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.

Surface components of HeLa cells that inhibit cytadherence of Chlamydia trachomatis

Isolated HeLa plasma membrane (PM) preparations and extracts containing either cell-surface proteins or lipids were examined for inhibition of adherence of radiolabeled Chlamydia trachomatis serovar E elementary bodies to glutaraldehyde-fixed HeLa monolayers. A dose-dependent adherence-inhibitory activity could be demonstrated with the PM. A urea extract as well as lipids from HeLa cells also inhibited chlamydial cytadherence. The inhibitory activity of the PM was trypsin-sensitive. It was absent when the urea extract was prepared from trypsin-treated HeLa cells. The urea extract was subjected to electrophoresis and protein blotting using a native gel system. Probing with radiolabeled chlamydial cytadhesin showed a single protein present in the urea extract that could represent a HeLa cell protein receptor for the chlamydiae.

Further characterization of an outer membrane protein of Chlamydia trachomatis with cytadherence properties

To further characterize the chlamydial cytadhesin (CCA), we have examined it for saturability of binding to HeLa cells that were grown as monolayers and in suspension. The CCA exhibited specific cytadherence properties of binding to HeLa cells that appeared to be saturable. The CCA showed a substantial decrease in binding to trypsin-treated HeLa cells in suspension. This finding, together with the fact that the CCA itself is known to be trypsin-sensitive, suggested a protein-protein type of interaction between CCA and HeLa cells. Periodate treatment of the CCA did not result in significant reduction in cytadherence, which implies that sugar moieties were probably not involved in CCA binding to HeLa cells. Whilst attempts to produce antibodies to the CCA in rabbits was unsuccessful, the CCA reacted with antibodies in a human serum known to contain high titer antibodies to Chlamydia trachomatis, suggesting it can be immunogenic, and is possibly expressed during human infection.

Catabolite repression vs derepression, an approach to differentiation during sporulation in Bacillus subtilis

Glutamine, like glucose, repressed sporulation and the synthesis of mycobacillin and dipicolinic acid by Bacillus subtilis, and these syntheses were depressed by dibutyryl cyclic GMP but not by dibutyryl cyclic AMP. Neither of these dibutyryl cyclic nucleotides affected sporulation or a number of spore-associated parameters in the strain under normal physiological conditions. Mutants insensitive to glutamine repression were indifferent to the addition of either of the dibutyryl cyclic nucleotides both in the presence and in the absence of glutamine. Sporulation resulted from the remission of repression obtained under the catabolically active state.

Host passage-dependent wheat germ agglutinin-binding proteins of Chlamydia trachomatis

Wheat germ agglutinin (WGA)-binding proteins in the highly purified elementary bodies (EB) of Chlamydia trachomatis were detected by an ELISA-like assay of immobilized EB. Trypsin-sensitivity of the WGA-binding moieties was detected only in the chlamydiae grown in HeLa cells. A nonionic detergent, beta-octyl-D-glucopyranoside (OG), was used to extract proteins from the purified EB. Proteins in the extract were resolved by SDS-PAGE and probed with 125I-labelled WGA. Several proteins reacted with WGA in a specific manner. Some of these WGA-binding proteins in the EB of serovars L1 and E exhibited altered molecular mass after adaptation in the two alternate hosts, HeLa and McCoy cells. These results suggest that WGA-binding proteins exist in chlamydiae.

A heat-labile protein of Chlamydia trachomatis binds to HeLa cells and inhibits the adherence of chlamydiae

From highly purified elementary bodies (EBs) of Chlamydia trachomatis, we have identified a protein of 38 kDa that selectively binds to monolayer cultures of HeLa cells. This protein, which we have named the chlamydial cytadhesin (CCA), is present on the surface of the EBs of three C. trachomatis serovars (B, E, and L1) that were examined. Localization of the CCA at the surface was confirmed by its ability to be labeled when viable EBs were iodinated and by its absence in preparations from trypsin-treated EBs. Viable EBs, but not heated or trypsin-treated EBs, inhibited the binding of the CCA to HeLa cells, indicating competition for a common receptor on the host cell membrane. A dose-dependent inhibition of adherence of radioactive EBs to HeLa cells was effected by extracts containing the CCA. This inhibition occurred even with extracts prepared from the EB of heterologous serovars. However, no inhibition could be demonstrated with extracts prepared from heat-treated EBs. Heat treatment of the extract resulted in the loss of ability of the CCA to bind to the host cells. HeLa cells preincubated with CCA-containing chlamydial extract showed reduced ability to bind labeled EBs and to develop cytoplasmic inclusions after infection. This protective activity was lost after exposure of the extract to heat. These findings indicate that the CCA is a thermolabile surface-exposed chlamydial adhesin; it may be useful in the development of vaccines for diseases caused by the pathogenic bacterium.

Ischemic preconditioning is not mediated by free radicals in the isolated rabbit heart

Preconditioning has been implicated to involve a free radical mechanism in the in vivo infarct size model. We have demonstrated preconditioning in the isolated rabbit heart and studied the effect of Mn-superoxide dismutase (SOD) on preconditioning. Buffer perfused control hearts (C) were subjected to 1-h global ischemia followed by 1-h reperfusion, and the percent recovery of developed tension (%DT; relative to preischemic) was measured via a left ventricular balloon connected to a polygraph recorder. The coronary effluent was assayed for lactate dehydrogenase release (LDH; IU/kg BW). Preconditioned hearts (P) received a single episode of 5-min ischemia and 5-min reperfusion before 1 h of ischemia and reperfusion. SOD treated hearts received SOD at 5 mg/L in the buffers at all times. The results show that while SOD attenuated enzyme release and functional loss in control hearts, it had no effect on preconditioned hearts. Therefore, preconditioning is unlikely to be mediated by superoxide anion in the isolated rabbit heart.

Extensive heterogeneity of the protein composition of Chlamydia trachomatis following serial passage in two different cell lines

To determine if the host-modulated adherence characteristics of the intracellular bacterial pathogen Chlamydia trachomatis were due to the acquisition of altered surface-exposed proteins, highly purified chlamydiae grown in two different host cells were analysed. Two serovars, L1 and E, were grown for multiple passages in both HeLa and McCoy host cells. Numerous protein differences in the chlamydial elementary bodies (EB) of each serovar grown in the two different hosts were detected by two-dimensional (2-D) gel electrophoresis and fluorography of radioactively labelled proteins. At least four to six serial passages in the alternative host were necessary before the changes were apparent. Iodination of suspensions of purified chlamydiae and 2-D electrophoresis revealed several surface proteins that were determined by the host cells in which the bacteria had replicated. These iodinated chlamydial proteins were removed by treatment of the iodinated EB with trypsin, indicating their location at the bacterial surface. Two of the major constituents of the outer-membrane complex, the cysteine- and methionine-rich 60 kDa and 40 kDa proteins, remained unchanged in both molecular mass and charge during the host adaptation. Several chlamydial proteins capable of binding iodinated host membrane preparations also exhibited host-dependent alterations. Immunoblotting experiments with a rabbit and a human polyclonal sera indicated that distinct host-specified chlamydial proteins were reactive with the two sera.

Adherence of multiple serovars of Chlamydia trachomatis to a common receptor on HeLa and McCoy cells is mediated by thermolabile protein(s)

Several aspects of the adherence of purified elementary bodies (EB) of Chlamydia trachomatis to HeLa and to McCoy cells were examined using different techniques, including an ELISA. Serovar-specific, biotinylated monoclonal antibodies were used to detect cell-bound chlamydiae. In addition, purified chlamydiae were biotinylated and their adherence properties were studied. The assays were done at 4 degrees C to exclude the energy-dependent internalization of the cell-bound EB and host-cell membrane recycling that occur at 37 degrees C. Saturation kinetics were routinely observed at 4 degrees C, and the rate of adherence remained linear for approximately 60 min. Lineweaver-Burk analysis of the kinetics data showed that adherence of any one serovar was competitively inhibited by other serovars of C. trachomatis. This competition for the same receptor on the two alternative hosts, HeLa and McCoy, was also seen when the adherence assays were done at 37 degrees C in the presence of sodium azide, an energy poison that inhibits endocytosis of cell-bound chlamydiae. Chlamydiae exposed to 56 degrees C for 5 min, or treated with low doses of trypsin, failed to exhibit competitive inhibition, having suffered considerable loss of the ability to adhere to host-cells. These data suggest that heat- and trypsin-labile chlamydial moieties participate in the adherence reaction, and that oculo-genital serovars of C. trachomatis, including that of lymphogranuloma venereum, attach to the same receptor on the host-cell membrane.

Repression of sporulation: isolation and characterization of repression-resistant mutants of Bacillus subtilis

The sporulation of Bacillus subtilis B34 was repressed by 24 h if glutamine or ammonium chloride but not glutamate was added at late log phase (70 h) when glucose and glutamate were nearly exhausted. Glutamine-resistant mutants were isolated by selective heat treatment during the delay period induced by glutamine. Glutamine-resistant mutants showed cross resistance not only against ammonium chloride but also against glucose just as glucose-resistant mutants showed resistance against nitrogenous catabolites.

Effects of aspirin and paracetamol on ATPases of human fetal brain: an in vitro study

In vitro effects of aspirin and paracetamol at the doses 200, 400, 600, 800 nmole/mg protein on ATPases activity were studied in the cerebrum and cerebellum of human fetus covering the age range from 10 weeks to 32 weeks of gestation. Both aspirin and paracetamol inhibit Na+K+ ATPase and Mg2+ ATPase in a dose dependent manner. The inhibition of Na+K+ ATPase and Mg2+ ATPase activity which may affect the release and uptake of biogenic amines in CNS, hinders the maturation of human fetal brain.

Characterization of versilin-sensitive sites in self-sensitive producer and sensitive non-producer or unrelated organism

Studies on self-sensitivity of producer mutant vs. sensitivity of non-producer parent and unrelated organism showed that versilin inhibited spore germination and sporulation in the self-sensitive producer mutant, non-producer parent Aspergillus versicolor N5 and the unrelated sensitive Trichophyton rubrum. Sporulation appeared to be more sensitive than spore germination. The inhibition of in vivo synthesis of protein was very marked, but inhibition of RNA and DNA was slight and moderate, respectively. Thus versilin was not specific in its action, but the principal sensitive site was protein synthesis, as further suggested by inhibition of polyU-directed in vitro synthesis of polyphenylalanine. The activation of leucine was unaffected, but the formation of leucyl-tRNA was severely inhibited in all three strains. The differences in sensitivities between the strains were the same, whether as whole cells or as cell-free extracts. Thus the nature of the sensitive site appeared to be identical in the self-sensitive producer and sensitive non-producer or unrelated organism.