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PubMed1991

[Problems and errors of magnetic resonance in the diagnosis of renal masses].

Since the impact of MRI on the diagnostic evaluation of renal masses is affected by the intrinsic complexity of the modality, the problems related to the specific knowledge, on the part of the radiologist, of the examination itself to make a correct diagnosis are carefully analyzed. The problems related to the technical features of the equipment are presented as well, with a special emphasis on the still inadequate spatial resolution of MRI, and on its long acquisition time and unfavorable signal-to-noise ratio. On the other hand, its good contrast resolution is mentioned, which will be further improved by the new gradient-echo sequence (GRE) and by the use of paramagnetic contrast media. As for diagnostic problems, the results are analyzed of a series of 62 patients showing US "solid" renal mass. MRI allowed lesion detection in 59/62 cases, with 95.1% sensitivity. False negatives were due solely to the poor image quality determined by motion artifacts. MRI did not provide significant information in the structural evaluation of the lesions when tissue characterization was concerned, but was helpful in the correct assessment of necrotic foci (thus allowing the calculation of viable neoplastic mass) and in the detection of collateral vessels. Finally, the spatial relationships of the mass could be easily assessed by MRI, thanks to both its multiplanarity and to its good capabilities in the visualization of vascular involvement.

Diagnostic Errors↗
PubMed2003

[The meaning and usefulness of spiral CT for radiolucent ureteric stones diagnosis: our experience].

The aim of this work was to report some case histories on the usefulness of spiral TC, used for several years both to diagnose renal colic and urinary lithiasis and to study radio lucent stones that are often difficult to be detected with traditional radiology. 13 patients, aged between 31 and 76 (average age: 54.2), were therefore examined. Eight of them had a ureteral colic when examined, while five patients had shown symptoms some days before being hospitalised in our ward. In all cases, ultrasonography showed a significant hydronephrosis, while direct radiography of the urinary tract could not detect any images that could be associated with radio-opaque lithiasis. All patients therefore underwent an abdominal spiral TC with no contrast medium within 24 hours after hospitalisation. The confrontation between the results obtained by ultrasonography and those obtained by spiral TC, showed the usefulness of the former method to detect stones located in the proximal ureter or in its intramural tract, while the latter could detect the lithiasis of the proximal ureter in 3 cases (23%), of the mid ureter in 2 cases (15.3%), and of the distal ureter in 8 cases (61%). The stones had, approximately, a 5 mm diameter in 5 cases. In 6 cases the diameter was between 6 and 10 mm, and more than 1 cm in 2 cases. Both methods proved to be equally accurate in the assessment of the hydronephrosis degree and of the thickness of the renal parenchyma. The therapy was medical in 2 cases and open surgery in 3 cases, while 8 patients were treated with ureterolitholapaxy with a ballistic searcher. The usefulness of TC in the study of urolithiasis nowadays is supported by a large literature which clearly supplies with documentary evidence the high sensitivity and specificity of such a method in diagnosing the presence of urolithiasis in general and above all of ureteric stones. Such a method not only makes an accurate evaluation of the stones location possible, but it can also assess the calculi dimensions and the indirect signs of the functionality of the kidney affected, without having to use the contrast medium. This method needs very limited execution times and allows a diagnostic of possible collateral pathologies. The main disadvantage of spiral TC, if compared to conventional radiology, is that the patient is exposed to a larger quantity of ionizing radiations, although such an inconvenience will be overcome by the new and more technologically advanced machines. According to our experience, though based on a limited number of cases, spiral TC allowed us to get a quick diagnosis of radio-lucent lithiasis, to see the seat and dimensions of the calculi and finally to chose the most effective treatment. We can therefore think of a diagnostic protocol, for ureteral colics with hydronephrosis or complicated by hyperpyrexia or sepsis, with spiral TC in order to have a quick diagnosis and start the most effective therapy in case an ultrasonographic research should not result diriment.

Adult↗
PubMed2001

[A holder for standardized radiological detection of ulnar capsule-ligament lesions of the thumb base joint].

AIM OF THE STUDY: To evaluate the usefulness of a self-constructed holding device for standardized, investigator-independent radiodiagnostics for ulnar capsulo-ligamentous lesions of the thumb metacarpophalangeal joint compared to the uninjured side. MATERIAL AND METHODS: A holding device for stress roentgenograms was constructed. Normal abduction arcs were evaluated in 20 degrees flexion in 28 healthy volunteers. The investigator-dependent variance was assessed. The study group comprised 123 consecutive patients (68 male, 55 female, aged 7 to 68 years, mean age 30 years). RESULTS: The normal arc of abduction was calculated to be 12 degrees (range 3 degrees to 24 degrees), while the mean individual difference in side by side comparison in volunteers was 0.3 degree (SD 2.69 degrees, range 0 degree-8 degrees). A rupture was diagnosed in 47 patients; 41 were operated. The preoperative diagnoses confirmed correct in all operated patients. A difference of greater than 6 degrees is indicative of a rupture with a sensitivity of 66.7% and a specificity of 96.9%. CONCLUSIONS: In summary, the holding device is useful for the practical work. Individual differences of less than 4 degrees are negative, between 4 degrees and 7 degrees questionable positive, between 7 degrees and 12 degrees are positive and over 12 degrees proof indicator of a rupture of the ulnar collateral ligament of the thumb metacarpophalangeal joint.

Adolescent↗
PubMed1979

Dopamine modulation of acetylcholine release from the guinea-pig brain.

The effect of dopamine (DA) and apomorphine (Apo) on acetylcholine (ACh) release from guinea-pig brain was investigated (i) in superfused slices of cerebral cortex, caudate nucleus, tuberculum olfactorium, brain stem and (ii) in unrestrained, unanaesthetized animals, provided with epidural parietal cups. DA reduced the ACh release only from slices of caudate nucleus, whereas Apo was also effective in the cerebral cortex. DA and Apo inhibition in caudate nucleus was antagonized by spiroperidol. The injection of DA (1.5 and 5 micromoles) into the cerebral ventricles (i.c.v.) caused a late, moderate behavioural stimulation and enhanced ACh outflow from the parietal cortex. The injection of Apo, either i.c.v. or i.p., promptly elicited similar effects. Spiroperidol 0.5--2 mg/kg i.p. counteracted the behavioural stimulation by Apo and amphetamine, but unexpectedly enhanced the cortical ACh outflow, leaving unaffected the cholinergic responses to Apo and Amphetamine. These results show that DA directly hinders ACh release from the striatal cholinergic structures surviving in vitro, via classical neuroleptic-sensitive receptors. On the other hand, the enhanced cortical ACh outflow caused by DA and DA-mimetic drugs in the unanaesthetized animals is suggestive of a disinhibition of the corticopetal cholinergic neurones, via neuroleptic-insensitive mechanisms. Hence, the 'paradoxical' effect of spiroperidol might represent the consequence of the increased activity of nigral DA cells with collaterals possibly involved in the control of the ascending cholinergic pathways.

Acetylcholine↗
PubMed2004

Small conductance Ca2+-activated K+ channel knock-out mice reveal the identity of calcium-dependent afterhyperpolarization currents.

Action potentials in many central neurons are followed by a prolonged afterhyperpolarization (AHP) that influences firing frequency and affects neuronal integration. In hippocampal CA1 pyramidal neurons, the current ascribed to the AHP (IAHP) has three kinetic components. The IfastAHP is predominantly attributable to voltage-dependent K+ channels, whereas Ca2+-dependent and voltage-independent K+channels contribute to the ImediumAHP (ImAHP) and IslowAHP (IsAHP). Apamin, which selectively suppresses a component of the mAHP, increases neuronal excitability and facilitates the induction of synaptic plasticity at Schaffer collateral synapses and hippocampal-dependent learning. The Ca2+-dependent components of the AHP have been attributed to the activity of small conductance Ca2+-activated K+ (SK) channels. Examination of transgenic mice, each lacking one of the three SK channel genes expressed in the CNS, reveals that mice without the SK2 subunit completely lack the apamin-sensitive component of the ImAHP in CA1 neurons, whereas the IsAHP is not different in any of the SK transgenic mice. In each of the transgenic lines, the expression levels of the remaining SK genes are not changed. The results demonstrate that only SK2 channels are necessary for the ImAHP, and none of the SK channels underlie the IsAHP.

Animals↗
PubMedDate not supplied

Distal splenorenal shunt and insulin secretion, plasma glucagon, and glucose homeostasis in cirrhosis.

Over the 1st postoperative yr, distal splenorenal shunt (DSRS) in cirrhotic patients is followed by a reduction in portal perfusion resulting from a spontaneous opening of portal-systemic collaterals. This can influence plasma levels of insulin and glucagon. Fasting plasma glucose, insulin, C-peptide, and glucagon and their 5-h responses to a protein meal (which directly stimulates the hormone secretions) were measured before and 3 and 12 mo after DSRS in 10 cirrhotic patients. Hormone effectiveness and pancreatic alpha- and beta-cell sensitivities to ammonia (NH3), amino acids, and glucose were also calculated. Liver function and portal vein diameter were assessed before each study. Seven cirrhotic patients treated with injection sclerotherapy of esophageal varices served as a control group. Liver function did not deteriorate in either patient group. An increase in fasting glucagon (from 181 +/- 22 to 242 +/- 22 and 255 +/- 22 pg/ml, p = 0.02) and NH3 (from 57 +/- 8 to 84 +/- 11 and 97 +/- 14 micrograms/dl, p = 0.04) and a decrease in glucagon effectiveness (from 0.56 +/- 0.06 to 0.39 +/- 0.05 and 0.035 +/- 0.03, p = 0.047) and portal vein diameter (from 16.0 +/- 1.1 to 11.3 +/- 0.8 and 9.4 +/- 0.6 mm, p < 0.001) was found only in DSRS patients. The elevation in glucagon was correlated with that of NH3 at 3 mo (r = 0.83, p = 0.003) and with the reduction of portal vein diameter at 1 yr (r = -0.81, p = 0.005). In cirrhosis, DSRS does not influence insulin secretion or its plasma level and effectiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1996

[Spiral CT angiography versus DSA in detection of carotid stenoses].

PURPOSE: To determine the value of spiral CT angiography for evaluation of internal carotid artery stenosis. METHODS: Spiral CT angiography was compared with selective intraarterial DSA in 40 patients with 72 internal carotid artery stenoses. Quantification of stenoses was performed according to the NASCET-study and categorized in mild (0-29%), moderate (30-69%), severe (70-99%) and occlusion (100%). RESULTS: The total agreement of spiral CT angiography with DSA in all stenoses was 78% (r = 0.933; p < 0.0001). In the mild stenoses group there was an agreement of 56% (r = 0.598; p = 138), in the moderate stenosis group there was an agreement of 59% (0.623; p = 0.0128) and in the group with severe stenosis the agreement was 97% (0.944; p < 0.0001). All occlusions were correctly interpreted by spiral CT angiography (r = 1; p = 0.0082). CONCLUSION: The agreement of spiral CT angiography with DSA is good. Especially SCTA allows a good correlation in the severe stenosis group and in the occlusion group. DSA remains the standard of reference, because of its ability to demonstrate tandem lesions and collateral flow.

Adult↗
PubMed1984

Kynurenic acid as an antagonist of hippocampal excitatory transmission.

Kynurenate, an endogenous tryptophan metabolite, was bath-applied to hippocampal slices while recording extracellular synaptic field potentials. Kynurenate antagonized the medial and lateral entorhinal projections to dentate granule cells, the Schaffer collateral projections to CA1 pyramidal cells, and inputs to the CA3 stratum radiatum of regio inferior with similar potencies. Concentration-response curves for these pathways paralleled theoretical antagonist curves with a Hill coefficient of 1, and the KdS were in the range of 130-400 microM. Projections to the stratum lucidum of regio inferior were much less sensitive to kynurenate. Inputs to CA3 pyramidal cells showed varying sensitivities to kynurenate, L-2-amino-4-phosphonobutanoic acid (L-APB), and (-)-baclofen depending on the placements of the stimulating and recording electrodes. When both electrodes were located in area CA3, outside the hilus of area dentata, all responses were insensitive to inhibition by L-APB. Under these conditions, responses recorded within the stratum radiatum were sensitive to inhibition by kynurenate and baclofen, while responses recorded within the stratum lucidum were insensitive to these drugs. When the stimulating electrode was placed within the hilus of area dentata, variable patterns of sensitivity to APB, baclofen, and kynurenate were observed from recording electrodes in area CA3. These results suggest that stimulation in the hilus, while recording in the stratum lucidum, produces responses that show composite effects resulting both from direct stimulation of mossy fibers and from stimulation of neuronal elements in the hilus which produce outputs to mossy fibers.

Action Potentials↗
PubMed1989

[The diagnostic value of radionuclide inferior veno-cavagraphy in Budd-Chiari syndrome].

To evaluate the diagnostic value of radionuclide inferior veno-cavagraphy (RIVC) for Budd-Chiari Syndrome, RIVC using Tc99m was performed on 106 patients with massive ascites. A positive RIVC result was defined as having at least two of the three following criteria: (1) a delay of more than 4 seconds in visualizing the heart; (2) sharply truncated inferior vena cava with marked hang-up of isotope activity; and (3) extensive collateral circulation. Of the 106 patients, 18 were RIVC positive and were later confirmed by operation or contrast venography to have Budd-Chiari Syndrome with IVC obstruction. Of the remaining 88 RIVC negative patients, 3 were shown by operation, computerized tomography and cardiac echo, respectively, to be Budd-Chiari Syndrome with IVC obstruction. Thus, the diagnostic sensitivity and specificity of RIVC for this syndrome was 85.7% and 100% respectively. If RIVC is combined with hepatic scintigraphy, it will help to elucidate the anatomic and functional change of IVC, as well as, liver parenchymal disease, such as liver cirrhosis, hepatic tumor or hepatic vein obstruction. RIVC is a simple safe, accurate, noninvasive and reproducible procedure. This study confirms the high diagnostic specificity and sensitivity of RIVC. We therefore recommend RIVC as the first-line study for IVC patency. Contrast venography may be used as a confirmatory study in preparation for surgical intervention.

Adolescent↗
PubMedDate not supplied

[Computerized tomography of pancreatic tumors].

Few pancreatic carcinomas (5-22%) are resectable at the time of diagnosis because this lesion is seldom diagnosed in an early stage. A considerable improvement in the rate of survival is described only for resectable tumors: it is extremely necessary to find an imaging technique for early diagnosis and for accurate staging of pancreatic carcinoma to discern operable from inoperable cancer. The sensitivity of CT in predicting that pancreatic carcinoma is unresectable has been described as approaching 100%. However the reverse is not true. More than one third of the tumors revealed with CT and interpreted as resectable cannot be excised. The major reason for errors with CT are failure to detected liver metastases, peritoneal implants, lymph node involvement and encasement of the great vessels by tumor. Significant progress has recently been made to improve the detection of these details with the recent introduction of helical CT with infusion of a bolus of contrast material and thin section collimation. Traditionally, when a single sequence of images was acquired during abdominal CT, the time of the acquisition was dominated by the requirement to scan during maximal hepatic enhancement, which unfortunately may not be optimal for evaluation of the pancreas. With the advent of helical CT, the acquisition of two sets of images after infusion of contrast material is now possible; the first one takes place during the arterial enhancement; it is useful to detect tumor vascular encasement and the maximum difference of tissue attenuation between normal greater pancreatic enhancement and hypodense pancreatic mass, less vascularizated. It appears that the peak parenchymal enhancement achieved with helical CT may improve the sensitivity of CT scanning in detecting pancreatic carcinoma, especially small tumors confined within the organ. The second phase takes place during the venous or portal enhancement and provides useful information about venous encasement and hepatic metastasis. Extraglandular extension with invasion of adjacent major arterial (celiac axis or its branches, superior mesenteric artery) and venous (portal, splenic, superior mesenteric) appear as soft-tissue attenuation thickening obscuring the perivascular fat, with deformity, thrombosis or occlusion of the vessels. In cases of venous occlusion, collateral vein can be identified. Dilatation of the small veins that surround the head of the pancreas might be used as an additional criterion of extrapancreatic extension of neoplasia. With the features of spiral CT (contrast material optimization and continuous scanning), the detection of small lesions in the liver and peritoneal implants has been increased. Helical CT seems not to detect anything else about lymph node involvement than conventional CT, limited by the same morphologic criteria. The only CT means of detection of node involvement by pancreatic carcinoma is the pathologic enlargement of lymph nodes without specificity for neoplastic or not neoplastic ones. In many cases 2D, 3D and MIP imaging are helpful to evaluate vasculature encasement, especially for visualization of vessels which lie in oblique, coronal or sagittal plane. Consequently helical CT has the potential to become an alternative angiographic technique. Many studies have been done to evaluate spiral CT potential impact and to compare the value of this technique with other ones in the initial diagnosis and staging of pancreatic carcinoma. One of these studies compares dual-phase helical CT and endoscopic endo-sonography. The Authors observe that the two techniques do not differ significant statistically in detecting pancreatic carcinoma, except endoscopic sonography is more sensitive than helical CT for tumors smaller than 15-20 mm. They found the accuracy to predict unresectable carcinoma is 100% for dual-phase helical CT and less for endoscopic endosonography (86%). (ABSTRACT TRUNCATED)

Humans↗
PubMed2006

Unique combination of anatomy and physiology in cells of the rat paralaminar thalamic nuclei adjacent to the medial geniculate body.

The medial geniculate body (MGB) has three major subdivisions, ventral (MGV), dorsal (MGD), and medial (MGM). MGM is linked with paralaminar nuclei that are situated medial and ventral to MGV/MGD. Paralaminar nuclei have unique inputs and outputs compared with MGV and MGD and have been linked to circuitry underlying some important functional roles. We recorded intracellularly from cells in the paralaminar nuclei in vitro. We found that they possess an unusual combination of anatomical and physiological features compared with those reported for "standard" thalamic neurons seen in the MGV/MGD and elsewhere in the thalamus. Compared with MGV/MGD neurons, anatomically, 1) paralaminar cell dendrites can be long, branch sparingly, and encompass a much larger area; 2) their dendrites may be smooth but can have well defined spines; and 3) their axons can have collaterals that branch locally within the same or nearby paralaminar nuclei. When compared with MGV/MGD neurons, physiologically, 1) their spikes are larger in amplitude and can be shorter in duration; 2) their spikes can have dual afterhyperpolarizations with fast and slow components; and 3) they can have a reduction or complete absence of the low-threshold, voltage-sensitive calcium conductance that reduces or eliminates the voltage-dependent burst response. We also recorded from cells in the parafascicular nucleus, a nucleus of the posterior intralaminar nuclear group, because they have unusual anatomical features that are similar to those of some of our paralaminar cells. As with the labeled paralaminar cells, parafascicular cells had physiological features distinguishing them from typical thalamic neurons.

4-Aminopyridine↗
PubMed1990

Positron emission tomography and interventional cardiology.

Current noninvasive diagnostic techniques have limited accuracy for detection of coronary artery disease (CAD) in symptomatic and (particularly) asymptomatic patients with silent disease. Furthermore, no standard noninvasive method provides reliable diagnostic information on the location of the coronary arteries involved, the severity of stenosis, the presence of collaterals and myocardial viability. Based on greater than 1,000 cardiac studies at the University of Texas, cardiac positron emission tomography (PET) with either generator-produced rubidium-82, cyclotron-produced N-13 ammonia, or F-18 deoxyglucose is suitable for 4 routine diagnostic purposes: (1) noninvasive diagnosis of CAD in either symptomatic or asymptomatic subjects with a sensitivity of 95 to 98% and specificity of 95 to 100%. This accuracy is now sufficient to schedule diagnostic catheterization and multivessel angioplasty with surgical backup on the basis of the PET scan. At the University of Texas we carry out PET in asymptomatic and symptomatic patients to direct those with mild disease to cholesterol-lowering reversal therapy and those with severe disease to percutaneous transluminal coronary angioplasty (PTCA); (2) assessment of physiologic severity of coronary artery stenosis as compared to automated quantitative coronary arteriographic analysis. Changes in stenosis severity are followed before and after interventions including PTCA, bypass surgery, vasodilator drugs and cholesterol control regimens for reversal of coronary atherosclerosis; (3) imaging myocardial infarction, ischemia, viability, zone at risk and sizing of these pathophysiologic processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗
PubMed1996

Excitation of central and peripheral terminals of primary afferent neurons by capsaicin in vivo.

In three groups of rats discharge activity was recorded (i) from the peripheral stump of the cut saphenous nerve (saphenous-receptor preparation); (ii) from the central stump of the cut L4 or L5 dorsal root (dorsal root preparation); or (iii) from the peripheral stump of the saphenous nerve segment cut at both ends (axon preparation) during slow intraarterial infusion of capsaicin (30-300 micrograms/kg/min for 5 min) into the carotid artery. Capsaicin produced excitation, i.e. an increase in frequency of action potentials in the same dose range (100-300 micrograms/kg/min) in both the saphenous-receptor and dorsal root preparations, while the axon preparations remained unresponsive. In the cat, close arterial injection of capsaicin (up to 20 micrograms) into a collateral branch of the saphenous artery failed to evoke discharges in the saphenous axon preparation, although similar injection of 4-aminopyridine (60 micrograms), a K+ channel blocking agent was readily effective. These results indicate that after systemic application of capsaicin the peripheral and central endings of primary afferent neurons are equally important sites for activation and are much more sensitive to capsaicin than the axons of the nerve trunk.

Animals↗
PubMed1985

Anatomy and physiology of the neuroendocrine arcuate nucleus.

The arcuate nucleus surrounds the ventral part of the third ventricle and contains densely packed small neurons with 1-3 dendrites. At least fifteen transmitters and neuropeptides have been found in perikarya of arcuate neurons. Each transmitter and neuropeptide have a characteristic distribution. In many cases distributions overlap (for example, dopamine and somatostatin, dopamine and neurotensin, neuropeptide Y and somatostatin) and alpha-MSH and beta-endorphin seem to have identical distributions but there are also distinctive neuronal populations containing only one of the described transmitters or neuropeptides (neuropeptide Y and alpha-MSH). Studies show extensive colocalization of dopamine and neurotensin and sparse colocalization of dopamine and GABA, neuropeptide Y and FMRF-NH2 and neuropeptide Y and somatostatin. Colocalization does not seem to be the rule in the arcuate, however, it is possible that colocalization may vary with the physiological state or sex of the animal. It also should be noted that our techniques may not be sensitive enough. To study efferent projections as a possible organizing principle within the arcuate, retrograde fluorescent tracing was combined with transmitter and neuropeptide immunohistochemistry. Mainly NPY and alpha-MSH neurons were studied and both peptides are present in projections to the preoptic area as well as to the midbrain periaqueductal gray. Some arcuate neurons were found to have collateral axons to both these areas. The arcuate communicates primarily with the pituitary gland, hypothalamus, limbic system, midbrain periaqueductal gray and autonomic nuclei of the brain stem. In this way, the arcuate may be involved in integrating emotional, sensory, vegetative homeostatic and autonomic functions with endocrine functions.

Animals↗
PubMed1979

Muscular dystrophy in the mouse: neuromuscular transmission and the concept of functional denervation.

The results of recent investigations by ourselves and others indicate that no form of denervation exists to any remarkable degree in dystrophic mouse skeletal muscles. This conclusion is based on the following information: Dystrophic nerve terminals liberate normal amounts of transmitter both spontaneously and during impulse-mediated activity. The characteristics of the release process, the size of the available store of transmitter, and the probability of release of transmitter in response to the invasion of an action potential appear to be normal. The sensitivity of the postsynaptic membrane to the transmitter is normal. Action potential generation in response to both direct and indirect excitation is normal. There is no unequivocal pharmacologic evidence of denervation in dystrophic skeletal muscle, even though dystrophic muscle fibers respond to surgical denervation in a normal fashion. Nerve terminal sprouting is extensive, but there is no evidence of collateral reinnervation.

Action Potentials↗
PubMed1996

Matching anonymous pre-posttests using subject-generated information.

Sensitive research issues call for anonymous questionnaires. This makes accurately matching pretests with posttests difficult or impossible. Various subject-generated coding schemes have been developed, but their accuracy has been unknown. This anonymous study, with 745 students, used subject-generated coding to match pretests with posttests. The matching was verified for accuracy with the use of a collateral, anonymous, sticker identification system. The coding system was able to accurately match 75.2% of all the pretest-posttest pairs. An additional 22.1% of the pairs were left unmatched and only 2.7% were matched incorrectly. Subject-generated coding systems can be very effective where confidentiality is important to protect.

Adolescent↗
PubMed1998

[Sympathetic nervous system and pain: pathophysiological mechanisms].

Sympathetic postganglionic neurons may be involved in the generation of pain, hyperalgesia and neurogenic inflammation under pathophysiological conditions. Experiments on animal models show that two categories of influence of the sympathetic neuron on afferent neurons can be distinguished and this distinction seems to be related as to whether sympathetic-afferent coupling develops after nerve lesion or after tissue trauma with inflammation. (1) Peripheral nerve lesion generates plastic changes of the afferent and sympathetic postganglionic neurons. This may lead to chemical coupling between sympathetic and afferent neurons which may entail activation and/or sensitization of primary afferent neurons by the sympathetic neurons. The mediator is probably noradrenaline and the afferent neuron expresses or upregulates functional adrenoceptors. The coupling may occur at different sites of the primary afferent neuron, e. g., at the lesion site, remote from the lesion site in the dorsal root ganglion or between nonlesioned sympathetic and afferent neurons which show collateral sprouting. The biochemical signals which trigger these changes probably are neurotrophic substances and their receptors which are synthesized by the peripheral neurons, Schwann cells and other cells in response to the peripheral lesions. (2) Sympathetic nerve terminals in peripheral tissues may serve as mediator elements in hyperalgesia and during inflammation following tissue trauma without nerve lesion. This function is largely independent of activity in the sympathetic neurons and independent of vesicular release of transmitter substances. The signals are probably synthesized and released from the sympathetic terminal or in association with it and belong to the prostaglandins (probably PGE(2) or PGI(2)). Furthermore, nerve growth factor (NGF) has a hyperalgesic action in inflammation which is at least in part dependent on the sympathetic nervous system.

English Abstract↗
PubMed2002

Effects of temperature on the early stages of rat spinal motoneurone development in vitro.

Effects of temperature on rat spinal motoneurone morphogenesis during the early stages of development were investigated in vitro through a statistical morphometric analysis, and examined in the frame of a basic theoretical aggregation growth model. Morphological measurements in the 31.0-39.4 degrees C range revealed that: (1) primary neurite initiation was promoted by increased temperatures; (2) collateral branches formation was particularly enhanced over 37 degrees C; and (3) the elongation properties of all processes were not significantly altered. In parallel, an Arrhenius analysis proved that: (4) an activation energy of about 23 kcal/mol was required for primary neurites to emerge from a soma. These results suggest that the very first molecular events underlying neuritogenesis are rather sensitive to temperature and could imply both the transport and assembly properties of microtubules.

Animals↗