Relationship between muscle strength and the time taken to complete a standardized walk-turn-walk test.

We examined the effects of age and gender on the relationship between knee strength and walking time during a walk-turn-walk test in 176 male and 168 female generally healthy participants of the Baltimore Longitudinal Study of Aging who were aged 21-89 years. Subjects were timed as they walked 50 ft (15.24 m), turned around, and walked back to the starting point, both at a comfortable pace and as fast as possible. Isokinetic concentric knee extensor strength was measured at 30 degrees /s by using a Kin-Com dynamometer. Both comfortable and fast gait times increased with increasing age for both women and men, starting in middle age. An interaction was found between gender and age showing that older women are slower than older men at both paces. Gait time decreased linearly with increasing knee extensor strength, plateauing at higher strength levels (>130 N m for comfortable gait, and 190 N m for fast gait). Most women occupied the linear part of the curve below the plateau. Adjustment for body size, age, physical activity, and particularly number of steps to complete the task removed the relationship between strength and gait time for the comfortable gait. Women took longer to complete the walk-turn-walk test than men at older ages, were on the linear part of the strength-gait time relationship, and used more steps to complete the task, all of which may contribute to their greater likelihood of frailty in later years.

Overexpression of BETA2/NeuroD induces neurite outgrowth in F11 neuroblastoma cells.

BETA2/NeuroD, a basic helix-loop-helix (bHLH) transcription factor, has been shown to play important roles in the development of the nervous system and the maintenance and formation of pancreatic and enteroendocrine cells. The gain of function of BETA2/NeuroD in neurogenesis has been shown in Xenopus embryos. In this study, we investigated the neurogenic potential of BETA2/NeuroD using neuroblastoma cell line, F11, which could be induced to differentiate into neurons in the presence of cAMP. To induce or block the expression of BETA2/NeuroD, expression vectors for the full-length and a C-terminal deletion mutant of BETA2 were constructed and their transactivation potential was verified using reporter genes containing the insulin promoter sequences. Overexpression of BETA2 with full-length construct induced neurite outgrowth in F11 cells in the absence of cAMP. In contrast, the C-terminal deletion mutant, BETA2(1--233), which has dominant negative activity, inhibited neurite outgrowth induced by cAMP in F11 cells. These results indicate that BETA2/NeuroD plays an important role in terminal differentiation of neuroblastoma cells. They also imply that BETA2/NeuroD or related bHLH factors plays an essential role for differentiation of F11 neuroblastoma cells.

Differential sensitivity of mice bred for stress-induced analgesia to morphine and ACEA-1011 in the formalin test.

The antinociceptive effect of morphine, an opioid receptor agonist, and ACEA-1011, a novel NMDA receptor/glycine site antagonist, was examined in the formalin test in mice selectively bred for high (HA) and low (LA) swim stress-induced analgesia (SSIA). A subcutaneous (SC) injection of formalin produced a biphasic nociceptive response in both lines. HA mice spent more time licking the injected paw than the LA mice in both phases of the formalin test. Morphine was equally potent in the early phase in both lines, but it was more potent in HA mice than in LA mice in the tonic late phase of the formalin test. Similarly, ACEA-1011 produced an equally potent antinociceptive effect in the early phase in both lines; however, the compound was more potent in LA mice than in HA mice in the tonic late phase of the formalin test. These data suggest that in HA mice antinociception in the tonic late phase of the formalin test is mediated largely by an opioid-mediated mechanism, whereas in the opioid-deficient LA line at least a nonopioid-mediated mechanism involving the NMDA receptor is also implicated.

Blockade of morphine tolerance by ACEA-1328, a novel NMDA receptor/glycine site antagonist.

Recent studies indicate that competitive and non-competitive NMDA receptor antagonists can block the development of morphine tolerance. Since glycine is considered to be a co-agonist for activation of NMDA receptors we examined the effect of a novel bioavailable NMDA receptor/glycine site antagonist, 5-nitro-6,7-dimethyl-1,4-dihydro-2,3-quinoxalinedione (ACEA-1328), on the development of morphine tolerance. Administration of ACEA-1328 (20 mg/kg) completely blocked tolerance to morphine-induced antinociception in the tail flick test in CD-1 mice, without affecting the basal nociceptive response or potentiating morphine-induced antinociceptive effects. These data suggest that inhibition of NMDA receptor activity via blockade of the glycine co-agonist site is potentially viable as a therapeutic approach for preventing development of morphine tolerance.

Morphine analgesia and tolerance in mice selectively bred for divergent swim stress-induced analgesia.

Morphine-induced analgesia and tolerance were examined in Swiss Webster mice selectively bred for high and low swim stress-induced analgesia. Morphine produced a dose-dependent analgesia in both lines; it was 4-fold more potent in the high analgesia line than in the low analgesia line. Despite the differences in morphine-induced analgesia, the degree of tolerance was the same in both lines. Together, these data suggest that selective breeding of mice for high and low swim stress-induced analgesia produced a striking difference in morphine-induced analgesia without affecting the degree of tolerance. Thus, while there is a common genetic determination in swim stress-induced and morphine-induced analgesia, the development of tolerance to morphine possibly relies on a different genetic background.

Characterization of the kafirin gene family from sorghum reveals extensive homology with zein from maize.

Electrophoretic analysis of translation products of polyadenylated RNA isolated from mid-maturation sorghum seed in the presence of [(35)S]met, [(3)H]leu, or [(3)H]val revealed two major proteins of kDa and 21 kDa. These products were not detected when [(3)H]lys was supplied as the radioactive substrate. Under similar electrophoretic conditions, kafirin (a major seed storage prolamin of sorghum), migrated as two bands of 22 kDa and 19 kDa. Sequence analysis of two cDNA clones (pSK8 and pSKR2) from sorghum seed mRNA revealed them to be highly homologous with each other and to the 22 kDa zeins from maize, suggesting that they represented kafirin cDNAs. Compared with pSKR2, pSK8 had an insertion of 24 nucleotides and a deletion of 24 nucleotides, so that the coding regions were nearly identical in length. The deduced amino acid sequence for these cDNA clones reveals that kafirin, like zein, is rich in glutamine and nonpolar amino acids, but contains no lysine. Both kafirin and zein have a 21 amino acid signal peptide exhibiting 80% homology and eight copies of a repetitive amino acid block in the C-terminal domain with the consensus: infI (supP) LL finP (supA) LN infQ (supP) LALANPAAYLQQQQ.The kafirin cDNAs were used as probes to screen a sorghum genomic library; one genomic clone (λGK.1) was sequenced and found to be very similar (97.8%) to the pSK8 cDNA clone. Clone λGK.1 contains features typical for a functional gene in that the intronless open reading frame encoding 268 amino acids is flanked at the 5' end by sequences corresponding to the CAAT and TATA promoter boxes (positioned at about -60 and -30 bp, respectively, from the transcriptional initiation site), and at the 3' end by a consensus polyadenylation signal. In common with zein genomic clones, kafirin clones contain a 15 basepair consensus sequence centered at postion -320 relative to the transcriptional initiation site. Under similar hybridization conditions, genomic reconstruction analysis using an oligonucleotide probe indicated the presence of less than 20 copies of kafirin per haploid sorghum genome compared with approximatley 140 copies of zein per haploid maize genome.