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Biomedical subjects

D R Sonneborn

Publications and source records attributed to D R Sonneborn.

16 recordsLinked to original sources
PubMed1999

Health insurance characteristics and health care evaluations among persons with rheumatic diseases in California.

OBJECTIVE: To describe the health insurance characteristics of a sample of persons with rheumatic diseases, to review their evaluations of health care, and to identify the health insurance characteristics associated with those evaluations. METHODS: Data were obtained from a mail survey of a random sample of persons (n = 2,484) on mailing lists of participating rheumatic disease organizations. The survey included specific aspects of health insurance coverage, demographic and health status information, and evaluations of health care. RESULTS: In California, managed care plans (MCPs) were providing health care to 59% of respondents under age 65. Among respondents under age 65, prescription drug coverage was almost universal, 60% had seen a plan rheumatologist, and 17% had been unable to obtain referrals to specialists (with significantly more respondents in MCPs reporting this problem). Among respondents age > or =65, 37% had seen a plan rheumatologist, and 11% reported being unable to obtain referrals to specialists. Overall, drug coverage was less common in this age group, although 90% of those in MCPs had drug coverage. Relatively few respondents in either age group knew about coverage for physical or occupational therapy or for assistive devices. Patient evaluations were more positive for non-MCPs. Limitation in access to physicians was the strongest predictor of poor evaluations of health plans and physician care. Having seen a plan rheumatologist was associated with more positive evaluations. CONCLUSION: Surveys of patient satisfaction or patient evaluations are required by many regulatory bodies. Managed care organizations should carefully evaluate whether limitations in access or services are worth the generalized negative perceptions that they may create among patients.

Adult↗
PubMed1985

Purification of a naturally produced, low molecular weight organic factor that reversibly blocks encystment of Blastocladiella emersonii zoospores.

The water mold Blastocladiella emersonii releases zoospore maintenance factor into the medium during zoosporogenesis. Extracellular factor mediates a reversible developmental block that maintains the motile, cell wall-less zoospore phenotype. A method for purifying the factor is reported that results in 75-120% recovery of biological activity. Analyses of purified factor by thin layer chromatography support the conclusion that factor activity resides in a single organic, low molecular weight molecular species. Other data (Gottschalk, W.K. & Sonneborn, D. R. (1985) J. Biol. Chem. 260, 6592-6599) independently support this conclusion and, in addition, support the conclusion that biological activity resides in an SH-containing cyclic ribotide.

Blastocladiella↗
PubMed1985

Evidence that Blastocladiella emersonii zoospore maintenance factor is a sulfhydryl group-containing cyclic ribotide.

Blastocladiella emersonii zoospore maintenance factor (ZMF), released into the medium during zoospore production, mediates a reversible developmental block to zoospore encystment (Gottschalk, W. K., and Sonneborn, D. R. (1981) Exp. Mycol. 5, 1-14 and (1982) Dev. Biol. 93, 165-180). Crude ZMF and purified ZMF display indistinguishable sensitivities/insensitivities to inactivations by several different chemical or enzymatic treatments. Such data have provided additional support for the conclusion (Gottschalk, W. K., and Sonneborn, D. R. (1985) J. Biol. Chem. 260, 6588-6591) that ZMF biological activity resides in a single molecular species. The inactivation analyses have provided substantial evidence that ZMF is a newly discovered SH-containing cyclic ribotide. At least one SH-containing side group and at least one free amino group linked to an imidazole, as well as a ribosyl moiety containing a cyclic 3',5'-phosphate, a 2'-free hydroxyl, and a 1'-linkage to the imidazole, appear to be essential structural requirements for ZMF-mediated encystment blockage. The proposed structure of biologically functional ZMF is similar to that of a key intermediate in the de novo pathway of purine nucleotide biosynthesis (5'-phosphoribosyl-5-aminoimidazole-4-N-succino-carboxamide), except that ZMF, and not 5'-phosphoribosyl-5-aminoimidazole-4-N-succinocarboxamide, contains a cyclic phosphate and at least one reduced SH group.

Adenylosuccinate Lyase↗
PubMed1982

Developmentally regulated interconversions between end product-inhibitable and noninhibitable forms of a first pathway-specific enzyme activity can be mimicked in vitro by protein dephosphorylation-phosphorylation reactions.

During the life cycle of Blastocladiella emersonii, dramatic shifts occur in the sensitivity of the first hexosamine biosynthetic pathway-specific enzyme [amidotransferase; 2-amino-2-deoxy-D-glucose-6-phosphate ketol-isomerase (amino-transferring), EC 5.3.1.19] to end product inhibition. These shifts are developmentally correlated with changes in the utilization of the end product (uridine-5'-diphospho-N-acetylglucosamine) for chitin synthesis [Selitrennikoff, C. P., Dalley, N. E. & Sonneborn, D. R. (1980) Proc. Natl. Acad. Sci. USA 77, 5998-6002]. Alterations in amidotransferase sensitivity to end product inhibition can be mimicked by in vitro protein dephosphorylation-phosphorylation reactions, as follows: (i) Zoospore end product-inhibitable amidotransferase activity can be converted to a noninhibitable form by an endogenous (zoospore) protein phosphatase (phosphoprotein phosphohydrolase EC 3.1.3.16) reaction; this noninhibitable form can be converted back to an inhibitable form either by an endogenous cAMP-independent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) reaction or with an added cAMP-dependent protein kinase. (ii) Noninhibitable amidotransferase activity from growing cells can also be converted to the inhibitable form with added protein kinase.

Blastocladiella↗
PubMed1980

Regulation of the hexosamine biosynthetic pathway in the water mold Blastocladiella emersonii: Sensitivity to endproduct inhibition is dependent upon the life cycle phase.

Chitin, a homopolymer of N-acetylglucosamine (GlcNAc), is the major macromolecular constituent of Blastocladiella emersonii cell walls. Zoospores do not possess a wall nor do they contain sufficient total hexosamine to account for the chitin content of the wall abruptly formed during germination. UDPGlcNAc, both the endproduct of hexosamine biosynthesis and the substrate for chitin synthesis, is present in zoospores in sufficient concentration to inhibit the first hexosamine pathway-specific enzyme activity. Net chitin accumulates in register with dry weight during exponential growth, but does not accumulate appreciably during the succeeding sporulation phase. Predicted relationships among net rates of chitin synthesis, UDPGlcNAc concentrations, and UDP plus UTP concentrations throughout the life cycle are explored, as are the assumptions upon which the predictions were based. We find that the sensitivity of the first hexosamine pathway-specific enzyme to endproduct inhibition is not constant throughout the life cycle; sensitivity is very high in the zoospore phase, decreases dramatically during germination, remains very low through the growth phase, and increases gradually to the zoospore level during sporulation. The organism appears to have evolved endproduct regulation in this case as an adaptation to "hard-times" phases of the life cycle-i.e., as a safeguard against overproduction of end product (UDPGlcNAc) when its utilization in cell wall (specifically chitin) synthesis is curtailed. Conversely, the organism effectively discards this mode of regulation during "good times," when the demands for end product are evidently greater than endproduct inhibition would otherwise permit.

Journal Article↗
PubMed1977

Alkaline phosphatase of Blastocladiella emersonii: partial purification and characterization.

Alkaline phosphomonoesterase (EC 3.1.3.1) activity from Blastocladiella emersonii, while displaying typically broad substrate specificity for phosphorylated organic compounds, exhibited nearly complete substrate preference for N-acetylglucosamine-6-phosphate over N-acetylglucosamine-1-phosphate. Enzyme in zoospore extracts was purified 43-fold by differential centrifugation followed by gel filtration (Sephadex G-200) and then by ion-exchange chromatography (diethylaminoethyl-cellulose). The partially purified enzyme displayed an apparent molecular weight (Sephadex G-200) of approximately 170,000. The activity of partially purified enzyme exhibited a pH optimum of pH 8.5, did not require a metal divalent cation, but was inhibitable by ethylenediaminetetraacetic acid. During the life cycle of the organism, the specific activity of the phosphatase decreased slightly during germination and early exponential growth but then increased about 4.5-fold during sporulation. B. emersonii alkaline phosphatase does not appear to be a repressible enzyme.

Acetylglucosamine↗
PubMed1976

The last two pathway-specific enzyme activities of hexosamine biosynthesis are present in Blastocladiella emersonii zoospores prior to germination.

Forward direction assays have been developed for the last two pathway-specific enzymes of hexosamine biosynthesis using crude extracts from Blastocladiella emersonii zoospores. The specific enzyme activities measured are substantially higher than those reported with enzyme preparations from other organisms. During the development of one of the assays, another enzyme activity was observed which converts one of the intermediates of the pathway, N-acetylglucosamine-6-phosphate, to N-acetylglucosamine. The finding of these three enzyme activities in zoospore extracts completes the demonstration that all the enzyme activities necessary to synthesize some 2% by weight as chitin early during zoospore germination (de novo cell wall formation) pre-exist in the zoospore. This demonstration is consistent with the conclusion that the hexosamine pathway is regulated at the post-translational level during zoospore germination.

Acetylglucosamine↗
PubMed1976

Chitin biosynthesis during Blastocladiella zoospore germination: evidence that the hexosamine biosynthetic pathway is post-translationally activated during cell differentiation.

De novo construction of a chitinous cell wall accompanies Blastocladiella emersonii zoospore germination. At least an order of magnitude increase in total hexosamine occurs during germination. This increase is into polymer (chitin) and occurs on schedule in the presence of cycloheximide. Uridine-5'-diphospho-N-acetylglucosamine (UDPGlcNAc), both the end product of hexosamine biosynthesis and a substrate for chitin biosynthesis, is a potent inhibitor of the activity of the first pathway-specific enzyme of hexosamine biosynthesis in zoospore extracts. Certain uridine nucleotides, not perceptibly influencing the activity of the first enzyme per se, counteract the inhibitory effects of UDPGlcNAc. The concentration of UDPGlcNAc in the zoospore is sufficient to act as an inhibitor of the enzyme, but the amount of UDPGlcNAc is sufficient, by over an order of magnitude, to account for the chitin synthesized during germination. Both the production of UDPGlcNAc and its utilization for chitin synthesis appear to be post-translationally regulated in zoospores and during zoospore germination.

Blastocladiella↗
PubMed1974

Protein degradation and protease activity during the late cycle of Blastocladiella emersonii.

Analysis of protein degradation during the life cycle of Blastocladiella emersonii showed that (i) protein degradation is especially high during two phases of differentiation (sporulation, 12%/h and germination, 5%/h) in contrast with a much smaller degradation rate in the other phases (growth and zoospores, less than 1%/hr); (ii) protein degradation during germination in growth medium, as well as most of the germination process, is quantitatively unaffected by cycloheximide; (iii) a caseinolytic protease (pH optimum 5.5, apparent molecular weight 55,000 to 60,000) is present in extracts of zoospores and germinating cells; (iv) this protease activity is very low (perhaps absent) in extracts of late growth phase cells, but reappears during induced sporulation; (v) a different class of caseinolytic protease activity (pH optima 7 and 10; apparent molecular weight 25,000 to 30,000) is found in cellular extracts of late growth phase and early phases of sporulation; (vi) the latter class of enzyme activity is released into the medium during later phases of sporulation and is replaced in the cells by the former class. Speculations as to the roles of protein degradation in cell differentiation are discussed.

Carbon Radioisotopes↗
PubMed1971

Zoospore germination in Blastocladiella emersonii: cell differentiation without protein synthesis?

Evidence is presented to suggest that several early events of zoospore germination in the water mold, Blastocladiella emersonii, are not dependent upon concomitant protein synthesis. The events involve abrupt, dramatic changes in cell architecture. On account of this evidence, as well as evidence available from other sources, we question whether differential protein synthesis provides an exclusive and sufficient mechanism for phenotypic change (i.e., cell differentiation). Rather, we argue that mechanisms for bringing about structural alterations in the preformed machinery of the cell should also be given attention.

Carbon Isotopes↗