The Loss of Creatine Phosphokinase (CK) from Intramuscular Injection Sites in Rabbits. A Predictive Tool for Local Toxicity

Abstract The CK activity was measured in muscle tissue taken from the injected area (dorsal longissimus muscle) and the contralateral side of the injection site 72 hours after intramuscular injection into rabbits of 1 ml of different dilutions of propylene glycol orglycerol formal in distilled water or 0.9% saline. The total loss of CK activity from the injection site was calculated as the difference between the CK concentration in the normal muscle tissue and that of the injection site from the same animal. From the results the arbitrary amount of muscle tissue depleted of CK activity was further calculated and compared with the severity of the gross pathological findings. A large necrotic area at the injection site was present in all samples with more than 1 g of muscle tissue depleted of CK activity. Minor and probably acceptable pathological changes were found in samples with less than 1 g of muscle tissue depleted of CK activity. The local damaging effect of drug preparations for intramuscular use can thus be evaluated from the calculated amount of muscle tissue depleted of CK activity.     

Carbonic anhydrase inhibition increases retinal oxygen tension and dilates retinal vessels

Background Carbonic anhydrase inhibitors (CAIs) increase blood flow in the brain and probably also in the optic nerve and retina. Additionally they elevate the oxygen tension in the optic nerve in the pig. We propose that they also raise the oxygen tension in the retina. We studied the oxygen tension in the pig retina and optic nerve before and after dorzolamide injection. Also the retinal vessel diameters during carbonic anhydrase inhibition were studied.Methods A polarographic oxygen electrode was placed transvitreally immediately over the retina or the optic disc in anaesthetised pigs. The oxygen tension was recorded continually and 500 mg dorzolamide was injected intravenously. Retinal vessel diameters were analysed from monochromatic fundus photographs taken before and after injection of dorzolamide.Results Baseline retinal oxygen tension (RPO₂) was 3.34±0.50 kPa (mean ± SD, n=6) and baseline optic nerve oxygen tension (ONPO₂) was 3.63±1.00 kPa. RPO₂ was increased by 0.36±0.11 kPa (n=6, P=0.025) and ONPO₂ by 0.73±0.34 kPa (n=6, P=0.003) 30 min after dorzolamide administration. The retinal arterioles was significantly dilated by 13±7% (n=5, P=0.016) and the retinal venules by 12±8% (n=5, P=0.030) 30 min after injection of dorzolamide.Conclusion Retinal and optic nerve oxygen tension increased with systemic administration of dorzolamide. The retinal vessels dilated, probably causing increased blood flow inducing the observed increase in RPO₂. The increased oxygenation of retina by CAI may offer therapeutic possibilities in ischaemic diseases of the retina and optic nerve.These results were partly presented at the annual meeting of the Association for Research in Vision and Ophthalmology in May 2002     

Genetics of corneal disease for the ocular surface clinician

Advances in the understanding of inherited corneal and external diseases may allow interventions that prevent the substantial vision impairment currently caused by these diseases. The observant clinician may first recognize inherited corneal and external diseases based on clinical examination and a careful family history. Researchers using positional cloning and candidate gene techniques have identified several disease-causing genes. Identification of the genes responsible for inherited corneal and external diseases will lead to more definitive diagnoses and represent the first step in development of effective therapies. Future endeavors are directed toward identifying additional inherited corneal and external diseases, the genes that cause them, and possible gene therapies to improve visual outcomes.     

A multi-centre study of therapeutic efficacy and safety of platelet components treated with amotosalen and ultraviolet A pathogen inactivation stored for 6 or 7 d prior to transfusion

Bacteria in platelet components (PC) may result in transfusion-related sepsis (TRS). Pathogen inactivation of PC with amotosalen (A-PC) can abrogate the risk of TRS and hence facilitate storage to 7 d. A randomized, controlled, double-blinded trial to evaluate the efficacy and safety of A-PC stored for 6-7 d was conducted. Patients were randomized to receive one transfusion of conventional PC (C-PC) or A-PC stored for 6-7 d. The primary endpoint was the 1 h corrected count increment (CCI) with an acceptable inferiority of 30%. Secondary endpoints included 1- and 24-h count increment (CI), 24-h CCI, time to next PC transfusion, red blood cell (RBC) use, bleeding and adverse events. 101 and 100 patients received A-PC or C-PC respectively. The ratio of 1-h CCI (A-PC:C-PC) was 0·87 (95% confidence interval: 0·73, 1·03) demonstrating non-inferiority (P = 0·007), with respective mean 1-h CCIs of 8163 and 9383; mean 1-h CI was not significantly different. Post-transfusion bleeding and RBC use were not significantly different (P = 0·44, P = 0·82 respectively). Median time to the next PC transfusion after study PC was not significantly different between groups: (2·2 vs. 2·3 d, P = 0·72). Storage of A-PCs for 6-7 d had no impact on platelet efficacy.     

A Physiological Model of the Effect of Hypoglycemia on Plasma Potassium

Background

Adrenaline release and excess insulin during hypoglycemia stimulate the uptake of potassium from the bloodstream, causing low plasma potassium (hypokalemia). Hypokalemia has a profound effect on the heart and is associated with an increased risk of malignant cardiac arrhythmias. It is the aim of this study to develop a physiological model of potassium changes during hypoglycemia to better understand the effect of hypoglycemia on plasma potassium.

Method

Potassium counterregulation to hypokalemia was modeled as a linear function dependent on the absolute potassium level. An insulin-induced uptake of potassium was modeled using a negative exponential function, and an adrenaline-induced uptake of potassium was modeled as a linear function. Functional expressions for the three components were found using published data.

Results

The performance of the model was evaluated by simulating plasma potassium from three published studies. Simulations were done using measured levels of adrenaline and insulin. The mean root mean squared error (RMSE) of simulating plasma potassium from the three studies was 0.09 mmol/liter, and the mean normalized RMSE was 14%. The mean difference between nadirs in simulated and measured potassium was 0.12 mmol/liter.

Conclusions

The presented model simulated plasma potassium with good accuracy in a wide range of clinical settings. The limited number of hypoglycemic episodes in the test set necessitates further tests to substantiate the ability of the model to simulate potassium during hypoglycemia. In conclusion, the model is a good first step toward better understanding of changes in plasma potassium during hypoglycemia.     

The role of Ephs, Ephrins, and growth factors in Kaposi sarcoma and implications of EphrinB2 blockade

Kaposi sarcoma (KS) is associated with human herpesvirus (HHV)-8 and is dependent on the induction of vascular endothelial growth factors (VEGFs). VEGF regulates genes that provide arterial or venous identity to endothelial cells, such as the induction of EphrinB2, which phenotypically defines arterial endothelial cells and pericytes, and represses EphB4, which defines venous endothelial cells. We conducted a comprehensive analysis of the Eph receptor tyrosine kinases to determine which members are expressed and therefore contribute to KS pathogenesis. We demonstrated limited Eph/Ephrin expression; notably, the only ligand highly expressed is EphrinB2. We next studied the biologic effects of blocking EphrinB2 using the extracellular domain of EphB4 fused with human serum albumin (sEphB4-HSA). sEphB4-HSA inhibited migration and invasion of the KS cells in vitro in response to various growth factors. Finally, we determined the biologic effects of combining sEphB4-HSA and an antibody to VEGF. sEphB4-HSA was more active than the VEGF antibody, and combination of the 2 had at least additive activity. sEphB4-HSA reduced blood vessel density, pericyte recruitment, vessel perfusion, and increased hypoxia, with an associated increase in VEGF and DLL4 expression. The combination of sEphB4-HSA and VEGF antibody is a rational treatment combination for further investigation.     

Synthesis rates of total liver protein and albumin are both increased in patients with an acute inflammatory response

The general perception that catabolism and inflammation are associated with a high synthesis rate of total liver protein and a low albumin synthesis rate has been challenged in recent years by several studies in man, indicating that the synthesis rate of albumin in response to a catabolic insult is increased rather than decreased. Thus changes in liver protein synthesis rates in conjunction with catabolism and acute inflammation in man need to be characterized better. The aim of the present study was to measure protein synthesis rates of total liver protein and albumin during a state of acute inflammation. Patients (n = 10) undergoing acute laparoscopic cholecystectomy due to acute cholecystitis were investigated. FSRs (fractional synthesis rates) of total liver protein (liver biopsy specimens) and albumin (plasma samples) were investigated as early as possible during the surgical procedure, using a flooding dose of L-[2H5]phenylalanine. The results were compared with a reference group of patients without cholecystitis undergoing elective laparoscopic cholecystectomy (n = 17). FSR of total liver protein was 60% higher (P < 0.001) and the FSR of albumin was 45% higher (P < 0.01) in the cholecystitis patients compared with the control group. In conclusion, the synthesis rates of total liver protein and albumin are both increased in patients with an acute general inflammatory reaction undergoing laparoscopic cholecystectomy.