Transfer of resistance traits from carrot into tobacco by asymmetric somatic hybridization: Regeneration of fertile plants

Transfer of methotrexate and 5-methyltryptophan resistance from carrot (Daucus carota) to tobacco (Nicotiana tabacum) was achieved by fusion between leaf mesophyll protoplasts of tobacco and irradiated cell culture protoplasts of carrot. Some of the regenerated somatic hybrids exhibited normal tobacco morphology with coexpression and independent segregation of the transferred resistance markers. Chromosomal instability resulted in aneuploid somatic hybrids with significantly lower chromosome number than predicted by simple addition of parental chromosome number. The methotrexate resistance phenotype was correlated with the expression of carrot-specific dihydrofolate reductase as judged by isozyme and immunological characteristics of the enzyme. The genomic construct of these somatic hybrids made the transmission of the resistance character into the next sexual generation possible.

Optical coherence tomography--a new imaging method in ophthalmology

An improvement of examination methods in ophthalmology, technical digitalisation and knowledge of validity of examinations in various diseases contributes to early diagnostics, thereby leading to an opportunity for early treatment of eye disorders. Standard introduction of the so-called optical coherence tomography into the ophthamological clinical practice facilitated new options for a detailed analysis of pathological processes in the particular layers of the retina (Fig. 2, Ref. 5). Full Text (Free, PDF) www.bmj.sk.

Mechanical injuries of the eye

BACKGROUND

Traumatic mechanical damage of the eye can cause serious morphological and functional changes in eye structures. Thorough examination and appropriate approach are essential in successful treatment and maintenance of visual functions.

MATERIAL AND METHODS

In the years 2005-2007, 78 patients with mechanical eye injury were treated at the Department of Ophthalmology, Faculty of Medicine, Comenius University, Bratislava. We treated 17 eyes with globe contusions, 19 eyes with penetrating injuries, 16 eyes with intraocular foreign bodies, 2 eyes with perforating injuries and 24 eyes with globe ruptures.

RESULTS

Final visual acuity better than 5/50 was achieved in 7 eyes (41.2%) with contusion, 15 eyes (78.9%) wih penetrating injuries, 10 eyes (62.5%) with intraocular foreign bodies and in 5 eyes (20.8%) with globe ruptures. Twelve eyes (50.0%) from the group of patients with globe ruptures were without light perception.

CONCLUSION

Traumatic mechanical damage of the eye can result in serious morphological and functional impact on eye tissue structures. Globe rupture often causes a visual loss despite advances in diagnostic and surgical procedures. Proper examination and appropriate approach are essential in successful treatment and saving the visual functions. Modern diagnostic and surgical procedures can save many eyes and maintain their useful function (Tab. 9, Fig. 2, Ref. 12).

Rabbit's intraocular pressure after instillation of timolol and aminoacid lysine, arginine, glycine or taurine mixture

AIM

Presented experimental work was aimed to examine a pharmacokinetic efficiency of 0.5% Timolol mixtures with 4 free amino acids, present in conjunctival sac: lysine, arginine, glycine or taurine on the IOP physiological values in rabbits.

METHODS

The experimental work was performed on 5 female rabbits of the New Zealand White species. After instillation at 8.00 a.m. into the left conjunctival sac: a) the 10% L-lysine x 2HCl x 2H2O in 0.5% Timolol; b) the 10% L-arginine x HCl in 0.5% Timolol; c) the 10% L-glycine x HCl in 0.5% Timolol; d) the 10% L-taurine x HCl in 0.5% Timolol, the IOP was measured before and in 5th, 15th, 30th, 60th, 120th, 180th and 240th min and in 24 hours. The right eye of the same rabbit was used as control with the instillation of both 0.5% Timolol and amino acids alone into the conjunctival sac.

RESULTS

a) The IOP has decreased after mixture of 10% lysine in 0.5% Timolol with two spikes--not significant decrease up to 60th min and a high significant decrease between 120th to 240th min; b) The mixture of 10% arginine in 0.5% Timolol decreased the IOP values with a high significance (from 2.1 to 4 torr); c) The 10% glycine in 0.5% Timolol showed a significant IOP decrease (excluding measurement in 5th min) in all measured times, the biggest IOP decrease was observed in 60th min (mean value 8.5 torr), the decrease was 3.3 torr also in 24th hours; d) The 10% taurine in 0.5% Timolol showed also a significant IOP decrease (excluding measurement in 5th min) in all measured times with maximum in 180th min (with a decrease to 6.7 torr) and the decrease showed a significantly low level--3.3 torr--also in 24 hours.

CONCLUSIONS

The results proved that the mixture of antiglaucomatic 0.5% Timolol and amino acid (lysine, arginine, glycine or taurine) contains a new biologically active substance, the "specific bioantiglaucomatic" created by interaction. Compared to the substances alone, mixture of amino acid in the antiglaucomatic decreased the physiologic IOP in rabbits with a high significance. The effect on IOP based on the interaction of the mixture of amino acid with antiglaucomatic is specific and its efficacy together with time was changed depending on the type of amino acid. Our in vitro produced bioantiglaucomatic fulfilled the physiological criteria for the IOP reduction (Fig. 4, Ref 12). Full Text (Free, PDF) www.bmj.sk.

New chimera proteins for fluorescence correlation spectroscopy

A new class of chimera proteins has been developed. They are ideally suited for detection by fluorescence correlation spectroscopy (FCS), a new technology to analyze molecular interactions. The molecular structure of these chimera proteins consists of four domains: a N-terminal (His)6-tag for affinity chromatography followed by an eight amino acid epitope for immunodetection, a polypeptide affinity domain (ADF) for target specific interaction and a C-terminal Green Fluorescent Protein (GFPuv) for reporting of interaction with the target by FCS. We designed, prepared and characterized a prototype of ADF-GFP proteins capable of specific interaction with DNA fragments bearing nuclear factor (NF)-kappaB sites. ADF NF-kappaB p50 and a non-DNA-binding deletion mutant (p35) combined with GFPuv were inserted in a procaryotic vector and expressed in E. coli. Following affinity purification the fluoroproteins p50-GFPuv and p35-GFPuv were employed in specific protein-protein and protein-DNA interaction studies. FCS analysis as well as EMSA showed that p50-GFPuv revealed a fully functional ADF. We present a model for the preparation of GFP fusion proteins capable of specific interaction with proteins, lipids or nucleic acids. The rational design allows any polypeptide fragment to be incorporated into the chimeric protein. So a new series of bio-molecules with different binding specificities and assays can be developed.

The free amino acids and the aqueous humor pH after antiglaucomatics in vitro

Authors present comparison of the previous results on the influence of free amino acids of the aqueous humor in rabbits and human on the pH of the aqueous humor in vitro. Four clinically used antiglaucomatics were added (2% Trusopt--pH 5.33; 0,005% Xalatan--pH 6.4; 0.5% Timoptol--pH 6.80 and 1% Pilocarpine--pH 5.87) into the aquired aqueous humor of rabbits (pH 7.59) and human (pH 7.11 +/- 0.11). After their instillation pH of the aqueous humor immediately decreased towards acid levels. The pH changes after Timoptol, Xalatan and Pilocarpine showed a similar time pattern and after return to the baseline values the pH shifted to alkaline levels. In case of Trusopt instillation the pH value reached the baseline of the aqueous humor after 240 min. Almost no pH changes were recorded from 240 min up to 24 hours after all tested antiglaucomatics. From the wiev on the speed of activity and effectivity depending on time required to reach the initial pH value of the aqueous humor we to make this order: Pilocarpine>Timoptol>Xalatan>Trusopt. Comparing our results the effect of antiglaucomatics is connected with different composition and also with shift of the aqueous humor pH towards slightly alkaline level (similar effect in rabbits and human). Results presented in this work are theoretical but also practical contribution to the treatment of glaucoma. (Fig. 1, Ref. 38.).

Anandamide activates vanilloid receptor 1 (VR1) at acidic pH in dorsal root ganglia neurons and cells ectopically expressing VR1

The vanilloid receptor type 1 (VR1) is a heat-activated ionophore preferentially expressed in nociceptive neurons of trigeminal and dorsal root ganglia (DRG). VR1, which binds and is activated by capsaicin and other vanilloid compounds, was noted to interact with the endocannabinoid anandamide (ANA) and certain inflammatory metabolites of arachidonic acid in a pH-dependent manner. At pH < or = 6.5 ANA induced (45)Ca(2+) uptake either in primary cultures of DRG neurons or cells ectopically expressing C-terminally tagged recombinant forms of VR1 with an EC(50) = approximately 10 microm at pH 5.5. Capsazepine, a potent antagonist of vanilloids, inhibited ANA-induced Ca(2+) transport in both cell systems. Vanilloids displaced [(3)H]ANA in VR1-expressing cells, suggesting competition for binding to VR1. Ratiometric determination of intracellular free calcium and confocal imaging of the VR1-green fluorescent fusion protein revealed that, at low pH (< or =6.5), ANA could induce an elevation of intracellular free Ca(2+) and consequent intracellular membrane changes in DRG neurons or transfected cells expressing VR1. These actions of ANA were similar to the effects determined previously for vanilloids. The ligand-induced changes in Ca(2+) at pH < or = 6.5 are consistent with the idea that ANA and other eicosanoids act as endogenous ligands of VR1 in a conditional fashion in vivo. The pH dependence suggests that tissue acidification in inflammation, ischemia, or traumatic injury can sensitize VR1 to eicosanoids and transduce pain from the periphery.

Analysis of the native quaternary structure of vanilloid receptor 1

Vanilloid receptor subtype 1 (VR1) is a ligand-gated channel that can be activated by capsaicin and other vanilloids as well as by protons and heat. In the present study, we have analyzed the oligomeric state of VR1. Co-immunoprecipitation of differently tagged VR1 molecules indicated that VR1 can form oligomers. Using two different heterologous VR1 expression systems as well as endogenous VR1 expressed in dorsal root ganglion cells, we analyzed oligomer formation using perfluoro-octanoic acid polyacrylamide gel electrophoresis. Results were confirmed both with chemical cross-linking agents as well as through endogenous cross-linking mediated by transglutaminase. Our results clearly show that VR1 forms multimers in each of the expression systems with a homotetramer as a predominant form. The oligomeric structure of VR1 may contribute to the complexity of VR1 pharmacology. Finally, differences in glycosylation between the systems were observed, indicating the need for caution in the use of the heterologous expression systems for analysis of VR1 properties.

Ligand-induced dynamic membrane changes and cell deletion conferred by vanilloid receptor 1

The real time dynamics of vanilloid-induced cytotoxicity and the specific deletion of nociceptive neurons expressing the wild-type vanilloid receptor (VR1) were investigated. VR1 was C-terminally tagged with either the 27-kDa enhanced green fluorescent protein (eGFP) or a 12-amino acid epsilon-epitope. Upon exposure to resiniferatoxin, VR1eGFP- or VR1epsilon-expressing cells exhibited pharmacological responses similar to those of cells expressing the untagged VR1. Within seconds of vanilloid exposure, the intracellular free calcium ([Ca(2+)](i)) was elevated in cells expressing VR1. A functional pool of VR1 also was localized to the endoplasmic reticulum that, in the absence of extracellular calcium, also was capable of releasing calcium upon agonist treatment. Confocal imaging disclosed that resiniferatoxin treatment induced vesiculation of the mitochondria and the endoplasmic reticulum ( approximately 1 min), nuclear membrane disruption (5-10 min), and cell lysis (1-2 h). Nociceptive primary sensory neurons endogenously express VR1, and resiniferatoxin treatment induced a sudden increase in [Ca(2+)](i) and mitochondrial disruption which was cell-selective, as glia and non-VR1-expressing neurons were unaffected. Early hallmarks of cytotoxicity were followed by specific deletion of VR1-expressing cells. These data demonstrate that vanilloids disrupt vital organelles within the cell body and, if administered to sensory ganglia, may be employed to rapidly and selectively delete nociceptive neurons.

Epidural resiniferatoxin induced prolonged regional analgesia to pain

Adequate treatment of cancer pain remains a significant clinical problem. To reduce side effects of treatment, intrathecal and epidural routes of administration have been used where appropriate to reduce the total dose of agent administered while achieving regional control. Resiniferatoxin (RTX), an ultrapotent capsaicin analog, gives long-term desensitization of nociception via C-fiber sensory neurons. We evaluate here the analgesic effect on rats of epidurally administered RTX, using latency of response to a thermal stimulus in unrestrained animals. Results were compared with those for systemically administered RTX. Vehicle or graded doses of RTX were injected subcutaneously (s.c.) or through an indwelling lumbar (L4) epidural catheter as a single dose. Both routes of application of RTX produced profound thermal analgesia, reaching a plateau within 4-6 h and showing no restoration of pain sensitivity over 7 days. Vehicle was without effect. For the epidural route, the effect was selective as expected for the targeted spinal cord region, whereas the subcutaneous administration of RTX had a generalized analgesic effect. At doses yielding a tripling of back paw withdrawal latency, epidural treatment was 25-fold more effective than the subcutaneous route of application. Consistent with the regional selectivity of the lumbar epidural route, the front paws showed no more effect than by systemic RTX treatment. Binding experiments with [3H]RTX provided further evidence of the segmental desensitization induced by epidural RTX. We conclude that epidural administration of RTX at the lumbar spinal level produces profound, long-lasting, segmental analgesia to C-fiber mediated pain in the rat.

Differential effects of free and liposome-associated 1-O-octadecyl-2-O-methylglycerophosphocholine on protein kinase C

Incorporation of ET-18-OCH3 into well-characterized liposomes known as ELL-12 has eliminated its gastrointestinal and hemolytic toxicity without loss of growth inhibiting activity. ET-18-OCH3, but not ELL-12, blunted the increase in membrane protein kinase C (PKC) activity induced by 12-O-tetradecanoylphorbol 13-myristate (TPA) and markedly reduced levels of PKC alpha in NIH 3T3 fibroblasts. Furthermore, prolonged treatment with ELL-12 neither inhibited TPA-induced translocations of PKC alpha and PKC delta to the particulate fraction nor caused down-regulation, and did not affect the cellular distribution of TPA-insensitive PKC zeta. In Jurkat T cells, where ELL-12 markedly induced apoptosis that was blocked by an inhibitor of caspase-3-like activities, it had no effect on PKC activity or translocation induced by TPA. Thus, it seems unlikely that PKC is involved in the therapeutic effects of ELL-12.

Fusion of the binding domain of Raf-1 kinase with green fluorescent protein for activated Ras detection by fluorescence correlation spectroscopy

Ras proto-oncogenes play a central role in cell proliferation by the regulation of signal transduction pathways from receptors of the outer cell membrane to the nucleus via the activation of transcription factors. Wild-type Ras cycles between the activated GTP-bound and the inactivated GDP-bound state, and the GTPase reaction is a timer for the interaction between Ras-GTP and effector molecules such as Raf-1 protein kinase. Mutations of ras resulting in the loss of the intrinsic GTPase activity result in autonomous proliferation. Mutated Ras is found in a variety of human tumors. Therefore, monitoring of GTP-loaded conformation of Ras related proteins could be utilised in cancer diagnosis. To develop a fluorescence based bioassay we have coupled the gene for the N-terminal Ras binding domain (RBD) of Raf-1 protein kinase with the gene for the green fluorescent protein (GFP). The chimeric fusion protein RBDGFP was identified by immunoblotting and subsequently investigated by fluorescence correlation spectroscopy (FCS), a new analytical technology allowing the measurement of characteristic diffusion times of fluorescently labeled molecules. Molecular interactions increase the molecular weight and influence the diffusion time of RBDGFP. FCS diffusion value of the recombinant protein was in coincidence with the molecular weight of the construct. Fluorimetric measurements of RBDGFP versus GFP showed clearly that the recombinant protein contains functional GFP. Increased FCS transition times indicated the interaction of RBDGFP with its corresponding antibody. Suboptimal binding of the fusion protein to activated Ras, how ever, resulted in a modest influence on the diffusion value. Taken together our rational design and construct shows the way for a ready characterisation of novel GFP-connected fusion proteins employing FCS.

Up-regulation of the Pit-2 phosphate transporter/retrovirus receptor by protein kinase C epsilon

The membrane receptors for the gibbon ape leukemia retrovirus and the amphotropic murine retrovirus serve normal cellular functions as sodium-dependent phosphate transporters (Pit-1 and Pit-2, respectively). Our earlier studies established that activation of protein kinase C (PKC) by treatment of cells with phorbol 12-myristate 13-acetate (PMA) enhanced sodium-dependent phosphate (Na/Pi) uptake. Studies now have been carried out to determine which type of Na/Pi transporter (Pit-1 or Pit-2) is regulated by PKC and which PKC isotypes are involved in the up-regulation of Na/Pi uptake by the Na/Pi transporter/viral receptor. It was found that the activation of short term (2-min) Na/Pi uptake by PMA is abolished when cells are infected with amphotropic murine retrovirus (binds Pit-2 receptor) but not with gibbon ape leukemia retrovirus (binds Pit-1 receptor), indicating that Pit-2 is the form of Na/Pi transporter/viral receptor regulated by PKC. The PKC-mediated activation of Pit-2 was blocked by pretreating cells with the pan-PKC inhibitor bisindolylmaleimide but not with the conventional PKC isotype inhibitor Gö 6976, suggesting that a novel PKC isotype is required to regulate Pit-2. Overexpression of PKCepsilon, but not of PKCalpha, -delta, or -zeta, was found to mimic the activation of Na/Pi uptake. To further establish that PKCepsilon is involved in the regulation of Pit-2, cells were treated with PKCepsilon-selective antisense oligonucleotides. Treatment with PKCepsilon antisense oligonucleotides decreased the PMA-induced activation of Na/Pi uptake. These results indicate that PMA-induced stimulation of Na/Pi uptake by Pit-2 is specifically mediated through activation of PKCepsilon.

Sphingosine-1-phosphate in cell growth and cell death

Recent evidence suggests that branching pathways of sphingolipid metabolism may mediate either apoptotic or mitogenic responses depending on the cell type and the nature of the stimulus. While ceramide has been shown to be an important regulatory component of apoptosis induced by tumor necrosis factor alpha and Fas ligand, sphingosine-1-phosphate (SPP), a further metabolite of ceramide, has been implicated as a second messenger in cellular proliferation and survival induced by platelet-derived growth factor, nerve growth factor, and serum. SPP protects cells from apoptosis resulting from elevations of ceramide. Inflammatory cytokines stimulate sphingomyelinase, but not ceramidase, leading to accumulation of ceramide, whereas growth signals also leading to accumulation of ceramide, whereas growth signals also stimulate ceramidase and sphingosine kinase leading to increased SPP levels. We propose that the dynamic balance between levels of sphingolipid metabolites, ceramide, and SPP, and consequent regulation of different family members of mitogen-activated protein kinases (JNK versus ERK), is an important factor that determines whether a cell survives or dies.

Inhibition of Raf-1 protein kinase by antisense phosphorothioate oligodeoxyribonucleotide is associated with sensitization of human laryngeal squamous carcinoma cells to gamma radiation

BACKGROUND

Previous studies suggest a central role for Raf-1 protein kinase in mitogenic and radiation damage responsive signaling pathways.

PURPOSE

Here we report that the expression and enzymatic activity of Raf-1 protein are inhibited in SQ-20B cells exposed to raf antisense oligodeoxyribonucleotide (As-ODNs) directed against the translation initiation site of human c-raf-1 cDNA. In contrast, treatment of SQ-20B cells with an equimolar concentration of raf sense oligodeoxy-ribonucleotide (S-ODNs) had no effect on the expression and activity of Raf-1.

RESULTS

We have observed radiosensitization of raf As-ODNs-treated SQ-20B cells. The dose modifying factor of As-ODNs treatment was approximately 1.4.

CONCLUSIONS

These studies demonstrate that raf As-ODNs is a DNA sequence-specific radiosensitizer that may have potential for use in the radiation therapy of cancers.

Development of a rapid approach to identification of tyrosine phosphorylation sites: application to PKC delta phosphorylated upon activation of the high affinity receptor for IgE in rat basophilic leukemia cells

In rat basophilic leukemia cells (RBL-2H3) activation of the high affinity receptor for IgE induces tyrosine phosphorylation of PKC delta. We carried out solid phase synthesis of 15 amino acid long oligopeptides corresponding to the sequences around each of the 19 tyrosine residues in PKC delta. Only three oligopeptides, corresponding to tyrosine 52, 155, and 565, were phosphorylated when exposed to lyn kinase. Single mutants in each of these three tyrosine residues of PKC delta were prepared. Upon expression in the RBL-2H3 cells, only the mutant in tryosine 52 showed abolition of the IgE-antigen induced tyrosine phosphorylation.

Protein kinase C epsilon is localized to the Golgi via its zinc-finger domain and modulates Golgi function

Protein kinase C (PKC) is a multigene family of serine/threonine kinases that are central to many signal transduction pathways. Among the PKC isozymes, only PKC epsilon has been reported to exhibit full oncogenic potential. PKC epsilon also displays unique substrate specificity and intracellular localization. To examine the interrelationship between the biological effects and domain structure of PKC epsilon, NIH 3T3 cells were stably transfected to overexpress different epitope-tagged fragments of PKC epsilon. The overexpressed proteins each contain the epsilon-tag peptide at the C terminus to allow ready detection with an antibody specific for the tag. The holo-PKC epsilon was found to localize with the Golgi network and other compartments, whereas the zinc-finger domain localized exclusively at the Golgi. Golgi-specific glycosaminoglycan sulfation was strongly inhibited in cells overexpressing either holo-PKC epsilon or its zinc-finger domain, while the secretion of sulfated glycosaminoglycans into the medium was impaired in cells expressing the PKC epsilon zinc-finger domain. Thus, these results suggest that PKC epsilon may be involved in specifically regulating Golgi-related processes. Further, the results indicate that PKC epsilon domains other than the kinase domain may also have biological activity and that the zinc-finger domain may function as a subcellular localization signal.

The dual-function hamster receptor for amphotropic murine leukemia virus (MuLV), 10A1 MuLV, and gibbon ape leukemia virus is a phosphate symporter

Previously, we showed that the amphotropic receptor homolog in hamster cells functions as a receptor not only for amphotropic murine leukemia viruses and 10A1 murine leukemia virus but also for gibbon ape leukemia virus (C.A. Wilson, K. B. Farrell, and M. V. Eiden, J. Virol. 68:7697-7703, 1994). Here, we demonstrate that this receptor functions as a sodium-dependent Pi transporter and that Na-Pi uptake can be specifically blocked following infection with either amphotropic murine leukemia virus, 10A1 murine leukemia virus, or gibbon ape leukemia virus.

The cellular receptor for gibbon ape leukemia virus is a novel high affinity sodium-dependent phosphate transporter

The primate type C retrovirus gibbon ape leukemia virus (GaLV) has been shown to use a widely expressed, multiple membrane-spanning protein of unknown function as its cell surface receptor on human cells (GLVR1) (Johann, S. V., Gibbons, J. J., and O'Hara, B. (1992) J. Virol. 66, 1635-1640; O'Hara, B., Johann, S. V., Klinger, H. P., Blair, D. G., Rubinson, H., Dunni, K.J., Sass, P., Vitek, S. M., and Robins, T. (1990) Cell Growth Diff. 1, 119-127). Here we present evidence that the receptor for GaLV (GLVR1) functions as a sodium-dependent transporter of inorganic phosphate. GLVR1 is shown to have approximately 3-4-fold higher affinity for phosphate than other mammalian phosphate transporters described to date. Productive infection of GLVR1-expressing cells by GaLV, but not other retroviruses, results in the complete blockade of GLVR1-specific uptake of inorganic phosphate. Since productive infection of cells with GaLV is generally not cytotoxic, it is likely that more than one phosphate transporter exists on the cell surface. Our data suggest that GLVR1 represents a sodium-dependent phosphate transporter that differs from other mammalian phosphate transporters in structure, affinity for phosphate, and function.

Overexpressed protein kinase C-delta and -epsilon subtypes in NIH 3T3 cells exhibit differential subcellular localization and differential regulation of sodium-dependent phosphate uptake

To examine the biological properties of protein kinase C (PKC)-delta and -epsilon NIH 3T3 cells were stably transfected with metallothionein-based expression vectors that overexpressed these isoforms. In addition to their inducibility by Zn2+, the protein levels of these two PKC subtypes, but not that of endogenous PKC-alpha, increased with increasing cell density. An unexpected role for Mg2+ in the subcellular localization of PKC-delta was found. This isoenzyme was predominantly membrane-associated when cell fractionation was carried out in the absence of Mg2+ but cytosolic when the fractionation was performed in the presence of 10 mM Mg2+. In contrast, the predominant localization of cytosolic PKC-alpha and of membrane-associated PKC-epsilon was not influenced by Mg2+. In vivo and in vitro studies of [3H]phorbol 12,13-dibutyrate binding in the overexpressing cell lines confirmed the cytosolic localization of PKC-alpha, the membrane-associated state of PKC-epsilon, and the presence of PKC-delta at both locations. Readdition of serum for 5 min to serum-starved, quiescent cell lines initiated the redistribution of PKC-alpha to the particulate fraction, while the location of PKC-delta and PKC-epsilon was not affected. Zn(2+)-induced overexpression of PKC-delta- and PKC-epsilon-stimulated sodium-dependent phosphate uptake. Overexpression of PKC-delta caused an increase in the Vmax of Na+/P(i) uptake, while overexpression of PKC-epsilon resulted in a decrease in Km for orthophosphate. A further stimulation of Na+/P(i) uptake in the overexpressing cells could be achieved by phorbol ester activation of endogenous PKC-alpha. These results suggest that each of the three PKC isotypes contribute to the regulation of sodium-dependent phosphate uptake, but through distinct mechanisms.

GABA-induced chemokinesis and NGF-induced chemotaxis of embryonic spinal cord neurons

During CNS development, neuroblasts proliferate within germinal zones of the neuroepithelium, and then migrate to their final positions. Although many neurons are thought to migrate along processes of radial glial fibers, increasing evidence suggests environmental factors also influence nerve cell movement. Extracellular matrix molecules are thought to be involved in guiding neuronal migration, and molecules such as NGF and GABA exert trophic effects on immature neurons. The nature of the signals that initiate and direct neuroblast migration, however, is unknown. In vitro, NGF and GABA promote neurite outgrowth from cultured cells, and NGF induces axonal chemotaxis (directed migration along a chemical gradient). At earlier developmental stages, these molecules could influence neuroblast movement. Therefore, we investigated whether these molecules induce embryonic neuronal migration. Using an in vitro microchemotaxis assay, we show that rat embryonic spinal cord neurons migrate toward picomolar NGF and femtomolar GABA beginning at embryonic day 13 (E13). Cells exhibit chemotactic responses to NGF while GABA stimulates chemokinesis (increased random movement). GABA effects are mimicked by muscimol and inhibited by bicuculline and picrotoxin, suggesting GABA motility signals are mediated by GABA receptor proteins. Expression of GABA receptors by embryonic cord cells has been previously reported (Mandler et al., 1990; Walton et al., 1993). We used polymerase chain reaction analysis to demonstrate the presence of NGF and trk mRNA in E13 and E14 cord cells, indicating the cells express message for both NGF and high-affinity NGF receptors. Immunohistochemistry of E13 spinal cord sections indicates that NGF and GABA colocalize in fibers close to the target destinations of migrating neurons, suggesting diffusible gradients of these molecules provide chemoattractant signals to migratory cells. Thus, in vitro, neuroblast migration is induced by specific signaling molecules that are present in the developing spinal cord, and may stimulate migration of embryonic neurons prior to synaptogenesis.

Heterogeneous amino acids in Ras and Rap1A specifying sensitivity to GAP proteins

Guanosine triphosphatase (GTPase) activity of Ras is increased by interaction with Ras-GAP (GTPase-activating protein) or with the GAP-related domain of the type 1 neurofibromatosis protein (NF1-GRD), but Ras is not affected by interaction with cytoplasmic and membrane forms of Rap-GAP; Rap1A, whose effector function can suppress transformation by Ras, is sensitive to both forms of Rap-GAP and resistant to Ras-GAP and NF1-GRD. A series of chimeric proteins composed of portions of Ras and Rap were constructed; some were sensitive to Ras-GAP but resistant to NF1-GRD, and others were sensitive to cytoplasmic Rap-GAP but resistant to membrane Rap-GAP. Sensitivity of chimeras to Ras-GAP and cytoplasmic Rap-GAP was mediated by amino acids that are carboxyl-terminal to the effector region. Residues 61 to 65 of Ras conferred Ras-GAP sensitivity, but a larger number of Rap1A residues were required for sensitivity to cytoplasmic Rap-GAP. Chimeras carrying the Ras effector region that were sensitive only to Ras-GAP or only to cytoplasmic Rap-GAP transformed NIH 3T3 cells poorly. Thus, distinct amino acids of Ras and Rap1A mediate sensitivity to each of the proteins with GAP activity, and transforming potential of Ras and sensitivity of Ras to Ras-GAP are at least partially independent properties.

The phosphorylation site of Ca(2+)-dependent protein kinase from alfalfa

A 50 kDa, calcium-dependent protein kinase (CDPK) was purified about 1000-fold from cultured cells of alfalfa (Medicago varia) on the basis of its histone H1 phosphorylation activity. The major polypeptide from bovine histone H1 phosphorylated by either animal protein kinase C (PK-C) or by the alfalfa CDPK gave an identical phosphopeptide pattern. The phosphoamino acid determination showed phosphorylation of serine residues in histone H1 by the plant enzyme. Histone-related oligopeptides known to be substrates for animal histone kinases also served as substrates for the alfalfa kinase. Both of the studied peptides (GKKRKRSRKA; AAASFKAKK) inhibited phosphorylation of H1 histones by bovine and alfalfa kinases. The results of competition studies with the nonapeptide (AAASFKAKK), which is a PK-C specific substrate, suggest common features in target recognition between the plant Ca(2+)-dependent kinase and animal protein kinase C. We also propose that synthetic peptides like AAASFKAKK can be used as a tool to study substrates of plant kinases in crude cell extracts.

[Reaction of the fibrose eyeball covering upon the suture material synthetic and absorbable "Dexon". (Experimental study) (author's transl)]

The present paper deals with the results of 20 eyes of experimentally operated laboratory animals, whose perforating wounds (of cornea and those of sclerocorneal region) have been suturated with a new type of absorbable synthetic suture material "Dexon" thickness being 6-0. The synthetic absorbable suture material "Dexon" is made of polyglycol acid, and it has been introduced to market by the firm Davis and Geck (U.S.A.). The inflammatory tissue reaction to the presence of the suture material "Dexon" is prominent and can by compared to the reaction to chromic resorbable suture materials (catgut or collagen). The suture material "Dexon" start to resorb in the course of the 2nd-3rd weeks after operation. The suture material "Dexon" can be used at an advantage in the operation where it is possible to cover the knots by a conjuctival lobe (in sclerocorneal region or in strabismus surgery) in this way the tendency to overgrowing of epithelial cells along the suture channels can be prevented. The "Dexon" material is sufficiently flexible and firm and has no antigenic properties, therefore it appears very prospective for ophthalmosurgery.