Quality of life of patients with 3D-printed arm prostheses in a rural area of Sierra Leone.

INTRODUCTION: In Sierra Leone, access to prostheses is limited due to absence of practical knowledge, materials, trained staff, and high cost. This paper investigates the impact of a 3D printed prosthesis on the health-related quality of life (HRQoL) in prosthesis recipients. METHODS: Patients with upper extremity amputations were included in this case study from December 2018 until July 2019. Data on the HRQoL was gathered until April 2020 in Masanga Hospital, central rural Sierra Leone. At two follow-up moments the HRQoL was assessed by applying the standard EQ-5D-5L questionnaire. These two follow-up moments varied between one week and just over a year after receiving the prosthesis. A second patient questionnaire was used to assess prosthesis satisfaction. RESULTS: Seven patients were included. The results of the EQ-5D-5L questionnaire show no deterioration of the HRQoL in any patient and the overall HRQoL increased by almost 20% compared to the null measurement. One patient was lost to follow up after the first re-visit. The responses to the second questionnaire indicated that patients are satisfied with the prosthesis and use it in various situations. Patients often mentioned they feel more included in society when wearing the prosthesis. One patient says wearing the prosthesis helped in accepting the amputation. As a result, enough self-confidence was experienced without the prosthesis and the patients stopped wearing the prosthesis. DISCUSSION: The overall HRQoL in patients wearing a 3D-printed prosthesis increases compared to not wearing one. Assessing the HRQoL at regular intervals is important for the long-term follow-up and to safeguard sustainability and long-term success of this project. Nevertheless, defining the HRQoL is challenging due to cultural differences and misunderstandings. Therefore, the use of alternative questionnaires to define the HRQoL should be investigated. To improve and warrant long-term success, identifying long-term problems is important, and the second questionnaire accounts for this need.

[Transition from paediatric to adult care: management of adolescents with inflammatory bowel disease]. / Transitie van kinder- naar volwassenenzorg.

The transfer of adolescent patients with inflammatory bowel disease (IBD) to adult gastroenterology services is often troublesome. Failed transition can have adverse effects on the course of disease. We present two cases of adolescent IBD patients and their transition process. We identify requirements for successful transition and discuss potential barriers. We illustrate and emphasise that the medical teams on each side (paediatric and adult), as well as the patient and the parents should actively participate in the process of transition. The medical team should, preferably during a local transition clinic, regularly evaluate disease knowledge and self-management skills of the patient and make an individual transition plan to fill the gaps in knowledge and/or skills. Patients should be willing to learn to become more independent and parents should be stimulated to create an environment so that their child can actually try to become more independent. Lastly, we present the Rotterdam model for transition of IBD patients.

SSR149415, a non-peptide vasopressin V1b receptor antagonist, has long-lasting antidepressant effects in the olfactory bulbectomy-induced hyperactivity depression model.

Olfactory bulbectomy (OBX) in rats causes several behavioral and neurochemical CNS changes, reminiscent of symptoms of human depression. Such depression-like behavior after OBX can be reversed with antidepressants. Recently, a connection between the vasopressin 1b (V1b) receptor and the development of depression has been suggested; therefore, a vasopressin V1b receptor antagonist (SSR149415) was investigated in the OBX model. Male rats received olfactory bulbectomy or sham surgery. After recovery, animals received 14 consecutive daily doses of SSR149415 (10 or 30 mg/kg), imipramine (20 mg/kg), or vehicle (5% hydroxy-propyl methylcellulose). Animals were tested in an open field after acute treatment, on days 7 and 14 of treatment and 1 week after cessation of treatment. Similar to imipramine, repeated, but not acute, administration of SSR149415 completely reversed OBX-induced hyperactivity, leaving activity in shams unaffected. This reversal of OBX-induced hyperactivity in the SSR149415 treated rats was still present 7 days after cessation of treatment. Although the behavioral effects of treatment with SSR149415 were specific for the OBX animals, adrenal gland weights were reduced in both sham and OBX animals treated with 30 mg/kg SSR149415. Chronic but not acute administration of SSR149415 normalizes OBX-induced hyperactivity up to 1 week after cessation of treatment, suggesting that a V1b receptor antagonist may have long-lasting antidepressant activity.

AMPA receptor antagonists reverse effects of extended habit training on signaled food approach responding in rats.

RATIONALE: Dopamine D1 receptor stimulation is critically involved in early appetitive phases of learning in various behavioral paradigms. However, extended habit training was previously shown to reduce the ability of dopamine D1 receptor antagonists such as R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride (SCH-23390) to disrupt behavioral performance. OBJECTIVE: The present study aimed to evaluate whether coadministration of glutamate alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) receptor antagonists restores sensitivity to acute blockade of D1 receptors. MATERIALS AND METHODS: Adult male Wistar rats were presented with 45-mg food pellets delivered to the food tray, which was immediately preceded by a 400-ms tone (2.8 kHz, 78 dB). During each training and test session, there were 28 food-tone presentations with an average intertrial interval of 70 s, and each head entry into the food tray was recorded. Drug tests were conducted on either day 3 or 9 of the training using independent groups of animals. The main dependent variable was the number of trials during which no head-entry response was made during the 10-s period immediately after the food delivery. RESULTS: Longer training duration enhanced the resistance of the signaled food approach behavior to extinction and to disrupting effects of supplementary food ration. Similarly, acute administration of SCH-23390 (0.04-0.16 mg/kg) dose-dependently reduced the number of omitted trials when given before the test session on day 3 but much less so when injected on day 9. AMPA receptor antagonists, NBQX (10 mg/kg) or GYKI-52466 (3-10 mg/kg), had no effects on their own but significantly enhanced the disrupting effects of SCH-23390 (0.08 and 0.16 mg/kg) when given on day 9 but not on day 3 of the training. CONCLUSIONS: These results indicate that AMPA receptor blockade restores sensitivity to appetitive behavior-disrupting effects of SCH-23390 in subjects exposed to extended training protocol.

Strain specificity and cholinergic modulation of visuospatial attention in three inbred mouse strains.

The tremendous increase in the use of mouse inbred strains and mutant mice to study the molecular basis of psychiatric disorders urges for a better understanding of attentional performance in mice. To this aim, we investigated possible strain differences in performance and cholinergic modulation of visuospatial attention in three widely used mouse inbred strains (129S2/SvHsd, C57BL/6JOlaHsd and DBA/2OlaHsd) in the five-choice serial reaction time task. Results indicated that after extended training, performance of 129S2/SvHsd mice was superior to that of C57BL/6JOlaHsd and DBA/2OlaHsd mice in terms of attention, omission errors, inhibitory control and latencies to correct choice. Increasing the attentional load resulted in comparable decrements in attention in all strains and inhibitory control impairments that were most pronounced in DBA/2OlaHsd mice. Further pharmacological evaluation indicated that all strains showed attentional impairments after treatment with the muscarinic and nicotinic antagonists scopolamine and mecamylamine, respectively. 129S2/SvHsd mice were less sensitive, whereas DBA/2OlaHsd mice appeared more sensitive to the detrimental effects of mecamylamine. In addition, subchronic, but not acute, nicotine treatment slightly improved attentional performance in all strains to the same extent. In conclusion, our data indicate strain specificity with particularly good performance of 129S2/SvHsd mice and strong cholinergic involvement in visuospatial attention in mice.

Reduced attention in mice overproducing corticotropin-releasing hormone.

Data from several studies suggest that unrestrained secretion of corticotropin-releasing hormone in the CNS produces several signs and symptoms of depression. Recent evidence indicates that blockade of the CRH receptor 1 reduced depression scores in depressed patients. One of the symptoms that occur is depression is impairment in attentional processes. Whether these impairments are due to alterations in the CRH system are so far unknown. In order to investigate whether overproduction of CRH alters attentional process, transgenic mice overproducing CRH were tested on an operant five choice serial reaction time task, a task which taxes sustained and divided attention. Mutants showed impaired autoshaping. During initial discrimination learning, transgenics performed below wildtype level, but with extended training with long stimulus durations, transgenic animals reached similar accuracy levels as wildtype mice. When animals were tested at shortest stimulus duration (0.5s), a mild but significant impairment in accurate responding emerged in transgenics. This was accompanied by longer correct response latencies, while incorrect latencies did not differ between groups, suggesting attentional impairment in CRH transgenics. Because these animals have been reported to also show increased anxiety-related behaviour, animals were treated with the anxiolytic benzodiazepine diazepam. Diazepam failed to affect accuracy, but transgenic mice showed a stronger behavioural disinhibition. This suggests that the attentional impairment seen in CRH overexpressors is independent of alterations in anxiety-like behaviour. These findings may have implications for understanding the pathophysiology of psychiatric disorders such as depression, where it has been suggested that an overactivity of the CRH system accounts for a variety of symptoms, including hyper-arousal and attentional impairment.

Molecular characterisation of antidepressant effects in the mouse brain using gene expression profiling.

Antidepressants are widely used for the treatment of psychiatric disorders, including depression and anxiety. Although they are efficient drugs, there are several unsolved questions regarding their clinical pharmacology. Furthermore, the molecular mechanisms of action of antidepressants are still poorly understood and the molecular targets and pathways remain to be identified. To address these issues, we performed a gene expression analysis in mice treated with two commonly used antidepressants with differing pharmacology (paroxetine or mirtazapine) for 1, 7 or 28 days. We quantified the effects of these treatments on gene expression in the mouse brain with cDNA-microarrays containing 3624 expressed sequence tags (ESTs) representing murine genes expressed in the brain. We found that both drugs led to downregulation of four common genes. In addition, although it was possible to identify common targets for the two drugs, the expression profiles of the drugs differed in a fundamental manner, and the longer the treatment duration, the greater the difference in the profiles. These findings suggest that antidepressants with different pharmacologies can share molecular targets even though the primary pathways at which they act are different.

Mice overexpressing CRH show reduced responsiveness in plasma corticosterone after a5-HT1A receptor challenge.

Corticotropin-releasing hormone (CRH) overproduction and serotonergic dysfunction have both been implicated in a range of psychiatric disorders, such as anxiety and depression, and several studies have shown interactions between these two neurotransmitter systems. In this study, we investigated the effects of CRH challenge on hypothalamo-pituitary-adrenal (HPA) axis activity in female transgenic mice overproducing CRH. Furthermore, the effects of mild stress on HPA axis activity and body temperature were investigated in these mice. Pre- and post-synaptic 5-HT1A receptor function were studied by monitoring body temperature and plasma corticosterone levels after challenge with the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propyl-amino)-tetralin (8-OH-DPAT). Hypothermia in response to 8-OH-DPAT treatment did not differ between transgenic and wild type mice, indicating unaltered somatodendritic 5-HT1A autoreceptor function in mice overproducing CRH. In wild type mice 8-OH-DPAT increased plasma corticosterone levels, but not in transgenic animals. CRH injection, however, increased corticosterone levels in both groups. These data suggest desensitization of post-synaptic, but not pre-synaptic, 5-HT1A receptors in mice overproducing CRH. These findings resemble those seen in depressed patients following 5-HT1A challenge, which is in accord with the hypothesized role of CRH in the pathogenesis of depression.

Functional analysis of the hexose transporter homologue HXT5 in Saccharomyces cerevisiae.

The HXT5 gene encodes a functional hexose transporter that has moderate affinity for glucose (K(m)=10 mM), moderate to low affinity for fructose (K(m)=40 mM) and low affinity for mannose (K(m)>100 mM). The sole presence of Hxt5p in an otherwise hexose transport null mutant is sufficient to sustain a flux through glycolysis from glucose to fermentative products. However, the presence of HXT5 as the sole hexose transporter gene results in extremely poor growth on glucose, which suggests the involvement of glucose repression in the transcriptional regulation of HXT5. From Northern blot analysis on the members of the HXT family and studies with HXT5 tagged with the green fluorescent protein (GFP), it is evident that HXT5 is transcribed and translated during conditions of relatively slow growth, during growth on non-fermentable carbon sources and in particular during sporulation. In wild-type batch cultivations on fermentable carbon sources, Hxt5p is abundant in stationary phase or after depletion of the fermentable carbon source, which seems independent of the carbon source. The deletion of HXT5 does not result in a clear phenotype. A shift of stationary phase cells to fresh glucose medium resulted in somewhat slower resumption of growth in the hxt5 deletion strain compared to the wild-type strain. The abundance of Hxt5p during stationary phase, sporulation and low glucose conditions suggests that HXT5 is a 'reserve' transporter, which might be involved in the initial uptake of glucose after the appearance of glucose. Other possible functions of the protein encoded by HXT5 will be discussed in the context of the results.

Regulation of the hypothalamic-pituitary-adrenocortical system in mice deficient for CRH receptors 1 and 2.

Recent investigations in mouse lines either deficient for the CRH receptor 1 (CRHR1) or 2 (CRHR2) suggest that the CRH neuronal system may comprise two separate pathways that can be coordinately and inversely activated in stress-induced hypothalamic-pituitary-adrenal (HPA) response and anxiety-like behavior. We generated mice deficient for both CRHR1 (Crhr1(-/-)) and CRHR2 (Crhr2(-/-)) to investigate the HPA system regulation in the absence of known functionally active CRH receptors under basal conditions and in response to different ethologically relevant stressors. To elucidate possible gene dose effects on the action of both CRH receptors, our analysis included heterozygous and homozygous CRHR1- or CRHR2-deficient mice, mutants lacking both CRH receptors, compound mutants with homozygous and heterozygous deficiency for either of the receptors, and their wild-type littermates. Both male and female Crhr1(-/-)Crhr2(-/-) mutants were viable, fertile, and indistinguishable in size from wild-type littermates. We show that the endocrine phenotype of mice lacking both CRHRs is dominated by the functional loss of CRHR1. CRHR2 does not compensate for CRHR1 deficiency, nor does the lack of CRHR2 exacerbate the CRHR1-dependent impairment of the HPA system function. Within the intraadrenal CRH/ACTH system, our data suggest different roles for CRHR1 and CRHR2 in fine-tuning of adrenocortical corticosterone release.

Co-consumption of sugars or ethanol and glucose in a Saccharomyces cerevisiae strain deleted in the HXK2 gene.

In previous studies it was shown that deletion of the HXK2 gene in Saccharomyces cerevisiae yields a strain that hardly produces ethanol and grows almost exclusively oxidatively in the presence of abundant glucose. This paper reports on physiological studies on the hxk2 deletion strain on mixtures of glucose/sucrose, glucose/galactose, glucose/maltose and glucose/ethanol in aerobic batch cultures. The hxk2 deletion strain co-consumed galactose and sucrose, together with glucose. In addition, co-consumption of glucose and ethanol was observed during the early exponential growth phase. In S.cerevisiae, co-consumption of ethanol and glucose (in the presence of abundant glucose) has never been reported before. The specific respiration rate of the hxk2 deletion strain growing on the glucose/ethanol mixture was 900 micromol.min(-1).(g protein)(-1), which is four to five times higher than that of the hxk2 deletion strain growing oxidatively on glucose, three times higher than its parent growing on ethanol (when respiration is fully derepressed) and is almost 10 times higher than its parent growing on glucose (when respiration is repressed). This indicates that the hxk2 deletion strain has a strongly enhanced oxidative capacity when grown on a mixture of glucose and ethanol.

Effects of the monoamine oxidase A inhibitor moclobemide on hippocampal plasticity in GR-impaired transgenic mice.

A reduction in glucocorticoid receptor (GR) function leads to hippocampus-dependent allocentric spatial learning deficits, altered novelty exploration and disrupted hippocampal long-term potentiation (LTP) in transgenic mice expressing a GR antisense construct. After continuous long-term treatment of these mice with moclobemide (a reversible inhibitor of monoamine oxidase A), spatial navigation performance but not accuracy improved during initial acquisition. These changes were associated with a shift of the threshold for the induction of hippocampal LTP at low stimulation frequencies. Moreover, novel object exploration increased in both control and transgenic animals following long-term treatment with moclobemide. These findings open the possibility that antidepressants might improve hippocampal function under conditions of impaired stress hormone regulation, and that these drugs might in part act through this mechanism to attenuate cognitive deficiency in disorders such as depression.

Behavioural analysis of four mouse strains in an anxiety test battery.

Differences in locomotor activity, exploratory activity and anxiety-like behaviour of C57BL/6ChR,C57BL/6J, Swiss Webster/J and A/J strain were investigated in an anxiety battery. The battery consisted of paradigms studying spontaneous behaviour after a mild stressor, tasks of innate anxiety (light-dark box, elevated plus maze, novel object exploration), response to a conflict situation (Vogel conflict), conditioned fear and response to inescapable swim stress. Locomotor activity was studied in an open field and compared with locomotion in the other tests. Exploratory behaviour was studied in a 16-hole board task. The data confirm previous studies suggesting that A/J mice are a relatively anxious strain. Also, the data indicated that locomotor activity was independent of the paradigm employed, while the rank order of strain-dependent effects on anxiety-related behaviour changed as a function of the task under study. Our data provide further support for the notion that choice of strain is essential in studies of anxiety-related behaviour. Influence of strain should be considered in pharmacological and lesion studies, as well as in studies with mutant mice. In addition, the data indicate that different anxiety paradigms tax different aspects of anxiety, suggesting that a battery of different tests should be used in studies of anxiety-related behaviour.

Differential inhibition of the yeast bc1 complex by phenanthrolines and ferroin. Implications for structure and catalytic mechanism.

o-Phenanthroline and m-phenanthroline both inhibit the electron transfer activity of lauryl maltoside-solubilized yeast bc1 complex progressively with time. Pre-steady-state kinetics indicate that these compounds bind to the complex on the intermembrane space side, thereby blocking reduction of cytochrome b via the ubiquinol oxidation site. o-Phenanthroline is additionally capable of chelating an iron atom derived from the Rieske Fe-S cluster, thereby distorting the structure of the Rieske protein. EPR analysis shows that the secondary effect of o-phenanthroline occurs after initial inactivation and that m-phenanthroline, which lacks chelating activity, does not affect the Rieske Fe-S cluster. Spectral analysis shows that the b and c1 cytochromes are still dithionite-reducible after inactivation by o-phenanthroline, indicating that they remain intact. Inactivation by o-phenanthroline can be prevented by the addition of Fe2+. Surprisingly, ferroin, the o-phenanthroline-ferrous sulfate complex, also inhibits the bc1 complex activity. In contrast to o-phenanthroline, this effect is instantaneous. The two types of inhibition are clearly distinguishable by pre-steady-state reduction kinetics. Interestingly, ferroin can only inhibit electron transfer activity by about 50%. This behavior is discussed in relation to the dimeric structure of the bc1 complex, and we conclude that ferroin binds to only one of the two protomers. The rate of inactivation by o-phenanthroline is dependent on the incubation temperature and can be quantitated in terms of the half-life for a certain temperature, the time at which the bc1 activity is reduced to 50%. In contrast to the solubilized form, the bc1 complex in intact mitochondria is insensitive to o-phenanthroline, suggesting that the inactivation rate by o-phenanthroline is dependent on accessibility of the complex to the agent. Reaction with o-phenanthroline is thus a useful technique for study of structural stability of the bc1 complex under different conditions and should provide a sensitive tool for determination of the relative stability of mutant enzymes.

The locus coeruleus noradrenergic system in the rat brain studied by dual-probe microdialysis.

A dual-probe microdialysis technique was applied to the locus coeruleus (LC) and prefrontal cortex (PFC) of the brain of conscious rats. One probe was implanted close to the LC and was used to apply receptor-specific compounds by retrograde microdialysis. The effects of the LC infusions were recorded by a sampling noradrenaline by a second probe that was implanted in the ipsilateral prefrontal cortex. Infusion of sodium channel blocker tetrodotoxin (1 microM; 90 min) into the LC decreased extracellular noradrenaline in the PFC to approximately 20% of control values. Infusion of alpha2-adrenoceptor agonist clonidine (100 microM, infused during 15 or 45 min) near to the LC, decreased extracellular noradrenaline in the PFC to 35 and 20% of controls, respectively. These results indicate that > 80% of the extracellular levels of noradrenaline in the PFC is derived from LC innervation, and confirms the importance of alpha2-autoreceptors on noradrenergic neurons in the LC. Infusion of the cholinergic receptor agonist, carbachol (100 microM, 45 min) near to the LC increased extracellular noradrenaline in the PFC to approximately 150% of controls. Infusions of the excitatory amino-acid agonists NMDA and kainate into the LC caused marked increases in extracellular noradrenaline in the PFC to 240 and 200% of controls, respectively. The experiments with clonidine, carbachol, NMDA and kainate were repeated in anesthetized rats. Clonidine and carbachol were similarly effective as in conscious animals but the effects of NMDA and kainate on extracellular noradrenaline in the PFC were clearly suppressed: 145 and 130% of controls, respectively. These results suggest that increased arousal or behavioural activation might have contributed to the increases in extracellular noradrenaline that was seen after infusion of the glutamate agonists. These results also provide evidence for localization of cholinergic-, NMDA-, non-NMDA-receptor on noradrenergic neurons in the LC. Finally it is concluded that dual-probe microdialysis is a useful method to further investigate the pharmacology of LC-noradrenergic neurons. Carbachol and clonidine are suitable tools for a rapid and reversible stimulation or inhibition, respectively, of noradrenergic LC neurons.

The aromatic domain 66(YWYWW)70 of subunit VIII of the yeast ubiquinol-cytochrome c oxidoreductase is important for both assembly and activity of the enzyme.

The aromatic character of the region 66(YWYWW)70 of the 11-kDa subunit VIII of ubiquinol-cytochrome c oxidoreductase (bc1 complex) of the yeast Saccharomyces cerevisiae has previously been demonstrated to be important for assembly of a functional complex [Hemrika et al. (1994) FEBS Lett. 344, 15-19]. Especially the aromatic nature of residue 66 appeared to be relevant, as the very low level (5%) of bc1 complex in the mutant 66(SASAA)70 was restored to nearly 70% of the wild-type level in a phenotypic revertant with the sequence 66(FASAA)70. In the present study, three other site-directed mutants (66(SAYAA)70, 66(SASAW)70 and 66(SWYWW)70) were constructed and analysed. The data indicate that the presence of one aromatic residue is enough for a substantial level of assembly and that its position modulates the level of both assembly and electron transfer activity. The results also confirm the relevance of this region of subunit VIII for the formation of the Q(out) reaction domain, as reported by Hemrika et al. [(1993) Eur. J. Biochem. 215, 601-609]. It is further shown that the lowered specific activity of the mutant described by these authors is not due to the introduction of a cysteine in the sequence of subunit VIII.

New evidence for the dimeric nature of NADH:Q oxidoreductase in bovine-heart submitochondrial particles.

The initial velocity of NADH oxidation by bovine-heart submitochondrial particles was measured at pH 8.0 after pretreatment of these particles with different amounts of the inhibitor piericidine A together with 0.035 mM NADH. The amount of piericidine A required to fully inhibit the NADH oxidation activity extrapolated to exactly 1.0 per Fe-S cluster 2 of NADH:Q oxidoreductase. When no reducing equivalents from NADH were present during the pretreatment, this ratio was 1.2. The difference is explained by assuming that NADH:Q oxidoreductase binds piericidine A more effectively in the reduced state than in the oxidized state. It was also found that after Q10-extraction and reincorporation of submitochondrial particles, the amount of piericidine A required to fully inhibit the NADH oxidation activity of the particles increased with the amount of Q10 present during reincorporation. This is explained by assuming that binding of piericidine A, to the inhibitory site of NADH:Q oxidoreductase requires Q10. When 0.035 mM NADPH instead of NADH was present during the pretreatment of submitochondrial particles with piericidine A, the amount of inhibitor per cluster 2 required to fully inhibit the initial NADH-oxidation activity extrapolated to 0.5. This result strongly suggests that NADH:Q oxidoreductase is a functional dimer.

Pre-steady-state reduction kinetics of QH2:cytochrome c oxidoreductase and the Q-pool: evidence for a special quinone not in rapid equilibrium with the Q-pool.

The pre-steady-state kinetics of the reduction of the prosthetic groups of QH2:cytochrome c oxidoreductase in bovine heart submitochondrial particles were studied in relation to the kinetics of the Q-10 reduction, using duroquinol as substrate. The prosthetic groups, including semiquinone, were measured with EPR and low-temperature-diffuse reflectance spectroscopy, the samples being prepared with the rapid-freeze quench technique. For the determination of the redox state of ubiquinone in the pre-steady state the rapid chemical quench technique was used as an extension of the rapid-freeze quench technique, and Q-10 and QH2-10 were measured with reversed-phase HPLC after extraction with petroleum ether. Ubiquinone was reduced biphasically, 8% of total Q-10 (equal to 1 mol Q-10/mol cytochrome c1), being reduced within 5 ms, and the rest, the Q-pool, at a much lower rate. The initial rapid reduction of this special Q-10 was accompanied by rapid formation of Qi and rapid reduction of a large part of the cytochrome b-562. Both semiquinone formation and reduction of b-562 showed transient kinetics due to a contribution of the reaction pathway via centre o when the iron-sulphur cluster and cytochrome c1 were oxidised. The majority of the special quinol was located at centre i, probably bound, but also at centre o some bound quinol was formed. This was visible when antimycin was present, the antimycin-insensitive bound quinol being totally sensitive to myxothiazol. Myxothiazol alone accelerated the reduction of the Q-pool via centre i, but also the equilibration of cytochrome b-562 with the Q-pool. Antimycin drastically lowered the rate of reduction of the Q-pool and additionally seemed to block the rapid electron transfer from part of the Rieske iron-sulphur cluster to cytochrome c1. It is concluded that, during the pre-steady-state, cytochrome b-562 is not in equilibrium with the Q-pool and that the rate of equilibration is probably determined by the rate of dissociation of the special bound quinol from centre i.