Identification and functional characterization of DR6, a novel death domain-containing TNF receptor

Tumor nectosis factor (TNF) receptors are key players in inflammation and immune regulation. A new member of this family, termed death receptor-6 (DR6), has been identified. Like other death receptors, DR6 is a type I transmembrane receptor, possesses four extracellular cysteine-rich motifs and a cytoplasmic death domain. DR6 is expressed in most human tissues and abundant transcript was detected in heart, brain, placenta, pancreas, thymus, lymph node and several non-lymphoid cancer cell lines. DR6 interacts with TRADD, which has previously been shown to associate with TNFR1. Furthermore, ectopic expression of DR6 in mammalian cells induces apoptosis and activation of both NF-kappaB and JNK.

Clinical appraisal of creatinine clearance as a measurement of glomerular filtration rate

The plasma creatinine and the endogenous creatinine clearances are two of the most commonly used tests in clinical medicine to assess glomerular filtration rate. However, the contribution that tubular secretion of creatinine has on the total endogenous creatinine clearance (Ccr) is not generally known, nor are the effects renal insufficiency has on the tubular secretion of creatinine. To assess the above, 123 human subjects, with a wide range of renal function, underwent simultaneous Ccr and inulin clearances (Cin). The results indicate that: (1) Ccr approximates Cin only when Cin is normal; (2) a normal plasma creatinine of Ccr is not measurable evidence of a normal Cin; and (3) with progressive decline in Cin, there is progressive increase in the tubular secretion of creatinine, leading to a progressive disparity between Ccr and Cin.

An accelerated assay for the identification of lifespan-extending interventions in Drosophila melanogaster

Recent advances in aging research have uncovered genes and genetic pathways that influence lifespan in such diverse organisms as yeast, nematodes, flies, and mice. The discovery of genes and drugs that affect lifespan has been delayed by the absence of a phenotype other than survivorship, which depends on the measurement of age at death of individuals in a population. The use of survivorship to identify genetic and pharmacological interventions that prolong life is time-consuming and requires a large number of homogeneous animals. Here, we report the development of an assay in Drosophila melanogaster using the expression of molecular biomarkers that accelerates the ability to evaluate potential lifespan-altering interventions. Coupling the expression of an age-dependent molecular biomarker to a lethal toxin reduces the time needed to perform lifespan studies by 80%. The assay recapitulates the effect of the three best known environmental life-span-extending interventions in the fly: ambient temperature, reproductive status, and calorie reduction. Single gene mutations known to extend lifespan in the fly such as Indy and rpd3 also extend lifespan in this assay. We used this assay as a screen to identify drugs that extend lifespan in flies. Lipoic acid and resveratrol were identified as being beneficial in our assay and shown to extend lifespan under normal laboratory conditions. We propose that this assay can be used to screen pharmacological as well as genetic interventions more rapidly for positive effects on lifespan.

Development of diet-induced insulin resistance in adult Drosophila melanogaster

The fruit fly Drosophila melanogaster is increasingly utilized as an alternative to costly rodent models to study human diseases. Fly models exist for a wide variety of human conditions, such as Alzheimer's and Parkinson's Disease, or cardiac function. Advantages of the fly system are its rapid generation time and its low cost. However, the greatest strength of the fly system are the powerful genetic tools that allow for rapid dissection of molecular disease mechanisms. Here, we describe the diet-dependent development of metabolic phenotypes in adult fruit flies. Depending on the specific type of nutrient, as well as its relative quantity in the diet, flies show weight gain and changes in the levels of storage macromolecules. Furthermore, the activity of insulin-signaling in the major metabolic organ of the fly, the fat body, decreases upon overfeeding. This decrease in insulin-signaling activity in overfed flies is moreover observed when flies are challenged with an acute food stimulus, suggesting that overfeeding leads to insulin resistance. Similar changes were observed in aging flies, with the development of the insulin resistance-like phenotype beginning at early middle ages. Taken together, these data demonstrate that imbalanced diet disrupts metabolic homeostasis in adult D. melanogaster and promotes insulin-resistant phenotypes. Therefore, the fly system may be a useful alternative tool in the investigation of molecular mechanisms of insulin resistance and the development of pharmacologic treatment options.

Neuronal Expression of p53 Dominant-Negative Proteins in Adult Drosophila melanogaster Extends Life Span

Hyperactivation of p53 leads to a reduction in tumor formation and an unexpected shortening of life span in two different model systems . The decreased life span occurs with signs of accelerated aging, such as osteoporosis, reduction in body weight, atrophy of organs, decreased stress resistance, and depletion of hematopoietic stem cells. These observations suggest a role for p53 in the determination of life span and the speculation that decreasing p53 activity may result in positive effects on some aging phenotypes . In this report, we show that expression of dominant-negative versions of Drosophila melanogaster p53 in adult neurons extends life span and increases genotoxic stress resistance in the fly. Consistent with this, a naturally occurring allele with decreased p53 activity has been associated with extended survival in humans . Expression of the dominant-negative Drosophila melanogaster p53 constructs does not further increase the extended life span of flies that are calorie restricted, suggesting that a decrease in p53 activity may mediate a component of the calorie-restriction life span-extending pathway in flies.

Characterization of a p75(NTR) apoptotic signaling pathway using a novel cellular model

The p75 neurotrophin receptor (p75(NTR)) belongs to the tumor necrosis factor receptor/nerve growth factor receptor superfamily. In some cells derived from neuronal tissues it causes cell death through a poorly characterized pathway. We developed a neuronal system using conditionally immortalized striatal neurons, in which the expression of p75(NTR) is inducibly controlled by the ecdysone receptor. In these cells p75(NTR) induces apoptosis through its death domain in a nerve growth factor-independent manner. Caspases 9, 6, and 3 are activated by receptor expression indicating the activation of the common effector pathway of apoptosis. Cell death is blocked by a dominant negative form of caspase 9 and Bcl-X(L) consistent with a pathway that involves mitochondria. Significantly, the viral flice inhibitory protein E8 protects from p75(NTR)-induced cell death indicating that death effector domains are involved. A p75(NTR) construct with a deleted death domain dominantly interferes with p75(NTR) signaling, implying that receptor multimerization is required. However, in contrast to the other receptors of the family, p75(NTR)-mediated apoptosis does not involve the adaptor proteins Fas-associated death domain protein or tumor necrosis factor-associated death domain protein, and the apical caspase 8 is not activated. We conclude that p75(NTR) signals apoptosis by similar mechanisms as other death receptors but uses different adaptors and apical caspases.

Age-related changes in the renin-aldosterone system. Physiological effects and clinical implications

Age-related changes in the renin-aldosterone system in normal humans are well documented. The most pronounced changes are observed at the extremes of life: plasma renin activity and plasma aldosterone levels are highest in the newborn, and lowest in the elderly population. There is a close temporal and directional relationship between the age-related decrease in plasma renin activity and the age-related decrease in plasma aldosterone. The renin-aldosterone system is also influenced by sex and race. The activation of the renin-aldosterone system in newborns and infants probably represents an important physiological mechanism designed to maintain positive sodium balance. The decreases in plasma renin activity and plasma aldosterone levels observed in elderly persons are usually only modest, and are not associated with clinical alterations in fluid or electrolyte metabolism. The superimposition of a disease process, or the injudicious prescription of a drug, inhibiting renin release or angiotensin II production, could theoretically facilitate sodium wasting in newborns or infants, or precipitate hyporeninaemic hypoaldosteronism in older adults. The primary clinical importance of age-related changes in the renin-aldosterone system relates to its impact on the proper classification of an individual's renin-aldosterone profile when attempting to diagnose a clinical condition (e.g. low, normal or high renin hypertension). This is particularly true for newborns, infants and children to age 4, and for adults entering the sixth decade of life.

Heteromerization of the gammac chain with the interleukin-9 receptor alpha subunit leads to STAT activation and prevention of apoptosis

Interleukin-9 (IL-9) is a cytokine with pleiotropic effects on mast cell and T cell lines. It exerts its effects through the IL-9R complex consisting of IL-9Ralpha and the common gammac subunit. Here we report functional evidence for receptor heteromerization for efficient signal transduction, and we define minimal requirements in the two receptor subunits for IL-9R function. Tyrosine 336 of the IL-9Ralpha and the membrane-proximal segment of gammac are both crucial for signaling. The activated IL-9R complex employs the Janus kinases JAK1 and JAK3 for subsequent activation of the signal transducer and activator transcription (STAT) factors STAT-1, STAT-3, and STAT-5. This process is independent of Tyk2. We demonstrate further that the activated STAT complexes consist of STAT-1 and STAT-5 homodimers and STAT-1-STAT-3 heterodimers. Finally, we show that IL-9R signaling in a T cell line does not result in detectable mitogen-activated protein kinase activation and leads to unsustained proliferation. Nonetheless, these T cells are efficiently protected from dexamethasone-induced apoptosis. These results further define the molecular architecture of the IL-9R and its specific connections to various biologic responses.

dSir2 and Dmp53 interact to mediate aspects of CR-dependent lifespan extension in D. melanogaster

Calorie Restriction (CR) is a well established method of extending life span in a variety of organisms. In the fruit fly D. melanogaster, CR is mediated at least in part by activation of dSir2. In mammalian systems, one of the critical targets of Sir2 is the tumor suppressor p53. This deacetylation of p53 by Sir2 leads to inhibition of p53's transcriptional activity. We have recently shown that inhibition of Dmp53 activity in the fly brain through the use of dominant-negative (DN) constructs that inhibit DNA-binding can extend life span. This life span extension appears to be related to CR, as CR and DN-Dmp53 donot display additive effects on life span. Here we report that life span extension by DN-Dmp53 expression is highly dynamic and can be achieved even when DN-Dmp53 is expressed later in life. In addition, we demonstrate that life span extension by activation of dSir2 and DN-Dmp53 expression are not additive. Furthermore, we show that dSir2 physically interacts with Dmp53 and can deacetylate Dmp53-derived peptides. Taken together, our data demonstrate that Dmp53 is a down stream target of dSir2 enzymatic activity and mediates some aspects of the life span extending effects of CR.

A HIGH SPEED VACUUM CENTRIFUGE SUITABLE FOR THE STUDY OF FILTERABLE VIRUSES

1. A high speed centrifuge is described in which the speed is limited only by the strength of the material of which the rotor is made. It carries sixteen tubes, each of which conveniently accommodates 7 cc. of fluid. 2. The centrifuge operates in a very high vacuum and therefore requires only a small amount of driving energy. The arrangement has been found to eliminate the possibility of producing injurious frictional heat. 3. The rotating parts are supported by anair-bearing and are driven by compressed air. 4. The centrifuge has been successfully operated at a speed of 30,000 revolutions per minute, representing a maximum centrifugal force in the fluid of 95,000 times gravity. 5 Celluloid tubes used for centrifugation of fluid at high speeds are described. 6. Experiments are described in which good sedimentation of the yellow fever virus was obtained.

Expression of dominant-negative Dmp53 in the adult fly brain inhibits insulin signaling

In Drosophila melanogaster, p53 (Dmp53) is an important mediator of longevity. Expression of dominant-negative (DN) forms of Dmp53 in adult neurons, but not in muscle or fat body cells, extends lifespan. The lifespan of calorie-restricted flies is not further extended by simultaneously expressing DN-Dmp53 in the nervous system, indicating that a decrease in Dmp53 activity may be a part of the CR lifespan-extending pathway in flies. In this report, we show that selective expression of DN-Dmp53 in only the 14 insulin-producing cells (IPCs) in the brain extends lifespan to the same extent as expression in all neurons and this lifespan extension is not additive with CR. DN-Dmp53-dependent lifespan extension is accompanied by reduction of Drosophila insulin-like peptide 2 (dILP2) mRNA levels and reduced insulin signaling (IIS) in the fat body, which suggests that Dmp53 may affect lifespan by modulating insulin signaling in the fly.

A simulation study on transcellular fluid shifts induced by hemodialysis

A computer-based model has been developed to predict the changes in serum sodium, urea concentration, and osmolality as well as transcellular fluid distribution which occur during hemodialysis. Sodium and urea transfers across the dialyzer membrane and transcellular fluid shifts in response to the sodium transfer were modeled assuming that only sodium and its accompanying anions are important as effective osmotic substances in extracellular fluid. Model predictions were consistent with values measured in five patients who were studied on hemodialysis at three different dialysate sodium concentrations equal to 7% below and 7% above the predialysis serum concentration. The measurements and model predictions indicate that serum sodium concentration decreases and intracellular fluid volume increases in dialyses with dialysate Na+ concentration used in conventional hemodialysis, whereas serum sodium concentration increases and intracellular volume decreases in high sodium dialyses. An analysis of model predictions indicates that a reasonable estimation of total body water and the intracellular to extracellular volume ratio enables us to accurately predict the magnitude of transcellular fluid shifts induced by hemodialysis as well as the postdialysis serum sodium concentration and osmolality.

Propranolol in human plasma and breast milk

To assess the problem of continuing propranolol therapy in a breast-feeding mother, studies were performed to determine simultaneously plasma and breast milk concentrations of propranolol after single dose (40 mg) and continuous dose (40 mg 4 times daily) treatment with this drug. Breast milk and plasma concentrations of propranolol peaked between 2 and 3 hours after dosing. Propranolol concentrations in breast milk were less than 40 and 64 percent, respectively, of peak plasma propranolol concentrations after single dose and continuous dose administration. It was estimated that the maximal cumulative propranolol load to this breast-feeding infant, consuming 500 ml of whole milk, when the mother received 40 mg of propranolol 4 times daily would be 21 microgram/24 hours. This dose is considerably less than the usual therapeutic dose of propranolol for infants.

New tricks of an old molecule: lifespan regulation by p53

As guardian of the genome the tumor suppressor p53 controls a crucial point in protection from cellular damage and response to stressors. Activation of p53 can have beneficial (DNA repair) or detrimental (apoptosis) consequences for individual cells. In either case activation of p53 is thought to safeguard the organism at large from the deleterious effects of various stresses. Recent data suggest that the function of p53 might also play a role in the regulation of organismal lifespan. Increased p53 activity leads to lifespan shortening in mice, while apparent reduction of p53 activity in flies leads to lifespan extension. Although the mechanism by which p53 regulates lifespan remains to be determined, these findings highlight the possibility that careful manipulation of p53 activity during adult life may result in beneficial effects on healthy lifespan.

Effects of calcium entry blockers on renin-angiotensin-aldosterone system, renal function and hemodynamics, salt and water excretion and body fluid composition

The renal effects of the calcium entry-blocking drugs diltiazem, nifedipine, verapamil and nitrendipine are reviewed. Although nifedipine stimulates plasma renin activity on a short-term basis, none of the calcium entry blockers produces a clinically significant sustained effect on any of the components of the renin-angiotensin-aldosterone system. Although all of the calcium entry blockers effectively lower blood pressure, none adversely affects renal function; glomerular filtration rate and effective renal plasma flow are maintained. Diltiazem may increase glomerular filtration rate via attenuation of the intrarenal effects of angiotensin II or norepinephrine. Although diltiazem and nifedipine increase salt and water excretion on a short-term basis, none of the calcium entry blockers produces a clinically significant sustained effect on salt and water excretion; serum electrolytes, urinary sodium and potassium excretion, body fluid composition and body weight are unchanged. Thus, calcium entry blockers can be expected to assume a prominent role in the treatment of hypertension because of their ability to lower blood pressure while preserving renal perfusion and function.

Role of angiotensin converting enzyme inhibitors in essential and renal hypertension. Effects of captopril and enalapril on renin-angiotensin-aldosterone, renal function and hemodynamics, salt and water excretion, and body fluid composition

Among the many generic classes of drugs currently being used for the treatment of hypertension, few, following long-term therapy, improve or correct the underlying renal function and hemodynamic abnormalities encountered in patients with sustained hypertension. This review focuses on the renal effects of the angiotensin converting enzyme inhibitors captopril and enalapril. Each drug is discussed in terms of its short- and long-term effects on the renin-angiotensin-aldosterone system, renal function and hemodynamics, salt and water excretion, and body fluid composition. Data are presented that demonstrate that enalapril, used alone or in combination with diuretic therapy, has the unique ability to control hypertension, to improve glomerular filtration rate and effective renal plasma/renal blood flow, and to decrease renal vascular resistance, without producing adverse effects on salt and water excretion or body fluid composition. If the safety of enalapril is confirmed in long-term studies, the drug will clearly assume a prominent role as either first- or second-step (in combination with a diuretic) therapy in the treatment of hypertension.

Short- and long-term effects of calcium entry blockers on the kidney

The renal effects of the calcium entry-blocking drugs diltiazem, nifedipine, nitrendipine, nicardipine and verapamil are reviewed. Although nifedipine may acutely increase plasma renin activity, most of the calcium entry blockers have no sustained effect on any of the components of the renin-angiotensin-aldosterone system. Although all of the calcium entry blockers effectively lower blood pressure, none adversely affects renal function: Glomerular filtration rate and effective renal plasma flow are maintained. Diltiazem may increase glomerular filtration rate via attenuation of the intrarenal effects of angiotensin II or norepinephrine. Although all of the calcium entry blockers acutely increase salt and water excretion, most of the calcium entry blockers have no clinically sustained effect on salt and water excretion; serum electrolytes, urinary sodium and potassium excretion, body fluid composition and body weight are usually unchanged. Calcium entry blockers can be expected to assume a prominent role in the treatment of hypertension because of their ability to lower blood pressure while preserving renal perfusion and function.

A randomized, double-blind, placebo-controlled trial to evaluate the effect of enalapril in patients with clinical diabetic nephropathy

It is unknown if the antiproteinuric effect of angiotensin-converting enzyme (ACE) inhibitors reflects attenuation in the rate of progression of diabetic nephropathy. We report the results of a randomized, double-blind clinical trial designed to evaluate the longitudinal (18-month) effect of the ACE inhibitor, enalapril (5 to 40 mg/d), versus a placebo on 24-hour urinary protein excretion and on the rate of progression of renal disease in 33 patients with clinical diabetic nephropathy. Systemic blood pressure was controlled throughout the trial with conventional antihypertensive drugs. Glomerular filtration rate (GFR), determined by Tc99mDTPA renal clearance, and urinary protein excretion were monitored at 3-month intervals. Enalapril, in contrast to placebo therapy, was associated with an initial (40%) and sustained (33%) decrease in urinary protein excretion. Patients randomized to both enalapril or placebo experienced mean decreases in GFR, from 1.01 mL/s/1.73 m2 (61 mL/min/1.73 m2) to 0.85 mL/s/1.73 m2 (51 mL/min/1.73 m2), and from 1.06 mL/s/1.73 m2 (64 mL/min/1.73 m2) to 0.97 mL/s/1.73 m2 (58 mL/min/1.73 m2), respectively. Eleven of 18 patients (61%) randomized to enalapril, and 10 of 15 (66%) patients randomized to placebo, had a decrease in GFR; their rates of progression were -1.18 mL/min/1.73 m2/mo and -1.00 mL/min/1.73 m2/mo, respectively. In the absence of changes in blood pressure, the addition of an ACE inhibitor to patients with clinical diabetic nephropathy could not be shown to confer a unique renal protective effect. A prolonged decrease in 24-hour protein excretion could not be shown to predict attenuation in the progression of established clinical diabetic nephropathy.

Renal effects of diltiazem in primary hypertension

Although the calcium channel blocker diltiazem has been shown to be an effective antihypertensive agent, its effect on renal function, salt and water excretion, and body fluid composition has not been well characterized in patients with primary hypertension. Therefore, these parameters were prospectively studied in 18 subjects with primary hypertension after placebo and 8 weeks of diltiazem monotherapy. Diltiazem monotherapy was confirmed to be an effective antihypertensive agent. Although mean arterial pressure was reduced from 121 to 108 mm Hg, diltiazem had no overall effect on glomerular filtration rate, renal plasma blood flow, salt and water excretion, or body fluid composition. Renal vascular resistance, however, was decreased. In subjects with pretreatment glomerular filtration rates of 80 ml/min/1.73 m2 or less, diltiazem therapy was associated with marked improvement in glomerular filtration rate (48%) and effective renal plasma flow (36%). Since the filtration fraction was unchanged, changes in glomerular filtration rate may have been related to the attenuated intrarenal effects of angiotensin II or norepinephrine, or both.

AN IMPROVED AIR-DRIVEN TYPE OF ULTRACENTRIFUGE FOR MOLECULAR SEDIMENTATION

1. A description is given of the construction details and operation characteristics of an improved type of air-driven ultracentrifuge operating in vacuum and suitable for the determination of sedimentation constants of protein molecules. 2. The rotor of the centrifuge is made of a forged aluminum alloy; it is oval in shape, measures 185 mm. at its greatest diameter, and weighs 3,430 gm. It carries a transparent cell located at a distance of 65 mm. from the axis of rotation and designed to accommodate a fluid column 15 mm. high. 3. The rotor has been run repeatedly over long periods at a speed of 60,000 R.P.M., which corresponds to a centrifugal force of 260,000 times gravity in the center of the cell. At this speed no deformation of the rotor nor leakage of the cell has been observed. 4. The sharp definition of sedimentation photographs taken at high speed serves to indicate the absence of detectable vibrations in the centrifuge. 5. When a vacuum of less than 1 micron of mercury is maintained in the centrifuge chamber, the rise in the rotor temperature amounts to only 1 or 2 degrees C. after several hours' run at high speed. 6. There has been no evidence of convection currents interfering with normal sedimentation of protein molecules in the centrifugal field. 7. A driving air pressure of about 18 pounds per square inch is sufficient to maintain the centrifuge at a steady speed of 60,000 R.P.M. With a driving pressure of 80 pounds per square inch, it can be accelerated to this speed in less than 20 minutes, and also brought to rest in about the same length of time by the application of the braking system. 8. The adaptation of Svedberg's optical systems to this centrifuge for photographically recording the movement of sedimentation boundaries is described.

Effect of nifedipine on renal function in patients with essential hypertension

Twenty-six essential hypertensive patients were entered into a protocol to assess the blood pressure and renal effects of the dihydropyridine calcium antagonist nifedipine (30-120 mg/day given in divided doses) administered for 4 weeks. Nifedipine monotherapy effectively lowered blood pressure in 73% of the patients. Glomerular filtration rate and effective renal plasma flow were increased 13.3 and 19.6%, respectively. The filtration fraction and urinary albumin excretion remained unchanged. Renal vascular resistance was markedly reduced (25.2%). Changes observed in renal function were independent of the patients' initial glomerular filtration rate. Furthermore, there was no correlation between the systemic and renal effects of nifedipine monotherapy. Patients with a poor systemic blood pressure response exhibited increases in both glomerular filtration rate (+13%) and effective renal plasma flow (+20%), changes comparable with increases in glomerular filtration rate (+13%) and effective renal plasma flow (+19%) observed in patients achieving a goal blood pressure response (diastolic blood pressure less than or equal to 90 mm Hg, or a greater than or equal to 10 mm Hg decrease in diastolic blood pressure, or both). These results suggest that nifedipine monotherapy has the potential to improve renal function abnormalities encountered in the essential hypertensive state independently of its effect on systemic blood pressure.

Effects of maternal state on the responsiveness to nest odors of hooded rats

Two experiments were designed to determine if pregnant and lactating rats are differentially attracted to their own bedding at various stages of the reproductive cycle and whether they will discriminate between their own nest materials and those of virgins and other lactating animals. We found that from just before birth until the second week postpartum, rats are attracted to their own bedding but do not differentiate between their own and that of other maternal animals. It is suggested that the responsiveness to nest odors in prepartum pregnant animals is a result of hormonal events prior to parturition. In addition, early maternal activities are thought to be facilitated by changes in responsiveness to olfactory stimuli and also by the presence of an attractant which contributes to nest odors.