The role of arachidonic acid in vasogenic brain edema

Arachidonic acid is released rapidly from cellular membrane phospholipids after pathological insults associated with the delayed development of brain edema. Intracerebral injection of arachidonic acid caused significant increases in brain water and sodium content with decreases in potassium content and Na+,K+-ATPase activity. The 125I-labeled bovine serum albumin spaces in brain (a measure of blood-brain barrier permeability) rose threefold 24 h after arachidonic acid injection. There was gross and microscopic evidence of edema. Saturated fatty acids and monounsaturated fatty acids were not effective. These data indicate that the endothelial cells of the blood-brain barrier are target sites for the action of arachidonic acid. It is hypothesized that the increased permeability of endothelial cells to macromolecules and water results from alterations of membrane phospholipids and increased vesicular transport, changes that are responsible for the delayed development of vasogenic edema.     

Clinical implications of developments in in vitro fertilisation.

During February 1979 to December 1983, 831 infertile couples were treated by in vitro fertilisation and embryo transfer. The problems they faced included deciding on the number of oocytes to be collected at laparoscopy, the numbers to be donated or fertilised, the numbers of embryos to be transferred and frozen, and whether abnormal embryos should be used for research or discarded. The 831 patients received a total of 1530 treatment cycles. Of the 763 patients for whom complete data were available, 136 (17.8%) became pregnant. The rate of pregnancy, however, increased dramatically from 7.4% when only one embryo was transferred to 21.1% and 28.1% when two and three embryos were transferred, respectively. The chance of multiple pregnancy also increased with the number of embryos transferred, but the risk (2% for twins) was far outweighed by the relatively poor result after transferring a single embryo. Out of 40 embryos freeze-thawed, 23 survived thawing and were transferred; of these, 4 (17%) resulted in pregnancy. Thirty four transfers of donor oocyte embryos also resulted in four pregnancies (12%), but two of these ended in abortion. Neither microscopy nor any other available test can determine the potential of an oocyte to result in pregnancy, so that discarding oocytes that may look abnormal simply reduces the chances of conception--both for the patient and for any prospective recipient of donor oocyte embryos. In any case, abnormal embryos tend to die when growth is allowed to continue in vitro. Probably all oocytes harvested from a patient should be inseminated and the utilisation of the embryos decided once the number developed is known.     

Inhibition of nucleotidyl transferase enzymes by metal ions in combination with 5-amino-1-formylisoquinoline thiosemicarbazone.

Inhibition of urchin polymerases by the metal ions Fe⁺² and Cu⁺² is modulated by exogenous ligands and the resultant inhibition is further a function of the polymerase class. The DNA polymerase β is singularly resistant to Fe⁺² and Cu⁺² metal ions alone and in combination with the title ligand. DNA polymerase α and the RNA polymerases II and III show varying degrees of sensitivity to the title inhibitor.     

A simple and sensitive colorimetric method for the determination of long-chain free fatty acids in subcellular organelles

A colorimetric assay for the determination of long-chain free fatty acids (FFA) is described. The FFA were extracted from subcellular organelles with chloroform:heptane:methanol. The copper soaps of FFA were determined colorimetrically with diphenylcarbazide. There are three advantages to employing the present modified procedure. (a) The sensitivity has been increased approximately twofold over that of the previous procedure of K. Falholt, B. Lund, and W. Falholt (1973, Clin. Chim. Acta46, 105–111); (b) it takes less time to complete the assay compared to the tedious procedures currently available; and (c) the presence of bovine serum albumin, a known FAA-binding protein, does not interfere with the assay procedure. The assay shows a linear response over the range of 10 to 130 nmol of FFA. The recovery of free fatty acids from mitochondria is 99%.     

Polyglutamylfolate synthesis in Neurospora crassa: changes in pool size following growth in glycine- and methionine-supplemented media

The effect of media supplements on total and polyglutamylfolate concentrations has been examined in Neurospora crassa wild type (FGSC 853), an ethionine-resistant mutant (FGSC 1212), and a methionine auxotroph (FGSC 1330) which lacks folylpolyglutamate synthetase. When the culture medium contained 1 mm glycine, folate concentrations in the wild type were increased by over 90% and more p-[³H]aminobenzoate was incorporated into folates. Growth in l-methionine-supplemented media (1–5 mm) decreased folate levels and labeling in all three strains. In the wild type, this effect of l-methionine was reversed on transfer to unsupplemented media but p-[³H]aminobenzoate pulse-chase experiments suggested that exogenous methionine did not increase the turnover of labeled folates. At 1 mm, d-methionine did not affect polyglutamylfolate labeling but l-methionine reduced ³H incorporation by 65% in the wild type. Ion-exchange chromatography showed that p-[³H]aminobenzoate was incorporated in formyl- and methyltetrahydrofolates which in the wild type, were principally hexaglutamyl derivatives. Glycine-supplemented growth yielded labeled folates that were 24% heptaglutamates but these and pentaglutamates were lacking when l-methionine was supplied. The specific activity of GTP cyclohydrolase was not significantly affected by culture in l-methionine-containing media. Dialysis and gel filtration both lowered enzyme activities and product formation was not changed when up to 10 μmol of l-methionine was added to the reaction system. The data suggest that methionine or its metabolic products exerts some control over folate production which is distinct from the established inhibition of methylenetetrahydrofolate reductase by AdoMet.     

Proximity of lectin receptors on the cell surface measured by fluorescence energy transfer in a flow system.

Molecules of the lectin concanavalin A have been labeled separately with the fluorescein and rhodamine chromophores and jointly bound to the surface of transformed Friend erythroleukemia cells. The two dyes constitute an ideal donor-acceptor pair for fluorescence resonance energy transfer thereby permitting the determination of the proximity relationships between bound ligand molecules and the corresponding surface receptors. The transfer efficiency at saturation (about 57%) was measured in a multiparameter flow system using laser excitation at 488 nm and detection of fluorescein and rhodamine emission intensities as well as the emission anisotropy of the rhodamine fluorescence for each cell. The degree of energy transfer was estimated from the quenching of donor emission, the sensitization of acceptor emission, and the depolarization of acceptor fluorescence. The system has been modeled according to a formalism developed by Gennis and Cantor (Biochemistry 11: 2509, 1972). We estimate the separation between the surfaces of bound lectin molecules at saturation to be 0-40 A, a range possibly characteristic for micropatches induced by ligand binding.     

Attachment of tail fibers in bacteriophage T4 assembly: role of the phage whiskers.

The collar and whiskers of bacteriophage T4 extend outward from the top of the tail and play a role in regulating retraction of the tail fibers (Conley &; Wood, 1975). The collar and whiskers also are required for efficient tail fiber attachment during phage assembly. The structural gene for the collar/whisker protein is called wac. In vitro, infected-cell extracts that contain tail fibers activate whiskerless (wac) tail fiberless particles and ordinary (wac⁺) tail fiberless particles at equal rates if the extracts contain the wac⁺ gene product. However, extracts that contain tail fibers but no wac⁺ gene product activate wac particles about ten times more slowly. In vivo, whiskers are not essential for plaque formation, but a wac mutation causes a delay in the appearance of intracellular phage and a fivefold decrease in the burst size of infectious particles.The effect of the whiskers on tail fiber attachment is due to an interaction between the whisker and the distal half of the tail fiber, similar if not identical to the interaction that controls tail fiber retraction in complete phage. The following observations support this view: a slow rate of in vitro tail fiber attachment similar to that described above is seen with wac⁺ particles when they are pretreated with anti-whisker serum, or when the tail fibers carry a mutational alteration in gp36, a structural protein in the distal half fiber near the central kink. Lack of whiskers does not affect the slow rate of attachment of proximal half fibers to the baseplate of fiberless particles, but lack of whiskers greatly decreases the rate at which particles with attached proximal half fibers are activated by addition of distal half fibers. Since whiskers normally are attached to the phage only after head—tail union (Coombs &; Eiserling, 1977; Terzaghi et al., 1978), these findings explain why tail fibers do not attach efficiently to the baseplates of free tails.     

The chemistry of human transcortin. The effects of pH, urea, salt, and temperature on the binding of cortisol and progesterone.

The interaction of cortisol and progesterone with pure transcortin was investigated. The temperature dependence of cortisol and progesterone binding is a result of the predominantly negative enthalpy of binding which suggests a very good fit between ligand and protein such that the bonds formed are of the van der Waals type. The optimal pH of cortisol (8.0) and progesterone (8.5) binding suggests involvement of cysteine, histidine, and/or tyrosine residues in the binding process. Transcortin is irreversibly denatured at pH 4.0. The effect of sodium chloride on the binding of both steroids is small. At lower sodium chloride concentrations (less than 0.15 m), binding decreases somewhat with decreasing salt concentration. Urea produces a progressive decrease in the association constants of both steroids which is completely reversible up to 2.0 m and 30% reversible at 3.0 m. Scatchard analysis of cortisol binding in the presence of a constant amount of progesterone and vice versa confirms earlier data obtained on plasma that cortisol and progesterone do not bind at two independent sites. It is not possible, however, to decide whether they bind at the same site or at two interdependent (interacting) sites.     

Hyperparathyroidism in pregnancy: case report and review of the literature.

The apparent incidence of hyperparathyroidism (HPT) is low in pregnancy but will likely increase now that more asymptomatic HPT is being diagnosed. However, since the serum calcium levels are decreased in pregnant women, mild primary HPT may go unrecognized. In untreated cases of HPT, complications during pregnancy or during the neonatal period have included spontaneous abortion, stillbirth, neonatal death, neonatal tetany and hypercalcemia. A review of the literature indicates a substantial improvement in fetal outcome when parathyroidectomy is done during pregnancy, as in the case reported here. Therefore, parathyroidectomy is the treatment of choice when the diagnosis is made during pregnancy, although oral phosphate therapy may be an alternative if surgery is contraindicated.