| 1. |
- Forsell, Johan
(författare)
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Development of photoreceptor organs in teleosts, Molecular and immunocytochemical studies
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many vertebrate animals are known to have multiple sites for photoreception that are not involved in vision. Extraretinal photoreception is indicated to play a crucial role in early development, physiology and behavior, as well as in later biological processes. This thesis encompasses four studies investigating the neuromorphological, neurochemical and molecular basis for extraretinal photosensitivity in teleosts (bony fishes) during development. The first study, investigating developing Atlantic halibut, identified the pineal organ as the only photoreceptor organ with a capacity to mediate photic information crucial for embryonic behavioral processes such as vertical migration and hatching. In the second study, Atlantic herring and cod were investigated, as they have very different early life strategies: during early development the herring is demersal (bottom-dwelling), wheras the cod is pelagic. In both species, extraretinal photosensory organs develop before the retina. The temporal difference was more pronounced in the demersal herring embryos than in the pelagic cod. Furthermore, herring embryos possess additional "deep" photoreceptors in the brain, previously not shown in developing teleosts. In the third study, two opsin (the protein part of the photopigment) genes were isolated from the halibut pineal, and characterized as coding for a UV-sensitive and a green-sensitive opsin. Both are expressed in the embryonic pineal organ. At first, UV-sensitive opsin predominates, but during subsequent development green-sensitive opsin prevails, possibly reflecting the switch from a pelagic to a demersal life. Finally, in the fourth study the presence of UV-sensitive opsin in extraretinal and retinal photoreceptors was investigated in various teleosts from different habitats and with different life strategies. UV-sensitive pineal photoreceptors were only found in the halibut, but UV-sensitive cones were identified in the retina of halibut, salmon, zebrafish,turbot and three cichlid species. In conclusion, a general developmental pattern can be outlined insofar that extraretinal photoreceptors differentiate earlier than retinal photoreceptors. An earlier differentiation of extraretinal photosensory structures in species with demersal eggs, as compared to those with pelagic embryonic life, is suggested to reflect (1) an early adaptation to the photic environment encountered by the eggs and larvae, and (2) the general developmental programme of the CNS.
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| 2. |
- Forsell, Johan, et al.
(författare)
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Molecular identification and developmental expression of UV and green opsin mRNAs in the pineal organ of the Atlantic halibut.
- 2002
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Ingår i: Developmental Brain Research. - 0165-3806. ; 136:1, s. 51-62
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Tidskriftsartikel (refereegranskat)abstract
- The pineal organ is the only differentiated photoreceptor organ present in embryos and early larvae of the Atlantic halibut (Hippoglossus hippoglossus). We investigated the molecular identity of opsins in the pineal organ, and their expression during different life stages. Using RT-PCR we identified two 681-bp gene sequences, named HPO1 and HPO4, in cDNA from adult pineal and whole embryos. The predicted amino acid sequences showed highest identity to the transmembrane regions of teleostean RH2 green cone opsins (HPO1, 72-91%) and SWS-1 UV cone opsins (HPO4, 71-83%). In situ hybridization revealed expression of HPO1 and HPO4 mRNA transcripts in photoreceptors in the pineal organ of embryos, larvae and adults. HPO1 and HPO4 mRNA transcripts were also expressed in the larval retina. Our study provides molecular evidence for short and middle wavelength light sensitive photoreceptors in the pineal organ of Atlantic halibut throughout life, and suggests that pineal photoreception may play an important role during embryonic and larval life stages, especially at the time when the retina does not possesses corresponding photoreceptor capacity.
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| 3. |
- Giron, Maria Stella T, et al.
(författare)
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Psychotropic drug use in elderly people with and without dementia
- 2001
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Ingår i: International Journal of Geriatric Psychiatry. - : Wiley. - 0885-6230 .- 1099-1166. ; 16:9, s. 900-906
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveTo determine the prevalence of psychotropic drug use in very old persons with and without dementia in two time periods, and describe the patterns of psychotropic drug use between institutions and non-institutions.MethodsDescriptive analysis on a sample of subjects aged 81+ from a population-based study in Stockholm, Sweden. Psychotropic drug use data were collected from the 1987-1989 and 1994-1996 periods of the study. The diagnosis of dementia was based on the DSM III-R.ResultsAbout 41% of the subjects used at least one psychotropic drug in both periods. Women and subjects in institutions more commonly used psychotropic drugs. The most commonly reported were, in rank order, hypnotics-sedatives, anxiolytics, antipsychotics and antidepressants. Hypnotics-sedatives and anxiolytics were the most commonly used in both institutions and non-institutions. More persons with dementia used psychotropic drugs in both periods. The use of newer drugs, for example, SSRI, was evident. Multivariate analyses showed increased risk for psychotropic drug use among subjects in institutions.ConclusionsThis study confirms the high rate of psychotropic drug use in the very old, particularly in persons with dementia. Psychotropic drug use was high among subjects living in institutions.
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| 4. |
- Giron, Maria Stella T, et al.
(författare)
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Sleep problems in a very old population : drug use and clinical correlates
- 2002
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Ingår i: The journals of gerontology. Series A, Biological sciences and medical sciences. - 1079-5006 .- 1758-535X. ; 57:4, s. M236-40
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Tidskriftsartikel (refereegranskat)abstract
- Background. Complaints of disturbed or dissatisfied sleep are common among older people. This study aimed to evaluate the prevalence of sleep problems in very old persons and its relation to physical and mental health and drug use. Methods. This is a cross-sectional analysis of sleep problems in a population of old persons living in Stockholm, Sweden. There were 641 subjects aged 81+ years; 77.8% were women, 91.4% were noninstitutionalized, and 68.6% lived alone. All persons underwent a comprehensive medical and psychiatric interview and examination. Sleep problems were assessed using the Clinical Psychopathological Rating Scale (CPRS). Covariates included chronic medical conditions, depression, dementia, pain, self-rated health, activities of daily living, use of hypnotics-sedatives, use of other psychotropic drugs, and use of nonpsychotropic drugs. Results. More than one third of subjects were identified with sleep problems. They were more common among women and persons using a higher number of drugs. Poor self-rated health, depression, and pain were related to the presence of sleep problems. Among persons with sleep problems and depression, only 19.2% used antidepressants, and 46.2% used hypnotics-sedatives. Among persons with sleep problems and pain, 63.2% used analgesics, and 47.0% used hypnotics-sedatives. One or more chronic diseases, use of hypnotics-sedatives, use of other psychotropic drugs, and use of nonpsychotropic drugs were also related to sleep problems. After multivariate analysis, factors significantly related to sleep problems were female gender, depression, pain, and hypnotic-sedative use. Conclusions. Sleep problems were common in this very old population. These results suggest the importance of carefully assessing an older person's complaints to accurately diagnose and effectively treat sleep problems.
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| 5. |
- Gustafsson, Fredrik, et al.
(författare)
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Particle Filters for Positioning, Navigation and Tracking
- 2002
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 50:2, s. 425-437
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Tidskriftsartikel (refereegranskat)abstract
- A framework for positioning, navigation and tracking problems using particle filters (sequential Monte Carlo methods) is developed. It consists of a class of motion models and a general non-linear measurement equation in position. A general algorithm is presented, which is parsimonious with the particle dimension. It is based on marginalization, enabling a Kalman filter to estimate all position derivatives, and the particle filter becomes low-dimensional. This is of utmost importance for high-performance real-time applications. Automotive and airborne applications illustrate numerically the advantage over classical Kalman filter based algorithms. Here the use of non-linear models and non-Gaussian noise is the main explanation for the improvement in accuracy. More specifically, we describe how the technique of map matching is used to match an aircraft's elevation profile to a digital elevation map, and a car's horizontal driven path to a street map. In both cases, real-time implementations are available, and tests have shown that the accuracy in both cases is comparable to satellite navigation (as GPS), but with higher integrity. Based on simulations, we also argue how the particle filter can be used for positioning based on cellular phone measurements, for integrated navigation in aircraft, and for target tracking in aircraft and cars. Finally, the particle filter enables a promising solution to the combined task of navigation and tracking, with possible application to airborne hunting and collision avoidance systems in cars.
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| 6. |
- Hellgren, Johan, 1966-, et al.
(författare)
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Bias of feedback cancellation algorithms in hearing aids based on direct closed loop identification
- 2001
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Ingår i: IEEE transactions on speech and audio processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1063-6676 .- 1558-2353. ; 9:8, s. 906-913
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Tidskriftsartikel (refereegranskat)abstract
- The undesired effects of acoustic feedback of hearing aids can be reduced with an internal feedback path that is an estimate of the external feedback path. This paper analyzes the limiting estimate of the feedback for feedback cancellation schemes that apply some recursive prediction error method with a quadratic norm, e.g., least mean square (LMS) and recursive least squares (RLS), to the output and input signals of the hearing aid to identify the feedback path. The data used for identification is then collected in closed loop and the estimate used in one recursion will affect the data used in succeeding recursions. These properties have to be considered in the analysis. The analysis shows that the limiting estimate may be biased if there is an error in the used model of the input signal to the hearing aid, and that the system is not identifiable unless a second input signal to the system is added to the output of the hearing aid or the signal processing of the hearing aid used to modify the signal to the impaired ear is nonlinear. The limiting estimate is presented as the solution to an optimization problem in the frequency domain. An analytical expression of the limiting estimate is presented for a special case. For other cases an algorithm is presented that can be used to find a numerical solution. The results can be useful when the model structure used with the recursive identification is chosen.
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| 7. |
- Holmqvist, Bo, et al.
(författare)
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The early ontogeny of neuronal nitric oxide synthase systems in the zebrafish.
- 2004
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 207:Pt 6, s. 923-935
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Tidskriftsartikel (refereegranskat)abstract
- To examine a putative role for neuronal nitric oxide synthase (nNOS) in early vertebrate development we investigated nNOS mRNA expression and cGMP production during development of the zebrafish Danio rerio. The nNOS mRNA expression in the central nervous system (CNS) and periphery showed a distinct spatio-temporal pattern in developing zebrafish embryo and young larvae. nNOS mRNA expression was first detected at 19 h postfertilisation (h.p.f.), in a bilateral subpopulation of the embryonic ventrorostral cell cluster in the forebrain. The number of nNOS mRNA-expressing cells in the brain slowly increased, also appearing in the ventrocaudal cell cluster from about 26 h.p.f., and in the dorsorostral and hindbrain cell cluster and in the medulla at 30 h.p.f. A major increase in nNOS mRNA expression started at about 40 h.p.f., and by 55 h.p.f. the expression constituted cell populations in differentiated central nuclei and in association with the proliferation zones of the brain, and in the medulla and retina. In parts of the skin, nNOS mRNA expression started at 20 h.p.f. and ended at 55 h.p.f. Between 40 and 55 h.p.f., nNOS mRNA expression started in peripheral organs, forming distinct populations after hatching within or in the vicinity of the presumptive swim bladder, enteric ganglia, and along the alimentary tract and nephritic ducts. Expression of nNOS mRNA correlated with the neuronal differentiation pattern and with the timing and degree of cGMP production. These studies indicate spatio-temporal actions by NO during embryogenesis in the formation of the central and peripheral nervous system, with possible involvement in processes such as neurogenesis, organogenesis and early physiology.
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