Extraneous Factor Research Articles

Serum Glutathione Reductase and Cystic Fibrosis

Extract: Serum glutathione reductase (NADPH:GSSG oxidoreductase, EC. 1.6.4.2 (GR)) has been examined in cystic fibrosis subjects (CF), obligate CF heterozygotes, and control subjects. Serum protein concentration was similar in the three groups. Regardless of the units used to express activity (milligrams of protein or milliliters of serum) or whether or not samples were dialyzed against water or phosphate buffer, mean serum GR in CF was greater than in control subjects (P ≤ 0.002) in all series over several years. Under the above assay conditions no difference in serum GR between control subjects and carriers was detected. Calculated and assayed values of combined control and CF sera agreed as did expected and observed 50% activity in 1:2 sera dilutions in CF, control subjects, and carriers. Addition of FAD to incubation media did not effect enzyme activity in the three groups. Differences between CF and control subjects persisted after dialysis in membranes permitting passage of molecules of approximately 12,000 mol wt or less. These findings would tend to exclude the effect of extraneous serum factors in explaining the differences between CF and control subjects. The percentage of initial GR activity after four days storage (0-4°) was significantly greater in CF than in control subjects (P < 0.025). The effect of heparin on serum GR was recorded as the percentage of activity after incubation with heparin vs. activity in the standard assay for individual subjects. The effect of incubation with 5 μg/ml heparin on serum GR activity was greater in control subjects than in carriers (P < 0.0005) and CF (P < 0.0005). Mean serum GR activity in CF and carriers was unaffected by heparin, whereas mean activity in control subjects was decreased. In no control was the percentage of initial activity with heparin greater than the mean of CF and carrier groups. Only 3 of 20 CF and 4 of 20 carrier individuals had percentages lower than the control mean. The CF and carrier distributions were clearly different from the control distribution. Serum GR was determined in seven non-CF individuals with chronic obstructive pulmonary disease (COPD). Activity in the COPD was different from CF and no different from control subjects. In none of these controls or COPD was serum GR as great as the CF mean. Serum GR in no CF was as low as the mean of control subjects or COPD. It is concluded that serum GR activity is greater in CF than in control subjects, carriers, and non-CF COPD subjects; that the difference in activity is not attributable to an extraneous serum factor, that the activity difference is not secondary to chronic respiratory disease; that in comparison with control subjects, GR from CF serum behaves differently after storage; and that serum GR from CF and carriers behaves differently from control GR in the presence of heparin.Speculation: Abnormal activity of glutathione reductase may be fundamentally related to the pathogenesis of cystic fibrosis.

Asteroidal collisions

Taff (1973) has concluded that asteroidal collisions rates are much lower than those found by previous authors. His calculations are found to be in error as a consequence of inclusion of an extraneous and incorrect factor of ∼10 −5. The assumption of molecular chaos in the asteroid belt, while not strictly correct, is not an important source of error in calculations of asteroidal collision rates.

BIOASSAY OF ANTIBIOTIC P-9 BY THE DIRECT RESPONSE OF STEM RUST OF WHEAT

A simple medium was found for the production of antibiotic P-9 used in experiments for the control of stem rust of wheat.A rust-infection bioassay method for the estimation of the potency of different production lots of filtrate was developed; potency was measured as the proportionate inhibition of stem rust (Puccinia graminis Pers. f. sp. tritici Erikss. &amp; Henn. race 15B) infection on wheat seedlings in relation to log concentration of the material under test. The data from the bioassays took the form of a sigmoid curve when the concentrations were plotted arithmetically and of a straight line when they were plotted logarithmically. The slope of a weighted mean regression line based on 11 assays was regarded tentatively as characterizing pure antibiotic P-9.When the data of the 11 assays were adjusted for differences in potency between assays, the weighted mean regression line was statistically significant at the 1% point of probability. It is hoped that the slope of this line characterizes the pure antibiotic P-9 sufficiently well to be a useful tool in estimations of the relative purity of fractions obtained in the progressive purification of the antibiotic. Regression lines that differ from it substantially in slope may be suspected of influence from some extraneous factor.

Steroid requirements of housefly larvae.

IT has been known for some time that with very few exceptions1 insects require only the unsaponifiable, not the saponifiable, fractions of lipids. According to Hobson, for example, the larvae of Lucilia sericata require cholesterol as an extraneous growth factor, and they are capable of synthesizing neutral fat from a lipid-free peptone diet under sterile conditions. Since then, many insects have been found to require a sterol (zoosterol, phytosterol or mycosterol) as growth factor.

SPERM FILTRATES AND DIALYZATES

1. Solutions obtained by filtration and dialysis of suspensions of living sperm in sea-water activate ova of the same species.2. Tests indicate that the effect is produced by some substance derived from the sperm, and not by some extraneous parthenogenetic factor.3. Ova of Nereis exposed to specific sperm filtrates form fertilization membranes, complete their maturation and some develop into abnormal trochophores. Ova of sea-urchins fail to form membranes but do undergo nuclear and cell division.4. Ova exposed to filtrates and dialyzates are rendered more susceptible to the action of hypertonic sea-water, and to the entrance of sperm.5. In normal fertilization sperm exposed to "fertilizin" undergo profound modification in chemical structure and organization; and unless such modification occurs the sperm fail to fertilize the egg, even though they may enter it. It is possible that substances localized in the surface of the sperm head activate the ovum. Such localization is transitory.6. Such substances, when given off by sperm into sea-water or egg-water, either because of dilution, decomposition, or admixture with waste products given off by sperm, produce definite changes in such ova, but are unable to effect complete activation of ova of the same species.

On the Ellipse-Glissette Elimination Problem

The problem in question is to determine the equation of the curve traced out by any point of an elliptic or hyperbolic disc which touches two fixed rectangular axes. Mechanically constructed figures of different forms of the curve have been given by Tait, who also showed that the same glissette can be traced either by means of an ellipse or a hyperbola. If p, q are the coordinates of the tracing point referred to the axes of the disc as axes of coordinates, the glissette is clearly the θ eliminant ofand Cayley stated that it would be found to be of order 8 in x, y. The actual elimination was first performed by Muir, who obtained in the first instance an equation of order 10. On dividing by an extraneous quadratic factor a lengthy equation of order 8 was obtained; and subsequently Lord M'Laren verified the accuracy of the terms of highest order in this equation.

The Eliminant of a Set of Quaternary Quadrics

1. The “dialytic” method of elimination, in the case of more than one variable, is not without its drawbacks, as most mathematicians know. The requisite derived equations are not always easily obtained, the difficulty being due as often to the existence of too many as of too few; and, when this has been got over, it not unfrequently happens that the order of the resulting determinant is alarmingly high, and unaccompanied by any hope of a successful guess as to the character of the extraneous factor. The discoverer's original paper affords sufficient testimony of this, and very little has been done since its appearance to put matters on a sounder footing. The most noteworthy improvement, due to Cayley, is more interesting theoretically than practically, his main object being the detection of the extraneous factor when there is an over-plus of equations. Nothing, indeed, will be found more conducive to an understanding of the limitations of the method than a careful comparison of the application of this process of Cayley's to the problem of eliminating x, y, z from the three ternary quadricswith Sylvester's original treatment of the same problem, and the latter especially as commented on in footnotes by the author himself.2. The want of definiteness in the mode of arriving at the exact number of derived equations is not without its compensating advantage, as it leaves that scope for the exercise of ingenuity which is half the charm of mathematical work.