[Electrolyte secretion in saliva]. / A secreção eletrolítica da saliva.

Because they are easily accessible and because their secretion can be obtained in an almost pure form, the salivary glands are an adequate model for the study of hydroelectrolytic secretion of secreting epithelia which cannot generate an action potential. It is generally accepted that the salivary secretion occurs in two stages: in the acini, where primary saliva is formed similar in ionic constituents to plasmatic water, and in the ducts of the adenomer, where such original saliva is modified by absorption and secretion of electrolytes. Departing from Thaysen's hypothesis, the mechanisms responsible for the preparation of final saliva are reviewed. The authors briefly discuss the evolution of the ideas about salivary secretion emphasizing recent works which modified early theories, particularly the role of the Na-K ATPase and the cotransportation of the Cl- ion. Ideas about what occurs along the ducts are also reviewed, starting with the hypothesis of Brusilow and Cook, which was later on gradually modified. Recent works are compared to those of the authors. Certain topics, such as the impermeability of duct walls to water, existence of a threshold for the transport of Na+, possibility of experimentally obtaining saliva with higher osmotic pressure than plasma are stressed. Finally, the role of loop diuretics which interfere in potassium transport channels is discussed.

Masseteric electromyographic silent period duration in patients with temporomandibular joint dysfunction

The present study compared the duration of the electromyographic silent period (SP) of the masseter muscles elicited by chin-tapping in normal asymptomatic adults (N=39) and in a group with sympstoms of temporomandibular joint dysfunction (TMJD)(N=3).EMG activity was recorded from right (RM) and left (LM) masseter muscles using bipolar surface electrodes coupled to a DISA 1500 EMG-system.During maximal clenching, ten taps were applied downwards to the chin with a reflex hammer. The mean SP durations obtained for the normal group were 25.45ñ4.20 ms (RM) and 25.33ñ4.18ms (LM), whereas the TMJD group presented significantly greater values (P<0.01,Student t-test) of 41.89ñ12.94ms (RM) and 42.40ñ12.99ms (LM).The upper limits of normality calculated for RM and LM were 32.36 ms and 31.21 ms, respectively. Eighty-four percent of patients with TMJD showed SP durations above these limits. The results indicate that the measurement of masseteric SP duration may be used as an objective diagnostic method of TMJ disorders, provided that borderline values are interpreted with caution along with clinical impressions

Masseteric electromyographic silent period duration in patients with temporomandibular joint dysfunction.

1. The present study compared the duration of the electromyographic silent period (SP) of the masseter muscles elicited by chin-tapping in normal asymptomatic adults (N = 39) and in a group with symptoms of temporomandibular joint dysfunction (TMJD) (N = 31). 2. EMG activity was recorded from right (RM) and left (LM) masseter muscles using bipolar surface electrodes coupled to a DISA 1500 EMG-System. During maximal clenching, ten taps were applied downwards to the chin with a reflex hammer. 3. The mean SP durations obtained for the normal group were 25.45 +/- 4.20 ms (RM) and 25.33 +/- 4.18 ms (LM), whereas the TMJD group presented significantly greater values (P less than 0.01, Student t-test) of 41.89 +/- 12.94 ms (RM) and 42.40 +/- 12.99 ms (LM). The upper limits of normality calculated for RM and LM were 32.36 ms and 31.21 ms, respectively. Eighty-four percent of patients with TMJD showed SP durations above these limits. 4. The results indicate that the measurement of masseteric SP duration may be used as an objective diagnostic method of TMJ disorders, provided that borderline values are interpreted with caution along with clinical impressions.

[Role of the atria in controlling body fluids]. / Papel dos átrios no controle dos fluidos corpóreos.

The atria play a major role in the regulation of body fluids. Since the work of Henry and col., techniques of atrial distention have shown the existence of volume receptors which perceive the fulness of blood volume, the left atrium in particular. When blood volume increases, receptors originate a neuro-humoral reflex in which the afferent path would be the vagus nerve, the hypotalamus would be the center, and the efferent path would be the inhibition of the hypophysis ADH secretion, provoking a decreased water reabsorption and, consequently, diuresis. This mechanism would have precedence over the osmotic regulation. Added to the investigations of the authors, these experiments also point to an increased sodium excretion, for which release of a natriuretic factor in a non-determined site was claimed as responsible. In 1981, de Bold and col. reported a hormone produced in atrial cardiocites (ANF) that would be released upon stretching of the atrium and that would act upon the nephron through different mechanisms to cause deep diuresis and natriuresis. This publication gave origin to numerous investigations. The formula of the responsible peptide was determined. The hormone was sinthesized and the pharmaceutical industry launched many synthetic products. The physiologic and physiopathologic implications of this discovery and the therapeutic potential of these synthetic derivatives are discussed.

Atrial volume receptors. Demonstration of an effective "threshold" of left atrial distension by an inflated balloon to induce increased diuresis in the anesthetized dog.

1. The intraatrial balloon technique was used to study the effect of distension of the left atrium on the urinary flow of anesthetized dogs. The balloon was inflated with 0.3, 0.4 or 0.5 ml saline/kg body weight, respectively, in three experimental groups, each containing 10 mongrel dogs. Intraatrial pressure, arterial blood pressure, ECG and respiratory excursions were continuously monitored in all experiments. Urine flow, inulin and p-aminohippuric acid clearance, urine osmolarity, total sodium and total potassium excretion were measured during the control period, after inflation of the balloon and 30 min after deflation. 2. Left atrial distension with 0.3 ml/kg caused essentially no increase in diuresis. Inflation with 0.4 ml/kg induced a 60% increase of mean urinary flow with respect to the control period. Inflation with 0.5 ml/kg elicited a mean increase in diuresis of 110%. 3. When it occurred, increased diuresis was accompanied by a decrease of urine osmolarity that was compatible with a decrease of antidiuretic hormone activity, and by an increase in total sodium excretion. There were no statistically significant changes in glomerular filtration rate and effective renal plasma flow. 4. The demonstration of a "threshold" for the distension of the left atrium that is capable of inducing diuresis in the anesthetized dog and of overcoming strong opposing hemodynamic effects provides additional indirect evidence for the role of the left atrial stretch receptors in the regulation of body fluid volume.

Atrial volume receptors: demostration of an effective threshold of left atrial distension by an inflated balloon to induced increased diuresis in the anesthetized dog

1. The intraatrial balloon technique was used to study the effect of distension of the left atrium on the urinary flow of anesthetized dogs. The ballon was inflated with 0.3, 0.4 or 0.5 ml saline/Kg weight, respectively, in three experimental groups, each containing 10 mongrel dogs. Intraatrial presssure, arterial blood pressure, ECG and respiratory excursions were continuously monitored in all experiments. Urine flow, inulin and p-aminohippuric acid clearance, urine osmolarity, total sodium and potassium excretion were measured during the control period, after inflation of the ballon and 30 min after deflation. 2. Left atrial distension with 0.3 ml/Kg caused essentially no increase in diuresis. Inflation with 0.4 ml/Kg induced a 60% increase of mean urinary flow with respect to the control period. Inflation with 0.5 ml/Kg elicited a meanincrease in diuresis of 110%. 3. When it occurred, increased ddiuresis was accompanied by a decrease of urine osmolarity that was compatible with a decrease of antidiuretic hormone activity, and by increase in total sodium excretion. there were no statistically significant changes in glomerular filtration rate and effective renal plasma flow. 4. The demonstration of a "threshold" for the distension of the atrium that is capable of inducing diuresis in the anesthetized dog aand of overcoming strong opposing hemodynamic effects provides additional indirect evidence for the role of the left atrial stretch receptors in the regulation of body fluid volume

[Sodium transport and potassium excretion by the salivary ducts of the dog's submandibular gland (author's transl)]. / Transporte de sódio e excreção de potássio pelos ductos salivares da glândula submandibular do cão.

In order to study the possibility of the existence of a threshold for the transport capacity for sodium by the salivary ducts of the dog's submandibular gland 10 mongrel dogs were rendered hypernatremic by the intravenous infusion of a hypertonic sodium solution. The main excretory duct was canulated and the vegetative branch of the chorda tympani nerve was maximally excited for 20-minute periods intercalated by similar periods of rest. A threshold for sodium transport was observed, dependent on the amount of sodium offered to the salivary ducts and on the salivary flow. This threshold is around 75 uEq/min with a flow of saliva of 1.3 ml per minute. The excretion of potassium in these experiments did not show a trend to reach a threshold.

[Role of the atrial stretch receptors in the regulation of the fluids of the anesthetized dog (author's transl)]. / Papel dos receptores de distensão atriais na regulação do volume dos fluidos do cão anestesiado.

The role of the atrial stretch receptors in the regulation of the body fluids was investigated in the anesthetized dog. Two groups of 15 animals each were used. In the first group the distention was performed by the inflation with saline solution of a balloon previously introduced in the left atrium. In the second group the right atrium was distended. In the experiments with the left atrium diuresis was induced in all animals. In the right atrium only in 5 dogs the distention resulted in diuresis, in the remaining 10 animals there was, on the contrary, antidiuresis. In the experiments with diuresis, this was accompanied by a urine with a lower osmolarity than in the control period and a greater sodium excretion. Being more pronounced the hemodynamic changes in the animals in which the right atrium was distended, one could not in this experimental set-up conclude that the right atrium plays a role similar to the one of the left atrium in regulating the body fluids in the anesthetized animal.