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Biomedical subjects

J Mills

Publications and source records attributed to J Mills.

At least 91 records · Page 5Linked to original sources
PubMed1997

Incidence and epidemiology of nosocomial infections in patients infected with human immunodeficiency virus.

In a prospective study, we investigated the incidence, characteristics, and risk factors of nosocomial infections (NIs) in patients with human immunodeficiency virus disease. There was a total of 528 admissions of 405 eligible patients; 46 NIs (8.7% per discharge) were identified in 39 patients. The proportional frequencies of NIs were as follows: 16 skin and/or soft-tissue infections (including localized catheter-associated infections), 3.0%; 14 respiratory tract infections, 2.7%; 11 bloodstream infections, 2.1%; and 5 urinary tract infections, 0.9%. The most common etiologic agents were Staphylococcus aureus (27.6%), Pseudomonas aeruginosa (13.8%), and Enterobacter cloacae (13.8%). The duration of hospitalization was not significantly prolonged by NI in the cohort.

AIDS-Related Opportunistic Infections↗
PubMed1997

Constitutive expression of p50 homodimer in freshly isolated human monocytes decreases with in vitro and in vivo differentiation: a possible mechanism influencing human immunodeficiency virus replication in monocytes and mature macrophages.

Human immunodeficiency virus type 1 (HIV-1) replicates more efficiently in vitro in differentiated macrophages than in freshly isolated monocytes. We investigated whether this may be partly explained by changes in expression of NF-kappaB with monocyte differentiation. We demonstrated that constitutive expression of NF-kappaB in primary human monocytes changed significantly with differentiation in vitro to monocyte-derived macrophages (MDMs) and differentiation in vivo to alveolar macrophages (AMs). Freshly isolated monocytes constitutively expressed high levels of transcriptionally inactive p50 homodimer which decreased with time in culture in favor of the transcriptionally active p50/p65 and p50/RelB heterodimers. As in MDMs, AMs constitutively expressed p50/p65 and p50/RelB although at lower levels. HIV infection of fresh monocytes failed to induce p50/p65 as seen in MDMs. The replacement of p50 homodimers with transcriptionally active heterodimers following time in culture may partially explain the progressive increase in susceptibility of monocytes to HIV infection during in vitro culture. The change in NF-kappaB components with monocyte differentiation in vivo may also explain the different transcriptional activities of these cell populations in HIV-infected individuals.

Cell Differentiation↗
PubMed1997

Leukemia inhibitory factor (LIF) binding protein attenuates the phlogistic and abolishes the chondral effects of LIF in goat joints.

OBJECTIVE: To investigate the ability of murine leukemia inhibitory factor (LIF) binding protein (mLBP) to attenuate the effects of recombinant human LIF (rhLIF) in goat radiocarpal joints in vivo. METHODS: Endotoxin-free saline (1 ml) containing either 0.5 or 1 microg of rhLIF was injected into the left and right radiocarpal joints of male angora goats. One hour later the right radiocarpal joints were injected with either 1 or 5 microg of naturally occurring mLBP in 1 ml saline, while the left radiocarpal joints (controls) received 1 ml saline vehicle alone. Goat joints were examined for clinical features of inflammation and synovial fluid (SF) was aspirated on Day 0 (before injection) and Days 2 and 6 postinjection. Leukocyte counts and concentrations of keratan sulfate were determined in the SF. Proteoglycan synthesis and proteoglycan content of cartilage was determined ex vivo in cartilage explants obtained at Day 6. RESULTS: Preliminary time course studies in vitro showed that mLBP had to be added to cartilage explant cultures within 1 h of rhLIF for effective antagonism to occur. In joints injected with either 0.5 or 1 microg rhLIF significant increases in swelling, effusion volume, leukocyte counts, and SF keratan sulfate concentrations were observed relative to controls. Statistically significant depressions of ex vivo proteoglycan synthesis and in proteoglycan content of articular cartilage were also observed relative to controls. In joints injected with 1 microg rhLIF followed by 1 microg mLBP, statistically significant improvement was only observed in the rate of ex vivo cartilage proteoglycan synthesis. The observed rate did not differ significantly from that obtained in joints treated with vehicle alone. In contrast, in joints injected with 0.5 microg rhLIF followed by 5 microg mLBP, statistically significant improvement was observed in all variables. Treatment with 5 microg mLBP effectively negated the effects of rhLIF on joint swelling, effusion volume, leukocyte infiltration, and cartilage proteoglycan catabolism. CONCLUSION: Murine LBP has the ability to attenuate the phlogistic effects of rhLIF in radiocarpal joints of goats and also abolishes the stimulatory effect of rhLIF on cartilage proteoglycan catabolism and depression of ex vivo proteoglycan synthesis. These antiinflammatory and chondral effects suggest that a humanized derivative of mLBP could be a clinically useful antagonist for LIF in inflammatory diseases.

Animals↗
PubMed1996

Molecular characterisation of formamidase from Methylophilus methylotrophus.

A 3.2-kbp PstI fragment of DNA encoding formamidase from the methylotrophic bacterium Methylophilus methylotrophus which had previously been cloned (pNW3) [Wyborn, N.R., Scherr, D.J. & Jones, C.W. (1994) Microbiology 140, 191-195], was subcloned as a 2.3 kbp HindIII fragment (pNW323). Nucleotide sequencing showed that the subclone contained two genes which encoded formamidase (fmdA) and a possible regulatory protein (fmdB). Predicted molecular masses for FmdA and FmdB were 44438 Da (compared with approximately 44500 Da by electrospray mass spectrometry and 51000 Da by SDS/PAGE of the purified enzyme) and 12306 Da, respectively. The derived amino acid sequence of formamidase was supported by N-terminal amino acid sequencing of the enzyme and of proteolytic fragments prepared from it using V8 endoproteinase and was 57% similar to that of the acetamidase from Mycobacterium smegmatis. The structural similarities between these two enzymes, and their existence as a separate class of bacterial amidase, were confirmed by immunological investigations.

Amidohydrolases↗
PubMed1996

Surface CD4 is critical to in vitro HIV infection of human alveolar macrophages.

The CD4 glycoprotein is the major cellular receptor for HIV. CD4 surface expression of monocytes decreases with time in culture while their susceptibility to HIV-1 increases. Our aim was to investigate whether this phenomenon occurs in macrophages that have differentiated in vivo by investigating CD4 expression and HIV-1 infection of human alveolar macrophages (AMs). Using flow cytometry to detect CD4 expression by Leu-3a labeled indirectly with fluorescein isothiocyanate or allophycocyanin, we found that CD4 was expressed at low but detectable levels, despite the high background autofluorescence well described in AMs. This finding was supported by the detection of CD4 mRNA in AMs using RT-PCR. T cell contamination of mRNA extracts of AMs was excluded by amplifying in parallel with primers to the constant region of the T cell receptor. Despite this low level of surface CD4, recombinant soluble CD4 and anti-CD4 antibody completely inhibited HIV-1 infection of AMs. We conclude that CD4, although expressed at low levels on the surface of AMs, appears to be critical to HIV-1 infection of these cells.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Managing HIV. Part 3: Mechanisms of disease. 3.1 Structure and function of HIV.

The discovery of HIV in 1983 is a landmark of medical science in the 20th century. HIV is a fragile but stealthy virus that thrives within the cells of the immune system itself, subverting the body's defences against disease. Knowing the structure and life cycle of the virus is the key to understanding how it is transmitted, how it causes disease and how best to prevent or control infection.

AIDS Vaccines↗
PubMed1996

Phorbol esters but not the cholinergic agonists oxotremorine-M and carbachol increase release of the amyloid precursor protein in cultured rat cortical neurons.

Conventional secretory processing of the amyloid precursor protein is nonamyloidogenic, releasing carboxyl-terminus-truncated amyloid precursor protein derivatives while cleaving the amyloid beta-peptide within its sequence. Alternative processing routes are potentially amyloidogenic, yielding the amyloid beta-peptide segment intact. In continuous cell lines, secretory processing of the amyloid precursor protein is regulated by both protein kinase C and muscarinic receptor stimulation. However, the first and second messenger systems that regulate amyloid precursor protein release in central neurons are still under investigation. In the present investigation, we examined whether or not first and second messengers of cholinergic neurotransmission increase production of soluble derivatives of the amyloid precursor protein in primary cultures of rat cortical neurons. Activation of protein kinase C by the phorbol esters phorbol 12,13-dibutyrate and phorbol 12-myristate 13-acetate increased production of the soluble form of the amyloid precursor protein dramatically. In contrast, activation of muscarinic receptors by oxotremorine-M or carbachol did not result in a significant increase in amyloid precursor protein release. Similarly, chemically induced depolarization using 35 mM KCl did not alter production of soluble amyloid precursor protein derivatives. Our data suggest that although protein kinase C stimulation plays an important role in regulating release of the amyloid precursor protein, cholinergic neurotransmission does not regulate its release in cultured rat cortical neurons.

Amyloid beta-Protein Precursor↗
PubMed1996

Cell proliferation and regulation of negative growth factors in mouse liver foci.

Foci of altered hepatocytes are preneoplastic lesions capable of progressing to hepatocellular carcinomas. To characterize the growth of preneoplastic hepatic lesions, size of hepatic foci was analyzed with regard to growth factor regulation and hepatocyte proliferation in focal and non-focal hepatocytes. Twelve-day-old female B6C3F1 mice were initiated with a single dose of the potent mutagen N-nitrosodiethylamine (DEN) (5 mg/kg body weight). Beginning at 6 weeks of age, mice were exposed for 16 weeks to 2038 p.p.m. unleaded gasoline (UG) vapor or 1 p.p.m. ethinyl estradiol (EE) in the diet. Analysis of hepatic foci demonstrated that UG significantly increased, but EE significantly decreased the size of DEN-initiated foci. Hepatic labeling index (LI), as measured by the incorporation of 5-bromo-2'-deoxyuridine, was similar in non-focal hepatocytes at 16 weeks in all groups (0.4-0.8%) and greatly increased in hepatic foci. Hepatocyte LI was significantly increased in DEN/UG foci (29%, n = 41) and significantly decreased in DEN/EE foci (6%, n = 23) relative to DEN/control focal hepatocytes (18%, n = 25). The mean LI of foci correlated with the focal size differences observed in the treatment groups. Immunohistochemical analysis with antibodies directed to the negative growth regulator transforming growth factor-beta 1 (TGF-beta1) demonstrated a consistent decrease of TGF-beta 1 in DEN/Ct and DEN/UG hepatic foci relative to non-lesion hepatocytes. Similar results were seen with mannose 6-phosphate/insulin-like growth factor-II receptor (M6P/IGF-II R), which facilitates activation of latent TGF-beta 1. In contrast, only 50% of DEN/EE foci had decreased levels of TGF-beta 1 and M6P/IGF-II R relative to non-focal hepatocytes. These data suggest that proliferative responses observed in hepatic foci may be correlated with foci size. In contrast, chemically induced proliferative responses in non-focal hepatocytes after subchronic exposure cannot necessarily be used to predict proliferative effects in preneoplastic cell populations. Furthermore, these studies suggest that hepatic foci may occur by M6P/IGF-II R enhancing activation of latent TGF-beta 1 in non-focal hepatocytes but not in the focal hepatocytes, thereby affording focal hepatocytes a selective growth advantage.

Air Pollutants↗
PubMed1996

Human immunodeficiency virus grown in CD4-expressing cells is associated with CD4.

Using a CD4-capture immunoassay for gp120, several strains of human immunodeficiency virus type 1 (HIV-1) grown in CD4-expressing T lymphoblastoid cells were found to contain little CD4-reactive gp120 (0.3-1.0 ng/ml) relative to virus titre (10(3.2)-10(5.0) TCID50/ml) and p24 antigen (80-1000 ng/ml). The measured CD4-reactive gp120 concentrations of HIV-1 suspensions grown in CD4-negative human neuroblastoma cells were 100- to 10,000-fold greater than those of HIV-1 grown in CD4-positive lymphoblastoid cells, even though both virus suspensions contained abundant viral gp120 as shown by immunoblot assay. It was postulated that CD4 derived from host cells might be associated with virions, concealing the binding domains of gp120. CD4 association with HIV-1 virions grown in CD4-positive cells was demonstrated directly by immunoblot assay of sucrose gradient-purified virus suspensions and by specific co-sedimentation of 125I-labelled OKT4 with virions propagated in CD4-expressing cells. CD4 coating of primary HIV-1 isolates grown in peripheral blood mononuclear cells was also observed. The biological significance of CD4 coating of HIV particles remains to be determined.

CD4 Antigens↗
PubMed1996

Human immunodeficiency virus type 1 Nef binds directly to Lck and mitogen-activated protein kinase, inhibiting kinase activity.

It is now well established that human immunodeficiency virus type I (HIV-1) Nef contributes substantially to disease pathogenesis by augmenting virus replication and markedly perturbing T-cell function. The effect of Nef on host cell activation could be explained in part by its interaction with specific cellular proteins involved in signal transduction, including at least a member of the src family kinase, Lck, and the serine/threonine kinase, mitogen-activated protein kinase (MAPK). Recombinant Nef directly interacted with purified Lck and MAPK in coprecipitation experiments and binding assays. A proline-rich repeat sequence [(Pxx)4] in Nef occurring between amino acid residues 69 to 78 is highly conserved and bears strong resemblance to a defined consensus sequence identified as an SH3 binding domain present in several proteins which can interact with the SH3 domain of various signalling and cytoskeletal proteins. Binding and coprecipitation assays with short synthetic peptides corresponding to the proline-rich repeat sequence [(Pxx)4] of Nef and the SH2, SH3, or SH2 and SH3 domains of Lck revealed that the interaction between these two proteins is at least in part mediated by the proline repeat sequence of Nef and the SH3 domain of Lck. In addition to direct binding to full-length Nef, MAPK was also shown to bind the same proline repeat motif. Nef protein significantly decreased the in vitro kinase activity of Lck and MAPK. Inhibition of key members of signalling cascades, including those emanating from the T-cell receptor, by the HIV-1 Nef protein undoubtedly alters the ability of the infected T cell to respond to antigens or cytokines, facilitating HIV-1 replication and contributing to HIV-1-induced disease pathogenesis.

Amino Acid Sequence↗
PubMed1996

Zidovudine resistance is suppressed by mutations conferring resistance of human immunodeficiency virus type 1 to foscarnet.

Both foscarnet (PFA) and zidovudine (AZT) select for drug-resistant variants of human immunodeficiency virus type 1 (HIV-1), but the interactions between the mutations causing such resistance are unknown. The introduction of the previously identified PFA resistance mutation W to G at codon 88 (W88G), E89K, L92I, or Q161L into an HIV-1 strain having the four known AZT resistance mutations completely reversed high-level AZT resistance. Two additional PFA resistance mutations, W88S and S156A, partially suppressed AZT resistance. Phenotypic reversion of AZT resistance by W88S, W88G, E89K, L921, and S156A was associated with a concomitant suppression of PFA resistance. The degree to which PFA resistance mutations reversed AZT resistance was directly correlated with each mutation's ability to confer high-level PFA resistance (> or = 5.0-fold) and AZT hypersusceptibility in a wild-type genetic background. Highly PFA-resistant HIV- 1 strains were hypersusceptible to AZT; conversely, AZT-resistant strains with M41L and T215Y; M41L, L210W, and T215Y; or M41L, D67N, K70R, and T215Y mutations were 2.2- to 2.5-fold hypersusceptible to PFA. Prolonged in vitro selection of wild-type or AZT-resistant HIV-1 strains with the combination AZT and PFA failed to generate coresistant virus, indicating that dual resistance was relatively difficult to achieve. Strains selected by passage in PFA plus AZT were phenotypically PFA resistant and AZT susceptible despite multiple reverse transcriptase mutations known to confer AZT resistance. These data show that PFA resistance mutations can phenotypically reverse AZT resistance and that AZT and PFA resistance might be mutually exclusive. The reciprocal interactions between AZT and PFA resistance-conferring mutations have implications for structure-function studies of the HIV-1 reverse transcriptase.

Antiviral Agents↗
PubMed1996

Human immunodeficiency virus type 1 replication is blocked prior to reverse transcription and integration in freshly isolated peripheral blood monocytes.

Peripheral blood monocytes are resistant to productive human immunodeficiency virus type 1 (HIV-1) infection in vitro immediately after isolation. No viral cDNA (either early or late transcripts) was detected by PCR in monocytes exposed to virus on the day of isolation. In contrast, in monocytes cultured for as little as 1 day, initiated and completed reverse transcripts were readily detectable within 24 h of infection with both HIV-1(Ba-L) and primary isolates. The levels of initiated, partially completed, and completed viral DNA copies found 24 h after infection increased progressively with time in culture before infection. Unlike quiescent T lymphocytes, there appeared to be no block or delay in the integration of viral DNA into the genome of susceptible cultured monocytes. With an Alu-PCR method designed to specifically detect proviral DNA being used, integration events were found within 24 h of infection in monocytes cultured for a day or more after isolation. No integration signal was found in freshly isolated monocytes up to 7 days following exposure to the virus. Cloning and sequencing of Alu-PCR-amplified DNA confirmed integration in HIV-1-infected cultured monocytes. Our finding that in vitro replication of HIV-1 is clearly blocked prior to the initiation of reverse transcription in freshly isolated peripheral blood monocytes suggests that these cells may not be susceptible to infection in vivo. Further studies to clarify this possibility and the nature of the block to infection should provide useful information for treatment strategies against HIV-1.

Base Sequence↗
PubMed1996

Discontinuation of antiepileptic drug treatment after two seizure-free years in children with cerebral palsy.

OBJECTIVE: The risk of seizure relapse after antiepileptic drug (AED) discontinuation in children has been reported to vary between 6% and 40%. It has been suggested that neurologic deficit and mental retardation are poor prognostic factors for seizure relapse after AED discontinuation. Because epileptic children with cerebral palsy (CP) have neurologic deficits, and many have mental retardation, it is important to know their risk for seizure relapse. METHODS: AED treatment was discontinued in 65 children with CP and histories of epilepsy after 2 seizure-free years. All of the patients were followed until they had seizure relapses or for at least 2 years without seizures after AEDs were stopped. Multiple factors were analyzed for possible association with seizure relapse. RESULTS: Twenty-seven patients (41.5%) had seizure relapses. Patients with spastic hemiparesis had the highest relapse rate (61.5%), and those with spastic diplegia had the lowest rate (14.3%). No other factor correlated significantly with the risk of seizure relapse. CONCLUSIONS: Discontinuation of AEDs in children with CP can, and should, be practiced when possible after patients have been seizure-free for at least 2 years. AED discontinuation in patients with spastic hemiparesis is significantly more likely to lead to seizure relapse than in patients with other CP types, but no other factor is yet known to increase the chance of relapse.

Adolescent↗
PubMed1995

Genomic structure of an attenuated quasi species of HIV-1 from a blood transfusion donor and recipients.

A blood donor infected with human immunodeficiency virus-type 1 (HIV-1) and a cohort of six blood or blood product recipients infected from this donor remain free of HIV-1-related disease with stable and normal CD4 lymphocyte counts 10 to 14 years after infection. HIV-1 sequences from either virus isolates or patient peripheral blood mononuclear cells had similar deletions in the nef gene and in the region of overlap of nef and the U3 region of the long terminal repeat (LTR). Full-length sequencing of one isolate genome and amplification of selected HIV-1 genome regions from other cohort members revealed no other abnormalities of obvious functional significance. These data show that survival after HIV infection can be determined by the HIV genome and support the importance of nef or the U3 region of the LTR in determining the pathogenicity of HIV-1.

Adult↗
PubMed1995

Characterisation of foscarnet-resistant strains of human immunodeficiency virus type 1.

Foscarnet is a broad-spectrum viral DNA polymerase inhibitor active in vitro and in vivo against human immunodeficiency virus type 1 (HIV-1). Strains of HIV-1 resistant to foscarnet were selected by in vitro passage in increasing concentrations of drug. Reduced susceptibility to foscarnet was evident at the levels of both HIV-1 replication and reverse transcriptase. Biologically cloned, foscarnet-resistant strains with distinct genotypes were hypersensitive to zidovudine, azidodeoxyuridine, nevirapine, and R82913 but had unchanged susceptibility to zalcitibine and didanosine. The reverse transcriptase of foscarnet-resistant strains had unique substitutions Glu89-Lys, Leu92-Ile, or Ser156-Ala, the third being associated with six polymorphic changes. Introduction of these mutations into wild-type HIV-1 by site-directed mutagenesis confirmed their role in foscarnet resistance. In the three-dimensional structure of the reverse transcriptase enzyme these amino acids are located close to the template strand of the template primer and far away from the putative pyrophosphate binding site, suggesting that the mechanism by which HIV-1 becomes resistant to foscarnet is indirect. Foscarnet resistance is thus likely to be mediated through an altered interaction of the mutant enzyme with the template strand of the template primer which distorts the geometry of the polymerase active site and thereby decreases foscarnet binding.

Amino Acid Sequence↗