Variations in prolactin and growth hormone production during cellular growth in clonal strains of rat pituitary cells.

A permanent, clonal strain of rat pituitary tumor cells (GH3-cells) spontaneously synthesizes and secretes prolactin (rPRL) and growth hormone (rGH) into the culture medium. The rates of hormone production (microng extracellular hormone/mg cell protein/24 hours) and synthesis (vida infra) as well as the rate of [3H]thymidine incorporation into DNA (DNA synthesis) have been studied. During logarithmic growth rPRL and rGH production increased to 160 and 250% of the value at day 2 after plating, while during the plateau phase of cell growth hormone production decreased to initial values. The fluctuations in rPRL production could be fully explained by variations in the rate of rPRL synthesis: [3H]eucine incorporated into rPRL as measured with immunoprecipitation and polyacryl-amide gel electrophoresis. Also the rates of synthesis and production of rGH showed parallel changes during exponential and plateau phase of growth, but this hormone was probably degraded intracellularly. The relative reduction in the rate of synthesis of rPRL and rGH during the plateau of growth corresponded closely to the fall in the rate of DNA synthesis. The reduction in rPRL synthesis could not be explained through an inhibition by extra-cellular rPRL accumulation or by cell to cell interaction occurring in dense cultures. The intracellular concentrations of both hormones were unaltered during logarithmic growth, but rose to 500% for rPRL and 200% for rGH during the plateau phase. In spite of the marked variations in basal rPRL and rGH production the GH3 cultures of different ages were equally able to increase rPRL and decrease rGH production in response to thyrotropin releasing hormone (3 X 10(-7) M) and 17beta-estradiol (10(-8)M).     

The effect of A13+ on the physical properties of membrane lipids in Thermoplasma acidophilum.

Using Electron Paramagnetic Resonance Spectroscopy, Al³⁺ was shown to produce a dramatic decrease of membrane lipid fluidity on the microorganism $\text{Thermoplasma}\text{acidophilum}$ at a pH > 2. The ability of Al³⁺ to alter lipid fluidity was enhanced with increasing pH (from 3 to 5). At pH 4, 10^?2 M Al³⁺ increased the lower lipid phase transition by 39°C, and a detectable change was observed with AlCl₃ concentrations as low as 10^?5 M. The ability of Al³⁺ to increase the lower lipid phase transition temperature of $\text{T.}\text{acidophilum}$ is the largest of any cation/lipid interaction yet reported.     

Relationship of growth temperature and thermotropic lipid phase changes in cytoplasmic and outer membranes from Escherichia coli K12

Purified cytoplasmic and outer membranes isolated from cells of wild type Escherichia coli grown at 12, 20, 37 and 43°C were labelled with the fatty acid spin probe 5-doxyl stearate. Electron spin resonance spectroscopy revealed broad thermotropic phase changes. The inherent viscosity of both membranes was found to increase as a function of elevated growth temperature. The lipid order to disorder transition in the outer membrane but not the cytoplasmic membrane was dramatically affected by the temperature of growth. As a result, the cytoplasmic membrane presumably existed in a gel + liquid crystalline state during cellular growth at 12 and 20°C, but in a liquid crystalline state when cells were grown at 37 and 43°C. In contrast, the outer membrane apparently existed in a gel + liquid crystalline state at all incubation temperatures. Data presented here indicate that the temperature range over which the cell can maintain the outer membrane phospholipids in a mixed (presumedly gel + liquid crystalline) state correlates with the temperature range over which growth occurs.     

Effects of sodium chloride on the plasma membrane of halotolerant Dunaliella primolecta: an electron spin resonance study

Electron spin resonance spectroscopy was used to monitor the in vivo microviscosity of the plasma membrane and lipid extracts of the salt tolerant alga, Dunaliella primolecta. The fluidity of the plasma membrane decreased as the algae were adapted to and suspended in higher sodium chloride concentrations [2–24% (w/v)]. Both biochemical modification and a physical interaction between Na⁺ and lipids were implicated.When the microviscosity of the plasma membrane and that of lipid extracts were determined as a function of temperature, two or three lipid phase transformations were observed. There were always transformations at 9–14° C and 39–43° C. These were interpreted as the onset and completion of the lipid phase transition of at least a major lipid component of the membrane, possibly the entire membrane. These transformation temperatures were independent of the salt concentration to which the algae were adapted or suspended. This suggests that D. primolecta exists with some of its membrane in the solid-fluid mixed lipid state. With a NaCl concentration of 8% (w/v) or greater in the growth medium, a third transformation occurred around 20–22° C. It was the result of a lipid-lipid interaction and was not related to adaptation.Abbreviations ESR electron spin resonance spectroscopy - 2 T hyperfine splitting - S order parameter - 5-DS or 5-doxyl-stearate 2-(3-carboxylpropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl     

Comparison of environmental tobacco smoke concentrations and mutagenicity for several indoor environments

Environmental tobacco smoke (ETS) is a major source for indoor air pollution. Although ETS-caused indoor air pollution has been well studied in the developed countries, few studies have examined ETS indoor air pollution in China, which currently has the largest population of tobacco smokers. In this study, respirable-particulate (RP) from ETS-contaminated (RP-ETS) indoor air was collected and measured in 5 different indoor environments during the winter in the northwestern Liaoning Province, China. The extractable portion of RP-ETS (ERP-ETS) was obtained by dichloromethane extraction and used in the Salmonella mutagenicity assay in the presence of S9 using strains TA98, TA100, and TA1538. The percentage of RP-ETS attributable to ETS (ETS-RP) and the percentage of ERP-ETS attributable to ETS (ETS-ERP) were estimated by measuring the concentration of solanesol, an ETS marker. Comparative results in 5 different indoor environments were: (1) the concentration of RP-ETS ranged from 197.3 to 1227.6 microg/m(3) and approximately 64.7 to 92. 0% of the RP-ETS originated from ETS; (2) the concentration of ERP-ETS ranged 88.8 to 601.5 microg/m(3) and approximately 83.1 to 95.4% of the ERP-ETS originated from ETS; (3) the mutagenic potency (revertants/m(3)) of ERP-ETS ranged from 60.4 to 595.5 for TA98, from 33.7 to 312.8 for TA100, and from 49.7 to 475.2 for TA1538. The data indicate that the extent of ETS pollution and the potential health hazards of ETS to humans in the five indoor environments are in the following increasing order: rural bedrooms, urban living rooms, office rooms, restaurants, and passenger cars in that area.     

Reduced [3H]IP3 binding but unchanged IP3 receptor levels in the rat hippocampus CA1 region following transient global ischemia and tolerance induction

Changes in inositol (1,4,5)-trisphosphate (IP3) binding properties and the protein level of the IP3 receptor have been reported in different pathological conditions in the brain, e.g. cerebral ischemia, Alzheimer's disease, and Huntingtons disease. We used the 4-vessel occlusion model in rat brain to investigate the effect of transient ischemia insults on the IP3 receptor mRNA level, the IP3 receptor protein level and [3H]IP3 binding. Recirculation periods were limited (1-72 h) to avoid the development of delayed neuronal death. We found that the IP3 receptor mRNA levels were decreased after damage-inducing ischemia (9 min) in the hippocampus CA1 and CA3 regions. The mRNA levels were unaltered after tolerance-inducing ischemia (3 min). However, [3H]IP3 binding was significantly reduced after both damage- and tolerance-inducing ischemia in the hippocampus CA1 region. Furthermore, all investigated brain areas showed a decreased [3H]IP3 binding when tolerance-inducing ischemia was followed by a second ischemic insult (3 + 8.5 min ischemia). The IP3 receptor protein levels remained constant in all investigated brain areas. These results indicate that a reduced [3H]IP3 binding capability in the particularly vulnerable areas occurs as an early consequence of cerebral ischemia, before IP3 receptor protein levels are reduced in these areas. Structural or conformational changes altering IP3 binding may be of necessity on the pathway leading to down-regulation of IP3 receptor protein levels, as observed by others.     

Topologic distribution of different types of neurons in the human putamen

OBJECTIVE: To test the assumption that the various types of neuron in the human putamen appear to be randomly distributed and to quantify the way in which they are arranged, stochastic geometry, multivariate analysis and the interactive evaluation technique were employed. STUDY DESIGN: Twenty-seven human putamina without demonstrable signs of neurologic change were dissected out, fixed in 4% formalin and embedded in paraffin. The 20-micron paraffin sections were stained in an aldehyde-fuchsin and cresyl-violet solution, which makes it possible to distinguish between seven different neuron populations in the putamen. The gravity centers, size and form factors of these neurons were determined morphometrically under a light microscope. The data obtained were used to calculate the spatial distribution of the neurons by interactive and structure analytical methods. RESULTS: Visual point field analysis revealed an irregular arrangement of the different types of neurons. Point process analysis detected a significant hard core process of type 1 and a cluster process of type 6 neurons. With nearest neighborhood analysis, significant differences were found between certain populations of neurons and Poisson processes. Comparison of the results of multivariate cluster analysis with the investigator-dependent results of visual point field analysis showed clear differences. CONCLUSION: By means of structure analytical methods, the arrangement of different populations of neurons can be demonstrated. Some neuronal distributions are detectable only by using one of these techniques. The question of random or nonrandom distribution of the neurons in the human putamen can now be answered definitively: arrangement of the different populations of neurons is structured.     

Biosynthesis of alginate. 3. Tritium incorporation with polymannuronic acid 5-epimerase from Azotobacter vinelandii

Incubation of polymannuronic acid in tritiated water with the polymannuronic acid C-5-epimerase isolated from Azotobacter vinelandii led to incorporation of tritium into the glycuronan. Hydrolysis of the labelled glycuronan and separation of the uronic acids demonstrated that 92% of the activity was present in the guluronic acid produced by the epimerase. There was also a small, but significant, incorporation into the mannuronic acid. The results are discussed in relation to the present knowledge of the enzymic epimerisations, and it is suggested that the first step in the reaction is an abstraction of H-5.