Seasonal Variability and Transport of Suspended Microfungi in a Southeastern Salt Marsh

Tidally induced fluctuations and transports of microfungi were investigated. Samples were collected at three depths from three stations positioned at a transect in a large salt marsh creek. Samples were taken every 1.5 h for 50 consecutive h during neap tides and 50 consecutive h during the corresponding spring tides. In each season, microfungi concentrations fluctuated out of phase with the tides during both neap and spring tides. Mean concentrations of suspended microfungi did not vary appreciably throughout the year. Fungi were exported from the marsh during the majority of the tidal cycles studied. The results suggest that microfungi may serve as indicators of water mass movements.     

Base-catalyzed oligomerization of levoglucosenone

Heating levoglucosenone in aqueous triethylamine gives a dimer and two trimers in yields of 8, 18, and 56%, respectively. These compounds have been isolated crystalline, and their structures and stereochemistry have been investigated by ¹³C- and ¹H-n.m.r. and other spectroscopic methods. These data indicate that the dimer is apparently formed by Michael addition to provide a C-3-C-4 linkage. Similar reactions provide a non-olefinic, C-3-C-4-linked, cyclic trimer and an olefinic, cyclic trimer containing two C-3-C-4 linkages and one C-2-C-3 linkage.     

A study of the control of NADP(+)-dependent isocitrate dehydrogenase activity during gonadotropin-induced development of the rat ovary

The concentration of cytoplasmic NADP(+)-dependent isocitrate dehydrogenase increased 20.2-fold during gonadotropin-induced development of the immature rat ovary. Measurement was by protein (Western) blotting using polyclonal antibodies raised against purified enzyme from the porcine corpus luteum. The increase in enzyme concentration during development correlated well with the 18.5-fold increase observed for the specific activity of the enzyme in the cytosolic fraction. An immunochemical similarity was demonstrated between the cytoplasmic enzyme from the ovary, testes, placenta, skeletal muscle, brain, liver, kidney, mammary and adrenal gland. However the mitochondrial NADP(+)-dependent isocitrate dehydrogenase from these tissues was found to be immunochemically distinct from the cytoplasmic enzyme. The concentration of the substrate D(+/-)-threo-isocitrate in the ovaries was measured by fluorometry and found to increase 3.1-fold during hormone-induced development. The intracellular concentration of substrate was estimated to be of the same order of magnitude as the enzyme concentration. We conclude that the increase in cytoplasmic NADP(+)-dependent isocitrate dehydrogenase activity observed during the gonadotropin-stimulated development of the rat ovary is due to increased concentration of enzyme rather than to an activation of the enzyme. The activity of the enzyme in vivo appears to be regulated by the availability of the substrate D(+/-)-threo-isocitrate.     

Structural studies on site-directed mutants of domain 3 of Xenopus laevis oocyte 5 S ribosomal RNA

Base substitutions have been introduced into the highly conserved sequences of loops D and E within domain 3 of Xenopus laevis oocyte 5 S rRNA. The effects of these mutations on the solution structure of this 5 S rRNA have been studied by means of probing with nucleases, and with chemical reagents under native and semi-denaturing conditions. The data obtained with these mutants support the graphic model of Xenopus oocyte 5 S rRNA proposed by Westhof et al. In particular, our results rule out the existence of long-range base-pairing interactions between loop C and either loop D or loop E. The data also confirm that loops D and E in the wild-type 5 S RNA adopt unusual secondary structures and illustrate the importance of nucleotide sequence in the formation of intrinsic local loop conformations via non-canonical base-pairs and specific base-phosphate contacts. Consistent with this conclusion is our observation that the domain 3 fragment of Xenopus oocyte 5 S rRNA adopts the same conformation as the corresponding region in the full-length 5 S rRNA.     

Plasmodium chabaudi AS: erythropoietic responses during infection in resistant and susceptible mice.

The course of anemia and the erythropoietic response in the bone marrow, spleen, and blood were studied during Plasmodium chabaudi AS infection in resistant C57BL/6 (B6) and susceptible A/J (A) mice. Infections in B6 mice were characterized by moderate levels of both parasitemia and anemia and survival. In contrast, A mice experienced high parasitemia, severe anemia, and high mortality rates. During the period of anemia, erythropoiesis, as measured by in vivo 59Fe incorporation, was significantly more depressed in bone marrow and more increased in the spleen in resistant B6 mice. The increase in splenic 59Fe incorporation was a function of the size of the spleen. Bone marrow CFU-E were decreased to 50% of control in both strains, while splenic CFU-E were increased twofold greater in B6 mice compared to those in A mice. However, the absolute numbers of CFU-E per spleen in the two strains were not significantly different during peak parasitemia. Bone marrow BFU-E were transiently increased before peak parasitemia whereas splenic BFU-E peaked during peak parasitemia. A mice had significantly lower numbers of BFU-E per spleen on all days except at peak parasitemia. The frequency of blood-borne BFU-E and plasma erythropoietin titers was increased earlier and to a greater extent in A mice. These results suggest that an impaired amplification of late-stage splenic erythropoiesis may be an important determinant in the severity of anemia and lethality of infection with P. chabaudi AS in A mice. Moreover, these results demonstrate that the defective amplification of splenic erythropoiesis in A mice is neither caused by a defect in the mobilization of BFU-E from the bone marrow to the spleen nor caused by a defect in erythropoietin production.     

VH restriction among human cold agglutinins. The VH4-21 gene segment is required to encode anti-I and anti-i specificities.

We previously reported that human autoantibodies with cold agglutinin activity contained a single human VH gene segment (VH4-21) which was also responsible for the cross-idiotypic specificity characteristic of the cold agglutinin response. To confirm and extend this observation we have analyzed at the nucleotide level the H and L chains of six new cold agglutinin molecules derived from different patients. We found that regardless of whether the antibody recognizes the i or the I red cell Ag, restriction at the VH gene segment level is absolute. We also found that even in the absence of somatic mutation the VH4-21 gene segment can encode both anti-i and anti-I specificities. Finally, although the VH4-21 gene segment is essential for cold agglutinin activity, the other genetic elements that contribute to the V region of the antibody molecules can be extremely diverse. The structural information provided in this report sharply restricts the requirement for encoding pathogenic cold agglutinin activity to one of the components of the H chain V region, specifically the VH gene segment. The implications of this apparently absolute requirement for a single VH gene segment, unprecedented in the human autoimmune response, are discussed.     

Effects of indomethacin on fetal renal function, renal and umbilicoplacental blood flow and lung liquid production.

The effects of indomethacin (10 mg/kg i.v. to the ewe and 12 mg/kg i.v. to the fetus) were examined in 8 chronically catheterized fetal sheep (117-138 days gestation). These doses suppressed fetal 6-keto-prostaglandin F1 alpha and thromboxane B2 levels. Fetal arterial PO2 increased (P < 0.01); PCO2 (P < 0.001) and pH fell (P < 0.001) and arterial pressure did not change. Placental blood flow increased in 4 of the 5 fetuses in which blood flows were measured. Lung liquid flow rate fell (P < 0.001). Fetal renal blood flow did not change but its distribution did, i.e. flow to the inner part of the renal cortex decreased (P < 0.05). Urine flow rates did not change but there was a natriuresis (P < 0.02), kaliuresis (P < 0.02) and chloriuresis (P < 0.02). Urinary osmolality rose (P < 0.001) and free water clearance fell (P = 0.004). It is concluded that when indomethacin is administered to both ewe and fetus, the resulting fall in prostaglandin I2 and thromboxane A2 levels causes marked changes in fetal blood gas status, renal function and lung liquid production. These effects are more profound than those seen when indomethacin is given only to the fetus. They do not however, explain the reason why clinical use of indomethacin is associated with a reversible oligohydramnios.     

Developmental variation in copper,zinc and metallothionein mRNA in brindled mutant and nutritionally copper deficient mice

The concentrations of copper, zinc and metallothionein-I (MT-I) mRNA were determined in the liver, kidney and brain of the brindled mutant mouse from birth until the time of death. Despite accumulation of copper in the kidney of the mutant, MT-I mRNA concentrations were normal. There was no difference between the MT-I mRNA in the brain of mutant and normal in the first 10 days of life, but after day 10 metallothionein mRNA levels were increased in the mutant. The concentration of copper was very low in the liver of the mutant, and on day 6 after birth the metallothionein mRNA was also reduced by about 50%. This reduction was not seen in copper-deficient 6-day-old pups, despite very low hepatic copper levels. This suggests that the lower hepatic MT-I mRNA in the day 6 brindled mouse was not simply due to the reduction in hepatic copper and also that hepatic copper is not regulating metallothionein gene expression the liver of neonatal mice. After day 12 hepatic MT-I mRNA levels were elevated in mutant and in copper deficient mice, both of which die at 14 to 16 days. These increases and the increase in brain MT-I mRNA in older mutant mice are likely to be caused by stress. Overall the results support the conclusions that the brindled mutation does not cause a constitutive activation of the metallothionein genes, and that the differences in metallothionein mRNA between mutant and normal are most probably secondary consequences of the mutation.     

Detection of covalent enzyme-substrate complexes of nitrilase by ion-spray mass spectroscopy

Nitrilase from Rhodococcus ATCC 39484 was found to consist of two species of Mr 40,258 +/- 2 and 40,388 +/- 2 Da. When the enzyme was incubated with nitrile substrates and the reaction quenched with acid, higher Mr species were observed. The mass differences were consistent with addition of a substrate molecule to each species. These results represent the first reported demonstration that this, or any other nitrilase forms a covalent intermediate with its substrates. The observation that the intermediate, suggested to be either a thioimidate or an acylenzyme, can be trapped by acidification indicates that the rate of breakdown of the intermediate is rate-limiting.