Chlorination for low-cost household water disinfection - A critical review and status in three Latin American countries

Chlorination has historically provided microbiologically safe drinking water in public water supplies. Likewise, chlorine has also been introduced as a low-cost disinfection method in rural and marginalized communities, both at community and household level, as well as during emergencies. Although this practice is common and well established for use as a household water treatment technology in the Global South, several challenges in effective and efficient implementation still need to be addressed. Here, we explored these issues by a literature review and narrowed them to the status of three Latin American countries (Mexico, Colombia, and Brazil). Overall, it was found that although guidance on household-based chlorination includes information on health risks and hygiene, this may not create enough incentive for the user to adapt the method satisfactorily. Physicochemical quality of the water influences chlorination efficiency and it is found that variations in quality are rarely considered when recommending chlorine doses during implementation. These are far more often based on a few measurements of turbidity, thereby not considering dissolved organic matter, or seasonal and day-to-day variations. Other factors such as user preferences, chlorine product quality and availability also represent potential barriers to the sustainable use of chlorination. For chlorination to become a sustainable household water treatment, more focus should therefore be given to local conditions prior to the intervention, as well as support and maintenance of behavioural changes during and after the intervention.

A critical overview of household slow sand filters for water treatment

Household, or point-of-use (POU), water treatments are effective alternatives to provide safe drinking water in locations isolated from a water treatment and distribution network. The household slow sand filter (HSSF) is amongst the most effective and promising POU alternatives available today. Since the development of the patented biosand filter in the early 1990s, the HSSF has undergone a number of modifications and adaptations to improve its performance, making it easier to operate and increase users' acceptability. Consequently, several HSSF models are currently available, including those with alternative designs and constant operation, in addition to the patented ones. In this scenario, the present paper aims to provide a comprehensive overview from the earliest to the most recent publications on the HSSF design, operational parameters, removal mechanisms, efficiency, and field experiences. Based on a critical discussion, this paper will contribute to expanding the knowledge of HSSF in the peer-reviewed literature.

UVC inactivation of MS2-phage in drinking water - Modelling and field testing

UVC disinfection has been recognised by the WHO as an effective disinfection treatment to provide decentralized potable water. Under real conditions there are still unknowns that limit this application including the influence of suspended solids and natural organic matter. This work aims to investigate the influence of two key parameters, suspended solids and natural organic matter, on the efficiency of UVC disinfection of surface water to achieve the drinking water quality requirements established by the WHO for point of use (POU) technologies. Kaolinite (turbidity agent) and humic acids (HA, model of organic matter) were used in a factorial design of experiments (Turbidity from 0 to 5 NTU, and HA from 0 to 3.5 mg/L) to investigate their effect on UVC inactivation of MS2 phage in surface water. A collimated beam (12 W) and a commercial UVC disinfection flow system (16 W) designed to provide drinking water at households were used. The UVC flow system both in the laboratory and in the field was able to achieve the reduction requirements established by WHO (LRV >3.5 for all tested conditions), confirming the good performance of the studied UVC disinfection system. The results found in the lab were used to establish a numerical model that predicts the disinfection rate constant as a function of water turbidity and transmittance at 254 nm (confidence level>95%). The model permitted to elucidate the critical effect of low concentrations of HA in reducing the inactivation rate by 40% for 3.5 mg/L-HA compared with 0, the non-significant detrimental effect of turbidity lower than 5 NTU, and the lack of synergistic effects between both parameters at these levels. The UVC flow system was also tested in the field, in Tzabalho, Chiapas (Mexico), and Antioquia (Colombia), with spiked MS2 into natural surface water. This investigation opens a potential application to monitor the performance of UVC systems with surface water by monitoring transmittance at 254 nm as a tool to control UVC domestic systems to deliver safe drinking water in a household without the need of expensive and laborious biological monitoring tools.

Drinking water treatment by multistage filtration on a household scale: Efficiency and challenges

Universalising actions aimed at water supply in rural communities and indigenous populations must focus on simple and low-cost technologies adapted to the local context. In this setting, this research studied the dynamic gravel filter (DGF) as a pre-treatment to household slow-sand filters (HSSFs), which is the first description of a household multistage filtration scale to treat drinking water. DGFs (with and without a non-woven blanket on top of the gravel layer) followed by HSSFs were tested. DGFs operated with a filtration rate of 3.21 m³ m^-2.d^-1 and HSSFs with 1.52 m³ m^-2.d^-1. Influent water contained kaolinite, humic acid and suspension of coliforms and protozoa. Physical-chemical parameters were evaluated, as well as Escherichia coli, Giardia spp. cysts and Cryptosporidium spp. oocyst reductions. Removal was low (up to 6.6%) concerning true colour, total organic carbon and absorbance (λ = 254 nm). Nevertheless, HMSFs showed turbidity decrease above 60%, E. coli reduction up to 1.78 log, Giardia cysts and Cryptosporidium oocysts reductions up to 3.15 log and 2.24 log, respectively. The non-woven blanket was shown as an important physical barrier to remove solids, E. coli and protozoa.

Predatory bacteria in combination with solar disinfection and solar photocatalysis for the treatment of rainwater

The predatory bacterium, Bdellovibrio bacteriovorus, was applied as a biological pre-treatment to solar disinfection and solar photocatalytic disinfection for rainwater treatment. The photocatalyst used was immobilised titanium-dioxide reduced graphene oxide. The pre-treatment followed by solar photocatalysis for 120 min under natural sunlight reduced the viable counts of Klebsiella pneumoniae from 2.00 × 10⁹ colony forming units (CFU)/mL to below the detection limit (BDL) (<1 CFU/100 μL). Correspondingly, ethidium monoazide bromide quantitative PCR analysis indicated a high total log reduction in K. pneumoniae gene copies (GC)/mL (5.85 logs after solar photocatalysis for 240 min). In contrast, solar disinfection and solar photocatalysis without the biological pre-treatment were more effective for Enterococcus faecium disinfection as the viable counts of E. faecium were reduced by 8.00 logs (from 1.00 × 10⁸ CFU/mL to BDL) and the gene copies were reduced by ∼3.39 logs (from 2.09 × 10⁶ GC/mL to ∼9.00 × 10² GC/mL) after 240 min of treatment. Predatory bacteria can be applied as a pre-treatment to solar disinfection and solar photocatalytic treatment to enhance the removal efficiency of Gram-negative bacteria, which is crucial for the development of a targeted water treatment approach.

Elimination of water pathogens with solar radiation using an automated sequential batch CPC reactor

Solar disinfection (SODIS) of water is a well-known, effective treatment process which is practiced at household level in many developing countries. However, this process is limited by the small volume treated and there is no indication of treatment efficacy for the user. Low cost glass tube reactors, together with compound parabolic collector (CPC) technology, have been shown to significantly increase the efficiency of solar disinfection. However, these reactors still require user input to control each batch SODIS process and there is no feedback that the process is complete. Automatic operation of the batch SODIS process, controlled by UVA-radiation sensors, can provide information on the status of the process, can ensure the required UVA dose to achieve complete disinfection is received and reduces user work-load through automatic sequential batch processing. In this work, an enhanced CPC photo-reactor with a concentration factor of 1.89 was developed. The apparatus was automated to achieve exposure to a pre-determined UVA dose. Treated water was automatically dispensed into a reservoir tank. The reactor was tested using Escherichia coli as a model pathogen in natural well water. A 6-log inactivation of E. coli was achieved following exposure to the minimum uninterrupted lethal UVA dose. The enhanced reactor decreased the exposure time required to achieve the lethal UVA dose, in comparison to a CPC system with a concentration factor of 1.0. Doubling the lethal UVA dose prevented the need for a period of post-exposure dark inactivation and reduced the overall treatment time. Using this reactor, SODIS can be automatically carried out at an affordable cost, with reduced exposure time and minimal user input.

Inactivation and injury assessment of Escherichia coli during solar and photocatalytic disinfection in LDPE bags

Solar disinfection (SODIS) of Escherichia coli suspensions in low-density polyethylene bag reactors was investigated as a low-cost disinfection method suitable for application in developing countries. The efficiency of a range of SODIS reactor configurations was examined (single skin (SS), double skin, black-backed single skin, silver-backed single skin (SBSS) and composite-backed single skin) using E. coli suspended in model and real surface water. Titanium dioxide was added to the reactors to improve the efficiency of the SODIS process. The effect of turbidity was also assessed. In addition to viable counts, E. coli injury was characterised through spread-plate analysis using selective and non-selective media. The optimal reactor configuration was determined to be the SBSS bag (t(50)=9.0min) demonstrating the importance of UVA photons, as opposed to infrared in the SODIS disinfection mechanism. Complete inactivation (6.5-log) was achieved in the presence of turbidity (50NTU) using the SBSS bag within 180min simulated solar exposure. The addition of titanium dioxide (0.025gL(-1)) significantly enhanced E. coli inactivation in the SS reactor, with 6-log inactivation observed within 90min simulated solar exposure. During the early stages of both SODIS and photocatalytic disinfection, injured E. coli were detected; however, irreversible injury was caused and re-growth was not observed. Experiments under solar conditions were undertaken with total inactivation (6.5-log) observed in the SS reactor within 240min, incomplete inactivation (4-log) was observed in SODIS bottles exposed to the same solar conditions.

Comparative in vitro cytotoxicity study of carbon nanotubes and titania nanostructures on human lung epithelial cells

The aim of this study is to assess in vitro cytotoxic effects of titania nanostructures and carbon nanotubes (CNTs) by exposing A549 lung epithelial cell line to these materials. Titania nanotubes (TiNTs) were grown by hydrothermal treatment of TiO(2) nanoparticles, followed by annealing them at 400°C. The titania nanostructures obtained on annealing (mixture of nanotubes and nanorods) were hollow and open ended, containing 3-5 layers of titania sheets, with an internal diameter ∼3-5 nm and external diameter ∼8-10 nm, and a specific surface area of 265 m(2)/g. As-supplied single walled (SWCNTs) and microwave plasma enhanced chemical vapour deposition (MPCVD) grown multi walled carbon nanotubes (MWCNTs) were used in this study. The lengths and diameters of the SWCNTs were 5-10nm and 0.5-3 nm respectively. The lengths and diameters of the MWCNTs were 25-30 μm and 10-30 nm respectively. The cell viability was evaluated using the MTT (3-(4,-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium) assay. No significant cytotoxic effects of titania nanostructures were observed over a period of a week of testing time, while the presence of CNTs in some cases demonstrated significant cytotoxic effects. Finally, possible reason of cytotoxicity is discussed in the light of microstructures of materials.

Photocatalytic inactivation of Cryptosporidium parvum on nanostructured titanium dioxide films

Control of waterborne gastrointestinal parasites represents a major concern to water industries worldwide. In developed countries, pathogens in drinking water supplies are normally removed by sand filtration followed by chemical disinfection. Cryptosporidium spp. are generally resistant to common disinfection techniques and alternative control strategies are being sought. In the current study, the photocatalytic inactivation of C. parvum oocysts was shown to occur in buffer solution (78.4% after 180 min) and surface water (73.7% after 180 min). Viability was assessed by dye exclusion, excystation, direct examination of oocysts and a novel gene expression assay based on lactate dehydrogenase 1 (LDH1) expression levels. Collectively, this confirmed the inactivation of oocysts and scanning electron microscopy (SEM) confirmed cleavage at the suture line of oocyst cell walls, revealing large numbers of empty (ghost) cells after exposure to photocatalytic treatment.

Electrochemical growth of titanium oxide nanotubes: the effect of surface roughness and applied potential

Aligned titanium dioxide nanotubes may be grown on the surface of titanium metal by electrochemical oxidation in the presence of fluoride ion. There are a number of salient parameters that have been reported to affect the nanotube growth i.e., the nature, pH and concentration of the fluoride electrolyte, the cell potential and process time for anodisation. Furthermore, it has been reported that the nanotubes as grown are amorphous and can be converted to a mixture of anatase and rutile crystalline phases by heat treatment at elevated temperatures. There have been no studies reported investigating the effect of surface roughness of the parent titanium metal on nanotube growth. In this work the electrochemical growth of titanium oxide nanotubes on titanium foil was investigated using an ammonium fluoride/ammonium sulphate electrolyte. The results confirm that the anodisation potential controls pore diameter. The surface coverage of nanotubes was dependent on the surface roughness of the parent titanium metal. AFM measurements on untreated titanium foil showed relatively high microscale roughness and low nanoscale roughness. SEM analysis of these samples showed nanotube growth to be confined to depressions or valleys on the surface and the nanotubes were of uniform pore diameter. Mechanically polishing the surface of the parent titanium decreased the microscale roughness and increased the nanoscale roughness which, resulted in more uniform surface coverage. However, this led to an increased variation in pore diameter and shape of the nanotubes. XRD was used to determine crystal structure before and after annealing at 460 degrees C.

Reprogramming following somatic cell nuclear transfer in primates is dependent upon nuclear remodeling

BACKGROUND

Somatic cell nuclear transfer (SCNT) requires cytoplast-mediated reprogramming of the donor nucleus. Cytoplast factors such as maturation promoting factor are implicated based on their involvement in nuclear envelope breakdown (NEBD) and premature chromosome condensation (PCC). Given prior difficulties in SCNT in primates using conventional protocols, we hypothesized that the ability of cytoplasts to induce nuclear remodeling was instrumental in efficient reprogramming.

METHODS

NEBD and PCC in monkey (Macaca mulatta) SCNT embryos were monitored by lamin A/C immunolabeling.

RESULTS

Initially, a persistent lamin A/C signal from donor cell nuclei after fusion with cytoplasts was observed indicative of incomplete NEBD following SCNT and predictive of developmental arrest. We then identified fluorochrome-assisted enucleation and donor cell electrofusion as likely candidates for inducing premature cytoplast activation and a consequent lack of nuclear remodeling. Modified protocols designed to prevent premature cytoplast activation during SCNT showed robust NEBD and PCC. Coincidently, over 20% of SCNT embryos reconstructed with fetal fibroblasts progressed to blastocysts. Similar results were obtained with other somatic cells. Reconstructed blastocysts displayed patterns of Oct-4 expression similar to fertilized embryos reflecting successful reprogramming.

CONCLUSIONS

Our results represent a significant breakthrough in elucidating the role of nuclear remodeling events in reprogramming following SCNT.

Mutations in bile salt export pump (ABCB11) in two children with progressive familial intrahepatic cholestasis and cholangiocarcinoma

Fatal peripheral cholangiocarcinoma developed in 2 girls with progressive familial intrahepatic cholestasis, ABCB11 mutations, and absent bile salt export pump (BSEP) expression. BSEP deficiency may cause cholangiocarcinoma through bile-composition shifts or bile-acid damage within cells capable of hepatocytic/cholangiocytic differentiation. This observation suggests the need for hepatobiliary-malignancy surveillance and early consideration for liver transplantation.

Results of an analysis of cardiac function in 2,812 patients treated with lapatinib

583

Background: Lapatinib is an orally bioavailable reversible, dual tyrosine kinase ErbB1 and ErbB2 inhibitor. Trastuzumab, an ErbB2 inhibitor, has been associated with cardiotoxicity. Methods: Left ventricular ejection fraction (LVEF) was monitored every 8 weeks using MUGA or echocardiogram. Cardiac risk factors including age, underlying cardiovascular disease, previous exposure to AC, trastuzumab, or mediastinal/left sided radiation (XRT) were also collected. LVEF data were evaluated for ≥ NCI CTC grade 3, or ≥ 20% decline relative to baseline (& below institutional LLN). Results: 1.3%, 37 of the 2812 subjects who have received lapatinib in all trials to date have experienced decreased LVEF. 22 of 37 patients received lapatinib monotherapy, the remaining 15 received lapatinib in combination with other chemotherapeutic agents. 68% (25/37) of patients were female, median age was 59 years. Decreased LVEF occurred within 9 weeks of treatment onset in 68% of cases. The event resolved/improved in 57% of cases: in 50% of these, lapatinib treatment was continued. Average event duration was 5 weeks. Four of 37 patients were symptomatic (0.1% incidence). Most symptomatic events responded promptly to standard CHF therapy. The majority of patients (92%, 34/37) had confounding factors that may have contributed to the event, including previous exposure to AC, trastuzumab or XRT, and/or medical history. 8 of 34 patients had a positive lapatinib dechallenge (LVEF recovered): 3 were symptomatic (signs of CHF) and 5 asymptomatic. 3 patients had no contributing factors: 1 experienced symptomatic decreased LVEF, the remaining 2 died due to disease progression whilst LVEF decrease was ongoing. 16 of 1307 patients participating in placebo controlled studies experienced decreased LVEF. Of these 8 are known to have received lapatinib, giving an incidence of 1.2% (8/654). Conclusions: Lapatinib-associated LVEF decrease is rarely symptomatic and generally reversible/non-progressive. Incidence was 1.3% in our population, less than the 3–6% incidence of asymptomatic LVEF decreases observed in the general population. Pharmacogenetic studies are ongoing to determine whether there is a link between ErbB2 polymorphisms and lapatinib cardiotoxicity.

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An impedimetric sensor for monitoring the growth of Staphylococcus epidermidis

There is a need for accurate, reliable methods of detecting bacteria for a range of applications. One organism that is commonly found in urinary catheter infections is Staphylococcus epidermidis. Current methods to determine the presence of an infection require the removal of catheters. An alternative approach may be the use of in vivo sensing for bacterial/biofilm detection. This work investigates electrical impedance spectroscopy to detect the growth of Staphylococcus epidermidis RP62A on gold electrodes fabricated on a flexible substrate. Impedance spectra measured during biofilm formation on the electrode surface showed an increase in charge transfer resistance (RCT) with time.

Nuclear reprogramming by xenopus oocytes

The aim of this contribution is to relate amphibian nuclear transplantation work to prospects for stem cell creation and hence to the long-term aim of cell replacement in humans. The methods used include the transplantation of single somatic cell nuclei to enudeated unfertilized eggs of Xenopus, and also the transfer of multiple somatic cell nuclei to the nucleus (germinal vesicle) of a growing ovarian oocyte. A key difference between these types of recipient cell is that eggs immediately induce DNA replication in transplanted nuclei, whereas an oocyte induces no DNA replication, but directly reprograms an injected nucleus to a new pattern of transcriptional activity. We summarize the extent and success of past and current nuclear reprogramming in experiments with enucleated frog eggs, and also those carried out with growing oocytes. We discuss possible mechanisms of nuclear reprogramming, and the possible contribution of such knowledge for stem cell creation and cell replacement in humans.

Monitoring genotoxicity during the photocatalytic degradation ofp-nitrophenol

p-Nitrophenol is a common structural unit of many pesticides and was chosen as a model compound to monitor genotoxicity during photocatalytic degradation. The genotoxicity of p-nitrophenol (PNP) and its breakdown products was measured using a bioluminescent bacterial bioassay, Vitotox. The genotoxic potential decreased with the concomitant photocatalytic degradation of the parent PNP concentration. The rate of genotoxicity reduction was slower than the rate of removal of the parent PNP, due to the formation of genotoxic by-products. After 6 h of photocatalytic treatment the total genotoxicity was removed. These results indicate that bioassays can be used as a simple and highly sensitive method for monitoring the general toxicity of chemical pollutants before, during and after photocatalytic treatment or other destructive processes.

Rapid loss of estrogenicity of steroid estrogens by UVA photolysis and photocatalysis over an immobilised titanium dioxide catalyst

The presence of low levels of natural and synthetic steroid estrogens in the aquatic environment, and their biological effects on aquatic organisms, are presently issues of concern. In this study, we investigated the temporal removal of estrogenic activity of several potent and environmentally relevant steroid estrogens by photocatalysis over an immobilised titanium dioxide (TiO2) catalyst. We used a recombinant yeast assay to measure estrogenic activity, which provided detection limits within the reactor of 53 ng/l for 17beta-estradiol and 17alpha-ethinylestradiol, and 100 ng/l for estrone. Pseudo-first-order kinetic data showed that photocatalysis over titanium dioxide was equally effective at removing the estrogenic activity of all three steroid substrates in aqueous solutions (initial concentrations of 10 microg/l) with a 50% reduction in estrogenicity within 10 min. In control experiments without TiO2 catalyst, the rate of UVA photolysis of the steroid substrates varied, but was most effective with 17alpha-ethinylestradiol followed by estrone, and was least effective with 17beta-estradiol (0.42, 0.2 and < 0.1 times the rate achieved with photocatalysis, respectively). The application of photocatalysis for the removal of steroid compounds within STW effluent released into the aquatic environment is discussed.

Nuclear reprogramming and stem cell creation

The transplantation of a somatic cell nucleus to an enucleated egg results in a major reprogramming of gene expression and switch in cell fate. We review the efficiency of nuclear reprogramming by nuclear transfer. The serial transplantation of nuclei from defective first-transfer embryos and the grafting of cells from such embryos to normal host embryos greatly increases the proportion of nuclei that can be seen to have been reprogrammed. We discuss possible reasons for the early failure of most nuclear transfers from differentiated cells and describe the potential value of growing oocytes, rather than unfertilized eggs, as a source of nuclear reprogramming molecules and for the eventual identification of these molecules. Nuclear transfer provides a possible route for the creation of stem cells from adult somatic cells.

The first half-century of nuclear transplantation

Fifty years after Briggs and King first succeeded in obtaining normal tadpoles from transplanted embryo nuclei in vertebrates, two general principles have emerged from work in amphibia and mammals. One is the conservation of the genome during cell differentiation. A small percentage of adult or differentiated cells have totipotent nuclei, and a much higher percentage of cells committed to one pathway of cell differentiation have multipotent nuclei. The other is the remarkable reprogramming capacity of cell, and especially egg, cytoplasm. The eventual identification of reprogramming molecules and mechanisms could facilitate a route toward cell replacement therapy in humans.

Oxidative stress and heart failure

Despite advances in treatment, chronic congestive heart failure carries a poor prognosis and remains a leading cause of cardiovascular death. Accumulating evidence suggests that reactive oxygen species (ROS) play an important role in the development and progression of heart failure, regardless of the etiology. Under pathophysiological conditions, ROS have the potential to cause cellular damage and dysfunction. Whether the effects are beneficial or harmful will depend upon site, source and amount of ROS produced, and the overall redox status of the cell. All cardiovascular cell types are capable of producing ROS, and the major enzymatic sources in heart failure are mitochondria, xanthine oxidases and the nonphagocytic NADPH oxidases (Noxs). As well as direct effects on cellular enzymatic and protein function, ROS have been implicated in the development of agonist-induced cardiac hypertrophy, cardiomyocyte apoptosis and remodelling of the failing myocardium. These alterations in phenotype are driven by redox-sensitive gene expression, and in this way ROS may act a potent intracellular second messengers. Recent experimental studies have suggested a possible causal role for increased ROS in the development of contractile dysfunction following myocardial infarction and pressure overload, however the precise contribution of different cellular and enzymatic sources involved remain under investigation.

A reliable method for total RNA extraction from frozen human bone marrow samples taken at diagnosis of acute leukaemia

This report describes a newly developed method using Trizol LS reagent that can reliably extract high quality total RNA from frozen human leukaemic bone marrow samples. Extraction of total RNA from 71 frozen leukaemic bone marrow samples obtained at the time of diagnosis produced a median yield of 145 micro g/ml leukaemic bone marrow. Total RNA samples could be reverse transcribed into cDNA and used successfully in the reverse transcription polymerase chain reaction amplification of B2M transcripts in 68 of 71 cases. A multivariate linear regression analysis revealed that significant predictors of RNA yield were both sample volume (< 1 ml v > 1 ml; p = 0.003) and peripheral blood white cell count (< 5 x 10(9) v >or= 5 x 10(9) white blood cells/litre; p = 0.011). The percentage of blasts present, leukaemia subtype, and sample storage period at -80 degrees C (up to 945 days) were not predictors of total RNA yield. This method of total RNA extraction should be of interest to diagnostic and research staff using frozen bone marrow samples for molecular analyses. Similarly, the lack of association between sample storage period at -80 degrees C and total RNA yield should be of interest to the administrators of tumour banks housing frozen bone marrow samples.

From intestine to muscle: nuclear reprogramming through defective cloned embryos

Nuclear transplantation is one of the very few ways by which the genetic content and capacity for nuclear reprogramming can be assessed in individual cells of differentiated somatic tissues. No more than 6% of the cells of differentiated tissues have thus far been shown to have nuclei that can be reprogrammed to elicit the formation of unrelated cell types. In Amphibia, about 25% of such nuclear transfers form morphologically abnormal partial blastulae that die within 24 h. We have investigated the genetic content and capacity for reprogramming of those nuclei that generate partial blastulae, using as donors the intestinal epithelium cells of feeding Xenopus larvae. We have analyzed single nuclear transplant embryos obtained directly from intestinal tissue, thereby avoiding any genetic or epigenetic changes that might accumulate during cell culture. The expression of the intestine-specific gene intestinal fatty acid binding protein is extinguished by at least 10(4) times, within a few hours of nuclear transplantation. At the same time several genes that are normally expressed only in early embryos are very strongly activated in nuclear transplant embryos, but to an unregulated extent. Remarkably, cells from intestine-derived partial blastulae, when grafted to normal host embryos, contribute to several host tissues and participate in the normal 100-fold increase in axial muscle over several months. Thus, cells of defective cloned embryos unable to survive for more than 1 day can be reprogrammed to participate in new directions of differentiation and to maintain indefinite growth, despite the abnormal expression of early genes.

The role of the coiled-coil motif in interactions mediated by TPD52

TPD52 (D52)-like proteins are small coiled-coil motif-bearing proteins first identified through their expression in human breast carcinoma that mutually interact in hetero- and homomeric fashions. However, it has been unclear whether the coiled-coil motif is sufficient, or even necessary, for these interactions to occur. We have therefore examined the binding activities of a panel of C-terminally deleted D52 proteins in both the yeast two-hybrid system and pull-down assays. In the yeast two-hybrid system, interactions were only detected when regions C-terminal to the coiled-coil motif were also present. However, using pull-down assays, interactions were detected for all deletion mutants which included the coiled-coil motif. This suggests that the coiled-coil motif is indeed necessary for interactions mediated by D52 proteins, but that C-terminal protein regions facilitate and/or stabilize these interactions.

Identification of MAL2, a novel member of the mal proteolipid family, though interactions with TPD52-like proteins in the yeast two-hybrid system

The TPD52 (tumor protein D52)-like proteins are small coiled-coil motif-bearing proteins which were first identified though their expression in human breast carcinoma. TPD52-like proteins are known to interact in hetero-and homomeric fashions, but there are no known heterologous binding partners for these proteins. We now report the cloning of a novel member of the MAL proteolipid family, named MAL2, though its interaction with a TPD52L2 bait in a yeast two-hybrid screen. MAL2 is predicted to be 176 residues (19 kDa) with four transmembrane domains and is 35.8% identical to MAL, a proteolipid required in apical vesicle transport. The MAL2 prey bound all TPD52-like baits tested in the yeast two-hybrid system and in vitro translation of MAL2 produced a single 19-kDa (35)S-labeled protein which specifically bound full-length GST-Tpd52 in GST pull-down assays. The gene MAL2, which was localized to human chromosomal band 8q23 and shown to consist of four exons, is predominantly expressed in human kidney, lung, and liver. Our study has therefore identified a novel member of the MAL proteolipid family and potentially implicates TPD52-like proteins in vesicle transport.

The hD52 (TPD52) gene is a candidate target gene for events resulting in increased 8q21 copy number in human breast carcinoma

Chromosome band 8q21 is frequently overrepresented in human cancer, but to date no 8q21 target gene has been proposed. The hD52 (TPD52) gene is of potential significance in breast and other cancers due to its location and expression pattern. Fine mapping of hD52 placed this locus within the peak of the 8q21 amplicon delineated in the SK-BR-3 breast carcinoma cell line, and a positive association between hD52 gene dosage and transcript levels was subsequently demonstrated in four breast carcinoma cell lines, including SK-BR-3. Increased copy number (ICN) was measured using Southern blot analyses in 3/32 human breast carcinomas at hD52, and the related hD54 gene in 20q13.2-q13.3. Subsequent immunohistochemical analysis of hD52 expression in 19 breast carcinomas with varying hD52 gene dosages demonstrated a significant positive association between hD52 dosage and hD52 expression using a Spearman rank correlation coefficient (r(s) = 0.573, alpha = 0.01) and a Wilcoxon rank-sum test (alpha = 0.05). On the basis of its map location and expression pattern in breast carcinoma, we therefore propose hD52 as a candidate target gene at chromosome band 8q21.

Identification and in situ hybridization mapping of a mouse Tpd52l1 (D53) orthologue to chromosome 10A4-B2

We report the identification of a mouse cDNA Tpd52l1 (tumor protein D52-like 1), which represents the first demonstrated orthologue of the human TPD52L1 (alias D53) gene, a member of the breast carcinoma-associated TPD52 (alias D52) gene family. In situ hybridization mapping located the Tpd52l1 gene to chromosome 10A4-10B2. Since the TPD52L1 gene is found at human chromosome 6q22-->q23, the mouse and human TPD52L1 loci are syntenically conserved.

A developmental bias in reading frame usage by human fetal thymic TCRBDJ transcripts is not present in genomic TCRBDJ rearrangements

We have previously reported that reading-frame usage and functional diversification is developmentally regulated, with virtually all TCRB DJ mRNA transcripts using a single reading frame at 8 weeks of gestational age, tapering to 50% by adult life. We used the polymerase chain reaction to create genomic libraries of DJ rearrangements in the TCRB locus from thymuses at 7.7, 10, and 16 weeks of gestational age, and from adult thymuses. Clones were randomly picked and sequenced to determine junctional sequences and reading-frame utilization. The resulting data address the hypothesis that cells bearing genomic joints in reading frame one are preferentially selected during fetal life. This hypothesis predicts that reading-frame bias would also be observed among genomic DJ joints. Instead, we observed random utilization of the three possible D-region reading frames among genomic D1s1 ==> J1s1 joints during fetal life. Similar results were obtained at 7.7 weeks of gestational age in a second thymus in which both RNA and DNA were simultaneously isolated and used to create libraries of TCRBDJ transcripts or rearrangements. We conclude that reading-frame utilization is random among genomic D1s1-JB1s1 rearrangements and that the preferential usage of a single reading frame among mRNA transcripts of TCRB DJ transcripts is the result of preferential transcription of genomic TCRB DJ joints in a single reading frame, or that TCRB DJ transcripts have a longer half-life than transcripts in reading frames two or three.

Cloning of a third member of the D52 gene family indicates alternative coding sequence usage in D52-like transcripts

D52 proteins are emerging as signalling molecules which may be regulators of cell proliferation. Having previously reported the existence of the human D52 gene family, comprising the hD52 and hD53 genes expressed in human breast carcinoma, we report the identification of a novel human gene hD54 (TPD52L2), which represents a third D52 gene family member. In situ mapping placed the hD54 gene on human chromosome 20q13.2-q13.3, a localization distinct from those of both hD52 and hD53 genes. The identified hD54 cDNAs predicted three hD54 isoforms, suggesting that alternatively-spliced transcripts may be produced from D52-like genes. This was confirmed by directly sequencing reverse transcriptase-polymerase chain reaction (RT-PCR) products amplified from D52-like gene transcripts expressed in developing and adult rat tissues, and by performing sequence analyses of the expressed sequence tag divisions of nucleotide databases. Alternative splicing of sequences encoding two regions, termed ins2 and ins3, was identified in one or more D52-like genes, with these alternative splicing events being differentially regulated. The functional consequences of alternative splicing were examined by characterizing the protein-protein interactions mediated by a truncated hD53 isoform within the yeast two-hybrid system. This hD53 isoform displayed altered interaction capabilities with respect to those of full-length hD53, suggesting that alternative splicing within the D52 gene family functions in part to alter the protein-protein interaction capabilities of encoded isoforms.

Identification of homo- and heteromeric interactions between members of the breast carcinoma-associated D52 protein family using the yeast two-hybrid system

The hD52 gene was originally identified through its elevated expression level in human breast carcinoma. Cloning of D52 homologues from other species has indicated that D52 may play roles in calcium-mediated signal transduction and cell proliferation. Two human homologues of hD52, hD53 and hD54, have also been identified, demonstrating the existence of a novel gene/protein family. Since D52-like protein sequences are all predicted to contain a coiled-coil domain, we used the yeast two-hybrid system and glutathione S-transferase pull-down assays to investigate whether homo- and/or heteromeric interactions occur between D52-like proteins. Analyses of yeast strains co-transfected with paired D52-like constructs indicated that D52-like fusion proteins interact in homo- and heteromeric fashions through their predicted coiled-coil domains. Similarly, extensive two-hybrid screenings of a human breast carcinoma expression library identified hD53 and hD52 as potential interactors for both hD52 and hD53 baits. Thus, D52-like proteins appear to exert and/or regulate their activities through specific interactions with other D52-like proteins, which in turn may be intrinsic to potential roles of these molecules in controlling cell proliferation.

Definition of the tumor protein D52 (TPD52) gene family through cloning of D52 homologues in human (hD53) and mouse (mD52)

Cloning is reported of a cDNA homologue to the breast carcinoma-associated D52 cDNA, termed D53, and of a mouse D52 cDNA (HGMW-approved symbols TPD52L1 and TPD52). Human D53 and mouse D52 proteins are predicted to be 52 and 86% identical to human D52, respectively. Analysis of the three protein sequences identified a coiled-coil domain and N- and C-terminally located PEST domains in each. The conservation of homology between the D52 and the D53 sequences, combined with a lack of homology between these and known proteins, defines a new mammalian gene/protein family, the D52 family. The human D52 locus has been previously mapped to chromosome 8q21, and using in situ mapping in the present study, a human D53 locus was mapped to chromosome 6q22-q23. We observed coexpression of the human D52 and D53 genes in some breast tumors and derivative cell lines and found that maintenance of D52 and D53 transcript levels in estrogen receptor-positive MCF7 breast carcinoma cells depends upon estradiol. However, D52 and D53 genes were specifically expressed in HL-60 and K-562 leukemia cells, respectively, with 12-O-tetra-decanoylphorbol-13-acetate treatment decreasing D52 and D53 transcript levels in these cell lines. The presence of a coiled-coil domain, combined with observed co- or independent expression of the D52 and D53 genes, suggests that D52 and D53 proteins may be capable of hetero- and/or homodimer formation.

Stromelysin-3 in the biology of the normal and neoplastic mammary gland

Stromelysin-3 (ST3) is an extracellular proteinase predominantly expressed in fibroblasts. The particular structural features and in vitro functions of this molecule suggest it could be the first member of a new subgroup of the matrix metalloproteinase family. ST3 is transiently expressed during mammary gland post-weaning involution, embryonic implantation, various organogeneses, and during amphibian metamorphosis. Moreover, ST3 is expressed in a panel of human invasive carcinomas including breast, colon, and head and neck carcinomas. Almost all ST3-expressing tissues show intense extracellular matrix remodeling activities including the loss of basement membrane integrity. Thus, either directly, or indirectly in association with other proteinases, ST3 might be involved in tissue remodeling processes occurring in both physiological and pathological processes. In vitro and in vivo studies using malignant cells stably transfected in such a way as to modulate their ST3 expression levels indicate that ST3 modifies neither cell proliferation nor invasive properties, but rather favors tumor cell survival in host tissues. This hypothesis is consistent with clinical data showing that ST3 expression could be predictive of tumor progression leading to metastases.

A screening method to identify genes commonly overexpressed in carcinomas and the identification of a novel complementary DNA sequence

We describe a differential screening method for cDNA libraries which used a combination of subtracted and PCR-amplified cDNA probes, and which can be applied to the selection of genes expressed in multiple tissues. This technique was used to identify genes commonly overexpressed in breast and basal cell carcinomas. These represent stromally dependent, invasive tumors with and without metastatic capacity. Thus, this screening sought to identify genes involved in the early stages of tumor progression. We identified a total of 16 genes, including c-erbB-2 and tissue inhibitor of metalloproteinases 3 whose products have been implicated in tumorigenesis or invasion. We also identified a novel sequence (D52) showing little homology with others described in any species, which maps to the human chromosomal band 8q21. In situ RNA hybridizations of breast carcinoma sections indicated that the D52 gene was expressed in cancer cells, whereas other genes identified in the differential screening were expressed in fibroblastic or inflammatory cells within the tumor stroma. Thus, the procedure developed in this study selected genes expressed in a diversity of cell types, indicating its potential usefulness in other systems.

The tissue inhibitor of metalloproteinases-3 gene in breast carcinoma: identification of multiple polyadenylation sites and a stromal pattern of expression

BACKGROUND

Tissue inhibitor of metalloproteinases-3 (TIMP3) is the third member of the TIMP family of proteins, believed to play a significant role in controlling extracellular matrix remodeling.

MATERIALS AND METHODS

Differential screening of a human breast carcinoma cDNA library using substracted and PCR-amplified cDNA probes identified a 4.6-kb TIMP3 cDNA, which was used for further cDNA library screenings, Northern blot hybridizations, and the synthesis of riboprobes for in situ RNA hybridization analyses.

RESULTS

The 4.6-kb full-length TIMP3 cDNA contains 3.7 kb of 3'-untranslated sequence. Additional TIMP3 cDNAs subsequently identified were colinear with the original sequence, but revealed use of four different polyadenylation signals within the 3'-untranslated region, which accounted for the 4.6-, 2.7-, 2.5-, and 2.1-kb TIMP3 transcripts noted in this and in previous studies. In situ RNA hybridizations demonstrated that in breast carcinoma the TIMP3 gene was predominantly expressed by fibroblastic cells within the tumor stroma adjacent to cancer cells. TIMP3 transcripts were also strongly detected in fibroblastic decidual cells of pregnant endometrium.

CONCLUSIONS

Modulating the length of the 3'-untranslated region may represent a mechanism by which TIMP3 gene expression is controlled in tissues. The strong expression of the TIMP3 gene by fibroblastic cells in breast carcinoma supports the importance of tumor stroma as a source of factors influencing human carcinoma growth and progression.

A novel subpopulation of primed T cells in the human fetus

Virgin and memory T cells reciprocally express high levels of the RA or the RO isoforms of CD45, respectively. In an examination of T cell expression of these two CD45 isoforms during human development, the RO+RA- "memory" T cells were infrequent in the newborn blood and spleen, but comprised approximately half of the T cells in adult tissues. These anticipated findings probably reflect the immunologic naivete of the newborn. Surprisingly, however, RO+RA- T cells were relatively abundant in fetal spleen and in cord blood samples from premature births, comprising approximately 25% and 10% of the T cells in these tissues, respectively. This early peripheral wave of RO+RA- T cells was composed of polyclonal T cells in both the CD4 and CD8 subpopulations. The fetal RO+ cells of CD4+ phenotype frequently expressed the CD25-alpha chain subunits that characterize high affinity IL-2 receptors, and were able to proliferate in response to exogenous IL-2. In further contrast with their RO+ memory T cell counterparts in adults, the fetal T cells were unresponsive to mitogenic anti-CD2 and anti-CD3 antibodies. We conclude that the data suggest an embryonic population of autoreactive T cell clones with anergic characteristics.

A novel subpopulation of primed T cells in the human fetus

Virgin and memory T cells reciprocally express high levels of the RA or the RO isoforms of CD45, respectively. In an examination of T cell expression of these two CD45 isoforms during human development, the RO+RA- "memory" T cells were infrequent in the newborn blood and spleen, but comprised approximately half of the T cells in adult tissues. These anticipated findings probably reflect the immunologic naivete of the newborn. Surprisingly, however, RO+RA- T cells were relatively abundant in fetal spleen and in cord blood samples from premature births, comprising approximately 25% and 10% of the T cells in these tissues, respectively. This early peripheral wave of RO+RA- T cells was composed of polyclonal T cells in both the CD4 and CD8 subpopulations. The fetal RO+ cells of CD4+ phenotype frequently expressed the CD25-alpha chain subunits that characterize high affinity IL-2 receptors, and were able to proliferate in response to exogenous IL-2. In further contrast with their RO+ memory T cell counterparts in adults, the fetal T cells were unresponsive to mitogenic anti-CD2 and anti-CD3 antibodies. We conclude that the data suggest an embryonic population of autoreactive T cell clones with anergic characteristics.

The direct clinical examination: an alternative method for the assessment of clinical psychiatry skills in undergraduate medical students

Because of dissatisfaction with the traditional long case procedure as a method of examining the clinical competence of medical students undertaking a psychiatry term, an alternative 'direct' method whereby two examiners observe the interaction between student and patient has been developed and is described. This method of examining allows the examiners to set and evaluate case-specific tasks. It is demonstrated that the two examiners achieve satisfactory interrater reliability both with respect to the mark awarded and the difficulty the patient presents and that, as one would wish, these two measures do not correlate. Students' opinions regarding the examination were assessed pre- and post-examination using visual analogue scales. The students found the examination stressful but rated the method as an appropriate form of clinical assessment both before and after their examination. The method is seen as having several advantages which must be set against the disadvantage of its being relatively expensive of examiners' time.

Three non-overlapping regions of chromosome arm 11p allele loss identified in infantile tumors of adrenal and liver

Tumor and constitutional chromosome arm 11p genotypes were compared in 6 hepatoblastoma (HB) patients and 2 adrenal adenoma (AA) patients, with one HB patient and both AA patients displaying clinical features associated with the Beckwith-Wiedemann syndrome (BWS). Using up to 14 chromosome 11 polymorphic markers, loss of constitutional heterozygosity (LOH) was demonstrated in both AA patients and in 4 of 6 HB patients. This identified three distinct and non-overlapping regions of 11p within which LOH occurred, which were defined as lying distal to the gamma-globin locus (11p15.5), proximal to the gamma-globin locus but distal to 11p13 (LOH being detected at 11p15.1), and restricted to the 11p13 region. Specific LOH within each 11p15 region was observed in HB, and this represents the first demonstration by a single study of LOH clearly affecting separate regions of chromosome band 11p15 in a particular tumor type. One AA showed LOH restricted to 11p13 loci, implicating the involvement of the WT1 gene. The second AA patient presented with genitourinary abnormalities and we therefore examined sequences coding for 3 zinc finger domains of WT1 in both AAs. No point mutations were identified in sequence from either patient. Nonetheless our results indicate that 3 separate 11p loci may be significant in the development of tumors which arise in association with BWS.

The 11p15.5 ribonucleotide reductase M1 subunit locus is not imprinted in Wilms' tumour and hepatoblastoma

We have utilized the polymerase chain reaction (PCR) to amplify a transcribed Taq1 polymorphism in the ribonucleotide reductase M1 subunit (RRM1) gene at chromosome 11p15.5, to investigate whether this locus is subjected to imprinting in embryonal tumours. The polymorphism was amplified from cDNA from 6 Wilms' tumours, one hepatoblastoma and corresponding samples of adjacent kidney or liver from individuals who were constitutionally heterozygous for the polymorphism. Taq1 digestion of PCR products revealed that both alleles were transcribed in all samples where both were present at the genomic level, indicating that the RRM1 locus is not subjected to imprinting in Wilms' tumour or hepatoblastoma.

Equivalent expression of paternally and maternally inherited WT1 alleles in normal fetal tissue and Wilms' tumours

Observations of non-random maternal 11p allele loss in Wilms' tumour (WT) have implied the possible involvement of an imprinted 11p locus in WT aetiology. A proposed 11p13 Wilms' tumour gene, WT1, has recently been isolated and encodes a zinc finger DNA-binding protein, the 3' untranslated region of which contains a polymorphic dinucleotide repeat (CA repeat) motif. We have exploited this transcribed CA repeat to examine the allelic expression pattern of WT1 and thereby determine whether transcriptional imprinting of this gene occurs. DNA and reverse-transcribed RNA from tumours and normal tissue were subjected to the polymerase chain reaction (PCR) using radiolabelled primers flanking the CA repeat. The gene was seen to be expressed from both of the constitutive alleles in 9-week human fetal kidney, all informative Wilm's tumours and neonatal kidney tissue adjacent to the tumours. In one tumour, known to be heterozygous for a point mutation in zinc finger 2, direct sequencing confirmed that both mutant and wild-type transcripts were being expressed. These results demonstrate that this gene is not subject to transcriptional imprinting in tumours or normal fetal kidney.

The M1 subunit of ribonucleotide reductase refines mapping of genetic rearrangements at chromosome 11p15

We report the first use of the ribonucleotide reductase M1 subunit (RRM1) locus as a marker to assist in defining genetic rearrangements at 11p15. Our sample consisted of 21 Wilms' tumors from 18 patients, and one adrenal adenoma from a patient with Beckwith-Wiedemann syndrome, preexisting chromosome 11 maps being refined by the use of the RRM1 locus in all cases. Significantly, one Wilms' tumor showed loss of heterozygosity at the RRM1 locus only, whereas the adrenal adenoma showed a maintenance of heterozygosity at the RRM1 locus, loss having been previously demonstrated at the c-Ha-ras locus. The relevance of this finding to the location of one or more disease-associated loci at 11p15 is discussed.

Short-term expansion of receptive fields in rat primary somatosensory cortex after hindpaw digit denervation

The immediate effect of changing the driving cutaneous input to locations within primary somatosensory cortex (SI) was examined by denervating one or more digits of the rat hindpaw by amputation or local anesthesia. When all or part of a receptive field of a cluster of neurons was denervated, it was found that the cortical location recorded from gained responsiveness to cutaneous stimulation of hindpaw areas bordering the denervated region. In 22 of the 29 animals studied this expansion took place within 5 min of the denervation.

Virgin and memory T cells have different requirements for activation via the CD2 molecule

T cells can be divided into unprimed virgin (T0) and primed memory (T') subpopulations by their expression of different isoforms of the leukocyte common antigen. We have separated the CD4+ T cells into T0 and T' subpopulations and examined their capacity to respond to activation signals via the CD2 receptor molecule. On stimulation with a mitogenic combination of anti-CD2 antibodies, the T' population was induced to express IL-2 receptor, increased levels of the 4F2 antigen and to proliferate, whereas the response of the T0 populations was reflected solely by a minimal increase in the 4F2 antigen. The addition of IL-2 or monocytes to T0 cells stimulated with anti-CD2 antibodies did not enhance their expression of the IL-2 receptor or proliferation. However, T0 cells stimulated with the triad of anti-CD2 antibodies, monocytes, and IL-2 responded with high levels of IL-2 receptor expression and proliferation. The T0 subpopulation could also be induced to respond when cultured with anti-CD2 antibodies and phorbol myristate acetate. The results suggest that in order to respond to stimulation via the CD2 molecule, virgin T helper cells require additional signals that can be jointly provided by monocytes and IL-2. In contrast, memory T helper cells can be activated via CD2 signal transduction alone.

Differential activation requirements for virgin and memory T cells

Most studies of the activation requirements for T cells have used either T cell lines or populations of normal T cells that consist of a mixture of virgin and Ag-primed T cells. These two subpopulations of T cells can now be distinguished in humans by their reactivity with mAb. The anti-CD45R antibody HB10 identifies virgin T cells (T degrees) that are non-reactive to recall Ag and relatively poor at providing help for B cell differentiation. Conversely, memory T cells (T') that can react to recall Ag and enhance Ig production are non-reactive with anti-CD45R, but can be identified with the UCHL1 antibody. We have used these antibodies to separate the T degrees and T' populations and examine their activation requirements. On activation CD45R+ cells rapidly began to lose the CD45R Ag and express the UCHL1 Ag in increased amounts, whereas the UCHL1+ cells retained this phenotype. Both populations responded to PHA in the presence of monocytes, but when triggered by an antibody to CD3 only the T' cells were induced to express IL-2R, produce IL-2, and to proliferate. The T degrees population of cells remained relatively quiescent by all of these parameters. However, anti-CD3 stimulation conditioned the T degrees cells for IL-2 responsiveness, inasmuch as the addition of rIL-2 resulted in significant IL-2R expression and proliferation. When the CD4+ T degrees and CD4+ T' subpopulations were isolated and examined in the same assays similar results were obtained. The data indicate that fundamental differences exist in the triggering requirements for T degrees and T' cells.

Differential activation requirements for virgin and memory T cells

Most studies of the activation requirements for T cells have used either T cell lines or populations of normal T cells that consist of a mixture of virgin and Ag-primed T cells. These two subpopulations of T cells can now be distinguished in humans by their reactivity with mAb. The anti-CD45R antibody HB10 identifies virgin T cells (T degrees) that are non-reactive to recall Ag and relatively poor at providing help for B cell differentiation. Conversely, memory T cells (T') that can react to recall Ag and enhance Ig production are non-reactive with anti-CD45R, but can be identified with the UCHL1 antibody. We have used these antibodies to separate the T degrees and T' populations and examine their activation requirements. On activation CD45R+ cells rapidly began to lose the CD45R Ag and express the UCHL1 Ag in increased amounts, whereas the UCHL1+ cells retained this phenotype. Both populations responded to PHA in the presence of monocytes, but when triggered by an antibody to CD3 only the T' cells were induced to express IL-2R, produce IL-2, and to proliferate. The T degrees population of cells remained relatively quiescent by all of these parameters. However, anti-CD3 stimulation conditioned the T degrees cells for IL-2 responsiveness, inasmuch as the addition of rIL-2 resulted in significant IL-2R expression and proliferation. When the CD4+ T degrees and CD4+ T' subpopulations were isolated and examined in the same assays similar results were obtained. The data indicate that fundamental differences exist in the triggering requirements for T degrees and T' cells.

Morphologic analysis of the interactions between lymphocytic choriomeningitis virus-specific cloned cytotoxic T cells and virus infected targets

The interactions between lymphocytic choriomeningitis virus-specific cloned cytotoxic T lymphocytes (CTL) and virus infected targets have been examined by electron microscopy. CTLs, which were readily differentiated from target cells by the presence of cytoplasmic granular inclusions, made intimate contact with infected cells. Some CTLs contacted infected cells via numerous interdigitating processes; others were observed thrusting finger-like protrusions deep into the target cell; some were seen with their plasma membranes lying closely opposed to that of the infected cell. The majority (55%) of bound CTLs had their Golgi apparatus oriented towards the target cell and 42% of bound CTL had granular inclusions in close proximity to the contact zone. Evidence is presented which suggests that the contents of the granular inclusions are released by CTLs in contact with infected cells. Granules appeared to be released close to the target cell rather than from random sites on the CTL surface. Examination of supernatants from effector-target cell incubation mixtures by negative staining revealed membranes bearing lesions with an internal diameter of approximately 15 nm.