Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 21
Filter
1.
Case Rep Womens Health ; 27: e00193, 2020 Jul.
Article in English | MEDLINE | ID: mdl-32292709

ABSTRACT

BACKGROUND: Multiloculated pelvic cysts are commonly misdiagnosed as ovarian tumors or malignancies. We report 2 patients diagnosed with subserosal adenomyotic cysts and peritoneal inclusion cysts, mimicking multiloculated pelvic tumors. We discuss their clinical presentation, investigations, operation findings, and histopathology, present a literature review. CASES: Case 1 was a 44-year-old patient with abnormal uterine bleeding. Imaging showed an enlarging multiloculated cystic structure over the right uterine wall. She underwent a diagnostic laparoscopy and right salpingo-ophorectomy. Intra-operatively, she was found to have multiple subserosal uterine cysts, diagnosed as adenomyotic cysts on histology.Case 2 was a 50-year-old patient with history of laparoscopic cystectomy done 20 years ago. She was incidentally found to have a multiloculated cystic lesion in the pelvis. The lesion was located midline, anterior and superior to the uterus and bladder. She underwent a total abdominal hysterectomy, bilateral salpingo-ophorectomy, and bladder peritonectomy. Intra-operatively, multiple cystic lesions were noted over the anterior and fundus of uterus, bladder peritoneum, and pelvic side walls. The condition was confirmed to be peritoneal inclusion cysts on histology. CONCLUSION: Subserosal adenomyotic cysts are a rare presentation of adenomyosis. They typically occur in premenopausal women. Treatment is usually by hormonal medications or surgical excision.Many patients with peritoneal inclusion cysts have a history of peritoneal insults. Surgical excision is the most commonly described management as they often mimic malignancy. Both conditions are unusual presentations of multiloculated pelvic masses. A high recurrence rate is found, hence long-term follow-up with imaging is essential.

2.
Obes Rev ; 19(12): 1630-1641, 2018 12.
Article in English | MEDLINE | ID: mdl-30253050

ABSTRACT

With their novel, insulin-independent mechanism, sodium-glucose cotransporter-2 (SGLT2) inhibitors are a major turning point in the management of type 2 diabetes mellitus. At present, there are several SGLT2 inhibitors available or in development, and these oral anti-hyperglycaemic agents lower plasma glucose through the inhibition of SGLT2-mediated reuptake of filtered glucose in the kidney. This unique mechanism of action is also expected to result in other beneficial effects, such as weight loss and blood pressure reduction. In various studies, including randomized controlled trials and real-world studies, patients treated with SGLT2 inhibitors have reported weight loss of around 1 to 3 kg. This review describes the characteristics of weight loss associated with SGLT2 inhibitor therapy, the clinical factors affecting SGLT2 inhibitor-associated weight loss and the possible underlying mechanisms of SGLT2 inhibitor-associated weight loss, including changes in metabolism and body composition, and the role of a reduction in insulin dose and compensatory hyperphagia. Understanding the weight loss effect of SGLT2 inhibitors, its related factors and underlying mechanisms can aid clinicians in optimal treatment decision-making, provide valuable insight on both obesity and diabetes management and reveal areas of future research and new therapeutic options.


Subject(s)
Diabetes Mellitus, Type 2/drug therapy , Obesity/drug therapy , Sodium-Glucose Transporter 2 Inhibitors/therapeutic use , Weight Loss/drug effects , Blood Glucose , Diabetes Mellitus, Type 2/blood , Humans , Hypoglycemic Agents/therapeutic use , Obesity/blood , Sodium-Glucose Transporter 2 Inhibitors/blood , Treatment Outcome
3.
Comput Vis Image Underst ; 151: 3-13, 2016 10.
Article in English | MEDLINE | ID: mdl-27818606

ABSTRACT

With the increasing use of efficient multimodal 3D imaging, clinicians are able to access longitudinal imaging to stage pathological diseases, to monitor the efficacy of therapeutic interventions, or to assess and quantify rehabilitation efforts. Analysis of such four-dimensional (4D) image data presenting pathologies, including disappearing and newly appearing lesions, represents a significant challenge due to the presence of complex spatio-temporal changes. Image analysis methods for such 4D image data have to include not only a concept for joint segmentation of 3D datasets to account for inherent correlations of subject-specific repeated scans but also a mechanism to account for large deformations and the destruction and formation of lesions (e.g., edema, bleeding) due to underlying physiological processes associated with damage, intervention, and recovery. In this paper, we propose a novel framework that provides a joint segmentation-registration framework to tackle the inherent problem of image registration in the presence of objects not present in all images of the time series. Our methodology models 4D changes in pathological anatomy across time and and also provides an explicit mapping of a healthy normative template to a subject's image data with pathologies. Since atlas-moderated segmentation methods cannot explain appearance and locality pathological structures that are not represented in the template atlas, the new framework provides different options for initialization via a supervised learning approach, iterative semisupervised active learning, and also transfer learning, which results in a fully automatic 4D segmentation method. We demonstrate the effectiveness of our novel approach with synthetic experiments and a 4D multimodal MRI dataset of severe traumatic brain injury (TBI), including validation via comparison to expert segmentations. However, the proposed methodology is generic in regard to different clinical applications requiring quantitative analysis of 4D imaging representing spatio-temporal changes of pathologies.

4.
Hum Brain Mapp ; 36(3): 827-38, 2015 Mar.
Article in English | MEDLINE | ID: mdl-25339630

ABSTRACT

The origin, structure, and function of the claustrum, as well as its role in neural computation, have remained a mystery since its discovery in the 17th century. Assessing the in vivo connectivity of the claustrum may bring forth useful insights with relevance to model the overall functionality of the claustrum itself. Using structural and diffusion tensor neuroimaging in N = 100 healthy subjects, we found that the claustrum has the highest connectivity in the brain by regional volume. Network theoretical analyses revealed that (a) the claustrum is a primary contributor to global brain network architecture, and that (b) significant connectivity dependencies exist between the claustrum, frontal lobe, and cingulate regions. These results illustrate that the claustrum is ideally located within the human central nervous system (CNS) connectome to serve as the putative "gate keeper" of neural information for consciousness awareness. Our findings support and underscore prior theoretical contributions about the involvement of the claustrum in higher cognitive function and its relevance in devastating neurological disease.


Subject(s)
Basal Ganglia/anatomy & histology , Connectome/methods , Diffusion Tensor Imaging/methods , Gray Matter/anatomy & histology , Nerve Net/anatomy & histology , Adolescent , Adult , Female , Humans , Male , Middle Aged , Neural Pathways/anatomy & histology , Young Adult
5.
Brain Imaging Behav ; 9(4): 678-89, 2015 Dec.
Article in English | MEDLINE | ID: mdl-25376330

ABSTRACT

Mapping aging-related brain structure and connectivity changes can be helpful for assessing physiological brain age (PBA), which is distinct from chronological age (CA) because genetic and environmental factors affect individuals differently. This study proposes an approach whereby structural and connectomic information can be combined to estimate PBA as an early biomarker of brain aging. In a cohort of 136 healthy adults, magnetic resonance and diffusion tensor imaging are respectively used to measure cortical thickness over the entire cortical mantle as well as connectivity properties (mean connectivity density and mean fractional anisotropy) for white matter connections. Using multivariate regression, these measurements are then employed to (1) illustrate how CA can be predicated--and thereby also how PBA can be estimated--and to conclude that (2) healthy aging is associated with significant connectome changes during adulthood. Our study illustrates a connectomically-informed statistical approach to PBA estimation, with potential applicability to the clinical identification of patients who exhibit accelerated brain aging, and who are consequently at higher risk for developing mild cognitive impairment or dementia.


Subject(s)
Aging/pathology , Brain/pathology , Connectome/methods , Diffusion Tensor Imaging/methods , Magnetic Resonance Imaging/methods , Adolescent , Adult , Brain/growth & development , Cohort Studies , Data Interpretation, Statistical , Female , Humans , Male , Middle Aged , Multivariate Analysis , Organ Size , Young Adult
6.
Brain Inj ; 29(4): 438-45, 2015.
Article in English | MEDLINE | ID: mdl-25518865

ABSTRACT

OBJECTIVE: To demonstrate a set of approaches using diffusion tensor imaging (DTI) tractography whereby pathology-affected white matter (WM) fibres in patients with intracerebral haemorrhage (ICH) can be selectively visualized. METHODS: Using structural neuroimaging and DTI volumes acquired longitudinally from three representative patients with ICH, the spatial configuration of ICH-related trauma is delineated and the WM fibre bundles intersecting each ICH lesion are identified and visualized. Both the extent of ICH lesions as well as the proportion of WM fibres intersecting the ICH pathology are quantified and compared across subjects. RESULTS: This method successfully demonstrates longitudinal volumetric differences in ICH lesion load and differences across time in the percentage of fibres which intersect the primary injury. CONCLUSIONS: Because neurological conditions such as intracerebral haemorrhage (ICH) frequently exhibit pathology-related effects which lead to the exertion of mechanical pressure upon surrounding tissues and, thereby, to the deformation and/or displacement of WM fibres, DTI fibre tractography is highly suitable for assessing longitudinal changes in WM fibre integrity and mechanical displacement.


Subject(s)
Cerebral Hemorrhage/pathology , Diffusion Magnetic Resonance Imaging/methods , Diffusion Tensor Imaging/methods , Adult , Brain/blood supply , Brain/pathology , Brain Mapping/methods , Female , Humans , Longitudinal Studies , Middle Aged , White Matter/pathology
7.
Singapore Med J ; 55(6): 334-47, 2014 Jun.
Article in English | MEDLINE | ID: mdl-25017409

ABSTRACT

The Ministry of Health (MOH) have updated the clinical practice guidelines on Diabetes Mellitus to provide doctors and patients in Singapore with evidence-based treatment for diabetes mellitus. This article reproduces the introduction and executive summary (with recommendations from the guidelines) from the MOH clinical practice guidelines on Diabetes Mellitus, for the information of SMJ readers. Chapters and page numbers mentioned in the reproduced extract refer to the full text of the guidelines, which are available from the Ministry of Health website: http://www.moh.gov.sg/content/moh_web/healthprofessionalsportal/doctors/guidelines/cpg_medical.html. The recommendations should be used with reference to the full text of the guidelines. Following this article are multiple choice questions based on the full text of the guidelines.


Subject(s)
Diabetes Mellitus/diagnosis , Diabetes Mellitus/therapy , Practice Guidelines as Topic , Evidence-Based Medicine , Humans , Public Health , Singapore
8.
J Neurosurg Sci ; 58(3): 129-44, 2014 Sep.
Article in English | MEDLINE | ID: mdl-24844173

ABSTRACT

The integration of longitudinal brain structure analysis with neurointensive care strategies continues to be a substantial difficulty facing the traumatic brain injury (TBI) research community. For patient-tailored case analysis, it remains challenging to establish how lesion profile modulates longitudinal changes in cortical structure and connectivity, as well as how these changes lead to behavioral, cognitive and neural dysfunction. Additionally, despite the clinical potential of morphometric and connectomic studies, few analytic tools are available for their study in TBI. Here we review the state of the art in structural and connectomic neuroimaging for the study of TBI and illustrate a set of recently-developed, patient-tailored approaches for the study of TBI-related brain atrophy and alterations in morphometry as well as inter-regional connectivity. The ability of such techniques to quantify how injury modulates longitudinal changes in cortical shape, structure and circuitry is highlighted. Quantitative approaches such as these can be used to assess and monitor the clinical condition and evolution of TBI victims, and can have substantial translational impact, especially when used in conjunction with measures of neuropsychological function.


Subject(s)
Brain Injuries/pathology , Connectome , Neuroimaging , Animals , Brain Mapping , Humans , Magnetic Resonance Imaging/methods , Neuroimaging/methods , Personal Health Services
9.
Front Neuroinform ; 8: 19, 2014.
Article in English | MEDLINE | ID: mdl-24616696

ABSTRACT

Throughout the past few decades, the ability to treat and rehabilitate traumatic brain injury (TBI) patients has become critically reliant upon the use of neuroimaging to acquire adequate knowledge of injury-related effects upon brain function and recovery. As a result, the need for TBI neuroimaging analysis methods has increased in recent years due to the recognition that spatiotemporal computational analyses of TBI evolution are useful for capturing the effects of TBI dynamics. At the same time, however, the advent of such methods has brought about the need to analyze, manage, and integrate TBI neuroimaging data using informatically inspired approaches which can take full advantage of their large dimensionality and informational complexity. Given this perspective, we here discuss the neuroinformatics challenges for TBI neuroimaging analysis in the context of structural, connectivity, and functional paradigms. Within each of these, the availability of a wide range of neuroimaging modalities can be leveraged to fully understand the heterogeneity of TBI pathology; consequently, large-scale computer hardware resources and next-generation processing software are often required for efficient data storage, management, and analysis of TBI neuroimaging data. However, each of these paradigms poses challenges in the context of informatics such that the ability to address them is critical for augmenting current capabilities to perform neuroimaging analysis of TBI and to improve therapeutic efficacy.

10.
Clin Neurol Neurosurg ; 115(10): 2159-65, 2013 Oct.
Article in English | MEDLINE | ID: mdl-24011495

ABSTRACT

OBJECTIVE: To inverse-localize epileptiform cortical electrical activity recorded from severe traumatic brain injury (TBI) patients using electroencephalography (EEG). METHODS: Three acute TBI cases were imaged using computed tomography (CT) and multimodal magnetic resonance imaging (MRI). Semi-automatic segmentation was performed to partition the complete TBI head into 25 distinct tissue types, including 6 tissue types accounting for pathology. Segmentations were employed to generate a finite element method model of the head, and EEG activity generators were modeled as dipolar currents distributed over the cortical surface. RESULTS: We demonstrate anatomically faithful localization of EEG generators responsible for epileptiform discharges in severe TBI. By accounting for injury-related tissue conductivity changes, our work offers the most realistic implementation currently available for the inverse estimation of cortical activity in TBI. CONCLUSION: Whereas standard localization techniques are available for electrical activity mapping in uninjured brains, they are rarely applied to acute TBI. Modern models of TBI-induced pathology can inform the localization of epileptogenic foci, improve surgical efficacy, contribute to the improvement of critical care monitoring and provide guidance for patient-tailored treatment. With approaches such as this, neurosurgeons and neurologists can study brain activity in acute TBI and obtain insights regarding injury effects upon brain metabolism and clinical outcome.


Subject(s)
Brain Injuries/physiopathology , Brain Injuries/surgery , Brain/physiopathology , Electroencephalography , Neurosurgical Procedures/methods , Surgery, Computer-Assisted/methods , Adult , Brain Mapping , Epilepsy/diagnosis , Epilepsy/physiopathology , Female , Glasgow Coma Scale , Glasgow Outcome Scale , Humans , Image Processing, Computer-Assisted , Magnetic Resonance Imaging , Male , Middle Aged , Monitoring, Intraoperative , Treatment Outcome
11.
Clin Neurophysiol ; 124(11): 2129-45, 2013 Nov.
Article in English | MEDLINE | ID: mdl-23746499

ABSTRACT

OBJECTIVE: EEG source localization is demonstrated in three cases of acute traumatic brain injury (TBI) with progressive lesion loads using anatomically faithful models of the head which account for pathology. METHODS: Multimodal magnetic resonance imaging (MRI) volumes were used to generate head models via the finite element method (FEM). A total of 25 tissue types-including 6 types accounting for pathology-were included. To determine the effects of TBI upon source localization accuracy, a minimum-norm operator was used to perform inverse localization and to determine the accuracy of the latter. RESULTS: The importance of using a more comprehensive number of tissue types is confirmed in both health and in TBI. Pathology omission is found to cause substantial inaccuracies in EEG forward matrix calculations, with lead field sensitivity being underestimated by as much as ≈ 200% in (peri-) contusional regions when TBI-related changes are ignored. Failing to account for such conductivity changes is found to misestimate substantial localization error by up to 35 mm. CONCLUSIONS: Changes in head conductivity profiles should be accounted for when performing EEG modeling in acute TBI. SIGNIFICANCE: Given the challenges of inverse localization in TBI, this framework can benefit neurotrauma patients by providing useful insights on pathophysiology.


Subject(s)
Brain Injuries/diagnosis , Brain Injuries/physiopathology , Brain/anatomy & histology , Brain/physiology , Electroencephalography , Models, Anatomic , Models, Neurological , Adult , Brain/pathology , Brain/physiopathology , Brain Injuries/pathology , Head/anatomy & histology , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Organ Size , Reference Values , Young Adult
12.
Neuroscience ; 206: 17-24, 2012 Mar 29.
Article in English | MEDLINE | ID: mdl-22266346

ABSTRACT

An ultra-slow oscillation (<0.01 Hz) in the network-wide activity of dissociated cortical networks is described in this article. This slow rhythm is characterized by the recurrence of clusters of large synchronized bursts of activity lasting approximately 1-3 min, separated by an almost equivalent interval of relatively smaller bursts. Such rhythmic activity was detected in cultures starting from the fourth week in vitro. Our analysis revealed that the propagation motifs of constituent bursts were strongly conserved across multiple oscillation cycles, and these motifs were more consistent at the electrode level compared with the neuronal level.


Subject(s)
Cerebral Cortex/physiology , Nerve Net/physiology , Action Potentials/physiology , Animals , Electrophysiology , Periodicity , Rats , Rats, Wistar
13.
J Neurosci Methods ; 179(2): 284-91, 2009 May 15.
Article in English | MEDLINE | ID: mdl-19428539

ABSTRACT

A device to facilitate high-density seeding of dissociated neural cells on planar multi-electrode arrays (MEAs) is presented in this paper. The device comprises a metal cover with two concentric cylinders-the outer cylinder fits tightly on to the external diameter of a MEA to hold it in place and an inner cylinder holds a central glass tube for introducing a cell suspension over the electrode area of the MEA. An O-ring is placed at the bottom of the inner cylinder and the glass tube to provide a fluid-tight seal between the glass tube and the MEA electrode surface. The volume of cell suspension in the glass tube is varied according to the desired plating density. After plating, the device can be lifted from the MEA without leaving any residue on the contact surface. The device has enabled us to increase and control the plating density of neural cell suspension with low viability, and to prepare successful primary cultures from cryopreserved neurons and glia. The cultures of cryopreserved dissociated cortical neurons that we have grown in this manner remained spontaneously active over months, exhibited stable development and similar network characteristics as reported by other researchers.


Subject(s)
Diffusion Chambers, Culture/instrumentation , Electrophysiology/instrumentation , Neurons/physiology , Neurophysiology/instrumentation , Action Potentials/physiology , Animals , Cell Culture Techniques , Cell Survival/physiology , Cells, Cultured , Cryopreservation , Diffusion Chambers, Culture/methods , Electrophysiology/methods , Microelectrodes , Nerve Net/cytology , Nerve Net/physiology , Neuroglia/cytology , Neuroglia/physiology , Neurons/cytology , Neurophysiology/methods , Rats
14.
Singapore Med J ; 48(11): 986-9, 2007 Nov.
Article in English | MEDLINE | ID: mdl-17975686

ABSTRACT

INTRODUCTION: We piloted the use of a blood beta-hydroxybutyrate meter as a point-of-care testing in an emergency department (ED) to establish its role in distinguishing ketosis/ketoacidosis from simple hyperglycaemia, and develop guidelines for its use in the ED. METHODS: 111 consecutive patients presenting with capillary glucose levels exceeding 14 mmol/L had a simultaneous blood ketone measurement at triage. This was correlated with clinical diagnosis, venous bicarbonate levels and urine ketone testing. RESULTS: The median beta-hydroxybutyrate levels was 5.7 (range 4.3-6.0) mmol/L for patients with diabetic ketoacidosis (DKA) and 0.1 (0.0-3.2) mmol/L for the remaining patients. Only 47.7 percent could provide urine samples in the ED. A blood ketone result of 3.5 mmol/L yielded 100 percent specificity and sensitivity for the diagnosis of DKA. CONCLUSION: This is a useful tool that allows clinicians to immediately distinguish between simple hyperglycaemia and potentially life-threatening ketotic states. We formulated simple guidelines for its utilisation in an ED setting.


Subject(s)
Diabetic Ketoacidosis/diagnosis , Emergency Service, Hospital , Ketone Bodies/blood , Mass Screening , Point-of-Care Systems , 3-Hydroxybutyric Acid/blood , Adolescent , Adult , Aged , Aged, 80 and over , Bicarbonates/blood , Blood Glucose/metabolism , Diabetic Ketoacidosis/blood , Diagnosis, Differential , Female , Humans , Hyperglycemia/blood , Hyperglycemia/diagnosis , Male , Middle Aged , Pilot Projects , Practice Guidelines as Topic , Predictive Value of Tests , Singapore , Triage
16.
Clin Endocrinol (Oxf) ; 60(5): 600-7, 2004 May.
Article in English | MEDLINE | ID: mdl-15104563

ABSTRACT

BACKGROUND: Thyroid-associated ophthalmopathy (TAO) occurs in 25-50% of patients with Graves' disease (GD) and is occasionally seen in hypothyroid Hashimoto's disease or euthyroid individuals. The link between TAO and hyperthyroidism remains unclear. We hypothesized that qualitative or quantitative differences in thyroid antibodies might determine individual predisposition to these features. METHODS: In a prospective study over 3 years, thyroid antibody levels were measured in all patients diagnosed at the Singapore National Eye Centre to have GD. These patients had no known history of thyroid disease, presented with eye complaints and diagnosis was made by an ophthalmologist. A total of 31 patients were identified. Antibody levels were compared against 71 consecutive patients referred to a thyroid clinic (TC) for thyrotoxic symptoms in whom the diagnosis of GD was confirmed by a thyroidologist. FINDINGS: Thyroid autoantibody profiles of patients diagnosed at the ophthalmology centre (OC) and TC differed markedly. OC patients had significantly higher TSI (P = 0.003) but lower TPOAb (P = 0.008) and TgAb levels (P < 0.001). In contrast, TC patients had higher free T4 (P = 0.048) and higher TBII levels (P < 0.001). Antibody levels were correlated with four parameters of ophthalmopathy--chronic lid retraction, lid swelling, proptosis and extraocular myopathy (EOM). On univariate logistic regression analysis, TSI was a positive predictor and TPOAb and TgAb negative predictors of all four features. In the absence of TgAb, the odds ratios for individual TAO features ranged from 2.8 to 7.9, with corresponding values of 3.9-10.2 when TPOAb was absent. In stepwise logistic regression analysis, TSI was the strongest independent predictor of all aspects studied: lid fullness P = 0.001, proptosis P = 0.001, lid retraction P = 0.008, EOM P = 0.009. Among smokers, TPOAb were significantly lower (P = 0.044) but no association between smoking and the other antibodies was observed. INTERPRETATION: The study demonstrates markedly different thyroid autoantibody profiles in newly diagnosed GD patients with ophthalmic dominant as opposed to thyroid dominant features. It suggests differing antibody patterns are associated with predisposition to hyperthyroidism and orbitopathy. In addition, an association between smoking and low TPOAb levels was noted.


Subject(s)
Autoantibodies/blood , Graves Disease/immunology , Thyroid Hormones/immunology , Adult , Autoantibodies/analysis , Chi-Square Distribution , Female , Humans , Immunoglobulins, Thyroid-Stimulating/analysis , Iodide Peroxidase/immunology , Logistic Models , Male , Middle Aged , Prospective Studies , Receptors, Thyrotropin/analysis , Thyroglobulin/immunology , Thyroid Function Tests
17.
Singapore Med J ; 42(3): 115-6, 2001 Mar.
Article in English | MEDLINE | ID: mdl-11405562

ABSTRACT

We present a case of a man who developed gynaecomastia after ingestion of "Dong Quai" pills. "Dong Quai" is the Chinese name for the herb Angelica polymorpha var. sinensis which is widely used as a panacea for gynaecological problems, and it is also proclaimed as an invigorating tonic for both women and men. The pharmacological effects of "Dong Quai" are likely related to the phytoestrogen that it contains. This report highlights the potential adverse effects associated with its consumption in the male, especially for the processed "Dong Quai" pills which may contain significantly higher levels of phytoestrogen than its original herbal product.


Subject(s)
Drugs, Chinese Herbal/adverse effects , Gynecomastia/etiology , Adult , Angelica sinensis , Drugs, Chinese Herbal/therapeutic use , Gonadal Steroid Hormones/blood , Humans , Male , Medicine, Chinese Traditional
18.
J Pept Res ; 53(2): 188-200, 1999 Feb.
Article in English | MEDLINE | ID: mdl-10195456

ABSTRACT

Three 1 ns length molecular dynamics simulations of an RGD peptide (Ac-Pen-Arg-Gly-Asp-Cys-NH2, with Pen denoting penicillamine) have been performed in aqueous solution, one for the disulfide bridged, and two for the unbridged form. The trajectories were analyzed to identify conformations explored by the two forms and to calculate several properties: NMR vicinal coupling constants, order parameters, dipole moments and diffusion coefficients, in an effort to describe the physical role of the disulfide bond. The cyclic peptide was able to explore several distinct backbone conformations centered around a turn-extended-turn structure. However, its flexibility was limited and it appeared to be 'locked in' into a a family of structures characterized by a high dipole moment and a well-defined conformation of the pharmacophore, which has been previously identified as biologically active. Excellent agreement between the simulated and observed NMR vicinal coupling constants indicates that realistic structures were sampled in the cyclic peptide simulation. The linear form of the peptide was much more flexible than the cyclic one. In the two independent 1 ns simulations of the linear form the explored conformations could be roughly grouped into two classes, of cyclic-like and extended type. Within each simulation the peptide switched between the two classes of structures several times. Exact matches between conformations in the two linear peptide simulations were not found; several conformational regions with backbone rms deviations below 1A were identified, suggesting that representative structures of the linear form have also been identified. In the linear peptide simulations the RGD pharmacophore is able to adopt a wide range of conformations, including the one preferred by the cyclic form. The lower biological activity of the linear peptide compared to the cyclic one may be correlated with the lower population of this structure in the absence of the disulfide bond.


Subject(s)
Antineoplastic Agents/chemistry , Models, Molecular , Oligopeptides/chemistry , Chemistry, Physical/methods , Disulfides/chemistry , Magnetic Resonance Spectroscopy , Peptides, Cyclic/chemistry , Protein Conformation , Solutions
20.
Ann Trop Paediatr ; 18(3): 225-30, 1998 Sep.
Article in English | MEDLINE | ID: mdl-9924560

ABSTRACT

With the recent availability of a chlorofluorocarbon (CFC)-free metered dose inhaler (MDI) (Airomir), a patient survey was carried out to evaluate awareness of the role of CFCs in our environment and acceptance of this new inhaler. A questionnaire survey was conducted on parents and guardians of 201 children. Depending on respondents' preference, the interview was conducted in English (71%), Chinese (23%), Malay (5%) or Tamil (1%). A 'taste' test was also conducted on 103 of these children. Only 13% (26/201) of parents/guardians were aware that MDIs contained CFCs. Although 70% of children were in favour of the new taste of the CFC-free inhaler, the cost of the new inhaler was an important consideration for parents and guardians in their decision to switch to the new inhaler. The majority (93%) were willing to switch if its cost were equivalent to their current inhaler. This study has provided pertinent information with regard to acceptance of CFC-free inhalers which should be considered when making the inevitable switch to environmentally friendly inhalers.


Subject(s)
Air Pollution/prevention & control , Chlorofluorocarbons/supply & distribution , Nebulizers and Vaporizers/standards , Patient Acceptance of Health Care/psychology , Adult , Albuterol/therapeutic use , Asthma/drug therapy , Bronchodilator Agents/therapeutic use , Child , Child, Preschool , Female , Humans , Male , Middle Aged , Singapore , Surveys and Questionnaires , Taste
SELECTION OF CITATIONS
SEARCH DETAIL
...