Correlation of inhibition of fructose 1,6-bisphosphatase by AMP and the presence of the nucleotide-binding domain

Chicken liver fructose 1,6-bisphosphatase binds to blue dextran-Sepharose affinity columns and is eluted by AMP, an allosteric inhibitor of the enzyme. On the other hand, bumblebee fructose 1,6-bisphosphatase, which is not inhibited by AMP, does not bind to blue dextran-Sepharose. Chicken liver 1,6-bisphosphatase binds 3.6 mol of AMP/mol of enzyme, while the bumblebee enzyme binds no AMP. However, bumblebee fructose 1,6-bisphosphatase can be activated by subtilisin, indicating that it possesses a protease-sensitive region similar to that present in mammalian fructose 1,6-bisphosphatase.     

Multiple forms of phosphofructokinase in developing rabbit and guinea pig tissues.

Multiple forms of phosphofructokinase in striated muscle and cardiac muscle of developing rabbit (Oryctolagus cuniculus) undergo changes with development, but not in brain and liver. The cardiac muscle of the 1-day-old rabbit contains phosphofructokinase A₄ together with the four hybrid forms which were tentatively called A₃C, A₂C₂, AC₃, and C₄. In older animals, phosphofructokinase C₄ disappears first, followed by the hybrid forms, and only phosphofructokinase A₄ persists in the adult animal. Both phosphofructokinase A₄ and phosphofructokinase C₄, as well as their hybrid forms, are present in developing embryonic brain and also in the brains of adult animals. Developing rabbit liver contains a single form of phosphofructokinase, but two isoenzymes are consistently seen in guinea pig liver. In striated muscle from fetal and 1-day-old rabbit, two isoenzymes are found, tentatively identified as A₄ and the A₃C hybrid. The results suggest that fetal phosphofructokinase A₄ and phosphofructokinase C₄, and their hybrids, might be present in striated muscle. Guinea pig tissues show a pattern of phosphofructokinase isoenzymes different from that in rabbit tissues.     

Field and storage testing Bt potatoes for resistance to potato tuberworm (Lepidoptera: Gelichiidae)

Potato tuberworm, Phthorimaea operculella (Zeller), is the most serious insect pest of potatoes worldwide. The introduction of the Bacillus thuringiensis (Bt) toxin gene through genetic engineering offers host plant resistance for the management of potato tuberworm. We report on the field and storage studies to evaluate Bt-cry5 potato lines for resistance to potato tuberworm in Egypt under natural infestations and their agronomic performance in both Egypt and Michigan. From 1997 to 2001, field experiments were conducted at the International Potato Center (CIP) Research Station, Kafr El-Zyat, Egypt, and/or Agricultural Genetic Engineering Institute (AGERI), Giza, Egypt, to evaluate resistance to tuberworm. A total of 27 Bt-transgenic potato lines from six different Bt constructs were evaluated over a 5-yr period. After harvest and evaluation of the agronomic trials, storage evaluation of potato tuberworm damage was done at the CIP Research Station. The 1997 field trial was the first field test of genetically engineered crops in Egypt. Field tests to assess potato tuberworm resistance in Egypt were able to differentiate between the Bt-transgenic lines and the nontransgenic lines/cultivars in 1999, 2000, and 2001. The Bt-cry5-Spunta lines (Spunta-G2, Spunta-G3, and Spunta-6a3) were the most resistant lines in field with 99-100% of tubers free of damage. In the 2001 storage study, these lines were also over 90% free of tuberworm damage after 3 mo. NYL235-4.13, which combines glandular trichomes with the Bt-cry5/gus fusion construct, also had a high percentage of clean tubers in the field studies. In agronomic field trials in Michigan from 1997 to 2001, the Bt-transgenic lines in most instances performed similar to the nontransgenic line in the agronomic trials; however, in Egypt (1998-1999), the yields were less than one-half of those in Michigan. Expression of the Bt-cry5 gene in the potato tuber and foliage will provide the seed producer and grower a tool in which to reduce potato tuberworm damage to the tuber crop in the field and storage.     

A technique for the determination of the available oxygen in living carp (Cyprinus carpio) muscle

A polarographic method for the measurement of the available oxygen in the muscle of living carp by the use of a platinum microelectrode is proposed. The oxygen and the reference electrodes were assembled in a single insertion piece which was implanted in the muscle of a living carp maintained in a special experimental chamber. Curves for normal oxygen levels corresponding to air-saturated water, as well as to a carbogene-saturated water, were obtained. The method can be considered adequate for the measurement of tissue oxygen in living fishes.     

Effects produced on isolated rat heart mitochondria by beryllium sulfate.

Beryllium sulfate increases the rate of oxygen uptake by isolated rat heart mitochondria. This effect is proportional to the Be²⁺ concentration. Beryllium binds to a limited number of sites on the isolated mitochondria and stimulates the mitochondrial ATPase. These effects, which appear to be related to an uncoupling of respiration, cause swelling of the mitochondria.     

Metabolic activity of the Sticker's lymphosarcoma

Some parameters (glycolysis, respiration, levels of glycolytic enzymes) of the lymphoid cells from the Sticker's lymphosarcoma were established in order to better define the biochemical behavior of the venereal tumor of the dog. For comparative purposes lymphocytes from peripheral blood of normal and tumor-bearing dogs were also studied. Lactic acid produced by the tumor cells during aerobic glycolysis is liberated in the reaction medium. Oxygen uptake is enhanced in the presence of succinate, but not with pyruvate, alpha-ketoglutarate, or malate as substrates. Higher levels of some of the enzymes from the glycolytic pathways as well as differences on the physicochemical and kinetic properties of the glycolytic regulatory enzymes are found in Sticker's tumor cells, when compared with the lymphocytes from peripheral blood of normal and tumor-bearing dogs. A fructose-bisphosphate positively modulated pyruvatekinase is found in the tumor cells.     

Comparative levels of muscle glycolytic enzymes in mammals, fish, echinoderm and molluscs.

1. Levels of glycolytic enzymes were determined in terms of units of enzyme/mg protein in rat striated muscle, carp lateral muscle, holothuria longitudinal muscle of the body wall, and a snail foot muscle. 2. An attempt has been made to correlate levels of glycolytic enzymes as a parameter to establish a "biochemical distance" at molecular level and correlate this with the phylogenetic position in animals sufficiently separated in the animal tree of evolution. 3. The possibility of a peculiar kinetic behaviour of the glycolytic pathway in each muscle tissue studied, has been analyzed as the profiles of the ratios of pairs of enzymes bearing a substrate-product dependence. 4. A possible "futile synthesis" of some glycolytic enzymes, such as FDP-aldolase in the case of fish muscle, is proposed.