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Biomedical subjects

S C Lo

Publications and source records attributed to S C Lo.

At least 19 recordsLinked to original sources
PubMed1992

High frequency of antibodies to Mycoplasma penetrans in HIV-infected patients.

Mycoplasma penetrans, a novel mycoplasma isolated from HIV-1-infected patients with AIDS, has pathogenic properties associated with in-vivo virulence. Enzyme-linked immunosorbent assay and western blotting detected a more than 100 times higher frequency of antibodies to the mycoplasma in serum from HIV-1-infected patients with AIDS (40%) than from HIV-negative controls (0.3%). Serum from 20% of HIV-1-infected, symptom-free individuals also had M penetrans specific antibodies. The antibodies' major immunoreactivity was directed against P35 and P38, the two main lipid-associated membrane protein antigens of the organism. Patients attending sexually transmitted disease clinics had a low frequency of antibody (0.9%). None of 178 HIV-negative patients with different non-AIDS diseases, many associated with immune dysfunction and/or low white cell counts, tested positive for the antibodies. M penetrans, apparently not a commensal and not a simple opportunist, is uniquely associated with HIV-1 infection and AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1992

A comparison of case retrieval times: film versus picture archiving and communications systems.

One of the advantages that a picture archiving and communications system (PACS) is supposed to provide over a film-based operation is improved performance in retrieving images. Although it seems self-evident that this should be so, this experiment was intended to verify this and to provide some time comparisons for the two methods. The experiment consisted of randomly selecting ultrasound and computed tomography cases and determining how long it took to retrieve files at a PACS workstation or in person from the file room. To simulate actual retrieval volumes, a total of 40 cases from current to 6 months old, 20 cases from the past year, and 10 cases more than 1 year old was selected. Results indicate that PACS retrieval can indeed be faster than file room retrieval. However, the difference is less for recent cases than for older cases. For cases 6 or fewer months old, the workstation retrieval was approximately 2.5 minutes faster per case than the film file room. This time difference increased markedly when extended to the 1-year and older-than-1-year groups. This report details the results of this study and provides information about the reliability of the two archives.

Filing↗
PubMed1992

Mycoplasma penetrans sp. nov., from the urogenital tract of patients with AIDS.

An unusual mycoplasma, which was isolated from the urine of a human immunodeficiency virus-positive male homosexual patient, has an elongated flask shape and two unique sharply divided internal compartments. The tiplike compartment is densely packed with fine granules, and the body compartment is loosely filled with coarse granules consistent with ribosomal structures. The organism has properties of adherence, hemadsorption, and cytadsorption and invades many different types of mammalian cells. Adhesion and penetration apparently involve the terminally located tiplike structure. Cholesterol is required for growth, and the mycoplasma ferments glucose and hydrolyzes arginine, but does not hydrolyze urea. The results of DNA homology studies revealed that this organism is not genetically related to previously described mycoplasma species that have the same biochemical properties. The results of serologic studies demonstrated that this organism is antigenically distinct from all previously described mycoplasmas. We propose that this new mollicute species should be named Mycoplasma penetrans sp. nov. The type strain is strain GTU-54-6A1 (= ATCC 55252).

Acquired Immunodeficiency Syndrome↗
PubMed1992

Selective detection of Mycoplasma fermentans by polymerase chain reaction and by using a nucleotide sequence within the insertion sequence-like element.

A new assay using the polymerase chain reaction to amplify a 206-nucleotide specific gene sequence within the insertion sequence-like element of Mycoplasma fermentans has been developed. The unique insertion sequence-like element exists in multiple copies in the M. fermentans genome. The assay selectively amplifies DNA from all strains of M. fermentans tested. In contrast, DNA from other species of human and nonhuman mycoplasmas, common tissue culture-contaminating mycoplasmas, and bacteria, as well as human, monkey, and mouse tissues do not produce the amplified DNA products specific for M. fermentans.

Animals↗
PubMed1991

Newly discovered mycoplasma isolated from patients infected with HIV.

Mycoplasmas have been isolated from patients with acquired immunodeficiency syndrome (AIDS) and they may contribute to the pathogenesis of this disease. We have isolated repeatedly a previously unknown mycoplasma from the urine of an HIV-positive male homosexual and, subsequently, from the urine of 5 HIV-positive patients with AIDS. The mycoplasma was not found in the urine of 98 healthy control subjects. The organism has an unusual tip-like structure with densely packed fine granules and metabolizes both glucose and arginine for growth. Antigenic and DNA analyses show the organism to be distinct from other known mycoplasmas. The mycoplasma displays in-vitro activities associated with virulence in vivo. In addition, electronmicroscopy shows that the mycoplasma can invade and attach to various human and animal cells. We are investigating whether the new mycoplasma has a role in human disease.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Enhancement of HIV-1 cytocidal effects in CD4+ lymphocytes by the AIDS-associated mycoplasma.

Coinfection with Mycoplasma fermentans (incognitus strain) enhances the ability of human immunodeficiency virus type-1 (HIV-1) to induce cytopathic effects on human T lymphocytes in vitro. Syncytium formation of HIV-infected T cells was essentially eliminated in the presence of M. fermentans (incognitus strain), despite prominent cell death. However, replication and production of HIV-1 particles continued during the coinfection. Furthermore, the supernatant from cultures coinfected with HIV-1 and the mycoplasma contained a factor that inhibited the standard reverse transcriptase enzyme assay. The modification of the biological properties of HIV-1 by coinfection with mycoplasma may be involved in the pathogenesis of acquired immunodeficiency syndrome (AIDS).

Acquired Immunodeficiency Syndrome↗
PubMed1991

Mycoplasma fermentans (incognitus strain) infection in the kidneys of patients with acquired immunodeficiency syndrome and associated nephropathy: a light microscopic, immunohistochemical, and ultrastructural study.

We studied renal tissues from 203 patients with acquired immunodeficiency syndrome (AIDS). Of the 203 patients, 20 showed light-microscopic changes characteristic of AIDS-associated nephropathy (AAN). Fifteen of the 20 (group A) were examined by immunohistochemistry using Mycoplasma fermentans (incognitus strain)-specific monoclonal antibodies and electron microscopy. Renal tissues from all 15 AAN patients showed positive staining for the incognitus strain mycoplasmal antigens within glomerular endothelial and epithelial cells, glomerular basement membrane, tubular epithelial cells and casts, and mononuclear interstitial cells. Ultrastructural study of these 15 cases revealed mycoplasma-like structures in various locations including glomerular epithelial and endothelial cells, glomerular basement membrane, tubular epithelial cells and casts, and mononuclear interstitial cells. In a parallel study, renal tissues from 15 patients with AIDS with essentially normal renal histology or mild interstitial mononuclear cell infiltration (group B) were also examined. These tissues showed no evidence of incognitus strain mycoplasmal infection in renal parenchymal cells; however, occasional scattered mononuclear interstitial cells were positive for the antigens of this organism. Renal tissues from five patients dying with non-AIDS diseases (group C) showed no staining for the incognitus strain antigens in any location. Therefore, infection of renal parenchymal cells by M fermentans (incognitus strain) in the kidneys of AIDS patients is apparently associated with AAN.

AIDS-Associated Nephropathy↗
PubMed1991

Treatment of hepatitis B virus-associated membranous nephropathy with adenine arabinoside and thymic extract.

Previously we found that corticosteroid treatment in the hepatitis B virus (HBV)-associated membranous nephropathy (HBVMN) was not associated with a favorable outcome. To distinguish the differences of the HBV DNA in macrophage, T and B cells among HBVMN patients with or without corticosteroid treatment, serial studies at different time points were investigated. HBV DNA appeared as an "episomal" molecule as with 3.2 kb in macrophage, T and B cells. This molecule disappeared after 12 months among HBVMN patients without corticosteroid treatment. HBV DNA, by contrast, appeared as episomal form even three years later in T cells, with frequent proteinuria among HBVMN patients with corticosteroid treatment. This finding indicates that the use of corticosteroids leads to a potential risk of enhancing HBV viral replication in T cells. We studied 24 HBVMN patients who had previously received corticosteroid treatment and had persistent proteinuria, who were administered combination therapy with adenine arabinoside for two weeks and thymic extract (Thymostimulin) for six months to decrease urine protein loss and obtain seroconversion. These 24 patients had heavy (22 of 24, 91.6%) or mild (2 of 24, 8.4%) proteinuria prior to adenine arabinoside and thymostimulin treatment. All 24 patients demonstrated HBV DNA in mononuclear cells and simultaneously exhibited sera positive with HBsAg and HBeAg. In contrast, after treatment only one case (4.2%) had heavy and two cases (8.4%) mild proteinuria; HBV DNA was demonstrated in macrophage (4 of 24, 16.7%), T cells (9 of 24, 37.5%), and B cells (6 of 24, 25%) as well as serum (24 of 24, 100%) prior to treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvants, Immunologic↗
PubMed1991

Histopathology and doxycycline treatment in a previously healthy non-AIDS patient systemically infected by Mycoplasma fermentans (incognitus strain).

The newly recognized human pathogenic mycoplasma M. fermentans (incognitus strain) causes a fatal systemic infection in experimental monkeys, infects patients with AIDS, and apparently is associated with a fatal disease in previously healthy non-AIDS patients. An apparently immunocompetent male who lacked evidence of HIV infection developed fever, malaise, progressive weight loss, and diarrhea and had extensive tissue necrosis involving liver and spleen. M. fermentans (incognitus strain) was centered at the advancing margins of these necrotizing lesions. Following the treatment of 300 mg doxycycline per day for 6 weeks, he recovered fully. He has no fever or diarrhea, and his abnormal liver function tests have returned to normal. He regained all lost strength and 14 kg of lost weight and has remained disease free for more than 1 year.

Acquired Immunodeficiency Syndrome↗
PubMed1991

In vitro antimicrobial susceptibility testing for the newly identified AIDS-associated Mycoplasma. Mycoplasma fermentans (incognitus strain).

Mycoplasma fermentans (incognitus strain) has recently been recognized as a possible infectious pathogen in humans. This mycoplasma is associated with an acute fatal disease in previously healthy patients who do not have the acquired immunodeficiency syndrome. Many patients with the acquired immunodeficiency syndrome suffer a systemic infection with this microbe. Quantitative assay of antimicrobial susceptibility for M fermentans (incognitus strain) in cultures to representative antibiotics has revealed that the microbe is not sensitive to erythromycin, the most commonly used antibiotic for human mycoplasma infections. The testing shows that M fermentans (incognitus strain) is sensitive in vitro to the antibiotics tetracycline, doxycycline, chloramphenicol, clindamycin, lincomycin, and ciprofloxacin.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Identification of an insertion-sequence-like genetic element in the newly recognized human pathogen Mycoplasma incognitus.

Cloned 2.2-kb DNA (plasmid psb-2.2) of Mycoplasma incognitus, a pathogen in AIDS and non-AIDS patients [Lo et al., Am. J. Trop. Med. Hyg. 41 (1989) 364-376; 601-616], contains a 1405-bp genetic element closely resembling bacterial insertion sequence (IS) elements. This IS-like element has 29-bp terminal inverted repeats with seven mismatches, is immediately flanked by 3-bp direct repeats, and has typical stem-and-loop structures at or near both the termini. Two potential open reading frames (ORF-1 and ORF-2) encode 143 amino acids (aa) and 103 aa, respectively, in this IS-like element. Part (57 aa) of the deduced aa sequence of ORF-2 has a significant homology (43%) with the putative transposase of Escherichia coli IS3. In this study, a series of synthetic oligodeoxyribonucleotides each containing a specific sequence of a selected segment in psb-2.2, have been used as probes which reveal that the IS-like element occurs more than ten times in the genome of M. incognitus. This potentially transposable element has many characteristic features in common with bacterial IS elements.

Amino Acid Sequence↗
PubMed1990

Availability of Lo's mycoplasma.

The name of the reviewer of The History of Modern Mathematics [David F. Rowe and John McCleary, Eds. (Academic Press, San Diego, CA, 1989)] (22 June, p. 1561) was incorrectly printed. It should have been Joan L. Richards, not "Juan" L. Richards.

Mycoplasma↗
PubMed1990

The formation of bile canaliculi in human hepatoma cell lines.

Hepatocytes, known as polarized epithelial cells, are composed of sinusoid, basolateral and bile canalicular domains. Each domain contains proteins specific for it. Our studies indicate that the well-differentiated human hepatoma cell lines HepG2 and HuH-7 formed bile canaliculi in tissue culture, whereas the poorly differentiated hepatoma cell lines HA22T/VGH and SK-HEP-1 did not. We also used the 9B2 monoclonal antibody, previously shown to be specific for the human bile canalicular domain, to study formation of bile canaliculi in these human hepatoma cell lines. All four cell lines synthesize the 140-kD 9B2 antigen. Studies using peroxidase-antiperoxidase staining and immunoelectron microscopy revealed that the 9B2 antigen was first detected in cytoplasm and packaged in microvilli-lined vesicles, then vectorially transported to the cell surface and eventually fused with microvilli-lined vesicles from neighboring cells to form bile canaliculi in well-differentiated hepatoma cell lines. However, the 9B2 antigen of poorly differentiated lines was synthesized in cytoplasm, then transported directly to and evenly distributed on the cell membrane. These results lead us to conclude that human hepatoma cell lines could serve as a good in vitro model to study the formation of bile canaliculi in human hepatocytes. The bile canaliculi of human hepatocytes may be preformed and assembled in the intracellular, microvilli-lined vesicles, then vectorially transported to the cell surface, where they form the bile canaliculi through vesicles fusion. Finally, formation of bile canaliculi and transport of 9B2 antigen may be related to the differentiation of hepatocytes or progression stages of human hepatoma cells.

Antibodies, Monoclonal↗
PubMed1990

Contrast information of digital imaging in laser film digitizer and display monitor.

A 10-bit or 12-bit gray scale is provided in commercial laser film digitizers. The true contrast resolution on the digitized image within a laser spot area of 200 microns in diameter is limited by both the quantum mottle and instrumentation noise. In this report, we investigated the mean value, standard deviation, and adjacent pixel correlation coefficient on a calibrated step wedge film with two laser digitizers. The results were disappointing, because we found that the evaluated contrast information is inferior to the manufacturers' specifications. On the output side, the brightnesses of different gray levels from a clinical monitor were measured with a narrow angle luminance probe and evaluated by a brief human perception study. In addition, the implications for teleradiology applications are discussed.

Data Display↗
PubMed1990

Encapsidation of truncated human hepatitis B virus genomes through trans-complementation of the core protein and polymerase.

Mutational analyses and complementation tests were used to analyze the strategy of packaging and of replication of human hepatitis B virus (HBV). By creating new restriction enzyme sites and by varying the genome length of HBV mutants, we identified that the mutated genomes could be encapsidated through trans-complementation of the polymerase and/or core protein. This study demonstrates that the polymerase of HBV, similar to that of duck hepatitis B virus (DHBV), is synthesized de novo instead of through a core-polymerase fusion protein. The results also indicate that both the polymerase and the core protein can be supplied in trans during viral packaging, and that the complementation is not due to recombination between the cotransfected plasmids. Furthermore, HBV genome deleted down to 2.4 kb is still able to be encapsidated, as measured by the endogenous polymerase reaction. Taken together, these results provide a basis for using HBV as a vector to deliver foreign genes into hepatocytes and for defining the location of the packaging signal on the HBV genome.

Capsid↗
PubMed1990

Studies of natural anticoagulant proteins and anticardiolipin antibodies in patients with the lupus anticoagulant.

Components of the natural anticoagulant system (NAS) and anticardiolipin antibodies were examined in 21 patients with lupus anticoagulant (LA), 13 of whom had past histories of thrombotic episodes. No relationship could be shown between the antigenic levels of protein C and S (PC, PS) and a history of thrombosis. Inhibition of the anticoagulant activity of activated protein C (APC) was observed using plasma from 20/21 patients when phospholipid vesicles were used as the surface for the coagulation reaction. This effect was not affected by the addition of PS. When platelet membranes were employed only 2/21 patients demonstrated inhibition of APC. Under the latter condition, PS functional activity was inhibited in 7/21 patients, six of whom had a past history of thrombosis. Reduced antithrombin III or heparin cofactor II levels were observed in a total of 4/21 patients and may have contributed to the development of thrombosis in three of these patients. Antibodies specifically directed against these proteins were not detected suggesting the possibility of an associated constitutional deficiency. Anticardiolipin antibodies, though elevated in 17/21 patients, did not serve as a useful marker for an increased risk of thrombosis, and the level did not correlate with inhibition of the activity of APC or PS. We conclude that the mechanism of thrombosis in patients with LA is multi-factorial. A subset of patients in whom LA specifically inhibits PS function may represent patients who are at significant risk from thrombosis.

Antibodies↗
PubMed1989

Dimerization of hepatitis B viral X protein synthesized in a cell-free system.

Hepatitis B viral X protein (HBx), a 17-kDa polypeptide, has been demonstrated as a trans-acting factor. In this study, we report that the HBx was able to form a dimer, a feature very similar to many well known trans-acting factors. In vitro synthesized HBx, after immunoprecipitation and analysis by SDS-PAGE, appeared as one prominent 17-kDa band (monomer) and a faint 34-kDa band (dimer). The amount of dimer increased if the sample of immunoprecipitated HBx was not treated with 2-mecaptoethanol, indicating the dimer was held together by the disulfide linkage. Dimerization of a truncated HBx established that the four cysteine residues close to the N-terminus are sufficient for the dimerization process.

Cell-Free System↗