Key design elements of successful acute ischemic stroke treatment trials

PURPOSE

We review key design elements of positive randomized controlled trials (RCTs) in acute ischemic stroke (AIS) treatment and summarize their main characteristics.

METHOD

We searched Medline, Pubmed and Cochrane databases for positive RCTs in AIS treatment. Trials were included if (1) they had a randomized controlled design, with (at least partial) blinding for endpoints, (2) they tested against placebo (or on top of standard therapy in a superiority design) or against approved therapy; (3) the protocol was registered and/or published before trial termination and unblinding (if required at study commencement); (4) the primary endpoint was positive in the intention to treat analysis; and (5) the study findings led to approval of the investigational product and/or high ranked recommendations. A topical approach was used, therefore the findings were summarized as a narrative review.

FINDINGS

Seventeen positive RCTs met the inclusion criteria. The majority of trials included less than 1000 patients (n = 15), had highly selective inclusion criteria (n = 16), used the modified Rankin score as a primary endpoint (n = 15) and had a frequentist design (n = 16). Trials tended to be national (n = 12), investigator-initiated and performed with public funding (n = 11).

DISCUSSION

Smaller but selective trials are useful to identify efficacy in a particular subgroup of stroke patients. It may also be of advantage to limit the number of participating countries and centers to avoid heterogeneity in stroke management and bureaucratic burden.

CONCLUSION

The key characteristics of positive RCTs in AIS treatment described here may assist in the design of further trials investigating a single intervention with a potentially high effect size.

Age-specific information resources to address the needs of young people with stroke: a scoping review protocol

BACKGROUND AND AIMS

Young people with stroke (YPwS) persistently experience challenges with disability, social reintegration, employment, and financial stability to provide for themselves and their families. The aims of this scoping review are to (1) identify and collate information resources for YPwS and evidence-based self-managements programs and (2) identify gaps in age-specific resources available for YPwS after traditional rehabilitation services have ended and/or who are returning to live in the community.

METHODS

We will include both qualitative and quantitative studies, including all study designs. Participants will be community-dwelling adults aged between 18 and 65 years with a clinical diagnosis of stroke. We will include information resources and evidence-based self-managements programs for YPwS. Search terms will include stroke, young people, and community dwelling. We will search electronic databases such as MEDLINE. The reference lists of included studies, systematic reviews, and stroke guidelines and stroke-specific websites will also be searched. We will also contact Stroke Support Organizations and international/national allied health professional organisations to gather information resources about YPwS. We will also conduct a comprehensive environmental scan of additional resources using the search engine Google. The titles, abstracts, full-text articles, and contents of the resources identified by the search will be assessed against the inclusion and exclusion criteria to identify potentially relevant resources.

RESULTS AND CONCLUSIONS

Existing resources and self-management programs will be collated and categorized according to the type of needs addressed such as physical, emotions, activities of daily living, information, relationships, and social needs as well as the key gaps identified.

Mitigating effects of desert dust storms in asthmatic children: health visitors’ perceptions, Cyprus

Background

Countries of the Mediterranean basin such as Cyprus are experiencing frequent desert dust storm (DDS) events that adversely impact children with asthma. As school health visitors (SHVs) have important role in asthma management, we examined SHVs practices and perceptions on asthma management and their level of engagement in school-based interventions to mitigate DDS- health effects.

Methods

A descriptive cross-sectional survey was conducted among SHVs across state schools in Cyprus via an anonymous questionnaire, which rated the importance of asthma management measures (10-point scale), current implementation of these practices (1=never - 5=always), and regulatory authorities’ preparedness to respond to DDS events (1-5 Likert scale).

Results

Responses from 78 of the 93 SHVs (84%), with an average work experience of 13.5 years (SD 7.3), revealed discordance between high perception of the importance of asthma management measures and their actual implementation, with poor scoring especially in assessment of asthma control (M = 2.4, SD = 1.5), tracking school absenteeism (M = 2.1, SD = 1.0) and monitoring of asthma triggers (M = 1.9, SD = 1.4). Any DDS-related measures (e.g. air quality real-time monitoring, warnings, recommendations, awareness campaigns, etc) were implemented very infrequently. Ratings of authorities’ preparedness were moderate (<3.5), and only slightly higher in the health versus the educational or other government services. SHVs who recognized the severity of DDS and potential impact on asthmatic children were more likely to support school-based interventions for DDS events (OR = 7.3, 95% CI: 2.1-25.3).

Conclusions

Asthma management practices in school settings in Cyprus are suboptimal and responses during DDS are fragmented. While SHV’s awareness and support for interventions is high, this is not reflected in current practices. A concerted effort is needed for adoption of policies and implementation of action plans for DDS within school settings.

Key messages

• Suboptimal asthma management policies and practices were found to be implemented in schools in Cyprus, a country highly exposed to dust events.

• School health visitors recognize the health impact of desert dust on asthmatic children and support the plan for dust-mitigation programmes in schools, despite authorities’ low preparedness.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Human Trisomic iPSCs from Down Syndrome Fibroblasts Manifest Mitochondrial Alterations Early during Neuronal Differentiation

BACKGROUND

The presence of mitochondrial alterations in Down syndrome suggests that it might affect neuronal differentiation. We established a model of trisomic iPSCs, differentiating into neural precursor cells (NPCs) to monitor the occurrence of differentiation defects and mitochondrial dysfunction.

METHODS

Isogenic trisomic and euploid iPSCs were differentiated into NPCs in monolayer cultures using the dual-SMAD inhibition protocol. Expression of pluripotency and neural differentiation genes was assessed by qRT-PCR and immunofluorescence. Meta-analysis of expression data was performed on iPSCs. Mitochondrial Ca²⁺, reactive oxygen species (ROS) and ATP production were investigated using fluorescent probes. Oxygen consumption rate (OCR) was determined by Seahorse Analyzer.

RESULTS

NPCs at day 7 of induction uniformly expressed the differentiation markers PAX6, SOX2 and NESTIN but not the stemness marker OCT4. At day 21, trisomic NPCs expressed higher levels of typical glial differentiation genes. Expression profiles indicated that mitochondrial genes were dysregulated in trisomic iPSCs. Trisomic NPCs showed altered mitochondrial Ca²⁺, reduced OCR and ATP synthesis, and elevated ROS production.

CONCLUSIONS

Human trisomic iPSCs can be rapidly and efficiently differentiated into NPC monolayers. The trisomic NPCs obtained exhibit greater glial-like differentiation potential than their euploid counterparts and manifest mitochondrial dysfunction as early as day 7 of neuronal differentiation.

Targeting Mitochondrial Network Architecture in Down Syndrome and Aging

Mitochondria are organelles that mainly control energy conversion in the cell. In addition, they also participate in many relevant activities, such as the regulation of apoptosis and calcium levels, and other metabolic tasks, all closely linked to cell viability. Functionality of mitochondria appears to depend upon their network architecture that may dynamically pass from an interconnected structure with long tubular units, to a fragmented one with short separate fragments. A decline in mitochondrial quality, which presents itself as an altered structural organization and a function of mitochondria, has been observed in Down syndrome (DS), as well as in aging and in age-related pathologies. This review provides a basic overview of mitochondrial dynamics, from fission/fusion mechanisms to mitochondrial homeostasis. Molecular mechanisms determining the disruption of the mitochondrial phenotype in DS and aging are discussed. The impaired activity of the transcriptional co-activator PGC-1α/PPARGC1A and the hyperactivation of the mammalian target of rapamycin (mTOR) kinase are emerging as molecular underlying causes of these mitochondrial alterations. It is, therefore, likely that either stimulating the PGC-1α activity or inhibiting mTOR signaling could reverse mitochondrial dysfunction. Evidence is summarized suggesting that drugs targeting either these pathways or other factors affecting the mitochondrial network may represent therapeutic approaches to improve and/or prevent the effects of altered mitochondrial function. Overall, from all these studies it emerges that the implementation of such strategies may exert protective effects in DS and age-related diseases.

Giant Heterometallic [Mn36Ni4]0/2- and [Mn32Co8] "Loops-of-Loops-and-Supertetrahedra" Molecular Aggregates

We report the synthesis, crystal structures and magnetic properties of the giant heterometallic [Mn₃₆Ni₄]^2−/0 (compounds 1, 2)/[Mn₃₂Co₈] (compound 3) “loops-of-loops-and-supertetrahedra” molecular aggregates and of a [Mn₂Ni₆]²⁺ compound (cation of 4) that is structurally related with the cation co-crystallizing with the anion of 1. In particular, after the initial preparation and characterization of compound [Mn₂Ni₆(μ₄-O)₂(μ₃-OH)₃(μ₃-Cl)₃(O₂CCH₃)₆(py)₈]²⁺[Mn₃₆Ni₄(μ₄-O)₈(μ₃-O)₄(μ₃-Cl)₈Cl₄(O₂CCH₃)₂₆(pd)₂₄(py)₄]²⁻ (1) we targeted the isolation of (i) both the cationic and the anionic aggregates of 1 in a discrete form and (ii) the Mn/Co analog of [Mn₃₆Ni₄]²⁻ aggregate. Our synthetic efforts toward these directions afforded the discrete [Mn₃₆Ni₄] “loops-of-loops-and-supertetrahedra” aggregate [Mn₃₆Ni₄(μ₄-O)₈(μ₃-O)₄(μ₃-Cl)₈Cl₂(O₂CCH₃)₂₆(pd)₂₄(py)₄(H₂O)₂] (2), the heterometallic Mn/Co analog [Mn₃₂Co₈(μ₄-O)₈(μ₃-O)₄(μ₃-Cl)₈Cl₂(μ₂-OCH₂CH₃)₂(O₂CCH₃)₂₈(pd)₂₂(py)₆] (3) and the discrete [Mn₂Ni₆]²⁺ cation [Mn₂Ni₆(μ₄-O)₂(μ₃-OH)₄(μ₃-Cl)₂(O₂CCH₃)₆(py)₈](ClO₄)(OH) (4). The structure of 1 consists of a mixed valence [Mn28IIIMn8IINi4II]²⁻ molecular aggregate that contains two Mn8IIINi2II loops separated by two Mn6IIIMn4II supertetrahedral units and a [Mn2IIINi6II]²⁺ cation based on two [Mn^IIINi3II(μ₄-O)(μ₃-OH)_1.5(μ₃-Cl)_1.5]⁴⁺ cubane sub-units connected through both mono- and tri-atomic bridges provided by the μ₄-O²⁻ and carboxylate anions. The structures of 2–4 are related to those of the compounds co-crystallized in 1 exhibiting however some differences that shall be discussed in detail in the manuscript. Magnetism studies revealed the presence of dominant ferromagnetic interactions in 1–3 that lead to large ground state spin (S_T) values for the “loops-of-loops-and-supertetrahedra” aggregates and antiferromagnetic exchange interactions in 4 that lead to a low (and possibly zero) S_T value. In particular, dc and ac magnetic susceptibility studies revealed that the discrete [Mn₃₆Ni₄] aggregate exhibits a large S_T value ~ 26 but is not a new SMM. The ac magnetic susceptibility studies of the [Mn₃₂Co₈] analog revealed an extremely weak beginning of an out-of-phase tail indicating the presence of a very small relaxation barrier assignable to the anisotropic Co²⁺ions and a resulting out-of-phase ac signal whose peak is at very low T.

Intranasal Midazolam versus Rectal Diazepam for the Management of Canine Status Epilepticus: A Multicenter Randomized Parallel-Group Clinical Trial

Background

Intranasal administration of benzodiazepines has shown superiority over rectal administration for terminating emergency epileptic seizures in human trials. No such clinical trials have been performed in dogs.

Objective

To evaluate the clinical efficacy of intranasal midazolam (IN‐MDZ), via a mucosal atomization device, as a first‐line management option for canine status epilepticus and compare it to rectal administration of diazepam (R‐DZP) for controlling status epilepticus before intravenous access is available.

Animals

Client‐owned dogs with idiopathic or structural epilepsy manifesting status epilepticus within a hospital environment were used. Dogs were randomly allocated to treatment with IN‐MDZ (n = 20) or R‐DZP (n = 15).

Methods

Randomized parallel‐group clinical trial. Seizure cessation time and adverse effects were recorded. For each dog, treatment was considered successful if the seizure ceased within 5 minutes and did not recur within 10 minutes after administration. The 95% confidence interval was used to detect the true population of dogs that were successfully treated. The Fisher's 2‐tailed exact test was used to compare the 2 groups, and the results were considered statistically significant if P < .05.

Results

IN‐MDZ and R‐DZP terminated status epilepticus in 70% (14/20) and 20% (3/15) of cases, respectively (P = .0059). All dogs showed sedation and ataxia.

Conclusions and Clinical Importance

IN‐MDZ is a quick, safe and effective first‐line medication for controlling status epilepticus in dogs and appears superior to R‐DZP. IN‐MDZ might be a valuable treatment option when intravenous access is not available and for treatment of status epilepticus in dogs at home.

Discrete and encapsulated molecular grids: homometallic Mn15 and heterometallic Mn24Ni2 aggregates

Two molecular grid-like clusters are reported, one is a discrete [3 × 5] grid and the other a [3 × 4] grid within a Mn12Ni2 loop. Both Mn24Ni2 and Mn15 aggregates display novel and aesthetically pleasing structures with the former one being among the highest nuclearity heterometallic MnxMy clusters (M = any transition metal ion).

Perturbations to the IGF1 growth pathway and adult energy homeostasis following disruption of mouse chromosome 12 imprinting

Aim

Disruption to insulin-like growth factor (IGF) signalling pathways during early life causes growth retardation and defects of developing metabolic organs that can alter set points of energy homeostasis for a lifetime. Inheritance of two maternal copies of human chromosome 14q32.2 (Temple syndrome) causes severe foetal growth retardation and post-natal failure to thrive. Disruption of imprinted gene dosage in the orthologous region on mouse chromosome 12 also affects growth. Here, we investigated whether altering chromosome 12-imprinted gene dosage can affect IGF signalling.

Methods

We investigated mice with a transgene insertion at the imprinted domain of chromosome 12. This lesion causes misexpression of neighbouring genes such that the expression of non-coding RNAs is elevated, and levels of delta-like homologue 1 (Dlk1), retrotransposon-like 1 (Rtl1) and deiodinase 3 (Dio3) transcripts are reduced.

Results

We observed three key phenotypes in these mice: (i) embryonic growth retardation associated with altered expression of IGF1 binding proteins, (ii) peri-natal failure to thrive accompanied by hypothyroidism and low serum IGF1. Unexpectedly this phenotype was growth hormone independent. (iii) Adult animals had reduced glucose tolerance as a result of endocrine pancreatic insufficiency.

Conclusions

We propose that all of these phenotypes are attributable to impaired IGF action and show for the first time that the chromosome 12 cluster in the mouse is an imprinted locus that modulates the IGF signalling pathway. We propose that growth retardation observed in human Temple syndrome might have a similar cause.

Fitness trade-offs and the maintenance of alternative male morphs in the bulb mite (Rhizoglyphus robini)

Alternative reproductive phenotypes (ARPs) occur across a wide range of taxa. Most ARPs are conditionally expressed in response to a cue, for example body size, that reliably correlates with the status of the environment: individuals below the (body size) threshold then develop into one morph, and individuals above the threshold develop into the alternative morph. The environmental threshold model provides a theoretical framework to understand the evolution and maintenance of such ARPs, yet no study has examined the underlying fitness functions that are necessary to realize this. Here, we empirically examined fitness functions for the two male morphs of the bulb mite (Rhizoglyphus robini). Fitness functions were derived in relation to male size for solitary males and in relation to female size under competition. In both cases, the fitness functions of the two morphs intersected, and the resulting fitness trade-offs may play a role in the maintenance of this male dimorphism. We furthermore found that competition was strongest between males of the same morph, suggesting that fitness trade-off in relation to male size may persist under competition. Our results are a first step towards unravelling fitness functions of ARPs that are environmentally cued threshold traits, which is essential for understanding their maintenance and in explaining the response to selection against alternative morphs.

In vitro methylation of specific regions in recombinant DNA constructs by excision and religation

The first imprinted genes were identified in the early 1990s (e.g., refs. 1,2) and there are now over 40 mammalian genes known to be regulated by genomic imprinting (for an up-to-date list, see ref. 3). The details of the mechanism that discriminates between the active and silent alleles of these genes, based on their parent of origin, may differ from one imprinted gene to the next, but must include some form of epigenetic mark that distinguishes alleles that have passed through the male or female germline (4-7). The addition of methyl groups to cytosine residues of CpG dinucleotides might provide such a mark, since regions of differential methylation have been identified in the vicinity of many of the known imprinted genes (8,9). Moreover, analysis of imprinted gene expression in a methyltransferase knockout (Dnmt1(-/-)) mouse has shown that the imprint is lost in a number of cases, resulting in either two silent alleles (Igf2, Igf2r and Kvlqt) or two expressed alleles (H19, p57(kip2), Snrpn, and Xist) (4,10-12). Although there may be exceptions (for instance, imprinted expression of Mash2 is maintained in Dmnt1(-/-) embryos; ref. 13), differential methylation is likely to be an important aspect of the imprinting mechanism that is relevant to most of the imprinted genes in mammals. There is accumulating evidence that methylation is also important for the imprinting of plant genes (reviewed in ref. 14).

A study of the flood events in Cyprus

Abstract. Almost every year, localised and in some cases more widespread floodings affect parts of Cyprus, causing damages to properties destruction to infrastructure and housing and sometimes the loss of human life. Various factors such as the meteorological situation and type and intensity of precipitation, the geomorphology, the geology and the human intervention to geomorphology are responsible for flood events. In the present study, only the meteorological situation and the associated mechanisms are examined in an attempt to gain the essential knowledge for improvement of local weather forecasts. The study period covers a thirteen-year period, from 1994 to 2006, in which 43 cases of flooding were reported, mainly over urbanized areas. The dominant favorable weather conditions for flood events are either the existence of a depression or weather conditions of convectional type. According to these two factors, the flood events were classified into two categories; the "instability'' category which includes isolated flood events of short duration, and the "depression'' category which includes widespread flood events of long duration.

Vertigo and imbalance caused by a small lesion in the anterior insula

The exact location of the vestibular cortex in humans has not yet been established. Isolated lesions in the insula are exceptional. We describe a patient with recurrent episodes of vertigo and imbalance following a small lesion in the anterior insula. Myogenic and neurogenic vestibular evoked potentials were both performed using auditory stimuli. The former was recorded from the sternocleidomastoid muscle and the latter from the parietal areas on the scalp. Brainstem auditory evoked potentials, threshold latency series, pure tone audiometry and video nystagmography were also performed, as was brain MRI. All evoked potential studies and pure tone audiometry were within normal limits, ruling out peripheral and brainstem causes for the patient's symptoms. Video nystagmography revealed high slow phase velocities bilaterally with caloric stimulation, and saccadic tracking on the smooth pursuit examination. The MRI revealed a small lesion in the right anterior insula. To our knowledge this is the first reported case of vestibular symptoms and signs from a lesion in the anterior insula on MRI. In addition, its effects on the nystagmogram suggest that this area may be part of the pathway that controls smooth pursuit.

Liver-specific deletion of insulin receptor substrate 2 does not impair hepatic glucose and lipid metabolism in mice

AIMS/HYPOTHESIS

Hepatic insulin resistance is thought to be a critical component in the pathogenesis of type 2 diabetes but the role of intrinsic insulin signalling pathways in the regulation of hepatic metabolism remains controversial. Global gene targeting in mice and in vitro studies have suggested that IRS2 mediates the physiological effects of insulin in the liver. Reduced hepatic production of IRS2 is found in many cases of insulin resistance. To investigate the role of IRS2 in regulating liver function in vivo, we generated mice that specifically lack Irs2 in the liver (LivIrs2KO).

MATERIALS AND METHODS

Hepatic insulin signalling events were examined in LivIrs2KO mice by western blotting. Glucose homeostasis and insulin sensitivity were assessed by glucose tolerance tests and hyperinsulinaemic-euglycaemic clamp studies. The effects of high-fat feeding upon glucose homeostasis were also determined. Liver function tests were performed and expression of key metabolic genes in the liver was determined by RT-PCR.

RESULTS

Proximal insulin signalling events and forkhead box O1 and A2 function were normal in the liver of LivIrs2KO mice, which displayed minimal abnormalities in glucose and lipid homeostasis, hepatic gene expression and liver function. In addition, hepatic lipid homeostasis and the metabolic response to a high-fat diet did not differ between LivIrs2KO and control mice.

CONCLUSIONS/INTERPRETATION

Our findings suggest that liver IRS2 signalling, surprisingly, is not required for the long-term maintenance of glucose and lipid homeostasis, and that extra-hepatic IRS2-dependent mechanisms are involved in the regulation of these processes.

Isolation by distance and a chromosomal cline in the Cayapa cytospecies of Simulium exiguum, the vector of human onchocerciasis in Ecuador

The population genetic structure of the Cayapa cytospecies of Simulium exiguum, the vector of onchocerciasis, was analysed using allozyme frequency and chromosomal inversion polymorphism data from 6 and 15 populations respectively, collected in Ecuador. Eight allozyme loci were scored. No unique allozyme markers were found enabling us to identify biting adults of the vector from the non-vector Bucay cytotype. Mannose-phosphate isomerase (Mpi) contributed largely to the significant heterogeneity in gene frequency among populations of the Cayapa cytospecies and also to the overall population structuring (F(ST) = 0.015 +/- 0.014) which fitted the isolation by distance model. However, heterozygote deficits were recorded for Mpi in four of the six populations, which could indicate that selection is acting at this locus but this hypothesis will require further convincing evidence. Furthermore the significant population structuring of allozymes was not evident when Mpi was omitted from the analysis. All inversion polymorphisms (IIS-B, IIS-F, IIL-A and IIL-B) were in Hardy-Weinberg equilibrium, showed significant heterogeneity between populations and revealed the occurrence of an altitudinal cline in inversion IIS-B frequency. The inversion polymorphisms revealed a significant degree of population structuring (F(ST) = 0.083 +/- 0.027), which can be explained by the isolation by distance model. A UPGMA cluster analysis revealed the relatively remote, high altitude Rio Mira populations to be the most genetically distinct.

A conserved structural element in horse and mouse IGF2 genes binds a methylation sensitive factor

The equine IGF2 gene has been cloned and characterised. It spans a 9 kb region, which is substantially less than the corresponding human gene. Three coding exons and three untranslated leader exons, all highly homologous to those in other species, were identified. Downstream of the polyadenylation site in exon 6, a dinucleotide repeat sequence was identified. Three putative promoters (P1-P3) were localised in the 5' region of the gene. RNase protection analysis revealed two active promoters in fetal tissues, P2 and P3, whereas P3 was the only promoter active in adult tissues. This represents a transcriptional pattern different from that in humans or rodents. A novel structural element, an inverted repeat, is predicted in the 3' region of the IGF2 gene. This repeat is conserved between species and located in a region which is differentially methylated in the human and mouse genes and might therefore be involved in the imprinting mechanism. The inverted repeat acquires a stem-loop structure in vitro with a hybrid A/B-DNA conformation in the stem area. Both in horse and mouse, a methylation-sensitive protein binds this structure with a strong requirement for the loop area. Furthermore, the protein might be developmentally regulated.

The potential for dispersal of onchocerciasis in Ecuador in relation to the distribution of the vector Simulium exiguum (Diptera:Simuliidae)

The future dispersal of onchocerciasis in Ecuador is dependent on the distribution of cytotypes of the vector species complex Simulium exiguum. Over the last 14 years, collections of larvae have been made from over 25 rivers, between 80-1600 m altitude, from various sites on both sides of the Andes. Analysis of larval polytene chromosomes was used to determine the distributions of each cytotype. On the western side of the Andes, the Cayapa cytotype (the only cytotype directly incriminated as a vector) has a distribution from Santo Domingo de los Colorados northwards. The Quevedo and Bucay cytotypes occur from Santo Domingo de los Colorados southwards. On the eastern side of the Andes, the Aguarico cytotype occurs in the Rio Aguarico and a new cytotype is present in the tributaries of the Rio Napo. Whether the disease will spread south of Santo Domingo and on the eastern side of the Andes depends on vector capacity of the cytotypes and the dispersal patterns of individuals infected with onchocerciasis. At present the Aguarico, Bucay and Quevedo cytotypes are known to be efficient hosts, but their biting preferences and biting densities have not yet been evaluated.

Four new cytotypes of the onchocerciasis vector blackfly Simulium guianense in Brazil

Simulium (Trichodagmia) guianense is an important Amazonian vector of onchocerciasis. Examination of the polytene chromosome banding patterns of larvae from five sites in Brazil revealed the occurrence of four cytotypes, designated A, B, C and D. The chromosomal standard, Simulium guianense A, occurred at two localities in Goias State (on the Rio Tocantins and Rio Mucambão) where it was the only cytotype. The other three sites examined yielded one different cytotype from each: B from Rio Oyapoque in Amapa State, C from Rio Tocantins in Maranhão State, and D from Rio Xingu in Para State. All cytotypes differed by at least two fixed inversions, but a sex determining system was not evident in any cytotype. As the cytotypes have been found allopatrically it is not certain that they represent sibling species; sampling of sympatric populations would resolve this. During certain times of the year, voracious anthropophagy by S.guianense sensu lato occurs at the localities sampled for cytotypes A, C and D (biting data are not available for the cytotype B locality). In some other areas, however, S.guianense s.l. is entirely zoophilic. Further studies are needed, therefore, to elucidate the biting habits, vectorial capacity, geographic distribution and taxonomic status of these four, and perhaps additional, cytotypes comprising the S.guianense complex.

Cytogenetical analysis of the Simulium damnosum complex (Diptera: Simuliidae) in Guinea Bissau

In a 3-year study during 1990-92, larval collections of the Simulium damnosum complex from the River Corubal system in Guinea Bissau revealed that the only sibling species present were S. sirbanum and the Konkouré form of S.konkourense, but not S.damnosum s.s. which had been found at some of the localities (Saltinho and Cusselinta) in a previous survey by Quillévéré et al. (1981). Their differential distributions were seasonally consistent between years. S. sirbanum was concentrated in the upper reaches of the Corubal, moving downstream at the end of the dry season to exploit new breeding grounds, whereas S. konkourense seemed to be concentrated in the lower reaches and moved upstream in the middle of the dry season. Since the previous survey, it appears that S. konkourense has largely replaced S. sirbanum and S. damnosum s.s. in the lower reaches of the Corubal. S. sirbanum was consistently associated with man-biting behaviour and, although infection studies were not performed, it is likely that S. sirbanum is the main vector of onchocerciasis in Guinea Bissau as S. konkourense does not seem to be anthropophilic. Among five polymorphic inversions in S. sirbanum, the frequency of inversion IL-B increased during the dry season; IL-2 and IIL-7 showed homozygous disadvantage whereas IIL-3 and IIIL-6 did not; IS-2 tended to be fixed in all populations. Simulium konkourense populations in the River Corubal differ from those found upstream in its tributary the River Koumba, in the Fouta Djallon of Guinea, by their sex chromosomes (having no sex-linked inversions) and biting preferences, indicating that the populations are not freely interbreeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytological and isoenzyme analysis of the Bucay and Quevedo cytotypes of the Onchocerciasis vector Simulium exiguum (Diptera: Simuliidae) in Ecuador

Four cytotypes of Simulium exiguum occur in Ecuador, where this morphospecies is the primary vector of onchocerciasis. In this paper, we give the first full description of the banding pattern of the larval polytene chromosomes of the Quevedo cytotype and assess its degree of genetic separation from the Bucay cytotype. Both cytotypes differ from the chromosomal standard sequence (of the Cayapa cytotype) by the fixed inversions IIL-5 and IIL-6. The Quevedo cytotype additionally differs from the standard and Bucay cytotypes by possessing a differentiated X chromosome, which is indicated by the inversion IIS-A. As the degree of reproductive isolation between the Bucay and Quevedo cytotypes has not yet been established, they must be regarded as intraspecific variants of the same species. In fact, isoenzyme characterizations showed that the Bucay and Quevedo cytotypes are differentiated only to the extent expected of incipient species or geographical populations. Moreover, the sibling species status previously given to the Bucay cytotype needs be reassessed, there being inadequate analysis from areas in Ecuador where Bucay occurs in sympatry with the standard Cayapa cytotype. No isoenzyme electromorphs were discovered that identified all or most adult females of any one (cytotypepure) collection.