Measurements of ultracold-neutron lifetimes in solid deuterium

We present the first measurements of the survival time of ultracold neutrons (UCNs) in solid deuterium (SD2). This critical parameter provides a fundamental limitation to the effectiveness of superthermal UCN sources that utilize solid ortho-deuterium as the source material. These measurements are performed utilizing a SD2 source coupled to a spallation source of neutrons, providing a demonstration of UCN production in this geometry and permitting systematic studies of the influence of thermal up-scatter and contamination with para-deuterium on the UCN survival time.

Corticotropin-releasing factor is preferentially colocalized with excitatory rather than inhibitory amino acids in axon terminals in the peri-locus coeruleus region

Corticotropin-releasing factor(CRF)-immunoreactive terminals form synaptic specializations with locus coeruleus (LC) dendrites in rat brain. Within these terminals, CRF-immunoreactive dense core vesicles are colocalized with non-labeled dense core vesicles and clear vesicles, implicating other neuromodulators in the actions of CRF on LC neurons. Excitatory (glutamate) and inhibitory (GABA) amino acid afferents to the LC, have been identified which regulate noradrenergic responses to sensory stimuli. This study was designed to determine whether these amino acid neurotransmitters are colocalized with CRF in terminals within the LC/peri-LC region in the rat. Sections through the LC region that were dually labeled using immunohistochemical techniques to visualize either CRF and glutamate or CRF and GABA were examined using electron microscopy. Numerous terminals that contained immunolabeling for both CRF and glutamate (e.g. 30% of 106 CRF-immunoreactive terminals and 13% of 232 glutamate-immunolabeled terminals) were observed in the peri-LC. Additionally, single labeled CRF and glutamate terminals were often apposed to one another or found to converge on common dendritic targets. In contrast, relatively few terminals exhibited immunolabeling for both GABA and CRF (5% of 317 CRF-immunoreactive terminals). However, evidence for a postsynaptic effect of CRF on GABA-containing profiles included synapses between CRF axon terminals and GABA-labeled dendrites (10% of 317 CRF-labeled terminals), as well as appositions between CRF- and GABA-labeled terminals. These results indicate that CRF is preferentially colocalized with glutamate in the rostrolateral LC region and may impact on glutamate neurotransmission in the LC via presynaptic or postsynaptic actions. They argue against colocalization of CRF with GABA, although CRF may modulate GABA release via postsynaptic effects in the peri-LC region.

The influence of calcium on granular sludge in a full-scale UASB treating paper mill wastewater

Calcium precipitation can have a number of effects on the performance of high-rate anaerobic performance including cementing of the sludge bed, limiting diffusion, and diluting the active biomass. The aim of this study was to observe the influence of precipitation in a stable full-scale system fed with high-calcium paper factory wastewater. Granules were examined from an upflow anaerobic sludge blanket reactor (volume 1,805 m3) at a recycled paper mill with a loading rate of 5.7-6.6 kgCOD.m(-3).d(-1) and influent calcium concentration of 400-700 gCa m(-3). The granules were relatively small (1 mm), with a 200-400 microm core of calcium precipitate as observed with energy dispersive X-ray spectroscopy. Compared to other granules, Methanomicrobiales not Methanobacteriales were the dominant hydrogen or formate utilisers, and putative acidogens were filamentous. The strength of the paper mill fed granules was very high when compared to granules from other full-scale reactors, and a partial linear correlation between granule strength and calcium concentration was identified.

Evidence for coexistence of enkephalin and glutamate in axon terminals and cellular sites for functional interactions of their receptors in the rat locus coeruleus

The authors previously showed that a subset of axon terminals in the locus coeruleus (LC) contains methionine5-enkephalin (ENK) and gamma-aminobutyric acid (GABA) immunoreactivities. However, numerous ENK-labeled terminals lacked GABA and exhibited synaptic specializations that were characteristic of excitatory-type transmitters. To determine whether ENK coexists with glutamate in the LC, preembedding immunoperoxidase detection of ENK or immunogold-silver was combined with postembedding identification of glutamate using a gold marker. Indeed, 28% of the ENK-labeled axon terminals examined (n = 250 axon terminals) also contained glutamate. To define further sites for functional interactions between opiate ligands and excitatory amino acid receptors, the ultrastructural localization of the mu-opioid receptor (MOR) was examined with respect to either the kainate receptor (KAR) or the R1 subunit of the N-methyl-D-aspartate (NR1)-type glutamate receptor in the LC. Gold-silver labeling for MOR and peroxidase labeling for either KAR or NR1 indicated that the MOR often was localized to the plasma membrane of dendrites that also exhibited immunolabeling for either glutamate receptor subtype. In contrast to the KAR, which was identified primarily in somata and dendrites, NR1 immunoreactivity also was found frequently in axon terminals as well as in glial processes. Glial processes containing NR1 occasionally exhibited immunolabeling for MOR and sometimes were directly apposed to MOR-containing dendrites in the LC. Furthermore, NR1-labeled receptors in axon terminals sometimes were presynaptic to MOR-labeled dendrites. The authors concluded that ENK and glutamate may be cotransmitters in LC afferents. Moreover, ligands at the KAR may modulate directly MOR-containing neurons in the LC, whereas actions at NR1 receptors may affect opioid-sensitive neurons through multiple cellular mechanisms, i.e., through presynaptic, postsynaptic, or glial actions.

Localization of mu-opioid receptors to locus coeruleus-projecting neurons in the rostral medulla: morphological substrates and synaptic organization

The increase in discharge activity of locus coeruleus (LC) neurons following precipitated opiate withdrawal has been reported to be caused, in part, by excitatory amino acid release most likely originating from the nucleus paragigantocellularis lateralis (PGCl) in the rostral ventral medulla. Activation of glutamate-containing neurons in the PGCl may depend on changes in the occupancy of opioid receptive sites located on LC-projecting neurons which subsequently effect excitatory amino acid release in the LC during opiate withdrawal. To determine whether the mu-opioid receptor (MOR) is localized to plasmalemmal sites of LC-projecting neurons in the PGCl, we combined retrograde transport of the protein-gold tracer, wheat germ agglutinin-conjugated to inactive horseradish peroxidase (WGA-AU-apoHRP), from the LC with immunocytochemical detection of MOR in the same section of tissue throughout the rostral medulla. Light microscopic analysis indicated that neurons containing either the retrograde tracer or immunoperoxidase labeling for the MOR were numerous throughout the ventral medulla and that individual PGCl neurons contained both WGA-Au-apoHRP as well as MOR. By electron microscopy, WGA-Au-apoHRP was commonly identified in lysosomes within somata and large proximal dendrites. The somata contained either spherical or invaginated nuclei and were often surrounded by numerous myelinated axons. Gold deposits could also be identified in the cytoplasm of smaller dendritic processes in the PGCl, although these were not necessarily associated with lysosomes. The smaller dendritic processes were often the target of afferent input by axon terminals containing heterogeneous types of synaptic vesicles. Of 150 cellular profiles exhibiting WGA-Au-apoHRP retrograde labeling, 31% contained immunoperoxidase labeling for MOR. These results indicate that the MOR is distributed along plasmalemmal sites of morphologically diverse neurons in the PGCl which project to the LC.

Distinction among eight opiate drugs in urine by gas chromatography-mass spectrometry

Opiates are commonly abused substances, and forensic urine drug-testing for them requires gas chromatographic-mass spectrometric (GC-MS) confirmation. There are also medical reasons to test urine for opiates, and confirmation procedures other than GC-MS are often used for medical drug-testing. A thin-layer chromatographic (TLC) method distinguishes morphine, acetylmorphine, hydromorphone, oxymorphone, codeine, dihydrocodeine, hydrocodone, and oxycodone in clinical specimens. In certain clinical circumstances, GC-MS confirmation is requested for opiates identified by TLC, but, to our knowledge, no previous report examines all of the above opiates in a single GC-MS procedure. We find that they can be distinguished by GC-MS analyses of trimethylsilyl (TMS) ether derivatives, and identities of 6-keto opiates can be further confirmed by GC-MS analysis of methoxime (MO)-TMS derivatives. Inclusion of deuterium-labeled internal standards permits identification of the opiates in urine at concentrations below the TLC cutoff level of 600 ng/ml, and the GC-MS assay is linear over a concentration range that spans that level. This GC-MS procedure has proved useful as a third-stage identification step in a medical drug-testing sequence involving prior immunoassay and TLC.

Magnetic resonance imaging of soft tissue expanders used in the management of musculoskeletal sarcomas

A soft tissue expander is surgically inserted into the body to displace radiosensitive organs from the treatment field in a small number of patients receiving radiotherapy for musculoskeletal sarcoma. MRI is routinely used to monitor the response to the radiotherapy, local recurrence and complications of treatment. This study retrospectively reviews MRI of soft tissue expanders in seven patients with musculoskeletal sarcomas; six arising in the pelvis and one in the retroperitoneum. In the absence of an appropriate clinical history, the soft tissue expander may be mistaken for a pathological fluid collection such as abscess, post-operative seroma or even recurrent tumour. MRI of the soft tissue expanders and potential errors in image interpretation are illustrated.

Beyond hospital walls: educating pediatric nurses for the next millennium

As pediatric units in acute care hospitals close, as lengths of stay shorten, and as increasing numbers of procedures are completed on an outpatient basis, faculty must find different learning experiences for their prelicensure students. Some programs have discontinued pediatric rotations, others are seeking clinical experiences in community settings. These community experiences hopefully produce a more well-rounded, globally thinking nurse to practice in the 21st century, yet they also raise a number of concerns.

Design of a ruthenium-cytochrome c derivative to measure electron transfer to the radical cation and oxyferryl heme in cytochrome c peroxidase

A new ruthenium-labeled cytochrome c derivative was designed to measure the actual rate of electron transfer to the Trp-191 radical cation and the oxyferryl heme in cytochrome c peroxidase compound I {CMPI(FeIV = O,R.+)}. The H39C,C102T variant of yeast iso-1-cytochrome c was labeled at the single cysteine residue with a tris (bipyridyl)ruthenium(II) reagent to form Ru-39-Cc. This derivative has the same reactivity with CMPI as native yCc measured by stopped-flow spectroscopy, indicating that the ruthenium group does not interfere with the interaction between the two proteins. Laser excitation of the 1:1 Ru-39-Cc-CMPI complex in low ionic strength buffer (2 mM phosphate, pH 7) resulted in electron transfer from RuII* to heme c FeIII with a rate constant of 5 x 10(5) s-1, followed by electron transfer from heme c Fe II to the Trp-191 indolyl radical cation in CMPI(FeIV = O,R*+) with a rate constant of k(eta) = 2 x 10(6) s-1. A subsequent laser flash led to electron transfer from heme c to the oxyferryl heme in CMPII-(FeIV = O,R) with a rate constant of k(etb) = 5000 s-1. The location of the binding domain was determined using a series of surface charge mutants of CcP. The mutations D34N, E290N, and A193F each decreased the values of k(eta) and k(etb) by 2-4-fold, consistent with the use of the binding domain identified in the crystal structure of the yCc-CcP complex for reduction of both redox centers [Pelletier, H., & Kraut, J. (1992) Science 258, 1748-1755]. A mechanism is proposed for reduction of the oxyferryl heme in which internal electron transfer in CMPII(FeIV = O,R) leads to the regeneration of the radical cation in CMPII-(FeIII,R*+), which is then reduced by yCcII. Thus, both steps in the complete reduction of CMPI involve electron transfer from yCcII to the Trp-191 radical cation using the same binding site and pathway. Comparison of the rate constant k(eta) with theoretical predictions indicate that the electron transfer pathway identified in the crystalline yCc-CcP complex is very efficient. Stopped-flow studies indicate that native yCcII initially reduces the Trp-191 radical cation in CMPI with a second-order rate constant ka, which increases from 1.8 x 10(8) M-1 s-1 at 310 mM ionic strength to > 3 x 10(9) M-1 s-1 at ionic strengths below 100 mM. A second molecule of yCcII then reduces the oxyferryl heme in CMPII with a second-order rate constant kb which increases from 2.7 x 10(7) M-1 s-1 at 310 mM ionic strength to 2.5 x 10(8) M-1 s-1 at 160 mM ionic strength. As the ionic strength is decreased below 100 mM the rate constant for reduction of the oxyferryl heme becomes progressively slower as the reaction is limited by release of the product yCcIII from the yCcIII-CMPII complex. Both ruthenium photoreduction studies and stopped-flow studies demonstrate that the Trp-191 radical cation is the initial site of reduction in CMPI under all conditions of ionic strength.

Crosslinking of apolipoprotein E by products of lipid peroxidation

Apolipoprotein E (APOE) genotype and advancing aging are interacting ri sk factors in the expression of late onset and sporadic Alzheimer's Disease (AD). We tested the hypothesis that 2 products of lipid peroxidation, malondialdehyde (MDA) and 4 hydroxy-2-nonenal (HNE), covalently modify APOE and alter its metabolism. In vitro, both HNE and MDA crosslinked purified APOE3 and APOE4. HNE was a more potent crosslinker than MDA, and purified APO3 was more susceptible to crosslinking by HNE than was purified APOE4. In P19 neuroglial cultures, oxidative stress with lipid peroxidation led to increased intracellular accumulation of anti-HNE and anti-APOE immunoreactive proteins of approximately 50 kDa. Intercellular accumulation of the 50 kDa APOE-immunoreactive protein (APOE-50) was not prevented by cyclohexamide, suggesting formation by post-translational mechanisms. In CSF, a 50 kDa APOE-immunoreactive protein co-migrated with proteins most immunoreactive for HNE and MDA adducts, containing NaB3H4-reducible bonds. These proteins were in CSF from adult subjects (with or without dementia), and in AD patients homozygous for APOE3 or APOE4 alleles. These data suggest that HNE covalently crosslinks APOE in P19 neuroglial cultures to form a 50 kDa protein, and that similar modifications of APOE appear to occur in vivo.

The diagnosis of iron deficiency in patients with rheumatoid arthritis and anemia: an algorithm using simple laboratory measures

OBJECTIVE

Anemia of chronic disorders (ACD) and iron deficiency are common features in rheumatoid arthritis (RA), but may be difficult to distinguish without marrow sampling, which is invasive, time consuming, and expensive. We sought simple laboratory measures that identified patients with absent marrow iron stores (iron deficiency).

METHODS

45 anemic patients with RA underwent marrow sampling in addition to a complete blood count and serum ferritin and iron saturation measurements.

RESULTS

47% of patients had iron deficiency. These patients had significantly lower mean corpuscular volume (MCV), serum ferritin, and iron saturation. A 3 step algorithm was developed using these laboratory variables to identify iron deficiency. This algorithm correctly classified 94% patients with iron deficiency and 85% with ACD.

CONCLUSION

Our study demonstrates that iron deficiency may be reliably identified by measuring serum ferritin, MCV, and iron saturation in many patients with RA, thereby avoiding the trauma and expense of marrow sampling.

Identifying the physiological electron transfer site of cytochrome c peroxidase by structure-based engineering

A technique was developed to evaluate whether electron transfer (ET) complexes formed in solution by the cloned cytochrome c peroxidase [CcP(MI)] and cytochromes c from yeast (yCc) and horse (hCc) are structurally similar to those seen in the respective crystal structures. Site-directed mutagenesis was used to convert the sole Cys of the parent enzyme (Cys 128) to Ala, and a Cys residue was introduced at position 193 of CcP(MI), the point of closest contact between CcP(MI) and yCc in the crystal structure. Cys 193 was then modified with a bulky sulfhydryl reagent, 3-(N-maleimidylpropionyl)-biocytin (MPB), to prevent yCc from binding at the site seen in the crystal. The MPB modification has no effect on overall enzyme structure but causes 20-100-fold decreases in transient and steady-state ET reaction rates with yCc. The MPB modification causes only 2-3-fold decreases in ET reaction rates with hCc, however. This differential effect is predicted by modeling studies based on the crystal structures and indicates that solution phase ET complexes closely resemble the crystalline complexes. The low rate of catalysis of the MPB-enzyme was constant for yCc in buffers of 20-160 mM ionic strength. This indicates that the low affinity complex formed between CcP(MI) and yCc at low ionic strength is not reactive in ET.

Apolipoprotein E associates with beta amyloid peptide of Alzheimer's disease to form novel monofibrils. Isoform apoE4 associates more efficiently than apoE3

Late-onset and sporadic Alzheimer's disease are associated with the apolipoprotein E (apoE) type 4 allele expressing the protein isoform apoE4. Apolipoprotein E binds avidly to beta amyloid (A beta) peptide, a major component of senile plaque of Alzheimer's disease, in an isoform-specific manner. The apoE4 isoform binds to A beta peptide more rapidly than apoE3. We observed that soluble SDS-stable complexes of apoE3 or apoE4, formed by coincubation with A beta peptide, precipitated after several days of incubation at 37 degrees C with apoE4 complexes precipitating more rapidly than apoE3 complexes. A beta(1-28) and A beta(1-40) peptides were incubated in the presence or absence of apoE3, apoE4, or bovine serum albumin for 4 d at 37 degrees C (pH 7.3). Negative stain electron microscopy revealed that the A beta peptide alone self-assembled into twisted ribbons containing two or three strands but occasionally into multistranded sheets. The apoE/A beta coincubates yielded monofibrils 7 nm in diameter. ApoE4/A beta coincubates yielded a denser matrix of monofibrils than apoE3/A beta coincubates. Unlike purely monofibrillar apoE4/A beta coincubates, apoE3/A beta coincubates also contained double- and triple-stranded structures. Both apoE isoforms were shown by immunogold labeling to be uniformly distributed along the A beta peptide monofibrils. Monofibrils appeared earlier in apoE4/A beta than in apoE3/A beta in time-course experiments. Thus apoE3 and apoE4 each interact with beta amyloid peptide to form novel monofibrillar structures, apoE4 more avidly, a finding consistent with the biochemical and genetic association between apoE4 and Alzheimer's disease.

Human immunodeficiency virus infection of monocytes: relationship to Fc-gamma receptors and antibody-dependent viral enhancement

Antibodies that augment human immunodeficiency virus (HIV) infectivity of monocytes through Fc receptor (FcR) type III for IgG have been found in the blood of sero-positive patients and immunized chimpanzees. This study investigated the effect of acute and chronic HIV infection, as well as protein kinase C activators capable of up-regulating latent HIV, on the expression of these receptors. In addition, the frequency of this antibody-dependent enhancement (ADE) phenomenon was estimated using purified IgG from HIV-1 seropositive individuals at various clinical stages of infection. The existence of an FcR-dependent pathway for ADE of HIV-1 infection in peripheral blood monocytes and promonocytic U937 cells was confirmed in sera from a small subset of patients, and the phenomenon extended to FcR types I and II. The level of ADE activity was minimal, however, and no relationship between the presence or magnitude of the ADE phenomenon and clinical stage was uncovered. Finally, perturbations which activate a latent HIV infection were shown to concomitantly up-regulate FcR on infected and uninfected cells. This suggests a positive feedback loop linking up-regulation of latent infection, enhanced expression of low affinity HIV receptors such as FcR, and viral spread.

Final outcome of ursodeoxycholic acid treatment in 126 patients with radiolucent gallstones

One hundred and twenty-six patients with radiolucent gallstones in 'functioning' gallbladders were treated with 8-10 mg ursodeoxycholic acid (UDCA) kg/day and followed to a treatment conclusion. Complete or partial gallstone dissolution was achieved in 74 (59 per cent). However, only 22 achieved complete gallstone dissolution, as judged by two normal oral cholecystograms; ultrasonograms were performed in 16 of these patients, and all were normal. UDCA was stopped in 76 patients: because of cystic duct obstruction (n = 12), severe biliary pain (n = 13), non-response (n = 25) or partial stone dissolution with arrested progress (n = 26). Life-table analysis showed that complete gallstone dissolution rates at four years were 25-30 per cent (two normal oral cholecystograms) and 17-19 per cent (two normal oral cholecystograms plus one ultrasonogram). All patients with complete gallstone dissolution had shown partial stone dissolution at 6-12 months; of those with partial stone dissolution at six months, only 25 per cent went on to complete gallstone dissolution, and then always within two years. Efficacy correlated inversely with stone size but not with age, sex, obesity or on-treatment saturation indices. Acquired surface gallstone calcification developed in 13 patients (life-table analysis 22 +/- 7 per cent at four years); none of these patients achieved complete gallstone dissolution and only five achieved partial stone dissolution. Thus, despite relatively high partial gallstone dissolution rates, the ultimate efficacy of UDCA in achieving complete gallstone dissolution is low.

The effects of altered N-linked oligosaccharide structures on maturation and targeting of lysosomal enzymes in Dictyostelium discoideum

We have examined the relationship of N-linked oligosaccharide structures to the proper targeting and proteolytic processing of two lysosomal enzymes, alpha-mannosidase and beta-glucosidase, in the slime mold Dictyostelium discoideum. Two different mutant strains, HL241 and HL243, each synthesize the same nonglucosylated, truncated, lipid-linked oligosaccharide precursor, Man6GlcNAc2. [3H]Mannose-labeled N-linked oligosaccharides were studied following their release from immunoprecipitated alpha-mannosidase and beta-glucosidase by digestion with peptide:N-glycosidase F. The oligosaccharides from both mutants resembled each other, but they were smaller and contained fewer anionic groups than those from the wild-type. The oligosaccharides from the mutants strains were reduced in sulfate and Man-6-P content, and all Man-6-P was in the form of acid-stable phosphodiesters. Pulse-chase radiolabeling experiments using [35S] methionine indicated that the precursor forms of both enzymes were smaller than wild-type, and that this difference was due solely to differences in N-linked oligosaccharides. The precursor forms of the enzymes were not over-secreted, but appeared to be proteolytically processed into mature forms at approximately 50% the rate of wild-type. This is mainly due to their prolonged retention in the rough endoplasmic reticulum, but, ultimately, both enzymes were properly targeted to lysosomes. These studies indicate that a reduction in the amount of sulfation, phosphorylation or size of the N-linked oligosaccharides in these mutants is not critical for the proteolytic processing and targeting of the lysosomal enzymes, but that these changes may influence their rate of exit from the rough endoplasmic reticulum.