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Biomedical subjects

R Stanescu

Publications and source records attributed to R Stanescu.

At least 19 recordsLinked to original sources
PubMed2000

False-negative diffusion-weighted MR findings in acute ischemic stroke.

BACKGROUND AND PURPOSE: Lesions associated with acute stroke are often missed by diffusion-weighted imaging (DWI), suggesting that the sensitivity of this technique for detecting acute ischemic stroke may not be as high as initially thought. Our aim was to estimate the rate of false-negative DWI studies in patients with persistent neurologic deficit due to an ischemic stroke and to identify which stroke lesions are most likely to be missed by DWI. METHODS: We reviewed MR images obtained within 48 hours after stroke onset in 139 patients admitted for symptoms consistent with ischemic stroke in whom the deficit lasted more than 24 hours. Cases of negative initial DWI findings with an ischemic lesion visible on follow-up MR studies and a final diagnosis of arterial ischemic stroke were analyzed in terms of delay between onset of symptoms and initial DWI (MR latency), size and vascular distribution of the lesions, and relationship to findings in patients with positive initial DWI results. RESULTS: We found eight cases (5.8%) of false-negative initial DWI studies, of which four were positive on initial fluid-attenuated inversion recovery (FLAIR) imaging. Follow-up FLAIR/DWI showed a hyperintensity matching clinical presentation in all eight patients. The mean size of the lesion was 0.19 +/- 0.16 cm3. False-negative studies occurred more often in cases of stroke in the posterior (19%) than in the anterior (2%) circulation or when DWI was obtained within 24 hours after symptom onset. Of the six false-negative vertebrobasilar stroke lesions, five were located in the brain stem. In all, 31% of patients with vertebrobasilar ischemic stroke had a false-negative initial DWI study during the first 24 hours. CONCLUSION: A false-negative DWI study is not uncommon during the first 24 hours of ischemic stroke. Vertebrobasilar stroke should therefore not be ruled out on the basis of early negative DWI, especially when symptoms persist and are suggestive of this diagnosis.

Acute Disease↗
PubMed1999

Sources of mathematical thinking: behavioral and brain-imaging evidence.

Does the human capacity for mathematical intuition depend on linguistic competence or on visuo-spatial representations? A series of behavioral and brain-imaging experiments provides evidence for both sources. Exact arithmetic is acquired in a language-specific format, transfers poorly to a different language or to novel facts, and recruits networks involved in word-association processes. In contrast, approximate arithmetic shows language independence, relies on a sense of numerical magnitudes, and recruits bilateral areas of the parietal lobes involved in visuo-spatial processing. Mathematical intuition may emerge from the interplay of these brain systems.

Adult↗
PubMed1999

[Diffusion MRI and cerebral ischemia. When to calculate the coefficient of diffusion?].

INTRODUCTION: There are two types of diffusion images: so-called "diffusion-weighted" images (DWI) and apparent diffusion coefficient (ADC) images. For certain authors, ADC mapping is crucial for interpreting diffusion images while for others the ADC map adds no further sensitivity or specificity compared with diffusion weighted images. The objective of this work was to determine those situations where ADC mapping modifies image interpretation. MATERIAL AND METHODS: T2-weighted and diffusion-weighted (DIF) MRI sequences were acquired in 197 patients with suspected cerebral ischemia (< or = 48 hr). For each lesion (239 lesions in the 197 patients), we analyzed MRI interpretation with and without ADC mapping and compared the interpretations with the final diagnosis established on clinical data and complementary explorations. RESULTS: We observed 3 groups. In group A (36% of the lesions), ADC mapping did not change image interpretation. This group was subdivided into 3 subgroups. A1: T2 and DIF weighted images are normal: no lesions and normal ACD map (n = 38 patients); A2: High intensity signal on T2 and low intensity signal on DIF: ischemic sequelae, ADC always increased (n = 32 lesions); A3: T2 normal and high intensity signal on DIF: hyper acute ischemia and ADC always decreased (n = 16 patients) In group B (high intensity signal on T2 and DIF, 54.5% of the lesions), ADC mapping changed the MRI interpretation: there was acute ischemia if the ADC was decreased (n = 113) and "pseudo-ischemic" lesions if the ADC was normal or increased (n = 17 patients). Group C was comprised of 23 lesions with a false negative ADC (9.5%). These lesions were always small recent ischemic lesions (< or = 5 mm) with a high intensity signal on DIF and a strictly normal ADC map. CONCLUSION: ADC mapping was found to be useful in 54.5% of the lesions and should not be considered as solely a research tool but also as a useful tool for routine clinical practice.

Adult↗
PubMed1995

Abnormal collagen cross-linking in the cartilage of a diastrophic dysplasia patient.

The abnormal organization of the cartilage collagen in diastrophic dysplasia is not generally reflected in the levels of the major stabilizing cross-link, hydroxylysyl-pyridinoline. However, in one case there was a marked decrease in the pyridinoline concomitant with the appearance of two unknown components in the cross-link region of the chromatogram. A decrease in cross-linking of this magnitude could lead to mechanically weakened cartilage. Insufficient material was available to characterize these unknown components. The disorganization of cartilage in some cases of diastrophic dysplasia could therefore be due to post-translational modifications, including defective cross-linking.

Amino Acids↗
PubMed1994

Non-collagenous protein screening in the human chondrodysplasias: link proteins, cartilage oligomeric matrix protein (COMP), and fibromodulin.

A gel-electrophoretic screening for link proteins, cartilage oligomeric matrix protein (COMP), and fibromodulin abnormalities was performed in fetuses, newborn infants, and children with various types of chondrodysplasia. Microdissected freeze-dried sections of upper tibial growth cartilage were extracted with 4M guanidinium chloride in the presence of proteolysis inhibitors. After dialysis against 8M urea, the extracts were submitted to stepwise ion-exchange chromatography to separate the large proteoglycans (aggrecans) from the other components. The latter were analyzed by gel electrophoresis, electrotransferred onto nitrocellulose membranes, and reacted with specific antibodies. Control samples from individuals with apparently normal growth were analyzed in the same runs. Two link protein bands with abnormal electrophoretic migration were found in a sporadic case of spondylometaphyseal dysplasia, Kozlowski type. Three link protein bands with the same migration as in the control samples were found in thanatophoric dysplasia, homozygous achondroplasia, achondrogenesis type II, hypochondrogenesis, Goldblatt syndrome, Desbuquois dysplasia, pseudoachondroplasia, and diastrophic dysplasia. In several pathologic cases with normal electrophoretic pattern of the link proteins, small link protein fragments appeared after reduction. The gel electrophoretic pattern of COMP was studied in thanatophoric dysplasia, diastrophic dysplasia, homozygous achondroplasia, fibrochondrogenesis, hypochondrogenesis, Goldblatt syndrome, and Kniest dysplasia. In all these cases the pattern was the same as in the control samples. The main band of fibromodulin had a normal migration rate in fibrochondrogenesis, Desbuquois dysplasia, Kniest dysplasia, and pseudoachondroplasia. It was delayed in diastrophic dysplasia.

Carrier Proteins↗
PubMed1993

Multiple epiphyseal dysplasia, Fairbank type: morphologic and biochemical study of cartilage.

We have performed histochemical, immunohistochemical, electron microscopic, and biochemical studies on the upper tibial cartilage from a case of multiple epiphyseal dysplasia, Fairbank type. Most chondrocytes had intracytoplasmic inclusions which took the stains for proteins and were resistant to microbial collagenase digestion. The electron microscopic study showed that the inclusions are dilatations of the rough endoplasmic reticulum containing a material with alternately wide electron dense and electron lucent layers. Both in optical and in electron microscopy the inclusions fixed antibodies against the core protein of the large cartilage proteoglycans (aggrecans). They didn't stain with antibodies against type II collagen. The gel electrophoretic pattern of the large proteoglycans was different from normal controls. The morphologic and biochemical alterations found in multiple epiphyseal dysplasia are similar to those already described in pseudoachondroplasia (Stanescu et al.: Eur J Pediatr 138:121-225, 1982; Stanescu et al.: J Bone Joint Surg 66A:817-836, 1984). However, the inclusions are smaller and the growth cartilage much less disorganized in multiple epiphyseal dysplasia. The similarity of morphologic and biochemical abnormalities strongly suggests that the two diseases have a similar pathogenesis and belong to the same bone dysplasia family.

Cartilage↗
PubMed1993

The epidermal growth factor-like domain of the large proteoglycans from articular cartilage (aggrecans). Estimate of content at different ages and in osteoarthritis.

Sequencing of cDNA clones has shown that the carboxy terminal domain of the core protein of large proteoglycans (aggrecans) from human cartilage contains an epidermal growth factor-like (EGF-like) domain which is alternatively spliced. In a previous study it was found that the domain of the translated protein can be recognized by polyclonal antibodies to mouse EGF. A competitive enzyme-linked immunoabsorbent (ELISA) assay has been developed to evaluate the EGF-like domain content of aggrecans at various ages and in osteoarthritis. Fetal aggrecans digested with protease free chondroitinase ABC were adsorbed on polyvinyl chloride microtiter plates followed by blocking with bovine serum albumin and goat serum. Mixtures of known amounts of protein of digested aggrecans and constant amounts of anti-mouse EGF antibodies were incubated and added to plates. The second antibody was peroxidase-conjugate F(ab')2. Fetal, newborn and child aggrecan proteins have a higher content of EGF-like domain than aggrecan proteins from cartilage of older humans. Three areas of cartilages from osteoarthritic joints were separated: cartilages with normal macroscopic appearance, erosion border cartilage and osteophytic cartilage. Values derived from these samples were compared with values derived from nonosteoarthritic aged humans. The content of aggrecans from osteoarthritic cartilage with normal macroscopic appearance was similar to or slightly lower than the latter. The aggrecans from osteophytes had a higher EGF-like domain content. The aggrecans from the erosion border had a variable content, close to noneroded cartilages, to osteophytes or in between the values obtained for noneroded cartilages and for osteophytes. Variations in the amount of newly synthesized aggrecans, in the proteolysis of the carboxy terminal domain of aggrecans and in the alternating splicing of the EGF-like domain might explain the results shown here.

Aged↗
PubMed1993

Early lesions of the articular surface in a strain of mice with very high incidence of spontaneous osteoarthritic-like lesions.

Our study was designed to see if the lesions of the articular surface represent an early event in the development of some types of articular degeneration. We examined the ultrastructural appearance of the articular surface labelled in vitro with cationized ferritin in several age groups of a substrain of C57BL/6 mice that develop a high incidence of osteoarthritic-like lesions. We found that as early as the age of 2 1/2 months the articular femoral and patellar surfaces presented abnormalities that became more severe with age. Alterations of the articular surface is a precocious event in this type of osteoarthritic-like degeneration.

Aging↗
PubMed1992

Type II collagen defect in two sibs with the Goldblatt syndrome, a chondrodysplasia with dentinogenesis imperfecta, and joint laxity.

We report on a syndrome of spondylo-epimetaphyseal dysplasia, dentinogenesis imperfecta, and ligamentous hyperextensibility in two sibs born to nonconsanguineous parents. This chondrodysplasia was characterized by severe shortness of stature and an osteoporosis without fractures. Electron microscopic examination of the cartilage documented large vacuoles of dilated rough endoplasmic reticulum within the cytoplasm of chondrocytes. Gel electrophoresis of pepsin-soluble collagen extracted from cartilage demonstrated the presence of type II collagen chains with an abnormal mobility. Prolyl and lysyl hydroxylations were slightly increased. The abnormal molecules melted at a higher temperature than the normal ones. CNBr peptide mapping of type II collagen showed an altered electrophoretic migration of peptides CB 11, CB 8, and CB 10,5 whereas CB 9,7 looked normal. In addition, two small non-collagenous proteins isolated from cartilage were not found in an age-matched control individual but were detected in a normal newborn infant. The quantitation of proline-labelled collagen synthesized by dermal fibroblasts demonstrated a 50% reduction of total collagen. This decrease essentially affected the amount of extracellular type I collagen, which was secreted less efficiently than in control cells. Nevertheless, type I collagen chains behaved normally on 5% polyacrylamide gels. The reduced mRNA levels of alpha 1I and alpha 2I chains might reflect either a transcriptional defect or a decreased stability of mRNA transcripts. We suggest that the association of both pathological chondrocytes producing altered collagen type II and decreased synthesis of type I could be responsible for this peculiar phenotype. The overmodification of alpha 1II CNBr peptides is consistent with the presence of a single-base substitution in the COL2A1 gene. Whether there is a direct causal relationship between the type II collagen defect and the underexpression of type I collagen will require clarification.

Abnormalities, Multiple↗
PubMed1992

Lethal short limb dwarfism with dysmorphic face, omphalocele and severe ossification defect: Piepkorn syndrome or severe "boomerang dysplasia"?

The authors report a case of lethal neonatal dwarfism characterized by striking micromelia, fused rudimentary and supernumerary digits, large, soft head, pronounced hypertelorism, protruding eyes set laterally, enormous omphalocele and severe deficiency of tubular bone and spine ossification. Histologic examination showed lack of ossification of the cartilaginous anlage of many tubular bones. The cartilage had irregularly distributed chondrocytes. The matrix contained hypocellular and degenerated areas with scattered large chondrocytes. In a few bones a very disorganized growth cartilage was present. The case is similar to that described by Piepkorn et al. (1977) and may represent a severe form of "boomerang dysplasia" (Kozlowski et al., 1981; Tenconi et al., 1983; Kozlowski et al., 1985; Winship et al., 1990).

Abnormalities, Multiple↗
PubMed1991

Metaphyseal anadysplasia: a metaphyseal dysplasia of early onset with radiological regression and benign course.

We report on 4 boys (including 2 maternally related first cousins) with a metaphyseal dysplasia of early onset and regressive evolution. Diagnosis is possible in the first months. Distal metaphyses of long bones are very irregular. Femoral necks seem hypoplastic and the edges of the metaphyses are almost vertical; femoral shaft is bowed. Those anomalies disappear after 2 years. The main manifestations are slight shortness and a light varus deformity of the lower limbs. Stature is not affected. The upper tibial growth cartilage, studied in one case, showed wide proliferative and hypertrophic zones with an unusual appearance of the last hypertrophic cells and an abnormal zone of cartilage calcification and resorption. The name "metaphyseal anadysplasia" is suggested for this early and regressive disorder. We are aware of other forms of regressive metaphyseal dysplasia which deserve further delineation. Therefore infants whose radiological changes of metaphyseal dysplasia do not fall into one of the well-defined types should be followed and prediction of the adult height should not be made on the basis of the findings on the initial examination.

Bone Diseases, Developmental↗
PubMed1991

Morphological and biochemical studies of a mouse mutant (fro/fro) with bone fragility.

The mutation fragilitas ossium (fro) was discovered in a random-bred stock of mice during an experiment aimed at detecting recessive lethal mutations after treatment of the postmeiotic germ cells of male mice with tris (1-aziridinyl)phosphine sulphide. The affected mice were moderately runted and had deformities in all four limbs. The radiological and histological findings indicate that the mutant is similar to human osteogenesis imperfecta. The ash content of long bones was lower in the mutant. A defect of type I collagen could not be detected. The electrophoretic patterns of alpha bands of type I and V collagen and CB derived peptides of type I collagen from bone and skin showed no abnormalities. The total collagen synthesis and secretion in cultures of dermal fibroblasts, as well as the gel electrophoresis of procollagen and collagen chains synthesized, and of their CB peptides, were the same as those found in the controls. The percentage of type I and type V collagen synthesized was similar; that of type III was lower in the mutants. Bone osteonectin was found to be decreased by 30% and bone sialoprotein by 5%. The mRNA level for osteonectin was decreased in the fibroblasts of the mutant by about 50%. Whether the defective expression of the osteonectin in fro/fro mice is due to a mutation in the gene itself or its regulatory site(s), or is secondary to other factors remains to be established. The fro/fro mouse may represent a model for some forms of human bone fragility without collagen abnormalities.

Animals↗
PubMed1990

Homozygous achondroplasia: morphologic and biochemical study of cartilage.

We have performed histochemical, immunohistochemical, electron microscopic, and biochemical studies on the upper tibial cartilage from a case of homozygous achondroplasia. The growth zone was narrow and disorganized. Columnization was absent except for a few areas with short rows of cells. Hypertrophy was reduced to scattered clusters of cells. The provisional calcification was patchy and primary trabeculae were thick and irregularly arranged. Islands of fibrous or fibrocartilagineous tissue were found along the growth zone. The matrix did not stain with safranin O and lacked metachromasia, except for pericellular rims around the hypertrophic cell clusters. Staining with antibodies against the large proteoglycan monomers and chondroitin-4-sulfate was weakly positive. Electron microscopic examination showed that only a few cells had degenerative signs. In most areas of the matrix, proteoglycan granules were absent. Areas with dense collagen fibers were seen. In contrast to the growth zone, the cartilage of the remaining epiphyses had normal histochemical, immunohistochemical, and electron microscopic appearance. The large proteoglycan monomers had a normal composition and hydrodynamic size. Type II and XI collagen, pepsin fragments of type IX collagen, and several noncollagenous proteins extracted from cartilage had a normal electrophoretic migration. It is suggested that a mutation affecting a matrix component or a regulatory pathway present only or predominantly in the growth area of the chondroepiphysis might explain the findings.

Achondroplasia↗
PubMed1990

Interaction between macrophages and articular surfaces: an in vitro transmission and scanning electron microscopy study.

Interactions between macrophages and articular surfaces were studied in an in vitro model which has been described before. Either stimulated peritoneal macrophages or a purified population of bone marrow macrophages were incubated with mice femoral heads which were either untreated or were digested with collagenase, trypsin or hyaluronidase prior to incubation. Scanning electron microscopy (EM) examination showed that macrophages attached to the surface and in their vicinity tags and fibers were visible. Transmission EM was used after labeling the surfaces with cationized ferritin employed as a sensitive marker to define the integrity of the articular surface. Alterations of the surface of various degrees of intensity were seen in all the sections examined. No adhering macrophages were found, due probably to detachment of cells during tissue processing for transmission EM. Attachment of macrophages to the surface and alterations of the latter were seen also when hyaluronic acid was added to the incubation medium or when the surfaces had been treated with hyaluronidase before incubation.

Animals↗
PubMed1988

Recessive lethal chondrodysplasia, "round femoral inferior epiphysis type".

Four cases of a sublethal form of chondrodysplasia are reported. The micromelic dwarfism is severe and on X-ray pictures the most striking feature is the shape of the lower femoral epiphysis, which is relatively well developed and rounded. The mode of inheritance is presumably autosomal recessive.

Epiphyses↗
PubMed1988

Comparative histopathology of the growth cartilage in short-rib polydactyly syndromes type I and type III and in chondroectodermal dysplasia.

The histopathology of growth cartilage of long bones was studied in two cases of chondroectodermal dysplasia (Ellis-Van Creveld syndrome), a case of short-rib polydactyly (SRP) type I (Saldino-Noonan syndrome), three cases of short-rib polydactyly (SRP) type III (Verma-Naumoff syndrome), and a case with polydactyly without other skeletal abnormalities but with visceral malformations. The lesions were qualitatively similar in chondroectodermal dysplasia and SRP I: regular concave ossification line, short, slightly irregular columns, regularly dispersed hypertrophic chondrocytes. In SRP III, the ossification line was irregular and the hypertrophic cells had a discontinuous distribution in clusters. No amylase resistant PAS intracytoplasmic inclusions were found. Short, slightly or markedly irregular primary trabeculae, some of them with wide cartilaginous cores, tongue prolongations and islands of cartilage situated along the periost were found in chondroectodermal dysplasia, SRP I and III. The case of polydactyly without other skeletal abnormalities had a normal morphology of the growth plate. These data suggest that there is a relationship between chondroectodermal dysplasia and SPR type I, and that SRP type III is distinct from SRP type I.

Ellis-Van Creveld Syndrome↗