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F Conti

Publications and source records attributed to F Conti.

At least 55 records · Page 3Linked to original sources
PubMed1988

Cytochrome oxidase histochemistry reveals regional subdivisions in the rat periaqueductal gray matter.

The identification of different anatomical regions of the periaqueductal gray matter of rats was addressed in the present study by using the histochemical staining for the mitochondrial enzyme cytochrome oxidase. At caudal and middle levels, cytochrome oxidase histochemistry clearly demonstrates the existence of four subdivisions: dorsal, dorsolateral, ventrolateral and medial, whereas in sections from the rostral periaqueductal gray matter only two concentric bands are identifiable on the basis of the degree of cytochrome oxidase activity.

Animals↗
PubMed1988

Characterization of antisera to glutamate and aspartate.

Antisera were raised in rabbits against glutamate (Glu) and aspartate (Asp) conjugated to the invertebrate carrier protein hemocyanin (HC) with glutaraldehyde (GA). The antisera were characterized by testing their immunocytochemical staining properties on sections cut at the level of the ventral cochlear nucleus (VCN) from fixed brains of normal rats after absorption with conjugates of compounds structurally similar and biologically relevant to Glu and Asp. Optimal staining with Glu antiserum was obtained at a dilution of 1:10,000 and was completely blocked by 303 micrograms/ml of the Glu-HC conjugate. No crossreactivity with any of 11 compounds tested was observed. Optimal staining with the Asp antiserum was obtained at 1:8000 dilution and was completely blocked by 225 micrograms/ml of the Asp-HC conjugate. Of 10 compounds tested for crossreactivity, only L-asparagine demonstrated a measurable (about 10%) crossreactivity with the Asp antiserum. The specificity of the two antisera was also tested by immunoblot analysis against 11 compounds conjugated to HC with GA. Listed in order of staining intensity, from greatest to least, conjugates that reacted with the Glu antiserum were Glu greater than Gly-Glu greater than Asp-Glu = Asp greater than N-carbamyl (NC)-Glu greater than Asn = Gln = GABA. Conjugates that reacted with the Asp antiserum, in order of decreasing staining intensity, were Asp greater than Glu-Asp = Asn greater than Gly-Asp greater than Glu. No other compounds tested for crossreactivity reacted with the two antisera in the immunoblot analysis. Glu-like immunoreactivity in rat dorsal root ganglia and somatosensory cortex, and the comparative distribution of Glu- and Asp-like immunoreactivities in the latter tissue, are presented as examples of staining patterns obtained with the two antisera.

Animals↗
PubMed1988

Glutamate-positive corticocortical neurons in the somatic sensory areas I and II of cats.

Combined retrograde transport-immunocytochemical experiments were carried out on cats to study the morphology, laminar distribution, and percentages of corticocortical projecting neurons of somatosensory area I (SI) and II (SII) showing immunoreactivity to an antiserum raised against the amino acid glutamate (Glu). A previously characterized anti-Glu serum (Conti et al., 1987a, b; Hepler et al., 1987) was used in conjunction with HRP. This tracer was injected either in SI to label retrogradely neurons in ipsilateral SII (SII-SI association neurons) and contralateral SI (SI-SI callosal neurons) or in SII to label retrogradely neurons in ipsilateral SI (SI-SII association neurons) and contralateral SII (SII-SII callosal neurons). In sections from SI and SII processed for simultaneous visualization of Glu and HRP (Bowker et al., 1982), and containing the cells from which every one of the 4 corticocortical projections arise, 3 types of labeled neurons were observed: (1) single-labeled neurons showing the homogeneous brown immunoreaction product of Glu (Glu-positive neurons); (2) single-labeled neurons containing the granular black reaction product of retrogradely transported HRP (Glu-negative, association or callosal neurons); and (3) double-labeled neurons in which both the black HRP granules and the brown immunostaining were present (Glu-positive, association or callosal neurons). Double-labeled neurons were all pyramidal in shape and were distributed intermingled with Glu-negative corticocortical neurons in all layers of SI and SII known to give rise to association and callosal projections. Counts from 25-micron-thick sections showed that of 432 association and callosal neurons sampled from SI and SII, 214 (49.5%) were Glu-negative and 218 (50.5%) Glu-positive. In counts carried out on 5-micron-thick sections, the percentage of Glu-positive corticocortical neurons raised to about 70%. The 2 populations of single- and double-labeled corticocortical neurons showed no difference in their perikaryal cross-sectional areas. The present results show that a large fraction of association and callosal neurons of SI and SII are immunoreactive for Glu, and, therefore, these neurons probably use this excitatory amino acid, or a closely related compound, as neurotransmitter.

Animals↗
PubMed1987

D-[3H]aspartate retrograde labelling of callosal and association neurones of somatosensory areas I and II of cats.

Experiments were carried out on cats to ascertain whether corticocortical neurones of somatosensory areas I (SI) and II (SII) could be labelled by retrograde axonal transport of D-[3H]aspartate (D-[3H]Asp). This tritiated enantiomer of the amino acid aspartate is (1) taken up selectively by axon terminals of neurones releasing aspartate and/or glutamate as excitatory neurotransmitter, (2) retrogradely transported and accumulated in perikarya, (3) not metabolized, and (4) visualized by autoradiography. A solution of D-[3H]Asp was injected in eight cats in the trunk and forelimb zones of SI (two cats) or in the forelimb zone of SII (six cats). In order to compare the labelling patterns obtained with D-[3H]Asp with those resulting after injection of a nonselective neuronal tracer, horseradish peroxidase (HRP) was delivered mixed with the radioactive tracer in seven of the eight cats. Furthermore, six additional animals received HRP injections in SI (three cats; trunk and forelimb zones) or SII (three cats; forelimb zone). D-[3H]Asp retrograde labelling of perikarya was absent from the ipsilateral thalamus of all cats injected with the radioactive tracer but a dense terminal plexus of anterogradely labelled corticothalamic fibres from SI and SII was observed, overlapping the distribution area of thalamocortical neurones retrogradely labelled with HRP from the same areas. D-[3H]Asp-labelled neurones were present in ipsilateral SII (SII-SI association neurones) in cats injected in SI. In these animals a bundle of radioactive fibres was observed in the rostral portion of the corpus callosum entering the contralateral hemisphere. There, neurones retrogradely labelled with silver grains were present in SI (SI-SI callosal neurones). Association and callosal neurones labelled from SI showed a topographical distribution similar to that of neurones retrogradely labelled with HRP. The laminar patterns of corticocortical neurones labelled with D-[3H]Asp or with HRP were also similar, with one exception. In the inner half of layer II, SII-SI association neurones and SI-SI callosal neurones labelled with the radioactive marker were much less numerous than those labelled with HRP. In cats injected in SII, D-[3H]Asp retrogradely labelled cells were present in ipsilateral SI (SI-SII association neurones). Their topographical and laminar distribution overlapped that of neurones labelled with HRP but, as in cats injected in SI, association neurones labelled with silver grains were unusually rare in the inner layer III.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Membranes modification of differentiating proerythroblasts. Variation of 1,6-diphenyl-1,3,5-hexatriene lifetime distributions by multifrequency phase and modulation fluorimetry.

The fluorescence emission of 1,6-diphenyl-1,3,5-hexatriene (DPH) in K562 cell membranes has been studied using multifrequency phase and modulation fluorimetry. The DPH decay data collected at various modulation frequencies were analysed by assuming either a model of discrete exponential components or a model of continuous lifetime distribution. The fits showed smaller values of the reduced chi square using the model of continuous lifetime distribution. The K562 cell membranes dynamics were investigated during the cell differentiation along the erythroid pathway. By using the continuous lifetime distribution method for the analysis of the DPH decay, marked variations were observed during the four initial days of the erythroid differentiation. Namely, the width of the DPH lifetime distribution increased by a factor of about two, while the center value of the distribution remained constant. By using the discrete exponential components model for the analysis of the DPH decay no variations were observed during the K562 differentiation.

Cell Differentiation↗
PubMed1987

Single acetylcholine receptor channel currents recorded at high hydrostatic pressures.

A technique for performing patch-clamp experiments under high hydrostatic (oil) pressure is described. The method allows the transfer of whole cell or membrane patches in a recording configuration into a pressure vessel, where pressure can be increased up to 60 MPa (approximately equal to 600 bar). We have studied in this way the pressure dependence of single acetylcholine receptor channels in excised "outside-out" membrane patches from cultured rat muscle cells. In the range of 0.1 to 60 MPa the open channel conductance in 140 mM NaCl solutions did not vary by more than 2%, which implies that the translocation of sodium ions through the channel pore does not involve steps with significant activation volumes. At high acetylcholine concentrations (20 microM) bursts of single-channel activity allowed measurements of the mean open and mean closed times of the channel. Pressurization to 40 MPa increased both mean open and mean closed times giving apparent activation volumes of about 59 and 139 A3, respectively. This implies a net volume increase of 80 A3, associated with the transition from the agonist-free state to the open state of the channel, which may be partially associated with the agonist-binding step. All the observed pressure effects were reversible. The activation volumes for the gating of acetylcholine receptor channels are comparable to those of sodium and potassium channels in the squid giant axon, suggesting that there is some basic common mechanism in the operation of ion-channel proteins.

Animals↗
PubMed1987

Effects of hydrostatic pressure on membrane processes. Sodium channels, calcium channels, and exocytosis.

A patch-clamp study under high hydrostatic pressure was performed by transferring cells or membrane patches into a pressure vessel (Heinemann, S. H., W. Stühmer, and F. Conti, 1987, Proceedings of the National Academy of Sciences, 84:3229-3233). Whole-cell Na currents as well as Ca currents were measured at pressures up to 40 MPa (approximately 400 atm; 1 MPa = 9.87 atm) in bovine adrenal chromaffin cells. Ca currents were found to be independent of pressure within experimental resolution. The mean amplitude and the gating kinetics of Na currents were affected by less than 20% at 10 MPa. This lack of a pronounced effect is surprising since the high-pressure nervous syndrome (HPNS), a disorder at high pressures known to result from impaired nervous transmission, manifests itself at pressures as low as 5 MPa. The results show that ion channels involved in transmission cannot be implicated in HPNS. However, when exocytosis was studied at high pressure by monitoring the cell capacitance (Neher, E., and A. Marty, 1982, Proceedings of the National Academy of Sciences, 79:6712-6716), more drastic effects were seen. The degranulation evoked by dialyzing the cell with 1 microM free Ca2+ could be slowed by a factor of 2 by application of 10 MPa. The same effect was observed for the degranulation of rat peritoneal mast cells stimulated with 40 microM of the GTP analogue GTP-gamma-S. According to these results, the process of exocytosis is the most likely site at which hydrostatic pressure can act to produce nervous disorders. Furthermore, we demonstrate that pressure can be a useful tool in the investigation of other cellular responses, since we were able to separate different steps occurring during exocytosis owing to their different activation volumes.

Adrenal Medulla↗
PubMed1987

Glutamate-positive neurons in the somatic sensory cortex of rats and monkeys.

The morphology and laminar distribution of neurons labeled with an antiserum prepared against glutamic acid (Glu) conjugated to keyhole limpet hemocyanin have been studied in the somatic sensory cortex of rats and monkeys. In both species, the vast majority of immunostained neurons are pyramidal; some nonpyramidal neurons are also present. Positive neurons are observed in all cortical layers, although variations are found in the percentage of Glu-positive neurons in the different layers. In rats they are most numerous in layer V (36%), followed by layer II (33%), layer III (32%), and layer VI (29%). In layer IV, 13% of all neurons are positive. Immunoreactive neurons are very sparse in layer I. In monkeys, Glu-positive neurons represent 51% of all neurons in layer V, 49% in layer III, 40% in layers II and VI, and 19% in layer IV. No differences are evident in the laminar distribution of Glu-positive neurons among cytoarchitectonic areas 3a, 3b, 1, and 2. As in rats, Glu-positive neurons are very sparse in layer I. Since Glu and GABA metabolisms are closely related, double-labeling experiments were performed in which thin, adjacent paraffin sections were stained alternately with the anti-Glu serum and with an anti-GABA serum. The 2 populations are almost completely segregated, even though a small fraction of neurons (less than 5%) are labeled by the antisera against both antigens.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Callosal projections from area SII to SI in monkeys: anatomical organization and comparison with association projections.

The present research was aimed at ascertaining in the macaque monkey the reciprocity of the heterotopical callosal connections between SI and SII, with particular regard to the connectivity of the hand representation, and at comparing the topographical and laminar pattern of these callosal connections with those of association connections entertained by these areas. Horseradish peroxidase (HRP) was unilaterally injected into area SI in five monkeys. The sites of HRP delivery included the trunk and the hand zones preliminarily identified by recording multi-unit responses to peripheral stimulation by means of microelectrodes. Anterograde and retrograde labelling was studied in SII of both sides. The results showed the complete reciprocity of the heterotopical callosal connections between SI and SII. In the latter area both callosal axon terminals and neurones were found, which were labelled from either the trunk or the hand zone of contralateral SI. Labelling of callosal axon terminals occurred mainly in layer IV and in the lowermost part of layer III. Labelled callosal neurones were mainly in the lower half of layer III, whereas few occurred in infragranular layers. Topographically, the distribution of callosal terminals and cell bodies duplicated the distribution of association terminals and cell bodies labelled in SII on the side ipsilateral to HRP injection. The laminar pattern of termination of association fibres from SI was similar to that of callosal fibres. However, the distribution of association-projecting neurones in SII showed a striking difference from that of callosal-projecting neurones. Unlike the latter neurones, which were mainly located in supragranular layers, association cell bodies overwhelmingly dwelt in layers V and VI and were less numerous in layers II and III. This laminar pattern of association SII-SI cells corresponds to the "feed-backward" model and fits the laminar pattern of their axon terminations (Friedman: Brain Res. 273: 147-151, '83). The association and callosal inputs and outputs of area SII are discussed in relation to the function of the forward and backward type of reciprocal connections entertained with SI in the ipsilateral hemisphere and to the function of SII in the interhemispheric exchange of somatosensory information.

Animals↗
PubMed1986

Effects of hydrostatic pressure on lipid bilayer membranes. I. Influence on membrane thickness and activation volumes of lipophilic ion transport.

Measurements of membrane capacitance, Cm, were performed on lipid bilayers of different lipidic composition (diphytanoyl phosphatidylcholine PPhPC, dioleoyl phosphatidylcholine DOPE, glycerylmonooleate GMO) and containing n-decane as solvent. In the same membranes, the absorption of the lipophilic ions dipicrylamine (DPA-) and tetraphenylborate (TPhB-), and the kinetics of their translocation between the two membrane faces have been studied. The data were obtained from charge pulse relaxation measurements. Upon increasing pressure the specific capacity Cm increased in a fully reversible and reproducible way reflecting a thinning of the membrane that is attributed to extrusion of n-decane from the black membrane area. High pressure decreased the rate constant, ki, for lipophilic ion translocation. After correcting for changes in the height of the energy barrier for translocation due to membrane thinning the pressure dependence of ki yields an apparent activation volume for translocation of approximately 14 cm3/mol both for DPA- and TPhB-. Changes in lipophilic ion absorption following a step of pressure developed with a rather slow time course due to diffusion limitations in solution. The stationary concentration of membrane absorbed lipophilic ions increased with pressure according to an apparent volume of absorption of about -10 cm3/mol. The relevance of the results for the interpretation of the effects of pressure on nerve membrane physiology is discussed.

Hydrostatic Pressure↗
PubMed1986

Effects of hydrostatic pressure on lipid bilayer membranes. II. Activation and reaction volumes of carrier mediated ion transport.

Measurements of voltage relaxations following brief charge-pulses applied to lipid bilayers have been performed at different hydrostatic pressures in the presence of the neutral carriers cyclo (D-Val-L-Pro-L-Val-D-Pro)3(PV) and valinomycin. From double-exponential relaxations observed in membranes containing PV-K+ complexes estimates were obtained of the amount of membrane absorbed complexes, NMS, and of the rate of complex translocation, kMS. The pressure dependence of kMS corresponded to an activation volume for translocation of approximately 12 cm3/mol independent of ionic strength and K+ concentration. The pressure dependence of NMS strongly varied with K+-concentration suggesting a major role of ion-complexation in solution which is estimated to involve a reaction volume of 25.5 cm3/mol, while the volume of absorption of a PV-K+ complex by the membrane was estimated -7.5 cm3/mol. The relaxations observed in the presence of valinomycin contained three exponentials and could be used to estimate four rate constants and one absorption parameter which characterize the valinomycin-mediated transport. When the transport of Rb+ was tested, the rate constant for the complex dissociation, kD, and the total concentration of free and complexed carriers in the membrane, No, were found to be pressure insensitive. The translocation rates for the complex, kMS and for the free carrier, kS, were instead markedly pressure dependent according to estimated activation volumes in the range of 11 to 18 cm3/mol. The recombination rate constant kR was also pressure dependent according to an activation volume of 12-14 cm3/mol. The study of the valinomycin-K+ transport yielded similar results as far as N.,ks, and kms are concerned, but in this case kR was pressure independent, while kD was increased by pressure. The net volume change associated with the transfer of a free ion to the membrane in the form of a valinomycin-ion complex was nevertheless very similar for K+ and Rb+. It is concluded that pressure affects the transmembrane mobility of liposoluble molecules, whether charged or not, mostly by increasing the effective viscosity of the hydrocarbon core of the bilayer. The pressure dependence of the membrane uptake of amphipathic compounds seems also to obey the general rule: that of involving a negative volume change. However, when the compounds arise from a complexation reaction in solution or at the membrane solution interface possible positive volumes of complexation may make effective uptake to be reversed rather than increased by pressure.

Biological Transport, Active↗
PubMed1986

Amiodarone and desethylamiodarone distribution in the atrium and adipose tissue of patients undergoing short- and long-term treatment with amiodarone.

The time to onset of action of amiodarone is often long in patients treated for arrhythmias; one reason might be a slow entry of the drug into the target organ, the heart. Amiodarone and desethylamiodarone, its active metabolite, were measured in the plasma, atrial tissue and pericardial fat of patients undergoing cardiac surgery. Two groups were studied: patients treated with amiodarone for less than 28 days (short-term group) and those treated for 28 days or more (long-term group). Plasma levels of amiodarone in the two groups were not different, whereas levels of desethylamiodarone were significantly higher in the long-term group. Average concentrations of amiodarone in the atrium were higher with longer treatment periods (30.2 +/- 5.6 versus 13.2 +/- 2.5 micrograms/g wet weight of tissue); the same was true for desethylamiodarone (40.3 +/- 7.7 versus 15.7 +/- 3.7 micrograms/g). Amiodarone concentrations in fat were also significantly higher in the long-term than in the short-term group. Atrium/plasma concentration ratios of desethylamiodarone were higher than those of amiodarone, whereas fat plasma concentration ratios of desethylamiodarone were lower. In conclusion, the equilibration of amiodarone and desethylamiodarone concentrations between myocardium and plasma appears to occur slowly in patients undergoing long-term treatment with amiodarone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1986

Bilateral receptive fields and callosal connectivity of the body midline representation in the first somatosensory area of primates.

Experiments were performed in order to study the receptive field (RF) organization and the callosal connectivity of the trunk representation zone in areas 3b and 1 of the postcentral cortex of macaque monkeys. Multiunit microelectrode recordings showed that neurons responding to tactile stimulation of bilateral RFs across the midline of the body were contained in three topographically distinct zones of the trunk map. In one zone, at the junction between cytoarchitectonic areas 3b and 1, RFs straddled the dorsal midline of the trunk. In the other two zones, one located caudally in area 1 in front of the postcentral dimple, and the other rostrally in area 3b in the depth of the posterior bank of the central sulcus, RFs straddled the ventral midline of the trunk. The first one and the other two zones are referred to here as the dorsal and the ventral midline representation zones, respectively. Elsewhere in the trunk map, neurons responded only to stimulation of contralateral RFs. The callosal connectivity of the trunk map was studied by means of the transport of horseradish peroxidase (HRP). Multiple injections of HRP in electrophysiologically identified sites of the trunk representation in one hemisphere labeled both callosal fiber terminals and callosally projecting neurons in the contralateral homotopic cortex. Dense patches of callosal neurons intensely labeled with HRP were present in the cortical regions representing the body midlines and were distributed for the most part in layer III. Some neurons lightly labeled with HRP were scattered in other zones of the trunk map. Callosal terminations were densest within the midline zones and very sparse or absent in the lateral trunk zones. Correlation of physiological and anatomical data obtained either separately or from the same animal demonstrated that cortical regions containing bilateral-field neurons also contained the highest density of labeled callosal terminations and neurons. This correlation suggests a role for the corpus callosum in the perception of the body midline, either by generating the bilateral RFs of these neurons or by coordinating the activity of the regions containing neurons with thalamically generated bilateral RFs.

Abdomen↗