| 88721. |
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| 88722. |
- Holmberg, Anna, 1974, et al.
(författare)
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Enteric Control
- 2007
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Ingår i: Fish Larval Physiology, Eds RN Finn and BG Kapoor. - Enfield, NH, USA : Science Publishers. - 9781578083886 ; , s. 553-572
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 88723. |
- Holmberg, Anna, 1974, et al.
(författare)
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Ontogeny of the gut motility control system in zebrafish Danio rerio embryos and larvae
- 2004
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 207:23, s. 4085-4094
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Tidskriftsartikel (refereegranskat)abstract
- Using digital motion analysis, the ontogeny of the cholinergic, tachykinin and pituitary adenylate cyclase-activating polypeptide (PACAP) control systems was studied in zebrafish Danio rerio larvae, in vivo. For the first time we show that the regular propagating anterograde waves that occur in the zebrafish larval gut before and around the onset [at 5-6 days post fertilization (d.p.f.)] of feeding are modulated by acetylcholine or atropine, PACAP and NKA (neurokinin A). At 3 d.p.f., when no spontaneous motility has developed, application of acetylcholine did not affect the gut. However, at 4 d.p.f., acetylcholine increased and atropine reduced the frequency of propagating anterograde waves. At 5 d.p.f., NKA increased and PACAP reduced the wave frequency. This suggests that both excitatory and inhibitory pathways develop at an early stage in the gut, independent of exogenous feeding. Immunohistochemistry established the presence of gut neurons expressing PACAP and NKA in the proximal part of the developing gut from the first stage investigated (2 d.p.f.) and before regular motility was observed. I d.p.f. (PACAP) or 2 d.p.f. (NKA) stages later the whole gut was innervated. This supports physiological results that gut motility is under neuronal control during the period when regular motility patterns develop.
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| 88724. |
- Holmberg, Anna, 1974, et al.
(författare)
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The effects of endogenous and exogenous nitric oxide on gut motility in zebrafish Danio rerio embryos and larvae
- 2006
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 209:13, s. 2472-2479
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Tidskriftsartikel (refereegranskat)abstract
- Using motion analysis, the ontogeny of the nitrergic control system in the gut was studied in vivo in zebrafish Danio rerio embryos and larvae. For the first time we show the presence of a nitrergic tonus, modulating both anterograde and retrograde contraction waves in the intestine of developing zebrafish. At 4 d.p.f. (days post fertilisation), the nitric oxide synthase (NOS) inhibitor L-NAME (three boluses of 50-100 nl, 10(-3) mol l(-1)) increased the anterograde contraction wave frequency by 0.50 +/- 0.10 cycles min(-1). Subsequent application of the NO donor sodium nitroprusside (SNP; three boluses of 50-100 nl, 10(-4) mol l(-1)) reduced the frequency of propagating anterograde waves (-0.71 +/- 0.20 cycles min(-1)). This coincided with the first appearance of an excitatory cholinergic tonus, observed in an earlier study. One day later, at 5 d.p.f., in addition to the effect on anterograde contraction waves, application of L-NAME increased (0.39 +/- 0.15 cycles min(-1)) and following SNP application reduced (-1.61 +/- 0.36 cycles min(-1)) the retrograde contraction wave frequency. In contrast, at 3 d.p.f., when no spontaneous motility is observed, application of L-NAME did not induce contraction waves in either part of the gut, indicating the lack of a functional inhibitory tonus at this early stage. Gut neurons expressing NOS-like immunoreactivity were present in the distal and middle intestine as early as 2 d.p.f., and at 1 day later in the proximal intestine. In conclusion, the present study suggests that a nitrergic inhibitory tonus develops shortly before or at the time for onset of exogenous feeding.
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| 88725. |
- Holmberg, Anna, 1974, et al.
(författare)
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TTX-sensitive and TTX-insensitive control of spontaneous gut motility in the developing zebrafish (Danio rerio) larvae
- 2007
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Ingår i: JOURNAL OF EXPERIMENTAL BIOLOGY. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 210:6, s. 1084-1091
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneous regular gut motility in zebrafish begins around 4 days post fertilisation (d.p.f.) and is modulated by release of acetylcholine and nitric oxide. The role of intrinsic or extrinsic innervation for initiating and propagating the spontaneous contractions, however, is not well understood. By creating spatiotemporal maps, we could examine spontaneous motility patterns in zebrafish larvae in vivo at 4 and 7 d.p.f. in more detail. Tetrodotoxin (TTX) was added to elucidate the importance of nervous control. Anterograde and retrograde contraction waves originated in the same region,just posterior to the intestinal bulb. This area correlates well with the distribution of Hu (human neuronal protein C/D)-immunoreactive nerve cell bodies. Whereas numerous immunoreactive nerve cells were present in the mid and distal intestine at both 4 and 7 d.p.f., fewer cells were seen anterior to the origin of contractions. The overall frequency of contractions(1.16±0.15 cycles min–1, N=14 at 4 d.p.f.;1.05±0.09 cycles min–1, N=13 at 7 d.p.f.) and the interval between individual anterograde contraction waves (54.8±7.9 s at 4 d.p.f., N=14; 56.9±4.4 s, N=13 at 7 d.p.f.)did not differ between the two stages but the properties of the contractions were altered. The distance travelled by each wave increased from 591.0±43.8 μm at 4 d.p.f. (N=14) to 719.9±33.2 μm at 7 d.p.f. (N=13). By contrast, the velocity decreased from 4 d.p.f.(49.5±5.5 μm s–1, N=12) to 7 d.p.f.(27.8±3.6 μm s–1, N=13). At 4 d.p.f., TTX did not affect any of the parameters whereas at 7 d.p.f. anterograde frequency(control 1.07±0.12 cycles min–1, N=8; TTX 0.55±0.13 cycles min–1, N=8) and distance travelled (control 685.1±45.9 μm, N=8; TTX 318.7±88.7 μm, N=6) were decreased. In conclusion, enteric or extrinsic innervation does not seem to be necessary to initiate spontaneous contractions of the gut in zebrafish larvae. However, later in development,nerves have an increasingly important role as modulators of intestinal activity.)
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| 88726. |
- Holmberg, Britt, et al.
(författare)
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Algebra på dubbel tallinje
- 2020
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Ingår i: Nämnaren. ; 2020:1, s. 7-12
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 88727. |
- Holmberg, Britt
(författare)
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Analysera mera i geometri
- 2011
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Ingår i: Nämnaren. ; 2011:4, s. 10-15
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Inom undervisningen i geometri behöver vi utmana elevernas nyfikenhet med frågeställningar och ge dem tid att undersöka geometriska objekt. Praktiskt arbete där eleverna själva upplever och upptäcker samband ökar möjligheten att förstå geometri. Eleverna behöver många tillfällen att få resonera, diskutera och göra egna erfarenheter.
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| 88728. |
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| 88729. |
- Holmberg, Britt
(författare)
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"Jag räknade med fingrarna"
- 2019
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Ingår i: Nämnaren. - 0348-2723. ; :2019-2, s. 9-13
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Genom intervjuer med elever i åk 3 har författaren fått syn på olika sätt som elever använder sina fingrar på när de räknar. När fingrarna får representera ett antal finns goda möjligheter att utveckla god taluppfattning och effektiva räknestrategier, men då de används för dubbelräkning ger det ofta problem.
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| 88730. |
- Holmberg, Britt
(författare)
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"Jag räknade med fingrarna" - en studie om elevers beräkningsstrategier i subtraktion i årskurs 3
- 2018
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the study is to investigate how students in third grade solve subtractions problems and what strategies they use. Earlier research (Neuman, 1987; Svenson & Sjöberg, 1982) has shown that students leave third grade without sufficient knowledge in simple arithmetic. After a diagnose with 43 students in two classes, the students with many incorrect answers or using long time to solve the problems were selected for an interview. 18 students from the two classes were interviewed and videotaped during the last semester in grade 3 (nine years old). In the study the student’s strategies solving subtraction problems with and without fingers were studied. Semi structured interview was used as method in the study. The student’s strategies were analyzed with variation theory (Marton, 2015). Variation theory as a theoretical tool makes it possible to analyze how students experience numbers in different ways. Result of the study show that 60 % of the students are using “double counting”/”keeping track” with fingers as strategy for solving simple subtraction problems. When using double counting the students tend to see numbers as single units instead of groups of number that can be composed or decomposed. Double counting/keeping track as the only strategy for solving addition and subtraction problems indicate that students can have difficulties developing advanced computational skills. Seven of the 18 students did not use fingers for computation but showed difficulties in solving the subtraction problems. There was no difference among the students using or not using fingers, both groups had problems and did not use effective strategies.
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