Effects of Low pH on Lactate Dehydrogenase Kinetics of Diving and Nondiving Reptiles

The properties of lactate dehydrogenase were examined in two snake species, Nerodia rhombifera and Elaphe obsoleta, and a turtle species, Pseudemys scripta. Our purpose was to compare the LDH activity of reptiles with limited anaerobic capabilities with that of the well established diver Pseudemys. The Michaelis-Menten kinetics of LDH and its susceptibility to inhibition by elevated pyruvate concentrations were investigated in the brain and heart of the three species. All tissue incubations and enzyme activity determinations were done at a pH of 7.0 in order to stimulate a diving blood pH in the three species. In both tissues the LDH activity of the snakes was higher than that of Pseudemys at pyruvate concentrations ranging between .03 mM and .50 mM. The Km values of the snakes were lower than those of Pseudemys, suggesting a greater enzyme-substrate affinity in the snake tissues. The Vmax values were higher in the snake tissues indicating a faster conversion of substrate to product. Heart LDH activity was reduced to an equal extent by high pyruvate concentrations in each of the three species. Elaphe brain LDH was most susceptible to pyruvate inhibition, but Nerodia and Pseudemys brain LDH were inhibited to an equal extent. The results indicate that the kinetic behavior of brain and heart LDH of the three species is similar at a pH of 7.4 and a pH of 7.0. The results also suggest that the LDH of Pseudemys is no better adapted to withstand anaerobic conditions than that of Nerodia or Elaphe at a pH of 7.0

Age and Huddling as Determinants of Metabolic Rate in Grasshopper Mice (Onychomys leucogaster)

The metabolic rates of grasshopper mice (Onychomys leucogaster) were determined every third day from birth to adulthood. Metabolic rates were quantitated by measuring oxygen consumption in an open circuit system. There was a rapid fall in oxygen consumption from the third day after birth until the ninth day. Mice which were housed separately assumed a constant metabolic rate at an earlier age than mice which were kept with litter-mates. The greatest increases in metabolism occurred when immature mice were separated from litter-mates for oxygen consumption determinations. It is concluded that huddling plays an important role in reducing the metabolic rate of young grasshopper mice

Hematology as Related to Diving Characteristics of Elaphe obsoleta, Nerodia erythrogaster, Nerodia Fasciata and Nerodia rhombifera

The diving capabilities of Nerodia erythrogaster flavigaster and Nerodia fasciata confluens were investigated and the results were compared with similar studies on Nerodia rhombifera rhombifera and Elaphe obsoleta obsoleta (Baeyens et al., 1978). In addition, morphological and hematological parameters contributing to underwater survival were examined. The duration of underwater survival for N. erythrogaster and N. fasciata was approximately one hour with no difference between the species. The lung volumes of the two species were also similar but were significantly less than lung volumes reported for E. obsoleta. There were no significant differences in hemoglobin concentration, red blood cell count or hematocrit between N. rhombifera, N. erythrogaster, N. fasciata, and E. obsoleta. Based on similarities in underwater tolerance, lung morphology and hematology, Nerodia more closely resembles the terrestrial E. obsoleta than those reptiles specifically adapted to an underwater existance

Relationship Between Physical Conditioning and Plasma High Density Lipoprotein-Cholesterol Concentration

Five subjects (three females and two males) took part in an exercise regimen in order to determine if aerobic exercise results in an increase in high-density lipoprotein-cholesterol levels (HDL-C) in the plasma. The exercise regimen consisted of running three miles a day, five days per week for six months. Running speed was at such a pace that the subjects attained a minimum of 60% of their maximal heart rate reserve (MHRR). Before the training program began the following parameters were measured in all of the subjects: height, weight, percent body fat, maximal oxygen consumption (Vₒ₂ max), vital capacity, resting heart rate, resting blood pressure, HDL-C, plasma triglycerides (TG), and plasma cholesterol (TC). These same measurements were retaken every two months and at the conclusion of the study. The exercise protocol produced significant changes in Vₒ₂ max and resting heart rate. None of the other parameters were significantly changed. The results of this study have shown that aerobic exercise does not cause significant changes in HDL-C levels

Oxygen Toxicity in the Mammalian Liver

The effect of hyperbaric oxygen tensions on the oxygen consumption of mouse liver homogenates was investigated. It was found that hyperbaric oxygen rapidly inhibits the oxidative metabolism of the mammalian liver. Mouse liver homogenate exposed to an oxygen tension of 3837.8 mm Hg for 30 minutes demonstrated a 50.6% reduction in oxygen consumption compared to controls exposed to nitrogen at ambient pressure. The effects of reduced glutathione as a protective agent against hyperbaric oxygen toxicity were also examined. Liver homogenates pretreated with reduced glutathione and exposed to hyperbaric oxygen tensions demonstrated greater activity than untreated controls. It is concluded that: (1) Reduced glutathione protects important enzymes associated with oxidative metabolism by keeping them in a reduced and viable state, and (2) Reduced glutathione can stimulate oxygen consumption by increasing succinate formation through a reduced glutathione - succinate shunt

On-line scheduling method of manufacturing system based on VS algorithm for reference pattern

In this paper, a scheduling method is developed provide planning for manufacturing plants with multiple coordinating cells. The controls for reconfigurable manufacturing systems have to be capable not only of identifying exceptions on-line, but also simultaneously developing on-line strategies for unpredictable customer order changes or inaccurate estimate of processing times. The approach exploits virtual supervisor (VS) concept developing an algorithm which provides access to all system information during program execution and thus can readily monitor the overall system performance creating reference pattern. The goal is to minimize expected costs of part tardiness and/or earliness. A solution methodology based on a combined Lagrangian relaxation, VS-Patterns, Maxwell equations and temporal difference is developed to reduce the computational requirements for large problems. Sequences pattern shows that near optimal schedules can be obtained a dual solution for on-line implementation

Some Physiological and Morphological Adaptations for Underwater Survival in Natrix rhombifera and Elaphe obsoleta

The submergence times of the diamondback water snake (Natrix rhombifera) and black rat snake (Elaphe obsoleta) were compared. Both species could easily survive underwater for periods greater than one hour. Furthermore, there was no difference in time of underwater survival in the two species. Some physiological and morphological parameters which may contribute to the ability of N. rhombifera and E. obsoleta to remain submerged were also examined. E. obsoleta was found to have a greater lung volume and larger and more numerous alveoli than N. rhombifera. Both species demonstrated a bradycardia upon submergence but it was less pronounced than the bradycardia of the true diving animals. It is concluded that N. rhombifera has few physiological adaptations for diving and that some of the physiological attributes for an aquatic existence have already developed in E. obsoleta

Editorial: Executive Function and Education

status: publishe