Biomedical subjects
Publications and source records attributed to P Nelson.
Mouse neuroblastoma cells grown in vitro are capable of generating action potentials in response to electrical stimulation. A wide spectrum of responses was observed with different cells ranging from passive responses to action potentials. A hypothesis is proposed concerning the acquisition of electrical excitability as neuroblasts mature into neurons.
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In an effort to understand better the transplacental water flux induced by osmotic forces, 17 near-term guinea-pig placentae were perfused on both sides with an artificial cell-free fluid containing dextran. Maternal and fetal arterial inflow rates were kept constant by syringe pumps and inflow and outflow pressures were recorded continuously. Precise measurements of outflow rates were made by weight determination and transplacental fluid shifts calculated by weight changes during placental passage. The content of dextran T 40 in the perfusion fluid was altered in stepwise manner from 0 to 60 to 120 g/l, and the effects of all possible combinations of fetal--maternal concentration differences on the transplacental fluid shift were observed. On the average, about 1 X 10(-3) ml/min/g placenta was moved per 1 g/l concentration difference. In two experiments venous colloid osmotic pressures were recorded continuously. In ten experiments the oncotic fluid shift was counterbalanced by an additional hydrostatic pressure difference; an average 1 mmHg hydrostatic pressure counterbalancing 15 g/l of dextran concentration osmotic force. The calculated hydraulic conductance, Lp, was approximately 0.017 ml/min/mmHg/g and the reflection coefficient, s, for dextran T 40 was 0.1. Both parameters characterize the isolated guinea-pig placenta as leaky.
Experimental allergic encephalomyelitis (EAE) serves as a model for autoimmune diseases mediated by T lymphocytes. Following sensitization to rat, mouse or guinea pig myelin basic protein (MBP) in complete Freund's adjuvant, inbred mouse strains PL/J (H-2u), SJL/J (H-2s) and (PL/J X SJL/J)F1((PLSJ)F1) develop EAE. Whereas sensitization to the N-terminal 37 amino-acid peptide of rat or guinea pig MBP [MBP(1-37)] induces EAE in PL/J mice, immunization to the C-terminal peptide (89-169) leads to EAE in SJL/J mice. The immune response to MBP in (PLSJ)F1 mice is not co-dominant; sensitization to the N-terminal peptide induces EAE, while sensitization to the C-terminal peptide does not. We have generated MBP-specific T-cell clones restricted to class II (Ia) antigens of the major histocompatibility complex (MHC) from PL/J and (PLSJ)F1 mice following sensitization to rat MBP. Two such I-Au-restricted T-cell clones that proliferate in response to the encephalitogenic N-terminal MBP peptide and recognize a shared determinant with mouse (self) MBP cause paralysis in 100% of (PLSJ)F1 mice tested. Paralysis is induced even when recipients are injected with as few as 1 X 10(5) cloned T cells. Relapsing paralysis followed in two-thirds of the recipients after recovery from acute paralysis, whereas one-third developed chronic persistent paralysis, a form of EAE not usually seen. Histopathology revealed intense perivascular inflammation, demyelination and remyelination within the central nervous system of paralysed mice. The experimental disease induced with these clones shares important features with human demyelinating diseases such as multiple sclerosis. This is the first demonstration that T-cell clones that respond to a defined self-antigen can induce clinical and histological autoimmune disease.
Data are reported on special and regular education students' perceptions of control at school and the importance to the students of having such control. For both special and regular education populations, comparisons were made between students enrolled in experimental and nonexperimental programs. Findings indicate comparability among the four groups with regard to areas in which control is valued. Perceptions of control at school for those in the standard special education group were lower than the ratings of regular education students and lower than those given by special education students in the experimental program.
To respond to massive changes in health care delivery, nursing curriculum redesign requires that we return to our roots in the community and the visionary leadership of Lillian Wald, whose Henry Street Settlement (1,2) remains a model for community-based leadership. Wald's mission--to serve those in need, wherever they may be found--remains our legacy. But while the challenge of preparing students to function within a multitude of settings is not new, the changes now confronting faculty, students, and the entire health care system are taking place at a startling pace.
Deep in Lechuguilla Cave, a researcher ponders slots carved millions of years ago by dripping sulfuric acid. Though the cave was formed by acid bubbling up from below, here gases condensed on the chamber's ceiling and then rained down as acid. Scientists think Mars may also hold caves carved by sulfuric acid. On Earth, almost all other caves are formed by flowing water.