Mechanism of action and therapeutic route for a muscular dystrophy caused by a genetic defect in lipid metabolism

CHKB encodes one of two mammalian choline kinase enzymes that catalyze the first step in the synthesis of the membrane phospholipid phosphatidylcholine. In humans and mice, inactivation of the CHKB gene (Chkb in mice) causes a recessive rostral-to-caudal muscular dystrophy. Using Chkb knockout mice, we reveal that at no stage of the disease is phosphatidylcholine level significantly altered. We observe that in affected muscle a temporal change in lipid metabolism occurs with an initial inability to utilize fatty acids for energy via mitochondrial β-oxidation resulting in shunting of fatty acids into triacyglycerol as the disease progresses. There is a decrease in peroxisome proliferator-activated receptors and target gene expression specific to Chkb^−/− affected muscle. Treatment of Chkb^−/− myocytes with peroxisome proliferator-activated receptor agonists enables fatty acids to be used for β-oxidation and prevents triacyglyerol accumulation, while simultaneously increasing expression of the compensatory choline kinase alpha (Chka) isoform, preventing muscle cell injury.

Mutations in the CHKB gene cause muscular dystrophy. Here, the authors show that in mouse models of the disease changes in lipid metabolism are associated with decreased PPAR signaling, and show PPAR agonists can rescue expression of injury markers in myocytes in vitro.

Tuberculosis diagnostics in Fiji: how reliable is culture?

SETTINGS

Acid-fast bacilli (AFB) smear microscopy and Mycobacterium tuberculosis culture are the first-line diagnostic tests for tuberculosis (TB). The contamination of TB cultures significantly reduces the reliability of TB diagnosis.

OBJECTIVE

To investigate factors associated with TB culture contamination in Fiji, and the relative diagnostic performance of culture compared to microscopy.

DESIGN

All tests performed at the Daulakao Mycobacterium Reference Laboratory (DMRL) in Fiji from 2010 to 2012 were reviewed. Study variables included AFB smear and TB culture results, age and type of specimen, referring TB testing centre and patient age.

RESULTS

Of 5708 specimens reviewed, 70% had both AFB smear and culture results recorded; 421 specimens were contaminated; 2.7% of specimens were either degraded or had no result recorded. There was moderate agreement (κ = 0.577) between the two tests. Culture was more likely to be positive at higher AFB smear scores. Culture contamination was associated with distance from the DMRL, sample age and operator-associated factors.

CONCLUSION

Increases in the speed of referral from TB testing centres or the addition of preservatives to sputum specimens may results in less culture contamination. The planned introduction of liquid culture techniques in combination with culture on Ogawa media is likely to increase the sensitivity of TB diagnosis in Fiji.

Evaluation of the implementation of the Xpert® MTB/RIF assay in Fiji

SETTING

All Xpert® MTB/RIF tests performed in the three TB (tuberculosis) treatment centres in Fiji from June 2012 to February 2013.

OBJECTIVES

To determine 1) the number of Xpert tests performed in each centre, 2) the association between sputum quality and Xpert results, 3) the agreement of Xpert with acid-fast bacilli (AFB) smear microscopy and TB culture and 4) error rates.

DESIGN

Retrospective review of records.

RESULTS

A total of 415 Xpert tests were performed in the study period. Mycobacterium tuberculosis was detected in 69 (16.6%) samples. No rifampicin resistance was detected. M. tuberculosis was detected from 60 (18.7%) good-quality sputum samples. A total of 43 (10.4%) errors occurred during this period. M. tuberculosis was detected in 10 (2.9%) smear-negative specimens. There was a substantial and an almost perfect agreement between Xpert and AFB microscopy (κ = 0.793) and culture results (κ = 0.818), respectively.

CONCLUSION

Although a good correlation between Xpert and the two tests were shown in the study, Xpert should not replace the routine first-line TB diagnostic tests used in Fiji for reasons related to logistics and sustainability. A further evaluation of the assay's performance is required over a longer time period to gauge its diagnostic value in detecting smear-negative, Xpert-positive cases in Fiji.

The innate resistance of Trypanosoma copemani to human serum

Trypanosoma copemani is known to be infective to a variety of Australian marsupials. Characterisation of this parasite revealed the presence of stercorarian-like life-cycle stages in culture, which are similar to T. rangeli and T. cruzi. The blood incubation infectivity test (BIIT) was adapted and used to determine if T. copemani, like T. cruzi and T. rangeli, has the potential to grow in the presence of human serum. To eliminate any effects of anticoagulants on the complement system and on human high density lipoprotein (HDL), only fresh whole human blood was used. Trypanosoma copemani was observed by microscopy in all human blood cultures from day 5 to day 19 post inoculation (PI). The mechanism for normal human serum (NHS) resistance in T. copemani is not known. The results of this study show that at least one native Australian trypanosome species may have the potential to be infective for humans.

Microsatellite typing and population structuring of Trypanosoma evansi in Mindanao, Philippines

Trypanosoma evansi, a blood-borne protozoan parasite with an extensive geographical range is the causative agent of the livestock disease known as surra. A total of 140 out of 179 T. evansi isolates collected between 2006 and 2007 from 44 villages (comprising of 16 reported surra outbreaks) in 3 provinces (Agusan del Sur (ADS), Surigao del Sur (SDS) and Agusan del Norte (ADN)) in Mindanao, Philippines were each successfully genotyped using a suite of 7 polymorphic microsatellites. The study identified 16 multi locus genotypes (MLG) within the T. evansi isolates and evidence of the spread of surra outbreaks from one village to another, most likely due to the movement of infected animals. Genotyping provided evidence of population sub-structuring with 3 populations (I, II and III (only 1 isolate)) identified. The most abundant population was II, which was the predominant population in ADS and SDS (p=0.022). In addition, buffalo mortality was statistically higher in outbreak areas associated with isolates from population I (13.6%) than with isolates from population II (6.9%) (p=0.047). The present study has highlighted the utility of microsatellite loci to improve understanding of the epidemiology of T. evansi and in tracking surra outbreaks.

Estimating the impact of Trypanosoma evansi infection (surra) on buffalo population dynamics in southern Philippines using data from cross-sectional surveys

Despite the widespread problem with surra (Trypanosoma evansi) in livestock, there are no published studies on its impact on host populations, probably because of the large financial and time cost involved in performing longitudinal studies. During 2002-6, a cross-sectional survey for T. evansi infection involving 1732 buffaloes from 71 villages in southern Philippines was carried out. Other livestock animals (horses, cattle and goats) in every surveyed village were also tested for infection with T. evansi but domestic buffaloes were the primary survey target. Seroprevalence ranged from 6% to 21% and 13% to 100% for buffaloes in low and high risk areas, respectively. Key demographic parameters were estimated from the age structured distributions of the sampled buffalo population for each sex. All areas were dominated by females (69%) and the annual calving rate for areas of 100% and low seroprevalence was 15% and 47%, respectively. Males were removed at a relatively high annual rate of 27% in all areas. In the main reproductive years (4-10) female removal/mortality was <1% and 10% for low and high risk areas, respectively. Older females were removed/died at a rate similar to males regardless of area. In high risk areas there were consistently more 2-year than 1-year old females and the reverse was true for the low risk areas. This implies that females were imported to the high risk areas for breeding. By assuming a stable age structure and similar size populations in each area, it was estimated that 28% of female calves need to be moved from low to high risk areas to maintain the observed age structure. In high risk areas, surra imposes significant financial losses due to reduced fertility, high mortality/removal rate and the necessity to import replacement buffaloes.

A comparison of trapping methods for Tabanidae (Diptera) in North Queensland, Australia

The ability to monitor the abundance and diversity of tabanid flies over wide areas requires effective and low-cost surveillance methods. Such monitoring activities help to quantify the risk of transmission of pathogens by tabanids. Here we examine the effectiveness and practicality of two types of trap (canopy traps and Nzi traps) and two types of attractant (octenol and carbon dioxide) for monitoring tabanid flies in tropical Australia. The Nzi trap consistently caught more tabanids and more species of tabanids than the canopy trap. It was also more robust and therefore required less maintenance in remote locations. The use of attractants substantially increased capture rates, both of individuals and species, and traps using both attractants were consistently the most effective. However, in remote locations, where it is not possible to check traps frequently, the use of attractants may not be feasible. When attractants were not used, the canopy trap caught very few tabanids, but the Nzi trap remained effective enough to be useful as a monitoring device. In addition, the number of tabanid species caught by the Nzi traps remained high, and included those that were most abundant. We therefore conclude that, in this region, Nzi traps are preferable for tabanid monitoring and that attractants greatly improve their effectiveness. However, for longterm monitoring, especially in remote locations, Nzi traps without attractants are a satisfactory option.

Genetic variability of Trypanosoma evansi isolates detected by inter-simple sequence repeat anchored-PCR and microsatellite

Studies on genetic variability in Trypanosoma evansi have been limited by a lack of high-resolution techniques. In this study, we have investigated the use of inter-simple sequence repeats (ISSR) and microsatellites in revealing polymorphism among T. evansi isolates. Twelve ISSR primers and five microsatellite loci were used to generate polymorphic bands and alleles, respectively, to investigate the genetic variability among T. evansi isolates from Africa and Asia. Seven of the twelve ISSR primers showed variability between isolates with a total of 71 fragments of which 49(69%) were polymorphic. Microsatellite analysis revealed a total of 60 alleles. On average the ISSR markers revealed a higher genetic diversity (23%) than microsatellites (21.1%). The two techniques showed a strong agreement of r=0.95 for Dice and r=0.91 for Jaccard indices in estimating the genetic distances between isolates. The distance UPGMA tree revealed two major clusters of T. evansi which correlate with the minicircle classification of subtype A and B. The cophenetic correlation coefficient between Dice and Jaccard based matrices were r=0.79 for microsatellites and r=0.73 for ISSR indicating a strong agreement between dendrograms. The results suggest that both ISSR and microsatellites markers are useful in detecting genetic variability within T. evansi.

Immunization with recombinant beta-tubulin fromTrypanosoma evansiinduced protection againstT. evansi,T. equiperdumandT. b. bruceiinfection in mice

The beta-tubulin gene of Trypanosoma evansi (STIB 806) was cloned and expressed in Escherichia coli. The predicted amino acid sequence of T. evansi beta-tubulin shows 100%, 99.8%, 99.1%, and 98.6% homology with T. equiperdum, T. b. brucei, T. cruzi and T. danilewskyi, respectively, but is diverse from that of T. cyclops, showing only 51.6% of homology. Recombinant beta-tubulin was expressed as inclusion bodies in E. coli. It was purified and renatured for immunological studies. Mice immunized with the renatured recombinant beta-tubulin were protected from lethal challenge with T. evansi STIB 806, T. equiperdum STIB 818 and T. b. brucei STIB 940, showing 83.3%, 70% and 76.7% protection, respectively. Serum collected from the rabbit immunized with recombinant beta-tubulin inhibited the growth of T. evansi, T. equiperdum and T. b. brucei in vitro. Serum from mice and rabbits immunized with recombinant beta-tubulin recognized only T. evansi beta-tubulin and not mouse beta-tubulin. The results of this study demonstrated that the recombinant T. evansi beta-tubulin is a potential candidate for the development of a vaccine to prevent animal trypanosomiasis caused by these three trypanosome species.

Exercise-associated hyponatremia, renal function, and nonsteroidal antiinflammatory drug use in an ultraendurance mountain run

OBJECTIVE

To study biochemical parameters and renal function in runners completing a 60 km mountain run and to investigate the incidence of exercise-associated hyponatremia (EAH). To assess the effects of nonselective nonsteroidal antiinflammatory medication (NSAIDs) and cyclooxygenase-2 (COX-2) selective nonsteroidal antiinflammatory medication (COXIBs) on these parameters.

DESIGN

Observational cohort study.

SETTING

Kepler Challenge 60 km mountain run, Te Anau, New Zealand, December 2003.

PARTICIPANTS

One hundred thirty-one of the 360 runners entered in the race were prospectively enrolled as volunteers on the day before the race.

MAIN OUTCOME MEASURES

Subjects were weighed at race registration the day before the race and at the finish line. Blood was taken within 5 minutes of finishing and was analyzed for serum sodium, creatinine, urea, and potassium concentrations, and hematocrit. Participants were questioned about medication use in the 24 hours before and during the race (NSAIDs, COXIBs, other medications).

RESULTS

Complete data sets were obtained on 123 runners. Five athletes were biochemically hyponatremic [(Na) 130-134 mM] and four were hypernatremic [(Na) 146-148 mM]. Hyponatremia was associated with a mean weight gain of 1.32 kg (range, -1.5 to 1.6 kg). Serum [Na] varied inversely with weight change. Estimated creatinine clearance did not vary with percent weight loss. Estimated creatinine clearance declined with increasing runner age. Sixty-five percent of runners did not use any medication, whereas 20% had used NSAIDs and 15% had taken COXIBs. There were no statistically significant differences between NSAID and COXIB users in any measured parameters or between all NSAID and COXIB users when compared with nonusers.

CONCLUSIONS

Mild asymptomatic EAH was found to occur in 4% of the volunteer ultraendurance mountain runner study group and was associated with a mean weight gain of 1.32 kg (range, -1.5 to 1.6 kg) during the race. Seven percent gained weight but remained normonatremic, suggesting other compensatory mechanisms. Hypernatremia was found in 3% and was associated with a mean weight loss. Postrace serum sodium concentration varied inversely with percent weight change. Runners using any NSAID were more likely to become hyponatremic. Estimated creatinine clearance increased with increasing age. Elevated serum creatinine concentration at the end of the race returned to normal when remeasured the week after the race. Thirty-five percent of runners were found to use NSAIDs or COXIBs. The measures of weight change and of serum sodium, potassium, urea, and creatine concentration did not differ between NSAID and COXIB users or between all nonsteroidal antiinflammatory users and nonusers.

Experimental Trypanosoma evansi infection in the goat. I. Clinical signs and clinical pathology

A strain of Trypanosoma evansi isolated from an equine case of surra in Mindanao, Philippines was used to infect intravenously two groups (A and B) of five male goats aged 8-10 months. Animals of groups A and B received 5000 and 50 000 trypanosomes, respectively, and five further animals (group C) served as uninfected controls. Four of the 10 infected goats died 8-78 days after inoculation. Group C goats gained weight (mean 22.8 g/day) while infected goats in groups A and B lost weight (means of 21.4 and 45.0 g/day, respectively). Parasitaemia fluctuated regularly between peaks and troughs, with repeated periods of about 6 days during which no trypanosomes were detected in the blood. Clinical signs and clinico-pathological changes in infected goats were not pathognomonic in the absence of parasites in the blood, and leucocytosis was not a reliable indicator of infection. It was concluded that in endemic areas fluctuating fever, progressive emaciation, anaemia, coughing, testicular enlargement and diarrhoea are suggestive of surra; confirmation, however, may necessitate examination of blood every few days for trypanosomes, and possibly other diagnostic tests.

Experimental Trypanosoma evansi infection in the goat. II. Pathology

Infection of male goats aged 8-10 months with 5000 or 50 000 organisms of a Mindanao strain of Trypanosoma evansi was observed over a period of 90 days. The infection induced clinical disease which was lethal, especially at the higher dose rate. Lesions were more acute in goats that received the higher dose. Gross and microscopical changes were not pathognomonic, except in the presence of demonstrable trypanosomes. At necropsy, a combination of lymphadenopathy, splenomegaly, hepatomegaly, testicular enlargement, anaemic signs and consolidation of the anterior lobes of the lungs was suggestive of surra. Testicular changes, especially aspermia, indicated probable infertility. The cytopathology of the lungs, liver, intestine, kidneys, testes, bone marrow, brain and other organs was immunological in nature, characterized by mononuclear infiltration of interstitial tissues, with minor cellular damage and the presence of trypanosomes. B- and T- cell responses were observed in the lymphatic system, but the findings indicated immunosuppression in the lymph nodes, spleen and bone marrow during the third month after infection. Exudative inflammatory changes were mild. It is suggested that the cytopathology of most haemophilic trypanosomal infections is predominantly an immunological process.

Characterization of Trypanosoma evansi type B

A distinctive feature of Trypanosoma evansi is the possession of a kinetoplast that contains homogeneous DNA minicircles, but lacks DNA maxicircles. Two major sequence variants of the minicircle have been described and here we have sequenced the type B variant and designed a specific PCR test to distinguish it from type A. Further a test based on maxicircles to distinguish T. brucei brucei from T. evansi was designed and evaluated. Using the designed PCR tests, we detected three type B isolates from camel blood samples collected in northern Kenya, more than 20 years after the first isolation of type B. Comparison of minicircle sequences from all four type B isolates shows >96% identity within the group, and 50-60% identity to type A minicircles. Phylogenetic analysis based on minicircle sequences reveals two clusters, one comprising isolates of type A and one of type B, while random amplification of polymorphic DNA show slight polymorphic bands within type B. Most T. evansi isolates analysed were heterozygous at a repetitive coding locus (MORF2). All type B isolates had one genotype designated 3/5 based on the alleles present. Three camel isolates, which had homogenous type A minicircles, lacked the RoTat 1.2 gene, while another five isolates were T. b. brucei, based on the heterogeneity of their minicircles and presence of maxicircles as demonstrated by PCR amplification of the gene for cytochrome oxidase subunit 1. Our results confirm the existence of T. evansi type B isolates, T. b. brucei and existence of T. evansi type A without RoTat 1.2 gene in Kenyan isolates.

Biomechanical assessment of lateral stiffness elements in the suspension system of a backpack

The purpose of this study was to examine the change in load distribution characteristics associated with adding lateral stiffness elements (rods) to a rucksack (backpack). A load distribution mannequin was instrumented with two 3D load cells to allow determination of the load applied to the shoulders and upper torso independent of the load applied to the hips and lower trunk. Position and mass of the payload (25 kg) were fixed at the centre of the volume of the rucksack and held constant during all testing. It was hypothesized that lateral rods would provide a force bridge that transfers part of the vertical load of the pack from the upper back and shoulders to the hip belt thereby reducing the vertical load on the torso, and possibly reducing the horizontal reaction force that produces a shear load on the spine. Results showed that these active stiffness elements shifted 14% of the vertical load from the upper torso to the pelvic region with lumbar shear load remaining relatively unchanged for all combinations of shoulder strap and waist belt tension. The lateral rods also provided a mean increase of 12% in the extensor moment at the L3-L4 level, thus reducing some demand on the erector spinae muscles.

Detection of Trypanosoma evansi in camels using PCR and CATT/T. evansi tests in Kenya

Camel trypanosomosis (Surra) causes high morbidity and is an impediment to the camel husbandry in Kenya. The lack of a sensitive diagnostic test has hindered the collection of accurate epidemiological data and institution of control programmes. A cross-sectional study was conducted in three districts of Kenya to estimate the prevalence of Trypanosoma evansi (T. evansi) and to compare four diagnostic tests: polymerase chain reaction (PCR), card agglutination test (CATT/T. evansi), microhaematocrit centrifugation technique (MHCT) and mouse inoculation (MI). A total of 549 camels were randomly sampled. The overall prevalence of Surra was 5.3% using MHCT, 26.6% using PCR and 45.9% using CATT/T.evansi. There was a significant difference (P < 0.001) between PCR and CATT/T.evansi test, MHCT and MI in detection of T. evansi. The prevalence of T. evansi was 39.8% in Samburu, 24.7% in Nanyuki and 14.4% in Isiolo districts using PCR. A male camel was 2.6 times more likely to be infected with T. evansi compared to a female camel (OR = 3.0% CI: 1.6, 4.1), while an adult camel was 2.2 times more likely to be infected compared to non-adults (OR = 2.2; 95% CI: 1.2, 5.0). There was a poor association between the presence of the published clinical signs and seropositivity (kappa = 0.12), PCR (kappa = 0.11) and MHCT (kappa = 0.05). However, there was a higher agreement between farmers' classification of disease with the PCR test (kappa = 0.5, n = 61). The mean PCV varied with age, presence of infection, locality and gender, with the lowest mean PCV being recorded in MHCT-positive animals (20.97 +/- 0.5) and from infected calves (19.5 +/- 1.2). This study shows that PCR was more sensitive in detecting T. evansi than other tests used. Further, the prevalence of T. evansi in the camel herds sampled is higher than that previously reported in Kenya, and that the judgment by camel keepers may be a reliable "pen-side" diagnostic test for Surra. Considering the low sensitivity of parasitological techniques in detection of chronic T. evansi infection and high cost of PCR, development of a sensitive pen side diagnostic test, with a low cost is still a priority.

A suite of objective biomechanical measurement tools for personal load carriage system assessment

For application to military and civilian needs, Defence Research and Development Canada--Toronto contracted Queen's University, Kingston to develop a suite of biomechanical assessment and analytical tools to supplement human-based load carriage system assessment methods. This suite of tools permitted efficient objective evaluation of biomechanical aspects of load-bearing webbing, vests, packs and their components, and therefore contributed to early system assessment and a rapid iterative design process. This paper is a summary of five assessment and analytical tools. A dynamic load carriage simulator was developed to simulate cadence of walking, jogging and running. The simulator comprised a computer-controlled pneumatic platform that oscillated anthropometrically weighted mannequins of varying dimensions from which measures of skin contact pressure, hip reaction forces and moments and relative pack-person displacements were taken. A stiffness tester for range of motion provided force-displacement data on pack suspension systems. A biomechanical model was used to determine forces and moments on the shoulders and hips, and validated using a static load distribution mannequin. Subjective perceptual rating systems were used gather soldier feedback during a standardized mobility circuit. Objective outcome measures were validated by means of other objective measures (e.g., Optotrak, video, Instron, etc.) and then compared to subjective ratings. This approach led to development of objective performance criteria for load carriage systems and to improvements in load carriage designs that could be used both in the military and in general.

The development and validation of an antibody-ELISA to detect Trypanosoma evansi infection in cattle in Australia and Papua New Guinea

Trypanosoma evansi is exotic to Australia and Papua New Guinea (PNG). However, it might have been introduced to Papua (Indonesia); thus, there is a risk of it entering PNG and thence Australia. Because of logistical difficulties in PNG and northern Australia, surveillance for T. evansi must rely on serological tests. The accuracy of an Ab-ELISA using a detergent extract of T. evansi and three antigen fractions purified from the detergent extract using stepwise precipitation with saturated ammonium sulphate (AS) were compared. The ELISA using the AS 40-50% fraction had greater discriminatory power compared to the ELISA using the other antigen fractions. This ELISA then was compared with two commercial tests: the Card Agglutination Test for trypanosomiasis/T. evansi (CATT) and Suratex. CATT/T. evansi at 1/4 serum dilution has higher sensitivity and the ELISA has higher specificity. There is no likely benefit in combining antibody detection tests to improve the accuracy of diagnosis. Furthermore, the combination of Suratex (which was independent of the antibody tests) with the CATT or the ELISA did not improve the sensitivity. None of the tests was sufficiently sensitive to be used confidently to determine freedom from infection in animals imported into Australia from countries where T. evansi infection is endemic.

Evaluation of an antibody-ELISA using five crude antigen preparations for the diagnosis of Trypanosoma evansi infection in cattle

Attempts were made to improve the accuracy of an antibody-detection ELISA for the detection of Trypanosoma evansi infection in cattle by improving the method of preparation of the crude antigen used. An IgG-ELISA was performed with five different antigen preparations: crude soluble antigen, soluble and insoluble fractions of crude antigen treated with 0.1% formalin and whole formalin-fixed trypanosomes treated with either trypsin or 2-mercaptoethanol. An IgM-ELISA using crude soluble antigen was also performed. Each ELISA was evaluated using serum from 44 Indonesian cattle infected with T. evansi and 262 uninfected cattle from Australia. There was no significant difference between the sensitivity or specificity of the IgG-ELISA using each of the five antigens. The IgM-ELISA using a crude untreated lysate was significantly less sensitive (p<0.05) than the IgG-ELISA using the same antigen, trypsin-treated antigen or the 0.1% formalin-treated soluble antigen (68, 64 and 64%, respectively). These results show that these modifications to the method of producing crude antigens for the Ab-ELISA does not improve the accuracy of diagnosis of T. evansi infection in cattle.

Evaluation and improvement of parasitological tests for Trypanosoma evansi infection

Research was undertaken to critically evaluate parasitological tests for the detection of Trypanosoma evansi in blood. The relative sensitivity of mouse inoculation (MI), the haematocrit centrifugation technique (HCT) and a modified miniature anion-exchange centrifugation technique (MAECT) were compared using blood and buffy coat. The effect that storage of blood prior to inoculation into mice has on the reliability of the MI test was also evaluated. The tests may be ranked in increasing order of sensitivity: HCT, MAECT with whole blood, MI with whole blood, MAECT with buffy coat and MI with buffy coat. The latter was able to detect 1.25 T. evansi per 4ml of blood. The reliability of the MI test was not reduced with storage of blood containing at least 25 T. evansi per ml for up to 21h prior to inoculation into mice. These results demonstrate that sensitivity of the MI and MAECT are increased approximately 10-fold through the use of buffy coat in place of whole blood. Although, the MI is marginally more sensitive MAECT is better suited to field use.

The susceptibility of two species of wallaby to infection with Trypanosoma evansi

OBJECTIVE

To determine the susceptibility of the agile wallaby (Macropus agilis) and the dusky pademelon (Thylogale brunil) to infection with Trypanosoma evansi.

METHOD

Two agile wallabies and three dusky pademelons were experimentally infected with between 5 x 10(4) and 10 x 10(4) T evansi from a cryopreserved stabilate isolated from an indonesian buffalo. Animals were observed twice daily for clinical signs and blood was collected every 3 days to determine parasitaemia. Necropsy was conducted on animals that died or were euthanised when in extremis and representative tissue sections examined.

RESULTS

All wallabies developed a high parasitaemia by 6 days after infection, which persisted until death or euthanasia in extremis, between days 8 and 61. Clinical signs included anorexia, weakness and ataxia. Anaemia occurred in one wallaby that survived for 61 days. Gross pathological changes varied between animals. They included pericarditis, serous atrophy of fat, splenomegaly, ulcerative gastritis and enteritis. Histological changes were characterised by a mononuclear cell infiltration of the connective tissue of most organs with little cellular destruction. Striking lesions were seen in the choroid, heart, stomach and small intestine.

CONCLUSION

Agile wallabies and pademelons are highly susceptible to infection with T evansi. Wallabies, therefore, have the potential to spread T evansi within New Guinea and Australia if infection is introduced. Mortality is likely to be high thereby acting as an indicator of recent introduction. Histological changes seen in wallabies infected with T evansi are diagnostic for infections occurring in Australia and Papua New Guinea.

Surveys in Papua New Guinea to detect the presence of Trypanosoma evansi infection

OBJECTIVE

To confirm serological evidence that Trypanosoma evansi is present in Papua New Guinea.

DESIGN

Three surveys were undertaken in PNG during 1997/1998. Animals were selected for sampling on the basis of convenience. Samples of blood were examined for the presence of T evansi by the haematocrit centrifugation technique (HCT) and mouse inoculation test (MI). Sera were tested in the field using the card agglutination test for trypanosomiasis/T evansi (CATT). Bovine sera were tested at James Cook University using an antibody-detection ELISA (Ab-ELISA). Results from testing bovine sera with the Ab-ELISA and sera from wallabies with the CATT were analysed using FreeCalc to determine the probability that animals in these populations were infected with T evansi.

RESULTS

A total of 545 serum samples were collected, during the three surveys of which 39 cattle, two pig and three agile wallaby samples were positive with the CATT. All bovine sera collected were negative when tested with an Ab-ELISA. T evansi was not isolated using the HCT or the MI from any of these animals.

CONCLUSION

Based on the Ab-ELISA results it was concluded that T evansi infection was not present in cattle in villages around Balimo at a minimum expected prevalence of 10% (P < 0.05) and, based on the CATT results, that infection was not present in wallabies on the Bula plain at a minimum expected prevalence of 10% (P < 0.1). These results indicate that it is unlikely that T evansi is endemic in PNG.

Resting frontal electroencephalographic asymmetry in depression: inconsistencies suggest the need to identify mediating factors

Two studies of the relationship between depression and resting frontal electroencephalographic (EEG) activity are reported. Although considerable research supports the theory of left and right hemispheric specialization for approach and withdrawal behaviors, only four studies involving clinically depressed individuals have been published to date. Despite methodological similarities with published research, no significant differences in frontal activation emerged between depressed and nondepressed participants with either college students having high Beck Depression Inventory scores (Study 1) or with individuals diagnosed with DSM-III-R depression (Study 2). Post hoc analyses in Study 2 revealed one effect confined to lateral frontal leads during the first 2 min of EEG data; this finding was significant in only one of three reference montages. Results are discussed in light of methodological considerations and mediating variables such as temperament and coping styles.

Primary care physicians' recognition of and attitudes toward domestic violence

PURPOSE

Physicians fail to identify the majority of domestic violence victims, even though they are often the first and only individuals to whom a victim may present. The present study was designed to assess primary care physicians' recognition of and attitudes toward domestic violence.

METHOD

Of the 148 primary care physicians in three midwestern counties, all the women and a random sample of the men were included in the survey, for a total of 83. A seven-page questionnaire was developed that contained items about demographics and practice characteristics, and questions about the following aspects of domestic violence: knowledge, attitudes, importance, and prevalence in practice; attitudes toward responsibility; current practices and protocols used; level of education and domestic violence received; and opinions on how best to distribute information and/or education concerning domestic violence. The questionnaire was mailed in 1994. Follow-up was conducted through phone calls, remailings, and visits to the physicians' offices. Responses were examined using chi-square tests and two-tailed t-tests.

RESULTS

The response rate was 63% (52 of 83); 53% of those responding were family physicians and 47% were general internists; 34% were women. Although all of the physicians agreed that finding and treating domestic violence is important, less than half agreed that domestic violence was a significant problem in their patient populations. Almost 96% of the physicians believed that more should be done to educate physicians about domestic violence, and 94% agreed that domestic violence should be included in a doctor's professional medical training; yet nearly half said they would not participate in a domestic violence forum. Even though 41% noted that they had received some type of formal education about domestic violence, 57% felt that their medical education had inadequately prepared them to deal with domestic violence, and less than 25% reported that they had been trained to diagnose domestic violence. The family physicians and the female physicians had received more education about domestic violence and were more comfortable addressing domestic-violence situations. The older physicians were less comfortable addressing domestic violence and were less likely to agree that education about domestic violence should be a part of medical training.

CONCLUSION

Interventions by the medical community to increase physician awareness of domestic violence and available treatment resources are necessary, and domestic-violence information should be included in formal medical curricula.

Generation of tunable, narrow-band mid-infrared radiation through a 532-nm-pumped KTP optical parametric amplifier

We report generation of broadly tunable (2.5-4 µm), narrow-band (0.04-0.35 cm-1) pulsed infrared radiation through a nanosecond optical parametric amplifier based on potassium titanyl phosphate (KTP) pumped by the second harmonic of a 10-Hz Nd:YAG laser. Input radiation at signal wavelengths of 615-662 nm was derived from a pulsed tunable dye laser system. Advantages of this device are simplicity, the broad range of infrared wavelengths to which a single dye in the dye laser provides access, and conversion efficiencies >10% at modest levels (<150 µJ) of input radiation.

Abnormality of smooth pursuit eye movement initiation: specificity to the schizophrenia spectrum?

Schizophrenia patients have a deficiency of smooth pursuit eye movement initiation. We addressed whether this deficit is specifically related to a predisposition for schizophrenia. Thirty-two relatives of schizophrenia patients, eight schizotypals, 13 psychiatric comparison, and 33 nonpsychiatric subjects were assessed on smooth pursuit initiation. The nonpsychiatric subjects had significantly higher eye accelerations than did subjects in the other three groups, who did not significantly differ. The relatives were subdivided into three groups: (a) those with a schizophrenia spectrum disorder (n = 4) performed similarly to the schizotypals; (b) those with a major depression history (n = 7) were similar to the psychiatric comparison subjects; and (c) those with no psychiatric history differed from the nonpsychiatric subjects only on 30 degrees/s targets. There was also a significant relationship between offspring and parent eye accelerations to 30 degrees/s targets (r = .476). These results suggest that pursuit initiation deficits may be associated with a nonspecific, genetically transmitted neurological abnormality among schizophrenia spectrum disorder subjects.

Treatment of epilepsy by stimulation of the vagus nerve

We treated 14 patients with medically refractory partial seizures by stimulation of the vagus nerve in two single-blind pilot studies. Patients received stimulation through an implantable, programmable NeuroCybernetic Prosthesis, consisting of a pulse generator and a lead-electrode assembly. The mean reduction in seizure frequency after 14 to 35 months of vagal stimulation was 46.6%. Of the 14 patients, five (35.7%) had a 50% or greater reduction in seizure frequency. Two patients, one of whom had had 10 to 100 seizures per day before stimulation, have been seizure-free for over 1 year. Adverse events were primarily limited to initial hoarseness and a tingling sensation at the electrode site in the neck when the device was activated. Most patients tolerated the device and stimulation well. There were no permanent adverse events. Some cases of medically refractory partial seizures are improved by vagal stimulation.

STL: a spatio-temporal characterization of focal interictal events

An innovative method for on-line processing of array ECoG data, the Spatio-Temporal Laplacian, intended for intraoperative epileptic focus localization is presented. This method simultaneously involves the spatial and temporal characteristics of the potential field manifestations peculiar to focal interictal events. A 3-Dimensional (x, y and t) sample space is used to explain and apply the Spatio-Temporal Laplacian (STL) transformation. In particular, a focal interictal event is detected through the coincident spatial and temporal sharpness that it introduces in this sample space. Preliminary results from two subjects are presented and compared with standard bioplar derivation signals, traditionally used in the focus localization task.

Electrophysiological studies of cervical vagus nerve stimulation in humans: I. EEG effects

Evidence from studies of experimental animals indicates that electrical stimulation of the vagus nerve alters EEGs under certain stimulus parameters. We report EEG effects of electrical stimulation of the vagus nerve in 9 patients with medically intractable seizures as part of a clinical trial of chronic vagal stimulation for control of epilepsy. The mechanism of action of the vagal antiepileptic effect is unknown, and we believed that analysis of electrophysiologic effects of vagal nerve stimulation would help elucidate the brain areas affected. The left vagus nerve in the neck was stimulated with a programmable implanted stimulator. Stimulation at various stimulus frequencies and amplitudes had no noticeable effect on EEG activity whether the patient was under general anesthesia, awake, or asleep, but vagus nerve stimulation may interrupt ongoing ictal EEG activity.

Electrophysiologic studies of cervical vagus nerve stimulation in humans: II. Evoked potentials

Evidence from studies of experimental animals indicates that electrical stimulation of the vagus nerve not only can alter the EEG but evokes activity in specific brain areas. We report effects of electrical stimulation of the vagus nerve in 9 patients with medically intractable seizures as part of a clinical trial of chronic vagal stimulation for control of epilepsy. The left vagus nerve in the neck was stimulated with a programmable implanted stimulator. Effects of stimulus amplitude, duration, and rate were studied. Noncephalic reference recording of the vagus nerve evoked potential showed some unusual properties: a scalp negative component occurred with a latency of 12 ms, very high amplitude (< or = 60 microV), and widespread scalp distribution. Field distribution studies indicated that this potential was myogenic in origin and generated in the region of the stimulating electrodes in the neck area. Chemically induced muscle paralysis confirmed this observation. Bipolar scalp recording showed several small-amplitude topographically distinct potentials occurring in 30 ms. No effect, either acute or chronic, could be detected on pattern-reversal evoked potentials, auditory brainstem evoked potentials, auditory 40-Hz potentials, or cognitive evoked potentials.

Absence of cortical white matter changes in three patients undergoing long-term vigabatrin therapy

Chronic administration of the experimental antiepileptic drug vigabatrin (gamma-vinyl GABA) to animals has been shown to cause dose-dependent neuropathological changes characterized by a microvacuolation in specific white matter tracts. This finding has led to some concern as to whether similar pathologic changes might occur in patients taking this medication. Here we report on analysis of tissue specimens taken during neurosurgery from three patients undergoing chronic vigabatrin therapy (4 g/day). The first patient, a 34-year-old woman, had taken vigabatrin for 2 years prior to surgery, the second, a 50-year-old man, had taken the drug for 1 year, and a 34-year-old man had taken the drug for 5.3 years. For comparison, similar specimens were taken from three other patients not taking vigabatrin who were undergoing surgery for intractable epilepsy. Specimens from each subject were prepared in an identical manner and examined with light and electron microscopy. All specimens were examined in a blinded fashion. There was some minor nonspecific myelinic splitting seen in both controls and vigabatrin-treated patients but there was no evidence for any drug-induced lesions similar to that seen in experimental animals.

Epidural lipomatosis in steroid-treated patients

Epidural lipomatosis is a condition in which excess adipose tissue is deposited circumferentially about the spinal cord in the epidural space. It is most frequently seen in patients on chronic steroid treatment for a variety of medical problems and can present as nonspecific back pain, radiculopathy, or frank spinal cord compression. Diagnosis and treatment have generally relied on multi-level decompressive laminectomy after myelography and computed tomography. The immunocompromised state and the reported postoperative mortality (22%) of these patients, however, suggests that nonoperative therapy may be preferable whenever possible. Five cases of epidural lipomatosis are reported, and previous literature is reviewed for presentation, evaluation, and treatment of this condition.

3-D computer animation of electrophysiological responses

Traditional methods for displaying electrophysiological data, that use time as the axis on a plot, are inadequate for displaying data from simultaneous multi-channel recordings. New methods proposed here plot the instantaneous value of the data on a third axis over a 2-dimensional spatial map of the tissue. The resulting 3-D computer-generated surfaces are animated over time to reveal simultaneous coherent waves of activity over the entire slice. This method was implemented for displaying multi-channel evoked potential data from rat hippocampal and human cortical slices. In rat hippocampal slice, stimulation of the Schaffer collateral-commissural pathway in stratum radiatum (SR) near CA2 elicited evoked extracellular responses along the length of CA1 from the alveus to stratum lacunosum moleculare (SLM). 3-D plotting and subsequent animation of these responses translated differential latencies of activation elicited across the slice into coherent moving patterns. These evoked waves of extracellular activity appeared to propagate along hippocampal laminae and were not readily visible in the individual plots. Human temporal cortical slices were stimulated in the white matter and evoked responses recorded in an array format. Upon plotting and animation, activity was seen to propagate vertically to the pial surface and thereafter move radially away from the stimulation site. Animation of 3-D plots of electrophysiological activity can provide instantaneous visual information on correlated changes in amplitude and latency over an entire brain slice. This means of displaying data can reduce a large number of complex wave forms to simple events and allow the simultaneous visualization of general patterns of activity in a large group of neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Outcome for West syndrome following surgical treatment

We report the case of an 18-month-old child with infantile spasms and a hypsarrhythmic electroencephalogram (EEG) pattern associated with a porencephalic cyst. Surgical removal of the cyst and its surrounding tissue was performed following failure of medical therapy. Postoperatively, the patient has been free of infantile spasms for 12 months and the EEG has normalized. He has been maintained on the same preoperative antiepileptic medications. This case suggests that surgical treatment is helpful in selected patients with infantile spasms and focal CNS lesions.

Inhibition of hematopoietic progenitor colony growth by a monoclonal antibody against the transferrin receptor: comparison of unconjugated antibody with an immunotoxin containing recombinant ricin A chain

We studied an immunotoxin consisting of recombinant ricin A chain (rRA) conjugated to 454A12 MoAb, a monoclonal antibody which recognizes an epitope on the human transferrin receptor, and compared the ability of 454A12 MoAb-rRA immunotoxin to inhibit the growth of erythroid burst-forming units (BFU-e) and myeloid colony-forming units (CFU-c) with unconjugated 454A12 MoAb. A significant reduction in BFU-e colony growth was observed at 0.001 microgram/ml of 454A12 MoAb-rRA versus 0.1 microgram/ml of unconjugated 454A12 MoAb (p = 0.005). Comparison of the effects of 454A12 MoAb-rRA and 454A12 MoAb on myeloid colony development gave markedly different results. Unconjugated antibody had no effect on CFU-c colony growth; in contrast, 0.01 microgram/ml of 454A12 MoAb-rRA reduced the number of colonies from 139 per 1 X 10(5) to 75 per 1 X 10(5) cells plated (p = 0.0005). No myeloid progenitor colonies developed at 0.1 microgram/ml of immunotoxin. These observations suggest that 454A12 MoAb-rRA inhibits growth by a potent, ricin A chain-mediated toxic effect on any proliferating cells expressing transferrin receptors, whereas the 454A12 MoAb exerts a selective inhibitory effect primarily on erythroid progenitors by perturbing the transferrin cycle. While growth factor receptors expressed on hematopoietic cells represent promising targets for immunotoxin therapy, our data indicate that an immunotoxin could inhibit cellular proliferation by a different mechanism than the corresponding unconjugated MoAb. Depending on the antibody used, these differences may be important in trials using immunotoxins for in vivo treatment or in vitro purging of malignant hematopoietic cells.

TDAT--time domain analysis tool for EEG analysis

An interactive design and analysis tool for displaying and quantifying multiple channels of data is presented. The system allows one to easily visualize multiple data channels and simultaneously observe the effects of filters on the data and to evaluate signal detection algorithms. The software is designed for a workstation environment; it will find application in a variety of applications where one needs to simultaneously visualize multiple data channels. TDAT is being used for the design and evaluation of filters and detection algorithms for electroencephalogram (EEG) waveforms, and it is serving as a prototype of a paperless system to be used by electroencephalographers. This paper describes the general software structure of the system and illustrates many of the system features with examples.

Vagus nerve stimulation in humans: neurophysiological studies and electrophysiological monitoring

Evidence from studies of experimental animals indicates that electrical stimulation of the vagus nerve alters behavioral and electrographic seizure activity. We report on effects of electrical stimulation of the vagus nerve in five patients with medically intractable seizures as part of a clinical trial of chronic vagal stimulation for control of epilepsy. The mechanism of action of the vagal antiepileptic effect is unknown, and it is hoped that analysis of electrophysiological effects of vagal nerve stimulation will help elucidate which brain areas are affected. Stimulation of the left vagus nerve in the neck was accomplished with a programmable implanted stimulator. Effects of stimulus amplitude, duration, and rate were studied. Noncephalic reference recording of the vagus-nerve-evoked potential showed some unusual properties: a scalp negative component occurred with latency of 12 ms, very high amplitude (up to 60 microV), and widespread scalp distribution. Field distribution studies indicate that this potential is generated in the neck, in the region of the stimulating electrodes. Muscle paralysis confirms this observation. Stimulation at various frequencies had no noticeable effect on electroencephalographic (EEG) activity regardless of whether the patient was under general anesthesia, awake, or asleep.

Efficacy and safety of vagus nerve stimulation in patients with complex partial seizures

A clinical trial of chronic intermittent vagal stimulation in five patients suggests that the procedure may be safe and effective as adjunctive treatment of medically intractable seizures of partial onset. Patients tolerated well the implantation of the neurocybernetic prosthesis and the vagal stimulation without serious physiological or lifestyle changes. Stimulation of the vagus nerve either reduced the seizure frequency or decreased the duration or intensity of seizures. Adverse side effects were limited to a tingling sensation in the throat and hoarseness during stimulation. A major complication was mechanical interruption of the wire-electrode circuitry, with consequent cessation of stimulation. The small number of patients and the relatively short follow-up period make this a pilot study, but the results are promising.

Surgical technique for implantation of the neurocybernetic prosthesis

The surgical technique for the implantation of the neurocybernetic prosthesis is described in detail. This procedure is straightforward and is easily carried out by surgeons familiar with carotid surgery.

Toward the ideal electrocorticography array

Several features desirable in the design of electrocorticography arrays are listed. A new electrocorticography system is described and compared with types that are commercially available. This system offers several advantages over older systems and results in significant saving of time in the operating room.

Distribution and physical properties of BCA200, a Mr 200,000 glycoprotein selectively associated with human breast cancer

Of 122 mouse monoclonal antibodies selective for human breast cancer, 13 immunoprecipitated an acidic glycoprotein from SK-Br-3 and ZR-75-30 human breast cancer cells. The antigen (BCA200) migrates with an apparent molecular weight of 200,000 on reducing and 180,000 on nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggesting a single polypeptide chain with a folded domain stabilized by a disulfide bond. Cross-blocking and sandwich immunoassays detected at least three distinct antigenic determinants on BCA200. Scatchard experiments measured 1,000,000 to 5,000,000 antigen copies per SK-Br-3 cell. The tissue distribution of BCA200 was studied using two monoclonals to different epitopes. Neither antibody stained any cells in human blood. When frozen sections of 20 normal human tissues were immunoperoxidase stained, the only positive structures were mucinous glands of colon, transitional epithelium of bladder, sweat glands of skin, and acinar epithelium of breast. Antibody 454C11 stained 16 of 21 breast tumor frozen sections and 9 of 12 breast cancer cell lines, while antibody 520C9 stained 5 of 20 breast tumors and 4 of 10 breast cancer lines. Cross-reaction was observed with lung, prostatic, pancreatic, endometrial, and ovarian cancer, but not with lymphoma, melanoma, colon, stomach, bladder, or esophageal cancer. When conjugated to ricin A chain, 10 of 13 antibodies produced immunotoxins selectively cytotoxic to SK-Br-3 breast cancer cells.

Spontaneous epileptiform discharges in isolated human cortical slices from epileptic patients

Human epileptic in vitro brain slices were obtained at ablative neurosurgical procedures and examined for spontaneous extracellular field potentials. Electrical events resembling interictal spikes and seizure discharges were observed in tissue from the electrocorticographic epileptic foci, but not in control tissue. It appears that important differences between the epileptic focus and normal tissue are maintained in vitro.

NeuroSIG: the computer network of the Congress of Neurological Surgeons

A sophisticated computer network has been developed specifically for use by the Congress of Neurological Surgeons. This network provides a variety of communication and information features. These include public and private message transmission, teleconferencing, numerous data libraries, programs that may be downloaded and executed on the user's own computer, high resolution color graphics image transmission, an extensive neurosurgical database, and extensive on-line "help" features. The system can be accessed using almost any personal computer and a telephone modem.

Micromorphological characterisation of normal human bone surfaces as a function of age

Endosteal surfaces of human bone specimens, principally from the sixth rib, from subjects ranging in age from seven weeks to 87 years were studied using the secondary electron imaging mode in the scanning electron microscope. Specimens were examined after the removal of cells only, or after the removal of cells and organic matrix. Morphological differences made it possible to identify the age group to which a specimen belonged. The most obvious of these was the ratio of active to resting bone surfaces, which collagen matrix which was deposited at endosteal surfaces was different in the different age groups. In neonates, collagen was organised as a parallel fibred continuum. It was present in more discrete bundles in adults, although these still branched and anastomosed with one another. The bundles were parallel over limited domains which described large angles with respect to one another. The conformation of resorbed surfaces indicated that the behaviour pattern of osteoclasts changes with age. Shallow gutters, or annular zones around resorption bays were most common in neonates. The elongation ratio of resorption tracks was greatest in infants and juveniles, indicating that osteoclast translocation was greatest during resorption at these ages. The texture of the floors of resorption bays was smooth in specimens from subjects up to 13 years, while in adults the collagen fibre bundle organisation in the resorbed tissue was often visible. This difference may reflect a more equal mineralization in the ground substance and collagen compartments of the bone matrix in children than in adults.

Changes in the mineral density distribution in human bone with age: image analysis using backscattered electrons in the SEM

We report a study to test the feasibility of studying mineral density distributions in bone using the backscattered electron signal in scanning electron microscopy. Samples were human sixth ribs ranging in age from 8 weeks to 59 years, embedded in polymethylmethacrylate (PMMA), cut, polished, and carbon coated. The proportions of pixels falling in a uniform set of gray level slices of the BSE signal were determined using a microcomputer-based image analysis system interfaced directly to the SEM. The amount of high-density bone gradually increased with age at the expense of low-density bone, and there was an associated compression of the range of the mineral density distribution. Age-related differences were noted between the density distributions in the outer and inner rib cortices. The distribution in the inner cortex in neonates was influenced by the inclusion of densely mineralized endochondral bone and cartilage trabeculae formed at the growth cartilage zone. In adults it appeared that greater bone turnover occurred in the outer cortex, perhaps reflecting a differential mechanical loading across the rib. The technique enabled rapid, unbiased discrimination between the bone of neonates, children, and adults.

Effect of mineral content of human bone on in vitro resorption

Osteoclasts, mechanically isolated from chick long bones, were grown in vitro on slices of human rib and femur. Evidence of their activity was assessed by secondary electron and backscattered electron (BSE) imaging in the SEM. BSE imaging was also used to study the relative degree of mineralisation of the bone matrix in which resorption had taken place. All bone phases were resorbed, from osteoid through to densely mineralised interstitial bone and reversal (cement) lines. Resorbing osteoclasts crossed reversal lines between osteons of different mineral density and moved both from higher to lower and lower to higher density phases. Where single loci spanned reversal lines, and thus breached bone of two different mineral densities, depth of demineralisation was inversely related to mineral density. The presence of an annular zone around some resorption loci, which may be caused by demineralisation beneath the osteoclast clear zone, was confirmed. Also, BSE imaging of polished substrata showed that significantly more osteoclastic activity had occurred at their surfaces than was apparent from the amount of cavitation present.

A study of lamellar organisation in juvenile and adult human bone

The scanning electron microscope (SEM) has been used to study the three-dimensional organisation of collagen in slices of human rib and femur which were "etched" by chick osteoclasts, mechanically isolated and grown on their surfaces in vitro. Collagen organisation in the two bones showed a spectrum of appearances, ranging from lamellae of approximately equal thickness, but alternating fibre orientations, to an almost exclusive orientation of collagen apparently in a longitudinal direction. The rib contained a smaller component of transversely oriented collagen which may be related to a different functional loading. The thickness of circumferential lamellae was less than that of osteonal lamellae in the two adult ribs examined. Also, in the rib there was a trend towards increased average lamellar thickness with age in the range studied. This may be related to the fact that more of the lamellae in the rib cortex in children have been formed circumferentially. Correlation of results obtained with the SEM and the polarised light microscope (PLM) from the same substratum demonstrated that the latter grossly exaggerated the apparent component of collagen with a transverse orientation. This will always be true unless sections comparable with the lamellar thickness are used with the PLM.

Myelomeningocele occurring within a lumbosacral teratoma: case report

The occurrence of a myelomeningocele completely embodied within a lumbosacral teratoma is extremely rare. We report on the clinical presentation, radiological appearance, surgical treatment, and histological make up of such a lesion.

Membrane electrical properties and prediction of motor-unit type of medial gastrocnemius motoneurons in the cat

Membrane electrical properties [time constant, action potential afterhyperpolarization (AHP), rheobase, input resistance, and axonal conduction velocity] were measured in motoneurons of cat medial gastrocnemius (MG) motor units. Motor units were classified on the basis of their mechanical responses as fast twitch, fast fatiguing (FF); fast twitch with intermediate fatigue resistance (FI); fast twitch, fatigue resistant (FR); or slow twitch, fatigue resistant (S; 11, 22). Motoneuron membrane time constant, estimated from the voltage response at the onset or termination of long (50-100 ms) current pulses and corrected for voltage-response nonlinearities (32), was found to differ significantly among the major motor-unit types, increasing in the order FF less than FR less than S. Afterhyperpolarization magnitude, half-decay time, and duration were all significantly greater for the fast (FF + FI + FR) versus the slow (S) motor units. The AHP half-decay time was correlated with muscle unit twitch time over the entire motoneuron population and within the type S motor-unit population. There was no significant correlation between twitch time and AHP half-decay time among the types FF and FR motor-unit populations. In agreement with previous studies, we found a significant difference in both rheobase and input resistance among the major motor-unit types, with rheobase increasing in the order S less than FR less than FF and input resistance decreasing in that order (S greater than FR greater than FF). The differences in input resistance were present both before and after correcting for voltage-response nonlinearities (32). Also in agreement with previous studies, the mean axonal conduction velocity was significantly faster among the fast (FF + FI + and FR) compared with the slow (S) motor units. These data were used to examine the properties alone to determine motor-unit type, which has traditionally been defined on the basis of the muscle unit's mechanical properties (11, 22). We used a discriminant analysis program to classify 73 mechanically typed motor units for which we had measures of rheobase, input resistance, membrane time constant, and AHP half-decay time. This model was able to properly classify 71 of the 73 motor units of this data set, indicating that the motor units of this data set could be grouped into three categories representing the three major motor-unit types (FF, FR, and S) on the basis of their rheobase, input resistance, membrane time constant, and AHP half-decay time.(ABSTRACT TRUNCATED AT 400 WORDS)