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Biomedical subjects

J E Roberts

Publications and source records attributed to J E Roberts.

At least 55 records · Page 3Linked to original sources
PubMed1998

Measuring oxygen tension in the anterior chamber of rabbits.

PURPOSE: Measuring the concentration of oxygen in the aqueous humor without penetrating the eye would provide a new dimension in understanding aqueous humor and corneal dynamics. In this study a preinvasive method was developed for determining the cameral oxygen concentration in anesthetized rabbits by measuring the excited-state lifetime of a phosphorescent dye. METHODS: A scanning ocular fluorometer was designed to excite phosphorescence with a brief flash of light and to measure the decay of luminescence for as long as 1000 microsec after excitation. The measurement window was scanned through the depth of the anterior chamber or fixed at the mid-anterior chamber. A depot of the phosphorescent dye Pd-uroporphyrin was injected into the vitreous of eight pigmented rabbits, and within a few days the dye was measurable in the anterior chamber. The excited-state lifetime of this dye is inversely correlated to oxygen concentration and was calibrated by measuring the lifetime of dye in cuvettes equilibrated with oxygen-nitrogen mixtures. Oxygen tensions were determined from lifetimes measured in the open eye, under a polymethylmethacrylate (PMMA) contact lens, under two oxygen-permeable contact lenses, and immediately after lid closure. RESULTS: Oxygen tension in the mid-anterior chamber before placing a PMMA contact lens was 23 +/- 3 mm Hg (mean +/- SD; n = 6). After 20 minutes of PMMA lens wear, oxygen tension decreased to 4 +/- 2 mm Hg. When the focal diamond was scanned through the anterior chamber, oxygen tension was 24 +/- 5 mm Hg near the corneal endothelium and decreased to 17 +/- 8 mm Hg near the crystalline lens. Under the PMMA contact lens this gradient reversed: Oxygen tensions near the endothelium and lens were 3 +/- 2 mm Hg and 6 +/- 2 mm Hg, respectively. Lid closure for 10 minutes or longer decreased the mid-anterior chamber oxygen tension from 21 +/- 2 mm Hg (n = 19 measurements from seven animals) to 10 +/- 3 mm Hg (n = 15 measurements from five animals). CONCLUSIONS: Measuring excited-state lifetime of phosphorescent dyes in the anterior chamber provides a useful method for determining oxygen concentration in vivo, without penetrating the eye. Cameral oxygen tension under PMMA contact lenses are significantly lower than in the uncovered eye. The profile of oxygen tension through the anterior chamber suggests that oxygen is supplied transcorneally to the aqueous humor.

Animals↗
PubMed1997

Effects of paramagnetic cations on the nonexponential spin-lattice relaxation of rare spin nuclei in solids.

Nonexponential spin-lattice relaxation is often observed for rare spin nuclei in the solid state. Deviation from single-component decay may be amplified by the coupling of rare spin nuclei to paramagnetic centers. Nonexponential spin-lattice relaxation was observed in derivatized silica gels resins. This phenomenon was localized and enhanced when paramagnetic transition metal cations were bound to surface functional groups. A stretched exponential analysis method was determined to be robust in fitting nonexponential relaxation curves for silica gels both with and without bound paramagnetic ions. Spin-lattice relaxation rates (T1(-1)) for functional group nuclei increased as a function of percent surface coverage with metal ion. The magnitude of the relaxation rate increase was dependent upon internuclear distances from the paramagnetic center. At low surface coverages, a semi-random distribution of paramagnetic centers increased the degree of stretching of spin-lattice relaxation decays, as measured by decreases in the calculated stretching parameter beta. At higher surface coverages, calculated beta values reached a limiting value, indicating that while the spin-diffusion mechanism in metal-exchanged silica gels is restricted, it is not completely diminished.

Cations↗
PubMed1997

Temporal variability in global self-esteem and specific self-evaluation as prospective predictors of emotional distress: specificity in predictors and outcome.

Recent studies have found that temporal variability and reactivity in self-esteem (SE) are associated with risk for depressive symptoms subsequent to life stress. It is unclear, however, whether it is variability uniquely in SE that is critical, or whether variability in other domains, such as specific self-evaluation (SSE) and affect, would show similar effects. Further, the specificity of these effects to depression is unknown. In the present study, initially nondepressed women completed 7 daily ratings of SE, SSE, and affect. Over a 6-week prospective interval, the interactions of stressful life events and variability in both SE and SSE predicted changes in depression, particularly in individuals with more severe worst lifetime episodes of depressive symptoms. These effects were independent of average level of SE and SSE, as well as neuroticism and self-concept uncertainty. In contrast, variability in affect failed to predict changes in depression in interaction with life stress. Finally, none of the predictor variables interacted with stressful life events in predicting changes in anxiety.

Adult↗
PubMed1997

Melatonin inhibits growth of cultured human uveal melanoma cells.

The effects of melatonin on the growth of human uveal melanoma cells were studied in vitro. Three continuous uveal melanoma cell lines were tested. Cells were plated into multi-well plates. After 24 h, melatonin was added to the medium at concentrations from 0.001 to 1000 nM. Cells were collected and counted after 5 days and compared with the controls. Melatonin inhibited the growth of melanoma cells in a dose-dependent manner (0.1-10 nM) with a mean inhibition rate of 50%. The uptake of bromodeoxyuridine (BrdU) by the melanoma cells was also measured. Melatonin inhibited the uptake of BrdU of melanoma cells at concentrations of 0.1-10 nM with a mean inhibition rate of 40%. These results indicate that melatonin may offer a new treatment for metastatic uveal melanoma.

Bromodeoxyuridine↗
PubMed1997

Lifetime episodes of dysphoria: gender, early childhood loss and personality.

The roles of gender, early childhood loss and personality as risk factors for lifetime episodes of dysphoria were examined in a large sample of college students (N = 557). Dysphoria classifications were based on the Inventory to Diagnose Depression (IDD) and the IDD-Lifetime Version. Brief dysphoria was defined as meeting DSM-III-R symptom criteria for major depression without meeting the two-week duration criteria, whereas protracted dysphoria required that the duration criteria were also met. Although females reported higher levels of depressive symptoms and neuroticism than did males, and were more likely to have a lifetime history of episodes of dysphoria, males were more susceptible to the adverse effects of early childhood loss. Males with loss were more likely to have a history of protracted dysphoria and to report higher levels of neuroticism than were males who did not experience an early parental loss. Neuroticism, in turn, acted as a trait vulnerability characteristic to episodes of dysphoria in both males and females. Interestingly, the effects of gender on lifetime experience of dysphoria were mediated by neuroticism: females' increased vulnerability to episodes of dysphoria was due to their elevated levels of neuroticism.

Adolescent↗
PubMed1996

Life stress and treatment course of recurrent depression: II. Postrecovery associations with attrition, symptom course, and recurrence over 3 years.

Life stress was studied in relation to postrecovery attrition, symptom course, and recurrence of depression over 3 years. Participants were 67 individuals with recurrent depression who had responded to treatment. Life stress was assessed for the prior 12 weeks at acute treatment entry (T1), initial recovery (T2), and after 17 weeks of sustained recovery (T3). Severe life events at T1 predicted greater attrition, a more favorable postrecovery symptom course, and a lower likelihood of recurrence over 3 years. Life stress at T2 was not predictive of outcomes. Finally, undesirable life events at T3 tended to predict a worse symptom course and a higher likelihood of recurrence, particularly for individuals on medication. The findings are discussed in terms of (a) different processes influenced by life stress over time and (b) limitations of existing longitudinal research for studying the effects of life stress over prolonged intervals.

Adult↗
PubMed1996

Adult attachment security and symptoms of depression: the mediating roles of dysfunctional attitudes and low self-esteem.

Three studies investigated the relation between adult attachment security and symptoms of depression. Study l examined the overall magnitude of the association between adult attachment and depression, and Studies 2 and 3 tested whether this relation was mediated by dysfunctional attitudes and low self-esteem. Results from the three studies were consistent with a mediation model. This model suggests that insecure adult attachment styles are associated with dysfunctional attitudes, which in turn predispose to lower levels of self-esteem. Such depletions in self-esteem are directly associated with increases in depressive symptoms over time. Insecure attachment appears to lead to depressive symptoms in adulthood through its impact on self-worth contingencies and self-esteem.

Adult↗
PubMed1996

A comparison of conflict tactics in the supervisory process.

This study investigated three different tactics clinical supervisors in communication disorders predicted they would use in a specific conflict situation. One hundred-sixty supervisors were asked to read one of three case scenarios describing a conflict situation within the supervisory process. All scenarios depicted a student-clinician who had not completed a reading assignment requested by the supervisor. The scenarios differed only in the supervisee's response to the supervisor's question about the incomplete assignment. Subjects were asked to indicate how likely they might be to use each of 15 comments that reflected categories of conflict tactics: avoidance, competitive, or collaborative tactics. Supervisors' choice of tactics differed depending on the response of the supervisee. Overall, supervisors most often chose collaborative responses, followed by avoidance responses and (least often) competitive responses. Implications are discussed in terms of impact on the supervisory process in communication disorders.

Communication↗
PubMed1996

The effect of L-cysteine and N-acetylcysteine on porphyrin/heme biosynthetic pathway in cells treated with 5-aminolevulinic acid and exposed to radiation.

The effects of L-cysteine (LC) and N-acetylcysteine (NAC) on porphyrin accumulation in a human dermal microvascular endothelial cell line (HMEC-1) and a human epidermoid carcinoma cell line (A431) loaded with 5-aminolevulinic acid (ALA) and exposed to ultraviolet A (UVA) and blue light radiation were determined. Porphyrin accumulation was decreased in the presence of 0.1-7.5 mM LC (24.8%-31.4% suppression in HMEC-1 cell; 35.8%-48.9% suppression in A431 cells), and in the presence of 0.1-10.0 mM NAC (30.9%-58.0% suppression in HMEC-1 cells; 8.5%-45.3% in A431 cells). The suppression occurred in a LC or NAC dose-dependent fashion. The above was associated with partial reversal of suppression of ferrochelatase (FeC) activity in HMEC-1 cells and in A431 cells. As compared to FeC activity in cells treated with ALA and irradiation, enzyme activity was higher (by 31.9%-62.1%) in the presence of LC (1.0 mM or 5.0 mM) and in the presence of NAC (1.0 mM or 5.0 mM). These data indicate that LC and NAC have protective effects on porphyrin- and irradiation-induced diminution of FeC activity in HMEC-1 cells and A341 cells in vitro.

Acetylcysteine↗
PubMed1996

Quality of center child care and infant cognitive and language development.

The relations between quality of center-based child care and infant cognitive and language development were examined in a sample of 79 African-American 12-month-old infants. Both structural and process measures of quality of child care were collected through interviews with the center director and observation of the infant classroom. Results indicated that quality of infant care positively correlated with scores on standardized assessments of cognitive development (Bayley Scales of Infant Development), language development (Sequenced Inventory of Communication Development), and communication skills (Communication and Symbolic Behavior Scales). In addition, quality of care in child care centers and at home was positively related. Analyses that adjusted for this association between quality of care at home and in child care suggested that the process measure of quality of child care independently related to the infant's cognitive development, and one structural measure, the infant-adult ratio, independently related to the infant's overall communication skills. Neither child nor family factors was found to moderate the association between child care quality and infant development. These findings, in conjunction with the growing child care literature, suggest that researchers and policymakers should focus on how quality of child care can be improved to enhance, not impair, infant development.

Black or African American↗
PubMed1995

Developmental implications of early-life otitis media.

This symposium addressed possible relationships between early-life otitis media (OM) and various components of child development. The existence and nature of such relationships are of substantial theoretical and practical consequence. Particularly at issue are policies concerning optimal frequencies of examination and screening for middle-ear disease as well as the relative appropriateness of conservative vs. aggressive regimens of management.

Age Factors↗
PubMed1995

Visible light induced changes in the immune response through an eye-brain mechanism (photoneuroimmunology).

The immune system is susceptible to a variety of stresses. Recent work in neuroimmunology has begun to define how mood alteration, stress, the seasons, and daily rhythms can have a profound effect on immune response through hormonal modifications. Central to these factors may be light through an eye-brain hormonal modulation. In adult primates, only visible light (400-700 nm) is received by the retina. This photic energy is then transduced and delivered to the visual cortex and by an alternative pathway to the suprachiasmatic nucleus (SCN). The SCN is a part of the hypothalamic region in the brain believed to direct circadian rhythm. Visible light exposure also modulates the pituitary and pineal gland which leads to neuroendocrine changes. Melatonin, norepinephrine and acetylcholine decrease with light activation, while cortisol, serotonin, gaba and dopamine levels increase. The synthesis of vasoactive intestinal polypeptide (VIP), gastrin releasing peptide (GRP) and neuropeptide Y (NPY) in rat SCN has been shown to be modified by light. These induced neuroendocrine changes can lead to alterations in mood and circadian rhythm. All of these neuroendocrine changes can lead to immune modulation. An alternative pathway for immune modulation by light is through the skin. Visible light (400-700 nm) can penetrate epidermal and dermal layers of the skin and may directly interact with circulating lymphocytes to modulate immune function. However, even in the presence of phototoxic agents such as eosin and rose bengal, visible light did not produce suppression of contact hypersensitivity with suppresser cells. In contrast to visible light, in vivo exposure to UV-B (280-320 nm) and UV-A (320-400 nm) radiation can only alter normal human immune function by a skin mediated response. Each UV subgroup (B, A) induces an immunosuppressive response but by differing mechanisms involving the regulation of differing interleukins and growth factors. Some effects observed in humans are: inhibition of allergic contact dermatitis; inhibition of delayed hypersensitivity to an injected antigen; prolongation of skin-graft survival and induction of a tumor-susceptible state. The following article will review much of the progress in this field and explore possible areas of future research.

Animals↗
PubMed1995

Early experience with a new ePTFE vascular prosthesis for hemodialysis.

BACKGROUND: An expanded polytetrafluoroethylene (ePTFE) graft for hemodialysis designed for immediate cannulation was tested. The graft contains a cannulation segment consisting of a stretch ePTFE base tube surrounded by flat and round ePTFE fibers that are secured by a thin, perforated ePTFE cover. This study reports our early experience with this new vascular prosthesis. PATIENTS AND METHODS: Between June 1994 and March 1995, 48 arteriovenous grafts were implanted in 47 patients for whom autogenous fistula construction was impossible. Mean patient age was 57 years (range 37 to 85), 86% of the patients were black, and 60% were men. Twenty-two (46%) grafts were in the forearm, 19 (39%) in the upper arm, and 7 (15%) in the groin. Unassisted and assisted patency rates were calculated by the Kaplan-Meier method. The times of first hemodialysis relative to implantation and the times to hemostasis after first decannulation were recorded. Explanted grafts were histologically evaluated with hematoxylin and eosin and Gram's stains. RESULTS: The unassisted and assisted 6-month patency rate were 42% and 73%, respectively. Five of the first 10 graft were lost to management and technical errors, after which the respective patency rates were 56% and 82%. Eleven of 22 thrombosed grafts were salvaged, 9 with urokinase thrombolysis and 2 with surgical thrombectomy. Twenty-eight grafts were cannulated within 7 days. The time to hemostasis was usually 2 to 4 minutes and always less than 15 minutes. Histologic analysis of a graft explanted at 40 days showed good fibrous incorporation and capillary ingrowth between the cover and round fibers. CONCLUSIONS: This new ePTFE vascular prosthesis can be safely cannulated immediately after implantation, avoiding the morbidity of temporary central venous catheter hemodialysis. After an initial period of familiarization, patency similar to that of other ePTFE arteriovenous grafts was achieved. For patients requiring urgent hemodialysis, this graft is an ideal alternative that allows immediate, safe cannulation.

Adult↗
PubMed1995

Prospective surveillance for otitis media with effusion among black infants in group child care.

OBJECTIVE: To document the prevalence of otitis media with effusion (OME) in 102 black children observed prospectively between 6 and 24 months of age. METHODS: Study children attended nine different center-based child care facilities. Middle ear status was assessed by pneumatic otoscopy and tympanometry every 2 weeks. RESULTS: All children, except one, had OME during the period of observation. The proportion of child-examinations revealing bilateral OME ranged from 76% between 6 and 12 months of age to 30% between 21 and 24 months of age. Effusions were considered purulent in only 13% of examinations revealing middle ear fluid. The mean incidence of purulent OME was 2.13 episodes per child per year. Sixty-six children had at least 4 months of continuous bilateral OME during the period of observation; 57 were followed without placement of tympanostomy tubes. Bilateral OME had resolved before the second birthday in 95% of these children, and within 3 months of achieving the 4-month criterion in 50% of subjects. CONCLUSIONS: Persistent bilateral OME occurs commonly between 6 and 18 months of age in infants who enter group child care during the first year of life. In this study, spontaneous resolution of bilateral effusion by 2 years of age was typical.

Acoustic Impedance Tests↗
PubMed1995

Life events and bipolar disorder: implications from biological theories.

Although a number of studies suggest that stressful life events play a role in bipolar disorder, methodological flaws impose serious limitations on this literature. Nonetheless, better designed studies indicate that life events influence the course of bipolar disorder. Little is known, however, about the nature of events that are of particular importance to this disorder. Given the strong biological vulnerability and the unique clinical aspects of bipolar disorder, certain forms of stress may have stronger interactions with vulnerability characteristics. Three major biological theories of bipolar disorder are discussed, with particular attention to their implications for investigations of life events. Although tenuous, these models suggest that greater attention needs to be paid to particular dimensions of life events and the course of disorder.

Bipolar Disorder↗
PubMed1995

Otitis media in early childhood and cognitive, academic, and behavior outcomes at 12 years of age.

Examined the association between otitis media with effusion (OME) during the first 3 years of life and cognitive and academic performance and behavioral outcomes at 12 years of age in 56 socioeconomically disadvantaged children attending a research childcare program. OME history was prospectively documented from birth through 3 years during well and illness periods. Standardized tests of intelligence and academic achievement and measures of behavior were administered when children were 12 years of age. OME during early childhood was not related to intellectual performance, academic achievement, behavior, or attention. Results do not support a long-term relationship between a history of OME and later developmental outcomes. Generalizations of these findings to other populations should be done cautiously.

Child↗
PubMed1995

Age-related changes in the human lens as monitored by detection of porphyrin excited states.

Previous studies have shown that the triplet state lifetimes of various porphyrins are increased by several orders of magnitude when they are bound to lens protein. Flash photolysis studies of mesotetra (p-sulfonatophenyl)porphyrin (TPPS) on intact bovine lenses indicated a biexponential decay of the triplet state with lifetimes of 160 microsecond and 1.6 ms. Here we extend those measurements to TPPS associated with intact human lenses. Steady-state fluorescence measurements indicate that TPPS binds to both young and old human lenses. In an intact young human lens, the TPPS triplet state is observed to decay biexponentially with lifetimes of 50 and 680 microsecond. As the age of the lens increases, the lifetime of the shorter-lived component lengthens while that of the longer-lived component decreases slightly. In order human lenses, the two lifetimes coalesce and the triplet decay exhibits purely monoexponential behavior. These photophysical characteristics apparently are due to age-related modification(s) of the protein in the human lens resulting in an increasingly more homogeneous environment around the porphyrin.

Aging↗