Lucien Girardier

Fish oil decreases natural resistance of mice to infection with Salmonella typhimurium.

Mortality rate in mice fed fish oil for 4 weeks was remarkably higher after a very low peroral (PO) challenge with Salmonella typhimurium, as compared with those fed diets rich in either corn oil or hydrogenated coconut oil, or a low fat (chow) diet. None of the surviving mice fed the fish oil diet showed bacterial counts in their spleens, unlike 45.4% to 66.6% of surviving mice fed high fat or low fat diets. The spleens of mice fed fish oil presented the highest number of bacteria 7 days after intraperitoneal infection with the same bacterial strain. Thus, the current studies demonstrate that a diet rich in fish oil decreases host resistance to infection.

Neural Regulation of Insulin Secretion in the Dog

The effects of stimulation of the mixed autonomic nerve to the dog pancreas has been studied under conditions in which both pancreaticoduodenal vein blood flow and insulin concentration were determined. Stimulation resulted in increased insulin output, which was blocked by prior administration of atropine. Blood flow was reduced by stimulation in proportion to the rate of stimulation. At 40 stimuli/s a maximum effect was found at 1 min with a gradual return toward base line despite continued application of the stimulus. Atropinization had no effect on blood flow changes. Insulin responses to 0.1 g/kg glucose were reduced on the average 40% by simultaneous stimulation of the pancreatic nerve at 40 cycles/s in atropinized animals. These studies establish this preparation as a reproducible model for the direct examination of autonomic influences on endocrine pancreatic function. From them it is concluded that the nerve supply to the endocrine pancreas of the dog is sufficient to inhibit insulin secretion by activation of the sympathetic nerves and to stimulate insulin secretion by activation of the parasympathetic nerves.

Glucagon Release Induced by Pancreatic Nerve Stimulation in the Dog

A direct neural role in the regulation of immunoreactive glucagon (IRG) secretion has been investigated during stimulation of mixed autonomic nerves to the pancreas in anesthetized dogs. The responses were evaluated by measurement of blood flow and hormone concentration in the venous effluent from the stimulated region of pancreas. Electrical stimulation of the distal end of the discrete bundles of nerve fibers isolated along the superior pancreaticoduodenal artery was invariably followed by an increase in IRG output. With 10-min periods of nerve stimulation, the integrated response showed that the higher the control glucagon output, the greater was the increment. Atropinization did not influence the response to stimulation. That the preparation behaved in physiologic fashion was confirmed by a fall in IRG output, and a rise in immunoreactive insulin (IRI) output, during hyperglycemia induced by intravenous glucose (0.1 g/kg). The kinetics of this glucose effect on IRG showed characteristics opposite to those of nerve stimulation: the lower the control output, the less the decrement. Furthermore, during the control steady state, blood glucose concentration was tightly correlated with the IRI/IRG molar output ratio, the function relating the two parameters being markedly nonlinear. Injection or primed infusion of glucose diminished the IRG response to simultaneous nerve stimulation. Measurement of IRG was inferred to reflect response of pancreatic glucagon secretion on the basis of the site of sample collection (the superior pancreaticoduodenal vein), the absence of changes in arterial IRG, and similar responses being obtained using an antibody specific for pancreatic glucagon. THESE STUDIES SUPPORT A ROLE FOR THE AUTONOMIC NERVOUS SYSTEM IN THE CONTROL OF GLUCAGON SECRETION: direct nerve stimulation induces glucagon release. Such sympathetic activation may be interpreted as capable of shifting the sensitivity of the A cell to glucose in the direction of higher glycemia for a given glucagon output. The experimental model employed is valid for further studies of regulatory mechanisms of endocrine pancreatic function in vivo.

Potentiation of the thermogenic antiobesity effects of ephedrine by dietary methylxanthines: Adenosine antagonism or phosphodiesterase inhibition?

Current concepts about the mechanisms underlying the therapeutic effects of dietary methylxanthines (caffeine, theophylline, and theobromine) favor their actions as antagonists of adenosine receptors, and attribute their other possible modes of action, namely those associated with translocation of intracellular calcium, inhibition of phosphodiesterase enzyme (PDE) activity, or the release of catecholamines, to high (near-toxic) doses. From studies measuring the respiration rate of brown adipose tissue (BAT), evidence is provided here that at concentrations compatible with therapeutic doses, the ability of methylxanthines (25 to 50 mumol/L) to potentiate the thermogenic effect of the sympathomimetic drug, ephedrine (0.25 mumol/L), particularly under conditions of caloric restriction, involves a minor contribution of adenosine antagonism, but could mainly be explained by the inhibition of PDE activity. In view of current interest in the pharmacological stimulation of metabolic rate to assist the management of obesity with low-calorie regimens, the targeting of PDE activity is therefore a rational approach in the search for drugs that could potentiate sympathomimetic stimulation of metabolic rate.

Etude de la propagation de l'excitation dans le ventricule de rat au moyen de solutions hypertoniques

ZusammenfassungIn einer morphophysiologischen Untersuchung wird zum Mechanismus der Erregungsleitung, insbesondere der intercellulären Erregungsleitung, am rechten Ventrikel des Rattenherzens Stellung genommen. Wenn die Tonizität der physiologischen Standardlösung sowie in Ca++-armen oder Cl−-freien Lösungen erhöht wird, verändern sich die Strukturen am Discus intercalaris und das sarcoplasmatische Reticulum: dieses Phänomen wurde als Grundlage der Methode unserer Untersuchungen benutzt. Folgende Ergebnisse wurden erhalten:1.Am normalen Discus intercalaris sind drei Typen von Membrananlagerungen zu erkennen: a) interfibrilläre Regionen (zwei parallel gelagerte Plasmamembranen), b) Nexus oder „tight junctions“ (Verschmelzung der beiden Doppelmembranen in eine Tripelmembran) und c) Desmosomen (Haftstellen, wo die Myofibrillen in den Discus intercalaris einstrahlen).2.Eine Erhöhung der Tonizität der Standardlösung verlangsamt die Erregungsleitung, aber in Ca++-armen oder Cl−-freien Lösungen wird dieser Effekt unterdrückt.3.Unabhängig von der Art der Lösung wird durch die Hypertonie eine Erweiterung der interfibrillären Regionen am Discus intercalaris erzeugt.4.Bei Ca++-armen Lösungen (0,275 mM/l) findet man eine verminderte Haftfähigkeit an den Desmosomen, was bei Hypertonie außer der Erweiterung der interfibrillären Regionen zu einer Ablösung der Desmosomen führt. Die Nexus bleiben dabei jedoch erhalten; auch bei starkem Auseinandertreten der Zellen kann ein Nexus nicht in seine Membraneinheiten zerlegt werden, sondern er wird aus den aneinandergrenzenden Zellen herausgerissen und ist als erhaltene Struktur auf der gegenüberliegenden Zelle zu finden.5.Bei partieller Ablösung des Discus intercalaris in hypertonischen, Ca++-armen oder Cl−-freien Lösungen wird die Erregungsleitung nicht verlangsamt. Dabei scheint die Erhaltung des Nexus maßgebend zu sein.6.Zusätzlich wurde mit Diffusionstracern nachgewiesen, daß die interfibrillären Regionen des Discus intercalaris über die Tubuli des sarcoplasmatischen Reticulums mit dem Extracellulärraum in Verbindung stehen.7.Es wird angenommen, daß der Nexus Stelle eines niedrigen elektrischen Widerstandes darstellt.8.Der Mechanismus der Erregungsleitungsverlangsamung bei Übergang von der Standardlösung in Hypertonie wird in Zusammenhang mit der Erweiterung des sarcoplasmatischen Reticulums diskutiert.SummaryIn a combined morphophysiological investigation the spread of excitation, in particular the cell-to-cell transmission of excitation in the right ventricle of rat heart, was studied. Upon increasing the osmolality of the physiological standard solution as well as of a low-Ca++ or a Cl−-free medium, a gradual disruption of the intercalated disc can be obtained in association with a swelling of the sarcoplasmic reticulum. These changes provided the basis for our work. Our results were the following:1.A normal intercalated disc is comprised of three different structures: a) unspecialized interfibrillar regions, b) nexuses (i. e. tight junctions) where the two double membranes merge into a three-layered structure, and c) desmosomes fixation points at which the two parallel membranes show electron-dense areas on their inner surface.2.Increasing the tonicity of the medium produced a drop of the propagation velocity in standard solution, but little change in low-Ca++ and Cl-free media.3.Regardless of the composition of the solution the hypertonicity brought about a widening of the intermembrane cleft in the interfibrillar regions of the intercalated disc.4.In low-Ca++ media (0,275 mM/l) the cohesion of the desmosomes was weakened leading to their complete disruption in hypertonic media, in addition to the aforementioned widening of the intermembrane space. In contrast, the tight junctions were preserved. Even when the cells were strongly dissociated from one another, it remained impossible to tear the nexuses apart, but they could be torn off, so that one of the two neighboring cells concerned carried the whole structure, and the other showed a tear in its membrane.5.Even after partial disruption of the intercalated discs in hypertonic low-Ca++ or Cl−-free solution, the propagation velocity was not reduced. Of importance, in this connection, seems to be the preservation of the tight junctions.6.In addition, diffusion tracer studies showed that interfibrillar regions of the intercalated disc are in continuity with the extracellular space via the sarcotubular system.7.It is suggested that the tight junctions represent a low-resistance electrical pathway.8.The mechanism which accounts for the reduction in propagation velocity observed upon increasing the tonicity of the standard solution is discussed in connection with the swelling of the sarcotubular system.

Differential effects of high-fat diets varying in fatty acid composition on the efficiency of lean and fat tissue deposition during weight recovery after low food intake.

The energetics of body weight recovery after low food intake was examined in the rat during refeeding for 2 weeks with isocaloric amounts of high-fat (HF) diets providing 50% of energy as either lard, coconut oil, olive oil, safflower oil, menhaden fish oil, or a mixture of all these fat types. The results indicate that for both body fat and protein, the efficiency of deposition was dependent on the dietary fat type. The most striking differences were found (1) between diets rich in n-3 and n-6 polyunsaturated fatty acids (PUFA), with the diet high in fish oil resulting in a greater body fat deposition and lower protein gain than the diet high in safflower oil; and (2) between diets rich in long-chain (LCT) and medium-chain triglycerides (MCT), with the diet high in lard resulting in a greater gain in both body fat and protein than the diet high in coconut oil. Furthermore, the diet high in olive oil (a monounsaturated fat) and the mixed-fat diet (containing all fat types) were found to be similar to the fish oil diet in that the efficiency of fat deposition was greater (and that of protein gain lower) than with the diet high in safflower oil. Neither the efficiency of fat gain nor that of protein gain were found to correlate with fasting plasma insulin, the insulin to glucose ratio, or plasma lipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired metabolic response to nerve stimulation in brown adipose tissue of hypothyroid rats.

In brown adipose tissue of the rat, chemically or surgically induced hypothyroidism caused the following effects. A large decrease of the magnitude of the metabolic response to electrical nerve stimulation. The deactivation half-time of the response was reduced to 70% of the control value, with no change in catechol O-methyltransferase activity. Pre-incubation of tissues with norepinephrine, 10(-5) M, increased the response to subsequent nerve stimulation almost to that of the controls. The catecholamine analogue dose-response curves were shifted to the right. The shift was very pronounced for isoproterenol (K50 426 nM versus 2 nM), somewhat less marked for norepinephrine (7373 nM versus 194) and very slight for phenylephrine (2803 nM versus 1649); there was almost no change in Emax values. An increase of octanoate oxidative capacity. A decrease of the capacity of the stereoselective binding of (-)-[3H]dihydroalprenolol of the high-affinity (Kd 2.0 nM) sites to a fourth of the control value and an increase by a factor of 2.9 of the Kd of the low-affinity binding sites. This decrease of binding to the beta-receptors was not sufficient quantitatively to explain the decrease in the metabolic response, suggesting the existence of an additional defective reaction which could occur between the binding to the beta-receptors and the activation of the triglyceride lipase. These results show that the sharp decrease of the metabolic response of brown adipose tissue to nerve stimulation has multiple causes. The findings are discussed in the context of the drastic decrease of cold resistance in hypothyroid rats.

Dietary supplementation with fish oil enhances in vivo synthesis of tumor necrosis factor.

Studies reported here investigate the influence of dietary fat types on cytokine production in response to endotoxin (LPS) challenge. Tumor necrosis factor (TNF) serum levels were markedly higher (by 10-fold) in mice fed chronically a diet rich in fish oil rather than either a diet rich in corn or coconut oil or a low fat diet. This in vivo hyper-responsiveness in LPS-induced TNF production following fish oil consumption concorded with similar exaggerated in vitro TNF release from macrophages exposed to LPS. These data suggest that high consumption of fish oils, by virtue of their high content of omega-3 polyunsaturated fatty acids, can lead to an exaggerated production of mediators of inflammation with potentially adverse consequences on the outcome and severity of infectious diseases.

Untersuchungen zur Ultrastruktur des Rattenherz-Muskels mit Besonderer Bercksichtigung des Sarcoplasmatischen Retikulums

SummaryThe ultrastructure of the right ventricular heart muscle of the rat was examined with special attention directed at the sarcoplasmic reticulum. Besides the conventional methods of electron microscopical investigation, the application of ferritin as a tracer and serial sectioning of tissues gave the following results:1.The sarcoplasmic reticulum is composed of a system of transverse tubules (T-system), and of a system of longitudinal tubules (L-system).2.The T-system is composed of branching tubules which form an anastomic network connected with extracellular space. The cell membrane (inner sarcolemma) is in direct continuity with the membranes of the T-tubules. The basement membrane (outer sarcolemma) extends into the depth of the cell, following the invaginations of the cell membrane. Numerous T-tubules have a longitudinal course over short stretches.3.A communication may occasionally be demonstrated between the tubules of the T-system and tubules which appear to belong to the L-system. The limitations of the present methods of identification of tubules as belonging to the one or the other system are discussed.4.No classical triads (such as found in skeletal muscle) could be demonstrated at the points of contact between the T-system and the L-system. Instead, formations were demonstrated which were characterised by the absence of membrane thickenings of synaptic type. For such formations the name of triadoid system is suggested. Ferritin can diffuse into the lateral cisternae of the triadoid system.5.The T-system and the triadoid system put the mitochondria in close contact with the extracellular space.6.Tubules of the sarcoplasmic reticulum open into the intercalated discs; the ferritin granules can be demonstrated in the intercellular space inspite of closure by desmosomal complexes and nexus formations.7.Intermediate invaginations at the level of the M band were observed: they may conceivably be connected with the L-system.8.The structure of the sarcoplasmic reticulum in the subsarcolemmal regions was extensively discussed.9.The significance of the various components of the sarcoplasmic reticulum in the light of the physiologic properties of the heart muscle was discussed.ZusammenfassungDie Ultrastruktur des Rattenherzmuskels (rechter Ventrikel) wurde unter besonderer Berücksichtigung des sarcoplasmatischen Retikulums untersucht. Dabei konnten nach verschiedenen üblichen elektronenmikroskopischen Präparationsverfahren sowie durch Anwendung von Ferritin als Tracersubstanz und Interpretation von Serienschnitten folgende Befunde erhoben werden:1.Das sarcoplasmatische Retikulum besteht aus einem transversalen tubulären System (T-System) und einem longitudinalen tubulären System (L-System).2.Das T-System ist aus sich verzweigenden und anastomosierenden Kanälchen aufgebaut, die mit dem Extracellulärraum frei in Verbindung stehen. Die Zellmembran (inneres Sarcolemm) geht kontinuierlich in die Membran der T-Tubuli über. Die Basalmembran (äußeres Sarcolemm) setzt sich bis in die Tiefe der Zelle fort, indem sie den Einstülpungen der Zellmembran folgt. Manche T-Tubuli können über kurze Strecken einen longitudinalen Verlauf einschlagen.3.Es wurden Befunde gewonnen, aus denen hervorgeht, daß Teile des L-Systems zum T-System hin geöffnet sein könnten, wobei die Frage diskutiert wird, inwieweit in bestimmten Fällen mit den angewandten Methoden überhaupt eine sichere Unterscheidung von T- und L-System möglich ist.4.An den Kontaktstellen zwischen T- und L-System werden keine charakteristischen Triaden gefunden: für triadenähnliche Formationen wird der Name „Triadoid” vorgeschlagen. Triadoide unterscheiden sich von den echten Triaden der Skeletmuskulatur, da sich keine synapsenartigen Membranverdichtungen an den Kontaktstellen befinden. In die lateralen Cisternen der Triadoide kann Ferritin diffundieren.5.Die Mitochondrien stehen über das T-System und die Triadoide in enger Beziehung zum Extracellulärraum.6.An den Disci intercalares münden Tubuli des sarcoplasmatischen Retikulums, so daß Ferritin trotz der Abdichtung des Intercellulärspaltes durch Desmosomen und Nexusstrukturen in diesen gelangen kann.7.Es wurden intermediäre Invaginationen auf der Höhe der M-Streifen beobachtet, die möglicherweise mit dem L-System eine Beziehung haben.8.Über den Aufbau des sarcoplasmatischen Retikulums in den subsarcolemmalen Zonen wird ausführlich berichtet.9.Weiterhin wird erörtert, welche Bedeutung die verschiedenen Strukturelemente des sarcoplasmatischen Retikulums für die physiologischen Eigenschaften des Herzmuskels haben.Die Ultrastruktur des Rattenherzmuskels (rechter Ventrikel) wurde unter besonderer Berucksichtigung des sarcoplasmatischen Retikulums untersucht. Dabei konnten nach verschiedenen ublichen elektronenmikroskopischen Praparationsverfahren sowie durch Anwendung von Ferritin als Tracersubstanz und Interpretation von Serienschnitten folgende Befunde erhoben werden: 1. Das sarcoplasmatische Retikulum besteht aus einem transversalen tubularen System (T-System) und einem longitudinalen tubularen System (L-System). 2. Das T-System ist aus sich verzweigenden und anastomosierenden Kanalchen aufgebaut, die mit dem Extracellularraum frei in Verbindung stehen. Die Zellmembran (inneres Sarcolemm) geht kontinuierlich in die Membran der T-Tubuli uber. Die Basalmembran (auseres Sarcolemm) setzt sich bis in die Tiefe der Zelle fort, indem sie den Einstulpungen der Zellmembran folgt. Manche T-Tubuli konnen uber kurze Strecken einen longitudinalen Verlauf einschlagen. 3. Es wurden Befunde gewonnen, aus denen hervorgeht, das Teile des L-Systems zum T-System hin geoffnet sein konnten, wobei die Frage diskutiert wird, inwieweit in bestimmten Fallen mit den angewandten Methoden uberhaupt eine sichere Unterscheidung von T- und L-System moglich ist. 4. An den Kontaktstellen zwischen T- und L-System werden keine charakteristischen Triaden gefunden: fur triadenahnliche Formationen wird der Name „Triadoid” vorgeschlagen. Triadoide unterscheiden sich von den echten Triaden der Skeletmuskulatur, da sich keine synapsenartigen Membranverdichtungen an den Kontaktstellen befinden. In die lateralen Cisternen der Triadoide kann Ferritin diffundieren. 5. Die Mitochondrien stehen uber das T-System und die Triadoide in enger Beziehung zum Extracellularraum. 6. An den Disci intercalares munden Tubuli des sarcoplasmatischen Retikulums, so das Ferritin trotz der Abdichtung des Intercellularspaltes durch Desmosomen und Nexusstrukturen in diesen gelangen kann. 7. Es wurden intermediare Invaginationen auf der Hohe der M-Streifen beobachtet, die moglicherweise mit dem L-System eine Beziehung haben. 8. Uber den Aufbau des sarcoplasmatischen Retikulums in den subsarcolemmalen Zonen wird ausfuhrlich berichtet. 9. Weiterhin wird erortert, welche Bedeutung die verschiedenen Strukturelemente des sarcoplasmatischen Retikulums fur die physiologischen Eigenschaften des Herzmuskels haben.

Hyperthermia induced by pre-pontine knife-cut: Evidence for a tonic inhibition of non-shivering thermogenesis in anaesthetized rat

Temperature of colon, interscapular brown adipose tissue (IBAT) and paw skin (index of vasomotor activity) were monitored before and after microwire knife lesions at the pre-pontine or/and the post-mammillary levels in the urethane-anaesthetized rats at room temperature of 23-24 degrees C. Following the pre-pontine, but not the post-mammillary cut, colonic and IBAT temperatures increased by 3-4 degrees C within 90-240 min. IBAT temperature rose faster with a shorter latency and attained a higher steady-state value than colonic temperature; skin temperature, however rose by only 0.8 degrees C. A procaine microinjection into the pre-pontine area transiently increased by more than 1 degree C both colonic and IBAT temperatures, with similar kinetics as for the knife cut. Cardiac output distribution was measured using radiolabelled microspheres. Brown adipose tissue (BAT) was found to be the only organ to which the fractional blood flow increased dramatically (12 times over baseline value) during the development of hyperthermia. Propanolol, injected after the hyperthermia had fully developed, decreased IBAT and then colonic temperatures. Hexamethonium decreased both colonic and IBAT temperatures with a concomitant rise in skin temperature while tubocurarine was without effect. It is concluded that the hyperthermia observed after the pre-pontine lesion results from an increased sympathetic stimulation of BAT thermogenesis triggered by the release of a tonic inhibitory control on its heat production. Such an inhibitory system would be located somewhere between the lower midbrain and the upper pons.