Thermocapillary Flow and Aggregation of Bubbles on a Solid Wall.

Theory suggests that thermocapillary flow about neighboring bubbles in liquids on hot walls pulls the bubbles together. A temperature gradient perpendicular to the wall establishes a surface tension gradient at the bubble-liquid interface, which in turn sustains a shear stress gradient that pumps adjacent fluid away from the wall. Neighboring bubbles are mutually entrained in this flow and also respond thermophoretically to lateral temperature gradients in the temperature near field. The theory predicts that the aggregation velocity scales with the temperature gradient, the radius of the bubbles, the derivative of the surface tension with respect to temperature, and the reciprocal of the liquid's viscosity. Bubble aggregation experiments under controlled conditions were performed to test the theory. Scaling the experimental bubble trajectories according to the theory substantially collapses all of the data onto a master curve when the interbubble separation is greater than 3 radii, which suggests that the theory is correct. Calculated velocities agree with the experimental results when hindrance of bubble motion due to the wall is included. Values for the parameter that describes the hindrance effect are obtained from fitting the data to the theory, from independent measurements, and from direct hydrodynamic calculation. The results of the three determinations agree within 15% of the possible range of the value of the parameter. Copyright 2000 Academic Press.

A substitutional mutation in the DNA binding domain of the androgen receptor causes complete androgen insensitivity syndrome.

DNA analysis of the androgen receptor gene in a patient with complete androgen insensitivity syndrome identified a substitutional mutation (tyrosine converted to cysteine at position 571) in the DNA binding domain. In vitro transfection experiments with the patients' androgen receptor gene, indicated normal expression of the androgen receptor in transfected COS-7 cells compared to the wild type gene. There was also no evidence of impaired thermal stability of the 5 alpha-dihydrotestosterone-androgen receptor complex. However, the capacity of the androgen receptor to activate target gene transcription was found to be completely disrupted in a luciferase assay. These results confirmed that only one substitutional mutation in the DNA binding domain was related to the pathogenesis of the complete androgen insensitivity syndrome.

CAG repeat length in the androgen receptor gene of infertile Japanese males with oligozoospermia.

We analysed the CAG repeat length in exon 1 of the androgen receptor gene in 59 idiopathic Japanese infertile males with oligozoospermia; 36 fertile males were also analysed as controls. The number of CAG repeats in infertile males ranged from 14 to 32 (mean 21.2+/-4.2), whereas the number of CAG repeats in fertile males ranged from 16 to 31 (mean 21.4+/-3.5). Among infertile males, six possessed a short form of 14 CAG repeats and three possessed 15 CAG repeats. On the other hand, fertile males did not possess the short form of 14 or 15 CAG repeats. The incidence of infertile males with 14 and 15 CAG repeats was significantly higher (P<0.05) than that of fertile males. Although the sample size is small, the results suggest that the reduction of CAG repeats in exon 1 of the androgen receptor is closely related to impaired spermatogenesis in infertile Japanese males.

Molecular analysis of the androgen receptor gene in 4 patients with complete androgen insensitivity.

Androgen insensitivity syndromes are due to defects in the androgen receptor gene. In this study, we analyzed the androgen receptor gene in four cases with complete androgen insensitivity syndrome. In patient 1, one substitutional mutation [arginine (codon CGC) to cysteine (codon TGC) at position 774] of exon F was identified. This position was located in the hormone binding domain and appeared to be one hot spot of mutations because the mutations at the same position in several unrelated cases were reported before. In patient 2, one substitutional mutation [tyrosine (codon TAT) to cysteine (codon TGT) at position 571] of exon B was identified. This position was located in the DNA binding domain. In patients 3 and 4 (siblings), one substitutional mutation [arginine (codon CGA) to glutamine (codon CAA) at position 752] of exon E was identified. Taken together, these abnormalities might be related to the pathogenesis of complete androgen insensitivity.

Single nucleotide substitution of the androgen receptor gene in a case with receptor-positive androgen insensitivity syndrome (complete form).

Complete androgen insensitivity syndrome is caused by X chromosome linked disorder resulting in a target organ insensitivity to androgen. Two variants have been described in this syndrome. In the first, the binding of [3H]dihydrotestosterone (17 beta-hydroxy-5 alpha-androstan-3-one) to the androgen receptor is undetectable (receptor-negative), whereas in the second variant normal levels of androgen receptor are detectable but the binding of [3H] dihydrotestosterone to the androgen receptor is significantly thermolabile under certain conditions (receptor-positive). In receptor-negative cases, genetic disorders of the androgen receptor gene have been demonstrated. On the other hand, the genetic disorder of androgen receptor in receptor-positive cases is little known. In this study, the gene structure of androgen receptor in a receptor-positive case using a polymerase chain reaction technique is studied in the fibroblasts cultured from genital skin. The results demonstrate that the substitution of nucleotide (guanine-->cytosine) in exon G of the androgen receptor causes the replacement of an amino acid in position 820 (glycine-->alanine) which occurs in the hormone-binding domain of the androgen receptor. The substitution of nucleotide may explain the thermolability of the androgen receptor in a case with receptor-positive androgen insensitivity syndrome.