Discrepancy in prevalence of Huntington's disease in two Swedish regions.

BACKGROUND: Huntington's disease (HD) is a neurodegenerative disease with an autosomal dominant pattern of inheritance. The prevalence varies between different geographical regions with an estimated average in Europe of about 6/100 000. Parts of northern Sweden are known to have an accumulation of HD, but no prevalence studies have been undertaken for 50 years. OBJECT: The aim of this study was to estimate the prevalence of HD in the two different Swedish counties of Jämtland and Uppsala and compare them with the reported prevalence in Europe. METHOD: Patients registered with the diagnosis of HD were identified through medical records in each county. Presymptomatic patients were excluded. We also compared the annual number of individuals with HD registered in the database of the National Board of Health and Welfare in these regions, with all of Sweden. RESULTS: The prevalence of HD was found to be 22.1/100 000 in Jämtland and 4.9/100 000 in Uppsala county. The mean age was 62.2 years and 61.8 years, respectively. The annual average of patients with HD registered at inpatient care was 1.5/100 000 in Jämtland, 0.44/100 000 in Uppsala county, and 0.56/100 000 in all of Sweden. CONCLUSION: The prevalence of patients with the diagnosis of HD is four times higher in the county of Jämtland than in the county of Uppsala, where the prevalence is more similar to the average in Europe. Our results support earlier findings of regional variations of HD prevalence with an accumulation in certain parts of northern Sweden.

Milrinone and esmolol decrease cardiac damage after resuscitation from prolonged cardiac arrest.

BACKGROUND: Long-term survival after cardiac arrest (CA) due to shock-refractory ventricular fibrillation (VF) is low. Clearly, there is a need for new pharmacological interventions in the setting of cardiopulmonary resuscitation (CPR) to improve outcome. Here, hemodynamic parameters and cardiac damage are compared between the treatment group (milrinone, esmolol and vasopressin) and controls (vasopressin only) during resuscitation from prolonged CA in piglets. METHODS: A total of 26 immature male piglets were subjected to 12-min VF followed by 8-min CPR. The treatment group (n=13) received i.v. (intravenous) boluses vasopressin 0.4 U/kg, esmolol 250 µg/kg and milrinone 25 µg/kg after 13 min, followed by i.v. boluses esmolol 375 µg/kg and milrinone 25 µg/kg after 18 min and continuous esmolol 15 µg/kg/h infusion during 180 min reperfusion, whereas controls (n=13) received equal amounts of vasopressin and saline. A 200 J monophasic counter-shock was delivered to achieve resumption of spontaneous circulation (ROSC) after 8 min CPR. If ROSC was not achieved, another 200 J defibrillation and bolus vasopressin 0.4 U/kg would be administered in both groups. Direct current shocks at 360 J were applied as one shot per minute over maximally 5 min. Hemodynamic variables and troponin I as a marker of cardiac injury were recorded. RESULTS: Troponin I levels after 180 min reperfusion were lower in the treatment group than in controls (P<0.05). The treatment group received less norepinephrine (P<0.01) and had greater diuresis (P<0.01). There was no difference in survival between groups. CONCLUSION: The combination of milrinone, esmolol and vasopressin decreased cardiac injury compared with vasopressin alone.

Adrenaline increases blood-brain-barrier permeability after haemorrhagic cardiac arrest in immature pigs.

BACKGROUND: Adrenaline (ADR) and vasopressin (VAS) are used as vasopressors during cardiopulmonary resuscitation. Data regarding their effects on blood-brain barrier (BBB) integrity and neuronal damage are lacking. We hypothesised that VAS given during cardiopulmonary resuscitation (CPR) after haemorrhagic circulatory arrest will preserve BBB integrity better than ADR. METHODS: Twenty-one anaesthetised sexually immature male piglets (with a weight of 24.3 ± 1.3 kg) were bled 35% via femoral artery to a mean arterial blood pressure of 25 mmHg in the period of 15 min. Afterwards, the piglets were subjected to 8 min of untreated ventricular fibrillation followed by 15 min of open-chest CPR. At 9 min of circulatory arrest, piglets received amiodarone 1.0 mg/kg and hypertonic-hyperoncotic solution 4 ml/kg infusions for 20 min. At the same time, VAS 0.4 U/kg was given intravenously to the VAS group (n = 9) while the ADR group received ADR 20 µg/kg (n = 12). Internal defibrillation was attempted from 11 min of cardiac arrest to achieve restoration of spontaneous circulation. The experiment was terminated 3 h after resuscitation. RESULTS: The intracranial pressure (ICP) in the post-resuscitation phase was significantly greater in ADR group than in VAS group. VAS group piglets exhibited a significantly smaller BBB disruption compared with ADR group. Cerebral pressure reactivity index showed that cerebral blood flow autoregulation was also better preserved in VAS group. CONCLUSIONS: Resuscitation with ADR as compared with VAS after haemorrhagic circulatory arrest increased the ICP and impaired cerebrovascular autoregulation more profoundly, as well as exerted an increased BBB disruption though no significant difference in neuronal injury was observed.

Hyperglycaemia increases S100ß after short experimental cardiac arrest.

BACKGROUND: Hyperglycaemia is associated with aggravated ischaemic brain injury. The main objective of this study was to investigate the effects on cerebral perfusion of 5 min of cardiac arrest during hyperglycaemia and normoglycaemia. METHODS: Twenty triple-breed pigs (weight: 22-29 kg) were randomised and clamped at blood glucose levels of 8.5-10 mM [high (H)] or 4-5.5 mM [normal (N)] and thereafter subjected to alternating current-induced 5 min-cardiac arrest followed by 8 min of cardiopulmonary resuscitation and direct current shock to restore spontaneous circulation. RESULTS: Haemodynamics, laser Doppler measurements and regional venous oxygen saturation (HbO2) were monitored, and biochemical markers in blood [S100ß, interleukin (IL)-6 and tumour necrosis factor (TNF)] quantified throughout an observation period of 3 h. The haemodynamics and physiological measurements were similar in the two groups. S100ß increased over the experiment in the H compared with the N group (P < 0.05). IL-6 and TNF levels increased across the experiment, but no differences were seen between the groups. CONCLUSIONS: The enhanced S100ß response is compatible with increased cerebral injury by hyperglycaemic compared with normoglycaemic 5 min of cardiac arrest and resuscitation. The inflammatory cytokines were similar between groups.

Physical therapy in Huntington's disease--toward objective assessments?

BACKGROUND AND PURPOSE: Physical therapy is recommended for the treatment of Huntington's disease, but reliable studies investigating its efficacy are almost non-existent. This may in part be due to the lack of suitable outcome measures. Therefore, we investigated the applicability of novel quantitative and objective assessments of motor dysfunction in the evaluation of physical therapy interventions aimed at improving gait and posture. METHODS: Twelve patients with Huntington disease received a predefined twice-weekly intervention focusing on posture and gait over 6 weeks. The GAITRite mat and a force plate were used for objective and quantitative assessments. The Unified Huntingtons Disease Rating Scale Total Motor Score, the timed Up &Go test, and the Berg Balance Scale were used as clinical outcome measures. RESULTS: Significant improvements were seen in GAITRite measures after therapy. Improvements were also seen in the Up & Go test and Berg Balance Scale, whereas force plate measures and Total Motor Scores did not change. CONCLUSIONS: The results suggest that physical therapy has a positive effect on gait in Huntington's disease. The study shows that objective and quantitative measures of gait and posture may serve as endpoints in trials assessing the efficacy of physical therapy. They should be explored further in larger trials applying a randomized controlled setting.

Improved neuroprotective effect of methylene blue with hypothermia after porcine cardiac arrest.

BACKGROUND: Induced mild hypothermia and administration of methylene blue (MB) have proved to have neuroprotective effects in cardiopulmonary resuscitation (CPR); however, induction of hypothermia takes time. We set out to determine if MB administered during CPR could add to the histologic neuroprotective effect of hypothermia. METHODS: A piglet model of extended cardiac arrest (12 min of untreated cardiac arrest and 8 min of CPR) was used to assess possible additional neuroprotective effects of MB when administered during CPR before mild therapeutic hypothermia induced 30 min after restoration of spontaneous circulation (ROSC). Three groups were compared: C group (n = 8) received standard CPR; PH group (n = 8) received standard CPR but 30 min after ROSC these piglets were cooled to 34°C; the PH+MB group (n = 8) received an MB infusion 1 min after commencement of CPR and the same cooling protocol as the PH group. Three hours later, the animals were killed. Immediately after death, the brains were harvested pending histological and immunohistological analysis. RESULTS: Circulatory variables were similar in the groups except that cardiac output was greater in the PH+MB group 2-3 h after ROSC. Cerebral cortical neuronal injury and blood-brain barrier disruption was greatest in the C group and least in the MB group. The neuroprotective effect of MB and hypothermia was significantly greater than that of delayed hypothermia alone. CONCLUSION: Administration of MB during CPR added to the short term neuroprotective effects of induced mild hypothermia induced 30 min after ROSC.

Sex differences in cerebral injury after severe haemorrhage and ventricular fibrillation in pigs.

BACKGROUND: Experimental studies of haemorrhagic shock have documented a superior haemodynamic response and a better outcome in female animals as compared with male controls. Such sexual dimorphism has, nevertheless, not been reported after circulatory arrest that follows exsanguination and shock. We aimed to study differences in cerebral injury markers after exsanguination cardiac arrest in pre-pubertal piglets. The hypothesis was that cerebral injury is less extensive in female animals, and that this difference is independent of sexual hormones or choice of resuscitative fluid. METHODS: Thirty-two sexually immature piglets (14 males and 18 females) were subjected to 5 min of haemorrhagic shock followed by 2 min of ventricular fibrillation and 8 min of cardiopulmonary resuscitation, using three resuscitation fluid regimens (whole blood, hypertonic saline and dextran, or acetated Ringers' solution plus whole blood and methylene blue). Haemodynamic values, cellular markers of brain injury and brain histology were studied. RESULTS: After successful resuscitation, female piglets had significantly greater cerebral cortical blood flow, tended to have lower S-100beta values and a lower cerebral oxygen extraction ratio. Besides, in female animals, systemic and cerebral venous acidosis were mitigated. Female piglets exhibited a significantly smaller increase in neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) expression in their cerebral cortex, smaller blood-brain-barrier (BBB) disruption and significantly smaller neuronal injury. CONCLUSION: After resuscitation from haemorrhagic circulatory arrest, cerebral reperfusion is greater, and BBB permeability and neuronal injury is smaller in female piglets. An increased cerebral cortical iNOS and nNOS expression in males implies a mechanistic relationship with post-resuscitation neuronal injury and warrants further investigation.

Aspartate: possible neurotransmitter in cerebellar climbing fibers.

Autoradiography demonstrated prominent retrograde labeling of olivocerebellar climbing fiber neurons after injection of tritiated D-aspartate into the rat cerebellar cortex or deep nuclei. Mossy fiber systems originating in the brainstem and spinal cord remained unlabeled. Potassium ion-induced depolarization of cerebellar slices resulted in calcium ion-dependent release of endogenous L-aspartate, L-glutamate, gamma-aminobutyric acid, and glycine. A 26 percent decrease in aspartate release was observed after 3-acetylpyridine-induced destruction of the inferior olive, supporting the hypothesis that aspartate is a neurotransmitter in climbing fibers.

Temporary circulatory support with extra corporeal membrane oxygenation in adults with refractory cardiogenic shock.

OBJECTIVE: Early and long-term survival in patients suffering from cardiogenic shock is poor. Treatment with mechanical assist devices is complicated and expensive but claim to improve survival. We reviewed our experience of venoarterial extracorporeal membrane oxygenation (ECMO) in patients with acute cardiogenic shock. DESIGN: ECMO was used in 52 patients with cardiogenic shock. They were divided into those not operated upon previously (n=19) and those having had cardiac surgery prior to circulatory collapse (n=33). RESULTS: Twenty-six patients were weaned from ECMO. Early mortality for all patients was 48%. Mortality beyond 30 days was 5.8%, with no mortality in the non-cardiotomy group. Long-term survival for patients in the non-cardiotomy group was 63%, as compared to 33% in post-cardiotomy patients (p=0.07). Age over 55 years, female gender or cannulation site did not appear to influence survival. CONCLUSION: Mortality for patients in cardiogenic shock is very high. Treatment with ECMO in patients with refractory cardiogenic shock can be performed with good survival especially in non-surgical patients.

Intracerebral administration of neuronal nitric oxide synthase antiserum attenuates traumatic brain injury-induced blood-brain barrier permeability, brain edema formation, and sensory motor disturbances in the rat.

The role of nitric oxide (NO) in traumatic brain injury (TBI)-induced sensory motor function and brain pathology was examined using intracerebral administration of neuronal nitric oxide synthase (nNOS) antiserum in a rat model. TBI was produced by a making a longitudinal incision into the right parietal cerebral cortex limited to the dorsal surface of the hippocampus. Focal TBI induces profound edematous swelling, extravasation of Evans blue dye, and up-regulation of nNOS in the injured cerebral cortex and the underlying subcortical areas at 5 hours. The traumatized animals exhibited pronounced sensory motor deficit, as seen using Rota-Rod and grid-walking tests. Intracerebral administration of nNOS antiserum (1 : 20) 5 minutes and 1 hour after TBI significantly attenuated brain edema formation, Evans blue leakage, and nNOS expression in the injured cortex and the underlying subcortical regions. The nNOS antiserum-treated rats showed improved sensory motor functions. However, administration of nNOS antiserum 2 hours after TBI did not influence these parameters significantly. These novel observations suggest that NO participates in blood-brain barrier disruption, edema formation, and sensory motor disturbances in the early phase of TBI, and that nNOS antiserum has some potential therapeutic value requiring additional investigation.

Post-injury treatment with a new antioxidant compound H-290/51 attenuates spinal cord trauma-induced c-fos expression, motor dysfunction, edema formation, and cell injury in the rat.

The neuroprotective efficacy of post-injury treatment with the antioxidant compound H-290/51 (10, 30, and 60 minutes after trauma) on immediate early gene expression (c-fos), blood-spinal cord barrier (BSCB) permeability, edema formation, and motor dysfunction was examined in a rat model of spinal cord injury (SCI). SCI was produced by a longitudinal incision into the right dorsal horn of the T10-11 segment under Equithesin anesthesia. Focal SCI in control rats resulted in profound up-regulation of c-fos expression, BSCB dysfunction, edema formation, and cell damage in the adjacent T9 and T12 segments at 5 hours. Pronounced motor dysfunction was present at this time as assessed using the Tarlov scale and the inclined plane test. Treatment with H-290/51 (50 mg/kg, p.o.) 10 and 30 minutes after SCI (but not after 60 minutes) markedly attenuated c-fos expression and motor dysfunction. In these groups, BSCB permeability, edema formation, and cell injuries were mildly but significantly reduced. These observations suggest that (i) antioxidants are capable of attenuating cellular and molecular events following trauma, and (ii) have the capacity to induce neuroprotection and improve motor function if administered during the early phase of SCI, a novel finding.

A new mechanical connector for distal coronary artery anastomoses in coronary artery bypass grafting: a randomized, controlled study.

OBJECTIVE: A new mechanical anastomotic device was evaluated, aiming at its future use in minimally invasive techniques or limited access surgery in patients undergoing coronary artery bypass grafting. METHODS: Between April and December 2002, a total of 60 patients scheduled for elective multivessel bypass grafting were randomly assigned. One vein graft-coronary artery anastomosis per patient was either performed with the St Jude Medical ATG coronary connector system (n = 30; St Jude Medical Inc, St Paul, Minn) or hand sewn (n = 30). Selective coronary angiography or coronary magnetic resonance imaging of the studied graft and vessel was included in the 6-month follow-up. RESULTS: Twenty-eight of the connectors were successfully implanted. Two patients were excluded from the study because of conversion to hand-sewn anastomoses. Six connector-made anastomoses were bleeding at the anastomotic site. At the time of follow-up (190 postoperative days), all control anastomoses and grafts were patent, whereas 26% of the connector anastomoses were occluded. One graft in each group was patent but with stenosis. CONCLUSION: The St Jude Medical ATG coronary connector system for distal anastomoses represents a new concept for sutureless anastomoses in cardiac surgery. This randomized, controlled study shows lower graft patency for anastomoses performed with the connector than for hand-sewn control anastomoses. It illustrates the importance of controlled studies when evaluating new technical equipment in medicine.

Bridge to heart transplantation with the HeartMate device in Gothenburg, Sweden.

BACKGROUND: Patients rapidly deteriorating while waiting for heart transplantation present a major problem. Our strategy for this entity is the HeartMate left ventricular assist device (LVAD) VELVAS, an electrically driven implantable LVAD. Herein we report our initial experience. METHODS: The medical records of all the patients who received HeartMate LVAS at our institution were reviewed. RESULTS: From January 1997 through May 2004, 19 patients received a HeartMate. The mean age was 39 (15 to 61) years and 84% were men. The diagnoses were: dilated cardiomyopathy (n = 8), ischemic heart disease (n = 6), myocarditis (n = 3), congenital heart disease (n = 1), and hypertrophic cardiomyopathy (n = 1). Mean time on LVAD was 113 (10 to 353) days. Ten patients were discharged from the hospital to their homes awaiting transplant or recovery. Three patients showed recovery of heart function and were subsequently weaned from mechanical support. Thirteen patients underwent heart transplantation. Three patients died during LVAD treatment. Major adverse events occurred in nine patients, including severe right heart failure (n = 3), severe bleeding (n = 3), stroke (n = 1), hepatic failure (n = 1), and septicemia (n = 2). Nine of the 13 transplanted patients are alive and well today. CONCLUSION: HeartMate LVAS is a valuable option for patients rapidly deteriorating while awaiting a heart transplant. Our results are comparable with those reported from larger centers.

A method of predicting the image noise in paediatric multi-slice computed tomography images.

The purpose of this study was to develop an equation with which to determine the tube current to be used in order to obtain a certain image noise level for differently sized children undergoing multi-slice computed tomography examination. The relationship between image noise and detector dose for different examination protocols was established for a LightSpeed Ultra, an eight slice CT from GEMS, using homogeneous water phantoms of different sizes. Three different anatomical areas (head, thorax and abdomen) were studied in 111 patients between 0 and 17 y of age. The mean ratio between the calculated and the measured noise in patient images was established for the different areas. Head examinations showed the best correlation (measured-to-calculated noise ratio = 1.01). In the thorax, the calculated noise was generally higher than the measured noise (ratio = 0.74), and in the abdomen, the opposite result was found (ratio = 1.20).

Brain stem terminations of the trigeminal and upper spinal ganglia innervation of the cerebrovascular system: WGA-HRP transganglionic study.

The central projections of the nerve fibers innervating the middle cerebral and basilar arteries were investigated by transganglionic tracing of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) in the rat. WGA-HRP was applied to the exposed basilar and/or middle cerebral arteries. Sections of the brain, trigeminal and upper spinal ganglia were reacted with tetramethylbenzidine for detection of the tracer. The results demonstrate that trigeminal neurons that innervate the middle cerebral artery project to the trigeminal main sensory nucleus, pars oralis, and the dorsocaudal two-fifths of pars interpolaris of the trigeminal brain stem nuclear complex. Terminals were also visible in the ipsilateral nucleus motorius dorsalis nervi vagi (dmnX) and in the lateral nucleus tractus solitarius (nTs) bilaterally at the level of the obex. The ventral periaqueductal gray, including the dorsal raphe and C2 dorsal horn, were also innervated by nerve fibers from the middle cerebral artery. Ipsilateral trigeminal rhizotomy prior to WGA-HRP application over the middle cerebral artery impeded the visualization of nerve terminations throughout the brain stem. Pretreatment with capsaicin reduced the density of labeled neurons and terminals within the trigeminal ganglion and the brain stem, respectively, following WGA-HRP application over the middle cerebral artery. Basilar artery fibers terminate in the C2 dorsal horn, the cuneate nuclei, dmnX, and nTs bilaterally. A few projections were also labeled in the ventral periaqueductal gray. Unilateral upper two spinal dorsal rhizotomy prior to WGA-HRP application over the exposed basilar artery resulted in terminal labeling within the C2 dorsal horn, the cuneate nucleus, dmnX, and nTs contralateral to the rhizotomy, whereas the ipsilateral side was devoid of any labeling. Bilateral superior cervical ganglionectomy prior to WGA-HRP administration to the middle cerebral and basilar arteries did not alter the visualization of nerve terminations throughout the brain stem.

Development of a novel biomarker of free radical damage in reperfusion injury after cardiac arrest.

In a porcine model of cardiopulmonary resuscitation (CPR), we investigated changes in the plasma levels of 8-iso-PGF(2alpha), a marker for oxidative injury, and 15-keto-dihydro-PGF(2alpha), an inflammatory response indicator during the post-resuscitation period after cardiac arrest. Twelve piglets were subjected to either 2 or 5 min (VF2 and VF5 group) of ventricular fibrillation (VF) followed by 5 min of closed-chest CPR. Six piglets without cardiac arrest were used as controls. In VF5 group, 8-iso-PGF(2alpha) in the jugular bulb plasma (draining the brain) increased four-fold. Jugular bulb 8-iso-PGF(2alpha) in the control group remained unchanged. The 15-keto-dihydro-PGF(2alpha) also increased four-fold in the VF5 group. Thus, 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha) measurements in jugular bulb plasma may be used as biomarkers for quantification of free radical catalyzed oxidative brain injury and inflammatory response in reperfusion injury.

Climbing Fibre Plasticity in the Cerebellum of the Adult Rat.

The present paper reports an example of collateral sprouting, and provides a detailed morphological description of newly formed axonal branches, terminal arborizations, and synapses in the central nervous system of an adult mammal. By means of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L), we demonstrate that the climbing fibres, which survive a subtotal lesion of the inferior olive in the rat, emit collateral sprouts and develop new terminal plexuses forming new synaptic contacts on Purkinje cell dendrites. Adult climbing fibres thus show striking plastic capabilities that represent the morphological basis of the functional reinnervation of Purkinje cells.

Monoamine cell distribution in the cat brain stem. A fluorescence histochemical study with quantification of indolaminergic and locus coeruleus cell groups.

The distribution of monoaminergic cell bodies in the brainstem of the cat has been examined with Falck-Hillarp fluorescence histochemical technique. Quantitative determinations indicate that the cat brainstem contains about 60,300 indolaminergic (IA) cells. The majority of these (about 46,700, or 77.5%) are located within raphe nuclei. The largest number is contained within nucleus raphe dorsalis (RD), accounting for around 24,300 IA cells, while raphe pallidus (RP) holds about 8,000 raphe centralis superior (RCS) 7,400, raphe magnus (RM) 2,400, raphe obscurus (RO) 2,300, linearis intermedius (LI) 2,100, and the raphe pontis (RPo) only some 280 IA cells. The IA cells represent, however, only part of the neuronal population of raphe nuclei, which, in addition, hold varying numbers of other medium-sized and small-sized neurons. Thus, quantification in Nissl-stained material indicate that the IA cells make up about 70% of the medium-sized cells in RD, 50% in RP, 35% in RCS and RO, 25% in LI, 15% in RM, and only 10% in RPo. The substantial numbers of small-sized perikarya observed in all raphe nuclei may represent interneurons. Significant numbers of IA cells were consistently located outside the raphe nuclei at all brainstem levels. In all, these amounted to approximately 13,600, or 22.5% of the total number of IA cells. Thus, IA cells occurred in the myelinated bundles, and sometimes in reticular formation, bordering the raphe nuclei; in the ventral brainstem forming a lateral extension from the ventral raphe (RP, RM, RPo, RCS, and LI) to the position of the rubrospinal bundle; in the periventricular gray and subjacent tegmentum of dorsal pons and caudal mesencephalon; in the locus coeruleus (LC) complex; around the motor trigeminal nucleus; caudal to the red nucleus; and in the interpeduncular and interfascicular nuclei. The wide distribution of IA cells leads to a considerable mixing with catecholaminergic (CA) cell groups. Our observations on CA cell distribution are essentially in accordance with previous reports. Quantifications indicate that the LC complex contains about 9,150 CA cells, unilaterally. A previously unnoticed group of scattered CA cells was found in relation to the vestibular nuclei and extending dorsally toward the deep cerebellar nuclei.

Reinnervation of cerebellar Purkinje cells by climbing fibres surviving a subtotal lesion of the inferior olive in the adult rat. I. Development of new collateral branches and terminal plexuses.

Cerebellar climbing fibres react by collateral sprouting after subtotal lesions of the inferior olive, and the newly formed branches are able to reinnervate neighbouring denervated Purkinje cells. In the present paper, we used the Phaseolus vulgaris leucoagglutinin (PHA-L) tracing technique to label the climbing fibres and study their plasticity in detail at the light microscopical level. The specific objectives were to study the time course and morphological aspects of their sprouting, to estimate their extent of growth, and to compare the newly formed terminal plexuses with normal climbing fibres. Intraperitoneal injection of 3-acetylpyridine induced degeneration of the majority of the olivary neurones, which terminate as climbing fibres in the cerebellar cortex. Regularly, small numbers of neurones survived in the inferior olive. In the cerebellar cortex scattered surviving climbing fibres were found, which were devoid of any sign of injury. Already 3 days after the lesion, surviving climbing fibres had emitted collateral branches, which elongated for some distance through the molecular layer and ended with a number of varicosities and very fine branchlets. By 7 days, it was possible to recognize new developing arbours which grew in the molecular layer with the same orientation as normal climbing fibres. At longer survival times, extensive terminal arbours had developed and double labelling experiments confirmed that they terminated around the proximal dendrites of Purkinje cells. The newly formed terminal plexuses resembled, in all essential aspects, normal climbing fibres. In addition, from 1 month onward, it was evident that every surviving climbing fibre was able to form several new terminal plexuses reinnervating a number of neighbouring Purkinje cells. The result of this process was the formation of large clusters of newly formed plexuses around the parental arborization. Quantitative estimates indicated that the domain of innervation of single surviving climbing fibres could be increased by more than six times. It is concluded that climbing fibres surviving a subtotal olivary lesion are capable of extensive sprouting, axonal growth, and formation of new terminal plexuses, which resemble normal climbing fibres. Previous electrophysiological evidence indicates that this reinnervation is functional. The high specificity with which sprouting olivary axons reinnervate the proximal Purkinje cell dendrites suggests the existence of precise interactions between the growing fibres and their target. This example of "homotypic" collateral sprouting and reinnervation may thus provide a useful model for the study of nerve-target interactions.

Reinnervation of cerebellar Purkinje cells by climbing fibres surviving a subtotal lesion of the inferior olive in the adult rat. II. Synaptic organization on reinnervated Purkinje cells.

A salient feature of the cerebellar Purkinje cells is the highly ordered distribution of their excitatory afferents on the dendritic tree. Climbing fibres synapse exclusively on the proximal dendrites, whereas parallel fibres articulate with the distal branches, the so-called spiny branchlets. This input organization is lost following the removal of climbing fibres. Such denervation results in the formation of a large number of new spines on the proximal dendrites, and these become contacted by sprouting parallel fibres, which thereby extend their domain of innervation. We have previously shown that the climbing fibres surviving a subtotal lesion of the inferior olive sprout and reinnervate neighbouring Purkinje cells. In the present ultrastructural study, we have investigated the features of Purkinje cells reinnervated by sprouting climbing fibres. The objectives were to examine the fine morphology of the newly formed synapses and to determine whether the modifications of Purkinje cell morphology and afferent organization are reversed by this reinnervation. Surviving climbing fibres were labelled by the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) and immunohistochemically visualized by means of the gold-substituted silver peroxidase technique, 2 and 6 months after 3-acetylpyridine lesions of the inferior olive in adult rats. Sprouting climbing fibres and newly formed arborizations were identified in the light microscope, isolated, and cut in serial ultrathin sections for electron microscopic analysis. The labelled boutons belonging to newly formed terminal plexuses exhibited the typical morphological features of climbing fibre terminals, i.e., a high number of round synaptic vesicles and a few small mitochondria. Most frequently they formed asymmetric synapses on stubby thorns protruding from the proximal Purkinje cell dendrites. In some instances, however, the postsynaptic element consisted of long slender spines or spines showing an atypical morphology. A number of labelled boutons was also in contact with the perikarya of reinnervated Purkinje cells, either articulating with spines or synapsing directly on the smooth somatic surface. The proximal dendrites of denervated Purkinje cells were characterized by large numbers of spines, which were frequently postsynaptic to parallel fibres. By contrast, Purkinje cells reinnervated by the sprouting climbing fibres generally showed a lower number of spines on their proximal dendrites, indicating a reversal of this morphological change. The aberrant parallel fibre input was also decreased on reinnervated dendrites or had completely disappeared. Nevertheless, some reinnervated Purkinje cells showed the persistence of some parallel fibre synapses on their proximal dendrites. On occasion, climbing fibre and parallel fibre boutons synapsed on the same spine.