A genetic register for von Hippel-Lindau disease

A genetic register for von Hippel-Lindau disease was set up in the north west of England in 1990. Population statistics, clinical features, age at onset, and survival of 83 people affected with von Hippel-Lindau (VHL) disease were studied. In addition, the effectiveness of the screening programme used and the occurrence of central nervous system haemangioblastomas in the general population were examined. The diagnostic point prevalence of heterozygotes in the North Western Region was 1 center dot 18/100 000 (1/85 000) people, with an estimated birth incidence of 2 center dot 20/100 000 (1/45 500) live births. The mutation rate was estimated directly to be 1 center dot 4 x 10(-6)/gene/generation (1/714 200). The mean age at onset of first symptoms was 26 center dot 25 years, with cerebellar haemangioblastoma being the most common presenting manifestation (34 center dot 9% of cases). The mean age at diagnosis of VHL disease was 30 center dot 87 years. Overall, 50 patients (60 center dot 2%) developed a cerebellar haemangioblastoma, 34 (41 center dot 0%) a retinal angioma, 21 (25 center dot 3%) a renal cell carcinoma, 12 (14 center dot 5%) a spinal haemangioblastoma, and 12 (14 center dot 5%) a phaeochromocytoma. Mean age at diagnosis of renal cell carcinoma (38 center dot 9 years) was significantly higher than that for cerebellar haemangioblastoma (30 center dot 0 years) and retinal angioma (21.1 years). Mean age at death was 40 center dot 9 years with cerebellar haemangioblastoma being the most common cause (47 center dot 7% of deaths). A total of 65 VHL manifestations were diagnosed asymptomatically following appropriate clinical and radiological screening tests, and failure to detect manifestations of VHL disease in spite of appropriate screening occurred on only two occasions. The use of DNA linkage analysis and direct mutation testing reduced the personal risk of carrying the VHL gene to below 1% in 14 people. In addition to the 83 clinically affected subjects, three obligate carriers who were considered to be lesion free in spite of extensive screening tests were identified. Fourteen percent of all CNS haemangioblastomas on the regionally based Cancer Registry were found to occur as part of VHL disease, but investigations for VHL in apparently sporadic disease appeared to be limited.

Psychiatric comorbidity and length of stay in the general hospital. A critical review of outcome studies

The authors critically reviewed 26 international and American outcome studies that assessed the effect of psychiatric comorbidity on length of stay for medical/surgical inpatients. Three generations of American studies were defined according to the rigorousness of the methodology. Eighty-nine percent of all studies with sample sizes greater than 110 and 75% of the prospective, rigorously controlled, American studies found a significant association between psychiatric comorbidity and increased length of stay. The findings lead to the conclusion that impaired cognition associated with delirium and dementia, depressed mood, and other personality variables contributes to prolonged hospital stays and greater utilization of hospitals and other health resources after discharge. Recommendations for future research are suggested.

Cellular localisation of the ataxia-telangiectasia (ATM) gene product and discrimination between mutated and normal forms

The recently cloned gene (ATM) mutated in the human genetic disorder ataxia-telangiectasia (A-T) is involved in DNA damage response at different cell cycle checkpoints and also appears to have a wider role in signal transduction. Antibodies prepared against peptides from the predicted protein sequence detected a approximately 350 kDa protein corresponding to the open reading frame, which was absent in 13/23 A-T homozygotes. Subcellular fractionation, immunoelectronmicroscopy and immunofluorescence showed that the ATM protein is present in the nucleus and cytoplasmic vesicles. This distribution did not change after irradiation. We also provide evidence that ATM protein binds to p53 and this association is defective in A-T cells compatible with the defective p53 response in these cells. These results provide further support for a role for the ATM protein as a sensor of DNA damage and in a more general role in cell signalling, compatible with the broader phenotype of the syndrome.

Heteronuclear ribonucleoproteins C1 and C2, components of the spliceosome, are specific targets of interleukin 1beta-converting enzyme-like proteases in apoptosis

Apoptosis induced by a variety of agents results in the proteolytic cleavage of a number of cellular substrates by enzymes related to interleukin 1beta-converting enzyme (ICE). A small number of substrates for these enzymes have been identified to date, including enzymes involved in DNA repair processes: poly(ADP-ribose) polymerase and DNA-dependent protein kinase. We describe here for the first time the specific cleavage of the heteronuclear ribonucleoproteins (hnRNPs) C1 and C2 in apoptotic cells induced to undergo apoptosis by a variety of stimuli, including ionizing radiation, etoposide, and ceramide. No cleavage was observed in cells that are resistant to apoptosis induced by ionizing radiation. Protease inhibitor data implicate the involvement of an ICE-like protease in the cleavage of hnRNP C. Using recombinant ICE-like proteases and purified hnRNP C proteins in vitro, we show that the C proteins are cleaved by Mch3alpha and CPP32 and, to a lesser extent, by Mch2alpha, but not by ICE, Nedd2, Tx, or the cytotoxic T-cell protease granzyme B. The results described here demonstrate that the hnRNP C proteins, abundant nuclear proteins thought to be involved in RNA splicing, belong to a critical set of protein substrates that are cleaved by ICE-like proteases during apoptosis.

The dalbergioid legumes (Fabaceae): delimitation of a pantropical monophyletic clade

A monophyletic pantropical group of papilionoid legumes, here referred to as the "dalbergioid" legumes, is circumscribed to include all genera previously referred to the tribes Aeschynomeneae and Adesmieae, the subtribe Bryinae of the Desmodieae, and tribe Dalbergieae except Andira, Hymenolobium, Vatairea, and Vataireopsis. This previously undetected group was discovered with phylogenetic analysis of DNA sequences from the chloroplast trnK (including matK) and trnL introns, and the nuclear ribosomal 5.8S and flanking internal transcribed spacers 1 and 2. All dalbergioids belong to one of three well-supported subclades, the Adesmia, Dalbergia, and Pterocarpus clades. The dalbergioid clade and its three main subclades are cryptic in the sense that they are genetically distinct but poorly, if at all, distinguished by nonmolecular data. Traditionally important taxonomic characters, such as arborescent habit, free stamens, and lomented pods, do not provide support for the major clades identified by the molecular analysis. Short shoots, glandular-based trichomes, bilabiate calyces, and aeschynomenoid root nodules, in contrast, are better indicators of relationship at this hierarchical level. The discovery of the dalbergioid clade prompted a re-analysis of root nodule structure and the subsequent finding that the aeschynomenoid root nodule is synapomorphic for the dalbergioids.

Ataxia telangiectasia-mutated gene product inhibits DNA damage-induced apoptosis via ceramide synthase

DNA double-stranded breaks (dsb) activate surveillance systems that identify DNA damage and either initiate repair or signal cell death. Failure of cells to undergo appropriate death in response to DNA damage leads to misrepair, mutations, and neoplastic transformation. Pathways linking DNA dsb to reproductive or apoptotic death are virtually unknown. Here we report that metabolic incorporation of 125I-labeled 5-iodo-2'deoxyuridine, which produces DNA dsb, signaled de novo ceramide synthesis by post-translational activation of ceramide synthase (CS) and apoptosis. CS activation was obligatory, since fumonisin B1, a fungal pathogen that acts as a specific CS inhibitor, abrogated DNA damage-induced death. X-irradiation yielded similar results. Furthermore, inhibition of apoptosis using the peptide caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone did not affect CS activation, indicating this event is not a consequence of induction of apoptosis. ATM, the gene mutated in ataxia telangiectasia, is a member of the phosphatidylinositol 3-kinase family that constitutes the DNA damage surveillance/repair system. Epstein-Barr virus-immortalized B cell lines from six ataxia telangiectasia patients with different mutations exhibited radiation-induced CS activation, ceramide generation, and apoptosis, whereas three lines from normal patients failed to manifest these responses. Stable transfection of wild type ATM cDNA reversed these events, whereas antisense inactivation of ataxia telangiectasia-mutated gene product in normal B cells conferred the ataxia telangiectasia phenotype. We propose that one of the functions of ataxia telangiectasia-mutated gene product is to constrain activation of CS, thereby regulating DNA damage-induced apoptosis.

A late methanogen origin for molybdenum-dependent nitrogenase

Mounting evidence indicates the presence of a near complete biological nitrogen cycle in redox-stratified oceans during the late Archean to early Proterozoic (c. 2.5-2.0 Ga). It has been suggested that the iron (Fe)- or vanadium (V)-dependent nitrogenase rather than molybdenum (Mo)-dependent form was responsible for dinitrogen fixation during this time because oceans were depleted in Mo and rich in Fe. We evaluated this hypothesis by examining the phylogenetic relationships of proteins that are required for the biosynthesis of the active site cofactor of Mo-nitrogenase in relation to structural proteins required for Fe-, V- and Mo-nitrogenase. The results are highly suggestive that among extant nitrogen-fixing organisms for which genomic information exists, Mo-nitrogenase is unlikely to have been associated with the Last Universal Common Ancestor. Rather, the origin of Mo-nitrogenase can be traced to an ancestor of the anaerobic and hydrogenotrophic methanogens with acquisition in the bacterial domain via lateral gene transfer involving an anaerobic member of the Firmicutes. A comparison of substitution rates estimated for proteins required for the biosynthesis of the nitrogenase active site cofactor and for a set of paralogous proteins required for the biosynthesis of bacteriochlorophyll suggests that Nif emerged from a nitrogenase-like ancestor approximately 1.5-2.2 Ga. An origin and ensuing proliferation of Mo-nitrogenase under anoxic conditions would likely have occurred in an environment where anaerobic methanogens and Firmicutes coexisted and where Mo was at least episodically available, such as in a redox-stratified Proterozoic ocean basin.

Phylogenetic systematics of the tribe Millettieae (Leguminosae) based on chloroplast trnK/matK sequences and its implications for evolutionary patterns in Papilionoideae

Phylogenetic relationships in the tribe Millettieae and allies in the subfamily Papilionoideae (Leguminosae) were reconstructed from chloroplast trnK/matK sequences. Sixty-two accessions representing 57 traditionally recognized genera of Papilionoideae were sampled, including 27 samples from Millettieae. Phylogenies were constructed using maximum parsimony and are well resolved and supported by high bootstrap values. A well-supported "core Millettieae" clade is recognized, comprising the four large genera Millettia, Lonchocarpus, Derris, and Tephrosia. Several other small genera of Millettieae are not in the core Millettieae clade. Platycyamus is grouped with Phaseoleae (in part). Ostryocarpus, Austrosteenisia, and Dalbergiella are neither in the core Millettieae or Phaseoleae clade. These taxa, along with core Millettieae and Phaseoleae, form a monophyletic sister group to Indigofereae. Cyclolobium and Poecilanthe are close to Brongniartieae. Callerya and Wisteria belong to a large clade that includes all the legumes that lack the inverted repeat in their chloroplast genome, which confirms previous rbcL and phytochrome gene family phylogenies. The evolutionary history of four characters was examined in Millettieae and allies: the presence of canavanine, inflorescence types, the dehiscence of pods, and the presence of winged pods. trnK/matK sequence analysis suggests that the presence of a pseudoraceme or pseudopanicle and the accumulation of nonprotein amino acids are phylogenetically informative for Millettieae and allies with only a few exceptions.

Percentage of canals filled in apical cross sections - anin vitrostudy of seven obturation techniques

AIM

To compare the apical density of several obturation techniques when used in palatal roots of extracted maxillary molars.

METHODOLOGY

Seventy extracted molars were randomly divided into seven groups with 10 teeth each. The palatal root canals were instrumented to size 60 MAF, coated with Kerr's Pulp Canal Sealer, and obturated using one of seven techniques. The palatal roots were separated from the crowns, decalcified, and sectioned horizontally at 2 and 4 mm from the apex. The cross-sections were photographed through a microscope, the photos were analysed, and the amount of area in the canal that was obturated with gutta-percha was measured. The means for the 20 sections per group were calculated and the means were compared using mixed analysis of variance test.

RESULTS

Simplifill used in accordance with the manufacturer's directions and Thermafil had the greatest mean obturated area, but neither were statistically better than mechanical lateral or warm vertical compaction (WVC; Schilder Technique). Simplifill as recommended and Thermafil were statistically better than cold lateral (P = 0.0210 and 0.0433, respectively), WVC (continuous wave) (P = 0.0006 and 0.0015), and the modified Simplifill group (P = 0.0010 and 0.0012). In addition, mechanical lateral and WVC (Schilder) had statistically more obturated area than WVC (continuous wave) (P = 0.0054 and 0.0073) and modified Simplifill (P = 0.0015 and 0.0016). Cold lateral and WVC (continuous wave) had significantly more obturated area than modified Simplifill (P = 0.0040 and 0.0087).

CONCLUSIONS

Simplifill as recommended, Thermafil, mechanical lateral and WVC (Schilder) obturation techniques created more complete obturation using gutta-percha at the 2 and 4 mm levels than cold lateral, WVC (continuous wave), and Simplifill not used as directed.

Functional and computational assessment of missense variants in the ataxia-telangiectasia mutated (ATM) gene: mutations with increased cancer risk

The functional consequences of missense variants are often difficult to predict. This becomes especially relevant when DNA sequence changes are used to determine a diagnosis or prognosis. To analyze the consequences of 12 missense variants in patients with mild forms of ataxia-telangiectasia (A-T), we employed site-directed mutagenesis of ataxia-telangiectasia mutated (ATM) cDNA followed by stable transfections into a single A-T cell line to isolate the effects of each allele on the cellular phenotype. After induction of the transfected cells with CdCl2, we monitored for successful ATM transcription and subsequently assessed: 1) intracellular ATM protein levels; 2) ionizing radiation (IR)-induced ATM kinase activity; and 3) cellular radiosensitivity. We then calculated SIFT and PolyPhen scores for the missense changes. Nine variants produced little or no correction of the A-T cellular phenotype and were interpreted to be ATM mutations; SIFT/PolyPhen scores supported this. Three variants corrected the cellular phenotype, suggesting that they represented benign variants or polymorphisms. SIFT and PolyPhen scores supported the functional analyses for one of these variants (c.1709T>C); the other two were predicted to be "not tolerated" (c.6188G>A and c.6325T>G) and were classified as "operationally neutral." Genotype/phenotype relationships were compared: three deleterious missense variants were associated with an increased risk of cancer (c.6679C>T, c.7271T>G, and c.8494C>T). In situ mutagenesis represents an effective experimental approach for distinguishing deleterious missense mutations from benign or operationally neutral missense variants.

Anaerobically regulated aldolase gene of maize. A chimaeric origin?

The sequence of the anaerobically induced fructose 1,6-bisphosphate aldolase gene of maize is presented. Analysis of the upstream sequences of the aldolase gene reveals a six base-pair sequence (TGGTTT) with perfect homology to one of the sub-regions of the anaerobic regulatory element (ARE) which is responsible for the anaerobic induction of the maize alcohol dehydrogenase 1 gene (Adh1). In the aldolase gene this sequence is located at position -70 relative to the start of transcription, in a small segment proven by functional analysis to be important for expression of the aldolase gene. Since this six base-pair sequence has been shown to be critical for anaerobic induction of the Adh1 mRNA, is in the functional promoter region of aldolase and is also present in a homologous position in Adh2 (another anaerobically-induced gene), we suggest this hexanucleotide is essential for anaerobic regulation of each of these genes. The maize aldolase gene is about 50% homologous at the amino acid level to the animal aldolase gene but has a completely different intron/exon structure. While the rat aldolase gene has nine introns the maize gene has a single large intron near the N terminus of the coding region. Because there is 55% homology downstream from the intron and very little homology upstream, we suggest that the maize gene has acquired a 5' region containing signals for anaerobic regulation and fortuitously adding a new N-terminal region to the protein. We must suppose that the plant gene has lost the remaining introns.

Testing for mutations of the ataxia telangiectasia gene in radiosensitive breast cancer patients

BACKGROUND AND PURPOSE

To determine if clinical radiosensitivity in breast cancer patients is related to mutations of the ataxia telangiectasia gene (ATM).

MATERIALS AND METHODS

Fifteen patients who had developed a severe late reaction to a standard radiotherapy schedule were examined for evidence of increased in vitro radiosensitivity using the MTT assay. Mutation analysis was performed using a protein truncation assay.

RESULTS

No mutations were detected in the 15 patients despite evidence of increased in vitro radiosensitivity.

CONCLUSIONS

Testing for the ATM gene is unlikely to be useful for predicting clinical response to radiotherapy in breast cancer patients.

Sensation seeking and collegiate vulnerability to internet dependence

Past research on Internet dependence has suggested that those who are Internet dependent spend more time on-line, use chat rooms more frequently, play MUDs more often, and web surf more than nondependent Internet users, but few studies have examined how personality characteristics interact with Internet dependence. This study investigates how Internet usage, preferences, attitudes toward the Internet, and Internet behaviors are correlated with sensation seeking. It was predicted that participants who were higher in Internet usage and Internet behaviors would be higher in sensation seeking. Results indicated that Internet dependents tended to spend more time online, use E-mail, surf the web, use chat rooms, use MUDs, and visit cybersex sites more often than nondependent Internet users. However, dependents scored significantly lower on sensation seeking, thrill and adventure seeking, and excitement seeking than nondependent Internet users. It was concluded that dependents interact with the internet using a motivation scheme dissimilar to the physical thrill and excitement that typically characterize sensation seeking archetypes.

Protein kinase A inhibitors enhance radiation-induced apoptosis

In addition to a role for de novo protein synthesis in apoptosis we have previously shown that activation of a protein phosphatase or loss of activity of a kinase is also important in radiation-induced apoptosis in human cells [Baxter, and Lavin (1992): J Immunol 148:149-1954]. We show here that some inhibitors of protein kinases exacerbate radiation-induced apoptosis in the human cell line BM13674. The specific protein kinase A inhibitor isoquinoline sulfonamide (20 microM) gave rise to significantly increased levels of apoptosis at 2-6 h postirradiation compared to values after radiation exposure only. The same concentration of isoquinolinesulfonamide, which was effective in increasing apoptosis, reduced activity markedly. A 66% inhibition of cyclic AMP-dependent protein kinase A activity occurred in unirradiated cells at this concentration of H89 and activity was reduced to 58% in irradiated cells. Calphostin C, a specific inhibitor of protein kinase C, at a concentration of 0.1 microM, which caused 68% inhibition of enzyme activity in irradiated cells, failed to enhance the level of radiation-induced apoptosis. Other kinase inhibitors did not lead to an additional increase in apoptosis over and above that observed after irradiation. The results obtained here provide further support for an important role for modification of existing proteins during radiation-induced apoptosis.

Anterior segment ischaemia following segmental scleral buckling

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Delayed suprachoroidal haemorrhage after glaucoma operations

Delayed suprachoroidal haemorrhage occurred in 13 eyes in a consecutive series of 432 cases undergoing trabeculectomy or anterior chamber (A/C) tube drainage operations. Aphakia and vitrectomy were associated with an increased risk of haemorrhage, whilst advanced age, myopia, systemic hypertension and high preoperative intraocular pressure were not. Haemorrhage occurred more often after A/C tube drainage operations than after trabeculectomy. An explanation for this may be that eyes requiring A/C tube drainage operations have had multiple previous operations including lens extraction and vitrectomy, have a higher pre-operative intraocular pressure and a greater fall in pressure after operation when compared to eyes undergoing trabeculectomy. Post-operative hypotony should be avoided in high-risk eyes.

Absence of ATM truncations in patients with severe acute radiation reactions

PURPOSE

Severe acute toxicity limits the effective use of radiotherapy in patients who are radiosensitive, and it is not usually possible to identify these radiohypersensitive (R-H) individuals before treatment commences. Five such R-H patients were detected over a 3-year period. We undertook this study to determine whether the severe acute radiohypersensitivity of these five individuals showed any correlation with cellular and molecular parameters known to be abnormal in radiosensitivity-related syndromes such as ataxia-telangiectasia (A-T).

METHODS AND MATERIALS

Lymphoblastoid cells were isolated from fresh blood from the 5 R-H individuals who had previously demonstrated clinical R-H at least 9 months prior to sampling. Lymphoblastoid cell lines (LCLs) were established to determine the extent of postradiation chromosomal aberrations, cell cycle delay, cell proliferation, and tumor suppressor p53 protein stabilization. The polymerase chain reaction (PCR) and protein truncation (PTT) assays were used to test for the possibility of mutations in the gene mutated in A-T, termed ATM.

RESULTS

LCLs derived from R-H subjects retained a significantly higher degree of radiation-induced chromosomal aberrations when compared to normal control LCLs. p53 stabilization by ionizing radiation appeared normal in all but one R-H subject. There was no evidence of A-T gene truncation mutations in any of the R-H subjects tested.

CONCLUSIONS

All R-H subjects in this study had their cellular radiosensitivity confirmed by the chromosomal aberration assay. Delayed p53 stabilization at 4 hours postirradiation in one R-H subject suggested that different etiologies may apply in the radiohypersensitivity investigated in this study.

The physical and adhesive properties of dental cements used for atraumatic restorative treatment

Atraumatic restorative treatment (ART), a recently reported field dentistry technique, involves removal of carious debris using only hand instruments and placement of a glass-ionomer cement (GIC) restoration. While small ART-GIC restorations are effective short-term replacements for lost tooth form, many larger ART-GIC restorations are defective after two years. Presently, resin-modified GICs (R-M GIC) are available which require no special activation equipment and handle easily in field settings. This study measured the compressive, tensile, and shear bond strengths to enamel and dentin of a conventional ART-GIC (Fuji IX) and two R-M GICs (Fuji Plus and Advance) at a powder-to-liquid ratio of 3.6:1. The compressive strengths of the GICs tested were significantly different. Fuji IX had the highest compressive strength, and Advance had the lowest strength (p < 0.05). The tensile strength of the R-M GICs was greater than that of the ART-GIC. Fuji Plus showed the highest shear bond strength to enamel and dentin and was significantly different from both Fuji IX and Advance. A clinical protocol is presented followed by case reports where the ART technique was used for management of acute caries in a modern dental setting.

Bistratene A causes phosphorylation of talin and redistribution of actin microfilaments in fibroblasts: possible role for PKC-delta

Bistratene A is a marine toxin which induces phosphorylation of cellular proteins. Our current evidence indicates that this occurs through activation of protein kinase C-delta. In fibroblasts bistratene A causes rounding up of the cells and a rapid disappearance of vinculin staining and actin stress fibers as detected by fluorescence immunohistochemistry. Phosphorylation of the focal adhesion protein, talin, is increased after bistratene A treatment and this is inhibited by calphostin C, a specific inhibitor of PKC. No changes in the phosphorylation status of vinculin, tubulin, or vimentin were observed in the presence of the toxin. Treatment with bistratene A caused a redistribution of PKC-delta from cytosolic and membrane compartments to the nuclear fraction. There was no effect on the subcellular distribution of any other PKC isoform. These results demonstrate that phosphorylation of talin is implicated in the disruption of actin microfilaments in fibroblasts by bistratene A and that this is most likely mediated by PKC-delta.

Pathogenesis of pupillary capture after posterior chamber intraocular lens implantation

Pupillary capture is an unusual complication of posterior chamber intraocular lens implantation and may occur in the early or late postoperative period. We describe a series of patients with early or late onset pupillary capture and describe the pathogenesis. Early capture results from mechanical factors and is usually preventable. Late capture may be mechanical but is usually a sequel to the formation and subsequent contraction of iridocapsular synechiae. Synechiae result from lens epithelial or iris stromal hyperplasia and myofibroblastic metaplasia; they may be minimised by an atraumatic technique and adequate control of postoperative inflammation. The effect of pupillary capture is largely cosmetic, and we encountered no specific complications attributable to it.

von Willebrand factor arginine 1205 substitution results in accelerated macrophage-dependent clearance in vivo

BACKGROUND

Enhanced von Willebrand factor (VWF) clearance is important in the etiology of type 1 and type 2 von Willebrand disease (VWD). More than 20 different VWF point mutations have already been reported in patients with enhanced clearance. These include the VWD-Vicenza variant, which is characterized by an Arg1205His substitution in the VWF D3 domain. Critically, however, the molecular mechanisms through which single amino acid substitutions in VWF result in enhanced clearance of this complex multimeric glycoprotein have not been defined.

OBJECTIVES

In this study, we have investigated the biological basis underlying the enhanced clearance of the VWF-R1205H variant.

METHODS

Using VWF(-/-) mice, in vivo clearance rates were determined for a series of full-length and truncated recombinant VWF variants. In addition, the role of macrophages in modulating enhanced VWD-Vicenza clearance was investigated using clodronate liposome administration.

RESULTS

Our findings demonstrate that substitutions of R1205 with histidine, cysteine or serine all result in markedly reduced survival of full-length recombinant VWF. Importantly, D'A3 fragments containing these same R1205 substitutions also demonstrated significantly enhanced clearance. In contrast to the reduced in vivo survival observed with R1205H, clearance of R1204H was not enhanced. Recent studies have demonstrated that hepatic and splenic macrophages play key roles in regulating VWF clearance. Importantly, macrophage-depletion also served to markedly attenuate the enhanced clearance phenotypes associated with VWF-R1205H, VWF-R1205S and VWF-R1205C.

CONCLUSIONS

Collectively, these novel findings demonstrate a specific and critical role for the R1205 residue in modulating macrophage-mediated clearance of VWF in vivo.

The bistratenes: new cytotoxic marine macrolides which induce some properties indicative of differentiation in HL-60 cells

The biological effects of cytotoxic macrolide polyethers, the bistratenes, isolated from the ascidian Lissoclinum bistratum, have been examined. Bistratene A was toxic to HL-60 human promyelocytic leukemia cells with an IC50 value of 424 nM. At lower concentrations (10-100 nM), bistratene A induced the incomplete differentiation of these cells along the monocyte/macrophage pathway. These effects were not due to inhibition of DNA synthesis. Bistratene B had similar effects to bistratene A. At micromolar concentrations these compounds enhance the phospholipid-dependent activity of type II protein kinase C from bovine spleen. The bistratenes provide new probes for studying the molecular mechanisms governing cell growth and differentiation.

Variability in wheat based on low-copy DNA sequence comparisons

The chromosomes of the B genome of hexaploid wheat (AABBDD) do not pair completely with those of any of the diploid species with genomes similar to B. Various biochemical and molecular analyses have suggested that each of the five diploid species in section Sitopsis of Triticum are ancestral to B. These observations have led to the hypothesis that the B genome may be polyphyletic, descending from more than one diploid ancestor. This hypothesis may account for differences between the wheat B genome and the diploids and also for variability that currently exists among different wheat accessions. In this study, we cloned and compared nucleotide sequences for three low-copy DNA fragments from the B and D genomes of several wheat accessions and from diploid relatives of the B and D genomes. Our results suggested that the amount of DNA sequence variability in wheat is low, although somewhat more variability existed in the B genome than in the D genome. The B genome of wheat was significantly diverged from all the Sitopsis diploid species, and Triticum speltoides was closer to B than to other members of this section. The D genome of wheat was very similar to that of its progenitor, Triticum tauschii. No evidence for a polyphyletic origin of the B genome was found. A more parsimonious hypothesis is that the wheat B genome diverged from its diploid ancestor after the original hybridization event occurred.