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Biomedical subjects

L Seitz

Publications and source records attributed to L Seitz.

7 recordsLinked to original sources

Encrypted storage of medical data on a grid.

OBJECTIVES: In this article we present grids as an architecture for medical image processing and health-care networks. We argue that confidential patient data should not be stored unprotected on a grid and explain why access control systems alone do not offer sufficient protection. The objective of our work is to propose a method that complements access control systems on a grid architecture and thus makes the storage of confidential data more secure. METHODS: Effective protection can be achieved by storing confidential data in encrypted form. This raises the problem of how authorized users get access to the data, since they need to have the decryption keys. RESULTS: Our proposal details a key management architecture, that allows encrypted storage and still enables users to access decryption keys for data they are authorized to see. To achieve this functionality we use distributed keyservers storing redundant shares of the keys. CONCLUSIONS: The resulting architecture achieves our primary objective of making the storage of confidential data more secure without loosing the data sharing properties of the grid architecture. Furthermore our architecture is robust against breakdowns and denial of service attacks. It scales well with the number of users and does not introduce a single point of failure into the system.

Access to Information↗

Studies on (beta,1-->5) and (beta,1-->6) linked octyl Gal(f) disaccharides as substrates for mycobacterial galactosyltransferase activity.

The emergence of multi-drug resistant (MDR) strains of Mycobacterium tuberculosis (MTB) and the continuing pandemic of tuberculosis emphasizes the urgent need for the development of new anti-tubercular agents with novel drug targets. The recent structural elucidation of the mycobacterial cell wall highlights a large variety of structurally unique components that may be a basis for new drug development. This publication describes the synthesis, characterization, and screening of several octyl Galf(beta,1-->5)Galf and octyl Galf(beta,1-->6)Galf derivatives. A cell-free assay system has been utilized for galactosyltransferase activity using UDP[14C]Galf as the glycosyl donor, and in vitro inhibitory activity has been determined in a colorimetric broth microdilution assay system against MTB H37Ra and three clinical isolates of Mycobacterium avium complex (MAC). Certain derivatives showed moderate activities against MTB and MAC. The biological evaluation of these disaccharides suggests that more hydrophobic analogues with a blocked reducing end showed better activity as compared to totally deprotected disaccharides that more closely resemble the natural substrates in cell wall biosynthesis.

Antitubercular Agents↗

Altered immunomodulating and toxicological properties of degraded Quillaja saponaria Molina saponins.

Quillaja saponins are readily hydrolyzed under physiological conditions, yielding deacylated forms that are significantly less toxic than their precursors. Yet, deacylated saponins are unable to stimulate a strong primary immune response. Although deacylated saponins elicit a strong total IgG response, their capacity to stimulate a Thl type IgG isotype profile (i.e. high levels of IgG2a and IgG2b) has been significantly diminished. Instead, an IgG profile closer to that of a Th2 immune response is stimulated (i.e. high IgG1 levels). Deacylated saponins have also lost their capacity to elicit an effective T cell immunity, as shown by their stimulation of a marginal lymphoproliferative response and their inability to elicit the production of cytotoxic lymphocytes (CTL). Modification of the immune-modulating properties brought by the degradation of quillaja saponins during vaccine storage may change the intended immune response from a Th1 to a Th2 type. This alteration would have negligible effects on vaccines depending on Th2 immunity mediated by neutralizing antibodies. However, the performance of vaccines directed against intracellular pathogens as well as therapeutic cancer vaccines may be seriously affected by the loss of their capacity to stimulate both a Th1 immune response and the production of CTL.

Adjuvants, Immunologic↗

Plasma corticosterone and testosterone levels during the annual reproductive cycle of male brown anoles (Anolis sagrei).

The objective of the present study was to determine the plasma levels of testosterone and corticosterone in male Anolis sagrei during the annual reproductive cycle and to examine the relationships between seasonal change in the levels of these hormones, male reproductive activity, and body condition. Both testosterone and corticosterone levels in adult males captured in the Miami, Florida, area varied significantly with month and with season (i.e., breeding vs. nonbreeding period), although they were not significantly correlated with each other or with body mass. Mean monthly testosterone levels were higher during the breeding season (March-August) than during the nonbreeding season, with the one exception that the highest mean testosterone level occurred in February immediately before the beginning of the breeding season. Testosterone levels in the overall sample of 144 males were significantly correlated with testes mass but not with any of the other measured variables. Corticosterone levels were highest during the nonbreeding season and lowest during the breeding season. Corticosterone levels on a monthly basis were negatively correlated with monthly changes in testes mass and positively correlated with monthly changes in abdominal fat-body mass.

Animals↗