Monoclonal antibodies to human platelet glycoprotein IIb beta that initiate distinct platelet responses

Hybridomas secreting monoclonal antibodies (MoAbs) to human platelet membrane glycoprotein IIb (GPIIb) were prepared by fusing cells of a mouse myeloma line to spleen cells from a BALB/c mouse immunized with purified GPIIb. Six of the hybridomas secreted MoAbs that recognized epitopes on the 23,000-dalton, disulfide-linked subunit of GPIIb, GPIIb beta. All six of these MoAbs agglutinated platelets in the absence of calcium. The agglutination titers of three of the MoAbs, however, were enhanced between 2 and 6 log2 dilutions when titrated in the presence of mmol/L of calcium. The enhancement in titer was the result of MoAb- induced platelet activation followed by platelet aggregation, a reaction that could also be initiated by the monovalent Fab fragments prepared from one of the MoAbs. The MoAbs did not significantly agglutinate platelets from patients with Glanzmann's thrombasthenia, confirming biochemical evidence that there is a paucity of GPIIb beta in the membranes of these cells. Our results show that MoAbs to epitopes on GPIIb beta initiate distinct platelet responses; therefore, they should be useful for studying the ways in which regions of surface glycoproteins are involved in platelet-platelet interactions. In addition, these reagents may prove of value in diagnosing and typing patients with Glanzmann's thrombasthenia.     

Work in progress: the application of temporal filtering techniques to hybrid subtraction in digital subtraction angiography

Temporal filtering methods were applied to iodine signal-to-noise ratio (SNR) restoration in intravenous hybrid subtraction digital subtraction angiography (DSA). For equal detected exposure rates hybrid subtraction had approximately 35% of the SNR of temporal subtraction. When matched filtering was applied to a DSA run, the filtered result had approximately two times higher SNR than the peak contrast image in the run. Thus, when matched filtering techniques were applied to the hybrid image sequence, the resultant SNR increased to about 70% of that of temporal subtraction. With an additional factor-of-two increase in exposure rate for the hybrid run, SNR parity with temporal subtraction could be achieved. This compared with a factor-of-nine increase in exposure that would be required if no filtering were performed. Experimental hybrid matched filter results, generated with intravenous canine DSA studies, supported the predictions in SNR performance.     

SUXAMETHONIUM-INDUCED HYPERKALAEMIA IN PATIENTS WITH SEVERE INTRA-ABDOMINAL INFECTIONS

In nine patients, undergoing repeat operations because of severeintra-abdominal infection developing after major abdominal surgery,serum potassium concentrations were monitored during inductionof anaesthesia. Four patients showed an increase of serum potassiumranging from 2.5 to 3.1 mmol/ litre above baseline values within3–6 min after suxamethonium 100 mg i.v. In five patientsthere was no change. The four patients demonstrating an increasehad suffered from pyrexia and leucocyt-osis for at least 2 weeks.The other five had signs of infection for no more than 9 days.It is concluded that patients with signs of severe intra-abdominalinfection lasting longer than 1 week represent an additionalcategory susceptible to suxamethonium-induced hyperkalaemia.They should receive only non-depolarizing muscle relaxants.When the use of suxamethonium is unavoidable, the injectionof a non-depolarizing muscle relaxant before the administrationof suxamethonium is recommended.     

MALIGNANT HYPERTHERMIA IN BELGIAN LANDRACE PIGS RESTED OR EXCERCISED BEFORE EXPOSURE TO HALOTHANE

Thirteen of 31 Belgian Landrace pigs developed malignant hyperthermia(MH) after breathing halothane. A short period of exercise 1h before the administration of the triggering agent increasedthe incidence of the syndrome to 100% in eight similar pigs.Clinical symptoms were more marked and developed more rapidlyin the exercised pigs. All the reacting pigs became typicallyacidotic, developed rigor and died. Serum Na⁺, K+, Ca2⁺, c.p.k.,l.d.h. and protein concentrations were increased to a variableextent during the reaction and there was an increase in p.c.v.also. No hyper-glycaemia was detected in pigs which were restedbefore receiving halothane. Four of the eight exercised pigsbecame markedly hyperglycaemic and plasma noradrenaline increasedto higher values. Phosphocreatine and ATP decreased to low valuesand lactate increased in the muscles of all pigs which reacted.At the time of death, muscle glycogen had decreased significantlyin the rested, but not in the exercised, MH pigs. ^*Present address: ARC Meat Research Institute, Langford, BristolBS18 7DY.     

Frostbite: experimental assessment of tissue damage using Tc-99m pyrophosphate. Work in progress

We designed an experimental model using a new method of freezing to study the pathogenesis and treatment of frostbite. Frostbite was simulated in a manner that closely resembles that which occurs in a natural environment. We used a radionuclide imaging technique to monitor the evolution and extent of tissue damage relative to temperature, rate of freezing, and controlled rewarming. Characteristic sequential changes were demonstrated on sequential nuclear scans. Nonperfusion, followed by perfusion, and finally again by nonperfusion occurred in all areas in which necrosis developed. The reappearance of nonperfusion corresponded to vascular injury and thrombosis evidenced at pathologic examination. We determined that lack of tissue perfusion corresponded to tissue injury. We believe that our experimental model provides an effective means of evaluating potential therapeutic regimens.