Resonance electroconformational coupling: A proposed mechanism for energy and signal transductions by membrane proteins

Recent experiments show that membrane ATPases are capable of absorbing free energy from an applied oscillating electric field and converting it to chemical bond energy of ATP or chemical potential energy of concentration gradients. Presumably these enzymes would also respond to endogenous transmembrane electric fields of similar intensity and waveform. A mechanism is proposed in which energy coupling is achieved via Coulombic interaction of an electric field and the conformational equilibria of an ATPase. Analysis indicates that only an oscillating or fluctuating electric field can be used by an enzyme to drive a chemical reaction away from equilibrium.In vivo, the stationary transmembrane potential of a cell must be modulated to become locally oscillatory if it is to derive energy and signal transduction processes.     

Aminopyridazine derivatives and TXA2-PGI2 balance

Experiments carried out under the conditions adopted showed the strong affinity of aminopyridazine derivatives for the eicosanoids TXA2 and PGI2. But this affinity depended on the chemical structure of the molecule: a small change in the radical grafted onto the pyridazine ring could completely modify the pharmacological activity of the molecule. Consequently it should be possible to control the properties of pyridazine derivatives according to pharmacological needs. Thus: --pyridazin-3-one derivatives were mainly active on TXA2 biosynthesis: 2-aminoalkyl 5-arylidene 6-methyl (4H) pyridazin-3-ones inhibited the TXA2-synthesizing activity of cardiac tissue whereas 3-amino 4,6-diaryl pyridazin-3-ones were specific inhibitors of the TXA2 synthetase in vitro, but these effects were weak. --pyridazine derivatives were devoid of any effect on the TXA2-synthesizing activity of cardiac tissue: they acted on either TXA2 synthetase or PGI2 synthetase according to the radicals grafted onto the pyridazine ring. --none of the compounds under study was active on the PGI2-synthesizing activity of cardiac tissue.     

Comparative effects of some 3-amino 4,6-diarylpyridazines on the biosynthesis in vitro of TXA2 and PGI2- and on the TXA2- and PGI2-synthesizing activities of cardiac tissue

Some 3-amino 4,6-diarylpyridazine derivatives were tested for their effects on TXA2 and PGI2 biosyntheses in vitro and on the TXA2- and PGI2-synthesizing activities of cardiac tissue. Horse platelet and aorta microsomes were used as sources of thromboxane and prostacyclin synthetases respectively. The TXA2- and PGI2-synthesizing activities of cardiac tissue were studied on isolated perfused rabbit hearts (the heart microsomes being used both as TXA2 synthetase and PGI2 synthetase sources). TXB2 and 6-keto PGF1 alpha were determined by RIA. Among the compounds under study, 3-morpholino 4,6-diphenylpyridazine (III) was shown to inhibit specifically the TXA2 synthetase. Substitution of the morpholino group by a dimethylamino one (I) reinforced the inhibiting effects on TXA2 synthetase but it also revealed a slight anti-prostacyclin synthetase action of the molecule. Replacement of 3-morpholino moieties by either a 3-hydrazino (IV), or a 2-dimethylaminoethylamino (V), or a 2-morpholinoethylamino group (VI) abolished completely the effects of the molecule on TXA2 and PGI2 synthetases. Likewise the addition of chlorine on the para-position on the phenyl ring of I neutralized all its inhibitory effects both on TXA2 and PGI2 synthetases in vitro. None of the 3-amino 4,6-diarylpyridazine derivatives was active on either the TXA2- or PGI2-synthesizing activities of cardiac tissue.     

The periosteum in experimental avian hyperostosis induced by MAV 2-0 myeloblastosis virus. Differential diagnosis from osteopetrosis

Diaphyseal tibial bones of 11-14-17 th day-old hatched chicks infected with retrovirus myeloblastic MAV 2-0 were examined by conventional optical microscopy. The characteristic lesion is osteoblastic hyperplasia with the development of spongious bone. The new formed bone contains abnormal chondroid tissue. The relation between osseous and cartilaginous tissues in this experimental model is discussed. As connective tissue took part in the constitution of this hyperostosis, this osteopathy may be considered as an hyperplastic, monodermic mesenchymatous, pluritissular tumour. The numerous works concerning the "avian hyperostosis osteopetrosis" are commented.     

Effect of anthropometric characteristics and socio-economic status on physical performances of pre-pubertal children living in Bolivia at low altitude

We have previously observed that 11-year-old children of low socio-economic status (LSES) showed a delayed physical growth of approximately 2 years and developed lower normalized short-term power output than children of high socio-economic status (HSES) of the same age. In contrast, maximal oxygen uptake per unit of fat free mass was no different in either group. The aim of this study was to evaluate the effect of anthropometric characteristics between HSES and LSES prepubertal children in aerobic and anaerobic performance. To compare children of the same body dimensions, 11-year-old boys (n = 30) and girls (n = 31) of LSES and 9-year-old boys (n = 21) and girls (n = 27) of HSES were studied. Anthropometric measurements, (direct test), maximal anaerobic power (P _max, force-velocity test) and mean anaerobic power ( , Wingate test) were determined. In these children having the same body dimensions: mean were the same in LSES and HSES children [1.2 (SD 0.2)1-min^–1];P _max and were lower in LSES subjects [154.0 (SD 33.2) vs 174.6 (SD 38.4) W and 116.3 (SD 23.3) vs 128.2 (SD 28.0) W, respectively]; the linear relationships between and fat free mass were the same in LSES and HSES boys but, in the girls, the LSES group had lower values. For anaerobic performance, the relationships were significantly different: the slopes were the same but LSES values for the both sexes were lower. These results would suggest that factors other than differences in body dimensions alone were responsible for the lower performance of LSES girls and boys. Cultural factors and motor learning, structural and functional alterations of muscle induced by marginal malnutrition have been discussed.     

Evaluation of physical fitness from field tests at high altitude in circumpubertal boys: comparison with laboratory data

Field tests of running and laboratory tests were performed in La Paz [high altitude (HA), 3700 m] and in Clermont-Ferrand [low altitude (LA), 300 m] to investigate their validity at HA. Prepubertal boys of mean ages 10.6 years (HA1,n = 16; LA1,n = 28) and pubertal boys of 13.7 years (HA2,n = 12; LA2,n = 41) took part in the study. All the boys performed a 30-m sprint (v _30m), a 30-s shuttle run (v _3os) and a progressive shuttle run test until their maximal aerobic velocity (v _maxsRT). Maximal oxygen consumption was extrapolated from the last test. . In the laboratory, the boys performed a force-velocity test (P _max), a Wingate test (P _Wing) and a graded test to measure maximal oxygen consumption ; direct method) on a cycle ergometer. At similar ages, there was no significant difference between HA and LA boys forv _30m andP _max. Thev _30s of HA boys was 3%–4% lower than those of LA boys (P<0.05); there was no significant difference forP _Wing. Significant relationships were observed at both altitudes betweenP _max (watts per kilogram) andv _30m (HA:r=0.76; LA:r=0.84) and betweenP _Wing andv _30s (HA:r=0.67; LA:r = 0.77); the slopes and the origins were the same at HA and LA. The ,v _maxSRT and were lower by 9%, 12% and 20%, respectively, at HA than at LA (P<0.05). However, the relationships between and (litres per minute) at HA (r=0.88) and at LA (r=0.93) were identical. In conclusion, chronic hypoxia did not modify performance in very short dash exercises. The influence of HA appeared when the exercise duration increased and, during a maximal shuttle run test, performance was reduced by 10% at HA. Moreover, it was possible to assessP _max,P _Wing and at HA as well as at LA from field tests.     

The six genes of the Rubisco small subunit multigene family from Mesembryanthemum crystallinum,a facultative CAM plant

The nucleotide sequences of the entire gene family, comprising six genes, that encodes the Rubisco small subunit (rbcS) multigene family in Mesembryanthemum crystallinum (common ice plant), were determined. Five of the genes are arranged in a tandem array spanning 20 kb, while the sixth gene is not closely linked to this array. The mature small subunit coding regions are highly conserved and encode four distinct polypeptides of equal lengths with up to five amino acid differences distinguishing individual genes. The transit peptide coding regions are more divergent in both amino acid sequence and length, encoding five distinct peptide sequences that range from 55 to 61 amino acids in length. Each of the genes has two introns located at conserved sites within the mature peptide-coding regions. The first introns are diverse in sequence and length ranging from 122 by to 1092 bp. Five of the six second introns are highly conserved in sequence and length. Two genes, rbcS-4 and rbcS-5, are identical at the nucleotide level starting from 121 by upstream of the ATG initiation codon to 9 by downstream of the stop codon including the sequences of both introns, indicating recent gene duplication and/or gene conversion. Functionally important regulatory elements identified in rbcS promoters of other species are absent from the upstream regions of all but one of the ice plant rbcS genes. Relative expression levels were determined for the rbcS genes and indicate that they are differentially expressed in leaves.     

Effects of endurance training on the cardiovascular system and water compartments in elderly subjects

Pickering, Gisèle P., Nicole Fellmann, BéatriceMorio, Patrick Ritz, Aimé Amonchot, Michel Vermorel, and JeanCoudert. Effects of endurance training on the cardiovascularsystem and water compartments in elderly subjects. J. Appl. Physiol. 83(4): 1300-1306, 1997.Theeffects of endurance training on the water compartments and thecardiovascular system were determined in 10 elderly subjects [age62 ± 2 yr, pretraining maximal oxygen consumption(O_{2 max})/kg = 25 ± 2 ml · min¹ · kg¹body wt]. They trained on a cycloergometer 3 times/wk for 16 wk(50-80%O_{2 max},then 80-85%O_{2 max}). They werechecked at 8 wk, 16 wk, and 4 mo after detraining. Training improvedO_{2 max} (+16%) andinduced plasma volume expansion (+11%). No change in total body water,extracellular fluid, interstitial and intracellular fluid volumes,fat-free mass, and body weight was detected in this small sample withtraining. Body fat mass decreased (2.1 ± 2.2 kg).Echocardiography at rest showed increased fractional shortening andejection fraction and decreased left ventricular end-systolic dimension(P < 0.05). Blood volume expansioncorrelates with cardiac contractility and has an impact on cardiacfunction. These improvements are precarious, however, and arecompletely lost after 4 mo of detraining, when elderly subjects losethe constraints and the social stimulation of the imposed protocol.