Cardiac arrhythmias associated with treadmill claudication testing

Eighty-one consecutive patients of an average age of 58 years with suspected lower limb arterial disease underwent standard 5-minute treadmill claudication testing. Prior to, during, and after testing the patients were monitored electrocardiographically. The number of electrocardiographic abnormalities seen in 81 patients undergoing study increased from 33 (40.6%) at rest to 49 (60.5%) with exercise. The commonest abnormalities encountered with exercise were the development and increased incidence of paroxysmal beats and ST-T wave changes which, in some instances, became life-threatening, aborting the test. Since the principal hazard for patients with claudication appears to derive from an increase propensity to cardiac mortality and morbidity, rather than from the consequences of impaired circulation to the limb, electrocardiographic monitoring during treadmill claudication testing, though little practiced, is strongly advised.

Mechanism of defective lysogenization by phage P1 in a lon-mutant of Escherichia coli K-12

Phage P1 cannot lysogenize a lon- mutant of Escherichia coli K-12, which is defective in the regulation of cellular division cycle to result in snake formation (14). P1 mutants, called P1pla, can lysogenize the lon- host. These mutations have been classified into two complementation groups: one is cis-dominant; the other is trans-dominant. A temperature-sensitive lon- mutant was isolated, which exhibited the lon- phenotype at 42 C but not at 33 C. A temperature-shift experiment of the P1-lysogenic derivative of the lon- ts mutant showed lysis of the culture and induction of the phage production. It is proposed that P1 plasmid may be under a certain regulatory circuit of the division cycle of the host bacterium by indirectly regulating the production of P1 immune repressor, or alternatively by directly derepressing the functions of P1 prophage.

Effect of sex difference and pregnancy on the normal reactive hyperemia curve

The 10-min reactive hyperemia reaction was studied in a group of normal males, 10 normal females, 10 females in each trimester of pregnancy, and 10 females 6 wk postpartum. Sex difference had a marked effect on the hyperemic reaction, in that 5 and 15 s after release of circulatory arrest, the mean forearm blood flow in normal males was significantly reduced below that of normal females. During pregnancy there was a shift in the reaction of the pregnant female toward that in the normal male. In the 1st trimester of pregnancy, 5 s after circulatory arrest the mean forearm blood flow was diminished below that of the normal female; in the 2nd and 3rd trimesters at 5 s, the reaction was significantly diminished below that of the normal female. At 6wk postpartum, the reaction was essentially the same as in the nonpregnant female. Although these changes may be explained by a hormonal difference, they portray that there may be a marked difference in vascular reactivity due to sex difference only.

Subclavian steal in Takayasu's arteritis. A hemodynamic study by means of ultrasonic Doppler flowmetry

Blood flow in the vertebral artery and the upper extremity was studied in five cases of Takayasu's arteritis with subclavian steal by use of ultrasonic Doppler flowmetry and finger plethysmography. The diagnosis of subclavian steal was made by observation of flow reversal in the vertebral artery on the subclavian steal side during grip exercise and, in addition, the vertebral flow change with brachial artery occlusion. The blood flow increase of both internal cartotid and non-affected (non-subclavian steal side) vertebral arteries during a common carotid compression was almost normal in patients with Takayasu's arteritis in this study. During carotid compression on the side of the subclavian steal, ipsilateral vertebral blood flow greatly decreased, and the amplitude the ipsilateral finger plethysmogram decreased slightly or moderately. It is suggested that there are significantly important factors in suppressing sumptoms of vertebrobasilar ischemia in these patients with Takayasu's arteritis with subclavian steal. These factors are believed to be (1) good function of the circle of Willis, (2) good blood supply to the brain stem, and (3) collateral circulation to the distal subclavian artery not via the vertebral artery.

Endogenous carbon monoxide production in alloxanized rats

The endogenous production of carbon monoxide (Vco) in thirty-three diabetic rats induced by alloxan and in fifteen normal rats was measured by serial determinations of the expired carbon monoxide and of the increase of carbon monoxide in the blood during rebreathing in a closed system. Vco (mean +/- S.E., micronl/250g/hr) in the group of alloxanized rats 24, 48, 72, 96, 120 and over 144 hours after the alloxan injection was 6.2 +/- 2.9, 8.4 +/- 2.1, +/- 1.8, 10.7 +/- 3.5, 16.4 +/- 2.0 and 16.5 +/- 2.2, respectively, whereas it was 5.9 +/- 0.4 for the control. This indicates that the alloxanized group maintaining a high blood sugar level for over 120 hours has a three-fold higher Vco than the control.

Tuna cytochrome c at 2.0 A resolution. II. Ferrocytochrome structure analysis

The x-ray crystal structure analysis of tuna ferrocytochrome c has been extended from 2.45 to 2.0 A resolution. The overall folding is unchanged and is the same as has been reported for tuna ferricytochrome c (Swanson R., Trus, B.L., Mandel, N., Mandel, G., Kallai, O.B., and Dickerson, R.E. (1977) J. Biol. Chem. 252, 759-755). No significant structural differences are observed between oxidation states. Difference map studies using reoxidized crystals of ferrocytochrome c confirm the absence of a conformation change. A detailed analysis of hydrogen bonding shows the presence of six beta or 310 bends of type II with obligatory glycines in the 3rd residue position. This explains 6 of the 10 nearly invariant glycines in the molecule. Close packing contacts account for three more, and only the invariant glycine 1 remains a mystery.

Hemodynamic effects of nitroglycerin ointment in congestive heart failure

The hemodynamic effects of nitroglycerin absorbed transcutaneously from an ointment base were determined in 10 patients with chronic congestive heart failure (9 with ischemic heart disease and 1 with cardiomyopathy). The response was characterized by a decrease in pulmonary capillary wedge pressure from an average of 30 to 19 mm Hg, and an increase in cardiac index from 1.7 to 2.2 liter/min per m2, with concomitant decreases in systemic and pulmonary vascular resistance and an increase in venous capacitance. Mean arterial pressure decreased from 85 to 80 mm Hg, and heart rate remained unchanged. The hemodynamic effects persisted for 3 to 6 hours. These results indicate that nitroglycerin ointment is a hemodynamically potent vasodilating agent with potential value in the therapy of congestive heart failure.

Fate of viral RNA of murine leukemia virus after infection

[3H]Uridine-labeled Rauscher leukemia virus was used to infect mouse embryo fibroblasts. After the infected cells were separated into nuclear and cytoplasmic fractions nucleic acid was extracted by sodium dodecyl sulfate-phenol-chloroform treatment and analyzed by Cs2SO4 and sucrose density gradient centrifugation. Between 45 and 70 min after infection a transient and synchronized shift of the acid-insoluble radioactive peak toward the RNA-DNA hybrid region occurred in both the nuclear and cytoplasmic fractions. The density of the cytoplasmic hybrid shifted to 1.56 g/ml (RNA equals about 50%), while the sedimentation rate decreased from 36 S to 14 S; however, the density of the nuclear hybrid shifted to 1.58-1.48 g/ml (RNA equals 57-17%, respectively), while its sedimentation rate remained about 65 S. The hybrids in both the nuclear and the cytoplasmic fractions still showed hybrid density after heat denaturation. The processes of the early stages of RNA tumor virus infection are discussed with regard to the functions of viral RNA-dependent DNA polymerase (reverse transcriptase) and a possible integration of viral genetic information into the host chromosome.

Bacterial mutants defective in plasmid formation: requirement for the lon + allele

Bacterial mutants defective in plasmid formation were selected for their inability to be transduced to chloramphenicol resistance by bacteriophage PlCM. The mutants isolated are indistinguishable from a lon mutant strain. Both the lon strain and the mutants isolated here show very poor lysogenization by P1 and very low transduction to Gal(+) by the plasmid formation of the lambdagal(8)-Nam7am53cI(857). The lon(+) gene function of the host bacteria is indispensable for plasmid formation, even though P1 and lambda(+) can grow normally on the lon strains and lambda(+) can be integrated normally in lon as well as in the lon(+) bacteria. Phage mutants that can persist as plasmids in lon strains were isolated from P1CM. The function of the lon(+) gene is discussed with regard to plasmid formation.