Effects of vasomotor- and mediator-induced hypotension on bronchomotor tone in swine

We studied the sympathetic neural response on airways to hypotensive stimuli in 19 swine in vivo. The effects of pharmacologically induced hypotension with nitroprusside (NTP) and hypotension elicited by intravenous compound 48/80 (48/80), a mast cell degranulating agent, were compared after equivalent reductions in mean arterial blood pressure (MAP). Reduction of the MAP to 60% of base line with NTP in six swine caused an increase in plasma epinephrine (E) from 60 +/- 28 to 705 +/- 276 pg/ml (P = 0.032) and plasma norepinephrine (NE) from 270 +/- 46 to 796 +/- 131 pg/ml (P = 0.032). Comparable reduction in MAP elicited with 48/80 in six other swine caused a substantially greater increase in both plasma E (9,581 +/- 4,147 pg/ml; P = 0.012 vs. NTP group) and plasma NE (2,239 +/- 637 pg/ml; P = 0.041 vs. NTP group). Catecholamine secretion attenuated mediator-induced changes in lung resistance (RL). In animals receiving 48/80, RL increased from 2.97 +/- 0.31 to 7.44 +/- 0.56 cmH2O.l-1.s. In animals having ganglionic blockade with 7.5 mg/kg iv hexamethonium and beta-adrenergic blockade with propranolol (4.0 mg/kg iv followed by 40 micrograms/kg-1.min-1), comparable doses of 48/80 caused an increase in RL to 18.6 +/- 4.55 cmH2O.l-1.s (P less than 0.04 vs. swine receiving neither hexamethonium nor propranolol).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of weather and feeding on body temperature and activity in the snake Masticophis flagellum

1. 1.|Body temperature (T_b) and activity of the snake Masticophis flagellum were studied by radiotelemetry in an outdoor enclosure.

2. 2.|Mean diurnal T_b varied little over a wide range of weather conditions, but weather variation was accompanied by major changes in sun exposure and in the timing and duration of activity.

3. 3.|Recently fed snakes reduced activity and exhibited neither a thermophilic response nor increased precision of thermoregulation compared to fasting snakes.

Experimental investigations of benthic reentry by migrating meiobenthic copepods

The resettlement behavior of meiobenthic copepods, which actively migrated from sediments in a seagrass bed, was investigated in a shallow subtidal area in Tampa Bay, Florida, U.S.A. Experimental studies were conducted to determine whether meiobenthic copepods after emerging from sediments at sunset reenter the sedimentary substratum or select other subhabitats, water and seagrass blades. Migrating copepods were collected with emergence traps and transferred to experimental aquaria in the field which contained sediment, seagrass-blade and water treatments. Settlement into each type of treatment was measured in separate 2-h and 9-h experiments. Differences in densities of copepod taxa retrieved from emergence traps and introduced into experimental aquaria were recorded as were differing relative proportions of each copepod species returning to the substratum treatments. Settlement patterns of total copepods and three dominant copepod species, Zausodes arenicolus, Halicyclops sp. and Robertsonia hamata, departed from those expected by chance. The populations of R. hamata and Halicyclops sp. which settled were generally skewed towards males and a close matching of males and copepodites within treatment dishes was evident. Similar to nighttime-emergence patterns, timing and magnitude of postmigration reentry differs among copepod taxa and such reentry may be linked to reproductive events. Complex behavioral processes previously noted for fish and macrofaunal organisms in seagrass beds may also be important in recruitment and reassortment of meiobenthic copepods.     

Subculturing of a polychlorinated biphenyl-dechlorinating anaerobic enrichment on solid media.

An anaerobic culture capable of dechlorinating polychlorinated biphenyls was subcultured under strict anaerobic conditions on solid media containing sterilized river sediment. The dechlorination activity was transferred as a bacterial colony on a solid medium three times. After two transfers on solid medium, the culture was no longer methanogenic but still dechlorinated a mixture of tri- and tetrachlorobiphenyls. This demonstrates that anaerobic bacteria are responsible for the polychlorinated biphenyl dechlorination and can be grown without polychlorinated biphenyl on solid media.     

Effects of epidermal growth factor on apo B mRNA levels and apo B accumulation in the media of primate hepatocytes in culture.

EGF has been shown to augment albumin and apolipoprotein A-I secretion by cynomolgus monkey hepatocytes in primary culture without stimulating cell division. This study was undertaken to determine what effect EGF had on apo B secretion by those hepatocytes. The results indicate that EGF (3 nM final concentration) severely inhibits the rate at which apo B accumulates in the culture medium of primate hepatocytes. That effect was evident within 48 hours of treatment, and by 72 hours the rate that apo B accumulated was less than half that of cells treated with a hormone-free medium. However, the apo B mRNA levels in the EGF-treated cells were more than double those of hepatocytes given the hormone-free medium. These data indicate that EGF has a potent effect on the rate at which apo B accumulates in the culture medium of primate hepatocytes and that the effect is independent of apo B gene expression.     

The compact domain conformation of human Glu-plasminogen in solution.

A complete understanding of the accelerating mechanisms of plasminogen activation and fibrinolysis necessarily requires structural information on the conformational forms of plasminogen. Given the absence of high-resolution structural data on plasminogen the use of lower resolution approaches has been adopted. Two such approaches have previously indicated a compact conformation of Glu-plasminogen (Tranqui, L., Prandini, M., and Chapel, A. (1979) Biol. Cellulaire, 34, 39-42; Bányai, L. and Patthy, L. (1985) Biochim. Biophys. Acta, 832, 224-227) whereas a third has suggested a fairly extended conformation (Mangel, W., Lin, B. and Ramakrishnan, V. (1990) Science, 248, 69-73). Native Glu-plasminogen has been investigated using small-angle X-ray scattering (SAXS) experiments. It is concluded that this molecule in solution is compact (radius of gyration, RG 3.05 +/- 0.02 nm and maximum intramolecular distance, Im 9.1 +/- 0.3 nm) and that the data are consistent with the right-handed spiral structure observed using electron microscopy by Tranqui et al. (1979). A spiral structure of native plasminogen would have important implications for the conformational response of plasminogen to fibrin and concomitant stimulation of plasminogen activation.     

A recombinant adenovirus expressing an Epstein-Barr virus (EBV) target antigen can selectively reactivate rare components of EBV cytotoxic T-lymphocyte memory in vitro.

While the bulk of a virus-induced cytotoxic T-lymphocyte (CTL) response may focus on a few immunodominant viral antigens, in certain tumor virus systems the detectability of clones recognizing other, subdominant antigens can assume particular importance. By using the human CTL response to Epstein-Barr virus (EBV) as a model system, here we show that even rare components of virus-specific memory can be selectively reactivated in vitro when the relevant target antigen is expressed in autologous stimulator cells from a recombinant adenovirus (RAd) vector. We generated a replication-deficient adenovirus, RAd-E3C, which in skin fibroblast cultures expressed the EBV nuclear antigen EBNA3C at a 10- to 100-fold-higher level than that naturally present in EBV-transformed lymphoblastoid cell lines (LCLs). Initial experiments with a donor whose polyclonal CTL response to LCL stimulation contained a strong EBNA3C-specific component showed that these CTLs could be efficiently reactivated by in vitro stimulation either with RAd-E3C-infected fibroblasts or with RAd-E3C-infected peripheral blood mononuclear cells. Then we studied donors whose responses to LCL stimulation contained little if any detectable EBNA3C reactivity but were dominated by clones recognizing other EBV target antigens; in vitro stimulation with RAd-E3C-infected peripheral blood mononuclear cells selectively reactivated EBNA3C-specific CTL clones from these individuals, with the epitope specificities of responses subsequently identified at the peptide level. This RAd-based approach could be applied more generally to screen for human CTL responses against any candidate target antigen expressed by tumor cells.     

Determination of half-reaction equilibrium in a ping-pong enzyme mechanism

Substituted enzyme (or ping-pong) mechanisms usually involve enzymes that exist in two forms that alternate during the catalytic reaction. A method is described here for determining the position of the equilibrium of a half reaction in a ping-pong enzyme mechanism that is based on the kinetics of the burst reaction which occurs upon addition of reactants that recycle the enzyme from one form to another. The theoretical basis for the analysis is developed, and the method is applied to the half reaction of the aldimine form of aspartate transaminase with difluoro-oxaloacetate. Special issue dedicated to Herman Bachelard     

Photoaffinity labelling of a cytokinin-binding integral membrane protein in plant mitochondria

Two target polypeptides were detected by photoaffinity labelling of purified mung bean mitochondria using tritiated 2-azido-N⁶-benzylaminopurine. SDS-PAGE and fluorography of total mitochondrial proteins after the photoaffinity reaction showed a labelled 32 kDa polypeptide (intensely labelled) and a 57 kDa polypeptide (less intensely labelled). The latter was assumed to be the and/or subunit of F₁ATPase since it was the most abundant polpeptide in gels stained with Coomassie Blue. Partial purification of F₁ATPase demonstrated that the 32 kDa polypeptide was not a component of the ATPase complex. Fractionation experiments showed that the 32 kDa protein was integrally associated with mitochondrial membranes and could be enriched by simple washing and detergent extraction procedures.