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Biomedical subjects

D Grant

Publications and source records attributed to D Grant.

At least 55 records · Page 3Linked to original sources
PubMed1999

Intestinal transplantation: 1997 report of the international registry. Intestinal Transplant Registry.

BACKGROUND: Small bowel transplantation is an evolving procedure. We reviewed the world experience since 1985 to determine the current status of this procedure. METHODS: All of the known intestinal transplant programs were invited to contribute to an international registry using a standardized report form. RESULTS: Thirty-three intestinal transplant programs provided data on 273 transplants in 260 patients who were transplanted on or before February 28, 1997. The number of procedures per year has increased at a linear rate since 1990, with 58 transplants performed in 1996. Two-thirds of the recipients were children or teenagers. The short gut syndrome was the most common indication for transplantation. The types of transplants included the small bowel with or without the colon (41%); the intestine and liver (48%); and multivisceral grafts (11%). The 1-year graft/patient survival for transplants performed after February 1995 was 55%/69% for intestinal grafts; 63%/66% for small bowel and liver grafts; and 63%/63% for multivisceral grafts. Transplants since 1991 and programs that had performed at least 10 transplants had significantly higher graft survival rates. Seventy-seven percent of the current survivors had stopped total parenteral nutrition (TPN) and resumed oral nutrition. CONCLUSIONS: Transplantation has become a lifesaving procedure for (1) patients with intestinal failure who cannot be maintained on total parenteral nutrution and (2) patients who require abdominal evisceration to completely remove locally aggressive tumors. The 5-year survival rate of intestinal transplantation with large series is comparable to lung transplantation.

Adolescent↗
PubMed1999

A cytosine analog that confers enhanced potency to antisense oligonucleotides.

Antisense technology is based on the ability to design potent, sequence-specific inhibitors. The G-clamp heterocycle modification, a cytosine analog that clamps on to guanine by forming an additional hydrogen bond, was rationally designed to enhance oligonucleotide/RNA hybrid affinity. A single, context-dependent substitution of a G-clamp heterocycle into a 15-mer phosphorothioate oligodeoxynucleotide (S-ON) targeting the cyclin-dependent kinase inhibitor, p27(kip1), enhanced antisense activity as compared with a previously optimized C5-propynyl-modified p27(kip1) S-ON and functionally replaced 11 C5-propynyl modifications. Dose-dependent, sequence-specific antisense inhibition was observed at nanomolar concentrations of the G-clamp S-ONs. A single nucleotide mismatch between the G-clamp S-ON and the p27(kip1) mRNA reduced the potency of the antisense ON by five-fold. A 2-base-mismatch S-ON eliminated antisense activity, confirming the sequence specificity of G-clamp-modified S-ONs. The G-clamp-substituted p27(kip1) S-ON activated RNase H-mediated cleavage and demonstrated increased in vitro binding affinity for its RNA target compared with conventional 15-mer S-ONs. Furthermore, incorporation of a single G-clamp modification into a previously optimized 20-mer phosphorothioate antisense S-ON targeting c-raf increased the potency of the S-ON 25-fold. The G-clamp heterocycle is a potent, mismatch-sensitive, automated synthesizer-compatible antisense S-ON modification that will have important applications in the elucidation of gene function, the validation of gene targets, and the development of more potent antisense-based pharmaceuticals.

Animals↗
PubMed1999

Technical experiences with a microsurgical model of lymphatic reconstruction after intestinal transplantation in rats.

The surgical procedure of intestinal transplantation disrupts the graft's lymphatic drainage. Despite morphological regeneration, the functional impairment of the lymphatic system may contribute to many pathophysiological changes after transplant. We describe the technical details and results of a microsurgical model of lymphatic reconstruction (LR), which immediately reconstitutes lymphatic drainage of the intestinal graft in rats. A total of 42 orthotopic intestinal transplants with LR was performed. The patency of the LR was assessed between postoperative days 2 and 100 using either methylene-blue staining of the lymphatic vessels or mesenteric lymphoradiography. A total patency rate of 88% was achieved. Genetic background, occurrence of rejection, and immunosuppressive treatment with cyclosporine did not affect the patency rate. Technical aspects and potential applications of this model are discussed.

Anastomosis, Surgical↗
PubMed1999

Cellular penetration and antisense activity by a phenoxazine-substituted heptanucleotide.

One of the major barriers to the development of antisense therapeutics has been their poor bioavailability. Numerous oligonucleotide modifications have been synthesized and evaluated for enhanced cellular permeation with limited success. Phenoxazine, a tricyclic 2' deoxycytidine analog, was designed to improve stacking interactions between heterocycles of oligonucleotide/RNA hybrids and to enhance cellular uptake. However, the bioactivity and cellular permeation properties of phenoxazine-modified oligonucleotides were unknown. Incorporation of four phenoxazine bases into a previously optimized C-5 propyne pyrimidine modified 7-mer phosphorothioate oligonucleotide targeting SV40 large T antigen enhanced in vitro binding affinity for its RNA target and redirected RNAse H-mediated cleavage as compared with the 7-mer C-5 propynyl phosphorothioate oligonucleotide (S-ON). The phenoxazine/C-5 propynyl U 7-mer S-ON showed dose-dependent, sequence-specific, and target-selective antisense activity following microinjection into cells. Incubation of the phenoxazine/C-5 propynyl U S-ON with a variety of tissue culture cells, in the absence of any cationic lipid, revealed unaided cellular penetration, nuclear accumulation, and subsequent antisense activity. The unique permeation properties and gene-specific antisense activity of the 7-mer phenoxazine/C-5 propynyl U S-ON paves the way for developing potent, cost-effective, self-permeable antisense therapeutics.

Animals↗
PubMed1999

Use of the haemopoietic progenitor cell count of the Sysmex SE-9500 to refine apheresis timing of peripheral blood stem cells.

The Sysmex SE-9500 automated cell counter provides an estimate of immature cells referred to as 'haemopoietic progenitor cells' (HPC). The aim of this study was to relate the HPC count to CD34+ cell levels in mobilized peripheral blood and to determine whether the HPC count was valuable in predicting apheresis yields of CD34+ cells. Studies were performed on 114 samples from 67 patients undergoing progenitor cell mobilization. HPC cells were undetectable in the steady state. On the day of apheresis the HPC and CD34 counts were weakly correlated, with the median HPC count being 2.3-fold greater than the CD34+ cell count. The HPC count did not include the CD34+ cells as immunomagnetic depletion of CD34+ cells did not significantly reduce the HPC count. CD34+ cell counts predicted for apheresis yield (r = 0.773) on that day as did the HPC count (r = 0. 623). The optimal strategy to prevent unnecessary harvesting while minimizing the risk of missing an adequate harvest, and minimizing laboratory investigations, was to screen all samples for HPC and limit CD34+ cell measurements to those with an HPC count <10 x 106/l (19/114 samples). If the CD34+ cell count was also <10 x 106/l then harvesting should not be carried out.

Antigens, CD34↗
PubMed1999

CD40-deficient dendritic cells producing interleukin-10, but not interleukin-12, induce T-cell hyporesponsiveness in vitro and prevent acute allograft rejection.

The induction of an immune response or tolerance is mediated by corresponding subsets of dendritic cells (DC). However, the property of tolerogenic DC is not clear. Recently, we have characterized a population of CD11c+ splenic DC derived from long-term mixed leucocyte culture (LT-MLC), which are able to proliferate upon stimulation and have a strong primary mixed leucocyte reaction (MLR)-stimulating activity in conventional MLR. In this study, we show that, in contrast to the irradiated ones, non-irradiated LT-MLC-derived DC induce polyclonal antigen-specific T-cell hyporesponsiveness when cocultured with allogeneic splenocytes for 3-11 days. The degree of the hyporesponsiveness increased with the length of coculture. Although these DC expressed major histocompatibility complex class II and B7 costimulatory molecules, which are down-regulated during coculture, they expressed very low or undetectable CD40 before and after coculture, respectively. The CD40-deficient DC spontaneously produce interleukin-10 (IL-10), but not IL-12. The skewed balance between IL-10 and IL-12 is associated with their capability to induce T-cell hyporesponsiveness, because a neutralizing antibody to IL-10, exogenous recombinant IL-12 or lipopolysaccharide (LPS) significantly blocked the hyporesponsiveness. Accordingly, infusion of a small number of non-irradiated LT-MLC-derived DC (5x105) significantly prolonged the survival of a vascularized heterotopic murine heart transplant, whereas irradiated DC accelerated graft rejection. These data suggest that CD40-deficient DC producing IL-10, but not IL-12 can induce T-cell hyporesponsiveness in vitro and in vivo.

Adoptive Transfer↗
PubMed1999

A maize map standard with sequenced core markers, grass genome reference points and 932 expressed sequence tagged sites (ESTs) in a 1736-locus map.

We have constructed a 1736-locus maize genome map containing1156 loci probed by cDNAs, 545 probed by random genomic clones, 16 by simple sequence repeats (SSRs), 14 by isozymes, and 5 by anonymous clones. Sequence information is available for 56% of the loci with 66% of the sequenced loci assigned functions. A total of 596 new ESTs were mapped from a B73 library of 5-wk-old shoots. The map contains 237 loci probed by barley, oat, wheat, rice, or tripsacum clones, which serve as grass genome reference points in comparisons between maize and other grass maps. Ninety core markers selected for low copy number, high polymorphism, and even spacing along the chromosome delineate the 100 bins on the map. The average bin size is 17 cM. Use of bin assignments enables comparison among different maize mapping populations and experiments including those involving cytogenetic stocks, mutants, or quantitative trait loci. Integration of nonmaize markers in the map extends the resources available for gene discovery beyond the boundaries of maize mapping information into the expanse of map, sequence, and phenotype information from other grass species. This map provides a foundation for numerous basic and applied investigations including studies of gene organization, gene and genome evolution, targeted cloning, and dissection of complex traits.

Chromosome Mapping↗
PubMed1999

Cardiac metal contents after infusions of manganese. An experimental evaluation in the isolated rat heart.

RATIONALE AND OBJECTIVES: Manganese dipyridoxyl diphosphate (MnDPDP), a contrast agent for liver MRI, releases free Mn2+ in a graded manner. The aim of the study was to compare the effects of brief versus prolonged infusions of MnDPDP and manganese chloride (MnCl2) on cardiac function, metabolism, Mn accumulation, and tissue metal content. METHODS: Isolated perfused rat hearts received 1-minute or 10-minute infusions of MnDPDP (100 microM, 1000 microM) or of MnCl2 (10 microM, 100 microM). Physiologic indices were measured intermittently, and tissue high-energy phosphate compounds and Ca/Fe/Mg/Mn/Zn contents were measured after a standardized Mn washout. RESULTS: One-minute and 10-minute infusions induced, respectively, minor and marked depressions of contractile function and corresponding elevations in myocardial Mn content. MnCl2 was markedly more potent than MnDPDP. Ten-minute infusions of the highest concentration of MnDPDP and MnCl2 lowered tissue Mg and elevated tissue Ca (MnCl2), whereas high-energy phosphates were unaffected. CONCLUSIONS: Mn uptake after Mn infusion is strongly related to the duration, concentration, and dose of free Mn ions. Differences in Mn accumulation between MnDPDP and MnCl2 were more pronounced after the 10-minute infusion.

Animals↗
PubMed1999

Forced expiratory maneuvers in very young children. Assessment of flow limitation.

The application of negative expiratory pressure (NEP) to the airway opening during forced expiratory maneuvers has recently been described as a noninvasive method to assess whether flow limitation is achieved in adults. This methodology has great potential for extending the measurement of forced expiratory maneuvers to young children who may not produce maximal efforts as reproducibly as adults. We used NEP to assess flow limitation in 10 children between 3 and 5 yr of age. NEP was well tolerated by all subjects. With the application of NEP, there was not a step increase in flow, a finding consistent with flow limitation for the subjects. In addition to visual inspection, we proposed a method to quantify the change in flow during a short NEP. The flow-volume curves obtained with and without NEP were visually the same, other than the flow transients produced by NEP. The calculated values of FVC and FEF25-75 were not significantly different when measured from flow- volume curves with and without NEP. There was a statistically significant increase in FEV1 with NEP; however, the group mean increase in FEV1 was less than 2%. We conclude that NEP may be a useful technique to determine whether flow limitation has been achieved in young children performing forced expiratory maneuvers.

Child, Preschool↗
PubMed1999

Xenotransplantation.

As transplantation waiting lists lengthen because of the shortage of donor organs, the death rates of patients continue to rise. Xenotransplantation offers the potential to solve the problem of organ shortage br providing an unlimited supply of healthy donor organs. However, there are several barriers to xenotransplantation, including graft rejection, potential xenozoonosis, physiologic incompatibilities and ethical concerns. Experimental xenotransplantation studies continue in several areas, ranging from tissue to whole- organ grafting. Clinical studies continue in the area of tissue xenotransplantation. Trials with extracorporeal xenografts in an acute setting to support fulminant organ failure are likely to begin in the near future. The reintroduction of whole-organ xenotransplantation must be based on sound scientific analysis with broad societal input so as to offer the maximal benefit to transplant recipients and their families.

Animals↗
PubMed1998

Bacterial expression of two human aryl sulfotransferases.

The effect of replacing a single codon in the N-terminal of human aryl sulfotransferase (HAST) 1 and 3 with one that is more commonly found in E. coli genes was assessed. The pKK233-2 E. coli expression vector was employed and the polymerase chain reaction (PCR) was used to introduce the 5' nucleotide substitution, at the same time maintaining the fidelity of the amino acid sequence. The data indicates that this change had a minimal effect on protein production, subcellular localization or, in the case of HAST3, catalytic activity. In general, the pKK233-2 E. coli vector has been less than optimal for expressing human sulfotransferase cDNAs.

Animals↗
PubMed1998

Strategies to prevent thrombosis in xenotransplants.

Coagulation remains a major barrier to successful xenotransplantation. Identification of the role of complement activation in HAR and prevention of complement activation by high expression of DAF and CD59 has largely overcome HAR. Understanding the molecular basis of DXR and identification of novel strategies to prevent activation of endothelial cells using monoclonal antibodies, soluble inhibitors of coagulation, vaccination, antisense constructs, and recombinant DNA technology offers the promise of overcoming the thrombosis associated with xenotransplantation.

Acute Disease↗