"Tell me about yourself": The patient-centered interview.
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Communication↗
Biomedical subjects
A J Adler
Publications and source records attributed to A J Adler.
Tubulins in the primate retina: evidence that xanthophylls may be endogenous ligands for the paclitaxel-binding site.
The xanthophylls-lutein, zeaxanthin, and meso-zeaxanthin (L&Z)-are found in the central region of the primate retina, which is called the macula lutea (yellow spot). How they are anchored there and what their function is has been debated for over 50 years. Here, we present evidence that they may be bound to the paclitaxel (Taxol) binding site of the beta-tubulin subunit of microtubules and that a major function may be to modulate the dynamic instability of microtubules in the macula. Also, we compare nucleic acid and amino acid sequences of tubulins that are in human brain with those we have isolated from human-retina and monkey-macula cDNA libraries. In so doing, we suggest that in primates, class I beta-tubulin consists of at least two subtypes (beta(Ia) and beta(Ib)). Alignment analysis of the sequences of the genes for beta(Ia) and beta(Ib) indicates that the corresponding mRNAs may have other functions in addition to that of coding for proteins. Furthermore, we show that there are at least five different types of beta-tubulin in the macula lutea of rhesus monkey.
Alkaloids↗
In vivo CD4+ T cell tolerance induction versus priming is independent of the rate and number of cell divisions.
In vitro studies have suggested that tolerance induction (i.e., anergy) is associated with an inability of T cells to proliferate vigorously upon Ag recognition. In vivo, the relationship between T cell proliferation and tolerance induction is less clear. To clarify this issue, we have been studying a model system in which naive CD4+ T cells specific for the model Ag hemagluttinin (HA) are adoptively transferred into different transgenic founder lines of mice expressing HA as a peripheral self-Ag. When transferred into two lines whose HA expression differs by at least 1000-fold, HA-specific T cells undergo multiple rounds of cell division before reaching a nonresponsive (i.e., tolerant) state. While the proliferative response is more rapid in mice expressing higher levels of HA, the T cells become tolerant regardless of the level of peripheral HA expression. When the T cells encounter HA expressed as a viral Ag, they proliferate at a similar rate and undergo the same number of divisions as with self-HA, but they do not become tolerant. These results indicate that a tolerizing stimulus can induce similar T cell mitotic rates as a priming stimulus. Therefore, CD4+ T cell tolerance induction in vivo is not the result of an insufficient proliferative response elicited upon TCR engagement.
Adoptive Transfer↗
Human interphotoreceptor matrix contains serum albumin and retinol-binding protein.
It is usually assumed that IRBP (interphotoreceptor retinoid-binding protein) is the only protein present in the interphotoreceptor matrix (IPM) capable of shuttling visual-cycle retinoids between photoreceptors and the retinal pigment epithelium. However, this laboratory previously presented qualitative evidence (Western blots) that serum albumin is present in human IPM. Furthermore, Ong and coworkers (1994) found that cultured RPE cells synthesize serum retinol-binding protein (RBP) and secrete it, mainly into the apical culture medium, which would correspond to the IPM in intact eyes. As both of these proteins can bind all- trans -retinol and 11- cis -retinal, it was of interest to quantify the amounts of albumin and RBP in human IPM. We used radial immunodiffusion to accomplish this. The average molar ratio of serum albumin to IRBP in these samples was 1.9; that of RBP to IRBP was 0.015. The presence of a high concentration of serum albumin in the IPM in situ was confirmed by the intense immunohistochemical staining seen in sections of fresh human eyes. The human case is not unique; various concentrations of albumin were found in the IPM of all vertebrate species examined (by gel electrophoresis). These results indicate that both serum albumin, because of its very high concentration in the IPM, and RBP, because of its comparatively tight binding to retinoids, need to be considered, along with IRBP, as proteins that may participate in visual-cycle transport. The accompanying paper addresses this concern.
Extracellular Matrix↗
IRBP enhances removal of 11- cis -retinaldehyde from isolated RPE membranes.
Interphotoreceptor retinoid-binding protein (IRBP) greatly enhances the conversion of all- trans -retinol to 11- cis -retinal by the retinal pigment epithelium (RPE) and facilitates 11- cis -retinal release from the RPE. However, the mechanisms by which IRBP exerts these effects are not clear. Using a model system of purified bovine IRBP and isolated bovine RPE membranes, we investigated the possibility that IRBP may favor the delivery of all- trans -retinol to, or the release of 11- cis -retinal from, RPE membranes. As the interphotoreceptor space contains serum retinol-binding protein (RBP) and serum albumin in addition to IRBP, we similarly examined the exchange of retinoids between RPE membranes and human RBP or bovine serum albumin (BSA). Isolated RPE membranes were loaded with radioactive 11- cis -retinal and incubated with solutions of IRBP, RBP, BSA or with buffer alone. Membranes (pellet) and retinoid-binding protein or buffer (supernatant) were separated by centrifugation and analysed for radioactive 11- cis -retinal. Membranes incubated with buffer alone released only 4-5% of their 11- cis -retinal, while 25 microm IRBP removed 18-35%. More retinal was released as the membrane concentration was reduced. In contrast, RBP and BSA removed little retinal, even though both proteins are capable of binding this retinoid. Similar results were obtained with bovine liver membranes, consistent with the idea that the effects of IRBP do not depend on an RPE surface receptor for IRBP. IRBP was also markedly superior to RBP and BSA in removing all- trans -retinol from RPE membranes. In addition, IRBP efficiently delivered bound all- trans -retinol to membranes; however, in contrast to their differential removal of retinoids, all three binding proteins delivered comparable amounts of retinol to membranes. (This result supports the practice of using BSA as a retinoid carrier in in vitro experimental systems). We conclude that, whereas IRBP shares with other retinoid-binding proteins the ability to deliver retinol to membranes, IRBP is unique in its capacity to remove 11- cis -retinal from membranes. This may be the feature of IRBP that drives the vitamin A cycle to efficiently produce 11- cis -retinal.
Animals↗
CD4+ T cell tolerance to parenchymal self-antigens requires presentation by bone marrow-derived antigen-presenting cells.
T cell tolerance to parenchymal self-antigens is thought to be induced by encounter of the T cell with its cognate peptide-major histocompatibility complex (MHC) ligand expressed on the parenchymal cell, which lacks appropriate costimulatory function. We have used a model system in which naive T cell receptor (TCR) transgenic hemagglutinin (HA)-specific CD4+ T cells are adoptively transferred into mice expressing HA as a self-antigen on parenchymal cells. After transfer, HA-specific T cells develop a phenotype indicative of TCR engagement and are rendered functionally tolerant. However, T cell tolerance is not induced by peptide-MHC complexes expressed on parenchymal cells. Rather, tolerance induction requires that HA is presented by bone marrow (BM)-derived cells. These results indicate that tolerance induction to parenchymal self-antigens requires transfer to a BM-derived antigen-presenting cell that presents it to T cells in a tolerogenic fashion.
Animals↗
Does the use of topical lidocaine, epinephrine, and tetracaine solution provide sufficient anesthesia for laceration repair?
OBJECTIVE: To determine: 1) the effectiveness of lidocaine, epinephrine, and tetracaine (LET) solution in eliminating or reducing the pain experienced in suturing superficial lacerations in adult patients; and 2) the effectiveness of LET in reducing the pain of local anesthetic injection. METHODS: A prospective, randomized, double-blind study in which 60 adult patients with superficial lacerations were entered was conducted in the ED of a community-based teaching hospital affiliated with the University of Toronto. Following application of the LET or placebo (sterile water) solution to the laceration, a visual analog pain scale was recorded by the patient upon needle probing of the wound margin. If probing was painless, the laceration was repaired using LET alone. If injection of local anesthetic was required, an additional pain scale was elicited to quantify the attenuation of the pain of injection by the prior application of LET. RESULTS: Pain scale values on needle probing were significantly reduced in the LET group vs the placebo group (medians of 4.0 vs 5.0 cm, respectively; p < 0.05). Only 13 of the 30 patients in the LET group required additional anesthetic, while all 30 patients in the placebo group requested local anesthetic. Pain scale values on injection of local anesthetic were not significantly different between the LET and placebo groups (medians of 3.5 vs 5.0 cm, respectively; p = 0.09), although there was a trend for lower pain scale values for those patients who received LET. No adverse effects were noted after the application of either LET or placebo solution. Follow-up was achieved for 54 of 60 patients with only 1 complication (a wound infection) reported in the LET group. CONCLUSIONS: Significantly fewer patients require an injectable anesthetic when LET is applied. Those who do require an injection may experience less discomfort. These advantages should be balanced against the 20 to 30 minutes necessary for the LET to take effect.
Adult↗
Retinyl palmitate in macaque retina-retinal pigment epithelium-choroid: distribution and correlation with age and vitamin E.
Retinyl palmitate (RP) and retinyl stearate (RS) are of central importance in the visual cycle because they are the major storage molecules for retinol. In some tissues (e.g. liver) the amount of vitamin A (mostly in the form of retinyl ester) is positively correlated with both the amount of alpha-tocopherol (alpha-T) and age. Furthermore, alpha-T is a noncompetitive inhibitor of the hydrolysis of RP. We measured RP, RS, alpha-T and beta+gamma-tocopherol (beta+gamma-T) as functions of distance from the foveal center (eccentricity) in the retina-RPE-choroid (NRC) of rhesus monkeys using high-pressure liquid chromatography. It was found that the central and peripheral NRC differed with respect to these parameters. The concentration (pmoles sq mm-1) of RP was higher in the central NRC than in the peripheral NRC and was at a maximum in the region of the fovea. Furthermore, although in the peripheral NRC. RP was well correlated with age and alpha-T (similar to other tissues), in the central NRC, RP per sq mm was more clearly related to photoreceptor density. These differences imply that the central NRC controls the concentration of RP within it, while the concentration of RP in the peripheral NRC is determined by its environment (e.g. nutrients available from blood) and the age of the individual.
Age Factors↗
Is beta-carotene an antioxidant?
An hypothesis is presented that is opposed to the conventional viewpoint that beta-carotene is an in vivo free-radical scavenger. It is suggested that there are biochemical reasons why beta-carotene, other carotenoids, and especially their metabolites may be harmful to mammalian systems. Finally, the hypothesis that the macular pigment carotenoids, lutein and zeaxanthin, are free-radical scavengers is challenged.
Animals↗
Effect of garlic and fish-oil supplementation on serum lipid and lipoprotein concentrations in hypercholesterolemic men.
This study examined the effects of garlic and fish-oil supplementation (alone and in combination) on fasting serum lipids and lipoproteins in hypercholesterolemic subjects. After an initial run-in phase, 50 male subjects with moderate hypercholesterolemia were randomly assigned for 12 wk to one of four groups: 1) 900 mg garlic placebo/d + 12 g oil placebo/d; 2) 900 mg garlic/d + 12 g oil placebo/d; 3) 900 mg garlic placebo/d + 12 g fish oil/d, providing 3.6 g n-3 fatty acids/d; and 4) 900 mg garlic/d + 12 g fish oil/d. In the placebo group, mean serum total cholesterol, low-density-lipoprotein cholesterol (LDL-C), and triacylglycerols were not significantly changed in relation to baseline. Mean group total cholesterol concentrations were significantly lower with garlic+fish oil (-12.2%) and with garlic (-11.5%) after 12 wk but not with fish oil alone. Mean LDL-C concentrations were reduced with garlic+fish oil (-9.5%) and with garlic (-14.2%) but were raised with fish oil (+8.5%). Mean triacylglycerol concentrations were reduced with garlic+fish oil (-34.3%) and fish oil alone (-37.3%). The garlic groups (with and without fish oil) had significantly lower ratios of total cholesterol to high-density-lipoprotein cholesterol (HDL-C) and LDL-C to HDL-C. In summary, garlic supplementation significantly decreased both total cholesterol and LDL-C whereas fish-oil supplementation significantly decreased triacylglycerol concentrations and increased LDL-C concentrations in hypercholesterolemic men. The combination of garlic and fish oil reversed the moderate fish-oil-induced rise in LDL-C. Coadministration of garlic with fish oil was well-tolerated and had a beneficial effect on serum lipid and lipoprotein concentrations by providing a combined lowering of total cholesterol, LDL-C, and triacylglycerol concentrations as well as the ratios of total cholesterol to HDL-C and LDL-C to HDL-C.
Adult↗
Vitamin E, retinyl palmitate, and protein in rhesus monkey retina and retinal pigment epithelium-choroid.
PURPOSE: To measure the amounts of vitamin E, retinyl palmitate, and protein in the primate retina and its supporting tissues-the retinal pigment epithelium and choroid. To compare the amounts and concentrations of these materials in the central retina with those in the peripheral retina and to compare the concentration of vitamin E in the retina with that in plasma. Finally, to compare these results in rhesus monkey with existing measurements in humans. METHODS: Ocular tissues from rhesus monkeys (Macaca mulatta) were extracted with a two-phase solvent system. Components in the extract were separated by reverse-phase high-pressure liquid chromatography. Two detectors in series monitored the effluent: Vitamin E was quantified with an internal standard and fluorescence detection, whereas retinyl palmitate was quantified with an external standard and ultraviolet light detection. RESULTS: Amounts of vitamin E, retinyl palmitate, and protein in tissues from rhesus monkey compared reasonably well with those reported for humans. The content of vitamin E in the peripheral neural retina was moderately correlated with its protein content and, to a greater extent, with the concentration of vitamin E in the plasma; however, the content of vitamin E in the central neural retina correlated only with the amount of protein in the central neural retina. CONCLUSIONS: These results are consistent with rhesus monkey as a model for the use of vitamin E by human ocular tissues. The amount of vitamin E in the central neural retina appears to be more closely regulated than the amount of vitamin E in the peripheral neural retina.
Animals↗
Radial distribution of tocopherols in rhesus monkey retina and retinal pigment epithelium-choroid.
PURPOSE: To map vitamin E as a function of distance from the foveal center in the primate retina and retinal pigment epithelium (RPE)-choroid. METHODS: Eyecups from rhesus monkeys were dissected with circular trephines so that the innermost disc, centered on the fovea, was in the center of a series of concentric rings. Two different types of dissection were performed. For one type, the authors used circular trephines with diameters of 1, 4, 8, and 10 mm (1,4-D), whereas for the other type the diameters were 2, 5, 8, and sometimes 10 mm (2,5-D). When possible, the neural retina was separated from the RPE-choroid. Tissues were analyzed for vitamin E, retinyl palmitate, and protein. RESULTS: Surface area, volume, and protein were used as indexes of the amount of tissue analyzed. Distributions of vitamin E in neural retina were dependent on the tissue metric used and type of dissection performed. However, regardless of the tissue metric used, the central 1-mm disc of the 1,4-D was, on average, higher in vitamin E content than was the central 2-mm disc of the 2,5-D. This was particularly true when volume was the tissue metric. From the average values of vitamin E in a series of concentric discs, a composite plot of the vitamin E concentration in the neural retina was generated that took into consideration both types of dissection. That plot displayed a local maximum in the fovea and then precipitously declined to a minimum in the region between 0.5 and 1.0 mm eccentricity (near the foveal crest); at greater eccentricities, the vitamin E concentration rose to a value similar to that in the fovea, i.e., the composite plot indicated that vitamin E has a V-shaped distribution in the central neural retina. Vitamin E distribution in the RPE-choroid, with surface area as the tissue metric, also was measured. For this tissue, the foveal region displayed a local maximum. CONCLUSIONS: By combining the results of two different types of dissection, the authors found that in the neural retina, vitamin E displayed a minimum near the foveal crest. This minimum correlated anatomically with the site at which areolar (geographic) atrophy frequently occurs in retinal pigment epithelial cells in the human disease, age-related macular degeneration.
Animals↗
The effect of aluminum on the vanadium-mediated oxidation of NADH.
Aluminum catalyzes the oxidation of NADH by vanadate both in the presence and absence of a reducing sugar. The effect of aluminum is concentration dependent and inhibitable with superoxide dismutase but not catalase. The fructose-6-phosphate-free reaction is characterized by an initial lag phase which can be eliminated by preincubating aluminum with NADH, but is not altered by preincubating aluminum with vanadate, suggesting that the effect of aluminum is not directly on vanadate. Aluminum also catalyzes vanadyl-mediated oxidation of NADH, and this effect is similarly inhibitable by superoxide dismutase as well as catalase. It is suggested that aluminum catalyzes the oxidation of NADH by vanadium though enhancing the production of superoxide radicals and that this effect may account in part of the biological toxicity associated with aluminum, particularly when associated with the accumulation of other trace elements such as vanadium.
Aluminum↗
Exchange of retinol between IRBP and CRBP.
During a bleach, all-trans-retinol passes from the photoreceptor outer segments to the retinal pigment epithelium (RPE), where retinol is found associated with cellular retinol-binding protein (CRBP). Interphotoreceptor retinoid-binding protein (IRBP) is thought to facilitate this exchange, but the transfer of retinol between IRBP and CRBP has not been explored. In this study we used a mixture of purified IRBP and CRBP as a model system to measure the amount and rate of retinol transfer between the two proteins. When retinol is transferred from IRBP to CRBP, its absorbance maximum shifts from 330 to 350 nm. By monitoring the increase in absorbance at 350 nm after mixing CRBP with IRBP-bound retinol, we measured the amount and time course of retinol transfer from IRBP to CRBP. To complement the absorbance measurements, the IRBP and CRBP in these mixtures were subsequently separated by size-exclusion HPLC and individually analysed for retinol content by scanning the effluent with a multiple-diode-array detector. As determined by measuring the change in absorbance at 350 nm, the mean percentage of IRBP-bound retinol transferred to CRBP was 103 +/- 11% (n = 9). The mean half-time of the transfer was 4.2 +/- 1.3 sec; time to reach equilibrium was 30-60 sec. IRBP that was separated from the mixture by HPLC contained little or no retinol, while the isolated CRBP was nearly saturated with retinol. No detectable transfer from CRBP to IRBP was observed. The distribution of retinol between these two proteins was consistent with the nearly 100-fold higher affinity of CRBP for retinol compared with IRBP. Both the degree and time-course of transfer support the idea that this difference in affinity contributes to the flow of retinol to the RPE during a bleach in vivo and, therefore, may play a role in the physiological regeneration of rhodopsin.
Animals↗
Specific steroid response from a nonspecific DNA element.
A fundamental dilemma of steroid hormone regulation is how specific transcription is attained in vivo when several receptors recognize the same DNA sequence in vitro. We have identified an enhancer of the mouse sex-limited protein (Slp) gene that is activated by androgens but not by glucocorticoids in transfection. Induction requires a consensus hormone response element (HRE) and multiple auxiliary elements within 120 base pairs. Androgen specificity relies on a dual function to augment androgen but prevent glucocorticoid action from a site that both receptors can bind. The nonreceptor factors are the dominant force in transcriptional specificity, although HRE sequence variations can affect the stringency and magnitude of hormonal response. The effect of HRE variations suggests that receptor position is altered relative to the other factors. Thus protein interactions that elicit specific gene regulation are established by the array of DNA elements in a complex enhancer and can be modulated by subtle sequence differences that may influence precise protein contacts.
Androgens↗
Adult rabbit brain synthesizes retinoic acid.
Tissues of adult rabbit brain were shown to enzymatically oxidize retinol and retinaldehyde to retinoic acid, a potent stimulator of gene expression. Rates of retinoic acid synthesis by the cerebrum, cerebellum, and meninges were comparable to, or exceeded, rates measured with rat liver, an organ known to have a relatively high capacity to synthesize retinoic acid. These results, taken together with previous observations that the adult brain contains retinoic acid-activated transcription factors and cellular retinoid-binding proteins, suggest that retinoids may play an important role in the adult central nervous system.
Animals↗
The stringency and magnitude of androgen-specific gene activation are combinatorial functions of receptor and nonreceptor binding site sequences.
The mechanism by which specific hormonal regulation of gene expression is attained in vivo is a paradox in that several of the steroid receptors recognize the same DNA element in vitro. We have characterized a complex enhancer of the mouse sex-limited protein (Slp) gene that is activated exclusively by androgens but not by glucocorticoids in transfection. Potent androgen induction requires both the consensus hormone response element (HRE) and auxiliary elements residing within the 120-bp DNA fragment C' delta 9. Multiple nonreceptor factors are involved in androgen specificity, with respect to both the elevation of androgen receptor activity and the inactivity of glucocorticoid receptor (GR), since clustered base changes at any of several sites reduce or abolish androgen induction and do not increase glucocorticoid response. However, moving the HRE as little as 10 bases away from the rest of the enhancer allows GR to function, suggesting that GR is repressed by juxtaposition to particular factors within the androgen-specific complex. Surprisingly, some sequence variations of the HRE itself, within the context of C' delta 9, alter the stringency of specificity, as well as the magnitude, of hormonal response. These HRE sequence effects on expression correspond in a qualitative manner with receptor binding, i.e., GR shows a threefold difference in affinities for HREs amongst which androgen receptor does not discriminate. Altering the HRE orientation within the enhancer also affects hormonal stringency, increasing glucocorticoid but not androgen response. The effect of these subtle variations suggests that they alter receptor position with respect to other factors. Thus, protein-protein interactions that elicit specific gene regulation are established by the array of DNA elements in a complex enhancer and can be modulated by sequence variations within these elements that may influence selection of precise protein contacts.
Animals↗
Water immersion: lessons from antiquity to modern times.
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Balneology↗