Primary cultures of rat pancreatic acinar cells in serum-free medium

Summary Rat pancreatic acinar cells were isolated and cultured in Ham's F12 medium with 15% bovine calf serum. Caerulein, insulin, somatostatin, and dexamethasone (DEX) had no effect on intracellular or secreted amylase in these cultured cells. A serum-free medium, using Waymouth's MB 752/1 supplemented with albumin, epidermal growth factor (EGF), DEX, and HEPES, was then developed to avoid serum factors that might mask hormonal effects. In this SF medium, pancreatic acinar, cells maintained the morphological and ultrastructural characteristics of freshly isolated cells and secreted amylase in response to the secretagogue, carbamyl choline. Insulin, at a concentration of 1 μg/ml, significantly increased intracellular and secreted amylase activity after 3 d. This model cell system can be used to study the regulation of the synthesis of amylase and other pancreatic enzymes in vitro.     

Antibiotic Susceptibilities of Serratia marcescens and Enterobacter liquefaciens

Production of 5'-nucleotides by Serratia marcescens and Enterobacter liquefaciens correlates with deoxyribonuclease production, indicating the close relationship between these two organisms. To determine further relationships, susceptibilities of 279 strains of the tribe Klebsielleae were determined by the high-potency disc method, agar-dilution method, or both, by using 14 antibiotics. Ninety-seven per cent of S. marcescens (201 of 207 strains) and 100% of E. liquefaciens (17 strains) had minimum inhibitory concentration (MIC) of 100 mug/ml or greater with colistin and polymyxin B. With these two antibiotics, 93% of other Enterobacter species (28 strains) had MIC values of less than 1.6 mug/ml, and 100% of Klebsiella (27 strains) had MIC values less than 1.6 mug/ml. Consistent patterns were not noted with the other antibiotics tested, but the results with colistin and polymyxin B provide additional evidence of the close relationship of S. marcescens and E. liquefaciens.     

The flight of pipistrelle bats Pipistrellus pipistrellus during pregnancy and lactation

A group of 20 pipistrelle bats were taken into captivity and allowed free flight and association within a flight room where they gave birth to and successfully reared 17 young. The flight of the females was recorded during pregnancy, early lactation and post-lactation by using stroboscopic stereophotogrammetry (153 flights reconstructed in total). During the investigation body mass was altering owing to reproductive condition, and changes in mass were recorded daily for all (adult and juvenile) bats during the entire study period, which lasted from two weeks before the last birth until release, when the oldest baby was 43 days old. All bats were individually marked, and detailed morphological measurements were made. Pregnant and post-lactating bats were heavier than lactating bats, which showed the lowest wingbeat frequencies. The flight speeds of pregnant, lactating and post-lactating bats showed no significant differences, and this may be because the pregnant bats appeared to have a wider scope for selecting flight speed than the other two reproductive groups, or than animals studied previously. The group of bats as a whole decreased flight speed (scaling as M^-043) and increased wingbeat frequency (scaling as M^0.58) as their mass increased. Wingbeat amplitude showed no relation to body mass, wing area or span, flight speed or frequency. A flight performance model applied to the experimental results and optimum flight conditions is used to predict cost of transport and mechanical power for steady flight, and equilibrium wingbeat amplitude which is compared with observations.     

Strain distribution pattern in AXB and BXA recombinant inbred strains for loci on murine Chromosomes 10, 13, 17, and 18

Strain distribution patterns (SDPs) of selected loci previously mapped to murine Chromosomes (Chrs) 10, 13, 17, and 18 are reported for the AXB, BXA recombinant inbred (RI) strain set derived from the progenitor strains A/J (A) and C57BL/6J (B). The loci included the simple sequence length polymorphisms (D10Nds1, D10Mit2, D10Mit10, D10Mit14, D13Mit3, D13Nds1, D13Mit10, D13Mit13, D13Mit7, D13Mit11, D17Mit18, D17Mit10, D17Mit20, D17Mit3, D17Mit2, D18Mit17, D18Mit9, and D18Mit4), the restriction fragment length polymorphisms Pdea and Csfmr, and the biochemical marker AS-1. These loci were chosen because they map to genomic regions that had few or no genetic markers in the AXB, BXA RI set. Several of these loci also were typed in backcross progeny of matings of the (AXB)F₁ to strain A or B. The strain distribution patterns for chromosomes 10, 13, 17, and 18 are reported, and the gene order and map distances determined from the backcross data. The addition of these markers to the AXB, BXA RI strain set increases the genomic region over which linkage for new markers can be detected.     

The effect of autocorrelation in environmental variability on the persistence of populations: an experimental test

Despite its significance regarding the conservation and management of biological resources, the body of theory predicting that the correlation between successive environmental states can profoundly influence extinction has not been empirically validated. Identical clonal populations from a model experimental system based on the collembolan Folsomia candida were used in the present study to investigate the effect of environmental autocorrelation on time to extinction. Environmental variation was imposed by variable implementation (present/absent) of a culling procedure according to treatments that represented six patterns of environmental autocorrelation. The average number of culling events was held constant across treatments but, as environmental autocorrelation increased, longer runs of both favourable and unfavourable culling tended to occur. While no difference was found among the survival functions for the various treatments, the time taken for 50% of the component populations to become extinct decreased significantly with increasing environmental autocorrelation. Similarly, analysis of all extinct populations demonstrated that time to extinction was shortened as environmental autocorrelation increased. However, this acceleration of extinction can be fully offset if sequential introduction is used in place of simultaneous introduction when founding the populations.     

Optimal choice between feedforward and feedback control in gene expression to cope with unpredictable danger

All organisms face risks of unpredictable danger caused by harmful physical environments, pathogens, parasites or predators. Organisms may have several alternative ways of coping with such dangers. These differ in cost, effectiveness and activation time. We study the conditions under which it is optimal to use different alternatives for damage control. As an example we consider a microbe (such as E. coli), which may experience heat shocks that cause denaturation of proteins in the cell. To restore the denatured proteins the organism produces heat-shock proteins (HSP). There are two different pathways for production of HSP. Some HSP are produced immediately after a heat shock (feedforward control), but additional HSP may be produced thereafter, stimulated by the presence of denatured proteins (feedback control). Feedforward is based solely on heat-shock intensity without accurate information on the resulting amount of denatured proteins. We examine the optimal combination of the two pathways that minimizes the sum of the damage caused by the presence of untreated denatured proteins and the production cost of HSP. The optimal response depends on the time delay for feedback control, the effectiveness of HSP in processing denatured proteins, the production cost of HSP, the severity of damage by denatured proteins and the probability distribution of the abundance of denatured protein conditional on heat-shock intensity. We find that feedforward control should always be used. Additional HSP may be produced by feedback control when the abundance of denatured protein is large whilst no feedback control should be used when it is small. All the HSP are produced by feedforward control when the maximum is close to the mean of denatured protein abundance conditional on the heat-shock intensity.     

Genetic heterogeneity in Bacillus sporothermodurans as demonstrated by ribotyping and repetitive extragenic palindromic-PCR fingerprinting

Thirty-eight strains of Bacillus sporothermodurans isolated from ultra-high-temperature (UHT)-treated milk or sterilized milk (UHT isolates) and from animal feed or raw milk (farm isolates) were characterized by automated ribotyping and by repetitive extragenic palindromic (REP)-PCR fingerprinting. By investigating the genetic relationships among isolates from these various sources, the relative importance of different contamination sources could be evaluated. The results of the separate clustering analyses of the PvuII and EcoRI ribopatterns and the REP-PCR patterns were largely consistent with each other and revealed the existence of two main clusters; there was one homogeneous group containing all (REP-PCR) or most (ribotyping) of the UHT isolates, and there was a second more diverse group comprising the farm isolates. A combined three-dimensional analysis of all data showed that three German UHT isolates did not belong to the compact group containing the majority of the UHT isolates. These results demonstrate that B. sporothermodurans is more heterogeneous than previously assumed and that most of the UHT isolates form a genetically distinct subgroup and are capable of producing highly heat-resistant spores. The close genetic relationship of these UHT isolates suggests a clonal origin of a few predominant strains of B. sporothermodurans that can be found in UHT-treated or sterilized milk products.     

The ESS in an asymmetric generalized war of attrition with mistakes in role perception

We derive the ESS for the generalized asymmetric war of attrition, where payoffs to contestants may vary in time and may depend on some characteristic, called the "role" of an individual. We use the same approach as Hammerstein & Parker (1982), who examined an asymmetric war of attrition. We consider two roles, A and B. Role A is assumed to be favoured with respect to payoffs. It is assumed that there is always a true asymmetry, so in each contest one individual has role A and the other has role B. It is assumed that roles are assigned to contestants at random and that they can make mistakes in role perception. It is shown that, under certain assumptions about shapes of payoff functions and probabilities of making mistakes, there is an ESS which can be characterized by two probability distributions with non-overlapping support. Individuals who perceive their role as A should choose larger persistence times. This ESS structure is similar to that in the asymmetric war of attrition. In that model, the resource values and the cost rates are constant. We consider situations where all these values may change in time and where rewards and costs may be equal after some finite time. Such shapes of payoff functions arise naturally in competitive patch depletion (Sjerps & Haccou, 1994a,b). As a result, the probability density functions that specify the conditional strategies are no longer necessarily negative exponentials (as in the war of attrition), but may have very different shapes. Furthermore, under some conditions there is a maximum persistence time, at which there can be an atom of probability. We give explicit expressions as well as numerical approximations for the ESS.     

Establishment success and extinction risk in autocorrelated environments

We consider establishment success (and extinction risk of small populations) in fluctuating environments, by means of an inhomogeneous branching process model. In this model it is assumed that individuals reproduce asexually during discrete reproduction periods. Within each period individuals reproduce independently and have random numbers of offspring. Expected numbers of offspring vary over reproduction periods due to random environmental changes. Previous simulation results indicated that there is a positive autocorrelation between the establishment probabilities of invaders in successive reproduction periods when environmental states are independently distributed. This result was never formally proved. In this paper we prove that this is indeed true, regardless of the form of the distribution of environmental states or the offspring distribution (under a monotonicity condition, which holds for biologically realistic models). Furthermore, we prove that it is also true for positively autocorrelated environmental states. We show by a counterexample that in environments with a strong negative autocorrelation establishment probabilities can be negatively autocorrelated. This was further examined through simulations. Our results imply that in independent, positively autocorrelated and weakly negatively autocorrelated environments the probability of success of invasion in different independently varying sites is the highest, followed by sequential invasion. For environments with a strong negative autocorrelation, sequential invasion has the highest probability of success. Effects of autocorrelation were further examined with simulations. From the results it appears that the expected length of 'runs of bad luck' is the most crucial factor for establishment success.     

Identification, physiological actions, and distribution of TPSGFLGMRamide: a novel tachykinin-related peptide from the midgut and stomatogastric nervous system of Cancer crabs

In most invertebrates, multiple species-specific isoforms of tachykinin-related peptide (TRP) are common. In contrast, only a single conserved TRP isoform, APSGFLGMRamide, has been documented in decapod crustaceans, leading to the hypothesis that it is the sole TRP present in this arthropod order. Previous studies of crustacean TRPs have focused on neuronal tissue, but the recent demonstration of TRPs in midgut epithelial cells in Cancer species led us to question whether other TRPs are present in the gut, as is the case in insects. Using direct tissue matrix assisted laser desorption/ionization Fourier transform mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation, we found that at least one additional TRP is present in Cancer irroratus, Cancer borealis, Cancer magister, and Cancer productus. The novel TRP isoform, TPSGFLGMRamide, was present not only in the midgut, but also in the stomatogastric nervous system (STNS). In addition, we identified an unprocessed TRP precursor APSGFLGMRG, which was detected in midgut tissues only. TRP immunohistochemistry, in combination with preadsorption studies, suggests that APSGFLGMRamide and TPSGFLGMRamide are co-localized in the stomatogastric ganglion (STG), which is contained within the STNS. Exogenous application of TPSGFLGMRamide to the STG elicited a pyloric motor pattern that was identical to that elicited by APSGFLGMRamide, whereas APSGFLGMRG did not alter the pyloric motor pattern.