Desiccation tolerance in the chlorophyte green alga Ulva compressa: does cell wall architecture contribute to ecological success?

MAIN CONCLUSION

Desiccation leads to structural changes of the inner pectic cell wall layers in Ulva compressa. This contributes to protection against mechanical damage due to desiccation-rehydration cycles. Ulva compressa, characterized by rbcL phylogeny, is a common species in the Mediterranean Sea. Ulva as an intertidal species tolerates repeated desiccation-rehydration cycles in nature; the physiological and structural basis were investigated under experimental conditions here. Desiccation to 73% relative water content (RWC) led to a significant decrease of the maximum quantum yield of photosystem II (F v/F m) to about half of the initial value. A reduction to 48 or 27% RWC caused a more drastic effect and thalli were only able to recover fully from desiccation to 73% RWC. Relative electron transport rates were stimulated at 73% RWC, but decreased significantly at 48 and 27% RWC, respectively. Imaging-PAM analysis demonstrated a homogenous desiccation process within individual thallus discs. The different cell wall layers of U. compressa were characterized by standard staining procedures, i.e. calcofluor white and aniline blue for structural components (cellulose, callose), ruthenium red for pectins and toluidine blue for acidic polysaccharides. Already a reduction to 73% RWC caused severe changes of the cell walls. The inner pectin-rich layers followed the shrinkage process of the cytoplasm, while the outer denser fibrillar layers maintained their shape. In this way, the thalli were not plasmolyzed during water loss, and upon recovery not negatively influenced by any mechanical damage. Transmission electron microscopy corroborated the arrangement of the different layers clearly distinguishable by their texture and electron density. We suggest the flexibility of the pectin-rich cell wall layers as a major contribution to desiccation tolerance in Ulva.

Ancient administrative handwritten documents: X-ray analysis and imaging

Handwritten characters in administrative antique documents from three centuries have been detected using different synchrotron X-ray imaging techniques. Heavy elements in ancient inks, present even for everyday administrative manuscripts as shown by X-ray fluorescence spectra, produce attenuation contrast. In most cases the image quality is good enough for tomography reconstruction in view of future applications to virtual page-by-page `reading'. When attenuation is too low, differential phase contrast imaging can reveal the characters from refractive index effects. The results are potentially important for new information harvesting strategies, for example from the huge Archivio di Stato collection, objective of the Venice Time Machine project.

Transcriptomics of desiccation tolerance in the streptophyte green alga Klebsormidium reveal a land plant-like defense reaction

BACKGROUND

Water loss has significant effects on physiological performance and survival rates of algae. However, despite the prominent presence of aeroterrestrial algae in terrestrial habitats, hardly anything is known about the molecular events that allow aeroterrestrial algae to survive harsh environmental conditions. We analyzed the transcriptome and physiology of a strain of the alpine aeroterrestrial alga Klebsormidium crenulatum under control and strong desiccation-stress conditions.

PRINCIPAL FINDINGS

For comparison we first established a reference transcriptome. The high-coverage reference transcriptome includes about 24,183 sequences (1.5 million reads, 636 million bases). The reference transcriptome encodes for all major pathways (energy, carbohydrates, lipids, amino acids, sugars), nearly all deduced pathways are complete or missing only a few transcripts. Upon strong desiccation, more than 7000 transcripts showed changes in their expression levels. Most of the highest up-regulated transcripts do not show similarity to known viridiplant proteins, suggesting the existence of some genus- or species-specific responses to desiccation. In addition, we observed the up-regulation of many transcripts involved in desiccation tolerance in plants (e.g. proteins similar to those that are abundant in late embryogenesis (LEA), or proteins involved in early response to desiccation ERD), and enzymes involved in the biosynthesis of the raffinose family of oligosaccharides (RFO) known to act as osmolytes). Major physiological shifts are the up-regulation of transcripts for photosynthesis, energy production, and reactive oxygen species (ROS) metabolism, which is supported by elevated cellular glutathione content as revealed by immunoelectron microscopy as well as an increase in total antiradical power. However, the effective quantum yield of Photosystem II and CO2 fixation decreased sharply under the applied desiccation stress. In contrast, transcripts for cell integrative functions such as cell division, DNA replication, cofactor biosynthesis, and amino acid biosynthesis were down-regulated.

SIGNIFICANCE

This is the first study investigating the desiccation transcriptome of a streptophyte green alga. Our results indicate that the cellular response is similar to embryophytes, suggesting that embryophytes inherited a basic cellular desiccation tolerance from their streptophyte predecessors.

Osmotic stress in Arctic and Antarctic strains of the green alga Zygnema (Zygnematales, Streptophyta): effects on photosynthesis and ultrastructure

The osmotic potential and effects of plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are most closely related and may represent different isolates of the same species, in contrast, strain B and G are separate lineages. Incipient plasmolysis in the cells was determined by light microscopy after incubating cells in sorbitol solutions ranging between 200 mM and 1000 mM sorbitol for 3, 6 and 24 h. In Zygnema strain B and G incipient plasmolysis occurred at ∼600 mM sorbitol solution (720 mOsmol kg⁻¹, ψ = −1.67 MPa) and in strains D and E at ∼300 mM (318 mOsmol kg⁻¹, ψ = −0.8 MPa) sorbitol solution. Hechtian strands were visualized in all plasmolysed cells, which is particularly interesting, as these cells lack pores or plasmodesmata. Ultrastructural changes upon osmotic stress were a retraction of the condensed cytoplasm from the cell walls, damages to chloroplast and mitochondrial membranes, increasing numbers of plastoglobules in the chloroplasts and membrane enclosed particles in the extraplasmatic space. Maximum photosynthetic rates (P_max) in light saturated range were between 145.5 μmol O₂ h⁻¹ mg⁻¹ Chl a in Zygnema G and 752.9 μmol O₂ h⁻¹ mg⁻¹ Chl a in Zygnema E. After incubation in 800 mM sorbitol for 3 h P_max decreased to the following percentage of the initial values: B: 16.3%, D: 16.8%, E: 26.1% and G: 35.0%. Osmotic stress (800 mM sorbitol) decreased maximum photochemical quantum yield of photosystem II (F_v/F_m) when compared to controls. Maximum values of relative electron transport rates of photosystem II (rETR_max) decreased after incubation in 400 mM sorbitol in Zygnema D and E, while they decreased in Zygnema B and G only after incubation in 800 mM sorbitol. The kinetics of the rETR curves were similar for the Arctic strains Zygnema B and G, but distinct from the Antarctic strains Zygnema D and E, which were similar when compared with each other. This suggests that the investigated Arctic Zygnema sp. strains might be better adapted to tolerate osmotic water stress than the investigated strains from the Antarctic.

Plasmolysis effects and osmotic potential of two phylogenetically distinct alpine strains of Klebsormidium (Streptophyta)

The osmotic potential and effects of plasmolysis were investigated in two different Klebsormidium strains from alpine habitats by incubation in 300-2,000 (3,000) mM sorbitol. Several members of this genus were previously found to tolerate desiccation in the vegetative state yet information was lacking on the osmotic potentials of these algae. The strains were morphologically determined as Klebsormidium crenulatum and Klebsormidium nitens. These species belong to distinct clades, as verified by phylogenetic analysis of the rbcL gene. K. crenulatum is part of to the K. crenulatum/mucosum ('F' clade) and K. nitens of the 'E2' clade. Plasmolysis occurred in K. crenulatum at 800 mM sorbitol (961 mOsmol kg(-1), Ψ = -2.09 MPa) and in K. nitens at 600 mM sorbitol (720 mOsmol kg(-1), Ψ = -1.67 MPa). These are extraordinarily high osmotic values (very negative osmotic potentials) compared with values reported for other green algae. In K. crenulatum, the maximum photosynthetic rate (Pmax) in the light-saturated range was 116 μmol O(2) h(-1) mg(-1) chl a. Incubation in 1,000 mM sorbitol decreased Pmax to 74.1% of the initial value, whereas 2,000 mM sorbitol (Ψ = -5.87 MPa) lead to an almost complete loss of oxygen production. In K. nitens, Pmax was 91 μmol O(2) h(-1) mg(-1) chl a under control conditions and incubation in 800 mM sorbitol did not decrease Pmax, 2,000 mM sorbitol decreased Pmax only to about 62.6% of the initial value whereas 3,000 mM sorbitol stopped oxygen evolution. This indicated a broader amplitude for photosynthesis in the examined strain of K. nitens. Control samples and samples plasmolysed for 3 h in 800 mM sorbitol (K. nitens), 1,000 mM sorbitol (K. crenulatum), or 2,000 mM sorbitol were investigated by transmission electron microscopy after chemical or high-pressure freeze fixation. In cells undergoing plasmolysis the protoplasts were retracted from the cell wall, the cytoplasm appeared dense, vacuoles were small and fragmented, and the cytoplasm was filled with ribosomes. Thin cytoplasmic strands were connected to the cell wall; 2,000 mM sorbitol increased the effect. The content of soluble carbohydrates in these two strains was investigated by HPLC, as this is one known mechanism for cells to maintain high osmotic pressure of the cytosol. Both Klebsormidium species contained diverse soluble carbohydrates, including a dominant mixed peak of unidentified oligosaccharides, and more minor amounts of raffinose, sucrose, glucose, xylose, galactose, mannose, inositol, fructose, glycerol, mannitol, and sorbitol. The total content of soluble carbohydrates was approximately 1.2% of the dry weight, indicating that this is not a major factor contributing to the high osmotic potential in these strains of Klebsormidium.

PPARS, insulin resistance and type 2 diabetes

It is clear that the PPAR receptors are exciting targets for therapeutic compounds likely to impact on insulin sensitivity, lipid and glucose homeostasis and vascular disease. The PPARgamma receptor agonists rosiglitazone and pioglitazone are very useful additions to the treatment options for type 2 diabetes. Currently they have limited licences, particularly in Europe, and hopefully as further clinical trial data becomes available these will be extended. Clinical outcome studies are important to ensure that the surrogate effects on glucose and other parameters translate into improved outcomes. There is exciting potential for these agents with the possibility of a combination of effects not only on glucose and lipid homeostasis but also on coagulation and thrombosis, blood pressure and microalbuminuria, which are likely to impact on vascular disease. If the current lack of evidence of serious hepatic toxicity persists they have an advantage over metformin in terms of tolerability and can be used in patients with impaired renal function. In addition to potential effects on diabetic outcome it will be of tremendous interest to determine whether these compounds, which improve insulin sensitivity and beta-cell function, will impact on the natural history of the disease. From what is known of the PPAR receptor systems it is likely that compounds acting as agonists or partial agonists for these receptors will have differing effects and it is possible to envisage the tailoring of compounds to enhance wanted effects and diminish unwanted effects, particularly fluid retention and weight gain. The future certainly looks exciting in this area.

The GM2 gangliosidoses databases: allelic variation at the HEXA, HEXB, and GM2A gene loci

The GM2 gangliosidoses are a group of recessive disorders characterized by accumulation of GM2 ganglioside in neuronal cells. The genes responsible for these disorders are HEXA (Tay-Sachs disease and variants), HEXB (Sandhoff disease and variants), and GM2A (AB variant of GM2 gangliosidosis). We report the establishment of three relational locus-specific databases recording allelic variation at the HEXA, HEXB, and GM2A genes and accessed at the GM2 gangliosidoses home page (http://data.mch.mcgill.ca/gm2-gangliosidoses). Submission forms are available for the addition of new mutations to the databases. The databases are available online for users to search and retrieve information about specific alleles by a number of fields describing mutations, phenotypes, or author(s).

A novel karyopherin-beta homolog is developmentally and hormonally regulated in fetal lung

To investigate molecular mechanisms of lung organogenesis, we used representational difference analysis to search for glucocorticoid-inducible genes in developing lung in a fetal rat model. Messenger RNA prepared from fetal and adult rat lung was used to prepare "representative amplicons." Adult-lung complementary DNA (cDNA) amplicons were used as "driver" in successive rounds of subtractive hybridization/amplification to isolate target fetal lung-specific cDNAs. A single clone, which was conserved and had near-perfect homology to eight human/rodent expressed sequence tags, was used as template for 5' and 3' rapid amplification of cDNA ends and SPICE (system for polymerase chain reaction amplification of cDNA ends) reactions to obtain the 3.6-kb cDNA, LGL2 (Genbank, AF 110195) encoding a deduced polypeptide (lgl2) of 963 amino acids. Northern analysis confirmed that LGL2 is differentially expressed in fetal lung (maximal during the pseudoglandular stage, gestational Days 14 to 16), induced by glucocorticoid, and enriched in epithelium relative to the mesenchyme. LGL2 was also detected in human fetal lung at gestational Week 16 as well as in human and rat fetal brain, heart, intestine, and kidney. We mapped LGL2 to chromosome 1p33-34.2. Comparison with sequences in the genome database identified lgl2 as a member of the karyopherin-beta family of nuclear import proteins, with greatest homology to transportin SR. Maximal expression of LGL2 in the pseudoglandular stage of development is coordinate with that of key transcription factors that regulate prominent signal transduction pathways in fetal lung organogenesis. We propose a role for lgl2 in nuclear import of transcription factors that regulate signal transduction during fetal lung development.

Tay-Sachs disease carrier screening: a model for prevention of genetic disease

Tay-Sachs disease (TSD) is an autosomal-recessive, progressive, and ultimately fatal neurodegenerative disorder. Within the last 30 years, the discovery of the enzymatic basis of the disease, namely deficiency of the enzyme hexosaminidase A, made possible both enzymatic diagnosis of TSD and heterozygote identification. In the last decade, the cloning of the HEXA gene and the identification of more than 80 associated TSD-causing mutations has permitted molecular diagnosis in many instances. TSD was the first genetic condition for which community-based screening for carrier detection was implemented. As such, the TSD experience can be viewed as a prototypic effort for public education, carrier testing, and reproductive counseling for avoiding fatal childhood disease. More importantly, the outcome of TSD screening over the last 28 years offers convincing evidence that such an effort can dramatically reduce incidence of the disease.

A novel developmentally regulated gene in lung mesenchyme: homology to a tumor-derived trypsin inhibitor

We used differential display-PCR (DD-PCR) to identify glucocorticoid-inducible genes that regulate lung development in late gestation. DD-PCR, a method to screen for differentially expressed genes, is based on a comparison of mRNAs isolated from a subset of two or more cell populations by analysis of RT-PCR products on DNA-sequencing gels. We isolated cDNA probes representing mRNAs expressed in primary cultures of rat lung fibroblasts, but not in epithelial cells, on fetal day 20. A day 20 glucocorticoid-treated fibroblast cDNA library was screened with a single probe to isolate the 3.1-kb cDNA late-gestation lung 1 (LGL1; GenBank accession no. AF109674) encoding a deduced polypeptide of 188 amino acids. Northern analysis confirmed that LGL1 is expressed in human, rat, and mouse fetal lungs, induced by glucocorticoid, developmentally regulated in fibroblasts but not detectable in epithelium. In situ hybridization confirmed LGL1 expression in the mesenchyme, but not in the epithelium, of fetal rat lung, kidney, and gut. The predicted LGL1 gene product (lgl1) showed 81% homology to P25TI, a polypeptide trypsin inhibitor recently identified in human glioblastoma and neuroblastoma cells but not detected in normal human tissues. Both lgl1 and P25TI belong to the CRISP family of cysteine-rich extracellular proteins. Trypsin is produced by both normal bronchial epithelial and lung adenocarcinoma cells. Although additional studies will be necessary to clearly establish a functional role for lgl1, we propose that lgl1 has a role in normal lung development that is likely to be via regulation of extracellular matrix degradation.

Urinary basic fibroblast growth factor. A biochemical marker for preosseous fibroproliferative lesions in patients with fibrodysplasia ossificans progressiva

Angiogenesis is a prominent histopathologic feature of preosseous fibroproliferative lesions in patients who have fibrodysplasia ossificans progressiva. Basic fibroblast growth factor is an extremely potent in vivo stimulator of angiogenesis, and has been implicated in the growth of solid tumors. An enzyme linked immunosorbent assay for basic fibroblast growth factor was performed on urine samples from patients who had active (n = 28) and inactive (n = 39) fibrodysplasia ossificans progressiva, and compared with urine samples from normal age and gender matched control subjects (n = 54). Median basic fibroblast growth factor levels were 2705 pg/g of creatinine in the normal control group, 5058 pg/g of creatinine in patients with inactive fibrodysplasia ossificans progressiva (no significant difference), and 8793 pg/g of creatinine in patients with active fibrodysplasia ossificans progressiva. Female subjects, both normal and with fibrodysplasia ossificans progressiva, had higher levels of urinary basic fibroblast growth factor than did male subjects. There was no correlation of urinary basic fibroblast growth factor levels with age or severity of preexisting disability. These data document an elevation of urinary basic fibroblast growth factor during acute flareups of fibrodysplasia ossificans progressiva and provide a biochemical basis for considering antiangiogenic therapy for inhibiting endochondral osteogenesis in this disorder.

[Tolerance and effectiveness of propiverine hydrochloride in 752 patients with symptoms of detrusor hyperactivity and increased sensitivity and irritability of the urinary bladder: results of a study monitoring drug utilization]

In a post-marketing surveillance study of 752 patients suffering from urgent incontinence, mixed urgent-stress incontinence, reflex incontinence, urgency and enuresis were treated with propiverine hydrochloride. Clinical efficacy of propiverine hydrochloride was verified by the improvement of symptoms related to detrusor hyperactivity, hypersensitivity and hyperreflexia during a 12-week surveillance period: daytime and overnight urinary incontinence, as well as the frequency, nocturia, urgency in day time and at night decreased. These results are well demonstrated by decreased pad use and statistically significant decrease of Gaudenz urgency score during treatment, confirming the efficacy of propiverine hydrochloride already proved in clinical trials. The safety profile of propiverine hydrochloride displayed characteristic anticholinergic symptoms (dry mouth, accommodation disorders, constipation, tiredness, dizziness) with decreasing incidence during the 12-week treatment period. The residual urine volume decreased also. Serious adverse events were observed rarely and could be explained by the lack of consideration of contraindications, warnings and interactions with other drugs. The positive risk-benefit relationship of propiverine hydrochloride in the treatment of detrusor hyperactivity, hypersensitivity and hyperreflexia was reconfirmed in this post-marketing drug surveillance study.

Formation of a ternary complex between GM2 activator protein, GM2 ganglioside and hexosaminidase A

The GM2 activator is a 17 kDa protein required for the hydrolysis of GM2 ganglioside by the lysosomal enzyme hexosaminidase A (HexA). The activator behaves as a substrate binding protein, solubilizing GM2 ganglioside monomers from micelles (in vitro) or membranes (in vivo). However, the activator also shows a high order of specificity for activation of lysosomal hydrolases and has been predicted to form a ternary complex with the heterodimeric enzyme (alphabeta) Hex A and GM2 ganglioside. We demonstrated a transient interaction between HexA and the GM2 activator. A chimeric protein containing the FLAG epitope sequence upstream of the GM2 activator was expressed in Escherichia coli and purified using the M1 immunoaffinity (anti-FLAG) column. Binding of the FLAG-GM2 activator (FLAG-AP) fusion protein to the M1 column led to the specific retardation of Hex A applied to the column. Other proteins were not retarded by the column nor did they compete with Hex A for binding to FLAG-AP. Hex A and GM2 ganglioside could be simultaneously bound to the column, but the binding of each ligand was independent of the other. The homodimeric (beta beta) isozyme Hex B did not bind to the immobilized activator. The alpha alpha homodimer, HexS, bound weakly, confirming that a hexosaminidase alpha subunit is required for interaction of enzyme and activator.

A chronic GM2 gangliosidosis variant with a HEXA splicing defect: quantitation of HEXA mRNAs in normal and mutant fibroblasts

Over 72 mutations have been identified in the HEXA gene of which only four (T538C, A590C, G805A, and C1495T) are believed to cause a chronic form of Tay-Sachs disease (TSD). We identified a novel HEXA mutation (IVS7, -7 G-->A) leading to chronic TSD in a Canadian patient of English ancestry. The second allele in this patient was the exon 11 4-bp insertion mutation (/1277TATC), which is the most frequent TSD allele in Ashkenazi Jews. The IVS7, -7 G-->A mutation introduces a new 3' splice acceptor site 5 bp upstream of the normal intron 7 splice acceptor site. The mutation leads to reduction of steady-state levels of HEXA mRNA by more than 80%. Two mRNA species are produced by the IVS7, -7 G-->A allele; a normal nRNA species and an mRNA lacking exon 8. No mRNA species that was spliced at the upstream 3' splice acceptor site was detected. We used competitive PCR to quantitate mRNA species in fibroblasts obtained from this patient. We compared the amounts of three identified mRNA species to HEXA mRNA levels in cells from normal individuals and from individuals heterozygous for /1277TATC. The steady-state level of HEXA mRNA in cells from a normal individual was 17.3 pg/microg RNA. An individual heterozygous for /1277TATC produced 8.7 pg of normal HEXA mRNA/microg RNA. The HEXA mRNA species with the insertion mutation was present in patient cells at 4.8% of the level of normal HEXA nRNA in homozygous normal cells. In fibroblasts from the patient carrying the IVS7, -7 G-->A mutation, the steady-state level of exon 8-deleted HEXA mRNA was 5.9% the level of that produced by homozygous normal cells. The level of normal HEXA nRNA in this patient's cells was 10.4%.

Identification of candidate active site residues in lysosomal beta-hexosaminidase A

The beta-hexosaminidases (Hex) catalyze the cleavage of terminal amino sugars on a broad spectrum of glycoconjugates. The major Hex isozymes in humans, Hex A, a heterodimer of alpha and beta subunits (alphabeta), and Hex B, a homodimer of beta subunits (betabeta), have different substrate specificities. The beta subunit (HEXB gene product), hydrolyzes neutral substrates. The alpha subunit (HEXA gene product), hydrolyzes both neutral and charged substrates. Only Hex A is able to hydrolyze the most important natural substrate, the acidic glycolipid GM2 ganglioside. Mutations in the HEXA gene cause Tay-Sachs disease (TSD), a GM2 ganglioside storage disorder. We investigated the role of putative active site residues Asp-alpha258, Glu-alpha307, Glu-alpha323, and Glu-alpha462 in the alpha subunit of Hex A. A mutation at codon 258 which we described was associated with the TSD B1 phenotype, characterized by the presence of normal amounts of mature but catalytically inactive enzyme. TSD-B1 mutations are believed to involve substitutions of residues at the enzyme active site. Glu-alpha307, Glu-alpha323, and Glu-alpha462 were predicted to be active site residues by homology studies and hydrophobic cluster analysis. We used site-directed mutagenesis and expression in a novel transformed human fetal TSD neuroglial (TSD-NG) cell line (with very low levels of endogenous Hex A activity), to study the effects of mutation at candidate active site residues. Mutant HEXA cDNAs carrying conservative or isofunctional substitutions at these positions were expressed in TSD-NG cells. alphaE323D, alphaE462D, and alphaD258N cDNAs produced normally processed peptide chains with drastically reduced activity toward the alpha subunit-specific substrate 4MUGS. The alphaE307D cDNA produced a precursor peptide with significant catalytic activity. Kinetic analysis of enzymes carrying mutations at Glu-alpha323 and Asp-alpha258 (reported earlier by Bayleran, J., Hechtman, P., Kolodny, E., and Kaback, M. (1987) Am. J. Hum. Genet. 41,532-548) indicated no significant change in substrate binding properties. Our data, viewed in the context of homology studies and modeling, and studies with suicide substrates, suggest that Glu-alpha323 and Asp-alpha258 are active site residues and that Glu-alpha323 is involved in catalysis.

The Val192Leu mutation in the alpha-subunit of beta-hexosaminidase A is not associated with the B1-variant form of Tay-Sachs disease

Substitution mutations adversely affecting the alpha-subunit of beta-hexosaminidase A (alphabeta) (EC 3.2.1.52) result in Tay-Sachs disease. The majority affect the initial folding of the pro-alpha chain in the endoplasmic reticulum, resulting in its retention and degradation. A much less common occurrence is a mutation that specifically affects an "active-site" residue necessary for substrate binding and/or catalysis. In this case, hexosaminidase A is present in the lysosome, but it lacks all alpha-specific activity. This biochemical phenotype is referred to as the "B1-variant form" of Tay-Sachs disease. Kinetic analysis of suspected B1-variant mutations is complex because hexosaminidase A is heterodimeric and both subunits possess similar active sites. In this report, we examine a previously identified B1-variant mutation, alpha-Val192Leu. Chinese hamster ovary cells were permanently cotransfected with an alpha-cDNA-construct encoding the substitution and a mutant beta-cDNA (beta-Arg211Lys), encoding a beta-subunit that is inactive but normal in all other respects. We were surprised to find that the Val192Leu substitution, produced a pro-alpha chain that did not form alpha-beta dimers and was not transported to the lysosome. Finally, we reexamined the hexosaminidase activity and protein levels in the fibroblasts from the original patient. These data were also not consistent with the biochemical phenotype of the B1 variant of Tay-Sachs disease previously reported to be present. Thus, we conclude that the Val192Leu substitution does not specifically affect the alpha-active site.

Gene therapy for amyotrophic lateral sclerosis (ALS) using a polymer encapsulated xenogenic cell line engineered to secrete hCNTF

The gene therapy approach presented in this protocol employs a polymer encapsulated, xenogenic, transfected cell line to release human ciliary neurotrophic factor (hCNTF) for the treatment of Amyotrophic Lateral Sclerosis (ALS). A tethered device, containing around 10(6) genetically modified cells surrounded by a semipermeable membrane, is implanted intrathecally; it provides for slow continuous release of hCNTF at a rate of 0.25 to 1.0 micrograms/24 hours. The semipermeable membrane prevents immunologic rejection of the cells and interposes a physical, virally impermeable barrier between cells and host. Moreover, the device and the cells it contains may be retrieved in the event of side effects. A vector containing the human CNTF gene was transfected into a line of baby hamster kidney cells (BHK) with calcium phosphate using a dihydrofolate reductase-based selection vector with a SV40 promoter and contains a HSV-tk killer gene. hCNTF is a potent neurotrophic factor which may have utility for the treatment of ALS. Systemic delivery of hCNTF in humans has been frustrated by peripheral side effects, the molecule's short half life, and its inability to cross the blood-brain barrier. The gene therapy approach described in this protocol is expected to mitigate such difficulties by local intrathecal delivery of a known quantity of continuously-synthesized hCNTF from a retrievable implant.

Tay-Sachs disease screening and diagnosis: evolving technologies

Tay-Sachs disease (TSD) is an autosomal recessive, progressive, and fatal neurodegenerative disorder. Within the last 25 years, the discovery of the enzymatic basis of the disease, the deficiency of the enzyme hexosaminidase A, has made possible both enzymatic diagnosis of TSD and heterozygote identification. TSD is the first genetic condition for which a community-based heterozygote screening program was attempted with the intention of reducing the incidence of a genetic disease. In this article we review the clinical, biochemical, and molecular features of TSD as well as the development of laboratory technology that has been deployed in community genetic screening programs. We describe the assay procedures used and some of the limitations in their accuracy. We consider the impact of DNA-based technology on the process of identification of individuals carrying mutant genes associated with TSD and we discuss the social context within which genetic screening occurs.

What young people think and do when the option for cystic fibrosis carrier testing is available

We report findings in phase II of a pilot study of cystic fibrosis (CF) carrier screening/testing by mutation analysis. Phase I has been reported elsewhere. Eligible participants in phase II (n = 815) were students (15 to 17 years of age) in public high schools. An educational component (exchange of information and discussion about common genetic disorders including CF) preceded, by one week or more, voluntary participation in the screening component which required a blood sample. The uptake rate for screening was 42%. Nine carriers (2pq = 0.0260) were identified, all with the delta F508 mutation; students were also tested for G551D, G542X, W1282X, and -549-mutations, but no carriers of these alleles were found. Carriers had positive views of the education and testing experiences. Persons identified as 'non-carriers' were also surveyed (n = 135, response rate 41%). As in phase I, the majority (83%) again understood that a negative DNA test had not excluded them from possible carrier status. Students who participated in the informational component but were not screened served here as controls in the follow up survey (n = 208, response rate 53%). Their views were similar to those of the screened non-carriers, and similar also to those held by students, adults, pregnant women, couples, and CF relatives in other communities.

A Pst+ polymorphism in the HEXA gene with an unusual geographic distribution

A polymorphic variant in the human HEXA gene is described. This gene encodes the alpha-subunit of hexosaminidase A, the enzyme which is deficient in Tay-Sachs disease (TSD). In individuals carrying the polymorphism there is a T-->C transition at position -6 in intron 13. The substitution creates a site for the restriction endonuclease Pst1. This variant has an unusual ethnogeographic distribution. It occurs on 1.4% of non-TSD carrier chromosomes in Ashkenazi Jews. All individuals ascertained carrying the Pst+ allele have ancestry in Lithuania, Belarus and Ukraine. By contrast, no individuals carrying the Pst+ allele have been detected among non-Jewish Lithuanians, Jews of Sephardic origin or in several other ethnic groups. Two unrelated non-Jewish families have been identified in which the Pst+ variant occurs. In both cases the variant occurs on a chromosome carrying a novel TSD mutation (G772C) association with the B1 phenotype. The Pst+ G772C chromosomes are of Scots-Irish descent.

Inpatient vs outpatient treatment for substance dependence revisited

Miller and Hester's 1986 review of inpatient versus outpatient alcohol treatment studies concluded with no "justification" for inpatient treatment. Further examination of these studies revealed shortcomings such as the use of random assignment designs which excluded psychiatrically-complicated patients. Carrier Foundation's inpatient/outpatient study of private psychiatric patients with alcohol and/or cocaine dependence includes a patient-treatment matching design to address weaknesses in the existing literature. Patients with high psychiatric severity and/or a poor social support system are predicted to have a better outcome in inpatient treatment, while patients with low psychiatric severity and/or a good social support system may do well as outpatients without incurring the higher costs of inpatient treatment. Preliminary results from 183 inpatients and 120 outpatients indicated outpatients, regardless of level of psychiatric severity, were 4 times more likely to be early treatment failures (chi-square = 41.2, df = 1, p < .01). While the determination of long-term follow-up status of early treatment failures is currently underway, this finding underscores the potential risk of early treatment failure in outpatient compared to inpatient substance abuse treatment programs and the importance of addressing the issue of early attrition in conducting outcome analyses.

A new Tay-Sachs disease B1 allele in exon 7 in two compound heterozygotes each with a second novel mutation

Three novel Tay--Sachs Disease (TSD) mutations have been identified in two unrelated, non-Jewish compound heterozygous patients. A G772C transversion mutation causing an Asp258His substitution is shared by both patients. The mutant enzyme had been characterized, on the basis of previous kinetic studies (1) as a B1, or alpha-subunit active site mutation. This is the first B1 mutation not found in codon 178 (exon 5). A C508T transition causing an Arg170Trp substitution also occurred in one of the patients. The third mutation is a two base deletion occurring in exon 8 involving the loss of either nts 927-928 or 929-930 in codon 310. The deletion creates an inframe termination codon 35 bases downstream. The Arg170Trp mutation was also detected in a third unrelated TSD patient. In both families this allele was traced to French Canadian ancestors originating in the Estrie region of the province of Quebec. This mutation is the third TSD allele unique to the French Canadian population and the ancestral origins of the carrier parents are distant from the center of diffusion of the more common 7.6 kb deletion mutation which is in the eastern part of the province.

The intron 7 donor splice site transition: a second Tay-Sachs disease mutation in French Canada

Mutations at the hexosaminidase A (HEXA) gene which cause Tay-Sachs disease (TSD) have elevated frequency in the Ashkenazi Jewish and French-Canadian populations. We report a novel TSD allele in the French-Canadian population associated with the infantile form of the disease. The mutation, a G-->A transition at the +1 position of intron 7, abolishes the donor splice site. Cultured human fibroblasts from a compound heterozygote for this transition (and for a deletion mutation) produce no detectable HEXA mRNA. The intron 7 + 1 mutation occurs in the base adjacent to the site of the adult-onset TSD mutation (G805A). In both mutations a restriction site for the endonuclease EcoRII is abolished. Unambiguous diagnosis, therefore, requires allele-specific oligonucleotide hybridization to distinguish between these two mutant alleles. The intron 7 + 1 mutation has been detected in three unrelated families. Obligate heterozygotes for the intron 7 + 1 mutation were born in the Saguenay-Lac-St-Jean region of Quebec. The most recent ancestors common to obligate carriers of this mutation were from the Charlevoix region of the province of Quebec. This mutation thus has a different geographic centre of diffusion and is probably less common than the exon 1 deletion TSD mutation in French Canadians. Neither mutation has been detected in France, the ancestral homeland of French Canada.

The French Canadian Tay-Sachs disease deletion mutation: identification of probable founders

Tay-Sachs disease (TSD) is an inherited neurodegenerative ganglioside storage disorder caused by deficiency of the hexosaminidase A enzyme. A deletion allele (FCD) at the HEXA locus has attained high frequency in the French Canadian population. The distribution of affected probands shows a likely center of diffusion for this mutation located in the Bas-St.-Laurent and Gaspésie regions of the province of Quebec. We have reconstructed the genealogies of 15 obligate carriers of the FCD allele to an average depth of 12 generations identifying 60 ancestors and 80 European founders common to all of them. The ancestral origins of the European founders show a significantly greater number of individuals born in the French provinces of Normandy and Perche than expected based on information regarding the origins of the 8,500 immigrants who settled the colony of New France during the French regime. We have identified common ancestors among the 10 who were born in Quebec who appear to be likely candidates for the origin of the FCD mutation. One such couple had 11 children, 5 of whom settled in regions of Quebec or New Brunswick that today have elevated heterozygote frequencies for the FCD. The five offspring are ancestors of all known carriers. By contrast, the absence of FCD alleles among TSD probands in France suggests that the mutation did not occur in a European founder.

Specificity and sensitivity of hexosaminidase assays and DNA analysis for the detection of Tay-Sachs disease gene carriers among Ashkenazic Jews

Tay-Sachs disease (TSD), a neurodegenerative disorder resulting from a deficiency of the lysosomal enzyme hexosaminidase A (HexA), clusters in Ashkenazic Jews. Population-based screening programs to detect carriers of TSD genes by means of HexA assays have been active since the 1970s. The recent characterization of 3 mutations in the HEXA gene (in exon 7, exon 11, and intron 12), which account for over 90% of HEXA mutations in Ashkenazim, appeared to offer better options for screening and diagnosis. The relative frequencies of the three mutations in Montreal are similar to those reported in four other North American populations. We compared enzyme and DNA analyses to determine specificity and sensitivity of each test when the other was used as the confirmatory procedure. Neither procedure has a sensitivity of 1.0. Maximum sensitivity and specificity were achieved by using both tests together. The findings here are likely to apply to most cases where the variant screened enzyme phenotype can result from more than one mutation.

Novel Tay-Sachs disease mutations from China

We describe three HEXA mutations associated with infantile Tay-Sachs disease (TSD) in three unrelated nonconsanguineous Chinese families. Novel mutations were found in two of these families. The third is a previously reported mutation (G-->A transition at nt 1444) (Nakano et al., 1988). Direct sequencing of PCR products identified a novel insertion of an A after nt 547 in family 1. This change generates an early termination codon 6 bp downstream from the insertion site. Allele-specific oligonucleotide hybridization confirmed homozygosity in the proband. Single strand conformational polymorphism analysis and direct sequencing of amplified exon 13 revealed a T-->C transition at nt 1453 with the corresponding amino acid substitution W485R in the second family. This mutation creates an Fnu4HI restriction site. The proband is homozygous for this allele. When the site-specific mutagenized alpha cDNA carrying the T-->C transition at nt 1453 was expressed in COS 1 cells hexosaminidase S activity was not detectable above background. A G-->A transition at nt 1444 (exon 13) corresponding to the E482K substitution was found in the third family. This mutation occurs at a CpG dinucleotide. It has been reported in an Italian TSD proband and causes defective intracellular transport of the alpha-subunit from the rough endoplasmic reticulum to the Golgi apparatus.

A glycine250--> aspartate substitution in the alpha-subunit of hexosaminidase A causes juvenile-onset Tay-Sachs disease in a Lebanese-Canadian family

The mutation causing juvenile Tay-Sachs disease (TSD) in two sibs of Lebanese-Maronite origin is described. An mRNA-containing extract of cultured fibroblasts obtained from one of the probands was used as a template to amplify the coding sequence of the hexosaminidase A (Hex A) alpha-subunit. Sequencing of amplified cDNA fragments revealed a single alteration, guanine to adenine at nt 749 creating a G250D mutation. The mutation introduces a new recognition site for the restriction enzyme Eco RV, permitting identification of heterozygotes for this allele following PCR amplification and Eco RV digestion of exon 7 sequences from genomic DNA templates. In order to test the effect of this substitution, an in vitro mutagenized cDNA construct was introduced into a mammalian expression vector and transfected into monkey Cos-1 cells separately or along with a beta-cDNA expression vector. When the mutant alpha-cDNA was the only gene introduced into COS cells no enzymatic activity above endogenous COS cell activity was detected. Cotransfection of normal alpha-cDNA and beta-cDNA followed by immunoprecipitation of human Hex A resulted in 20-fold increase in the ratio between positive and negative (mock transfection) control values. This allowed the detection of some residual activity (12% of the positive control) when the mutant alpha-cDNA replaced its wild-type counterpart. The predicted protein environment in which the mutation occurs is compared to that of the adult-onset Tay-Sachs disease mutation caused by a Gly269-->Ser substitution in exon 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of beta-thalassemia genes in Quebec immigrants of Mediterranean, southeast Asian, and Asian Indian origins

Beta-thalassemia minor occurs at 5% frequency (on average) in populations migrant (since 1945) from Mediterranean countries to the province of Quebec. Individuals of Southeast Asian/Chinese and Asian Indian origin now living in the province also carry beta-thalassemia genes at similar frequencies. We characterized beta-thalassemia genes on 68 chromosomes (19 patients and 30 carriers identified by screening) to describe heterogeneity of beta-thalassemia alleles and to evaluate desirability of DNA tests in carrier screening. Thirteen different mutations account for 74% of the 68 beta-thalassemia chromosomes: seven occur on Mediterranean chromosomes (IVS I,nt110, Non 39, IVS I,nt6, IVS I,nt1G----A, IVS II,nt1, Fr8, IVS II,nt745) another three on SE Asian chromosomes (Fr 41-42, IVS II,nt654, HbE) and yet another three on Asian Indian chromosomes (IVS I,nt5, 619 bp del, IVS I,nt1G----T). Twenty-six percent (18/68) of the chromosomes carried none of 17 alleles accounting for 92-96% of beta-thalassemia molecular pathology in reference populations. The Italian beta-thalassemia chromosomes in the Quebec sample least resembled those in the corresponding source population. Until the spectrum of mutations in Quebec populations is fully defined, phenotype assay remains the most reliable and efficient method for beta-thalassemia carrier screening.

Risk factors for falls as a cause of hip fracture in women. The Northeast Hip Fracture Study Group

BACKGROUND

Although even in the elderly most falls are not associated with fractures, over 90 percent of hip fractures are the result of a fall. Few studies have assessed whether the risk factors for falls are also important risk factors for hip fracture.

METHODS

To examine the importance of risk factors for falls in the epidemiology of hip fracture, we performed a case-control study of 174 women (median age, 80 years) admitted with a first hip fracture to 1 of 30 hospitals in New York and Philadelphia. Controls, matched to the case patients according to age and hospital, were selected from general surgical and orthopedic surgical hospital services. Information was obtained by direct interview.

RESULTS

As measured by the odds ratio, increased risks for hip fracture were associated with lower-limb dysfunction (odds ratio = 1.7; 95 percent confidence interval, 1.1 to 2.8), visual impairment (odds ratio = 5.1; 95 percent confidence interval, 1.9 to 13.9), previous stroke (odds ratio = 2.0; 95 percent confidence interval, 1.0 to 4.0), Parkinson's disease (odds ratio = 9.4; 95 percent confidence interval, 1.2 to 76.1), and use of long-acting barbiturates (odds ratio = 5.2; 95 percent confidence interval, 0.6 to 45.0). Of the controls, 44 (25 percent) had had a recent fall. The case patients were more likely than these controls to have fallen from a standing height or higher (odds ratio = 2.4; 95 percent confidence interval, 1.0 to 5.7). Of those with hip fracture the younger patients (less than 75 years old) were more likely than the older ones (greater than or equal to 75 years old) to have fallen on a hard surface (odds ratio = 1.9; 95 percent confidence interval, 1.04 to 3.7).

CONCLUSIONS

A number of factors that have been identified as risk factors for falls are also associated with hip fracture, including lower-limb dysfunction, neurologic conditions, barbiturate use, and visual impairment. Given the prevalence of these problems among the elderly, who are at highest risk, programs to prevent hip fracture should include measures to prevent falls in addition to measures to slow bone loss.

Allele-specific amplification of genomic DNA for detection of deletion mutations: identification of a French-Canadian Tay-Sachs mutation

A rapid and efficient method for the detection of a 7.6-kb deletion in the beta-hexosaminidase A alpha-subunit gene, a mutant allele causing Tay-Sachs disease in French Canadians, is described. The protocol involves PCR (polymerase chain reaction) amplification of target sequences on normal and mutant chromosomes. Three amplification primers, a single 5' primer complementary to normal and mutant DNA templates and two 3' primers specific for normal and mutant DNA templates are required. The primers direct amplification of two unique fragments (normal and mutant) that are easily separated by gel electrophoresis. Allele-specific oligonucleotide hybridization using normal and mutant probes to genomic DNA samples from normal, heterozygous and homozygous individuals confirms these results and is consistent with results of genotypic classification of individuals using Southern analysis. The method is applicable to detection of deletion mutations in cases where some deletion-flanking sequence is known.

More than one mutant allele causes infantile Tay-Sachs disease in French-Canadians

Two Tay-Sachs disease (TSD) patients of French-Canadian origin were shown by Myerowitz and Hogikyan to be homozygous for a 7.6-kb deletion mutation at the 5' end of the hexosaminidase A alpha-subunit gene. In order to determine whether all French-Canadian TSD patients were homozygotes for the deletion allele and to assess the geographic origins of TSD in this population, we ascertained 12 TSD families of French-Canadian origin and screened for occurrence of mutations associated with infantile TSD. DNA samples were obtained from 12 French-Canadian TSD families. Samples were analyzed using polymerase-chain-reaction (PCR) amplification followed by hybridization to allele-specific oligonucleotides (ASO) or by restriction analysis of PCR products. In some cases Southern analysis of genomic DNA was performed. Eighteen of the 22 independently segregating mutant chromosomes in this sample carried the 7.6-kb deletion mutation at the 5' end of the gene. One chromosome carried the 4-nucleotide insertion in exon 11 (a "Jewish" mutation). In this population no individuals were detected who had the substitution at the splice junction of exon 12 previously identified in Ashkenazi Jews. One chromosome carried an undescribed B1 mutation; this allele came from a parent of non-French-Canadian origin. Patients in three families carried TSD alleles different from any of the above mutations. The 5' deletion mutation clusters in persons originating in southeastern Quebec (Gaspé) and adjacent counties of northern New Brunswick.

Beta-thalassemia genes in French-Canadians: haplotype and mutation analysis of Portneuf chromosomes

beta-Thalassemia minor occurs at approximately 1% frequency in French-Canadians--in families residing in Portneuf County (population approximately 40,000) of Quebec province. We found eight different RFLP haplotypes at the beta-globin gene cluster in 37 normal persons and in 12 beta-thalassemia heterozygotes from six families. beta-Thalassemia genes in these families associated with two haplotypes only: Mediterranean I and Mediterranean II. There were two different beta-thalassemia mutations segregating in the Portneuf population: an RNA processing mutation (beta(+)IVS-1,nt110) on haplotype I (five families) and a point mutation leading to chain termination (beta(0) nonsense codon 39) on haplotype II (one family). The distribution of 5' haplotypes on normal beta A Portneuf chromosomes compared with other European populations was most similar to that in British subjects (data for French subjects have not yet been reported). Genealogical reconstructions traced the ancestry of carrier couples to settlers emigrating from several different regions of France to New France in the 17th century. These findings indicate genetic diversity of a greater degree among French-Canadians than recognized heretofore.

The musculoskeletal manifestations of progeria. A literature review

Although a superficial similarity exists between the musculoskeletal disorders associated with natural aging and those of progeria, an in-depth analysis reveals profound differences in the pathophysiology between the two processes. The protean manifestations of progeria can best be explained on the basis of the vascular changes found at autopsy. A disorder of the vascular endothelium may predispose progeric vessels to atherosclerotic changes. The unique musculoskeletal manifestations of progeria arise from the effects of premature atherosclerosis on the vascularized connective tissues.

Controlled study of renal osteodystrophy in patients undergoing dialysis. Improved response to continuous ambulatory peritoneal dialysis compared with hemodialysis

To assess the effect of different dialysis modalities on renal osteodystrophy, a controlled study was performed in six patients undergoing continuous ambulatory peritoneal dialysis and six hemodialysis-treated patients. All patients were enrolled at the initiation of dialysis, and age, sex, cause of renal failure, prior treatment of renal osteodystrophy, and baseline serum and bone histologic variables were similar in the two groups. After initial blood samples and bone biopsy specimens (with double-tetracycline labels) were obtained, renal osteodystrophy in both groups received comparable treatment with aluminum hydroxide to maintain serum phosphorus levels between 3.5 and 5.5 mg/dl, and with calcium carbonate and calcitriol to maintain total serum calcium levels between 10 and 11 mg/dl. Blood and bone samples were obtained again after nine months. All patients were asymptomatic at the beginning and end of the study. Phosphorus values were well controlled, and total calcium increased similarly in both groups. Although ionized calcium levels increased in both groups, the final level was higher in hemodialysis-treated patients than in patients undergoing continuous ambulatory peritoneal dialysis (2.82 +/- 0.07 meq/liter and 2.5 +/- 0.05 meq/liter, respectively; p = 0.005). Amino-terminal parathyroid hormone levels normalized in both groups, and histologic improvement of osteitis fibrosa occurred in a similar proportion of patients in both groups; however, quantitative improvement was greater in the hemodialysis-treated patients. Osteomalacia, assessed qualitatively and by dynamic histomorphometric measurements, was ameliorated to a much greater degree in patients undergoing continuous ambulatory peritoneal dialysis compared with hemodialysis-treated patients. Bone aluminum staining was absent in all biopsy specimens. Overall, bone histologic findings improved to a greater degree in patients undergoing continuous ambulatory peritoneal dialysis. When patients undergoing continuous ambulatory peritoneal dialysis or hemodialysis and receiving similar treatment for renal osteodystrophy were compared, patients treated with continuous ambulatory peritoneal dialysis appeared to have a greater improvement in their metabolic bone disease.

Osteopetrosis: MR characteristics at 1.5 T

Four patients with proved osteopetrosis (three with the infantile malignant form and one with the benign form) were examined with magnetic resonance imaging at 1.5 T. All patients were studied in the coronal and sagittal planes using both short and long repetition time/echo time sequences. The infantile malignant form was characterized by a complete lack of signal from the marrow alternating with a signal intensity equivalent to that of the intervertebral disks, resulting in a "stepladder" appearance. In the benign form or after successful marrow transplantation in the infantile malignant form, intermediate or high signal intensity in the vertebrae was noted, suggesting the presence of some marrow elements.

Idiopathic familial acroosteolysis: histomorphometric study of bone and literature review of the Hajdu-Cheney syndrome

We describe a 27-year-old man with familial acroosteolysis involving 9 fingers. Bone biopsy of an affected digit showed osteolysis with no tetracycline deposition, rare osteoclasts, increased vascularity, and numerous mast cells. In contrast, the iliac crest bone showed active bone remodeling and normal double-tetracycline labeling. We believe mast cells deserve further study as possible factors in this form of localized osteolysis.

Respiratory complications of metatropic dwarfism

Two infants with clinical and radiologic features of metatropic dwarfism presented in the neonatal period with episodes of cyanosis. Diagnostic studies to determine the etiology of these spells, including electrocardiogram, electroencephalogram, arterial blood gases, and metabolic and sepsis studies, were unremarkable. Chest roentgenograms revealed the characteristic long, narrow thoracic cage with no evidence of parenchymal disease. Cervical spine stability evaluation, pulmonary function studies, and chest impedance monitoring with qualitative air flow thermistor studies and transcutaneous oxygen monitoring were carried out. Both patients demonstrated a significant increase in resistance of the respiratory system following passive maneuvering of the head from a neutral position, suggestive of hypopharyngeal air flow obstruction. Obstructive sleep apnea resulting in cyanosis was documented in both patients. All other studies failed to yield a cause for the episodes of cyanosis. Our investigation failed to alter the clinical course which resulted in respiratory arrest and death by 7 months of age. A table is presented for the differentiation of skeletal dysplasias presenting in the perinatal period.