Biomedical subjects
Publications and source records attributed to Y L Chan.
We report a case of abdominal actinomycosis demonstrated on computed tomography (CT) as an isolated mesenteric mass with radiating linear and nodular densities. The lesion mimicked a mesenteric tumor with desmoplastic reaction. The clinical and radiological features of this uncommon entity are reviewed.
A case of voluntary habitual dislocation of the hip with sonographic diagnosis of the "vacuum phenomenon" is described. This was seen as a characteristic hyperechoic interface between the acetabular fossa and the dislocating femoral head.
Bicarbonate transport was studied in vivo by separate microperfusion experiments of early and late distal tubules. Total CO2 was measured by microcalorimetry and fluid absorption by 3H-inulin. Significant bicarbonate absorption was observed in all experimental conditions. Bicarbonate transport was load-dependent upon increasing the luminal bicarbonate concentration from 15 to 50 mM in both early and late distal tubule segments and remained constant at higher concentrations at a maximum rate of 100-110 pmol/min per mm. At low lumen bicarbonate concentrations (15 mM), higher rates of bicarbonate absorption were observed in early (32.9 +/- 4.57 pmol/min per mm) as compared to late distal tubules (10.7 +/- 3.1 pmol/min per mm). Amiloride and ethyl-isopropylamiloride both inhibited early but not late distal tubule bicarbonate absorption whereas acetazolamide blocked bicarbonate transport in both tubule segments. Fluid absorption was significantly reduced in both tubule segments by amiloride but only in early distal tubules by ethyl-isopropylamiloride. Substitution of lumen chloride by gluconate increased bicarbonate absorption in late but not in early distal tubules. Bafilomycin A1, an inhibitor of H-ATPase, inhibited late and also early distal tubule bicarbonate absorption, the latter at higher concentration. After 8 d on a low K diet, bicarbonate absorption increased significantly in both early and late distal tubules. Schering compound 28080, a potent H-K ATPase inhibitor, completely blocked this increment of bicarbonate absorption in late but not in early distal tubule. The data suggest bicarbonate absorption via Na(+)-H+ exchange and H-ATPase in early, but only by amiloride-insensitive H+ secretion (H-ATPase) in late distal tubules. The study also provides evidence for activation of K(+)-H+ exchange in late distal tubules of K depleted rats. Indirect evidence implies a component of chloride-dependent bicarbonate secretion in late distal tubules and suggests that net bicarbonate transport at this site results from bidirectional bicarbonate movement.
The amino acid sequence of the rat 40S ribosomal subunit protein S25 was deduced from the sequence of nucleotides in a recombinant cDNA. Ribosomal protein S25 has 125 amino acids and has a molecular weight of 13,733. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 19 to 22 copies of the S25 gene. The mRNA for the protein is about 550 nucleotides in length. Rat S25 is homologous to ribosomal proteins from other eukaryotes (human and yeast).
The amino acid sequence of the rat 60S ribosomal subunit protein L8 was deduced from the sequence of nucleotides in a recombinant cDNA. Ribosomal protein L8 has 257 amino acids and has a molecular weight of 28,007. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 4 or 5 copies of the L8 gene. The mRNA for the protein is about 950 nucleotides in length. Rat L8 is homologous to ribosomal proteins from other eukaryotes and to proteins from eubacterial, archaebacterial, and chloroplast ribosomes.
The amino acid sequence of the rat 60S ribosomal subunit protein L11 was deduced from the sequence of nucleotides in a recombinant cDNA. Ribosomal protein L11 has 178 amino acids and a molecular weight of 20,239. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 6-8 copies of the L11 gene. The mRNA for the protein is about 800 nucleotides in length. Rat L11 is homologous to ribosomal proteins from other eukaryotes and is related to the L5 family of proteins from eubacterial and archaebacterial ribosomes.
The sonographic appearance of the sternocleidomastoid muscles of 36 children with congenital muscular torticollis was studied. Sternocleidomastoid tumour was detected in all of them and the images were more complex than described in the literature. A patchy echo-texture was as frequent as a homogeneous echo-texture, and was more common in the younger child. The echo-genicity of the mass could be hyperechoic, isoechoic or hypoechoic relative to normal muscle. A hypoechoic rim surrounding the mass was frequently present. Change of the proportion of the mass relative to the entire muscle-mass complex in different ages matching clinical observations was also noted. These sonographic findings would be important in establishing a sonographic diagnosis. The higher sensitivity of ultrasound in detection of sternocleidomastoid tumour over clinical methods, and the importance of the sonographic findings in the management of congenital muscular torticollis were also discussed.
Three cases of intracranial teratomas occurring at the basal ganglia of three young male patients were reported. Their radiologic appearances closely resembled each other with multicystic tumor masses located deep in the basal ganglia. Histology showed teratocarcinoma, combined immature teratoma and germinoma, and teratoma with malignant transformation. These tumours represent a distinct clinico-radiologic group of lesions and serve as an addition to the dearth of information reported about the histological subtypes of intracranial teratomas.
The single rat ribosomal protein P2 gene containing introns has been characterized. It has 2275 nucleotides distributed in 5 exons and 4 introns. The sequence of amino acids encoded in the exons corresponds exactly to that derived before from a cDNA. Only this one P2 gene in a family of approximately 9 members has introns and is expressed. There are two transcriptional start sites (adjacent cytidine residues) located in a tract of 10 pyrimidines flanked by GC-rich regions. The P2 gene, like other mammalian ribosomal protein genes, lacks a TATA box; however, it has at positions -30 to -27 the sequence TTTA which may be a degenerate TATA box and may serve the same function. The architecture of the P2 gene, and especially the structure of the promoter region, resembles that of other mammalian ribosomal protein genes. This suggests that the common features contribute to the coordinate regulation of their transcription and that the stoichiometry of P2 (it is present in 2 copies in the ribosome) is achieved by regulation of the translation of its mRNA.
The amino acid sequence of the rat 40S ribosomal subunit protein S28 was deduced from the sequence of nucleotides in a recombinant cDNA. Ribosomal protein S28 has 69 amino acids and has a molecular weight of 7,836. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 8-10 copies of the S28 gene. The mRNA for S28 is about 450 nucleotides in length. Rat S28 is homologous to Saccharomyces cerevisiae S33.
The amino acid sequence of the rat 60S ribosomal subunit protein L23 was deduced from the sequence of nucleotides in two recombinant cDNAs. Ribosomal protein L23 has 140 amino acids and a molecular weight of 14,856. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 7-9 copies of the L23 gene. The mRNA for the protein is about 600 nucleotides in length. Rat L23 is homologous to Saccharomyces cerevisiae L17a and related to Escherichia coli L14 and other members of the prokaryotic L14 family.
The amino acid sequence of the rat 40S ribosomal subunit protein S18 was deduced from the sequence of nucleotides in a recombinant cDNA. S18 has 152 amino acids and has a molecular weight of 17,707. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 10-13 copies of the S18 gene. The mRNA for the protein is about 600 nucleotides in length. Rat S18 is identical to mouse S18 (also referred to as KE3) and is related to Escherichia coli S13 and to other S13-like ribosomal proteins from Bacillus subtilis, from Bacillus stearothermophilus, and from plant mitochondria (Nicotiana tabacum and Zea mays).
This study was designed to examine the intracellular mechanism of inhibitory action of high concentration of angiotensin II (ANG II) on proximal tubular transport in rat kidneys by microperfusion methods. Perfusion of ANG II (10(-6) M) to peritubular capillaries caused a reduction of both fluid and HCO3- transport (Jv and JHCO3-, respectively) by 33 and 26%, respectively. These inhibitory effects were blocked by the ANG II-receptor antagonist [Sar1, Ile8]ANG II (10(-5) M). Similar degrees of inhibition on Jv and JHCO3- were observed when ionomycin (10(-7) and 10(-6) M), a Ca2+ ionophore, was added to capillary perfusate. Moreover, there was no additive effect when both ANG II and ionomycin were perfused together through capillaries, suggesting that both agents work via the same mechanism, presumably by increasing cytosolic Ca2+ concentration ([Ca2+]i). Inhibitory effects of ANG II on proximal tubular transport were still observed in a Ca2(+)-free perfusate containing ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, indicating that these effects do not require influx of Ca2+ from extracellular medium. Furthermore, the observation that TMB-8, an agent that prevents intracellular Ca2+ mobilization, completely eliminated the effect of ANG II strongly suggests that intracellular Ca2+ rather than Ca2+ influx mediates effects of ANG II on proximal tubular transport. Direct measurement of [Ca2+]i by use of fura-2 in isolated proximal tubular cells showed slight but statistically significant increases in [Ca2+]i. Taken together, these observations support the idea that intracellular Ca2+ serves as a second messenger in the inhibitory effect of high concentrations of ANG II on Jv and JHCO3- in proximal tubule of kidney.
Serum calcitonin and serum parathyroid hormone (PTH) were measured in 50 patients undergoing regular haemodialysis for end-stage chronic renal failure, and an analysis of osteoclast and osteoblast activities was made in bone biopsies obtained by iliac crest trephine. Osteoclast and osteoblast activities were studied in a multivariate analysis in relation to factors which might reasonably be thought to influence activity, namely serum calcitonin, serum PTH, serum calcium, serum inorganic phosphate, and bone aluminium. Only serum PTH correlated strongly with osteoclast activity (p = 0.0047). Serum PTH correlated also with osteoblast activity (p = 0.0024). Serum inorganic phosphate correlated negatively with osteoblast activity (p = 0.0082). Serum calcitonin did not correlate with osteoclast or osteoblast activities but did correlate strongly with bone aluminium in a multivariate analysis (p = 0.0078). Bone aluminium did not correlate independently with osteoclast or osteoblast activities. This study affirms the implied powerful role of PTH in influencing osteoclast and osteoblast activities in end-stage chronic renal failure.
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Our previous studies have shown that angiotensin II (Ang II) has a dose-dependent biphasic effect on bicarbonate and sodium transport and 4-beta-phorbol-12-myristate-13-acetate can simulate the stimulatory effect of Ang II on Na+/H+ exchange in the proximal convoluted tubules (PCT) of the rat kidney. This study was designed to further investigate the possible role of phosphoinositide turnover in mediating the biphasic effect of Ang II. Rat PCT was perfused in vivo with Ringer's solution containing [3H]inulin as a volume marker. Bicarbonate flux (JHCO3) was determined by total CO2 changes between the collected fluid and the original perfusate as analyzed by microcalorimetry. Luminal perfusion with 10(-11) M Ang II or 10(-8) M 4-beta-phorbol-12-myristate-13-acetate stimulated both fluid reabsorption (JV) and JHCO3, these effects can be blocked by 2 x 10(-4) M 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8), a blocker of intracellular calcium mobilization. Interestingly, Ang II at 10(-9) M or 2 x 10(-4) M TMB-8 have no effect on JV or JHCO3 individually. However, JV and JHCO3 significantly decreased when PCT were perfused simultaneously with 10(-9) M Ang II and 10(-4) M 1-(5-isoquinolinesulfonyl)-2-methylpiperazine; whereas JV and JHCO3 significantly increased when PCT were perfused with 10(-9) M Ang II and 2 x 10(-4) M TMB-8 together. These results suggest that PKC and intracellular calcium play a critical role in mediating the biphasic effect of Ang II on bicarbonate and sodium transport in PCT.
The amino acid sequences of rat ribosomal proteins L27a and L28 were deduced from the sequences of nucleotides in recombinant cDNAs and confirmed from the NH2-terminal amino acid sequences of the proteins. L27a contains 147 amino acids (the NH2-terminal methionine is removed after translation of the mRNA) and has a molecular weight of 16 476. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 18-22 copies of the L27a gene. The mRNA for the protein is about 600 nucleotides in length. L27a is homologous to mouse L27a (there are 3 amino acid changes) and to yeast L29. Rat ribosomal protein L28 has 136 amino acids (its NH2-terminal methionine is also processed after translation) and has a molecular weight of 15 707. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 9 or 10 copies of the L28 gene. The mRNA for the protein is about 640 nucleotides in length. L28 contains a possible internal duplication of 9 residues. Corrections are recorded in the sequences reported before for rat ribosomal proteins S4 and S12.
The amino acid sequence of the rat 40 S ribosomal subunit protein S20 was deduced from the sequence of nucleotides in two recombinant cDNAs. Ribosomal protein S20 has 119 amino acids and has a molecular weight of 13,364. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 16-19 copies of the S20 gene. The mRNA for the protein is about 600 nucleotides in length. Rat S20 is homologous to Xenopus laevis S22 and is related to Mycoplasma capricolum S10 and to Escherichia coli S10. The protein contains a possible internal duplication of seven residues.