Abnormal binding of factor VIII is linked with the substitution of glutamine for arginine 91 in von Willebrand factor in a variant form of von Willebrand disease

von Willebrand factor (vWf) is a multimeric plasma glycoprotein that functions in hemostasis as the initiator of platelet adhesion to damaged blood vessels and as the carrier of Factor VIII (FVIII). Montgomery et al. (Montgomery, R.R., Hathaway, W.E., Johnson, J., Jacobsen, L., and Muntean, W. (1982) Blood 60, 201-207) reported a variant of von Willebrand disease characterized by the abnormal interaction between FVIII and a defective vWf. To identify the molecular basis of this abnormal interaction, we isolated platelet RNA from members of one of the affected families and determined the nucleotide sequence of the FVIII-binding domain encoded by the vWf mRNA. A single G to A transition at nucleotide 2561 was linked with disease expression and results in the substitution of Gln for Arg91 in mature vWf. A restriction fragment containing this mutation was introduced into a full-length vWf expression vector, and both wild type and mutant vWf were expressed in COS-7 cells. In a solid-phase binding assay, expressed vWf was captured with anti-vWf monoclonal antibody AVW1 and then incubated with 6.25-400 milliunits of recombinant FVIII. After washing, vWf-bound FVIII activity was determined with a chromogenic assay. Mutant vWf showed reduced binding of FVIII compared with wild type, suggesting that the substitution of Gln for Arg91 is the likely basis for the abnormal vWf/FVIII interaction in this von Willebrand disease variant.     

Mobility of the spin-labeled side chains of some novel antifolate inhibitors in their complexes with dihydrofolate reductase

Four spin-labeled inhibitors of dihydrofolate reductase (DHFR) have been synthesized, each of which has the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) reporting group at a different distance from the 2,4-diaminopyrimidine moiety by which the inhibitors are anchored and oriented in the active site. Inhibitors in which the TEMPO group is attached by a short side chain are weakly bound to DHFR from bacteria (Streptococcus faecium and Lactobacillus casei), to the bovine enzyme and to recombinant human DHFR. However, binding is sufficiently tight, especially in the ternary complexes with NADPH, for recording of the EPR spectra of the bound ligands. The spectra indicate that when these inhibitors are bound to the enzyme the TEMPO group is highly immobilized with correlation time, tau c, 4-20ns. Inhibitors that have the reporter group attached to the glutamate moiety of methotrexate bind to all four DHFRs more tightly than the inhibitors with shorter side chains by factors of up to 10(6). However, in most complexes formed by the inhibitors with longer side chains immobilization of the TEMPO group is slight (tau c 0.2-4 ns). These results are in general agreement with predictions from X-ray crystallographic results including thermal factors but there are some unanticipated differences between some results for bacterial and eukaryotic enzymes. Three of the splin-labeled inhibitors would provide good probes for distance measurements in and around the active site of mammalian DHFR.     

Lipid and carbohydrate metabolism in premenopausal women given subdermal estradiol implants

Fifteen premenopausal women were studied before and 6 weeks after receiving subcutaneous implants of 100 mg estradiol. Serum estradiol levels doubled; increases were also seen in fasting serum total cholesterol and in high-density lipoprotein cholesterol (HDL). This increase was confined to the HDL2 subfraction, and was not reflected in the HDL apolipoproteins. Low density lipoprotein (LDL) cholesterol levels were unchanged, as were those of apolipoprotein B, the major protein component of LDL. Carbohydrate metabolism was assessed in a subgroup of 12 women. Estrogen implantation reduced fasting plasma glucose levels but did not alter the plasma glucose response to an oral glucose tolerance test. Plasma insulin levels were unchanged both in the fasted state and during the glucose tolerance test. Our findings indicate that parenteral administration of estradiol can alter lipid and carbohydrate metabolism in premenopausal women.     

Messenger RNA sorting in enterocytes. Co-localization with encoded proteins.

This study describes the intracellular compartmentalization of three different mRNAs in the polarized rat fetal enterocyte. They encode proteins that are known to be localized within different regions of the epithelial cell namely (i) the apical, membrane-bound glycoprotein, lactase-phlorizin hydrolase (lactase), (ii) the mitochondrially localized enzyme, carbamoylphosphate synthetase (CPS), and (iii) the cytoplasmically localized enzyme, phosphoenolpyruvate carboxykinase (PEPCK). These mRNAs are found in close proximity to their respective protein products, i.e. the apical membrane, mitochondria and cytoplasm, respectively. The significance of these observations is twofold; (i) they indicate that mRNAs are sorted into specific domains of the cytosol of intestinal epithelial cells; and (ii) they imply the presence of two distinct pathways of mRNA targeting one that allows transport of mRNAs that are translated on ribosomes associated with the rough endoplasmic reticulum (lactase mRNA), and the other that allows sorting of mRNAs that are translated on free polysomes (CPS and PEPCK mRNA).     

Maintenance of the Adult Rat Superior Cervical Ganglion In Vitro: Comparison of Organ and Explant Culture Systems

Abstract: Concentrations of selected intermediates of energy metabolism whole rat superior cervical ganglia maintained in vitro by an organ culture technique were compared with values measured in small slices of this maintained under essentially the same conditions. Rates of incorporation [³H]leucine into trichloroacetic acid-precipitable material in whole ganglia mained constant for at least 48 h: however, the oxidation-reduction state tissue as indexed by (NAD):(NADH) ratios calculated from measured amounts of lactate and pyruvate decreased more than 50% within ³h in vitro . Ganglion explants prepared by cutting the tissue into ³⁰⁰-pm transverse sections played (NAD):(NADH) ratios that were about three times greater than noted in whole ganglia maintained in vitro for the same period of time. explants contained significantly higher concentrations of pyruvate and α-ketoglutarate than whole ganglia maintained in culture. Maintenance of vorable metabolic state may support the extensive growth of neurites seen explant cultures of superior cervical ganglia. Outgrowth of processes containing catecholamines could be detected readily in explant cultures of ganglia adult rats; however, this was somewhat slower and less consistent than growth observed in explants from neonatal rats. Outgrowth of neurites adult ganglia was minimal without the addition of Nerve Growth Factor.     

Marine macroalgae as foods for fishes: an evaluation of potential food quality

Synopsis A revitalized view of feeding by herbivorous marine fishes is sought through two questions. First, What characteristics of major taxa of algae identify them as predictably high or low quality foods? Second, are marine algae valuable foods for fishes which do not mechanically disrupt cell walls and do not harbor specialized enzymes or microbes capable of lysing cell walls? Energy, ash and nutrient content of 16 species of marine algae were employed to assess food quality of fleshy red, green, brown and calcareous red algae. On the basis of ash, calories, total protein and total lipid content, fleshy algae should be superior to calcareous algae as foods for fishes; in addition, green algae should be superior to brown algae and brown algae superior to red algae. When the probable digestibility of storage and extracellular carbohydrates is considered, green and red algae are predicted superior to brown algae as food. Two species of damselfishes (Pomacentridae) from the Gulf of California,Eupomacentrus rectifraenum andMicrospathodon dorsalis, eat red and green algae and ignore brown and calcareous algae. They feed, therefore, in a fashion consistent with predictions based only on algal chemistry. These fishes absorb at least 20–24% of the biomass, 57–67% of the protein, 46–56% of the lipid and 37–44% of the carbohydrate contained in algae eaten in the wild. Since these damselfishes do not masticate their food, it appears that herbivorous fishes can digest major fractions of algal nutrients without mechanical destruction of algal cells.     

Migration of IgA-bearing lymphocytes into salivary glands

The relative migratory properties of [¹²⁵I]iododeoxyuridine-labeled dividing mesenteric lymph node (MLN) and peripheral lymph node (PLN) cells were assessed in mice using the adoptive transfer system. MLN cells from virgin donors showed a greater tendency to localize in MLN, small intestine, and mammary glands (lactating recipients only) of virgin and lactating recipients. In addition, MLN cells were shown to selectively localize in the salivary (submandibular and sublingual) glands. The relative migratory properties of MLN and PLN cell populations were identical when donor cells were obtained from virgin or lactating animals. Selective depletion of IgA-bearing cells from the MLN transfer cell population abrogated the preferential localization in control mucosal tissues and salivary glands. These data show that the salivary glands can be included as an additional mucosal area populated by gut-derived IgA-bearing cells and provides direct evidence that the common mucosal immune sytstem extends to secretory tissue in the oral cavity.     

Cytochrome P-450 heme and the regulation of δ-aminolevulinic acid synthetase in the liver

Hepatic δ-aminolevulinic acid synthetase was induced in rats injected with allylisopropylacetamide. The induction process was studied in relation to experimental perturbation of cytochrome P-450 in the liver. Animals were treated with either administered endotoxin or exogenous heme, both of which accelerate degradation of cytochrome P-450 heme. These manipulations were effective in blocking induction of δ-aminolevulinic acid synthetase, and the effect of each compound was proportional to its ability to stimulate degradation of cytochrome P-450 heme. The findings suggest that the heme moiety of cytochrome P-450 dissociates reversibly from its apoprotein and, prior to its degradation, mixes with endogenously synthesized heme to form a pool that regulates δ-aminolevulinic acid synthetase activity. A similar or identical heme fraction appears to mediate stimulation of heme oxygenase, which suggests that the regulation of δ-aminolevulinic acid synthetase and of heme oxygenase in the liver are closely interrelated.