Relationship between peptide selectivities of human transporters associated with antigen processing and HLA class I molecules

Efficiency of presentation of a peptide epitope by a MHC class I molecule depends on two parameters: its binding to the MHC molecule and its generation by intracellular Ag processing. In contrast to the former parameter, the mechanisms underlying peptide selection in Ag processing are poorly understood. Peptide translocation by the TAP transporter is required for presentation of most epitopes and may modulate peptide supply to MHC class I molecules. To study the role of human TAP for peptide presentation by individual HLA class I molecules, we generated artificial neural networks capable of predicting the affinity of TAP for random sequence 9-mer peptides. Using neural network-based predictions of TAP affinity, we found that peptides eluted from three different HLA class I molecules had higher TAP affinities than control peptides with equal binding affinities for the same HLA class I molecules, suggesting that human TAP may contribute to epitope selection. In simulated TAP binding experiments with 408 HLA class I binding peptides, HLA class I molecules differed significantly with respect to TAP affinities of their ligands. As a result, some class I molecules, especially HLA-B27, may be particularly efficient in presentation of cytosolic peptides with low concentrations, while most class I molecules may predominantly present abundant cytosolic peptides.     

Pro: intraoperative transesophageal echocardiography is a cost-effective strategy for cardiac surgical procedures

TEE is an expensive but useful intraoperative diagnostic strategy for cardiac surgical procedures. It can alter surgical management with tremendous potential benefits to the patient. It also has the potential to avoid unnecessary surgery and reduce the risk of complications such as reoperation, thromboembolism, and stroke. As with any new technology, the indications for its use must be evaluated on the basis of cost, benefits, and efficacy to determine the true value and cost-effectiveness in a particular application. Based on the information presented in this report, it can be concluded that TEE is a cost-effective strategy for valvular and congenital heart repairs. Current data are very convincing that TEE has the potential to be cost-effective in reducing the risk of stroke in selected populations of cardiac surgical patients. As experience with the use of TEE in its various applications increases and the technology itself continues to improve, it will undoubtedly become a more valuable and cost-effective strategy for cardiac surgery.     

Random noise in the spectra of evoked otoacoustic emissions

Adult male rats were given an oral dose of 10 mg/kg aspartame 14C-labelled in the methanol carbon. At timed intervals of up to 6 hours, the radioactivity in plasma and several organs was investigated. Most of the radioactivity found (>98% in plasma, >75% in liver) was bound to protein. Label present in liver, plasma and kidney was in the range of 1-2% of total radioactivity administered per g or mL, changing little with time. Other organs (brown and white adipose tissues, muscle, brain, cornea and retina) contained levels of label in the range of 1/12 to 1/10th of that of liver. In all, the rat retained, 6 hours after administration about 5% of the label, half of it in the liver. The specific radioactivity of tissue protein, RNA and DNA was quite uniform. The protein label was concentrated in amino acids, different from methionine, and largely coincident with the result of protein exposure to labelled formaldehyde. DNA radioactivity was essentially in a single different adduct base, different from the normal bases present in DNA. The nature of the tissue label accumulated was, thus, a direct consequence of formaldehyde binding to tissue structures. The administration of labelled aspartame to a group of cirrhotic rats resulted in comparable label retention by tissue components, which suggests that liver function (or its defect) has little effect on formaldehyde formation from aspartame and binding to biological components. The chronic treatment of a series of rats with 200 mg/kg of non-labelled aspartame during 10 days resulted in the accumulation of even more label when given the radioactive bolus, suggesting that the amount of formaldehyde adducts coming from aspartame in tissue proteins and nucleic acids may be cumulative. It is concluded that aspartame consumption may constitute a hazard because of its contribution to the formation of formaldehyde adducts.     

Methodology of serial ECG classification using an adaptation of the NOVACODE for Q wave myocardial infarction in the Bypass Angioplasty Revascularization Investigation (BARI)

Serial electrocardiographic (ECG) changes are a critical component of the diagnostic algorithm for classification of myocardial ischemic events in large-scale clinical trials. This study describes a computerized serial ECG classification program developed at the St. Louis University Core ECG Laboratory for use in the Bypass Angioplasty Revascularization Investigation (BARI) trial, in which patients with multivessel coronary artery disease were randomized to receive either coronary artery bypass grafting or percutaneous transluminal coronary angioplasty. The St. Louis University program detects and codes serial changes in Q, ST, and T wave items according to Minnesota code (MC) criteria using a modified NOVACODE hierarchical classification system. Measurements using a seven-power calibrated coding loupe are used to generate the MC from a customized software program. Significant minor or major changes are detected by the serial comparison program and referred to a physician coder for verification. Serial comparison coding rules are used to adjust for weaknesses in the standard MC classification system resulting from instability at decision boundaries. Of 4,244 BARI randomized and registry study participants with follow-up ECGs received at the Core ECG Laboratory as of March 1995, a grade 2 MC Q wave progression was noted in 568 participants (13.4%) using MC criteria alone, as compared with 367 (8.6%) after the St. Louis University coding rules were applied. The incidence of grade 1 MC Q wave progressions was 16.4% (697/4,244) versus 6.1% (259/4,244) when the St. Louis University program was applied. Intraobserver variability for grade 2 Q wave progression codes determined from a sample of 812 serial.     

Circadian expression of tryptophan hydroxylase mRNA in the chicken retina

Many aspects of retinal physiology are controlled by a circadian clock located within the eye. This clock controls the rhythmic synthesis of melatonin, which results in elevated levels during the night and low levels during the day. The rate-limiting enzyme in melatonin biosynthesis in retina appears to be tryptophan hydroxylase (TPH)[G.M. Cahill and J.C. Besharse, Circadian regulation of melatonin in the retina of Xenopus laevis: Limitation by serotonin availability, J. Neurochem. 54 (1990) 716-719]. In this report, we found that TPH mRNA is strongly expressed in the photoreceptor layer and the vitread portion of the inner nuclear layer; the message is also expressed, but to a lesser extent, in the ganglion cell layer. The abundance of retinal TPH mRNA exhibits a circadian rhythm which persists in constant light or constant darkness. The phase of the rhythm can be reversed by reversing the light:dark cycle. In parallel experiments we found a similar pattern of expression in the chicken pineal gland. However, whereas a pulse of light at midnight suppressed retinal TPH mRNA by 25%, it did not alter pineal TPH mRNA, suggesting that there are tissue-specific differences in photic regulation of TPH mRNA. In retinas treated with kainic acid to destroy serotonin-containing amacrine and bipolar cells, a high amplitude rhythm of TPH mRNA was observed indicating that melatonin-synthesizing photoreceptors are the primary source of the rhythmic message. These observations provide the first evidence that chick retinal TPH mRNA is under control of a circadian clock.     

Oral health week

This article reports on the Oral Health Week held in December 1994 and focuses on an initiative by the BDA which organised dentists and volunteers from Age Concern in a project to look at oral health for the elderly. It examines the aims and the results of the week and draws some useful conclusions on improving the outcome if a project such as this were attempted again.     

Anticonvulsant and antibiotic prophylaxis in head injury

The evidence for and against the prophylactic use of anticonvulsants and antibiotics in head injury is reviewed. There is a lack of blinded placebo-controlled trials in this area. On balance there is no compelling evidence to support the use of either anticonvulsant or antibiotic prophylaxis in head injury, with the possible exception of antibiotic prophylaxis in compound depressed skull fractures and penetrating brain injuries.