Spirometry in the Lung Health Study: II. Determinants of short-term intraindividual variability

The Lung Health Study (LHS) is a randomized clinical trial designed to determine whether a smoking intervention program and use of an inhaled bronchodilator (BD) can reduce the rate of decline of FEV1 in cigarette smokers with airflow limitation. During recruitment, spirometry was performed at second and third screening visits, a mean of 21 d apart. A total of 5,887 smokers, 35 to 60 yr of age and of whom 63% were men, met the study eligibility requirements. Smokers taking physician-prescribed BDs or with an FEV1 < 50% or > 90% predicted were excluded, as were those whose FEV1/FVC ratio was greater than 70%. Two inhalations of isoproterenol were given to determine BD response during the second visit. A serial dilution methacholine challenge test was done during the third visit to determine nonspecific airway reactivity. Ninety-five percent of the differences between FEV1 measured at the two visits were within 240 ml for women and within 320 ml for men (coefficients of repeatability). The best independent predictors of the mean short-term (between visit) intraindividual FEV1 variability were factors indicating intrinsic airway reactivity of the participants: bronchodilator response, methacholine reactivity, and the presence of wheezing; as well as factors influenced by the quality of spirometry testing: the difference between the highest and second highest FEV1s and peak flows during baseline spirometry, and the time to reach peak flow (PEFT).

Volume spirometers need automated internal temperature sensors

Spirometer temperature was measured automatically during all years of the Lung Health Study. Short- and long-term changes in temperature were analyzed for the 23 dry-rolling-seal volume spirometers used at the 10 clinical centers involved in the study. Within-test-session spirometer temperature increased a mean of 0.3 degrees C, and as much as 3.0 degrees C during methacholine challenge testing. The maximal change in spirometer temperature during a test day exceeded 4 degrees C more than 5% of the time. Month-to-month changes of more than 15 degrees C were not uncommon. If ambient temperature had been assumed to apply to all maneuvers and used for BTPS corrections, FEV1, and FVC measurement errors of up to 6% would have occurred. When using volume spirometers, the temperature of air inside the spirometer should be measured accurately during each breathing maneuver.

Cultivating expertise in oncology nursing: methods, mentors, and memories

PURPOSE

To explore the development of clinical expertise and the role of mentoring experiences in this process for oncology nurses involved in direct patient care.

DESIGN

Multi-institutional, descriptive, qualitative.

SETTING

Six sites in different regions of the United States; rural and urban cancer and noncancer centers.

SAMPLE

38 oncology nurses (mean age = 35 years; average time in nursing = 10 years and in oncology = 7 years; 47% bachelor of science in nursing, 29% diploma, 13% associate degree in nursing, and 11% master's prepared).

METHODS

Phenomenological; content analysis of interviews.

FINDINGS

Development of clinical expertise and professional commitment requires a combination of protégée- and mentor-initiated behaviors. Protégée learning included reading, watching, attending, doing, asking questions, seeking peer support, seeking new opportunities, and associating with others. Mentor contributions included modeling standards and beliefs, coping effectively, explaining knowledge, and believing in, challenging, and supporting the protégée personally and professionally. The absence of mentoring also was of concern to nurses. True mentoring required on interpersonal connection and commitment between the protégée and mentor.

IMPLICATIONS FOR NURSING PRACTICE

Mentoring enhances the development of expert nurses who combine competent clinical practice with strong interpersonal commitment to their patients and the oncology nursing profession. The benefits of mentoring outcomes for individual oncology nurses, their patients, the institutional setting, and the profession need further exploration, especially given the focus on advanced practice and healthcare reform.

Polyamines influence transglutaminase activity and cell migration in two cell lines

Transglutaminases (TGAs) catalyze the cross-linking of proteins through formation of gamma-glutaminyl-epsilon-lysine bonds and incorporation of small-molecular-weight amines, including polyamines, into the gamma-glutamine sites of proteins. Tissue TGA has been shown to establish covalent cross-links between cytoskeletal proteins using polyamines as substrates, and protein-polyamine conjugates have been identified in a variety of cells. We have shown previously that polyamines are required for cell migration in IEC-6 cells [S. A. McCormack, M. J. Viar, and L. R. Johnson. Am. J. Physiol. 264 (Gastrointest. Liver Physiol. 27): G367-G374, 1993]. In this study, we explored the relationship between cell migration, polyamines, and tissue TGA activity in two cell lines and found that while both IEC-6 and Caco-2 cells required normal levels of polyamines to migrate across a denuded surface, tissue TGA activity responded differently to polyamine deficiency brought about by treatment with alpha-difluoromethylornithine (DFMO). DFMO is a specific and irreversible inhibitor of ornithine decarboxylase, a rate-limiting enzyme of polyamine biosynthesis. In IEC-6 cells, tissue TGA activity decreased significantly with DFMO treatment concurrent with a rise in inactive TGA protein as measured by Western blot analysis. On the other hand, in Caco-2 cells, tissue TGA activity and protein increased significantly with DFMO treatment. In both cell lines, addition of polyamines to the DFMO treatment restored cell migration, tissue TGA activity, and protein to control levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Polyamine deficiency causes reorganization of F-actin and tropomyosin in IEC-6 cells

In earlier work we have shown that polyamine-deficient IEC-6 cells lose most of their ability to migrate. In this report we describe the effect of polyamine deficiency on the cytoskeleton of migrating IEC-6 cells. Cells were grown on cover slips for 4 days. One-third of the monolayer was removed, and the remainder was incubated for 6 h. The monolayers were fixed and stained with rhodamine phalloidin for actin filaments and by immunocytochemistry for tropomyosin. In control cells, actin filaments were found as stress fibers traversing the cell, in a thin actin cortex often visible on only one edge of the cell, and in fine fibers extending into the lamellipodia. Tropomyosin was found in the same distribution. A Western blot showed that tropomyosin was present as 35- and 37-kDa isoforms. In polyamine-deficient cells, actin stress fibers were less dense, whereas the actin cortex was greatly increased in density and lamellipodia were less extensive. Tropomyosin distribution was similar and included a 30-kDa isoform not seen previously. In spite of the obvious changes in the distribution of these cytoskeletal proteins, the concentrations of filamentous actin, beta-actin mRNA, and the higher molecular weight tropomyosin isoforms did not change. In all cases the addition of putrescine to polyamine-deficient cells prevented the changes described. We conclude that polyamines are essential for migration in this system because of their effects on the organization of cytoskeletal actin, tropomyosin, and perhaps other proteins as well.

Secretin inhibits induction of ornithine decarboxylase activity by gastrin in duodenal mucosa and IEC-6 cells

Ornithine decarboxylase (ODC) catalyzes the first rate-limiting step in polyamine biosynthesis, and increased ODC activity is one of the earliest biochemical events associated with the induction of cellular proliferation. The current study examines the regulation of ODC activity in rat duodenal mucosa and IEC-6 cells (a line of normal rat intestinal crypt cells) in response to the trophic hormone, gastrin, and its inhibitor, secretin. Rats were fasted 22 h before the various treatments, and ODC activity was measured in scraped duodenal mucosa. Gastrin significantly increased ODC activity within 3 h to 4.3 times control levels. The effect of gastrin was totally inhibited by 5 micrograms/kg secretin. In doses of 5 or 10 micrograms/kg, secretin had no effect on basal ODC. Epidermal growth factor (EGF) and refeeding fasted rats also significantly increased ODC activity in duodenal mucosa, but the effects of EGF and refeeding were not prevented by secretin. In cultured IEC-6 cells, ODC activity was significantly increased after exposure to gastrin, 5% dialyzed fetal bovine serum (FBS), EGF, and asparagine. Secretin in doses ranging from 10(-10) to 10(-6) M caused a linear and significant inhibition of the stimulation of ODC activity by gastrin. No dose of secretin affected basal ODC activity or enzyme activity stimulated by 5% dialyzed FBS, EGF, or asparagine in IEC-6 cells. The ODC mRNA levels in IEC-6 cells were also increased after exposure to gastrin. Administration of secretin significantly prevented the stimulated expression of the ODC gene in cells treated with gastrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Input from the amygdala to the rat nucleus accumbens: its relationship with tyrosine hydroxylase immunoreactivity and identified neurons

Both tyrosine hydroxylase-positive fibres from the mesolimbic dopamine system and amygdala projection fibres from the basolateral nucleus are known to terminate heavily in the nucleus accumbens. Caudal amygdala fibres travelling dorsally via the stria terminalis project densely to the nucleus accumbens shell, especially in the dopamine rich septal hook. The amygdala has been associated with the recognition of emotionally relevant stimuli while the mesolimbic dopamine system is implicated with reward mechanisms. There is behavioural and electrophysiological evidence that the amygdala input to the nucleus accumbens is modulated by the mesolimbic dopamine input, but it is not known how these pathways interact anatomically within the nucleus accumbens. Using a variety of neuroanatomical techniques including anterograde and retrograde tracing, immunocytochemistry and intracellular filling, we have demonstrated convergence of these inputs on to medium-sized spiny neurons. The terminals of the basolateral amygdala projection make asymmetrical synapses predominantly on the heads of spines which also receive on their necks or adjacent dendrites, symmetrical synaptic input from the mesolimbic dopamine system. Some of these neurons have also been identified as projection neurons, possibly to the ventral pallidum. We have shown a synaptic level how dopamine is positioned to modulate excitatory limbic input in the nucleus accumbens.

Expression of protooncogenes c-fos and c-myc in healing of gastric mucosal stress ulcers

The current study determines the hypothesis that expression of protooncogenes c-fos and c-myc is involved in the mechanism of polyamine-stimulated healing in gastric mucosal stress ulcers. Rats were fasted 22 h, placed in restraint cages, and immersed in water to the xiphoid process for 2-6 h. Animals were killed either immediately after stress or at 2-h intervals up to 24 h after 6 h of stress. Stress caused both visible lesions and induction of ornithine decarboxylase (ODC) activity in the oxyntic gland mucosa after 2 h. Increased ODC activity was paralleled by increases in the mucosal polyamines putrescine, spermidine, and spermine. Exposure to stress led to appearance of c-fos mRNA and oncoprotein in the gastric oxyntic gland mucosa at 2 h and its disappearance by 4 h. Baseline expression of c-myc was enhanced significantly after 6 h of stress and remained elevated for 4 h. This change in the expression of c-fos and c-myc mRNA and oncoprotein preceded an increased rate of [3H]thymidine incorporation into mucosal DNA. Administration of alpha-difluoromethylornithine (DFMO, 500 mg/kg ip) totally prevented the marked increases in ODC activity and polyamine levels. DFMO also completely inhibited the expression of c-fos and significantly decreased c-myc mRNA and oncoprotein in the gastric mucosa of stressed rats. The healing process, which was significant by 12 h, was markedly inhibited by DFMO. These results show that 1) mucosa exposed to stress exhibits increased expression of c-fos and c-myc following increased polyamine synthesis and 2) inhibition of polyamine biosynthesis by DFMO decreases both protooncogene expression and mucosal healing.

Phototoxicology. 1. Light-enhanced toxicity of TNT and some related compounds to Daphnia magna and Lytechinus variagatus embryos

Many environmental pollutants interact with solar near-ultraviolet (nuv) light in a manner which greatly increases their toxic effects. The phenomenon of light-mediated toxicity (phototoxicity) is only now becoming generally recognized to any significant degree. Manufacture of, and loading munitions with, the explosive 2,4,6-trinitrotoluene (TNT) in past decades caused contamination of soils and sediments at levels exceeding 1000 ppm and of waters at levels near saturation (100 ppm). Manufacture of TNT produces numerous nitrated by-products, and most of these compounds, including TNT, can be metabolized by many species, including bacteria, fungi, plants, and mammals. This study investigated the phototoxicity of TNT, and 2,3-, 2,4-, 2,6-, and 3,4-dinitrotoluene (DNT) and -diaminotoluene (DAT), and the major metabolites 2-amino-4,6-dinitrotoluene (2A) and 4-amino-2,6-dinitrotoluene (4A), to Daphnia magna (acute toxicity) and Lytechinus variagatus (sea urchin) embryos (subacute, developmental toxicity). Most of the compounds were weakly toxic or nontoxic in the dark. All were phototoxic to sea urchins. In D. magna, 2,3- and 3,4-DNT/DAT and 4A were not toxic but were phototoxic, and 2A was toxic and phototoxic; the other isomers were not toxic or phototoxic to this species.

Phototoxicology. 3. Comparative toxicity of trinitrotoluene and aminodinitrotoluenes to Daphnia magna, Dugesia dorotocephala, and sheep erythrocytes

2,4,6-Trinitrotoluene (TNT) and compounds associated with its production are toxic and phototoxic to a wide range of biota. The planarian Dugesia dorotocephala, but not Daphnia magna, metabolized TNT (1 mg/liter) to 4-amino-2,6-dinitrotoluene (4A; 0.4 mg/liter) and 2-amino-4,6-dinitrotoluene (2A; 0.2 mg/liter). Coexposure to near-ultraviolet (nuv) light enhanced the toxicity of 2A more than that of TNT and 4A. The toxicities of TNT, 4A, and 2A to Du. dorotocephala were all decreased by glutathione (GSH) conjugation. This suggests that all had mechanisms of toxic action involving formation of quinone-GSH conjugates. Dark and light mechanisms for TNT and 2A depended on GSH conjugation, but the specific mechanisms may be different for each compound. The dark and light mechanisms of toxic action for 4A appeared to be fundamentally different in that the dark toxic mechanism of action was less dependent on GSH conjugation. Hemolysis studies using sheep erythrocytes showed that the light-enhanced toxic mechanism of action for TNT, 2A, and/or 4A did not involve cellular membrane damage in response to nuv-induced anions.

Phototoxicology. 2. Near-ultraviolet light enhancement of Microtox assays of trinitrotoluene and aminodinitrotoluenes

Coexposure of 2,4,6-trinitrotoluene (TNT), 2-amino-4,6-dinitrotoluene (2A), or 4-amino-2,6-dinitrotoluene (4A) to near-ultraviolet (nuv) light (lambda max-354 nm) significantly enhanced their toxicity toward Photobacterium phosphoreum (Microtox bioassay) during 30 min but not 15 min. Based on the slopes of the dose-response lines, the nuv coexposure and dark toxic mechanisms of action for TNT, 2A, and 4A appeared to be similar. nuv coexposure of binary mixtures significantly enhanced (supraadditivity) the toxicity of these compounds to P. phosphoreum. Under normal laboratory lighting, the toxicity of TNT + 2A and 2A + 4A mixtures were supraadditive but the toxicity of TNT + 4A mixtures could be explained by simple addition. Supporting these conclusions, the response curves of alpha-terthienyl, a compound known not to require nuv for toxicity, were similar in the dark and with nuv coexposure. In contrast, angelicin and psoralen, compounds known to require nuv coexposure to damage DNA, gave response curves having different slopes in the dark and with nuv coexposure. The nuv coexposure Microtox assay was able to detect and quantify phototoxicity in psoralen, angelicin, alpha-terthienyl, anthracene, TNT, and aminodinitrotoluenes.

Regulation of transglutaminase activity by polyamines in the gastrointestinal mucosa of rats

Transglutaminases catalyze the covalent cross-linking of protein and are involved in the mechanism of polyamine-dependent mucosal healing. The current study examined the effect of polyamines on transglutaminase activity in gastrointestinal mucosa. Rats were fasted 22 hr before experiments and enzyme activity was measured as the Ca(++)-dependent covalent incorporation of [3H]-putrescine into acid-precipitable protein. In some of the experiments, mucosal ornithine decarboxylase (ODC) activity and polyamine levels were also examined. Transglutaminase activity in both gastric and duodenal mucosa increased significantly after polyamine administration. Treatment with alpha-difluoromethylornithine (DFMO) decreased both basal ODC activity and putrescine levels in the duodenal mucosa. DFMO also significantly decreased mucosal transglutaminase activity. In stress or hypertonic NaCl-induced gastric mucosal injury models, increased polyamine biosynthesis was associated with increased transglutaminase activity, which was completely prevented by DFMO. Exogenous polyamines returned transglutaminase activity toward control levels in the presence of DFMO. In conclusion, these results indicate that: (i) luminal polyamines increase transglutaminase activity in gastric and duodenal mucosa; (ii) polyamine depletion caused by the inhibition of ODC is accompanied by a significant decrease in transglutaminase activity; and (iii) exogenous polyamines significantly reverse the decrease in transglutaminase activity caused by polyamine depletion.

Surgical management of atypical lateral tracheal collapse in a dog

Tracheal collapse is often diagnosed in small-breed dogs through use of conventional radiography or fluoroscopy, by which the dorsoventral orientation of the collapse can be seen. In the dog of this report, an unusual lateral form of tracheal collapse was diagnosed by means of bronchoscopy after multiple radiographic procedures had failed to define a cause for cough and dyspnea. Surgical reinforcement of the abnormal region of the trachea resulted in resolution of clinical signs and in reduction in dynamic airway collapse, which was documented on follow-up bronchoscopy.

Nerve growth factor receptor (p75)-immunoreactivity in the normal adult feline trigeminal system and following retrogasserian rhizotomy

The 75 kDa protein nerve growth factor receptor [NGFr(p75)] is a neurotrophin receptor that is able to bind different members of the neurotrophin family of molecules implicated in affecting neuronal survival. Here we describe the light microscopic distribution of NGFr(p75)-immunoreactivity (IR) within the feline trigeminal brainstem sensory nuclear complex and trigeminal ganglion of normal adult subjects and in subjects 10 and 30 days following retrogasserian rhizotomy. Within the trigeminal ganglion of normal subjects, numerous fibers and most of the neuronal cell bodies showed NGFr(p75)-IR that varied in intensity, while cells and fibers with NGFr(p75)-IR were less numerous within the mesencephalic trigeminal nucleus. Within the main sensory and spinal trigeminal nuclei, NGFr(p75)-IR formed a reproducible pattern that varied between the different subnuclei. The NGFr(p75)-IR consisted both of dense pockets and a low level NGFr(p75)-IR that was selective to the trigeminal neuropil. Following rhizotomy, most of the NGFr(p75)-IR was lost from the main sensory and spinal trigeminal nuclei, except in regions where the upper cervical roots and cranial nerves VII, IX, and X project. In contrast, examination of the central root that was still attached to the trigeminal ganglion showed increased NGFr(p75)-IR in fibers and supporting cells, as did the motor root within the peripheral mandibular division. These results indicate that the majority of the NGFr(p75)-IR within the main sensory and spinal trigeminal nuclei originates from primary trigeminal afferents and that retrogasserian rhizotomy leads to an up-regulation of NGFr(p75)-IR in the part of the central root that is contiguous with the ganglion.

Decreased expression of protooncogenes c-fos, c-myc, and c-jun following polyamine depletion in IEC-6 cells

Direct exposure of small intestinal mucosal cells to luminal polyamines stimulates proliferation. This study tests the hypothesis that the protooncogenes c-fos, c-myc, c-jun, and junB are involved in the mechanism by which polyamines modulate mucosal growth. Studies were conducted in the IEC-6 cell line, derived from rat small intestinal crypt cells. Cells were grown in Dulbecco's minimal essential medium containing 5% dialyzed fetal bovine serum (dFBS) in the presence of absence of alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase, which is the rate-limiting enzyme for polyamine synthesis. Cellular polyamine levels, cell growth, and relative abundance of c-fos, c-myc, c-jun, and junB mRNAs, were measured at 1, 2, 4, 6, 8, and 12 days after initial plating. The intracellular polyamines, spermidine and spermine, and their precursor, putrescine, in DFMO-treated cells decreased significantly at 2 days and remained depleted thereafter. Although DFMO profoundly decreased growth and final cell number, both control and DFMO-treated cells entered a plateau phase by 6 days. In control cells, c-myc and c-jun mRNA levels significantly increased on days 4-6 and then returned to a basal level of expression, which was maintained thereafter. c-fos mRNA in quiescent cells after 24 h serum deprivation was significantly stimulated by 5% dFBS, although a steady-state level of c-fos mRNA was undetectable in control cells. Treatment with DFMO not only prevented increased expression of c-myc and c-jun protooncogenes at 4 days, but also significantly reduced steady-state levels of c-myc and c-jun mRNA between 6 and 12 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Polyamines are necessary for cell migration by a small intestinal crypt cell line

Studies from our laboratory have shown that polyamines are essential for the normal repair of duodenal erosions induced in vivo in a rat stress-ulcer model. In that model, the inhibition of ornithine decarboxylase, a rate-limiting enzyme of polyamine biosynthesis, with alpha-difluoromethylornithine (DFMO) almost entirely prevented healing. Healing could be restored by oral polyamines. In this paper, we have investigated whether the polyamines are required for the early stages of epithelial restitution using an IEC-6 cell culture model of cell migration. Treatment of the cells with DFMO for 4 days reduced cell migration 80%. Migration could be restored to normal by concomitant treatment with putrescine (PUT), spermidine (SPD), or spermine (SPM), but not by their addition during the migration period (6 h) only. If DFMO treatment was not begun until the migration period, it still reduced cell migration 20%, and this deficit could not be restored by concomitant addition of the polyamines. Intracellular polyamine levels at these times, i.e., 6 h or 4 days, were an important factor in these results. Only PUT was undetectable after 6 h of DFMO. SPD and SPM were still at normal levels at 6 h. SPD was undetectable at 4 days, but SPM was still at 40% of normal. These data give added importance to PUT because its absence reduced cell migration after only 6 h, while SPD and SPM were still present in normal amounts. Perhaps exogenous SPD and SPM restored cell migration when present with DFMO for 4 days treatment primarily because they contributed to intracellular PUT through the acetyltransferases.(ABSTRACT TRUNCATED AT 250 WORDS)

t haplotypes in the mouse compromise sperm flagellar function

The t haplotypes are variant forms of the proximal portion of chromosome 17 in the mouse. The t haplotypes alter spermatogenesis and many also contain lethal factors. Although the lethal factors vary between t haplotypes, all t haplotypes have the same effect on sperm, that of altering sperm function in fertilization. It is not clear, however, whether the nature of the sperm dysfunction is the same in all t haplotypes. Studies to date have focused on only one or two aspects of sperm function or have not examined sperm from males carrying different t haplotypes. In addition, factors within the t haplotypes interact with the genetic background, so that comparisons to sperm from t/+ or +/+ mice having different alleles at loci outside the t haplotypes may not be valid. To determine the nature of the sperm dysfunction caused by the t haplotypes, we have studied sperm from mice of the same genetic strain carrying none, one, or two t haplotypes. Sperm from tw32/+, tw5/+, and tw32/tw5 mice exhibited premature hyperactivation, a type of vigorous but nonprogressive motility correlated with fertility, while their rates of capacitation (the ability to undergo the acrosome reaction in response to zona proteins) and spontaneous acrosome reaction were similar to those of wild-type sperm. In addition, sperm flagellar curvature was abnormal: flagella from heterozygotes had an acute bend in the midpiece, giving the sperm a "fishhook" appearance, while the entire flagellum of sperm from tw32/tw5 mice was curled. Also, fewer sperm from tw32/tw5 mice were initially motile. Since all of these motility defects were dependent on exogenous calcium, the t haplotypes could specify an abnormal, calcium-sensitive component of the flagellum. The motility defects could also contribute to the dysfunction of these sperm by inhibiting their passage to the site of fertilization in vivo.

Transglutaminase in response to hypertonic NaCl-induced gastric mucosal injury in rats

BACKGROUND

Polyamines serve as substitutes for transglutaminase-catalyzed protein cross-linking and are essential to the healing of gastric mucosal lesions. This study determines whether transglutaminase and protein cross-linking have a role in the healing of hypertonic NaCl-induced gastric lesions.

METHODS

Rats were fasted 22 hours before given 1 mL 3.4 Mol/L NaCl intragastrically. Gastric mucosa was examined histologically and grossly, and transglutaminase activity was measured as the Ca(2+)-dependent covalent incorporation of [3H]putrescine into acid-precipitable protein.

RESULTS

Transglutaminase activity increased significantly from 2 to 8 hours, peaking between 4 and 6 hours after NaCl administration. Lesions were significantly produced after 2 hours, and damage paralleled transglutaminase activity. Dansylcadaverine (200 mg/kg orally), a specific inhibitor of protein cross-linking, prevented the increases in transglutaminase activity and significantly delayed healing but had no effect on lesion formation.

CONCLUSIONS

These results indicate that (1) hypertonic NaCl-induced gastric mucosal damage is associated with a significant increase in transglutaminase activity and (2) increased transglutaminase activity is involved in the mechanism of normal mucosal healing.

Effect of putrescine on S-adenosylmethionine decarboxylase in a small intestinal crypt cell line

Two key enzymes in polyamine biosynthesis are ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC). SAMDC decarboxylates S-adenosylmethionine, which then donates aminopropyl groups for spermidine and spermine synthesis. The purpose of our study was to determine whether putrescine, taken up from medium or synthesized endogenously by ODC, alters SAMDC activity. Studies were conducted in the IEC-6 cell line derived from rat small intestinal crypt cells. Cells were grown in Dulbecco's minimal essential medium containing 5% dialyzed fetal bovine serum (dFBS). They were deprived of serum for 24 h before experiments. Basal SAMDC activity was increased significantly by > or = 10(-4) M of putrescine. Lower doses had no significant effect. The same doses of putrescine decreased ODC activity to near zero. Asparagine at 10 mM or 5% dFBS not only stimulated ODC activity and the intracellular putrescine levels but also increased significantly SAMDC activity as well. ODC activity peaked at 3 h, and the maximum level of SAMDC occurred 3-4 h after exposure to asparagine or serum. Treatment with DL-alpha-difluoromethylornithine (DFMO), a specific ODC inhibitor, prevented the increases in both cellular putrescine levels and SAMDC activity in asparagine- and serum-treated cells. In the presence of DFMO, exogenous putrescine returned SAMDC activity toward control levels but had no effect on ODC. A very slight increase of SAMDC half-life in IEC-6 cells grown in the presence of putrescine was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Migration of IEC-6 cells: a model for mucosal healing

Cell migration is the principal force behind the early restitution of erosions of the mucosa of the gastrointestinal tract. Despite the importance of cell migration to healing, no attempts to study the process in culture have been reported. We have attempted to standardize conditions for migration and test the migration responses of the small intestinal epithelial crypt cell line IEC-6 in some experimental situations already well known in vivo. We found good correspondence between in culture and in vivo on the following points: 1) migration was independent of DNA synthesis; 2) DNA synthesis was not concentrated at the wound edge; and 3) inhibition of actin polymerization stopped migration altogether. In addition, the presence of an extracellular matrix maximized migration. Protein inhibitors with different modes of action inhibited cell migration to different degrees, not always commensurate with their inhibition of protein synthesis. Cell surface proteoglycans were important; hyaluronic acid had an effect, but the secretion of a migration-stimulating substance by wounded cells was equivocal. Significantly, alpha-difluoromethylornithine (DFMO), which inhibits ornithine decarboxylase and polyamine synthesis, almost totally prevented cell migration. Because DFMO also prevents healing of mucosal erosions in vivo, we believe that this model can be used, keeping in mind its spatial limitations, to study the process of cell migration involved in the early restitution of mucosal erosions.

Clinical pulmonary function testing in dogs and cats

Pulmonary function testing is a relatively new area in clinical veterinary medicine, with few individuals currently obtaining TBFVL and pulmonary mechanics on a clinical cases of respiratory disease in dogs and cats. ABG analysis is a technique available to all veterinarians through commercial laboratories or local hospitals. Information obtained from these tests will allow for a better understanding of the pathophysiology of naturally occurring diseases as well as assisting in the determination of the efficacy of various therapeutic agents (such as bronchodilators), which to date has been lacking in veterinary medicine.

Circadian rhythm of ornithine decarboxylase activity in small intestine of fasted rats

The aim of this study was to determine whether the circadian changes in ornithine decarboxylase (ODC) activity of different segments of the small intestine were governed by factors other than food intake. First, the effects of fasting on mucosal ODC activity were examined. The results indicate that mucosal ODC activity in 24 hr and 48 hr fasted rats decreased significantly compared with ad libitum-fed rats. Second, the circadian rhythm of mucosal ODC activity was characterized by measuring mucosal ODC activity in fasted rats at four time points (09:00, 15:00, 21:00, and 03:00 hr; light period: 06:00-18:00 hr). The results from this study indicate that there is a detectable baseline ODC activity in different segments of fasting intestine. In duodenum, mucosal ODC activity was highest at 15:00 hr (light period), a time at which the rat was normally not eating. In jejunum and ileum, mucosal ODC activity increased between 21:00 and 03:00 hr (dark period). The observation that small intestine exhibits a distinct circadian rhythm of ODC activity in fasted rats suggests that not only food but also intrinsic factors can modulate physiologic oscillations in mucosal ODC activity.

Role of transglutaminase and protein cross-linking in the repair of mucosal stress erosions

We have recently demonstrated that polyamines are absolutely required for gastric and duodenal mucosal repair after stress. Polyamines act as substrates for transglutaminase and facilitate protein cross-linking. The current study tests whether transglutaminase and protein cross-linking are involved in the mechanism of mucosal healing. Rats were fasted 22 h, placed in restraint cages, and immersed in water to the xiphoid process for 6 h. Animals were killed immediately or 4, 12, or 24 h after stress. Gastric and duodenal mucosa were examined histologically and grossly, and transglutaminase activity was measured. Transglutaminase activity in gastric and duodenal mucosa was increased significantly from 0 to 8 h, peaking 4 h after the 6-h stress period. By 12 h, enzyme activity in duodenal mucosa had returned to control values while gastric mucosal transglutaminase did not decrease to control values until 24 h. Mucosal recovery from lesions produced by stress was evident 12 h after stress and was almost complete by 24 h. Dansylcadaverine (100 mg/kg, orally), a specific inhibitor of protein cross-linking, not only prevented the increases in transglutaminase but significantly decreased healing in both tissues. Oral administration of the polyamine spermidine (100 mg/kg) immediately after stress totally prevented inhibition of repair caused by blocking ornithine decarboxylase with difluoromethylornithine (DFMO, 500 mg/kg). Administration of dansylcadaverine, together with spermidine, significantly prevented the beneficial effect of spermidine on mucosal healing in the DFMO-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Ornithine decarboxylase in large bowel mucosa: regulation by gastrin, secretin and EGF

Rats were fasted 48 h and then injected once with either saline, pentagastrin, EGF, secretin or combinations of secretin and pentagastrin or EGF. Another group of rats was fasted and refed. Animals were killed 4 h later and ODC assayed in mucosa of the cecum, proximal colon, and distal colon. EGF significantly increased ODC activity in all 3 tissues. Secretin had no effect by itself on ODC or ODC stimulated by EGF. Pentagastrin significantly increased ODC of the cecum, and secretin completely inhibited the effect of pentagastrin. Refeeding fasted rats significantly induced activity in all three tissues. Immunocytochemistry using a highly specific polyclonal ODC antibody showed that ODC was confined to the crypt cells of the proximal colon. Antibody dilution techniques demonstrated that gastrin, EGF and refeeding increased the level of enzyme in these cells. Refeeding in addition caused the appearance of enzyme in surface epithelial cells. These results showed that colonic mucosal ODC is present in proliferative cells and is regulated by the same peptides known to regulate growth in this tissue. Colonic mucosal ODC also responds the same way as it does in the oxyntic gland and small bowel mucosa.