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Biomedical subjects

D M Dwyer

Publications and source records attributed to D M Dwyer.

At least 19 recordsLinked to original sources
PubMed2000

Dissection of the functional domains of the Leishmania surface membrane 3'-nucleotidase/nuclease, a unique member of the class I nuclease family.

Class I nucleases are a family of enzymes that specifically hydrolyze single-stranded nucleic acids. Recently, we characterized the gene encoding a new member of this family, the 3'-nucleotidase/nuclease (Ld3'NT/NU) of the parasitic protozoan Leishmania donovani. The Ld3'NT/NU is unique as it is the only class I nuclease that is a cell surface membrane-anchored protein. Currently, we used a homologous episomal expression system to dissect the functional domains of the Ld3'NT/NU. Our results showed that its N-terminal signal peptide targeted this protein into the endoplasmic reticulum. Using Ld3'NT/NU-green fluorescent protein chimeras, we showed that the C-terminal domain of the Ld3'NT/NU functioned to anchor this protein into the parasite cell surface membrane. Further, removal of the Ld3'NT/NU C-terminal domain resulted in its release/secretion as a fully active enzyme. Moreover, deletion of its single N-linked glycosylation site showed that such glycosylation was not required for the enzymatic functions of the Ld3'NT/NU. Thus, using the fidelity of a homologous expression system, we have defined some of the functional domains of this unique member of the class I nuclease family.

Animals↗
PubMed2000

Invasive pneumococcal infection in Baltimore, Md: implications for immunization policy.

BACKGROUND: Streptococcus pneumoniae is a leading cause of infectious morbidity and mortality. Although blacks are known to have a higher incidence of invasive pneumococcal infection than whites, detailed analyses of these differences and their implications for vaccine prevention have not been reported. OBJECTIVE: To describe the epidemiological characteristics of invasive pneumococcal infection in Baltimore, Md, and its implications for immunization policy. METHODS: Analysis of active, laboratory-based surveillance during 1995 and 1996 among residents of the Baltimore metropolitan area. RESULTS: Of 1412 cases, 615 patients (43.6%) were classified as white and 766 (54.2%) as black. The annual incidence of invasive pneumococcal infection among white and black residents of the Baltimore metropolitan area was 17.8 and 59.2 per 100000 population, respectively (P<.01). Among patients aged 18 years and older, the median age of blacks with invasive pneumococcal infections was 27 years younger than that of whites (P<.01). Among males 40 to 49 years old, blacks had a 12-fold higher average incidence than whites (average incidence, 114.5 and 9.3, respectively; P<.01). By the age of 65 years, 83.8% of cases had occurred in black adults, as compared with 43.8% in white adults (P<.01). In a regression model, age, black race, male sex, low median family income, and county prevalence of acquired immunodeficiency syndrome were each independently associated with a higher incidence of pneumococcal infection. CONCLUSIONS: Young urban black adults in the Baltimore metropolitan area have a dramatically higher incidence of invasive pneumococcal infection than whites. The vast majority of cases of invasive pneumococcal infection in blacks occur before age 65 years. Current immunization efforts have not addressed the high incidence of pneumococcal infection in this population.

Adult↗
PubMed2000

Pathogenic leishmania secrete antigenically related chitinases which are encoded by a highly conserved gene locus.

Recently, we identified and characterized a single-copy chitinase gene (LdCht1) from Leishmania donovani, a protozoan pathogen of humans. It has been hypothesized that this parasite enzyme plays a critical role in the survival of all Leishmania species within their sandfly vectors and for their transmission to humans. Thus, in the current study, pulse-field gel electrophoresis and Southern hybridization with the LdCht1 gene probe were used to demonstrate that this chitinase gene has been conserved across species lines of various pathogenic Leishmania. Further, immunoprecipitation and enzyme activity assays using an anti-LdCht1-peptide serum were used to show that the chitinases produced and released by this group of parasites possessed both highly conserved antigenic epitopes and enzyme activities. Results of these studies demonstrate that the chitinase gene locus and enzyme activity have been conserved across species lines among this group of human pathogens.

Animals↗
PubMed2000

Structurally conserved soluble acid phosphatases are synthesized and released by Leishmania major promastigotes.

Previously it was reported that promastigotes of virtually all pathogenic Leishmania species, except Leishmania major, release a structurally conserved soluble acid phosphatase (AcP) activity during their growth in vitro (P. S. Doyle and D. M. Dwyer, Exp. Parasitol. 77, 435-444 1993). In the current study we used a highly sensitive fluorogenic detection method to demonstrate that soluble AcPs were in fact produced by promastigotes of several different strains of L. major. These L. major AcP activities were readily immunoprecipitated with a rabbit antibody previously generated against the L. donovani AcP. Results of metabolic labeling and immunoprecipitations demonstrated that AcPs produced by the L. majors strains examined had an apparent molecular mass of approximately 77 kDa. Results of Southern hybridization analysis with an L. donovani AcP gene probe showed that the AcP gene loci were conserved in the L. major strains examined. Taken together, these results indicate that the AcP enzyme has been structurally and functionally conserved throughout the evolution of pathogenic species of Leishmania. Such conservation suggests that the AcPs play a functional role in the growth and survival of this group of important human pathogens.

Acid Phosphatase↗
PubMed1999

Risk of meningococcal infection in college students.

CONTEXT: The number of meningococcal outbreaks on college campuses have been increasing in the past few years. However, no published studies have documented the incidence of invasive meningococcal infection in college students or whether the incidence is higher than in the general population of the same age. OBJECTIVE: To compare the incidence of invasive meningococcal infection in Maryland college students with that of the general population of the same age. DESIGN: Retrospective cohort study. SETTING AND PATIENTS: Maryland residents with meningococcal infection from 1992-1997 identified from active, laboratory-based, statewide surveillance for invasive meningococcal disease. MAIN OUTCOME MEASURES: Incidence of invasive meningococcal infection. RESULTS: Of 228 patients with invasive meningococcal infection, 67 were aged 16 to 30 years; 11 and 3 of these attended Maryland 4- and 2-year colleges, respectively. Of these, 12 (86%) had infection caused by Neisseria meningitidis serogroups included in the current meningococcal vaccine. The average annual incidence was 1.74 per 100000 among students in 4-year schools vs 1.44 per 100000 for the general population of the same age (P=.60). Among students in 4-year schools, the incidence was 3.24 per 100000 in on-campus residents vs 0.96 per 100000 in off-campus residents (relative risk, 3.4; 95% confidence interval, 1.0-11.6; P=.05). CONCLUSIONS: The incidence of meningococcal infection in college students is similar to the incidence in the general population of the same age, but college students residing on campus appear to be at higher risk than those residing off campus.

Adolescent↗
PubMed1999

Prevention and control of epidemic keratoconjunctivitis in a teaching eye institute.

PURPOSE: To determine if an ongoing infection control program is associated with a reduction in rates of nosocomial outbreaks of epidemic keratoconjunctivitis (EKC) and outbreak morbidity from nosocomial EKC in a large teaching eye institute. METHODS: The number of nosocomial EKC outbreaks, the number of affected patients, and the total number of patient visits were collected for each year between 1984 and 1997. An infection control program was implemented in 1992. The program included specified methods of patient screening and isolation, handwashing, instrument disinfection, medication distribution, and furlough of infected employees. The program included two levels of intensity of infection control measures, for non-outbreak and outbreak conditions. We compared rates per 100,000 patient visits of nosocomial outbreaks of EKC and affected patients for the 6-year period after the program was implemented, 1992-1997, with corresponding rates for 1984-1991. RESULTS: One, to three nosocomial outbreaks of EKC occurred annually in the period 1984-1991. After the implementation of the infection control program, no nosocomial outbreaks occurred in three of six years studied. In the pre-infection control years 1984-1991, there were 3.89 outbreaks and 54.09 affected patients per 100,000 visits, respectively. For the post-infection control years 1992-1997, the corresponding rates were 0.54 outbreaks and 5.66 affected patients per 100,000 patient visits. Rates for both outbreaks and affected patients were significantly lower for the post-implementation period (p < 0.005 and p < 0.0005, respectively). CONCLUSIONS: An ongoing infection control program was associated with decreased rates of nosocomial EKC outbreaks and outbreak morbidity from nosocomial EKC in our institute. Although several reports have described infection control measures that terminated individual outbreaks of nosocomial EKC, this study demonstrates that an ongoing infection control program may preemptively reduce nosocomial EKC outbreaks.

Baltimore↗
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

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↗