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Biomedical subjects

T McGraw

Publications and source records attributed to T McGraw.

At least 19 recordsLinked to original sources
PubMed2004

DT-MRI denoising and neuronal fiber tracking.

Diffusion tensor imaging can provide the fundamental information required for viewing structural connectivity. However, robust and accurate acquisition and processing algorithms are needed to accurately map the nerve connectivity. In this paper, we present a novel algorithm for extracting and visualizing the fiber tracts in the CNS, specifically in the brain. The automatic fiber tract mapping problem will be solved in two phases, namely a data smoothing phase and a fiber tract mapping phase. In the former, smoothing of the diffusion-weighted data (prior to tensor calculation) is achieved via a weighted TV-norm minimization, which strives to smooth while retaining all relevant detail. For the fiber tract mapping, a smooth 3D vector field indicating the dominant anisotropic direction at each spatial location is computed from the smoothed data. Neuronal fibers are then traced by calculating the integral curves of this vector field. Results are expressed using three modes of visualization: (1) Line integral convolution produces an oriented texture which shows fiber pathways in a planar slice of the data. (2) A streamtube map is generated to present a 3D view of fiber tracts. Additional information, such as degree of anisotropy, can be encoded in the tube radius, or by using color. (3) A particle system form of visualization is also presented. This mode of display allows for interactive exploration of fiber connectivity with no additional preprocessing.

Algorithms↗
PubMed1998

Oral midazolam premedication and postoperative behaviour in children.

We examined the effect of oral midazolam premedication on postoperative behaviour. Seventy children (ASA Physical Status 1 and 2; aged 1-10 yrs) were assigned randomly in a prospective, blinded fashion to receive either midazolam 0.5 mg.kg-1 (maximum 10 mg) or placebo. Behaviour assessments were made prior to medication, during induction of anaesthesia and 15 min following arrival to recovery room. The baseline behavioural evaluation scores were not significantly different. The children receiving midazolam cried significantly less during induction (P < or = 0.02). At one week follow-up, eight of 35 subjects receiving placebo had experienced adverse behaviour changes (nightmares, night terrors, food rejection, anxiety, negativism); 19 of 35 of the midazolam group experienced these changes (P < or = 0.02). At four week follow-up, most behaviour changes had resolved. Children given preoperative oral midazolam were less likely to cry and fight while being anaesthetized, and preoperative sedation was associated with increased incidence of adverse postoperative behaviour changes.

Administration, Oral↗
PubMed1994

Preparing children for the operating room: psychological issues.

Children respond psychologically to the prospect of surgery in a variable and age-dependent manner. This review summarizes the psychoanalytic, cognitive, behavioural and family system models of child development. It then reviews studies of hospitalization and anaesthesia in children. These studies suggest that younger children, children previously anaesthetized, and children who experience turbulent anaesthetic inductions are at particular risk for postoperative behavioural disturbances. Strategies of dealing with children and their parents during the perioperative period are discussed. Such strategies include: allowing a parent to be present during induction of anaesthesia, administering sedative premedication, creating a supportive environment, educating children and parents (verbal descriptions, tours, books, videos), and establishing rapport with children and their parents. Age-specific techniques of establishing rapport with children are discussed. If children are less anxious during the perioperative period, not only will they often exhibit less behavioural disturbances postoperatively, but they may face subsequent medical care more easily.

Adolescent↗
PubMed1992

Acute lymphoid changes and ongoing immune activation in SIV infection.

Two features of simian immunodeficiency virus (SIV) infection are emphasized: a transitory decrease in CD4 T cells in the first 2 weeks of infection followed by CD8 T-cell rise, and immune cell activation occurring by 4 weeks and persisting throughout the illness. The short-term changes included a fall in CD4 T cells by 2 weeks with partial recovery by 4 weeks and a CD8 rise that starts at 2 weeks. Subsequent characterization of CD4 T cells showed reduced expression of HLA-DR and CD25 (IL-2 receptor alpha chain) antigens later in SIV infection. Immune cell activation is evident in increased serum levels of neopterin and soluble CD8 antigen. Serum beta 2-microglobulin changes are less marked. Activation of CD8 T cells is reflected by increased percentages of cells expressing HLA-DR antigen. The B-cell numbers increased late in the course of SIV infection. Increased expression of the CD78 (Leu 21) activation phenotype was also seen in some monkeys. The immune activation changes (serum neopterin levels) induced by SIV infection in rhesus macaques appear to be associated with duration of illness, although the number of monkeys observed until death were too few for conclusive data. Thus, immune activation as well as T-cell deficiency may reflect significant immunopathogenic processes in SIV-induced disease.

Animals↗
PubMed1991

Toxoplasma serology, parasitemia and antigenemia in patients at risk for toxoplasmic encephalitis.

In order to further characterize the pathogenesis of Toxoplasma gondii infection in patients with AIDS and AIDS-related complex (ARC), a cohort of HIV- and Toxoplasma-infected individuals were identified and prospectively followed. Four hundred and 10 HIV-infected individuals followed in the San Francisco General Hospital AIDS Clinic were screened for antibodies to Toxoplasma between November 1986 and November 1988. Of the 67 (16%) individuals seropositive for Toxoplasma antibodies, 33 (49%) were followed monthly for a mean duration of 7.5 months. One hundred and 11 follow-up blood samples were obtained in order to determine Toxoplasma serology and the incidence of parasitemia. In general, Toxoplasma immunoglobulin (Ig) G antibodies remained stable over time. Detection of Toxoplasma antigenemia and parasitemia was uniformly negative, including those specimens obtained from two individuals within 45 days of their developing toxoplasmic encephalitis.

Animals↗
PubMed1989

Postexposure immunotherapy of simian immunodeficiency virus (SIV) infected rhesus with an SIV immunogen.

An inactivated whole simian immunodeficiency virus (SIV) immunogen given to healthy, seropositive rhesus macaques 4 months after infection had no effect on the humoral immune response to SIV, the presence of antigenemia, cell-associated viremia, or disease course. Further immunotherapeutic trials in this highly susceptible animal model should be carried out sooner after exposure, before significant loss of CD4 cells has occurred. The SIV infected macaque model will continue to serve an essential role in development and testing of anti-AIDS drugs and immunogens.

Animals↗
PubMed1986

Nucleotide sequence of the small double-stranded RNA segment of bacteriophage phi 6: novel mechanism of natural translational control.

The lipid-containing bacteriophage phi 6 has a genome composed of three segments of double-stranded RNA. We determined the nucleotide sequence of a cDNA copy of the smallest RNA segment. The coding sequences of the four proteins on this segment were identified. These sequences were clustered. Three of the genes had overlapping initiation-termination codons. All noncoding sequences were at the ends of the molecule. The genes of the small double-stranded RNA segment comprised two translational polarity groups. We propose that the translational coupling is the result of an inability of ribosomes to bind independently to two of the four genes. Translation of these genes occurred when ribosomes were delivered to them by translation of an upstream gene.

Bacteriophages↗
PubMed1985

cDNA cloning of portions of the bacteriophage phi 6 genome.

Phage phi 6 has a genome consisting of three pieces of double-stranded RNA. Single-stranded RNA was prepared from phi 6 nucleocapsids by in vitro transcription with the phage RNA polymerase. These transcripts were polyadenylated and used as templates for the preparation of cDNA copies. The resulting DNA was cloned into the PstI restriction nuclease site of plasmid pBR322. Insert-bearing plasmids were annealed to phi 6 RNA to assign the inserts to their proper segments. In this way we identified inserts corresponding to the large, medium, and small segments. Two large overlapping inserts of the small segment constitute the complete complement of the segment as determined by the sequence analysis of the DNA. In vitro coupled transcription and translation showed that the small segment inserts were able to direct the synthesis of the four known genes in the small segment. Two overlapping inserts in the medium segment constitute the entire segment and were shown to direct the in vitro synthesis of two of the three known proteins of the medium segment. Several inserts bearing about one-third the complement of the large segment were also isolated, and one of these directed the synthesis of a peptide that resembles protein P1. Restriction endonuclease maps were prepared for the inserts, and by in vitro synthesis it was possible to refine the genetic map of phi 6. A chimeric plasmid was constructed that combines plasmids pUC8 and RSF1010. Inserts placed on this plasmid were transformed to Pseudomonas phaseolicola, the natural host of phage phi 6. It was possible to refine further the genetic map by complementation of nonsense mutants of phi 6 with the cDNA.

Acetyltransferases↗
PubMed1983

Molecular cloning of bacteriophage PRD1 genomic fragments.

DNA from bacteriophage PRD1 was extracted and partially digested with restriction endonuclease HaeII. The digest was cloned into the PstI site of plasmid pBR322 by homopolymer tailing with guanidylate tails on the plasmid and cytidylate tails on the phage DNA. Insert bearing plasmids were isolated by transforming E. coli strains for tetracycline resistance and screening for ampicillin sensitivity. These strains were then screened for the ability to accomplish marker rescue of nonsense mutants of bacteriophage PRD1. Additional clones were isolated by screening transformants with radioactively labeled probe PRD1 DNA fragments using colony hybridization. A genetic map was generated by the marker rescue capabilities of overlapping cloned inserts. This map allowed the ordering of fourteen of the known PRD1 complementation groups.

Bacteriophages↗
PubMed1983

Establishment of a physical and genetic map for bacteriophage PRD1.

DNA was isolated from the lipid-containing bacteriophage PRD1 and subjected to restriction endonuclease analysis. The total genome size is 14.7 kb. PRD1 DNA was resistant to cutting by fifteen restriction endonucleases with six base specificity. HaeII made thirty-seven cuts in the DNA, MboI made one cut, and MnlI made six cuts. DNA that was not treated with protease yielded two fewer fragments when treated with HaeII. Evidence is presented to indicate that the PRD1 DNA has protein at the ends of the DNA. The thirty-eight HaeII fragments were ordered using the ladder technique of Smith and Birnstiel (1976) on MboI and MnlI fragments of the genome. Clones of HaeII partial digests of PRD1 DNA in pBR322 were analyzed by HaeII digestion and were then assigned to specific regions of the genome by their HaeII fragment composition. A comparison of the marker rescue characteristics of the cloned DNA with the overall restriction fragment map generated a physical map of the genome. Some genes that have not been mapped because of a lack of mutants or leakiness at restrictive conditions were mapped by studying the in vitro protein synthesis of restriction endonuclease fragments.

Bacteriophages↗