Biomedical subjects

A Loomis

Publications and source records attributed to A Loomis.

12 recordsLinked to original sources

PubMed2003

Recharging cationic DNA complexes with highly charged polyanions for in vitro and in vivo gene delivery.

The intravenous delivery of plasmid DNA complexed with either cationic lipids (CL) or polyethyleneimine (PEI) enables high levels of foreign gene expression in lung. However, these cationic DNA complexes cause substantial toxicity. The present study found that the inclusion of polyacrylic acid (pAA) with DNA/polycation and DNA/CL complexes prevented the serum inhibition of the transfection complexes in cultured cells. The mechanism mediating this increase seems to involve both particle size enlargement due to flocculation and electrostatic shielding from opsonizing serum proteins. The use of pAA also increased the levels of lung expression in mice in vivo substantially above the levels achieved with just binary complexes of DNA and linear PEI (lPEI) or CL and reduced their toxicity. Also, the use of a "chaser" injection of pAA 30 min after injection of the ternary DNA/lPEI/pAA complexes further aided this effort to reduce toxicity while not affecting foreign gene expression. By optimizing the amount of pAA, lPEI, and DNA within the ternary complexes and using the "chaser" injection, substantial levels of lung expression were obtained while avoiding adverse effects in lung or liver. These developments will aid the use of cationic DNA complexes in animals and for eventual human gene therapy.

Acrylic Resins↗

PubMed1999

Layer-by-layer deposition of oppositely charged polyelectrolytes on the surface of condensed DNA particles.

DNA can be condensed with an excess of poly-cations in aqueous solutions forming stable particles of submicron size with positive surface charge. This charge surplus can be used to deposit alternating layers of polyanions and polycations on the surface surrounding the core of condensed DNA. Using poly-L-lysine (PLL) and succinylated PLL (SPLL) as polycation and polyanion, respectively, we demonstrated layer-by-layer architecture of the particles. Polyanions with a shorter carboxyl/backbone distance tend to disassemble binary DNA/PLL complexes by displacing DNA while polyanions with a longer carboxyl/backbone distance effectively formed a tertiary complex. The zeta potential of such complexes became negative, indicating effective surface recharging. The charge stoichiometry of the DNA/PLL/SPLL complex was found to be close to 1:1:1, resembling poly-electrolyte complexes layered on macrosurfaces. Recharged particles containing condensed plasmid DNA may find applications as non-viral gene delivery vectors.

Anions↗

PubMed1998

Effects of the analytical treatment of exposure data on associations of cancer and occupational magnetic field exposure.

Epidemiological studies of cancer among workers exposed to magnetic fields have yielded inconsistent results. This variability may be partly explained by differences in study methods. To assess sensitivity to such methods, data from a previous study of brain cancer and leukemia among electric power company workers were reanalyzed using alternative models, which incorporated uncertainty about the intensity of historical exposures, alternative cut points for categorizing the exposure variable for analysis, and a range of lags for describing cancer latency. Mortality rate ratios for leukemia ranged from 0.8-1.5. For brain cancer, increasing cumulative magnetic field exposure was associated with increasing mortality in virtually all models, with rate ratios between 1.3-3.4 for the most exposed workers. These rate ratios are consistent with previous analyses suggesting a 1.5-3.0-fold increase in the risk of brain cancer but no association with leukemia, and confirm that the previous results are not dependent on arbitrary decisions in applying the exposure data.

Brain Neoplasms↗

PubMed1997

Gene transfer using a novel fusion protein, GAL4/invasin.

The delivery of DNA to target cells using simple, defined, nonviral systems has become an area of intense interest in gene therapy. We describe here the development and characterization of one such novel system. A recombinant, bifunctional, fusion protein was expressed and purified from Escherichia coli. This protein consists of the DNA-binding domain of the yeast transcription factor GAL4 fused to the cell binding, internalization domain of the Yersinia pseudotuberculosis inv gene product, invasin. This protein, GAL4/Inv, together with poly-L-lysine, formed complexes with a chloramphenicol acetyltransferase (CAT) reporter plasmid that contains eight repeats of the GAL4 consensus recognition sequence. These complexes were shown to transfect target cells in an invasin receptor-dependent manner, resulting in transient CAT expression. A simple, targeted DNA delivery vehicle, as we describe here, represents a viable approach to nonviral gene delivery.

Adhesins, Bacterial↗

PubMed1995

Functional characterization of the human interleukin-15 receptor alpha chain and close linkage of IL15RA and IL2RA genes.

Interleukins-2 and -15 (IL-2 and IL-15) are cytokines with overlapping but distinct biological effects. Their receptors share two subunits (the IL-2R beta and -gamma chains) that are essential for signal transduction. The IL-2 receptor requires an additional IL-2-specific alpha subunit for high affinity IL-2 binding. Recently, a murine IL-15-specific alpha subunit was identified, cloned, and shown to be structurally related to IL-2R alpha. However, the murine IL-15R alpha alone bound IL-15 with a 1000-fold higher affinity than that seen with IL-2R alpha and IL-2. We now extend these studies into the human system with the isolation of three differentially spliced human IL-15R alpha variants that are all capable of high affinity binding of IL-15. The cytoplasmic domain of IL-15R alpha, like that of IL-2R alpha, is dispensable for mitogenic signaling, suggesting that the primary role of the alpha chains is to confer high affinity binding. At high concentrations, IL-15, like IL-2, is able to signal through a complex of IL-2R beta and -gamma in the absence of the alpha subunit. Furthermore, the IL15RA and IL2RA genes have a similar intron-exon organization and are closely linked in both human and murine genomes. However, the distribution of expression of the IL-15R alpha is much wider than that of the IL-2R alpha, suggesting a broader range of cellular targets for IL-15.

Amino Acid Sequence↗

PubMed1995

Identification and cloning of a novel IL-15 binding protein that is structurally related to the alpha chain of the IL-2 receptor.

Interleukin-15 (IL-15) is a novel cytokine of the four-helix bundle family which shares many biological activities with IL-2, probably due to its interaction with the IL-2 receptor beta and gamma (IL-2R beta and gamma c) chains. We report here the characterization and molecular cloning of a distinct murine IL-15R alpha chain. IL-15R alpha alone displays an affinity of binding for IL-15 equivalent to that of the heterotrimeric IL-2R for IL-2. A biologically functional heteromeric IL-15 receptor complex capable of mediating IL-15 responses was generated through reconstruction experiments in a murine myeloid cell line. IL-15R alpha is structurally similar to IL-2R alpha; together they define a new cytokine receptor family. The distribution of IL-15 and IL-15R alpha mRNA suggests that IL-15 may have biological activities distinct from IL-2.

Amino Acid Sequence↗

PubMed1989

Birth weight outcomes in a teenage pregnancy case management project.

While many comprehensive health care programs for pregnant adolescents are designed to improve the birth weights of the babies born, few provide statistical evidence that they were able to do so. In this study, information was gathered prospectively on 411 mothers in a Teenage Pregnancy and Parenting Program (TAPP) that coordinated medical, educational, and social services through individual case management and agency-level coordination, information on the mothers, their pregnancy, and services received. The low birth weight rate for TAPP participants was significantly lower than the rate for San Francisco teens prior to the establishment of the program (8.1% versus 12.0% p less than 0.05). The mean weights of babies born to teens in TAPP were significantly higher than those in San Francisco after controlling for differences in the race, infant gender, parity, and age (p less than 0.0001). Participation in the TAPP program prior to delivery was more strongly associated with better birth weight outcomes than was race, age, parity, or gender. Participation in the TAPP program was associated with significantly better birth weights independent of receiving a minimal number of prenatal medical visits adequate for the gestational age of the baby at birth. Our results provide evidence of better health outcomes for the babies of teens who had case management that included continuous individual counseling and coordination of health, education, psychosocial, and nutrition services.

Adolescent↗

PubMed1988

Services to adolescent fathers.

Until recently, service programs for adolescent fathers have been rare. Such a program for teenage fathers and service characteristics that encourage the involvement of teenage fathers are described. In particular, fathers who did not live with the mothers of their babies had dramatically greater participation in prenatal activities if they used teenage father services. Services to fathers and fathers' participation in prenatal activities also were associated with higher birthweights. Engaging adolescent fathers in pilot fatherhood projects thus has high potential to benefit teenage fathers and mothers and their infants.

Adolescent↗

PubMedDate not supplied

Hypothesis: naked plasmid DNA is taken up by cells in vivo by a receptor-mediated process.

Following the initial demonstration that intramuscularly-injected naked plasmid DNA (pDNA) is expressed in myofibers, it was shown that pDNA can be used for vaccination purposes. More recent studies have indicated that naked pDNA can also achieve high levels of transgene expression in vivo. This efficiency of naked pDNA expression, especially via intravascular route, is truly astounding. In this prospective review, we examine the possible mechanisms of naked pDNA uptake. The possible mechanisms; (a) large membrane disruption, (b) small membrane pores, and (c) receptor-mediated endocytosis, are considered in turn. Some recent original laboratory data relevant to these hypotheses are also presented.

Animals↗

PubMedDate not supplied

Changing attitudes about end-of-life decision making of medical students during third-year clinical clerkships.

To better define the learning objectives of ethics curricula and evaluate changes in medical students' attitudes about end-of-life decision making, enrolled students (N = 96) of a pilot medical ethics program were surveyed at the beginning and end of their third-year clinical clerkship about their experiences and attitudes about end-of-life decision making. At the end of their clinical clerkship year, the majority of students had participated in end-of-life decisions, prioritized patient autonomy and quality-of-life issues, were concerned about legal liability, were polarized over issues such as physician-assisted suicide, and gained confidence in their ethical decision-making ability. To train future physicians such that clinical practice is consistent with ethical guidelines and legislation on end-of-life care, medical ethics curricula should focus on symptom relief, clarification of legal issues, and resolution of conflicts between personal beliefs and public opinion about such issues as physician-assisted suicide. Appropriate role-modeling and mentoring by residents and attending physicians should also be emphasized.

Adult↗

PubMedDate not supplied

Qualitative outcome assessment of a medical ethics program for clinical clerkships: a pilot study.

This study assessed the usefulness of an open-ended case analysis test instrument for evaluating the effects of a 1-year ethics course on medical students' decision-making skills. Through case-oriented seminars in gynecology, internal medicine, obstetrics, pediatrics, psychiatry, and surgery, third-year medical students were taught a structured analytic framework for analyzing clinical ethical problems stressing the interactive relationships among medical indications, patient preferences, quality of life, and contextual (social, legal, economic) matters. At precourse, the students were given a test case and asked to provide a line of reasoning for their clinical decisions. At postcourse, the students were given the same case. Content analysis of pre- and postcourse responses of a random student sample revealed increases in student awareness in the following areas: 1) consideration of informed consent, 2) professional liability, 3) physician-assisted suicide, and 4) resource utilization. With some modifications, open-ended case analysis holds promise for evaluating medical ethics courses. The authors make recommendations for future research in evaluating the true impact of clinical ethics courses in medical education.

Clinical Clerkship↗

PubMedDate not supplied

Caged DNA does not aggregate in high ionic strength solutions.

The assembly of DNA into compact particles that do not aggregate in physiologic salt solution occurs naturally in chromatin and viral particles but has been challenging to duplicate using artificial constructs. Cross-linking amino-containing polycations in the presence of DNA with bisimidoester cross-linker leads to the formation of caged DNA particles that are stable in salt solutions. This first demonstration of caged DNA provides insight into how natural condensation processes avoid aggregation and a promising avenue for developing nonviral gene therapy vectors.

Cross-Linking Reagents↗