Hydrated electrons induce the formation of interstrand cross-links in DNA modified by cisplatin adducts.

Double-stranded oligonucleotides containing cisplatin adducts, with and without a mismatched region, were exposed to hydrated electrons generated by gamma-rays. Gel electrophoresis analysis demonstrates the formation of cisplatin-interstrand crosslinks from the cisplatin-intrastrand species. The rate constant per base for the reaction between hydrated electrons and the double-stranded oligonucleotides with and without cisplatin containing a mismatched region was determined by pulse radiolysis to be 7 × 109 and 2 × 109 M-1 s-1, respectively. These results provide a better understanding of the radiosensitizing effect of cisplatin adducts in hypoxic tumors and of the formation of interstrand crosslinks, which are difficult for cells to repair.

Presence of parasite DNA in clinically unaffected nasal mucosa during cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis.

OBJECTIVES: We aimed to detect Leishmania DNA carriage in nasal mucosa of individuals with cutaneous leishmaniasis (CL) caused by Leishmania (Viannia) braziliensis. METHODS: A cross-sectional study was performed in all individuals with CL without nasal lesions (n = 153) attended within 2 years in an endemic area of L. (Viannia) braziliensis in Bahia (Brazil). An otorhinolaryngologist assessed the clinical status of the nasal mucosa by anterior rhinoscopy and endoscopic examinations. Swab samples were collected for parasite DNA detection by PCR from all individuals before standard treatment for leishmaniasis. A second evaluation 3 months after treatment was performed to assess clinical outcomes. RESULTS: Parasite DNA was detected in 7.8% (12/153) of clinically healthy nasal mucosa of individuals with CL. Interestingly, DNA was more frequently identified in individuals with more skin lesions (median 1.5, interquartile range (IQR) 1-3.5 versus 1.0, IQR 1-1.5; p 0.044), or larger injuries (median 2.7, IQR 2-3.8 versus 1.6, IQR 1-2.5; p 0.013). Additionally, the disease of those individuals with positive PCR evolved more frequently to unusual forms of leishmaniasis (recidiva cutis and disseminated) (45.5% (5/11) versus 11.5% (14/122); p 0.009), and required more cycles of treatment to reach clinical cure (median 2, IQR 1-4 versus 1, IQR 1-2; p 0.05). CONCLUSION: These findings suggest an early parasite tropism to nasal mucosa in L. (Viannia) braziliensis infection and a clinical phenotype of CL cases associated with parasite DNA in nasal mucosa. Future studies should evaluate whether PCR of nasal swab samples could serve as a prognostic tool for individuals at risk of mucocutaneous leishmaniasis.

Fertility Life Table of Tetranychus palmarum Flechtmann & Noronha (Acari: Tetranychidae) in Oil Palm.

Some species of spider mites belonging to the Tetranychidae family are known to associate with oil palm (Elaeis guineensis Jacq. - Arecaceae). The occurrence of Tetranychus palmarum Flechtmann & Noronha (Acari, Tetranychidae) was verified on oil palm seedlings under greenhouse conditions in the State of Pará in Northern Brazil. Plants with colonies of T. palmarum presented yellowish spots on leaflets and leaves with chlorosis. The objective of this study was to access the biology and fertility life table of T. palmarum in E. guineensis leaves. The experiment was conducted under four constant temperatures, 22, 25, 28, and 31°C, at 70 ± 10% RH under a 12:12 LD photoperiod. The duration of the egg-to-adult period was 18.4 and 9.8 days, at 22 and 31°C, respectively. The parameters of the fertility life table showed that 28°C is most suitable for the development and reproduction of T. palmarum, with higher values for reproductive parameters (R o , r m , and λ) and lower values for duplicating the population (TD). Therefore, it is apparent that the best temperature conditions for the development of T. palmarum are found in the warmer regions of Brazil, such as those observed in northern Brazil.

Plasmodium falciparum-infected erythrocytes induce tissue factor expression in endothelial cells and support the assembly of multimolecular coagulation complexes.

BACKGROUND: Plasmodium falciparum malaria infects 300-500 million people every year, causing 1-2 million deaths annually. Evidence of a coagulation disorder, activation of endothelial cells (EC) and increase in inflammatory cytokines are often present in malaria. OBJECTIVES: We have asked whether interaction of parasitized red blood cells (pRBC) with EC induces tissue factor (TF) expression in vitro and in vivo. The role of phosphatidylserine-containing pRBC to support the assembly of blood coagulation complexes was also investigated. RESULTS: We demonstrate that mature forms of pRBC induce functional expression of TF by EC in vitro with productive assembly of the extrinsic Xnase complex and initiation of the coagulation cascade. Late-stage pRBC also support the prothrombinase and intrinsic Xnase complex formation in vitro, and may function as activated platelets in the amplification phase of the blood coagulation. Notably, post-mortem brain sections obtained from P. falciparum-infected children who died from cerebral malaria and other causes display a consistent staining for TF in the EC. CONCLUSIONS: These findings place TF expression by endothelium and the amplification of the coagulation cascade by pRBC and/or activated platelets as potentially critical steps in the pathogenesis of malaria. Furthermore, it may allow investigators to test other therapeutic alternatives targeting TF or modulators of EC function in the treatment of malaria and/or its complications.

Neutralizing antibodies to interferon beta-1b are not associated with disease worsening in multiple sclerosis.

The clinical impact of neutralizing antibodies (NAbs) on interferon beta (IFNbeta) efficacy was studied in three large patient cohorts comprising 6698 multiple sclerosis (MS) patients receiving IFNbeta-1b across North America, Europe, and Australia. In North America and Europe, NAb testing was generally undertaken because of a poor clinical response; in Australia, it was mandatory for every patient. Of the 6697 patients tested, 28.9% had at least one NAb titre > or = 20 neutralizing units (NU)/ml, 14.4% had NAb titres > or = 100 NU/ml and 7.7% had NAb titres > or = 400 NU/ml. The NAb-positive rate of 37.0% in Australia was significantly greater than those in North America (21.3%) and Europe (27.6%), and this was observed at every NAb titre level. Our results suggest that NAbs are not responsible for poor clinical responses and that NAb status is of little clinical value. These findings will need to be confirmed in a large independent study.

Effects of creating a non-specific, virus-hostile environment in the nasopharynx on symptoms and duration of common cold.

The Common Cold remains the most frequent symptomatic viral infection in man. Current best therapies are all symptomatic. New pharmacological therapies are likely to be prescription-bound, and as most Common Cold infections are successfully treated without the intervention of a Physician, there is a need for effective non-prescription therapy options. Aim of this study is to propose a new type of approach, based on the concept of making a hostile biological environment for virus survival and spreading at the point of infection, the nasopharynx. The hypothesis was advanced that infections could be controlled using a physical biological approach to create an environment at the point of infection, that is inhibitory to the survival, and persistence of infecting virus, and of viruses newly released from infected mucosal epithelial cells. A nasal irrigation spray, designed to deliver a low pH gel to the nasal cavity, was developed and tested in this study. The study was a randomised, parallel, double-blind, placebo-controlled evaluation of three formulations of irrigation nasal spray in 441 subjects. The objective was to test whether the formulations reduced Cold severity and Cold duration compared to a placebo nasal spray. Subjects were recruited, and supplied with the product when healthy, and were instructed to begin treating and recording symptom severity once they experienced the "first signs" of a Common Cold. To qualify, subjects had to volunteer that they had at least one of the symptoms: sore/scratchy throat, runny nose or congested nose. The product was used 4 times daily, with at least 4 hours separating each dose, for a maximum of 7 days. Efficacy was assessed by an Interactive Voice Recall System whereby subjects were required to contact the investigation site, by telephone, twice daily when they were asked to assess the severity of their symptoms using a four point ordinal scale where 0 = "absent", and 3 = "severe". The symptoms assessed were sore throat, runny nose, blocked nose, cough and tired/run-down feeling. Two formulations demonstrated significant effects. A hydroxy methyl propyl cellulose based formulation reduced symptom severity compared with placebo by 17% and a Poloxamer based formulation reduced severity by 21%. Duration of illness was reduced with a hydroxy methyl propyl cellulose based formulation by 1.5 days to 2.4 days (according to the dose) and by a Poloxamer based formulation by 2.5 days. Results of this study suggest that the creation of a non virus-specific, inhibitory environment in the nasopharynx holds promise as an effective method of controlling the severity and duration of the Common Cold.

Solution structure of an arabinonucleic acid (ANA)/RNA duplex in a chimeric hairpin: comparison with 2'-fluoro-ANA/RNA and DNA/RNA hybrids.

Hybrids of RNA and arabinonucleic acid (ANA) as well as the 2'-fluoro-ANA analog (2'F-ANA) were recently shown to be substrates of the enzyme RNase H. Although RNase H binds to double-stranded RNA, no cleavage occurs with such duplexes. Therefore, knowledge of the structure of ANA/RNA hybrids may prove helpful in the design of future antisense oligonucleotide analogs. In this study, we have determined the NMR solution structures of ANA/RNA and DNA/RNA hairpin duplexes and compared them to the recently published structure of a 2'F-ANA/RNA hairpin duplex. We demonstrate here that the sugars of RNA nucleotides of the ANA/RNA hairpin stem adopt the C3'-endo (north, A-form) conformation, whereas those of the ANA strand adopt a 'rigid' O4'-endo (east) sugar pucker. The DNA strand of the DNA/RNA hairpin stem is flexible, but the average DNA/RNA hairpin structural parameters are close to the ANA/RNA and 2'F-ANA/RNA hairpin parameters. The minor groove width of ANA/RNA, 2'F-ANA/RNA and DNA/RNA helices is 9.0 +/- 0.5 A, a value that is intermediate between that of A- and B-form duplexes. These results rationalize the ability of ANA/RNA and 2'F-ANA/RNA hybrids to elicit RNase H activity.

Scale Insects (Hemiptera: Coccoidea) on Myrciaria dubia (Myrtaceae) in Brazil.

Commercial cultivation of the fruit tree Myrciaria dubia (Myrtaceae) is being developed in Brazil but phytophagous insects, including scale insects (Hemiptera: Coccoidea), can become pests in plantations. The coccids Ceroplastes jamaicensis White, Coccus viridis (Green), Parasaissetia nigra (Nietner), Pseudokermes vitreus (Cockerell) (Coccidae), and the diaspidid Pseudaonidia trilobitiformis (Green) were collected on M. dubia in the municipality of Belém and Tomé-Açu, state of Pará (PA), metropolitan and Northeast Pará mesoregions, Brazil. A key to species of Coccoidea recorded on M. dubia, based on adult females, is provided. Photographs for all scale insects reported on M. dubia are provided. Ceroplastes jamaicensis is recorded for the first time for Brazil and is herein reported for the first time associated with this host.

Antibacterial action of doped CoFe2O4 nanocrystals on multidrug resistant bacterial strains.

The bactericidal effect of pristine and doped cobalt ferrite nanoparticles has been evaluated against multiple drug resistant clinical strains by assessing the number of colony-forming units (CFU). Monophasic polycrystalline ferrites have been prepared by the malate-glycolate sol-gel autocombustion method as confirmed by the X-ray diffraction study. Various changes occurring during the preparative stages have been demonstrated using TG-DTA analysis which is well complemented by the FTIR spectroscopy. The antibacterial studies carried out demonstrate a bactericidal effect of the nanoparticles wherein the number of CFU has been found to decrease with doping. Cellular distortions have been revealed through SEM. Variation in the number of CFU with dopant type has also been reported herein.

Inhibitory potency of R-region specific antisense oligonucleotides against in vitro DNA polymerization and template-switching reactions catalysed by HIV-1 reverse transcriptase.

Antisense oligonucleotides (AONs) targeted to the R-region near the 5'-LTR of HIV-1 genomic RNA inhibited both the synthesis of (-) strong stop DNA and the first template-switch reaction catalysed by HIV-1 reverse transcriptase (RT) in vitro. The 18 nucleotide (nt) AONs used were identical in sequence but differed in the sugar component of the 3'-terminal nucleotide, with either 2'-deoxy-D-ribose (DNA), 2'-deoxy-L-ribose (L), or arabinose (ARA) in this position. All three AONs hybridized to complementary 18 nt RNA (T(m) approximately 70 degrees C) and specifically interacted with the target RNA HIV-1 sequence at 37 degrees C. L was unable to serve as primer for RT-catalysed DNA polymerization, whereas priming from ARA was about 30% that noted with DNA. Each of the three AONs resulted in similar 85-95% decreases in the amount of full length (-) strong stop DNA and up to 75% decreases in the first template-switch reaction products formed by RT, implying that elongation of the AONs did not enhance the inhibitory activity in vitro. A concomitant increase in a truncated DNA product corresponding to polymerization termination at the 5'-end of the AON was noted, indicating that RT was unable to displace the AON. Interestingly, near maximal inhibition in vitro an AON:target RNA template ratio of 1:1 was noted. Our results confirm the validity of our in vitro system for the analysis of potential antisense oligonucleotide inhibitors, and suggest that antisense oligonucleotides directed to the R-region of HIV-1 RNA may be effective inhibitors of the initial stages of HIV-1 proviral DNA synthesis.

Circulating immune complexes in neurologic disease.

Sera from patients with multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), subacute sclerosing panencephalitis (SSPE), and myasthenia gravis (MG) were assayed for immune complexes. Three techniques were used: a modified Raji cell assay, the 125I-Clq polyethyleneglycol assay, and a solid-phase clq assay. Immune complex levels were elevated in sera of some patients with MS, ALS, and SSPE, but the elevations were modest when compared with active systemic lupus erythematosus (SLE). In some cases, abnormalities were detected in only one assay system; in other cases, abnormalities were detected by two or three assay systems. In MS, immune complex elevations correlated with active disease and with decreased suppressor cell activity. Of two ALS patients with antecedent poliomyelitis, one had markedly increased levels of immune complexes in two assays. In MG, levels of immune complexes did not differ from those of controls.

Improved delayed visual reproduction test performance in multiple sclerosis patients receiving interferon beta-1b.

We assessed neuropsychological function longitudinally in 30 MS patients who participated in the pivotal trial of interferon beta-1b (IFN-beta-1b). Nine patients received high-dose IFN-beta-1b (8.0 million units), eight low-dose IFN-beta-1b (1.6 MIU), and 13 placebo. There was significant improvement in Wechsler Memory Scale Visual Reproduction-Delayed Recall scores between years 2 and 4 of the trial in MS subjects receiving high-dose IFN-beta-1b. Motoric performance, MRI lesion area, and depression rating scores did not correlate with this finding. Comparison of MRI at baseline and at years 2 and 4 revealed significant changes over time for the total cohort (p < 0.02). Mean lesion area in the high-dose group did not change over time, whereas the low-dose and placebo groups had increases in total lesion area of 28 and 36%, respectively, at year 4. Expanded disability status scale scores did not change significantly between years 2 and 4 of the trial, nor did they correlate with MRI lesion area at any assessment point. We conclude that high-dose IFN-beta-1b improves delayed visual reproduction test performance in MS patients, a finding unlikely to be explained by practice effects or brain lesion area.

Interferon beta decreases T cell activation and interferon gamma production in multiple sclerosis.

Interferons (IFN) are biological molecules with anti-viral, anti-proliferative and immunomodulatory actions. There is evidence that IFN-gamma increases the frequency of exacerbations of multiple sclerosis (MS) whereas IFN-beta may reduce their frequency. Here we present evidence that IFN-beta significantly decreases concanavalin A (Con A)-induced proliferation of peripheral blood mononuclear cells (PBMC) of MS patients and healthy individuals. Similar results were obtained when PBMC were activated through the T cell receptor (TcR) by anti-CD3 monoclonal antibody or independently of it by phorbol ester and Ca2+ ionophore. These effects of IFN-beta were also noted when IFN-gamma and IFN-beta were added together. Furthermore, IFN-beta decreased proliferation when added to cells that were already pre-activated. Activated CD4+ and CD8+ T cells were downregulated to approximately the same extent. Analysis of cytokine production showed that IFN-gamma production by Con A activated PBMC was increased in MS when compared to controls. IFN-beta significantly decreased IFN-gamma production in MS patients and control individuals. Con A activated cultures treated with IFN-beta showed decreased IL2R expression and accumulation of IL2. These results show that IFN-beta decreases T cell activation and IFN-gamma production in vitro, effects that may be beneficial in MS.

Preferential increase of IL-2R+ CD4+ T cells and CD45RB- CD4+ T cells in the central nervous system in experimental allergic encephalomyelitis.

We examined lymphocytes isolated from the spinal cord (SC), peripheral blood (PB) and lymph nodes (LN) draining the immunization site of Lewis rats with acute experimental allergic encephalomyelitis (EAE). Cells were analysed for T cell subset markers CD4 (mAb W3/25) and CD8 (mAb OX8), for IL-2R (mAb OX39), and for high molecular mass leukocyte common antigen (LCA, CD45RB) expression (mAb OX22). T cells expressing high (CD45RB+) or low (CD45RB-) molecular mass LCA are of different maturational stages and/or separate lineages. CD4+ T cells were more predominant in SC than in PB and LN; CD8+ T cells were scarce in SC but common in PB and LN. Activated CD4+ T cells (IL-2R+) were common in the SC and LN but infrequent in blood. CD4+ T cells that were CD45RB+ were scarce in the SC. In contrast, the majority of CD4+ T cells in the PB and LN were CD45RB+. The preferential accumulation of IL-2R+ CD4+ T cells and of CD45RB- CD4+ T cells in the central nervous system (CNS) indicates that a selective mechanism directs cell egress into CNS lesions in EAE.

Activated suppressor cell function in multiple sclerosis--clinical correlations.

Activated suppressor cell function mediated by either freshly isolated peripheral blood mononuclear cells (MNCs), freshly isolated CD8+ lymphocytes or by CD8+ cell lines, has previously been found to be reduced compared to controls in multiple sclerosis (MS) patients with progressive disease (MS-P). In this study, we found that suppressor activity mediated by CD8+ cell lines, derived from MS patients with stable disease (MS-S) patients and maintained in culture for 14 days, was significantly greater (45 +/- 6%) compared to that mediated by MS-P patients' CD8+ cells (11 +/- 4%, P less than 0.005). The MS-S suppressor values were, however, suggestively reduced compared to controls (60 +/- 6%, P less than 0.05). MNC-mediated suppressor values for the MS-S group (61 +/- 5%) did not differ from the control group (67 +/- 6%). Values for the MS-P group (7 +/- 6%) were significantly reduced compared to MS-S and control groups. Cytotoxic activity mediated by CD8+ cell lines showing defective suppressor function did not differ from control values. The cell lines in MS and control did not differ with respect to their rate of proliferation in the presence of IL-2 and OKT3. Suppressor function in this assay was ablated if exogenous IL-2 was removed from the culture media. These data suggest that defective activated suppressor function is characteristic of the progressive form of MS, although a suppressor defect is also partially expressed in stable MS patients when CD8+ cell lines are studied.

Simultaneous cell surface phenotype and cell cycle analysis of lymphocytes by flow cytometry.

A method for the simultaneous measurement of cell surface components and nucleic acids (DNA and RNA) of human lymphocytes by flow cytometry has been developed, thereby providing a means of analyzing cell surface changes during the various phases of the cell cycle. Unfixed cells were coated with fluorescein-conjugated concanavalin A (F Con A) or surface antigen-specific antibody, fixed sequentially with paraformaldehyde and methanol, treated with specific nucleases, and then stained with propidium iodide. Neither portion of the procedure (cell surface staining, nucleic acid staining) interfered significantly with the other. Cell cycle phases of phytohemagglutinin-stimulated human lymphocytes as determined by this method were comparable with those identified by acridine orange staining. Cell cycle-specific blocking agents were used to additionally demonstrate the specificity of the staining procedure. Simultaneous measurement of cell cycle phase and detection of surface receptors for Con A and T lymphocyte surface determinants was performed with this method.

Myelin-associated glycoprotein (MAG) and rat brain-specific 1B236 protein: mapping of epitopes and demonstration of immunological identity.

The myelin-associated glycoprotein (MAG) and the brain 1B236 protein are 100-kDa glycoproteins containing 30% carbohydrate that exist in two developmentally regulated forms and are specific to the nervous system. Recent cDNA cloning experiments in several laboratories using primarily immunological means of identification have determined the complete primary sequence of a rat brain glycoprotein that seems to correspond to both MAG and 1B236, suggesting that these proteins are identical. However, MAG was previously considered to be an oligodendrocyte/myelin specific component in the CNS at all ages, whereas 1B236 was thought to be primarily a neuronal component in adult rats but synthesized by oligodendrocytes at the time of active myelination. The composite term 1B236/MAG was proposed to describe the molecule identified by the cDNAs. In order to explore further the relationship between MAG and 1B236, as well as their developmentally regulated forms, experiments were carried out on rat samples utilizing synthetic peptides corresponding to sequences throughout the 1B236 molecule, antisera raised to synthetic peptides in the C-terminus of 1B236 that distinguish between the two developmentally regulated forms, and well-characterized polyclonal and monoclonal antibodies raised to purified MAG. Epitope mapping demonstrated that reactive sites were distributed throughout the extracellular and intracellular domains of 1B236/MAG. Only antibodies reacting with the smaller of the two forms of 1B236/MAG detected the glycoprotein in the peripheral nervous system. Both anti-MAG and anti-1B236 antibodies revealed a drastic reduction of the level of 1B236/MAG in 25-day-old myelin-deficient rats and in adult quaking mice, and both types of antibodies revealed a slight shift of 1B236/MAG toward higher apparent Mr in quaking mice as had previously been reported for MAG. The results indicate that MAG and 1B236 are almost certainly identical since they cannot be distinguished immunologically by the reagents available and that quantitatively most of the glycoprotein is associated with oligodendrocytes and myelin rather than neurons at all ages.

Charles Bonnet syndrome: an early marker for dementia?

OBJECTIVE: To clarify the neuropsychological function in patients with Charles Bonnet Syndrome. DESIGN: Control group comparison study. SETTING: University of Chicago Hospitals. PARTICIPANTS: The neuropsychological function of 15 older adults with presenting complaints of visual hallucinations who met criteria for Charles Bonnet Syndrome (CBS) were compared with 11 demographically matched controls to determine if there was any evidence of functional brain impairment. CBS patients were screened for focal brain lesions and epileptic disturbance via MRI and EEG and also received pattern visual evoked potentials and ophthalmological examinations. MEASUREMENTS: Scores from the Wechsler Adult Intelligence Scale-Revised, Mattis Dementia Rating Scale, Wechsler Memory Scale, and the Auditory Verbal Learning Test were compared. RESULTS: Significant differences were found between the two groups on the neuropsychological measures. Moreover, 14 of 14 subjects had ocular abnormalities and six of eight had abnormal age-corrected pattern visual evoked potentials indicative of dysfunction in the visual system. CONCLUSIONS: The results of the study indicate that patients diagnosed with Charles Bonnet Syndrome evidence neuropsychological changes commonly associated with the early stages of dementia. Therefore, in patients with impaired vision, the appearance of cognitive deficits, albeit subtle, occur with the onset of visual hallucinations. We propose that isolated visual hallucinations in the older adult may be an indication of the early stages of dementia.

Molecular specificity of L2 monoclonal antibodies that bind to carbohydrate determinants of neural cell adhesion molecules and their resemblance to other monoclonal antibodies recognizing the myelin-associated glycoprotein.

L2 monoclonal antibodies and HNK-1 have been shown to bind to related carbohydrate determinants in the myelin-associated glycoprotein (MAG) and several adhesion molecules of the nervous system including neural cell adhesion molecule (N-CAM), L1 and J1. It is shown here that MAG is the principal component in human white matter binding the L2 antibodies, but the most prominent antigens with the L2 epitopes in human gray matter are of higher Mr. It is also shown that the L2 antibodies resemble HNK-1 in binding to some 19-28 kDa glycoproteins and some sulfated, glucuronic acid-containing sphingoglycolipids of the peripheral nervous system (PNS). In addition, monoclonal and polyclonal antibodies raised to human MAG are shown to cross react with bovine N-CAM due to the presence of common carbohydrate constituents. The results further emphasize the shared antigenicity between MAG, N-CAM and other adhesion molecules. In addition, they demonstrate that the L2 antibodies belong to a family of monoclonal antibodies (including HNK-1, human IgM paraproteins associated with neuropathy, and others) that are characterized by reactivity against carbohydrate determinants shared by human MAG, the 19-28 kDa glycoproteins of the PNS and the sulfated, glucuronic acid-containing sphingoglycolipids of the PNS.

Pericarotid cluster headache.

Cluster headache is generally not associated with recognised disease, and the pathogenesis remains unclear. The onset of typical cluster headaches is reported in a patient with nasopharyngeal carcinoma. The tumor encircled the internal carotid artery but did not extend intracranially. It thus appears possible that cluster headaches may be triggered by processes involving the carotid artery.