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Biomedical subjects

R D Page

Publications and source records attributed to R D Page.

At least 55 records · Page 3Linked to original sources
PubMed1994

Coexistent trigeminal neuralgia, hemifacial spasm, and hypertension: preoperative imaging of neurovascular compression. Case report.

The case is reported of a 60-year-old woman with left-sided trigeminal neuralgia, hemifacial spasm, and hypertension. Compression of the left trigeminal, facial, and vagus nerves by the anterior and posterior inferior cerebellar arteries and a persistent trigeminal artery variant were demonstrated by magnetic resonance angiography using a novel sequence. At operation the angiographic appearances were confirmed, and decompression was performed with the placement of polyvinyl sponge at all three levels. Postoperatively, the patient had complete relief from the trigeminal neuralgia and hemifacial spasm and has sustained normotension without medication.

Arteries↗
PubMed1993

Thalamotomy for the alleviation of levodopa-induced dyskinesia: experimental studies in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated parkinsonian monkey.

This work set out to test the hypothesis that thalamotomy in the area of the thalamus which receives the input from the medial segment of the globus pallidus would decrease or prevent levodopa-induced dyskinesia. Peak dose dyskinesia is a major problem in the treatment of parkinsonian patients with levodopa therapy but this remains the best pharmacological agent for treating the condition. The hypothesis was derived from previous work which has suggested that reduced pallidal inhibition of the thalamus results in dyskinesia [Crossman (1990) Movement Dis. 5, 100-108]. A neuroanatomical tracing study was carried out prior to the thalamotomy work, using the anterograde tracer wheatgerm-agglutinin conjugated to horseradish peroxidase. This delineated the anterior part of the ventrolateral thalamus in the primate in terms of its afferent inputs. Wheatgerm agglutinin-horseradish peroxidase was injected into the medial segment of the globus pallidus bilaterally in three Macaca fascicularis and traced to terminals in the ventral thalamus and other brain areas. The appropriate thalamic area involved was plotted on atlas sections in preparation for stereotactic thalamotomy. Previous studies of neuronal input to the ventral thalamus are confusing due to the different nomenclatures used by different workers. Early workers used cytoarchitectonic boundaries which do not correspond with function. There are also differences in nomenclature between man, monkey and other animals. The current study maps the pallidal terminal territory within the thalamus in terms of stereotactic co-ordinates related to a published macaque atlas [Shantha et al. (1968) A Stereotaxic Atlas of the Java Monkey Brain. S. Karger, Basel] and can thus be used by other workers in the field. A well-established primate model of Parkinsonism was used for the thalamotomy study. Eight monkeys (Macaca fascicularis) were rendered parkinsonian with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Regular dosing with levodopa or apomorphine reliably resulted in peak-dose dyskinesia which was scored in terms of its choreic and dystonic components. A radiofrequency electrode was used to create the ablative lesions. Chorea was always reduced and frequently abolished by a thalamotomy located in the pallidal terminal territory. This result was obtained after 10 thalamotomies in a total of six animals. Four animals received bilateral lesions, with an interval between operations and two animals underwent unilateral surgery.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1993

Videothoracoscopic surgery.

Although thoracoscopy has been used for diagnostic and minor therapeutic procedures for many years, there have been few reports of its use in performing major intrathoracic procedures which have traditionally required formal thoracotomy. We report our initial experience in this field. Fifty patients (M:F = 1.63:1, mean +/- SD age = 41.8 +/- 20.4 years, range = 14-80) underwent 54 endoscopic intrathoracic operations. The procedures carried out included wedge excision of solid pulmonary mass (10), pleurectomy (25), lung biopsy (14), and miscellaneous procedures (5). Under general anaesthesia a laparoscope attached to a video monitor was introduced into the chest. One or two additional stab incisions were made as needed for the introduction of standard surgical or endoscopic instruments and staplers. There were no deaths. One patient developed a second pneumothorax 7 days after endoscopic pleurectomy, necessitating open pleurodesis. All patients were discharged home between 2 and 11 days after surgery (mean +/- SD = 3.8 +/- 2.0 days). Endoscopic thoracic surgery is a safe and useful technique for certain cases. It merits further investigation and assessment.

Adolescent↗
PubMed1992

The use of thalamotomy in the treatment of levodopa-induced dyskinesia.

Peak dose dyskinesia is a major problem in the treatment of parkinsonian patients with levodopa and yet this remains the best pharmacological agent for treating the condition. The hypothesis which this research set out to test was that thalamotomy in the area of the thalamus which receives the input from the medial segment of the globus pallidus would decrease or prevent the dyskinesia. A well established primate model of parkinsonism was used. Eight monkeys (Macaca fascicularis) were rendered parkinsonian with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Regular dosing with levodopa or apomorphine reliably resulted in peak dose dyskinesia. Thalamotomy was carried out using a radiofrequency electrode. To ensure that the appropriate area of the thalamus was targeted, that is the area receiving the pallidal input, an anatomical tracing study was carried out. The anterograde anatomical tracer horseradish peroxidase, covalently bound to wheatgerm agglutinin, was injected into the medial segment of the globus pallidus bilaterally in three monkeys. The target site for thalamotomy was accurately worked out from the tracings obtained. Chorea was usually abolished and always reduced by a thalamotomy in the pallidal terminal territory. This result was obtained after 10 thalamotomies: 4 animals receiving bilateral lesions, with an interval between operations, and 2 animals undergoing unilateral surgery. Lesions in three control sites were carried out and had no permanent effect on chorea. The effect of lesions in other areas was also assessed. Dystonia was not relieved by any thalamic lesion. Thalamotomy is a long established procedure used to help parkinsonian tremor. Appropriately placed thalamotomy should be considered for the relief of disabling peak dose dyskinesia, which is predominantly choreic, in parkinsonian patients on otherwise successful levodopa therapy.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1992

Normothermic arrest with continuous hyperkalaemic blood: initial experience.

The requirement for hypothermia in myocardial protection has recently been questioned. Between October 1990 and May 1991, diastolic arrest was achieved using continuous perfusion with normothermic, hyperkalaemic blood in 257 consecutive patients undergoing cardiac surgery. The mean age was 59.8 +/- 9.3 years (range 28-84 years). Coronary artery surgery was performed in 210 patients, valve replacements in 18, combined procedures in 22, and 7 patients had miscellaneous procedures. Eleven patients (4.3%) had undergone previous cardiac surgery, and 65 (25.3%) required urgent or emergency operations. Hyperkalaemic blood (7-20 mmol/l) was delivered antegradely in 190 (72.8%) patients (mean aortic root pressure 60-80 mmHg), retrogradely in 62 (25.3%) patients (mean coronary sinus pressure less than 40 mmHg), and by a combined route in 5 (1.9%). Sinus rhythm returned immediately after removal of the aortic clamp in 235 (91.4%) patients. Weaning from bypass was achieved without circulatory support in 207 (82.5%) patients. Of 233 patients undergoing non-emergency coronary artery surgery, single valve or combined procedures, 11 died, giving an operative mortality of 4.7%. Of 155 patients with good left ventricular function requiring coronary artery surgery, 3 (1.9%) died. The in-hospital mortality for the group as a whole was 7.3%. Sixteen (6.2%) patients sustained perioperative myocardial infarctions; of these 6 died. We conclude that continuous, normothermic, hyperkalaemic arrest is a simple and safe method of myocardial protection. It may avoid the damage associated with hypothermia, ischaemia and reperfusion.

Adult↗
PubMed1992

Endoscopy assisted microthoracotomy: initial experience.

BACKGROUND: Although thoracoscopy has been used for diagnostic and minor therapeutic procedures for many years, there have been few reports of its use in performing major intrathoracic procedures, which have traditionally required formal thoracotomy. METHODS: Twenty one patients (M:F 1.2:1; mean (SD) age 47.1 (18.8), range 17-75 years) underwent endoscopic intrathoracic surgery. Eight had unidentified peripheral masses on the chest radiograph, eight required lung biopsy, and five had recurrent or persisting pneumothoraces. Under general anaesthesia a laparoscope attached to a video monitor was introduced into the chest. One or two additional stab incisions were made as needed for the introduction of standard surgical or endoscopic instruments and staplers. RESULTS: There were no complications or deaths, though one patient developed a second pneumothorax seven days after endoscopic pleurectomy, necessitating open pleurodesis. All patients were discharged home from two to six days after surgery (mean (SD) 3.7 (1.2) days). CONCLUSION: Endoscopic thoracic surgery is a safe and useful technique for certain cases. It merits further investigation and assessment.

Adolescent↗
PubMed1992

Ultra-pure polymerized bovine hemoglobin blood substitute: effects on the coronary circulation.

The effects of stroma-free hemoglobin (SFHgb) on the coronary circulation remain unclear. An intact canine model utilizing intracoronary adenosine to abolish the confounding effect of autoregulation was used to study maximal myocardial oxygen delivery during progressive hemodilution with polymerized bovine SFHgb. The circumflex coronary artery was instrumented with a flow probe, hydraulic constrictor, and proximal and distal catheters for adenosine infusion and distal pressure measurement, respectively. This preparation was used to generate diastolic coronary pressure-flow relations during maximal vasodilation. Maximal coronary conductance and maximal myocardial oxygen delivery were determined in two groups of 7 dogs each following hemodilution, first with 6% hetastarch (Control), followed by further hemodilution with ultra-pure, polymerized, bovine SFHgb. After hemodilution with SFHgb, maximal coronary flow increased slightly without evidence of coronary vasoconstriction. Since hemodilution with this material increases oxygen carrying capacity, maximal oxygen delivery is greater than Control, despite the very low canine hematocrit. These findings suggest: 1) SFHgb can provide adequate oxygen delivery to the myocardium despite extreme degrees of hemodilution, and 2) in this intact model, there is no evidence of adverse coronary vasomotion.

Animals↗
PubMed1991

The quantitation of bovine embryo viability using a bioluminescent assay for lactate dehydrogenase.

Forty-seven bovine embryos, ranging from the four-cell to expanded blastocyst stage, with grades ranging from excellent to poor, were collected non-surgically from superovulated Holstein heifers. A viability assay based on the measurement of bioluminescent emission from the media surrounding an embryo was tested. This assay measured the activity of the enzyme lactate dehydrogenase (LDH) released into the media by the embryos. Lactate dehydrogenase has been reported to be released into media by nonviable embryos. The assay used is simple, rapid and nonsubjective, requiring approximately 5 min to complete. The LDH assay proved to be a practical method for distinguishing between nonviable and viable embryos. Viability was determined by the observation of embryo development in culture following the LDH assay. The activity of LDH in the media of nonviable embryos was consistently higher than for viable embryos (P<0.001), with no overlap between the two groups. Thus, the LDH assay was shown to be a reliable test of embryo viability.

Journal Article↗
PubMed1991

Early rupture of a saphenous vein graft.

Early rupture of a saphenous vein graft used for coronary artery surgery has not been previously reported. In a 69-year-old man having a third coronary by-pass procedure, one of the saphenous vein grafts ruptured on the 8th postoperative day. The other vein graft showed marked aneurysm formation at two sites. Histological examination of the ruptured graft revealed that this was due to a bacterial infection within the wall of the vein. Although he survived an emergency operation to control the haemorrhage and replace the ruptured graft, he died some days later of mediastinitis. It appeared that both the rupture of the graft and the ensuing mediastinitis were due to a primary infective process within the saphenous vein used for the graft.

Aged↗
PubMed1991

Prostaglandin regulation of H+ secretion in amphibian epithelia.

The role of prostaglandins in regulating H+ excretion in amphibian epithelia was investigated. The abdominal skin of the southern leopard frog Rana pipiens and the urinary bladder of the toad Bufo marinus were used to measure proton excretion across their mucosal surface. Prostaglandin F2 alpha (PGF2 alpha) produced a dose-dependent inhibition of H+ excretion across the frog skin. Frogs pretreated with ibuprofen (30 mg.kg-1.day-1 for 3 days) showed an enhanced proton excretion similar to that observed when frogs are placed in chronic metabolic acidosis. The number of mitochondria-rich cells, the cells responsible for proton excretion, was also increased in frog skins after chronic metabolic acidosis or ibuprofen treatment. Mezerein and the phorbol ester 4 beta-phorbol 12-myristate 13-acetate (4 beta-PMA), activators of protein kinase C (PCK), decreased H+ excretion in frog skin, whereas the inactive phorbol 4 alpha-PMA was without an effect. The inhibition of proton excretion was similar to that observed with PGF2 alpha and suggested that the effects of PGF2 alpha and activation of PKC were mediated through a common pathway. Frogs pretreated with ibuprofen not only had an enhanced proton excretion rate but also had a decrease in cytosolic PKC activity. In another amphibian tissue, the toad urinary bladder, PGE2 inhibited proton excretion at low doses but enhanced H+ excretion at higher doses. Toads maintained under chronic metabolic acidosis had enhanced proton excretion rates and also had a threefold increase in cellular PGE2 concentration, which was consistent with the observation that PGE2 enhanced proton excretion at high doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphibians↗
PubMed1990

Esophagogastrectomy via left thoracophrenotomy.

Esophagogastrectomy is generally considered to be the treatment of choice for resectable tumors of the esophagus. Although many approaches and techniques have been advocated, since April 1983 we have used a left thoracophrenotomy approach for most lesions of the lower two thirds of the esophagus and gastric cardia. Stapling instruments have been used for mobilization of the stomach and fashioning of the esophagogastric anastomosis. One-hundred fifteen patients undergoing resection of malignant tumors with this technique were retrospectively reviewed. Perioperative mortality was 8.7% (10/115). The rate of anastomotic leakage was 1.7% (2/115), and benign narrowing of the anastomosis requiring dilation developed in 16 patients. The rate of recurrent anastomotic tumor was 4.3%. Eighteen patients had complications, and the mean postoperative hospital stay was 13 days. Survival at 3 years was 22.1%. During the period of study, 22 patients underwent esophageal resection by some other approach; the reasons for this are described. The advantages of the left thoracophrenotomy approach are discussed.

Adult↗
PubMed1990

Adaptive changes of H+ secreting cells in the epidermis of the leopard frog Rana pipiens.

1. Mitochondria-rich (MR) cells in the integument of the southern leopard frog, Rana pipiens, berlandieri, were stained with AgNO3 under a variety of environmental and metabolic treatment conditions known to increase H+ excretion rates across the skin. In this tissue AgNO3 proved to be a good stain for discriminating the MR cell populations from the granular cells. 2. High salinity adapted southern frogs showed no change in the MR cell population. The inability of the MR cell number to significantly increase suggested that the increased H+ excretion rates previously seen in these animals were not due to increased MR cell proliferation. 3. The MR cell population was found to increase in the NaNO3 adapted frogs, demonstrating the contribution of altered extracellular Cl- concentrations on the regulation of MR cell density. 4. Animals that were placed in chronic metabolic acidosis or pre-treated with ibuprofen demonstrated an increased MR cell population. The current observations are consistent with previous findings that these treatment regimes increase H+ excretion, suggesting that one of the cellular adaptive mechanisms responsible for increasing H+ excretion involves increasing the MR cell density. 5. The results further suggest that prostaglandins may play a role in regulating H+ excretion in MR cells, and that either changes in intracellular pH or prostaglandin formation regulates cell proliferation.

Adaptation, Physiological↗
PubMed1990

Combined multiple valve procedures and myocardial revascularisation.

We report a series of 21 consecutive patients undergoing combined multiple valve procedures and myocardial revascularisation between 1978 and 1988. There were 11 females and 10 males with a mean age of 58.5 (+/- 5.7) years. All patients were in NYHA Class 2 or more and 12 patients (57%) had angina. The mean left ventricular segment score was 7.9 (+/- 3.3). Five patients had undergone previous cardiac surgery. In all patients the aetiology of the valvular dysfunction was rheumatic. The first patient in the series was operated on using ischaemic arrest. The remaining 20 operations were performed using cardioplegia (2 crystalloid, 18 blood). A mean of 1.63 grafts per patient were inserted. There were 20 aortic valve replacements, 1 aortic valvotomy, 13 mitral valve replacements, 7 open mitral valvotomies, 1 mitral valve repair, and 1 tricuspid valve replacement. 1 patient had 3 valves replaced. Five deaths occurred in the series; all were due to low cardiac output and occurred prior to discharge from hospital. Follow-up ranged from 7 to 111 months (mean = 46 +/- 33). Three patients developed mitral paravalvular leaks, two of which were successfully repaired at 2 months and 2 years postoperatively. The third was asymptomatic. There were no late deaths and all survivors improved to NYHA Class 1 and had no angina. Early death was associated with increased perfusion time (p less than 0.01), the need for postoperative inotropic support (p less than 0.01) and high blood loss. No preoperative predictors of early death were identified. Multiple valve procedures and myocardial revascularisation carry a significant early mortality but are justified by the satisfactory long-term outcome.

Cardiac Output, Low↗
PubMed1990

Emergency surgery for haematoma-forming aneurysmal haemorrhage.

Patients with intracerebral haematomas (ICH) secondary to aneurysmal bleeds usually have a poor prognosis or die if treated conservatively. Younger patients with rupture of a middle cerebral artery (MCA) aneurysm and temporal haematomas have the potential to return to useful life. They should be assessed separately from other subarachnoid haemorrhage (SAH) patients and considered for emergency surgery. Seven such cases are presented, five made an acceptable recovery. The experience of other units as represented in the literature is considered.

Adult↗
PubMed1990

Serum progesterone and milk production and composition in dairy cows fed two concentrations of nitrate.

Forty clinically normal lactating Holstein cattle from a herd involved in a natural outbreak of chronic nitrate toxicosis were divided into 2 equal groups according to production, stage of lactation, age, and apparent pregnancy state (pregnant or nonpregnant). One group was fed a low-nitrate ration (average of 356 ppm on dry matter basis in concentrate; less than 400 ppm in free-choice hay for 1st 5 wks of study). The 2nd group was fed a high-nitrate (HN) ration (average of 1,600 ppm in protein concentrate-amemded corn silage; 4,000 ppm in free-choice hay for the 8-week study). At the end of the study, the 2 groups were classified according to their starting reproductive status: nonpregnant (open); early pregnant (less than 60 da); midpregnant (average of 105 da). Milk production, milk fat, and milk nitrate concentrations were similar for cows fed both rations. Serum progesterone concentration (SPC) was depressed (P less than 0.05) in cows fed the HN ration. This effect was prominent in open, luteal phase cows, less prominent but still apparent in early pregnant cows, and absent in midpregnant cows. The early reproductive problems of chronic nitrate toxicosis may be due to depression of SPC. A possible mechanism of inhibition of luteal progesterone synthesis by inhibition of cytochrome P-450 is presented.

Animal Feed↗
PubMed1990

Prostaglandin F2 alpha inhibits acidification in H(+)-secreting epithelia.

The role of prostaglandins in the regulation of acidification mechanisms in H(+)-secreting epithelia has been investigated in the abdominal skin of the southern leopard frog, Rana pipiens. Exogenous administration of prostaglandin (PG) E2 and PGF1 alpha (10(-7) M) to the serosal media of paired skins mounted in modified Ussing chambers showed no significant alteration on H+ excretion rates. PGF2 alpha exhibited a dose-dependent inhibition of acidification in both the mucosal and serosal media of animals in normal acid-base states. The ED50 was determined to be 5 X 10(-8) M. Animals placed in an NH4Cl-induced chronic metabolic acidosis demonstrated enhanced H+ excretion from normal which was inhibited by PGF2 alpha (10(-8) M). Frogs treated with ibuprofen (30 mg/kg/day for 3 days) stimulated mucosal acidification to a magnitude similar to the chronic metabolic acidosis animal, and this was inhibited by PGF2 alpha (10(-8) M) during the recovery phase. PGF2 alpha produced effects on both the mucosal proton excretion system and the serosal Na+/H+ exchanger mechanism. PGF2 alpha appears to function in this H(+)-secreting epithelia to maintain a low basal H+ excretion rate and to regulate intracellular pH.

Acidosis↗