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In routine clinical practice the variations of the radial artery are the main reason for technical failure during transradial catheterization. If these variations are well documented, however, they do not represent a problem in the transradial approach. Therefore, we report here a rare case of the radial artery which is very strange but potentially valuable for the clinical practice: it arises at a right angle from the brachial artery and passes behind the biceps brachii tendon. Based on our findings and on an extensive literature review, we propose for the first time a clinically oriented classification of the variations of the radial artery. This classification is related to the catheterization success at the usual access site of the radial artery at the wrist.

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A new, easily applicable technique providing en face preparations for light microscopy observations of the rat aorta and human thin wall arteries is described here. The major steps of the technique include attachment of the fixed and flattened vessel with the endothelium face down on a glass slide, covered with a water-soluble adhesive medium; drying and softening the vessel wall with another water-soluble medium; removal of the adventitia and most of the media; detaching the layer by placing the glass slide in water; and final attachment of the layer with the endothelium upwards. On such 'thinned-wall' preparations, 40-50 microm in thickness, the stained endothelial cells are clearly visible. Because of the preparation thickness and the use of water-soluble media during the preparation, some subendothelial lipid accumulations, characteristic of the early stages of atherosclerosis process, are well preserved.

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In this work the authors summarize the extensive information available concerning the best-known variant muscular structure in the region of the human axilla--the axillary arch. Emphasis has been placed on the common morphology and variety of the axillary arches. From the anatomical descriptions, the authors extract the characteristics of a group of "typical" axillary arches and also noted the descriptions of a group of "unusual" axillary arches found in the recent literature. The axillary arch terminology, incidence in human population, innervation and origin are discussed. The clinical significance of the axillary arch is presented briefly and the need of a new concept for the axillary arch is stated. In conclusion, for the purpose of clinical practice, a new term--"clinical" axillary arch is defined, and its proper clinically oriented classification is presented.

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During routine anatomical dissection in the hypothenar region of the left hand of a 64-year-old female cadaver, a number of variant structures were observed. The most prominent finding in our case was a supernumerary muscle hitherto unknown in the anatomical literature. This variant muscle had a muscular body formed by the connection of two deeply situated muscular bellies--medial and lateral. The lateral belly originated from the flexor retinaculum, the medial one--from the hamate bone. The common muscular body inserted to the antero-lateral surface of the base of the fifth proximal phalanx. Due to its location and possible function, we named the variant muscle "deep abductor-flexor" of the little finger. The flexor digiti minimi brevis muscle showed two proximal tendons--the medial tendon was attached to the hamulus of the hamate bone while the aberrant lateral tendon originated from the lateral part of the flexor retinaculum. Both, the aberrant lateral tendon of the flexor digiti minimi brevis and the lateral belly of the "deep abductor-flexor", passed over the palmar branch of the ulnar nerve, which define their possible clinical significance in ulnar nerve compression. Therefore, the variations of the hypothenar muscles are reviewed and their relation to the compression of the ulnar nerve is discussed.

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In order to study the incidence of the axillary arch in the Bulgarian population, we examined the axillary regions of 56 formol-carbol fixed human cadavers and observed two cases with a unilateral axillary arch. In the first case, the variant structure was situated on the right side of a 58-year-old female cadaver. The axillary arch extended from the lateral border of the latissimus dorsi to the posterior layer of the pectoralis major tendon. In the second case, the axillary arch was found on the left side of a 63-year-old male cadaver and had the same attachment points as in the first case. The innervation and blood supply of the arches are discussed. We have also reviewed extensive information concerning the clinical importance of the axillary arch, and for the first time, it was summarized clearly for clinicians. The summary consists of three parts: "diagnosis" of the axillary arch by physical investigation or imaging techniques; the axillary arch and surgical interventions in the region of the axilla; the axillary arch as an entrapment site for the axillary vessels and nerves.

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Since the definition of supraclavicular nerve entrapment syndrome by Gelberman et al. (Gelberman et al. [1975] J. Bone Joint Surg. Am. 57:119) a number of clinical cases of this specific entrapment neuropathy have been reported. In all these cases, the nerve injury has been attributed to the location of the supraclavicular nerve branch in a narrow canal in the clavicle. However, in the anatomical literature, variations in the course of the supraclavicular nerves have not only been ascribed to bony canals but also to abnormal fibrous and muscular structures. Considering the fact that the existence of a narrow site with rigid walls along the course of a nerve is essential for the development of an entrapment neuropathy, our study examines all the variant anatomical structures with a possible role in supraclavicular nerve entrapment. We describe three groups of anatomical structures with close relation to the course of the supraclavicular nerves-transclavicular canals, fibrous bands, and unusual muscular structures. Based on the characteristics of the variations found, for the first time, we suggest that in addition to the bony canals through the clavicle certain fibrous and muscular structures could also be an anatomical basis for supraclavicular nerve entrapment syndrome.

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Inspite of the detailed description of the iliopsoas muscle complex, interesting variations of its main parts--the psoas major and the iliacus muscles can still be encountered. These variations may clarify some aspects of the embryological development of the iliopsoas and have certain clinical importance because of the frequent co-existence with an unusual femoral nerve by its formation and course. We present in our report a case of bilateral variations of the psoas major and the iliacus muscles combined with variations of the left and the right femoral nerves, which were found during the anatomical dissection of a female human cadaver. The most remarkable finding was noted on the left side, where an undescribed variant muscle accessory iliopsoas, was observed. It was the only finding of such a muscle among 108 human cadavers examined over a period of 22 years. The accessory iliopsoas was formed by the connection of two accessory muscles--accessory psoas major and accessory iliacus. The clinical significance of the described variant muscles and their importance as an additional factor in the femoral neuropathy are also a matter of discussion in our report.

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The detailed knowledge of the molecular process of mechanotransduction is still an unsolved question. The investigation of the intramembranous structure of the cutaneous mechanoreceptors may play an important role in elucidating this problem. In this relation, Herbst sensory corpuscles in ducks were studied for the first time using the freeze-etching and thin sectioning techniques. Herbst corpuscles have the basic structural components valid for most of the encapsulated mechanoreceptors in mammals: a capsule made of perineural cells, a lamellar complex of modified Schwann cells, surrounding the non-myelinated part of the receptor nerve fiber and its ending. Freeze-etching replicas reveal that the plasmalemmae of the capsule cells, modified Schwann cells and axolemmae of parts of the nerve fiber differ in both density and pattern of distribution of intramembranous particles (IMPs) as well as IMP size. On all the plasmalemmae the IMP density is higher on the P-face (2000-3300 microm(-2)) than the respective E-face (800-1500 microm(-2)). The axolemma of the ending of the receptor nerve fiber expresses higher density of IMPs than its shaft. The mean IMP size for all the plasmalemmae varies between 5.5 and 7.5 nm. Many tight junctions occur between the capsule cells. These results indicate that the non-myelinated axolemma as well as the plasmalemmae of other components of Herbst corpuscles are specialized in terms of content and distribution of IMPs. The IMPs may represent various kinds of mechanosensitive channel proteins or related membrane-bound proteins participating in the process of mechanotransduction.

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Both synaptic sites in situ from rat cerebral cortex and isolated ones in synaptosomal and growth cone fractions derived from it were studied during postnatal development. Freeze-etching technique and image analysis were used to determine the size of the intramembranous particles in the pre- and postsynaptic sites. At each age investigated, the greatest mean particle size was established on the E-face of the postsynaptic sites and ranges from 6.2 nm (day 0) to nearly 10 nm (day 90). The continuous mean particle size increase from birth to maturity shows the same rate but a different rhythm for the two synaptic sites. The results indicate that fractionation do not disturb the correlation between the particle size and age thus outlining the stability of the developing synaptic membrane morphology to physical treatments.

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In the present study, a case of a cadaver is reported in which variations of some branches of both subclavian arteries occur. Among the most impressive findings is the lack of the right inferior thyroid artery combined with an abnormal ramification of the right superior thyroid artery, the terrace-like course of the left inferior thyroid artery and variations in the course of the prevertebral segment of both vertebral arteries with a high entry into the transverse cervical foramen of one of them. A morphometric description of the arterial variations has been carried out and their possible significance for the surgical and diagnostic practice is outlined.

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Isolated growth cones from the cerebral cortex of newborn rats were studied using the freeze-etching technique. The intramembranous structure of their plasma membranes was examined in detail and synaptic sites were found. Their membrane morphology was compared with that of the synaptic sites in adult animals and several differences between them were established. The importance of the present results for understanding the formation and development of the synaptic sites in the cerebral cortex is outlined.

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In the present review, both subkinds of the method for membrane splitting, namely freeze-etching and freeze-fracturing techniques, are presented. After a brief historical survey, a mechanism of their action is described. Special attention is paid to the consecutive stages in applying these techniques--fixation, fracturing, etching, replication, cleaning and observation. A new idea for a better cleaning of the replicas and an explanation of the different occurrence of intramembranous particles on the membrane fracture faces are proposed. Finally, the application of the freeze-etching and freeze-fracturing techniques to visualize the intramembranous structure of membranes in the central nervous system is outlined.

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During synaptogenesis the plasma membrane of neurons undergoes considerable changes and large portions of it develop to synaptic membranes. This transformation is brought about by biochemical and morphological changes. The aim of the present investigation was to study by morphological methods the in vivo changes of some basic components of the neuronal membranes during the early postnatal period, when active synaptogenesis occurs. The cerebral cortex of Wistar rats was used for preparation of either growth cones (up to postnatal day 10) or synaptosomes (postnatal days 14-30). Our studies were focused on the changes occurring in integral membrane proteins and cholesterol domains, and in certain carbohydrate residues and anionic sites. In the first days after birth relatively few intramembranous particles are found in the plasma membranes of growth cones, few and small cholesterol domains, scarce lectin-binding and anionic sites. During the following days there is a clear tendency for increase of the number of all of the studied structures until the appearance of typical synaptic membranes. Throughout the studied developmental period the protein and the cholesterol molecules were found to occupy distinct membrane domains. The structure of the developing neuronal membrane, poor on proteins and cholesterol, and its maturation to the fully functional synaptic membrane is discussed.

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As part of our investigations on the changes in the cortex of different stages of ontogeny, the aim of this study was to analyse the cholesterol distribution in the auditory cortex of adult rats. The light microscopic Schultz reaction as well as electron microscopic thin sections and freeze-etching combined with a cholesterol specific marker were applied to cholesterol demonstration. High and low cholesterol areas were found in the plasma membrane and membranes of some organelles. A low cholesterol content was observed in the membranes of the Golgi apparatus, mitochondria and junctional contacts. A very low cholesterol content was found in the pre- and postsynaptic membranes. High cholesterol contents were present in the neuronal and glial non-junctional plasma membranes. The cholesterol distribution in the membranes of the endoplasmic reticulum and nuclear envelope appeared to be different.

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The intramembranous organization of the interparanodal myelin lamellae in CNS was investigated by means of the freeze-etching technique. The density of the IMPs is about equal on both P- and E-fracture faces of every myelin sheath but varies between the myelin sheaths. The morphology of the myelin tight junctions was also described. The nature of the IMPs and the functional significance of their mode of distribution were discussed.

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The intramembranous structure of the postsynaptic membranes in the rat visual cortex was examined. Simple, complex and mixed synapses were differentiated according to the shape of the postsynaptic particle aggregations. The present data support the existence of all intermediate stages schematically presented in the hypothesis describing a synapse division. The advantage of the freeze-etching technique for the study of the shape of the active zones is emphasized.

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