Effect of rising temperature on the heat resistance of Listeria monocytogenes in meat emulsion

The heat resistance of a strain of L. monocytogenes was determined both in broth and in meat emulsion. The D -values for meat emulsion were approximately two to three times higher than those for broth and also the z -value increased significantly. The micro-organism proved to be more resistant when the cells were heated up slowly (0·5°C/min) to constant temperatures of 60, 63 and 66°C in meat emulsion. The D ₆₀, D ₆₃ and D ₆₆ were, respectively 12·95, 5·4 and 2·3 min. Results may have implications in the survival of Listeria monocytogenes in particular food preparations.     

Effect of pH, temperature and culture medium composition on the production of an extracellular cysteine proteinase by Micrococcus sp. INIA 528

Growth and proteinase production by Micrococcus sp. INIA 528 in a batch-operated laboratory fermentor were investigated, with trypticase soy broth as the basal medium for studies on optimum temperature, pH and medium composition. Maximum growth was recorded at 34°C and pH 715, whereas optimum temperature and pH for proteinase production were 31°C and pH 6.25. Maximum rate of enzyme production occurred during the late log and early stationary phases of growth. Addition of 5.0 g 1^-1 yeast extract, 1.0 g 1^-1 glucose, 1.0 g 1^-1 MgSO₄ or 1.0 g 1^-1 K₂HPO₄ to basal medium resulted in a lower enzyme yield, but supplementation of basal medium with 2.5 g 1^-1 (NH₄)₂SO₄ increased enzyme production by 45%. A high initial biomass added to fresh broth supplemented with 2.5 g 1^-1 (NH₄)₂SO₄ only increased enzyme activity by 19%, compared to the maximum enzyme activity achieved with the standard inoculum.     

Physical factors affecting the toxicity of sprays to stored product insects; the quantity of carrier in which a given amount of active ingredient is applied

The problem of whether a given amount of active ingredient is more effectively applied in concentrated or dilute form is discussed. If y is percentage mortality and x ₁ and x ₂ are respectively log-concentration of active ingredient and log-volume (or deposit) of insecticide applied, y may be regarded as a uniform, continuous function of x ₁ and x ₂. The amount of active ingredient is constant, i.e. x ₁+ x ₂= k , so that
dx/dx₁=−dy/dx₂=δy/δx₁−δy/δx₂
Probit mortality, Y , can be substituted for y in (4). Thus, whether an active ingredient is better applied in concentrated or dilute form depends on the relative magnitudes of ∂ y /∂ x ₁ and ∂ y /∂ x ₂, or of ∂ Y /∂ x ₁ and ∂ Y /∂ x ₂. Equation (4) is true whenever an insecticide consists of an active ingredient in a diluent, whatever the dosage-mortality relationship. Previous work is discussed in the light of (4) and its probit form, and it appears that the concentration at which an active ingredient is best applied can depend upon the nature and quantity of the active ingredient, and the method of application of the spray. There may be other facto*** The probit form of (4) is applied to the probit plane and confirmed experimentally. Flour beetles, Tribolium castaneum Herbst were sprayed with pyrethrins in Shell oil P 31, and it was found that ∂ Y /∂ x ₁ > ∂ Y /∂ x ₂, so that a given quantity of pyrethrins was more toxic in concentrated solution than in dilute.     

Studies of the extracellular proteolytic activity produced by Propionibacterium acnes

Of several commercial media tested, trypticase soya broth containing 0.4% (w/v) D-sorbitol was superior as a growth medium for the production of extracellular proteinase by Propionibacterium acnes (strain P-37). Extracellular proteinase, production of which was shown to be growth-associated by both batch and continuous culture studies, was partially purified by 70% (NH₄)₂SO₄ saturation, Sephadex G-75 chromatography and ion exchange on DEAE-Sephadex A-50. It was shown to be a heterogeneous mixture of at least three molecular species of enzyme. Proteinase I was inhibited by EDTA (10^-3 mol/l) and PMSF (5 millimol/l) and stimulated by CaCl₂ (190% at 10^-3 mol/l). It had a molecular weight of 20 to 30000 and a broad pH optimum from 6.5 to 7.5. Proteinase II was an alkaline proteinase with a molecular weight of 30 to 40000 which was not significantly inhibited by EDTA (10^-2 mol/l) nor stimulated by CaCl₂. Proteinase III represented a minor proportion of the recovered proteolytic activity, had a molecular weight of 20 to 30000 and was most active in the alkaline pH range. This enzyme was inhibited by EDTA (10^-4 mol/l) and PMSF (5 millimol/l), and stimulated by CaCl₂ (250% at 10^-2 mol/l).     

CaMKII associates with CaV1.2 L-type calcium channels via selected β subunits to enhance regulatory phosphorylation

Calcium/calmodulin-dependent kinase II (CaMKII) facilitates L-type calcium channel (LTCC) activity physiologically, but may exacerbate LTCC-dependent pathophysiology. We previously showed that CaMKII forms stable complexes with voltage-gated calcium channel (VGCC) β_1b or β_2a subunits, but not with the β₃ or β₄ subunits ( Grueter et al. 2008 ). CaMKII-dependent facilitation of Ca_V1.2 LTCCs requires Thr498 phosphorylation in the β_2a subunit ( Grueter et al. 2006 ), but the relationship of this modulation to CaMKII interactions with LTCC subunits is unknown. Here we show that CaMKII co-immunoprecipitates with forebrain LTCCs that contain Ca_V1.2α₁ and β₁ or β₂ subunits, but is not detected in LTCC complexes containing β₄ subunits. CaMKIIα can be specifically tethered to the I/II linker of Ca_V1.2 α₁ subunits in vitro by the β_1b or β_2a subunits. Efficient targeting of CaMKIIα to the full-length Ca_V1.2α₁ subunit in transfected HEK293 cells requires CaMKII binding to the β_2a subunit. Moreover, disruption of CaMKII binding substantially reduced phosphorylation of β_2a at Thr498 within the LTCC complex, without altering overall phosphorylation of Ca_V1.2α₁ and β subunits. These findings demonstrate a biochemical mechanism underlying LTCC facilitation by CaMKII.     

Reduced Development of Grey Mould (Botrytis cinerea) in Bean and Tomato Plants by Calcium Nutrition

Fertilization of bean plants grown in perlite with 1 and 3 mM CaCl₂ or Ca(NO₃)₂ reduced severity of grey mould as compared with control plants or plants fertilized with 5 mM of the compounds. Fertilization with Ca(NO₃)₂ reduced severity leaf grey mould and fruit ghost spots of tomato plants grown in perlite by 70 and 45%, respectively. The rate of decrease varied with the position of the fruits on the plants. Leaves from plants treated with calcium or otherwise [KNO₃, (NH₄)₂SO₄] produced less ethylene than leaves of nontreated plants. Rate of growth of B. cinerea was lower on growth medium prepared from washings from leaves of calcium fertilized plants than from leaves from other treatments. The fertilizer combination Ca(H₂PO₄)₂+ CaSO₄ (1 and 3 g/kg soil) applied once to tomato plants grown in soil reduced severity of leaf grey mould by 80 % (significant at P = 0.05) but 1–3 g CaSO₄/kg soil only tended to reduce disease severity (30–40 %, not significant) as compared with the control. The compounds CaCl₂ and Ca(NO₃)₂ increased significantly ( P = 0.05) the growth of B. cinerea on synthetic medium when applied at rates of 1 0–10.0 mM whereas reduction of growth was observed with 0.1 mM of the compounds and of CaSO₄.     

Irreversible blockade of sigma-1 receptors by haloperidol and its metabolites in guinea pig brain and SH-SY5Y human neuroblastoma cells

We evaluated the effect of haloperidol (HP) and its metabolites on [³H](+)-pentazocine binding to σ₁ receptors in SH-SY5Y human neuroblastoma cells and guinea pig brain P₁, P₂ and P₃ subcellular fractions. Three days after a single i.p. injection in guinea pigs of HP (but not of other σ₁ antagonists or (−)-sulpiride), [³H](+)-pentazocine binding to brain membranes was markedly decreased. Recovery of σ₁ receptor density to steady state after HP-induced inactivation required more than 30 days. HP-metabolite II (reduced HP, 4-(4-chlorophenyl)-α-(4-fluorophenyl)-4-hydroxy-1-piperidinebutanol), but not HP-metabolite I (4-(4-chlorophenyl)-4-hydroxypiperidine), irreversibly blocked σ₁ receptors in guinea pig brain homogenate and P₂ fraction in vitro . We found similar results in SH-SY5Y cells, which suggests that this process may also take place in humans. HP irreversibly inactivated σ₁ receptors when it was incubated with brain homogenate and SH-SY5Y cells, but not when incubated with P₂ fraction membranes, which suggests that HP is metabolized to inactivate σ₁ receptors. Menadione, an inhibitor of the ketone reductase activity that leads to the production of HP-metabolite II, completely prevented HP-induced inactivation of σ₁ receptors in brain homogenates. These results suggest that HP may irreversibly inactivate σ₁ receptors in guinea pig and human cells, probably after metabolism to reduced HP.     

Note: Influence of different heating media on thermal resistance of Neosartorya fischeri isolated from papaya fruit

E. RAJASHEKHARA, E.R. SURESH AND S. ETHIRAJ. 1996. A heat-resistant mold identified as a strain of Neosartorya fischeri was isolated from microbiologically spoiled papaya fruits. The optimum heat activation temperature and time for the ascospores of the test mold was found to be 80°C for 15–30 min. The decimal reduction times ( D -values) at 85°, 87° and 89°C in phosphate buffer (pH 7·0) as heating medium were 35·25, 11·1 and 3·90 min respectively and hence the calculated z -value was 4·0°C. In grape and mango juices as heating media, the D _80°C and the D _85°C values were increased as the °Brix level raised from 10 to 45. In commercial fruit juices of mango, orange, pineapple and mango-pineapple blend as heating media D _85°C values were greater than those observed for phosphate buffer.     

Stomatal response to humidity: implications for transpiration

Abstract. Transpiration rates from apple leaves are analysed in terms of the ratio of latent heat flux (λ E ) to leaf net radiation ( Q ₁) and the climatological resistance ( r_i ). Increases in stomatal resistance with increasing leaf to air vapour pressure gradient ( D ), described by an empirical model, are incorporated in the analysis. This humidity effect causes the proportion of energy dissipated as latent heat to fall as Q ₁ increases, so that leaf transpiration rates in high energy environments are likely to be similar to those in lower energy environments. Boundary layer resistance ( r _a) exerts an increasingly important effect on transpiration rates as Q ₁ increases. At constant Q ₁ stomatal closure in response to increasing D results in very small changes in leaf temperature ( T ₁) across a wide range of ambient vapour pressure deficits (δ e ); r _a is then the major factor determining T ₁. The implications of these results are discussed.     

Swimming performance, oxygen consumption and excess post-exercise oxygen consumption in adult transgenic and ocean-ranched coho salmon

Routine oxygen consumption ( M o ₂) was 35% higher in 1 day starved and 21% higher in 4 day starved adult transgenic coho salmon Oncorhynchus kisutch relative to end of migration ocean-ranched coho salmon. Critical swimming speed ( U _crit) and M o ₂ at U _crit ( M o _2max) were significantly lower in 4 day starved transgenic coho salmon (1·25 BL s⁻¹; 8·79 mg O₂ kg⁻¹ min⁻¹) compared to ocean-ranched coho salmon (1·60 BL s⁻¹; 9·87 mg O₂ kg⁻¹ min⁻¹). Transgenic fish swam energetically less efficiently than ocean-ranched fish, as indicated by a poorer swimming economy at U _crit ( M o _2max     ). Although M o _2max was lower in transgenic coho salmon, the excess post-exercise oxygen consumption (EPOC) measured during the first 20 min of recovery was significantly larger in transgenic coho salmon (44·1 mg O₂ kg⁻¹) compared with ocean-ranched coho salmon (34·2 mg O₂ kg⁻¹), which had a faster rate of recovery.     

Differential Effects of 4'-Chlorodiazepam on Expressed Human GABAA Receptors

Abstract: The interactions of the atypical benzodiazepine 4'-chlorodiazepam (Ro 5-4864) with functionally expressed human GABA_A receptor cDNAs were determined. Cotransfection of human α₂, β₁, and γ₂ subunits was capable of reconstituting a 4'-chlorodiazepam recognition site as revealed by a dose-dependent potentiation of t -[³⁵S]butylbicyclophosphorothionate ([³⁵S]TBPS) binding to the GABA-activated chloride channel. This site is found on GABA_A receptor complexes containing sites for GABA agonist-like benzodiazepines and neuroactive steroids. The importance of the α subunit was further demonstrated as substitution of either α₁ or α₃ for the α₂ subunit did not reconstitute a 4'-chlorodiazepam recognition site that was capable of modulating [³⁵S]TBPS binding under the same experimental conditions. The 4'-chlorodiazepam modulatory site was shown to be distinct from the benzodiazepine site, but the phenylquinolines PK 8165 and PK 9084 produced effects similar to 4'-chlorodiazepam, consistent with the previous analysis of the 4'-chlorodiazepam site in brain homogenates. Further analysis of the subunit requirements revealed that coexpression of α₂ and β₁ alone reconstituted a 4'-chlorodiazepam recognition site. It is interesting, however, that the 4'-chlorodiazepam site was found to inhibit [³⁵S]TBPS binding to the GABA-activated chloride channel. Thus, the 4'-chlorodiazepam site may be reconstituted with only the α and β polypeptides.     

Isoform-Specific Effects of Apolipoproteins E2, E3, and E4 on Cerebral Capillary Sequestration and Blood-Brain Barrier Transport of Circulating Alzheimer's Amyloid β

Abstract: Cerebral capillary sequestration and blood-brain barrier (BBB) permeability to apolipoproteins E2 (apoE2), E3 (apoE3), and E4 (apoE4) and to their complexes with sAβ_1–40, a peptide homologous to the major form of soluble Alzheimer's amyloid β, were studied in perfused guinea pig brain. Cerebrovascular uptake of three apoE isoforms was low, their blood-to-brain transport undetectable, but uptake by the choroid plexus significant. Binding of all three isoforms to sAβ_1–40 in vitro was similar with a K _D between 11.8 and 12.9 n M . Transport into brain parenchyma and sequestration by BBB and choroid plexus were negligible for sAβ_1–40-apoE2 and sAβ_1–40-apoE3, but significant for sAβ_1–40-apoE4. After 10 min, 85% of sAβ_1–40-apoE4 taken up at the BBB remained as intact complex, whereas free sAβ_1–40 was 51% degraded. Circulating apoE isoforms have contrasting effects on cerebral capillary uptake of and BBB permeability of sAβ. ApoE2 and apoE3 completely prevent cerebral capillary sequestration and blood-to-brain transport of sAβ_1–40. Conversely, apoE4, by entering brain microvessels and parenchyma as a stable complex with sAβ, reduces peptide degradation and may predispose to cerebrovascular and possibly enhance parenchymal amyloid formation under pathological conditions.     

Environmental induction of Na+ transporter affinity in Atlantic salmon embryos

Atlantic salmon ( Salmo salar L.) alevins hatched from eggs transferred from high- to low-Na water at 250° days, before the onset of the phase of increasing whole egg sodium content (at ∼380°days), showed a significantly reduced K _m for Na⁺ transport, whereas transfer at 400° days did not produce any change in K _m . Alevins hatched from eggs given acid shocks of 1, 3, 7 or 14 days duration initiated at 250 or 400° days showed no significant changes in Na⁺ transporter K _m . Extended acid exposure (38 days) from 250°days to hatching resulted in a slight lowering of K _m (P<0.05). A 24-day acid exposure from 400°days to hatching had no effect on Na⁺ transporter K _m . Alevins hatched from eggs incubated throughout in acidified water had a significantly reduced K _m compared to controls (P<0.01).
The timing and duration of periods of Na depletion of eggs is considered with respect to environmental induction of increased Na transporter affinity in teleost embryos as a mechanism of long-term physiological adaptation to the gradual acidification of natural waters.     

The Effect of Sugars and Polyols on the Heat Resistance of Salmonellae

S ummary . The heat resistance at 65° of 3 strains of salmonellae in solutions of sugars or polyols was enhanced as the concentration of the solutes increased. There was no linear relationship between heat resistance and water activity ( a_w ), but for all solutes except glycerol there was a linear relationship between log D ₆₅ and concentration (% w/w) of solute. Comparison of D ₆₅ at a particular a_w or percentage (w/w) solute concentration showed that the value decreased in the order: sucrose > glucose > sorbitol > fructose > glycerol. In glycerol, D ₆₅ values were always very much lower than in any other solute. With sucrose–glycerol or sucrose–glucose mixtures, heat resistance depended both on the total concentration (% w/w) of solutes present and also on the a_w of the solution.     

Replacement of histidine in position 105 in the α₅ subunit by cysteine stimulates zolpidem sensitivity of α₅β₂γ₂ GABA(A) receptors

Zolpidem is a positive allosteric modulator of GABA_A receptors with sensitivity to subunit composition. While it acts with high affinity and efficacy at GABA_A receptors containing the α₁ subunit, it has a lower affinity to GABA_A receptors containing α₂, α₃, or α₅ subunits and has a very weak efficacy at receptors containing the α₅ subunit. Here, we show that replacing histidine in position 105 in the α₅ subunit by cysteine strongly stimulates the effect of zolpidem in receptors containing the α₅ subunit. The side chain volume of the amino acid residue in this position does not correlate with the modulation by zolpidem. Interestingly, serine is not able to promote the potentiation by zolpidem. The homologous residues to α₅H105 in α₁, α₂, and α₃ are well-known determinants of the action of classical benzodiazepines. Other studies have shown that replacement of these histidines α₁H101, α₂H101, and α₃H126 by arginine, as naturally present in α₄ and α₆, leads to benzodiazepine insensitivity of these receptors. Thus, the nature of the amino acid residue in this position is not only crucial for the action of classical benzodiazepines but in α₅ containing receptors also for the action of zolpidem.     

Effects of river flow on larval growth and survival of Japanese seaperch Lateolabrax japonicus (Pisces) in the Chikugo River estuary, upper Ariake Bay

The abundance and growth history of larval and juvenile Japanese seaperch Lateolabrax japonicus were investigated in the Chikugo River estuary, upper Ariake Bay, from 1990 to 2000. Growth during the larval period (up to 15 mm standard length, L _S, the size at recruitment into the estuary) was backcalculated using sagittal otolith microstructures by the biological intercept method. Growth rates in length declined at body sizes >14 mm L _S. High freshwater discharge through the Chikugo River was associated with high temperatures of the upper Ariake Bay where the larvae spend their planktonic life. Mean larval stage duration (days) from hatch to 15 mm ( D ₁₅) varied between 48·8 and 76·2 days and was inversely correlated with the estimated mean temperature history [mean daily temperature (° C) experienced by the larvae during the period from hatch to 15 mm, T ₁₅]. Mean abundance (number m⁻²) of larvae and juveniles was highest in years when T ₁₅, D ₁₅ and freshwater discharge were at intermediate levels. Although the abundance was not correlated with either of these variables, an exponential relationship between abundance and D ₁₅ was found when data collected during the highest river discharge years (1990, 1991 and 1998) were excluded. The increase in freshwater discharge through the Chikugo River probably had the potential to enhance or diminish Japanese seaperch recruitment in two ways: 1) it could increase recruitment probability by increasing temperature and larval growth and 2) high river flow also had the potential to decrease the probability of immigration into the river by increasing larval seaward dispersion, predation due to decreased turbidity and starvation due to decreased zooplankton prey abundance in the estuary.     

The insecticidal action of some D.D.T. analogues and chlorinated (4-chlorophenyl)-ethanes

The insecticidal effectiveness of D.D.T. is dependent upon the combination of the two chlorophenyl groups with the trichloroethane group. Modification of the latter group results in a loss of toxicity. The toxicity of the compounds possessing =CH.CC1₃, =CH.CHC1₂ and =CH.CH₂C1 groups decreases as the degree of chlorination decreases.
None of the chlorinated (4-Chlorophenyl)-ethane compounds are of the same order of toxicity as D.D.T. The relative potency increases with increasing chlorine content of the side-chain, although complete chlorination results in a compound possessing negligible toxicity. A relationship between toxicity and chlorine content is also seen in the ethylenic compounds, which were formed as intermediates in the synthesis of the ethane derivatives. The comparatively non-toxic ethylenic derivatives of D.D.T. when contrasted with (4-CIC₆H₄) CC1=CC1₂, suggests that the spatial configuration of the molecule may be of importance.     

Chronic Ethanol Administration Regulates the Expression of GABAA Receptor α1 and α5 Subunits in the Ventral Tegmental Area and Hippocampus

Abstract: Ethanol dependence and tolerance involve perturbation of GABAergic neurotransmission. Previous studies have demonstrated that ethanol treatment regulates the function and expression of GABA_A receptors throughout the CNS. Conceivably, changes in receptor function may be associated with alterations of subunit composition. In the present study, a comprehensive (1–12 weeks) ethanol treatment paradigm was used to evaluate changes in GABA_A receptor subunit expression in several brain regions including the cerebellum, cerebral cortex, ventral tegmental area (VTA) (a region implicated in drug reward/dependence), and the hippocampus (a region involved in memory/cognition). Expression of α₁ and α₅ subunits was regulated by ethanol in a region-specific and time-dependent manner. Following 2–4 weeks of administration, cortical and cerebellar α₁ and α₅ subunit immunoreactivity was reduced. In the VTA, levels of α₁ subunit immunoreactivity were significantly decreased after 12 weeks but not 1–4 weeks of treatment. Hippocampal α₁ subunit immunoreactivity and mRNA content were also significantly reduced after 12 but not after 4 weeks of treatment. In contrast, α₅ mRNA content was increased in this brain region. These data indicate that chronic ethanol administration alters GABA_A receptor subunit expression in the VTA and hippocampus, effects that may play a role in the abuse potential and detrimental cognitive effects of alcohol.