Genetic control of the mitochondrial form of superoxide dismutase in hexaploid wheat

Extracts of mature grains of a large number of aneuploid derivatives of Triticum aestivum cv. Chinese Spring and of the members of five wheat-alien chromosome addition series were subjected to isoelectric focusing in polyacrylamide gels in order to study the genetic control of superoxide dismutase (SOD). Evidence was obtained that homologous structural genes for the mitochondrial form of SOD are located in the long arms of the homoeologous group 2 chromosomes of Chinese Spring and in chromosome 2R of Secale cereale cv. Imperial. The SOD gene loci located in chromosomes 2A, 2B, 2D, and 2R were designated Sod-A1, Sod-B1, Sod-D1, and Sod-R1, respectively. Chromosome-arm pairing data indicate that 2DL is not homoeologous to either 2AS or 2BL. The results of this study suggest, however, that 2BL is partially homoeologous to both 2AL and 2DL.Technical article No. 21074 of the Texas Agricultural Experiment Station. This work was supported by USDA Grant 83-CRCR-1-1322 to GEH.     

Analysis of EMG measurements during bicycle pedalling

Activity of eight leg muscles has been monitored for six test subjects while pedalling a bicycle on rollers in the laboratory. Each electromyogram (EMG) data channel was digitized at a sampling rate of 2 kHz by a minicomputer. Data analysis entailed generating plots of both EMG activity regions and integrated EMG (IEMG). For each test subject, data were recorded for five cases of pedalling conditions. The different pedalling conditions were defined to explore a variety of research hypotheses. This exploration has led to the following conclusions: Muscular activity levels of the quadriceps are influenced by the type of shoes worn and activity levels increase with soft sole shoes as opposed to cycling shoes with cleats and toeclips. EMG activity patterns are not strongly related to pedalling conditions (i.e. load, seat height and shoe type). The level of muscle activity, however, is significantly affected by pedalling conditions. Muscular activity bears a complex relationship with seat height and quadriceps activity level decreases with greater seat height. Agonist (i.e. hamstrings) and antagonist (i.e. quadriceps) muscles of the hip/knee are active simultaneously during leg extension. Regions of peak activity levels, however, do not overlap. The lack of significant cocontraction of agonist/antagonist muscles enables muscle forces during pedalling action to be computed by solving a series of equilibrium problems over different regions of the crank cycle. Regions are defined and a solution procedure is outlined.     

Catabolism of myo-Inositol to Precursors Utilized for De Novo Glycerolipid Biosynthesis

Systemic injection of [2-3H]myo-inositol into frogs resulted in the incorporation of more than half of the label into glycerolipid classes other than phosphoinositides in retinal rod outer segment membranes. Following methanolysis and differential extraction of isolated lipid classes, radioactivity was recovered primarily in the aqueous phase. After phospholipase C hydrolysis of the total membrane lipids, 97% of the radioactivity was extractable with organic solvents, and 70% of the label in lipids was in 1,2-diglycerides. These results indicate that the label was incorporated primarily into the glyceryl moiety of the membrane glycerolipids. Intraocular injection of frog eyes or in vitro incubation of frog retinas with [2-3H]myo-inositol resulted in the incorporation of radioactivity almost exclusively into phosphoinositides in rod outer segment membranes. Incubation of retinas with [U-14C]glucuronic acid did not result in the formation of labeled retinal lipids. These results suggest that myo-inositol can be catabolized systemically to precursors utilized for glycerolipid biosynthesis in the retina.     

Incorporation of [3H]thymidine into DNA and of [35S]sulfate into sulfatides of oligodendroglial cells during development: Effect of malnutrition

Incorporation of [³H]thymidine into DNA and of [³⁵S]sulfate into sulfatides of oligodendroglial cells isolated from brain slices incubated with the radioactive precursor was studied in normal and malnourished rats at different ages. The pattern and the values of incorporation of [³H]thymidine into DNA were similar in both groups of animals. The maximum value of incorporation was observed at 7 days of age decreasing rapidly thereafter and leveling off between 18–21 days. In both groups of animals labeling of sulfatides attained a maximum at 18 days of age, showing similar values of incorporation up to that age. However, at 21 days of age; the values corresponding to malnourished rats were found to be 40% lower in comparison to controls. The results suggest that (a) proliferation of oligodendroglial cells stops at similar ages in normal and malnourished rats, (b) expression of sulfatide synthesis by oligodendroglial cells is similar in both groups of animals up to 18 days, and (c) the starved rats seem to be unable to maintain normal synthesis of these galactolipids throughout the entire period of active myelinogenesis.     

Neonatal malnutrition in the rat affects the delivery of sulfatides from microsomes and their entry into myelin

Brain slices from 18 day old normal and malnourished rats were incubated in the presence of [³⁵S]sulfate to explore its incorporation into sulfatides of a total brain homogenate and the appearance of labeled sulfatides in different subcellular fractions. While the incorporation of label into sulfatides of the total homogenate was similar in both groups of animals, in subcellular fractions separated on a linear sucrose density gradient, labeling of sulfatides in malnourished animals was relatively higher in the region corresponding to the microsomal fraction. Time course incorporation and pulse-chase experiments were carried out to explore the kinetics of labeling of microsomal and myelin sulfatides. In pulse-chase experiments, normal controls showed a decrease in the specific radioactivity of sulfatides in the microsomal fraction after the chase, which was not observed in malnourished animals, while the appearance of labeled sulfatides in the myelin fraction of the latter group of animals was found to be lower than in normals. These results suggest that in neonatal malnutrition there is a defect in the transport of de novo synthesized sulfatides towards myelin or/and a problem in the assembly of these lipids into the myelin membrane.     

Cloning and Characterization of Yeast LEU4, One of Two Genes Responsible for α-Isopropylmalate Synthesis

By complementation of an alpha-isopropylmalate synthase-negative mutant of Saccharomyces cerevisiae (leu4 leu5), a plasmid was isolated that carried a structural gene for alpha-isopropylmalate synthase. Restriction mapping and subcloning showed that sequences sufficient for complementation of the leu4 leu5 strain were located within a 2.2-kilobase SalI-PvuII segment. Southern transfer hybridization indicated that the cloned DNA was derived intact from the yeast genome. The cloned gene was identified as LEU4 by integrative transformation that caused gene disruption at the LEU4 locus. When this transformation was performed with a LEU4fbr LEU5 strain, the resulting transformants had lost the 5',5',5'-trifluoro-D,L-leucine resistance of the recipient strain but were still Leu+. When it was performed with a LEU4 leu5 recipient, the resulting transformants were Leu-. The alpha-isopropylmalate synthase of a transformant that carried the LEU4 gene on a multicopy plasmid (in a leu5 background) was characterized biochemically. The transformant contained about 20 times as much alpha-isopropylmalate synthase as wild type. The enzyme was sensitive to inhibition by leucine and coenzyme A, was inactivated by antibody generated against alpha-isopropylmalate synthase purified from wild type and was largely confined to the mitochondria. The subunit molecular weight was 65,000-67,000. Limited proteolysis generated two fragments with molecular weights of about 45,000 and 23,000. Northern transfer hybridization showed that the transformant produced large amounts of LEU4-specific RNA with a length of about 2.1 kilonucleotides. The properties of the plasmid-encoded enzyme resemble those of a previously characterized alpha-isopropylmalate synthase that is predominant in wild-type cells. The existence in yeast of a second alpha-isopropylmalate synthase activity that depends on the presence of an intact LEU5 gene is discussed.     

Mixing patterns in Amazon lakes

The diel mixing patterns of two small floodplain lakes, Lago Jacaretinga in the Amazon drainage, and Lago Cristalino in the Rio Negro system, were investigated during both the high-water and low-water states of the Amazon River hydrograph. Measurements included temperature, oxygen, ammonia, phosphate, and chlorophyll. In both lakes thermal stratification developed during the day and was eroded at night. During the low-water period when the lakes were shallow, nocturnal circulation extended to the lake bottom, whereas when the lakes were deeper (greater than about 5 m), circulation did not reach the bottom and an anoxic hypolimnion developed. During the low-water period, percent of oxygen concentrations were relatively high but always less than saturation. Low oxygen concentrations were observed during the high-water period. At all times nocturnal mixing supplied a significant amount of oxygen to the lake ecosystems. Nighttime upward mixing of recycled nitrogen and phosphorus also appeared to be important nutrient sources for algal productivity.     

The innervation of the pyloric region of the crab,Cancer borealis: Homologous muscles in decapod species are differently innervated

Summary The muscles of the pyloric region of the stomach of the crab,Cancer borealis, are innervated by motorneurons found in the stomatogastric ganglion (STG). Electrophysiological recording and stimulating techniques were used to study the detailed pattern of innervation of the pyloric region muscles. Although there are two Pyloric Dilator (PD) motorneurons in lobsters, previous work reported four PD motorneurons in the crab STG (Dando et al. 1974; Hermann 1979a, b). We now find that only two of the crab PD neurons innervate muscles homologous to those innervated by the PD neurons in the lobster,Panulirus interrruptus. The remaining two PD neurons innervate muscles that are innervated by pyloric (PY) neurons inP. interruptus. The innervation patterns of the Lateral Pyloric (LP), Ventricular Dilator (VD), Inferior Cardiac (IC), and PY neurons were also determined and compared with those previously reported in lobsters. Responses of the muscles of the pyloric region to the neurotransmitters, acetylcholine (ACh) and glutamate, were determined by application of exogenous cholinergic agonists and glutamate. The effect of the cholinergic antagonist, curare, on the amplitude of the excitatory junctional potentials (EJPs) evoked by stimulation of the pyloric motor nerves was measured. These experiments suggest that the differences in innervation pattern of the pyloric muscles seen in crab and lobsters are also associated with a change in the neurotransmitter active on these muscles. Possible implications of these findings for phylogenetic relations of decapod crustaceans and for the evolution of neural circuits are discussed.Abbreviations ACh acetylcholine - Carb carbamylcholine - cpv muscles of the cardio-pyloric valve - cpv7n nerve innervating muscle cpv7 - cv muscles of the ventral cardiac ossicles - cv1n nerve innervating muscle cvl - cv2n nerve innervating muscle cv2 - EJP excitatory junctional potential - IC inferior cardiac neuron - IV inferior ventricular neuron - IVN inferior ventricular nerve - LP lateral pyloric neuron - LPG lateral posterior gastric neuron - lvn lateral ventricular nerve - mvn medial ventricular nerve - p muscles of the pylorus - PD pyloric dilator neuron - PD _in intrinsic PD neuron - PD _ex extrinsic PD neuron - pdn pyloric dilator nerve - PY pyloric neuron - pyn pyloric nerve - STG stomatogastric ganglion - VD ventricular dilator neuron     

Kinetics of the 5′-nucleotidase and the adenosine deaminase in subcellular fractions of rat brain

Suspensions of rat brain microsomes, synaptosomes, and synaptic vesicles were able to convert adenosine to inosine by means of adenosine deaminase. Isosbestic points of this transformation, at 222, 250 and 281 nm, remained unchanged with time-course. This fact suggests that adenosine deaminase (ADA, E.C. 3.5.4.4) is located on the surface of the vesicles whereas purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4) is located inside the vesicles. Kinetic parameters of the particulate 5-nucleotidase (5N, E.C. 3.1.3.5) and adenosine deaminase were analogous to those of the cytosolic enzymes. These results suggest that soluble and particulate enzymes represent different pools of the same molecular species.     

Heterogeneous localization of some purine enzymes in subcellular fractions of rat brain and cerebellum

The activity of guanine deaminase (GAH, E.C. 3.5.4.3) was lower in rat cerebellum soluble and microsomal fractions than in rat brain subfractions. Adenosine deaminase (ADA, E.C. 3.5.4.4) activity was released in higher proportion than guanine deaminase, purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4), 5-nucleotidase (5N, E.C. 3.1.3.5), and lactate (LDH, E.C. 1.1.1.27) and malate (MDH, E.C. 1.1.1.37) dehydrogenase in press-juices of rat brain. Furthermore, nerve ending-derived fractions (synaptosomes and synaptic vesicles) showed an enrichment of adenosine deaminase and also of 5-nucleotidase. The action of deoxycholate over the subfractions did not increase the activity of either enzyme. The contrary occurred with the remaining enzymes studied. Thus, it is possible that one set of enzymes are located on the surface of the particulate vesicles, whereas another set are located inside these vesicles, suggesting a compartmentation of purine catabolic enzymes in different areas of the central nervous system.