Elevated extracellular K+ enhances arachidonic acid release in MDCK-D1 cells

Depolarization can alter the expression of membrane receptors and change certain receptor-mediated events, but previous studies have not assessed the impact of depolarization on generation of arachidonic acid and its metabolites (AA) in nonexcitable tissues. We assessed AA generation in Madin-Darby canine kidney (MDCK) cells grown for 3 days in increased extracellular [K+], which is known to acutely depolarize these cells. Growth under these conditions resulted in decreases in the number of alpha 1-adrenergic receptors (alpha 1 AR), a small decrease in receptor-mediated phosphoinositide hydrolysis, but increases in alpha 1 AR-mediated prostaglandin E2 formation and AA release. Calcium ionophore (A23187)-, melittin-, and bradykinin-stimulated AA release were also enhanced. The reduction in alpha 1 AR number and increased AA release were substantially reduced or eliminated when K(+)-treated cells were grown in the absence of extracellular calcium. The results provide evidence that hormone-stimulated AA release and prostaglandin production can be enhanced by chronic exposure to elevated extracellular K+ concentration, perhaps as a consequence of a depolarization-induced enhancement in phospholipase A2 activity. The results provide evidence for the parallel and independent regulation of the pathways for receptor-mediated phosphoinositide hydrolysis (phospholipase C activation) and AA release (phospholipase A2 activation) in MDCK cells.

Identification of hydroxyalkenals formed from omega-3 fatty acids

The highly toxic lipid peroxidation product, 4-hydroxynonenal, is formed from the decomposition of hydroperoxides of omega-6 fatty acids. In this study the analogous hydroxyalkenals formed from the decomposition of hydroperoxides of omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid) were isolated and identified using TLC densitometry, HPLC and GC/Mass Spectrometry. The major hydroxyalkenal formed from both fatty acids was a diene analog of 4-hydroxynonenal, 4-hydroxynona(2,6)dienal, while 4-hydroxyhexanal was a minor product. Measurement of specific omega-3 lipid peroxidation products may be important in studies using dietary fish oil.

What is the perception of the CFO: manager or technician?

This survey indicates that while both CEOs and CFOs feel that the ideal CFO should be more management oriented, both still place an emphasis on the technical characteristics of the job. This technical emphasis is seen when both CFOs and CEOs were asked to list the most and least important characteristics of the role of the ideal CFO. And while many CEOs view their CFOs as being viable candidates for possible CEO positions in the future, twice as many CFOs view themselves as possible CEOs in the future.

Alpha 2 adrenergic agonists stimulate Na+-H+ antiport activity in the rabbit renal proximal tubule

The role of adrenergic agents in augmenting proximal tubular salt and water flux, was studied in a preparation of freshly isolated rabbit renal proximal tubular cells in suspension. Norepinephrine (NE, 10(-5) M) increased sodium influx (JNa) 60 +/- 5% above control value. The alpha adrenergic antagonist, phentolamine (10(-5) M), inhibited the NE-induced enhanced JNa by 90 +/- 2%, while the beta adrenergic antagonist, propranolol, had a minimal inhibitory effect (10 +/- 2%). The alpha adrenergic subtype was further defined. Yohimbine (10(-5) M), an alpha2 adrenergic antagonist but not prazosin (10(-5) M), an alpha1 adrenergic antagonist completely blocked the NE induced increase in JNa. Clonidine, a partial alpha2 adrenergic agonist, increased JNa by 58 +/- 2% comparable to that observed with NE (10(-5) M). Yohimbine, but not prazosin, inhibited the clonidine-induced increase in JNa, confirming that alpha2 adrenergic receptors were involved. Additional alpha2 adrenergic agents, notably p-amino clonidine and alpha-methyl-norepinephrine, imparted a similar increase in JNa. The clonidine-induced increase in JNa could be completely blocked by the amiloride analogue, ethylisopropyl amiloride (EIPA, 10(-5) M). The transport pathway blocked by EIPA was partially inhibited by Li and cis H+, but stimulated by trans H+, consistent with Na+-H+ antiport. Radioligand binding studies using [3H]prazosin (alpha1 adrenergic antagonist) and [3H]rauwolscine (alpha2 adrenergic antagonist) were performed to complement the flux studies. Binding of [3H]prazosin to the cells was negligible. In contrast, [3H]rauwolscine showed saturable binding to a single class of sites, with Bmax 1678 +/- 143 binding sites/cell and KD 5.4 +/- 1.4 nM. In summary, in the isolated rabbit renal proximal tubular cell preparation, alpha2 adrenergic receptors are the predominant expression of alpha adreno-receptors, and in the absence of organic Na+-cotransported solutes, alpha2 adrenergic agonists enhance 22Na influx into the cell by stimulating the brush border membrane Na+-H+ exchange pathway.

Compartmentation of alpha 2-adrenergic receptors in human erythroleukemia (HEL) cells

We have identified alpha 2-adrenergic receptors on human erythroleukemia (HEL) cells, a suspension-grown cell line related to human platelets. properties of receptors were assessed in intact cells by binding of the antagonist [3H]yohimbine and by inhibition of cAMP accumulation. [3H]Yohimbine labeled 5900 +/- 2100 receptors/cell with a Kd of 3.6 +/- 0.9 nM (n = 7). alpha 2-Adrenergic receptors were potently coupled to inhibition of adenylate cyclase, with EC50 values for epinephrine, UK-14,304, and p-aminoclonidine in the low nM range. Treatment of cells with pertussis toxin abolished this response. In radioligand binding studies with membrane preparations [3H]yohimbine and [3H]UK-14,304 bound to the same number of sites (71 versus 69 fmol/mg of protein), and epinephrine competed for [3H]yohimbine binding in a biphasic manner. After addition of GTP, no high affinity [3H]UK-14,304 binding was detected, and epinephrine competed for [3H]yohimbine binding with lower affinity at both 4 degrees and 37 degrees. In studies with intact cells, we detected no specific binding of [3H]UK-14,304 at either 37 degrees or 4 degrees. At 37 degrees, epinephrine competed for all [3H]yohimbine binding sites with a low apparent affinity (Ki = 21 microM), whereas at 4 degrees epinephrine (up to 1 mM) was able to compete for only 59 +/- 13% of [3H]yohimbine-binding sites. The potency of epinephrine in competing for [3H]yohimbine sites in intact cells at 4 degrees was greater than at 37 degrees (Ki = 1 microM) and was similar to that observed with membranes in the presence of GTP. We hypothesize that sites not detectable by epinephrine at 4 degrees are sequestered within the cell. Treatment of HEL cells with pertussis toxin reduced the proportion of receptors on the surface from 51 +/- 12% to 23 +/- 7% (n = 3, p less than 0.05) of the total sites. Treatment of HEL cells with epinephrine (100 microM, 1 hr) reduced the cell surface component to 25 +/- 8% (n = 3) of the total sites. This treatment was not accompanied by significant desensitization of the ability of epinephrine to inhibit cAMP accumulation. We conclude that alpha 2-adrenergic receptors exist in more than one compartment in HEL cells and that interaction of receptors with a guanine nucleotide-binding protein or with agonist may regulate this compartmentation. These cells provide a new model system for the study of expression and metabolism of alpha 2-adrenergic receptors.

Amiloride interacts with renal alpha- and beta-adrenergic receptors

We have used radioligand binding techniques to assess whether amiloride and certain analogues of amiloride (ethylisopropyl amiloride and benzamil) can bind to adrenergic receptors in the kidney. We found that amiloride could compete for [3H]rauwolscine (alpha 2-adrenergic receptors), [3H]prazosin (alpha 1-adrenergic receptors), and [125I]iodocyanopindolol (beta-adrenergic receptors) binding in rat renal cortical membranes with inhibitor constants of 13.6 +/- 5.7, 24.4 +/- 7.4, and 83.6 +/- 13.5 microM, respectively. Ethylisopropyl amiloride and benzamil were from 2- to 25-fold more potent than amiloride in competing for radioligand binding sites in studies with these membranes. In addition, amiloride and the two analogues competed for [3H]prazosin sites on intact Madin-Darby canine kidney cells and amiloride blocked epinephrine-stimulated prostaglandin E2 production in these cells. We conclude that amiloride competes for binding to several classes of renal adrenergic receptors with a rank order of potency of alpha 2 greater than alpha 1 greater than beta. Binding to, and antagonism of, adrenergic receptors occurs at concentrations of amiloride that are lower than previously observed "nonspecific" interactions of this agent.

Interactions of amiloride with alpha- and beta-adrenergic receptors: amiloride reveals an allosteric site on alpha 2-adrenergic receptors

Interaction of amiloride with adrenergic receptors was studied using radioligand binding techniques. Amiloride competed for [3H]prazosin binding to alpha 1-adrenergic receptors on rat renal cortical membranes and BC3H-1 muscle cell membranes. Non-linear regression analysis of radioligand binding isotherms showed that amiloride increased Kd without a change in Bmax, suggesting the drug binds competitively in a mutually exclusive manner with the radioligand at the receptor-binding site. Similarly, amiloride competitively blocked [125I]iodocyanopindolol binding to beta-adrenergic receptors on both tissues. The addition of guanylyl 5'-imidodiphosphate or sodium chloride did not alter the interaction of amiloride with alpha 1- or beta-adrenergic receptors. The interaction of amiloride with alpha 2-adrenergic receptors was more complex and revealed an allosteric site. In both rat renal cortical membranes and intact human platelets, amiloride increased the Kd for [3H]rauwolscine binding, as well as decreasing the apparent Bmax. In binding experiments where amiloride competed for [3H]rauwolscine-binding sites, pseudo-Hill slopes of less than 1.0 were obtained for both platelet and renal alpha 2 receptors. In addition, amiloride increased the rate of [3H]rauwolscine dissociation from renal alpha 2 receptors. In the presence of 100-120 mM sodium chloride, the Ki for amiloride competition was decreased an average of 54% in renal membranes; in contrast, sodium increased the Kd of the agonist epinephrine. Taken together, these data support the hypothesis that alpha 2-adrenergic receptors, but not alpha 1- or beta-adrenergic receptors, have an allosteric site to which amiloride binds and which we propose to be a cation-binding site.

DNA sequences of human papillomavirus types 11, 16 or 18 in invasive cervical carcinoma of Western Australian women

The presence of human papillomavirus (HPV) types 11, 16 and 18 in 77 biopsies of cervical intraepithelial neoplasia (dysplasia) and carcinoma of the uterine cervix of a sample of women from Western Australia was examined using "Southern" blot hybridisation. HPV-DNA was found in 17 of the 23 dysplasias and 43 of the 54 invasive carcinomas examined but not in the 5 biopsies obtained from areas assessed as normal by colposcopy and histology. Five of 11 biopsies of mild to moderate dysplasias contained HPV type 11 (HPV-11), 2 HPV-16 and 1 HPV-18. Of 12 severe dysplasias/carcinoma in situ, 2 contained HPV-11, 4 HPV-16 and 2 HPV-18. One biopsy contained both HPV-11 and HPV-16. Of 45 squamous cell carcinomas examined for HPV-DNA, 24 contained HPV-16, 5 HPV-11 and 1 HPV-18. Both HPV-11 and HPV-16 were found in 6 of the squamous cell carcinomas and 2 contained both HPV-16 and HPV-18. Of 6 adenosquamous carcinomas examined, 3 contained HPV-DNA, 2 with HPV-16 and 1 with HPV-11. HPV types 16 or 18 were also found in 2 of 3 adenocarcinomas. This study shows a strong association between the papillomavirus and uterine cervical cancer in a sample of women from Western Australia. HPV-16 was more frequently associated with severe dysplasia and cancer than with mild or moderate dysplasia supporting the view that this HPV genotype may have a greater oncogenic potential than HPV-11.

Neural tube-derived factors influence differentiation of neural crest cells in vitro: effects on activity of neurotransmitter biosynthetic enzymes

Previously, we have demonstrated that a factor present in chick embryo extract or medium conditioned by neural tube cells supports adrenergic differentiation of some neural crest cells in vitro. These studies have been extended here to examine the effects of this factor(s) on the development of enzymes involved in neurotransmitter biosynthesis. The time course of expression of choline acetyltransferase (ChAT), a marker for cholinergic cells, and dopamine-beta-hydroxylase (DBH), a marker for adrenergic cells, was examined in neural crest cell cultures grown under three conditions: in medium containing 10% embryo extract, in medium containing 2% embryo extract, and in medium containing 2% embryo extract that was conditioned by neural tube cells (NTCM). Significant levels of DBH activity were measured in neural crest cell cultures grown in 10% embryo extract containing medium or in NTCM, while only low levels were present in cultures grown in medium containing 2% embryo extract. In contrast, ChAT activity was inhibited by NTCM in comparison to levels in both 10 and 2% embryo extract containing medium. As a preliminary characterization of the factor(s) present in chick embryo extract, we have fractionated embryo extract and find that a pool of 10 kDa or less can support adrenergic differentiation of some neural crest cells. These results suggest that low molecular weight factors present in embryo extract and NTCM support adrenergic expression of neural crest cells, whereas NTCM suppresses cholinergic expression.

The influence of neural tube-derived factors on differentiation of neural crest cells in vitro. I. Histochemical study on the appearance of adrenergic cells

The neural crest gives rise to numerous derivatives including adrenergic and cholinergic neurons, supportive cells of the nervous system, and melanocytes. In tissue culture, neural crest cells explanted from both cranial and trunk regions were found to differentiate into adrenergic neuroblasts or into pigmented cells when grown in medium containing 10% chick embryo extract. When the embryo extract concentration was lowered to 2%, no catecholamine-containing cells (as assayed by formaldehyde-induced fluorescence) were detected, although pigment cells were observed. These results suggest the presence of a factor(s) in embryo extract that promotes or supports adrenergic differentiation. To examine the possible tissue sources of this factor(s), neural tube, notochord, or somite cells were used to condition medium containing 2% embryo extract. When neural crest cells were grown in medium conditioned by neural tube cells, adrenergic neuroblasts were observed in all cultures. However, somite- and notochord conditioned medium did not support adrenergic differentiation. In addition, medium supplemented with extracts derived from central nervous system components did support adrenergic expression, whereas medium supplemented with embryo extract from which the neural tissue was removed did not. Direct contact with neural tube cell ghost membranes was unable to substitute for high embryo extract concentrations or for neural tube-conditioned medium. These results suggest that the neural tube makes a diffusible factor(s) that will support adrenergic differentiation of neural crest cells.

Interpreting and Reporting Qualitative Research

The aims of this paper were to clarify the nature and purpose of qualitative research and to suggest specific guidelines for reporting the results of qualitative studies. Confusion about the purpose of qualitative research and the absence of a standardized format for reporting such research make it difficult to assess the validity of qualitative studies. Four general purposes of qualitative research were discussed: instrument development, illustration of results, description, and conceptualization. A framework for reporting qualitative research that provides a guide for assuring consistency across original study purpose, study design, and final report was presented and can be used for either evaluating or writing a report of qualitative research.

A silver carbonate method for cell counts of neurons and glial elements on paraffin embedded brain tissue

A modification of the Del Rio-Hortega method for the demonstration of central nervous system elements is presented. This silver impregnation technique is particularly useful for the classification of cell types for quantitative differential cell counts. Formalin fixed paraffin sections are immersed in formol-ammonium bromide for 1 1/2 hours; this solution is an excellent mordant for various silver nitrate stains. The samples are stained for 20 to 60 minutes in a silver carbonate solution (25 ml of 25% silver nitrate combined with 200 ml of 5% sodium carbonate) and then reduced in a 1% formaldehyde solution to which 20 drops of acetic acid have been added. Finally, the slides are fixed in sodium thiosulfate, rinsed in tap water, dehydrated, cleared, and mounted. This procedure will enable this investigator to identify neurons, oligodendroglia, and astrocytes on the basis of their nuclear staining as well as to demonstrate the laminae of brain tissue since the method allows differentiation of cell layers and fiber tracts.

Seasonal distribution of pathogenic free-living amebae in Oklahoma waters

Pathogenic free-living amebae cause serious human disease, including infection of the eye and the central nervous system. The purpose of this study was to sample aquatic environments in the Tulsa, Oklahoma, area year-round for the presence of these disease-causing amebae. A total of 34 pathogenic isolates were obtained from 2,016 processed water and swab samples. Pathogenicity was determined by the ability of amebae to cause death in mice after intranasal inoculation. Pathogenic amebae were isolated during every month of the year and were identified as Naegleria australiensis (38%), Acanthamoeba species (35%), N. fowleri (18%), and leptomyxid amebae (9%). Pathogenic leptomyxids have not previously been reported from the environment. The greatest percentage of recovery of pathogens occurred during the spring and autumn. The prevalence of pathogenic free-living amebae in the sampled waters was 1 pathogen/3.4 l water.