Influence of magnesium sulphate on evoked activity of rat brain after exposure to short-term hypoxia

Young Wistar rats (aged 12, 25 and 35 days) were exposed to short-term (60 min) hypobaric hypoxia of 41 kPa. Cortical afterdischarges (ADs) were evoked by repeated direct stimulation of the sensorimotor cortex and the duration of ADs was monitored to examine the influence of magnesium sulphate injection (0.3 g/kg b.w.). In 12-day-old hypoxia-exposed rats, an increase of the mean duration of ADs after the repeated stimulation appeared. This effect was prevented by magnesium administration. In 25- and 35-day-old rats exposed to hypoxia a shortening of ADs was registered but no specific effect of magnesium sulphate pretreatment was observed. The brain susceptibility and ability to terminate evoked seizures is discussed.     

Association of hypokalaemia and hypophosphataemia

A prospective study of 13 patients with hypokalaemia due to a variety of causes demonstrated that six had hypophosphataemia. In 10 patients the plasma inorganic phosphate level rose on correction of the hypokalaemia. Before treatment seven patients had an excessive rate of excretion of phosphate relative to creatinine in the urine. Following correction of the hypokalaemia 11 patients had an increase in renal tubular reabsorption of phosphate relative to creatinine. It is suggested that hypokalaemia may be causally related to the hypophosphataemia, and that in chronic potassium depletion this may affect bone mineralization.     

Appearance of formate in blood after ethanol ingestion.

Human and rabbit bloods after ingestion of ethanol were analyzed for carboxylic acids, and were found to contain not only acetate but also formate. The formate level in the rabbit serum was 0.35μmole/ml at 4 hours after introduction of 10ml of 40% ethanol/kg into the stomach. Administration of [1-¹⁴C] ethanol or [2-¹⁴C]ethanol resulted in the presence of radioactivity in serum acetate, but not in serum formate. Pretreatment with tryptophan significantly increased serum formate, and pretreatment with folate suppressed the appearance of formate.     

Dopamine receptor function after chronic ingestion of ethanol.

Investigations of physiologic, behavioral and biochemical correlates of CNS dopamine receptor function indicate that chronic ingestion of ethanol by mice results in “sub-sensitive” dopamine receptors.     

A comparative study of magnesium sulphate tolerance in saline-water mosquito larvae

The waters in which saline-water mosquito larvae are found can differ substantially in the types and ratios of ions present. Inland saline waters are more likely to contain high levels of MgSO₄ than are coastal ones. We undertook a study to determine if Aedes dorsalis, an inland species, is more tolerant of MgSO₄ than Aedes taeniorhynchus, a coastal one. The effects of MgSO₄ concentration were tested on all of the aquatic life stages of both species. Egg hatching was adversely affected at higher concentrations yet eggs would hatch in waters in which larvae could not survive. Younger larvae were more sensitive to MgSO₄ toxicity than the third and fourth instars. No differences in larval tolerance to MgSO₄ were observed between the two species indicating that neither species is ‘preadapted’ for MgSO₄ tolerance. Pupae of both species were completely insensitive to the levels of MgSO₄ tested. Larvae of A. taeniorhynchus reared in MgSO₄-rich media showed substantial increases in tolerance to subsequent MgSO₄ stress, possibly through an induction of Mg²⁺ and SO₄^2? transport systems. Increased tolerance to MgSO₄ required the presence of both Mg²⁺ and SO₄^2? in the rearing medium. When larvae of both species were subjected to steadily increasing concentrations of seawater, A taeniorhynchus survived much higher concentrations than did A. dorsalis. Therefore, while the process of induction is very important in extending the ionic range over which larvae can survive and develop, the possible ionic range for each species is finite. The differences in ionic range for each species probably accounts for the diversity of ionic tolerance and species distribution observed in the field.