The range of phenylalanine hydroxylase activity was determined by measuring the conversion of radioactive phenylalanine to tyrosine in liver and kidney of various vertebrates. Rodents (rats, mouse, gerbil, hamster and guinea pig) were found to have the highest liver phenylalanine hydroxylase activity among all animals studied. They are also the only species that possessed a significant kidney phenylalanine hydroxylase activity which was about 25% of that found in the liver of the same animal. The synthetic dimethyl-tetrahydro-pteridine, used as a cofactor for the enzyme assay in most studies, catalyzed non-enzymatic hydroxylation of phenylalanine to tyrosine. Inclusion of boiled-blank and strict control of timing between incubation and product measurement were essential precautions to minimize erroneous results from substrate contamination and non-enzymatic hydroxylation.
Meconium specimens from 18 infants with cystic fibrosis (CF) had strong trypsin inhibitory activity (TIA). The same specimen, which contained increased quantities of undigested proteins, had normal concentrations of immunoreactive trypsin (IRT), but deficient trypsin catalytic activity (TCA). TIA was not detected in any specimen from non-CF infants who had high concentration of proteins comparable to that of CF infants. Subjecting meconium supernatant of CF infants to Sephadex G-75 gel filtration revealed that TCA was greatly enhanced in effluents after fractions were activated by porcine trypsin. TCA was present in the same fractions with IRT. The findings suggested that proteases were secreted into the intestinal lumen in CF infants prior to birth. Deficient proteolysis in the disease might be due to the presence of a trypsin inhibitor.
Serum phenylalanine (phe) concentrations during and following phe challenges and liver phenylalanine hydroxylase (PH) activity were compared in 13 phenylketonuric (PKU) patients. These patients were separated into two groups: eight patients with no detectable PH activity (PH°) and five patients with residual PH activity (PH‐) ranging from 9 to 24% of the activity obtained in 10 non‐PKU subjects. The rise in serum phe concentration during 3 days of oral loading did not differentiate the two groups. However, the difference in serum phe concentration of the PH° and PH‐ groups reached statistical significance at 24 h postloading (p<0.01). We concluded that combined results from multiple measurements during the oral challenge, namely serum phe concentration after termination of loading, serum phe clearance rate, post‐loading phe tolerance index and urinary metabolite excretion, make a better indicator for predicting residual PH activity for the majority of PKU subjects than peak phe concentrations during phe challenge.
Background:
Postoperative (post-op) pain following minimally-invasive cardiac surgery (MICS) may complicate outcomes in patients having surgery performed through a right mini-thoracotomy. Regional anaesthesia, by delivery of local anaesthetic agents to the paravertebral space using a paravertebral catheter (paravertebral block, PVB) may be useful to reduce post-op pain, however, few studies have reported outcomes on patients undergoing MICS with the use of a PVB.
Methods:
Ninety consecutive patients who underwent MICS at Vancouver General Hospital between January 2016 and May 2019 were included in this retrospective study. Data were collected for 53 patients who only had routine pain control (control) and 37 patients who had a PVB (PVB). Primary outcomes were post-op opioid use and hospital length of stay (LOS). Peri-operative (peri-op) death and stroke were secondary outcomes. Statistical analyses were performed using ANOVA single factor and t-tests.
Results:
Patient demographics and operative times were comparable between the two groups. The average total amount of opioid consumed in the PVB group was lower at 155.3 mg morphine equivalents, compared to 193.9 mg in the control group, however, the difference was not statistically significant (p=0.39) (Figure 1). However, the percentage of patients who did NOT receive any oxycodone was almost double in the PVB group (43.2% vs 24.5%, PVB vs control, respectively. p=0.06). The average LOS for the PVB group was significantly lower than the control group (5.4 vs 8.3 days, PVB vs control, respectively. p=0.006) (Figure 1). There were no peri-op deaths or strokes.
Conclusion:
In our experience, addition of a regional anesthetic was associated with ~20% reduction in the amount of opioid narcotic required. Although not statistically significant, this may be a clinically important difference, as the LOS was significantly lower in the PVB group. Outcomes in patients undergoing MICS may be improved with the addition of a PVB.
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