Genetic polymorphism of the beta-tubulin gene of Onchocerca volvulus in ivermectin naïve patients from Cameroon, and its relationship with fertility of the worms.

Observations of low response of patients infected with Onchocerca volvulus to ivermectin suggest that the parasite may be under a selection process toward potential resistance. To limit the extension of this phenomenon, it is crucial to characterize the genes of O. volvulus that are involved. For this, O. volvulus adult worms collected before the introduction of ivermectin in an onchocerciasis endemic area of central Cameroon were genotyped for beta-tubulin. To derive a baseline to investigate the selective pressure of ivermectin, we analysed (1) the frequency distribution of the beta-tubulin alleles, and (2) the relationship between the different beta-tubulin related genotypes and the fertility status of the female worms. The frequency of allele b of the beta-tubulin gene was very low, as it was observed in West Africa. We observed a deficit of heterozygous female worms leading to Hardy Weinberg disequilibrium, which might be explained by a shorter life-span of these worms compared to the homozygous worms. Unexpectedly, our results also show that the heterozygous female worms were much less fertile than the homozygotes: more than two thirds of the homozygotes were fertile, whereas only 37% of the heterozygotes were fertile. These results will be further considered when analysing post-treatment data.

Evidence for macrofilaricidal activity of ivermectin against female Onchocerca volvulus: further analysis of a clinical trial in the Republic of Cameroon indicating two distinct killing mechanisms.

During a 3-year trial of the effects of ivermectin (Mectizan) on adult worms and microfilariae of Onchocerca volvulus in the Republic of Cameroon, comparison was made between the percentages of calcified and uncalcified moribund (M) and dead (D) adult female worms dying following (a) the standard dose (150 microg/kg) given annually; (b) high doses (400, then 800 microg/kg) given annually; and (c and d) these same doses given at 3-monthly intervals. In the killing of adult female O. volvulus worms, the relative rôles of (a) natural causes; (b) a presumed, direct, anthelminthic, macrofilaricidal action of ivermectin; and (c) a potentially fatal pleomorphic ovarian neoplasm (PN), of which the incidence is increased by ivermectin treatment, are herein further investigated and discussed. It is concluded that ivermectin per se has a considerable direct macrofilaricidal action against female worms and that this lethal effect is supplemented by the drug's ability in some worms to increase the incidence, and the spread throughout the body of the worm, of the potentially fatal PN ovarian tumour. In moribund and dead ivermectin-treated female worms that were heavily invaded by PN, it is probable that the neoplasm was chiefly responsible for their death, but the additional direct anthelminthic action of the drug, which by itself has been responsible for the death of many other female worms, cannot be excluded as having played a supplementary lethal rôle. Similar problems as to the exact means by which adult female worms are killed may arise now that ivermectin is used in Africa for the mass treatment of lymphatic filariasis; or if and when the macrofilaricidal actions on O. volvulus of other drugs, which are closely related to ivermectin, come to be investigated.

The co-administration of ivermectin and albendazole--safety, pharmacokinetics and efficacy against Onchocerca volvulus.

A randomized, double-blind, placebo-controlled trial was conducted, to determine whether the co-administration of ivermectin with albendazole is safe and more effective against Onchocerca volvulus than ivermectin alone, and whether a significant pharmacokinetic interaction occurs. Forty-two male onchocerciasis patients received ivermectin (200 mug/kg) alone, albendazole (400 mg) alone or the combination. Safety was determined from the results of detailed clinical and laboratory examinations before treatment, during hospitalization and on day 30. Microfilaricidal efficacy was estimated from the reductions in skin counts between day 0 (pretreatment) and day 30. To determine efficacy against the adult worms, two independent observers examined histology slides prepared from nodules excised on day 180; changes in the skin counts of skin microfilariae between days 30 and 365 provided additional indicators of the level of adulticidal activity. Pharmacokinetic parameters for ivermectin and albendazole sulphoxide were defined over 72 h post-treatment. The co-administration of ivermectin with albendazole did not produce more severe adverse effects than ivermectin alone. Both nodule examiners found that the combination was not macrofilaricidal and that it was not clearly superior to ivermectin alone in the effects on reproductive activity; this was supported by the similar efficacy of the two regimens in the suppression of skin microfilariae. There was no significant pharmacokinetic interaction. Although the co-administration of ivermectin with albendazole appears safe, it offers no advantage over ivermectin alone in the control of onchocerciasis. The combination does not require an alteration in the dosage of either component.

Neoplastic change in Onchocerca volvulus and its relation to ivermectin treatment.

A pleomorphic neoplasm (PN) is described from sections of Onchocerca volvulus worms in nodules excised from Cameroonian patients. PN is confined to older, non-fecund, female worms, and those classed as moribund/dead. It is mainly composed of small, roundish, basophilic cells of diverse sizes, often forming a 'rosette' pattern around amorphous eosinophilic centres. The cells have a high nuclear/cytoplasmic ratio and up to 2-3 mitoses/high-power field; some become grossly enlarged, highly polymorphic and contain large, irregular blocks of chromatin. The eukaryotic PN cells first appear posteriorly in the pseudocoelom, probably from ovarian cells; they spread anteriorly, invading or compressing the uteri. Ivermectin treatment increased the prevalence PN from 3.7% of 1422 female worms in 637 patients before treatment to 17.5% of 1134 worms in 511 patients after 3 years treatment. Ivermectin at 400-800 microg/kg annually, or at 150 microg/kg or 400-800 microg/kg 3-monthly, over 3 years, did not increase the PN prevalence significantly, as compared with standard doses of 150 microg/kg annually. In other small series of African patients, PN prevalence increased in worms 2, 4, 6 and 10 months after ivermectin treatment; but there was no increase after treatment with amocarzine, albendazole or diethylcarbamazine and suramin. PN may partly account for the increased macrofilaricidal action of ivermectin on female O. volvulus in patients treated for 3 years at 3-monthly intervals.

Efficacy of repeated doses of ivermectin against Mansonella perstans.

Treatment of Mansonella perstans infection, although seldom necessary, is difficult. In a 3 year's trial of normal and high-dose annual and 3-monthly ivermectin treatment against Onchocerca volvulus, the effects on M. perstans were recorded and related to the cumulative dose received. The World Health Organization's African Programme for Onchocerciasis Control may thus reduce the endemicity of M. perstans.

Toxicity of the explosives 2,4,6-trinitrotoluene, hexahydro-1,3,5-trinitro-1,3,5-triazine, and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine in sediments to Chironomus tentans and Hyalella azteca: low-dose hormesis and high-dose mortality.

The toxicity of the explosives 2,4,6-trinitrotoluene (TNT); hexahydro-1,3,5-trinitro-1,3,5-triazine (royal demolition explosive [RDX]); and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (high-melting explosive [HMX]), was evaluated in spiked sediment with two freshwater invertebrates. The midge Chironomus tentans and the amphipod Hyalella azteca demonstrated significant toxic effects after exposure to TNT and its degradation products, 1,3,5-trinitrobenzene (TNB) and 2,4-diamino-6-nitrotoluene (2,4-DANT). Significant reductions in survival of C. tentans exposed to TNT, TNB, and 2,4-DANT were observed at nominal sediment concentrations as low as 200 mg/kg. Hyalella azteca was more sensitive to TNT, TNB, and 2,4-DANT than the midge, where significant reductions in survival were observed at nominal concentrations of 50, 100, and 200 mg/kg, respectively. Survival of the midge and the amphipod was unaffected after exposure to RDX or HMX at the highest concentrations of 1,000 and 400 mg/kg, respectively. Growth of the midge, measured as total weight, was significantly reduced by 2,4-DANT. However, significantly increased growth was observed after exposure to sublethal concentrations of RDX and HMX. Although significant reductions in amphipod survival were observed at high concentrations of TNB, growth was significantly increased at sublethal concentrations. The results of the current investigation suggest that organisms exposed to explosives at contaminated sites may be affected at concentrations less than 25 mg/kg through hormetic growth enhancement and at higher concentrations through increased mortality.

DDT toxicity and critical body residue in the amphipod Leptocheirus plumulosus in exposures to spiked sediment.

The lethal and sublethal toxicity of dichlorodiphenyltrichloroethane (DDT) to the estuarine amphipod Leptocheirus plumulosus was determined using sediment spiked with (14)C-labeled compound. Juvenile amphipods were exposed to concentrations up to 9.9 nmol/g dry weight (3.5 microg/g). Acute effects on survival were determined in a 10-day experiment. Chronic effects on survival, growth, and reproduction were assessed in a 28-day experiment. The DDT in the sediments transformed to dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethylene (DDE), and polar metabolites during the 14-day sediment storage prior to exposing the amphipods. The mixture of DDT and its breakdown products (tDDT) was comprised mostly of DDT at the beginning of the exposures. DDD was the prevalent compound at termination of the 28-day exposure. Complete mortality occurred at sediment concentrations of tDDT as low as 7 nmol/g (2.3 microg/g) in both acute and chronic experiments. Most of the mortality appeared to have occurred within the first 4 days of exposure. No sublethal reductions in growth or reproduction were observed in the 28-day experiment. In the 10-day experiment, where amphipods did not receive supplemental food, growth was significantly increased in DDT treatments where survival was not affected. The concentration of tDDT in amphipod tissues was determined at exposure termination. In the 10-day experiment, a mean body residue of 14 nmol/g wet weight was associated with significant mortality (30%). Lower critical body residues were observed in the 28-day experiment, where the median lethal tissue residue (LR(50)) was 7.6 (6.8--8.4, 95% confidence interval) nmol/g wet weight. Based on previous studies, the lethal critical body residue for L. plumulosus is similar to those determined for freshwater amphipods and substantially lower than those determined for cladocerans and polychaetes.

Studies on the macrofilarial population of Onchocerca volvulus in hyper-endemic villages of the Central province of Cameroon.

The population structure of Onchocerca volvulus macrofilariae was studied in villages of central Cameroon where onchocerciasis is hyper-endemic. One nodule selected at random was removed from each of 576 adult males, and examined by histology. The numbers of male and female worms/nodule, and the status of the female worms (fecund, non-fecund, or dead) were recorded. The observations were analysed to evaluate whether the mean numbers of worms of each category varied in relation to the patient's age, the level of endemicity in his village, the anatomical localization of the nodule, the weight of the nodule, and the total number of palpable nodules harboured by the patient. The results obtained were very similar to those reported from West Africa. The mean numbers of dead female worms/nodule were relatively high in the villages with the lowest levels of endemicity. The mean numbers of fecund females and of live males were significantly higher in the nodules located around the knees. These results provide information which might be useful in modelling the population dynamics of O. volvulus, and also in the context of trials of any potentially macrofilaricidal drugs.

Cloning of the proto-oncogene c-src from rat testis.

The cellular homolog of the oncogene v-src, the proto-oncogene c-src, was cloned from rat testis using a high stringency polymerase chain reaction. Rat c-src cDNA shared identity with chicken and mouse, and Rous sarcoma virus c-src and v-src, respectively. Rat c-Src protein was 98% homologous to both human and mouse c-Src. Interestingly, rat Src contained one extra amino acid compared to the mouse protein. As expected, the rat testis Src lacked the six extra residues common to the neuronal Src identified in human and mouse. Reporting of the cDNA sequence for non-neuronal, rat c-src should facilitate experimentation into cell growth and transformation using rat tissues as models of human disease.

In situ tolerance within the central nervous system as a mechanism for preventing autoimmunity.

Multiple sclerosis (MS) is believed to be an autoimmune disease in which autoreactive T cells infiltrate the central nervous system (CNS). Animal models of MS have shown that CNS-specific T cells are present in the peripheral T cell repertoire of healthy mice and cause autoimmune disease only when they are activated by immunization. T cell entry into the CNS is thought to require some form of peripheral activation because the blood-brain barrier prohibits trafficking of this tissue by naive cells. We report here that naive T cells can traffic to the CNS without prior activation. Comparable numbers of T cells are found in the CNS of both healthy recombinase activating gene (Rag)(-/)- T cell receptor (TCR) transgenic mice and nontransgenic mice even when the transgenic TCR is specific for a CNS antigen. Transgenic T cells isolated from the CNS that are specific for non-CNS antigens are phenotypically naive and proliferate robustly to antigenic stimulation in vitro. Strikingly, transgenic T cells isolated from the CNS that are specific for myelin basic protein (MBP) are also primarily phenotypically naive but are unresponsive to antigenic stimulation in vitro. Mononuclear cells from the CNS of MBP TCR transgenic but not nontransgenic mice can suppress the response of peripheral MBP-specific T cells in vitro. These results indicate that naive MBP-specific T cells can traffic to the CNS but do not trigger autoimmunity because they undergo tolerance induction in situ.

Evaluation of serotype prediction by cpsA-cpsB gene polymorphism in Streptococcus pneumoniae.

New pneumococcal conjugate vaccines covering a limited number of serotypes are likely to come into widespread use over the next few years. It is unknown what effect this will have on the relative importance of different serotypes as causes of pneumococcal infection. Hence, it will be important to monitor serotype prevalence before, during, and after the introduction of new vaccines. We have investigated the ability of a PCR method based on polymorphisms in two genes common to the different capsule loci to predict the serotype of 93 clinical isolates of Streptococcus pneumoniae submitted to the Central Public Health Laboratory in 1997. Of 70 isolates with vaccine serotypes, 65 were predicted to belong to the correct serotype; this number was improved to 69 with the inclusion of two additional patterns to the database. Of 23 isolates with other serotypes, 19 were correctly predicted as non-vaccine serotypes, the discrepancy lying with four isolates of 6A (non-vaccine serotype) that were indistinguishable from isolates of 6B (vaccine serotype). In situations in which culture of the organism is not feasible, this method could potentially be applicable directly to clinical specimens and could be a valuable aid to the surveillance of pneumococcal serotypes.

OXA-17, a further extended-spectrum variant of OXA-10 beta-lactamase, isolated from Pseudomonas aeruginosa.

Pseudomonas aeruginosa isolates 871 and 873 were isolated at Hacettepe University Hospital in Ankara and were highly resistant to ceftazidime (MIC, 128 microg/ml). Each produced three beta-lactamases, with pIs of 5.3, 6.1, and 7.9. The beta-lactamase with a pI of 5.3 was previously shown to be PER-1 enzyme. The antibiograms of the isolates were not entirely explained by production of PER-1 enzyme, insofar as ceftazidime resistance was incompletely reversed by clavulanate. The enzymes with pIs of 6.1 and 7.9 were therefore investigated. The enzyme with a pI of 6.1 proved to be a novel mutant of OXA-10, which we designated OXA-17, and had asparagine changed to serine at position 73 of the protein. When cloned into Escherichia coli XL1-blue, OXA-17 enzyme conferred greater resistance to cefotaxime, latamoxef, and cefepime than did OXA-10, but it had only a marginal (two- to fourfold) effect on the MIC of ceftazidime. This behavior contrasted with that of previous OXA-10 mutants, specifically OXA-11, -14, and -16, which predominately compromise ceftazidime. Extracted OXA-17 enzyme had relatively greater activity than OXA-10 against oxacillin, cloxacillin, and cefotaxime but, in terms of kcat/Km, it had lower catalytic efficiency against most beta-lactams. The enzyme with a pI of 7.9 was shown by gene sequencing to be OXA-2.

Cavernous angiomas of the cauda equina: case report and review of the literature.

BACKGROUND: Cavernous hemangiomas of the spine and spinal cord are relatively uncommon lesions that are being discovered more frequently because of the increased use of magnetic resonance imaging (MRI). We present a rare case of a symptomatic cavernous hemangioma of the cauda equina. CASE DESCRIPTION: A 49-year-old woman presented to our institution with the chief complaint of low back pain of acute onset. On physical examination the patient was found to be tender to percussion over the lumbar spine, had tenderness over the sciatic nerve, loss of pinprick sensation over the right lateral foot and loss of the Achilles' reflex on the right. In addition, she was found to have a large postvoid urinary bladder residual volume. MRI revealed a 20 mm x 11 mm nonenhancing, heterogenous mass obliterating the spinal canal at the L4 level. At operation, this lesion was found to be adherent to the nerve roots and was completely resected. Pathology revealed this lesion to be a cavernous angioma of the cauda equina. A review of the pertinent literature is presented. CONCLUSIONS: Cavernous hemangiomas of the cauda equina are extremely rare lesions that may present as low back pain, neurologic deficit, or as subarachnoid hemorrhage. They can be successfully treated with surgical excision.

Outcome after urgent surgery for grade IV subarachnoid hemorrhage.

BACKGROUND: Outcome after subarachnoid hemorrhage (SAH) in patients presenting with poor clinical grade has historically been dismal. As a result, many poor-grade patients have been excluded from early, aggressive surgery. We present a consecutive series of 27 patients with acute (less than 24 h since clinical onset) Grade IV SAH treated with early surgery. METHODS: All patients were treated with immediate ventricular drainage, rigid hemodynamic control, early angiography and surgery within 24 h of presentation. Patients were followed for a minimum of 6 months and their outcomes categorized using a four-tiered scale: 1) independent and working, 2) impaired but independent, 3) severely impaired and dependent, and 4) dead. RESULTS: Seven patients died within 48 h of admission. The remaining 20 patients survived to discharge. At the time of discharge eight of these patients were considered to be impaired but independent and twelve were considered severely impaired and dependent. At follow-up, seven patients were independent and working, six were impaired but independent, five were severely impaired and dependent, and two severely impaired patients had subsequently died. CONCLUSIONS: We conclude that urgent surgery for poor-grade SAH can produce quality survival for a higher percentage of patients than is historically reported with delayed surgery.

Conservation of restriction sites in isolates of Streptococcus pneumoniae with diverse restriction fragment patterns.

Separation of large restriction fragments by pulsed-field gel electrophoresis is a commonly used method for epidemiological typing of Streptococcus pneumoniae and many other bacterial species. Information on the genetic changes underlying the restriction fragment polymorphisms that allow discrimination between isolates is scarce. In this study fragments adjacent to ApaI sites in a clinical isolate of S. pneumoniae were cloned and used to probe HindIII and HindIII-plus-ApaI genomic DNA digests from other isolates with very different ApaI fragment patterns. If for a given isolate the HindIII fragment detected by the probe was reduced in size on digestion with ApaI, it was deduced that the ApaI site was conserved in that isolate. The results demonstrate that of six ApaI sites in PN93/908 examined, five were retained in 11 genetically different isolates and one was retained in 2 isolates but lost in 9 others. It was concluded that point mutations at restriction sites are unlikely to account for the restriction fragment length polymorphism observed and that much of the polymorphism may be due to DNA rearrangements, possibly resulting from the insertion or deletion of mobile DNA elements.

Onchocerciasis control in Uganda: how can self-sustaining, community-based treatment with ivermectin be achieved?

In Uganda, the control of onchocerciasis by mass treatment with ivermectin (Mectizan) began in 1990 and has expanded greatly since 1992. The parties involved in the programme are the Uganda Ministry of Health and its National Onchocerciasis Task Force, the Mectizan Donation Programme, the African Programme for Onchocerciasis Control, a number of non-governmental development organizations and the communities where the disease is endemic. Their aim is to make the programme self-sustaining, without further outside aid, within a period of 12 years. The methodology of the ivermectin-distribution programme, based on community-directed treatment, is outlined; the constraints under which the four co-operating parties have to work are described and the effects of the social changes produced by community-directed distribution are discussed, all in terms of influence on the achievement of a programme that will be able to sustain itself without the need for outside aid.

Induced hypervolemia and inotropic support for acute cerebral arterial insufficiency: an underused therapy.

BACKGROUND: Hypervolemia and induced systemic hypertension are generally considered the standard approach to the treatment of vasospasm. Despite evidence in favor of its efficacy, this therapy is used rarely in acute cerebrovascular occlusion. We present a case supporting this treatment paradigm. CASE DESCRIPTION: A patient developed aphasia and hemiplegia 8 h after carotid endarterectomy caused by embolic occlusion of the middle cerebral artery. Hyperdynamic/hypervolemic therapy was instituted. Serial angiograms filmed over the next 8 h demonstrated reperfusion of the hemisphere, through collateral flow. The patient's symptoms resolved. CONCLUSIONS: We believe this case demonstrates the effectiveness of hypervolemia and inotropic support in the treatment of acute embolic stroke by inducing dilatation of the leptomeningeal collateral circulation.

Treatment of blunt injury to the carotid artery by using endovascular stents: an early experience.

Identification of blunt carotid injury prior to the development of ischemic symptoms requires aggressive screening of patients at risk. The treatment of these lesions has centered around long-term anticoagulation therapy. However, studies have revealed that many of these lesions persist despite medical treatment, as does the risk of distal embolization. The authors present a series of six patients who were successfully treated by means of endovascular stent placement for nonpenetrating carotid injuries. In the authors' experience this treatment requires only temporary anticoagulation therapy, results in immediate reconstruction of the injured vessel, obliterates pseudoaneurysms, and prevents distal embolization.

Traumatic bilateral jugular vein thrombosis: case report and review of the literature.

OBJECTIVE AND IMPORTANCE: Thrombosis of the internal jugular vein (IJV) with associated elevated intracranial pressure (ICP) is a rare complication of central venous catheterization but has not been reported as a result of blunt trauma. CLINICAL PRESENTATION: An 18-year-old male patient was observed to be obtunded after an assault. The initial examination was remarkable for somnolence, bruising of the anterior neck, and diffuse, edematous swelling of the face and scalp. The results of computed tomography of the brain were normal. An angiogram obtained on the 2nd hospital day to rule out carotid injury revealed bilateral IJV thromboses to the cranial base. An ICP monitor was placed with an opening pressure of 33 mm Hg. The central venous pressure was measured to be 9 mm Hg. A catheter was passed through the left IJV thrombus and into the sigmoid sinus, where the pressure was 17 mm Hg. INTERVENTION: An intravascular stent was deployed in the left IJV. ICP rapidly normalized. A regimen of coumadin was administered to the patient for 6 weeks, at which time the stent remained patent. CONCLUSION: We conclude that traumatic jugular vein thrombosis can be associated with significant elevation in ICP and that treatment with an endovascular stent can affect the rapid correction of intracranial hypertension in patients who are candidates for anticoagulation.