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- Fetz, E. E., et al.
(författare)
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Autogenetic inhibition of motoneurones by impulses in group Ia muscle spindle afferents.
- 1979
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 293, s. 173-195
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Tidskriftsartikel (refereegranskat)abstract
- 1. Inhibitory post‐synaptic potentials evoked by adequate stimulation of group Ia muscle spindle afferents of homonymous and synergistic muscles and by selective electrical stimulation of tendon organ afferents were analysed in motoneurones of triceps surae and plantaris. 2. Selective activation of Ia afferents was verified to occur with brief stretches of triceps surae and plantaris 35 micrometer or less in amplitude with an initial muscle tension of 5 N; stretches of 30‐‐35 micrometer were estimated to activate 80‐‐90% of Ia afferents in these muscles. Under the same conditions the lowest thresholds for group Ib tendon organ afferents were about 40 micrometer. 3. Stretches less than or equal to 30 micrometer evoked i.p.s.p.s in 80% of triceps surae and plantaris motoneurones; lowest thresholds for evoking i.p.s.p.s wef triceps surae and plantaris motoneurones; lowest thresholds for evoking i.p.s.p.s were 10 micrometer or less. However, such low thresholds for stretch‐evoked i.p.s.p.s, lower than the thresholds for activation of Ib afferents, were found mainly in spinalized, unanaesthetized (after decerebration) or lightly anaesthetized animals. The latencies of these i.p.s.p.s indicated disynaptic and trisynaptic coupling between Ia afferents and motoneurones. The i.p.s.p.s were evoked (i) from the homonymous and synergistic muscles stretched together, (ii) from the homonymous muscles alone and (iii) from the synergistic muscles alone. 4. Control experiments showed that i.p.s.p.s could be evoked by stretches sub‐threshold for discharging motoneurones, thus showing that those i.p.s.p.s were not mediated by Renshaw cells. The stretch‐evoked i.p.s.p.s disappeared after sectioning the nerves from the corresponding muscles, further excluding their mediation by afferents other than group Ia afferents from thf stretched muscle. 5. In order to selectively activate tendon organ afferents, thresholds for excitation of Ia afferents by electrical stimuli were increased to a level above the threshold for Ib afferents by prolonged muscle vibration (Coppin, Jack & MacLennan, 1970). I.p.s.p.s evoked by stimuli near threshold for Ib afferents appeared with latencies indicating disynaptic coupling. Later (trisynaptic) components of Ib i.p.s.p.s required somewhat stronger stimuli. 6. Amplitudes of Ia i.p.s.p.s evoked by muscle stretches activating about 80% of muscle spindle afferents were compared with amplitudes of Ib i.p.s.p.s due to less than 50% of tendon organ afferents of the same muscles. The Ia i.p.s.p.s were much smaller (16‐‐35%) than the Ib i.p.s.p.s. The amplitudes of such Ia and Ib i.p.s.p.s constituted about 10 and 25‐‐66%, respectively, of the maximal i.p.s.p.s evoked by electrical stimulation of all group I afferents. 7. We conclude that inhibition of motoneurones may be evoked from Ia muscle spindle afferents from homonymous and synergistic muscles as well as from Ib tendon organ afferents... © 1979 The Physiological Society
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| 2. |
- Harrison, P. J., et al.
(författare)
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Shared reflex pathways of group I afferents of different cat hind‐limb muscles.
- 1983
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 338, s. 113-128
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Tidskriftsartikel (refereegranskat)abstract
- The convergence of group I muscle afferents of different muscle origin onto interneurones in spinal reflex pathways has been investigated using the technique of spatial facilitation of the transmission from afferents to motoneurones. The investigated pathways are those of non‐reciprocal inhibition and of oligosynaptic excitation of motoneurones. Extensive convergence has been found of group I afferents from muscles operating at the same and different joints onto the interneurones interposed in both excitatory and inhibitory, disynaptic and trisynaptic pathways to motoneurones. Convergence has been found between muscle spindle Ia and/or tendon organ Ib afferents from different muscles, thereby extending observations on convergence of these subgroups of group I afferents from the same muscles. The results show that group I afferents of different muscles influence motoneurones via shared neuronal pathways and that transmission from these afferents is influenced by afferents originating in other muscles. The afferent information forwarded to individual motoneurones is therefore the ensemble picture of the length and tension of many muscles. © 1983 The Physiological Society
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| 3. |
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| 4. |
- Morrell, Jane M., et al.
(författare)
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Sperm morphology and chromatin integrity in Swedish warmblood stallions and their relationship to pregnancy rates
- 2008
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Ingår i: Acta Veterinaria Scandinavica. - : BioMed Central. - 0044-605X .- 1751-0147. ; 50
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Tidskriftsartikel (refereegranskat)abstract
- Background: Artificial insemination is not as widely used in horses as in other domestic species, such as dairy cattle and pigs, partly because of the wide variation in sperm quality between stallion ejaculates and partly due to decreased fertility following the use of cooled transported spermatozoa. Furthermore, predictive tests for sperm fertilising ability are lacking. The objective of the present study was to assess sperm morphology and chromatin integrity in ejaculates obtained from II warmblood breeding stallions in Sweden, and to evaluate the relationship of these parameters to pregnancy rates to investigate the possibility of using these tests predictively. Methods: Aliquots from fortyone ejaculates, obtained as part of the normal semen collection schedule at the Swedish National Stud, were used for morphological analysis by light microscopy, whereas thirtyseven were used for chromatin analysis (SCSA) by flow cytometry. The outcome of inseminations using these ejaculates was made available later in the same year. Results: Ranges for the different parameters were as follows; normal morphology, 27-79.5%; DNA-fragmentation index (DFI), 4.8-19.0%; standard deviation of DNA fragmentation index (SD_DFI) 41.5-98.9, and mean of DNA fragmentation index (mean_DFI), 267.7-319.5. There was considerable variation among stallions, which was statistically significant for all these parameters except for mean_DFI (P less than 0.001, P less than 0.01, P less than 0.001 and P less than 0.2 respectively). There was a negative relationship between normal morphology and DFI (P less than 0.05), between normal morphology and SD_DFI (P less than 0.001), and between normal morphology and mean_DFI (P less than 0.05). For specific defects, there was a direct relationship between the incidence of pear-shaped sperm heads and DFI (P less than 0.05), and also nuclear pouches and DFI (P less than 0.001), indicating that either morphological analysis or chromatin analysis was able to identify abnormalities in spermiogenesis that could compromise DNA-integrity. A positive relationship was found between normal morphology and pregnancy rate following insemination (r = 0.789; P less than 0.01) and a negative relationship existed between DFI and pregnancy rate (r = -0.63; P less than 0.05). Sperm motility, assessed subjectively, was not related to conception rate. Conclusion: Either or both of the parameters, sperm morphology and sperm chromatin integrity, seem to be useful in predicting the fertilising ability of stallion ejaculates, particularly in determining cases of sub-fertility.
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| 5. |
- Persson, Emil, et al.
(författare)
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Discrepancy between Health Care Rationing at the Bedside and Policy Level
- 2018
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Ingår i: Medical decision making. - : SAGE PUBLICATIONS INC. - 0272-989X .- 1552-681X. ; 38:7, s. 881-887
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Tidskriftsartikel (refereegranskat)abstract
- Background. Whether doctors at the bedside level should be engaged in health care rationing is a controversial topic that has spurred much debate. From an empirical point of view, a key issue is whether there exists a behavioral difference between rationing at the bedside and policy level. Psychological theory suggests that we should indeed expect such a difference, but existing empirical evidence is inconclusive. Objective. To explore whether rationing decisions taken at the bedside level are different from rationing decisions taken at the policy level. Method. Behavioral experiment where participants (n = 573) made rationing decisions in hypothetical scenarios. Participants (medical and nonmedical students) were randomly assigned to either a bedside or a policy condition. Each scenario involved 1 decision, concerning either a life-saving medical treatment or a quality-of-life improving treatment. All scenarios were identical across the bedside and policy condition except for the level of decision making. Results. We found a discrepancy between health care rationing at policy and bedside level for scenarios involving life-saving decisions, where subjects rationed treatments to a greater extent at the policy level compared to bedside level (35.6% v. 29.3%, P = 0.001). Medical students were more likely to ration care compared to nonmedical students. Follow-up questions showed that bedside rationing was more emotionally burdensome than rationing at the policy level, indicating that psychological factors likely play a key role in explaining the observed behavioral differences. We found no difference in rationing between bedside and policy level for quality-of-life improving treatments (54.6% v. 55.7%, P = 0.507). Conclusions. Our results indicate a robust bedside effect in the life-saving domain of health care rationing decisions, thereby adding new insights to the understanding of the malleability of preferences related to resource allocation.
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