Survivin and the inner centromere protein INCENP show similar cell-cycle localization and gene knockout phenotype

BACKGROUND

Survivin is a mammalian protein that carries a motif typical of the inhibitor of apoptosis (IAP)proteins, first identified in baculoviruses. Although baculoviral IAP proteins regulate cell death, the yeast Survivin homolog Bir1 is involved in cell division. To determine the function of Survivin in mammals, we analyzed the pattern of localization of Survivin protein during the cell cycle, and deleted its gene by homologous recombination in mice.

RESULTS

In human cells, Survivin appeared first on centromeres bound to a novel para-polar axis during prophase/metaphase, relocated to the spindle midzone during anaphase/telophase, and disappeared at the end of telophase. In the mouse, Survivin was required for mitosis during development. Null embryos showed disrupted microtubule formation, became polyploid, and failed to survive beyond 4.5days post coitum. This phenotype, and the cell-cycle localization of Survivin, resembled closely those of INCENP. Because the yeast homolog of INCENP, Sli15, regulates the Aurora kinase homolog Ipl1p, and the yeast Survivin homolog Bir1 binds to Ndc10p, a substrate of Ipl1p, yeast Survivin, INCENP and Aurora homologs function in concert during cell division.

CONCLUSIONS

In vertebrates, Survivin and INCENP have related roles in mitosis, coordinating events such as microtubule organization, cleavage-furrow formation and cytokinesis. Like their yeast homologs Bir1 and Sli15, they may also act together with the Aurora kinase.

Induction of beta-platelet-derived growth factor receptor in rat hepatic lipocytes during cellular activation in vivo and in culture

A consistent response to liver injury is the activation of resident mesenchymal cells known as lipocytes (Ito, fat-storing cells) into a proliferating cell type. In cultured lipocytes, platelet-derived growth factor (PDGF) is the most potent proliferative cytokine, but requires the activation-dependent expression of its receptor protein (Friedman, S. L., and M. J. P. Arthur. 1989. J. Clin. Invest. 84:1780-1785); the role of PDGF receptor (PDGFR) in liver injury is unknown. We have examined PDGFR gene expression in freshly isolated lipocytes during liver injury and correlated these findings with a culture model of cellular activation. Whereas lipocytes from normal rats had no detectable transcript for the beta-PDGFR subunit, this mRNA was induced within 1 h after a dose of carbon tetrachloride (CCl4). In contrast, alpha subunit mRNA was detected in normal cells, but was unchanged after liver injury. Similar results were observed in lipocytes from bile duct-obstructed rats, although beta-PDGFR induction was less marked. By immunoblot, induction of beta-PDGFR protein in lipocytes isolated from CCl4-treated animals correlated with mRNA increases. In contrast to lipocytes, endothelial cells from normal liver expressed low levels of alpha- and beta-receptor subunit mRNA, which did not increase with injury. Using a beta-PDGFR antibody, receptor protein could be identified within fibrotic septa in CCl4-treated animals in regions where cells expressed proliferating cell nuclear antigen (PCNA). In cultured lipocytes activated by growth on uncoated plastic, beta-PDGFR transcripts appeared within 3 d after plating, which coincided with the onset of cellular proliferation. In contrast, quiescent cells in suspension culture had no detectable beta-PDGFR mRNA. These results indicate that beta-PDGF receptor induction by lipocytes is an early event during hepatic injury in vivo and in primary culture.

Unravelling the complexities of the NF-κB signalling pathway using mouse knockout and transgenic models

The nuclear factor-kappaB (NF-kappaB) signalling pathway serves a crucial role in regulating the transcriptional responses of physiological processes that include cell division, cell survival, differentiation, immunity and inflammation. Here we outline studies using mouse models in which the core components of the NF-kappaB pathway, namely the IkappaB kinase subunits (IKKalpha, IKKbeta and NEMO), the IkappaB proteins (IkappaBalpha, IkappaBbeta, IkappaBvarepsilon and Bcl-3) and the five NF-kappaB transcription factors (NF-kappaB1, NF-kappaB2, c-Rel, RelA and RelB), have been genetically manipulated using transgenic and knockout technology.

Oral biofilms: emerging concepts in microbial ecology

Oral biofilms develop under a range of different conditions and different environments. This review will discuss emerging concepts in microbial ecology and how they relate to oral biofilm development and the treatment of oral diseases. Clues to how oral biofilms develop may lie in other complex systems, such as interactions between host and gut microbiota, and even in factors that affect biofilm development on leaf surfaces. Most of the conditions under which oral biofilms develop are tightly linked to the overall health and biology of the host. Advances in molecular techniques have led to a greater appreciation of the diversity of human microbiota, the extent of interactions with the human host, and how that relates to inter-individual variation. As a consequence, plaque development may no longer be thought of as a generic process, but rather as a highly individualized process, which has ramifications for the treatment of the diseases it causes.

Bcl-2 expression in adult and embryonic non-haematopoietic tissues

The B-cell leukaemia/lymphoma-2 (bcl-2) proto-oncogene is unusual as its product appears to provide survival advantage to B cells by blocking apoptosis. In this study, the expression of bcl-2 has been examined in normal non-haematopoietic tissues, embryos, and psoriatic skin by immunohistochemical staining. Bcl-2 protein expression is mainly observed in cell populations with a long life and/or proliferating ability such as duct cells in exocrine glands, basal keratinocytes, cells at the bottom of colon crypts, and neurons. In the skin of both adult and embryo and also embryonic kidney and cartilage, bcl-2 expression was observed in cells which were undergoing morphological transition from undifferentiated stem cells to committed precursor cells. The finding of bcl-2 expression in the terminal differentiated syncytial trophoblast, but not cytotrophoblast, and in some cells responsive to hormone stimulation such as in the endometrium and myometrium suggests that the gene expression may be related to hormone responsiveness. As no bcl-2 localization was seen in the benign hyperproliferative skin condition psoriasis, this does not suggest a straight-forward link to proliferation. These observations support the view that the bcl-2 gene may have an important role in cell development, maturation, and the path to terminal differentiation.

Breath hydrogen testing in bacterial overgrowth of the small intestine

The indirect, noninvasive technique of breath hydrogen (H2) analysis was evaluated in 45 patients suspected of having bacterial overgrowth of the small intestine. Bacterial overgrowth, defined as a jejunal culture yielding at least 10(5) organisms/ml, was present in 27 patients. After dietary preparation and a 12-h fast, subjects received in random order and on separate days 50 g of glucose or 50 g of rice flour in the form of two pancakes. Normal values were established in 20 healthy controls. Twelve of 27 patients with proven bacterial overgrowth had an elevated (greater than 15 ppm) fasting breath H2 level on at least 1 test day. Fifteen of 18 patients with negative cultures had low fasting breath H2 levels. Based on values in controls, a positive breath test was defined as an increase in breath H2 of greater than or equal to 12 ppm after glucose or greater than or equal to 14 ppm after rice flour. A 2-h glucose breath H2 test had a sensitivity of 93% and a specificity of 78% in the diagnosis of overgrowth. The predictive value of a positive test was 86% and that of a negative test was 88%. The combination of both a high fasting breath H2 level and a diagnostic rise of breath H2 after glucose was present in 41% of patients with overgrowth and in none of the patients without overgrowth. Extending the test to 4 h did not increase sensitivity, but decreased specificity. Rice flour was a less satisfactory substrate in predicting the presence of bacterial overgrowth. In conclusion, a high fasting breath H2 level after dietary preparation suggests bacterial overgrowth but lacks sensitivity. The finding of a rise in breath H2 of at least 12 ppm within 2 h of a 50-g glucose challenge is a simple screen for bacterial overgrowth. The combined criteria of a high fasting breath H2 level and a significant rise after glucose are specific for bacterial overgrowth.

Two-dimensional electrophoresis of plasma lipoproteins: recognition of new apo A-I-containing subpopulations

Two-dimensional electrophoresis has been used to resolve 12 distinct apo A-I-containing high-density lipoprotein (HDL) subpopulations in human plasma. The subpopulations were quantitated by 125I-labeled, monospecific antibody and phosphor-imaging. Modification and standardization of the agarose electrophoresis (first dimension) enabled us to recognize new HDL subpopulations. Lipoprotein mobilities in agarose were expressed relative to the mobility of the sample's endogenous albumin. We demonstrated the presence of lipoproteins with mobilities faster than and similar to albumin, as well as subpopulations with mobilities slower than albumin. We refer to these as pre alpha, alpha and pre beta, respectively. Lipoprotein molecular sizes were determined with a non-denaturing polyacrylamide gradient gel electrophoresis (PAGE) (2% to 36%) in the second dimension. Internal standard of 125I-labeled proteins of known molecular size was run simultaneously in each gel permitting accurate size determination. We have demonstrated that ultracentrifugally-isolated lipoproteins are different from the native apo A-I-containing subpopulations. The major difference observed was the loss of pre beta 1 and pre beta 2 particles from the d < 1.21 g/ml fractions to the d > 1.21 g/ml fractions. Possible physiologic and pathologic implications of these findings are also discussed.

Zf9, a Kruppel-like transcription factor up-regulated in vivo during early hepatic fibrosis

Wound repair in the liver induces altered gene expression in stellate cells (resident mesenchymal cells) in a process known as "activation." A zinc finger transcription factor cDNA, zf9, was cloned from rat stellate cells activated in vivo. Zf9 expression and biosynthesis are increased markedly in activated cells in vivo compared with cells from normal rats ("quiescent" cells). The factor is localized to the nucleus and the perinuclear zone in activated but not quiescent cells. Zf9 mRNA also is expressed widely in nonhepatic adult rat tissues and the fetal liver. The zf9 nucleotide sequence predicts a member of the Kruppel-like family with a unique N-terminal domain rich in serine-proline clusters and leucines. The human zf9 gene maps to chromosome 10P near the telomere. Zf9 binds specifically to a DNA oligonucleotide containing a GC box motif. The N-terminal domain of Zf9 (amino acids 1-201) is transactivating in the chimeric GAL4 hybrid system. In Drosophila schneider cells, full length Zf9 transactivates a reporter construct driven by the SV40 promoter/enhancer, which contains several GC boxes. A physiologic role for Zf9 is suggested by its transactivation of a collagen alpha1(I) promoter reporter. Transactivation of collagen alpha1(I) by Zf9 is context-dependent, occurring strongly in stellate cells, modestly in Hep G2 cells, and not at all in D. schneider cells. Our results suggest that Zf9 may be an important signal in hepatic stellate cell activation after liver injury.

Occupational asthma caused by latex in a surgical glove manufacturing plant

A 33-year-old latex glove inspector was diagnosed as having occupational asthma on the basis of peak flow and methacholine-responsiveness changes related to workplace exposure. She had latex sensitivity by skin prick testing. This finding led to a survey of her workplace. Of the 81 workers, 84% completed a questionnaire to assess work-related respiratory symptoms, 79% underwent skin prick testing to latex and six other workplace chemicals, and 62% performed workshift spirometry. Seven workers had spirometric changes consistent with asthma, of whom five had greater than or equal to 15% fall in FEV1 during the workshift. Six of these workers underwent methacholine-challenge testing, and three were found to have a significant improvement in responsiveness to methacholine away from work, suggestive of occupational asthma. Two of these workers had positive skin test responses to latex. Including the index case, 6% of workers who had pulmonary function testing had findings of latex-related occupational asthma. Skin test responses to latex occurred in 11% of workers tested. Our findings suggest that latex should be considered among the causes of occupational asthma.

Convergent evolution of similar function in two structurally divergent enzymes

An example of two related enzymes that catalyse similar reactions but possess different active sites is provided by comparing the structure of Escherichia coli thioredoxin reductase with glutathione reductase. Both are dimeric enzymes that catalyse the reduction of disulphides by pyridine nucleotides through an enzyme disulphide and a flavin. Human glutathione reductase contains four structural domains within each molecule: the flavin-adenine dinucleotide (FAD)- and nicotinamide-adenine dinucleotide phosphate (NADPH)-binding domains, the 'central' domain and the C-terminal domain that provides the dimer interface and part of the active site. Although both enzymes share the same catalytic mechanism and similar tertiary structures, their active sites do not resemble each other. We have determined the crystal structure of E. coli thioredoxin reductase at 2 A resolution, and show that thioredoxin reductase lacks the domain that provides the dimer interface in glutathione reductase, and forms a completely different dimeric structure. The catalytically active disulphides are located in different domains on opposite sides of the flavin ring system. This suggests that these enzymes diverged from an ancestral nucleotide-binding protein and acquired their disulphide reductase activities independently.

Twelve hundred open cholecystectomies before the laparoscopic era. A standard for comparison

Records of 1200 consecutive open cholecystectomies, performed by a teaching service of a large, urban hospital in the years immediately preceding the laparoscopic era, were reviewed for morbidity and mortality rates. The mortality rate in this series was 1.8%, chiefly in the older age groups. Only two ductal injuries were incurred. A review of published series from 1952 through 1990 revealed a mean mortality rate of 1.53%. These recent observations on the morbidity and mortality after open operation should provide a useful standard of comparison with ongoing similar studies of laparoscopic cholecystectomy.

A comparison of human dental plaque microcosm biofilms grown in an undefined medium and a chemically defined artificial saliva

The growth and pathogenic properties of dental plaque result from interactions between the microbiota and the oral environment and have been studied in laboratory experimental systems ranging from single or a few species (such as in chemostats) to dental plaque microcosms. Microcosm plaque is an in vitro version of natural plaque and has been explored as a microflora model because it is sited a more manipulable and controllable environment. It is obtained as microcosm biofilms in an 'artificial mouth' plaque culture system by culturing the bacteria in natural plaque-enriched saliva (i.e. salivary bacteria where a whole-saliva donor has abstained from oral hygiene for 24 h to increase the plaque bacteria in the saliva). The aim here was to examine whether a new, chemically defined analogue of saliva (defined medium mucin, DMM) could substitute for a previously used, chemically undefined medium (basal medium mucin, BMM) as an analogue of saliva for large-scale biofilm culturing. DMM contains various ions, mucin, amino acids, vitamins and growth factors at concentrations generally similar to those in saliva, whereas BMM contains yeast extract, peptones and mucin. To model the nutrient functions of salivary proteins, amino acids equivalent to 5 g/l casein were also included in DMM. In earlier studies, BMM-grown plaques were similar to natural plaques in structure, composition, growth rate and pH response to substrates. Their doubling-time patterns over a 20-day period were similar, except that the DMM-grown plaques showed biphasic growth patterns that were more pronounced than with BMM. Variation in enzyme profiles between BMM- and DMM-grown plaque, measured using the API-ZYM technique, provided evidence of nutritional effects on plaque composition. It was concluded that realistic growth rates and patterns are generated in microcosm plaque biofilms by supplying both DMM and BMM. However, the use of DMM enables specific modifications to be made to nutrient conditions during large-scale culture in our 'artificial mouth' biofilm system.

STAT activation by epidermal growth factor (EGF) and amphiregulin. Requirement for the EGF receptor kinase but not for tyrosine phosphorylation sites or JAK1

The epidermal growth factor (EGF) receptor activates several signaling cascades in response to the ligands EGF and amphiregulin (AR). One of these signaling events involves the tyrosine phosphorylation of STATs (signal transducers and activators of transcription), a process believed to require the activation of a tyrosine kinase of the JAK family. In this report we demonstrate that EGF- and AR-induced STAT activation requires the intrinsic kinase activity of the receptor but not the presence of Jak1. We show that both wild type (WT) and truncated EGF receptors lacking all autophosphorylation sites activate STAT 1, 3, and 5 in response to either EGF or AR. Furthermore, relative to cells expressing WT receptor, ligand-induced tyrosine phosphorylation of the STATs was enhanced in cells expressing only the truncated receptor. These results provide the first evidence that (i) EGF receptor-mediated STAT activation occurs in a Jak1-independent manner, (ii) the intrinsic tyrosine kinase activity of the receptor is essential for STAT activation, and (iii) tyrosine phosphorylation sites within the EGF receptor are not required for STAT activation.

Epidemiology of venous thromboembolism in Asian patients undergoing major orthopedic surgery without thromboprophylaxis. The SMART study

BACKGROUND

In Asian patients undergoing surgery, the incidence of venous thromboembolism (VTE) is thought to be low relative to Western patients, and the routine use of thromboprophylaxis is controversial.

OBJECTIVES

The aim of this work was to study the epidemiology of VTE in Asian patients undergoing orthopedic surgery without thromboprophylaxis.

PATIENTS AND METHODS

We performed a prospective observational study of a cohort of consecutive Asian patients hospitalized for total hip or knee replacement or hip fracture surgery without thromboprophylaxis. The primary study outcome was the incidence of the composite of symptomatic VTE or sudden death at hospital discharge. This outcome was also assessed at 1 month's follow-up.

RESULTS

Between April 2001 and July 2002, 2420 patients were enrolled. Median age was 68 years and the median duration of hospital stay was 13 days. The rate of symptomatic VTE or sudden death as notified by investigators was 2.3%[55 patients, 99% confidence interval (CI) 1.6, 3.2] and 1.2% (28 patients, 99% CI 0.7, 1.8) after adjudication by an independent committee. Chronic heart failure, varicose veins and a history of VTE were independent risk factors (P < 0.05) for the occurrence of the primary endpoint. At 1 month's follow-up, the incidence of adjudicated symptomatic VTE or sudden death was 1.5% (35/2264 patients).

CONCLUSION

In Asian patients, the incidence of symptomatic VTE after major orthopedic surgery is not low, consistent with the rates observed in Western countries. The use of thromboprophylaxis should be considered in Asian patients undergoing such high-risk surgical procedures.

Carboxy terminus of human herpesvirus 8 latency-associated nuclear antigen mediates dimerization, transcriptional repression, and targeting to nuclear bodies

Human herpesvirus 8 (HHV-8; also known as Kaposi's sarcoma-associated herpesvirus) is the causative agent of Kaposi's sarcoma and certain B-cell lymphomas. In most infected cells, HHV-8 establishes a latent infection characterized by the expression of latency-associated nuclear antigen (LANA) encoded by open reading frame 73. Although unrelated by sequence, there are functional similarities between LANA and the EBNA-1 protein of Epstein-Barr virus. Both accumulate as subnuclear speckles and are required for maintenance of the viral episome. EBNA-1 also regulates viral gene expression and is required for cell immortalization, suggesting that LANA performs similar functions in the context of HHV-8 infection. Here we show that LANA forms stable dimers, or possibly higher-order multimers, and that this is mediated by a conserved region in the C terminus. By expressing a series of truncations, we show that both the N- and C-terminal regions localize to the nucleus, although only the C terminus accumulates as nuclear speckles characteristic of the intact protein. Lastly, we show that LANA can function as a potent transcriptional repressor when tethered to constitutively active promoters via a heterologous DNA-binding domain. Domains in both the N and C termini mediate repression. This suggests that one function of LANA is to suppress the expression of the viral lytic genes or cellular genes involved in the antiviral response.

Parathyroidectomy promotes wound healing and prolongs survival in patients with calciphylaxis from secondary hyperparathyroidism

BACKGROUND

Calciphylaxis is a rare but life-threatening condition occasionally affecting patients with secondary hyperparathyroidism. Parathyroidectomy has been advocated as the only potentially curative intervention.

METHODS

Between January 1989 and May 2000, 13 patients with pathologic/clinical criteria of calciphylaxis were treated at our institution. Of these 13 patients, 7 were managed with medical therapy alone, and 6 were referred for parathyroidectomy. The medical records were reviewed, and patients/relatives were interviewed.

RESULTS

All patients had cutaneous wounds requiring local debridement predominantly located on the lower extremities or abdominal wall. Six patients underwent subtotal (3.5 gland) parathyroidectomy without morbidity. All 6 had significant reductions in parathyroid hormone levels after surgery (mean decrease, 94% +/- 0%), and all reported resolution of pain and healing of cutaneous wounds. Of the remaining 7 patients who had medical management alone, 5 eventually died of complications related to calciphylaxis. In comparing the 2 groups, patients who underwent parathyroidectomy had a significantly longer median survival than those who did not have surgery (36 vs 3 months, P =.021).

CONCLUSIONS

Calciphylaxis frequently causes gangrene, sepsis, and eventual death. Parathyroidectomy can be performed with minimal morbidity and is associated with resolution of pain, wound healing, and a significantly longer median survival. Therefore, patients with secondary hyperparathyroidism and signs/symptoms of calciphylaxis should be referred promptly for consideration of parathyroidectomy.

BC200 RNA in normal human neocortex, non-Alzheimer dementia (NAD), and senile dementia of the Alzheimer type (AD)

BC200 RNA is a polyadenylated 200 nucleotide primate brain-specific transcript with 80% homology to the left monomer of the human Alu family of repetitive elements. Whether this transcription product contributes anything to normal brain gene function or is a residue of post transcriptional processing of brain heterogeneous nuclear RNA (hnRNA) is uncertain. However, the high abundance, tissue-specific expression and nucleotide sequence characteristics of BC200 RNA suggests that the generation of this small RNA is associated with some brain cell function. Sustained levels of the BC200 RNA transcript may be indicative of a genetically competent and normally functioning cerebral neocortex. In this investigation, we have measured the abundance of the BC200 RNA transcript in total RNA isolated from 18 temporal neocortices (Brodman area 22) of brains with no pathology and those affected with neurodegenerative disease. Neocortices were examined from 3 neurologically normal brains, 5 non-Alzheimer demented [NAD; 3 Huntington's chorea (HC), 1 amyotrophic lateral sclerosis (ALS) and 1 dementia unclassified] and 10 Alzheimer disease (AD) affected brains. Our results indicate a strong BC200 presence in both the normal brains and NAD affected neocortices, but a 70 per cent reduction in BC200 signal strength in AD afflicted brains. These results may be related to the observation that Alzheimer brains exhibit marked deficits in the abundance of neuron-specific DNA transcripts; these deficits are consistent with the idea that AD is characterized by an impairment in the primary generation of brain gene transcription products.

Coordinated induction of VEGF receptors in mesenchymal cell types during rat hepatic wound healing

Homology PCR has been used to identify receptor tyrosine kinases (RTKs) expressed during activation of rat hepatic stellate cells, the key fibrogenic mesenchymal element in the liver. Partial cDNAs encoding several RTKs were cloned from stellate cells activated in vivo, including those of Flt-1, Flk-1, c-met, PDGFR, and Tyro10/DDR2. RNAse protection from cells activated in vivo demonstrated biphasic induction of flt-1 and flk-1 mRNAs, receptors for vascular endothelial growth factor (VEGF). Culture-activation of stellate cells was associated with increased [125I]VEGF binding and Flt-1 and Flk-1 receptor protein. Induction of VEGF binding sites correlated with an 2.5-fold increase in DNA synthesis in response to VEGF, but only if cells were activated by growth on collagen 1, whereas cells maintained in a quiescent state on a basement membrane-like substratum (EHS matrix) were nonproliferative. In both stellate and endothelial cells VEGF-induced mitogenesis was augmented by co-incubation with basic fibroblast growth factor (bFGF), a cytokine with known synergy with VEGF. These findings suggest that the cellular targets of VEGF in liver may not be confined to sinusoidal endothelial cells, and that VEGF responses reflect combined effects on both hepatic stellate cells and sinusoidal endothelium.

Mechanism of oxime reactivation of acetylcholinesterase analyzed by chirality and mutagenesis

Organophosphates inactivate acetylcholinesterase by reacting covalently with the active center serine. We have examined the reactivation of a series of resolved enantiomeric methylphosphonate conjugates of acetylcholinesterase by two oximes, 2-pralidoxime (2-PAM) and 1-(2'-hydroxyiminomethyl-1'-pyridinium)-3-(4'-carbamoyl-1-pyridinium) (HI-6). The S(p) enantiomers of the methylphosphonate esters are far more reactive in forming the conjugate with the enzyme, and we find that rates of oxime reactivation also show an S(p) versus R(p) preference, suggesting that a similar orientation of the phosphonyl oxygen toward the oxyanion hole is required for both efficient inactivation and reactivation. A comparison of reactivation rates of (S(p))- and (R(p))-cycloheptyl, 3,3-dimethylbutyl, and isopropyl methylphosphonyl conjugates shows that steric hindrance by the alkoxy group precludes facile access of the oxime to the tetrahedral phosphorus. To facilitate access, we substituted smaller side chains in the acyl pocket of the active center and find that the Phe295Leu substitution enhances the HI-6-elicited reactivation rates of the S(p) conjugates up to 14-fold, whereas the Phe297Ile substitution preferentially enhances 2-PAM reactivation by as much as 125-fold. The fractional enhancement of reactivation achieved by these mutations of the acyl pocket is greatest for the conjugated phosphonates of the largest steric bulk. By contrast, little enhancement of the reactivation rate is seen with these mutants for the R(p) conjugates, where limitations on oxime access to the phosphonate and suboptimal positioning of the phosphonyl oxygen in the oxyanion hole may both slow reactivation. These findings suggest that impaction of the conjugated organophosphate within the constraints of the active center gorge is a major factor in influencing oxime access and reactivation rates. Moreover, the individual oximes differ in attacking orientation, leading to the presumed pentavalent transition state. Hence, their efficacies as reactivating agents depend on the steric bulk of the intervening groups surrounding the tetrahedral phosphorus.

Secretion of cholesterol-rich lipoproteins by perfused livers of hypercholesterolemic rats

Rats maintained on a high-fat diet supplemented with propylthiouracil develop a hypercholesterolemia, an increased serum level of apolipoprotein (apo) E, abnormal very low density lipoproteins (VLDL) and low density lipoproteins (LDL), and a fatty liver which contains cholesterol ester as its major lipid. The fatty liver secretes apoE into a recirculating perfusate at a significantly higher rate and produces cholesterol ester-rich, apoC-deficient VLDL with slower electrophoretic mobility than the triacylglycerol-rich VLDL produced by perfused normal livers. LDL, secreted in significant quantities by the perfused fatty liver, but not by the normal liver, is also cholesterol rich and contains apoE as well as apoB. The incorporation of [(3)H]leucine into apoVLDL and apoLDL secreted by the livers of the hypercholesterolemic animals and the apoVLDL secreted by the normal liver corresponds to the pattern visualized when the apoproteins are separated by polyacrylamide gel electrophoresis. Similar patterns are noted when non-recirculating perfusates are studied. These results indicate that the cholesterol ester-rich, apoC-deficient VLDL and the apoE-containing LDL found in the serum of hypercholesterolemic rats are not solely catabolic remnants of VLDL and chylomicrons but are secreted by the liver. Separation of the perfusate lipoproteins by agarose gel filtration revealed that most of the apoE secreted by the livers of hypercholesterolemic rats is found in the VLDL and LDL, whereas apoE secreted by the normal livers is distributed equally between VLDL, high density lipoproteins, and a low molecular weight fraction which corresponds to the virtually delipidated apoprotein. Thus the distribution of apoE among the lipoprotein fractions may be related to the total amount of cholesterol being transported in the circulation.

Well-defined sulfobetaine-based statistical copolymers as potential antibioadherent coatings

The potential use of novel poly(sulfobetaine) copolymers as antibioadherent coatings was investigated using Pseudomonas aeruginosa as a model microorganism and human macrophages and 3T3 mouse embryonic fibroblasts. Two well-defined statistical copolymers with narrow molecular weight distributions were prepared by group transfer copolymerization of n-butyl methacrylate (nBuMA) with either 10 or 30 mol % 2-(dimethylamino)ethyl methacrylate (DMAEMA). Sulfobetainized nBuMA-DMAEMA copolymers (poly[sulfobetaine-stat-nBuMA]) were obtained by treating these precursor polymers with 1,3-propanesultone under mild conditions. Both proton NMR spectroscopy and elemental microanalyses indicated that essentially all the DMAEMA residues were derivatized in both copolymers. Poly(methyl methacrylate) (PMMA) discs were coated with the sulfobetainized nBuMA-DMAEMA copolymers and the bioadherent properties of these coated materials were compared with those of PMMA. Statistically significantly fewer (p<.05) bacteria, macrophages, and fibroblasts adhered to the poly(sulfobetaine-stat-nBuMA)-coated PMMA than to the uncoated PMMA. The poly(sulfobetaine-stat-nBuMA) copolymer containing the higher proportion (30 mol %) sulfobetainized DMAEMA residues proved to be the more effective antibioadherent coating. The antibioadherent properties of these coating materials may allow the cost-effective production of dirt-resistant, easy to clean work surfaces, bioinert coatings for medical devices, and antifouling coatings for marine, agricultural, and industrial applications.

Late-onset X-linked sideroblastic anemia. Missense mutations in the erythroid delta-aminolevulinate synthase (ALAS2) gene in two pyridoxine-responsive patients initially diagnosed with acquired refractory anemia and ringed sideroblasts

X-linked sideroblastic anemia (XLSA) is caused by mutations of the erythroid-specific delta-aminolevulinate synthase gene (ALAS2) resulting in deficient heme synthesis. The characteristic hypochromic, microcytic anemia typically becomes manifest in the first three decades of life. Hematologic response to pyridoxine is variable and rarely complete. We report two unrelated cases of highly pyridoxine-responsive XLSA in geriatric patients previously diagnosed with refractory anemia and ringed sideroblasts. A previously unaffected 77-yr-old male and an 81-yr-old female were each found to have developed severe hypochromic, microcytic anemia with ringed sideroblasts in the bone marrow, which responded dramatically to pyridoxine with normalization of hemoglobin values. Sequence analysis identified an A to C transversion in exon 7 (K299Q) of the ALAS2 gene in the male proband and his daughter. In the female proband a G to A transition was identified in exon 5 (A172T). This mutation resulted in decreased in vitro stability of bone marrow delta-aminolevulinate synthase activity. Each patient's recombinant mutant ALAS2 enzyme had marked thermolability. Addition of pyridoxal 5'-phosphate in vitro stabilized the mutant enzymes, consistent with the observed dramatic response to pyridoxine in vivo. This late-onset form of XLSA can be distinguished from refractory anemia and ringed sideroblasts by microcytosis, pyridoxine-responsiveness, and ALAS2 mutations. These findings emphasize the need to consider all elderly patients with microcytic sideroblastic anemia as candidates for XLSA, especially if pyridoxine responsiveness is demonstrated.

A common requirement for the catalytic activity and both SH2 domains of SHP-2 in mitogen-activated protein (MAP) kinase activation by the ErbB family of receptors. A specific role for SHP-2 in map, but not c-Jun amino-terminal kinase activation

The ErbB family of receptors, which include the epidermal growth factor receptor (EGFR), ErbB2, ErbB3, and ErbB4 mediate the actions of a family of bioactive polypeptides. EGF signals through EGFR, whereas heregulin (HRG) signaling is initiated through binding to either ErbB3 or ErbB4. In this report we studied the role of protein-tyrosine phosphatase SHP-2 in ErbB-mediated activation of mitogen-activated protein kinase (MAPK) by overexpressing SHP-2 mutants in COS-7 cells. We demonstrate that enzymatic activity and both NH2- and COOH-terminal SH2 domains of SHP-2 are required for EGF-induced MAPK activation, but not for c-Jun amino-terminal kinase stimulation or MAPK activation which occurred in response to myristoylated son of sevenless, activated Ras, or phorbol ester. Dominant-negative forms of SHP-2 had no effect on EGF-stimulated interaction of GRB2 with EGFR or SHC, nor did they influence phosphorylation of SHC and SHC/EGFR association. The same mutant SHP-2 structures that inhibited EGF-mediated stimulation of MAPK also blocked HRG alpha/beta-induced MAPK activation. EGF or HRG beta caused SHP-2 SH2 domains to engage multiple phosphotyrosine proteins, and mutation of either domain disrupted these associations. These results demonstrate that SHP-2 performs a common and essential function(s) in ligand-stimulated MAPK activation by the ErbB family of receptors.