Mahmoud Melling

Alterations of biochemical and two-dimensional biomechanical properties of human skin in diabetes mellitus as compared to effects of in vitro non-enzymatic glycation.

OBJECTIVE The aim of this study was to evaluate whether multiaxial analysis of diabetes-specific biomechanical changes generated in vitro by non-enzymatic glycation of human skin samples from healthy subjects reflect the changes seen in skin from subjects with diabetes mellitus. DESIGN Descriptive study. BACKGROUND Non-enzymatic glycation of skin in vitro causes an increased stiffness comparable to in vivo changes seen in diabetic patients. These changes are probably due to increased cross-linking of collagen molecules. METHODS Skin specimens from 7 subjects with diabetes mellitus and 7 controls (age range: 74-90) were analyzed for biomechanical changes using a multiaxial tensile testing device. Control skins from healthy individuals in the age range of 50-65 yr were artificially glycated. One part of these samples was coincubated with the glycation inhibitor aminoguanidine. Glycation of tissues was determined by measuring fluorescence of solubilized samples. Multiaxial biomechanical analysis allows the determination of maximum (a(I)) and minimum elastic modulus (a(II)). These parameters describe the amplitude of the elastic stress response, which is exponentially related to strain. RESULTS Principal stresses, both maximum and minimum, were increased in skins from diabetic subjects as compared to controls. The increases of the principal stresses were comparable to those obtained by in vitro glycation of normal skins. CONCLUSION These results, which can be detected unequivocally with the multiaxial test mode, show that our in vitro model closely reflects changes in skin samples from individuals with diabetes mellitus. Aminoguanidine partially inhibited these as well as biochemical changes. RELEVANCE Multiaxial testing of in vitro glycated skin samples can be used as a model for in vivo changes caused by diabetes mellitus. In addition, therapeutical effects of aminoguanidine, an inhibitor of non-enzymatic glycation, can be monitored in this model.

Differential scanning calorimetry, biochemical, and biomechanical analysis of human skin from individuals with diabetes mellitus

The aim of this work was to compare biochemical, two‐dimensional biomechanical and calorimetric parameters of diabetic skin vs. control skin. Skin specimens taken from the palms and backs of the hands of aged persons with non‐insulin‐dependent diabetes mellitus (NIDDM) and of controls (CO) were compared (age range 68–85 years). Only skin specimens from individuals with diabetes mellitus (DM) showed an increased fluorescence specific for the formation of advanced glycation end‐products (AGEs) and the presence of tissue AGEs, such as Ne‐(Carboxymethyl)lysine (CML). Differential scanning calorimetry (DSC) revealed an elevation of the heat flow per unit mass during collagen denaturation in diabetic skin samples. However, the temperatures of the heat flow maximum and the onset of the phase transformation were not uniformly altered. Young′s moduli were found to be increased in diabetic skin and correlated with AGE‐fluorescence and tissue AGEs. The ratio between the Youngs moduli, which defines a measure for the degree of anisotropy, was higher for dorsal skins from hands. In dorsal skin specimens from diabetic subjects the degree of anisotropy was more pronounced than in healthy controls. In general, neither of the measured parameters showed any correlation with age. However, E1 moduli were clearly associated with the duration of diabetes. Anat Rec 259:327–333, 2000.

Supernumerary Tendons of the Abductor pollicis

During a study of variants of the tendon of the abductor pollicis longus (APL) muscle, in 1 of 110 upper extremities prepared, we recorded the rare finding of a division of the APL muscle tendon into 7 sections in the first tunnel. Whereas the actual main tendon inserted at the base of the first metacarpal bone, as depicted in the textbooks, the supernumerary tendons attached to the fascia of the opponens pollicis muscle to the radial edge of the abductor pollicis brevis muscle and to the dorsoradial third of the base of the first metacarpal bone. All accessory tendons were arranged in a radial formation around the main tendon within the same synovial sheath, but the main tendon occupied a separate compartment. In 80% of the upper extremities prepared for this study, the classical description of the abductor tendon did not apply. The classical representation of a single abductor tendon applied to only 20% of the upper extremities examined. In about one third of the wrists prepared, the first tunnel was clearly divided by a septum, so that 2 or more osteofibrous tunnels were present within the main tunnel. The number, thickness and length of such accessory tendons have a functional significance in the development of de Quervains stenosing tendovaginitis and possibly also have a practical significance, as they may be regarded as a source of transplant material for plastic reconstructions.

Atomic force microscopy imaging of the human trigeminal ganglion.

This paper describes an investigation of gangliocytes via imaging semithin sections of two human trigeminal ganglia with an atomic force microscope (AFM). Whereas semithin sections are usually employed for transmission electron microscopy, we adopted this special type of sample preparation for our AFM studies to extract topographical data from the gangliocyte itself and from the nucleus, the nucleolus, the crystal-arranged lipofuscin granules, and the cell-surrounding mantle cells; simultaneously we characterized the samples with error signal mode. This AFM-related technique revealed no information concerning friction force and elasticity due to the presence of the embedding material (epoxy), but it gave additional topographical contrast. These are the first images of the human trigeminal ganglion by AFM.

Rare variant of the brachial artery: superficial lateral inferior type VII EAB.

This study concerns a variant of the brachial artery with a modified origin and course. The artery was studied in 418 upper limbs removed from cadavers. In one upper limb the left brachial artery bifurcated into: (1) a superficial brachial a. (the variant) crossing superficially to the bicipital aponeurosis in the cubital region and assuming the course, position, and supply area of the radial artery, and (2) the deep brachial a. (another variant). An embryologic interpretation of this anomaly is based on a variant vascular development derived from the eighth intersegmental artery. The variant is termed according to Adachis classification schedule as arteria brachialis superficialis lateralis inferior Type VII with the addition EAB (epiaponeurosis bicipitalis, i.e., superficial to the bicipital aponeurosis). Accurate information concerning unusual patterns of the arteries in the upper limbs is clinically relevant, especially in the avoidance of accidental intra‐arterial injection with reflectory vascular occlusion leading to necrosis. Clin. Anat. 13:216–222, 2000.

Changes of Biochemical and Biomechanical Properties in Dupuytren Disease

BACKGROUND The major biochemical characteristic of Dupuytren disease is the progressive and irreversible deposition of excess fibrous collagen characterized by an enhanced type III collagen proportion. OBJECTIVE To investigate the influence of changes of the collagen spectrum on the biophysical properties of the palmar aponeurosis. DESIGN Variably affected palmar regions from 30 individuals with Dupuytren disease were classified according to histologic test results and clinical stage. Biochemical, biomechanical, and thermal contracture studies were performed. RESULTS The relative type III collagen content increased with increasing tissue involvement and was found to correlate with calorimetric and biomechanical properties with the exception of the Young modulus. In experiments on the thermal isometric contracture, the collagen denaturation temperature decreased with increasing type III collagen content, ie, increasing involvement. To study the dependence of biophysical properties from the collagen type distribution independent of structural changes, as seen in Dupuytren disease, we investigated rat skins from animals of an age range characterized by dramatic changes in type III collagen content (0-18 months). Biomechanical data also correlated significantly with type III collagen content in rat skin with the exception of the time constant of stress relaxation. CONCLUSION In light of these results, we suggest that structural changes, such as reduced collagen fibril diameters, associated with alterations in the type III collagen proportion may influence biophysical properties of connective tissues in the involved palmar aponeurosis in addition to alterations of the cross-linking pattern.

Comparison of palmar aponeuroses from individuals with diabetes Mellitus and Dupuytren's contracture

It is well known that Dupuytrens contracture is often associated with diabetes mellitus. Palmar fascia from individuals with diabetes mellitus and/or Dupuytrens contracture as well as controls were subjected to differential scanning calorimetry, biomechanical and biochemical analysis. The collagen denaturation temperature of the palmar aponeurosis from individuals with diabetes mellitus in the presence (71.0°C) or absence of Dupuytrens contracture (70.6°C) was increased as compared with controls (68.5°C), while this parameter was significantly reduced (about 3.5°C) in contracture bands of Dupuytrens contracture. Stress relaxation experiments revealed that the viscous fraction was slightly reduced in diabetes mellitus (6.5%) vs. controls (8.3%), whereas in Dupuytrens contracture, irrespective of additional diabetes mellitus, a pronounced increase of this parameter was seen (36.5% vs. 24.5%) in the presence of diabetes mellitus. The time constants were significantly elevated by both disorders, this increase being more pronounced in Dupuytrens contracture. Taken together, these changes can be explained by increased cross‐linking in diabetes mellitus, while in Dupuytrens contracture other structural changes, such as increased collagen type III content and loss of fascicular organization, play an additional role besides the finding of reduced cross linking. Anat Rec 255:401–406, 1999.

Morphological study of the healthy human oculomotor nerve by atomic force microscopy

This study concerns an investigation of oculomotor nerves via imaging semithin sections with an atomic force microscope (AFM). The study used 10 oculomotor nerves removed from individuals aged between 40 and 60 years old at time of death. We adopted semithin sections for our AFM studies to extract topographical data of the fibers of this nerve. Both light microscope and electron microscope images of the same samples were employed to augment our capabilities for orientation in the AFM analyses. Transverse sections of the oculomotor nerve, imaged via AFM, show clearly identifiable ring-like nerve fibers with the myelinated axons. The samples were simultaneously characterized by error signal mode and lateral force microscopy. These AFM-related techniques revealed no information concerning friction force and elasticity due to the presence of the embedding material (epoxy resin), but showed the myelinated nerve fibers with ring-like structures corresponding to the myelin sheaths. These are the first AFM images of physiological human oculomotor nerves, containing clear three-dimensional representations of these samples.

Biomechanical stability of abductor pollicis longus muscles with variable numbers of tendinous insertions

In the course of a study of different variants of the tendon of the abductor pollicis longus (APL) muscle, the unusual finding of a tendon with six subdivisions was observed in the first compartment. Using this preparation and others with various numbers of tendons (2, 3, 4, and 6), we intended to establish whether the multitendoned muscles increased the strength of the thumb.

Three-Dimensional Morphological Characterization of Optic Nerve Fibers by Atomic Force Microscopy and by Scanning Electron Microscopy

A comparative study of scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging of the healthy human optic nerve was carried out to determine the similarities and the differences. In this study we compared the fine optic nerve structures as observed by SEM and AFM. The fibers of the right optic nerve of a 61-year-old man show different arrangements in transverse sections taken from the same individual 5 mm central to the optic canal and 5 mm peripheral to the optic chiasma; this difference can be recognized by light microscopy (LM), SEM, and AFM. AFM revealed such typical optic nerve fibers (taken from a point 5 mm central to the optic canal) with annular and longitudinal orientations, which were not visible by SEM in this form. By contrast, LM and SEM visualized other structures, such as pia mater and optic nerve fibers loosely arranged in bundles, none of which was visualized by AFM. The images, however, taken 5 mm peripheral from the optic chiasma show shapeless nerve fibers having a wavy course. Our results reveal that more detailed information on optic nerve morphology is obtained by exploiting the advantages of both SEM and AFM. These are the first SEM and AFM images of healthy human optic nerve fibers, containing clear representations of the three dimensions of the optic nerve.