Expiratory effects of vagal stimulation in newborn kittens

Expiratory effects of electrical stimulation of vagal afferents were studied in 12 kittens during the first week of life. Animals anesthetized with ketamine (30 mg/kg, im) and acepromazine (1.1 mg/kg, im), tracheostomized, and paralyzed were artificially ventilated after bilateral vagotomy. Rectified and "integrated" activity of the C5 root of phrenic nerve, systemic blood pressure, and the stimulus train were recorded. The optimal stimulus parameters for expiratory prolongation were chosen. The results varied between animals. We found three types of response: A, expiratory prolongation when stimulus was applied within the initial 80% of control expiratory time (TEc); beyond this delay, a decreased response or no effect was observed in four kittens; B, graded expiratory prolongation was recorded to the end of this phase in three kittens; and C, expiratory prolongation when stimulus delay was less than 40% of TEc and expiratory shortening when the stimulus given with greater delays was observed in one kitten. Nonsignificant effects were observed in the remaining four animals. Types A and B of response suggest activation of the slowly adapting pulmonary stretch receptors. However, amplitude of stimulus and frequency of pulses were higher than those used in adult animals. Type C response indicates that fibers from both rapidly and slowly adapting stretch receptors could be activated. Our results imply that if the expiratory insensitive phase is present in kittens, it can be affected by experimental conditions. This is in contradiction to characteristics of expiratory response to vagal stretch receptor input in adult cats.

Effects of tonic vagal input on breathing pattern in newborn rabbits

Respiratory effects of positive and negative pressure breathing were studied in 1- and 4-day-old rabbit pups anesthetized with ketamine (50 mg/kg, im) and acepromazine (3 mg/kg, im). We recorded tidal volume (VT), tracheal pressure (Ptr), and integrated diaphragmatic EMG (DiEMG). Inspiratory (TI) and expiratory time (TE) were measured from the records of DiEMG. During breathing with increased Ptr by 1 or 2 cmH2O, VT, minute ventilation (VE), and respiratory rate (f) decreased. Changes in f relied on a TE prolongation. Neither DiEMG nor its rate of rise (DiEMGt) were affected. Except for VT decrease during positive Ptr, all other effects disappeared after vagotomy. Our results indicate that an increase in tonic vagal activity interacts with the mechanisms controlling TE and has no effect on depth and duration of inspiration. When Ptr decreased by 1 and 2 cmH2O, VE increased due to an increase in f. Increase in f relied on shortening of both TI and TE; the TE effect being more pronounced. DiEMG and DiEMGt also increased. Adverse effects of lung deflation and vagotomy strongly suggest that the respiratory reflex stimulation due to decrease in Ptr does not rely on inhibition of the slowly adapting stretch receptor activity. Therefore other excitatory vagal inputs must be responsible for this response. We propose two vagally mediated inputs: the irritant and/or the cardiac receptors.

Effects of early hypoxia on breathing pattern in rabbit pups before and after vagotomy

We examined the influence of vagal pulmonary receptors exerted on the breathing pattern and inspiratory activities of phrenic nerve and intercostal electromyograms (EMG) during hypoxia in rabbit pups. Animals in their second week of life were anaesthetized with ketamine (50 mg/kg) and acepromazine (3 mg/kg) and tracheostomized. While they breathed spontaneously, we recorded tidal volume (VT), integrated phrenic activity (PHR), integrated external intercostal EMG (INT), and blood pressure (BP). To prevent secondary ventilatory depression, animals were exposed to 12% O2 (balanced with N2) for no longer than 5 min before and after vagotomy. All measurements were taken from 1 min following the onset of hypoxic exposure until the end of the run. During hypoxia, VT, PHR, and INT increased in intact rabbit pups. There was an almost immediate decrease in BP that was maintained during the total period of hypoxia exposure. Hypoxia resulted in inconsistent changes in inspiratory (TI) and expiratory (TE) time in intact animals. Following vagotomy, PHR, INT, VT, BP, and TE responses were the same as in intact animals. However, TI significantly decreased in all animals. In response to hypoxia with and without vagal feedback, INT increased less than PHR in most cases. Qualitatively similar effects of hypoxia were observed in an adult rabbit. The results reveal that the increase in VT and the shortening of TI in response to hypoxia do not depend on vagal feedback in rabbits during the early postnatal period. In fact TI shortening was significant only without vagal feedback.

Characterization of the genes specifying two metacyclic variable antigen types in Trypanosoma brucei rhodesiense

Bloodstream trypanosomes evade the immune system of their mammalian host by sequentially expressing a large number of different variable surface glycoproteins (VSGs). In contrast, metacyclic trypanosomes, the final developmental stage in the tsetse fly, express a much more restricted set of VSGs. These metacyclic VSGs are the first to be exposed to the immune system of the mammalian host after infection and may offer the potential for the eventual development of a vaccine. We have identified cDNAs for two VSGs in cDNA libraries prepared from amplified metacyclic populations of Trypanosoma brucei rhodesiense and show that they correspond to two different metacyclic serotypes. Determination of the cDNA sequences shows that metacyclic VSG mRNAs are similar to VSG mRNAs expressed during the bloodstream stage. Southern blots demonstrate that the metacyclic VSG genes are located near chromosomal telomeres. No evidence of gene rearrangement associated with expression of these VSGs was found.

Respiratory effects of progressive asphyxia in rabbit pups and adult rabbits

Effects of prolonged airway occlusion were investigated in anesthetized and vagotomized 9-to 15-day-old pups and adult rabbits. The changes and temporal relationships between “integrated” phrenic activity, external intercostal electromyogram (INT), and esophageal pressure (Pes) were examined. Each occlusion resulted in hyperpnea, apnea, and gasping. Blood pressure recorded during the occlusion showed a marked decrease. During hyperpnea, the rate of changes and maximal amplitudes in Pes and INT were similar in both age groups. The increase in integrated phrenic activity (PHR) was significantly greater in young rabbits. In both age groups, changes in INT during gasping followed a similar time course and exceeded those in PHR. Maximal values of the three parameters were concurrent in adults, whereas the increase in INT peaked later than PHR and Pes in rabbit pups. In adult rabbits, PHR, INT, and Pes, during the last gasp, decreased to the values of the first hyperpnea breath. In rabbit pups, Pes of the last gasp decreased significantly below this value while INT was still elevated. This Pes decrease could result from inspiratory muscle dysfunction in the pups. Thus in rabbit pups, 1) greater changes in PHR were necessary to produce a given change in Pes than in adult rabbits; 2) activity of the external intercostal muscles was not efficient in developing pressure under conditions of asphyxia; and 3) the independent activation of diaphragmatic and intercostal motoneurons is not of vagal origin. Additionally, the results led us to conclude that Pes can serve as a close approximation of respiratory drive in adult rabbits. This parameter, however, cannot be used as an index of central inspiratory activity during gasping in rabbit pups.

Abdominal vagotomy does not modify endotoxic shock in rats

Bilateral subdiaphragmatic vagotomy does not improve the clinical course nor the survival of Sprague-Dawley rats injected intravenously with E. coli lipopolysaccharide. These results show that whatever peripheral signals are elicited by endotoxin to generate the centrally mediated hypotensive response, they are not conveyed to the central nervous system by abdominal vagal afferent fibers.

Respiratory effects of stimulation of intercostal muscles and saphenous nerve in kittens

Effects of intercostal muscle stimulation were studied in 2- to 7-day-old kittens under ketamine-acepromazine anesthesia. Animals were vagotomized, paralyzed, and artificially ventilated. Stimuli applied during inspiration (TI) inhibited this phase. Stimulus strength necessary for TI inhibition decreased with time. However, an all-or-nothing effect was not always observed. Stimulation during expiration (TE) prolonged this phase. The responsiveness increased with increasing stimulus delay. The effects of intercostal muscle stimulation were compared with those recorded during saphenous nerve stimulation. Stimulation during TI prolonged this phase. Phrenic activity increased after a short-lasting decrease in the on-going activity. Stimulation during the first 50% of TE had variable effects, whereas stimulation with longer delay shortened this phase. Our results indicated that the pattern of breathing in newborns can be affected by both intercostal muscle and other somatic efferents. However, the mechanisms controlling respiratory timing may differ in newborns and in adults. Different effects of respiratory muscle and saphenous nerve stimulation suggest different transmitters involved or different sites of interaction of these inputs with the medullary respiratory rhythm generator.

Phrenic activity and intercostal muscle emg during inspiratory loading in newborn kittens

The effects of airway occlusions at functional residual capacity (FRC) on both "integrated" phrenic activity (Phr) and intercostal muscle electromyogram (intEMG) were studied in intact and vagotomized spontaneously breathing kittens during the 1st wk of life. Animals were anesthetized im with a mixture of ketamine (30 mg/kg) and acepromazine (1.1 mg/kg). In the intact kittens, inspiratory loading led to a significant increase in peak amplitudes of both Phr and intEMG and prolongation of inspiratory (TI) and expiratory (TE) times. Mean values of rate of rise of Phr and intEMG measured at 200 ms (intEMG200) from the onset of inspiration were unaffected. The results indicated that in newborns the vagal component of the load compensation is of great importance. Following vagotomy, airway occlusion produced a significant increase in mean values of TI and intEMG only. These small but significant changes suggest that most of the load compensation reflex is dependent on prolongation of TI. Increased intEMG200 during loading in the vagotomized kittens, observed during several trials, implies that the intercostal fusion-alpha interaction may operate in newborns.

Naloxone attenuates the hypotension induced by Hageman factor

The hypotension induced in the pentobarbital anesthesized rat by the i.v. administration of an active Hageman factor fragment (Hff) is significantly attenuated by naloxone. This effect is specific because the opiate antagonist does not modify the hypotension elicited by rat urinary kallikrein, bradykinin or nitroglycerin. These results suggest that the contact activation of endogenous Hageman factor could result in the generation of vasoactive opioid peptides derived from circulating large molecular weight precursors.

Papilledema in two patients with acromegaly and intrasellar pituitary tumors

Two patients had bilateral papilledema complicating acromegaly. Both patients had enlarged blind spots, but otherwise visual fields were normal. Suprasellar extension of the pituitary tumors was diligently sought with the use of visual field examination, pneumoencephalography, internal carotid arteriography, and computed axial tomography, and tumor extension did not exist. Transphenoidal and transethmoidal routes were used to perform partial hypophysectomies in these patients. The procedure was completely successful in one patient and partially successful in the other patient. After hypophysectomy, papilledema resolved in both patients. This beneficial effect may be the result of anatomical changes, the reduction in growth hormone levels, or both. These observations suggest that the acromegaly may be different from papilledema that occurs secondary to suprasellar expansion of pituitary tumors.

Effect of prostacyclin (PGI2) on renal function and renin secretion in hypophysectomized dogs

The effect of PGI2, the principal metabolite of arachidonic acid in mammalian arterial and venous tissues, on renal function and renin secretion was investigated in anesthetized, hypophysectomized dogs undergoing a maximal water diuresis. PGI2 in a concentration of 0.04 microgram/kg/min significantly increased urine flow and urinary sodium and potassium excretion in the absence of changes in glomerular filtration rate or blood pressure. The fact that PCI2 significantly increased free water clearance and distal delivery of sodium and inhibited distal fractional rea0sorption of glomerular filtrate is suggestive of an effect on proximal as well as distal sites of the nephron. PGI2 increased renin secretion rates threefold. This promotion of renin release may have been caused by an increase of ion flux across the macula densa or by an increase in renal blood flow. On a molar basis, PGI2 is about 10 times more potent than PGE2 with regard to natriuresis, diuresis and renin release when studied under identical conditions. Thus, PCI2 may be the major prostaglandin involved in the regulation of salt and water excretion.

Effect of indomethacin on renal function and plasma renin activity in dogs with chronic renovascular hypertension

The effect of indomethacin on plasma renin activity (PRA) and renal function was examined in conscious dogs with chronic renovascular hypertension before or after volume expansion. PRA did not change following the infusion of indomethacin: PRA was 5.18 +/- 1.46 ng/ml/h during control periods and was 5.01 +/- 0.95 ng/ml/h (p greater than 0.1) after 80 min of infusion of indomethacin. Mean arterial blood pressure (MABP) was 121.6 +/- 7.4 mm Hg during control periods and was 122.0 +/- 4.6 mm Hg (p greater than 0.1) after 80 min of infusion of indomethacin. Infusion of indomethacin into these dogs undergoing diuresis did not change inulin or p-aminohippuric acid clearance. Sodium excretion (UNaV) showed slight but not signifcant decreases with the infusion of indomethacin. UNaV was 109.3 +/- 25.7 muEq/min during control periods and was 69.6 +/- 21.0 muEq/min (0.05 less than p less than 0.1) after 80 min of infusion of indomethacin. The results suggest that renin release, sodium excretion, and blood pressure in the dog with chronic renovascular hypertension in uninfluenced by indomethacin.

Disappearing carotid defects

Large intraluminal cervical carotid artery filling defects consistent with mural thrombi were angiographically demonstrated during acute hemispheric neurologic episodes. These thrombi disappeared benignly as shown by serial angiography in 2 patients treated with intravenous heparin and spontaneously in 1 patient treated surgically. Thus, partially obstructing cervical carotid artery thrombi may lyse either with the use of anticoagulant therapy or else spontaneously. The etiology of the thrombi may partly be related to underlying atheromatous disease.

Erythrocytes cultured from bone marrow

The long-range objective of this study is in vitro tissue culture of bone marrow stem cells to produce erythroid cells of sufficient volume for clinical transfusion. Bone marrow from dogs and patients was cultured in 29 experiments lasting up to 15 weeks. Peripheral erythroid cells from dogs were cultured in three control experiments. Optimal tissue culture media was NCTC 109 augmented with vitamin B12, erythropoietin (EP), folic acid, and 9% fetal protein in 60 mm glass Petri dishes. Additional media and Step III EP was added at 2 to 4 day intervals. Peripheral erythroid cells in culture all were dead within 4 weeks. Marrow erythroic cells in culture proliferated as demonstrated by (1) Fe59 incorporation into cells during culture, (2) H3 thymidine uptake into cultured cells, (3) microscopic evidence of mitoses, and (4) total erythrocyte concentration in cultures far exceeding that of peripheral culture controls. For as yet unexplained reasons the total mature red blood cell concentration in the culture media remained essentially constant throughout the studies. This is a first step in achieving the ultimate goal of bulk erythrocyte production from tissue culture.