Bradykinin-induced nociceptor sensitization to heat is mediated by cyclooxygenase products in isolated rat skin

Bradykinin can excite C-polymodal nociceptors and sensitize them to heat and it can also enhance prostaglandin synthesis, but it is unclear whether these effects are causally related. The role of cyclooxygenase products was investigated using two enantiomers of the cyclooxygenase inhibitor flurbiprofen of which S(+)- is more potent than R(-)-flurbiprofen. Single-unit activity was recorded from mechano-heat-sensitive, polymodal C-fibers in the isolated rat skin-saphenous nerve preparation. Bradykinin pretreatment (10 microM, 5 min) induced a 219 +/- 26% increase in the number of spikes evoked by noxious heat stimulation and a drop in the heat threshold by 5.2 +/- 0.6 degrees C in a fully reproducible manner. S(+)-flurbiprofen (1 microM) abolished the bradykinin-induced heat sensitization but did not alter the unconditioned heat response itself. Under R(-)-flurbiprofen (1 microM) bradykinin still induced a significant heat sensitization which was reduced by 33 +/- 21% (P = 0.11) of its previous extent; this effect may be due to the limited purity of the enantiomer preparation or to a cyclooxygenase-independent action of flurbiprofen. The heat sensitization suppressed by S(+)-flurbiprofen could be significantly restored (to 43 +/- 12%) by addition of PGE(2) plus PGI(2) (10 microM both) to bradykinin. Neither S(+)- nor R(-)-flurbiprofen had an influence on the magnitude of the excitatory effect of bradykinin. It is concluded that (i) cyclooxygenase products are the main mediators of nociceptor sensitization to heat following bradykinin treatment in the isolated rat skin; (ii) PGE(2)/I(2) are essential but perhaps not the only relevant cyclooxygenase products involved and (iii) neither S(+)- nor R(-)-flurbiprofen inhibit the unconditioned noxious heat response and the excitatory bradykinin response of the polymodal C-nociceptors.

The neprilysin family in health and disease

The mammalian neprilysin (NEP) family comprises at least seven members: NEP itself, Kell blood group antigen (KELL), the endothelin-converting enzymes (ECE-1 and ECE-2), the enzyme PEX, associated with X-linked hypophosphataemia, "X-converting enzyme" (XCE) a CNS-expressed orphan peptidase and a soluble, secreted endopeptidase (SEP). These zinc metallopeptidases are all type II integral membrane proteins. Where identified, these enzymes have roles in the processing or metabolism of regulatory peptides and therefore represent potential therapeutic targets. A distinct feature of ECE-1 species is their existence as distinct isoforms differing in their N-terminal cytoplasmic tails. These tails play a role in enzyme targeting and turnover with di-leucine and tyrosine-based motifs affecting localization. Additional anchorage of these enzymes can also occur through palmitoylation. Bacterial homologues of the neprilysin family exist, for example the products of the pepO genes from L. lactis and S. parasanguis, and a recently described gene product of P. gingivalis which is an ECE-1 homologue that can catalyse the conversion of big endothelin to endothelin. A genomics based approach to understanding the functions of this proteinase family is aided by the completion of the C. elegans and Drosophila genomes, both of which encode multiple copies of NEP-like enzymes.

COX-2 in brain and spinal cord implications for therapeutic use

Following the discovery of inducible COX-2 in arthritic joint fluid and immunocompetent cells a revolution in the field of antiinflammatory treatment was expected. The detection of a constitutive COX-2 in the kidney, in stomach and central nervous system destroyed this hypotheses. Further experiments in animal models were done to elucidate the role of the constitutive COX-2 in different physiological and pathophysiological states. In central nervous system was shown that the constitutive COX-2 is the predominant isoform of cyclooxygenases in brain and spinal cord and is highly regulated by different mediators. After experimental induction of peripheral inflammation a significant induction of COX-2 gene, protein expression and synthesis of prostaglandins in the spinal cord was detected. It was concluded that COX-2 is strongly involved in pain mediation processing in the spinal cord. The detection of COX-2 in the brain endothelial cells and its role in fever led to new insights of development and time course of temperature elevation. Probably, the use of selective COX-2 inhibitors decreases fever more effective than classical antipyretics. Furthermore, newer results show a role of COX-2 in differentiation and maturation processes in brain. These findings implicate new ways for the treatment of Alzheimer's disease and other degenerative brain disorders. Clinical and experimental results with selective COX-2 inhibitors show a better safety profile than non-selective COX inhibitors. The clinical use after drug registration will be decide on the further role of this new class of drugs in analgesic/antiinflammatory therapy and on new fields of clinical use.

Spinal cyclooxygenase-2 is involved in development of allodynia after nerve injury in rats

Increased spinal cyclooxygenase activity is associated with nociception induced by tissue inflammation. In the present study, we examined the changes of cyclooxygenase-1 and cyclooxygenase-2 protein expression in several regions of the CNS associated with pain perception, and the role of spinal cyclooxygenase activity in the development of allodynia following nerve injury. Allodynia was induced by ligation of the left L5 and L6 spinal nerves in rats. Using western blot analysis, we found that the cyclooxygenase-2 protein levels in the dorsal spinal cord and thalamus (but not in the ventral spinal cord, cingulate cortex and locus coeruleus) increased significantly one day after nerve ligation, compared with those in the sham animals. The cyclooxygenase-2 protein levels in the above tissues were similar in nerve-injured and sham animals three and 14 days after surgery. In contrast, cyclooxygenase-1 protein was not detectable in any of the neural tissues examined one, three, and 14 days after nerve injury. In the behavioral experiments, we observed that intrathecal injection of 100microg of indomethacin immediately or one day after nerve ligation attenuated the development of tactile allodynia. However, intrathecal injection of indomethacin had no effect on established allodynia two weeks after nerve injury.Collectively, our results suggest that cyclooxygenase-2 is preferentially up-regulated in the dorsal spinal cord and thalamus in response to nerve injury in rats. Spinal cyclooxygenase-2 probably plays an important role in the early development, but not in the maintenance, of tactile allodynia caused by the nerve injury in this rat model of neuropathic pain.

Novel mutation in the CPT II gene in a child with periodic febrile myalgia and myoglobinuria

We have identified a novel missense mutation in the carnitine palmitoyltransferase II (CPT II) gene in a child with CPT II deficiency characterized clinically by episodes of myalgia and myoglobinuria induced by intercurrent febrile illnesses. The patient was heterozygous for a G-to-A substitution at codon 487, changing an encoded glutamic acid to a lysine (E489K), while the other allele carried the common S113L mutation. This case enlarges the spectrum of mutations in patients with CPT II deficiency, and confirms the association of the S113L mutation with the muscular form.

[Clinical experience with rhenium-188 HEDP therapy for metastatic bone pain]

Rhenium-188 hydroxyethylidene diphosphonate (Re-188 HEDP) is a new radiopharmaceutical for treatment of metastatic bone pain. Re-188 is a generator-produced radionuclide emitting high energy beta and gamma rays and having a relative short physical half-life makes it of especially interesting for therapeutic purpose. Seven patients (pts) with multiple painful bone metastases were treated with Re-188 HEDP. Five pts with prostate cancer and 2 pts with breast cancer received a fixed activity of 3000 MBq of Re-188 HEDP intravenously in two steps. Complete blood counts were determined, blood chemistry examinations and urine-analysis were performed before and 1, 2, 3, 4, 6, 8, 12 weeks following the treatment. A visual analogue score, a verbal rating scale, the Spitzer index and the Karnofsky score were used to assess pain and performance status. Three hours after Re-188 HEDP administration at 1 m from the anterior mid-trunk of the pts gamma and at the patient body surface beta-radiation dose measurements were made, together with urine radioactivity measurements. Three pts become pain-free, 2 pts exhibited partial pain improvement and 1 patient gave no response to the Re-188 HEDP therapy. In 1 patient due to central nervous system metastasis the modification of the pain intensity could not be evaluated. Three pts displayed a flare reaction within 1 week after the treatment. Transient decreases in platelet and white blood cell counts were observed. There were no significant changes in the liver and renal functions. Radiation dose rate values of 6.3 +/- 1.0 microSv/h for gamma, and of 183 +/- 40 s-1 for beta-radiation were found. 25-32% of the administered dose was eliminated via the urinary tract in the first three hours. The preliminary data suggests that Re-188 HEDP is an effective radiopharmaceutical in treatment for metastatic bone pain. An administered activity of 3000 MBq can bring about a pain reduction without causing any clinically significant bone marrow toxicity.

Heme oxygenase type 2 plays a role in formalin-induced nociception

Although much attention has been focused in recent years on nitric oxide synthase (NOS) as an enzyme intimately involved in many types of nociceptive signaling, the enzyme heme oxygenase (HO) has received little attention. Yet, HO produces gaseous second messenger molecule CO which, like NO, has proven to be an important neurotransmitter in the CNS. In these studies we provide detailed evidence that HO activity is critical to formalin-induced licking behavior in mice. The HO inhibitor tin protoporphyrin (Sn-P) dose-dependently reduced formalin-stimulated licking behavior in both phases of the formalin assay. This apparent analgesic effect was unlikely due to the non-specific effects of this agent as Sn-P did not alter rotarod performance, and the blood-brain barrier impermeant HO inhibitor zinc protoporphyrin (Zn-P) had little effect on licking times. We also hypothesized that heme oxygenase type 2 (HO-2) was the specific isoform of HO involved in nociception. Mice with a targeted disruption of the HO-2 gene were found to have greatly reduced licking times. Furthermore, Sn-P did not further reduce licking times when administered to HO-2 knockout animals. Taken together our evidence indicates that HO plays an important role in nociceptive signaling related to inflammatory-type pain, and that HO-2 is the isozyme mediating this nociception.

Inhibition of inducible nitric oxide synthase in persistent pain

The present study was undertaken to investigate the role of inducible nitric oxide synthase in a rat model of persistent pain. The effects of L-N6 (1-iminoethyl) lysine (L-NIL), a relatively potent and relatively selective inhibitor of inducible nitric oxide synthase, were investigated in carrageenan induced hyperalgesia L-NIL (0.1 microMole) injected intraplantar or intrathecal markedly enhanced carrageenan induced hyperalgesia. These effects were reversed during the third hour by co-administration of L-arginine (900 mg/kg i.p.) but not D-arginine. Methylene blue (MB), a soluble guanylate cyclase inhibitor, administered intrathecally (0.1 microg) had no effect on L-NIL potentiation of carrageenan hyperalgesia but abolished antinociception induced by L-arginine. Obtained results suggest that nitric oxide derived from inducible nitric oxide synthase play an inhibitory role in carrageenan produced hyperalgesia in rat.

The prevalences of cytochrome c oxidase negative and superpositive fibres and ragged-red fibres in the trapezius muscle of female cleaners with and without myalgia and of female healthy controls

The association of cytochrome c oxidase negative fibres (COX-negative) and ragged-red fibres (RR-fibres) with work related trapezius myalgia has been proposed. Hitherto studies have been small or without control groups. The aim of the present study was to investigate the prevalences of RR-fibres and COX-negative fibres in female cleaners with (n=25) and without (n=23) trapezius myalgia and in clinically healthy female teachers (n=21). The cleaners did mainly floor cleaning requiring monotonous loading on the trapezius muscle. A questionnaire covering background data and aspects of pain (prevalence, duration, intensity and influence on daily living) was answered. Biopsies were obtained from the trapezius muscle by an open surgical technique. The three groups did not differ in prevalence of COX-negative or COX-superpositive (i.e. type-I fibres with extremely strong brownish reaction in both the COX and SDH/COX stainings) fibres. The prevalence of COX-negative fibres was age dependent. Two subgroups of RR-fibres were present when stained for COX; COX-negative (73%) and COX-superpositive (26%) fibres. Forty-two percent of the COX-negative fibres were RR-fibres and 79% of the COX-superpositive were RR-fibres. A significantly (P=0.002) higher proportion of the COX-superpositive fibres in the cleaners were RR-fibres compared to the teachers. Multivariate regression analysis revealed that age, occupation as cleaner and a tender point in the trapezius were significantly associated with increased prevalences of RR-fibres; a cleaner with a tender point had a 4.35 higher prevalence of RR-fibres compared to a teacher without a tender point. No correlations between other pain related variables and prevalence of RR-fibres were noted. In conclusion, RR-fibres but not COX-negative or COX-superpositive fibres were correlated with cleaning work tasks and with a tender point in the trapezius.

Functional interplay between gelatinases and hyperalgesia in endotoxin-induced localized inflammatory pain

The role of ECM-degrading proteinases in normal developmental processes and in pathological conditions is extensively studied. However, few reports describe the role ECM-degrading proteinases play in modulating hyperalgesia. The goal of this study is to describe the regulation of gelatinases during endotoxin mediated local inflammation, induced by intra plantar endotoxin (ET; 1.25 microg/50 microl) injection in Balb/c mice, and to correlate that with hyperalgesia. ET injections induced hyperalgesia, as determined by hot plate and paw pressure tests, which peaked by 24 h and recovered by 48 h post-injection. Contralateral paw of ET injected mice and saline injected paws in control mice elicited no hyperalgesia. Zymography showed that ET and saline injected paws elicited increased gelatinase activity by 9 h after injection. However, only the former maintained high levels of expression of a 90 kD gelatinase up to at least 96 h post ET injection, while in the latter gelatinase expression was down regulated by 24 h. Interestingly, the 90-kD gelatinase was upregulated in the contralateral paw of the ET-injected mice beyond 48 h post injection. Saline injection in that paw, during a time when gelatinases are upregulated, induced hyperalgesia. Intraperitoneal injection of either ZnCl(2) (100 microM), thymulin (5 microg/100 microl), or morphine (2 mg/kg/100 microl) reversed the ET-induced hyperalgesia and suppressed gelatinase activity. Furthermore, intraperitoneal injection of MPI, an ECM-degrading proteinase inhibitor, reversed ET induced hyperalgesia. Taken together, the above suggests that a functional interplay exists between gelatinase upregulation triggered by ET injections and hyperalgesia. The exact mechanism underlying such correlation remains to be determined.

Analgesic and anti-inflammatory effects of phosphodiesterase inhibitors

The aim of the present study was to investigate the role of phosphodiesterase (PDE) enzyme inhibitors namely rolipram and theophylline in pain and inflammation in experimental animals. Rolipram, a selective PDE IV inhibitor and theophylline a nonspecific PDE inhibitor exerted dose dependent analgesic and anti-inflammatory effect against acetic acid-induced writhing in mice and carrageenan-induced paw edema in rats, respectively. Nimesulide (1, 2 mg/kg) produced significant anti-inflammatory effect. Further, nimesulide (0.5 mg/kg) potentiated analgesic effect of rolipram but it failed to modulate the anti-inflammatory effect of PDE inhibitors. Present study suggests that PDE enzymes might be playing a role in nociceptive and inflammatory responses in animals.

Neuronal nitric oxide synthase mRNA upregulation in rat sensory neurons after spinal nerve ligation: lack of a role in allodynia development

Pharmacological evidence suggests a functional role for spinal nitric oxide (NO) in the modulation of thermal and/or inflammatory hyperalgesia. To assess the role of NO in nerve injury-induced tactile allodynia, we examined neuronal NO synthase (nNOS) expression in the spinal cord and dorsal root ganglia (DRG) of rats with tactile allodynia because of either tight ligation of the left fifth and sixth lumbar spinal nerves or streptozotocin-induced diabetic neuropathy. RNase protection assays indicated that nNOS mRNA (1) was upregulated in DRG, but not spinal cord, neurons on the injury side beginning 1 d after nerve ligation, (2) peaked (approximately 10-fold increase) at 2 d, and (3) remained elevated for at least 13 weeks. A corresponding increase in DRG nNOS protein was also observed and localized principally to small and occasionally medium-size sensory neurons. In rats with diabetic neuropathy, there was no significant change in DRG nNOS mRNA. However, similar increases in DRG nNOS mRNA were observed in rats that did not develop allodynia after nerve ligation and in rats fully recovered from allodynia 3 months after the nerve ligation. Systemic treatment with a specific pharmacological inhibitor of nNOS failed to prevent or reverse allodynia in nerve-injured rats. Thus, regulation of nNOS may contribute to the development of neuronal plasticity after specific types of peripheral nerve injury. However, upregulation of nNOS is not responsible for the development and/or maintenance of allodynia after nerve injury.

Continuous propofol administration for suxamethonium-induced postoperative myalgia

The effect of continuous propofol administration on creatine kinase and suxamethonium-induced postoperative myalgia was evaluated in 50 patients randomised into two groups of 25 patients each. Induction of anaesthesia was identical in all patients. Anaesthesia was maintained with 66% nitrous oxide in oxygen supplemented by either isoflurane 1% or continuous propofol. Creatine kinase was measured before and after operation. Myalgia was evaluated postoperatively by a blinded observer. The median level of myalgia was reduced significantly in the continuous propofol group (p = 0.011). The median creatine kinase value increased significantly in the isoflurane group (from 90 to 160 IU, p = 0.001).

Local expression of inducible nitric oxide synthase in an animal model of neuropathic pain

Peripheral nerve injury is associated with local inflammation and neuropathic pain. In this study we investigated the local expression of the inducible isoform of nitric oxide synthase (iNOS) following a chronic constriction injury (CCI) to the sciatic nerve, a rat model of neuropathic pain. Western blot analysis and immunohistochemical co-localization methods were used to identify temporal and spatial expression of iNOS and its cells of origin. Changes in mRNA were analyzed by RT-PCR and iNOS specific primers. We report that CCI injury induced local iNOS expression in both macrophages and Schwann cells within and distal to the injury site. The local increase in iNOS mRNA expression paralleled both the temporal and spatial protein expression. This study supports the hypothesis that CCI is associated with a local inflammatory reaction mediated at least in part by iNOS. Local activation of the iNOS-NO system may play an important role in the pathogenesis of peripheral nerve injury and neuropathic pain.

Induction of cyclooxygenase-2 causes an enhancement of writhing response in mice

Pretreatment of mice with lipopolysaccharide for 16 h enhanced the number of acetic acid-induced writhing reactions by 2 to 3-fold. In the peritoneal exudates at 10 min after acetic acid injection, 6-keto-prostaglandin F1alpha was detected as a major prostanoid, and this level increased by several-fold by the pretreatment with lipopolysaccharide. The writhing reaction and the prostaglandin formation were almost completely suppressed by indomethacin. However, the lipopolysaccharide-induced enhancement of writhing reaction and an increment of 6-keto-prostaglandin F1alpha level were diminished by the administration of cyclooxygenase-2-selective inhibitors, such as NS-398, nimesulide, or L-745337, to a level similar to the mice that did not receive lipopolysaccharide. Cyclooxygenase-2 protein in the exudates became detectable at 5-48 h after the lipopolysaccharide-pretreatment. These results suggest that the increased prostaglandin production by cyclooxygenase-2 could be responsible for enhancement of the acetic acid-induced writhing reaction by lipopolysaccharide pretreatment.

[Effect of contrical on proteolytic enzymes of blood serum in acute emotional-pain stress]

General proteolytic and antitryptic blood serum activity in acute emotionally-painful stress was investigated as well as that on the background of the before injected contrical. It was determined that in case of a stress there increases the general proteolytic activity of blood serum and at the same time antiproteolytic activity decreases. The coefficient of the relation of antiproteolytic activity to proteolytic activity of blood serum in case of a stress may become of 50% of the control. The introduction of inhibitor of proteinase contrical before the beginning of stressor influence promotes the decrease of general proteolytic activity to the level of the control indexes.

Differential effect of selective cyclooxygenase-2 (COX-2) inhibitor NS 398 and diclofenac on formalin-induced nociception in the rat

Prostaglandins (PGs) are known to be involved in inflammatory and nociceptive processing. Since the discovery of at least two isozymes of cyclooxygenase (COX), inhibition of COX-2 has been suggested to be responsible for the therapeutic effects of nonsteroidal anti-inflammatory drugs (NSAIDs). In the present study, the effects of a rather selective COX-2 inhibitor, NS-398 (0.3-27 mg/kg i.p.), were studied using the rat formalin test as a model of acute nociception. Diclofenac (non-selective COX inhibitor; 0.3-27 mg/kg i.p.) was used as a control. NS-398 revealed antinociceptive activity only at a dose (27 mg/kg) which results in plasma concentrations which most likely do not selectively inhibit COX-2. By contrast, diclofenac inhibited formalin-induced flinching behaviour over the whole dose range tested. Our results suggest that PGs mediating nociception in the formalin test of the rat are most likely produced via the COX-1 as well as COX-2 pathways. Thus, in an acute model of nociception a non-selective COX inhibitor may offer advantages as compared to a selective COX-2 inhibitor.

Structural changes in male trapezius muscle with work-related myalgia

Muscular changes in male forest machine operators with work-related neck and shoulder myalgia were studied. Enzyme cyto- and immunohistochemical analysis was carried on muscle biopsies obtained from ten myalgic subjects (M), nine non-myalgic selected in the same work place (NM) and six healthy young men (C). The M group displayed a significant increase in type IIA fibres in comparison to the C group. This hypertrophy was accompanied by a parallel increase in the capillary bed. Both the M and NM groups exhibited an increase in fibres with a disorganised mitochondrial pattern. Interestingly, fibres lacking cytochrome c oxidase occurred in the M group (0.9%) but also in the NM group (0.5%), suggesting a mitochondrial defect. Central nuclei (5.2%) and developmental myosin (3%) were also more frequent in the M group. These changes are probably related to injury-regeneration cycles. These data support the association between the work conditions and muscle changes in work-related trapezius myalgia.

[Changes in aminopeptidase N located on neutrophils derived from patients with chronic pain]

It is known that aminopeptidase N (APN) and neutral endopeptidase (NEP) in the central nervous system (CNS) regulate opioid peptides, leading to pain modulation. To examine whether these enzymes located on human neutrophils (PMNs) play a role in several modalities of pain, we measured the activity of these enzymes located on PMNs derived from patients with chronic pain and compared this with that of healthy volunteers. APN activity in the group of patients with chronic pain was significantly increased compared with that in group of healthy volunteers (4.25 +/- 0.17, n = 36 vs 3.53 +/- 0.21, n = 24, nmol.min-1.10(6) cells, P > 0.05, mean +/- SE). But NEP activity showed no differences in two groups. These results suggest that APN located on PMNs from patients with chronic pain may act as an indicator of continuous painful condition and there may be a pain-modulating system in the blood.

Drug interactions in human neuropathic pain pharmacotherapy

Current practice predicates the use of multiple drug combinations in the treatment of neuropathic pain. These combinations may be required because of multiple pain symptoms directly arising from neuropathic pathology, other symptoms attributable to the chronicity and severity of the patient's pain or conditions unrelated to their pain. A fear exists that combination drug use or the addition of a new drug to a therapeutic regimen may lead to increased drug toxicity or decreased efficacy. Many of the drug interactions of significance to neuropathic pain physicians involve the cytochromes P450 2D6 and 3A3/4 isoenzymes. Drug interactions should be more predictable based on the knowledge of which compounds induce, inhibit or are metabolized by specific cytochrome P450 enzymes. Mechanisms of induction or inhibition of biotransformation via the P450 hepatic enzyme system are discussed and various inducers, inhibitors and substrates relating to neuropathic pain pharmacotherapy are listed.

The potential role of spinal cord cyclooxygenase-2 in the development of Freund's complete adjuvant-induced changes in hyperalgesia and allodynia

Chronic inflammatory conditions produce a state of hyperalgesia which is evident from a few hours to days after administration of an inflammatory stimulus. The molecular mechanisms involved in the initiation of hyperalgesia are not well understood and in this study we have investigated the role of prostaglandins in this process in the rat. Unilateral intraplantar injection of Freund's complete adjuvant produces an immediate localized swelling (oedema) with the development of altered pain responses in the ipsilateral paw such as a reduced threshold to noxious stimuli (hyperalgesia) and lowered thresholds such that normally innocuous stimuli produce a pain response (allodynia). We have monitored levels of cyclooxygenase messenger RNA and prostaglandins in lumbar spinal cord in parallel with these behavioural responses (oedema, hyperalgesia and allodynia) and identified a marked increase in cyclooxygenase-2 messenger RNA (3-fold), maximal at 2-4 h after Freund's complete adjuvant, followed by a significant increase in 6-keto prostaglandin F1alpha and prostaglandin E2 which is maximal by 8 h. Pretreatment of animals with the unselective cyclooxygenase inhibitor indomethacin attenuated oedema (approximately 40%) and allodynia (80-100%), but had no effect on the development of mechanical hyperalgesia. Pretreatment with the cyclooxygenase-2 selective inhibitors DuP 697, flosulide and SC58125 also attenuated allodynia (by 80-100%) but had no effect on the development of oedema or mechanical hyperalgesia. The marked increase in cyclooxygenase-2 messenger RNA in the lumbar spinal cord following intraplantar Freund's complete adjuvant suggests that the cyclooxygenase enzyme and its product may have a role in the adaptive response that occurs in the lumbar spinal cord during a peripheral inflammatory reaction. Pharmacological analysis reveals that prostaglandins are directly involved in the development of allodynia. However, these studies show that the development of mechanical hyperalgesia does not require the production of prostaglandins indicating that more than one pathway mediates the altered pain responses associated with a peripheral inflammatory lesion.

Elevated plasma vasopressin and normal cerebrospinal fluid angiotensin-converting enzyme in chronic pain disorder

The study was performed proceeding from the hypothesis that pain proneness in chronic pain disorder (CPD) is a result of alterations in central mechanisms regulating pain sensations. To elucidate the function of the central renin-angiotensin system, the levels of angiotensin-converting enzyme (ACE) and arginine vasopressin (AVP) in cerebrospinal fluid (CSF) and peripheral blood were measured in 15 CPD patients and 19 healthy controls. Plasma AVP levels (p = .01) as well as the serum osmolality (p = .01) were significantly higher in the CPD group. No significant differences in CSF ACE levels were found. AVP is a stress-related peptide, but central antinociceptive effects have also been reported. Elevated plasma AVP levels possibly may constitute a response to chronic stress.

Induction of spinal cord neuronal nitric oxide synthase (NOS) after formalin injection in the rat hind paw

The nitric oxide synthase (NOS) inhibitor L-nitroarginine methyl ester has been found to exhibit antinociceptive activity in a rat model of pain [Kitto, K.F. et al., Neurosci. Lett., 148 (1992) 1-5; Lee, J.H. et al., NeuroReport, 3 (1992) 841-844; Moore, P.K. et al., Br. J. Pharmacol., 102 (1991) 198-202]. We investigated the hypothesis that hind paw injection of formalin increases the number of dorsal horn neuronal nitric oxide synthase (nNOS) containing neurons. Results showed a bilateral increase in the number of nNOS-positive neurons at the L4-5 dorsal horn area following formalin injection. The increase was always greater on the ipsilateral side compared to the contralateral side. This upregulation of nNOS following formalin stimulation of the hind paw suggested that nitric oxide (NO) may play a role in the central mechanism of hyperalgesia that follows peripheral inflammation.

Investigation by polymerase chain reaction of enteroviral infection in patients with chronic fatigue syndrome

1. Chronic fatigue syndrome is characterized by muscle fatigue and pain at rest, symptoms which are usually exacerbated with exercise. Although various studies have shown minor, non-specific morphological and biochemical changes in muscle of patients with chronic fatigue syndrome, no consistent defect has been identified. Some have suggested that an enteroviral infection in muscle may cause the chronic muscle fatigue seen in patients with chronic fatigue syndrome, with acute infection directly and irreversibly impairing mitochondrial function, and persistent infection depressing muscle protein synthesis and metabolism. 2. To clarify the involvement of enterovirus infection in chronic fatigue syndrome, muscle biopsies from a group of patients with chronic fatigue syndrome were examined for the presence of enteroviral RNA by reverse transcriptase-polymerase chain reaction techniques in relation to functional studies of muscle mitochondria and the muscle RNA/DNA ratio. 3. Fifty-eight percent of patients reported an uncharacterized 'viral infection' before the onset of their illness, but none of the muscle samples from 34 patients contained detectable amounts of enteroviral RNA. Muscle tissue had a general reduction in the RNA/DNA ratio and mitochondrial enzyme activities with no specific abnormality in the activity of enzymes encoded partially on the mitochondrial genome (cytochrome-c oxidase) or nuclear genome (citrate synthase, succinate reductase). 4. These data provide no evidence of an enteroviral infection in muscle of patients with chronic fatigue syndrome, although this does not exclude a role of enterovirus in initiating the disease process. The general reduction in RNA/DNA ratio and mitochondrial enzyme activities is consistent with a general reduction in habitual activity.

Mitochondrial DNA deletions in muscle fibers in inclusion body myositis

Inclusion body myositis (IBM) is an autoimmune, inflammatory myopathy where morphological changes of muscle, including ragged red fibers, have indicated mitochondrial dysfunction in some muscle fibers. In this study enzyme histochemical analysis showed that cytochrome c oxidase (COX)-deficient muscle fibers were present at a frequency ranging from 0.5 to 5% of the muscle fibers in a series of 20 IBM patients. In age-matched controls, only occasional COX-deficient muscle fibers were present. Polymerase chain reaction (PCR) analysis of DNA extracted from muscle tissue of the IBM patients showed multiple mtDNA deletions. PCR analysis of isolated, single muscle fibers showed presence of mtDNA with only one type of deletion and deficiency of wild-type mtDNA in each COX-deficient muscle fiber. This finding was supported by results from in situ hybridization using different mtDNA probes on consecutive sections. A 5 kb deletion was identified in all 20 IBM patients. DNA sequencing of the breakpoint region showed that this deletion was the so-called "common deletion." Most but not all of the investigated deletion breakpoints were flanked by direct repeats. COX-deficient fibers were more frequent among fibers with positive immunostaining with antibodies directed toward a regeneration marker, the Leu-19 antigen, than in the entire fiber population. These results show that COX deficiency in muscle fiber segments in IBM is associated with deletions of mtDNA. Clonal expansion of mtDNA with deletions may take place in regenerating muscle fibers following segmental necrosis.

Influence of emotional-algic stress on the activity of carboxypeptidase H--an enzyme involved in processing rat brain neuropeptides

It was established that the activity of carboxypeptidase H increases in divisions of the brain of rats during a one-time emotional-algic stress. The most substantial increase in the activity of the enzyme is observed in the hypophysis and the hypothalamus. The changes in activity were less marked with chronic emotional-algic stress. The involvement of carboxypeptidase H in the development of stress reactions, as well as the possibility of the participation of the soluble form of the enzyme in the processing of secretory peptides, and of the membrane-bound form in the processing of neuropeptides with a central action, is hypothesized.

Pharmacological and biochemical demonstration of the role of cyclooxygenase 2 in inflammation and pain

Nonsteroidal antiinflammatory drugs (NSAIDs) are widely used for the treatment of inflammatory diseases, but significant side effects such as gastrointestinal erosion and renal damage limit their use. NSAIDs inhibit the enzyme cyclooxygenase (COX), which catalyzes the conversion of arachidonic acid to prostaglandins (PGs) and thromboxane. Two forms of COX have been identified--COX-1, which is constitutively expressed in most tissues and organs, and the inducible enzyme, COX-2, which has been localized primarily to inflammatory cells and tissues. In an animal model of acute inflammation (injection of carrageenan into the footpad), edema was produced that was associated with marked accumulation of COX-2 mRNA and thromboxane. A selective inhibitor of COX-2 (SC-58125) inhibited edema at the inflammatory site and was analgesic but had no effect on PG production in the stomach and did not cause gastric toxicity. These data suggest that selective inhibition of COX-2 may produce superior antiinflammatory drugs with substantial safety advantages over existing NSAIDs.

Time-course of nociceptive disorders induced by chronic loose ligatures of the rat sciatic nerve and changes of the acetylcholinesterase transport along the ligated nerve

Changes in the axonal transport of acetylcholinesterase (AChE) were studied in the painful mononeuropathy induced by setting 4 loose ligatures around the right sciatic nerve of the rat. Since changes in the axonal transport of AChE can be used to assess axonal degeneration/regeneration, we used this marker to investigate whether the time course of pain-related behavioral disorders observed following chronic constriction injury (CCI) to the sciatic nerve are related to the time course of the regeneration of the injured axons. In addition, a comparison was made between changes in AChE observed in this model of nerve injury and those observed after sciatic nerve crush. The rats were examined for pain-related disorders daily during the first postoperative week then at 7, 14 and 21 days after nerve ligation. The pain-related disorders, only detected from 7 days after ligation, were maximal at 14 days postinjury, and began to lessen at the end of the 3rd postoperative week. Within the first 3 days after loose ligation, the AChE transport dropped to 40% of its normal value, but recovered rapidly during the 3rd week post-surgery, indicating that most of the injured neurons were reconnecting their target cells. Thus, the injury produced by the loose ligatures was registered by the neurons several days before the first nociceptive manifestations of the injury, and the pain-related disorders lasted after most of the re-elongating axons had reconnected their target.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of emotional-painful stress, hypoxia, and adaptation to it on the activity of enzymes for metabolizing glutathione and concentration of glutathione in rat organs]

The stress activates glutathione peroxidase in the heart, liver, and kidney, glutathione transferase in the heart and liver, inhibits gamma-glutamyl transferase in the liver; the activity of glutathione reductase and the content of reduced glutathione were unchanged. Two-four-minute hypercapnic hypoxia unchanged the activity of glutathione metabolic enzymes. The activity of the above enzymes decreases in some organs at the death caused by 2-15-minute hypoxia. Long-term intermittent adaptation to hypobaric hypoxia lowers the activity of glutathione peroxidase, -transferase and -reductase. The biological value of the two types of enzymatic responses may be different: stress-induced activation of glutathione metabolic enzymes can enhance resistance to stress and xenobiotics; however, their inhibition during hypoxic adaptation may produce the opposite effect.

Increased nitric oxide synthase immunoreactivity in rat dorsal root ganglia in a neuropathic pain model

In rats, tight ligation of L5 and L6 spinal nerves produces symptoms of thermal hyperalgesia and mechanical allodynia, mimicking the symptoms which characterise painful peripheral neuropathies in humans. Immunoreactivity for nitric oxide synthase (NOS) was investigated in lumbar (L1, L4, L5 and L6) dorsal root ganglia from naive controls and from rats surviving for 3, 7, and 14 days after unilateral ligation of the L5 and L6 spinal nerves. Quantitative analysis revealed significant increases in the percentage of NOS-immunoreactive cell profiles in L5 and L6 ganglia on the operated side at all time points, with the number of labelled profiles increasing with time following ligation, but L1 and L4 ganglia were unaffected. These findings suggest that nitric oxide may have a role in the generation and/or maintenance of neuropathic pain.

[The effect of emotional-pain stress on the activity of carboxypeptidase N--the enzyme of neuropeptide processing in the rat brain]

Activity of carboxypeptidase N [correction of H] increased under emotional-algic stress in the rat pituitary gland and hypothalamus. Carboxypeptidase N [correction of H] seems to be involved in development of the stress response, and soluble forms of the enzyme take part in processing of secretory peptides. Membrane-bound forms take part in processing of the neuropeptides specific by their central action.

Exercise-induced myalgia in hypothyroidism

Recurrent rhabdomyolysis is very uncommon in hypothyroid myopathy. A 30-year-old woman is reported, who presented with exercise-induced myalgias and high levels of serum creatine kinase but no muscle weakness. Muscle biopsy showed signs of a recurrent rhabdomyolysis. Hypothyroidism was diagnosed by serum hormone levels. The myopathy rapidly improved with thyroxine treatment.

Decrease of hippocampal choline acetyltransferase activity induced by formalin pain

The involvement of the hippocampal choline acetyltransferase (ChAT) activity in the response to tonic pain was investigated in rats injected with formalin, either 50 microliters 10% or 50 microliters 0.1%. Hippocampal ChAT activity was found to be reduced both 30 and 60 min after injection of the higher concentration of formalin but only 30 min after the lower one. Results indicate that the decrease in ChAT activity depends upon the presence of the nociceptive input rather than its magnitude. The hippocampal formation is involved in the specific behavioural response to pain, namely licking.

Are poor metabolisers of sparteine/debrisoquine less pain tolerant than extensive metabolisers?

It has recently been shown that O-demethylation of the opioid drug codeine to morphine depends on the sparteine/debrisoquine oxygenase (CYP2D6) which in man exhibits genetic polymorphism. Morphine may be an endogenously formed substance in mammalians. Therefore, it may be hypothesized that the final step in an endogenous synthesis of morphine from codeine also depends on CYP2D6. CYP2D6, which is present in the liver and presumably also in the brain, is not expressed in subjects who are poor metabolisers of the sparteine/debrisoquine type. We have determined sensitivity to painful stimuli in 94 extensive metabolisers and 82 poor metabolisers of sparteine in 2 phasic (pain thresholds to heat and pressure) and 1 tonic (cold pressor test) experimental pain model. Extensive and poor metabolisers did not differ significantly in the 2 phasic pain models neither with respect to pain detection nor pain tolerance thresholds. However, for the cold pressor test, peak pain ratings and area under the pain rating-time curve during 2 min were significantly higher in poor than in extensive metabolisers (P = 0.0024 and 0.044). Furthermore, a substantially higher fraction of poor metabolisers prematurely withdrew their hand from the ice water during the cold pressor test due to intolerable pain (32 vs. 18%, P = 0.0545). We conclude that poor metabolisers of sparteine may be less tolerant to tonic pain than extensive metabolisers, and we hypothesize that this may be related to an inherited defect in endogenous synthesis of morphine via CYP2D6 in the brain.

[The effect of alcohol consumption on carboxypeptidase N activity in rat brain during chronic emotional-painful stress]

With ethanol consumption, activity of carboxypeptidase H was increased in all the brain regions of rats with chronic emotional-painful stress. The most distinct increase of enzyme activity was found in the striatum membrane fraction and in the hippocampus. Carboxypeptidase H appears to be involved in development of stress reactions under conditions of ethanol consumption via the enkephalinergic system.

Myalgia and elevated creatine kinase activity associated with subcutaneous injections of diluent

A 16-year-old boy with short stature and mild primary hypothyroidism received subcutaneous injections of either recombinant human growth hormone or placebo in diluent that contained glycerol and m-cresol as a preservative. While he was receiving the study drug, myalgia developed and serum creatine kinase values were elevated. Both resolved when injections were stopped and recurred when injections of diluent alone were given. The myalgia and elevated creatine kinase activity were apparently caused by a component of the diluent.

Pain-related increases in spinal cord membrane-bound protein kinase C following peripheral nerve injury

Neuropathic pain following nerve injury is thought to involve central nervous system Ca(2+)-mediated neuronal plastic changes. This study provides evidence that induction and/or maintenance of post-injury neuropathic pain behaviors in the rat is associated with increases in membrane-bound protein kinase C (PKC), a Ca(2+)-dependent process known to mediate central nervous system neuronal plasticity. In addition, spinal cord administration of GM1 ganglioside, an intracellular inhibitor of PKC translocation/activation, reverses both increased levels of membrane-bound PKC and pain-related behaviors. Thus, persistent post-injury neuropathic pain may be mediated by the initiation of excitatory neuropathological processes resulting from an increase in membrane-bound PKC.

Contribution of protein kinase C to central sensitization and persistent pain following tissue injury

This paper provides evidence that central sensitization and persistent nociception following formalin-induced tissue injury in rats is dependent on the production of protein kinase C. Persistent nociceptive behavior in rats induced by subcutaneous formalin injection was significantly reduced by intrathecal pretreatment with a phospholipase C inhibitor (neomycin), and an inhibitor of protein kinase C (W-7), and was significantly enhanced by a phorbol ester (phorbol 12-myristate 13-acetate, PMA) and a stimulator of protein kinase C (SC-10). It is expected that noxious inputs associated with tissue injury produce a release of aspartate and glutamate within the spinal dorsal horn which by acting at ionotropic (NMDA) and metabotropic excitatory amino acid receptors produce an increase in intracellular messengers such as calcium and diacylglycerol which stimulate protein kinase C.

Endometrial phospholipases A2, polycystic ovaries and pelvic pain

OBJECTIVE

To compare the activity of calcium independent phospholipase A2 in the endometrium of women with polycystic ovaries and in women with normal ovaries, and to investigate the influence of chronic pelvic pain on phospholipase A2 activity.

DESIGN

A prospective descriptive study.

SETTING

The Samaritan Hospital for Women and the Unit of Metabolic Medicine, St Mary's Hospital Medical School, London.

SUBJECTS

73 women attending the Samaritan Hospital for Women for clip sterilization, infertility, early recurrent miscarriage or pelvic venous congestion. 45 of these women had no pelvic pain, 22 had normal ovaries and 23 had polycystic ovaries diagnosed by ultrasound. The other 28 women had chronic pelvic pain, 14 of them had normal ovaries and 14 polycystic ovaries.

INTERVENTIONS

Endometrial tissue was obtained at curettage or from the excised uterus in the proliferative or secretory phase of the menstrual cycle. The activities of calcium dependent (type 1) and calcium independent (type 2) phospholipase A2 isoenzymes were measured in all endometrial samples.

RESULTS

In all the women phospholipase A2 type 1 activity, was significantly higher in the secretory phase than in the proliferative phase (P less than 0.001). There was no difference between women with normal ovaries and those with polycystic ovaries at either stage of the cycle irrespective of whether or not chronic pelvic venous congestion was present. In women with normal ovaries, both with and without chronic pelvic pain, phospholipase A2 type 2 activity was significantly higher in the secretory phase than in the proliferative phase (P less than 0.02 and P less than 0.05 respectively) but in women with polycystic ovaries, with and without chronic pelvic pain, there was no significant difference in activity between the two phases of the cycle. Women with polycystic ovaries had markedly higher proliferative phase type 2 activity than women with normal ovaries (P less than 0.001). Secretory phase type 2 activity was similar in all the women investigated.

CONCLUSION

These data suggest that phospholipase A2 type 2 activity is increased in proliferative phase endometrium of women with polycystic ovaries but that the increase is not associated with chronic pelvic venous congestion.

[Kinetic properties of rat heart cathepsin D under normal conditions, during emotional-pain stress and in the post-stress period]

Cathepsin D preparations have been isolated from the heart of healthy animals and stress-surviving rats by the method of affine chromatography with the hemoglobin-biogel-P300 sorbent. To analysis of the obtained data permits concluding that acute stress stimulates activation of the catalytic function of cathepsin D in the heart. But the period after the stress accompanied by the consecutive proteolysis rate reduction, that can be explained, probably, by a change in enzyme conformation. The concentration of Ca2+ (10(-6), 10(-5) M) and cAMP (10(-7), 10(-6) M) exert a regulating influence on the cathepsin D activity in the heart in acute stress period and after it.

Muscle soreness and serum enzyme activity following consecutive drop jumps

The purpose of this study was to evaluate changes in muscle soreness and serum enzyme activity following consecutive drop jumps. Seven male subjects (mean age 30.6 years) performed drop jumps from a 80-cm box height every 7 s until exhaustion (mean = 114 drop jumps). A questionnaire was used to assess muscle soreness (0 = no pain, 7 = unbearable painful) both pre- and post-exercise (0, 12, 24, 36 and 48 h, and 3, 4 and 5 days after the exercise). Blood samples were also taken from three subjects at each of these times. For the other four subjects, blood samples were taken pre-exercise and 0, 12 and 36 h and 5 days post-exercise only. Although there was large inter-subject variability in the development of muscle soreness, all the subjects reported muscle soreness in their lower extremity muscles, especially in the quadriceps femoris. Muscle soreness developed significantly (P less than 0.01) over time, its peak (mean +/- S.E. = 3.7 +/- 0.7) occurring 12-48 h post-exercise. Serum enzyme activity changed significantly over time (P less than 0.05), but the changes were small. Not one subject showed a large increase in creatine kinase, and the average increase was less than 1.3 times as much as the pre-exercise level throughout the period of study. These results suggest that the muscle damage that occurs after drop jumping is not associated with a large release of muscle enzymes into the blood, and muscle soreness is not necessarily related to enzyme elevation following drop jumps.

Effects of ibuprofen on exercise-induced muscle soreness and indices of muscle damage

Thirty-two volunteers participated in a two-period crossover study in which ibuprofen was tested against an identical placebo for its effectiveness in reducing muscle soreness and damage after two bouts of downhill running. Subjective soreness, quadriceps isometric strength and isometric endurance time at 50 percent of maximum strength, serum activities of creatine kinase, lactate dehydrogenase and aspartate transaminase and serum levels of creatinine and urea were recorded at intervals up to 72 hours after exercise. Each downhill run produced muscle soreness, and a decline in muscle strength and 50 percent endurance time, although these parameters were unaffected by ibuprofen treatment. All serum parameters measured increased after both runs, but for the three enzymes this increase was smaller after the second run. Serum creatine kinase and urea levels were higher in the ibuprofen group after both runs. These results indicate that ibuprofen is not an appropriate treatment for delayed onset muscle soreness and damage.

[Abnormal regulation of carnitine palmitoyltransferase in monozygotic twins as the cause of rhabdomyolysis]

Severe myalgias, accompanied by reddish brown discolouration of the urine, occurred after strenuous exercise (all-day hockey competition) in a 21-year-old competitive athlete. Creatine kinase concentration was 1914 U/l, but there were no abnormal physical findings. The myalgias disappeared within three days. A biopsy from the lateral vastus muscle in the patient and his monozygotic twin brother showed normal total activity of carnitine palmitoyltransferase (CPT), but residual activity after inhibition with malonyl-CoA and Triton X-100 was clearly reduced in both brothers. Thus the illness was a rhabdomyolysis due to a, presumably inherited, abnormal regulation of CPT. The symptoms can be precipitated by fasting, marked physical exertion, cold or viral infection.

Platelet phenolsulphotransferase activity and 'abdominal migraine'

Low platelet phenolsulphotransferase activity has been reported in adult patients with dietary sensitive migraine. Platelet activity of this enzyme was therefore measured in children having 'abdominal migraine' with probable dietary trigger and in controls. No significant difference was found in activity between the two groups. There was no significant correlation between platelet phenolsulphotransferase activity and age.

Current modalities in arthritic diseases

Little progress has been made in identifying the etiologies of the major rheumatologic diseases, which substantially limits our ability to identify truly disease-modifying treatments. Despite this constraint, major advances in the suppression of the signs and symptoms of these diseases have been made. Second-line drugs such as methotrexate have gained wide acceptance among rheumatologists and may supplant gold as the major therapy for rapidly advancing rheumatoid arthritis. The nonsteroidal anti-inflammatory drugs (NSAIDs), however, remain the first line of treatment for arthritic conditions. In recent years, much has been learned about how the NSAIDs suppress the inflammation and pain of arthritis. Even here, however, several inconsistencies exist with our current understanding. New findings in neurobiology may shed light on some of these puzzling features. Although the number of NSAIDs currently available seems a bit overwhelming, rationale exists for their continued development. Many patients do not have a response to some or all of these agents, with noncompliance because of gastrointestinal intolerance being among the probable causes. New compounds that offer improved safety in this regard are greatly needed.

Platelet MAO in patients with idiopathic pain disorders

Patients with idiopathic pain syndromes have been compared to healthy volunteers and patients with neurogenic pain syndromes as concerns the activity of the enzyme monoamine oxidase (MAO) in thrombocytes. In both patients with idiopathic pain syndromes and in patients with neurogenic pain syndromes an increased frequency of patients with low platelet MAO activity was found. As low platelet MAO activity has been suggested to reflect low central serotoninergic activity the results are in line with findings of reduced concentrations of the serotonin metabolite 5-HIAA in CSF in patients with idiopathic pain syndromes. The results would also give some support for the suggestion that idiopathic pain syndromes might be a variant of depressive disease.

The effect of aerobic exercise on serum creatine kinase activities

Aerobic exercise is now a common form of recreational exercise among young women. In a previous study, more than a third of a group of young mothers volunteering blood samples to establish a creatine kinase (CK) reference range for Duchenne muscular dystrophy (DMD) carrier detection regularly participated in aerobic exercise programs. Aerobic exercise programs include eccentric exercises. As eccentric exercise is known to produce a delayed CK peak, this study was carried out to determine the effect of aerobic exercise on serum CK activities. The postexercise serum CK activity peak was monitored in 15 young women (age range 20-23 years) following aerobic exercise classes (45 minutes on 3 consecutive days). Peak values at 24-48 hours following the last class ranged from 90 to 3473 U/liter, or 1.55 to 34.71 times resting values. It is concluded that aerobic exercise programs should be excluded in order to obtain accurate resting serum CK values for muscle disease diagnosis.

Muscle soreness and serum creatine kinase activity following isometric, eccentric, and concentric exercise

Serum creatine kinase (CK) activity and subjective ratings of muscle soreness were assessed in 28 college women following three different arm flexion exercise regimens. The subjects were randomly assigned to an eccentric, isometric, or concentric exercise regimen. Each regimen was equated for total work time and work-to-rest ratio. Blood samples for determination of serum CK activity and perceived soreness ratings were obtained prior to and 5, 10, and 25 h following each exercise. Significant increases in perceived soreness ratings were observed for each exercise regimen. The magnitude of the post-exercise increase in perceived soreness was greatest for the eccentric and the isometric exercises with minimal soreness following the concentric exercise. A small but significant increase in serum CK activity was observed following the three exercises (eccentric = 35.8%, concentric = 37.6%, isometric = 34.0%). The post-exercise serum CK increases did not differ significantly among the three regimens. The rise in serum CK activity suggests that muscle damage occurred during all three tasks. However, due to multiple factors which can affect serum CK levels, the increase in serum CK activity may not provide a sensitive indicator of the magnitude of the injury.