Fine Structure of Maxillary Palps in Adults of Hermetia illucens (Diptera: Stratiomyidae)

A relevant species in waste management but also in forensic, medical, and veterinary sciences is the black soldier fly, Hermetia illucens (Linnaeus; Diptera: Stratiomyidae). An ultrastructural study by scanning electron microscopy (SEM) was conducted for the first time on maxillary palps of both sexes, describing in detail the morphology and distribution of sensilla and microtrichia. The maxillary palps, composed of two segments, show sexual dimorphism in length and shape. In both sexes, the first segment is covered only by microtrichia, but the second one is divided into two parts: the proximal one, covered only by microtrichia, and the distal one containing both microtrichia and sensory structures. These structures include two types of sensory pits and one of chaetic sensilla. Due to sexual dimorphism in palp size, females have a higher number of sensory pits. The sexual dimorphism of palps and the presence and role of sensilla in H. illucens was discussed in comparison to other species of the family Stratiomyidae and of other Diptera. This study may represent a base for further investigations on mouthpart structures of this species, involved in key physiological activities, such as feeding, mating and oviposition.

IL-1 Gene Cluster is Not Linked to Aggressive Periodontitis

The interleukin-1 (IL-1) gene family has been associated with susceptibility to periodontal diseases, including aggressive periodontitis (AgP); however, the results are still conflicting. The present study investigated the association between IL-1 genes and AgP using 70 markers spanning the 1.1-Mb region, where the IL-1 gene family maps, and exploring both the linkage disequilibrium (LD) and the haplotype structure in a case-control study including 95 patients and 121 control individuals. No association between AgP and IL1A, IL1B, and IL1RN genes was found in either single-point or haplotype analyses. Also, the LD map of the region 2q13–14 under the Malécot model for multiple markers showed no causal association between AgP and polymorphisms within the region (p = 0.207). In conclusion, our findings failed to support the existence of a causative variant for generalized AgP within the 2q13–14 region in an Italian Caucasian population.

Surnames in Siberia: a study of the population of Yakutia through isonymy

We studied the isonymic structure of the Republic of Sakha (Yakutia), in the Russian Federation, using the surname distributions of 491,259 citizens above 18 years registered as residents in 2002. These were distributed in 35 districts and 497 towns and settlements of the Republic. The number of different surnames was 44,625. Matrices of isonymic distances between the 35 districts were tested for correlation with the geographic distance between the population centers of gravity of the districts. We found that, for the whole of Yakutia, Nei's distance was correlated with geographic distance (r = 0.693 +/- 0.027). A dendrogram of the 35 districts was built from the distance matrix, using the UPGMA method. The clusters identified by the dendrogram correlate with the geographic position of the districts. The correlation of random inbreeding calculated from isonymy, F(ST), with latitude was positive and highly significant but weak (r = 0.23). So, inbreeding was highest in the Arctic districts, and lowest in the South. Average alpha for 497 towns was 107, for 35 districts it was 311, and for the Republic 433. The value of alpha was higher for Russian than for the local languages. The geographical distribution of alpha, high in the Center and South-East and lower in the North-West, is compatible with the settlement of groups of migrants moving from the South-East toward the center and the North of Yakutia. It is proposed that low-density demic diffusion of human populations results in high inbreeding and may have been a general phenomenon in the early phases of human radiations.

General preadaptation of viral infectors to their hosts

We tested the hypothesis of optimal adaptation of viral infectors to eukaryotic hosts, using (1) correlation in codon and amino acid usage between organisms, and (2) canonical correlation between groups of hosts and infectors. The codon correlations between parasites and hosts vary, being low between swine and African swine fever virus (ASF; r = 0.18), and highest between potato and potato virus X (r = 0.60). The correlations might indicate different stages of evolution toward optimal adaptation of the parasite codon distribution to the host tRNA pools. The amino acid correlations vary from r = 0.71 between pig and ASF, to 0.88 between catfish and its herpesvirus. It was observed that both in virus and hosts, there is a negative correlation between frequency of an amino acid and molecular weight. Therefore, it was advanced that viral infectors might be preadapted to their hosts because of similarities of the tRNA pools of hosts, and that evolution toward optimization would be dependent on the size of the divergence between the codon distributions of infector and host. Preadaptation does not imply origin of the virus by lateral transfer from the present host, since the correlation of the molecular weight of amino acids with their abundance in proteins is a general phenomenon.

Surnames in Texas: a population study through isonymy

To study the isonymy structure of Texas, we analyzed the surname distributions of 3.6 million telephone users registered for the year 1996 in 232 towns distributed in the 7 regions of the state. The number of different surnames was 235,740. Matrices of isonymy distances between towns and between geographic regions were constructed and tested for correlation with geographic distance. We found that isonymy distances between the seven regions showed borderline or no correlation with geographic distance, with r = 0.089 +/- 0.232, r = 0.492 +/- 0.232, and r = 0.337 +/- 0.232 for Lasker's, Euclidean, and Nei's distances, respectively. Isonymy distances between towns were significantly correlated with geographic distance, with r = 0.249 +/- 0.006 for Lasker's distance, r = 0.338 +/- 0.006 for the Euclidean distance, and r = 0.418 +/- 0.006 for Nei's distance. Two dendrograms, one for the 7 regions and one for the 232 towns, were built from the matrices of Nei's distances. The dendrogram for regions indicates that a main surname differentiation exists between the East and West areas of Texas, with West Texas being predominantly Hispanic and East Texas being predominantly English-speaking. The dendrogram for the towns confirms in detail the differences identified by the matrix of distances between regions. Random inbreeding calculated from isonymy, F(ST), was highest in the west and in the south of the state. It was lowest in the area of Austin and Houston. Average Fisher's alpha for towns was 734, for regions it was 1,047, and for Texas as a whole it was 1,230. The geographic distribution of alpha in the state shows distinctly lower values in the traditionally Hispanic west and higher values in the east and on the Gulf of Mexico.

Amino acid and codon use: in two influenza viruses and three hosts

OBJECTIVE

The aim of this study was to compare the use of amino acids and codons in influenza viruses A and B and in their common hosts, to highlight any relevant difference.

METHODS

The frequency of the 20 amino acids and of the 61 codons was studied in influenza viruses A, B, and in man, pig, and chicken. The correlation in amino acid and codon use among these hosts was calculated.

RESULTS

The correlation between the frequency of the 20 amino acids and the molecular weight was also calculated and it was very similar in all studied hosts, ranging from 0.506 to 0.595. The correlation of codon frequency among these organisms was highest between man and chicken (r=0.974), and lowest between pig and virus B (r=0.147).

CONCLUSIONS

The important correlation in codon use among the three hosts and the two viruses suggests there was a remote lateral gene transfer among the three hosts and the two viruses. The higher use of alanine, leucine, and proline in man versus virus A is significant.

A genetic association study of dopamine metabolism-related genes and chronic headache with drug abuse

To assess the role of dopamine metabolism-related genes in the genetic liability to chronic headache with drug abuse (DA). We performed a genetic association study using four functional polymorphisms of the dopamine receptor 4 (DRD4), dopamine transporter (DAT), mono-amino-oxidase A (MAOA) and cathecol-O-methyl-transferase (COMT) genes in 103 patients with chronic daily headache associated with DA (CDHDA). Control samples were 117 individuals without headache or DA (controls) and 101 patients with episodic migraine without aura and without DA (MO). No differences were found at the COMT and MAOA genes among the three groups investigated. Allele 4 of DRD4 was significantly overrepresented in patients with MO compared with both controls and CDHDA. Allele 10 of the DAT gene was significantly underrepresented in patients with CDHDA when compared with the MO group. Genetic variability at the DRD4 gene is involved in the predisposition to episodic MO but not to DA, while liability to CDHDA may involve genetic variability at the DAT gene in comparison with episodic MO.

Surnames and dialects in France: population structure and cultural evolution

To study the isonymy structure of France as related to local language variations, the surname distributions of 6.03 million telephone users registered for the year 2002 were analysed in the 21 conterminous regions, their 94 departments and in 809 towns of the Country. For regions and departments the differences among local dialects were quantified according to the dialecto-metrization of the Atlas Linguistique Français. We found that Lasker's distance between regions was correlated with geographic distance with r=0.692+/-0.040, while Euclidean (r=0.546+/-0.058) and Nei's (r=0.610+/-0.048) distances were less correlated. Slightly lower correlations were observed for departments. Also, dialectometric distance was correlated with geography (r=0.582+/-0.069 for regions and r=0.617+/-0.015 for departments). The correlations between Lasker and dialectometric matrix distances for regions and departments are r=0.625+/-0.046 and 0.544+/-0.014, respectively, indicating that the common cause generating surname and language diversity accounts for about 35% of the differentiation. Both Lasker and dialectometric distances identify very similar boundaries between Poitou, Centre, Bourgogne and Franche Comptée at the North, and Aquitaine, Limousin, Auvergne, Rhône-Alpes in the South. Average Fisher's alpha for France was 7877 the highest value observed for the European countries studied to date. The size of alpha in most French towns indicates considerable recent immigration.

Surnames in Argentina: a population study through isonymy

In order to study the isonymic structure of Argentina, the surname distributions of 22.6 million electors registered for the year 2001 were analyzed in the 24 districts (distritos) and 541 municipalities (municipios) of the country. The number of different surnames found was 414,441. Matrices of isonymic distances between districts were constructed and tested for correlation with the geographic distance between the capital towns of the districts. We found that, for the whole of Argentina, Euclidean distance was correlated with the log of geographic distance (r=0.480+/- 0.067). A dendrogram of the 24 regions was built from the matrix of Euclidean distances, using the UPGMA method. The clusters identified by the dendrogram are coincident with conterminous geographical regions of the country. Random inbreeding calculated from isonymy, F(ST), was highest in La Rioja, Corrientes, and Santiago del Estero. It was lowest in the area of Buenos Aires and in the north-central region of Santa Fé. Average Fisher's alpha for municipalities was 358; for districts, it was 422; and for Argentina as a unit, it was 602. The geographical distribution of alpha in 541 municipalities, high in the east and lower in the west of the country, is compatible with the settlement in the 20th century of subsequent waves of immigrants moving from the North Atlantic coast toward the foot of the Andes and toward the south. The present structure of Argentina indicates that migration dominates over drift.

Linkage disequilibrium analysis of case-control data: an application to generalized aggressive periodontitis

Several studies have shown a role for the involvement of interleukin (IL)-1 gene cluster polymorphisms in the risk of periodontal diseases. In the present study, we tested polymorphisms, derived from genes of the IL-1 cluster, for association with generalized aggressive periodontitis (GAP) through both allelic association and by constructing a linkage disequilibrium (LD) map of the 2q13-14 disease candidate region. The IL-1RN (VNTR) genotype distribution observed was significantly different in GAP and control subjects (P=0.019). We also observed some evidence for an association between GAP and the IL-1B(+3953) polymorphism (P=0.039). The pattern of association in the region, represented as an LD map, identifies a recombination hot area between the IL-1B(+3953) and IL-1B(-511) polymorphisms. Multilocus modelling of association with disease gives a location for the peak association at the IL-1B(+3953) marker, although support for the peak is not significant. Haplotype analysis identifies a IL-1B(+3953)-IL-1B(-511) haplotype as having the lowest P-value in the region. Recognition of the presence of a recombination hot area between the IL-1B(+3953) and IL-1B(-511) polymorphisms will have an important bearing on future efforts to develop higher resolution SNP analysis in this region for both this and other diseases for which this cluster is implicated.

Isolation by language and distance in Belgium

The isonymy structure of trilingual Belgium was studied using the surname distributions for 1,118,004 private telephone users. The users were distributed in 77 Flemish, 76 French, and 3 German speaking towns, selected on a geographic basis to form an approximately regular grid over Belgium. Lasker's distance was found to be considerably higher between languages than within languages. For the whole of Belgium, irrespective of language, it was highly correlated with linear geographic distance, with r = 0.721+/-0.014, which is the highest correlation observed in European countries to date. Within Belgium and within languages, the correlation was highest among the Flemish (r = 0.878 +/- 0.007), and lowest among the French (r = 0.631+/-0.020). Isolation by distance in Belgium is the highest we have found in Europe, and as high as in Switzerland where the different languages are separated by geographical barriers. This is not the case in Belgium, so that the considerable isolating power of languages emerges clearly from the present analysis. From the comparison of Lasker's distance between (9.48) and within (8.16) languages, and from its regression over geographic distance (b = 0.01206), it was possible to establish a quantitative relationship between the isolating power of languages and that of geographic distance as (9.48-8.16)/0.01206 = 109 kilometres. This transformation of language distance into an equivalent geographic distance, given here for Belgium, can be applied to any similar geo-linguistic situation.

The names of Spain: a study of the isonymy structure of Spain

In order to estimate the isonymy structure of Spain, we studied surname distribution in 283 Spanish towns based on 3.625 million telephone users selected from 6.328 million users, downloaded from a commercial CD-ROM which contains all 13 million users in the country. Since in Spain the surname is made by the paternal and the maternal surname, it was possible to classify surnames according to parental origin. Two matrices of isonymy distances, one for paternal and one for maternal surnames, were constructed and tested for correlation with geographic distance. For the whole of Spain, Euclidean distance was significantly but weakly correlated with geographic distance both for paternal and maternal surnames, with r = 0.205 +/- 0.013 and r = 0.263 +/- 0.012, respectively. Two dendrograms of the 283 sampled towns were built from the two matrices of Euclidean distance. They are largely colinear. Four main clusters identified by the dendrograms are correlated with geography. Given the surname structure of Spain, we were able to calculate from isonymy and for each town 1). total or expressed inbreeding, 2). random or expected inbreeding, and 3). local inbreeding. Total inbreeding, F(IT), was highest in the North Atlantic regions and lowest along the Mediterranean Coast. The lowest levels were found in Andalusia, Catalunyia, Valencia, and Navarra. Random inbreeding, F(ST), had a similar geographical pattern. Local inbreeding, F(IS), was relatively uniform in the whole of Spain. In towns, random inbreeding dominates over local inbreeding. From the analysis, it emerges that the northwestern area of Spain is the most inbred.

Response to a plaque control regimen on different levels of gingival inflammation

BACKGROUND

The purpose of the present study was to evaluate the effectiveness of an oral hygiene regimen in subjects presenting with substantially different severity of plaque-associated gingivitis.

METHODS

The study population was selected from among a large pool of subjects undergoing an experimental gingivitis trial. At completion of the 21-day plaque accumulation period, 2 sub-groups of subjects were identified on the basis of uppermost and lowest quartile for Gingival Index (GI), respectively classified as highly-inflamed (Hinf; n=17; GI: 1.07+/-0.10) and slightly-inflamed (Sinf; n=22; GI: 0.28+/-0.09) groups. An oral hygiene regimen, based on use of amine fluoride/stannous fluoride-containing toothpaste and mouthrinse, was then prescribed for 21 days.

RESULTS

Plaque Index (PI), GI, gingival crevicular fluid (GCF) and Angulated Bleeding Index (AngBI) significantly decreased after treatment in both HInf and SInf groups (p<0.001). However, PI (0.77+/-0.41 vs 0.43+/-0.33, p<0.01), GI (0.23+/-0.30 vs 0.08+/-0.11, p<0.05), GCF (15.23 +/-7.11 vs 7.66+/-2.93, p<0.0000) remained significantly greater in the Hinf group compared to the Sinf group.

CONCLUSIONS

These results suggest that 1) an oral hygiene regimen based on amine/stannous fluoride-containing toothpaste and mouthrinse is effective in reducing plaque-associated gingivitis, regardless of pre-existing severity of gingival inflammation; 2) the level of improvement in gingival status, however, is dependent on the pre-existing severity of the inflammatory condition.

A genetic association study of migraine with dopamine receptor 4, dopamine transporter and dopamine-beta-hydroxylase genes

We assessed the role of some dopamine metabolism genes in the genetic susceptibility to migraine. We performed an association study using three functional polymorphisms: a 48-base-pair (bp) tandem repeat in the D4 dopamine receptor gene ( DRD4), a 40-bp tandem repeat in the dopamine transporter gene ( DAT) and a dinucleotide repeat in the dopamine beta-hydroxylase ( DBH) gene. Allelic and genotypic frequencies for each polymorphism were assayed in two migraine populations (93 individuals with migraine with aura (MA) and 101 with migraine without aura (MO)) and were compared with those in a control group (117 individuals). No significant differences were found between control and migraine groups for DAT and DBH polymorphisms. Instead, the distribution of alleles for the DRD4 gene in the MO group was significantly different from those in both MA and control groups, with the shortest and longest alleles being less frequent in MO. Our data indicate that MO, but not MA, shows significant genetic association with DRD4.

Isonymy and isolation by distance in the Netherlands

The isonymy structure of the Netherlands was studied using the surname distribution of 2.4 million private telephone users selected from a 1996 commercial CD-ROM containing the names of 6.3 million users in the country. The users were distributed in 226 towns selected on a geographic basis to form an approximately regular grid throughout the Netherlands. Names of telephone users in each town were downloaded from the CD-ROM, with private users being selected for inclusion in the analysis. The shortest linear distance between several nearest neighboring towns was less than 2 km (e.g., Kampen and Ijsselmuiden, Krommen and Zaandijk, Hendrikdo and Papendrecht) and the longest distance was 326 km (Delfzijl and Oostburg ZL). The number of different surnames revealed by the analysis was 126,485. Lasker's distance, the negative value of the logarithm of isonymy between localities, was found to be significantly correlated with linear geographic distance, with r = 0.47 +/- 0.006. A dendrogram built using the matrix of isonymy distances, using the nearest neighbor-joining method, separates the Dutch towns into several clusters, most of them correlated with traditional Dutch regions. Comparisons with the results of previous analyses of the structure of other European countries are given. From the present analysis, isolation by distance emerges clearly, and it is relevant, although much weaker than in Switzerland, Austria, Italy, and Germany. The random component of inbreeding estimated from isonymy indicates a considerable degree of homogeneity in the Netherlands.

Cytokine imbalance in pregnancies with fetal chromosomal abnormalities

BACKGROUND

The aim of the present study is to investigate the levels of some of the cytokines which may be involved in the mechanisms leading to the impairment of placental perfusion and to the onset of uterine contractions in pregnancies with fetal genetic abnormalities compared with controls.

METHODS

The amniotic fluid and maternal plasma levels of interleukin-6, interleukin-8 and tumour necrosis factor-beta in patients with fetal chromosomal abnormalities were measured, as well as in euploid pregnancies in the seventh week of gestation.

RESULTS

An increase of interleukin-6 (P = 0.034) and a decrease of interleukin-8 (P < or =0.0001) in amniotic fluid, and a decrease of interleukin-6 in the maternal plasma (P = 0.026) was shown in pregnancies with fetal chromosomal abnormalities. A positive correlation was observed between amniotic interleukin-8 and serum interleukin-6 in the presence of fetal aneuploidy (P < 0.006).

CONCLUSION

Further investigations of cytokine imbalance in pregnancies with poor outcome as a consequence of genetic disorders rather than infection is warranted.

CD34(+) cell subsets and long-term culture colony-forming cells evaluated on both autologous and normal bone marrow stroma predict long-term hematopoietic engraftment in patients undergoing autologous peripheral blood stem cell transplantation

OBJECTIVE

The aim of this study was to evaluate which CD34(+) cell subset contained in leukapheresis products could be regarded as the most predictive of long-term hematopoietic recovery after autologous peripheral blood stem cell transplantation (auto-PBSCT).

MATERIALS AND METHODS

Based on data from 34 patients with hematologic malignancies, doses of CD34(+) cells and CD34(+) cell subsets, defined by the expression of HLA-DR, CD38, CD117 (c-kit/R), CD123 (alpha subunit of IL-3/R), CD133 (AC133), and CD90 (Thy-1) antigens, were correlated with the number of short-term (i.e., colony-forming cells [CFC]) and long-term culture CFC (LTC-CFC) (generated at week 5 of culture) and with the kinetics of hematopoietic engraftment following auto-PBSCT. The capacity of autologous stroma (AS), normal human bone marrow stroma, and M2-10B4 murine cell line to sustain CD34(+) cell growth was comparatively evaluated in the LTC assay.

RESULTS

Our data demonstrated that some of the most primitive progenitor subsets (CD34(+)CD117(-)HLA-DR(-), and CD34(+)CD38(+)HLA-DR(-)) showed the strongest correlation with LTC-CFC numbers generated within the AS, whereas no significant correlation was noted using normal bone marrow stroma. Multivariate analysis showed that the only CD34 cell subset independently associated with long-term (3 to 6 months) platelet engraftment after auto-bone marrow transplantation was the CD34(+)CD117(-)HLA-DR(-) phenotype; long-term erythrocyte engraftment was correlated with CD34(+)CD38(+)HLA-DR(-) cell content. The latter further influenced platelet engraftment in the first 3 months after auto-PBSCT. The most predictive parameters for neutrophil engraftment were CD34(+)CD38(+)HLA-DR(-) cell subtype and the total LTC-CFC quantity infused.

CONCLUSIONS

These data further support the hypothesis that the type of stromal feeders influences the frequency of LTC-CFC, possibly because they differ in their ability to interact with distinct subsets of hematopoietic stem cells. Furthermore, as the use of AS in LTC assay can mimic in vitro the human bone marrow microenvironment, it can be speculated that this culture system could be a useful means to study the kinetics of recovery of bone marrow stroma following chemotherapy and PBSCT. From these results, it can be concluded that some CD34(+) cell subsets appear to be more reliable predictors of long-term hematopoietic recovery rates than total CD34(+) cell quantity.

[Prenatal steroids, cesarean section, and cerebral hemorrhage in newborns with birth weight under 1500 g]

OBJECTIVE

To identify perinatal risk and protective factors for peri-intraventricular hemorrhage (PIVH) in 214 very low birth weight (VLBW) infants.

METHOD

Perinatal risk and protective factors for PIVH were examined by univariate analysis and by multivariate logistic regression analysis that adjusted simultaneously for the effects of year of birth and perinatal characteristics. Because mode of delivery and antenatal use of steroid represent the only factors, among those considered, that could in most cases be controlled by the clinician, we calculated for each of the four combinations the relative risk of PIVH.

RESULTS

By univariate analysis, antenatal steroid administration, cesarean section delivery, increasing birth weight and increasing gestational age were protective perinatal factors. By using logistic regression, significant protective factors against PIVH included a complete course of antenatal steroid therapy and increasing gestational age. Intrauterine growth retardation was associated with an increased risk of PIVH. The relative risk of intraventricular hemorrhage for each of the four combination of mode of delivery and antenatal steroid exposure demonstrate that antenatal steroid exposure and cesarean section delivery are most protective with a relative risk of 14% compared with vaginal delivery and no antenatal steroid exposure.

CONCLUSIONS

Association of antenatal steroid administration with cesarean section delivery has an important role in lowering the risk of PIVH in VLBW infants.

Plasminogen activator system in serum and amniotic fluid of euploid and aneuploid pregnancies

OBJECTIVE

To compare euploid and aneuploid pregnancies with respect to maternal serum and amniotic fluid (AF) levels of the components of the plasminogen system.

METHODS

The study population consisted of 123 single pregnancies at the 17th gestational week, 16 with minor chromosomal abnormalities, 15 aneuploid, and 92 euploid.

RESULTS

Both groups with chromosomal abnormalities had significantly higher serum levels of urokinase plasminogen activator and its complexed form with its type-1 inhibitor compared with euploid pregnancies. In AF, tissue plasminogen activator was significantly lower in the aneuploid than the euploid group, whereas type-1 inhibitor of plasminogen activator was significantly higher in the cases with minor chromosomal abnormalities compared with euploid. At cutoff levels set at 100% sensitivity, the complexed form of urokinase plasminogen activator with its type-1 inhibitor had the strongest specificity (66.3%); after logarithmic transformation, its serum level was 7.53 times higher in aneuploidies than euploidies.

CONCLUSION

Aneuploid pregnancies appear to be accompanied by abnormalities of the plasminogen activation system, which could lead to impaired placental perfusion and thus to abortion, fetal death, and fetal growth restriction.

Isonymy structure of USA population

The isonymy structure of the 48 states of the continental United States of America was studied using the surname distributions of 18 million telephone users, distributed in 247 towns. The shortest linear distance between nearest neighbor towns included in the sample was 12.0 km. The largest distance was 4,577 km. The number of different surnames found in the whole analysis was 899,585. Lasker's distance was found to be significantly but weakly correlated with the geographic distance, with r = 0.21 +/- 0.01. A dendrogram of the 48 states was built from the matrix of isonymy distances: it divides the US into several clusters, in general correlated with geography. A notable exception is California and New Jersey, which cluster together. Wisconsin is separated from all other states. An important cluster is formed by Texas, Colorado, New Mexico, Nevada, and Arizona, together with Illinois and Florida. It was observed that Hispanic surnames are among the most frequent in Illinois, as they are in New Jersey and California. No main distinction among the states clearly attributable to surnames of French origin was detected; however, New Hampshire, Vermont, and Maine which have a considerable number of these surnames belong to the same northeastern cluster. From the present analysis, the great mobility of the US population emerges clearly, and it seems relevant that the practical absence of isolation by distance is seen also considering only small towns. It appears that groups of different origin are well-mixed over the whole area of the United States. The values of isonymy indicate that the south-central area of the USA has the highest level of inbreeding. In fact, the heterogeneity in surname composition is greater in the coastal areas, particularly on the East Coast, than anywhere else in the USA.

Elements of the surname structure of Austria

The isonymy structure of Austria was studied using the surname distributions in 1081002 private telephone users selected from about 4000000 registered in a 1996 commercial CD-ROM, which contains all Austrian users. The sample was distributed in 120 towns representing an approximately uniform distribution over the country. The number of different surnames found in the whole analysis was 140766. Lasker's distance, the negative value of the logarithm of isonymy between localities, was found to be linearly and significantly correlated with the log of geographic distance, with r = 0.565 +/- 0.011. A dendrogram was built with the matrix of isonymy distance, using the Unweighted Pair-Group Method using Arithmetic averages, UPGMA. It separates the Austrian towns in five main clusters, one along the central portion of the country, another one which occupies the northern region of central Austria; then comes a third cluster at the north-eastern part, a fourth cluster in the western region, and finally a small cluster towards the border with Slovenia. Within each, small subclusters with specific geographic distributions could be delimited. The main clusters correspond fairly well to the classic regions of Austria. The results were compared with those obtained in similar analyses of Switzerland, Germany, Italy and Venezuela. From the present analysis, isolation by distance emerges clearly, and it is stronger than in Germany but smaller than that observed in Italy, Switzerland and Venezuela. The random component of inbreeding estimated from isonymy, at the level of resolution used here, indicates that the inbreeding level in Austria is rather uniform.

Allele and genotype frequencies for D1S80 and 3'APOB in Recanati, Central Italy

The VNTR 3'APOB and D1S80 loci were studied in a sample of 179 individuals living in the Recanati Area (Central Italy). For 3'APOB, we found 34 genotypes and 11 alleles. The system was in Hardy-Weinberg equilibrium. The observed and expected heterozygosity were 0.788 and 0.798 respectively. The discrimination power was 0.96, the a-priori paternity exclusion power was 0.619 and the polymorphism information content was 0.773. For D1S80, we found 45 genotypes and 18 alleles. The system deviated significantly from Hardy-Weinberg equilibrium. The observed and expected heterozygosity were 0.696 and 0.790 respectively. The discrimination power was 0.96, the a-priori paternity exclusion power was 0.617 and PIC was 0.767. The Recanati sample was compared with the general Italian frequencies for the 3'APOB locus. A difference of borderline significance was detected (P = 0.04). For D1S80, the sample was compared with a sample from Southern Italy and no significant difference was detected.

A two-locus model for non-syndromic congenital dysplasia of the hip (CDH)

Complex segregation analysis was conducted in a sample of 171 pedigrees collected through probands affected by non-syndromic dysplasia of the hip (CDH) treated in Ferrara's CDH Centre in the period 1991-6. The analysis favoured a two-locus model, in which the accepted segregation model at the major locus was compatible with recessive transmission, with a gene frequency of the deleterious allele of around 0.20. For the other locus, among the Mendelian hypotheses tested, the recessive model turned out to be the most parsimonious. When ultrasonographic level was examined as an indication of severity, a significant improvement in the fit of the model was observed, giving clear evidence that information on the severity of CDH is important for a better definition of the hereditary transmission model.

Isonymy and isolation by distance in Italy

The isonymy structure of Italy was studied using the surname distribution of 5,043,580 private telephone users selected from a 1996 commercial CD-ROM that contains all 24 million users in the country. The users were distributed in 123 towns selected on a geographic basis. The 123 towns were either on the main communication roads of the country or at the ends of such roads. The shortest distance between nearest neighbor towns was 5.3 km (Carrara and Massa), and the largest distance was 1,136 km (Aosta and Castrignano del Capo). The number of different surnames found in the whole analysis was 215,623. Lasker's distance, the negative value of the logarithm of random isonymy between localities, was linearly and significantly correlated with the logarithm of geographic distance, with r = 0.63 +/- 0.008. A dendrogram was built from the matrix of isonymy distances, using UPGMA. It separates the Italian towns into 5 main clusters: 1 in the southern portion of the country, a second cluster toward the center, and 3 in the northern area of Italy. Within each cluster small subclusters with specific geographic distributions could be related to regional borders. Comparisons with the results of a previous analysis of Switzerland and Germany's structures are given. From the present analysis isolation by distance emerges clearly, although it is less strong than in Switzerland and stronger than in Germany. The random component of inbreeding estimated from isonymy indicates that the southern area of Italy is on average more inbred than the northern area. In fact, the heterogeneity is greater in the northern area, particularly in the plain of the Po River, than anywhere else in Italy.

Spontaneous sister chromatid exchange and chromosome aberration frequency in humans: the familial effect

The possible effects of environmental and genetic factors on spontaneous frequencies of sister chromatid exchanges (SCEs) and cells with chromosome aberrations (CAs) in human lymphocytes were investigated by analysing 177 completed families (mother, father and at least one child). After removing the effects of methodological, biological and life-style factors by the use of multifactor analysis of variance (MANOVA), SCEs and CAs residuals were analysed by simple correlation analysis and principal component analysis. SCEs and CAs inter-familiar variability was higher than that found within families. A significant correlation was found between the average SCE frequencies shared by parents (the so-called 'midpoint parents', or 'midparent') and offspring (linear slope b=0.26+/-0.07, p<0.05), but also between mother and father (b=0.23+/-0.11, p<0.05) suggesting the presence of an effective environmental factor. The midparent-offspring correlation was found to be sustained by the mother-offspring relationship (b=0.28+/-0.08, p<0.05), being the father-offspring correlation not significant (b=0.16+/-0.11, p0.05). Concerning CAs, no statistically significant correlation between parents was found, but the strong relationship between mother and offspring was confirmed (b=0.468+/-0.11, p<0.001). The SCEs correlation between mother vs. offspring disappeared for older offspring (over 23 years old). The obtained findings strongly showed that the genetic make-up is barely detectable in the presence of domestic environment factors which are shown to play the major role in determining the interfamilial variability of SCE and CA in a general population. These results strengthen the suitability of the use of SCEs and CAs analysis in human cytogenetic surveillance for the detection of effective environmental factors.

Combined segregation and linkage analysis of nonsyndromic orofacial cleft in two candidate regions

We applied a complex segregation analysis to 46 pedigrees with a total of 121 nuclear families and 660 individuals, to verify hypotheses regarding the inheritance of OFC and linkage with markers on chromosomes 6 and 2. The POINTER program for segregation analysis strongly rejected the hypothesis of no familial transmission of OFC in these families. When the hypothesis of a two-locus model was tested with COMDS, the analysis showed the presence of at least two loci and the model assuming a dominant major gene and a recessive modifier locus was statistically accepted. Given the fitted two-locus model, we tested for a possible linkage between the major OFC locus and the two markers studied. For D6S259, the estimate of the recombination fraction was theta = 0.098, corresponding to a LOD score around 2.1. On the contrary, the data analysis concerning the D2S378 marker showed an estimate of the recombination fraction not significantly different from the independence hypothesis.

Isonymy and isolation by distance in Germany

The isonymy structure of Germany was studied using the surname distributions of 5,150,310 private telephone users selected from 39,000,000 users registered in a 1996 commercial CD-ROM, which contains all telephone users in the country. The users were distributed in 106 towns selected on a geographic basis. Germany was subdivided into 50 adjacent rectangles, each 115 x 80 km, and at least the largest town in the rectangle was selected for study; the private telephone users in that district were downloaded from the CD-ROM and included in the analysis. The shortest distance between nearest neighbor towns was 10.7 km (Travemunde and Lübeck), and the largest distance was 69.8 km (Meppen and Osnabruck). The number of different surnames found in the whole analysis was 462,526. Lasker's distance, the negative value of the logarithm of isonymy between localities, was found to be linearly and significantly correlated with geographic distance (r = 0.51 +/- 0.010). A dendrogram was built with the matrix of isonymy distances, using UPGMA. This method separates the German towns into two main clusters, one in the southern half of the country and the other in the northern half. Within each cluster small subclusters with specific geographic distributions could be delimited. The two main clusters correspond fairly well to the north-south division of German sublanguages (Nieder- and Mitteldeutsch in the north vs. Frankisch-Alemannisch in the south). The other clusters are related to minor sublanguages. Comparisons with the results of a previous analysis of Switzerland's structure are given. From the present analysis isolation by distance emerges clearly, although it is less strong than in Switzerland and indicates that Germany has a fairly homogeneous isonymy structure. The random component of inbreeding estimated from isonymy indicates that eastern Germany is on average more inbred than western Germany.

Isonymy and the genetic structure of Switzerland. II. Isolation by distance

Isolation by distance in Switzerland was detected comparing the surname distributions between Cantons. The decay of isonymy with geographic distance between Cantons was consistent with Malecot's exponential decay of kinship. Lasker's distance was defined as the negative value of the logarithm of isonymy between localities, and it was found that it is linearly and significantly correlated with the log of geographic distance, both within and between languages. The peculiar geographic and linguistic structure of the Confederation, where mountain barriers exist at short distances separating different languages, might explain the rapid changes in surname similarity. It was predicted that the frequency of markers linked to the Y chromosome would show a similar association with distance in Switzerland.

Detection of genetic structures at short distances in the Pisa area

The genetic structure of the population of the urban and suburban area of the town of Pisa in Tuscany in Central Italy was studied in 1,174 adults residing in 4 zones in each of 3 sampling areas, using the phenotype and gene frequencies of 9 red cell enzymes. The area investigated has a surface of about 30 km2. The enzymes were: acid phosphatase (ACP1), adenosine deaminase (ADA), adenylate kinase (AK1), esterase D (ESD), glyoxalase I (GLOI), glutamic-pyruvic transaminase (GPT), 6-phosphogluconate dehydrogenase (6-PGD), phosphogluco-mutase 1 (PGM1), and phosphoglycollate phosphatase (PGP). For the analysis of the distributions of phenotype and gene frequencies, standardised variances, kinship profiles, analysis of correspondences and isonymy were used. It was found that in this area genetic differentiation (possibly due to recent immigration) can be perceived even at short geographic distances, indicated by the significant regression of kinship on distance, especially visible in the ADA and GPT systems.

Autosomal dominant polycystic kidney disease linked to PKD2 locus in a family with severe extrarenal manifestations

We report a large three-generation autosomal dominant polycystic kidney disease family from Northern Italy found to be associated with the PKD2 locus. Hepatic involvement (liver cysts, fibrosis, cholelithiasis or jaundice), subarachnoidal hemorrhage (1 case) and esophageal diverticula (1 case) were present in affected individuals. Among the older members, the males (aged 54-61 years) had hepatic cysts or fibrosis and were on chronic hemodialysis, the females (aged 69 and 70 years) had hepatic cysts, hepatomegaly, mild fibrosis and a mild and moderate renal impairment, respectively. In this family, clinical findings do not differ substantially from those reported for PKD1.

Searching for migraine genes: exclusion of 290 cM out of the whole human genome

A linkage and association analysis was made on 14 Italian families with recurrent migraine. We analyzed five chromosomal regions surrounding the candidate genes 5HT1D (1p36.3-34.3), 5HT1B (6q13), 5HT2A (13q14-21), 5HT transporter (17q11.2-12), CACNLB1 (17q11.2-22) and FHM (19p13), using 29 DNA polymorphic markers. All two-point lod scores were negative, and the chi 2 sib-pair analyses were not significant, thus indicating the probable exclusion of these regions as sites of migraine genes in our population.

A two-locus model for hereditary non-polyposis colorectal cancer in Modena, Italy

Complex segregation analysis was conducted in a series of patients with hereditary non-polyposis colorectal cancer (HNPCC) ascertained through probands registered in the Cancer Registry of the Health Care District of Modena, Northern Italy. Altogether there were 125 nuclear families segregating for HNPCC, for a total of 672 individuals. The analysis favoured a two-locus model, with both susceptibility genes rare and dominant. The gene frequency of the deleterious allele at the major locus is estimated to be low qm = 0.004 and for the second locus the estimate is even lower q = 0.00003. Both genes defining the two-locus model seem to be highly penetrant. The lifetime penetrance of the abnormal gene at the major locus is estimated to be 0.73 for female, while the estimation for male is higher, 0.85.

Isonymy and the genetic structure of Switzerland. I. The distributions of surnames

The surname distribution of the population of Switzerland was studied using a sample of 1,702,000 private users registered for the year 1994 in the Helvetic Telephone Directory. These users were distributed in four linguistic areas, in 26 Cantons and 271 Communes of the Confederation. Estimates of unbiased random isonymy, of Fisher's alpha, an indicator of abundance of surnames converging to the allele effective number in standard genetic polymorphisms, and of Karlin-McGregor's v, an indicator of immigration rates, were calculated for each Commune, each Canton, each linguistic area and for the whole Confederation. The Commune with the highest value of alpha was Geneva (alpha = 5312) followed by Versoix (3713) and by the Communes of Vaud on the north shore of Lake Leman, Chavannes (3381), Montreux (3200), Nyon (3114) and Lausanne (3109). The Italian-speaking Communes of the Ticino were next. The lowest value (alpha = 29) was observed in Poschiavo, south of the Berninapass; alpha = 39 was observed in Einsiedeln (Schwyz); then Mels and Widnau (62 and 67, Canton of St Gallen), Frutingen in Bern (72), and Appenzell (80). Accordingly, the highest consanguinity values were observed in the Grisons and in the nucleus of the founding Cantons, while the lowest were observed in the Cantons of Geneva and Vaud, preferential areas of immigration to Switzerland from abroad. The effect of subdivision on isonymy is large at the Commune level, and decreases in Cantons and linguistic groups. French and Italian languages indicate minor, German and Romanisch major inbreeding.

Clinical effect of tetracycline demineralization and fibrin-fibronectin sealing system application on healing response following flap debridement surgery

The aim of this controlled clinical trial was to assess the effect on healing following tetracycline (TTC) conditioning and fibrin-fibronectin sealing system (FFSS) application in association with flap debridement surgery (FDS) in 11 patients under treatment for moderate to severe periodontitis. Selection criteria included the presence of two bilateral, homologous, non-molar, interproximal sites with probing depth > or = 5 mm. The areas bilateral to the trial sites were matched for number and type of the teeth, and similar periodontal involvement. After initial therapy, a split-mouth design was used in which one area was treated by flap debridement surgery alone (control), and the contralateral area was treated following surgery with a 4-minute burnishing application of 100 mg/ml TTC solution and FFSS (test). Fibrin glue was applied with a syringe on the demineralized root surfaces and surrounding bone margins. Healing by primary intention was encouraged by flap repositioning with interrupted sutures left in place for 14 days. A monthly maintenance recall program was followed. Patients were clinically evaluated at baseline and 6 months and the following measurements were taken: gingival index, plaque control record, clinical attachment level, probing depth, recession, bleeding on probing. Statistical evaluation indicated that both approaches resulted in significant probing depth reduction and clinical attachment gain. However, the differences in healing between the test and control groups were not clinically nor statistically significant. These results suggest there is no additional benefit with TTC demineralization and topical FFSS application in conjunction with flap debridement surgery.

Effect of pretreatment with ketorolac tromethamine on post-operative pain following periodontal surgery

A double-blind, randomized, single-dose clinical trial to evaluate the analgesic efficacy of preoperative ketorolac tromethamine administration on periodontal postoperative pain was designed. One group received 20 mg ketorolac immediately before periodontal flap surgery, and the other group received placebo. Naproxen sodium was allowed postoperatively as rescue medication. The visual analog scale was used to estimate pain. Postoperative pain was assessed hourly for the first 10 h on the day of surgery, and 4 x daily on the 1st and 2nd postsurgical days. Timing and dose of rescue analgesic remedication were also recorded. Results indicated that preoperative treatment with ketorolac significantly reduced initial pain intensity and delayed the onset of postoperative pain as compared to placebo. Incidence and amount of naproxen consumption was similarly small in both ketorolac- and placebo-treated groups. No adverse reactions related to preoperative medication were observed.

Clinical effect of subgingival tetracycline irrigation and tetracycline-loaded fiber application in the treatment of adult periodontitis

A controlled clinical trial was carried out to compare the clinical effect of combined antimicrobial-mechanical treatment modalities on moderate-to-deep periodontal pockets in patients with adult periodontitis. Twelve patients having at least three nonadjacent sites of periodontitis were included in the split-mouth study. Gingival Index, Plaque Record, bleeding on probing, probing depth, attachment level, and recession depth were recorded immediately before treatment. In the control site, supragingival and subgingival scaling was performed with an ultrasonic scaler. One experimental site received supplemental irrigation with 15 mL of a 100-mg/mL tetracycline solution, while the other received a tetracycline-loaded fiber after mechanical instrumentation. Fibers were left in place for 10 days. Reevaluation 30 and 60 days after treatment showed that all three treatment modalities were effective in improving clinical parameters. No adjunctive effect on the healing response was obtained by augmenting mechanical debridement with tetracycline.

Serum cholesterol concentrations in parasuicide

OBJECTIVE

To evaluate whether people who have committed parasuicide have low serum cholesterol concentrations.

DESIGN

Results of blood tests in subjects admitted to hospital for parasuicide compared with those of a control group of non-suicidal subjects; comparison in subgroup of parasuicide subjects of two sets of blood test results (one set from admission for parasuicide and the other from admission for some other illness).

SETTING

General hospital, Ferrara, Italy.

SUBJECTS

331 parasuicide subjects aged 44 (SD 21) years (109 with two sets of blood test results) and 331 controls.

MAIN OUTCOME MEASURES

Serum cholesterol concentrations and possible association with parasuicide, considering sex, violence of method of parasuicide, and underlying psychiatric disorder.

RESULTS

Lower serum cholesterol concentrations (4.96 (SD 1.16) mmol/l) were found in the parasuicide subjects than in the controls (5.43 (1.30); P < 0.001), regardless of sex and degree of violence of parasuicide method. Both men and women with two sets of blood test results had lower cholesterol concentrations after parasuicide. Linear regression analysis showed that the difference in cholesterol concentrations was significantly related to the length of time between the taking of the two sets of blood samples.

CONCLUSION

The study showed low cholesterol concentrations after parasuicide. This finding agrees with previous studies, which suggest an association between low cholesterol concentration and suicide.

Phylogeny inferred from codon usage pattern in 31 organisms

We employed the Codonusage database to analyze the codon usage pattern in 31 organisms from all the main biological taxa. We tested the similarity in codon usage pattern between each organism and all the others by the Pearson linear correlation coefficient. The 465 values obtained were located in a 31 x 31 triangular matrix from which a correlation distance matrix was calculated. An evolutionary dendrogram was then constructed from these distances. The results showed a fair correlation between codon usage patterns and phylogenetic relationships, at least for organisms which diverged in rather recent times (end of Jurassic--beginning of Cretaceous).

The usage of oligopeptides in proteins correlates negatively with molecular weight

We scanned the Swissprot databank to study the distribution of oligopeptides in sequenced proteins. We observed that in 7839,000 amino acids in the bank, the frequency is strongly and negatively correlated with molecular weight. The correlation coefficient is -0.63 for single amino acids, -0.58 for dipeptides, -0.54 for tri- and -0.46 for tetrapeptides. In subsets of proteins of man, mouse, rat drosophila, yeast and E. coli, the correlations were very similar to those for the total database. The intensity of the correlation diminishes linearly with the length of the peptide. We attributed the loss of dominance of molecular weight in determining the frequency of oligopeptides of higher order, to the emergence of function in longer oligopeptides. In the case of dipeptides, we observed that those composed of the same amino acid are in great excess in comparison with their expectation. The WW dipeptide is singular, in the sense that is observed/expected ratio is 13.5 standard deviations above the average ratio.

Healing response of human buccal gingival recessions treated with expanded polytetrafluoroethylene membranes. A retrospective report

Twenty-four (24) deep wide buccal gingival recessions were treated with ePTFE membrane according to guided tissue regeneration principles (GTR). Factors affecting the surgical outcome of the regenerative procedure were retrospectively analyzed. In 16 cases, the barrier membrane was used in conjunction with tetracycline root conditioning and fibrin-fibronectin system application, and 8 cases were treated with the membrane alone. Healing response was evaluated 12 months after surgery. Since no difference was observed between the two treatment protocols, all available data were grouped. Mean recession depth was reduced from 4.6 mm to 1.3 mm postoperatively, which represents an average root coverage of 71.7%. Fifty percent (50%) of the cases showed clinical attachment gain greater than or equal to 4 mm and a mean increase of keratinized tissue of 1.0 mm was observed. Baseline recession depth and extent of membrane exposure at the reentry procedure significantly influenced the amount of newly-formed tissue under the membrane. Recession reduction positively correlated with the preoperative recession depth and the regenerated tissue gain. Treatment was also affected by tooth location, recession reduction, and attachment gain, being significantly greater in upper than lower archs. Results suggest that GTR technique represents a predictable procedure to improve the soft tissue conditions of deep mucogingival defects. Randomized controlled trials of other forms of management of mucogingival defects as compared to the GTR technique will be necessary to fully evaluate the utility of the GTR technique.

Haematological profile in cancer patients: analysis of circadian pattern

This study was intended to evaluate whether unusual circadian patterns in blood cells exist in cancer patients. Ten patients (five men and five women) suffering from advanced malignancy were compared with a control group of apparently healthy volunteers, of comparable age and sex. After synchronization of daily activities, meals and rest of the two groups, blood samples were taken four times (at 8.00 a.m., 12.00 a.m., 4.00 p.m. and 8.00 p.m.) in a single day. The total red and white cell counts, haemoglobin, platelet count, and neutrophil, lymphocyte, eosinophil, monocyte and basophil differential white cell counts were analysed by both conventional (Student's t-test; multifactorial analysis of variance) and inferential statistics (single and mean cosinor). The average values for platelets (P = 0.04), white blood cells (P = 0.004) and lymphocytes (P << 0.001) showed significant changes with time, independently of disease state. Cosinor analysis indicated a circadian rhythmicity for haemoglobin (P = 0.02), eosinophils (P = 0.014), and lymphocytes (P = 0.001) in healthy subjects, and for eosinophils only (P = 0.024) in cancer patients.

A set of Alu-free frequent decamers from mammalian genomes enriched in transcription factor signals

We have recently reported that the statistical analysis of the frequency distribution of short oligonucleotides within mammalian and viral genomes allows the production of sets of DNA sequences enriched in signals for transcription factors. Such statistical approaches could facilitate the identification of new promoter regions playing a role in the transcriptional regulation of gene expression. In the case of mammalian oligonucleotides, we found that the published set of frequent decamers enriched in transcriptional motifs is not suitable for studies on genes of Homo sapiens and evolutionarily related genomes, because it contains decameric sequences belonging to genomic repeats. We report here that most of the decameric sequences of DNA repeats belong to Alu repeats. Accordingly, we produced a subset of Alu-free frequent decamers. In addition, we eliminated from the subset of Alu-free frequent decamers those that are frequently present within other common human repeats, including (GT)n, (AT)n, (CA)n, (ATT)n, (CAA)n and (GTT)n. The Alu-free (repeats-free) subset of frequent mammalian decamers is enriched in signals for transcription factors and allows the identification of putative signals in genes, such as those coding for plasminogen activator, adenosine deaminase and p53, that contain a large number of Alu-like repeats interspersed within our genomic sequences. The newly generated compilation of frequent decamers described here might be used to locate genomic regions playing functional roles in the expression of genes of Homo sapiens and related primates.

Identification of a set of frequent decanucleotides in plants and in animals

We studied the frequency distribution of 1,048,576 oligonucleotides 10 bp long in a sample of 1.961 Mbase of genes from plants, made of 635 sequences extracted from GenBank 71.0, with the aim of detecting transcription control signals. Among all decamers, 3255, or 0.3%, had a frequency 10 times higher than the mean and were subjected to further statistical analysis. For each of the 3255 decamers (parents), we counted the individual frequencies of the 30 decamers (progeny) differing from the parent by one base mutation, and calculated two variance/mean chi-squares for the progeny, with and without the parent decamer. By studying the distribution of the ratio between the two chi-squares we observed that out of 3255 decamers > 10 times frequent than average, 432 had a chi-square ratio > 1.9. In this residual set, which corresponds to < 0.04 per cent of all possible decamers, only 15 known eukaryotic transcription control elements were found; on the other hand, it included 29 decanucleotides that matched with decanucleotides of a set of Drosophila, 24 with a set from mammals, 13 with a set from yeast and four with a set of viruses--all sets identified with the statistical procedures here described. These decanucloetides are highly repetitive and seem to be present throughout all higher organisms, whereas they are uncommon in mammalian viruses.