A comparative study of the total carbon dioxide in the ocular fluids, cerebrospinal fluid, and plasma of some mammalian species

Abstract

The distribution of chloride between the aqueous humour and plasma shows characteristic variations according to the mammalian species examined (Davson, Matchett & Roberts, 1952). Thus in the guinea-pig the concentrations in the two fluids are such that there is a deficiency of the ion in the aqueous humour, compared with the concentration in a plasma-dialysate, the value of the ratio: Concentration in aqueous humour/Concentration in plasma (RAq) being 0 935, compared with the value of 1P02 for the ratio: concentration in dialysate/concentration in plasma (RDia1). In the horse, by contrast, the value of RAq is 1-14, indicating a large excess of chloride in the aqueous humour. In general, the variations in the distribution-ratio for the cerebrospinal fluid (RCf) are by no means so great, and in all the species examined there is an excess of chloride in this fluid (Davson, 1955): in consequence, the ocular and cerebrospinal fluids of the guinea-pig, for example, show a difference in chloride concentration of 21 %; in the horse, on the other hand, the ratios are very close, the difference being less than 4 %. The problem naturally arises as to whether the excesses of chloride are compensated by deficiencies of bicarbonate, and vice versa.In the present study the bicarbonate distributions have been determined in a number of species. Characteristic variations have, indeed, been observed, and an attempt has been made to relate these variations with the buffering requirements of the intraocular contents; since the buffering capacity of the aqueous humour depends not only on its bicarbonate concentration, but also on its rate of renewal, the latter factor, measured by the rate of turnover of 24Na, has been examined in a number of species. Wherever possible simultaneous studies have been carried out on the cerebrospinal fluid, as it is con-

A Comparison of the Concentrations of Certain Nitrofurans in the Aqueous Humour and Cerebrospinal Fluid of the Dog

“…It has been pointed out that drug concentrations attained in cerebrospinal fluid are regulated by the rates of entry and exit of the drug (Davson, 1956;Pappenheimer, Heisey & Jordan, 1961;Rall & Zubrod, 1962;Schanker, Prockop, Schou & Sisodia, 1962). Since drug-to-drug differences in the concentration ratios of the aqueous humour and cerebrospinal fluid to plasma were obtained, the rates of disappearance for some of the drugs from both fluids were determined.…”

“…An interval of at least 30 days was maintained between experiments to allow eacn dog to recuperate. Although re-use of animals for such studies has been avoided on general principles by some (Davson, 1956), no evidence of significant changes in distribution ratios was demonstrable in the dogs used in the present studies. The results obtained originally, and in the same animals 30 days later, are presented in Table 1.…”

The effect of acetazoleamide on the chemical composition of the aqueous humour and cerebrospinal fluid of some mammalian species and on the rate of turnover of 24na in these fluids

“…The changes in bicarbonate concentration in the cerebrospinal fluid and aqueous humour were small (a fall of 1-3 %) in spite of large falls in plasma concentration (15-45 %); the chloride in the cerebrospinal fluid fell by 1-2 %, that of the aqueous humour on two occasions rose by 2-3 % and on one fell by 3 %. (For convenience the total CO2 estimated during this work has been described as 'bicarbonate'; in an earlier paper (Davson & Luck, 1956) it was shown that no serious error was introduced by ignoring the free CO2 component so far as normal distributions were concerned. If any changes in the relative pH of the fluids occur as a result of acetazoleamide they are very small, none of the animals showing signs of an uncompensated acidosis even when there were marked falls in plasma total CO2.…”

“…In certain species, notably the rabbit, cat and dog, the aqueous humour contains a considerably higher concentration of bicarbonate than a dialysate of plasma (Davson & Luck, 1956). In the rabbit the excess of bicarbonate is associated with a deficiency of chloride, whereas in the cat and dog actual excesses of both anions are present in the aqueous humour.…”

Intracranial pressure waves: characterization of a pulsation absorber with notch filter properties using systems analysis

“…7A-C, respectively. 13 The relationship between elastic arteries and the venous system in a closed cranial cavity was initially diagrammed by Davson,15 and the adapted versions of the diagram are shown in Fig. 7D-F, which correspond to Fig.…”