The product of the tobacco mosaic virus resistance gene N: similarity to toll and the interleukin-1 receptor

The products of plant disease resistance genes are postulated to recognize invading pathogens and rapidly trigger host defense responses. Here we describe isolation of the resistance gene N of tobacco that mediates resistance to the viral pathogen tobacco mosaic virus (TMV). The N gene was isolated by transposon tagging using the maize Activator transposon. A genomic DNA fragment containing the N gene conferred TMV resistance to TMV susceptible tobacco. Sequence analysis of the N gene shows that it encodes a protein of 131.4 kDa with an amino-terminal domain similar to that of the cytoplasmic domain of the Drosophila Toll protein and the interleukin-1 receptor (IL-1R) in mammals, a nucleotide-binding site (NBS), and 14 [corrected] imperfect leucine-rich repeats (LRR). The sequence similarity of N, Toll, and IL-1R suggests that N mediates rapid gene induction and TMV resistance through a Toll-IL-1-like pathway.

Microarray analysis of replicative senescence

BACKGROUND

Limited replicative capacity is a defining characteristic of most normal human cells and culminates in senescence, an arrested state in which cells remain viable but display an altered pattern of gene and protein expression. To survey widely the alterations in gene expression, we have developed a DNA microarray analysis system that contains genes previously reported to be involved in aging, as well as those involved in many of the major biochemical signaling pathways.

RESULTS

Senescence-associated gene expression was assessed in three cell types: dermal fibroblasts, retinal pigment epithelial cells, and vascular endothelial cells. Fibroblasts demonstrated a strong inflammatory-type response, but shared limited overlap in senescent gene expression patterns with the other two cell types. The characteristics of the senescence response were highly cell-type specific. A comparison of early- and late-passage cells stimulated with serum showed specific deficits in the early and mid G1 response of senescent cells. Several genes that are constitutively overexpressed in senescent fibroblasts are regulated during the cell cycle in early-passage cells, suggesting that senescent cells are locked in an activated state that mimics the early remodeling phase of wound repair.

CONCLUSIONS

Replicative senescence triggers mRNA expression patterns that vary widely and cell lineage strongly influences these patterns. In fibroblasts, the senescent state mimics inflammatory wound repair processes and, as such, senescent cells may contribute to chronic wound pathologies.

Congestion of right liver graft in living donor liver transplantation

BACKGROUND

Left liver graft from a small donor will not meet the metabolic demands of a larger adult recipient. One solution to this problem is to use a right liver graft without a middle hepatic vein (MHV). However, the need for drainage from the MHV tributaries has not yet been described.

METHODS

Five right liver grafts without a MHV were transplanted in patients including two hepatitis B virus-cirrhosis, two fulminant hepatic failure and one secondary biliary cirrhosis. The graft weight ranged from 650 to 1,000 g, corresponding to 48 to 83% of the standard liver volume of the recipients.

RESULTS

Two of five recipients were complicated with severe congestion of the right median sector immediately after reperfusion, followed by prolonged massive ascites and severe liver dysfunction. One of the patients died of sepsis with progressive hepatic dysfunction 20 days after the operation.

CONCLUSIONS

Preservation and reconstruction of the MHV tributaries is recommended to prevent congestion of the right liver graft without MHV.

Interleukin-8 and its receptor CXCR2 in the tumour microenvironment promote colon cancer growth, progression and metastasis

BACKGROUND

Colorectal cancer (CRC) is a leading cause of death in the United States. Increased level of interleukin-8 (IL-8) and CXCR2 on tumours and in the tumour microenvironment has been associated with CRC growth, progression and recurrence in patients. Here, we aimed to evaluate the effects of tissue microenvironment-encoded IL-8 and CXCR2 on colon cancer progression and metastasis.

METHODS

A novel immunodeficient, skin-specific IL-8-expressing transgenic model was generated to evaluate colon cancer growth and metastasis. Syngeneic mouse colon cancer cells were grafted in CXCR2 knockout (KO) mice to study the contribution of CXCR2 in the microenvironment to cancer growth.

RESULTS

Elevated levels of IL-8 in the serum and tumour microenvironment profoundly enhanced the growth of human and mouse colon cancer cells with increased peri-tumoural angiogenesis, and also promoted the extravasation of the cancer cells into the lung and liver. The tumour growth was inhibited in CXCR2 KO mice with significantly reduced tumour angiogenesis and increased tumour necrosis.

CONCLUSION

Increased expression of IL-8 in the tumour microenvironment enhanced colon cancer growth and metastasis. Moreover, the absence of its receptor CXCR2 in the tumour microenvironment prevented colon cancer cell growth. Together, our study demonstrates the critical roles of the tumour microenvironment-encoded IL-8/CXCR2 in colon cancer pathogenesis, validating the pathway as an important therapeutic target.

Hepatocellular carcinoma treated with percutaneous radio-frequency ablation: evaluation with follow-up multiphase helical CT

PURPOSE

To determine serial changes in hepatocellular carcinomas (HCCs) treated with percutaneous radio-frequency (RF) ablation at long-term follow-up multiphase helical computed tomography (CT).

MATERIALS AND METHODS

There were 43 nodular HCCs in 40 patients at follow-up CT performed not less than 12 months after RF ablation. All patients underwent follow-up multiphase helical CT immediately, 1 month, and then every 3 months after percutaneous RF ablation. The serial changes in attenuation, enhancement pattern, shape, other findings, and volume of the ablated lesions were analyzed at follow-up CT.

RESULTS

Thirty-eight (88%) of 43 ablated lesions were of low attenuation, with absence of contrast material enhancement at immediate and 1-month follow-up CT, which is suggestive of successful treatment. The remaining five lesions (12%) showed peripheral nodular enhancement, suggesting residual viable tumor. Compared with volume changes at immediate follow-up CT, the mean percentages of volume change at 1, 4, 10, 16, and 19 months were 79%, 50%, 27%, 11%, and 6%, respectively. Of 43 ablated lesions, 24 (56%) were mostly round at immediate CT and remained unchanged at subsequent follow-up CT. Peripheral rim enhancement was seen in 34 (79%) of 43 lesions at immediate CT but resolved in all 34 lesions at 1-month follow-up CT. Other associated findings included iatrogenic arteriovenous shunt in 10 patients, perihepatic hemorrhage in three, and pneumothorax in one.

CONCLUSION

Follow-up multiphase helical CT of HCCs treated with percutaneous RF ablation showed variable findings in the treated lesions and surrounding liver parenchyma.

Mycobacterial diseases and antitumour necrosis factor therapy in USA

OBJECTIVE

In North America, tuberculosis and nontuberculous mycobacterial (NTM) disease rates associated with antitumour necrosis factor α (anti-TNFα) therapy are unknown.

METHODS

At Kaiser Permanente Northern California, the authors searched automated pharmacy records to identify inflammatory disease patients who received anti-TNF therapy during 2000-2008 and used validated electronic search algorithms to identify NTM and tuberculosis cases occurring during anti-TNF drug exposure.

RESULTS

Of 8418 anti-TNF users identified, 60% had rheumatoid arthritis (RA). Among anti-TNF users, 18 developed NTM and 16 tuberculosis after drug start. Anti-TNF associated rates of NTM and tuberculosis were 74 (95% CI: 37 to 111) and 49 (95% CI: 18 to 79) per 100 000 person-years, respectively. Rates (per 100, 000 person-years) for NTM and tuberculosis respectively for etanercept were 35 (95% CI: 1 to 69) and 17 (95% CI: 0 to 41); infliximab, 116 (95% CI: 30 to 203) and 83 (95% CI: 10 to 156); and adalimumab, 122 (95% CI: 3 to 241) and 91 (95% CI: 19 to 267). Background rates for NTM and tuberculosis in unexposed RA-patients were 19.2 (14.2 to 25.0) and 8.7 (5.3 to 13.2), and in the general population were 4.1 (95% CI 3.9 to 4.4) and 2.8 (95% CI 2.6 to 3.0) per 100, 000 person-years. Among anti-TNF users, compared with uninfected individuals, NTM case-patients were older (median age 68 vs 50 years, p<0.01) and more likely to have RA (100% vs 60%, p<0.01); whereas, tuberculosis case-patients were more likely to have diabetes (37% vs 16%, p=0.02) or chronic renal disease (25% vs 6%, p=0.02).

CONCLUSIONS

Among anti-TNF users in USA, mycobacterial disease rates are elevated, and NTM is associated with RA.

Enhanced detection of intracardiac sources of cerebral emboli by transesophageal echocardiography

We performed transesophageal echocardiography in 50 consecutive hospitalized patients with recent transient ischemic attack or stroke of embolic origin to determine whether transesophageal echocardiography is more sensitive than transthoracic echocardiography in detection of possible intracardiac sources of embolism. Twenty-six of 50 patients with a negative transthoracic echocardiogram for potential source of emboli had a transesophageal echocardiography study that demonstrated at least one intracardiac abnormality. Abnormalities noted by transesophageal echocardiography included five of 50 patients with either a left atrial or left atrial appendage clot, four patients with a patent foramen ovale, and nine patients with spontaneous echocardiographic contrast. In 11 of 50 patients with no other source of embolism, we found highly mobile filamentous strands on the mitral valve, which have not been described previously. These mitral valve echo strands may represent a fissured surface or fibrosis that can serve as a nidus for thrombus formation. We detected no unexpected left ventricular thrombus or left atrial myxoma. Factors significantly associated with a greater likelihood of a positive transesophageal echocardiography study included left atrial enlargement, atrial fibrillation, and a calcified or thickened mitral valve. Our study suggests that transesophageal echocardiography is a valuable addition to transthoracic echocardiography in investigating potential intracardiac sources of embolism.

Expansins: ever-expanding numbers and functions

Expansins were first identified as cell-wall-loosening proteins that, at least in part, mediate pH-dependent extension of the plant cell wall and growth of the cell. More recently, it has been realized that expansins belong to two protein families, the alpha-and beta-expansins, and that they appear to be involved in regulating, besides cell expansion, a variety of plant processes, including morphogenesis, softening of fruits, and growth of the pollen tube of grasses through the stigma and the style. The Arabidopsis genome contains 26 alpha-expansin genes and the rice genome at least 26. There are more beta-expansin genes in monocots than in dicots, at least 14 in rice and five in Arabidopsis. Expansin genes are differentially regulated by environmental and hormonal signals, and hormonal regulatory elements have been found in their promoter regions. An analysis of exon/intron structure led to the hypothesis that alpha-and beta-expansins evolved from a common ancestral gene.

Synthesis and anticonvulsant activities of N-Benzyl-2-acetamidopropionamide derivatives

Studies have demonstrated that 2-substituted N-benzyl-2-acetamidoacetamides (2) are potent anticonvulsants. A recent investigation has led to the hypothesis that an important structural feature in 2 for maximal anticonvulsant activity is the placement of a small, substituted heteroatom moiety one atom from the C(2) site. This paper validates this hypothesis. Twelve derivatives of N-benzyl-2-acetamidopropionamide have been prepared in which six different heteroatom substituents (chloro, bromo, iodo, oxygen, nitrogen, and sulfur) were incorporated at the C(3) site. Highly potent activities were observed for the two oxygen-substituted derivatives, N-benzyl-2-acetamido-3-methoxypropionamide (18) and N-benzyl-2-acetamido-3-ethoxypropionamide (19). The ED50 values in mice following intraperitoneal (i.p.) dosing for the maximal electroshock-induced seizure test for 18 and 19 were 8.3 and 17.3 mg/kg, respectively. These values compared favorably to the ED50 value found for phenytoin (ED50 = 6.5 mg/kg). Comparable activities were observed for 18 and 19 upon oral (p.o.) administration to rats (18, ED50 = 3.9 mg/kg; 19, ED50 = 19 mg/kg; phenytoin, ED50 = 23 mg/kg). Evaluation of the individual stereoisomers for 18 demonstrated that the principal anticonvulsant activity resided in the (R)-stereoisomer. The ED50 value for (R)-18 was 4.5 mg/kg, and the ED50 for (S)-18 exceeded 100 mg/kg. This difference in activity for the two stereochemical isomers surpassed comparable values for other members within this class of compounds. The protective indices (PI = TD50/ED50) (where TD50 represents a neurotoxic dose impairing rotorod performance) for (R)-18 in mice (i.p.) and in rats (p.o.) were 6.0 and > 130, respectively.

Hepatocellular carcinoma treated with percutaneous radio-frequency ablation: usefulness of power Doppler US with a microbubble contrast agent in evaluating therapeutic response-preliminary results

PURPOSE

To evaluate the usefulness of power Doppler ultrasonography (US) with a microbubble contrast agent in assessing the therapeutic response of hepatocellular carcinomas (HCCs) treated with percutaneous radio-frequency (RF) ablation.

MATERIALS AND METHODS

Forty patients with 45 nodular HCC lesions 1.0-3.8 cm in diameter underwent power Doppler US before and after intravenous injection of a microbubble contrast agent. The same procedures were repeated after US-guided percutaneous RF ablation. The results of these studies were compared with those of three-phase helical computed tomography (CT) performed immediately after RF ablation.

RESULTS

Before RF ablation, nonenhanced power Doppler US demonstrated flow signals within tumor in 33 of 45 HCCs. After contrast agent administration, flow signals increased or newly appeared in all cases. After RF ablation, none of the ablated tumors showed intratumoral flow signals at nonenhanced power Doppler US, whereas six showed marginal intratumoral flow signals at contrast agent-enhanced power Doppler US. These six tumors were found to have small enhancing foci, suggestive of viable tumor, in corresponding areas at immediate follow-up CT. Additional RF ablation or transcatheter arterial chemoembolization was performed in these tumors.

CONCLUSION

The results of power Doppler US with a microbubble contrast agent in HCCs treated with RF ablation correlated well with those of contrast-enhanced CT. Preliminary data suggest that contrast-enhanced power Doppler US can be a promising noninvasive technique for assessing therapeutic response.

Differential induction and suppression of potato 3-hydroxy-3-methylglutaryl coenzyme A reductase genes in response to Phytophthora infestans and to its elicitor arachidonic acid

Induction of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is essential for the biosynthesis of sesquiterpenoid phytoalexins and steroid derivatives in Solanaceous plants following stresses imposed by wounding and pathogen infection. To better understand this complex step in stress-responsive isoprenoid synthesis, we isolated three classes of cDNAS encoding HMGR (hmg1, hmg2, and hmg3) from a potato tuber library using a probe derived from an Arabidopsis HMGR cDNA. The potato cDNAs had extensive homology in portions of the protein coding regions but had low homology in the 3' untranslated regions. RNA gel blot analyses using gene-specific probes showed that hmg1 was strongly induced in tuber tissue by wounding, but the wound induction was strongly suppressed by treatment of the tissue with the fungal elicitor arachidonic acid or by inoculation with an incompatible or compatible race of the fungal pathogen Phytophtora infestans. The hmg2 and hmg3 mRNAs also accumulated in response to wounding, but in contrast to hmg1, these mRNAs were strongly enhanced by arachidonic acid or inoculation. Inoculation with a compatible race of P. infestans resulted in similar patterns in HMGR gene expression of hmg2 and hmg3 except that the magnitude and rate of the changes in mRNA levels were reduced relative to the incompatible interaction. The differential regulation of members of the HMGR gene family may explain in part the previously reported changes in HMGR enzyme activities following wounding and elicitor treatment. The suppression of hmg1 and the enhancement of hmg2 and hmg3 transcript levels following elicitor treatment or inoculation with the incompatible race parallel the suppression in steroid and stimulation of sesquiterpenoid accumulations observed in earlier investigations. The results are discussed in relation to the hypothesis that there are discrete organizational channels for sterol and sesquiterpene biosynthesis in potato and other Solanaceous species.

Lipid-derived signals that discriminate wound- and pathogen-responsive isoprenoid pathways in plants: methyl jasmonate and the fungal elicitor arachidonic acid induce different 3-hydroxy-3-methylglutaryl-coenzyme A reductase genes and antimicrobial isoprenoids in Solanum tuberosum L

Induction of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR; EC 1.1.1.34) is essential for the synthesis of steroid derivatives and sesquiterpenoid phytoalexins in solanaceous plants following mechanical injury or pathogen infection. Gene-specific probes corresponding to different HMGR genes (hmg1 and hmg2) were used to study HMGR expression in potato tissue following treatment with methyl jasmonate, a lipoxygenase product of linolenic acid, or arachidonic acid, an elicitor present in the lipids of the potato late blight fungus Phytophthora infestans. Treatment of potato discs (2.2 cm in diameter) with low concentrations (0.45-45 nmol per disc surface) of methyl jasmonate nearly doubled the wound-induced accumulation of hmg1 transcripts and steroid-glycoalkaloid (SGA) accumulation, reduced the abundance of hmg2 transcripts, and did not induce phytoalexins. High concentrations of methyl jasmonate (2-4.5 mol per disc surface) suppressed hmg1 mRNA and SGA accumulation but did not affect hmg2 mRNA abundance or induce phytoalexins. In contrast, arachidonate treatment strongly suppressed hmg1 and strongly induced hmg2 mRNA in a concentration-dependent manner. There was a corresponding suppression of SGA accumulation and an induction of sesquiterpene phytoalexin accumulation by this elicitor. Lipoxygenase inhibitors reduced the wound-induced accumulation of hmg1 transcripts and suppressed SGA levels, effects that were overcome by exogenous methyl jasmonate (45 nmol per disc surface). The results (i) suggest that methyl jasmonate can function as a signal for hmg1 expression and SGA induction following wounding and (ii) indicate that the arachidonate- and jasmonate-response pathways are distinct in relation to HMGR gene expression and isoprenoid product accumulation. The results also are consistent with placement of the HMGR activities encoded by hmg1 and hmg2 within discrete steroid and sesquiterpenoid biosynthetic channels.

Optical coherence tomography evaluation of zotarolimus-eluting stents at 9-month follow-up: comparison with sirolimus-eluting stents

OBJECTIVE

To evaluate the vascular response at 9 months after zotarolimus-eluting stent (ZES; Endeavor) implantation using optical coherence tomography (OCT). These findings were compared with those after implantation of a sirolimus-eluting stent (SES; Cypher Select).

DESIGN

Cross-sectional observational study with prospective OCT registry.

SETTING

Nine months after ZES or SES implantation.

PATIENTS AND METHODS

A total of 68 patients (32 ZES and 36 SES) underwent OCT at 9 months after stent implantation. The neointima hyperplasia (NIH) thickness inside each strut and percentage of NIH area at every 1 mm cross section were measured.

MAIN OUTCOME MEASUREMENT

The degree of neointimal coverage and the prevalence of malapposition at 9 months after ZES and SES implantation using OCT.

RESULTS

The mean (SD) NIH thickness (251.2 (110.0) mum vs 85.5 (53.3) mum, p<0.001) and percentage of NIH area (27.9 (9.1)% vs 11.2 (7.1)%, p<0.001) were significantly greater in ZES than in SES. The prevalence of uncovered strut as well as malapposed strut was significantly lower in ZES than in SES (0.3% vs 12.3%, p<0.001 and 0.08% vs 2.6%, p<0.001). Thrombus was not observed in ZES (0.0% in ZES vs 27.8% in SES, p = 0.001).

CONCLUSIONS

Neointimal coverage in ZES was almost complete and malapposition was very rare at 9-months' follow-up.

Conspicuity of hepatocellular nodular lesions in cirrhotic livers at ferumoxides-enhanced MR imaging: importance of Kupffer cell number

PURPOSE

To correlate the conspicuity of hepatocellular carcinomas and dysplastic nodules on ferumoxides-enhanced magnetic resonance (MR) images with the number of Kupffer cells in the hepatic lesions, as compared with that in background liver in histopathologic findings.

MATERIALS AND METHODS

Sixty-nine histopathologically proved moderately or poorly differentiated hepatocellular carcinomas, 10 well-differentiated hepatocellular carcinomas, and 19 dysplastic nodules were retrospectively studied in 68 patients with cirrhosis who underwent ferumoxides-enhanced MR imaging. The contrast-to-noise ratio between the nodules and surrounding parenchyma was calculated at T2-weighted fast spin-echo imaging, and the difference in the number of Kupffer cells between the nodules and surrounding hepatic tissue was calculated histopathologically. The results of MR imaging and histopathologic examination were correlated.

RESULTS

All 69 moderately or poorly differentiated hepatocellular carcinomas had high contrast-to-noise ratios at MR imaging and large differences in the number of Kupffer cells. Six of the 10 well-differentiated hepatocellular carcinomas had contrast-to-noise ratios of zero or nearly zero, and five of these had little difference in the number of Kupffer cells. All 19 dysplastic nodules had contrast-to-noise ratios of zero or nearly zero, and there were virtually no differences in the number of Kupffer cells.

CONCLUSION

Hepatocellular nodule conspicuity at ferumoxides-enhanced MR imaging depends on differences in the number of Kupffer cells within a nodule and the surrounding cirrhotic liver; moderately or poorly differentiated hepatocellular carcinomas can be distinguished from well-differentiated hepatocellular carcinomas and dysplastic nodules.

Post-interventional immunosuppressive treatment and vascular restenosis in Takayasu's arteritis

OBJECTIVE

To investigate the outcome of vascular interventions and the effect of post-interventional immunosuppressive treatment on the occurrence of vascular restenosis in patients with Takayasu's arteritis (TA).

METHODS

Forty-two patients with TA who had undergone vascular intervention and had serial angiographies before and after intervention were enrolled. The demographic and clinical data were collected at the time when the interventions were performed, and the intervention modalities and post-interventional medical treatments were evaluated.

RESULTS

Sixty-three interventions were performed in 42 patients. Twenty (31.7%) interventions restenosed 24.0 +/- 21.9 months after intervention; the likelihood decreasing as time passed. Estimates of arterial patency after intervention were 90.1% at 1 yr, 75.5% at 2 yr, 68.4% at 3 yr, 61.6% at 5 yr and 49.3% at 10 yr. According to the log rank test, interventions that were performed during the stable stage of the disease (P = 0.039) and those that were followed by treatment with glucocorticoids and immunosuppressive agents (P = 0.044) were independent variables for the maintenance of arterial patency. Their hazard ratios were 0.30 and 0.41, respectively.

CONCLUSION

Restenosis occurred in 31.7% of TA patients after intervention. A lower restenosis rate was observed when the vascular interventions were performed at the stable stage and when post-interventional immunosuppressive treatment was implemented.

Molecular cloning of a metallothionein-like gene from Nicotiana glutinosa L. and its induction by wounding and tobacco mosaic virus infection

The cloning and characterization of genes expressed in plant disease resistance could be an initial step toward understanding the molecular mechanisms of disease resistance. A metallothionein-like gene that is inducible by tobacco mosaic virus and by wounding was cloned in the process of subtractive cloning of disease resistance-response genes in Nicotiana glutinosa. One 530-bp cDNA clone (KC9-10) containing an open reading frame of 81 amino acids was characterized. Genomic Southern blot hybridization with the cDNA probe revealed that tobacco metallothionein-like genes are present in few or in one copy per diploid genome. Northern blot hybridization detected strong induction of a 0.5-kb mRNA by wounding and tobacco mosaic virus infection, but only mild induction was detected when copper was tested as an inducer. Methyl jasmonate, salicylic acid, and ethylene were also tested as possible inducers of this gene, but they had no effect on its expression. The possible role of this gene in wounded and pathogen-stressed plants is discussed.

Traumatic cerebrospinal fluid leakage: risk factors and the use of prophylactic antibiotics

Cerebrospinal fluid (CSF) leakage following head trauma is often difficult to diagnose, but is of considerable importance in view of the possibility of fistula formation and meningitis. It is unclear whether specific clinical or radiological signs point to an increased risk of CSF leakage. Previous studies have been largely anecdotal and uncontrolled, leading us to perform a retrospective control study comparing the clinical and radiological features of patients with overt CSF leakage, and those without. Of the 293 patients studied, 115 had clinical CSF leakage and 170 did not, with incomplete documentation in eight patients. The group with CSF rhinorrhoea had significantly greater incidence of periorbital haematoma (chi square = 8.642). This suggests that patients with head injuries and features of periorbital haematoma are at greater risk of unobserved dural tear and delayed CSF leakage. Frontal and ethmoid fractures in particular were also associated with CSF leakage (chi square = 5.46). The use of prophylactic antibiotics was studied. There was a significantly greater incidence of meningitis in the group which received prophylactic antibiotics (p = 0.024). There was no significant difference in the incidence of meningitis in those patients with CSF fistulae treated by surgical or conservative methods.

Fluorescent retrograde neuronal tracers that label the rat facial nucleus: a comparison of Fast Blue, Fluoro-ruby, Fluoro-emerald, Fluoro-Gold and DiI

Many fluorescent retrograde tracers are commercially available for neuroanatomical studies. They have been used with varying success in different models and can be very effective in the study of the facial nerve and nucleus. We compare the tracers Fast Blue (FB), Fluoro-ruby, Fluoro-emerald, Fluoro-Gold (FG), and DiI in the rat facial nucleus after application to the buccal division of the nerve. There were no significant differences between counts of cells on the left and right sides of the brain stem with any of the tracers. FB produced a lower sample variation than the other tracers, and together with DiI, demonstrated greater axonal labelling when applied to the surface of the epineurium. FB and FG resulted in strong retrograde labelling of the facial nucleus after only 2 days from injection. All the tracers produced adequate cell labelling after 1 week from nerve application. This labelling persisted for up to 8 weeks for most tracers except FG, which did not produce satisfactory labelling at 8 weeks.