PubMed Health⌕ Search

Biomedical subjects

S B Hansen

Publications and source records attributed to S B Hansen.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cerebral 6-[(18)F]fluoro-L-DOPA (FDOPA) metabolism in pig studied by positron emission tomography.

We measured 6-[(18)F]fluoro-L-DOPA (FDOPA) uptake and metabolism in the brain of 4-month-old female pigs (n = 8) using a high-resolution positron emission tomograph (PET) in 3D mode. The mean net blood-brain clearance of FDOPA (K(i)(D)) to striatum was 0.011 ml g(-1) min(-1). Correcting for the elimination of decarboxylated metabolites from striatum (k(loss) = 0.004 min(-1)) increased the apparent magnitude of the estimate of K(i)(D) by 50%, at the expense of doubling the variance of the mean estimate. The mean decarboxylation rate of FDOPA in striatum relative to the cerebellum input (k(3)(s)) was 0.008 min(-1). For multicompartmental analyses, the FDOPA partition volume (V(e)(D)) was constrained to the individual value observed in cerebellum (mean = 0.53 ml g(-1)), with correction for the presence in brain of the plasma metabolite 3-O-methyl-FDOPA (OMFD). Using the first 60 min of the dynamic PET scans, the rate constant of FDOPA decarboxylation (k(3)(D)) was estimated to be 0.037 min(-1 )in striatum, but was not significantly different than zero in frontal cortex. Fitting of a compartmental model correcting for elimination of decarboxylated metabolites to the complete PET frame-sequence (120 min) increased the variance of the estimate of k(3)(D) in striatum. The magnitude of k(3)(D) in striatum of young pig was less than values estimated previously in neonatal piglet, adult monkey, and human. MRI-based simulations predicted that recovery of radioactivity from pig striatum was highly sensitive to the volume of interest. We conclude that the spatial resolution of our tomograph reduces the apparent magnitude of k(3)(D) in striatum. However, anaesthetised pigs are an appropriate experimental model for PET studies of DOPA decarboxylation in striatum.

Aging↗
PubMed1999

Uptake and distribution of a new SSRI, NS2381, studied by PET in living porcine brain.

This study tests the utility of a new selective serotonin reuptake inhibitor (SSRI), [11C]NS2381 {(+/-)-(8-[11C]methyl-3-(4-trifluoromethyl-phenyl)-8-azabicyclo[3.2.1]oc t-2-ene)}, as positron-emitting radioligand for labelling serotonin (5-HT) reuptake sites in living brain. Studies of monoamine uptake were carried out initially in vitro using rat brain synaptosomes. They showed that NS2381 and its precursor NS2435 are selective inhibitors of serotonin (5-HT) uptake. Then, studies were carried out in vivo on the uptake and distribution of [11C]NS2381 in living porcine brain. They showed that the radiotracer accumulates readily in brain, and binds reversibly in regions rich in serotonin uptake sites (e.g. raphe, basal ganglia and thalamus). In addition, [11C]NS2381 was displaced from brain tissue by the potent SSRI citalopram. The enantiomers of [11C]NS2381 were, in general, found to be similar to the racemate in terms of their uptake and distribution in living pig brain. Thus, [11C]NS2381 fulfilled several criteria of a PET radioligand for studying 5-HT uptake sites in the living brain.

Animals↗
PubMed1998

Quantitative PET analysis of regional cerebral blood flow and glucose and oxygen metabolism in response to fenfluramine in living porcine brain.

The serotonin agonist fenfluramine has been used widely in humans for studying neuronal activation. We carried out the present study in order to determine whether anesthetized pigs could be used for studying effects of fenfluramine on cerebral functions using positron emission tomography (PET). We obtained quantitative measures of regional cerebral blood flow (rCBF) and of glucose and oxygen utilization (rCMRglc and rCMR(O2)) during intravenous administration of fenfluramine, using [15O]water, [18F]FDG and [15O]oxygen, respectively. Fenfluramine (25 mg/h i.v.) caused a significant rise in rCBF and, to a lesser extent, in rCMR2(O2), but it failed to affect rCMRglc. The findings indicate that quantitative estimation of rCBF by repeated injection of [15O]water was more sensitive than either rCMRO2 or rCMRglc for detecting effects of fenfluramine on serotonin neurotransmission in living porcine brain.

Animals↗
PubMed1998

Detection of cholangiocarcinoma in primary sclerosing cholangitis by positron emission tomography.

Primary sclerosing cholangitis (PSC) predisposes to cholangiocarcinoma (CC), which usually is widespread in the liver at the time of the diagnosis and which has a median survival of approximately 6 months. Positron emission tomography (PET) is a noninvasive scanning method that allows the assessment of metabolism in vivo by means of positron-emitting radiolabeled tracers. [18F]Fluoro-2-deoxy-D-glucose (FDG) is a glucose analogue that accumulates in various malignant tumors because of their high glucose metabolic rates. The purpose of the study was to develop a PET method to detect small CC tumors in patients with PSC. PET scanning of the liver was performed after intravenous injection of 200 MBq FDG in 9 patients with PSC, 6 patients with PSC + CC, and 5 controls. The scanning was performed at successive time intervals for a total of 90 minutes with simultaneous successive arterial blood sampling for radioactivity concentration determination. In each of the PSC + CC patients, 2 to 7 "hot spots" were seen, with volumes of 1.0 to 45 mL (median, 4.4 mL). There were no hot spots in the two other patient groups. The localization of hot spots was confirmed by single-blind evaluation. Data were analyzed by the Gjedde-Patlak plot, yielding values of the net metabolic clearance of FDG, K [mL min(-1) 100 mL(-1) tissue]. In the CC hot spots, maximum K values were 1.59 to 4.17 (median, 2.34; n = 6); in the reference liver tissues of these patients, K values were 0.40 to 0.69 (median, 0.49); in PSC patients, they were 0.23 to 0.53 (median, 0.36); and in controls, they were 0.20 to 0.34 (median, 0.31). The difference between K in CC hot spots and the other groups was statistically significant (P < .001). We conclude that FDG-PET seems to be able to detect small CC tumors and may be useful in the therapeutic management of PSC.

Adult↗
PubMed1998

Effects of positive pressure ventilation and inspired oxygen on pulmonary vascular resistance and tissue oxygen delivery in neonatal pigs.

Management of pulmonary vascular resistance in neonates with congenital heart disease is important for stabilization before and after surgical interventions. Thus, we determined which combination of positive end-expiratory pressure ventilation and fraction of oxygen in the inspired air increases pulmonary vascular resistance without compromising delivery of oxygen to the tissue. Eight piglets were anesthetized, intubated and ventilated. Pulmonary flow and pulmonary arterial and left atrial pressures were monitored continuously. At all levels of inspired oxygen (1.00, 0.21 and 0.15), ventilation at a pressure of 15 cm of water increased pulmonary vascular resistance. At all levels of positive pressure ventilation, a fraction of 0.15 of inspired oxygen increased pulmonary vascular resistance. The combination of a ventilatory pressure of 15 cm of water and inspired oxygen of 1.00, or ventilatory pressure at 5 cm of water and oxygen delivery of 0.15, produced similar changes in pulmonary vascular resistance (19.1 +/- 2.8 vs. 20.0 +/- 3.8 mmHg/(L/min)) and cardiac output (0.78 +/- 0.07 vs. 0.93 +/- 0.10 L/min) but, the higher level of positive pressure plus 1.00 inspired oxygen gave a significantly higher arterial oxygen saturation (0.99 +/- 0.03 vs. 0.72 +/- 0.19%) and delivery of oxygen to the tissues (13.7 +/- 2.9 vs. 7.4 +/- 1.5 ml O2/min, p < 0.05). Thus, both high positive pressure ventilation and hypoxia increase pulmonary vascular resistance. Only high pressure ventilation plus high concentrations of inspired oxygen, however, increased pulmonary vascular resistance without compromising delivery of oxygen, suggesting that this combination is a superior means of increasing pulmonary vascular resistance.

Animals↗
PubMed1998

Absolute cerebral blood flow and blood volume measured by magnetic resonance imaging bolus tracking: comparison with positron emission tomography values.

The authors determined cerebral blood flow (CBF) with magnetic resonance imaging (MRI) of contrast agent bolus passage and compared the results with those obtained by O-15 labeled water (H215O) and positron emission tomography (PET). Six pigs were examined by MRI and PET under normo- and hypercapnic conditions. After dose normalization and introduction of an empirical constant phi Gd, absolute regional CBF was calculated from MRI. The spatial resolution and the signal-to-noise ratio of CBF measurements by MRI were better than by the H215O-PET protocol. Magnetic resonance imaging cerebral blood volume (CBV) estimates obtained using this normalization constant correlated well with values obtained by O-15 labeled carbonmonooxide (C15O) PET. However, PET CBV values were approximately 2.5 times larger than absolute MRI CBV values, supporting the hypothesized sensitivity of MRI to small vessels.

Animals↗
PubMed1998

Cerebral blood flow measurements by magnetic resonance imaging bolus tracking: comparison with [(15)O]H2O positron emission tomography in humans.

In six young, healthy volunteers, a novel method to determine cerebral blood flow (CBF) using magnetic resonance (MR) bolus tracking was compared with [(15)O]H2O positron emission tomography (PET). The method yielded parametric CBF images with tissue contrast in good agreement with parametric PET CBF images. Introducing a common conversion factor, MR CBF values could be converted into absolute flow rates, allowing comparison of CBF values among normal subjects.

Adult↗
PubMed1998

Latissimus dorsi cardiomyoplasty: a chronic experimental porcine model. Feasibility study of cardiomyoplasty in Danish Landrace pigs and Göttingen minipigs.

Cardiomyoplasty is an experimental treatment for end-stage heart failure. We hypothesized that the porcine latissimus dorsi muscle (LDM) in an experimental porcine model is a suitable surrogate for a clinically relevant evaluation of this concept. Fourteen Danish Landrace (DL) pigs and six Göttingen minipigs (GM) were studied. The LDM was evaluated immediately after surgical dissection and in various phases: phase 1 (n = 4)--outcome of a partial vascular isolation (vascular delay), 2 to 3 weeks prior to heart wrapping in DL pigs; phase 2 (n = 6)--long-term flap survival of nonstimulated LDM cardiomyoplasty in DL pigs; phase 3 (n = 6)--outcome of nonstimulated cardiomyoplasty in GM; phase 4--one DL pig had dynamic cardiomyoplasty performed and was subjected to low-intensity LDM stimulation for 8 months. Isolation of the LDM of DL pigs and GM as a pedicled graft had no acute deleterious impact on the global blood supply. In phase 1a, partial vascular isolation and in situ recovery of the LDM resulted in a muscle encapsulated in fibrotic tissue, which hampered a later heart wrap. In phase 1b, a less extensive dissection diminished fibrosis and allowed subsequent wrapping. In phase 2, after 6 weeks of nonstimulated LDM cardiomyoplasty, the LDM of DL pigs was viable, with excellent heart-muscle integration. In phase 3, the same procedure applied in GM yielded the same result as that in DL pigs, but with a higher success rate owing to the learning phase.

Animals↗
PubMed1998

Medtronic Hall versus St. Jude Medical mechanical aortic valve: downstream turbulences with respect to rotation in pigs.

BACKGROUND AND AIMS OF THE STUDY: Turbulences downstream of mechanical aortic valves are known to contribute to most valve-related complications such as thrombosis, embolization or damage to blood components. In vitro studies have demonstrated the impact of the orientation of prostheses on transvalvular energy loss. This study evaluates the influence of valve orientation on turbulences in the supravalvular aorta in pigs. METHODS: A rotation device which could carry a Medtronic Hall (MH) or St. Jude Medical (SJM) aortic valve prosthesis (23 mm) was constructed and implanted into four healthy pigs. Turbulence measurements using pulsed Doppler ultrasonography were carried out 3 cm downstream of the valve, while the prostheses were rotated in 45 degrees steps. Reynold's normal stress values (RNS) were calculated as key markers for turbulent stresses. RESULTS: Turbulences downstream of MH and SJM valves demonstrated a significant change with rotation. The MH valve showed minimum RNSmean values with orientation of the large orifice to the right posterior aortic wall, which is the area of highest velocities during ejection. With this orientation, aortic flow almost complied with physiologic conditions. Increase of turbulence was observed with any other position. The SJM valve revealed significant turbulent flow at any orientation. Minimum RNSmean values were also measured with one orifice facing the right posterior wall of the aorta. CONCLUSION: With optimum orientation (major orifice facing the right posterior aortic wall) the MH valve matches the aortic flow pattern to near-normal physiology. The flow patterns of the SJM valve are less susceptible to rotation, but cannot attain the optimum RNS values of the MH prosthesis.

Animals↗
PubMed1997

In vivo estimation of cerebral blood flow, oxygen consumption and glucose metabolism in the pig by [15O]water injection, [15O]oxygen inhalation and dual injections of [18F]fluorodeoxyglucose.

There is a need for suitable non-primate laboratory animals for studies of brain function by positron emission tomography (PET). To provide a comparative index of the circulatory physiology of the pig, we have applied novel PET tracer methodology to seven anaesthetized pigs, and measured cerebral regional oxygen consumption (CMR[O2]), cerebral blood flow (CBF), and cerebral glucose metabolism (CMR[glc]). Blood flow and flow-metabolism couple were estimated for selected cerebral regions of interest. We found an average hemispheric CMR(O2) of 171 +/- 18 micromol/100 cm3/min. Individual hemispheric CBF measurements varied between 33 and 41 ml/100 cm3/min, with an average of 37 +/- 3 ml/100 cm3/min at an average PaCO2 of 4.3 +/- 0.9 kPa. The blood flow dependency on arterial PCO2 was calculated from the results of the carbon dioxide response in two pigs in which the CBF measurements obeyed the equation CBF (ml/100 cm3/min) = 8.9 PaCO2 (kPa). In each pig, CMR(glc) was studied twice with a double-injection FDG method. In the first session, the values of CMR(glc) averaged 27 +/- 3 and 23 +/- 4 micromol/100 cm3/min, estimated by multilinear and linear regression analysis, respectively. In the second session, the corresponding averages were 27 +/- 3 and 24 +/- 3 micromol/100 cm3/min, respectively. The average oxygen extraction fraction was 0.46 +/- 0.09 and the oxygen-glucose ratio was 6.1 +/- 0.8. The findings indicate that the pig is suitable for PET studies of cerebral blood flow, cerebral oxygen consumption and glucose metabolism.

Administration, Inhalation↗
PubMed1997

Cortical sites of sustained and divided attention in normal elderly humans.

Human brain mechanisms subserving attention have been assigned to prefrontal, midfrontal, and posterior parietal cortices, as well as to the anterior cingulate and the thalamus. To map these mechanisms in the brain, most studies have used selective attention tasks; few studies have mapped the brain under sustained or divided attention. The present study was designed to create maps of regional activity associated with sustained and divided attention using two different sensory modalities: visual checkerboard stimulation and vibrotactile stimulation of the right hand. Five cerebral PE-tomograms of 15O-labeled water uptake were acquired from 16 elderly healthy subjects during sustained or divided attention to the frequency of stimulation. To locate active brain regions, the t-statistic map of relative changes in cerebral blood flow was coregistered to the subjects' averaged brain MR images and to the standard Talairach brain coordinate system. Attention was associated with activity in two sites, the right middle frontal gyrus (Brodmann area 46) and the right inferior parietal lobule (Brodmann area 40). The frontal site was more active when the subjects attended to the visual stimulus and when the attention was divided, while the parietal site was more active during attention to the vibrotactile stimulus and during simple sustained attention. Our observations are consistent with the hypotheses (1) that the right posterior parietal attention center subserves attention to several sensory modalities and (2) that a cortical network of specific neuronal sites subserves both sustained and divided attention. These hypotheses must be tested in further studies.

Aged↗
PubMed1997

PET neuroimaging with [11C]venlafaxine: serotonin uptake inhibition, biodistribution and binding in living pig brain.

The brain binding kinetics and distribution of the antidepressant venlafaxine, labelled with 11C in the O-methyl position, was studied by PET after intravenous injection in anesthetized pigs. In addition, venlafaxine's action on serotonin (5-HT) uptake was studied in vitro in blood platelets obtain from humans or pigs. Venlafaxine resembled imipramine, paroxetine and citalopram in causing a dose-dependent inhibition of 5-HT uptake in blood platelets from pigs and humans. Venlafaxine-derived radioactivity entered the living brain readily and showed higher binding potentials in diencephalic and telencephalic regions than in cerebellum. Acute administration of an antidepressant drug (i.e. imipramine, citalopram or paroxetine) enhanced the distribution and altered the binding of venlafaxine in certain brain regions. The findings show that [11C]venlafaxine is not an ideal PET radiotracer mainly because of its relatively low binding potentials and its lack of specificity for the 5-HT transporter in living brain.

Animals↗
PubMed1997

Haemodynamic and metabolic effects of gallopamil as additive to calcium-containing and calcium-free cardioplegic solutions in mature pig hearts.

Myocardial haemodynamic and metabolic effects of the calcium-channel blocker gallopamil as additive to calcium-containing (St Thomas Hospital, STH) and calcium-free (Bretschneider procaine-containing, BRT) crystalloid cardioplegic solutions were evaluated. Adult pig hearts (weight 0.033 kg) were randomized to four groups and perfused with 1 litre of cold (4 degrees C) cardioplegic solution; group A: BRT without gallopamil, n = 9, group B: BRT with gallopamil (0.4 microM), n = 8, group C: gallopamil-free STH, n = 8, and group D: STH with gallopamil (0.4 microM), n = 8. After storage at 4 degrees C for 6 hours the hearts were reperfused with blood/Ringer solution in a modified Langendorff model for 60 min. Developed left ventricular pressure, rate-pressure product and +dP/dt were lower in gallopamil-treated hearts during reperfusion (p < 0.05), as were oxygen extraction and oxygen uptake (p < 0.05) and lactate release (p < 0.05). Myocardial blood flow was greater in gallopamil-treated hearts (p < 0.05). In hearts comparable in size and anatomy to the human heart, gallopamil added to both cardioplegic solutions reduced cardiac function and oxygen uptake despite increased myocardial blood flow. The findings suggest reduced myocardial protection after addition of gallopamil to cardioplegic solutions.

Animals↗
PubMed1996

Arterial bypass graft spasm: an examination of the role of high flow demands and endothelial function in the porcine GEA.

This study examined why an artery becomes vulnerable to spasm when used as a bypass graft. We hypothesized that high flow demands would decrease pressure distally in the conduit (afterload), thus increasing the sensitivity to vasoconstrictors. Furthermore, perioperative endothelial dysfunction would additionally sensitize the artery to constrictors. Six gastroepiploic arteries (GEA, 1.0-1.5 mm diameter, 11 cm length) were harvested from adult pigs (110-125 kg) and mounted on a computer-controlled perfusion system. The inflow pressure was set at 80 mmHg and outflow resistance was adjusted to simulate normal (in situ) or high (coronary bypass graft) flow demands. Gastroepiploic flow and distal pressures were measured at baseline [B] and after adding norepinephrine (NE, 10(-9) M to 10(-5) M). Under normal flow demand, a minimal pressure drop existed across the GEA and flow decreased only at high NE concentrations. High flow demand decreased distal GEA pressure and increased the sensitivity to NE. To block endothelial function N-Monomethyl-L-Arginine, Monoacetate (L-NMMA, 10(-5) M) was then added. Under high flow demand, blocking endothelial function resulted in an additional fivefold increase in sensitivity to NE (ED50 from 9.75 10(-8) M to 2.11 10(-8) M, P < 0.05). It was shown that in long narrow arterial grafts, high flow demands cause cumulative pressure losses. Even with normal endothelial function, these pressure losses render the artery responsive to vasoconstrictors. Endothelial dysfunction additionally increases the sensitivity of the artery. Anastomosis of a small arterial graft to a large myocardial perfusion bed may result in reduced distal conduit pressure and may predispose to the development of myocardial ischemia even when low doses of vasoconstrictors are used. Perioperative endothelial dysfunction may exacerbate this effect.

Abdominal Muscles↗
PubMed1996

Improved recovery after cold crystalloid cardioplegia using low-dose glutamate enrichment during reperfusion after aortic unclamping: a study in isolated blood-perfused pig hearts.

Increased glutamate utilization is a part of the metabolic adaptation to oxygen deprivation by the heart. The effect of low-dose L-glutamate (2 mmol/L) during continuous reperfusion after aortic unclamping on postcardioplegic recovery was studied in pig hearts similar in size, anatomy, and function to the human adult heart. After cold crystalloid cardioplegic arrest (CCC) with Bretschneider solution no 3, hearts were excised from pigs weighing 70-80 kgs (heart weight, average +/- SEM: 308 +/- 4 grams), and reperfused in an isolated blood-perfused heart model for 120 minutes. Three groups of hearts were compared. One group of hearts was subjected to 30 minutes of CCC only (30 min group; n = 9), another group of hearts to 90 minutes of CCC and storage (Control group: n = 16), and a third group to 90 minutes of CCC and storage, but with L-glutamate added to the blood reperfusate (2 mmol/L) (Glutamate group: n = 18). In the Control group 14 of 16 hearts (88%) needed electrical defibrillation after start of reperfusion, significantly more (p < 0.05) than the 8 of 18 (44%) in the Glutamate group; the difference between the 30-min (2 of 9 [22%]) and the Glutamate group was not significant (p = 0.48). Developed left-ventricular pressure (DLVP) and positive dP/dtmax (+dP/dtmax) was significantly higher in the Glutamate group than in the Control group during early reperfusion (DLVP: p < 0.05: +dP/dtmax: p < 0.01) and the entire reperfusion (DLVP and +dP/dtmax: p < 0.05), while reperfusion responses in the Glutamate and 30-min groups were not significantly different. Furthermore, myocardial oxygen uptake was significantly higher in the Glutamate group than in the Control group (p < 0.001), but not higher than that in the 30-min group. Decreased lactate release was found in the Glutamate group compared to the Control group during early reperfusion (p < 0.01), and the entire reperfusion (p < 0.001). No differences were found between the Control and Glutamate groups in alanine exchange. Thus, L-glutamate has a beneficial effect in pig hearts on both functional and metabolic recovery after cold crystalloid cardioplegia and storage when present in a concentration even as low as 2 mmol/L during continuous reperfusion after aortic unclamping. A possible mechanism is a glutamate-induced stimulation of the malate-aspartate shuttle leading to increased intramyocardial lactate utilization.

Adult↗
PubMed1996

Examination of epimysial leads used to stimulate the latissimus dorsi muscle.

Cardiomyoplasty is a new surgical treatment for heart failure in which the patient's latissimus dorsi muscle (LDM) is isolated, wrapped around the heart, and electrically stimulated to provide cardiac assistance. At present, long term stimulation of the LDM is achieved with intramuscular electrodes, which produce minimal nerve damage. This study examined the use of epimysial electrodes by measuring the epimysial lead characteristics during a four-week LDM training. Lead resistance started at 463 +/- 41 omega after implantation, decreased during the following week (251 +/- 16 omega), and remained less than the initial value during the last three weeks (weeks two: 282 +/- 19 omega and week four: 341 +/- 28 omega). The recruitment properties were similar to nervecuff electrodes: low threshold voltages (week one: 0.75 +/- 0.12, week two: 0.90 +/- 0.33, week four: 0.52 +/- 0.10 V) and a very steep recruitment curve with low saturation voltages. Histological examination revealed normal muscle fibers with no inflammatory response. Epimysial leads may be more convenient for most surgeons because the design does not require any free-dissection of the nerve nor guiding a needle around the nerve with the risk of perforating vessels or nerve branches. These results indicate that epimysial leads are worthy of further investigation.

Analysis of Variance↗
PubMed1995

Superiority of acid extractable glycogen for detection of metabolic changes during myocardial ischaemia.

Various methods for extraction and isolation of myocardial glycogen show different yields and identify different glycogen subsets. The aim of the present study was to identify a glycogen fraction exposed to changes during myocardial ischaemia. Endomyocardial biopsies from 10 pigs were sampled before cardioplegia, after cardioplegic arrest, and after reperfusion. Glycogen yields were compared following five extraction procedures: (1) hot alkaline tissue digestion, (2) homogenization in perchloric acid and subsequent determination in homogenate, (3) homogenization in perchloric acid and subsequent determination in supernatant, (4) homogenization in perchloric acid and subsequent determination in the precipitate redissolved in hot alkaline and (5) homogenization in homogenisation buffer with lysating capacity. Glycogen was isolated on filter-paper and determined enzymatically. Hot alkaline tissue digestion yielded the highest glycogen amounts (63.5 +/- 18.3 nmol/mg wet weight). Glycogen yields in perchloric homogenate and supernatant were 51%, perchloric precipitate 47%, and buffer 30% of these obtained with hot alkaline. Glycogen yields in hot alkaline were comparable to the sum of those obtained in perchloric supernatant ("acid extractable glycogen") and redissolved precipitate ("heavily extracted glycogen") confirming that glycogen yields obtained with hot alkaline digestion represent "total glycogen". Acid extractable glycogen showed superior analytical characteristics compared with the other methods. Acid extractable glycogen demonstrated a consistent decrease during ischaemia whereas total glycogen and glycogen extracted in homogenization buffer tended to decrease. Glycogen in perchloric precipitate remained unchanged during ischaemia. These findings support a revival of the concept that tissue contains two forms of glycogen. Decreases in myocardial glycogen content during myocardial ischaemia are best observed with acid extractable glycogen.

Animals↗