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D Venieratos

Publications and source records attributed to D Venieratos.

13 recordsLinked to original sources
PubMed2005

A new morphometric method for the sella turcica and the hypophyseal fossa and its clinical relevance.

The sella turcica and the hypophyseal fossa should be considered different entities, the latter being part of the former. Their morphology and dimensions correlate to some extent with those of the contained pituitary gland and have, for this reason, attracted the interest of anatomists and radiologists. With the application of MRI, however, these data are of limited use in the diagnosis of pituitary disorders, although they remain valuable with regard to a microsurgical approach to the hypophysis. The proposed morphometric method was applied to 20 dry skulls. We first made casts of the corresponding sellae. Their volumes were then measured by immersion. The frontal section of each hypophyseal fossa was obtained through its deepest point and magnified. The Cartesian co-ordinates of the contour of the section were used to evaluate the corresponding area and centroid. The volume of each fossa was finally obtained by the use of Pappus' theorem applied to solids of rotation. The volumes of the sellae obtained as above ranged from 460 mm3 to 1570 mm3 with a mean value of 835 mm3. These figures are comparable to those reported from previous authors. To our knowledge the method described has enabled a close approximation of the volumes of the hypophyseal fossae to be made for the first time. These volumes ranged from 24 mm3 to 300 mm3, with a mean value of 157 mm3. Similar numerical methods might be applicable in vivo by the use of MR imaging.

Anthropometry↗
PubMed2001

[Abnormal ramification of the axillary artery: sub-scapular common trunk].

In a man's dissected cadaver we observed an unusual branching of the right axillary artery, which gives a large collateral branch. This branch is the origin of several important arteries as the subscapular artery (with its usual branches), the anterior and posterior circumflex humeral arteries, the proDunda brachii a. and the ulnar collateral artery. The frequency of this variation is evaluated to be 0.45% and is comparable to those found in the literature. We propose to name this artery as common subscapular trunk. The trunk described by us possesses a diameter equal to 6.30 mm and is larger than the continuation or the axillary artery, which courses as superficial brachial artery.

Axillary Artery↗
PubMed1998

Classification of communications between the musculocutaneous and median nerves.

In 16 out of 79 cadavers 22 communications were found between the musculocutaneous and median nerves. In six subjects they were present bilaterally. There were three types, based on the sites of communication. Type I: The communication was proximal to the entrance of the musculocutaneous nerve into coracobrachialis (9/22); Type II: The communication was distal to the muscle (10/22); Type III: The nerve as well as the communicating branch did not pierce the muscle (3/22). Bilateral communications were not necessarily of the same type. The possible clinical implications of these communications (relating either to the surgical approach to the shoulder joint, or to entrapment syndromes) are discussed.

Brachial Plexus↗
PubMed1991

Classification of human maxillar sinuses according to their geometric features.

119 casts of maxillary sinuses have been taken out of 60 dry skulls. In these specimens, the volume V, the area of the basal (i.e. corresponding to the nasal cavity) surface S and the height h have been measured. The sinuses are subsequently arranged into 4 classes, according to their similarity to solids of revolution such as: semi-ellipsoid (class a: 15% of specimens); paraboloid (class b: 30%); hyperboloid (class c: 47%) and cone (class d: 8%). As criterion for this classification, the value of the coefficient K, equal to v/Sh has served. Beyond the eventual anatomical and anthropological interest of this classification, a clinical interest may exist in combination with Computed Tomography or eventually with Echography. The asymmetry that exists between maxillary sinuses (56% of our sample comprises pairs of sinuses arranged in different classes) suggests the eventual necessity of separate radiography of each individual sinus.

Algorithms↗
PubMed1987

A quantitative estimation of the divergence between the trabecular system and the stress trajectories in the upper end of the human femoral bone.

In the frame of the widely accepted theory that the internal architecture of the cancellous part of the bones is strongly influenced by the mechanical stresses that predominate inside them, a quantification of the convergence between the direction of the principal stresses and that of the trabeculae has been attempted, by measuring the angle between these 2 directions, in frontal sections of the upper end of a series of femoral bones (left and right), taken out from embalmed human cadavers. This study suggests that there is a fairly good convergence between trabeculae and stress (compressive as well as tensile), since the angles which have been measured have a mean value of +/- 7 degrees. It is further observed that this convergence is better (i.e. the angle is lesser) in those parts of the section where the corresponding stress (compressive or tensile) is greater. This result may prove particularly useful in connection to the effort of elucidating the mechanism that governs the influence of bone stress to osteogenesis.

Adult↗
PubMed1986

Quantitative method for the classification of human mandibular condyles.

This study is concerned with the classification of mandibular condyles on the basis of the shape of their frontal section. In a previous work, Yale et al. [Oral Surg. 16: 572-577, 1963] had divided mandibular condyles into 4 groups: flat, convex, angled, and round. The distinction between them had been found upon simple inspection. In this paper a quantitative method is proposed, in which mandibular condyles may be classified into the same 4 groups according to inequalities concerning measurable parameters of their frontal section. The process is greatly facilitated by the use of a programmable computer. The proposed method has been applied to a sample of 254 human mandibles (hence 508 condyles); the percentage of each group has been the following; flat 11%; convex 38%; angled 41%, and round 10%. It is plausible to surmise that the quantitative character of the proposed method may be of significant use in oral radiology as well as in anthropological research.

Classification↗
PubMed1986

[Abnormal course of the right common carotid artery. Anatomic presentation of a case report].

In a woman's cadaver, anatomical dissection reveals that the right common carotid artery follows an irregular course. Namely, after being directed towards the left lobe of the thyroid gland, it surrounds the latter in form of collar in close connection with its lower and right surfaces. In this way, trachea is almost completely covered from the front by this artery. The most probable cause of this anomaly may be a disproportional elongation of the ascending aorta during embryonic life of this woman. This hypothesis is corroborated by the fact that other arteries of this woman (thoracic aorta and common iliac artery) are also disproportionally elongated, in conjunction with the assessment of a greater caliber of all her large arteries.

Aged↗
PubMed1983

A reaction-diffusion theory of morphogenesis with inherent pattern invariance under scale variations.

In the framework of reaction-diffusion theory we deal with the problem of pattern regulation in morphogenesis. A generic model is proposed where the kinetic terms follow constraints imposed by scale invariance considerations. These constraints allow a class of kinetic schemes to be formulated so that, starting with an initially homogeneous morphogen distribution in the field, a stable gradient is established of the form: S(chi,L) = Lpf(chi/L). Here L is the length of the morphogenetic field, chi is the position variable and f(chi/L) is some monotonic function of the relative distance. With this distribution a scale invariant gradient can be constructed which leads to pattern regulation. A linear stability analysis of the model permits the definition of the parameter values enabling the system to abandon the homogeneous state spontaneously. Simulations of the evolution of the system towards its final stable state result in approximate pattern invariance for different field lengths. The accuracy of this invariance is in agreement with some recent quantitative experimental findings in both developing and regenerating systems.

Animals↗
PubMed1979

Allosteric oscillatory enzymes: influence of the number of protomers on metabolic periodicities.

The study of a concerted allosteric model for an enzyme activated by the reaction product shows that this system can generate sustained metabolic oscillations regardless of the number of protomers constituting the enzyme. The analysis extends the results previously obtained in a dimeric model for the phosphofructokinase reaction which produces glycolytic periodicities. When the substrate and product concentrations evolve on comparable time scales, the amplitude of oscillations significantly drops as the number of enzyme subunits evolves from 2 to 8. The width of the domain of substrate injection rates which produce oscillations and the periodic variation in enzyme activity also depend on the number of protomers and on the time scale structure of the system. Theoretical predictions are compared with the experiments on glycolytic oscillations in yeast and muscle, and with the structural characteristics of phosphofructokinase. The results are also discussed in relation with the mechanism of cyclic AMP oscillations in the slime mold Dictyostelium discoideum.

Allosteric Regulation↗
PubMedDate not supplied

Small angle dislocations of the newt limb axes can test the validity of several regeneration models.

We describe two experiments on the regenerating forelimbs of the urodele Triturus cristatus. In the first, a contralateral grafting is performed where the anteroposterior axis of the regenerating blastema coincides with the dorsoventral axis of the host stump. In the second, the regenerating blastema is ipsilaterally rotated on the stump at angles 90 degrees or 270 degrees. For these experimental setups several regeneration models, each based on different reference frames (cartesian versus polar coordinates), have diverging predictions for the resulting supernumerary outgrowths. We have analyzed these outgrowths morphologically and histologically and we conclude that both experiments are well described by a hierarchical extension of the Polar Coordinate Model.

Amputation, Surgical↗