PubMed Health⌕ Search

Biomedical subjects

M Gabel

Publications and source records attributed to M Gabel.

At least 55 records · Page 3Linked to original sources
PubMed1993

Protein degradation in different feedstuffs labelled with 15N by using the nylon bag technique.

The nylon bag technique was used to determine the Nitrogen (N) and 15N degradation of 15N labelled feedstuffs in the rumen. The N and 15N degradation values were calculated according to Orskov and McDonald (1979) and ranged from 46.8 to 92.0 and from 61.8 to 93.6%, respectively. The differences between N and 15N degradation values of high fibre content feedstuffs are the highest, thus the measuring errors were greatest here. But differences also existed in concentrates. This study indicated that especially barley had a higher proportion of microbial N in the bag residues after the washing than the other concentrates. Therefore it is necessary to correct the N degradation values not only in cases of high fibre content but also in cases of low nitrogen content of feedstuffs. The calculation of the N degradation values could be possible on the basis of crude fibre and crude protein contents of feedstuffs. But experiments with a much larger number of 15N labelled feedstuffs have to be realized to give an accurate prediction of N degradation.

Animal Feed↗
PubMed1993

Comparative assessment of regional left atrial perfusion by laser Doppler and radionuclide microsphere techniques.

OBJECTIVE: The aim was to study the relation between left atrial microcirculatory flux, using laser Doppler flowmetry (LDF), and blood flow, using radiolabelled microspheres (MS). METHODS: Studies were done in five anaesthetised dogs. LDF probes were sewn to the appendage and body of the left atrium. Radionuclide spheres (15 microns) were used to quantitate blood flow at baseline, and during atrial pacing at 3.5 Hz, atrial fibrillation, and intravenous adenosine infusion (1 mg.kg-1 x min-1). RESULTS: In the left atrial body, both MS and LDF perfusion increased significantly during pacing and adenosine infusion; only LDF registered significant increases during atrial fibrillation. In the left atrial appendage, MS flow failed to increase significantly with any intervention and LDF perfusion increased significantly only during atrial fibrillation. There was a significant but weak correlation (r = 0.36, p < 0.05) between LDF and MS when data from all sample sites (n = 40) were compared, but good correlation when only baseline and pacing data were compared (r = 0.72, p = 0.0004, n = 20). In four additional dogs with heart failure [mean left atrial pressure 25.3(SD 7.4) mm Hg] produced by three weeks of rapid right ventricular pacing, flux values at baseline were increased significantly compared to control dogs and the responses registered by LDF to pacing, atrial fibrillation, and adenosine infusion were attenuated markedly. CONCLUSIONS: (1) Microcirculatory flux detected by LDF can identify the direction, and to a lesser extent, the magnitude of changes in regional atrial perfusion; and (2) LDF may be useful in identifying abnormalities of vasodilator reserve that accompany chronic left atrial myocardial dysfunction.

Animals↗
PubMed1993

Determination of left atrial volume using sonomicrometry: a cast validation study.

We developed a technique for left atrial (LA) volume estimation using two pairs of sonomicrometers sewn to the anteroposterior (LAX) and mediolateral (SAX) LA diameters and validated the method against water displacement of LA casts in 15 dogs. LA pressure was adjusted to a preselected level (5, 10, or 15 mmHg) by dextran infusion and was matched by postmortem infusion of casting resin (Conthane DPEN-18402). LA volume was modeled empirically as an ellipsoid of revolution without regression constants [(SAX)2(LAX)]. There was a strong correlation between the calculated LA volume and water displacement of the LA body [r = 0.87, standard error of estimate (SEE) = 3.3 ml, P = 0.0001] but a weaker correlation against water displacement of the entire LA (body+appendage, r = 0.81, SEE = 3.9 ml, P = 0.0003). The appendage volume fraction (appendage volume/total LA volume), as determined by water displacement of the casts, increased with increasing LA size (r = 0.78, P = 0.001). These data indicate that, in the normal canine heart, LA volume can be estimated accurately with high temporal and spatial resolution sonomicrometry using two atrial dimensions, and the contribution of appendage to total LA volume may become significant as the atrium enlarges.

Animals↗
PubMed1993

Influence of pericardium on left atrial compliance and pulmonary venous flow.

We studied seven open-chest anesthetized dogs to test the hypothesis that left atrial (LA) compliance is increased after pericardiectomy and to determine the effect of pericardiectomy on left atrial reservoir and conduit function. Two orthogonal sonomicrometer crystal pairs were used to estimate LA volume, and LA filling was assessed with a pulmonary vein (PV) flow probe. The left ventricular (LV) systolic (JFTI) and diastolic (KFTI) PV flow integrals were used as indexes of LA reservoir and conduit function, respectively. Diastolic LV transmitral flow was assessed with transesophageal Doppler echocardiography. Data were acquired over a wide range of intracardiac pressures and volumes obtained by intravenous hetastarch infusion both before and after pericardiectomy. The mean dynamic stiffness constant of the LA diastolic pressure-volume relation was significantly greater before pericardiectomy than afterwards (0.15 +/- 0.04 vs. 0.08 +/- 0.03 ml-1, P < 0.05). Data were analyzed before and after pericardiectomy at three matched levels of left atrial pressure (LAP; 7, 13, and 20 mmHg). The J-to-KFTI ratio increased significantly with volume infusion and was significantly less after pericardiectomy than before (1.2 +/- 0.7 vs. 1.2 +/- 0.6, 1.8 +/- 0.6 vs. 2.2 +/- 0.9, and 2.0 +/- 0.8 vs. 2.6 +/- 0.9 at low, mid, and high levels of LAP, respectively; P < 0.05 at mid and high levels of LAP). Peak early transmitral velocity increased with both volume infusion and pericardiectomy. We conclude that pericardiectomy increases LA compliance and early LV filling rate and is accompanied by a relatively greater augmentation in conduit than reservoir function of the left atrium.

Animals↗
PubMed1993

Altered left atrial compliance after atrial appendectomy. Influence on left atrial and ventricular filling.

Previous studies have shown regional differences in atrial distensibility. We studied 12 open-chest dogs to test the hypothesis that left atrial compliance is decreased after removal of the left atrial appendage and to determine the effect of altered atrial compliance on atrial reservoir and conduit function. Sonomicrometer crystal pairs were used to measure the long- and short-axis diameters of the left atrium over a wide range of intracardiac pressures and volumes obtained by intravenous hetastarch infusion both before and after suture ligation of the left atrial appendage (appendectomy). Pulmonary venous flow was measured with an ultrasonic flowmeter, and transmitral flow velocities were measured with transesophageal Doppler echocardiography. After appendectomy, the diastolic pressure-volume relation was shifted upward and to the left in six of seven dogs. The mean dynamic stiffness constant of the left atrial diastolic pressure-volume relation was significantly greater after appendectomy than before (0.20 +/- 0.11 [mean +/- SD] versus 0.14 +/- 0.08 ml-1, p < 0.01); the mean y intercept was slightly, but significantly, less after appendectomy (0.6 +/- 0.3 versus 1.3 +/- 0.6 mm Hg, p < 0.05). The left atrial reservoir volume (maximum minus minimum left atrial volume) was significantly less after appendectomy at matched left atrial pressures. The systolic to diastolic flow integral ratio of pulmonary venous flow (JFTI/KFTI), an index of the relative reservoir to conduit functions of the left atrium, increased significantly with volume infusion only before appendectomy; at matched left atrial pressure, JFTI/KFTI was significantly less afterwards.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Influence of loading conditions and contractile state on pulmonary venous flow. Validation of Doppler velocimetry.

BACKGROUND: Although recent studies suggest that pulmonary venous flow velocities may be used to evaluate left ventricular diastolic function, the influence of loading conditions and contractile state on the magnitude and pattern of pulmonary venous flow are poorly understood. METHODS AND RESULTS: Fourteen anesthetized open-chest mongrel dogs were instrumented with pulmonary venous flow probes, atrial sonomicrometer crystal paris, and high-fidelity micromanometers; transesophageal Doppler echocardiography was used to obtain simultaneous pulmonary venous flow velocities. Measurements were made over a wide range of left atrial pressure obtained by either intravascular volume infusion and inferior vena caval balloon inflation (n = 8), halothane inhalation (n = 6), or phenylephrine infusion (n = 5). There was an excellent correlation for pulmonary venous systolic (J) to diastolic (K) time integral between the Doppler and flow probe signal (r = 0.94; SEE, 0.18). When left atrial pressure was increased by volume infusion, there was a significant linear relation between mean left atrial pressure and the Doppler J/K peak (r = 0.64; SEE, 3.4 mm Hg) and flow velocity-time integral ratio (r = 0.75; SEE, 2.9 mm Hg). By contrast, when left atrial pressure was elevated by halothane-induced cardiac depression, there was no correlation. The independent determinants of the pattern of pulmonary venous flow (stepwise multiple linear regression analysis) under all conditions were atrial systolic shortening, aortic systolic pressure, heart rate, and left ventricular end-systolic dimension (cumulative r = 0.80). CONCLUSIONS: The pattern of pulmonary venous flow can be measured accurately with Doppler velocities and is differentially influenced by loading conditions and myocardial contractile state; in the absence of myocardial contractile dysfunction, the pattern of pulmonary venous flow may provide an estimate of left atrial pressure; and pulmonary venous flow is determined largely by atrial systolic function.

Animals↗
PubMed1991

[Growth studies of bulls of the black pied dairy cattle breed during low feed levels. 3. Anabolism and energy metabolism at empty body weight at slaughter].

In two long-term individual feeding experiments with rations very rich in roughage, nutrient and energy retention in the course of live weight development of black-and-white dairy bulls were determined. For this purpose, a total of 123 animals were slaughtered at the age of 5, 9, 12, 15, 18, 21 and 24 months, and the total body was analysed of 97 animals. The ascertained protein, fat and energy retention per day showed a clear dependence of the implemented level of nutrition. The results received compare well with the findings of earlier studies (PIEPER et al., 1984a). At a nutrition level (maintenance = 1.0) of 1.38 = 473 g gain of empty body [table: see text] at a nutrition level of 1.48 [context: see table] live weight range between 150 and 450 kg. The dynamics of the nutrient and energy retention in the course of live weight development is depicted in tables.

Animal Nutritional Physiological Phenomena↗
PubMed1991

[Growth studies of bulls of black-and-white dairy cattle during low feed levels. 4. Derivation of energy requirements].

On the basis of two long-term individual feeding experiments the growth-related energy requirement values for low live weight gains (500, 600 and 700 g daily cumulative live weight gain per animal derived by Pieper et al. in 1984 (1984b) were ascertained more precisely. The differences from the recommendations of the GDR feed evaluation system found earlier (Pieper et al. 1984) were confirmed. In general one can say that the differentiation of energy requirement in dependence of live weight gain with live weight being equal is greater than according to the GDR feed evaluation system (1986). Under consideration of a norm factor of 1.05 this results in the live weight range of between 50 and 500 kg and with a cumulative live weight gain of 500 g/animal and day in an energy expenditure of 4.44 kEFUcattle/kg live weight gain, of 600 g/animal and day i an energy expenditure of 4.08 kEFUcattle/kg live weight gain and of 700 g/animal and day in an energy expenditure of 3.82 kEFUcattle/ kg live weight gain.

Animal Feed↗
PubMed1991

Effects of pericardiectomy on canine pulmonary blood volume during hypervolaemia.

STUDY OBJECTIVE: The aim was to determine the effect of the pericardium on the pulmonary blood volume response to intravascular volume loading. DESIGN: Changes in pulmonary lung volume were measured from radioactive counts over the lung during radionuclide ventriculography. Baseline measurements, and repeat measurements after infusion of 21 ml.kg-1 of the dog's own blood, were made both before and after a pericardiectomy. SUBJECTS: Ten closed chest, anaesthetised dogs were studied. MEASUREMENTS AND MAIN RESULTS: Prior to and following pericardiectomy, volume loading produced equivalent and significant increases in left atrial, mean pulmonary artery, and right atrial pressures (all p less than 0.05). Before pericardiectomy, radionuclide lung counts increased from 1606(SEM 348) to 1870(402) with volume loading, corresponding to a 16% rise in lung counts from baseline (p less than 0.05). Following pericardiectomy, a similar volume load did not result in a significant rise in lung counts [1588(245) to 1697(255), 9%, p = 0.16], but was accompanied by an increase in left ventricular diastolic volume, from 39.7(6.6) to 58.7(6.4) ml, p less than 0.05, and a decrease in systemic vascular resistance index, from 122,600(14,600) to 86,600(10,000) dynes.s.cm-5 x kg, p less than 0.05. CONCLUSIONS: These data support the concept that removal of the pericardium is accompanied by reduced pulmonary blood volume overload in response to intravascular volume loading. The mechanism appears to be related to improved left ventricular diastolic filling, perhaps the result of diminished ventricular interaction, and to redistribution of excess intravascular volume from the pulmonary to the systemic circuit.

Animals↗
PubMed1991

Differential effect of neuropeptide-Y on membrane potential of cells in renal arterioles of the hydronephrotic mouse.

1. The effects of neuropeptide-Y (NPY) on the membrane potential of vascular smooth muscle cells were studied in renal arterioles of hydronephrotic mouse kidneys. 2. Kidney vessels are only weakly coupled with length constants of less than 10 microns and are most probably 'multiunit' vessels. 3. The vasoconstrictor peptide NPY reversibly depolarizes only smooth muscle cells in arterioles at distances greater than 200 microns from the glomerulus, whereas no changes of the membrane potential can be evoked close to the glomerulus (distance less than 50 microns). 4. The depolarizations, when present, are dose dependent. 5. Regardless of distance from the glomerulus cells respond uniformly to application of the vasoconstrictor angiotensin II.

Angiotensin II↗
PubMed1991

Influence of splenectomy on hemodynamics during cardiac tamponade.

The effect of prior splenectomy on the hemodynamics of cardiac tamponade was investigated in 15 closed-chest pentobarbital sodium-anesthetized dogs. Hemodynamics were compared at baseline and during staged cardiac tamponade (pericardial pressures of 5, 10, and 15 mmHg) at control (n = 15) and after splenectomy (n = 8) and sham operation (n = 7). The fall in mean arterial pressure with cardiac tamponade was significantly greater in splenectomized dogs than in either sham-operated or control dogs (P less than 0.001). Cardiac output was more depressed at the third level of cardiac tamponade in splenectomized than in sham-operated or control dogs (12.8 +/- 14.5 vs. 29.3 +/- 8.7 and 25.4 +/- 9.4 ml.min-1.kg-1, respectively; both P less than 0.05 vs. splenectomy). Hemodynamic failure, defined as an inability to maintain mean arterial pressure greater than 50 mmHg for 5 min, occurred at a lower pericardial pressure in splenectomized than in sham-operated dogs (13.1 +/- 3.8 vs. 18.1 +/- 3.5 mmHg, P less than 0.05). Hematocrit increased significantly with cardiac tamponade in controls and sham-operated but not splenectomized dogs. The percent increase in hematocrit from baseline to the third stage of cardiac tamponade was 19.6 +/- 9.8 and 22.3 +/- 5.6% in control and sham dogs, respectively. Thus the canine spleen plays an important role in cardiovascular compensation to cardiac tamponade. Parallel changes in hematocrit suggest that a part of this response is due to splenic autotransfusion.

Animals↗
PubMed1990

Hemodynamic efficacy of rapid saline infusion and dobutamine versus saline infusion alone in a model of cardiac rupture.

Despite recent reports describing survival after cardiac rupture, the effectiveness of circulatory support while awaiting definitive surgical treatment is controversial. To assess the efficacy of volume expansion and pharmacologic support in cardiac tamponade due to cardiac rupture, a model of hemorrhagic cardiac tamponade was developed and treatment with rapid saline infusion and dobutamine was compared with rapid saline infusion alone in 15 closed chest dogs. A right ventricular wound of reproducible size was produced by deflating an aortic valvuloplasty balloon that had previously been passed by way of the internal jugular vein into the pericardial space and through a stab wound in the right ventricular free wall. Hemodynamic values were compared at baseline, during tamponade and after a rapid infusion (1 liter at 100 ml/min) of either saline solution alone or saline solution plus dobutamine (20 micrograms/kg per min). Atrial and pericardial pressures increased significantly in both groups. Mean arterial pressure, cardiac output and stroke volume increased with combined saline and dobutamine infusion to values similar to those at baseline (91 +/- 19%, 114 +/- 43% and 94 +/- 37% of baseline, respectively). In contrast, saline infusion alone caused a small increase in cardiac output but failed to significantly increase mean arterial pressure or stroke volume (76.8 +/- 14.2%, 55 +/- 18% and 51 +/- 17% of baseline, respectively). Combined rapid infusion of saline solution and dobutamine infusion has a more beneficial hemodynamic effect and may be more effective than rapid saline infusion alone in resuscitating patients with hemorrhagic cardiac tamponade due to cardiac rupture.

Animals↗
PubMed1990

[The energy requirements of Holstein-Friesian heifers during rearing and pregnancy under the tropical conditions of Cuba. 1. Determination of dry matter and energy assimilation and of the live weight development and energy expenditure].

In an individual feeding experiment with 48 Holstein-Friesian heifers divided into 3 groups, the effect of various energy levels on live weight development and energy expenditure in the age bracket of 97 days (78 kg live weight) to conception (350 kg LW) and from conception to calving (500 kg LW) was investigated. Rations with differing concentrate--roughage ratios were used. The differentiation of energy intake per day between groups 1 and 2 and group 3 amounted to 7.5% in the 1st development period and to 20% between group 1 and groups 2 and 3 in the 2nd development period. There were significant differences in the live weight gain of 95 g/animal and day in the first development period (up to conception) and of 81 g/animal and day in the second period of development (from conception to calving). Under the tropical climatic conditions the energy expenditure in these studies was approximately 10% under the energy expenditure recommended by the NRC (1978). While there was a clear reciprocal relation between energy expenditure and live weight gain in the first period of development, this relation was less distinct in the second period of development.

Age Factors↗
PubMed1990

[The energy requirements of Holstein-Friesian heifers during rearing and pregnancy under the tropical conditions of Cuba. 2. Generalization of the results and derivation of the energy requirements].

Experimental results of an individual feeding experiment with 48 Holstein-Frisian heifers were generalized with regard to live weight development and energy intake by means of the Janoschek function and the extended e-function resp. The requirement of metabolizable energy was derived from the results of energy intake on dependance on live weight and live weight gain. In comparison with the data of the NRC (1978) a requirement by 10% lower was the result. Due to adding a 10% deficiency supplement at present required under Cuban conditions of production the use of the NRC recommendations (1978) is still justified. Without the addition of the deficiency supplement the results showed good agreement with requirement data of INRA 1978.

Animal Feed↗
PubMed1990

Cardiac tamponade in left ventricular dysfunction.

Echocardiographic and hemodynamic data were measured in closed-chest dogs during graded cardiac tamponade (pericardial pressure 5, 10, and 15 mm Hg) before and after production of diffuse ischemic left ventricular dysfunction. Left ventricular dysfunction was produced by intracoronary injection of nonradioactive microspheres (54 +/- 3.9 mm diameter). Changes in left atrial pressure with cardiac tamponade were influenced by coexisting left ventricular dysfunction. Left atrial pressure increased with tamponade and was equal to pericardial pressure before left ventricular dysfunction was produced. However, after left ventricular dysfunction was produced, left atrial pressure was significantly higher than pericardial pressure before tamponade, but it fell toward pericardial pressure when tamponade was produced. Pulsus paradoxus (greater than 10 mm Hg) was present in all animals with cardiac tamponade before left ventricular dysfunction but in only one animal afterward. During each level of tamponade, the inspiratory fall of aortic systolic pressure was greater before than with left ventricular dysfunction. The slope of the linear regression between pericardial pressure and millimeters of mercury of inspiratory fall in aortic systolic pressure was significantly greater before than with left ventricular dysfunction (0.74 +/- 0.12 versus 0.32 +/- 0.12, p less than 0.05). Left ventricular dysfunction caused a leftward and upward shift of the pericardial pressure-volume relation. As a result, right atrial and ventricular collapse occurred with significantly smaller volumes of pericardial fluid after than before left ventricular dysfunction. We conclude that pulsus paradoxus may be absent in cardiac tamponade with coexisting left ventricular dysfunction and unequal filling pressures. Echocardiographic signs of cardiac tamponade may occur with small effusions in the presence of left ventricular dysfunction.

Animals↗
PubMed1989

Amlodipine, a long-acting calcium antagonist drug reduces ischemia-induced ventricular conduction delay in pig hearts.

The effects of amlodipine, a novel, long-lasting calcium channel blocking agent, on ischemia-induced myocardial conduction delay was studied in anesthetized pigs paced at a constant heart rate. Acute coronary occlusion (3 minutes) significantly lengthened time to onset, time to peak and duration of bipolar electrograms recorded from both subendocardial and subepicardial left ventricular sites. After intravenous injection of amlodipine (0.3 mg/kg, n = 6), subsequent periods of ischemia greatly reduced (p less than 0.01) all indexes of subepicardial conduction delay. In the subendocardium, amlodipine decreased only time to onset (-25 +/- 4%, p less than 0.01) within the ischemic zone. Significant delays in all indexes were present during repeated ischemic periods in the placebo-treated control group (n = 5). Amlodipine also increased regional myocardial blood flow within the nonischemic myocardium by 25 +/- 10% and decreased mean aortic pressure by 7 +/- 2% without altering flow in the ischemic region. Left atrial pressure remained unchanged. Indexes of ischemia-induced conduction delay were more rapidly restored after reperfusion in amlodipine-pretreated than in control animals. In conclusion, amlodipine produced a beneficial blood flow-independent effect on ischemia-induced injury potentials. The effect may help to reduce the likelihood of development of lethal ventricular arrhythmias in the early stage of myocardial ischemia in the clinical setting.

Amlodipine↗
PubMed1988

Cardiac tamponade: a comparison of right versus left heart compression.

It has been postulated that in cardiac tamponade, the hemodynamic effects of compression of the right heart chambers and great veins are more important than are the effects of left heart compression. In 10 anesthetized dogs with surgically compartmented pericardium, the hemodynamic effects of right atrial and right ventricular compression were compared with the hemodynamic effects of left atrial and left ventricular compression. The effects of right heart compression, left heart compression, and then effects of combined right and left heart compression, were compared at three levels of intrapericardial pressure: 10, 15 and 20 mm Hg. Aortic mean pressure decreased significantly at each level of intrapericardial pressure with right-sided tamponade but not with left-sided tamponade. Left atrial mean pressures decreased significantly with right-sided tamponade and increased with left-sided and combined tamponade. Right atrial mean pressures increased significantly with right-sided and combined tamponade, but not with left-sided tamponade. Heart rate increased significantly with each of the three varieties of tamponade. Cardiac output and stroke volume, which decreased with each variety of tamponade, were significantly lower during right-sided than during left-sided tamponade. Combined tamponade lowered stroke volume more than did right-sided tamponade, and lowered cardiac output more at 15 and 20 mm Hg intrapericardial pressure. It is concluded that, in this preparation, right-sided cardiac compression has more important hemodynamic effects than does left-sided compression. However, left-sided tamponade still makes a significant contribution to the total hemodynamic picture of cardiac tamponade.

Animals↗