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101.
Anterior pituitary glands of intact diestrous and gonadectomized female rats were incubated with a supramaximally active dose of LH-RH. Puromycin (P) and cycloheximide (C) did not consistently affect the LH release from glands of ovariectomized rats. In intact rats, LH release induced by LH-RH occurred in two phases, an initial one (relatively slow rate of release) and a secondary one (high rate of release). P and C had no effect on the initial phase, but prevented the secondary one. Pre-incubation with LH-RH prevented the effect of P and C added after 4 hours. Since P and C did not affect the total amount of LH present in media and hypophyses, the LH-released during the P- and C-sensitive phase is not newly formed LH. It is concluded that LH-RH induces the synthesis of protein which is necessary for LH-RH-induced LH release. The initial phase of LH release is made possible by protein already present in the glands at the beginning of the experiment. 相似文献
102.
A chronic 90-day inhalation of polyethylsiloxane fluid at a concentration of 10 and 2 mg/m3 produced local irritation and general toxic effect on rats. Local irritation induced catarrhal-desqueamative tracheitis that was accompanied by a microfocal interstitial process in the lungs. The general toxic effect gave rise to interstitial myocarditis that was followed by focal cardiosclerosis and dystrophic lesions of vascular walls and areas of liver parenchyma. Changes in the thymus-lymph system and adrenal structure suggested prolonged protective tension of the animal body. A chronic 90-day inhalation of polyethylsiloxane at a concentration of 0.2 mg/m3 brought about no pathological lesions in the microstructure of animal organs. 相似文献
103.
A recent paper discussed the way in which microprocessors are being used for teaching computer science at Strathclyde University. This article discusses an alternative system being implemented at Rhodes University. The chief difference between the two is the attitude towards breakdowns. 相似文献
104.
C Lechi GP Rasi G Covi E Arosio G Zannini A Lechi 《Canadian Metallurgical Quarterly》1976,25(7):236-238
10 Patients with positive orthostatic dysregulation were investigated with regard to venous capacity, heart frequency and arterial blood pressure both lying down and sitting up. The venous capacity was reduced by 14% after dehydroergotamine (DHE) in the lying position, which is an expression of increased venous tone. There is no change in venous capacity following the administration of beta blockers in the lying position. Under orthostatic conditions beta blockers bring about an approximate normalization of the venous capacity reaction, whereas the abnormal response following placebo administration is only slightly altered by DHE. 相似文献
105.
1. Cross-correlation analysis has been used to quantify the responses of cat soleus tendon organs to repetitive twitch contractions of: (a) different motor units within the muscle, (b) single motor units at different muscle lengths, and (c) single motor units when the pulse-train pattern of stimulation delivered to the motor unit axon was altered. 2. Ib afferents were observed which responded to each of several hundred successive motor unit twitches with identical numbers of spikes and with relatively invariant latencies. 3. The present results show that tendon organs are sensitive to subtle alterations in motor unit twitch wave form and amplitude, and that this sensitivity is reflected in the precise timings of their afferent discharge. 4. Examination of these tendon organ responses indicates that the forces produced by single motor units couples to the receptor capsule are well above threshold. Calculations based on these results, and earlier soleus motor unit and muscle fibre data, suggest that the absolute force threshold for tendon organs may be as little as 4 mg, which is less than the estimated minimum twitch force generated by individual soleus muscle fibres. 5. Considering the number of tendon organs in a muscle, and the likelihood that every motor unit is connected with at least one receptor, the sensitivity of tendon organs ensures that every twitch of every motor unit will be reflected in the population of afferent signals projecting to the spinal cord. 相似文献
106.
In the light and electron microscopes, long tubular bones of Wistar rats that were flown for 22 d onboard the Cosmos-605 biosatellite and were exposed to a ground-based simulation experiment were examined. About half of the flight rats showed osteoporosis of metaphyses which was usually combined with a decrease of the mass of the primary spongiosa in the vicinity of the epiphyseal cartilaginous plate. This gives evidence that the growth of the bones could have been inhibited in flight. The light and electron microscopy of bones of flight rats revealed wide osteocyte lacunae which could have been produced by perilacunar osteolysis. In the simulation experiment, reduction in the metaphyseal spongiosa occurred only in one-third of the rats and was less pronounced than in flight rats; no decrease of the mass of the primary spongiosa near the cartilaginous plate was noted. Histological investigation of bones 27 d postflight demonstrated that that time period was not enough to eliminate all the changes in the bones tested. 相似文献
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