Reactive hyperemia in Raynaud's disease

We studied reactive hyperemia after ischemia, after cold, and after cold plus ischemia, in normal subjects, in fingers with Raynaud's phenomenon, and in fingers without Raynaud's phenomenon in hands where other fingers were affected by Raynaud's phenomenon. The results obtained demonstrate the existence of a criohyperdysestesia both in fingers with Raynaud's phenomenon and in fingers without Raynaud's phenomenon in hands where other fingers are affected by it.     

Reactive hyperemia is not responsible for stimulating muscle protein synthesis following blood flow restriction exercise

Blood flow restriction (BFR) to contracting skeletal muscle during low-intensity resistance exercise training increases muscle strength and size in humans. However, the mechanism(s) underlying these effects are largely unknown. We have previously shown that mammalian target of rapamycin complex 1 (mTORC1) signaling and muscle protein synthesis (MPS) are stimulated following an acute bout of BFR exercise. The purpose of this study was to test the hypothesis that reactive hyperemia is the mechanism responsible for stimulating mTORC1 signaling and MPS following BFR exercise. Six young men (24 ± 2 yr) were used in a randomized crossover study consisting of two exercise trials: low-intensity resistance exercise with BFR (BFR trial) and low-intensity resistance exercise with sodium nitroprusside (SNP), a pharmacological vasodilator infusion into the femoral artery immediately after exercise to simulate the reactive hyperemia response after BFR exercise (SNP trial). Postexercise mixed-muscle fractional synthetic rate from the vastus lateralis increased by 49% in the BFR trial (P < 0.05) with no change in the SNP trial (P > 0.05). BFR exercise increased the phosphorylation of mTOR, S6 kinase 1, ribosomal protein S6, ERK1/2, and Mnk1-interacting kinase 1 (P < 0.05) with no changes in mTORC1 signaling in the SNP trial (P > 0.05). We conclude that reactive hyperemia is not a primary mechanism for BFR exercise-induced mTORC1 signaling and MPS. Further research is necessary to elucidate the cellular mechanism(s) responsible for the increase in mTOR signaling, MPS, and hypertrophy following acute and chronic BFR exercise.     

Post pressure hyperemia in the rat

In prior studies in man, we have demonstrated that pressure-induced hyperemia lasts for prolonged periods as compared to the short-term hyperemia created by proximal arterial occlusion. We have analyzed this phenomenon in our well-studied rat model of skin blood flow. Skin blood flow was measured using laser Doppler techniques in Wistar Kyoto rats at the back, a nutritively perfused site, and at the plantar surface of the paw, where arteriovenous anastomotic perfusion dominates. A customized pressure feedback control device was used to vary applied pressures. At the back, pressures in excess of 80 mmHg resulted in occlusion, whereas at the paw 150 mmHg was required. The peak hyperemic flow after release of pressure was comparable to that elicited by proximal arterial occlusion with a blood pressure cuff. However, the post pressure hyperemia peak descended to a plateau value, which was 50-100% greater than baseline and continued for up to 20 min while the peak following proximal arterial occlusion returned to baseline within 4 min. At the back, post pressure hyperemia reached a maximum after application of 100 mmHg pressure. The application of higher pressures than required for occlusion produced no greater hyperemic response. At the paw, maximum post pressure hyperemia occurred at 100 mmHg, although this pressure level was not totally occlusive. Higher pressures resulted in no greater hyperemia. At the back, 10 min of occlusion produced a maximal peak value whereas 1 min was sufficient at the paw. The application of pressure to a heated probe with subsequent release, produced a hyperemic response. Normalized to baseline blood flow, there was no difference between the hyperemic responses at basal skin temperature and at 44 degrees C. There is a prolonged hyperemic response following local pressure occlusion compared to a much shorter period following proximal ischemic occlusion. One can presume two different mechanisms, one related to ischemia and the other a separate pressure related phenomenon. The thermal vasodilatory response is additive, not synergistic with the post pressure hyperemia we have demonstrated. This finding suggests that different mechanisms are involved in thermal vasodilation and post pressure hyperemia.     

Reactive thiol groups in rat liver acid phosphatase

Dimeric rat liver acid phosphatase P1 of Mr 92,000 is inactivated by p-chloromercuribenzoate and fluorescein mercuriacetate (FMA). The enzyme is protected against the mercurials by the substrate analogue Pi. The reaction with FMA is accompanied by changes in absorbance at 495 nm and in fluorescence emission at 520 nm that are characteristic of reaction of this compound with thiol groups. Titration of P1 with FMA monitored by spectrophotometry or by fluorimetry indicated that equivalence is reached at an FMA/P1 ratio of 3. Since FMA can act as a bifunctional reagent, it is likely that P1 contains either 3 or 6 reactive thiol groups per molecule. Analysis of FMA inactivation/modification data by a statistical method suggests that of 6 reactive thiol groups, 2 are essential so that there are probably 3 thiol groups per subunit, one of which is located at the active site. If the total thiol number is 3, analysis suggests 1 essential thiol per subunit.     

A comparative study of reactive hyperemia in human forearm skin and muscle

Reactive hyperemia (RH) in forearm muscle or skin microcirculation has been considered as a surrogate endpoint in clinical studies of cardiovascular disease. We evaluated two potential confounders that might limit such use of RH, namely laterality of measurement and intake of non-steroidal anti-inflammatory drugs (NSAIDS). Twenty-three young non-smoking healthy adults were enrolled. In Experiment 1 (n=16), the RH elicited by 3 min of ischemia was recorded in the muscle (strain gauge plethysmography, hand excluded) and skin (laser Doppler imaging) of both forearms. In Experiment 2 (n=7), RH was determined in the dominant forearm only, one hour following oral acetylsalicylic acid (1 g) or placebo. In Experiment 1, peak RH was identical in both forearms, and so were the corresponding durations of responses. RH lasted significantly less in muscle than in skin (p=0.003), a hitherto unrecognized fact. In the skin, acetylsalicylate reduced duration (43 vs. 57.4 s for placebo, p=0.03), without affecting the peak response. In muscle, duration tended to decrease with acetylsalicylate (21.4 vs. 26.0 s with placebo, p=0.06) and the peak increase in blood flow was blunted (27.2 vs. 32.4 ml/min/100 ml tissue with placebo, p=0.003). We conclude that, when using RH as a surrogate endpoint in studies of cardiovascular disease, a confounding by laterality of measurement need not be feared, but NSAIDS may have an influence, although perhaps not on the peak response in the skin.     

Reactive oxygen and ischemia/reperfusion injury of the liver

Pharmacological experiments suggested that reactive oxygen species contribute to ischemia-reperfusion injury of the liver. Since there is no evidence that quantitatively sufficient amounts of reactive oxygen are generated intracellularly to overwhelm the strong antioxidant defense mechanisms in the liver and cause parenchymal cell injury, the role of reactive oxygen in the pathogenesis remains controversial. This paper reviews the data and conclusions obtained with pharmacological intervention studies in vivo, the sources of reactive oxygen in the liver as well as the growing evidence for the importance of liver macrophages (Kupffer cells) and infiltrating neutrophils in the pathogenesis. A comprehensive hypothesis is presented that focuses on the extracellular generation of reactive oxygen in the hepatic sinusoids, where Kupffer cell-derived reactive oxygen species seem to be involved in the initial vascular and parenchymal cell injury and indirectly also in the recruitment of neutrophils into the liver. Reactive oxygen species may also contribute to the subsequent neutrophil-dependent injury phase as one of the toxic mediators released by these inflammatory cells.     

Reactive modifications of the autonomous time structure in the human organism

The spectrum of biological rhythms exhibits characteristic principles of biological time structure which also rule the functional behaviour. With increasing period lengths the rhythms become increasingly complex. In the long-wave section the rhythmic functions find their corresponding cycles in the environment, whereas the shorter waves represent only endogenous autonomous rhythms, which maintain an internal time order by means of frequency- and phase-coordination. Under resting conditions and in a state of complete adaptation only a few spontaneous rhythms dominate in the spectrum. However, under loading conditions as well as in pathological situations further periodicities come up. The spectrum of rhythms can be divided into certain blocks, with the period lengths predominating in each of these whole number frequency ratios forming a harmonic system. Frequency- and phase coordination establish a system of co-action which favours the functional economy of the organism. A tripartite organization of the autonomous rhythms involves different functional behaviours with regard to frequency, amplitude, and phase. Slower rhythms act upon the faster rhythms preferably by modulating their frequencies, while changes of the faster rhythms influence the slower ones by enhancing their amplitudes, multiplying their period lengths and shifting their phases. In principle the reactions of living systems are periodically structured. Reactive periodicity brings to appearance an endogenous time structure, which prefers whole number relationships with the spontaneous rhythms. The phase position of reactive periods depends on the stimulus. The amplitudes dampen down with increasing compensation. From the medical point of view so-called circaseptan (about 7 days) reactive periods are of predominant interest. This periodicity can be observed in numerous adaptive and compensating processes. It does not depend on the external week cycle and was already known to the antiquity.     

Bioactive nitric oxide concentration does not increase during reactive hyperemia in human skin.

This study examined whether nitric oxide (NO) is involved in the cutaneous response to reactive hyperemia (RH) in the human forearm. We enrolled seven healthy volunteers. NO concentrations were monitored using a NO selective amperometric electrode (ISO-NOP200, World Precision Instruments) inserted into the skin of the forearm. Laser-Doppler flowmetry (Moor Instruments) was used for monitoring skin blood flow (SkBF) at the same site. SkBF and NO levels were monitored and recorded continuously throughout the experiment. An intradermal microdialysis probe was inserted adjacent to the NO electrode for drug delivery. Data collection began 140 min after the NO electrodes and microdialysis probes were inserted. RH was achieved by the inflation of a blood pressure cuff to 25 mmHg above systolic pressure for 7 min after which the pressure in the cuff was abruptly released. Acetylcholine (ACh) was given by microdialysis probe at the end of RH study to verify the ability of the electrode system to detect changes in the NO concentration. SkBF and NO data before RH and immediately, 2, 5, 7, and 10 min after cuff deflation were used for analysis. SkBF increased immediately after release of the occlusion (P < 0.0001) and remained elevated for 2 min. No significant NO changes occurred with the increases in LDF. ACh induced increases in both SkBF and NO (P < 0.000 and P < 0.037, respectively). We conclude that RH increases SkBF by mechanisms that do not require a measurable increase in NO concentrations.     

Hyaluronidase treatment of coronary glycocalyx increases reactive hyperemia but not adenosine hyperemia in dog hearts

Because adenosine is commonly used for inducing maximal coronary hyperemia in the clinic, it is imperative that adenosine-induced hyperemia (AH) resembles coronary hyperemia that can be attained by endogenous stimuli. In the present study we hypothesized that coronary reactive hyperemia (RH) is limited compared with AH due to the presence of the glycocalyx and that the AH response is therefore unable to detect glycocalyx modifications. In anesthetized open-chest dogs, blood flow and pressure were measured in the left circumflex artery. RH after 15-s occlusion was compared with an intracoronary infusion of adenosine (650 microg; AH) during control conditions and after intracoronary treatment of the glycocalyx with hyaluronidase (20.000 U, 2 x 20 min; n = 6) or heat-inactivated hyaluronidase (n = 5). During control, coronary conductance during RH was 1.49 +/- 0.15 ml.mmHg(-1).min(-1) and 76 +/- 7% of coronary conductance during AH (P < 0.05). After hyaluronidase, RH conductance increased (P < 0.01) by 43 +/- 13% and became 93 +/- 4% of AH conductance (P = NS). Heat-inactivated hyaluronidase had no effect on RH and AH conductance. Our results demonstrate that adenosine-induced coronary hyperemia profoundly exceeds RH and that the difference is virtually abolished on selective removal of the glycocalyx. It is concluded that, compared with RH, adenosine-induced coronary hyperemia is not affected by modification of the glycocalyx. This glycocalyx insensitivity should be taken into account when using adenosine-induced coronary hyperemia as a marker for vasodilating capacity to an ischemic stimulus.     

Cholinergic nerves in the human liver

Summary The cholinergic innervation of the human liver was studied. Slices (150–200m thick) of human liver and of the greater hepatic blood vessels (hepatic artery and vein, portal vein) were incubated in a solution of 6-hydroxydopamine (6-HDA) in order to obtain a selective degeneration of adrenergic nerves. Controls were prepared from samples incubated with buffer alone. The slices were cut on a cryostat into 15–20m thick sections and processed for the histochemical detection of cholinesterases.Cholinergic nerve fibres innervate the extra hepatic and the intrahepatic branches of the hepatic artery, the portal vein as well as the hepatic vein. Fewer cholinergic fibres innervate the hepatocytes and the hepatic sinusoids. The 6-HDA treatment does not seem to alter the pattern of the cholinergic innervation of the liver. The findings indicate the presence of a cholinergic parasympathetic innervation in the human liver.     

Mechanisms involving the endothelium in reaction of reactive hyperemia

The experiments on anesthetized dogs and on test-preparations of isolated vascular rings of femoral artery used for detection of appearance of vasoactive substances in venous blood demonstrated that the response of reactive hyperemia is accompanied by the appearance of vasodilation substances in the blood, the concentration of which taking into account the reaction of relaxation of vascular preparation, increases with the occlusion duration. Chemical inhibition of endothelium of a studied bed by saponin essentially decreases the reactive hyperemia and relaxation of test-preparation. The rise of pressure in an overlapped part of a bed and the decrease in the deformation of endothelium with the help of dimerized glutaraldehyde treatment affected the hyperemia and vascular preparation reaction in the similar way. We concluded that the reaction of reactive hyperemia is the result of the vasoactive substances secretion by endothelium in response to a decrease in intravascular pressure.     

Role of the endothelium in the development of reactive hyperemia

The experiments on anesthetized dogs demonstrated that reaction of the femoral vessels reactive hyperemia essentially decreased after chemical inhibition of endothelium by saponin, inhibition of lipoxygenase by quercetin and guanylate cyclase by methylene blue. Reaction was increased after cyclooxygenase inhibition by indomethacin. We concluded that the endothelium plays an important role in reaction of reactive hyperemia by endothelium-derived relaxing factor release.     

Hepatocarcinogenesis in human liver

Due to the development of the imaging techniques and liver surgery, pathologists are encountered more frequently with preneoplastic liver lesions. Well-defined stages of human hepatocarcinogenesis have been distinguished recently. Dysplastic foci represent the earliest stage of this process. Small-cell dysplastic foci are tumor precursors, but the large-cell form of this lesion does not progress further. The next stage is the dysplastic nodule, this larger lesion can be recognized by imaging techniques and gross examination of the specimen. Low- and high-risk forms are distinguished based on the level of cytological and structural atypia. The small hepatocellular carcinomas have a diameter of less than 2 cm by definition. The small HCC of indistinctly nodular type is equivalent of in situ carcinomas in other organs and designated sometimes as early HCC. The small HCC of the distinctly nodular type can be interpreted as advanced cancer despite its small size. The distinction between these lesions can be facilitated by ancillary techniques. The so-called capillarization of the liver sinusoids during the progression is characterized by the increased expression of endothelial markers as CD31 and CD34. Immunostaining for CD44, beta-catenin and p53 has prognostic value. Molecular biological techniques reveal gradual epigenetic and DNA changes during the process of hepatocarcinogenesis. Global gene expression profiling of hepatocellular carcinomas may result in a new classification of this tumor and can reveal new potential therapeutic targets.     

Reactive oxygen species in the killing of Pseudomonas aeruginosa by human leukocytes

Pseudomonas aeruginosa (PA) infects hosts with compromised host defenses. An important defense mechanism is the generation of reactive oxygen species (ROS) by white blood cells (WBCs). What roles do ROS play in host defense against PA? Human WBCs killed PA in vitro, and they generated a respiratory burst as measured by the production of H₂O₂. ROS efficiently killed PA; in acellular assays, less than 10mm of H₂O₂ or OCl^- eliminated all bacteria in 90 min. However, WBCs with suppressed production of ROS (caused by hypoxia) killed PA normally. In addition, none of the antioxidants vitamin C, N-acetylcysteine, superoxide dismutase, or catalase affected PA killing by WBCs. Thus, PA stimulates WBCs to produce ROS, which can kill the bacteria, but disturbances of WBC ROS production do not interfere with the killing of PA. WBCs have robust, redundant mechanisms for PA elimination.