Effect of long-term Intralipid administration in mice

Intralipid was administered intravenously to mice at a level of 2 g kg-1 day-1 for 23 days. No alterations in phagocytic index, liver or spleen size were observed in the chronically injected mice as compared with control mice that received saline injections. Tissue distribution of 0.45 micron multilamellar liposomes of egg phosphatidylcholine:cholesterol (2:1) was similar in mice that had been chronically injected with Intralipid to that in control mice. Mice chronically given the same total amount of phospholipid in the form of 0.2 micron liposomes of phosphatidylcholine:cholesterol (2:1) rather than as a lipid-triglyceride emulsion showed altered tissue distribution of entrapped label with decreased liver uptake and increased splenic uptake, which is indicative of reticuloendothelial blockade. Tissue distribution of [14C]dipalmitoylphosphatidylcholine Intralipid was compared with that of [14C]dipalmitoylphosphatidylcholine 0.2 micron MLV of phosphatidylcholine:cholesterol (2:1). Intralipid was taken up 2- to 3-fold less by liver and 5- to 10-fold less by spleen than liposomes. Blood levels of Intralipid were higher than those of liposomes. [14C]dipalmitoylphosphatidylcholine Intralipid was eliminated from the body at a faster rate than [14C]dipalmitoylphosphatidylcholine liposomes. The lack of reticuloendothelial blockade caused by Intralipid as compared with liposomes appears to be related to its diminished uptake into reticuloendothelial tissues. This diminished uptake may be related to differences in apolipoprotein uptake of Intralipid, which is primarily in the form of a phospholipid monolayer, and liposomes, which have their phospholipid organized into a bilayer.     

Transient response of forests to CO2-induced climate change: simulation modeling experiments in eastern North America

Summary The temporal response of forests to CO₂-induced climate changes was examined for eastern North America. A forest stand simulation model was used with the assumption that climate will change at a constant rate as atmospheric CO₂ doubles, and then as CO₂ doubles again. Before being used to project future vegetation trends, the simulation model FORENA was verified by its ability to reproduce long, temporal sequences of plant community change recorded by fossil pollen and by its ability to reproduce today's vegetation. The simulated effects of changing monthly temperature and precipitation included a distinctive dieback of extant trees at most locations, with only partial recovery of biomass in areas of today's temperate deciduous forest. In the southern portion of today's deciduous-coniferous transition forests the simulated dieback was indistinct and recovery by deciduous tree species was rapid. In more northerly transition areas, the dieback not only was clearly expressed, but occurred twice, when new dominant species replaced extant conifers, then were themselves replaced, as climate change continued. Boreal conifers also underwent diebacks and were replaced by deciduous hardwoods more slowly in the north than in the south. Transient responses in species composition and carbon storage continued as much as 300 years after simulated climate changes ceased.Environmental Sciences Division Publication No. 2625     

Growth, dry matter partitioning, and diurnal activities of RuBP carboxylase in citrus seedlings maintained at two levels of CO2

The long-term response of citrus rootstock seedlings to CO₂ enrichment was examined in Carrizo estrange ( Poncirua trifoliata (L.) Raf. x Citrus sinensis (L.) Osbeck] and Swingle citrumelo ( P. trifoliate x C. parodist Macf.]. Plaotlets 14 weeks old were transferred to outdoor controlled-environment chambers and maintained for 5 months from Feb. 14 to July 21. During this period, new growth (cm) of citrange and citrumelo shoots at 660 μl1⁻¹ was 94 and 69% greater, respectively, than at 330 μ1 1⁻¹. Total dry weight of both rootstock shoots had increased by over 100%. Growth of few species is affected this markedly by elevated CO₂ levels.
More carbon was partitioned to above-ground organs in CO₂-enriched citrus seedlings. Stem dry matter per unit length was also 32 and 44% greater in citrange and citrumelo, respectively. Total leaf area was increased by 124% in citrange and 85% in citrumelo due to greater leaf number and size. Variations in overall relative growth rate appeared to be related to the rapid, sequential, flush-type growth in citrus, in which an entire shoot segment with its associated leaves remains an active sink until fully expanded. RuBP carboxylase (EC 4.1.1.39) activity in leaves of recently-expanded flushes was higher in citrumelo plants grown at 660 vs 330 μ1 1⁻¹ CO₂ and changed diurnally for citrange (but not citrumelo) leaves at both CO₂ levels. The results are consistent with the hypothesis that positive long-term effects of CO² enrichment may be greater in species or during growth periods where sink capacity for carbon utilization is high.     

Promoter recognition by Escherichia coli RNA polymerase. Effects of substitutions in the spacer DNA separating the -10 and -35 regions

A family of variants of the PRM promoter of lambda phage was constructed, bearing nine base pair substitutions in a stretch of the spacer DNA separating the contacted -10 and -35 regions. The substituted sequences were chosen for their potential to adopt structures different from those of average B-form DNA and thus to affect the interaction of RNA polymerase with the two contacted regions. Characterization of the promoters in vitro and in vivo provides additional support for the lack of specific contacts in the substituted spacer region and shows that a small change in the relative rotational orientation of the -10 and -35 regions is inconsequential to promoter function. However, a 2-3-fold reduction in promoter activity is observed with promoters bearing substitutions of nonalternating dG-dC base pairs in either orientation. This corroborates other studies indicating the anomalous behavior of such sequences and suggests that the structure of the spacer DNA can modulate promoter recognition.     

Brain peptides and glial growth. I. Glia-promoting factors as regulators of gliogenesis in the developing and injured central nervous system

Glia-promoting factors (GPFs) are peptides of the central nervous system which accelerate the growth of specific glial populations in vitro. Although these factors were first discovered in the goldfish visual system (Giulian, D., Y. Tomozawa, H. Hindman, and R. Allen, 1985, Proc. Natl. Acad. Sci. USA., 83:4287-4290), we now report similar peptides are found in mammalian brain. The cerebral cortex of rat contains oligodendroglia-stimulating peptides, GPF1 (15 kD) and GPF3 (6 kD), as well as astroglia-stimulating peptides, GPF2 (9 kD) and GPF4 (3 kD). The concentrations of specific GPFs increase in brain during periods of gliogenesis. For example, GPF1 and GPF3 are found in postnatal rat brain during a peak of oligondendroglial growth while GPF2 and GPF4 are first detected at a time of astroglial proliferation in the embryo. Stab wound injury to the cerebral cortices of rats stimulates astroglial proliferation and induces marked elevations in levels of GPF2 and GPF4. Our findings suggest that two distinct classes of GPFs, those acting upon oligodendroglia and those acting upon astroglia, help to regulate cell growth in the developing and injured central nervous system.     

Male-like behaviour in an all-female lizard: relationship to ovarian cycle

A quantitative analysis of the relationship between pseudocopulatory behaviour and the ovarian cycle in the parthenogenetic lizard Cnemidophorus uniparens indicates (1) that this behaviour is frequently and regularly expressed by captive individuals, and (2) that the sexual role, either male-like or female-like, exhibited by an animal is correlated with its ovarian state. The expression of female-like behaviour patterns was associated with and primarily limited to the vitellogenic stage of the cycle. Male-like behaviour patterns occurred most frequently during post-ovulatory stages but was not limited to these stages. Neither behavioural role was ever expressed by non-reproductive individuals. Reproductive individuals often alternated in assuming the female-like and male-like roles during the progress of the ovarian cycle. These observations suggest that pseudosexual behaviour is hormonally activated in this species. However, it also appears that the prevailing social situation is an important factor determining which behavioural role is taken. This work strengthens the hypothesis that pseudosexual behaviour in all-female lizards occurs as the result of natural selection.     

The effect of phytoplankton and suspended sediment on the growth of Corbicula fluminea (Bivalvia)

Juvenile Corbicula fluminea Müller (1774) were cultured at 15.3 °C in the laboratory on eight combinations of suspended sediment and phytoplankton. Sediment concentrations were 2.6, 25, 50, and 150 mg l^–1. Chlorophyll a levels were 15.6 and 62.5 µg l^–1. Clam tissue growth was found to be independent of silt concentration but increased at the higher chlorophyll level (p < 0.05). The growth experiment was repeated at 24 °C with chlorophyll a concentrations of 18.9 and 112.6 µg l^–1. Growth was again greater at the higher phytoplankton level (p < 0.05). These results demonstrate that Asiatic clam populations are food-limited most of the growing season in the Northern and Western portions of California's eutrophic Sacramento-San Joaquin Delta where chlorophyll a levels average less than the lower of these values. Comparisons of clam growth in the laboratory and estuary support the food limitation hypothesis as at the higher food concentration laboratory tissue growth was 2.3 and 3.8 times greater during the high and low temperature evaluations than in the estuary.     

Captan alters transcription in Escherichia coli permeabilized by toluene

RNA synthesis was measured in toluenized E. coli by the incorporation of radiolabeled precursor into either acid precipitable or phenol extracted RNA. Exposure to captan (100 microM) caused a 2.6 fold increase in the apparent rate of RNA synthesis. When captan was tested for its effect on the initiation of RNA synthesis, using either rifampicin-treated cells or by measuring the incorporation of gamma [32P]ATP or gamma [32P]GTP, no change was observed in the number of RNA chains being initiated. Thus, captan does not exert its influence at the level of initiation of nascent chains. However, captan did have an effect on chain growth. From calculations of the incorporation of precursors molecules, RNAs isolated from treated cells were measured to be an average of 2.7 times longer than those from untreated cells. RNA chain lengths were also analyzed by polyacrylamide gel electrophoresis. By this latter technique it was also shown that cells exposed to captan synthesized RNAs that were longer than those of untreated cells. Alterations in the degradation of RNA molecules do not account for the captan mediated response in RNA synthesis.     

Comparison of fiber types in skeletal muscles from ten animal species based on sensitivity of the myofibrillar actomyosin ATPase to acid or copper

Summary Comparisons were made of the histochemical characteristics of skeletal muscle from 10 animal species. The basic comparison was made from the staining patterns for the myofibrillar actomyosin ATPase produced by preincubation of fresh frozen cross-sections of muscle at alkaline pH (10.30) or acid pH (4.60) with those produced by preincubation in media containing Cu²⁺ at alkaline pH (10.30), near neutral pH (7.40), or acid pH (4.60). Muscle sections were also stained for reduced nicotinamide adenine dinucleotide tetrazolium reductase and alpha-glycerophosphate dehydrogenase to provide an indication of the relative oxidative and glycolytic capacity of the different fiber types. Type II fibers in mixed fibered muscles were either very sensitive, moderately sensitive, or relatively insensitive to inactivation of the myofibrillar actomyosin ATPase after acid preincubation. These fibers were identified as type IIA1, IIA2, and IIA3, respectively. The myofibrillar actomyosin ATPase of the type I fibers of these muscles, with the exception of those in mouse muscle, was activated by pretreatment with acid. A separation of animal species was possible based on the stability of the IIA1 fibers to inclusion of Cu²⁺ in the preincubation medium. For one group of animals (rat, mouse, monkey, man, dog, rabbit, and cow), a reciprocal relationship existed between lability to acid and stability to Cu²⁺ for type IIA1 and IIA3 fibers, respectively. For the second group of animals (horse, ass, and cat) there was a parallel relationship between lability or stability of the type IIA1 and IIA3 fibers to pretreatment with either acid or Cu²⁺ Visiting scholar from the Laboratory of Biomechanics and Physiology, College of General Education, Yamaguchi University, Yamaguchi 753, JapanSupported in part by Washington State Equine Research Program grant #105 3925 0042