Showing papers by "Université de Montréal published in 1968"

Relationship between Sodium Intake and Norepinephrine Storage during the Development of Experimental Hypertension

Abstract: It has been reported that storage of norepinephrine by the sympathetic nervous system was decreased in rats made hypertensive by the administration of desoxycorticosterone trimethylacetate (DOCA) and sodium chloride. The present investigation indicated that the storage of norepinephrine was impaired at an early stage of treatment with DOCA and NaCl (1 week), and preceded the appearance of hypertension. The role of sodium and sympathetic activity, the two major factors suspected of contributing to the development of the abnormality in storage of norepinephrine, was studied in normotensive and hypertensive rats. The withdrawal of sodium from the diet of hypertensive rats for 2 weeks lowered the blood pressure to normotensive levels and simultaneously restored to normal the storage and binding capacity as well as the endogenous norepinephrine content of the sympathetic storage granules in the heart. Sodium restriction or depletion in normotensive rats caused a slight decrease in blood pressure and the retention of norepinephrine in the storage granules was increased. These findings suggested that the capacity of the sympathetic granules to bind and store norepinephrine was influenced by the state of sodium balance and showed that the capacity of storage could be correlated with the level of blood pressure. The finding that treatment with a long-acting ganglionic blocker could restore the blood pressure and the norepinephrine storage capacity in hypertensive animals to normal suggested a neurogenic component in the development of this form of hypertension.

Aspirin: Dissolution Rates of Two Polymorphic Forms

Abstract: Two polymorphic forms of aspirin were characterized; the rates of dissolution of single crystals and of tablets were studied. One forms dissolves 50 percent faster than the other.

A possible enzyme barrier for gamma-aminobutyric acid in the central nervous system.

Abstract: Publisher Summary High concentrations of y-amino butyric acid (GABA) in blood did not result in an elevation of brain GABA levels A barrier exists which restricts the passage of GABA from blood to nervous tissue But recent histochemical studies on the distribution of GABA-a-keto-glutarate transaminase in the mammalian central nervous system suggested that the barrier may be in part a reflection of high GABA-transaminase activity in the walls of cerebral blood vessels and in the cells lining the cerebrospinal fluid spaces To explore this suggestion further, the paper has a study that was conducted on the distribution of GABA-transaminase in kidney and liver GABA appears to pass freely from blood to kidney, since as much as fifty per cent of the total GABA injected can be recovered from urine Similarly, the concentration of GABA in liver after injection parallels that of the blood The paper consists of the histochemical procedures for the localization of GABA-transaminase The method is based on the fact that, in the course of the metabolism of GABA to succinic acid, NADH is formed, which in turn reduces a tetrazolium salt (Nitro BT) to its formazan form Formazan is insoluble and will precipitate out at sites in the tissue where the combined presences of GABA-a-keto glutarate transaminase and succinic semialdehyde dehydrogenase have caused the conversion of GABA to succinic acid When sections of mammalian brain are incubated with a transaminase medium, strong formazan precipitation occurs at sites where GABA-transaminase and succinic semialdehyde dehydrogenase are present in combination Although the presence of both enzymes is a prerequisite for the reaction, recent studies suggested that the transamination step is rate limiting with respect to the histochemical demonstration of GABA metabolism As a conclusion, the paper states that the ependymal cell layer which lines the cerebrospinal fluid spaces is among the sites in the central nervous system which exhibit strong GABA-transaminase activity The paper also has a brief on the specificity of the histochemical reaction for GABA In order to determine the specificity of the histochemical reaction for GABA transaminase in kidney, hydrazinopropionic acid (1 5 mg/kg) was injected into a mouse and its kidney was sectioned two hours later Such sections, when incubated in the transaminase medium, were identical in appearance to normal sections which had been incubated in a control medium lacking GABA

Increased Monoamine Oxidase Activity during the Development of Cardiac Hypertrophy in the Rat

Abstract: In rats, the increase in heart mass during normal growth is accompanied by a marked increase in the concentration of monamine oxidase (MAO). Similarly, cardiac hypertrophy resulting from experimental hypertension (induced either by desoxycorticosterone acetate (DOCA) and sodium or by renal artery stenosis) is also associated with a pronounced increase in MAO concentration. Conversely, the delayed growth of the heart occurring during sodium restriction is accompanied by a lower MAO activity. These changes in MAO, independent of the cause, appear closely related to the mass of the heart. However, the reduction in norepinephrine storage observed in the heart and other tissues of rats made hypertensive with DOCA and sodium cannot be explained by the changes in the concentration of MAO. The MAO activity of other tissues of the hypertensive rats is similar to that in the tissues of normal rats, with the exception of the kidney in which the MAO concentration is reduced. The subcellular distribution of MAO is sim...

The nature of the PR interval.

Abstract: Selective perfusion of the sinus and A-V nodes in dogs and simulation experiments with a system of two interacting relaxation oscillators were used to study the nature of the PR interval. The PR interval duration appears to be composed of a relatively fixed conduction delay, and of a labile portion determined by the local excitability of the A-V node region.

Renal excretion of hydrogen in primary gout.

Abstract: Acidification of the urine and urinary excretion of hydrogen was studied in ten gouty subjects (age 24–56, mean 38) with normal renal function. In three gouty patients on low purine intake, urinary pH and net acid excretion were not different from that found in normal controls. Furthermore, the response to ammonium chloride load was similar in both groups. In contrast, gouty patients on high purine intake showed permanent aciduria with lowered ammonium excretion and a diminished response to ammonium chloride load. In the four gouty subjects given ammonium chloride during high purine intake, mean urinary uric acid excretion decreased by 300 mg. day while serum urate did not change. This decrement was closely related to the progressive increase in urinary ammonium. Three gouty subjects given equivalent amount of dilute hydrochloric acid failed to show a similar response. The present study indicates that protein and purine intake may influence urinary acidification in primary gout. The data further suggest a possible relationship between ammonia and uric acid production during high purine intake and ammonium chloride load.

The effect of starvation in the normal dog including the Dalmatian coach hound

Abstract: Metabolic balance studies were undertaken during a 12-day fasting period in 6 mongrel and 4 Dalmatian dogs. No evidence of ketosis could be demonstrated during this period. Plasma bicarbonate concentration remained normal. Mean urinary ammonia and titratable acid fell markedly so that net acid excretion dropped from 59 to 23 mEq./day. Mean total urinary nitrogen excretion decreased from 7.2 to 3.3 Gm./day during starvation. A modest rise in urinary pH (0.18 unit) was observed during fasting. No change in urinary or plasma uric acid values could be demonstrated in either mongrel or Dalmatian dogs. Serum phospholipids, cholesterol and triglycerides were not modified during starvation while nonesterified fatty acids rose from 740 to 1000 μEq./L. These data contrast markedly with those observed in human subjects who develop ketosis, increased urinary ammonia and decreased uric acid excretion during fasting. Canine resistance to ketosis during starvation could be related to more efficient utilization of mobilized lipids.

Action spectrum and quantal thresholds of retinomotor responses in the brook trout, Salvelinus fontinalis (Mitchill)

Abstract: The radiant energy per unit area required to trigger retinomotor responses was determined for eight wavelengths. The curve's maximum at 520 nanometres corresponds to two microwatts per steradian per square metre. The threshold requires the absorption of 7000 quanta per second per square degree of the field by the scotopic pigment.