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Biomedical subjects

R Hussain

Publications and source records attributed to R Hussain.

At least 109 records · Page 6Linked to original sources
PubMed1991

Experience of erythropoietin in anemia of end stage renal disease.

Recombinant human erythropoietin 50 units/kg intravenous twice a week was given to 9 anemic patients and end stage renal disease (ESRD) who were undergoing dialysis at the Kidney Centre. Of the total, 8 required no transfusion since the initiation of therapy and their haematocrit increased to approximately 29% or more with the improvement in general condition, sense of well being and exercise tolerance. One patient showed an increase in serum creatinine and two iron deficiency during therapy. In all cases blood pressure remained adequately controlled. No organ dysfunction or any other complication was observed.

Adult↗
PubMed1990

Assurance of consistent peak-velocity measurements with a variety of duplex Doppler instruments.

To assess the need for quality control when measuring peak velocities with Doppler ultrasonography, 17 duplex Doppler instruments from six manufacturers were compared by using a flow phantom that had been calibrated for peak velocities ranging from 23 to 75 cm/sec. Variations in peak-velocity measurements among machines averaged 23% when tested at the same flow rate with a Doppler flow phantom, indicating that scientific articles that document peak velocities for various disease processes should be accompanied by equipment calibration data. Doppler string and flow phantoms were compared, and each was found to have deficiencies. Techniques for quality assurance procedures for Doppler measurements are given that should achieve consistent peak-velocity measurements on serial scans of patients undergoing treatment for vascular conditions.

Blood Flow Velocity↗
PubMed1990

Quantitation of IgM antibodies to the M. leprae synthetic disaccharide can predict early bacterial multiplication in leprosy.

Quantitative enzyme-linked immunosorbent assays detecting IgM to the soluble Mycobacterium leprae crude sonicate (CD75) and the synthetic disaccharide antigen coupled to bovine serum albumin (ND-BSA) were assessed for their ability to determine early infection in families/household contacts of leprosy patients and employees of a leprosy center working in close contact with leprosy patients. Although IgM to both antigens (CD75 and ND-BSA) correlated with the bacterial index (BI) assessed histologically on skin-biopsy samples, the level of IgM antibodies to ND-BSA was a much more sensitive indicator of low bacterial loads. A 4.4-fold difference in antibody levels was observed between the mean group levels of endemic controls (N = 116) and tuberculoid leprosy patients with a BI of 0 (N = 88), increasing to sevenfold in tuberculoid leprosy patients with a BI of 1 (N = 20). Using a statistical cut off with endemic controls (mean + 2 S.D.), household/family contacts showed 30% seropositivity (N = 180) as compared to staff contacts who showed 17% seropositivity (N = 55). Percent seropositivity in family contacts was not related to the type of leprosy of the index case (lepromatous vs. tuberculoid) or the duration of treatment of the index case. Age of the individual in the family contact group had a significant influence on seropositivity. These results support the hypothesis that, in this community, factors other than the viable bacterial load of the index case, such as genetic susceptibility, may be influencing the high rate of seropositivity in family contacts. IgM ND-BSA antibodies seem to provide a good indicator of low antigenic loads and could prove to be useful in detecting subclinical infection before the onset of disease. Follow-up studies of these seropositive individuals are in progress to understand the relationship between seropositivity and the progress of clinical disease.

Antibodies, Bacterial↗
PubMed1989

T-cell recognition of the 18-kilodalton antigen of Mycobacterium leprae.

The 18-kilodalton (kDa) antigen of Mycobacterium leprae was expressed as a fusion protein with a 2-kDa leader peptide and used in proliferation assays with peripheral blood cells. Fifty percent of untreated tuberculoid leprosy patients and 93% of long-term leprosy contacts responded to the recombinant protein in lymphocyte transformation tests. Comparison of the stimulation indices in the two groups showed that the contacts responded more strongly than the tuberculoid leprosy patients. Seventy percent of Mycobacterium bovis BCG-vaccinated European donors responded, although with low stimulation indices. The isolation of 18-kDa antigen-responsive T-cell lines from a BCG-vaccinated British donor confirmed that the 18-kDa antigen contains at least one cross-reactive epitope. These results indicate that the 18-kDa protein is an important antigen in the immune response to leprosy.

Amino Acid Sequence↗
PubMed1989

Cellular immune responses of leprosy contacts to fractionated Mycobacterium leprae antigens.

Antigens of armadillo-derived Mycobacterium leprae sonic extract were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotted onto a nitrocellulose membrane, and the unstained blot was converted into 20 fractions of antigen-bearing particles. These were tested in cellular proliferation assays, and reproducible results were obtained between batches of fractions. Peripheral blood mononuclear cells from healthy contacts of leprosy patients (presumed to have protective immunity) were tested with the fractions to investigate which antigens they recognized. A small group of tuberculoid leprosy patients were also tested. Both groups showed a wide range of responses. Almost every fraction stimulated proliferation with at least one donor, yet none was clearly immunodominant or inhibitory in either group. Thus, protective immunity did not appear to be associated with proliferation caused by any single fraction.

Antigens, Bacterial↗
PubMed1989

Quantitative antibody ELISA for leprosy.

Quantitative enzyme-linked immunosorbent assays (ELISAs) were established to measure IgM and IgG antibody levels to soluble Mycobacterium leprae sonicate (CD60) and to the synthetic disaccharide antigen based on the phenolic glycolipid-I antigen of M. leprae coupled to bovine serum albumin in 46 leprosy patients. Separate reference pools for IgM and IgG antibody were established. The reciprocal of the antibody titer was expressed as the number of arbitrary units in the reference pools which was subsequently used as the calibrator for assessment of units in individual test sera. The dose-response relationship for both IgM and IgG was highly specific and reproducible for both isotypes, as indicated by the intra- and inter-assay coefficients of variation. The distribution of antibody levels are in general agreement with the results from previous studies against different M. leprae antigens. The lepromatous group showed 10- to 100-fold higher IgM antibodies to both the soluble sonicate antigen and the disaccharide as compared to the control group. Very low to undetectable levels of IgM antibodies were observed in the tuberculoid group of leprosy patients. IgG antibodies, on the other hand, were not only present but showed considerable overlap with the lepromatous patient group. Optimized ELISAs, such as the one described in this study, would allow one to address issues such as antibody changes with treatment, antigen clearance, and correlation with other immune parameters associated with disease pathogenesis and protection.

Antibodies, Bacterial↗
PubMed1988

The structure of phenindamine base and salts in the solute state.

High-field NMR (13C and 1H) studies of phenindamine are reported which establish structures of the free base and some of its salts in the solute condition. The base exists as a mixture of two isomers which differ in double bond position (9-9a or 4a-9a) while most salts are 9-9a isomers. The clinically employed tartrate (Thephorin) is exceptional in being a 4a-9a ene. Salts of both double bond type exist in solution as mixtures of protonated epimers of variable epimeric ratio, that of the tartrate in D2O being approximately 1:1.

Chemical Phenomena↗
PubMed1987

IgG antibody subclasses in human filariasis. Differential subclass recognition of parasite antigens correlates with different clinical manifestations of infection.

The four subclasses of IgG are distinct in structure, function, and degree of participation in the antibody response to complex antigens. Looking for differential responsiveness of potential pathogenetic significance, we have analyzed both quantitatively and qualitatively the filaria-specific IgG subclass responses of 20 patients with lymphatic filariasis presenting either with chronic lymphatic obstructive pathology and elephantiasis (CP) or with asymptomatic microfilaremia (MF). Subclass-specific monoclonal antibodies were used in an enzyme-linked immunosorbent assay to study IgG filarial antibodies quantitatively and in immunoblot analyses to determine qualitatively the subclass antibody specificities. Quantitatively, the most significant differences among patient groups were in levels of IgG4, which were more than 17 times higher in MF patients (geometric mean, 64.7 micrograms/ml) than in those with CP (mean, 3.7 micrograms/ml). When qualitative analyses were done on the same sera, major differences were noted, particularly in the recognition profiles of the IgG1, IgG3, and IgG4 responses. IgG1 and IgG3 responses to antigens were seen especially to antigens with m.w. greater than 68,000 in all patients with elephantiasis, whereas MF patients showed most of their reactivity to antigens less than 68,000. For IgG4, the MF patients showed prominent recognition of antigens throughout the entire range of m.w., whereas those with CP had very little IgG4 recognition of antigens of any m.w. Interestingly, this relationship was essentially reversed in the IgG3 antibody responses (especially to antigens greater than 68,000) and, to a lesser extent, the IgG1 responses. These findings demonstrate correlations of potential cause/effect significance between IgG4 antibody responsiveness and the immunomodulated asymptomatic MF form of clinical filariasis and between IgG3/IgG1 antibody responsiveness and the clinical presentation of CP.

Adult↗
PubMed1987

The clinical and immunologic responses of normal human volunteers to low dose hookworm (Necator americanus) infection.

Five normal human volunteers were exposed to approximately 50 infective larvae of Necator americanus and were observed for the development of clinical signs or symptoms and for changes in blood eosinophil levels, IgG antibody titers, total and parasite-specific IgE, and lymphocyte blastogenic responses for 6-10 weeks. Bronchoalveolar lavage was performed on four subjects prior to infection and at times when larval migration through the pulmonary tree was likely. Eggs were demonstrated in the stools of four volunteers who remained untreated for more than 6 weeks; one volunteer had to be treated at day 40 because of severe gastrointestinal symptoms. All others also complained of abdominal pain and flatulence between days 35-40. All volunteers developed marked blood eosinophilia which peaked between days 38-64 and ranged from 1,350-3,828 eosinophils/mm3. Small increases in total and parasite-specific IgE and IgG were noted in some volunteers. One volunteer showed a significant lymphocyte blastogenic response. With the exception of mucosal erythema, bronchoalveolar lavage results were unremarkable. Our data indicate that a single small inoculum of hookworm larvae is capable of producing significant transient gastrointestinal morbidity and marked blood eosinophilia but does not induce other prominent T cell- and B cell-dependent immune responses.

Adult↗
PubMed1986

Use of monoclonal antibodies to quantify subclasses of human IgG. II. Enzyme immunoassay to define antigen specific (anti-filarial) IgG subclass antibodies.

Because of their single epitope specificity, monoclonal antibodies (Mcabs) may perform with different levels of efficiency in immunoassays depending on the accessibility of the particular epitope recognized. In order to develop assays capable of detecting specific antibodies of each of the four human IgG subclasses, we have evaluated by ELISA the performance characteristics of a panel of Mcabs raised to the subclass proteins. At least one Mcab to each of the four subclasses was identified that was specific in its ability to capture its own relevant IgG subclass without any associated light chain, allotype or isoallotype activity and that was able to function effectively as a probe in an optimized, quantitative ELISA. When IgG subclass antibodies were measured in sera from patients with filariasis using specific filarial antigen, the sensitivities of each subclass antibody assay varied; for IgG1 and IgG4 antibodies the sensitivity of detection was 50 ng/ml and for IgG2 and IgG3, 10 ng/ml. The potency of the Mcab, determined by its titration for use as a probe, did not correlate with the sensitivity of the assay. These Mcabs were also capable of defining IgG subclass antibody responses qualitatively in immunoblot analyses with little or no non-specific binding. The availability of such highly characterized Mcabs for use in quantitative and qualitative definition of specific IgG subclass antibody responses should greatly improve our detection and subsequent understanding of the role of these IgG subclasses in various disease states.

Antibodies↗
PubMed1986

Use of monoclonal antibodies to quantify subclasses of human IgG. I. Development of two-site immunoenzymometric assays for total IgG subclass determinations.

Dissection of the IgG antibody response into its subclass components has been difficult largely because of the lack of adequate supplies of specific reagents. The development of monoclonal antibodies (Mcab) promises to overcome this problem, but the use of such antibodies has certain inherent problems. It has been shown recently that Mcabs which were avid, potent and specific for well defined epitopes may partially or completely lose their activity depending on the assay system in which they were used. In order to identify Mcabs that would be specific and useful as capture antibodies in a simple two-site enzymometric assay, a panel of 18 Mcabs was screened and one Mcab to each of the four IgG subclasses was identified for quantitation of subclass levels in human serum.

Antibodies, Monoclonal↗
PubMed1986

Time-resolved X-ray diffraction studies of the B in equilibrium D structural transition in the DNA double helix.

Because of the relation between topology and function, there has been much interest in the structural transitions of the various conformations of DNA polymers. The x-ray fiber diffraction analysis system at the Daresbury Synchrotron Radiation Source was used to study the reversible transition between the B and D forms of the synthetic DNA poly[d(A-T)].poly[d(A-T)]. The gradual progression of conformations between these two forms indicates that the DNA double helix does not undergo a change of handedness during this transition.

DNA↗
PubMed1986

IgE responses in human filariasis. IV. Parallel antigen recognition by IgE and IgG4 subclass antibodies.

Immediate hypersensitivity responses are highly modulated in filariasis, and with few exceptions, the majority of infected individuals do not develop allergic manifestations. One possible mechanism for this modulated responsiveness could involve the high levels of IgG "blocking antibodies" shown to be present in filariasis and other chronic helminth infections. When immunoblot analyses were done to analyze the immunoglobulin (Ig) E and IgG antibody responses of patients simultaneously, remarkable similarity in the patterns of antigen binding was observed. In this study, the four IgG subclasses were analyzed in a similar manner in relation to IgE. The results clearly demonstrate that IgG4 was primarily responsible for this "parallel" recognition that was seen previously between IgG and IgE antibodies. These results lend additional support to the possibility that IgG4 may play an important role in modulating IgE-mediated allergic responses in vivo.

Adolescent↗
PubMed1986

Identification of circulating parasite antigen in patients with bancroftian filariasis.

Because many cases of lymphatic filariasis cannot be diagnosed either clinically or by immunodiagnostic test based on antibody detection, recent efforts have been more directed towards developing methods for detecting parasite antigen in the blood or urine. Using a solid phase (Sepharose 4B) two-site immunoradiometric assay (IRMA) employing hyperimmune rabbit antifilarial antisera, we have previously shown (Hamilton et al., 1984) that essentially all cases of patent (ie. microfilaremic) infection in patients with bancroftian filariasis can be detected by this semi-quantitative assay as well as some individuals with amicrofilaremic (i.e., 'cryptic') infection. The present communication reports the results of studies that identify a prominent circulating antigen detected by this IRMA in sera from patients with microfilaremia. The antigen was eluted from Sepharose-bound rabbit polyclonal antiserum that had been reacted with known antigen positive sera. It was run in SDS-PAGE, blotted to nitrocellulose paper and identified autoradiographically using 125I-labelled rabbit antifilarial antiserum. Its high molecular weight (approximately 200 kD), stability to acid and boiling, and sensitivity to pronase and periodate suggest its being a glycoprotein. Isolation of this antigen will permit the development of specific reagents (such as monoclonal antibodies) which should enhance both the sensitivity and utility of the currently available antigen detection systems.

Adolescent↗
PubMed1985

Comparison of immunoblot and immunoprecipitation methods for analyzing cross-reactive antibodies to filarial antigens.

Qualitative analysis of antibody responses in helminth infections is essential not only for developing better immunodiagnostic antigens but also for understanding immune recognition and its relevance to immunopathogenesis and protective immunity. In this study 2 qualitative analytic methods (immunoprecipitation and immunoblotting) were compared for the ability to define the extent of cross-reactivity in the serum antibodies from patients with various forms of filariasis (caused by Brugia malayi, Wuchereria bancrofti, Loa loa and Tetrapetalonema perstans) or other non filarial helminth infections (ascariasis, strongyloidiasis, trichinosis, echinococcosis and schistosomiasis). Our results demonstrated that the spectrum of cross-reactive antibodies identified by immunoprecipitation was limited because of the selective radiolabeling of particular filarial antigens, while immunoblotting was able to detect a much wider range of cross-reactive antibodies in both filarial and non-filarial serum pools. In addition, this latter procedure was easily adapted for simultaneous analysis of different antibody isotopes (e.g., IgE and IgG) to the same antigens in individual sera. Immunoblotting thus provides an excellent tool for studying the spectrum of antibodies of different isotypes evoked during helminth infections and for discriminating between those responses that are species-specific and those that are cross-reactive.

Antibodies↗
PubMed1985

Filarial parasite-specific T cell lines: induction of IgE synthesis.

The development of T lymphocyte lines and clones of defined specificity has provided an important method for investigating T cell recognition of foreign antigens as well as T cell influence on B cell activity. We described previously a parasite-specific T cell line (TCL) derived from a patient with a naturally acquired filarial infection and elevated levels of serum IgE. The TCL is composed of Leu-3+ helper cells and is maintained independent of exogenous growth factors. In the present study, we used these T cells to investigate their immunoregulatory function on the in vitro IgE response. These parasite-specific T cells can provide isotype-specific help for antigen-induced IgE production by B cells in vitro. Autologous T cells profoundly suppress IgE production in a concentration-dependent manner. Furthermore, soluble factors generated from these filarial-specific TCL after antigen stimulation are able to induce the production of IgE in normal human cells not already synthesizing measurable amounts of IgE in vitro. Partial physicochemical characterization of this factor has shown that it is heat labile, has an m.w. between 10,000 and 30,000 M(r), and is a mannose-rich glycoprotein.

Absorption↗
PubMed1985

Prominence of IgG4 in the IgG antibody response to human filariasis.

The four subclasses of IgG are distinct in structure, function, and degree of participation in the response to complex antigens. Because these differences could have important pathogenetic significance, we analyzed total and filaria antigen-specific IgG of each subclass in 31 patients with different clinical manifestations of Bancroftian filariasis. Subclass-specific, affinity-purified polyclonal antibodies were prepared from antisera raised in sheep immunized with purified myeloma IgG subclass proteins. These were radiolabeled (125I) and used to detect IgG1, IgG2, IgG3, and IgG4 in solid phase radioimmunoassays (SPRIA). The antigen-specific SPRIA was used with Brugia malayi adult antigen (BmA) bound to Sepharose 4B, whereas measurement of total IgG subclass levels in each serum was with goat anti-human IgG bound to the solid matrix. Quantification of total subclass levels was by reference to the WHO 67/97 standard, and of specific subclass antibody by development of standards from high titered sera. Although there were modest increases of total IgG1 and IgG2 in patients with filariasis compared with normals, the most striking finding was the extreme elevation of both total, and particularly, filaria antigen-specific IgG4. These elevations were seen for essentially all patients, but the relative proportion of the total IgG antibody response accounted for by IgG4 antibody was particularly marked (up to 95%) in patients with either microfilaremia or the tropical pulmonary eosinophilia syndrome. The meaning of this special prominence of the IgG4 antibody response to filarial infection is not yet clear, but the question of whether these antibodies play a role in immediate hypersensitivity reactions as either reagins or blocking antibodies is being investigated for its potential pathogenetic significance.

Absorption↗