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D H Berg

Publications and source records attributed to D H Berg.

18 recordsLinked to original sources
PubMed1994

Human cytomegalovirus maturational proteinase: expression in Escherichia coli, purification, and enzymatic characterization by using peptide substrate mimics of natural cleavage sites.

The proteolytic processing of the human cytomegalovirus (HCMV) assembly protein, resulting in truncation of its C terminus, is an essential step in virion maturation. The proteinase responsible for this cleavage is the amino-terminal half of the protein encoded by the UL80a open reading fame. We have obtained high expression levels of this 256-amino-acid HCMV proteinase, assemblin, in Escherichia coli. In addition to the 28-kDa proteinase, a 15-kDa protein comprising the first 143 amino acids and a 13-kDa protein comprising the last 113 amino acids of the 28-kDa HCMV proteinase were present. Both the 28-kDa proteinase and the 15-kDa protein were purified by a two-step chromatographic procedure utilizing anion exchange in urea and dithiothreitol and size exclusion in NaSCN and dithiothreitol. Activation of the purified 28-kDa proteinase required denaturation in urea as well as complete reduction of all five cysteine residues in the molecule. Removal of the urea by dialysis with retention of the reducing agent yielded an active proteinase. Addition of glycerol to 50% enhanced the activity. The HCMV proteinase cleaved the peptides RGVVNASSRLAK and SYVKASVSPE, which are mimics of the maturational (M)- and release (R)-site sequences, respectively, in the UL80a-encoded protein. The cleavage site in the peptides was at the same Ala-Ser scissile bond as observed in the UL80a protein. The Km value for the cleavage of RGVVNASSRLAK (M-site mimic) by the proteinase was similar to that for SYVKASVSPE (R-site mimic), but the turnover (kcat) of the M-site peptide mimic substrate by the proteinase was six to eight times faster. The peptide homologs of the herpes simplex virus type 1 M- and R-site sequences in the UL26-encoded protein were also cleaved by the HCMV proteinase, although at rates slower than those for the HCMV substrates. The HCMV proteinase was inhibited by Zn2+ and by alkylating agents, but only at very high inhibitor concentrations. The purified 15-kDa protein, subjected to the same activation conditions as the 28-kDa proteinase, had no enzymatic activity against the HCMV M- and R-site peptide substrates.

Amino Acid Sequence↗
PubMed1993

Kringle glycosylation in a modified human tissue plasminogen activator improves functional properties.

Native tissue plasminogen activator (ntPA) has a variable glycosylation site on its kringle-2 domain. We have examined the effects of kringle glycosylation on functional properties by studying the simplified tPA molecule, tPA-6. tPA-6 is composed of kringle-2 and the serine protease domains and, like ntPA, cells expressing tPA-6 process it into two glycoforms: the monoglycosylated tPA-6-primary (tPA-6P, type II) with N-linked glycosylation at Asn-448 in the serine protease domain and diglycosylated tPA-6-variant (tPA-6V, type I) with glycosylation at Asn-448 and at Asn-184 in kringle-2. When the two glycoforms were separated, we found that purified tPA-6V had reduced fibrin-stimulated plasminogenolytic activity toward Glu-plasminogen when compared to purified tPA-6P. However, in the presence of fibrin, tPA-6V unexpectedly exhibited a sixfold increase in selectivity toward Lys-plasminogen. In addition, tPA-6V was less susceptible than tPA-6P to plasmin-mediated conversion to the two-chain form. By site-directed mutagenesis of tPA-6, we eliminated variable glycosylation at Asn-184 and engineered a new glycosylation signal at a remnant site in the kringle. This derivative, designated tPA-6D, was secreted with complete kringle glycosylation. Like the naturally occurring tPA-6V, tPA-6D had lower rates of fibrin-stimulated Glu-plasminogen activation, increased specificity toward Lys-plasminogen, and greater resistance to plasmin digestion. Although the activity of tPA-6D could be stimulated by fibrin, its activity was not stimulated significantly by fibrinogen, and in human plasma the rate of fibrinogen depletion was reduced threefold. Although fibrin binding to kringle-2 of tPA-6D was slightly improved, there was a substantial increase in the dissociation constant (kd) for lysine binding, demonstrating a lack of correlation between these ligand-binding sites. Overall, our data demonstrate the marked effect of kringle glycosylation on functional properties. In addition, we have generated a derivative with properties that potentially improve clot specificity and single-chain half-life and reduce the potential for plasminogen activation in the plasma.

Base Sequence↗
PubMed1990

Characterization of a modified human tissue plasminogen activator comprising a kringle-2 and a protease domain.

To study structure/function relationships of tissue plasminogen activator (t-PA) activity, one of the simplest modified t-PA structures to activate plasminogen in a fibrin-dependent manner was obtained by constructing an expression vector that deleted amino acid residues 4-175 from the full-length sequence of t-PA. The expression plasmid was introduced into a Syrian hamster cell line, and stable recombinant transformants, producing high levels of the modified plasminogen activator, were isolated. The resulting molecule, mt-PA-6, comprising the second kringle and serine protease domains of t-PA, produced a doublet of plasminogen activator activity having molecular masses of 40 and 42 kDa. The one-chain mt-PA-6 produced by cultured Syrian hamster cells was purified in high yield by affinity and size exclusion chromatography. The purified mt-PA-6 displayed the same two types of microheterogeneity observed for t-PA. NH2-terminal amino acid sequencing demonstrated that one-chain mt-PA-6 existed in both a GAR and a des-GAR form. Purified mt-PA-6 also existed in two glycosylation forms that accounted for the 40- and 42-kDa doublet of activity produced by the cultured Syrian hamster cells. Separation of these two forms by hydrophobic interaction chromatography and subsequent tryptic peptide mapping demonstrated that both forms contained N-linked glycosylation at Asn448; in addition, some mt-PA-6 molecules were also glycosylated at Asn184. Plasmin treatment of one-chain mt-PA-6 converted it to a two-chain molecule by cleavage of the Arg275-Ile276 bond. This two-chain mt-PA-6, like t-PA, had increased amidolytic activity. The fibrinolytic specific activities of the one- and two-chain forms of mt-PA-6 were similar and twice that of t-PA. The plasminogen activator activity of one-chain mt-PA-6 was enhanced greater than 80-fold by CNBr fragments of fibrinogen, and the one-chain enzyme lysed human clots in vitro in a dose-dependent manner. The ability to produce and purify a structurally simple plasminogen activator with desirable fibrinolytic properties may aid in the development of a superior thrombolytic agent for the treatment of acute myocardial infarction.

Amino Acid Sequence↗
PubMed1985

Reality construction at the family/society interface: the internalization of family themes and values.

An important component of the socialization function of the family continues to be the preparation of the young for integration into society. Empirical data, particularly from therapeutic settings, indicate that some children are notably well prepared for the world outside their families, while others have hardly been prepared at all. Adolescence is typically the time when these coping skills are most obvious. This paper addresses the issue of socialization of the young for participation in society. Building upon the "family theme" motif, the family is viewed as a micro-society. The issue of congruence between family themes and societally shared meanings is considered, utilizing ideas from the social construction of reality theories of Berger and Luckmann (1966). Three ideal-types of family themes are developed relative to their external world meanings. Previous work on family themes typically has failed to deal with the interpretative function of family meanings. How the family "explains" the family-external meanings is addressed.

Adaptation, Psychological↗
PubMed1979

Transportation or CT scanners: a theory and method of health resources allocation.

Cost containment and access to appropriate care are the two most frequently discussed issues in contemporary health policy. Conceiving of the health services available in specific regions as "packages" of diverse items, the authors of this article consider the economic trade-offs among the various resources needed for appropriate care. In the discussion that follows, we examine the trade-offs between two divergent offering of the health care system: high technology medicine and support services. Specifically, we examine several strategies designed to achieve an optimal mix of investments in CT scanners and transportation resources in the South Chicago region. Using linear programming as a method for examining these options, the authors found that 1) the proper location of CT scanners is as important for cost containment as optimal number, and 2) excess capacity in the utilization of a single resource--CT scanners--need not imply inefficiency in the overall delivery of the service. These findings help demonstrate the importance of viewing health care as a package of interrelated services, both for achieving cost containment and for providing access to appropriate care.

Catchment Area, Health↗
PubMed1978

The isolation and characterization of narasin, a new polyether antibiotic.

Narasin is a new polyether antibiotic produced by a strain of Streptomyces aureofaciens. It is purified by organic solvent extraction and silica gel chromatography. Narasin is active in vitro against gram-positive bacteria, anaerobic bacteria, and fungi and is effective in protecting chickens from coccidial infections.

Animals↗
PubMed1976

The structure of narasin and a related ionophore.

Using electron impact and field desorption mass spectrometry, structures are proposed for narasin and a related ionophore, A28086B, derived from fermentation. The ionic fragmentation of these compounds and their derivatives is discussed and compared with that of salinomycin, whose structure has been determined by X-ray diffraction.

Chemical Phenomena↗
PubMed1976

A30641, a new epidithiodiketopiperazine with antifungal activity.

A new antibiotic, designated A30641, having in vitro activity against Gram-positive bacteria and fungi has been isolated from a strain of Aspergillus tamarii. Chemical and physical characterization indicate that it is a member of the class of antibiotics containing the epidithiodiketopiperazine moiety.

Animals↗
PubMedDate not supplied

Surreptitious learning: menarche and menstrual product advertisements.

The purpose of this study was to examine the messages conveyed in menstrual product advertisements with specific concern given to information that could be learned about menstruation and the female body by menarcheal girls. Over 200 advertisements from popular women's magazines were analyzed using constant comparative analysis. The core variable was Heightening Insecurities. The themes identified in menstrual product advertisements function to heighten insecurities in the female adolescent reader. The findings revealed that the advertisements were a reflection of the negative societal views of menstruation and, because the advertisements function to heighten insecurities, they also function to perpetuate and maintain the silence and shame which surrounds menstruation in our society.

Adaptation, Psychological↗
PubMedDate not supplied

Virginity and tampons: the beginner myth as a case of alteration.

Using an inductive analytical approach to the portrayal of menstruating women in menstrual product advertisements, we discovered that tampon advertisements directed to adolescents provide a unique case of myth alteration. The beginner myth contends that tampon use by young women threatens virginity. With considerable deftness, the tampon advertisements we analyzed addressed the beginner myth, both dispelling the myth and at the same time retaining it to the degree that it sustained the need for specialized tampons.

Adolescent↗
PubMedDate not supplied

The portrayal of the menstruating woman in menstrual product advertisements.

Because menstrual product advertisements act as mediators of a subset of meanings of femininity linked to menstruation, we performed a comparative conceptual analysis of these advertisements to explicate media-constructed realities of contemporary women. We sought to understand the portrayed women's definition of menstruation and their status as menstruating women. Textual and conceptual analyses led us to conclude that the portrayed women, in an attempt to avoid others' discovery of their menstruation, employed a complex menstrual management system, which often includes feminized menstrual products, to act as an antidote to a tainted state of femininity.

Adaptation, Psychological↗
PubMedDate not supplied

The extended curse: being a woman every day.

Inductive analysis of the portrayal of menstruating women in contemporary menstrual product advertisements revealed a profound shift in the meaning of feminine hygiene over the last few decades. The phrase sanitary protection has been replaced by a more euphemistic phrase, feminine hygiene, to refer to menstrual management products. What first appeared to be mere euphemistic substitution, on further analysis, was revealed to involve considerably more than semantics. In the case of panty liners, it was found that the marketing of these specialized products involves the invocation of negative definitions of femaleness and a concomitant subscription to altered definitions of femininity. These altered meanings, conveyed in recent menstrual product advertisements, have serious implications for contemporary women's self-images.

Advertising↗
PubMedDate not supplied

Extracted image analysis: a technique for deciphering mediated portrayals.

A technique for analyzing print media that we have developed as a consequence of our interest in the portrayal of women in menstrual product advertising is reported. The technique, which we call extracted image analysis, involves a unique application of grounded theory and the concomitant heuristic use of the concept of ideal type (Weber, 1958). It provides a means of heuristically conceptualizing the answer to a variant of the "What is going on here?" question asked in analysis of print communication, that is, "Who is being portrayed/addressed here?" Extracted image analysis involves the use of grounded theory to develop ideal typologies. Because the technique re-constructs the ideal types embedded in a communication, it possesses considerable potential as a means of identifying the profiles of members of identifiable groups held by the producers of the directed messages. In addition, the analysis of such portrayals over time would be particularly well suited to extracted image analysis. A number of other possible applications are also suggested.

Female↗