ABSTRACT
Parieto-occipital sulcus is one of the major sulcus of the cerebral hemisphere which separates the occipital lobe from the parietal lobe. Morphology of this sulcus varies with age, sex, manual skill, handedness and in many diseases. For various clinical investigations and surgery, detailed morphological knowledge of this sulcus is very much essential for the surgeons and radiologists. This study is carried out to establish a normal standard in length of the parieto-occipital sulcus in different age and sex groups of Bangladeshi people. A cross-sectional, descriptive type of study was conducted in the department of Anatomy, Mymensingh Medical College, Bangladesh from July 2016 to July 2017. About 60 specimens were collected from medico-legal cases and divided into four age groups including, Group A (20-29 years), Group B (30-39 years), Group C (40-49 years) and Group D (50 years and above). The mean length of parieto-occipital sulcus was 3.92±0.559cm to 3.29±0.434 cm in male and 3.81±0.715cm to 3.03±0.551cm in female. The difference in mean length of the parieto-occipital sulcus for both left and right hemisphere between male and female was statistically non-significant in all age groups. For statistical analysis, differences between age and sex groups were analyzed by using students unpaired 't' test. In this study, the length of the parieto-occipital sulcus showed gradual decreasing values with advancing age.
Subject(s)
Occipital Lobe , Parietal Lobe , Humans , Female , Male , Adult , Bangladesh , Cross-Sectional Studies , Occipital Lobe/anatomy & histology , Middle Aged , Young Adult , Parietal Lobe/anatomy & histology , Age Factors , Sex Factors , South Asian PeopleABSTRACT
This cross-sectional descriptive purposive study was conducted among 150 (70 right and 80 left) fully ossified dry human scapulae of Bangladeshi people from January 2019 to December 2019 in the Department of Anatomy, Mymensingh Medical College, Mymensingh. Shape of the glenoid cavity was observed as pear, oval or inverted comma shape. Morphometric parameters such as length and breadth of glenoid cavity were measured by digital Vernier slide calipers. In this study, 19.13% cases were found inverted comma shaped, 35.65% cases were oval and 45.22% cases were pear shaped. The mean±SD length of glenoid cavity was 37.5±3.61 mm and 36.19±3.68 mm on right and left sided scapulae respectively and mean±SD breadth was 23.6±2.73 mm on right and 23.42±2.75 mm on left side respectively. Mean±SD glenoid cavity index was 62.89±4.39 on right and 64.61±4.74 on left sided scapulae. Morphometric analysis of glenoid fossa of scapula might help clinicians in shoulder and its associated diseases.
Subject(s)
Glenoid Cavity , South Asian People , Humans , Glenoid Cavity/diagnostic imaging , Glenoid Cavity/anatomy & histology , Cross-Sectional Studies , Scapula/anatomy & histology , Asian PeopleABSTRACT
This cross-sectional descriptive purposive study was done on 150 (70 right and 80 left) fully ossified dry human scapulae of Bangladeshi people to find out the variation in length of acromiocoracoid and acromioglenoid distance. Sample collection was carried out in the Department of Anatomy, Mymensingh Medical College, Bangladesh from January to December 2019. Any kind of damaged or broken scapulae were excluded to maintain standard measurement. Length of these distances was measured with the help of digital Vernier slide calipers. The mean±SD acromiocoracoid distance were 35.8±4.64 mm and 36.32±5.55 mm on right and left sided scapulae respectively and the mean±SD acromioglenoid distance were 27.69±3.43 mm on right sided scapulae and 28.18±3.26 mm on left sided scapulae. These data are important to compare Bangladeshi scapulae to those from various other races that could contribute to demographic studies of shoulder disease probability and management in Bangladeshi population.
Subject(s)
Asian People , Scapula , Humans , Bangladesh , Cadaver , Cross-Sectional Studies , Scapula/anatomy & histologyABSTRACT
Femoral morphometric variation is a dynamic system for different region, which is influenced by geographical, physiological and environmental factors, due to the adaptation, functional and remodeling responses of bones. This descriptive cross-sectional study was conducted on 150 (64 right and 86 left) fully ossified dry human femur of Bangladeshi people to find out the variation of mid shaft antero-posterior and transverse diameter of femur. Sample was collected in the Department of Anatomy, Mymensingh Medical College (MMC), Bangladesh from January 2019 to December 2019. All samples were assessed to eliminate fractured, pathologically damaged and remodeled bones. The diameters were measured with the help of digital Vernier slide calipers. The mean±SD mid shaft antero-posterior diameter of right and left femur were 25.03±2.86 mm and 25.54±2.65mm respectively. The mean±SD transverse diameter of right and left femur was 24.24±2.43mm and 24.54±2.38mm respectively. The knowledge of variations in the parameters of dry femora will help the orthopedicians for the treatment and management of femoral shaft fracture. These data also provide information about mid shaft diameter of femur of Bangladeshi people and to compare these data to those from various other races. Thus it could contribute for the design of well-fitting prosthesis which suits the Bangladeshi population. This value may be considered while making a best-fit femoral prosthesis.
Subject(s)
Femur , Humans , Asian People , Cross-Sectional Studies , Femur/anatomy & histologyABSTRACT
Background: Treatment of vitiligo is still a challenge in dermatology. Literature is sparse on the definitive clinical role of basic fibroblast growth factor (bFGF) in vitiligo patients. Aims: We decided to generate a consensus in an attempt to answer some critical questions related to the management of vitiligo and the role of bFGF. Materials and Methods: A Delphi method among 21 experts across India was conducted. A consensus (agreement was 75% or greater) was taken on 27 statements on the prevalence, epidemiology, and treatment of vitiligo and the role of bFGF in the management of vitiligo. The consensus process was completed after two rounds. Results: Topical corticosteroid therapy is the first-line therapy for vitiligo; however, its adverse effects are widely known, especially in sensitive areas. Topical calcineurin inhibitors are preferred in stable vitiligo of the face, neck, genitals, or intertriginous regions as an alternative to topical corticosteroids. Topical bFGF is a relatively newer therapy with a promising role in stable vitiligo. bFGF is safe and effective in inducing repigmentation of vitiligo lesions. Combination therapy of bFGF with other topical therapies, phototherapy, and surgical procedures can be beneficial in patients of vitiligo. Conclusion: This consensus would complement the currently available literature on bFGF and help the practitioner to recognize the unmet need in the treatment of vitiligo.
ABSTRACT
The central sulcus (CS) is a prominent landmark of the brain, separating the parietal lobe from the frontal lobe and the primary motor cortex from the primary somatosensory cortex. Variations in the morphology of the central sulcus are seen with respect to the length and depth of the central sulcus. This study was done to establish a normal standard of length and depth of central sulcus in different age and sex groups of Bangladeshi people. Interhemispheric age and gender differences of the central sulcus were done by cross sectional descriptive study which was performed into four categories- Group A (20 to 29 years), Group B (30 to 39 years), Group C (40 to 49 years) and Group D (50 years & above). The specimens were collected from morgue in the department of Forensic Medicine, Mymensingh Medical College, Bangladesh by purposive sampling technique. The length of central sulcus was measured by using thread and the depth was measured by using wooden stick at middle of the upper, middle and lower third of the central sulcus in superolateral surface. The mean length of central sulcus was 10.51±0.529cm to 9.78±0.996cm in male and 10.27±0.786cm to 8.83±0.379cm in female. Depth of the central sulcus was 1.333±0.100cm to 1.029±0.125cm in male and 1.173±0.144cm to 1.01±0.200cm in female. The difference in mean length & depth of the central sulcus for both left and right hemisphere between male and female was statistically non significant in all age groups. In present study the length and depth of the central sulcus showed gradual decreasing values with advancing age. Knowledge of morphometry of central sulcus is not only important during neurosurgery of brain but also holds tremendous significance in diagnosis and management of diseases of the cerebral cortex. The present study will help to increase the information pool on the length and depth of the central sulcus of Bangladeshi people which will minimize the dependency on foreign standards.
Subject(s)
Cerebral Cortex , Autopsy , Bangladesh , Cadaver , Cross-Sectional Studies , Female , Humans , MaleABSTRACT
Placenta is the mirror of maternal and fetal status; it reflects the changes due to complications in pregnancy of mother. The growth and survival of the fetus in utero is directly related to formation, development and maturation of the placenta. Placental index was correlated to poor pregnancy outcomes. Placental index can help to identify fetal growth restriction which is result of placental insufficiency and is characterized by insufficient trasnsplacental transport of nutrients and oxygen. This cross sectional descriptive study would provide information about the ratio of placental index in different gestational age group in Bangladeshi women. To achieve this aim the study was performed on 60 human placenta and corresponding fetuses and gestational age (in weeks) categorized as Group A (28-32), Group B (33-37), Group C (38-40). These sample and information were collected from normal pregnancy in Gynecology and Obstetrics Department of Mymensingh Medical College Hospital from July 2009 to June 2010. After preservation in 10% formal saline, study was done in Department of Anatomy in Mymensingh Medical College. In this study, the mean±SD placental index was in Group A (0.187±0.113), Group B (0.153±0.025) and Group C (0.166±0.025) and also observed that mean placental index decreased with age up to certain level then increase in Group C. The mean placental index was maximum in Group A (0.187±0.113) and was minimum in Group B (0.153±0.025). The mean difference of placental index between Groups A&B, A&C and B&C was statistically not significant. Observed findings of this study were compared with those of Western and Bangladeshi researches.
Subject(s)
Fetal Growth Retardation , Placenta , Cross-Sectional Studies , Female , Gestational Age , Humans , Infant, Newborn , Infant, Small for Gestational Age , PregnancyABSTRACT
This cross sectional descriptive study was performed on 80 human placenta and umbilical cord to find out the variation in length of umbilical cord of healthy Bangladeshi mother in relation to different gestational age. This study was conducted in the Department of Anatomy, Mymensingh Medical College, Mymensingh, from January to December 2018. The specimens were collected from the Department of Gynaecology and Obstetrics, Mymensingh Medical College Hospital, Mymensingh, Bangladesh by purposive sampling technique. According to gestational age the collected samples were divided into three groups. They were Group A (28 to 36 weeks), Group B (37 to 40 weeks) and Group C (above 40 weeks) and examined morphologically by fine dissection method. The length of umbilical cord was measured with the help of flexible tape in cm. For statistical analysis, differences of length between age groups were analyzed by using unpaired student 't' test. The mean±SD length of umbilical cord was 56.15±7.61cm in Group A, 62.54±8.78cm in Group B and 68.54±10.53cm in Group C. It was also observed that the mean length of the umbilical cord was increased with increase of gestational age. The mean difference of length of umbilical cord between Groups A and C was statistically highly significant (p<0.001), difference between Groups A and B was statistically moderately significant (p<0.01) but the difference between Groups B and C was statistically significant (p<0.05). This study was done to provide information about the length of umbilical cord in different gestational ages of healthy pregnancies.
Subject(s)
Mothers , Umbilical Cord , Bangladesh , Cross-Sectional Studies , Female , Gestational Age , Humans , PregnancyABSTRACT
Current efforts to achieve neuromorphic computation are focused on highly organized architectures, such as integrated circuits and regular arrays of memristors, which lack the complex interconnectivity of the brain and so are unable to exhibit brain-like dynamics. New architectures are required, both to emulate the complexity of the brain and to achieve critical dynamics and consequent maximal computational performance. We show here that electrical signals from self-organized networks of nanoparticles exhibit brain-like spatiotemporal correlations and criticality when fabricated at a percolating phase transition. Specifically, the sizes and durations of avalanches of switching events are power law distributed, and the power law exponents satisfy rigorous criteria for criticality. These signals are therefore qualitatively and quantitatively similar to those measured in the cortex. Our self-organized networks provide a low-cost platform for computational approaches that rely on spatiotemporal correlations, such as reservoir computing, and are an important step toward creating neuromorphic device architectures.
ABSTRACT
This cross sectional descriptive study was performed on 70 postmortem vermiform appendices (male 34 and female 36) to find out the various positions of vermiform appendix of Bangladeshi people. The specimens were collected from autopsy laboratory of the Department of Forensic Medicine, Mymensingh Medical College, Mymensingh, Bangladesh by purposive sampling technique from October 2016 to March 2017. The collected samples were divided into four age groups. They were Group A (upto 20 years), Group B (21 to 40 years), Group C (41 to 60 years) and Group D (above 60 years). Dissection was performed according to standard autopsy technique. During postmortem examination abdominal cavity was routinely exposed by classical midline incision from xiphoid process to the symphysis pubis and a semicircular incision around the umbilicus and the flaps were reflected to give a good view of the abdominal cavity along with its contents and then the taeniae coli of the caecum were identified. The three taeniae coli of the caecum converge at the base of the appendix and become its longitudinal muscle coat. The anterior caecal taeniae coli acts as the best guide for identification of the vermiform appendix. The relation of the base of the appendix to the caecum is constant but the position of the vermiform appendix, which is variable, was studied in relation to caecum and the terminal part of the ileum. Accordingly the position of the vermiform appendix was noted either retrocaecal, pelvic, preileal or postileal, subcaecal. All data were recorded in the predesigned data sheet, analyzed by SPSS program (version 21, 2012) and compared with the findings of other national and international studies and standard text books. Among 70 specimens, 44(62.9%) vermiform appendices were retrocaecal in position. The next common position was pelvic which was in 22(31.4%) specimen followed by postileal in 3(4.3%) specimen and subcaecal was observed only in 1(1.4%) specimen. In this study in all age groups incidence of retrocaecal vermiform appendix was highest and it was about 67.6%, 50%, 69.2% and 72.7% in Group A, B, C, D respectively. Pelvic position was 7.1%, 46.9%, 23.1% and 27.3% in Group A, B, C, D respectively. Subcaecal vermiform appendix was absent in Group A, B and Group D. On the other hand postileal vermiform appendix was absent in Group C and Group D. The findings of this study may help the physician and the surgeons for proper diagnosis, management and treatment of disease of vermiform appendix.
Subject(s)
Appendix/anatomy & histology , Autopsy , Bangladesh , Cadaver , Cross-Sectional Studies , Ethnicity , Female , Humans , MaleSubject(s)
Acne Vulgaris/drug therapy , Anti-Inflammatory Agents/therapeutic use , Arthritis, Infectious/drug therapy , Dapsone/therapeutic use , Dermatologic Agents/therapeutic use , Methotrexate/therapeutic use , Minocycline/therapeutic use , Pregnenediones/therapeutic use , Pyoderma Gangrenosum/drug therapy , Acne Vulgaris/economics , Acne Vulgaris/pathology , Anti-Inflammatory Agents/administration & dosage , Anti-Inflammatory Agents/economics , Arthritis, Infectious/economics , Arthritis, Infectious/pathology , Cost-Benefit Analysis , Dapsone/administration & dosage , Dermatologic Agents/administration & dosage , Dermatologic Agents/economics , Drug Therapy, Combination/economics , Humans , Methotrexate/administration & dosage , Minocycline/administration & dosage , Pregnenediones/administration & dosage , Pyoderma Gangrenosum/economics , Pyoderma Gangrenosum/pathology , Skin/pathologyABSTRACT
We report a detailed study of neuromorphic switching behaviour in inherently complex percolating networks of self-assembled metal nanoparticles. We show that variation of the strength and duration of the electric field applied to this network of synapse-like atomic switches allows us to control the switching dynamics. Switching is observed for voltages above a well-defined threshold, with higher voltages leading to increased switching rates. We demonstrate two behavioral archetypes and show how the switching dynamics change as a function of duration and amplitude of the voltage stimulus. We show that the state of each synapse can influence the activity of the other synapses, leading to complex switching dynamics. We further demonstrate the influence of the morphology of the network on the measured device properties, and the constraints imposed by the overall network conductance. The correlated switching dynamics, device stability over long periods, and the simplicity of the device fabrication provide an attractive pathway to practical implementation of on-chip neuromorphic computing.
ABSTRACT
Natural computers exploit the emergent properties and massive parallelism of interconnected networks of locally active components. Evolution has resulted in systems that compute quickly and that use energy efficiently, utilizing whatever physical properties are exploitable. Man-made computers, on the other hand, are based on circuits of functional units that follow given design rules. Hence, potentially exploitable physical processes, such as capacitive crosstalk, to solve a problem are left out. Until now, designless nanoscale networks of inanimate matter that exhibit robust computational functionality had not been realized. Here we artificially evolve the electrical properties of a disordered nanomaterials system (by optimizing the values of control voltages using a genetic algorithm) to perform computational tasks reconfigurably. We exploit the rich behaviour that emerges from interconnected metal nanoparticles, which act as strongly nonlinear single-electron transistors, and find that this nanoscale architecture can be configured in situ into any Boolean logic gate. This universal, reconfigurable gate would require about ten transistors in a conventional circuit. Our system meets the criteria for the physical realization of (cellular) neural networks: universality (arbitrary Boolean functions), compactness, robustness and evolvability, which implies scalability to perform more advanced tasks. Our evolutionary approach works around device-to-device variations and the accompanying uncertainties in performance. Moreover, it bears a great potential for more energy-efficient computation, and for solving problems that are very hard to tackle in conventional architectures.
ABSTRACT
We report on the tuning of the Kondo effect in thin Au films containing a monolayer of cobalt(II) terpyridine complexes by altering the ligand structure around the Co(2+) ions by depositing a thin Au capping layer on top of the monolayer on Au by magnetron sputtering (more energetic) and e-beam evaporation (softer). We show that the Kondo effect is slightly enhanced with respect to that of the uncapped film when the cap is deposited by evaporation, and significantly enhanced when magnetron sputtering is used. The Kondo temperature (TK) increases from 3 to 4.2/6.2 K for the evaporated/sputtered caps. X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy investigation showed that the organic ligands remain intact upon Au e-beam evaporation; however, sputtering inflicts significant change in the Co(2+) electronic environment. The location of the monolayer-on the surface or embedded in the film-has a small effect. However, the damage of Co-N bonds induced by sputtering has a drastic effect on the increase of the impurity-electron interaction. This opens up the way for tuning of the magnetic impurity states, e.g. spin quantum number, binding energy with respect to the host Fermi energy, and overlap via the ligand structure around the ions.
ABSTRACT
The low energy electronic structure of Gd has been investigated experimentally by infrared reflectance spectroscopy, and theoretically from first principles, using the fully relativistic Dirac linear-muffin-tin-orbital (LMTO) method in the local spin density approximation (LSDA) as well as within the LSDA + U approach. The reflectance of a Gd single crystal was measured with the electric field in the plane perpendicular to the c-axis for temperatures between 50 K and slightly above the Curie temperature (293 K) in the frequency range between 100 and 12 000 cm(-1) (0.013-1.5 eV). As Gd enters the ferromagnetic state, the dissipative part of the optical conductivity exhibits interesting spectral weight transfers over the whole spectral range measured. It is shown that the ab initio calculations reproduce well the experimental spectra for the ferromagnetic state and allow one to explain the microscopic origin of the optical response of Gd in terms of interband transitions.
Subject(s)
Gadolinium/chemistry , Magnets/chemistry , Models, Theoretical , Quantum Theory , Spectrophotometry, Infrared , Crystallography, X-Ray , Temperature , VibrationABSTRACT
The mutual interaction of localized magnetic moments and their interplay with itinerant conduction electrons in a solid are central to many phenomena in condensed-matter physics, including magnetic ordering and related many-body phenomena such as the Kondo effect, the Ruderman-Kittel-Kasuya-Yoshida interaction and carrier-induced ferromagnetism in diluted magnetic semiconductors. The strength and relative importance of these spin phenomena are determined by the magnitude and sign of the exchange interaction between the localized magnetic moments and also by the mean distance between them. Detailed studies of such systems require the ability to tune the mean distance between the localized magnetic moments, which is equivalent to being able to control the concentration of magnetic impurities in the host material. Here, we present a method for doping a gold film with localized magnetic moments that involves depositing a monolayer of a metal terpyridine complex onto the film. The metal ions in the complexes can be cobalt or zinc, and the concentration of magnetic impurities in the gold film can be controlled by varying the relative amounts of cobalt complexes (which carry a spin) and zinc complexes (which have zero spin). Kondo and weak localization measurements demonstrate that the magnetic impurity concentration can be systematically varied up to â¼800 ppm without any sign of inter-impurity interaction. Moreover, we find no evidence for the unwanted clustering that is often produced when using alternative methods.
Subject(s)
Crystallization/methods , Gold/chemistry , Nanoparticles/chemistry , Magnetic Fields , Materials Testing , Spin LabelsABSTRACT
We propose a general approach to generate parametric maps. It consists in a multi-stage hierarchical scheme where, starting from the kinetic analysis of the whole brain, we then cascade the kinetic information to anatomical systems that are akin in terms of receptor densities, and then down to the voxel level. A-priori classes of voxels are generated either by anatomical atlas segmentation or by functional segmentation using unsupervised clustering. Kinetic properties are transmitted to the voxels in each class using maximum a posteriori (MAP) estimation method. We validate the novel method on a [11C]diprenorphine (DPN) test-retest data-set that represents a challenge to estimation given [11C]DPN's slow equilibration in tissue. The estimated parametric maps of volume of distribution (VT) reflect the opioid receptor distributions known from previous [11C]DPN studies. When priors are derived from the anatomical atlas, there is an excellent agreement and strong correlation among voxel MAP and ROI results and excellent test-retest reliability for all subjects but one. Voxel level results did not change when priors were defined through unsupervised clustering. This new method is fast (i.e. 15 min per subject) and applied to [11C]DPN data achieves accurate quantification of VT as well as high quality VT images. Moreover, the way the priors are defined (i.e. using an anatomical atlas or unsupervised clustering) does not affect the estimates.
Subject(s)
Brain Mapping/methods , Diprenorphine , Positron-Emission Tomography/methods , Radiopharmaceuticals , Algorithms , Atlases as Topic , Bayes Theorem , Brain/anatomy & histology , Calibration , Carbon Radioisotopes , Cluster Analysis , Humans , Image Processing, Computer-Assisted , Kinetics , Magnetic Resonance Imaging , Models, Statistical , Nonlinear Dynamics , Normal Distribution , Reproducibility of ResultsABSTRACT
OBJECTIVE: To investigate striatal adenosine A2A receptor availability in patients with Parkinson disease (PD) with and without levodopa-induced dyskinesias (LIDs). While providing effective relief from the motor symptoms of PD, chronic levodopa use is associated with development of LIDs. A2A receptors are expressed on the bodies of indirect pathway medium spiny striatal neurons and on dopamine terminals and play a role in modulating dopamine transmission. A2A antagonists have antiparkinsonian activity by boosting levodopa efficacy. We aimed to study A2A receptor availability in patients with PD with and without LIDs using PET and [¹¹C]SCH442416, an A2A antagonist. METHODS: Six patients with PD with and 6 without LIDs were studied withdrawn 12 hours from medication. Their PET findings were compared with 6 age-matched healthy controls. Using spectral analysis, [¹¹C]SCH442416 regional volumes of distribution (V(T)) were computed for the caudate, putamen, and thalamus and binding potentials (BP(ND)) reflecting the ratio of specific:nonspecific uptake were compared between groups. RESULTS: A2A binding in the caudate and putamen of subjects with PD with LIDs was far higher (p = 0.026 and p = 0.036, respectively) than that of subjects with PD without LIDs, which lay within the control range. Thalamic A2A availability was similar for all 3 groups. CONCLUSION: Patients with PD with LIDs show increased A2A receptor availability in the striatum. This finding is compatible with altered adenosine transmission playing a role in LIDs and provides a rationale for a trial of A2A receptor agents in the treatment of these motor complications.
Subject(s)
Corpus Striatum/metabolism , Dyskinesia, Drug-Induced/physiopathology , Parkinson Disease/physiopathology , Receptor, Adenosine A2A/metabolism , Adenosine/metabolism , Adenosine A2 Receptor Antagonists/metabolism , Aged , Animals , Antiparkinson Agents/adverse effects , Antiparkinson Agents/therapeutic use , Corpus Striatum/anatomy & histology , Dyskinesia, Drug-Induced/metabolism , Female , Humans , Levodopa/adverse effects , Levodopa/therapeutic use , Male , Middle Aged , Parkinson Disease/drug therapy , Positron-Emission Tomography , Pyrazoles/metabolism , Pyrimidines/metabolismABSTRACT
BACKGROUND: Elevated striatal dopamine synthesis capacity is thought to be fundamental to the pathophysiology of schizophrenia and has also been reported in people at risk of psychosis. It is therefore unclear if striatal hyperdopaminergia is a vulnerability marker for schizophrenia, or a state feature related to the psychosis itself. Relatives of patients with schizophrenia are themselves at increased risk of developing the condition. In this study we examined striatal dopamine synthesis capacity in both members of twin pairs discordant for schizophrenia. METHOD: In vivo striatal dopamine synthesis capacity was examined using fluorine-18-l-dihydroxyphenylalanine (18F-DOPA) positron emission tomography (PET) scans in seven twin pairs discordant for schizophrenia and in a control sample of 10 healthy control twin pairs. RESULTS: Striatal 18F-DOPA uptake was not elevated in the unaffected co-twins of patients with schizophrenia (p=0.65) or indeed in the twins with schizophrenia (p=0.89) compared to the control group. Levels of psychotic symptoms were low in the patients with schizophrenia who were in general stable [mean (s.d.) Positive and Negative Syndrome Scale (PANSS) total=56.8 (25.5)] whereas the unaffected co-twins were largely asymptomatic. CONCLUSIONS: Striatal dopamine synthesis capacity is not elevated in symptom-free individuals at genetic risk of schizophrenia, or in well-treated stable patients with chronic schizophrenia. These findings suggest that striatal hyperdopaminergia is not a vulnerability marker for schizophrenia.