Biomedical subjects

B Walter

Publications and source records attributed to B Walter.

At least 37 records · Page 2Linked to original sources

PubMed2001

Oxidative state and histological changes in muscles of mastication after conditioning training.

Stress due to endurance training of striated muscles leads to adaptive changes in the distribution of muscle fiber types (i.e. ratio of type I and type II fibers). Moreover, severe training leads to tissue hypoxia and oxidative stress in muscles. In the current study, we examined the relationship between histological changes and oxidative state in muscles of mastication during the acute adaptation phase to a sustained muscle load. Six domestic pigs received build-ups on the molar teeth in order to induce a sustained load of the muscles of mastication for a duration of four weeks. Afterwards the masseter (M1, M2, M3), medial pterygoid (PM), temporal (TP1, TP2), and geniohyoid muscles (GH) were removed and the fiber type distribution was determined by enzyme histochemistry. Additionally, the tissue content of glutathione and lipid peroxidation (LPO) products were measured. The above treatment led to muscle fiber transformation of type II into type I (M1, M2, TP2, PM) and a decrease of the GSH content (M1, M2 and TP2). The changes in the GSH/GSSG ratio were in accordance with the changes in proportions of muscle fiber types, with the lowest GSH/GSSG ratios in the most stressed muscles of the treated animals. No significant changes in LPO products were found. The decrease of the GSH/GSSG ratio in the most stressed muscles indicates an increased intracellular oxidative stress, which may be caused by tissue hypoxia during the chronic phase of muscle adaptation.

Adaptation, Physiological↗

PubMed2001

Effects of 28-day mechanical and chewing stress on content of bound and diffusible ions in muscles of mastication.

Type I and type II muscle fibres have different ion concentrations. Muscles adapt to chronic stress by changing of fibre types and remodelling of the myosin heavy chains in the muscle fibres. The present investigation on ionic change during muscular contraction was carried out on 10-week-old pigs (6 treated animals, 6 controls) over a 28-day period. Six pigs received acrylic build-ups to induce mechanical advancement of the lower jaw and chronic chewing stress. Muscle tissue was taken from the masseter (M1, M2, M3), temporal (TP1, TP2), medial pterygoid (PM) and geniohyoid (GH) muscles by a standardized method. Eighty-four muscle samples were used for histological fibre differentiation with mATPase. Energy-dispersive X-ray microanalysis of muscles was carried out in an environmental scanning electron microscope. Endurance stress in the stressed muscles was seen as an increase of type I fibres (P < 0.001). This histological change and ionic alterations were measured in the anterior region of the masseter (M1 and M2) and in the posterior region of the temporal muscle (TP2). Smaller changes were found in the medial pterygoid muscle. We measured in this muscles increases in potassium, sulphur, chloride (P < 0.05) and even larger increases in phosphate (up to 1.5 mmol/g to 2.3 mmol/g, P < 0.001) and sodium (3-fold, P < 0.001). The results reveal the effects of chronic stress on muscle fibres and ion concentration in the muscle. Chronic stress resulted in an increase of type I fibres and increased ion concentration in the same muscle region. These are considered to be indicators of more efficient contraction. The changes in ion concentration are an important factor in muscle contraction.

Animals↗

PubMed2001

Intrauterine growth restriction induces up-regulation of cerebral aromatic amino acid decarboxylase activity in newborn piglets: [18F]fluorodopa positron emission tomographis study.

There is evidence that intrauterine growth restriction (IUGR) is associated with altered dopaminergic function in the immature brain. However, the relevant enzyme activities have not been measured in the living neonatal brain together with brain oxidative metabolism. Therefore, fluorine-18-labeled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) was used together with positron emission tomography to estimate the activity of the aromatic amino acid decarboxylase in the brain of 10 newborn IUGR piglets (2 to 5 d old; body weight, 908 +/- 109 g) and in 10 normal-weight (3 to 5 d old; body weight, 2142 +/- 373 g) newborn piglets. The regional transport of FDOPA to the brain and the clearance rate of labeled metabolites from brain tissue were broadly similar in the two groups. However, the regional rate constant for back flux from the brain was markedly increased in IUGR piglets for striatum (72%) and frontal cortex (83%) (p < 0.05). Furthermore, the rate constant for conversion of FDOPA to fluorodopamine was markedly increased (between 48% in cerebellum and 91% in mesencephalon, p < 0.05) in all brain regions of IUGR piglets studied. Thus, it is suggested that IUGR induces an up-regulation of aromatic amino acid decarboxylase activity that is not related to alterations in brain oxidative metabolism.

Animals↗

PubMed2001

[National socialist "children's euthanasia" program in the province of Westphalia (1940-1945)].

As part of the organization structure of the "Reich committee for scientifically registering genetic and inherent serious illnesses" "childrens' special wards" were established in the province Westphalia in the child-psychiatry St. Johannesstift in Niedermarsberg (end of 1940), and then in the Provinzialheilanstalt Aplerbeck (end of 1941). The establishment thereof and personnel recruiting were done in close operation with provincial authorities. In Niedermarsberg external nurses were also employed. When the activities in the Marsberger ward became public despite efforts to keep them secret, the provincial association felt forced to establish a replacement ward in Dortmund-Aplerbeck. This ward was integrated stronger into the hospital-internal and regional care structures regarding personnel and institutional aspects than the previous ward. The actions of "child euthanasia" were based on a combination of hierarchical decision-making structures, limited responsibility, and scientific justification. The people performing these activities were provided action options withdrawal possibilities. For the affected parents the events were shifted into a psychological grey area which did not force decisions in principle. The internal conditions of the "childrens' special wards", the procedures and the "treatments" of the children were clearly regulated; the "euthanasia" activities themselves can be comprehended only in fragments from testimonies. By analyzing the reception books in connection with the medical files it is possible to make statements regarding the number of deaths, the death rate and cause, and also several social characteristics of the children. The fate of the children in the Westphalian "childrens' special wards" shows that the work in these regional "Reich committee wards" was limited to caring, observing, selecting and killing. The attempts of scientific justification are exposed as cover-ups.

Child↗

PubMed2001

Headache and sferics.

Many patients with migraine believe weather is a trigger for their headaches. The objective of this study was to determine if very low frequency sferics, pulse-shaped electromagnetic fields originating from atmospheric discharges (lightning), are precipitating factors. The occurrence of sferics impulses is characterized by a daily, as well as an annual, periodicity and is thought to be associated with various pathological processes. The diaries of 37 women suffering from migraine and tension-type headaches were analyzed over a period of 6 months and correlated with daily sferics activity and other weather phenomena in the area of Giessen, Germany. From October through December (autumn), sferics activity was correlated with the occurrence of migraine (r = 0.33, P<.01); however, there was no correlation in July and August (summer), when the thunderstorm activity had been very intense. In summer, tension-type headaches were associated with other weather parameters such as temperature (r = 0.36, P<.01) and vapor pressure (r = 0.27, P<.05).

Adult↗

PubMed2000

Effects of betamethasone administration to the fetal sheep in late gestation on fetal cerebral blood flow.

Glucocorticoid administration to women at risk of preterm delivery to accelerate fetal lung maturation has become standard practice. Antenatal glucocorticoids decrease the incidence of intraventricular haemorrhage as well as accelerating fetal lung maturation. Little is known regarding side effects on fetal cerebral function. Cortisol and synthetic glucocorticoids such as betamethasone increase fetal blood pressure and femoral vascular resistance in sheep. We determined the effects of antenatal glucocorticoid administration on cerebral blood flow (CBF) in fetal sheep. Vehicle (n = 8) or betamethasone (n = 8) was infused over 48 h via the jugular vein of chronically instrumented fetal sheep at 128 days gestation (term 146 days). The betamethasone infusion rate was that previously shown to produce fetal plasma betamethasone concentrations similar to human umbilical vein concentrations during antenatal glucocorticoid therapy. Regional CBF was measured in 10 brain regions, using coloured microspheres, before and 24 and 48 h after onset of treatment, and during hypercapnic challenges performed before and 48 h after onset of betamethasone exposure. Betamethasone exposure decreased CBF in all brain regions measured except the hippocampus after 24 h of infusion (P < 0.05). The CBF decrease was most pronounced in the thalamus and hindbrain (45-50% decrease) and least pronounced in the cortical regions (35-40% decrease). It was mediated by an increase in cerebral vascular resistance (CVR, P < 0.05) and led to a decrease in oxygen delivery to subcortical and hindbrain structures of 30-40%, to 8.6 +/- 1.1 ml x (100 g)(-1) x min(-1), and 40-45 %, to 11.0 +/- 1.6 ml x 100 g(-1) x min(-1), respectively (P < 0.05). After 48 h of betamethasone treatment, the reduction in CBF was diminished to about 25-30 %, but was still significant in comparison to vehicle-treated fetuses in all brain regions except three of the five measured cortical regions (P < 0.05). CVR and oxygen delivery were unchanged in comparison to values at 24 h of treatment. The CBF increase in response to hypercapnia was diminished (P < 0.05). These observations demonstrate for the first time that glucocorticoids exert major vasoconstrictor effects on fetal CBF. This mechanism may protect the fetus against intraventricular haemorrhage both at rest and when the fetus is challenged. Betamethasone exposure decreased the hypercapnia-induced increase in CBF (P < 0.05) due to decreased cerebral vasodilatation (P < 0.05).

Animals↗

PubMed2000

Altered renal function in growth-restricted newborn piglets.

The effect of intrauterine growth restriction (IUGR) on renal hemodynamics and excretory functions was studied in 76 newborn piglets 12-27 h old. The experiments were performed on anesthetized animals divided into normal-weight piglets and IUGR piglets according to their birth weight. The "normal-weight" category included animals with a birth weight >40th percentile (piglets heavier than 1,220 g); the IUGR category included animals with a birth weight >5th and <10th percentiles (piglets with a birth weight between 733 g and 853 g). Cardiac output and renal blood flow were measured by the colored microsphere technique. Urine was collected from catheters placed in the ureters. This animal model of naturally occurring growth retardation in swine gives asymmetric growth with an increase in the mean ratio of brain weight to liver weight from 1.02 to 1.85 (P<0.01). Thus there was only a small reduction in brain weight (11%). In contrast, the reduction in the weight of liver (50%) and kidney (46%) was proportional to that in body weight (46%). Heart rate, cardiac output, arterial blood gases, and pH were similar in normal-weight and IUGR piglets, but arterial blood pressure and arterial glucose content were significantly reduced in IUGR piglets (P<0.01). Moreover, IUGR piglets had higher plasma catecholamine levels (P<0.05). Renal blood flow and renal vascular resistance were similar in the normal-weight and in the IUGR groups. However, in IUGR animals, glomerular filtration rate was significantly less than in the controls (P<0.05). Normal-weight and IUGR newborn piglets reabsorbed sodium very efficiently, the fractional sodium excretion was less than 1% in both groups. We conclude that renal blood flow is maintained in relation to kidney and body weight in IUGR newborns, but that important renal excretory functions are compromised due to IUGR.

Animals↗

PubMed2000

Reduced muscle vascular resistance in intrauterine growth restricted newborn piglets.

It has been shown that asymmetrical intrauterine growth restriction is denoted by disproportional reduction of muscle mass compared to body weight reduction. However, the effects of IUGR on regional vascular resistance and blood flow of skeletal muscles and their contractile function have not been studied until now. Therefore, muscle blood flow (MBF) and isometric force output of serial stimulated hindlimb plantar flexors was measured in thiopental -anesthetized normal weight (NW; n = 9) and intrauterine growth restricted (IUGR; n = 9) one-day-old piglets. Additionally, muscle vascular resistance (MVR) and thyroid hormones were estimated. MBF was found to be markedly increased in IUGR piglets by 36% with a concomitant MVR reduction of 37% (p < 0.05). Isometric force of the plantar flexors was considerably higher in NW than in IUGR piglets (p < 0.05). However, amount of muscle fatigue was more pronounced in NW piglets (9.1+/-2.8%) than was in IUGR piglets (3.7+/-2.3%) (p < 0.05). Furthermore, specific tension of NW muscles (18.8+/-0.7 N/cm2) was significantly lower than for IUGR muscles (21.2+/-0.9 N/cm2) (P<0.05). IUGR newborn piglets exhibited increased plasma levels of thyroxine (T4) (p < 0.05), whereas triiodothyronine (T3) showed similar values in both animal groups. These data clearly indicate that muscle hemodynamics and contractile function are more developed in newborn IUGR piglets. Furthermore it is suggested that the improved tolerance to fatigue during isometric contractions may indicate an increased oxidative capacity of calf muscles due to intrauterine growth restriction.

Animals↗

PubMed2000

Comparison between inulin clearance and endogenous creatinine clearance in newborn normal weight and growth restricted newborn piglets.

The effect of intrauterine growth restriction (IUGR) and acute oxygen deprivation on renal plasma flow (RPF), renal excretory function (Inulin clearance and endogenous creatinine clearance) and urine flow were studied in twenty newborn piglets 12 to 27 hours old. The experiments were performed on anesthetized animals divided into normal weight piglets and intrauterine growth restricted (IUGR) piglets according to birth weights. The "normal weight" category included animals with a birth weight > 40th percentile (piglets heavier than 1220 g); the IUGR category included animals with a birth weight > 5th and < 10th percentiles (piglets with a birthweight between 733 g and 853 g). This animal model of naturally occurring growth restriction in swine gives asymmetric growth with an increase in the mean ratio of brain weight to liver weight from 1.02 to 2.02 (p < 0.01). There was only a small reduction in brain weight (11%). In contrast, the reduction in weight of liver (55%) and kidney (41%) was proportional to that in body weight (48%). Arterial blood pressure, heart rate, arterial blood gases, pH and RPF were similar in normal weight and IUGR piglets. However inulin clearance and creatinine clearance were significantly lower in the growth restricted piglets (p < 0.01). Severe hypoxia induced a moderate tachycardia, combined with pronounced metabolic acidosis and strongly reduced renal plasma flow and renal excretory function in both groups (p < 0.05). Comparison between inulin and creatinine clearances in normal weight and IUGR piglets revealed a markedly higher clearance of creatinine as of inulin at every experimental stages (p < 0.05, p < 0.01). Alterations of renal excretion due to severe hypoxia and early recovery were similar in both animal groups investigated. Regression analysis rendered a linear correlation between inulin clearance and creatinine clearance among the experimental stages for normal weight as well as IUGR piglets (p < 0.001). Thus, endogenous creatinine clearance is suggested to be a reliable indicator for renal excretory function in newborn piglets. It accurately reflects proportional effects of long-term alterations of renal function due to intrauterine growth restriction as well as acute effects of severe oxygen deprivation. However, using standard methods of plasma and urine creatinine measurement, quantitative determination of GFR by endogenous creatinine clearance is not possible.

Animals↗

PubMed2000

[Sonographic diagnosis of an unusual recurrence of Chilaiditi syndrome after hemicolectomy].

A 71-year old patient presented with acute abdominal pain, nausea and emesis 3 months after right hemicolectomy for Chilaiditi's syndrome. The initial ultrasound examination revealed a loop of thick walled small intestine between the anterior surface of the right liver lobe and the diaphragm. In addition, small amounts of perihepatic fluid were found. The chest x-ray confirmed a recurrence of Chilaiditi's syndrome with intestinal gas under the right diaphragm. Elongation and flaccid of intestinal and hepatic suspensory ligaments are thought to be the principal predisposing factors. However, in our patient, a wedge-shaped enlarged lobus caudatus served as a guide rail for the bowel and facilitated access to the space under the right diaphragm. Although the patient recovered completely after 3 days of conservative therapy a high risk of recurrence remains. In summary, ultrasound examination can reliably diagnose Chilaiditi's syndrome and should also be used, as the method of choice in the follow-up of this rare syndrome, thus avoiding unnecessary x-ray exposure.

Abdomen↗

PubMed2000

Effect of mild hypothermia on cerebral oxygen uptake during gradual cerebral perfusion pressure decrease in piglets.

OBJECTIVE: To study the effect of mild hypothermia on cerebral oxygen metabolism and brain function in piglets during reduced cerebral blood flow because of gradual reduction of the effective cerebral perfusion pressure (CPP). DESIGN: Comparison of two randomized treatment groups: normothermic group (NT; n = 7) and hypothermic group (HT; n = 7). SETTING: Work was conducted in the research laboratory of the Institute for Pathophysiology, Friedrich Schiller University, Jena, Germany. SUBJECTS: Fourteen piglets (14 days old) of mixed German domestic breed. INTERVENTION: Animals were anesthetized and mechanically ventilated. An epidural balloon was gradually inflated to increase intracranial pressure to 25 mm Hg, 35 mm Hg, and 45 mm Hg every 30 mins at adjusted mean arterial blood pressures. After determination of baseline CPP (NT, 79+/-14 mm Hg; HT, 84+/-9 mm Hg), CPP was reduced to approximately 70%, 50%, and 30% of baseline (NT, 38.1+/-0.5 degrees C; HT, 31.7+/-0.5 degrees C). MEASUREMENTS AND MAIN RESULTS: Every 25 mins after the gradual CPP reductions. Mild hypothermia induced a reduction of the cerebral metabolic rate of oxygen (CMRO2) to 50%+/-15% of baseline values (baseline values, 352+/-99 micromol x 100 g(-1) x min(-1)) (p < .05). Moreover, the electrocorticogram was altered to a pattern of reduced delta activity (p < .05) but unchanged higher frequency activity. The cerebral oxygen balance in HT animals remained improved until CPP reduction to 50%, indicated by a reduced cerebral arteriovenous difference of oxygen but elevated brain tissue Po2 (p < .05). Further CPP reduction gave rise to a strong CMRO2 reduction (NT, 19+/-21%; HT, 15+/-15%; p < .05). However, the high-frequency band of electrocorticogram was less reduced in hypothermic animals (p < .05). CONCLUSIONS: Mild whole body hypothermia improves cerebral oxygen balance by reduction of brain energy demand in juvenile piglets. The improvement of brain oxygen availability continues during a mild to moderate CPP decrease. A loss of the difference in CMRO2 between the hypothermic and normothermic piglets together with the fact that brain electrical activity was less suppressed under hypothermia during severe cerebral blood flow reduction indicates that hypothermic protection may involve some other mechanisms than reduction of brain oxidative metabolism.

Analysis of Variance↗

PubMed2000

Coupling of cerebral blood flow and oxygen metabolism in infant pigs during selective brain hypothermia.

Studies documenting the cerebral hemodynamic consequences of selective brain hypothermia (SBH) have yielded conflicting data. Therefore, the authors have studied the effect of SBH on the relation of cerebral blood flow (CBF) and CMRO2 in the forebrain of pigs. Selective brain hypothermia was induced in seven juvenile pigs by bicarotid perfusion of the head with extracorporally cooled blood. Cooling and stepwise rewarming of the brain to a Tbrain of 38 degrees C, 25 degrees C, 30 degrees C, and 38 degrees C at normothermic Ttrunk (38 degrees C) decreased CBF from 71 + 12 mL 100 g(-1) min(-1) at normothermia to 26+/-3 mL 100 g(-1) min(-1) and 40+/-12 mL 100 g(-1) min(-1) at a Tbrain of 25 degrees C and 30 degrees C, respectively. The decrease of CMRO2 during cooling of the brain to a Tbrain of 25 degrees C resulted in a mean Q10 of 2.8. The ratio between CBF and CMRO2 was increased at a Tbrain of 25 degrees C indicating a change in coupling of flow and metabolism. Despite this change, regional perfusion remained coupled to regional temperatures during deep cerebral hypothermia. The data demonstrate that SBH decreases CBF and oxygen metabolism to a degree comparable with the cerebrovascular and metabolic effects of systemic hypothermia. The authors conclude that, irrespective of a change in coupling of blood flow and metabolism during deep cerebral hypothermia, cerebral metabolism is a main determinant of CBF during SBH.

Animals↗

PubMed2000

Accelerated contractile function and improved fatigue resistance of calf muscles in newborn piglets with IUGR.

Asymmetrical intrauterine growth restriction is denoted by disproportional reduction of muscle mass compared with body weight reduction. However, effects on contractile function or tissue development of skeletal muscles were not studied until now. Therefore, isometric force output of serial-stimulated hindlimb plantar flexors was measured in thiopental-anesthetized normal weight (NW) and intrauterine growth-restricted (IUGR) 1-day-old piglets under conditions of normal, reduced (aortic cross clamping), and reestablished (clamp release) blood supply (measured by colored microspheres technique). Furthermore, muscle fiber type distribution was determined after histochemical staining, specific muscle force of the plantar flexors [quotient from absolute force divided by muscle mass (N/g)] was calculated, and glycogen content and morphometric data of the investigated muscles were estimated. Regional blood flow of hindlimb muscles was similar in NW (6 +/- 2 ml. min(-1). 100 g(-1)) and IUGR piglets (8 +/- 1 ml. min(-1). 100 g(-1)). Isometric muscle contractions induced a marked increase in regional blood flow of 4.1-fold in NW and 5-fold in stimulated hindlimb muscles of IUGR piglets (baseline blood flow). Specific force of NW piglet muscles (5.2 +/- 0.2 N/g) was significantly lower than IUGR piglet muscles (6.1 +/- 0.6 N/g; P < 0.05). Isometric muscle contractions (NW: 32.7 +/- 4.7 N; IUGR: 21.7 +/- 4.0 N) resulted in a higher rate of force decrease in the calf muscles of NW animals compared with IUGR piglets (8 +/- 2 vs. 3 +/- 1%; P < 0. 01). Functional restoration of contractile performance after hindlimb recirculation was nearly complete in IUGR piglets (98 +/- 1%), whereas in NW piglets a deficit of 9 +/- 3% was found (P < 0. 01). Muscle fiber type estimation revealed an increased proportion of type I fibers in flexor digitalis superficialis and gastrocnemius medialis in IUGR piglets (P < 0.05). These data clearly indicate that contractile function is accelerated in newborn IUGR piglets.

Animals↗

PubMed2000

Effect of severe normocapnic hypoxia on renal function in growth-restricted newborn piglets.

To examine the effects of intrauterine growth restriction and acute severe oxygen deprivation on renal blood flow (RBF), renovascular resistance (RVR), and renal excretory functions in newborns, studies were conducted on 1-day-old anesthetized piglets divided into groups of normal weight (NW, n = 14) and intrauterine growth-restricted (IUGR, n = 14) animals. Physiological parameters, RBF, RVR, and urinary flow, were similar in NW and IUGR piglets, but glomerular filtration rate (GFR) and filtration fraction were significantly less in IUGR animals (P < 0.05). An induced 1-h severe hypoxia (arterial PO(2) = 19 +/- 4 mmHg) resulted in, for both groups, a pronounced metabolic acidosis, strongly reduced RBF, and increased fractional sodium excretion (FSE; P < 0.05) with a less-pronounced increase of RVR and arterial catecolamines in IUGR piglets. Of significance was a smaller decrease in RBF for IUGR piglets (P < 0.05). Early recovery showed a transient period of diuresis with increased osmotic clearance and elevated FSE in both groups (P < 0.05). However, GFR and renal O(2) delivery remained reduced in NW piglets (P < 0.05). We conclude that, in newborn IUGR piglets, RBF is maintained, although GFR is compromised. Severe hypoxemia induces similar alterations of renal excretion in newborn piglets. However, the less-pronounced RBF reduction during hypoxemia indicates an improved adaptation of newborn IUGR piglets on periods of severely disturbed oxygenation. Furthermore, newborn piglets reestablish the ability for urine concentration and adequate sodium reabsorption early after reoxygenation so that a sustained acute renal failure was prevented.

Acidosis↗

PubMed2000

Relation between brain tissue pO2 and dopamine synthesis of basal ganglia--a 18FDOPA-PET study in newborn piglets.

Perinatal hypoxic-ischemic cerebral injury is a major determinant of neurologic morbidity and mortality in the neonatal period and later in childhood. There is evidence that the dopaminergic system is sensitive to oxygen deprivation. However, the respective enzyme activities have yet not been measured in the living neonatal brain. In this study, we have used 18F-labelled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) together with positron emission tomography (PET) to estimate the activity of the aromatic amino acid decarboxylase (AADC), the ultimate enzyme in the synthesis of dopamine, in the brain of newborn piglets under normoxic and moderate asphyxial conditions. The study was performed on 8 newborn piglets (2-5 days old). In each piglet PET studies were performed under control conditions and during 2-hour asphyxia. Simultaneously, brain tissue pO2 was recorded, cerebral blood flow (CBF) was measured with colored microspheres and cerebral metabolic rate of oxygen (CMRO2) was determined. Asphyxia was induced by lowering the inspired fraction of oxygen from 0.35 to 0.10 and adding about 6% CO2 to the inspired gas. Asphyxia elicited a more than 3-fold increase of the CBF (p < 0.01) so that CMRO2 remained unchanged throughout the asphyxial period. Despite this, brain tissue pO2 was reduced from 19 +/- 4 mm Hg to 6 +/- 3 mm Hg (p < 0.01). Blood-brain transfer of FDOPA as well as permeability-surface area product (PS) from striatum were unchanged. Striatal synthesis rate of fluoro-dopamine from FDOPA (k3) was, however, significantly increased (p < 0.01). This increase of the AADC activity is associated with reduced brain tissue pO2. Asphyxia-induced CBF increase impedes an alteration of brain oxidative metabolism.

Animals↗

PubMed2000

Effects of paced respiration on heart period and heart period variability.

The present study investigated psychophysiological responses to paced respiration of different frequencies. Twenty men and 20 women (mean age: 24.3 years) underwent five breathing conditions (paced with 0.15 Hz, 0.20 Hz, 0.25 Hz, 0.30 Hz, and unpaced), each lasting 5 min. As dependent physiological measures heart period, and different heart period variability (HPV) parameters were assessed. Psychological variables consisted of mood estimates as well as rated accuracy and effort to follow the pacing rhythm. HPV decreased with higher breathing frequencies, under paced and unpaced conditions, whereas mood ratings did not change. Subjects indicated more effort and less accuracy in following the pacing signal, the more its frequency differed from their spontaneous breathing frequency. The comparison of a spontaneous breathing condition with a frequency-matched paced condition revealed that pacing per se provoked a reduction in heart period. Because this decrease was not accompanied by changes in any of the HPV frequency components, their validity as measures of autonomic control needs to be questioned.

Adult↗

PubMed1999

Stimulation of CD95 (Fas) blocks T lymphocyte calcium channels through sphingomyelinase and sphingolipids.

Calcium influx through store-operated calcium release-activated calcium channels (CRAC) is required for T cell activation, cytokine synthesis, and proliferation. The CD95 (Apo-1/Fas) receptor plays a role in self-tolerance and tumor immune escape, and it mediates apoptosis in activated T cells. In this paper we show that CD95-stimulation blocks CRAC and Ca(2+) influx in lymphocytes through the activation of acidic sphingomyelinase (ASM) and ceramide release. The block of Ca(2+) entry is lacking in CD95-defective lpr lymphocytes as well as in ASM-defective cells and can be restored by retransfection of ASM. C2 ceramide, C6 ceramide, and sphingosine block CRAC reversibly, whereas the inactive dihydroceramide has no effect. CD95-stimulation or the addition of ceramide prevents store-operated Ca(2+) influx, activation of the transcriptional regulator NFAT, and IL-2 synthesis. The block of CRAC by sphingomyelinase metabolites adds a function to the repertoire of the CD95 receptor inhibiting T cell activation signals.

Animals↗

PubMed1999

Controlled brain hypothermia by extracorporeal carotid blood cooling at normothermic trunk temperatures in pigs.

Cerebral hypothermia improves outcomes after brain injury. A technique is presented for isolated brain cooling in pigs by cooling the natural blood supply of the brain. Under general anesthesia both common carotid arteries were exteriorized. One proximal carotid artery was connected to both distal carotid arteries and a heat exchanger in this line controlled brain temperature. The second proximal carotid artery was connected to an external jugular vein and a heat exchanger in this arteriovenous shunt was used to clamp trunk temperature. Thalamic brain temperatures of anesthetized juvenile pigs (N = 8) were clamped at 38, 25, and 30 degrees C while trunk core temperature was clamped at 38 degrees C. Approximately 7 min were needed to decrease brain temperature from 38 to 25 degrees C, reducing brain electric activity by 76% and increasing the temperature differences between different brain sites. Mean arterial blood pressure, heart rate, and cardiac output showed no significant change. Re-establishment of normothermic brain temperature led to a virtually complete recovery of brain electric activity. The technique is suitable for investigations of ischemic and traumatic injuries.

Animals↗