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Biomedical subjects

P J Morin

Publications and source records attributed to P J Morin.

At least 19 recordsLinked to original sources
PubMed1995

Genetic analysis of growth inhibition by GAL4-L kappa B-alpha in Saccharomyces cerevisiae.

I kappa B proteins bind to and regulate Rel/NF- kappa B transcription factors. We showed previously that a fusion protein (GAL4-p40) containing the DNA-binding domain of GAL4 and sequences of chicken l kappa B-alpha (p40) inhibits growth in the yeast Saccharomyces cerevisiae. We now show that p40 must be bound to DNA to inhibit yeast growth, p40 proteins, bound to DNA either as GAL4 or LEXA fusion proteins, inhibit yeast growth. In contrast, p40 proteins that cannot bind to DNA, such as full-length p40, a GAL4-l kappa B fusion protein containing a mutant GAL4 DNA-binding domain, and a fusion protein (GAD-p40) containing the transcriptional activation domain of GAL4 fused to p40, each failed to inhibit cell growth. As with GAL4-VP16, GAL4-p40 needs a functional cellular ADA2 gene to exert its growth-inhibitory effect in S. cerevisiae. Using a high copy suppression strategy, we have isolated three S. cerevisiae genes that restore normal growth to yeast expressing GAL4-p40 or LEXA-p40. We have termed these rescuing genes collectively as SIK genes, for "Suppressors of 1 kappa B." Expression of the SIK genes specifically suppresses the growth-inhibitory activity of GAL4-p40 and LEXA-p40 because SIK gene expression cannot block GAL4-VP16-mediated growth inhibition in S. cerevisiae. SIK1 encodes a novel protein that contains a COOH-terminal repeat that has been found in many microtubule-binding proteins. SIK2 encodes NH2-terminal acetyltransferase, and SIK3 encodes the yeast ribosomal S4 protein. None of the SIK proteins binds directly to p40 sequences in vitro, suggesting that the SIK proteins are likely to act downstream of the direct point of growth inhibition by GAL4-p40. Our results may be useful for devising strategies for identifying vertebrate inhibitors of l kappa B proteins and of other proteins that inhibit growth in S. cerevisiae.

Amino Acid Sequence↗
PubMed1993

Inhibition of kinesin synthesis and rapid anterograde axonal transport in vivo by an antisense oligonucleotide.

Synthetic antisense oligonucleotides have been used to inhibit specific protein synthesis in vivo. Antisense oligonucleotides directed to kinesin heavy chain were injected into the vitreous of anesthetized rabbits in order to assess the effects on transport in the retinal ganglion cells whose axons form the optic nerve. The antisense oligonucleotide specifically inhibited retinal kinesin synthesis by 82 +/- 7% (n = 4). The rapid axonal transport of the membrane proteins into the optic nerve was concomitantly inhibited by 70 +/- 10% (n = 4). These results provide direct evidence for the specific role of kinesin in rapid anterograde transport in vivo and indicate the utility of antisense oligonucleotides to explore neuronal dynamics in a specific neuronal cell type in a living animal.

Animals↗
PubMed1993

Amyloid precursor protein is synthesized by retinal ganglion cells, rapidly transported to the optic nerve plasma membrane and nerve terminals, and metabolized.

We have investigated the synthesis, axonal transport, and processing of the beta-amyloid precursor protein (APP) in in vivo rabbit retinal ganglion cells. These CNS neurons connect the retina to the brain via axons that comprise the optic nerve. APP is synthesized in retinal ganglion cells and is rapidly transported into the optic nerve in small transport vesicles. It is then transferred to the axonal plasma membrane, as well as to the nerve terminals and metabolized with a t1/2 of less than 5 h. A significant accumulation of C-terminal amyloidogenic or nonamyloidogenic fragments is seen in the optic nerve 5 h after [35S]-methionine, [35S]cysteine injection, which disappears by 24 h. The major molecular mass species of APP in the optic nerve is approximately 110 kDa, and is an APP isoform that does not contain a Kunitz protease inhibitor domain. Higher molecular mass species containing this sequence are seen mostly in the retina. A protease(s) that can potentially cleave APP to generate an amyloidogenic fragment is present in the same optic nerve membrane compartment as APP.

Amino Acid Sequence↗
PubMed1992

AAT1, a gene encoding a mitochondrial aspartate aminotransferase in Saccharomyces cerevisiae.

We have isolated a gene, AAT1, encoding an aspartate aminotransferase (AspAT) from a Saccharomyces cerevisiae genomic library. AAT1 encodes a 451 amino acid protein with a predicted molecular weight of 51,687, which is likely to be the yeast mitochondrial AspAT. Sequence comparison of this yeast AspAT with AspATs from other organisms shows a high degree of homology in regions previously shown to be important for catalysis. However, the yeast mitochondrial AspAT contains four obvious insertions with respect to all other known AspATs, suggesting that the AAT1-encoded protein represents a distinct AspAT.

Amino Acid Sequence↗
PubMed1992

The C terminus of the NF-kappa B p50 precursor and an I kappa B isoform contain transcription activation domains.

The p50 subunit of the NF-kappa B transcription complex is derived from the N-terminal half of a larger precursor protein, p105. Although a fair amount is known about functions located within the p50 sequences, less is known about the C-terminal half of p105. In this report, we have identified a potent transcription activation domain located in the C terminus of mouse p105. In addition, the I kappa B beta proteins chicken p40 and human MAD-3, proteins that are related to the p105 C terminus, strongly activated transcription in chicken cells and yeast when fused to GAL4 DNA-binding sequences. Furthermore, chicken p40 is primarily located in the nucleus of chicken cells when overexpressed from a retroviral vector. Our results suggest novel models for the function and regulation of NF-kappa B transcription complexes.

Amino Acid Sequence↗
PubMed1991

Isolation and characterization of rapid transport vesicle subtypes from rabbit optic nerve.

Subcellular fractionation of rabbit optic nerve resolves three populations of membranes that are rapidly labelled in the axon. The lightest membranes are greater than 200 nm and are relatively immobile. The intermediate density membranes consist of 84 nm vesicles which disappear from the nerve with kinetics identical to those of the rapid component. A third population of membranes, displaying a distinct protein profile, is present in the most dense region of the gradient. Immunological characterization of these membranes suggests the following. (1) The lightest peak contains rapidly transported glucose transporter and most of the total glucose transporters present in the nerve; this peak is therefore enriched in axolemma. (2) The intermediate peak contains rapidly transported glucose transporters and synaptophysin, an integral synaptic vesicle protein, and about half of the total synaptophysin; this peak therefore contains transport vesicles bound for both the axolemma and the nerve terminal, and these subpopulations can be separated by immunoadsorption with specific antibodies against the aforementioned proteins. (3) The heaviest peak contains rapidly transported synaptophysin and tachykinin neuromodulators and about half of the total synaptophysin, and 80% of the total tachykinins present in the nerve; this peak appears to represent a class of synaptic vesicle precursor bound for the nerve terminal exclusively. (4) Synaptophysin is present in the membranes of vesicles carrying tachykinins. (5) Both the intermediate and the heaviest peaks are enriched in kinesin heavy chain, suggesting that both vesicle classes may be transported by the same mechanism.

Adenosine Triphosphatases↗
PubMed1989

Low molecular weight GTP-binding proteins are associated with neuronal organelles involved in rapid axonal transport and exocytosis.

Recent evidence suggests that low molecular weight GTP-binding proteins may play important roles in a variety of membrane transport processes. In order to address the question of whether these proteins are involved in transport processes in the nerve axon, we have assessed their presence in rapid transport membranes from rabbit optic nerve. We report the characterization of a group of low molecular weight GTP-binding proteins which are constituents of rapid transport vesicles. Although these proteins are components of rapid transport vesicles, they are apparently not major rapidly transported species. They are localized in cytosolic as well as in membrane fractions of axons, and the membrane-associated form behaves as an integral membrane protein(s). These proteins are also found in association with a variety of vesicular and organellar components of neurons including coated vesicles, synaptic vesicles, synaptic plasma membranes, and mitochondria. We discuss the possible roles of these proteins in rapid axonal transport and exocytosis.

Animals↗
PubMed1978

Scanning electron microscope study on flat type membrane oxygenator after prolonged extracorporeal circulation.

Despite adequate anticoagulation, thrombi may develop onto any foreign surface subjected to circulating blood. Although the efficiency of membrane oxygenators can decrease, distal embolization can be more critical and dangerous. Scanning electron microscope observations carried out on the Travenol Modulung oxygenator used both on dogs and on patients for prolonged partial cardiopulmonary by-pass pointed out the following observations. Caution must be observed when translating the results from dogs to human beings. Heparin management can be delicate and critical. The problem of blood transfusion can be extremely important and must be extensively investigated.

Adult↗
PubMed1977

Implantable artificial lung. Preliminary report.

The ultimate treatment of chronic respiratory insufficiency is pulmonary replacement by an artificial organ, homologous lung transplantation, or chronic paracorporeal respiratory supplementation. The woven capillary membrane oxygenator appears to be a major development toward implantable artificial organs. The four units tested are made up of screens 3.5 by 4.0 cm. of capillary tubing 0.3 mm. I.D. by 0.64 mm. O.D. assembled into rectangular blocks. Units made up by five, ten, twenty, and forty screens have been assembled and tested according to the protocol suggested by Galletti. The maximum oxygen transfer rate with blood was 48 ml. per minute per square meter. Water carbon dioxide transfer rate was 23.1 ml. per minute per square meter. The pressure drops in the liquid phase were 8.5, 15.3, 13.8, 17.6 mm. Hg at 1 L. per minute flow. These results indicate that the woven capillary membrane lung is an acceptably efficient oxygenator. The characteristics of design and performance suggest that this oxygenator can be made to be implanted into the chest or used as a paracorporeal respiratory assistance device.

Artificial Organs↗
PubMed1975

Nature of deposits in a tubular membrane oxygenator after prolonged extracorporeal circulation: a scanning electron microscope study.

Although silicone fibers are among the most compatible with tissue and blood, numerous deposits are observed after their prolonged usage in a capillary membrane oxygenator, even when the blood has been properly heparinized. The scanning electron microscope (SEM) study shows that the morphology of these deposits varies greatly, depending upon the part of the unit from which the sample is taken. The area close to the inlet is the most severely affected. The outlet zone is affected to a lesser degree, and the areas in between are only slightly affected.

Animals↗