QRS planarity studies in the vectorcardiogram. Clinical and experimental studies

Vectorcardiograms in 163 clinical subjects of normal and various abnormal conditions obtained by Frank lead system and in 17 dogs of experimental myocardial injury or intra-ventricular conduction disturbances by McFee-Parungao method were transformed by exchange of axes of co-ordinates by the method of McFee et al. The non-planarity index, from the axes of the transformed frontal plane, was significantly higher during myocardial injury and bundle branch blocks as well as from diffuse intra-myocardial conduction disturbances than during normal clinical cases and the control records in animal experiments. The non-planarity index was not increased in localized block of the conduction system in dogs. Therefore, results suggest that this index might be a useful parameter to assess these conditions.

Effects of intraocular irrigating solutions on the electroretinographic b-wave

We studied the effects of physiologic saline, lactated Ringer's solution, and BSS (balanced salt solution) on the electroretinogram of the rabbit in vitro. The b-wave amplitudes decreased when the retina was incubated in lactated Ringer's solution or BSS. These amplitudes recovered to 60% to 70% of the original level when the retina was re-immersed in the control medium. With physiologic saline, the b-wave amplitude recovered only to about 30% after 20 minutes of incubation, and recovery was nil after 60 minutes of incubation time. Extended contact with physiologic saline produced permanent damage to the retina. Bicarbonate ion and glucose were shown to be essential for maintaining the ERG amplitude.

Ion movement in and out of the vitreous space after vitrectomy. An experimental study on the in vivo eyecup preparation of rabbits

Osmotic pressure and ion movements in and out of the vitreous space after open-sky vitrectomy were studied in the in vivo eyecup of rabbits. The osmotic pressure of several hypo-osmotic solutions rose over a period of time by the penetration of ions from the surrounding tissue; increases in the concentration of sodium, chloride, potassium, and calcium were documented. Appearance and disappearance of ions were independent of the total osmolarity and depended on the concentration gradient for each ion.

Species and strain differences in the butylated hydroxytoluene (BHT)-producing induction of hepatic drug oxidation enzymes

Five week-old, Wistar-JCL male and female rats and C57BL/6N male mice give a 0.5% butylated hydroxytoluene (BHT)-containing diet for 6 days produced a marked increase in hepatic weight and microsomal protein content. However, the augmentations of cytochrome P-450 content and drug oxidation activities were much more significant, i.e. 2.5-fold and more than three-fold increases were observed on a body weight basis, respectively. BHT-induced cytochrome P-450 cannot be distinguished from phenobarbital (PB)-induced cytochrome in many respects we have examined: i.e. 1) a broad substrate specificity; 2) absence of the blue shift in the CO-binding difference spectrum; 3) no rise in the peak height ratio of ethylisocyanide difference spectrum; 4) absence of alpha-naphthoflavone inhibition of p-nitroanisole demethylase activity; 5) marked increases of 50,000 and 54,000 molecular weight polypeptides in SDS-polyacrylamide gel electrophoresis. However, the induction of 46,000 molecular weight polypeptide by BHT in rats was more conspicuous than that by PB, and this induction was not observed in mice. In contrast to this marked induction, the administration of BHT to MC nonresponsive DBA/2N mice produced neither heptic enlargement nor induction of cytochromes, but did not produce an extremely high mortality.

The suppressive effect of hepatic 9,000 x G supernatant fraction from 3-methylcholanthrene-treated rats on the mutagenic activity of 2-acetylaminofluorene

Hepatic 9,000 x g supernatant (S9) fraction from 3-methylcholanthrene (MC)-treated rats showed a significantly low activity in the in vitro conversion of 2-acetylaminofluorene (AAF) to mutagen(s), while S9 fraction from untreated or phenobarbital (PB)-treated rats showed a remarkable activity. The S9 fraction from MC-treated rats actually suppressed the PB-S9 mediated AAF mutagenicity. Since the suppressive effect of MC-S9 was lost by the addition of 10(-4) M alpha-naphthoflavone (alpha-NF), rat specific cytochrome P-448 may be responsible for this suppressive effect.

Effect of dietary protein deficiency on rat hepatic drug-metabolizing enzyme system

We have examined the effect of dietary protein deficiency on rat hepatic drug-metabolizing enzyme system for a period of two months. Cytochrome P-450 and b5 contents in liver microsomes, which were plotted on semilogarithmic paper as a function of the time of deficiency, showed biphasical reductions during protein deficiency: rapid decreases in the first 3 weeks were followed by more gradual decreases. However, the three enzymatic activities examined, i.e. aminopyrine demethylase, aniline hydroxylase and p-nitroanisole demethylase, were not reduced at a uniform rate. In the earlier phase, activities of the former two enzymes were reduced more rapidly than that of the last phase. This biphasical and non-uniform reduction of enzymatic activities suggests the existence of two or more cytochrome P-450 subspecies in non-depleted male rats. Intraperitoneal administration of well-known environmental pollutants, polychlorinated dibenzofurans and biphenyls (100 micrograms and 100 mg/kg, respectively) to the depleted rats resulted in a marked induction of drug-metabolizing enzymes. However, as the deficiency became more severe (2 months), the induction declined to a considerable degree, especially in the case of polychlorinated biphenyl administration.

The interaction of divalent copper and the microsomal electron transport system. A re-examination of the effects of copper chelates on the function of cytochrome P-450

Lipophilic chelates of divalent copper, possessing superoxide dismutase-like activity, have been proposed to enhance the decay of oxycytochrome P-450 to explain their inhibitory effect on microsomal mixed-function oxidation reactions (Richter, C., Azzi, A., Weser, U., and Wendel, A. (1977) J. Biol. Chem. 252, 5061-5066). The present investigation, however, failed to provide evidence in favor of this hypothesis. In particular, it was found that the reported inhibition of cytochrome P-450-catalyzed hydroxylation reactions by copper-tyrosine is associated with an inhibition rather than a stimulation of the formation of hydrogen peroxide, the product of the dismutation of the superoxide radicals generated as a result of the decay of oxycytochrome P-450. The attenuation of both these reactions was shown to be the consequence of an impaired function of the NADPH-cytochrome P-450 reductase. Additional sites of interaction of copper chelates and the microsomal electron transport system appear to exist since divalent copper was found to undergo reduction reactions with NADPH and NADH as electron donors. These reduction reactions do not involve superoxide radicals and, therefore, are unrelated to the ability of copper chelates to function in a superoxide dismutase-like manner.