The in vitro synthesis of RNA within the rat nodose ganglion following vagotomy

Observational pilot study of patients with carpal tunnel syndrome treated with Nucleo CMP Forte™

AIM

Carpal tunnel syndrome (CTS) is a very common entrapment neuropathy characterized by pain and paresthesia in the territory of the median nerve. Although this syndrome has a considerable impact on the patient's quality of life, its medical treatment is far from optimal.

MATERIAL & METHODS

We performed an observational study to evaluate Nucleo CMP Forte^TM in patients with electromyography-confirmed, mild-moderate CTS. Pain was assessed using a visual analog scale, electromyogram and the SF-36.

RESULTS

Pain decreased significantly after 6 months. Quality of life improved significantly in the pain dimensions. No significant differences were observed in electromyographic findings. No adverse events were reported.

CONCLUSIONS

Nucleotides could prove useful for the nonsurgical treatment of CTS. Further studies are necessary to confirm this.

Type III sodium channel mRNA is expressed in embryonic but not adult spinal sensory neurons, and is reexpressed following axotomy

1. In situ hybridization with subtype-specific probes was used to ask whether there is a change in the types of sodium channels that are expressed in dorsal root ganglion (DRG) neurons after axotomy. 2. Types I and II sodium channel mRNA are expressed at moderate-to-high levels in control DRG neurons of adult rat, but type III sodium channel mRNA is not detectable. 3. When adult rat DRG neurons are examined by in situ hybridization 7-9 days following axotomy, type III sodium channel mRNA is expressed at moderate-to-high levels, in addition to types I and II mRNA that are present at relatively high levels. 4. To determine whether the expression of type III sodium channel mRNA following axotomy represents up-regulation of a gene that had been expressed at earlier developmental stages, we also studied DRG neurons from embryonic (E17) rats. In these embryonic DRG neurons, type I sodium channel mRNA is expressed at low levels, type II mRNA at high levels, and type III at high levels. 5. These results demonstrate altered expression of sodium channel mRNA in DRG neurons following axotomy, and suggest that in at least some DRG neurons, there is a de-differentiation after axotomy that includes a reversion to an embryonic mode of sodium channel expression. Different channel characteristics, as well as an altered spatial distribution of sodium channels, may contribute to the electrophysiological changes that are observed in axotomized neurons.

Cytochrome oxidase activity in vagal and glossopharyngeal visceral sensory neurons of the rat: effect of peripheral axotomy

Cytochrome oxidase (CO) activity, an endogenous metabolic marker, was examined in visceral sensory neurons of the rat nodose and petrosal ganglia by using enzyme histochemistry. In the normal nodose and petrosal ganglia, nerve cells showed various degrees of staining intensity. The population of darkly stained neurons in the nodose ganglion was higher than in the petrosal ganglion. Axotomy of the peripheral axons of these bipolar sensory neurons was used to study potential changes in ganglionic cellular metabolism associated with loss of afferent inputs and/or injury. Peripheral axotomy had a significant effect on CO activity in the nodose ganglion. By 3 days after axotomy, darkly stained neurons decreased in number and lightly stained neurons, which were not observed in the normal ganglion, appeared in the nodose ganglion. At 7 days after axotomy, the average population of these lightly stained neurons increased to 29% in the nodose ganglion. Subsequently, the population decreased so that at 14 days and 21 days, 19% and 7% respectively of neurons were stained lightly. Even at 28 days after axotomy, the lightly stained neurons were still observed. In the petrosal ganglion, no remarkable change was observed at any stage after axotomy. These results suggest that metabolic activity decreases in some nodose neurons after peripheral nerve section.

Axotomy alters putative neurotransmitters in visceral sensory neurons of the nodose and petrosal ganglia

Acute peripheral axotomy of the visceral sensory neurons of the vagus and glossopharyngeal nerves removes peripheral depolarizing and trophic influences to their sensory ganglia. To study axotomy-induced changes in the putative neurotransmitters of visceral sensory neurons, rats were sacrificed 1, 3, 7 or 14 days after transection of either the cervical vagus and superior laryngeal nerves (to affect peripheral axotomy of the nodose ganglion) or the glossopharyngeal and carotid sinus nerves (to affect peripheral axotomy of the petrosal ganglion). The numbers of tyrosine hydroxylase (TH)-immunoreactive (ir), vasoactive intestinal peptide (VIP)-ir, calcitonin-gene-related peptide (CGRP)-ir, and substance P (SP)-ir neurons in the respective ganglia were analyzed in axotomized and control ganglia. In the nodose ganglion, axotomy of the cervical vagus resulted in a rapid (by 1 day) reduction in the number of TH-ir cells, whereas VIP-ir neurons were dramatically increased in number by 3 days. CGRP- and SP-ir cells in the nodose ganglion were relatively unaffected by axotomy. In the petrosal ganglion, axotomy of the glossopharyngeal and carotid sinus nerves greatly reduced the number of TH-ir cells but did not alter the number VIP-ir neurons. CGRP- and SP-ir neurons in the petrosal ganglion were reduced in number by axotomy. Thus, axotomy of visceral sensory neurons differentially changed the content and perhaps the expression of putative transmitters. Differential changes were seen among transmitters in a single ganglia and between ganglia. These data demonstrate the plasticity of putative neurotransmitter systems in visceral afferent systems of adult rats.

Effects of advancing age on the central response of rat facial neurons to axotomy: light microscope morphometry

Following axotomy, the regrowth of peripheral axons takes longer in older individuals than in young ones. The present study compares central responses of facial motor neurons to a crush injury of the facial nerve in 3-month-old and 15-month-old male rats sampled through 28 days post-crush (dpc). Neuronal somata, nuclei, and nucleoli were measured in 30 microns brain stem sections within subdivisions of the facial nucleus that contain the cell bodies responsible for the movement of the vibrissae. The temporal patterns of change in the size of the three structures were interpreted with reference to the re-establishment of functional connections, i.e., the return of voluntary vibrissae activity, which is delayed by 4 days in the older animals relative to the younger ones. There was no age-related difference in the pattern of somal swelling and recovery, nor was there an age-related difference in the response of nuclei and nucleoli to axotomy through 4 dpc. Both nuclei and nucleoli increased in size in animals of both age groups, but after 4 dpc in the older animals nuclear enlargement was prolonged and the nucleolar increases were less robust compared to the younger animals. The greatest age difference appeared with the re-establishment of functional connections. In the 3-month-old animals, the resumption of whisker activity coincided with vigorous transient increases in the sizes of nuclei and nucleoli; in the 15-month-old animals, there was little nuclear response to functional recovery and a comparatively small increase in nuclear sizes.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphorylation of superior cervical ganglion proteins during regeneration

The incorporation of radioactive phosphate into proteins of both normal and regenerating ganglia of the sympathetic nervous system of the rat is reported. The incorporation reactions were carried out in vitro by incubating homogenates of excised ganglia with [gamma-32P]ATP under various conditions. It was found that incorporation of phosphate into proteins of regenerating ganglia in the molecular mass range 10,000-100,000 daltons increased up to 40% over incorporation into proteins from control ganglia during the first 3 days following injury and returned to control levels after 14 days. Analysis of the proteins by two-dimensional electrophoresis revealed that only few, i.e., less than 20, became radioactively labelled in homogenates of superior cervical ganglia in the presence of Ca2+, and even fewer in the presence of cyclic AMP. Furthermore, all these proteins fell within a narrow pI range of 4-6. The growth-associated protein, variously designated GAP-43, B-50, F-1, and pp46, has an enhanced level of expression and phosphorylation in regenerating ganglia compared with controls at day 3. Injury also caused consistently higher levels of incorporation into two other proteins with molecular masses at positions 55,000 and 85,000 and pI values of 5.1 and 4.5, respectively; the former protein most probably is beta-tubulin. The fact that both proteins are found in the 15,000 g pellet after the tissue has been solubilized in 0.5% nonionic detergent indicates that they may indeed by components of filament assemblies. Thus, the results suggest that protein phosphorylation is a mechanism involved in cytoskeletal function in regenerating nerve.

Morphological alterations in dorsal root ganglion neurons after peripheral axon injury: association with changes in metabolism

Axotomized rat sensory ganglion neurons have been shown to undergo rapid metabolic changes in the first 2 weeks after injury. The present study examined selected morphological features of these neurons over the same time period. Parameters studied included the position of the cell nucleus (eccentricity) and soma, nuclear, and nucleolar size over time periods primarily in the first 2 weeks after a unilateral crush injury of the sciatic nerve. Comparisons were made with normal ganglia and ganglia contralateral to the injury. The eccentricity of the nucleus in injured neurons was significantly altered within 1 day after injury and remained so over the entire time period studied. Alterations in neuron soma included an initial decrease in size at 1 day followed by a significant bilateral increase at 3 days after injury. Nuclear and nucleolar size changes were phasic with significant increases size peaking at 3-4 and 8-11 days after injury. These alterations coincided temporally with known changes in RNA synthesis occurring in these neurons after injury. Significant alterations in all parameters were observed on the uninjured side. Preliminary studies of the bilateral changes suggested that the trauma of the operation may be the major factor in this response. The data suggest that significant morphological alterations parallel the rapidly fluctuating change in neuronal metabolism after axon injury.

Reciprocal regulation of tachykinin- and vasoactive intestinal peptide-gene expression in rat sensory neurones following cut and crush injury

The relative abundance of preprotachykinin- (PPT), actin- and vasoactive intestinal peptide- (VIP) mRNA's was measured in L5 dorsal root ganglia of rats after resecting or crushing the sciatic nerve. PPT-mRNA levels fell to 40% of control values 3, 6 and 9 days following nerve resection. Crushing produced a lesser fall at 3 and 6 days with a partial recovery at 9 days. Following resection actin-mRNA levels transiently rose to twice control values and had returned to normal by day 9. VIP-mRNA was not detectable in control ganglia but increasing amounts of VIP-mRNA were present 3, 6 and 9 days after nerve injury. The results are discussed in terms of the control mechanisms operating.

Herpes simplex virus latent infection: reactivation and elimination of latency after neurectomy

Section of the sciatic nerve during the period of herpes simplex virus (HSV) latent infection was performed to evaluate residual latency in mouse dorsal root ganglion. In control mice without sciatic neurectomy, latency was present in 90-100%, while in those which underwent a neurectomy procedure, latent infection was surprisingly decreased to 28-50%. To investigate the hypothesis that the decrease of latency resulted from HSV reactivation and replication (with subsequent neuron destruction), groups of mice were treated with acyclovir to inhibit HSV reactivation, after having undergone a neurectomy procedure. Acyclovir treatment largely prevented the neurectomy-related elimination of latency and supported the hypothesized mechanism.

Differential effects of axotomy on immature and mature hamster facial neurons: a tritiated-uridine autoradiographic study

In this study, tritiated-uridine incorporation was autoradiographically examined following axotomy of hamster facial motor neurons (HFMN) at the critical development age of 15 days postnatal and in the adult. The postoperative times selected were 0.5, 1, 2, and 4 days. In the 15-day operative series, no changes in incorporation were observed at any of the postoperative times, except at 4 days postoperative, when there was a decrease in tritiated-uridine incorporation in the axotomized neurons relative to the controls. In the adult operative series there were no changes in incorporation at 0.5 or 1 day postoperative, relative to the controls. At 2 days postoperative in the adult, there was a transient increase in tritiated-uridine incorporation that returned to control levels by 4 days postoperative. When axotomized and control cytoplasmic/nuclear grain densities were compared, no changes were found in either operative series. These results of the time course of axotomy-induced changes in RNA synthesis in HFMN corroborate our previous findings of an age-dependent reactive sequence in HFMN and lend support to the hypothesis that the young neurons are synthesizing at peak capacity related to final growth and cannot be stimulated further by axotomy. As discussed, the transient increase in RNA levels in the adult, the lack of any changes in the rate of transfer of RNA from the nucleus to the cytoplasm, and the decrease in RNA levels in the 15-day neurons may be related to the presence of an unusual intranucleolar body within the nucleolus of HFMN that contains ribosomal precursors.

Effect of cutting or crushing the rat sciatic nerve on synthesis of substance P by isolated L5 dorsal root ganglia

Following cutting or crushing the rat sciatic nerve, synthesis of substance P by L5 dorsal root ganglia in vitro was reduced respectively to 20 and 40 per cent of control values. By day 64 the ability to synthesise substance P had been fully restored in crushed neurones but in cut neurones remained at a low level. We conclude that substance P synthesis is a more sensitive index of the effect of nerve injury than is substance P content and further that regenerating axons are able to support substance P synthesis before they reach their target tissue.

Incorporation of [32P]phosphate into nucleotides of the dorsal root ganglia of regenerating rat sciatic nerve

[32P]Phosphate incorporation into nucleotides of the dorsal root ganglia (DRG) was studied after a crush lesion of the rat sciatic nerve. DRG were labelled during a 2-h, in vitro incubation in a balanced salt solution containing [32P]orthophosphate, 1, 2, 4 and 8 days after the crush lesion. Nucleotides were analyzed by HPLC on an ion-exchange column. An increased incorporation of 32P was found in DRG of the injured nerve for all the studied time periods. This increase was unevenly distributed among the nucleotides. UTP, CTP and ADP showed the largest and most persistent increases in labelling. The specific activity of 4 analyzed nucleotides (ATP, ADP, UTP and CDP) remained constant in DRG from crushed nerves. Thus, the observed increase in 32P-labelling could not solely be due to an increased uptake of label but must also reflect an enhanced metabolism of nucleotides in regenerating DRG. The finding that alterations of nucleotide metabolism could be observed within one day after the crush lesion suggests that this response can be used as a valuable tool for studies of the initial events of regeneration.

The activity of neutral ribonucleases in nuclei of rat sympathetic ganglia and effects of nerve injury

Nuclei were isolated from homogenates of rat superior cervical ganglion by a conventional differential centrifugation technique with approximately 60% recovery. Ribonuclease activity at pH 7.1 (neutral ribonuclease) was associated with the "nuclei fraction" and represented 19% of the overall activity in normal ganglia. Ribonuclease in the "nuclei fraction" was stimulated variably by the sulfhydryl blocker N-ethylmaleimide indicating that a proportion was bound to the endogenous ribonuclease inhibitor present in these ganglia. The total activity of nuclear ribonuclease was increased 2-6 days after postganglionic nerve injury, such that the inhibitor-bound form of the enzyme increased maximally by 600% at day 4. The percentage of the total ganglionic activity in the "nuclei fraction" decreased in injured ganglia as a result of a rise in the activity of non-nuclear components. The changes in nuclear ribonuclease activity were distinct from those in the 850 g supernatant indicating that specific nuclear enzymes are being affected during regeneration.

Changes of ornithine decarboxylase activity in dorsal root ganglion cells after axon injury: possible relationship to alterations in neuronal chromatin

An autoradiographic technique was used to detect changes in ornithine decarboxylase in rat dorsal root ganglion neurons after sciatic nerve lesions. Binding of [3H]difluoromethylornithine ([3H]DFMO) to tissue sections of L5 ganglia was compared between axotomized and unoperated ganglia at 0.5, 1, 2, 3, 4, 5, 7, 8, 9, 11, 14, and 30 days after a crush lesion of the sciatic nerve. The [3H]DFMO binding to axotomized ganglion neurons was elevated compared with the unoperated side at 0.5, 1, 5, 7, 8, and 11 days postoperation. Enzymatic measurements of ornithine decarboxylase on ganglia at 1, 4, 8, and 9 days after sciatic nerve crush confirmed basic patterns of enzyme activity comparisons derived from autoradiography. Compared with patterns of [3H]actinomycin D binding to nuclei during the same periods after axotomy, [3H]DFMO binding increased prior to increases in [3H]actinomycin D binding within the first week. After that time, changes in both variables occurred in parallel. The data suggest that increased activities of ornithine decarboxylase or concentrations of polyamines may be linked to the induction of increased RNA synthesis in the early phases of the axon reaction.

Alkaline ribonuclease activity is increased in rat sympathetic ganglia after nerve injury

Ribonuclease activity at pH 7.1 ("alkaline" ribonuclease) was determined in homogenates of rat superior cervical ganglion up to 5 days after postganglionic nerve injury under optimal conditions of assay. Measurements were performed in the presence and absence of the sulfhydryl blocking agent, N-ethylmaleimide, to assess the proportion of "alkaline" ribonuclease apparently bound to endogenous inhibitor. Total ribonuclease activity per ganglion was stimulated 1.3 fold by 1 day after injury and remained elevated over the 5 day period. Free ribonuclease activity accounted for about 60% of the observed increase in total activity at day 1, but had returned to control level by day 3. At day 3 the entire 90% increase in total activity was attributable to ribonuclease bound to endogenous inhibitor (i.e. latent activity). These changes are occurring at times after nerve injury when marked alterations in RNA turnover have been observed, implicating "alkaline" ribonucleases in the control of RNA metabolism during nerve regeneration.

Ribonuclease activities in rat sympathetic ganglia: evidence for the presence of an endogenous inhibitor of alkaline ribonuclease

Using 3H-labeled rat brain mature RNA as substrate, substantial ribonuclease activity was detected in homogenates of rat superior cervical ganglia with acidic (pH 5.5) and neutral (pH 7.0-7.5) optima. Very little activity could be measured at greater than pH 8. The acidic and neutral activities differed in the optimal conditions required for assay, and showed differential sensitivity to the sulfhydryl blocking agent, N-ethylmaleimide. Only the neutral activity was stimulated, optimally by 2 mM N-ethylmaleimide, and the magnitude of stimulation indicated that the contributing ribonucleases exist largely in a latent form in the ganglion. Ribonucleases in other tissues with neutral pH dependence, known usually as "alkaline" ribonucleases, are subject to an N-ethylmaleimide-sensitive endogenous inhibitor protein. The existence of a similar inhibitor in rat superior cervical ganglia was indicated by the latency of neutral ribonuclease activity and confirmed by observing the effect of a soluble fraction from the ganglia on the activity of pancreatic ribonuclease A.

Sequential changes of sensory neuron (fluoride-resistant) acid phosphatase in dorsal root ganglion neurons following neurectomy and rhizotomy

Five to seven days after sciatic nerve section in rats, fluoride-resistant acid phosphatase (FRAP) expression in dorsal root ganglion (drg) neurons was markedly decreased. The decrease was in contrast to increased acid phosphatase which has been reported to occur in other neurons after nerve section. FRAP expression in ganglion neurons subsequently increased 14-21 days after nerve section; this preceded the restitution of enzyme expression in the spinal cord substantia gelatinosa. FRAP expression in drg neurons was not decreased after dorsal root section.

Alterations of [3H]actinomycin D binding to axotomized dorsal root ganglion cell nuclei: an autoradiographic method to detect changes in chromatin structure and RNA synthesis

An autoradiographic method was developed to quantify on a comparative basis the binding of [3H]actinomycin D (Act D) to the cell nuclei of frozen, unfixed sections of spinal sensory ganglia in rats. After a crush lesion of the sciatic nerve, alterations of [3H]Act D binding were found in L5 and L6 dorsal root ganglia which corresponded to changes in RNA synthesis observed in other studies. An increase in Act D binding was seen at 1 to 3 days postoperation, followed by a decrease at 5 to 7 days. By 9 to 11 days a second increase in binding occurred, followed by a decrease at 14 days. Contralateral ganglia exhibited an increase in Act D binding only at 5 days compared with unoperated controls. The timing of the response in axotomized ganglia differed with the distance of the lesion from the cell body. The observed patterns of Act D binding confirm that changes of chromatin structure are closely associated with the alterations of RNA and protein synthesis occurring after axon injury. The method may be useful as an indicator for alterations in RNA synthesis related to changes in chromatin structure in complex tissues.

Increased in vitro labeling of stable RNA within the rat nodose ganglion following abdominal vagotomy

An in vitro procedure for labeling of RNA in the excised rat nodose ganglion was used to evaluate the changes in incorporation of [3H]uridine into ganglionic RNA following transection of the abdominal vagus nerves. Significant increases in the incorporation into 28S, 18S and 4S RNA were observed at 1 day after injury, which were maximal at 4 days before returning to unoperated control level by 7 days. A second transient increase in the labelling of these RNA species occurred between 9 and 11 days after injury. Comparison of the time course of these increases with those seen previously following cervical vagus nerve crush injury indicate that the time of onset of the increase in incorporation in independent of the site of injury, but that the maximal response is delayed by 1 day with the more distal lesion. These data are consistent with the existence of separate signals for initiating and modulating the cell body response to axon injury, which are transported retrogradely from the site of injury at rates exceeding the slow component of axoplasmic transport.

Morphometric measurements and RNA content of axotomized feline cervical motoneurons

Microspectrophotometric estimates of RNA content and morphometric measurements of cytoplasmic, nuclear and nucleolar areas were made on 30 to 60 motoneurons (somal areas greater than 1000 microns2) ipsilateral and contralateral to brachial plexotomy performed unilaterally on adult cats 2-90 days before sacrifice. Nerve cells of unoperated animals were also assayed. Somal and cytoplasmic areas of axotomized motoneurons were larger than those of the corresponding, contralateral motor nerve cells 4, 6 and 75 days postoperatively. Because of between animal variability, it could not be determined, however, whether this difference was due to an increase in the area of the axotomized motoneurons or to a decrease in the area of the contralateral nerve cells. Nucleolar sizes did not change. In contrast, nuclei of axotomized motoneurons showed a temporary but unequivocal areal decrease. The cytoplasmic RNA content of axotomized motoneurons fell 14-28 days postoperatively but rose thereafter, being increased slightly but significantly 75-90 days after operation. At no postoperative interval, however, did the nucleolar RNA content of the axotomized cells deviate unequivocally from the unoperated or zero day condition. The following points may be emphasized: 1. these results differ from similar measurements of axotomized motoneurons of rodents and lagomorphs; 2. the data do not provide certain evidence of change in either morphometric parameters or RNA content of motoneurons on the side contralateral to surgery, although the possibility of a decrease in the size of these uninjured neurons should be considered; 3. morphometric and RNA measurements on axotomized peripheral (extrinsic) neurons of spinal anterior horn of cat contrast with similar measurements on axotomized central (intrinsic) neurons of cat red nucleus.

Uridine metabolism in the goldfish retina during optic nerve regeneration: whole retina studies

Accumulation of radioactivity from [3H]uridine in incubations of whole goldfish retinas is increased in the ipsilateral retina during a period of regeneration that follows unilateral optic nerve crush. Brief incubations to investigate the nature of enhanced labeling of the acid-soluble fraction showed a peak uptake 4 days following crush, with a gradual decrease to control levels by 21 days following crush. That nucleoside uptake may not mediate the effect is supported by the observation that the rate of uptake of 5'-deoxyadenosine, a nonmetabolizable nucleoside analog, is the same in post-crush (PC) and normal (N) retinal incubations. Following brief incubations of PC and N retinas with [3H]uridine, there is enhanced labeling in PC retinas relative to N retinas of recovered UMP, UDP, UTP, and uridine nucleotide sugars, whereas recovery of labeled uridine itself is slightly decreased. The results suggest that the increased accumulation of radioactivity in PC retinas following incubation with uridine reflects an increase in the activities of retinal uridine kinase and uridine nucleotide kinases.