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Biomedical subjects

R Mohamed

Publications and source records attributed to R Mohamed.

At least 19 recordsLinked to original sources
PubMed2006

Isolated limb infusion with cytotoxic agent for treatment of localized refractory cutaneous T-cell lymphoma.

We described a 57-yr-old male diagnosed with cutaneous T-cell lymphoma that had failed multiple treatment options, as his disease was mainly confined to one limb. We attempted a novel approach in this condition using a technique of intra-arterial limb infusion with cytotoxic agent Melphalan (ILI) which has been proven beneficial in management of localised malignant melanoma. This treatment approach was well tolerated with mild myelosuppression and moderate limb toxicity. However, a significant improvement has been noted in the affected limb. This case demonstrated the successful use of isolated limb infusion with Melphalan in the management of localised cutaneous T-cell lymphoma. However, this result needs to be confirmed and further study is recommended. We are unaware there have been similar cases reported in the literature.

Antineoplastic Agents, Alkylating↗
PubMed2001

Basic fibroblast growth factor corrects proliferative derangement of bone marrow stroma and CD34(+) population following allogeneic stem cell transplantation.

OBJECTIVE: Following stem cell transplantation (SCT), the integrity of the hematopoietic microenvironment is important for the recovery of bone marrow. We studied the effects of basic fibroblast growth factor (bFGF) on the proliferation of clonogenic progenitors and bone marrow stroma from patients receiving cytokine-mobilized allogeneic stem cell transplants (SCT). MATERIALS AND METHODS: Patient bone marrow mononuclear cells were studied at a minimum of 6 months after transplantation. Control and patient samples were divided into two fractions, one to establish the adherent stroma layers (SL) and the other to select for the progenitor population. SL from normal subjects or from patients were supplemented with 0 (control), 2, or 20 ng/mL bFGF in combination with heparan sulfate, and the resulting area of the dish covered by stroma was quantitated in each group. At 3 weeks of culture, a monocellular suspension was prepared by exposing SL to 0.1% trypsin. Cells then were cultured in the colony-forming unit fibroblast (CFU-F) assay, which was supplemented with 0 (control), 2, or 20 ng/mL bFGF. With the second fraction, CD34(+) cells were selected with paramagnetic beads, and 1 x 10(4) cells were incubated in cross-culture studies on preformed SL from patient or control origin (with or without the addition of bFGF). SL adherent CD34(+) cells were covered with agar and cultured for 6 days. Aggregates of >20 cells were scored as blastic colonies (CFU-bl). RESULTS: At 3 weeks of culture, the median surface area of dishes covered by monoloayers from 13 patients was 40% (range 10-50% vs normal 55%, range 30-60%; p = 0.00006) and improved significantly, matching control values, in dishes supplemented with bFGF. Addition of bFGF to stroma monolayers had no effect on the number of CFU-F in both patient and control samples. Selected CD34(+) cells from patients receiving transplants and cultured on normal stroma gave significantly fewer CFU-bl than control samples (median 36, range 3-121 vs 147, range 10-184; p = 0.006), but colony numbers corrected following exposure to bFGF. Normal CD34(+) cells proliferated poorly on stroma from patients (median CFU-bl 37.5, range 6-84; p = 0.02), but also expanded significantly following bFGF supplementation (104, range 6-117; p = 0.001). CONCLUSIONS: Following SCT, poor SL and CD34(+) proliferation can be corrected by addition of bFGF.

Adolescent↗
PubMed2000

Increased apoptosis of bone marrow cells and preserved proliferative capacity of selected progenitors predict for clinical response to anti-inflammatory therapy in myelodysplastic syndromes.

To determine the relation of apoptosis and clonal proliferation in the bone marrow (BM) to the effectiveness of a therapeutic protocol described to downmodulate monokine activity in patients with myelodysplastic syndromes (MDS). Prior to protocol therapy, BM stroma was cultivated and selected CD34(+) cells were studied in stroma and cytokine-dependent clonogenic assays. The TUNEL assay was used to establish the degree of apoptosis occurring in the marrow and CD34(+) population. The effectiveness of oral ciproloxacin 500 mg b. i.d., pentoxifylline 800 mg t.i.d., and dexamathasone 4 mg t.i.d. (CPD) antiinflammatory therapy was correlated with the intensity of cell apoptosis and proliferation of BM progenitor cells. Seventeen patients were studied. Twelve patients (10 transfusion dependent) received therapy for a median of 99 days (range 49-284). Toxicity caused four patients to discontinue the drug combination. Six patients fulfilled response criteria. Four patients became transfusion independent, and 50% reduction in the need for blood transfusions was noted in one patient. Blood parameters of one untransfused patient increased by >30%. Blood count remained unsupported in three patients, even at a median of 12 months after trial discontinuation. Apoptosis of marrow cells and selected CD34(+) progenitors was detected in a median of 49.5% (range 3. 6%-90%) and 10.6% (range 3.6%-100%; p < 0.01), respectively. In patients who responded to therapy, the median apoptosis rate in the bone marrow population was 71%, in contrast to the nonresponder's rate of 13% (p = 0.002). Overall clonogenic growth of selected precursors corresponded significantly with response to CPD protocol (p = 0.004). In some patients with MDS, ineffective hematopoiesis is related to high apoptotic index despite proliferation of the CD34(+) precursors. These patients seem to benefit from CPD cytokine modulatory therapeutic strategy.

Anti-Inflammatory Agents↗
PubMed1999

Cryopreservation of the bone marrow from patients with acute myeloid leukaemia leads to functional abnormalities.

We compared the performance of the stroma (SL) and haematopoietic progenitors before (group A) or following cryopreservation from patients in complete remission (CR) of acute myeloid leukaemia before autologous transplantation (AML) (group B), to similarly treated normal cells (groups A and B). From each group, fibroblastic (F) colony-forming units (CFU) and SL were established and their growth quantitated. Upon confluence of SL, 1 x 10(4)selected CD34+ cells from patient or control samples (of group A and B) were seeded on pre-formed SL from AML or control group A and B layers and adhesive precursors were scored for the formation of blastic (-b1) CFU (>20 cells). Lastly, CD34+ cells from the 4 progenitor sources were cultured in the presence of growth factors and scored for the production of granulocyte-macrophage (GM) CFU, erythroid burst forming units (BFU-E) and mixed colonies (CFU-MIX). In the patients, CFU-F numbers were decreased and by 5 wk SL failed to reach confluence. Group A AML CD34+ progenitors gave a mean of 119.2 (SD 80.4) CFU-bl/10(4) CD34+ cells, but following cryopreservation these numbers declined (83.2, SD 72.71; p = 0.009). Although AML SL prior to cryopreservation supported control CFU-bl adequately, contrary to the norm, this property decreased in group B stroma (mean 50.9/10(4)CD34+ cells, SD 49.33; p =(0.02). Group B AML samples gave significantly fewer CFU-MIX and BFU-E than pre-freezing cultures and than control samples at the first 2-growth factor combination but numbers improved following further addition of cytokines. We conclude that cryopreservation of the bone marrow of patients in CR of AML results in an inhibition of the proliferation of the CD34+ precursors. It also modifies the stroma, leading to reductions in the support of normal clones.

Acute Disease↗
PubMed1999

Contribution of extracranial lymphatics and arachnoid villi to the clearance of a CSF tracer in the rat.

The objective of this study was to determine the relative roles of arachnoid villi and cervical lymphatics in the clearance of a cerebrospinal fluid (CSF) tracer in rats. 125I-labeled human serum albumin (125I-HSA; 100 micrograms) was injected into one lateral ventricle, and an Evans blue dye-rat protein complex was injected intravenously. Arterial blood was sampled for 3 h. Immediately after this, multiple cervical vessels were ligated in the same animals, and plasma recoveries were monitored for a further 3 h after the intracerebroventricular injection of 100 micrograms 131I-HSA. Tracer recovery in plasma at 3 h averaged (%injected dose) 0.697 +/- 0.042 before lymphatic ligation and dropped significantly to 0.357 +/- 0. 060 after ligation. Estimates of the rate constant associated with the transport of the CSF tracer to plasma were also significantly lower after obstruction of cervical lymphatics (from 0.584 +/- 0. 072/h to 0.217 +/- 0.056/h). No significant changes were observed in sham-operated animals. Assuming that the movement of the CSF tracer to plasma in lymph-ligated animals was a result of arachnoid villi clearance, we conclude that arachnoid villi and extracranial lymphatic pathways contributed equally to the clearance of the CSF tracer from the cranial vault.

Animals↗
PubMed1997

Posttransplantation chronic hepatitis in fulminant hepatic failure.

Non-A, non-B or seronegative hepatitis is the leading indication for liver transplantation in patients with fulminant hepatic failure (FHF). We examined protocol annual review liver allograft biopsy specimens in consecutive adult patients transplanted for FHF in an attempt to determine the extent of the histological changes. One hundred eleven biopsy specimens from 41 patients transplanted for fulminant seronegative hepatitis and 34 from a comparison group of 16 patients transplanted for other causes of FHF (11 paracetamol overdose, 2 idiosyncratic drug reaction, 3 Wilson's disease) were available. Specimens were analyzed using standard proforma without knowledge of the original diagnosis. Chronic hepatitis was present in 29 patients (71%) transplanted for fulminant seronegative hepatitis (23 mild, 3 moderate, and 3 severe) compared with 5 patients (31%, all mild) transplanted for other causes of FHF. Twenty-five patients (61%) grafted for seronegative FHF had fibrosis (13 mild, 9 moderate, and 3 severe) in contrast to 4 fibrosis (25%) (all mild) in the comparison group. Excluding early allograft failure because of primary graft nonfunction or vascular complications, six patients with seronegative FHF required retransplantation (2 = chronic rejection; 1 = severe hepatitis with panacinar necrosis, resembling original liver; and 3 = chronic hepatitis with precirrhotic fibrosis and prominent cholestasis of unknown cause). One patient in the comparison group had a second graft (chronic rejection). Posttransplantation chronic hepatitis is more frequent and severe in patients transplanted for seronegative hepatitis. Graft survival may be adversely influenced by the development of chronic hepatitis, which may represent persistent or recurrent disease.

Adolescent↗
PubMed1996

Effect of liver transplantation on QT interval prolongation and autonomic dysfunction in end-stage liver disease.

Both a prolonged QT interval and disturbance of autonomic nervous system function are markers of poor prognosis in patients with diabetes mellitus and alcoholic liver disease (ALD). We studied the prevalence of abnormal QT interval and autonomic nervous system dysfunction in 53 consecutive patients with end-stage liver disease before and after orthotopic liver transplantation (OLT). The maximum QT interval in any lead (QTmax) was assessed by two independent observers. The QTmax, corrected for heart rate (QTcmax) was prolonged in 44 patients (83%), although increased QT dispersion was not found. There was a significant correlation between the QTcmax and Child-Pugh score but not with etiology. Evidence of parasympathetic dysfunction was present in 41 patients (77%), and sympathetic dysfunction was present in 20 patients before OLT. Fifty-two patients underwent transplantation. There was significant improvement in the QTcmax interval after OLT (P < .001); 32 of the 44 patients with prolonged QTcmax ( > 440 milliseconds) improved. Repeat testing was not performed in 7 patients, because they had died or had not undergone transplantation. Indices of parasympathetic function improved in 27 patients after OLT, but no improvement was observed in 8. Improvement in sympathetic dysfunction was observed in 13 of the 19 patients tested. There was no association between QTcmax, autonomic dysfunction, and survival. These results suggest that both prolonged QTcmax and some tests of autonomic function are temporary and arise as a consequence of liver dysfunction.

Adolescent↗
PubMed1995

Alterations in both the hematopoietic microenvironment and the progenitor cell population follow the recovery from myeloablative therapy and bone marrow transplantation.

Experimental data are conflicting, but suggest that after recovery from bone marrow transplantation (BMT), alterations in clonogenic growth and myeloid microenvironment remain. To further characterize this abnormality, light-density marrow cells from 15 patients who were in remission from hematologic malignancies and had undergone BMT (eight allogeneic and seven autologous) were studied in two culture systems after their marrows had reconstituted and were compared to normal. The preconditioning regimen for transplantation was fractionated total-body irradiation (TBI) 12 Gy, cyclophosphamide 120 mg/kg, and total nodal irradiation 6 Gy. Bone marrow mononuclear cells (MNCs) from the patients and controls were divided in two fractions; stromal layers (SL) were prepared from the first fraction. To examine the attributes of the stroma, the petri dish surface covered by the SL was measured after 5 weeks in culture, and representative layers were trypsinized and stained with Sudan black, butirate esterase, and acid and alkaline phosphatases. Stromal layers were also studied for their support in the development of blastic colonies (CFU-BI). From the second fraction, the CD34+ population was selected with immunomagnetic beads, and 1 x 10(4) progenitors from patients or controls were seeded onto the opposite group of preformed stroma. Stroma-adhesive precursors were scored for the formation of CFU-BI (> 20 cells) on day 5 of culture. Nonadherent selected CD34+ cells were recovered by standardized washing and quantitated in clonogenic assays (CFU-GM). The median patient age was 26 (SD 6.65) years, and eight of 15 patients were female. The median infused bone marrow (BM) MNC number was 0.9 x 10(8)/kg (SD 0.31). Grafts were studied at a median of 37 (SD 48.43) months from transplant. SL from the patients failed to reach confluence by 5 weeks (median dish area covered 55.5% [SD 32.38] vs. control: 100% [SD 2.35]; p = 0.0001). BMT CD34+ progenitors gave 19.5 (SD 42.2) CFU-Bl, significantly lower than those from normal individuals (127 [SD 62.2]; p = 0.01) when panned on control stroma, while control CD34+ cells were poorly supported on BMT layers (corrected for surface, median 2.5 [SD 42.2] CFU-Bl; p = 0.039). Although numbers of stroma nonadherent CFU-GM were not different between the groups (median BMT 56 [SD 54.5] vs. control 62.5 [SD 60.76]; p > 0.05), the ratio of CFU-Bl to CFU-GM showed a significant reduction in adherent CD34+ progenitors in BMT patients (median 0.28 [SD 0.44] vs. normal 2.09 [SD 1.3]; p = 0.04). None of the values were significantly different between patients receiving allogeneic or autologous grafts. We conclude that post-BMT stroma is defective and supports CFU-Bl growth poorly. Moreover, we documented a significant reduction within the CD34+ cells in the adherent primitive clonogenic precursors that was compensated by a proportional increase in the more mature CFU-GM.

Adult↗
PubMed1994

Wilson's disease--a review of cases at University Hospital, Kuala Lumpur.

The clinical course of 18 patients with Wilson's disease is reported. There were 13 males and five females of whom one is Malay. The prevalence of Wilson's disease in Malaysia is probably the same as elsewhere. Being a genetic syndrome, the genetic carrier rate for Wilson's disease is probably lower amongst the Malays. At diagnosis, the clinical signs were predominantly hepatic in 10 patients, neurological in five patients with three asymptomatic cases. All patients were commenced on penicillamine but poor compliance was observed in many patients. Two patients defaulted follow-up and seven patients died. Out of the nine surviving patients, only four are well with no clinical symptoms.

Adolescent↗
PubMed1992

Prevalence of antibodies to Pseudomonas pseudomallei exotoxin and whole cell antigens in military personnel in Sabah and Sarawak, Malaysia.

Sera from 420 military personnel serving in Sabah and Sarawk, Malaysia, were tested for antibodies to Pseudomonas pseudomallei exotoxin and whole cell antigens by enzyme-linked immunosorbent assay procedure (ELISA). Data showed that 54.4% of serum samples were positive for antibodies to P. pseudomallei exotoxin and 65.7% were positive for antibodies to the whole cell antigens. Samples gave much lower titers for anti-exotoxin antibodies compared to titers against crude whole cell antigens. The incidence of antibody to exotoxin was highest in the age groups ranging from 26 to 32 years, where the positive rates were higher than 40% and 30% for military personnel serving in Sarawak and Sabah, respectively.

Adolescent↗
PubMed1991

Antibody to Pseudomonas pseudomallei exotoxin in sheep exposed to natural infection.

Specific antibody to Pseudomonas pseudomallei exotoxin was detected in sheep sera exposed to natural infection. An enzyme-linked immunosorbent assay (ELISA) was used. Serum antitoxin was present in 49.3% of sera obtained from a flock of sheep naturally exposed to P. pseudomallei infection. Among these sera, 17.0% gave titers of 10,000. In contrast, serum antitoxin was present in only 6.0% of sera collected from sheep kept on a melioidosis-free farm. The ELISA reactivity of all positive sera could be completely absorbed with purified P. pseudomallei exotoxin. Similarly, preincubation of the exotoxin-coated wells with specific antiserum inhibited the ELISA reactivity of sheep sera. The results indicate that exotoxin is produced in vivo during infection by P. pseudomallei.

Animals↗
PubMed1989

Abnormality in DNA-protein binding in ataxia-telangiectasia nuclear extracts.

Anomalies in DNA replication, repair and recombination in ataxia-telangiectasia (A-T) point to a defect in structure or function of chromatin. In this study we have compared DNA-protein binding in nuclear extracts from control and A-T cells using two assay systems, filter-binding and DNA-accessibility. Interestingly, the extent of DNA protein binding over a range of protein concentration was significantly lower in A-T extracts. In addition the accessibility of the restriction enzyme Eco R1 to protein-bound plasmid was greater when A-T extracts were used. This is in keeping with the reduced binding observed in the filter-binding assay.

Ataxia Telangiectasia↗
PubMed1989

Inhibition of macromolecular synthesis in cultured macrophages by Pseudomonas pseudomallei exotoxin.

Pseudomonas pseudomallei exotoxin was found to be a potent inhibitor of protein and DNA synthesis in cultured macrophages. Inhibition of DNA synthesis occurred at toxin concentrations as low as 1-2 micrograms/ml and inhibition of 3H-thymidine uptake was almost complete at concentrations of 8 micrograms/ml or more. A close correlation between cell damage and inhibition by DNA synthesis was observed. For protein synthesis, inhibition was obtained at much lower doses (0.06-2.0 micrograms/ml) of the toxin. At similar toxin concentrations, DNA synthesis was marginally affected. Further, it was shown that protein synthesis inhibition occurred almost immediately after incubation, reaching its maximal inhibitory effect of 70% after 6 hr. DNA synthesis, however, was minimally affected by a similar toxin concentration even after 10 hr of incubation. The inhibition of macromolecular synthesis in macrophages by P. pseudomallei exotoxin may be relevant to its modulatory effect on the host defense mechanism.

Bacterial Proteins↗
PubMed1988

Reduced DNA topoisomerase II activity in ataxia-telangiectasia cells.

Considerable evidence supports a defect at the level of chromatin structure or recognition of that structure in cells from patients with the human genetic disorder ataxia-telangiectasia. Accordingly, we have investigated the activities of enzymes that alter the topology of DNA in Epstein Barr Virus-transformed lymphoblastoid cells from patients with this syndrome. Reduced activity of DNA topoisomerase II, determined by unknotting of P4 phage DNA, was observed in partially purified extracts from 5 ataxia-telangiectasia cell lines. The levels of enzyme activity was reduced substantially in 4 of these cell lines and to a lesser extent in the other cell line compared to controls. DNA topoisomerase I, assayed by relaxation of supercoiled DNA, was found to be present at comparable levels in both cell types. Reduced activity of topoisomerase II in ataxia-telangiectasia is compatible with the molecular, cellular and clinical changes described in this syndrome.

Ataxia Telangiectasia↗
PubMed1988

Resistance of Pseudomonas pseudomallei to normal human serum bactericidal action.

The effect of human normal serum (HNS) on Pseudomonas pseudomallei was determined. It is apparent from our data that the organism is resistant to the normal serum bactericidal mechanism. Ancillary experiments to confirm this serum-resistant property of P. pseudomallei were done by examining the effects of growth phase conditions of the bacteria (i.e., logarithmic and stationary phases) and different buffered systems used as diluent in our bactericidal assay. Results obtained showed similar degree of resistance to serum bactericidal killing by 5 strains of the organisms tested. The possible survival advantage of serum-resistance property to P. pseudomallei as bacterial pathogens known to invade the blood stream is discussed.

Adult↗
PubMed1987

A defect in DNA topoisomerase II activity in ataxia-telangiectasia cells.

DNA topoisomerase type I and II activities were determined by serial dilution in nuclear extracts from control and ataxia-telangiectasia lymphoblastoid cells. Topoisomerase I activity, assayed by relaxation of supercoiled plasmid DNA, was found to be approximately the same in both cell types. In order to remove interference from topoisomerase I, the activity of topoisomerase II was measured by the unknotting of knotted P4 phage DNA in the presence of ATP. The activity of topoisomerase II was markedly reduced in two ataxia-telangiectasia cell lines, AT2ABR and AT8ABR, compared to controls. This reduction in activity was detected with increasing concentration of protein and in time course experiments at a single protein concentration. A third cell line, AT3ABR, did not have a detectably lower activity of topoisomerase II when assayed under these conditions. The difference in topoisomerase II activity in the ataxia-telangiectasia cell lines examined may reflect to some extent the heterogeneity observed in this syndrome.

Ataxia Telangiectasia↗
PubMed1986

Ataxia-telangiectasia cell extracts confer radioresistant DNA synthesis on control cells.

We have investigated in greater detail the radioresistant DNA synthesis universally observed in cells from patients with ataxia-telangiectasia (A-T). The approach employed in this study was to permeabilize cells with lysolecithin after gamma-irradiation and thus facilitate the introduction of cell extract into these cells. This permeabilization can be reversed by diluting the cells in growth medium. Cells treated in this way show the characteristic inhibition (control cells) or lack of it (A-T cells) after exposure to ionizing radiation. Introduction of A-T cells extracts into control cells prevented the radiation-induced inhibition of DNA synthesis normally observed in these cells. A-T cell extracts did not change the level of radioresistant DNA synthesis in A-T cells. Control cell extracts on the other hand did not influence the pattern of inhibition of DNA synthesis in either cell type. It seems likely that the agent involved is a protein because of its heat lability and sensitivity to trypsin digestion. It has a molecular weight (MW) in the range 20-30 000 D. The development of this assay system for a factor conferring radioresistant DNA synthesis on control cells provides a means of purifying this factor, and ultimately an approach to identifying the gene responsible.

Ataxia Telangiectasia↗