The relation between hip impact velocity and hip impact force differs between sideways fall techniques.

Fall techniques that reduce fall severity may decrease the risk of hip fractures. A fundamental variable for fall severity is impact force, but impact velocity is also used. The purpose of the study was to determine whether impact velocity is valid to determine differences in fall severity between different techniques. Five young adults with martial arts (MA) experience performed sideways falls from kneeling height using three techniques: Block with arm (Block) and MA techniques with and without use of the arm to break the fall. In addition, one subject also performed MA falls from standing height. Linear regression analysis showed a moderate relation between hip impact velocity and force, which was depended on technique. In falls with comparable impact velocities, forces in MA falls were lower than forces in Block falls. Hence, differences in impact force could not be predicted by velocity. In conclusion, hip impact velocity may be useful to make an approximate prediction of impact force within fall techniques. However, to determine differences between techniques it was not always a valid predictor. When direct impact force measurements are not possible, methods combining impact velocity with energy estimates before and after impact might be more valid.     

On the origin of the limited control of mitochondrial respiration by the adenine nucleotide translocator

A thermodynamic control theory previously developed has been applied to mitochondrial oxidative phosphorylation with emphasis on the role of delta microH and coupling and within the paradigm of delocalized chemiosmotic coupling. The basis for the observed distribution of flux control over the participating enzymes is shown to lie in the relative magnitudes of so-called delta microH elasticity coefficients, i.e., the delta microH dependencies of the different mitochondrial processes. In particular the relatively strong delta microH dependence of mitochondrial respiration is responsible for the significant role of the adenine nucleotide translocator in the control of oxidative phosphorylation. Uncoupling decreases the control exerted by this translocator on respiration but increases that exerted on phosphorylation.     

NAD(P)+-independent aldehyde dehydrogenase from Pseudomonas testosteroni. A novel type of molybdenum-containing hydroxylase

Aldehyde dehydrogenase from Pseudomonas testosteroni was purified to homogeneity. The enzyme has a pH optimum of 8.2, uses a wide range of aldehydes as substrates and cationic dyes (Wurster's blue, phenazine methosulphate and thionine), but not anionic dyes (ferricyanide and 2.6-dichloroindophenol), NAD(P)+ or O2, as electron acceptors. Haem c and pyrroloquinoline quinone appeared to be absent but the common cofactors of molybdenum hydroxylases were present. Xanthine was not a substrate and allopurinol was not an inhibitor. Alcohols were inhibitors only when turnover of the enzyme occurred in aldehyde conversion. The enzyme has a relative molecular mass of 186,000, consists of two subunits of equal size (Mr 92,000), and 1 enzyme molecule contains 1 FAD, 1 molybdopterin cofactor, 4 Fe and 4 S. It is a novel type of NAD(P)+-independent aldehyde dehydrogenase since its catalytic and physicochemical properties are quite different from those reported for already known aldehyde-converting enzymes like haemoprotein aldehyde dehydrogenase (EC 1.2.99.3), quino-protein alcohol dehydrogenases (EC 1.1.99.8) and molybdenum hydroxylases.     

On the biosynthesis of free and covalently bound PQQ. Glutamic acid decarboxylase from Escherichia coli is a pyridoxo-quinoprotein

Analysis of glutamic acid decarboxylase (GDC) (EC 4.1.1.15) from Escherichia coli ATCC 11246 revealed the presence of six pyridoxal phosphates (PLPs) as well as six covalently bound pyrroloquinoline quinones (PQQs) per hexameric enzyme molecule. This is the second example of a pyridoxo-quinoprotein, suggesting that other atypical pyridoxoproteins (PLP-containing enzymes) have similar cofactor composition. Since the organism did not produce free PQQ and its quinoprotein glucose dehydrogenase was present in the apo form, free PQQ is not used in the assemblage of GDC. Most probably, biosynthesis of covalently bound cofactor occurs in situ via a route which is different from that of free PQQ. Thus, organisms previously believed to be unable to synthesize (free) PQQ could in fact be able to produce quinoproteins with covalently bound cofactor. Implications for the role of PQQ in eukaryotic cells are discussed.     

Kinetic analysis of short-term effects of alpha-agonists on gluconeogenesis in isolated rat hepatocytes

Isolated hepatocytes from fasted rats were perifused with glycerol as gluconeogenic substrate. Stimulation of gluconeogenesis with phenylephrine (10(-5) M) as alpha-adrenergic agonist consisted of two distinct phases. The first phase was a transient stimulation of gluconeogenesis and was accompanied by transient changes in cytosolic and mitochondrial redox state; this phase was abolished by the transaminase inhibitor aminooxyacetate. The second phase was a stable stimulation of less magnitude, without change in redox state and insensitive to addition of aminooxyacetate. It is concluded that the first phase is due to a transient enhancement of flux through the malate/aspartate shuttle and that the stable phase is probably due to a stimulation of mitochondrial glycerol-3-phosphate dehydrogenase and glycerol kinase.     

Comparison of enzyme-linked immunosorbent and virus neutralization assays for the serology of reovirus infections in laboratory animals

An enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of reovirus-specific IgM and IgG serum antibodies in rodents, detecting reovirus group reactive antibodies, was compared with reovirus types 1, 2 or 3 specific virus neutralization (VN) assays. To this end, serum samples were collected from specific pathogen-free (SPF) BALB/c RIVM mice, after experimental infection with any of the three mammalian reovirus serotypes. The majority (seven out of twelve) of the reovirus type 1-infected and one third (two out of six) of the reovirus type 3-infected mice died within 15 days after infection, whereas all (six out of six) of the reovirus type 2-infected animals survived. Using reovirus type 2 antigen in the ELISA, reovirus-specific IgM antibodies could be demonstrated within 1 week after infection in all the mice infected with reovirus types 2 or 3 and in the majority of the mice infected with type 1. Similarly, reovirus-specific IgG could be detected within 3 weeks in all the surviving mice infected with reovirus types 2 or 3 and within 5 weeks in all surviving mice infected with reovirus type 1. These results coincided well with the data obtained in the VN assays, in which all the infected animals also could be detected within 1 week after infection. As expected, titers were detected most rapidly and to the highest levels in the homologous VN assays. Given the sensitivity and the specificity of the ELISA system demonstrated in this paper and its suitability for incorporation in automated systems, the ELISA system should be considered valuable for the routine serologic diagnosis of reovirus infections in rodents.     

Potential bias in inbreeding depression estimates when using pedigree relationships to assess the degree of homozygosity for loci under selection

A potential bias in estimation of inbreeding depression when using pedigree relationships to assess the degree of homozygosity for loci under selection is indicated. A comparison of inbreeding coefficients based on either pedigree or genotypic frequencies indicated that, as a result of selection, the inbreeding coefficient based on pedigree might not correspond with the random drift of allelic frequencies. Apparent differences in average levels of both inbreeding coefficients were obtained depending on the genetic model (additive versus dominance, initial allelic frequencies, heritability) and the selection system assumed (no versus mass selection). In the absence of selection, allelic frequencies within a small population change over generations due to random drift, and the pedigree-based inbreeding coefficient gives a proper assessment of the accompanying probability of increased homozygosity within a replicate by indicating the variance of allelic frequencies over replicates. With selection, in addition to random drift, directional change in allelic frequencies is not accounted for by the pedigree-based inbreeding coefficient. This result implies that estimation of inbreeding depression for traits under either direct or indirect selection, estimated by a regression of performance on pedigree-based coefficients, should be carefully interpreted.Deceased     

Study of the dynamics of neutralization escape mutants in a chimpanzee naturally infected with the simian immunodeficiency virus SIVcpz-ant.

Here we report on the use of spectral map analysis of time-paired sequential neutralization data of 11 serum samples of a chimpanzee naturally infected with a simian immunodeficiency virus (SIVcpz-ant) and 8 primary consecutive SIVcpz-ant isolates, taken at about 4-month intervals. The analysis reveals the existence of three SIVcpz-ant isolate and serum neutralization clusters. Each cluster groups virus isolates and/or sera based on similarities of their neutralization spectra. On average, neutralization escape mutants emerged after 15 months and mounted a neutralization response approximately 8 months later. The entire gp160 regions of eight consecutive isolates were sequenced and analyzed by a new statistical method called polygram, which allowed the deduction of amino acid sequence motifs of gp160 which were specific for SIVcpz-ant isolates belonging to the same isolate neutralization clusters. Changes in specific amino acid quadruplets in V1, V2, C3, V4, V5, and CD4 domains of gp120 and gp40 were seen to correlate with the neutralization clusters with most of the specific changes occurring in the V4 region. This method of analysis may facilitate an understanding of the study of the dynamic interplay between human immunodeficiency virus (HIV) and host neutralization responses as well as providing possible insights into mechanisms of persistence of HIV-1-related lentiviruses in their natural hosts.