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Biomedical subjects

M Ahmed

Publications and source records attributed to M Ahmed.

At least 37 records · Page 2Linked to original sources
PubMed2004

The effect of vitamin D status on the severity of bone disease and on the other features of primary hyperparathyroidism (pHPT) in a vitamin D deficient region.

A clear relationship between vitamin D status and the clinical indices of primary hyperparathyroidism (pHPT) severity has not been convincingly established. We proposed that such a relationship might exist, in so far as vitamin D deficiency could contribute to the severity of metabolic bone disease and promote the growth of the parathyroid tumor. Accordingly, we undertook a retrospective study and analyzed the clinical, biochemical, radiological and histopathological findings in a group of 49 patients who underwent parathyroidectomy at our center. Patients who had skeletal X-rays were grouped, according to their X-ray findings, in group A (19 patients; 45%) if they had severe bone changes, or group B (23 patients; 55%) if they had mild or no bone changes. Patients were also stratified according to their 25-hydroxyvitamin D (25-OHD) levels in tertiles. The 2 groups were compared using Fisher's exact test or analysis of variance as appropriate. Group A patients were younger (p=0.001), had more musculoskeletal symptoms (p=0.0003), and complained more frequently of fatigue (p=0.02). They had higher alkaline phosphatase (AP; p=0.0002), PTH index (p=0.0007), and serum Ca level (p=0.006). There were more patients from the lower and middle vitamin D tertiles and fewer patients from the upper vitamin D tertile in group A (p=0.02). Post-operative severe hypo-calcemia was more prevalent in group A patients (p<0.0001). Resected parathyroid tumors were larger in size in group A patients (p=0.01), and weighed more (p=0.01). There was a positive correlation between the weight of the parathyroid tumor and the PTH index (p=0.002), and AP level (p=0.0007). We concluded that vitamin D deficiency is a contributing factor to both the severity of bone disease and the high activity of parathyroid tumors seen in many patients with pHPT in vitamin D deficient regions.

Adenoma↗
PubMed2004

Differential bone turnover in an angulated fracture model in the rat.

We have developed a simple rat model of angulated tibial fracture which elicits substantial differences in bone formation and resorption within the same bone. In 35 rats the right mid-tibia was manually fractured and fixed with an intramedullary 17-gauge cannula needle. Twenty tibias were fixed in anterior angulation (27 +/- 5 degrees) and 15 in posterior angulation (31 +/- 5 degrees). Serial X-rays were taken over a 12-week period. All fractures healed completely within five weeks. In both groups, bone thickness was already significantly greater on the concave side than on the convex side at week 3 and remained so until the end of the experiment. The thickness on the convex side decreased dramatically within 3 to 5 weeks and gradually thereafter. For morphological analysis of bone mineralization, 3 rats from each group were given calcein and alizarin red injected at different time points up to 14 weeks. Maximum new bone formation was noted within the first 3 weeks. Over the ensuing weeks, new bone formation remained intense on the concave side, but it was virtually absent on the convex side. These results show that angulated fracture deformity reproducibly exhibits differential bone turnover, which can be exploited in research on local regulatory factors. To exemplify the utility of the model, an immunohistochemical study on two local markers was done. Callus tissue of five rats in the anterior angulation group at week 3 post-fracture was stained for the cytokine IL- 1beta, a stimulator of bone resorption, and the neuropeptide CGRP, an inhibitor of resorption, showing clear differences in positive staining between the concave and convex sides. Our in-vivo model offers a means of analyzing morphologically and quantitatively the differential expression and action of factors involved in local bone turnover.

Animals↗
PubMed2004

Acid sphingomyelinase and inhibition by phosphate ion: role of inhibition by phosphatidyl-myo-inositol 3,4,5-triphosphate in oligodendrocyte cell signaling.

There is ample evidence that both acid (ASMase) and neutral (NSMase) sphingomyelinases play a role in cell death so inhibitors of either enzyme could have significant value as protectors against neurodegeneration. We used a fluorogenic sphingomyelinase substrate, 6-hexadecanoylamino-4-methylumbelliferyl-phosphorylcholine, and a [(14)C]choline-labeled sphingomyelin substrate to screen large numbers of phosphocompounds for inhibition of ASMase in extracts of human oligodendroglioma cells (HOG) and neonatal rat oligodendrocytes. Non-competitive inhibition was observed with inorganic phosphate and AMP, which was a more potent inhibitor of ASMase than cyclic AMP, ADP or ATP. However, other nucleotide phosphates, sugar phosphates, nucleotide sugars and glycerol phosphate did not inhibit ASMase. Our key finding was that phosphatidyl-myo-inositol 3,4,5-triphosphate [PtdIns (3,4,5)P(3)] was a much more potent inhibitor of ASMase than lysophosphatidic acid or phosphatidyl-myo-inositol 4,5-diphosphate [PtdIns(4,5)P(2)]. When PtdIns(3,4,5)P(3) was added to cultured cells we observed 50% inhibition of ASMase but no inhibition of other lysosomal hydrolases. After transfection of HOG cells with the tumor supressor phosphatase and tensin homolog protein (PTEN), which hydrolyses PtdIns(3,4,5)P(3) to PtdIns(4,5)P(2), we observed a two-fold increase in ASMase activity. Furthermore, the phosphatidylinositol-3-kinase inhibitor wortmannin (which reduces PtdIns(3,4,5)P(3) levels) also resulted in activation of ASMase. We propose that the small amount of ASMase activity associated with detergent-resistant cell membranes (Rafts) is regulated by PtdIns(3,4,5)P(3) and is most likely involved in receptor clustering and capping.

Adenosine Monophosphate↗
PubMed2004

Combination radiofrequency thermal ablation and adjuvant IV liposomal doxorubicin increases tissue coagulation and intratumoural drug accumulation.

There has been marked interest in minimally-invasive, image-guided radiofrequency (RF) tumour ablation (i.e. coagulating tumour using short duration heating ( < 15 min) by directly applying temperatures > 50 degrees C via needle electrodes) to treat focal liver, renal, breast, bone and lung tumours. In spite of advances in RF technology and improved understanding of tumour biophysiology that now enable experimental treatment of tumours up to 5cm, investigators have been unable to achieve complete ablation in many cases, particularly at the tumour margins and adjacent to blood vessels. One strategy for overcoming these limitations has been to take advantage of complementary interactions between RF thermal ablation and chemotherapy, particularly liposomal doxorubicin preparations, to attempt more complete tumour destruction. This paper will review published laboratory investigations demonstrating that this combined treatment paradigm has the unique potential both to potentiate preferential delivery of cytotoxic agents in liposome vehicles and to maximize the completeness of ablation of a treated tumour. New confirmatory data describing increased tumour destruction with RF ablation combined with different liposome preparations, documenting increased lipid peroxidation and expanding on previously published tumour growth studies is presented. Additionally, early clinical data including a randomized, pilot clinical study on 10 patients with primary and metastatic liver tumours, in which a non-optimized combination of RF ablation and IV liposomal doxorubicin (Doxil) increased the volume of tumour destruction 25-30% compared to RF alone, will also be described in detail.

Antibiotics, Antineoplastic↗
PubMed2004

Sensory hypoinnervation in club foot.

We have compared the density of nerve fibres in the synovium in club foot with that of specimens obtained from the synovium of the hip at operations for developmental dysplasia. The study focused on the sensory neuropeptides substance P; calcitonin gene-related peptide; protein gene product 9.5, a general marker for mature peripheral nerve fibres; and growth associated protein 43, a neuronal marker for new or regenerating nerve fibres. In order to establish whether there might be any inherent difference we analysed the density of calcitonin gene-related peptide-positive nerve fibres in the hip and ankle joints in young rats. Semi-quantitative analysis showed a significant reduction in the number of sensory and mature nerve fibres in the synovium in club foot compared with the control hips. Calcitonin gene-related peptide (CGRP) positive fibres were reduced by 28%, substance P-positive fibres by 36% and protein gene product 9.5-positive fibres by 52% in club foot. The growth associated protein 43-positive fibres also seemed to be less in six samples of club foot. No difference in the density of CGRP-positive nerve fibres was observed in the synovium between ankle and hip joints in rats. The lack of sensory input may be responsible for the fibrosis and soft-tissue contractures associated with idiopathic club foot.

Animals↗
PubMed2004

Road traffic accident among motor vehicle drivers in selected high ways.

To assess the knowledge of the motor vehicle driver about the causes of road traffic accidents. This cross sectional study was conducted among the 107 motor vehicle drivers of selected Bus & Truck terminal & taxi stands of Dhaka city. The study was carried out during April to June 2002 at the Department of Health Promotion & Health Education of NIPSOM. The study showed about 55.1% learned driving from a friend. Out of 107 respondent 20.6% showed very high speed is one of the reason for road traffic accident.39.3% claimed for poor maintenance of roads. Regarding engine/vehicle defect 46.7% said head light defect. Increased earning is one of the reasons of very fast driving 35.5% respondent opined. These may be the reason of accident proneness of the society along with factor like family pressure, job dissatisfaction etc. Majority of the driver who took part in this study used light vehicle 54.2% and the rest 30.8% were heavy and 15% like medium light vehicle. Most of the respondent 67.3% was working as professional over for 3-6 years. 41.1% for 3 and 26.2% for 6 years. There were significant relationship (p < 0.002) between very fast driving and defective road and also engine defect were highly significant association (p < 0.005) with road traffic accident It is revealed that formal education, driving license through Bangladesh road traffic authority without unnecessary botheration, proper implementation of traffic law, training of drivers and increase level of public awareness through mass communication could reduce the road traffic accident

Accident Proneness↗
PubMed2004

Enhancement of pathogenicity of Bacillus thuringiensis by gamma rays.

Studies were conducted on the enhancement of pathogenicity of Bacillus thuringiensis by gamma rays on various species of termites. The results showed that the 72 hrs old and 60 or 70 kr irradiated culture of B. thuringiensis were more pathogenic than the non-irradiated ones. 168 hrs old and 150 kr (1.5 kGy) irradiated B. thuringiensis caused quicker mortality rate than the non-irradiated one as it shows maximum enhancement ratio (1.32).

Animals↗
PubMed2004

Bilateral giant angiomyolipoma of kidneys: a case report and review of literature.

Angiomyolipoma is uncommon benign tumor of the kidney. Bilateral and multiple lesions are associated with tuberous sclerosis. We report a case with bilateral giant angiomyolipomas in a patient who had no other features of tuberous sclerosis. In this case, the involvement of the kidneys was diffuse rather than usual well-circumscribed lesions.

Adult↗
PubMed2003

Bradykinin stimulates respiratory drive by activating pulmonary sympathetic afferents in the rabbit.

We recently identified a vagally mediated excitatory lung reflex by injecting hypertonic saline into the lung parenchyma (Yu J, Zhang JF, and Fletcher EC. J Appl Physiol 85: 1485-1492, 1998). This reflex increased amplitude and burst rate of phrenic (inspiratory) nerve activity and suppressed external oblique abdominal (expiratory) muscle activity. In the present study, we tested the hypothesis that bradykinin may activate extravagal pathways to stimulate breathing by assessing its reflex effects on respiratory drive. Bradykinin (1 microg/kg in 0.1 ml) was injected into the lung parenchyma of anesthetized, open-chest and artificially ventilated rabbits. In most cases, bradykinin increased phrenic amplitude, phrenic burst rate, and expiratory muscle activity. However, a variety of breathing patterns resulted, ranging from hyperpnea and tachypnea to rapid shallow breathing and apnea. Bradykinin acts like hypertonic saline in producing hyperpnea and tachypnea, yet the two agents clearly differ. Bradykinin produced a higher ratio of phrenic amplitude to inspiratory time and had longer latency than hypertonic saline. Although attenuated, bradykinin-induced respiratory responses persisted after vagotomy. We conclude that bradykinin activates multiple afferent pathways in the lung; portions of its respiratory reflexes are extravagal and arise from sympathetic afferents.

Animals↗
PubMed2003

Purification and quantification of opioid peptides in bone and joint tissues--a methodological study in the rat.

The occurrence of methionine-enkephalin-Arg(6)-Phe(7) (MEAP) and dynorphin B (DYNB) representing two main precursors of opioids was analyzed in specimens from rat cortical bone, periosteum, bone marrow and joint tissue by radioimmunoassay (RIA). MEAP and DYNB were extracted in a solution of 4% EDTA in 2 M acetic acid previously proven suitable for extraction of sensory and autonomic neuropeptides in bone and joints. In crude extracts of cortical bone, the immunoreactive (ir) levels of both opioids were under the detection limit of RIA. As for DYNB this also applied to crude extracts of joints and periosteum. Therefore, two purification methods were tested and compared, i.e. reverse phase C 18 and ion exchange chromatography. RIA of the elution fraction disclosed a significant difference between the two methods in terms of recovery, i.e. <5% and 50%, respectively. Thus, purification by ion exchange chromatography prior to RIA appeared to be the most suitable by providing measurable levels of both MEAP and DYNB in all tissues analyzed (highest in bone marrow, lowest in cortical bone). The described method offers a means of quantifying opioid peptides in bone and joints, which may be utilized in the analysis of regulatory mechanisms of nociception, growth and immune responses in different conditions.

Animals↗