Polarity proteins regulate mammalian cell–cell junctions and cancer pathogenesis

Polarity pathways regulate important functions during the formation and maintenance of cell–cell junctions and during morphogenesis. In addition, cell polarity pathways are emerging as critical regulators of initiation and progression of carcinoma by functioning as tumor suppressors, downstream of oncogenes, or promoters of the metastatic process (Figure 2). It is highly likely that further analysis of cell polarity proteins and the pathways they control will identify novel biomarkers and potential drug targets for managing and treating patients with carcinoma.

References and recommended reading

Papers of particular interest, published within the period of review, have been highlighted as:

• of special interest

•• of outstanding interest

Cooled neutrophils become deposited in the microcirculation after infusion: A potential mechanism for microvascular disruption following tissue hypothermia

1. We examined whether changes in rigidity and adhesiveness of neutrophils exposed to cooling and rewarming observed in vitro might impair microvascular perfusion in vivo. Neutrophils from donor rats were fluorescently (calcein-AM) or radioactively (Indium-111) labelled, incubated at 10 or 37 °C in vitro, and infused into recipients. Changes in transit rate and adhesive behaviour within post-capillary venules was quantified in m. extensor digitorum longus (EDL) using intravital microscopy, and tissue distribution determined.

2. There was an increased propensity of cooled cells to undergo adhesion following transfer into the recipient rat. However, cooling had no effect on median transit (354 μm s⁻¹) or rolling (14 μm s⁻¹) velocities during the first 5 min after infusion suggesting that cooling promotes adhesion, but does not delay passage through capillaries. Cooled neutrophils subsequently transformed to stationary adhesion. Their immobilisation was higher than for cells held at 37 °C (P<0.05), and once immobilised they remained firmly adherent to the vessel wall. Cooled, radiolabelled neutrophils showed tissue-specific accumulation after 3 min, but were cleared to the same extent as warmed cells by 20 min.

3. Our data suggest that cooling and rewarming of neutrophils impairs their ability to transit microvessels, reflecting changes in adhesive and mechanical properties observed in vitro, and may contribute to cold-associated circulatory pathology.

Acute effect of a single whole-body cryostimulation on prooxidant–antioxidant balance in blood of healthy, young men

1. We have examined the prooxidative–antioxidative reaction to extremely low temperatures (−130 °C) during a one-time cryostimulation in 15 young, clinically healthy individuals.

2. The total lipid peroxides as the total oxidative status (TOS) and the total antioxidative status (TAS) were measured in blood plasma collected in the morning of the day of cryostimulation, 30 min after the cryostimulation, and on the following morning.

3. The level of stress expressed by total oxidative status in plasma, resulting from exposure to extremely low temperatures, was statistically significantly lowered 30 min after leaving the cryochamber than prior to the exposure. The next day, the TOS level still remained lower than the initial values. The TAS level decreased after leaving the cryochamber and remained elevated the following day.

Low-temperature tolerance of false codling moth Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa

(1) The low-temperature tolerance of false codling moth (FCM) Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a significant aspect of this pest's population dynamics and has implications for post-harvest control and sterile insect technique programs.

(2) Here, we report results of experiments examining the effects of time, temperature and their interactions on low-temperature tolerance in adult FCM. In addition, using a variety of thermal pre-treatments, we examine the potential for hardening responses over several hours to improve low-temperature tolerance in FCM.

(3) Lower lethal temperature assays showed significant effects of time, temperature and significant interactions between time and temperature on survival (p<0.0001 in all cases). The temperature at which the probability of survival of 50% of the FCM population after 2 h of exposure was −4.5 °C, which varied significantly to −0.5 °C in 10 h. Gender and early adult age did not affect low-temperature tolerance of FCM.

(4) Using a range of non-lethal, low- and high-temperature pre-treatments, FCM survival could not be increased (p>0.84) and thus limited evidence for rapid cold hardening was found. These results are discussed with respect to microclimate temperatures in typical FCM environments and have implications for understanding population dynamics in this species and the diversity of low-temperature responses of insects.

The effects of melanocortin agonists and antagonists on leptin-induced fever in rats

1. Over three experiments, separate groups of adult male Sprague–Dawley rats received intracerebroventricular (ICV) injections of either vehicle, recombinant rat leptin (1 μg), or leptin (4 μg), then two ICV injections, 30 min apart of vehicle/vehicle, leptin (4 μg)/vehicle, vehicle/α-MSH (300 ng), or leptin/α-MSH, and then vehicle/vehicle, leptin (4 μg)/vehicle, vehicle/ SHU-9119 (200 ng; a MC 3/4 receptor antagonist), or leptin/SHU-9119. Core temperatures (T_c), food intake and body weights were monitored.

2. Four microgram leptin resulted in the induction of fever, an effect blocked by injection of α-MSH. Antagonism of MC 3/4 receptors with SHU-9119 did not augment leptin-induced fever, but did block the inhibitory actions of leptin on food intake.

3. These data demonstrate the inhibitory effects of exogenous α-MSH on leptin-induced fever, but suggest that endogenous melanocortin action at MC 3/4 receptors does not tonically inhibit febrigenesis caused by leptin administration.

Adaptation to oxidative stress and impact of chronic oxidative stress on immunity in heat-stressed broilers

1. Glutathione peroxidase activity and serum malondialdehyde of heat-stressed broilers were increased in the early period of heat exposure, and then these parameters decreased.

2. The lesion scores of bursa of Fabricius in heat-stressed broilers were increased and decreased in accordance with the activity of glutathione peroxidase and serum malondialdehyde.

3. High environmental temperature had not affected relative bursa of Fabricius weight and NDV-HI titer of heat-stressed broilers.

4. We concluded that heat-stressed broilers could adapt to oxidative stress, and environmental temperature set at 38±2 °C had not affected humoral immunity.

Antioxidative defense organization in retroperitoneal white adipose tissue during acclimation to cold—The involvement of l-arginine/NO pathway

1. Retroperitoneal white adipose tissue (RpWAT) antioxidative defense was investigated in untreated, l-arginine-treated and N^ω-nitro-l-arginine methyl ester (l-NAME)-treated rats kept at 4±1 °C (1, 3, 7, 12, 21 and 45 days) and compared to control rats at 22±1 °C.

2. Cold-acclimation-induced RpWAT weight decrease was accompanied by a decline in glutathione level and increased activity of manganese superoxide dismutase (MnSOD), glutathione S-transferase (GST), catalase, glutathione peroxidase and glutathione reductase at different time-points.

3. l-arginine accelerated RpWAT weight decrease, the increase in MnSOD and GST activities and the prolonged increase of catalase, MnSOD and GST activities. l-NAME delayed cold-induced catalase activity increase and tissue weight decrease. Prolonged l-NAME-treatment had a similar effect on RpWAT as l-arginine.

4. Results suggest the involvement of l-arginine/NO pathway in RpWAT oxidative metabolic augmentation induced by cold-acclimation.

Bioenergetic responses of sub-adult sea cucumber Apostichopus japonicus (Selenka) (Echinodermata: Holothuroidea) to temperature with special discussion regarding its southernmost distribution limit in China

1. This paper investigated the bioenergetic responses of the sea cucumber Apostichopus japonicus (wet weights of 36.5±1.2 g) to different water temperatures (5, 10, 15, 20, 25 and 30 °C) in the laboratory.

2. Results showed that theoretically the optimal temperatures for energy intake and scope for growth (SFG) of sub-adult A. japonicus was at 15.6 and 16.0 °C, respectively. The aestivation threshold temperature for this life-stage sea cucumber could be 29.0 °C by taking feeding cessation as the indication of aestivation.

3. Our data suggests that A. japonicus is thermo-sensitive to higher temperature, which prevents it from colonising sub-tropical coastal zones. Therefore, water temperature plays an important role in its southernmost distribution limit in China.

4. The potential impact of global ocean warming on A. japonicus might be a northward shift in the geographical distribution.

The EU Biocidal Products Directive and the consequences for Dinsinfectants

The title of my presentation suggests or at least anticipates that the EU legislative process, to provide a harmonised regulatory platform for biocides in the EU, has been finalised when this symposium takes place.When adapted and subsequently implemented in the EU member states (estimation Q3 1999), this directive will have a major impact on the market of disinfectants for both the suppliers of active substances and formulators supplying disinfectant products to customers and consumers. This presentation will focus on (technical) regulatory consequences rather than economical or business effects.

• • scope: which products will fall under the regime of this directive, which are excluded?

• • principle: one product—one authorization and mutual recognition; lead times involved?

• • procedure: how will the simplified procedures foreseen (hopefully) help the disinfectant supplier?

• • data requirements: why do the dossier requirements for products and particularly actives need to be so excessively costly and what is the role of risk assessment?

• • transitional arrangements: what can and can't disinfectant suppliers do to keep their products on the market or to introduce new products?

• • review programme: what will happen to the availability of active substances?

The directive itself will not give sufficiient answers to all issues mentioned above to allow a harmonised interpretation across the EU. A number of technical guidance documents is therefore being developed covering Common Principles, Data Requirements and Conditions to include an Active Substance on Annex I. The workability of the whole directive will very much be dependent on the practical details to be dealt with in these documents.Disinfectant suppliers also do recognize the merits of the directive (improved protection of man and the environment, harmonisation across EU, etc.), provided however that it does not undermine the efforts of our industry to deliver better hygiene with safe, effective but also affordable disinfectants.     

Metabolic rate, maximum metabolism, and advantages of torpor in the fat mouse Steatomys pratensis natalensis Roberts, 1921 (Dendeomurinae)

1. The fat mouse Steatomys pratensis natalensis (mean body mass 37.4±0.43 (se)) has a low euthermic body temperature T_b=30.1–33.8 °C and a low basal metabolic rate (BMR)=0.50 ml O₂ g⁻¹ h⁻¹.

2. Below an ambient temperature (T_a)=15 °C, the mice were hypothermic.

3. The lowest survivable T_a=10 °C.

4. Torpor is efficient in conserving energy between T_a=15–30 °C, below T_a=15 °C, the mice arouse.

5. Euthermic and torpid mice were hyperthermic at T_a=35 °C.

6. Thermal conductance was 0.159 ml O₂ g⁻¹ h⁻¹ °C⁻¹, 98.8% of the expected value.

7. Non-shivering thermogenesis (NST) was 2.196 ml O² g⁻¹ h⁻¹ (3.69×BMR).

8. Maximal oxygen consumption, however, was 3.83 ml O₂ g⁻¹ h⁻¹ (6.44×BMR), indicating that other methods of heat production are additive.

9. Because fat mice conserve energy by torpor only between T_a=15–30 °C, we suggest that torpor may be a more important mechanism for surviving food shortages than for surviving cold weather.

Effect of gestational and postnatal environmental temperature on metabolic rate in the altricial rodent, Phyllotis darwini

1. In the altricial rodent, Phyllotis darwini, we found higher body temperatures and faster developmental rates of the thermoregulatory capacity in neonates born from cold- than warm-acclimated mothers.

2. This difference could be explained by maternal effects on the litter, such as high levels of catecholamines and thyroxin levels, high concentration of the uncoupled protein and larger quantity of brown adipose tissue as a consequence of cold acclimation.

3. The exposition of mothers and the maintenance of cold condition during the early development might be responsible of the high metabolism and better thermoregulatory capacity of newborns.

Divergence in morphometric and life history traits in two thermally contrasting Andean populations of Rhinella spinulosa (Anura: Bufonidae)

(1) We studied the variation in characters of two Andean populations of Rhinella spinulosa with different larval thermal regimes as a function of geographic origin and temperature.

(2) In both populations, survival and growth rate were greater at the higher temperature. Size at metamorphosis was only determined by locality, while there was a divergence in growth rate and age at metamorphosis as a function of locality and temperature.

(3) Variation was found in seven of the 12 morphological characters evaluated in post-metamorphic toadlets, which was determined only by their locality of origin.

Trade-off between energy budget, thermogenesis and behavior in Swiss mice under stochastic food deprivation

(1) The role of metabolic rate, thermogenesis and behavior in trade-off strategy was examined in Swiss mice under stochastic food deprivation (FD).

(2) For the mice under severe FD, food intake on feeding days increased, and basal metabolic rate (BMR) and nonshivering thermogenesis decreased significantly. The duration of activity decreased but resting behavior increased significantly on feeding days.

(3) It suggested that a trade-off between increased food intake and decreased energy expenditure related to lower BMR, thermogenesis and activity might be employed to meet reduced calorie intake caused by unpredictable FD.

Inverse relationship of protein concentration and binding activity of alpha-galactoside receptors from sugarcane membranes

1. 1. The binding activity of purified α-galactoside receptor proteins from a number of plant species decreases when the protein concentration is increased from 2 ng/ml to 100 μg/ml.

2. 2. The apparent loss of binding activity at high protein concentrations corresponds to the formation of high molecular weight multimers.

3. 3. Raffinose and melibiose cause a ligand-dependent increase in binding activity and a corresponding decrease in the relative abundance of multimers at any given protein concentration.

4. 4. The self-inhibition of binding activity at high protein concentrations arises from a competition between ligand binding by oligomers and self-association of these oligomers into multimeric species which have little or no binding activity.

Resistance mechanisms of bacteria to antimicrobial compounds

A range of antimicrobial compounds (bactericides) commonly termed biocides, microbicides, sanitizers, antiseptics and disinfectants are available, all of which are claimed by their producers to kill bacteria. Resistance has been defined as the temporary or permanent ability of an organism and its progeny to remain viable and/or multiply under conditions that would destroy or inhibit other members of the strain. Bacteria may be defined as resistant when they are not susceptible to a concentration of antibacterial agent used in practice. Traditionally, resistance refers to instances where the basis of increased tolerance is a genetic change, and where the biochemical basis is known. Antimicrobial substances target a range of cellular loci, from the cytoplasmic membrane to respiratory functions, enzymes and the genetic material. However, different bacteria react differently to bactericides, either due to inherent differences such as unique cell envelope composition and non-susceptible proteins, or to the development of resistance, either by adaptation or by genetic exchange. At low concentrations bactericides often act bacteriostatically, and are only bacteriocidal at higher concentrations. For bactericides to be effective, they must attain a sufficiently high concentration at the target site in order to exert their antibacterial action. In order to reach their target site(s), they must traverse the outer membrane of the gram negative bacteria. Bacteria with effective penetration barriers to biocides generally display a higher inherent resistance than those bacteria which are readily penetrated. The rate of penetration is linked to concentration, so that a sufficiently high bactericide concentration will kill bacteria with enhanced penetration barriers. It has been indicated that susceptible bacterial isolates acquire increased tolerance to bactericides following serial transfer in sub-inhibitory concentrations. Whereas the basis of bacterial resistance to antibiotics is well know, that of resistance to antiseptics, disinfectants and food preservatives is less well understood.Three mechanisms of resistance that have been reported include:

• limited diffusion of antimicrobial agents through the biofilm matrix,

• interaction of the antimicrobial agents with the biofilm matrix (cells and polymer),

• enzyme mediated resistance,

• level of metabolic activity within the biofilm

• genetic adaptation

• efflux pumps and

• outer membrane structure.

     

Induction by 3, 5, 3′ l-triiodothyronine of l-ornithine decarboxylase in rat heart muscle

Injection of 3,5,3′ l-triiodothyronine (15 μg/100 g) induces a biphasic enhancement of rat heart ornithine decarboxylase (EC. 4.1.17) activity after 4 and 21 hours. This induction is observed after each daily injection, but to a lesser extent.The properties of partially purified basal enzyme and induced enzyme, at 21h, after single injections have been compared.

1) Affinity for ornithine is the same for both enzymes, but affinity for pyridoxal-phosphate is 40-fold higher for the induced one.

2) Thermostability studies suggest that basal and induced enzymes have different conformations.

3) The two enzymes have similar immunoreactivity.

4) The comparisons of the time-dependent activity curve after injection and of the antigen/activity ratio suggests that triiodothyronine induces the synthesis of new molecules of enzymes and that an inhibition of the enzyme activity also occurs which explains the biphasic induction.

Pulmonary gas exchange kinetics during exercise: physiological inferences of model order and parameters

1. 1. The ventilatory and pulmonary gas exchange responses during moderate exercise can be appropriately modelled with first-order dynamics.

2. 2. A delay term, reflecting tissue-to-lung transit time, is needed for accurate characterization, however.

3. 3. The O₂ uptake time constant ( reflects the enzymatically controlled tissue O₂ utilization.

4. 4. is appreciably longer than , consequent to the tissue CO₂ capacitance.

5. 5. As typically longer than , transient errors in alveolar and arterial blood gas tensions are predicted: small for P_CO2 but much larger for P_O2.

6. 6. At work rates above the lactate threshold, a slow and delayed component of V̇_O2 induces an additional V̇ component (“excess” V̇_O2), leading to more rapid fatigue.

7. 7. The ventilatory compensation for the metabolic acidemia at these work rates is slow, with compensation being poor for rapid-incremental exercise.

8. 8. A justifiable control model of the coupling of ventilation to metabolism must cohere with these demonstrable physiological characteristics.