Radiotherapy residents' knowledge of and attitudes toward management of cancer pain

PURPOSE

To evaluate the fund of knowledge of and attitudes toward cancer pain management of radiotherapy residents across the nation.

METHODS

Radiotherapy (XRT) residents who had completed at least a year of training were surveyed by questionnaire. Residents (n = 10) from a training program who had been given instructional resources in cancer pain management skills were compared with residents from across the nation (n = 61). A validated survey used in national Cancer Pain Initiative Role Model Programs was administered by mail. The survey contained 30 questions that evaluated attitude alone (A), knowledge alone (K), and how attitude affects the application of knowledge (A/K).

RESULTS

The residents from the training program scored significantly higher in K (p < 0.005) and A/K (p < 0.04) than did the residents across the nation. No difference in scores evaluating A were detected (p = 0.26). Compared with the baseline knowledge of physicians in practice who had attended a workshop on cancer pain management, the national XRT residents had significantly lower scores in A (p < 0.006) and K (p < 0.001); however, no difference was found in A/K scores. After the workshop, the physicians in practice had significant gains in cancer pain management skills (p < 0.006). When the post-instruction survey was compared with the national XRT resident scores, there were marked differences in A (p < 0.00001), K (p < 0.00001) and A/K (p < 0.01).

CONCLUSIONS

XRT residents in the United States are empathetic, but knowledge of cancer pain management is lacking. Instruction in the principles of cancer pain management can make a profound difference in knowledge and attitude. There is a need to recognize cancer pain management as a significant aspect of radiotherapeutic practice.

Sickle cell-related pain: perceptions of medical practitioners

Pain is the most common problem encountered by patients with sickle cell disease (SCD). We report the results of a survey sent to hematologists and emergency department (ED) physicians regarding their perceptions and practices concerning pain and its management. Hematologists and ED physicians differed considerably in their perceptions about the natural history of the pain, and about the percentage of patients who are addicted to analgesics. Fifty-three percent of the ED physicians and 23% of the hematologists thought that more than 20% of patients are addicted. These beliefs and perceptions about SCD-related pain and the prevalence of addiction must be addressed if clinical care is to be changed substantively.

Palliation of intractable cancer pain by MRI-guided cingulotomy

CASE REPORT

Three cases of intractable pain arising from widespread metastatic cancer with poor response to opioids were treated with MRI-guided cingulotomy.

RESULTS AND CONCLUSIONS

In most cases, MRI-guided cingulotomy was associated with significant pain relief and reduced opioid use. To provide insight into the role of MRI-guided cingulotomy in oncologic pain refractory to more conservative measures, the relative risks and benefits of cingulotomy are discussed, along with the course of one patient who experienced postoperative cognitive impairment. This report also describes the relevant neurosurgical and pharmacotherapeutic issues associated with management of pain in patients with widespread metastatic disease.

Growth cone interactions with purified cell and substrate adhesion molecules visualized by interference reflection microscopy

The migration of growth cones on substrates consisting of naturally occurring cell adhesion molecules has been extensively studied in cell culture. However, relatively little is known about how growth cones contact the substrate or how the patterns of contact change as growth cones move forward. We have examined the interactions of chick retinal ganglion cell growth cones with laminin, merosin, N-cadherin, L1 and poly-L-lysine by time-lapse interference reflection microscopy (IRM) using a laser scanning confocal microscope. In images obtained by IRM, areas of a cell that are closely apposed to the substrate appear dark whereas areas that are farther away appear light. Growth cones on Jaminin and merosin were almost uniformly light, indicating that very little of the membrane was in close contact with the substrate. Growth cones on N-cadherin had a mottled appearance with some relatively large dark gray areas. The proximal portions of filopodia often were dark, in contrast to those on laminin and merosin which were light. In addition, growth cones on N-cadherin had numerous dark gray punctate regions of close association with the substrate. Growth cones on L1 had darker regions than growth cones on other substrates and these comprised a larger fraction of their area. There also were differences in the temporal dynamics of growth cone interactions with different substrates and these differences correlated with differences in rates of growth. None of the contacts observed in growth cones were as dark or stable as focal contacts of fibroblasts.

Rapid coupling of calcium release to depolarization in Limulus polyphemus ventral photoreceptors as revealed by microphotolysis and confocal microscopy

Microphotolysis and confocal microscopy were used to investigate the timing of calcium release and of the electrical response in Limulus polyphemus ventral photoreceptors. The fluorescent dyes Fluo-3 and Calcium Green-5N were used to monitor local Ca2+ elevations. Photolysis of caged inositol trisphosphate (InsP3) close to the plasma membrane of the light-sensitive rhabdomeral (R-) lobe resulted in Ca2+ elevation within 10-20 msec, 20-45 msec before the physiological response to light normally would be detected. Inward ionic current flow and depolarization followed InsP3-induced calcium release within 2.5 +/- 3.3 msec. Voltage-clamping the cells and removal of extracellular Ca2+ did not affect the timing of the Ca2+ elevation that followed the photolysis of caged InsP3 or its relationship to the electrical response. In contrast to the physiological response to light, which only released calcium within the R-lobe, photolysis of InsP3 elevated Cai in both lobes, although with much greater effect in the R-lobe, as compared with the bulk of the A-lobe, suggesting the presence of InsP3-sensitive calcium stores in both lobes. Photolysis of caged calcium [o-nitrophenyl EGTA (NPE)] at the edge of the R-lobe activated an inward ionic current within 1.8 +/- 0.7 msec. This NPE-induced current reversed at a membrane potential of 10 +/- 6 mV in the range typical of that of the light-activated current under physiological conditions. Calcium release, therefore, activates an inward current rapidly enough to contribute to the electrical response to light.

Intravenous methadone for cancer pain unrelieved by morphine and hydromorphone: clinical observations

Methadone is a very effective second-line opioid for treatment of cancer pain. However, the starting doses of methadone indicated on opioid conversion charts may over-estimate the dose of intravenous (i.v.) methadone needed. In this report, we describe four patients with cancer-related pain treated with continuous i.v. morphine and hydromorphone. Because of persistent pain and opioid side effects limiting increases in opioid dose, each patient was switched to i.v. methadone. All four patients had excellent pain relief without significant side effects at a dose that, according to the available conversion charts, was approximately 3% of the calculated equianalgesic dose of hydromorphone. When converting from continuous i.v. hydromorphone to continuous i.v. methadone, much lower doses than those suggested by the opioid conversion charts should be used as starting doses.

High-dose epidural infusion of opioids for cancer pain: cost issues

The safety and efficacy of intraspinal opioids as therapy for selected patients with cancer pain are well-established. The choice of the appropriate drug is influenced by many variables that are to date incompletely elucidated. The cost of therapy is an increasingly important component of decision-making. This report describes the management of a patient who achieved excellent pain control with the administration of epidural sufentanil and bupivacaine. Daily Average Wholesale Price for sufentanil was, however, $698. Until the data comparing the efficacy of different epidurally administered opioids in the treatment of cancer pain are available, we suggest that treatment with more costly opioids be reserved for patients for whom analgesia cannot be achieved after maximizing epidural morphine analgesia with aggressive side-effect management.

Cerebrospinal fluid distribution of opioids after intraventricular & lumbar subarachnoid administration in sheep

The study of opioid distribution in blood and cerebrospinal fluid (CSF) is required to understand pharmacokinetic-pharmacodynamic relationships following lumbar intrathecal (it) and intracerebroventicular (i.c.v.) administration, and to investigate the contributions of spinal or supraspinal sites of action. The sheep model developed for pharmacokinetic study of analgesics allows atraumatic sampling of plasma and CSF after drug administration by the intravenous (i.v.), i.c.v., and it routes in an unanesthetized animal. Five adult female sheep were prepared with femoral vascular catheters, lumbar it and epidural cannulae, i.c.v. cannulae, and cisterna magna cannulae. Hydromorphone, methadone, naloxone, and [14C] sucrose were injected and collected by two methods: 1) injection into the i.c.v. cannula with lumbar CSF samples collected via the lumbar cannula and 2) injection into the lumbar cannula and cisternal CSF samples collected via ventriculocisternal cannula. Hydromorphone, morphine, and [14C] sucrose were detected at 90-105 min in lumbar CSF after i.c.v. injection. Hydromorphone and [14C] sucrose were detected in i.c.v. cerebrospinal fluid at 50 min after lumbar i.t. injection. Methadone was not detected in i.c.v. cerebrospinal fluid after i.t. injection, nor was methadone significantly detected in lumbar CSF after i.c.v. injection. These data indicate that i.c.v. and i.t. administration of lipophilic opioids produces CSF distributions different from those of hydrophilic opioids. This suggests that lipophilic opioids such as methadone or naloxone exert their effects predominantly on tissues near the site of injection. The study of i.t. and i.c.v. opiate administration and CSF pharmacokinetics may therefore have direct clinical implications.

Limulus ventral photoreceptors contain two functionally dissimilar inositol triphosphate-induced calcium release mechanisms

Injections of inositol 1,4,5 triphosphate (InsP3) into Limulus ventral photoreceptors give rise to a rapid depolarization and an elevation of intracellular calcium concentration (Cai). This response to InsP3 is followed by a period of desensitization that persists as long as Cai remains elevated (feedback inhibition). Limulus ventral photoreceptors have two types of lobe: a light-sensitive rhabdomeric lobe (R lobe), and a light-insensitive arhabdomeric lobe (A lobe). Evidence showing the presence of feedback inhibition has been so far demonstrated only in the R lobe. In this study, simultaneous measurements of Cai were made using aequorin and double-barreled calcium-sensitive electrodes in each type of lobe. We carefully checked the location of the R lobe and A lobe by scanning a microspot of light across the whole photoreceptor. We then inserted a double-barreled calcium-sensitive microelectrode with InsP3 in either type of lobe. In the R lobe, injections of InsP3 led to a large Cai increase, a rapid depolarization and feedback inhibition; a brief flash of light induced a rapid depolarization and a Cai increase measured by both aequorin and the calcium-sensitive electrode. In the A lobe, injection of InsP3 led to an increase in Cai measured by the calcium-sensitive electrode but to no depolarization or aequorin luminescence. Further there was no evidence of feedback inhibition in the A lobe; the elevation of Cai caused by the first injection did not desensitize the photoreceptor to a second injection of InsP3 3 s later. To verify that the aequorin and the cell membrane respond to an increase in Cai, we presented a brief flash of light. Following a uniform illumination, there is indeed a typical large luminescence increase and a receptor potential. The calcium-sensitive electrode measures a small and slow Cai increase because its tip is located in the A lobe and it is measuring Ca2+ diffusing from the R lobe. Our observation that the InsP3-induced Cai increase in the A lobe is not apparently accompanied by a subsequent desensitization to InsP3 may suggest that there are more than one type of InsP3 receptor in the same cell. Alternatively, the InsP3 receptor could be the same but some additional factor, which confers feedback inhibition, could be missing in the A lobe.

Latencies of calcium elevation and depolarization in Limulus ventral photoreceptors injected with GDP-beta S

We have used confocal fluorescence microscopy and fluorescent calcium indicators to investigate the relationship between light-induced elevation of intracellular calcium ion concentration (Cai) and depolarization in small volumes of cytosol close to the microvillar plasma membrane of the ventral photoreceptor of Limulus polyphemus. We prolonged the latency of the light response by treatment of cells with hydroxylamine and injection of the G-protein blocker, guanosine-5'-O-(2-thiodiphosphate (GDP-beta S). Such treatment increased the latency of the cell's response from approximately 20 to 50 ms. In both treated and untreated cells we observed a close correlation between the times at which we first detected the electrical response and the elevation of Cai. We obtained 18 out of 54 and 12 out of 22 recordings, in untreated and treated cells respectively, for which the elevation of Cai was detected simultaneous with, or 1-4 ms prior to, the electrical response to light. The prolonged latent period exhibited by treated cells may make possible future investigation of the effects on the initial response to light of local photolytic release of caged compounds at the microvillar membrane.

Commissural myelotomy for intractable cancer pain: report of two cases

PATIENTS

We describe two patients with cancer-related low back and bilateral lower extremity pain that failed pharmacologic treatment.

RESULTS

In both cases, commissural myelotomy provided significant pain relief. The role of myelotomy in the management of cancer pain is discussed.

Teaching cancer pain management: durability of educational effects of a role model program

BACKGROUND

Inadequate management of cancer related pain has resulted primarily from attitudinal barriers and a lack of knowledge about clinical assessment, the administration of analgesics, and therapeutic interventions.

METHODS

Fifty health-care providers (13 physicians, 21 nurses, and 16 pharmacists), working as a team, participated in a Role Model Program that presented principles of cancer pain management. A questionnaire that evaluated the fund of knowledge and attitudes regarding cancer pain management was administered prior to the 1-day workshop, at the end of the workshop, and at 4 and 12 months follow-up. The workshop consisted of lectures and discussion groups; in the discussion groups, concepts were clarified, cases presented, and barriers to optimal cancer pain management identified.

RESULTS

Significant improvements in attitudes (P < 0.01), knowledge (P < 0.01), and total scores (P < 0.002) were observed when the preworkshop responses were compared with those obtained immediately after instruction. Scores on the questionnaire were the same or slightly better at both 4 and 12 months in follow-up, demonstrating no loss in acquired knowledge or attitude. Comparison of the postworkshop scores with those at 12 months follow-up were significantly better in attitude (P < 0.03), and in total score (P < 0.01); improvements in knowledge also approached significance (p < 0.06). These represented continuing improvements because significant differences in the attitude scores (P < 0.05) and the total score (P < 0.05) were observed when the 4-month and 12-month follow-up responses were evaluated. The effectiveness of the program in the transference of knowledge was also measured; in the first year of the program, more than 4500 health-care professionals were subsequently informed about cancer pain management from the Role Model Participants.

CONCLUSIONS

Significant improvements were observed immediately in both attitude and knowledge of cancer pain management principles after the 1-day Role Model Workshop. These improvements continued, as determined at 4 and 12 months follow-up. The Role Model Participants were highly motivated to share the learned principles of cancer pain management with other health-care professionals. These results are consistent with other Role Model Programs that both instruct and involve the participants. The Role Model Program is an efficient and effective means of educating health-care professionals in the concepts of cancer pain management.

Inappropriate use of naloxone in cancer patients with pain

Opioid overdose is rarely the primary cause of altered mental status in cancer patients receiving opioid therapy. The inappropriate administration of naloxone to reverse an abnormal mental status can cause severe withdrawal symptoms and pain. To illustrate this problem, we report the case of a patient inappropriately treated with naloxone and the results of a retrospective review of the medical records of 15 consecutive patients with cancer treated with naloxone in the emergency department over a 5-month period. We offer guidelines for a more thoughtful approach to the management of patients with cancer who present with encephalopathy.

How to use instant relaxation methods

Relaxation methods can be used by nurses to help patients suffering from stress related to their illness. Nurses can also use the methods themselves to relieve tension related to their work. This article describes how to carry out simple techniques 'on the spot'.

Light activated calcium release in Limulus ventral photoreceptors as revealed by laser confocal microscopy

Using confocal imaging and fluorescent calcium indicators, light-induced elevation of intracellular Ca2+ concentration ([Ca2+]i) in Limulus ventral photoreceptors was shown to be initiated within 4 microns of the light-sensitive plasma membrane. Within 500 ms, elevation of [Ca2+]i spread throughout the light-sensitive rhabdomeral lobe of the photoreceptor, but barely penetrated the arhabdomeral lobe. During saturating illumination of measurement spots near the plasma membrane, [Ca2+]i rose at rates of 1-2 mM/s after a latent period of 14-40 ms, reaching peak concentrations of approximately 150 microM. Rapid elevation of [Ca2+]i persisted in the absence of extracellular Ca2+ and was therefore ascribed to release from intracellular stores. The elevation of [Ca2+]i was always detectable within 5 ms of the electrical response of the photoreceptor to light. In 14 out of 54 measurements, detection of elevated calcium preceded the electrical response. Cyclopiazonic acid, an inhibitor of endoplasmic reticulum Ca-pumps, greatly reduced the elevation of [Ca2+]i during bright flashes and the sensitivity of the electrical response to dim flashes. However, the maximal response to bright flashes was not diminished. Therefore, although the calcium release that we detect may be fast enough to contribute to the electrical response we are unable to demonstrate that it is absolutely required.

Subarachnoid neurolytic block under general anesthesia in a 3-year-old with neuroblastoma

CASE REPORT

A 3-year-old boy with neuroblastoma complained of severe pain in the left lower extremity. Pharmacologic management had previously been attempted, but severe pain continued, and further upward titration was complicated by sedative effects.

METHODS AND RESULTS

Because the focus of treatment had become the controlling of pain, a lumbosacral subarachnoid neurolytic block was performed under general anesthesia. One-time neurolysis was more acceptable to the family than a procedure like epidural analgesia, that requires greater management. Contrast medium was used to monitor the spread of the neurolytic. An epidural catheter was inserted during the neurolytic block procedure for possible future use. The short-term results were good--pain reports and opioid doses decreased greatly, although with increased incontinence. The boy had new abdominal distention and pain 5 days after neurolysis. Opioid doses and sedatives were increased. He died 3 days later.

Guidelines for the clinical use of transdermal fentanyl

Transdermal (TTS) fentanyl therapy has emerged as an effective alternative to the use of oral opioids for the control of pain in certain cancer patients. These patients are those with moderate to severe chronic pain, with a stable baseline pain pattern. Patients receiving this treatment should first be titrated to stable pain relief with oral opioids and should have recourse during therapy to fast-acting, short-duration analgesics for the control of incident pain. TTS fentanyl dosing schedules should be based upon the patient's requirement for rescue dosing and duration of effective pain control. The average requirement to change fentanyl patches is every 72 h, although 48-h dosing is necessary in a few patients. This novel route of fentanyl administration allows convenient outpatient treatment, the possibility of a lower incidence of side effects, and may thus aid compliance.

Measurement of cytosolic Ca2+ concentration in Limulus ventral photoreceptors using fluorescent dyes

Several Ca-sensitive fluorescent dyes (fura-2, mag-fura-2 and Calcium Green-5N) were used to measure intracellular calcium ion concentration, Cai, accompanying light-induced excitation of Limulus ventral nerve photoreceptors. A ratiometric procedure was developed for quantification of Calcium Green-5N fluorescence. A mixture of Calcium Green-5N and a Ca-insensitive dye, ANTS, was injected in the cell and the fluorescence intensities of both dyes were used to calculate the spatial average of Cai within the light-sensitive R lobe of the photoreceptor. In dark-adapted photoreceptors, the initial Cai was 0.40 +/- 0.22 microM (SD, n = 7) as measured with fura-2. Cai peaked in the light-sensitive R lobe at 700-900 ms after the onset of an intense measuring light step, when the spatial average of Cai within the R lobe reached 68 +/- 14 and 62 +/- 37 microM (SD, n = 5) as measured with mag-fura-2 and Calcium Green-5N, respectively. The rate of Cai rise was calculated to be approximately 350 microM/s under the measuring conditions. The resting level of Mg2+ was estimated to be 1.9 +/- 0.9 mM, calculated from mag-fura-2 measurements. To investigate the effect of adapting light on the initial Cai level in the R lobe, a 1-min step of 420 nm background light was applied before each measurement. The first significant (P < 0.05) change in the initial level of Cai occurred even at the lowest adapting light intensity, which delivered approximately 3 x 10(3) effective photons/s. The relative sensitivity of the light-adapted photoreceptors was linearly related to the relative Cai on a double log plot with slope between -4.3 and -5.3. We were unable to detect a Cai rise preceding the light-activated receptor potential. The Cai rise, measured with Calcium Green-5N, lagged 14 +/- 5 ms (SD, n = 32) behind the onset of the receptor potential at room temperature in normal ASW. In the absence of extracellular Ca2+ and at 10 degrees C, this lag increased to 44 +/- 12 ms (SD, n = 17).

Unambiguous total synthesis of the enantiomers of myo-inositol 1,3,4-trisphosphate: 1L-myo-inositol 1,3,4-trisphosphate mobilizes intracellular Ca2+ in Limulus photoreceptors

Syntheses of the enantiomers of myo-inositol 1,3,4-trisphosphate are described. 1,4-Di-O-allyl-myo-inositol was regioselectively p-methoxybenzylated at the 3-position to give 1,4-di-O-allyl-3-O-(p-methoxybenzyl)-myo-inositol followed by benzylation of the remaining free hydroxyl groups to give the key intermediate 1,4-di-O-allyl-2,5,6-tri-O-benzyl-3-O-(p-methoxybenzyl)-myo-inositol. Removal of the p-methoxybenzyl and allyl groups gave 2,4,5-tri-O-benzyl-myo-inositol which was phosphitylated with bis(benzyloxy)(diisopropylamino)phosphine to give the fully protected trisphosphite triester. Oxidation using tert-butyl hydroperoxide gave 2,5,6-tri-O-benzyl-1,3,4-tris(dibenzylphospho)-myo-inositol, and deprotection using sodium in liquid ammonia gave racemic myo-inositol 1,3,4-trisphosphate. Deprotection of the key intermediate 1,4-di-O-allyl-2,5,6-tri-O-benzyl-3-O-(p-methoxybenzyl)-myo-inositol by isomerization of allyl groups followed by mild acid hydrolysis gave 2,4,5-tri-O-benzyl-1-O-(p-methoxybenzyl)-myo-inositol, which was converted to the diastereoisomeric (bis-(-)-camphanates. The diastereoisomers were separated by column chromatography and the camphanates and the p-methoxybenzyl group removed by saponification and acid hydrolysis, respectively, for each diastereoisomer to give the enantiomers of 2,4,5-tri-O-benzyl-myo-inositol. The absolute configurations of the latter were established by conversion of 1L-2,5,6-tri-O-benzyl-3-O-(p-methoxybenyl)-myo-inositol to the known 1L-1,2,4,5,6-penta-O-benzyl-myo-inositol. Phosphorylation and deblocking gave the D- and L-enantiomers of myo-inositol 1,3,4-trisphosphate. Biological evaluation in Limulus photoreceptors showed that 1L-myo-inositol 1,3,4-trisphosphate was much more active than the D-enantiomer, producing repetitive bursts of depolarization due to mobilization of intracellular calcium.

Facilitation of the responses to injections of inositol 1,4,5-trisphosphate analogs in Limulus ventral photoreceptors

Injection of inositol 1,4,5-trisphosphate and its metabolically resistant analogs InsP3S3 and L-chiro-2,3,5-InsP3 into the ventral photoreceptors of Limulus results in the release of calcium from internal stores and in a current flow into the cells. We show here that the dependence of the current response on the amount of analog injected is supralinear. The injections also facilitate the responses to subsequent injections. We analyze the kinetics of the responses either by very slow application of the analogs directly into the lobe that is sensitive to InsP3 and light or by delivering a pulse into the nonsensitive lobe of the cell, in both cases creating a ramp of rising concentration in the sensitive region. Typically, a long latent period was followed by a strong brief inward current. The ratio between the latency and the duration of the response, defined as twice the time from half-amplitude to the peak of the response, reaches values greater than 10. Our analysis shows that this value cannot be attained within realistic models whose only nonlinearity is the cooperative binding of the ligand to its receptor. The observed ratio, however, can be achieved with a positive feedback model. Treatments that lead to partial depletion of calcium stores reversibly increase the latency of the response. We conclude that the mechanisms of the response of Limulus ventral eye to the metabolically resistant analogs of InsP3 probably involves a positive feedback mechanism and that the carrier of the feedback is likely to be Ca2+.

Neurochemical basis of interleukin 2-modified discrimination behaviour

We trained one group of rats to discriminate 0.8 mg/kg intraperitoneal (i.p.) d-amphetamine from 1 ml/kg saline and the other to discriminate 0.3 mg/kg i.p. (+/-)-ethylketocyclazocine (EKC) from saline. Recombinant human interleukin 2 (rIL-2), 2 x 10(6) U/kg (or 8.2 nmol/kg) given i.p. 1 h prior to tests, potentiated responses elicited by 0.4 mg/kg d-amphetamine. This potentiation of d-amphetamine responses was suppressed by the opioid receptor antagonist naloxone (1 mg/kg) when administered i.p. together with IL-2. IL-2 (4 x 10(6) U/kg) alone produced EKC-like responses in the EKC-trained animals. The cytokine also potentiated 0.1 mg/kg EKC responses at 2 x 10(6) U/kg, an action that was suppressed by 1 mg/kg naloxone. Data from the present study show that IL-2 exerts the same neurochemical action as that previously observed with IFN-alpha for both d-amphetamine and EKC discrimination in rats.

The light response of Drosophila photoreceptors is accompanied by an increase in cellular calcium: effects of specific mutations

Photoreceptors of dissociated Drosophila retinae were loaded with the fluorescent Ca2+ indicators, fluo-3 and Calcium Green-5N. In fluo-3-loaded, wild-type photoreceptors, a rapid increase in fluorescence (Ca2+ signal) accompanied the light-evoked inward current. Removal of extracellular Ca2+ greatly reduced the Ca2+ signal, indicating Ca2+ influx as its major cause. In Calcium Green-5N-loaded trp mutants, which lack a large fraction of the Ca2+ permeability underlying the light-evoked inward current, the Ca2+ signal was smaller relative to wild-type photoreceptors. Fluo-3-loaded norpA mutant photoreceptors, which lack a light-activated phospholipase C, generated no light-evoked inward current and no Ca2+ signal. The phosphoinositide pathway therefore appears necessary for both excitation and changes in cytosolic free Ca2+ concentration.

The opioid mechanism of interferon-alpha action

Rats were trained to discriminate the opioid receptor agonist ethylketocyclazocine (EKC) (0.3 mg/kg body weight, intraperitoneally) from saline. Interferon-alpha (IFN-alpha), when substituted for EKC, elicited a dose-related increase in EKC-like responses. This generalization of EKC responses was blocked by the opioid antagonist naloxone (1 mg/kg). Potentiation of responses to a low dose (0.1 mg/kg) of EKC by IFN-alpha (1 x 10(6) U/kg or 0.22 nmol/kg) was also observed. Data thus indicate the involvement of opioid neurons on the action of IFN-alpha. d-Amphetamine (0.8 mg/kg) was shown to potentiate both EKC (0.1 mg/kg) and IFN-alpha (1 x 10(6) U/kg). The present study confirms our previously proposed opioid-mediated dopaminergic mechanism of IFN-alpha.

Fast desensitization of the response to InsP3 in Limulus ventral photoreceptors

In Limulus ventral photoreceptor cells the time-course of the desensitization of InsP3 response was measured by an injection-pair paradigm. Pressure pulses of InsP3 were delivered into the cell with various interpulse intervals. The desensitization of the response to the second injection of each pair approached totality at 200 ms, which is the duration of the response to a single pressure pulse of InsP3. Lowering extracellular calcium did not affect the time-course of the desensitization. Lowering the temperature slowed down both the time-course of the response to InsP3 and the time-course of the desensitization to the same extent. These findings suggest that the desensitization is powerful enough and its onset fast enough to contribute to the transience of the InsP3 response. The time-course of the desensitization suggests it may influence light adaptation.

A lingering elevation of Cai accompanies inhibition of inositol 1,4,5 trisphosphate-induced Ca release in Limulus ventral photoreceptors

Injection of inositol 1,4,5 trisphosphate (InsP3) into Limulus ventral photoreceptors causes an elevation of intracellular free Ca concentration (Cai) and depolarizes the photoreceptors. When measured with the photoprotein aequorin, the InsP3-induced Cai increase follows the time course of depolarization and declines within 1-2 s. However, sensitivity to further injections of InsP3 remains suppressed for several tens of seconds. The possibility that the suppression of Ca release (feedback inhibition) is due to a small lingering elevation of Cai, below the existing detection limit of aequorin, was investigated by measuring Cai with Ca-sensitive electrodes. Double-barreled, Ca-selective microelectrodes were used to pressure inject InsP3 and measure Cai at the same point. Light or InsP3 injections into the light-sensitive compartment depolarized the photoreceptors and induced an elevation of Cai that persisted for tens of seconds. Injections of InsP3 during the decay of Cai showed that sensitivity to InsP3 recovered as resting Cai approached the prestimulus level. The relationship between elevated Cai and feedback inhibition was very steep. An elevation of Cai of 1 microM or more was associated with inhibitions of 79 +/- 12.4% (SEM; n = 7) for the InsP3-induced Cai increase and of 76 +/- 8% for depolarizations. With a residual Cai elevation of 0.01 microM or less, the mean inhibition was 10 +/- 7.4% for InsP3-induced Cai increase and 6.6 +/- 4% for InsP3-induced depolarization. Injections of InsP3 into a light-insensitive compartment within the cell induced elevations of Cai with no associated depolarizations or feedback inhibition. To verify that a sustained elevation of Cai is necessary for inhibition of InsP3-induced Cai increase and depolarization, we injected ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) between two injections of InsP3. Injection of 1 mM EGTA or the related Ca chelator BAPTA, delivered 750 ms after the first injection of InsP3, restored the peak depolarization caused by the second injection of InsP3 to > 80 +/- 3% of control, compared with 13 +/- 8% without an intervening injection of EGTA. Measurement of Cai with aequorin showed that an intervening injection of EGTA partially restored the InsP3-induced Cai increase. The results suggest that feedback inhibition of InsP3-induced Cai increase and depolarization is mediated by a lingering elevation of Cai and not by depletion of intracellular Ca stores.

Effects of capsaicin on cutaneous vasodilator responses in humans

The neurovascular responses to noxious electrically evoked axon reflex (EAR) stimulation and iontophoretic application of endothelium-dependent [acetylcholine (ACh)] and independent [sodium nitrite (NaNO2)] vasodilator substances were examined in human forearm skin using laser Doppler flowmetry, before and after repeated topical applications of the neurotoxin capsaicin (chronic capsaicin pre-treatment). Following 3 or 4 days of capsaicin pre-treatment the normal vasodilator response to acute application of capsaicin was significantly reduced as was the EAR response. There were, however, no significant changes in the vasodilator responses to either ACh or NaNO2, suggesting that the neurogenic axon reflex is in series with the endothelial and microvascular smooth muscle mechanisms of vasodilatation. Recovery of normal EAR occurred within 2-4 weeks of cessation of capsaicin pre-treatment.

Transdermal fentanyl: suggested recommendations for clinical use

Transdermal fentanyl offers the advantage of providing continuous administration of a potent opioid in the absence of needles and expensive drug-infusion pumps for the treatment of cancer pain. When transdermal fentanyl is initiated, it may be necessary to change the dose every 24-48 hr until an appropriate dose is titrated to the needs of the patient. This should be done by providing short-acting opioids as rescue analgesics for breakthrough pain. Well-accepted principles established for chronic opioid use in cancer pain management should apply to the administration of transdermal fentanyl as well. These include dose titration, the coadministration of adjuvant drugs to counteract opioid side effects and enhance analgesia, and the need to reassess the patient continuously for recurrent tumor and other new sources of pain. Further clinically relevant studies are needed and include 1) the determination of the relative potency of transdermal fentanyl, especially in comparison with oral and parenteral morphine; 2) a prospective study of the side-effect profile of transdermal fentanyl in relationship to oral morphine; and 3) the role of oral transmucosal administration of fentanyl in selection of starting doses of transdermal fentanyl and as a means to provide rescue doses for breakthrough pain.

The latency of the response of Limulus photoreceptors to inositol trisphosphate lacks the calcium-sensitivity of that to light

The latent period before depolarization of Limulus ventral photoreceptors by light flashes was compared with that following brief, intracellular, pressure-injection of d-myo-inositol 1,4,5 trisphosphate. At temperatures between 18 degrees C and 22 degrees C and with an extracellular calcium concentration of 10 mM, the responses of 4 cells to light and to injections of 100 microM inositol trisphosphate displayed average latencies of 71 and 56 ms, respectively. The latencies of responses to InsP3 included an estimated 20 ms dead-time inherent in the injection method. Reducing the temperature lengthened the latency of the response to light (Q10 approximately 3.2 between 7 and 22 degrees C) more than that to inositol trisphosphate (Q10 approximately 2.3). Bathing the photoreceptors in seawater containing no added calcium and 1 mM of the calcium chelator EGTA greatly increased the latency of the light response at all temperatures, but did not increase the latency of the response to inositol trisphosphate. We conclude that the response to inositol trisphosphate lacks the calcium- and temperature-sensitive latent period which characterizes the response to light. If inositol trisphosphate acts, via the release of stored calcium, to stimulate an intermediate in the visual cascade, then that intermediate would appear to be downstream from the latency-generating mechanism.

The management of intractable bone pain: a clinician's perspective

Bone metastases occur in up to 85% of patients (at autopsy) who have breast, lung, and prostate cancer, and are a common cause of pain and neurological morbidity in patients with these and other cancers. The management of pain, the most common complication of bone metastasis, requires a knowledge of specific clinical syndromes and the associated neurological and orthopedic morbidities, as well as an understanding of current antitumor and pharmacological therapies. Knowledge of these potential complications are important in the design of clinical trials that seek to evaluate the effectiveness of new treatments for bone metastasis. Although radiation therapy in combination with analgesic drug therapies remains the mainstay of treatment, much recent interest in drugs with specific effects on bone elements, especially the osteoclast, offer the promise of providing effective pain relief with fewer side effects than is currently possible with conventional therapies.

Contouring structures for 3-dimensional treatment planning

Three-dimensional (3-D) treatment planning is a labor-intensive process with contouring of the target volume and critical normal tissues being a significant time-consuming component. The use of 3-D treatment planning on a routine basis may be limited by the time required to complete treatment plans. Despite the need to increase the efficiency of the process, there is little literature addressing the speed and accuracy of contouring systems. In an attempt to initiate systematic analysis of the contouring process, data sets consisting of 10 CT images each were developed on two patients with esophageal carcinoma. Nine different operators manually contoured structures (target volume, spinal canal, lungs) on the data sets using four different contouring systems present in our department. These included both commercially available systems and those developed by the authors. There was a wide variation in the hardware and software characteristics of these systems. The time required to contour the CT data sets was recorded and analyzed. The contouring accuracy was assessed by comparison with a standard template derived from the CT data set for each image. The contouring time was found to be dependent on the system design, previous contouring experience, and the type of drawing instrument (lightpen vs mouse). The mean contouring time ranged from 26 minutes per patient for the fastest system to 41 minutes for the slowest. Potential clinically significant errors in contouring were rare for the spinal canal and lungs but present at a greater rate for the target volume (30.3%). The implications of this finding are discussed.

Pain syndromes in the cancer patient

Paraneoplastic syndromes affect the nervous system in a very small percentage of patients with cancer. In those patients, portions of the nervous system are damaged or destroyed, usually in association with a small and often occult neoplasm elsewhere in the body. Current evidence suggests that these syndromes occur when the body mounts an immune response to an antigen shared between the tumor and the nervous system. The immune attack is then misdirected against that portion of the nervous system that possesses the "onconeural" antigen.

Injection of inositol trisphosphorothioate into Limulus ventral photoreceptors causes oscillations of free cytosolic calcium

Limulus ventral photoreceptors contain calcium stores sensitive to release by D-myo-inositol 1,4,5 trisphosphate (InsP3) and a calcium-activated conductance that depolarizes the cell. Mechanisms that terminate the response to InsP3 were investigated using nonmetabolizable DL-myo-inositol 1,4,5 trisphosphorothioate (InsPS3). An injection of 1 mM InsPS3 into a photoreceptor's light-sensitive lobe caused an initial elevation of cytosolic free calcium ion concentration (Cai) and a depolarization lasting only 1-2 s. A period of densensitization followed, during which injections of InsPS3 were ineffective. As sensitivity recovered, oscillations of membrane potential began, continuing for many minutes with a frequency of 0.07-0.3 Hz. The activity of InsPS3 probably results from the D-stereoisomer, since L-InsP3 was much less effective than InsP3. Injections of 1 mM InsP3 caused an initial depolarization and a period of densensitization similar to that caused by 1 mM InsPS3, but no sustained oscillations of membrane potential. The initial response to InsPS3 or InsP3 may therefore be terminated by densensitization, rather than by metabolism. Metabolism of InsP3 may prevent oscillations of membrane potential after sensitivity has recovered. The InsPS3-induced oscillations of membrane potential accompanied oscillations of Cai and were abolished by injection of ethyleneglycol-bis (beta-aminoethyl ether)-N,N'-tetraacetic acid. Removal of extracellular calcium reduced the frequency of oscillation but not its amplitude. Under voltage clamp, oscillations of inward current were observed. These results indicate that periodic bursts of calcium release underly the oscillations of membrane potential. After each burst, the sensitivity of the cell to injected InsP3 was greatly reduced, recovering during the interburst interval. The oscillations may, therefore, result in part from a periodic variation in sensitivity to a constant concentration of InsPS3. Prior injection of calcium inhibited depolarization by InsPS3, suggesting that feedback inhibition of InsPS3-induced calcium release by elevated Cai may mediate desensitization between bursts and after injections of InsPS3.