Epidemiology of necrotizing ulcerative gingival lesions in adolescents

OBJECTIVE AND BACKGROUND

Relatively little is known about the epidemiology of necrotizing ulcerative gingival lesions (NUG) in adolescent populations. Most studies have comprised special target groups, such as military recruits, HIV patients, or severely malnourished subjects.

METHODS

A multistage random cluster sampling scheme was used to obtain a sample of 9203 students aged 12-21 years from 98 of a total of 618 high schools in Santiago, Chile. Students were given a clinical oral examination and questionnaire information was obtained on smoking and oral hygiene habits, dental attendance patterns, and diabetic status. The diagnostic criteria for NUG were the presence of necrosis and ulceration of at least one interproximal papillae.

RESULTS

The estimated prevalence of NUG was 6.7% (95% CI = [6.2; 7.3]). A multivariable logistic regression analysis showed that last seeing a dentist more than 1 year ago (OR = 1.60), or never (OR = 1.93), and reporting diabetes (OR = 2.12) showed a significant positive association with the presence of NUG; whereas neither gender nor smoking were important predictors. Students aged 18-21 years were more, albeit statistically insignificantly, likely to have NUG than were younger students (OR = 1.40).

CONCLUSIONS

Our observation that reporting to be diabetic was positively associated with the presence of NUG is interesting, as diabetes has never been addressed as a possible risk factor. As the association between diabetes and periodontitis in adults is thought to relate to impaired function of neutrophils, microangiopathy, and impaired wound healing this finding suggests a significant role of the host response also for the occurrence of NUG.

Domestic scorpion control with pyrethroid insecticides in Mexico

Scorpion stings cause more morbidity in Mexico than any other country, leading to about 100 deaths annually. In 1999, the State of Morelos reported nine deaths among 30663 cases of scorpion sting. To replace lindane used for scorpion control, field trials of pyrethroid pesticides were undertaken in Morelos during 1998-2000 at the village of Chalcatzingo (population initially with 2760 inhabitants and 530 houses). Pre-intervention surveys detected scorpions (Scorpiones: Buthidae) of two species in the majority of houses: Centruroides limpidus limpidus Karsch outnumbering Vaejovis mexicanus smithi Koch. Scorpion prevalence was assessed, pre- and post-spray, directly by searching (40 min/house) and by householder reports of sightings inside houses. Pre-intervention perceptions of scorpion abundance were similar for all areas, with sightings in 12-18% of houses, whereas daytime searches detected more infestations in eastern parts of the village (prevalence 17% indoors, 22% outdoors) than in other sectors (9% indoors, 14% outdoors). Pyrethroids were evaluated as residual treatments in separate sectors of Chalcatzingo, with almost complete coverage indoors and peridomestically, using the following four formulations: bifenthrin 10% wettable powder (WP) applied at 50mg a.i./m2, cyfluthrin 10% WP (Solfac 10 WP) at 44-55 mg a.i./m2, deltamethrin 2.5% suspension concentrate (Biothrin 25 SC) at 11 mg a.i./m2 and 5% WP (K-Othrine 50 WP) at 35 mg a.i./m2. Phase 1 compared bifenthrin 10 WP, Solfac 10 WP and Biothrin 25 SC sprayed in December 1998; phase 2 compared Solfac 10 WP and K-Othrine 50 WP sprayed in June and again in December 2000, with follow-up surveys of scorpions one month post-spray and subsequently. Scorpion prevalence was reduced by 64-77% peridomestically one month post-spray and by 83, 46 and 15% in houses sprayed with cyfluthrin WP, bifenthrin WP or deltamethrin SC, respectively. Householder reports of sighting scorpions indoors were 33-85% below pre-intervention levels. Cumulative effects of the three spray-rounds over 3 years reduced scorpion prevalence by approximately 60% in the deltamethrin WP re-sprayed area and by approximately 90% in the cyfluthrin WP re-sprayed area. Householder sightings also fell by 67 and 28% in the cyfluthrin and delta-methrin re-sprayed areas, respectively. Operational efficacy of these products against scorpions at the dosages applied was ranked as cyfluthrin WP > bifenthrin WP > deltamethrin SC > WP. Reported cases of scorpion sting intoxication fell by 17% during this study after having risen by approximately 40% over four previous years.

Effect of acute cigarette smoking, alone or with alcohol, on gastric barrier function in healthy volunteers

BACKGROUND

Smoking is a risk factor for gastroduodenal ulcer and gastric adenocarcinoma. However, the pathophysiological mechanisms induced by acute cigarette smoking in the human gastric mucosa are poorly understood.

AIM

To evaluate the effect of acute cigarette smoking, alone or with alcohol, on the gastric permeability to sucrose, a specific marker of mucosal damage in the stomach.

SUBJECTS AND METHODS

Twenty healthy volunteers (8 smokers/12 non-smokers) were studied. Each fasted subject ingested 500 ml of a 20% sucrose solution and the amount of sucrose excreted in a 5-hour urine collection was measured by gas chromatography Four sucrose permeability tests were carried out: 1. basal, 2. while smoking 5 cigarettes, 3. after drinking 50 ml of a 40 degrees alcoholic beverage, 4. a combination of 2+3.

RESULTS

Sucrose excretion increased after alcohol ingestion (40.5 +/- 6.0 mg vs 143.1 +/- 28.9 mg, p = 0.002), but was not modified by acute cigarette smoking (34.4 +/- 5.9 mg). When alcohol and cigarettes were simultaneously consumed, the increase in alcohol-induced sucrose excretion was significantly reduced (73.1 +/- 16.6 mg, p = 0.03). Basal sucrose excretion was similar in smokers and non-smokers. However, in acute cigarette smoking, a decrease in sucrose excretion was observed in smokers (p = 0.02) but not in non-smokers.

CONCLUSIONS

These results indicate that acute cigarette smoking may tighten the gastric mucosa in habitual smokers and this is associated with a smaller increase of gastric permeability induced by alcohol.

[The tuberous breast: a review]

The tuberous breast is one of the most challenging problem in breast surgery. Pediatricians, gynaecologists and plastic surgeons are particularly concerned with the treatment of these young patients. A good assessment of the pathology and a precise knowledge of the surgical procedures are keypoints for a successful treatment. A case report will precede a literature overview of this very complex problem.

The need for continuous immunosuppression with cyclosporin A to maintain an experimental model of uveal melanoma

We investigated the need for continuous immunosuppression to maintain experimental tumours derived from human uveal melanoma cells implanted in the choroid of pigmented rabbits. Two groups of pigmented rabbits immunosuppressed with cyclosporin A (CsA) were implanted with human uveal melanoma cells in the suprachoroidal space. After 5 weeks, CsA was discontinued in group 2. Animals were treated with prophylactic antibiotics and examined weekly for tumour growth, weight and secondary effects; blood urea nitrogen levels were measured every two weeks. Autopsies and histopathological studies were performed after death or euthanasia at the end of week 12. The difference between the groups in the development of ophthalmoscopic tumours was not statistically significant 5 weeks after implantation. Tumours in group 1 grew progressively throughout the experiment, whereas group 2 tumours showed marked regression 3-4 weeks after discontinuing CsA. Tumours in group 1 were significantly larger and had greater mitotic activity and showed more ciliary body, optic nerve and extrascleral invasion than tumours in group 2, which showed massive fibrosis, minimal mitotic activity and marked inflammatory cell infiltration. Continuous immunosuppression with CsA seems to be necessary to maintain tumour growth in this experimental model of uveal melanoma.

Metabolic characteristics of multiparous Angus and Brahman cows grazing in the Chihuahuan Desert

Understanding metabolic differences between breeds of cattle is important when selecting for production in semiarid environments. Spring-calving multiparous Angus and Brahman cows (n = 8/breed) grazing in the Chihuahuan Desert were used to evaluate metabolic hormone status in February (i.e., 3rd trimester of pregnancy), May (i.e., early lactation), and September (i.e., late lactation) 2000. Crude protein in ruminal digesta collected from grazing companion ruminally cannulated cows during these months was 5.6, 6.0, and 10.3%, respectively. Angus cows were heavier (P < 0.01) than Brahman cows across months. Body condition scores among breed groups were 4.4, 3.6, and 4.6 in February, May, and September with Brahman cows tending (P < 0.10) to have greater body condition than Angus cows in May. Brahman cows tended to have greater fecal output per 100 kg BW than Angus cows in February (0.9 > 0.7 +/- 0.1, P < 0.10). Brahman cows had greater serum concentrations of leptin than Angus cows in September (1.8 > 0.70 +/- 0.1 ng/mL; P < 0.05), and serum concentrations of insulin were greater (P < 0.01) in Brahman than Angus cows throughout the study. Brahman cows also had greater (P < 0.01) serum concentrations of glucose during February and May than Angus cows. Serum concentrations of triiodothyronine were greatest (P < 0.01) during September and lowest during February and May in both breed groups and were greater (P < 0.01) in Brahman than in Angus cows in February, May, and September. Pregnancy rate and 205-d adjusted weaning weights were similar (P > or = 0.46) among breed groups. Results suggest that Brahman and Angus cows are sensitive to the seasonal dynamics of forage quality in the Chihuahuan Desert. Brahman cattle appear to have greater concentrations of metabolic hormones and metabolites than Angus cows in this environment, but Angus cows experience greater fluctuations in BW.

Temperature-controlled surface plasmon resonance in VO (2) nanorods

The optical properties of VO(2) nanoparticles formed in an amorphous SiO(2) host by stoichiometric ion implantation of vanadium and oxygen and thermal annealing have been determined and correlated with the particle size and morphology. The results show that that the temperature-controlled semiconductor-to-metal phase transition of the VO(2) nanophase precipitates turns on the classical surface plasmon resonance, with specific features that depend on the size and aspect ratio of the VO(2) particles. This effect improves the optical contrast between the metallic and semiconducting states in the near-IR region of the spectrum as a result of dielectric confinement that is due to the SiO(2) host. A fiber-optic application is demonstrated, as is the ability to control the characteristics of the phase transition by using ion implantation to dope the VO(2) nanoparticles with tungsten or titanium ions.

[Skin necrosis after prophylactic treatment with heparin]

The authors present a case of cutaneous necrosis following local injection of heparin. The physiopathology and the clinical aspect are discussed.

Detection of central pelvic recurrent disease with transvaginal color Doppler ultrasound in women treated for gynecological malignancy

OBJECTIVE

To evaluate color Doppler characteristics of small recurrent tumors detected within the central pelvis in follow-up patients treated for gynecological malignancy.

PATIENTS AND METHODS

A prospective study was performed on 340 patients who were being monitored following treatment for gynecological malignancies. A selected group of 27 patients, with small pelvic masses located in the central region of the pelvis, underwent a color Doppler examination. A subjective assessment of the vascularization (vascular score), the lowest resistance index (RI), the highest peak velocity (PSV) and the highest time averaged maximum velocity (TAMXV) of the vessels detected within the lesion were analyzed.

RESULTS

In 16 patients the pelvic mass was found to be benign while in 11 patients a malignant recurrence was diagnosed. Gray-scale examination could not differentiate between benign and malignant lesions. The color score of tumor recurrences was significantly higher in comparison to that in benign lesions (color score 3 in 54% vs. 0%, P < 0.005). The malignant lesions showed significantly lower mean values of RI and significantly higher mean values of PSV and TAMXV when compared with benign lesions (0.39 +/- 0.09 vs. 0.81 +/- 0.22, P < 0.0001; 19.3 +/- 4.7 vs. 10.5 +/- 5.6 cm/s, P < 0.0001; 8.9 +/- 3.7 vs. 4.3 +/- 2.7 cm/s, P < 0.005).

CONCLUSIONS

Color Doppler analysis added to transvaginal gray-scale ultrasonography seems to be a helpful tool in the diagnosis of recurrent tumors in the central region of the pelvis.

Relationships of metabolic hormones and serum glucose to growth and reproductive development in performance-tested Angus, Brangus, and Brahman bulls

Understanding mechanisms that regulate growth and reproduction are important for improving selection strategies in cattle. In this study, Angus, Brangus, and Brahman bulls (n = 7 per breed) of similar age were selected from a group of 65 weanlings. Bulls were evaluated after weaning (i.e., approximately 6 mo of age) for 112 d for serum concentrations of metabolic hormones and glucose, growth, and reproductive traits. Performance data and blood sera were collected on d 0, 28, 56, 84, and 112. Sera were also collected in periods from d 50 to 59 (56D) and 103 to 112 (112D). Angus bulls were heavier (P < 0.05) throughout the study than Brahman bulls and were heavier than Brangus bulls on d 56, 84, and 112. Initial and final BW for Angus, Brangus, and Brahman bulls were 292.7, 260.6, and 230.4 and 468.3, 435.6, and 350.7 +/- 12 kg, respectively. Conversely, Brahman bulls had greater hip height (P < 0.05) than Brangus, and Brangus were taller (P < 0.05) than Angus. Angus bulls had the greatest (P < 0.05) scrotal circumference (SC) and Brahman bulls the least. Mean SC across days was 31.5, 29.7, and 25.0 +/- 0.6 cm for the three respective breeds. Serum testosterone was greater (P < 0.01) in Angus and Brangus bulls (10.0 and 8.9 +/- 1.4 ng/mL) than in Brahman bulls (4.0 +/- 1.4 ng/mL) throughout the study. After d 112, 100, 86, and 57% of the Angus, Brangus, and Brahman bulls passed a breeding soundness exam (P = 0.51). Serum concentrations of IGF-I and leptin were greater (P < or = 0.06) in Angus bulls on d 56, 84, and 112 than in Brangus and Brahman bulls. Serum concentrations of GH (P < 0.08) and glucose (P < 0.03) were greater in Brangus bulls than in Angus or Brahman bulls throughout the study. Prediction analyses suggested that serum concentrations of leptin could be used to predict (P < or = 0.08) BW and SC (R2 > 0.82) in the 56D and 112D periods among these breeds. Leptin was also useful in predicting (P < or = 0.09) serum concentrations of GH and testosterone in the 112D period (R2 > 0.32). Residual correlation analyses with the effect of breed removed suggested that leptin was correlated (r > or => 0.53, P < 0.05) with both SC and serum testosterone. Angus and Brahman cattle differ in phenotype, level of adiposity, and rate of sexual development. Data herein suggest that these characteristics could be due to varying mechanisms by which metabolic hormones such as leptin, GH, and(or) IGF-I are regulated.

Clinical and laboratory evaluation of the safety of a bioartificial liver assist device for potential transmission of porcine endogenous retrovirus

BACKGROUND

The potential risk of transmission of porcine endogenous retroviruses (PERV) from xenogeneic donors into humans has been widely debated. Because we were involved in a phase I/II clinical trial using a bioartificial liver support system (BLSS), we proceeded to evaluate the biosafety of this device.

MATERIALS AND METHODS

The system being evaluated contains primary porcine hepatocytes freshly isolated from pathogen-free, purpose-raised herd. Isolated hepatocytes were installed in the shell, which is separated by a semipermeable membrane (100-kD nominal cutoff) from the lumen through which the patients' whole blood is circulated. Both before and at defined intervals posthemoperfusion, patients' blood was obtained for screening. Additionally, effluent collected from a clinical bioreactor was analyzed. The presence of viral particles was estimated by reverse transcriptase-polymerase chain reaction (RT-PCR) and RT assays. For the detection of pig genomic and mitochondrial DNA, sequence-specific PCR (SS-PCR) was used. Finally, the presence of infectious viral particles in the samples was ascertained by exposure to the PERV-susceptible human cell line HEK-293.

RESULTS

PERV transcripts, RT activity, and infectious PERV particles were not detected in the luminal effluent of a bioreactor. Culture supernatant from untreated control or mitogen-treated porcine hepatocytes (cleared of cellular debris) also failed to infect HEK-293 cell lines. Finally, RT-PCR, SS-PCR, and PERV-specific RT assay detected no PERV infection in the blood samples obtained from five study patients both before and at various times post-hemoperfusion.

CONCLUSION

Although longer patient follow-up is required and mandated to unequivocally establish the biosafety of this device and related bioartificial organ systems, these analyses support the conclusion that when used under standard operational conditions, the BLSS is safe.

Assessing the economic return of specializing in orthodontics or oral and maxillofacial surgery

BACKGROUND

The authors determined the economic returns from an educational investment in the specialties of orthodontics and oral an maxillofacial surgery. They also addressed problems found in previous studies.

METHODS

The marginal return for specializing in orthodontics or oral and maxillofacial surgery was determined using net present value and internal rate of return, or IRR, with the income of the general dentist serving as the common opportunity cost. Extreme scenario, threshold and one-way sensitivity analyses were used to account for variation in the data.

RESULTS

The median group of orthodontists broke even 5.9 years after specialty training and had a working lifetime net return of $271,536 above that of general dentists; the IRR for them was 10.36 percent. The median group of oral and maxillofacial surgeons broke even 2.3 years after training and had a working lifetime net return of $587,563 above that of general dentists; the IRR for them was 25.30 percent.

CONCLUSIONS

Under the most likely conditions, the authors found a positive economic return to dentists in both specialties from their additional dental training.

PRACTICE IMPLICATIONS

The positive financial returns brought by specialization indicate that the demand for additional dental education should continue within an environment of increased educational investment costs.

Plasmodium falciparum circumsporozoite (CS) protein peptides specifically bind to HepG2 cells

Hepatocyte invasion by malaria parasites is mediated by specific molecular interactions. Several lines of evidence suggest the importance of the surface plasmodial circumsporozoite (CS) protein in the sporozoite invasion of hepatocytes. Identification of the sequences involved in binding to hepatocytes is an important step towards understanding the structural basis for the sporozoite-hepatocyte interaction. In this study, binding assays between Plasmodium falciparum CS peptides and HepG2 cells were performed. Fifteen overlapping residue 20 mer long peptides, spanning the entire CS sequence, were tested in HepG2 cell binding assays. Five High Binding Activity Peptides (HBAPs) to HepG2 cells were identified: 4593, (NANPNANPNANP); 4383, (NSRSLGENDDGNNEDNEKLR); 4388, (GNGQGHNMPNDPNRNVDENA); 4389, (HNMPNDPNRNVDENANANSA) and 4390, (DPNRNVDENANANSAVKNNN). The HBAP HepG2 interaction is independent of charge and amino-acid composition, but sequence dependent. Four HBAPs (4383, 4388, 4389 and 4390) are bound with similar affinity to a 50 kDa molecule. These HBAPs define three Hepatocyte Binding Sequences (HBSs): HBS-1, located between residues 68 and 87 (HBAP 4383); HBS-11, the repeat NANP region (HBAP 4593), for which anti repeat antibodies are able to specifically inhibit sporozoite invasion of hepatocytes have been reported; and HBS-111, between residues 286 and 315 (HBAPs 4388, 4388 and 4390), respectively. Interestingly, HBS 111 carries two earlier-reported B-epitopes (underlined) in peptides 4388, 4389 and 4390 (GNGQGHNMPNDPNRNVD ENANANSAVKNN) in its sequence. The HBSs reported here show lesser interspecie-variability than the entire protein in species invading the same kind of hepatic cells. This data supports these HBSs' important role in CS-protein function; they could be used as ligand by the sporozoite to invade hepatic cells.

Tts, a processive beta-glucosyltransferase of Streptococcus pneumoniae, directs the synthesis of the branched type 37 capsular polysaccharide in Pneumococcus and other gram-positive species

The type 37 capsule of Streptococcus pneumoniae is a homopolysaccharide built up from repeating units of [beta-d-Glcp-(1-->2)]-beta-d-Glcp-(1-->3). The elements governing the expression of the tts gene, coding for the glucosyltransferase involved in the synthesis of the type 37 pneumococcal capsular polysaccharide, have been studied. Primer extension analysis and functional tests demonstrated the presence of four new transcriptional start points upstream of the previously reported tts promoter (ttsp). Most interesting, three of these transcriptional start points are located in a RUP element thought to be involved in recombinational events (Oggioni, M. R., and Claverys, J. P. (1999) Microbiology 145, 2647-2653). Transformation experiments using either a recombinant plasmid containing the whole transcriptional unit of tts or chromosomal DNA from a type 37 pneumococcus showed that tts is the only gene required to drive the biosynthesis of a type 37 capsule in S. pneumoniae and other Gram-positive bacteria, namely Streptococcus oralis, Streptococcus gordonii, and Bacillus subtilis. The Tts synthase was overproduced in S. pneumoniae and purified as a membrane-associated enzyme. These membrane preparations used UDP-Glc as substrate to catalyze the synthesis of a high molecular weight polysaccharide immunologically identical to the type 37 capsule. In addition, UDP-Gal was also a substrate to produce type 37 polysaccharide since a strong UDP-Glc-4'-epimerase activity is associated to the membrane fraction of S. pneumoniae. These results indicated that Tts has a dual biochemical activity that leads to the synthesis of the branched type 37 polysaccharide.

Metastatic carcinoma of the breast resembling early gastric carcinoma

We describe a case of gastric metastasis from a lobular carcinoma of the breast in a 45-year-old woman who had undergone a left mastectomy with axillary dissection 7 years earlier. At the current presentation, she had been experiencing progressive epigastric discomfort for 3 months. The initial diagnosis was early gastric carcinoma, diffuse type, based on gastric biopsy findings and ultrasonographic endoscopy. A definitive diagnosis of metastatic breast cancer was confirmed after subtotal gastrectomy of a presumed primary early gastric carcinoma. Although gastrointestinal metastases from breast cancer are not rare, the early stage of the gastric lesion and the absence of further disease dissemination make this case unusual. The onset of gastrointestinal symptoms in a patient with a history of breast carcinoma should prompt the physician to rule out the possibility of gastric metastases.

The EMBL nucleotide sequence database

The EMBL Nucleotide Sequence Database (http://www.ebi.ac.uk/embl/) is maintained at the European Bioinformatics Institute (EBI) in an international collaboration with the DNA Data Bank of Japan (DDBJ) and GenBank at the NCBI (USA). Data is exchanged amongst the collaborating databases on a daily basis. The major contributors to the EMBL database are individual authors and genome project groups. Webin is the preferred web-based submission system for individual submitters, whilst automatic procedures allow incorporation of sequence data from large-scale genome sequencing centres and from the European Patent Office (EPO). Database releases are produced quarterly. Network services allow free access to the most up-to-date data collection via ftp, email and World Wide Web interfaces. EBI's Sequence Retrieval System (SRS), a network browser for databanks in molecular biology, integrates and links the main nucleotide and protein databases plus many specialized databases. For sequence similarity searching a variety of tools (e.g. Blitz, Fasta, BLAST) are available which allow external users to compare their own sequences against the latest data in the EMBL Nucleotide Sequence Database and SWISS-PROT.

The InterPro database, an integrated documentation resource for protein families, domains and functional sites

Signature databases are vital tools for identifying distant relationships in novel sequences and hence for inferring protein function. InterPro is an integrated documentation resource for protein families, domains and functional sites, which amalgamates the efforts of the PROSITE, PRINTS, Pfam and ProDom database projects. Each InterPro entry includes a functional description, annotation, literature references and links back to the relevant member database(s). Release 2.0 of InterPro (October 2000) contains over 3000 entries, representing families, domains, repeats and sites of post-translational modification encoded by a total of 6804 different regular expressions, profiles, fingerprints and Hidden Markov Models. Each InterPro entry lists all the matches against SWISS-PROT and TrEMBL (more than 1,000,000 hits from 462,500 proteins in SWISS-PROT and TrEMBL). The database is accessible for text- and sequence-based searches at http://www.ebi.ac.uk/interpro/. Questions can be emailed to interhelp@ebi.ac.uk.

InterPro--an integrated documentation resource for protein families, domains and functional sites

MOTIVATION

InterPro is a new integrated documentation resource for protein families, domains and functional sites, developed initially as a means of rationalising the complementary efforts of the PROSITE, PRINTS, Pfam and ProDom database projects.

RESULTS

Merged annotations from PRINTS, PROSITE and Pfam form the InterPro core. Each combined InterPro entry includes functional descriptions and literature references, and links are made back to the relevant parent database(s), allowing users to see at a glance whether a particular family or domain has associated patterns, profiles, fingerprints, etc. Merged and individual entries (i.e. those that have no counterpart in the companion resources) are assigned unique accession numbers. Release 1.2 of InterPro (June 2000) contains over 3000 entries, representing families, domains, repeats and sites of post-translational modification (PTMs) encoded by 6581 different regular expressions, profiles, fingerprints and Hidden Markov Models (HMMs). Each InterPro entry lists all the matches against SWISS-PROT and TrEMBL (more than 1000000 hits from 264333 different proteins out of 384572 in SWISS-PROT and TrEMBL).

Plasmodium falciparum AMA-1 erythrocyte binding peptides implicate AMA-1 as erythrocyte binding protein

The role of AMA-1 during merozoite invasion has not yet been determined. However, reported experimental evidence suggests that this protein can be used, in particular as erythrocyte-binding protein, since, Fab fragments against this protein are able to block merozoite invasion. Using a previously described methodology, eight peptides with high binding activity to human erythrocyte, scattered along the different domains and having around 130 nM affinity constants, were identified in the Plasmodium falciparum AMA-1 protein. Their binding activity was sialic acid independent. Some of these peptides showed homology with the erythrocyte binding domains of one of the apical organelle protein family, MAEBL, identified in rodent malarial parasites. One of these peptides shares amino acid sequence with a previously reported B-cell epitope which induces antibodies to block parasite growth. The critical residues were identified for erythrocyte binding conserved peptides 4313 (DAEVAGTQYRLPSGKCPVFG), 4321 (VVDNWEKVCPRKNLQNAKFG), 4325 (MIKSAFLPTGAFKADRYKSH) and 4337 (WGEEKRASHTTPVLMEKPYY). All conserved peptides were able to block merozoite invasion of new RBC and development, suggesting that these peptides are involved in P. falciparum invasion.

A screen for new trithorax group genes identified little imaginal discs, the Drosophila melanogaster homologue of human retinoblastoma binding protein 2

The proteins encoded by two groups of conserved genes, the Polycomb and trithorax groups, have been proposed to maintain, at the level of chromatin structure, the expression pattern of homeotic genes during Drosophila development. To identify new members of the trithorax group, we screened a collection of deficiencies for intergenic noncomplementation with a mutation in ash1, a trithorax group gene. Five of the noncomplementing deletions uncover genes previously classified as members of the Polycomb group. This evidence suggests that there are actually three groups of genes that maintain the expression pattern of homeotic genes during Drosophila development. The products of the third group appear to be required to maintain chromatin in both transcriptionally inactive and active states. Six of the noncomplementing deficiencies uncover previously unidentified trithorax group genes. One of these deficiencies removes 25D2-3 to 26B2-5. Within this region, there are two, allelic, lethal P-insertion mutations that identify one of these new trithorax group genes. The gene has been called little imaginal discs based on the phenotype of mutant larvae. The protein encoded by the little imaginal discs gene is the Drosophila homologue of human retinoblastoma binding protein 2.