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.

Incidence of chronic groin pain following open mesh inguinal hernia repair, and effect of elective division of the ilioinguinal nerve: meta-analysis of randomized controlled trials.

PURPOSE: Chronic post-operative groin pain is a substantial complication following open mesh inguinal hernia repair. The exact cause of this pain is still unclear, but entrapment or trauma of the ilioinguinal nerve may have a role to play. Elective division of this nerve during hernia repair has been proposed in an attempt to reduce the incidence of chronic groin pain. METHODS: We performed a meta-analysis of nine randomized controlled trials comparing preservation versus elective division of the ilioinguinal nerve during this operation. RESULTS: A substantial proportion of patients having open mesh inguinal hernia repair experience chronic groin pain when the ilioinguinal nerve is preserved (estimated rate of 9.4% at 6 months and 4.8% at 1 year). Elective division of the nerve resulted in a significant reduction of groin pain at 6-months post-surgery (RR 0.47, p = 0.02), including moderate/severe pain (RR 0.57, p = 0.01). However, division of the nerve also resulted in an increase of subjective groin numbness at this time point (RR 1.55, p = 0.06). At 12-month post-surgery, the beneficial effect of nerve division on chronic pain was reduced, with no significant difference in the rates of overall groin pain (RR 0.69, p = 0.38), or of moderate-to-severe groin pain (RR 0.99, p = 0.98) between the two groups. The prevalence of groin numbness was also similar between the two groups at 12-month post-surgery (RR 0.79, p = 0.48). CONCLUSIONS: Routine elective division of the ilioinguinal nerve during open mesh inguinal hernia repair does not significantly reduce chronic groin pain beyond 6 months, and may result in increased rates of groin numbness, especially in the first 6-months post-surgery.

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.

Interleukin-6 mediated upregulation of CYP1B1 and CYP2E1 in colorectal cancer involves DNA methylation, miR27b and STAT3.

BACKGROUND: The pro-inflammatory cytokine interleukin-6 (IL6) promotes colorectal cancer (CRC) development. It is also known to regulate cytochrome P450 (CYP450) enzymes, which are involved in CRC tumour initiation and promotion via activation of chemical carcinogens. Here, IL6 regulation of CYP450 expression was investigated in CRC. METHODS: The effect of IL6 on CYP 1A1, 1B1 and 2E1 expression was determined in vitro using CRC cell lines HCT116 and SW480, and CYP450 expression was determined by immunohistochemistry in CRC tissues previously shown to have increased levels of IL6. RESULTS: In mechanistic studies, IL6 treatment significantly induced CYP1B1 and CYP2E1, but not CYP1A1, gene expression in HCT116 and SW480 cells. CYP2E1 expression regulation occurred via a transcriptional mechanism involving STAT3. For CYP1B1 regulation, IL6 downregulated the CYP1B1-targeting microRNA miR27b through a mechanism involving DNA methylation. In clinical samples, the expression of CYP1B1 and CYP2E1, but not CYP1A1, was significantly increased in malignant tissue overexpressing IL6 compared with matched adjacent normal tissue. CONCLUSIONS: Colonic inflammation with the presence of IL6 associated with neoplastic tissue can alter metabolic competency of epithelial cells by manipulating CYP2E1 and CYP1B1 expression through transcriptional and epigenetic mechanisms. This can lead to increased activation of dietary carcinogens and DNA damage, thus promoting colorectal carcinogenesis.

Surgical treatment of dorsal hemivertebrae associated with kyphosis by spinal segmental stabilisation, with or without decompression.

This retrospective case series examined the effectiveness of spinal segmental stabilisation, with or without decompression, in nine dogs with neurological deficits associated with dorsal hemivertebrae. Data on signalment, preoperative neurological status, imaging findings, surgical techniques and outcome were evaluated. All cases occurred in young or adult, small-breed dogs with neurological signs ranging from progressive moderate pelvic limb ataxia to non-ambulatory paraparesis. Six dogs also showed urinary and faecal incontinence. In each dog, one or more dorsal thoracic hemivertebra(e) were detected by radiography and MRI. In all dogs, hemivertebra(e) were associated with kyphosis and reduced vertebral canal diameter. All dogs were surgically managed with spinal segmental stabilisation, using Steinmann pins and orthopaedic wires and/or sutures attached to the spinous processes. Three dogs also underwent additional decompressive surgery. Post-operative follow-up ranged from 1.5 to 5.5 years. Immediate or delayed post-operative complications occurred in three dogs, including implant migration or loosening. Eight dogs showed long-term gait improvement, with resolution of incontinence if previously present. At 2-6 years post-surgery, four dogs were neurologically normal, three had mild residual ataxia, one had moderate ambulatory paraparesis, and one dog relapsed 3.5 years after surgery, resulting in severe paraparesis. Spinal segmental stabilisation techniques, with or without decompression, can result in satisfactory outcomes in small dogs with hemivertebrae and mild to moderate neurological signs. Further adaptations might be required to avoid implant loosening and allow continued growth in immature dogs.

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.

Expression of COX-2, NF-kappaB-p65, NF-kappaB-p50 and IKKalpha in malignant and adjacent normal human colorectal tissue.

BACKGROUND: Cyclooxygenase-2 (COX-2) is selectively over-expressed in colorectal tumours. The mechanism of COX-2 induction in these tumours is not fully understood, although evidence suggests a possible link between nuclear factor (NF)-kappaB and COX-2. We hypothesised an association between COX-2 expression and NF-kappaB-p65, NF-kappaB-p50 and IkappaB-kinase-alpha (IKKalpha) in both epithelial and stromal cells in human colorectal cancer. METHODS: Using immunohistochemistry, we measured COX-2, NF-kappaB-p65, NF-kappaB-p65 nuclear localisation sequence (NLS), NF-kappaB-p50, NF-kappaB-p50 NLS and IKKalpha protein expression in matched colorectal biopsy samples comprising both non-tumour and adjacent tumour tissue from 32 patients with colorectal cancer. RESULTS: We have shown that stromal cells of malignant and surrounding normal colorectal tissue express COX-2. In all cell types of malignant tissue, and in vascular endothelial cells (VECs) of neighbouring normal tissue, COX-2 expression was strongly associated with NF-kappaB-p65 expression (Pearson's correlation, P=0.019 for macrophages, P=0.001 for VECs, P=0.002 for fibroblasts (malignant tissue), and P=0.011 for VECs (non-malignant tissue)) but not NF-kappaB-p50 or IKKalpha. CONCLUSIONS: These data suggest that in these cells COX-2 induction may be mediated through activation of the canonical NF-kappaB pathway. Finally, the lack of association between COX-2, NF-kappaB-p65 or IKKalpha in stromal cells with the clinical severity of colorectal cancer as determined by Duke's stage, suggests that COX-2, NF-kappaB-p65 and IKKalpha expression are possibly early post-initiation events, which could be involved in tumour progression.

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.

Upregulation of cyclooxygenase-2 is accompanied by increased expression of nuclear factor-kappa B and I kappa B kinase-alpha in human colorectal cancer epithelial cells.

Cyclooxygenase-2 (COX-2) is selectively overexpressed in colorectal tumours. The mechanism of COX-2 induction is not fully understood, but requires de novo messenger RNA and protein synthesis, indicating regulation at the transcriptional level. Sequence analysis of the 5'-flanking region of the COX-2 gene shows two nuclear factor-kappa B (NF-kappa B) sites. Inhibition of this protein in model cell culture systems attenuates COX-2 expression and implies that NF-kappa B plays an important role in COX-2 induction. We measured COX-2, NF-kappa B and I kappa B kinase alpha (IKK alpha) protein expression in matched colonic biopsy samples comprising both nontumour and adjacent tumour tissue from 32 colorectal cancer patients using immunohistochemistry. There was none or very little expression of COX-2, NF-kappa B and IKK alpha in non-neoplastic colon epithelial cells, while the expression of all three of these proteins was significantly increased (P<0.05, Wilcoxon's signed rank test) in adjacent cancerous cells. Moreover, all three proteins were found to be coexpressed in the neoplastic epithelium, with the expression of COX-2 and NF-kappa B highly correlated (Pearson's correlation, P<0.005). There was no apparent correlation between enhanced COX-2, NF-kappa B or IKK alpha expression and tumour Dukes' stages. Our results are compatible with the hypothesis that IKK alpha and NF-kappa B are involved in COX-2 induction in these tumours and the lack of association between COX-2 expression and severity of disease as measured by Dukes' stage is consistent with the proposal that COX-2 expression is an early postinitiation event.

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 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 occurs 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 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.

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)