Biomedical subjects

Ronald L A W Bleys

Publications and source records attributed to Ronald L A W Bleys.

6 recordsLinked to original sources

PubMed2006

Changes in neuronal connectivity after stroke in rats as studied by serial manganese-enhanced MRI.

Loss of function and subsequent spontaneous recovery after stroke have been associated with physiological and anatomical alterations in neuronal networks in the brain. However, the spatiotemporal pattern of such changes has been incompletely characterized. Manganese-enhanced MRI (MEMRI) provides a unique tool for in vivo investigation of neuronal connectivity. In this study, we measured manganese-induced changes in longitudinal relaxation rate, R(1), to assess the spatiotemporal pattern of manganese distribution after focal injection into the intact sensorimotor cortex in control rats (n=10), and in rats at 2 weeks after 90-min unilateral occlusion of the middle cerebral artery (n=10). MEMRI data were compared with results from conventional tract tracing with wheat-germ agglutinin horseradish peroxidase (WGA-HRP). Distinct areas of the sensorimotor pathway were clearly visualized with MEMRI. At 2 weeks after stroke, manganese-induced changes in R(1) were significantly delayed and diminished in the ipsilateral caudate putamen, thalamus and substantia nigra. Loss of connectivity between areas of the sensorimotor network was also identified from reduced WGA-HRP staining in these areas on post-mortem brain sections. This study demonstrates that MEMRI enables in vivo assessment of spatiotemporal alterations in neuronal connectivity after stroke, which may lead to improved insights in mechanisms underlying functional loss and recovery after stroke.

Animals↗

PubMed2006

Innervation of the wrist joint and surgical perspectives of denervation.

PURPOSE: Because our experience with the techniques used in denervation surgery of the wrist joint often has proven insufficient in treating chronic pain we conducted an anatomic study to clarify the exact contributions of the nerves supplying the wrist joint. Our goal was to reveal all periosteal and capsular nerve connections and if necessary adjust our technique used in denervation surgery. METHODS: Innervation of the wrist joint was investigated by microdissection and histologic examination of 18 human wrists. An acetylcholinesterase method was used to identify the nerves, both in whole-mount preparations and in sections. RESULTS: We found that the main innervation to the wrist capsule and periosteal nerve network came from the anterior interosseous nerve, lateral antebrachial cutaneous nerve, and posterior interosseous nerve. The palmar cutaneous branch of the median nerve, the deep branch of the ulnar nerve, the superficial branch of the radial nerve, and the dorsal branch of the ulnar nerve also were found to have connections with the capsule. The periosteal nerve branches did not appear to play a major role in the innervation of the capsule and ligaments; here the specific articular nerve branches proved more important. The posterior and medial antebrachial cutaneous nerves did not connect to the wrist capsule or periosteum but rather terminated in the extensor and flexor retinaculum. CONCLUSIONS: Based on our findings we propose to denervate the wrist by making 2 incisions. With one palmar and one dorsal incision it should be possible to disconnect the periosteum from the capsule and interrupt the majority of the capsular nerve branches.

Acetylcholinesterase↗

PubMed2006

The segmental pectoralis major free flap: anatomical features of its vascular pedicle.

BACKGROUND: The pectoralis major muscle may be suited for free transplantation of a segment of the muscle. We investigated the length and diameter of its vascular pedicle to determine its feasibility. METHODS: The length of the pedicle, its arterial diameter, and its entry point into the muscle were determined in 17 cadaveric flaps. RESULTS: The pedicle length up to the medial border of the pectoralis minor muscle averaged 6.6 cm. The mean external arterial diameter was 1.8 mm, and the venous diameter was consistently larger. The vascular pedicle consistently entered the muscle lateral to the midpoint of, and a mean of, 8.8 cm caudal to the clavicular line. CONCLUSION: The vascular length and diameter are sufficient for microvascular anastomosis. Although an anatomic landmark for the cranial border of the flap could not be defined, the sternocostal part of the pectoralis major muscle may potentially be used as a segmental free flap.

Anastomosis, Surgical↗

PubMed2003

The nerve supply to the clavicular part of the pectoralis major muscle: an anatomical study and clinical application of the function-preserving pectoralis major island flap.

The purpose of this study was to investigate the nerve supply to the clavicular part of the pectoralis major muscle so that the innervation to this part can be maintained in the muscle-preserving pectoralis major island-flap transfer. Although methods have been described that include a limited portion of the muscle while leaving the upper parts undisturbed with an intact motor innervation, reports on anatomical studies of this nerve supply are brief. The distal distribution of the nerves, the spatial relationship to the main vascular pedicle, and the ways to preserve them during surgical procedures remain unclear. Surgically relevant features of the clavicular part of the pectoralis major muscle were studied by dissection. The nerve supply to this part was examined on 11 sides of eight formalin-fixed cadavers. Two fresh cadavers were used for dissection, intraarterial polymer injection, and application of a nerve-preserving surgical technique. In all subjects, a separate nerve innervated the clavicular and upper medial sternocostal portions of the pectoralis major muscle. This nerve arises craniomedial to the main vascular pedicle of the flap and divides into several branches. These branches run in a fascia on the deep surface of the pectoralis major muscle, superficial to the origin and distal course of the vascular pedicle. Most branches to the clavicular part end medial to the coracoid process. The course of the branches to the upper sternocostal part is more medial. Based on their anatomical findings, the authors propose a surgical technique for transfer of the pectoralis major island flap to the head and neck area through a tunnel in the deltopectoral groove, lateral to the origin of the vascular pedicle. Head and neck reconstruction was performed using this technique. The presented method is a muscle-preserving procedure that maintains maximal donor-site function and morphology.

Cadaver↗

PubMed2002

Ageing and diabetes: implications for brain function.

Diabetes mellitus is associated with moderate cognitive deficits and neurophysiological and structural changes in the brain, a condition that may be referred to as diabetic encephalopathy. Diabetes increases the risk of dementia, particularly in the elderly. The emerging view is that the diabetic brain features many symptoms that are best described as "accelerated brain ageing." The clinical characteristics of diabetic encephalopathy are discussed, as well as behavioural (e.g. spatial learning) and neurophysiological (e.g. hippocampal synaptic plasticity) findings in animal models. Animal models can make a substantial contribution to our understanding of the pathogenesis, which shares many features with the mechanisms underlying brain ageing. By unravelling the pathogenesis, targets for pharmacotherapy can be identified. This may allow treatment or prevention of this diabetic complication in the future. We discuss changes in glutamate receptor subtypes, in second-messenger systems and in protein kinases that may account for the alterations in synaptic plasticity. In addition, the possible role of cerebrovascular changes, oxidative stress, nonenzymatic protein glycation, insulin and alterations in neuronal calcium homeostasis are addressed.

Aging↗

PubMedDate not supplied

A study of neovascularization in the rat ischemic hindlimb using Araldite casting and Spalteholtz tissue clearing.

INTRODUCTION: Understanding neovascularization is an important prerequisite for therapeutic advances aimed at the salvation of ischemic tissues. We explored an alternative strategy to corrosion casting for visualizing neovascularization in a rat hindlimb ischemia model. METHODS: Rats were subjected to hindlimb ischemia by femoral artery ligation. Directly after femoral artery occlusion and at 7, 14, 21 and 28 days postsurgery, rats were sacrificed, and neovascularization was evaluated by vascular casting with Araldite plastic and subsequent Spalteholtz tissue clearing. RESULTS: Semitransparent preparations were obtained, in which the casted arteries could be directly and three-dimensionally visualized in detail and in relation to the surrounding tissue. In the vascular casts, collateral formation and recanalization of previously thrombosed arteries were demonstrated. CONCLUSIONS: We describe an alternative approach to study neovascularization in animal models. This method, which combines Araldite plastic vascular casting with Spalteholtz tissue clearing, preserves all vasculature as well as the surrounding tissue. In a small time series in rat ischemic hindlimbs, we show that restoration of blood flow after ischemia not only involves newly formed collaterals, but also recanalization of previously thrombosed arterial segments.

Animals↗