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Biomedical subjects

L W Roberts

Publications and source records attributed to L W Roberts.

At least 37 records · Page 2Linked to original sources
PubMed1995

Source localization for template implants with particular reference to stepping-source afterloaders.

Source localization from radiographs can be very difficult for template-guided implants if the needle images overlap. At UCSF several techniques to make this task easier have been developed. The techniques include selection of an optimum simulator gantry angle, use of different types of dummies, and differential dummy loading. In addition, several modifications have been made in our brachytherapy planning computer program to facilitate source entry. As a result of these improvements, source localization is now accomplished in much less time with improved accuracy.

Brachytherapy↗
PubMed1993

Gender difference in mate preference among law students: divergence and convergence of criteria.

We examined six hypotheses derived from evolutionary theory regarding sex differences in mate-selection criteria. The subjects were 160 law students who viewed color photographs of live models that were paired with different status cues such as costume variation and descriptions of income and occupation. A multivariate analysis of variance and regression analyses revealed highly significant sex differences in the following responses: reported willingness to engage in unqualified sexual relations; reported willingness to have sexual relations with stimulus persons as compared with the willingness to engage in higher investment relationships such as dating and marriage; the effects of stimulus persons' status and physical attractiveness in determining thresholds of initial acceptability; and tradeoffs, that is the ability of high physical attractiveness to compensate for low status, and of high status to compensate for low physical attractiveness. Law students also responded to nine statements concerning prospective spouses' relative income, occupational prestige, and physical attractiveness. These responses exhibited sex differences consistent with those found in the experimental manipulation.

Adult↗
PubMed1993

Laboratory evaluation of repellents against four anopheline mosquitoes (Diptera: Culicidae) and two phlebotomine sand flies (Diptera: Psychodidae).

Deet, the lactone CIC-4, and the piperidine compounds A13-37220 and A13-35765 were evaluated for initial repellency against laboratory-reared Anopheles albimanus Wiedemann, An. freeborni Aitken, An. gambiae Giles, An. stephensi Liston, and Phlebotomus papatasi (Scopoli) using a dose-response testing procedure on human volunteers. In addition, deet and CIC-4 were tested against Lutzomyia longipalpis (Lutz & Neiva). In general, the repellency of A13-37220, A13-35765, and CIC-4 was not markedly different from that of deet against each species tested; however, the different species varied greatly in response to the repellents. Overall, An. stephensi, L. longipalpis, and P. papatasi were the most sensitive, and An. albimanus the most tolerant species. The four repellents subsequently were tested against An. stephensi and An. albimanus to determine the duration of repellency. AI3-37220 provided effective (> 90%) protection against An. stephensi bites for 7 h, whereas deet, AI3-35765, and CIC-4 provided 6, 5, and 3 h of protection, respectively. Each of the four compounds provided < 1 h of protection against An. albimanus bites.

Animals↗
PubMed1992

"America responds to AIDS," but did college students? Differences between March, 1987, and September, 1988.

To assess thoughts, perceptions, attitudes, and behavior related to AIDS, data were collected from 2 similar samples of college students. The sets of data were collected 18 months apart. Results indicate increased awareness and knowledge and changed attitudes and behaviors in some cases, but the absolute magnitudes of the differences are small for most between-group comparisons. Also, the evidence suggests that many students lack detailed knowledge and fail to see the implications of their knowledge for change in their own behavior. These findings imply educational efforts must go beyond merely providing knowledge and explicitly link facts to personal belief systems and decision making.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Comparative sensitivity of four Anopheles (Diptera: Culicidae) to five repellents.

Five repellents were evaluated against Anopheles albimanus Wiedemann An. freeborni Aitken, An. gambiae Giles, and An. stephensi Liston, using a "free choice," dose-response testing procedure on rabbits. Overall, deet was the most effective repellent based on effective dosages (ED50's and ED95's), except against An. albimanus. An. albimanus was significantly more tolerant to deet compared with dimethyl phthalate or ethyl hexanediol. Permethrin was effective against all four anopheline species at the ED50 levels; however, the ED95 values were higher compared with the other repellents. There were significant differences in sensitivity of some of the four species to all the repellents tested, except dimethyl phthalate and indalone. The variability in the response of these anopheline species to repellents confirm that the extrapolation of repellent data from one anopheline species to another is unreliable and that comprehensive tests are needed for each species.

Animals↗
PubMed1991

Repellency of two deet formulations and Avon Skin-So-Soft against biting midges (Diptera: Ceratopogonidae) in Honduras.

Two U.S. military issue deet repellent formulations (75% deet liquid and 33% deet lotion) and Avon Skin-So-Soft were tested against ceratopogonid midges under field conditions in Honduras. Test subjects were U.S. military personnel deployed to Honduras for training. Culicoides furens accounted for 96.3% of all midges collected. The liquid and lotion formulations of deet and Avon Skin-So-Soft provided 97.9, 95.9 and 71.4% protection, respectively, compared with the untreated control. Both deet formulations provided significantly better protection (P less than 0.05) than Avon Skin-So-Soft. The latter provided protection by trapping the midges in the oily film and not by repelling the insects as did the deet formulations.

Animals↗
PubMed1990

Cutaneous myiasis caused by the African tumbu fly (Cordylobia anthropophaga).

We describe a patient with cutaneous myiasis caused by the African tumbu fly (Cordylobia anthropophaga). This case demonstrates the need for a detailed travel history and an understanding of the fly life cycle to prevent erroneous diagnosis and to expedite prompt treatment. The nature of the lesions, larval morphological features, histological characteristics, and immune response directed toward fly maggots are described.

Abdomen↗
PubMed1989

Mechanical transmission of Trypanosoma brucei rhodesiense by Glossina morsitans morsitans (Diptera:Glossinidae).

Interrupted feedings of teneral, laboratory-reared Glossina morsitans morsitans were used to study mechanical transmission of Trypanosoma brucei rhodesiense. Intervals between exposure of individual flies on parasitaemic rats and refeeding on clean rats were varied from five minutes to 24 hours. Direct transmissions were demonstrated at each interval up to 160 minutes after exposure. Proboscis dissections showed that active trypanosomes were present up to 320 minutes after exposure. No mechanical transmissions from bovine to bovine occurred in 39 attempts, when groups of 20-120 flies exposed on parasitaemic bovines were transferred immediately to uninfected cattle, but two of 40 individual flies exposed on parasitaemic bovines mechanically transmitted trypanosomes to clean rats. Proboscis dissections made immediately after flies were exposed to a bovine with a parasitaemia of 4.8 x 10(-4) trypanosomes/microliters of blood showed that 11 of 20 (55%) had active trypanosomes in the food canal. The mean number of trypanosomes per proboscis was 29.4 (+/- 20.5). Of 20 flies exposed on a bovine with a low parasitaemia, however, only one trypanosome was seen in proboscis dissections. The parasitaemia of the infected donor was an important factor in mechanical transmission. The mechanical transmission of trypanosomes from one host to another may largely depend on the infectivity threshold of the recipient host, and individual mechanically-infected tsetse flies may not transmit an infective dose.

Animals↗
PubMed1988

Improved dose distribution with customized I-125 source loading in temporary interstitial implants.

I-125 sources are being used in temporary interstitial implants of various sites. Radiation safety considerations favor its use over other available radioisotopes. Cost containment is achieved by using the same sources for a number of patients. Loading I-125 seeds into implant catheters at our institutions permit customized source arrangement to optimize the implant dose patterns. Clinical examples are given for which the dose distributions achieved with customized source loading are superior to those achievable with standard Ir-192 ribbons.

Brachytherapy↗
PubMed1988

Suppurative chondritis: its incidence, prevention, and treatment in burn patients.

A retrospective study of 317 cases of suppurative otochondritis occurring in a population of 4794 burned patients successively admitted to one institution between 1967 and 1984 is presented. During the study interval, the incidence of the disease decreased from 20 percent to less than 3 percent in patients with burns of one or both ears. The bacterial species associated with chondritis, principally Pseudomonas aeruginosa and Staphylococcus species, did not change. Patients admitted later than the second postburn day exhibited a significantly greater incidence of chondritis. The crucial factors in prevention of this complication appear to be avoidance of pressure on burned ears and topical chemotherapeutic control of local Pseudomonas infection. Systemic antibiotic prophylaxis did not appear to influence the incidence in the studied population. Several approaches to clinical management of suppurative chondritis are reviewed.

Adult↗
PubMed1987

Gibberellin-mediated synergism of xylogenesis in lettuce pith cultures.

Major gibberellins (GAs) in lettuce (Lactuca sativa L. cv Romaine) pith explants have been identified by gas chromatography-mass spectrometry (GC-MS) or GC-selected ion monitoring (GC-SIM) as GA(1), 3-epi-GA(1), GA(8), GA(19), and GA(20). Treatment of pith explants with indole-3-acetic acid (IAA) (57 micromolar) plus kinetic (0.5 micromolar) induced xylogenesis. In this xylogenic treatment, the concentration of a biologically active, polar GA-like substance(s) increased during the first 2 days of culture, although all of the above GAs decreased (as measured by GC-SIM). In non-xylogenic treatments, where explants were cultured without exogenous hormones, or with IAA or kinetin alone, the concentration of the biologically active, polar GA-like substance(s) decreased during the first two days of culture, as did all of the above GAs (as measured by GC-SIM). Treatment of pith explants with exogenous GA(1) alone did not induce xylogenesis, but GA(1) at very low concentrations (0.0014 and 0.003 micromolar) synergized xylogenesis in the IAA plus kinetin-treated cultures. These results suggest that changes in the concentration of certain endogenous GAs may be involved in xylogenesis mediated by IAA plus kinetin in lettuce pith cultures.

Journal Article↗
PubMed1984

Introduction of xylem differentiation in lactuca by ethylene.

Evidence was obtained to support the hypothesis that ethylene is involved in xylem differentiation in primary pith explants of Lactuca sativa L. cv Romaine cultured in vitro. Xylem elements differentiated when explants were supplied indole-3-acetic acid (IAA) in combination with either the ethylene biosynthetic precursor 1-aminocyclopropane-1-carboxylic acid (ACC), the ethylene-releasing agent 2-chloroethylphosphonic acid (CEPA), or kinetin. In contrast, no xylem elements differentiated in the presence of IAA, kinetin, ACC, or CEPA alone, or when kinetin was supplied together with ACC or CEPA. These results show that ethylene will substitute qualitatively for cytokinin during auxin-induced xylogenesis, and suggest that both ethylene and auxin are required for xylem differentiation in Lactuca.

Journal Article↗
PubMed1981

Probing by Glossina morsitans morsitans and transmission of Trypanosoma (Nannomonas) congolense.

Successive probings on nine mice each by 32 Glossina morsitans morsitans infected with Trypanosoma (Nannomonas) congolense resulted in 54% of the mice (156/288) becoming parasitemic. A second trial with 25 surviving infected flies resulted in transmission by probing to 37.3% (84/225) of the host mice. The patterns of transmission were similar in the two trials, with transmission rates in the first and second probings higher than those for feedings to repletion after nine consecutive probings. Infected flies probed significantly more times and required more time to engorge than noninfected flies. Probing transmissions by cyclically infected flies may be important in the spread of trypanosomes in endemic areas, since feeding interruptions can result in transmission to more than one host at each feeding interval.

Animals↗