Showing papers by "Rambam Health Care Campus published in 1991"

A mutation in CYP11B1 (Arg-448----His) associated with steroid 11 beta-hydroxylase deficiency in Jews of Moroccan origin.

Abstract: Steroid 11 beta-hydroxylase (P450c11) deficiency (failure to convert 11-deoxycortisol to cortisol) causes less than 10% of cases of congenital adrenal hyperplasia in most populations, but it is relatively frequent in Jews of Moroccan origin. P450c11 is encoded by the CYP11B1 gene which is located on chromosome 8q22 along with a homologous gene of unknown function, CYP11B2. To identify mutations in CYP11B1 associated with 11 beta-hydroxylase deficiency in Moroccan Jews, oligonucleotides were used that selectively amplified portions of CYP11B1 in polymerase chain reactions without amplifying CYP11B2. Sequence analysis of amplified fragments from one patient revealed a single base substitution in exon 8, codon 448 from CGC (arginine) to CAC (histidine). This residue is within the "heme binding" peptide that contains a cysteine that is a ligand to the heme group. The equivalent of Arg-448 is found in every known eukaryotic P450, and therefore it seems likely that a mutation of this residue would adversely affect enzymatic activity. 11 of 12 affected alleles from six Moroccan Jewish families carried the mutation in codon 448. This mutation is not normally present in CYP11B2 and thus appears to have arisen in CYP11B1 as a true point mutation rather than a gene conversion.

Phagocytosis of lipase-aggregated low density lipoprotein promotes macrophage foam cell formation. Sequential morphological and biochemical events.

Abstract: Macrophages internalize aggregated low density lipoprotein (LDL) by LDL receptor-dependent phagocytosis. To investigate this model of foam cell formation, we have used human and mouse macrophages to characterize biochemically and morphologically the fate of ingested phospholipase C-modified low density lipoprotein (PLC-LDL). When LDL was digested with phospholipase C, it lost phospholipid and aggregated. Human monocyte-derived macrophages rapidly ingested and degraded 125I-PLC-LDL. The degraded PLC-LDL released free cholesterol, measured either as free sterol mass or by the stimulation of [14C]oleate incorporation into cellular cholesteryl ester. Esterification was blocked by chloroquine, a weak base that inhibits lysosomal degradation. Macrophages exposed to PLC-LDL exhibited a 30-fold to a 50-fold increase in esterified sterol: by light microscopy, cytoplasmic inclusions were abundant. The inclusions were stained with oil red O, indicating that they were neutral lipid droplets. By electron microscopy, mouse peritoneal macrophages incubated with PLC-LDL contained numerous membrane-bounded vacuoles and cytoplasmic inclusions that were not surrounded by a limiting membrane. Pulse-chase experiments demonstrated that vacuoles filled with particulate material appeared first. Subsequently, the macrophages exhibited vacuoles containing multivesicular bodies. Last, inclusions that were homogeneously electron-dense and that lacked a tripartite membrane accumulated in the cytoplasm of the cells. These results are consonant with the following model of foam cell formation. Cultured macrophages rapidly ingest PLC-LDL that is initially localized in phagosomes. The aggregated lipoprotein subsequently is digested in secondary lysosomes, thus releasing free cholesterol that is reesterified, forming cytoplasmic cholesteryl ester droplets lacking a tripartite membrane.

Insulin effects on glucose and potassium metabolism in vivo : evidence for selective insulin resistance in humans

Abstract: The effects of insulin on in vivo glucose use and potassium uptake in healthy humans are well documented. However, the interrelationship between these two processes is not fully defined. In order to characterize it, we have used the euglycemic clamp technique on six normal volunteers, two patients with acanthosis nigricans and insulin resistance (AN), and one patient with idiopathic nonazotemic hyperkalemia (HK). In the basal state, all patients had normal fasting blood sugar, the AN patients had fasting hyperinsulinemia (600% of controls), and the HK patient had an elevated plasma potassium level of 5.1 mmol/L (n = 4.2 ± 0.2 mmol/L). During low dose (1 mU/kg·min), and high dose (10 mU/kg·min) insulin infusions, normals used glucose at a rate of 220 ± 10 and 470 ± 20 mg/ M2 min, respectively. The HK patient had a normal glucose use at both infusion rates, but the AN patients had a 20% decrease of glucose use compared to normals at the two infusion rates. In normal patients, plasma potassium fell by 0.7 an...