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Biomedical subjects

R Ahmad

Publications and source records attributed to R Ahmad.

At least 91 records · Page 5Linked to original sources
PubMed1993

The effects of cobalt-hexammine and cobalt-pentammine cations on the solution structure of calf-thymus DNA. DNA condensation and structural features studied by FTIR difference spectroscopy.

The interaction of calf-thymus DNA with cobalt-hexammine and cobalt-pentammine cations was investigated, in aqueous solution at pH 6-7 with cation/DNA(phosphate) molar ratios r = 1/80, 1/40, 1/20, 1/10, 1/4, 1/2 and 1, using Fourier Transform infrared (FTIR) difference spectroscopy. Correlations between spectral changes, DNA condensation and helical stabilization due to the cation interaction as well as conformational features are established. At a very low cation concentration (r = 1/80), the binding of cobalt-hexammine cation with DNA is through the H-bond formation between cation NH3 groups and the PO2 groups of the backbone, resulting in duplex stability. As the cation concentration increases, hydrogen bonding expands towards guanine N-7 and O-6 atoms. At r > 1/20, DNA condensation occurs with major reduction in the intensity of several DNA in-plane vibrations and that of the phosphate group. The cobalt-pentammine cation binding is via the PO2 groups (directly) at very low metal cation concentration (r = 1/80) and the guanine N-7 and the O-6 groups (indirectly) at higher ratios. At r > 1/10, DNA condensation begins with some degree of direct cation-base binding. No major conformational changes from the B-family structure were observed before and after DNA collapse, in the presence of cobalt-ammine cations.

Animals↗
PubMed1993

A bifurcated endobronchial tube in the management of laryngotracheo-oesophageal cleft repair.

We describe the management of laryngotracheo-oesophageal cleft Type III using a bifurcated endobronchial tube. When the cleft was opened for repair, we were able to obtain effective control of the airway, which is the main problem in this rare congenital anomaly. Commercial tubes are not available, so we made the tube on the day of surgery, immediately before operation.

Anesthesia, Inhalation↗
PubMed1993

Resistance to recombinant human erythropoietin due to aluminium overload and its reversal by low dose desferrioxamine therapy.

Seventeen severely anaemic and transfusion-dependent haemodialysis patients with a haemoglobin less than 7 g/dl were treated with recombinant human erythropoietin (r-Hu-EPO). Aluminium toxicity was diagnosed by a positive desferrioxamine (DFO) test and bone biopsy. Seven out of eight patients without aluminium toxicity responded to r-Hu-EPO therapy. Similarly all patients with aluminium toxicity (n = 4) but pre-treated with standard dose of DFO prior to r-Hu-EPO therapy responded but none of the patients with untreated aluminium toxicity (n = 5) responded to r-Hu-EPO therapy. In order to achieve adequate response in these patients, r-Hu-EPO and DFO had to be given in combination. The dose of desferrioxamine used to reverse r-Hu-EPO resistance was less and also used for a short time. We therefore confirm r-Hu-EPO resistance owing to aluminium overload and report its successful and safe reversal with low dose DFO therapy.

Aluminum↗
PubMed1992

Suppression of the renin-angiotensin-aldosterone axis with erythropoietin therapy by a negative feedback loop.

To investigate the pathophysiology of hypertension in patients receiving recombinant human erythropoietin (rHuEpo) we studied its effects on the renin-aldosterone axis of chronic haemodialysis (HD) patients not receiving antihypertensive drugs. Nine severely anaemic normotensive HD patients received rHuEpo 50 U/kg bodyweight, thrice weekly after each HD. The dose was increased by 25 U/kg bodyweight every 4 weeks to a maximum of 100 U/kg or until an increase of Hb or Hct of 2 g/dl or 7% was achieved. Blood samples were taken after 30 min supine rest and while seated 10 min later after gentle ambulation. Results expressed as mean +/- SEM: therapy in normotensive HD patients by a negative feedback loop, before the development of hypertension.

Adult↗
PubMed1992

Haemodialysis-related porphyria cutanea tarda and treatment by recombinant human erythropoietin.

Haemodialysis-related porphyria cutanea tarda is a rare, but serious and mutilating skin condition, resulting from extremely high plasma porphyrin levels because of their inadequate clearance by haemodialysis. The treatment is very difficult as chloroquine is ineffective and venesection, the conventional treatment of this disease, is not always an option because of anaemia of end-stage renal disease. We report a case of haemodialysis-related porphyria cutanea tarda and her successful management by recombinant human erythropoietin treatment.

Erythropoietin↗
PubMed1992

Phlebotomy for erythropoietin-induced malignant hypertension.

Four patients on regular dialysis treatment whose blood pressure was well controlled, developed malignant hypertension while receiving maintenance recombinant human erythropoietin (r-Hu-EPO). None of these patients had a haematocrit greater than 35% at any stage, and clinically, none had any evidence of fluid overload. Initially, they were all managed by stopping r-Hu-EPO and intensification of antihypertensive therapy. However, none of the patients responded, and venesection of 500 ml of blood was performed in each case with swift and sustained response.

Adult↗
PubMed1992

Effect of fluoride concentrations on overdenture abutments.

This study evaluated the preventive effect of four concentrations of fluoride. Twenty-five extracted caries-free anterior teeth from patients aged 50-70 were prepared as overdenture abutments. The teeth were sectioned mesiodistally into two halves. The teeth were covered with a protective varnish, leaving a window on the root surface and one on the cut dentin of the occlusal. The root halves were randomly divided into 5 groups of 10 specimens and each group received a different 5-minute topical treatment prior to being placed in the demineralizing solution. The treatments were: Group 1: distilled H2O only; Group 2: 100 ppm F-, Group 3: 250 ppm F-, Group 4: 500 ppm F-; and Group 5: 1000 ppm F-. The teeth were cycled for 6 hours in a demineralizing solution and for 17 hours in a fluoride-free remineralizing solution. The cycling was maintained for 10 days. The root halves were sectioned and prepared for histologic examination. The depth of the lesions were measured from standardized photo-micrographs by means of a sonic digitizer. The conclusions were: (1) the lesions on the root surface were too small to be measurable, (2) the lesions on dentin were all of similar depth, and (3) the lesions had bands within them and the width of these bands showed a dose response to the fluoride concentration of the topical application.

Aged↗
PubMed1992

Portal vein thrombosis following sclerotherapy.

We present the case of a woman with idiopathic portal hypertension who underwent sclerotherapy for bleeding esophageal varices. She had a rebleed 27 months after complete eradication of esophageal varices. Endoscopy showed bleeding gastric varices. Ultrasonography, and later splenoportography, revealed a large thrombus in the right branch of the portal vein causing gross dilation of the portal and splenic vein. A proximal splenorenal shunt was done to decompress the portal system and hence gastric varices. Repeat endoscopy 4 weeks after surgery revealed complete disappearance of the gastric varices, while ultrasonography at 38 weeks showed marked decompression of the portal system with complete disappearance of the thrombus from the right branch of the portal vein. No new thrombus formation was seen.

Adult↗
PubMed1991

A spirostanol glycoside from Cestrum nocturnum.

A new steroidal saponin named nocturnoside A has been isolated from the methanolic extract of the fresh leaves of Cestrum nocturnum and has been characterized by 13C NMR spectroscopy to be 3-O-[beta-D-glucopyranosyl(1----3)-beta-D-glucopyranosyl(1----2)-beta-D- glucopyranosyl((3----1)-beta-D-xylopyranosyl)(1----4)-beta-D- galactopyranosyl) (25R)-spirost-5-ene-2 alpha,3 beta-diol.

Carbohydrate Sequence↗
PubMed1991

Low-dose desferrioxamine test for the diagnosis of aluminium-related bone disease in patients on regular haemodialysis.

Bone biopsy in an invasive method of diagnosing aluminium related bone disease (ABD). Toxic side-effects have been reported with the currently used 'high-dose Desferrioxamine (DFO) tests.' A low-dose DFO test was evaluated for the diagnosis of ABD in 28 symptomatic patients (13 male) on regular haemodialysis treatment. DFO 0.5 g diluted in 100 ml of 0.9% sodium chloride was given intravenously during the first 2 h of dialysis. Aluminium estimation before (t1) and 48 h after DFO challenge (t2) were made by DC plasma emission spectrometry. Following the DFO test bone biopsy was performed and the specimen stained for aluminium using soluchrome zurine. The DFO test was considered positive if the t2 concentration was 150 micrograms/l or treble the amount of t1. Nineteen patients (8 male) fell into this group and all except two had ABD. Of the nine remaining patients (5 male) who had a negative DFO test none had ABD. We conclude that ABD can be diagnosed safely in the majority of patients using a low-dose DFO test, thereby avoiding toxic side-effects.

Adult↗
PubMed1991

Delayed recovery of renal function in patients with acute renal failure due to accelerated hypertension.

Five patients with acute renal failure due to accelerated hypertension required regular dialysis treatment for 2-12 months (mean 8.8), before recovering sufficient renal function for dialysis to be withdrawn. Two patients who had prior evidence of chronic renal impairment remained off dialysis for 20 and 27 months before decompensating again to require regular dialysis treatment. Two patients with no prior history of renal disease have remained independent of dialysis for 32 and 48 months. The fifth patient was lost to follow-up after a 7 month dialysis-free period. Delayed recovery of renal function following accelerated hypertension is a distinct possibility and should be considered in such patients before contemplating long term strategies such as renal transplantation.

Acute Kidney Injury↗
PubMed1991

Bronchial reactivity in patients undergoing long-term haemodialysis for chronic renal failure.

Trapping of neutrophils within the lung occurs in patients undergoing haemodialysis and is also a possible mechanism in the pathogenesis of bronchial hyper-responsiveness. Falls in peak expiratory flow rate occur in most dialysis patients, and some develop overt asthmatic symptoms. To see whether these changes in airway function are secondary to increases in bronchial reactivity during haemodialysis, we therefore performed histamine challenge testing in 6 non-asthmatic patients before and after haemodialysis. No change in reactivity was observed, suggesting that haemodialysis does not commonly result in bronchial hyper-reactivity in non-asthmatic individuals.

Adult↗