Mu opioid receptor localization in the basolateral amygdala: An ultrastructural analysis

Receptor binding studies have shown that the density of mu opioid receptors (MORs) in the basolateral amygdala is among the highest in the brain. Activation of these receptors in the basolateral amygdala is critical for stress-induced analgesia, memory consolidation of aversive events, and stress adaptation. Despite the importance of MORs in these stress-related functions, little is known about the neural circuits that are modulated by amygdalar MORs. In the present investigation light and electron microscopy combined with immunohistochemistry was used to study the expression of MORs in the anterior basolateral nucleus (BLa). At the light microscopic level, light to moderate MOR-immunoreactivity (MOR-ir) was observed in a small number of cell bodies of nonpyramidal interneurons and in a small number of processes and puncta in the neuropil. At the electron microscopic level most MOR-ir was observed in dendritic shafts, dendritic spines, and axon terminals. MOR-ir was also observed in the Golgi apparatus of the cell bodies of pyramidal neurons (PNs) and interneurons. Some of the MOR-positive (MOR+) dendrites were spiny, suggesting that they belonged to PNs, while others received multiple asymmetrical synapses typical of interneurons. The great majority of MOR+ axon terminals (80%) that formed synapses made asymmetrical (excitatory) synapses; their main targets were spines, including some that were MOR+. The main targets of symmetrical (inhibitory and/or neuromodulatory) synapses were dendritic shafts, many of which were MOR+, but some of these terminals formed synapses with somata or spines. All of our observations were consistent with the few electrophysiological studies which have been performed on MOR activation in the basolateral amygdala. Collectively, these findings suggest that MORs may be important for filtering out weak excitatory inputs to PNs, allowing only strong inputs or synchronous inputs to influence pyramidal neuronal firing.

Evidence of mephedrone chronic abuse through hair analysis using GC/MS

Mephedrone is a synthetic derivative of cathinone which is becoming more common on the recreational drug market. Several intoxications following mephedrone abuse have been reported though published papers have focused essentially on analytical approaches for biological fluids and only one has involved a hair sample. After the development and validation of a new method, the first series of positive results for mephedrone in hair specimens is reported here. After decontamination of the hair strand in methylene chloride, hair segments were cut into small pieces with scissors, weighed and incubated overnight in Soerensen buffer pH 7.0 in the presence of deuterated 3,4-methylenedioxymethamphetamine (MDMA) at 40°C. The incubation medium was extracted using ethyl acetate after alkalinisation with 1N sodium hydroxide (NaOH). Before injection, the dry extract was derivatized using a mixture of heptafluorobutyric anhydride/ethyl acetate (100:50, v/v), evaporated and dissolved in ethyl acetate (25μl). After introduction of 1μl of the extract onto a splitless injector, chromatographic separation was achieved on a HP 6890 gas chromatograph equipped with a 5-MS capillary column. Detection was achieved in single ion monitoring mode (m/z 254-119-210 for mephedrone, m/z 258-213 for MDMA-d5) using a 5973 MSD operating in electron impact mode. Sixty-seven hair specimens were tested for mephedrone. Thirteen of them were found positive for mephedrone with concentrations ranging from 0.2 to 313.2ng/mg with a mean concentration of 26.8ng/mg. It was difficult to compare our findings due to a lack of reference data, nevertheless mephedrone seems well incorporated into hair (concentrations in the ng/mg range) like other stimulant drugs such as amphetamines or cocaine. The aim of this work was to develop a specific and accurate method for mephedrone analysis in hair specimens and its application to a large number of samples (n=67). The developed analytical method appears sensitive enough to reveal occasional to regular use of mephedrone.

Postsynaptic targets of GABAergic basal forebrain projections to the basolateral amygdala

Recent studies indicate that the basolateral amygdala, like the neocortex and hippocampus, receives GABAergic inputs from the basal forebrain in addition to the well-established cholinergic inputs. Since the neuronal targets of these inputs have yet to be determined, it is difficult to predict the functional significance of this innervation. The present study addressed this question in the rat by employing anterograde tract tracing combined with immunohistochemistry at the light and electron microscopic levels of analysis. Amygdalopetal axons from the basal forebrain mainly targeted the basolateral nucleus (BL) of the amygdala. The morphology of these axons was heterogeneous and included GABAergic axons that contained vesicular GABA transporter protein (VGAT). These axons, designated type 1, exhibited distinctive large axonal varicosities that were typically clustered along the length of the axon. Type 1 axons formed multiple contacts with the cell bodies and dendrites of parvalbumin-containing (PV+) interneurons, but relatively few contacts with calretinin-containing and somatostatin-containing interneurons. At the ultrastructural level of analysis, the large terminals of type 1 axons exhibited numerous mitochondria and were densely packed with synaptic vesicles. Individual terminals formed broad symmetrical synapses with BL PV+ interneurons, and often formed additional symmetrical synapses with BL pyramidal cells. Some solitary type 1 terminals formed symmetrical synapses solely with BL pyramidal cells. These results suggest that GABAergic neurons of the basal forebrain provide indirect disinhibition, as well as direct inhibition, of BL pyramidal neurons. The possible involvement of these circuits in rhythmic oscillations related to emotional learning, attention, and arousal is discussed.

Secondary ion and laser ablation mass spectrometry for the quantitative characterization of styrene-butadiene copolymers

Styrene-butadiene copolymers were analyzed by static secondary ion mass spectrometry (S-SIMS) and laser ablation Fourier transform ion cyclotron resonance mass spectrometry (LA-FTICRMS) to obtain quantitative information based on specific ions. Silver deposition was performed on polystyrene, butadiene rubber and styrene-butadiene rubber. Under these experimental conditions, new secondary ions were detected, in particular silver-cationized butadiene [M(butadiene) - Ag](+) and styrene [M(styrene) - Ag](+) monomers. In contrast, LA-FTICRMS experiments did not require pretreatment. At high laser power density, UV photons (193, 266 and 355 nm) allowed the detection of styrene and butadiene monomers at m/z 104 and 54, respectively. The use of the observed ions by SIMS or LA-FTICRMS ensures that quantitative information on the relative distribution of each monomer is obtained. However, the silver coating thickness in the SIMS experiment seems to have an important influence on the quantitative information obtained. For LA-FTICRMS experiments, the best results are obtained at a wavelength of 355 nm.

Historical PCDD inputs and their source implications from dated sediment cores in Queensland (Australia)

Recent investigations have demonstrated the presence of an unidentified source of polychlorinated dibenzo-p-dioxins (PCDDs) in the coastal zone of Queensland (Australia). The present study provides new information on the possible PCDD sources and their temporal input to this environment. Two estuarine sediment cores were collected in northern Queensland for which radiochemical chronologies were established. Core sections from different depositional ages, up to three centuries, have been analyzed for 2,3,7,8-substituted PCDDs and polychlorinated dibenzofurans (PCDFs). Variations of PCDD concentrations in the sediment cores over several centuries of depositional history were relatively small, and elevated PCDD levels were still present in sediment slices from the early 17th century. PCDD/F isomer patterns and congener profiles in sediments deposited during the last 350 years were almost identical and correlated well to the characteristic profiles observed in surface sediments and soils from the entire Queensland coastline. Profiles were dominated by higher chlorinated PCDDs, in particular octachlorodibenzodioxin (OCDD), whereas PCDF concentrations were below or near the limit of detection. These results indicate the presence of a PCDD source prior to industrialization and production of commercial organochlorine products. Further, the present study demonstrates that PCDD input patterns have been similar along an extensive but localized area over at least several centuries, contributing relatively high concentrations of PCDDs to the coastal system of Queensland.

Characterization by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry of the major photoproducts of temoporfin (m-THPC) and bacteriochlorin (m-THPBC)

The photobleaching of 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (temoporfin, m-THPC) and 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (bacteriochlorin, m-THPBC) was studied in ethanol-water (1 : 99, v/v) and in physiological medium (phosphate-buffered saline, PBS) with or without fetal calf serum (FCS). m-THPC solution was irradiated with the laser radiation of 650 nm, whereas m-THPBC solution underwent two consecutive irradiations at 532 and 650 nm. The photoproducts were characterized by UV-visible absorption spectrophotometry and by matrix-assisted laser desorption/ionization (MALDI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). Independent of the solvent used, the phototransformation of either photosensitizer yielded the formation of 5,10,15,20-tetrakis (m-hydroxyphenyl)porphyrin (m-THPP) through a major dehydrogenation process.

Interactive effects of elevated CO2 concentration and nitrogen supply on partitioning of newly fixed 13C and 15N between shoot and roots of pedunculate oak seedlings (Quercus robur)

Pedunculate oak (Quercus robur L.) seedlings were grown for 3 or 4 months (second- and third-flush stages) in greenhouses at two atmospheric CO2 concentrations ([CO2]) (350 or 700 micromol mol(-1)) and two nitrogen fertilization regimes (6.1 or 0.61 mmol N l(-1) nutrient solution). Combined effects of [CO2] and nitrogen fertilization on partitioning of newly acquired carbon (C) and nitrogen (N) were assessed by dual 13C and 15N short-term labeling of seedlings at the second- or third-flush stage of development. In the low-N treatment, root growth, but not shoot growth, was stimulated by elevated [CO2], with the result that shoot/root biomass ratio declined. At the second-flush stage, overall seedling biomass growth was increased (13%) by elevated [CO2] regardless of N fertilization. At the third-flush stage, elevated [CO2] increased growth sharply (139%) in the high-N but not the low-N treatment. Root/shoot biomass ratios were threefold higher in the low-N treatment relative to the high-N treatment. At the second-flush stage, leaf area was 45-51% greater in the high-N treatment than in the low-N treatment. At the-third flush stage, there was a positive interaction between the effects of N fertilization and [CO2] on leaf area, which was 93% greater in the high-N/elevated [CO2] treatment than in the low-N/ambient [CO2] treatment. Specific leaf area was reduced (17-25%) by elevated [CO2], whereas C and N concentrations of seedlings increased significantly in response to either elevated [CO2] or high-N fertilization. At the third-flush stage, acquisition of C and N per unit dry mass of leaf and fine root was 51 and 77% greater, respectively, in the elevated [CO2]/high-N fertilization treatment than in the ambient [CO2]/low-N fertilization treatment. However, there was dilution of leaf N in response to elevated [CO2]. Partitioning of newly acquired C and N between shoot and roots was altered by N fertilization but not [CO2]. More newly acquired C and N were partitioned to roots in the low-N treatment than in the high-N treatment.

Alpha ganglion cells of the rabbit retina lose antagonistic surround responses under dark adaptation

Alpha ganglion cells from the midperiphery of the rabbit retina were recorded intracellularly under visual control, in a superfused everted eyecup, and labeled with HRP. Their physiology and large somata with broad dendritic arbors identified them as uniform populations of ON- and OFF-center alpha ganglion cells, which typically displayed transient/sustained light-evoked responses. When dark adapted, the light-evoked responses from both ON- and OFF-center alpha ganglion cells were more sustained than those generally seen under light-adapted conditions. During dark-adapted (scotopic) conditions, stimulation with dim full-field illumination and small spots, either positioned over the soma or displaced 450 microns from the soma, all elicited pure center responses. After light adaptation (photopic conditions), the displaced small spots that previously evoked center responses elicited antagonistic surround responses from both ON- and OFF-center cells. Thus, as originally described in cat retina (Barlow et al., 1957), the receptive-field organization of ganglion cells changed between dark and light adaptation, and an absence or presence of surround antagonism was indicative of scotopic versus photopic states.

Toxicity of iron oxides and metabolites of benzo[a]pyrene alone or in combination in cells culture and identification by laser microprobe mass spectrometry

The goal of the gas-phase studies of well-characterized transition-metal systems is to enhance our understanding of the chemistry and sometimes of the toxic, carcinogenic effects of transition metal oxide clusters and compounds. The analysis of inorganic solids by time of flight laser microprobe mass spectrometry (TOF-LMMS) shows the formation of clusters in the mass spectra which can be used for the identification of inorganic particles. First, we have applied non-resonance ionization (delta = 226 nm) or resonant ionization (delta = 293.7 nm) of iron to study the non stoichiometric Fe1-xO, Fe3O4, Fe2O3 compounds in positive mode by TOF-LMMS. The positive mass spectra are characterized by many differences between the clusters detected and their intensities. Then, we have analysed the benzo[a]pyrene (BaP), the 1-hydroxbenzo[a]pyrene (1-OH-BaP) and the 3-hydroxybenzo[a]pyrene (3-OH-BaP) of TOF-LMMS and by Fourier Transform Irons Cyclotron Resonance Mass Spectrometry (FT-ICR-MS). It is possible to distinguish these different compounds by their respective fingerprint. Later on, we have studied toxic effects of iron oxides (Hematite Fe2O3 and Magnetite Fe3O4), benzo[a]pyrene (BaP) and Pyrene, alone or in combination. The LC50 was appreciated by colony-forming cell culture method. Cells were observed by electron microscopy and the valence of particles was analysed by TOF-LMMS. With Fe2O3 we have observed a significant decrease (20%) at higher concentration (0.5 mmol/l) and smaller quantities of BaP were highly toxic. The association of BaP at the LC10 dose (0.05 mumol/l) with growing doses of Fe2O3 or Fe3O4 (0.0125; 0.025; 0.05; 0.1; 0.2 mmol/l), appeared to increase the toxic effect of BaP 3 to 4 times. These results suggest that Fe2O3 and Fe3O4 alone are not very toxic but the association of one of these compounds with BaP increases the toxicity of the latter. On the other hand, TOF-LMMS seems to show a metabolization of iron oxide into reduced form. But, it is necessary to raise the ambiguity about the iron which is always in the cells present. For that purpose, studies with iron oxides enriched by 54Fe isotope have begun.

The organization of the turtle inner retina. II. Analysis of color-coded and directionally selective cells

Color coding and directional selectivity (DS) of retinal neurons were studied in the Pseudemys turtle by using similar intracellular recording and staining techniques as in the preceding paper (J. Ammermüller and H. Kolb, 1995, J. Comp. Neuronal. 358:1-34). Color-coded responses were elicited by red (621 or 694 nm), green (525 or 514 nm), and blue (455 nm) light flashes. In addition to red/green and yellow/blue types of chromaticity horizontal cells, in our sample of 305 identified cells we found that 17% of bipolar cells, 6.5% of amacrine cells, and 18% of ganglion cells exhibit color-coded responses. DS responses were found in 37% of the tested ganglion cells and 41% of the tested amacrine cells. Two morphologically identified bipolar cell types, B10 and B11, were red-ON/blue-OFF and red-OFF/green, blue-ON, respectively. Of five identified amacrine cell types, three were red-OFF/blue-ON center (A1, A3, A23b), one was red-OFF/green-ON center (A32), and one (A33) was double color-opponent of red-ON/blue-OFF center:red-OFF/blue-ON surround. Five ganglion cell types had variously color-coded centers (G14 and G24) or surrounds (G3 and G18), including one type, G6, that was double color-opponent (red-OFF/green-ON center:red-ON/green-OFF surround). Responses to colors were found primarily in sustained responses of bipolar and ganglion cells. However, in amacrine cells, transient components of the response also showed color dependence. Red-OFF-center responses were found in ganglion cells that were in a position to make connections at the strata 2/3 border with the red-OFF bipolar cell (B11); red-ON-center responses occurred in ganglion cells with branches in stratum 4 of the IPL where the red-ON-center bipolar (B10) ended. Blue-ON-center signals appeared to be processed mainly in strata 1-2/3, and blue-OFF-center signals in strata 3-5 of the IPL, with contributions of amacrine cells and bipolar cells. Labeled DS amacrine cells could be identified as A9, A20, and A22, and ganglion cells as G19, G20, and G24. The latter type (G24) showed DS and color coding. All response types (ON-center, OFF-center, ON-OFF) were encountered. DS amacrine cells were monostratified near the middle of the IPL, whereas DS ganglion cells were mono-, bi-, and multistratified, although all DS ganglion cells had one feature in common: they had dendrites in stratum 1 of the IPL.(ABSTRACT TRUNCATED AT 400 WORDS)

Interaction study of alpha Ni3S2 with guinea pig alveolar macrophages by resonance ionization mass spectrometry

Studies on the mechanism of nickel toxicity and carcinogenesis in humans and animals have generated a great deal of interest in metal-induced diseases. However, little information exists on the cell structures implicated in nickel metabolism. The present study reports on the application of energy dispersive spectrometry (EDS) and resonance ionization spectrometry coupled with mass spectrometry (RIMS). This study deals with the uptake, incorporation and biological transformation of alpha Ni3S2 and their consequent binding to cell constituents. A RIMS technique was achieved instrumentally by coupling a commercial time-of-flight laser microprobe mass spectrometer with a dye laser. The most interesting result of this investigation was the loss of sulphur with emergence in the mass spectrum of a calcium signal in some metabolized particles. Secondly, spectral analysis of ionized cluster ions of type (NixSy)+ differs from those obtained from standards of alpha Ni3S2 showing that nickel is in an elemental form. EDS analysis of particles generated from alpha Ni3S2 in different compartments of a cell confirmed a decrease of concomitant sulphur with the appearance of an organic Ni-P complex, either with the phosphate groups of membrane phospholipids or with phospho-transferring proteins. This study showed that RIMS is a sensitive and specific analytical technique to understand the interaction of alpha Ni3S2 with cells.

Lanthanide particles in the lung of a printer

Lanthanides were extracted from the lung tissue of a subject with a history of potential exposure to carbon-arc lamp emissions in printing shops. The characterization of inorganic particles was performed by energy dispersive X-ray spectroscopy (EDS) on a transmission electron microscope (TEM) and laser microprobe mass analysis (LAMMA). Both techniques showed the presence of elemental Ce, La and Nd at concentrations higher than the average concentration measured in 41 other workers who had died of cancer at various sites. The lung content of other prismatic and compact particles did not show any statistically significant differences between the case and the control group.

Measurement of metallic particles extracted from the lung parenchyma of two electricians and one electrotechnician

This paper reports the chemical nature of particles extracted from the lung parenchyma of two electricians and one electrotechnician. Results indicate that these workers retained particles that are qualitatively representative of their work history. The concentration of nickel in the lung of these workers was statistically higher (Mann-Whitney, p < 0.013) than the concentrations measured in the lungs of 39 other workers who died of different types of cancers.

Synaptic inputs to physiologically defined turtle retinal ganglion cells

Two physiologically distinct, HRP-marked turtle retinal ganglion cells were examined for their morphology, GABAergic, glycinergic, and bipolar cell synaptic inputs, using electron-microscopic autoradiography and postembedding immunocytochemistry. One cell was a color-opponent, transient ON/OFF ganglion cell. Its center response to red was a sustained hyperpolarization, and its center response to green was a depolarization with increased spiking at onset. The HRP-injected cell most resembled G6, from previous Golgi-impregnation studies (Kolb, 1982; Kolb et al., 1988). It was a narrow-field bistratified cell, whose two broad dendritic strata peaked at approximately levels L20-25 (sublamina a) and L60 (sublamina b) of the inner plexiform layer. Bipolar cell synapses onto G6 were found evenly distributed between its distal and proximal dendritic strata, spanning L20-75. These inputs probably originated from several different bipolar cells, reflecting the complexity of the center response. GABAergic inputs were found onto both the distal and proximal strata, from near L20-L85. Only a few glycinergic inputs, confined to dendrites at L50-70, were observed. A second ganglion cell type that we physiologically characterized and HRP-injected had sustained ON-center, sustained OFF-surround responses. Two examples were studied; both were bistratified in sublamina b, near L60-70 and L85-100, with branches up to near L40. They resembled G10, from previous Golgi-impregnation studies (Kolb, 1982; Kolb et al., 1988). One cell was partially reconstructed to look at the distributions of GABAergic and glycinergic amacrine cell, and bipolar cell inputs. Although synapses from bipolar cells were equally divided between the two major dendritic strata of G10, the inputs to the distal stratum were close to the soma, and the inputs to the more proximal stratum were on the peripheral dendrites. This arrangement may reflect input from two distinct types of ON-bipolar cell. GABAergic and glycinergic inputs to G10 costratified to both strata and to the distal branches; but where glycinergic inputs were found distributed throughout the arbor, GABAergic inputs appeared to be confined to peripheral dendrites. We hypothesize on the neural elements involved and the circuitry that may underlie the physiologically recorded receptive fields of these two very different ganglion cell types in the turtle retina.

[Pain after sympathectomy]

Surgical sympathectomies and chemical sympatholyses bring about a true sympathetic deafferentation. This leads to central retrograde degenerescence reactions of the pre-ganglionic neurons, to a reduction of the muscular tone and to a secondary neurovascular disorder at the edge of the sympathetic denervation zone. In a limited number of cases, a radiculalgia-like functional painful syndrome may develop. There are variations in the degree of seriousness and evolution, but the outcome is always spontaneously favourable. Forty seven cases of radiculalgias are reported; the onset is sudden, most often at night, and the untoward effects gradually wear off with the recovery of some degree of peripheral vasomotor tone. Although classical antalgic therapies do not seem to affect the spontaneous evolution of this syndrome, the use of membrane stabilizers such as nifedipine does however induce an immediate functional improvement of the neurovascular disorders. This leads to a dramatic sedation of the pain, provided calcium inhibitors were not administered prior to the sympathectomy.

GABA-ergic and glycinergic pathways in the inner plexiform layer of the goldfish retina

GABA-ergic and glycinergic circuitry in the inner plexiform layer of the goldfish retina was evaluated by electron microscopic autoradiography of 3H-GABA and 3H-glycine uptake, combined with retrograde horseradish peroxidase (HRP) labeling of ganglion cells. GABA-ergic and glycinergic synapses were found on labeled ganglion cells throughout the inner plexiform layer. This reinforces the idea that physiological evidence of GABA-ergic and glycinergic influence on a variety of ganglion cells in goldfish and carp often reflects direct inputs. Double-labeled synapses are presented as evidence of direct type Ab amacrine cell input to on-center ganglion cells. At least one population of type Aa sustained-off GABA-ergic amacrine cell is proposed, on the basis of profuse GABA-ergic inputs onto bipolar cells in sublamina a. Similar GABA-labeled profiles are shown to synapse onto HRP-labeled probable off-center ganglion cells. Thus GABA-ergic amacrine cells not only provide the predominant feedback to depolarizing (on-center) and hyperpolarizing (off-center) bipolar cells but also provide feed-forward inputs to on- and off-center ganglion cells. Large-caliber GABA-ergic dendrites present in both sublaminae a and b resemble those expected of a previously described bistratified, transient amacrine cell. These processes synapse onto HRP-labeled ganglion cell profiles in both sublaminae. Two morphologies of glycinergic amacrine cell are proposed on the basis of light microscopic autoradiography, 1) the previously described small pyriform cell and 2) a multipolar cell. The differential connectivity of the glycinergic neurons described, however, remains indistinguishable. Whereas abundant glycinergic inputs to ganglion cells occur throughout the inner plexiform layer, contacts between glycinergic profiles and bipolar cells are extremely rare. Therefore, interpreting the meaning of glycinergic input to ganglion cells will require further study of amacrine cell circuitry.

Serotonergic and serotonin-accumulating neurons in the goldfish retina

Autoradiography of goldfish retinas incubated in micromolar levels of 3H-serotonin displayed 3 kinds of labeled somas in the inner nuclear layer: S1 amacrine cells with heavy labeling, large somas, and a sparse distribution (approximately 93/mm2); S2 amacrine cells with moderate labeling, smaller somas, and a denser distribution (approximately 500/mm2); and a subset of bipolar cells with light labeling, small somas, and a very dense distribution (approximately 4000/mm2). Serotonin-like immunoreactivity was observed only in S1 amacrine cells and their synaptic terminals. Radiolabeled terminals in the inner plexiform layer formed 4 strata that were differentially assigned to the 3 cell types. S1 amacrine cells arborized in sublayers 1 and 5, received inputs from type a1 bipolar cells and amacrine cells, and made synapses on other amacrine cells, type a1 bipolar cells and unidentified processes. Thus, S1 amacrine cells seem to receive significant input from "off-center" pathways. S2 amacrine cells arborized in sublayer 3 and made synapses onto amacrine cells. Labeled bipolar cell terminals were exclusively located in sublayer 2 and were identified as type a2 mixed rod-cone bipolar cells. We conclude that the S1 amacrine cell is truly serotonergic and that radiolabeling of S2 amacrine cells and type a2 bipolar cells is due to cross-specificity for another carrier or processes unrelated to their neurochemical identities. These observations partially reconcile many previous observations on the types, numbers, and synaptologies of teleost retinal neurons identified by different markers for indoleaminergic transmission.

Comparison of the growth promoting activities and toxicities of various auxin analogs on cells derived from wild type and a nonrooting mutant of tobacco

A naphthaleneacetic acid tolerant mutant isolated from a mutagenized culture of tobacco mesophyll protoplasts and impaired in root morphogenesis has been previously characterized by genetic analysis. To understand the biochemical basis for naphthaleneacetic acid resistance, cells derived from this mutant and from wild-type tobacco were compared for their ability to respond to various growth regulators. The growth promoting abilities and cytotoxicities of auxin analogs were different for mutant and wild-type cells. These different activities were not correlated with increased rate of conjugation or breakdown of the auxins by mutant cells. These observations, as well as previous studies on the interaction of the mutant with Agrobacterium, suggest that mutant resistance to auxins is not a result of a specific modification of the process by which auxins induce cell killing, but to a more general alteration of the cellular response to auxin. A screening of auxin-related molecules which induce cell death in wild-type cells but not mutant cells without promoting growth in either was performed. p-Bromophenyleacetic acid was found to display these characteristics.

Auxin effect on the transmembrane potential difference of wild-type and mutant tobacco protoplasts exhibiting a differential sensitiity to auxin

The effects of 1-naphthaleneacetic acid (NAA) and other auxin analogs on the transmembrane potential difference (Em) were compared on tobacco protoplasts isolated from two genotypes differing in their sensitivity to auxins. For both types, NAA modifies Em by inducing at low doses a hyperpolarization, the amplitude of which increased with auxin concentration. Above an optimal concentration this hyperpolarization was reduced and even nullified. However, for the mutant type, this electrical response was shifted toward higher NAA concentrations, as its growth response. In the presence of structural analogs of auxin which have been showed to modify the dose-response curve for growth, the Em was altered: the growth-stimulatory molecule (picloram) initiated hyperpolarization, whereas the growth-inhibitory substance (4-bromophenylacetic acid) caused depolarization. These results provide evidence for a specific action of auxin at the membrane level related to its biological activity.

Three distinct morphological classes of receptors in fish olfactory organs

Three morphologically distinct classes of receptor-neurons are proposed: (1) type I ciliar cells, (2) microvillar cells and (3) type II ciliar cells. Retrograde transport of horseradish peroxidase by axons in the olfactory nerve to the olfactory organs of goldfish (Carassius auratus) and channel catfish (Ictalurus punctatus) provided evidence that these axon-bearing cells are present in the organs of both species. Goldfish olfactory organs were also studied with scanning electron microscopy, dissociated with papain for isolated cell preparations, and processed for ultrastructural localization of acid phosphatase activity. Type I ciliar cells are similar to ciliar olfactory receptors found in all vertebrate classes. Microvillar cells are present in the olfactory organs of most fishes and in the tetrapod vomeronasal organ. In goldfish and catfish, type I ciliar and microvillar cells are concentrated on the inner third of each lamella, nearest to the median raphe. Type II ciliar cells have often been described as respiratory-type or ciliated nonsensory cells. They are structurally similar to respiratory epithelial cells in the nasal cavities of tetrapods and have motile cilia that beat synchronously, indicative of their role in mediating fluid flow over the olfactory epithelium. In goldfish they occur singly and in aggregates throughout the organ. In catfish they are segregated from type I ciliar and microvillar cells on the outer two-thirds of each lamella. In goldfish and catfish they have axons that pass through the olfactory nerve to the olfactory bulb; hence, they are receptor-neurons as well as analogous to respiratory epithelium. In addition to the three receptor types described above, cells resembling receptors with rodlike distal processes were seen filled with horseradish peroxidase and observed with scanning and transmission electron microscopy. Cells of similar structure have been documented elsewhere, often called "rod cells," and sometimes considered a separate receptor type in fishes. In this study, a number of rodlike processes were found with their ciliar or microvillar components partially fused. High levels of acid phosphatase activity were localized to these processes, and examples were found that corresponded to each of the three receptor types. Olfactory receptor turnover is believed to persist through life. The evidence presented supports the hypothesis that fusion of their dendritic apical processes marks an early stage of receptor cell senescence.

Culture conditions of protoplast-derived cells of nicotiana sylvestris for mutant selection

Large numbers of protoplasts showing reproducible high plating efficiency can be isolated from in vitro propagated, haploid and diploid, plants of Nicotiana sylvestris. Their successful use in the selection of biochemical mutants depends on the establishment of suitable selection parameters: culture medium, cell density, age of cells at selection etc. Plating of protoplasts at low densities as well as simulation and reconstruction experiments of mutant selection were employed to optimize such selection parameters. The results show that some of the principles determined for tobacco protoplast cultures manipulated at low densities or in view of mutant selection are of more general value. However, requirements specific to N. sylvestris protoplast cultures have also been established; they play a decisive part in the successful isolation of resistant mutants in this species.