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Biomedical subjects

J R O'Brien

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

161 records · Page 9Linked to original sources
PubMed1967

Some interactions between human platelets and glass: von Willebrand's disease compared with normal.

If native or heparinized blood is passed slowly through a column of glass beads at room temperature, the number of platelets removed from the initial drop emerging from the column is less than that removed from the final drop. At 4 degrees C. this difference disappears. If the blood is passed rapidly through such columns at room temperature fewer platelets are removed, but the initial-final difference persists. Von Willebrand's platelets are removed normally at slow speeds; at fast speeds abnormally few platelets are removed. Platelets emerging from all such columns are in aggregates. On adding glass beads to normal heparinized plasma, the platelets at once become more rounded and after about 50 seconds' delay they aggregate: the delay and rate of aggregation can be quantitated. Aggregation occurs best at 20 to 30 degrees C. and is not inhibited by the addition of some enzyme inhibitors. In von Willebrand's disease all these glass-induced aggregation phenomena occur normally and aggregation in response to adenosine diphosphate (ADP), serotonin creatinine sulphate (5-HT), adrenaline, collagen, and glass is also normal.

Blood Platelets↗
PubMed1966

Causes of birth asphyxia and trauma.

Causes of birth asphyxia and trauma were determined in the 208 most severely affected infants of 10,995 consecutive live births; 159 infants had cerebral disturbances, 39 had fractures and palsies, and 10 had fractures or palsies in addition to cerebral disturbances. Most frequent causes of birth asphyxia and trauma were: prolonged labour, midforceps or breech delivery in full-term infants; abruption placentae, difficult breech delivery, and maternal sedation in premature infants; and unattended precipitate deliveries in immature infants. Asphyxia following normal labour and delivery usually occurred in infants with fetal malnutrition.Improved obstetrical management with more frequent use of Cesarean section delivery might have been of value in preventing much of this fetal injury.Asphyxia and trauma due to complications of delivery were twice as frequent on the ward as on the private service. This may have been due in part to a lower Cesarean section rate on the ward service. A monthly review of birth asphyxia and trauma is recommended to help maintain a high standard of obstetrical practice.

Abruptio Placentae↗
PubMed1966

Effect of aggregating agents and their inhibitors on the mean platelet shape.

The ;swirling' seen when platelet-rich plasma is stirred is caused by the average asymmetry of the platelets and a technique for recording the swirling is reported. After the addition of adenosine diphosphate, 5-hydroxytryptamine, thrombin, and collagen, platelets become rounded and more symmetrical immediately before they become sticky. Monoiodo-acetate and adenosine prevent both the change in shape and sticking whereas E.D.T.A. and p-tosyl arginine methylester prevent sticking but the shape still changes. Adrenaline produces sticking but no change in shape. The effects of temperature and E.D.T.A. are also reported. All these findings are discussed and diagrammatic representations of some reactions are tentatively proposed.

Blood Platelets↗
PubMedDate not supplied

Platelet responses to cardiopulmonary bypass. Assessment by a shear stress activation technique.

Platelet responses before and during cardiopulmonary bypass were studied using a shear stress activation technique. Whole blood was passed through a 10 microns micro-porous filter and the percentage of platelets retained was determined. Retention in control subjects (n = 20, age 62 +/- 11 years) was 65.2 +/- 15.1%. Patients with ischaemic heart disease (n = 20, age 61 +/- 9 years) had significantly higher retention at 82.6 +/- 13.2%, p less than 0.001. In valvular heart disease (n = 15, age 57 +/- 14 years) the retention rate was 43.5 +/- 15.4%, lower than both controls and ischaemic heart disease patients (p less than 0.001). In vitro haemodilution had no significant effect on platelet retention. High retention rates were maintained in patients undergoing coronary artery surgery. During valve surgery retention increased before aortic cross-clamp removal (83.5 +/- 13.4%) compared with baseline values (p less than 0.001) and remained high 24 hours postoperatively (79.6 +/- 9.4%). Platelet retention also increased within 20 minutes of thoracotomy without cardiopulmonary bypass (n = 10, age 57 +/- 8 years, 79.3 +/- 11.6% versus 61.6 +/- 10.9% baseline, p less than 0.01) and remained high 24 hours postoperatively. Significant differences in platelet responses, assessed by shear stress activation, were demonstrated between healthy controls and patients with ischaemic and valvular heart disease. Surgery, with or without extracorporeal circulation, caused a significant increase in platelet retention.

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