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B Mackler

Publications and source records attributed to B Mackler.

15 recordsLinked to original sources
PubMed1992

Ischemia/reperfusion: a new hypothesis for the developmental toxicity of cocaine.

It has been shown that multiple exposures of gravid rats to cocaine during late gestation result in significant incidences of severe malformations. Hind limb reduction defects were frequent findings in this study. Other studies have shown that comparable abnormalities can be induced in experimental animals by various procedures including vascular clamping, direct fetal exposure to epinephrine, uterine handling following laparotomy, as well as by exposure to hyperbaric oxygen. This paper reviews these and other studies, and presents a novel mechanistic hypothesis that explains their common findings. It is proposed that in each instance, conceptual hypoxia results from hypoperfusion caused by transient vasoconstriction. Following the resumption of normal perfusion, reactive oxygen species are generated by the ischemia/reperfusion mechanisms thought to underlie many pathobiologic lesions. It is proposed that the conceptus is particularly vulnerable to the toxicity of oxygen radicals because of its low antioxidant activities and the highly reduced state of its undifferentiated cells. Sensitivity to cocaine and uterine handling appears to be enhanced during late gestation and it is hypothesized that this results from changes in oxygenation and iron content that increase both the substrate and catalyst for generation of reactive oxygen species.

Animals↗
PubMed1992

Studies of the role of ischemia/reperfusion and superoxide anion radical production in the teratogenicity of cocaine.

The administration of multiple doses of cocaine on a single day during late gestation is teratogenic in rats in which hind limb ectrodactyly is a major finding (Webster and Brown-Woodman, '90). We have previously hypothesized that these limb malformations result from the generation of reactive oxygen species during the process of ischemia/reperfusion in vivo. In order to study the direct effects of cocaine versus the aberrant oxygenation it may induce, we have developed a system for culturing rat embryos between days 14 and 15 of gestation. Growth and development of cultured embryos are comparable to that of in vivo controls. Exposure to normoxia (95% O2) with or without cocaine failed to induce limb malformations and exposure to a single long period of hypoxia (20% O2) only reduced limb growth in the anterior-posterior axis. By contrast, embryos receiving multiple brief exposures to hypoxia developed a significant incidence of hind limb ectrodactyly that appeared indistinguishable from that induced by cocaine in vivo. By incubating day 14 embryos in a nitroblue tetrazolium derivative, 1-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), it was shown that superoxide anion radical appears in the digital rays following two episodes of reperfusion. Little reaction product was seen under the other conditions. Finally, mitochondrial electron transport particles prepared from teratogenically sensitive limb buds spontaneously "leak" electrons to form superoxide anion radical whereas those from insensitive heart fail to do so. We propose that cocaine and other exposures that can transiently reduce conceptual oxygenation during late gestation are teratogenic by virtue of their capacity to induce ischemia/reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Asymmetric development of mitochondrial activity in rat embryos as a determinant of the defect patterns induced by exposure to hypoxia, hyperoxia, and redox cyclers in vitro.

Previous study has shown that midorganogenesis-stage rat embryos exposed to strong redox cyclers under moderate hypoxia in vitro develop severe necrotic defects on the right side. Similar effects can be produced by exposure to severe hypoxia alone. Studies presented here indicate that exposure to severe but survivable hyperoxia induces comparable necrotic degeneration on the left sides of all embryos. We hypothesize that the basis of these axially asymmetric defects is relatively precocious mitochondrial maturity on the left side of the embryo. In order to investigate this hypothesis, we compared mitochondrial oxygen utilization (NADH oxidase activities) on either side of rat embryos between days 11 and 14 of gestation. Activities were consistently higher on the left side during this period and significantly higher on day 11. We also found that the asymmetric embryotoxicity induced by niridazole, a strong redox cycler, could be attenuated by prior culture under hyperoxic conditions. We propose that mitochondrial immaturity on the right results in inadequate energy generation under hypoxic conditions, either directly or as a result of redox cycling. On the other hand, necrosis associated with hyperoxic conditions results from "leakage" of superoxide from functionally mature mitochondria on the left side.

Abnormalities, Drug-Induced↗
PubMed1979

Catecholamine elevation in iron deficiency.

Iron-deficient rats have increased blood and urinary catecholamines regardless of whether anemia is or is not present. The catecholamine response in both iron-deficient and control animals is largely temperature dependent, showing little difference at the isothermic temperature of 30 degrees C but a two- to threefold increase in iron-deficient animals over controls at lower temperatures. The iron-deficient rat is unable to maintain body temperature at 4 degrees C and this is independent of anemia or of food intake. When animals are run on the treadmill for 4 h, body temperatures increase but the difference observed at 4 degrees C between iron-deficient and control animals persists. The underlying abnormality in temperature regulation and in catecholamine response disappeared after 6 days of iron therapy.

Animals↗
PubMed1979

Lactic acidosis as a result of iron deficiency.

Iron-deficient rats have an impaired work performance, even when their anemia is corrected by exchange transfusion. Muscle activity is associated with a higher blood lactate concentration than is observed in iron-replete animals. The accumulation of lactate is a result of excessive production as lactate clearance from the blood was shown to be unaffected. By adjusting the work load to a lower level, it was possible to divide iron-deficient animals into two groups, one capable of continued treadmill running and another in which animals stopped before 20 min. In the former, blood lactate concentration reached a plateau at moderate levels, whereas it continued to increase in the latter until the animal stopped running. Levels of alpha-glycerophosphate oxidase in skeletal muscle mitochondria were found to be much lower in the second group (P < 0.001). Lactate infusion into normal animals was shown to interfere with work performance, and maintenance of a normal pH in iron-deficient and iron-replete animals did not prevent the impairment in work associated with high blood lactate concentrations. Additional evidence was obtained that energy substrate (blood glucose and free fatty acids, muscle glycogen) was adequate in irondeficient animals. Oxygen tension in their vena caval blood was higher than in controls. Furthermore, the in situ behavior of electrically stimulated gastroenemius and soleus muscles appeared similar to that of control animals. Because the stimulation of the single muscle in the iron-deficient animal did not result in appreciable elevation of blood lactate and did not show impaired contractility further supported the hypothesis that the elevation of blood lactate caused the decreased work performance. It is concluded that iron deficiency by a depletion in the iron-containing mitochondrial enzyme, alpha-glycerophosphate oxidase, impairs glycolysis, resulting in excess lactate formation, which at high levels leads to cessation of physical activity.

Acidosis↗
PubMed1979

Iron deficiency in the rat: effects on phenylalanine metabolism.

Concentrations of phenylalanine in the plasma were markedly elevated in iron-deficient rats and appeared to vary directly with the degree of iron deficiency. Plasma concentrations of phenylalanine returned to control levels within one week after treatment of the iron-deficient rats with iron dextran. The elevated levels of plasma phenylalanine were probably not produced by a deficiency in liver phenylalanine hydroxylase because levels of activity of the enzyme were found to be normal in the livers of the iron-deficient animals.

Animals↗
PubMed1979

Effects of maternal absorption of phenobarbital upon rat offspring development and function.

Sixty Sprague-Dawley derived primaparous rats were administered Luminal (sodium phenobarbital) subcutaneously in doses of either 80 mg/kg, 40 mg/kg, or 0 mg/kg (saline) on Days 9-21 of gestation. The two drug groups delivered litters significantly later with evidence of increased resorption at the higher dose. The higher dose offspring were lighter in weight at birth and at adulthood, but not at weaning. The lower drug dose offspring were developmentally accelerated compared with the other two groups. Acquisition of a conditioned avoidance response (CAR) was negatively correlated with increased drug dose. In appetitive operant paradigms, saline offspring received more reinforcements on fixed ratio sequential schedules, and the lower drug dose offspring received significantly fewer reinforcements than either of the other two groups on an FR-concurrent schedule. Both groups of drug offspring were able to obtain their reinforcements with a lower expenditure of effort than the saline offspring. The higher drug dose offspring made significantly more incorrect (early and late) responses on a schedule which rewarded a delayed response (DRL).

Animals↗
PubMed1978

Iron deficiency in the rat: biochemical studies of brain metabolism.

Studies were performed to determine the effects of iron deficiency on brain metabolism in rats. Concentrations of cytochrome pigments, oxidative phosphorylation, and catalase and monoamine oxidase activities in brain tissue were unaffected by iron deficiency. However, activities of aldehyde oxidase, a key enzyme in the pathway of serotonin degradation, were significantly reduced, and concentrations of serotonin and total 5-hydroxyindole compounds were elevated in brain tissue of iron-deficient animals. Aldehyde oxidase activities and concentrations of 5-hydroxyindole compounds in brain tissues returned to approximately normal values one week after treatment of iron deficient animals with iron dextran.

Aldehyde Oxidoreductases↗
PubMed1977

Clofibrate effects: mitochondria vs exercise tolerance in aging hamsters.

Mitochondria in skeletal and cardiac muscle have been found to be less stable in aging hamsters, in contrast to preparations from young animals. We have found previously that clofibrate (Atromid-S) will reverse this degeneration in the older hamsters. This study examined the exercise tolerance of aged hamsters, to see if clofibrate had a parallel effect on exercise tolerance as had been shown for muscle mitochondria stability. Maximal duration of exercise for hamsters on a treadmill was measured in a control and treatment group before and after treatment with clofibrate. There was no improvement in exercise tolerance with clofibrate. We conclude that inferences of functional effects in intact animals from changes found in isolated tissue preparations should be drawn with caution.

Aging↗
PubMed1976

Iron deficiency in the rat. Physiological and biochemical studies of muscle dysfunction.

Work performance on a treadmill has been evaluated in normal and iron-deficient rats. Anemia was removed as a variable by adjusting the hemoglobin of all animals to the same concentration. At a hemoglobin compatible with normal work performance, iron-deficient animals showed a marked impairment of running ability as compared to control animals. Iron therapy corrected the disability within 4 days. Concentrations of the cytochrome pigments and myoglobin, and rates of oxidative phosphorylation with pyruvate-malate, succinate, and alpha-glycerophosphate as substrates were all reduced in mitochondrial preparations from skeletal muscle of iron-deficient rats, but only the rate of phosphorylation with alpha-glycerophosphate as substrate increased significantly and in parallel with the recovery in work performance of the iron-deficient rats treated with iron dextran.

Anemia, Hypochromic↗
PubMed1976

Further characterization of a low-molecular weight allergen fragment isolated from the green pea.

A low molecular weight allergen fragment present in the pea dialysate fraction was purified by ion-exchange chromatography and gel filtration. The highly purified allergen fragment inhibits both antigen-indiced passive cutaneous anaphlaxix reactions in guinea-pigs sensitized with rabbit anti-pea extract sera and Prausnitz-Küstner reactions in non-allergic volunteers sensitized with the sera of patients sensitive to green peas. Preliminary analysis of the purified allergen fragment indicates that it is a glycoprotein with a molecular weight of 1800 +/- 250.

Allergens↗
PubMed1975

Studies of the development of congenital anomalies in rats. III. Effects of inhibition of mitochondrial energy systems on embryonic development.

Pregnant rats were treated with various inhibitors of mitochondrial oxidative energy metabolism and with lowered oxygen tension, and the embryo fetuses examined for the occurrence of congenital malformations and for changes in enzymatic activities. Treatment with all agents tested resulted in the production of skeletal anomalies. Sodium phenobarbital was the most teratogenic of the drugs tested and produced a high incidence of malformations which included cleft palate, tail anomalies, spinal retroflexion, domed head, and facial hypoplasia. Diphenylhydantoin produced a low incidence of syndactyly and oligodactyly. In addition to its effects on fetal growth and development chloramphenicol appeared to interfere with implantation. Tissue preparations from embryos exposed to sodium phenobarbital and chloramphenicol showed markedly lowered levels of DPNH oxidase activity. Cytochrome oxidase activity was also markedly lowered in the preparations from chloramphenicol-exposed embryos. Enzyme activities in preparations from embryos exposed to malonate and diphenylhydantoin appeared unaffected, although the drugs are strong inhibitors of electron transport in vitro; the lack of apparent effect may be due to the fact that both drugs do not bind to the enzyme preparations and were diluted 100- to 200-fold during preparation and assay of the tissue homogenates.

Abnormalities, Drug-Induced↗
PubMed1975

The isolation of allergens from the green pea.

The aqueous extract of green peas was separated into 3 fractions (albumin, legumin, and vicilin) by dialysis against distilled water and isoelectric precipitation. The major antigenic and all of the allergenic activity of the pea extract was associated with the albumin fraction. The albumin fraction retains its allergenicity upon heating at 60 degrees C for 30 min or boiling at 100 degrees C for 5 min, but becomes partially inactivated by autoclaving at 120 degrees C for 15 min. The allergenic determinant expressed by the albumin fraction appears to be common to several other members of the legume family. In addition, the pea dialysate fraction was shown to specifically inhibit precipitin and passive cutaneous anaphylaxis (PCA) reactions involving rabbit antipea serum and the pea albumin fraction, and histamine release from passively sensitized monkey lung tissue using the serum of pea-sensitive patients.

Albumins↗
PubMed1975

Protective effects of atromid-S in vivo on mitochondrial stability in tissues of aged hamsters.

Atromid-S and nicotinic acid (hypocholesterolemic agents) were tested in vivo for their effects on mitochondrial yields and oxidative phosphorylation in tissues of aging hamsters. It was observed that atromid-S increased mitochondrial yields from both heart and skeletal muscle (39 and 64%, respectively), while nicotinic acid increased the yield only from skeletal muscle (97%). Efficiency (P:0 ratios) and rates of oxidative phosphorylation remained unchanged by drug treatment. Atromid-S treatment only partially protected against loss of controlled phosphorylation on prolonged storage of heart and skeletal muscle mitochondria of aging hamsters. It appeared that atromid-S may produce its effects on mitochondrial yields by decreasing the fragility of the mitochondria from the aging animals. The effects of the drug were not permanent, and values returned to control levels after 3 weeks from cessation of treatment.

Aging↗