bluuebunny/crossref_metadata_2025 huggingface dataset:
FAT METABOLISM IN ELDERLY PATIENTS WITH SEVERE HYPOTHERMIA
Authors: Stoner H. B. , Little R. A. , Frayn K. N.
Published: December 2014

Elderly patients with accidental hypothermia (core temperatures 25·0–35·5 °C) have been studied to determine the effect of low temperature on energy metabolism. The respiratory exchange ratios were low (median 0·75). Concentrations of plasma glycerol, non‐esterified fatty acids and ketone bodies were high, and, except in the case of glycerol, rose with the duration of the hypothermia. Plasma glucose concentrations were often high but extremely variable. Arteriovenous differences across the forearm showed net release of glycerol and extraction of ketone bodies. Despite the hypothermia the mean extraction ratios for acetoacetate and 3‐hydroxybutyrate were very similar to published values in normal, fasting, euthermic subjects. It was concluded that, in agreement with other work showing inhibition of glucose utilization at low temperature, fat is the main fuel used at very low body temperatures.
THYROID HORMONE METABOLISM AFTER ACCLIMATIZATION TO A WARM OR COLD TEMPERATURE UNDER CONDITIONS OF HIGH OR LOW ENERGY INTAKE
Authors: Macari M. , Dauncey M. J. , Ingram D. L. , Ramsden D. B.
Published: December 2014

The separate effects of ambient temperature and energy intake on the metabolism of thyroid hormones in the young pig have been investigated. Piglets were kept singly from 4 weeks of age at 10 or 35 °C on a high (H), or low (L) energy intake, such that H = 2L. At the tenth week of age blood samples were taken 16–21 h after the last meal for the determination of plasma concentrations of thyroxine (T4) and 3,5,3‐triiodothyronine (T3). At the end of the tenth week of age the fractional disappearance rate (K) of T4 was determined and finally the K value for T3 was estimated.

Plasma concentrations of T4 and T3 were greater in animals on a high intake than in those on a low intake, (P 〈 0·02), but the temperature at which the animals lived had no significant effect. The values of K for T4 and T3 were greater at 10 than at 35 °C (P 〈 0·010 and P 〈 0·05), and energy intake had no significant effect. Calculations of the catabolic rates in nmol/kg.h revealed that for T4 the rate was greater at 10 than at 35 °C (P 〈 0·001) and on a high than on a low intake (P 〈 0·01). Similar differences were found between the mean values of T3 with respect to both temperature and energy intake, but the variance was large and they did not reach statistical significance.

It is concluded that the metabolism of thyroid hormones is influenced independently by both ambient temperature and energy intake.
STATISTICAL ANALYSIS OF ONGOING ACTIVITY OF NEURONES IN THE SUBSTANTIA GELATINOSA AND IN LAMINA III OF CAT SPINAL CORD
Authors: Steedman Wilma M. , Iggo A. , Molony V. , Korogod S. , Zachary S.
Published: December 2014

Intracellular recordings from substantia gelatinosa (s.g.) neurones in chloralose‐anaesthetized cats and in decerebrate preparations revealed the existence of ongoing synaptic activity. 59% of s.g. neurones showed ongoing spiking activity at rates of more than one per second. The ongoing activity of twenty s.g. neurones was subjected to statistical analysis. Stationarity was established for the activity of each neurone, the interspike interval (i.s.i.) distributions were bell‐shaped, and no evidence of dependency of the length of an interval on the one preceding it was found. The mechanism of spike generation in these neurones is therefore an example of a renewal stochastic process. The pattern of ongoing discharge of twelve neurones recorded in lamina III was markedly different, and generated in each case a unimodal asymmetric i.s.i. histogram with a sharp rise to mode after a short dead time and a slow decay. The activity was stationary only in the long term, and there was strong evidence of dependency of intervals. The spike generating mechanism was therefore an example of a non‐renewal stochastic process. The different patterns of activity are discussed in relation to differences in cutaneous input, and it is suggested that the pattern of activity in the s.g. neurones is the result of convergence on the neurones of a large number of small independent excitatory influences, whereas that of the neurones in lamina III is the result of excitation by powerful synchronous synaptic inputs. It is re‐emphasized that statistical analysis of neural impulse sequences is a valuable technique in investigation of the function of a neurone within its network.
EFFECT OF CHANGES IN AIRWAY PRESSURE ON BREATHING PATTERN IN CONSCIOUS DOGS
Authors: Davies A. , Nadal J. A. , Weinmann Gail
Published: December 2014

The effect of brief (400 ms) or sustained (several breaths) application of positive or negative intrapulmonary air pressure was studied in three exercising conscious dogs. Changes in inspiratory duration (T1), expiratory duration (TE) and tidal volume (VT) were measured with the dogs' vagus nerves at body temperature and cooled to a temperature which abolished the Hering‐Breuer inflation reflex (7 °C). Comparison of these results with those obtained with anaesthetized dogs leads us to suggest that there exists in conscious dogs a reflex inspiratory promoting drive.
EFFECTS OF BODY TEMPERATURE ON VENTILATION, BLOOD GASES AND ACID‐BASE BALANCE IN EXERCISING FOWL
Authors: Gleeson Michael , Brackenbury John H.
Published: December 2014

In order to determine the influence of hyperthermia on respiratory, blood gas and acid‐base changes in exercising birds, we exercised domestic fowl on a treadmill at ambient temperatures of 5, 20, 30 and 35 °C for 10 min at graded running speeds up to 4·3 km. h−1. Ventilation and gas exchange were measured continuously and arterial blood gases, pH and the concentration of lactic acid in arterial blood were measured in samples taken during the last minute of each run. During exercise at 5 °C rectal temperature did not change significantly from rest (isothermic condition) and there was no sign of thermal influence on respiratory pattern, such as was observed at higher ambient temperatures. At any given running speed, increased ambient temperature caused increased ventilation by an increase in respiratory frequency (f) together with a decrease in tidal volume (VT). Under isothermic conditions, at low running speeds, birds maintained an isocapnic hyperpnoea: arterial Pco2, PO2 and pH and oxygen extraction were unchanged. However at higher speeds (ca. 〉 2·5 km. h−1) some hyperventilation occurred with subsequent falls in arterial Pco, and oxygen extraction. Arterial pH also fell significantly ( P 〈 0·01). During hyperthermic exercise, oxygen extraction, arterial Pco, and bicarbonate concentration all fell significantly (P 〈 0·01) and progressively with increasing work load, and birds hyperventilated at all running speeds. This produced a significant arterial hypocapnia and alkalosis at the lower speeds (P 〈 0·05) but this was replaced by a hypocapnic metabolic acidosis at the higher running speeds. Blood lactate concentration rose steeply at speeds above ca. 2·5 km. h−1 but arterial pH fell by only 0·1 units or less partly as a result of buffering by blood bicarbonate. It is concluded that both hyperthermia and lactacidosis are causes of hyperventilation and arterial hypocapnia during heavy running exercise in birds. However, ventilatory adjustments similar to those observed in resting hyperthermic birds, viz. increased f and reduced VT prevent severe arterial hypocapnia from occurring in hyperthermic exercising birds.
THE ENLARGED CAROTID BODY OF THE CHRONICALLY HYPOXIC AND CHRONICALLY HYPOXIC AND HYPERCAPNIC RAT: A MORPHOMETRIC ANALYSIS
Authors: Dhillon D. P. , Barer Gwenda R. , Walsh Mary
Published: December 2014

Rats were subjected to chronic hypoxia (10% O2) or hypoxia and hypercapnia (l0% O2 + 4% CO2) for 3–4 weeks and their carotid bodies (twenty‐three from twenty rats) were compared with those of litter‐mate controls. Both chronic exposures, which simulated high altitude or chronic lung disease, caused a 4–10‐fold increase in carotid body volume. The larger increases were attributed to higher fixation‐perfusion pressures. The organs were fixed by perfusion with glutaraldehyde. Semi‐thin (1 µm) sections for light microscopy and ultra‐thin sections for electron microscopy were cut at regular intervals and were examined by stereological techniques to determine the nature of the enlargement. The proportion occupied by blood vessels was much increased in both chronic hypoxia and hypoxia plus hypercapnia; the endotheliun appeared stretched with conspicuous fenestrations. There were increased numbers of endothelial cells which suggested new growth as well as stretching of endothelium and the mean transectional area of the vessels was increased. The mean surface area of blood vessels per unit area of carotid body was unaltered but the total surface area of blood vessels in the whole carotid body was greatly increased. Both the Type 1 cell nucleus and cytoplasm were increased in size. The proportion nucleus/cytoplasm was unaltered in hypoxia but reduced in hypoxia plus hypercapnia. There were fewer Type 1 cell nuclei per unit area but the estimated total number of Type 1 cell nuclei per carotid body was increased 2‐4‐fold; this was interpreted as Type 1 cell hyperplasia. Some of the dense‐cored vesicles in Type 1 cells were enlarged with eccentric dense cores but their number per unit area of cytoplasm was decreased. Their mean size was not significantly altered. However, the total number of vesicles per carotid body was presumed to be increased because their decreased density in the cell was offset by a greater increase in total Type 1 cell volume. The harmonic and arithmetic mean distances between endothelium and the boundary of glomus tissue were significantly reduced. The harmonic mean distance is an indication of the diffusion distance for gases to and from blood and glomus tissue. The arithmetic mean distance is a measure of the amount of tissue in between. The significance of the vascular enlargement and hyperplasia and the Type 1 cell hyperplasia cannot be assessed at present. We do not know if enlargement is associated with the same, greater, or lesser activity of the organ for a given stimulus.
THE EFFECTS OF PANCREATECTOMY ON THE SHEEP FETUS IN UTERO
Authors: Fowden Abigail L. , Comline R. S.
Published: December 2014

The effects of the removal of the fetal pancreas on the fetal metabolite concentrations and body weight have been investigated in chronically catheterized sheep fetuses during the last third of gestation. Between 390 and 1175 mg of pancreatic tissue was removed under halothane anaesthesia from sixteen fetuses between 113 and 121 d of gestation (term = 147 ± 2 d). In six fet‐uses from which 928 ± 58 mg of pancreas had been removed the insulin level (3·4 ± 0·3 µu./ml, n = 6) was below or equal to the limit of sensitivity of the assay. As only very small pieces of pancreas, if any, could be found in these fetuses at delivery, removal of the pancreas was regarded as complete in these animals. Pancreatectomy was incomplete in five fetuses from which 659 ± 62 mg of pancreas had been removed. Insulin was detected in the plasma of these fetuses although the mean concentration (9·1 ± 0·7 µu./ml, n = 5) was significantly less than that in sham‐operated animals (P 〈 0·01). Small fragments of pancreas (0–26 mg) containing endocrine cells were found in these fetuses at delivery. Fetuses from which less than 50% of the pancreas had been removed had plasma insulin and metabolite concentrations similar to those of the sham‐operated fetuses. Significant amounts of histologically normal pancreas were found in these fetuses at delivery. The plasma concentrations of glucose, fructose and α‐amino nitrogen were significantly greater in the incompletely and completely pancreatectomized fetuses than in the sham‐operated animals (P 〈 0·01). In addition, the completely pancreat‐ectomized animals also had higher plasma levels of lactate and free fatty acids than the sham‐operated fetuses (P 〈 0·01). There were no significant differences in the urea concentrations between sham‐operated and pancreatectomized fetuses, but the fetal to maternal concentration difference in arterial plasma urea was greatest in the completely pancreatectomized fetuses (P 〈 0·05). The hypoinsulinaemic fetuses were significantly smaller in birth weight than the sham‐operated animals (P 〈 0·02). The results show that removal of about 70% of the fetal pancreas will produce hypoinsulinaemia in the fetus and confirm that the pancreas is essential for normal growth and development in utero.
MAMMARY DEVELOPMENT AND REGRESSION DURING LACTATION IN GOATS IN RELATION TO MILK SECRETION
Authors: Knight C. H. , Peaker M.
Published: December 2014

Mammary development was assessed in lactating goats using a combination of biopsy (for analysis of nucleic acids) and udder volumes (for determination of gross size). Single biopsies were shown to be highly representative of the composition of the whole gland provided that they were taken from carefully selected sites. Results indicated an increase in both milk yield and the size of the mammary cell population (DNAt) over the first three weeks of lactation. Yield, but not DNAt, continued to increase until peak lactation at around week eight. As milk yield fell between weeks eight and twenty‐three the size of the cell population also decreased; beyond week twenty‐three and until week thirty‐six DNAt stabilized but yield continued to fall. It is concluded that the first part of the increase in milk yield during ascending (early) lactation in goats can be attributed to proliferation of secretory cells, but subsequently there is an increase in the amount produced by each cell. Likewise, declining lactation is initially characterized by a loss of cells, and yield per cell falls later.
CARDIOVASCULAR RESPONSES IN THE DIABETIC RAT
Authors: Charocopos Fotis , Gavras Haralambos
Published: December 2014

Cardiac and regional haemodynamics have been studied in 12‐ and 15‐week‐old streptozotocin‐diabetic rats and in non‐diabetic controls. Reduced cardiac output has been found in the 15‐week‐old diabetic rats (64 ± 13 ml/min, mean ± S.D.), while 12‐week‐old diabetic rats expressed normal values (104 ± 25 ml/min, mean ± S.D.). Renal blood flows of 12‐ and 15‐week‐old diabetic rats (3·4 ± 1 ml/min. g and 3·7 ± 1 ml/min. g, mean ± S.D. respectively) were similarly decreased, when compared to those of non‐diabetic rats (5·47 ± 1 ml/min. g). This finding could be only partly attributed to the increased plasma renin activity of the 12‐ and 15‐week‐old diabetic rats (16·6 ± 6 ng/ml. h and 19·3 ± 4 ng/ml. h respectively), which were higher than normal (4 ± 1 ng/ml. h). Otherwise the circulations of the brain, heart, gastrointestinal and musculocutaneous systems were similar in the diabetic and non‐diabetic rats. In conclusion, while cardiac output was decreased only in the 15‐week‐old diabetic rats, renal perfusion was altered at an earlier stage of the diabetic process.
THE MEASUREMENT OF INTRACELLULAR SODIUM ACTIVITY AND ITS RELATIONSHIP TO THE ACTION OF CALCIUM IONS UPON THE LOW‐SODIUM CONTRACTURE IN FROG ATRIAL TRABECULAE
Authors: Chapman R. A. , Tunstall J.
Published: December 2014

If the Na concentration of the solution bathing a frog atrial trabecula is reduced a contracture rapidly develops and then relaxes spontaneously. If the Ca concentration of the low‐Na solution is raised during this relaxation a further contracture may develop. The amplitude of this Ca‐addition contracture depends in a complex manner upon [Na]o. It also shows a time dependence which is similar to the rate of spontaneous relaxation and the time course of the fall in aiNa as measured by ion‐sensitive micro‐electrodes. These observations are discussed in terms of transmembrane ion movements, the processes occurring during spontaneous relaxation and a possible compartmentalization of both intracellular Ca and Na ions. A relationship between [Na]i and [Na]o is derived from the contracture data that compares well with direct measurements made using ion‐sensitive micro‐electrodes.
MAGNESIUM ABSORPTION FROM THE DIGESTIVE TRACT OF SHEEP
Authors: Care A. D. , Brown R. C. , Farrar A. R. , Pickard D. W.
Published: December 2014

Factors affecting absorption of Mg from the ovine rumen have been studied using either a pouch constructed from part of the dorsal rumen or by an isolated washed rumen technique in vivo. Net absorption of Mg against the prevailing electrochemical gradient was observed. An increase in the K/Na ratio within the rumen led to an increase in the potential difference across the rumen wall, blood positive, and to a decrease in the net efflux of Mg from the rumen. This decrease was due to an increase in Mg influx into the rumen. The addition of ammonium chloride (30 mmol/l) to the rumen contents also led to a reduction in net Mg absorption but to no significant change in potential difference. The effects of high K/Na ratio and high ammonium ion concentration within the rumen were additive in causing decreases in net effluxes of both Mg and Na. An inverse relationship was demonstrated between the Ca concentration in the rumen and the net absorption rate of Mg. It was concluded that the efflux ofMg across the rumen wall depends at least in part on a functional system for Na transport.
THE REGULATION OF PAROTID AND SUBMANDIBULAR SALIVARY SECRETION IN SHEEP
Authors: Carr D. H.
Published: December 2014

During eating the parotid and submandibular salivary glands of sheep are stimulated via parasympathetic and sympathetic pathways. The response of the glands depends on the nature of the diet and the duration of a meal. In anaesthetized animals a continual activity in the parasympathetic nerve supply to the parotid gland reflects the excitatory effects of rumino‐reticular (gastric) distension and contraction. This activity is reduced by high levels of rumino‐reticular distension and increased osmolality of venous blood. It is argued that in conscious sheep these factors are important in determining the volume of saliva that is normally produced. Mechanoreceptors in the parotid glands of sheep are also a source of considerable afferent activity. Some of these receptors are active during naturally stimulated secretion and it is suggested they may also have a role in regulating salivary gland function.
THE TOPOGRAPHY OF ELECTRICAL SYNCHRONY AMONG β‐CELLS IN THE MOUSE ISLET OF LANGERHANS
Authors: Meda Paolo , Orci Lelio , Atwater Illani , Bangham Andrew , Rojas Eduardo , Gonçalves Ari
Published: December 2014

β‐Cells in microdissected islets of Langerhans produce rhythmical bursts of electrical activity. This was monitored with two micro‐electrodes simultaneously and the frequency and phase (collectively referred to as synchrony) of the two signals was investigated. At any instant two impaled cells produced bursts of the same frequency even when separated by up to 400 µm. When the electrode tips were separated by less than about 20 µm and current injection showed the cells to be ionically coupled the two signals were in phase and had almost identical shape. The phase relations between cells further apart were variable, the leading cell usually being located deeper within the islet than the other impaled cell. Increasing the glucose concentration increased electrical activity, reduced any phase lags and made the shape of the bursts more similar. There was less lag between the responses from two cells when the glucose concentration was suddenly reduced, than when it was suddenly increased. Qualitatively similar observations were made in glibenclamide‐treated mice, a treatment previously shown to increase dye coupling between islet cells. However, the response to increasing glucose concentrations showed less phase lag; likewise the phase lag between bursts was reduced. Furthermore the response to current injected into one cell could be detected at much larger distances (up to 80 µm) than in control islets. This suggests that electrical coupling of β‐cells was improved in sulphonylurea‐treated mice. Electron microscopy of both control and glibenclamide‐treated mouse islets fixed at the end of each electrophysiological experiment showed the region impaled by the electrodes to be well preserved and, whenever the electrodes penetrated at least 20 µm into the islet, to contain a large proportion of β‐cells. The data support the view that, within an islet, most but not necessarily all cells are electrically synchronized, and that the coupling can be modulated by natural and pharmacological secretagogues.
THE INFLUENCE OF AGE ON FLUID AND SODIUM CHLORIDE DISTRIBUTION IN RAT AORTIC WALL
Authors: Law R. O.
Published: December 2014

Fluid, Na+ and Cl− content and distribution have been examined in incubated segments of thoracic and abdominal aorta from male Wistar rats aged 1, 3 and 18 months. Na+ and Cl− were determined under conditions of total metabolic blockade (cyanide+iodoacetate). The total aortic mural fluid content, relative to solute‐free dry weight, fell from 1 to 3 months, due mainly to relative contraction of the extracellular (e.c.) (inulin) space. It increased from 3 to 18 months due mainly to an increased intracellular (i.c.) (non‐inulin) space. Total mural free and bound Na+ content, as well as i.c. Na+ content and concentration, fell from 1 to 3 months and increased from 3 to 18 months. No bound Na+ was detectable in segments which had been incubated in the presence of chondroitinase ABC. I.c. Cl− content and concentration fell from 1 to 3 months, but thereafter did not alter significantly. Bound Cl− in the aortic wall of 3‐month‐old rats was markedly reduced by incubation in the presence of a non‐specific protease preceded by treatment with glycerol. The results are discussed in relation to previously established age‐related characteristics of aortic and arterial walls.
FUNCTION OF THE LOWER INTESTINE AND OSMOREGULATION IN THE OSTRICH: PRELIMINARY ANATOMICAL AND PHYSIOLOGICAL OBSERVATIONS
Authors: Skadhauge E. , Warüi C. N. , Kamau J. M. Z. , Maloiy G. M. O.
Published: December 2014

The gross anatomy of the lower intestine of the African ostrich (Struthio camelus) was investigated in four adult birds shot in the wild. The presence of 80 cm long paired caeca, and approximately 10 m of colon between ileum and the cloaca was confirmed. Urine, but not faeces, was found in the coprodeum. Retrograde flow into the colon was not observed. Samples of contents from the lower intestine were secured from these birds and the water content, osmolality and concentrations in the supernatant of short‐chain fatty acids (SCFA), acetate, Na, K and Cl and pH were measured. In the caeca and the orad wide part (2‐3 m) of the colon an avid production of SCFA takes place since the concentration of SCFA reached around 200 mM in these segments. As judged from a pronounced fall in the concentrations of Na and SCFA along the length of the colon, these ions are absorbed together with water. The water content falls from 92 to 67% (i.e. from 11‐5 to 2·0 ml H2O/g dry matter). The mid‐gut fermentation of carbohydrate is in agreement with the observation that the birds were feeding exclusively on Euphorbia heterochroma. This succulent plant (water content 87%) apparently makes the birds independent of surface water. Laboratory studies were performed on two captive male chicks. Hyperosmotic NaCl loading was unable to activate the nasal glands to secretion. Their ducts passed directly from the frontal/lacrimal bone to the nasal cavity. Dehydration confirmed a maximal osmolality of the cloacal urine of around 800 mosmol/l, the osmotic urine to plasma ratio being 2·5. Feeding of either a low‐ or a high‐NaCl diet did not affect the transepithelial electrical potential difference of the coprodeal wall. It remained less than 5 mV, lumen negative.
THE EFFECTS OF CORTISOL ON THE CONCENTRATION OF GLYCOGEN IN DIFFERENT TISSUES IN THE CHRONICALLY CATHETERIZED FETAL PIG
Authors: Fowden Abigail L. , Comline R. S. , Silver Marian
Published: December 2014

The effect of exogerious cortisol on glycogen deposition in a number of fetal tissues was investigated in chronically catheterized fetal pigs between 80 and 95 d of gestation (term 114 d). Intravascular infusion of cortisol for 48 h increased the fetal plasma concentration of cortisol 4‐fold to a value similar to that observed in piglets near to term. After infusion of cortisol, the concentration of glycogen in the lung was lower while the levels in skeletal muscle and liver were higher than those found in unoperated fetuses. There were no detectable changes in either skin or cardiac muscle glycogen after cortisol infusion. High endogenous cortisol concentrations were observed in some of the catheterized control fetuses and in two unoperated fetuses adjacent to the site of cortisol infusion. These fetuses also had detectable changes in lung, liver and skeletal muscle glycogen. When the data from all the fetuses, whether infused, control catheterized or unoperated, were combined there was a significant positive correlation between both liver and skeletal muscle glycogen concentrations and log plasma cortisol (r = 0·70 and 0·72 respectively, P 〈 0·01). Lung glycogen levels were inversely related to log plasma cortisol (r = ‐0·67, P 〈 0·01). No relation between either cardiac or skin glycogen concentration and fetal plasma cortisol could be detected. These observations demonstrate that cortisol has a marked effect on tissue glycogen levels in the immature fetal pig and suggest that the changes in glycogen concentrations observed in the liver, lung and skeletal muscle before term may be due to the pre‐partum surge in fetal cortisol.
THE BLOOD RHEOLOGY OF MAN AND VARIOUS ANIMAL SPECIES
Authors: Amin T. M. , Sirs J. A.
Published: December 2014

A comparative study has been made of the blood rheology, and its component factors, in horse, sheep, cattle, goat, camel, pig, dog, rabbit and man. The erythrocyte flexibility of horse red cells is high relative to man, that of pig, dog, camel and rabbit comparable, but less flexible, and sheep, cattle and goat relatively inflexible. The erythrocyte flexibility of horse, sheep, cattle and goats does not vary with the plasma fibrinogen level, as occurs with human and rabbit cells. Washing erythrocytes and then suspending them in isotonic saline makes the erythrocytes of all species relatively inflexible. There is a factor in horse plasma, which is not fibrinogen, that makes horse and human erythrocytes suspended in it very flexible. The blood viscosity of all species is comparable at high shear rates (230 s‐1) due to the shape of the cells compensating for their flexibility. The variations of blood viscosity at low shear rates (11·5 s‐1) were also found to depend on the erythrocyte flexibility, and only influenced indirectly by the fibrinogen concentration. There is no significant effect of temperature on the erythrocyte flexibility of horse, sheep, cattle, goat and a small number of human subjects. This is reflected in the way the viscosity of these bloods varies with temperature.
AIRWAY RESPONSES TO LOW CONCENTRATIONS OF ADRENALINE AND NORADRENALINE IN NORMAL SUBJECTS
Authors: Berkin K. E. , Thomson N. C. , Inglis G. C. , Ball S. G.
Published: December 2014

Airway, cardiovascular and metabolic responses were measured in six normal subjects during separate infusions of adrenaline and noradrenaline. Four incremental infusion rates of the catecholamines (4, 10, 25 and 62·5 ng.kg−1.min−1) produced circulating levels of adrenaline and noradrenaline within the physiological range. Maximal expiratory flow rates at 25% of vital capacity measured from partial flow‐volume curves increased sequentially with increasing adrenaline concentration. Increases in maximal expiratory flow rates at 25% and 50% of vital capacity measured from complete flow‐volume curves were not statistically significant, nor were the changes in specific conductance. Small but insignificant changes were observed in heart rate and blood pressure during adrenaline infusion. Plasma glucose increased and serum potassium fell during adrenaline infusion. No significant airway, cardiovascular or metabolic responses were seen during noradrenaline infusion. These results suggest that adrenaline, at concentrations found in physiological circumstances, influences flow rates in small airways. Circulating noradrenaline does not appear to be important in the control of airway calibre in normal subjects.
AN ANALYSIS OF SOME BEHAVIOURAL EFFECTS OF THE VIBRATION AND NOISE COMPONENTS OF TRANSPORT IN PIGS
Authors: Stephens D. B. , Sharman D. F. , Ingram D. L. , Bailey K. J.
Published: December 2014

The reactions of pigs to the vibration and noise components of transport were examined with the use of an apparatus which simulated these factors. The pigs were trained to switch off the apparatus by pressing a switch panel with their snouts. It was found that vibration was aversive but that noise was not. The pigs switched off the apparatus more frequently when the vibration was fast and when they had been fed a large meal before the test. Although the sedative tranquillizing drug azaperone decreased the number of times the apparatus was switched off, the effect appeared to be non‐specific because azaperone also reduced the number of responses that pigs would make in order to receive food.
ASSESSMENT OF THE OPTICAL CONTRIBUTIONS TO THE AGE‐RELATED DETERIORATION IN VISION
Authors: Morrison J. D. , McGrath C.
Published: December 2014

Contrast sensitivities were measured in human observers of different ages in response to sinusoidal grating patterns generated by laser interferometer and cathode ray tube (c.r.t.). The former method bypasses the effects of the optical media to assess directly the contrast sensitivity of the retina/visual system, while the over‐all assessment including optical media is made to the c.r.t. display. The ratio of the two sets of values gives the contrast ratio of the optical media. The latter assessment does not include the effects of wide‐angle light scattering which were measured by comparing the responses of eyes with a Perspex lens implant or without any lens at all (i.e. without the major source of scattering) with natural eyes. With increasing age, c.r.t. contrast sensitivities remained steady until the sixth decade when they declined while laser interference fringe contrast sensitivities declined continuously, apart from some abnormally low results for teenage observers. In contrast, the optical contrast did not vary systematically with age nor did its rate of change with spatial frequency vary. The latter was always less than the rate for laser interference fringe contrast sensitivities indicating that the retina/visual system always sets the limit to visual resolution. Wide‐angle light scattering was not found to contribute significantly to the changes in ageing nor did reduced retinal illumination, as reproduced by reduced pupil diameter or viewing through a neutral density filter. We therefore conclude that the age‐related deterioration is primarily caused by changes within the central nervous system rather than the optical media, the transmission quality of which remains unaffected.
A MORPHOMETRIC STUDY OF THE ENDOCRINE AND EXOCRINE CAPILLARIES OF THE PANCREAS
Authors: Henderson J. R. , Moss M. C.
Published: December 2014

In passing from islets to the exocrine part of the gland, pancreatic capillaries change their character. Islet capillaries are significantly wider than exocrine ( 5·27 µm, diameter compared with 4·35 µm), thinner walled and have many more fenestrations µm‐1 of endothelium (1·3 compared with 0·13). The point of transition at the edge of the islet is very abrupt, for capillaries that are in contact with both endocrine and exocrine tissue (‘edge capillaries’) have significantly more fenestrae on the side facing the endocrine cells than the side facing exocrine (1·46 fenestrae µm−1 compared with 0·3 µm−1). The structure of these edge capillaries suggests that the factors operating to induce the formation of fenestrae do so over extremely short distances. The relationship between fenestrations, the high blood flow and high water flux seen in endocrine glands is discussed.
SYNAPTIC ARRANGEMENTS FORMED BY SEROTONIN‐IMMUNOREACTIVE AXONS IN THE SUBSTANTIA GELATINOSA OF THE RAT SPINAL CORD
Authors: Maxwell D. J. , Léránth Cs. , Verhofstad A. A. J.
Published: December 2014

Ultrastructural properties of serotonin‐immunoreactive axons in the rat's substantia gelatinosa were examined in order to determine the synaptic arrangements that they form in the neuropil. Some immunoreactive varicosities formed synaptic associations with somata or dendrites suggesting that serotoninergic systems are capable of influencing the activity of these structures post‐synaptically. No examples of axo‐axonic synapses were found. Most varicosities, however, did not form identifiable synaptic junctions, but were closely associated with somata, dendrites or axons. Some of these associations may be functional but morphological evidence for this is lacking.
OSMOTIC AND IONIC REGULATION DURING DEHYDRATION IN A LARGE BIRD, THE EMU (DROMAIUS NOVAEHOLLANDIAE): AN IMPORTANT ROLE FOR THE CLOACA‐RECTUM
Authors: Dawson T. J. , Herd R. M. , Skadhauge E.
Published: December 2014

The emu, a large (40 kg) flightless bird, has low water requirements yet it has a limited ability to produce concentrated urine. To clarify the factors involved in excretion and water conservation by the emu the patterns of excretion during water restriction were examined. Additionally, kidney function was studied, as also was the role of the cloaca and rectum in the final modification of excreta. Following water restriction the osmolality of the excreta fluid increased to a maximum level at 6 d of 428±39(8) mosmol (mean±S.E.M. (n)), the urine to plasma ratio being 1·35±0·12(8). In normally hydrated birds almost all Na and Cl were excreted in the fluid fraction but a third of the K was associated with the solid fraction of the excreta. After water restriction for 9 d the pattern of excretion of K did not change but the majority of Na (79%) and Cl (73%) were excreted in the solid phase, possibly associated with urates. In ureteral urine most of the nitrogen was excreted as uric acid or urates; a large fraction, 36±4(4)%, was not identified. The glomerular filtration rate (G.F.R.) was 41·3±2·2(6) ml/kg.h. This value is low when compared with other birds and may be related to the large size of the emu. The G.F.R. decreased by 30% after 7 d water restriction. The cloaca‐rectum appears to play a major role in the modification of excreta. In vivo perfusion studies showed transepithelial net transport rates of water and major electrolytes to be large. Transport of water from an isosmotic solution, 3·36±0·17 ml/kg.h, was approximately 10 times the maximum value reported for birds previously. The Na and Cl transport rates were also comparatively high.
THE EFFECT OF DINITROPHENOL ON MAGNESIUM TRANSPORT ACROSS AN ISOLATED PREPARATION OF SHEEP RUMEN EPITHELIUM
Authors: Martens H.
Published: December 2014

Mg transport across an isolated preparation of sheep rumen epithelium was studied in vitro. The efflux (flux from the mucosal side to serosal side) and the influx (flux with serosal to mucosal side) were estimated with 28Mg. Under physiological conditions a significant net efflux of Mg was observed, in which the unidirectional efflux was seven to eight times that of the influx. In experiments where ATP synthesis was blocked by the addition of dinitrophenol, Mg efflux was reduced to that of the influx. These observations support the conclusion that Mg absorption across the rumen wall of the sheep is an active process.
MORPHOLOGICAL ABNORMALITIES IN MYELINATED NERVE FIBRES CAUSED BY LEIURUS, CENTRUROIDES AND PHONEUTRIA VENOMS AND THEIR PREVENTION BY TETRODOTOXIN
Authors: Love S. , Duchen L. W. , Cruz-Höfling M. A.
Published: December 2014

Morphological changes in peripheral nerve caused by the venoms of the scorpions Leiurus quinquestriatus and Centruroides sculpturatus were compared with those caused by Phoneutria nigriventer spider venom. Both scorpion venoms are known to delay the inactivation of sodium currents, Centruroides venom also altering the voltage dependence of sodium gating. Venom was injected by means of a glass micropipette into the sciatic nerves of anaesthetized mice. After survival times ranging from 15 min to 24 h the nerves were examined by light and electron microscopy. The two scorpion venoms caused alterations virtually identical to those produced by Phoneutria venom, which included swelling of the nodal axoplasm and accumulation of fluid in the periaxonal space of myelinated fibres. These alterations were most marked after 1 to 2 h and had largely disappeared by 24 h. Pre‐treatment of the nerves with tetrodotoxin, which specifically blocks sodium channels, completely prevented both the nodal axoplasmic swelling and the periaxonal oedema. It seems likely that these effects result from an action common to the three venoms and that this is probably a delay in the inactivation of sodium current at the node of Ranvier.
THE EFFECT OF PANCREATECTOMY ON THE UPTAKE OF METABOLITES BY THE SHEEP FETUS
Authors: Fowden Abigail L. , Silver Marian , Comline R. S.
Published: December 2014

The effects of fetal pancreatectomy on the uptake of oxygen, glucose and lactate by the fetus, uterus and uteroplacental tissues were investigated in chronically catheterized sheep during the last third of gestation. Pancreatectomy reduced the uptake of glucose by the fetus but had little apparent effect on glucose uptake by the uterus or uteroplacental tissues. The mean umbilical uptake of glucose by the pancreatectomized fetuses was 10·4 ± 1·1, µmol/kg.min (n = 4) which was significantly less than the value observed in the intact fetuses (24·5 ± 2·7, µmol/kg.min, n = 4, P 〈 0·01). When all the data from the pancreatectomized and intact fetuses were combined, there was a significant positive correlation between the plasma insulin concentration in utero and the umbilical uptake of glucose (r = 0·95, n = 14, P 〈 0·01). The glucose/oxygen quotient in the pancreatectomized fetuses (0·32 ± 0·02, n = 9) was significantly less than the value observed in the intact fetuses (0·59 ± 0·04, n = 6, P 〈 0·01). There was also a significant positive correlation between the glucose/oxygen quotient and the plasma concentration of insulin in the fetus (r = 0·73, n = 59, P 〈 0·01). Pancreatectomy had no significant effect on the fetal lactate/oxygen quotient or on the uptake of oxygen or lactate by any of the tissues. These observations demonstrate that the endogenous concentration of insulin is a physiological regulator of glucose uptake by the fetal tissues.
THE LOCATION AND CHARACTERISTICS OF SYMPATHETIC PREGANGLIONIC NEURONES IN THE LOWER THORACIC SPINAL CORD OF DOG AND CAT
Authors: Bennett J. A. , McWilliam P. N. , Goodchild C. S. , Kidd C.
Published: December 2014

The retrograde transport of horseradish peroxidase from a white ramus communicans has been used to define the precise segmental location of sympathetic preganglionic cell bodies in the spinal cord of the cat and dog. All labelled cells were found ipsilaterally and were confined to the spinal cord segment from which the ramus originated. Most lay in the intermediolateral cell column and the immediately adjacent white matter, though others were scattered in more medial areas of the grey matter. We suggest that the observed distribution of sympathetic preganglionic neurones, the orientation of their processes and the paths taken by their axons are a direct result of cell migration during the embryological development of the spinal cord.
THE ROLE OF INGESTION IN THE DEVELOPMENT OF THE SMALL INTESTINE IN FETAL SHEEP
Authors: Trahair J. F. , Robinson P. M. , Harding R. , Bocking A. D. , Silver M.
Published: December 2014

We have examined the influence of preventing the passage of swallowed fluid on the development of the small intestine during late gestation in fetal sheep. In four fetuses at 90 d of gestation, the oesophagus was ligated and fistulated, causing swallowed fluid to enter the amniotic sac. Tissue was removed from proximal and distal parts of the small intestine for histological analysis at 136 d (term is 147 d). The body weights of the four experimental fetuses were not significantly different from those of fourteen age‐and breed‐matched fetuses which were used as controls. However, the width of the mucosal layers at both sites in the small intestine was reduced by approximately 25% in the fistulated fetuses. This was largely attributable to a reduction in villus height ofapproximately 30% The densities ofvilli and crypts increased significantly at the proximal and distal sites respectively. These findings indicate that the ingestion of fluid during late gestation plays a role in promoting growth of the mucosal elements of the small intestine. The way in which this occurs is not clear although it may be mediated either by trophic factors present in either amniotic or pulmonary fluid, or by the release of gastrointestinal hormones, such as gastrin, as a result of gut distension.
ANION CONTROL OF SODIUM ABSORPTION IN THE COLON
Authors: Roediger W. E. W. , Deakin E. J. , Radcliffe B. C. , Nance S.
Published: December 2014

The regulatory functions of anions in colonic absorption of sodium are unknown. Absorption of sodium ions was assessed with chloride, butyrate, nitrite, sulphate and oxalate anions in segments of proximal/distal colon and in defunctioned colon. Efficiency of sodium absorption was related to availability of CO2 in mucosal cells: CO2 availability was enhanced (P 〈 0·01) by sodium nitrite or diminished (P 〈 0·01) in defunctioned colon. Sodium nitrite stimulated absorption of sodium in the distal colon where bicarbonate secretion predominated and n‐butyrate stimulated absorption of sodium in the proximal colon where hydrogen ion secretion predominated. Sodium absorption was very significantly diminished (P 〈 0·01) in defunctioned colon. Results indicate that sodium absorption in the colon is both a double anion exchange system as well as cation/anion co‐transport. Anions act differently on sodium absorption along the length of the colon and prolonged lack of anions plays a part in sodium malabsorption of the defunctioned colon.
THE MEASUREMENT OF LIVER BLOOD FLOW IN CONSCIOUS CALVES
Authors: Harrison F. A. , Hills F. , Paterson J. Y. F. , Saunders R. C.
Published: December 2014

Observations were made following single I.V. injections or during continuous I.V. infusions of sulphobromophthalein (BSP) in three Jersey calves (3‐5 months of age) which had an indwelling hepatic vein catheter, surgically implanted under general anaesthesia. Simultaneous sampling of blood from a peripheral (jugular) vein and an hepatic vein enabled calculations of hepatic plasma flow (E.H.P.F.) based on the Fick principle. Estimates of E.H.P.F. in nine single injection experiments gave a mean flow of 38·6 ml.min−1. kg−1 compared to 32·6 ml.min−1 kg−1 estimated in seven continuous infusion experiments. The over‐all mean haematocrit in the three calves was 30·0% and the E.H.P.F. values are equivalent to hepatic blood flows of 55 and 47 ml.min−1. kg−1 respectively. In thirteen out of fourteen experiments the plasma clearance of BSP in jugular vein blood after a single i.v. injection of 5 mg BSP.kg−1 body weight was best fitted by a double exponential model of distribution of BSP. Parameters from these exponentials were used to calculate E.H.P.F. by the method of Clarkson, Hardy‐Smith & Richards (1976) and gave values of 11·3 ml.min−1. kg−1, clearly indicating that the method cannot be applied in conscious calves.
ISOLATION OF DUCTS FROM THE PANCREAS OF COPPER‐DEFICIENT RATS
Authors: Arkle S. , Lee C. M. , Cullen M. J. , Argent B. E.
Published: December 2014

A technique is described, involving tissue dissociation and micro‐dissection, for the isolation of interlobular ducts from the pancreas of copper‐deficient rats. The average length and outside diameter of the isolated ducts were 589·0±18·6 and 78·1±1·6 µm (mean ± S.E.M., n = 425) respectively. Between twenty and fifty ducts could be obtained from each pancreas. Frequently, the smaller intralobular ducts, which had outside diameters of between 15 and 25 µm, were observed as branches of the interlobular ducts. Light and electron microscopy showed that the isolated ducts were structurally intact, and that the epithelial cells possessed all the typical ultrastructural features of duct cells within the gland of copper‐replete rats. The isolated ducts consumed oxygen at a rate of 2·27±0·55 ml O2/min.100 g wet weight duct epithelium (n = 6). The concentrations of ATP, ADP and AMP in the ducts were 3·78±0·81, 0·68±0·19 and 0·41±0·13 mmol/l duct epithelium (n = 8) respectively. These data give values for ATP:ADP and ATP:AMP ratios of 5·6:1 and 9·2:1 respectively, and an energy charge of 0·85±0·01 (n = 8) suggesting that the epithelial cells are healthy and in a stable metabolic state. In the presence of the phosphodiesterase inhibitor 3‐isobutyl‐1‐methylxanthine (0·67 mM), the basal concentration of cyclic AMP in the isolated ducts was 17·4±0·7 µmol/1 duct epithelium (n = 3). Secretin (0·1 nM‐1 µM) caused a dose‐related increase in cyclic AMP content up to a maximum of 376·0±85·3 µmol/l duct epithelium (n = 4). This indicates that the epithelial cells possess secretin receptors, and that these receptors can be functionally linked to adenylate cyclase.
CHANGING BASAL AND STIMULATED ACTIVITY OF THE RENIN‐ANGIOTENSIN SYSTEM DURING THE SECOND HALF OF GESTATION IN THE ANAESTHETIZED PIGLET
Authors: Pipkin Fiona Broughton , Colenbrander Ben , MacDonald Alastair A.
Published: December 2014

Concentrations of components of the renin‐angiotensin system were studied in eighty anaesthetized pig fetuses aged between 57 and 112 d of gestation (term = 114±1 d). Plasma renin concentration rose from a mean value of 3·2±0·4 ng.ml−1.h−1 (mean ± S.E.M.) at 57 d to 17·5±2·7 ng.ml−1. h−1 at 93 d of gestation and thereafter declined to 5·0±1·6 ng. ml−1. h−1 just prior to term. There was no distinct pattern of change in plasma renin substrate concentrations during gestation; the concentration near term (0·33±0·10 µg.ml−1) was not different from that at 57 d (0·50±0·18 µg.ml−1) or that at 93d (0·31±0·08 µg.ml−1) of gestation. Plasma angiotensin II concentrations increased from 33 (log10 (mean ± S.E.M.) = 1·554±0·050) pg.ml−1 at 60 d to 232 (2·365±0·225) pg.ml−1 at 105 d of gestation, after which it decreased to 50 (1·699±0·100) pg.ml−1 in 20‐d‐old neonatal piglets. Haemorrhage of 10‐20% estimated blood volume produced no consistent changes in plasma renin substrate concentrations, and inconsistent changes in renin and angiotensin II concentrations at 85‐90 d of gestation, but a consistent increase in both renin and angiotensin II concentrations thereafter. These results indicate that the components of the renin‐angiotensin system are present in the circulation of the pig fetus, and that their responses to stimuli develop during the second half of gestation.