non-Asian Origin Research Articles

Fusarium wilt of banana and Wallace's line: Was the disease originally restricted to his Indo-Malayan region?

The edible bananas originated in Asia. Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. cubense, is a lethal disease of this important food crop. Also known as Panama disease, it impacts on a wide range of cultivars and, like its host, is now found throughout the tropical regions of the world. Although most authorities believe that the pathogen co-evolved with banana, a non-Asian origin is also possible. Before global collections of F. oxysporum f sp. cubense became available, there was scant evidence to support either of these hypotheses. New information on genetic diversity in the fungus, and its ancestry, confirms that it most likely originated in south and southeast Asia. The available data indicate that the eastern limit of its native range was probably defined by the 1910 version of Wallace’s line; its distribution coincided with his Indo-Malayan region. We believe that this is the first time that Wallace’s line has been shown to delimit the distribution of a microorganism, F. oxysporum f sp. cubense.

Lymphoepithelial carcinoma of the larynx and hypopharynx: Study of eight cases with relationship to Epstein-Barr virus and p53 gene alterations, and review of the literature

Eight cases of lymphoepithelial carcinoma (LEC) of the larynx and hypopharynx were evaluated for clinicopathologic features, and the presence of the Epstein-Barr virus (EBV) and p53 alterations. The seven men and one woman, all of non-Asian descent, averaged 64 years of age. Eighty-eight percent had histologically confirmed cervical lymph node metastasis at diagnosis. None had systemic disease. Seven of eight patients available for follow-up (mean, 17.7 months) were alive and free of disease, although one did develop recurrent tumor in the neck. Four tumors were composed, histologically, of pure LEC. Four others had foci of both LEC and conventional squamous cell carcinoma. All eight tumors exhibited alterations in p53 expression, but none was positive for EBV. Combining these 8 cases with the 15 previously published cases in the English literature indicate that LEC in this site is a rare, rather aggressive tumor, primarily of older adults (mean, 62 years) with a propensity for early cervical lymph node metastasis and eventual distant dissemination and death from disease in about one third of patients. Although p53 alterations are common and of no apparent prognostic significance, LEC at this site seems to have little, if any, relationship to the EBV in patients of non-Asian origin.

Rates of testosterone‐induced suppression to severe oligozoospermia or azoospermia in two multinational clinical studies

Two multicentre studies of the contraceptive efficacy of azoospermia and severe oligozoospermia were conducted in 16 centres in 10 countries. They used a common protocol of weekly testosterone injections for sperm suppression, the patterns and degrees of which were compared among men from different population groups. Six hundred and seventy normal, health volunteers, of whom 205 were Asian (mostly Chinese) and 465 of non-Asian origin, were given weekly injections of testosterone enanthate, 200 mg IM, during the suppression (6-month) and efficacy (12-month) phases. Patterns of sperm suppression were assessed by semen analysis at monthly or 2-weekly intervals. Sperm counts suppressed more slowly in the Asian than in the non-Asian men in the first 2 months of injections but subsequently suppressed to lower sperm concentrations below 5 million/ml, 3 million/ml or azoospermia at 6 months were 97.1% 95.6%, and 66.7%, respectively for non-Asian men, compared to 99.4%, 98.4% and 89.2%, respectively for Asian men. In conclusion, a hormonal contraceptive method based on regular testosterone injections can suppress spermatogenesis to azoospermia or severe oligozoospermia in 97% of men, regardless of their ethnic origin.

Insulin resistance, diabetes, and risk markers for ischaemic heart disease in Asian men and non-Asian in Bradford.

To examine the hypothesis, in a community not studied before, that insulin resistance associated with centralised adiposity is the mechanism underlying the predisposition of Asian immigrant communities to both ischaemic heart disease and diabetes mellitus. Cross sectional study within one socioeconomic stratum. Two factories in the textile sector in Bradford, West Yorkshire. Male manual workers of Asian (110) and non-Asian origin (156) aged 20-65 years. Diabetes was almost three times more prevalent in the Asian group. Two hours after an oral glucose load Asian men had double the serum insulin concentrations of non-Asian men (p < 0.0001). Asian men also had significantly lower concentrations of plasma total cholesterol (p < 0.03), high density lipoprotein cholesterol (HDL) (HDL2, p < 0.0001; HDL3, p < 0.0001), and apolipoprotein AI (p < 0.0001). Fasting plasma triglyceride concentrations were slightly higher (p = 0.072) in the Asian men; thus the ratio of triglyceride cholesterol was higher (p = 0.006). The inter-relation between serum insulin and plasma lipid concentrations indicated metabolic differences between the ethnic groups. Insulin concentrations were associated with cholesterol concentrations in the Asian men only and there was a lack of association between triglyceride, low density lipoprotein cholesterol, and HDL cholesterol in this group. The risk marker profile in the Asian men was therefore quite different to that of their non-Asian counterparts and was associated with a greater tendency to centralised adiposity. These data support the insulin resistance hypothesis and thus have important implications for strategies for the prevention of heart disease in Asian communities in the United Kingdom.

The molecular basis of α-thalassemias: Frequent occurrence of dysfunctional α loci among non-Asians with Hb H disease

Study of Asians has previously indicated that deletion of α-globin structural genes is the predominant lesion in α-thalassemias and that Hb H disease occurs when three of four normal α loci per cell are deleted. To test the generality of this model, Hb H disease DNAs of both Asian and non-Asian origin were analyzed by restriction endonuclease mapping using the technique of Southern (1975). Whereas in normal DNA, α sequences are present in a single Eco RI fragment of cellular DNA approximately 22.5 kb long, fragments of 22.5, 20 and 2.6 kb were found in various Hb H disease DNAs. The 20 kb Eco RI fragment alone, in which a single α-globin structural locus resides, was found in Asian Hb H disease DNA. This finding is consistent with the deletion model of α-thalassemia. In contrast, seven of eight non-Asian Hb H disease DNAs displayed a more complex molecular composition. The fragment patterns observed were 22.5 kb alone, 22.5 plus 2.6 kb, 20 plus 2.6 kb and 20 kb alone. Non-Asian Hb H disease DNAs contained one, two or three α loci per cell in contrast to the one locus predicted by the simple deletion model of α-thalassemia. The data are best explained by the existence of defective α loci in certain individuals with α-thalassemia, particularly outside the Asian population. Restriction mapping of the 20 kb Eco RI fragment found in Asian and some non-Asian Hb H disease DNAs demonstrated a striking similarity in the placement of restriction sites about the single α gene compared with sites about the two genes in the 22.5 kb Eco RI fragment seen in normal DNA. These data are consistent with origin of the 20 kb fragment from the 22.5 kb normal Eco RI fragment by either unequal crossing-over or a deletion event. The molecular heterogeneity and frequent occurrence of defective α loci in non-Asian Hb H disease DNAs described here may explain, in part, the clinical heterogeneity of α-thalassemias and the absence of the homozygous deletion state (hydrops fetalis) in non-Asians. Further study of cellular DNA fragments containing the defective α loci identified in this work may indicate the types of specific mutations responsible for abnormal globin gene expression and complement similar studies on abnormal β genes in β-thalassemias.