Biomedical subjects

J M Gregoire

Publications and source records attributed to J M Gregoire.

5 recordsLinked to original sources

PubMed1998

An in vivo method for measuring the mechanical properties of the skin using ultrasound.

In this study, we report a new and original device called the "echorheometer," comprising a suction system with an ultrasound scanner (A-mode, TM-mode and B-mode) that enables the simultaneous visualization and measurement of the deformation of skin structures in vivo. With the scanner described here, high resolution is obtained using a strongly focused, wide-band 20-MHz center frequency transducer, with an axial resolution of 0.07 mm. This device can determine, noninvasively, not only those skin structures that are involved in the deformation, but also their morphological variation and their extent of involvement with the degree of stress applied. Using this device, the behavior of the dermis and subcutaneous fat, while under suction, was investigated on the volar forearm of 10 volunteers. The results showed that the resistance to the applied vertical stress is essentially due to the dermis rather than the subcutaneous fat, and that there is a certain amount of infiltration of fluid into the tissues under suction. In addition, it was shown that the dermal response to an applied suction is initially due to its own natural tension and that, with increasing deformation, the intrinsic dermal elasticity has a greater contribution to the resistance of stress. With this information, we hope to develop a mechanical model to define appropriate mechanical parameters for skin. This will allow the evaluation of changes in the dermis and also enable therapeutic intervention to be assessed. Furthermore, it could also be applied to studies of skin ageing and the assessment of cosmetic product efficacy (emolliency, hydratation, etc.).

Adult↗

PubMed1995

The GATA-3 gene is expressed during human kidney embryogenesis.

GATA-3 is a transcription factor involved in the differentiation of T lymphocytes and additionally expressed in several chicken and mouse embryonic tissues. Using in situ hybridization, we found that the human GATA-3 gene is selectively expressed in the developing kidney. GATA-3 mRNA is first detected in the Wolffian duct from the time of its emergence in the embryonic intermediate mesoderm and further expressed in the collecting ducts of the mesonephros until its involution. In the metanephros, GATA-3 is expressed in the ureteric bud where it is constitutively transcribed, throughout development, along the branching process that gives rise to the whole collecting system of the definitive kidney. Besides the Wolffian duct and derivatives, we also report the expression of GATA-3 gene in the glomerular mesangium and adjacent endocapillary cells, in both meso- and metanephros. This early and specific expression of the GATA-3 gene suggests a role for this transcription factor in the differentiation of the human kidney.

DNA-Binding Proteins↗

PubMed1995

The sinus node and the autonomic nervous system in normals and in sick sinus patients.

To determine the evolution with age, of extrinsic and intrinsic sinus node electrophysiological parameters and to assess the role of each component of the autonomic nervous system relative to age in patients with and without sick sinus syndrome, electrophysiological studies of sinus node function were performed in 227 patients subdivided into four groups according to the results of their electrophysiological testings: group I included patients with normal extrinsic and intrinsic sinus node function, group II patients with exclusive extrinsic sinus dysfunction, group III patients with exclusive intrinsic sinus dysfunction and group IV patients with extrinsic and intrinsic sinus node dysfunction. The electrophysiological study was performed 4 times: at basal state, after sympathetic, autonomic and parasympathetic blockades. Whatever the sinus node function (normal or abnormal) the extrinsic sinus node electrophysiological variables did not correlate with age; inversely all the electrophysiological measurements of the intrinsic sinus node (normal or abnormal) lengthened progressively with age, suggesting an ageing phenomenon of the intrinsic sinus node throughout life. Moreover, the study of the percentage of chronotropy of the sinus node electrophysiological variables shows a predominance of vagal tone in young subjects, whereas sympathetic activity is most prominent in elderly patients with and without sick sinus syndrome. Besides, sympathetic activity increases and vagal tone decreases with increasing age in normals whereas the age-related modifications of each component of the autonomic nervous system in sick sinus patients vary according to the type of sinus node dysfunction. The sinus node (normal or pathological) represents an equilibrated system: the age-related modification of the autonomic nervous system counterbalances the senescence of the intrinsic sinus node in such a way that the basal electrophysiological characteristics remain stable throughout life.

Adolescent↗

PubMed1993

The sinus node function: normal and pathological.

To determine the evolution with age, of extrinsic and intrinsic sinus node electrophysiological parameters and to assess the role of each component of the autonomic nervous system relative to age in patients with and without sick sinus syndrome, electrophysiological studies of sinus node function were performed in 223 patients subdivided into four groups according to the results of their electrophysiological testings: group I included patients with normal extrinsic and intrinsic sinus node function, group II patients with exclusive extrinsic sinus dysfunction, group III patients with exclusive intrinsic sinus dysfunction and group IV patients with extrinsic and intrinsic sinus node dysfunction. The electrophysiological study was performed twice: at basal state and after autonomic blockade. Whatever the sinus node function (normal or abnormal) the extrinsic sinus node electrophysiological variables did not correlate with age; inversely all the electrophysiological measurements of the intrinsic sinus node (normal or abnormal) lengthened progressively with age, suggesting an ageing phenomenon of the intrinsic sinus node throughout life. Moreover, the study of the percentage of chronotropy of the sinus node electrophysiological variables shows a predominance of vagal tone in young subjects, whereas sympathetic activity is most prominent in elderly patients with and without sick sinus syndrome. The sinus node (normal or pathological) represents an equilibrated system: the age-related modification of the autonomic nervous system counterbalances the senescence of the intrinsic sinus node in such a way that the basal electrophysiological characteristics remain stable throughout life.

Adolescent↗

PubMed1991

Influence of the measurement location on the resistance index in the umbilical arteries: a hemodynamic approach.

A computer model was used to study the primary factors generating the reduction in resistance index, (S-D)/S, values observed by ultrasonic Doppler measurements in the umbilical artery, from the fetal insertion to the placental insertion (S represents the amplitude of the systolic peak and D the amplitude of the diastolic peak). This hemodynamic approach shows that the placental resistance is the primary factor, the viscosity and the cord length playing secondary roles. Clinically, the position of the measurement along the cord is an important factor. To increase the sensitivity of the index, the Doppler measurement must be performed near the fetal insertion, whereas a measurement near the placental insertion will make the Doppler examination more specific.

Blood Flow Velocity↗