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Biomedical subjects

C J O'Brien

Publications and source records attributed to C J O'Brien.

At least 19 recordsLinked to original sources
PubMed2000

Locally advanced melanoma: results of postoperative hypofractionated radiation therapy.

BACKGROUND: High rates of locoregional recurrence have been reported from surgical series of locally advanced melanoma. In this study, the outcomes of patients treated with surgery and postoperative hypofractionated radiation therapy were reviewed to assess local recurrence and survival. METHODS: From 1989 to 1998, 174 patients with International Union Against Cancer Stage I-III melanoma received postoperative radiation therapy, either as a component of their initial management or following surgery for recurrence. Radiation was delivered to the primary site in 35 cases and involved regional lymph nodes in 139. The indications for irradiation included microscopically positive surgical margins or other adverse pathologic features. All patients received a hypofractionated schedule of 30-36 grays (Gy) in 5-7 fractions over 2.5 weeks. RESULTS: Recurrence within the radiation fields was identified in 20 patients (11%) at a median time of 6 months. There was no difference in recurrence rates for patients with microscopically positive margins compared with other indications for adjuvant treatment. The main complication of treatment was symptomatic arm lymphedema in 58% of patients following axillary dissection and postoperative irradiation. The median disease specific survival for the entire group was 25 months from radiation therapy, and the 5-year survival was 41%. The only factor that predicted significantly for decreased survival was infield recurrence (the median survival periods were 13 months and 35 months for those with and without infield recurrence, P < 0.0001). The median time to the development of distant metastasis was 19 months. CONCLUSIONS: Despite the high incidence of distant metastasis, locoregional control remains an important goal in the management of melanoma. Compared with published surgical data, postoperative adjuvant radiation therapy given according to a hypofractionated schedule was effective in reducing local recurrence in patients at high risk of locoregional failure.

Adolescent↗
PubMed2000

The use of clinical criteria alone in the management of the clinically negative neck among patients with squamous cell carcinoma of the oral cavity and oropharynx.

BACKGROUND: Management of the clinically negative neck among patients with oral and oropharyngeal squamous cell carcinoma at the Royal Prince Alfred Hospital, Sydney, Australia has been based on the site and stage of the primary cancer, the likely incidence of microscopic nodal involvement, the treatment modality used for the primary cancer, and whether the neck will be entered during resection or reconstruction. This report analyzes the results of treatment when patients are allocated to either treatment or observation of the neck based on these clinical factors. METHODS: This is a prospectively documented series of 162 consecutively treated patients with squamous cell carcinoma of the oral cavity and oropharynx and clinically negative necks, treated by 1 surgeon (C.J.O.). There were 128 oral cavity and 34 oropharyngeal cancers clinically staged at T1 for 62 patients, T2 for 61, T3 for 16, and T4 for 23 patients. Management of the neck consisted of elective neck dissection (END) in 96 patients (12 bilateral), elective radiotherapy in 8, and observation in 58. Neck treatment correlated with the T stage in a statistically significant way. Forty-six patients underwent postoperative radiotherapy, which was directed to the neck in 22 patients because of pathological findings following neck dissection. Free-flap reconstruction was used in 90 patients. RESULTS: Metastatic squamous cell carcinoma was identified in 32 of 108 neck dissections (30%). There was 1 positive node in 15 necks, 2 positive nodes in 11 necks, and 3 or more positive nodes in 6 necks. Extracapsular spread was present in 8 of 32 positive END specimens (25%). Regional control rates in the neck at 3 years were 94% for END, 100% for elective radiotherapy, and 98% for patients initially observed and then treated by therapeutic neck dissection. Death with uncontrolled disease in the neck occurred in 4 of 96 patients (4%) after END and 1 of 58 patients (2%) after neck observation. Overall disease-specific survival was 83%, comprising an 86% rate for patients with pathologically negative necks and 68% if pathologically positive. Disease-specific survival was 86% at 3 years for patients having END, 67% following radiotherapy, and 94% for the observation group. CONCLUSIONS: Elective neck dissection was performed in most patients, and occult metastatic disease was found in nearly 30% of neck dissections. Observation was most frequently used for patients with early stage disease, and subsequent development of neck metastases was uncommon (9%) in this group. Selective treatment of the clinically negative neck based on the primary tumor site and stage led to a high rate of regional disease control in this series.

Adult↗
PubMed2000

Measurement of a novel optic disc topographic parameter, "spikiness", in glaucoma.

BACKGROUND: Structural changes in the lamina cribrosa have been implicated in the pathogenesis of glaucomatous optic atrophy, but not observed. This paper presents a novel parameter of topographic variability within the optic disc, termed "spikiness", which may reflect glaucoma-related changes in the lamina. METHODS: Four age-matched groups of normal patients (n=12, mean age 64.8 years) and patients with ocular hypertension (n=14, mean age 63.1), primary open-angle glaucoma (n=11, mean age 70) and low-tension glaucoma (n=15, mean age 66.3) were recruited. Images of normal and glaucomatous eyes from the Heidelberg Retina Tomograph were imported into ERDAS image processing software where the spikiness data (30 consecutive mean surface height values across the base of the optic cup in both the vertical and horizontal meridians) were extracted in a format that facilitated further statistical analysis. RESULTS: Significant differences in topographic variability (spikiness) existed in the vertical (F=3.64, P=0.01) but not the horizontal meridian (F=1.25, P=0.3) through the optic disc. Spikiness was inversely related to Humphrey mean deviation (P<0.05), and cup-disc ratio (P<0.004) and was directly related to nerve fibre layer thickness (P<0.005). Of particular interest was the finding that the spikiness measure was the only optic disc parameter to significantly discriminate low tension glaucoma from primary open angle glaucoma. CONCLUSION: A new measure of surface variability (topography) at the floor of the optic cup has been described. The new index of spikiness may represent a measurement of lamina cribrosa fragility which has been implicated, but not previously estimated, in glaucomatous eyes.

Aged↗
PubMed2000

Measurement of peripapillary retinal nerve fiber layer volume in glaucoma.

PURPOSE: To measure peripapillary retinal nerve fiber layer volume in normal subjects and patients with ocular hypertension, primary open-angle glaucoma, and low-tension glaucoma. METHODS: Sixty-five subjects were classified into four groups of normal subjects and subjects with ocular hypertension, primary open-angle glaucoma, and low-tension glaucoma on the basis of intraocular pressure measurements, visual field loss, and optic disk appearance. Groups were matched for sex, age, and optic disk area. Peripapillary retinal nerve fiber layer volume measurements were made with a modification of software version 1.11 of the Heidelberg Retina Tomograph confocal scanning laser ophthalmoscope. Retinal nerve fiber layer volume measurements were taken at 0.1-mm increments from the disk margin for a global 360-degree assessment and at four predefined segments using two different reference planes. Statistical analysis was carried out using analysis of variance with Bonferroni correction. RESULTS: Retinal nerve fiber layer volume measurements showed a gradation from normal to ocular hypertension and from ocular hypertension to glaucoma groups. Mean group measurements showed statistically significant differences (P <.05) in peripapillary retinal nerve fiber layer volume for most segmental measures between the groups. Measurements with the default reference plane in the 0.0-mm to 0.1-mm and 0.1-mm to 0.2-mm increments for the superotemporal segment showed the greatest differences between groups (P <.00005). CONCLUSION: Peripapillary retinal nerve fiber layer volume measurements differ between groups of normal subjects and patients with ocular hypertension, primary open-angle glaucoma, and low-tension glaucoma. This measure offers a further method of assessment of retinal nerve fiber layer in patients with glaucoma and glaucoma suspects.

Aged↗
PubMed2000

Neck dissection and ipsilateral radiotherapy in the management of cervical metastatic carcinoma from an unknown primary.

BACKGROUND: In a small proportion of patients presenting with metastases to cervical lymph nodes the primary cancer remains occult despite thorough evaluation. The present report examines patterns of failure and outcome following an initial treatment strategy directed principally at the clinically involved side of the neck. METHODS: From a prospectively compiled computerized database 38 patients were identified with metastatic squamous cell carcinoma from an occult primary site. These patients were evaluated with respect to initial treatment, subsequent detection of a primary tumour, neck recurrence and survival characteristics. RESULTS: Thirty-seven of 38 patients were treated with curative intent and all had neck dissection. Adjuvant radiotherapy was given to 34 of the 37 (90%; 32 postoperatively and two pre-operatively). Radiotherapy was directed at the ipsilateral neck alone in 24 patients while 10 received comprehensive treatment to both sides of the neck and potential occult primary sites. The rate of control of disease in the ipsilateral neck was 91% while the failure rate in the contralateral neck was 16% (six patients). A primary cancer was ultimately identified in five patients (13%). Disease-specific survival was 63% at 4 years. Clinical N3 stage, extracapsular tumour extension and involved surgical margins predicted for poorer survival on univariate analysis. Analysis using multiple risk factors found that only involved surgical margins predicted for treatment failure. CONCLUSIONS: Despite generally advanced disease at presentation, patients presenting with cervical metastasis from an unknown primary carcinoma have a reasonable survival expectation and aggressive treatment is warranted, but approximately half will develop recurrent disease. Careful follow-up is required if effective salvage treatment is to be instituted.

Aged↗
PubMed2000

Squamous carcinoma of the head and neck: molecular mechanisms and potential biomarkers.

Squamous cell carcinoma (SCC) of the head and neck remains a major health problem worldwide. Recent advances in cell biology suggest that cancer results from the accumulation of specific genetic mutations, many of which have now been identified. These mutations can cause the activation of genes that promote cellular proliferation or inhibit cell death (oncogenes), or they may inactivate genes that inhibit proliferation or promote cell death (tumour suppressor genes). Although there is no known set sequence of events leading to the formation of SCC of the head and neck, there is evidence that many of the genomic mutations implicated in other forms of cancer have an aetiological role in these tumours. Certain viruses, notably Epstein-Barr virus and some types of human papillomaviruses, are causally related to some head and neck cancers. There is now the prospect of using molecular markers to achieve earlier diagnosis and to aid in the prediction of both tumour behaviour and likely responses to particular treatment modalities.

Biomarkers, Tumor↗
PubMed2000

Prevalence and distribution of ret/ptc 1, 2, and 3 in papillary thyroid carcinoma in New Caledonia and Australia.

The world's highest incidence of thyroid cancer has been reported among females in New Caledonia, a French overseas territory in the Pacific located between Australia and Fiji. To date, no molecular genetic studies in this population are available. Over the past few years, the oncogenic rearrangement of the ret protooncogene (ret/ptc) has been studied in papillary carcinomas in different populations. In this study, we investigated the prevalence and distribution of ret/ptc1, 2, and 3 in papillary thyroid carcinoma from the New Caledonian population and compared the pattern with that of an Australian population. Fresh-frozen and paraffin-embedded papillary carcinomas from 27 New Caledonian and 20 Australian patients were examined for ret rearrangements by means of RT-PCR with primers flanking the chimeric region, followed by hybridization with radioactive probes. ret/ptc was present in 70% of the New Caledonian and in 85% of the Australian samples. Multiple rearrangements were detected and confirmed by sequencing in 19 cases, 4 of which had 3 types of rearrangements in the same tumor. This study demonstrates a high prevalence of ret/ptc in New Caledonian and Australian papillary carcinoma. The findings of multiple ret/ptc in the same tumor suggest that some thyroid neoplasms may indeed be polyclonal.

Adolescent↗
PubMed1999

Effects of dipivefrin and pilocarpine on pupil diameter, automated perimetry and LogMAR acuity.

BACKGROUND: A study was carried out to ascertain, in ophthalmologically normal subjects, the short-term effects of dipivefrin hydrochloride 0.1% on visual performance and make comparisons with pilocarpine. METHODS: Twelve normal volunteers aged 20-26 years attended on three occasions. One eye, randomly selected, received one drop of either pilocarpine 2%, dipivefrin or saline 0.9%. High- and low-contrast LogMAR acuity at 6 m and pupil diameter (measured by infra-red pupillometry) were recorded at baseline (T0) and at intervals up to 90 min following instillation of drops. Program 30-2 of the Humphrey Visual Field Analyzer (HFA) was run at T0 and at 60 min after treatment instillation (T60). Saline was always instilled at visit 1, to allow for learning effects. On visits 2 and 3 either pilocarpine or dipivefrin was randomly instilled into the treated eye. RESULTS: Pilocarpine significantly worsened the field global indices mean deviation (P < 0.001) and pattern standard deviation (P < 0.01) compared with T0. There was no significant change with dipivefrin. A significant (P = 0.01) pupil dilation from 5.44 mm (SD 0.79) at T0 to 6.19 mm (SD 1.09) at T90 occurred with dipivefrin. Pilocarpine caused significant miosis. No significant changes in LogMAR values were found with dipivefrin. Pilocarpine significantly (P < 0.01) increased LogMAR values (i.e. reduced acuity) compared with dipivefrin. At T30 the mean increase in LogMAR was 0.76 (SD 0.30) for high and 0.83 (SD 0.11) for low contrast. By T90 recovery of acuity was virtually complete. CONCLUSIONS: In normals dipivefrin causes mydriasis but does not affect the central visual field global indices (as assessed by STATPAC), or high- and low-contrast LogMAR acuity. Pilocarpine adversely affects the visual field and both measures of acuity. Knowledge of these effects is of value in glaucoma therapy and when monitoring the progression of visual loss.

Adult↗
PubMed1999

Location of sentinel lymph nodes in patients with cutaneous melanoma: new insights into lymphatic anatomy.

BACKGROUND: Accurate staging of melanoma patients by sentinel node (SN) biopsy can be achieved only if all SNs draining a given melanoma site are identified and removed for detailed histologic examination. Lymphoscintigraphy with a radiolabeled colloid provides an objective and reliable method of locating SNs and demonstrates that confident prediction of their location is not possible on clinical grounds. STUDY DESIGN: Lymphatic drainage pathways demonstrated by preoperative lymphoscintigraphy for 1,759 patients with primary cutaneous melanomas were reviewed, and locations of SNs in these patients were documented. An SN was defined as any node receiving direct lymphatic drainage from a primary melanoma site. RESULTS: In many instances the cutaneous lymphatic drainage pathways were found to be at variance with longheld concepts of lymphatic anatomy. Several new pathways were identified, draining to SNs in unexpected sites. These included triangular intermuscular space SNs (from upper back and, rarely, upper limb primaries), paraaortic and retroperitoneal SNs (from upper and lower back primaries), and costal margin SNs with onward drainage to internal mammary nodes (from periumbilical primaries). Occasional drainage to node fields on the opposite side of the body was noted from head, neck, and trunk primaries, and drainage to interval nodes (by definition, SNs) outside recognized lymph node fields was also observed. CONCLUSIONS: Knowledge of the possibility of these unusual lymphatic drainage patterns and SN sites should help to ensure the accuracy and completeness of SN identification. Preoperative lymphoscintigraphy to definitively locate SNs is recommended for every patient undergoing an SN biopsy procedure.

Antimony↗
PubMed1999

Application of prognostic scoring systems in differentiated thyroid carcinoma.

BACKGROUND: Total thyroidectomy is widely practised in Australasia for papillary and follicular thyroid carcinoma. Data from large overseas series have demonstrated that patients with these cancers may be separated into risk groups based on clinicopathological prognostic factors. Furthermore, evidence suggests that low-risk patients may be safely treated with less than total thyroidectomy. The aim of the present paper was to determine what proportion of our patients with papillary and follicular thyroid cancer were in the low-risk group in order to select candidates for less aggressive treatment. METHODS: A prospectively documented series of 175 previously untreated patients with papillary and follicular thyroid carcinoma, treated principally by total thyroidectomy over a 10-year period, was divided into risk groups using the Mayo Clinic, Lahey Clinic and Memorial Hospital prognostic scoring systems. Complication rates for 103 patients treated by total thyroidectomy were also studied and reported. RESULTS: Women outnumbered men by 2.3:1. There were 128 papillary carcinomas (73%) and 47 follicular cancers (27%). These tumours were < 4 cm in diameter in 81% of patients, and 41% of patients were 40 years of age or younger. Low-risk patients accounted for 75, 81 and 45% of the study group, respectively, when the three prognostic scoring systems were applied to our patient population. The rates for recurrent laryngeal nerve palsy and permanent hypoparathyroidism for patients having total thyroidectomy were 1 and 1.9%, respectively. In the low-risk group there were no permanent complications. CONCLUSION: Most patients treated at Royal Prince Alfred Hospital during the past 10 years were low-risk patients who may have been eligible for less aggressive surgical treatment.

Adenocarcinoma, Follicular↗
PubMed1999

Spontaneous intralesional haemorrhage in dysembryoplastic neuroepithelial tumours: a series of five cases.

Five patients with dysembryoplastic neuroepithelial tumour (DNT) showing extensive secondary haemorrhage, a finding not previously associated with these neoplasms, are described. The clinical presentations, neuroimaging findings, and histopathological features of these patients are reviewed. One patient, a previously asymptomatic 12 year old girl, presented with an acute intracerebral haemorrhage into a DNT. A further four young adults with histories of intractable partial and generalised seizures dating from childhood showed significant chronic haemorrhages within DNT, the MRI appearances in one patient giving a false impression of a cavernoma. Histopathology disclosed vascular abnormalities within these tumours which, together with other factors discussed, may have predisposed these tumours to haemorrhage.

Brain Neoplasms↗
PubMed1998

Desmoplastic and desmoplastic neurotropic melanoma: experience with 280 patients.

BACKGROUND: It has been suggested that desmoplastic melanoma (DM) and desmoplastic neurotropic melanoma (DNM) are associated with worse prognoses and higher local recurrence rates than other forms of melanoma. In the current study, a large series of patients with DM and DNM treated at a tertiary referral center was reviewed. METHODS: For 190 patients with DM and 90 patients with DNM accrued over a 10-year period, clinical features were recorded and all available histopathology was reviewed. The associations between clinical and pathologic variables, biologic behavior, and eventual outcome were analyzed. RESULTS: The male-to-female ratio was 1.75:1 and the median patient age 61 years. The median tumor thickness was 2.5 mm, and 44% of cases were amelanotic. Five-year survival was 75%. Significant predictors of overall survival were a high mitotic rate (P=0.003) and tumor thickness (P=0.011). All the DNMs exceeded 1.5 mm in thickness and were graded as Clark's level IV or V. There was a significant increase in local recurrence when neurotropism was present (P < 0.001). The rate of local recurrence was not higher for DM than for other cutaneous melanomas. CONCLUSIONS: There was no statistically significant difference in survival for patients with DM and those with DNM, and overall survival for both was similar to that for patients with other cutaneous melanomas. However, there was a lower rate of regional lymph node metastasis at initial presentation and as the first recurrence for both DM and DNM. The local recurrence rate was higher when the surgical clearance margin was <1 cm and when neurotropism was present.

Adult↗
PubMed1998

Sensory recovery in noninnervated radial forearm free flaps in oral and oropharyngeal reconstruction.

BACKGROUND: Reinnerveration of free flaps used in oral and oropharyngeal reconstruction may provide a high level of sensory return. Spontaneous recovery of sensation in noninnervated flaps may also occur. OBJECTIVE: To evaluate the extent of spontaneous sensory return among patients who underwent radial forearm free flap reconstruction in the oral cavity and oropharynx. METHODS: A total of 40 patients were evaluated by 2 independent examiners. The median patient age was 60 years, and the median time from surgery was 47 months. A total of 29 patients had received postoperative radiotherapy. The mean flap size was 25 cm2. The following sensory modalities were tested: light touch, pinprick, hot and cold, and moving and static 2-point discrimination. RESULTS: Recovery of sensation of at least 1 modality was noted in 32 patients (80%), however, only 5 patients (13%) had return of all 5 modalities. Eight patients (20%) had no sensory return. There was a trend to improved sensory recovery in flaps placed in the alveolar and retromolar trigone areas; however, on multivariate analysis, sensory return could not be predicted by any of the following factors: patient age, flap site, flap size, length of follow-up, and use of postoperative radiotherapy. CONCLUSIONS: Complete sensory recovery was uncommon, unpredictable, and variable, although some recovery of sensation occurred in 80% of patients. It is not valid to rely on spontaneous sensory recovery for sensory innervation of free flaps. Correlation of sensory return with function is still needed.

Adult↗
PubMed1998

High incidence of the Cys 282 Tyr mutation in the HFE gene in the Irish population--implications for haemochromatosis.

A simple PCR-SSOP approach based on a single PCR product has been developed to screen the HFE gene for the haemochromatosis-associated mutations Cys 282 Tyr and His 63 Asp. Using this approach the prevalence of these mutations in a cohort (30) of haemochromatosis patients and normal controls (404) was determined. Ninety percent of the haemochromatosis patients were homozygous for the Cys 282 Tyr mutation. In the normal population we found an increased incidence of the Cys 282 Tyr mutation (17.3%; 95% confidence limits 0.136-0.209) which was also reflected in the higher frequency of Cys 282 Tyr homozygotes (1.24%; 95% confidence limits 0.0016-0.0232). Linkage disequilibrium analysis confirmed the association between A*03 and Cys 282 Tyr. However, strong linkage disequilibrium occurred with the HLA-A*03-associated allele HLA-B*14 but not the HLA-A*03-associated allele HLA-B*07. The His 63 Asp was found to be in linkage disequilibrium with HLA-A*29.

Cysteine↗
PubMed1998

Evaluation of 250 free-flap reconstructions after resection of tumours of the head and neck.

BACKGROUND: Microvascular free-tissue transfer is now the primary method of reconstruction in many centres. The aim of this study was to evaluate the applications, complications and limitations of free-flap reconstruction in a series of patients with tumours of the head and neck. METHODS: This study reviewed prospectively accessioned computerized records in a dedicated head and neck database. Patients treated between 1987 and 1995 with a minimum of a 1-year follow-up were reviewed. There were 242 patients with a mean age of 58 years (172 men and 70 women). The most common tumour sites were oral cavity (42%), oropharynx (32%) and hypopharynx (11%). Mucosal squamous carcinoma accounted for 87% of primary cancers. RESULTS: Among the 250 free flaps, the radial forearm flap (205) and free jejunum (25) predominated. There were 21 episodes of vascular occlusion (8%), failure of 10 flaps (4%) and two patients died peri-operatively (0.8%). A second free flap was used in five of 10 cases of flap failure. The fistula rate was 4.4% among 203 patients at risk for this complication, which comprised four of 178 forearm flaps and five of 25 free jejunal grafts. Four of 16 jaw reconstructions failed. CONCLUSIONS: A 96% success rate was achieved using free-tissue transfer for head and neck reconstruction. The overall complication rate was low but jaw reconstruction and free jejunal grafts posed the greatest problems because of failure of radial bone and fistulas, respectively. The radial forearm septocutaneous flap was very reliable and remains our mainstay for oral reconstruction.

Adult↗
PubMed1998

Parotid and submandibular sialadenitis treated by salivary gland excision.

BACKGROUND: The purpose of the present study was to compare and contrast the clinicopathological features and treatment outcome of chronic sialadenitis involving the parotid and submandibular glands, among patients who were treated by excision of the affected gland. METHODS: In a series of 88 patients treated over an 8-year period, 47 had parotid sialadenitis and 41 had submandibular sialadenitis. In the parotid group, 63% of patients were symptomatic for longer than 6 months compared with 27% in the submandibular group. Calculi were implicated in the disease process in 24% of patients with parotid sialadenitis, compared with 73% of patients with submandibular disease. RESULTS: Patients with parotid sialadenitis had superficial (n = 14) or near-total parotidectomy (n = 35), while those with submandibular sialadenitis underwent total gland excision. Complications occurred twice as frequently in the parotidectomy group. The rate of temporary facial nerve weakness was 29% after parotidectomy while marginal mandibular nerve dysfunction occurred after 12% of submandibular excisions. Both procedures were highly effective in permanently relieving the symptoms of sialadenitis. CONCLUSIONS: Parotid sialadenitis is infrequently associated with stones and tends to run a longer course before surgical intervention is necessary. Submandibular sialadenitis usually presents earlier, is secondary to calculi and requires early intervention.

Chronic Disease↗
PubMed1998

Role of the endothelium in modulating functional responses of isolated bovine anterior ciliary arteries to vasoconstrictor agonists.

BACKGROUND/AIMS: Endothelium dependent vasodilatation is an important regulator of blood flow to the eye but its role has not been investigated in vessels supplying the ciliary body. This study assessed the role of the endothelium in modulating vasoconstrictor responses of the intraocular bovine anterior ciliary artery. METHODS: Bovine anterior ciliary arteries (n = 33) were mounted in a myograph, containing physiological salt solution at 37 degrees C, for isometric force measurement. Cumulative concentration-response curves were obtained to the constrictor agonists 5-hydroxytryptamine (5-HT), noradrenaline, phenylephrine, prostaglandin, F2 alpha, endothelin-1, and KCl in both endothelium intact and denuded arteries. RESULTS: All vasoconstrictors produced sustained contractile responses which were unaffected by the removal of the endothelium. Responses to 5-HT were also unaffected by inhibition of nitric oxide synthase. CONCLUSION: These results indicate that neither agonist stimulated nor basal release of nitric oxide from the endothelium modulates responses to vasoconstrictor agonists in the isolated bovine anterior ciliary artery when measured in a no flow isometric system.

Animals↗