Electronic methods for the analysis of the human post-canine dentition

The human post-canine dentitions are described and analyzed, in terms of the relative plane surface area of the occlusal surface, by electronic methods. Dental casts are duplicated and the marked duplicates are then photographed in a 1:1 relationship. The photographic negatives are digitized, i.e., the points marked on the casts are converted to X and Y coordinates which are recorded on punched cards. Computer facilities are used to convert the X and Y coordinates into mensurational data and to calculate the relative plane surface areas of the crown components and the total relative plane surface of the crown. The accuracy of this method was verified by the statistical analyses.     

The effects of induced prenatal hypothyroidism on lamb mandibular third primary molars.

Intrauterine thyroidectomies were performed on nine lambs on or about the ninety-sixth postconception day. Seven other control and shamoperated lambs, and the cretin lambs were sacrificed immediately after birth. The mandibles were removed and sectioned at the midline. The right side molars were removed by dissection and caliper measured. The distal cusps of the third primary molars were sectioned, dehydrated, and embedded in Bioplastic. A slow speed diamond saw was used to section the plastic blocks and the embedded teeth. Subsequent grinding and polishing produced high quality 75 micrometer sections of the lamb molar cusps. No significant differences in tooth size or enamel thickness existed. Microscopic examinations show that parts of the cretin enamel were poorly calcified, an observation that was correlated to the intrauterine thyroidectomies. The data suggest that hypothyroidism alters ameloblastic activity during the secretory phase of enamel formation.     

Using Routine Surveillance Data to Estimate the Epidemic Potential of Emerging Zoonoses: Application to the Emergence of US Swine Origin Influenza A H3N2v Virus

Background

Prior to emergence in human populations, zoonoses such as SARS cause occasional infections in human populations exposed to reservoir species. The risk of widespread epidemics in humans can be assessed by monitoring the reproduction number R (average number of persons infected by a human case). However, until now, estimating R required detailed outbreak investigations of human clusters, for which resources and expertise are not always available. Additionally, existing methods do not correct for important selection and under-ascertainment biases. Here, we present simple estimation methods that overcome many of these limitations.

Methods and Findings

Our approach is based on a parsimonious mathematical model of disease transmission and only requires data collected through routine surveillance and standard case investigations. We apply it to assess the transmissibility of swine-origin influenza A H3N2v-M virus in the US, Nipah virus in Malaysia and Bangladesh, and also present a non-zoonotic example (cholera in the Dominican Republic). Estimation is based on two simple summary statistics, the proportion infected by the natural reservoir among detected cases (G) and among the subset of the first detected cases in each cluster (F). If detection of a case does not affect detection of other cases from the same cluster, we find that R can be estimated by 1−G; otherwise R can be estimated by 1−F when the case detection rate is low. In more general cases, bounds on R can still be derived.

Conclusions

We have developed a simple approach with limited data requirements that enables robust assessment of the risks posed by emerging zoonoses. We illustrate this by deriving transmissibility estimates for the H3N2v-M virus, an important step in evaluating the possible pandemic threat posed by this virus. Please see later in the article for the Editors'' Summary     

On the groove configuration of mandibular molars: The unreliability of the “dryopithecus pattern” and a new method for classifying mandibular molars

The long-used qualitative nomenclature for the cusp-groove pattern of lower molars, and the definition applying to it, was investigated and found to be unsatisfactory for the repetitive classification of lower molars. Moreover, developmental grooves per se were found to represent the results of highly variable environmental phenomena and therefore their use cannot be justified as an evolutionary determinant. A simple, but effective classification for lower molars, based on cusp size, cusp number, distal fovea, and distal marginal ridge was presented.     

Physician Survey to Determine How Dengue Is Diagnosed,Treated and Reported in Puerto Rico

Dengue is a major cause of morbidity in Puerto Rico and is well-known to its physicians. Early case identification and timely initiation of treatment for patients with severe dengue can reduce medical complications and mortality. To determine clinical management and reporting practices, and assess knowledge of dengue and its management, a survey was sent to 2,512 physicians with a medical license in Puerto Rico. Of the 2,313 physicians who received the survey, 817 (35%) completed the questionnaire. Of the respondents, 708 were currently practicing medicine; 138 were board certified (Group 1), 282 were board eligible (Group 2), and 288 had not finished residency (Group 3). Although respondents clinically diagnosed, on average, 12 cases of dengue in the preceding three months, 31% did not report any suspected cases to public health officials while about half (56%) reported all cases. Overall, 29% of respondents correctly identified early signs of shock and 48% identified severe abdominal pain and persistent vomiting as warning signs for severe dengue with the proportion of correct respondents highest in Group 1. Reportedly about sixty percent (57%) appropriately never give corticosteroids or prophylactic platelet transfusions to dengue patients. One third (30%) of respondents correctly identified administration of intravenous colloid solution as the best treatment option for dengue patients with refractory shock and elevated hematocrit after an initial trial of intravenous crystalloids, and nearly one half (46%) correctly identified administration of a blood transfusion as the best option for dengue patients with refractory shock and decreased hematocrit after a trial of intravenous crystalloids. Even though dengue has been endemic in Puerto Rico for nearly 4 decades, knowledge of dengue management is still limited, compliance with WHO treatment guidelines is suboptimal, and underreporting is significant. These findings were used to design a post graduate training course to improve the clinical management of dengue.     

An atypical Bronze Age mandible from Żerniki Górne,Poland

The unusual anatomical features of a Bronze Age mandible are described. Of particular interest were the shelf-like ridges which were located approximately midway along the rami. These ridges probably formed the insertion areas for the masseter muscles. Of two possible explanations presented to account for the unusual morphological variations, the more likely is the congenital absence of the superficial portions of the masseter muscles. However, an alternative explanation is presented suggesting the presence of shortened superficial portions of the masseter muscle which could explain the contour of the shelf.     

Requirement for ERCC-1 and ERCC-3 gene products in DNA excision repair in vitro. Complementation using rodent and human cell extracts.

Numerous rodent cell lines exist that have defects in nucleotide excision repair of DNA caused by alterations in genes that fall into 10 different complementation groups. The precise roles in the repair of these genes are unknown. We report here that extracts from Chinese hamster ovary cells of excision repair-defective complementation groups 1 and 3 are defective in DNA excision repair in a cell-free system. In vitro complementation can be achieved by mixing extracts from the two groups with one another. In addition, extracts from a human cell line representing xeroderma pigmentosum complementation group B could complement rodent complementation group 1 extracts, but not group 3 extracts. This is consistent with an identity of the ERCC-3 and xeroderma pigmentosum group B genes. Cellular evidence points toward a defect in the incision of damaged DNA in group 1 and 3 mutants. Since the ERCC-1 and ERCC-3 proteins are required for the in vitro reaction, it appears that both gene products are directly involved in the enzymatic incision of damaged DNA, or in preincision reactions. The experiments reported here provide the biochemical basis of an approach to analyze the function of these nucleotide excision repair proteins.     

Similarities in Restriction Fragment Patterns of Mitochondrial DNAs of PhytophthoraSpecies Strongly Depend on the Restriction Enzyme Used Due to Heterogeneous Base Distribution and Sequence Conservation

Mitochondrial DNAs of six morphologically different Phytophthora species were digested with 15 restriction enzymes. The numbers of restriction fragments obtained differed considerably from those theoretically expected for random base distribution. Enzymes with relatively many G and C in their recognition sequences produced significantly larger numbers of fragments. Moreover, fragments generated by most of these enzymes were more often shared by two or more species than those from enzymes with more A and T in their recognition sequence. It is concluded that base distribution in mitochondrial DNA of Phytophthora is heterogeneous,AT-rich stretches occurring scattered over the mitochondrial genome and GC-rich regions present in conserved sequences, presumably genes. A practical consequence for taxonomic RFLP studies is that optimal enzymes can be selected, depending on the desired level of resolution.     

Tetrapod phylogeny inferred from 18S and 28S ribosomal RNA sequences and a review of the evidence for amniote relationships [published erratum appears in Mol Biol Evol 1991 May;8(3):398]

The 18S ribosomal RNAs of 21 tetrapods were sequenced and aligned with five published tetrapod sequences. When the coelacanth was used as an outgroup, Lissamphibia (living amphibians) and Amniota (amniotes) were found to be statistically significant monophyletic groups. Although little resolution was obtained among the lissamphibian taxa, the amniote sequences support a sister-group relationship between birds and mammals. Portions of the 28S ribosomal RNA (rRNA) molecule in 11 tetrapods also were sequenced, although the phylogenetic results were inconclusive. In contrast to previous studies, deletion or down- weighting of base-paired sites were found to have little effect on phylogenetic relationships. Molecular evidence for amniote relationships is reviewed, showing that three genes (beta-hemoglobin, myoglobin, and 18S rRNA) unambiguously support a bird-mammal relationship, compared with one gene (histone H2B) that favors a bird- crocodilian clade. Separate analyses of four other genes (alpha- crystallin A, alpha-hemoglobin, insulin, and 28S rRNA) and a combined analysis of all sequence data are inconclusive, in that different groups are defined in different analyses and none are strongly supported. It is suggested that until sequences become available from a broader array of taxa, the molecular evidence is best evaluated at the level of individual genes, with emphasis placed on those studies with the greatest number of taxa and sites. When this is done, a bird-mammal relationship is most strongly supported. When regarded in combination with the morphological evidence for this association, it must be considered at least as plausible as a bird-crocodilian relationship.