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Biomedical subjects

T Rahman

Publications and source records attributed to T Rahman.

At least 19 recordsLinked to original sources
PubMed2005

The kinesinlike protein Subito contributes to central spindle assembly and organization of the meiotic spindle in Drosophila oocytes.

In the oocytes of many species, bipolar spindles form in the absence of centrosomes. Drosophila melanogaster oocyte chromosomes have a major role in nucleating microtubules, which precedes the bundling and assembly of these microtubules into a bipolar spindle. Here we present evidence that a region similar to the anaphase central spindle functions to organize acentrosomal spindles. Subito mutants are characterized by the formation of tripolar or monopolar spindles and nondisjunction of homologous chromosomes at meiosis I. Subito encodes a kinesinlike protein and associates with the meiotic central spindle, consistent with its classification in the Kinesin 6/MKLP1 family. This class of proteins is known to be required for cytokinesis, but our results suggest a new function in spindle formation. The meiotic central spindle appears during prometaphase and includes passenger complex proteins such as AurB and Incenp. Unlike mitotic cells, the passenger proteins do not associate with centromeres before anaphase. In the absence of Subito, central spindle formation is defective and AurB and Incenp fail to properly localize. We propose that Subito is required for establishing and/or maintaining the central spindle in Drosophila oocytes, and this substitutes for the role of centrosomes in organizing the bipolar spindle.

Amino Acid Sequence↗
PubMed2001

Clinical management of acute hepatic failure.

Acute hepatic failure is a rare clinical syndrome associated with high mortality. Hepatic failure leads to a well-recognised pattern of clinical signs and symptoms, sometimes with rapid deterioration and progression to multi-organ failure. Early recognition of this syndrome is essential for appropriate treatment; once identified, patients benefit from early interventional support and treatment in the intensive care unit. Aggressive management may allow stabilisation of patients before their transfer to specialist liver units. At present, orthotopic liver transplantation is the only treatment modality that provides significant improvement in outcome. This review examines the aetiology and clinical presentation of acute hepatic failure, providing guidelines regarding patient management. We present a critical appraisal of specific clinical areas, including the management of cardiovascular, cerebral, renal, coagulopathic and infective complications. Liver transplantation is discussed as well as emerging therapies including non-biological and hybrid liver support systems that may provide a "bridge to transplantation".

Brain Edema↗
PubMed2001

Towards the control of a powered orthosis for people with muscular dystrophy.

The paper describes the development of a passive/active orthosis for people with limited anti-gravity strength in their arms. This is symptomatic of conditions such as muscular dystrophy and spinal muscular atrophy. A passive orthosis was designed and developed using linear elastic elements. The system is being tested with children with disabilities and preliminary results are encouraging. An RT200 robot was also used as a test-bed for an active orthosis. The robot was instrumented with a six-axis force/torque sensor at the end-effector. The force acted as the input to the robot. The robot kinematics and dynamics were modelled. A number of control schemes were implemented on the test-bed including force proportional to velocity and acceleration; these schemes were evaluated with two subjects.

Arm↗
PubMed2001

Selective and divergent regulation of cortical 5-HT(2A) receptors in rabbit.

It is well established that repeated administration of both 5-hydroxytryptamine(2) (5-HT(2)) receptor agonists and antagonists decreases the density of 5-HT(2A) and 5-HT(2C) receptors. However, the regulation of these two receptors has not been studied in the same tissue. Therefore, we examined the effects of repeated daily injections of the 5-HT(2) receptor agonists (+/-)-2,5-dimethoxy-4-iodoamphetamine (DOI) and D-lysergic acid diethylamide (LSD) and the antagonists d-2-bromolysergic acid diethylamide hydrogen tartrate (BOL) and alpha-phenyl-2-(2-phenylethyl)-4-piperidinemethanol (MDL 11,939) on rabbit cortical 5-HT(2A) and 5-HT(2C) receptors. Repeated administration of DOI, LSD, or BOL decreased cortical 5-HT(2A) receptor density but had no effect on the density of cortical 5-HT(2C) receptors. Repeated administration of the selective 5-HT(2A) receptor antagonist MDL 11,939 significantly increased 5-HT(2A) receptor density. This unexpected outcome also occurred without any change in cortical 5-HT(2C) receptor density. The down-regulation of 5-HT(2A) receptors produced by chronic administration of BOL was associated with a decrease in DOI-elicited head bobs, whereas 5-HT(2A) receptor up-regulation produced by MDL 11,939 was associated with an increase in DOI-elicited head bobs compared with controls. These studies demonstrate that 5-HT(2A) receptor antagonists can both down- and up-regulate the density of cortical 5-HT(2A) receptors and these changes in receptor density have functional consequences for 5-HT(2A) receptor-mediated behaviors. Furthermore, because DOI, LSD, and BOL have approximately equal affinities for the 5-HT(2A) and 5-HT(2C) receptors, these results suggest that different mechanisms regulate 5-HT(2A) and 5-HT(2C) receptor density, in that chronic occupation of 5-HT(2C) receptors does not modulate their density in rabbit frontal cortex.

Animals↗
PubMed2000

Suture closure of femoral arterial puncture sites after coronary angioplasty followed by same-day discharge.

BACKGROUND: The purpose of this study was to determine whether immediate suture closure of 8F femoral arterial puncture sites can facilitate same-day discharge after coronary angioplasty. METHODS AND RESULTS: After coronary angioplasty, 100 patients were randomly assigned to immediate sheath removal with the double-suture Prostar-Plus device or delayed sheath removal with application of a c-clamp. After suture closure, mobilization at 4 hours after sheath removal and discharge 4 hours later were planned. Patients treated with the c-clamp had sheaths removed 4 hours after percutaneous transluminal coronary angioplasty, were mobilized 6 hours later, and discharged the following day. Patients were assessed for groin complications at 8, 24, and 72 hours. Overall, patients who received suture closure were mobilized at 7.1 +/- 5.3 hours and discharged 11. 15 +/- 6.22 hours after sheath removal versus 15.49 +/- 3.9 hours and 21.9 +/- 3.8 hours for patients with the c-clamp (P <.001). Initial failure of the suture device occurred in 5 patients, with 1 requiring surgery for an entrapped device. After the procedure, patients with suture closure more frequently had an ooze of blood (55% vs 24%, P <.001) and a trend to more overt external bleeding (10% vs 2%, P = not significant). Hematomas were reported by 20% of patients in both groups at 72 hours. Overall, patients preferred the suture closure method of sheath removal when assessed by a simple questionnaire. An economic analysis by cost minimization demonstrated potential hospital cost saving. CONCLUSIONS: Suture closure of 8F arterial puncture sites can facilitate early mobilization and same-day discharge and is considered acceptable by more patients compared with application of the c-clamp. There is potential to realize cost savings with a strategy of same-day discharge.

Angioplasty, Balloon, Coronary↗
PubMed2000

Classroom evaluation of the Arlyn Arm robotic workstation.

High school and junior high school students with neuromuscular weakness and other disorders of the arms evaluated a recently commercialized robotic workstation, the Arlyn Arm, to carry out art projects and science experiments. These tasks were designed for independent execution with the workstation using standard or custom-designed tools. Each task was divided into subtasks, and the execution time of each subtask was determined as a measure of efficiency. Special attention was given to the causes of required experimenter intervention. While subjects easily accomplished some subtasks, others required considerable intervention. Most of these interventions could be avoided by further customizing accessories. It is concluded that the Arlyn Arm workstation could be of considerable benefit in a classroom setting to persons with severe neuromuscular disorders.

Adolescent↗
PubMed2000

Optimal digital filtering for tremor suppression.

Remote manually operated tasks such as those found in teleoperation, virtual reality, or joystick-based computer access, require the generation of an intermediate electrical signal which is transmitted to the controlled subsystem (robot arm, virtual environment, or a cursor in a computer screen). When human movements are distorted, for instance, by tremor, performance can be improved by digitally filtering the intermediate signal before it reaches the controlled device. This paper introduces a novel tremor filtering framework in which digital equalizers are optimally designed through pursuit tracking task experiments. Due to inherent properties of the man-machine system, the design of tremor suppression equalizers presents two serious problems: 1) performance criteria leading to optimizations that minimize mean-squared error are not efficient for tremor elimination and 2) movement signals show ill-conditioned autocorrelation matrices, which often result in useless or unstable solutions. To address these problems, a new performance indicator in the context of tremor is introduced, and the optimal equalizer according to this new criterion is developed. Ill-conditioning of the autocorrelation matrix is overcome using a novel method which we call pulled-optimization. Experiments performed with artificially induced vibrations and a subject with Parkinson's disease show significant improvement in performance. Additional results, along with MATLAB source code of the algorithms, and a customizable demo for PC joysticks, are available on the Internet at http:¿tremor-suppression.com.

Algorithms↗
PubMed2000

Tremor suppression through impedance control.

This paper presents a method for designing tremor suppression systems that achieve a specified reduction in pathological tremor power through controlling the impedance of the human-machine interface. Position, rate, and acceleration feedback are examined and two techniques for the selection of feedback coefficients are discussed. Both techniques seek a desired closed-loop human-machine frequency response and require the development of open-loop human-machine models through system identification. The design techniques were used to develop a tremor suppression system that was subsequently evaluated using human subjects. It is concluded that nonadaptive tremor suppression systems that utilize impedance control to achieve a specified reduction in tremor power can be successfully designed when accurate open-loop human-machine models are available.

Acceleration↗
PubMed2000

Analysis of arm trajectories of everyday tasks for the development of an upper-limb orthosis.

Spatiotemporal arm and body movements of able-bodied subjects performing nine everyday tasks were recorded for the purpose of guiding the development of an upper-limb orthosis. To provide a user the opportunity to carry out these tasks with natural movements, the orthosis should allow replication of the measured trajectories. We outline the orthosis architecture, which supports the user's upper arm and forearm, and analyze the movement data to obtain orthosis design specifications. Trajectories were obtained using six-degree-of-freedom magnetic position sensors affixed to the wrist, elbow, shoulder, trunk and head. Elbow trajectory data were decomposed into ranges along the principle Cartesian axes to provide a generally useful envelope measure. The smallest Cartesian parallel-piped that contained the elbow trajectories for most tasks was approximately 30 cm front/back, 15 cm side/side, and 17 cm up/down. A rough lower bound estimate obtained by asking subjects to repeat the tasks while minimizing elbow movement substantially reduced movement in the up/down and side/side dimensions. Elbow angles were generally in the range 50 degrees-150 degrees, and the angle of the forearm with respect to vertical was 10 degrees-110 degrees. Raw trajectory data may be downloaded from www://asel.udel.edu/robotics/orthosis/range.h tml.

Activities of Daily Living↗
PubMed2000

Evaluation of an isometric and a position joystick in a target acquisition task for individuals with cerebral palsy.

Individuals with cerebral palsy (CP) with upper limb disability have difficulty operating standard computer input devices such as, a mouse and a keyboard. The present study evaluated the performance of unimpaired individuals and those with CP in the use of a zero-order spring-centered position joystick and a zero-order isometric joystick when interacting with the computer. We hypothesize that the isometric device due to its stiff resistance would provide better control on cursor movement than the position joystick. The subjects acquired differently sized targets at different distances by positioning a cursor on the target. Performance with the position joystick was superior to that of the isometric joystick. The time to acquire the target was directly proportional to the cursor-target distance A, and indirectly proportional to the target size W. Subjects chose to move more slowly toward the smaller and closer targets and they increased speed for larger and more distant targets. The phase-plane diagram that plots values of the velocity profile of the cursor over its displacement revealed the presence of one large amplitude movement that accounts for the peak velocity of the cursor, and several submovements. Fitts' index of difficulty, log(e)(2W/A) was found to be a good predictor of the movement time in a cursor positioning task for both, unimpaired individuals and those with CP.

Adult↗
PubMed1999

Designing an interface to optimize reading with small display windows.

The extent of electronic presentation of text in small display windows is mushrooming. In the present paper, 4 ways of presenting text in a small display window were examined and compared with a normal page condition: rapid serial visual presentation (RSVP), RSVP with a completion meter, sentence-by-sentence presentation, and sentence-by-sentence presentation with a completion meter. Dependent measures were reading efficiency (speed and comprehension) and preference. For designers of hardware or software with small display windows, the results suggest the following: (a) Though RSVP is disliked by readers, the present methods of allowing self-pacing and regressions in RSVP are efficient and feasible, unlike earlier tested methods; (b) slower reading in RSVP should be achieved by increasing pauses between sentences or by repeating sentences, not by decreasing the presentation rate within a sentence; (c) completion meters do not interfere with performance and are usually preferred; (d) the space-saving sentence-by-sentence format is as efficient and as preferred as the normal page format.

Adult↗
PubMed1999

Human--machine load sharing in rehabilitation robotics.

A force-assist mechanism has been developed to mount on the Chameleon - a wheelchair mounted rehabilitation robot. The device will amplify the forces applied by the user, making it possible to lift a large weight with a small force. This paper describes the test-bed development; instrumentation of the Chameleon with power assistance; and preliminary results on system efficacy.

Biomechanical Phenomena↗
PubMed1998

Performance statistics of a head-operated force-reflecting rehabilitation robot system.

Researchers in the rehabilitation engineering community have been designing and developing a variety of passive/active devices to help persons with limited upper extremity function to perform essential daily manipulations. Devices range from low-end tools such as head/mouth sticks to sophisticated robots using vision and speech input. While almost all of the high-end equipment developed to date relies on visual feedback alone to guide the user providing no tactile or proprioceptive cues, the "low-tech" head/mouth sticks deliver better "feel," because of the inherent force feedback through physical contact with the user's body. However, the disadvantage of a conventional head/mouth stick is that it can only function in a limited workspace and the performance is limited by the user's strength. It therefore seems reasonable to attempt to develop a system that exploits the advantages of the two approaches: the power and flexibility of robotic systems with the sensory feedback of a headstick. The system presented in this paper reflects the design philosophy stated above. This system contains a pair of master-slave robots with the master being operated by the user's head and the slave acting as a telestick. Described in this paper are the design, control strategies, implementation and performance evaluation of the head-controlled force-reflecting telestick system.

Adult↗
PubMed1998

Using pharmacoeconomic analysis to make drug insurance coverage decisions.

Our objective was to institute a cost-effectiveness-based reimbursement eligibility and coverage scheme for drugs in the Canadian province of British Columbia. All applications from drug manufacturers requesting Pharmacare (British Columbia government-funded drug insurance plan) coverage were evaluated by the Pharmacoeconomic Initiative (PI) of British Columbia. PI recommendations are according to a majority decision reached by a multidisciplinary volunteer expert committee and are based on a critical evaluation of pharmacoeconomic studies submitted by manufacturers seeking reimbursement eligibility. Coverage for drugs is universal and completely free for the financially indigent. Others are charged a small copayment and/or a deductible. PI assessments are evidence-based. Published guidelines from the Canadian Coordinating Office of Health Technology Assessment (CCOHTA) and/or Ontario Ministry of Health guidelines for the economic evaluation of pharmaceuticals are recommended for preparing submissions to the PI. Between January 1996 and December 1996, the PI made recommendations on 21 submissions; 4 of these were cost-effectiveness or cost-utility analyses; 3 were cost-minimisation analyses; 6 were cost comparisons or cost-consequence analyses; and 8 were provincial formulary budget impact studies. Of the 21 PI recommendations, 18 were accepted by Pharmacare and decisions are pending for 2 others, thus providing a concordance rate of 95% (18/19; kappa = 0.89). A total of 7 of the 21 products were recommended for formulary inclusion by the PI; 4 were as per drug company requests (i.e. full-benefit status) and 3 were recommended under restricted use. Only 5 of 21 submissions, of which 4 had favourable reviews, complied with either the CCOHTA or the Ontario Ministry of Health guidelines. Most studies were conducted, not from a societal perspective, but from the perspective of the provincial healthcare system. Most of the analysis were short term and therefore discounting was not applied. Sensitivity analysis was not performed in more than half (52%) of the submissions, and 48% of applications used inappropriate comparators. Ontario is the only other Canadian province with a similar process, with cost-effectiveness criteria for reimbursement eligibility. However, analysis in that province during the same approximate time period demonstrated a low concordance between Ontario Drug Benefit and PI decisions (kappa = 0.07). Currently, the mandated or suggested use of technology assessments of pharmaceuticals with cost effectiveness as the primary end-point is a reality in several countries worldwide. Our results, based on actual experience from implementing such a programme, suggest that while industry is slow to adapt to the new reporting requirements it may also be sceptical about the importance of cost effectiveness and guideline compliance in decision-making.

British Columbia↗
PubMed1997

Detection of postoperative deep-venous thrombosis using technetium-99m-labeled tissue plasminogen activator.

UNLABELLED: The current noninvasive methods of deep-venous thrombosis (DVT) detection in the asymptomatic patient are sufficiently inaccurate so as to preclude their routine use. This present study reports the accuracy of scintigraphic scanning with 99mTc-rt-PA in asymptomatic postoperative patients using contrast venography as the gold standard. METHODS: Fifty-three consecutive postarthroplasty patients (30 THR, 23 TKR) (16 women, 37 men; mean age 71 yr; range 52-85 yr) underwent scintigraphic scanning with 99mTc-rt-PA and contrast venography, on the operated leg, in order to assess the accuracy of this new technique in these asymptomatic patients. RESULTS: Eighty-four segments were of diagnostic quality on contrast venography. Of the 15 thrombosed segments, 14 had positive scans. In the 69 nonthrombosed segments, 63 had negative scans. Thus, scintigraphic scanning with 99mTc-rt-PA had a sensitivity of 93% and a specificity of 91%. CONCLUSION: This study demonstrated that scintigraphic scanning with modified 99mTc-rt-PA is accurate in the detection of DVT in patients undergoing total hip or total knee arthroplasty.

Aged↗
PubMed1995

Isolation and characterization of Helicobacter pylori strains from peptic ulcer patients in Dhaka, Bangladesh.

To study the association of Helicobacter pylori with peptic ulcer and the associated histopathological changes, to characterize the isolated strains in terms of their protein profile, 83 peptic ulcer cases were studied. A high association of H pylori with peptic ulcer (duodenal ulcer 77%, gastric ulcer 75%) and gastritis (74%) was observed. Age and smoking did not have any relationship with H pylori infection. The infection was predominantly associated with the 'quiescent' form of chronic gastritis. Comparative sodium dodecyl sulfate polyacrylamide gel electrophoresis of whole cell extracts of the local isolates and a reference strain from Australia showed a general homogeneity between the strains with obvious interstrain differences. However, the difference between the local isolates and the reference strain was more marked. Significant association of H. pylori with peptic ulcer along with strain variations were observed.

Bacterial Proteins↗