Hospital food service: is a chilled meal system best?

Royal Prince Alfred Hospital, Sydney, introduced the first chilled meal system into a major Australian hospital twenty years ago. Recently the food service has been converted back to a centralised system with conventional food production. The change has resulted in reduced operating costs and better quality food. This suggests that a chilled food system is not always the most economical form of hospital food service.

Tritium gas exchange with aromatic and aliphatic hydrocarbons over metal containing ZSM-5 and related zeolites

Platinum and palladium containing Y-zeolite, mordenite and ZSM-5 catalyse efficient exchange at 100°C between elemental tritium and aromatic or aliphatic hydrocarbons, the tritium orientation in the organic molecule showing characteristics of both metal and zeolite catalysis. The hydrogen forms of the same zeolites (i.e. without metal) also activate elemental tritium for aromatic exchange at 120-150�C, which shows that a metal component is not necessary for activation of elemental hydrogen even at modest temperatures.

Metal-catalysed exchange of alkyl and silyl hydrogen in organosilanes with tritium gas over Raney nickel as measured by 3H N.M.R

Analysis by tritium n.m.r, of triethylsilane, tetramethylsilane, hexamethyldisiloxane and chlorodimethylsilane exchanged with tritium gas over Raney nickel at 100°C shows that exchange readily occurs in alkyl substituents as well as with silyl hydrogen; novel species involving charge-transfer intermediates in dissociative adsorption at the C-H as well as the Si-H bonds are proposed to explain the data.

The intramitochondrial location of cytochrome c peroxidase in wild-type and petite Saccharomyces cerevisiae

Cytochemical and ultrastructural analysis of wild-type cells of Saccharomyces cerevisiae, grown aerobically in a glucose-limited chemostat, shows that cytochrome c peroxidase is localized between the membranes of the cristae, that is, in the intracristal space. This enzyme is thus positioned appropriately within the organelle to act as an alternate terminal oxidase for the respiratory chain. The proximity of the peroxidase to major sites of generation of its two substrates may account for the small leakage of hydrogen peroxide from yeast mitochondria, as compared with the larger outflow from mammalian mitochondria. In the cytoplasmic petite mutant, gross distortion of promitochondrial membrane arrangement is evident. Nevertheless, cytochrome c perioxidase activity is present in the same amounts as is found in wild-type cells, and is localized predominantly within annuli of membrane which constitute the promitochondria in these cells. No unequivocal evidence was obtained for the localization of catalase in microbodies or other organelles in either wild-type or petite cells.

The effect of vasopressin (Pitressin) administration on sodium, potassium and urea excretion in rats with and without diabetes insipidus (DI), with a note on the excretion of vasopressin in the DI rat

The effect of the administration of vasopressin as subcutaneous Pitressin Tannate in oil (PTO) was studied in the Brattleboro rat. Rats with hereditary hypothalamic diabetes insipidus (DI), and rats heterozygous for this abnormality, were used. A minimum dose of 1000 mu. of PTO/24 h was necessary to restore the urinary volume and osmolality of DI rats to values comparable with those of heterozygous rats. The urinary excretion of antidiuretic activity in DI rats was shown to be related to the dose of PTO. Sodium and urea excretion, but not potassium excretion, were reduced by up to 50% in the DI rat. No comparable changes were produced in the heterozygous rat. The possible mechanisms of these actions of vasopressin are discussed.

The effect of vasopressin (Pitressin) administration and dehydration on the concentration of solutes in renal fluids of rats with and without hereditary hypothalamic diabetes insipidus

1. The method of sequential centrifugation has been used to obtain fluid samples from both the renal papilla and inner medulla of the rat.2. Experiments were carried out on Brattleboro rats with hereditary hypothalamic diabetes insipidus (DI; homozygous recessive), and on their (heterozygous) litter-mates with normal quantities of neurohypophysial vasopressin. Initial classification of the animals by measurement of urine volume and osmolality was confirmed by post-mortem bio-assay of the pituitary glands, in thirty-five out of forty-seven animals.3. In rats with DI, urine osmolalities comparable to those of heterozygous rats were obtained after four daily injections of 1 u. Pitressin Tannate in Oil (PTO). Under these conditions, when dehydration was superimposed for 72 hr, urine osmolality did not increase markedly. In heterozygous rats dehydrated for the same period of time, urine osmolality increased by some twofold.4. In rats with DI, the administration of PTO induced a rise of both sodium and urea concentrations in renal fluids and in urine. Dehydration during PTO administration caused a further rise of urea concentrations only. Dehydration per se significantly raised urinary and renal fluid urea concentrations, but sodium concentrations did not rise.5. In heterozygous rats dehydration per se increased both urea and sodium concentrations in renal fluids and urine.6. The evidence is discussed that the action of vasopressin involves factors apart from increasing the permeability of the distal nephron to water and urea.

Changes of sodium and urea concentrations in the renal papillary interstitial fluid on dehydration of rats

1. The isolated renal papillae of a rat were centrifuged in a two tube assembly which allowed fluid from the tissue to separate into the lower tube.2. The papillae were centrifuged for 15 min at 300 g and 1500 g consecutively.3. After intraperitoneal injection of Na (131)I-diatrizoate, the activities of urine, and fluid samples obtained from the papilla, were compared. It was found at 1500 g that the median value for papillary fluid activity was 1.52% of the activity of urine. This is evidence that the papillary fluid was virtually free from any contamination from the terminal collecting ducts.4. It is considered that the fluid sample obtained from the papillae by centrifugation at 1500 g is a representative and reproducible sample of interstitial fluid.5. The method was used to demonstrate changes in solute concentrations in the renal papillary fluid, following dehydration of rats.