[The implantation window]. / La fenêtre implantatoire.

BACKGROUND: Embryo implantation is a complex event involving apposition followed by adhesion of the blastocyst to the maternal endometrium, and finally invasion of this endometrium. Though implantation could occur in any human tissue, the endometrium is the only tissue where embryo implantation cannot occur except during a restricted period called the implantation window. During this window, the endometrium is highly receptive to the embryo. MATERIAL: and methods. We reviewed the literature concerning the different factors involved in improved endometrial receptivity and implantation. RESULTS: Maternal - embryo crosstalk is favored by the implantation window. Endometrial receptivity results from the acquisition of ligands or receptors facilitating apposition, then adhesion of the embryo, or from the loss of components preventing it. The molecular basis of the implantation window remains to be defined. CONCLUSION: Despite progress in assisted reproduction technologies, the lack of control of implantation remains a major obstacle to successful pregnancy. It is of prime importance to determine the characteristic features of a receptive endometrium and, among the many markers proposed by in vitro studies, to analyze in humans those demonstrated by knock-out experiments to play a crucial role in mice.

Gelatinase A expression and localization in human breast cancers. An in situ hybridization study and immunohistochemical detection using confocal microscopy.

The gelatinase A (72 kDa type IV collagenase) is a matrix metallo-proteinase which degrades basement membrane collagens. Various studies emphasize its role in stromal invasion of cancers, but there is some controversy about its origin. Gelatinase A was localized by immunohistochemistry using confocal microscopy in 15 human mammary carcinomas. In addition, the cells responsible for the synthesis of this enzyme were detected by in situ hybridization. Most invasive and non-invasive tumour cells were labelled by immunohistochemistry. Of particular interest was the pattern observed in some pre-invasive areas. Gelatinase A was found in fibroblasts in close contact with pre-invasive tumour clusters. Confocal observation allowed a more precise localization of gelatinase A to the periphery of tumour clusters along the basement membranes and in peritumour fibroblasts. The malignant epithelial cells were negative by immunohistochemistry in these areas. By in situ hybridization, mRNAs encoding gelatinase A were detected only in fibroblasts in close contact with pre-invasive and well differentiated tumour clusters. These findings support the hypothesis that peritumour fibroblasts produce gelatinase A and that breast cancer cells may bind this enzyme to their cell surface and/or internalize it.

[Current trends in experimental peripheral nerve regeneration]. / Nouvelles orientations en régénération nerveuse périphérique expérimentale.

Large posttraumatic defects in the peripheral nervous system need to discover methods to solve the demand of nerve grafts. There is no definite answer now. The authors present a model for nervous regeneration studies. Experiments are performed in the Wistar rat. A venous isograft is used to bridge defects of various size in a divided rat sciatic nerve. The venous tube is a guide for axonal regeneration. In one series, the tube is filled with physiological saline and, in a second one, neonatal Schwann cells are injected in the venous isograft. Results recorded are a combination of quantitative methods: neurophysiology and morphometry. The injection of neonatal Schwann cells is able to stimulate nerve regeneration but not completely.

Effect of heme on allylisopropylacetamide-induced changes in heme and drug metabolism in the rhesus monkey (Macaca mulatta).

In rhesus monkeys, in which porphyria was induced by the administration of allylisopropylacetamide (AIA), hepatic delta-aminolevulinic acid synthase (ALA-S) was increased. Cytochrome P-450 and associated monooxygenase activities and microsomal heme oxygenase activity were decreased in these animals. Administration of heme for 4 days concurrently with AIA prevented the induction of hepatic ALA-S but produced further decreases in cytochrome P-450 and monooxygenase activities. The decrease in heme oxygenase activity elicited by AIA alone was partially reversed. Administration of heme alone caused an impairment of hepatic drug metabolism but had no significant effect on heme metabolism. The porphyric monkeys showed elevation of porphyrin levels in blood and urine. When heme was administered concurrently with AIA, blood porphyrin levels were further elevated, while the urinary excretion of porphyrins was lower than that following treatment of monkeys with AIA. Following the administration of heme alone, blood and urinary porphyrin levels were minimally affected. These results suggest that repeated heme administration in the primate may adversely affect drug metabolism by the liver.

Hemopexin metabolism in patients with altered serum levels.

The rates of synthesis and degradation of hemopexin (Hx) were studied in vivo to determine the cause of altered serum levels of this protein as seen in hemolytic anemias, chronic neuromuscular diseases, and acute intermittent porphyria. The synthetic and fractional catabolic rates of Hx were measured in patients exhibiting low, normal, or elevated serum Hx levels. It was found that the elevated levels were mainly due to increased synthesis rather than decreased catabolism of Hx. In patients with elevated serum Hx levels, the mean synthetic rate of Hx (13 +/- 1.0 mg/kg/day) was twice that of the patients with normal Hx levels (6.6 +/- 0.3), whereas the fractional catabolic rate was 35.3 +/- 7.1% of the i.v. pool per day vs. 26.5 +/- 0.8 for controls. The low serum Hx levels observed in patients with sickle cell anemia appeared to be due to increased Hx catabolism (36.0 and 40.0% of the i.v. pool per day vs. 26.5 +/- 0.8 for controls) with no compensatory increase in synthesis. This latter finding is in agreement with a study in rhesus monkeys in which repeated administration of a large dose of heme caused an increase in the catabolism of hemopexin without a concurrent increase in its synthesis (J LAB CLIN MED 100:451, 1982). Our results indicate that although both synthesis and catabolism are increased in patients with elevated Hx levels, only catabolism is increased in patients with sickle cell anemia.

Quantification of acute phase reactants after muscle biopsy.

Blood concentrations of six acute phase reactants (ESR, neutrophil count, fibrinogen, haptoglobin, alpha 1-antitrypsin, and ferritin), parameters of muscle necrosis (myoglobin, CK, ALT, and AST) as well as hemopexin, iron, and TIBC were determined before and for 7 consecutive days after muscle biopsy in patients and in a control group. A muscle biopsy was chosen as a standardized surgical procedure that induces a mild transient inflammatory response. After muscle biopsy, a significant increase occurred in five (ESR, neutrophil count, fibrinogen, haptoglobin, and alpha 1-antitrypsin) of the six acute phase reactants. The concentration of serum ferritin did not show a significant change. A significant decrease was noted in the serum iron concentration and a significant increase occurred with CK and myoglobin secondary to the muscle biopsy. Thus the inflammation of a muscle biopsy produces a significant acute phase reaction.

Effect of heme administration on hemopexin metabolism in the rhesus monkey.

Clinical conditions such as hemolytic anemias and certain neuromuscular diseases in which serum hemopexin levels are either increased or decreased were simulated in rhesus monkeys by administering heme intravenously daily at three dose levels over a period of 10 days. At the lower dose of heme (0.02 to 0.04 mg/kg/day), serum hemopexin levels were elevated to 150% of control (control = 53.3 +/- 2.8 U/100 ml). At the higher dose of heme (5.0 mg/kg/day), hemopexin levels decreased to 60% of control. After an intermediate dose of heme (0.6 mg/kg/day), no change was seen in the circulating hemopexin levels. These changes appeared to be specific for hemopexin, since neither the serum haptoglobin levels nor the transferrin level was affected by the heme administration at any of the dose levels. Parameters of hemopexin metabolism revealed that after administration of the low dose of heme there was a 76% increase in the net rate of hemopexin synthesis, resulting in a 65% increase in the intravascular pool size of hemopexin. At the intermediate dose there was a 43% increase in the rate of hemopexin synthesis accompanied by a 33% increase in catabolism, resulting in no net change in serum hemopexin concentrations. At the high dose of heme there was a 57% increase in catabolism of hemopexin without a concurrent increase in synthesis, resulting in lowered circulating hemopexin levels. These findings seem to indicate a relationship between the amount of heme presented to the liver and net hemopexin synthesis.

Collagen localization in normal and fibrotic human skeletal muscle.

The distribution of types I to IV collagen, types I and III p-N collagen, and fibronectin in human skeletal muscle was studied by immunofluorescence using purified antibodies to those proteins. In normal muscle, types I and III collagen, types I and III p-N collagen, and fibronectin were localized in the endomysium and perimysium. Type IV collagen was restricted to basement membrane. Type II collagen was not present. In Duchenne's musclar dystrophy and dermatomyositis/polymyositis (DM/PM), the prominently increased endomysial and perimysial fibrosis consisted of types I and III collagen, types I and III p-N collagen, and fibronectin. In DM/PM, thickening of the walls of perimysial venular and arteriolar vessels was associated with accumulation of types I and III collagen, types I and III p-N collagen, and fibronectin, as well as type IV collagen. There was no disease-specific accumulation of collagen, p-N collagen, or fibronectin.