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Biomedical subjects

A Kaplan

Publications and source records attributed to A Kaplan.

At least 19 recordsLinked to original sources
PubMed1992

A sequence in beta-hexosaminidase from Dictyostelium discoideum required for sorting of proteins to a compartment involved in developmentally induced secretion.

To study the sorting of proteins in Dictyostelium discoideum, we used vector constructs that contain cDNA coding for the entire beta-hexosaminidase protein to prepare transformants of a mutant that lacks this enzyme activity. These transformants overexpressed active, normally processed beta-hexosaminidase. The overexpressed enzyme colocalized with other acid hydrolases in the soluble fraction of vesicles in the lysosomal region of Percoll gradients. The sorting of other hydrolases was unaltered. We also prepared transformants with constructs that contain 22 (Hex 22-Inv), 70 (Hex 70-Inv), and 532 (Hex 532-Inv) amino-terminal amino acids from beta-hexosaminidase fused in frame with the coding sequence for the yeast SUC2 gene product, invertase. Fusion molecular masses were those expected for fully N-glycosylated proteins. Hex 22-Inv was rapidly (t1/2 less than 30 min) and quantitatively secreted. The others were slowly (t1/2 greater than 5 h) and partially secreted. Each expressed invertase activity. During growth, the invertase activity of Hex 70-Inv and Hex 532-Inv was retained to the same extent as that of endogenous lysosomal enzymes. Most of the Hex 70-Inv migrated in Percoll gradients with vesicles of intermediate density (d = 1.055), but a portion co-migrated with lysosomal enzymes at d = 1.08. Hex 70-Inv was sulfated, and its N-glycosides were resistant to endoglycosidase H, indicating Golgi processing. Hex 70-Inv and Hex 532-Inv, like endogenous lysosomal enzymes, were subject to developmentally induced secretion.

Animals↗
PubMed1992

Comparative evaluation of the elasticity and flexibility of bioimpregnated knitted grafts.

Longitudinal elasticities of whole human blood clot, whole canine blood clot, Factor XIII cross-linked fibrin, glutaraldehyde-fixed human albumin, and formaldehyde-fixed collagen, gelatin and collagen/gelatin were determined and normalized to human whole blood clot. Matrices of a knitted Dacron graft were then impregnated with albumin, collagen, and collagen/gelatin and their longitudinal elasticities were determined and normalized to a preclotted graft. Comparisons were also made for the longitudinal elasticities of a virgin graft, a manipulated control for a preclotted graft, and a manipulated control for the matrix-impregnated grafts. Flexibilities were then calculated based on the weights and elasticities of these grafts and normalized to the flexibility of the preclotted graft. Fibrin had twice and 39 times more longitudinal elasticity than human blood clot and collagen, respectively. The preclotted graft has longitudinal elastic properties similar to a virgin graft, and is 2.8, 2, and 1.4 times more elastic than the albumin, collagen and collagen/gelatin grafts, respectively. The preclotted graft was 2.5, 2, and 1.4 times more flexible than the albumin, collagen and collagen/gelatin grafts, respectively.

Albumins↗
PubMed1991

Alcohol and other drugs: the response of the political and medical institutions.

Formal and informal social control in shaping individual behaviors toward the use of alcohol and other drugs is discussed. Emphasis is placed on formal social control as it occurs in two major institutions. The state, which embodies the political and legal structures of the society is discussed in terms of the social control of some of the consequences of drinking, such as public drunkenness, alcoholism, operating vehicles with specific blood alcohol levels, and crime and alcohol use. The medical institution's involvement in alcohol and drug control is discussed in terms of the physician's role in diagnosing alcohol and drug dependent individuals. Two contemporary cases, those of pregnant addicts and alcohol-related organ transplant patients, illustrate the significant interactions between the responses of the political and medical institutions, and the broader influences that help shape these responses.

Alcoholism↗
PubMed1990

Methaemoglobinaemia due to accidental sodium nitrite poisoning. Report of 10 cases.

Nitrates and nitrites are widely used in the food and chemical industry. Poisoning with these agents may be potentially life-threatening as a result of the production of methaemoglobin. A group of 10 patients suffering from moderate to severe methaemoglobinaemia after accidental intoxication with a sodium nitrite salt is described. One patient died but the other 9 recovered rapidly. The low mortality rate was attributed to prompt diagnosis and institution of appropriate therapy with methylene blue and ascorbic acid.

Adult↗
PubMed1989

Characteristics of the sulfation of N-linked oligosaccharides in vesicles from Dictyostelium discoideum: in vitro sulfation of lysosomal enzymes.

Lysosomal enzymes from Dictyostelium discoideum contain unusual sulfated N-linked oligosaccharides, whose synthesis has been well studied in vivo. However, little is known about the properties of the pertinent sulfotransferases. To study these transferases, we have prepared a cell-free system which transfers 35SO4 from 3'-phosphoadenosine 5'-phosphosulfate to either endogenous or exogenous acceptors. We found that the 35SO4 was released from macromolecules by protein N-glycanase F to yield a mixture of anionic oligosaccharides with 1-6 negative charges. Some of the labeled molecules contained acid-stable methyl phosphodiesters but none contained phosphomoesters or acid-labile diesters. The sulfate was found in molecules with the acid stability characteristic of esters of primary alcohols. In all these ways, the products resembled those generated in vivo. We also demonstrated that a membrane-associated form of beta-hexosaminidase and the precursor of alpha-mannosidase were among the products. In addition, glycoproteins prepared from a sulfation-deficient mutant strain could act as exogenous acceptors in permeabilized vesicles.

Chromatography, Ion Exchange↗
PubMed1989

The 5'-flanking region of the gene encoding the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase is crucial for growth of the cyanobacterium Synechococcus sp. strain PCC 7942 at the level of CO2 in air.

Transformation of the high-CO2-requiring mutants (hcr) O221 and E1 derived from the cyanobacterium Synechococcus sp. strain PCC 7942 by a wild-type DNA library restored their ability to grow at the level of CO2 in air. A plasmid (pE12) containing a 10-kilobase DNA insert was rescued from a O221 heterogenote and proved to transform both O221 and E1 to the wild-type phenotype. The capacity of the pE12 subclones to confer the wild-type phenotype to O221 transformants enabled the mapping of the mutation in O221 (designated hcrO221) within a 232-base-pair PstI-BstXI DNA restriction fragment. Sequence analysis revealed two open reading frames (ORFs) at positions -1745 to -1262 (ORFI) and -1218 to -393 (ORFII) upstream of the rbcL gene. A 3-kilobase PstI fragment of O221 was cloned, and hcrO221 was found to be a point mutation within the PstI-BstXI region -1309 nucleotides upstream of the rbcL gene. The significance of this flanking region for adaptation to air levels of CO2 was further demonstrated by the generation of new hcr mutants following insertional inactivation of wild-type DNA in the BstXI site. Electron microscopy revealed aberrant carboxysome structures in growing cells of the hcr mutants, a defect that was possibly related to the mutation, since transformation with pE12 derivatives restored the carboxysome structure to normal.

Air↗
PubMed1978

Receptor-mediated uptake of lysosomal enzymes.

This paper reviews the evidence for two different forms of carbohydrate-mediated recognition of lysosomal enzymes by cell surface receptors. The recognition marker on lysosomal enzymes which are rapidly pinocytosed by fibroblasts contains phosphate, probably linked to D-mannose as a phosphomannosyl moiety. The fraction of lysosomal hydrolases bearing this recognition marker for fibroblasts varies, depending on the tissue source. Another form of recognition accounts for rapid plasma clearance of infused lysosomal enzymes in the rat. This rapid clearance is mediated by receptors on Kupffer cells and other reticuloendothelial cells that recognize mannosyl residues on the glycoprotein hydrolases.

Animals↗
PubMed1977

Purification and properties of a triacylglycerol lipase from Mycobacterium phlei.

In order to study the metabolism of triacylglycerol in mycobacteria, an intracellular particulate triacylglycerol lipase (EC 3.1.1.3) was purified 800-fold from stationary phase cells of Mycobacterium phlei. Extraction of whole cell suspensions with 5% Triton X-100, followed by ion-exchange chromatography of the extract on two successive DEAE-cellulose columns produced a preparation which was nearly homogeneous by the criterion of analytical isoelectric focusing in acrylamide gels (one band, pI. 3.8) and by polyacrylamide gel electrophoresis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved the preparation into six protein bands. Lipase activity stable to electrophoresis in sodium dodecyl sulfate was extracted from the 40 000 molecular weight region of the gels. ith phosphate or maleate buffer the enzyme exhibits a broad pH optimum around 6.0 with sigmoid saturation kinetics (Hill number 2), and an apparent Km of 8.8 mM for tripalmitoylglycerol. Citrate and other carboxylic acids increase the apparent V up to 3-fold with the Hill number approaching 1.0. In a series of p-nitrophenyl esters tested (C2-C18), p-nitrophenylmyristate was hydrolyzed most rapidly. The saturation curve for p=nitrophenylmyristate was sigmoid and unaffected by citrate. The role of this activity in the metabolism of triacylglycerols by Mycobacteria is discussed.

Anions↗
PubMed1977

Immunotherapy with autologous white cell infusions ("lymphocytes") in the treatment of recurrrent glioblastoma multiforme: a preliminary report.

Autologous leukocytes (10(7) to 10(9)), obtained with the Haemonetic's Leukaphoresis apparatus, were inoculated directly into recurrent glioblastoma tumors via indwelling catheters or by direct intratumoral injection through existing craniotomy openings. The rational use for autologous leukocyte (lymphocyte) infusions was based on in vitro autologous lymphocyte cytotoxicity to glioblastoma cells in the absence of serum inhibitory factors. Seven of 17 patients treated had life expectancy under 1 month; all patients had received definitive surgery, and all but two received radiation, nitrosourea chemotherapy and/or dexamethasone, and showed evidence of clinically recurrent disease. Following autologous leukocyte infusion (lymphocyte/granulocyte ratio 1:1), eight patients sustained clinical improvement and were alive up to 17 months later. No neurotoxicity ascribable to the procedure has been observed. One patient, who was comatose at the time of single leukocyte infusion, returned to full activity and lived for 17 months without an increase in tumor mass by brain scan. These results suggest that infusions of autologous leukocytes (lymphocyte-monocytes) directly into glioblastoma may be a viable additional treatment for glioblastoma and certainly warrants further evaluation.

Adult↗
PubMed1977

Phosphohexosyl components of a lysosomal enzyme are recognized by pinocytosis receptors on human fibroblasts.

Human beta-glucuronidase (beta-D-glucuronide glucuronosohydrolase, EC 3.2.1.31), like many other glycoprotein lysosomal hydrolases, is specifically taken up from the culture medium by human fibroblasts. Prior work has indicated that the enzyme exhibits charge heterogeneity and that "high-uptake" forms, i.e., those rapidly internalized by human fibroblasts, are more acidic than slowly internalized forms. Here we present two lines of evidence that the acidic group required for the high-uptake property of certain forms of the enzyme is a phosphate on, or in proximity to, a D-mannose-type carbohydrate. The first line of evidence was obtained from analysis of inhibition of enzyme pinocytosis by yeast mannans, phosphorylated sugars, and sugars. Mannans that contained phosphate were more potent inhibitors than those that did not contain phosphate. D-Mannose 6-phosphate was a more potent inhibitor than either D-mannose 1 phosphate or 2-deoxy-D-glucose 6-phosphate. D-Mannose and certain related sugars were weak pinocytosis inhibitors, while 2- and 4-epimers of mannose were noninhibitory. Competitive inhibition was demonstrated and the apparent Kis estimated for the following compounds: Saccharomyces cerevisiae mannan from mutant X2180-mnnl, 3 X 10(-6) M; mannan from wild-type S. cerebisiae, 3 X 10(-5) M; D-mannose 6-phosphate, 6 X 10(-5) M; L-fucose, 4 X 10(-2) M; and D-mannose, 6 X 10(-2) M. The second line of evidence comes from the observation that alkaline phosphatase [orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] treatment of human platelet beta-glucuronidase abolished its "high-uptake" activity, without diminishing its catalytic activity, and converted some forms of the heterogeneous enzyme to less acidic forms.

Alkaline Phosphatase↗
PubMed1977

Phosphohexosyl recognition is a general characteristic of pinocytosis of lysosomal glycosidases by human fibroblasts.

We recently presented data showing that mannose-6-phosphate was a potent competitive inhibitor of pinocytosis of human platelet beta-glucuronidase, and that treatment of "high-uptake" forms of the enzyme with alkaline phosphatase destroyed the high-uptake property of the enzyme without diminishing its catalytic activity. These data indicate that phosphate is a necessary component of the recognition marker on the enzyme for pinocytosis by human fibroblasts, and suggest that the phosphate on high-uptake forms of the enzyme is present as a phosphohexosyl moiety. Results presented here show that mannose-6-phosphate is also a potent inhibitor of pinocytosis of the following enzyme preparations: (a) beta-glucuronidase from human spleen, liver, placenta, and urine; (b) beta-hexosaminidase and beta-galactosidase from human platelets; (c) beta-hexosaminidase from human fibroblast secretions. Alkaline phosphatase treatment of all these enzymes except beta-galactosidase, which was unstable to the incubation conditions and could not be tested, greatly diminished the uptake activity of the enzymes without diminishing their catalytic activity. These results suggest that phosphohexosyl recognition is a general characteristic of pinocytosis of lysosomal glycosidases.

Alkaline Phosphatase↗
PubMed1976

Four-phase study of computer-assisted and slide-tape methods of stimulating clinical endodontic problems.

1. Computer-assisted instruction of stimulated clinical endodontic problems is superior to a slide-tape presentation for test selection but not for diagnosis and treatment planning. 2. The lack of a difference in diagnosis is likely due to the already superior performance of students in diagnosis at the University of Kentucky without computer assistance. A study with students of less background might reveal a difference in presentation methods. 3. Students with high GPSs score higher on a written test of endodontic clinical judgment. 4. Reliable results on the effects of a human tutor's supplementing machine instruction were not obtained. 5. Students felt that the problems presented in this study were useful in preparing for clinical treatment of patients. 6. After some exposure to machine methods of instruction, students divided into three sizable groups, one preferring a human teacher, another preferring a machine, and the third having no preference. The decision to use only machine or human instruction cannot then be made from student attitudes. 7. Students liked the active participation and immediate responses of the computer but not the time necessary to complete the problems. 8. Students liked the self-pacing, speed, and convenience of the slide-tape method but not the incompleteness of the problems presented by this method. 9. It appears that there is some justification from this study for offering both slide-tape and computer-assisted presentations to students.

Attitude↗