Electrolyte transport in rat colon: comparative effects of intestinal resections and bypass

In the present study the influence of different types of intestinal resection (50% distal and 50% proximal small bowel resection) and bypass (50% jejunoileal bypass) upon water and electrolyte (Na and K) colonic transport was examined. Four weeks after resections and bypasses no significant changes in wet and dry tissue weights, serum sodium and potassium values were found in comparison to sham-operated controls. In vivo net absorption of sodium, measured in micromoles of 22Na+ which disappeared from the medium during a determined period (15, 30, 45 and 60 min), in sham-operated animals, showed a gradual increase with the increase in the perfusion time, rising from 144 +/- 20 mumol at 15 min of perfusion to 425 +/- 28 mumol at 60 min. One month after the resection, Na absorption, expressed as total absorption and as micromoles per square centimeter, was not significantly modified in animals distally and proximally resected, but did significantly increase in bypassed rats with respect to sham-operated animals. When the results were calculated taking into account the tissue wet weight, the values of the resected rats continued to show no modifications; however, there was a compensation in the bypassed rats. These data demonstrate that the increase in the absorptive capacity of the colon in bypassed rats is due to morphological changes, which could originate from the trophic influence of enteroglucagon or from the effect of the secretions which flowed directly into the colon from the blind loop, an action which does not occur in resected rats. The effects of resection and bypass upon K+ colonic secretion showed no significant differences among the groups studied.(ABSTRACT TRUNCATED AT 250 WORDS)     

Identification of guanine and adenine nucleotides as activators of glucose-1,6-bisphosphatase activity from rat skeletal muscle.

Glucose-1,6-bisphosphatase activity in rat skeletal muscle extracts was lost after exhaustive dialysis or precipitation with ammonium sulfate. Most of the original activity was recovered when the boiled extract was added to the ammonium sulfate precipitate. Qualitative analysis of the boiled extract revealed that the activator was either a nucleoside or a nucleotide. The results show that at concentrations between 0.05 and 1 mM, only guanine and adenosine derivatives are effective as activators, the former being more powerful. However, only guanosine, ADP, and AMP have an activating effect at the concentrations found in the boiled extract. The results of assays in vitro suggest that adenine nucleotides could be physiological modulators of glucose-1,6-bisphosphatase activity during muscle contraction.     

Enolase Activity and Isoenzyme Distribution in Human Brain Regions and Tumors

Abstract: The distribution of enolase (EC 4.2.1.11) activity and isoenzymes in various regions of human brain at different ages (from 23 weeks of gestation to 95 years) and in brain tumors has been determined. Total enolase activity increased in all regions with age. No significant differences were found in the relative proportions of αα-, αγ-, and γγ-enolase isoenzymes in the various brain regions, determined by agarose gel electrophoresis. Type αα-enolase was the predominant isoenzyme, and αγ-enolase represented a substantial proportion of the total enolase activity. Astrocytomas, anaplastic astrocytomas, glioblastomas, and meningiomas possessed lower enolase activity than normal brain. Among astrocytic tumors, total enolase activity correlated with malignancy. Astrocytomas possessed the lowest and glioblastomas the highest enolase activity. All tumors possessed a higher proportion of αα-enolase and a lower proportion of γγ-enolase than the normal human brain. Among astrocytic tumors, glioblastomas were the tumors with the highest proportion of αα-enolase and lowest proportion of γγ-enolase.     

Nitric oxide synthase inhibitors decrease human polymorphonuclear leukocyte luminol-dependent chemiluminescence

Nitric oxide synthase (NOS) inhibitors have been reported to modulate luminol-dependent chemiluminescence (CL) in rat macrophages, whereas the potent oxidant peroxynitrite (ONOO^-) was shown to react with luminol to yield CL in a cellfree system. We evaluated the role of the -arginine/NOS pathway in luminol CL by phorbol ester-activated human polymorpho-nuclear (PMN) leukocytes using the NOS inhibitors N^G-monomethyl- -arginine ( -NMMA) and N-iminoethyl- -omithine ( -NIO). Nitric oxide (·NO) release was determined by oxidation of oxymyoglobin. In addition, the effect of NOS inhibitors on superoxide anion O₂^-) production was measured. Luminol CL was notably diminished by -NMMA in a dose-dependent manner. Superoxide dismutase (SOD) also decreased luminol CL and -NMMA potentiated light emission decrease produced by SOD. Nitric oxide and O₂^·- production was significantly decreased by -NMMA; moreover, luminol-dependent CL but not O₂^·- production was attenuated by -NIO. These data suggest that products of catalytic activity of both ·NO synthase and NADPH oxidase are required to elicit maximal luminol CL in this system. These studies demonstrate that the NOS synthase pathway is involved in luminol CL by human PMN, and they suggest that ONOO would be an unrecognized mediator in this phenomenon.     

The effect of bedrock type,temperature and moisture on species richness of Pyrenean Scots pine (Pinus sylvestris L.) forests

The relationship between environmental parameters (bedrock type, temperature and moisture index) and understorey species richness was studied from a large phytosociological data base on Pyrenean Scots pine (Pinus sylvestris L.) forests. Generalized linear models were used to test this relationship. Total species richness and species richness of the different life forms were considered. The results suggest different patterns for the different life forms, and that the richest forest was on the calcareous bedrock of north-facing slopes at low altitudes.     

Effects of fructose 2,6-bisphosphate on phosphoglucomutase from plants

Fructose 2,6-bisphosphate affects phosphoglucomutase from plant and animal sources in a similar way. As previously found with rabbit muscle phosphoglucomutase, fructose 2,6-bisphosphate cannot substitute for glucose 1,6-bisphosphate as a cofactor in the reaction catalyzed by phosphoglucomutase from potato tubers, pea seeds, and string-beans. In the presence of glucose 1,6-bisphosphate, fructose 2,6-bisphosphate inhibits phosphoglucomutase from potato tubers. Activation of phosphoglucomutase from plant sources by fructose 2,6-bisphosphate reported by others was probably due to contamination of the commercial preparation of fructose 2,6-bisphosphate by glucose 1,6-bisphosphate.     

A method for determination of glucose 1,6-bisphosphatase

A sensitive and specific method to measure glucose 1,6-bisphosphatase activity, which allows the identification of the reaction products is described. [U-14 C]Glucose 1,6-P2, synthesized by the glucose 1-P kinase activity of phosphofructokinase, is used as substrate. The reaction products are separated and identified by chromatography on ion-exchange paper.     

Neuropeptide K is present in human cerebrospinal fluid

Neurokinin A-like immunoreactivity (NKA-LI) in human cerebrospinal fluid (CSF) was determined by radioimmuno assay (RIA) combined with high performance liquid chromatography (HPLC). The major immunoreactive component did not coelute with NKA, but coeluted with neuropeptide K (NPK), which contains the NKA sequence in its C-terminus. Trypsin treatment of this component from human CSF and of synthetic NPK, produced a substance which coeluted with NKA in the HPLC system. When the NKA-LI was oxidized with hydrogen peroxide and rechromatographed, the immunoreactivity coeluted with NPK sulfoxide. The results indicate that the main part of the NKA-LI in CSF is identical with NPK. The mean concentration of NPK measured in CSF from 6 healthy subjects by HPLC-RIA was 23 +/- 11 (SD) pmol/L.     

Fructose 2,6-bisphosphate and 6-phosphofructo-2-kinase during liver regeneration.

Glycogen and fructose 2,6-bisphosphate levels in rat liver decreased quickly after partial hepatectomy. After 7 days the glycogen level was normalized and fructose 2,6-bisphosphate concentration still remained low. The 'active' (non-phosphorylated) form of 6-phosphofructo-2-kinase varied in parallel with fructose 2,6-bisphosphate levels, whereas the 'total' activity of the enzyme decreased only after 24 h, similarly to glucokinase. The response of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase from hepatectomized rats (96 h) to sn-glycerol 3-phosphate and to cyclic AMP-dependent protein kinase was different from that of the enzyme from control animals and similar to that of the foetal isoenzyme.