Biomedical subjects

G E Nilsson

Publications and source records attributed to G E Nilsson.

At least 19 recordsLinked to original sources

PubMed2004

Muscle dysfunction during exercise of a single skeletal muscle in rats with congestive heart failure is not associated with reduced muscle blood supply.

AIM: Inadequate muscle blood flow is a possible explanation for reduced fatigue resistance in patients with congestive heart failure (CHF). METHODS: In rats with post-infarction CHF we electrically stimulated the soleus muscle (SOL) in situ with intact blood supply. Contractile properties, blood flow, high-energy phosphates and metabolites were measured during 30 min of intermittent stimulation, and in addition capillarization of SOL was recorded. RESULTS: During stimulation, SOL contracted more slowly in rats with CHF compared with sham-operated rats. However, the blood flow in SOL was unaltered and capillary density was maintained in CHF rats. Further, the content of ATP, ADP, AMP, NAD, CrP, P(i) and lactate in SOL was not different between the groups. CONCLUSION: The cause of contractile dysfunction in a single exercising skeletal muscle in rats with CHF cannot be explained simply by reduced blood supply. In addition, absence of changes in high-energy phosphates and metabolites indicate that the oxidative metabolism of SOL is intact in rats with CHF.

Animals↗

PubMed2002

Cardiovascular effects of prostaglandin F(2 alpha) and prostaglandin E(2) in Atlantic cod (Gadus morhua).

Little is known of the cardiovascular functions of prostaglandins in non-mammalian vertebrates. There are indications that prostaglandins may have a function in haemostasis by constricting blood vessels in filament arteries in the fish gill after injury. Our aim was to examine the cardiovascular effect of the prostaglandins F(2 alpha) (PGF(2 alpha)) and E(2) (PGE(2)) with emphasis on branchial circulation. Intra-arterial injections of PGF(2 alpha) (10, 40, 160, 400 nmol kg(-1)) in cod caused a dose-dependent increase in ventral aortic blood pressure, a reduction in cardiac output, and an increase in gill vascular resistance. A contraction of filament arteries was observed with in vivo microscopy only seconds after injection. PGF(2 alpha) may therefore possibly be involved in a haemostatic vasoconstriction. In contrast, the most significant effects of PGE(2) appeared to be on the heart. PGE(2) also reduced dorsal aortic blood pressure.

Animals↗

PubMed2002

Spectral signature and heterodyne efficiency for different wavelengths in laser Doppler flowmetry.

Laser Doppler perfusion monitoring and imaging technologies generate time traces and two-dimensional flow maps of the microcirculation. With the goal of reaching different tissue depths, these technologies are equipped with lasers operating at different wavelengths lambda. The fact that the average scattering angle, at a single scattering event, between a photon and a red blood cell increases with lambda is compensated for by a 1/lambda effect in the scattering vector, rendering the average frequency shift virtually independent of the choice of wavelength. Monte Carlo simulations showed that the corresponding spectral signature of the Doppler signals for lambda = 632.8 nm and 780 nm were close to identical. The theoretical predictions were verified by calculating the centre-of-gravity (COG) frequency of the laser Doppler power spectral density for the two wavelengths from forearm and finger skin, representing a low and high perfusion area, respectively (forearm COG= 123 against 121 Hz, finger COG = 220 against 212 Hz). When the wavelength changes from 632.8 nm to 780 nm, the heterodyne efficiency of the detector and, thereby, the inherent system amplification increase. For tissues with identical microvascular flow conditions, the output signal therefore tends to increase in magnitude when shifting to longer wavelengths.

Humans↗

PubMed2002

Guidelines for visualization of cutaneous blood flow by laser Doppler perfusion imaging. A report from the Standardization Group of the European Society of Contact Dermatitis based upon the HIRELADO European community project.

This report reviews how to set up a laser Doppler perfusion imaging system intended for visualization of skin blood perfusion, capture images and evaluate the results obtained. A brief summary of related papers published in the literature within the areas of skin irritant and allergy patch testing, microdialysis and skin tumour circulation is presented, as well as early applications within other fields such as diabetology, wound healing and microvascular research.

Humans↗

PubMed2001

Effect of anoxia and adenosine on cerebral blood flow in the leopard frog (Rana pipiens).

The effect of anoxia on cerebral blood velocity (CBV) on the dorsal surface of telencephalon was examined in the leopard frog, Rana pipiens, using a stereomicroscope. During exposure to anoxia, a transient 228% increase in CBV velocity was seen after 20 min, but CBV fell back to basal values after a further 20 min of anoxia. Topical application of 50 microM adenosine during normoxia caused a 52% increase in CBV, while 250 microM adenosine caused no further increase. At both concentrations, the effect was completely inhibited by the adenosine receptor blocker aminophylline (250 microM). Superfusing the brain with aminophylline during anoxia did not affect the anoxia-induced increase in CBV. We conclude that adenosine can stimulate CBV in R. pipiens. However, unlike in other anoxia-tolerant animals, adenosine seems not to be a main mediator of the anoxia induced increase in CBV in the frog.

Adenosine↗

PubMed2001

Does anoxia induce cell swelling in carp brains? In vivo MRI measurements in crucian carp and common carp.

Although both common and crucian carp survived 2 h of anoxia at 18 degrees C, the response of their brains to anoxia was quite different and indicative of the fact that the crucian carp is anoxia tolerant while the common carp is not. Using in vivo T(2) and diffusion-weighted magnetic resonance imaging (MRI), we studied anoxia induced changes in brain volume, free water content (T(2)), and water homeostasis (water diffusion coefficient). The anoxic crucian carp showed no signs of brain swelling or changes in brain water homeostasis even after 24 h except for the optic lobes, where cellular edema was indicated. The entire common carp brain suffered from cellular edema, net water gain, and a volume increase (by 6.5%) that proceeded during 100 min normoxic recovery (by 10%). The common carp recovered from this insult, proving that the changes were reversible and suggesting that the oversized brain cavity allows brain swelling during energy deficiency without a resultant increase in intracranial pressure and global ischemia. It is tempting to suggest that this is a function of the large brain cavity seen in many ectothermic vertebrates.

Animals↗

PubMed2001

Surviving anoxia with the brain turned on.

Crucian carp is one of few vertebrates that tolerate anoxia. It maintains brain ATP during anoxia partially by reducing ATP consumption. However, unlike turtles, which become comatose during anoxia, this fish remains physically active. This striking difference in anoxic survival strategy is reflected all the way down to the cellular level.

Adaptation, Physiological↗

PubMed2000

Low mass-specific brain Na+/K+-ATPase activity in elasmobranch compared to teleost fishes: implications for the large brain size of elasmobranchs.

Elasmobranch fishes have long been noted for having unusually large brains for ectotherms, and therefore may be exceptions to the rule that vertebrates in general devote less than 8% of their resting metabolic rate to the central nervous system. The brain mass of sharks, skates and rays is often several times larger than that of teleost fishes of the same size. Still, the underlying reasons for this have remained unclear. Ion pumping by the Na+/K+-ATPase is the single most energy consuming process in the brain. In this study, Na+/K+-ATPase activity was measured in the brain of four species of elasmobranchs and 11 species of teleosts. While the average brain mass of the elasmobranchs examined was approximately three times that of the teleosts, the mean specific Na+/K+-ATPase activity was only about one-third of that of the teleosts. Thus, the total brain Na+/K+-ATPase activity was similar in elasmobranchs and teleosts. This suggests that the large brain size of elasmobranchs is at least partly related to a low mass-specific rate of brain energy use.

Animals↗

PubMed2000

Branchial and circulatory responses to serotonin and rapid ambient water acidification in rainbow trout.

Although the branchial and cardiovascular effects of serotonin (5-hydroxytryptamine) have only partially been characterized, a physiological role for serotonin in the cardiorespiratory responses of fish to environmental changes such as reduced Ph has been suggested. Therefore, we have characterized and compared the effects of serotonin and a rapid reduction of Ph in the ambient water (from pH 8.8 to pH 4.0) on ventral and dorsal aortic blood pressures, heart rate, cardiac output, and arterial pH in rainbow trout, Onchorhynchus mykiss. In addition, the circulation in the branchial microvasculature was observed using in vivo epi-illumination microscopy. The fall in water Ph and injection of serotonin (100 nmol/kg) both increased the branchial resistance and reduced the efferent filamental artery (EFA) blood velocity. Nevertheless, quantitatively, the responses to the two stimuli were different. Although acid exposure caused a much more profound increase in branchial resistance compared with serotonin, the blood flow in the observable distal portion of the EFA was only reduced by 60% in acid water, while it stopped with serotonin. Regardless of the marked branchial resistance elevation, a constriction of the efferent filamental vasculature could not be seen during acid exposure, as occasionally was the case with serotonin. While methysergide completely abolished the serotonin-induced branchial events, it only modestly suppressed the acid-induced reduction of EFA blood velocity. In contrast, all of the systemic changes induced by serotonin and acidic water were insensitive to methysergide. In conclusion, acidic water and injected serotonin elevate the branchial resistance, but the involvement of a serotonergic component in the acidic response appears negligible.

Animals↗

PubMed2000

Brain blood flow during hypercapnia in fish: no role of nitric oxide.

Very little is known about the regulation of cerebral blood flow (CBF) in lower vertebrates, especially fish. In mammals, hypercapnia causes cerebral vasodilation and increased CBF through mechanisms that involve the production of nitric oxide (NO). We have used epi-illumination microscopy in vivo to observe effects of hypercapnia on venular erythrocyte velocity, used as an index of CBF velocity, in rainbow trout (Oncorhynchus mykiss) and crucian carp (Carassius carassius). Rainbow trout exposed to a pCO(2) of 7.5 mmHg displayed a small increase of CBF velocity in two out of five fishes, while dorsal aortic blood pressure (P(DA)) did not change. Exposing trout to a pCO(2) of 22.5 mmHg, resulted in an 80% increase in CBF velocity and a 21% increase in P(DA). Trout exposed to a pCO(2) of 75 mmHg showed an additional increase in blood pressure, while no further increase was seen in CBF velocity compared to a pCO(2) of 22. 5 mmHg. By contrast, no change in CBF velocity was seen in crucian carp, even at a pCO(2) of 75 mmHg. None of the circulatory changes seen in the trout could be blocked by superfusing the brain surface with the NO synthase blocker N(G)-nitro-L-arginine. The results point at striking species differences in the responses of CBF and P(DA) to hypercapnia in fish, and that the hypercapnia induced increase in CBF velocity seen in rainbow trout is independent of NO production.

Animals↗

PubMed2000

Effects on skin blood flow by provocation during local analgesia.

Although topical analgesia cream has been used for several years, little is known about its effects on the microcirculation. Previous studies have shown a vasoconstrictive effect after short application times and a vasodilatation after longer application. It has also been shown that vasomotion does not occur in the analgesized skin. The present study was undertaken to investigate the alterations in skin blood perfusion following local cooling, local heating and pin-pricking after the establishment of analgesia. In 11 healthy volunteers, skin analgesia was attained by use of a eutectic mixture of lidocaine and prilocaine (EMLA, Astra Pain Control AB, Sweden) applied to the skin three hours prior to provocation. The changes in skin blood perfusion, after applying three different provocation methods, were studied using the laser Doppler technique. Local cooling and heating to temperatures of +10 and +45 degrees C, respectively, were applied for 9 s by use of a copper probe (O12 mm). In the pin-prick provocation method, a combined effect of deflection and penetration of the skin to in total 3 mm was attained. Identical provocation methods were applied to placebo treated and untreated skin areas. After heat provocation, significant differences in the perfusion response between the treatments were seen (P < 0.0001). Skin areas treated with analgesia cream responded with a slow increase in perfusion that persisted beyond the four minute measurement period. Placebo and untreated areas decreased their perfusion over time. After cooling a significant reduction in skin perfusion was seen, irrespective of the treatment. Similarly, after pin-pricking a perfusion increase was seen for all treatments. The findings indicate that topical analgesia influences the myogenic control of the blood flow in those vascular plexa measured by laser Doppler following heat provocation. No differences could be seen in the response to pin-pricking and cooling for the different treatments.

Adolescent↗

PubMed1999

Relationships between sex and the size and number of forebrain gonadotropin-releasing hormone-immunoreactive neurones in the ballan wrasse (Labrus berggylta), a protogynous hermaphrodite.

This study is the first to examine the brain gonadotropin-releasing hormone (GnRH) cell population phenotype in a protogynous and monandric sequentially hermaphroditic fish. Male ballan wrasse (Labrus berggylta) had on average higher numbers of GnRH-immunoreactive (GnRH-ir) cells within the brain preoptic area (POA) than females, a difference not found in GnRH-ir cells in other brain regions. Furthermore, in males, but not females, the number of these POA GnRH-ir cells correlated with body size. Maturational state (prespawning or postspawning) had marked effects on mean profile sizes (but not numbers) of both GnRH-ir cell bodies and cell nuclei, even when existing differences in body size and allometric relationships had been taken into account. Postspawning males tended to have larger GnRH-ir profiles in all brain regions relative to both prespawning males and females. Moreover, the GnRH-ir cell number in POA, and the cell body profile size in both POA and at the level of the anterior commissure, correlated with gonad size in spermiated prespawning males, indicating a relationship between both size and number of GnRH cells and male gonadal development. These results suggest that temporary changes in the size of brain GnRH-ir neurones are coupled to the male spawning cycle, and that permanent POA GnRH-ir cell number changes are involved in the process of sex change in sequential hermaphrodites. However, smaller males had no more preoptic GnRH-ir cells than equally sized females, which may argue against a proximate inducing role of GnRH cell number changes in naturally occurring sex reversal.

Animals↗

PubMed1999

Hypoxia stimulates cerebral blood flow in the estuarine crocodile (Crocodylus porosus).

The effect of N2 respiration on cerebral blood flow (CBF) velocity on the dorsal surface of cerebellum was examined in the estuarine crocodile, Crocodylus porosus, using epi-illumination microscopy. Twelve minutes of N2 respiration resulted in a 126% increase in CBF velocity. N2 respiration had no effect on blood pressure, indicating an underlying cerebral vasodilation. In addition, heart rate increased significantly. Systemic injections of aminophylline and the NO synthase (NOS) inhibitor nitro-L-arginine (L-NA) did not affect the hypoxia induced increase in CBF. We conclude that C. porosus responds to hypoxia with adenosine and nitric oxide (NO) independent cerebral vasodilation, and that this is likely to be a mechanism protecting the brain from energy deficiency during prolonged dives.

Alligators and Crocodiles↗

PubMed1999

Extracellular levels of amino acid neurotransmitters during anoxia and forced energy deficiency in crucian carp brain.

The crucian carp is one of the few vertebrates that has the ability to survive long periods of anoxia. A devastating event in the anoxic mammalian brain is a massive release of excitatory neurotransmitters, particularly glutamate. Using microdialysis to measure extracellular levels of several amino acid neurotransmitters and related compounds in the telencephalon of crucian carp in vivo, we show here that this species avoids a release of glutamate during anoxia, which is probably related to its ability to maintain energy charge. Instead, 6 h of anoxia produced a doubling of the extracellular level of GABA, the major inhibitory neurotransmitter in brain. The release of GABA may be a mechanism for lowering neuronal activity and energy use, thereby facilitating the maintenance of energy charge. Perfusing the microdialysis probe with a high-K+ Ringer showed that the telencephalon had the ability to release both glutamate and GABA. Moreover, if energy deficiency was produced during anoxia, by inhibiting glycolysis with iodoacetate (IAA), the resulting release of GABA was more rapid and profound than that of glutamate, possibly reflecting a second line of anoxia defence aimed at minimising the effect of a temporary energy failure.

Amino Acids↗

PubMed1999

Tissue-specific changes in RNA synthesis in vivo during anoxia in crucian carp.

The overall energy budget for protein synthesis (i.e., transcription plus translation) is thought to consist of fixed and variable components, with RNA synthesis accounting for the former and protein synthesis the latter. During anoxia, the downregulation of protein synthesis (i.e., the variable component), to reduce energetic demand, is an important aspect of survival in crucian carp. The present study examines RNA synthesis during anoxia by labeling with [(3)H]uridine. A novel synthesis rate calculation is presented, which allows for the tissue-specific salvage of uridine, with synthesis rates finally expressed relative to DNA. After 48 h anoxia, the decline (29%) in brain RNA synthesis and increases in the heart and liver (132 and 871%, respectively) support known RNA functions during hypoxic/anoxic survival. This study provides evidence that, in an anoxia-tolerant species, survival mechanisms involving RNA are able to operate because tissue-specific restructuring of the RNA synthesis process enables fixed synthesis costs to be maintained; this may be as vital to survival as exploiting the variable energetic demand of protein synthesis.

Animals↗

PubMed1999

Brain blood flow and blood pressure during hypoxia in the epaulette shark Hemiscyllium ocellatum, a hypoxia-tolerant elasmobranch.

The key to surviving hypoxia is to protect the brain from energy depletion. The epaulette shark (Hemiscyllium ocellatum) is an elasmobranch able to resist energy depletion and to survive hypoxia. Using epi-illumination microscopy in vivo to observe cerebral blood flow velocity on the brain surface, we show that cerebral blood flow in the epaulette shark is unaffected by 2 h of severe hypoxia (0.35 mg O2 l-1 in the respiratory water, 24 C). Thus, the epaulette shark differs from other hypoxia- and anoxia-tolerant species studied: there is no adenosine-mediated increase in cerebral blood flow such as that occurring in freshwater turtles and cyprinid fish. However, blood pressure showed a 50 % decrease in the epaulette shark during hypoxia, indicating that a compensatory cerebral vasodilatation occurs to maintain cerebral blood flow. We observed an increase in cerebral blood flow velocity when superfusing the normoxic brain with adenosine (making sharks the oldest vertebrate group in which this mechanism has been found). The adenosine-induced increase in cerebral blood flow velocity was reduced by the adenosine receptor antagonist aminophylline. Aminophylline had no effect upon the maintenance of cerebral blood flow during hypoxia, however, indicating that adenosine is not involved in maintaining cerebral blood flow in the epaulette shark during hypoxic hypotension.

Adenosine↗

PubMed1999

Principles and practice of the laser-Doppler perfusion technique.

This paper reviews the development and use of laser-Doppler perfusion monitors and imagers over the past two decades. The enormous interest in microvascular blood perfusion coupled with the 'ease of use' of the technique has led to 1500+ publications citing its use. However, useful results can only be achieved with an understanding of the basic principles of the instrumentation and its application in the various clinical disciplines. The basic theoretical background is explored and definitions of blood perfusion and laser-Doppler perfusion are established. The calibration method is then described together with potential routes to standardisation. A guide to the limitations in application of the technique gives the user a clear indication of what can be achieved in new studies as well as possible inadequacy in some published investigations.

Artifacts↗

PubMed1998

A mathematical analysis on the biological zero problem in laser Doppler flowmetry.

The biological zero (BZ) problem is a critical issue inherent in laser Doppler flowmetry (LDF). It causes confusion when measuring low tissue blood flows. Many experimental studies have been done on the question of whether the BZ flux should be subtracted from the normally measured flux in various situations. However this problem can only be solved after a proper mathematical analysis. Only then can we clearly define and formulate what flux is truly meaningful in blood perfusion measurement and what movement generates the BZ flux and how can we correctly remove it. Following this motivation, the movement of moving blood cells (MBC's) is decomposed into a net translation and a random wondering based on in vivo observations. This important step leads to a clear definition of the BZ and net perfusion flux and reveals that subtraction of BZ flux from the normal flux will certainly cause an underestimation of the net flux. Using this decomposition, the relationship between the net, BZ and normal flux is established which leads to the correct formula to recover the net flux from the BZ and normal fluxes. This recovered net flux is shown to be bounded by the normal flux and the normal flux minus the BZ flux. Numerical studies, preliminary phantom model and clinical evaluations manifest that the new approach is more accurate and reasonable at measuring low net fluxes. In contrast, subtracting BZ flux causes a systematic underestimation of perfusion and is apparently inappropriate even from a methodological point of view. In addition to the novel BZ solution, a general density function of the speed of MBC's is given which is more faithful than the Maxwell density used in [4]. This general density function offers new possibilities for further theoretical developments in LDF.

Capillaries↗