A study of the effects of gonadal hormone administration on some enzymes of amino acid metabolism in the oviduct of the immature domestic fowl.
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1. Electrophoresis of extracts of turkey spermatozoa for lactate dehydrogenase activity revealed the usual five tissue LDHs (LDH-1 to LDH-5). 2. The presence of LDH-X (the spermatozoan-specific isozyme) was not obvious. 3. Only one band was present on electrophoresis of fowl spermatozoan extracts and it coincided with LDH-1 (heart type). 4. Kinetic investigations, the use of inhibitors and the heat-stability test confirmed that the fowl spermatozoan LDH was probably LDH-1 and not LDH-X.
The effects of glucagon and insulin on phosphofructokinase activity in isolated chicken hepatocytes were studied. Phosphofructokinase activity was decreased in extracts of hepatocytes exposed to glucagon both at subsaturating (0.2 mM) and saturating (5 mM) concentrations of fructose 6-phosphate. Both effects were still present after Sephadex G-25 gel filtration and subsequent ammonium sulfate precipitation. Half-maximal effects of glucagon were found between 10(-11) and 10(-10) M glucagon. Insulin alone had no effect but decreased the action of glucagon.
Isolated kidney tubules synthesize glucose actively from fructose, lactate, glycerol and pyruvate and, to a lesser extent, from a variety of amino acids. Ethanol stimulated gluconeogenesis from pyruvate and inhibited it from lactate. The aminotransferase inhibitor, aminooxyacetate, greatly reduced synthesis from lactate but not from pyruvate. Quinolinate inhibited gluconeogenesis from both precursors, indicating an active role for cytosolic phosphoenolpyruvate carboxykinase (PEPCK) in the gluconeogenic pathway. Incorporation of lactate or glucose into triglycerides was relatively low, and since no fatty acid synthase (FAS) activity could be detected, probably represented chain elongation or reesterification.
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The influence of some serotoninergic agents on nitrazepam-induced sleep was studied in 5-8-day-old chicks. Nitrazepam (0.4-51.2 mg/kg) induced behavioural sleep in chicks dose-dependently. 5-Hydroxytryptamine (5-HT; 10-20 mg/kg) hypnotised young chicks. Similarly, 5-HT (5-20 mg/kg) shortened the onset and significantly prolonged the duration of nitrazepam-induced sleep in chicks and increased the proportion of chicks that were hypnotized by nitrazepam; these effects were dose-dependent. 5-Hydroxytryptophan (5-HTP; 2-8 mg/kg) did not induce sleep but dose-dependently shortened the onset and profoundly prolonged the duration of nitrazepam (1.6 mg/kg)-induced sleep. Cyproheptadine (0.5-2 mg/kg) delayed the onset of nitrazepam sleep and reduced the proportion of chicks that were hypnotized by nitrazepam. Parachlorophenylalanine (PCPA, 200 mg/kg) completely blocked nitrazepam-induced sleep. Nitrazepam sleep was associated with synchronization of the electroencephalogram (EEG) of the hyperstriatum, optic tectum and pontine reticular formation. 5-HT synchronized the EEG of the hyperstriatum and the pontine reticular formation while the electromyograph (EMG) activity was profoundly reduced. These behavioural and electrocortical data suggest that 5-HT may be involved in nitrazepam-induced sleep in young chicks.
The behavioural effects of beta,beta'-iminodipropionitrile (IDPN) were studied in chicks and adult fowls. Repeated administration of IDPN (75 mg/kg) for 5 days induced behavioural changes in chicks and adult fowls characterized by excitation, choreiform head and neck movements and circling (ECC-syndrome). Both acute and chronic administration of IDPN induced EEG desynchronization, EMG activation and enhancement of photic-evoked response (PER) in the hyperstriatum and pontine reticular formation while a decrease in PER was observed in the optic tectum. d-Amphetamine (2.5-5 mg/kg), apomorphine (0.1-0.25 mg/kg), piribedil (2.5-5 mg/kg), atropine (2.5-5 mg/kg), hyoscine (2.5-5 mg/kg) and cyproheptadine (0.5 mg/kg) potentiated the circling and choreiform head and neck movements. These activities were antagonized by pimozide (1 mg/kg), physostigmine (0.5 mg/kg) and quipazine (2.5-5 mg/kg). The results suggest that dopaminergic, serotoninergic and cholinergic mechanisms may be involved in IDPN-induced behavioural effects in chicks.
Pituitary glands and hypothalami from broiler fowl heads were incubated alone or together with histamine, gamma-aminobutyric acid (GABA) or acetylcholine (ACh) as well as with catecholamines or neurotransmitter antagonists. Histamine and ACh stimulated, whereas GABA inhibited, the hypothalamus-induced release of prolactin, responses blocked by their specific antagonists. The dopamine antagonist pimozide, but not adrenergic (both alpha and beta), serotoninergic or cholinergic antagonists, prevented the actions of histamine and GABA. None of the antagonists except the cholinergic blocker, atropine, affected ACh-induced release of prolactin. Neither histamine nor ACh prevented inhibition of prolactin release by dopamine or stimulation of prolactin release by noradrenaline. GABA did not affect the response to noradrenaline. Furthermore, histamine, GABA and ACh had no effects on thyrotrophin releasing hormone-stimulated release of prolactin directly at the pituitary level. These results suggest that histamine and GABA affect prolactin release from chicken pituitaries in vivo by modifying the activity of the dopaminergic system. Acetylcholine may stimulate the secretion of prolactin releasing factor from the hypothalamus.
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The physiological responses of joint capsule sensory receptors in the ankle joint of the chicken were studied by recording the electrical activity from single sensory afferent nerve fibres dissected from the parafibular nerve. All units included in this study were sensitive to mechanical stimulation of the joint capsule and were classified with respect to nerve conduction velocity, receptive field size and response threshold. Rapidly adapting mechanoreceptors formed 23% of the receptors present in the sample and responded to the mechanical probe by giving a single response or a short burst of activity at the onset of stimulation. The majority of units identified showed a slowly adapting response and on the basis of conduction velocity were divided into group IV (CV 2.5 m/s), group III (CV 2.5-20 m/s) and those units conducting over 20 m/s. Group IV units had single spot-like receptive fields and mechanical thresholds ranging from 0.6 to 60 g. Group III units could be divided into two groups based on receptive field size. One group had spot-like receptive fields 1-2 mm in diameter, whereas in the other group the receptive fields were larger (over 2 x 3 mm). The large receptive field units had significantly faster conduction velocities, lower mechanical thresholds and steeper stimulus-response curves than small receptive field units. In response to movement of the joint very few of the receptors, whether rapidly or slowly adapting, were found to be excited by moving the joint by hand in the middle of its physiological range. The physiological properties of these avian mechanoreceptive fine afferent units suggest that while some are activated by normal joint movement and non-noxious local mechanical stimulation of the joint capsule, others have nociceptive functions. The receptors present in the ankle joint were correlated with the anatomical structures found in the avian joints and their physiological properties compared and contrasted to the joint receptors found in mammals.