Processing and secretion of alpha-mannosidase forms by Dictyostelium discoideum

We are studying the biosynthesis and processing of acid hydrolases from Dictyostelium discoideum. We prepared antibody to highly purified alpha-mannosidase from the spent medium of stationary phase cultures. It precipitated alpha-mannosidase but not beta-hexosaminidase, alpha-glucosidase, beta-glucosidase, or any of the major proteins in cell lysates or secretions. The antibody precipitated a 150,000- and an 80,000-dalton protein in addition to mature forms (56,000-62,000 daltons) of alpha-mannosidase subunits. The possibility that the 150,000 and 80,000 dalton bands were precursors of mature forms was evaluated by pulse-chase experiments. Following a 20-min pulse labeling period, only the 150,000-dalton protein was detected in the immunoprecipitate. Apparent conversion of this form into 80,000- and 60,000-dalton forms was observed following a 30-min chase. During the next 90 min continued accumulation of 60,000-dalton and appearance of 62,000-dalton forms was observed while the 80,000-dalton form disappeared. The fate of the 150,000-dalton precursor depended on nutritional conditions. In cells conditioned with fresh growth medium intracellular processing predominated. Less than 10% of either the precursor or mature forms was secreted in 8 hr. However, when cells were shifted from growth medium to starvation buffer, secretion of precursor soon predominated. After a 1-hr lag period, cells began secreting 150,000-dalton precursor into the medium. After 4 hr in starvation buffer, the rate of secretion of 150,000-dalton form increased by at least an order of magnitude while processing was markedly diminished. This may be a case where nutritional conditions control the sorting of an acid hydrolase precursor.

Domestic breeding of patas monkeys (Erythrocebus patas)

Two reproductive strategies were used in the management of a patas monkey (Erythrocebus patas) breeding colony. The first strategy involved placement of all animals into one-male harem units for breeding, parturition, and infant rearing. The second strategy involved a reduction in the number of males, movement of pregnant females to individual cages, and formation of new groups with females and neonates. The second strategy resulted in an increased percentage of females having successful births and an increased survival of neonates. The percentage of females becoming pregnant did not change.

Cimetidine impairs the elimination of theophylline and antipyrine

In 7 healthy subjects theophylline and antipyrine elimination were determined before and during a course of oral cimetidine in a dose of 1 g/day. Plasma clearance of theophylline was reduced from 71.2 +/- 10.1 ml/min to 56.0 +/- 18.5 ml/min and the plasma clearance of antipyrine from 53.7 +/- 14.2 ml/min to 48.1 +/- 11.7 ml/min. Elimination half-life of theophylline was prolonged from 5.1 +/- 1.6 to 8.1 +/- 1.4 h. All these changes were statistically significant. Volume of distribution of theophylline (31.7 +/- 8.4 L before and 39.2 +/- 5.6 L during cimetidine administration) and plasma binding of theophylline (44.7 +/- 3.8% before and 44.3 +/- 3.1% during cimetidine administration) were not significantly different. Similarly, volume of distribution of antipyrine (45.8 +/- 14.0 vs. 47.6 +/- 17.9) was not significantly affected by cimetidine administration. We conclude that cimetidine impairs the elimination of theophylline and antipyrine in healthy subjects.

Anaemia: a practical approach for nursing and paramedical specialties

Anaemia is only a symptom and not, in itself, a diagnosis. Its importance lies in the fact that it signals underlying disease which is often correctable. By definiton anaemia is a reduction in red cell mass and this is reflected in reduced haemoglobin, packed cell volume, or red cell count in the peripheral blood. To understand the mechanisms of its development normal blood formation must be briefly reviewed.

The role of continuous-flow blood fraction separators in clinical practice

Continuous-flow blood fraction separators facilitate the efficient exchange of large volumes of plasma or red cells and therefore have clinical application in the rapid correction of abnormalities located predominantly in either of these compartments. Plasmapheresis has been successfully used in managing 2 patients with previously refractory myasthenia gravis, in reducing the antibody titre in a rhesus-sensitized woman, and in diminishing anti-A titre in a patient requiring bone marrow transplantation from an ABO-incompatible but HLA- and MLC-identical sibling. Continuous-flow red cell exchange effectively reduced the haemoglobin S concentration in an individual with sickle cell disease prior to general anaesthesia and abdominal surgery. Complications were not encountered although the procedures were carried out repetitively over prolonged periods of time. All 5 patients tolerated their exchanges without discomfort. As with any new and expensive technique, caution should attend the introduction of continuous-flow plasma or red cell exchange into clinical medicine. Careful evaluation of the safety and the benefits is needed to establish perspective and to distinguish between established and developmental indications.

Effects of frontalis EMG feedback and reinforcement on frontalis EMG level

This experiment employed a between-subjects design (N = 40) to investigate the effects of feedback and reinforcement on the lowering of frontalis electromyographic (EMG) activity. The feedback and reinforcement manipulations were combined in a 2 x 2 factorial design and each subject underwent one baseline and two training sessions on three consecutive days. The analogue feedback signal was a 55 dB tone whose pitch varied as a function of EMG activity, while the reinforcement consisted of points which were exchangeable for money. The training sessions were each divided into 10 2-min baseline periods and 10 2-min trial periods. The results indicated that although analogue feedback did not result in lowered EMG levels, trial period EMG level was significantly lower than baseline level under conditions of reinforcement. These results pose problems for Budzynski and Stoyva's (1972) views concerning the therapeutic usefulness of frontalis EMG feedback training.

Cardiovascular effects of novel amphetamine analogs in anesthetized rats

In albino, adult Sprague Dawley rats, anesthetized with urethane intraperitoneally, the effects of the exo- and endo-isomers of 2-amino-5,8-dimethoxybenzonorbornene were studied on arterial blood pressure and heart rate. Both compounds produced an immediate rise in systemic arterial pressure followed by an immediate maximal depressor response. The depressor effect was sustained beyond 30 minute duration, but declined in intensity with time to nearly preinjection levels. Both compounds decreased heart rate in varying degrees. Evidence of marked bradycardia and onset of toxicity was observed at doses of 12.8 mg/kg (exo) and 19.2 mg/kg (endo). The biphasic response seen after intravenous injection of the compounds suggests an initial vasoconstrictory followed by a vasodilatory effect.

Transfer chemical laser: modeling of a cw DF-CO(2) laser

The chemical kinetics characterizing a DF-CO(2) transfer chemical laser were verified by utilizing a subsonic laser system which, for most conditions, could be approximated as premixed and at constant pressure. In such a laser, fluid dynamic effects are minimized, and the role of the kinetics model in characterizing the DF-CO(2) system is emphasized. Predictions of zero power gain, DF(v) number densities, thermocouple temperatures, and laser power were compared with data for an optical cavity pressure range of 21-79 Torr. The results show that the kinetics model gives an accurate description of the DP-CO(2) optical cavity. Mixing phenomena were found to become important at cavity pressures below 40 Torr.

Regional distribution of a 133Xe labelled gas volume inspired at constant flow rates

We measured the regional distribution of 480 ml of 133Xe labelled gases inspired from FRC at constant inspiratory flow rates ranging from 0.1 to 6 litres/s. The gases used were air and 20% O2 in helium. At low inspiratory flow rates the gas was preferentially delivered to the dependent region of the lung. At maximal inspiratory flows, all regions of the lung were more evenly ventilated. The rate of redistribution was found to be slower and more even than in previous studies using smaller volumes of inspired gas. Assuming equal and synchronous changes of pleural surface pressure, these results can be reasonably predicted by the mechanical time constant theory applied to a simple two-compartment lung model based on equal regional resistances. Breathing the HeO2 mixture did not significantly change ventilation distribution at any flow rate.