Functional interactions between tumor and peripheral nerve: changes in excitability and morphology of primary afferent fibers in a murine model of cancer pain.

We used a murine model to investigate functional interactions between tumors and peripheral nerves that may contribute to pain associated with cancer. Implantation of fibrosarcoma cells in and around the calcaneus bone produced mechanical hyperalgesia of the ipsilateral paw. Electrophysiological recordings from primary afferent fibers in control and hyperalgesic mice with tumor revealed the development of spontaneous activity (0.2-3.4 Hz) in 34% of cutaneous C-fibers adjacent to the tumor (9-17 d after implantation). C-fibers in tumor-bearing mice exhibited a mean decrease in heat threshold of 3.5 +/- 0.10 degrees C. We also examined innervation of the skin overlying the tumor. Epidermal nerve fibers (ENFs) were immunostained for protein gene product 9.5, imaged using confocal microscopy, and analyzed in terms of number of fibers per millimeter of epidermal length and branching (number of nodes per fiber). Divergent morphological changes were linked to tumor progression. Although branching of ENFs increased significantly relative to control values, in later stages (16-24 d after implantation) of tumor growth a sharp decrease in the number of ENFs was observed. This decay of epidermal innervation of skin over the tumor coincided temporally with gradual loss of electrophysiological activity in tumor-bearing mice. The development of spontaneous activity and sensitization to heat in C-fibers and increased innervation of cutaneous structures within the first 2 weeks of tumor growth suggest activation and sensitization of a proportion of C-fibers. The decrease in the number of ENFs observed in later stages of tumor development implicates neuropathic involvement in this model of cancer pain.

Strategic financial planning: opportunities at an inopportune time?

In this article, the author discusses the process hospitals need to initiate to implement competitive capital formation strategies, as well as issues governing boards need to address as society evaluates alternative delivery systems and who shall manage available resources.

Is the decision to merge really a question of access to capital?

Institutional mergers are not a panacea for hospitals with financial or operating problems, and the apparent advantage of multihospital systems does not lie in their access to capital and human resources. The critical disadvantage of independent hospitals may be the result of attitudes held by governing boards. This article suggests that boards adopt new business tenets, especially regarding accountability, risk, pricing, competition, regulation, innovation, resource management, and purpose.

The non-selective cannabinoid receptor agonist WIN 55,212-2 attenuates responses of C-fiber nociceptors in a murine model of cancer pain.

Pain from cancer can be severe, difficult to treat, and greatly diminishes patients' quality of life. It is therefore important to gain new information on the mechanisms of cancer pain and develop new treatment strategies. We have used a murine model of bone cancer pain to investigate underlying peripheral neural mechanisms and novel treatment approaches. In this model, implantation of fibrosarcoma cells into and around the calcaneous bone produces mechanical and thermal hyperalgesia in mice. C-fiber nociceptors in tumor-bearing mice develop spontaneous ongoing activity and sensitization to thermal stimuli. However, it is unclear whether sensitization of nociceptors to mechanical stimuli underlies the mechanical hyperalgesia seen in tumor-bearing mice. We therefore examined responses of C-fiber nociceptors to suprathreshold mechanical stimuli in tumor-bearing mice and found they did not differ from those of C-nociceptors in control mice. Thus, sensitization of C-fiber nociceptors to mechanical stimulation does not appear to underlie tumor-evoked mechanical hyperalgesia in this murine model of bone cancer pain. We also examined the effect of the non-selective cannabinoid receptor agonist, WIN 55,212-2, on spontaneous activity and responses evoked by mechanical stimuli of C-fiber nociceptors innervating the tumor-bearing paw. Selective CB1 and CB2 antagonists were administered to determine the contribution of each receptor subtype to the effects of WIN 55,212-2. Intraplantar administration of WIN 55,212-2 attenuated spontaneous discharge and responses evoked by mechanical stimulation of C-fiber nociceptors. These effects were inhibited by prior intraplantar administration of selective CB1 (AM281) or CB2 (AM630) receptor antagonists but not by vehicle. These results indicate that activation of either CB1 or CB2 receptors reduced the spontaneous activity of C-fiber nociceptors associated with tumor growth as well as their evoked responses. Our results provide further evidence that activation of peripheral cannabinoid receptors may be a useful target for the treatment of cancer pain.

Response properties of mechanoreceptors and nociceptors in mouse glabrous skin: an in vivo study.

The increasing use of transgenic mice for the study of pain mechanisms necessitates comprehensive understanding of the murine somatosensory system. Using an in vivo mouse preparation, we studied response properties of tibial nerve afferent fibers innervating glabrous skin. Recordings were obtained from 225 fibers identified by mechanical stimulation of the skin. Of these, 106 were classed as A beta mechanoreceptors, 51 as A delta fibers, and 68 as C fibers. A beta mechanoreceptors had a mean conduction velocity of 22.2 +/- 0.7 (SE) m/s (13.8--40.0 m/s) and a median mechanical threshold of 2.1 mN (0.4--56.6 mN) and were subclassed as rapidly adapting (RA, n = 75) or slowly adapting (SA, n = 31) based on responses to constant force mechanical stimuli. Conduction velocities ranged from 1.4 to 13.6 m/s (mean 7.1 +/- 0.6 m/s) for A delta fibers and 0.21 to 1.3 m/s (0.7 +/- 0.1 m/s) for C fibers. Median mechanical thresholds were 10.4 and 24.4 mN for A delta and C fibers, respectively. Responses of A delta and C fibers evoked by heat (35--51 degrees C) and by cold (28 to -12 degrees C) stimuli were determined. Mean response thresholds of A delta fibers were 42.0 +/- 3.1 degrees C for heat and 7.6 +/- 3.8 degrees C for cold, whereas mean response thresholds of C fibers were 40.3 +/- 0.4 degrees C for heat and 10.1 +/- 1.9 degrees C for cold. Responses evoked by heat and cold stimuli increased monotonically with stimulus intensity. Although only 12% of tested A delta fibers were heat sensitive, 50% responded to cold. Only one A delta nociceptor responded to both heat and cold stimuli. In addition, 40% of A delta fibers were only mechanosensitive since they responded neither to heat nor to cold stimuli. Thermal stimuli evoked responses from the majority of C fibers: 82% were heat sensitive, while 77% of C fibers were excited by cold, and 68% were excited by both heat and cold stimuli. Only 11% of C fibers were insensitive to heat and/or cold. This in vivo study provides an analysis of mouse primary afferent fibers innervating glabrous skin including new information on encoding of noxious thermal stimuli within the peripheral somatosensory system of the mouse. These results will be useful for future comparative studies with transgenic mice.

Enhanced responses of spinal dorsal horn neurons to heat and cold stimuli following mild freeze injury to the skin.

The effects of a mild freeze injury to the skin on responses of nociceptive dorsal horn neurons to cold and heat stimuli were examined in anesthetized rats. Electrophysiological recordings were obtained from 72 nociceptive spinal neurons located in the superficial and deep dorsal horn. All neurons had receptive fields (RFs) on the glabrous skin of the hindpaw, and neurons were functionally divided into wide dynamic range (WDR) and high-threshold (HT) neurons. Forty-four neurons (61%) were classified as WDR and responded to both innocuous and noxious mechanical stimuli (mean mechanical threshold of 12.8 +/- 1.6 mN). Twenty-eight neurons (39%) were classified as HT and were excited only by noxious mechanical stimuli (mean mechanical threshold of 154.2 +/- 18.3 mN). Neurons were characterized for their sensitivity heat (35 to 51 degrees C) and cold (28 to -12 degrees C) stimuli applied to their RF. Among WDR neurons, 86% were excited by both noxious heat and cold stimuli, while 14% responded only to heat. For HT neurons, 61% responded to heat and cold stimuli, 32% responded only to noxious heat, and 7% responded only to noxious cold. Effects of a mild freeze injury (-15 degrees C applied to the RF for 20 s) on responses to heat and cold stimuli were examined in 30 WDR and 22 HT neurons. Skin freezing was verified as an abrupt increase in skin temperature at the site of injury due to the exothermic reaction associated with crystallization. Freezing produced a decrease in response thresholds to heat and cold stimuli in most WDR and HT neurons. WDR and HT neurons exhibited a mean decrease in response threshold for cold of 9.0 +/- 1.3 degrees C and 10.0 +/- 1.6 degrees C, respectively. Mean response thresholds for heat decreased 4.0 +/- 0.4 degrees C and 4.3 +/- 1.3 degrees C in WDR and HT neurons, respectively. In addition, responses to suprathreshold cold and heat stimuli increased. WDR and HT neurons exhibited an 89% and a 192% increase in response across all cold stimuli, and a 93 and 92% increase in responses evoked across all heat stimuli, respectively. Our results demonstrate that many spinal neurons encode intensity of noxious cold as well as noxious heat over a broad range of stimulus temperatures. Enhanced responses of WDR and HT neurons to cold and heat stimuli after a mild freeze injury is likely to contribute to thermal hyperalgesia following a similar freeze injury in humans.

Differential expression of sigE by Mycobacterium tuberculosis during intracellular growth.

The Mycobacterium tuberculosis sigE gene encodes a sigma factor that is a member of the extracytoplasmic function subfamily of sigma factors. Using RT-PCR we demonstrated that sigE is expressed in M. tuberculosis bacilli during growth in human macrophages beginning after 30 min but before 6 h after infection through at least 5 days after infection, but that sigE is not expressed by M. tuberculosis bacteria during growth in Middlebrook 7H9 broth medium. However, sigE expression can be induced by treatment of broth cultures with hydrogen peroxide. Further, sigE is not expressed by M. tuberculosis bacilli during attachment or growth in type II pneumocytes. Using a green fluorescent protein (GFP) reporter gene fused to the sigE promoter, we observed induction of GFP expression following macrophage infection. Western blotting confirmed that sigE protein expression correlated with mRNA expression in induced systems. Analysis of the region of the M. tuberculosis genome encoding sigE suggested it is part of an operon consisting of sigE-orf1-htrA-orf2. The data presented in this report showed that sigE is differentially expressed by M. tuberculosis bacilli in macrophages and might play a role in the pathogenesis of this organism.

Functional interactions between tumor and peripheral nerve in a model of cancer pain in the mouse.

Cancer is usually accompanied by pain, which tends to increase in relation to metastatic infiltration and destruction. In the United States, 30% to 40% of newly diagnosed cancer patients and 67% to 90% of patients with advanced cancer report moderate to severe pain. Relief for approximately 90% of patients with cancer-related pain may be provided by the World Health Organization's "analgesic ladder," which involves progressing from non-opioid (e.g., acetaminophen, ibuprofen) to weak opioid (e.g., codeine), to strong opioid (e.g., morphine, fentanyl) intervention for pain relief. The severity of cancer pain is affected by diverse factors. In addition to the obvious factors of tumor size and degree of metastatic destruction, the type of tumor and its location are also important factors that contribute to pain severity. Severe cancer pain is especially associated with tumors involving bone destruction and nerve infiltration. Cancer pain seems to involve diverse mechanisms, including characteristics of both nociceptive and neuropathic pain. Unfortunately, even opioid analgesics often produce poor pain relief against neuropathic pain derived from peripheral nerve or root damage common to cancers involving bone metastases and nerve infiltration. In addition, these drugs may induce adverse side effects since they affect various physiological functions, including hormone secretion, neurotransmitter release, feeding, gastrointestinal motility, and respiratory activity. Currently, drug therapies utilizing antidepressants and anticonvulsants are being used to relieve neuropathic pain whereas cancer pain is treated largely with opiods in cancer patients.