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Biomedical subjects

C Alexandre

Publications and source records attributed to C Alexandre.

At least 163 records · Page 9Linked to original sources
PubMed1986

[Effects of weightlessness on phosphorus and calcium metabolism and bone remodeling].

Weightlessness results in negative calcium balance which can only reflect a redistribution of calcium in the body: the loss of calcium in the faeces and/or urine is constant, but an increase in urinary hydroxyproline indicating bone collagen destruction is not always detectable; moreover, a slowing down of collagen maturation may be suspected. Bone analysis by histomorphometry in animals and by indirect, non-invasive methods in man shows a decrease in bone mass. However, this bone tissue atrophy might only reflect excessive ageing of the bone during weightlessness, as suggested by slow bone formation and lack of variation in bone resorption. Since the experimental results obtained in men and animals during simulated weightlessness on earth are not strictly identical with those observed in space- flights, their validity may be questioned. Additional studies (notably histomorphometric studies) are therefore required for a better knowledge, as well as prevention, of the problems raised by human life in space.

Animals↗
PubMed1986

Pharmacokinetics and bioavailability of ranitidine in normal subjects and cirrhotic patients.

Pharmacokinetic parameters of ranitidine were determined comparatively in nine cirrhotic patients and eight healthy volunteers after administration of a single oral (150 mg) or intravenous dose (50 mg). Bioavailability was virtually the same in patients and in normal subjects, and there was no significant difference between the two groups for total plasma clearance, intravenous elimination half-life, or volume of distribution. The mean maximum plasma concentration was 43% higher in patients than in volunteers, but the difference was not significant. The values for the kinetic parameters did not significantly differ between patients with and without ascites or with and without hepatocellular insufficiency. These results indicate that ranitidine kinetics are not appreciably altered in cirrhotic patients and that reduction of dosage is not required in such patients unless their renal function is impaired.

Adult↗
PubMed1986

Effects of metabolism inhibitors, antiestrogens and antiandrogens on the androgen and estrogen induced sexual behavior in Japanese quail.

The relative contribution of androgenic and estrogenic metabolites of testosterone to the activation of sexual behavior was studied in Japanese quail by using inhibitors of testosterone metabolism, antiestrogens and antiandrogens. These compounds were tested in castrated birds whose sexual behavior had been activated by silastic implants of testosterone (T) or daily injections of testosterone propionate (TP) or diethylstilboestrol (DES). The aromatase inhibitor ATD only depressed T-induced behavior when injected at high doses and the 5 alpha-reductase inhibitor, 4MA was inactive in this respect. The antiestrogens, tamoxifen (TAM) and nitromifene citrate (CI-628) strongly depressed sexual behavior but they also drastically reduced the crowing behavior which is typically androgen-dependent which throws some doubts on the specificity of their action. The antiandrogens, flutamide and cyproterone acetate (CA), only had limited inhibitory effects on the copulatory behavior but similarly decreased only marginally the crowing. As they strongly depressed the cloacal gland growth, it can be ascertained that they were injected in sufficient amounts and their lack of action on crowing questions the ability of these compounds to inhibit brain processes even when they are androgen-dependent. Taken together with the results of previous experiments which tested the behavioral effects of the testosterone metabolites, the present data confirm the implication of both androgenic and estrogenic metabolites of testosterone in the activation of behavior. Their interaction remains, however, poorly defined and its understanding will probably require the identification of the biochemical processes which in the brain mediate the behavior.

Androgens↗
PubMed1986

Uncalcified cartilage resorption in human fetal cartilage canals.

In the human fetus, epiphyses appear as a solid avascular cartilaginous mass until the eleventh week of development. Around the third fetal month of development, vascular canals coming from the perichondrium are recognized in the mineralized epiphyseal cartilage. Whether cartilage canals develop by passive inclusion or active chondrolysis is still a matter of controversy. We studied the relationships between the intracanalar cells and the surrounding matrix on human fetal epiphyses embedded in glycol methacrylate. At the blind end of canals both stellate fibroblast-like cells and vacuolated macrophages are observed. These cellular foci show all characteristics of active chondrolysis (loss of metachromasia, lacunae containing cells intimately associated with matrix, and presence of granular debris). Similar resorptive foci have been observed in the pannus of rheumatoid joints and in the embryonic chick growth plate composed of uncalcified cartilage. A cellular cooperation (fibroblast/macrophage) is necessary for uncalcified cartilage breakdown. In the human fetus, monocytes/macrophages have been recognized in the peripheral blood as early as the twelfth week of gestation. Our observations support the view that chondrolysis due to both fibroblasts (of mesenchymal origin) and macrophages is the basic mechanism for cartilage canal development.

Abortion, Spontaneous↗
PubMed1986

Importance of quantitative histology of bone changes in monoclonal gammopathy.

Quantitative histology of bone changes, using undecalcified transiliac bone biopsies (UTBB), was performed blindly in 46 individuals with monoclonal gammopathy (MG), including 17 with MG of undetermined significance (MGUS) and 29 with overt multiple myeloma (MM). Three MGUS presented an excess of osteoclastic resorption (OR) in the vicinity of clusters of tumour cells and developed overt B cell malignancies, chronic lymphocytic leukaemia, Waldenström's disease and MM respectively. On the other hand, MGUS with normal OR remained stable (median follow-up = 28 months), with one exception who developed a systemic amyloidosis. In MM, excessive OR was only observed in areas invaded by myeloma cells. OR was frequently normal in active MM lacking myeloma cells in UTBB. Active MM without lesions on radiography had excessive OR. IgA and pure Bence Jones MM appeared more osteoclastic than IgG cases (P less than 0.05). Of major interest was the finding that one third of MM presented histological bone changes similar to osteoporosis, osteosclerosis or osteoblastic metastasis. Two major findings must be emphasized from the current data: UTBB could be of major interest for the early detection of a B cell malignancy; heterogeneity of myeloma bone condition is unexpected. If some changes appear directly related to the tumour (i.e. excessive OR or osteoblastic dysfunction), some others are probably accidentally associated with it (i.e. osteoporosis), both needing treatment other than chemotherapy.

Aged↗
PubMed1986

Permanent preservation of whole alizarin red S skeletons by clearing and embedding in polyester resins.

A one-step clearing and embedding procedure for alizarin red S stained skeletons is described. Embryos are fixed in formalin, skinned and eviscerated. After staining in a 10 mg/liter solution of alizarin red S in 5% aqueous KOH, specimens are dehydrated in a graded series of acetone-polyester monomer solutions. Finally, the specimens are embedded at room temperature in the polyester resin. A special reusable metallic mold is described for embedment of large fetuses. Specimens previously cleared in glycerol can be processed with this method.

Anthraquinones↗
PubMed1984

Paget's disease of bone. A scanning electron microscopic study.

Paget's disease is a human bone dysplasia with a probable viral origin. SEM studies on anorganic and acid etched biopsies confirm the osteocondensation and the structural and textural abnormalities (presence of woven bone). Corrosion casts revealed a complex scaffolding structure of vascular channels. On resting fronts, the domains are small and irregular and surfaces are different from human fetal woven bone. Mineralizing fronts extend largely on bone surfaces and present evidence of abnormal thickness. Resorption surfaces extend irregularly in multiple directions and are often found unusually deep. Irregularity of osteoclastic lacunae was also evidenced. This SEM study suggests that an osteoblastic qualitative dysfunction could be associated with the osteoclastic changes.

Bone and Bones↗
PubMed1983

Embedding iliac bone biopsies at low temperature using glycol and methyl methacrylates.

A mixture of pure and anhydrous glycol methacrylate and methyl methacrylate is used as an embedding medium for iliac bone biopsies. Infiltration is carried out at -20 C with the embedding medium and a cold inactivated catalyst-initiator system. Raising the temperature to 4 C initiates polymerization and limits the peak temperature of polymerization to 25 C. In this way, such thermolabile enzymes as osteoclastic acid phosphatase are preserved. After staining, sections are dehydrated in polyethylene glycol 400 30% in 2-propanol. This gives flat sections and improves staining properties.

Acrylates↗
PubMed1983

Histochemical identification of osteoclasts. Review of current methods and reappraisal of a simple procedure for routine diagnosis on undecalcified human iliac bone biopsies.

Osteoclasts are known to have a high acid phosphatase content. We have adapted the simple simultaneous mono-coupling azo-dye method of Grogg and Pearse to undecalcified bone sections. A cold embedding in a mixture of glycol and methyl methacrylate was shown to well preserve the enzyme activity. Sodium alpha-naphtyl phosphate (1 mg/ml) and fast violet B (2 mg/ml) are used in 0.1 M acetate buffer, pH 5.0. The addition of 1 mM L(+) sodium tartrate selectively inhibits the acid phosphoprotein phosphatase ("osteoblastic acid phosphatase") but not osteoclastic lysosomal acid phosphatase. Counterstaining with phosphomolybdic aniline blue WS leads to well contrasted sections, providing accurate measurements of osteoclast number.

Acid Phosphatase↗