DNA methylase extracted with low salt from mouse Krebs II ascites cell nuclei has been degraded stepwise by trypsin treatment. Degradation, accompanied by a limited reduction in size of the native enzyme, leads to the progressive introduction of several nicks so that, eventually, fragments of 14, 18, 24 and 28 kD are released on denaturation. This illustrates the domain structure of the enzyme. In contrast to ascites cell nuclear extracts, preparations from liver nuclei are already nicked and the major from of the enzyme contains a 100 kD fragment though the native molecular weight is unchanged. Newborn mouse liver contains more undegraded enzyme that is mostly firmly-bound within the nucleus. Trypsin treatment increases the de novo activity of the enzyme and prevents its aggregation in the absence of salt, even in the presence of high concentrations of native DNA.

Animals↗

PubMedDate not supplied

Cytogenetic evaluation of bone marrow cells from rats exposed to styrene vapor for one year.

This report presents the cytogenetic findings in bone marrow cells of rats exposed to styrene vapor. Male and female Sprague-Dawley rats were exposed to 0,600 and 1000 ppm of styrene vapor by inhalation 6 hr per day, 5 days a week, for a period of one yr. Blind scoring of metaphase spreads prepared from bone marrow cells collected at the end of the last exposure revealed that neither the 600 ppm nor the 1000 ppm exposures to styrene vapor produced an incidence of chromosomal anomalies higher than those occurring spontaneously. It is interpreted that styrene is non-clastogenic within the present exposure regimen.

Animals↗

PubMedDate not supplied

DNA methylation and G+C rich DNA.

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Cytosine↗

PubMedDate not supplied

Noninvasive glucose monitoring of the aqueous humor of the eye: Part I. Measurement of very small optical rotations.

We have described the concept of using the aqueous humor glucose as a measure of the blood glucose concentration, with a view to developing a noninvasive glucose monitor for diabetic individuals. We have conceived of a scleral lens that houses a light source, polarizers, other electro-optic units, and a light detector, and which measures the optical rotation of the aqueous humor continuously. We have built an optical bench mock-up of the glucose sensor and assessed the limits of its capabilities. We have described a physical method, employing the Faraday effect, that modulates the incident light and uses a compensator to introduce a feedback mechanism giving a null-point technique capable of measuring extremely small rotations with an accuracy of 0.4 s of arc. We have used this and have measured the optical rotations of glucose solutions from 0.02 to 0.1%, and have demonstrated linearity in both cases. Miniaturization of the technique is discussed.

Animals↗

PubMedDate not supplied

Noninvasive glucose monitoring of the aqueous humor of the eye: Part II. Animal studies and the scleral lens.

We have discussed the nature of a scleral lens that will allow us to follow changes in aqueous humor glucose levels in animals by a method based on optical rotation and a technique described in an earlier paper. We have shown how this lens can be micro-miniaturized and can be used in humans as a non-invasive glucose monitor. We have described preliminary experiments designed to show the correlation between the blood glucose assay (BGA) and the aqueous humor glucose concentration as determined by chemical assay (AGA) and by optical rotation determination (ARD). The last mentioned has been obtained by paracentesis directly into a microcell used in conjunction with instrumentation capable of measuring optical rotations as low as 0.0013 degrees (4.5") corresponding to 20 mg/dl glucose with a sensitivity of 0.0001 degrees (0.36"). The variability among normal rabbits as a function of individuality and diurnal changes is described, and the correlation between AGA and ARD shown to be essentially 1.0. Such rabbits are examined when undergoing very rapid decreases in BGA (insulin treatment) or very rapid increases in BGA (bolus of glucose). The AGA and ARD are shown to lag behind the BGA, and this is discussed in terms of the rate of change of BGA with respect to time and its concomitant change in AGA/ARD as well as a simple procedure that would materially reduce this lag.

Animals↗