High-frequency interconversion of turbid and clear plaque strains of bacteriophage f1 and associated host cell death

Under normal cultivation conditions, a mixture of turbid and clear plaques is often apparent in cultures of bacterial cells infected with filamentous bacteriophages. Beginning with a culture of wild-type filamentous phage f1, which itself produces turbid plaques, a clear plaque strain (c1) was isolated. From c1, the turbid plaque strain t1 was isolated; from t1, the clear plaque strain c2 was isolated; and from c2, the turbid plaque strain t2 was isolated. Each of these strains was generated with a frequency of approximately 1 x 10(-4). Although filamentous phages have been thought not to induce host cell death, both turbid and clear plaque strains of f1 killed host bacteria. Plating of bacterial cells 1 h after infection revealed that colonies produced by cells infected with either wild-type f1 or strain c2 were smaller than those derived from uninfected cells, and that colony formation by infected cells was reduced by 15% and 38%, respectively. The time course of bacterial growth revealed that, at 4 h after infection, the number of CFU per milliliter of culture of cells infected with wild-type f1 or with strain c2 was reduced by 27% and 95%, respectively, compared with that for uninfected cells. Microculture analysis also revealed that the percentages of nondividing cells in f1 or c2 infected were 19% and 52%, respectively, 4 h after infection with wild-type f1 or with strain c2; no such cells were detected in cultures of uninfected cells. Negative staining and electron microscopy showed that 20% and 61% of cells infected with wild-type f1 or with strain c2 were dead 4 h postinfection. Finally, although the rates of DNA synthesis were similar for infected and uninfected cells, the rates of RNA and protein synthesis were markedly reduced in infected cells.

Frequent presence of neuroendocrine small cells in thymic carcinoma: a light microscopic and immunohistochemical study

AIMS

Neuroendocrine differentiation has been described in conventional carcinomas of various organs. Small cells postulated to be neuroendocrine cells were observed previously in some thymic carcinomas. This study was conducted to confirm and characterize the presence of neuroendocrine small cells in thymic carcinomas by light microscopy and immunohistochemistry.

METHODS AND RESULTS

Twenty-two thymic carcinomas were studied by light microscopy to detect the presence of small neuroendocrine-like cells. They were found in four of 10 squamous cell carcinomas (SCC) and seven of eight adenosquamous carcinomas (ASC). No small cells were observed in three lymphoepithelioma-like carcinomas (LELC) and one adenocarcinoma. The small cells were located within the tumour nests and constituted less than 1% of the entire tumour. In one case, small cells also extended outside the tumour nests. Rosette formation was seen in three cases. They were proved to be neuroendocrine cells by their immunoreactivity to neuron-specific enolase, chromogranin A, and/or synaptophysin. A few scattered neuroendocrine small cells were found only by immunohistochemistry in one case each of SCC, ASC, and LELC. The small cells were also strongly positive for cytokeratin (CK) 8 and CK18 but negative for CK19 and CK20. The predominant carcinoma cells other than the neuroendocrine small cells also displayed neuroendocrine markers in 68% of the cases studied.

CONCLUSIONS

Neuroendocrine small cells can be recognized by light microscopic examination in approximately 61% of thymic SCC and ASC. Neuroendocrine markers, CK8 and CK18 can aid in confirming their presence. The neuroendocrine small cells present in thymic carcinomas are different from the main carcinoma cells displaying immunohistochemical neuroendocrine markers. The presence of neuroendocrine small cells could be an useful marker for the differentiation of thymic carcinomas from thymomas and carcinomas of other sites.

p16INK4 gene mutation and allelic loss of chromosome 9p21-22 in Taiwanese hepatocellular carcinoma

BACKGROUND

The p16INK4 (MTS1/CDNK2A) gene, located on chromosome 9p21, is an inhibitor of cyclin-dependent kinase 4. Various data have shown that it is frequently inactivated in several types of cell lines and primary human cancers.

MATERIALS AND METHODS

Thirty cases with hepatocellular carcinoma were studied for possible p16INK4 gene mutation in Taiwan. Homozygous deletion was determined using polymerase chain reaction (PCR). The p16INK4 gene mutation was first screened by single strand conformation polymorphism, then direct DNA sequencing was performed on the cases with mobility shifts. Deletion mapping of chromosome 9p21-22 was also carried out with two polymorphic microsatellite markers (D9S925 and D9S168) using PCR.

RESULTS

One of the 30 cases had homozygous deletion at exon 3 of the p16INK4 gene. Another tumor had altered electrophoresed mobility in exon 2 with G to T transversion in the first nucleotide of codon 61 by direct sequencing causing a stop codon (GAG-->TAG). At the D9S925 and D9S168 loci, six out of 24 (25%) and three out of 19 (16%) informative cases showed loss of heterozygosity, respectively.

CONCLUSION

Point mutation and homozygous deletion of the p16INK4 gene are present in a subset of hepatocellular carcinomas in Taiwan. The patterns of the p16INK4 gene alteration are, however, different from those from other regions. In addition, allelic loss on chromosome 9p21-22 is not an uncommon event in hepatocellular carcinomas. Therefore, the significance of chromosome 9p loss deserves to be extensively investigated.

Generalized granuloma annulare associated with granulomatous mycosis fungoides

We describe a 68-year-old man with plaque stage mycosis fungoides (MF) for 8 years. He developed tumorous lesions of granulomatous MF (GrMF) and generalized granuloma annulare (GA) after a previously indolent clinical course. Since then, the clinical course was aggressive with involvement of the bone marrow and lymph nodes, and leukemic change occurred. Systemic chemotherapy was given, but the patient died 9 months later due to neutropenic fever and septic shock. GA in malignant lymphoma has been reported most frequently in association with Hodgkin's disease. To the best of our knowledge, GA associated with GrMF has never been reported in the English language literature. The prognostic significance of the association of granulomatous inflammation and malignancy is reviewed.

Asparagine as a nitrogen source for improving the secretion of mouse alpha-amylase in Saccharomyces cerevisiae protease A-deficient strains

A modified chemically defined medium was achieved by using asparagine as a nitrogen source to increase the production of secreted mouse alpha-amylase in several Saccharomyces cerevisiae protease A-deficient (pep4) strains. The specific productivity (quantity) and the 53 kDa non-glycosylated active form (quality) of mouse salivary alpha-amylase in liquid medium containing asparagine was remarkably improved compared to media containing other nitrogen sources, including ammonium sulphate, glutamic acid, arginine, casamino acids, yeast extract and peptone. Similar improvement was also observed on starch solid agar regarding the clarity and size of the halo zone formed by alpha-amylase activity. Compared with ammonium sulphate, advantages of using asparagine as the nitrogen source in liquid or solid medium included increasing the cell mass of test strains, recovering the viability of protease-deficient strains to levels similar to the wild-type strain, and increasing the copy number of the mouse alpha-amylase expression vector in test strains. In turn, these advantages apparently contributed to the increase of secretion of mouse alpha-amylase in several test strains and especially in the protease A-deficient strains. In addition to demonstrating the use of modified chemically defined medium to improve the quality and quantity of secreted mouse alpha-amylase, this study also provides a new strategy to improve the secretion of heterologous proteins in protease A deficient strains.

Requirement for phosphoglucose isomerase of Xanthomonas campestris in pathogenesis of citrus canker

A mutant (XT906) of Xanthomonas campestris pv. citri, the causal agent of citrus canker, was induced by insertion of the transposon Tn5tac1 and isolated. This mutant did not grow or elicit canker disease in citrus leaves but was still able to induce a hypersensitive response in a nonhost plant (the common bean). The mutant was also unable to grow on minimal medium containing fructose or glycerol as the sole carbon source. A 2.5-kb fragment of wild-type DNA that complemented the mutant phenotype of XT906 was isolated. Sequence analysis revealed that this DNA fragment encoded a protein of 562 amino acids that shows homology to phosphoglucose isomerase (PGI). Enzyme activity assay confirmed that the encoded protein possesses PGI activity. Analysis of the activity of the promoter of the pgi gene revealed that it was inhibited by growth in complex medium but induced by culture in plant extract. These results demonstrate that PGI is required for pathogenicity of X. campestris pv. citri.

The pilA gene of Xanthomonas campestris pv. citri is required for infection by the filamentous phage cf

Host factors that are important for infection of Xanthomonas campestris pv. citri by the filamentous bacteriophage cf were investigated by transposon mutagenesis with Tn5tac1. A mutant, XT501, that was resistant to cf infection was recovered, showing that the gene inactivated by the transposon is required for infection by the phage but not for cf replication or assembly. A 1.7-kb SacI-ApaI DNA fragment from XT501 containing the bacterial DNA flanking one end of the transposon was cloned and shown to be required for cf infection. Nucleotide sequence analysis of the 1.7-kb fragment reveals the presence of an ORF that encodes a protein of 146 amino acids. This protein shows 42% identity to the type 4 prepilin encoded by the pilA genes of other bacteria. The pilA gene of X. campestris pv. citri is thus essential for infection by the bacteriophage cf.

The primary immunity determinant in modulating the lysogenic immunity of the filamentous bacteriophage cf

Bacteriophage cf is the first single-stranded DNA phage that has been shown to set up a stable lysogenic state with its genome integrated into the host chromosome. From the isolation and characterization of a virulent mutant, cf-tv2, we report the first investigation into the mechanisms of the immunity established by the filamentous bacteriophage. The mutation in cf-tv2 enables the phage to produce plaques on lawns of cf lysogenic cells. The mutation was defined as a 49-nucleotide deletion located in a 0.59 kb NcoI/KpnI fragment of cf replicative form DNA. Two messages, cM1 and cM2, transcribed from the immunity region of wild-type cf but in opposite directions, were detected. In cf-tv2, the 49-nucleotide deletion abolishes cM2 transcription. The primer extension assay suggests a possible RNA-RNA interaction directed by base-pairing of the cM1 and cM2 RNAs. A frameshift mutation of the open reading frame ORF 165, encoded by cM2, resulted in a 10(5) plating efficiency on the cf lysogen. These observations suggest that both RNA-RNA interaction and repressor protein inhibition are involved in the mechanism of cf immunity. A model is proposed for the regulation of cf immunity.

Transcription of the genome of the filamentous bacteriophage cf from both plus and minus DNA strands

The filamentous bacteriophage cf infects the bacterium Xanthomonas campestris pv. citri. Northern blot analysis with probes derived from various restriction fragments of cf replicative form (RF) DNA has revealed the presence of five major phage-specific transcripts in infected cells. Four of these transcripts were shown to be derived from the region of the cf genome extending from gene II to gene VIII and are consistent with the cascade model of transcription proposed for Ff coliphages. These transcripts overlap with each other and terminate upstream of an efficient Rho-independent transcription terminator. Unlike the well-characterized Ff phages, in which only the minus strand of viral DNA serves as a transcription template, both strands of the RF DNA of phage cf appeared to be transcribed. Thus one of the five major cf transcripts was shown to be derived from a region of the viral minus strand that contains an open reading frame encoding a putative polypeptide of 165 amino acids. Primer extension analysis mapped the transcriptional initiation site of this RNA to a cytosine residue at position 870. A partial transcription map of phage cf revealed two independent regions of transcriptional activity. The region with the highest activity coincides with that encoding the polypeptides required in the largest amounts during the cf infection cycle.

A variant of Saccharomyces cerevisiae pep4 strain with improved oligotrophic proliferation, cell survival and heterologous secretion of alpha-amylase

A variant of Saccharomyces cerevisiae pep4 strain 20B12, with improved oligotrophic proliferation, cell survival and secretion of heterologous mouse alpha-amylase, is described. Previously we reported a procedure to enrich NI transformants that are not inhibited by cytotoxic expression of hepatitis B virus surface antigen in the secretion pathway of the protease-A-deficient (pep4) strain. To use the NI cells as a host for heterologous expression, we tried to amend the introduced pYAS/12S vector and obtain a host strain, NI-C, with stable NI phenotype and trp1 marker restored. Southern analysis of genomic DNA of NI-C suggested that the original pYAS/12S was abnormally rearranged and not completely corrected. Further assay showed that the viability and mitotic ability of the NI-C strain were increased. While using the NI-C strain as host for plasmid transformation and heterologous expression of mouse alpha-amylase, we observed that transformed colonies grew more quickly and secreted more alpha-amylase than general yeast strains. A further test showed that the NI-C strain was able to use mouse alpha-amylase as a positive selection marker to form transformed colonies on nitrogen-starved plates that contain starch as the sole carbon source. The results imply that the NI-C variant is an improved pep4 strain that can be used for heterologous expression and for the development of new selective markers in the yeast transformation system.

Subcutaneous panniculitic T-cell lymphoma developing in a child with idiopathic myelofibrosis

PURPOSE

Subcutaneous panniculitic T-cell lymphoma is reported in a child with idiopathic myelofibrosis. Both disease entities are rarely seen in children.

PATIENT AND METHODS

A girl aged 5 years and 9 months had pancytopenia and severe constitutional symptoms. Idiopathic myelofibrosis was subsequently diagnosed.

RESULTS

A transient response was achieved after treatment with a course of high-dose methylprednisolone therapy. However, proptosis and skin nodules developed during tapering of steroid therapy. A computed tomography scan of the orbit also revealed a mass lesion in the right lacrimal gland region. A skin biopsy specimen showed a subcutaneous panniculitic T-cell lymphoma. The clinical course was marked by high fever, profound pancytopenia, massive gastrointestinal bleeding, and severe, recurrent infections. Her condition rapidly deteriorated, and she died from polymicrobial sepsis 4 months after her initial examination.

CONCLUSIONS

Subcutaneous panniculitic T-cell lymphoma is a distinctive clinicopathologic entity that is rarely seen in children. The association of myelofibrosis and peripheral T-cell lymphoma as seen in this has been rarely reported.

Congenital malignant rhabdoid tumor presenting as a cutaneous nodule: report of 2 cases with review of the literature

OBJECTIVE

The congenital occurrence of malignant rhabdoid tumor (MRT) is rare. Initial presentation of congenital MRT as a skin tumor is even more rare. We report 2 cases in which a cutaneous nodule appeared prior to the discovery of the primary tumor.

METHODS

Histologic, ultrastructural, and immunohistochemical studies were performed on skin nodules from 2 neonates. Other congenital examples of MRT in the literature were reviewed.

RESULTS

Both neonates were male and both were fullterm. Skin nodules were noted at birth. The tumors were located on the right neck in case 1 and on the right back in case 2. The primary tumors were later found in the kidney and the right chest wall, respectively. The skin biopsy of the first case had been interpreted as undifferentiated sarcoma, and MRT was diagnosed after the renal tumor was examined. In the second case, a correct diagnosis was promptly made based on the skin biopsy owing to experience with the first case.

CONCLUSIONS

Congenital MRT is very uncommon and may present as a skin tumor at birth. Since MRT exhibits various histologic patterns, the diagnosis should be made by a complete pathologic study with proper clinical correlation. To our knowledge, the unique mode of manifestation in these 2 cases is described for the first time. We suggest that MRT should be considered when making the differential diagnosis in such a clinical setting.

Thymic carcinoma arising in thymoma is associated with alterations in immunohistochemical profile

Thymic carcinoma is an uncommon tumor. Most cases appear to arise de novo, but in rare instances they can arise in thymomas. We report the clinicopathologic features and immunohistochemical profile of five cases of thymic carcinoma accompanied by a component of thymoma. Immunohistochemical studies were performed with the avidin-biotin-peroxidase complex method using monoclonal antibodies to p53(DO7), CD99(O13), epithelial membrane antigen, CD5(NCL-CD5-4C7), vimentin (V9), and cytokeratins 7, 8, 18, and 19. The patients consisted of three men and two women with a median age of 57 years. One patient had myasthenia gravis, and the other four presented with chest symptoms. One patient had concurrent adenocarcinoma of the lung with metastasis. Four of the patients died within 15 months. The thymomas consisted of two large polygonal cell thymomas, two squamoid thymomas, and one spindle cell thymoma. The malignant components included two undifferentiated carcinomas, one spindle cell carcinoma, one squamous cell carcinoma, and one clear cell carcinoma with squamous differentiation. There was no correlation between the histologic types of the thymoma and the thymic carcinoma. In three cases, excluding the two squamoid thymomas, the thymic carcinomas occurred in the necrotic areas of the thymoma. They showed upregulated expression of epithelial membrane antigen and cytokeratins 7, 8, 18, and 19, similar to the so-called "interface phenomenon" described in the invasion front of other types of carcinoma. Increased p53 protein expression was observed in all five carcinomas, and there was loss of CD99+ immature T lymphocytes. Among the thymic carcinomas, only the squamous component of the clear-cell carcinoma stained for CD5, a marker commonly expressed in thymic carcinomas. Paradoxically, a squamoid thymoma, but not its associated spindle cell carcinoma, expressed CD5, suggesting the acquisition of an "aggressive" phenotype by the squamoid thymoma, but with loss of the marker on malignant transformation. One undifferentiated carcinoma acquired vimentin immunoreactivity, whereas four other carcinomas and all five thymomas were negative. In conclusion, thymic carcinoma can arise in any histologic type of thymoma, including spindle cell thymoma, which is generally regarded as a benign neoplasm. The prognosis appears to be poor. Tumor necrosis in a thymoma should alert the pathologist to search for malignant change. The malignant change is commonly associated with increased expression of epithelial membrane antigen, cytokeratin subtypes, or p53 protein, and loss of CD99+ immature T lymphocytes, and is occasionally associated with a change in the expression of CD5 or vimentin.

Disassociation of sigma subunit from RNA polymerase of Xanthomonas oryzae pv. oryzae by phage Xp10 infection

The sigma subunit of Xanthomonas oryzae pv. oryzae is disassociated from host RNA polymerase after phage Xp10 infection. To clarify the possible mechanism for this observation, sigma subunit was purified and an antiserum against sigma subunit was prepared. Immunoprecipitation of RNA polymerase by the anti-core RNA polymerase antiserum, followed by immunoblotting with anti-sigma subunit antibody, revealed that sigma subunit was lost from RNA polymerase within 10 minutes after Xp10 infection. Loss of sigma subunit was not observed under other stress conditions including heat and cold stress, starvation and growth to stationary phase. Two-dimensional immunoblotting analysis did not reveal any covalent modification of either sigma subunit or RNA polymerase after Xp10 infection. These results suggest that separation of th subunit from RNA polymerase may be due to competition with other binding factors.

Keloidal dermatofibroma: report of 10 cases of a new variant

Dermatofibroma is a common cutaneous tumor. Unusual variants of dermatofibroma that exhibit various epidermal changes or different cellular composition have been described. We observed 10 cases of a novel variant of dermatofibroma characterized by keloidal change within the tumor. Formalin-fixed, paraffin-embedded tissues were used for histochemical and immunohistochemical studies. The patients consisted of six women and four men; median age was 34 years (17 to 59 years). All tumors occurred on the extremities, and six were present for at least 2 years. Tenderness was mentioned in four cases. They were described as erythematous or brown papules 1 cm or smaller. Clinical appearance did not deviate from that of ordinary dermatofibromas. Microscopically, the excised tumors showed a superficial circumscribed area of keloidal change under an atrophic epidermis in an otherwise ordinary dermatofibroma. In the keloidlike area, multinucleated giant cells, hemorrhage, hemosiderin deposits, and scattered KiM1P-positive histiocytes, but not factor XIIIa-positive or CD34-positive cells were present among the thick collagen fibers. There were no known recurrences. This variant dermatofibroma should not be overlooked as a simple keloidal scar. The observation of keloidal change in dermatofibromas may support the connotation that trauma is a possible cause of dermatofibroma. The fact that Asian people are more prone to develop keloid may have led us to find this new variant.

Granulocytic sarcoma presenting as a giant breast tumor in a pregnant woman: a case report

We report a case of granulocytic sarcoma (chloroma) presenting as a giant breast tumor in a pregnant woman with no history of leukemia. The case was initially diagnosed as medullary carcinoma on a biopsy specimen and a modified radical mastectomy was performed. The diagnosis of granulocytic sarcoma requires the pathologist's high index of suspicion. The presence of immature eosinophils was an important clue. Leder's chloroacetate esterase stain; immunostaining for myeloperoxidase, CD34, CD43, CD68, and lysozyme; and ultrastructural finding of cytoplasmic lysosomal granules and Auer bodies all aided in confirming the diagnosis. It is imperative to recognize granulocytic sarcoma to avoid unnecessary surgery. Granulocytic sarcoma should be included in the differential diagnosis of breast tumors, especially in tumors with diffuse proliferation of small tumor cells.

Leukemia cutis as the initial manifestation of acute nonlymphocytic leukemia in a young child

A 15-month-old boy was well except for asymptomatic, erythematous, wheal-like papuloplaques, macules, and nodules on his face and four extremities. It was misdiagnosed by a pediatrician and treated as urticaria for six months. Later, he was sent to our hospital for evaluation of prolonged fever. Acute nonlymphocytic leukemia (M5) with leukemia cutis was diagnosed by results of hematologic examination and examination of a skin biopsy specimen. After one course of chemotherapy, all of the skin lesions completely resolved and had not recurred. Five months after acute nonlymphocytic leukemia was diagnosed, bone marrow relapse and central nervous system involvement were noted.

Cutaneous involvement in polyvinylpyrrolidone storage disease: a clinicopathologic study of five patients, including two patients with severe anemia

Polyvinylpyrrolidone (PVP), formerly a plasma expander, has continued to be inappropriately used in Taiwan for intravenous injection as a "blood tonic." Five cases of PVP storage disease with cutaneous involvement were studied. Two patients presented with cutaneous eruptions mimicking collagen vascular disease and chronic pigmented purpuric dermatosis. Two other cases were found incidentally: one was with a metastatic tumor and the other in a pemphigus lesion. The fifth case was seen in a blind skin biopsy specimen taken to exclude Niemann-Pick disease after hematologic examination of a bone marrow smear. The latter patient and the patient with a collagen vascularlike disease also had severe anemia and serious orthopedic and neurologic complications due to massive infiltration of PVP-containing cells in the bone marrow with destruction of the bone. Severe irreversible anemia due to PVP storage disease has not been reported before. Three patients admitted having a history of receiving intravenous injection of PVP. The samples obtained from two of them indeed contained 5% PVP as determined by chemical analysis. PVP storage disease can be diagnosed by its histopathologic features. The skin biopsy specimens all showed a variable number of characteristic blue-gray vacuolated cells around blood vessels and adnexal structures with positive tinctorial reactions to mucicarmine, colloidal iron, and alkaline Congo red and negative to periodic acid-Schiff (PAS) and alcian blue. The PVP storage cells were shown to be CD68+ macrophages. The presence of PVP in the skin induced little or no inflammatory reaction. Only the pelvic mass in one patient had a foreign body granuloma formation. Our study showed that systemic parenteral administration of PVP preparation could result in the accumulation of PVP storage cells in the skin, with or without clinical eruptions. The diagnosis of systemic PVP storage disease can be established by performing a skin biopsy for pathologic study. It is important for pathologists and clinicians to be aware of this iatrogenic storage disease to avoid misdiagnosis for hereditary storage disease, osteomyelitis, or signet-ring cell carcinoma. Serious hematologic and orthopedic complications can be caused by repeated massive intravenous injection of PVP. Therefore, PVP preparations should be strictly prohibited for systemic administration.

Simultaneous occurrence of papulonecrotic tuberculide and erythema induratum and the identification of Mycobacterium tuberculosis DNA by polymerase chain reaction

The simultaneous occurrence of two tuberculides in one patient is rare. We report the case of a 32-year-old man presenting with both papulonecrotic tuberculide and erythema induratum. Mycobacterial DNA was identified from both skin lesions by polymerase chain reaction using formalin-fixed and paraffin-embedded tissues, suggesting that tuberculides are related to tuberculosis. New skin lesions developed after the patient discontinued his medication on his own initiative, 2 months after triple antituberculous therapy had been started. It is important to continue therapy for a prolonged period.

p53 expression and proliferative activity in Bowen's disease with or without chronic arsenic exposure

A comparative study of Bowen's disease (BD) with or without chronic arsenic exposure may contribute to understanding arsenic carcinogenesis. We compared the p53 overexpression and proliferative activity of 26 cases of BD with chronic arsenic exposure (group I) and 22 comparable cases of BD without chronic arsenic exposure (group II) by immunohistochemical method on formalin-fixed, paraffin-embedded tissues with antibodies PAb1801 and MIB-1, respectively. We also included in this study two squamous cell carcinomas that developed from BD in group I and one in group II. Two paired BD lesions in the same individual of one patient in group I and of three patients in group II were also studied. The significant p53(+) (>10% stained cells) rates were 42.3% (11 of 26) and 9.1% (2 of 22) for groups I and II, respectively, and the difference was statistically significant (P = .01). The p53 expression in different lesions of the same individual remained consistently the same. Squamous cell carcinomas that developed in 2 cases of p53(+) BD in group I were also positive, but the one in 1 case of p53(-) BD in group II was negative. No significant statistical difference in proliferative activity was found between group I BD and group II BD (P= .769), nor between p53(+) cases (>10% stained cells) and p53(-) cases (<10% stained cells) in group I BD (P = .519). This study showed that significant overexpression of p53 protein was higher in BD with chronic arsenic exposure. Therefore, arsenic carcinogenesis of BD might be different from that of BD unrelated to arsenic, and alteration of p53 plays a more important role in the pathogenesis of BD with chronic arsenic exposure. Overexpression of p53 was not a prerequisite for developing squamous cell carcinoma and was not affected by proliferative activity.

Novel and frequent mutations of hepatitis B virus coincide with a major histocompatibility complex class I-restricted T-cell epitope of the surface antigen

We examined the full-length hepatitis B virus (HBV) envelope (surface antigen or HBV small surface antigen [HBsAg]) sequences of 12 different liver samples from 10 different hepatoma-containing chronic carriers. Surprisingly, novel and frequent mutations occurred predominantly at amino acids 40 and 47 of HBsAg, in addition to within a known protective B-cell epitope (so-called group a determinant of HBsAg 124-148). Approximately 58% of chronic carriers contain mutations at the group a determinant. The mutation frequency at the hotspot codons 40 and 47 is approximately 83%, 1 order of magnitude higher than at the known polymorphic sites of subtype-specific determinants at codons 122 and 160, which is approximately 4%. This new mutational domain is found to coincide with a major histocompatibility complex class I-restricted T-cell epitope. The potential biological significance of this novel mutation in the immunopathogenesis of HBV chronic carriers is discussed.

Primary chondrosarcoma of the heart: a case report

Chondrosarcoma involving the heart has been previously reported but is extremely rare. Most chondrosarcoma described in the literature are secondary, and the primary site can be identified. We present an unusual case of primary cardiac chondrosarcoma which originated in the left atrium. Severe pulmonary edema was the first presentation. The sarcoma subsequently metastasized to the mandible and finally recurred in the right heart causing severe pulmonary emboli and myocardial failure.

Single-stranded DNA binding protein from bacteriophage cf: characterization, gene localization and protein-ssDNA complex

The single-stranded DNA binding protein from the filamentous bacteriophage cf has been purified and characterized. The first 12 amino acids, resulting from the N-terminal amino acid sequencing analysis of the protein, agree with an open reading frame (ORF) on the cf genome. The ORF contains 294 bp and codes for a 98 a.a. protein of molecular weight 10.8 kDa, consistent with the result from the denaturing protein gel analysis. The protein appears to be a homodimer as evident from the apparent molecular weight of about 22 kDa obtained from native protein gel analysis. The gene location of the protein has been identified as gene V of the cf single stranded genome, same as that from the M13 phage. The GVP of cf shows a strong sequence homology to the ssDNA binding proteins of Ff, IKe and Pf3 filamentous phages. The DNA binding wing of GVP, conserved among the filamentous phages, has been predicted for cf. To further characterize the protein, the GVP-ssDNA complex of cf has been purified from the infected host (Xanthomonas campestris pv. citri) by density gradient centrifugation. Transmission electron microscopy (TEM) images of the complex showed that it is about 1200 nm in length and 9 nm in diameter and it has a highly regular morphology with a central groove shadow running along the entire structure, but without any apparent helical pattern seen in the M13 complex. The GVP-ssDNA complex of cf seems more rigid than that of M13. Our computer modeling study suggested that this difference between the two complexes may be due to the additional 11 or 12 amino acids at the C-terminal end of the cf-GVP.