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Biomedical subjects

A Kaplan

Publications and source records attributed to A Kaplan.

At least 19 recordsLinked to original sources
PubMed1995

The genomic region of rbcLS in Synechococcus sp. PCC 7942 contains genes involved in the ability to grow under low CO2 concentration and in chlorophyll biosynthesis.

Several genes involved in the ability of Synechococcus sp. PCC 7942 to grow under different CO2 concentrations were mapped in the genomic region of rbcLS (the operon encoding the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase). Insertion of a cartridge encoding kanamycin resistance within open reading frame (ORF) 78, designated ccmJ, located 7 kb upstream of rbcLS, resulted in a kanamycin-resistant, high-CO2-requiring mutant, M3, which does not contain normal carboxysomes. ccmJ shows significant homology to csoS1 encoding a carboxysomal shell polypeptide in Thiobacillus neopolitanus. Analysis of the polypeptide pattern of a carboxysome-enriched fraction indicated several differences between the wild type and the mutant. The amount of the ribulose-1,5-bisphosphate carboxylase/oxygenase subunits was considerably smaller in the carboxysomal fraction of the mutant when compared to the wild type. On the basis of the sequence analyses, ORF286 and ORF466, located downstream of ccmJ, were identified as chlL and chlN, respectively, which are involved in chlorophyll biosynthesis in the dark.

Algal Proteins↗
PubMed1995

Apheresis technologies: an international perspective.

The developments in apheresis techniques and their clinical applications world-wide are technologically driven. In the past, apheresis survey statistics have high-lighted both the differences by region in clinical practice and in the types of technologies utilized. Such differences have provided a basis for the scientific and clinical assessments of these apheresis technologies and their clinical outcomes and have stimulated the marketing and business development of new technologies world-wide. A review of the regional practices and technologies utilized provides a perspective on the future role of apheresis and its developments in clinical practice. While technology is a driving force for the development of new techniques for clinical practice, it is not the only market force. For technology introduction, several other important issues need to be considered. Regulations at the local and, most importantly, the federal level impact the timing for new technology introduction. Reimbursement by healthcare payers is critically important from the initiation of the development of a technology through its clinical use. Clinical trials are critically important to show the safety and clinical- and cost-effectiveness of the technology in order for payers to provide reimbursement for its use, but these trials are sometimes long and costly. Research funding availability at the governmental and commercial levels critically impacts new technology investigation and its introduction. Apheresis technology developments offer new hopes and promises for the clinical team; however, their development, introduction, and utilization will be influenced by the prevailing market forces.

Blood Component Removal↗
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↗
PubMed1988

Molecular cloning of the cDNA which encodes beta-N-acetylhexosaminidase A from Dictyostelium discoideum. Complete amino acid sequence and homology with the human enzyme.

beta-N-Acetylhexosaminidase A (EC 3.2.1.52), the product of the nag A gene, is a lysosomal enzyme which is developmentally regulated in Dictyostelium discoideum. The enzyme plays a role during the slug stage of development in the maintenance of pseudoplasmodia of normal size. We used a homogeneous preparation of deglycosylated enzyme subunits to generate antibody. The antibody was suitable for screening a lambda gt11 cDNA expression library derived from the mRNA of late log stage axenic cells. We isolated seven positive clones. One of these contains the complete coding sequence of the protein. We also isolated a genomic clone which contains 800 base pairs of 5'-flanking sequence and 728 base pairs of coding sequence. Analysis of the sequences and of primer extension studies indicates an inferred transcript size of 1665 bases which closely matches the 1.8-kilobase mRNA size estimated by Northern blot analysis of poly(A+) mRNA from the organism. The sequence contains an open reading frame which encodes a protein of 59,787 kDa. This equals the apparent molecular weight in sodium dodecyl sulfate-polyacrylamide gels of in vitro translated enzyme. The amino terminus of the purified enzyme appeared to be blocked, but internal peptide sequences were obtained by automated Edman degradation of gel-purified peptides generated by treatment of protein subunits with staphylococcal V-8 protease. These sequences are included in the inferred sequence. In addition to a typical signal sequence, the open reading frame encodes a second candidate transmembrane region, a serine-rich region, and four potential N-glycosylation sites. These are discussed with regard to the localization and processing of the enzyme during its biogenesis. Beginning at amino acid 100 of the Dictyostelium enzyme sequence, 36% of its amino acids are identical to the corresponding sequence of the beta chain, and 33% are identical with those of the alpha chain of human beta-N-acetylhexosaminidase. This is strong evidence that the Dictyostelium enzyme is homologous to the alpha and beta chains of the human enzyme.

Amino Acid Sequence↗
PubMed1988

Corynebacterium aquaticum infection in a patient with chronic granulomatous disease.

Patients with chronic granulomatous disease are uniquely susceptible to infection with catalase-producing bacteria. Staphylococcus aureus, Klebsiella, Escherichia coli and Serratia marcescans are common infecting organisms. A 17-month-old boy with Corynebacterium aquaticum bacteremia is reported. This is only the third documented infection with this non-JK diphtheroid and the first case infection in a patient with chronic granulomatous disease. It is likely that our patient's underlying immune defect predisposed him to infection with this unusual, catalase-producing organism. Although these bacteria are common contaminants and rarely infecting agents, true infection should be considered in patients with chronic granulomatous disease from whom a diphtheroid is isolated.

Corynebacterium↗