Purification and characterization of a lysophospholipase from human amnionic membranes

We have identified the presence of a lysophospholipase in human placental tissues and have purified this enzyme from the amnion. The specific activity was highest in the amnion and decreased across adjacent tissues. The purification involved the use of DEAE-Sephadex, phenyl-Sepharose, hydroxylapatite, and sulfylpropyl Sephadex chromatography. The activity of the purified enzyme toward palmitoyl lysophosphatidylcholine is 2.5 mumol min-1 mg-1 and the pH optimum is 7.0. The enzyme is not inhibited by EDTA and does not appear to have a metal ion requirement. The enzyme may be of membrane origin; the purified enzyme requires the presence of detergent during storage. The effects of substrate composition and physical state on enzymatic activity were explored. The enzyme was not active toward mono-, di-, or triglycerides, nor toward diacyl phospholipid. The enzyme was active toward myristoyl and palmitoyl lysophosphatidylcholine at concentrations where these substrates spontaneously form micelles or where Triton X-100 was used to induce co-micellization of the substrate at low concentrations with detergent. A role for this enzyme in processing the lysophospholipid product of phospholipase A action must be considered in evaluating arachidonic acid production in human fetal membranes and placental tissue, particularly during the initiation of labor.     

CONDITIONS OF ILLUMINATION AND ZOOSPOROGENESIS IN KLEBSORMIDIUM FLACCIDUM1

The filamentous green alga Klebsormidium flaccidum will produce zoospores when cultured on a diurnal regime of 8-hr light and 16-hr dark. Zoosporogenesis is inhibited by interruption of the dark period with light of sufficient intensity and duration. The relationship between intensity and maximum time of interruption before total inhibition of zoosporogenesis is nonlinear.     

Understanding of elderly patients' resuscitation preferences by physicians and nurses.

We compared the understanding by family physicians and nurses of their elderly outpatients'' preferences for cardiopulmonary resuscitation and mechanical ventilation under 3 scenarios reflecting varying qualities of life. Physicians and nurses correctly predicted patients'' treatment preferences in from 59% to 84% and 53% to 78% of cases, respectively, for the various decisions. For most decisions, neither physicians nor nurses were significantly more accurate in their predictions than expected by chance alone. Moreover, nurses and physicians did not significantly agree with one another in their predictions of patients'' preferences for any of these decisions. These results suggest that while nurses'' and physicians'' perceptions of patients'' preferences for life-sustaining treatment are not necessarily similar, neither nurses nor physicians systematically understand their elderly patients'' resuscitation preferences.     

Mutagen-induced fetal anomalies and death following treatment of females within hours after mating

In an earlier study (Generoso et al., 1987), it was observed that the mutagen, ethylene oxide (EtO), produced remarkable increases in the incidence of developmental abnormalities and death of fetuses when early zygotic stages were exposed. This is a major finding in experimental induction of embryopathy, implicating genetic damage to the zygotes as the likely cause. In the subsequent study reported here, 3 other mutagens--ethyl methanesulfonate (EMS), ethyl nitrosourea (ENU), and triethylene melamine (TEM), were studied for embryopathic effects following exposure of dictyate oocytes, prefertilization oviducal eggs and sperm, early pronuclear zygotes, zygotes undergoing pronuclear DNA synthesis, and two-cell embryos. All 4 mutagens produced developmental abnormalities among living fetuses following exposure of early pronuclear zygotes (the only stage studied for this endpoint in this report). With respect to stage specificity and gestational timing of death of conceptuses, EMS and EtO on one hand and ENU and TEM on the other, are very similar to one another. EMS, like EtO, produced a high incidence of midgestation and late fetal deaths only in prefertilization oviducal eggs and sperm and in early pronuclear eggs. In contrast, ENU and TEM produced high losses of conceptuses in all postmating stages studied but death occurred primarily prior to or around the time of implantation. Thus, the frequency of induction and the expression of embryopathy, which ranged from early embryonic preimplantation and late fetal deaths to subtle fetal anomalies, are dependent upon the stage exposed and the mutagen used.     

Olfactory adaptation as an aspect of odor similarity

Two experiments examined self-adaptation within and cross-adaptationbetween two structurally different substances with almost identicalbitter chocolate odors, trimethyl pyrazine (TMP) and 2-propionyl-3-methylfuran (PMF). The first experiment charted psychophysical functionsfor odor intensity under steady-state self- and cross-adaptationwith adapting concentrations matched in perceived intensityat two different levels. Participants breathed an adapting concentrationcontinuously for 2 min and then rated test concentrations everyminute during momentary respites from the adapting stimulus.Both self-adaptation and cross-adaptation weakened the intensityof low test concentrations proportionally more than higher onesand thereby steepened the psychophysical functions. Adaptingstimuli at matched levels caused equivalent self-adaptation(i.e. altered the functions equivalently) and equivalent, thoughweaker, cross-adaptation (i.e. exhibited symmetry of cross-adaptation).The second experiment examined whether cross-adaptation to TMPand PMF would prove relatively specific. At a matched perceivedintensity of adapting stimulus, adaptation to TPM and PMF againproduced equal amounts of self-adaptation and of cross-adaptationto each other, though not on three other test stimuli: anethole,ethyl butyrate and 2,3 pentanedione. Both TMP and PMF showedsome generality as cross-adapting stimuli, with PMF showinga bit more than TMP. The present protocols and others discussedherein offer opportunities to consider functional criteria forthe relatedness of similar-smelling substances.     

Stochastic simulation of clonal growth in the tall goldenrod,Solidago altissima

Summary As clonal plants grow they move through space. The movement patterns that result can be complex and difficult to interpret without the aid of models. We developed a stochastic simulation model of clonal growth in the tall goldenrod, Solidago altissima. Our model was calibrated with field data on the clonal expansion of both seedlings and established clones, and model assumptions were verified by statistical analyses.When simulations were based on empirical distributions with long rhizome lengths, there was greater dispersal, less leaf overlap, and less spatial aggregation than when simulations were based on distributions with comparatively short rhizome lengths. For the field data that we utilized, variation in rhizome lengths had a greater effect than variation for either branching angles or rhizome initiation points (see text). We also found that observed patterns of clonal growth in S. altissima did not cause the formation of fairy rings. However, simulations with an artificial distribution of branching angles demonstrate that fairy rings can result solely from a plant's clonal morphology.Stochastic simulation models that incorporated variation in rhizome lengths, branching angles, and rhizome initiation points produced greater dispersal and less leaf overlap than deterministic models. Thus, variation for clonal growth parameters may increase the efficiency of substrate exploration by increasing the area covered and by decreasing the potential for intraclonal competition. We also demonstrated that ramet displacements were slightly, but consistently lower in stochastic simulation models than in random-walk models. This difference was due to the incorporation of details on rhizome bud initiation into stochastic simulation models, but not random-walk models. We discuss the advantages and disadvantages of deterministic, stochastic simulation, and random-walk models of clonal growth.     

Functional regulation of brain pyruvate dehydrogenase: Postnatal development, anesthesia and food-deprivation

The activity of brain pyruvate dehydrogenase complex (PDHC), is regulated by reversible phosphorylation of the alpha subunit of the E1 component (pyruvate dehydrogenase, EC 1.2.4.1) of PDHC. Using an in vitro back-titration assay, we have evaluated the postnatal development of E1 phosphorylation, as well as the effects of acute pentobarbital administration and food-deprivation on cerebral cortical E1 phosphorylation in synaptosomal and free mitochondrial compartments of the albino rat. Between birth and postnatal day 25, the back-titration phosphorylation increased ca 4-fold, with the largest increase occurring between days 15 and 20. The phosphorylation of E1 in the synaptosomal, but not free mitochondrial fraction, was decreased during pentobarbital anesthesia. Following 72 h of food-deprivation, E1 phosphorylation was decreased in both subcellular fractions.

The postnatal increase in E1 back-titration phosphorylation is consistent with and similar in magnitude to previously reported increases in the specific enzymatic activity of PDHC. These results also highlight the potential importance of localized subcellular alterations in mitochondrial metabolism and further validate the back-titration phosphorylation of E1 as a valuable tool for the study of central nervous system PDHC metabolism.     

Failure to kindle seizures after repeated intracerebral administration of arginine vasopressin

In an attempt to kindle seizures with arginine-vasopressin (AVP), we injected AVP into the amygdala or hippocampus of rats. Although behavioral and electrographic alterations were sometimes observed, seizures failed to develop, even in rats that had previously been kindled with electrical stimulation. This and previous failures to kindle seizures by intraventricular injections of AVP call into question the possibility of AVP kindling.     

Growth inhibition of 3T3 fibroblasts by lysosomotropic amines: correlation with effects on intravesicular pH but not vacuolation

The effects of five lysosomotropic amines on the growth of Swiss 3T3 fibroblasts were measured and compared with effects on intravesicular pH. Tributylamine and benzylamine, amines that affect intravesicular pH without causing vacuolation, were found to inhibit cell growth to a similar extent as vacuologenic amines previously tested. Excellent correlation between the half-maximal concentrations for the growth and pH effects were found for tributylamine, benzylamine, chloroquine, and ammonium chloride. The results suggest that growth inhibition by these amines is a direct result of their effects on pH and not due to other effects (such as vacuolation). In contrast, a 100-fold difference in the half-maximal concentrations was found for methylamine, suggesting that methylamine inhibits growth by a mechanism unrelated to pH.     

Adrenergic and local control of O2 uptake during and after severe hypoxia

The distribution of whole-body O2 supply during severe hypoxia and recovery and its relation to the regional distribution of O2 deficit and repayment was studied. Mongrel dogs were anesthetized, paralyzed, and ventilated to maintain an end-tidal PCO2 between 35 and 40 Torr. In one group, the alpha- and beta-adrenergic receptors were blocked to eliminate neural and humoral adrenergic influences. In a second group, alpha-adrenergic receptors were stimulated to decrease O2 delivery by excessive vasoconstriction. In a third group, beta-adrenergic receptors were stimulated to increase O2 delivery. Whole-body and hindlimb muscle O2 uptake and vascular responses were measured during normoxic control, 15 or 30 min of severe hypoxia (9% O2 in N2), and 20 or 30 min of normoxic recovery, respectively. The whole-body O2 deficit and excess O2 uptake in recovery were partitioned into muscle and nonmuscle areas. The data showed that neural or humoral influences had little effect on the regional distribution of the total O2 deficit and O2 excess in recovery. The O2 deficit could be decreased somewhat by increasing delivery, but the amount of excess O2 used in recovery was unaffected. This suggested that the excess O2 use in recovery was more a function of an energy deficit during hypoxia and not an O2 deficit.