Effect of heat shock on browning-related enzymes in minimally processed iceberg lettuce and crude extracts

The effects of heat shock on PPO and POD activity in minimally processed Iceberg lettuce was examined during storage (10 days). The results were compared with the effect of temperature on crude extracts of these enzymes (in vitro analysis). Fresh-cut lettuce washed at 50 degrees C showed significantly lower PPO and POD activity throughout storage than lettuce washed at 4 degrees C and 25 degrees C. These results were consistent with a sensory analysis in which the panellists found the lowest browning scores in those samples treated at 50 degrees C.When PPO and POD were analysed in vitro, the samples treated at 50 degrees C showed a rapid loss of POD activity and a similar but slower loss of PPO activity in all tissues, while incubation at 4 degrees C and 25 degrees C showed no significant loss of activity. While heat shock did not lead to significant loss of activity it did repress the synthesis of PPO and POD during storage.     

Ascertainment of gastroschisis using the ICD-9-CM surgical procedure code

OBJECTIVE: To determine the effectiveness of using the ICD-9-CM procedure code 54.71 for case ascertainment of gastroschisis. METHODS: Using procedure code 54.71, we queried a statewide hospital discharge database to identify all cases coded as undergoing surgical repair of gastroschisis. Each retrieved case was verified as having gastroschisis by review of the hospital record. All gastroschisis cases were then matched to the Florida Birth Defect Registry (FBDR) dataset. This registry uses a passive system of multiple data sources and employs the ICD-9-CM diagnostic code 756.79 to identify gastroschisis and other abdominal wall defects. RESULTS: Of 93 cases identified by using code 54.71, 92 were confirmed by record review to have gastroschisis. The FBDR identified 87 of the 92 cases (95%). The FBDR missed three of the remaining five cases because of linkage difficulties between inconsistent data elements in the respective data files. The other two cases were not identified by the FBDR because the source database (AHCA discharge) truncates the entry of ICD-9-CM diagnostic codes when more than 10 of them are listed in the medical record. CONCLUSIONS: Use of the surgical procedure code was demonstrated to be superior to the diagnostic code as a method for identification of gastroschisis cases. The same approach may be useful in the detection of malformations other than gastroschisis.     

The Autolysin LytA Contributes to Efficient Bacteriophage Progeny Release in Streptococcus pneumoniae

Most bacteriophages (phages) release their progeny through the action of holins that form lesions in the cytoplasmic membrane and lysins that degrade the bacterial peptidoglycan. Although the function of each protein is well established in phages infecting Streptococcus pneumoniae, the role—if any—of the powerful bacterial autolysin LytA in virion release is currently unknown. In this study, deletions of the bacterial and phage lysins were done in lysogenic S. pneumoniae strains, allowing the evaluation of the contribution of each lytic enzyme to phage release through the monitoring of bacterial-culture lysis and phage plaque assays. In addition, we assessed membrane integrity during phage-mediated lysis using flow cytometry to evaluate the regulatory role of holins over the lytic activities. Our data show that LytA is activated at the end of the lytic cycle and that its triggering results from holin-induced membrane permeabilization. In the absence of phage lysin, LytA is able to mediate bacterial lysis and phage release, although exclusive dependence on the autolysin results in reduced virion egress and altered kinetics that may impair phage fitness. Under normal conditions, activation of bacterial LytA, together with the phage lysin, leads to greater phage progeny release. Our findings demonstrate that S. pneumoniae phages use the ubiquitous host autolysin to accomplish an optimal phage exiting strategy.Streptococcus pneumoniae (pneumococcus), a common and important human pathogen, is characterized by the high incidence of lysogeny in isolates associated with infection (34, 44). Pneumococcal bacteriophages (phages) share with the majority of bacteriophages infecting other bacterial species the “holin-lysin” system to lyse the host cell and release their progeny at the end of the lytic cycle. Genes encoding both holins and lysins (historically termed “endolysins”) are indeed found in the genomes of all known pneumococcal phages (8, 28, 31, 37). Supporting this mechanism, a lytic phenotype in the heterologous Escherichia coli system was achieved only by the simultaneous expression of the Ejh holin and the Ejl endolysin of pneumococcal phage EJ-1 (8). When these proteins were independently expressed, cellular lysis was not perceived. Similar results were shown for pneumococcal phage Cp-1, not only in E. coli, but also in the pneumococcus itself (28).Phage lysins destroy the pneumococcal peptidoglycan network due to their muralytic activity, whereas holins have been shown in S. pneumoniae to form nonspecific lesions (8), most likely upon a process of oligomerization in the cytoplasmic membrane, as observed for the E. coli phage λ (13, 14, 43). It was generally proposed that holin lesions allow access of phage lysins to the cell wall (52, 54), as the majority of phage lysins, including the pneumococcal endolysins, lack a typical N-terminal secretory signal sequence and transmembrane domains (8). However, recent evidence also highlights the possibility for a holin-independent targeting of phage lysins to the cell wall, where holin lesions seem to be crucial for the activation of the already externalized phage lysins (42, 50, 51). Regardless of the mechanism operating in S. pneumoniae to activate phage lysins, holin activity compromises membrane integrity.Pneumococcal cells present their own autolytic activity, mainly due to the presence of a powerful bacterial cell wall hydrolase, LytA (an N-acetylmuramoyl-l-alanine-amidase), responsible for bacterial lysis under certain physiological conditions (47). Although other bacterial species also encode peptidoglycan hydrolases, the extensive lysis shortly after entering stationary phase caused by LytA is a unique feature of S. pneumoniae. Interestingly, LytA is translocated across the cytoplasmic membrane to the cell wall—where it remains inactive—in spite of the absence of a canonical N-terminal sequence signal (7). In the cell wall, autolysin activities are tightly regulated by mechanisms that seem to be related to the energized state of the cell membrane. In fact, depolarizing agents are able to trigger autolysis in Bacillus subtilis (16, 17), and bacteriocin-induced depletion of membrane potential triggers autolysis of some species of the genera Lactococcus and Lactobacillus, closely related to streptococci (29). It is therefore possible that the holin-inflicted perturbations of the S. pneumoniae cytoplasmic membrane upon the induction of the lytic cycle may trigger not only the lytic activity of the phage lysin, but also that of inactive LytA located in the cell wall. Accordingly, LytA could also participate in the release of phage particles at the end of the infectious cycle, especially considering its powerful autolytic activity. Previous studies have suggested a role for the host autolytic enzyme in the release of phage progeny (11, 38), but in fact, the evidence is unclear and dubious, considering that the existence of phage-encoded lysins was unknown or very poorly understood and some of the experimental conditions used to show a role of LytA could have also affected the activity of the phage lysin (38).To clarify the possible role of the bacterial autolysin in host lysis, we used the S. pneumoniae strain SVMC28, lysogenic for the SV1 prophage (34), which contains a typical “holin-lysin” cassette, and a different host strain lysogenized with the same SV1 phage. Our results show that LytA is activated by the holin-induced membrane disruption, just like the phage endolysin. In the absence of the endolysin, LytA is capable of mediating host lysis, releasing functional phage particles able to complete their life cycle. Still, sole dependence on LytA results in an altered pattern of phage release that may reduce phage fitness. Importantly, we also show that, together with the endolysin, the concurrent LytA activation is critical for optimal phage progeny release.     

Role of biliary brush cytology in primary sclerosing cholangitis

OBJECTIVE: To assess the role of brush cytology in the routine evaluation of patients with primary sclerosing cholangitis (PSC). STUDY DESIGN: From January 1995 to June 2000, 64 brush cytology specimens were obtained from 21 patients who had at least one cytologic sample obtained during endoscopic retrograde cholangiography. All patients had a diagnosis of primary sclerosing cholangitis. Cases were classified as benign, atypical or malignant according to major cytologic criteria (nuclear contour and chromatin irregularities) and minor cytologic criteria (polarity, cellularity, nuclear enlargement, mitosis, increased nuclear/cytoplasmic ratio) used by us to diagnose biliary brush cytology. Follow-up was available in all cases. RESULTS: Diagnoses were benign (13), atypical (5) and malignant (3) on cytology. Follow-up of the 13 benign cases showed bile duct stones (2), gallbladder adenocarcinoma at cholecystectomy (1), ascending cholangitis (1) and clinically/cytologically by benign follow-up (9). Five of 13 benign cases had subsequent liver transplantation for liver failure, with explants showing changes of primary sclerosing cholangitis. Of the 3 malignant cases, 1 had carcinoma in situ on biopsy, with the explanted liver showing high grade dysplasia; the second patient had cholangiocarcinoma on explant; and the third had hepatocellular carcinoma on liver five needle aspiration. The 5 patients with atypical cytology were reclassified on review as reactive (3) and atypical not otherwise specified (2). Follow-up showed benign disease in 3 of 3 atypical cases reclassified as reactive; 2 of 2 reclassified as atypical not otherwise specified showed low grade dysplasia in the explant. CONCLUSION: The overall incidence of malignancy was low (3 of 21) in patients with PSC. Bile duct brushing is a sensitive method of detecting neoplasia in the setting of PSC when well-defined cytologic criteria are applied.     

Is stomatal conductance optimized over both time and space in plant crowns? A field test in grapevine (Vitis vinifera)

Crown carbon gain is maximized for a given total water loss if stomatal conductance (g_s) varies such that the marginal carbon product of water (?A/?E) remains invariant both over time and among leaves in a plant crown, provided the curvature of assimilation rate (A) versus transpiration rate (E) is negative. We tested this prediction across distinct crown positions in situ for the first time by parameterizing a biophysical model across 14 positions in four grapevine crowns (Vitis vinifera), computing optimal patterns of g_s and E over a day and comparing these to the observed patterns. Observed water use was higher than optimal for leaves in the crown interior, but lower than optimal in most other positions. Crown carbon gain was 18% lower under measured g_s than under optimal g_s. Positive curvature occurred in 39.6% of cases due to low boundary layer conductance (g_bw), and optimal g_s was zero in 11% of cases because ?A/?E was below the target value at all g_s. Some conclusions changed if we assumed infinite g_bw, but optimal and measured E still diverged systematically in time and space. We conclude that the theory's spatial dimension and assumption of positive curvature require further experimental testing.     

Evolution of age-dependent sex-reversal under adaptive dynamics

We investigate the evolution of the age (or size) at sex-reversal in a model of sequential hermaphroditism, by means of the function-valued adaptive dynamics. The trait is the probability law of the age at sex-reversal considered as a random variable. Our analysis starts with the ecological model which was first introduced and analyzed by Calsina and Ripoll (Math Biosci 208(2), 393–418, 2007). The structure of the population is extended to a genotype class and a new model for an invading/mutant population is introduced. The invasion fitness functional is derived from the ecological setting, and it turns out to be controlled by a formula of Shaw–Mohler type. The problem of finding evolutionarily stable strategies is solved by means of infinite-dimensional linear optimization. We have found that these strategies correspond to sex-reversal at a single particular age (or size) even if the set of feasible strategies is considerably broader and allows for a probabilistic sex-reversal. Several examples, including in addition the population-dynamical stability, are illustrated. For a special case, we can show that an unbeatable size at sex-reversal must be larger than 69.3% of the expected size at death.     

Effects of different nutrients on bacterial growth in a pilot distribution system

The growth of bacterial communities in drinking water distribution systems can lead to the development of problems incompatible with water quality requirements. This study was carried out in order to determine which factors promote bacterial growth in distribution networks. A pilot distribution system was used to perform these experiments. After addition of three different inorganic elements to the network (N, P and S) the results obtained show that they did not contribute to the growth or bacteria either in the circulating water or on the surface of the pipes of the distribution system. However, when organic carbon was added an increase in the number of circulating bacteria was observed though the number of bacteria in the biofilms of the network was constant. These results indicate that in the drinking water of the Barcelona distribution system the factor that controls the growth of bacteria is organic carbon. Moreover, bacteria from the biofilm growing on the surface of the pipes may cause the problems of bacterial growth.     

ORIGINAL ARTICLE: Mass extinctions in the Azores during the last glaciation: fact or myth?

Aim The influence of the last glaciation on the shallow‐water marine malacofauna of the Azores Islands is reviewed. We test, for this fauna, the ‘Pleistocene temperature theory’ of J.C. Briggs, which hypothesizes that a (supposed) lack of endemics in the older (Azorean endemic) fauna resulted from extinctions caused by a severe drop in sea surface temperatures during the Pleistocene. Location Santa Maria Island, Azores, Portugal. Methods We compare the fossil mollusc fauna of Prainha, Praia do Calhau and Lagoinhas Pleistocene outcrops with the recent mollusc fauna of the Azores Islands. We dated the fossil fauna, using shells of Patella aspera Röding, 1798, by standard U/Th methodology at the GEOTOP laboratory (Université du Québec à Montreal, Canada). Results Dating of the shells of P. aspera indicates that the deposition of the lower unit of the Prainha outcrop corresponded to Marine Oxygen Isotope Substage 5e (MISS 5e). Not a single endemic Azorean species of mollusc that is present in the Pleistocene fossil record has since become extinct, and we found no signs of ‘mass extinctions’ in the littoral marine molluscs of the Azores. The only species that were extirpated from these islands were thermophilic molluscs and littoral bivalves living in fine sand. Main conclusions Our results do not support Briggs’‘Pleistocene temperature theory’. Nor did we find evidence supporting the hypothesis that most of the marine organisms now present in the Azores recolonized the islands after the last glacial maximum.     

Effect of mitomycin C and bromodeoxyuridine on Fanconi anemia lymphocytes.

The authors studied the effect of mitomycin C (MMC) and bromodeoxyuridine (BrdU) on the induction of chromosome aberrations on lymphocytes of four patients with Fanconi anemia (FA) and of one normal subject. A control culture and six experiments were designed to test the possible synergic effect of MMC and BrdU. Their results revealed no evidence of MMC-BrdU synergism on the induction of chromosome aberrations in FA lymphocytes. However, chromosomes showed more damage when FA cells were harvested 24 h after MMC stress than when cells were harvested shortly after treatment. This can be explained by a DNA repair defect or by a toxic effect of oxygenation of cells during the procedure.     

Effect of CRF in the median eminence on gonadotropin levels in conscious female rats

To evaluate whether the median eminence (ME) is the site of action of CRF (corticotropin releasing factor) in inhibiting LH levels in female rats, we have injected CRF (1 nmol) directly into the ME and then measured plasma LH and FSH concentrations in conscious ovariectomized (OVX) rats in the absence or presence of a single dose of estradiol benzoate (EB). CRF caused a significant decrease in plasma LH levels in both OVX and OVX + EB rats at 30 min postinjection, in comparison to the values obtained in animals injected with water only. Injection into the ME of water had no effect on plasma LH levels in either OVX or OVX + EB animals. The results suggest that CRF probably inhibits LH secretion, at least in part by a central action on GnRH release in ME.