Hydrodynamic and diffusion considerations of rapid-mix experiments with red blood cells

From studies of the oxygenation rate of red blood cells (RBC) using rapid-mix techniques, it has been suggested that RBC are surrounded by a stagnant layer of water that does not (or cannot) mix with the rest of the water. A consideration of the appropriate hydrodynamics and convective diffusion rates shows that a mixer can reduce the resolution time to approximately 1 ms (or possibly less) and give a diffusion layer around the TBC that is approximately 1 micron thick. In stopped flow equipment it expands to approximately 4 micron over approximately 10 ms, whereas in continuous flow work the diffusion layers expands slightly less rapidly and less far. Thus the rate of oxygenation of TBC should be slower when measured by stopped flow techniques than by continuous flow apparatus for which the rate will depend weakly on the Reynolds number of the flow in the interrogation tube.

Fetal morphology in mice exposed to halothane

The teratogenic potential of subanesthetic and anesthetic exposure to halothane was studied in Swiss/ICR mice. Two treatment regimens were employed: daily exposure of males and females for nine weeks prior to conception and on days 1 through 17 of pregnancy; and exposure of females only on days 6 through 15 of pregnancy. Mice were exposed to subanesthetic concentrations of halothane for 0.025, 0.1, 0.4, and 1.2 MAC hours/day; anesthetic exposure was 4.0 MAC hours/day. Fetal morphologic development was normal at the two lowest exposures. Exposures of 0.4 MAC hours/day and more were associated with decreased fetal ossification. At the 1.2 MAC hour/day exposure, renal pelvic masturation was retarded and the incidence of skeletal variants was increased. The incidences of major malformations and minor anomalies were not increased following exposure to subanesthetic concentrations of halothane. Anesthetic exposure to 4.0 MAC hours/day was lethal to both dams and embryos, and resulted in major developmental malformations in surviving fetuses. These effects were probably due to altered maternal physiologic status. It is concluded that exposure of mice to subanesthetic concentrations of halothane does not result in important morphologic abnormalities in their offspring.

Renal effects of enflurane anesthesia in Fischer 344 rats with pre-existing renal insufficiency

Chronic renal insufficiency was produced surgically in Fischer 344 rats in order to evaluate the effects of enflurane anesthesia in animals with impaired renal function. Three groups of rats were anesthetized with enflurane: a control group without impairment of renal function (n = 7); a group with minimal impairment of renal function (n = 6); and a group with moderately severe renal impairment (n = 9). Another group of rats with moderately severe renal impairment (n = 8) was anesthetized with halothane. Two hours of anesthesia resulted only in mild transient depression of urea clearance in all groups. Six hours of anesthesia resulted in a 5 to 10 ml/day increase of urinary output in all groups and small increases in urea nitrogen levels in both groups with moderately severe renal impairment. Deterioration of the model was noted late in the experiment; at sacrifice, animals that had been anesthetized with enflurance and four with halothane had terminal renal failure. The morphological lesion in both groups was similar, resembling glomerulonephritis. Thus, there was no difference in the renal response to enflurane or halothane anesthesia among rats with chronic renal insufficiency.

Effects of isoniazid treatment on selected hepatic mixed-function oxidases

The hepatic microsomal content of cytochromes P-450 and b5, the defluorination rates of four volatile fluorinated ether anesthetics, and the activities of selected mixed-function oxidases were compared following administration of either isoniazid, phenobarbital, beta-naphthoflavone, or saline to male Fischer 344 rats. Isoniazid treatment significantly increased the rate of metabolism of p-nitroanisole, ethoxyresorufin, aniline, methoxyflurane, enflurane, isoflurane, and sevoflurane, significantly decreased the rate of metabolism of aminopyrine, and did not alter the activity of NADPH-cytochrome c reductase or the microsomal contents of cytochromes b5 and P-450 per mg of microsomal protein. The pattern of catalytic activities associated with isoniazid induction did not resemble that of either phenobarbital or beta-naphthoflavone induction. Furthermore, isoniazid treatment resulted in a shift in the (reduced cytochrome P-450 plus CO) absorption maximum from 450 to 451 nm. This shift in absorption, coupled with the observation that the total microsomal cytochrome P-450 content is not elevated, suggests that there is an increased production of one species of cytochrome P-450. The great enhancement of enflurane defluorination following isoniazid treatment was of particular interest because other enzyme-inducing agents, including phenobarbital, 3-methylcholanthrene, phenytoin, and beta-naphthoflavone, have not been found to increase enflurane defluorination to a clinically significant level.

Effect of phenytoin (DPH) treatment on methoxyflurane metabolism in rats

The toxicity and metabolism of the fluorinated anesthetic methoxyflurane were compared in Fischer 344 rats pretreated with phenytoin or phenobarbital. Treatment with either drug potentiated the polyuric effects of methoxyflurane by more than 100%. Also, serum inorganic fluoride (F-) levels and urinary F- excretions after methoxyflurane exposure were comparable in phenytoin- and phenobarbital-treated rats, a 26 to 49% increase as compared to rats treated with methoxyflurane alone. In vitro, 10-fold increases in the rate of hepatic microsomal methoxyflurane defluorination were observed after treatment of rats with either phenytoin or phenobarbital. Kinetic studies with microsomes demonstrated inhibition of methoxyflurane defluorination in the presence of phenytoin. Defluorination of three additional fluorinated ether anesthetics, enflurane, isoflurane and sevoflurane, also was examined in vitro. Phenytoin and phenobarbital treatment resulted in similar enhancement of defluorination of the latter two anesthetics, but not enflurane. Phenytoin and phenobarbital treatment increase defluorination of fluorinated ether anesthetics to approximately the same extent in vitro and in vivo in Fischer 344 rats.

Carcinogenicity of halothane in Swiss/ICR mice

A simplified in-vivo bioassay system was used to test the carcinogenic potential of halothane in Swiss/ICR mice. Halothane was tested only at its maximum tolerated dose, and histologic examination was performed only on tumor masses and other grossly abnormal tissues found at necropsy. Two groups, each of 15 timed pregnant mice, were exposed to either halothane, 500 ppm (0.05 per cent), or compressed air for two hours on days 10--19 of pregnancy. Five days after birth the offspring were similarly exposed, three times weekly, for 78 weeks. After a ten-week, no-treatment, observation period, all remaining mice were examined by necropsy. Mice dying or killed in extremis before final sacrifice at 88 weeks of age also underwent complete gross necropsy unless extensive cannibalism or autolysis precluded examination. The incidences of malignant tumors, hepatomas or modular hyperplasias, and benign tumors in halothane-treated mice were 7, 6, and 20 per cent, respectively; there were similar incidences of these lesions in control animals. It is concluded that under the conditions of this experiment, lifetime administration of halothane at its maximum tolerated dose is not associated with an increased incidence of neoplasia in Swiss/ICR mice.

Fluroxene mutagenicity

The commercially available volatile anesthetic fluroxene (2,2,2-trifluoroethyl vinyl ether) which contains the stabilizer N-phenyl-1-napthylamine, was tested for mutagenicity using four strains of S. typhimurium, TA1535, TA1537, TA98 and TA100, and one strain of E. coli, WP2. In addition, purified fluroxene; N-phenyl-1-napthylamine; trifluoroethanol, a major metabolite of fluoroxene; and urine from rats anesthetized with fluroxene were tested. Several procedures were utilized including exposure of bacteria to vapor in desiccators and in liquid suspension. Results indicate that fluroxene, but not its stabilizer, was mutagenic to strains TA1535, TA100 and WP2 only in liquid suspension and only in the presence of a rat-liver enzyme system. Trifluoroethanol and urine from fluroxene-treated rat were not mutagenic to any strain of bacteria. These findings indicate that fluroxene is a promutagen which requires preincubation before it is recognized. Further experiments were performed with enzymes prepared from mouse, hamster and human liver. Fluroxene was mutagenic only in the presence of enzymes prepared from Aroclor 1254 pretreated rodents. Since fluroxene was not mutagenic in the presence of enzymes prepared from three human livers, the significance of these findings to man are unclear.

Effects of pretreatment with anti-inflammatory drugs on ozone-induced lung damage in rats

The effects of pretreatment with acetylsalicylic acid (aspirin), hydrocortisone, indomethacin, and heparin administered ip against the pulmonary edema produced by O3-exposure (4 ppm for 4 hr) were studied in rats. These anti-inflammatory drugs were found to alter the injurious effect of O3 on lung differently. First, aspirin at the high dose (125 mg/kg) accentuated O3-induced lung injury, and had no effect at the low dose (10 mg/kg); second, hydrocortisone (50 mg/kg) failed to have any effect; third, indomethacin at a high dose (20 mg/kg) offered a significant degree of protection, but had no effect at the low dose (2.5 mg/kg); and fourth, heparin (1000 units/kg) also offered a significant degree of protection against the lung damage normally induced by O3-exposure. Several mechanisms for the favorable and unfavorable interactions of anti-inflammatory drugs with O3-exposure are discussed.

Amorphous Solid Water: A Neutron Diffraction Study

The structure factor of amorphous solid D(2)O deposited from the vapor at 10 degrees K has been obtained by measuring the neutron diffraction spectrum in the wave vector transfer from 0.8 to 12.3 reciprocal angstroms. The results indicate that the phase investigated is amorphous and has a liquiid-like structure factor. The Fourier-transformed structure e factor yields a real space pair distribution function consistent with local tetrahedral coordination and hydrogen bonding, as in other condensed phases of water. The intramolecular OD separation is 1.00 angstrom; the lack of data for very large wave vector transfer and the expected near equality of the intramolecular DD separation and intermolecular O . . . D separation make it impossible to determine the intramolecular DOD angle with precision. The neutron scattering data presented are complementary to the x-ray diffraction studies of Venkatesh, Rice, antd Narten.

Amorphous Solid Water: An X-ray Diffraction Study

Water vapor that condenses on a metal surface at 10 degrees K forms a noncrystalline phase of estimated density 1.2 grams per cubic centimeter. X-ray diffraction data of high precision and resolution have been analyzed to yield oxygen atom pair correlation functions. The positional correlation in amorphous solid water extends over only a few molecular radii, and the radial distribution of nearneighbor oxygen atoms in amorphous solid water is qualitatively different from that found in the low-pressure ice modifications. Amorphous solid water is a useful material for liquid water models because it can be studied under conditions such that the effects of static disorder and thermal excitation can be separated.

The stability theory of nonpolynomial kinetics

The results of an investigation of the formal stability behavior of equivalent classes of kinetic equations (generated by stability constraint specifications) that are general enough to include nonpolynomial kinetics are outlined. The immediate motivation for the study arose from the need for a comprehensive theory when steric interactions in biosynthetic networks are explicitly taken into account.

Model for constraint and control in biochemical networks

A model is proposed for biochemical networks which takes into account substrate and modifier effects on enzyme activity and the different time scales on which the relevant processes occur. Sources of global constraint that can be utilized in metabolic regulation are indicated, and the relation of the model to the experiments of Kauffman on switching networks is analyzed. The biological significance of the model and possible systems in which it might be tested are discussed.