Liver microsomal drug-metabolizing enzyme system: functional components and their properties

The liver microsomal drug-metabolizing enzyme system consists of two protein components, cytochrome P-450 and NADPH-cytochrome c reductase, and a lipid, phosphatidylcholine. Cytochrome P-450 serves as the binding site for oxygen and substrate while the reductase acts as an electron carrier shuttling electrons from NADPH to cytochrome P-450. The phospholipid facilitates the transfer of electrons from NADPH-cytochrome c reductase to cytochrome P-450 but itself is not an electron carrier. Different cytochromes P-450 and P-448 have been purified; the spectral, catalytic, and immunological properties as well as the molecular weight (determined by SDS-gel electrophoresis) of all these hemeproteins differ from one another. The presence of multiple cytochrome P-450s may explain the species, strain, age, tissue, and sex differences as well as the effect of inducers and nutritional status in mammlian drug metabolism.     

Nitrogen retention in men fed isolated soybean protein supplemented with L-methionine, D-methionine, N-acetyl-L-methionine, or inorganic sulfate

The ability of various sulfur-containing compounds to replace L-methionine (L-Met) was investigated by metabolic balance studies in man. N-acetyl-L-Methionine (AcMet), D-methionine (D-Met), and sodium sulfate (Na2SO4) were used to supplement a diet deficient in sulfur amino acids. The daily diet contained 4.5 g nitrogen (N) from isolated soybean protein (SB) and 4.5 g from glycine and alanine (9 g total N). SB diet was given alone or supplemented to six adult men for periods of 9 days after a standardization period with an equal N eggwhite diet, preceded by a 2-day zero N adaptation period. Supplements provided equivalent amounts of sulfur to that present in 420 ml L-Met, the amount added to SB to bring the total sulfur amino acid content to 900 mg/day. AcMet was as benfeficial as L-Met in improving N balance but D-Met was not as effective as L-Met. Difference between balances obtained with L-Met and Na2SO4 was not significant due to large variation in response to Na2SO4. While addition of D-Met to SB did not result in significantly greater N retention than unsupplemented SB, NA2SO4 addition did cause increased N retention.     

Ectodomain phosphorylation of beta-amyloid precursor protein at two distinct cellular locations

The beta-amyloid precursor protein (betaAPP) is a transmembrane protein that is exclusively phosphorylated on serine residues within its ectodomain. To identify the cellular site of betaAPP phosphorylation, we took advantage of an antibody that specifically detects the free C terminus of beta-secretase-cleaved betaAPP containing the Swedish missense mutation (APPssw-beta). This antibody previously established the cellular location of the beta-secretase cleavage of Swedish betaAPP as a post-Golgi secretory compartment (Haass, C., Lemere, C., Capell, A., Citron, M., Seubert, P., Schenk, D., Lannfelt, L., and Selkoe, D. J. (1995) Nature Med. 1, 1291-1296). We have now localized the selective ectodomain phosphorylation of betaAPP to the same compartment. Moreover, the phosphorylation sites of betaAPP were identified at Ser198 and Ser206 of betaAPP695 by tryptic peptide mapping, mass spectrometry, and site-directed mutagenesis. Intracellular phosphorylation of betaAPP was inhibited by Brefeldin A and by incubating cells at 20 degrees C, thus excluding phosphorylation in the endoplasmic reticulum or trans-Golgi network. Ectodomain phosphorylation within a post-Golgi compartment occurred not only with mutant Swedish betaAPP, but also with wild type betaAPP. In addition to phosphorylation within a post-Golgi compartment, betaAPP was also found to undergo phosphorylation at the cell surface by an ectoprotein kinase. Therefore, this study revealed two distinct cellular locations for betaAPP phosphorylation.     

A practical guide to topical therapy in children

OBJECTIVE: To determine the duration of time to the recurrence of pain attributable to endometriosis after the discontinuation of treatment with danazol or a GnRH agonist (GnRH-a) in patients who have had a satisfactory response to the treatment. DESIGN: Retrospective study. SETTING: Nine academic medical centers in three countries. PATIENT(S): Three hundred twenty-seven women with diagnosed and staged endometriosis who were treated with at least 6 months of danazol or a GnRH-a and who experienced significant pain relief with therapy. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Duration of pain relief after completion of treatment as determined by a patient-initiated report of pain recurrence or increase in pain severity requiring intervention. RESULT(S): The median time to the recurrence of pain was 6.1 months for patients treated with danazol and 5.2 months for patients treated with a GnRH-a. CONCLUSION(S): Although there was a lack of uniformity in treatment effects across sites, the analyses have taken into account major covariant effects. The time to the recurrence of endometriosis-associated pain after danazol treatment was slightly longer than that after GnRH-a treatment.     

Neutropenia due to antibodies against Type III Fc receptors on neutrophil granulocytes: 3 children with different clinical courses

Three children (girls) suffered from neutropenia mediated by anti-neutrophil IgG-Fc receptor type III (Fc gamma RIII) antibodies. The first patient (newborn) had asymptomatic and transient neutropenia caused by maternal Fc gamma RIII iso-antibodies. The second patient (6 months), whose neutropenia was diagnosed as a 'benign neutropenia of childhood' caused by transient anti-NAI autoantibodies, suffered from mild bacterial infections. The third patient (12 years) suffered from serious infections. The anti-Fc gamma RIII autoantibodies showed neither anti-NA1 nor anti-NA2 specificity. She also developed autoimmune thyroiditis (Graves' disease). Both the duration of the neutropenia and the seriousness of the bacterial infection were variable in our patient group. The first two patients both made spontaneous recoveries, while the third patient depended ultimately on granulocyte-colony stimulating factor (G-CSF).     

Choline availability modulates the expression of TGFbeta1 and cytoskeletal proteins in the hippocampus of developing rat brain

Choline availability influences long-term memory in concert with changes in the spatial organization and morphology of septal neurons, however little is known concerning the effects of choline on the hippocampus, a region of the brain also important for memory performance. Pregnant rats on gestational day 12 were fed a choline control (CT), choline supplemented (CS), or choline deficient (CD) diet for 6 days and fetal brain slices were prepared on embryonic day 18 (E18). The hippocampus in these brain slices was studied for the immunohistochemical localization of the growth-related proteins transforming growth factor beta type 1 (TGFbeta1) and GAP43, the cytoskeletal proteins vimentin and microtubule associated protein type 1 (MAP1), and the neuronal cell marker neuron specific enolase (NSE). In control hippocampus, there was weak expression of TGFbeta1 and vimentin proteins, but moderately intense expression of MAP1 protein. These proteins were not homogeneously distributed, but were preferentially localized to cells with large cell bodies located in the central (approximately CA1-CA3) region of the hippocampus, and to the filamentous processes of small cells in the fimbria region. Feeding a choline-supplemented diet decreased, whereas a choline-deficient diet increased the intensity of immunohistochemical labeling for these proteins in E18 hippocampus. GAP43 and NSE were localized to peripheral nervous tissue but not hippocampus, indicating that the maturation of axons and neurite outgrowth in embryonic hippocampus were unaffected by the availability of choline in the diet. These data suggest that the availability of choline affects the differentiation of specific regions of developing hippocampus.     

Comparative study of psychiatric morbidity among workers at a paint factory in Nigeria

A fetal lamb model was developed to investigate the capacity of fetal articular cartilage for repair after the creation of a superficial defect. Superficial defects, 100 micrometers deep, were made in the articular cartilage of the trochlear groove in the distal aspect of the femur in eighteen fetal lambs that were halfway through the 145-day gestational period; the contralateral limb was used as a sham control. The wounds were allowed to heal in utero for three, seven, fourteen, twenty-one, or twenty-eight days. Seven days after the injury, the defects were filled with a hypocellular matrix, which stained lightly with safranin O. At twenty-eight days, the staining of the matrix was similar to that of the sham controls and the chondrocyte density and the architectural arrangement of the cell layers had been restored. An inflammatory response was not elicited, and no fibrous scar tissue was observed.