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M H Laudat

Publications and source records attributed to M H Laudat.

62 records · Page 4Linked to original sources
PubMedDate not supplied

Characterization of specific low-density lipoprotein binding sites in human term placental microvillous membranes.

Purified microvillous membranes prepared from normal term human placenta were studied for their ability to bind specifically low-density lipoprotein (LDL). Electron microscopic examination of the membrane preparations revealed essentially microvilli-like structures, and the enzyme analyses a 14-17-fold enrichment in the membrane markers 5'-nucleotidase and alkaline phosphatase. The binding of [125I]LDL was dependent on time, temperature, pH and protein concentration; it was saturable with a low capacity (130.4 +/- 22.2 ng/mg of membrane protein) and presented a high affinity (apparent Ka 6.12 +/- 1.32 micrograms protein per ml). These high-affinity binding sites were specific for LDL (high-density lipoprotein induced less competition than unlabelled LDL) and were sensitive to pronase digestion. Unlike the binding of LDL to other tissues, the [125I]LDL binding to microvillous membranes did not require divalent cations. The presence of specific LDL receptors on the placental microvillous membranes, located at the effective site of exchange between the maternal blood and the placental tissue, supports the concept that human placenta utilizes LDL-cholesterol for its progesterone synthesis.

Female↗
PubMedDate not supplied

[Decreased number of insulin receptors in obesity: studies in the obese hyperglycemic mouse (author's transl)].

The insulin-receptor interaction is impaired in liver, adipocyte and myocardium plasma membranes of the obese hyperglycemic (ob/ob) mouse. A decreased numer of receptors rather than an altered affinity for the hormone appears to be responsible for this defect. Some studies were conducted with respect to the specificity and the reversibility of the degect. 1) It involves the insulin receptor predominantly if not exclusively. 2) It is largely reversible. a) Fasting ob/ob mice for 40 hr or longer periods improved insulin binding significantly. b) Steptozotocin treatment of ob/ob mice also improved insulin binding in liver membranes. c) In fasting and in streptozotocin-treated mice, glucagon binding exhibited a shift opposite to that of insulin, i.e., it was decreased. These data suggest the possibility that the hormone may "down regulate" its own receptor. Although the mechanism(s) of such regulation, if it is verified, remain(s) to be established, similar observations reported with some other peptide hormones and with catecholamines suggest that this phenomenon may be of general interest in endocrine physiology and patho-physiology.

Adipose Tissue↗
PubMedDate not supplied

[Adrenal hyperandrogenism due to enzyme disturbance of late onset (author's transl)].

In the context of hyperandrogenism, the group of hyperandrogenism due to disturbances in hormon-synthesis of late onset is worthy of being considered separately, not by virtue of its prevalence but by the fact that its course may be one of isolate hirsutism (3 cases out of 11 in this study), or even sterility. The diagnosis may be of varying difficulty, because of the incomplete nature of the block. Eleven cases are reported, ten due to a partial deficit in 21 hydroxydation, and one due to a deficit in 11 hydroxydation. The presence of cortisone precursors is often more significant in stimulation tests. Estimation of blood testosterone levels may give somewhat high results in certain cases, but it must be emphasized that it may be diminished dexamethasone and the estimateion of delta 4 androstenedione is of value. In difficult cases, the diagnosis of a minor or incomplete disturbance is based upon a combination of biological, statistical and dynamic arguments. However this diagnosis is important since cortisone at low inhibitory doses are effective, in particular against menstrual disorders, sometimes making it possible to rapidly correct sterility.

Adolescent↗