Novel stem cell technologies are powerful tools to understand the impact of human factors on Plasmodium falciparum malaria

Plasmodium falciparum parasites have a complex life cycle, but the most clinically relevant stage of the disease is the invasion of erythrocytes and the proliferation of the parasite in the blood. The influence of human genetic traits on malaria has been known for a long time, however understanding the role of the proteins involved is hampered by the anuclear nature of erythrocytes that makes them inaccessible to genetic tools. Here we overcome this limitation using stem cells to generate erythroid cells with an in-vitro differentiation protocol and assess parasite invasion with an adaptation of flow cytometry to detect parasite hemozoin. We combine this strategy with reprogramming of patient cells to Induced Pluripotent Stem Cells and genome editing to understand the role of key genes and human traits in malaria infection. We show that deletion of basigin ablates invasion while deletion of ATP2B4 has a minor effect and that erythroid cells from reprogrammed patient-derived HbBart α-thalassemia samples poorly support infection. The possibility to obtain patient-secific and genetically modifed erythoid cells offers an unparalleled opportunity to study the role of human genes and polymorphisms in malaria allowing preservation of the genomic background to demonstrate their function and understand their mechanisms.

Identifying proteins bound to native mitotic ESC chromosomes reveals chromatin repressors are important for compaction

Epigenetic information is transmitted from mother to daughter cells through mitosis. Here, to identify factors that might play a role in conveying epigenetic memory through cell division, we report on the isolation of unfixed, native chromosomes from metaphase-arrested cells using flow cytometry and perform LC-MS/MS to identify chromosome-bound proteins. A quantitative proteomic comparison between metaphase-arrested cell lysates and chromosome-sorted samples reveals a cohort of proteins that were significantly enriched on mitotic ESC chromosomes. These include pluripotency-associated transcription factors, repressive chromatin-modifiers such as PRC2 and DNA methyl-transferases, and proteins governing chromosome architecture. Deletion of PRC2, Dnmt1/3a/3b or Mecp2 in ESCs leads to an increase in the size of individual mitotic chromosomes, consistent with de-condensation. Similar results were obtained by the experimental cleavage of cohesin. Thus, we identify chromosome-bound factors in pluripotent stem cells during mitosis and reveal that PRC2, DNA methylation and Mecp2 are required to maintain chromosome compaction.

Chromosome Analysis Using Benchtop Flow Analysers and High Speed Cell Sorters

The use of the DNA dyes Hoechst (HO) and chromomycin A3 (CA3) has become the preferred combination for the bivariate analysis of chromosomes from both human and animals. This analysis requires a flow cytometer equipped with lasers of specific wavelength and of higher power than is typical on a conventional bench top flow cytometer. In this study, we have investigated the resolution of chromosome peaks in a human cell line with normal flow karyotype using different combinations of DNA dyes on a number of flow cytometers available in a flow cytometry core facility. Chromosomes were prepared from the human cell line using a modified polyamine isolation buffer. The bivariate flow karyotypes of different DNA dyes combination; 4′‐6‐diamidino‐2‐phenylindole (DAPI) or Hoechst with propidium iodide (PI), obtained from different flow cytometers were compared to the reference flow karyotype of DAPI or Hoechst with chromomycin A3, generated from a Mo‐Flo cell sorter using laser power settings of 300 mW each of UV and 457 nm. Good chromosome separation was observed in most of the flow cytometers used in the study. This study demonstrates that chromosome analysis and sorting can also be performed on benchtop flow cytometers equipped with the standard solid state 488 and 355 nm lasers, using a DNA dye combination of DAPI or Hoechst with PI. © 2018 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Plasminogen Activators t-PA, u-PA and Its Inhibitor (PAI) in Normal Males and Females

We determined the plasma levels of tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI) activity and their antigen levels including urokinase plasminogen activator (u-PA) in 33 male and 27 female normal subjects. Males had mean t-PA activity of 0.50 iu/ml which was significantly lower (p <0.01) than the females 0.64 iu/ml. Males had higher (p <0.001) mean PAI activity (15.5 AU/ml) as compared to females 10.3 AU/ml. The respective mean levels of t-PA and PAI antigen were significantly higher (p <0.01) in males (8.1 ng/ml and 17.6 ng/ml) than in females (6.2 ng/ml and 12.1 ng/ml). The mean u-PA level in males was 1.54 ng/ml which was significantly higher (p <0.01) than in females with 1.02 ng/ml. In post-venous occlusion studies, females had a greater mean response of 8.6 fold in t-PA activity as compared to males with a mean of 4.5 fold increase. The mean t-PA antigen response in males was 2.0 fold increase as compared to 2.6 fold increase in the females. No significant responses were seen in both sexes in either PAI activity or antigen levels when compared with the resting state. In zymography studies, free t-PA, its inhibitor complexes and u-PA were demonstrated in the euglobulin fractions of stored plasma. This study demonstrates that significant differences in t-PA, u-PA and PAI exist between male and female subjects which should be taken into account when determining their levels in clinical conditions.

A First Generation Comparative Chromosome Map between Guinea Pig (Cavia porcellus) and Humans

The domesticated guinea pig, Cavia porcellus (Hystricomorpha, Rodentia), is an important laboratory species and a model for a number of human diseases. Nevertheless, genomic tools for this species are lacking; even its karyotype is poorly characterized. The guinea pig belongs to Hystricomorpha, a widespread and important group of rodents; so far the chromosomes of guinea pigs have not been compared with that of other hystricomorph species or with any other mammals. We generated full sets of chromosome-specific painting probes for the guinea pig by flow sorting and microdissection, and for the first time, mapped the chromosomal homologies between guinea pig and human by reciprocal chromosome painting. Our data demonstrate that the guinea pig karyotype has undergone extensive rearrangements: 78 synteny-conserved human autosomal segments were delimited in the guinea pig genome. The high rate of genome evolution in the guinea pig may explain why the HSA7/16 and HSA16/19 associations presumed ancestral for eutherians and the three syntenic associations (HSA1/10, 3/19, and 9/11) considered ancestral for rodents were not found in C. porcellus. The comparative chromosome map presented here is a starting point for further development of physical and genetic maps of the guinea pig as well as an aid for genome assembly assignment to specific chromosomes. Furthermore, the comparative mapping will allow a transfer of gene map data from other species. The probes developed here provide a genomic toolkit, which will make the guinea pig a key species to unravel the evolutionary biology of the Hystricomorph rodents.

Chromosomal evolution among leaf-nosed nectarivorous bats--evidence from cross-species chromosome painting (Phyllostomidae, Chiroptera)

Background

New World leaf-nosed bats, Phyllostomidae, represent a lineage of Chiroptera marked by unprecedented morphological/ecological diversity and extensive intergeneric chromosomal reorganization. There are still disagreements regarding their systematic relationships due to morphological convergence among some groups. Their history of karyotypic evolution also remains to be documented.

Results

To better understand the evolutionary relationships within Phyllostomidae, we developed chromosome paints from the bat species Macrotus californicus. We tested the potential of these paints as phylogenetic tools by looking for chromosomal signatures in two lineages of nectarivorous phyllostomids whose independent origins have been statistically supported by molecular phylogenies. By examining the chromosomal homologies defined by chromosome painting among two representatives of the subfamily Glossophaginae (Glossophaga soricina and Anoura cultrata) and one species from the subfamily Lonchophyllinae (Lonchophylla concava), we found chromosomal correspondence in regions not previously detected by other comparative cytogenetic techniques. We proposed the corresponding human chromosomal segments for chromosomes of the investigated species and found two syntenic associations shared by G. soricina and A. cultrata.

Conclusion

Comparative painting with whole chromosome-specific paints of M. californicus demonstrates an extensive chromosomal reorganization within the two lineages of nectarivorous phyllostomids, with a large number of chromosomes shared between M. californicus and G. soricina. We show that the evolution of nectar-feeding bats occurs mainly by reshuffling of chiropteran Evolutionarily Conserved Units (ECUs). Robertsonian fusions/fissions and inversions seem to be important modifiers of phyllostomid karyotypes, and autapomorphic character states are common within species. Macrotus californicus chromosome paints will be a valuable tool for documenting the pattern of karyotypic evolution within Phyllostomidae radiation.

Tracking chromosome evolution in southern African gerbils using flow-sorted chromosome paints

Desmodillus and Gerbilliscus (formerly Tatera) comprise a monophyletic group of gerbils (subfamily Gerbillinae) which last shared an ancestor approximately 8 million years ago; diploid chromosome number variation among the species ranges from 2n = 36 to 2n = 50. In an attempt to shed more light on chromosome evolution and speciation in these rodents, we compared the karyotypes of 7 species, representing 3 genera, based on homology data revealed by chromosome painting with probes derived from flow-sorted chromosomes of the hairy footed gerbil, Gerbillurus paeba (2n = 36). The fluorescent in situ hybridization data revealed remarkable genome conservation: these species share a high proportion of conserved chromosomes, and differences are due to 10 Robertsonian (Rb) rearrangements (3 autapomorphies, 3 synapomorphies and 4 hemiplasies/homoplasies). Our data suggest that chromosome evolution in Desmodillus occurred at a rate of ~1.25 rearrangements per million years (Myr), and that the rate among Gerbilliscus over a time period spanning 8 Myr is also ~1.25 rearrangements/Myr. The recently diverged Gerbillurus (G. tytonis and G. paeba) share an identical karyotype, while Gerbilliscus kempi, G. afra and G. leucogaster differ by 6 Rb rearrangements (a rate of ~1 rearrangement/Myr). Thus, our data suggests a very slow rate of chromosomal evolution in Southern African gerbils.

Management of chronic kidney disease in the elderly

Both chronic kidney disease (CKD) and end-stage renal disease are strongly age related. Although the morbidity and mortality of CKD have significantly improved in recent years because of a greater understanding of its pathophysiology and evidence-based approach to management, the application of this evidence to the elderly CKD patients is often fraught with difficulty. This is because, besides age, the clinical and biological variables that are widely prevalent in the elderly, such as multiple co-morbidities, functional impairments and polypharmacy, and quality of life and functional outcome measures, which are pertinent to this age group, have generally not been incorporated into the available evidence. This paper reviews the current evidence with a view to providing a framework for diagnosing and managing CKD in the elderly. Special references are made to age-related physiological changes in the renal system, assessment of renal function, and management of metabolic complications and end-stage renal disease.

Laser excitation power and the flow cytometric resolution of complex karyotypes

The analytical resolution of individual chromosome peaks in the flow karyotype of cell lines is dependent on sample preparation and the detection sensitivity of the flow cytometer. We have investigated the effect of laser power on the resolution of chromosome peaks in cell lines with complex karyotypes. Chromosomes were prepared from a human gastric cancer cell line and a cell line from a patient with an abnormal phenotype using a modified polyamine isolation buffer. The stained chromosome suspensions were analyzed on a MoFlo sorter (Beckman Coulter) equipped with two water-cooled lasers (Coherent). A bivariate flow karyotype was obtained from each of the cell lines at various laser power settings and compared to a karyotype generated using laser power settings of 300 mW. The best separation of chromosome peaks was obtained with laser powers of 300 mW. This study demonstrates the requirement for high-laser powers for the accurate detection and purification of chromosomes, particularly from complex karyotypes, using a conventional flow cytometer.

Molecular cytogenetic characterization of the genome organization of the 6-banded armadillo (Euphractus sexcinctus)

Xenarthra, as the probable earliest offshoot of the placental tree, represents a key taxon for understanding mammalian phylogeny. To gain further insight into the chromosomal evolution and genome organization of the xenarthrans, we have established the first genome-wide comparative chromosome map between human and the 6-banded armadillo (Euphractussexcinctus, 2n = 58), a basal species on the Xenarthra branch, by reciprocal cross-species chromosome painting. In total, 22 human autosomal paints revealed 41 homologous segments in the euchromatic genome of E. sexcinctus. Our results provide further support for the notion that the 2 human homologous segmental associations, i.e. HSA 2/8 and 7a/10p, could constitute the synapomorphies that unite the xenarthrans. Moreover, we propose that the putative ancestral Xenarthra karyotype closely resemble the 2n = 54 karyotype of the E. sexcinctus, consisting of the equivalents of HSA1p, 1q, 2a, 2b, 2c/8c, 3/21, 4a, 4b/8b, 5, 6a, 6b, 7a/10p, 7b/16p, 8a, 9, 10q, 11, 12a/22a, 12b/22b, 13, 14/15, 16q/19q, 17, 18, 19p, 20, and X. In addition, we have analysed the C-banding patterns of E. sexcinctus, and cloned, FISHmapped and sequenced 7 novel repetitive DNA segments, providing further information on the complexity of genome architecture of E. sexcinctus.

Development of quantitative-fluorescence polymerase chain reaction for the rapid prenatal diagnosis of common chromosomal aneuploidies in 1,000 samples in Singapore

INTRODUCTION

We aimed to develop a rapid quantitative-fluorescence polymerase chain reaction (QF-PCR) to detect common foetal aneuploidies in the Singapore population within 48 hours of sample collection in order to alleviate parental anxiety.

METHODS

DNA from 1,000 foetal samples (978 amniotic fluids, 14 chorion villi and eight foetal blood samples) was analysed using a QF-PCR of 19 microsatellite markers located on chromosomes 13, 18, 21, X and Y. A total of 523 samples were archived before the QF-PCR analysis (archived), while QF-PCR was performed and the results obtained within 48 hours of sample collection in the remaining 477 samples (live). The results were confirmed with their respective karyotypes.

RESULTS

In total, 47 autosomal trisomies (T) were found: 30 among the archived (three T13, 12 T18, 15 T21) and 17 among the live (four T18, 13 T21) samples. The QF-PCR results were verified with their respective karyotypes. We achieved 100 percent sensitivity (lower 95 percent confidence interval [CI], 92.8 percent) and specificity (lower 95 percent CI, 99.5 percent), and the time taken from sample collection to the obtaining of results for the 477 live samples was less than 48 hours.

CONCLUSION

Prenatal diagnostic results of common chromosomal abnormalities can be released within 48 hours of sample collection using QF-PCR. Parental anxiety is alleviated and clinical management is enhanced with this short waiting time.

Avian comparative genomics: reciprocal chromosome painting between domestic chicken (Gallus gallus) and the stone curlew (Burhinus oedicnemus, Charadriiformes)--an atypical species with low diploid number

The chicken is the most extensively studied species in birds and thus constitutes an ideal reference for comparative genomics in birds. Comparative cytogenetic studies indicate that the chicken has retained many chromosome characters of the ancestral avian karyotype. The homology between chicken macrochromosomes (1-9 and Z) and their counterparts in more than 40 avian species of 10 different orders has been established by chromosome painting. However, the avian homologues of chicken microchromosomes remain to be defined. Moreover, no reciprocal chromosome painting in birds has been performed due to the lack of chromosome-specific probes from other avian species. Here we have generated a set of chromosome-specific paints using flow cytometry that cover the whole genome of the stone curlew (Burhinus oedicnemus, Charadriiformes), a species with one of the lowest diploid number so far reported in birds, as well as paints from more microchromosomes of the chicken. A genome-wide comparative map between the chicken and the stone curlew has been constructed for the first time based on reciprocal chromosome painting. The results indicate that extensive chromosome fusions underlie the sharp decrease in the diploid number in the stone curlew. To a lesser extent, chromosome fissions and inversions occurred also during the evolution of the stone curlew. It is anticipated that this complete set of chromosome painting probes from the first Neoaves species will become an invaluable tool for avian comparative cytogenetics.

Refining quantitative fluorescent polymerase chain reaction for prenatal detection of X chromosomal anomalies in the major Southeast Asian populations

INTRODUCTION

This study aimed to refine the current quantitative fluorescent polymerase chain reaction (QF-PCR) screen to detect X chromosome anomalies for prenatal diagnosis in the major Southeast-Asian populations.

METHODS

100 amniotic fluid samples from Chinese, Malay and Indian origins were subjected to QF-PCR using the X chromosome markers, HPRT, X22 and AMXY, along with the autosomal marker D21S1411.

RESULTS

Out of the 100 samples tested by markers X22 and HPRT, eight samples were homozygous for both markers, of which seven were resolved by comparison with the autosomal marker D21S1411.

CONCLUSION

99 percent of samples could be tested for X chromosome copy numbers, increasing the stringency for detection of X chromosome anomalies by QF-PCR. All results were confirmed by cytogenetics.

Report of a female patient with mental retardation and tall stature due to a chromosomal rearrangement disrupting the OPHN1 gene on Xq12

We report on a patient with mental retardation, seizures and tall stature with advanced bone age in whom a de novo apparently balanced chromosomal rearrangement 46,XX,t(X;9)(q12;p13.3) was identified. Using array CGH on flow-sorted derivative chromosomes (array painting) and subsequent FISH and qPCR analysis, we mapped and sequenced both breakpoints. The Xq12 breakpoint was located within the gene coding for oligophrenin 1 (OPHN1) whereas the 9p13.3 breakpoint was assigned to a non-coding segment within a gene dense region. Disruption of OPHN1 by the Xq12 breakpoint was considered the major cause of the abnormal phenotype observed in the proband.

Flow analysis and sorting of microchromosomes (<3 Mb)

BACKGROUND

The analysis and isolation of high numbers of chromosomes smaller than 3 Mb in size (microchromosomes) with good purity is dependent primarily on the detection sensitivity of the flow cytometer and the precision of the sort unit. The aim of this study was to investigate the capability of using a conventional flow cytometer for the detection and sorting at high purity microchromosomes with an estimated size of 2.7 Mb.

METHODS

Chromosomes were isolated from a human cell line containing a pair of X-derived microchromosomes, using a modified polyamine isolation buffer. The chromosome preparation was labeled with Hoechst and Chromomycin and analyzed and purified using a MoFlo sorter (DAKO) configured for high-speed sorting. The purity of the flow-sorted microchromosomes was assessed by reverse chromosome painting.

RESULTS

Improved resolution of the peak of microchromosomes in a bivariate plot of Hoechst versus Chromomycin fluorescence was obtainable after discriminating clumps and debris based on gating data within a FSC versus pulse width plot.

CONCLUSIONS

Chromosomes of smaller size, less than 3 Mb, can be detected with high resolution and flow-sorted with high purity using a conventional flow sorter.

Ultra-high resolution array painting facilitates breakpoint sequencing

OBJECTIVE

To describe a considerably advanced method of array painting, which allows the rapid, ultra-high resolution mapping of translocation breakpoints such that rearrangement junction fragments can be amplified directly and sequenced.

METHOD

Ultra-high resolution array painting involves the hybridisation of probes generated by the amplification of small numbers of flow-sorted derivative chromosomes to oligonucleotide arrays designed to tile breakpoint regions at extremely high resolution.

RESULTS AND DISCUSSION

How ultra-high resolution array painting of four balanced translocation cases rapidly and efficiently maps breakpoints to a point where junction fragments can be amplified easily and sequenced is demonstrated. With this new development, breakpoints can be mapped using just two array experiments: the first using whole-genome array painting to tiling resolution large insert clone arrays, the second using ultra-high-resolution oligonucleotide arrays targeted to the breakpoint regions. In this way, breakpoints can be mapped and then sequenced in a few weeks.

The RASSF1A isoform of RASSF1 promotes microtubule stability and suppresses tumorigenesis

The RASSF1A isoform of RASSF1 is frequently inactivated by epigenetic alterations in human cancers, but it remains unclear if and how it acts as a tumor suppressor. RASSF1A overexpression reduces in vitro colony formation and the tumorigenicity of cancer cell lines in vivo. Conversely, RASSF1A knockdown causes multiple mitotic defects that may promote genomic instability. Here, we have used a genetic approach to address the function of RASSF1A as a tumor suppressor in vivo by targeted deletion of Rassf1A in the mouse. Rassf1A null mice were viable and fertile and displayed no pathological abnormalities. Rassf1A null embryonic fibroblasts displayed an increased sensitivity to microtubule depolymerizing agents. No overtly altered cell cycle parameters or aberrations in centrosome number were detected in Rassf1A null fibroblasts. Rassf1A null fibroblasts did not show increased sensitivity to microtubule poisons or DNA-damaging agents and showed no evidence of gross genomic instability, suggesting that cellular responses to genotoxins were unaffected. Rassf1A null mice showed an increased incidence of spontaneous tumorigenesis and decreased survival rate compared with wild-type mice. Irradiated Rassf1A null mice also showed increased tumor susceptibility, particularly to tumors associated with the gastrointestinal tract, compared with wild-type mice. Thus, our results demonstrate that Rassf1A acts as a tumor suppressor gene.

Prenatal detection of unbalanced chromosomal rearrangements by array CGH

BACKGROUND

Karyotype analysis has been the standard method for prenatal cytogenetic diagnosis since the 1970s. Although highly reliable, the major limitation remains the requirement for cell culture, resulting in a delay of as much as 14 days to obtaining test results. Fluorescent in situ hybridisation (FISH) and quantitative fluorescent PCR (QF-PCR) rapidly detect common chromosomal abnormalities but do not provide a genome wide screen for unexpected imbalances. Array comparative genomic hybridisation (CGH) has the potential to combine the speed of DNA analysis with a large capacity to scan for genomic abnormalities. We have developed a genomic microarray of approximately 600 large insert clones designed to detect aneuploidy, known microdeletion syndromes, and large unbalanced chromosomal rearrangements.

METHODS

This array was tested alongside an array with an approximate resolution of 1 Mb in a blind study of 30 cultured prenatal and postnatal samples with microscopically confirmed unbalanced rearrangements.

RESULTS

At 1 Mb resolution, 22/30 rearrangements were identified, whereas 29/30 aberrations were detected using the custom designed array, owing to the inclusion of specifically chosen clones to give increased resolution at genomic loci clinically implicated in known microdeletion syndromes. Both arrays failed to identify a triploid karyotype. Thirty normal control samples produced no false positive results.

CONCLUSIONS

Analysis of 30 uncultured prenatal samples showed that array CGH is capable of detecting aneuploidy in DNA isolated from as little as 1 ml of uncultured amniotic fluid; 29/30 samples were correctly diagnosed, the exception being another case of triploidy. These studies demonstrate the potential for array CGH to replace conventional cytogenetics in the great majority of prenatal diagnosis cases.

Corrosion behaviour of high copper dental amalgams

This study evaluated the corrosion behaviour of two high copper dental amalgam alloys [Dispersalloy (Dentsply-Caulk) and Tytin (Kerr)] in different electrolytes. Amalgam specimens were prepared, coupled to a copper wire, cemented into glass tubes and polished to a 600-grit finish. A corrosion cell was prepared using a carbon counter-electrode, a standard calomel electrode as the reference and amalgam as the working electrode. The alloys were tested in the following mediums at 37 degrees C: (i) artificial saliva based on Fusayama's solution (FS), (ii) artificial saliva with citric acid adjusted to pH 4.0 (FC) and (iii) 1% sodium chloride solution (SC). Corrosion potentials (E(corr)) and corrosion rates (I(corr)) were determined using potentiostatic and impedance spectroscopy methods. Data was subjected to anova/Scheffe's post hoc test at 0.05 significance level. For both alloys, the corrosion potential in FS was significantly greater than in SC. Corrosion potential of Tytin in FS and SC was also significantly greater than in FC. The corrosion rate of Dispersalloy in FC was significantly greater than in FS and SC. For Tytin, corrosion rate in SC was significantly greater than in FS and FC. Although no significant difference in corrosion potential/rate was observed between the alloys when tested in FS, significant differences were observed when electrochemical testing was carried out in FC and SC. The corrosion behaviour of high copper amalgam alloys are both material and environment dependent. Certain food substances may increase the corrosion of high copper amalgams.

Applications of combined DNA microarray and chromosome sorting technologies

The sequencing of the human genome has led to the availability of an extensive mapped clone resource that is ideal for the construction of DNA microarrays. These genomic clone microarrays have largely been used for comparative genomic hybridisation studies of tumours to enable accurate measurement of copy number changes (array-CGH) at increased resolution. We have utilised these microarrays as the target for chromosome painting and reverse chromosome painting to provide a similar improvement in analysis resolution for these studies in a process we have termed array painting. In array painting, chromosomes are flow sorted, fluorescently labelled and hybridised to the microarray. The complete composition and the breakpoints of aberrant chromosomes can be analysed at high resolution in this way with a considerable reduction in time, effort and cytogenetic expertise required for conventional analysis using fluorescence in situ hybridisation. In a similar way, the resolution of cross-species chromosome painting can be improved and we present preliminary observations of the organisation of homologous DNA blocks between the white cheeked gibbon chromosome 14 and human chromosomes 2 and 17.

Plasminogen activators and inhibitors in normal late pregnancy, postpartum and in the postnatal period

Tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA) and plasminogen activator inhibitors (PAI) are elevated in late pregnancy with t-PA and u-PA remaining so at 6 weeks postnatal. PAI-2 remains at postpartum but was absent by 6 weeks postnatal unlike PAI activity which was absent at postpartum and returned to nonpregnant level at postnatal. The potential fibrinolytic response to stress is much reduced in pregnancy thus increasing the risk of thromboembolism.

Chromosome paints from single copies of chromosomes

We have used OmniPlex library technology to construct chromosome painting probes from single copies of flow sorted chromosomes. We show that this whole genome amplification technology is particularly efficient at amplifying single copies of chromosomes for the production of paints and that single aberrant chromosomes can be analysed in this way using reverse chromosome painting. The efficient generation of painting probes from single copies of sorted chromosomes has the advantage that the probe must be specific for the chromosome sorted and will not suffer from contamination from other chromosomes particularly in situations where flow karyotype peaks are poorly resolved. These initial results suggest that OmniPlex whole genome amplification will be equally effective in other cytogenetic applications where only small amounts of DNA are available, i.e. from single cells or from small pieces of microdissected tissue.

The Alvarado score and acute appendicitis

INTRODUCTION

This is a retrospective study to assess the accuracy of the Alvarado score in predicting appendicitis for patients with right iliac fossa pain.

MATERIALS AND METHODS

This is a retrospective study of consecutive patients with suspected appendicitis. The Alvarado score was computed from the admission notes and correlated with the final outcome of the patient. Patients discharged without surgery were reviewed in the outpatient's clinic to ascertain that they did not need surgery.

RESULTS

There were 148 patients in the study and 63 had appendectomies with intention to treat appendicitis. The normal appendicectomy rate was 21%. The number of patients with score 1-4, 5-6, 7-8 and 9-10 were 46, 40, 44 and 18, respectively, while the number of appendicitis in each group were 0, 2 (5%), 30 (68%) and 18 (100%), respectively. The positive and negative predictive values of Alvarado's scores of 7 or more were 77% and 97.6%, respectively.

CONCLUSION

Alvarado score is a useful tool in the diagnosis of appendicitis, especially at both ends of the scale.

Helicobacter pylori in familial clusters based on antibody profile

Studies have shown a high prevalence of Helicobacter pylori infection in close communities and that intrafamilial spread during early childhood may be a route of transmission. A total of 72 household members from 21 families were enrolled in this study. Sera from individuals showed 50/72 (69.4%) seropositive for IgG against H. pylori by ELISA. Western blots showed diversity in the protein profiles with molecular masses ranging from approximately 8 to 130 kDa. Cohen's kappa statistical analysis of the blot patterns showed that nine families demonstrated similar profiles (100%), while 4 other families showed varying similarities (17-50%). The results support the hypothesis of intrafamilial transmission of H. pylori. Furthermore, serological studies can be used as an effective approach to determine the familial status in relation to H. pylori infection.

Macrophages/microglia as 'sensors' of injury in the pineal gland of rats following a non-penetrative blast

The pineal gland of adult rats was examined immunohistochemically and electron microscopically following exposure of the animals to a single blast equivalent to 110 kg TNT explosive. The most dramatic feature in rats killed at 7, 14 and 21 days after the blast was the upsurge of a large number of macrophages/microglia intensely immunostained with OX-42, OX-18, OX-6 and ED1 antibodies. These antibodies recognise the complement type three (CR3) receptors, major histocompatibility complex class I and class II (MHC I and MHC II) antigens and monocyte/macrophage antigens. Cell counts in OX-42 immunostained sections showed a two-fold increase at these intervals but returned to normal values at 28 days. The immunolabelled cells appeared extremely hypertrophic after the blast when compared with those in normal rats. In the latter and in rats killed at 28 days after the blast, immunoreactive cells were sparsely distributed. Ultrastructural study confirmed a wider occurrence of perivascular macrophages/microglia after the blast and the cells were laden with massive amounts of phagosomes resembling degenerating pinealocyte processes. It is concluded that the seemingly quiescent macrophages/microglia present normally in pineal gland were activated by the external blast force. The induced changes including the increase in cell numbers and endocytosis, however, were reversible in longer surviving animals.

Ultrastructural changes of macroglial cells in the rat brain following an exposure to a non-penetrative blast

The present study examined the ultrastructural changes in astrocytes and oligodendrocytes in rats following an exposure to a non-penetrative blast. At 1 and 7 days after the blast, the astrocytes in the cerebral and cerebellar cortex were hypertrophied; their end-feet associated with the blood vessels were also swollen, bearing sparsely distributed organelles. The above changes were not observed in experimental rats when the survival interval was prolonged. It is concluded from this study that the blast could have disrupted the integrity of the blood-brain barrier resulting in possible abnormal entry of serum-derived substances thereby leading to astrocytic hypertrophy. The reversible nature of the changes is evidenced by the seemingly normal appearance of astrocytes in rats killed at 14, 21 and 28 days after the blast. Oligodendrocytes remained unaffected at various time intervals after the blast.

Studies of the choroid plexus and its associated epiplexus cells in the lateral ventricles of rats following an exposure to a single non-penetrative blast

The choroid plexus in rats exhibited ultrastructural changes following a non-penetrative blast. The immunophenotypic features of epiplexus cells associated with the choroid plexus epithelium were also altered. In rats killed at 1 and 7 days after the blast, the intercellular spaces between the epithelial cells were greatly widened, coupled with the massive eruption and possible extrusion of the apical cytoplasm into the ventricular lumen. Associated with these changes was the passage of some monocytes/lymphocytes across the epithelium. The incidence of such a migratory phenomenon was more frequent in rats killed 7 days after the blast. In rats killed 14 days after the blast, the ultrastructural changes of the epithelial cells became less pronounced. At 21 and 28 days after the blast, the ultrastructure of the choroid plexus was comparable to that of normal specimens. The immunoreactivity of epiplexus cells in terms of their cell number and staining intensity with the monoclonal antibodies OX-42, OX-18, OX-6 and ED1 was noticeably augmented at 7 and 14 days after the blast; this, however subsided at 21 and 28 days. It is concluded that the choroid plexus is extremely sensitive to a blast wave as manifested by its structural alterations and the vigorous expression of CR3 receptors and MHC antigens by the epiplexus cells. It is suggested that a possible immune response might have been triggered in the cerebrospinal fluid ventricular system following the blast.

The response of neurons and microglia to blast injury in the rat brain

Rats subjected to a single non-penetrative blast were examined for possible neuronal damage and glial reaction by immunohistochemistry and electron microscopy. The most dramatic feature in rats killed between 1 and 14 days after the blast was the widespread response of microglial cells in various parts of the brain in which the cells were hypertrophied and their surface antigens, like complement type three receptors (CR3), were upregulated. The blast wave also induced the vigorous expression of major histocompatibility complex (MHC) class I and II (Ia) antigen. In rats killed 21 days after the blast, the elevated immunoreactivity of microglia had subsided and at 28 days both the microglial external morphology and immunoreactivity were comparable to those of normal animals. In rats killed 4-7 days after the blast, the neurons in the cerebral and cerebellar cortex appeared normal except for the occurrence of some 'darkened' dendrites. The incidence of 'darkened' dendrites was most common in rats killed at day 14 but they were absent at 21 and 28 days. Microglial cells were closely associated with some of the 'darkened' dendrites. Results in this study show that a non-penetrative blast in rats provokes a widespread microglial activation suggesting increased endocytosis and immunological responses. However, it remains uncertain whether such a drastic response was a direct activation of the cells by the blast wave or elicited indirectly by some chemical factors released from the damaged brain tissues.

Medical selection of military pilots: a Republic of Singapore Air Force perspective

A comprehensive selection examination in the Republic of Singapore Air Force (RSAF) aims to minimise medical wastage of military pilots who have to function safely in the unnatural environment. Of the 8642 applicants examined, 657 (7.6%) were rejected for non-medical reasons before completion of medical examination. Of the remaining 7778, 58.7% passed the selection examination while 41.3% failed. Ophthalmological (34.3%), anthropometry (23.7%), and ENT (13.7%) conditions were the three major causes for failure (71.7%). Myopia and astigmatism accounted for 57.6% while squints accounted for 22.1% of the ophthalmological conditions. Amongst ENT conditions, 70.8% were for marked vasomotor rhinitis, sinusitis and nasal septum deviation with marked narrowing of one or both nasal passages, while 22.4% were for permanent abnormal hearing threshold shifts above the minimum standards.

Concentration of plasminogen activators and inhibitor in the human endometrium at different phases of the menstrual cycle

The concentrations of tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA) and plasminogen activator inhibitor (PAI-1) have been determined in endometrial curettings obtained from 46 subfertile women during proliferative, early or late secretory phases of the menstrual cycle. t-PA activity and antigen concentrations was significantly higher (P < 0.001) in late secretory endometrium than in proliferative or early secretory endometrium. Higher concentrations of PAI-1 antigen (P < 0.05) were also noted in late secretory phase than in proliferative and early secretory endometrium. However, u-PA concentration was not significantly different and no PAI activity could be demonstrated in the menstrual phases studied. Zymography studies confirmed the presence of both t-PA and u-PA in the endometrium. Ovarian hormonal patterns may therefore influence the activity of plasminogen activators especially of t-PA in the endometrium during various phases of the menstrual cycle.

Plasminogen activators t-PA, u-PA and its inhibitor (PAI) in normal males and females

We determined the plasma levels of tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI) activity and their antigen levels including urokinase plasminogen activator (u-PA) in 33 male and 27 female normal subjects. Males had mean t-PA activity of 0.50 iu/ml which was significantly lower (p less than 0.01) than the females 0.64 iu/ml. Males had higher (p less than 0.001) mean PAI activity (15.5 AU/ml) as compared to females 10.3 AU/ml. The respective mean levels of t-PA and PAI antigen were significantly higher (p less than 0.01) in males (8.1 ng/ml and 17.6 ng/ml) than in females (6.2 ng/ml and 12.1 ng/ml). The mean u-PA level in males was 1.54 ng/ml which was significantly higher (p less than 0.01) than in females with 1.02 ng/ml. In post-venous occlusion studies, females had a greater mean response of 8.6 fold in t-PA activity as compared to males with a mean of 4.5 fold increase. The mean t-PA antigen response in males was 2.0 fold increase as compared to 2.6 fold increase in the females. No significant responses were seen in both sexes in either PAI activity or antigen levels when compared with the resting state. In zymography studies, free t-PA, its inhibitor complexes and u-PA were demonstrated in the euglobulin fractions of stored plasma. This study demonstrates that significant differences in t-PA, u-PA and PAI exist between male and female subjects which should be taken into account when determining their levels in clinical conditions.

A plasmin generation method for the determination of tissue plasminogen activator (t-PA) activity in blood

A plasmin generation method to determine tissue plasminogen activator (t-PA) activity in plasma is described. A protein solution of homogenized fibrin was used as a stimulator in the presence of plasminogen and the plasmin generated was measured by the release of para-Nitroanilide (p-NA) from the chromogenic substrate S-2251. Plasmin generation by 5 iu/mL t-PA in the presence of 1 CU/mL of plasminogen and 850 micrograms/mL of fibrin solution reaches a peak at about 5 h incubation whilst in plasma, plasmin generation peaks after about 16 h incubation. The highest t-PA activity in plasma was determined using an assay involving 18 h incubation. In the 21 subjects studied by this method the t-PA activity at rest ranged from 0.34 to 0.92 iu/mL with a mean of 0.57 +/- 0.15 iu/mL of plasma whilst in the post-occlusion state the activity ranged from 1.12 to 18.0 iu/mL, with a mean of 5.25 +/- 4.49 iu/mL of plasma. We also found that subjects who developed petechiae during occlusion had significantly higher t-PA activity both at pre- and post-occlusion when compared with those who did not develop petechiae. The t-PA activity of acid-treated plasma stored at -70 degrees C showed no significant changes in activity after 12 weeks of storage when compared with the t-PA activity of the same plasma tested prior to storage.

Synchronous primary hepatocellular carcinoma and multiple early gastric cancer--a case report

A rare case of synchronous primary hepatocellular carcinoma and multiple early gastric cancer in a patient is reported. Both the tumours were successfully resected at one operation.

An unusual case of peritonitis

Though peritonitis is a common complication in Continuous Ambulatory Peritoneal Dialysis (CAPD), tuberculous peritonitis has been reported in only twelve CAPD patients in the world English literature to date. Successful outcome in those reported cases involved antituberculous therapy and in the majority, catheter removal and conversion to maintenance haemodialysis. We report in this article our first case of tuberculous peritonitis in a CAPD patient. The diagnosis was made at laparotomy in our patient and she improved with antituberculous therapy. CAPD was continued without interruption. In haemodialysis patients, mortality from tuberculosis is reported to be high due to atypical presentation and delay in diagnosis. To avoid this delay, we recommend that the clinician have high index of suspicion for tuberculous peritonitis in CAPD patients with sterile peritonitis. Early diagnosis carries a good prognosis, and CAPD need not necessarily be discontinued in these patients.

Selective visceral angiography in obscure postoperative gastrointestinal bleeding

Postoperative gastrointestinal bleeding may be difficult to diagnose and treat. Selective visceral angiography localised the bleeding site in seven out of ten episodes of obscure postoperative gastrointestinal haemorrhage, and in two cases radiological embolisation was used successfully to control the bleeding. Angiography, preferably during an episode of haemorrhage, is recommended whenever possible for patients with undiagnosed postoperative gastrointestinal bleeding.