Biomedical subjects

Craig Skinner

Publications and source records attributed to Craig Skinner.

5 recordsLinked to original sources

PubMed2007

The dihydrolipoamide acetyltransferase is a novel metabolic longevity factor and is required for calorie restriction-mediated life span extension.

Calorie restriction (CR) extends life span in a wide variety of species. Recent studies suggest that an increase in mitochondrial metabolism mediates CR-induced life span extension. Here we present evidence that Lat1 (dihydrolipoamide acetyltransferase), the E2 component of the mitochondrial pyruvate dehydrogenase complex, is a novel metabolic longevity factor in the CR pathway. Deleting the LAT1 gene abolishes life span extension induced by CR. Overexpressing Lat1 extends life span, and this life span extension is not further increased by CR. Similar to CR, life span extension by Lat1 overexpression largely requires mitochondrial respiration, indicating that mitochondrial metabolism plays an important role in CR. Interestingly, Lat1 overexpression does not require the Sir2 family to extend life span, suggesting that Lat1 mediates a branch of the CR pathway that functions in parallel to the Sir2 family. Lat1 is also a limiting longevity factor in nondividing cells in that overexpressing Lat1 extends cell survival during prolonged culture at stationary phase. Our studies suggest that Lat1 overexpression extends life span by increasing metabolic fitness of the cell. CR may therefore also extend life span and ameliorate age-associated diseases by increasing metabolic fitness through regulating central metabolic enzymes.

Cell Cycle↗

PubMed2006

A chimeric tetravalent dengue DNA vaccine elicits neutralizing antibody to all four virus serotypes in rhesus macaques.

DNA shuffling and screening technologies were used to produce chimeric DNA constructs expressing antigens that shared epitopes from all four dengue serotypes. Three shuffled constructs (sA, sB and sC) were evaluated in the rhesus macaque model. Constructs sA and sC expressed pre-membrane and envelope genes, whereas construct sB expressed only the ectodomain of envelope protein. Five of six, and four of six animals vaccinated with sA and sC, respectively, developed antibodies that neutralized all 4 dengue serotypes in vitro. Four of six animals vaccinated with construct sB developed neutralizing antibodies against 3 serotypes (den-1, -2 and -3). When challenged with live dengue-1 or dengue-2 virus, partial protection against dengue-1 was observed. These results demonstrate the utility of DNA shuffling as an attractive tool to create tetravalent chimeric dengue DNA vaccine constructs, as well as a need to find ways to improve the immune responses elicited by DNA vaccines in general.

Animals↗

PubMed2005

Tetravalent neutralizing antibody response against four dengue serotypes by a single chimeric dengue envelope antigen.

We employed DNA shuffling and screening technologies to develop a single recombinant dengue envelope (E) antigen capable of inducing neutralizing antibodies against all four antigenically distinct dengue serotypes. By DNA shuffling of codon-optimized dengue 1-4 E genes, we created a panel of novel chimeric clones expressing C-terminal truncated E antigens that combined epitopes from all four dengue serotypes. DNA vaccines encoding these novel chimeras induced multivalent T cell and neutralizing antibody responses against all four dengue serotypes in mice. By contrast, a mixture of four unshuffled, parental DNA vaccines failed to produce tetravalent neutralizing antibodies in mice. The neutralizing antibody titers for some of these antigens could be further improved by extending the sequences to express full-length pre-membrane and envelope proteins. The chimeric antigens also protected mice against a lethal dengue-2 virus challenge. These data demonstrate that DNA shuffling and associated screening can lead to the selection of multi-epitope antigens against closely related dengue virus serotypes and suggest a broad utility for these technologies in optimizing vaccine antigens.

Animals↗

PubMed2005

A basis for electronic cognitive simulation: the heuristic patient.

Although medical trainees are expected to become expert quickly and safely, limited electronic methods are available to rehearse medical cognition for common outpatient and non-emergent inpatient problems. We conducted a series of formal observational sessions designed to determine what interaction requirements are desirable for student rehearsal of medical management by using an electronic patient. The studies utilized both manual and electronic methods for a student to evaluate and manage patients with medical and surgical problems. We observed the following major requirements for an effective simulation experience: the user must have a trial-and-error experience with the patient; the user must have unconstrained access to query and treat the patient; anatomic and physiologic values in the patient must change appropriately in response to user actions; and the user must be able to control certain time-related aspects of the simulation. When these requirements are implemented within a simulation, user-directed management of an electronic patient, by itself, becomes a strong aid to learning by trial- and-error techniques. We conclude that the heuristic patient is a practical and useful concept. Once fully developed, it would allow rehearsal of patient care decision making, intrinsically demonstrating trainee knowledge deficits, and resulting in self-directed learning.

Clinical Clerkship↗

PubMed2004

Amino acid metabolism in the Zucker diabetic fatty rat: effects of insulin resistance and of type 2 diabetes.

We investigated amino acid metabolism in the Zucker diabetic fatty (ZDF Gmi fa/fa) rat during the prediabetic insulin-resistant stage and the frank type 2 diabetic stage. Amino acids were measured in plasma, liver, and skeletal muscle, and the ratios of plasma/liver and plasma/skeletal muscle were calculated. At the insulin-resistant stage, the plasma concentrations of the gluconeogenic amino acids aspartate, serine, glutamine, glycine, and histidine were decreased in the ZDF Gmi fa/fa rats, whereas taurine, alpha-aminoadipic acid, methionine, phenylalanine, tryptophan, and the 3 branched-chain amino acids were significantly increased. At the diabetic stage, a larger number of gluconeogenic amino acids had decreased plasma concentrations. The 3 branched-chain amino acids had elevated plasma concentrations. In the liver and the skeletal muscles, concentrations of many of the gluconeogenic amino acids were lower at both stages, whereas the levels of 1 or all of the branched-chain amino acids were elevated. These changes in amino acid concentrations are similar to changes seen in type 1 diabetes. It is evident that insulin resistance alone is capable of bringing about many of the changes in amino acid metabolism observed in type 2 diabetes.

Amino Acids↗