Purified viral neuraminidase vaccine to control influenza.

The control of influenza by immunoprophylaxis is difficult because of the antigenic mutability of the influenza virus and the unpredictability of its epidemiologic behaviour. The inactivated whole-virus vaccine currently used is not ideal. Vaccination with pure neuraminidase is suggested. The induced antineuraminidase antibody will restrict viral invasion. Mild illness may or may not occur. On subsequent exposure to influenza virus the individual will produce antihemagglutinin and antineuraminidase antibodies and will be resistant to both infection and illness. Since antigenic changes are less frequent in the viral neuraminidase than in the viral hemagglutinin, the vaccine would be usable for longer periods than the presently used inactivated whole-virus vaccine.     

A photoaffinity label for the thromboxane A2/prostaglandin H2 receptor in human blood platelets

A photoactive iodoarylazide derivative (I-APA-PhN3) of the competitive thromboxane A2/prostaglandin H2 (TXA2/PGH2) antagonist 13-azaprostanoic acid is evaluated. Upon photoactivation, the compound was found to inhibit specifically and irreversibly human platelet aggregation induced by the TXA2/PGH2 mimetic U46619. In receptor-binding studies using [3H]U46619, I-APA-PhN3 exhibited an IC50 of 300 nM for inhibition of U46619 binding. Photoactivation of I-APA-PhN3 resulted in an irreversible 58% reduction in specific binding of U46619. This compound and its corresponding ratio-iodinated form will prove to be useful tools for the isolation and purification of the TXA2/PGH2-binding protein in human platelets.     

Direct Evidence for Changes in the Resistance of Legume Root Nodules to O2 Diffusion

Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O₂ diffusion. Here we describeexperiments using O₂ specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O₂ concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m^–3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O₂ concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O₂ concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O₂ concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O₂ fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O₂ concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N₂or air. Key words: Oxygen, root nodules, air spaces     

Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications

Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of individuals representing 54 species of frogs, two species of salamanders, a caecilian, and a lungfish. Eight of these sites were present in all species examined, and two were found in all but one species. Alignment of these conserved restriction sites revealed, among anuran 28S rRNA genes, five regions of major length variation that correspond to four of 12 previously identified divergent domains of this gene. One of the divergent domains (DD8) consists of two regions of length variation separated by a short segment that is conserved at least throughout tetrapods. Most of the insertions, deletions, and restriction-site variations identified in the 28S gene will require sequence-level analysis for a detailed reconstruction of their history. However, an insertion in DD9 that is coextensive with frogs in the suborder Neobatrachia, a BstEII site that is limited to representatives of two leptodactylid subfamilies, and a deletion in DD10 that is found only in three ranoid genera are probably synapomorphies.      

"Pyruvate recycling" and its influence on the estimation of the pentose pathway in intact liver and Morris hepatoma 5123TC cells

The phenomenon of "pyruvate recycling" is demonstrated in perfused rat liver, rabbit liver in situ and in Morris Hepatoma 5123TC cells and quantitatively measured using [2-14C]pyruvate and the method of Friedmann et al. (1971). Various metabolites, viz. lactate, DHAP, glucose, glucose 6-P and fructose 6-P were isolated and degraded following the metabolism of [2-14C]pyruvate and [2-14C]glycerol in order to assess the 14C-distributions imparted by "pyruvate recycling" reactions. The labelling of DHAP, lactate, glucose and glucose 6-P showed 14C randomizations consistent with the operation and the quantitative extent of "pyruvate recycling". These findings support the proposal that the actions of "pyruvate recycling" may account for the failure to find significant levels of 14C isotope at C-1 of glucose 6-P following the metabolism of [4,5,6-14C]- or [6-14C]glucose by L-type pentose pathway metabolism in aerobic intact tissues. "Pyruvate recycling" diminishes the measured value of the L-type pentose cycle in intact tissues and qualifies one of the mechanistic predictions of the L-type pentose pathway which was unravelled by tracing its reactions with labelled ribose 5-P and liver enzymes (Horecker et al., 1954; Williams et al., 1978a,b) in vitro. The demonstration of an association of L-type pentose pathway reactions with "pyruvate recycling" by way of the common reactions of their triose-P intermediates qualifies the superficial acceptance of the predictions of the L-type pathway in vitro for the distribution of isotopic labels by aerobic tissues in vivo.     

Mechanism and quantitative contribution of the pentose pathway to the glucose metabolism of Morris hepatoma 5123C

An investigation of the mechanism and quantitative contribution of the pentose phosphate pathway in the glucose metabolism of Morris Hepatoma 5123C is reported. Morris Hepatoma 5123C has an active non-oxidative segment of pentose pathway as judged by its ability to convert ribose 5-P to hexose 6-P in a standard assay. Based on compliance with qualitative and quantitative criteria, the cells exhibit the L-type pentose pathway reaction sequence rather than the F-type pathway. This compliance included the formation of intermediates characteristic of the L-type pathway, namely arabinose 5-P, octulose mono- and bisphosphates and sedoheptulose 1,7-bisphosphate, during the dissimilation of ribose 5-P to hexose 6-P. The intermediary role of arabinose 5-P was suggested by the incorporation of its carbon into various intermediates and products of the pentose pathway. Intermediary roles for ido octulose mono- and bisphosphates were supported by their participation in the reaction catalyzed by the phosphotransferase enzyme of the L-type pentose pathway. Presence of L-type PP reactions was further affirmed by 14C-prediction labelling experiments using [5-14C]- and [2-14C]glucose as specifically labelled substrates. Using two methods of measurement, the F-type pentose cycle made a negligibly small contribution to glucose metabolism, while the measured value of the L-type pentose pathway accounted for 30% (approx.) of the total glucose metabolism of these cells, a value consistent with the high activity of the enzymes of the L-type pentose pathway in Morris Hepatoma 5123C cells and the very high activity of the non-oxidative segment of the pathway in vitro. The findings validate the proposal that the L-type pentose pathway reactions constitute the non-oxidative segment of the pathway in Morris Hepatoma 5123C cells. Reasons involving pyruvate recycling reactions show why there is low incorporation of 14C-isotope in C-1 of glucose 6-P, when [4,5,6-14C]glucose and [6-14C]glucose are L-type PP test substrates in intact cells.     

Relative sensitivity of photosynthesis and respiration to freeze-thaw stress in herbaceous species : importance of realistic freeze-thaw protocols

The relative effect of a freeze-thaw cycle on photosynthesis, respiration, and ion leakage of potato leaf tissue was examined in two potato species, Solanum acaule Bitt. and Solanum commersonii Dun. Photosynthesis was found to be much more sensitive to freezing stress than was respiration, and demonstrated more than a 60% inhibition before any impairment of respiratory function was observed. Photosynthesis showed a slight to moderate inhibition when only 5 to 10% of the total electrolytes had leaked from the tissue (reversible injury). This was in contrast to respiration which showed no impairment until temperatures at which about 50% ion leakage (irreversible injury) had occurred. The influence of freeze-thaw protocol was further examined in S. acaule and S. commersonii, in order to explore discrepancies in the literature as to the relative sensitivities of photosynthesis and respiration. As bath cooling rates increased from 1°C/hour to about 3 or 6°C/hour, there was a dramatic increase in the level of damage to all measured cellular functions. The initiation of ice formation in deeply supercooled tissue caused even greater damage. As the cooling rates used in stress treatments increased, the differential sensitivity between photosynthesis and respiration nearly disappeared. Examination of agriculturally relevant, climatological data from an 11 year period confirmed that air cooling rates in the freezing range do not exceed 2°C/hour. It was demonstrated, in the studies presented here, that simply increasing the actual cooling rate from 1.0 to 2.9°C/hour, in frozen tissue from paired leaflet halves, meant the difference between cell survival and cell death.