Biomedical subjects
Publications and source records attributed to J R Davis.
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A mathematical model was defined to estimate the degree of in vivo activity against Plasmodium falciparum sporozoites expressed by volunteers vaccinated with a synthetic peptide comprising the immunodominant epitope of the circumsporozoite protein. Relative to the course of infection in non-immunized controls, infections in vaccinated volunteers corresponded to the neutralization or delay of development of greater than 99% of challenge sporozoites.
To investigate the kinetics of monocyte/macrophage activation in falciparum malaria we determined urinary neopterin values serially in experimentally infected volunteers. Three subjects who had been immunized with irradiated sporozoites via mosquito bites served as controls. These individuals remained aparasitaemic, afebrile and without a rise in neopterin after challenge by infective mosquitoes. Four non-immune subjects developed Plasmodium falciparum parasitaemia, fever (3 of 4) and sharp rises in neopterin. Parasite densities reached 10-100 parasitized erythrocytes per microliter before elevations in temperature or neopterin levels were detected. Onset of fever preceded the rise in neopterin excretion by one day. Prompt chemotherapy was associated with the clearance of parasites from the blood and the return of temperature and neopterin levels to normal.
The FiltraCheck-UT1 (FC) is a disposable colorimetric urine screen for bacteriuria that requires less than 1 min to perform. The results of the FC and two other urine screens, the Bac-T-Screen (BTS) and the Chemstrip LN test strip (LN), were compared with quantitative culture method. A total of 551 urine specimens were tested. The sensitivity of FC, BTS, and LN for probable pathogens at greater than or equal to 10(5) CFU/ml was 94.8%, 97.4%, and 77.9% respectively. These values for specimens with probable pathogens at greater than or equal to 10(4) CFU/ml were 91.1%, 92.1%, and 74.3%, respectively. When the LN was combined with the FC or BTS as a urine screen, the sensitivity for probable pathogens was improved.
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X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterised by selective susceptibility to Epstein-Barr virus and frequent association with malignant lymphomas chiefly located in the ileocecal region, liver, kidney and CNS. Taking advantage of a large bacterial clone contig, we obtained a genomic sequence of 197620 bp encompassing a deletion (XLP-D) of 116 kb in an XLP family, whose breakpoints were identified. The study of potential exons from this region in 40 unrelated XLP patients did not reveal any mutation. To define the critical region for XLP and investigate the role of the XLP-D deletion, detailed haplotypes in a region of approximately 20 cM were reconstructed in a total of 87 individuals from 7 families with recurrence of XLP. Two recombination events in a North American family and a new microdeletion (XLP-G) in an Italian family indicate that the XLP gene maps in the interval between DXS1001 and DXS8057, approximately 800 kb centromeric to the previously reported familial microdeletion XLP-D.
Rectal dysplasia and carcinoma associated with human papillomavirus infection are increasing in prevalence among homosexual men, particularly those infected with the human immunodeficiency virus. We report a case involving a 39-year-old homosexual man with AIDS who developed a persistent rectal ulcer. A biopsy of the ulcer revealed severe squamous dysplasia, and human papillomavirus type 33 was detected in rectal tissue with use of in situ DNA hybridization. This genotype of virus has not been previously associated with anal or rectal dysplasia in homosexual men, including those infected with the human immunodeficiency virus. The rectal ulcer resolved after 2 months of oral therapy with 60 mg/d of isotretinoin, a retinoid.
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Three social-interaction behaviors of a withdrawn chronic schizophrenic were increased using a discriminated avoidance ("nagging") procedure. The three behaviors were: (a) voice volume loud enough so that two-thirds of his speech was intellibible at a distance of 3m; (b) duration of speech of at least 15 sec; (c) placement of hands and elbows on the armrests of the chair in which he was sitting. "Nagging" consisted of verbal prompts to improve performance when the behaviors did not meet their criteria. A combined withdrawal and multiple-baseline design was used to evaluate the effectiveness of the procedure, and the contingency was sequentially applied to each of the three behaviors in each of four different interactions to determine the degree of stimulus and response generalization. Results indicated that the contingency was the effective element in increasing the patient's appropriate performance, and that there was a high degree of stimulus generalization and a moderate degree of response generalization. After the patient's discharge from the hospital, the durability of improvement across time and setting was determined in followup sessions conducted at a day treatment center and at a residential care home. Volume and duration generalized well to the new settings, while arm placement extinguished immediately.
When reviewing the broad area that relates environments to addiction one is faced with an enormous volume of research with differing environmental and psychosocial factors, contrasting populations, a variety of addictive substances, and a range of addiction processes. For all these factors, there are important outcome variables. To survey this disparate literature, it is helpful to use a multiaxial model as a framework or taxonomy. In this way it is possible to see the effects that environments, broadly conceived, exert on addictive behaviors. A variety of environments is considered: interpersonal, organizational, cultural and physical, as one axis or dimension. The influence of this dimension on a second dimension relating to type of addiction is also examined. Finally, a dimension pertaining to the "life history" of addictions, from acquisition through maintenance, cessation, and relapse is considered in relation to the first two dimensions. While a variety of environmental factors affect addictive behaviors, current research indicates the need to take individual differences, cognitive mediation, and the interaction of the person with the environment into account. Significant areas that need further exploration are the failure of addictions to occur in some environments, and the development of secondary prevention approaches. Implications for intervention and directions for future research are suggested.