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Biomedical subjects

P Carter

Publications and source records attributed to P Carter.

At least 163 records · Page 9Linked to original sources
PubMed1976

Kinetics of the IgM and IgG immunological response to sheep erythrocytes and bluetongue virus in mice.

The IgM and IgG response of mice to sheep erythrocytes (SRBC) and bluetongue virus (BTV) was determined by means of haemolytic plaque assays. Maximum primary IgM response to SRBC occurred after 4 days but declined rapidly to 4% of the maximum by Day 9. A lag period of about 2 days was observed in the appearance of IgG haemolytic plaque-forming cells (PFC) but they reached a maximum after 6-9 days. Secondary immunization resulted in the stimulation particularly of IgG PFC and from Day 6 onwards IgG predominated in the immunological response. The IgM response to BTV was remarkably similar to that observed when SRBC were used as antigen. IgG PFC, however, appeared within a day of the IgM, reaching a peak on Days 4-5. From then onwards, IgG PFC predominated in the response. At BTV concentrations of up to 10 mug per mouse, the virulent strain of BTV type 3 produced the weakest response. At higher antigen concentrations there was very little difference in the response to the serotypes tested, although the virulent strain of BTV type 4 tended to produce the strongest response.

Animals↗
PubMed1975

Arterial hypertension and neurofibromatosis: renal artery stenosis and coarctation of abdominal aorta.

A 10-year-old girl had arterial hypertension, generalized neurofibromatosis, coarctation of the abdominal aorta and multiple stenoses at the origin of each renal artery. After resection of the stenotic areas and reimplantation of the renal arteries in the aorta, her arterial pressure decreased substantially. However, hypertension recurred and radiologic follow-up 4 1/2 years later showed distinct progression of the coarctation and renewed stenosis of all renal arteries at their origin. The stenotic areas showed eccentric intimal proliferation, frequently bulging into the lumen, with small nodular aggregates of smooth muscle cells and proliferation of fibrous tissue containing spindle-shaped nuclei in a palisading pattern. Hypertension associated with neurofibromatotic vascular disease has been described in 47 other patients in the literature. These patients have been young (mean age, 14 years) and predominantly male. In contrast to fibromuscular dysplasia, in which 95% of all stenoses are found in the distal two thirds of the renal arteries, in vascular neurofibromatosis more than 50% of the stenoses are found at the origin.

Adolescent↗
PubMedDate not supplied

Engineering of tyrosyl tRNA synthetase.

The gene encoding the enzyme tyrosyl tRNA synthetase from Bacillus stearothermophilus has been systematically altered using synthetic oligonucleotides as mutagens. The construction of mutations has been facilitated by using strains of bacteria defective in mismatch repair and also by utilising a genetic marker in the M13 strain (such as an amber mutation, or an EcoK or EcoB site) which allows selection for the progeny of M13 replication derived from the minus (mutagenized) strand. Several mutations have been constructed in the ATP binding site to elucidate the roles of individual residues in catalysis and substrate binding and it has even been possible to construct mutants which have improved affinity for ATP. Mutations in various surface lysine and arginine residues have allowed us to identify potential contacts with the tRNA, and indicate that a cluster of basic residues close to the C-terminus of the enzyme probably makes important interactions with the tRNA.

Amino Acyl-tRNA Synthetases↗
PubMedDate not supplied

A large increase in enzyme-substrate affinity by protein engineering.

A single point mutation has been engineered in the tyrosyl-tRNA synthetase that improves its affinity (KM) for its substrate ATP by a factor of 100. In the crystal structure of the tyrosyl tRNA synthetase (of Bacillus stearothermophilus), the side-chain hydroxyl of Thr 51 appears to make a weak hydrogen bond with the AMP moiety of the substrate intermediate, tyrosyl adenylate. In the absence of substrate, however, the hydroxyl group should make a strong hydrogen bond with water which would favour dissociation of the enzyme-substrate complex. We have used oligodeoxynucleotide-directed mutagenesis to construct two point mutants at this site: one to remove the hydroxyl group (Thr 51 leads to Ala 51) and the other, in addition, to distort the local polypeptide backbone (Thr 51 leads to Pro 51). We report here that both mutants have increased activity (kcat/KM for ATP) but one mutant (Pro 51) shows a massive 25-fold increase due mainly to a lowered KM for ATP. This demonstrates dramatically the potential of in vitro mutagenesis for improving the affinity of an enzyme for its substrate.

Amino Acyl-tRNA Synthetases↗
PubMedDate not supplied

Hydrogen bonding and biological specificity analysed by protein engineering.

The role of complementary hydrogen bonding as a determinant of biological specificity has been examined by protein engineering of the tyrosyl-tRNA synthetase. Deletion of a side chain between enzyme and substrate to leave an unpaired, uncharged hydrogen-bond donor or acceptor weakens binding energy by only 0.5-1.5 kcal mol-1. But the presence of an unpaired and charged donor or acceptor weakens binding by a further approximately 3 kcal mol-1.

Amino Acyl-tRNA Synthetases↗
PubMedDate not supplied

Axillary versus rectal temperatures in preterm infants under radiant warmers.

Twenty-five preterm neonates were studied to determine whether monitoring of body temperature may be accomplished by taking axillary instead of rectal temperatures. Both axillary and rectal temperatures were taken simultaneously 12 times over a two-day period. Temperatures were recorded at three, five, eight, and ten minutes. The researchers concluded that an axillary measurement of temperature may be adequately substituted for rectal measurement of temperature.

Axilla↗