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Biomedical subjects

K Dunn

Publications and source records attributed to K Dunn.

At least 91 records · Page 5Linked to original sources
PubMed1984

Postcoital intervention. A family-planning-clinic experience of 213 cases.

A retrospective study of the outcome of postcoital intervention for the prevention of pregnancy in 201 women who attended the Victorian Family Planning Clinic from January 1982 to September 1983 is presented. Four pregnancies resulted from a total of 213 treatments performed. As a follow-up assessment could only be carried out in 107 cases, the rate of failure of postcoital treatment according to the recommended regimen was estimated as 4%. The reasons for attendance and the methods of contraception involved are considered in general, and the four cases in which the treatment failed are described in more detail. Recommendations are made with regard to subsequent contraception.

Adult↗
PubMed1984

Efficacy of orally administered immune serum globulin against type III group B streptococcal colonization and systemic disease in an infant rat model.

We established an experimental animal model of the gastrointestinal colonization and systemic disease following oral challenge of type III group B streptococcal strain in 3-day-old newborn rats. Two type III group B streptococcal strains isolated from the cerebrospinal fluid of septic newborn infants produced colonization in 57-87% of the challenged animals and 13-31% of these colonized animals developed systemic disease. Using this new animal model, we evaluated the effect of orally administered human immune serum globulin on the colonization and systemic disease. This antiserum contained 21 micrograms/ml of type III group B streptococcal antibody of human IgG class. Animals fed with immune serum globulin developed significantly lower rates of colonization and systemic disease than those of control (albumin or saline) (23 versus 71%, p less than 0.001 for colonization; 7 versus 31%, p less than 0.05 for systemic disease). However, rates of the development of systemic disease among the colonized animals were not significantly different between the two groups (33 versus 43%, p greater than 0.1). These findings suggest that orally administered immune serum globulin is beneficial in the prevention of colonization and systemic disease in this rat model and that this protective effect of oral immune serum globulin occurs primarily at the mucosal level.

Administration, Oral↗
PubMed1983

The family health project: cardiovascular risk reduction education for children and parents.

The principles of family support and of social learning theories were applied to a feasibility study of working directly with family units in a health education program. Twenty-four Anglo, Black, and Mexican-American families of young elementary school children participated in a 3-month cardiovascular risk reduction education project which included eight weekly evening sessions designed to assist families to decrease the frequency of consumption of foods high in sodium and in saturated fats, and to increase the frequency of aerobic exercise. Statistically significant differences between randomly assigned treatment and control groups were noted for reported consumption of high sodium foods and of foods high in saturated fats. Experimental subjects gained more knowledge of factors influencing cardiovascular risk, even though the intervention was behaviorally, rather than cognitively, based. This method of health promotion is deserving of further study.

Adolescent↗
PubMed1982

Electron microscopic visualization of recA-DNA filaments: evidence for a cyclic extension of duplex DNA.

As visualized by electron microscopy, RecA protein binds in a highly cooperative manner to single-stranded fd DNA in solutions of 0.01 M Tris (pH 7.5). The resulting nucleoprotein filament loops are 1.25 micrometers in length, have a fiber diameter of 12 nm and show an indication of a 4.5 nm repeat along the axis of the compact fibers. RecA binds to linear duplex fd DNA in solutions of 0.01 M Tris (pH 7.5) to yield chains of beads which, in the presence of Mg2+ and ATP, coalesce into smooth filaments with a length of 1.9 micrometers (the length of protein-free fd duplex DNA) and have a fiber diameter of 12 nm. In solutions containing Mg2+ and ATP-gamma-S, however, RecA binds to duplex DNA in a highly cooperative manner to yield rigid filaments 3.0 micrometers in length. These filaments are 12 nm in diameter and show a very clear 7.5 nm axial repeat. This extension of DNA to 150% of its usual length in the apparent absence of any single-stranded components suggests that the DNA helix must also be highly unwound and provides new insights into the mode of RecA action.

Adenosine Triphosphate↗
PubMed1982

Comparison of the composition of faecal fluid in Crohn's disease and ulcerative colitis.

We determined the ionic composition of faecal fluid from 13 patients with Crohn's disease limited to the colon, 10 with diffuse ulcerative colitis, and eight with ulcerative proctitis. The Crohn's and colitis groups had similar proportions of colon surface involved radiographically and similar 24 hour faecal weights. However, Crohn's patients' faecal fluid had arithmetically lower mean sodium and statistically lower mean chloride (34.8 mmol/l +/- 16.2 SD vs. 53.1 mmol/l +/- 23.1 SD) and higher potassium (49.2 mmol/l +/- 20.2 SD vs. 33.0 mmol/l +/- 13.8 SD) concentrations (p less than 0.05 for each) and much higher osmolality (487.1 mOsmol/kg +/- 87.1 SD vs. 341.1 mOsmol/kg +/- 88.9 SD, p less than 0.001). Separation of these patients using the faecal osmotic gap agreed with the clinical classification in 86% of cases. The diarrhoea of proctitis patients had a nearly normal ionic composition which was clearly distinguishable from that of diffuse colitis. These results suggest differences in the composition and perhaps the pathogenesis of the diarrhoea of Crohn's and ulcerative colitis. The composition of fluid may prove a useful, non-invasive method for classifying patients with inflammatory bowel disease and, in ulcerative colitis, determining the extent of the inflammatory process.

Chlorides↗
PubMed1981

Filamentous bacteriophage contract into hollow spherical particles upon exposure to a chloroform-water interface.

The bacteriophage M13 is a 1 micrometer long filament consisting of a circular single-stranded DNA loop firmly held within a tubular protein and capsid. We report here that exposure to a chloroform-water interface initiates a 20 fold contraction of each filament into a hollow protein sphere. In these 0.04 micrometer diameter particles, termed M13 "spheroids," two thirds of the DNA is apparently extruded through a hole in the wall of the spheroid; the portion of DNA remaining inside the shell centers about the origins of M13 DNA replication. These results suggest that the filament, upon exposure to a membrane environment, undergoes an ordered change whereby the DNA is released into the cell and the coat protein is changed to a form more easily solubilized by the membrane lipids.

Binding Sites↗
PubMed1981

Metacontrast investigations of sustained-transient channel inhibitory interactions.

The metacontrast paradigm was exploited to study possible inhibitory interactions between sustained and transient channels. Variations and measures of target disinhibition or target recovery. The former type of target recovery is taken as evidence for interchannel sustained-on-transient inhibition; the latter, as evidence for intrachannel transient-on-transient inhibition.

Discrimination Learning↗
PubMed1980

The presence of RNA in a double helix inhibits its interaction with histone protein.

The binding of core histones (H2A, H2B, H3, H4) to a circular plasmid DNA and to a circular DNA-RNA hybrid molecule of similar size has been compared. Circular hybrid molecules were formed from single stranded fd DNA by synthesis of the complimentary strand with ribonucleotides using wheat germ RNA polymerase II. Upon reconstitution of plasmid DNA circles with histone, the sedimentation profiles of the DNA remained sharp by increased several fold in rate. Material from the peak fractions of these sedimentations appeared to be condensed circular loops of nucleosomes when examined by electron microscopy (EM), and the mass ratio of DNA to histone (at the histone concentrations which produced the fastest sedimentations) was typical of native chromatin. In contrast, the sedimentation behavior of DNA-RNA hybrid circles after addition of histone remained unchanged except for a minor fraction which exhibited a broad and faster sedimentation rate. Examination by EM revealed that most of the molecules appeared identical to protein free hybrid circles while the minor, faster sedimenting fraction appeared to be two or more circles bound together by protein aggregates. Finally, a linear molecule consisting of about 3000 base pairs of duplex DNA covalently joined on both ends to 1500 base pairs of RNA-DNA hybrid helix was constructed. Reconstitution of this molecule with core histone showed nucleosome formation only on the central DNA duplex region. Isopycnic banding of fixed hybrid-histone mixtures showed that little or no histone had bound to the bulk of the full hybrid molecules. We suggest that the presence of RNA in a nucleic acid duplex inhibits the condensation of the duplex into a nucleosomal structure by histone.

Chromosome Banding↗
PubMed1977

Induction of Marek's disease virus antigens by IdUrd in a chicken lymphoblastoid cell line.

Marek's disease virus (MDV) antigens, as detected by immunofluorescence, were induced in a lymphoblastoid cell line, MSB-I, in the presence of IdUrd. When treated with 20 microng/ml of IdUrd there was no increase in the number of cells producing virus particles. If IdUrd was removed, an increase in virus production followed. Activation of the MDV genome appeared to require incorporation of IdUrd into cellular DNA and occurred during the first 12 h of culture. Expression of the activated genome required de novo protein synthesis and occurred during the next 12 h. The MDV genome in high producer MSB-I cells could be activated with low concentrations of IdUrd, whereas low producer MSB-I cells could not be activated with IdUrd to any great extent.

Animals↗
PubMedDate not supplied

Three-dimensional microscopy data exploration by interactive volume visualization.

This paper presents a new volume visualization approach for three-dimensional (3-D) interactive microscopy data exploration. Because of their unique image characteristics, 3-D microscopy data are often not able to be visualized effectively by conventional volume visualization techniques. In our approach, microscopy visualization is carried out in an interactive data exploration environment, based on a combination of interactive volume rendering techniques and image-based transfer function design methods. Interactive volume rendering is achieved by using two-dimensional (2-D) texture mapping in a Shear-Warp volume rendering algorithm. Image processing techniques are employed and integrated into the rendering pipeline for the definition and searching of appropriate transfer functions that best reflect the user's visualization intentions. These techniques have been implemented successfully in a prototype visualization system on low-end and middle-range SGI desktop workstations. Since only 2-D texture mapping is required, the system can also be easily ported to PC platforms.

Actins↗
PubMedDate not supplied

Neonatal T-cell tolerance to minimal immunogenic peptides is caused by clonal inactivation.

The mechanisms underlying T-lymphocyte tolerance induced in neonatal mice are still unknown. It is unclear whether the tolerant state is the result of inactivation of T cells on exposure to antigen during development or of active suppression by other T cells specific for the same antigen. To distinguish between these two hypotheses, we have analysed the specificity of tolerance to three cytochrome peptides which differ by only a single amino-acid substitution in the epitope recognized by proliferative T cells. The peptides stimulate proliferative responses which are highly specific with minimal cross-reactivity. As antigen-induced clonal inactivation would address the same cells normally activated by that antigen, the specificity of tolerance should exactly match that of the proliferative response to the antigen, and each cytochrome peptide should induce tolerance to itself alone. Conversely, as T-suppressor (Ts) and T-proliferative (Tp) cells almost invariably seem to recognize distinct, non-overlapping determinants on protein antigens, suppressor-mediated tolerance should not be affected by substitutions in the proliferative T-cell epitope. Tolerance would depend solely on the existence of a shared suppressor determinant, so each cytochrome peptide should induce cross-tolerance to the others. We found that the specificity of tolerance matched that of the proliferative response: each peptide induced tolerance for itself but the response to the variants was unaltered. This result strongly supports the hypothesis of clonal inactivation as an important mechanism in induction of neonatal tolerance.

Animals↗
PubMedDate not supplied

EMT knowledge of ambulance traffic laws.

OBJECTIVE: The safe operation of ambulances using warning lights and siren requires both the public and emergency medical technician (EMT) drivers to understand and obey relevant traffic laws. However, EMTs may be unfamiliar with these laws. The purpose of this study was to evaluate EMTs' knowledge of traffic laws related to the operation of ambulances with warning lights and sirens. METHODS: North Carolina EMTs participating in a statewide EMS conference October 6-8, 1995, completed a five-question survey. Knowledge of ambulance speed limits, yielding at intersections, yielding in roadways, and following distances was assessed using a multiple-choice format. Demographic data pertaining to EMT age, years of experience, paid vs volunteer status, driver's education courses, and past accident involvement were also obtained. Proportions were compared using chi-square analysis, alpha = 0.05. RESULTS: Two-hundred ninety-three of 308 (95%) EMTs attending the conference completed questionnaires. The median number of correct responses to the five knowledge questions was 1 (range 0-4). Thirty-three percent of the EMTs knew that other vehicles are required by law to yield while either approaching or being overtaken by an ambulance with warning lights and sirens; 2% knew that due regard for safety is the only requirement of an ambulance approaching a red light at an intersection; 14% knew that the minimum following distance behind an ambulance is one city block; and 28% knew that there is no speed limit on ambulances with warning lights and sirens. Respondents were more likely to score above the median if they had taken one or more emergency driver's education courses or had nine years or more of EMS experience. CONCLUSION: In this sample, EMT knowledge of basic traffic laws pertaining to ambulance operation is poor. Emergency driver's education courses and increased experience appear to be related to increased knowledge scores. Increased training for EMTs about traffic laws may improve the safe operation of ambulances.

Accidents, Traffic↗
PubMedDate not supplied

Effect of a ground critical care transport service on air medical helicopter utilization.

OBJECTIVE: To investigate the effect of adding a ground critical care ambulance service on the utilization of the pre-existing helicopter air ambulance. METHODS: A retrospective review of the requests for the helicopter was performed during each of three periods: one year prior to initiation of the ground service; the first six months after initiation of the ground service, during which the ground critical care ambulance operated 12 hours daily; and the subsequent six months, during which the ground critical care ambulance operated 24 hours daily. To control for any increase in the demand for health care services, hospital admission rates were used to standardize the helicopter utilization data. Means were compared using ANOVA. RESULTS: Prior to initiation of the ground service, flight requests averaged 82 per month. During the period when the ground service was in place on a 24-hour basis, flight requests averaged 105 per month, a significant increase (p = 0.0010). Although hospital admissions during the same period increased (2,410 to 2,624, p = 0.0001), demand for the helicopter service increased at a faster rate. Flights per 100 admissions increased from 2.3 to 2.9, which is statistically significant (p = 0.0152). CONCLUSION: The attempt to decrease the demand for a helicopter air ambulance by initiating a parallel ground ambulance service was not successful. Programs adding a ground critical care ambulance to existing helicopter services should not expect a decrease in utilization of the helicopter. These services should be viewed as complementary but not interchangeable.

Air Ambulances↗