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Biomedical subjects

K L Wilson

Publications and source records attributed to K L Wilson.

54 records · Page 3Linked to original sources
PubMed1993

Persistent posttraumatic orbital-antral fistula.

The case of a symptomatic persistent orbital--antral fistula after silicone orbital floor reconstruction is presented. Intermittent diplopia with Valsalva maneuvers was the patient's chief complaint. Periorbital cellulitis was a suspected complication of the fistula. This case emphasizes the importance of an often overlooked goal of orbital floor reconstruction, that is, isolation of the orbital cavity from the maxillary sinus. Greater care in positioning alloplastic implants may improve their function. Autogenous materials may be superior in orbital floor reconstruction.

Adult↗
PubMed1993

Reconstruction of composite facial defects: the combined application of multiple reconstructive modalities.

OBJECTIVE: To describe the combined use of craniofacial skeletal reconstruction, tissue expansion and microvascular free tissue transfer in the repair of major composite facial defects. DESIGN: Case series with an integrated team approach. SETTING: Craniofacial unit, university teaching hospital. PATIENTS: Three cases were selected to best illustrate the combined use of the three modalities in reconstruction of acute traumatic, congenital and post-traumatic facial defects. A 15-year-old boy had a shotgun wound to the face; a 23-year-old man had Treacher Collins syndrome; and a 55-year-old woman had a post-traumatic composite defect of the central midface. INTERVENTIONS: Preoperatively, complete neurologic, ophthalmologic and dental examinations, anthropometric analysis, prosthodontic assessment, computed tomography and computer graphics. Operatively, craniofacial exposure followed established surgical principles. Skeletal reconstruction was performed to provide accurate positioning of bony segments and three-dimensional stability. Bone grafting was used when necessary to restore bony continuity and increase stability. Tissue expansion was used to provide more locally available tissue for wound closure and resurfacing composite defects. Microsurgical free tissue transfer was used to provide functional replacement of deficient tissues. RESULTS: The results of the modalities used for reconstruction of these composite facial defects are illustrated for each case described. CONCLUSIONS: The use of multiple modalities, including craniofacial skeletal reconstruction, tissue expansion and free tissue transfer, allow the surgeon to address the specific functional and anatomical requirements associated with composite facial defects that are characterized by a combined deficiency of multiple tissues in the craniofacial region.

Adolescent↗
PubMed1992

A role for ADP-ribosylation factor in nuclear vesicle dynamics.

Two distinct steps in nuclear envelope assembly can be assayed in vitro: the protein-mediated binding of nuclear-specific vesicles to chromatin, and the subsequent fusion of these vesicles to enclose the chromatin within a double nuclear membrane. Nuclear vesicle fusion, like fusion in the secretory pathway, requires ATP and cytosol and is inhibited by nonhydrolysable GTP analogues. The sensitivity of nuclear vesicle fusion to GTP-gamma S requires a GTP-dependent soluble factor, the properties of which are strikingly similar to a GTP-dependent Golgi binding factor (GGBF) that inhibits Golgi vesicle fusion in the presence of GTP-gamma S and belongs to the ADP-ribosylation factor (ARF) family of small GTPases. In the presence of GTP-gamma S, ARF proteins and alpha-, beta-, gamma-, delta-COP ('coatomer') subunits are associated with Golgi transport vesicles, but the exact roles of ARF proteins in secretion are not yet understood. We report here that purified ARF1 and GGBF have GTP-dependent soluble factor activity in the nuclear vesicle fusion assay. Our results show that the function of ARF is not limited to the Golgi apparatus, and indicate that there may be a link between the formation of nuclear vesicles during mitosis and proteins involved in secretion.

ADP-Ribosylation Factor 1↗
PubMed1992

GTP hydrolysis is required for vesicle fusion during nuclear envelope assembly in vitro.

Nuclear envelope assembly was studied in vitro using extracts from Xenopus eggs. Nuclear-specific vesicles bound to demembranated sperm chromatin but did not fuse in the absence of cytosol. Addition of cytosol stimulated vesicle fusion, pore complex assembly, and eventual nuclear envelope growth. Vesicle binding and fusion were assayed by light and electron microscopy. Addition of ATP and GTP to bound vesicles caused limited vesicle fusion, but enclosure of the chromatin was not observed. This result suggested that nondialyzable soluble components were required for nuclear vesicle fusion. GTP gamma S and guanylyl imidodiphosphate significantly inhibited vesicle fusion but had no effect on vesicle binding to chromatin. Preincubation of membranes with 1 mM GTP gamma S or GTP did not impair vesicle binding or fusion when assayed with fresh cytosol. However, preincubation of membranes with GTP gamma S plus cytosol caused irreversible inhibition of fusion. The soluble factor mediating the inhibition by GTP gamma S, which we named GTP-dependent soluble factor (GSF), was titratable and was depleted from cytosol by incubation with excess membranes plus GTP gamma S, suggesting a stoichiometric interaction between GSF and a membrane component in the presence of GTP gamma S. In preliminary experiments, cytosol depleted of GSF remained active for fusion of chromatin-bound vesicles, suggesting that GSF may not be required for the fusion reaction itself. We propose that GTP hydrolysis is required at a step before the fusion of nuclear vesicles.

Animals↗
PubMed1992

Phosphorylation of myosin-II regulatory light chain by cyclin-p34cdc2: a mechanism for the timing of cytokinesis.

To understand how cytokinesis is regulated during mitosis, we tested cyclin-p34cdc2 for myosin-II kinase activity, and investigated the mitotic-specific phosphorylation of myosin-II in lysates of Xenopus eggs. Purified cyclin-p34cdc2 phosphorylated the regulatory light chain of cytoplasmic and smooth muscle myosin-II in vitro on serine-1 or serine-2 and threonine-9, sites known to inhibit the actin-activated myosin ATPase activity of smooth muscle and nonmuscle myosin (Nishikawa, M., J. R. Sellers, R. S. Adelstein, and H. Hidaka. 1984. J. Biol. Chem. 259:8808-8814; Bengur, A. R., A. E. Robinson, E. Appella, and J. R. Sellers. 1987. J. Biol. Chem. 262:7613-7617; Ikebe, M., and S. Reardon. 1990. Biochemistry. 29:2713-2720). Serine-1 or -2 of the regulatory light chain of Xenopus cytoplasmic myosin-II was also phosphorylated in Xenopus egg lysates stabilized in metaphase, but not in interphase. Inhibition of myosin-II by cyclin-p34cdc2 during prophase and metaphase could delay cytokinesis until chromosome segregation is initiated and thus determine the timing of cytokinesis relative to earlier events in mitosis.

Amino Acid Sequence↗
PubMed1992

The effects of dexamethasone on fibronectin expression in cultured human trabecular meshwork cells.

Topical administration of glucocorticoids to the eye can lead to the development of ocular hypertension. This increase in intraocular pressure is caused by the heightened resistance to flow of aqueous humor from the eye, presumably at the trabecular meshwork (TM). This study reports the effects of dexamethasone (DEX) on the expression of the extracellular matrix protein fibronectin (FN) in cultured human TM cells (HTM). The expression of FN was evaluated in four HTM cell strains by epifluorescence microscopy and immunoblotting and autofluorography of electrophoretically separated cell proteins. There was a heterogeneous response of the four cell strains tested. Treatment of cell strain HTM4 with DEX (10(-7) mol/l) for 17 d caused an approximate doubling of cell-associated and secreted FN. This DEX-induced increase in FN expression was progressive after the first 7 d of treatment and was blocked partially with a glucocorticoid antagonist, cortexolone. By contrast, DEX treatment induced an intermediate 50-60% increase in FN expression in cell strains HTM10 and HTM2; in HTM6, FN was unchanged after exposure to the glucocorticoid. This model system may be useful to examine molecular changes associated with corticosteroid-induced ocular hypertension and evaluate glaucomatous changes in the TM because increased FN deposition occurs in the aqueous humor outflow pathway of patients with open-angle glaucoma.

Adolescent↗
PubMed1990

A lamin-independent pathway for nuclear envelope assembly.

The nuclear envelope is composed of membranes, nuclear pores, and a nuclear lamina. Using a cell-free nuclear assembly extract derived from Xenopus eggs, we have investigated how these three components interact during nuclear assembly. We find that the Xenopus embryonic lamin protein LIII cannot bind directly to chromatin or membranes when each is present alone, but is readily incorporated into nuclei when both of the components are present together in an assembly extract. We find that depleting lamin LIII from an extract does not prevent formation of an envelope consisting of membranes and nuclear pores. However, these lamin-depleted envelopes are extremely fragile and fail to grow beyond a limited extent. This suggests that lamin assembly is not required during the initial steps of nuclear envelope formation, but is required for later growth and for maintaining the structural integrity of the envelope. We also present results showing that lamins may only be incorporated into nuclei after DNA has been encapsulated within an envelope and nuclear transport has been activated. With respect to nuclear function, our results show that the presence of a nuclear lamina is required for DNA synthesis to occur within assembled nuclei.

Animals↗
PubMed1989

Xenorhabdus luminescens (DNA hybridization group 5) from human clinical specimens.

An unusual isolate from a human leg wound was identified as Xenorhabdus luminescens. This finding led to the discovery or isolation of four additional strains, two from blood and two from wounds. Three of the five strains were from patients in San Antonio, Tex. Three strains were studied by DNA-DNA hybridization (S1 nuclease-trichloroacetic acid method) and were 77 to 100% related to each other, 34% related to the type strain of X. luminescens, 35 to 40% related to three of Grimont's other DNA hybridization groups of X. luminescens, and 9% related to the type strain of Xenorhabdus nematophilus. The new group of five strains was designated X. luminescens DNA hybridization group 5. All five strains were very inactive biochemically and fermented only D-glucose and D-mannose. The key reactions for recognizing this new organism are yellow pigment production, negative test for nitrate reduction to nitrite, weak bioluminescence (10 to 15 min of dark adaptation is required to see the weak light produced), and a unique hemolytic reaction on sheep blood agar plates incubated at 25 degrees C. Two case histories of strains from wounds are given; these suggest that X. luminescens DNA hybridization group 5 may be a new bacterial agent that causes wound infections. The two cases of wound infection, along with the two blood isolates, suggest that the new organism is clinically significant.

Aged↗
PubMed1988

A trypsin-sensitive receptor on membrane vesicles is required for nuclear envelope formation in vitro.

The reformation of functioning organelles at the end of mitosis presents a problem in vesicle targeting. Using extracts made from Xenopus laevis frog eggs, we have studied in vitro the vesicles that reform the nuclear envelope. In the in vitro assay, nuclear envelope growth is linear with time. Furthermore, the final surface area of the nuclear envelopes formed is directly dependent upon the amount of membrane vesicles added to the assay. Egg membrane vesicles could be fractionated into two populations, only one of which was competent for nuclear envelope assembly. We found that vesicles active in nuclear envelope assembly contained markers (BiP and alpha-glucosidase II) characteristic of the endoplasmic reticulum (ER), but that the majority of ER-derived vesicles do not contribute to nuclear envelope size. This functional distinction between nuclear vesicles and ER-derived vesicles implies that nuclear vesicles are unique and possess at least one factor required for envelope assembly that is lacking in other vesicles. Consistent with this, treatment of vesicles with trypsin destroyed their ability to form a nuclear envelope; electron microscopic studies indicate that the trypsin-sensitive proteins is required for vesicles to bind to chromatin. However, the protease-sensitive component(s) is resistant to treatments that disrupt protein-protein interactions, such as high salt, EDTA, or low ionic strength solutions. We propose that an integral membrane protein, or protein tightly associated with the membrane, is critical for nuclear vesicle targeting or function.

Animals↗
PubMed1987

STE16, a new gene required for pheromone production by a cells of Saccharomyces cerevisiae.

Genes required for mating by a and alpha cells of Saccharomyces cerevisiae (STE, "sterile," genes) encode products such as peptide pheromones, pheromone receptors, and proteins responsible for pheromone processing. a-specific STE genes are those required for mating by a cells but not by alpha cells. To identify new a-specific STE genes, we have employed a novel strategy that enabled us to determine if a ste mutant defective in mating as a is also defective in mating as alpha without the need to do crosses. This technique involved a strain (K12-14b) of genotype mata1 HML alpha HMR alpha sir3ts, which mates as a at 25 degrees and as alpha at 34 degrees. We screened over 40,000 mutagenized colonies derived from K12-14b and obtained 28 a-specific ste mutants. These strains contained mutations in three known a-specific genes--STE2, STE6 and STE14--and in a new gene, STE16. ste16 mutants are defective in the production of the pheromone, a-factor, and exhibit slow growth. Based on the distribution of a-specific ste mutants described here, we infer that we have identified most if not all nonessential genes that can give rise to a-specific mating defects.

Crosses, Genetic↗
PubMed1986

Sequences upstream of the STE6 gene required for its expression and regulation by the mating type locus in Saccharomyces cerevisiae.

The STE6 gene of Saccharomyces cerevisiae is an a-specific gene; it is repressed in alpha cells by the alpha 2 product of the mating type locus. To study the role of sequences upstream of STE6 in its regulation and expression, we have determined the DNA sequence of the promoter region, identified the start sites for the STE6 transcript, and identified sequences governing its transcription. Deletions that remove DNA upstream of the STE6 gene were produced and assayed for effects on regulation and expression. The deletions defined two intervals upstream of the STE6 transcription initiation sites. One contains all or part of a negative element; the other contains all or part of a positive element. The negative element is required for repression of STE6 by alpha 2: deletions lacking this element express STE6 constitutively. Such deletions remove a 31-base-pair site, located 135 base pairs upstream of the first transcript start site, that is highly homologous to sites present in the upstream regions of four other genes repressed by alpha 2. These sites are presumably responsible for repression of the a-specific genes by alpha 2. The positive element (a putative upstream activation site) is required for expression of STE6. The deletions define the left boundary of the proposed upstream activation site. Sequence homologies between STE6 and other a-specific genes are found in this region and may mediate activation of this set of genes.

Base Sequence↗
PubMed1984

Negative regulation of STE6 gene expression by the alpha 2 product of Saccharomyces cerevisiae.

The alpha 2 product of the alpha mating type locus of Saccharomyces cerevisiae is proposed to be a negative regulator of a set of dispersed genes concerned with specialized properties of a cells. This set of genes includes those, termed a-specific STE genes (STE2, STE6, and STE14), which are required for mating by a cells but not by alpha cells. We cloned the STE6 gene to determine whether its expression is limited to a cells and, if so, whether its expression is inhibited in alpha cells by the alpha 2 product. Expression of STE6 was assayed in two ways: by blot hybridization, RNA and by beta-galactosidase activity in strains carrying a STE6-lacZ hybrid gene. We found that STE6 expression was limited to a cells and was negatively regulated by the alpha 2 product. STE6 RNA was not detectable in strains containing the wild-type alpha 2 gene product. Expression of STE6 was at least 150-fold lower in alpha cells than in a cells, based on beta-galactosidase activities in a and alpha cells carrying the STE6-lacZ gene. These results confirmed that the alpha 2 product is a negative regulator of gene expression and showed that it acts at the level of RNA production. We also examined the phenotype of a mutant carrying an insertion mutation of the STE6 gene, the ste6::lacZ allele. In addition, an a-specific defect in mating, this mutant was greatly reduced (but not completely deficient) in a-factor production. Other phenotypes characteristic of a cells--Barrier activity, agglutination, and response to alpha-factor--were normal. STE6 thus appears to be necessary for biosynthesis of a-factor.

Cloning, Molecular↗
PubMed1977

Distance distortions in memory for spatial locations.

The present study examined developmental differences in the effect of route extensity on the memory for the locations of objects in a spatial array. Kindergarten and adult subjects were trained to remember the locations of 4 objects. During this training, objects were either connected by a combination of indirect, looped train tracks and direct train tracks (experimental subjects) or connected by entirely direct train-track routes (control subjects). Analyses of actual interobject distances, from subjects' reproductions of object locations on a response board (without train tracks), revealed that children, but not adults, distort distance in terms of the nature of travel observed between objects. Further testing revealed that differences in the amount of time taken for travel could not account for the results obtained with children.

Adult↗
PubMed1976

Nicotine-like actions of cis-metanicotine and trans-metanicotine.

The actions of the cis- and trans-isomers of metanicotine were observed on isolated rabbit aortic strips and ileal segments. The data are interpreted as showing a nicotine-like action on these preparations for both cis-metanicotine and trans-metanicotine. This hypothesis is supported in part by the demonstration that the action of the metanicotine isomers was affected by hexamethonium, cocaine, phenotolamine, reserpine and atropine in a manner similar to that previously seen in studies with nicotine. In dose-response studies on the aortic strip, trans-metanicotine was significantly less active than nicotine. cis-Metanicotine in turn was less active than trans-metanicotine and nicotine. Additionally, four pyridino compounds, 3-pyridylacet acid, N-(3 pyridlyacetyl) glycine, nicotinuric acid and trans-4-(3-pyridyl)-3-butenoic acid, were tested for both agonist and antagonist activity. No stimulatory activity was found with these compounds in either the aortic strip or ileal preparations. In aortic strip preparations, pretreatment with either 3-pyridylacetic acid or N-(3-pyridylacetyl) glycine provided a moderate to marked reduction in the contractile response to trans-metanicotine, whereas pretreatment with trans-4-(3-pyridyl)-3-butenoic acid caused a slight reduction.

Animals↗
PubMedDate not supplied

TPEN, a Zn2+/Fe2+ chelator with low affinity for Ca2+, inhibits lamin assembly, destabilizes nuclear architecture and may independently protect nuclei from apoptosis in vitro.

We used Xenopus egg extracts to examine the effects of TPEN, a chelator with strong affinities for Zn2+, Fe2+, and Mn2+, on nuclear assembly in vitro. At concentrations above 1 mM, TPEN blocked the assembly of the nuclear lamina and produced nuclei that were profoundly sensitive to stress-induced balloon-like 'shedding' of nuclear membranes away from chromatin-associated membranes. TPEN-arrested nuclei were also defective for DNA replication, which could be explained as secondary to the lack of a lamina. Imaging of TPEN-arrested nuclei by field emission in-lens scanning electron microscopy (FEISEM) revealed clustered, structurally-perturbed nuclear pore complexes. TPEN-arrested nuclei were defective in the accumulation of fluorescent karyophilic proteins. All detectable effects caused by TPEN were downstream of the effects of BAPTA, a Ca2+/Zn2+ chelator that blocks pore complex assembly at two distinct early stages. Surprisingly, TPEN-arrested nuclei, but not control nuclei, remained active for replication in apoptotic extracts, as assayed by [32P]-dCTP incorporation into high molecular weight DNA, suggesting that TPEN blocks a metal-binding protein(s) required for nuclear destruction during programmed cell death.

Animals↗