷28 d后小鼠比目鱼肌收缩特性的改变和快慢肌纤维类型的转化有关。     

Reactivity of isolated arteries from hypertensive rabbits]

Isolated vessels (aorta thoracica, a pulmonalis, a. femoralis, a. renalis) of neurogenous-interoceptive and nephrogenous hypertensive rabbits showed a changed sensitivity to several vasoactive agents. An increased reactivity to noradrenaline, histamine, and serotonin in the aorta of neurogenous hypertensive rabbits, in the a. pulmonalis of neurogenous and renal hypertensive rabbits and in the a. femoralis of renal hypertensive animals in comparison with controls could be shown. Also registered was a hyperactivity to BaCl2 and KCl. All vessels of hypertensive rabbits were hyporeactive to angiotensin. They increased vascular reactivity was seen already in the 3rd week after removal of one kideny and pressoric receptors respectively. It is supposed that a "true supersensitivity" of the vascular smooth muscle cells of the hypertensive arteries does exist.