Adaptability of a broad spectrum of randomly selected patients to a variable design progressive lens: report of a nationwide clinical trial

BACKGROUND

Through continuously improved design, progressive lenses have become the presbyopic lens style of choice by some practitioners. Studies have shown them to be preferred by patients but growth has been modest over the last 35 years. Many practitioners may remember early problems now eliminated. This stigma may prevent many patients from benefiting from improved technology.

METHODS

An invitation to be involved in a study was sent to practitioners nationally. Each was asked to induct ten patients; obtaining personal and prescription information as well as preferences, adaptive experience, age and occupation. Practitioners were asked to target current presbyopes so that conversion success could be better evaluated.

RESULTS

The 1,713 patients in the study had an average age of 49.4 years, 28 percent of whom were currently wearing bifocals or trifocals. Of these, 85 percent preferred the study PAL over their current multifocal. Most adapted in less than two weeks. A similar percentage was also seen across the variety of occupations in the study.

CONCLUSIONS

With a confidence level of 95 percent, the findings of this large scale study regarding acceptance of the study PAL were extremely positive. Success is apparently influenced by fitting skills as most failures were recorded in a few isolated practices where acceptance level dropped to less than 40 percent. Without these, the balance of practitioners averaged over a 90 percent acceptance level in patients converting from a wide range of lens styles, as well as patients of a wide variety of ages and occupations.

Modulation of antagonist binding to histamine H1-receptors by sodium ions and by 2-amino-2-hydroxymethyl-propan-1,3-diol HCl

1. NaCl (100 mM) reduced the potency of (+)-N-methyl-4-methyldiphenhydramine ((+)-QMDP) as an inhibitor of the binding of [3H]-mepyramine to histamine H1-receptors on guinea-pig cerebellar membranes to a greater extent than that of mepyramine, consistent with the greater inhibitory effect of Na+ on the binding of [3H]-QMDP than on the binding of [3H]-mepyramine. 2. The concentration of 2-amino-2-hydroxymethyl-propan-1,3-diol HCl (Tris, HCl) buffer, pH 7.5, present had little effect on the temelastine-insensitive binding of [3H]-mepyramine, but caused a concentration-dependent inhibition of the binding of [3H]-mepyramine sensitive to 1 microM temelastine (H1-receptor binding), with an approximate IC50 of 75 mM, assuming that complete inhibition would have been achieved. 3. Inhibition of [3H]-mepyramine binding by Na+ was more marked in 10 mM than in 50 mM Tris HCl and was not evident in 200 mM Tris HCl. 4. The Kd for the temelastine-sensitive binding of [3H]-mepyramine measured in 10 mM Tris HCl, 0.24 +/- 0.01 nM, was increased by 2.2 +/- 0.2 fold by 100 mM NaCl, without any significant change in the maximum binding (Bmax). The Bmax for [3H]-mepyramine was similarly unchanged in 50 mM Tris HCl, but the Kd was increased 2.5 +/- 0.2 fold. 5. The Kd for the temelastine-sensitive binding of [3H]-mepyramine was also increased in 50 mM,compared with 10 mM, N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulphonic acid] KOH (HEPES.KOH)buffer (Kd 0.25 +/- 0.02 nm in 10 mM HEPES), but the evidence for an interaction between HEPES and Na+ was less clear.6. The effect of 100 mM NaCl on the inhibition of [3H]-mepyramine binding in 10 mM Tris HCl was examined for a range of antagonists. The decrease in potency caused by Na+ was greatest for triprolidine, (+)-chlorpheniramine and benzilylcholine (9.6-10.3 fold increase in K1 values) but the binding of mepyramine and promethazine was much less affected (1.8 and 1.9 fold increase in Kd respectively). The Kd for temelastine was not significantly changed. In contrast to the general decrease in antagonist affinity in the presence of Na+, the for MDL 16,455A (4-[1-hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]butyl]-alpha,alpha-dimethylbenzene acetic acid) was increased, but only by 1.5 fold.7. It is concluded that Na+ can act as an allosteric effector of the binding of antagonists at the histamine HI-receptor. Tris HCl also appears to have an allosteric action at the H1-receptor.

Calcium-dependence of histamine- and carbachol-induced inositol phosphate formation in human U373 MG astrocytoma cells: comparison with HeLa cells and brain slices

1. Histamine (1 mM) induced an accumulation of inositol monophosphate ([3H]-IP1) in the U373 MG human astrocytoma cell line which increased with time in the presence of 30 mM Li+. After a 30 min incubation period with 1 mM histamine [3H]-IP1 was the major product detected (84 +/- 1% of total [3H]-IPx) and was present at a level 11 (+/- 1) fold of basal accumulation. 2. Concentration-response curves for histamine-induced [3H]-IP1 accumulation in U373 MG cells (EC50 5.4 +/- 0.5 microM) were shifted to the right in a parallel fashion by mepyramine (slope of a Schild plot 0.99 +/- 0.08), yielding a Kd for mepyramine of 3.5 +/- 0.3 nM, consistent with the involvement of histamine H1-receptors. 3. The temelastine-sensitive binding of [3H]-mepyramine to a membrane fraction from U373 MG cells was hyperbolic and had a mean Kd of 2.5 +/- 1.0 nM. The maximum amount of temelastine-sensitive binding was 86 +/- 19 pmol g-1 membrane protein. 4. Carbachol also induced [3H]-IP1 accumulation in U373 MG cells, 2.8 (+/- 0.1) fold of basal with 1 mM carbachol, with an EC50 of 48 +/- 8 microM. Pirenzepine shifted carbachol concentration-response curves to the right (slope of Schild plot 0.89 +/- 0.07) giving a Kd for pirenzepine of 0.10 +/- 0.01 microM, suggesting that phosphoinositide hydrolysis in U373 MG cells is mediated by the M3-, rather than the M1-, muscarinic receptor subtype. 5. [3H]-IP1 accumulation induced by both 1 mM histamine and by 1 mM carbachol increased when the Ca2+ concentration of the medium was increased from 'zero' (no added Ca2+) to 0.3 mM. Histamine-stimulated [3H]-IP1 accumulation was further increased, although not so markedly, as the Ca2+ was raised to 4 mM. The same pattern was apparent with histamine-induced accumulations of [3H]-IP2 and [3H]-IP3. In contrast, [3H]-IPx accumulation in response to carbachol increased between 0.3 and 1.3 mM, but thereafter remained unchanged ([3H]-IP1) or declined ([3H]-IP2 and [3H]-IP3). 6. In HeLa cells, [3H]-IP1 accumulations induced by 1 mM histamine and 1 mM carbachol showed the same pattern of Ca2+ dependence and were independent of extracellular Ca2+ above 0.3 mM (histamine) or 1.3 mM (carbachol). The response to carbachol appeared to be mediated by an M3-muscarinic receptor (apparent Kd for pirenzepine 0.09 microM). 7. In cross-chopped slices of guinea-pig cerebral cortex and guinea-pig cerebellum, [3H]-IPI accumulation induced by 1 mM histamine in the presence of 10 mM Li+ increased as the extracellular Ca2+ was increased from 0.3 to 2.5 mM, but a further increase to 4 mM had no further effect. In contrast the response to histamine in rat cerebral cortex increased markedly between 1.3 and 4 mM Ca2+. Accumulations of [3H]-IP1 induced by carbachol in guinea-pig or rat cerebral cortical slices were not increased as extracellular Ca2+ was raised from 0.3 to 4 mM.8. Nimodipine (100 nM) and w-conotoxin (3 microM) had no significant effect on histamine-induced [3H]-IP1accumulation in rat cerebral cortical slices or in U373 MG cells. 9. We conclude that histamine-induced [3H]-IP1 accumulation in U373 MG cells does appear to have a component dependent on the extracellular Ca2+ concentration. The degree of Ca2+-dependence approaches that observed in guinea-pig cerebral cortex but is much less than in rat cerebral cortex.Whether U373 MG cells will be of use as a model system for the apparent Ca2+-entry component observed in guinea-pig or rat brain slices remains to be established.

Generalized imitation and response-class formation in children with autism

An experimental analysis of imitation was conducted to examine the influence of response topography on generalization of imitation across three response types. Four children with autism were presented with both reinforced training trials and nonreinforced probe trials of models from vocal, toy-play, and pantomime response types. The probe trials were used to examine generalization within each response type. A multiple baseline design was used to analyze percentage of matching and nonmatching responses to models across response types. This study, the first to analyze imitative response classes in children with autism, showed that imitation generalized from reinforced training models to nonreinforced probe models within a response type, but it did not generalize across response types. Thus, functional response classes determined by topographical boundaries were exhibited within generalized imitation.

Studies of O-specific polysaccharide chains of Pseudomonas solanacearum lipopolysaccharides consisting of structurally different repeating units

The structures of the O-antigenic polysaccharide chains of lipopolysaccharides of a number of Pseudomonas solanacearum strains were elucidated mainly with the help of methylation analysis and 13C NMR spectroscopy, including a computer-assisted 13C NMR-based analysis. Six structurally distinct but related polysaccharides were identified. They have a backbone which is built up of three L-rhamnopyranosyl residues and one 2-acetamido-2-deoxy-D-glucopyranosyl residue, and is unsubstituted or substituted with a residue of L-xylopyranose or L-rhamnopyranose as a monosaccharide side chain. The lipopolysaccharides of most of the strains contain polysaccharide chains consisting of at least two structurally different types of repeating units. Three of the polysaccharides are common to more than one strain.

Desensitization of histamine H1 receptor-mediated inositol phosphate accumulation in guinea pig cerebral cortex slices

1. Histamine stimulated the production of [3H]-inositol phosphates in untreated (control) guinea-pig cerebral cortex slices with a best-fit EC50 of 17 +/- 4 microM, and a best-fit maximum response of 385 +/- 23% over basal accumulation. 2. Histamine pretreatment desensitized guinea-pig cortex slices to a subsequent challenge with histamine, which was observed as a reduction in the best-fit maximum response to 182 +/- 32% over basal accumulation. 3. The time-course for the histamine-induced production of [3H]-inositol phosphates was approximately linear over 90 min of stimulation in both control and histamine pretreated slices. The rate of production in pretreated slices was significantly slowed compared to control, such that by 90 min of histamine stimulation the desensitized slices produced 2.8 times the basal [3H]-inositol phosphate accumulation compared to 5.3 fold the basal [3H]-inositol phosphate accumulation in the control slices. 4. Displacement of [3H]-mepyramine binding to homogenates of guinea-pig cerebral cortex by mepyramine and histamine revealed that histamine pretreatment did not alter the apparent affinity of the H1 receptor for histamine (control Kd = 6.3 +/- 0.7 microM, desensitized Kd = 7.9 +/- 1.6 microM) or mepyramine (control Kd = 3.4 +/- 0.8 nM, desensitized Kd = 3.4 +/- 1.3 nM), nor was there any reduction in the calculated maximum number of [3H]-mepyramine binding sites (control Bmax = 192 +/- 31 fmol mg-1 protein, desensitized Bmax = 220 +/- 50 fmol mg-1 protein). 5. The histamine-mediated desensitization of response in guinea-pig slices was mediated by the HI receptor subtype, since the attentuated maximum histamine-stimulated [3H]-inositol phosphate accumulation could not be prevented by inclusion of an H2- (ranitidine) and an H3- (thioperamide) receptor antagonist during the pretreatment period.6. The desensitized histamine-stimulated [3H]-inositol phosphate accumulation recovered to 90% of control levels over a period of 150 min after the removal of the conditioning dose of histamine, with a half-time of recovery of about 95 min.

Carbachol-induced phosphoinositide metabolism in slices of rat substantia nigra pars reticulata

Carbachol produced an approximately 2-fold stimulation, with respect to basal, of [3H]inositol monophosphate ([3H]IP1) accumulation in microdissected slices of rat substantia nigra pars reticulata (SNr), measured as a percentage of [3H]inositol incorporation. The response to carbachol was inhibited by 75 +/- 7% by 1 microM pirenzepine, consistent with a muscarinic M1 receptor-mediated response. Carbachol-induced [3H]IP1 accumulation was not reduced by pretreatment of the SNr slices with NMDA, in contrast to the 85% inhibition observed in striatal slices. The results suggest that measurement of carbachol-induced phosphoinositide hydrolysis may be a feasible approach for studying muscarinic M1 receptor function in slices of SNr.

Locus of action of Ni2+ on histamine-induced inositol phosphate formation in brain slices and in HeLa cells

Histamine-induced [3H]inositol monophosphate ([3H]IP1) accumulation in slices of rat cerebral cortex and guinea-pig cerebral cortex and cerebellum was inhibited in a concentration-dependent manner by Ni2+ ions. The effect of Ni2+ on the concentration-response curve for histamine in rat cerebral cortex was consistent with non-competitive inhibition. In membranes from guinea-pig cerebral cortex inhibition by Ni2+ of the binding of [3H]mepyramine had the characteristics expected for an allosteric inhibitor at the histamine H1 receptor. Ni2+ had no effect on carbachol-induced [3H]IP1 formation in HeLa cells, but displaced the concentration-response curve for histamine to the right. The evidence suggests that Ni2+ can act at two sites to block histamine-induced [3H]IP1 accumulation in brain slices; at the level of the H1 receptor and on a probable Ca2+ entry component. In HeLa cells only the direct H1 receptor action is evident.

Characteristics of histamine H1 receptors on HeLa cells

The affinities of antagonists at histamine H1 receptors on HeLa cells have been determined from inhibition of histamine-induced inositol phosphate formation in intact and from inhibition of [3H]mepyramine binding to HeLa cell membranes. The dissociation constants of mepyramine and (+)-chlorpheniramine were similar to values for binding to H1 receptors in other mammalian tissues, but much lower than the values reported in an earlier study with [3H]mepyramine and HeLa cell membranes. Evidence is presented that under conditions employed in the earlier study the binding of [3H]mepyramine is largely to secondary, non-H1 receptor sites.

Molecular markers of differentiation in Caenorhabditis elegans obtained by promoter trapping

Differentiation of specific cell types during animal development can be detected by monitoring expression of appropriate genes. For this study, six different beta-galactosidase expression patterns which can be used as differentiation markers in the nematode Caenorhabditis elegans are described. An earlier promoter trap screen identified pools of recombinant plasmids which gave patterns of beta-galactosidase expression when used to transform C. elegans. Each recombinant plasmid contained a random fragment of C. elegans genomic DNA fused upstream of a promoterless lacZ gene. Six of these pools were chosen, and individual pattern-producing plasmids within these pools were identified. The expression patterns have been characterized more thoroughly than in the original screen, thereby providing molecular markers for differentiation of several cell types. Many of the expression patterns involve more than one cell type. The genomic origin of the inserts of active plasmids were determined through localization on the physical genome map.

In vitro development of zygotes from prepubertal gilts after microinjection of DNA

The effect of pronuclear microinjection of DNA and culture in excised mouse oviducts on the development of porcine zygotes was assessed in this study. Precocious ovulation was induced in prepubertal gilts with pregnant mare's serum gonadotrophin and hCG. Zygotes received either pronuclear microinjection of buffer alone, buffer containing a DNA construct, or no microinjection. Zygotes were cultured in vitro in either modified Krebs-Ringer bicarbonate medium (KRB) for 144 h or in mouse oviduct (MO) explant culture with KRB for 48, 72, 96, or 120 h. Pronuclear microinjection of DNA resulted in a lower (P less than .05) cleavage index (CI) than did buffer or no microinjection (CI 2.16 +/- .10 vs 2.80 +/- .13 and 2.93 +/- .10). The CI loss was greatest for DNA-injected zygotes at the two-cell stage of development. Coculture of zygotes in MO resulted in a higher CI (P less than .01) than did culture in KRB. Culture in MO for 72 h was the most beneficial system compared with MO for 48, 96, or 120 h (P less than .05; CI 3.25 +/- .12 vs 2.66 +/- .18, 2.79 +/- .14, and 2.40 +/- .14, respectively). Microinjection of DNA, not merely the mechanical procedure, was detrimental to early zygote development and may be the cause of low pregnancy rates.

Histamine-induced inositol phosphate accumulation in HeLa cells: lithium sensitivity

1. In the presence of 10 mM Li+ the histamine-stimulated accumulation of [3H]-inositol monophosphates [( 3H]-IP1) in HeLa cells prelabelled with [3H]-inositol increased over 10-20 min to a plateau level, which was normally maintained up to 60 min. Levels of [3H]-inositol bis- and trisphosphates [( 3H]-IP2 and [3H]-IP3) initially increased rapidly but declined to near basal levels by 20 min. 2. The same pattern of histamine-induced [3H]-IP1 accumulation was observed in cells in which [3H]-inositol was present 30 min before and during the incubation with histamine. Concentration-response curves for histamine measured in the presence of 10 mM Li+ were closely similar in cells prelabelled for 24 h with [3H]-inositol and in cells exposed to [3H]-inositol for only 30 min before addition of histamine, without removing the [3H]-inositol. The EC50 for histamine was 1.6 +/- 0.2 microM. 3. [3H]-IP1 accumulation induced by a sub-maximal concentration of histamine, 1 microM, also reached a plateau, but at a lower level than with 1 mM histamine. 4. Addition of 10 mM NaF at the plateau phase of [3H]-IP1 accumulation induced by 1 mM histamine resulted in a further increase in the level of [3H]-IP1. The level of [3H]-IP1 in the presence of histamine + NaF was 1.4 +/- 0.2 fold of that of the sum of the responses to histamine and NaF acting alone (basal levels subtracted). 5. Addition of 1 microM mepyramine at the plateau phase of [3H]-IP1 accumulation induced by 1 mM histamine in the presence of 10mM Li + resulted in a decline in the level of [3H]-IP1, implying that the metabolism of [3H]-IP1 is not completely blocked by 10mM Li' in HeLa cells. 6. Omission of the 15 min preincubation period with 10mM Li+ before stimulation with 100 microM histamine for 15 min resulted in an approximate halving of the level of [3H]-IP1, without any significant change in basal accumulation. Periods of preincubation with 10mM Li' longer than 15min did not produce any further increase in the level of [3H]-IP1 induced by histamine. 7. Basal and histamine-induced levels of [3H]-IP, increased as the concentration of Li+ was increased from 0 to 60mm, but the effect on the histamine-induced response was greater than on the basal level. Increasing the concentration of Li+ from 0 to 60 mm had only a small and mostly statistically insignificant effects on the levels of [3H]-1P2 and [3H]-1P3. The EC50 for histamine-induced [3H]-4P1 accumulation in the presence of 30mm Li + was 2.4 +/- 0.4 microM. 8. The results indicate that IP1 metabolism in HeLa cells is much less sensitive to Li+ than in mammalian brain. The plateau phase of histamine-induced [3H]-IP1 accumulation in the presence of 10mM Li+ thus represents a steady-state level. On a simple model the plateau level will be proportional to the rate of [3H]-IP1 formation at that time. The lower the concentration of Li' present, the better the approximation will be. The information obtained is thus not the same as when [3H]-1P, metabolism is completely blocked, in which case [3H]-IP1 accumulated can be used to calculate a mean rate of formation over the whole of the incubation period.

New dental products and equipment

Reviewing current advances, new products, and equipment in dentistry is difficult due to the lack of scientific publication in professional journals. The majority of information available is garnered from nonrefereed sources as well as from information provided by the manufacturers themselves. However, it is clear that several significant technical and innovative advances were made in 1990 and 1991. Among the more significant developments, major advances were made in dental handpiece technology with the introduction of wear-resistant ceramic rotor bearings and fused fiberoptic bundles for increased light transmission. Refinement of delivery systems continues primarily on the asepsis and infection control front. The use of laser technology is rapidly advancing for dental treatment. Food and Drug Administration approval has been granted to two different types of laser units. Video imaging and computer simulation are advancing in delivery of esthetic restorations as well as diagnosis and treatment planning of complex maxillofacial treatments. Dental radiography is moving forward rapidly into the realm of digital imaging and analysis. Many other important advances are outlined in the text.

Inhibition by cations of antagonist binding to histamine H1-receptors: differential effect of sodium ions on the binding of two radioligands

1. Measurements have been made of the inhibition by mono- and divalent cations of the binding of [3H]-(+)-N-methyl-4-methyldiphenhydramine ([3H]-QMDP) to histamine H1-receptors in homogenates of guinea-pig cerebellum. 2. The binding of [3H]-QMDP was inhibited by monovalent cations with an order of potency Li+ = Na+ greater than K+ greater than Cs+ = Rb+. The IC50 for Li+ was 39 mM, but that for K+ was 132 mM. Hill coefficients for inhibition curves for Li+ and Na+ were less than 1. 3. Divalent cations also inhibited the binding of [3H]-QMDP. The most potent cations examined were Hg2+, Cd2+ and Zn2+, with IC50 values of 5, 17 and 41 microM, respectively. Ca2+ and Mg2+ were relatively weak inhibitors (IC50 12 and 34 mM, respectively). The potency of Ni2+, Co2+ and Mn2+ was intermediate between these groups. Hill coefficients for inhibition curves for Hg2+, Cd2+ and Zn2+ were greater than 1, but Hill coefficients for the other cations were less than 1. 4. Both mono- and divalent cations also inhibited the binding of [3H]-mepyramine. The divalent cations were approximately equipotent in inhibiting the binding of [3H]-QMDP and [3H]-mepyramine. The same was true for Li+. However, Na+ was markedly more effective against [3H]-QMDP binding than against the binding of [3H]-mepyramine. 5. The effect of 40 mM Li+ on the parameters of binding of [3H]-mepyramine was to increase the best-fit value of the concentration giving half-maximal binding EC50, by approximately 2 fold without having any significant effect on the maximum amount of binding. Cd2+ (15 microM) caused both an increase in EC 0 and a decrease in Bmax (32 +/- 4% inhibition). Na+, 100 mm, had no significant effect on either EC50 or Bmax for [3H]-mepyramine binding.

Dental equipment asepsis

In the past, dental equipment was designed for function and esthetics with little regard for the potential for cross-contamination. Recent advances in equipment technology are making all forms of treatment equipment much easier to disinfect and sterilize. The use of barrier materials and effective sterilizing and disinfecting agents has further enhanced the capability of the dental staff to provide truly aseptic conditions in the treatment room. The overriding factor in all aspects of equipment sterilization and asepsis will continue to be practicality and cost. Protection procedures cannot completely overshadow delivery of quality patient care. Costs to the patient must be minimized, while allowing practitioners to provide optimum service. Common sense and experience will dictate practical standards and the profession must use all available means to assure that the standards are followed.

Maintaining dental equipment. Prevent problems before they occur

Routine monitoring, maintenance and repair of essential dental systems will help to ensure a smoothly functioning dental office. Careful planning and attention to detail will help to prevent catastrophic mechanical failures that can be so devastating to a clinical schedule.

Inhibition by cations of antagonist binding to histamine H1-receptors

The binding of the quaternary radioligand [3H] QMDP to the histamine H1-receptor was inhibited by a series of mono- and di-valent cations. The order of potency was Hg2+ greater than Cd2+ greater than Zn2+ greater than Ni2+ greater than Co2+ greater than Mn2+ greater than Ca2+ greater than Mg2+ greater than Li+ = Na+ greater than K+ greater than Cs+. The binding of [3H] mepyramine, a tertiary amine, was inhibited by the divalent cations to a similar extent as the binding of [3H] QMDP. Li+ also had a similar potency against the two ligands, but Na+ was a much more potent inhibitor of the binding of [3H] QMDP than that of [3H] mepyramine.

Characteristics of histamine-induced inositol phospholipid hydrolysis in HeLa cells

HeLa cells, a human epithelial carcinoma, contain Histamine H1-receptors, as defined by [3H] mepyramine binding studies. Histamine, via H1-receptors, stimulates the production of inositol phosphates (IP) with an EC50 of 1.2 microM. Preincubation of HeLa cells with histamine, followed by a further histamine challenge results in a slower time course of [3H] IP production, suggesting the occurrence of H1-receptor desensitisation.

Technology assessment in the Coronary Artery Surgery Study

The majority of the 26 technology assessment articles from the Coronary Artery Surgery Study (CASS) follow the original purpose of the registry and evaluate the therapeutic capabilities of coronary artery bypass graft surgery. However, these registry data have also been used to identify risk factors for cardiovascular disease, to test diagnostic technologies, and to evaluate technological processes. Consideration of quality of life issues and the availability of cost data provide valuable additions to the continued use of the CASS for technology assessment.