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G Myers

Publications and source records attributed to G Myers.

At least 37 records · Page 2Linked to original sources
PubMed1995

From apartheid to integration: the role of the Witwatersrand Medical library in health care services in Johannesburg, South Africa.

Adapting to change is always difficult; all the more so when changes in the administrative structure of health care are part of a national political transformation toward democracy. As South Africa moves from apartheid to integration in its health services, the Witwatersrand Medical Library (WML) will have to adopt innovative strategies to cope with increasing demands on its resources by sub-Saharan African medical libraries and with expected decreases in state funding for health and education. WML also will have to address the lack of hospital library services in the Johannesburg region by expanding its academic branches at University of the Witwatersrand Medical School's teaching hospitals to serve both hospital and academic health care staff. This article discusses these challenges in the context of rapidly changing academic health care services in Johannesburg.

Health Policy↗
PubMed1995

Analysis of data on delayed development from the 1971-72 outbreak of methylmercury poisoning in Iraq: assessment of influential points.

In this paper we report additional results from the analysis of dose-response data on delayed development from the outbreak of methylmercury poisoning in rural Iraq during the winter of 1971-72. The discussion is focused on the importance of four influential points for the estimation of the population threshold for the effects of methylmercury. The point is made that while this study was important for establishing a dose-response relationship in humans, the uncertainty in the parameters of this relationship is large, and further human studies are needed.

Child Development↗
PubMed1994

The World Health Organization Global Programme on AIDS proposal for standardization of HIV sequence nomenclature. WHO Network for HIV Isolation and Characterization.

The World Health Organization Global Programme on AIDS (WHO/GPA) is conducting a large-scale collaborative study of human immunodeficiency virus type 1 (HIV-1) variation, based in four potential vaccine-trial site countries: Brazil, Rwanda, Thailand, and Uganda. Through the course of this study, it was crucial to keep track of certain attributes of the samples from which the viral nucleotide sequences were derived (e.g., country of origin and viral culture characterization), so that meaningful sequence comparisons could be made. Here we describe a system developed in the context of the WHO/GPA study that summarizes such critical attributes by representing them as standardized characters directly incorporated into sequence names. This nomenclature allows linkage of clinical, phenotypic, and geographic information with molecular data. We propose that other investigators involved in human immunodeficiency virus (HIV) nucleotide sequencing efforts adopt a similar standardized sequence nomenclature to facilitate cross-study sequence comparison. HIV sequence data are being generated at an ever-increasing rate; directly coupled to this increase is our deepening understanding of biological parameters that influence or result from sequence variability. A standardized sequence nomenclature that includes relevant biological information would enable researchers to better utilize the growing body of sequence data, and enhance their ability to interpret the biological implications of their own data through facilitating comparisons with previously published work.

AIDS Vaccines↗
PubMed1994

Mutational trends in V3 loop protein sequences observed in different genetic lineages of human immunodeficiency virus type 1.

Highly variable international human immunodeficiency virus type 1 envelope sequences can be assigned to six major clades, or phylogenetically defined subtypes, designated A through F. These subtypes are approximately equidistant in terms of evolutionary distance measured by nucleotide sequences. This radiation from a common ancestral sequence may have been in step with the spread of the pandemic. In this study, V3 loop protein sequence relationships within these major clades are analyzed to determine how the different lineages might be evolving with respect to this biologically important domain. The V3 loop has been shown to influence viral phenotype and to elicit both humoral and cellular immune responses. To identify patterns in V3 loop amino acid evolution, we cluster the sequences by a phenetic principle which evaluates protein similarities on the basis of amino acid identities and similarities irrespective of evolutionary relationships. When phenetic clustering patterns are superimposed upon phylogenetic subtype classifications, two interesting mutational trends are revealed. First, a set of identical, or highly similar, V3 loop protein sequences can be identified within two otherwise dissimilar genetic subtypes, A and C. Second, the D subtype sequences are found to possess the most radically divergent set of V3 loop sequences. These and other patterns characteristic of the V3 loop reflect the acquisition of specific biological properties during the apparently recent evolution of the human immunodeficiency virus type 1 lineages.

Amino Acid Sequence↗
PubMed1994

A novel hantavirus associated with an outbreak of fatal respiratory disease in the southwestern United States: evolutionary relationships to known hantaviruses.

Four Corners hantavirus (FCV) is the tentative name of the suspected etiologic agent of the newly identified hantavirus-associated respiratory distress syndrome (HARDS). The identification in HARDS patients of serum immunoglobulin M and immunoglobulin G antibodies that cross-reacted with Hantaan, Seoul, and Puumala virus antigens first suggested that FCV is a hantavirus. Limited nucleotide sequence data from the FCV glycoprotein-2 (G2) confirmed that FCV is a hantavirus and showed that it is most closely related to Prospect Hill and Puumala viruses. We have molecularly cloned approximately 95% of the sequences of the M and S segments of the FCV genome encoding the envelope glycoproteins and nucleocapsid protein N from the lungs of a patient with HARDS. The nucleotide sequence has been determined for 2,632 bases. The nucleotide sequence data show that FCV is a new member of the Puumala virus and Prospect Hill virus division of the hantavirus genus. Phylogenetic tree analyses indicate that the M and S segments have evolved in parallel. Therefore, the novel pathogenic activity of FCV is not likely to be the result of recent reassortment of segments from less pathogenic viruses.

Amino Acid Sequence↗
PubMed1993

Solution structure of the V3 loop of a Thailand HIV isolate.

The principal neutralizing determinant (PND) of human immunodeficiency virus (HIV) is located inside the third variable loop (designated the V3 loop) of the envelope glycoprotein gp120. The V3 loop is typically 35 amino-acids long, and the 1st and the 35th residues in the loop are invariant cystines involved in a disulfide-bridge. Although PNDs from different HIV isolates contain a conserved GPG-sequence, the amino acids flanking the conserved sequence show hypervariability among HIV isolates; the GPG and the two flanking regions are collectively referred to as the GPG-crest or the PND. The amino acid sequence variability in the GPG-crest gives rise to different antigenic specificities for different PNDs from different HIV isolates. By combining two-dimensional nuclear magnetic resonance (2D NMR) and molecular modeling techniques, we have developed a method to study (1) the global tertiary fold of the V3 loops of HIV and (2) the local structure of the PND at the tip of the V3 loop. In this article, we report the results of our structural studies on the V3 loop of a Thailand HIV isolate. The sequential assignment is made by combining DQF-COSY, TOCSY, and NOESY/ROESY experiments. Various intra- and inter-residue inter-proton distances are estimated by full-matrix analyses of the NOESY data at 100 and 400 ms of mixing times and of the ROESY data at 60 and 200 ms of mixing times. 100 inter-residue distances are used as structural constraints in a simulated annealing procedure to derive energetically stable structures. Two functional motifs in the V3 loop, i.e., the glycosylation site and the GPG-crest, form defined structures: a turn is located at the glycosylation site, and the GPG-crest forms a protruding domain with a type-II GPGQ turn. The other regions of the V3 loop are rather flexible--especially the C-terminal DIRKAYC-stretch. These flexible regions of the V3 loop lead to conformational flexure of the entire V3 loop without altering the local structures of the glycosylation site or the GPG-crest. However, the ROESY experiments revealed no slow exchange among different V3 loop conformations, and therefore the flexible conformations are in fast exchange within the NMR time scale. The extent of this conformational flexibility is also discussed.

Amino Acid Sequence↗
PubMed1993

A system for pattern matching applications on biosequences.

ANREP is a system for finding matches to patterns composed of (i) spacing constraints called 'spacers', and (ii) approximate matches to 'motifs' that are, recursively, patterns composed of 'atomic' symbols. A user specifies such patterns via a declarative, free-format and strongly typed language called A that is presented here in a tutorial style through a series of progressively more complex examples. The sample patterns are for protein and DNA sequences, the application domain for which ANREP was specifically created. ANREP provides a unified framework for almost all previously proposed biosequence patterns and extends them by providing approximate matching, a feature heretofore unavailable except for the limited case of individual sequences. The performance of ANREP is discussed and an appendix gives a concise specification of syntax and semantics. A portable C software package implementing ANREP is available via anonymous remote file transfer.

Base Sequence↗
PubMed1993

A distinct African lentivirus from Sykes' monkeys.

Asymptomatic infection with simian immunodeficiency virus (SIV) has been demonstrated in African Sykes' monkeys (Cercopithecus mitis albogularis), and virus isolation confirmed infection with a novel SIV from Sykes' monkeys (SIVsyk). Macaques inoculated with SIVsyk became persistently infected but remained clinically healthy. We utilized polymerase chain reaction amplification to generate a full-length, infectious molecular clone of SIVsyk. The genome organization of SIVsyk is similar to that of the other primate lentiviruses, consisting of gag, pol, vif, vpr, tat, rev, env, and nef. A unique feature is the absence of the highly conserved NF-kappa B binding site in the long terminal repeat. SIVsyk is genetically equidistant from other primate lentiviruses. Thus, SIVsyk represents a new group that is distinct from the four previously recognized primate lentivirus groups: human immunodeficiency virus type 1 (HIV-1), SIV from sooty mangabeys (SIVsmm) and HIV-2, SIV from African green monkeys (SIVagm), and SIV from mandrills (SIVmnd). The genetic differences between SIVsyk and SIVagm, isolates derived from monkeys of the same genus, underscore the potential for other distinct SIVs which have yet to be isolated and characterized.

Africa↗
PubMed1992

AIDS origin.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Molecular epidemiology of HIV transmission in a dental practice.

Human immunodeficiency virus type 1 (HIV-1) transmission from infected patients to health-care workers has been well documented, but transmission from an infected health-care worker to a patient has not been reported. After identification of an acquired immunodeficiency syndrome (AIDS) patient who had no known risk factors for HIV infection but who had undergone an invasive procedure performed by a dentist with AIDS, six other patients of this dentist were found to be HIV-infected. Molecular biologic studies were conducted to complement the epidemiologic investigation. Portions of the HIV proviral envelope gene from each of the seven patients, the dentist, and 35 HIV-infected persons from the local geographic area were amplified by polymerase chain reaction and sequenced. Three separate comparative genetic analyses--genetic distance measurements, phylogenetic tree analysis, and amino acid signature pattern analysis--showed that the viruses from the dentist and five dental patients were closely related. These data, together with the epidemiologic investigation, indicated that these patients became infected with HIV while receiving care from a dentist with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Transmission of human immunodeficiency virus in a dental practice.

OBJECTIVE: To determine if patients of a dentist with the acquired immunodeficiency syndrome (AIDS) became infected with human immunodeficiency virus (HIV) during their dental care and, if so, to identify possible mechanisms of transmission. DESIGN: Retrospective epidemiologic follow-up of the dentist, his office practice, and his former patients. SETTING: The practice of a dentist with AIDS in Florida. PARTICIPANTS: A dentist with AIDS, his health care providers and employees, and former patients of the dentist, including eight HIV-infected patients. MEASUREMENTS: Identification of risks for HIV transmission (if present), degree of genetic relatedness of the viruses, and identification of infection control and other office practices. RESULTS: Five of the eight HIV-infected patients had no confirmed exposures to HIV other than the dental practice and were infected with HIV strains that were closely related to those of the dentist. Each of the five had invasive dental procedures, done by the dentist after he was diagnosed with AIDS. Four of these five patients shared visit days (P greater than 0.2). Breaches in infection control and other dental office practices to explain these transmissions could not be identified. CONCLUSION: Although the specific incident that resulted in HIV transmission to these patients remains uncertain, the epidemiologic evidence supports direct dentist-to-patient transmission rather than a patient-to-patient route.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Problems in measuring heart rate variability of patients with congestive heart failure.

Heart rate variability (HRV) has become an important noninvasive measure of the integrity of the autonomic nervous system in various disease states. The power spectrum of HRV is a means to separate the instability oscillations of the various feedback mechanisms that contribute to cardiovascular homeostasis. The reliability of HRV data is largely unexplored. The day-to-day correlations in the low and mid-frequency components of HRV spectra average 91%, and that of the high-frequency component averages 81%. The correlations among spectral and nonspectral measures of HRV (SD) for the same data segment average 50-60%, suggesting that they encode similar information. Heart rate variability spectra exhibit diurnal variation consistent with physiologic expectation: respiratory sinus arrhythmia (thought to be mediated by parasympathetic tone) and to a lesser extent, the low-frequency spectral component (thought to be of mixed sympathetic-parasympathetic origin) are higher at night than in the daytime; the mid-frequency component (associated with the baroreflex, which is more excited when the patient is upright) is slightly higher during the daytime. Increased frequency of ectopic beats, such as occurs in congestive heart failure, reduces the reliability of the power spectrum since the number of usable data segments falls off rapidly with even small increases in rate of ectopy, and the variance of the estimate (in the method of averaged periodograms) is inversely proportional to the square root of the number of data segments. Using shorter data segments increases the number of segments available, but reduces resolution. Interpolation over ectopic beats (by either linear or cubic splint interpolation) increases the apparent power in low frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiography↗