Tunable orbital angular momentum in high-harmonic generation.

Optical vortices are currently one of the most intensively studied topics in optics. These light beams, which carry orbital angular momentum (OAM), have been successfully utilized in the visible and infrared in a wide variety of applications. Moving to shorter wavelengths may open up completely new research directions in the areas of optical physics and material characterization. Here, we report on the generation of extreme-ultraviolet optical vortices with femtosecond duration carrying a controllable amount of OAM. From a basic physics viewpoint, our results help to resolve key questions such as the conservation of angular momentum in highly nonlinear light-matter interactions, and the disentanglement and independent control of the intrinsic and extrinsic components of the photon's angular momentum at short-wavelengths. The methods developed here will allow testing some of the recently proposed concepts such as OAM-induced dichroism, magnetic switching in organic molecules and violation of dipolar selection rules in atoms.

VEGF-A acts via neuropilin-1 to enhance epidermal cancer stem cell survival and formation of aggressive and highly vascularized tumors.

We identify a limited subpopulation of epidermal cancer stem cells (ECS cells), in squamous cell carcinoma, that form rapidly growing, invasive and highly vascularized tumors, as compared with non-stem cancer cells. These ECS cells grow as non-attached spheroids, and display enhanced migration and invasion. We show that ECS cell-produced vascular endothelial growth factor (VEGF)-A is required for the maintenance of this phenotype, as knockdown of VEGF-A gene expression or treatment with VEGF-A-inactivating antibody reduces these responses. In addition, treatment with bevacizumab reduces tumor vascularity and growth. Surprisingly, the classical mechanism of VEGF-A action via interaction with VEGF receptors does not mediate these events, as these cells lack VEGFR1 and VEGFR2. Instead, VEGF-A acts via the neuropilin-1 (NRP-1) co-receptor. Knockdown of NRP-1 inhibits ECS cell spheroid formation, invasion and migration, and attenuates tumor formation. These studies suggest that VEGF-A acts via interaction with NRP-1 to trigger intracellular events leading to ECS cell survival and formation of aggressive, invasive and highly vascularized tumors.

Structural and biochemical changes underlying a keratoderma-like phenotype in mice lacking suprabasal AP1 transcription factor function.

Epidermal keratinocyte differentiation on the body surface is a carefully choreographed process that leads to assembly of a barrier that is essential for life. Perturbation of keratinocyte differentiation leads to disease. Activator protein 1 (AP1) transcription factors are key controllers of this process. We have shown that inhibiting AP1 transcription factor activity in the suprabasal murine epidermis, by expression of dominant-negative c-jun (TAM67), produces a phenotype type that resembles human keratoderma. However, little is understood regarding the structural and molecular changes that drive this phenotype. In the present study we show that TAM67-positive epidermis displays altered cornified envelope, filaggrin-type keratohyalin granule, keratin filament, desmosome formation and lamellar body secretion leading to reduced barrier integrity. To understand the molecular changes underlying this process, we performed proteomic and RNA array analysis. Proteomic study of the corneocyte cross-linked proteome reveals a reduction in incorporation of cutaneous keratins, filaggrin, filaggrin2, late cornified envelope precursor proteins, hair keratins and hair keratin-associated proteins. This is coupled with increased incorporation of desmosome linker, small proline-rich, S100, transglutaminase and inflammation-associated proteins. Incorporation of most cutaneous keratins (Krt1, Krt5 and Krt10) is reduced, but incorporation of hyperproliferation-associated epidermal keratins (Krt6a, Krt6b and Krt16) is increased. RNA array analysis reveals reduced expression of mRNA encoding differentiation-associated cutaneous keratins, hair keratins and associated proteins, late cornified envelope precursors and filaggrin-related proteins; and increased expression of mRNA encoding small proline-rich proteins, protease inhibitors (serpins), S100 proteins, defensins and hyperproliferation-associated keratins. These findings suggest that AP1 factor inactivation in the suprabasal epidermal layers reduces expression of AP1 factor-responsive genes expressed in late differentiation and is associated with a compensatory increase in expression of early differentiation genes.

AP1 factor inactivation in the suprabasal epidermis causes increased epidermal hyperproliferation and hyperkeratosis but reduced carcinogen-dependent tumor formation.

Activator protein one (AP1) (jun/fos) factors comprise a family of transcriptional regulators (c-jun, junB, junD, c-fos, FosB, Fra-1 and Fra-2) that are key controllers of epidermal keratinocyte survival and differentiation, and are important drivers of cancer development. Understanding the role of these factors in epidermis is complicated by the fact that each member is expressed in defined cell layers during epidermal differentiation, and because AP1 factors regulate competing processes (that is, proliferation, apoptosis and differentiation). We have proposed that AP1 factors function differently in basal versus suprabasal epidermis. To test this, we inactivated suprabasal AP1 factor function in mouse epidermis by targeted expression of dominant-negative c-jun (TAM67), which inactivates function of all AP1 factors. This produces increased basal keratinocyte proliferation, delayed differentiation and extensive hyperkeratosis. These findings contrast with previous studies showing that basal layer AP1 factor inactivation does not perturb resting epidermis. It is interesting that in spite of extensive keratinocyte hyperproliferation, susceptibility to carcinogen-dependent tumor induction is markedly attenuated. These novel observations strongly suggest that AP1 factors have distinct roles in the basal versus suprabasal epidermis, confirm that AP1 factor function is required for normal terminal differentiation, and suggest that AP1 factors have a different role in normal epidermis versus cancer progression.

A prospective study on histochemical observation of thyroid gland at prepubertal Black Bengal goat.

In the present study, Period Acid Schiff (PAS), Verhoeff's and Van Gieson stains were used in the Department of Anatomy and Histology to observe the histochemical architecture of thyroid gland at prepubertal Black Bengal goat. Thyroid follicular cells were cuboidal in prepubertal goats. These cells showed moderate PAS-positive reaction in prepubertal group. PAS activity in the basement membrane of the thyroid follicles was mild in prepubertal Black Bengal goats. The lumen of the thyroid follicles contained homogenous intense PAS positive colloid materials in prepubertal goats. Parafollicular cells showed intense PAS positive reaction for glycogen in prepubertal goats. Capsule, connective tissue septa, interfollicular connective tissue of the thyroid gland mainly composed of collagen fiber. The wall of blood vessels in the capsule and interfollicular blood capillaries was composed of collagen fiber and elastic fiber. Elastic fiber formed the inner layer of the blood vessels showed blue black to black color. Inner layer of the capsule penetrated the gland parenchyma divided the gland into indistinct lobe and lobules. Collagen fiber distributed around the thyroid follicle formed the interfollicular stroma of the thyroid gland. The results of the present study can also be used to compare with that of human specially in AutoImmune Thyroiditis (AIT).

Intracellular pathways linking hypoxia to activation of c-fos and AP-1.

Organisms respond to hypoxia through detection of blood oxygen levels by sensors at peripheral chemoreceptors and by receptors in certain key cells of the body. The pathways over which peripheral chemoreceptor signals are transmitted to respiratory muscles are well established. However, the intracellular pathways that transmit hypoxic stimulus to gene activation are just being identified. Using anti-sense c-fos strategy, we have shown that c-fos is essential for the activation of activator protein-1 transcription factor complex (AP-1) and subsequent stimulation of downstream genes such as tyrosine hydroxylase (TH; Mishra et al. 1998). The purpose of the present study was to identify intracellular pathways that link hypoxia to activation of c-fos. The results of the present study show that hypoxia causes Ca2+ influx through L-type voltage gated Ca2+ channels and that hypoxia-induced c-fos gene expression is Ca2+/calmodulin dependent. We also demonstrate that hypoxia activates the extracellular-regulated kinase (ERK) and p38, but not JNK. Further, phosphorylation of ERK is essential for c-fos activation via SRE cis-element. Further characterization of nuclear signalling pathways provides evidence for the involvement of Src, a non receptor protein tyrosine kinase, and Ras, a small G protein, in the hypoxia-induced c-fos gene expression. These results suggest a possible role for non-receptor protein tyrosine kinases in propagating signals from G-protein coupled receptors to the activation of immediate early genes such as c-fos during hypoxia.

Dual influence of nitric oxide on gene regulation during hypoxia.

It is being increasingly recognized that nitric oxide (NO) is associated with many physiological processes, including regulation of gene expression. NO shares certain similarities with molecular oxygen (O2). Previous studies have shown that hypoxia up-regulates c-fos, an immediate early gene, and tyrosine hydroxylase (TH), a late response gene that encodes rate limiting enzyme in catecholamine synthesis. Given the similarities between NO and O2, we hypothesized that NO inhibits hypoxia-induced up-regulation of c-fos and TH. Experiments were performed on rat pheochromocytoma (PC12) cells. c-fos and TH mRNA's were analysed by Northern blot and promoter activities by reporter gene assays, respectively. Hypoxia (1% O2 for 6 h) up-regulated c-fos and TH mRNA and increased c-fos promoter activity. Hypoxia-induced c-fos mRNA expression, and promoter activities were significantly potentiated in presence of spermine nitric oxide (SNO), a NO donor. By contrast, SNO significantly inhibited TH mRNA expression and TH promoter activity during hypoxia. Electrophoretic mobility shift-assay showed increased binding of AP-1 and HIF-1 transcription factors to the TH promoter in cells exposed to hypoxia. SNO abolished the binding of AP-1 and HIF-1 to the TH promoter during hypoxia, suggesting that inhibition of hypoxia-induced TH transcription by NO are due to reduced binding of AP-1 and HIF-1 transcription factors. These result demonstrate that NO has both positive and negative influence on gene regulation by hypoxia and suggest that although NO resembles O2 does not always inhibit gene expression during low oxygen.

Role of c-fos in hypoxia-induced AP-1 cis-element activity and tyrosine hydroxylase gene expression.

Previous studies have demonstrated that hypoxia stimulates expression of the c-fos gene in intact animals and isolated cells. The purpose of the present study was to assess the functional significance of c-fos activation during hypoxia. Using antisense c-fos strategy, we tested the hypothesis that c-fos is essential for activation of activator protein-1 transcription factor complex (AP-1) and subsequent stimulation of down stream genes such as tyrosine hydroxylase (TH) gene during hypoxia. Experiments were performed on rat pheochromocytoma 12 (PC12) cells. AP-1 activity was determined by a reporter gene assay using a luciferase expression vector driven by two copies of an AP-1 cis-element (AP-1-Luc). Cells transfected with AP-1-Luc construct were exposed to normoxia (21% O2) or to varying intensities and/or durations of hypoxia. AP-1 activity increased in response to hypoxia. The magnitude of the response depended on the intensity and duration of the hypoxic stimulus. Increases in AP-1 activity could not be elicited in neuroblastoma cells, indicating that hypoxia-induced increase in AP-1 activity is a cell selective phenomenon. Antisense c-fos abolished hypoxia-induced AP-1 activation in PC12 cells. Hypoxia increased tyrosine hydroxylase-chloramphenicol acetyl transferase activity (TH-CAT), and antisense c-fos and mutations at AP-1 binding sites in TH promoter abolished this effect. These results provide direct evidence that c-fos is essential for functional activation of AP-1 and subsequent activation of delayed response genes such as TH in PC12 cells.

Massive air embolism: a case report.

We describe a case where massive air embolism occurred while infusing fluid under pressure with a pressurized infusion system, with fluid bags which contained volumes of air from the manufacturer. We suggest that anesthesiologists be meticulous in de-airing the infusion bag before connecting it to the intravenous infusion system. Also, if the manufacturers of crystalloid solutions would produce their product devoid of air, then this inherent risk would be substantially decreased.

Na(+)-K(+)-ATPase activity of different regions of rat brain in response to immunization and bone marrow cytokine treatment.

The bone marrow cytokine (Bio-Immuno Modulator, BIM or BM-Fr1) has been suggested to correct immunoincompetence by modulating brain Na(+)-K(+)-ATPase. The brain region affected and mechanism of action of BM-Fr1 are unknown, however. Here we report that immunization of immunocompetent rats indirectly inhibited Na(+)-K(+)-ATPase activity (59%) in the left cerebral lobe (LC) and irrespective of BM-Fr1 treatment, stimulation of the enzyme was observed in the LC at the peak of immune response. BM-Fr1 treatment, which corrected immunoincompetence in malnourished rats, also modulated a different LC Na(+)-K(+)-ATPase profile to that seen in immunocompetent animals. Immunogen and BM-Fr1 seem to exert their influence in brain via a cytosolic inhibitor protein of Na(+)-K(+)-ATPase. Thus we suggest that (1) BM-Fr1 plays an important role in immune homeostatasis by modulating Na(+)-K(+)-ATPase activity of LC and (2) Na(+)-K(+)-ATPase is not the receptor for either immunogen or BM-Fr1.

Cardiac myotrophin exhibits rel/NF-kappa B interacting activity in vitro.

Myotrophin is a soluble-12 kilodalton protein isolated from hypertrophied spontaneously hypertensive rat and dilated cardiomyopathic human hearts. We have recently cloned the gene coding for myotrophin and expressed it in Escherichia coli. In the present study, the expression of myotrophin gene was analyzed, and at least seven transcripts have been detected in rat heart and in other tissues. We have further analyzed the primary structure of myotrophin protein and identified significant new structural and functional domains. Our analysis revealed that one of the ankyrin repeats of myotrophin is highly homologous specifically to those of myotrophin is highly homologous specifically to those of I kappa B alpha/rel ankyrin repeats. In addition, putative consensus phosphorylation sites for protein kinase C and casein kinase II, which were observed in I kappa B alpha proteins, were identified in myotrophin. To verify the significance of these homologies, kappa B gel shift assays were performed with Jurkat T cell nuclear extract proteins and the recombinant myotrophin. Results of these assays indicate that the recombinant myotrophin has the ability to interact with NF-kappa B/rel proteins as revealed by the formation of ternary protein-DNA complexes. While myotrophin-specific antibodies inhibited the formation of these complexes, rel-specific p50 and p65 antibodies supershifted these complexes. Thus, these results clearly indicate that the myotrophin protein to be a unique rel/NF-kappa B interacting protein.

Bacterial expression of human respiratory syncytial viral phosphoprotein P and identification of Ser237 as the site of phosphorylation by cellular casein kinase II.

The phosphoprotein P gene of human respiratory syncytial virus has been cloned and the protein expressed in Escherichia coli. The expressed protein was soluble, unphosphorylated, and constituted approximately 10% of the total bacterial protein. Electrophoretic and antigenic analyses demonstrated the identity of the recombinant protein with viral P protein and P protein synthesized in reticulocyte lysates. Purified recombinant P protein was efficiently phosphorylated in vitro by purified native as well as recombinant casein kinase II (CKII) or by the CKII activity in uninfected cell extracts. Through deletions and site-directed mutagenesis, the site of CKII phosphorylation was mapped to a single serine residue (Ser237) near the C-terminal end of the P protein.

An Na+/K(+)-ATPase inhibitor protein from rat brain cytosol.

A protein isolated from rat brain cytosol is found to inhibit Na+/K(+)-ATPase in rat brain and kidney and H+/K(+)-ATPase from toad gastric mucosa, but has no effect on Ca2+,Mg(2+)-ATPase and Ca(2+)-ATPase isolated either from rat testis or goat spermatozoa. The inhibitor has been partially purified by ammonium sulphate precipitation followed by gel-filtration through Sephadex G-100. The inhibitor seems to bind at or close to the ATP binding site of Na+/K(+)-ATPase, such that the binding of the inhibitor to ATPase is reversible and competitive in nature with respect to the substrate. Optimum inhibition is observed at around the phase transition temperature of brain Na+/K(+)-ATPase and the inhibitory activity is only partially dependent on -SH or -NH2 group(s) of the inhibitor protein.