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D M Dwyer

Publications and source records attributed to D M Dwyer.

At least 37 records · Page 2Linked to original sources
PubMed1999

Retrospective revaluation or mediated conditioning? The effect of different reinforcers.

It is becoming accepted that the associative strength of a cue can change in its absence. However, the rules that govern the association of the representations of absent cues are in dispute. There is evidence to support both the idea that the representation of a cue is associated in the same fashion as the cue itself (e.g. Holland, 1990) and the contrary idea that the representation will be associated in the opposite manner to the cue itself (e.g. Dickinson & Burke, 1996). In three experiments an aversion to almond was formed by the pairing of the induction of nausea by lithium chloride injection with a context previously paired with almond. In addition in the third experiment an aversion was formed to almond when a flavoured solution previously paired with quinine was drunk in a context previously paired with almond. These results suggest that the rules governing the association of the representations of absent cues depend on the type of reinforcer.

Animals↗
PubMed1998

The Ld Cht1 gene encodes the secretory chitinase of the human pathogen Leishmania donovani.

Leishmania donovani promastigotes were shown to release chitinase activity during their growth in vitro. A PCR-based strategy identified a single copy ORF capable of encoding the L. donovani chitinase (Ld Cht1, 1374 bp). Ld Cht1 was shown to be actively transcribed by L. donovani promastigotes using reverse transcription and PCR amplification. The deduced aa sequence of Ld Cht1 showed high conservation to known chitinases including the putative active and two substrate binding sites. Antiserum generated against four peptides derived from its deduced aa sequence immunoprecipitated an approx. 50-kDa in vitro transcription/translation product of Ld Cht1. Further, this antiserum also immunoprecipitated both the native L. donovani 50-kDa Cht1 protein and the native chitinase activity synthesized and released by these parasites. Cumulatively, these data demonstrated that Ld Cht1 encoded the chitinase of this important human pathogen.

Amino Acid Sequence↗
PubMed1998

Leishmania: amastigotes synthesize conserved secretory acid phosphatases during human infection.

Leishmania donovani is the major causative agent of Old World human visceral leishmaniasis (VL). In vitro, both promastigotes and axenic amastigotes of L. donovani constitutively secrete soluble acid phosphatases (SAcPs), which contain conserved antigenic epitopes. These SAcPs are the most abundant and best characterized secretory proteins of this parasite. The aim of this study was to determine whether this enzyme was produced by intracellular amastigotes during the course of human infection. To that end, sera from acutely infected leishmaniasis patients were tested for anti-SAcP antibodies using L. donovani promastigote culture supernatants. Our results showed that VL patient sera from different endemic foci immunoprecipitated parasite SAcP enzyme activity. Further, these VL patient sera recognized the 110- and 130-kDa SAcPs in both Western blots and radioimmunoprecipitation assays. Results of tunicamycin experiments demonstrated that VL patient anti-SAcP antibodies were directed against the polypeptide backbone of the parasite SAcPs. In addition, both radiolabeled L. donovani SAcPs and native enzyme activities were immunoprecipitated by sera from patients with various forms of cutaneous leishmaniasis. Together, these studies demonstrate that Leishmania amastigotes produce SAcPs during the course of human infections.

Acid Phosphatase↗
PubMed1998

Implications of calreticulin function in parasite biology.

Calreticulin (CR) is a Ca(2+)-binding, multifunctional protein. The amazing array of CR-associated functions range from intracellular activities in secondary messenger release, protein folding and the modulation of gene expression to potential interactions with host receptors and signaling machinery and recognition by the host immune system. The multifunctional nature of CR may impact upon the ability of cells to recognize extracellular stimuli and coordinate appropriate responses. Identification of CR isolated from parasites and the conservation of its functions suggests that investigations into the contributions of CR to various aspects of parasite biology should be undertaken because it may reveal information regarding parasite interaction with the host and how the parasite may modulate its response to the host.

Journal Article↗
PubMed1998

Serotype distribution of invasive group B streptococcal isolates in Maryland: implications for vaccine formulation. Maryland Emerging Infections Program.

Invasive group B streptococcal (GBS) infection is a major health problem among infants and adults. The formulation of GBS vaccines depends on knowledge of the GBS serotype distribution. Serotype V GBS infection appears to have recently emerged, suggesting that the serotype distribution changes over time. GBS isolates from 210 pediatric patients, 23 pregnant women, and 314 nonpregnant adults with invasive infection in Maryland were studied. The predominant serotypes from infants with early-onset disease were as follows: serotype III, 38% of isolates; serotype Ia, 36%; serotype V, 13%; and serotype II, 11%. Although the majority (60%) of isolates among infants with late-onset infection were serotype III, serotype Ia (23%) was also common. The predominant serotype among isolates from nonpregnant adult patients was serotype V, accounting for 29% of the isolates. The serotype distribution differs between pediatric patients and adults and is changing over time. The inclusion of a relatively small number of serotypes in a GBS vaccine could provide protection against the vast majority of isolates.

Adult↗
PubMed1997

A framework for capturing clinical data sets from computerized sources.

The pressure to improve health care and provide better care at a lower cost has generated the need for efficient capture of clinical data. Many data sets are now being defined to analyze health care. Historically, review and research organizations have simply determined what data they wanted to collect, developed forms, and then gathered the information through chart review without regard to what is already available institutionally in computerized databases. Today, much electronic patient information is available in operational data systems (for example, laboratory systems, pharmacy systems, and surgical scheduling systems) and is accessible by agencies and organizations through standards for messages, codes, and encrypted electronic mail. Such agencies and organizations should define the elements of their data sets in terms of standardized operational data, and data producers should fully adopt these code and message standards. The Health Plan Employer Data and Information Set and the Council of State and Territorial Epidemiologists in collaboration with the Centers for Disease Control and Prevention and the Association of State and Territorial Public Health Laboratory Directors provide examples of how this can be done.

Abstracting and Indexing↗
PubMed1997

Transmission of Mycobacterium tuberculosis by a fiberoptic bronchoscope. Identification by DNA fingerprinting.

CONTEXT: An ongoing restriction fragment length polymorphism (RFLP) study of Mycobacterium tuberculosis isolates from tuberculosis (TB) cases revealed an identical 10-banded IS6110 RFLP pattern unique to 2 patients diagnosed as having TB 6 months apart. Their only identifiable link was care at the same hospital. OBJECTIVE: To determine if nosocomial transmission had occurred. DESIGN: Traditional and molecular epidemiologic investigation. MEASUREMENTS: We reviewed medical charts and bronchoscopic records, examined hospital locations visited by both patients, evaluated hospital ventilation systems, and observed cleaning and disinfection of bronchoscopes. RESULTS: A patient with cough, hoarseness, and fever underwent bronchoscopy and was diagnosed as having TB. A second patient with a mediastinal mass underwent bronchoscopy 2 days later and was diagnosed as having small cell carcinoma. Following 6 months of chemotherapy and radiation therapy, the second patient developed fever and an infiltrate of the right upper lobe of the lung. Bronchoscopic washings revealed acid-fast bacilli and were culture positive for M tuberculosis. Both patients had undergone bronchoscopy with the same instrument in the same operating room with no intervening bronchoscopies. Bronchoscope cleaning and disinfection procedures were inconsistent with national guidelines. CONCLUSIONS: A contaminated bronchoscope was the most likely source of M tuberculosis transmission between these 2 patients. The RFLP analysis of M tuberculosis isolates was responsible for detecting this nosocomial source of transmission and led to the implementation of public health measures to prevent further spread of infection and disease. This study emphasizes the need for continued vigilance in endoscope cleaning techniques.

Adult↗
PubMed1997

Two tandemly arrayed genes encode the (histidine) secretory acid phosphatases of Leishmania donovani.

Leishmania donovani promastigotes constitutively secrete a glycosylated and phosphorylated acid phosphatase activity. This secretory acid phosphatase (SAcP) was purified from L. donovani culture supernatants and amino-acid sequence was obtained from both the N-terminus and a tryptic peptide fragment derived from the isolated protein. A polymerase chain reaction (PCR)-based strategy, using degenerate oligo primers designed from the amino-acid sequence data, identified two single-copy, tandemly arrayed open reading frames (ORFs) capable of encoding the L. donovani SAcP (SAcP-1, 2052 bp and SAcP-2, 2124 bp). Both SAcP-1 and -2 were shown to be actively transcribed by L. donovani promastigotes by reverse transcription (RT) and PCR amplification. The deduced amino-acid sequences of SAcP-1 and SAcP-2 show high conservation to each other in four regions: a 23-amino-acid signal peptide; a catalytic domain containing several potential N-linked glycosylation sites; a Ser/Thr-rich repeat region containing multiple potential phosphorylation sites and a common C-terminus. Within the catalytic domain, the L. donovani SAcPs possess two conserved consensus sequences characteristic of histidine acid phosphatases (AcPs). Furthermore, antisera to native L. donovani SAcP immunoprecipitated in vitro transcription/translation products of both SAcP-1 and SAcP-2. Cumulatively, these data indicate that the acid phosphatase activity constitutively secreted by L. donovani promastigotes is composed of two (histidine) AcP isoforms that are encoded by SAcP-1 and SAcP-2, respectively.

Acid Phosphatase↗
PubMed1997

Weight loss in rats produced by running: effects of prior experience and individual housing.

To investigate factors affecting activity-based anorexia (ABA) or activity-stress (AS), rats were given 2-hr access to a running wheel immediately prior to their daily 1.5-hr food access during the light cycle. This produced a reduction in food intake, a steady increase in running, and a large drop in body weight with a prolonged delay before weight recovery began. Experiment 1 found that these effects were reduced in rats with prior experience of eating at this time of day. In contrast, prior experience of running in the wheel when on ad lib food enhanced these effects in Experiment 2, where a subsequent change for half the subjects to individual housing produced a further decrease in body weight. The latter factor was investigated from the outset of Experiment 3 and again individually housed rats showed greater weight loss than did group-housed rats. This experiment also found that in rats of the same age a low initial body weight predicts greater vulnerability to ABA. It was concluded that ABA results from activity-induced reduction of feeding, which prolongs adaptation to a new feeding schedule and is accentuated by social isolation.

Animals↗
PubMed1997

Handwashing and glove use in a long-term-care facility.

OBJECTIVES: To determine glove use and handwashing practices, the factors associated with infection control practices, and the frequency of potential microbial transmission in a long-term-care facility (LTCF). DESIGN: Observational study of 230 staff-resident interactions in an LTCF. We recorded resident characteristics, type of activity, staff credentials, and movements of the staff member's hands, then used the LTCF's guidelines to judge appropriateness of glove use and handwashing. SETTING: 255-bed, university-based LTCF in Baltimore, Maryland. PARTICIPANTS: A systematic sample of staff-resident interactions. RESULTS: Gloves were worn in 139 (82%) of 170 interactions when indicated, but changed appropriately in only 1 (16%) of 132. Hands were washed when needed before an interaction in 27%, during an interaction in 0%, and after an interaction in 63%. Gloves were less likely to be used when caring for residents with gastrostomy tubes compared with other residents (relative risk, 0.85; 95% confidence interval, 0.73-0.98). Guidelines were followed more frequently during wound care than during other activities. Microbial transmission potentially could have occurred in 158 (82%) of 193 evaluable interactions. CONCLUSIONS: We documented marked deficiencies in glove and handwashing, demonstrated the possible impact of these deficiencies, and identified factors associated with inadequate handwashing and glove use. This information can be used in future educational and research efforts to improve infection control practices.

Baltimore↗
PubMed1997

Activity-based anorexia in rats as failure to adapt to a feeding schedule.

Progressive weight loss resulting from restriction to a daily 1.5-hr feeding period and access to a running wheel, the Activity-Based Anorexia (ABA) effect, was obtained in 3 experiments. However, bodyweight recovered when adaptation to the feeding schedule preceded access to the wheel (Experiment 1), when feeding was at the start of the dark period (Experiments 2 and 3), and when wheel access was denied in the 4 hr before food (Experiment 4). It was concluded that ABA results from interference with adaptation to a new feeding schedule due to the development of anticipatory behavior.

Adaptation, Psychological↗
PubMed1997

Parkville virus: a novel genetic variant of human calicivirus in the Sapporo virus clade, associated with an outbreak of gastroenteritis in adults.

This report describes the characterization of Parkville virus, the etiologic agent of an outbreak of foodborne gastroenteritis, that has the morphology of a calicivirus and genetic properties that distinguish it from previously identified strains in the Sapporo/Manchester virus clade. Sequence analysis of the Parkville virus genome showed it contained the RNA-dependent RNA polymerase motifs GLPSG and YGDD characteristic of members of the family Caliciviridae with an organization identical to that reported for the Manchester virus where the capsid region of the polyprotein is fused to the RNA polymerase. Parkville virus however, demonstrates considerable sequence divergence from both the Manchester and Sapporo caliciviruses, providing the first indications that genetic diversity exists within caliciviruses of this previously homogeneous clade. On the basis of recent advances in the genetic characterization of members of the family Caliciviridae, we propose a new interim phylogenetic classification system in which Parkville virus would be included with Manchester and Sapporo virus as a separate group distinct from the small round-structured viruses (Norwalk-like viruses) that also cause diarrhea in humans.

Adult↗
PubMed1996

Isolation and characterization of Leishmania donovani calreticulin gene and its conservation of the RNA binding activity.

Calreticulin has been implicated in multiple cell functions. Recently, we have shown that both human and simian calreticulin are RNA binding proteins and that their binding activity is due to phosphorylation. To demonstrate that the RNA binding property of calreticulin is an intrinsic part of this multi-functional molecule and is evolutionarily conserved, we isolated and characterized the calreticulin gene from the unicellular parasite, Leishmania donovani. Amino acid sequence homology between human and Leishmania calreticulin (L. d. cal) is limited, but like the human homologue, L. d. cal binds Ca+2, can be phosphorylated in vitro and binds certain RNA sequences in a phosphorylation-dependent manner. Unlike human calreticulin, L. d. cal is glycosylated and its binding to endogenous Leishmania RNA is phosphorylation-independent. The binding of L. d. cal to Leishmania RNA suggests that the RNA binding activity of calreticulin has remained evolutionarily conserved.

Amino Acid Sequence↗
PubMed1996

Conservation of low-copy gene loci in Old World leishmanias identifies mechanisms of parasite evolution and diagnostic markers.

Genome plasticity has been hypothesized to be a driving force behind parasite speciation. We have evaluated divergence in single and low-copy genes in terms of locus organization, chromosomal localization and gene expression in Leishmania infantum, L. major, L. tropica and three widely divergent geographic isolates of L. donovani. Seventeen genes of low to moderate copy number (1-4 copies/haploid genome) were analyzed to identify restriction fragment length polymorphisms (RFLPs) providing heritable markers distinguishing Old World (OW) leishmanias. These RFLP markers were conserved in parasite isolates from primary infections demonstrating their utility as diagnostic tools. The species designations established by RFLP analysis of field isolates was confirmed by use of monoclonal antibodies. All 17 genes were present in each OW leishmania analyzed except LSIP (A45), which was absent from L. infantum. The 17 genes were found to be distributed among 9 distinct chromosomes. However, in spite of variations in chromosome karyotypes among the various OW leishmanias, individual gene probes localized to a similar sized chromosome from each isolate. These observations coupled with a molecular tree derived from RFLP data suggest that the OW leishmanias comprise a monophyletic lineage, with species associated with cutaneous disease exhibiting the greatest level of divergence. Data from this study supports previous observations that species causing cutaneous and visceral disease have diverged primarily by nucleotide substitutions. Such nucleotide divergence may not only lead to changes in protein function and antigenicity, but may also alter gene regulation programs as exemplified by the finding that the LdI-9-5 and LdE-6-1 genes were expressed only in visceralizing leishmanias.

Animals↗
PubMed1996

An outbreak of viral gastroenteritis in a nursing home: importance of excluding ill employees.

BACKGROUND: In May 1994, 43 persons in a nursing home were reported with gastroenteritis. An outbreak investigation was conducted to determine risk factors for gastroenteritis among residents and staff. METHODS: Data were analyzed using contingency tables; relative risks (RR) and statistical significance were determined with Fisher's Exact Test. The chi-squared statistic to perform a goodness of fit test for the binomial distribution was used to determine whether cases occurred randomly and independently of each other. Stools were tested for bacterial enteric pathogens, ova, and parasites and were examined by electron microscopy, Southern hybridization, and reverse transcription-polymerase chain reaction. Paired sera were collected to detect fourfold rises in antibody titer by enzyme immunoassay against Norwalk viruses. RESULTS: Of 121 residents, 62 (51%) had gastroenteritis, as did 64 (47%) of the 136 staff. The index case was a nurse who became ill at work and continued to work, while symptomatic, for another 2 days. Only residents who had received medications from this nurse between May 17 and May 20 became ill on the first day of the outbreak (13 of 35 versus 0 of 5). Nurses and nurse aides were more likely than employees without direct resident contact to be cases (46 of 68 versus 18 of 58; RR, 2.18; P < .001). Bacterial stool cultures and parasite examinations were negative. Results of electron microscopy, polymerase chain reaction with Southern hybridization, and enzyme immunoassay indicated the causative agent was a small, round, structured virus similar to the Snow Mountain Agent. CONCLUSION: To minimize outbreaks in nursing homes, we recommend that ill staff be excluded from work until symptoms resolve.

Adult↗
PubMed1996

Identification of childhood vaccine providers in Maryland.

The purpose of the study was to compare the utility of an American Medical Association (AMA)-derived list and a Maryland State Department of Health and Mental Hygiene (state)-derived list of potential childhood vaccine providers (CVPs) in identifying true childhood vaccine providers for the Vaccines for Children (VFC) program in Maryland. A telephone survey of a sample of physicians from the two lists was used to determine their status as providers of routine vaccinations to children. Results showed a significant difference between the two lists. The state-derived list was composed of an estimated 60.7% CVPs, whereas the AMA-derived list was composed of an estimated 36.7% CVPs. Using the capture-recapture method, it was estimated that there are about 2077 CVPs in Maryland. Based on this figure, the state-derived list would have identified 71.7% of the state's CVPs, and the AMA-derived list would have identified 59.4%. Using the AMA-derived list would have required contacting approximately 1800 extra providers to identify the additional 350 CVPs (16.8%) not identified in the state-derived list. Accurate, up-to-date lists of providers that include pertinent practice characteristics would enhance the ability to contact specific providers for VFC program enrollment and for other clinical and public health purposes.

Adolescent↗
PubMed1996

Pulmonary tuberculosis in a high school student and a broad contact investigation: lessons relearned.

A case of acid-fast bacillus smear-positive cavitary tuberculosis (TB) was diagnosed in a high school senior (Student A) who lived in a community with a low prevalence for TB. A broad TB investigation was conducted in July 1994 among persons who attended the high school graduation with Student A. Follow-up investigations three months later focused on close contacts at highest risk. A positive tuberculin skin test (TST) was defined as induration of > or = 5 mm after placement of purified protein derivative. We determined the TST results and the estimated costs incurred by the local health department for the broad screening that was conducted. TST results were available for 122/161 (75%) close contacts, and for 1804 persons with nonclose contact with Student A. Her family members were known to have had prior positive TSTs. Positive TSTs were found among 3/122 (2.5%) close contacts, versus 34/1804 (1.9%) persons with nonclose contact. Only one close contact had conversion of TST from negative to positive, and no other active TB case was identified. We estimate the broad TST screening cost the local health department $36,507. Broad TST screening was costly and diverted staff from their customary public health service priorities. Local health departments and clinicians should follow the recommendations of the American Thoracic Society and the Centers for Disease Control and Prevention regarding TB contact investigations.

Adolescent↗