Dental Amalgam and Antibiotic- and/or Mercury-resistant Bacteria

Mercury emitted from dental amalgam may select for increased numbers of antibiotic- or mercury-resistant commensal bacteria in patients and increase their risk for bacterial diseases that are resistant to common therapies. We hypothesized that the presence of dental amalgams would increase the level of mercury-, tetracycline-, ampicillin-, erythromycin-, or chloramphenicol-resistant oral and urinary bacteria as compared with levels in children receiving composite fillings. Samples were collected at baseline, 3–6 months after the initial dental treatment, and annually for 7 years of follow-up. There were no statistically significant differences between treatment groups in the numbers of bacteria growing on antibiotic- or mercury-supplemented plates. This study provided no evidence that amalgam fillings on posterior teeth influenced the level of antibiotic- or mercury-resistant oral or urinary bacteria as detected by culture.

Influence of tubule orientation on cone-shaped texture development in laser-ablated dentin

In the present paper, the influence of tubule orientation on surface texture development was studied. Specimens of dentin with a wide range of tubule orientations were extracted from caries-free human teeth, processed using KrF laser radiation, and analyzed by scanning electron microscopy. When a transverse cross section of dentin cut perpendicularly to the tooth axis is processed with KrF laser radiation, a cone-like topography develops in the inner dentin where tubules are parallel to the laser beam. When laser processing is carried out in the outer dentin, because tubules are significantly tilted with respect to the laser beam, flat surfaces are achieved. The surface texture after laser processing depends effectively on the angle between the tubules and the laser beam. The dependency of cone growth on tubule orientation was confirmed using a simple differential ablation model.

[Reconstruction of velopharyngeal sphincter in secondary Cleft Palate: surgical alternative]

There are numerous surgical procedures for the repair of Cleft Palate (CP). Since 1998, in children with CP we use a modified Wardill-Kilner technique, with a large section of the nasal mucous layer at the level of the muscular insertion on the hard palate and lateral nasopharingeal wall, obtaining a push-back and reorientation of the muscular fibres without dissection, diminishing this way the risks of haemorrhages and fibrosis, simplifying the intervention. It allows a lower operative time and a short internment. The aim of our study was to evaluate the results of this operative procedure specially in the development of the speech in 73 children operated on from 1998 until 2000 in our hospital. We verify a competence of the velopharingeal sphincter with ideal results in speech in 88,8% of the cases.

Mapping of a locus for adult plant resistance to downy mildew in broccoli (Brassica oleracea convar. italica)

The identification of the gene Pp523, conferring downy mildew resistance to adult plants of broccoli (Brassica oleracea convar. italica), led to the construction of a genetic map that included this resistance locus, 301 amplified fragment length polymorphisms, 55 random amplified polymorphic DNAs, 46 inter-simple sequence repeats, three simple sequence repeats, four other PCR markers and a flower colour locus, all gathered into nine major linkage groups. Nineteen additional molecular markers were clustered into one group of four markers, one group of three markers and six pairs of markers. The map spans over 731.9 cM, corresponding to 89.5% of the 818 cM estimated to be the total genome length. A significant number of the mapped markers, 19.3%, showed distorted segregation. The average distance between mapped adjacent markers is 1.64 cM, which places this map among the densest published to date for this species. Using bulked segregant analysis, we identified a group of molecular markers flanking and closely linked in coupling to the resistance gene and included these in the map. Two markers linked in coupling, OPK17_980 and AT.CTA_133/134, are located at 3.1 cM and 3.6 cM, respectively, at each side from the resistance gene. These markers can be used for marker-assisted selection in breeding programs aiming at the introgression of this gene in susceptible B. oleracea genotypes. The fine mapping of the genomic region surrounding the Pp523 resistance gene is currently being carried out, a basic condition for its isolation via positional cloning.

Small dose of recombinant factor VIIa (rFVIIa) to perform percutaneous liver biopsies in cirrhotic patients

Low levels of vitamin K-dependent coagulation factors, synthesized in the liver, play a key role in the hypocoagulable state of end-stage liver disease patients. Recombinant factor VII (rFVIIa) has been developed for, and currently is used in the treatment of patients with hemophilia A and B with inhibitors. Some experience was gained with rFVIIa in liver diseases since 1995. We used a low dose of rFVIIa to perform percutaneous liver biopsy in three patients, all of them with abnormal coagulation, impeditive of the percutaneous liver biopsy. The first one was a 29 years old man with alcoholic cirrhosis and a liver nodule; the second was a 32 years old man with post hepatitis C cirrhosis and excessive alcohol intake; the third was a 53 years old man with chronic hepatitis C and a congenital deficit of factor VII. A single dose of 5 micrograms/Kg of rFVII administered before liver biopsies raised levels of factor VII to acceptable values during more than 5 hours in the first two patients. We conclude that a small dose of rFVIIa can be enough to correct the abnormal coagulation of cirrhotic patients, permits percutaneous liver biopsy, and is cost-effective, compared to transjugular access.

[Crohn disease with unusual cutaneous expression]

Perianal fistula is a frequent complication of Crohn's disease. The diagnosis of the later may be difficult if cutaneous disease is dominant, and sometimes an important clinical challenge. The authors report a case of a 34 year old male complaining of painful perianal nodules for the three last years. Cutaneous histopathological examination was inespecific and colonoscopy normal. Pelvic CT scan and fistulography showed an intercommunicated fistular system invading both isquiorectal fossae, without intestinal communication. Repetition of colonoscopy showed normal mucosa, but in two of the biopsy samples noncaseous granulomas were found at the submucosa. The authors explain their main difficulties to reach the diagnosis of Crohn's disease and discuss the investigation and the evolution of the patient.

[HCV genotypes. Liver histopathology and immunologic profile in four groups of patients]

AIM

Study on the prevalence of MCV genotypes, and correlation with liver pathology and immunological parameters.

PATIENTS AND METHODS

77 chronic hepatitis C patients (52 males, 25 females), mean age 44 +/- 14 years, belonging to four groups: (1) 23 (11 males) without other aetiology, (II) 19 (18 males) excessive drinkers, (III) 18 (12 males) haemodialysed, (IV) 17 (11 males) renal transplantation patients Genotyping was done by PCR (primers of the core, and hybridisation with specific probes). Serum Igs A, G, and M (by nephelometry), and peripheral blood lymphocyte (PBL) subsets (by flow cytometry) were determined.

RESULTS

One genotype was found in 62 patients (1b 69.2%, 1a 21.5%, 2a 3.1%, 2b 3.1%, 3a 9.2%), and two genotypes in 4 patients (1b + 3a in 1 of group 1, 1b + 2a in 2 and 1a + 3a in 1 of group 111). Twelve cases (15.6%) were not identified (NI). Relative prevalence was not different in the four groups, but in 7 drug addicts 1 b was not found (Ia in 71.4%, 3 a 28.6%) The relationship between genotypes and age was significant (p < 0.05): in the 34 patients with less than 40 years, 1b was found in 38.2%, in the others in 41.2%, and NI in 20.6%; in those with 40-60 years, 1b was found in 68.8%, in the others in 15.6%, M in 15.6%; in those above 60 years, 1b was found in 90.9%, in the others in 9.1%. Of those identified, only genotype 1 (1a and 1b) was associated to moderate or severe activity, and infected 11/13 cases of cirrhosis or severe fibrosis. IgM (g/dL) was lower in 1b than in the others: 1.58 + 1.23 vs. 2.53 + 1.93 (p < 0.01). PBL (per mm3) were lesser in 1b than in the others, with significance for the CD8+: 540t239 vs. 739 + 420 (p < 0.01).

CONCLUSIONS

Genotype 1b was the most prevalent in Portuguese patients, more significantly in the elderly, and was absent in drug addicts. The prevalence of genotypes is similar in general patients, in chronic haemodialysed, in renal transplantation recipients and in alcoholics. More severe liver pathology was associated with 1b and 1a genotypes. IgM and CD8+ had lower mean values in 1b infected patients. Other genotypes are certainly important in Portugal.

Role of codon 160 in the sensitivity of human O6-alkylguanine-DNA alkyltransferase to O6-benzylguanine

O6-Alkylguanine-DNA alkyltransferase (AGT) is a DNA repair protein that provides protection from alkylating agents such as dacarbazine, temozolomide, and 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), which are used for cancer chemotherapy. O6-Benzylguanine (BG) is an inhibitor of AGT that sensitizes tumors to these agents. BG is currently in clinical trials. It is possible that the presence of resistant forms of AGT may limit the effectiveness of this strategy. Previous studies have shown that the AGT mutant G160R, which may occur naturally as a result of a polymorphism in the AGT gene, is resistant to BG, whereas the mutants G160W and G160A are actually more sensitive to the inhibitor. To examine other mutations at this site, a random sequence was placed at codon 160 in the AGT cDNA, and a plasmid library was constructed to express these sequences in Escherichia coli. After selection with BG and N-methyl-N'-nitro-N-nitrosoguanidine, BG-resistant mutants were obtained and analyzed. Eleven different amino acid substitutions were found to impart BG resistance by this assay. The most resistant mutants contained histidine or arginine, which had EC50 values of 12 and 4.7 microM, respectively, compared with the wild-type EC50 of 0.08 microM, but nine other alterations led to at least a 10-fold rise in the EC50 value. Three additional mutations at codon 160 were constructed by site-directed mutagenesis, and these led to 6- to 11-fold increases in resistance to BG. Comparisons of the properties of mutants G160R and G160E showed that the presence of DNA enhanced the reaction with BG much more strongly when an acidic residue was present at this position. This may account for the lack of selection of the G160E mutation even though it did impart resistance to BG. These results indicate that many alterations of AGT at position 160 can lead to significant resistance to BG.

Alteration of the conserved residue tyrosine-158 to histidine renders human O6-alkylguanine-DNA alkyltransferase insensitive to the inhibitor O6-benzylguanine

The DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT) protects cells from alkylation damage. O6-Benzylguanine (BG) is a potent inactivator of human AGT (ED50 of 0.1 microM) that is currently undergoing clinical trials to enhance chemotherapy by alkylating agents. In a screen of AGT mutants randomly mutated at position glycine-160, we found that the double mutant Y158H/G160A protected Escherichia coli from killing by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) even in the presence of BG and that the AGT activity of this mutant was strongly resistant to BG (ED50 of 180 microM). Because the single mutant G160A was not resistant to BG, this suggested that the presence of the charged histidine residue at position 158 was responsible. This hypothesis was confirmed by the construction of the single mutation Y158H. The Y158H-mutant AGT was slightly less active than wild-type AGT for the repair of methylated DNA in vitro, but it protected E. coli from killing by MNNG even in the presence of BG and had an ED50 for the inactivation by BG of 620 microM. In contrast, mutant Y158F had an ED5o of 0.2 microM. Previous studies (M. Xu-Welliver et al., Cancer Res., 58: 1936-1945, 1998) have shown that mutant P140K is highly resistant to BG (ED50 of >1200 microM). Models of human AGT suggest that the side chain of the lysine inserted into this mutant is close to tyrosine-158 and that the positively charged lysine side-chain may interfere with BG binding. The double mutants P140K/Y158H and P140K/Y158F resembled P140K and Y158H in being highly resistant to BG, but the use of a sensitive assay for reaction of BG with AGT indicated that their abilities to react were in the order P140K/ Y158H < P140K < P140K/Y158F. These results confirm that the presence of a positively charged residue close to the active site of human AGT renders it highly resistant to BG without substantially affecting activity toward methylated DNA substrates. Such mutants may limit the value of BG therapy if they arise in malignant cells during chemotherapy, but the mutant sequences may be useful for gene therapy approaches in which BG-resistant human AGTs are used to prevent hematopoietic toxicity. At least 28 AGT sequences (from 25 species) have now been described. In 25 of these, the position equivalent to 158 in the human AGT is also a tyrosine, and in the other 3, it is a phenylalanine. The importance of an aromatic ring side chain at this position is emphasized by previous studies (S. Edara et al., Carcinogenesis, 16: 1637-1642, 1995), which show that the replacement by alanine renders human AGT inactive. Our results show that histidine can also substitute for tyrosine at this position.

[Refractory severe ulcerative colitis. Experience with cyclosporine]

A case of severe ulcerative colitis refractory to steroid therapy is reported. The authors look at cyclosporine use in this clinical setting and make a short review of cyclosporine usefulness and major side effects.

Distribution of bismuth in the rat after oral dosing with ranitidine bismuth citrate and bismuth subcitrate

Bismuth preparations are used world-wide for the management of peptic ulcer disease, for eradication of Helicobacter pylori, and in the prevention and treatment of diarrhoea. However neurological toxicity of bismuth has always been a major concern and evidence has been found of the absorption of bismuth. Recent studies have suggested that the absorption of bismuth increases when bismuth salts are used with ranitidine hydrochloride. The absorption and deposition of bismuth as a result of the use of the new drug ranitidine bismuth citrate have not been yet clarified. After 15 days of twice daily oral gavage with bismuth subcitrate, 13.7 mg kg(-1) day(-1) to eight rats, deposition of bismuth was found in all the tissues studied, especially the kidney (30.81 +/- 8.59 microg g(-1) dry weight). A similar pattern of distribution and tissue concentrations was found when bismuth subcitrate was given with ranitidine hydrochloride 8.6 mg kg(-1) day(-1) to another eight rats, although this combination resulted in lower brain levels (3.12 + 1.31 microg g(-1) dry weight) than after administration of bismuth subcitrate alone (4.77 +/- 0.97 microg g(-1) dry weight). When six rats were given ranitidine bismuth citrate by gavage at 22.8 mg kg(-1) day(-1) for 15 days, kidney levels were lower (4.24 +/- 1.75 microg g(-1) dry weight) and brain levels were below detection limits; the bismuth concentrations in the faeces from this group were also significantly lower (1603 +/- 104.0 microg g(-1) dry weight) than for the two other groups. After dosing with bismuth alone or in association with ranitidine hydrochloride, bismuth was detected in several organs and deposition was not influenced by gastric pH. Blood levels correlate poorly with organ deposition and brain deposition was not always associated with encephalopathy. After administration of ranitidine bismuth citrate, significantly lower concentrations of bismuth were found in the kidney and bismuth was not detectable in the brain, suggesting lower bismuth absorption. This was confirmed by higher levels in the faeces after dosing with ranitidine bismuth citrate. Thirty days after dosing with ranitidine bismuth citrate or bismuth subcitrate, bismuth could not be detected in any of the organs examined but could be found in the urine. In conclusion, bismuth was deposited in the kidney, brain, lung and liver of rats after oral dosing with bismuth subcitrate. After oral dosing with an equivalent amount of bismuth in the form of ranitidine bismuth citrate, significantly lower concentrations of bismuth were deposited in the kidney; in the brain bismuth was not detectable.

Effects of a self-etching primer on enamel shear bond strengths and SEM morphology

PURPOSE

To study a dental adhesive system containing a self-etching primer, by evaluating the enamel shear bond strengths and comparing the SEM interfacial morphology.

MATERIALS AND METHODS

100 flat enamel bonding sites were prepared to 600-grit on proximal surfaces of caries-free human molars. The bonding surfaces were treated with Clearfil Liner Bond 2 as recommended by the manufacturer, or combined with various acidic etchants. A composite rod (Clearfil Photo Anterior) was applied to the bonding area in two increments in a Teflon mold and polymerized for 100 s. After 24 h of water storage, the specimens were thermocycled and the shear bond strengths measured using an Instron testing machine. Forty extra molar crowns were roughened and treated with Clearfil Liner Bond 2 and alternative etchants, as described. A low-viscosity resin was bonded to the occlusal surfaces of these crowns, which were further demineralized and deproteinized. Field-Emission SEM examinations were carried out to evaluate the effects of different treatments on enamel surfaces.

RESULTS

The mean shear bond strengths were in the range of 18.1 MPa to 25.9 MPa, without significant differences between pairs of means. The failures were predominantly of the adhesive type. The use of alternative etchants resulted in the deepest etching patterns. The use of Clearfil Liner Bond 2, according to manufacturer's directions, resulted in a poorly-defined etching pattern. Regardless of the alternative etchant used, the use of the self-etching primer did not affect the mean enamel shear bond strength.

[Prognosis in unstable angina as a function of the clinical presentation]

OBJECTIVE

To assess the prognosis of Unstable Angina according to its clinical presentation using Braunwald's Classification.

DESIGN

Retrospective study of hospital admissions from January 1982 to September 1990.

SETTING

Coronary Care Unit and a Cardiology Department of a Central Hospital.

PATIENTS

There were 132 patients, 109 men and 23 women, with a mean age of 56 +/- 9 years, all submitted to cardiac catheterization at least 90 days after hospital admission followed up during 34.2 +/- 24.2 months.

MATERIAL AND METHODS

Patients were divided in three groups according to the clinical presentation of Unstable Angina: Group A--Aggravated Chronic Angina and/or "De Novo" Angina; Group B--Angina at Rest but not in the last 48 hours, and Group C--Angina at Rest in the last 48 hours. Group A was also sub-divided, and the patients with Unstable Angina after myocardial infarction were excluded. The previous clinical profile was evaluated as well as the circumstances in which Unstable Angina occurred, need of Coronary Care Unit, angiographic findings and follow-up.

RESULTS

Within the 132 patients, 86 were in the group A, (59 with Aggravated Angina and 27 with "De Novo" Angina), 11 in group B, and 35 in group C. The group with Aggravated Angina had higher incidence of previous myocardial infarction and bypass surgery (p < 0.01 and p = 0.05), compared to group with "De Novo" Angina and B, and also three vessels disease associated to ventricular dysfunction. "Culprit Lesion" appeared more frequently as eccentric type I in group A, and as concentric in group C. Revascularization procedures were performed in 95 patients (CABG in 66 and PTCA in 29) being respectively: 21 and 6 were urgent, 19 and 18 were elective and 26 and 5 were late procedures. CABG were more frequent in group A. There were 73 major cardiac events in 44 patients (8 deaths, 12 myocardial infarction and 53 new episodes of Unstable Angina), which were more frequent in group with Aggravated Angina and group C. The chance of patients with major cardiac events was in a 78 months follow-up, about 25% for group with "De Novo" Angina, 50% for patients with Aggravated Chronic Angina, and was greater than 75% in patients with Angina at Rest and episodes in the last 48 hours (p < 0.05)--Log-rank Test. The worse prognosis was seen in patients with Aggravated Chronic Angina, when a gathering of clinic patterns of Braunwald's classification were present.

CONCLUSIONS

In summary, the group with Aggravated Angina and group C had more severe disease, required more urgent CABG and PTCA, and had also a higher incidence of cardiac events. The group with better prognosis was the group with "De Novo" Angina, which should be distinguished of the group with Aggravated Angina who was the worst prognosis.

Relief formation in polished amalgam surfaces

The relief produced in the surface of dental amalgam as a result of polishing was studied by scanning electron microscopy in traditional low-copper amalgams, high-copper dispersant-type amalgams, and high-copper single-composition amalgams. Specimens were polished metallographically in two planes at right angles to each other. Micrographs were taken of the edge between the planes; the profile of one of the polished planes could be traced and the microstructural phases recognized. The traced lines were analyzed by a computer that calculated the mean levels of the phases and the mean deviation (roughness) of all the phases along the scanned distance. Recesses were seen in the surface of the gamma-2 phase. The gamma-1 phase attained the highest level, protruding above the phases of the alloy particles. The results indicate that well-polished amalgam surfaces have a structural relief that contributes to the roughness and limits the degree of smoothness that can be obtained in an amalgam surface.

Polishability of dental amalgam as influenced by condensation pressure and primary mercury content

The polishability of some amalgam products was studied by determining the roughness (Rs) of metallographically polished specimens. The surface porosity of the specimens was also measured and was found to be closely correlated with the roughness. Two manipulative variables, condensation pressure and primary (precondensation) mercury content, were examined with respect to their effect on porosity and polishability. For the condensation pressures 14 and 20 MPa no differences could be observed in the effect on the surface properties studied. The primary mercury content was varied in three steps--the normal, recommended level and 5% more and less than this. For those products having a recommended precondensation mercury content of 50% or less, the 5% decrease in mercury resulted in a pronounced increase in porosity and Rs. The results indicate that polishability is for some products markedly improved by avoiding a dry mix.

Surface roughness and porosity of dental amalgam

The surface roughness of seven different products of dental amalgam was determined and the contribution of their porosity content and alloy particle size to that surface property was assessed. A significant correlation between roughness and porosity was found. In all amalgams the small voids were the most frequent. It was also found that the amalgam products which exhibited the highest frequency of big voids presented significantly higher surface roughness values. No significant correlation was found between roughness and alloy particle size.