Fine-scale genetic structure due to adaptive divergence among microhabitats.

It has been suggested that adaptive evolution on ecological timescales shapes communities. However, adaptation among environments relies on isolation or large selection coefficients that exceed migration effects. This reliance is tempered if adaptation is polygenic-does not depend on one allele completely replacing another but instead requires small allele frequency changes at many loci. Thus, whether individuals can evolve adaptation to fine-scale habitat variation (for example, microhabitats) is not resolved. Here we analyze the genetic divergence of the teleost fish, Fundulus heteroclitus, among microhabitats that are <200 m apart in three separate saltmarshes using 4741 single-nucleotide polymorphisms (SNPs). Among these SNPs, 1.3-2.3% have large and highly significant differences among microhabitats (mean FST=0.15; false discovery rate ⩽1%). The divergence among microhabitats for these outlier SNPs is larger than that among populations, exceeds neutral expectation and indicates surprising population structure among microhabitats. Thus, we suggest that polygenic selection is surprisingly effective in altering allele frequencies among many different SNPs that share similar biological functions in response to environmental and ecological differences over very small geographic distances. We acknowledge the evolutionary difficulty of large genetic divergence among well-connected habitats. Therefore, these studies are only the first step to discern whether natural selection is responsible and capable of effecting genetic divergence on such a fine scale.

Mitochondrial epileptic encephalopathy, 3-methylglutaconic aciduria and variable complex V deficiency associated with TIMM50 mutations.

Mitochondrial encephalopathies are a heterogeneous group of disorders that, usually carry grave prognosis. Recently a homozygous mutation, Gly372Ser, in the TIMM50 gene, was reported in an abstract form, in three sibs who suffered from intractable epilepsy and developmental delay accompanied by 3-methylglutaconic aciduria. We now report on four patients from two unrelated families who presented with severe intellectual disability and seizure disorder, accompanied by slightly elevated lactate level, 3-methylglutaconic aciduria and variable deficiency of mitochondrial complex V. Using exome analysis we identified two homozygous missense mutations, Arg217Trp and Thr252Met, in the TIMM50 gene. The TIMM50 protein is a subunit of TIM23 complex, the mitochondrial import machinery. It serves as the major receptor in the intermembrane space, binding to proteins which cross the mitochondrial inner membrane on their way to the matrix. The mutations, which affected evolutionary conserved residues and segregated with the disease in the families, were neither present in large cohorts of control exome analyses nor in our ethnic specific exome cohort. Given the phenotypic similarity, we conclude that missense mutations in TIMM50 are likely manifesting by severe intellectual disability and epilepsy accompanied by 3-methylglutaconic aciduria and variable mitochondrial complex V deficiency. 3-methylglutaconic aciduria is emerging as an important biomarker for mitochondrial dysfunction, in particular for mitochondrial membrane defects.

[Nutraceuticals in the combat against oral cancer].

Head and neck squamous cell carcinoma (HNSCC), the eighth most common cancer worldwide, accounts for approximately 600,000 new cases per year. The mobile tongue is the most common site for oral cancer and is associated with a poorer survival than other HNSCC sites. Standard therapeutic strategies have failed to significantly improve survival rates that have remained around 50% over the past four decades. In the last decade intense investigations on oral cancer highlighted the mandatory role of the tumor microenvironment (TME), in addition to the genetic aberrations and molecular biology changes within the cancer cells. Furthermore, the molecular crosstalk between cancer cells and TME components (i.e., cancer-associated fibroblasts, inflammatory pro-tumorigenic cells, etc.) has a crucial role in growth, invasion, spread and metastases of the cancer cells and consequently leads to poor prognosis. Recent studies suggest that plant-derived dietary agents nutraceuticals, especially curcumin and green tea, have the advantage to combat both malignant cells and TME components, unlike standard anti-cancer protocols that target only cancer cells. However, due to a very low bioavailability, nutraceuticals do not currently constitute an integral part of these protocols. Ongoing developments in nanotechnology for improved delivery are expected to overcome their challenging pharmacokinetics.

The expression and role of Lysyl oxidase (LOX) in dentinogenesis.

AIM: To establish whether eliminating Lysyl oxidase (LOX) gene would affect dentine formation. METHODOLOGY: Newborn wild-type (wt) and homo- and heterozygous LOX knock-out (Lox(-/-) and Lox(+/-) , respectively) mice were used to study developing tooth morphology and dentine formation. Collagen aggregation in the developing dentine was examined histochemically with picrosirius red (PSR) staining followed by polarized microscopy. Because Lox(-/-) die at birth, adult wt and Lox(+/-) mouse tooth morphologies were examined with FESEM. Human odontoblasts and pulp tissue were used to study the expression of LOX and its isoenzymes with Affymetrix cDNA microarray. RESULTS: No differences between Lox(-/-) , Lox(+/-) and wt mice developing tooth morphology were seen by light microscopy. Histochemically, however, teeth in wt mice demonstrated yellow-orange and orange-red polarization colours with PSR staining, indicating thick and more densely packed collagen fibres, whilst in Lox(-/-) and Lox(+/-) mice, most of the polarization colours were green to green-yellow, indicating thinner, less aggregated collagen fibres. Fully developed teeth did not show any differences between Lox(+/-) and wt mice with FESEM. Human odontoblasts expressed LOX and three of four of its isoenzymes. CONCLUSIONS: The data indicate that LOX is not essential in dentinogenesis, even though LOX deletion may affect dentine matrix collagen thickness and packing. The absence of functional LOX may be compensated by LOX isoenzymes.

Immunoprofile of focal lymphocytic infiltration in minor salivary glands of healthy individuals.

AIM: To characterize the immunohistochemical profile of the inflammatory cells included in the focal lymphocytic infiltration in the minor salivary glands of healthy individuals. MATERIALS AND METHODS: Tissue samples of the labial and palatal salivary glands from 46 postmortem subjects, demonstrating the presence of focal lymphocytic infiltration were quantitatively evaluated for the presence of T- and B-cell lymphocytes, plasma cells and macrophages by immunohistochemical and morphometric methods. RESULTS: B-cell lymphocytes, the predominant cell population in labial (67.5%) and palatal salivary glands (60.8%), were more frequent than T-cell lymphocytes in both glands (P < 0.001). Among the T-cell lymphocytes, CD(4)-positive cells were significantly more prevalent than the CD(8)-positive cells (P < 0.001). Plasma cells were almost absent, comprising only 0.01% of the focal lymphocytic infiltration cells of the labial and palatal salivary glands. CONCLUSIONS: Focal lymphocytic infiltration in the samples of the salivary glands obtained from healthy individuals is devoid of plasma cells. This can serve as an additional means to differentiate between focal lymphocytic infiltration in patients with Sjögren's syndrome, in which plasma cells are abundant, and focal lymphocytic infiltration in individuals with other causes of focal sialadenitis.

Giant cell granuloma of the jawbones--a proliferative vascular lesion? Immunohistochemical study with vascular endothelial growth factor and basic fibroblast growth factor.

AIM: To estimate the angiogenic activity in central giant cell granuloma (CGCG) by immunohistochemical stains for vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). VEGF and bFGF immunoreactivity of the lesional mononuclear (MC) and giant (GC) cells was also investigated. METHOD: The study consisted of 41 cases of CGCG. Vascularity was quantified by microvascular volume (MVV) as determined by point counting. In five cases of CGCG, regions at the surrounding border, which demonstrated reactive vascular-rich inflammatory areas, served as control. Immunoreactivity of the MC and GC was assessed as the percentage of VEGF- and bFGF-positive cells from the total number of the respective cell type. RESULTS: Within CGCG lesions the extent of angiogenesis was low; MVV did not exceed 5% for either VEGF (88% of lesions) or bFGF (78% of lesions). The mean MVV of VEGF- and bFGF-positive blood vessels was 2.9% +/- 2.4% and 3.46% +/- 2.35%, respectively, significantly lower than in the control areas (27.5% +/- 7.3% and 28.08% +/- 5.5%, respectively) (P = 0.043). VEGF-positive and bFGF-positive MC and GC were found in nearly all lesions and in less than half of the lesions, respectively. CONCLUSION: The low mean MVV of VEGF- and bFGF-positive blood vessels implies low angiogenic activity, which does not support the designation of CGCG as a true proliferative vascular lesion. MC and GC immunoreactivity for the angiogenic factors is assumed to play an important role in the osteoclastogenesis process, thus contributing to additional growth of the CGCG lesions.

Herpes simplex infection--Part II: Management of HSV infections.

Oral and perioral herpes simplex virus infections are commonly seen and managed by the dental practitioner. Many topical and oral antiviral agents are available in Israel. However, only a few regimens are based on solid evidence. The purpose of this study was to review the mode of action of antiviral agents and to present therapeutic regimens supported by randomized control trials.

Immunohistochemical expression of glucocorticoid and calcitonin receptors as a tool for selecting therapeutic approach in central giant cell granuloma of the jawbones.

Aggressive cases of central giant cell granuloma (CGCG) have been arbitrarily treated with steroids and calcitonin. The aim of this study was to develop a practical tool, based on the relative percentage of positively stained cells for glucocorticoid and/or calcitonin receptors, for selecting the appropriate therapeutic agents to treat CGCG. Forty-one formalin-fixed, paraffin-embedded blocks of CGCG were immunohistochemically stained for glucocorticoid and calcitonin receptors. Percentage of positive lesional mononuclear and giant cells was estimated for each case. Intense staining was considered as staining 50% or more of the cells. Correlations among staining scores were analysed by Spearman's test. All cases stained for glucocorticoid receptor. Heterogeneity among cases showed as intense staining in both cell types (21 lesions), in only one cell type (13 lesions) and weakly in both cell types (7 lesions). Only 23 cases demonstrated staining for calcitonin receptor, of which 15 stained intensely in both cell types and 7 in only one cell type. Among staining scores of both receptors, no significant statistical correlation was found (P>0.05). It can therefore be suggested that the relative percentage of immunohistochemically stained mononuclear and giant cells for glucocorticoid and/or calcitonin receptors can serve as a reliable and practical tool for selecting the appropriate therapeutic agent to treat CGCG. The clinical application of this method should be assessed in well controlled clinical studies, especially in cases of aggressive lesions, before initiating and during therapeutic treatment.

Estimation of the cortical connectivity by high-resolution EEG and structural equation modeling: simulations and application to finger tapping data.

Today, the concept of brain connectivity plays a central role in the neuroscience. While functional connectivity is defined as the temporal coherence between the activities of different brain areas, the effective connectivity is defined as the simplest brain circuit that would produce the same temporal relationship as observed experimentally between cortical sites. The most used method to estimate effective connectivity in neuroscience is the structural equation modeling (SEM), typically used on data related to the brain hemodynamic behavior. However, the use of hemodynamic measures limits the temporal resolution on which the brain process can be followed. The present research proposes the use of the SEM approach on the cortical waveforms estimated from the high-resolution EEG data, which exhibits a good spatial resolution and a higher temporal resolution than hemodynamic measures. We performed a simulation study, in which different main factors were systematically manipulated in the generation of test signals, and the errors in the estimated connectivity were evaluated by the analysis of variance (ANOVA). Such factors were the signal-to-noise ratio and the duration of the simulated cortical activity. Since SEM technique is based on the use of a model formulated on the basis of anatomical and physiological constraints, different experimental conditions were analyzed, in order to evaluate the effect of errors made in the a priori model formulation on its performances. The feasibility of the proposed approach has been shown in a human study using high-resolution EEG recordings related to finger tapping movements.

Herpes simplex virus infection: part I--Biology, clinical presentation and latency.

Oro-facial manifestations of herpes simplex virus (HSV) infections are very common, and include primary herpetic gingivo-stomatitis, recurrent herpes labialis and recurrent intra-oral herpes. Recent research in molecular biology has advanced our knowledge of the HSV pathogenesis and behavior. Understanding the exact mechanism of HSV latency and reactivation enables improvement of drug therapy and prevention strategies of HSV infections. The aim of this review is to update the recent development in the biological and clinical research related to HSV infection, focusing on oral and perioral lesions.

Treatment modalities for chemo--and radiotherapy-induced oral mucositis--critical analysis and practical guidelines.

Oral mucositis (OM), an inevitable side effect of almost all anti-cancer treatments, affects the patient's physiological functions and their psychological well being. In spite of numerous treatment modalities for this condition, there is still a lack of evidence-based clinical trials that can provide a single efficient pharmacologic agent or intervention for either prevention or treatment of OM. This study analyses and summarizes some of the more "accepted" modalities for treatment of OM. It is recommended that these modalities rely on simple, convenient and innocuous interventions, which should be adjusted for each individual complaint. Well-designed, controlled and standardized studies are necessary to validate effectiveness of available, as well as newly developed interventions for OM.

Oral cancer: diagnostic options as an aid to histology in order to predict patients at high risk for malignant transformation.

Oral cancer continues to afflict the general population in growing numbers with a relatively low survival rate. Today, through histology, the potential danger of a pre-cancerous lesion can be detected, yet it does not reflect with certainty its biologic behavior. Recent studies have shown that some pre-cancerous lesions with mild dysplasia may undergo malignant transformation and lesions with severe dysplasia may remain quiet. Our goal is to locate the relatively small population of patients that are at high risk for malignant transformation at an early stage of carcinogenesis so they can be treated effectively. Methods that can identify the molecular and DNA changes may provide the data needed to predict the true malignant potential of a pre-cancerous lesion and its potential for transformation with a higher degree of certainty. The purpose of this article was to review some of the diagnostic options that are being studied and their link to carcinogenesis.

Urine polymerase chain reaction as a screening tool for the detection of congenital cytomegalovirus infection.

OBJECTIVES: To define the incidence of congenital cytomegalovirus (CMV) infection in a defined population in Israel as diagnosed by urine polymerase chain reaction (PCR), and to assess the utility of this method for screening for congenital CMV infection. DESIGN: A convenient sample of urine specimens from asymptomatic newborns were subjected to CMV PCR. Positive results were validated by urine tube culture and by determination of serum CMV IgM antibodies. Maternal CMV IgG was determined in a representative sample of mothers. Newborns with positive urine specimens underwent full clinical evaluation. Epidemiological characteristics of the mothers were extracted from the medical records. SETTINGS: Two medical centres in Israel with different population characteristics. PATIENTS: A total of 2000 newborns (1000 in each medical centre). MAIN OUTCOME MEASURE: Presence of CMV DNA in the urine. RESULTS: Despite significant epidemiological differences between the populations in the two hospitals, the CMV seroprevalence was similar, 80.5% and 85%. Fourteen of the 2000 newborns screened (0.7%) were PCR positive. Urine culture was positive in nine of 10 specimens; IgM was positive in only two of 13 newborns with positive PCR. Eleven newborns underwent full or partial evaluation, and only one (9%) was symptomatic. CONCLUSIONS: The incidence of congenital CMV infection in the study population was 0.7%; over 90% were asymptomatic. Urinary CMV PCR is a reliable, rapid, and convenient method, and thus may serve as a screening tool for the detection of congenital CMV infection.

Estudio comparativo de los cambios relacionados con la edad en las glándulas salivales palatinas y labiales / A comparative study of age-related changes between palatal and labial salivary glands

Objetivos: El proposito de este artículo es comparar los cambios histomorfométricos relacionados con la edad entre glandulas salivales palatinas y labiales (GSP y GSL respectivamente).Diseño del estudio: Se realizó un análisis del volumen proporcional medio (VPM) del componente acinar (CA), del componente ductal (CD) y del componente inflamatorio (CI) de 120 muestras de GSP y GSL, obtenidas de sujetos sin historia previa conocida de patología o tumores de glándulas salivales. Las muestras se dividieron en grupos de edad: jovenes (n=30, =30 años), adultos (n=45, 31-60 años) y ancianos (n=45, >60 años).Resultados: En GSP, se apreció una disminución significativa del VPM del CA (p<0,0001) y concomitantemente un aumento significativo del VPM del CD (p<0,0001), para todos los grupos de edad. En GSL, se apreció una disminución significativa del VPM del CA (p=0,002) y concomitantemente, un aumento del VPM del CD (p=0,002), entre los grupos de edad adultos y ancianos. Se observó un aumento significativo del VPM del CI en GSP entre los grupos de edad jóvenes y adultos (p<0,0001), mientras que en GSL esta diferencia se hizo evidente entre los grupos adultos y ancianos (p<0,0001). Los componentes ductal e inflamatorio demostratron el mismo patrón de cambios relacionados con la edad tanto en GSP como en GSL. Conclusiones: A la vista de estos resultados, se sugiere que los cambios prematuros y continuos en GSP, en comparación con GSL, pueden explicar parcialmente su implicación más frecuente en los procesos patológicos (AU)

PCNA in palate and tongue mucosal dysplastic lesions induced by topically applied 4NQO in desalivated rat.

OBJECTIVES: Saliva has been suggested to have a protective role against carcinogens in the oral cavity in animals. Water-soluble 4NQO is a suitable carcinogen to use in examining the role of saliva in oral cancer. The purpose of this study was to follow the changes induced by the carcinogen at the molecular level, as well as the effect of lack of saliva on these changes. MATERIALS AND METHODS: Topical application to the palate of a 0.5% 4NQO solution dissolved in glycol was used for 4 months to induce malignant transformation in a desalivated rat model. Histomorphometric analysis of proliferating cell nuclear antigen (PCNA), a cell cycle regulator and a proliferation marker, was performed. RESULTS: Manifestation of PCNA significantly increased as the observed histologic changes progressed from hyperkeratosis, to mild or moderate dysplasia, severe dysplasia and squamous cell carcinoma. Differences in manifestation of PCNA among the diagnostic groups was significant (p< 0.05). In the desalivated group, PCNA expression was significantly higher than in control and normal groups, in both tongue and palate after 2 and 4 months (p< 0.05). CONCLUSIONS: An unknown component of saliva has a temporary anti-carcinogenic protective effect, which can both delay and decrease the level of proliferation induced by the carcinogen 4NQO. The specific salivary component and the mechanism by which this protective effect is rendered are yet to be discovered.

Histopathological morphometric evaluation of 2 different hydroxyapatite-bone derivatives in sinus augmentation procedures: a comparative study in humans.

BACKGROUND: Xenografts to augment the maxillary sinus have been used extensively. The aim of the present study was to evaluate, qualitatively and quantitatively, two different HA derivatives of natural and synthetic sources on newly formed bone in the augmented sinus. METHODS: A bilateral sinus augmentation procedure with simultaneous (16 out of 20 sites) or subsequent implant placement was performed in 10 patients. The antrum was randomly filled with a deproteinized, bovine hydroxyapatite mineral (B-HA) on one side and a non-ceramic resorbable hydroxyapatite (NC-HA) on the other. Cylindrical specimens were harvested from the augmented core at 12 months. Decalcified specimens were sectioned at a cross-horizontal plane and stained with hematoxylin and eosin for histopathologic and histomorphometric examinations. Tissue area fractions of bone, marrow, and the grafted particles were calculated for each specimen from the lateral to the deep region, and changes in values were compared within each material and between them. RESULTS: New bone formation was evident. B-HA and NC-HA particles were observed in all specimens surrounded by newly formed bone in direct connection or by soft tissue marrow. Morphometrically in the B-HA sites, from the lateral to deeper area, bone area fraction increased from 29.8% to 54.2% (average 42.1%) and marrow area fraction decreased from 37.9% to 26.7% (average 33.3%). The mineral area fraction decreased from 32.3% to 19.1% (average 24.7%). All increasing/decreasing patterns were statistically significant (P < 0.001). In the NC-HA sites, from the lateral to deeper area, bone area fraction increased from 25% to 36.5% (average 32.3%) and marrow area fraction decreased from 51.6% to 41.9% (average 43.2%) (P <0.001). The mineral area fraction decreased from 29% to 21.7% (average 24.6%) (P = 0.038). Comparison between the two HA derivative groups showed a significant difference between the bone area fraction averages (P = 0.0053) and between the increasing patterns along the core depth (P = 0.0006). There was also a significant difference between the decreasing marrow patterns (P = 0.003), but not between their averages. Comparison between the mineral area fractions showed no differences. CONCLUSIONS: B-HA and NC-HA were proven to be biocompatible materials. Although the B-HA-augmented sites showed a higher percentage of bone formation at 12 months, both are suitable bone derivatives in sinus augmentation procedures and can accommodate osseointegrated implants.

Porous bovine bone mineral in healing of human extraction sockets: 2. Histochemical observations at 9 months.

BACKGROUND: Porous bovine bone mineral (PBBM) has been used in ridge preservation procedures following tooth extractions. The aim of this study was to investigate histochemically tissue sockets grafted with PBBM at 9 months post-extraction. By using different histochemical stainings, characteristics of the newly formed bone; i.e., lamellar/woven ratio at different socket depths, were investigated and the arrangement of bone around the grafted material, as well as the nature of the amorphous organic material found in all specimens, were examined. METHODS: After extraction of 15 single-rooted maxillary teeth from 15 patients, socket sites were grafted with PBBM particles (250 to 1,000 mu). Primary soft tissue closure of the grafted site was established using the rotated split palatal pedicle flap technique. At 9 months, a cylindrical tissue specimen, 2.5 mm in diameter, was trephined from each previously grafted site followed by placement of a screw-shaped implant. Horizontal tissue section cuts, 5 mu wide, were prepared for histological examination. Histochemical staining included alcian blue, periodic-acid Schiff, Mallory trichrome, reticulin, Van Gieson, and picrosirius red (PSR). PSR stained slides were further evaluated morphometrically, using polarized microscopy to determine the amount of lamellar versus woven bone in superficial, mid and deep specimen section cut areas. RESULTS: All staining methods revealed that newly formed bone encircled and adhered to the grafted material in most specimens. Mallory trichrome staining showed osteoblasts present within an osteoid layer, lining the interface zone of PBBM particles and the new osseous tissue. Morphometric evaluation of the PSR stained slides disclosed a constant pattern of increased osseous tissue in a coronal-apical direction. An average of 17.1% osseous tissue with 1:12.9 lamellar/woven bone ratio was calculated in the superficial area. The average bone tissue fraction was 48.3% with a lamellar/woven ratio of 1:3.8 in the mid section area and in the deep area, it increased to 63.9%, with a lamellar/woven ratio average of 1:1.7. Differences between ratios at these sites were statistically significant (P<0.001). An amorphous organic substance was noted in most grafted particles. This material usually attached cell striae and harbored glycoproteins as revealed by periodic-acid Schiff and alcian blue stainings. Mallory trichrome staining showed denatured protein within the decalcified mineral particles; reticulin, Van Gieson stainings, and polarization of PSR stained sections refuted the existence of collagen in the grafted particles. CONCLUSIONS: Cancellous PBBM is a biocompatible filler agent in extraction socket sites and an acceptable graft for edentulous ridge preservation at sites prepared to receive endosseous implants. The osteoconductivity of PBBM was determined based on promoting osseous ingrowth and close integration with the newly generated bone. Grafted particles were not significantly resorbed at 9 months. Further studies are needed to determine the resorbable capability, as well as the nature and significance of the amorphous organic substance of PBBM observed in the grafted particles.

Immediate loading of single-tooth implants: immediate versus non-immediate implantation. A clinical report.

The hypothesis of the present study was that immediate loading of implant-supported restorations replacing single missing teeth could be a successful procedure. The present study compared the clinical success of immediately loaded single-tooth implants placed in fresh extraction sites to that of immediately loaded single-tooth implants placed in healed sites. From the years 1997 to 1998, 26 patients, ranging in age from 18 to 70 years, presented for the placement of 28 immediately loaded implants intended to support single-tooth ceramometal restorations. Nineteen implants were placed into fresh extraction sites, and 9 implants were placed into healed sites. Temporary prefabricated acrylic resin crowns were prepared and adjusted. At the time of traditional second-stage surgery (3 to 6 months after implantation), the implants were restored with single-tooth ceramometal prostheses. The survival rates were 82.4% and 100% for immediate and non-immediate implants, respectively. Follow-up ranged from 6 to 24 months from the day of implant placement, with a mean of 13 months for the immediate implants and 16.4 months for the non-immediate implants. Radiographic marginal bone loss after 3 to 6 months did not extend beyond the abutment-implant junction. Within the limits of the present investigation, immediate loading of single-tooth implants placed in healed sites is a possible treatment alternative. Immediate loading of single-tooth implants placed in fresh extraction sites carried a risk of failure approximating 20% in this patient population.

The effect of desalivation on 4-nitroquinoline-1-oxide-induced tongue carcinogenesis: a morphometric study of nucleolar organizer regions.

Saliva is an important factor in the oral cavity and could be significant in protecting against carcinogens. In experimental models of carcinogenesis, saliva was shown to have a temporary protective effect against the carcinogens DMBA and 4-nitroquinoline-oxide (4NQO). Silver-stained nucleolar organizer regions (AgNORs) are considered markers for both proliferative capacity and prognosis. The purpose of the present study was to investigate the effect of desalivation on AgNOR parameters in lesions induced by the carcinogen 4NQO in a rat model, in order to trace early nuclear changes. The study group consisted of 120 male Wistar-derived rats. The experimental group (n=56) underwent surgical desalivation; the control group (n=56) underwent a sham operation, and both groups were administered a solution of 0.001% 4NQO in the drinking water. A normal group (n=8) did not receive surgery and drank tap water. Rats were sacrificed at 7, 14, 22, and 28 weeks. Formalin fixed, paraffin embedded sections of the tongue were silver-stained and AgNOR parameters were analyzed using computerized image analysis. In both desalivated and control groups, the nuclear area was significantly higher than the normal. This difference was already evident at 7 weeks. The mean AgNOR area was significantly higher in the desalivated group at week 7 and continued to increase over time. The mean AgNOR number was also significantly higher in the desalivated group at week 7. Differences between the desalivated and control groups diminished with time. These changes in proliferative activity, as expressed by AgNOR parameters, presented earlier changes in comparison to those observed in microscopic examination of the same slides. Results suggest that saliva in the oral cavity can delay malignanttransformation, but continued exposure to the carcinogen overrides this effect. AgNOR stain seems to be sensitive and allows for early identification of intranuclear changes.