Some endocrine influences on hypothalamic hyperphagia

After combined ovariectomy and adrenalectomy, rats with ventromedial hypothalamic lesions did not express hyperphagia if offered standard pelleted diet. A high-fat diet or a liquid diet would induce them to do so, however, Therefore, adrenal (and ovarian) secretions are not necessary for the expression of hyperphagia. When hyperphagia occurred, it showed the characteristic stasis in body weight at an elevated level. This implies that even after ovariectomy, adrenalectomy, and damage to the brain, the capacity for weight regulation survives.     

Mechanism of hypothalamic influences on bile formation]

Acute experiments were conducted on male rats; it was revealed that electrical stimulation of the nuclei of the anterior hypothalamus led to reduction of choleresis and to a fall of the potassium content in the bile, increase of permeability of the connective tissue stroma of the liver and of cell membranes of hepatocytes. Stimulation of the posterior hypothalamic nuclei induced an increase in choleresis, of the concentration of potassium ions and cholates in the liver, and also of the cholinesterase activity in the serum and homogenates of the liver. Permeability of connective tissue structures of the liver and of the intercellular spaces of hepatocytes proved to fall. The influences of the hypothalamus on bile formation included a change in the functional activity of hepatocytes and of the production of a fluid fraction of the bile.     

Corticofugal influences on pontine unit activity

Unit responses of the nuclei pontis (NP) and reticular pontine nuclei (RPN) to stimulation of the frontobasal cortex (proreal, orbital, and basal temporal regions) and of the dorsal hippocampus were studied in cats. Stimulation of the various cortical structures was found to induce phasic and (less frequently) tonic responses in neurons of NP and RPN. The main type of unit response in RPN was primary excitation, whereas in NP it was primary inhibition. The largest number of responding neurons in the pontine nuclei was observed to stimulation of the proreal gyrus. In the cerebro-cerebellar relay system neurons of the reticular tegmental nucleus and ventromedial portion of NP showed the highest ability to respond. In the oral and caudal reticular pontine nuclei the regions of predominant influence of cortical structures were located in zones of these nuclei where neurons with rostral and (to a lesser degree) caudal projections were situated.M. Gorkii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 12, No. 4, pp. 358–367, July–August, 1980.     

Anesthesia effect on rabbit hypothalamic neuron impulse activity

Neuronal impulse activity in the thermoregulation center in the anterior and posterior sections of the rabbit hypothalamus was studied in chronic experiments and in intravenously injected anesthetics (urethane and chloralose). Anesthesia decreased the neuronal firing rate, changed the impulse activity pattern, and decreased the number of neurons responding to skin thermal stimulation. These changes were most pronounced in the posterior hypothalamic section.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 574–579, September–October, 1991.     

Role of sensory signals in the development of cortical influences on hypothalamic structures]

Neuron discharges of the hypothalamic ventro-medial and posterior nuclei were registered in immobilized cats during electrical stimulation of the ipsi- and contralateral nerves of the brachial plexus, the 1st and the 2nd somatosensory regions (SI and SII) and the visual regions of the cortex and the reticular formation (RF) of the mesencephalon. A reversible cold block of the SI and SII failed to change the effect of the nerve stimulation. Stimulation of the postero-ventral thalamic nucleus did not change the initial activity of the hypothalamic neurons and gave rise to no neuron activity that appeared on stimulation of the SII. A conclusion was drawn that cortico-hypothalamic influences that appeared on stimulation of the nerves and the postero-ventral nucleus of the thalamus were pronounced weakly.     

Environmental influences on the activity of captive apes

Forty-one zoological gardens in seven European countries were visited to investigate activity level in captive environments for great apes. Forty-three groups of gorillas and 68 groups of orangutans were observed. The seven factors quantified for each of the environments were size of the enclosure, usable surface area, frequency of feeding, number of animals, and number of objects (stationary, temporary, and movable). Activity level of each group was measured by instantaneous scan sampling for one hour on two consecutive days. For both species, the factors most highly related to activity level were number of animals, and stationary, temporary, and movable objects. The usefulness of these variables for predicting group activity level was different for the two species, however. Factors important for gorillas were stationary and temporary objects, while stationary and movable objects were significant for orangutans. These findings suggest that objects within environments may be more important for captive apes than the size or construction of the enclosure. Also, the types of objects that need to be included in environments may be related to the natural behavior of the individual species.     

Pharmacological effects on acetylcholinesterase activity of hypothalamic and cortical structures

The kinetics of cholinesterase activity in the sensomotor cortex, hippocampus, and anterior hypothalamus was determined in 93 rats by an electrometric method using an automatic recording system. The localization of acetylcholinesterase in the cell structures was revealed histochemically. In the control animals acetylcholinesterase was distributed unevenly among these structures. In rats aged 1 month its activity was higher in the sensomotor cortex. At later age periods (6, 12, 24 months) the acetylcholinesterase activity was highest in the posterior hypothalamus. While the unevenness of distribution of this substance continued to be observed, the level of its activity fell with age. A redistribution of acetylcholinesterase activity compared with the control was found 15 min after subcutaneous injection of adrenalin (300 µg/kg). Its activity was maximal in the anterior hypothalamus. The acetycholinesterase activity in all these structures was lowered after subcutaneous injection of chloral hydrate (300 mg/kg). Meanwhile the differences in the character of its distribution between the individual structures disappeared. These results indicate definite correlation between the functional state of the CNS and the distribution of acetylcholinesterase activity in the brain structures studied.A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 1, pp. 47–53, January–February, 1973.     

Phylloplane microfungal metabolite influences activity of RuBisCO

The phylloplane microbes are known to affect systemic acquired resistance in plants against a broad spectrum of pathogens. The influence of phylloplane microbes and their metabolites on physiology and biochemistry of plants is well-documented but their effect on the physiology and functioning of chloroplasts and mitochondria is not well understood. The present study was conducted to understand the impact of metabolite of a dominant phylloplane microfungi (Fusarium oxysporum) isolated from the phylloplane of Lycopersicon esculentum on activity of RuBisCO. Activity of RuBisCO (EC 4.1.1.39) in chloroplasts of fungal metabolite treated and untreated eight-week old tomato plants were studied. Significant increase in the activity of RuBisCO (P???0.01), isolated from plants inoculated with the fungal metabolite was observed. The fungal metabolite could elicit the enzyme activity by about two folds (P???0.05) within 72–96?h of treatment of tomato plants. The result demonstrates that probably phylloplane microfungi and/or their metabolites influence the photosynthetic efficiency of plants.     

Characterization of corticotropin-releasing factor activity from sheep hypothalamic extracts

Sheep hypothalamic extracts, chromatographed on Sephadex G-25, revealed 3 peaks with CRF biological activity. The first eluting peak co-chromatographed with ACTH. After separation from ACTH by CMC, this CRF peak contained vasopressin immunoactivity and pressor activity. The second eluting CRF peak also contained vasopressin immunoactivity and pressor activity and was found to represent the presumed authentic vasopressin. The third eluting CRF peak contained vasopressin immunoactivity but no pressor activity. Further processing of this putative CRF on Sephadex G-10 resulted in a 500-fold purification. The material is inactivated by proteolytic enzymes. We tentatively conclude that this CRF is a peptide with a molecular weight of 700–1000 and that it shares common antigenic determinants with vasopressin.     

Laryngeal influences on breathing pattern and posterior cricoarytenoid muscle activity

Receptors responding to transmural pressure, airflow, and contraction of laryngeal muscles have been previously identified in the larynx. To assess the relative contribution of these three types of receptors to the reflex changes in breathing pattern and upper airway patency, we studied diaphragmatic (DIA) and posterior cricoarytenoid muscle (PCA) activity in anesthetized dogs during spontaneous breathing and occluded efforts with and without bypassing the larynx. Inspiratory duration (TI) was longer, mean inspiratory slope (peak DIA/TI) was lower, and PCA activity was greater with upper airway occlusion than with tracheal occlusion (larynx bypassed). Bilateral section of the superior laryngeal nerves eliminated these differences. When respiratory airflow was diverted from the tracheostomy to the upper airway the only change attributable to laryngeal afferents was an increase in PCA activity. These results confirm the importance of the superior laryngeal nerves in the regulation of breathing pattern and upper airway patency and suggest a prevalent role for laryngeal negative pressure receptors.