A novel Escherichia coli vector for oxygen-inducible high level expression of foreign genes

By utilizing the oxygen-sensitive Escherichia coli Mn-superoxide dismutase (Mn-SOD) promoter, we have developed a vector system that expresses high levels of cloned foreign genes. The promoter for the bacterial Mn-SOD, as well as both 5'-untranslated and transcriptional termination sequences were ligated to a synthetic linker containing two restriction enzyme cloning sites. The vector also contained the gene for beta-lactamase, which confers ampicillin resistance to the host bacterium and provides a selectable marker. After screening and selection, high level of expression was achieved by exposure to the superoxide-generating agent paraquat (methyl viologen) as the inducer. To test the vector, both native and mutated human Mn-SOD cDNAs were cloned and expressed, respectively. To determine the optimal concentration of inducer necessary for maximal expression, recombinant bacteria were exposed to increasing concentrations of paraquat and subsequently assayed for superoxide dismutase (SOD) activity. The highest expression was induced by 20 microM paraquat, and approached 50% of total soluble protein.

Modified Thiersch grafting in stable vitiligo

Medical management of vitiligo usually gives complete repigmentation in up to 60 to 90% of cases (4, 7). Modified Thiersh grafting, in which psoralen without UVA or solar radiation was used successfully, is described.

Sneddon-wilkinson disease and arthritis

Sneddon-Wilkinson disease (subcorneal pustular dermatosis) is an uncommon disorder. An unusual association with seronegative arthritis is reported with review of literature.

Probable mechanisms of loss of Merkel cells in completely depigmented skin of stable vitiligo

Vitiligo is frequently associated with segmental involvement. It spares paralyzed limbs in transverse myelitis. There is spontaneous repigmentation of vitiligo lesional skin (VL) in diabetic neuropathy. Increased neuropeptide in VL and adjacent normal skin of vitiligo (ANS) along with thickened nerve fibers showing ultrastructural abnormalities all indicate a neural pathogenesis (1). Loss of Merkel cells has been observed in early vitiligo lesional skin (2). Recently, catecholamines have been found to play a major role in initiating the cascade of events leading to loss of melanocytes (1, 3, 4). To investigate the presence of Merkel cells in the completely depigmented skin of stable vitiligo (SV), a study was undertaken using TROMA 1, a monoclonal antibody specific for adult Merkel cells. No TROMA 1-positive cells were observed in SV, whereas normal numbers of these cells were seen in ANS. This new finding further supports the hypothesis of neural involvement in vitiligo.

Absence of Merkel cells in lesional skin of vitiligo [corrected]

BACKGROUND

In vitiligo, other than loss of melanocytes and melanin pigment in the lesional skin, keratinocytes are also involved. Human fetal Merkel cells are now generally considered to be derived from the epidermis. To date, no observations on Merkel cells in lesional skin of active vitiligo have been reported.

METHODS

Merkel cells were identified by indirect immunofluorescence microscopy using the monoclonal antibody TROMA 1.

RESULTS

No TROMA 1-positive cells were observed in the vitiliginous skin lesions in any of the specimens examined, whereas normal numbers of these cells were seen in the adjacent pigmented skin.

CONCLUSIONS

This finding suggests that the processes that lead to damage of keratinocytes in vitiligo also involve other keratin-expressing cells such as the Merkel cells.

Focal gaps in the basement membrane of involved and uninvolved skin of vitiligo: are they normal?

It has been suggested that, in vitiligo, the structural abnormalities may not be restricted to melanocytes alone, but also to keratinocytes of involved and uninvolved skin. Focal gaps in the vitiligo epidermal basement membrane have been furthermore interpreted as evidence of extramelanocyte alterations. To understand the occurrence of the gaps we undertook a study to establish which cells are related to them. Immunofluorescence and immunoperoxidase techniques were used to visualize, in involved, uninvolved, and control skin, the basement membrane, melanocytes, and Merkel cells. Double staining was performed with fluorescein-coupled anti-collagen IV antibodies and rhodamin-coupled antibodies against Nicein (GB3), a hemidesmosome component. Propidium iodide staining was used to detect infiltrating lymphocytes. The basement membrane structure was always found to be intact and unaltered. Absence of staining in areas of uninvolved skin was related to the presence of Merkel cells, melanocytes, and infiltrating lymphocytes. Gaps in the epidermal basement membrane are thus due to lack of staining caused by the presence of immigrant cells.

The toxicity of high-dose superoxide dismutase suggests that superoxide can both initiate and terminate lipid peroxidation in the reperfused heart

Recently, we described an anomalous bell-shaped dose-response curve for the protection of the reoxygenated isolated myocardium by superoxide dismutase (SOD). SOD is dramatically protective up to a point (5 micrograms/ml in the perfusate) beyond which it loses its ability to protect and, at very high doses (50 micrograms/ml), exacerbates the injury. We proposed that O2-. may serve as both initiator and terminator of lipid peroxidation, such that over scavenging the radical may increase net lipid peroxidation via increased chain length. We examined the ability of U74389F, a lipid peroxidation inhibitor, to ameliorate the toxicity of high-dose SOD in the isolated perfused rabbit heart preparation. The results show a significant improvement in the percent recovery of developed tension of hearts treated with U74389F and overdosed with MnSOD, as well as a decrease in thiobarbituric acid reactive substances.

Malignant lymphoma and dermatitis herpetiformis

We report 2 cases of dermatitis herpetiformis (DH) with lymphoma: a non-Hodgkin's malignant histiocytic lymphoma and a rare phenotype of Hodgkin's disease. With these 2 cases, 32 cases of DH complicated by lymphoma have now been documented. Reviewing the literature we show that the majority of lymphomas (78.1%) arises from the gastro-intestinal tract and that almost all cases of DH with lymphoma are associated with coeliac disease. The possible preventive role of a gluten-free diet is discussed.

Multiwavelength analysis of the kinetics of reduction of cytochrome aa3 by cytochrome c

Some new approaches to the kinetic study of the reduction of cytochrome aa3 by cytochrome c are presented. The primary innovations are the use of a spectrometer which can acquire multiwavelength data as fast as every 10 microseconds, and the application of a variety of analytical methods which can utilize simultaneously all of the time-resolved spectral data. These techniques include singular value decomposition (SVD), deconvolutions based on pure Gaussian models for absorption peaks, deconvolutions based on isolated absorption spectra for the pure components, and simulations of SVD-deduced and actual experimental difference spectra. The reduction characteristics of the anaerobic resting enzyme can be distinguished from those of pulsed forms. In the former case, only two electrons can be bound by cytochrome aa3, whereas in the latter case complete reduction of the enzyme is achieved.

Tat protein of human immunodeficiency virus type 1 represses expression of manganese superoxide dismutase in HeLa cells

Using a HeLa cell line stably transfected with the tat gene from human immunodeficiency virus type 1, we have found that the expression of the regulatory Tat protein suppresses the expression of cellular Mn-containing superoxide dismutase (Mn-SOD). This enzyme is one of the cell's primary defenses against oxygen-derived free radicals and is vital for maintaining a healthy balance between oxidants and antioxidants. The parental HeLa cells expressed nearly equivalent amounts of Cu,Zn- and Mn-SOD isozymes. Those cells expressing the Tat protein, however, contained 52% less Mn-SOD activity than parental cells, whereas that of the Cu,Zn enzyme was essentially unchanged. The steady-state levels of Mn-SOD-specific RNAs were also lower in the HeLa-tat cell line than in the parental line. No difference was seen in the steady-state levels of Cu,Zn-SOD-specific RNAs. In addition to the decreased Mn-SOD-activity, HeLa-tat cell showed evidence of increased oxidative stress. Carbonyl proteins were markedly higher, and total cellular sulfhydryl content decreased in cell extracts at a faster rate, probably reflecting ongoing lipid peroxidation. HeLa and HeLa-tat extracts were incubated with radiolabeled Mn-SOD transcripts, and the reaction products were subjected to UV crosslinking, digestion with ribonuclease A, and electrophoretic analysis. The results suggest a direct interaction between Tat protein and Mn-SOD gene transcripts.

Vitiligo: where do we stand?

Vitiligo is a puzzling disorder characterized by a disappearance of epidermal and/or follicular melanocytes by unknown mechanisms. This very common disorder involving 1-4% of the world population is thus of great importance for the practicing dermatologist. The cellular and molecular mechanisms leading to the destruction of melanocytes in this disorder have not yet been elucidated, making it of major interest for the cell biologist involved in melanocyte research. Recent advances in this field, due largely to the availability of techniques for culturing normal human melanocytes, opened new perspectives in the understanding of vitiligo. Although vitiligo has long been considered a disorder confined to the skin, there is now good evidence that it also involves the extracutaneous compartment of the "melanocyte organ." It is also clear that vitiligo is not only a melanocyte disorder, but that it also involves cells, such as keratinocytes and Langerhans cells, found in the epidermis and follicular epithelium. The three prevailing theories of the pathogenesis of vitiligo are the immune hypothesis, the neural hypothesis, and the self-destruct hypothesis. New hypotheses suggest that vitiligo may be due to (1) a deficiency in an unidentified melanocyte growth factor, (2) an intrinsic defect of the structure and function of the rough endoplasmic reticulum in vitiligo melanocytes, (3) abnormalities in a putative melatonin receptor on melanocytes and (4) a breakdown in free radical defense in the epidermis. None of these hypotheses has been demonstrated, and according to the available data, it is likely that the loss of epidermal and follicular melanocytes in vitiligo may be the result of several different pathogenetic mechanisms.