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Biomedical subjects

B E Porter

Publications and source records attributed to B E Porter.

11 recordsLinked to original sources
PubMed2001

A nationwide survey of self-reported red light running: measuring prevalence, predictors, and perceived consequences.

A United States probability sample of 880 licensed drivers participated in a telephone survey of red light running perceptions and behaviors. Despite most drivers believing red light running was problematic and dangerous, approximately one in five respondents reported running one or more red lights when entering the last ten signalized intersections. Among several demographic and attitude variables, only age group predicted recent red light running. Specifically, younger respondents were more likely to be violators. Drivers also reported being more likely to run red lights when alone, and were typically in a hurry when speeding up to be beat red lights. Contrary to expectations, frustration was not as important for predicting red light running as it was for other driving behaviors, such as speeding, tailgating, weaving, and gesturing angrily at others. Additionally, drivers perceived and received few consequences for running red lights. Less than 6% had received a traffic ticket for red light running and most believed that police would catch less than 20% of violators. Slightly more than one in ten had been involved in a red light running crash. Respondents most commonly suggested legal initiatives to reduce red light running. Accordingly, we recommend traffic safety experts pursue interventions that apply immediate and consistent negative consequences to violators to change the public's red light running perceptions and behavior.

Accidents, Traffic↗
PubMed1999

Distinct structures and functions of related pre- and postsynaptic carbohydrates at the mammalian neuromuscular junction.

Carbohydrates that terminate in beta-linked N-acetylgalactosamine (betaGalNAc) residues are concentrated in the postsynaptic apparatus of the skeletal neuromuscular junction and have been implicated in the differentiation of the postsynaptic membrane. We now report that distinct synapse-specific betaGalNAc-containing carbohydrates are associated with motor nerve terminals. Two monoclonal antibodies that recognize distinct betaGalNAc-containing epitopes, CT1 and CT2, both stain synaptic sites on skeletal muscle fibers. However, CT1 selectively stains nerve terminal, whereas CT2 selectively stains the postsynaptic apparatus. Likewise, CT1 and CT2 selectively stain motoneuron-like and muscle cell lines, respectively. Using the cell lines, we identify distinct CT1- and CT2-reactive glycolipids and glycoproteins. Finally, we show that GalNAc modulates the adhesion of motoneuron-like cells to recombinant fragments of a synaptic cleft component, laminin beta2. Together, these results show that pre- as well as postsynaptic membranes bear and are affected by distinct but related synapse-specific carbohydrates.

Acetylgalactosamine↗
PubMed1995

Distinct adhesive properties of ciliary and choroid neurons from the avian ciliary ganglion.

The avian ciliary ganglion (CG) contains two populations of neurons: ciliary neurons, which innervate striated muscle, and choroid neurons, which innervate vascular smooth muscle. We used cell size (ciliary cells are larger) and somatostatin immunoreactivity (which is restricted to choroid cells) as markers to compare the adhesive properties of these two neuronal types. Similar numbers of freshly dissociated embryonic chick ciliary and choroid neurons adhered to laminin (laminin 1) and polylysine, consistent with the fact that each population comprises about half of the ganglionic neurons. In contrast, severalfold more ciliary neurons than choroid neurons adhered to a recombinant fragment of a synapsespecific basal lamina protein, s-laminin/laminin beta 2. Moreover, severalfold more ciliary neurons than choroid neurons adhered to a plastic surface when assayed by the method of Needels et al. in serum-free medium. Adhesion to s-laminin and plastic appears to be mediated by different cell surface components, as adhesion to recombinant s-laminin is inhibited by the tripeptide, LRE, and by Ca2+ ions, but not by heparin, whereas adhesion to plastic is LRE and Ca2+ insensitive but heparin sensitive. Both adhesive differences are apparent at embryonic day 8, soon after the ciliary and choroid neurons have begun to form synapses. Thus, two sets of neurons in the CG that send axons through different nerves and innervate different targets also show distinct adhesive behaviors.

Animals↗
PubMed1995

Gated migration: neurons migrate on but not onto substrates containing S-laminin.

Components of the extracellular matrix influence migration of diverse cell types. Some, such as laminin, promote neuronal migration, whereas others are nonpermissive or inhibitory. Here, we demonstrate that a recombinant fragment of s-laminin, a homologue of the laminin B1 chain, is a barrier to neuronal migration. NSC-34 (motoneuron-like) and ciliary ganglion cells were plated on substrates coated with alternating stripes of laminin and a mixture of laminin plus s-laminin. On these patterned substrates, cells seldom crossed from s-laminin-free to s-laminin-containing regions. Mutation of the tripeptide LRE, an adhesive site in s-laminin, abolished s-laminin's ability to block border crossing. However, overall rates of migration were similar on the two substrates. This behavior contrasts with that of previously reported barrier molecules, which decreases rates of cell migration when mixed with permissive substrates. Instead, s-laminin appears to block cell migration through a "gating" mechanism that acts primarily at borders.

Amino Acid Sequence↗
PubMed1995

A motoneuron-selective stop signal in the synaptic protein S-laminin.

Motor axons preferentially reinnervate original synaptic sites on denervated muscle fibers. We have shown that components of synaptic basal lamina direct this selectivity, and we identified a protein, s-laminin, that is concentrated in synaptic basal lamina. Here, we report that a recombinant s-laminin fragment inhibits neurite outgrowth promoted by laminin. A tripeptide sequence in this fragment, Leu-Arg-Glu (LRE), contributes to this inhibition and is itself sufficient to inhibit outgrowth. LRE-mediated inhibition is selective for motoneuron-like cells and is observed in mixtures with several, but not all, outgrowth-promoting substrates. Growth cones extending on laminin stop for up to several hours upon contacting deposits of the s-laminin fragment. Thus, LRE may serve as a cell type-selective and context-dependent target-derived signal that plays a role in synapse formation.

Amino Acid Sequence↗
PubMed1993

S-laminin: mapping to mouse chromosome 9 and expression in the linked mutants tippy and ducky.

S-Laminin, a homologue of the laminin B1 chain, is present in a subset of basal laminae, including those of the skeletal neuromuscular junction and the renal glomerulus. Here, we show that the distribution and apparent size of murine S-laminin are similar to those documented previously for rat and human. We then use interspecific backcross analysis to map the S-laminin (Lams) gene to mouse chromosome 9. Thus, it is unlinked to genes for the laminin A, B1, and B2 chains. Finally, because the Lams gene mapped near two mutations that affect neuromuscular function, ducky (du) and tippy (tip), we assayed S-laminin by Southern blotting, immunoblotting, and immunohistochemistry in these mutants. No abnormality of the S-laminin gene or protein was detectable in either mutant.

Animals↗
PubMed1992

Renal artery bullet embolism.

Bullet embolism is a well-recognized phenomenon. While bullet embolism is not common, renal artery bullet embolism appears to be very rare. We report three cases of bullet embolism to a renal artery. Autopsy findings and bullet types are presented. Such cases are of particular interest to both the medical examiner and the clinician. Failure to consider this phenomenon clinically could lead to infarction of a kidney. A consideration of this phenomenon at autopsy could shorten the dissection time required to retrieve the bullet.

Adult↗
PubMed1989

Primary sequence of a motor neuron-selective adhesive site in the synaptic basal lamina protein S-laminin.

S-laminin, a novel homolog of laminin, is concentrated in a subset of basal laminae including the basal lamina that passes between motor nerve terminals and muscle fibers at the neuromuscular junction. Here we used recombinant fragments to localize a neuronal attachment site to the C-terminal 10% of s-laminin. We then used synthetic peptides spanning the active fragment to identify the primary sequence of the adhesive site as Leu-Arg-Glu (LRE): neurons attach to an immobilized LRE-containing peptide, and soluble LRE blocks attachment of neurons to the s-laminin fragment. Whereas ciliary ganglion neurons (which normally innervate muscle fibers) adhered well both to laminin and to an s-laminin fragment, sensory and central neurons and several neuronal cell lines all adhered well to laminin but poorly to the s-laminin fragment. Together, these results define a motor neuron-selective attachment site on s-laminin.

Amino Acid Sequence↗
PubMed1985

Restoration of cell volume and the reversal of carbohydrate transport and growth inhibition of osmotically upshocked Escherichia coli.

Resumption of growth in osmotically upshocked Escherichia coli was effected only by an external stimulus (betaine treatment) in severe upshock, but was spontaneous in less severe upshock. In either case, growth resumption was preceded by a reversal of glucose transport inhibition, and that reversal was preceded by a recovery of cell volume. We hypothesize that deformation of the membrane by osmotic stress results in conversion of a membrane component of the transport system to a less functional conformation, which results in the inhibition of transport and the consequent inhibition of growth. Relief of the deformation would then allow recovery to a more functional conformation, reversal of transport inhibition, and then resumption of growth.

Betaine↗