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Biomedical subjects

L C John

Publications and source records attributed to L C John.

At least 19 recordsLinked to original sources
PubMed2001

Assessment of murine lung tumour development: a comparison of two techniques.

Two techniques (surface photographic analysis [SPA] and microscopic tumour analysis [MTA]) are described for assessing the stage of tumour development induced by intraperitoneal 4-(methyl nitrosamino)- 1-(3 pyridyl)-1-butanone in syngeneic A/J mice. Parameters used to assess the number and size of tumours were surface tumour count (STC), surface tumour area (STA). and relative tumour surface area (RTSA)--all using SPA; and mean tumour count (MTC), mean tumour area, and relative tumour area (RTA)--all using MTA. In a study examining the possible effects of Millipore chamber implantation on lung tumours, the stage of tumour development was assessed in 239 mice using both SPA and MTA. Statistically significant correlations (Spearman-Rank) were apparent between the derived parameters: STC vs. MTC (r = 0.6, P <0.0001); STA vs. mean tumour area (r = 0.5, P <0.0001); RTSA vs. RTA (r = 0.4, P <0.0001). Therefore, it is concluded that SPA--the simpler technique--is an appropriate method for assessing the stage of tumour development in this model.

Animals↗
PubMed1999

An unusual cause of unilateral facial pain.

Cardiac pain that is referred to the face is a common symptom in patients with angina pectoris, but unilateral facial pain referred from a non-ischaemic cardiac source is rare. We report a case of unilateral facial pain that occurred in relation to a large pericardial effusion and which resolved on drainage of the effusion.

Aged↗
PubMed1996

Surgical research.

Explore the source record for details and available documents.

General Surgery↗
PubMed1996

Peri-infarct pursestring for repair of subacute cardiac rupture.

A 55-year-old woman presented with cardiac tamponade after an inferior myocardial infarction. At surgical exploration there was an extensive area of hematoma associated with cardiac rupture. Rather than infarctectomy and ventricular repair an alternative approach was taken. The patient was successfully managed by the placement of a peri-infarct pursestring together with a superficial stitch closing the exit point of the cardiac rupture.

Female↗
PubMed1996

Subcutaneously implanted tumour: an hypothesized novel approach to individualized immunotherapy for lung carcinoma.

A novel approach to immunotherapy for the treatment of lung carcinoma is hypothesized. If a lung tumour removed at operation is implanted subcutaneously within a Millipore chamber in that patient, then a local immune response may be induced. It is suggested that this subcutaneously induced immune response could improve the prognosis of the underlying tumour either of its own accord or by its use as an adoptive immunotherapy. Spread of the tumour locally would be prevented by containment within the Millipore chamber. The hypothesis has been supported by experimental observations from a pilot study.

Animals↗
PubMed1996

Mismatch of aortotomy and saphenous vein graft size: a simple solution.

Bleeding may occur at the proximal anastomosis of an aortocoronary bypass graft due to the aortotomy being larger than the vein graft diameter. This results in the wall of the vein being under tension, so that the anastomotic suture or further stitches may cut through. A partial thickness suture placed as a pursestring around the aortotomy may alleviate this situation, resulting in a smaller aortotomy with reduced vein wall tension, improved hemostasis, and a more satisfactory anastomotic vein contour.

Anastomosis, Surgical↗
PubMed1996

Current methods to reduce the adverse haematological consequences of cardiopulmonary bypass.

Bleeding remains a significant cause of morbidity after cardiac surgery and results in a major demand on blood transfusion capacity. The aetiology is multifactorial, but platelet dysfunction is the most important cause. Because of the potential risks of heterologous blood transfusion, a number of techniques have been developed to reduce its need. These can broadly be divided into three categories. First, modification of bypass methods and the use of agents such as aprotinin can reduce blood loss. Second, more use can be made of the patient's own blood through predonation of autologous blood or blood conservation techniques. Finally, transfusion policy can be modified so that a lower postoperative haemoglobin level is accepted. However, a method with which to preoperatively predict those patients who will bleed significantly remains elusive.

Aprotinin↗
PubMed1995

Potential use of the intercostal artery as an in situ graft: a cadaveric study.

The third to eighth intercostal arteries (ICAs) were bilaterally dissected in 10 cadavers to assess their length and possible routes to coronary arteries if used as in situ grafts. The mean lengths for the intercostal arteries harvested were 27.0 +/- 2.9 cm on the left and 27.4 +/- 3.2 cm on the right. The shortest anatomic route to the coronary arteries of the in situ ICAs harvested was medial to the lung and either superior to or inferior to the hilum. By using either the superior or inferior routes in situ ICAs were long enough to reach the major coronary artery territories in all cadavers. The most suitable ICAs for grafting the coronary arteries and the shortest routes were as follows: left anterior descending--left fifth ICA by inferior route; circumflex coronary artery-left fifth ICA by inferior route; and right coronary artery-right seventh ICA by inferior route. We conclude that it is anatomically feasible to use the intercostal artery as an in situ graft in coronary artery operation.

Aged↗
PubMed1995

Retrograde pulmonary embolectomy by flushing of the pulmonary veins.

A glue embolization of a cerebral arteriovenous malformation in a 3-year-old boy was complicated by a massive pulmonary embolus due to glue entering the venous circulation. Attempted pulmonary embolectomy via pulmonary arteriotomy after emergency cardiopulmonary bypass was unsuccessful. However, retrograde flushing of the pulmonary veins with cold saline solution produced large quantities of embolus through the pulmonary arteriotomy. Bypass was discontinued uneventfully with no residual cardiopulmonary problems.

Cardiopulmonary Bypass↗
PubMed1993

Reduction of heparin binding to and inhibition of platelets by aprotinin.

The direct effect of aprotinin on in vitro platelet function was assessed by hemostatometry (n = 10). No significant enhancement was demonstrated. However, aprotinin reduced platelet inhibition secondary to heparin. Hemostatometry demonstrated a significant preservation of in vitro platelet function (n = 25) (p = 0.04), which was particularly marked (p = 0.003) in the subgroup (n = 7) demonstrating a severe inhibition of platelet function with heparin. Aprotinin significantly reduced the binding of tritium-labeled heparin to both nonactivated (n = 25) (p = 0.004) and activated platelets (n = 25) (p < 0.0001). We conclude that interference with heparin-induced inhibition of platelet function by aprotinin may be one of its hemostatic actions in cardiac surgery. This effect is probably secondary to aprotinin reducing binding of heparin to platelets.

Adenosine Diphosphate↗
PubMed1993

Different anticoagulants and platelet reactivity in cardiac surgical patients.

A technique for assessing platelet reactivity to shear stress from nonanticoagulated blood samples was employed to compare the relative effects of an unfractionated heparin, a low-molecular-weight heparin, and hirudin. The in vitro platelet effect of unfractionated heparin (5 U/mL) was measured in 290, the effect of a low-molecular-weight heparin (1 anti-Xa unit/mL) in 74, and the effect of hirudin (8 micrograms/mL) in 50 cardiac surgical patients. The relative proportions of patients exhibiting an enhanced platelet reactivity, a mild to moderate inhibition, and a severe inhibition were, respectively: 8.6%, 58.6%, and 32.8% for unfractionated heparin; 22%, 66%, and 12% for the low-molecular-weight heparin; and 6%, 66%, and 28% for hirudin. At the concentrations examined, a significantly greater proportion (p < 0.01) of the patients exhibited enhanced platelet reactivity and a significantly smaller proportion (p < 0.01) showed severely inhibited platelet reactivity associated with the low-molecular-weight heparin versus the unfractionated heparin, whereas there was no significant difference between the patients treated with hirudin and unfractionated heparin. Although the relevance of this study is limited because the clinically appropriate concentration of the alternative anticoagulants and comparative doses are unknown, it can be inferred that low-molecular-weight heparin may reduce the blood loss associated with cardiopulmonary bypass.

Anticoagulants↗
PubMed1993

Coronary artery anastomotic contour--a method for individual surgeons to assess their suture techniques.

A method is described whereby individual surgeons may monitor their coronary graft suturing techniques. The coronary artery anastomotic contour is measured quantitatively in corrosion resin cast models made of anastomoses between long saphenous vein and the left anterior descending coronary artery of a pig's heart. The relevant parameter assessing the contour is the mean anastomotic narrowing expressed as a percent (MAN%). To provide an example of the potential of the method, a single surgeon compared a continuous suture technique (n = 30) with an interrupted one (n = 30) using corrosion resin models. There was significantly less (P < 0.05) narrowing of the anastomotic contour with the interrupted technique (mean MAN% = 0.3 +/- 2.9) than with the continuous (mean MAN% = 10.5 +/- 3).

Anastomosis, Surgical↗
PubMed1993

Inhibition of platelet function by heparin. An etiologic factor in postbypass hemorrhage.

The effect of heparin (5 U/ml) on platelet function was examined by hemostatometry in vitro. A wide individual variation of this effect was found in 290 patients who underwent cardiac operations: 8.6% (25) experienced a proaggregatory effect, 58.6% (170) experienced a mild to moderate inhibition of platelet function, and 32.8% (95) experienced a severe inhibition. No significant difference was found among patient characteristics, including antiplatelet medication, in these three subgroups. In vitro measurements correlated significantly with ex vivo measurements, that is, from blood taken after heparinization (p < 0.0001; r = 0.97, n = 15). In 111 patients who underwent cardiac surgical intervention, a significant correlation (p < 0.0001; 0.4 < r < 0.52) was found between preoperative measurements of the degree of inhibition of platelet function by heparin and the total postoperative blood loss after 4, 12, and 18 hours. Similarly, there was a significant difference (p < 0.0001) in the total blood loss at 4, 12, and 18 hours between the subgroups that showed, in vitro, a mild to moderate inhibition of platelet function preoperatively compared with a severe inhibition (713 +/- 43 ml versus 1172 +/- 76 ml at 18 hours). It is concluded that platelet inhibition as a result of heparin varies among patients and appears to be a previously unrecognized etiologic factor in bleeding after cardiopulmonary bypass.

Blood Platelets↗