NF-Y binds to the CCAAT box motif of the FGF-4 gene and promotes FGF-4 expression in embryonal carcinoma cells

FGF-4 appears to be the first fibroblast growth factor (FGF) expressed during embryogenesis, and its expression is critical for early mammalian development. FGF-4 is expressed in the embryonic cell lines, F9, D3, and NT2/D1; but its expression in these cells is repressed upon differentiation. Transcription of the FGF-4 gene in embryonic cells is regulated by an enhancer in the third exon and by a positive regulatory region upstream of the transcription start site. A CCAAT box motif within the positive regulatory region has been shown to support FGF-4 expression, but the factor that binds to this site in vivo has not been identified. In this report, we demonstrate that the transcription factor complex NF-Y binds to the FGF-4 CCAAT box motif when nuclear extracts from each of the embryonic cell lines and their differentiated cells were examined by gel mobility shift analyses. Importantly, we demonstrate that expression of a dominant-negative NF-YA mutant protein reduces the expression of FGF-4 promoter/reporter gene constructs in F9 EC cells. Hence, we provide strong evidence that the transcription factor NF-Y is involved in the expression of the FGF-4 gene.

Differential expression of NADPH-diaphorase between electrophysiologically-defined classes of pyramidal neurons in rat ventral subiculum, in vitro

The subiculum is the major output region of the hippocampal formation. We have studied pyramidal neurons in slices of rat ventral subiculum to determine if there is a correlation between nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) activity and electrophysiological phenotype. The majority of NADPH-d-positive pyramidal neurons were found in the superficial cell layer (i.e. nearest to the hippocampal fissure) of the subiculum and appreciable NADPH-d activity was absent from pyramidal neurons in area CA1. This distribution of NADPH-d activity was mimicked by that of immunoreactivity for the neuronal isoform of nitric oxide synthase. Subicular pyramidal neurons were classified, electrophysiologically, as intrinsically burst-firing or regular spiking. After electrophysiological characterization, neurons were filled with Neurobiotin and revealed using fluorescence immunocytochemistry. The slices containing these neurons were also processed for NADPH-d. NADPH-d activity was found in six out of eight regular spiking neurons but was not found in any of 13 intrinsically burst-firing neurons (P=0.0008, Fisher's Exact Test). We conclude that in rat ventral subiculum, NADPH-d activity is present in a proportion of pyramidal neurons and indicates the presence of the neuronal isoform of nitric oxide synthase. Furthermore, amongst pyramidal neurons, NADPH-d activity is distributed preferentially to those with the regular spiking phenotype. The distribution of regular spiking neurons suggests that they may not be present to the same extent in all subicular output pathways. Thus, the actions of nitric oxide may be relatively specific to particular hippocampal connections.

Rho proteins play a critical role in cell migration during the early phase of mucosal restitution

In the intestine, several growth factors stimulate migration of epithelial cells, contributing to the maintenance of tissue integrity. The Ras-like GTPase Rho regulates a signal transduction pathway linking growth factor receptors to the formation of actin stress fibers and focal adhesions, presumed to be important for motility. Using an in vitro wound-induced migration assay, we have examined the role of Rho GTPases in the migration of IEC-6 and Caco-2 cells, and provide evidence that the Rho GTPases play an essential role in the initial phase of mucosal wound healing. Treatment of the cells with Clostridium difficile toxins A and B, inhibitors of the Rho family GTPases inhibited migration in a dose-dependent fashion. Microinjection of the inhibitory exchange factor Rho-guanine nucleotide dissociation inhibitor (GDI), or Clostridium botulinum C3 ADP-ribosyl transferase (C3) toxin, a Rho-ADP-ribosylating exoenzyme, potently inhibited migration. Microinjection of RhoT19N, a dominant negative form of RhoA, or in vitro ADP-ribosylated RhoA impaired the ability of cells to migrate. Rho-GDI and C3 exoenzyme also inhibited EGF-induced migration of IEC-6 cells. These results demonstrate that Rho is required for endogenous and EGF-induced migration of small intestinal crypt cells, and that Rho proteins are essential elements of a mechanism by which growth factors induce cell migration to restitute mucosal integrity.

Polyamines are important for attachment of IEC-6 cells to extracellular matrix

The inhibition of ornithine decarboxylase, a rate-limiting enzyme of polyamine biosynthesis, with alpha-difluoromethylornithine in IEC-6 cells (small intestinal crypt cell line) reduces cell migration by 70%, inhibits protein cross-linking, and affects the cytoskeletal assembly. The current study examines the effects of intracellular polyamine depletion on attachment of IEC-6 cells to different matrices. Polyamine deficiency inhibited cell attachment to plastic, laminin, fibronectin, collagen IV, and Matrigel by different extents. Intracellular putrescine restored attachment to all matrices. The presence of a specific inhibitor of protein cross-linking also inhibited attachment to laminin in a dose-dependent manner. The inhibition of cell attachment to plastic and Matrigel was correlated with the inhibition of cell migration. Immunofluorescence studies showed that polyamines are essential for the correct expression of the integrin subunit alpha 2 but not for the expression of the alpha 1-subunit. This study demonstrates that polyamines are important for cell attachment and expression of the integrin alpha 2 beta 1, a putative receptor for collagen and laminin. The impairment of protein cross-linking and the inhibition of the expression of cell surface receptors that bind extracellular matrix (ECM) proteins may be part of the mechanism by which polyamine deficiency retards cell migration in the small intestine.

Polyamines are necessary for normal expression of the transforming growth factor-beta gene during cell migration

The current study tests the hypothesis that intracellular polyamines are involved in the regulation of gene expression of transforming growth factor-beta (TGF-beta) during epithelial cell migration after wounding. Administration of alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase (the first rate-limiting enzyme for polyamine synthesis), depleted cellular polyamines putrescine, spermidine, and spermine in IEC-6 cells. DFMO also significantly reduced basal levels of TGF-beta mRNA in unwounded cells. Gene expression of TGF-beta was dramatically stimulated after wounding of a monolayer of cells not treated with DFMO. TGF-beta mRNA levels significantly increased from 4 to 12 h after wounding, peaking at 6 h at a level eight times the prewounding control. Increased levels of TGF-beta mRNA in IEC-6 cells after wounding were paralleled by an increase in TGF-beta content. Depletion of intracellular polyamines in DFMO-treated cells significantly inhibited increased expression of the TGF-beta gene in response to wounding. Cell migration also significantly decreased in DFMO-treated cells. In the presence of DFMO, exogenous TGF-beta restored cell migration to normal. These results indicate that 1) polyamine depletion induced by DFMO is associated with decreases in the expression of the TGF-beta gene and cell migration in IEC-6 cells and 2) exogenous TGF-beta reverses the inhibitory effect of polyamine depletion on cell migration. These findings suggest that polyamines are required for epithelial cell migration in association with their ability to regulate TGF-beta gene expression.

Use of an amphotericin B lipid complex for treatment of blastomycosis in dogs

OBJECTIVE

To evaluate efficacy and nephrotoxicity of amphotericin B lipid complex used for treatment of dogs with naturally developing blastomycosis.

DESIGN

Prospective clinical trial.

ANIMALS

11 dogs with blastomycosis.

PROCEDURE

All dogs were treated with an amphotericin B lipid complex. Two dogs received a cumulative dose of 8 mg/kg of body weight, 1 received a cumulative dose of 10 mg/kg, and 8 received a cumulative dose of 12 mg/kg.

RESULTS

The 2 dogs that received a cumulative dose of 8 mg/kg and 1 of the dogs that received a cumulative dose of 12 mg/kg had a relapse of blastomycosis within 30 days after treatment. Seven of the remaining 8 dogs were clinically free of blastomycosis 6 months after treatment. One dog died of an unrelated cause 5.5 months after treatment, but did not have clinical signs of blastomycosis at the time of death. There were not any adverse clinical effects attributable to drug administration in any of the dogs in this study, and none of the dogs developed clinical signs of renal disease or failure.

CLINICAL IMPLICATIONS

Amphotericin B lipid complex was a safe and effective treatment for blastomycosis in these dogs.

Relationship between polyamines, actin distribution, and gastric healing in rats

Intragastric administration of 3.4 M NaCl damages the gastric mucosa and increases the activity of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine synthesis. Polyamines are essential for the repair of gastric erosions. Little is known about the restitution of damaged mucosa except that cell migration is essential. Actin is the principal cytoskeletal protein and is essential for migration. This investigation determines the relationship between polyamines, actin, and gastric healing. Rats were fasted for 22 h and given 1.0 ml of 3.4 M NaCl intragastrically and killed 1, 2, 4, 8, and 10 h later. The mucosa was assayed for ODC activity and stained for G- and F-actin. F-actin was concentrated below the damaged mucosa at 1.5, 2, and 4 h. There was no increase in F-actin distribution at any time point, when NaCl-treated animals were given alpha-difluoromethylornithine (DFMO), a specific inhibitor of ODC. In addition, DFMO significantly prevented the healing of the mucosal lesions. Spermidine treatment after DFMO + NaCl significantly prevented the effects of DFMO. Cytochalasin D, a potent actin-disrupting drug, significantly delayed normal gastric mucosal healing. The endogenous polyamines increased significantly in NaCl animals. Data indicate that increases in polyamine synthesis after damage influence the distribution of F-actin in vivo, which may play a part in the healing of mucosal erosions.

Expression of the ornithine decarboxylase gene in response to asparagine in intestinal epithelial cells

Refeeding fasted rats significantly stimulates mucosal growth and ornithine decarboxylase (ODC), the rate-limiting enzyme in the biosynthesis of polyamines, but the exact mechanism responsible for induction of ODC at the molecular level is unknown. Of normal dietary constituents, the amino acid asparagine markedly increases ODC activity and mucosal growth when administered intragastrically. The current study examined the expression of the ODC gene in IEC-6 cells (a line of normal rat small intestinal crypt cells) after exposure to asparagine. Cells were grown in Dulbecco's minimal essential medium containing 5% dialyzed fetal bovine serum. They were deprived of serum for 24 h before experiments. Exposure to asparagine at the dose of 10 mM resulted in the rapid increase in ODC mRNA levels. The increased expression of the ODC gene began 1 h after and peaked between 3 and 5 h after treatment with asparagine. Maximum increases in ODC mRNA levels were approximately fivefold the normal value. Increased levels of ODC mRNA in cells exposed to asparagine were paralleled by increases in ODC protein and enzyme activity and cellular polyamine levels. The half-life of mRNA for ODC in unstimulated IEC-6 cells was approximately 30 min and increased to > 2 h in cells exposed to 10 mM asparagine. The half-life of ODC activity also was increased in asparagine-treated cells. When cellular protein synthesis was inhibited by cycloheximide, asparagine superinduced ODC mRNA levels. Furthermore, asparagine also significantly stimulated DNA synthesis in IEC-6 cells. These results indicate that 1) asparagine stimulates ODC in IEC-6 cells through multiple pathways and 2) increased ODC mRNA levels result partly from a delay in the rate of degradation. These findings suggest that luminal amino acids stimulate gut mucosal growth in association with their ability to regulate ODC gene expression.

Role of ornithine decarboxylase in enterocyte mitochondrial function and integrity

We examined the role of ornithine decarboxylase (ODC) and polyamine biosynthesis in regulating mitochondrial function and integrity along the crypt-villus axis in male Sprague-Dawley rats. Isolated villus tip enterocytes from control rats demonstrated a greater cellular capacity for glucose oxidation than crypt enterocytes. Mitochondrial enzyme activities were similar along the crypt-villus axis. The role of ODC was assessed by treating experimental rats with the irreversible ODC inhibitor alpha-difluoromethylornithine (DFMO) for 24 h. Animals receiving DFMO demonstrated a decreased CO2 production from [2-(14)C]pyruvate along the entire crypt-villus axis coupled with an increase in lactate production in the upper cell populations. CO2 production from [14C]glucose and total ATP levels were not affected by DFMO treatment. Ultrastructural examination revealed localized mitochondrial swelling and bursting only in enterocytes corresponding to the population of cells newly emerged from the crypt during DFMO treatment. In DFMO-treated animals, 2 microM spermine completely prevented the structural mitochondrial injury and restored the metabolic crypt-villus gradient. These results suggest that as enterocytes migrate from the crypt up the villus, mitochondrial function increases to handle the increased metabolic demands placed on the cell by nutrient absorption. ODC activity and polyamines are necessary for this increased mitochondrial function and have a role in the maintenance of mitochondrial integrity in maturing enterocytes migrating from the crypt onto the villus.

Light microscopic localization of calcitonin gene-related peptide in the normal feline trigeminal system and following retrogasserian rhizotomy

Calcitonin gene-related peptide (CGRP) is a neuropeptide that has been implicated in the transmission and modulation of primary afferent nociceptive stimuli. In this study, we describe the light microscopic distribution of CGRP immunoreactivity (IR) within the feline trigeminal ganglion and trigeminal nucleus of normal adult subjects and in subjects 10 and 30 days following complete retrogasserian rhizotomy. Within the trigeminal ganglion of normal subjects, cell bodies and fibers showed CGRP-IR, whereas immunoreactive fibers were rare in the central root region. Within the normal spinal trigeminal and main sensory nuclei, CGRP-IR was seen to form a reproducible pattern that varied between the different nuclei. Following rhizotomy, most, but not all, of the CGRP-IR was lost from the spinal trigeminal and main sensory nuclei, except in regions where the upper cervical roots and cranial nerves VII, IX and X project into the trigeminal nucleus. The pattern seen at 10 days contained more CGRP-IR than that seen at 30 days and suggests that degenerating fibers still show CGRP-IR. In contrast to the decrease seen in the nuclei after rhizotomy, examination of the central root that was still attached to the trigeminal ganglion showed an increase in CGRP-IR within fibers, some of which ended in growth conelike enlargements. Rhizotomy induced a dramatic increase in CGRP-IR within trigeminal motoneurons and their fibers, which was strongest 10 days after rhizotomy and weaker at 30 days, which was still stronger than normal. These results indicate that the majority of CGRP-IR found in the trigeminal nucleus originates from trigeminal primary afferents and that an upregulation of CGRP-IR occurs in trigeminal motoneurons and in regenerating fibers in the part of the central root that was still attached to the ganglion. In addition, the persistence of CGRP-IR fibers in the trigeminal nucleus provides one possible explanation for the preservation of pain in humans following trigeminal rhizotomy.

Role of nonmuscle myosin II in polyamine-dependent intestinal epithelial cell migration

The current study determines whether nonmuscle myosin II is involved in the process requiring polyamines for the stimulation of cell migration in an in vitro model that mimics the early stages of epithelial restitution. Treatment with alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase (ODC), for 4 days totally inhibited ODC activity and depleted intracellular polyamines in the IEC-6 cells. Nonmuscle myosin II concentrations in DFMO-treated cells were decreased by 75%, and stress fibers were sparse or absent. The most striking feature of DFMO-treated cells was the appearance of many small punctate foci of myosin II in the cell interior. Migration of DFMO-treated cells was reduced by 80%. In the presence of DFMO, exogenous putrescine not only returned nonmuscle myosin II levels and distribution toward normal but also restored cell migration to control levels. The administration of wortmannin, an inhibitor of myosin light chain kinase, significantly inhibited cell migration over the denuded area in control cells and in those treated with DFMO + polyamines. These results indicate that 1) polyamine depletion by DFMO is associated with decreased concentration and reorganization of nonmuscle myosin II in IEC-6 cells and 2) exogenous spermidine reverses the inhibitory effects of DFMO.

A light and electron microscopic study of NADPH-diaphorase-, calretinin- and parvalbumin-containing neurons in the rat nucleus accumbens

The rat nucleus accumbens contains medium-sized, spiny projection neurons and intrinsic, local circuit neurons, or interneurons. Sub-classes of interneurons, revealed by calretinin (CR) or parvalbumin (PV) immunoreactivity or reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, were compared in the nucleus accumbens core, shell and rostral pole. CR, PV and NADPH-diaphorase-containing neurons are shown to form three non-co-localising populations in these three areas. No significant differences in neuronal population densities were found between the subterritories. NADPH-diaphorase-containing neurons could be further separated morphologically into three sub-groups, but CR- and PV-immunoreactive neurons form homogeneous populations. Ultrastructurally, NADPH-diaphorase-, CR- and PV-containing neurons in the nucleus accumbens all possess nuclear indentations. These are deeper and fewer in neurons immunoreactive for PV than in CR- and NADPH-diaphorase-containing neurons. CR-immunoreactive boutons form asymmetrical and symmetrical synaptic specialisations on spines, dendrites and somata, while PV-immunoreactive boutons make only symmetrical synaptic specialisations. Both CR- and PV-immunoreactive boutons form symmetrical synaptic specialisations with medium-sized spiny neurons and contact other CR- and PV-immunoreactive somata, respectively. A novel non-carcinogenic substrate for the peroxidase reaction (Vector Slate Grey, SG) was found to be characteristically electron-dense and may be distinguishable from the diaminobenzidine reaction product. We conclude that the three markers used in this study are localised in distinct populations of nucleus accumbens interneurons. Our studies of their synaptic connections contribute to an increased understanding of the intrinsic circuitry of this area.

Altered distribution of the nuclear receptor RAR beta accompanies proliferation and differentiation changes caused by retinoic acid in Caco-2 cells

All epithelial cells require retinoic acid for growth, maintenance, and differentiation. Although the epithelial cells that line the gastrointestinal tract are exposed to extreme retinoid concentration fluctuations in luminal fluid, whether proliferation and differentiation in these cells are significantly affected is not known. We have investigated this question using Caco-2 cells as a model because, although they are derived from a colon adenocarcinoma, they differentiate spontaneously in a manner similar to enterocytes in the small intestine. We found that retinoic acid caused maximum inhibition of cell growth and ornithine decarboxylase activity during the proliferative period. Retinoic acid increased brush border enzyme activities only in differentiating cells but stimulated transglutaminase activity in cells at all stages. In untreated proliferating cells, we found an early peak of transglutaminase activity that has not been reported before. Retinoic acid in intestinal cells acts through its nuclear receptor, RAR beta. The nuclear distribution of this receptor has not been demonstrated. In this study, we show that RAR beta responds to increasing concentrations of retinoic acid with a shift to the nuclear membrane in undifferentiated cells and progressive aggregation, diffusion, and loss in differentiated cells. We conclude that retinoic acid can inhibit proliferation and stimulate differentiation in Caco-2 cells depending on concentration and cell stage, and that these effects are accompanied by changes in distribution, as well as by the loss of RAR beta.

The cellular basis for interaction of sterility factors in the mouse t haplotype

The t haplotypes are variant forms of the proximal one-third of chromosome 17 in the mouse. They contain four inversions (relative to the wildtype DNA) extending over most of this region and house a number of male sterility factors. Males carrying two complete t haplotypes (t/t) are sterile, as are males homozygous for S2, the sterility factor located in the most distal (relative to the centromere) inversion. Males homozygous for the sterility factor S1, located in the most proximal inversion, are not sterile; however, if such a male also is heterozygous for other sterility factors, then sterility results. It has been suggested therefore that homozygosity for S1 enhances the detrimental action of other sterility factors. Sperm from t/t males have severe motility defects and are unable to penetrate investment-free eggs, while sperm from fertile t/+ mice have less serious motility defects and exhibit a delay in penetration of investment-free eggs. To determine whether homozygosity for S1 enhances the cellular defects exhibited by sperm from mice heterozygous for other sterility factors, we compared the motility and egg-penetrating ability of sperm from fertile mice homozygous for S1 to that of sperm from mice carrying one complete t haplotype and one proximal or distal partial t haplotype. The data suggest that sperm from males carrying a proximal partial t haplotype and a complete t haplotype have serious defects in motility and penetration of the investment-free egg, and support the hypothesis that S1 enhances the detrimental effects of other sterility factors within the t haplotype.

Gastrin stimulates expression of protooncogene c-myc through a process involving polyamines in IEC-6 cells

The current study tested the hypothesis that the protooncogene c-myc is involved in the mechanism by which gastrin modulates mucosal cell proliferation. Studies were conducted in the IEC-6 cell line, derived from rat small intestinal crypt cells. Administration of gastrin resulted in the rapid appearance of c-myc mRNA in IEC-6 cells. The increased expression of c-myc began 1 h and peaked 4 h after exposure to gastrin. Maximum increase in c-myc mRNA levels was 7.5-fold the normal value. When cellular protein synthesis was inhibited by addition of cycloheximide, gastrin superinduced c-myc mRNA levels. Gastrin also significantly increased the mRNA levels for ornithine decarboxylase (ODC), the rate-limiting enzyme for polyamine biosynthesis, enzyme activity, and intracellular polyamines in IEC-6 cells. Treatment with alpha-difluoromethylornithine (DFMO), a specific inhibitor of ODC, not only completely depleted intracellular polyamines but also significantly prevented the increased expression of c-myc in cells exposed to gastrin. These results show that 1) gastrin stimulates both polyamine biosynthesis and the expression of the c-myc protooncogene, and 2) depletion of intracellular polyamines by DFMO significantly prevented the increased expression of c-myc by gastrin.

Structural requirements of analogues of polyamines for migration and growth of IEC-6 cells

Healing of gastrointestinal mucosal lesions occurs through two processes: an early one involving cell migration and a later one in which cell division replaces lost cells. Both processes require the presence of polyamines, but the mechanism of action of these compounds is unknown. In the present study, we examined the ability of analogues of spermidine and spermine to support migration and growth of IEC-6 cells that have been grown in alpha-difluoromethylornithine to inhibit polyamines. All analogues of spermidine with the general formula x-3 (referring to the numbers of carbon atoms on either side of the central nitrogen), where x = 2-12, competed with spermidine for entry into the cells. However, in addition to spermidine (x = 4), only compounds for which x = 2, 3, or 6 supported migration and only those for which x = 2 or 7 supported growth. Spermine analogues 3-x-3, for which x = 3, 6, 9, or 12, competed for entry into the cells, but only compounds for which x = 3 or 6 supported migration and only the compound for which x = 3, in addition to spermine (x = 4), supported growth. In addition, analogues 2-3-2, 3-2-3, and 2-(3)2, a branched compound, supported both migration and growth but entered the cell via a mechanism different than that for spermidine and spermine. These data define some of the specific structural requirements for polyamines to produce their physiological effects.

Flow visualization with air and smoke in a bypass graft model under steady flow conditions

A new technique for visualizing the steady flow of a new type of test fluid is presented that produces quality photographic results at Reynolds numbers typically found in arterial bypass grafts. Room air functions as the test fluid and smoke from burning incense sticks provides the tracer particles. As an example of this new technique, photographic results are presented for a Reynolds number flow of 205 through a Plexiglas model of an end-to-side distal anastomosis with a 45 degrees junction angle. The advantages of this technique are that it is simple, convenient, and applicable to a wide variety of flow conditions found in the human cardiovascular system.

Uptake, disposition, and persistence of acrylonitrile in rainbow trout

The uptake and disposition of [2,3-14C]acrylonitrile-derived 14C were studied in rainbow trout by water exposure. Trout were exposed to [14C]ACN at 5.3 micrograms/liter and sampled at various times during a 24-hr uptake phase. After transfer to fresh water, fish were sampled to 72 hr for the estimation of elimination rates and the half-life of 14C. Throughout these experiments several fish were also sacrificed for whole-body autoradiography. The uptake of 14C in carcass and viscera began to level off at 24 hr and the apparent elimination studies, the 14C appeared to persist in both muscle and octanol-water partition coefficient (log p = -0.92). The t1/2 of 14C in muscle in two such experiments was calculated to be 117 and 102 hr. The autoradiographs of whole-body sections of exposed trout also revealed a slow loss of 14C from muscle. Muscle extracts prepared from exposed fish were essentially nondialyzable. When dialyzed muscle extract was analyzed for protein and 14C after SDS-PAGE electrophoresis, most of the 14C was associated with a single protein band with a mobility comparable to standards in the 10,000 Dalton range. These studies indicate that the long halflife of 14C seen in trout muscle may be due to covalent binding of 14C to a protein with a molecular weight of approximately 10,000 Daltons.

Inhibition of ornithine decarboxylase activity but not expression of the gene by cimetidine in intestinal mucosal cells

Cimetidine has been shown to inhibit normal and carcinoma cell growth but the mechanism of the antiproliferative action is incompletely understood. The current study determined the influence of cimetidine on ornithine decarboxylase (ODC) activity, which is the initial rate-limiting enzyme in polyamine biosynthesis, in rat duodenal mucosa and IEC-6 cells (a line of normal rat intestinal crypt cells). Rats were fasted 22 hr before the various treatments and ODC activity was measured in scraped duodenal mucosa. Administration of pentagastrin and epidermal growth factor (EGF) and refeeding fasted rats significantly increased ODC activity in duodenal mucosa. Cimetidine completely inhibited increases in ODC activity in the mucosa stimulated by pentagastrin and EGF, but not by refeeding. Ranitidine and H1-receptor antagonist chlorpheniramine had similar inhibitory effects on ODC activity induced by gastrin. In cultured IEC-6 cells, cimetidine caused a linear and significant inhibition of the stimulation of ODC activity in response to pentagastrin, EGF, 5% dialyzed fetal bovine serum (FBS) and asparagine. ODC messenger RNA (mRNA) levels in IEC-6 cells were significantly increased after exposure to 5% dialyzed FBS and asparagine. Although cimetidine almost completely prevented the induction of ODC activity in IEC-6 cells exposed to serum or asparagine, the increases in ODC mRNA levels were not inhibited by the compound.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of smoking and smoking cessation on longitudinal decline in pulmonary function

Effects of cigarette smoking and smoking cessation on rate of FEV1 decline over 6 yr were examined in 4,451 Japanese-American men from the Honolulu Heart Program who were 45 to 68 yr of age at baseline (1965-1968). Within-person regression was used to calculate annual change in FEV1. Rates of FEV1 decline varied strongly with smoking status and increased significantly with age. Overall, men who continued to smoke experienced steeper rates of decline compared with men who never smoked (-33 ml/yr versus -22 ml/yr, respectively; p = 0.0001). Rates of decline for those who quit smoking during the first 2 yr (-32 ml/yr) were nearly the same as those who continued smoking (-34 ml/yr). After quitting, their rates of decline diminished to a level (-19 ml/yr) similar to that of men who had never smoked (-21 ml/yr). FEV1 decline in continuing smokers was significantly associated with duration of smoking, whereas associations with intensity and pack-years were of borderline significance. Among 216 men with impaired pulmonary function, those who quit smoking had significantly slower rates of FEV1 decline than did those who continued smoking. Potential reasons for quitting included respiratory conditions and stroke. These results extend previous reports of accelerated rates of FEV1 decline in the persons who continue to smoke, and they indicate that smoking cessation leads to less steep rates of decline in pulmonary function over a short period of time in middle-aged men, as well as in men with established pulmonary impairment.

Effects of cigarette smoking on lung function in four population samples in the People's Republic of China. The PRC-US Cardiovascular and Cardiopulmonary Epidemiology Research Group

As part of an ongoing study of cardiopulmonary risk factors in the People's Republic of China, we conducted lung function tests and obtained information about smoking habits on 6,765 Chinese men and women 35 to 56 yr of age residing in or around Beijing in the north and in or around Guangzhou in the south. Within each region, separate urban and rural populations were recruited. This study examined the relationship between tobacco consumption (both manufactured cigarettes and leaf tobacco) and lung function in a subset of current smokers and never smokers who had acceptable lung function data. All methods were strictly standardized. Overall, tobacco smoking was associated with a statistically significant mean difference in FEV1 among men (-89 ml) and women (-52 ml) relative to never smokers after adjusting for age, height, and residence. Differences between smokers of cigarettes and smokers of leaf tobacco were not significant. Among the subset of smokers who smoked only cigarettes, this decrement increased with increasing duration of cigarette smoking, but it was small (-4 ml/yr of smoking for FEV1 for both men and women) in comparison with the effects of smoking reported from western countries. Although the smoking effect tended to increase with increasing dose, these differences were small and generally not statistically significant. The relatively small smoking effect in this study may result from differences between developed and developing countries in the cumulative dose of tobacco products. Alternative explanations or contributing factors such as racial differences in susceptibility and differences in the form and delivery of tobacco cannot be discounted.

Polyamines alter intestinal glucose transport

Polyamines are required for the growth of all eukaryotic cells. Enterocytes respond to luminal nutrients with large increases in polyamine synthesis, even though they are mature, nonproliferating cells. The role of polyamines in these cells is unknown. The current experiments examined whether polyamines affected intestinal transport of glucose, since absorption is the primary activity of enterocytes and since polyamines are known to affect membrane function and stability. Glucose transport was examined in rabbit brush-border membrane vesicles (BBMV). BBMV from rabbits given 5% alpha-difluoromethylornithine (DFMO) in their drinking water 24 h before they were killed transported significantly less glucose than control vesicles [38% decrease in maximal transport rate (Jmax)]. Orogastric administration of spermine, spermidine, or putrescine to DFMO-treated animals 24 h before they were killed prevented the decrease. In rabbits receiving only orogastric spermine, glucose transport was significantly increased (64% increase in Jmax), whereas in vivo spermidine and putrescine decreased Jmax. This increase in Jmax caused by in vivo administration of spermine was not dependent on protein synthesis. Addition of polyamines whether in vivo or in vitro decreased Michaelis constant in vesicles from control and DFMO-treated animals. The change in glucose transport induced by DFMO or polyamines was not related to altered membrane lipid composition or fluidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Sperm from mice carrying one or two t haplotypes are deficient in investment and oocyte penetration

The t haplotypes, mutant forms of the proximal third of mouse chromosome 17 (the t complex), contain factors that contribute to defective sperm function in fertilization. Males carrying two t haplotypes (tx/ty mice) are sterile; their sperm have very poor motility and are unable to penetrate zona-free eggs. Although males carrying one t haplotype (t/+) are fertile, genetic evidence suggests that the sperm carrying the normal form of chromosome 17 (+t) are dysfunctional in fertilization, and some or all sperm have abnormal motility. Some of the same genetic factors that cause sterility in tx/ty males probably contribute to the dysfunction of +t sperm from t/+ males; however, it is unclear which steps in gamete interaction are defective in sperm from t/+ males, or whether the defects are similar to those observed in sperm from tx/ty males. We have developed a unique low sperm:egg ratio IVF assay for sperm function in fertilization. Using this assay, we have shown that tw5/+ sperm are less able than congenic +/+ sperm to penetrate the zona (probably due to their abnormal motility) and to penetrate the zona-free oocyte. Since tw5/tw32 sperm are unable to complete these same two steps in sperm-egg interaction, these specific deficits could be involved in both transmission ratio distortion and sterility. We have also shown that tw5/tw32 sperm are deficient in their ability to bind to the zona and to the oolemma. These results suggest that t haplotypes contain loci which affect a number of sperm functions and thus could be a rich source of genes important for sperm-egg interaction.