Frank J. Dowd

Upregulation of PIP3-dependent Rac exchanger 1 (P-Rex1) promotes prostate cancer metastasis

Excessive activation of G-protein-coupled receptor (GPCR) and receptor tyrosine kinase (RTK) pathways has been linked to prostate cancer metastasis. Rac activation by guanine nucleotide exchange factors (GEFs) plays an important role in directional cell migration, a critical step of tumor metastasis cascades. We found that the upregulation of P-Rex1, a Rac-selective GEF synergistically activated by Gβγ freed during GPCR signaling, and PIP3, generated during either RTK or GPCR signaling, strongly correlates with metastatic phenotypes in both prostate cancer cell lines and human prostate cancer specimens. Silencing endogenous P-Rex1 in metastatic prostate cancer PC-3 cells selectively inhibited Rac activity and reduced cell migration and invasion in response to ligands of both epidermal growth factor receptor and G-protein-coupled CXC chemokine receptor 4. Conversely, expression of recombinant P-Rex1, but not its ‘GEF-dead’ mutant, in non-metastatic prostate cancer cells, such as CWR22Rv1, increased cell migration and invasion through Rac-dependent lamellipodia formation. More importantly, using a mouse xenograft model, we showed that the expression of P-Rex1, but not its mutant, induced lymph node metastasis of CWR22Rv1 cells without an effect on primary tumor growth. Thus, by functioning as a coincidence detector of chemotactic signals from both GPCRs and RTKs, P-Rex1-dependent activation of Rac promotes prostate cancer metastasis.

Characterization of gill Na/K-ATPase activity and ouabain binding in Antarctic and New Zealand nototheniid fishes

The effects of thermal acclimation in two Nototheniid species, the stenothermal Antarctic Trematomous bernacchii and the eurythermal New Zealand Notothenia angustata, were investigated. Serum osmolality, gill Na/K-ATPase activity, sodium pump density and ouabain affinity were determined. Both fish were acclimated at their upper and lower viable thermal temperatures. Warm acclimation (+4 degrees C) of the T. bernacchii significantly decreased their serum osmolality from 550 to 450 mOsm/kg compared to cold-acclimation (-1.5 degrees C) and this was accompanied by a two-fold increase in gill Na/K-ATPase activity. Warm-acclimation (+14 degrees C) of N. angustata did not significantly change their serum osmolality from 330 mOsm/kg or gill Na/K-ATPase activity compared to the cold-acclimated (+4 degrees C) N. angustata. Using [(3)H]ouabain binding techniques, the B(max) and K(d) values of gill Na/K-ATPase enzymes were determined. No difference in the B(max) or K(d) of the warm-acclimated T. bernacchii accounted for the increase in Na/K-ATPase activity. We conclude that the change in gill Na/K-ATPase activity in the warm-acclimated T. bernacchii is not mediated by an increase in the number of enzyme sites and is not reflected in a change in ouabain affinity for Na/K-ATPase.

A Ca2+-ATPase from rat paratoid gland plasma membranes has the characteristics of an ecto-ATPase

A Ca(2+)-ATPase with an apparent Km for free Ca2+ = 0.23 microM and Vmax = 44 nmol Pi/mg/min was detected in a rat parotid plasma membrane-enriched fraction. This Ca(2+)-ATPase could be stimulated without added Mg2+. However, the enzyme may require submicromolar concentrations of Mg2+ for its activation in the presence of Ca2+. On the other hand, Mg2+ could substitute for Ca2+. The lack of a requirement for added Mg2+ distinguished this Ca(2+)-ATPase from the Ca(2+)-transporter ATPase in the plasma membranes and the mitochondrial Ca(2+)-ATPase. The enzyme was not inhibited by several ATPase inhibitors and was not stimulated by calmodulin. An antibody which was raised against the rat liver plasma membrane ecto-ATPase, was able to deplete this Ca(2+)-ATPase activity from detergent solubilized rat parotid plasma membranes, in an antibody concentration-dependent manner. Immunoblotting analysis of the pellet with the ecto-ATPase antibody revealed the presence of a 100,000 molecular weight protein band, in agreement with the reported ecto-ATPase relative molecular mass. These data demonstrate the presence of a Ca(2+)-ATPase, with high affinity for Ca2+, in the rat parotid gland plasma membranes. It is distinct from the Ca(2+)-transporter, and immunologically indistinguishable from the plasma membrane ecto-ATPase.

Candida Albicans Infections

Candida albicans are common opportunistic fungal organism that can cause skin infections, mucosal infections, or systemic infections, especially in immunocompromised or neutropenic patients. Candida albicans is dimorphic and is usually diagnosed empirically or microscopically. The treatment of these infections includes a choice between: a polyene (e.g., nystatin), an azole (e.g., fluconazole) or an echinocandin (e.g., caspofungin), depending on severity and resistance.

Blood Lipid Disorders

Blood lipid disorders are classified in various categories usually based on excess cholesterol or triglycerides or both. Elevated blood lipids pose a cardiovascular risk. Various drugs can be used to treat hyperlipidemias. These drugs target important synthesis pathways, transport pathways or gastrointestinal absorption.

Deep Mycotic Infections

Systemic fungal disease (mycotic disease) is caused by several fungal organisms. These can infect several tissues however the lung is a major site of entry and infection. Infections are difficult to eradicate and are associated with considerable morbidity and even death. Immunocompromised individuals are more susceptible to fungal disease. Individuals living in an area endemic to certain fungi are also at greater risk. Extended drug therapy is required and involves the use of one or more antifungal drugs.

Ventricular Fibrillation and Flutter

Ventricular fibrillation leads to sudden death and must be reversed to save the patients life. This is done by electrical defibrillation, sometimes preceded by mechanical cardiopulmonary resuscitation. The latter can be life-saving until a defibrillator is available. Implantable cardioverter defibrillator, cardiac resynchronization therapy are used chronically to prevent ventricular fibrillation. Drugs may be of complementary use by virtue of their antiarrhyhmic effects, and other benefit to the cardiovascular system.

Migraine and Cluster Headaches

Migraine headache is a disorder characterized by episodic pain preceded in some cases by a prodrome and aura. The disorder has a vascular component, an inflammatory component and a component of amplification of sensory input in the brain, intensifying the pain. The pain is sometimes relieved by conventional analgesics such as non-steroidal anti-inflammatory drugs. However, more often, the condition is treated with drugs that are, in some cases, more selective for this disorder. These agents generally interact with serotonergic or dopaminergic transmission, as well as other important mediators.

Atrial Fibrillation and Atrial Flutter

Atrial fibrillation is a condition characterized by rapid and non-functional contractions of the atria, the upper chambers of the heart. Atrial flutter is similar to atrial fibrillation in its characteristics and treatment. Atrial fibrillation is an arrhythmic condition in which the upper chambers of the heart (atria) depolarize very rapidly and irregularly. Atrial flutter is a rapid arrhythmia in which the rhythm is regular at a rate of between 250–350 beats per minute. The pathophysiology and treatment of atrial flutter is very similar to that of atrial fibrillation.

Torsades de Pointes

Abstract Torsades de pointes (torsades), is a type of ventricular tachycardia associated with long QT. Three major gene mutations are responsible for most of the disorders. Mutiple other gene mutations are linked to the remaining cases of long QT and torsades. It is often precipitated by stress. Chronic treatment often includes pacing with a pacemaker or implanted cardioverter-defibrillator. Beta adrenergic receceptor blockers are also helpful in many of the cases.