Mutations at the mouse microphthalmia locus are associated with defects in a gene encoding a novel basic-helix-loop-helix-zipper protein

Mice with mutations at the microphthalmia (mi) locus have some or all of the following defects: loss of pigmentation, reduced eye size, failure of secondary bone resorption, reduced numbers of mast cells, and early onset of deafness. Using a transgenic insertional mutation at this locus, we have identified a gene whose expression is disrupted in transgenic animals. This gene encodes a novel member of the basic-helix-loop-helix-leucine zipper (bHLH-ZIP) protein family of transcription factors, is altered in mice carrying two independent mi alleles (mi and miws), and is expressed in the developing eye, ear, and skin, all anatomical sites affected by mi. The multiple spontaneous and induced mutations available at mi provide a unique biological resource for studying the role of a bHLH-ZIP protein in mammalian development.

Preoperative portal vein embolization: an audit of 84 patients

Preoperative portal vein embolization (PVE) was performed in 84 patients before extensive liver resection for various diseases. By the criteria of liver volumetric determination, some patients were candidates for PVE, whereas others were not, even though the same surgical procedure, such as extended right lobectomy (ERL), was scheduled. PVE using gelatin sponge powder induced hypertrophy in the nonembolized lobe (0%-171%; median, 30%) and proportional atrophy in the embolized lobe in 2 weeks without eliciting any major inflammatory or necrotic reaction, as evidenced histologically and by the minimal elevations in the serum aspartate transaminase (AST) and alanine transaminase (ALT) values. Alterations in the total bilirubin level and prothrombin time were also insignificant and transient, indicating that hepatocyte functions were not impaired by PVE. Not all patients who undergo PVE proceed with the scheduled hepatic resection procedure, so it is a great advantage that gelatin sponge causes minimal damage compared with other embolizing materials such as cyanoacrylate and absolute ethanol, which have been reported to induce an inflammatory reaction or histological alteration. Our multiple regression analysis showed that three factors, diabetes mellitus, a high total bilirubin level at the time of PVE, and being male, each reduced the extent of hypertrophy in the nonembolized lobe (r2 =.30). By contrast, cholestasis appeared to accelerate the process of atrophy in the embolized lobe (r2 =.16). In conclusion, PVE by gelatin sponge powder is a safe and effective preoperative maneuver that induces hypertrophy of the section of the liver that will remain after partial hepatectomy.

Melanocyte development in vivo and in neural crest cell cultures: crucial dependence on the Mitf basic-helix-loop-helix-zipper transcription factor

The more than 20 different Mitf mutations in the mouse are all associated with deficiencies in neural crest-derived melanocytes that range from minor functional disturbances with some alleles to complete absence of mature melanocytes with others. In the trunk region of wild-type embryos, Mitf-expressing cells that coexpressed the melanoblast marker Dct and the tyrosine kinase receptor Kit were found in the dorsolateral neural crest migration pathway. In contrast, in embryos homozygous for an Mitf allele encoding a non-functional Mitf protein, Mitf-expressing cells were extremely rare, no Dct expression was ever found, and the number of Kit-expressing cells was much reduced. Wild-type neural crest cell cultures rapidly gave rise to cells that expressed Mitf and coexpressed Kit and Dct. With time in culture, Kit expression was increased, and pigmented, dendritic cells developed. Addition of the Kit ligand Mgf or endothelin 3 or a combination of these factors all rapidly increased the number of Dct-positive cells. Cultures from Mitf mutant embryos initially displayed Mitf-positive cells similar in numbers and Kit-expression as did wild-type cultures. However, Kit expression did not increase with time in culture and the mutant cells never responded to Mgf or endothelin 3, did not express Dct, and never showed pigment. In fact, even Mitf expression was rapidly lost. The results suggest that Mitf first plays a role in promoting the transition of precursor cells to melanoblasts and subsequently, by influencing Kit expression, melanoblast survival.

Mutations in microphthalmia, the mouse homolog of the human deafness gene MITF, affect neuroepithelial and neural crest-derived melanocytes differently

The mouse microphthalmia (Mitf) gene encodes a basic-helix-loop-helix-zipper transcription factor whose mutations are associated with abnormalities in neuroepithelial and neural crest-derived melanocytes. In wild type embryos, Mitf expression in neuropithelium and neural crest precedes that of the melanoblast marker Dct, is then co-expressed with Dct, and gradually fades away except in cells in hair follicles. In embryos with severe Mitf mutations, neural crest-derived Mitf-expressing cells are rare, lack Dct expression, and soon become undetectable. In contrast, the neuroepithelial-derived Mitf-expressing cells of the retinal pigment layer are retained, express Dct, but not the melanogenic enzyme genes tyrosinase and Tyrp1, and remain unpigmented. The results show that melanocyte development critically depends on functional Mitf and that Mitf mutations affect the neural crest and the neuroepithelium in different ways.

Intermediate-density lipoprotein and cholesterol-rich very low density lipoprotein in angiographically determined coronary artery disease

The relationship between the concentrations of intermediate-density lipoprotein (IDL) and other lipoproteins and the extent of coronary artery disease (CAD) was studied in 182 consecutive patients evaluated by selective coronary cineangiography. On univariate analysis, the extent of CAD correlated significantly and positively with very low density lipoprotein (VLDL) cholesterol, IDL cholesterol and low-density lipoprotein (LDL) cholesterol, and negatively with high-density lipoprotein (HDL) cholesterol. Analysis of four subgroups divided by IDL cholesterol and LDL cholesterol levels indicated that moderately increased levels of IDL cholesterol were closely associated with a high frequency of CAD. Moreover, multi-variate regression analysis demonstrated that IDL cholesterol for men, LDL cholesterol for men and women and HDL cholesterol for men were significant variables of use in the final weighting procedure. IDL cholesterol was closely associated with cholesterol-rich VLDL. This study shows that IDL and cholesterol-rich VLDL combine to contribute to the development of CAD.

Cloning of MITF, the human homolog of the mouse microphthalmia gene and assignment to chromosome 3p14.1-p12.3

The mouse microphthalmia (mi) gene encodes a basic-helix-loop-helix-zipper protein whose mutations may lead to loss of pigmentation in the eye, inner ear and skin, and to reduced eye size and early onset deafness. Mice with mutations at mi serve as models for human pigment disturbances in skin and eye that may be combined with sensorineural deafness. We have now obtained cDNA and genomic clones of the human homolog of mouse mi, identified a restriction fragment length polymorphism in the gene, and mapped the gene by somatic cell hybrid and fluorescence in situ hybridization techniques to a region of human chromosome 3 that shows a disrupted syntenic conservation with the region on mouse chromosome 6 to which mi maps. These studies will help to verify if any of the hereditary pigment disturbances in humans are due to mutations in this gene.

Evidence of effectiveness of a fracture liaison service to reduce the re-fracture rate

SUMMARY

We assessed the ability of a fracture liaison service (FLS) to directly reduce re-fracture risk. Having a FLS is associated with a ∼40% reduction in the 3-year risk of major bone and ∼30% of any bone re-fracture. The number needed to treat to prevent a re-fracture is 20.

INTRODUCTION

FLS have been promoted as the most effective interventions for secondary fracture prevention, and while there is evidence of increased rate of investigation and treatment at institutions with a FLS, only a few studies have considered fracture outcomes directly. We therefore sought to evaluate the ability of our FLS to reduce re-fracture risk.

METHODS

Historical cohort study of all patients ≥50 years presenting over a 6-month period with a minimal trauma fracture (MTF) to the emergency departments of a tertiary hospital with a FLS, and one without a FLS. Baseline characteristics, mortality and MTFs over a 3-year follow-up were recorded.

RESULTS

Five hundred fifteen patients at the FLS hospital and 416 patients at the non-FLS hospital were studied. Over 3 years, 63/515 (12%) patients at the FLS hospital and 70/416 (17%) at the non-FLS hospital had a MTF. All patients were analysed in an intention-to-treat analysis regardless of whether they were seen in the FLS follow-up clinic. Statistical analysis using Cox proportional hazard models in the presence of a competing risk of death from any cause was used. After adjustment for baseline characteristics, there was a ∼30% reduction in rate of any re-fracture at the FLS hospital (hazard ratio (HR) 0.67, confidence interval (CI) 0.47-0.95, p value 0.025) and a ∼40% reduction in major re-fractures (hip, spine, femur, pelvis or humerus) (HR 0.59, CI 0.39-0.90, p value 0.013).

CONCLUSIONS

We found a ∼30% reduction in any re-fractures and a ∼40% reduction in major re-fractures at the FLS hospital compared with a similar non-FLS hospital. The number of patients needed to treat to prevent one new fracture over 3 years is 20.

Gene expression profiles in Ciona intestinalis tailbud embryos

A set of 3423 expressed sequence tags derived from the Ciona intestinalis tailbud embryos was categorized into 1213 independent clusters. When compared with DNA Data Bank of Japan database, 502 clusters of them showed significant matches to reported proteins with distinct function, whereas 184 lacked sufficient information to be categorized (including reported proteins with undefined function) and 527 had no significant similarities to known proteins. Sequence similarity analyses of the 502 clusters in relation to the biosynthetic function, as well as the structure of the message population at this stage, demonstrated that 390 of them were associated with functions that many kinds of cells use, 85 with cell-cell communication and 27 with transcription factors and other gene regulatory proteins. All of the 1213 clusters were subjected to whole-mount in situ hybridization to analyze the gene expression profiles at this stage. A total of 387 clusters showed expression specific to a certain tissue or organ; 149 showed epidermis-specific expression; 34 were specific to the nervous system; 29 to endoderm; 112 to mesenchyme; 32 to notochord; and 31 to muscle. Many genes were also specifically expressed in multiple tissues. The study also highlighted characteristic gene expression profiles dependent on the tissues. In addition, several genes showed intriguing expression patterns that have not been reported previously; for example, four genes were expressed specifically in the nerve cord cells and one gene was expressed only in the posterior part of muscle cells.

This study provides molecular markers for each of the tissues and/or organs that constitutes the Ciona tailbud embryo. The sequence information will also be used for further genome scientific approach to explore molecular mechanisms involved in the formation of one of the most primitive chordate body plans.

Alpha-amylase genes (amyR2 and amyE+) from an alpha-amylase-hyperproducing Bacillus subtilis strain: molecular cloning and nucleotide sequences

amyR2, amyE+, and aroI+ alleles from an alpha-amylase-hyperproducing strain, Bacillus subtilis NA64, were cloned in temperate B. subtilis phage p11, and the amyR2 and amyE+ genes were then recloned in plasmid pUB110, which was designated pTUB4. The order of the restriction sites, ClaI-EcoRI-PstI-SalI-SmaI, found in the DNA fragment carrying amyR2 and amyE+ from the phage genome was also found in the 2.3-kilobase insert of pTUB4. Approximately 2,600 base pairs of the DNA nucleotide sequence of the amyR2 and amyE+ gene region in pTUB4 were determined. Starting from an ATG initiator codon, an open reading frame was composed of a total 1,776 base pairs (592 amino acids). Among the 1,776 base pairs, 1,674 (558 amino acids) were found in the cloned DNA fragment, and 102 base pairs (34 amino acids) were in the vector pUB110 DNA. The COOH terminal region of the alpha-amylase of pTUB4 was encoded in pUB110. The electrophoretic mobility in a 7.5% polyacrylamide gel of the alpha-amylase was slightly faster than that of the parental alpha-amylases. The NH2 termination portion of the gene encoded a 41-amino acid-long signal sequence (Ohmura et al., Biochem. Biophys. Res. Commun. 112:687-683, 1983). The DNA sequence of the mature extracellular alpha-amylase, a potential RNA polymerase recognition site and Pribnow box (TTGATAGAGTGATTGTGATAATTTAAAAT), and an AT-rich inverted repeat structure which has free energy of -8.2 kcal/mol (-34.3 kJ/mol) were identified. The AT-rich inverted repeat structure seemed to correspond to the hyperproducing character. The nucleotide sequence around the region was quite different from the promoter region of the B. subtilis 168 alpha-amylase gene which was cloned in the Escherichia coli vector systems.

Adaptive changes in membrane lipids of barophilic bacteria in response to changes in growth pressure

The lipid compositions of barophilic bacterial strains which contained docosahexaenoic acid (DHA [22:6n-3]) were examined, and the adaptive changes of these compositions were analyzed in response to growth pressure. In the facultatively barophilic strain 16C1, phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) were major components which had the same fatty acid chains. However, in PE, monounsaturated fatty acids such as hexadecenoic acid were major components, and DHA accounted for only 3.7% of the total fatty acids, while in PG, DHA accounted for 29.6% of the total fatty acids. In response to an increase in growth pressure in strain 16C1, the amounts of saturated fatty acids in PE were reduced, and these decreases were mainly balanced by an increase in unsaturated fatty acids, including DHA. In PG, the decrease in saturated fatty acids was mainly balanced by an increase in DHA. Similar adaptive changes in fatty acid composition were observed in response to growth pressure in obligately barophilic strain 2D2. Furthermore, these adaptive changes in response were also observed in response to low temperature in strain 16C1. These results confirm that the general shift from saturated to unsaturated fatty acids including DHA is one of the adaptive changes in response to increases in pressure and suggest that DHA may play a role in maintaining the proper fluidity of membrane lipids under high pressure.

Dynamic joint control training for knee ligament injuries

The purpose of this study was to introduce dynamic joint control training and to assess its effects in improving neuromuscular coordination of injured knees using the Kin-Com Isokinetic Dynamometer. Although four patients had a sensation of "giving way" on one knee, all eight knees were trained for 3 months using unstable boards with added sudden force given by a therapist. The training group (four patients) was examined during four sessions and the control group (five subjects) was examined during three sessions within a 3 month period. All subjects were instructed to react to the sudden forward movement of the input arm of the Kin-Com Isokinetic Dynamometer with contraction of the hamstring. Results of the first and final trials of peak torque time (PTT) and rising torque value (RTV) of the hamstring between the training and control groups showed significant improvement. There was no correlation between isometric muscle strength (IMS) and PTT in the total 76 sessions. There is a strong implication that simple muscle training does not increase the speed of muscular reaction but dynamic joint control training has the potential to shorten the time lag of muscular reaction.

Comparison of pressure resistances of spores of six bacillus strains with their heat resistances

The pressure resistances of the spores of six Bacillus strains were examined at 5 to 10(deg)C and were compared with their heat resistances. The pressure treatments (at 981 MPa for 40 min and at 588 MPa for 120 min) did not inactivate the spores of B. stearothermophilus IAM12043, B. subtilis IAM12118, and B. licheniformis IAM13417. However, these spores had large differences in heat resistance. The spores of B. megaterium IAM1166 were 9.3 times more pressure resistant but 246 times less heat resistant than those of B. stearothermophilus IAM11001. The spores of B. coagulans IAM1194 were activated by the pressure treatments. There was no correlation between these pressure and heat resistances.

Chitosan and sodium alginate based bioadhesive tablets for intraoral drug delivery

Bioadhesive tablets for intraoral drug delivery were prepared by directly compressing the drug with a mixture of chitosan and sodium alginate in weight ratios of 4:1, 1:1 and 1:4, and the adhesion and release characteristics of the prepared systems were evaluated in vitro and in vivo. Ketoprofen was used as a model drug. The magnitudes of the adhesion force of chitosan/alginate tablets were observed to be comparable to that of Aftach, which is a typical commercial preparation of an oral mucosal adhesive tablet. Increasing the chitosan content in the tablets resulted in a decrease in the release rate of ketoprofen. When the tablets were administered to the sublingual site of rabbits, ketoprofen from the tablets with chitosan/alginate was rapidly absorbed without an initial sharp peak. Furthermore, the plasma concentration curves for the tablet with a 1:4 chitosan/alginate ratio showed a sustained release 3 h after administration. The data presented suggest that tablets prepared from chitosan and alginate are potential candidates for intraoral drug delivery.

Relationship between copper, zinc and metallothionein in hepatocellular carcinoma and its surrounding liver parenchyma

BACKGROUND/AIM

Accumulation of copper (Cu) in hepatocellular carcinoma (HCC), especially in small tumors, is greater than that in the surrounding liver parenchyma. Metallothionein (MT) is considered to be present as Cu-MT, Zn,Cu-MT or Zn-MT. The aim of this study was to determine the presence and localization of Cu-MT and Zn-MT in HCC and surrounding liver parenchyma.

METHODS

In 16 HCC patients, surgically resected specimens including HCC and surrounding liver parenchyma were evaluated.

RESULTS

The level of Cu present in small HCC (<4 cm in diameter) was significantly greater than that in the surrounding liver parenchyma (p<0.05). However, the level of Cu in large HCC (>4 cm in diameter) was similar to that in the surrounding liver parenchyma. Analysis by Sephadex G-75 gel filtration revealed that the peak fraction due to Cu was identical to that due to MT in 14 (87.5%) of 16 HCC, the peak fraction due to Cu and Zn was identical to that due to MT in 2 (12.5%) HCC, and the peak fraction due to Zn was identical to that of MT in none of 16 HCC.

CONCLUSIONS

Accumulation of Cu in small HCC, in which Cu was present as Cu-MT or Zn, Cu-MT, was greater than that in the surrounding liver parenchyma. Cu accumulation and the presence of MT in the liver may be related to carcinogenesis of HCC, because of the similarity of these findings in the experimental data of Long-Evans rats with a cinnamon-like coat color who develop HCC spontaneously.

Quantitative approach to the histopathology of the biopsied right ventricular myocardium in patients with diabetes mellitus

For the purpose of studying the clinicopathology of the biopsied myocardium in patients with diabetes mellitus, the diameter of right ventricular myocardial cells and diffuse perimysial fibrosis of biopsied myocardium were measured quantitatively. Seven healthy controls and nine diabetic patients without hypertension or coronary arterial disease were subjected to this study. The degree of diabetic complications was mild to moderate. The diameter of myocardial cells was measured and the degree of diffuse perimysial fibrosis was assessed by the point-counting method using a square grid, in which the distance between the points was 10 micron. Over 2000 points which lay on the longitudinally cut myocardial cells and on the interstitial fibrosis stained by the Mallory-Azan method were measured. Percentage fibrosis was calculated according to the formula: percentage fibrosis = (points lying on the interstitial fibrosis)/[(points lying on the myocardial cell) + (points lying on the interstitial fibrosis)] X 100. The results were as follows. The mean diameter of right ventricular myocardial cells in patients with diabetes mellitus was significantly larger than that of controls (P less than 0.01). The percentage fibrosis of diabetic patients was significantly higher than that of controls (P less than 0.01). There was no significant correlation between the histopathological measurements and clinical features. It is concluded that hypertrophy of myocardial cells and interstitial fibrosis of the myocardium exist even in mild diabetes mellitus.

Necrotizing tubulointerstitial nephritis associated with adenovirus infection

We report 10 autopsy cases of necrotizing tubulointerstitial nephritis induced by adenovirus (ADV). Hemorrhagic, necrotizing tubulitis with intranuclear inclusion bodies was observed in the kidneys of five bone marrow transplant recipients and five patients treated with intensive chemotherapy for malignancies (four cases of leukemia and one case of lung cancer). It was histopathologically demonstrated that necrobiotic tubular cells had inclusion-bearing cells of three types: "smudge cells," Cowdry A intranuclear inclusion cells, and full-type intranuclear-containing cells. Immunofluorescent examination with anti-ADV antibody demonstrated specific fluorescence on the affected tubular cells of all 10 kidneys. Specific antigens for ADV type 11 were also revealed in all but one case by an immunofluorescent test using type-specific antiserum and convalescent serum containing high titer antibody to this serotype. Electron microscopy revealed intranuclear crystalline arrays of viral particles, 75 to 80 nm in diameter, in each of the seven cases examined. Extrarenal involvement, indicated by ADV-induced cytopathologic change, was confined to bladder or prostate. Hemorrhagic cystitis was recorded in all the bone marrow transplant cases as well as in one leukemia case. Adenovirus type 11 was isolated from urine in all five cases tested during these episodes. Renal failure was ascribed to ADV infection in two of five patients who died from renal dysfunction. The presence of hemorrhagic cystitis and localization of invasive infection in urogenital organs suggested that renal infection might occur by ascending route from the bladder. We propose that ADV should be added as a viral agent to the pathogenetic list of tubulointerstitial nephritis.

Distribution of polyunsaturated Fatty acids in bacteria present in intestines of deep-sea fish and shallow-sea poikilothermic animals

The lipid and fatty acid compositions in nine obligate and facultative barophilic bacteria isolated from the intestinal contents of seven deep-sea fish were determined. Phospholipid compositions were simple, with phosphatidylethanolamine and phosphatidylglycerol predominating in all strains. Docosahexaenoic acid (DHA; 22:6n-3), which has not been reported in procaryotes except for deep-sea bacteria, was found to be present in eight strains at a level of 8.1 to 21.5% of total fatty acids. In the other strain, eicosapentaenoic acid (EPA; 20:5n-3) was present at a level of 31.5% of total fatty acids. Other fatty acids observed in all strains were typical of marine gram-negative bacteria. Subcultures from pouches prepared from intestinal contents of five deep-sea fish by the most-probable-number (MPN) method were analyzed for fatty acids, and all subcultures contained DHA and/or EPA. Accordingly, viable cell counts of bacteria containing DHA and EPA were estimated at a maximum of 1.3 x 10(sup8) and 2.4 x 10(sup8) cells per ml, respectively, and accounted for 14 and 30%, respectively, of the total cell counts in the intestinal contents of the deep-sea fish. In the case of 10 shallow-sea poikilothermic animals having bacterial populations of 1.1 x 10(sup6) to 1.9 x 10(sup9) CFU per ml in intestinal contents, no DHA was found in the 112 isolates examined, while production of EPA was found in 40 isolates from cold- and temperate-sea samples. These results suggest that DHA and EPA are involved in some adaptations of bacteria to low temperature and high pressure.

A study of factors influencing prognosis after resection of hepatic metastases from colorectal and gastric carcinoma

OBJECTIVE

The aim of this study is to determine the absolute contraindication for hepatic resection for colorectal metastases and investigate the value of hepatectomy for gastric metastases by comparing it with the results of colorectal metastases performed with the same criteria.

METHODS

A retrospective cohort study was conducted in patients undergoing hepatic resection for metastatic colorectal (n = 64) and gastric (n = 17) carcinomas. Common predictive factors for both metastases were analyzed by the stratified Cox proportional hazard model. In this model, the different baseline hazard was set for each disease, whereas the risk of each covariate was assumed to be equal in both gastric and colorectal metastases.

RESULTS

Overall 1-, 2-, and 5-yr survival rates after hepatectomy for colorectal and gastric metastases were 90%, 73%, 42%, and 47%, 22%, 0%, respectively. Factors controlling prognosis were as follows: age > or = 60, extrahepatic metastases, serosal invasion, grade of lymph node metastases, tumor cell differentiation of the primary lesion(s), carcinoembryonic antigen level, tumor-exposed surgical margin, and blood transfusion. In particular, presence of extrahepatic metastases showed the markedly high-risk ratio among these eight variables.

CONCLUSIONS

Hepatectomy, if possible, is indicated in patients with hepatic metastases from colorectal carcinoma if there are no extrahepatic metastases and if the primary disease is controlled. It is indicated only in carefully selected patients with metastases from gastric carcinoma.

Anatomical keys and pitfalls in living donor liver transplantation

The surgery of living donor liver transplantation is more technically challenging than cadaveric whole liver transplantation and liver resection for the treatment of various pathological conditions. It requires a thorough understanding of the intra- and extra-hepatic anatomical relationships between the portal vein, hepatic artery, biliary tract, and hepatic vein, and also their respective contributions to liver physiology. Although a precise understanding of general anatomical principles is the key to correctly performing living donor liver transplantation procedures, anatomic anomalies are often present, and the means of detecting them and the surgical methods of coping with them represent technical challenges. In this monograph, we describe the anatomical keys and pitfalls of living donor liver transplantation surgery based on our own experience with more than 1800 hepatectomies, and 150 living donor liver transplantations. We also elaborate on techniques of selective intermittent vascular occlusion and their teleological and practical background.

Molecular analysis of mutations induced by acrolein in human fibroblast cells using supF shuttle vector plasmids

Types of mutations induced by acrolein in the supF gene on the shuttle vector plasmid pMY189 replicated in normal human fibroblast cells were examined. Base sequence analysis of 92 plasmids with mutations in the supF gene revealed that the majority of the mutations were base substitutions (76%) and the others were deletions and insertions (24%). Single base substitutions were most frequently found (46%), while multiple base substitutions were 18% and tandem (two adjacent) base substitutions were 12% of the mutations. Of the base substitution mutations, G:C to T:A transversions were 44% and G:C to A:T transitions were 24%. The mutations were distributed not randomly but located at several hotspots. Acrolein produced DNA intra-strand cross-links between guanine residues, which might be responsible for rather high induction of the tandem base substitution mutations.

Varied B-cell immunophenotypes of Hodgkin/Reed-Sternberg cells in classic Hodgkin's disease

AIMS

Recent analyses have suggested that Hodgkin's or Reed-Sternberg (HRS) cells in most cases of classic Hodgkin's disease are derived from germinal centre B-cells. However, there is controversy over which B-cell antigens are expressed in HRS cells.

METHODS AND RESULTS

We studied 51 cases of classic Hodgkin's disease to immunohistochemically characterize HRS cells for pan-B-cell markers and specific markers for plasma cells. HRS cells expressed CD20 (L26) in 18 cases (35%), CD19 (B4) in nine (18%) and CD79a (mb-1) in 13 (25%). Furthermore, HRS cells were positive for CD138 (B-B4) in 24 cases (45%) and for PCA-1 in 24 (45%). In 41 (80%) cases, HRS cells expressed more than one B-cell marker. We then subclassified cases into those positive for plasma cell markers (n = 27) (group 1) and those negative for them (n = 24) (group 2). The average age in group 1 (40 years) was younger than in group 2 (54 years) (P < 0.05). The percentage of nodular sclerosis (NS) subtype in group 1 (52%) was 1.5 times greater than in group 2 (33%) (P < 0.05). With regard to Epstein-Barr virus encoded small RNA (EBER) in-situ hybridization, 14 cases (64%) were positive in group 2, but only seven cases (31%) were positive in group 1 (P < 0.025).

CONCLUSION

In most cases of classic Hodgkin's disease, HRS cells expressed later stage of B-cell development. We consider that two different clinicopathological groups may correlate with the two different expressions of B-cell markers.

Phosphorylation of tyrosine residues of calmodulin in Rous sarcoma virus-transformed cells

Calmodulin, a wide-spread eukaryotic Ca2+-binding protein, was phosphorylated at its tyrosine residues in Rous sarcoma virus (RSV)-transformed chicken and rat cells but not in normal chicken embryo fibroblasts. In contrast, serine and threonine phosphorylation of calmodulin was found to occur in both normal and virus-transformed cells. In an in vitro system containing purified src kinase from RSV-transformed cells, tyrosine phosphorylation of calmodulin by the src kinase was inhibited by Ca2+. Furthermore, the tyrosine-phosphorylated calmodulin showed slower mobility than that of nonphosphorylated calmodulin in NaDodSO4/polyacrylamide gel electrophoresis when Ca2+ was present. These results suggest that the structure of calmodulin Ca2+ complex may be altered by tyrosine phosphorylation. It is thus inferred that Ca2+ may regulate the level of tyrosine phosphorylation of calmodulin in RSV-transformed cells, and phosphorylation in turn may attenuate the function of this protein in vivo.

Identification of the Catalytic Residues of Bifunctional Glycogen Debranching Enzyme

Eukaryotic glycogen debranching enzyme (GDE) possesses two different catalytic activities (oligo-1,4-->1,4-glucantransferase/amylo-1,6-glucosidase) on a single polypeptide chain. To elucidate the structure-function relationship of GDE, the catalytic residues of yeast GDE were determined by site-directed mutagenesis. Asp-535, Glu-564, and Asp-670 on the N-terminal half and Asp-1086 and Asp-1147 on the C-terminal half were chosen by the multiple sequence alignment or the comparison of hydrophobic cluster architectures among related enzymes. The five mutant enzymes, D535N, E564Q, D670N, D1086N, and D1147N were constructed. The mutant enzymes showed the same purification profiles as that of wild-type enzyme on beta-CD-Sepharose-6B affinity chromatography. All the mutant enzymes possessed either transferase activity or glucosidase activity. Three mutants, D535N, E564Q, and D670N, lost transferase activity but retained glucosidase activity. In contrast, D1086N and D1147N lost glucosidase activity but retained transferase activity. Furthermore, the kinetic parameters of each mutant enzyme exhibiting either the glucosidase activity or transferase activity did not vary markedly from the activities exhibited by the wild-type enzyme. These results strongly indicate that the two activities of GDE, transferase and glucosidase, are independent and located at different sites on the polypeptide chain.