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Biomedical subjects

A Contreras

Publications and source records attributed to A Contreras.

At least 37 records · Page 2Linked to original sources
PubMed2001

Convergence of two global transcriptional regulators on nitrogen induction of the stress-acclimation gene nblA in the cyanobacterium Synechococcus sp. PCC 7942.

Cyanobacteria respond to environmental stress conditions by degrading their phycobilisomes, the light harvesting complexes for photosynthesis. The expression of nblA, a key gene in this process, is controlled by the response regulator NblR in Synechococcus sp. PCC 7942. Here we show that, under nitrogen stress, nblA is also regulated by NtcA, the global regulator for nitrogen control. NtcA activation of nblA was found to be nitrogen-specific and did not take place under sulphur stress. Transcripts from the two major transcription start points (tsp) for the nblA gene were induced in response to nitrogen and sulphur starvation. The most active one (tspII) required both NblR and NtcA to induce full nblA expression under nitrogen starvation. NblR and NtcA bound in vitro to a DNA fragment from the nblA promoter region, suggesting that, under nitrogen stress, both NblR and NtcA activate the main regulated promoter (PnblA-2) by direct DNA-binding. The structure of PnblA-2 differs from that of the canonical NtcA-activated promoter and it is therefore proposed to represent a novel type of NtcA-dependent promoter. We analysed expression patterns from ntcA and selected NtcA targets in NtcA(-), NblR(-) and wild-type strains, and discuss data suggesting further interrelations between phycobilisome degradation and nitrogen assimilation regulatory pathways.

Bacterial Proteins↗
PubMed2001

Aggressive periodontitis associated with Fanconi's anemia. A case report.

BACKGROUND: Fanconi's anemia is an autosomal recessive disease associated with chromosomal breakage as well as pancytopenia, skin pigmentation, renal hypoplasia, cardiac defects, microcephaly, congenital malformations of the skeleton, hypogonadism, and increased risk of leukemia. The present report describes the periodontal clinical and microbiological status of an 11-year old male having Fanconi's anemia. METHODS: Polymerase chain reaction analysis to detect human cytomegalovirus (HCMV), Epstein-Barr type 1 virus, and herpes simplex virus (HSV) was performed on paper-point samples pooled from either 3 periodontal sites with advanced attachment loss or 3 gingivitis sites with no clinical attachment loss. Anaerobic bacterial culture examination was performed on the pooled periodontitis sample. RESULTS: The patient suffered from pancytopenia, allergy, asthma, hearing impairment, and mental retardation. Dentition consisted of 7 primary teeth, 11 erupted permanent teeth, and 14 unerupted permanent teeth. Most erupted teeth showed severe gingival inflammation with some gingival overgrowth and various degrees of periodontal attachment loss. Genomes of HCMV and HSV were detected in the pooled periodontitis sample and HCMV in the pooled gingivitis sample. The periodontitis sample but not the gingivitis sample revealed HCMV mRNA of major capsid protein, suggestive of active viral infection. The periodontitis sample also yielded Actinobacillus actinomycetemcomitans (1.1% of total isolates), FusobActerium species (7.9%), Campylobacter species (2.2%), Peptostreptococcus micros (3.4%), and Candida albicans (0.3%). CONCLUSIONS: Oral features of Fanconi's anemia may include increased susceptibility to periodontitis. It is likely that underlying host defense impairment coupled with periodontal infection by HCMV and A. actinomycetemcomitans contribute to the severe type of periodontitis associated with Fanconi's anemia.

Actinobacillus Infections↗
PubMed2000

Herpesviruses in periodontal pocket and gingival tissue specimens.

Human cytomegalovirus (HCMV) and Epstein-Barr virus type 1 (EBV-1) are frequently detected in crevicular fluid of deep periodontal pockets, but little or no information is available on occurrence of herpesviruses in gingival tissue. This investigation studied the presence of herpesviruses in periodontal pockets and the corresponding gingival tissues from 11 periodontally healthy and 14 periodontitis sites. A nested-polymerase chain reaction was employed to identify the presence of HCMV, EBV-1, EBV-2, herpes simplex virus, human herpesvirus (HHV)-6, HHV-7 and HHV-8 in each test sample. In healthy periodontal sites, HCMV was detected in 1 (9%) and EBV-1 in 2 (18%) pocket samples, and HCMV was detected in 2 (18%) and EBV-1 in 3 (27%) gingival tissue samples. In periodontitis lesions, HCMV was detected in 9 (64%) pocket samples and in 12 (86%) gingival tissue samples, and EBV-1 was detected in 6 (43%) pocket samples and in 11 (79%) gingival tissue samples. HHV-6 and HHV-8 were detected exclusively in gingival tissue samples. The present findings confirm the frequent presence of HCMV and EBV-1 in periodontitis lesions and suggest using gingival tissue specimens for detecting periodontal HHV-6, HHV-7 and HHV-8.

Adult↗
PubMed2000

Importance of Dialister pneumosintes in human periodontitis.

Anaerobic bacteria play important roles in the pathogenesis of human periodontitis. This study examined the relationship between a potentially new periodontopathic bacterium Dialister pneumosintes and periodontal disease. A total of 73 women and 62 men aged 18 to 86 years participated in the study. Using a 16S rRNA polymerase chain reaction identification method, the presence of D. pneumosintes was determined in paper-point samples from periodontal pockets of 105 periodontitis and 30 gingivitis patients. D. pneumosintes was detected in 83% of patients having severe periodontitis and in 19% of patients having slight periodontitis. We suggest adding D. pneumosintes to the group of suspected periodontal pathogens.

Adolescent↗
PubMed2000

Herpesviruses: a unifying causative factor in periodontitis?

Human cytomegalovirus and Epstein-Barr virus type 1 are discussed in this review as they relate to destructive periodontal disease in humans. Genomes of the two herpesviruses occur frequently in severe adult periodontitis, localized and generalized juvenile periodontitis, Papillon-Lefèvre syndrome periodontitis, Down's syndrome periodontitis, HIV-associated periodontitis and acute necrotizing ulcerative gingivitis. Herpesvirus infections generally involve a mild or asymptomatic primary phase followed by an asymptomatic latent phase interrupted sporadically by periods of activation, where viral replication and possibly clinical disease become manifest. Herpesvirus reactivation is triggered by a number of immunosuppressing factors, some of which have also been shown to be risk indicators of periodontal disease. Available evidence argues for the involvement of active cytomegalovirus infection in the initiation and progression of localized juvenile periodontitis and possibly other types of periodontal disease. In periodontal disease, herpesviruses may cause release of tissue-destructive cytokines, overgrowth of pathogenic periodontal bacteria, and initiation of cytotoxic or immunopathogenic events. Understanding the significance of herpesviruses in the causation and pathogenesis of destructive periodontal diseases may have important implications in future prevention and treatment of the diseases.

Adult↗
PubMed2000

Frequency of 530-bp deletion in Actinobacillus actinomycetemcomitans leukotoxin promoter region.

Actinobacillus actinomycetemcomitans strains showing a 530-bp deletion in the promoter region of the leukotoxin gene operon elaborate high amounts of leukotoxin that may play a role in the pathogenesis of periodontal disease. This study used polymerase chain reaction detection to determine the occurrence of the 530-bp deletion in 94 A. actinomycetemcomitans strains from individuals of various ethnic backgrounds. Eleven blacks and one Hispanic subject but no Caucasian or Asian subjects showed the 530-bp deletion in the leukotoxin promoter region, suggesting that the deletion is mainly a characteristic of individuals of African descent. A. actinomycetemcomitans strains exhibiting a deletion in the leukotoxin promoter region occurred both in individuals having severe periodontitis and in adolescents revealing no evidence of destructive periodontal disease.

Actinobacillus Infections↗
PubMed2000

Herpesviruses in human periodontal disease.

Recent studies have identified various herpesviruses in human periodontal disease. Epstein-Barr virus type 1 (EBV-1) infects periodontal B-lymphocytes and human cytomegalovirus (HCMV) infects periodontal monocytes/ macrophages and T-lymphocytes. EBV-1, HCMV and other herpesviruses are present more frequently in periodontitis lesions and acute necrotizing ulcerative gingivitis-lesions than in gingivitis or periodontally healthy sites. Reactivation of HCMV in periodontitis lesions tends to be associated with progressing periodontal disease. Herpesvirus-associated periodontitis lesions harbor elevated levels of periodontopathic bacteria, including Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Bacteriodes forsythus, Prevotella intermedia, Prevotella nigrescens and Treponema denticola. It may be that active periodontal herpesvirus infection impairs periodontal defenses, thereby permitting subgingival overgrowth of periodontopathic bacteria. Alteration between latent and active herpesvirus infection in the periodontium might lead to transient local immunosuppression and explain in part the episodic progressive nature of human periodontitis. Tissue tropism of herpesvirus infections might help explain the localized pattern of tissue destruction in periodontitis. Absence of herpesvirus infection or viral reactivation might explain why some individuals carry periodontopathic bacteria while still maintaining periodontal health. Further studies are warranted to delineate whether the proposed herpesvirus-periodontopathic bacteria model might account for some of the pathogenic features of human periodontal disease.

Bacteria, Anaerobic↗
PubMed2000

Herpesvirus in localized juvenile periodontitis.

Herpesvirus genomic sequences can be detected in gingival crevicular fluid of adult periodontitis lesions. Herpesviruses are immunosuppressive and may facilitate establishment of subgingival pathogens. Electron microscopic studies have identified nuclear and cytoplasmic virus-like inclusions in gingival inflammatory cells from localized juvenile periodontitis (LJP). The present study aimed to determine if herpesviruses occur in LJP lesions and if human cytomegalovirus (HCMV) activation is associated with elevated levels of subgingival Actinobacillus actinomycetemcomitans, the putative bacterial pathogen of LJP. Eleven systemically healthy patients exhibiting LJP (10-23 yr) were studied. In each patient, subgingival samples were pooled from 3 periodontitis lesions around first molar and incisor teeth (5-11 mm periodontal pocket depth) and from 3 gingivitis/healthy sites around canines (2-3 mm periodontal pocket depth). Polymerase chain reaction (PCR) was used to detect herpesvirus DNA and HCMV cDNA of major capsid protein transcripts, indicative of viral activation. Selective culture and 16S rRNA PCR were used to identify A. actinomycetemcomitans. Of 11 deep periodontal samples, 8 showed HCMV, 7 showed Epstein-Barr virus type 1 (EBV-1), 1 showed EBV type 2, 6 showed herpes simplex virus (HSV) and 8 showed viral co-infection. Of 11 shallow periodontal samples, 2 showed HCMV, 2 showed EBV-1, 1 showed HSV and 2 showed viral co-infection. The difference in occurrence of HCMV and viral co-infection between deep and shallow periodontal sites was statistically significant (p =0.031). HCMV activation was detected in deep pockets of all 5 virally positive patients with early LJP (aged 10-14 years) but only in 1 of 3 virally positive LJP patients older than 14 years, and not in any shallow pocket tested. HCMV activation appeared related to absence of radiographic crestal alveolar lamina dura, a possible indication of periodontal disease progression. A. actinomycetemcomitans tended to be more prevalent in samples showing active than latent HCMV infection. The present findings are consistent with the notion that periodontal herpesvirus infection and possibly HCMV activation constitute important features of the etiopathogenesis of LJP.

Adolescent↗
PubMed2000

Herpesviruses 6, 7 and 8 in HIV- and non-HIV-associated periodontitis.

Human herpesviruses, especially cytomegalovirus and Epstein Barr virus type-1, occur with higher frequency in subgingival specimens from periodontitis lesions than from healthy/gingivitis sites. Little or no information is available on the relationship between herpesvirus 6 (HHV-6), herpesvirus 7 (HHV-7) and herpesvirus 8 (HHV-8) and periodontal disease. This study determined the periodontal occurrence of HHV-6, HHV-7 and HHV-8 in 21 HIV-seropositive and 14 HIV-negative adults affected by periodontitis. Gingival biopsy specimens and paper-point samples of subgingival plaque were collected from sites showing 5 mm or more in probing depth. Nested polymerase chain reaction methodology was employed in herpesvirus identification. In the HIV-seropositive periodontitis group, 90% of gingival biopsies and 62% of subgingival plaque samples revealed at least one of the test viruses. HHV-6 occurred in 71%, HHV-7 in 67% and HHV-8 in 24% of gingival biopsies. In the HIV-negative adult periodontitis group, 43% of gingival biopsies showed at least 1 of the test viruses, with HHV-6 present in 21% and H HV-7 in 29% of gingival biopsies and with no detection of HHV-8. The combined occurrence of the 3 test herpesviruses was significantly higher in HIV-seropositive than in HIV-negative adult periodontitis patients (p = 0.008). The human periodontium might constitute a site of infection or reservoir for HHV-6, -7, -8.

Adult↗
PubMed2000

Aneurysm of the anterior leaflet of the mitral valve secondary to aortic valve endocarditis.

Aneurysm of the anterior mitral leaflet is a rare complication of infective aortic valve endocarditis, the natural evolution of which is generally its rupture, with subsequent acute and severe mitral regurgitation. Its presence cannot be recognized with transthoracic echocardiography and even in surgery. We describe a 78-year-old man with aortic valve endocarditis, in whom transesophageal echocardiography was essential for the diagnosis of this complication, its therapeutic management, and the postoperative follow-up after simple valve repair. In addition, the most appropriate surgical approach is discussed.

Aged↗
PubMed2000

Molecular identification of Dialister pneumosintes in subgingival plaque of humans.

Dialister pneumosintes is a nonfermentative, anaerobic, gram-negative rod that grows with small, circular, transparent, shiny, smooth colonies on blood agar. Even though D. pneumosintes has been recovered from deep periodontal pockets, little is known about the relationship between the organism and destructive periodontal disease. This study describes a rapid PCR method to identify D. pneumosintes in periodontal samples. The PCR identification method detected as little as 10 pg of D. pneumosintes DNA or about 1 to 10 cells without nonspecific amplification of various periodontopathic bacteria. Twelve of 22 subgingival samples from adult periodontitis lesions yielded D. pneumosintes either by culture or by PCR identification. In culture-positive samples, D. pneumosintes averaged 3.9% (0.001 to 10.8%) of total isolates. Studies are needed to delineate virulence factors of D. pneumosintes pertinent to periodontal disease.

Cloning, Molecular↗
PubMed2000

Herpesviruses and periodontopathic bacteria in Trisomy 21 periodontitis.

BACKGROUND: Little is known about the etiology and pathogenesis of periodontal disease in Trisomy 21 patients. This study determined the occurrence of herpesviruses and putative periodontopathic bacteria in Trisomy 21 periodontitis. METHODS: Nineteen Trisomy 21 patients (17 to 37 years of age) contributed subgingival samples from molar and bicuspid teeth presenting interproximal periodontitis lesions (probing depths, 5 to 8 mm) and from shallow periodontal sites (probing depths, 1 to 3 mm). Samples were obtained at baseline, and at 1 and 4 weeks after subgingival debridement by means of hand instruments and ultrasonic scalers. Epstein-Barr virus type 1 and 2 (EBV-1 and EBV-2), human cytomegalovirus (HCMV), and herpes simplex virus (HSV) were identified by sensitive and specific nested polymerase chain reaction. Putative periodontopathic bacteria were identified by means of non-selective and selective culture. RESULTS: Of 19 Trisomy 21 periodontitis lesions, 6 (32%) were positive for EBV-1, 5 (26%) were positive for HCMV, 3 (16%) were positive for HSV, and 2 (11%) showed viral co-infection. Of 19 shallow periodontal sites, only one revealed HCMV. Prevotella intermedia, Bacteroides forsythus, and Capnocytophaga species were detected in higher proportions in deep than in shallow periodontal pockets (P = 0.02). Subgingival debridement did not reduce genomic herpesvirus presence but caused a decrease in proportions of Porphyromonas gingivalis and Capnocytophaga species. CONCLUSIONS: Periodontal herpesvirus-bacteria coinfections may play important roles in the pathogenesis of destructive periodontal disease in Trisomy 21 patients. Herpesviruses may reduce the periodontal defense and promote growth of subgingival bacteria capable of causing periodontal breakdown.

Adolescent↗
PubMed2000

Human herpesviruses and Porphyromonas gingivalis are associated with juvenile periodontitis.

BACKGROUND: Although herpesviruses have been associated with adult periodontitis, their relationship with juvenile periodontitis (JP) has not been established. This case-control study examined possible associations between JP and pathogenic bacteria, the human cytomegalovirus (HCMV), and the Epstein-Barr type 1 virus (EBV-1). METHODS: Subjects were participants in a larger survey of schoolchildren in North-Central Jamaica. Subgingival plaque samples from 15 subjects with JP, 20 with incipient periodontitis (IP), and 65 randomly-selected healthy controls were assayed for Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans using a 16S rRNA polymerase chain reaction (PCR) identification method, and for HCMV and EBV-1 using nested PCR identification. RESULTS: Strong bivariate associations were found between JP and P. gingivalis (odds ratio [OR] = 12.7; 95% CI = 2.6, 61.4), HCMV (OR = 10.0; 95% CI = 2.7, 36.3), and A. actinomycetemcomitans (OR = 8.0; 95% CI = 2.3, 27.5), but not EBV-1. In multivariate analyses, P. gingivalis remained a significant explanatory variable (OR = 7.8; 95% CI = 1.5, 40.9); however, the associations were marginal for HCMV (OR = 4.6; 95% CI = 0.9, 22.7), and non-significant for A. actinomycetemcomitans (OR = 2.0; 95% CI = 0.4, 9.7). The associations with JP and the extent of attachment loss were even stronger when both P. gingivalis and HCMV were detected together. P. gingivalis (OR = 3.9; 95% CI = 1.3, 12.0) and EBV-1 (OR = 3.3; 95% CI = 1.0, 10.3) were the only significant explanatory variables in the multivariate analysis of IP. CONCLUSIONS: P. gingivalis is the strongest and most stable indicator of periodontitis in Jamaican adolescents. Co-infection with P. gingivalis and HCMV appears to be particularly deleterious to periodontal health.

Actinobacillus Infections↗
PubMed2000

P190-B, a Rho-GTPase-activating protein, is differentially expressed in terminal end buds and breast cancer.

Microdissection and differential display PCR were used to identify genes preferentially expressed in the highly proliferative terminal end buds (TEBs) in the mammary gland of 45-day-old virgin rats. One clone exhibited 87% homology to the human p190-B gene encoding a novel Rho-Gap. Using in situ hybridization, p190-B was detected in both the TEBs and the terminal ducts, with the highest expression observed in the outer layer of TEBs. During normal mammary gland development, p190-B mRNA expression was highest in the virgin mammary gland and decreased during late pregnancy and lactation. Interestingly, increased levels of p190-B mRNA relative to the normal mammary gland were seen in a subset of murine mammary tumors that appeared to be less well differentiated and potentially more aggressive. Transient transfection of a p190-B expression construct into MCF-10A human mammary epithelial cells resulted in disruption of the actin cytoskeleton, which suggests a role for p190-B in regulating the signaling pathways that influence cell migration and invasion. These results suggest that p190-B may be required for virgin mammary gland development, and its aberrant expression may occur in breast cancer.

Actins↗
PubMed1999

Biliary duct injury: partial segment IV resection for intrahepatic reconstruction of biliary lesions.

A technique for intrahepatic reconstruction of the biliary tree after complex high injuries is described. The fundament of the procedure is the removal of a wedge of segment IV at the level of the hilar plate. When the hilar plate is reached and no adequate exposure of the ducts can be obtained, removing a 1 x 1-in wedge of segment IV between the gallbladder bed and the round ligament exposes the left and right ducts. An anteroposterior view of the plate is obtained instead of a caudocephalic dissection, exposing healthy, nonscarred ducts for reconstruction. We have used this approach in 22 patients, and adequate exposure of the ducts has been obtained, with a high success rate of patency of the anastomosis at a mean follow-up of 3 years. Twenty patients have a patent anastomosis, with a good quality of life and no restenosis.

Adult↗
PubMed1999

Herpesvirus infection of inflammatory cells in human periodontitis.

Human cytomegalovirus (HCMV) and Epstein-Barr virus type 1 (EBV-1) are frequently detected in human periodontitis lesions. However, no information is available on the types of gingival cells infected by herpesviruses. The present study determined the presence of herpesviruses in polymorphonuclear neutrophils, monocytes, macrophages and T and B lymphocytes in biopsies of periodontitis lesions from 20 adults. A nested polymerase chain reaction method was employed to detect HCMV, EBV-1, EBV-2, human herpes virus-6 and herpes simplex virus (HSV) in periodontal tissue biopsy and in gingival cell fractions separated by immunomagnetic cell sorting. Tissue specimens from 18 (90%) and cell fractions from 14 (70%) patients demonstrated herpesviruses. Periodontitis-derived monocytes and macrophages revealed HCMV in cell fractions from 11 (55%) patients and HSV in cells from 1 (5%) patient. T lymphocytes harbored HCMV in cell fractions from 4 (20%) patients and HSV in cell fractions from 4 (20%) patients. B lymphocytes showed EBV-1 in cell fractions from 9 (45%) patients. Periodontal polymorphonuclear neutrophils demonstrated no herpesviruses. This study suggests that HCMV mainly infects periodontal monocytes, macrophages and less frequently T lymphocytes and that EBV-1 infects periodontal B lymphocytes. The possible etio-pathologic significance of periodontal herpesvirus infection is discussed.

Adult↗
PubMed1999

Microbiological features of Papillon-Lefèvre syndrome periodontitis.

Papillon-Lefevre syndrome patients exhibit hyperkeratosis palmo-plantaris and severe periodontitis. The syndrome is an autosomal recessive trait, but the mechanism of periodontal destruction is not known. This report presents the clinical and microbiological features of an 11-year old girl with Papillon-Lefèvre syndrome. Clinical examination included conventional periodontal measurements and radiographic analysis. In samples from 3 deep periodontal lesions, the occurrence of major suspected periodontopathic bacteria was determined by selective and non-selective culture and polymerase chain reaction (PCR) identification, and the presence of cytomegalovirus and Epstein-Barr type 1 virus by a nested-PCR detection method. 10 of 22 available teeth demonstrated severe periodontal breakdown. Major cultivable bacteria included Actinobacillus actinomycetemcomitans (3.4% of total isolates), Prevotella nigrescens (16.4%), Fusobacterium nucleatum (14.3%) and Peptostreptococcus micros (10.6%). A. actinomycetemcomitans, P. nigrescens, Porphyromonas gingivalis and Eikenella corrodens were identified by PCR analysis. The patient's non-affected parents and older brother revealed several periodontal pathogens but not A. actinomycetemcomitans. The viral examination demonstrated cytomegalovirus and Epstein-Barr type 1 virus in the subgingival sample of the Papillon-Lefèvre syndrome patient. The father and brother yielded subgingival cytomegalovirus but not Epstein-Barr type 1 virus. We hypothesize that human herpesviruses in concert with A. actinomycetemcomitans play important rôles in the development of Papillon-Lefèvre syndrome periodontitis.

Aggregatibacter actinomycetemcomitans↗