Change in nuclear DNA content and pollen size with polyploidisation in the sweet potato (Ipomoea batatas, Convolvulaceae) complex.

Genome size evolution and its relationship with pollen grain size has been investigated in sweet potato (Ipomoea batatas), an economically important crop which is closely related to diploid and tetraploid species, assessing the nuclear DNA content of 22 accessions from five Ipomoea species, ten sweet potato varieties and two outgroup taxa. Nuclear DNA amounts were determined using flow cytometry. Pollen grains were studied using scanning and transmission electron microscopy. 2C DNA content of hexaploid I. batatas ranged between 3.12-3.29 pg; the mean monoploid genome size being 0.539 pg (527 Mbp), similar to the related diploid accessions. In tetraploid species I. trifida and I. tabascana, 2C DNA content was, respectively, 2.07 and 2.03 pg. In the diploid species closely related to sweet potato e.g. I. ×leucantha, I. tiliacea, I. trifida and I. triloba, 2C DNA content was 1.01-1.12 pg. However, two diploid outgroup species, I. setosa and I. purpurea, were clearly different from the other diploid species, with 2C of 1.47-1.49 pg; they also have larger chromosomes. The I. batatas genome presents 60.0% AT bases. DNA content and ploidy level were positively correlated within this complex. In I. batatas and the more closely related species I. trifida, the genome size and ploidy levels were correlated with pollen size. Our results allow us to propose alternative or complementary hypotheses to that currently proposed for the formation of hexaploid Ipomoea batatas.

Physical mapping of rDNA and heterochromatin in chromosomes of 16 Coffea species: a revised view of species differentiation.

The chromosome organization among 15 wild diploid Coffea species and cultivated tetraploid C. arabica was determined by fluorochrome banding (CMA, DAPI) and double fluorescence in-situ hybridization (FISH) of 5S and 18S rDNA achieved on the same chromosome plates. Two to five chromosome pairs (plus one putative chromosome B) are marked. Overall, there are two SAT-chromosome pairs for East African species and one for the Malagasy and the West and Central African species. 18S rDNA loci are telomeric and strongly marked the SAT-chromosome pairs. Generally, only one pericentromeric 5S rDNA locus characterized East African species, while an additional minor locus co-localized with the 18S rDNA-SAT locus for the Malagasy species and West and Central African species. A combination of rDNA FISH plus CMA and DAPI banding patterns enables identification of almost all the species, even those for which the genetic or botanical status is still being discussed. C. arabica clearly appears to be an allotetraploid species, including one genome from East Africa and one from West and Central Africa. However, since the minor 5S rDNA-SAT locus present in West/Central African genomes is not detected, two evolutionary hypotheses could be put forward for C. arabica. Considering only the diploid species, global trends are obvious in rDNA signal patterns, genome size variations, and geographic distribution of the species, but there are no clear evolutionary trends. However, complex interactions between these factors and environmental growing conditions exist, which have resulted in loss and gain of rDNA loci and probably also in copy repeat number variations in each rDNA family.

Decline of oropharyngeal cancer in Chiangmai province, Thailand, between 1988 and 1999.

A decline of oropharyngeal cancer has already been predicted for Thailand since the early 1960s. To substantiate these predictions it was the purpose of this study to examine trends in the incidence of oropharyngeal cancer in the province of Chiangmai, (1988-1999). Data on cancer incidence were extracted from the annual reports of the Cancer Registry, Cancer Unit, Faculty of Medicine, Chiangmai University, Thailand (1992-1999) and an IARC report on cancer in Thailand (1988-1991). The age-standardized annual incidence per 100000 of oral cancer in males dropped from 3.6 (1988-1991) to 1.2 in 1999 (P for trend 0.0002) and in females from 2.6 (1988-1991) to 1.1 in 1999 (P for trend 0.007). Similar trends in males and females for cancer of the tongue, oropharynx and hypopharynx were seen. The age-standardized annual incidence for cancer of the lip, salivary gland and nasopharyngeal carcinoma remained unchanged. Changes of traditional oral habits such as betel quid chewing and smoking of traditional cigars seem to have resulted in a marked decrease of oral cancer in both men and women in the recent past.

Ethnic and geographic differences and similarities of HIV/AIDS-related mucocutaneous diseases. Danida Study Groups.

BACKGROUND: A study on HIV/AIDS-related mucocutaneous manifestations has been carried out in three different ethnic and geographic areas, namely Brazil, Denmark, and Thailand. METHODS: The Brazil cohort comprised 110 patients, the Danish cohort 150, and the Thai cohort 206 patients. The majority of the Brazil and Thai cohort patients belonged to groups III and IV according to the CDC clinical staging system, whereas the patients in Denmark called their doctors earlier and only 8% were classified in groups III and IV. RESULTS: In all three areas the number of mucocutaneous diseases correlated well with the progression of the HIV disease. Ethnic differences were not identified, whereas geographic differences related to skin infections were marked. In the Asian cohort a generalized fungal infection was detected with characteristic mucocutaneous symptoms caused by Penicillium marneffei. CONCLUSIONS: Teaching efforts about mucocutaneous signs as markers of HIV infection may be of value, particularly in developing areas, to allow earlier diagnosis. In future guidelines for classification of HIV/AIDS-related mucocutaneous diseases geographic considerations should be included.

Miang chewing in northern Thai villagers.

The habit of chewing miang, composed of fermented tea leaves was studied among 100 farmers of Northern Thai origin. It was disclosed that the majority of miang chewers were 'multi-habituees' in that this habit was combined with other oral habits such as betel quid chewing, banana cigar and Thai cigarette smoking and alcohol consumption. Among women the most prevalent habit combination was miang chewing and khi yo cigar smoking whereas men showed a more differentiated habit pattern. A total of 37 men and 21 women showed oral lesions that could be related to the practice of one or several habits. Oral precancerous lesions such as leukoplakia were, however, only found among miang chewers who in addition indulged in other oral habits (betel quid chewing, smoking, alcohol usage).

Precancerous and other oral mucosal lesions related to chewing, smoking and drinking habits in Thailand.

In a field study (1979-1984) four out of six major hilltribes of Northern Thailand, namely the Lahu, Karen, Lisu and Meo, as well as a group of rural Thai, were examined. Chewing, smoking and drinking habits and lesions of the oral mucosa (leukoedema, preleukoplakia, leukoplakia and chewer's mucosa) were recorded. 1866 individuals were examined. Considerable differences in the chewing and smoking habits among the various tribes were recorded and some of them were considered tribe-specific. Chewing of betel and miang was more prevalent among older people; these habits seem to have lost their attraction for the younger people. Cigarette smoking was more prevalent among middle-aged individuals. Leukoedema was observed in 12.4%, preleukoplakia in 1.8%, leukoplakia in 1.1% and chewer's mucosa in 13.1%. Men and the older generation were affected more often, except that more women (Karen and Thai) revealed chewer's mucosa. A positive correlation could be demonstrated between some mucosal lesions (leukoedema, chewer's mucosa) and some smoking and chewing habits.

Ultrastructural findings in the oral mucosa of betel chewers.

Eighteen biopsies of the oral mucosa of northern Thai hilltribe betel chewers were studied histologically and by transmission and scanning electron microscopy (TEM, SEM). Clinically, varying stages of epithelial atrophy and one case of submucous fibrosis were observed. Histologically, epithelial atrophy with marked reduction of the rete pegs, hyperortho- and/or parakeratosis, and subepithelial edema and inflammatory changes were the prominent findings. On the ultrastructural level, cytoplasmic projections of the basal cells into the subepithelial stroma were seen. The basal membrane frequently revealed gaps; the interepithelial space was widened and unusual microvilli were observed on cell surfaces (SEM). Intercellularly, cristalloid material of unknown origin was also seen. The subepithelial connective tissue was characterized by dense bundles of collagen fibres adjacent to which masses of amorphous material were located. While some of the ultrastructural findings in the epithelium of betel chewers are indicative of early dysplastic changes, the nature of the juxta-epithelial stromal alterations is still unknown. Current hypotheses regarding the etiology of oral submucous fibrosis are briefly discussed.

Lesions of the facial and trigeminal nerve in leprosy. An evaluation of 43 cases.

Facial and trigeminal nerve involvement was studied in 43 leprosy patients, 5.7% of the 750 Thai national in-patients of a leprosy rehabilitation centre. Involvement of the facial nerve occurred late in the disease and had an average duration of 12.1 years. The zygomatic branches of this nerve were the most frequently affected. Hypaesthesia and anaesthesia were most often observed in the maxillary divisions. Periorbital surgical procedures to prevent severe ocular complications are evaluated and discussed.