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Biomedical subjects

H Davis

Publications and source records attributed to H Davis.

At least 145 records · Page 8Linked to original sources
PubMed1988

A shigellosis outbreak traced to commercially distributed shredded lettuce.

In the period August 30-October 7, 1986, 347 persons in adjacent west Texas counties (Ector and Midland) contracted culture-confirmed Shigella sonnei gastroenteritis. A case-control study showed an increased risk of acquiring shigellosis in Ector County with eating at outlets of fast-food Restaurant A, and in Midland County with eating at Restaurant B or C. A second case-control study, of persons who had eaten at Ector County outlets of Restaurant A, showed an increased risk of acquiring shigellosis with eating foods containing shredded lettuce and tomatoes, which were served together (odds ratio = 68.8; 95% confidence interval 8.5-293.1). All implicated restaurants received shredded lettuce produced at one lettuce-shredding plant; two implicated restaurants did not receive tomatoes from the lot delivered to other implicated restaurants. The lettuce-shredding plant distributed shredded lettuce and intact lettuce; restaurants that received only intact lettuce were not involved in the outbreak. Investigation at the lettuce-shredding plant suggested that a food handler might have been the source of contamination and that the method of processing might have allowed cross-contamination to occur. In the laboratory, the outbreak strain of S. sonnei multiplied rapidly on shredded lettuce at 22 C and survived on refrigerated shredded lettuce for at least seven days. This outbreak, one of the largest outbreaks of Shigella infections in the United States in the last decade, indicates that a large, geographically widespread shigellosis outbreak can result from contaminated shredded lettuce that is distributed commercially.

Adolescent↗
PubMed1988

The accuracy of industry data from death certificates for workplace homicide victims.

This study compared death certificate data on usual industry for workplace homicide victims in five urban Texas counties, with medical examiners' data on the industries where victims were working when injured. The overall positive predictive value of the death certificate data was 72 per cent. Death certificate data on usual industry underestimated the number of victims working in high-risk industries when injured, partly because of victims whose usual industry was recorded as student, housewife, or military personnel.

Death Certificates↗
PubMed1988

Maternal language environment of children with mental retardation.

Maternal language directed towards children with mental retardation and children matched either for language ability or chronological age was compared in free-play and instruction situations. Results were consistent with the hypothesis that mothers of children with retardation match their verbal behavior to their children's language ability while at the same time adopting a more pervasive teaching role. Specifically, they were more directive, but only in free-play. When explicitly asked to instruct their child, they changed very little in comparison with control mothers, whose directive behavior altered to levels previously adopted in free-play by mothers of children with mental retardation.

Child Language↗
PubMed1987

Evidence for an immune response to HLA class I antigens in the vanishing-bileduct syndrome after liver transplantation.

The relation between donor and recipient status for HLA class I and II antigens in 62 patients undergoing liver transplantation was examined with particular reference to a well-defined variant of chronic rejection, the vanishing-bileduct (VBD) syndrome. A complete mismatch for class I antigens was more common in those with the VBD syndrome than in those with normal graft function or chronic graft malfunction unrelated to the syndrome (p less than 0.025). In contrast, a complete mismatch for class II antigens was considerably less common in those with the VBD syndrome than in those without (p less than 0.02). The association of a complete mismatch for class I and a partial or complete match for class II antigens with the VBD syndrome was highly significant (p less than 0.0005). These findings support the hypothesis that in the VBD syndrome both class I antigen expression on bileduct epithelium and immunological interaction at the level of class II antigens are required for the rejection process to occur. In addition, high-titre donor-specific antibodies to class I antigen, which were present in 6 of 14 of those with the VBD syndrome but in none of those without (p less than 0.0005), may be involved in the pathogenesis of bileduct damage.

Adolescent↗
PubMed1987

Effect of neural crest ablation on development of the heart and arch arteries in the chick.

Mesenchymal derivatives of the neural crest contribute to the connective tissues and blood vessels of the pharyngeal arches, and participate in the septation of the outflow tract of the heart. The present study was designed to determine the nature and timing of alterations in the development of the heart and arch arteries subsequent to diminished neural crest contributions. The neural crest contributing to the three caudalmost pharyngeal arches was ablated bilaterally in chick embryos and compared with sham or unoperated controls. Heart development was studied by scanning electron microscopy. Arch artery development was studied microscopically after intravascular injection of India ink and clearing of the specimen. Neural crest ablation caused morphological changes in most hearts. Hearts in experimental animals commonly were elongate and were subject to inappropriate development of ventricular and atrial areas. A surgical effect delayed the disappearance of arch arteries one and two, and removal of neural crest produced an additional delay. Neural crest ablation caused failure of arch arteries three, four (right), and six to develop to the proper size in some animals. Survival of those whose sixth arch arteries achieved the proper size caused group measurements to reach normal values again by stage 32. Closure of arch arteries in some animals and maintenance in others produced greater variability in experimental animals than in controls. It is significant that heart morphology was altered before septation of the outflow tract normally occurs. This indicates at the least that another factor, such as altered blood flow, contributes to the abnormal development. Altered flow may result from changes in pharyngeal arch mesenchyme and arch artery endothelium.

Animals↗
PubMed1987

Workplace homicides of Texas males.

A review of Texas death certificates for 1975-84 identified 779 civilian males whose deaths were homicides that occurred in the workplace. Injuries from firearms caused 81 per cent of the deaths. The overall rate of workplace homicide was 2.1/100,000 male workers/year. Males employed in taxicab service had the highest rate of workplace homicide. 78.2/100,000 male workers/year. Males employed in certain retail trade industries, law enforcement, and the private-security industry also had high rates of workplace homicide. Male workers greater than or equal to 65 years old were at especially high risk, with a workplace-homicide rate 3.5 times that of younger workers. A review of medical examiners' records in five urban counties indicated that 32 per cent of victims who had worked in eating-and-drinking places and 5 per cent of other workers had blood or cerebrospinal-fluid alcohol levels greater than or equal to 0.10 g/dl. These results provide a base for designing effective strategies to prevent workplace homicides.

Adolescent↗
PubMed1987

Fatal occupational injuries of women, Texas 1975-84.

A review of Texas death certificates for 1975-84 identified 348 cases of fatal occupational injuries of civilian females. Homicides accounted for 53 per cent and motor vehicle-related injuries accounted for 26 per cent of the deaths. Injuries from firearms caused 70 per cent of the homicides. One hundred thirty-three deaths occurred to women employed in the retail trade industry; of these, 77 per cent resulted from homicide. Women workers in gasoline service stations, food-bakery-and-dairy stores, and eating-and-drinking places had especially high risks of homicide. Texas female heavy-truck drivers had the highest fatal-injury rate, with motor-vehicle-related injuries causing 89 per cent of their deaths. These results indicate that effective strategies to prevent fatal occupational injuries of Texas women will need to address the problems of workplace violence and the hazards posed by motor vehicles.

Accidental Falls↗
PubMed1986

Sequential nonstress testing with use of each fetus as its own control.

The sequential nonstress tests of 126 high-risk fetuses were assessed for baseline fetal heart rate, acceleration frequency, amplitude, and duration and the observance of fetal heart rate decelerations. In 108 fetuses (563 tests) with normal perinatal outcomes, no significant trends in these parameters were found. In 18 fetuses (104 tests) with perinatal compromise, 16 had significantly declining acceleration frequencies, 15 had decreasing acceleration duration, four had rising mean baseline rates, and seven, in their last test before delivery, had repetitive late or severe variable decelerations. The last tests of 11 of these 18 fetuses met institutional criteria for reactivity. When the nonstress tests of compromised fetuses were viewed sequentially, acceleration frequency declined by an average of 59% and acceleration duration by an average of 40%. Sequential assessment of the nonstress test, when compared with the use of standard reactivity criteria, improved test sensitivity from 39% to 89% and negative predictive value from 91% to 98%. We conclude that sequential nonstress test assessment in individual fetuses may improve the diagnostic value of this modality and lead to earlier recognition of fetal compromise.

Female↗
PubMed1986

Retinal hemorrhage thresholds for Q-switched neodymium-Yag laser exposures.

Thresholds for retinal vitreal and contained hemorrhages were determined for 1064 nm laser light at 30-nsec and 4-nsec pulsewidths. Rhesus monkeys received graded exposures from a neodymium-yag laser onto either the macular or extramacular region of the retina. Contained hemorrhages appeared as concentric ring structures with white punctate centers. The vitreal hemorrhage was characterized by the presence of choroidal blood in the vitreal chamber at the exposure site. The 30-nsec contained hemorrhage threshold (ED50) was 1.7 mJ on the macula and 2.1 mJ for an extramacular exposure. The 30-nsec vitreal hemorrhage macular threshold was 2.3 mJ, and the extramacular threshold was 6.6 mJ. The threshold for the 4-nsec pulsewidths to produce a hemorrhage (vitreal or contained) on the retina (macula or extramacular) was 340 microJ.

Animals↗
PubMed1986

Percent acceleration time: a new method of fetal assessment.

The percent acceleration time (PAT) is a fetal heart rate parameter, which may be derived from the nonstress test (NST). It is based on measurement of the duration of individual movement-associated fetal heart rate accelerations (MAFAs), obtained during a nonstress test, and is calculated by the formula: (formula, see text) The authors studied 148 fetuses undergoing four or more serial nonstress tests who were delivered within one week of their last test. Percent acceleration time of fetuses with normal outcomes had a mean value of 15.5 +/- 10.0 (SD)%, correlated well with the frequency and amplitude of movement-associated fetal heart rate accelerations but was independent of gestational age and mean baseline fetal heart rate. No normal fetus had a percent acceleration time of less than 5% on its last nonstress test, while only one abnormal fetus had a percent acceleration time that exceeded the mean percent acceleration time of the normal group. All abnormal fetuses had a significant progressive decline in percent acceleration time (mean: 50.6%). Percent acceleration time values were more sensitive in identifying fetuses with perinatal compromise than were conventional criteria for nonstress test reactivity, and may provide a useful alternative to assessment of fetal status when other quantitative methods are unavailable (continuous ultrasound visualization) or less reliable (maternal perception, tokodynamometry, palpation).

Female↗
PubMed1985

Training professionals in behaviour modification.

This paper examines the general issues to be considered in training non-psychologists in the social, health and education services to use a behaviour modification approach in their work. The work in this area is considered in relation to the justification of such training, the personnel involved, the length and content of courses and the methods of teaching. Attention is also given to the evaluation of the effectiveness of the teaching methods including the problems of subsequent maintenance of the knowledge and skills taught. Though behavioural techniques have attracted enormous research efforts, relatively little has been directed at the problems of training personnel in their use.

Behavior Therapy↗