On the eating habits of Chrotopterus auritus Australis, Thomas, 1905 (Mammalia, Chiropterea, Phyllostomidae)

Previous work suggests a primary vagal bradycardia during hypoxic excitation of the arterial chemoreceptors. In this study we examined whether tachycardia, resulting from withdrawal of vagal inhibition of the cardiac pacemaker, may also occur during hypoxia. Cats with cervical spinal section were ventilated with hypoxic gas mixtures or allowed to remain apneic in expiration while heart rate was continually monitored. During recovery from halothane anesthesia or following electrolytic midcollicular decerebration, the bradycardic response to hypoxic or asphyxic stimulation was reduced or was reversed to tachycardia. The extent of reduction or reversal of the bradycardia was positively correlated with the level of the arterial pressure which was adjusted by either hemorrhage or infusion of phenylephrine. These findings indicate a tachycardic component of the vagal response to hypoxia, integrated in the pontomedullary region of the brainstem and resulting from interaction between the chemoreceptor and baroreceptor reflexes.     

Effect of electric stimulation rate on the indicators of systolic and diastolic activity of the left ventricle

The interrelationship of the indices of the systolic and diastolic myocardial activity with reference to the cardiac contractions rate was studied in acute experiments in isolated feline hearts. The study had demonstrated that moderate tachycardia (a 30% increase of the cardiac contractions rate) produced a beneficial inotropic effect, and increased the diastolic compliance of the myocardium. Severe tachycardia (a 80--100% increase of the contractions rate) produced a negative inotropic effect decreasing the myocardial compliance. Proceeding from the obtained results a conclusion is drawn that the cardiac contractions rate is an important factor in the regulation of not only the systolic, but also the diastolic myocardial activity.     

Structure of afferent flow in a cutaneous nerve during painful and non-painful mechanical stimulation of cat skin

Using the colliding impulses method, a quantitative characteristic of afferent flows encoding signals from a receptors totality is given. The frequency spectrum of impulsation in the cutaneous nerve, relative quantity of active A-, Adelta- and C-fibres, and their distribution by impulsation frequency under skin stimulation with pins and needles are found. The afferent impulse flow registered in the nerve under pinning of skin is characterized by a high density determined by the quantity of excited fibres and their impulsation frequency. Nonmyelinated fibres directly excited under painful stimulation generate high frequency impulsation due to which the flow density in the nerve increases. The quantity of active myelinated fibres and the frequency of their impulsation under pricking do not increase considerably in comparison with the same characteristics under unnoxious stimulation of cutaneous receptors.     

Participation of individual brain regions in the development of acute prolapse of the brain

Acute experiments were conducted on cats; the stereotaxis method was applied to search for morphological formations whose stimulation led to acute brain prolabination. This effect resulted from stimulation of the area hypothalamic lateralis, zona incerta, zonae H1 and H2, parafascicular, interstitial, and interpeduncular nuclei, and nucleus Darkschevitch. Against the background of the histological picture of acute prolabination, signs of brain edema and swelling were revealed in stimulation of the area hypothalamica lateralis, zone incerta, zonae H1 and H2.     

Radiation-induced chromosomal aberrations in human lymphocytes. I. Dependence on the dose of gamma-rays and an anomaly at low doses

Cultures of human lymphocytes obtained from blood of healthy adult donors were irradiated with different doses of 60Co gamma-rays and the irradiated cells were analysed in metaphase 50 h after irradiation. The effect (total yield of aberrations of chromosome type, or total yield of exchange type aberrations) produced by the lowest dose (5 rad) appears to be statistically significant in a sample of 1500 cells. In the usual dose range (25-400 rad), both parabolic and linear-quadratic equations give a satisfactory fit of experimental data (dicetrics, fragments, or all aberrations of chromosome type). Low doses of gamma-rays, however, produced more aberrations than expected, if one extrapolates dose-effect curves from higher doses. Both relations should be considered, therefore, merely as empirical equations. Dicentrics show at low doses (10-30 rad) a plateau which appears to be statistically significant. Some indications are obtained that the total number of chromosome-type aberrations is a more reliable criterion of cytogenetic damage than the usually accepted yield of dicentrics and rings.     

Annular Ring Microstrip Antennas for Millimeter Wave Applications

This work presents a fullwave analysis for annular ring microstrip antennas on uniaxial anisotropic substrates. The effect of the anisotropic substrates on the antenna performance at the millimeter wave band is investigated. The analysis is performed in the Hankel transform domain using Hertz vector potentials and Galerkin Method. Numerical results are presented for the antenna main characteristics such as resonant frequency and radiation pattern.