Validation of a washing and sanitizing procedure for cantaloupes at a mexican packing facility.

In-plant validation of an alternative washing and sanitizing method was conducted at a cantaloupe packing operation in Mexico. This method consisted of a spray water wash followed by spraying warm (55 to 60 degrees C) 2% (L)-lactic acid solution and was compared with the existing method of spray washing the melons with tap water followed by immersion in a chlorinated water tank. Surface samples (100 cm(2)) were collected from 160 melons subjected to each processing method and tested for counts of aerobic bacteria, coliforms, and Escherichia coli. The aerobic plate counts from cantaloupes washed in the dump tank ranged from 3.6 to 5.2 log CFU/cm(2) and were significantly higher (P < 0.05) than those from melons treated with the alternative spray method, which ranged from 1.8 to 2.6 log CFU/cm(2). Coliform counts for cantaloupes treated in the dump tank were 0.2 to 2.2 log CFU/cm(2) and were below the detection level (-6.0 log CFU/cm(2)) on cantaloupes treated by the spray method. Growth of E. coli was observed in 2.5% of the samples of cantaloupes treated in the dump tank and in none of the samples of cantaloupes treated by lactic acid spray (P < 0.05). These results support the elimination of dump tanks in cantaloupe packing operations established by the Mexican government for certification of firms exporting cantaloupes to the United States. When a sanitizer is to be applied to the product, lactic acid seems to be a viable option, at least for products such as cantaloupes whose quality is not affected by an acid wash.

Phosphodiesterase 3A expression is modulated by nitric oxide in rat pulmonary artery smooth muscle cells.

Phosphodiesterases (PDEs) limit vasodilation in response to a variety of signaling cascades by metabolizing the cyclic nucleotides cAMP and cGMP. The objective of this study was to test the hypothesis that NO regulates expression of PDE3A, a cGMP-inhibited PDE. Incubation of rat pulmonary artery smooth muscle cells (rPaSMCs) with the NO-donor compound S-nitroso-glutathione (GSNO) increased PDE3A gene expression in a dose- and time-dependent manner. NO-donors increased PDE3A protein levels. Total and milrinone inhibitable cAMP PDE activity were increased 2.8 ± 0.1- and 2.0 ± 0.1-fold respectively in extracts of rPaSMCs exposed to GSNO. The effects of GSNO on PDE3A gene expression were mimicked by the soluble guanylate cyclase (sGC) activators YC-1 and BAY 41-2272 and blocked by the sGC inhibitor ODQ. Incubation of rPaSMC with interleukin-1ß and tumor necrosis factor-α induced PDE3A gene expression, an effect which was inhibited by L-NIL, an antagonist of NO synthase 2, or ODQ. Actinomycin D, an inhibitor of RNA polymerase, blocked the GSNO-induced increase of PDE3A mRNA levels, whereas cycloheximide, an inhibitor of protein translation, did not. These observations suggest that NO modulates PDE3A gene expression via mechanisms dependent upon cGMP synthesis and gene transcription. Prolonged exposure to NO may alter the sensitivity of vascular smooth muscle to cGMP- or cAMP-dependent vasodilators, as well as PDE isoform-selective inhibitors.

Time course of training-induced microcirculatory changes and of vegf expression in skeletal muscles of spontaneously hypertensive female rats.

Exercise-induced vessel changes modulate arterial pressure (AP) in male spontaneously hypertensive rats (SHR). Vascular endothelial growth factor (VEGF) is important for angiogenesis of skeletal muscle. The present study evaluated the time course of VEGF and angiogenesis after short- and long-term exercise training of female SHR and Wistar Kyoto (WKY) rats, 8-9 weeks (200-250 g). Rats were allocated to daily training or remained sedentary for 3 days (N = 23) or 13 weeks (N = 23). After training, the carotid artery was catheterized for AP measurements. Locomotor (tibialis anterior and gracilis) and non-locomotor skeletal muscles (temporalis) were harvested and prepared for histologic and protein expression analyses. Training increased treadmill performance by all groups (SHR = 28%, WKY = 64%, 3 days) and (SHR = 141%, WKY = 122%, 13 weeks). SHR had higher values of AP than WKY (174 +/- 4 vs 111 +/- 2 mmHg) that were not altered by training. Three days of running increased VEGF expression (SHR = 28%, WKY = 36%) simultaneously with an increase in capillary-to-fiber ratio in gracilis muscle (SHR = 19%, WKY = 15%). In contrast, 13 weeks of training increased gracilis capillary-to-fiber ratio (SHR = 18%, WKY = 19%), without simultaneous changes in VEGF expression. Training did not change VEGF expression and capillarity of temporalis muscle. We conclude that training stimulates time- and tissue-dependent VEGF protein expression, independent of pressure levels. VEGF triggers angiogenesis in locomotor skeletal muscle shortly after the exercise starts, but is not involved in the maintenance of capillarity after long-term exercise in female rats.

Time course of training-induced microcirculatory changes and of vegf expression in skeletal muscles of spontaneously hypertensive female rats

Exercise-induced vessel changes modulate arterial pressure (AP) in male spontaneously hypertensive rats (SHR). Vascular endothelial growth factor (VEGF) is important for angiogenesis of skeletal muscle. The present study evaluated the time course of VEGF and angiogenesis after short- and long-term exercise training of female SHR and Wistar Kyoto (WKY) rats, 8-9 weeks (200-250 g). Rats were allocated to daily training or remained sedentary for 3 days (N = 23) or 13 weeks (N = 23). After training, the carotid artery was catheterized for AP measurements. Locomotor (tibialis anterior and gracilis) and non-locomotor skeletal muscles (temporalis) were harvested and prepared for histologic and protein expression analyses. Training increased treadmill performance by all groups (SHR = 28 percent, WKY = 64 percent, 3 days) and (SHR = 141 percent, WKY = 122 percent, 13 weeks). SHR had higher values of AP than WKY (174 ± 4 vs 111 ± 2 mmHg) that were not altered by training. Three days of running increased VEGF expression (SHR = 28 percent, WKY = 36 percent) simultaneously with an increase in capillary-to-fiber ratio in gracilis muscle (SHR = 19 percent, WKY = 15 percent). In contrast, 13 weeks of training increased gracilis capillary-to-fiber ratio (SHR = 18 percent, WKY = 19 percent), without simultaneous changes in VEGF expression. Training did not change VEGF expression and capillarity of temporalis muscle. We conclude that training stimulates time- and tissue-dependent VEGF protein expression, independent of pressure levels. VEGF triggers angiogenesis in locomotor skeletal muscle shortly after the exercise starts, but is not involved in the maintenance of capillarity after long-term exercise in female rats.

Internalization of bacterial pathogens in tomatoes and their control by selected chemicals.

The effect of different washing or sanitizing agents was compared for preventing or reducing surface and internal contamination of tomatoes by Salmonella Typhimurium and Escherichia coli O157:H7. The tomatoes were inoculated by dipping them in a bacterial suspension containing approximately 6.0 log CFU/ml of each pathogen and then rinsing them with tap water, hypochlorite solution (250 mg/liter), or lactic acid solution (2%, wt/vol). All treatments were applied by dipping or spraying, and solutions were applied at 5, 25, 35, and 55 degrees C. With the exception of the lactic acid dip at 5 degrees C, all treatments reduced both pathogens on the surfaces of the tomatoes by at least 2.9 cycles. No significantly different results were obtained (P > 0.05) with the dipping and spraying techniques. For internalized pathogens, the mean counts for tomatoes treated with water alone or with chlorine ranged from 0.8 to 2.1 log CFU/g. In contrast, after lactic acid spray treatment, all core samples of tomatoes tested negative for Salmonella Typhimurium and, except for one sample with a low but detectable count, all samples tested negative for E. coli O157:H7 with a plate count method. When the absence of pathogens was verified by an enrichment method, Salmonella was not recovered from any samples, whereas two of four samples tested positive for E. coli O157:H7 even though the counts were negative. Few cells of internalized pathogens were able to survive in the center of the tomato during storage at room temperature (25 to 28 degrees C). The average superficial pH of tomatoes treated with tap water, chlorine, or lactic acid was 4.9 to 5.2, 4.1 to 4.3, and 2.5, respectively (P < 0.05), whereas no differences were observed in the internal pH (3.6 to 3.7) of the tomatoes treated with different sanitizers. The general practice in the tomato industry is to wash the tomatoes in chlorinated water. However, chlorine is rapidly degraded by organic matter usually present in produce. Therefore, lactic acid sprays may be a more effective alternative for decontaminating tomato surfaces. The use of warm (55 degrees C) sprays could reduce pathogen internalization during washing.

sGC and PDE5 are elevated in lambs with increased pulmonary blood flow and pulmonary hypertension.

Utilizing aortopulmonary vascular graft placement, we established a lamb model of pulmonary hypertension that mimics congenital heart disease with increased pulmonary blood flow. We previously demonstrated that endothelial nitric oxide synthase (eNOS) is increased in lambs at age 4 wk. However, these lambs display a selective impairment of endothelium-dependent pulmonary vasodilation that is suggestive of a derangement downstream of NO release. Thus our objective was to characterize potential alterations in the expression and activity of soluble guanylate cyclase (sGC) and phosphodiesterase type 5 (PDE5) induced by increased pulmonary blood flow and pulmonary hypertension. Late-gestational fetal lambs (n = 10) underwent in utero placement of an aortopulmonary vascular graft (shunt). Western blotting analysis on lung tissue from 4-wk-old shunted lambs and age-matched controls showed that protein for both subunits of sGC was increased in shunted lamb lungs compared with age-matched controls. Similarly, cGMP levels were increased in shunted lamb lungs compared with age-matched controls. However, PDE5 expression and activity were also increased in shunted lambs. Thus although cGMP generation was increased, concomitant upregulation of PDE5 expression and activity may have (at least partially) limited and accounted for the impairment of endothelium-dependent pulmonary vasodilation in shunted lambs.

Cyclic-GMP-binding, cyclic-GMP-specific phosphodiesterase (PDE5) gene expression is regulated during rat pulmonary development.

Increased nitric oxide (NO) production plays a critical role in the mammalian pulmonary vascular adaptation to extrauterine life. NO activates soluble guanylate cyclase, increasing intracellular cGMP concentrations, thereby inducing relaxation of vascular smooth muscle. cGMP is inactivated by cyclic nucleotide phosphodiesterases (PDEs). One PDE isozyme, PDE5, specifically hydrolyzes cGMP, is abundant in lung tissues, and modifies the pulmonary vasodilatory response to exogenous NO. To investigate the regulation of PDE5 gene expression during pulmonary development, PDE5 mRNA levels, as well as cGMP-metabolizing PDE enzyme activity, were measured in the lungs of perinatal and adult rats. RNA blot hybridization revealed that PDE5 mRNA was detectable in fetal lung tissue as early as 18.5 d of the 22-d term gestation and reached maximal levels in neonatal lungs. mRNA levels in adult rat lungs were 3-4-fold less than the levels measured in lungs of 1- and 8-d-old rats. Pulmonary cGMP hydrolytic activity in 1-d-old animals was 30-fold greater than the cGMP hydrolytic activity of adult rat lungs. Zaprinast, a specific PDE5 antagonist, inhibited 52 and 56% of cGMP hydrolytic activity in lungs of 1- and 8-d-old rats, respectively, but only 18% of the activity in adult lungs. In situ hybridization revealed that PDE5 mRNA transcripts were present in the vascular smooth muscle cells of neonatal and adult lungs. PDE5 mRNA was also detected in the alveolar walls of neonatal rat lungs. These results demonstrate that the gene encoding PDE5 is abundantly expressed in the lungs of perinatal rats, and is available to participate in the mammalian pulmonary vascular transition to extrauterine life. Extravascular PDE5 gene expression in neonatal lungs suggests a potentially important nonvascular role for this enzyme during pulmonary development.

Pulmonary soluble guanylate cyclase, a nitric oxide receptor, is increased during the perinatal period.

Nitric oxide (NO) has an important role in the pulmonary vasodilatation associated with the transition from fetal to neonatal life. NO activates pulmonary soluble guanylate cyclase (sGC), an obligate heterodimer composed of alpha1- and beta1-subunits, increasing synthesis of guanosine 3',5'-cyclic monophosphate (cGMP) and leading to vasodilation. In this study, regulation of sGC subunit expression during pulmonary development was examined. RNA blot hybridization revealed abundant alpha1- and beta1-subunit mRNA in lungs of late-gestation fetal and neonatal Sprague-Dawley rats, with markedly reduced levels detected in adult lungs. Pulmonary sGC enzyme activity in the presence of 1 mM sodium nitroprusside, a NO-donor compound, was approximately sevenfold greater in 1- and 8-day-old rats than in adult rats (P < 0.03). With the use of immunoblot techniques, pulmonary alpha1-subunit concentrations closely correlated with mRNA levels. With in situ hybridization, alpha1- and beta1-subunit mRNAs were readily detected in pulmonary vascular and bronchial smooth muscle cells as well as alveolar and serosal epithelial cells in lungs of 1-day-old rats. In adult lungs, sGC subunit mRNAs were present at low levels and were found nearly exclusively in bronchial and vascular smooth muscle cells. These results demonstrate that abundant pulmonary sGC is available to respond to the increased NO produced during the perinatal period. High-level expression of sGC subunit genes outside the vasculature of lungs of 1-day-old rats suggests an important role for NO-cGMP signal transduction in the perinatal regulation of pulmonary epithelial function and bronchial tone.

Hyporesponsiveness to inhaled nitric oxide in isolated, perfused lungs from endotoxin-challenged rats.

Inhaled nitric oxide (iNO) causes selective pulmonary vasodilation and improves oxygenation in patients with the adult respiratory distress syndrome (ARDS). Approximately 30% of ARDS patients fail to respond to iNO. Because sepsis syndrome often accompanies a decreased response to iNO, we investigated NO responsiveness in isolated, perfused lungs from rats exposed to lipopolysaccharide (LPS). Eighteen hours after intraperitoneal injection of 0.5 mg/kg LPS, rat lungs were isolated, perfused, and preconstricted with U-46619. Ventilation with 0.4, 4, and 40 parts per million by volume NO vasodilated LPS-pretreated lungs 75, 47, and 42% less than control lungs (P < 0.01 value differs at each concentration). The diminished vasodilatory response to iNO was associated with decreased NO-stimulated guanosine 3',5'-cyclic monophosphate (cGMP) release into the perfusate. Soluble guanylate cyclase activity did not differ in lung extracts from LPS-pretreated and control rats. LPS increased pulmonary cGMP-phosphodiesterase (PDE) activity by 40%. The PDE-sensitive cGMP analogue 8-bromoguanosine 3',5'-cyclic monophosphate vasodilated lungs from LPS-pretreated rats less than lungs from control rats. In contrast, the PDE-insensitive 8-para-chlorophenylthioguanosine 3',5'-cyclic monophosphate vasodilated lungs equally from both groups. After LPS challenge, the rat pulmonary vasculature becomes hyporesponsive to iNO. Hyporesponsiveness to iNO appears partly attributable to increased pulmonary cGMP-PDE activity.