The influence of diet on the growth of Stenonema vicarium (Walker) (Ephemeroptera: Heptageniidae)

Laboratory studies compared the growth rate of Stenonema vicarium (Walker) nymphs on diets of detritus and natural stream periphyton. In three consecutive runs of the experiment, growth rates were consistently higher on periphyton (mean growth rate = 2.1% wet wt. d⁻¹) than detritus (mean = 1.8% wet wt. d⁻¹). The starting date of each run also significantly influenced growth rates. In each treatment growth rates generally decreased over the course of the 3 runs, and ca. one-half of the nymphs in the last run did not molt or grow. It appeared that growth of S. vicarium may be partially controlled by seasonal factors.     

Glutamine synthetase isozymes in elasmobranch brain and liver tissues

Glutamine synthetase is present as isozymic forms in the elasmobranchs Squalus acanthias (dogfish shark) and Dasyatis sabina (stingray). Subcellular fractionation of elasmobranch brain and liver tissue shows the enzyme to be predominantly cytosolic in the former tissue and mitochondrial in the latter. For the cytosolic brain enzyme, the subunit Mr equals 42,000 in the stingray and 45,000 in the shark, as determined by sodium dodecyl sulfate-gel electrophoresis/Western blotting. The subunit Mr = 45,000 and 47,000, respectively, for stingray and dogfish mitochondrial liver enzymes. Translation of total brain RNA from both species gives immunoprecipitable nascent peptides of the same size as their respective mature enzymes. However, in liver tissue, translation of glutamine synthetase mRNA yields peptides of higher Mr than that of the mature enzymes. In dogfish liver, Mr = 50,000 for the translation product and, in stingray liver, Mr = 48,000. This suggests that the translocation of the enzyme into liver mitochondria may be via a signal or leader sequence mechanism. The larger liver isozyme of elasmobranch glutamine synthetase is found in kidney where it is also known to be mitochondrial. The smaller cytosolic isozyme occurs in retina, heart, gill, and rectal gland tissue as well as in brain.     

Freeze-Thawing of Aquaspirillum magnetotacticum Cells Selectively Releases Periplasmic Proteins

Cells of the gram-negative bacterium Aquaspirillum magnetotacticum, when suspended in buffer and freeze-thawed, produced pinkish orange supernatant fluid. The fluid contained ≤2.0% of total extractable outer membrane component 2-keto-3-deoxyoctonate or of the cytoplasmic membrane marker succinic dehydrogenase. Electrophoretic banding patterns and difference spectra of proteins and hemoproteins released by freeze-thawing cells were distinct from those of membrane-associated substances and similar to those of periplasmic substances obtained by applying conventional fractionation methods to this organism.     

High-resolution 1H NMR study of the solution structure of alamethicin

A 1H NMR study of the peptide alamethicin, which forms voltage-gated ion channels in membranes, is described. The molecule was studied in methanol as a function of temperature and pH. A complete assignment of the spectra is given, including several stereospecific assignments. Alamethicin was found to have a structure substantially similar to the crystal although, in solution, the C-terminal dipeptide adopts a somewhat extended conformation. The overall conformation was insensitive to the ionization of the side chain of the only ionizable group, Glu-18.     

Primary structure analysis proves that protein phosphatases 2C1 and 2C2 are isozymes

The two recently discovered forms of protein phosphatase 2C, termed 2C1 and 2C2, were digested with CNBr or trypsin, and several peptides corresponding to two regions of the protein were sequenced. These studies revealed close homology between the two enzymes with 49 identities over the 62 residues that could be compared directly. The results establish that protein phosphatases 2C1 and 2C2 are the products of different genes. The C-terminus of protein phosphatase 2C2 has also been identified.     

Doppler studies in the growth retarded fetus and prediction of neonatal necrotising enterocolitis,haemorrhage, and neonatal morbidity.

In 82 consecutive cases of intrauterine growth retardation managed by established criteria fetal Doppler studies identified 29 fetuses with absence of end diastolic frequencies in the fetal aorta. These same fetuses were significantly more growth retarded (p less than 0.001) and had an earlier gestational age at delivery (p less than 0.001) than those with end diastolic frequencies present. A subgroup of these cases was analysed in more detail to examine the prognostic value of this phenomenon for the neonate. Two groups of neonates of equivalent gestational age and with a birth weight below 2000 g were compared. There were 26 neonates with absent end diastolic frequencies (group 1) and 20 with end diastolic frequencies (group 2) in the fetal aorta. Those in group 1 were more likely to suffer perinatal death (p less than 0.05), necrotising enterocolitis (p less than 0.01), and haemorrhage (p less than 0.05). Only 4 (15%) of the babies in group 1 had an uncomplicated neonatal period compared with 15 (75%) in group 2 (p less than 0.001). The circulatory changes identified in these cases may provide a more sensitive measure of critical fetal compromise than current techniques and thus allow the clinician to deliver the fetus before irreversible tissue damage has occurred.     

UV irradiation inhibits initiation of DNA replication from oriC in Escherichia coli

Summary Irradiation of Escherichia coli with UV light causes a transient inhibition of DNA replication. This effect is generally thought to be accounted for by blockage of the elongation of DNA replication by UV-induced lesions in the DNA (a cis effect). However, by introducing an unirradiated E. coli origin (oriC)-dependent replicon into UV-irradiated cells, we have been able to show that the environment of a UV-irradiated cell inhibits initiation of replication from oriC on a dimer-free replicon. We therefore conclude that UV-irradiation of E. coli leads to a trans-acting inhibition of initiation of replication. The inhibition is transient and does not appear to be an SOS function.     

cDNA Clones for Corn Leaf NADH:Nitrate Reductase and Chloroplast NAD(P):Glyceraldehyde-3-Phosphate Dehydrogenase : Characterization of the Clones and Analysis of the Expression of the Genes in Leaves as Influenced by Nitrate in the Light and Dark

cDNA clones were selected from a corn (Zea mays L.) leaf lambda gt11 expression library using polyclonal antibodies for corn leaf NADH:nitrate reductase. One clone, Zmnrl, had a 2.1 kilobase insert, which hybridized to a 3.2 kilobase mRNA. The deduced amino acid sequence of Zmnrl was nearly identical to peptide sequences of corn leaf NADH:nitrate reductase. Another clone, Zm6, had an insert of 1.4 kilobase, which hybridized to a 1.4 kilobase mRNA, and its sequence coded for chloroplastic NAD(P)⁺:glyceraldehyde-3-phosphate dehydrogenase based on comparisons to sequences of this enzyme from tobacco and corn. When nitrate was supplied to N-starved, etiolated corn plants, nitrate reductase, and glyceraldehyde-3-phosphate dehydrogenase mRNA levels in leaves increased in parallel. When green leaves were treated with nitrate, only nitrate reductase mRNA levels were increased. Nitrate is a specific inducer of nitrate reductase in green leaves, but appears to have a more general effect in etiolated leaves. In the dark, nitrate induced nitrate reductase expression in both etiolated and green leaves, indicating light and functional chloroplast were not required for enzyme expression.     

Fluorometric analysis of an attempt to reclaim ischemic flaps in rats with Fluosol

An experiment was designed to answer two questions as they apply to random skin-flap survival: Is there a therapy that can improve random skin-flap survival when given postoperatively? And if so, when does one start such a therapy? Fluosol-DA 20% (Fluosol) has increased random skin-flap survival when given preoperatively in our laboratory. An experiment was devised to see if it could rescue failing flaps. One-hundred Sprague-Dawley rats were divided into a control (N = 25) and five experimental groups (N = 15). All had 10 X 13 cm reverse McFarlane random flaps raised and reinset. The experimental groups underwent hemodilution with either Ringer's lactate or Fluosol at 4, 8, and 12 hours after flap elevation. All were kept in 50% oxygen for 72 hours postoperatively. The flaps and their corresponding necrotic areas were measured on day 7. As to when to institute a therapy, we simultaneously evaluated the use of a microfluorometer as a monitor of flap survival. Analysis of flap survival showed little difference between control and experimental Ringer's lactate or Fluosol groups. Analysis of the microfluorometric data led to the following points. First, as a monitor of flap viability, it is limited by a lack of specificity and sensitivity. Second, comparison of the data from portions of the flap destined to live with those destined to die suggests that it may not be failure of circulatory inflow that leads to flap death.