Efficacy of an iodine backflush for preventing new intramammary infections

Efficacy of an iodine backflush system for reducing new intramammary infection was tested in two 11-wk trials. Forty cows in each trial were paired by breed, age, stage of lactation, and intramammary infection status. Each pair was assigned randomly either to a group milked with clusters that were reverse flushed with water, 25 ppm iodine, water and air or to a group milked with clusters receiving no backflush treatment between cows. Backflushing clusters reduced infections caused by Corynebacterium bovis and coagulase-positive staphylococci in both trials. However, backflushing clusters produced no clear advantage for reducing new infections with coagulase-negative staphylococci, Gram-negative bacilli, or streptococci (species other than Streptococcus agalactiae). No differences in somatic cell counts between experimental groups were observed. Teat cup liners and teat ends were swabbed after 120 and 1200 milkings/liner. Total microbial counts were significantly greater for liners that were not backflushed than from backflushed liners at each swabbing. However, no differences were significant between groups for mean teat end microbial counts in either trial.

Mechanism of death in massive fluid infusion

To determine the effects of infusion of large volumes of crystalloid, a series of dogs was subjected to intravenous injection of oleic acid and moderate hypovolemic shock for 1 hour. They were then resuscitated with 50 cc/kg of Ringer's lactate over 1 hour in one group and 2 hours in the other. Eight of nine receiving the fast infusion died during the first 2 days, and seven of eight receiving the slow infusion lived for the full 3 days of the study. The dogs that died all had large intrapulmonary shunts and gross pulmonary edema at autopsy. Both groups received the same total amount of fluid. No differences in vascular pressure or cardiac function large enough to explain the differences were found. The critical difference was the rate of fluid infusion. The high-permeability pulmonary edema appears to have been aggravated by a transitent pulmonary overperfusion induced by fast infusion of fluid.

Fluid overload and post-traumatic respiratory distress syndrome

A series of dogs was given massive fluid infusions at two dose levels, 60 cc/kg and 100 cc/kg. The dogs were prepared in three ways: shock induced by bleeding; intravenous injection of oleic acid; and combined oleic acid injection and shock. The studies showed that type of injury was a more important determinant of lung dysfunction than the fluid dose. Shock animals were not hurt by fluid infusion; in oleic acid-injected dogs, the fluid infusion magnified the effect of oleic acid. When shock, oleic acid, and high fluid dose were combined, all animals died. The animals that died had high pulmonary artery diastolic pressures.

The effects of carbon dioxide on pulmonary mechanics in hyperventilating, normal volunteers

Transpulmonary pressure, air flow, and end-tidal carbon dioxide levels were measured in normal human volunteers during hypocapnic, eucapnic, and hypercapnic hyperventilation. Respiratory rate and tidal volumes were well matched at a minute ventilation of 52 L. on three inspired gas mixtures: 21 per cent oxygen and 79 per cent nitrogen; 5 per cent carbon dioxide, 21 per cent oxygen and 74 per cent nitrogen; and 12 per cent carbon dioxide, 21 per cent oxygen and 67 per cent nitrogen. Respiratory rate, tidal volume, lung compliance, resistance, and resistive work per liter were calculated with a digital computer. In 13 experiments in 7 normal volunteers, no net bronchoconstriction or bronchodilatation was observed when eucapnic hyperventilation was compared to hypocapnic or hypercapnic hyperventilation. During hyperventilation of this degree, a change in bronchomotor tone owing to alteration in arterial or alveolar PCO2 either does not occur or else is masked by other reflexes or mechanical factors acting on the bronchi.

Solar Cycle Variation of Exospheric Temperatures Mars and Venus: A Prediction for Mariner 6 and 7

Calculations have been made to determine the effects of variations in the extreme ultraviolet solar radiation on the upper atmospheres of mars and Venus. The results indicate that the exospheric temperature from 300 degrees K to 600 degrees K during the solar cycle, with a corresponding range on Venus of 450 degrees K to 850 degrees K. At the present time, the temperature of the Martain exosphere should be approximately 500 degrees K.