Biomedical subjects

T E Kennedy

Publications and source records attributed to T E Kennedy.

At least 37 records · Page 2Linked to original sources

PubMed1994

Netrins are diffusible chemotropic factors for commissural axons in the embryonic spinal cord.

The guidance of axons to their targets in the developing nervous system is believed to involve diffusible chemotropic factors secreted by target cells. Floor plate cells at the ventral midline of the spinal cord secrete a diffusible factor or factors that promotes the outgrowth of spinal commissural axons and attracts these axons in vitro. Two membrane-associated proteins isolated from brain, netrin-1 and netrin-2, possess commissural axon outgrowth-promoting activity. We show here that netrin-1 RNA is expressed by floor plate cells, whereas netrin-2 RNA is detected at lower levels in the ventral two-thirds of the spinal cord, but not the floor plate. Heterologous cells expressing recombinant netrin-1 or netrin-2 secrete diffusible forms of the proteins and can attract commissural axons at a distance. These results show that netrin-1 is a chemotropic factor expressed by floor plate cells and suggest that the two netrin proteins guide commissural axons in the developing spinal cord.

Animals↗

PubMed1994

The evolution of nursing research in the Army Nurse Corps.

The growth of nursing research has been richly nurtured in the military nursing community. Army nurses have been at the forefront of the growth of the discipline both within the military community and at civilian institutions after their departure from active duty. This paper describes the development of the nursing research program by the Army Nurse Corps (ANC) within the Army Medical Department (AMEDD) from its earliest stages through the present. It discusses the organizational structure of nursing research within the ANC and the leadership innovations being implemented to make nursing research responsive to the needs of the AMEDD into the next century.

Humans↗

PubMed1992

Long-term sensitization training in Aplysia leads to an increase in calreticulin, a major presynaptic calcium-binding protein.

Long-term memory for sensitization in Aplysia requires new protein and RNA synthesis. Here, we identify a late protein as calreticulin, the major Ca(2+)-binding protein of the lumen of the endoplasmic reticulum. An antiserum against Aplysia calreticulin reveals an enrichment of calreticulin immunoreactivity in presynaptic varicosities. Quantitative S1 nuclease analysis indicates that the steady-state level of calreticulin mRNA in Aplysia sensory neurons increases during the maintenance phase of long-term sensitization. The finding that this mRNA increases in expression late, some time after training, is consistent with the idea that long-term neuromodulatory changes underlying sensitization may depend on a cascade of gene expression in which the induction of early regulatory genes leads to the expression of late effector genes.

Amino Acid Sequence↗

PubMed1992

Long-term sensitization training in Aplysia leads to an increase in the expression of BiP, the major protein chaperon of the ER.

Long-term memory for sensitization of the gill- and siphon-withdrawal reflexes in Aplysia californica requires RNA and protein synthesis. These long-term behavioral changes are accompanied by long-term facilitation of the synaptic connections between the gill and siphon sensory and motor neurons, which are similarly dependent on transcription and translation. In addition to showing an increase in over-all protein synthesis, long-term facilitation is associated with changes in the expression of specific early, intermediate, and late proteins, and with the growth of new synaptic connections between the sensory and motor neurons of the reflex. We previously focused on early proteins and have identified four proteins as members of the immunoglobulin family of cell adhesion molecules related to NCAM and fasciclin II. We have now cloned the cDNA corresponding to one of the late proteins, and identified it as the Aplysia homolog of BiP, an ER resident protein involved in the folding and assembly of secretory and membrane proteins. Behavioral training increases the steady-state level of BiP mRNA in the sensory neurons. The increase in the synthesis of BiP protein is first detected 3 h after the onset of facilitation, when the increase in overall protein synthesis reaches its peak and the formation of new synaptic terminals becomes apparent. These findings suggest that the chaperon function of BiP might serve to fold proteins and assemble protein complexes necessary for the structural changes characteristic of long-term memory.

Amino Acid Sequence↗

PubMed1991

Duodenocaval fistula in peptic ulceration.

Duodenocaval fistula is usually caused by abdominal trauma. We report a patient in whom it was associated with peptic ulcer.

Duodenal Diseases↗

PubMed1990

G0 is a major growth cone protein subject to regulation by GAP-43.

G0, a GTP-binding protein that transduces information from transmembrane receptors, has been found to be a major component of the neuronal growth cone membrane. GAP-43, an intracellular growth cone protein closely associated with neuronal growth, stimulates GTP-gamma-S binding to G0. It does so through an amino-terminal domain homologous to G-linked transmembrane receptors. Thus, G0 in the growth cone may be regulated by intracellular as well as extracellular signals.

Amino Acid Sequence↗

PubMed1989

Development of a database of amino acid sequences for proteins identified and isolated on two-dimensional polyacrylamide gels.

As part of our continuing studies into the biochemical basis of long-term changes in neuronal function in Aplysia, we have developed a simple method for obtaining amino acid sequence information from proteins isolated on two-dimensional gels. Proteins isolated on preparative two-dimensional gels are digested in situ with Staphylococcus aureus V8 protease, and the resulting peptides electrophoresed, transferred to a polyvinylidene difluoride membrane, and sequenced in a gas-phase sequencer. The method is simple and should be applicable to a variety of other systems where the development of a two-dimensional gel database is underway.

Amino Acid Sequence↗

PubMed1989

Multiple cAMP-binding proteins in Aplysia tissues.

While it is recognized that cAMP is able to regulate distinct cellular processes differentially, the molecular basis for the diversity of its effects remains unclear. Using photoaffinity labeling with 32P-8 azido-cAMP and two-dimensional gel analysis, we have identified 26 electrophoretic variants of cAMP-binding proteins in the six different tissues of the marine mollusc Aplysia californica sampled. Some of these proteins are found in most tissues, others only in a few; still others appear to be restricted to a single tissue. All of these proteins bind cAMP specifically. The two-dimensional polyacrylamide gel electrophoretic patterns of binding proteins seen in the different tissues fall into three classes. One pattern is shared by the nervous system and embryos. The second is found in muscular tissues (heart, buccal muscle, siphon, and gill). The third pattern is specific to sperm. The presence of distinct subsets of cAMP-binding proteins in different tissues suggests that at least some of the diversity in cAMP's regulatory function may result from diversity in the proteins that bind it.

Animals↗

PubMed1989

5-HT modulates protein synthesis and the expression of specific proteins during long-term facilitation in Aplysia sensory neurons.

Long-term, but not short-term, facilitation induced by 5-HT in Aplysia sensory neurons is blocked by application of inhibitors of protein synthesis or RNA synthesis during the 1.5 hr training period. These findings suggest that genes and proteins not needed for the short-term process are required for long-term facilitation. To identify these proteins, we examined changes in overall and specific protein synthesis in sensory neurons. During the 1.5 hr period of stimulation, 5-HT initiated three temporally distinct changes in total protein synthesis: a small decrease at 0.5 hr, a small increase at 1 hr, and a second and larger increase at 3 hr. 5-HT also produced three temporally distinct changes in the synthesis of individual proteins that could be resolved on 2-D gels. First, there was an increase at 30 min in the rate of synthesis of 10 proteins and a decrease in the synthesis of 5 proteins. These changes in protein expression are rapid and transient, subsiding within 1-3 hr, and are transcription-dependent. Second, at 3 hr, there is a transient increase in 4 different proteins that also is transcription-dependent and lasts approximately 5 hr. Finally, at 24 hr, during the retention phase of facilitation, there was a sustained increase in the expression of two proteins.

Animals↗

PubMed1988

Sequencing proteins from acrylamide gels.

The analytical power of high-resolution two-dimensional gel electrophoresis has been coupled with molecular cloning techniques to allow the sequencing of proteins directly from preparative gels.

Amino Acid Sequence↗

PubMed1988

A quantitative analysis of 2-D gels identifies proteins in which labeling is increased following long-term sensitization in Aplysia.

Long-term memory for sensitization of the gill- and siphon-withdrawal reflex in Aplysia, produced by 4 days of training, is associated with increased synaptic efficacy of the connection between the sensory and motor neurons. This training is also accompanied by neuronal growth; there is an increase in the number of synaptic varicosities per sensory neuron and in the number of active zones. Such structural changes may be due to changes in the rates of synthesis of certain proteins. We have searched for proteins in which the rates of [35S]methionine labeling are altered during the maintenance phase of long-term memory for sensitization by using computer-assisted quantitative 2-D gel analysis. This method has allowed us to detect 4 proteins in which labeling is altered after 4 days of sensitization training.

Animals↗

PubMed1988

Sequencing of proteins from two-dimensional gels by using in situ digestion and transfer of peptides to polyvinylidene difluoride membranes: application to proteins associated with sensitization in Aplysia.

We have developed a method for obtaining partial internal amino acid sequence data from proteins isolated directly from preparative two-dimensional polyacrylamide gels. Proteins from a crude cell homogenate are separated using preparative two-dimensional polyacrylamide gel electrophoresis. Then, the gel is stained with Coomassie blue and the protein spots of interest are cut out. The in situ protein is digested with Staphylococcus aureus V8 protease in a second polyacrylamide gel and the peptides are separated by one-dimensional polyacrylamide gel electrophoresis. The peptides are then electroblotted onto a polyvinylidene difluoride membrane, visualized using Coomassie blue, cut out, and sequenced using an automated gas phase sequencer. Using this method, we have obtained amino acid sequence data for two proteins that are altered after long-term sensitization: actin and Aplysia protein 407. In addition, we have obtained amino acid sequence data for rat protein 425, a protein that appears to be homologous to Aplysia protein 407.

Actins↗

PubMed1987