Molecular mechanisms in endothelial regulation of cardiac function

Endothelium is now recognized as a massive, regionally specific, multifunctional organ. Given its strategic anatomic location between the circulating blood components and the vascular smooth muscle or the cardiac muscle, it is a biologically significant interface whose dysfunction can be a critical factor in various pathological conditions. Two types of endothelial cells are recognized in the heart, the endocardial endothelial (EE) cells and the microvascular endothelial cells (MVE). Both produce common autacoids and share similar roles in signal transduction induced by neurotransmitters, hormones or mechanical stimuli. They are however two distinct cell populations with dissimilar embryological origin, cytoskeletal organization, receptor mediated functions and electrophysiological properties. Both the MVE and EE are modulators of cardiac performance. Myocardial contraction may be modulated by cardioactive agents such as nitric oxide, prostanoids, endothelin, natriuretic peptides, angiotensin II, kinins, reactive oxygen species and adenyl purines released from the cardiac endothelium. Two mechanisms have been proposed for the signal transduction from EE to the underlying myocytes: stimulus-secretion-contraction coupling and blood-heart barrier. Nitric oxide, bradykinin and myofilament desensitizing agent are probably important in short-term regulation of myocardial functions. Endothelin and Angiotensin II are probably involved in long-term regulation. Besides its sensory function and paracrine modulation of myocardial performance, EE as a blood-heart barrier could be of significance for the ionic homeostasis of the cardiac interstitium. In cardiac diseases, the damage to EE or MVE leading to failure of the endothelial cells to perform its regulatory and modulator functions may have serious consequences. A better understanding of the endothelial signaling pathways in cardiac physiology and pathophysiology may lead to the development of novel therapeutic strategies.     

Functions and mechanisms of retrograde neurotrophin signalling

Neuronal connections are established and refined through a series of developmental programs that involve axon and dendrite specification, process growth, target innervation, cell death and synaptogenesis. Many of these developmental events are regulated by target-derived neurotrophins and their receptors, which signal retrogradely over long distances from distal-most axons to neuronal cell bodies. Recent work has established many of the cellular and molecular events that underlie retrograde signalling and the importance of these events for both development and maintenance of proper neural connectivity.     

Spatially and functionally distinct roles of the PI3-K effector pathway during NGF signaling in sympathetic neurons

NGF is a target-derived growth factor for developing sympathetic neurons. Here, we show that application of NGF exclusively to distal axons of sympathetic neurons leads to an increase in PI3-K signaling in both distal axons and cell bodies. In addition, there is a more critical dependence on PI3-K for survival of neurons supported by NGF acting exclusively on distal axons as compared to neurons supported by NGF acting directly on cell bodies. Interestingly, PI3-K signaling within both cell bodies and distal axons contributes to survival of neurons. The requirement for PI3-K signaling in distal axons for survival may be explained by the finding that inhibition of PI3-K in the distal axons attenuates retrograde signaling. Therefore, a single TrkA effector, PI3-K, has multiple roles within spatially distinct cellular locales during retrograde NGF signaling.     

Chronic wuchereriasis presenting as a vaginoperineal fistula: report of a case with aspiration cytologic diagnosis

BACKGROUND: Filariasis is often an occult disease with myriad presentations. Cytology has an established role in diagnosing clinically unsuspected cases. CASE: A 20-year-old female presented with recurring perineal ulcers, vaginal discharge and inguinal lymphadenopathy. Radiology revealed a vaginoperineal fistula. Fine needle aspiration (FNA) of the ulcer bed and smears prepared from the ulcer discharge showed an adult, gravid, female filarial worm and unsheathed larvae. Similar microfilariae were also seen in FNA smears from inguinal lymph nodes. The atypical clinical presentation and unusual parasite morphology posed initial difficulties in characterization of the microfilarial species. CONCLUSION: This case report highlights the morphologic clues to the dif ferential diagnosis offilarial species on cytologic specimens. Chronic wuchereriasis presenting as a vaginoperineal fistula has not been reported previously.     

Cutaneous relapse in Hodgkin's disease: a case report

BACKGROUND: Skin involvement in Hodgkin's disease is rare, can be seen in advanced stages of the disease and indicates a poor prognosis. CASE: A young male presented with multiple nodular lesions on the chest wall and matted cervical lymph nodes. Aspiration smears from skin lesions showed atypical mononuclear cells with a prominent nucleolus, many lymphocytes and plasma cells. Smears from the lymph nodes showed classical Reed-Sternberg cells in a polymorphous background. The cytologic diagnosis of Hodgkin's lymphoma was entertained and later confirmed on skin biopsy. Past history revealed that the patient had been diagnosed with Hodgkin's disease and treated for it 2 years earlier, but had been lost to follow-up during treatment. CONCLUSION: Cutaneous Hodgkin's disease should always be considered in smears from skin lesions showing atypical mononuclear cells in a polymorphous background, even in the absence of a definitive clinical diagnosis at the time of presentation.     

Changes in noradrenaline and histamine in monkey spinal cords traumatised by weight drop, compression and subsequent decompression

Levels of noradrenaline (NA) and histamine (H) in the spinal cord of monkeys at 8, 24 and 48 hr following 200 g/cm contusion injury, 50 g of compression injury at 8 hr and decompression for 16 and 40 hr following 8 hr of compression were studied in the traumatised and in an adjacent non-traumatised segment. The NA level doubled in the traumatised and non-traumatised segments at 8 hr contusion injury followed by a slow decline to control values at 24 and 48 hr of contusion injury. There was no change in NA content of the spinal cord segments at 8 hr of compression injury. Decompression for 16 hr following 8 hr of compression increased NA content of the traumatised segment. H levels decreased in the traumatised and non-traumatised segments at 24 and 48 hr of contusion injury. Compression for 8 hr elevated H in the traumatised and non-traumatised segments. On decompression H level was further increased in the traumatised segment.     

Cloning and Expression of Phytase appA Gene from Shigella sp. CD2 in Pichia pastoris and Comparison of Properties with Recombinant Enzyme Expressed in E. coli

The phytase gene appA_S was isolated from Shigella sp. CD2 genomic library. The 3.8 kb DNA fragment contained 1299 bp open reading frame encoding 432 amino acid protein (AppA_S) with 22 amino acid signal peptide at N-terminal and three sites of N-glycosylation. AppA_S contained the active site RHGXRXP and HDTN sequence motifs, which are conserved among histidine acid phosphatases. It showed maximum identity with phytase AppA of Escherichia coli and Citrobacter braakii. The appA_S was expressed in Pichia pastoris and E. coli to produce recombinant phytase rAppA_P and rAppA_E, respectively. Purified glycosylated rAppA_P and nonglycosylated rAppA_E had specific activity of 967 and 2982 U mg^-1, respectively. Both had pH optima of 5.5 and temperature optima of 60°C. Compared with rAppA_E, rAppA_P was 13 and 17% less active at pH 3.5 and 7.5 and 11 and 18% less active at temperature 37 and 50°C, respectively; however, it was more active at higher incubation temperatures. Thermotolerance of rAppA_P was 33% greater at 60°C and 24% greater at 70°C, when compared with rAppA_E. Both the recombinant enzymes showed high specificity to phytate and resistance to trypsin. To our knowledge, this is the first report on cloning and expression of phytase from Shigella sp.     

Purification and Characterization of a Novel Chemorepellent Receptor from Tetrahymena thermophila

Chemosensory transduction and adaptation are important aspects of signal transduction mechanisms in many cell types, ranging from prokaryotes to differentiated tissues such as neurons. The eukaryotic ciliated protozoan, Tetrahymena thermophila, is capable of responding to both chemoattractants (O'Neill et al., 1985; Leick, 1992; Kohidai, Karsa & Csaba, 1994, 1995) and chemorepellents (Francis & Hennessey, 1995; Kuruvilla, Kim & Hennessey, 1997). An example of a nontoxic, depolarizing chemorepellent in Tetrahymena is extracellular lysozyme (Francis & Hennessey, 1995; Hennessey, Kim & Satir, 1995). Lysozyme is an effective chemorepellent at micromolar concentrations, binds to a single class of externally facing membrane receptors and prolonged exposure (10 min) produces specific chemosensory adaptation (Kuruvilla et al., 1997). We now show that this lysozyme response is initiated by a depolarizing chemoreceptor potential in Tetrahymena and we have purified the membrane lysozyme receptor by affinity chromatography of solubilized Tetrahymena membrane proteins. The solubilized, purified protein is 42 kD and it exhibits saturable, high affinity lysozyme binding. Polyclonal antibodies raised against this 42 kD receptor block the in vivo lysozyme chemoresponse. This is not only the first time that a chemoreceptor potential has been recorded from Tetrahymena but also the first time that a chemorepellent receptor has been purified from any unicellular eukaryote. Received: 28 July 1997/Revised: 14 November 1997     

High-level expression of functional platelet-activating factor receptors on a human B lymphoblastoid cell line.

Binding of platelet-activating factor (PAF) was characterized in a human b lymphoblastoid cell line, ASK.0. [3H]PAF binding to these cells was time-dependent, reaching equilibrium at 60 minutes, and saturable. Scatchard analyses of saturation binding experiments revealed a single class of PAF binding sites (108,000 +/- 17,000 per cell) with a KD of 2.16 +/- 0.41 nM. That the binding sites were specific for PAF was demonstrated by competition studies. PAF was shown to increase the intracellular calcium concentrations of ASK.0 cells in a dose-dependent manner with an EC50 of 7 nM. We have, therefore, identified a B cell line expressing large numbers of functional PAF receptors.