Use of oxytocin and incidence of neonatal jaundice.

A retrospective controlled study using data from the Cardiff Births Survey examined a possible relation between oxytocin administration to induce or accelerate labour and the subsequent development of neonatal jaundice. Among 10 591 infants born in Cardiff between 1970 and 1972 the incidence of neonatal jaundice was higher in infants born after oxytocin administration than among others. Analysis by gestational age at delivery, birth weight, Apgar score, length of labour, sedative and analgesic therapy during labour, and suppression of lactation showed that this association held within all these categories except among small immature infants, who are at high risk of jaundice in any case.     

Factors influencing mechanical performance of neonatal high-frequency ventilators

Factors influencing the mechanical performance of neonatal high-frequency ventilators of diverse design were assessed under controlled conditions. Each of eight ventilators was coupled to in vitro models of the neonatal respiratory system simulating disease of varying severity. The principal performance characteristics examined were frequency dependence and load dependence of tidal volume delivered, peak inspiratory flow rate, and waveforms of pressure at either end of the endotracheal tube. Despite wide diversity of ventilator designs, including jets, flow interrupters, and oscillators, common features emerged. In almost all devices tidal volume increased with endotracheal tube size, was invariant with respiratory system compliance, and decreased with frequency of oscillation. Peak inspiratory flow rates for a given tidal volume and frequency were smallest in the group of oscillators compared with jets and flow interrupters. Proximal pressure was a poor indicator of distal pressure. These findings suggest that delivered tidal volume may be sensitive to endotracheal tube size and airway patency but relatively insensitive to changes in lung tissue or chest wall mechanical properties. In these regards high-frequency ventilation differs from pressure-limited conventional mechanical ventilation. Comparison of data obtained at different clinical centers using high-frequency ventilators of varying design may be possible by taking these factors into account.     

Factors affecting the incidence of hypertension.

The incidence of hypertension was determined among 10,173 patients of general practices in southwestern Ontario studied from 1978 to 1982. For both sexes the incidence of hypertension rose with increasing age. The incidence was higher among men than among women until age 50, after which it was similar for the two sexes. Obesity was positively associated with incidence for both sexes. In men this association diminished significantly with increasing age. The similar trend in women fell just short of statistical significance. In men but not women heavy alcohol consumption was positively related to the incidence of hypertension. However, the broad definition of this variable may have obscured a relation in women. Among men the effect of obesity on the incidence of hypertension was less for heavy drinkers than for light drinkers. Smoking was not related to the incidence of hypertension in either sex.     

Factors influencing the incidence of habituation for cytokinin of tobacco pith tissue in culture

Pith tissue of Nicotiana tabacum L. cv. Havana 425 exhibits a gradient in its tendency to habituate for cytokinin on an auxin-containing medium at 35° C, about 10° C above the standard culture temperature. Explants of pith from below the 8th to 11th internode, counting from the bottom of the plant, rarely habituate for cytokinin; explants from above this threshold habituate rapidly. The explants must also be above a critical size, about 20–30 mg, to habituate. There was a pronounced interaction between size and position effects; the threshold position for cytokinin habituation shifted upward with decreasing explant size.     

Factors influencing the efficiency of chelation therapy.

The purpose of the present study was to obtain new data on the effect of age, route, dose and time of metal and chelating agent administration on the efficiency of chelation therapy. The experiments were performed on 1-2 and 6-week-old rats which received radioisotopes of metals--203Pb, 115 mCd, 203Hg and 141Ce intraperitoneally or orally. Chelating agents calcium ethylenediaminetetraacetate (CaEDTA), calcium and zinc diethylenetriaminepentaacetate (CaDTPA, ZnDTPA), 2,3-dimercapto-propane-sulfonate-1 (DMPS), dimercaptosuccinic acid (DMSA) and sodium N-(4-methoxybenzyl)-D-glucamine dithiocarbamate monohydrate (MeOBDCG) were administered twice by intraperitoneal or oral administration as early (immediately and 24 hr after metals) or delayed treatment (24 and 48 or 48 and 72 hr after metals). The animals were killed six days after metal administration and the retention was determined in the whole body, carcass and gut. After intraperitoneal administration of metals and chelating agents chelation therapy had much lower efficacy in younger than older animals. After ingestion of metals oral chelation therapy was more effective in younger than older animals. In suckling rats the treatment effectively reduced metal retention and this was mostly due to decrease in gut retention. This treatment in sucklings was also very effective in condition of late administration. In older rats early oral DMPS treatment after 203Hg ingestion is contraindicated since it increases significantly mercury retention while DMSA and ZnDTPA treatments reduced mercury retention. Delayed oral treatment with ZnDTPA and DMSA caused increased cadmium retention in older rats and decreased retention in sucklings. Opposite to results with CaDTPA, MeOBDCG was effective in reducing cadmium retention also when given as delayed treatment.(ABSTRACT TRUNCATED AT 250 WORDS)