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M Peaker

Publications and source records attributed to M Peaker.

At least 127 records · Page 7Linked to original sources
PubMed1972

Nature and location of the receptors for salt-gland secretion in the goose.

1. The nature and location of the receptors which stimulate salt-gland secretion in the goose have been investigated.2. The rapid injection of homologous blood (sufficient to raise the blood volume by 16 and 9%) into the right atrium failed to induce secretion. In contrast, hypertonic sucrose, Na(2)SO(4) and LiCl initiated secretion.3. These results support the theory that osmoreceptors initiate secretion by detecting an increase in plasma tonicity.4. The minimal amount of hypertonic NaCl required to initiate secretion when infusions were made into a carotid artery or into various arteries and veins in the splanchnic region was not less than that required by an I.V. route.5. Cross-circulation and perfusion studies also showed that a raised [NaCl] in the blood perfusing the head was ineffective in evoking secretion and thus that plasma tonicity must be raised elsewhere in the body.6. Secretion in response to salt-loading was abolished or prevented by cutting the vagus nerves or blocking them with local anaesthetic. Stimulation of the cephalic end of the cut vagi in an isolated, perfused decerebrate head induced secretion, indicating that the afferent fibres from the receptors to the C.N.S. lie in the vagus nerves. Cutting the vagi below the heart, however, had no effect on the secretory response.7. Blocking nerves in the crop with local anaesthetic had no effect on secretion induced by salt-loading but when local anaesthetic was injected into the pericardial sac, secretion decreased immediately, stopped, and recovered with a time course similar to that seen after blocking the vagus nerves.8. Section of the vagi in the neck abolished the tachycardia observed in response to the injection of hypertonic NaCl into the right atrium.9. As in other species, stimulation of the ;secretory nerve' induced secretion in anaesthetized or decerebrate geese.10. Hexamethonium given I.V. or applied topically to the ;secretory nerve ganglion' blocked secretion in response to salt-loading or to secretory nerve stimulation.11. It appears that the receptors for salt-gland secretion are located in or near the heart and that afferent fibres from these receptors travel in the vagus nerves to the C.N.S.12. A possible scheme of the secretory reflex which initiates and maintains salt-gland activity is proposed.

Anesthesia, Local↗
PubMed1971

Salt-gland secretion and blood flow in the goose.

1. Salt-gland blood flow in the domestic goose has been measured using a combination of Sapirstein's indicator fractionation technique for organ blood flow and Fegler's thermodilution method for cardiac output.2. Nasal salt secretion was induced by giving 0.5 M-NaCl or 0.154 M-NaCl I.V. or by giving artificial sea water by stomach tube into the proventriculus.3. During secretion, salt-gland blood flow increased from 82.7 +/- 21.9 ml./100 g tissue. min to as high as 2179 ml./100 g. min (mean 1209 +/- 140).4. The rate of secretion in response to salt loading was very variable and was not correlated with the rate of blood flow.5. From the data obtained, it could be calculated that the median values for the percentage extraction of ions from the arterial plasma were Na 15%, K 35%, Cl 21% and water 5.8%.6. Atropine abolished secretion but not the increase in blood flow produced by salt loading.7. Unilateral complete denervation abolished secretion from and the increase in blood flow through the operated but not the control gland.8. Anaesthesia, induced by pentobarbitone sodium, almost completely blocked secretion and the increase in blood flow in the salt-gland in response to salt loading.9. In geese given 0.5 or 0.154 M-NaCl I.V. a positive, significant correlation was found between the total amount of nasal secretion collected over 30 min and the concentrations of Na and Cl in the nasal fluid. However, when the time course of secretion was followed in any one bird, the rate of secretion was inversely related to the concentrations of Na and Cl.10. Harderian gland blood flow was not affected by salt loading.

Animals↗
PubMed1971

Cardiovascular responses to salt-loading in conscious domestic geese.

1. The intravenous injection of large volumes of 0.5 M-NaCl that are usually used to induce nasal gland secretion in marine birds has been shown in geese to increase greatly plasma volume, cardiac output, heart rate and stroke volume at the time secretion commences after 2-8 min.2. There were no consistent changes in mean arterial blood pressure or in the distribution of the cardiac output to major organs except to the salt-glands whose share increased approximately fourteenfold. Salt-gland blood flow remained high for 10-20 min after cardiac output and heart rate had returned to nearly normal levels.3. The increases in plasma volume and venous return are unlikely to be the stimuli for salt-gland secretion because secretion was also initiated by giving artificial sea water into the proventriculus and this produced no changes in these variables at the time secretion commenced, 5-14 min later.4. At the start of secretion in orally loaded birds, the only detectable changes in the plasma were small increases in osmolality (from 1.3 to 4.6%), Na (from 0.3 to 6%) and Cl (from 1.3 to 7.1%) concentrations.

Animals↗
PubMed1971

Intracellular concentrations of sodium, potassium and chloride in the salt-gland of the domestic goose and their relation to the secretory mechanism.

1. The composition of the nasal salt-glands of geese was found to be Na 57 +/- 3.5 (S.E.), K 52.3 +/- 3.9 and Cl 78.3 +/- 11.0 m-equiv/kg fresh tissue. During secretion, the Na content was significantly raised to 72.4 +/- 3.4 m-equiv/kg.2. Salt-gland slices incubated in Krebs-Henseleit bicarbonate medium plus glucose (6 mM), in the presence of [(14)C]sucrose as an extracellular marker had the following composition, Na 85.3 +/- 3.1, K 37.1 +/- 3.1 and Cl 74.3 +/- 3.6 m-equiv/kg. The calculated intracellular concentrations were for Na 61.5 +/- 2.1, K 105.3 +/- 8.7 and Cl 37.8 +/- 5.0 m-equiv/l. intracellular water.3. Ouabain (10(-4)M) significantly decreased the tissue and cell K concentration and significantly increased the Na concentration.4. Acetylcholine (10(-6)M) and eserine (10(-4)M) in the incubation medium had no effect on intracellular composition.5. Raising the Na concentration of the medium to 172 m-equiv/l. and the Cl to 156 m-equiv/l. in two experiments had no effect on the calculated intracellular composition.6. These results do not support reports that the cells have a very high Na concentration (about 350 m-equiv/l. intracellular water). They are compatible with the hypothesis that the hypertonic secretion is formed across the luminal membrane of the secretory cell by an active Na(+) pump and there are no data to suggest that Na(+) is concentrated across the basal membrane by a ouabain-insensitive process.7. The data are discussed in relation to permeability studies and to electrical potential measurements within the gland by other workers.

Acetylcholine↗
PubMed1971

Intracellular concentrations of sodium, potassium and chloride in the lactating mammary gland and their relation to the secretory mechanism.

1. The intracellular (I.C.) concentrations of Na, K and Cl in mammary cells from lactating guinea-pigs have been calculated from the analysis of fresh tissue and the measurement of the extracellular (E.C.) space with [(14)C]sucrose and the milk content with [(14)C]lactose.2. Assuming that alveolar milk has the same concentration as teat milk, the intracellular concentrations were calculated to be K 115, Na 42 and Cl 66 m-equiv. l(-1) intracellular water.3. Intracellular concentrations were also calculated in slices incubated in Krebs-bicarbonate medium plus glucose. There was a large increase in the sucrose (E.C.) space and a rise in total tissue [Na] and [Cl]. On the assumption that the medium had equilibrated with the milk space as well as the E.C. space, the calculated I.C. concentrations of Na (43 m-equiv. l(-1)), and Cl (62) were very similar while [K] was somewhat higher (143 m-equiv. l(-1)I.C. water).4. The calculated I.C. concentrations of all three ions are all higher than in milk but the ratios between them are almost identical.5. Similar figures for the I.C. concentrations of Na, K and Cl have been obtained in the goat, cow and sheep mammary tissue incubated in vitro.6. Moderate changes in the concentrations of Na, K and Cl in the external medium had no effect on cell composition but during incubation without ions [(14)C]sucrose became distributed throughout the total tissue water indicating that sucrose had entered the I.C. compartment.7. Acetazolamide (10(-2)M), aldosterone (1.4 x 10(-6)M) and, in some experiments, lack of glucose lowered I.C. [Cl(-)], but oxytocin, vasopressin and low doses of insulin had no effect.8. The data are difficult to reconcile with the hypothesis of Zaks, Natochin, Sokolova, Tanasiichuk & Tverskoi (1965) that freshly secreted milk has the ionic composition of plasma.9. Comparison of I.C. ion concentrations and the membrane potential between the cells and milk suggests that Na(+) and K(+) are passively distributed across the apical membrane but that Cl(-) must be actively held in the cells. Across the basal membrane the data are consistent with the presence of a Na(+) pump and with Kinura's (1969) detection of a Na:K ATPase on the basal and lateral membranes. In addition another inward-facing Cl(-) pump may exist at this site.

Acetazolamide↗
PubMed1971

The permeability of mammary ducts.

1. The permeability of the teat mucosa of the goat has been studied in vitro and, as an isolated teat pouch, in vivo. In vivo the mucosa was found to be impermeable to radioactive Na, K, Cl and Rb isotopes and to labelled lactose, but permeable to (3)HOH, and to a lesser extent, urea.2. The permeability of the intramammary ducts has been assessed by comparison of the rates of passage from the blood of ions and urea relative to (3)HOH into various fractions of milk in different parts of the gland.3. Negligible quantities of ions were detected in the milk present in large ducts after an I.V. infusion or during a close arterial infusion to keep the venous blood concentrations constant. However, after approximately 25 min, milk in the alveoli had fully equilibrated with (3)HOH, and (24)Na(+) and was almost fully equilibrated with urea but not with (42)K(+) and (36)Cl(-).4. The quantity of milk in a fraction of milk was directly related to the amount of (3)HOH present in that fraction but not to the amounts of the other indicators (urea, labelled Na, K, Rb and Cl). Comparison of the concentration of these substances with (3)HOH in different milk fractions indicates that the mammary ducts are probably impermeable to ions and only slightly permeable to urea.5. The injection of [(14)C]lactose into the teat showed that after 10 and 20 min, 7 and 14% respectively of the radioactivity had reached the residual (alveolar) milk. Thus diffusion within the milk in the ducts could account for the small quantities of labelled ions found in milk within the ducts following intravascular injection.6. It is concluded that the large and medium-sized ducts in the mammary gland are impermeable to lactose and to the monovalent ions studied.7. In non-lactating animals, the ducts are more permeable to Na(+) and Cl(-) than in the lactating animals.8. The relative rates of passage of ions into residual (alveolar) milk was Na > Cl > K.

Animals↗
PubMed1971

The effects of oxytocin and milk removal on milk secretion in the goat.

1. When goats were milked each hour after being given a dose of synthetic oxytocin within the range thought to be released by the pituitary, there was a progressive rise in milk yield becoming statistically significant by 5 hr. The effect was reduced if the milk was not removed from the gland each hour.2. Milking transplanted glands each hour without injecting oxytocin also increased milk yield. The yield of the unmilked glands on the same animals was not affected. Massaging the transplanted glands had no effect on the milk yield.3. Oxytocin treatment and, to a lesser extent, frequent milking without oxytocin, altered milk composition. [Na], [Cl] and [non-casein protein] increased; [K] and [lactose] decreased.4. Oxytocin infusions permitted the leakage of [(14)C]lactose from milk to plasma and [(14)C]sucrose from plasma to milk.5. In some goats very small doses of oxytocin caused changes in milk composition and in one such animal these changes were mimicked by the close arterial infusion of bradykinin.6. Reasons are given for believing that the changes in composition are incidental to the main action of oxytocin in expelling milk and could be caused by a small number of leaks between the tight junctions connecting secretory cells.7. The increase in the rate of milk secretion following milk removal is probably of greater physiological significance than the small changes in milk composition and supports Levy's idea of a local negative feed-back via a chemical component of milk.

Animals↗