Familial retinoblastoma: variations in clinical presentation and management based on paternal versus maternal inheritance

BACKGROUND

Several studies have demonstrated the effect of parent-of-origin on retinoblastoma penetrance. The purpose of the current study was to assess differences in clinical presentation of paternally versus maternally inherited retinoblastoma.

METHODS

The clinical records of all children with familial retinoblastoma treated on a tertiary Ocular Oncology Service between December 1975 and May 2020 were reviewed retrospectively.

RESULTS

A total of 179 patients with familial retinoblastoma were included. Paternal inheritance (PI) was identified in 109 (61%) patients and maternal inheritance (MI) in 70 patients (39%). A comparison (PI vs MI) revealed PI patients were older at presentation (57.2 vs 24.4 months [P = 0.002]) with no difference in patient sex (53% females vs 57% males [P = 0.606]) or number of family members affected (3.2 vs 3.0 family members [P = 0.255]). PI patients had more advanced classification according to the International Classification of Retinoblastoma (ICRB) (group E: 31% vs 8% [P = 0.012)] and greater largest tumor in basal diameter (9.0 vs 6.2 mm [P = 0.040]) and thickness (5.6 vs 4.0 mm [P = 0.038]); they were also less likely to be located in the macula (40% vs 60% [P = 0.004]). There was no difference in tumor laterality (69% vs 64% bilaterality [P = 0.530]). PI patients required enucleation more frequently (34% vs 14% [P = 0.007]). There was no difference in need for plaque radiotherapy (P = 0.86) or chemotherapy (P = 0.85). One PI patient developed metastatic retinoblastoma, and there were no retinoblastoma-related deaths.

CONCLUSIONS

Patients with paternally inherited retinoblastoma presented at an older age, with larger, more peripheral tumors and more advanced ICRB group, and were more likely to require enucleation compared to those with maternally inherited retinoblastoma.

Likelihood of germline mutation with solitary retinoblastoma based on tumour location at presentation

BACKGROUND/AIMS

To evaluate the likelihood of germline mutation in patients presenting with solitary retinoblastoma based on tumour location at first examination.

METHODS

Retrospective analysis of solitary unilateral retinoblastoma for likelihood of germline mutation (family history of retinoblastoma and/or genetic testing indicating germline RB1 mutation and/or development of additional new or bilateral tumours) based on tumur location at presentation (macular vs extramacular).

RESULTS

Of 480 consecutive patients with solitary retinoblastoma, 85 were in the macula (18%) and 395 were extramacular (82%). By comparison (macular vs extramacular tumours), macular tumours had smaller basal diameter (12.7 mm vs 18.9 mm, p<0.001) and smaller tumour thickness (6.1 mm vs 10.7 mm, p<0.001). Patients with macular tumours demonstrated greater likelihood for germline mutation (23% vs 12%, OR=2.18, p=0.011), specifically based on family history of retinoblastoma (13% vs 2%, OR=4.64, p=0.004), genetic testing showing germline RB1 mutation (27% vs 15%, OR=2.04 (95% CI 1.04 to 4.01), p=0.039), development of new tumours (13% vs 3%, OR=5.16 (95% CI 2.06 to 12.87), p=0.001) and/or development of bilateral disease (9% vs 2%, OR=4.98 (95% CI 1.70 to 14.65), p=0.004).

CONCLUSIONS

Among patients with solitary unilateral retinoblastoma, those presenting with macular tumour (compared with extramacular tumour) show 2.18 times greater likelihood for germline mutation and an even higher likelihood of development of subsequent tumours. Solitary macular retinoblastoma should raise an index of suspicion for likely germline mutation and multifocal disease.

Choroidal Lymphoma: Diagnostic Value of Combined Indocyanine Green Angiography and Optical Coherence Tomography

OBJECTIVE

To compare multimodal imaging findings in patients with choroidal lymphoma (CL).

METHODS

Multicenter retrospective observational case series. Multimodal imaging features of patients with CL were reviewed with particular attention to the patterns of choroidal infiltration on indocyanine green angiography (ICGA) and optical coherence tomography (OCT).

RESULTS

Eighteen eyes of 15 patients were included in this study. Average tumor thickness on ultrasonography was 2.6 mm (range, 1.2-5.7 mm). Choroidal infiltration on ICGA was characterized by multifocal, round areas (300-500 microns diameter) of hypocyanescence in all cases, whereas OCT at the same region disclosed diffuse choroidal infiltration. By OCT, the tumor surface contour was primarily placid (22%), dome-shaped (11%), or undulating (67%).

CONCLUSIONS

In this analysis of eyes with CL, ICGA demonstrated multifocal sub-millimeter regions of choroidal hypocyanescence whereas OCT documented diffuse choroidal infiltration. This incongruence could be a distinctive diagnostic feature of choroidal lymphoma, assisting with differentiation from other pathological entities.

Conditional analysis on new tumor formation with solitary unilateral retinoblastoma in 482 consecutive patients

PURPOSE

The objective of the study was to understand dynamic risk (conditional analysis based on patient age) for new tumor development in patients with solitary unilateral retinoblastoma.

METHODS

This was a retrospective analysis.

RESULTS

Of 482 patients with solitary unilateral retinoblastoma, 55 new tumors developed in 20 patients (4%). Comparison (new tumor vs. no new tumor development) revealed those with new tumor demonstrated younger mean age at presentation (10 vs. 36 months, P < 0.001), greater likelihood of family history of retinoblastoma (35% vs. 3%, P < 0.001), and greater probability of primary tumor location in the macula (50% vs. 15%, P = 0.003). Conditional risk for new tumors (at age 6, 9, 12, 18, and 24 months) declined for those who presented at 0-3 months old (25%, 15%, 15%, 8%, and 0%), >3-6 months old (17%, 14%, 6%, 6%, and 0%), >6-9 months old (not applicable [na], 6%, 6%, 0%, and 0%), and >9-12 months (na, na, 3%, 3%, and 0%). Younger patients showed greater development of bilateral tumors (P < 0.001). Of patients with new tumors, those that occurred within 1 year from presentation were located in the preequatorial region in 46%, whereas those that occurred more than 1 year from presentation were preequatorial in 78%. Patients ≤24 months at initial presentation demonstrated all new tumors by 24 months of age. Older patients (>24 months at presentation) showed new tumors up to 56 months of age.

CONCLUSION

Children (≤24 months) with solitary unilateral retinoblastoma showed decreasing risk for new tumors up to 24 months of life. Later onset of new tumor was more likely located in preequatorial region.

Cyclin D1 expression and molecular genetic findings in periocular histiocytoses and neoplasms of macrophage-dendritic cell lineage

PURPOSE

Frequent activating mutations in the mitogen-activated protein kinase (MAPK) pathway genes have been identified in histiocytoses. MAPK signaling consistently upregulates Cyclin D1. The goal of this study was to determine whether Cyclin D1 expression by immunohistochemistry is a useful diagnostic marker for periocular histiocytoses and to further characterize their genetic basis.

DESIGN

Retrospective observational case series.

METHODS

Pathology records were searched for all patients with histiocytoses diagnosed between 1995-2020. Eleven histiocyte-rich inflammatory lesions and 10 xanthelasma served as controls. Cyclin D1 immunohistochemistry was performed on all tissues. A subset of histiocytoses was evaluated by next-generation sequencing (NGS) and droplet digital PCR (ddPCR).

RESULTS

There were 36 patients, 15 (42%) males and 21 (58%) females, with histiocytoses: 9 (25%) juvenile xanthogranuloma, 8 (22%) adult-onset asthma and periocular xanthogranuloma, 7 (19%) Langerhans cell histiocytosis, 5 (14%) Rosai-Dorfman disease, 5 (14%) xanthogranuloma not otherwise specified, 1 (3%) Erdheim-Chester disease, and 1 (3%) histiocytic sarcoma. Moderate-to-strong nuclear Cyclin D1 expression was present in ≥50% of lesional cells in histiocytoses (23/36, 64%), significantly more when compared to histiocyte-rich inflammatory lesions (0/11, 0%, P<.001) and xanthelasma (0/10, 0%, P<.001). Cyclin D1 was expressed in <10% of lesional cells in all 11 histiocyte-rich inflammatory lesions (P<.001) and all 10 xanthelasma lesions (P<.001). MAPK pathway gene mutations were detected in 12 of 14 (86%) histiocytoses successfully assayed by NGS and/or ddPCR.

CONCLUSIONS

Our study confirms that the Cyclin D1 immunohistochemical stain is a useful diagnostic marker for periocular histiocytoses, correlating with underlying mutations in MAPK pathway genes.

Iodine-125 Plaque Radiotherapy for Retinoblastoma Recurrence Following Intra-arterial Chemotherapy

PURPOSE

To assess the efficacy and toxicity of Iodine-125 (I-125) plaque radiotherapy for retinoblastoma following intra-arterial chemotherapy (IAC).

METHODS

Clinical records of patients with retinoblastoma who received I-125 plaque radiotherapy after IAC at the Ocular Oncology Service at Wills Eye Hospital between December 1, 2009 and April 30, 2020, were retrospectively reviewed.

RESULTS

Forty-one retinoblastomas in 41 eyes of 41 patients were treated with I-125 plaque radiotherapy after IAC at a median age of 32 months. The indication for plaque radiotherapy was solid tumor recurrence with or without overlying subretinal/vitreous seeds (n = 33, 80%), subretinal seeds alone (n = 6, 15%), and vitreous seeds alone (n = 2, 5%). The median irradiated basal diameter and thickness was 9 and 4 mm, respectively. Mean radiation dose to tumor apex was 3,483 centigray (cGy) delivered at mean rate of 35 cGy/hr. The irradiated site was controlled in 39 eyes (95%) at a median of 20 months after plaque radiotherapy for solid tumor (31 of 33, 94%), subretinal (6 of 6,100%), and vitreous seeds (2 of 2, 100%). A subgroup of tumors occurring within an ischemic retinal/choroidal field was identified on fluorescein angiography (n = 24) and demonstrated control in 22 of 24 (92%). Using Kaplan-Meier analysis, radiation complications at 2 years included vitreous hemorrhage (37%), retinopathy (28%), papillopathy (18%), and cataract (18%). Five eyes (12%) were enucleated for recurrence outside the irradiated area, chronic vitreous hemorrhage, and/or total retinal detachment.

CONCLUSIONS

Iodine-125 plaque radiotherapy provided 95% control for retinoblastoma tumors that failed IAC, including those in ischemic fields untreatable with further chemotherapy. Radiation complications should be anticipated in eyes exposed to substantial chemotherapy. [J Pediatr Ophthalmol Strabismus. 2022;59(3):164-171.].

Likelihood of Germline Mutation With Solitary Unilateral Retinoblastoma Based on Patient Age at Presentation: Analysis of 482 Consecutive Patients

PURPOSE

To evaluate the likelihood of germline retinoblastoma in patients presenting with solitary unilateral retinoblastoma, based on age at presentation.

METHODS

This retrospective case series of 482 consecutive patients presenting with solitary unilateral retinoblastoma analyzed the likelihood of germline retinoblastoma, defined as family history of retinoblastoma, germline retinoblastoma mutation documented on genetic testing, and/or development of bilateral disease and/or additional new tumors. This analysis was based on age at presentation (0 to 12 months vs older than 12 to 24 months vs older than 24 to 36 months vs older than 36 months) and a sub-study was conducted on infant age at presentation (0 to 3 months vs older than 3 to 6 months vs older than 6 to 9 months vs older than 9 to 12 months).

RESULTS

Of the overall group (482 consecutive patients) with solitary unilateral retinoblastoma, there were significantly different findings in the youngest age group (0 to 12 months old) with greater family history of retinoblastoma (10% vs 2% vs 1% vs 2%, P = .004), smaller median basal diameter (18.0 vs 20.0 vs 20.0 vs 20.0 mm, P = .014), smaller median tumor thickness (8.7 vs 10.0 vs 11.5 vs 10.0 mm, P = .002), greater macular tumor location (33% vs 16% vs 10% vs 8%, P < .001), and greatest likelihood of germline mutation (29% vs 17% vs 8% vs 9%, P = .001). By comparison, patients 1 year and younger (vs older than 1 year) demonstrated a 2.96 odds ratio (OR) (P = .001) for likelihood of germline retinoblastoma. For those classified as infants (1 year and younger) (n = 132 consecutive patients), the youngest patients (0 to 3 months old) demonstrated the greatest likelihood for germline mutation (61% vs 20% vs 24% vs 22%, P = .009) and greatest odds ratio (5.52, P = .002) compared to patients older than 3 to 12 months.

CONCLUSIONS

The youngest patients with solitary unilateral retinoblastoma showed the greatest likelihood of germline disease when evaluating all patients (1 year and younger vs older than 1 year of age) (OR = 2.96) and the substudy of infants (3 years and younger vs older than 3 to 12 months old) (OR = 5.52). [J Pediatr Ophthalmol Strabismus. 2021;58(6):355-364.].

Addressing Implicit Bias in First-Year Medical Students: a Longitudinal, Multidisciplinary Training Program

BACKGROUND

Studies show that implicit bias among healthcare providers contributes to health disparities. Despite this knowledge, most medical school curricula lack formal methods for assessing and reducing implicit bias among medical students.

PURPOSE

The purpose of this study was to create a longitudinal, multidisciplinary training program for first-year medical students to reduce implicit bias toward skin tone, to increase awareness of personal bias, and to measure changes in bias after a targeted intervention.

METHODS

First-year medical students participated in a three-part implicit bias training program that included visits to an art museum, a lecture on medical anthropology, and an interactive sociological discussion about bias in medical research. A control group did not participate in the training. All participants took the Harvard Implicit Association Test for Skin Tone and completed a questionnaire assessing awareness of implicit bias before and after the study activities were administered.

RESULTS

All participants indicated a bias toward light skin tone. In addition, a stronger bias score in the pre-test correlated with a stronger belief that the scores were inaccurate. Neither the experimental group nor the control group demonstrated a significant change in implicit bias, but the experimental group trended toward a decrease in bias. Power analysis suggested that significant results may have been obtained with a larger sample size. All participants indicated an awareness that implicit biases affect the provision of healthcare. When prompted to reflect on these biases, the experimental group provided richer, more detailed personal accounts of implicit bias in the healthcare environment after participating in the study.

CONCLUSIONS

First-year medical students who participated in this study were aware that implicit bias affects the provision of healthcare and therefore plays a role in perpetuating health disparities. However, they were less able to recognize bias in themselves. Providing opportunities for medical students to recognize and confront their own implicit biases is an important goal. This study suggests that a longitudinal, multidisciplinary curricular approach to building awareness and reducing implicit bias can produce promising results in medical students. We anticipate that further development and refinement of curricular activities may lead to significant results.

Neglected Coats Disease

Coats disease is a rare, non-hereditary retinal vascular abnormality that typically presents in the first two decades of life and is characterized by idiopathic retinal telangiectasia with progressive exudation. The authors describe a patient with Coats disease in which the family neglected treatment, demonstrating the natural course of this disease. [J Pediatr Ophthalmol Strabismus. 2020;57:e82-e85.].

Idiopathic Internal Jugular Vein and Subclavian Vein Thrombosis: A Rare Case Report

Venous thrombosis is a vascular disorder which is a consequence of Virchow's triad: hypercoagulability, venous stasis, and endothelial injury. While lower extremity deep venous thrombosis is common, upper torso thrombosis is a rare clinical condition and usually a complication of central venous catheterization or malignancy-related paraneoplastic syndromes. Herein, we present a rare case of a 64-year-old male who presented with right upper extremity and right facial swelling who was found to have a thrombus in the right internal jugular vein and right subclavian vein with no predisposing factors. He was successfully treated with anticoagulation without any complications.

Probing magnetic coupling between LnPc2 (Ln = Tb, Er) molecules and the graphene/Ni (111) substrate with and without Au-intercalation: role of the dipolar field

Lanthanides (Ln) bis-phthalocyanine (Pc), the so-called LnPc₂double decker, are a promising class of molecules with a well-defined magnetic anisotropy. In this work, we investigate the magnetic properties of LnPc₂ molecules UHV-deposited on a graphene/Ni(111) substrate and how they modify when an Au layer is intercalated between Ni and graphene. X-ray absorption spectroscopy (XAS), and linear and magnetic circular dichroism (XLD and XMCD) were used to characterize the systems and probe the magnetic coupling between LnPc₂ molecules and the Ni substrate through graphene, both gold-intercalated and not. Two types of LnPc₂ molecules (Ln = Tb, Er) with a different magnetic anisotropy (easy-axis for Tb, easy-plane for Er) were considered. XMCD shows an antiferromagnetic coupling between Ln and Ni(111) even in the presence of the graphene interlayer. Au intercalation causes the vanishing of the interaction between Tb and Ni(111). In contrast, in the case of ErPc₂, we found that the gold intercalation does not perturb the magnetic coupling. These results, combined with the magnetic anisotropy of the systems, suggest the possible importance of the magnetic dipolar field contribution for determining the magnetic behaviour.

Operating Quantum States in Single Magnetic Molecules: Implementation of Grover's Quantum Algorithm

Quantum algorithms use the principles of quantum mechanics, such as, for example, quantum superposition, in order to solve particular problems outperforming standard computation. They are developed for cryptography, searching, optimization, simulation, and solving large systems of linear equations. Here, we implement Grover's quantum algorithm, proposed to find an element in an unsorted list, using a single nuclear 3/2 spin carried by a Tb ion sitting in a single molecular magnet transistor. The coherent manipulation of this multilevel quantum system (qudit) is achieved by means of electric fields only. Grover's search algorithm is implemented by constructing a quantum database via a multilevel Hadamard gate. The Grover sequence then allows us to select each state. The presented method is of universal character and can be implemented in any multilevel quantum system with nonequal spaced energy levels, opening the way to novel quantum search algorithms.

Landau-Zener Transition in a Continuously Measured Single-Molecule Spin Transistor

We monitor the Landau-Zener dynamics of a single-ion magnet inserted into a spin-transistor geometry. For increasing field-sweep rates, the spin reversal probability shows increasing deviations from that of a closed system. In the low-conductance limit, such deviations are shown to result from a dephasing process. In particular, the observed behaviors are successfully simulated by means of an adiabatic master equation, with time averaged dephasing (Lindblad) operators. The time average is tentatively interpreted in terms of the finite time resolution of the continuous measurement.

Spin-communication channels between Ln(III) bis-phthalocyanines molecular nanomagnets and a magnetic substrate

Learning the art of exploiting the interplay between different units at the atomic scale is a fundamental step in the realization of functional nano-architectures and interfaces. In this context, understanding and controlling the magnetic coupling between molecular centers and their environment is still a challenging task. Here we present a combined experimental-theoretical work on the prototypical case of the bis(phthalocyaninato)-lanthanide(III) (LnPc₂) molecular nanomagnets magnetically coupled to a Ni substrate. By means of X-ray magnetic circular dichroism we show how the coupling strength can be tuned by changing the Ln ion. The microscopic parameters of the system are determined by ab-initio calculations and then used in a spin Hamiltonian approach to interpret the experimental data. By this combined approach we identify the features of the spin communication channel: the spin path is first realized by the mediation of the external (5d) electrons of the Ln ion, keeping the characteristic features of the inner 4 f orbitals unaffected, then through the organic ligand, acting as a bridge to the external world.

Single-molecule devices with graphene electrodes

Design, fabrication and low temperature characterization of a molecular spin transistor made of graphene electrodes and a TbPc₂ molecular dot are reported.

Coupling molecular spin centers to microwave planar resonators: towards integration of molecular qubits in quantum circuits

Strong coupling meets coordination chemistry: hints in the design of molecular qubits in hybrid quantum circuits.

Electrical readout of individual nuclear spin trajectories in a single-molecule magnet spin transistor

We present the electrical readout of time trajectories obtained from an isolated nuclear spin. The device, a TbPc(2) single-molecule magnet spin transistor, detects the four different nuclear spin states of the Tb(3+) ion with fidelities better than 69%, allowing us to measure individual relaxation times (T(1)) of several tens of seconds. A good agreement with quantum Monte Carlo simulations suggests that the relaxation times are limited by the current tunneling through the transistor, which opens up the possibility to tune T(1) electrically by means of bias and gate voltages.

Exchange biasing single molecule magnets: coupling of TbPc2 to antiferromagnetic layers

We investigate the possibility to induce exchange bias between single molecule magnets (SMM) and metallic or oxide antiferromagnetic substrates. Element-resolved X-ray magnetic circular dichroism measurements reveal, respectively, the presence and absence of unidirectional exchange anisotropy for TbPc(2) SMM deposited on antiferromagnetic Mn and CoO layers. TbPc(2) deposited on Mn thin films present magnetic hysteresis and a negative horizontal shift of the Tb magnetization loop after field cooling, consistent with the observation of pinned spins in the Mn layer coupled parallel to the Tb magnetic moment. Conversely, molecules deposited on CoO substrates present paramagnetic magnetization loops with no indication of exchange bias. These experiments demonstrate the ability of SMM to polarize the pinned uncompensated spins of an antiferromagnet during field-cooling and realize metal-organic exchange-biased heterostructures using antiferromagnetic pinning layers.

Coupling single molecule magnets to ferromagnetic substrates

We investigate the interaction of TbPc(2) single molecule magnets (SMMs) with ferromagnetic Ni substrates. Using element-resolved x-ray magnetic circular dichroism, we show that TbPc(2) couples antiferromagnetically to Ni films through ligand-mediated superexchange. This coupling is strongly anisotropic and can be manipulated by doping the interface with electron acceptor or donor atoms. We observe that the relative orientation of the substrate and molecule anisotropy axes critically affects the SMM magnetic behavior. TbPc(2) complexes deposited on perpendicularly magnetized Ni films exhibit enhanced magnetic remanence compared to SMMs in the bulk. Contrary to paramagnetic molecules pinned to a ferromagnetic support layer, we find that TbPc(2) can be magnetized parallel or antiparallel to the substrate, opening the possibility to exploit SMMs in spin valve devices.

Supramolecular spin valves

Magnetic molecules are potential building blocks for the design of spintronic devices. Moreover, molecular materials enable the combination of bottom-up processing techniques, for example with conventional top-down nanofabrication. The development of solid-state spintronic devices based on the giant magnetoresistance, tunnel magnetoresistance and spin-valve effects has revolutionized magnetic memory applications. Recently, a significant improvement of the spin-relaxation time has been observed in organic semiconductor tunnel junctions, single non-magnetic molecules coupled to magnetic electrodes have shown giant magnetoresistance and hybrid devices exploiting the quantum tunnelling properties of single-molecule magnets have been proposed. Herein, we present an original spin-valve device in which a non-magnetic molecular quantum dot, made of a single-walled carbon nanotube contacted with non-magnetic electrodes, is laterally coupled through supramolecular interactions to TbPc(2) single-molecule magnets (Pc=phthalocyanine). Their localized magnetic moments lead to a magnetic field dependence of the electrical transport through the single-walled carbon nanotube, resulting in magnetoresistance ratios up to 300% at temperatures less than 1 K. We thus demonstrate the functionality of a supramolecular spin valve without magnetic leads. Our results open up prospects of new spintronic devices with quantum properties.

Tunable quantum dot arrays formed from self-assembled metal-organic networks

The confinement of Ag(111) surface-state electrons by self-assembled, nanoporous metal-organic networks is studied using low-temperature scanning tunneling microscopy and spectroscopy as well as electronic structure calculations. The honeycomb networks of Co metal centers and dicarbonitrile-oligophenyl linkers induce surface resonance states confined in the cavities with a tunable energy level alignment. We find that electron scattering is repulsive on the molecules and weakly attractive on Co. The tailored networks represent periodic arrays of uniform and coupled quantum dots.

Single-molecule transport in three-terminal devices

Transport through single molecules has been studied using different test beds. In this paper we focus on three-terminal devices in which a molecule bridges the gap between two gold electrodes and a third electrode-the gate-is able to modulate the conduction properties of the junction. Depending on the electronic coupling, Γ, between the molecule and the gold electrodes, different transport regimes can be distinguished. We show measurements on junctions incorporating different single-molecule systems which demonstrate the distinction between these regimes, as well as the experimental limitations in controlling the exact value of Γ.

Chiral kagomé lattice from simple ditopic molecular bricks

Self-assembly techniques allow for the fabrication of highly organized architectures with atomic-level precision. Here, we report on molecular-level scanning tunneling microscopy observations demonstrating the supramolecular engineering of complex, regular, and long-range ordered periodic networks on a surface atomic lattice using simple linear molecular bricks. The length variation of the employed de novo synthesized linear dicarbonitrile polyphenyl molecules translates to distinct changes of the bonding motifs that lead to hierarchic order phenomena and unexpected changes of the surface tessellations. The achieved 2D organic networks range from a close-packed chevron pattern via a rhombic network to a hitherto unobserved supramolecular chiral kagomé lattice.

What is there left to learn about the Drosophila clock?

Circadian rhythms offer probably the best understanding of how genes control behavior, and much of this understanding has come from studies in Drosophila. More recently, genetic manipulation of clock neurons in Drosophila has helped identify how daily patterns of activity are programmed by different clock neuron groups. Here, we review some of the more recent findings on the fly molecular clock and ask what more the fly model can offer to circadian biologists.

Strong electronic correlations in LixZnPc organic metals

Nuclear magnetic resonance, electron paramagnetic resonance and magnetization measurements show that bulk LixZnPc are strongly correlated one-dimensional metals. The temperature dependence of the nuclear spin-lattice relaxation rate 1/T_{1} and of the static uniform susceptibility chi_{S} on approaching room temperature are characteristic of a Fermi liquid. Moreover, while for x approximately 2 the electrons are delocalized down to low temperature, for x-->4 a tendency towards localization is noticed upon cooling, yielding an increase both in 1/T_{1} and chi_{s}. The x dependence of the effective density of states at the Fermi level D(E_{F}) displays a sharp enhancement for x approximately 2, at the half filling of the ZnPc lowest unoccupied molecular orbitals. This suggests that LixZnPc is on the edge of a metal-insulator transition where enhanced superconducting fluctuations could develop.

Metal-organic honeycomb nanomeshes with tunable cavity size

We present a systematic study of metal-organic honeycomb lattices assembled from simple ditopic molecular bricks and Co atoms on Ag(111). This approach enables us to fabricate size- and shape-controlled open nanomeshes with pore dimensions up to 5.7 nm. The networks are thermally robust while extending over microm2 large areas as single domains. They are shape resistant in the presence of further deposited materials and represent templates to organize guest species and realize molecular rotary systems.

Identification of risk factors for urinary retention following total knee arthroplasty: a Singapore hospital experience

INTRODUCTION

Urinary retention is associated with an increased rate of urinary tract infections and deep sepsis following total joint arthroplasty. This study was carried out to investigate the incidence of urinary retention following total knee arthroplasty in a Singapore hospital, and to identify risk factors associated with the development of this complication in our patient population.

METHODS

The charts of 125 consecutive patients who underwent primary total knee arthroplasty between January and December 2004 were reviewed. The incidence of postoperative urinary retention was correlated with the following factors: age, gender, choice of anaesthesia, duration of surgery, and analgesic technique. Statistical analysis was performed with univariate and multivariate logistic regression models. There were 109 female and 16 male patients. The mean age of the patients was 67.5 years (range, 50-86 years).

RESULTS

Ten patients developed urinary retention, giving an overall rate of 8.0 percent (95 percent confidence interval [CI], 3.9-4.2). Male gender (odds-ratio [OR] is 5.9; 95 percent CI, 1.2-29.5; p-value is 0.03) and epidural analgesia (OR is 7.6; 95 percent CI, 1.7-35.0; p-value is 0.009) were found to be the only factors significantly associated with postoperative urinary retention. Patient age, duration of surgery and choice of anaesthesia were not found to be significantly associated with urinary retention.

CONCLUSION

In our patient population, male patients and patients receiving epidural postoperative analgesia are at increased risk of developing urinary retention following total knee arthroplasty.

Dengue viruses in the Caribbean. Twenty years of dengue virus isolates from the Caribbean Epidemiology Centre

The first isolate of a dengue virus in the Americas was obtained in Trinidad and Tobago in 1953, and several dengue virus isolates were obtained in subsequent years. However, the systematic isolation and typing of dengue viruses in support of virus surveillance and outbreak investigations did not start until the creation of the Caribbean Epidemiology Centre (CAREC) in 1975. Since then, over two thousand viral isolates have been obtained and typed from many countries in the English and Dutch-speaking Caribbean. In this communication, virological data from 17 countries between 1977 and 1996 are presented and analyzed together for the first time with available epidemiological data. Types 1, 2 and 4 were isolated over the period, and geographic and temporal patterns in the distribution of the most prevalent strains are presented. The historical surveillance data is critically assessed. A temporal correlation with reported dengue incidence and rainfall data in Trinidad and Tobago is reported. Recent changes in epidemiological patterns are described, including reference to two large later outbreaks. Risk assessment of complicated forms of dengue virus infections in the Caribbean has been attempted, with some success. The importance of ongoing systematic surveillance is discussed.

Dysregulated expression of IFN-gamma and IL-10 and impaired IFN-gamma-mediated responses at different disease stages in patients with genital herpes simplex virus-2 infection

Cell-mediated T-helper type-1 (Th1) responses play a vital role in the immunopathogenesis of genital infections caused by herpes simplex virus 2 (HSV-2). We investigated the role of Th responses in HSV-2 infection at different disease stages by analysing the production of Th cytokines in HSV-stimulated peripheral blood mononuclear cells (PBMCs). IFN-gamma production decreased over time following a recurrence, whereas levels of IL-10, and to a lesser extent IL-2, remained elevated during this period. In addition, PBMCs from asymptomatic seropositive individuals produced high levels of IFN-gamma and low levels of IL-10, in contrast to individuals with a history of genital ulcers. Following a recurrence, virus copy number in the genital lesions decreased progressively over time, in a manner similar to IFN-gamma production by HSV-2-stimulated PBMCs. Enhanced production of IFN-gamma may modulate HSV replication and B7 expression on monocytic cells of HSV-infected individuals. In contrast to seronegative controls, IFN-gamma failed to enhance B7 expression on monocytic cells of HSV-infected individuals. In addition, monocytic cells from HSV-2-infected individuals with recurrent disease supported greater HSV replication than did those of HSV-infected asymptomatic individuals or seronegative controls. Furthermore, addition of IFN-gamma resulted in enhanced HSV replication in monocytic cells of HSV-infected individuals with recurrent disease, in contrast to the inhibition observed in HSV-seropositive asymptomatic individuals and seronegative controls. Taken together, our results suggest that dysregulated production of IFN-gamma at different disease stages and the impaired ability of monocytic cells to respond to IFN-gamma may play a role in the pathogenesis of recurrent genital herpes disease.

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates from three Caribbean countries: Trinidad, Guyana, and St. Vincent

BACKGROUND

The percentage of Neisseria gonorrhoeae isolates resistant to antimicrobial agents commonly used for treatment is unknown in many Caribbean countries.

GOAL

To determine the antimicrobial susceptibility of N gonorrhoeae isolates from Trinidad (144 isolates), Guyana (70 isolates), and St. Vincent (68 isolates) so baseline data can be established for further studies, and to assist in establishing effective treatment guidelines.

STUDY DESIGN

Consecutive urethral and endocervical specimens from several clinics were collected and identified as N gonorrhoeae. Isolates of N gonorrhoeae were tested for their susceptibility to penicillin, tetracycline, ceftriaxone, ciprofloxacin, spectinomycin, and azithromycin. The presumptive identification of penicillinase-producing N gonorrhoeae and/or tetracycline-resistant N gonorrhoeae isolates based on MIC was confirmed by plasmid and tetM content analysis.

RESULTS

High percentages of penicillin and/or tetracycline resistance were observed in N gonorrhoeae isolates from Guyana (92.9%), St. Vincent (44.1%), and Trinidad (42.4%). Isolates from all three countries were susceptible to ceftriaxone, ciprofloxacin, and spectinomycin. One penicillinase-producing N gonorrhoeae/tetracycline-resistant N gonorrhoeae from Guyana had an MIC of 0.5 microg/l to ciprofloxacin. This and nine other isolates from Guyana also were resistant to azithromycin (defined as MIC > or = 2.0 microg/ml) as well as penicillin and tetracycline. A reduced susceptibility to azithromycin was displayed by 16% of the isolates from St. Vincent and 72% of the isolates from Guyana (MIC, 0.25-1.0 microg/ml). Most penicillinase-producing N gonorrhoeae isolates carried Africa-type plasmids (61/90), with 28 of 90 having Toronto-type plasmids and a single isolate carrying an Asia-type plasmid. The tetM determinant in tetracycline-resistant N gonorrhoeae isolates was predominantly of the Dutch type (68/91).

CONCLUSIONS

The high prevalence of N gonorrhoeae isolates from 3 of 21 English- and Dutch-speaking Caricom countries in the Caribbean with either plasmid-mediated or chromosomal resistance to penicillin and tetracycline supports international observations that these drugs should not be used to treat gonococcal infections. The detection of isolates with reduced susceptibility to drugs such as azithromycin, which currently are recommended for treatment in the region, attest to the importance of the continued monitoring of gonococcal antimicrobial susceptibility for the maintenance of effective treatment guidelines.

[Nutritional status of preschool children in Ciudad de La Habana from 1972 to 1993]

Two anthropometric surveys of children and adolescents have been carried out in Cuba with national samples. A third study done in the province of Ciudad de la Habana provided information on the physical characteristics of the population in that area and a baseline for the periodic evaluation of its nutritional status. This article compares the weight and height results obtained in these surveys for children 0 to 5 years old who lived in this province with the international reference standards proposed by WHO. The results show that, despite the economic difficulties the country has faced, the prevalence of malnutrition is low. In 1993, the prevalence of low height-for-age was 3.1%; that of low weight-for-height, 0.4%; and that of low weight-for-age, 1.5%. Overweight was the most common type of malnutrition, with a prevalence of 5.2%. Between 1972 and 1993, the prevalence of chronic malnutrition fell 32.6%, acute malnutrition was reduced by 69.2%; malnutrition of all types decreased by 44.4%; and overweight fell 48.5%.

Detection of viral DNA to evaluate outcome of antiviral treatment of patients with recurrent genital herpes

Culture of infectious virus, PCR amplification of viral DNA, and the appearance of genital skin lesions were used as markers to study the course of a recurrence of genital herpes in 40 patients treated with famciclovir or placebo. The highest frequency of patients with skin lesions occurred within the first 36 h following the onset of a recurrence, which also corresponded to the peak in the production of virus. While the timing of the peak in skin lesions was independent of the type of treatment, the frequency of lesions and the release of virus at the lesion site were both reduced by famciclovir treatment. Furthermore, patients receiving this antiviral agent showed a more rapid recovery time and a shorter period during which viral DNA could be detected at the lesion. PCR and then Southern blot hybridization greatly enhanced our ability to detect herpes simplex virus at the lesion site. This procedure proved to be of greater diagnostic value in assessing genital herpes than the standard culture method currently used. In addition, PCR was more sensitive in evaluating treatment effectiveness.

Regulated expression of a transfected human cardiac actin gene during differentiation of multipotential murine embryonal carcinoma cells

P19 embryonal carcinoma (EC) cells are multipotential stem cells which can be induced to differentiate in vitro into a variety of cell types, including cardiac muscle cells. A cloned human cardiac actin (CH-actin) gene was transfected into P19 cells, and stable transformants were isolated. Low levels of CH-actin mRNA were present in transformed EC cells, but a marked increase in the level of CH-actin mRNA was found as these cells differentiated into cardiac muscle. The accumulation of CH-actin mRNA paralleled that of the endogenous mouse cardiac actin mRNA. A chimeric gene, which consisted of the CH-actin promoter linked to the herpes simplex virus thymidine kinase coding region, was constructed and transfected into P19 cells. In these transformants, the thymidine kinase protein was located almost exclusively in cardiac muscle cells and was generally not detectable in EC or other nonmuscle cells. These results suggest that the transfected CH-actin promoter functions in the appropriate developmental and tissue-specific manner during the differentiation of multipotential EC cells in culture.

An integrated software system for microcomputer management of recombinant DNA data

A database-oriented system (pCP123) is described for the manipulation of recombinant DNA data. This system was developed within the context of an integrated software package with spreadsheet, database, graphing and programming capabilities. The system includes two databases, one of sites and another of regions, coordinately handled by a series of macro-programs operated from four user-define menus. A distinctive feature of the system is the possibility of handling both ends of defined functional or structural regions in situations of simulated deletions or insertions.

Covalently closed circles of adenovirus 5 DNA

The genome of adenoviruses is a double-stranded linear DNA molecule with inverted terminal repeats about 100 base pairs (bp) in length and a terminal protein covalently linked to the 5' nucleotide of each strand. Both of these features permit the formation of DNA circles, the inverted repeats allowing the circularization of single-stranded DNA and the terminal protein the joining of one or more molecules to yield double-stranded circles or concatemers. However, although the existence of covalently closed circles has been postulated, double-stranded viral DNA purified from virions or infected cells by conventional methods (that is, using proteases and phenol or chloroform) has always been obtained in a linear form. Here, we present evidence for the existence in adenovirus 5 (Ad5) infected cells of novel structures resulting from covalent head-to-tail joining of viral DNA molecules and show that these structures are due at least in part to the formation of covalently closed circles.