Erratum

The paper 'Interference of rheumatoid factor activity by aspartame, a dipeptide methyl ester' by Paul A. Ramsland, Bahereh F. Movafagh, Morris Reichlin and Allen B. Edmundson, J. Mol. Recognit. 1999; 12: 249--257, was published without the required colour plates. The publisher would like to apologise for this omission. The article is reprinted here in full. Please replace the previously published pages with those following. The electronic version of the article, including the colour plates, can be downloaded from the Wiley Interscience website at http://www.interscience.wiley.com. The plates have been included in the original paper, which appeared in Issue 4 of the journal.     

TCP-11, the product of a mouse t-complex gene,plays a role in stimulation of capacitation and inhibition of the spontaneous acrosome reaction

Tcp-11 is a candidate for a distorter gene within the t-complex on mouse chromosome 17; although t-complex genes appear to affect sperm function, relatively little is known about mechanisms whereby these genes might play a specific physiological role. We present evidence that the protein TCP-11 is found on the surface of mature epididymal spermatozoa. Although detected on both the acrosomal cap region of the head and the flagellum of acrosome-intact cells, it is absent from the heads of acrosome-reacted cells. When epididymal spermatozoa were incubated in the presence of anti-TCP-11 IgG Fab fragments for a total of 120 min and assessed using chlortetracycline fluorescence, we observed a stimulation of capacitation and an inhibition of spontaneous acrosome loss, suggestive of enhanced fertility compared with untreated suspensions. In vitro fertilization experiments confirmed that Fab-treated suspensions became fertile more quickly and then maintained high fertility. Because these responses were remarkably similar to those obtained using the TRH-related peptide FPP (fertilization promoting peptide; pGlu-Glu-ProNH₂) and adenosine, we investigated responses to Fab fragments, FPP, and adenosine. Results indicated that the Fab fragments appear to work at the same extracellular site as FPP, one that is distinct from the adenosine site of action. Further evidence for this conclusion was obtained using pGlu-Gln-ProNH₂, an FPP-related tripeptide known to competitively inhibit responses to FPP; as with FPP, pGlu-Gln-ProNH₂ inhibited the stimulatory effect of Fab fragments in a concentration-dependent manner. From these results we suggest that TCP-11 may be the receptor for FPP and that the adenylate clyclase/cyclic AMP pathway may be the signal transduction pathway activated by interactions between extracellular effector molecules (e.g., Fab fragments or FPP acting as an agonist) and TCP-11. A mechanism such as this that promotes capacitation but inhibits spontaneous acrosome loss in vivo would play a very important role by helping to maximize the fertilizing potential of the few spermatozoa that reach the site of fertilization. The fact that there is a human homolog of Tcp-11 suggests that this gene could play an important role in regulation of human, as well as mouse, sperm function. Mol. Reprod. Dev. 48:375–382, 1997. © 1997 Wiley-Liss, Inc.     

FPP modulates mammalian sperm function via TCP-11 and the adenylyl cyclase/cAMP pathway

Fertilization promoting peptide (FPP; pGlu-Glu-ProNH₂), which is found in seminal plasma, promotes capacitation but inhibits spontaneous acrosome loss in mammalian spermatozoa in vitro. Adenosine, known to modulate the adenylyl cyclase (AC)/cAMP pathway, elicits these same responses whereas FPP + adenosine produces an enhanced response, leading to the hypothesis that FPP and adenosine modulate the same signal transduction pathway but act via different receptors. TCP-11, the product of a t-complex gene, is the putative receptor for FPP: Fab fragments of anti-TCP-11 antibodies have the same effect as FPP on mouse spermatozoa and Gln-FPP, a competitive inhibitor of FPP, also competitively inhibits responses to the Fab fragments. In the present study, specific binding of ³H-FPP to sperm membranes was significantly inhibited by 200 nM Gln-FPP and anti-TCP-11 Fab fragments (1/25 dilution), thus confirming that FPP, Gln-FPP, and Fab fragments compete for the same binding site. In addition, spermatozoa treated with A23187 to induce the acrosome reaction bound significantly less ³H-FPP than untreated cells, suggesting that a large proportion of the FPP binding sites are associated with the acrosomal cap region; TCP-11 is located in this region. In other experiments, 100 nM FPP significantly stimulated cAMP production in mouse sperm membranes, permeabilized cells and intact cells. Furthermore, Gln-FPP inhibited production of cAMP in response to FPP but not to adenosine (10 μM) or its analogue NECA (100 nM), supporting the involvement of two different receptors. Finally, anti-TCP-11 Fab fragments (1/25 dilution) significantly stimulated cAMP production, whereas low Fab (1/200; nonstimulatory when used alone) plus adenosine (10 μM) significantly enhanced the stimulation of capacitation by adenosine. These results support the hypotheses that TCP-11 is the receptor for FPP and that FPP↔TCP-11 interactions modulate AC/cAMP. Mol. Reprod. Dev. 51:468–476, 1998. © 1998 Wiley-Liss, Inc.     

High specific torque is related to lengthening contraction-induced skeletal muscle injury.

Animal models implicate multiple mechanical factors in the initiation of exercise-induced muscle injury. Muscle injury has been widely studied in humans, but few data exist regarding the underlying cause of muscle injury. This study sought to examine the role of torque per active muscle volume in muscle injury. Eight subjects performed 80 electrically stimulated [via electromyostimulation (EMS)] eccentric contractions of the right and left quadriceps femoris (QF) through an 80 degrees arc at 120 degrees /s. Specific torque was varied by applying 25-Hz EMS to one thigh and 100-Hz EMS to the contralateral thigh. Transverse relaxation time (T2) magnetic resonance images of the QF were collected before and 3 days after the eccentric exercise bouts. Injury was assessed via changes in isometric force and ratings of soreness over the course of 14 days after exercise and by determining changes in T2 and muscle volume 3 days after exercise. The 100-Hz EMS induced greater force loss (P < 0. 05), soreness (P < 0.05), change in muscle volume (P = 0.03), and volume of muscle demonstrating increased T2 (P = 0.005) than the 25-Hz EMS. In addition, injury was found to be similar across the QF in all but the most proximal regions of the QF. Our findings suggest that, in humans, high torque per active volume during lengthening muscle contractions is related to muscle injury.     

Vernal nitrogen and phosphorus retention by forest understory vegetation and soil microbes

Northern hardwood forests experience annual maximal loss of nutrients during spring. The vernal dam hypothesis predicts that spring ephemeral herbs in northern hardwood forests serve as sinks for nutrients during this season and reduce the loss of nutrients from the terrestrial ecosystem. Soil microbes of northern hardwood forests also sequester nutrients during spring. We compared the vernal nutrient acquisition ability of a soil microbial community and an understory plant community with species of mixed leaf phenology. We monitored nitrogen and phosphorus pool sizes in understory vegetation and soil microbes during spring from 1999 through 2001 in a northern hardwood forest in the Catskill Mountains, New York. Vegetation nutrient content increased during two spring seasons by an average of 3.07 g N m^–2 and 0.19 g P m^–2 and decreased during one spring by 0.81 g N m^–2 and 0.10 g P m^–2. Evergreen, wintergreen, and deciduous plant species were able to sequester nutrients during spring. Soil microbial nutrient content decreased during one spring by 1.29 g N m^–2 and remained constant during the other two springs. Streamwater nitrogen losses were not correlated with biotic nutrient uptake suggesting a temporal disconnect between the two processes. We conclude that understory vegetation is a larger potential sink for vernal nutrients than are soil microbes in this northern hardwood forest and understory and species representing multiple phenologies are capable of vernal nutrient uptake.     

Assessment of skeletal muscle mass in men with spinal cord injury using dual-energy X-ray absorptiometry and magnetic resonance imaging.

The purpose of this study was to determine whether the proportion of skeletal muscle in the fat-free soft tissue mass (FFST) is the same in men with spinal cord injury (SCI) and able-bodied controls. Skeletal muscle mass and FFST of the midthigh were determined by using magnetic resonance imaging and dual-energy X-ray absorptiometry, respectively, in men with long-term (>2 yr) complete SCI (n = 8) and able-bodied controls of similar age, height, and weight (n = 8). Muscle mass (1.36 +/- 0.77 vs. 2.44 +/- 0.47 kg) and FFST (1.70 +/- 0.94 vs. 2.73 +/- 0.80 kg) were lower in the SCI group than in the controls (P < 0.05), but the lower ratio of muscle to FFST in the SCI group (0.80 +/- 0.09 vs. 0.91 +/- 0.10, P < 0.05) suggested that they had a lower proportion of muscle in the FFST than in controls. This notion was supported by analysis of covariance, in that the mean muscle adjusted to the mean FFST of the groups combined was lower in the SCI group. Despite the lower proportion of muscle in the FFST of the SCI group, the relation between muscle and FFST was strong in the SCI group (r = 0.99) and controls (r = 0.96). The findings suggest a disproportionate loss of muscle in the paralyzed thighs after SCI relative to other nonfat constituents, which may be accurately estimated in men with long-term SCI by dual-energy X-ray absorptiometry if the lower proportion of muscle in the FFST (approximately 15%) is taken into account.     

Bioenergetic adaptation of individual human diaphragmatic myofibers to severe COPD.

To assess the effect of severe chronic obstructive pulmonary disease (COPD) on the ability of human diaphragmatic myofibers to aerobically generate ATP relative to ATP utilization, we obtained biopsy specimens of the costal diaphragm from seven patients with severe COPD (mean +/- SE; age 56 +/- 1 yr; forced expiratory volume in 1 s 23 +/- 2% predicted; residual volume 267 +/- 30% predicted) and seven age-matched control subjects. We categorized all fibers in these biopsies by using standard techniques, and we carried out the following quantitative histochemical measurements by microdensitometry: 1) succinate dehydrogenase (SDH) activity as an indicator of mitochondrial oxidative capacity and 2) calcium-activated myosin ATPase (mATPase) activity, the ATPase that represents a major portion of ATP consumption by contracting muscle. We noted the following: 1) COPD diaphragms had a larger proportion of type I fibers, a lesser proportion of type IIax fibers, and the same proportion of type IIa fibers as controls. 2) SDH activities of each of the fiber types were higher in COPD than control diaphragms (P < 0.0001); the mean increases (expressed as percent of control values) in types I, IIa, and IIax were 84, 114, and 130%, respectively. 3) COPD elicited no change in mATPase activity of type I and IIa fibers, but mATPase decreased in type IIax fibers (P = 0.02). 4) Mitochondrial oxidative capacity relative to ATP demand (i.e., SDH/mATPase) was higher (P = 0.03) in each of the fiber types in COPD diaphragms than in controls. These results demonstrate that severe COPD elicits an increase in aerobic ATP generating capacity relative to ATP utilization in all diaphragmatic fiber types as well as the previously described fast-to-slow fiber type transformation (Levine S, Kaiser L, Leferovich J, and Tikunov B, N Engl J Med 337: 1799-1806, 1997).     

粉纹夜蛾新细胞克隆株Tn5B-40的研究(英文)

从Tn5B1-4细胞系中克隆并筛选出了新克隆株Tn5B-40,测定分析结果表明,该克隆株对病毒(AcNPV)的敏感性和生长特性与原始细胞无显著差异,但在重组蛋白表达方面,无论对β-半乳糖苷酶还是碱性磷酸酶都明显地高于野生型细胞系,其中β-半乳糖苷酶在第6天的表达为原始细胞株的2倍,碱性磷酸酶的表达在第9天最高为原始细胞株的1.4倍。因此,该细胞是一株高产病毒和高表达重组蛋白的新克隆株。