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Biomedical subjects

Y Khan

Publications and source records attributed to Y Khan.

At least 19 recordsLinked to original sources
PubMed2005

The brachial artery-basilic vein arterio-venous fistula in vascular access for haemodialysis--a review paper.

AIMS: To review the available literature regarding patency rates and complications of the brachial-basilic arterio-venous fistula (BBAVF) and to discuss this with relation to the current dialysis outcomes quality initiative guidelines. METHODS: An internet based literature search was performed using Pubmed, Medline and Medscape databases to identify all published reports of the BBAVF in the English language from which the full articles were retrieved and cross-referenced. RESULTS: Of 136 papers identified, 28 were directly relevant to this review including four prospective studies (one randomised trial, three non-randomised trials) and 24 retrospective studies. First described by Dagher in 1976, the BBAVF has since been modified to a two-stage procedure with initial fistula formation followed by superficialisation of the basilic vein 6 weeks later. It can be formed successfully in 95% of cases. Mean 1-year primary and secondary patency rates were 72 and 74.6%, respectively. Complications included haematoma (3.8%), stenosis (2.3%), thrombosis (9.7%), transient arm oedema (3.7%), steal syndrome (2.9%) and aneurysm/pseudoaneurysm formation (1.9%). The BBAVF had a lower rate of infection than prosthetic fistulas (3.6 vs. 16%). CONCLUSIONS: The BBAVF has good primary and secondary patency rates with lower rates of infection than prosthetic fistulas making it a preferred secondary access procedure.

Arteriovenous Shunt, Surgical↗
PubMed2004

Tissue-engineered bone formation in vivo using a novel sintered polymeric microsphere matrix.

We have evaluated in vivo a novel, polymer-based, matrix for tissue engineering of bone. A segmental defect of 15 mm was created in the ulna of New Zealand white rabbits to determine the regenerative properties of a porous polylactide-co-glycolide matrix alone and in combination with autogenous marrow and/or the osteoinductive protein, BMP-7. In this study four implant groups were used: 1) matrix alone; 2) matrix with autogenous marrow; 3) matrix with 20 microg of BMP-7; and 4) matrix with 20 microg of BMP-7 and autogenous marrow. The results showed that the degree of bone formation was dependent on the properties of the graft material. The osteoconductive sintered matrix structure showed significant formation of bone at the implant-bone interface. The addition of autogenous marrow increased the penetration of new bone further into the central area of the matrix and also increased the degree of revascularisation. The osteoinductive growth factor BMP-7 induced penetration of new bone throughout the entire structure of the implant. The most effective treatment was with the combination of marrow cells and osteoinductive BMP-7.

Animals↗
PubMed2003

Extracellular matrix production by human osteoblasts cultured on biodegradable polymers applicable for tissue engineering.

The nature of the extracellular matrix (ECM) is crucial in regulating cell functions via cell-matrix interactions, cytoskeletal organization, and integrin-mediated signaling. In bone, the ECM is composed of proteins such as collagen (CO), fibronectin (FN), laminin (LM), vitronectin (VN), osteopontin (OP) and osteonectin (ON). For bone tissue engineering, the ECM should also be considered in terms of its function in mediating cell adhesion to biomaterials. This study examined ECM production, cytoskeletal organization, and adhesion of primary human osteoblastic cells on biodegradable matrices applicable for tissue engineering, namely polylactic-co-glycolic acid 50:50 (PLAGA) and polylactic acid (PLA). We hypothesized that the osteocompatible, biodegradable polymer surfaces promote the production of bone-specific ECM proteins in a manner dependent on polymer composition. We first examined whether the PLAGA and PLA matrices could support human osteoblastic cell growth by measuring cell adhesion at 3, 6 and 12h post-plating. Adhesion on PLAGA was consistently higher than on PLA throughout the duration of the experiment, and comparable to tissue culture polystyrene (TCPS). ECM components, including CO, FN, LM, ON, OP and VN, produced on the surface of the polymers were quantified by ELISA and localized by immunofluorescence staining. All of these proteins were present at significantly higher levels on PLAGA compared to PLA or TCPS surfaces. On PLAGA, OP and ON were the most abundant ECM components, followed by CO, FN, VN and LN. Immunofluorescence revealed an extracellular distribution for CO and FN, whereas OP and ON were found both intracellularly as well as extracellularly on the polymer. In addition, the actin cytoskeletal network was more extensive in osteoblasts cultured on PLAGA than on PLA or TCPS. In summary, we found that osteoblasts plated on PLAGA adhered better to the substrate, produced higher levels of ECM molecules, and showed greater cytoskeletal organization than on PLA and TCPS. We propose that this difference in ECM composition is functionally related to the enhanced cell adhesion observed on PLAGA. There is initial evidence that specific composition of the PLAGA polymer favors the ECM. Future studies will seek to optimize ECM production on these matrices for bone tissue engineering applications.

Biodegradation, Environmental↗
PubMed2003

Respiratory problems in children with neurological impairment.

Children with severe neurological impairment have a high incidence of respiratory problems which are multifactorial and may be related to or dependent on the underlying disability. In addition, common respiratory conditions such as asthma will be represented in this group as in the general paediatric population. In order to maximise quality of life and reduce morbidity and mortality, each child should be carefully assessed and treated, making adjustments where necessary in the treatment regime to take account of the disability.

Asthma↗
PubMed2001

A novel amorphous calcium phosphate polymer ceramic for bone repair: I. Synthesis and characterization.

Traditional materials for bone repair or replacements such as autografts and allografts have a limited supply and other complications. Thus, alternative materials need to be explored. Three-dimensional, porous composites prepared from bioresorbable polymers and hydroxyapatite or other calcium phosphate ceramics are promising materials for the repair or replacement of diseased or damaged bone. However, in many cases the ceramic component of these composites is crystalline in nature, while bone apatite is made of a poorly crystalline, carbonated phosphate system. In this study, we synthesized a noncrystalline, carbonated calcium phosphate ceramic by carrying out the reaction within bioresorbable PLAGA microspheres using a modified emulsion/solvent evaporation technique, making each individual microsphere a composite. Sintering the composite microspheres together yielded a bioresorbable, porous, 3-dimensional scaffold that may be ideal for tissue ingrowth, making this composite scaffold potentially suitable for bone repair applications.

Bone Substitutes↗
PubMed2001

Tuberculosis in the belly: a review of forty-six cases involving the gastrointestinal tract and peritoneum.

BACKGROUND: Abdominal tuberculosis has varied presentation and can be confused with other conditions. METHODS: We report our experience with 46 patients. Charts of patients managed during 1984-97 were reviewed. RESULTS: Fifty-two percent were women and mean age was 46 years. Presenting symptoms were as follows: fever 70%; abdominal pain 70%; weight loss 68%; abdominal swelling 67%; change in bowel habit 39%; anorexia 30%; and sweating 30%. Common physical signs were as follows: fever 73%; ascites 61%; abdominal mass 13%; and doughy abdomen 9%. Thirty percent of patients either gave past history of TB or presented with active TB of other sites. TB skin test was positive in only 27% of patients. CT scans of abdomen were abnormal in 80%, showing ascites, peritoneal lesions or enlarged nodes. Ascitic fluid was diagnostic for TB on smear/culture in 33%. Peritoneal biopsy was performed by laparoscopy or laparotomy in 61%. It was positive for ganulomas in 97% and for smear/culture in 68%. Forty-two patients recovered after receiving anti-TB therapy for 9-12 months. Four patients died. One died within 1 month of initiation of therapy due to extensive TB, and death in the other 3 was due to unrelated causes. CONCLUSION: Abdominal TB should be suspected in patients with fever, abdominal pain and ascites. This condition carries good prognosis if promptly diagnosed and treated.

Adolescent↗
PubMed2001

Mortality statistics in South Karachi.

OBJECTIVE: To create an awareness amongst the medical profession in Pakistan about the importance of mortality statistics in epidemiological research and its correlation with the cause of death statement. METHODS: The original death registration forms and the statistical information, compiled into a database by the District Municipal Corporation, South Karachi, for the years 1995 to 1998 were evaluated. RESULTS: The total number of deaths reported from the District Municipal Corporation, South Karachi, for the years 1995 to 1998 were 7480. Of these 28% were females and 72% were males. The adult deaths were 99% whereas childhood deaths were 1%. The leading cause of death was cardiovascular disease (33%). However 49% of the deaths were classified as caused by non-specific or ill-defined conditions. CONCLUSION: The maintenance of records and compilation of death registry data by the District Municipal Corporation, South Karachi is satisfactory. The coverage of deaths in the years 1995 to 1998 was reasonable. The degree of precision of the age statement was moderately good as the 'National Identity Card' copy accompanied each adult death notification. As the cause of death statement was non-specific in 49% of the deaths, this data will have limited use in research or health planning. It is therefore essential to emphasize the importance of the death certification process to the medical profession.

Cause of Death↗
PubMed1998

Childhood bacterial meningitis in Saudi Arabia.

This study analysed the bacterial aetiology and outcome of childhood meningitis observed over an 11-year period. Charts of 70 children with this diagnosis were reviewed. Three children were under 1 month of age, five were between 1 and 3 months and 60 were between 3 months and 5 years. The remaining two were over 5 years. There were 36 females and 34 males. The presenting symptoms in decreasing order of frequency were fever 86%, vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%. Aetiological organisms were as follows: Haemophilus influenzae 66%, Streptococcus pneumoniae 24%, Neisseria meningitidis 4%, Group B Streptococci 4%, and Staphylococcus aureus 2%. All H. influenzae isolates except one were sensitive to ampicillin. None of the S. pneumoniae isolates were resistant to penicillin. Complications occurred in 26% of the patients and included subdural effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay 9%, hydrocephalus 6% and motor deficit 30%. One patient died. Among H. influenzae cases, one of the 15 patients treated with steroids developed hearing loss. In contrast, four out of 31 who did not receive steroid therapy suffered from hearing loss. Haemophilus influenzae type b is the predominant cause of childhood bacterial meningitis in Saudi Arabia. Universal H. influenzae type b vaccination for children is highly recommended.

Child↗
PubMed1997

Uncoupling of GABA(A) and benzodiazepine receptor binding activity in the hippocampal formation of schizophrenic brain.

A recent postmortem study has reported that there is a widespread upregulation of GABA(A) receptor binding activity throughout most subregions of the hippocampal formation of schizophrenic brain. The current study has been undertaken to determine whether the benzodiazepine (BZ) receptor, which is a component of the GABA(A) receptor complex, may also be upregulated in schizophrenics. Using a low-resolution film autoradiographic technique to localize [3H]flunitrazepam binding, the subregional and laminar distribution of specific BZ receptor binding was found to parallel that of the GABA(A) site, except in the area dentata where BZ binding was approximately 73% higher in the outer molecular layer. When BZ receptor binding was compared in the same normal control (n = 15) and schizophrenic (n = 8) cases in which the GABA(A) receptor was analyzed, there were very few differences noted between the two groups, except for small, though significant, increases in the stratum oriens of CA3 (30%), the subiculum (20-30%) and the presubiculum (15-20%) of the patient group. These latter increases overlapped with the subregions and laminae in schizophrenics showing the most marked increases of GABA(A) receptor binding. Using a high-resolution technique to evaluate specific BZ receptor binding on different neuronal subtypes, no difference was observed on either pyramidal or nonpyramidal neurons of sector CA3 where GABA(A) receptor activity had been found to be significantly increased on the latter neuronal subtype. The potential confounding effects of age, postmortem interval and exposure to either benzodiazepine or neuroleptic drugs do not account for the lack of marked differences in BZ receptor binding in the schizophrenic group. Taken together, the results of this study are consistent with the possibility that defective GABAergic integration in schizophrenia may be associated with an uncoupling in the regulation of the GABA(A) and BZ receptors.

Case-Control Studies↗
PubMed1997

Assessment of the postoperative visit after routine inguinal hernia repair: a prospective randomized trial.

Treatment of pediatric patients undergoing routine inguinal hernia repair usually includes a postoperative clinic visit. We prospectively assessed the necessity for the traditional postoperative visit. One hundred patients undergoing a routine inguinal hernia repair were randomly selected to receive either a follow-up visit at 4 weeks or a detailed instruction sheet and no follow-up visit. Parents were given a telephone questionnaire to determine overall satisfaction with their child's care and the usefulness of the follow-up visit or instruction sheet. Forty-seven of 50 parents of patients randomly assigned to a follow-up clinic visit (FU) and all 50 parents in the no follow-up group (NFU) completed the questionnaire. Sixty-eight percent of the FU group found the follow-up visit "helpful" and 59% found it "necessary." Fifty-six percent would have been satisfied with a telephone call instead of a visit. In the NFU group only 4% thought a follow-up visit would have been "helpful" and 4% thought a visit was "necessary." Ninety-six percent found the postoperative instruction sheet "helpful." There was no difference between groups in overall satisfaction with the care received as assessed on a 5-point scale (4.7 FU group v 4.7 NFU group). Accurate postoperative instruction and open access to follow-up when required is as effective as the traditional postoperative clinic visit for patients who have undergone routine inguinal hernia repair.

Appointments and Schedules↗
PubMed1997

A double blind cross over trial of theophylline prophylaxis for sleep hypoxaemia in Duchenne muscular dystrophy.

Twelve non-ambulant patients with Duchenne muscular dystrophy underwent a double-blind cross-over clinical trial of slow-release theophylline for the treatment of asymptomatic sleep hypoxaemia. Eight channel polysomnography was carried out at home to identify patients with sleep hypoxaemia and this was repeated whilst on the theophylline and placebo limbs of the trial. The trial design was effective in maintaining blinding but theophylline adversely affected sleep quality and sleep hypoxaemia. The overnight oxygen saturation was further reduced whilst on theophylline with reduced sleep efficiency and increased sleep fragmentation. This trial lends further evidence towards the theory that the underlying aetiology of sleep hypoxaemia is upper airway obstruction.

Adolescent↗
PubMed1997

Diaphragm thickness and inspiratory strength in patients with Duchenne muscular dystrophy.

BACKGROUND: There is little information on the morphometric characteristics of the diaphragm in patients with Duchenne muscular dystrophy. METHODS: The thickness of the diaphragm was measured at the zone of apposition using B mode ultrasonography in 10 boys with Duchenne muscular dystrophy of mean (SD) age 10.3 (1.3) years and 12 normal controls of mean (SD) age 11.3 (2.0) years during relaxation (DiTrelax) and during maximum effort inspiratory manoeuvres (DiTPimax) at functional residual capacity. RESULTS: DiTrelax was greater in the patients with Duchenne muscular dystrophy (1.74 (0.21) mm) than in controls (1.48 (0.20) mm), mean difference (95% CI) 0.26 (0.08 to 0.44), despite considerable impairment of maximum effort inspiratory mouth pressure (Pimax) (patients with Duchenne muscular dystrophy -37 (8) cm H2O, controls -80 (33) cm H2O), mean difference (95% CI) 43 (65 to 20). During a Pimax manoeuvre, compared with measurements taken during relaxation, the diaphragm thickened 1.6 times in patients with Duchenne muscular dystrophy and 2.3 times in controls (DiTPimax 2.62 (0.7) mm and 3.5 (0.85) mm, respectively), mean difference (95% CI) -0.88 (-1.58 to -0.18). CONCLUSIONS: Resting diaphragm thickness is increased in young patients with Duchenne muscular dystrophy with impaired respiratory muscle force. This finding could be analogous to the pseudo-hypertrophy that is observed in some limb muscle groups.

Child↗
PubMed1997

Is selective neck dissection sufficient treatment for the N0/Np+ neck?

OBJECTIVE: The purpose of this study was to evaluate the therapeutic role of selective neck dissection performed electively in the N0 patient. METHOD: Fifty-four patients with squamous cell carcinoma of the oral cavity, pharynx, and larynx, without clinical evidence of lymph node metastases, underwent 72 selective neck dissections over a 6-year period. The preoperative tumour and patient data were recorded in all patients. Mean follow-up was 59 months. Outcome data pertaining to pathologic nodal status, tumour recurrence, and survival were recorded on all patients. RESULTS: Eighty-one percent of patients were histologically and clinically node negative. Seven percent of N0/Np0 patients failed in the neck compared to 50% of patients with occult nodal metastases (N0/Np+). Salvage treatment following nodal recurrence was successful in only one patient. CONCLUSION: Selective neck dissection does not compromise survival and may minimize surgical morbidity in the N0/Np+ population.

Adult↗
PubMed1996

Differences in the subregional and cellular distribution of GABAA receptor binding in the hippocampal formation of schizophrenic brain.

Recent postmortem studies have reported a marked upregulation of GABAA receptor binding activity in the anterior cingulate and prefrontal cortices of schizophrenic subjects. Because the hippocampal formation is a key corticolimbic region that has also been implicated by both postmortem and brain imaging studies in the pathophysiology of this disorder, the current report has sought to determine whether alterations of GABAA receptor binding might also be detected in this region from 15 normal controls and 8 schizophrenic subjects. Using a low resolution autoradiographic approach, the results show a significant increase of specific GABAA receptor binding activity in the area dentata (granule cell layer), CA4, CA3 (str. oriens, str. pyramidale), subiculum, and presubiculum of the schizophrenic group. The magnitude of the increase was greatest in CA3 and lowest in the CA1 sector. When high resolution analyses were performed on emulsion-coverslip preparations, a modest increase of binding (43%, P = 0.05) was observed on pyramidal, but not non-pyramidal neurons in sector CA1. Rather unexpectedly, GABAA binding in sector CA3 was not significantly different on pyramidal cells, but was almost three-fold higher (P = 0.015) on non-pyramidal neurons of the schizophrenic group. There was no relationship of age or the postmortem interval to the parameters showing significant changes in the schizophrenic group. Moreover, patients both with and without neuroleptic exposure showed upregulation of GABAA receptor binding activity. Taking together the rather modest increase of binding activity in CA1 and the more marked upregulation in CA3, as well as the differential changes on pyramidal neurons of CA1 vs. non-pyramidal neurons in CA3, the findings reported here are consistent with the possibility that a disturbance of brain development could have occurred either perinatally or perhaps even well into the postnatal period, and have given rise to discreet subregional and cellular alterations of disinhibitory GABAergic modulation in sector CA3 of schizophrenics. Overall, the data reported here provide further evidence that alterations of GABAergic activity may occur in the hippocampal formation of schizophrenic patients.

Adult↗