Evidence that replication fork components catalyze establishment of cohesion between sister chromatids.

Accurate chromosome segregation requires that replicated sister chromatids are held together until anaphase, when their "cohesion" is dissolved, and they are pulled to opposite spindle poles by microtubules. Establishment of new cohesion between sister chromatids in the next cell cycle is coincident with replication fork passage. Emerging evidence suggests that this temporal coupling is not just a coincident timing of independent events, but rather that the establishment of cohesion is likely to involve the active participation of replication-related activities. These include PCNA, a processivity clamp for some DNA polymerases, Trf4/Pol final sigma (formerly Trf4/Pol kappa), a novel and essential DNA polymerase, and a modified Replication Factor C clamp--loader complex. Here we describe recent advances in how cohesion establishment is linked to replication, highlight important unanswered questions in this new field, and describe a "polymerase switch" model for how cohesion establishment is coupled to replication fork progression. Building the bridges between newly synthesized sister chromatids appears to be a fundamental but previously unrecognized function of the eukaryotic replication machinery.

Semantic priming of person recognition: categorial priming may be a weaker form of the associative priming effect.

An interactive activation and competition account (Burton, Bruce, & Johnston, 1990) of the semantic priming effect in person recognition studies relies on the fact that primes and targets (people) have semantic information in common. However, recent investigations into the type of relationship needed to mediate the semantic priming effect have suggested that the prime and target must be close associates (e.g., Barry, Johnston, & Scanlan, 1998; Young, Flude, Hellawell, & Ellis, 1994). A review of these and similar papers suggests the possibility of a small but non-reliable effect based purely on categorial relationships. Experiment 1 provided evidence that when participants were asked to make a name familiarity decision it was possible to boost this small categorial effect when multiple (four) primes were presented prior to the target name. Results from Experiment 2 indicated that the categorial effect was not due to the particular presentation times of the primes. This boosted categorial effect was shown to cross domains (names to faces) in Experiment 3 and persist in Experiment 4 when the task involved naming the target face. The similarity of the pattern of results produced by the associative priming effect and this boosted categorial effect suggests that the two may be due to the same underlying mechanism in semantic memory.

Evaluation of an unused 1952 Ridley intraocular lens.

PURPOSE: To evaluate an unused 1952 historic Ridley intraocular lens (IOL) brought to Bombay, India, in 1952 from an Oxford Ophthalmologic Conference in England and given to 1 of the authors during his residency. SETTING: Alcon Laboratories, Fort Worth, Texas, USA. METHODS: The Ridley IOL was evaluated at Alcon Laboratories, Inc., using the established procedures of its Intraocular R&D Laboratories. Various optical and physical aspects of the Ridley lens were evaluated including (1) dimensions, (2) weight, (3) power, (4) resolution efficiency and modulation transfer function (MTF), (5) surface sphericity by interferometry, (6) ultraviolet (UV)-visible transmission characteristic, (7) attenuated total reflectance (ATR)-Fourier transform infrared reflectance spectrum, and (8) cosmetics by visual inspection using light microscopy. RESULTS: This 8.5 mm diameter, 2.4 mm thick, 23 diopter biconvex IOL weighed 108 mg. The ATR spectrum, UV-visible transmission, and refractive index confirmed its poly-(methyl methacrylate) material. The 0.56 MTF value at 100 line pairs/mm, per the International Standards Organization--IOL Optics Standard, and 93% resolution efficiency in water, per the American National Standard Institute IOL Optics Standard, revealed the IOL's excellent optics. This was confirmed by 0.278 wave root mean square surface figure as measured by Zygo interferometer using a 633 nm wavelength. Visual inspection revealed rough edges with sharp corners and some surface scratches. Early clinical experience with Ridley IOLs in Bombay, India, is briefly given. CONCLUSION: The Ridley IOL had excellent optical quality, meeting the requirements of current IOL optics standards. The selection of its dimensions was guided by the human crystalline lens, and the Ridley IOL was half as bulky. Although its clinical results were mixed, successful cases inspired subsequent improvements, leading to modern, highly satisfactory IOLs. This IOL represented a revolutionary innovation in ophthalmology.