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Biomedical subjects

R Ali

Publications and source records attributed to R Ali.

At least 73 records · Page 4Linked to original sources
PubMed1998

Binding of circulating antibodies to reactive oxygen species modified-DNA and detecting DNA damage by a monoclonal antibody probe.

Circulating antibodies in the sera of normal, healthy humans of different age groups to native DNA (nDNA) and reactive oxygen species modified DNA (ROS-DNA) was studied by competition ELISA. Sera from the young population (< 50 years of age) showed negligible levels of anti-DNA antibodies. In contrast, anti-DNA antibodies were found in three sera from the moderately aged group (50-59 years) with a high binding to ROS-DNA (43-47%). In the aged group (> 60 years), four sera showed higher recognition of ROS-DNA (> 60% inhibition) over nDNA (55-60%). Oxidative lesions in human genomic DNA were immunochemically detected using the monoclonal anti-ROS-DNA antibody as a probe. The antibody has a high specificity for ROS-DNA and preferentially recognizes ROS-modified epitopes on nucleic acids. The study indicates low recognition of DNA isolated from the younger population, while in the age group 50-59 years, one DNA isolate showed a high inhibition (57%) in monoclonal antibody binding. Four DNA isolates from the aged group showed substantial inhibition in antibody activity to the extent of 49, 53, 64 and 69%. The results demonstrate an age-related increase in the levels of anti-DNA antibodies, with a higher recognition and binding to ROS-DNA. A high reactivity of DNA isolated from aged individuals by the monoclonal antibody indicates increased oxidative stress leading to DNA damage. It is suggested that free radical damage to DNA in vivo, particularly in the aged, alters its antigenicity and stimulates an immune response against modified DNA. These antibodies are cross-reactive to nDNA.

Adult↗
PubMed1998

Reactive oxygen species modified polyguanylic acid: immunogenicity and implications for systemic autoimmunity.

The effect of the hydroxyl radical on polyguanylic acid [poly(G)] was investigated with regard to progressive increase of autoantibodies against it in systemic lupus erythematosus (SLE) and progressive systemic sclerosis (PSS). Rabbits immunized with both native and ROS-poly(G) induced high titre antibodies. Immune IgG exhibited a high degree of specificity towards the immunogen, reiterated visually by a gel retardation assay. The induced antibodies showed a wide range of cross-reactivity with various synthetic polynucleotides exhibiting B-, A-, and allied conformations. The specificity of induced antibodies resembled the diverse binding characteristics of lupus anti-DNA autoantibodies. Moreover, sera from scleroderma patients showed binding to native and ROS-poly(G). SLE and PSS autoantibodies showed preferential recognition of ROS-poly(G) over native poly(G). These results demonstrate that the hydroxyl modified guanine residues in DNA and RNA can induce circulating SLE and PSS autoantibodies.

Animals↗
PubMed1998

Detection of oxidative DNA damage by a monoclonal antibody: role of lysyl residues in antigen binding.

Hydroxyl radical, a prominent entity of reactive oxygen species, is known to modify cellular DNA and has been implicated in several human diseases. A previously described monoclonal antibody (Mab) against reactive oxygen species-modified DNA (ROS-DNA), which preferentially recognizes ROS-modified epitopes on DNA, was used in this study. The epsilon-amino groups of lysine of the Mab were modified to study the role of these residues in Mab binding to ROS-DNA. The results demonstrate that modification of lysyl residues paralleled loss in Mab binding to ROS-DNA to the extent of 73%, suggesting the probable role of these positively charged amino acid residues in the complementarily determining regions of the Mab. The Mab was also used as an immunochemical probe to detect oxidative DNA damage in vivo in SLE. The Mab distinctly recognized five DNA samples out of eight from SLE patients and gave maximum inhibitions of 57, 58, 63, 64 and 70% in inhibition assay, while not reacting with DNA from normal, healthy population which served as negative control. High recognition of DNA isolates from SLE patients by the Mab having preferential binding to ROS-modified epitopes indicates increased oxidative stress in these patients leading to DNA damage which may contribute to the induction of antibodies cross-reacting with native DNA (nDNA).

Animals↗
PubMed1998

Immunochemical detection of oxidative DNA damage in cancer and aging using anti-reactive oxygen species modified DNA monoclonal antibody.

The formation of reactive oxygen species (ROS), although a normal cellular activity, is considerably enhanced under chronic inflammatory conditions and ischemia. These species have been implicated in various disorders, mutagenesis, carcinogenesis and aging. Of many macromolecules, DNA is the most susceptible to hydroxyl radical, the most reactive of the ROS. The present study is designed to detect oxidative DNA damage in cancer patients and healthy aged humans using an anti-ROS-DNA monoclonal antibody (mAb). Purified calf thymus DNA fragments (approximate size 400 bp) were modified with OH, generated by UV-irradiation (254 nm) of hydrogen peroxide. ROS-modified DNA was characterized by UV-spectroscopy, melting temperature, alkaline sucrose density gradient ultracentrifugation and ion-exchange chromatography. ROS-DNA showed single strand breaks, decrease in Tm, modification of thymine (58.3%) and guanine (20%). The mAb generated against ROS-DNA was characterized for antigen binding specificity by competition ELISA. Monoclonal antibody showed strong binding to ROS-modified DNA, its modified fragments, polynucleotides and bases. With the exception of native DNA, binding of unmodified polynucleotides and bases was much lower. The mAb distinctly recognized DNA samples from lymphocytes of healthy aged humans and gave maximum inhibitions of 49, 53, 64 and 70%, while not reacting with DNA from young population. Similarly, oxidative lesions in DNA from cancer patients were also efficiently recognized by the mAb. DNA from healthy controls served as negative control. The studies demonstrate that the mAb, although cross-reactive, preferentially binds ROS-modified epitopes on DNA. High reactivity of mAb to DNA samples from cancer patients and healthy aged humans indicates increased oxidative stress leading to DNA damage.

Aging↗
PubMed1998

Experience of non-fatal overdose among heroin users in Adelaide, Australia: circumstances and risk perceptions.

AIMS: To ascertain the prevalence and risk factors for non-fatal overdose among heroin users to assist in the development of an effective intervention. DESIGN: Cross-sectional design. SETTING: Community setting, principally metropolitan Adelaide. PARTICIPANTS: Current heroin users (used heroin in the previous six months). MEASUREMENTS: A structured questionnaire including the Severity of Dependence Scale. FINDING: Of 218 current South Australian heroin users interviewed in 1996, 48% had experienced at least one non-fatal overdose their life-time (median: two overdoses), and 11% had overdosed in the previous 6 months. At some time, 70% had been present at someone else's overdose (median: three overdoses). At the time of their own most recent overdose, 52% had been using central nervous system depressants in addition to heroin, principally benzodiazepines (33%) and/or alcohol (22%). The majority of overdoses occurred in a private home (81%) and in the presence of other people (88%). Unrealistic optimism regarding the risk of overdose was evident across the sample. Despite almost half the sample reporting having had an overdose, and the belief expressed by respondents that on average about 50% of regular heroin users would overdose during their life-time 73% had, during the previous 6 months, "rarely" or "never" worried about possibly overdosing. Optimism regarding the possibility of future overdose was reduced in those with recent experience of overdose in comparison to the rest of the sample. A targeted intervention aimed at the reduction of overdose among heroin users is outlined.

Adolescent↗
PubMed1998

Physical and mental health problems in amphetamine users from metropolitan Adelaide, Australia.

Phase I of this study was designed to inform the development of a range of responses to hazardous and harmful amphetamine use. Research techniques from Rapid Assessment Methodology (RAM) were utilized to collect data. A survey of current amphetamine users included the Short Form 36 (SF36) Health Status Questionnaire, for which South Australian population norms were published in 1995. This facilitated comparisons of the health of this sample of amphetamine users with that of the general population. The sample were found to have significantly poorer health than the general population. The self-reported prevalence of mental health problems in the sample was consistent with previous Australian research on amphetamine use. Approximately one-third of the sample reported that they had experienced symptoms of anxiety, depression, mood swings and aggressive outbursts prior to their use of amphetamines. Two-thirds of the sample reported symptoms of anxiety and depression since starting to use amphetamines, almost half reported mood swings and aggressive outbursts, and over a third reported panic attacks and paranoia. One of the most important findings was a strong association between mental and physical health problems and the severity of dependence on amphetamines. The implications of these results for interventions with amphetamine users are discussed.

Journal Article↗
PubMed1998

Immunological studies on DNA-lysine photoadduct.

Calf thymus native DNA was covalently linked with lysine by irradiation with 254 nm light. Thermal melting studies indicated a decrease of 16 degrees C in the Tm of DNA-lysine photoadduct over native DNA. The decrease in Tm was dependent of irradiation dose. The photoadduct was found to be a potent immunogen in experimental animal. Thymine-lysine photoconjugate in DNA-lysine photo-monoadduct appears to be the major immunodominant portion. A strong recognition of DNA-lysine photoadduct was observed with anti-DNA autoantibodies found in the sera of patients with SLE. Thymine-lysine conjugate in DNA-lysine photo-monoadduct appears to provide an immunodominant epitope(s) for SLE autoantibody recognition. The results suggests for the possible involvement of DNA-lysine photoadduct or similar modified structure(s) as a potential trigger for anti-DNA autoantibody production.

Antibodies, Antinuclear↗
PubMed1998

Correlates of retention on the South Australian Methadone Program 1981-91.

OBJECTIVES: To investigate correlates of retention on the South Australian Methadone Program during 1981-91. DESIGN: Retrospective study of a nonstratified random sample of 229 HIV-negative clients who received methadone between January 1981 and June 1991. Data were collected from clinical records of the 229 HIV-negative clients and also from the 40 clients known to be infected with HIV during the decade. RESULTS: Being HIV positive, receiving larger maximum doses of methadone, receiving methadone from a private pharmacy and enrolling later in the decade were all associated with longer retention times on the program. CONCLUSIONS: This study supports the findings of previous studies, that maximum dose of methadone is crucial to retention in methadone programs, But even allowing for maximum dose, obtaining methadone from a private pharmacy was also strongly associated with retention on the program. The more 'humane' clinic policy later in the decade is likely to have increased retention and reduced illicit drug use also.

HIV Seropositivity↗
PubMed1997

HIV prevalence and risk behaviour in needle exchange attenders: a national study. The Collaboration of Australian Needle Exchanges.

OBJECTIVE: To determine whether needle and syringe exchange programs represent feasible sites to describe the prevalence of HIV and related risk behaviour among injecting drug users. DESIGN: Cross-sectional survey. SETTING: 21 needle and syringe exchange programs in all Australian jurisdictions. PARTICIPANTS: All persons attending the needle and syringe exchange programs over one week in March 1995 were eligible to participate in the study once. INTERVENTION: Needle and syringe exchange attenders were asked to complete a brief, self-administered questionnaire and provide a finger-prick blood sample. MAIN OUTCOME MEASURES: Prevalence of HIV antibody, drug injecting and sexual behaviour, and survey cost. RESULTS: Completed questionnaires with blood samples suitable for testing were provided by 1005 (42%) of 2373 individuals who attended the needle and syringe exchange programs during the survey week. Women were more likely than men to participate in the survey but there was no difference in the response rate by age group. The HIV prevalence was 2.1% and was significantly higher in men who described themselves as homosexual, compared to men who described themselves as heterosexual (22.5% v. 0.7%; P < 0.001). Thirty-one per cent of respondents reported using a syringe after someone else in the preceding month. CONCLUSION: Cross-sectional surveys of needle exchange clients offer a practical method for monitoring risk behaviour and seroprevalence of bloodborne viral infections.

Adolescent↗
PubMed1997

Reactive oxygen species modified thymine and poly(dT) present unique epitope for human anti-DNA autoantibodies.

Hydroxyl radical, one of the most potent of all reactive oxygen species has been implicated in many human degenerative diseases and is known to modify adenine and thymine in cellular DNA. In the present studies, adenine, thymine and their synthetic homopolymers poly(dA), poly(dT) were ROS-modified and subsequently used as inhibitors of native DNA binding to human anti-DNA autoantibodies. Besides nDNA, modified thymine and poly(dT) were effective inhibitors of DNA-anti-DNA antibody interaction. The relative affinity of ROS-modified poly(dT) was better than that of native DNA. Visual detection of modified thymine and poly(dT) binding to affinity purified anti-DNA IgG by an indirect band shift assay support competition inhibition data. The enhanced recognition of ROS-DNA by anti-DNA autoantibodies, as reported earlier, could be due to the ROS-induced modification of thymine.

Adenine↗
PubMed1997

High salt and solvent induced Z-conformation in native calf thymus DNA.

The Z-DNA forming potentiality of native calf thymus DNA using spectrophotometric measurements and diethyl pyrocarbonate reactivity have been investigated. The Z value was evaluated from absorbance ratio for B- and Z-DNA and compared with the values obtained for native DNA. The results suggest that native DNA undergoes B- to Z-/Z-analogous transition to an extent of 20 per cent under constraint conditions. Possible Z-DNA formation was also characterized by hyper-reactivity of native DNA towards diethyl pyrocarbonate in aqueous solvent. The thermal melting profile of native and modified DNA and nuclease S1 digestibility data, in addition, reflects B- to Z-/Z-analogous transition in native DNA.

Animals↗
PubMed1997

Anti-ROS-DNA monoclonal antibody as molecular probe for oxidative DNA damage.

Modification of 400 bp (approximate size) calf thymus DNA with OH radical resulted in lowered Tm, modification of thymine (58.3%), guanine (20%) and single strand breaks. Monoclonal antibodies (mAb) generated against ROS-DNA were of IgG1 subclass. The mAb showed strong binding to ROS-DNA and ROS-modified bases and polymers, in particular, of thymine. The mAb, therefore, preferentially recognizes ROS-modified epitopes on nucleic acids. Distinct binding to DNA isolated from aged, but not from normal humans by the monoclonal antibody was observed. The antibody effectively recognized oxidative lesions in DNA from cancer patients. These studies demonstrate the potential application of the mAb as an immunochemical probe to detect oxidative DNA lesions.

Aging↗
PubMed1997

T-2 tetraol is cytotoxic to a chicken macrophage cell line.

Cytotoxic effects of T-2 tetraol, a T-2 toxin derivative, on the MQ-NCSU chicken macrophage cell line were quantified by direct in vitro exposure. Macrophage cultures were exposed to 1, 10, 20, 40, 80, 160, and 320 micrograms/mL of T-2 tetraol for 1 h. Macrophage viability after exposure to T-2 tetraol. Macrophage viability was reduced by increasing concentrations of T-2 tetraol (linear effect, P < or = 0.001; quadratic effect, P < or = 0.025). The ability of macrophages to adhere to glass surfaces was impaired by increasing concentrations of T-2 tetraol (linear effect, P < or = 0.003). This experiment demonstrates that T-2 tetraol is cytotoxic to chicken macrophages in vitro.

Animals↗
PubMed1996

Antigenicity of poly(dA-dT) . poly(dA-dT) photocrosslinked with 8-methoxypsoralen.

We report the formation of photocrosslink (diad-duct) between duplex poly(dA-dT) and 8-methoxypsoralen inferred on the basis of UV and fluorescence characteristics, Tm, nuclease S1 digestibility, and hydroxyapatite column chromatography. The photocrosslink was highly immunogenic inducing high titer antibodies in goat. The affinity constant of antigen-antibody interaction quantitated by precipitin titration was found to be 2.71 x 10(9) M-1, calculated by Langmuir isotherm plot. These antibodies were highly specific showing recognition of almost exclusively of nucleic acid-furocoumarin photoadducts and could be used as a probe to detect and quantitate DNA modified with furocoumarins in health and disease. Antibodies against poly(dA-dT)-furocoumarin photocrosslink might be a better probe because of repeated A-T sequences on the immunogen.

Animals↗
PubMed1996

Macrophage presentation of endogenous self-protein: the MHC class II presentation pathway is not accessible to intracellular C5 or alpha 1-antitrypsin.

This paper addresses the question of whether macrophages can present biosynthesized protein in a class II-restricted manner using the endogenous rather than the exogenous pathway of presentation. Two distinct self-antigens, the fifth component of complement (C5) and alpha 1-antitrypsin, were studied. Both antigens are serum proteins synthesized by hepatocytes and macrophages. To direct synthesis exclusively to macrophages chimeras were constructed by transfer of bone marrow from donors expressing the self-antigen into irradiated hosts deficient for the respective self-antigen. Macrophages from such mice were unable to present biosynthesized C5 to class II-restricted T cells, even when preactivated in vivo. While C5 production by macrophages is low and may not reach critical levels of intracellular protein required to access the class II presentation pathway, human alpha 1-antitrypsin, expressed as a transgene in mice, was synthesized at 600-fold higher levels than C5. Nevertheless, macrophage-synthesized alpha 1-antitrypsin in bone marrow chimeras was not presented in the context of class II--even in a mutant form which is sequestered in high amounts in the endoplasmic reticulum. We conclude that macrophages are unable to use the endogenous class II presentation pathway for these two model self-antigens. As a consequence MHC class II-restricted T cells specific for C5 and alpha 1-antitrypsin remain ignorant of the presence of self-antigen within macrophages and are neither tolerized nor rendered autoimmune.

Animals↗
PubMed1996

CtCdc55p and CtHa13p: two putative regulatory proteins from Candida tropicalis with long acidic domains.

The salt-tolerance gene HAL3 from Saccharomyces cerevisiae encodes a novel regulatory protein (Hal3p) which modulates the expression of the ENA1 sodium-extrusion ATPase (Ferrando et al., Mol. Cell. Biol. vol. 15, 1995, pp. 5470-5481). Hal3p contains an essential acidic domain rich in aspartates at its carboxyl terminus. We have isolated two cross-hybridizing genes from a genomic library of Candida tropicalis. One of the genes (CtHAL3) is a true homolog of HAL3 and it partially complements the salt sensitivity of a S. cerevisiae hal3 mutant. The activity of CtHAL3 was equivalent to that of an open reading frame (YKL088w) identified by genome sequencing of S. cerevisiae and with homology to HAL3. The other cross-hybridizing gene (CtCDC55) is a CDC55 homolog, encoding a protein with an internal acidic domain not present in the S. cerevisiae CDC55 product. Cdc55p is a regulatory subunit of protein phosphatase 2A and CtCDC55 complements the cold sensitivity of a S. cerevisiae cdc55 mutant. The presence of acidic domains in different putative regulatory proteins may suggest a role for this type of domain in molecular interactions.

Amino Acid Sequence↗