Magnesium loading effect on magnesium deficiency in endurance-trained subjects during prolonged restriction of muscular activity

The aim of this study was to evaluate the effect of magnesium (Mg) loading (10.0 mg Mg/kg body wt) and daily Mg supplements (5.0 mg Mg/kg body wt) on Mg deficiency shown by increased and not by decreased serum Mg concentration during hypokinesia (decreased km number/d). The studies were done during 30 d of prehypokinesia and 364 d of hypokinesia (HK) periods. Forty endurance-trained volunteers aged 22–26 yr with a peak VO2 max of 66.3 mL·kg⁻¹ min⁻¹ and with an average 15.0 km/d running distance were chose as subjects. They were equally divided into four groups:

Daily zinc supplementation effect on zinc deficiency in rats during prolonged restriction of motor activity

The objective of this investigation was to evaluate the effect of 47 mg zinc supplementation on deficiency of zinc in rats during 98 d of restriction of motor activity (hypokinesia), which appeared by higher plasma zinc concentration. One Hundred 13-week-old Sprague-Dawley male rats weighing 360–390 g were used to perform the studies: They were equally divided into four groups: 1. Unsupplemented control animals (UCA); 2. Unsupplemented hypokinetic animals (UHA); 3. Supplemented control animals (SCA); and 4. Supplemented hypokinetic animals (SHA). For the simulation of the effect of hypokinesia (HK), the UHA and SHA were kept in small individual cages made of wood, which restricted their movements in all directions without hindering food and water intake. The SCA and SHA received daily with their food an additional amount of zinc. Before and during the experimental period of 98 d, plasma, urinary and fecal zinc, balance of zinc, food intake, and body weight were determined at different intervals. In the SHA and UHA, the concentration of zinc in plasma, and the elimination of zinc in urine and feces increased significantly when compared with the SCA and UCA, whereas the balance of zinc was negative. The body weight and food intake decreased significantly in the SHA and UHA when compared with the SCA and UCA. The increased plasma concentration of zinc in both the SHA and UHA groups was in contrast to the observed hypozincnemia during prolonged immobilization as during prolonged hospitalization. This reaction suggests that there may be some other mechanisms that are affecting the process of control and regulation of zinc metabolism during prolonged HK. It was concluded that exposure to prolonged restriction of motor activity of rats induces significant increases in plasma concentration, fecal and urinary elimination of zinc in the presence of negative zinc balance and regardless the daily intake of large amounts of zinc with their food, leading to zinc deficiency.     

Seasonal changes of water,electrolytes and aldosterone levels in blood serum,brain and kidney of the Egyptian cobra “Naja haje haje”

 

• 1.The levels of water, Na, K, Ca and Mg in blood serum, brain and kidney and aldosterone level in blood of Naja haje haje were studied during the different phases of the annual cycle.
• 2.The water content in the tissues studied displayed only minor changes as the animals passed from one phase to the other.
• 3.A significant increase in Na was recorded in the brain during the different phases indicating a depressed sodium pump, whereas the blood Na level showed a significant decrease during hibernation.
• 4.K increased in blood serum, brain and kidney during hibernation, while a nonsignificant decrease was found in blood serum during arousal. The brain may act as a potassium reservoir.
• 5.An increase in Ca and Mg concentration was recorded in blood serum, brain and kidney during prehibernation and hibernation. The data suggested a homeostatic function in the transport and metabolism of these cations.
• 6.Aldosterone exhibited a highly significant decrease especially during hibernation. The aldosterone regulation of ionic composition is discussed.
• 7.Na/K and Ca/Mg ratios in the brain may explain the decreased excitability during winter torpor.

     

Chick growth and prey quality in the European Bee-eater (Merops apiaster)

1. In each of four replicate experiments we fed three groups of bee-eater chicks for 24 h on different diets: bees, dragonflies, and a mixture of the two.
2. Dry weight assimilation efficiency did not differ between treatments and was in the region of 40–50%. Caloric assimilation efficiency was about 60% and did not differ significantly between diets.
3. Mean Growth efficiency (wt. gain/intake) was highest in all four replicates in chicks fed on the mixed diet.
4. When metabolic requirements are taken into account, growth efficiency on the mixed diet varies less with variation in intake than on the two pure diets.
5. The advantage of feeding chicks on a mixed diet may partly explain why parents do not show exclusive preferences for energy-maximising prey types.

     

Correlation of the effects of citric acid cycle metabolites on succinate oxidation by rat liver mitochondria and submitochondrial particles

1. Succinate dehydrogenase is inhibited by citrate and β-hydroxybutyrate in a complex manner, both in mitochondria and submitochondrial particles. Kinetics of inhibition in the particles points to a competitive component in the mechanism involved.
2. Pyruvate, α-ketoglutarate, malate, and glutamate stimulate oxidation of succinate by mitochondria.
3. Stimulation by α-ketoglutarate and glutamate is not influenced by the presence of rotenone.
4. Stimulation by pyruvate is higher in the absence of rotenone and increases significantly in the presence of K⁺ and valinomycin. Pyruvate supplies in mitochondria reducing equivalents for malate dehydrogenase operating in the reverse direction-reduction of oxaloacetate to malate.
5. Stimulation by malate is higher in the presence of rotenone.

     

Interrelationship between metabolism of tritiated water, 22sodium and dry matter intake by beef cattle consuming wheat straw and poultry litter in free choice

• 1.1. Metabolism of tritiated water and ²²sodium was studied in six beef cows under Mediterranean summer conditions in order to find whether the turnover of these tracers can be used to evaluate pasture intake.
• 2.2. The diet of the cows included ad libitum access to two components which were given separately in different troughs: one was poultry litter and the other was wheat straw, to simulate the dry pasture.
• 3.3. Voluntary daily dry matter intake (111 g/kg^0.75) was unexpectedly high considering the low digestibility of the feed.
• 4.4. The assumptions of constant ratios of water intake to water turnover and of dry matter intake to water intake were confirmed. Consequently, dry matter intake was determined accurately from water turnover measurements.
• 5.5. Sodium intake was practically equal to sodium turnover and most of the sodium secreted in feces was of endogenous origin.
• 6.6. Pasture intake can be predicted from sodium turnover once the concentration in feed and water consumed is known.

     

Beta irradiation may induce stereoselectivity in the crystallization of optical isomers

A novel approach has been introduced to detect the manifestation of symmetry breaking weak interactions at molecular level. In the racemic conglomerate crystallization of D, L-sodium-ammonium tartrate the effect of³²P irradiation was studied by measuring the weight and optical purity of the crystalline phase as well as the size distribution of the crystallites. The high number of independent experiments (over 1000) permitted statistical analysis of the results. The following observations have been made:

1. Beta irradiation influences the crystallization process, irradiated samples yield more crystalline material.
2. The effect involves presumably crystal seed formation because from the irradiated solutions more and smaller crystallites are formed.
3. The presence of beta particles induces stereoselective crystallization, the crystalline phase shows optical activity characteristic of the “unnatural” L-isomer.
4. The above changes are attributed to the beta irradiation as the magnitude of the effects depends on the amount of added radioactivity. Optically active contaminants are highly unlikely sources of the differences between irradiated and control series.
5. In the absence of³²P the tartrate enantiomers have equal probability to form crystals, i.e., the contribution of mixing of weak interaction into the electromagnetic one is not measurable in this system.

     

Multisensory control of escape in the cockroach Periplaneta americana

1. All giant interneurons (GIs) were ablated from the nerve cord of cockroaches by electrocautery, and escape behavior was analyzed with high-speed videography. Animals with ablations retained the ability to produce wind-triggered escape, although response latency was increased (Table 1, Fig. 4). Subsequent lesions suggested that these non-GI responses depended in part on receptors associated with the antennae.
2. Antennal and cereal systems were compared by analyzing escape responses after amputating either cerci or antennae. With standard wind stimuli (high peak velocity) animals responded after either lesion. With lower intensity winds, animals lost their ability to respond after cereal removal (Fig. 6).
3. Removal of antennae did not cause significant changes in behavioral latency, but in the absence of cerci, animals responded at longer latencies than normal (Fig. 7).
4. The cercal-to-GI system can mediate short latency responses to high or low intensity winds, while the antennal system is responsive to high intensity winds only and operates at relatively longer latencies. These conclusions drawn from lesioned animals were confirmed in intact animals with restricted wind targeting the cerci or antennae only (Fig. 9).
5. The antennae do not represent a primary wind-sensory system, but may have a direct mechanosensory role in escape.

     

EPR characterization of oxide supported transition metal ions: Relevance to catalysis

EPR spectroscopy is a powerful tool to identify at a molecular level, the different steps of catalyst preparation, and of catalytic reactions:

1. Deposition of paramagnetic transition metal ions onto a support is monitored, and the coordination sphere of the metallic center is characterized by EPR.
2. The catalyst is also characterized after activation (thermal oxidation or reduction):

- the distribution among the different sites in zeolites can be determined;

- the dispersion of the active phase may be appreciated;

- the unsaturation degree of the active site may be evaluated using probe molecules such as water or¹³C enriched carbon monoxide.

1. The catalytic mechanisms can be investigated by studying the elementary steps of the catalytic reaction, as illustrated for methanol oxidation over Mo/SiO₂ catalysts whose EPR results have extended the reaction mechanism proposed on the basis of kinetic data. In addition, reaction intermediates may be isolated inquasi-in situ conditions as in the case of olefin oligomerization catalyzed by Ni/SiO₂ systems.

     

Effects of in vivo ethanol administration on Ca2+/Mg2+ ATPase and ATP-dependent Ca2+ uptake activity in synaptosomal membranes

1. Acute administration of ethanol (4 g/kg, i.p.) to mice inhibits the sequestration of calcium into endoplasmic reticulum-like organelles in synaptosomal membranes.
2. Ethanol administration inhibits both Ca²⁺-stimulated adenosine triphosphate hydrolysis and ATP-dependent calcium uptake in the vesicles at time of loss of righting reflex.
3. At recovery of righting reflex, the Ca²⁺-ATPase activity returns to normal levels, while the ATP-dependent uptake remains inhibited.
4. The effect of ethanol is specific for the sequestration (active transport) of calcium since calcium binding to synaptic membranes is not altered.
5. Alteration in mechanisms responsible for synaptosomal buffering of cytosolic Ca²⁺ levels by in vivo ethanol may contribute to altered transmitter release rates following ethanol adminstration.

     

Anaerobic respiration in latex ofHevea brasiliensis substrate and limiting factors

The site of anaerobic respiration in the latex is the serum. The main respiratory substrate is fructose. The CO₂ formation in serum is increased by additional fructose on the average about 2.5–3 times. Glucose does not influence CO₂ evolution by serum but slightly increases O₂ consumption. With respect to sugars, latex serum contains essentially only sucrose and a low amount of raffinose. During the incubation of serum sucrose is hydrolysed, the fructose component is immediately utilized in respiration and glucose accumulates. The rate of CO₂ formation in latex as influenced by fructose is negatively related to the rubber content of the latex. Latex with a high rubber content reacts only slightly or not at all on additional fructose. The main limiting factors of latex respiration and sugar utilization are the following:

1. The deficiency of substrate, due to low activity of β-fructofuranosidase.
2. The rate of glucose phosphorylation (D'Auzac, Jacob 1967).
3. Presumably the low activity of phosphoglucoisomerase.
4. The rubber content of the latex.
5. The concentration of CO₂ in latex; this factor may be important in vivo, in the laticiferous system.

     

Total recovery of O2 evolution and nanosecond reduction kinetics of chlorophyll-a II + (P-680+) after inhibition of water cleavage with acetate

Oxygen evolution and reduction kinetics of the photooxidized Chl-a_II ⁺ have been measured in oxygen-evolving complexes from the thermophilic cyanobacterium Synechococcus sp.

1. Incubation of PS II particles with acetate resulted in an inhibition of oxygen evolution and a retardation of the Chl-a_II ⁺=reduction kinetics from the nanosecond range to the microsecond range, indicating a modification of the donor side of photosystem II (PS II).
2. After the first two flashes given to a dark-adapted, acetate treated sample, Chl-a_II ⁺ was re-reduced with a half-life time of 160 μs by a component of the donor side of PS II. Under repetitive excitation Chl-a_II ⁺ was re-reduced in 500 μs by electron back reaction from the primary acceptor Q_A ^- (X-320^-). Obviously, in the presence of acetate only two electrons are available from the donor side.
3. Both oxygen evolution and nanosecond reduction kinetics of Chl-a_II ⁺ were restored to the control level when acetate was removed.
4. The results indicate a tight coupling between O₂ evolution and nanosecond reduction kinetics of Chl-a_II ⁺.
5. The reversible inhibition is probably due to a replacement of Cl^- by acetate within the water splitting enzyme.
6. Due to its strongly retarded kinetics, the reversibly modified system may facilitate investigations of the mechanism of the donor side.

     

A study on the rate of water transport of the clam katelysia opima in relation to environmental conditions

1. The neutral red technique was employed to study the rate of filtration in Katelysia opima.
2. The weight specific water filtration was found to be greater for younger clams compared to the older ones.
3. The rate of water filtration increased with decreasing salinity.
4. Water filtration was found to increase as temperature increased, reaching a maximum at 35°C. but then sharply decreasing at 39°C.
5. Light had no significant effect on the rate of filtration.
6. Suspended matter was found to affect the rate of water filtration.
7. The rate of filtration was low at high pH and high in low pH.
8. The rate of water filtration was found to be faster during high tide than during low tide.
9. The presence of the parasitic crab, Pennotheris sp., in the mantle cavity of clams had a marked effect on the particle filtration.
10. Accidental cut of the siphon tips had no effect on the rate of filtration.

     

Cocaine kindling in mice

Previous studies proposed the involvement of theN-methyl-D-aspartate (NMDA) type of glutamate receptors in the development of sensitization to the convulsive effect of cocaine (cocaine kindling). The present study was undertaken to determine, first, if cocaine kindling is associated with enhanced sensitivity of the NMDA receptor to the convulsive response ofN-methyl-D,L-aspartate (NMDLA), and second, whether in vivo modulation of nitric oxide synthase (NOS) function regulates the development of cocaine kindling. The following results were observed:

1. Cocaine-kindled animals were significantly more susceptible to the convulsive effect of the NMDA receptor agonist NMDLA than saline controls;
2. Pretreatment with the NOS inhibitor N^G-nitro-L-arginine methyl ester (L-NAME; 100 mg/kg; ip) blocked the development of cocaine kindling;
3. The protective effect of L-NAME was partially reversed with the coadministration of the NOS substrate,L-arginine (300 mg/kg; ip), but notD-arginine; and
4. L-Arginine (300 mg/kg; ip), but notD-arginine, amplified the development of cocaine kindling. Taken together, these findings suggest that supersensitivity of the NMDA receptor and activation of NOS may underlie the development of cocaine kindling.

     

Polymorphism of alpha-1 antitrypsin in dogs

• 1.1. A genetically determined polymorphism of alpha-1 antitrypsin is demonstrated in dog serum by isoelectric focusing in a pH range of 3.5–5.0, followed by direct immunoblotting using a specific antiserum.
• 2.2. Alpha 1 antitrypsin focuses as two major bands at isoelectric points of 4.60 and 4.64 or 4.67 and 4.7 in presumed homozygous animals. Heterozygotes show both sets of bands.
• 3.3. The results of seven crosses with 33 offspring are best explained by two codominant alleles, Pi^M and Pi^S at a single locus designated as Pi for proteinase inhibitor.
• 4.4. The concentration of alpha-1 antitrypsin in serum of healthy dogs was 2.65 ± 0.42 mg/ml and 2.19 ± 0.38 mg/ml in females andv males respectively.
• 5.5. The higher concentration in female dogs suggests that estrogens may influence the serum level of alpha-1 antitrypsin.

     

Neurotransmitters of cephalopods

1. ACh, dopamine, noradrenaline, 5-HT,l-glutamate, and GABA are widely distributed in cephalopods and probably all function as neurotransmitters; octopamine also occurs and at one site is known to act as a neuromodulator.
2. Several peptides are also present, as well as nitric oxide synthase.
3. In the brain and sense organs cholinergic, aminergic, serotonergic and glutamatergic systems seem to be the most important.
4. ACh is also active in the gut, vascular system and some body muscles: it is generally inhibitory. The ACh receptors are similar to the vertebrate nicotinic type.
5. The catecholamines are important in the gut and vascular system: they are generally excitatory. The NA receptors are like the α-adrenergic subtype of vertebrates, but the nature of the DA and OA receptors is less certain.
6. 5-HT is important in the gut but is endogenous in some chromatophore nerves and acts on receptors that seem like the vertebrate 5-HT₁ type.
7. l-glutamate is an excitatory transmitter at the chromatophore (and probably at other) nerve-muscle junctions and is an extremely strong candidate for being the excitatory transmitter at the squid giant synapse. There are NMDA receptors on Schwann-cells but the receptors on neurons and muscles are like the vertebrate kainate type.
8. Little is known about the mode of action of cephalopod peptides; nor has it ever been shown that they co-exist with conventional transmitters in these animals.
9. The structure of one (FMRFamide) receptor has been elucidated, but apart from this nothing is known of the molecular biology of receptors in cephalopods.

     

Chromium in the elderly

Several studies indicate that glucose tolerance improves and lipid levels decline in the elderly after supplementation with Cr-rich brewer's yeast or inorganic Cr. Other studies report equivocal results or no changes. Interpretation of these investigations is hampered by

1. Lack of a marker to identify Cr-deficient people
2. Artifactually high levels of dietary and body Cr, owing to inadequate analytic techniques and
3. The interplay of chronic health problems, medications, institutionalization, and dietary practices.

Investigators have studied the effects of aging on Cr in the body. In the rat, tissue retention of⁵¹Cr decreases, and organ distribution changes with age. In humans, plasma Cr levels of healthy eldery subjects are not different from those of young adults. There is no evidence of malabsorption in aged humans or animals. Nevertheless, higher urinary Cr losses are reported in elderly people. These data suggest that Cr retention may decrease with aging and that aging may alter Cr metabolism. Diets of many healthy elderly people contain <30 μg Cr. Two elderly men living under controlled conditions maintained Cr balance with 37 μg/d. However, these levels may be insufficient during the stresses and illnesses associated with aging.     

Experimental problems using electronic particle counters

The following scheme lists the problems which have been and will continue to be encountered in grazing experiments on natural particle assemblages. In some cases there are solutions, but many of the problems listed below remain intractable. To solve them will require innovative approaches, most probably combining the use of particle counters with other techniques to approach the problem to be solved from several angles at once. Variance between samples due to

- statistical causes (especially caused by large particles) and

- differences between experimental bottles and between experimentals and controls at start of experiment. Shifts in particle distribution during experiment due to

- increase in small particles

- growth of bacteria and other organisms due to excretion of grazers and

- breakage during handling by grazers into fragments. Processes, independent of grazing, leading to changes in particle size distribution due to

- primary production

- grazing by additional components and

- bacterial growth on detrital particles and the formation of detrital flocs.

     

Vocalizatons of chimpanzees in non-caged captivity

1. The chimpanzee vocal system is an emotionally linked vocal response developed on a standard pre-symbolic primate system.
2. Differences in number of sounds recorded by different observers may be due to personal choice, or due actual presence or absence of certain sound types in different living situations. Further research is needed in this case before comparisons can be made.
3. Idiosyncratic use of certain signals may serve as a basis for growth of local dialects in different areas. Spread of such dialects may be related to the amount of respect accorded to dominant animals. More study may shed light on the growth and development of pre-symbolic systems.

     

Habitability of the early earth: Clues from the physiology of nitrogen fixation and photosynthesis

In the absence of direct evidence concerning the nature of the early Earth environments, it is acceptable under the uniformitarian principle to attempt to define primitive habitats from modern procaryotic physiology. Combining the rock and fossil record with present phylogenetic reconstuctions, application of this paleoecological approach to the evolutionary biochemistry and physiology of nitrogen fixation and photosynthesis leads to several inferences about the nature of Archean environments:

1. To stimulate nitrogenase evolution and avoid its repression, the activity of the NH ₄ ⁺ ion was less than 10^?3, and probably lower.
2. To be consistent with a moderately protective ozone screen, while not also repressing nitrogenase activity, incursions of abiotic dissolved oxygen at levels in the range 10^?1.2?10^?3.5 PAL would have been acceptable.
3. To induce the formation and activity of RuBP carboxylase, the pCO₂ was less than 100 PAL.
4. To support Photosystem I activity, sulfide concentrations of at least 10^?4 M were present in the photic zone.
5. To avoid a too-rapid oxidation of sulfide, the pH was probably between 6–7, where H₂S exceeds HS^?.

Evolutionary ‘pressure’ to stimulate the later development of oxygenic photosynthesis (Photosystem II), would require several subsequent habitat modifications:

1. Lowering the sulfide to < 10^?4 M to inhibit Photosystem I.
2. Raising the pH above neutral (HS^? > H₂S), to mediate more rapid oxidation of HS^?.
3. Maintaining either an illumination below 300–400 lux (to avoid photosynthetic O₂ self-repression of nitrogen fixation), or an adequate local source of combined nitrogen (aNH ₄ ⁺ > 10^?4) to repress nitrogen fixation entirely.