Influence of Varied Silane Commercial Brands and Adhesive Application on Bond Strength and Stability to Lithium Disilicate Glass Ceramic.

OBJECTIVES: This study aimed to evaluate the impact of various commercial silane brands with varied chemical compositions with or without the application of an adhesive layer on the microshear bond strength and durability of a resin luting agent to lithium disilicate glass ceramic. METHODS AND MATERIALS: Lithium disilicate glass ceramic discs (EMX, IPS e.max Press, Ivoclar Vivadent) measuring 10 mm in diameter and 3 mm in thickness were fabricated (n=240). Surfaces were etched using 5% hydrofluoric acid and randomly assigned to 10 groups based on the commercial brand of silane used (n=24): [RP] RelyX Ceramic Primer (3M ESPE); [PS] Prosil (FGM); [SA] Silano (Angelus); [SM] Silano (Maquira); [SU] Silane (Ultradent); [GL] GLUMA Ceramic Primer (Kulzer); [CB] Ceramic Bond (VOCO); [MB] Monobond N (Ivoclar Vivadent); [CP] Clearfil Ceramic Primer (Kuraray); and [DE] 2-step silane (Dentsply Sirona). Half of the EMXs (n=12) received a thin adhesive layer (+) after the silane and prior to resin luting agent, while the other half (n=12) did not receive an adhesive layer (-). For the microshear bond strength test (µSBS), four light-cured resin luting agent cylinders (1 mm in diameter) were created on each EMX surface. Half of these specimens were tested after 24 hours, while the other half were stored in deionized water for 6 months. The µSBS test was conducted using a universal testing machine (DL 500, EMIC) at a crosshead speed of 1 mm/min until failure. The obtained data underwent statistical analysis using analysis of variance (ANOVA) and the Tukey test (α=0.05). RESULTS: There was significant influence of the silane commercial brand on bond strength. Notably, "universal primers" yielded lower bond strength results compared to "pure" silane solutions. Water storage had a detrimental effect on microshear bond strength for certain silane commercial brands. Additionally, the application of an adhesive layer negatively impacted bond strength results for all silanes. CONCLUSIONS: This study confirms the importance of both silane commercial brand and chemical composition in relation to bond strength of resin luting agents to lithium disilicate glass ceramic. Furthermore, the application of an adhesive layer may have an adverse effect on bond stability over time.

Plant size, latitude, and phylogeny explain within-population variability in herbivory.

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sparse data. We collected standardized surveys of herbivory for 503 plant species at 790 sites across 116° of latitude. With these data, we show that within-population variability in herbivory increases with latitude, decreases with plant size, and is phylogenetically structured. Differences in the magnitude of variability are thus central to how plant-herbivore biology varies across macroscale gradients. We argue that increased focus on interaction variability will advance understanding of patterns of life on Earth.

Características y frecuencia de tuberculosis antes y durante la pandemia por COVID-19 en adultos atendidos en un centro de atención primaria, Lima-Perú, 2019-2020

Objetivo: Determinar las características y la frecuencia de pacientes con tuberculosis (TBC), mayores de 18 años, en prepandemia (2019) y durante la pandemia por COVID-19 (2020), en un centro de salud (CS) de Lima-Perú. Materiales y métodos: Estudio descriptivo, retrospectivo, que incluyó historias clínicas de 100 pacientes >18 años adscritos al programa de TBC en el CS Los Libertadores (SMP-Lima, Perú), durante el período 2019-2020. Se analizaron variables sociodemográficas (sexo, lugar de procedencia, edad), clínicas (condición de ingreso/egreso, índice de masa corporal, comorbilidades, localización de tuberculosis, tipo de resistencia, esquema de tratamiento) y laboratoriales (baciloscopia, cultivo, métodos de prueba de sensibilidad). Se excluyó a pacientes que no contaban con todas las variables. Se elaboró una base de datos en Excel y se realizó un análisis estadístico descriptivo en SPSS de las variables cualitativas, expresadas en frecuencias, y de las variables cuantitativas, en medidas de tendencia central (media) y desviación estándar. Se determinó la prevalencia de TBC por año, de acuerdo con la población adscrita al centro de salud; dicha información fue obtenida por medio del Sistema de Información Gerencial de Tuberculosis (SIGTB). Resultados: En 2019, la prevalencia de tuberculosis fue de 0,0015 % (49 pacientes); en el 2020, 0,075 % (51 pacientes). En ambos años, predominó el sexo masculino y el grupo etario de 18 a 29 años; la localización predominante fue pulmonar. El 2020 se observó un aumento de la comorbilidad asociada a VIH y de la tasa de mortalidad (0,074), así como más casos positivos en la baciloscopia. Conclusiones: La prevalencia de TBC fue mayor en el 2020, primer año de la pandemia del COVID-19, debido a un menor abordaje de los programas de TBC por la situación que impuso la pandemia. Además del aumento de las tasas de mortalidad de TBC en ese mismo año, probablemente, por la tasa de abandono del tratamiento o una mayor comorbilidad con VIH y la diabetes.

Objective: To determine the characteristics and frequency of patients aged over 18 years with tuberculosis (TB) before (2019) and during (2020) the COVID-19 pandemic in a healthcare center (CS) in Lima, Peru. Materials and methods: A descriptive retrospective study that included medical records of 100 patients aged > 18 years enrolled in the TB program at CS Los Libertadores (SMP-Lima, Peru) from 2019 to 2020. Sociodemographic (sex, origin, age), clinical (admission/discharge status, body mass index, comorbidities, TB infection site, type of resistance, treatment regimen) and laboratory (smear microscopy, culture, drug susceptibility testing) variables were analyzed. Patients who did not have all the variables were excluded. An Excel database was prepared and a descriptive statistical analysis of the qualitative variables, expressed in frequencies, and quantitative variables, expressed in measures of central tendency (mean) and standard deviation, was performed using IBM SPSS Statistics. TB prevalence per year was determined, according to the population assigned to the healthcare center. Said information was obtained through the Tuberculosis Management Information System (SIGTB). Results: TB prevalence was 0.0015 % (49 patients) in 2019 and 0.075 % (51 patients) in 2020. In both years, the male sex and the age group between 18 and 29 years prevailed, and the most common site of infection were the lungs. In 2020, an increase in HIV comorbidity and mortality rate (0.074) was observed, as well as more positive smear microscopy cases. Conclusions: TB prevalence was higher in 2020, the first year of the COVID-19 pandemic, due to a reduced approach to TB programs as a result of the situation imposed by the pandemic. In addition, TB mortality rates raised in the same year, probably due to an increase in treatment dropouts or HIV and diabetes comorbidity rates.

Ant pollination of Paepalanthus lundii (Eriocaulaceae) in Brazilian savanna.

BACKGROUND AND AIMS: Ant-plant associations are widely diverse and distributed throughout the world, leading to complex ecological networks. Regarding ant-plant mutualism, ant pollination is a very rare interaction and few studies have shown the role of ants as pollinators. Therefore, we aimed to evaluate the role of ants as effective pollinators of Paepalanthus lundii (Eriocaulaceae) in a Brazilian savanna. METHODS: Fieldwork with experimental manipulation was conducted to evaluate the fitness of P. lundii, considering potential pollinators. For this, we mainly observed the number of seeds produced in different conditions: control, ant exclusion, exclusion of flying insects, and exclusion (entomophily test) of both ants and flying insects. Furthermore, we evaluated all floral visitors throughout the day, stigma receptivity, the numbers of male and female flowers, and patterns of species co-occurrence, which can indicate the presence of different pollinators in the plants at the same time. KEY RESULTS: We observed a relation between seed production and ant visits; Camponotus crassus was the most frequent floral visitor and the most effective pollinator. Also, we observed a statistical difference between the numbers of male and female flowers produced, with a greater number of male flowers. Furthermore, P. lundii presented flowering asynchrony, with 12 different types of maturation sequence, which indicates a cross-pollination system. Lastly, we observed an overlap of the greatest abundance of C. crassus and the time of plant stigmatic receptivity, and a pattern of non co-occurrence of ants, which shows the pollinator role of this ant. CONCLUSIONS: Our data provide evidence that previous generalizations neglecting the importance of ants as pollinators are wrong. Brazilian savanna can reveal a lot about the ant-pollination syndrome, since this environment presents peculiar characteristics related to this association. Thus, this study has great significance for the understanding of the ant-pollination syndrome, and for the understanding of the complex ecological networks present in these dry arid systems.

GABA withdrawal syndrome: GABAA receptor, synapse, neurobiological implications and analogies with other abstinences.

The sudden interruption of the increase of the concentration of the gamma-aminobutyric acid (GABA), determines an increase in neuronal activity. GABA withdrawal (GW) is a heuristic analogy, with withdrawal symptoms developed by other GABA receptor-agonists such as alcohol, benzodiazepines, and neurosteroids. GW comprises a model of neuronal excitability validated by electroencephalogram (EEG) in which high-frequency and high-amplitude spike-wave complexes appear. In brain slices, GW was identified by increased firing synchronization of pyramidal neurons and by changes in the active properties of the neuronal membrane. GW induces pre- and postsynaptic changes: a decrease in GABA synthesis/release, and the decrease in the expression and composition of GABAA receptors associated with increased calcium entry into the cell. GW is an excellent bioassay for studying partial epilepsy, epilepsy refractory to drug treatment, and a model to reverse or prevent the generation of abstinences from different drugs.

Microtubule organization and L-type voltage-activated calcium current in olfactory neuronal cells obtained from patients with schizophrenia and bipolar disorder.

Olfactory neuroepithelial cells in culture have been proposed as a model to study the physiopathology of psychiatric disorders and biomarker characterization for diagnosis. In patients with schizophrenia (SZ) and bipolar disorder (BD) diminished microtubule-associated proteins expression occurs, which might lead to aberrant microtubular organization and which in turn may affect Ca(2+) voltage-activated currents. The aim of this work was to characterize of microtubule organization as well as of the L-type Ca(2+) current in neuronal precursors obtained from nasal exfoliates of patients with SZ and BD. Microtubule organization was studied by immunofluorescence with a specific anti-III ß-tubulin antibody and by quantification of globular and assembled tubulin by Western blot. L-type current recording was performed by whole-cell patch-clamp technique and nifedipine superfusion. The results showed differential altered microtubular organization in neuronal precursors of SZ and BD. Short microtubules were observed in BD neurons, while extensive, unstained subcellular areas and disorganized microtubules were evident in SZ neuronal precursors. Patients with BD showed a decrease in amounts of tubulin in total homogenates and 40% decrease in the globular fraction. However, L-type current in BD was similar to that in healthy subjects (HS). In contrast, this current in SZ was 50% lower. These reduction in L-type current in SZ together with differential microtubule alterations are potential biomarkers that may differentiates SZ and BD.

A non-invasive method to isolate the neuronal linage from the nasal epithelium from schizophrenic and bipolar diseases.

Brain imaging and histopathological studies suggest that neurodevelopmental anomalies play a key role in the etiology of schizophrenia (SZ) and bipolar disorder (BD). New neuron formation and maturation occur in human olfactory epithelium throughout life. Therefore, the olfactory epithelium has been proposed as a model to study alterations in neurodevelopment, particularly in some psychiatric diseases. However, former studies were done with olfactory epithelium biopsies taken post mortem or under anesthesia from patients with SZ and BD. In this work we have developed a new method to obtain viable neural precursors by exfoliation of the anterior region of the medial lateral turbinate of the nasal cavity from healthy controls, and ambulatory patients. Cells were propagated to establish neural precursor banks. Thawed cells showed cytoskeletal phenotypes typical of developing neurons. They also conserved the ability to differentiate in presence of 2mM dibutyril-cyclic adenosine monophosphate, and maintained voltage-operated Ca(2+) currents in culture. Moreover, proportions of neuronal maturation stages were maintained in cultured exfoliates obtained from SZ and BD patients. Data support that neural precursors obtained from a nasal exfoliate are an excellent experimental model to later approach studies on biomarkers, neural development and cellular alterations in the pathophysiology of SZ and BD.

Hyperexcitability induced by GABA withdrawal facilitates hippocampal long-term potentiation.

In some mammals, epileptic seizures have been induced in the cerebral cortex, hippocampus and other limbic structures after the sudden suppression of chronically infused GABA. This hyperexcitability state induced by the endogenous neurotransmitter resembles the withdrawal seizure-responses to other GABA(A) receptor agonists such as benzodiazepines, barbiturates and alcohol. Hyperexcitability induced by GABA withdrawal also persists in in vitro preparation. Hippocampal slices, obtained from rats with seizures induced by GABA-withdrawal showed field potential oscillations and paroxysmal activity in the Ammon's horn region 1. During GABA-withdrawal hyperexcitability the threshold of hippocampal long-term potentiation (LTP) decreased to a point in which a brief frequency stimulation that normally failed to produce long lasting changes in synaptic strength, was now able to induce LTP. Facilitation of the LTP induction was associated with a decreased GABA(A)-mediated inhibitory activity, because the effect of the GABA(A) receptor antagonist, bicuculline, was occluded during hyperexcitability and the dose-response curve for bicuculline showed a 50% efficacy reduction with a shift in the effective concentration required for half-maximal activation from 4.5-1.1 microM relative to controls. Nevertheless, the dissociation constant of the antagonist did not change significantly. Our results support the idea that changes in hippocampal plasticity under altered inhibitory neurotransmission states, like those induced by withdrawal syndromes to anxiolytic, sedative or anticonvulsant drugs may be engaged during seizures.

Hippocampal hyperexcitability induced by GABA withdrawal is due to down-regulation of GABA(A) receptors.

The sudden interruption of an intracortical instillation of exogenous gamma-aminobutyric acid (GABA) generates an epileptic focus in mammals. Seizures elicited by GABA withdrawal (GW) last for weeks. A similar withdrawal-induced hyperexcitability is also produced by several GABA(A) receptor agonists. This work reports a quantitative analysis of GW-induced hyperexcitability produced in the hippocampus in vitro. GW produced a left-ward displacement of the input/output (I/O) function, suggesting that the postsynaptic component is predominant to explain the hyperexcitability. A decrease in the inhibitory efficacy of the GABA(A) receptor agonist, muscimol, confirmed that inhibition was impaired. Binding saturation experiments demonstrated a decrease in [(3)H]-muscimol binding after GABA withdrawal showing a close correlation with the development of hyperexcitability. All these modifications coursed without changes in receptor affinity (K(D)) for muscimol or bicuculline as demonstrated by both binding studies and Schild analysis. It is concluded that, in the CA1 region of the hippocampus, it is the number of functional GABA(A) receptors, and not the affinity of the receptor, what is decreased during GW-induced hyperexcitability.

Long-lasting effects of GABA infusion into the cerebral cortex of the rat.

In electrophysiological terms, experimental models of durable information storage in the brain include long-term potentiation (LTP), long-term depression, and kindling. Protein synthesis correlates with these enduring processes. We propose a fourth example of long-lasting information storage in the brain, which we call the GABA-withdrawal syndrome (GWS). In rats, withdrawal of a chronic intracortical infusion of GABA, a ubiquitous inhibitory neurotransmitter, induced epileptogenesis at the infusion site. This overt GWS lasted for days. Anisomycin, a protein synthesis inhibitor, prevented the appearance of GWS in vivo. Hippocampal and neocortical slices showed a similar post-GABA hyperexcitability in vitro and an enhanced susceptibility to LTP induction. One to four months after the epileptic behavior disappeared, systemic administration of a subconvulsant dose of pentylenetetrazol produced the reappearance of paroxysmal activity. The long-lasting effects of tonic GABAA receptor stimulation may be involved in long-term information storage processes at the cortical level, whereas the cessation of GABAA receptor stimulation may be involved in chronic pathological conditions, such as epilepsy. Furthermore, we propose that GWS may represent a common key factor in the addiction to GABAergic agents (for example, barbiturates, benzodiazepines, and ethanol). GWS represents a novel form of neurono-glial plasticity. The mechanisms of this phenomenon remain to be understood.

Neocortical hyperexcitability after GABA withdrawal in vitro.

The sharp interruption of the intracortical instillation of exogenous gamma-aminobutyric acid (GABA), generates an epileptic focus in mammals. Seizures elicited by GABA withdrawal last several days or weeks. The present work reports that GABA withdrawal-induced hyperexcitability can be produced in vitro: a sudden withdrawal of GABA (5 mM; 120 min) or benzodiazepine (60 microM flunitrazepam) from the superfusion, induced a gradual increase in the amplitude of the evoked population spike (PS) recorded on neocortical slices. PS enhancement reached 150% above the control value 2.5 h after GABA withdrawal. GABA withdrawal-induced hyperexcitability was facilitated by progesterone. PS enhancement induced by GABA withdrawal was associated with an impairment of GABA transmission occurring before epileptiform discharges were fully established. Paired pulse inhibition and evoked [3H]-GABA release appear decreased; suggesting that cortical hyperexcitability as a result of GABA withdrawal involves pre-synaptic changes. Specific muscimol binding decreased during GABA superfusion but recovered after GABA withdrawal. However, the sensitivity of the post-synaptic response to 3alpha-OH-5alpha-pregnan-20-one or allopregnanolone (alloP) was enhanced after GABA withdrawal, suggesting a functional change in the GABA(A) receptors. The changes described may be the cellular correlates of the withdrawal syndromes appearing after interruption of the administration of GABA(A) receptor agonists.

Allopregnanolone potentiates a GABA-withdrawal syndrome in the rat cerebral cortex.

We have studied the neuromodulatory effect of the neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone-3 alpha-5 alpha P-) in the GABA-withdrawal syndrome (GWS). This is a model of partial epilepsy consisting of an enduring paraoxysmal activity recorded at the site of GABA infusion that depends, for its induction, on GABA receptor activation. Rats were chronically implanted for frontal and occipital EEG recording with infusion cannulae fixed on the somatomotor cortical region. When the neurosteroid was infused after or concurrently with GABA, a potentiation of the GWS (i.e. shorter latency and prolonged duration) was observed. No modifications in EEG activity were detected when allopregnanolone was administered alone or prior to GABA administration. These results indicate a neuromodulatory effect of allopregnanolone, dependent on the presence of GABA at the receptor site.