A respiratory function monitor improves mask ventilation.

This study investigated whether the use of a respiratory monitor during simulated neonatal resuscitation reduced leak at the face mask. It showed the leak was more than halved, being reduced from 27% to 11% when 25 participants used the monitor to identify and correct the mask leak.

A 91-day feeding study in rats with caprenin.

Caprenin, a randomized triglyceride primarily comprising caprylic (C8:0), capric (C10:0), and behenic (C22:0) acids, was administered in a semi-purified diet to weanling Sprague-Dawley rats (25/sex/group) at dose levels of 5.23, 10.23 or 15.00% (w/w) for 91 days. Corn oil was added at 8.96, 5.91 and 3.00%, respectively, to provide essential fatty acids and digestible fat calories. Corn oil alone (12.14%) and a blend of medium-chain triglyceride (MCT) oil plus corn oil (11.21 and 3.13%, respectively) served as controls. All diets were formulated to provide about 4000 kcal/kg of diet and 26.8% of digestible calories from fat by assuming that corn oil, MCT oil, and caprenin provided 9, 7 and 5 kcal/g, respectively. Survival, clinical signs, body weight, feed consumption, feed efficiency, organ weights, organ-to-body-weight ratios, organ-to-brain-weight ratios, haematological values and clinical chemistry parameters were evaluated in all groups. Histopathology of a full complement of tissues was evaluated in the corn oil and MCT oil control groups as well as the high-dose caprenin group. Additional rats (n = 5/sex/group) were included in the study to determine whether there was marked storage of C22:0 in heart, liver or perirenal fat at the end of the 91-day feeding period. No significant differences in body weight gain were measured with the balanced caloric diets, although feed conversion efficiency was reduced in the high-dose caprenin group. No adverse effects from the ingestion of caprenin were detected, nor were significant amounts of C22:0 present in the fat extracted from the selected fat depot sites. These results establish a no-observable-adverse-effect level (NOAEL) of more than 15% (w/w) caprenin in the diet (or more than 83% of total dietary fat), which is equal to a mean exposure level of more than 13.2 g/kg/day for male rats and more than 14.6 g/kg/day for female rats.

A 20-month olestra feeding study in dogs.

Three groups of beagle dogs (five/sex/group) were fed olestra, a mixture of octa-, hepta- and hexa-esters of sucrose formed with long-chain fatty acids, at 0, 5 or 10% of the diet for 20 months. The objective of the study was to assess the potential chronic toxicity of olestra in a non-rodent species. The feed was supplemented with vitamins A and E to ensure that the diets were nutritionally adequate and comparable for all groups. The levels of supplementation were established in a 91-day feeding study. Survival was 100% and growth was not affected by olestra. Olestra-fed animals consumed more feed than controls, apparently to compensate for the caloric dilution of the diet by olestra, but the increases were generally not statistically significant. No biologically significant changes were seen in haematological or serum biochemical parameters or in vitamin D and vitamin K status of the animals. Histopathology revealed no olestra-related effects. Isolated incidences of soft stools, apparently resulting from the large amounts of undigested olestra, were noted in olestra-fed animals. The results of this study indicate that olestra was not toxic when fed to dogs at up to 10% of the diet for 20 months.

Chronic toxicity and carcinogenicity studies of olestra in Fischer 344 rats.

Two 2-year feeding studies were carried out in Fischer 344 rats with olestra, a mixture of the hexa-, hepta- and octaesters of sucrose formed with long-chain fatty acids. Olestra was fed at 0, 0.99, 4.76 or 9.09% (w/w) of the diet in the first study, and at 0 or 9.09% (w/w) of the diet in the second. Daily observations, feed consumption and body weights, ophthalmoscopic examinations, organ weights, serum chemistry, haematology, urinalysis and histopathological evaluations revealed no evidence of any adverse effects associated with olestra ingestion. Relative to controls, there was a higher incidence of basophilic liver foci in olestra-fed female rats at 12 months. At 24 months, foci were observed in most animals in all groups but were more numerous in olestra-fed females. The foci were not associated with hepatic tumours, alterations in liver function, or increases in liver weight and therefore not considered to represent a toxic response to olestra. Isolated statistically significant differences in mortality, mononuclear cell leukaemia, and pituitary adenomas were observed but were not considered to be related to olestra ingestion since they were not reproducible across the two studies, generally not dose responsive, not consistent between sexes, and the incidences were within the ranges for historical and contemporary laboratory controls. The results of the two studies show that olestra was not toxic or carcinogenic when fed to rats at up to 9% of the diet for 24 months.

Analysis of liver tissue for olestra following long-term feeding to rats and monkeys.

The potential for olestra to be absorbed and to accumulate in tissues was investigated by analysing liver tissue from rats and monkeys in long-term feeding studies using sensitive chromatographic methods. Studies with intravenously administered olestra indicated that absorbed olestra is predominantly taken up by the liver. In monkeys, 74% of the injected dose was detected in the liver, as intact olestra, 48 hr after dosing. In rats, 58-96% of the injected dose was found in the liver, as intact olestra, within 24 hr. No olestra was detected (limit, 34 micrograms/g) in the livers of 14 monkeys fed olestra at 8% of the diet for 29 months. Also, no olestra was found in samples of liver, heart, kidney, spleen, lymph nodes and adipose tissues from 26 monkeys fed olestra at 0, 2, 4 or 6% of the diet, in random order, for consecutive 2-month periods. No olestra was detected in the livers of 47 out of 50 rats fed olestra at levels of up to 9% of the diet for up to 2 years. The amounts (2-4 micrograms/g) detected in the other three rats were near the detection limit of the chromatographic method (1.6 micrograms/g). The results show that accumulation of olestra in the liver, the primary target organ for absorbed olestra, was less than 3 x 10(-6)% of the total amount eaten by rats over 24 months and less than 4 x 10(-5)% of the amount eaten by monkeys over 29 months. These results are consistent with previous studies which showed that olestra is essentially not absorbed from the gastro-intestinal tract.

A two-generation reproductive and developmental toxicity study of sucrose polyester.

Sucrose polyester (SPE) is a mixture of hexa-, hepta- and octa-esters of fatty acids with sucrose, and has physical and organoleptic properties similar to those of conventional dietary fats. Because SPE is neither absorbed nor metabolized it forms a bulk lipid phase in the small intestine, resulting in effects on the absorption and enterohepatic circulation of lipid-soluble materials, such as cholesterol and fat-soluble vitamins. Such effects could potentially alter the physiology of animals to the extent of interfering with reproduction and/or the normal development of the embryo/foetus. To determine the likelihood of such phenomena, Sprague-Dawley rats were continuously fed SPE at dietary levels of 1, 5 or 10% along with controlled levels of vitamins A and E for two generations, with a reproductive and a teratogenic phase in each generation. Body-weight gain of rats fed SPE was comparable to that of the controls throughout the study, but feed consumption increased with increasing levels of SPE. Pregnancy or lactation had no effect on these growth patterns. Throughout the study, SPE had no deleterious effect on mating, conception, embryonic development, foetal or post-natal viability, or on post-natal growth. Nor was there any treatment-related histopathology. Thus, it is concluded that SPE would not represent a reproductive or teratogenic hazard to human consumers of products containing SPE.

Annual and diurnal cycles in plasma testosterone and thyroxine in the male green sea turtle Chelonia mydas.

Male plasma testosterone (T) and thyroxine (T4) were monitored over several annual cycles in a captive breeding colony of green sea turtles, Chelonia mydas. Daily and annual water temperatures varied by only approximately 1 and 3 degrees, respectively. A pronounced season cycle in plasma T was evident in the population as a whole and in individual animals: plasma T was at a nadir (approximately 3 ng/ml) in September-November and then increased progressively to a peak (27-39 ng/ml) in April; levels began declining immediately thereafter, coincident with the onset of copulatory behavior. By contrast, plasma T4 remained uniform (approximately 9 ng/ml) throughout the year and, thus, could not readily account for the decline in androgen levels. Plasma hormones were relatively stable over a 24-hr period at three times a year, and there was a correlation for individual plasma T levels sampled in April and May. Thus, limited sampling should allow identification of seasonal rhythms and individual variability in plasma T levels. Testis mass and spermatogenic activity were significantly greater in January than in September; i.e., spermatogenesis and androgen secretion were not "uncoupled." Copulatory activity began in April but did not peak until May-June, after plasma T had significantly declined. However, there was a significant (but weak) correlation between individual peak levels of plasma T (i.e., in April) and the quantitative level of mating activity (time spent mounting and number of mates) measured for the entire subsequent season. Thus, green turtles do not exhibit the "postnuptial" type of testis cycle typical of many temperate-zone turtles, and the levels of plasma androgen may be important for initiating and maintaining sex behavior, although they are not tightly linked during the mating season.

Effect of EHDP on fracture healing in dogs.

Ethane-1-hydroxy-1,1-diphosphonate (EHDP) was administered subcutaneously to mature beagle dogs at dose levels of 0.1, 0.5, and 5.0 mg/kg/day for a 20 week period to determine the drug's effects on fracture healing. Uniform, transverse fractures of the midshaft radius were created in one limb and treated by external splintage. Drug-induced effects on fracture healing were monitored radiographically, histologically, and histomorphometrically; mechanical properties of the healing bones were determined in 4-point bending tests. At a dose of 0.1 mg/kg/day, ultimate load at failure and flexural rigidity of the fractured limbs equaled or exceeded that of saline control animals, and radiographic healing was normal. At a dose of 0.5 mg/kg/day ultimate load at failure and flexural rigidity of the fractured limbs proved inferior to saline control values, and radiographic healing appeared delayed. At a dosage of 5.0 mg/kg/day, there was obvious radiographic nonunion, and the callus of fractured radii had little inherent flexural rigidity or strength. Histomorphometrically, no differences were noted between control animals and the 0.1 or 0.5 mg/kg/day groups; however, mineralization activity appeared totally disrupted at the higher dosage level (5.0 mg/kg/day). In the 5.0 mg/kg/day group, EHDP-induced effects proved reversible with mineralization evident as early as 3 weeks following drug withdrawal. In mature beagle dogs EHDP proved to have dose-dependent and reversible inhibitory effects on secondary fracture healing.

Quantitative requirement of the hatchling green sea turtle, Chelonia mydas, for valine, leucine, isoleucine and phenylalanine.

Hatchling green sea turtles were fed purified diets containing 36% crude protein (N X 6.25) to determine the quantitative requirements for valine, leucine, isoleucine and phenylalanine. Expressed as percentage of total dry diet, the hatchling green sea turtle requires 1.3% valine, 1.6% leucine, 1.0% isoleucine and 1.0% phenylalanine (in the presence of 0.5% tyrosine). Within the range of isoleucine-leucine levels investigated, there was no apparent interrelationship between the quantitative requirements of these two amino acids. Growth rate was decreased at a high level of phenylalanine, 3.0% of the dry diet.

Quantitative requirements of the hatchling green sea turtle for lysine, tryptophan, and methionine.

The quantitative requirement for the amino acids lysine, tryptophan, and methionine was determined for the hatchling green sea turtle (Chelonia mydas). Hatchling green sea turtles were fed synthetic diets of purified substances with the composition of the diet varying in the amount of lysine, tryptophan or methionine present. The lysine requirement was found to be 4.8% of the crude protein (N X 6.25) or 1.7% of the dry diet. The tryptophan requirement was found to be 0.63% of the crude protein or 0.22% of the dry diet. The methionine requirement, in the presence of adequate cystine (3.1% of the crude protein), was found to be 1.5% of the crude protein or 0.49% of the dry diet.

Oxidation-reduction properties of Chromatium vinosum high potential iron-sulfur protein.

The oxidation-reduction properties of the high potential iron-sulfur protein (HIPIP) from Chromatium vinosum have been investigated. Both equilibrium and kinetic measurements demonstrate electron transport by HIPIP is pH independent in the pH range 7-11. The kinetics of reduction (potassium ferrocyanide, SO2, S2O42-, sodium ascorbate, and Rhodospirillum rubrum cytochrome c2) and oxidation (potassium ferricyanide and Rhodospirillium rubrum cytochrome c2) of HIPIP are reported. Based on the data obtained with different reactants and the influence of ionic strength, pH, and temperature on the kinetics of oxidation and reduction, a number of conclusions can be drawn. (1) HIPIP undergoes rapid outer-sphere electron transfer with no evidence of kinetic complexity and no indication of complex formation with various reactants. (2) The site of oxidation of reduced HIPIP has an apparent negative charge while the site of reduction of oxidized HIPIP is uncharged. (3) HIPIP appears to interact with a physiological reactant (R. rubrum cytochrome c2) at the same site as nonphysiological oxidants or reductants suggesting single minimum energy pathways for the oxidation and reduction processes. (4) Based on a comparison of the rates of oxidation and reduction with different reactants, it appears that steric restrictions and differences in oxidation-reduction potential are less important than electrostatic attraction and/or repulsion in determining the absolute rate constants. (5) The thermodynamic activation parameters indicate that both oxidation and reduction by the iron hexacyanides are driven entropically with the enthalpic terms making no contribution to HIPIP oxidation and a small contribution to HIPIP reduction. Based on the data reported here and available structural and physical-chemical information, possible mechanisms of the oxidation and reduction of HIPIP are discussed and their relative merits analyzed. The more likely mechanisms include electron transfer via a tyrosine residue, electron transfer through a nonaqueous media to the iron-sulfur chromophore, and direct interaction between the iron-sulfur chromophore and the different oxidants and reductants.

The reaction of Rhodospirillum rubrum cytochrome c2 with iron hexacyanides.

The reaction of Rhodospirillum rubrum cytochrome c2 with the nonphysiological reactants, ferrocyanide and ferricyanide has been investigated as a function of ionic strength, temperature and pH, using both stopped-flow and temperature-jump kinetic methods. The results are consistent with a complex reaction mechanism involving the formation of two intermediate complexes. The site of electron transfer appears to be at the front of the cytochrome c2 molecule near the hem e crevice with interacton of both ferri and ferrocyanide with a positively charged region of the molecule. Comparison of the proposed electron transfer mechanism of cytochrome c2 with ferro-ferricyanide is made with the mechanism proposed based upon structural considerations.