Foam property tests to evaluate the potential for longwall shield dust control

Tests were conducted to determine properties of four foam agents for their potential use in longwall mining dust control. Foam has been tried in underground mining in the past for dust control and is currently being reconsidered for use in underground coal longwall operations in order to help those operations comply with the Mine Safety and Health Administration's lower coal mine respirable dust standard of 1.5 mg/m³. Foams were generated using two different methods. One method used compressed air and water pressure to generate foam, while the other method used low-pressure air generated by a blower and water pressure using a foam generator developed by the U.S. National Institute for Occupational Safety and Health. Foam property tests, consisting of a foam expansion ratio test and a water drainage test, were conducted to classify foams. Compressed-air-generated foams tended to have low expansion ratios, from 10 to 19, with high water drainage. Blower-air-generated foams had higher foam expansion ratios, from 30 to 60, with lower water drainage. Foams produced within these ranges of expansion ratios are stable and potentially suitable for dust control. The test results eliminated two foam agents for future testing because they had poor expansion ratios. The remaining two foam agents seem to have properties adequate for dust control. These material property tests can be used to classify foams for their potential use in longwall mining dust control.

Chromosome 15q11-13 duplication syndrome brain reveals epigenetic alterations in gene expression not predicted from copy number

BACKGROUND

Chromosome 15q11-13 contains a cluster of imprinted genes essential for normal mammalian neurodevelopment. Deficiencies in paternal or maternal 15q11-13 alleles result in Prader-Willi or Angelman syndromes, respectively, and maternal duplications lead to a distinct condition that often includes autism. Overexpression of maternally expressed imprinted genes is predicted to cause 15q11-13-associated autism, but a link between gene dosage and expression has not been experimentally determined in brain.

METHODS

Postmortem brain tissue was obtained from a male with 15q11-13 hexasomy and a female with 15q11-13 tetrasomy. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was used to measure 10 15q11-13 transcripts in maternal 15q11-13 duplication, Prader-Willi syndrome, and control brain samples. Southern blot, bisulfite sequencing and fluorescence in situ hybridisation were used to investigate epigenetic mechanisms of gene regulation.

RESULTS

Gene expression and DNA methylation correlated with parental gene dosage in the male 15q11-13 duplication sample with severe cognitive impairment and seizures. Strikingly, the female with autism and milder Prader-Willi-like characteristics demonstrated unexpected deficiencies in the paternally expressed transcripts SNRPN, NDN, HBII85, and HBII52 and unchanged levels of maternally expressed UBE3A compared to controls. Paternal expression abnormalities in the female duplication sample were consistent with elevated DNA methylation of the 15q11-13 imprinting control region (ICR). Expression of non-imprinted 15q11-13 GABA receptor subunit genes was significantly reduced specifically in the female 15q11-13 duplication brain without detectable GABRB3 methylation differences.

CONCLUSION

Our findings suggest that genetic copy number changes combined with additional genetic or environmental influences on epigenetic mechanisms impact outcome and clinical heterogeneity of 15q11-13 duplication syndromes.

Molecular epidemiology of tuberculosis after declining incidence, New York City, 2001-2003

Tuberculosis incidence in New York City (NYC) declined between 1992 and 2000 from 51.1 to 16.6 cases per 100,000 population. In January 2001, universal real-time genotyping of TB cases was implemented in NYC. Isolates from culture-confirmed tuberculosis cases from 2001 to 2003 were genotyped using IS6110 and spoligotype to describe the extent and factors associated with genotype clustering after declining TB incidence. Of 2408 (91.8%) genotyped case isolates, 873 (36.2%) had a pattern indistinguishable from that of another study period case, forming 212 clusters; 248 (28.4%) of the clustered cases had strains believed to have been widely transmitted during the epidemic years in the early 1990s in NYC. An estimated 27.4% (873 minus 212) of the 2408 cases were due to recent infection that progressed to active disease during the study period. Younger age, birth in the United States, homelessness, substance abuse and presence of TB symptoms were independently associated with greater odds of clustering.

Clonal relationships in a shelter-associated outbreak of drug-resistant tuberculosis: 1983-1997

SETTING

An outbreak of tuberculosis caused by Mycobacterium tuberculosis resistant to isoniazid and streptomycin (HS-resistant) was documented in Boston's homeless population in 1984. Isolate relatedness was confirmed at the time by phage typing. In the late 1990s, cases of HS-resistant tuberculosis in the homeless were also documented, confirmed by RFLP typing using IS6110. None of the phage typed isolates from the 1980s were viable for performing RFLP analysis. We attempted to determine, using mixed-linker PCR (M-L PCR) finger-printing, whether or not these cases were all due to the same strain of M. tuberculosis.

DESIGN

Isolates from 10 HS-resistant patients-four non-viable isolates from the 1980s and six viable isolates from 1996-1997-were sent to the Centers for Disease Control and Prevention for M-L PCR fingerprinting. These results were combined with record reviews of older cases and an ongoing epidemiologic investigation.

RESULTS

Eight of 10 of the isolates were clonal, and the other two were strongly suspected matches. Epidemiologic investigation determined that transmission continued to occur after the initial outbreak in 1984-1985, and that a streptomycin-monoresistant variant of the strain was also circulating.

CONCLUSION

M-L PCR fingerprinting combined with epidemiology was able to document links between cases across 15 years.

[Spoligotypes of Mycobacterium tuberculosis in the Czech population (methods and pilot study)]

In the introduction the authors describe molecular genetic principles of spacer oligonucleotide typing of the M. tuberculosis complex and mention in detail the methodical procedure of implementation of this examination technique incl. computer analysis of results. In the pilot part of the study the authors describe examination of 71 strains of M. tuberculosis isolated from patients living in the capital of Prague and 37 strains from patients in the South Moravian region of the Czech Republic. In the group of Prague strains a total of 7 clusters was identified formed by 2-14 identical profiles of spoligotypes and 37 individually different profiles. In the South Moravian strains there were 6 clusters with 2-14 identical spoligotypes and 10 non-clustered profiles. In neither of the groups there were spoligotypes typical for the genetic family Beijing or Africa. The study is a preliminary molecular epidemiological analysis where DNA fingerprint RFLP profiles are compared with spoligotypes of strains of M. tuberculosis of patients from the capital of Prague and the South Moravian region of the Czech Republic.

Spacer oligonucleotide typing of bacteria of the Mycobacterium tuberculosis complex: recommendations for standardised nomenclature

Spacer oligonucleotide typing (spoligotyping) is widely used for differentiation of bacteria of the Mycobacterium tuberculosis complex. However, the absence of any standardised method for concise description of spoligotypes makes it difficult to compare the results from different laboratories. This paper describes unambiguous, interconvertible systems for the designation of spoligotype patterns, the adoption of which will be beneficial to mycobacterial research.

Molecular identification of streptomycin monoresistant Mycobacterium tuberculosis related to multidrug-resistant W strain

A distinct branch of the Mycobacterium tuberculosis W phylogenetic lineage (W14 group) has been identified and characterized by various genotyping techniques. The W14 group comprises three strain variants: W14, W23, and W26, which accounted for 26 clinical isolates from the New York City metropolitan area. The W14 group shares a unique IS6110 hybridizing banding motif as well as distinct polymorphic GC-rich repetitive sequence and variable number tandem repeat patterns. All W14 group members have high levels of streptomycin resistance. When the streptomycin resistance rpsL target gene was sequenced, all members of this strain family had an identical mutation in codon 43. Patients infected with the W14 group were primarily of non- Hispanic black origin (77%); all were US-born. Including HIV positivity, 84% of the patients had at least one known risk factor for tuberculosis.

Molecular characterization of Mycobacterium tuberculosis H37Rv/Ra variants: distinguishing the mycobacterial laboratory strain

The Mycobacterium tuberculosis strains H37Rv and H37Ra are the most commonly used controls for M. tuberculosis identification in the clinical and research laboratory setting. To reduce the likelihood of misidentification and possible cross-contamination with this laboratory neotype, it is important to be able to distinguish H37 from clinical isolates. To provide a reference for identifying H37, we used multiple molecular techniques to characterize H37 strains, including 18 of the most frequently used variants available through the American Type Culture Collection. Isolates were genotyped using gene probes to IS6110 and IS1085. In addition, we performed polymorphic GC-rich sequence typing (PGRS), spoligotyping, determination of variable number of tandem repeats (VNTR), and PCR amplification of the mtp40, msx4, and mpp8 polymorphic regions. Southern hybridization with IS6110 provided the most discrimination, differentiating the 18 H37 isolates into 10 discrete patterns made up of 9 H37Rv variants and 1 H37Ra variant. PGRS, IS1085, mpp8, and spoligotyping were not able to distinguish any H37 variants, while VNTR and msx4 discriminated two. Only IS6110 and spoligotyping could distinguish the H37 strain from clinical isolates. In summary, spoligotyping and IS6110 provide a rapid and accurate way to identify H37 contamination, though IS6110 can, in addition, classify many of the H37 variants that would otherwise require phenotypic segregation.

Use of spoligotype analysis to detect laboratory cross-contamination

Spoligotype analysis identified false-positive isolates of Mycobacterium tuberculosis caused by laboratory cross-contamination. Spoligotyping is faster, is less expensive than DNA fingerprinting, and can be used with a variety of media. Patients were reevaluated and had medications discontinued as a result of this investigation. Months of unnecessary patient follow-up and treatment were avoided.

Analysis of Mycobacterium tuberculosis transmission patterns in a homeless shelter outbreak

SETTING

From July 1997 through May 1998, ten tuberculosis (TB) cases were reported among men in a Syracuse New York homeless shelter for men.

OBJECTIVE AND DESIGN

Investigation to determine extent of, and prevent further, transmission of Mycobacterium tuberculosis.

RESULTS

Epidemiologic and laboratory evidence suggests that eight of the ten cases were related. Seven cases had isolates with matching six-band IS6110 DNA fingerprints; the isolate from another case had a closely related fingerprint pattern and this case was considered to be caused by a variant of the same strain. Isolates from eight cases had identical spoligotypes. The source case had extensive cavitary disease and stayed at the shelter nightly, while symptomatic, for almost 8 months before diagnosis. A contact investigation was conducted among 257 shelter users and staff, 70% of whom had a positive tuberculin skin test, including 21 with documented skin test conversions.

CONCLUSIONS

An outbreak of related TB cases in a high-risk setting was confirmed through the use of IS6110 DNA fingerprinting in conjunction with spoligotyping and epidemiologic evidence. Because of the high rate of infection in the homeless population, routine screening for TB and preventive therapy for eligible persons should be considered in shelters.

Treatment of lethal Ebola virus infection in mice with a single dose of an S-adenosyl-L-homocysteine hydrolase inhibitor

Ebola Zaire virus causes lethal hemorrhagic fever in humans, for which there is no effective treatment. A variety of adenosine analogues inhibit the replication of Ebola virus in vitro, probably by blocking the cellular enzyme, S-adenosyl-L-homocysteine hydrolase, thereby indirectly limiting methylation of the 5' cap of viral messenger RNA. We previously observed that adult, immunocompetent mice treated thrice daily for 9 days with 2.2-20 mg/kg of an adenosine analogue, carbocyclic 3-deazaadenosine, were protected against lethal Ebola virus challenge. We now report that a single inoculation of 80 mg/kg or less of the same substance, or of 1 mg/kg or less of another analogue, 3-deazaneplanocin A, provides equal or better protection, without causing acute toxicity. One dose of drug given on the first or second day after virus infection reduced peak viremia more than 1000-fold, compared with mock-treated controls, and resulted in survival of most or all animals. Therapy was less effective when administered on the day of challenge, or on the third day postinfection. Single or multiple doses of the same medications suppressed Ebola replication in severe combined immunodeficient mice, but even daily treatment for 15 consecutive days did not eliminate the infection.

The effectiveness of psychiatric treatment for HIV-infected patients

The study sought to determine the effectiveness of a model program of psychiatric care for human immunodeficiency virus (HIV)-infected patients. This was a cohort study of 126 HIV-positive outpatients referred for psychiatric evaluation and treatment (average follow up of 14 months) in a HIV-dedicated primary-care outpatient clinic in the inner city. A global outcome measure (encompassing symptom relief, functioning, and HIV-risk behaviors), and a measure of abstinence from alcohol and illicit substances were used. Fifty percent of patients improved, with 19% "nearly well" at follow-up. Abstinence was achieved 48% of the time. Good compliance with treatment and the absence of injection drug use were the primary predictors of good outcomes. Of the compliant patients, 94% improved, with 45.7% being nearly well. Psychiatric treatment of HIV-infected patients is effective when located in the HIV primary-care setting and administered by a multidisciplinary team under the direction of a psychiatrist, using evidence-based interventions.

In defence of patient/person human rights within national health care provision: implications for British nursing

One cannot fail to be aware of the 'human rights' that are vividly thrust into our living rooms by the world's media; but, what are human rights and are they of relevance to British nursing practice? In a democratic state such as the UK, human rights infringements or violations are not typified as occurring in a health care system outwardly appearing to safeguard the interests of the patient/person. This paper examines some of the issues and concludes that the notion of human rights remains inconspicuous and peripheral to the 'real world' of clinical nursing practice. It challenges British nurses to reflect on their practice and outwardly demonstrate that nursing's contemporary language of human rights does not remain simply rhetorical in nature.

Candidacidal activity of human salivary histatin recombinant variants produced by site-directed mutagenesis

Histatin 5 (Hst5) is a 24-amino acid (aa) member of the Hst family that is found in human salivary secretions and exhibits candidacidal activity. Hst5 contains a 13-aa region that alone is capable of killing fungal pathogens and is referred to as the functional domain. To investigate the role of specific aa located within the functional domain, the pRSET bacterial expression system was used to produce recombinant Hst5 (re-Hst5) and several re-variants that were generated by site-directed mutagenesis. The vector pRSETC expresses genes of interest as fusion proteins attached to the carboxy end of an N-terminal His6 tag that binds to nickel (Ni2+). The re-variants were generated using the polymerase chain reaction (PCR) and had Gly substituted for either the His, Glu or Lys/Arg within the functional domain. PCR products that encoded either the wild-type or variant forms of re-Hst5 were inserted into pRSETC and produced as fusion proteins which were affinity purified from cell lysates by Ni(2+)-Sepharose chromatography. Fusion proteins were digested with CNBr and re-Hsts were purified by reversed-phase high performance liquid chromatography (RP-HPLC). Re-Hsts were tested in bioassays to measure the ability to kill both Candida albicans (C. albicans) blastoconidia and spheroplasts which were generated by removal of the cell wall. In both assays, re-Hst5 displayed dose-dependent candidacidal activity that was nearly identical to that of native Hst5 purified from human salivary secretions. Re-Hst5 variants with either Glu or Lys/Arg substitutions demonstrated significantly lower candidacidal activity in both assays, while the variant with His mutated showed essentially no activity at physiological concentrations. These results indicate that acidic and basic aa within the functional domain contribute to candidacidal activity and that the His are essential for candidacidal activity. Additionally, since C. albicans spheroplasts were also susceptible to Hsts, the cell wall is not an essential component in the Hst mechanism of candidacidal action.

Structural organization of a Bacillus subtilis operon encoding menaquinone biosynthetic enzymes

Menaquinone (MK) is a non-protein component of the Bacillus subtilis (Bs) electron transport chain synthesized from chorismate through a series of MK-specific reactions. The genes encoding biosynthesis of the naphthoquinone ring of MK are clustered at 273 degrees on the Bs chromosome. A 3.9-kb region capable of rescuing men mutants blocked in the early stages of MK biosynthesis was sequenced and found to contain three major open reading frames (ORFs). The first ORF (menF) has a predicted size of 51.8 kDa and 34% amino-acid identity with the isochorismate synthases of Escherichia coli (EntC) and Aeromonas hydrophila (AmoA), ORF2 (menD) a predicted size of 60.2 kDa and 21% identity with MenD of E. coli. ORF3 has a predicted size of 21.4 kDa and 29% identity to triacylglycerol lipase of Psychrobacter immobilis. No sequence corresponding to menC was identified. Plasmid integrational studies of the men gene cluster had suggested the presence of promoters secondary to the previously identified p1 men promoter. Sequence analysis revealed a putative promoter region upstream from ORF3.

Functional comparison of native and recombinant human salivary histatin 1

Histatin 1 is a histidine-rich phosphoprotein present in human parotid saliva that possesses candidacidal activity and functions in mineralization by adsorbing to hydroxyapatite. The objective of the present study was to develop a system for recombinant production of histatin 1 and to examine the role of phosphorylation in the functional activities of this molecule. Native histatin 1 (containing a phosphoserine at residue 2) was purified from parotid saliva, whereas a bacterial expression system was used to produce a recombinant form of histatin 1 (re-Hst1) that lacked phosphorylated serine. Histatin 1 cDNA was inserted into the vector pGEX-3X, which expresses foreign genes as soluble fusion proteins attached to the carboxyl-terminus of glutathione S-transferase (GST). The GST/re-Hst1 fusion protein was isolated from cell lysates by affinity chromatography on glutathione (GSH)-Sepharose and digested with cyanogen bromide to separate re-Hst1 from the GST fusion partner. The digest was subjected to reversed-phase high-performance liquid chromatography on a C18 column, and re-Hst1 was eluted as a well-defined peak. The yield of re-Hst1 was 4 mg/L of bacterial culture. Amino-terminal sequencing and amino acid analysis confirmed the final product as re-Hst1. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that native histatin 1 and re-Hst1 had the same apparent molecular weights, while cationic PAGE showed that re-Hst1 was more basic. Phosphate analysis indicated 1 mol phosphate/mol of native histatin 1, while re-Hst1 lacked any detectable phosphate. Re-Hst1 demonstrated candidacidal activity comparable to that of native histatin 1, but displayed substantially lower binding to hydroxyapatite. These results show that phosphorylation of histatin 1 at residue 2 contributes significantly to its ability to bind to hydroxyapatite.

Hydroxylated aromatic inhibitors of HIV-1 integrase

Efficient replication of HIV-1 requires integration of a DNA copy of the viral genome into a chromosome of the host cell. Integration is catalyzed by the viral integrase, and we have previously reported that phenolic moieties in compounds such as flavones, caffeic acid phenethyl ester (CAPE, 2), and curcumin confer inhibitory activity against HIV-1 integrase. We now extend these findings by performing a comprehensive structure-activity relationship using CAPE analogues. Approximately 30 compounds have been prepared as HIV integrase inhibitors based on the structural lead provided by CAPE, which has previously been shown to exhibit an IC50 value of 7 microM in our integration assay. These analogues were designed to examine specific features of the parent CAPE structure which may be important for activity. Among the features examined for their effects on inhibitory potency were ring substitution, side chain length and composition, and phenyl ring conformational orientation. In an assay which measured the combined effect of two sequential steps, dinucleotide cleavage and strand transfer, several analogues have IC50 values for 3'-processing and strand transfer lower than those of CAPE. Inhibition of strand transfer was assayed using both blunt-ended and "precleaved" DNA substrates. Disintegration using an integrase mutant lacking the N-terminal zinc finger and C-terminal DNA-binding domains was also inhibited by these analogues, suggesting that the binding site for these compounds resides in the central catalytic core. Several CAPE analogues were also tested for selective activity against transformed cells. Taken together, these results suggest that the development of novel antiviral agents for the treatment of acquired immune deficiency syndrome can be based upon inhibition of HIV-1 integrase.

Perinatal regionalization versus hospital competition: the Hartford example

OBJECTIVES

The increasingly competitive health care environment may undermine effective traditional regional organizations. It is urgent to document the benefits of perinatal regionalization for the emerging health care system. We present a case study that illustrates many of the challenges to and benefits of perinatal regionalization in the 1990s.

BACKGROUND

The controversy in Hartford was sparked by a proposed merger of two major pediatric services into a full-service children's hospital. Community hospitals reacted with plans to upgrade their obstetrics/neonatal facilities toward level II (intermediate) or II+ (intensive) neonatal intensive care units (NICUs). The fear that unrestricted competition would drive up overall health care costs prompted the hospital association and Chamber of Commerce to retain consultants to evaluate the number and location of regional NICU beds.

METHODS

The consultant team interviewed stake-holders in area hospitals, health maintenance organizations, insurance companies, businesses, state agencies, and community groups, and analyzed quantitative data on newborn discharges.

RESULTS

The existing system worked remarkably well for clinical care, training, referrals, and provider and patient satisfaction. There was a high level of inter-hospital collaboration and regional leadership in obstetrics and pediatrics, but strong and growing competition between their hospitals. Hospital administrators enumerated the competitive threats that obligated them to compete and the financial disincentives to support the regional structures. Business leaders and insurance executives emphasized the need to control costs. Analysis of discharge data showed marginal adequacy of NICU beds but maldistribution between NICUs, particularly between level III and level II units. The consultants recommended no new beds based on population projections, declining lengths of stay nationally, and substantial gains available from aggressive back-transport of convalescing infants. The consultants emphasized the need for all stakeholders to support the regional infrastructure (referral, transport, education, evaluation, quality assurance) and to modify competition when it impaired effective regionalization.

CONCLUSIONS

Regionalization permits better care at lower cost, yet competition may disrupt this effective system. Active cooperation by stakeholders is vital. Substantial new research is required to define optimal regional organization.

Recombinant histatins: functional domain duplication enhances candidacidal activity

Histatin 3 (Hst3) is a 32-amino-acid (aa) His-rich protein with antimicrobial activity found in human salivary secretions. To explore further the structure/function relationship of Hst, we utilized a bacterial system for the efficient production of recombinant Hst3 (re-Hst3) and Hst variants. Previously, we demonstrated that the middle portion of Hst3 (aa 13-24) contains the functional domain responsible for killing Candida albicans. Using PCR and splice overlap extension, a Hst variant (re-Hst3rep) was made in which the functional domain was repeated in tandem. Using the pRSET bacterial expression system, re-Hst3 and the variant re-Hst3rep were produced as chimeric fusions and were isolated from bacterial sonicates by affinity chromatography. Affinity purified fusion proteins were digested with CNBr and re-Hst were separated from their fusion partners by reverse-phase high-performance liquid chromatography. The activity of re-Hst3 and re-Hst3rep was compared to that of native Hst3 from human salivary secretions in the C. albicans killing assay. The LD50 values for candidacidal activity of native Hst3, re-Hst3 and re-Hst3rep were 7.2, 6.8 and 4.1 nmol/ml, respectively. At lower concentrations re-Hst3rep was five times more active than native Hst3 or re-Hst3 and at even lower concentrations re-Hst3rep exhibited significant candidacidal activity while native Hst3 and re-Hst3 were inactive. These results demonstrate an expression system for production of biologically active functional Hst and Hst variants and shows that repetition of the functional domain of Hst3 enhances candidacidal activity.

Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing

Cytotoxic T lymphocytes (CTL) recognize antigenic peptides bound to major histocompatibility complex class I antigens on the cell surface of virus-infected cells. It is believed that the majority of peptides originate from cytoplasmic degradation of proteins assumed to be mediated by the "20S" proteasome. Cytosolic peptides are then translocated, presumably by transporters associated with antigen processing (TAP-1 and -2), into the lumen of the endoplasmic reticulum (ER) where binding and formation of the ternary complex between heavy chain, beta2-microglobulin (beta 2m) and peptide occurs. In this study, we have analyzed and compared the phenotype of two mutant cell lines, the thymoma cell line RMA-S and a small lung carcinoma cell line CMT.64, in order to address the mechanism that underlies the antigen processing deficiency of CMT.64 cells. Unlike RMA-S cells, vesicular stomatitis virus (VSV)-infected CMT.64 cells are not recognized by specific CTL. Interferon gamma (IFN-gamma) treatment of CMT.64 cells restores the ability of these cells to process and present VSV in the context of Kb. We show that although CMT.64 cells express a low level of beta 2m, the recognition of VSV-specific CTL is not restored by increasing the amount of beta 2m synthesized in CMT.64 cells. In addition, we find that CMT.64 cells express moderate levels of Kb heavy chain molecules, but most of it is unstable and rapidly degraded in the absence of IFN-gamma treatment. We infer that the antigen processing deficiency does not lie at the level of beta 2m or Kb production. We find also that the mRNAs for both TAP-1 and -2 are present in RMA and RMA-S cells but are absent in uninduced CMT.64 cells. Upon IFN-gamma induction, both mRNAs are highly expressed in CMT-64 cells. In addition, we find that the low molecular mass polypeptides 2 and 7, and additional components of the proteasome are induced by IFN-gamma in CMT-64 cells. Finally, introduction of the rat TAP-1 gene in CMT.64 cells restores CTL recognition of VSV-infected cells. These results indicate that a TAP-1 homodimer may translocate peptides in the ER and explain partially the CMT.64 defect and the RMA-S phenotype. These findings link a dysfunction in the transport and/or generation of antigenic peptides to the capacity of tumor cells to evade immunosurveillance and provide a unique model system to dissect this phenomenon.

The role of the proteasome in cellular protein degradation

Eukaryotic cells contain a major intracellular proteolytic activity known as the proteasome. The proteasome is a strongly conserved cylindrical structure of high molecular weight (650 kDa, approximately 20 S) and demonstrates multiple endopeptidase activities. The general structural, biochemical and genetic features of the proteasome are conserved from archaebacteria through yeast to humans. This structure fulfills an essential role by functioning as the proteolytic core of a 26 S multienzyme complex responsible for the energy-dependent degradation of ubiquitinated proteins. The bulk of intracellular proteolysis appears to be through the ubiquitin-dependent pathway. Incorporation of the proteasome into the 26 S multienzyme complex appears to confer both a specificity for ubiquitinated proteins as well as a means to tightly regulate proteolytic activity. Thus, one function of the proteasome is required for the degradation of either abnormal or certain regulatory proteins by the ubiquitin pathway. Proteasome subunits appear to be encoded by a related gene family as defined by extensive sequence similarities. The gene products are confined to either of two general classes: alpha-type which appear to be structural and beta-type which may be catalytic. Genes encoding at least two proteasome subunits map to the Major Histocompatibility Complex. Accumulating evidence points to the proteasome (or a specialized form) participating in the cytosolic degradation of these viral proteins upon cellular infection.(ABSTRACT TRUNCATED AT 250 WORDS)

MHC-linked LMP gene products specifically alter peptidase activities of the proteasome

Proteasomes are highly conserved macromolecular structures which function as endopeptidases. They are found in the cytoplasm and nucleus of eukaryotic tissues and consist of at least 14 non-identical subunits with molecular masses ranging from approximately 20 to 32K. Proteasomes are essential in the selective degradation of ubiquitinated and certain non-ubiquitinated proteins, acting as the proteolytic core of an energy-dependent 26S (1,500K) proteolytic complex. Two proteasome subunits, LMP2 and LMP7 (refs 4-7), are encoded within the major histocompatibility complex (MHC), implicating proteasomes in antigen processing. Here we determine the function of these two MHC-linked subunits by comparing the proteolytic activities of purified proteasomes containing (LMP+) or lacking (LMP-) these components. We find that proteasomes of both types have endopeptidase activity against substrates bearing hydrophobic, basic or acidic residues immediately preceding the cleavage site (the P1 position) and at sites following asparagine, glycine and proline residues. The activity of LMP+ proteasomes is much higher than that of LMP- proteasomes against substrates with hydrophobic, basic or asparagine residues at P1, whereas their activities are comparable when acidic and glycine residues are present at P1. The MHC-linked LMP2 and LMP7 subunits therefore function to amplify specific endopeptidase activities of the proteasome.

MHC-linked low-molecular mass polypeptide subunits define distinct subsets of proteasomes. Implications for divergent function among distinct proteasome subsets

Proteasomes are 650-kDa, multisubunit endopeptidases that might be involved in the MHC class I Ag processing pathway. We demonstrate the existence of multiple structurally distinct subsets of proteasomes. Distinct forms of proteasomes share a hypothetical core to which unique subunits are added. One of these subsets, LMP2+ proteasome, contains the product of the MHC-linked Lmp-2 gene, and can be distinguished serologically and structurally from other proteasome subsets. The expression of LMP2+ and LMP2- proteasomes is variable among cell lines of different tissue types, and their relative abundance and subunit composition are regulated by IFN-gamma. LMP2+ proteasomes comprise 0 to 74% of total cellular proteasomes. Both LMP2+ and LMP2- proteasomes are proteolytically active. We suggest proteasome function might be regulated by subunit composition, and some, or all proteasome subsets, might participate in the production or delivery of peptides to MHC class I molecules. Both LMP2+ and LMP2- subsets can be further subdivided on the basis of the presence or absence of other unique subunits. Implications of the existence of structurally distinct forms of proteasomes in different tissue types is discussed.

MHC-linked low-molecular mass polypeptide subunits define distinct subsets of proteasomes. Implications for divergent function among distinct proteasome subsets

Proteasomes are 650-kDa, multisubunit endopeptidases that might be involved in the MHC class I Ag processing pathway. We demonstrate the existence of multiple structurally distinct subsets of proteasomes. Distinct forms of proteasomes share a hypothetical core to which unique subunits are added. One of these subsets, LMP2+ proteasome, contains the product of the MHC-linked Lmp-2 gene, and can be distinguished serologically and structurally from other proteasome subsets. The expression of LMP2+ and LMP2- proteasomes is variable among cell lines of different tissue types, and their relative abundance and subunit composition are regulated by IFN-gamma. LMP2+ proteasomes comprise 0 to 74% of total cellular proteasomes. Both LMP2+ and LMP2- proteasomes are proteolytically active. We suggest proteasome function might be regulated by subunit composition, and some, or all proteasome subsets, might participate in the production or delivery of peptides to MHC class I molecules. Both LMP2+ and LMP2- subsets can be further subdivided on the basis of the presence or absence of other unique subunits. Implications of the existence of structurally distinct forms of proteasomes in different tissue types is discussed.

Proteasome subunits encoded in the MHC are not generally required for the processing of peptides bound by MHC class I molecules

Antigen processing provides major histocompatibility complex (MHC) class I molecules with short peptides, which they selectively bind and present to cytotoxic T lymphocytes. The proteolytic system generating these peptides in the cytosol is unidentified, but their delivery into the endoplasmic reticulum is mediated by the TAP1-TAP2 transporter encoded in the MHC class II region. Closely linked to TAP1 and TAP2 are genes for the LMP2 and LMP7 proteins, which resemble components of proteasomes, proteolytic complexes known to degrade cytosolic proteins. This association has led to the common assumption that proteasomes function in this immunological pathway (discussed in ref. 15). We now show that the expression of stably assembled class I molecules and apparently normal peptide processing can be completely restored in the absence of LMP2 and LMP7 in the human lymphoblastoid cell line mutant 721.174 (refs 16, 17). The identity of LMP7 is directly confirmed by reconstitution of a proteasomal subunit after gene transfer. These results therefore dispute the hypothetical involvement of proteasomes in antigen processing, although a more subtle effect of LMP2 and LMP7 cannot be ruled out.

An ATP-stabilized inhibitor of the proteasome is a component of the 1500-kDa ubiquitin conjugate-degrading complex

Proteins conjugated to ubiquitin are degraded by a 26S (1500-kDa) proteolytic complex that, in reticulocyte extracts, can be formed by the association of three factors: CF-1, CF-2, and CF-3. One of these factors, CF-3, has been shown to be the proteasome, a 650-kDa multicatalytic protease complex. We have purified a 250-kDa inhibitor of the proteasome and shown that it corresponds to CF-2. In the presence or absence of ATP, this factor inhibited hydrolysis by the proteasome of both fluorogenic tetrapeptides and protein substrates. When the inhibitor, proteasome, and CF-1 were incubated together in the presence of ATP and Mg2+, degradation of ubiquitin-125I-lysozyme occurred. Both the inhibitory activity and the ability to reconstitute ubiquitin-125I-lysozyme degradation were very labile at 42 degrees C, but both activities were stabilized by ATP or a nonhydrolyzable ATP analog. SDS/PAGE indicated that the 250-kDa inhibitor fraction contained a major subunit of 40 kDa (plus some minor bands). The 125I-labeled inhibitor and purified proteasome formed a complex. When CF-1, ATP, and Mg2+ were also present, the 125I-labeled inhibitor along with the proteasome formed a complex of 1500 kDa. The inhibitor (CF-2) thus appears to be an ATP-binding component that regulates proteolysis within the 1500-kDa complex.

Structural and serological similarity of MHC-linked LMP and proteasome (multicatalytic proteinase) complexes

Major histocompatibility complex (MHC) class I molecules associate with peptides derived from endogenously synthesized antigens. Cytotoxic T-lymphocytes can thus scan class I molecules and bound peptide on the surface of cells for foreign antigenic determinants. Recent evidence demonstrates that the products of trans-acting, non-class I genes in the class II region of the MHC are required in the class I antigen-processing pathway. There are genes (called HAM1 and HAM2 in the mouse) in this region that encode proteins postulated to be involved in the transport of peptide fragments into the endoplasmic reticulum for association with newly synthesized class I molecules. But, the mechanism by which such peptide fragments are produced remains a mystery. At least two genes encoding subunits of the low-molecular mass polypeptide (LMP) complex are tightly linked to the HAM1 and HAM2 genes. We show that the LMP complex is closely related to the proteasome (multicatalytic proteinase complex), an intracellular protein complex that has multiple proteolytic activities. We speculate that the LMP complex may have a role in MHC class I antigen processing, and therefore that the MHC contains a cluster of genes required for distinct functions in the antigen processing pathway.

Evaluation of tympanic membrane thermometer for use with pediatric patients

To determine if a tympanic membrane thermometer is of benefit on a pediatric unit. Temperature readings using a tympanic membrane thermometer and an electronic thermometer were compared for 295 paired observations. The electronic temperature readings were done by rectal (n = 32), oral (n = 65), and axillary (n = 198) routes. Differences in tympanic and electronic readings were compared by paired t-tests, and the readings were also correlated. The nursing time in seconds was also compared between electronic and tympanic measurements. Parents and nurses rated their opinion of each type of measurement on a 0-5 Likert scale. Nurses rated the patient's response using the same scale. Results indicate that temperature readings differ by an average of .2- .5 degree between tympanic and electronic thermometers. Correlations are statistically significant but of low-to-moderate strength. Parents and nurses did not rate the types of instruments differently. The nurses rated the electronic axillary method as being more acceptable to toddlers. The tympanic membrane measurement took an average of 30-38 seconds less time to take. Tympanic membrane thermometry saves nursing time. Although the correlations were not strong between electronic and tympanic membrane measurements, the tympanic reading was closer to the electronic rectal reading than to axillary or oral readings.

A calcium-activated protease from Alzheimer's disease brain cleaves at the N-terminus of the amyloid beta-protein

Alzheimer's disease, Down's syndrome, and to a far lesser extent, normal aged brains exhibit abnormal extracellular deposits of amyloid. The major component of brain amyloid is the beta-protein, a 4Kd fragment of the larger beta-protein precursor. The finding of the abnormally processed beta-protein and a protease inhibitor (alpha 1-antichymotrypsin) in the amyloid deposits prompted us to search for proteases which may generate the beta-protein from its precursor. We now report on the presence and partial purification of one such proteolytic activity from Alzheimer's brain. Normal physiologic C-terminal cleavage of the secreted form of the beta-protein precursor occurs in the middle of the beta-protein suggesting that the beta-protein accumulates due to an alternative degradation pathway. We propose here that the protease activity we describe participates in this abnormal pathway.

The proteasome (multicatalytic protease) is a component of the 1500-kDa proteolytic complex which degrades ubiquitin-conjugated proteins

Mammalian cells contain two large proteolytic complexes, the 650-kDa proteasome (or multicatalytic protease) and the 1500-kDa (26 S) Ubiquitin-conjugate-degrading enzyme. Since the proteasome is also required for the ATP-dependent degradation of ubiquitinated proteins, we tested whether it may be a component of the larger complex. The proteasome normally is soluble in 38% ammonium sulfate. However, after preincubation of reticulocyte extracts with ATP, several proteasome activities appeared in the 38% ammonium sulfate pellet, including the ability to degrade hydrophobic peptides and 14C-casein. Also, following preincubation with ATP, the precipitable fraction could degrade 125I-lysozyme-ubiquitin (Ub) conjugates. The activities were not present after incubation without ATP or with a nonmetabolizable ATP analog. Nondenaturing gel electrophoresis indicated the ATP-dependent appearance of a new band which degraded proteasome substrates, and reacted with an anti-proteasome monoclonal antibody on Western blot. This new band appeared larger than the proteasome and migrated similarly to the larger Ub-conjugate-degrading complex. The formation of the larger complex required factor(s) present in the 38% ammonium sulfate pellet and either the 40-80% fraction or the purified proteasome from reticulocytes or muscle. After complex formation, hydrolysis of Ub-protein conjugates and also the non-ubiquitinated substrate, casein, was stimulated severalfold by ATP, but non-metabolizable ATP analogs had little or no effect. Thus, the proteasome corresponds to component CF-3 of Ganoth et al. (Ganoth, D., Leshinisky, E., Eytan, E., and Hershkov, A. (1989) J. Biol. Chem. 263 12412-12419) and undergoes an energy-dependent association with other factors to form the 1500-kDa, ATP-requiring proteolytic complex.

Maternal and fetal sequelae of anticoagulation during pregnancy in patients with mechanical heart valve prostheses

Previous reports indicate an increased risk of thrombotic and embolic events in patients with mechanical heart valve prostheses during pregnancy. We prospectively followed 50 pregnancies in 49 patients with 62 cardiac prostheses from presentation at the antenatal clinic through the remainder of the pregnancy. Of the 60 mechanical prostheses, 39 were Medtronic-Hall, 7 St. Jude Medical, 7 Starr-Edwards and 7 Björk-Shiley. Forty-three patients were in New York Heart Association functional class I or II and 6 were in functional class III or IV. Forty-five patients were in sinus rhythm and 4 had chronic atrial fibrillation. All patients received warfarin during the first and second trimesters. Forty-one pregnancies proceeded beyond 28 weeks. In 23 of these (group I) warfarin was replaced with heparin at 36 weeks gestation. In the remaining 18 (group II) warfarin was not substituted owing to premature onset of labor. The target prothrombin ratio (international normalized ratio) in patients receiving warfarin was 2.0 to 2.5. The partial thromboplastin time was maintained at 1.5 to 2.5 times the control value in patients receiving heparin. Eleven patients received dipyridamole plus warfarin for the duration of pregnancy. There were no maternal thromboembolic complications or deaths associated with pregnancy. Antepartum hemorrhage occurred in 1 patient at 35 weeks gestation. One patient (group I) experienced peripartum hemorrhage. All patients were hemodynamically stable before delivery, but 2 developed pulmonary edema during labor. The mean fetal birth weight was low (2.54 +/- 0.98 kg). There were 9 abortions (18%), 7 stillbirths (14%), 2 neonatal deaths (4%) and 2 instances of warfarin embryopathy (4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of the proteasome in various degradative processes in mammalian cells

Eukaryotic cells contain a 700-kDa proteolytic complex (the "proteasome" or multicatalytic endopeptidase complex), whose role in intracellular protein breakdown is unclear. It has been suggested that the proteasome functions in the rapid degradation of oxidant-damaged proteins and in the ATP-dependent proteolytic pathway. To test these possibilities, oxidant-damaged hemoglobin and albumin were produced by treating hemoglobin and albumin with phenylhydrazine, with hydroxyl radicals, or with both hydroxyl and superoxide radicals. After oxidant damage, these proteins were degraded more rapidly in erythrocyte extracts and also by the purified proteasome. However, complete removal of proteasomes from these extracts by immunoprecipitation (or inhibitors of its proteolytic activity) did not reduce the breakdown of oxidant-damaged hemoglobin and decreased degradation of hydroxyl- and superoxide-treated proteins by only 30-40%. Thus, erythrocytes must contain another proteolytic system for degradation of oxidant-damaged proteins. In contrast, immunoprecipitation of proteasomes with polyclonal or monoclonal antibodies prevented the ATP/ubiquitin-dependent degradation of lysozyme and also blocked the ATP-stimulated degradation of ubiquitin-conjugated lysozyme in reticulocyte and skeletal muscle extracts. These data indicate a critical role of the proteasome in the degradation of ubiquitin-conjugated proteins and suggest that the proteasome is associated with or is a component of the larger ubiquitin-conjugate-degrading enzyme complex.

Skeletal muscle proteasome can degrade proteins in an ATP-dependent process that does not require ubiquitin

The proteasome (the multicatalytic endoproteinase complex) in mammalian tissues hydrolyzes proteins and several types of peptides. When this structure was isolated rapidly from rabbit skeletal muscle in the presence of glycerol, its various peptidase and protease activities showed a large reversible activation by physiological concentrations of ATP (Ka = 0.3-0.5 mM). Hydrolysis of succinyl-Leu-Leu-Val-Tyr-(4-methylcoumaryl-7-amide) was stimulated up to 12-fold by ATP, whereas degradation of casein and bovine serum albumin increased 4- to 7-fold. Neither ADP nor AMP had any effect. CTP, GTP, UTP, and the nonhydrolyzable analogs adenosine 5'-[beta,gamma-imino]triphosphate (AMPP[NH]P) and adenosine 5'-[alpha,beta-methylene]triphosphate (AMP[CH2]PP) increased peptide hydrolysis as well as ATP did. However, only ATP stimulated casein breakdown and only in the presence of Mg2+. Thus, nucleotide binding allows activation of the peptidase functions, but ATP hydrolysis seems necessary for enhanced degradation of proteins. The ATP effect on proteolysis was reversible and did not require ubiquitin. Sensitivity to ATP was labile, and with storage at 4 degrees C the enzyme became fully active in the absence of ATP or Mg2+. The ATP-activated form closely resembles the proteasome complex described previously, which did not show ATP dependence: both have molecular masses of 650 kDa, contain the same 8-10 subunits, and are precipitated by the same antibodies. A similar ATP-activated form was found in rabbit liver but not in rabbit reticulocytes. The proteasome seems to represent a ubiquitin-independent, ATP-stimulated proteolytic activity within nucleated mammalian cells.