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Biomedical subjects

J P Clarke

Publications and source records attributed to J P Clarke.

At least 19 recordsLinked to original sources
PubMed2006

Sub-Tenon block: a learning curve of 100 cases.

This study measures the learning curve for accomplishing sub-Tenon blocks for ophthalmic surgery applicable to anaesthetists skilled in peribulbar techniques. We defined criteria for a good block in terms of chemosis, subconjunctival haemorrhage, globe movement and the need for additional peribulbar block. The overall success rate, by our definitions, was 72% and 56% for the two operators. The overall requirement for an additional peribulbar block was 10%. The rate of additional blocks and reduction in globe movement reached a plateau after about 60 procedures for both operators. The rates of chemosis (6% and 12% overall) and subconjunctival haemorrhage (6% and 12% overall) did not trend with increased experience. The results applied to both a cataract and a vitreo-retinal surgery casemix.

Adolescent↗
PubMed2000

A quality assurance index for brachytherapy treatment plan verification.

A method is described which provides an independent verification of a brachytherapy treatment plan. The method is applicable to any common geometric configuration and utilises a simple equation derived from a common form of non-linear regression. The basis for the index value is the relationship between the treatment time, prescribed dose, source strength and plan geometry. This relationship may be described mathematically as: Total Treatment Time proportional to (Prescribed Dose/Source Strength) x (a geometric term) with the geometric term incorporating three geometric components, namely the distance from source positions to points of dose normalisation d, the total length of the dwell positions L, and the number of source trains or catheters N. A general equation of the form GF = k (d)(-alpha) (L)(-beta) (N)(-gamma) is used to describe the plan geometry, where GF is what we have termed the geometric factor, k is a constant of proportionality and the exponents are derived from the non-linear regression process. The resulting index is simple to calculate prior to patient treatment and sensitive enough to identify significant error whilst being robust enough to allow for a normal degree of geometric distortion.

Brachytherapy↗
PubMed1998

[A rare dyspnea in internal medicine: platypnea-orthodeoxia after pneumonectomy].

BACKGROUND: A right-to-left shunting across a patent foramen ovale is a rare cause of acute respiratory failure after pneumonectomy. CASE REPORTS: We report two cases of posture dependent dyspnea (platypnea-orthodeoxia) secondary to postoperative right-to-left shunting across a patent foramen ovale. Both cases occurred three months after pneumonectomy, the first in a 63-year-old man and other in a 52-year-old man. CONCLUSION: A platypnea-orthodeoxia (dyspnea induced by the upright position with arterial deoxygenation relieved by recumbency) should lead to the diagnosis which is confirmed by echography or cardiac catheterization. The prognosis is good after surgical closure of the patent foramen ovale. The physiopathologic mechanism is poorly understood. We report two cases of platypnea-orthodeoxia.

Adenocarcinoma↗
PubMed1998

Radiographic evaluation of anterior cruciate ligament graft failure with special reference to tibial tunnel placement.

Graft failure in anterior cruciate ligament (ACL) reconstruction can result from anterior placement of the tibial tunnel. Conventional radiographic evaluation of this problem does not take into account potential changes in tibio-femoral relationship caused by ACL instability. A retrospective radiographic evaluation of failed as well as successful ACL reconstructions was carried out. Both published radiographs as well as those obtained of patients treated by the authors were evaluated for tibial tunnel placement, roof impingement, and tibial position relative to the femur. In the second part of the study, the radiographs were obtained under standard conditions in both failed ACL reconstructions and normal knees. The results of both parts of the study indicate that lateral radiographs of the extended knee with ACL instability are likely to show subtle anterior tibial subluxation. The subluxation can give the impression of roof impingement on the graft. However, the majority of the failed knees had similar tibial tunnel placement compared with successful reconstructions and would appear unimpinged once corrected for subluxation. The diagnosis of graft impingement by the femoral intercondylar roof has to take into account potential tibial subluxation. Impingement as a cause graft failure may be less common than previously thought.

Anterior Cruciate Ligament↗
PubMed1998

The effect of intraoperative ventilation strategies on perioperative atelectasis.

Several methods of ventilation have previously been shown to reduce intraoperative atelectasis and alveolar to arterial oxygen gradient (A-a DO2) in healthy patients. This study was designed to show firstly the relative intra-operative benefit and secondly if any method had an effect on atelectasis postoperatively. Using a factorial design we randomized 24 patients to each of the four ventilatory interventions (manual inflations, large tidal volumes, PEEP, and pressure control inverse ratio ventilation (IRV)). The A-a DO2 was used as the measure of atelectasis and data collected intra- and postoperatively for 24 hours. The mean pre-induction A-a DO2 was 80 mmHg. This study demonstrated that PEEP and IRV were most effective in reducing intraoperative A-a DO2 (P < 0.05 ANCOVA). Using more than one intervention did not improve the A-a DO2. No method had any effect on postoperative A-a DO2.

Aged↗
PubMed1997

The effects of inverse ratio ventilation on intracranial pressure: a preliminary report.

OBJECTIVE: To determine the effects of pressure control inverse ratio ventilation [PC-IRV], as compared with volume controlled normal ratio ventilation [VC], on the intracranial pressure [ICP] of patients with severe head injury. DESIGN: A prospective study with unblinded intervention. SETTING: The Intensive Therapy Unit of a base hospital. PATIENTS AND PARTICIPANTS: Nine cases of head injury requiring mechanical ventilation and intracranial pressure monitoring were studied. INTERVENTIONS: Patients were twice transferred from VC (1:E ratio 1:2) to PC-IRV (1:E ratio 2:1). Firstly, tidal volume was maintained at an equal value. Secondly, end tidal CO2 was maintained at an equal value. No other changes were made to ventilation, vasopressor therapy or ICP control. MEASUREMENTS AND RESULTS: Measurements were taken of ICP, mean arterial pressure (MAP) end tidal CO2 and respiratory parameters. In the first observation, there were significant changes in peak inspiratory pressure (PIP), mean airway pressure (Paw) and intrinsic positive end expiratory pressure (PEEP) but not for ICP, end tidal CO2, MAP and cerebral perfusion pressure (CPP). The correlation between change in ICP and change in end tidal CO2 was r = -0.74. In the second observation there were significant changes in tidal volume, PIP, Paw and intrinsic PEEP but not for ICP, MAP and CPP. The correlation between the change in ICP and the change in Paw was insignificant. CONCLUSIONS: PC-IRV has a minimal net effect on ICP. Changes in ICP correlate more strongly with changes in CO2 than changes in Paw.

Adolescent↗
PubMed1996

Distinct desmocollin isoforms occur in the same desmosomes and show reciprocally graded distributions in bovine nasal epidermis.

The adhesive core of the desmosome is composed of cadherin-like glycoproteins of two families, desmocollins and desmogleins. Three isoforms of each are expressed in a tissue-specific and developmentally regulated pattern. In bovine nasal epidermis, the three desmocollin (Dsc) isoforms are expressed in overlapping domains; Dsc3 expression is strongest in the basal layer, while Dsc2 and Dsc1 are strongly expressed in the suprabasal layers. Herein we have investigated whether different isoforms are assembled into the same or distinct desmosomes by performing double immunogold labeling using isoform-specific antibodies directed against Dsc1 and Dsc3. The results show that individual desmosomes harbor both isoforms in regions where their expression territories overlap. Quantification showed that the ratio of the proteins in each desmosome altered gradually from basal to immediately suprabasal and upper suprabasal layers, labeling for Dsc1 increasing and Dsc3 decreasing. Thus desmosomes are constantly modified as cells move up the epidermis, with continuing turnover of the desmosomal glycoproteins. Statistical analysis of the quantitative data showed a possible relationship between the distributions of the two isoforms. This gradual change in desmosomal composition may constitute a vertical adhesive gradient within the epidermis, having important consequences for cell positioning and differentiation.

Animals↗
PubMed1996

Expression of full-length desmosomol glycoproteins (desmocollins) is not sufficient to confer strong adhesion on transfected L929 cells.

Desmocollins are cadherin-like glycoproteins that are localized in desmosomes. They are thought to play a role in cell adhesion but direct evidence for this is currently unavailable. For this reason we have expressed cDNAs encoding full-length bovine desomocollin type 1a and type 1b in mouse fibroblast (L929) cells. This system has previously been used to demonstrate the adhesive properties of E-cadherin. E-cadherin-mediated cell-cell adhesion is thought to require interaction of the cytoplasmic domain with the catenins that are expressed in L-cells. Because L929 cells do not express cytoplasmic desmosomal components that may be required for desmocollin-mediated adhesion, we constructed a chimeric cDNA encoding the bovine type 1 extracellular domain linked to the mouse E-cadherin transmembrane and cytoplasmic domains. cDNAs were transfected into cells and clones that expressed heterologous protein at the cell surface were isolated. The full-length desmocollins apparently did not interact with any other molecules, but the chimeric protein did bind to endogenous mouse alpha- and beta-catenin. Surprisingly none of the desmocollin-transfected cell lines showed significant adhesive properties under conditions where cells transfected with E-cadherin exhibited strong adhesiveness. We conclude that desmcollin expression alone is not sufficient to confer adhesion on transfected cells and more than one desmosomal component may be required.

Animals↗
PubMed1995

Characterisation of a desmocollin isoform (bovine DSC3) exclusively expressed in lower layers of stratified epithelia.

Desmocollins are cadherin-like glycoproteins involved in cell adhesion and plaque formation in desmosome junctions. Three distinct isoforms, the products of different genes, have been found in bovine tissues. We have reported previously that one of these, DSC3, is expressed only in basal and lower suprabasal layers of stratified epithelia. Using RT-PCR we have now obtained the complete cDNA coding sequence of mature bovine DSC3. It has alternatively spliced 'a' and 'b' forms found in other desmocollins but is unique in having a 43 instead of a 46 base pair exon. We have characterised a monoclonal antibody, 07-4G, which is specific for the Dsc3 protein, recognising an epitope in the extracellular domain. Immunofluorescent staining with 07-4G confirms that this isoform is found only in stratified epithelia, being strongly expressed in the basal cell layers of these tissues. The intensity of expression fades gradually in the suprabasal layers and disappears completely below the upper limit of desmosome expression. These results suggest that Dsc3 plays an important role in cell epithelial differentiation.

Amino Acid Sequence↗
PubMed1995

[Horton disease of pulmonary localization].

A case of Horton's disease with interstitial pulmonary involvement is reported. Transbronchial biopsy of the lung and biopsy of the temporal artery provided evidence of giant cell lesions. Outcome was favourable with general corticosteroid therapy with regression of the pulmonary disease.

Aged↗
PubMed1994

A review of 19 sets of triplets: the positive results of vaginal delivery.

The outcome of 19 triplet pregnancies delivered at Waikato Women's Hospital is analyzed, with particular regard to the mode of delivery. During the period 1981-1992 the incidence of triplets was 1:1,945. Twelve sets of triplets were delivered by Caesarean section (63%) with 6 perinatal deaths occurring in this group, compared to none in 7 sets of triplets delivered vaginally (37%). All triplet pregnancies were correctly diagnosed antenatally by ultrasound examination at a mean gestational age of 19 weeks (range 11-28 weeks). The most common antenatal complications were preterm labour in 18 pregnancies (95%) and preeclampsia in 4 (21%). The mean gestation at delivery was 33 weeks (range 25-39 weeks). The outcome of triplet pregnancies was better in the group that delivered vaginally than those delivered by Caesarean section. Greater maturity of the infants delivered vaginally appeared to be the major factor for the lower neonatal morbidity and mortality.

Birth Weight↗
PubMed1991

Characterisation of the murine Hox-3.3 gene and its promoter.

The murine Hox-3.3 homeobox containing gene and its Xenopus homologue (XlHbox 1) produce two embryonic transcripts from two distinct promoters located approximately 9 kb apart. In order to begin to characterise one of these promoter regions (PRII), we have sequenced 3 kb of DNA immediately upstream of the transcription start site of the PRII transcript and analyzed the sequence for sequences known to bind transcription factors. Within this region are located a number of sequences that match known cis-elements. We have analysed the ability of two of these sequences that match to the Drosophila hunchback and Antennapedia/fushi-tarazu consensus binding sequences to specifically bind proteins extracted from embryos and from adult tissues. Using gel retention assays with oligonucleotides derived from these sequences, we show that both sequences specifically bind proteins present in extracts of mouse embryos and some, but not all extracts of various adult tissues. Protein binding cannot, however, be correlated with the known spatial domains of Hox-3.3 expression, suggesting that binding to these sequences is not simply related to activation of Hox-3.3 expression. A two base pair change in the most conserved region of the hunchback-like binding sequence completely abolishes protein binding. The presence of these highly conserved cis-acting elements that are known to be involved in regulation of the hunchback, even-skipped and engrailed genes in Drosophila suggests that these sequences may also be involved in the regulation of expression of Hox-3.3 and furthermore that regulation may in part at least involve binding of hunchback-like proteins (i.e. zinc-finger proteins) and Antennapedia-like homeobox-containing proteins.

Amino Acid Sequence↗
PubMed1989

[Takayasu's disease localized exclusively in the pulmonary artery].

A 35 year-old woman exhibited a stenotic lesion of the right pulmonary artery with a severe inflammatory syndrome. A diagnosis of Takayasu arteritis was made, although no aortographic abnormality was present. Involvement of pulmonary arteries during the course of Takayasu arteritis is frequent, but a localisation of the disease to the pulmonary arterial tree alone is a very rare condition.

Adult↗