Transfusion-associated adverse events incidence and severity after the implementation of an active hemovigilance program with 24 h follow-up. A prospective cohort study.

BACKGROUND: Hemovigilance (HV) is usually based on voluntary reports (passive HV). Our aim is to ascertain credible incidence, severity, and mortality of transfusion-associated adverse events (TAAEs) using an active HV program. STUDY DESIGN AND METHODS: Prospective cohort study to estimate transfusion risk after 46,488 transfusions in 5830 patients, using an active HV program with follow-up within the first 24 h after transfusion. We compared these results to those with the previously established passive HV program during the same 30 months of the study. We explored factors associated with the occurrence of TAAEs using generalized estimating equations models. RESULTS: With the active HV program TAAEs incidence was 57.3 (95% CI, 50.5-64.2) and mortality 1.1 (95% CI, 0.13-2.01) per 10,000 transfusions. Incidence with the new surveillance model was 14.0 times higher than with the passive. Most events occurred when transfusions had already finished (60.2%); especially pulmonary events (80.4%). Three out of five deaths and 50.3% of severe TAAEs were pulmonary. In the multivariate analysis surgical patients had half TAAEs risk when compared to medical patients (OR, 0.53; 95% CI, 0.34-0.78) and women had nearly twice the risk of a pulmonary event compared to men (OR, 1.84; 95% CI, 1.03-3.32). Patient's age, blood component type, or blood component shelf-life were unrelated to TAAEs risk. DISCUSSION: Active hemovigilance programs provide additional data which may lead to better recognition and understanding of TAAEs and their frequency and severity.

FGF4 retrogene on CFA12 is responsible for chondrodystrophy and intervertebral disc disease in dogs.

Chondrodystrophy in dogs is defined by dysplastic, shortened long bones and premature degeneration and calcification of intervertebral discs. Independent genome-wide association analyses for skeletal dysplasia (short limbs) within a single breed (PBonferroni = 0.01) and intervertebral disc disease (IVDD) across breeds (PBonferroni = 4.0 × 10-10) both identified a significant association to the same region on CFA12. Whole genome sequencing identified a highly expressed FGF4 retrogene within this shared region. The FGF4 retrogene segregated with limb length and had an odds ratio of 51.23 (95% CI = 46.69, 56.20) for IVDD. Long bone length in dogs is a unique example of multiple disease-causing retrocopies of the same parental gene in a mammalian species. FGF signaling abnormalities have been associated with skeletal dysplasia in humans, and our findings present opportunities for both selective elimination of a medically and financially devastating disease in dogs and further understanding of the ever-growing complexity of retrogene biology.

Genome-wide association mapping in dogs enables identification of the homeobox gene, NKX2-8, as a genetic component of neural tube defects in humans.

Neural tube defects (NTDs) is a general term for central nervous system malformations secondary to a failure of closure or development of the neural tube. The resulting pathologies may involve the brain, spinal cord and/or vertebral column, in addition to associated structures such as soft tissue or skin. The condition is reported among the more common birth defects in humans, leading to significant infant morbidity and mortality. The etiology remains poorly understood but genetic, nutritional, environmental factors, or a combination of these, are known to play a role in the development of NTDs. The variable conditions associated with NTDs occur naturally in dogs, and have been previously reported in the Weimaraner breed. Taking advantage of the strong linkage-disequilibrium within dog breeds we performed genome-wide association analysis and mapped a genomic region for spinal dysraphism, a presumed NTD, using 4 affected and 96 unaffected Weimaraners. The associated region on canine chromosome 8 (pgenome  =3.0 × 10(-5)), after 100,000 permutations, encodes 18 genes, including NKX2-8, a homeobox gene which is expressed in the developing neural tube. Sequencing NKX2-8 in affected Weimaraners revealed a G to AA frameshift mutation within exon 2 of the gene, resulting in a premature stop codon that is predicted to produce a truncated protein. The exons of NKX2-8 were sequenced in human patients with spina bifida and rare variants (rs61755040 and rs10135525) were found to be significantly over-represented (p=0.036). This is the first documentation of a potential role for NKX2-8 in the etiology of NTDs, made possible by investigating the molecular basis of naturally occurring mutations in dogs.

Epigenome-Wide Analysis Reveals DNA Methylation Alteration in ZFP57 and Its Target RASGFR2 in a Mexican Population Cohort with Autism.

Autism Spectrum Disorders (ASD) comprise a group of heterogeneous and complex neurodevelopmental disorders. Genetic and environmental factors contribute to ASD etiology. DNA methylation is particularly relevant for ASD due to its mediating role in the complex interaction between genotype and environment and has been implicated in ASD pathophysiology. The lack of diversity in DNA methylation studies in ASD individuals is remarkable. Since genetic and environmental factors are likely to vary across populations, the study of underrepresented populations is necessary to understand the molecular alterations involved in ASD and the risk factors underlying these changes. This study explored genome-wide differences in DNA methylation patterns in buccal epithelium cells between Mexican ASD patients (n = 27) and age-matched typically developing (TD: n = 15) children. DNA methylation profiles were evaluated with the Illumina 450k array. We evaluated the interaction between sex and ASD and found a differentially methylated region (DMR) over the 5'UTR region of ZFP57 and one of its targets, RASGRF2. These results match previous findings in brain tissue, which may indicate that ZFP57 could be used as a proxy for DNA methylation in different tissues. This is the first study performed in a Mexican, and subsequently, Latin American, population that evaluates DNA methylation in ASD patients.

The actress was on the balcony, after all: Eye-tracking locality and PR-availability effects in Spanish.

The relationship between syntactic ambiguity and locality has been a reliable cornerstone in theories of language comprehension with one exception: non-local preferences in object-modifying relative clauses preceded by two potential hosts (DP1 of DP2 RC). We test the offline and online effects of the availability of an alternative structure, the pseudo-relative, on the parsing of relative clauses. It has been claimed that pseudo-relatives are preferred to relative clauses because of their simplicity at the structural, interpretive and pragmatic levels, and act as a confound in the attachment literature (Grillo, 2012; Grillo & Costa, 2014). Our results show that attachment preferences are modulated by the availability of pseudo-relatives in offline and online tests. However, when this factor is controlled, parsing of relative clauses in Spanish is initially ruled by principles of locality, which can eventually be overridden by other factors.

Whole genome sequencing for mutation discovery in a single case of lysosomal storage disease (MPS type 1) in the dog.

Mucopolysaccharidosis (MPS) is a metabolic storage disorder caused by the deficiency of any lysosomal enzyme required for the breakdown of glycosaminoglycans. A 15-month-old Boston Terrier presented with clinical signs consistent with lysosomal storage disease including corneal opacities, multifocal central nervous system disease and progressively worsening clinical course. Diagnosis was confirmed at necropsy based on histopathologic evaluation of multiple organs demonstrating accumulation of mucopolysaccharides. Whole genome sequencing was used to uncover a frame-shift insertion affecting the alpha-L-iduronidase (IDUA) gene (c.19_20insCGGCCCCC), a mutation confirmed in another Boston Terrier presented 2 years later with a similar clinical picture. Both dogs were homozygous for the IDUA mutation and shared coat colors not recognized as normal for the breed by the American Kennel Club. In contrast, the mutation was not detected in 120 unrelated Boston Terriers as well as 202 dogs from other breeds. Recent inbreeding to select for recessive and unusual coat colors may have concentrated this relatively rare allele in the breed. The identification of the variant enables ante-mortem diagnosis of similar cases and selective breeding to avoid the spread of this disease in the breed. Boston Terriers carrying this variant represent a promising model for MPS I with neurological abnormalities in humans.

A Missense Variant in ALDH5A1 Associated with Canine Succinic Semialdehyde Dehydrogenase Deficiency (SSADHD) in the Saluki Dog.

Dogs provide highly valuable models of human disease due to the similarity in phenotype presentation and the ease of genetic analysis. Seven Saluki puppies were investigated for neurological abnormalities including seizures and altered behavior. Magnetic resonance imaging showed a diffuse, marked reduction in cerebral cortical thickness, and symmetrical T2 hyperintensity in specific brain regions. Cerebral cortical atrophy with vacuolation (status spongiosus) was noted on necropsy. Genome-wide association study of 7 affected and 28 normal Salukis revealed a genome-wide significantly associated region on CFA 35. Whole-genome sequencing of three confirmed cases from three different litters revealed a homozygous missense variant within the aldehyde dehydrogenase 5 family member A1 (ALDH5A1) gene (XM_014110599.2: c.866G>A; XP_013966074.2: p.(Gly288Asp). ALDH5A1 encodes a succinic semialdehyde dehydrogenase (SSADH) enzyme critical in the gamma-aminobutyric acid neurotransmitter (GABA) metabolic pathway. Metabolic screening of affected dogs showed markedly elevated gamma-hydroxybutyric acid in serum, cerebrospinal fluid (CSF) and brain, and elevated succinate semialdehyde in urine, CSF and brain. SSADH activity in the brain of affected dogs was low. Affected Saluki dogs had striking similarities to SSADH deficiency in humans although hydroxybutyric aciduria was absent in affected dogs. ALDH5A1-related SSADH deficiency in Salukis provides a unique translational large animal model for the development of novel therapeutic strategies.

Correction: DNA Sequence Variants in the Five Prime Untranslated Region of the Cyclooxygenase-2 Gene Are Commonly Found in Healthy Dogs and Gray Wolves.

[This corrects the article DOI: 10.1371/journal.pone.0133127.].

Scedosporium apiospermum and S. prolificans mixed disseminated infection in a lung transplant recipient: An unusual case of long-term survival with combined systemic and local antifungal therapy in intensive care unit.

Infections due Scedosporium spp. in lung transplant recipients are associated with disseminated disease with high mortality rates. The adjunctive local antifungal therapy may be a useful option when systemic treatment is insufficient and/or surgery is not feasible. We present a case of mixed disseminated infection due Scedosporium apiospermum and S. prolificans in a lung transplant recipient. Combined local and systemic antifungal therapy provided an unusual long-term survival in the intensive care unit.

Apexificación de un molar permanente a través de silicato tricálcico / Apexification of a permanent molar with tricalcium silicate

Paciente pediátrico de 9 años y género masculino, que acudió para valoración odontológica por presentar dolor dental tras ingerir alimentos fríos. El diagnóstico definitivo quedó establecido como pulpitis reversible del molar 3.6, decidiendo conducta terapéutica de recubrimiento pulpar directo con silicato tricálcico para lograr apexificación. La decisión clínica resultó exitosa, el seguimiento de la evolución permitió apreciar que el diente mantuvo su vitalidad, las raíces continuaron desarrollándose y no aparecieron signos o síntomas de lesiones periapicales.

9-year-old pediatric male patient, who came for dental evaluation because of dental pain after eating cold food. The definitive diagnosis was established as reversible pulpitis of the molar 3.6, deciding on the therapeutic behavior of the direct pulp coating with tricalcium silica to achieve apexification. The clinical decision was successful, the follow-up of the evolution identified the affected tooth as vital, the roots continued to develop, and no signs or symptoms of periapical lesions appeared.

DNA Sequence Variants in the Five Prime Untranslated Region of the Cyclooxygenase-2 Gene Are Commonly Found in Healthy Dogs and Gray Wolves.

The aim of this study was to investigate the frequency of regional DNA variants upstream to the translation initiation site of the canine Cyclooxygenase-2 (Cox-2) gene in healthy dogs. Cox-2 plays a role in various disease conditions such as acute and chronic inflammation, osteoarthritis and malignancy. A role for Cox-2 DNA variants in genetic predisposition to canine renal dysplasia has been proposed and dog breeders have been encouraged to select against these DNA variants. We sequenced 272-422 bases in 152 dogs unaffected by renal dysplasia and found 19 different haplotypes including 11 genetic variants which had not been described previously. We genotyped 7 gray wolves to ascertain the wildtype variant and found that the wolves we analyzed had predominantly the second most common DNA variant found in dogs. Our results demonstrate an elevated level of regional polymorphism that appears to be a feature of healthy domesticated dogs.

Factors associated with fatal occupational accidents among Mexican workers: a national analysis.

OBJECTIVE: To identify the factors associated with fatal occupational injuries in Mexico in 2012 among workers affiliated with the Mexican Social Security Institute. METHODS: Analysis of secondary data using information from the National Occupational Risk Information System, with the consequence of the occupational injury (fatal versus non-fatal) as the response variable. The analysis included 406,222 non-fatal and 1,140 fatal injuries from 2012. The factors associated with the lethality of the injury were identified using a logistic regression model with the Firth approach. RESULTS: Being male (OR=5.86; CI95%: 4.22-8.14), age (OR=1.04; CI95%: 1.03-1.06), employed in the position for 1 to 10 years (versus less than 1 year) (OR=1.37; CI95%: 1.15-1.63), working as a facilities or machine operator or assembler (OR: 3.28; CI95%: 2.12- 5.07) and being a worker without qualifications (OR=1.96; CI95%: 1.18-3.24) (versus an office worker) were associated with fatality in the event of an injury. Additionally, companies classified as maximum risk (OR=1.90; CI 95%: 1.38-2.62), workplace conditions (OR=7.15; CI95%: 3.63-14.10) and factors related to the work environment (OR=9.18; CI95%:4.36-19.33) were identified as risk factors for fatality in the event of an occupational injury. CONCLUSIONS: Fatality in the event of an occupational injury is associated with factors related to sociodemographics (age, sex and occupation), the work environment and workplace conditions. Worker protection policies should be created for groups with a higher risk of fatal occupational injuries in Mexico.

Cumplimiento de los criterios del indicador Prevención de infecciones de vías urinarias en un hospital de tercer nivel / Compliance of the Prevention of urinary tract infections indicator in a third level hospital

Introducción: según la incidencia que presenta el indicador Prevención de infecciones de vías urinarias, 80% de estas son ocasionadas en las unidades de salud por el uso de una sonda vesical. Con la finalidad de disminuir este problema, se implementó el indicador de calidad de los servicios de enfermería. Objetivo: identificar el cumplimiento de los criterios del indicador Prevención de infecciones de vías urinarias en pacientes con sonda vesical instalada en una unidad de tercer nivel. Métodos: estudio observacional, descriptivo, prospectivo, transversal del tipo sistemas de salud, en el que participaron 74 pacientes, en el periodo de septiembre a octubre del 2017, con un muestreo por conveniencia mediante observación al personal de enfermería que atiende pacientes con sonda vesical instalada durante el periodo de recolección de datos en los turnos matutino y vespertino, con el formato de sistema INDICAS (F1-PIVUPSVI/12). Se hizo el análisis mediante estadística descriptiva. Resultados: en relación con el nivel del cumplimiento del indicador Prevención de infecciones de vías urinarias en pacientes con sonda vesical instalada, este arrojó un 89.1% en rojo (66), equivalente a 70% o menos, y 18.9% en amarillo (8), que equivale al nivel del cumplimiento en un rango que va de 71 a 90%. Conclusiones: de acuerdo con datos estadísticos, se encuentra el indicador en rojo, con base en el sistema INDICAS de la Secretaría de Salud.

Introduction: According to the incidence showed by the Prevention of urinary tract infections in patients with a bladder catheter indicator, 80% of these infections is caused by the use of a bladder catheter. In order to reduce this problem, it was implemented the nursing service quality indicator. Objective: To identify compliance with the criteria of the indicator Prevention of urinary tract infections in patients with a bladder catheter in a third level unit. Methods: Observational, descriptive, prospective, cross-sectional, health systems sort of study, which included 74 patients from September to October of 2017, with a convenience sample by observation to the nursing staff that takes care of patients with bladder catheter installed during the period of data collection in the morning and afternoon shifts with INDICAS system format (F1-PIVUPSVI/12). Analysis was performed with descriptive statistics. Results: The level of compliance with the Prevention of urinary tract infections in patients with a bladder catheter indicator resulted in 89.1% in red (66), equivalent to 70% or less, and 18.9% in yellow (8), equivalent to a level of compliance ranging from 71 to 90%. Conclusions: According to statistical data, the indicator is in red, based on the Secretaría de Salud (Health Secretary) INDICAS system.

Clinical manifestations, response to treatment, and clinical outcome for Weimaraners with hypertrophic osteodystrophy: 53 cases (2009-2011).

OBJECTIVE: To evaluate clinical manifestations, response to treatment, and outcome for Weimaraners with hypertrophic osteodystrophy (HOD). DESIGN: Retrospective case series. ANIMALS: 53 dogs. PROCEDURES: Medical records were reviewed for signalment, vaccination history, clinical signs, laboratory test results, response to treatment, and relapses. Radiographs were reviewed. RESULTS: Clinical signs included pyrexia, lethargy, and ostealgia; signs involving the gastrointestinal, ocular, or cutaneous systems were detected. Of the 53 dogs, 28 (52.8%) had HOD-affected littermates. Dogs with HOD-affected littermates were more likely to relapse, compared with the likelihood of relapse for dogs with no HOD-affected littermates. All 53 dogs had been vaccinated 1 to 30 days before HOD onset; no difference was found between the number of dogs with a history of vaccination with a recombinant vaccine (n … 21) versus a nonrecombinant vaccine (32). Fifty (94.3%) dogs had radiographic lesions compatible with HOD at disease onset, and the other 3 (5.7%) had HOD lesions 48 to 72 hours after the onset of clinical signs. Twelve of 22 (54.5%) dogs treated with NSAIDs did not achieve remission by 7 days after initiation of treatment. All dogs treated initially with corticosteroids achieved remission within 8 to 48 hours. Of the 33 dogs that reached adulthood, 28 (84.8%) were healthy and 5 (15.2%) had episodes of pyrexia and malaise. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with corticosteroids was superior to treatment with NSAIDs in Weimaraners with HOD. It may be necessary to evaluate repeated radiographs to establish a diagnosis of HOD. Most HOD-affected Weimaraners had resolution of the condition with physeal closure.

Effect of the polymorphism BDNF rs6265 G/A in Mexican outpatient children with autism spectrum disorders / Efecto del polimorfismo rs6265 G/A del gen BDNF en niños mexicanos ambulatorios con trastornos del espectro autista

Abstract: Introduction: The study of autistic spectrum disorders (ASD) at the genetic level is extremely important to understand their origin. In Mexico, there are few works addressed from this perspective. Objective: We investigated the role of the Brain Derived Neurotrophic Factor (BDNF) gene variant rs6265 G/A for single nucleotide polymorphism analysis in Mexican children with ASD using a case-control association design. Method: We made a pilot study by case-control analysis adjusting by gender, age, and ancestry. Results: Our study found no association between the BDNF rs6265 gene polymorphism and ASD [p = .419, OR = 1.597 (.514, 4.967)] Discussion and conclusion: Worldwide, the results of case-control association studies with the rs6265 of BDNF are controversial and do not always replicate. This may be due to the ethnicity of our population and additional factors not studied in the present work. Our study suggests that the SNP rs6265 is not contributing for ASD susceptibility in Mexican population.

Resumen: Introducción: El estudio de los trastornos del espectro autista a nivel genético es de suma importancia para entender su origen. En México existen pocos trabajos abordados desde esta perspectiva. Objetivo: Investigamos el papel de la variante del gen rs6265 G/A del factor neurotrófico derivado del cerebro (BDNF) para el análisis del polimorfismo de un solo nucleótido en niños mexicanos con TEA por medio de un diseño de asociación de casos y controles. Método: Realizamos un estudio piloto mediante un análisis de casos y controles ajustando por género, edad y ancestría. Resultados: Nuestro estudio no encontró asociación entre el polimorfismo del gen BDNF rs6265 y TEA [p = .419, OR = 1.597 (.514, 4.967)]. Discusión y conclusión: A nivel mundial, los resultados de estudios de asociación caso-control con el rs6265 de BDNF son controvertidos y no siempre se replican. Esto puede deberse a la etnicidad de nuestra población y a otros factores no estudiados en el presente trabajo. El estudio sugiere que el SNP rs6265 no contribuye a la susceptibilidad al TEA en población mexicana.

Conocimiento y aplicación del consentimiento informado en pacientes del Hospital Escuela Universitario/Hospital Materno Infantil / Knowledge and Application of the Informed Consent in the patients of the Univers ity Hospital/ Maternal-Child Hospital

Antecedentes: En Honduras el Consentimiento Informado (CI) no ha sido objeto de estudio ni de publicación. Objetivo: Establecer el grado de conocimiento sobre el diagnóstico, tratamiento y pronóstico de su enfermedad y la aplicación del consentimiento informado en los pacientes ingresados en los servicios de Medicina Interna, Pediatría, Cirugía, Ginecología del Hospital Escuela Universitario (HEU)/Hospital Materno Infantil (HMI) Tegucigalpa en el período de marzo-mayo 2015. M étodos: Estudio cuantitativo, descriptivo, trasversal. La muestra fue 252 pacientes ingresados en las salas de los 4 servicios básicos (63 pacientes por servicio). Utilizando un muestreo no probabilístico. Los datos se recolectaron a través de una entrevista que constó de cuatro secciones: datos generales, conocimiento sobre su enfermedad, personal que le informó y aplicación del consentimiento informado. Para la validación del instrumento se realizó una prueba piloto. Los datos se presentan como frecuencias y porcentajes de las variables estudiadas. Se aplicó el CI a los participantes mayores de 18 años y el asentimiento informado a los mayores de 7 años, se guardó la conidencialidad de la información. Resultados : El 48% (120/252) de los pacientes tenía un grado de conocimiento insuiciente sobre su enfermedad. El Consentimiento Informado se aplicó en el 34% (86/252) de los pacientes entrevistados. El servicio que más aplicó el Consentimiento Informado fue Ginecología, ya que lo aplicó en el 62% (39/63) de sus pacientes. Conclusión: La mayoría de los pacientes tienen un grado de conocimiento insuiciente sobre su enfermedad. El porcentaje de aplicación del Consentimiento Informado por el personal de salud es bajo...(AU)

Trastornos hipertensivos del embarazo en sala de labor y parto del Hospital Escuela / Hypertensive Disorders of Pregnancy in the Labor and Delivery Ward of the Hospital Escuela

Los Trastornos Hipertensivos del Embarazo (THE) se caracterizan por presión arterial sistólica mayor o iguala 140 mm Hg o diastólica mayor o igual a 90 mm Hg. Representan la segunda causa de mortalidad materna en Honduras y provocan elevada morbimortalidad perinatal. Objetivo: Describir los datos clínico-epidemiológicos, evaluación, manejo y complicaciones materno-fetales de los trastornos hipertensivos del embarazo en el Hospital Escuela. Métodos:Estudio transversal, descriptivo, realizado del 16 de marzo al 26 de julio de 2010, se revisaron los expedientes clínicos de mujeres con diagnóstico de trastorno hipertensivo del embarazo, excluyendo los casos de hipertensión gestacional. Resultados: La prevalencia de los trastornos hipertensivos del embarazo es 7.8%, de estos 47% presentaron preeclampsia leve y 38% preeclampsia severa; se les realizó inducción y cesárea al 40% respectivamente. Se practicó cardiotocografía en reposo al 10.4% y prueba de provocación con oxitocina al 9%; se presentó crisis hipertensiva en el 35% de los casos. La principal complicación materna fue el Síndrome de HELLP y la principal complicación neonatal el Síndrome de Distrés Respiratorio (SDR), aproximadamente el 50% de los recién nacidos fueron pequeños para la edad gestacional. Se presentaron 8 muertes fetales, 11 muertes neonatales y una muerte materna. Conclusión: las mujeres con THE tienen el doble de riesgo de terminar su embarazo en cesárea comparado con las mujeres sin este trastorno. La mortalidad materna se asocia con eclampsia y Síndrome deHELLP (por sus siglas en inglés: H de hemolysis, EL de elevated liver enzymes y LP de low platelet count); la mortalidad perinatal con preeclampsia severa, APGAR menor a 7 al primer minuto, prematurez y restricción del crecimiento intrauterino...

Cytotaxonomy of Simulium cauchense Floch & Abonnenc and Simulium quadrifidum Lutz (Diptera: Simuliidae) in Brazilian Amazonia.

Simulium cauchense Floch & Abonnenc and Simulium quadrifidum Lutz are widely distributed in the Amazon region and are morphologically similar at the larval and pupal stages. Chromosomally, these species are readily distinguished by the position of the nucleolar organizer, which is in the short arm of chromosome I in S. cauchense and in the long arm of chromosomes III in S. quadrifidum. They also differ by three fixed inversions. Sex chromosomes are undifferentiated in both species. Chromosomal resolution of the two species allowed us to evaluate four structural features previously used as diagnostic aids at the larval stage. Characters that distinguish larvae of the two species are the number of branches and branching patterns of the dorsal abdominal setae and the dark band on each primary fan. Branching patterns of the gill histoblasts were often diagnostic, with S. quadrifidum exhibiting more proximal branching and S. cauchense more distal branching. Sites where both species occurred sometimes had larvae with one petiole branching proximally and the other distally; in these cases examination of the chromosomes permitted assignment of the specimen to species. Pigmentation patterns of larvae, on the other hand, are highly variable. Color typically is sex linked in both species.

Larval biometry of Simulium rubrithorax (Diptera: Simuliidae) and size comparison between populations in the states of Minas Gerais and Roraima, Brazil.

The number of larval instars of Simulium (Hemicnetha) rubrithorax Lutz (Diptera: Nematocera) was determined using the lateral length of the head capsule. In this study 1,035 larvae, of different sizes, were measured (639 from the state of Roraima and 396 from the state of Minas Gerais). A frequency distribution analysis was carried out on the measurements of the lateral length of the head capsule to determine the number of larval instars. The limits of each instar were defined by the lower frequency of the measurements falling in a range of values, by the presence of the "egg burster" that characterizes the first larval instar, and by the developmental stage of the gill histoblast. The determination of the instar number was tested using a Student's t-test (p < 0.05), the Dyar rule and the Crosby growth rule. The results indicate the existence of 7 larval instars for this species, although this result was not in accordance to the Crosby rule. Last-instar larvae from two widely separated geographical populations (Roraima and Minas Gerais), collected in habitats with different water temperature were compared and no differences (p > 0.05) were observed between them.

Cytotaxonomy of Simulium cauchense Floch & Abonnenc and Simulium quadrifidum Lutz (Diptera: Simuliidae) in Brazilian Amazonia

Simulium cauchense Floch & Abonnenc and Simulium quadrifidum Lutz are widely distributed in the Amazon region and are morphologically similar at the larval and pupal stages. Chromosomally, these species are readily distinguished by the position of the nucleolar organizer, which is in the short arm of chromosome I in S. cauchense and in the long arm of chromosomes III in S. quadrifidum. They also differ by three fixed inversions. Sex chromosomes are undifferentiated in both species. Chromosomal resolution of the two species allowed us to evaluate four structural features previously used as diagnostic aids at the larval stage. Characters that distinguish larvae of the two species are the number of branches and branching patterns of the dorsal abdominal setae and the dark band on each primary fan. Branching patterns of the gill histoblasts were often diagnostic, with S. quadrifidum exhibiting more proximal branching and S. cauchense more distal branching. Sites where both species occurred sometimes had larvae with one petiole branching proximally and the other distally; in these cases examination of the chromosomes permitted assignment of the specimen to species. Pigmentation patterns of larvae, on the other hand, are highly variable. Color typically is sex linked in both species.