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Biomedical subjects

R S Larson

Publications and source records attributed to R S Larson.

15 recordsLinked to original sources
PubMed1990

The leukocyte integrin LFA-1 reconstituted by cDNA transfection in a nonhematopoietic cell line is functionally active and not transiently regulated.

The functional activity of lymphocyte function-associated antigen 1 (LFA-1) on leukocytes can be regulated by T-cell receptor (TCR) stimulation and pharmacologic agents. It was of interest to determine if functionally active LFA-1 could be reconstituted on a nonhematopoietic, LFA-1-negative cell line. We report the expression of LFA-1 and diethylaminoethyl (DEAE) Mac-1 alpha beta heterodimers on the cell surface of a fibroblastoid cell line, COS, by DEAE dextran cotransfection of the alpha and beta subunit cDNAs. Immunoprecipitation studies demonstrated that the alpha and beta subunit was expressed in heterodimers. The alpha or beta subunit was expressed at lower levels after transfection with the alpha or beta subunit cDNA alone. Cotransfection of the alpha and beta subunit cDNAs, but not transfection of alpha or beta alone, was sufficient to reconstitute intercellular adhesion molecule-1 (ICAM-1) binding activity. Consistent with this observation, LFA-1 on the fibroblastoid cells possesses the activation epitope defined by the L16 monoclonal antibody (mAb). This epitope marks the conversion of LFA-1 from the low to high avidity state on peripheral blood T lymphocytes (PBLs) and is constitutively present on activated cell lines. In contrast to LFA-1 on leukocytes, the functional activity of LFA-1 on fibroblastoid cells was not influenced by phorbol ester treatment. Furthermore, the use of agents that interfere with intracellular signaling, a protein kinase C inhibitor, cAMP analogue, or the combination of a phosphodiesterase inhibitor and adenyl cyclase activator, did not affect the binding of COS cells expressing LFA-1 to purified ICAM-1.

Alkaloids↗
PubMed1989

Retinal detachment after neodymium:YAG laser posterior capsulotomy.

We reviewed the records of 397 patients who had undergone Nd:YAG laser posterior capsulotomy between July 1983 and August 1988. Of the 366 eyes that had been followed up for three months or more, 13 (3.6%) developed a retinal detachment after capsulotomy; of these 13 detachments, 11 (84.6%) occurred within the first year. The combination of male gender with axial myopia (greater than or equal to 25.00 mm), a history of lattice degeneration, or a history of retinal detachment in the fellow eye was a significant risk factor for the development of retinal detachment after YAG capsulotomy.

Cataract Extraction↗
PubMed1989

Neodymium:YAG laser zonulysis for treatment of lens subluxation.

Nine eyes with lens subluxation in seven patients (6 patients with Marfan's syndrome, 1 with idiopathic lens subluxation) were treated by neodymium:YAG (Nd:YAG) laser zonulysis. The procedure uses an Nd:YAG laser to lyse the zonules to obtain a clear aphakic visual axis. Pretreatment best-corrected visual acuity was 20/60 or worse in eight eyes (6 eyes less than or equal to 20/200). Movement of the crystalline lens was achieved after zonulysis in all cases (100%), and a clear aphakic visual axis, sufficient to maintain aphakic correction without diplopia or glare, was obtained in eight eyes (88.9%). The procedure was combined with optical iridotomy in three cases (33.3%). Five cases (55.6%) required more than one zonulysis treatment. Visual acuity improved two or more Snellen lines in all but one eye (7 eyes greater than or equal to 20/60). Four cases had complications which included: increased intraocular pressure (IOP), mild iritis, recurrent migration of the lens into the visual axis, and crystalline lens damage. The final two complications necessitated eventual surgical removal of the lens. These results suggest that Nd:YAG laser zonulysis may be of benefit as an alternative treatment modality for selected patients with lens subluxation.

Adult↗
PubMed1989

Primary structure of the leukocyte function-associated molecule-1 alpha subunit: an integrin with an embedded domain defining a protein superfamily.

The leukocyte function-associated molecule 1 (LFA-1, CD11a/CD18) is a membrane glycoprotein which functions in cell-cell adhesion by heterophilic interaction with intercellular adhesion molecule 1 (ICAM-1). LFA-1 consists of an alpha subunit (Mr = 180,000) and a beta subunit (Mr = 95,000). We report the molecular biology and protein sequence of the alpha subunit. Overlapping cDNAs containing 5,139 nucleotides were isolated using an oligonucleotide specified by tryptic peptide sequence. The mRNA of 5.5 kb is expressed in lymphoid and myeloid cells but not in a bladder carcinoma cell line. The protein has a 1,063-amino acid extracellular domain, a 29-amino acid transmembrane region, and a 53-amino acid cytoplasmic tail. The extracellular domain contains seven repeats. Repeats V-VII are in tandem and contain putative divalent cation binding sites. LFA-1 has significant homology to the members of the integrin superfamily, having 36% identity with the Mac-1 and p150,95 alpha subunits and 28% identity with other integrin alpha subunits. An insertion of approximately 200 amino acids is present in the NH2-terminal region of LFA-1. This "inserted/interactive" or I domain is also present in the p150,95 and Mac-1 alpha subunits but is absent from other integrin alpha subunits sequenced to date. The I domain has striking homology to three repeats in human von Willebrand factor, two repeats in chicken cartilage matrix protein, and a region of complement factor B. These structural features indicate a bipartite evolution from the integrin family and from an I domain family. These features may also correspond to relevant functional domains.

Amino Acid Sequence↗
PubMed1989

Neodymium: YAG laser vitreolysis for treatment and prophylaxis of cystoid macular oedema.

Eighteen eyes with vitreous strands adherent to the corneoscleral wound of previous cataract surgery were treated with neodymium: YAG laser to achieve vitreolysis. Twelve eyes were treated for management of cystoid macular oedema (CMO group) and six eyes were treated for prophylaxis of possible CMO (prophylactic group). In the CMO group, visual acuity improved two or more Snellen lines in 10 eyes (83.3%) and seven eyes had a post-laser visual acuity of 20/40 or better (one eye had a pre-treatment visual acuity of 20/40 or better). In the prophylactic group, visual acuity was either maintained at the pre-treatment level or improved in five eyes (83.3%) eighteen months after laser treatment. This procedure was complicated by retinal detachment in one case and elevation of intraocular pressure over 10 mmHg in another case.

Adult↗
PubMed1988

Chromosomal location of the genes encoding the leukocyte adhesion receptors LFA-1, Mac-1 and p150,95. Identification of a gene cluster involved in cell adhesion.

The adhesion receptors Mac-1, LFA-1, and p150,95 are cell surface alpha/beta heterodimers that play a key role in leukocyte adhesion processes. The genes for Mac-1, LFA-1, and p150,95 alpha subunits have been located to chromosome 16 by means of Southern blot analysis using a series of somatic cell hybrids. Chromosomal in situ hybridization has demonstrated that the genes for the three alpha subunits map to the short arm of chromosome 16, between bands p11 and p13.1, defining a cluster of genes involved in leukocyte adhesion. The gene encoding the LFA-1/Mac-1/p150,95 beta subunit, and defective in leukocyte adhesion deficiency, has been located on chromosome 21, band q22. The leukocyte adhesion receptor alpha and beta subunits are mapped to chromosomal regions that have been shown to be involved in cytogenetic rearrangements in certain patients with acute myelomonocytic leukemia and the blast phase of chronic myelogenous leukemia, respectively.

Animals↗
PubMed1988

Terbutaline stimulates aqueous humor flow in humans during sleep.

A randomized, double-masked study of the effect of terbutaline sulfate, a selective beta 2-agonist, on the rate of aqueous humor formation was performed in awake and sleeping normal human subjects. The rate of aqueous formation was measured by fluorophotometry. Both the drug- and placebo-treated eyes showed a statistically significant nocturnal reduction of the flow rate (36% suppression in the terbutaline-treated eyes and 43% suppression in the placebo-treated eyes). Terbutaline had no effect on daytime aqueous flow rates, but stimulated flow by 15% during sleep. The drug had no significant effect on intraocular pressure. This study confirms past observations that beta-agonists exert their maximal effects during sleep, when endogenous adrenergic stimulation is at a minimum.

Adult↗
PubMed1988

Isoproterenol stimulates aqueous flow in humans with Horner's syndrome.

Topical 1 percent isoproterenol in the presence of the phosphodiesterase inhibitor theophylline was tested for its ability to stimulate the rate of aqueous humor flow through the anterior chamber of the normal and the partially adrenergically denervated human eye (Horner's syndrome). Both the affected eye and the unaffected eye were observed to have lower flows at night than during the day. Isoproterenol had no significant effect on flow during the day in normal eyes or in Horner's syndrome, but during sleep this beta-adrenergic agonist increased flow in the normal eye by 34% and in the Horner's eye by 50%. We interpret the results as indicating that beta-adrenergic activity in the human eye can stimulate aqueous formation under some conditions. However, the observed stimulation could have been due to something other than increased beta-adrenergic activity in the ciliary epithelium.

Adrenergic beta-Agonists↗
PubMed1987

cDNA cloning and complete primary structure of the alpha subunit of a leukocyte adhesion glycoprotein, p150,95.

The leukocyte adhesion receptors, p150,95, Mac-1 and LFA-1 are integral membrane glycoproteins which contain distinct alpha subunits of 180,000-150,000 Mr associated with identical beta subunits of 95,000 Mr in alpha beta complexes. p150,95 alpha subunit tryptic peptides were used to specify oligonucleotide probes and a cDNA clone of 4.7 kb containing the entire coding sequence was isolated from a size-selected myeloid cell cDNA library. The 4.7-kb cDNA clone encodes a signal sequence, an extracellular domain of 1081 amino acids containing 10 potential glycosylation sites, a transmembrane domain of 26 amino acids, and a C-terminal cytoplasmic tail of 29 residues. The extracellular domain contains three tandem homologous repeats of approximately 60 amino acids with putative divalent cation-binding sites, and four weaker repeats which lack such binding sites. The cDNA clone hybridizes with a mRNA of 4.7 kb which is induced during in vitro differentiation of myeloid cell lines. The p150,95 alpha subunit is homologous to the alpha subunits of receptors which recognize the RGD sequence in extracellular matrix components, as has previously been shown for the beta subunits, supporting the concept that receptors involved in both cell-cell and cell-matrix interactions belong to a single gene superfamily termed the integrins. Distinctive features of the p150,95 alpha subunit include an insertion of 126 residues N-terminal to the putative metal binding region and a deletion of the region in which the matrix receptors are proteolytically cleaved during processing.

Amino Acid Sequence↗
PubMed1986

Chemical modification of bovine prothrombin fragment 1 in the presence of Tb3+ ions.

The formaldehyde-morpholine method for the conversion of gamma-carboxyglutamyl (Gla) residues to gamma-methyleneglutamyl (gamma-MGlu) residues has been applied to the modification of bovine prothrombin fragment 1. In the absence of Tb3+ ions or at Tb3+ ion concentrations of 2 Km app and 25 Km app the action of 10,000-fold molar excess of formaldehyde and morpholine, pH 5.0, converts the 10 Gla residues of the protein into 10 gamma-MGlu residues. Modification of the protein using the same conditions but increasing the Tb3+ concentration to 100 Km app provided a homogeneous protein containing 3 gamma-MGlu and 7 Gla residues, bovine 3 gamma-MGlu-fragment 1. The modified protein binds the same number of Ca2+ ions (6-7) as bovine fragment 1. However, the positive cooperatively associated with Ca2+ binding is abolished and the overall affinity for Ca2+ ions is reduced. Fluorescence titrations of 3 gamma-MGlu-fragment 1 using either Ca2+ or Mg2+ ions indicate that the modified protein retains a fluorescence quenching behavior similar to that of the native protein. The modified protein does not bind to phosphatidylserine/phosphatidylcholine vesicles in the presence of Ca2+ ions. Thus the metal ion-induced fluorescence transition exhibited by the bovine protein appears to be a necessary but not sufficient condition for phospholipid binding.

Amino Acids↗
PubMed1986

A partial genomic DNA clone for the alpha subunit of the mouse complement receptor type 3 and cellular adhesion molecule Mac-1.

A genomic clone coding for the alpha subunit of the mouse complement receptor type 3 and the cellular adhesion molecule Mac-1 has been isolated directly from a genomic library using synthetic oligonucleotide probes based on the amino-terminal amino acid sequence of the protein. The identity of the clone has been established by DNA sequencing and in vitro translation of hybrid-selected mRNA. The gene is present in a single copy in the murine genome. The region containing the amino-terminal exon has been sequenced. RNA gel blotting shows that the Mac-1 alpha-subunit mRNA is 6 kilobases in length. Mac-1 alpha-subunit mRNA is present in macrophages but not T lymphoma or L cells. During gamma interferon-stimulated maturation of the mouse premyelocytic cell line M1, Mac-1 alpha-subunit mRNA is induced. This corresponds with the tissue distribution of the Mac-1 alpha subunit, showing expression is regulated at least partially at the message level.

Animals↗
PubMedDate not supplied

Viscoelastic agents.

Viscoelastic materials possess a unique set of properties that result from their chemical structure. These properties enable them to protect the corneal endothelium and epithelium from mechanical trauma and to maintain an intraocular space, such as the anterior or vitreous chambers, even in the face of an open incision. Hence viscoelastic materials have been successfully applied to many areas of ophthalmic surgery, most notably anterior segment surgery, with few complications. There are currently three commercially available viscoelastic preparations, and several new preparations are in various stages of development.

Acrylic Resins↗