Carbon and nitrogen cycling in intertidal sediments near Doel,Scheldt Estuary

Carbon and nitrogen cycling in intertidal mud flat sediments in the Scheldt Estuary was studied using measurements of carbon dioxide, methane and nitrous oxide emission rates and pore-water profiles of CO₂, ammonium and nitrate. A comparison between chamber measured carbon dioxide fluxes and those based on CO₂ pore-water gradients using Fick's First law indicates that apparent diffusion coefficients are 2 to 28 times higher than bulk sediment diffusion coefficients based on molecular diffusion. Seasonal changes in gaseous carbon fluxes or CO₂ pore water concentrations cannot be used directly, or in a simple way, to determine seasonal rates of mineralization, because of marked seasonal changes in pore-water storage and exchange parameters.The annual amount of carbon delivered to the sediment is 42 mol m^–2, of which about 42% becomes buried, the remaining being emitted as methane (7%) or carbon dioxide (50%). Each year about 2.6 mol N m^–2 of particulate nitrogen reaches the sediment; 1.1 mol m^–2 is buried and 1.6 mol m^–2 is mineralized to ammonium. Only 0.42 mol m^–2 yr^–1 of the ammonium produced escapes from the sediments, the remaining being first nitrified (1.2 mol m^–2 yr^–1) and then denitrified (1.7 mol m^–2 yr^–1). Simple calculations indicate that intertidal sediments may account for about 14% and 30% of the total estuarine retention of nitrogen and carbon, respectively.     

First evidence of human meconium glycoasparagines

During a systematic study of carbohydrate material present inhuman meconium, in addition to the previously described mucins,glycolipids and free oligosaccharides, we have now characterizeda significant quantity of free glycoasparagines. These glycoasparagineshave been isolated from human meconium by a combination of ion-exchange,concanavalin A (ConA)-affinity and high-performance liquid (HPLC)chromatographies. Their structures have been established by400 MHz ¹H-NMR spectroscopy. These compounds are related toN-acetyllactosaminic type structures and are based on the commoncore These glycoasparagines are probably derived from both proteaseand partial exoglycosidase hydrolysis of fetal gastrointestinalN-glycosyl proteins. Their structures are discussed in the contextof the known catabolic pathways of N-glycans glycoasparagine N-glycosyl protein catabolism meconium NMR     

Endocytosis of androgen-binding protein (ABP) by spermatogenic cells

To test whether Sertoli cell-secreted ABP could serve as steroid carrier to the germ cell (GC) lineage, radiolabeled ABP and SHBG and gold SHBG were used for binding studies and for internalization studies based on transmission electron microscope analyses and autoradiography of the radiolabeled samples. The data clearly showed that: (1) rat and human germ cells possess a single class of binding sites for rat ABP and human SHBG respectively (K_d of 0.78 and 0.56 nM); (2) 1.7 × 10¹⁰ and 2.7 × 10¹⁰ sites/mg protein was found in the corresponding plasma membrane preparations; (3) the receptor peak was eluted in the same position as dextran blue: 2000 kDa (M_r = 2 × 106) for labeled rat ABP; (4) in the whole GC lineage, the labeled ligand was internalized through an endocytic pathway involving clathrin coated structures and the distribution was similar throughout the maturation step, however striking differences in the internalization rate were revealed with regard to the maturation step; and (5) this internalization occurred even in ligated seminiferous tubules, via the Sertoli cells cytoplasm. When isolated rat GC were incubated in the presence of ABP, a dose dependent increase in labeled secreted protein was observed for spermatocytes (50–250%) whereas ABP had no effect on spermatids. Addition of steroids and ABP caused a 200 and 50% increase in labeled secreted proteins for spermatocytes and spermatids respectively. 2-D SDS-PAGE analysis revealed that ABP alone increased the secretion of specific spermatocyte proteins whereas steroids in the presence of ABP resulted in the synthesis of new spermatocyte secreted proteins. Taken together these results strongly suggest that ABP may be required for spermatogenesis either as a steroid transmembrane carrier or on its own.     

Purification, characterization and ion binding properties of human brain S100b protein

Human brain S100b (beta beta) protein was purified using zinc-dependent affinity chromatography on phenyl-Sepharose. The calcium- and zinc-binding properties of the protein were studied by flow dialysis technique and the protein conformation both in the metal-free form and in the presence of Ca2+ or Zn2+ was investigated with ultraviolet spectroscopy, sulfhydryl reactivity and interaction with a hydrophobic fluorescence probe 6-(p-toluidino)naphthalene-2-sulfonic acid (TNS). Flow dialysis measurements of Ca2+ binding to human brain S100b (beta beta) protein revealed six Ca2+-binding sites which we assumed to represent three for each beta monomer, characterized by the macroscopic association constants K1 = 0.44 X 10(5) M-1; K2 = 0.1 X 10(5) M-1 and K3 = 0.08 X 10(5) M-1. In the presence of 120 mM KCl, the affinity of the protein for calcium is drastically reduced. Zinc-binding studies on human S100b protein showed that the protein bound two zinc ions per beta monomer, with macroscopic constants K1 = 4.47 X 10(7) M-1 and K2 = 0.1 X 10(7) M-1. Most of the Zn2+-induced conformational changes occurred after the binding of two zinc ions per mole of S100b protein. These results differ significantly from those for bovine protein and cast doubt on the conservation of the S100 structure during evolution. When calcium binding was studied in the presence of zinc, we noted an increase in the affinity of the protein for calcium, K1 = 4.4 X 10(5) M-1; K2 = 0.57 X 10(5) M-1; K3 = 0.023 X 10(5) M-1. These results indicated that the Ca2+- and Zn2+-binding sites on S100b protein are different and suggest that Zn2+ may regulate Ca2+ binding by increasing the affinity of the protein for calcium.     

Resistance to chenodeoxycholic acid (CDCA) treatment in obese patients with gall stones

In most patients with radiolucent gall stones who were given chenodeoxycholic acid (CDCA) in doses of 13-15 mg/kg body weight/day the bile became unsaturated in cholesterol, and their gall stones dissolved. The patients whose stones did not dissolve were significantly heavier and fatter than the responders, which suggested that obese patients might be “resistant” to the effects of CDCA. To test this hypothesis, 32 consecutive patients presenting for medical treatment of gall stones had their ideal body weight (IBW) and estimated body fat mass calculated. The eight most obese and the eight least obese patients were then selected, and their fasting bile lipid responses to CDCA 13-15 mg/kg/day were measured. The very obese patients were also given larger doses, and any changes in bile lipid composition were studied in relation to subsequent gall-stone dissolution.Before treatment the obese patients had a higher mean biliary cholesterol saturation index than the non-obese patients, and this difference was maintained during treatment with the normal dose of CDCA: the bile in the obese patients remained supersaturated while that in the non-obese became unsaturated with cholesterol. When the obese patients were given larger doses of CDCA their bile ultimately became unsaturated in cholesterol. Gall stones dissolved partially or completely in five of the eight non-obese patients after 6-18 months of 13-15 mg CDCA/kg/day, but none of the obese patients showed any response after comparable periods of treatment with this standard dose. With increased doses and unsaturated bile, however, three of the obese patients showed partial gall-stone dissolution after 3-12 months'' treatment and one showed complete gall-stone dissolution after three years'' treatment.These results suggest that when giving CDCA to patients with gall stones, larger than normal doses (some 18-20 mg/kg/day) should be prescribed. Alternatively the lipid composition of the patients'' bile should be monitored by duodenal intubation and the CDCA dose increased until the bile becomes unsaturated in cholesterol.     

Fluorescent study of tobacco mosaic virus protein

The synthesis of two new variants of gramicidin is described. It is shown that the changes in the aromatic side groups do not influence the single channel conductivity. Experiments in which solutions having different molarities on the two sides of the bilayer lipid membrane are described and their results compared with a rate theory analysis. It is concluded that the gramicidin pore contains approximately 10 equal potential maxima.     

Composés glucidiques et azotés et résistance à la sécheresse chez Ailanthus altissima

In Ailanthus altissima, carbohydrate and protein reserves are mainly localized in the tap-root. Under drought stress they are very quickly hydrolysed. Despite the water deficiency, an increase in starch synthesis is observed in the leaves and stem during the first stages of stress. Stimulation of the cambial activity of the stems and an increase in protein content have also been observed. Chemical analyses have shown a high proline content which increases markedly following drought stress, especially in the tap-root.     

Partial hypoxanthine-guanine phosphoribosyl transferase deficiency with full expression of the Lesch-Nyhan syndrome

Summary A patient with the full clinical expression of the classical Lesch-Nyhan syndrome is presented with a residual hypoxanthine-guanine phosphoribosyl transferase (HGPRT) activity of 5–10% in erythrocyte lysate and about 30% in fibroblast lysate. The activities of other erythrocyte enzymes of purine metabolism were typical for a classical Lesch-Nyhan patient. The effects of allopurinol therapy on the excretion of urinary purine metabolites were studied by a newly developed isotachophoretic technique.The unusually high residual activity of HGPRT in erythrodytes and fibroblasts of the patient enabled the enzymologic characterization of the mutant enzyme: in fibroblasts the affinities for the substrates hypoxanthine and guanine were normal. However, there was an increased apparent K _m for phosphoribosylpyrophosphate (PRPP), a complete absence of product inhibition by IMP and GMP, and a decreased heat stability. Addition of PRPP did not stabilize the mutant enzyme. In addition to the altered properties of the fibroblast enzyme, the K _m of the erythrocyte enzyme for hypoxanthine was also increased.Immunoprecipitation experiments revealed the presence of an approximately normal amount of material cross-reacting with anti-human HGPRT antiserum. However, it appeared that this cross-reacting material had a decreased stability. When intact erythrocytes were incubated with radiolabeled purine bases, no formation of IMP or GMP could be detected, despite the relatively high residual activity of HGPRT in the hemolysate. The results fit the following hypothesis: as a consequence of a structural mutation affecting the PRPP-site of the enzyme and a decreased heat stability, the activity of the mutant enzyme under in vivo conditions is virtually zero.In the erythrocytes of the patient's mother a normal HGPRT-activity was found. However, the activity in her fibroblasts was lower than normal, while a decreased heat stability and an intermediate behavior towards IMP could be shown.Hair root analysis of several members of the patient's family confirmed the heterozygosity of the mother, whereas no other heterozygotes could be detected. The family anamnesis did not show other cases of Lesch-Nyhan syndrome. These findings were taken as evidence that the patient described in this paper might represent a mutation orginating from the gametes in either of the maternal grandparents.     

The diffusion of gibberellins into agar and water during early germination of Pharbitis nil Choisy

Agar diffusion of imbibed seeds yielded significant amounts of diffusible Gibberellin-like substances. An analysis of the extractable and diffusible gibberellin-like substance, including an analysis of the remaining imbibition water of the seeds, indicated that a significant part of these gibberellin-like substances could be attributed to a net biosynthesis of these substances in the imbibing seeds. At the same time it was found that water diffusion yielded considerably more gibberellin-like activities than comparable agar diffusions i.e. 10 to 12 fold in general.Agar as well as water diffusion showed a temperature effect with regard to the yield of gibberellin-like substances particularly during the first 6 h of diffusion. The yield of these substances is lower at 10°C, and remains lower as shown with consecutive diffusions, in comparison with the yields at 20°C or 30°C.With both agar and water diffusion the sum of activities obtained with consecutive diffusions is always higher, often considerably higher, than equal periods of continuous diffusion which is probably due to inactivation and/or interference of inhibitory substances with the bioassay responses. Finally, water diffusates of both seeds and seedlings of the normal growing cv. Violet of Japanese morning glory contained considerably more gibberellin-like activities than those of the dwarf cv. Kidachi which indicated that normals synthesize more gibberellins than dwarfs.     

Goiter in Tibetan Medicine

The visit of two Tibetan physicians provided a unique opportunity to gain insight into a practice of medicine very different from that of Western civilization. Initial discussions indicated that the practice of medicine and mysticism were inextricably interwoven in the Tibetan culture. Accordingly, the focus of the study was directed to goiter, which is both common in the Himalayas and easy to define.In Tibetan medical practice, illness is considered to be derived from both proximate and distant causes. Three humors, “wind,” “bile,” and “phlegm” are thought to be responsible for normal mental and physical functions when in balance, but disease when out of balance. Goiter was thought to be due to an imbalance of these humors. The Western discovery that endemic goiter in the Himalayas was due to iodine deficiency explained the proximate cause but did not explain why some individuals have goiter and others do not in the same iodine deficient village.