Effect of 4-aminopyridine on cardiovascular functions in the dog

The drug 4-aminopyridine (4-AP) at a dose of 0.2 mg . kg-1 body weight intravenously is an effective antagonist of non-depolarizing neuromuscular blockade. We studied its cardiovascular effects in the canine heart using a right-heart bypass with extracorporeal circulation in seven dogs. This study demonstrates that 4-aminopyridine significantly augments arterial blood pressure, left ventricular dp/dt maximum, as well as left ventricular pressure at dp/dt mx. The highest values were obtained between two and 20 minutes after administration of 4-AP. Left ventricular end-diastolic pressure diminished slightly, but this was not statistically significant. Although the exact mechanism of action of 4-AP is not known, its positive inotropic effects may be of value in the reversal of non-depolarizing neuromuscular blockade in patients with impaired myocardial function of diverse aetiologies and it would be contra-indicated in patients with arterial hypertension and/or coronary artery disease.

The effect of tonsillectomy on impedance audiometry

In an experimental group of 22 patients undergoing elective tonsillectomies and having normal preoperative middle ear function, there is a significant development of abnormal tympanogram types, loss of crossed acoustic reflexes, and decrease in middle ear compliance on the first postoperative day when compared to a control group. Postoperative recovery of middle ear function begins at one week and is usually completed by one month. The loss of acoustic reflexes occurs in those patients with extreme changes in compliance and abnormal tympanogram types. The authors postulate that these changes in middle ear function in the immediate posttonsillectomy period might be due to the surgical disturbance of the peritubal lymphatic drainage, causing engorgement of the tympanic and tubular mucosa; and to abnormal swallowing with impaired coordination of the nasopharyngeal and tubal musculature. These data are helpful in investigating the tonsillar effect on middle ear function and disease.

Disposition of cefoxitin in the elderly

The pharmacokinetics off cefoxitin were studied after a single i.v. and i. m. dose of 15 mg/kg of cefoxitin to 15 younger people (15-55 years) and to 16 geriatric patients (66-94 years). The kinetics of the antibiotic follow an open two-compartment model for both administration routes. After i.m. administration of the antibiotic, there are modifications in the distribution with respect to i.v. administration, and there is a decrease in beta K21 and as a consequence, an increase in Vp. In geriatric patients, pharmacokinetic modifications take place with respect to those recorded in the younger people in both administration routes, there being a decrease in the following pharmacokinetic parameters: alpha, beta, K12, K21, K13 and Clp, together with an increase in the apparent distribution volume Vdss. A linear relationship has been established between the constant beta and the age of the patient. In spite of the pharmacokinetic modifications observed as a function of age, given the wide safety margin of the antibiotic, it is not necessary to modify the dosage regimen of cefoxitin in geriatric patients.

Nuclear processing of viral high-molecular-weight RNA in cells infected with herpes simplex virus type 1

Nuclear RNA isolated from cells infected by herpes simplex virus type 1, strain F, was fractionated on formamide-sucrose gradients into two major classes, greater and less than 45S. These two classes of labeled nuclear RNA were hybridized to viral DNA fragments generated by digestion with the restriction enzymes HindIII and BglII. Early in infection, only a few DNA fragments hybridized to RNA, with slight differences between the two classes. Late in infection, all DNA fragments hybridized, showing that all viral RNA was present in large precursor molecules greater than 14 kilobases. The fragments that correspond to late gene products hybridized more of the small RNA than the large RNA. This suggests that the mRNA corresponding to late genes accumulated after the large precursors have been cleaved. Large (greater than or equal to 45S) and small (< 45S) nuclear RNA and cytoplasmic RNA from cells late in infection were hybridized in excess to in vitro-labeled HindIII M and L fragments. More than 50% of the HIndIII M fragment annealed with the large nuclear RNA, but only 36% of it annealed with the cytoplasmic RNA. The HindIII L fragment hybridized large nuclear RNA and cytoplasmic RNA to the same extent (30% and 26%). These results suggest that RNA complementary to the HindIII M fragment, which is the template for immediate early polypeptides, was regulated in the nuclei at the posttranscriptional level. This seems to suggest that temporal regulation of RNA cleavage occurs in the nucleus.

[Postoperative haemodynamic evaluation of myocardial protection by physicochemical cardioplegia. Hyperkaliemic, hyperosmolar and acid solution at 4 degrees C (author's transl)]

Myocardial protection by a combination of cardiac hypothermia and chemical cardioplegia (high concentration of K+ and Mg++, hyperosmolarity, acid pH), was studied during 20 valve replacements. Essentially assessed on the basis of repeated measurements of postoperative cardiac output, the results were compared with those obtained previously using local hypothermia only (20 patients) and hypothermic cardioplegia using Ringer Lactate (20 patients). Analysis of haemodynamic data, which thus involved 60 patients, indicated the superiority of physicochemical cardioplegia, and this for clamping periods of up to 2 hours, but also showed the desirability of changes in the protection protocol during the ischaemia phase and during reperfusion which might improve the results.

Irradiation lesions of the growth plate in rabbits

The effects of gamma irradiation on the growth plate have been studied in nineteen rabbits with a 1,000 rads/skin dose. The rabbits were killed after one to ninety days. The growth plates were studied by microscopic examination, thymidine-H3 autoradiography, and fluorescence with radiographic measurement. Changes were already detected after twenty-four hours at the cell mitosis level, which showed the sensitiveness of the chondrocyte itself. The lesions were clearly seen with the optical microscope after seven days, and they were most advanced between the fourteenth and twenty-first day after irradiation. Regeneration of the cartilage began in the fourth week and the histological appearance became normal after seventy days. Fluorescence with tetracycline showed a temporary retardation of growth, with consequent shortening of the affected limb.

Lung lamellar bodies lack certain key enzymes of phospholipid metabolism

Palmitoyl CoA-glycerol-3-phosphate acyltransferase, phosphatidate phosphohydrolase, and phospholipase A were assayed in subcellular fractions of rat lung, including lamellar bodies, the putative site of storage and secretion of lung surfactant. The specific activity of each of these enzymes in lamellar bodies was relatively low and could be entirely accounted for by a small contamination of the lamellar bodies fraction by microsomes, as quantitated by the presence of the microsomal marker reduced triphosphopyridine nucleotide cytochrome c reductase. These data indicate that lamellar bodies are not the site of synthesis of the lipid component of pulmonary surfactant by pathways involving these enzymes.

Inguinal hernia: a common problem of premature infants weighing 1,000 grams or less at birth

Thirty percent of 37 consecutive surviving premature infants weighing 1,000 gm or less at birth were noted to develop inguinal hernias. Incarceration occurred in two infants. One infant suffered a cardiac arrest during repair of the hernia. In view of the increased survival now being reported in these tiny prematures, it is important that physicians recognize the high incidence and potential hazards of this congenital anomaly in surviving premature infants weighing 1,000 gm or less at birth.