Exercise tolerance at 4 and 6 ATA

Seven normal male subjects performed 5-min bicycle exercise ranging from 50-100% maximum oxygen uptake at 4 ATA and three were also studied at 6 ATA. At all pressures, the subjects breathed 0.2 ATA O2 plus nitrogen. All subjects were able to perform maximum work at all pressures. No pressure-dependent variations in heart rate, O2 uptake, or CO2 output were noted. At both 4 and 6 ATA, ventilation was decreased at exercise levels greater than 80% maximum O2 uptake. The magnitude of the decrease was not great, however, and signified only minor CO2 retention. In some instances exercise ventilation closely approached the 15-S maximum breathing capacity and these subjects noted severe dyspnea, possibly due to dynamic compression of large airways. In three subjects, respiratory frequency was measured as well as minute ventilation; this relationship did not change with depth. Subjects performing heavy exercise at 6 ATA noted disturbances of consciousness, presumably due to N2 narcosis.     

Effect of length of gestation on maternal cellular immunity to human trophoblast antigens

Maternal lymphocyte reactivity to human trophoblast antigens was studied in placentas of gestational ages 8 to 14 weeks and 32 to 34 weeks, respectively. Significant trophoblast lysis became apparent after 24 hours' incubation in the latter case compared with a time lag of 72 hours in the terminated gestations. Maternal cellular immunity, therefore, was not detected during the first 3 1/2 months of pregnancy, but was detectable by the time of parturition. The possible significance is discussed with respect to the antigenic stimulus and survival of the fetal allograft.     

Discovery of insect anti-juvenile hormones in plants.?2U

Two simple chromenes with anti-JH activity have been isolated and identified from the bedding plant Ageratum houstoianum. By contact and fumigation these compounds induce precocious metamorphosis and sterilization in several hemipteran species of insects. Certain holometabolous species are sterilized, forced into diapause, or both. Each of these biological actions is equivalent to removal of the corpora allata, which produce the JH's, and is reversible by treatment with exogenous JH. Thus, the action of these compounds is to stop the production or depress the titer of the JH's. To our knowledge, this is the first discovery of anti-JH, and we hope it will guide the way to the emergence of a fourth generation of safe and insect-specific pesticides.     

The acute effects of amitriptyline, iprindole and trazodone on blood pressure and heart rate in rats

The cardiovascular effects of the tricyclic anti-depressant amitriptyline, a monoamine uptake inhibitor, and iprindole and trazodone, two novel anti-depressants of unknown mechanism, were monitored in urethane anesthetized rats following intravenous (IV) or intracerebroventricular (IVT) injection. Amitriptyline (2 mg IV or 0.25 mg IVT) produced hypotension that might reflect an action of norepinephrine on the anterior hypothalamus. Iprindole (2 mg IV) produced hypertension and (0.25 mg IVT) tachycardia that is consistent with a partial beta-agonist mechanism. Trazodone (1 mg IV or 0.25 mg IVT) produced hypotension and bradycardia that is consistent with the activation of noradrenergic neurons in the anterior hypothalamus perhaps as a result of trazodone acting on presynaptic alpha 2 receptors or on presynaptic serotonin receptors to increase the release of norepinephrine. All three of these anti-depressants have the potential to precipitate cardiovascular complications, particularly in patients with pre-existing cardiovascular abnormalities.