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Biomedical subjects

J E Roberts

Publications and source records attributed to J E Roberts.

At least 91 records · Page 5Linked to original sources
PubMed1991

Detection of porphyrin excited states in the intact bovine lens.

Previous steady state and time resolved spectroscopic studies on porphyrins have shown that the triplet lifetimes of those sensitizers that bind to lens proteins are lengthened by several orders of magnitude. Presented here is an extension of this experiment to measure these transients in an intact bovine lens. As demonstrated by steady state fluorescence spectroscopy and flash photolysis, mesotetra (p-sulfonatophenyl)porphyrin (TPPS) binds to lens proteins. In air-saturated aqueous solution, TPPS has a triplet lifetime of 2 microseconds. In an intact bovine lens the triplet state decayed via biexponential kinetics with lifetimes of 0.16 and 1.6 microseconds. In addition to a lengthening of the lifetime there was a red shift in the triplet transient spectra of 10-20 nm of the porphyrin in the intact lenses.

Animals↗
PubMed1991

In vivo and photophysical studies on photooxidative damage to lens proteins and their protection by radioprotectors.

Photooxidation, whether initiated by an endogenous or exogenous sensitizer, is an important mechanism in light induced damage to the lens. One of the substrates for this damage is lens protein. A porphyrin sensitizer which binds to lens proteins [mesotetra(p-sulfonatophenyl) porphyrin (TPPS)] was found to photooxidize Skh-2 pigmented mice lens protein in vivo. Uroporphyrin, a model for a non-binding photosensitizer, did not induce photooxidative damage to the mouse lens. The radioprotector 3-amino-2-hydroxypropyl phosphorothioate (WR-77913) was investigated as an agent to retard or negate in vivo photooxidative damage to the lens. Intraperitoneal injections of WR-77913 prior to irradiation reduced the TPPS induced photodestruction of lens protein in Skh-2 pigmented mice. The mechanism of protection was also investigated. Thiols were found to quench both the triplet state of porphyrins and the reactive intermediate singlet oxygen on the order of 10(5) and 10(6) M-1 s-1 respectively. These are probably not fast enough to explain most of the protection afforded by thiols. An additional mechanism may be the accelerated photobleaching of porphyrins by thiols which protects tissue by reducing the absorptions due to the porphyrins.

Amifostine↗
PubMed1991

Enhanced tumour selectivity of photodynamic therapy in the rat colon using a radioprotective agent.

Radioprotective agents have been found to protect normal tissues during photodynamic therapy (PDT). We have investigated a phosphorylated thiol protectant WR-77913 (W7) with the photosensitizer aluminium sulphonated phthalocyanine (AISPc). We compared the effects of PDT on normal and tumour tissue in the rat colon, with and without this protectant. In normal colon no necrosis was seen in sites treated after administration of the W7. Necrosis of mean diameter 4.2 mm was seen in those given the protectant after light exposure. At tumour sites the area of necrosis was similar after light exposure before and after the administration of the protective agent. These results suggest a possible role for W7 in enhancement of selectivity of PDT action. Several mechanisms of protection against porphyrin phototoxicity by these drugs have been proposed, including acceleration of photobleaching. We used fluorescence to detect AISPc in strips of rat colon before and after laser treatment, with and without W7. However, a primary role for the photobleaching of AISPc as the mechanism for the protection shown is not supported by these observations.

Aluminum↗
PubMed1990

Phonological process decline from 2 1/2 to 8 years.

The phonological development of 145 children between the ages of 2 1/2 and 8 years was examined. Speech was assessed annually using a standardized articulation test and analyzed for the occurrence of both common and uncommon phonological processes. A marked decline in process usage was observed between the ages of 2 1/2 and 4 years and infrequent process usage was observed after the age of 4. Uncommon processes were used infrequently, even at 2 1/2 years. No sex differences were found. Race differences were found with respect to isolated processes.

Articulation Disorders↗
PubMed1990

Long-term impact of parental divorce on optimism and trust: changes in general assumptions or narrow beliefs?

Two studies were conducted to examine the long-term impact of parental divorce on beliefs about the self and others. In Study 1, college-aged children of divorce and students from intact families did not differ on 8 basic assumptions or on measures of depression. Those whose parents are divorced, however, were less optimistic about the success of their own future marriages. Assumptions about the benevolence of people best predicted the marital optimism of the parental divorce group, but not of the intact family group. In Study 2, assumptions about the benevolence of people were explored in terms of trust beliefs. College-aged children of divorce and a matched sample from intact homes differed only on marriage-related beliefs, not on generalized trust. Children of divorced reported less trust of a future spouse and were less optimistic about marriage. Exploratory analyses found that continuous conflict in family of origin adversely affected all levels of trust.

Adaptation, Psychological↗
PubMed1990

Photophysical studies on the binding of tetrasulfonatophenylporphyrin to lens proteins.

Previous studies have shown that mesotetra(p-sulfonatophenyl)porphine (TPPS) binds to lens proteins. This characteristic should increase the residence time of the sensitizer in the lens and therefore enhance the probability of inducing photooxidative damage to that tissue in vivo. Subsequent in vivo studies have verified that contention. The present studies were performed to determine the effect of such binding on the spectroscopy and photophysics of the porphyrins. It was found that the binding of TPPS (1) quenches the fluorescence of lens proteins, (2) causes a shift in the ground state absorption spectra, fluorescence excitation spectra and the triplet excited state spectrum of TPPS to longer wavelengths and (3) results in an increase in the triplet state lifetime of TPPS. In the presence of the isolated crystallins the average triplet lifetime increases in the following order: gamma less than beta less than alpha.

Animals↗
PubMed1990

Screening for potential in vivo phototoxicity in the lens/retina.

The eye is particularly vulnerable to damage from the phototoxic side effects of drugs since it is constantly subjected to ambient light. Presented here are several screens that can be used to determine the potential of drugs to cause light damage to the eye. These include a simple screen that takes into account the optical properties of the eye and the absorption spectra of the various drugs. This can be used to omit various drugs as potential photooxidants in the eye. In addition a second, more detailed screen is presented. This can be used to determine a) the quantitative potential for a drug to cause photooxidative damage in the eye, b) the mechanism by which it occurs and c) the in vivo verification of phototoxicity.

Animals↗
PubMed1989

A comparative study of plans for infant care made by adolescent and adult mothers.

This study evaluated the choices of primiparous adolescent and adult mothers about whom they believe will care for their infant after they go home from the hospital. The responses of 70 younger adolescents (age 14-17 years) and 37 older adolescents (age 18-19 years) were compared with 80 adult (age 20-25 years) primiparas regarding their plans for school or work, type of child care arrangements planned, and the father's anticipated involvement in the care of the baby. There were no statistical differences among our three age groups. The results show that first-time mothers in all three age groups more often expect themselves to be the primary care giver for their infant, all age groups expected their mother to help most when they lived with her, and about three quarters of each age group expect the husband/baby's father to help in some way.

Adolescent↗
PubMed1989

Language skills of children with different preschool experiences.

This study examined the language at age 5 of socioeconomically disadvantaged children who had been randomly assigned at birth to a language-enriched day care program with a parent education component, a parent education program without a language-enriched day care, or no treatment. The interventions were administered between the ages of 3 months to 5 years. Language measures, reflecting children's ability to manipulate topics, as well as their structural complexity, semantic diversity, and general talkativeness were examined. The results showed that the disadvantaged children who attended the language-enriched day care program with the parent education component used a significantly greater proportion of high quality topic manipulation skills and less low quality topic manipulation skills during conversation than did children in the other two groups. The day care effect on high quality topic manipulation was present even after adjusting for children's intelligence and for the amount of community day care experience of the children in the parent education alone and control groups. No significant treatment differences were found for structural, semantic, and talkativeness measures. Implications of the result for early language intervention are discussed.

Child Day Care Centers↗
PubMed1989

Comparison of endogenous and exogenous photosensitization in the lens using in vitro and photophysical studies.

Age related, photochemically induced damage to the lens can eventually lead to light-scattering areas which would be evidenced as an opacification of the lens. These modifications may occur at ambient radiation over an extended period, resulting from the initial absorption of radiation by relatively inefficient endogenous sensitizers (eg. tryptophan and/or 3 hydroxy kynurenine glucoside). However, the introduction of an efficient exogenous photosensitizer into the lens can markedly increase the rate by which these changes occur. Photophysical studies of various excited states of these endogenous and exogenous photosensitizers of the lens help explain these differing rates of photolytically induced damage in the lens.

Crystallins↗
PubMed1989

Otitis media in early childhood and cognitive, academic, and classroom performance of the school-aged child.

The relationship between the occurrence of otitis media during the first 3 years of life and cognitive, academic, and classroom performance during the third year of elementary school was evaluated in 44 socioeconomically disadvantaged children. The children attended a research day-care program where their otitis media experience and psychoeducational development were documented prospectively from birth. No significant relationship was found between otitis media in early childhood and performance on tests of verbal intelligence or academic achievement in the third year of school. The number of days of otitis media before 3 years of age was significantly correlated with teachers' ratings of children's attentional behavior in the classroom, however. Children with more early otitis media tended to be rated as less task oriented and less able to work independently than children with less otitis media. This was an exploratory study of a small number of children. Further study of the potential association is needed.

Child↗
PubMed1988

Physiological and 15N-NMR analysis of molecular nitrogen fixation by Methanococcus thermolithotrophicus, Methanobacterium bryantii and Methanospirillum hungatei.

Two mesophilic methanogenic bacteria, Methanobacterium bryantii strain MOH and Methanospirillum hungatei strain GP1 were demonstrated, using several different experimental approaches, to fix dinitrogen. Evidence includes (1) growth with N2 as the sole nitrogen source; (2) incorporation of 15N2 into cellular material (both soluble amino acid pools and insoluble cell protein and other macromolecules) detected by 15N-NMR spectroscopy; (3) acetylene reduction to ethylene by the cells, and inhibition of this reaction by bromoethanesulfonic acid (BES), a methanogen inhibitor. High-resolution 15N-NMR analysis of ethanol extracts of these organisms and cross-polarization magic-angle sample spinning analysis of the solid debris from these extracts are compared to labeled material from Methanococcus thermolithotrophicus, a methanogen previously determined to fix dinitrogen.

Clostridium↗
PubMed1988

Analysis of the structure of synthetic and natural melanins by solid-phase NMR.

The structures of one synthetic and two natural melanins are examined by solid-state NMR using cross polarization, magic angle sample spinning, and high-power proton decoupling. The structural features of synthetic dopa melanin are compared to those of melanin from malignant melanoma cells grown in culture and sepia melanin from squid ink. Natural abundance 13C and 15N spectra show resonances consistent with known pyrrolic and indolic structures within the heterogeneous biopolymer; 13C spectra indicate the presence of aliphatic residues in all three materials. These solid-phase experiments illustrate the promise of solid-phase NMR for elucidating structural information from insoluble biomaterials.

Animals↗
PubMed1988

The convergence between in-labor report and postpartum recall of parturition pain.

This non-experimental study was designed to investigate the congruence between in-labor report and postpartum recall of labor pain as measured by the McGill Pain Questionnaire (MPQ). Fifty married parturients, ages 19 to 39 at term with a normal pregnancy, served as subjects. Analysis of variance showed that postpartum report of labor pain on the Present Pain Intensity scale of the MPQ was not consistently congruent with pain reported during labor. In contrast, the Pain Rating Index of the MPQ provided postpartum data that was congruent with the in-labor report. Significant interaction effects, however, suggested that postpartially the women tended to devaluate the pain of early labor and inflate the pain of transitional labor when compared to their in-labor report. Theoretical and practical implications of the results for the measurement of labor pain are discussed.

Adult↗
PubMed1988

Otitis media in early childhood and its relationship to later phonological development.

The relationship between otitis media during the first 3 years of life and subsequent speech development was examined in 55 socioeconomically disadvantaged children who attended a research day-care program. The children were participants in a longitudinal study of child development in which the number of episodes of otitis media and the duration of each otitis episode were reported prospectively from infancy. Standardized tests of speech were administered between the ages of 2 1/2 and 8 years. No significant relationship was found between otitis media in early childhood and number of common phonological processes or consonants in error used during the preschool years. However, the number of days of otitis media before age 3 was associated with the total number of phonological processes used by children between the ages of 4 1/2 and 8 years. Although these findings suggest that phonological processes after age 4 1/2 tend to drop out more slowly for children with a history of otitis media than of children without histories, no consistent patterns were observed for individual phonological processes or for the total number of consonants in error in this age range.

Child↗
PubMed1987

Different clinical perspectives of good and poor therapy sessions.

This study investigated differences in causal attributions made by student clinicians taking actor and observer roles in good and poor therapy sessions. One hundred thirty-four graduate student clinicians in speech-language pathology were asked to imagine a hypothetical good or poor therapy session in which they took either the role of a clinician working with a client in a session or that of a clinician observing the session. To account for the session's hypothesized outcomes, clinicians taking the actor role cited client causes more frequently than other causes while clinicians taking the observer role cited clinician causes. These results are consistent with the actor-observer bias documented extensively in the psychological and educational literatures. Clinicians' causal attributions also differed for good and poor therapy sessions. Implications are discussed in terms of possible impact on the clinical training process in speech-language pathology.

Attitude of Health Personnel↗
PubMed1987

Patient use of a paediatric hospital casualty department in the east end of London.

This paper describes two surveys carried out at the accident and emergency department of Queen Elizabeth Hospital, a specialist children's hospital situated in the east end of London. Both studies explored factors influencing attendance at the accident and emergency department. One was based on an analysis of recorded information (hospital notes) for a random sample of attenders, spread over a 12-month period. The second was based on personal interviews with a sample of children's parents. Both studies found problems with access to general practitioner care to be the main factors influencing attendance.

Child↗