The CRTC-1 transcriptional domain is required for COMPASS complex-mediated longevity in C. elegans

Loss of function during aging is accompanied by transcriptional drift, altering gene expression and contributing to a variety of age-related diseases. CREB-regulated transcriptional coactivators (CRTCs) have emerged as key regulators of gene expression that might be targeted to promote longevity. Here we define the role of the Caenorhabditis elegans CRTC-1 in the epigenetic regulation of longevity. Endogenous CRTC-1 binds chromatin factors, including components of the COMPASS complex, which trimethylates lysine 4 on histone H3 (H3K4me3). CRISPR editing of endogenous CRTC-1 reveals that the CREB-binding domain in neurons is specifically required for H3K4me3-dependent longevity. However, this effect is independent of CREB but instead acts via the transcription factor AP-1. Strikingly, CRTC-1 also mediates global histone acetylation levels, and this acetylation is essential for H3K4me3-dependent longevity. Indeed, overexpression of an acetyltransferase enzyme is sufficient to promote longevity in wild-type worms. CRTCs, therefore, link energetics to longevity by critically fine-tuning histone acetylation and methylation to promote healthy aging.

A single-copy knockin translating ribosome immunoprecipitation toolkit for tissue-specific profiling of actively translated mRNAs in C. elegans

Here, we introduce a single-copy knockin translating ribosome immunoprecipitation (SKI TRIP) toolkit, a collection of Caenorhabditis elegans strains engineered by CRISPR in which tissue-specific expression of FLAG-tagged ribosomal subunit protein RPL-22 is driven by cassettes present in single copy from defined sites in the genome. Through in-depth characterization of the effects of the FLAG tag in animals in which endogenous RPL-22 has been tagged, we show that it incorporates into actively translating ribosomes and efficiently and cleanly pulls down cell-type-specific transcripts. Importantly, the presence of the tag does not impact overall mRNA translation, create bias in transcript use, or cause changes to fitness of the animal. We propose SKI TRIP use for the study of tissue-specific differences in translation and for investigating processes that are acutely sensitive to changes in translation like development or aging.

Alternative splicing in aging and longevity

Alternative pre-mRNA splicing increases the complexity of the proteome that can be generated from the available genomic coding sequences. Dysregulation of the splicing process has been implicated in a vast repertoire of diseases. However, splicing has recently been linked to both the aging process itself and pro-longevity interventions. This review focuses on recent research towards defining RNA splicing as a new hallmark of aging. We highlight dysfunctional alternative splicing events that contribute to the aging phenotype across multiple species, along with recent efforts toward deciphering mechanistic roles for RNA splicing in the regulation of aging and longevity. Further, we discuss recent research demonstrating a direct requirement for specific splicing factors in pro-longevity interventions, and specifically how nutrient signaling pathways interface to splicing factor regulation and downstream splicing targets. Finally, we review the emerging potential of using splicing profiles as a predictor of biological age and life expectancy. Understanding the role of RNA splicing components and downstream targets altered in aging may provide opportunities to develop therapeutics and ultimately extend healthy lifespan in humans.

Corrigendum: Splicing factor 1 modulates dietary restriction and TORC1 pathway longevity in C. elegans

This corrects the article DOI: 10.1038/nature20789.

Splicing factor 1 modulates dietary restriction and TORC1 pathway longevity in C. elegans

Ageing is driven by a loss of transcriptional and protein homeostasis and is the key risk factor for multiple chronic diseases. Interventions that attenuate or reverse systemic dysfunction associated with age therefore have the potential to reduce overall disease risk in the elderly. Precursor mRNA (pre-mRNA) splicing is a fundamental link between gene expression and the proteome, and deregulation of the splicing machinery is linked to several age-related chronic illnesses. However, the role of splicing homeostasis in healthy ageing remains unclear. Here we demonstrate that pre-mRNA splicing homeostasis is a biomarker and predictor of life expectancy in Caenorhabditis elegans. Using transcriptomics and in-depth splicing analysis in young and old animals fed ad libitum or subjected to dietary restriction, we find defects in global pre-mRNA splicing with age that are reduced by dietary restriction via splicing factor 1 (SFA-1; the C. elegans homologue of SF1, also known as branchpoint binding protein, BBP). We show that SFA-1 is specifically required for lifespan extension by dietary restriction and by modulation of the TORC1 pathway components AMPK, RAGA-1 and RSKS-1/S6 kinase. We also demonstrate that overexpression of SFA-1 is sufficient to extend lifespan. Together, these data demonstrate a role for RNA splicing homeostasis in dietary restriction longevity and suggest that modulation of specific spliceosome components may prolong healthy ageing.

Co-expression of phenylalanine hydroxylase variants and effects of interallelic complementation on in vitro enzyme activity and genotype-phenotype correlation

BACKGROUND

In phenylketonuria (PKU) patients, the combination of two phenylalanine hydroxylase (PAH) alleles is the main determinant of residual enzyme activity in vivo and in vitro. Inconsistencies in genotype-phenotype correlations have been observed in compound heterozygous patients and a particular combination of two PAH alleles may produce a phenotype that is different from the expected one, possibly due to interallelic complementation.

METHODS

A dual eukaryotic vector system with two distinct PAH proteins N-terminally fused to different epitope tags was used to investigate the co-expression of PAH alleles reported in patients with inconsistent phenotypes. PAH variant proteins were transiently co-transfected in COS-7 cells. PAH activity was measured by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS), and protein expression was measured by Western blot. Genotypes were compared with predicted PAH activity from the PAH locus-specific database (PAHvdb) and with phenotypes and tetrahydrobiopterin (BH4) responsiveness from more than 10,000 PKU patients (BIOPKU database).

RESULTS

Through the expression and co-expression of 17 variant alleles we demonstrated that interallelic interaction could be both positive and negative. The co-expressions of p.[I65T];[R261Q] (19.5% activity; predicted 43.5%) and p.[I65T];[R408W] (15.0% vs. 26.8% activity) are examples of genotypes with negative interallelic interaction. The co-expressions of p.[E178G];[Q232E] (55.0% vs.36.4%) and p.[P384S];[R408W] (56.1% vs. 40.8%) are examples of positive subunit interactions. Inconsistencies of PAH residual enzyme activity in vitro and of PKU patients' phenotypes were observed as well. The PAH activity of p.[R408W];[A300S] is 18.0% of the wild-type activity; however, 88% of patients with this genotype exhibit mild hyperphenylalaninemias (MHPs).

CONCLUSION

The co-expression of two distinct PAH variants revealed possible dominance effects (positive or negative) by one of the variants on residual PAH activity as a result of interallelic complementation.

You are what you host: microbiome modulation of the aging process

The critical impact that microbiota have on health and disease makes the interaction between host and microbiome increasingly important as we evaluate therapeutics. Here, we highlight growing evidence that, beyond disease, microbes also affect the most fundamental of host physiological phenotypes, the rate of aging itself.

Tetrahydrobiopterin, its mode of action on phenylalanine hydroxylase, and importance of genotypes for pharmacological therapy of phenylketonuria

In about 20%-30% of phenylketonuria (PKU) patients (all phenotypes of PAH deficiency), Phe levels may be controlled through phenylalanine hydroxylase cofactor tetrahydrobiopterin therapy. These patients can be diagnosed by an oral tetrahydrobiopterin challenge and are characterized by mutations coding for proteins with substantial residual PAH activity. They can be treated with a commercially available synthetic form of tetrahydrobiopterin, either as a monotherapy or as adjunct to the diet. This review article summarizes molecular and metabolic bases of PKU and the importance of the tetrahydrobiopterin loading test used for PKU patients. On the basis of in vitro residual PAH activity, more than 1,200 genotypes from patients challenged with tetrahydrobiopterin were categorized as predictive for tetrahydrobiopterin responsiveness or non-responsiveness and correlated with the loading test, phenotype, and residual in vitro PAH activity. The coexpression of two distinct PAH mutant alleles revealed possible dominance effects (positive or negative) by one of the mutations on residual activity as result of interallelic complementation. The treatment of the transfected cells with tetrahydrobiopterin showed an increase in residual PAH activity with several mutations coexpressed.

Splicing of phenylalanine hydroxylase (PAH) exon 11 is vulnerable: molecular pathology of mutations in PAH exon 11

In about 20-30% of phenylketonuria (PKU) patients, phenylalanine (Phe) levels can be controlled by cofactor 6R-tetrahydrobiopterin (BH(4)) administration. The phenylalanine hydroxylase (PAH) genotype has a predictive value concerning BH(4)-response and therefore a correct assessment of the mutation molecular pathology is important. Mutations that disturb the splicing of exons (e.g. interplay between splice site strength and regulatory sequences like exon splicing enhancers (ESEs)/exon splicing silencers (ESSs)) may cause different severity of PKU. In this study, we identified PAH exon 11 as a vulnerable exon and used patient derived lymphoblast cell lines and PAH minigenes to study the molecular defect that impacted pre-mRNA processing. We showed that the c.1144T>C and c.1066-3C>T mutations cause exon 11 skipping, while the c.1139C>T mutation is neutral or slightly beneficial. The c.1144T>C mutation resides in a putative splicing enhancer motif and binding by splicing factors SF2/ASF, SRp20 and SRp40 is disturbed. Additional mutations in potential splicing factor binding sites contributed to elucidate the pathogenesis of mutations in PAH exon 11. We suggest that PAH exon 11 is vulnerable due to a weak 3' splice site and that this makes exon 11 inclusion dependent on an ESE spanning position c.1144. Importantly, this implies that other mutations in exon 11 may affect splicing, since splicing is often determined by a fine balance between several positive and negative splicing regulatory elements distributed throughout the exon. Finally, we identified a pseudoexon in intron 11, which would have pathogenic consequences if activated by mutations or improved splicing conditions. Exonic mutations that disrupt splicing are unlikely to facilitate response to BH(4) and may lead to inconsistent genotype-phenotype correlations. Therefore, recognizing such mutations enhances our ability to predict the BH(4)-response.

Quantification of phenylalanine hydroxylase activity by isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry

BACKGROUND

Residual phenylalanine hydroxylase (PAH) activity is the key determinant for the phenotype severity in phenylketonuria (PKU) patients and correlates with the patient's genotype. Activity of in vitro expressed mutant PAH may predict the patient's phenotype and response to tetrahydrobiopterin (BH(4)), the cofactor of PAH.

METHODS

A robust LC-ESI-MSMS PAH assay for the quantification of phenylalanine and tyrosine was developed. We measured PAH activity a) of the PAH mutations p.Y417C, p.I65T, p.R261Q, p.E280A, p.R158Q, p.R408W, and p.E390G expressed in eukaryotic COS-1 cells; b) in different cell lines (e.g. Huh-7, Hep3B); and c) in liver, brain, and kidney tissue from wild-type and PKU mice.

RESULTS

The PAH assay was linear for phenylalanine and tyrosine (r(2)≥0.99), with a detection limit of 105 nmol/L for Phe and 398 nmol/L for Tyr. Intra-assay and inter-assay coefficients of variation were <5.3% and <6.2%, respectively, for the p.R158Q variant in lower tyrosine range. Recovery of tyrosine was 100%. Compared to the wild-type enzyme, the highest PAH activity at standard conditions (1 mmol/L L-Phe; 200 μmol/L BH(4)) was found for the mutant p.Y417C (76%), followed by p.E390G (54%), p.R261Q (43%), p.I65T (33%), p.E280A (15%), p.R158Q (5%), and p.R408W (2%). A relative high PAH activity was found in kidney (33% of the liver activity), but none in brain.

CONCLUSIONS

This novel method is highly sensitive, specific, reproducible, and efficient, allowing the quantification of PAH activity in different cells or tissue extracts using minimum amounts of samples under standardized conditions.

Molecular genetics and impact of residual in vitro phenylalanine hydroxylase activity on tetrahydrobiopterin responsiveness in Turkish PKU population

BACKGROUND

The prevalence of phenylalanine hydroxylase (PAH)-deficient phenylketonuria (PKU) in Turkey is high (1 in 6500 births), but data concerning the genotype distribution and impact of the genotype on tetrahydrobiopterin (BH(4)) therapy are scarce.

OBJECTIVE

To characterize the phenotypic and genotypic variability in the Turkish PKU population and to correlate it with physiological response to BH(4) challenge.

METHODS

We genotyped 588 hyperphenylalaninemic patients and performed a BH(4) loading test (20mg/kg bw) in 462 patients. Residual PAH activity of mutant proteins was calculated from available in vitro expression data. Data were tabulated in the BIOPKU database (www.biopku.org).

RESULTS

Eighty-eight mutations were observed, the most common missense mutations being the splice variant c.1066-11G>A (24.6%). Twenty novel mutations were detected (11 missense, 4 splice-site, and 5 deletion/insertions). Two mutations were observed in 540/588 patients (91.8%) but in 9 patients atypical genotypes with >2 mutations were found (8 with p.R155H in cis with another variant) and in 19 patients mutations were found in BH(4)-metabolizing genes. The most common genotype was c.1066-11G>A/c.1066-11G>A (15.5%). Approximately 22% of patients responded to BH(4) challenge. A substantial in vitro residual activity (average >25% of the wild-type enzyme) was associated with response to BH(4). In homozygous genotypes (n=206), both severity of the phenotype (r=0.83) and residual PAH activity (r=0.85) correlate with BH(4) responsiveness.

CONCLUSION

Together with the BH(4) challenge, these data enable the genotype-based classification of BH(4) responsiveness and document importance of residual PAH activity. This first report of a large-scale genotype assessment in a population of Turkish PKU patients also documents a high prevalence (47%) of the severe classic phenotype.

Genotype-predicted tetrahydrobiopterin (BH4)-responsiveness and molecular genetics in Croatian patients with phenylalanine hydroxylase (PAH) deficiency

Specific mutations in the gene encoding phenylalanine hydroxylase (PAH), located on chromosome 12q22-24.1, are linked to tetrahydrobiopterin (BH4; sapropterin)-responsive phenylketonuria (PKU). Diagnosis is usually done through the newborn screening for PKU, followed by a BH4 loading test. So far, more than 60 mutant alleles, presenting with a substantial residual PAH activity (average approximately 47%), were identified in more than 500 patients worldwide. We investigated the predictive value of BH4-responsive PAH mutations in Croatian population. From a group of 127 PKU patients, 62 were selected (based on the genotype) as potentially BH4-responsive and 39 loaded with BH4 (20 mg/kg). The overall frequency of BH4-responsiveness (>30% blood phenylalanine reduction within 24 h) was 36% (14 out of 39 patients with 23 different genotypes), significantly less than expected. The best responders were patients with mild hyperphenylalaninemia (4/4; 100%), followed by mild PKU (8/9; 89%), and classical PKU (2/26; 8%). The most common BH(4)-responsive genotypes were p.E390G/p.R408W and p.P281L/p.E390G. These genotypes correspond for approximately >30% residual PAH activity. The p.E390G mutation was 100% associated with BH4-responsiveness, regardless of the second allele (p.R408W, p.P281L, p.F55Lfs, p.L249P). With regard to the predicted relative PAH activity of recombinantly expressed mutant alleles, there was a significant (p<0.002) difference between BH4-responders and non-responders. In a general Croatian PKU population, disease-causing mutations were identified on 226 alleles (99%). There were 35 different mutations: 21 missense, 8 splice site, 3 nonsense, 2 single nucleotide deletions, and 1 in-frame deletion. Four mutations are reported for the first time: p.E76D, p.L333P, p.G346E, and IVS8-2A>G. Five mutations accounted for over two-thirds of investigated alleles: p.L48S, p.R261Q, p.P281L, p.E390G, and p.R408W. Thus, the Croatian PKU population seems to be more homogenous than some other Mediterranean or Central European populations. This study reveals the importance of a full genotype for the prediction of BH4-responsiveness. In contrast to previous assumption and with exception of the p.E390G mutation, single allele mutations are not reliable for the selection of potential PKU candidates for pharmacological therapy with BH4.

A simple selection strategy for evolving highly efficient enzymes

Combining tunable transcription with an enzyme-degradation tag affords an effective means to reduce intracellular enzyme concentrations from high to very low levels. Such fine-tuned control allows selection pressure to be systematically increased in directed-evolution experiments. This facilitates identification of mutants with wild-type activity, as shown here for an engineered chorismate mutase. Numerous selection formats and cell-based screening methodologies may benefit from the large dynamic range afforded by this easily implemented strategy.

Influence of the Textile Structure on the Degradation of Explanted Aortic Endoprostheses

OBJECTIVES

To investigate mechanisms of textile failure in explanted human aortic endoprostheses.

MATERIALS AND METHODS

Endoprostheses (n31) underwent optical and scanning electron microscopy, filament dynamometry, and saturation index measurement.

RESULTS

The macroscopic lesions observed in the Stentor and Vanguard devices were holes at the extremities of the stents and slipping of the warp yarns at the level of sutures or of the longitudinal seams. The macroscopic lesions observed in AneurX endoprostheses were holes, slipping of the warp yarns and ruptures of the ligatures. The macroscopic lesions observed in the two Talent endoprostheses were sections of fibers at the level of the suture holes and few areas lesions of wear, with sometimes holes at the contact of the stent extremities. Stentor, Vanguard and AneurX all demonstrated low saturation indexes of the fabric (44-59%) with an important anisotropy. Whereas the Talent endograft demonstrated a high index of saturation (124-131%) with a low anisotropy. We did not demonstrate significant polymer degradation in any of the endoprostheses.

CONCLUSIONS

It is essential to take into account the saturation index to optimally choose a woven textile for the construction of an endoprosthesis since this property of the textile may contribute to explain the macroscopic lesions observed. We did not observe significant polymer degradation by filament dynamometry but further studies are needed to confirm these data.

Mechanisms of Rupture of Knitted Polyester Vascular Prostheses: An In vitro Analysis of Virgin Prostheses

OBJECTIVES

Previous explant retrieval studies have shown ruptures occurring on the remeshing line and the guide line of two types of warp-knitted grafts. The aim of our study was to characterize the mechanisms these ruptures.

MATERIALS AND METHODS

We performed an in vitro study of the mechanical and chemical characteristics of virgin prostheses. We studied 2 virgin polyester warp-knitted grafts models: the Cooley Double Velour and the Microvel Double Velour constructed by Meadox (USA), using the following techniques: characterization and de-knitting of the textile structure, circumferential tensile strength, filament dynamometry, critical dissolution time of the filaments and scanning electron microscopy.

RESULTS

Both prostheses were constructed in the same way but the texturized yarns of the Cooley graft included twice as many filaments (54) than the Microvel (27). There was more adsorbed tension in the Cooley structure than in the Microvel. The circumferential tensile strength test demonstrated that the Cooley graft always ruptured on the remeshing line and the Microvel graft always ruptured at the interface between the remeshing line and the standard line. Filament dynamometry demonstrated a heterogeneous behavior of the filaments inside the yarns, mainly at the remeshing line of the Cooley graft (27.1 cN/tex +/- 11.5% versus 26.1 cN/tex +/- 2.2% for the guide line and 28 cN/tex +/- 6.7% for the standard knit). Critical dissolution time of the filaments was significantly lower for the Microvel grafts (2.5 sec versus 17.2 sec for the Cooley).

CONCLUSIONS

Rupture of knitted polyester prostheses are probably an underestimated phenomenon. They may occur at specific areas of the graft. Further studies are required to determine whether all grafts of this type are at risk.

What can we learn from explanted endovascular devices?

OBJECTIVE

To examine the durability of the Stentor and Vanguard endovascular devices in human implants.

METHODS

The textile covering, the polypropylene ligatures and the stent metal of 34 devices (25 Stentor, 9 Vanguard) with a mean duration of implantation of 28.8 +/- 16 months was examined by means of stereomicroscopy and scanning electron microscopy.

RESULTS

The polyester textile covering showed gaps along the sutured seam and isolated holes in the fabric. All of the examined polypropylene ligatures were worn, some ruptured. Four different types of stent corrosion were classified--pits (100%), bizarre craters (68%), large deficiencies (14%) and fractures (32%).

CONCLUSION

Holes in the polyester fabric and frame dislocations are specific for the design of Stentor and Vanguard grafts. The early corrosion of the stent metal Nitinol in these devices is surprising. Until more experience is gained with other devices, we have to be reminded, that the "gold standard" for the long-term durability of artificial vascular grafts is still "today's" conventional graft.

Corroded nitinol wires in explanted aortic endografts: an important mechanism of failure?

PURPOSE

To analyze surface alterations and fractures observed in the nitinol stent wires of explanted endovascular grafts used for treatment of abdominal aortic aneurysm.

METHODS

Twenty-one explanted Stentor devices and 1 Cragg stent were received from investigators in Germany and France. After macroscopy and photography, the explants were cleaned and the polyester coating removed. The frame was examined completely by stereomicroscopy, and irregularities were assayed by scanning electron microscopy and energy dispersive x-ray analysis (EDAX). The observed alterations were classified according to stereomicroscopic and electron microscopic morphology.

RESULTS

The mean implantation interval for the endografts was 29.1 +/- 13.2 months (range 5-46). All examined explants, even those retrieved after only a few months in situ, showed pitlike surface damage 10-25 microm in diameter. Larger, irregularly shaped surface alterations were observed in approximately 70% of the explants. Older explants (age >32 months) presented vast regions of decay, with bending of the wire and stress cracks in some areas. EDAX examination revealed decreased nickel concentration in the corroded regions.

CONCLUSIONS

Corrosion of the nitinol wire in endovascular grafts is confirmed. Presumably, the observed pitting and irregularly shaped corrosion defects are the precursors of material failure. They weaken the thin wire, which leads to stress cracks and eventually fracture of the stent wire under circulatory pulsation. Cell-induced electrochemical corrosion and active cellular destruction of surfaces are well-known mechanisms that must be investigated for their possible roles in the corrosion of stent metals.

Corroded nitinol wires in explanted aortic endografts: an important mechanism of failure?

PURPOSE

To analyze surface alterations and fractures observed in the nitinol stent wires of explanted endovascular grafts used for treatment of abdominal aortic aneurysm.

METHODS

Twenty-one explanted Stentor devices and 1 Cragg stent were received from investigators in Germany and France. After macroscopy and photography, the explants were cleaned and the polyester coating removed. The frame was examined completely by stereomicroscopy, and irregularities were assayed by scanning electron microscopy and energy dispersive x-ray analysis (EDAX). The observed alterations were classified according to stereomicroscopic and electron microscopic morphology.

RESULTS

The mean implantation interval for the endografts was 29.1 +/- 13.2 months (range 5-46). All examined explants, even those retrieved after only a few months in situ, showed pitlike surface damage 10-25 microm in diameter. Larger, irregularly shaped surface alterations were observed in approximately 70% of the explants. Older explants (age >32 months) presented vast regions of decay, with bending of the wire and stress cracks in some areas. EDAX examination revealed decreased nickel concentration in the corroded regions.

CONCLUSIONS

Corrosion of the nitinol wire in endovascular grafts is confirmed. Presumably, the observed pitting and irregularly shaped corrosion defects are the precursors of material failure. They weaken the thin wire, which leads to stress cracks and eventually fracture of the stent wire under circulatory pulsation. Cell-induced electrochemical corrosion and active cellular destruction of surfaces are well-known mechanisms that must be investigated for their possible roles in the corrosion of stent metals.

[Stent wire fractures and mesh loosening in explanted endovascular prosthesis]

Vascular grafts are available since the middle of the 50's. Explant retrieval studies still reveal not published material degradation today, after over 40 years of product development. Endovascular grafts exist since the beginning of the 90's. New developments and modifications have lead to numerous devices. The importance of explant retrieval studies grows.

MATERIALS AND METHODS

Among 33 stentgrafts, retrieved 5 to 43 months after implantation, the majority were 18 MinTec devices (17 Stentor, 1 Cragg). These 18 explants were examined by endoscopy, stereomicroscopy and scanning electron microscopy.

RESULTS

The following material degradation was observed. The textile coating showed holes along the longitudinal seam, the ligatures in-between the stentframes burst, allowing the frames to dislocate. Occasional fractures of the stent wire were seen accompanied by bowl-shaped alterations of the surface.

CONCLUSION

The Stentor device is, since its modification 1996, not available any longer. It was one of the most applied devices world-wide. The possible material deficiencies must be known by those performing patient follow-up. The occurrence of alterations within 43 months shows the importance of a continued follow-up besides clinical trials.

Influence of production, handling, and storage on phytonutrient content of foods

The goals of agricultural production have traditionally been to try to accommodate needs for: 1) adequate and reliable yields to provide a sufficient food supply in a growing world; 2) food safety; 3) taste; 4) convenience; 5) profit; and 6) variety. Alternative strategies to enhance any of these outcomes are typically evaluated as to their probable effects on the key outcome: yield. However, with the burgeoning consumer interest in foods that optimize health, attention is shifting from concerns over quantity alone to concerns over the constituents of foods that may promote health, and thus to the agricultural practices that will protect, and perhaps enhance these constituents of the food supply. This shift in focus requires new thinking and new strategies across all segments of the food production system. This paper summarizes selected aspects of crop production that are pivotal to the nutrient value of foods for human consumption and suggests some strategies for establishing a new research and production paradigm that will embrace nutrient quality among the priorities of agricultural research.

Enhancement of skeletal muscle regeneration

We have studied the effect of adding extra satellite cells or soluble factors from crushed muscle on regeneration of minced fragments from rat tibialis muscle. The muscle mince was wrapped in an artificial epimysium to prevent adhesions and cell immigration from adjacent muscles. Regeneration was quantitatively assessed by electrophoretic determination of the muscle-specific form of creatine kinase. Control minces exhibited three periods of change in creatine kinase activity during a 7-week regeneration period. Activity fell rapidly during the first week, then rose gradually from 1-3 weeks and increased more rapidly from 3-7 weeks. To augment the original complement of myogenic cells, satellite cells were isolated from the contralateral muscle, purified by density gradient centrifugation, and expanded in culture for 3 days before adding to the muscle mince. The added cells resulted in a 3-fold enhancement of creatine kinase activity throughout the regeneration period. Soluble muscle extract incorporated into a collagen matrix also stimulated regeneration when added to muscle mince. The extract accelerated the rate of creatine kinase increase during the 1-3 week period beyond that observed in the control or cell augmented mince, suggesting that factors in the extract may facilitate revascularization or reinnervation. The specific activity of creatine kinase was increased in regenerates augmented with both cells and extract, indicating that the effects enhance primarily myogenic processes.

Post-traumatic pancreatic pseudocyst: non-operative conservative management--report on 3 cases

The authors report on 3 cases of post-traumatic pancreatic pseudocysts in children. Complete healing occurred with non-operative conservative treatment and total parenteral nutrition. Daily follow-up with clinical evaluation, abdominal ultrasound and lab exams are detailed under definite criteria of selection and follow-up. This mode of treatment might be considered as an alternative to exploratory laparotomy and external drainage.

[Cantrell syndrome or the "shagreen skin" pentalogy. Apropos of 3 cases]

Three patients with incomplete forms of Cantrell syndrome underwent surgical therapy at the Department of Infantile Surgery in Strasbourg, France, between 1979 and 1990. One patient had a giant omphalocele. Another had a ventricular septal defect. Two of the three patients are alive and doing well. The nosology and prognostic factors in Cantrell syndrome are discussed.

Salt taste detection: an R-index approach to signal-detection measurements

The R-index approach to the signal-detection P(A) index of sensitivity was used to measure taste sensitivity to NaCl solutions. The R-index is the predicted probability of the correct choice of a signal, for a given signal-noise pair. For flow-wise and sipwise presentation, R-indices did not fluctuate significantly, provided subjects could not see the stimuli yet to be presented, indicating a lack of systematic sensitivity drift. The simultaneous measurement of more than one signal strength with reference to a common noise stimulus was seen to be a viable and sensitive procedure. Comparison of flow-wise and sipwise presentation of stimuli using R-indices, indicated that the former elicited greater subject sensitivity to NaCl taste.

Synaptinemal complexes in Schizophyllum commune

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