Maize leaf elongation: continuous measurements and close dependence on plant water status.

A simple method was developed for measuring extensive intact leaves of monocots on a minute-by-minute basis. Growth was markedly reduced by a slight reduction in leaf water potential. When plants mildly deficient in water were irrigated, growth resumed virtually instantly. The transitional rapid growth aftr watering suggests that water deficit increased cell extensibility.

Chromosomal and extrachromosomal instability of the cyclin D2 gene is induced by Myc overexpression.

We examined the expression of cyclins D1, D2, D3, and E in mouse B-lymphocytic tumors. Cyclin D2 mRNA was consistently elevated in plasmacytomas, which characteristically contain Myc-activating chromosome translocations and constitutive c-Myc mRNA and protein expression. We examined the nature of cyclin D2 overexpression in plasmacytomas and other tumors. Human and mouse tumor cell lines that exhibited c-Myc dysregulation displayed instability of the cyclin D2 gene, detected by Southern blot, fluorescent in situ hybridization (FISH), and in extrachromosomal preparations (Hirt extracts). Cyclin D2 instability was not seen in cells with low levels of c-Myc protein. To unequivocally demonstrate a role of c-Myc in the instability of the cyclin D2 gene, a Myc-estrogen receptor chimera was activated in two mouse cell lines. After 3 to 4 days of Myc-ER activation, instability at the cyclin D2 locus was seen in the form of extrachromosomal elements, determined by FISH of metaphase and interphase nuclei and of purified extrachromosomal elements. At the same time points, Northern and Western blot analyses detected increased cyclin D2 mRNA and protein levels. These data suggest that Myc-induced genomic instability may contribute to neoplasia by increasing the levels of a cell cycle-regulating protein, cyclin D2, via intrachromosomal amplification of its gene or generation of extrachromosomal copies.

The ribonucleotide reductase R2 gene is a non-transcribed target of c-Myc-induced genomic instability.

The c-Myc oncoprotein is highly expressed in malignant cells of many cell types, but the mechanism by which it contributes to the transformation process is not fully understood. Here, we show for the first time that constitutive or activated overexpression of the c-myc gene in cultured mouse B lymphocytes is followed by chromosomal and extrachromosomal amplification as well as rearrangement of the ribonucleotide reductase R2 gene locus. Electron micrographs and fluorescent in situ hybridization (FISH) demonstrate the c-Myc-dependent generation of extrachromosomal elements, some of which contain R2 sequences. However, unlike other genes that have been shown to be targets of c-Myc-dependent genomic instability, amplification of the R2 gene is not associated with alterations in R2 mRNA or protein expression. These data suggest that c-Myc-dependent genomic instability involves a greater number of genes than previously anticipated, but not all of the genes that are amplified in this system are transcriptionally upregulated.

Unique expression pattern of protein kinase C-theta: high mRNA levels in normal mouse testes and in T-lymphocytic cells and neoplasms.

A 2.2-kb cDNA that contains the entire coding region of mouse protein kinase C-theta (PKC-theta) was cloned from skeletal muscle mRNA using reverse transcription and the polymerase chain reaction (PCR). This clone was used as a probe to study the expression of this PKC isoform in normal and transformed hemopoietic cells and other normal tissues. By far the highest steady-state level of PKC-theta mRNA was found as a 2.8-kb transcript on a Northern blot of poly(A)+ RNA from testes. High levels were also found in skeletal muscle, spleen, T lymphomas and purified normal T lymphocytes, but these tissues and cells expressed two transcripts, 3.3 kb and 3.8 kb. Lower levels of similar size transcripts were found in normal brain, B lymphocytes and B-lymphocytic tumors and cell lines.

Activation of bcl-2 suppressible 40 and 44 kDa p38-like kinases during apoptosis of early and late B lymphocytic cell lines.

Activation of several different kinases characterizes the induction of apoptosis. Abelson virus transformed pre-B lymphocytes undergo apoptosis within 24 h of serum deprivation, PKA activation or gamma-irradiation, and the activity of two kinases of ca. 40 and 44 kDa is specifically induced during this apoptotic process. Bcl-2 expression prevents both apoptosis and the induction of these kinases. Immunologic and substrate similarities indicate that these kinases are related to the p38 family of MAP kinases. More mature cells of the B lymphocytic lineage, plasmacytomas, also exhibit induction of these kinases when apoptosis is induced by withdrawal of serum or IL-6. Treatment of the pre-B cells with ICE protease inhibitors when apoptotic stimuli are delivered prevents induction of the kinase activity, and partially inhibits apoptosis. These findings indicate that the induction of these 40 and 44 kDa p38 related kinases is a common feature of apoptosis in mouse B lymphocytic cells and may represent a step downstream of ICE proteases in the signal cascade that leads to programmed cell death.

Induction of plasmacytomas that secrete monoclonal anti-peptide antibodies by retroviral transformation.

ABL-MYC, a retrovirus that coexpresses v-abl and c-myc, was used to infect six BALB/c mice that had been immunized twice with a KLH-conjugated peptide that consisted of the 18 carboxyterminal amino acids of protein kinase C-eta (PKC-eta). All mice developed transplantable, monoclonal plasmacytomas, and five out of six plasmacytomas secreted antigen-specific antibodies, even after transplantation. All these antibodies recognized PKC-eta on Western blots of crude cell lysates and did not cross react with other isoforms of the PKC family.

FMC-HU-1-B: a lymphoma B-cell line with unusual characteristics.

A cell line (FMC-Hu-1-B) was established from a biopsy of an abdominal mass of a child with non-Burkitt's lymphoma. The establishment of the cell line initially required the presence of normal bone marrow stromal cells and phytohaemagglutinin stimulated leucocyte conditioned medium. The cell line lacked Epstein-Barr virus nuclear antigen and exhibited numerous chromosomal abnormalities. Cell-surface marker analysis using a panel of monoclonal antibodies revealed only markers of the B lineage. Within the B-cell lineage FMC-Hu-1-B seemed to occupy a level of maturation equivalent to normal mature B-cells (surface membrane IgM, secretion of immunoglobulin and FMC-1 positive). However, the cells also weakly expressed the common acute lymphoblastic leukaemia antigen, normally found on early precursors of B-cells. The cells appear to secrete auto-stimulatory growth factor(s).

Reactive mesothelial hyperplasia vs mesothelioma, including mesothelioma in situ: a brief review.

In biopsy tissue, discrimination between reactive mesothelial hyperplasia and epithelial mesothelioma can pose a major problem for the surgical pathologist. Confidence in the diagnosis is often proportional to the amount of tissue available for study and depends largely on findings of invasion and the extent and cytologic atypia of the lesion, because there is no marker specific for the mesothelium and that discriminates consistently among normal, hyperplastic, and neoplastic mesothelial tissue. Therefore, mesothelioma in situ is diagnosable only when invasive epithelial mesothelioma is demonstrable in the same specimen, in a follow-up biopsy specimen, or at autopsy. Comparison of 22 cases of mesothelioma in situ that fulfill these requirements for diagnosis with 141 invasive mesotheliomas and 78 reactive mesothelioses indicates that strong linear membrane-related labeling for epithelial membrane antigen and silver-labeled nucleolar organizer region-positive material that occupies 0.6677 microm2 or more of the nucleus in an atypical in situ mesothelial lesion of the pleura are found consistently in neoplastic mesothelial cells. Although these findings may engender suspicion of mesothelioma in situ in high-risk persons, the criteria for diagnosis of pure mesothelial lesions of this type are still under study. Mesothelioma in situ should be considered proved only when unequivocal invasion is identified in a different area of the pleura or at a different time; a diagnosis of pure mesothelioma in situ should not be made in patients not exposed to asbestos.

A human retinoblastoma cell line expressing the common acute lymphoblastic leukemia antigen and displaying an unusual chromosome abnormality.

A new continuous cell line derived from an untreated human retinoblastoma has been established. This cell line, FMC-RB1 is strongly positive for common acute lymphoblastic leukemia antigen and shows a number of ring chromosomes and two marker chromosomes considered to be derivations of chromosome #17; the nonrandom chromosomal changes associated with retinoblastoma, particularly the loss of a chromosome #13 or the deletion of 13q14 was not observed. The establishment of the cell line initially required the presence of bone marrow stromal cells. Morphologically, this cell line grew as a suspension of small round cells in grape-like clusters with periodic "shedding" of single cells. FMC-RB1 could be cloned in soft agar, even in the absence of bone marrow stromal cells as "feeders", making it suitable for a variety of biological studies.

Loss of heterozygosity in asbestos-induced mutations in a human mesothelioma cell line.

The relationship between occupational or environmental exposure to asbestos and the development of mesothelioma, typically after prolonged latency, has been accepted as one of cause and effect. Most studies have concluded that asbestos is not mutagenic to mammalian cells in vitro. We have studied the potential of crocidolite asbestos to induce mutations in a stable mesothelioma cell line, using a mutation assay that measures mutation at the autosomal HLA-A locus and permits clonal growth of mutant cells. The mesothelioma cell line chosen is more akin to the in vivo target cells of asbestos than human peripheral blood lymphocytes used in previous studies. Exposure of mesothelioma cells in culture to both 200 micrograms/ml and 50 micrograms/ml crocidolite for 72 hr did not result in a statistically significant difference in the mutation frequency (MF) in the HLA-A assay when compared to the spontaneous MF in these cells. Mutations in the mesothelioma cells were classified according to their molecular basis. Notwithstanding the lack of statistically significant change in overall MF, molecular analysis of mutants obtained following exposure of mesothelioma cells to crocidolite demonstrated a statistically significant increase in the class of mutations arising from loss of heterozygosity (LOH) events involving the selection locus (HLA-A) and more distal loci. Mutations following exposure to 200 micrograms/ml and 50 micrograms/ml crocidolite showed a greater frequency of LOH than did spontaneous mutants (P < 0.01 and P < 0.001, respectively). These results correlate with those obtained in an earlier study using lymphocytes. The mesothelioma cell-based assay may be useful in detecting the mutagenicity of other asbestiform fibers and man-made fibers.

Naproxen-induced pseudoporphyria. A clinical and ultrastructural study.

Pseudoporphyria is a condition clinically and ultrastructurally identical to porphyria cutanea tarda but with no associated abnormality of heme synthesis. A 45-year-old woman with bullae on the dorsa of her hands was found on investigation to have pseudoporphyria. Her symptoms remitted following the cessation of naproxen therapy.

Electron microscopy in surgical pathology: a selective review.

The high resolution provided by electron microscopy can contribute to histomorphological diagnosis by allowing the detection of structures which are invisible to the light microscope. These structures include characteristic nuclear or cytoplasmic contours, intercellular attachments and intracellular components. The recognition of such features may allow specific diagnosis in lesions which cannot be precisely categorized by light microscopy. Electron microscopy is particularly useful for the diagnosis of neoplasms. This review describes some of the characteristic morphological features which can be demonstrated in neoplastic cells by electron microscopy and briefly considers several areas where the technique is of special value. Electron microscopy is now an integral part of the diagnostic process in surgical pathology and can be regarded as a routine technique rather than a special procedure to be delegated to others.

Regenerative atypical squamous metaplasia in fibreoptic bronchial biopsy sites--a lesion liable to misinterpretation as carcinoma on rebiopsy: report of 5 cases.

Regenerative atypical squamous metaplasia at the site of a previous bronchial biopsy can be mistaken for carcinoma on rebiopsy. Five cases are reported, in three of which an erroneous diagnosis of squamous cell carcinoma led to unnecessary surgical resection.

Malignant Schwannoma of cranial nerves.

The clinical presentation and histopathological features of 5 cases of malignant Schwannoma of cranial nerves are described. The ultrastructural appearances of one case and the pattern of nerve sheath cell differentiation of these tumours are also discussed. These uncommon tumours often are not diagnosed at initial presentation. Since the cases provide evidence that early diagnosis and surgical treatment are vital in the management of patients with this tumour criteria for its diagnosis are suggested.

Pulmonary lymphomatoid granulomatosis with immunodeficiency terminating as malignant lymphoma.

Lymphomatoid granulomatosis was diagnosed in a 60-yr-old woman 2 yr after presentation with a multi-system disorder resembling sarcoidosis. Five months later autopsy revealed malignant lymphoma. Large aggregates of intracytoplasmic tubular structures resembling nucleocapsid material of the paramyxovirus group were found within cells of lymphoma deposits in the liver. Sequential immunological studies over more than 2 years demonstrated a relatively stable T-cell deficiency associated with variable B-cell dysfunction. The latter was characterized by the production of immunoglobulins of restricted electrophoretic mobility. Intermittent hypercalcaemia was associated with increases in serum IgG and appeared to be due to the presence of Ca-binding paraproteins. It is suggested that lymphomatoid granulomatosis may be a pre-malignant lymphoproliferation, with immune deficiency as a predisposing cause. The pattern of immunological abnormalities suggests that the lymphoma may have been due to B-cell malignant transformation.

Bone marrow metastases in disseminated alveolar rhabdomyosarcoma: case report with ultrastructural study and review.

A case of desseminated alveolar rhabdomyosarcoma in an 18-year-old male with leuco-erythroblastic anaemia is described. Numerous bizarre malignant cells, including frequent multinucleated giant cells, were seen in bone marrow aspirates, and osteolytic lesions appeared late in the clinical course. The primary site of the neoplasm remained undertermined during life and also at necropsy, which revealed minute pulmonary metastases and extensive lymph nodal, pleural and skeletal deposits. The diagnosis was confirmed on necropsy tissue by ultrastructural examination which demonstrated numerous thin (5 nm) and thick (15 nm) intracytoplasmic filaments in tumour cells, sometimes organized in bundles; scattered dense Z-band-like bodies, and rod-shaped structures were also seen. The fine structure of the rhabdomyosarcoma in the present case is compared with previous ultrastructural studies. Elongated, thick intracytoplasmic filaments whose diameter corresponds to that of myosin myofilaments are strong evidence for rhabdomyoblastic differentiation and are considered to be the sine qua non of a positive electron microscopic diagnosis of rhabdomyosarcoma. Orgaized bundles of filaments and Z-band-like dense bodies are usually present, and rod-shaped structures are found infrequently, but none of these are necessary for the ultrastructural diagnosis.

Asbestos, asbestosis, pleural plaques and lung cancer.

Inhalation of asbestos fibers increases the risk of bronchial carcinoma. It has been claimed that asbestosis is a necessary prerequisite for the malignancy, but epidemiologic studies usually do not have enough statistical strength to prove that asbestos-exposed patients without asbestosis are without risk. Several recent studies do actually indicate that there is a risk for such patients. In addition, case-referent studies of patients with lung cancer show an attributable risk for asbestos of 6% to 23%, which is much higher than the actual occurrence of asbestosis among these patients. Thus there is an increasing body of evidence that, at low exposure levels, asbestos produces a slight increase in the relative risk of lung cancer even in the absence of asbestosis. Consequently, all exposure to asbestos must be minimized.

Cilia and ciliogenesis in endometrial adenocarcinomas. An ultrastructural analysis.

Cilia in neoplastic cells were observed by electron microscopy in specimens from five of six consecutive patients with endometrial adenocarcinoma. Most cilia showed a range of defects, from misalignment and displacement of individual doublets to the absence of up to three peripheral doublets, the pattern varying from 9+2 to 6+2; the central pair of microtubules also was frequently missing. Single peripheral microtubules and displacement of the dynein arms were also observed. The high proportion of cilial defects in neoplastic cells (72%) compared with those in normal endometrium (26%), together with a broader spectrum of cilial abnormalities, suggests that the neoplastic state increases the number and range of cilial lesions.

The concept of mesothelioma in situ: implications for diagnosis and histogenesis.

The concept of mesothelioma in situ is explored by a detailed examination of seven patients, subsequently proven to have pleural malignant mesothelioma, who initially had no evidence of gross tumor and for whom biopsy material was available at this early presentation. The tissue was assessed by routine microscopy, the immunoperoxidase technique for epithelial membrane antigen and silver staining for nucleolar organizer regions. Tiny lesions of the pleura that merged with or were adjacent to microscopically flat monolayered or folded mesothelium with cytological atypia were observed. The atypical cells reacted positively to epithelial membrane antigen, and the nucleolar organizer region counts were elevated. These observations are considered to support the possibility of the presence of mesothelioma in situ. These findings are discussed in the light of the proposed concept of mesothelioma in situ, its histogenesis, and its possible clinical relevance.