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J Cameron

Publications and source records attributed to J Cameron.

At least 37 records · Page 2Linked to original sources
PubMed2001

Ultrastructural changes in postcapillary-sized venule morphology in aged mouse periodontal ligament.

The aim of this study was to compare the postcapillary-sized venule (PCV) morphology of four young ALCA mice (35 days) and four colony-related aged mice (365 days) using the transmission electron microscope (TEM). Right and left mandibular first molar mesial roots with associated periodontal ligament (PDL) and bony socket, were used for TEM assessment. Five PCV profiles were selected at each 160 microm interval, from the alveolar crest to the tooth apex. PCV profile dimensions were measured on standardised micrographs magnified x2900. Age affects were tested using multiple regression analysis. The number of PCV profiles in the tooth third of the PDL was higher in aged mice (p < 0.01) and comprised predominantly apericytic vessels (p < 0.001). The number of PCV profiles increased significantly (p < 0.001) in aged mice in the PDL middle circumferential third halfway down the molar root. Age had no significant affect on PCV diameter. Aged PDL permeability studies are needed to investigate whether the changes in aged PCV profile number are associated with functional modification of the PDL microvasculature.

Aging↗
PubMed1999

Action of mannitol in ciguatoxin-intoxicated rats.

This study reports the effects of mannitol on nerve conduction when used as a therapeutic agent in mammals following the administration of ciguatoxin. Electrophysiological studies were performed in vivo on the rat ventral coccygeal nerve. The absolute and relative refractory periods, conduction velocity and the supernormal response were measured in rats treated with i.p. ciguatoxin, both prior to, and following, the infusion of i.v. mannitol. Ciguatoxin induced significant prolongation of the absolute refractory period as well as significant slowing of the compound nerve conduction velocity. The magnitude of the supernormal response was significantly increased and the duration of the supernormal period extended in ciguatoxin-treated animals. Recordings collected following the infusion of mannitol in these ciguatoxin-treated animals showed that mannitol did not reverse the effects of ciguatoxin on nerve conduction in any of the parameters measured.

Animals↗
PubMed1999

Estimation of arterial mechanics in clinical practice and as a research technique.

1. Large conduit artery pathophysiology is associated with considerable morbidity with even normal ageing, irrespective of concurrent influences, associated with impaired arterial function. 2. Recent technical advances have enabled high-resolution non-invasive assessment of pulsatile arterial properties, but this has been largely confined to more muscular superficial arteries. There has been less study of arterial regions prone to disease that would, theoretically at least, benefit from pharmacological or other intervention to improve function. 3. Based on studies in animal models and, in particular, human arterial segments, specific pharmacological agents have been proposed as improving arterial behaviour. If this is to become a therapeutic target, it behoves increased effort to understand and measure meaningful indices of arterial function and to find ways of assessing response and outcome. 4. A number of different approaches to assessment and quantification of arterial mechanics are available in the literature. The present review compares and discusses some of these different techniques and looks at differences between arterial segments and evidence that appropriate intervention may beneficially modify arterial behaviour. 5. For clinical or research usefulness, assessment of arterial mechanics must provide more information than currently derived from simple numerical measurement of brachial blood pressure. This is particularly true because epidemiological risk evidence is based on brachial rather than central blood pressure recordings. There has been an explosion of work in this field in recent years and the present review does not pretend to reference all relevant material; rather, it tries to provide a broad coverage of the topic and hopes to support the need for continued endeavours in the field of arterial mechanics.

Animals↗
PubMed1999

Primary cardiac arrhythmias in children.

OBJECTIVES: Primary cardiac arrhythmias are much less common in children than adults. This study was performed to identify the characteristics of primary arrhythmias in pediatric patients in the Emergency Department (ED). METHODS: Retrospective review of ED visits of patients <18 years of age presenting between January 1991 and November 1996 with an Emergency Department diagnosis of primary cardiac arrhythmia. Secondary cardiac arrhythmias, ie, sinus tachycardia resulting from a fever, were excluded. Clinically significant arrhythmias were defined as those capable of altering cardiovascular stability. SITE: 26 Community Hospital EDs. RESULTS: A total of 2.3 million ED visits were reviewed and 320 arrhythmias in children were identified in 0.58 million patients under 18 years of age. The overall incidence of arrhythmias was 13.9 per 100,000 ED visits and 55.1 per 100,000 pediatric ED visits. The incidence of clinically significant arrhythmias was 5.7 per 100,000 ED visits and 22.5 per 100,000 patients <18 years of age. The mean patient age was 113 (+/-0.31) years with a peak in infancy and a second peak in late childhood and adolescence. The most common arrhythmias were: Sinus tachycardia: 160 (50%); Supraventricular tachycardia (SVT): 42 (13%); Nonspecific arrhythmia (NSA): 34 (10.6%); Bradycardia: 19 (6%); and Atrial fibrillation (a-fib): 15 (4.6%). The most common clinically significant arrhythmias by age group were: [table in text]. Nine patients had an additional diagnosis of Wolf-Parkinson-White syndrome, eight with Sinus tachycardia and one with SVT. There were four cardiac arrests noted all with ventricular fibrillation as the recorded arrhythmia. CONCLUSION: Primary arrhythmias are unusual ED presentations in children and atrial tachyarrhythmias are the most common rate and rhythm disturbance in this population.

Adolescent↗
PubMed1999

A fuzzy logic-controlled classifier for use in implantable cardioverter defibrillators.

PURPOSE: Implantable cardioverters defibrillators (ICDs) are increasingly used in the management of life-threatening arrhythmias. Correct recognition of a treatable arrhythmia is crucial to this application. However, the computational power of microprocessors currently used in ICDs limits the range of traditional algorithms available for this application. METHODS: Classification based on fuzzy inference systems (FIS) were trained to recognize different cardiac rhythms (AF, VF, SVT, VT) from the Ann Arbor Electrogram Library. The FIS used were designed using adaptive-network-based fuzzy inference methods to optimize the classification procedure. Only computational techniques suitable for ICD design were used. RESULTS: After pretraining with the ANFIS correct rhythm classification was observed for the rhythms studied. CONCLUSION: In this preliminary study, successful rhythm classification was demonstrated using fuzzy logic techniques. In view of the computational efficiency this may have application in ICD design.

Arrhythmias, Cardiac↗
PubMed1999

Molecular genetic characterisation of frontotemporal dementia on chromosome 3.

We have previously localized a locus causing familial nonspecific dementia to the centromeric region of chromosome 3 in a pedigree from the Jutland area of Denmark. This pedigree shows anticipation. Here we present further analysis of these anticipation data which are suggestive of trinucleotide repeat expansion involvement. We also outline our strategies to clone the mutant gene via its putative associated trinucleotide repeat sequence.

Adult↗
PubMed1999

Risk factors for detecting germline BRCA1 and BRCA2 founder mutations in Ashkenazi Jewish women with breast or ovarian cancer.

We ascertained 184 Ashkenazi Jewish women with breast/ovarian cancer (171 breast and 13 ovarian cancers, two of the former also had ovarian cancer) in a self-referral study. They were tested for germline founder mutations in BRCA1 (185delAG, 5382insC, 188del11) and BRCA2 (6174delT). Personal/family histories were correlated with mutation status. Logistic regression was used to develop a model to predict those breast cancer cases likely to be germline BRCA1/BRCA2 mutation carriers in this population. The most important factors were age at diagnosis, personal/family history of ovarian cancer, or breast cancer diagnosed before 60 years in a first degree relative. A total of 15.8% of breast cancer cases, one of 13 ovarian cancer cases (7.7%), and both cases with ovarian and breast cancer carried one of the founder mutations. Age at diagnosis in carriers (44.6 years) was significantly lower than in non-carriers (52.1 years) (p<0.001), and was slightly lower in BRCA1 than BRCA2 carriers. Thirty three percent of carriers had no family history of breast or ovarian cancer in first or second degree relatives. Conversely, 12% of non-mutation carriers had strong family histories, with both a first and a second degree relative diagnosed with breast or ovarian cancer. The predicted values from the logistic model can be used to define criteria for identifying Ashkenazi Jewish women with breast cancer who are at high risk of carrying BRCA1 and BRCA2 mutations. The following criteria would identify those at approximately 10% risk: (1) breast cancer <50 years, (2) breast cancer <60 years with a first degree relative with breast cancer <60 years, or (3) breast cancer <70 years and a first or second degree relative with ovarian cancer.

Adult↗
PubMed1998

Angiographic follow-up and clinical experience with the flexible Tantalum Cordis stent.

The Cordis stent is a flexible, highly radioopaque intracoronary stent engineered from a single Tantalum filament folded into a sinusoidal helical coil. It is premounted on a semicompliant balloon expandable stent delivery system. From September 1995-March 1996, 147 Cordis stents were deployed in 105 patients (aged 58+/-12 yr, 71% male). Clinical indications for stenting were unstable angina in 59 (55%), stable angina in 41 (38%), and acute myocardial infarction in 7 (7%). The target vessel was the right coronary artery in 45%, the left anterior descending in 31%, and the circumflex artery in 22%. One stent was deployed in a vein graft, and one stent was deployed in a left internal mammary artery graft. Stent deployment was achieved in all but one patient. Acute in-stent thrombosis occurred in 3 patients (2.9%). Two of these patients required urgent coronary artery bypass surgery. Subacute stent thrombosis occurred in 2 patients (1.9%). Minimum lumen diameter increased from 0.70+/-0.41 mm to 3.50+/-0.60 mm following stent placement. All patients received aspirin. Eighty-one patients (77%) received ticlopidine, and 4 patients (4%) received warfarin therapy. The mean hospital stay was 3.4+/-2.3 days. Six-month follow-up angiography was performed on 50 out of 55 eligible patients at one of the two institutions involved in this study. Computer-assisted quantitative coronary angiography defined a restenosis rate of 26%. Repeat revascularization was required in 8 patients (14.5%) at 6-mo follow-up. The Tantalum Cordis intracoronary stent is an effective and safe means of treating coronary lesions, even in patients with unstable ischemic syndromes. Acute and subacute rates of in-stent thrombosis were acceptable, and the long-term angiographic restenosis rates and need for repeat revascularization were favorable.

Angina Pectoris↗
PubMed1998

Gender differences in the renal nitric oxide (NO) system: dissociation between expression of endothelial NO synthase and renal hemodynamic response to NO synthase inhibition.

Many studies have shown that nitric oxide (NO) production is higher in the systemic vasculature of females than males and is stimulated during pregnancy, a high estrogen state. The present study was performed in rats to determine whether females had a greater expression of endothelial NO synthase (eNOS) in kidneys than did males; whether there were gender differences in the excretion of NO metabolites, nitrate/nitrite; and whether there were gender differences in the renal hemodynamic response to NO synthase inhibition. The renal levels of eNOS mRNA (as measured by ribonuclease protection assays) and protein (as measured by Western blot) were 80% higher in kidneys from females than from males (P < .001). Urinary excretion of NO metabolites, nitrate/nitrite, were not different between males and females. To inhibit eNOS, rats were treated with nitro-L-arginine methyl ester (L-NAME, 3 to 4 mg/kg/day) for 2 weeks. Although there were no differences in basal renal hemodynamics between males and females, when factored for kidney weight, chronic L-NAME increased renal vascular resistance by 130% in males but by only 60% in females, and decreased renal plasma flow by 40% in males but had no effect in females. These data show that although the renal levels of eNOS mRNA and protein are higher in females than in males, the renal vasculature of males is more responsive to NO synthase inhibition. The data suggest that the renal vasculature of males may be more dependent on NO than is the renal vasculature in females.

Animals↗