Activity of Gut-Derived Nisin-like Lantibiotics against Human Gut Pathogens and Commensals

Recent advances in sequencing techniques unveiled the vast potential of ribosomally synthesized and post-translationally modified peptides (RiPPs) encoded in microbiomes. Class I lantibiotics such as nisin A, widely used as a food preservative, have been investigated for their efficacy in killing pathogens. However, the impact of nisin and nisin-like class I lantibiotics on commensal bacteria residing in the human gut remains unclear. Here, we report six gut-derived class I lantibiotics that are close homologues of nisin, four of which are novel. We applied an improved lantibiotic expression platform to produce and purify these lantibiotics for antimicrobial assays. We determined their minimal inhibitory concentration (MIC) against both Gram-positive human pathogens and gut commensals and profiled the lantibiotic resistance genes in these pathogens and commensals. Structure-activity relationship (SAR) studies with analogs revealed key regions and residues that impact their antimicrobial properties. Our characterization and SAR studies of nisin-like lantibiotics against both pathogens and human gut commensals could shed light on the future development of lantibiotic-based therapeutics and food preservatives.

Association between human rhinovirus C and severity of acute asthma in children

A new and potentially more pathogenic group of human rhinovirus (HRV), group C (HRVC), has recently been discovered. We hypothesised that HRVC would be present in children with acute asthma and cause more severe attacks than other viruses or HRV groups. Children with acute asthma (n = 128; age 2-16 yrs) were recruited on presentation to an emergency department. Asthma exacerbation severity was assessed, and respiratory viruses and HRV strains were identified in a nasal aspirate. The majority of the children studied had moderate-to-severe asthma (85.2%) and 98.9% were admitted to hospital. HRV was detected in 87.5% and other respiratory viruses in 14.8% of children, most of whom also had HRV. HRVC was present in the majority of children with acute asthma (59.4%) and associated with more severe asthma. Children with HRVC (n = 76) had higher asthma severity scores than children whose HRV infection was HRVA or HRVB only (n = 34; p = 0.018), and all other children (n = 50; p = 0.016). Of the 19 children with a non-HRV virus, 13 had HRV co-infections, seven of these being HRVC. HRVC accounts for the majority of asthma attacks in children presenting to hospital and causes more severe attacks than previously known HRV groups and other viruses.

Serial viral infections in infants with recurrent respiratory illnesses

To better understand the viral aetiology of recurrent and prolonged illnesses, nasal secretions were prospectively collected from 285 infants at increased risk of developing asthma. Of these, 27 infants had recurrent (at least five) moderate-to-severe respiratory illnesses (MSIs). The viral aetiology of the 150 MSIs and 86 scheduled visits was analysed by molecular diagnostics. The demographic and clinical data were compared with infants who had 0-4 MSIs. Frequently ill infants had higher exposure to other children and more wheezing illnesses than less symptomatic children. Viruses were detected in 136 (91%) out of 150 MSIs, 14 (67%) out of 21 mild illnesses and 29 (45%) out of 65 asymptomatic visits. Human rhinovirus was the most common aetiological agent (61, 43 and 35% in MSIs, mild illnesses and asymptomatic visits, respectively). Mixed viral infections were generally associated with more severe illnesses (27, 0 and 5%, respectively). Among the 27 frequently ill infants, only eight (5.3%) out of 150 MSIs were prolonged (> or =2 weeks duration). Considering all samples, detection of the same virus strain > or =2 weeks apart was unusual (5.3% of all 244 positive findings). Human rhinovirus infections occur early, pervasively and repetitively in these high-risk infants. Infants with prolonged or recurrent respiratory illnesses most often have a series of infections rather than persistent infection with one virus strain.

Preoperative chemoradiation for patients with locally advanced adenocarcinoma of the pancreas

BACKGROUND

Improved resectability is a major theoretical benefit of preoperative chemoradiation for pancreatic cancer. Since 1994, patients at Duke University Medical Center with locally advanced pancreatic cancer have been treated with multimodality preoperative therapy. The purpose of this study was to review our experience with preoperative therapy for locally advanced pancreatic cancer and determine if an aggressive neoadjuvant regimen would not only downstage these tumors pathologically but also improve the odds of complete surgical resection.

METHODS

The charts of 25 patients treated with neoadjuvant chemoradiation at Duke University Medical Center with biopsy-proven, locally advanced adenocarcinoma of the pancreas were reviewed. Tumors were defined as locally advanced based on radiographic or intraoperative evidence of disease that abuts the superior mesenteric artery or vein (n = 22) or involves lymph nodes that are within the proposed radiation field (n = 3). All 25 patients received external beam radiotherapy (median dose 4500 cGy) in daily fractions of 180 cGy over 5 weeks. All patients concurrently received 5-fluorouracil (FU), and many also received mitomycin C or cisplatin, or both. Patients were given a 3- to 4-week break before a restaging computed tomographic (CT) scan was performed. Three patients were not restaged: one died from metastatic disease; one was reclassified as having a neuroendocrine tumor; and one was lost to follow-up.

RESULTS

On restaging after neoadjuvant therapy, 64% of patients had stable or decreased primary tumor size. Radiographically, two patients appeared potentially resectable, and seven others developed evidence of metastatic disease. Eight patients underwent exploration, but only five could be resected. Of the five patients resected, only one had negative margins and negative lymph nodes. This patient had significant pancreatitis on initial exploration. After neoadjuvant therapy, he had a complete response radiographically, and there was no residual cancer in his resection specimen. Pathologic examination of the other resection specimens suggested that despite significant tumor fibrosis, malignant cells persist even at the periphery of the lesions.

CONCLUSION

Although neoadjuvant chemoradiation has many theoretical advantages in managing pancreatic malignancy, true pathologic downstaging of locally advanced lesions into tumors that can be removed with negative nodes and margins appears to be a rare event with currently used therapeutic regimens.

Apoptosis of CD8+ T cells is mediated by macrophages through interaction of HIV gp120 with chemokine receptor CXCR4

CD8-positive T cells are thought to play an important role in the control of infection by human immunodeficiency virus (HIV) as a result of their cytotoxic activity and by releasing soluble factors. In AIDS patients, the absolute number of CD8+ T lymphocytes is decreased in peripheral blood and their turnover rate is increased, suggesting that there is more cell renewal and cell death occurring. Anti-retroviral therapy raises CD8+ T-cell counts in HIV-infected patients. Here we report that the death rate of CD8+ T cells by apoptosis increased markedly during HIV infection of peripheral blood mononuclear cells in vitro. Apoptosis is induced in a dose-dependent manner by recombinant envelope glycoprotein gp120 from HIV strain X4, or by stromal-derived factor-1 (SDF-1), the physiological ligand of the chemokine receptor CXCR4. Apoptosis is mediated by the interaction between tumour-necrosis factor-alpha bound to the membrane of macrophages (mbTNF) and a receptor on CD8+ T cells (TNF-receptor II, or TNFRII). The expression of both of these cell-surface proteins is upregulated by HIV infection or by treatment with recombinant gp120 or SDF-1. Apoptosis of CD8+ T cells isolated from HIV-infected patients is also mediated by macrophages through the interaction between mbTNF and TNFRII. These results indicate that the increased turnover of CD8+ T cells in HIV-infected subjects is mediated by the HIV envelope protein through the CXCR4 chemokine receptor.

Dopamine neurotoxicity in cortical neurons

Dopamine (DA), at concentrations greater than 100 microM, has previously been demonstrated to be toxic to mesencephalic, striatal and dorsal root ganglion cell cultures. Pharmacological experiments suggest that DA also may play a role in the cortical neurotoxicity caused by systemic administration of N-methyl-D-aspartate receptor antagonists such as phencyclidine and MK-801. In this study, the potential toxicity of DA in primary cortical cell cultures was determined in vitro. Using calcein and ethidium homodimer fluorescence as a marker for live and dead cells, respectively, we observed that a 24 h treatment with 10-100 microM DA produced a concentration-dependent increase in the number of ethidium homodimer-labelled cells. The cell death induced by 10 microM DA was dramatically reduced by co-administration of either superoxide dismutase and catalase or deferoxamine mesylate, an iron chelator. To verify this observation, the effects of 10 microM DA on the release of cytoplasmic lactate dehydrogenase (LDH) was measured. DA increased LDH release in a manner that was inhibited by both superoxide dismutase/catalase and deferoxamine. Nomifensine potentiated the effect of DA on LDH release, suggesting a protective role for DA uptake in this system. On the other hand, neither D1 nor D2 antagonists were able to prevent DA-induced LDH release. These data suggest that relatively low concentrations of DA can be injurious to cortical neurons through a mechanism that likely involves DA autooxidation and the formation of reactive oxygen species such as superoxide anion and hydroxyl radical. This mechanism may be important in the toxic effects of psychomotor stimulants such as amphetamine. However, the failure of DA receptor antagonists to affect DA-induced injury argues that the effect of DA on cortical neurons in culture does not model the toxic effect of phencyclidine and MK-801 observed in vivo.

Clinical correlates of body-size distortion

Body-size distortion has been considered a central symptom of eating disorders. We studied 35 female eating-disordered patients and 85 controls using a computer-based body-size estimation technique. We have found almost identical linear relationships between body-size distortion and weight:height ratios in both groups. In the clinical group, distortion scores were not correlated with scores on the Eating Attitudes Test or Beck Depression Inventory but were negatively correlated with body dissatisfaction as measured on the Eating Disorder Inventory. These results raise further questions about the role of body-size distortion both as a diagnostic criterion and as a complicating phenomenon in eating disorders.

Magnetic-resonance imaging used for determining fat distribution in obesity and diabetes

Computed-tomography scanning and magnetic-resonance imaging (MRI) have been used to quantify intraabdominal and subcutaneous fat depots. In this study MRI was used to define fat-distribution patterns in 24 obese females with non-insulin-dependent diabetes (NIDDM) and 12 females with simple obesity. Subjects had anthropometric measurements and single-slice abdominal scans performed at the umbilicus. In addition, in 10 of the nondiabetic females, measurements were repeated after 10 wk of a very-low-calorie diet. Nondiabetic females had significantly less intraabdominal fat (P less than 0.01) than did the diabetics but had equivalent subcutaneous fat. There was no significant relationship between waist-to-hip ratio and intraabdominal fat, subcutaneous fat, or their ratio. After a weight loss of 10.6 +/- 3.8 kg there were significant decreases in both intraabdominal and subcutaneous fat (P less than 0.01). Weight loss is associated with decreases in fat in both depots.

Body-image distortion among male and female college and high school students, and eating-disordered patients

For 179 male and female college and high school students, and 26 female eating-disordered patients body-image distortion was measured using a computer-based image-analysis of redrawn images of standardized human figures. Statistical analysis indicated that body-image distortion was the same for all groups. Body-image distortion was significantly and negatively related to weight:height ratio as a function of a simple polynomial. These results suggest this evaluation of distortion of body-image yields a quantitative measure reliably related to weight status but also suggests the technique, and possibly measurement of body-image distortion in general, may not be a valid discriminator between eating-disordered and normal persons.

Activity of Glyceraldehyde-3-Phosphate Dehydrogenase-NADP in Developing Leaves of Light-Grown Dianthus chinensis L

Quantitative histochemical methods were used to measure glyceraldehyde-3-phosphate dehydrogenase-NADP activity in developing and mature leaves of Dianthus chinensis L. The activity values were compared on the basis of illumination of developing leaves, the maturity of stomata, and the activity of enzymes concerned with carbohydrate oxidation. Activity on a kilogram dry weight per hour basis increased from the youngest primordia (50 mmol) to fully expanded leaves (1900 mmol) and then declined in older, senescing leaves. Enzymic activity increased from leaf base (400 mmol) to tip (1000 mmol) in leaf pair four, the tip of which was exposed to light, while activity of enzymes of carbohydrate oxidation decline. We propose that this leaf is beginning the transition to autotrophy, but does not fix significant amounts of atmospheric carbon because the stomata are not functional until leaf pair six.

Growth reponses of eggplant and soybean seedlings to mechanical stress in greenhouse and outdoor environments

Eggplant (Solanum melongena L. var. esculentum 'Burpee's Black Beauty') and soybean [Glycine max (L.) Merr. 'Wells II'] seedlings were assigned to a greenhouse or a windless or windy outdoor environment. Plants within each environment received either periodic seismic (shaking) or thigmic (flexing or rubbing) treatment, or were left undisturbed. Productivity (dry weight) and dimensional (leaf area and stem length) growth parameters generally were reduced more by mechanical stress in the greenhouse (soybean) or outdoor-windless environment (eggplant) than in the outdoor windy environment. Outdoor exposure enhanced both stem and leaf specific weights, whereas mechanical stress enhanced only leaf specific weight. Although both forms of controlled mechanical stress tended to reduce node and internode diameters of soybean, outdoor exposure increased stem diameter.

Calcitonin gene-related peptide-induced selective inhibition of gastric acid secretion in dogs

Calcitonin gene-related peptide (CGRP) is a 37-residue peptide recently characterized in the brain and found in high concentrations in the gut, particularly in the stomach and pancreas. The effects of intravenous infusion of human and rat CGRP (260 pmol . kg-1 . h-1) on gastric secretion and emptying and pancreatic exocrine secretion were studied in conscious dogs. CGRP inhibited by 60-75% gastric acid secretion stimulated by a meal, sham feeding, or step doses of bombesin but did not modify acid response to step doses of histamine or bethanechol. The inhibitory effect of CGRP is not due to blockage of postprandial or bombesin-stimulated gastrin release. CGRP did not influence basal or meal-stimulated pancreatic exocrine secretion or the rate of gastric emptying of a saline meal. These results indicate that CGRP is a potent and selective inhibitor of gastrin-mediated acid secretion in dogs and, under these conditions, did not alter other gastrointestinal functions such as gastric emptying or pancreatic exocrine secretion.

Spantide: failure to antagonize bombesin-induced stimulation of gastrin secretion in dogs

Spantide ([d-Arg1, d-Trp7,9, Leu11] substance P) was shown to function not only as a substance P receptor antagonist but also as a bombesin receptor antagonist. This study examined the effects of spantide on intravenous bombesin-induced stimulation of gastrin and acid secretion. Dogs were infused with spantide (1 or 10 nmol kg 1 hr 1) or saline and bombesin (60 pmol kg-1 hr-1), and the gastric acid and plasma gastrin responses were monitored. Spantide did not significantly modify gastrin or gastric acid secretion induced by bombesin. It is concluded that spantide may not be a useful bombesin antagonist for in vivo studies.

Cerebroventricular bombesin inhibits gastric acid secretion in dogs

Bolus injections of bombesin into a lateral cerebral ventricle of conscious beagle dogs inhibited pentagastrin-stimulated gastric acid secretion from both the innervated stomach (gastric fistula) and the vagally denervated Heidenhain pouch in a dose dependent manner. Bombesin (300 ng/kg), injected into the lateral ventricle, inhibited acid secretion from the gastric fistula and Heidenhain pouch by 66% +/- 5% and 93% +/- 4%, respectively. Central administration of bombesin also suppressed acid secretion in response to a meal by 52% +/- 15%; postprandial gastrin response was not affected. By contrast, intravenous infusion of bombesin stimulated both gastrin release and acid secretion without affecting the acid response to a submaximal dose of pentagastrin. The opposing effects of central and peripheral bombesin on acid secretion indicate that the gastric response to intracerebrally administered bombesin is mediated by the central nervous system. Furthermore, the inhibitory action of bombesin injected into the lateral cerebral ventricle is independent of the vagus and is not mediated by the inhibition of gastrin release. These observations demonstrate that bombesin-like peptides may act centrally to alter gastric secretion.

Corticotropin-releasing factor inhibits gastric emptying in dogs

The purpose of the present study was to evaluate the effect of ovine corticotropin-releasing factor (CRF) on the gastric emptying of a saline meal in conscious dogs. Intravenous infusion of CRF (220-880 pmol . kg-1 . h-1), induced a significant linear dose dependent inhibition of gastric emptying (16-71%). CRF action was not modified by naloxone and not associated with vomiting or other side effects. Intravenous infusion of sulfated cholecystokinin octapeptide (CCK-8, 50-200 pmol . kg-1 . h-1) inhibited gastric emptying by 29-52%. The relative potency of CRF with respect to CCK-8 is 4 times less. These studies demonstrated that CRF given intravenously in picomolar amount inhibits gastric emptying of a liquid meal in dogs through a mechanism unrelated to opiates. The role of endogenous CRF in stress-induced inhibition of gastric emptying needs to be investigated.

Influence of seismic stress on photosynthetic productivity, gas exchange, and leaf diffusive resistance of Glycine max (L.) Merrill cv Wells II

Relative growth rate (RGR), leaf water potential (psi w), transpiration rate (Tr), photosynthetic rate (Pn), and stomatal and mesophyll resistances to CO2 exchange were measured or calculated to determine how periodic seismic (shaking) stress decreased dry weight accumulation by soybean (Glycine max [L.] Merrill cv Wells II). Seismic stress was applied with a gyratory shaker at 240 to 280 revolutions per minute for 5 minutes three times daily at 0930, 1430, and 1930 hours. Fifteen days of treatment decreased stem length 21%, leaf area 17%, and plant dry weight 18% relative to undisturbed plants. Seismic stress also decreased RGR 4%, which was due entirely to decreased net assimilation rate. Transpiration decreased 17% and leaf psi w increased 39% 30 minutes after treatment. A reduction in Pn began within seconds after the onset of treatment and had declined 16% after 20 minutes, at which time gradual recovery began. Assimilation rate recovered fully before the next seismic treatment 5 hours later. Resistance analysis and calculation of leaf internal CO2 levels indicated that the transitory decrease in Pn caused by periodic seismic stress was due to increased stomatal resistance on the abaxial leaf surface.

Effects of seismic stress on the vegetative growth of Glycine max (L.) Merr. cv. Wells II

Vegetative plants of soybean [Glycine max (L.) Merr. cv. Wells II] grown in a greenhouse and agitated periodically on a gyratory shaker had shorter stems, less leaf area, and lower leaf and plant dry weight than did undisturbed greenhouse-grown (GG) plants after 16 d of treatment. Outdoor-grown (OG) plants, which were subject to additional environmental stresses including ultraviolet radiation, wind loading, and uncontrolled temperature and humidity fluctuations, were smaller and had less dry weight than GG controls, but growth was not inhibited further by gyratory shaking. Periodic shaking of GG soybeans resulted in the same plant and leaf dry weight as for the OG soybeans. Response of GG plants to mechanical stress depended on light intensity, with minimum growth reduction occurring under full light (FL) level, and maximum growth reduction occurring under lower light levels (24-45% FL). Reduction in dry weight gain due to mechanical stress corresponded to a decrease in relative growth rate (RGR). Decreases in net assimilation rate and leaf area ratio contributed equally to the lower RGR of shaken plants, indicating that seismic stress inhibits dry weight accumulation by decreasing both the photosynthetic efficiency and the assimilatory surface of soybean.

Calcitonin gene-related peptide: potent peripheral inhibitor of gastric acid secretion in rats and dogs

Calcitonin gene-related peptide is a 37-residue peptide recently characterized in central and peripheral nervous system. The pharmacologic or physiologic importance of this peptide is not known. We studied the effect of calcitonin gene-related peptide on exogenously stimulated gastric acid secretion (pentagastrin, histamine, bethanechol, and intracisternal thyrotropin-releasing hormone) in the urethane-anesthetized rat. Calcitonin gene-related peptide (2.6 nmol/kg X h) caused a 63%-78% inhibition of gastric acid secretion with all secretagogues tested. The inhibition of gastric acid response to pentagastrin was dose-dependent (2.6-2630 pmol/kg X h), rapid in onset, quickly reversible upon cessation of calcitonin gene-related peptide infusion, and not modified by acute vagotomy or indomethacin pretreatment. In conscious dogs, gastric fistula acid response to pentagastrin was inhibited in a dose-dependent manner by calcitonin gene-related peptide (2.6-260 pmol/kg X h). The acid response of the Heidenhain pouch to pentagastrin was also inhibited by calcitonin gene-related peptide (260 pmol/kg X h). These results show that calcitonin gene-related peptide is a potent inhibitor of gastric acid secretion in the rat as well as in the dog. Its inhibitory action could be demonstrated against various stimuli and appears to be independent of prostaglandin or vagal pathways.