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Biomedical subjects

J F Merlen

Publications and source records attributed to J F Merlen.

At least 91 records · Page 5Linked to original sources
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[The physiology of microcirculation].

Since the work of Harvey and Malpighi, there have been more questions than answers in the physiology of the microcirculation. The microvessels and the interstitial connective tissue form a true functional and structural unit in which the capillary is only a passive feature. It is subject to the constraint of the connective tissue that surrounds it, is only a reflection of the hydraulic conditions above and below it and is a luxury metabolic pathway compared with the importance of the derivative or shortcircuit arteriovenous pathway in which the metarteriole is of major importance. Continual renewal, apparent vasomotor character, and extreme permeability sum up the physiology of the microcirculation. The cybernetics is dominated by the arteriolo-venular functioning and by chain rections. Stasis, the opening of arterio-venous anastomoses, and sludge are the main pathological features. Investigation of capillary function remains difficult under clinical conditions, since different methods give a global picture, that of the vascular-tissue unit.

Capillaries↗
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[Calcinoses of the leg].

Calcinosis, wherever it appears, is no more than overloading of the conjunctive tissue with calcium. Arterial calcinoses are perhaps the type most frequently recognized : obliterating arteriopathy of middle aged and elderly subjects, arteritis in diabetics, Mönkeberg's arteriosclerosis. Venous calcinoses are either phleboliths, more rarely subcutaneous deposits, or atherocalcinosis of the inferior vena cava, or Cramer and Schilling's lesion. Subcutaneous calcinoses that appear to be nonvascular may give rise to some diagnostic problems. These concern the pathogenesis : calcium transfer by LERICHE and POLICARD, metaplasia of the conjunctive tissues and the elastic fibres, transformation of lipoproteins, hydraulic disturbances, Selye's calciphylaxia.

Arterial Occlusive Diseases↗
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[Microcirculation in white atrophy].

There are two clinical phenomena which, owing to the French School, are still subject to violent criticism: the phenomenon described by M. Raynaud (1862) and the white atrophy termed Milian's (1929). Perhaps badly defined by the authors, the facts have been reviewed, but microcirculation - that of gauges less than 30 to 50 m - does not occupy the whole picture. The proof is that in direct capillaroscopy, functional explorations and biopsy are strikingly monotonous and lacking in exactitude. Capillaroscopy provides the usual aspects of cicatrization, "capillary" neogenesis and their histogenic disorders: central avascular zone, corona limited with loops in "club" formation, or in "clusters" owing to their confluence, "key" loops at the periphery near to the normal loops. These "neocapillaries" pose problems of the immaturity of the neovascular elements and of hydraulics in venous stasis. Of course, there are disorders of capillary permeability, and these are linked especially with vascular neogenesis, but it would not be reasonable to speak of "cutaneous infarctus", or "vascularitis", the necessary criteria being absent. On the contrary, we believe that it all comes down to a "histoangiopathy" by deterioration of the pericapillary sheath of proteoglycanes and of the interstitial conjunctiva. The anomalies are of the type of the deteriorations in plastic polymers and the apparatus of the endarterial bloc, which are included. A "trapping" of the leucocytes in the declivitous areas must also play a part.

Atrophy↗
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[Drug therapy of angiolopathies].

The treatment of angiolopathies is rather difficult, at this time, at least concerning functional angiopathies. It is a fact that protection against cold represents, in all angilopathies, one of the main elements of the treatment besides medications which are essentially vasoactive drugs, myorelaxants or alpha-blockers, and possibly venous tonics. Fluorescein or Sodium fluoresceinate at 5%, administered in slow intra-venous injections, represents one of the best treatment of acrocyanosis, in combination with vitamins A and D, given at the beginning of fall. Other angiolopathies, especially those of organic nature, are represented by allergic vascularitis and will be treated accordingly. In infectious and toxic forms, antibiotics should be prescribed in addition to steroids, preferred in allergic forms, especially granulomatous forms. In conclusion, the treatment of angiolopathies is extremely difficult, and must be particularly adapted to the clinical forms.

Adrenergic alpha-Antagonists↗
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[Aging of veins and venules].

There is a distinction between natural ageing and excessive ageing. The problem is not only vascular, it is above all interstitial conjunctival; it is located in the trunk wall and in the initial collector walls; the capillary-venular section is, from this point of view, just a unit of structure and function. The clinical and anatomopathological aspects of venous ageing are known: they are those of phlebosclerosis and deposits of proteoglycanes, the lesions are non-homogenous, dispersed and constantly changing. The elderly patient lives in a state of stasis. Stasis creates exaggerated and uncontrollable histangic neogenesis, it is the backcloth of "micro-angiopathy of senescence", but if the membrane thickens, it is in order to counter the ill effects of stasis; it is a control reaction not one caused by lesion. It is vital to establish an analogy between vascular ageing and "plastic" ageing, the process of polymerization is the same and we shall produce the evidence of this on another occasion.

Aging↗
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[Ecchymotic patches of the fingers and Gardner-Diamond vascular purpura].

Ecchymotic patches on the fingers and vascular purpura in Gardner-Diamond syndrome are two benign but recurrent clinical disorders occurring chiefly in young women. They involve superficial cutaneous hemorrhagic signs. Both disorders testify to microvascular fragility without perturbation of general hemostasis. Diagnosis is easy for those familiar with the disorders. Ecchymotic episodes accompanied by sharp pain begin at the roots of the fingers. Microtraumatism is soon seen to be involved. Ecchymosis develops at the flexor muscles of the fingers but "capillary" resistance is only reduced in one third of cases. The pathogenic explanation involves rupture of a small post-capillary vein due to disorders in the control system of kinins and local metabolites. The autoerythrocyte sensitization syndrome described in 1955 by Gardner and Diamond is characterized by painful and febrile episodes followed by purpuric and ecchymotic lesions of the skin on various parts of the body, but not necessarily on the legs. Dysneurotonic effects are frequent but diagnosis is based upon promotion of the disorder by intradermal or subcutaneous injection of a minimal quantity of autologous blood. Immunological effects are considered but the ailment involves microvascular control disorders, notably of the capillary-vein segment, in particular at Copley's endo-endothelial fibrin film. Imbalance in fibrin formation and lysis is associated with perturbation of the kinin and serotonin systems. In addition to the use of certain bioflavonoids and calcium inhibitors, prevention and treatment should involve consideration of drugs which affect plasticity in the vascular wall and pericapillary interstitial conjunctiva and the rheological properties of blood flow and interstitial tissue.

Ecchymosis↗
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Capillaroscopy at the nail bed in functioning people aged 70 and over.

A long survey in an homogenous population of 150 healthy and functioning male and female subjects 70 years of age and over is reported. In vivo capillaroscopic patterns observed at the nail bed, besides the lips, the gums, the tongue and the bulbar conjunctiva, are described and sometimes compared with fingertip biopsy. Three patterns are distinguished: (1) type I the most frequent similar to the children's one (2) type II less frequent but rather peculiar to senescence (3) type III rather typical but intermediate. Permanent dilatation and congestion of venules and capillaries seem to be related to the permanent opening of pulpar arteriovenous anastomoses and belong to "senile microangiopathy".

Aged↗
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[Incidents and accidents due to sclerotherapy. Prevention of pigmentation].

Even though sclerotherapy is a method which, in careful and experienced hands, is entirely harmless, the assault on the venous endothelium can, nevertheless, precipitate incidents and accidents, which the authors enumerate briefly in order to pinpoint that of pigmentation. The authors consider that, although this is not certain, venous stasis is responsible for this, venous stasis causing erythrodiapedesis followed by the formation of haemosiderin and the increased activity of the dermic melanocytes, a process which is exacerbated by subjacent inflammation. An axon reflex releasing P substance (Van Euler and Gaddum) modulating the chemical influx on the endothelial receptors in the microcirculation. Prevention will be achieved by combatting the venous hypertension and stasis, and the formation of heamosiderin, melanoids, and the inflammatory process.

Catecholamines↗
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[The connective tissue component and its connections with the terminal circulatory unit in macrophlebopathies].

We forget too often that the primitive mesenchyme cells are at the origin of healthy microvessels, lymphatic canaliculi and the conjunctival interstitium. In our different disciplines we tend to study in isolation the terminal circulatory unit, the lymphatic system, and the conjunctival tissues. Why not refer from the outset to histangiopathy in clinical situations as common as varicose illness, certain post-thrombotic syndromes and, in its classic form, to histangiopathy of stasis? In varicose illness, the conjunctival component of the vein wall is quantitatively differentiated from the normal wall; it is responsible for histochemical anomalies, and the inhomogeneities encountered are determined by the variable conditions of mechanomorphosis. There are also those very specific immunological reactions which some people have made so bold as to deny and changes in the ultrastructure, especially lysosomal changes which are not necessarily irreversible. Since 1965, amongst the post-thrombotic syndromes, Mario Degni has, with the aid of anatomopathological sections, isolated a very specific situation following parietal inflammatory lesions not the affection of the wall and valvules; the treatment of this is especially singular because the conjunctiva play a major part here and "parietal lymphostasis" is absent. There are many microvasculoconjunctival connections in the histo-angiopathy of stasis which are to be met in macrophlebopathies; they are responsible for the various clinical, capillaroscopic and histological pictures. The part played by the derivative channels, the tissular canals and the lymphatic canaliculi is important. The part played by the conjunctiva is even more important because of its retroactive information regulation. In pathological cases it is a degradation of plastic polymers.

Chronic Disease↗