Phosphate deposition capacity of athletes during hypokinesia, phosphate loading, and ambulation

Hypokinesia (diminished movement) induces significant phosphate (P) excretion; however, little is known about the P deposition ability of the body during hypokinesia (HK). Using P loads, the aim of this study was to establish the deposition ability of the body to retain P during prolonged HK. Studies were done during a 30-d period of pre-HK and a 364-d period of HK. Forty male trained athletes aged 24.7 ± 8.0 yr were chosen as subjects. They were equally divided into four groups: unloaded ambulatory control subjects (UACS), unloaded hypokinetic subjects (UHKS), loaded ambulatory control subjects (LACS), and loaded hypokinetic subjects (LHKS). All hypokinetic subjects were limited to an average walking distance of 0.7 km/d. Loading tests with 85.0 mg of calcium phosphate/kg body weight were performed on the LACS and LHKS. Fecal P loss, urinary calcium (Ca) and P loss, serum P, Ca, and the ionized calcium (Ca_I) levels increased significantly (p≤0.05) in the LHKS and UHKS groups when compared with the LACS and UACS groups, respectively. Serum intact parathyroid hormone (iPTH) and the 1,25-dihydroxyvitamin D₃ [1,25-(OH)₂ D₃] levels decreased significantly (p≤0.05) in the LHKS and UHKS groups when compared with the LACS and UACS groups, respectively. After the P load, significant (p≤0.05) differences were observed between LHKS and UHKS groups regarding serum, urinary, and fecal P changes. Thus, the deposition capacity of P decreased significantly (p≤0.05) more in the LHKS group than in the UHKS group. The deposition of P, fecal P, urinary P and Ca, serum Ca_I, P, Ca, 1,25-(OH)₂ D₃, and iPTH changed insignificantly (p>0.05) in control groups when compared with their baseline values. It was shown that after the P load, significant differences were observed between the loaded and unloaded hypokinetic subjects regarding serum, urinary, and fecal P values and P retention. The oral P load intensified P loss from the body. It was concluded that the higher the P intake increased the greater P loss and the lower P deposition and thus the less likely it is for the P load to benefit hypokinetic subjects.     

Hydroxyl radical footprints reveal novel structural features around the NF I binding site in adenovirus DNA.

We have identified a number of as yet unknown structural abnormalities of the NF I-DNA binding site within the inverted terminal repetition of adenovirus DNA by probing it with a hydroxyl radical footprinting technique. NF I binding alters the accessibility of the deoxyribose moieties to hydroxyl radicals both at the 3' and at the 5' side of the recognition sequence 5'-TGG(N)6GCCAA-3'. A smooth bend at the 5' side of the binding sequence is already present in naked linear DNA and it is further enhanced by protein binding. This could be demonstrated not only by hydroxyl radical footprinting but also by studying the temperature dependent mobility during gel electrophoresis of DNA fragments carrying the NF I binding site at circularly permutated positions. We propose that the bent conformation at this site is responsible for facilitating protein/DNA interactions.     

Plasma trace elements concentrations in trained subjects after exposure to hypokinesia and daily hyperhydration

The objective of this investigation was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on blood plasma trace elements concentrations in physically healthy volunteers after exposure to 364 d of hypokinesia (decreased number of steps per day). The studies were performed after exposure to 364 d of Hypokinesia (HK) on 30 long-distance runners of volunteers who had a VO₂ max 67 mL/kg/min and were ranging in the age of 19–24 yrs. Prior to their exposure to HK all volunteers were on an average of 10,000 steps/d. For the simulation of the hypokinetic effect the volunteers were kept under an average of 3000 steps/d. All volunteers were divided into three equal groups. The first group of volunteers subjected to HK and received daily FSS (water 26 mL/kg body wt and sodium chloride 0.16 g/kg body wt.), the second groups of volunteers submitted only to HK, and the third group of volunteers underwent a normal ambulatory life and served as control. The content of manganese, calcium, magnesium, iron, lead, copper, tin, nickel, zinc and cobalamine were determined in blood plasma of volunteers. By the end of the hypokinetic period the blood plasma concentration of microelements increased significantly in the hypokinetic subjects (second group), whereas in the hyperhydrated subjects (first group) decreased. It was concluded that prolonged restriction of motor activity induced significant increases in blood trace elements concentrations whereas daily hyperhydration had a normalizing effect on their concentration in blood plasma. This indicates that daily hyperhydration may be used to normalize blood plasma concentrations of microelements in physically healthy volunteers subjected to prolonged restriction of motor activity.     

The Amaryllidaceae Alkaloid Haemanthamine Binds the Eukaryotic Ribosome to Repress Cancer Cell Growth

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Zinc metabolism in endurance-trained volunteers during prolonged restriction of muscular activity and chronic hyperhydration

The objective of this study was to evaluate the effects of hypokinesia (HK) and fluid- and salt supplementation (FSS) on zinc metabolism in endurance-trained volunteers (ETV) for a period of 364 d. Thirty long-distance runners aged 22–25 yr with a peak V_O2 of 67 mL/min/kg with an average 13.8 km/d running distance were chosen as subjects. They were equally divided into three groups:

A novel type of interaction between cruciform DNA and a cruciform binding protein from HeLa cells.

We recently identified and enriched a protein (CBP) from HeLa cells with binding specificity for cruciform-containing DNA. We have now studied the interaction of CBP with stable cruciform DNA molecules containing the 27 bp palindrome of SV40 on one strand and an unrelated 26 bp palindrome on the other strand by hydroxyl radical footprinting. The CBP-DNA interaction is localized to the four-way junction at the base of the cruciforms. CBP appears to interact with the elbows of the junctions in an asymmetric fashion. Upon CBP binding, structural distortions were observed in the cruciform stems and in a DNA region adjacent to the junction. These features distinguish CBP from other cruciform binding proteins, which bind symmetrically and display exclusively either contacts with the DNA backbone or structural alterations in the DNA.     

Complete cDNA sequence of chicken vigilin, a novel protein with amplified and evolutionary conserved domains.

The complete cDNA (4375 bp), coding for a new protein called vigilin, was isolated from chicken chondrocytes. The cDNA shows an open reading frame of 1270 amino acids which are organized in 14 tandemly repeated homologous domains. Each domain consists of two subdomains, one with a conserved sequence motif of 35 amino acids (subdomain A) and another one with a presumptive alpha-helical structure of 21-33 amino acids (subdomain B). 149 amino acids at the N-terminus and 71 amino acids at the C-terminus of vigilin do not show the characteristic domain structure. No sequence characteristic of a signal peptide has been found, which argues for an intracellular localisation of vigilin. Vigilin is highly expressed in freshly isolated chicken chondrocytes but little in chondrocytes after prolonged time in culture. Vigilin mRNA exists in two size species, 4.4 kb and 6.5 kb in length due to the usage of different polyadenylation sites. Comparison of the vigilin sequence with data bases showed a remarkable similarity to protein HX from Saccharomyces cerevisiae [Delahodde, A., Becam, A. M., Perea, J. & Jacq, C. (1986) Nucleic Acids Res. 14, 9213-9214]. The yeast protein consists of eight homologous domains with 11 conserved amino acid residues within a set of 35 amino acids. The N-terminal and C-terminal regions of vigilin and protein HX do not reveal any sequence similarity. These results, together with the demonstration of the characteristic vigilin sequence motif in a human cDNA clone, suggest that the repeats represent evolutionary conserved autonomous domains within a family of proteins found in yeast, chicken and man.     

Inverted repeats,stem-loops,and cruciforms: Significance for initiation of DNA replication

Inverted repeats occur nonrandomly in the DNA of most organisms. Stem-loops and cruciforms can form from inverted repeats. Such structures have been detected in pro- and eukaryotes. They may affect the supercoiling degree of the DNA, the positioning of nucleosomes, the formation of other secondary structures of DNA, or directly interact with proteins. Inverted repeats, stem-loops, and cruciforms are present at the replication origins of phage, plasmids, mitochondria, eukaryotic viruses, and mammalian cells. Experiments with anti-cruciform antibodies suggest that formation and stabilization of cruciforms at particular mammalian origins may be associated with initiation of DNA replication. Many proteins have been shown to interact with cruciforms, recognizing features like DNA crossovers, four-way junctions, and curved/bent DNA of specific angles. A human cruciform binding protein (CBP) displays a novel type of interaction with cruciforms and may be linked to initiation of DNA replication. © 1996 Wiley-Liss, Inc.     

Effect of daily hyperhydration on fluid-electrolyte changes in endurance-trained volunteers during prolonged restriction of muscular activity

The aim of this investigation was to evaluate the effect of a daily intake of fluid and salt supplementation on fluid and electrolyte losses in endurance-trained volunteers during prolonged restriction of muscular activity (hypokinesia). The studies were performed on 30 long-distance runners aged 23–26 who had a peak oxygen uptake of 65.5 mL/kg/min and had taken 13.8 km/d on average prior to their participation in the study. The volunteers were divided into three groups: The volunteers in the first group were placed under normal ambulatory conditions (control subjects), the second group of volunteers subjected to hypokinesia alone (hypokinetic subjects), and the third group of volunteers was submitted to HK and consumed daily 0.1 g sodium chloride (NaCl)/kg body wt and 26 mL water/kg body wt (hyperhydrated subjects). The second and third group of volunteers were kept under an average of 2.7 km/d for 364 d. During the pre-experimental period of 60 d and during the experimental period of 364 d sodium, potassium, calcium, and magnesium in urine and plasma were determined. Blood was also assayed for osmolality, hemoglobin, hematocrit, plasma volume, plasma renin activity and plasma aldosterone. Mean arterial blood pressure was also determined. In the hyperhydrated volunteers plasma volume and arterial blood pressure increased, whereas plasma osmolality, plasma renin activity, plasma aldosterone, hematocrit, hemoglobin concentration, and urinary excretion and concentrations of electrolytes in plasma decreased. In the hypokinetic volunteers, plasma volume and arterial blood pressure decreased significantly, whereas hematocrit values, hemoglobin concenfration, plasma osmolality, plasma renin activity, plasma aldosterone, and electrolytes in urine and plasma increased significantly during the experimental period. It was concluded that chronic hyperhydration may be used in minimizing fluid and electrolyte losses in endurance-trained volunteers during prolonged restriction of muscular activity.