Minoxidil reduces pulmonary vascular resistance in dogs and cattle

Minoxidil has a direct dilator effect on the systemic arterial smooth muscle. It is potentially an important drug in the treatment of systemic hypertension, especially when combined with beta blockade, which is used to control the associated tachycardia and increase in cardiac output. However, recent observations have suggested that minoxidil might cause pulmonary hypertension. Consequently, we examined the acute effect of monoxidil and propranolol, separately and in combination, on the pulmonary vasculature of the anesthetized dog and the awake calf during normoxia and hypoxia. In both species minoxidil reduced pulmonary vascular resistance. In the dogs this appeared to be the result of a direct action on the pulmonary vascular smooth muscle and in the cattle it was secondary to beta-receptor stimulation. Propranolol alone in the cattle increased the pulmonary pressor response to hypoxia. While we have not examined the possibility that chronic administration of minoxidil might cause pulmonary hypertension by some other mechanism, our acute studies suggest that it reduces, rather than increases, pulmonary vascular resistance. Furthermore, there seems to be a species difference in the mode of its action in dogs and cattle.     

Double-blind evaluation of 5-mum final filtration to reduce postinfusion phlebitis

A double-blind study was conducted to determine the effectiveness of 5-mum final filtration in preventing phlebitis secondary to intravenous fluid administration. An experimental administration set which contained distal portion of the tubing was used for patients randomly assigned to receive filtered intravenous solutions. An identical administration set minus the filter was used in the control group to allow double-blind evaluation of the injection site. Data were collected on 49 patients whose average age was eight years and one month. Most patients had a primary diagnosis of acute lymphocytic or myelocytic leukemia or solid tumor. The patients' injection sites were evaluated daily for clinical findings of phlebitis (erythema, induration, heat, erythematous-streak and discomfort). The incidence of phlebitis was significantly lower (p less than 0.01) in patients receiving filtered intravenous solutions. For the patients in this study, filtration of intravenous fluids with a 5-mum mesh filter appeared to be a feasible and effective means of reducing postinfusion complications.     

Kinematics of locomotion by cats with a single hindlimb deafferented

1. Cinematographic measurements were made of stepping by cats on a motor-driven treadmill, both normally and 2-3 wk after deafferentation of the LH (left hind) limb. 2. After surgery, rhythmic cycling of the LH limb was blurred whether the leg was dragged, as by some cats, or if it was lifted from the surface, as by others. 3. Interlimb coordination was also blurred with respect to normal, although distinct rhythms were still seen. The RH (right hind) limb descended prematurely and, in the walk, had a prolonged stance phase. The interval between touchdowns of hind- and forelimb on the left side no longer equaled that interval on the right side. 4. As is true for a normal cat, if the LH-deafferented animal stumbled, relatively normal single and interlimb cyclings were regained after several strides. 5. By kinematic analysis, force deficits were found in the deafferented LH limb both during the stance, when extensors should be most active, and the swing, when the limb failed to attain a normal position above the surface of the belt. Weight bearing by the LF (left fore) limb was altered in some animals. 6. At high speed, mean LH stance duration failed to decrease in the normal fashion. Inter-limb timings were reset to greater extent than in low-speed walking, as if the LH limb was being used only minimally. 7. It was concluded that both rhythm and force were impaired in the deafferented limb and also in the three intact limbs, whose weight bearing had to compensate for LH weakness. The changed mechanical demands after surgery were probably met by interactions between the remaining afferent input and central pattern generators so as to secure fairly effective and expedient locomotion.     

Differential effect of right and left vagal stimulation on right and left circumflex coronary arteries

In anasthetised, closed-chest dogs in complete heart block that were paced at a ventricular rate of 100 beats/min, vagal stimulation increased right coronary (RC) flow by 46% and conductance by 59%, but these increases were less than those measured in the left circumflex coronary (LCC) flow (66%) and conductance (80%). Both the right and left vagus nerves affected RC and LCC flow, the left vagus having the greater effect. The response to vagal stimulation is not limited at higher ventricular rates.     

Effects of radiation therapy on growing long bones

Characteristic radiographic changes were seen in six of 14 children who received radiation therapy to the epiphyseal plate of a long bone. These changes, which include metaphyseal sclerosis, metaphyseal fraying, and epiphyseal plate widening, resemble rickets. In three patients, these changes were followed by development of a broad metaphyseal band of increased density. The absence of metaphyseal changes may indicate sterilization of cartilage cells and may be predictive of significant limb shortening.