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Biomedical subjects

H Petit

Publications and source records attributed to H Petit.

At least 235 records · Page 13Linked to original sources
PubMed1981

[Oculocephalomotor disorders and bilateral thalamo-subthalamic infarction (author's transl)].

A 33-year-old woman on oral contraceptives suddenly developed neurological disorders characterised by decreased alertness, absence of motor and verbal spontaneity, anterograde amnesia with difficulties in verbal and visual learning. She also presented paralysis of upwards and downwards ocular movements affecting mainly saccadic movements while convergence was normal. An initial almost total absence of spontaneous head movements and later an impossibility to carry out downwards movements of the head. This apparently represents a syndrome still not reported in human pathology. The clinical course was favourable. CT scan suggested the presence of a paramedian infarct of the region supplied by the thalamosubthalamic artery of the type II b of Percheron. An analogy is suggested between these disorders of oculocephalomotor behaviour and those observed by Denny-Brown in experimental bilateral retrorubric lesions. The possibility of a lesion in the internal thalamic nucleis and the adjacent subthalamic region is considered.

Adult↗
PubMed1980

A scanning electron microscopic study of the inorganic and organic matrices comprising the mature shell of Amblema, a fresh-water mollusc.

The scanning electron microscope has been used to describe the morphology of the mature shell in a fresh-water bivalve. The structure of the organic and inorganic components within the nacre, the myostracum, and the prismatic layer is described. A transitional or intermediate zone, interposed between the prismatic layer and the nacre, was identified. In demineralized samples, the organic component of the nacre was found to consist of parallel matricial sheets interconnected by irregular transverse bridges. The structure of the mineral component of the nacre was found to vary with the method of specimen preparation. With polished-etched samples, brick-like units were seen. When shells were simply broken and fixed in osmium, the layers of nacreous material consisted of fusing rhomboidal crystals of aragonite which demonstrated subconchoidal fractures. On the inner surface of the shell, the rhomboidal crystals showed an apparent spiral growth pattern. The myostracum was characterized by regions of modified nacreous structure consisting of enlarged aragonite crystals with a pyramidal morphology. The peripheral aspect of the muscle scars was characterized by rhomboidal crystals, the latter fusing to form the typical nacreous laminae. The uniqueness of the anterior adductor scar is exemplified by the presence of pores, each pore walled by pyramidal units, for the insertion of adductor fibres. In most regions of the shell, the prismatic layer consisted of one prism unit thickness with a height of approximately 225--250 micrometer. However, in two specialized regions of the shell, this layer was seen to consist of multiple layers of stacked prisms. The organic matrices of the prismatic layer are arranged in a honeycomb-like arrangement and packed with mineralized spherical subunits.

Animals↗
PubMed1980

Morphological studies on the calcification process in the fresh-water mussel Amblema.

Light microscopy, transmission electron microscopy, scanning electron microscopy, various histochemical procedures for the localization of mineral ions, and analytical electron microscopy have been used to investigate the mechanisms inherent at the mantle edge for shell formation and growth in Amblema plicata perplicata, Conrad. The multilayered periostracum, its component laminae formed from the epithelia lining either the periostracal groove or the outer mantle epithelium (of the periostracal cul de sac), appears to play the major regulatory and organizational role in the formation of the component mineralized layers of the shell. Thus, the inner layer of the periostracum traps and binds calcium and subsequently gives rise to matricial proteinaceous fibrils or lamellar extensions which serve as nucleation templates for the formation and orientation of the crystalline subunits (rhombs) in the forming nacreous layer. Simultaneously, the middle periostracal layer furnishes or provides the total ionic calcium pool and the matrical organization necessary for the production of the spherical subunits which pack the matrical 'bags' of the developing prismatic layer. The outer periostracal layer appears to be a supportive structure, possibly responsible for the mechanical deformations which occur in the other laminae of the periostracum. The functional differences in the various layers of the periostracum are related to peculiar morphological variables (foliations, vacuolizations, columns) inherent in the structure and course of this heterogeneous (morphologically and biochemically) unit. From this study, using the dynamic mantle edge as a morphological model system, we have been able to identify at least six interrelated events which culminate in the production of the mature mineralized shell layers (nacre, prisms) at the growing edge of this fresh-water mussel.

Animals↗
PubMed1980

[Pseudo-tumoral cerebellar infarction and Arnold-Chiari malformation].

A pseudo-tumoral cerebellar infarction developed in a 48-year-old man over the course of several days. External drainage improved the patients condition, and a subsequent operation showed a type I Arnold-Chiari malformation with cerebellar amygdalae descending to the level of C2. The infarcted postero-external part of the cerebellar lobe and the left amygdala were resected. The left postero-inferior cerebellar artery was thrombosed between the inferior border of the malformation and the posterior arch of C2. Almost total clinical recovery occurred. The Arnold-Chiari malformation had been clinically silent until the present infarction. A low dysraphia with a dermal sinus, sacral dehiscence and a low cord were present, but had caused no clinical disorders. The genetic origin of the dysraphism was confirmed by the presence of lumbosacral myelomeningocele with hydrocephalus in a relative of the patient. The relationship between postero-inferior cerebellar artery thrombosis and an Arnold-Chiari malformation is discussed: a causal relationship, already suggested in previous reports, is likely in the present case.

Arnold-Chiari Malformation↗
PubMed1980

[Pseudo-tumoral cerebellar infarction. Diagnostic, therapeutic and prognostic aspects in 12 cases (author's transl)].

In those 12 observations, without associated lesion in the brain stem, diagnosis is done 3 times at autopsy, 8 times at surgical time, and once before it, on clinical and radiographic arguments. Diagnosis must be systematically evoked in front of vestibular symptoms, before severe signs, related to intracranial hypertension and brain stem compression, become evident. Iodoventriculography (7 times) and principally computerized tomography (2 times) bring conclusive arguments for diagnosis. Those infarcts are situated 9 times in the territory of the postero-inferior cerebellar artery and 3 times in the area supplied by the antero-superior cerebellar artery. Spontaneous evolution is always lethal, but prognosis after surgery is still severe (4 long term survivals in 9 cases) for the vascular system of those patients remains fragile.

Adult↗
PubMed1979

Morphological studies on the periostracum of the fresh-water mussel Amblema (Uniondae): light microscopy, transmission electron microscopy, and scanning electron microscopy.

The structure of the periostracum in the fresh-water mussel Amblema has been described using light microscopy, transmission elec;ron microscopy, and scanning electron microscopy. The structure and evolutive course of the periostracum was studied along its entire length, from the periostracal groove until it forms the tough outer covering of the shell. At least five structurally and functionally distinct regions were identified. In addition, the periostracum itself was seen to be a multilayered structure consisting of three major layers which are themselves subdivided into minor layers. From these morphological observations, a regulatory role for the various periostracal layers in mineral trapping, nucleation, and the subsequent formation of the prismatic and nacreous layers of the shell can be postulated.

Animals↗
PubMed1979

[Lumbosacral dysraphia and "long spinal cord" of delayed appearance (9 cases)].

Urinary disorders, deformities of the feet, and sensory of trophic disturbances appearing during, or increasing in severity at adolescence, were observed in 9 patients. In seven cases there appeared to be an abnormality of the teguments of the lumbosacral region, and in all cases, as shown by straight radiological examination of a spina bifida of L5 or S1, a sacral dehiscence and wide sacral canal, and a subjacent nervous tissue abnormality was suspected. Radiculography showed the presence of a "long spinal cord" terminating in the sacrum by a tumor mass. Examination of this mass in the seven operated cases demonstrated that the tumor was an intradural lipoma with a wedge-shaped penetration into the end of the medulla, fixing the cord in the sacrococcygial region, in the absence of the filum terminale and cauda equina. The etiology of this "long spinal cord" is discussed, and it appears to be the consequence of a dysraphia, which is also the cause of the lipoma. Mechanical factors appear later and produce neurological signs.

Adolescent↗
PubMed1978

Morphological studies on the mantle of the fresh-water mussel Amblema (Unionidae): scanning electron microscopy.

The scanning electron microscope has been used to describe the surface morphology of the mantle in mantle-shell preparations from the fresh-water mussel Amblema. In some regions (adductor muscle insertions), the mantle is firmly attached to the shell. In other areas (along the main course of the mantle), transient adhesions between the outer mantle epithelial cells and the nacre appear to temporally further compartmentalize the extrapallial fluid possibly as a prerequisite for the initial crystallization phenomenon. At the mantle edge, as well as at the isthmus, the periostracum was seen to extrude from the periostracal groove. At the siphonal edge, peculiar finger-like processes were identified; these may represent primitive photoreceptors. The epithelial cells of the outer mantle epithelium are all microvillated whereas those of the inner mantle epithelium are both microvillated and ciliated. Specific differences in surface morphology are described for various regions of the outer mantle epithelium. These may be related to precise regionalized functional differences of this tissue. Several functions of the mantle, in addition to shell formation, and based on its various morphologies, are also discussed.

Animals↗