Sex differences in dendritic atrophy of CA3 pyramidal neurons in response to chronic restraint stress

The present study investigated the effects of 21 days of chronic restraint stress on neural and endocrine parameters in male and female rats. Consistent with previous results, repeated restraint stress induced apical dendritic atrophy (a decrease in the number of apical branch points and dendritic length) of the CA3c pyramidal neurons in male rats. In contrast, female rats did not show significant dendritic atrophy in the apical field in response to repeated restraint stress. Female rats did show a decrease in the number of branch points in the basal dendritic tree compared to male rats in response to repeated restraint stress. Baseline and stress levels of plasma corticosterone were higher in female rats compared to male rats. Females exhibited slightly longer increases in corticosterone levels throughout the 21 days of restraint stress than males, indicating that the male corticosterone response to stress exhibited greater habituation. Plasma corticosteroid-binding globulin levels of female rats were also higher than those of male rats throughout the experiment. There was no change in plasma corticosteroid-binding globulin levels in male rats during the restraint stress, while there was a decrease in plasma corticosteroid-binding globulin levels in female rats during the restraint stress. Plasma estradiol levels in female rats also decreased in response to the chronic stress. In view of the qualitatively different dendritic atrophy found in males and females in appears unlikely that sex differences in the corticosteroid-binding globulin and corticosterone response can account for these morphological differences.

Treadmill running produces both positive and negative physiological adaptations in Sprague-Dawley rats

Exercise training produces a vast array of physiological adaptations, ranging from changes in metabolism to muscle mitochondrial biogenesis. Researchers studying the physiological effects of exercise often use animal models that employ forced exercise regimens that include aversive motivation, which could activate the stress response. This study examined the effect of forced treadmill running (8 wk) on several physiological systems that are sensitive to training and stress. Forced treadmill running produced both positive and negative physiological adaptations. Indicative of positive training adaptations, exercised male Sprague-Dawley rats had a decrease in body weight gain and an increase in muscle citrate synthase activity compared with sedentary controls. In contrast, treadmill running also resulted in the potentially negative adaptations of adrenal hypertrophy, thymic involution, decreased serum corticosteroid binding globulin, elevated lymphocyte nitrite concentrations, suppressed lymphocyte proliferation, and suppressed antigen-specific IgM. Such alterations in neuroendocrine tissues and immune responses are commonly associated with chronic stress. Thus treadmill running produces both positive training adaptations and potentially negative adaptations that are indicative of chronic stress. Researchers employing forced activity need to be aware that this type of exercise procedure also produces physiological adaptations indicative of chronic stress and that these changes could potentially impact other measures of interest.

A long-term increase in basal levels of corticosterone and a decrease in corticosteroid-binding globulin after acute stressor exposure

Adrenal glucocorticoids play an important role in mediating many of the behavioral and physiological effects of exposure to stressors. Focus has been primarily on the acute stress-induced rise in glucocorticoids [corticosterone (CORT) in the rat]. There are reports, however, that exposure to chronic stressors can produce an increase in basal CORT and a decrease in corticotropin-binding globulin (CBG). These changes occur subsequent to the stress-induced rise in CORT. The following experiments examined whether exposure to an acute stressor (100 5-sec inescapable tail shocks; IS) could also produce long term changes in basal CORT and CBG. We report that a single session of IS results in an increase in basal total serum CORT that persists 48-96 h after IS termination. The increase is present only at the diurnal trough (morning). CBG levels ae also decreased for 24-48 h. The decrease is present at both the diurnal peak (evening) as well as the trough (morning). These changes result in an increase in the percent and amount of biologically active CORT (unbound or free). Thus, glucocorticoid-sensitive targets are exposed to high levels of free CORT for several days after IS termination. The long term increase in free CORT reported here may play an important role in mediating some of the effects produced by IS as well as those produced by other acute stressors.

The impact of the nonpeptide corticotropin-releasing hormone antagonist antalarmin on behavioral and endocrine responses to stress

The nonpeptide CRH antagonist antalarmin has been shown to block both behavioral and endocrine responses to CRH. However, it's potential activity in blunting behavioral and endocrine sequelae of stressor exposure has not been assessed. Because antagonism of central CRH by alpha-helical CRH attenuates conditioned fear responses, we sought to test antalarmin in this regard. In addition, it remains unclear as to whether this is a result of receptor blockade during conditioning or during testing. Thus, we explored whether CRH mediates the induction or expression of conditioned fear (freezing in a context previously associated with 2 footshocks; 1.0 mA, 5 sec each). Furthermore, because rats previously exposed to inescapable shock (IS; 100 shocks, 1.6 mA, 5 sec each), demonstrate enhanced fear conditioning, we investigated whether this effect would be blocked by antalarmin. Antalarmin (20 mg/kg x 2 ml i.p.) impaired both the induction and expression of conditioned fear. In addition, antalarmin blocked the enhancement of fear conditioning produced by prior exposure to IS. Despite the marked behavioral effects observed in antalarmin-treated rats, antalarmin had no effect on IS-induced rises in ACTH or corticosterone. However, antalarmin did block the ACTH response produced by exposure to 2 footshocks.

Timecourse and corticosterone sensitivity of the brain, pituitary, and serum interleukin-1beta protein response to acute stress

Activation of peripheral immune cells leads to increases of interleukin-1beta (IL-1beta) mRNA, immunoreactivity, and protein levels in brain and pituitary. Furthermore, IL-1beta in brain plays a role in mediating many of the behavioral, physiological, and endocrine adjustments induced by immune activation. A similarity between the consequences of immune activation and exposure to stressors has often been noted, but the potential relationship between stress and brain IL-1beta has received very little attention. A prior report indicated that exposure to inescapable tailshocks (IS) raised levels of brain IL-1beta protein 2 h after IS, but only in adrenalectomized (and basal corticosterone replaced) subjects. The studies reported here explore this issue in more detail. A more careful examination revealed that IL-1beta protein levels in hypothalamus were elevated by IS in intact subjects, although adrenalectomy, ADX (with basal corticosterone replacement) exaggerated this effect. IL-1beta protein increases were already present immediately after the stress session, both in the hypothalamus and in other brain regions in adrenalectomized subjects, and no longer present 24 h later. Furthermore, IS elevated levels of IL-1beta protein in the pituitary, and did so in both intact and adrenalectomized subjects. IS also produced increased blood levels of IL-1beta, but only in adrenalectomized subjects. Finally, the administration of corticosterone in an amount that led to blood levels in adrenalectomized subjects that match those produced by IS, inhibited the IS-induced rise in IL-1beta in hypothalamus and pituitary, but not in other brain regions or blood.

Discrimination between changes in glucocorticoid receptor expression and activation in rat brain using western blot analysis

These studies investigated autoregulation of glucocorticoid receptor (GR) protein expression and activation in rat brain using western blot methodology. By comparing GR immunoblot reactivity present in various tissue subcellular preparations we were able to discriminate between corticosterone-induced changes in GR activation or GR protein expression. Our cytosolic tissue preparation yielded a similar pattern of treatment effects on relative GR as measured by receptor binding assay or western blot. In both cases, short-term adrenalectomy (18 h) produced no change in cytosolic GR. On the other hand, long-term adrenalectomy (3-14 days) resulted in a large increase in cytosolic GR, whereas acute (1-2 h) treatment with high dose corticosterone produced a large decrease in cytosolic GR. Western blot measurement of GR levels in a nuclear extract or whole-cell extract from the same brains indicated that acute corticosterone treatment produced a large increase in nuclear GR and no change in whole-cell GR. Thus, all of the decrease in cytosolic GR observed after acute corticosterone treatment could be accounted for by receptor redistribution to the nuclear tissue fraction as opposed to rapid receptor protein downregulation. Long-term treatment of rats with adrenalectomy or high dose corticosterone produced a large increase and decrease, respectively, in whole-cell GR, indicating genuine changes in receptor protein expression. These studies indicate that in vivo regulation of GR protein expression in the rat brain can be studied using western blot analysis of a whole-cell tissue preparation. This procedure has an important advantage over receptor binding studies in that GR protein expression can be measured in adrenal-intact rats. These studies also support the validity of using cytosolic receptor binding assays to estimate relative changes in GR occupation/activation when appropriate comparison groups are included.

Exogenous corticosterone reduces L-DOPA-induced dyskinesia in the hemi-parkinsonian rat: role for interleukin-1beta

While the etiology of Parkinson's disease (PD) remains unknown, there is overwhelming evidence that neuroinflammation plays a critical role in the progressive loss of dopamine (DA) neurons. Because nearly all persons suffering from PD receive l-DOPA, it is surprising that inflammation has not been examined as a potential contributor to the abnormal involuntary movements (AIMs) that occur as a consequence of chronic l-DOPA treatment. As an initial test of this hypothesis, we examined the effects of exogenously administered corticosterone (CORT), an endogenous anti-inflammatory agent, on the expression and development of l-DOPA-induced dyskinesia (LID) in unilateral DA-depleted rats. To do this, male Sprague-Dawley rats received unilateral medial forebrain bundle 6-hydroxydopamine lesions. Three weeks later, l-DOPA primed rats received acute injections of CORT (0-3.75 mg/kg) prior to l-DOPA to assess the expression of LID. A second group of rats was used to examine the development of LID in l-DOPA naïve rats co-treated with CORT and l-DOPA for 2 weeks. AIMs and rotations were recorded. Exogenous CORT dose-dependently attenuated both the expression and development of AIMs without affecting rotations. Real-time reverse-transcription polymerase chain reaction of striatal tissue implicated a role for interleukin-1 (IL-1) beta in these effects as its expression was increased on the lesioned side in rats treated with l-DOPA (within the DA-depleted striatum) and attenuated with CORT. In the final experiment, interleukin-1 receptor antagonist (IL-1ra) was microinjected into the striatum of l-DOPA-primed rats to assess the impact of IL-1 signaling on LID. Intrastriatal IL-1ra reduced the expression of LID without affecting rotations. These findings indicate a novel role for neuroinflammation in the expression of LID, and may implicate the use of anti-inflammatory agents as a potential adjunctive therapy for the treatment of LID.

Presence and changes in populations of yeasts on raw and processed poultry products stored at refrigeration temperature

A study was undertaken to determine populations and profiles of yeast species on fresh and processed poultry products upon purchase from retail supermarkets and after storage at 5 degrees C until shelf life expiration, and to assess the potential role of these yeasts in product spoilage. Fifty samples representing 15 commercial raw, marinated, smoked, or roasted chicken and turkey products were analyzed. Yeast populations were determined by plating on dichloran rose bengal chloramphenicol (DRBC) agar and tryptone glucose yeast extract (TGY) agar. Proteolytic activity was determined using caseinate and gelatin agars and lipolytic activity was determined on plate count agar supplemented with tributyrin. Populations of aerobic microorganisms were also determined. Initial populations of yeasts (log10 cfu/g) ranged from less than 1 (detection limit) to 2.89, and increased by the expiration date to 0.37-5.06, indicating the presence of psychrotrophic species. Highest initial populations were detected in raw chicken breast, wings, and ground chicken, as well as in turkey necks and legs, whereas roasted chicken and turkey products contained less than 1 log10 cfu/g. During storage, yeast populations increased significantly (P < or = 0.05) in whole chicken, ground chicken, liver, heart and gizzard, and in ground turkey and turkey sausage. Isolates (152 strains) of yeasts from poultry products consisted of 12 species. Yarrowia lipolytica and Candida zeylanoides were predominant, making up 39 and 26% of the isolates, respectively. Six different species of basidiomycetous yeasts representing 24% of the isolates were identified. Most Y. lipolytica strains showed strong proteolytic and lipolytic activities, whereas C. zeylanoides was weakly lipolytic. Results suggest that yeasts, particularly Y. lipolytica, may play a more prominent role than previously recognized in the spoilage of fresh and processed poultry stored at 5 degrees C.

Adaptation in the corticosterone and hyperthermic responses to stress following repeated stressor exposure

Previous studies have shown that repeated daily exposure to the same (homotypic) stressor results in habituation of the corticosterone (CORT) response. Others have found that the stress response to a more ethologically relevant stressor, social defeat, does not habituate and, in some cases, sensitisation has been observed. Similar observations have been noted when core temperature is examined. Although habituation and/or sensitisation have been reported during stressor exposure, little is known about the development of an anticipatory fever in response to daily stressor exposure. The aim of the present study was to compare systematically commonly used laboratory stressors (i.e. restraint, cage confinement and social defeat) using a common set of procedures and analyses. Specifically, we examined: (i) the development of an anticipatory fever to repeated (5 days) homotypic stressor exposure; (ii) the adaptation of the fever response during stressor exposure; and (iii) the resolution of the fever response to stressors presented at the same time each day. For comparison, adaptation of the CORT response was also examined to assess the degree to which habituation to repeated stressor exposure may represent a more general response observed across diverse physiological measures. Habituation was observed after restraint and cage confinement, but not observed in either the CORT or hyperthermic responses to repeated social defeat. Furthermore, no anticipatory fever response was observed with repeated exposure to restraint, cage confinement, or social defeat. These data suggest that habituation to repeated stressor exposure may not occur with all homotypic stressor paradigms. In addition, rats do not appear to entrain an anticipatory fever response to a stressor presented at the same time each day, at least not within 5-6 days of repeated exposure.

Yeasts Associated with Fruit Juice Concentrates

Populations and frequency of occurrence of yeasts in frozen apple, cherry, grape, orange, and pineapple juice concentrates were determined. Total yeast populations ranged from log₁₀ < 1.00 to 5.41 CFU/ml of diluted (1:4) concentrate and increased to 2.42-7.34 CFU/ml after 24 h of incubation at 25°C. One hundred fifty-four isolates from 33 samples of fruit juice concentrates represented 21 species and 12 genera. The most frequently isolated species were Saccharomyces cerevisiae (24.7% of isolates), Candida stellata (22.1%), and Zygosaccharomyces rouxii (14.3%), followed by, in decreasing order of frequency, Torulaspora delbrueckii , Rhodotorula mucilaginosa , Issatchenkia orientalis , Hanseniaspora occidentalis , Lodderomyces elongisporus , Kluyveromyces thermotolerans , Hanseniaspora guilliermondii , Candida glabrata , and Pichia anomala , each representing 3-8% of isolates. Candida magnoliae , Candida maltosa , Candida parapsilosis , Candida tropicalis , Clavispora lusitaniae , Cryptococcus humicolus , C. laurentii , Pichia membranaefaciens , and Sporidiobolus salmonicolor were represented by single isolates. Populations in various samples consisted of 24-100% S. cerevisiae , 52-100% C. stellata , and 3-56% for Z. rouxii . S. cerevisiae and Z. rouxii were isolated, respectively, from five and four types of fruit concentrates investigated. This may be the first observation of this high frequency of C. stellata in juice concentrates.

The effect of stressor controllability on stress-induced neuropeptide mRNA expression within the paraventricular nucleus of the hypothalamus

Many stressors elicit changes in corticotrophin (CRH), enkephalin (ENK), and neurotensin (NT) mRNA levels within the medial parvocellular region of the paraventricular nucleus of the hypothalamus (mpPVN), and the pattern of changes in mRNA levels appears to depend on the physical characteristics of the stressor. We questioned whether psychologically distinct stressors would cause different patterns of neuropeptide mRNA expression within the PVN. Psychologically distinct stressors were created by employing a paradigm of escapable (controllable) vs. non-escapable (yoked) tail shock. An adult male rats could terminate the stress stimulus by performing wheel-turning behaviour; his behaviour also terminated the stress for his yoked partner, who had no control over the termination of the shock. Four h post-stress, brains were collected and processed for in-situ hybridization histochemistry. Tail-shock stress stimulated a significant increase in CRH, ENK, and NT mRNA levels within the mpPVN. The number of CRH identified neurones coexpressing AVP mRNA was also significantly elevated in both stress groups. Moreover, the pattern and magnitude of the stress-induced increases in mRNA was similar in both stress groups. Additionally, no stress-induced changes in CRH mRNA levels were observed in the central nucleus of the amygdala. In sum, two psychologically distinct stressors, escapable vs. yoked tail shock stress, stimulated similar increases in CRH, NT, ENK, and AVP mRNA levels within the mpPVN. These results suggest that physical attributes of a stress, rather than psychological, may be the more important factors in determining the PVN mRNA response.

Long-term changes in mineralocorticoid and glucocorticoid receptor occupancy following exposure to an acute stressor

Stressors produce rapid activation of the hypothalamic-pituitary-adrenal axis, which typically resolves within 60-90 min following termination of the stressor. In addition, some stressors such as inescapable tailshock (IS) also produce elevated basal levels of corticosterone (CORT), and reduced serum levels of corticosteroid binding globulin (CBG). The elevated basal levels of CORT produced by IS are only observed at the trough of the circadian rhythm of CORT secretion, and are sustained for 2-3 days following stressor termination. The goal of the following experiments was to determine the extent to which the elevated basal levels of CORT observed following IS exposure produced greater corticosteroid receptor occupancy in the brain and pituitary. To do so, rats (n=8-10 per group) received either sham or bilateral adrenalectomy (with CORT replacement in their drinking water; 25 microg/ml) and were given 3 days to recover. Rats were then exposed to 100 ISs (1.6 mA, 5 s each) administered on a 60 s variable intertrial interval, or remained in their home cages. As seen previously, IS produced an increase in basal CORT (5 microg/dl) and a decrease in CBG (30% decrease). Rats were sacrificed 24 h following IS for trunk blood samples and brain dissections. IS exposure had very little effect on corticosteroid receptor protein expression as determined by mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) binding levels in ADX rats. In addition, no changes in whole cell GR levels (as detected by Western blot) were observed in sham rats exposed to IS. On the other hand, IS exposure led to greater occupancy of MR (ranging from 25%-50%) in hippocampus, hypothalamus, pituitary, and posterior cortex. IS also produced greater occupancy of GR (approximately 20%) in hypothalamus and posterior cortex. These long-term changes in corticosteroid receptor activation, evident 24 h after IS exposure, may be responsible for some of the long-term neural, behavioral and immune changes observed following this acute stress procedure.

Acute stress may facilitate recovery from a subcutaneous bacterial challenge

The effects of stress on the immune system vary with both the duration and type of stressor. Many studies suggest that stress may compromise an organism's ability to recover from immune challenge. However, recent findings suggest that stress may actually enhance some aspects of immune function. For example, exposure to a single session ( approximately 2 h) of intermittent inescapable tailshocks (IS) has been shown to activate the acute phase response and increase some aspects of macrophage function. Thus, the following experiments assessed whether IS exposure would alter local inflammation produced by peripheral injection of streptomycin-killed bacteria. Rats (Harlan Sprague Dawley) were exposed to IS (100 1. 6-mA, 60 s variable intertrial interval) and injected with Escherichia coli ( approximately 2.5 x 10(8) CFU s.c. posterior to the shoulder blades). The area of inflammation was measured until the inflammation had completely resolved (typically 7-8 days). When bacteria were administered immediately after IS, rats resolved inflammation significantly faster than did nonstressed rats. Since adrenalectomy did not reduce the effect of IS, it is unlikely that this effect is a result of elevated corticosterone levels. Furthermore, IS does not appear to alter the rat's ability to sequester bacteria in the subcutaneous space since no swelling of lymph nodes or chronic activation of the hypothalamic-pituitary-adrenal axis was observed.

Stress-induced sickness behaviors: an alternative hypothesis for responses during maternal separation

During maternal separation, some primate and nonprimate species show a biphasic (active/passive) response. The second stage is characterized by reduced activity, a hunched body posture, and other behaviors. Traditionally, the second stage has been referred to as "despair" and is considered an animal model for human depression. Recent research in psychoneuroimmunology suggests an alternative hypothesis--that behaviors occurring during the second passive phase represent stress-induced "sickness behaviors." This perspective more readily accounts for findings in widely divergent species, does not require assumptions regarding the ability to express complex emotional states, is empirically testable, and aligns the separation model with recent hypotheses regarding the nature and ontogeny of depressive illness.

Evidence that brief stress may induce the acute phase response in rats

Exposing rats to a single session of inescapable tail shock (IS) reduces corticosteroid binding globulin (CBG) 24 h later (Fleshner et al., Endocrinology 136: 5336-5342, 1995). The present experiments examined whether reductions in CBG are differentially affected by controllable vs. identical uncontrollable tail shock, are mediated by IS-induced glucocorticoid elevation, or reflect IS-induced activation of the acute phase response and whether IS produces fever. The results demonstrate that 1) equivalent reductions in CBG are observed in response to escapable tail shock or yoked IS, 2) IS-induced CBG reduction is not blocked by adrenalectomy in rats that receive basal corticosteroid replacement or by pretreatment with RU-38486, and 3) IS appears to activate the acute phase response, since IS reduces serum levels of an acute-phase negative reactant (CBG), increases serum levels of acute-phase positive reactants (haptoglobin and alpha 1-acid glycoprotein), and increases core body temperature 20-24 h later.

Endogenous glucocorticoids play a positive regulatory role in the anti-keyhole limpet hemocyanin in vivo antibody response

Glucocorticoids (GCs) are commonly reported to be immunosuppressive. Studies that support this involve the administration of synthetic GCs such as dexamethasone at high pharmacological doses and using in vitro assay systems that may have limited relevance to the role of GCs during normal in vivo immune responses. Therefore, the following experiments tested the conclusion that GCs are generally immunosuppressive. Adult male Sprague Dawley rats received adrenalectomy (ADX) or sham surgery. ADX rats were given either basal corticosterone (CORT) replacement in their drinking water (25 microg/ml) or no CORT. Rats were immunized with keyhole limpet hemocyanin (KLH), and blood samples were taken. ADX rats with no CORT replacement had reduced anti-KLH IgM and IgG responses compared with sham-operated controls. ADX rats that received basal CORT replacement had partially restored anti-KLH IgM, but still had suppressed anti-KLH IgG. Administration of GC receptor type I (RU28318) and type II (RU40555) receptor antagonists also reduced the anti-KLH IgM and IgG responses. ADX rats that received both basal CORT replacement and low dose injections of CORT on days 5 and 7 after KLH had anti-KLH IgG levels equal to those of sham-operated controls. Finally, the GC elevation 4-7 days after immunization may play a role in stimulating the IgM to IgG2a switch. GC receptor blockade reduced the anti-KLH IgG2a and splenic IFN-gamma, but not the anti-KLH IgG1, response. Given that IFN-gamma is an important regulator of the IgM to IgG2a switch, it is possible that the small rise in GC found 4-7 days after KLH facilitates IgG2a isotype switching.

The long term acute phase-like responses that follow acute stressor exposure are blocked by alpha-melanocyte stimulating hormone

Both intracerebroventricular (i.c.v.) IL-1beta and exposure to inescapable tail shock (IS) activate acute phase responses (APRs) that include increases in core body temperature (CBT), increases in hypothalamic-pituitary-adrenal activity, decreases in carrier proteins such as corticosterone binding globulin (CBG), aphagia and adipsia. A variety of data suggested that stressors produce APRs by inducing brain IL-1beta. The current series of studies further explored this possibility by determining whether the functional IL-1beta antagonist, alpha-melanocyte-stimulating hormone (alpha-MSH(1-13)), would block IS-induced APRs. Immediately following i.c.v. alpha-MSH(1-13) administration, rats were exposed to a single session of 100, 5 s, 1.6 mA ISs, or control treatment (home cage control). alpha-MSH(1-13) blocked IS-induced increased CBT, increased plasma corticosterone (CORT), decreased CBG, aphagia and adipsia 24 h after IS. The inhibitory effects of alpha-MSH(1-13) were shown not to be a consequence of alpha-MSH(1-13) producing its actions 24 h after its administration because alpha-MSH(1-13) given 24 h before IS did not block IS-induced increased CBT and CORT during IS. Additionally, alpha-MSH(1-13), given 24 h before IS, had no effect on increased CBT, increased CORT, decreased CBG, adipsia, or aphagia 24 h after IS. These data provide support for a specific mode of action for i.c.v. alpha-MSH(1-13), namely blockade of APRs with no impact on acute hyperthermia or increased levels of CORT produced during IS.

Molecular characterization of Yarrowia lipolytica and Candida zeylanoides isolated from poultry

Yeast isolates from raw and processed poultry products were characterized using PCR amplification of the internally transcribed spacer (ITS) 5.8S ribosomal DNA region (ITS-PCR), restriction analysis of amplified products, randomly amplified polymorphic DNA (RAPD) analysis, and pulsed-field gel electrophoresis (PFGE). ITS-PCR resulted in single fragments of 350 and 650 bp, respectively, from eight strains of Yarrowia lipolytica and seven strains of Candida zeylanoides. Digestion of amplicons with HinfI and HaeIII produced two fragments of 200 and 150 bp from Y. lipolytica and three fragments of 350, 150, and 100 bp from C. zeylanoides, respectively. Although these fragments showed species-specific patterns and confirmed species identification, characterization did not enable intraspecies typing. Contour-clamped heterogeneous electric field PFGE separated chromosomal DNA of Y. lipolytica into three to five bands, most larger than 2 Mbp, whereas six to eight bands in the range of 750 to 2,200 bp were obtained from C. zeylanoides. Karyotypes of both yeasts showed different polymorphic patterns among strains. RAPD analysis, using enterobacterial repetitive intergenic sequences as primers, discriminated between strains within the same species. Cluster analysis of patterns formed groups that correlated with the source of isolation. For ITS-PCR, extraction of DNA by boiling yeast cells was successfully used.

Blockade of alpha1 adrenoreceptors in the dorsal raphe nucleus prevents enhanced conditioned fear and impaired escape performance following uncontrollable stressor exposure in rats

Previous research has shown that the effect of exposure to uncontrollable stressors on conditioned fear responding and escape behavior in rats is dependent on serotonergic neural activity in the dorsal raphe nucleus (DRN). The role that norepinephrine released in the DRN plays in producing the behavioral consequences of exposure to inescapable tail shock in rats was investigated in the present study. The selective alpha1 adrenoreceptor antagonist benoxathian was injected into the DRN before exposure to inescapable tail shock or before behavioral testing conducted 24 h later. Benoxathian prevented the impairment of escape responding produced by inescapable shock, but did not reverse this effect when given before testing. The enhancement of conditioned fear produced by prior inescapable shock was attenuated by benoxathian administered before inescapable shock or before behavioral testing. These results support the view that noradrenergic input to the DRN is necessary to produce the behavioral effects of inescapable tail shock.

Performance of mycological media in enumerating desiccated food spoilage yeasts: an interlaboratory study

Dichloran 18% glycerol agar (DG18) was originally formulated to enumerate nonfastidious xerophilic moulds in foods containing rapidly growing Eurotium species. Some laboratories are now using DG18 as a general purpose medium for enumerating yeasts and moulds, although its performance in recovering yeasts from dry foods has not been evaluated. An interlaboratory study compared DG18 with dichloran rose bengal chloramphenicol agar (DRBC), plate count agar supplemented with chloramphenicol (PCAC), tryptone glucose yeast extract chloramphenicol agar (TGYC), acidified potato dextrose agar (APDA), and orange serum agar (OSA) for their suitability to enumerate 14 species of lyophilized yeasts. The coefficient of variation for among-laboratories repeatability within yeast was 1.39% and reproducibility of counts among laboratories was 7.1%. The order of performance of media for recovering yeasts was TGYC > PCAC = OSA > APDA > DRBC > DG 18. A second study was done to determine the combined effects of storage time and temperature on viability of yeasts and suitability of media for recovery. Higher viability was retained at -18 degrees C than at 5 degrees C or 25 degrees C for up to 42 weeks, although the difference in mean counts of yeasts stored at -18 degrees C and 25 degrees C was only 0.78 log10 cfu/ml of rehydrated suspension. TGYC was equal to PCAC and superior to the other four media in recovering yeasts stored at -18 degrees C, 5 degrees C, or 25 degrees C for up to 42 weeks. Results from both the interlaboratory study and the storage study support the use of TGYC for enumerating desiccated yeasts. DG18 is not recommended as a general purpose medium for recovering yeasts from a desiccated condition.

Comparison of the SIM, API 20C, and ID 32C Systems for Identification of Yeasts Isolated from Fruit Juice Concentrates and Beverages

Two commercial kits for identifying clinical yeast isolates, Analytab API 20C and BioMerieux Vitek Yeast ID 32C strips, and a simplified identification method (SIM) consisting of selected conventional tests and dedicated to foodborne yeasts, were evaluated for their performance in the identification of 166 yeast isolates from concentrated fruit juices and beverages. Twenty-five species representing 15 genera were identified. The percentage of isolates correctly identified by SIM was 91%, whereas the API 20C and ID 32C systems correctly identified 86 and 76%, respectively. The number of species not included in databases was 4 in SIM, 10 in API 20C, and 7 in ID 32C. Discrepant test reactions and errors in databases were responsible for failed and false identification. Nevertheless, the accuracy of individual test reactions was high, giving only 1.6% (SIM), 2.5% (API 20C), and 1.7% (ID 32C) discrepant results. Both commercial kits, if supplemented with a few tests necessary for identification of yeasts, can be easily applied to the SIM database developed for foodborne yeasts, thus offering a convenient and accurate identification procedure.

Use of indirect conductimetry to predict the growth of spoilage yeasts, with special consideration of Zygosaccharomyces bailii

In recent years, modeling for the purpose of predicting microbiological spoilage of foods has gained much interest. Predictive modeling requires a concentrated mathematical and experimental approach; to collect data of adequate quality is a technically demanding task when several experimental parameters are involved. Rapid, non-traditional, automated techniques are particularly useful in modeling. Of these, electrometric techniques appear to be most promising. Indirect conductimetry was used to study the effect of temperature, aw, pH and potassium sorbate concentration on the growth of Zygosaccharomyces bailii. The automated Malthus 2000 instrument proved to be convenient for gathering a large amount of data that were then used to develop polynomial models describing the response of the yeast to combinations of experimental factors in terms of conductimetric detection time and maximum rate of change in conductance. Results demonstrated that indirect conductimetry is suitable for monitoring the effect of environmental factors on the growth and activity of Z. bailii and perhaps other food spoilage yeasts.

Identification of Saccharomyces sensu stricto and Torulaspora yeasts by PCR ribotyping

18S rDNA + ITS1 and 25S rDNA PCR products covering more than 95% of the nuclear ribosomal DNA repeat unit of 28 Saccharomyces sensu stricto and Torulaspora yeasts and their anamorph forms were digested with HaeIII, MspI, HinfI and CfoI. Using combinations of two restriction enzymes, specific ribotyping patterns of six species were found. PCR ribotyping offers a convenient tool for quick identification of yeast isolates, but specificity of ribotyping patterns should be checked with a larger number of strains to avoid misidentification because of lack of variation within different taxa or because of strain-specific ribotyping patterns of species type strains.

Comparison of dichloran 18% glycerol (DG18) agar with general purpose mycological media for enumerating food spoilage yeasts

Dichloran 18% glycerol (DG18) agar was originally developed to enumerate xerophilic foodborne moulds. However, some laboratories are using DG18 agar as a general medium to enumerate foodborne moulds and yeasts. A collaborative study, with the participation of seven laboratories, was undertaken to compare DG18 agar with dichloran rose bengal chloramphenicol (DRBC) agar, tryptone glucose yeast extract chloramphenicol (TGYC) agar, and plate count agar supplemented with chloramphenicol (PCAC) for enumerating 14 species of common food spoilage yeasts. Comparison of the mean values of populations of all yeasts recovered on each medium revealed no significant differences among DRBC agar, PCAC, and TGYC agar, while each of these media supported the development of significantly (P < or = 0.05) higher numbers of colonies than DG18 agar. However, differences were only 0.08 to 0.10 log10 cfu/ml, making the practical significance questionable. The overall coefficient of variation (CV) for within laboratory repeatability was 1.71%, while the CV for reproducibility of counts obtained among laboratories was 6.96%. Compared to DRBC agar, TGYC agar, and PCAC, yeast colonies were smaller on DG18 agar. Growth of Brettanomyces anomalus, Cryptococcus albidus, and Rhodotorula mucilaginosa was particularly retarded or inhibited on DG18 agar. Based on the performance of media in supporting colony development and ease of counting colonies, the use of DG18 agar as a general enumeration medium for foodborne yeasts cannot be recommended.