Augmentation of human and rat lenticular glutathione in vitro by prodrugs of gamma-L-glutamyl-L-cysteine

A marked age-related decrease in glutathione (GSH) levels as well as depression of gamma-glutamylcysteine synthetase activity are factors that are believed to render the aged lens more susceptible to oxidative stress and, therefore, to cataractogenesis. Providing gamma-L-glutamyl-L-cysteine, the dipeptide precursor of GSH, would effectively bypass the compromised first step in its biosynthesis and should protect the lens from GSH depletion. Accordingly, some bioreversible sulfhydryl-, amino-, and C-terminal carboxyl-protected prodrug forms of this dipeptide were prepared. Sulfhydryl protection was in the form of an acetyl thioester, while the carboxyl group was protected as the ethyl ester. These prodrugs were evaluated for their GSH-enhancing activity in cultured human and rat lenses in vitro using an assay that measured the incorporation of [14C]glycine into lens GSH. Ethyl S-acetyl-gamma-L-glutamyl-L-cysteinate (2) raised GSH levels in human lenses by 25% and in rat lenses by >150%. These data suggest that 2 may have potential as an anticataract agent since ethyl gamma-L-glutamyl-L-cysteinate (1a), the des-S-acetyl analog of 2, had been shown (by others) to protect against experimental rodent cataracts. GSH augmentation by 1a was 2% in human lenses and 25% in rat lenses, considerably less than that shown by 2.     

Tactile evaluation of the response to double burst stimulation decreases, but does not eliminate, the problem of postoperative residual paralysis

BACKGROUND: Routine perioperative monitoring with accelero-myography might prevent residual block, whereas routine tactile evaluation of the response to train-of-four (TOF) nerve stimulation does not. The purpose of this prospective, randomised and blinded study was to evaluate the effect of manual evaluation of the response to double burst stimulation (DBS3.3) upon the incidence of residual block. METHODS: Sixty adult patients scheduled for elective abdominal surgery were included in the study. Pancuronium 0.08 to 0.1 mg kg-1 was given for relaxation and tracheal intubation. For maintenance of neuromuscular block, pancuronium 1-2 mg was administered. The patients were randomly allocated into two groups. In group DBS (double burst stimulation) the degree of block during anaesthesia was assessed by manual evaluation of the response to TOF nerve stimulation. During reversal, when no fade was detectable in the TOF response, the stimulation pattern was changed to DBS3.3. The trachea was extubated when the anaesthetist judged the neuromuscular function to have recovered adequately and no fade in the DBS3.3 response could be felt. In group CC (clinical criteria) patients were managed without the use of a nerve stimulator, and the level of neuromuscular block and reversal were evaluated solely on the basis of clinical criteria. In both groups, the TOF ratio was measured by mechanomyography immediately after tracheal extubation. Also, the ability to sustain head lift for 5 s, to protrude the tongue, to open the eyes, and to lift one arm to the opposite shoulder were tested. RESULTS: The TOF ratio, as measured immediately after tracheal extubation, was significantly lower in group CC than in group DBS (means: 0.68 and 0.78, respectively), and the incidence of residual neuromuscular block defined as a TOF ratio < 0.7 was significantly higher in group CC than in group DBS (57 and 24%, respectively). The time from the first TOF measurement until the TOF ratio reached 0.8 was significantly longer in group CC than in group DBs (means: 11.5 and 6.2 min, respectively). No significant differences between the two groups of patients were found in duration of anaesthesia, in times from end of surgery to injection of neostigmine, tracheal extubation or TOF ratio 0.8, in dose of pancuronium, or in any other postoperative variable. CONCLUSION: Routine perioperative manual evaluation of the responses to TOF and DBS3.3 decreased the incidence and the degree of residual block following the use of pancuronium. It did not, however, exclude clinically significant residual paralysis, nor did it influence the amount of pancuronium used during the operation, the duration of anaesthesia or the time from end of surgery to tracheal extubation or to sufficient recovery of neuromuscular function (TOF = 0.8).     

Striatal dopamine dynamics are altered following an intranigral infusion of iron in adult rats

Exercise has a noted effect on skin blood flow and temperature. We aimed to characterize the normal skin temperature response to exercise by thermographic imaging. A study was conducted on ten healthy and active subjects (age=25.8+/-0.7 years) who were exposed to graded exercise for determination of maximal oxygen consumption (VO2 max), and subsequently to constant loads corresponding to 50%, 70%, and 90% of VO2 max. The skin temperature response during 20 min of constant load exercise is characterized by an initial descending limb, an ascending limb and a quasi-steady-state period. For 50% VO2 max, the temperature decrease rate was - 0.0075+/-0.001 degrees C/s during a time interval of 390+/-47 s and the temperature increase rate was 0.0055+/-0.0031 degrees C/s during a time interval of 484+/-99 s. The level of load did not influence the temperature decrease and increase rates. In contrast, during graded load exercise, a continuous temperature decrease of -0.0049+/-0.0032 degrees C/s was observed throughout the test. In summary, the thermographic skin response to exercise is characterized by a specific pattern which reflects the dynamic balance between hemodynamic and thermoregulatory processes.     

Exposure effects on music preference and recognition

In three experiments, the effects of exposure to melodies on their subsequent liking and recognition were explored. In each experiment, the subjects first listened to a set of familiar and unfamiliar melodies in a study phase. In the subsequent test phase, the melodies were repeated, along with a set of distractors matched in familiarity. Half the subjects were required to rate their liking of each melody, and half had to identify the melodies they had heard earlier in the study phase. Repetition of the studied melodies was found to increase liking of the unfamiliar melodies in the affect task and to be best for detection of familiar melodies in the recognition task (Experiments 1, 2, and 3). These memory effects were found to fade at different time delays between study and test in the affect and recognition tasks, with the latter leading to the most persistent effects (Experiment 2). Both study-to-test changes in melody timbre and manipulation of study tasks had a marked impact on recognition and little influence on liking judgments (Experiment 3). Thus, all manipulated variables were found to dissociate the memory effects in the two tasks. The results are consistent with the view that memory effects in the affect and recognition tasks pertain to the implicit and explicit forms of memory, respectively. Part of the results are, however, at variance with the literature on implicit and explicit memory in the auditory domain. Attribution of these differences to the use of musical material is discussed.     

Structural features of thyroid hormone response elements that increase susceptibility to inhibition by an RTH mutant thyroid hormone receptor

The chicken lysozyme silencer F2 (F2) thyroid hormone response element (TRE) contains an unusual everted palindromic arrangement, has a high affinity for thyroid hormone receptor (TR) homodimers, and is especially sensitive to dominant negative inhibition by, the T3 resistance (RTH) mutant TR beta P453H. We used various TREs and TR mutations to determine the mechanisms for this sensitivity. Changing the F2 orientation from an everted palindrome to a direct repeat with a 4-bp gap (DR+4) (F2-DR) decreased the sensitivity to inhibition at high T3 concentrations, while a loss of this sensitivity occurred with a palindromic arrangement of these same half-sites. F2 contains the dinucleotide TG 5' to each consensus half-site conforming to the optimal TR-binding octamer, YRRGGTCA. A T to A change in position 1 of both F2 half-sites markedly reduced T3-induction, yet only slightly reduced TR homodimer or TR-retinoid X receptor (RXR) heterodimer binding. The TR beta ninth heptad mutation, L428R, prevents TR heterodimerization with RXR and eliminates the inhibitory effect of the P453H mutant TR on the F2-DR, but not the F2 element. Structural features of a TRE that favor strong TR binding of both TR homodimers and TR-RXR heterodimers containing the mutant TR, such as the everted palindromic conformation or the optimal TR-binding consensus octamer, enhance the sensitivity of a TRE to inhibition by the mutant TR. Thus, both half-site orientation and sequence contribute to the sensitivity of a given TRE to dominant negative inhibition by a mutant TR.     

Molecular typing shows a high level of HLA class I incompatibility in serologically well matched donor/patient pairs: implications for unrelated bone marrow donor selection

In comparison with HLA-matched sibling bone marrow transplants, unrelated donor transplants are associated with increased graft-versus-host disease and graft failure. This is likely in part due to HLA incompatibilities not identified by current matching strategies. High resolution DNA-based typing methods for HLA class II loci have improved donor selection and treatment outcome in unrelated donor bone marrow transplantation. By using DNA-based typing methods for HLA-A and -B on a cohort of 100 potential bone marrow donor/patient pairs, we find that serological typing for HLA class I is limited in its ability to identify incompatibilities in unrelated pairs. Furthermore, the incompatibilities identified are associated with the presence at high frequency of alloreactive cytotoxic T-lymphocyte precursors. DNA typing also indicates that HLA-C mismatches are common in HLA-A and -B serologically matched pairs. Such mismatches appear to be significantly less immunogenic with respect to cytotoxic T-lymphocyte recognition, but are expected to influence natural killer cell activity. Thus, improved resolution of HLA class I shows many previously undisclosed mismatches that appear to be immunologically functional. Use of high resolution typing methods in routine matching is expected to improve unrelated donor selection and transplant outcome.     

New endeavors and innovative programs in end of life care

This paper presents summaries of initiatives and demonstration programs developed by professional and patient care organizations to improve care at the end of life.     

Prognostic value of myocardial lactate dehydrogenase subunit ratio in heart transplant recipients

BACKGROUND: Allograft coronary artery disease (CAD) is a major long-term complication in heart transplant recipients. Unfortunately, methods for early estimation of the likelihood of development of the disease are not currently available. Lactate dehydrogenase (LDH) is composed of heart and muscle subunits. The prevalence of these subunits in LDH isoenzymes (LDH1 through LDH5) is an accurate indicator of myocardial metabolism and allows indirect estimation of oxygen availability to cardiocytes. This study investigated the prognostic value of myocardial LDH composition for the occurrence of morbid events in patients with severe allograft CAD. METHODS: Eighty-eight heart transplant recipients were followed up for a median of 4.3 years. The isoenzymes of LDH and the ratio of the heart and muscle subunits (H/M) were determined in 526 endomyocardial biopsy samples. RESULTS: Eleven patients (12%) died from allograft CAD during follow-up. They had significantly lower H/M ratios compared with event-free patients, with clear differences as early as 6 months after operation. A threshold value of 2.75 was derived from receiver operating characteristic curve analysis. Patients showing H/M values < or =2.75 had a significantly higher mortality rate than did those with higher values (p=.0003). Importantly, the H/M ratio emerged as the most powerful independent prognostic factor of death by allograft CAD (p=.001) in a multivariate model. CONCLUSIONS: Poor myocardial aerobic metabolism estimated through low H/M values was highly predictive of cardiac death resulting from severe allograft CAD. Analysis of LDH isoenzyme profile in routine endomyocardial biopsies might be of clinical value.