Neurochemical plasticity in the enteric nervous system of a primate animal model of experimental Parkinsonism

Emerging evidences suggest that the enteric nervous system (ENS) is affected by the degenerative process in Parkinson's disease (PD). In addition lesions in the ENS could be associated with gastrointestinal (GI) dysfunctions, in particular constipation, observed in PD. However, the precise alterations of the ENS and especially the changes in the neurochemical phenotype remain largely unknown both in PD and experimental Parkinsonism. The aim of our study was thus to characterize the neurochemical coding of the ENS in the colon of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys, a well-characterized model of PD. In the myenteric plexus, there was a significant increase in the number of neurons per ganglia (identified with Hu), especially nitric oxide synthase immunoreactives (IR) neurons in MPTP-treated monkeys compared to controls. A concomitant 72% decrease in the number of tyrosine hydroxylase-IR neurons was observed in MPTP-treated monkeys compared to controls. In contrast no change in the cholinergic or vasoactive intestinal peptide-IR population was observed. In addition, the density of enteric glial cells was not modified in MPTP-treated monkeys. Our results demonstrate that MPTP induces major changes in the myenteric plexus and to a lesser extent in the submucosal plexus of monkeys. They further reinforce the observation that lesions of the ENS occur in the course of PD that might be related to the GI dysfunction observed in this pathology.

Roles of dorsal column pathway and transient receptor potential vanilloid type 1 in augmentation of cerebral blood flow by upper cervical spinal cord stimulation in rats

Clinical and basic studies have indicated that upper cervical spinal cord stimulation (cSCS) significantly increases cerebral blood flow (CBF), but the mechanisms are incompletely understood. This investigation was conducted to differentiate between stimulation of dorsal column fibers and upper cervical spinal cord cell bodies in cSCS-induced increases in CBF and decreases in cerebrovascular resistance (CVR). cSCS (50 Hz, 0.2 ms, 1 min) was applied on the left C1-C2 dorsal column of pentobarbital anesthetized, ventilated and paralyzed male rats. Laser Doppler flowmetry probes were placed bilaterally over the parietal cortex, and arterial pressure was monitored. cSCS at 30%, 60%, and 90% of motor threshold (MT) produced vasodilation bilaterally in cerebral cortices. Subsequently, cSCS was applied at 90% MT, and ipsilateral responses were recorded. Ibotenic acid (0.3 mg/ml, 0.1 ml) placed on dorsal surface of C1-C2 (n=7) to suppress cell body activity, did not affect cSCS-induced %DeltaCBF (42.5+/-8.1% vs. 36.8+/-7.1%, P>0.05) and %DeltaCVR (-19.4+/-4.2% vs. -15.2+/-5.6%, P>0.05). However, bilateral transection of the dorsal column at rostral C1 (n=8) abolished cSCS-induced changes in CBF and CVR. Also, rostral C1 transection (n=7) abolished cSCS-induced changes in CBF and CVR. Resinferatoxin (RTX), an ultrapotent transient receptor potential vanilloid type 1 (TRPV1) agonist, was used to inactivate TRPV1 containing nerve fibers/cell bodies. RTX (2 microg/ml, 0.1 ml) placed on the C1-C2 spinal cord (n=7) did not affect cSCS-induced %DeltaCBF (60.2+/-8.1% vs. 46.3+/-7.7%, P>0.05) and %DeltaCVR (-25.5+/-3.5% vs. -21.4+/-8.9%, P>0.05). However, i.v. RTX (2 microg/kg, n=9) decreased cSCS-induced %DeltaCBF from 65.0+/-9.5% to 27.4+/-7.2% (P<0.05) and %DeltaCVR from -28.0+/-7.6% to -14.8+/-4.2% (P<0.05). These results indicated that cSCS-increases in CBF and decreases in CVR occurred via rostral spinal dorsal column fibers and did not depend upon C1-C2 cell bodies. Also, our results suggested that cerebral but not spinal TRPV1 was involved in cSCS-induced cerebral vasodilation.

Acute colitis enhances responsiveness of lumbosacral spinal neurons to colorectal distension in rats

Aim of this study was to examine excitability and responsiveness of lumbosacral spinal neurons to colorectal distension (CRD) in rats with colitis induced by dextran sulphate sodium (DSS). Extracellular potentials of single L6-S2 spinal neurons were recorded in pentobarbital anesthetized and paralyzed rats. Results showed that 40/154 (26%) and 53/156 (34%) neurons responded to noxious CRD (80 mmHg, 20 s) in DSS-treated and control animals, respectively. Neurons with long-lasting and low-threshold excitatory responses to CRD were more frequently encountered in DSS-treated than in control groups (P < 0.05). The mean maximal excitatory responses of neurons to noxious CRD in DSS-treated animals were significantly greater and the duration of responses was longer than those in control animals (P < 0.05). It was suggested that lumbosacral spinal neurons with colorectal input had increased excitability and responsiveness following colitis, which might play an important role in development of colonic hypersensitivity and viscerosomatic referred pain.

Spinal cord stimulation modulates intraspinal colorectal visceroreceptive transmission in rats

Previous studies have shown that spinal cord stimulation (SCS) of upper lumbar segments decreases visceromotor responses to mechanical stimuli in a sensitized rat colon and reduces symptoms of irritable bowel syndrome in patients. SCS applied to the upper cervical spinal dorsal column reduces pain of chronic refractory angina. Further, chemical stimulation of C1-C2 propriospinal neurons in rats modulates the responses of lumbosacral spinal neurons to colorectal distension. The present study was designed to compare the effects of upper cervical and lumbar SCS on activity of lumbosacral neurons receiving noxious colorectal input. Extracellular potentials of L6-S2 spinal neurons were recorded in pentobarbital anesthetized, paralyzed and ventilated male rats. SCS (50 Hz, 0.2 ms) at low intensity (90% of motor threshold) was applied to the dorsal column of upper cervical (C1-C2) or upper lumbar (L2-L3) ipsilateral spinal segments. Colorectal distension (CRD, 20 mmHg, 40 mmHg, 60 mmHg, 20s) was produced by air inflation of a latex balloon. Results showed that SCS applied to L2-L3 and C1-C2 segments significantly reduced the excitatory responses to noxious CRD from 417.6+/-68.0 to 296.3+/-53.6 imp (P<0.05, n=24) and from 336.2+/-64.5 to 225.0+/-73.3 imp (P<0.05, n=18), respectively. Effects of L2-L3 and C1-C2 SCS lasted 10.2+/-1.9 and 8.0+/-0.9 min after offset of CRD. Effects of SCS were observed on spinal neurons with either high or low-threshold excitatory responses to CRD. However, L2-L3 or C1-C2 SCS did not significantly affect inhibitory neuronal responses to CRD. C1-C2 SCS-induced effects were abolished by cutting the C7-C8 dorsal column but not by spinal transection at cervicomedullary junction. These data demonstrated that upper cervical or lumbar SCS modulated responses of lumbosacral spinal neurons to noxious mechanical stimulation of the colon, thereby, proved two loci for a potential therapeutic effect of SCS in patients with irritable bowel syndrome and other colonic disorders.

Hyperexcitability of convergent colon and bladder dorsal root ganglion neurons after colonic inflammation: mechanism for pelvic organ cross-talk

Clinical studies reveal concomitant occurrence of several gastrointestinal and urologic disorders, including irritable bowel syndrome and interstitial cystitis. The purpose of this study was to determine the mechanisms underlying cross-organ sensitization at the level of dorsal root ganglion (DRG) after acute and subsided gastrointestinal inflammation. DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) and Fast Blue were injected into the distal colon and urinary bladder of male rats, respectively. Convergent DRG neurons were found in L1-L3 and L6-S2 ganglia with an average distribution of 14% +/- 2%. The resting membrane potential (RMP) of cells isolated from upper lumbar (UL) ganglia was -59.8 +/- 2.7 mV, whereas lumbosacral (LS) neurons were more depolarized (RMP = -49.4 +/- 2.1 mV, P < or = 0.05) under control conditions. Acute trinitrobenzene sulfonic acid (TNBS) colitis (3 days) decreased voltage and current thresholds for action potential firing in LS but not UL convergent capsaicin-sensitive neurons. This effect persisted for 30 days in the absence of overt colonic inflammation. The current threshold for action potential (AP) firing in UL cells was also decreased from 165.0 +/- 24.5 pA (control) to 85.0 +/- 19.1 pA at 30 days (P < or = 0.05), indicating increased excitability. The presence of a subpopulation of colon-bladder convergent DRG neurons and their persistent hyperexcitability after colonic inflammation provides a basis for pelvic organ cross-sensitization.

Development of selective aryl hydrocarbon receptor modulators for treatment of breast cancer

The aryl hydrocarbon receptor (AhR) is a basic helix-loop-helix DNA-binding protein that forms a transcriptionally-active heterodimer with the AhR nuclear translocator (Arnt) protein. The nuclear AhR complex is a ligand-induced transcription factor and the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a high affinity ligand for the AhR. TCDD induces a diverse spectrum of tissue-, sex- and species-specific biochemical and toxic responses in Ah-responsive cells/tissues including the inhibition of 17beta-oestradiol (E2)-induced gene expression in the rodent uterus and mammary and in human breast cancer cell lines. TCDD also inhibits spontaneous and carcinogen-induced mammary tumour formation and growth in rodent models. Research in this laboratory has utilised the AhR as a target for developing anticancer drugs for treatment of breast cancer and two different structural classes of selective AhR modulators (SAhRMs) have been developed. Alternate-substituted (1,3,6,8- and 2,4,6,8-) alkyl polychlorinated dibenzofurans (PCDFs) and substituted diindolylmethanes (DIMs) bind the AhR and induce a pattern of AhR-oestrogen receptor (ER) inhibitory cross-talk similar to that observed for TCDD including inhibition of mammary tumour growth at doses < 1.0 mg/kg/day. In contrast, effective doses of these compounds do not induce hepatic CYP1A1-dependent activity or other AhR-mediated toxic responses induced by TCDD. These results indicate that SAhRMs may be an important new class of drugs for clinical treatment of breast cancer via AhR-ER inhibitory cross-talk.

Importance of phosphorylation for osteopontin regulation of biomineralization

Previous in vitro and in vivo studies demonstrated that osteopontin (OPN) is an inhibitor of the formation and growth of hydroxyapatite (HA) and other biominerals. The present study tests the hypotheses that the interaction of OPN with HA is determined by the extent of protein phosphorylation and that this interaction regulates the mineralization process. Bone OPN as previously reported inhibited HA formation and HA-seeded growth in a gelatin-gel system. A transglutaminase-linked OPN polymer had similar effects. Recombinant, nonphosphorylated OPN and chemically dephosphorylated OPN, had no effect on HA formation or growth in this system. In contrast, highly phosphorylated milk OPN (mOPN) promoted HA formation. The mOPN stabilized the conversion of amorphous calcium phosphate (a non-crystalline constituent of milk) to HA, whereas bone OPN had a lesser effect on this conversion. Mixtures of OPN and osteocalcin known to form a complex in vitro, unexpectedly promoted HA formation. To test the hypothesis that small alterations in protein conformation caused by phosphorylation account for the differences in the observed ability of OPN to interact with HA, the conformation of bone OPN and mOPN in the presence and absence of crystalline HA was determined by attenuated total reflection (ATR) infrared (IR) spectroscopy. Both proteins exhibited a predominantly random coil structure, which was unaffected by the addition of Ca(2+). Binding to HA did not alter the secondary structure of bone OPN, but induced a small increase of beta-sheet (few percent) in mOPN. These data taken together suggest that the phosphorylation of OPN is an important factor in regulating the OPN-mediated mineralization process.

Developmental analysis and computer modelling of bioengineered teeth

Here we present the developmental progression of bioengineered pig teeth from 1 to 25 weeks of development. We demonstrate that 2-25 week implants contained embryonic tooth bud- and cap-stage tooth structures consisting of dental epithelium expressing the sonic hedgehog gene and condensed dental mesenchyme. Implants harvested at 18-25 weeks also contained tooth bud-like structures, as well as mature tooth structures containing enamel, dentin and pulp tissues. Immunohistochemical analyses confirmed the expression of dentin- and enamel-specific proteins in differentiated bioengineered tooth tissues. Three-dimensional computer modelling further demonstrated a spatial organization of enamel, dentin and pulp tissues resembling that of natural teeth. We conclude that bioengineered teeth commonly exhibit morphological stages characteristic of naturally forming teeth. Furthermore, the presence of immature tooth buds at all times assayed and increased numbers of bioengineered tooth structures over time suggests that porcine dental progenitor cells maintain the ability to form teeth for at least 25 weeks.

Descending modulation of thoracic visceroreceptive transmission by C1-C2 spinal neurons

Extracellular potentials of single T3 neurons were recorded in pentobarbital anesthetized male rats. Thoracic esophageal distension (ED, 0.3-0.4 ml, 20 s) and intrapericardial injection of bradykinin (BK, 10(-5) M, 0.2 ml, 1 min) were used as noxious visceral stimuli. Chemical activation of C1-C2 neurons with glutamate pledgets (1 M, 1-3 min) decreased background activity and/or excitatory responses of 26/35 (74%) neurons to ED and 34/44 (77%) neurons to BK. After spinal transection at rostral C1 in five animals, glutamate at C1-C2 still significantly reduced excitatory responses of five neurons to BK. Data showed that intraspinal descending modulation of C1-C2 neurons primarily produced descending inhibition of excitatory responses of thoracic spinal neurons to noxious visceral stimuli.

Chemical activation of C(1)-C(2) spinal neurons modulates activity of thoracic respiratory interneurons in rats

Discharge patterns of thoracic dorsal horn neurons are influenced by chemical activation of cell bodies in cervical spinal segments C(1)-C(2). The present aim was to examine whether such activation would specifically affect thoracic respiratory interneurons (TRINs) of the deep dorsal horn and intermediate zone in pentobarbital sodium-anesthetized, paralyzed, artificially ventilated rats. We also characterized discharge patterns and pathways of TRIN activation in rats. A total of 77 cells were classified as TRINs by location, continued burst activity related to phrenic discharge when the respirator was stopped, and lack of antidromic response from selected pathways. A variety of respiration-phased discharge patterns was documented whose pathways were interrupted by ipsilateral C(1) transection. Glutamate pledgets (1 M, 1 min) on the dorsal surface of the spinal cord inhibited 22/49, excited 15/49, or excited/inhibited 3/49 tested cells. Incidence of responses did not depend on whether the phase of TRIN discharge was inspiratory, expiratory, or biphasic. Phrenic nerve activity was unaffected by chemical activation of C(1)-C(2) in this preparation. Besides supraspinal input, TRIN activity may be influenced by upper cervical modulatory pathways.

The expression of dentin sialophosphoprotein gene in bone

Dentin sialoprotein (DSP) and dentin phosphoprotein (DPP) are expressed as a single mRNA transcript coding for a large precursor protein termed dentin sialophosphoprotein (DSPP). DSP, DPP, and DSPP have been considered to be tooth-specific. To test for the expression of the dspp gene in bone, we performed Western immunoblots and reverse-transcription polymerase chain-reaction (RT-PCR). With Western immunoblots, we detected DSP in the Gdm/EDTA extracts of rat long bone, at a level of about 1/400 of that in dentin. Using RT-PCR, we detected DSPP mRNA in mouse calvaria. Similar to Western immunoblots, the results of RT-PCR indicated that the dspp gene is expressed at a lower level in bone than in dentin and odontoblasts. Analysis of the data shows that DSPP is not a tooth-specific protein, and that dramatically different regulatory mechanisms governing DSPP expression are involved in the bone and dentin.

Osteopontin posttranslational modifications, possibly phosphorylation, are required for in vitro bone resorption but not osteoclast adhesion

Osteopontin (OPN), a phosphorylated bone matrix glycoprotein, is an Arg-Gly-Asp (RGD)-containing protein that interacts with integrins and promotes in vitro attachment of a number of cell types, including osteoclasts. Gene knockout experiments support the idea that OPN is important in osteoclastic activity. We hypothesize that posttranslational modifications (PTMs) of OPN can influence its physiological function. Previous studies have suggested that phosphorylation of OPN and bone sialoprotein (BSP) is necessary for promoting osteoclast adhesion. However, no reports have explored the importance of phosphoserines and other PTMs in OPN-promoted bone resorption. To study this question, we determined the activities of different forms of OPN and BSP in three in vitro assays: attachment of osteoclasts; formation of actin rings; and bone resorption. For each assay, cells were incubated for 4-24 h, in the presence or absence of RGDS or RGES peptides, to test the involvement of integrin binding. In addition to OPN, activities of milk OPN (fully phosphorylated) and recombinant OPN (rOPN, no phosphate) were compared. We purified two forms of OPN (OPN-2 and OPN-5), which differ in the level of phosphorylation, and compared their activities. For comparison, the activities of BSP and recombinant BSP (rBSP) were determined. All forms of OPN, including rOPN, significantly increased attachment of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts. BSP and rBSP also promoted cell attachment. After 4 h of incubation, the proportion of cells with actin rings was increased with OPN, milk OPN, and BSP. In the presence of RGDS peptide, osteoclast retraction and the disruption of actin rings were observed, whereas no effect was seen with RGES. In the resorption assay, the number of pits and the total resorbed area per slice were increased in the presence of OPN, milk OPN, and BSP. As in other assays, the OPN enhancement of resorption was inhibited by RGDS, but not RGES, peptides. Significantly, rOPN and rBSP did not promote bone resorption. OPN-5 promoted resorption to a greater extent than OPN-2, and milk OPN significantly stimulated resorption to a greater extent than OPN. Our data suggest that: (1) the RGD sequence of OPN is essential in OPN-mediated cell attachment, actin ring formation, and bone resorption; and (2) some form of PTM, possibly phosphorylation, is necessary for in vitro osteoclastic bone resorption, but not for cell attachment and actin ring formation.

A comparative study of sialic acid-rich proteins in rat bone and dentin

Four sialic acid-rich (SA-rich) proteins found in bone and dentin, osteopontin (OPN), bone sialoprotein (BSP), bone acidic glycoprotein-75 (BAG-75), and dentin matrix protein 1 (DMP1), share some common features. We used SDS-PAGE and Western immunoblots to analyze and compare SA-rich proteins in bone and dentin extracts from rats with a single chromatographic procedure. OPN was detected in dentin extracts, with a relative level less than one-seventieth of that in bone. Both bone and dentin BSP demonstrated an extremely broad distribution pattern, probably due to a high degree of heterogeneity in post-translational modifications. BAG-75 in both bone and dentin was detected as an 83 kDa band, dramatically distinct from that of DMPI. Using a polyclonal antibody raised against a purified bone 57 kDa protein (a portion of DMPI), we detected 150 kDa protein bands in bone fraction; the same bands were recognized by antirecombinant rat DMPI antibody. Bands from dentin migrating at about 150 kDa in earlier fractions and progressing to 200 kDa in later fractions showed a clear immunoreactivity to the anti-57 kDa antibody. We conclude that the majority of DMPI in rat bone is processed into fragments, whereas that in dentin remains intact.

Intrapericardial algogenic chemicals evoke cardiac-somatic motor reflexes in rats

Many patients suffer from secondary muscle hyperalgesia after experiencing angina pectoris. Electrophysiological studies have also demonstrated electromyography (EMG) activities evoked during brief occlusion of the coronary artery in cats. Our objectives are: (1) to develop an animal model to study muscle changes resulting from cardiac dysfunction and (2) to investigate possible links between muscle hyperalgesia and EMG activities observed with ischemic heart diseases. Intrapericardial infusion of algogenic chemicals produced EMG activities in paraspinal muscles. Among these paraspinal muscles, the spinotrapezius produced the most consistent responses (38/53 animals). The evoked responses, in most cases, persisted longer than 90 s (29/53 muscles). The EMG activities consisted of three patterns of motor-unit discharge, namely single-unit, complex, and ventilation-related. The duration of the patterns, as well as the shape and amplitude of the motor-unit waveforms, are similar to the characteristics of muscle spasms. Since sensitization of muscle afferent fibers by noxious stimuli could produce angina-like pain, the spasm-like EMG activities might sensitize muscle afferent fibers that contribute to acute angina pain and secondary muscle hyperalgesia of cardiac patients.

[Study on immunonodulating activities of enzymolyzed loach protein]

The immunomodulating activities of enzymolyzed loach protein in mice were investigated by regular methods for immunology evaluation. The doses of enzymolyzed loach protein were 0.1, 0.2, 0.4 g.kg-1 bw, which were 5, 10, 20 times respectively as large as the recommended daily intake(0.02 g.kg-1 bw). After being successively fed with enzymolyzed loach protein at given doses for 30 days by ig respectively, the mice were detected by immunomodulation tests. The results indicated that enzymolyzed loach protein had significant modulating effects on all of test indexes and suggested it had apparent immunomodulating activities in mice. Based on the results described above, we speculate that the enzymolyzed loach protein may have immunomodulating functions and can enhance the immunity of body.

Afferent pathways for cardiac-somatic motor reflexes in rats

The present study used a rat model in which algogenic chemicals were infused into the pericardial sac to evoke spasmlike contractions in paraspinal muscles. The following techniques were used to study the roles of sympathetic (SCA) and vagal cardiac afferents (VCA) in electromyographic (EMG) responses to pericardial algogenic chemicals: chemical stimulation, electrical stimulation, and nerve transection. Activation with bradykinin (n = 46) produced a significantly higher peak response than infusion of an algogenic mixture (n = 53) containing chemicals that also activate VCA. Electrical stimulation of SCA produced bilateral EMG activities (7 of 7). Electrical stimulation of VCA did not evoke EMG activity but inhibited the chemically evoked EMG response (12 of 12). The chemically evoked response was decreased after transection of the left sympathetic chain (n = 22) and was increased after bilateral vagotomy (n = 19). These results suggest an excitatory and inhibitory role for SCA and VCA, respectively. Therefore, in addition to spinothalamic convergence of somatic and visceral afferents, activation of SCA to generate spasmlike muscle contractions could account in part for anginal pain, and VCA activation could attenuate this effect.

[Effects of radiofrequency catheter ablation in coagulation system]

OBJECTIVE

To investigate the pathogenesis and prophylactic therapy of peripheral vascular embolism after radiofrequency catheter ablation (RFCA).

METHOD

90 patients with supraventricular tachycardia (SVT) were divided into 3 groups. Group A did not use any anticoagulant before RFCA and group B used aspirin (ASA) before RFCA, group C used calcium channel blocker-amlodipine before RFCA. Blood samples were taken at 4 time points, i.e. before and after electrophysiologic examination, immediately after RFCA and 2 days after RFCA. For each blood example, blood levels of platelet alpha-granule membrane glycoprotein-140 (Gmp-140), thromboxane B(2) (TXB(2)), protein C (PC), protein S (PS) were measured.

RESULT

In group A, Gmp-140 and TXB(2) of the blood examples taken before electrophysiologic examination were significantly lower than those taken at the three other time points, but there was no significant change of PC and PS as compared with that at the three other time points. Ablation either on the left or right heart did not affect the levels of Gmp-140 and TXB(2); In group B and group C, the levels of Gmp-140 and TXB(2) of the samples were significantly lower than those of the corresponding points in group A.

CONCLUSION

It is indicated that platelet aggregability may be introduced by RFCA, but evolution of the anticoagulant system was not caused by RFCA, This may enhance the occurrence of thrombosis. ASA and amlodipine may prevent the occurrence of thrombosis.

Responses and afferent pathways of superficial and deeper c(1)-c(2) spinal cells to intrapericardial algogenic chemicals in rats

Electrical stimulation of vagal afferents or cardiopulmonary sympathetic afferent fibers excites C(1)--C(2) spinal neurons. The purposes of this study were to compare the responses of superficial (depth <0.35 mm) and deeper C(1)--C(2) spinal neurons to noxious chemical stimulation of cardiac afferents and determine the relative contribution of vagal and sympathetic afferent pathways for transmission of noxious cardiac afferent input to C(1)--C(2) neurons. Extracellular potentials of single C(1)--C(2) neurons were recorded in pentobarbital anesthetized and paralyzed male rats. A catheter was placed in the pericardial sac to administer a mixture of algogenic chemicals (0.2 ml) that contained adenosine (10(-3) M), bradykinin, histamine, serotonin, and prostaglandin E(2) (10(-5) M each). Intrapericardial chemicals changed the activity of 20/106 (19%) C(1)--C(2) spinal neurons in the superficial laminae, whereas 76/147 (52%) deeper neurons responded to cardiac noxious input (P < 0.01). Of 96 neurons responsive to cardiac inputs, 48 (50%) were excited (E), 41 (43%) were inhibited (I), and 7 were excited/inhibited (E-I) by intrapericardial chemicals. E or I neurons responsive to intrapericardial chemicals were subdivided into two groups: short-lasting (SL) and long-lasting (LL) response patterns. In superficial gray matter, excitatory responses to cardiac inputs were more likely to be LL-E than SL-E neurons. Mechanical stimulation of the somatic field from the head, neck, and shoulder areas excited 85 of 95 (89%) C(1)--C(2) spinal neurons that responded to intrapericardial chemicals; 31 neurons were classified as wide dynamic range, 49 were high threshold, 5 responded only to joint movement, and no neuron was classified as low threshold. For superficial neurons, 53% had small somatic fields and 21% had bilateral fields. In contrast, 31% of the deeper neurons had small somatic fields and 46% had bilateral fields. Ipsilateral cervical vagotomy interrupted cardiac noxious input to 8/30 (6 E, 2 I) neurons; sequential transection of the contralateral cervical vagus nerve (bilateral vagotomy) eliminated the responses to intrapericardial chemicals in 4/22 (3 E, 1 I) neurons. Spinal transection at C(6)--C(7) segments to interrupt effects of sympathetic afferent input abolished responses to cardiac input in 10/10 (7 E, 3 I) neurons that still responded after bilateral vagotomy. Results of this study support the concept that C(1)-C(2) superficial and deeper spinal neurons play a role in integrating cardiac noxious inputs that travel in both the cervical vagal and/or thoracic sympathetic afferent nerves.

Association of ARNT splice variants with estrogen receptor-negative breast cancer, poor induction of vascular endothelial growth factor under hypoxia, and poor prognosis

The aryl hydrocarbon receptor nuclear translocator (ARNT) is a basic helix-loop-helix transcription factor that forms heterodimers with the aryl hydrocarbon receptor (AhR) or hypoxia inducible factor-1alpha to activate transcription via xenobiotic response element or hypoxia response element, respectively. Thus, it plays a major role in two key biochemical pathways involved in tumor growth. We previously showed that estrogen receptor (ER)-negative breast cancer cell lines expressed a splice variant of ARNT that was associated with Ah nonresponsiveness. We have now used a sensitive PCR method to analyze the expression of the variant in a series of 92 breast cancers to assess interactions with the ER and prognosis. The splice variant could be detected in all of the cases examined, with high ratios of variant:full-length ARNT (> or =10) characterized in 10 cases. When the patient group was split into quartiles by increasing splice variant ratios, there was an inverse relationship of ER status to ARNT splice-variant ratios (P = 0.01, chi(2)). Univariate analysis showed that cases with high ARNT splice-variant ratios > or =10 had a worse relapse-free and overall survival (P > or = 0.03; hazard ratio, 2.7; and P = 0.006; hazard ratio, 3.9, respectively). In multivariate analysis for relapse-free and overall survival, ARNT splice-variant ratio was the strongest independent factor and, although inversely related to ER, remained a separate risk factor. At least two potential mechanisms could explain this phenomenon: the loss of aryl hydrocarbon receptor-mediated antiestrogenic activity or the blockade of a proapoptotic pathway induced by hypoxia. Because several enzymes involved in drug resistance are induced through a xenobiotic response element, the tumors presenting high ARNT splice-variant ratios may be specifically targeted by drugs normally degraded or inactivated. This study shows the biological importance of ARNT splice variants in the behavior of human breast cancer and suggests that the breast cell lines in which the splice variant was discovered may be useful models for further investigation.

Transcriptional activation of heat shock protein 27 gene expression by 17beta-estradiol and modulation by antiestrogens and aryl hydrocarbon receptor agonists

Heat shock protein 27 (Hsp 27) is expressed in mammary tumors and may play a role in tumor growth and response to anti-neoplastic drug therapy. 17beta-Estradiol (E2) induces Hsp 27 mRNA levels in MCF-7 human breast cancer cells, and we have investigated the comparative inhibitory mechanisms using the aryl hydrocarbon receptor (AhR) agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the direct-acting antiestrogen ICI 164,384. TCDD inhibited E2-induced Hsp 27 gene expression and analysis of the Hsp 27 gene promoter showed that the inhibitory response was associated with AhR interactions with a pentanucleotide motif at -3 to +2 in the promoter that corresponded to the core sequence of a dioxin responsive element. In contrast, ICI 164,384 induced Hsp 27 gene expression and reporter gene activity in MCF-7 cells and this represents one of the few examples of the estrogen receptor-alpha (ERalpha) agonist activity of the 'pure' antiestrogen ICI 164,384.

Identification and characterization of the carboxyl-terminal region of rat dentin sialoprotein

Two acidic proteins, dentin sialoprotein (DSP) and dentin phosphoprotein (DPP), are present in the extracellular matrix of dentin but not in bone. These two proteins are expressed in odontoblasts and preameloblasts as a single cDNA transcript coding a large precursor protein termed dentin sialophosphoprotein (DSPP). DSPP is specifically cleaved into two unique proteins, DSP and DPP. However, the cleavage site(s) of DSPP and the mechanisms for regulating the cleavages are unknown. To identify the specific site(s) of DSPP that are cleaved when the initial translation product is converted to DSP and DPP, we performed a detailed analysis (Edman degradation and mass spectrometry) on selected tryptic peptides of a size originating from the COOH-terminal region of rat DSP. After cleavage with trypsin, the DSP fragments were separated by a two-dimensional method (size-exclusion chromatography followed by reversed phase high performance liquid chromatography). We characterized 13 peptides from various regions of DSP. The analyses showed that peptide Ile(409)-Tyr(421) was the major COOH-terminal fragment, ending at Tyr(421) only 9 residues from the NH(2) terminus of DPP. Peptide Gln(385)-His(406) represented a second, minor COOH-terminal peptide that terminated at His(406). Both of these residues are well beyond the COOH terminus predicted previously by two independent studies estimating that rat DSP contained 360-370 amino acids. Careful studies on two peptides showed that, among 9 potential casein kinase II phosphorylation sites, 2 serines were phosphorylated. We found that rat DSP was heterogeneous with respect to phosphorylation, because this same peptide sequence eluted in two discrete peaks, one with 2 phosphoserines and the other having 1. The finding that 3 lysines just preceding the COOH termini were modified by a 43-Da substituent (possibly a carbamoyl substituent) suggests that the lysines in this region were particularly susceptible to attachment of this substituent.