Induction of macrophage growth by lipids

Lipoproteins from ascitic tumors in mice and lipids extracted from these lipoproteins induced growth of murine peritoneal macrophages in vitro. The lipid components with activity were examined by use of lipid vesicles or liposomes. Liposomes prepared from egg-yolk PC alone did not induce macrophage growth, but those prepared from mixtures of egg-yolk PC and cholesterol or cholesteryl esters other than cholesteryl oleate, or triglycerides other than triolein, enhanced 3H-TdR incorporation into macrophages. The free fatty acids examined had no effect on 3H-TdR incorporation. These results suggest that growth of macrophages is induced by ordinary lipids present in lipoproteins or cell membranes that the macrophages scavenge in the body.     

Induction of temporary sterility in female hamsters by an intraperitoneal silastic-PVP-PGF2alpha tube.

In the female hamster, temporary sterility for a period of 10 or 15 days was induced by an intraperitoneal Silastic-PVP-tube containing 3.5 or 1.0 mg of PGF2alpha, respectively. All Silastic-PVP-PGF2alpha tube hearing animals regained fertility and delivered normal litters at various times after the placement of the tube. The release rate of 3-H-PGF2alpha from the Silastic-PVP tube was described and their potential use as a drug delivery system discussed.     

Induction of retinal regeneration in vivo by growth factors

We have previously reported that basic fibroblast growth factor (bFGF) can induce retinal regeneration in the stage 22-24 chicken embryo. The present study was undertaken to identify the cellular source of the regenerate and to determine whether other growth factors also elicit regeneration in this animal model. Polymer implants containing bFGF were inserted into eyes of chicken embryos immediately after extirpation of the neural retina. The retinal pigment epithelium (RPE) was left intact. Evaluation by light microscopy revealed that in bFGF-treated eyes the new neural retina arose by transdifferentiation of the entire RPE layer. Differentiation of the new neural retina occurred in a sequence similar to that of normal development but proceeded in a reverse (vitread) direction. All retinal laminae had differentiated by Day 15. However, the regenerate displayed reversed polarity, with photoreceptors closest to the lens. The RPE, pecten, and optic nerve were absent. Focal areas of degeneration in the retinal regenerate became evident for the first time on Day 10. Retinal regeneration was also observed after treatment with higher doses of acidic fibroblast growth factor, but not with nerve growth factor-beta, transforming growth factor-beta 1, insulin, or insulin-like growth factors I or II. These results raise the possibility that FGFs may play a role in retinal differentiation during development.     

Compensatory growth of Phanerochaete velutina mycelial systems grazed by Folsomia candida (Collembola)

Phanerochaete velutina is a major agent of wood decomposition in temperate forests. It grows out of woody resources in search of other resources and is then vulnerable to grazing by invertebrates. The aim of this study was to determine how continuous grazing and grazing for only 2 days by different densities of collembola, Folsomia candida, affect mycelial development (radial extension, hyphal coverage and fractal dimension) of P. velutina growing across non-sterile soil. High density (80 collembola) continuous grazing resulted in different mycelial foraging patterns compared to controls and lower density (20 and 40 collembola) continuous grazing: radial extension rate was reduced from 8.4 mm day(-1) (control) to 6.9 mm day(-1) (80 collembola), hyphal coverage was reduced to 81% of controls and mass fractal dimension increased from 1.68 (control) to 1.72 (80 collembola). There was evidence of over-compensatory growth: when high density grazing ceased the new growth was considerably greater (38%) than in controls. Grazing also resulted in growth stimulation: at low density continuous grazing (20 collembola) hyphal coverage was 15.6% greater than in controls. The ecological implications of compensatory and stimulatory growth in fungal-invertebrate interactions are considered.     

Induction of podoplanin by transforming growth factor-beta in human fibrosarcoma

Podoplanin/aggrus is increased in tumors and its expression was associated with tumor malignancy. Podoplanin on cancer cells serves as a platelet-aggregating factor, which is associated with the metastatic potential. However, regulators of podoplanin remain to be determined. Transforming growth factor-beta (TGF-beta) regulates many physiological events, including tumorigenesis. Here, we found that TGF-beta induced podoplanin in human fibrosarcoma HT1080 cells and enhanced the platelet-aggregating-ability of HT1080. TGF-beta type I receptor inhibitor (SB431542) and short hairpin RNAs for Smad4 inhibited the podoplanin induction by TGF-beta. These results suggest that TGF-beta is a physiological regulator of podoplanin in tumor cells.     

Induction of temporary sterility in female hamsters by an intraperitoneal Silastic-PVP-PGF2α tube

In the female hamster, temporary sterility for a period of 10 or 15 days was induced by an intraperitoneal Silastic-PVP-tube containing 0.5 or 1.0 mg of PGF_2α, respectively. All Silastic-PVP-PGF_2α tube bearing animals regained fertility and delivered normal litters at various times after the placement of the tube. The release rate of ³H-PGF_2α from the Silastic-PVP tube was described and their potential use as a drug delivery system discussed.     

Cytokinin promotes growth cessation in the Arabidopsis root

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Transient growth requirement in Bacillus subtilis following the cessation of exponential growth

During an investigation of the parameters controlling mutations in Bacillus subtilis we observed that this bacterium exhibits a transient growth requirement for two nonessential amino acids (glutamic acid and isoleucine) during a type of postexponential growth on a minimal medium.     

Induction of linear tracks of DNA double-strand breaks by alpha-particle irradiation of cells

Understanding how cells maintain genome integrity when challenged with DNA double-strand breaks (DSBs) is of major importance, particularly since the discovery of multiple links of DSBs with genome instability and cancer-predisposition disorders. Ionizing radiation is the agent of choice to produce DSBs in cells; however, targeting DSBs and monitoring changes in their position over time can be difficult. Here we describe a procedure for induction of easily recognizable linear arrays of DSBs in nuclei of adherent eukaryotic cells by exposing the cells to alpha particles from a small Americium source (Box 1). Each alpha particle traversing the cell nucleus induces a linear array of DSBs, typically 10-20 DSBs per 10 mum track length. Because alpha particles cannot penetrate cell-culture plastic or coverslips, it is necessary to irradiate cells through a Mylar membrane. We describe setup and irradiation procedures for two types of experiments: immunodetection of DSB response proteins in fixed cells grown in Mylar-bottom culture dishes (Option A) and detection of fluorescently labeled DSB-response proteins in living cells irradiated through a Mylar membrane placed on top of the cells (Option B). Using immunodetection, recruitment of repair proteins to individual DSB sites as early as 30 s after irradiation can be detected. Furthermore, combined with fluorescence live-cell microscopy of fluorescently tagged DSB-response proteins, this technique allows spatiotemporal analysis of the DSB repair response in living cells. Although the procedures might seem a bit intimidating, in our experience, once the source and the setup are ready, it is easy to obtain results. Because the live-cell procedure requires more hands-on experience, we recommend starting with the fixed-cell application.     

Abscisic acid and cessation of apical growth in Salix pentandra

Effects of exogenous abscisic acid (ABA) on growth and transpiration in seedlings of two ecotypes of Salix pentandra L. were studied in phytotron experiments. Application of ABA resulted in increased stomatal resistance, reduced transpiration and reduced growth rate. ABA did not induce cessation of apical growth in seedlings grown under a 24-h photoperiod. The content of endogenous ABA in seedlings grown under 24-h (LD) or 12-h (SD) photoperiods was analysed from purified methanol extracts using gas chromatography and electron capture detection. No significant differences were found in the ABA contents of LD- and SD-grown plants. SD-induced cessation of apical growth was not associated with increased stomatal resistance or reduced transpiration rate.     

Mitochondrial dysfunction mediated by cytoplasmic acidification results in pollen tube growth cessation in Pyrus pyrifolia

The length of pollen tubes grown in synthetic media is normally shorter than those grown in vivo. However, the mechanism(s) underlying the cessation of pollen tube growth under culture conditions remain(s) largely unknown. Here, we report a previously unknown correlation between vacuolar function and the cell's ability to sustain mitochondrial functions in pear pollen tubes. The pear pollen tubes in vitro grew slowly after 15 hours post‐cultured (HPC) and nearly ceased growth at 18 HPC. There was increased malondialdehyde content and membrane ion leakage at 15 HPC compared with 12 HPC. Furthermore, cytoplasmic acidification mainly mediated by decreased vacuolar H⁺‐ATPase [V‐ATPase, Enzyme Commission (EC) 3.6.1.3] activity was observed in pollen tubes after 15 HPC, and this further resulted in mitochondrial dysfunction, including mitochondrial structure disruption, mitochondrial membrane potential collapse and decreases in both oxygen consumption and ATP production. Our findings suggest that vacuoles and mitochondria intimately linked in regulating pollen tube elongation.     

Induction of growth hormone release by Pueraria thunbergiana BENTH.

Puerariae Radix (PR), Puerariae Flos (PF), and Puerariae Surculus (PS) as well as their constituents were tested for induction of rat growth hormone (rGH) release by both rat pituitary cell culture and in vivo experimentation in order to develop them to novel drugs. Through a calibration curve of the rGH released by addition of rat growth hormone-releasing hormone (rGHRH) to rat pituitary cells, the 70 % ethanol extracts of PR and PS increased rGH release by about 1.6 and 1.7 times as high, respectively, as the control group (264.6 +/- 13.6 pM). However, each puerarin type as a representative constituent of PR in Korea Pharmacopeia (KP) and tectorigenin and an important ingredient of PF were twice as effective as in the control group. The acid hydrolysate of Puerariae Surculus (HPS) increased rGH release concentration-dependently, and its EC (50) was approximately 10.4 microg/ml. The T (max) value for rGH after injection of 20 microg/kg of rGHRH was 10 - 30 min, while the C (max) value was increased by approximately 12-fold compared to the control group (198.2 +/- 25.0 pM) and the AUC (0 - 45) was increased to 10 times the level of the control group (10,840.9 +/- 845.5 min. pM). On the other hand, T (max) for the HPS was 60 min, while C (max) was increased approximately to 5.8 fold compared to control (244.1 +/- 36.4 pM). C (max) for puerarin was 1,028.6 +/- 502.7 pM, that is, approximately 5.2 times as high as the control level. However, tectorigenin (20 microg/kg) was of no statistical significance. Therefore, we suggest that the HPS and puerarin act either on GH secretagogue receptors or on GHRH receptor of somatotrophin as possible agonists or an inhibitor on somatostatin receptor to release rGH, respectively.