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Various electrodes for intra-arterial detection of ascorbate dilution have proved not to meet the requirements for routine application in cardiac catheterization and surgery. The electrode described here has good mechanical and electrical properties and proved reliable in more than 300 cardiac catheterizations and more than 100 operations.

A modification of the dilution procedure for the Antistreptolysin O (ASO) titer is presented. This modification utilizes a serial dilution. It simplifies pipetting, reduces the total volume of serum and reagents needed, and allows for the adaptation of the ASO titer to automation.

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A nomogram is described which facilitates rapid calculation of the cardiac output from the integral of a dye dilution curve.

The disappearance rate of prolactin from the blood of female rats was assessed by bio-assay of the serum at intervals after intravenous injection. The intradermal pigeon crop sac method of assay was used. Dilution of the serum 1 to 3 and 1 to 15 with saline prior to assay obviated the inflammatory reaction between the skin and underlying crop sac of the pigeon and reduced the incidence of nonspecific responses which occurred with undiluted serum. The presence of bovine prolactin in dilute serum induced a moderate inflammatory reaction in some pigeons; ovine, porcine and murine (rat) prolactin in dilute serum did not. The serum concentration of each prolactin tested fell quickly within 1 min after injection. The rate of disappearance slowed during the next 2–3 min, then followed an exponential course. The latter rate was used in estimating the biological half-life (t1) of ovine (10–12 min), murine (10 min), bovine (3 min) and porcine (3 min) prolactin in the blood of adult castrate female rats. The t1 of o...

The increasing demands for ultramicro determinations in routine high volume application necessitate the development of rapid technics for processing serum specimens. The advances in ultramicro methodology and the availability of a variety of new sensitive instruments make possible the use of ultramicro technics on a routine basis. However, the precise dilution of samples of serum in the ultramicro range is still tedious. This report describes an ultramicro dilutor which can be easily constructed at low cost and makes possible rapid dilution of ultramicro samples of serum with reproducibility and accuracy equal to, or better than, those of dilution technics now used for micro samples.

The effect of dilution of serum on the concentration of free thyroxine was evaluated in an effort to determine the relationship between values previously obtained in a standard dialysis system employing diluted serum (1:150) and the concentration of free thyroxine in undiluted system. A theoretical analysis of thyroxine-binding by serum proteins in terms of a multiple equilibria system suggested that the free thyroxine concentration should be relatively independent of the concentration of serum proteins in the range of dilution considered. In order to test this prediction, experimental techniques were devised to measure free thyroxine in dialysis systems containing higher concentrations of protein. For this purpose, tracer 131I-thyroxine and 125I-iodide were used simultaneously. The results of these studies were in general accord with the theoretical formulation. The concentration of free thyroxine was also measured in the ultrafiltrate of 7 sera. Values were in the same order of magnitude as those obtain...

Excerpt The tests of urinary dilution and concentration, particularly the latter, are generally regarded as a simple and reliable means of detecting early impairment of renal function. They are bas...

1. 1. The metacyclic forms remain viable over long periods only when enveloped in the dry granules of faeces. 2. 2. A degree of humidity sufficient to reduce the faecal granules to a very soft state will, if maintained for about 3 days, result in the death of the organisms. 3. 3. Development of the metacyclic forms will take place only in salt contrations between 0·25 per cent. and 2·3 per cent. Viability is not immediately affected by any further degree of salt concentration. Development will proceed following an appropriate dilution of the liquid medium. 4. 4. Leptomonads become non-motile in salt concentrations of 4 per cent. and over, but will revive if the salinity is reduced to below 4 per cent, within a period which varies according to the concentration employed.

Although the widespread use of electronic particle counters has considerably improved platelet counting technics, problem areas remain. Solutions to these problems are suggested: separation of platelet-rich plasma from whole blood by augmentation of rouleaux followed by 2 min. of sedimentation; a modification of a microliter syringe which permits a 1:3,000 dilution in a single step; and finally a special calculator in circular slide rule format for translating machine counts into whole blood platelet counts.

In retesting pseudomonas isolates that had been designated by hospital laboratories as resistant to carbenicillin, 64% were found to be susceptible to carbenicillin by both the disk and broth-dilution techniques, 6% were intermediate, and 30% were resistant. The reasons for the variation in results were not readily identified in every instance but probably included deviations from the standardized disk technique, misidentification of bacterial isolates, and the use of antibiotic disks with diminished potency. The distribution pattern of sensitivity to carbenicillin of these supposedly resistant isolates studied in 1972 was surprisingly similar to that of an unselected population of Pseudomonas studied in 1968.

Excerpt Gaucher's disease is commonly accompanied. by anemia, which is usually ascribed to the replacement of bone marrow by colonization with the cerebroside-laden Gaucher cells; occasionally it m...

Human pituitary gonadotropin (HPG) was prepared from male urine and from postmenopausal urine by the same process and was assayed by four methods, namely by ovarian weight in intact rats, by uterine weight in intact mice, and by the ventral-prostatic weight and testicular weight in hypophy-sectomized rats. The relative potency (postmenopausal ÷ male) of the two preparations of HPG was 12.83 by the four methods of assay (total of 14 assays). When the specific activities of the two preparations of HPG were equalized by appropriate dilution of the more potent HPG (postmenopausal) with inert material, the relative potency was 1.12 by the four methods of assay (total of 14 assays). The mean index of discrimination using all possible combinations of assays was close to unity, and all values for the mean index of discrimination fell well within experimentally verified and allowable (P = 0.95) limits of fluctuation. It was concluded that no evidence for dissimilarity of HPG from these two sources was obt...

During a 10 min labeling period the uterus of the rat accumulates up to 10 × more 3H-uridine when this tracer is injected ip than when it is given sc. Incorporation into the RNA is enhanced by ip administration to an even greater extent than is total uptake. Intraperitoneal administration also greatly increases the variability of tracer uptake by the uterus. Tritium is distributed uniformly in different segments of the uterus after sc injections but is unequally distributed when ip injections are made. Aiming the needle toward one horn of the uterus when giving an ip injection clearly biases tracer distribution on the uterus. When plasma tritium is examined much less radioactivity is associated with uridine 10 min after an ip injection than after a sc injection. The converse is true of the acid-soluble fraction of the uterus (much less tritium is associated with uridine or UMP when the isotope was injected sc). Simultaneous studies with 14C-inulin and 3H-uridine indicate that much of the uridine given by ...

Changes in the rate of the net gas exchange of rat adipose tissue have been used to measure the insulinlike activity of sera from normal and hypophysectomized monkeys. The activity of normal serum when assayed undiluted corresponds on the average to that given by 97 μU insulin/ml of incubation medium, while the corresponding value for the serum of hyphophysectomized animals is 44 μU/ml. If the serum is diluted 1:3 for assay, then the average values for normal and hypophysectomized sera are 198 and 54 μU of insulin/ml, respectively. Thus, sera from hypophysectomized animals not only tend to show an insulinlike activity lower than that of sera from normal animals, but also fail to display the marked increase in values seen upon dilution of normal sera. The results are discussed in relation to the presence in normal sera of an insulin antagonist, the elaboration of which is dependent upon an intact pituitary.

A 35-year-old female had severe anaphylactoid reactions to pnlocaine and lignocaine on separate occasions Intradermal testing was positive to serial dilutions of both drugs and negative to bupivacaine, which was subsequently used uneventfully While intradermal testing for local anaesthetic allergy has limited application it would appear that when such texts are positive in high dilution they may discriminate between safe and unsafe anaesthetic agents.

Excerpt When the alveolar oxygen tension is suddenly lowered for several seconds and then raised above its initial level, the blood leaving the lungs temporarily contains an increased concentration...

The tube dilution method was used to test 33 strains of Pseudomonas pseudomallei for in vitro sensitivity to trimethoprim (TMP), sulfamethoxazole (SMZ), and a combination of the drugs maintaining a ratio of 20 parts SMZ to one part TMP. Results disclosed no activity by TMP alone except at extremely high levels. Twelve of 33 strains were sensitive to SMZ, and 75% of the strains were inhibited by the combination at therapeutically achievable levels. In no instance did TMP fail to potentiate the action of SMZ against the organism. In vitro susceptibility of the organism indicates that a combination of TMP and SMZ could be useful in the treatment of melioidosis.