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Biomedical subjects

R L Cabrini

Publications and source records attributed to R L Cabrini.

At least 37 records · Page 2Linked to original sources
PubMed1999

Evaluation of bone tissue on metallic implants by energy-dispersive x-ray analysis: an experimental study.

Osseointegration capacity of the different metallic implants depends on several variables. Osseointegration can be evaluated by using different methodologies, such as light microscopy and scanning or transmission electron microscopy. The aim of this study was to develop a qualitative and quantitative method to evaluate the presence of bone tissue on large metallic surfaces. A laminar implant was placed in each tibia of 10 Wistar rats. The animals were killed 30 days after surgery. Tibiae were resected, one for embedding in methyl methacrylate and the other for evaluation by energy-dispersive x-ray analysis. Light microscopy revealed osseointegration. Observation of the implant surface by scanning electron microscopy revealed the presence of a coating on the metallic surface that was rough in some areas and smooth in others. Analysis of the coating by energy-dispersive x-ray analysis showed the presence of Ca and P. Eighty percent (+/- 10%) of the metallic implant surface exhibited bone tissue. After confirmation of the occurrence of osseointegration capacity using light microscopy, the method described here allows qualitative and quantitative evaluation of the bone tissue found on large metallic surfaces.

Animals↗
PubMed1999

An experimental model to study implant corrosion.

Corrosion phenomena would appear to play a decisive role in metallic implant long term behaviour. This study presents a method to correlate results obtained in "in vivo" and "in vitro" studies on materials used for metallic implants. Samples of titanium and copper immersed in saline solution (pH 7.4 and 5.2) were used for the "in vitro" study. Implants of these same materials were placed in rat tibiae following the method previously described by Cabrini et al. The animals were killed 14 days post-implantation, the tibiae were resected, radiographed and embedded in acrylic resin. Polarization curves revealed high corrosion in copper implants and low corrosion in titanium implants. It is important to point out that the titanium samples suffered slightly higher corrosion when immersed in a lower pH medium (pH 5.2), as in chronic inflammatory processes. A passive film was found on titanium samples as opposed to the strong corrosion observed in the copper implants. Microscopy revealed osseointegration around titanium implants and a severe inflammatory reaction with abscesses surrounding the copper implants. The method presented herein would allow to correlate "in vivo" and "in vitro" studies on corrosion in different implant materials and establish their relation with cell response.

Abscess↗
PubMed1998

Effect of biphosphonates on abnormal mandibular growth of rats intoxicated with uranium.

Intoxication with uranium induces severe alterations in kidneys and in acute intoxications inhibits bone formation and bone growth. Administered at high doses, uranium leads to death, an event that can be prevented by the administration of ethane-1-hydroxy-1,1 biphosphonate (EHBP), which would presumably exert its effect via its chelating properties. Based on this information, the aim of the present study was to determine the best therapeutic method for treatment using biphosphonates to prevent mandibular growth alterations in animals that survive uranyl nitrate poisoning. Seven groups of Wistar rats weighing 14 g were used as follows: I, untreated control; II, one intraperitoneal injection (IPI) of 2 mg Kg(-1) of body weight of uranyl nitrate (238U). In groups III to VII animals were intoxicated as in Group II and in addition were given a single injection of 10 mg Kg(-1) of ethane-1-hydroxy-1, 1-biphosphonate (EHBP), or 3-amine-1, 1-hydroxypropylene-1, 1 biphosphonate (APD) as follows; Group III, IPI of EHBP given immediately after poisoning (0 h); IV, IPI of EHBP given at 24 h; V, subcutaneous injection (SCI) of EHBP at 0 h; VI, SCI of EHBP at 48 h; VII SCI of APD at 0 h. Survivors were killed on the sixtieth day. Body weight increase, survival rate, and biometric parameters of mandibular growth (Eratalay's method) were studied. Student's "t" test was used for statistical analysis. On day 60 there was only one survivor in Group II and none in Group IV. All animals in the other groups survived. Mandibular growth parameters showed the worst results in Group VII and the best in Group V for which no difference with the controls was observed. These results show that a single subcutaneous injection of EHBP given immediately after uranium poisoning, apart from preventing death, is capable of preventing undesirable alterations in mandibular growth.

Animals↗
PubMed1998

A technique for section thickness evaluation for microphotometry and image analysis of sectioned nuclei.

The exact knowledge of the section thickness is a requisite for making the necessary corrections on DNA measurements in tissue sections. Several methods have been proposed to evaluate section thickness, each of them with advantages and disadvantages depending on the type of specimen and equipment available. We herein report another method based on preparation of standard material whose optical density varies as a function of its thickness and is sectioned and measured alongside the tissue specimen. The standards consist of celloidin cylinders stained with the PAS reaction and embedded in paraffin. For prior characterization of the cylinders, sections of different thickness were obtained and mounted. The optical density of each section was measured by direct microphotometry or image analysis. The actual thickness of each section was evaluated following re-embedding of piled groups of sections in a paraffin block and transversal sectioning. The thickness was then measured with a micrometric eye-piece. Optical density and actual thickness of each section were plotted on a normogram curve. Once a given tissue is sectioned alongside with the reference cylinder, the actual thickness is determined by its optical density on the normogram curve.

Agar↗
PubMed1997

Skin alterations induced by long-term exposure to uranium and their effect on permeability.

The skin is a probable route of incorporation of uranium by percutaneous absorption. The changes in epidermal thickness and their effect on skin permeability after uranium exposure are reported herein. Two experiments (A and B) were performed in Wistar rats weighing 60 g. In experiment A the animals were exposed to U3O8 (0.012 g d(-1)) in 30 daily topical applications. In experiment B the animals were treated as in experiment A, followed by a period of non-exposure of 60 d. Samples of the treated area of skin were taken for histologic studies and for the study of the skin permeability. The epidermal thickness was measured on the histological sections. Epidermis was thinner in experimental than in control animals in both experiments. The values in the control groups were 41.05 +/- 14.03 microm (A) and 38.92 +/- 16.50 microm (B) and 21.35 +/- 10.29 microm (A) and 24.06 +/- 16.50 microm (B) in the experimental groups, the differences being statistically significant. Skin permeability was measured placing skin samples in a diffusion cell, in which the upper compartment was filled with a staining solution. The determinations were made with a spectrophotometer. The results revealed that the skin permeability in both experimental groups was higher than in the respective controls, 65% in experiment A and 77% in experiment B. The results revealed that a long term uranium exposure leads to an epidermal atrophy which in turn results in an increased permeability of the skin.

Administration, Topical↗
PubMed1997

Chronodynamic evaluation of the stages of osseointegration in zirconium laminar implants.

Osteogenesis occurs throughout all stages in life, due to both bone turnover and reparative processes. Thus, osseointegration (OI) can be described as the final step in a cascade of processes involved in bone healing in relation to implants. Ten groups of 5 Wistar rats each (mean = 90 g b.w.) were used. Under ether anesthesia a zirconium laminar implant was placed in the tibia following the method previously described by our laboratory (Cabrini et al Imp Dent 2:264-7, 1993). The animals were killed at Ohs, and 1, 2, 3, 6, 7, 10, 12, 14, and 60 days post-implantation. Tibiae were resected, radiographed and processed for their embedding in methyl methacrylate. Three sections, perpendicular to the major axis of the tibia, were obtained per implant and histologic and histomorphometric studies were carried out. Volume occupied by blood clot, woven bone, percentage of OI and OI bone tissue thickness, were determined. Histologic and histomorphometric studies as function of time revealed: a) at 6 days the presence of non-osseointegrated woven bone around the device is evident increasing in volume from 7 to 10 days post-implantation, and disappearing from day 12 to 14., b) at 14 days after implantation lamellar bone formation on the surface of the zirconium implants (OI) is noticeable. Additional bone growth is observed after 60 days. This study enables quantification of peri-implant reparative process response in an unloaded, necrotic trabeculae free model showing, in the different phases of the osseointegration process, the role of the blood clot and of the appearance and disappearance of woven bone and the final stages of osseointegration. Further investigation will allow comparison of results obtained under the effect of local and/or systemic factors that might affect osseointegration.

Animals↗
PubMed1997

Iron overloading inhibits endochondral ossification.

The development of bone disease in patients with chronic renal failure is well known. Renal patients frequently suffer anemia and iron oral therapy and/or transfusions are used to treat them. Recent findings show that iron could be a factor that provokes bone lesions but the alterations it causes are not well known. The aim of this work was to study the effect of iron intoxication on endochondral ossification, a recognized model for bone growth evaluation. Male Wistar rats weighing 250-300 g were used. They received 88 mg of dextran-iron per day intraperitoneally during 34 days. The experimental and control groups were killed on day 34. A histomorphometric study of the endochondral plate was performed on histologic sections of tibiae. The results obtained show that iron overloading inhibits endochondral ossification.

Animals↗
PubMed1996

Nucleolar organizer regions in parosteal and central osteosarcomas.

Silver stained nucleolar organizer regions (AgNOR) have revealed differences in the biological behavior of certain entities. This study involves a morphometric analysis of AgNOR in 6 central, classic osteosarcomas and 6 parosteal osteosarcomas. There was a statistically significant difference in the number of AgNOR per nucleus between central and parosteal osteosarcomas. Single AgNOR volume was smaller in central osteosarcomas as compared to parosteal osteosarcomas. However, this difference did not reach statistical significance. The parameter AgNOR number per nucleus revealed a cut off value such that 100% of central osteosarcoma cases lay above this value and 100% of parosteal osteosarcoma cases lay below this value. AgNOR demonstration involves a simple technique which can be performed on formalin fixed, paraffin embedded file material. Thus, it may be prudent to routinely assess AgNOR as a contributor to the determination of the pathophysiology of osteosarcomas.

Bone Neoplasms↗
PubMed1996

AgNOR mark epithelial foci in malignant transformation in hamster cheek pouch carcinogenesis.

Hamster cheek pouch mucosa is an accepted model of oral carcinogenesis. We herein examined the value of morphometric evaluation of silver-stained nucleolar organizer regions (AgNOR) in the detection of epithelial foci in malignant transformation following dimethyl-1,2-benzanthracene-induced carcinogenesis of hamster cheek pouch. AgNOR-related parameters were analyzed at different stages of the process of carcinogenesis (control epithelium, epithelium with no unusual microscopic features, "dysplastic" epithelium, exophytic and endophytic carcinomas). Morphometric evaluation of AgNOR revealed incipient cellular alterations which were not evident in routine preparations and contributed to the characterization of different stages of carcinogenesis in this model.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

An original orthodontic appliance for experimental mesial movements in rats.

The design of an original appliance to achieve mesial movement of the first upper molar on one side in rat is presented. The appliance is constructed in 0.4 mm stainless steel wire forming a parallelepiped 3 mm in width in its anterior sector, 4 mm in width in its posterior sector and 12 mm in length in its lateral branches. In addition a central longitudinal bar is welded to the structure. The lateral branches of the appliance slide freely through the tubes welded to the palatal aspect of the molar bands, cemented in turn to both first molars. A wire 2 mm in length is welded in the anchorage area to the mesial side of the molar tube at 3 mm from the anterior end of the appliance, which acts as a butt. A pre-formed nickel-titanium open coil spring 0.23 mm thick, lumen 0.60 mm and 5.00 mm in length is placed distal to the molar tube. The spring is compressed by 1 mm of its original length, the final force being approximately 50 g. The movement achieved was measured on plaster casts obtained from pre and postoperative impressions, and afforded values of 0.250 mm +/- 0.790 mm on the active side and 0.012 +/- 0.011 mm on the passive side. The histologic studies showed an extensive erosive area on the pressure side of the alveolar wall. The appliance presented will be useful to achieve models of experimental movements of only one molar towards mesial with a force of known magnitude.

Animals↗
PubMed1996

Histochemical demonstration of gamma-glutamyl transpeptidase activity in normal rat cartilage and bone.

The feasibility of histochemical detection of GGT activity in decalcified bone tissue is proved and the activity distribution pattern of GGT in normal rat cartilage and bone is described. The results suggest the association, in this model, between GGT activity and differentiation mechanisms rather than proliferative processes. The fact that GGT activity in adult tissues which are normally GGT negative has been linked to premalignant transformation confers significance to the study of GGT activity in normal tissues. The results contribute to the knowledge of the biological mechanisms in which GGT activity is involved and to the understanding of the behaviour of tissues which can be used as controls in carcinogenesis models.

Animals↗
PubMed1996

Effect of dexamethasone on osseointegration: a preliminary experimental study.

The peri-implant reparative process is one of the factors involved in osseointegration. Local and systemic factors may contribute to the peri-implant micro-environment. The aim of this study was to assess the effect of dexamethasone (DXM) on the first stages of the post-implantation reparative process using a quantitative osseointegration experimental model previously developed at our laboratory. A titanium laminar implant was inserted into the right tibiae of nine male Wistar rats under ether anesthesia, following a technique we previously described. Six rats received 120 micrograms/kg/day i.p. doses of DXM (Decadron Sidus, Argentina) for 14 days pre-implantation and 14 days post-implantation. The remaining three (controls) were injected with an equivalent volume of saline. On day 14 post-implantation, all animals were killed, and their tibiae were resected, radiographed, and processed before being embedded in methylmethacrylate. Microscopic observation and histomorphometric studies were performed. Results show that, in this experimental model, the extension of osteogenic peri-implant response was greater in DXM-treated animals than in controls. Thus, our laminar implant test may prove useful to study the effects of corticosteroids on the osseointegration process.

Animals↗
PubMed1994

Nucleolar organizer regions in lining epithelium adjacent to squamous cell carcinoma of human oral mucosa.

BACKGROUND: The value of silver staining of nucleolar organizer regions (AgNOR) counts as a diagnostic aid has been reported for several neoplastic entities. Previous studies have proved the value of the morphometric evaluation of AgNOR in the detection of incipient cellular alterations. METHODS: A morphometric analysis of AgNORs was performed in oral mucosa epithelium adjacent to squamous cell carcinoma compared with normal mucosa epithelium and the carcinomatous parenchyma. RESULTS: Highly statistically significant differences in all 5 AgNOR-related parameters assessed were found between normal mucosa and mucosa adjacent to cancer. Conversely, the corresponding nuclear parameters failed to exhibit significant differences. The parameter AgNOR contour index plotted for individual cases affords a cutoff value that could prove useful in identifying epithelia at early stages of transformation. CONCLUSIONS: AgNOR evidenced significant variations in epithelium adjacent to oral squamous cell carcinoma, which did not exhibit morphologic signs of atypia. Based on this study, AgNOR would be a quantitative, discriminative aid, easy to monitor in a pathology laboratory, in detecting incipient cellular alterations. These findings contribute to the issue of early diagnosis and to the knowledge of tumoral growth.

Carcinoma, Squamous Cell↗
PubMed1994

Lethality due to uranium poisoning is prevented by ethane-1-hydroxy-1,1-biphosphonate (EHBP).

The processes of uranium extraction, purification, and manufacture involve the risk of chemical intoxication. Acute uranium poisoning elicits renal failure which in turn may lead to death. Great efforts have been put into the search for a protective agent for acute uranium poisoning. Several chelating agents such as EDTA, Tiron, DTPA, or aminosalicylic acid have been experimentally assayed. However, even when these agents are able to reduce the mortality none of them achieve 100% survival. We herein present the use of EHBP to prevent mortality due to uranium poisoning. Rats weighing 14 g were employed in two different experiments: A) The surviving animals were killed on the 60th day; and B) The animals were killed on the 9th day. In both experiments 4 groups were considered: 1. untreated control; 2. one intraperitoneal (IP) injection of uranyl nitrate (2 mg kg-1 of body weight); 3. 1 IP injection of EHBP (10 mg kg-1 of body weight); and 4. treatments 2 and 3 combined. In both experiments 50% of the animals in group 2 died on the eighth day. All the animals of the other groups were alive at the end of the experiment. Histological analysis of the kidneys of the animals of experiment B revealed renal damage in the exposed animals, whereas no structural alterations were detected in the kidneys of the other three groups, including those given uranyl nitrate and treated with EHBP. These results show the efficiency of only one injection of EHBP to avoid renal damage and to counteract the mortality due to uranium poisoning with a success rate of 100%.

Animals↗
PubMed1994

Use of Zircalloy to induce bone regeneration. A 2-year follow-up study.

In a previous study we analyzed the behaviour of Zircalloy 4 particles employed in patients with significant loss of periodontal bone support which threatened the permanence in situ of the tooth. We herein present the results obtained after regular examination over a 2-year period of 6 patients submitted to this treatment. Our results reveal that all patients exhibited excellent gingivo-periodontal health with an increase in clinical insertion of 7 mm +/- 1 and a marked reduction in motility from 3 to 1. None of the cases featured added inflammation or expulsion of the implant material. In one of the cases it was possible to study the histology of the area by punch biopsy with a disposable needle (Sherwood-Medical). Analysis of the sample revealed the presence of bone tissue in intimate contact with implanted metallic particles of Zircalloy 4, producing osseointegration. This osseointegration would lead to filling of the periodontal bone defect. Macrophages loaded with metallic particles were found in the vicinity of particles which were not osseointegrated. These features may correspond to superficial areas related with soft tissue as observed in our study on alveolar filling in rats with the same type of particles.

Adult↗
PubMed1994

A method for the quality control of osseointegration in endosseous implants.

Metallic dental and orthopedic implants are essential therapeutic tool. The biologic success of an implant involves intimate contact between the implant and vital bone tissue, an event which has been termed osseointegration. The aim of the present study was to study the biocompatibility and biomechanic properties of different implant materials. Zircalloy 4 metallic cones (1.8 mm base x 2 mm height) were implanted in the diaphysis of the tibiae of 6 Wistar rats (90 g body weight) under i.p. Ethyl Urethane anesthesia. The animals were killed 30 days postimplantation, the tibiae were resected, and radiographed. One side chosen at random was used for the biomechanical study; whereas the other implant of each animal was processed for embedding in methyl-methacrylate. The bond of the implanted material to bone tissue was monitored immediately after resecting the tibiae by applying an extraction force to the base of the cone via a device designed ad hoc connected to a testing machine. Histological and radiographic analyses revealed the presence of bone tissue in contact with the implant surface. A force of about 35 g was necessary to separate the implant from the bone tissue. The system proposed renders possible the study of biocompatibility in histologic terms and in terms capacity to bond to bone tissue and could be a valuable research tool and the basis for quality control of all types of material, metallic or otherwise, used in endosseous implants.

Animals↗