Identification of a xyloglucan beta-xylopyranosyltransferase from Vaccinium corymbosum

Plant cell walls contain the hemicellulose xyloglucan, whose fine structure may vary depending on cell type, tissue, and/or plant species. Most but not all of the glycosyltransferases involved in the biosynthesis of xyloglucan sidechains have been identified. Here, we report the identification of several functional glycosyltransferases from blueberry (Vaccinium corymbosum bluecrop). Among those transferases is a hitherto elusive Xyloglucan:Beta-xylosylTransferase (XBT). Heterologous expression of VcXBT in the Arabidopsis thaliana double mutant mur3 xlt2, where xyloglucan consists only of an unsubstituted xylosylated glucan core structure, results in the production of the xylopyranose-containing "U" sidechain as characterized by mass spectrometry, glycosidic linkage, and NMR analysis. The introduction of the additional xylopyranosyl residue rescues the dwarfed phenotype of the untransformed Arabidopsis mur3 xlt2 mutant to wild-type height. Structural protein analysis using Alphafold of this and other related xyloglucan glycosyltransferase family 47 proteins not only identifies potential domains that might influence the regioselectivity of these enzymes but also gives hints to specific amino acids that might determine the donor-substrate specificity of these glycosyltransferases.

A large-scale forward genetic screen for maize mutants with altered lignocellulosic properties

The development of efficient pipelines for the bioconversion of grass lignocellulosic feedstocks is challenging due to the limited understanding of the molecular mechanisms controlling the synthesis, deposition, and degradation of the varying polymers unique to grass cell walls. Here, we describe a large-scale forward genetic approach resulting in the identification of a collection of chemically mutagenized maize mutants with diverse alterations in their cell wall attributes such as crystalline cellulose content or hemicellulose composition. Saccharification yield, i.e. the amount of lignocellulosic glucose (Glc) released by means of enzymatic hydrolysis, is increased in two of the mutants and decreased in the remaining six. These mutants, termed candy-leaf (cal), show no obvious plant growth or developmental defects despite associated differences in their lignocellulosic composition. The identified cal mutants are a valuable tool not only to understand recalcitrance of grass lignocellulosics to enzymatic deconstruction but also to decipher grass-specific aspects of cell wall biology once the genetic basis, i.e. the location of the mutation, has been identified.

Emerging Roles of β-Glucanases in Plant Development and Adaptative Responses

Plant β-glucanases are enzymes involved in the synthesis, remodelling and turnover of cell wall components during multiple physiological processes. Based on the type of the glycoside bond they cleave, plant β-glucanases have been grouped into three categories: (i) β-1,4-glucanases degrade cellulose and other polysaccharides containing 1,4-glycosidic bonds to remodel and disassemble the wall during cell growth. (ii) β-1,3-glucanases are responsible for the mobilization of callose, governing the symplastic trafficking through plasmodesmata. (iii) β-1,3-1,4-glucanases degrade mixed linkage glucan, a transient wall polysaccharide found in cereals, which is broken down to obtain energy during rapid seedling growth. In addition to their roles in the turnover of self-glucan structures, plant β-glucanases are crucial in regulating the outcome in symbiotic and hostile plant-microbe interactions by degrading non-self glucan structures. Plants use these enzymes to hydrolyse β-glucans found in the walls of microbes, not only by contributing to a local antimicrobial defence barrier, but also by generating signalling glucans triggering the activation of global responses. As a counterpart, microbes developed strategies to hijack plant β-glucanases to their advantage to successfully colonize plant tissues. This review outlines our current understanding on plant β-glucanases, with a particular focus on the latest advances on their roles in adaptative responses.

Research opportunities: Traditional fermented beverages in Mexico. Cultural, microbiological, chemical, and functional aspects

In Mexico, close to 200 fermented products have been described, of which, approximately 20 are beverages. They were obtained through rustic and ancestral fermentation methods by different indigenous Mexican communities; most of them were used in ceremonies, agricultural work, and other occasions. For their elaboration, different substrates obtained from plants are used, where uncontrolled and low-scale spontaneous anaerobic fermentation occurs. In Mexico, some of these products are considered as nutritional sources and functional beverages; the study of those products has revealed the presence of multiple compounds of biological importance. Additionally, elder generations attribute healing properties against diverse illnesses to these beverages. The aim of this review is to highlight the available information on twelve traditional Mexican fermented beverages, their traditional uses, and their fermentation processes along with toxicological, chemical, nutritional, and functional studies as seen from different areas of investigation. In the literature, pulque, cocoa, and pozol were the beverages with the greatest amount of described health properties; sendechó and guarapo were less characterized. Polyphenols, gallic and ferulic acid, anthocyanins and saponins were the most abundant molecules in all beverages. Finally, it is important to continue this research in order to determine the microorganisms that are involved in the fermentation process, as well as the organoleptic and beneficial properties they lend to the traditional Mexican fermented beverages.

A mixed-linkage (1,3;1,4)-β-D-glucan specific hydrolase mediates dark-triggered degradation of this plant cell wall polysaccharide

The presence of mixed-linkage (1,3;1,4)-β-d-glucan (MLG) in plant cell walls is a key feature of grass species such as cereals, the main source of calorie intake for humans and cattle. Accumulation of this polysaccharide involves the coordinated regulation of biosynthetic and metabolic machineries. While several components of the MLG biosynthesis machinery have been identified in diverse plant species, degradation of MLG is poorly understood. In this study, we performed a large-scale forward genetic screen for maize (Zea mays) mutants with altered cell wall polysaccharide structural properties. As a result, we identified a maize mutant with increased MLG content in several tissues, including adult leaves and senesced organs, where only trace amounts of MLG are usually detected. The causative mutation was found in the GRMZM2G137535 gene, encoding a GH17 licheninase as demonstrated by an in vitro activity assay of the heterologously expressed protein. In addition, maize plants overexpressing GRMZM2G137535 exhibit a 90% reduction in MLG content, indicating that the protein is not only required, but its expression is sufficient to degrade MLG. Accordingly, the mutant was named MLG hydrolase 1 (mlgh1). mlgh1 plants show increased saccharification yields upon enzymatic digestion. Stacking mlgh1 with lignin-deficient mutations results in synergistic increases in saccharification. Time profiling experiments indicate that wall MLG content is modulated during day/night cycles, inversely associated with MLGH1 transcript accumulation. This cycling is absent in the mlgh1 mutant, suggesting that the mechanism involved requires MLG degradation, which may in turn regulate MLGH1 gene expression.

Epidemiological profile of hospitalized self-harm in Chile differs from suicide profile. 2008-2017

Background

Suicide is a public health problem. The highest rates occur in men of 45-60 years old, and the most common methods are hanging, ingestion of pesticides, and firearms. Self-harm with or without suicide intention is the most critical factor identified for prevention, and it requires health care services. In Chile, the central-south regions are the most vulnerable areas. We described the epidemiological profile and trends of hospitalized self-harm in Chile between the years 2008 and 2017 and identified susceptible geographical regions and subpopulations.

Methods

We analyzed the codes X60-X84 (ICD-10) for self-harm, from the hospital discharge records of the Department of Health Statistics of Chile. Chilean population data (National Statistics Institute) and standard world population information were used to adjust self-injury rates by age. Administrative shapefiles containing boundaries of standard geographic locations were obtained from the Chilean National Congress website. We analyzed data by sex, groups of age, and by administrative Region. Self-injury mechanisms were grouped into six categories.

Results

For the period 2008-2017, 31,363 cases of self-harm were hospitalized. The global self-harm rate for the period was 20.9 per 100.000 inhabitants, 29.5 for women, and 12.0 for men. For age groups 10-19, 20-64, and 65 or more, these rates were 40.4, 15.1, and 7.9, respectively. The highest self-harm rates were observed in the north and central regions (Arica:43.5, O'higgins:37.9, Valparaiso:35.4). The most common methods of self-harm were drugs/substance use (89%), sharp and blunt objects use (4.4%), and hanging/drowning (3.1%). In men, the letality rate of self-harm was 2.5% and 0.6% in women.

Conclusions

In Chile, hospitalized self-harm rates are high in women and adolescents, mainly in the north and central regions of the country.

Key messages

Prevention of suicide should be targeted in different populations than the already known epidemiological profile of suicide. Self-harm should be a public health concern, for prevention and surveillance, especially in adolescents and women.

Inflammatory biomarkers in dentinal fluid as an approach to molecular diagnostics in pulpitis

AIM

To explore a set of inflammatory biomarkers obtained from dentinal fluid (DF) from patients with symptomatic irreversible pulpitis (IP), reversible pulpitis (RP) and normal pulp (NP).

METHODOLOGY

A cross-sectional exploratory study was performed, recruiting 64 patients on the basis of their respective pulp condition. DF samples were obtained from all patients (23, from IP patients; 20, from RP patients; and 21, from NP patients). Quantification of biomarkers was performed using a Luminex® MAGPIX platform system and multiplex assay kits. The Kruskal-Wallis test was used for comparisons with regard to pulp state. A simple logistic regression model and the odds ratio (OR) with a 95% level of confidence (P = 0.05) were used to evaluate associations between biomarker levels and pulpal diagnosis. The performance discrimination of the biomarkers was evaluated through the construction of a receiver operating characteristic (ROC) curve by calculating the area under the curve (AUC) for IP versus RP after logistic regression modelling. Youden criteria were used to establish cut-off points for biomarkers alone with AUC > 70 and P-value < 0.05, or estimated probabilities from the multivariable logistic model.

RESULTS

The biomarkers that had significantly higher values in participants with IP versus RP were IL-1α, VEGF-α and FGF acid (P < 0.05). FGF acid (OR: 12.62; P = 0.0085; CI 95% 1.91-83.29) and VEGF-α (OR: 2.61; P = 0.0252; CI 95% 1.13-6.03) were associated with pulp diagnoses of IP versus RP. The AUC-ROC curve for FGF acid was 0.79. The model containing FGF acid, IL-1α, IL-6 and TIMP-1 had an AUC-ROC of 0.92 for IP versus RP with a significant difference from the FGF acid ROC curve (P = 0.0231).

CONCLUSIONS

Dentinal fluid could be used to assay pulpal mediators in the molecular diagnosis of pulpitis. Despite the limitation of the clinical diagnostics used in the present study, it was possible to detect a difference between irreversible symptomatic pulpitis and reversible pulpitis associated with the following combined biomarkers: FGF acid + IL-6 + IL-1α, +TIMP-1.

Cell-Based Regenerative Endodontics for Treatment of Periapical Lesions: A Randomized, Controlled Phase I/II Clinical Trial

A randomized controlled phase I/II clinical trial was designed to evaluate the safety and efficacy of encapsulated human umbilical cord mesenchymal stem cells in a plasma-derived biomaterial for regenerative endodontic procedures (REPs) in mature permanent teeth with apical lesions. The trial included 36 patients with mature incisors, canines, or mandibular premolars showing pulp necrosis and apical periodontitis. Patients were randomly and equally allocated between experimental (REP) or conventional root canal treatment (ENDO) groups. On the first visit, cavity access and mechanical preparation of the root canal were performed. Calcium hydroxide medication was used, and the cavity was sealed. Three weeks later, patients were treated following their assigned protocol of ENDO or REP. Clinical follow-up examinations were performed at 6 and 12 mo. Categorical variables were evaluated by Fisher's exact test. Quantitative variables were compared using the Mann-Whitney test. The evolution over time of the percentage of perfusion units and the dimensions of lesion and cortical compromise were explored. After the 12-mo follow-up, no adverse events were reported, and the patients showed 100% clinical efficacy in both groups. Interestingly, in the REP group, the perfusion unit percentage measured by laser Doppler flowmetry revealed an increase from 60.6% to 78.1% between baseline and 12-mo follow-up. Sensitivity tests revealed an increase of the positive pulp response in the REP group at 12-mo follow-up (from 6% to 56% on the cold test, from 0% to 28% on the hot test, and from 17% to 50% on the electrical test). We present the first clinical safety and efficacy evidence of the endodontic use of allogenic umbilical cord mesenchymal stem cells encapsulated in a plasma-derived biomaterial. The innovative approach, based on biological principles that promote dentin-pulp regeneration, presents a promising alternative for the treatment of periapical pathology (ClinicalTrials.gov NCT03102879).

The Suitability of Orthogonal Hosts to Study Plant Cell Wall Biosynthesis

Plant cells are surrounded by an extracellular matrix that consists mainly of polysaccharides. Many molecular components involved in plant cell wall polymer synthesis have been identified, but it remains largely unknown how these molecular players function together to define the length and decoration pattern of a polysaccharide. Synthetic biology can be applied to answer questions beyond individual glycosyltransferases by reconstructing entire biosynthetic machineries required to produce a complete wall polysaccharide. Recently, this approach was successful in establishing the production of heteromannan from several plant species in an orthogonal host-a yeast-illuminating the role of an auxiliary protein in the biosynthetic process. In this review we evaluate to what extent a selection of organisms from three kingdoms of life (Bacteria, Fungi and Animalia) might be suitable for the synthesis of plant cell wall polysaccharides. By identifying their key attributes for glycoengineering as well as analyzing the glycosidic linkages of their native polymers, we present a valuable comparison of their key advantages and limitations for the production of different classes of plant polysaccharides.

Genetic dissection of cell wall defects and the strigolactone pathway in Arabidopsis

Defects in the biosynthesis and/or deposition of secondary plant cell wall polymers result in the collapse of xylem vessels causing a dwarfed plant stature and an altered plant architecture termed irregular xylem (irx) syndrome. For example, reduced xylan O-acetylation causes strong developmental defects and increased freezing tolerance. Recently, we demonstrated that the irx syndrome in the trichome birefringence-like 29/eskimo1 (tbl29/esk1) mutant is dependent on MORE AXILLARY GROWTH 4 (MAX4), a key enzyme in the biosynthesis of the phytohormone strigolactone (SL). In this report, we show that other xylan- and cellulose-deficient secondary wall mutants exhibit increased freezing tolerance correlated with the irx syndrome. In addition, these phenotypes are also dependent on MAX4, suggesting a more general interaction between secondary wall defects and SL biosynthesis. In contrast, MAX4 does not play a role in developmental defects triggered by primary wall deficiencies, suggesting that the interaction is restricted to vascular tissue. Through a reverse genetics approach, the requirement of different components of the SL pathway impacting the irx syndrome in tbl29 was evaluated. Our results show that the tbl29-associated irx phenotypes are dependent on the MAX3 and MAX4 enzymes, involved in the early steps of SL biosynthesis. In contrast, this signaling is independent on downstream enzymes in the biosynthesis and perception of SL such as MAX1 and MAX2.

A 2'-O-Methyltransferase Responsible for Transfer RNA Anticodon Modification Is Pivotal for Resistance to Pseudomonas syringae DC3000 in Arabidopsis

Transfer RNA (tRNA) is the most highly modified class of RNA species in all living organisms. Recent discoveries have revealed unprecedented complexity in the tRNA chemical structures, modification patterns, regulation, and function, suggesting that each modified nucleoside in tRNA may have its own specific function. However, in plants, our knowledge of the role of individual tRNA modifications and how they are regulated is very limited. In a genetic screen designed to identify factors regulating disease resistance in Arabidopsis, we identified SUPPRESSOR OF CSB3 9 (SCS9). Our results reveal SCS9 encodes a tRNA methyltransferase that mediates the 2'-O-ribose methylation of selected tRNA species in the anticodon loop. These SCS9-mediated tRNA modifications enhance susceptibility during infection with the virulent bacterial pathogen Pseudomonas syringae DC3000. Lack of such tRNA modification, as observed in scs9 mutants, specifically dampens plant resistance against DC3000 without compromising the activation of the salicylic acid signaling pathway or the resistance to other biotrophic pathogens. Our results support a model that gives importance to the control of certain tRNA modifications for mounting an effective disease resistance in Arabidopsis toward DC3000 and, therefore, expands the repertoire of molecular components essential for an efficient disease resistance response.

New Insights Into Wall Polysaccharide O-Acetylation

The extracellular matrix of plants, algae, bacteria, fungi, and some archaea consist of a semipermeable composite containing polysaccharides. Many of these polysaccharides are O-acetylated imparting important physiochemical properties to the polymers. The position and degree of O-acetylation is genetically determined and varies between organisms, cell types, and developmental stages. Despite the importance of wall polysaccharide O-acetylation, only recently progress has been made to elucidate the molecular mechanism of O-acetylation. In plants, three protein families are involved in the transfer of the acetyl substituents to the various polysaccharides. In other organisms, this mechanism seems to be conserved, although the number of required components varies. In this review, we provide an update on the latest advances on plant polysaccharide O-acetylation and related information from other wall polysaccharide O-acetylating organisms such as bacteria and fungi. The biotechnological impact of understanding wall polysaccharide O-acetylation ranges from the design of novel drugs against human pathogenic bacteria to the development of improved lignocellulosic feedstocks for biofuel production.

Growth- and stress-related defects associated with wall hypoacetylation are strigolactone-dependent

Mutants affected in the Arabidopsis TBL29/ESK1 xylan O-acetyltransferase display a strong reduction in total wall O-acetylation accompanied by a dwarfed plant stature, collapsed xylem morphology, and enhanced freezing tolerance. A newly identified tbl29/esk1 suppressor mutation reduces the expression of the MAX4 gene, affecting the biosynthesis of methyl carlactonoate (MeCLA), an active strigolactone (SL). Genetic and biochemical evidence suggests that blocking the biosynthesis of this SL is sufficient to recover all developmental and stress-related defects associated with the TBL29/ESK1 loss of function without affecting its direct effect-reduced wall O-acetylation. Altered levels of the MAX4 SL biosynthetic gene, reduced branch number, and higher levels of MeCLA, were also found in tbl29/esk1 plants consistent with a constitutive activation of the SL pathway. These results suggest that the reduction in O-acetyl substituents in xylan is not directly responsible for the observed tbl29/esk1 phenotypes. Alternatively, plants may perceive defects in the structure of wall polymers and/or wall architecture activating the SL hormonal pathway as a compensatory mechanism.

From structure to function - a family portrait of plant subtilases

Contents Summary 901 I. Introduction 901 II. Biochemistry and structure of plant SBTs 902 III. Phylogeny of plant SBTs and family organization 903 IV. Physiological roles of plant SBTs 905 V. Conclusions and outlook 911 Acknowledgements 912 References 912 SUMMARY: Subtilases (SBTs) are serine peptidases that are found in all three domains of life. As compared with homologs in other Eucarya, plant SBTs are more closely related to archaeal and bacterial SBTs, with which they share many biochemical and structural features. However, in the course of evolution, functional diversification led to the acquisition of novel, plant-specific functions, resulting in the present-day complexity of the plant SBT family. SBTs are much more numerous in plants than in any other organism, and include enzymes involved in general proteolysis as well as highly specific processing proteases. Most SBTs are targeted to the cell wall, where they contribute to the control of growth and development by regulating the properties of the cell wall and the activity of extracellular signaling molecules. Plant SBTs affect all stages of the life cycle as they contribute to embryogenesis, seed development and germination, cuticle formation and epidermal patterning, vascular development, programmed cell death, organ abscission, senescence, and plant responses to their biotic and abiotic environments. In this article we provide a comprehensive picture of SBT structure and function in plants.

International Nosocomial Infection Control Consortium report, data summary of 50 countries for 2010-2015: Device-associated module

BACKGROUND

We report the results of International Nosocomial Infection Control Consortium (INICC) surveillance study from January 2010-December 2015 in 703 intensive care units (ICUs) in Latin America, Europe, Eastern Mediterranean, Southeast Asia, and Western Pacific.

METHODS

During the 6-year study period, using Centers for Disease Control and Prevention National Healthcare Safety Network (CDC-NHSN) definitions for device-associated health care-associated infection (DA-HAI), we collected prospective data from 861,284 patients hospitalized in INICC hospital ICUs for an aggregate of 3,506,562 days.

RESULTS

Although device use in INICC ICUs was similar to that reported from CDC-NHSN ICUs, DA-HAI rates were higher in the INICC ICUs: in the INICC medical-surgical ICUs, the pooled rate of central line-associated bloodstream infection, 4.1 per 1,000 central line-days, was nearly 5-fold higher than the 0.8 per 1,000 central line-days reported from comparable US ICUs, the overall rate of ventilator-associated pneumonia was also higher, 13.1 versus 0.9 per 1,000 ventilator-days, as was the rate of catheter-associated urinary tract infection, 5.07 versus 1.7 per 1,000 catheter-days. From blood cultures samples, frequencies of resistance of Pseudomonas isolates to amikacin (29.87% vs 10%) and to imipenem (44.3% vs 26.1%), and of Klebsiella pneumoniae isolates to ceftazidime (73.2% vs 28.8%) and to imipenem (43.27% vs 12.8%) were also higher in the INICC ICUs compared with CDC-NHSN ICUs.

CONCLUSIONS

Although DA-HAIs in INICC ICU patients continue to be higher than the rates reported in CDC-NSHN ICUs representing the developed world, we have observed a significant trend toward the reduction of DA-HAI rates in INICC ICUs as shown in each international report. It is INICC's main goal to continue facilitating education, training, and basic and cost-effective tools and resources, such as standardized forms and an online platform, to tackle this problem effectively and systematically.

Loss of a Conserved tRNA Anticodon Modification Perturbs Plant Immunity

tRNA is the most highly modified class of RNA species, and modifications are found in tRNAs from all organisms that have been examined. Despite their vastly different chemical structures and their presence in different tRNAs, occurring in different locations in tRNA, the biosynthetic pathways of the majority of tRNA modifications include a methylation step(s). Recent discoveries have revealed unprecedented complexity in the modification patterns of tRNA, their regulation and function, suggesting that each modified nucleoside in tRNA may have its own specific function. However, in plants, our knowledge on the role of individual tRNA modifications and how they are regulated is very limited. In a genetic screen designed to identify factors regulating disease resistance and activation of defenses in Arabidopsis, we identified SUPPRESSOR OF CSB3 9 (SCS9). Our results reveal SCS9 encodes a tRNA methyltransferase that mediates the 2´-O-ribose methylation of selected tRNA species in the anticodon loop. These SCS9-mediated tRNA modifications enhance during the course of infection with the bacterial pathogen Pseudomonas syringae DC3000, and lack of such tRNA modification, as observed in scs9 mutants, severely compromise plant immunity against the same pathogen without affecting the salicylic acid (SA) signaling pathway which regulates plant immune responses. Our results support a model that gives importance to the control of certain tRNA modifications for mounting an effective immune response in Arabidopsis, and therefore expands the repertoire of molecular components essential for an efficient disease resistance response.

Numerous studies revealed the existence of nearly 110 ribonucleoside structures incorporated as post-transcriptional modifications in tRNA, with 25–30 modifications present in any one organism. Emerging evidence points to the critical role of tRNA modifications in various cellular responses to stimuli, including transcription of stress response genes and control of cell viability and growth. The primary function of tRNA modifications, and in particular tRNA methylations, are linked to different steps in protein synthesis including stabilization of tRNA structures, reinforcement of the codon-anticodon interaction, regulation of wobble base pairing, and prevention of frameshift errors. Furthermore, tRNA methylations are involved in the RNA quality control system and regulation of tRNA localization in the cell, all of which affect translation rate, but modifications in the anti-codon, which exhibit important roles in decoding mRNA are particularly important. We identified that the SCS9 gene from Arabidopsis encodes a tRNA 2´-O-ribose methyltransferase homologous to the TRM7 methyltransferase from yeast. We identify that SCS9 is crucial for the 2´-O-ribose methylation of nucleotides 32 and 34 of the tRNAs anticodon loop of certain tRNA molecules. We show that SCS9 is required for effectiveness of plant immunity and suggest the importance of precise tRNA modifications in this process.

Porphyromonas gingivalis, Treponema denticola and toll-like receptor 2 are associated with hypertensive disorders in placental tissue: a case-control study

AIM(S)

To explore the associations between the presence of periodontal pathogens and the expression of toll-like receptors (TLR-2 and TLR-4) in the placental tissue of patients with hypertensive disorders compared to the placentas of healthy normotensive patients.

MATERIAL AND METHODS

A case-control study was performed. From a cohort composed of 126 pregnant women, 33 normotensive healthy pregnant women were randomly selected, and 25 cases of patients with hypertensive disorders of pregnancy, including gestational hypertension and pre-eclampsia, were selected. Placental biopsy was obtained after aseptic placental collection at the time of delivery. All of the samples were processed and analysed for the detection of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Treponema denticola and Tannerella forsythia using the polymerase chain reaction (PCR) technique. Determination of the expressions of TLR-2 and TLR-4 was performed in samples of total purified protein isolated from placental tissues and analysed by ELISA. The data were assessed using descriptive statistics. The associations among variables were estimated through multiple logistic regression models and the Mann-Whitney test to evaluate the differences between the two groups.

RESULTS

A significant increase was observed in the expression of TLR-2 in the placentas of patients with hypertensive disorders (p = 0.04). Additionally, the multiple logistic regression models demonstrated an association between the presence of T. denticola and P. gingivalis in placental tissues and hypertensive disorders (OR: 9.39, p = 0.001, CI 95% 2.39-36.88 and OR: 7.59, p = 0.019, CI 95% 1.39-41.51, respectively).

CONCLUSIONS

In the present study, pregnant women with periodontal disease presented an association in the placental tissue between the presence of T. denticola and P. gingivalis and hypertensive disorders. Additionally, increased expression of TLR-2 was observed. However, further studies are required to determine the specific roles of periodontal pathogens and TLRs in the placental tissue of patients with pregnancy-related hypertensive disorders.

The RNA silencing enzyme RNA polymerase v is required for plant immunity

RNA-directed DNA methylation (RdDM) is an epigenetic control mechanism driven by small interfering RNAs (siRNAs) that influence gene function. In plants, little is known of the involvement of the RdDM pathway in regulating traits related to immune responses. In a genetic screen designed to reveal factors regulating immunity in Arabidopsis thaliana, we identified NRPD2 as the OVEREXPRESSOR OF CATIONIC PEROXIDASE 1 (OCP1). NRPD2 encodes the second largest subunit of the plant-specific RNA Polymerases IV and V (Pol IV and Pol V), which are crucial for the RdDM pathway. The ocp1 and nrpd2 mutants showed increases in disease susceptibility when confronted with the necrotrophic fungal pathogens Botrytis cinerea and Plectosphaerella cucumerina. Studies were extended to other mutants affected in different steps of the RdDM pathway, such as nrpd1, nrpe1, ago4, drd1, rdr2, and drm1drm2 mutants. Our results indicate that all the mutants studied, with the exception of nrpd1, phenocopy the nrpd2 mutants; and they suggest that, while Pol V complex is required for plant immunity, Pol IV appears dispensable. Moreover, Pol V defective mutants, but not Pol IV mutants, show enhanced disease resistance towards the bacterial pathogen Pseudomonas syringae DC3000. Interestingly, salicylic acid (SA)-mediated defenses effective against PsDC3000 are enhanced in Pol V defective mutants, whereas jasmonic acid (JA)-mediated defenses that protect against fungi are reduced. Chromatin immunoprecipitation analysis revealed that, through differential histone modifications, SA-related defense genes are poised for enhanced activation in Pol V defective mutants and provide clues for understanding the regulation of gene priming during defense. Our results highlight the importance of epigenetic control as an additional layer of complexity in the regulation of plant immunity and point towards multiple components of the RdDM pathway being involved in plant immunity based on genetic evidence, but whether this is a direct or indirect effect on disease-related genes is unclear.

Arabidopsis ocp3 mutant reveals a mechanism linking ABA and JA to pathogen-induced callose deposition

In the present study, we evaluated the role of the defense-related gene OCP3 in callose deposition as a response to two necrotrophic fungal pathogens, Botrytis cinerea and Plectosphaerella cucumerina. ocp3 plants exhibited accelerated and intensified callose deposition in response to fungal infection associated with enhanced disease resistance to the two pathogens. A series of double mutant analyses showed potentiation of callose deposition and the heightened disease resistance phenotype in ocp3 plants required the plant hormone abscisic acid (ABA) and the PMR4 gene encoding a callose synthase. This finding was congruent with an observation that ocp3 plants exhibited increased ABA accumulation, and ABA was rapidly synthesized following fungal infection in wild-type plants. Furthermore, we determined that potentiation of callose deposition in ocp3 plants, including enhanced disease resistance, also required jasmonic acid (JA) recognition though a COI1 receptor, however JA was not required for basal callose deposition following fungal infection. In addition, potentiation of callose deposition in ocp3 plants appeared to follow a different mechanism than that proposed for callose β-amino-butyric acid (BABA)-induced resistance and priming, because ocp3 plants responded to BABA-induced priming for callose deposition and induced resistance of a magnitude similar to that observed in wild-type plants. Our results point to a model in which OCP3 represents a specific control point for callose deposition regulated by JA yet ultimately requiring ABA. These results provide new insights into the mechanism of callose deposition regulation in response to pathogen attack; however the complexities of the processes remain poorly understood.

Enhanced disease resistance to Botrytis cinerea in myb46 Arabidopsis plants is associated to an early down-regulation of CesA genes

The cell wall is a protective barrier of paramount importance for the survival of plant cells. Monitoring the integrity of cell wall allows plants to quickly activate defence pathways to minimize pathogen entry and reduce the spread of disease. Counterintuitively, however, pharmacological effects as well as genetic lesions that affect cellulose biosynthesis and content confer plants with enhanced resistance against necrotrophic fungi. This kind of pathogens target cellulose for degradation to facilitate penetration and to generate glucose units as a food source. Our results points towards the existence of a transcriptional reprogramming mechanism in genes encoding cellulose synthases (CesAs) that occurs very soon after Botrytis cinerea attack and that results in a temporarily shut down of some CesA genes. Interestingly, the observed coordinated down-regulation of CesA genes is more pronounced, and occurs earlier, in myb46 mutant plants. In the resistant myb46 plants, pathogen infection induces transient down-regulation of CesA genes that concurs with a selective transcriptional reprogramming in a set of genes encoding structural cell wall proteins and extracellular remodelling enzymes. Together with previous indications, our results favour the hypothesis that CesAs are part of a surveillance system of the cell wall integrity that senses the presence of a pathogen and transduces that signal into a rapid transcriptional reprogramming of the affected cell.

MYB46 modulates disease susceptibility to Botrytis cinerea in Arabidopsis

In this study, we show that the Arabidopsis (Arabidopsis thaliana) transcription factor MYB46, previously described to regulate secondary cell wall biosynthesis in the vascular tissue of the stem, is pivotal for mediating disease susceptibility to the fungal pathogen Botrytis cinerea. We identified MYB46 by its ability to bind to a new cis-element located in the 5' promoter region of the pathogen-induced Ep5C gene, which encodes a type III cell wall-bound peroxidase. We present genetic and molecular evidence indicating that MYB46 modulates the magnitude of Ep5C gene induction following pathogenic insults. Moreover, we demonstrate that different myb46 knockdown mutant plants exhibit increased disease resistance to B. cinerea, a phenotype that is accompanied by selective transcriptional reprogramming of a set of genes encoding cell wall proteins and enzymes, of which extracellular type III peroxidases are conspicuous. In essence, our results substantiate that defense-related signaling pathways and cell wall integrity are interconnected and that MYB46 likely functions as a disease susceptibility modulator to B. cinerea through the integration of cell wall remodeling and downstream activation of secondary lines of defense.

OCP3 is an important modulator of NPR1-mediated jasmonic acid-dependent induced defenses in Arabidopsis

BACKGROUND

Upon appropriate stimulation, plants increase their level of resistance against future pathogen attack. This phenomenon, known as induced resistance, presents an adaptive advantage due to its reduced fitness costs and its systemic and broad-spectrum nature. In Arabidopsis, different types of induced resistance have been defined based on the signaling pathways involved, particularly those dependent on salicylic acid (SA) and/or jasmonic acid (JA).

RESULTS

Here, we have assessed the implication of the transcriptional regulator OCP3 in SA- and JA-dependent induced defenses. Through a series of double mutant analyses, we conclude that SA-dependent defense signaling does not require OCP3. However, we found that ocp3 plants are impaired in a Pseudomonas fluorescens WCS417r-triggered induced systemic resistance (ISR) against both Pseudomonas syrinagae DC3000 and Hyaloperonospora arabidopsidis, and we show that this impairment is not due to a defect in JA-perception. Likewise, exogenous application of JA failed to induce defenses in ocp3 plants. In addition, we provide evidence showing that the over-expression of an engineered cytosolic isoform of the disease resistance regulator NPR1 restores the impaired JA-induced disease resistance in ocp3 plants.

CONCLUSIONS

Our findings point to a model in which OCP3 may modulate the nucleocytosolic function of NPR1 in the regulation of JA-dependent induced defense responses.

Drought tolerance in Arabidopsis is controlled by the OCP3 disease resistance regulator

Water scarcity and corresponding abiotic drought stress is one of the most important factors limiting plant performance and yield. In addition, plant productivity is severely compromised worldwide by infection with microbial pathogens. Two of the most prominent pathways responsible for drought tolerance and disease resistance to fungal pathogens in Arabidopsis are those controlled by the phytohormones abscisic acid (ABA) and the oxylipin methyl jasmonate (MeJA), respectively. Here, we report on the functional characterization of OCP3, a transcriptional regulator from the homeodomain (HD) family. The Arabidopsis loss-of-function ocp3 mutant exhibits both drought resistance and enhanced disease resistance to necrotrophic fungal pathogens. Double-mutant analysis revealed that these two resistance phenotypes have different genetic requirements. Whereas drought tolerance in ocp3 is ABA-dependent but MeJA-independent, the opposite holds true for the enhanced disease resistance characteristics. These observations lead us to propose a regulatory role of OCP3 in the adaptive responses to these two stresses, functioning as a modulator of independent and specific aspects of the ABA- and MeJA-mediated signal transduction pathways.

Association of serum pepsinogen with atrophic body gastritis in Costa Rica

Individuals with atrophic gastritis (AG), especially atrophic body gastritis (ABG), are at increased risk of developing gastric cancer. Serum concentrations of pepsinogens (PG) have been proposed as markers for ABG. The aim of this study was to determine the risk factors for AG and ABG and the potential of using serum PG concentrations to detect ABG in a dyspeptic population in Costa Rica, which is one of the countries with the highest incidence and mortality rates of gastric cancer in the world. Seven biopsy specimens, a fasting blood sample and a questionnaire concerning sociodemographic factors were obtained from 501 consecutive dyspeptic patients. The serum PGI level and the PGI/PGII ratios were significantly lower in patients with ABG than in other groups (P<0.000). A cut-off point of 3.4 led to a sensitivity of 91.2% in identifying ABG, a negative predictive value of 98.1%, but a positive predictive value of only 11.2%. Helicobacter pylori were present in 93% of the patients and all those with peptic ulcers were positive. AG was associated with increased age, lower body mass index, high alcohol intake and low fruit consumption. ABG was associated with age, alcohol consumption and PGI/PGII<3.4. In dyspeptic patients with a high prevalence of H. pylori infection, serum PG levels provide an assessment of ABG but it is necessary to introduce other serological and genetic markers in order to achieve a better specificity. Those markers could be serum antibodies to H. pylori-CagA, cytokine gene polymorphisms or others.

[Bluetongue: isolation and characterization of the virus and identification of vectors in northeastern Argentina]

To establish if BTV was circulating in Argentina, 94 bovines from the Santo Tomé and Ituzaingó Departments of Corrientes Province were sampled every 30-60 days during 14 months. Red blood cells from those animals that showed seroconvertion with a c-ELISA were processed for virus isolation by inoculation in embryonated chicken eggs and cell cultures. Cells with CPE were positive by direct and indirect immunofluorescence with BTV specific reagents. These samples examined by electron microscopy showed virus particles with BTV morphological characteristics. Blood samples and tissue culture supernantants were positive by RT-PCR technique with primers corresponding to the segment 3 of the BTV genome. Haematophagous insects were captured in one farm using light traps and Culicoides insignis Lutz was the predominant species detected. This is the first isolation of BTV in Argentina from northeastern bovines without any disease symptom.

[Predicted duration of protective anti-HBs antigens in Peruvian health care workers after six years of vaccination]

Given the importance attributed to the protection of health care workers against viral Hepatitis B (VHB) by the World Health Organization (WHO) and the Center for Disease Control (CDC), in 1993, the Instituto Peruano del Seguro Social (Social Security Peruvian Institute), today known as ESSALUD, ruled the vaccination of personnel in risk working in the 4 national hospitals, using Cuban vaccine Heberbiovac HB (20mg, schedule 0, 1, 2 months). Our purpose was to evaluate the antibody persistence in the vaccinated individuals after six years from immunization, and the possible presence of HB virus infection markers. Sera from 144 health care workers were studied, for a 70.24% coverage, in relation to the initially seroprotected in the 1993 study. For markers detection, commercial immunoenzymatic methods were used. HBsAg and anti-HBc were negative in all the serology samples studied, thus we conclude that no evidence of infection by this virus was found in any of the vaccinated subjects. AntiHBs was positive, being all of them seroconverted, with seroprotection and hyperresponse as of 91.6% and 43.7% respectively. The mean life time of antiHBs (t 1/2) is three years,predicting that the antibodies level will be over 10 IU/l until after 15 years from the end of the schedule. The subjects under 40 had significantly higher levels of seroprotection and hyperresponse, being the females those that stayed in the upper categories of response. Evaluation of the post-reinforcement memory in the seroconverted, not protected cases, is recommended, as well as extend the work with ESSALUD to other hospitals in the country.

Micronuclei frequency in lymphocytes of individuals occupationally exposed to pesticides

Pesticides have been widely used in developing countries over the years. A large amount of these remains in the environment and organisms. Pesticide pollution is detrimental to human health. The effects can be seen on a short or a long-term basis and the symptoms can vary from headache to cancer. Only a minority of studies focuses on their genotoxic effect. This study assesses the genotoxic effect of the pesticides used at banana-packaging plants with binucleate micronuclei assay using cultured lymphocytes. The studied population included 32 exposed and 37 unexposed women from Costa Rica. There is no significant difference between the two groups. However, women who worked at the packaging plant and had stillbirths or spontaneous abortions were 1.45 times more (alpha = 0.06) likely to have an increased micronuclei frequency than their coworkers who lacked those disorders; this may indicate genetic susceptibility. In vitro pesticides studies and susceptibility biomarkers are needed to identify subgroups with higher risks.

[Capacity to predict a recurrence of lupus erythematosus using double-stranded anti-DNA antibodies and Farr technique]

BACKGROUND

Patients with inactive systemic lupus erythematosus (SLE) and elevated high affinity double-stranded anti-DNA antibodies (anti-dsDNA), measured using Farr technique, would have a risk of relapse that fluctuates between 40 to 80% according to different series.

AIM

To study the association between anti-dsDNA levels measured using Farr technique and disease activity and their predictive capacity for relapses.

MATERIAL AND METHODS

Anti-dsDNA antibodies were measured according to Farr method in 60 healthy subjects, 69 patients with other connective tissue diseases and in 120 patients with SLE. Farr positive were considered those individuals with anti-dsDNA levels over 10.4 IU/ml. Disease activity, assessed using MEX-SLEDAI score was related with anti-dsDNA levels in 101 patients. Forty seven patients with inactive disease were followed for 17 +/- 14 months.

RESULTS

Anti-dsDNA levels were 3 +/- 2.5 IU/ml (range 1-26) in subjects without LED, and 127 +/- 500 IU/ml (range 1-5280) in patients with LED. Sixty subjects had an active SLE and 43 (72%) were Farr positive; in 41 the disease was inactive and 13 (32%) were Farr positive (p < 0.001), OR 5.45. Twelve of the 47 followed patients had a relapse and 10 (83%) were Farr positive. Of those that did not have a relapse, 13 (37%) were Farr positive (p < 0.02, RR 5.22). Six of 15 patients that were followed for more than on year (40%), were Farr positive.

CONCLUSIONS

Elevated anti-dsDNA antibodies measured using Farr technique in patients with inactive generalised lupus erythematosus, predicted the risk of relapse. However less than half of patients with inactive disease and elevated Farr relapsed in a period of one year. The need to treat patients with inactive SLE and positive Farr should therefore be considered debatable.

Overexpression of copper-zinc superoxide dismutase in trisomy 21

Down's syndrome (DS), the most frequent of congenital birth defects, results from the trisomy of chromosome 21 in all cells of affected patients. This disease is characterized by developmental anomalies, mental retardation and features of rapid aging, particularly in the brain, where the occurrence of Alzheimer's disease is observed in trisomy 21 patients over the age of 35. Copper-zinc superoxide dismutase (CuZnSOD) is one of the proteins encoded by chromosome 21 (21q22.1). As a consequence of gene dosage excess, CuZnSOD activity is increased by 50% in all DS tissues. This work reports the SOD activity of a population of DS patients with complete trisomy 21, partial trisomy 21, translocations and mosaicism, in order to confirm the gene dosage effect of SOD on the clinical features of DS, and to help to establish which is the critical region of chromosome 21 in DS. CuZnSOD was measured in red blood cells using the Minami and Yoshikawa method. In the population with complete trisomy 21, SOD activity was increased by 42%; in the population with partial trisomy 21, translocations and mosaicism, SOD activity was normal. In the population diagnosed as DS, but not karyotyped, SOD activity was increased by 28%. No differences between sexes or among ages were found. We conclude that the 21q22.1 segment is not the critical region responsible for DS, as we have found normal SOD activity in patients with the clinical features of DS.

Distribution of enkephalin and its relation to serotonin in cat and monkey spinal cord and brain stem

The distribution of enkephalin (ENK)-like immunoreactivity (LI) in spinal cord and medulla oblongata of cat and gray monkey (Macaca fascicularis) was studied by use of immunofluorescence and peroxidase antiperoxidase (PAP) techniques. Possible coexistence between ENK- and 5-hydroxytryptamine (5-HT)-LI was also analyzed with double labeling immunofluorescence. Furthermore, in situ hybridization was used to demonstrate cell bodies in the brain stem expressing mRNA encoding for ENK. ENK-immunoreactive (IR) axonal varicosities and fibers were demonstrated throughout the spinal cord gray matter, with the highest density in the superficial dorsal horn, the area around the central canal, the intermediolateral cell column, the sacral parasympathetic nucleus, and in Onuf's nucleus. In the monkey ventral horn, ENK-IR varicose fibers could in some cases be demonstrated in very close apposition to cell bodies. A low degree of co-localization between ENK- and 5-HT-LI was seen in the spinal cord of both species. Still, fibers containing both compounds could as a rule be demonstrated in every section studied. The highest degree of coexistence was encountered in the motor nucleus of the ventral horn. Six weeks after a low thoracic spinal cord transection a decreased staining for ENK-LI was demonstrated in the ventral horn motor nucleus, whereas other parts of the spinal cord appeared unaffected. In the brain stem of cats after colchicine treatment, ENK-LI was found in a majority of the 5-HT-IR cell bodies in the raphe nuclei (nucleus raphe magnus, pallidus and obscurus) and in the lateral reticular nucleus (rostroventrolateral reticular nucleus). In cat not pretreated with colchicine, a few weakly stained ENK-IR cell bodies could be found in the midline raphe nuclei and in the lateral reticular nucleus with the PAP technique. In the monkey brain stem without colchicine treatment, using the PAP technique, heavily stained ENK-IR cell bodies could be seen in the lateral reticular nucleus whereas, as in the cat, only a few, weakly stained ENK-IR cell bodies could be seen in the midline raphe nuclei. Using in situ hybridization technique, ENK mRNA expressing cells were demonstrated in the lateral reticular nucleus while no convincing mRNA signal could be found over cell bodies in the raphe nuclei. It is concluded that part of the ENKergic innervation of the cord in both species derives from supraspinal or suprasegmental levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Distribution of calbindin D28k-like immunoreactivity (LI) in the monkey ventral horn: do Renshaw cells contain calbindin D28k-LI?

By use of indirect immunofluorescence and peroxidase-antiperoxidase immunohistochemistry, we show that the monkey (Macaca fascicularis) ventral horn harbors small- to medium-sized neurons in lamina VII as well as a dense network of fibers in laminae IX and VII that contain calbindin D28k (calbindin)-like immunoreactivity. The highest frequency of immunoreactive (IR) cell bodies was found at the levels of the cervical and lumbar intumescences. Furthermore, rostrocaudally oriented calbindin-IR fibers were encountered in the ventral and ventrolateral funiculi throughout the whole length of the cord, with the highest density at cervical and lumbar intumescences. Analysis at the EM level revealed calbindin-IR terminals in contact preferentially with dendrites of variable size and occasionally also large cell bodies, presumably belonging to motoneurons, in the lateral motor nucleus. The location of calbindin-IR neurons, as well as the distribution and ultrastructural characteristics of the calbindin-IR axonal system, makes it highly likely that these neurons are Renshaw cells that mediate recurrent inhibition to motoneurons.

Anatomy of dendrites in motoneurons supplying the intrinsic muscles of the foot sole in the aged cat: evidence for dendritic growth and neo-synaptogenesis

Motoneurons (MNs) supplying the intrinsic muscles of the foot sole (IFS) were studied in the aged cat (greater than 15y). Axon conduction velocity of IFS MNs was 30-40% slower in the aged than in young adult cats. IFS MNs that appeared intact during intracellular recordings and labeling with horseradish peroxidase (HRP) were subjected to anatomical investigation of their dendrites. The results were compared with corresponding data from young adult (less than 3y) cats. The average number of dendrites per IFS MN was twelve in both the aged and young adults. However, the branching was significantly more extensive in the aged cat, thus indicating that proliferation of dendritic branches may occur during the later part of life. Topological analysis revealed a significant difference in the frequency distributions of nodal vertices between young adult and aged cats. In the young adult, the dendritic branching pattern was compatible with trees generated by outgrowth from terminal segments, while in the aged there was a clear indication of collateral outgrowth of branches. The dendritic path distance and the length of terminal branches were similar in young adults and aged. The length of preterminal branches was shorter in the aged, while the combined dendritic length of a dendrite was larger compared to young adults. These data are consistent with the topological data, and add further evidence that the proliferation of branches in the aged cat may also take place from preterminal branches. Light microscopic analysis revealed the presence of "growth cone-like" extensions in the dendrites of the aged cats. Such profiles were not encountered in dendrites from young adults. Electron microscopic observations showed that these "growth cone-like" formations were not artifacts and that they were apposed by numerous axonal boutons, of which a number made synaptic contact. A distinct feature of the extensions was their rich content of mitochondria and membranous elements. It was suggested that these "growth cone-like" formations were sites at which novel synaptic connections are established, and that they may represent the initial stage of an outgrowth of new dendritic branches in the aged cat. Local dendritic branch diameter related closely to the amount of dendritic membrane area located distally in both young adults and aged. Curve fitting disclosed that this relationship was quite similar for both age groups, despite concurrent differences in combined dendritic length and branching degree.

[Oral pathology in 161 asymptomatic and symptomatic HIV-positive patients]

The aim of this study was to establish the prevalence of oral manifestations in HIV-infected patients and to correlate their frequency with the clinical stage. One hundred and sixty one HIV-positive individuals were examined, of whom 64 (40%) were in stages CDC-II and III and 97 (60%) in stage CDC-IV. The patients were examined at the AIDS out-patient clinic of the Instituto Nacional de la Nutrición Salvador Zubirán. The oral exams were performed by three examiners who were intra and inter calibrated, so that standard clinical criteria were followed. One hundred and twenty five patients (78%) showed one or more oral lesions. The proportion of patients with oral lesions increased significantly (p less than 0.05) according to the severity of the infection. Hairy leukoplakia (40%) and erythematous candidiasis (31%) were the most frequent lesions. When the prevalence of the different oral lesions was compared between the patients at early stages with the patients at the late stage no significant differences were found; only the pseudomembranous candidiasis and the exfoliative cheilitis were found with significantly higher values at stage CDC-IV than at earlier stages (p less than 0.001 and p less than 0.05 respectively). No association was found between oral candidiasis and tobacco use or xerostomia. Our study demonstrates that the prevalence and clinical features of the oral manifestations found showed similarities with those reported in other countries, but ulcero-necrotizing gingivitis was not found in our patients.

Postnatal development of cat hind limb motoneurons supplying the intrinsic muscles of the foot sole

The postnatal development of dendrite anatomy in alpha-motoneurons intracellularly labeled with horseradish peroxidase (HRP), innervating the intrinsic muscles of the sole of the foot (IFS MNs) in the cat, was investigated. The number of dendrites per neuron was about 11 and did not change from birth to adult. The number of branches per dendrite decreased during the same period by 20-25%. The net elimination of dendritic branches appeared to occur at distal branching points, as revealed by topological analysis. The dendritic branching pattern tended to be asymmetric at birth and the net decrease in dendritic branching postnatally did not alter this pattern. The length of preterminal branches (PTB) increased by a factor of 2, while terminal branch (TB) length increased by a factor of 3.3 postnatally. The large increase in TB length was attributed to both longitudinal growth and an apparent lengthening caused by resorption of distal branches during development. Dendritic length in the transverse spinal cord plane increased in parallel with the overall growth of the parent spinal cord segment, while dendritic growth along the rostro-caudal axis exceeded, by about one order of magnitude, dendritic growth in the transverse plane. Average branch diameter doubled from birth to adult. The decrease in branch diameter across branching points did not obey satisfactorily to the 'power rule' of Rall. However, the 1.5 power ratio of daughters-to-parents branch dropped from 1.18 to 1.08 between 3 weeks of age and adult. Tapering was evident in both PTBs and TBs. The rate of taper did not change postnatally. From birth onwards, 'local' branch diameter correlated closely with amount of membrane area and combined length of the dendritic branches located distal to the 'supporting' parent branch. These relations were similar in all age groups and are suggested to be properties intrinsic to the IFS MNs. The local branch diameter also co-varied with the number of distal dendritic branches, but in this case there was a systematic shift in the relationship with increasing postnatal age. It appears that the local diameter in IFS MN dendrites is a key indicator of the size of the distal dendritic arborization.

Oral lesions in Mexican HIV-infected patients

One hundred and twenty-five HIV-infected patients, of whom 49 (39%) were at early stages of the infection (CDC-II & III) and 76 (61%) in CDC IV, were prospectively examined. In 100 (80%) one or more oral mucosal lesions were observed; candidiasis (51%) and hairy leukoplakia (43%) were the commonest. Erythematous candidiasis was more often seen (35%) than the pseudomembranous type (16%), and appeared with the higher values at early than later stages. The prevalence of hairy leukoplakia, oral hyperpigmentation and xerostomia were incremented in groups CDC-IV. Pseudomembranous candidiasis and exfoliative cheilitis increased significantly with severity of disease. Our study demonstrates that oral alterations associated to HIV are a frequent finding, both at early (76%) and late (83%) stages of the infection in Mexican patients.