The quantitative effect of antimicrobial usage in Danish pig farms on the abundance of antimicrobial resistance genes in slaughter pigs

Research has long established the connection between antimicrobial use (AMU) and antimicrobial resistance (AMR) in production animals, and shown that the ceasing of AMU reduces AMR. Our previous study of Danish slaughter-pig production found a quantitative relationship between lifetime AMU and abundance of antimicrobial resistance genes (ARGs). This study aimed to generate further quantitative knowledge on how changes in AMU in farms influence the abundance of ARGs both with immediate effect and over time. The study included 83 farms that were visited from 1 to 5 times. From each visit, a pooled faecal sample was produced. The abundance of ARGs was obtained by metagenomics. We used two-level linear mixed models for estimating the effect of AMU on the abundance of ARGs against six antimicrobial classes. The lifetime AMU of each batch was calculated from usage during their three rearing periods; as piglets, weaners and slaughter pigs (rearing pathway). AMU at farm level was estimated as the mean lifetime AMU of the sampled batches from each farm. At batch level, AMU was measured as the deviation between the batch-specific lifetime AMU and the general mean lifetime AMU at the farm. For peroral tetracycline and macrolide use there was a significant quantitative linear effect on the abundance of ARGs in batches within individual farms, indicating an immediate effect of changed AMU from batch to batch within farms. These estimated effects between batches within farms were approximately 1/2-1/3 of the effect estimated between farms. For all antimicrobial classes, the effect of the mean farm-level AMU and the abundance of ARGs present in the faeces of slaughter pigs was significant. This effect was identified only for peroral use, except for lincosamides, where the effect was for parenteral use. The results also indicated that the abundance of ARGs against a specific antimicrobial class also increased by the peroral usage of one or several other antimicrobial classes, except for ARGs against beta-lactams. These effects were generally lower than the AMU effect of the specific antimicrobial class. Overall, the farm peroral mean lifetime AMU affected the abundance of ARGs at antimicrobial class level and abundance of ARGs of other classes. However, the difference of AMU of the slaughter-pig batches affected only the abundance of ARGs at the same antimicrobial class level in the same antimicrobial class. The results do not exclude that parenteral usage of antimicrobials may have an effect on the abundance of ARGs.

Effect of dexamethasone as an analgesic adjuvant to multimodal pain treatment after total knee arthroplasty: randomised clinical trial

OBJECTIVE

To investigate the effects of one and two doses of intravenous dexamethasone in patients after total knee arthroplasty.

DESIGN

Randomised, blinded, placebo controlled trial with follow-up at 90 days.

SETTING

Five Danish hospitals, September 2018 to March 2020.

PARTICIPANTS

485 adult participants undergoing total knee arthroplasty.

INTERVENTION

A computer generated randomised sequence stratified for site was used to allocate participants to one of three groups: DX1 (dexamethasone (24 mg)+placebo); DX2 (dexamethasone (24 mg)+dexamethasone (24 mg)); or placebo (placebo+placebo). The intervention was given preoperatively and after 24 hours. Participants, investigators, and outcome assessors were blinded. All participants received paracetamol, ibuprofen, and local infiltration analgesia.

MAIN OUTCOME MEASURES

The primary outcome was total intravenous morphine consumption 0 to 48 hours postoperatively. Multiplicity adjusted threshold for statistical significance was P<0.017 and minimal important difference was 10 mg morphine. Secondary outcomes included postoperative pain.

RESULTS

485 participants were randomised: 161 to DX1, 162 to DX2, and 162 to placebo. Data from 472 participants (97.3%) were included in the primary outcome analysis. The median (interquartile range) morphine consumptions at 0-48 hours were: DX1 37.9 mg (20.7 to 56.7); DX2 35.0 mg (20.6 to 52.0); and placebo 43.0 mg (28.7 to 64.0). Hodges-Lehmann median differences between groups were: -2.7 mg (98.3% confidence interval -9.3 to 3.7), P=0.30 between DX1 and DX2; 7.8 mg (0.7 to 14.7), P=0.008 between DX1 and placebo; and 10.7 mg (4.0 to 17.3), P<0.001 between DX2 and placebo. Postoperative pain was reduced at 24 hours with one dose, and at 48 hours with two doses, of dexamethasone.

CONCLUSION

Two doses of dexamethasone reduced morphine consumption during 48 hours after total knee arthroplasty and reduced postoperative pain.

TRIAL REGISTRATION

Clinicaltrials.gov NCT03506789.

Waking Up in Pain: a prospective unselected cohort study of pain in 3702 patients immediately after surgery in the Danish Realm

BACKGROUND

Acute and persistent pain after surgery is well described. However, no large-scale studies on immediate postoperative pain in the operating room (OR) exist, hindering potential areas of research to improve clinical outcomes. Thus, we aimed to describe the occurrence and severity of immediate postoperative pain in a large, unselected cohort.

METHODS

This was a prospective cohort study, encompassing all procedures in 31 public hospitals in the Danish Realm, during a 5-day period including the weekend. Data on procedures and anesthesia were collected and the main outcome was occurrence of moderate or severe pain in the OR. Secondary outcomes included pain, sedation and nausea in the OR or during the first 15 min in the postanesthesia care unit (PACU) including relevant risk factors. Descriptive and logistic regression statistics were used.

RESULTS

A total of 3675 procedures were included for analysis (87% inclusion rate). Moderate or severe pain occurred in 7.4% (95% CI 6.5% to 8.3%) of cases in the OR immediately after awakening, rising to 20.2% in the OR and/or PACU. Large intraprocedure and interprocedure variations occurred (0.0%-37.5%), and in 20% of cases with epidural-general anesthesia patients experienced moderate or severe pain. Independent risk factors were female sex, younger age, preoperative pain, daily opioid use and major surgical procedures.

CONCLUSION

Moderate or severe pain in the immediate postoperative phase occurred in 20% of all cases with procedure and anesthesiological technique variations, suggesting a need for identification of relevant procedure-specific risk factors and development of preventive treatments.

TRIAL REGISTRATION NUMBER

RoPR ID 43191.

Predicting effects of changed antimicrobial usage on the abundance of antimicrobial resistance genes in finisher' gut microbiomes

It is accepted that usage of antimicrobials (AMs) in food animals causes the emergence and spread of antimicrobial resistance (AMR) in this sector, while also contributing to the burden of AMR in humans. Curbing the increasing occurrence of AMR in food animals requires in-depth knowledge of the quantitative relationship between antimicrobial usage (AMU) and AMR to achieve desired resistance reductions from interventions targeting AMU. In the observational study, the relationships between lifetime AMU in 83 finisher batches from Danish farms and the AMR gene abundances of seven antimicrobial classes in their gut microbiomes were quantified using multi-variable linear regression models. These relationships and the national lifetime AMU in pigs were included in the predictive modelling that allowed for testing of scenarios with changed lifetime AMU for finishers produced in Denmark in 2014. A total of 50 farms from the observational study were included in validating the observational study and the predictive modelling. The results from the observational study showed that the relationship was linear, and that the parenteral usage of AMs had a high effect on specific AM-classes of resistance, whereas the peroral usage had a lower but broader effect on several classes. Three different scenarios of changed lifetime AMU were simulated in the predictive modelling. When all tetracycline usage ceased, the predicted interval reductions of aminoglycoside, lincosamide and tetracycline resistance were 4-42 %, 0-8 % and 9-18 %, respectively. When the peroral tetracycline usage of the 10 % highest users was replaced with peroral macrolide usage, the tetracycline resistance fell by 1-2 % and the macrolide and MLSb resistance increased by 5-8 %. When all extended-spectrum penicillin usage was replaced with parenteral lincosamide usage, the beta-lactam resistance fell by 2-7 %, but the lincosamide usage and resistance increased by 194 % and 10-45 %, respectively. The external validation provided results within the 95 % CI of the predictive modelling outcome at national level, while the external validation at farm level was less accurate. In conclusion, interventions targeting AMU will reduce AMR abundance, though differently depending on the targeted AM-class and provided the reduction of one AM-class usage is not replaced with usage of another AM-class. Predicting several classes of AMR gene abundance simultaneously will support stakeholders when deciding on interventions targeting AMU in the finisher production to avoid adverse and unforeseen effects on the AMR abundance. This study provides a sound predictive modelling framework for further development, including the dynamics of AMU on AMR in finishers at national level.

Expression studies of six human obesity-related genes in seven tissues from divergent pig breeds

Obesity has reached epidemic proportions globally and has become the cause of several major health risks worldwide. Presently, more than 100 loci have been related to obesity and metabolic traits in humans by genome-wide association studies. The complex genetic architecture behind obesity has triggered a need for the development of better animal models than rodents. The pig has emerged as a very promising biomedical model to study human obesity traits. In this study, we have characterized the expression patterns of six obesity-related genes, leptin (LEP), leptin receptor (LEPR), melanocortin 4 receptor (MC4R), fat mass and obesity associated (FTO), neuronal growth regulator 1 (NEGR)1 and adiponectin (ADIPOQ), in seven obesity-relevant tissues (liver; muscle; pancreas; hypothalamus; and retroperitoneal, subcutaneous and mesenteric adipose tissues) in two pig breeds (production pigs and Göttingen minipigs) that deviate phenotypically and genetically from each other with respect to obesity traits. We observe significant differential expression for LEP, LEPR and ADIPOQ in muscle and in all three adipose tissues. Interestingly, in pancreas, LEP expression is only detected in the fat minipigs. FTO shows significant differential expression in all tissues analyzed, and NEGR1 shows significant differential expression in muscle, pancreas, hypothalamus and subcutaneous adipose tissue. The MC4R transcript can be detected only in hypothalamus. In general, the expression profiles of the investigated genes are in accordance with those observed in human studies. Our study shows that both the differences between the investigated breeds and the phenotypic state with respect to obesity/leanness play a large role for differential expression of the obesity-related genes.

Accuracy of cryptorchidism diagnoses and corrective surgical treatment registration in the Danish National Patient Registry

PURPOSE

In recent years several Danish studies of the etiology, time trends and long-term health consequences of cryptorchidism have relied on diagnoses and surgical treatments registered in the National Patient Registry. We evaluated the diagnostic accuracy of these registry data.

MATERIALS AND METHODS

According to the Danish National Patient Registry, 16,168 males were diagnosed with cryptorchidism and 9,244 surgical treatments for cryptorchidism were performed between January 1, 1995 and October 10, 2009. We randomly selected 500 diagnosed cases, of which 284 had been managed surgically. We requested the medical records from the departments making the diagnoses and performing the surgery.

RESULTS

We successfully retrieved medical records for 452 diagnosed cases (90%) and 249 operations (88%). Overall positive predictive value of a registry diagnosis of cryptorchidism was 80% (95% CI 77-84) using the testicular position described by the physician performing the clinical examination as the gold standard. Similarly the positive predictive value of the surgical treatment registration was 99% (95% CI 98-100) using the type of procedure performed.

CONCLUSIONS

The data on cryptorchidism in the Danish National Patient Registry are quite accurate. In etiological research the limited misclassification will in most cases only slightly attenuate estimates of the true relative association. Thus, the registry has the potential to serve as a valuable research tool, although caution should be exercised when studying time trends or geographical differences.

Maternal alcohol consumption during pregnancy and semen quality in the male offspring: two decades of follow-up

BACKGROUND

Concurrent alcohol exposure has been associated with reduced fecundity, but no studies have estimated the effect of prenatal alcohol exposure on male fecundity. The aim of this study was to investigate the association between maternal alcohol consumption during pregnancy, semen quality and levels of reproductive hormones in young, adult men.

METHODS

From a Danish pregnancy cohort established in 1984-1987, 347 sons were selected for a follow-up study conducted in 2005-2006. Semen and blood samples were analyzed for conventional semen characteristics and reproductive hormones, respectively, and results were related to prospectively self-reported information on maternal alcohol consumption during pregnancy.

RESULTS

The sperm concentration decreased with increasing prenatal alcohol exposure. The adjusted mean sperm concentration among sons of mothers drinking >or=4.5 drinks per week during pregnancy was 40 (95% CI: 25-60) millions/ml. This concentration was approximately 32% lower compared with men exposed to <1.0 drink per week, who had a sperm concentration of 59 (95% CI: 44-77) millions/ml. The semen volume and the total sperm count were also associated with prenatal alcohol exposure; sons prenatally exposed to 1.0-1.5 drinks per week had the highest values. No associations were found for sperm motility, sperm morphology or any of the reproductive hormones, including testosterone.

CONCLUSIONS

These results indicate that prenatal exposure to alcohol may have a persisting adverse effect on Sertoli cells, and thereby sperm concentration. If these associations are causal they could explain some of the reported differences between populations and long-term changes in semen quality.

Prenatal alcohol exposure and cryptorchidism

AIM

A recently published study reported markedly increased risk of cryptorchidism among boys whose mothers had an average gestational alcohol intake of five or more drinks per week. The aim of this study is to follow up on this finding by estimating the association between prenatal alcohol exposure and persistent cryptorchidism.

METHODS

We used prospectively collected information on prenatal exposures and obstetric information on the birth of 5716 boys, collected from 1984 to 1987. During the 16-19 years of follow-up in a nationwide patient register, 270 cases of cryptorchidism were diagnosed and 185 of these boys underwent orchiopexy.

RESULTS

No positive association between the mothers' average weekly alcohol consumption and persistent cryptorchidism was observed. Binge drinking was nonsignificantly associated with an excess risk of orchiopexy (adjusted RR = 1.4; 95% CI 0.9-2.1), but not with having a diagnosis of cryptorchidism without orchiopexy.

CONCLUSIONS

Mothers' average weekly alcohol intake was not associated with persistent cryptorchidism, but binge drinking may be a risk factor.

Is smoking a risk factor for decreased semen quality? A cross-sectional analysis

BACKGROUND

Previous studies suggest a deleterious effect of cigarette smoking on semen quality, but their results have not been consistent. We studied the association between current smoking and semen characteristics and hormonal levels in a large group of healthy men.

METHODS

From 1987 to 2004, seven separate occupational or environmental semen quality studies were co-ordinated by our department. A total of 2562 men participated, each providing semen and blood sample and answering a questionnaire about lifestyle and factors related to health. Appropriate semen and smoking data were available for 2542 men.

RESULTS

Adjusting for study, age and other covariates, we observed an inverse dose-response relation between smoking and semen volume, total sperm count and percentage motile sperm. Heavy smokers had a 19% lower sperm concentration than non-smokers. We found a positive dose-response relationship between smoking and testosterone, LH and the LH/free testosterone ratios.

CONCLUSION

Current smoking in adult life moderately impairs the semen quality. It is well known that semen quality is associated to fecundity. Therefore, it would be sensible to advise men to abstain from smoking to avoid decreased fecundity.

Design and evaluation of a handheld impedance plethysmograph for measuring heart rate variability

Heart rate variability (HRV) analysis from 10s ECGs has been shown to be reliable. However, the short examination time warrants a user-friendly system that can be used for ad-hoc examinations without normal preparation, unlike ECG. A handheld device has been developed that can measure ultra-short HRV from impedance plethysmographic recordings of the pulse wave in distal superficial arteries. The prototype device was made user-friendly through a compact, pen-like design and the use of integrated metal electrodes that were especially designed for dry operation. The main signal processing was performed by a digital signal processor, where the discrete heart beats were detected using a correlation algorithm that could adapt to individual pulse wave shapes to account for biological variation. The novel device was evaluated in 20 mainly young volunteers, using 10 s time-correlated ECG recordings as the reference method. Agreement between the two methods in measuring heart rate and root mean square of successive differences in the heart beat interval (RMSSD) was analysed using correlation coefficients (Pearson's R2), mean differences with 95% confidence intervals and 95% limits of agreement, and Bland-Altman plots. The correlation between the two methods was R2 = 1.00 and R2 = 0.99 when heart rate and RMSSD were measured, respectively. The Bland-Altman plots showed suitable agreement between the novel device and standard 10 s ECGs, which was substantiated by 95% limits of agreement of the difference of +/- 0.1 beats min(-1) and approximately +/- 10 ms for heart rate and RMSSD, respectively. Therefore the evaluation showed no significant systematic error of the novel device compared with ECG.

Fecundability according to male serum inhibin B—a prospective study among first pregnancy planners

BACKGROUND

New biological markers of male fecundity are needed for use in large-scale epidemiological studies. We studied the association between male inhibin B and fecundability.

METHODS

Four hundred and thirty Danish couples without previous reproductive experience were followed from termination of contraception until pregnancy or for a maximum of six menstrual cycles. At enrolment we obtained semen samples (n = 418) and blood samples to measure reproductive hormones, including inhibin B (n = 343).

RESULTS

The fecundability odds ratio for an increment of male inhibin B by 1 log pg/ml was 1.428 (95% confidence interval 1.022-1.994), adjusted for factors influencing the crude estimate. Only inhibin B values below 100 pg/ml were strongly related to fecundability. We designed a receiver operating characteristic curve based on the 29 males with serum inhibin B #100 pg/ml. The area under the curve (AUC) for inhibin B was 0.787 and the corresponding AUCs for sperm density and FSH were 0.913 and 0.800, respectively.

CONCLUSION

Serum inhibin B may be a reliable marker of male fecundity for epidemiological research and may have some advantages over sperm density. Our findings do not support the replacement of sperm density by male inhibin B when obtaining sperm data is an option.

Lower sperm counts following prenatal tobacco exposure

BACKGROUND

Recent findings have indicated that prenatal exposure to tobacco smoke may cause lower sperm concentration in ejaculates of adult men. To extend the research on this hypothesis we investigated the dose-dependency of the association, controlling for other prenatal exposures.

METHODS

From 1987 to 1996, four separate occupational semen studies were conducted at three centres in Denmark. A total of 945 men provided semen and blood samples, and information on reproductive and lifestyle factors. In 2004, we collected data on the maternal smoking habits during pregnancy from 522 mothers of the participating men.

RESULTS

Adjusting for study subgroup, abstinence time and other factors, we found statistically non-significant differences in mean sperm concentrations: 65.0 x 10(6)/ml [95% confidence interval (CI) 51, 81] among sons of non-smokers; 59.1 x 10(6)/ml (95% CI 46, 75) among sons of mothers who had smoked 1-10 cigarettes/day; and 57.7 x 10(6)/ml (95% CI 40, 81) among those whose mothers had smoked >10 cigarettes/day. The former group had a higher odds ratio (OR) for oligozoospermia (sperm concentration < or =20 x 10(6)/ml) of 1.5 (95% CI 0.9, 2.8), the latter group an OR of 2.6 (95% CI 1.2, 5.8).

CONCLUSION

We observed a dose-dependent association between prenatal tobacco exposure, lower sperm concentration and higher risk of oligozoospermia.

A method to create reference maps for evaluation of ultrasound images of carotid atherosclerotic plaque

Ten formalin-fixed atherosclerotic carotid plaques removed by endarterectomy were molded into rectangular agar blocks containing fiducial markers on the top surface. Plaque and fiducial markers were imaged with 3-D multiangle ultrasound (US) spatial compounding as well as planar X ray. Subsequently, the blocks were decalcified, sliced, photographed and analyzed histologically. This gave a total of 123 slices. The plaque regions of the photographs were outlined and the outline adjusted to partly compensate for occasional displacement during slicing. Inside this outline, the material constitutions were found by incorporating the histologic information. From this set, slices with 1. too much tissue displacement due to cutting or 2. lack of identification of calcification as found by x ray, were removed. This resulted in 53 reference maps. The material types identified covered soft tissues, fibrous tissue, calcified tissue and unidentified tissues. The 53 reference maps can be used for direct automated quantitative comparison with US images.

Visual and quantitative evaluation of selected image combination schemes in ultrasound spatial compound scanning

Multi-angle spatial compound images are normally generated by averaging the recorded single-angle images (SAIs). To exploit possible advantages associated with alternative combination schemes, this paper investigates both the effect of number of angles (Ntheta) as well as operator (mean, median, mean-excluding-maximum (mem), root-mean-square (rms), geometric mean and maximum) on image quality (tissue delineation and artifacts), speckle signal-to-noise ratio (SNRs) and contrast. The evaluation is based on in vitro SAI (+/-21 degrees in steps of delta theta = 7 degrees) of formalin fixed porcine tissue containing adipose, connective and muscular tissue. Image quality increased with number of angles up to +/-14 degrees after which the improvements became debatable. The mem and median operators, which try to render the images more quantitatively correct by suppressing strong echoes from specular reflectors, provide some improvement in this regard. When combining the SAI with the mean operator, the SNR, increases--in general--with Ntheta. For Ntheta = 2, the SNRs increases with delta theta as expected. When Ntheta = 7, the highest SNRs is obtained for the mem, rms, and geometric mean operators, while the lowest SNRs is obtained for the maximum operator. When comparing SNRs for adipose and fibrous tissue, the level is close to 1.91 for adipose tissue but only 1.7 for fibrous tissue which contain relatively few organized scattering structures.

A method to obtain reference images for evaluation of ultrasonic tissue characterization techniques

A general problem when evaluating ultrasonic methods for tissue characterization is that "a golden standard" is seldom known. This paper describes a manual method to obtain a reference image, with the same geometry as the ultrasound image, indicating spatial location of the different tissue types present in the biological tissue scanned in vitro. A 30 x 10 x 2 mm3 piece of formalin fixed porcine tissue was molded into an agar block, which on the top surface, contained a set of fiducial markers, spaced 2.5 mm. The block was submerged into 20 degrees C water and a set of parallel 7.5 MHz spatial compound ultrasound images of tissue and fiducial markers were recorded each 0.5 mm. Guided by the fiducial markers, the agar block was subsequently cut into slices 2.5 mm thick, photographed and finally analyzed histologically identifying these tissues: collagen rich, collagen poor, micro vessels and muscle fibres. Due to: (1) the cutting procedure, (2) the finite size of the ultrasound beam and (3) the spatial variation in propagation velocity, the macroscopic photographs did not align completely with the ultrasound images. Likewise, the histological image is a geometrically distorted version of the macroscopic photograph, due to the histological preparation process. The histological information was "mapped back" into the format of the ultrasound images the following way: On the macroscopic images, outlines were drawn manually which defined the border of the tissue. These outlines were superimposed on the corresponding ultrasound images (identified via the fiducial markers) and modified to encompass what appeared to be tissue regions on the ultrasound images and subsequently re-applied to the macroscopic image. This modified macroscopic outline was used as guideline when drawing outlines identifying regions of the various tissue types. Specifically, the macroscopic image revealed the borders between the different tissues, while the histological image identified the four tissue types. A set of 12 reference images based on modified macroscopic outlines was created. The overlap between the ultrasound images and the macroscopic images--which are the geometrical basis for the final reference images--was between 77% and 93%. A set of 12 reference images spaced 2.5 mm, identifying spatial location of four different tissue types in porcine muscle has been created. With the reference images, it is possible to quantitatively compare different ultrasound based tissue classification techniques.

Developmental increase in asynchronous GABA release in cultured hippocampal neurons

Developmental changes in GABAergic synaptic transmission were examined in cultured hippocampal neurons using patch-clamp recordings and Ca(2+) imaging. In paired recordings, tetanization of the presynaptic GABAergic neuron with 80 pulses at either 40 or 80Hz was accompanied by tetanic depression of inhibitory postsynaptic responses. In neurons that had been cultured for more than two weeks, asynchronous inhibitory postsynaptic currents often appeared during the tetanus and continued for several seconds following stimulation. There was little asynchronous activity in neurons that had been cultured for shorter times. However, no age-related changes were observed in the amplitude of single synchronous inhibitory postsynaptic currents, paired-pulse depression or post-tetanic potentiation of inhibitory postsynaptic currents. Following equimolar replacement of extracellular Ca(2+) with strontium ions (Sr(2+)), single autaptic inhibitory postsynaptic currents were depressed in amplitude and asynchronous inhibitory postsynaptic currents were present on the decaying phase. Sr(2+)-induced asynchronous inhibitory postsynaptic currents showed no dependence on age in culture. Imaging of Ca(2+) in single GABAergic boutons was performed by including Fluo-3 in the patch pipette. During action potential firing induced by stimulating at 80Hz for 1s, intracellular calcium [Ca(2+)](i) increased rapidly in individual boutons. Following the stimulus, [Ca(2+)](i) decayed back to baseline within 10-15s. The half-time of decay increased from 1. 7+/-0.2s at 15days in vitro to 4.0+/-0.2s at 30days in vitro (P<0. 05), with a developmental profile that closely matched the increase in asynchronous inhibitory postsynaptic currents. We propose that the increase in tetanus-induced asynchronous GABA-release during the first month of synapse maturation in vitro is caused by a slowing of the Ca(2+)-clearing mechanisms in the GABAergic boutons. This results in larger and more prolonged elevations of [Ca(2+)](i) during tetanic stimulation, which leads to enhanced asynchronous transmitter release. We propose that the results of this study demonstrate a potentially important aspect of synapse maturation during development, and also imply that GABA release is up-regulated in conditions of decreased Ca(2+) buffering and clearing.

Various nitric oxide donors protect chick embryonic neurons from cyanide-induced apoptosis

The discovery of numerous biochemical effects of cyanide not directly related to the inhibition of the respiratory chain, including the involvement of apoptosis, has challenged the basis of traditional antidote treatment, which primarily depends on nitrite-induced conversion of hemoglobin into methemoglobin, releasing the blockade of cytochrome c oxidase by high-affinity binding of cyanide as cyanmethemoglobin. The fact that amyl nitrite has antidotal effects not related to methemoglobin formation has unfolded new mechanism of actions of nitrites including release of nitric oxide (NO). In this study, we characterized the effect of various NO donor compounds on cyanide-induced cell death in cultured chick embryonic neurons. Apoptosis was induced by treating the neuronal cultures with 1 mM NaCN for 1 h, followed by a cyanide-free incubation period of 23 h. Using this treatment protocol, we showed that cyanide-induced apoptosis was blocked in the presence of the different NO donors sodium nitroprusside, S-nitrosoglutathione, S-nitroso-N-acetylpenicillamin, nitroglycerin, 3-morpholinosydnonimine, and diethylamine nitric oxide, indicating independence of the redox-related species of NO released. The effect was confirmed to be mediated by NO, since exhausted NO donors did not afford protection, and the mechanism likely involved chemical modification of thiol groups, since the effect was completely reversed by dithiothreitol. Furthermore, NMDA antagonists protected against cyanide-induced cell death, whereas inhibitors of nitric oxide synthase increased cyanide-induced apoptotic damage, indicating a protective effect of endogenously generated NO, at least in cell cultures.

Tetanus-induced asynchronous GABA release in cultured hippocampal neurons

Asynchronous GABA release was studied in cultured hippocampal neurons using paired whole-cell recordings. Tetanization of the presynaptic GABAergic neuron was accompanied by a train of IPSCs which showed tetanic depression. Asynchronous IPSCs (asIPSCs) also developed during the train and continued for 1.85+/-0.3 s after the stimulation. The threshold frequency for evoking asIPSCs was 10 Hz, while maximal asynchronous activity was achieved at 40 Hz. Perfusion with EGTA-AM blocked asIPSCs. The elevation of [Ca(2+)](i) that accompanies presynaptic action potential firing triggers asynchronous release of GABA vesicles, thereby counteracting tetanic depression of synchronous IPSCs.

Release of synaptic zinc is substantially depressed by conventional brain slice preparations

Research on synaptically-released zinc is frequently done in vitro with acute brain slice preparations. We show here the in vitro hippocampal slice preparation has two major pitfalls for zinc research. First, up to 50% of the synaptic zinc is lost during slice cutting and/or the first 10 min of slice incubation, with the losses being most pronounced on the edges of the slice. Second, the release of the remaining zinc from a slice is substantially depressed (up to 50%) at the low temperatures (32 degrees C) typically used for brain slice studies. In concert, these effects reduce zinc release about 75% in vitro, compared to in vivo. Implications for research on synaptically-released zinc are discussed.

The effect of internal GTPgammaS on GABA-release in cultured hippocampal neurons

The effects of presynaptic guanosine-5'-O-(3-thio)triphosphate (GTPgammaS) on GABAergic inhibitory postsynaptic currents (IPSCs) were studied in cultured hippocampal neurons using whole-cell recordings. Inclusion of GTPgammaS (0.5-1 mM) in the presynaptic electrode reduced both the amplitude and paired-pulse depression of IPSCs, indicating that the probability of GABA-release had been reduced. Presynaptic GTPgammaS increased the depression of IPSCs by the GABA(B)-receptor-agonist baclofen (10 microM), and the effect of baclofen was poorly reversible after washing. Stimulation of the GABAergic neuron at 80 Hz for 1 s was accompanied by tetanic depression of the IPSCs by 52+/-6% and was followed by post-tetanic potentiation (PTP), reaching a peak value of 71+/-21% and lasting about 100 s. IPSCs evoked after tetanic stimulation were depressed and PTP was absent when tetanic stimulation was applied within 3 min after starting injection of GTPgammaS into the presynaptic neuron. At longer times, basal release underlying a single IPSC was depressed. This affected the ratios recorded in response to tetanic stimulations such that tetanic depression was abolished, while PTP increased to 117+/-34%. In conclusion, GTPgammaS reduces the probability of GABA-release in both a use- and time-dependent manner, most likely through an inhibitory action on presynaptic Ca2+-influx through voltage-gated Ca2+ channels or an interaction with small GTP-binding proteins in the nerve terminals.

Zinc-enriched (ZEN) terminals in mouse olfactory bulb

The present study was designed to localize zinc-enriched (ZEN) terminals in mouse olfactory bulb by means of ZnT3 immunocytochemistry (ICC) and zinc autometallography (AMG). The immunocytochemical staining of ZnT3 was closely correlated with the AMG pattern. ZEN terminals were defined as terminals showing both ZnT3 immunoreactivities and AMG granules. At the light microscopic level, dense staining patterns for ZnT3 immunoreactivity were seen in the granule cell layer and the olfactory glomerular layer. At the ultrastructural level, ZEN terminals were restricted to presynaptic terminals with single or multiple postsynaptic thickenings. The postsynaptic profiles contacting ZEN terminals appeared to be dendrites or somata of granule cells in the granule cell layer and periglomerular cells and mitral/tufted (M/T) cells in the olfactory glomerular layer. This suggests that two main sources of ZEN terminals are present in mouse olfactory bulb: (1) centrifugal fibres making asymmetrical synapses with granule cells and periglomerular cells, and (2) olfactory receptor terminals contacting dendritic profiles of M/T cells or periglomerular cells. The close correlation between ZEN terminals and the glutamatergic system is discussed.

Synthesis of an anti-methicillin-resistant Staphylococcus aureus (MRSA) carbapenem via stannatrane-mediated Stille coupling

[formula: see text] A short synthesis of carbapenem 1 is described. They key step involves the cross-coupling of an enol triflate with an amino-substituted sp3 carbon. This cross-couping, which allows the introduction of the complete side chain in one step, utilizes a stannatrane as the heteroalkyl transfer reagent.

Histochemically-reactive zinc in amyloid plaques, angiopathy, and degenerating neurons of Alzheimer's diseased brains

Excess brain zinc has been implicated in Alzheimer's neuropathology. Here we evaluated that hypothesis by searching the brains of Alzheimer's patients for abnormal zinc deposits. Using histochemical methods, we found vivid Zn2+ staining in the amyloid deposits of dense-core (senile) plaques, in the amyloid angiopathy surrounding diseased blood vessels, and in the somata and dendrites of neurons showing the characteristic neurofibrillary tangles (NFT) of Alzheimer's. In contrast, brains from age-matched, non-demented subjects showed only occasional staining for Zn2+ in scattered neurons and possible plaques. A role of abnormal zinc metabolism in Alzheimer's neuropathology is suggested.

Exercise induces recruitment of lymphocytes with an activated phenotype and short telomeres in young and elderly humans

This study was performed in order to investigate the type of T cells recruited to the blood in response to an acute bout of exercise with regard to mean lengths of telomeric terminal restriction fragments (TRF) and surface activation markers and with special emphasis on age-associated differences. Ten elderly and ten young humans performed maximal bicycle exercise. There was no difference in the number of recruited CD4+ and CD8+ cells between the young and elderly group. In both age groups the immediate increases could be ascribed to recruitment of CD28- cells (CD8+ and CD4+ cells) and memory cells (only CD8+ cells). Furthermore, after exercise mean TRF lengths were significantly reduced in blood mononuclear cells and in CD8+ cells from young subjects and in CD4+ cells from elderly subjects compared with lengths pre-exercise. These findings suggest that the mobilization of T lymphocytes during acute exercise is mainly a redistribution of previously activated cells with an increased replicative story than cells isolated from the blood at rest. Furthermore, elderly humans fulfilling the Senieur protocol have a preserved ability to recruit T lymphocytes in response to acute physical stress.

Post-tetanic potentiation of GABAergic IPSCs in cultured rat hippocampal neurones

1. Dual whole-cell patch-clamp recording was used to investigate post-tetanic potentiation (PTP) of GABAergic IPSCs evoked between pairs of cultured rat hippocampal neurones. Tetanization of the presynaptic neurone at frequencies (f) ranging from 5 to 100 Hz resulted in PTP of the IPSCs. Maximum PTP had a magnitude of 51.6 % just after the stimulus train, and lasted up to 1 min. PTP was shown to be dependent on the number of stimuli in the train, but independent of f at frequencies > or =5 Hz. 2. Blocking postsynaptic GABAA receptors with bicuculline during the tetanus did not affect the expression of PTP, showing that it is a presynaptic phenomenon. PTP was strongly affected by changing [Ca2+]o during the tetanus: PTP was reduced by lowering [Ca2+]o, and increased by high [Ca2+]o. 3. PTP was still present after presynaptic injection of BAPTA or EGTA, or following perfusion of the membrane-permeable ester EGTA-tetraacetoxymethyl ester (EGTA AM, 50 microM). On the other hand, EGTA AM blocked spontaneous, asynchronous IPSCs (asIPSCs), which were often associated with tetanic stimulation. 4. Tetanic stimulation in the presence of 4-aminopyridine (4-AP), which promotes presynaptic Ca2+ influx, evoked sustained PTP of IPSCs in half of the neurones tested. 5. The results indicate that PTP at inhibitory GABAergic synapses is related to the magnitude of presynaptic Ca2+ influx during the tetanic stimulation, leading to an enhanced probability of vesicle release in the post-tetanic period. The increase in [Ca2+]i occurs despite the presence of high-affinity exogenous and endogenous intracellular Ca2+ buffers. That PTP of IPSCs depends on the number, and not the frequency, of spikes in the GABAergic neurone is in accordance with a slow clearing of intracellular Ca2+ from the presynaptic terminals.

Activity-dependent depression of GABAergic IPSCs in cultured hippocampal neurons

Short-term depression of monosynaptic GABAergic inhibitory postsynaptic currents (IPSCs) evoked between pairs of cultured rat hippocampal neurons was investigated using dual whole cell patch-clamp recordings. Paired stimuli applied to the GABAergic neuron resulted in paired-pulse depression (PPD) of the second IPSC (IPSC2) at interpulse intervals from 25 to 2,000 ms. CGP 55845A, but not CGP 35348, reduced PPD marginally. Brief paired-pulse applications of exogenous GABA indicated that postsynaptic factors made only minimal contribution to PPD of IPSCs. IPSC1 and PPD was reduced on lowering [Ca2+]o and enhanced on increasing [Ca2+]o. The potassium-channel blocker 4-aminopyridine (4-AP), which increases presynaptic Ca2+ influx, enhanced IPSC1 and PPD. Chelation of residual Ca2+ in the GABAergic boutons with EGTA-AM enhanced PPD. Stimulation of the presynaptic neuron at frequencies (f) ranging from 2.5 to 80 Hz resulted in tetanic depression of IPSCs, which declined rapidly and reached a plateau depending on f and [Ca2+]o. CGP 55845A decreased tetanic depression in the first part of the train, but this could be overcome with continued stimulation. We show that GABAergic IPSCs are robustly depressed by paired-pulse stimulation in cultured hippocampal neurons. The depression of IPSCs is mainly independent of presynaptic GABAB receptors and could be caused by depletion of releasable vesicles. Depleted synapses recover with a slow time course, depending on factors that regulate [Ca2+]i in the GABAergic boutons.

Preparation of crystalline p-nitrobenzyl 2-formyl carbapenems by oxidative cleavage

Crystalline 1beta-methyl-2-formyl carbapenem pNB esters were prepared by osmium-mediated oxidative cleavage of the corresponding 2-vinyl derivatives. Reduction of the 2-formyl compounds gave the corresponding 2-hydroxymethyl derivatives, which are key intermediates for the anti-MRS carbapenem candidate (1).

Role of presynaptic L-type Ca2+ channels in GABAergic synaptic transmission in cultured hippocampal neurons

Using dual whole cell patch-clamp recordings of monosynaptic GABAergic inhibitory postsynaptic currents (IPSCs) in cultured rat hippocampal neurons, we have previously demonstrated posttetanic potentiation (PTP) of IPSCs. Tetanic stimulation of the GABAergic neuron leads to accumulation of Ca2+ in the presynaptic terminals. This enhances the probability of GABA-vesicle release for up to 1 min, which underlies PTP. In the present study, we have examined the effect of altering the probability of release on PTP of IPSCs. Baclofen (10 microM), which depresses presynaptic Ca2+ entry through N- and P/Q-type voltage-dependent Ca2+ channels (VDCCs), caused a threefold greater enhancement of PTP than did reducing [Ca2+]o to 1.2 mM, which causes a nonspecific reduction in Ca2+ entry. This finding prompted us to investigate whether presynaptic L-type VDCCs contribute to the Ca2+ accumulation in the boutons during spike activity. The L-type VDCC antagonist, nifedipine (10 microM), had no effect on single IPSCs evoked at 0.2 Hz but reduced the PTP evoked by a train of 40 Hz for 2 s by 60%. Another L-type VDCC antagonist, isradipine (5 microM), similarly inhibited PTP by 65%. Both L-type VDCC blockers also depressed IPSCs during the stimulation (i.e., they increased tetanic depression). The L-type VDCC "agonist" (-)BayK 8644 (4 microM) had no effect on PTP evoked by a train of 40 Hz for 2 s, which probably saturated the PTP process, but enhanced PTP evoked by a train of 1 s by 91%. In conclusion, the results indicate that L-type VDCCs do not participate in low-frequency synchronous transmitter release, but contribute to presynaptic Ca2+ accumulation during high-frequency activity. This helps maintain vesicle release during tetanic stimulation and also enhances the probability of transmitter release during the posttetanic period, which is manifest as PTP. Involvement of L-type channels in these processes represents a novel presynaptic regulatory mechanism at fast CNS synapses.

Circadian and ultradian variation in pancreatic secretion of meal-fed pigs after weaning

We studied the time structure of pancreatic secretion in two experiments involving seven 6- to 7-wk-old intact male pigs, surgically fitted with a jugular vein catheter for blood sampling, pancreatic catheter, and a duodenal T-cannula for chronic pancreatic juice sampling for 72 h at 30- to 60-min intervals. Pigs were kept in metabolic cages in a regimen of 12 h of light alternating with 12 h of darkness and were fed at 0800, 1500, and 2200 daily a standard diet based on barley, soybean meal, and fish meal. Beginning 4 d after surgical recovery, three 24-h collections of pancreatic juice and blood sampling were begun either at 0700 or 0800 every 2nd d for 5 d. Pancreatic secretion exhibited a pattern characterized by distinct meal-related secretions of the first phase (postprandial), containing large amounts of protein and enzymes (trypsin and chymotrypsin), and by non-food-stimulated secretions of the second phase with less protein and enzymes. During the dark span, the first phase was practically absent; the response of the pancreatic secretion to the 2200 meal was not very pronounced. Apart from the anticipated circadian rhythm demonstrable by single cosinor analysis on a group basis, a prominent 8-h component was almost invariably statistically significant. Moreover, an approximately 3.43-h component was also prominent. These data indicate that pancreatic secretions are circadian periodic and that their response to a standard meal is also circadian-stage dependent. The circadian components may have been free-running because the pigs were adjusting themselves to the changing phase and that resulted in the period being different from exactly 24 h.

A comparison of two methods to measure amylase, lipase, trypsin, and chymotrypsin activity and the effect of freezing and thawing on enzyme activities in pancreatic juice

An experiment was conducted to compare two methods, referred to as A and B, for measuring amylase, lipase, trypsin, and chymotrypsin activities in samples of pancreatic juice and to investigate the effect of freezing and thawing on enzyme activities. Three growing pigs were used in this study. A catheter was surgically inserted into the pancreatic duct and a simple T-cannula was placed in the duodenum to allow the return of collected pancreatic juice. Pancreatic juice was collected for a total of 24 h and 27 pooled 8-h samples were used in the analyses. Following collection and pooling, the samples were frozen at -80 degrees C, due to the large number of samples and analyses, and stored for 2 weeks. The samples were thawed and enzyme activities were determined with Method A. The samples were frozen again at -80 degrees C, stored for 2 weeks, and rethawed and enzyme activities were determined with Methods A and B. There was a direct relationship between Method A and Method B for measuring amylase, trypsin, and chymotrypsin activity (R2 = 0.95, 0.81, and 0.90, respectively). However, a poor relationship was observed between a titrimetric and a photometric method for determining lipase activity (R2 = 0.42). A second freezing, storage, and thawing did not affect (p > 0.3) the concentration of protein or amylase activity in pancreatic juice. However, the activities of chymotrypsin, trypsin, and, especially, lipase were decreased by 29.0% (p < 0.11), 40.4% (p < 0.01), and 82.9% (p < 0.001), respectively. In conclusion, either Method A or Method B can be used to measure amylase, trypsin, and chymotrypsin activities in pancreatic juice but a titrimetric method should be used to determine lipase activity. Furthermore, if the activities of lipase, trypsin, and chymotrypsin are to be determined, the sample should only be frozen and thawed once. If amylase activity will be determined, the sample can be repeatedly frozen and thawed.

Electrophoretic separation of proteolytic enzymes in pancreatic juice collected with the pouch or catheter method

CONCLUSION

The results of this study demonstrated that proteolytic enzymes in pancreatic juice from pigs prepared with the pouch method (PM) were nearly fully active or were fully active. When activation with enterokinase was carried out further inactivation and/or breakdown occurred for chymotrypsin C and cathodal trypsin. In addition, some inactivation and/or breakdown of proteolytic enzymes in pancreatic juice occurred during collection of pancreatic juice from PM pigs.

METHODS

Samples of pancreatic juice were collected from growing pigs using either the PM or the catheter method (CM). An isolated pouch was prepared where the pancreatic duct enters the duodenum, and three pigs were fitted with a pancreatic pouch re-entrant cannula. Three different pigs had a catheter surgically inserted into the pancreatic duct. Pooled 8-h samples of pancreatic juice were analyzed before and after activation with enterokinase. Chymotrypsin, trypsin, and elastase activities were identified in pancreatic juice after separation by electrophoresis in 1% agarose gels at pH 8.6 using N-acetyl-DL-phenylalanine-beta-naphthyl ester (Ac-Phe-beta ne) as a substrate.

RESULTS

This qualitative enzyme assay indicated that a considerable amount of chymotrypsin C, anodal trypsin, chymotrypsins A and B, elastase II, and cathodal trypsin were present in samples of nonactivated pancreatic juice from PM pigs. In contrast, the only active enzymes identified in pancreatic juice from CM pigs were very small amounts of chymotrypsin A and elastase II. The amounts of chymotrypsin C and cathodal trypsin were lower in activated than in nonactivated pancreatic juice from PM pigs. However, there were increases in the amounts of the other enzymes when pancreatic juice from PM pigs was activated. As expected, the activation of pancreatic juice from CM pigs resulted in the measurement of very high amounts of all the proteolytic enzymes. The amounts of anodal trypsin, chymotrypsins A and B, and elastase II were higher in activated pancreatic juice from CM pigs than from PM pigs.

Collection of pancreatic juice from growing pigs. A comparative study of the pouch method and the catheter method

CONCLUSION

The results of this study demonstrate that there are large differences in the amount of pancreatic juice secreted and in the chemical and enzymatic composition of pancreatic juice when the pouch and the catheter methods were used, and these differences must be taken into consideration in future studies with either method.

METHODS

A study was performed to compare the two most commonly used methods to collect pancreatic juice from growing pigs; namely, the pouch method (PM) and the catheter method (CM). In the first part of the study, three barrows (initial weight 37 kg) were fitted with a pancreatic pouch re-entrant cannula. An isolated pouch was prepared in which the pancreatic duct enters the duodenum. In the second part of the study, also with three barrows (initial weight 32 kg), a catheter was inserted into the pancreatic duct.

RESULTS

At several points during the 24-h collection, the hourly rate of pancreatic juice secretion in CM pigs was larger (p < 0.05) than for PM pigs. CM pigs also had a higher (p < 0.05) daily volume of secretion, 4.09 vs 2.63 L/24 h for PM pigs. The pH of pancreatic juice collected from CM pigs was consistently higher (p < 0.01) throughout the 24-h collection. In contrast, the concentration and daily output of bicarbonate did not differ between CM and PM pigs. The concentration of protein in pancreatic juice from PM pigs (7.21 g/L) was higher (p < 0.001) than for CM pigs (4.08 g/L). Specific amylase and lipase and total amylase activities were greater (p < 0.01) in pancreatic juice collected from PM pigs. Specific and total carboxyl ester hydrolase and colipase activities were substantially (p < 0.01) larger in pancreatic juice collected from CM pigs. A major difference between the methods was that trypsin and chymotrypsin were fully active in pancreatic juice from PM pigs, whereas virtually no trypsin or chymotrypsin activity was detected in pancreatic juice from CM pigs. Specific and total chymotrypsin activities did not differ between PM and CM pigs. Both specific and total trypsin activities were substantially higher in pancreatic juice from CM pigs: 3682 U/L and 12,752 U/24 h, respectively, vs 1031 U/L and 2639 U/24 h, respectively, in pancreatic juice from PM pigs.

Role of intrinsic burst firing, potassium accumulation, and electrical coupling in the elevated potassium model of hippocampal epilepsy

Perfusing rat hippocampal slices with high-K+ (7.5 mM) saline induced brief population bursts originating in CA3 at 0.5-1 Hz and spreading synaptically into CA1. In 42% of the slices the brief bursts evoked in CA1 gave way every 0.5-2 s to sustained ictal (or seizure) episode with tonic and clonic components. Paired intra- and extracellular recordings in the CA1 pyramidal layer were used to characterize the synaptic and nonsynaptic mechanisms generating the brief and sustained epileptiform events. The interictal, tonic, or clonic primary burst response in CA1 comprised a spindle-shaped, tight cluster (170-180 Hz) of five to seven population spikes. Bursts evoked between sequential seizures (interictal bursts) were initially small and progressively increased in size. Concurrently, basal extracellular K+ concentration ([K+]o] increased from 6.5 to 7.5 mM. The tonic event emanated from a large primary burst and comprised prolonged (> 1 s), self-sustained afterdischarge, associated with a rise in [K+]o to 12 mM. Bursts generated during the subsequent [K+]o decline (clonic bursts) also were large and followed by some afterdischarge. They became small during [K+]o undershoot to 6.5 mM. Intrinsically burst firing pyramidal cells (PCs) were recruited before or at the very onset of the primary population burst and fired repetitively during its course. Nonbursters were recruited > or = 10 ms after the beginning of the primary burst and fired, on average, only one spike. The PCs depolarized during the primary burst and subsequent afterdischarge. The primary depolarizing shift was larger in bursters than in nonbursters. Both bursters and nonbursters fired repetitively, albeit intermittently, during tonic and clonic afterdischarge. Throughout the interictal-ictal cycle intracellular spikes were time-locked to population spikes, indicating that PCs fire in tight synchrony. Differential recording of transmembrane potentials unmasked rapid (4-7 ms) transmembrane depolarizing potentials of up to 10 mV, coincident with population spikes. We conclude that in the high-K+ model of hippocampal epilepsy, the local generation of population bursts in CA1 is led by intrinsic bursters, which recruit and synchronize other PCs by synaptic, electrical, and K(+)-mediated excitatory interactions. The cycling between interictal, tonic, and clonic events appears to result from feedback interactions between neuronal discharge and [K+]o.

Development of digestive enzymes in pigs with emphasis on lipolytic activity in the stomach and pancreas

The effect of age and weaning on the activities of digestive enzymes with emphasis on the lipolytic enzymes before and after weaning was investigated. The activities of amylase, chymotrypsin, trypsin, carboxyl ester hydrolase, pancreatic lipase, and colipase in pancreatic tissue and the activity of gastric lipase in the cardiac mucosa of the stomach in 45 pigs were response variables. The activity of trypsin was not affected by weaning and the rate of increase was similar during the whole experiment. The activities of chymotrypsin and amylase decreased at weaning (P < .05). After weaning the activity of chymotrypsin increased more slowly than before weaning (P < .001), whereas the rate of increase of amylase activity remained unchanged. Lipase, colipase, and carboxyl ester hydrolase activities decreased at weaning (P < .001), whereas gastric lipase activity increased at weaning (P < .01). The development of lipase, colipase, and carboxyl ester hydrolase activity decreased postweaning (P < .01), whereas gastric lipase activity increased before weaning and remained constant after weaning. Pancreatic lipase had a considerably higher capacity for hydrolyzing tributyrin, and the total activity of pancreatic lipase was up to 600 times higher than that of gastric lipase. The lipolytic enzymes displayed a non-parallel pattern of development, and we suggest that this reflects the importance of these enzymes during the suckling and postweaning phases, respectively. However, the significance of gastric lipase for the digestion of fat in pigs remains to be elucidated.

Cooperative quizzes in the anatomy and physiology laboratory: a description and evaluation

Physiology educators read journals, such as this one, to gather ideas about curriculum and instruction. Most articles focus on curriculum (i.e., what is taught), but this paper will focus on instruction (i.e., how curriculum is implemented). Just as there are different types of curricula, there are different types of instruction. The most common strategy is lecture. Lectures are extremely efficient for delivering large amounts of information in a short period of time. A common laboratory strategy is discovery or inquiry-based learning (i.e., giving students tools, cognitive and physical, to deduce new information via investigations). A third instructional strategy is the use of cooperative learning. Proper conditions are required for each instructional strategy, and problems arise when the wrong combinations are put together. This paper will describe how a cooperative learning environment can be created in the anatomy and physiology laboratory through the use of cooperative quizzes. It will include a brief introduction to the pedagogical theory behind cooperative learning and an evaluation of the effectiveness of quizzes compared with more traditional methods.

Exocrine pancreatic secretions in growing pigs fed diets containing fish oil, rapeseed oil or coconut oil

Two experiments were performed to study the effect of feeding diets containing oils with different fatty acid composition on exocrine pancreatic secretions in growing pigs using two different methods to collect pancreatic juice. In the first experiment, three barrows (initial weight 37 kg) were fitted with a pancreatic pouch re-entrant cannula. An isolated pouch was prepared where the pancreatic duct enters the duodenum. In the second experiment, also using three barrows (initial weight 32 kg), a catheter was inserted into the pancreatic duct. Three wheat starch and fish meal-based diets were formulated to contain either 15 g fish oil, rapeseed oil or coconut oil/100 g. In both experiments, the diets were fed according to a 3 times 3 Latin square design. The volume of pancreatic juice secreted, pH and secretion of bicarbonate, protein, amylase, trypsin, lipase and colipase were not significantly affected by the diets in the first experiment. In the second experiment, chymotrypsin secretion was significantly greater in pigs fed the coconut oil diet, and secretion of carboxyl ester hydrolase was significantly higher in pigs fed the fish oil diet. When compared qualitatively, pigs in Experiment 2 secreted more pancreatic juice; the pancreatic juice had a higher pH, and trypsin, carboxyl ester hydrolase and colipase secretions were substantially higher whereas amylase secretion was lower than for pigs in Experiment 1. The fatty acid composition of the different oils had minor effects on exocrine pancreatic secretion in growing pigs. However, there were considerable differences between the two surgical methods used to collect pancreatic juice, and these differences may be explained by physiological changes induced by the two methods.

Spike after-depolarization and burst generation in adult rat hippocampal CA1 pyramidal cells

1. Intracellular recordings in adult rat hippocampal slices were used to investigate the properties and origins of intrinsically generated bursts in the somata of CA1 pyramidal cells (PCs). The CA1 PCs were classified as either non-bursters or bursters according to the firing patterns evoked by intrasomatically applied long ( > or = 100 ms) depolarizing current pulses. Non-bursters generated stimulus-graded trains of independent action potentials, whereas bursters generated clusters of three or more closely spaced spikes riding on a distinct depolarizing envelope. 2. In all PCs fast spike repolarization was incomplete and ended at a potential approximately 10 mV more positive than resting potential. Solitary spikes were followed by a distinct after-depolarizing potential (ADP) lasting 20-40 ms. The ADP in most non-bursters declined monotonically to baseline ('passive' ADP), whereas in most bursters it remained steady or even re-depolarized before declining to baseline ('active' ADP). 3. Active, but not passive, ADPs were associated with an apparent increase in input conductance. They were maximal in amplitude when the spike was evoked from resting potential and were reduced by mild depolarization or hyperpolarization (+/- 2 mV). 4. Evoked and spontaneous burst firing was sensitive to small changes in membrane potential. In most cases maximal bursts were generated at resting potential and were curtailed by small depolarizations or hyperpolarizations (+/- 5 mV). 5. Bursts comprising clusters of spikelets ('d-spikes') were observed in 12% of the bursters. Some of the d-spikes attained threshold for triggering full somatic spikes. Gradually hyperpolarizing these neurones blocked somatic spikes before blocking d-spikes, suggesting that the latter are generated at more remote sites. 6. The data suggest that active ADPs and intrinsic bursts in the somata of adult CA1 PCs are generated by a slow, voltage-gated inward current. Bursts arise in neurones in which this current is sufficiently large to generate suprathreshold ADPs, and thereby initiate a regenerative process of spike recruitment and slow depolarization.

Ionic basis of spike after-depolarization and burst generation in adult rat hippocampal CA1 pyramidal cells

1. Intracellular recordings in adult rat hippocampal slices were used to identify the ionic conductances underlying active spike after-depolarization (ADP) and intrinsic burst firing in the somata of CA1 pyramidal cells (PCs). To test the 'Ca2+ hypothesis', Ca2+ currents were suppressed by replacing the Ca2+ in the saline with either Mn2+ or Mg2+. Alternatively, the inorganic Ca2+ channel blockers Cd2+ (0.5 mM) or Ni2+ (2 mM) were added to the saline. To test the 'Na+ hypothesis', Na+ currents were blocked with tetrodotoxin (TTX; 0.5 microM). 2. The suppression of Ca2+ currents blocked the fast after-hyperpolarization (AHP) generated by the fast Ca(2+)-gated K+ current Ic, while enhancing the amplitude and duration of active spike ADPS. 3. Evoked and spontaneous burst firing was preserved undiminished following Ca2+ current suppression, while the propensity to fire bursts increased in many cases. The postburst medium AHP (generated primarily by the muscarine-sensitive voltage-gated K+ current, IM) was not affected by this treatment, which blocked the slow AHP (generated by the slow Ca(2+)-gated K+ current, IAHP). 4. TTX strongly suppressed active ADPs and intrinsic bursts before substantially reducing the threshold, rate of rise and amplitude of solitary spikes. 5. In Ca(2+)-free saline, caesium-filled PCs generated large, plateau ADPs following an initial burst of fast spikes. Application of TTX suppressed these ADPs before solitary fast spikes appeared to be reduced. 6. Injection of brief, just subthreshold depolarizing current pulses into bursters evoked slow depolarizing potentials lasting up to 50 ms. These persisted after suppression of Ca2+ currents and were entirely blocked by TTX. 7. We conclude that active spike ADPs and intrinsic bursts in the somata of adult CA1 PCs are generated by a low voltage-gated, persistent Na+ current. Burst termination is mediated by voltage-gated K+ currents activated during the burst (most likely IM), rather than by the Ca(2+)-gated K+ currents Ic and IAHP. The latter currents downregulate the innate tendency of CA1 PCs to burst (Ic) and limit the rate of spontaneous burst firing (IAHP).

Fast and one-step folding of closely and distantly related homologous proteins of a four-helix bundle family

Bovine acyl-coenzyme A binding protein is a four-helix bundle protein belonging to a group of homologous eukaryote proteins that binds medium and long-chain acyl-coenzyme A esters with a very high affinity. The three-dimensional structure of both the free and the ligated protein together with the folding kinetics have been described in detail for the bovine protein and with four new sequences reported here, a total of 16 closely related sequences ranging from yeasts and plants to human are known. The kinetics of folding and unfolding in different concentrations of guanidine hydrochloride together with equilibrium unfolding have been measured for bovine, rat and yeast acyl-coenzyme A binding protein. The bovine and rat sequences are closely related whereas the yeast is more distantly related to these. In addition to the three natural variants, kinetics of a bovine mutant protein, Tyr31 --> Asn, have been studied. Both the folding and unfolding rates in water of the yeast protein are 15 times faster than those of bovine. The folding rates in water of the two mammalian forms, rat and bovine, are similar, though still significantly different. A faster unfolding rate both for rat and the bovine mutant protein results from a lower stability of the native states of these. These hydrophobic regions, mini cores, have been identified in the three-dimensional structure of the bovine protein and found to be formed primarily by residues that have been conserved throughout the entire eukaryote evolution from yeasts to both plants and mammals as seen in the sample of 16 sequences. The conserved residues are found to stabilize helix-helix interactions and serve specific functional purposes for ligand binding. The fast one-step folding mechanism of ACBP has been shown to be a feature that seems to be maintained throughout evolution despite numerous differences in sequence and even dramatic differences in folding kinetics and protein stability. The protein study raises the question to what extent does the conserved hydrophobic residues provide a scaffold for an efficient one-step folding mechanism.

The pattern of the circadian rhythm of pancreatic secretion in fed pigs

The pattern of the circadian rhythm of pancreatic secretion was studied in four 6- to 7-wk-old intact male pigs that were kept in metabolic cages under 12 h light:12 h dark cycles and fed three times a day at 0800, 1500, and 2200. Three 24-h collections of pancreatic juice and blood were begun at 0800 every 2nd day during 5 d. A biphasic pattern of the exocrine pancreas was detected. Secretions during the first phase (postprandial peak) contained large amounts of protein and enzymes, and secretions appeared immediately after feed ingestion. Secretions during the second phase (between meals) had lesser amounts (P < .001) of protein and enzymes, but were of longer duration (P < .001). The output of protein and trypsin activity were generally correlated (P < .001) with each other, but the correlation of either with the volume outflow were small. However, these variables were correlated (P < .01) with the volume outflow at night during the second phase. Plasma concentrations of insulin and glucose increased after each meal, but the increase was significant (P < .05) only for insulin. Insulin and glucose concentrations were correlated (P < .01) with each other after the meals at 0800 and 1500. The results indicated a biphasic pattern of the exocrine pancreas and a monophasic pattern of the endocrine pancreas in pigs. The regulation of these patterns seems to vary during the 24-h period. Furthermore, feed enhanced secretion, but it did not seem to be the only factor controlling the circadian pattern.

Muscarinic modulation of intrinsic burst firing in rat hippocampal neurons

Intracellular recordings in rat hippocampal slices were used to examine how exogenous and endogenous cholinergic agonists modulate the firing pattern of intrinsically burst-firing pyramidal cells. About 24% of CA1 pyramidal cells generated all-or-none, high-frequency bursts of fast action potentials in response to intracellular injection of long positive current pulses. Application of carbachol (5 microM) converted burst firing in these neurons into regular trains of independent spikes. Acetylcholine (5 microM) exerted a similar effect, provided acetylcholine esterase activity was blocked with neostigmine (2 microM). Atropine (1 microM) reversed this cholinergic effect, indicating its mediation by muscarinic receptors. Cholinergic agonists also caused mild neuronal depolarization but the block of intrinsic burst firing was independent of this effect. Repetitive stimulation of cholinergic fibres in the presence of neostigmine (2 microM) evoked a slow cholinergic excitatory postsynaptic potential (EPSP) lasting about a minute. During the slow EPSP, burst firing could not be evoked by depolarizing pulses and the neurons fired in regular mode. These effects were prevented by pretreatment with atropine (1 microM). Exogenously applied cholinergic agonists and endogenously released acetylcholine also reduced spike frequency accommodation and suppressed the long-duration afterhyperpolarization in burst-firing pyramidal cells in an atropine-sensitive manner. A membrane-permeable cAMP analogue (8-bromo-cAMP; 1 microM) also reduced frequency accommodation and blocked the long-duration afterhyperpolarization, but did not affect intrinsic burst firing at all. Taken together, the data show that muscarinic receptor stimulation transforms the stereotyped, phasic response of burst-firing neurons into stimulus-graded, tonic discharge.

Variant firing patterns in rat hippocampal pyramidal cells modulated by extracellular potassium

1. The distribution of distinctive firing modes within the population of CA1 pyramidal cells and their modulation by the extracellular concentration of potassium ([K+]o) were investigated with intracellular recordings in rat hippocampal slices. 2. Pyramidal cells were injected with long (> 250 ms) and brief (3-5 ms) positive current pulses of increasing intensity. In normal [K+]o (3.5 mM), most cells (38 of 46 cells; 83%) were regular spiking neurons (generating accommodating trains of independent action potentials during long depolarizations and a single spike in response to brief stimuli). The remaining pyramidal cells (8 of 46; 17%) displayed differential tendencies to generate stereotyped clusters of action potentials, or bursts, according to which they were grouped into three subsets of endogenous bursters: grade I, bursting only when stimulated with long depolarizing current pulses (6 of 46; 13%); grade II, bursting also in response to brief stimulation (1 of 46; 2%); grade III, bursting also spontaneously even in absence of synaptic transmission (1 of 46; 2%). 3. Raising [K+]o from 3.5 to 7.5 mM (high [K+]o) significantly reduced resting membrane potential and input impedance but did not change the threshold potential for eliciting an action potential. 4. Raising [K+]o to 7.5 mM reversibly converted many regular spiking cells to bursters. Likewise, the burst tendency of normally bursting pyramidal cells increased to a higher grade in high [K+]o. Consequently, the fraction of bursters in high [K+]o (17 of 41 cells; 42%) was approximately 2.5-fold higher than in normal [K+]o and their differential distribution was shifted toward higher grades of bursting.(ABSTRACT TRUNCATED AT 250 WORDS)

Opponent effects of potassium on GABAA-mediated postsynaptic inhibition in the rat hippocampus

1. The effects of raising the concentration of extracellular potassium ([K+]o) on gamma aminobutyric acid (GABA)-mediated inhibitory postsynaptic potentials (IPSPs) were investigated in adult rat hippocampal slices using intracellular recording techniques. IPSPs were evoked in CA1 pyramidal neurons by direct activation of inhibitory interneurons in slices treated with glutamatergic antagonists to block excitatory synaptic transmission. The fast (Cl(-)-dependent, GABAA receptor-mediated) IPSPs (fIPSPs) were isolated from the slow (K(+)-dependent; GABAB receptor-mediated) IPSPs (sIPSPs) by intracellular injection of QX-314, which also suppressed fast (Na(+)-dependent) action potentials. 2. In normal (3.5 mM) and in high (7.5 mM) [K+]o, the peak fIPSP amplitude changed nonlinearly with membrane potential (VM) in a way consistent with outward rectification of the underlying conductance. The input conductance of the fIPSP (GfIPSP) measured around resting VM (about -67 mV) increased 1.7-fold on changing from normal to high-K+ saline, whereas resting VM depolarized 6.8 mV. Repolarizing VM reversed the increase in GfIPSP, suggesting that it was due to outward rectification. The resting input conductance of the neurons increased 1.4-fold in high K+. 3. The time course of fIPSPs was prolonged by high K+. The half time of fIPSP decay increased 1.4-fold, and in half of the neurons the decay became conspicuously multipeaked, suggesting that neurally evoked GABA release from inhibitory interneurons was prolonged. 4. In normal K+, the reversal potentials of fIPSPs (EfIPSP; -76.5 mV) was 9.7 mV more negative than resting VM. Polarizing VM 10-20 mV for 15 min with current injection did not change EfIPSP appreciably.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and characterization of variants of acyl-CoA-binding protein in the bovine liver

Four differently modified forms of acyl-CoA-binding protein (ACBP) were identified in ACBP purified from bovine liver. The majority of the purified ACBP was focused at pH 5.9 in isoelectric focusing and could be shown to be N-acetylated ACBP without any further modifications. Two minor peaks were focused at pH 5.25 and 4.85 respectively. Mass spectrometry and sequence determination showed that the pI 5.25 form was acetylated at Lys18 and that the pI 4.85 form was malonylated in the same position. Furthermore, it could be shown that non-enzymic glycosylation occurred during purification. The acetylated and malonylated variants of ACBP were only found in adult cattle.

Electrophysiological recordings from rat hippocampus slices following in vivo brain ischemia

Pyramidal neurons in area CA1 of the septal hippocampus degenerate 2-3 days after an episode of transient global cerebral ischemia. The purpose of this study was to investigate synaptic transmission and passive neuronal properties in the post-ischemic period prior to neuronal death. Electrophysiological recordings were made from area CA1 in hippocampal slices prepared from rats which had survived a period of 20 min of ischemia for up to 5 days. In septal slices, field responses were in area CA1 unaltered up to 24 h after the ischemic insult. Forty-eight hours after ischemia, the mean amplitude of the population spike, but not the field-EPSP, was significantly reduced. In septal slices prepared more than 48 h after ischemia field potentials were absent or strongly attenuated, whereas they were intact in slices prepared from the temporal pole. No spontaneous discharges were detected in slices prepared at any time from post-ischemic rats. Intracellular recordings were obtained from slices up to 48 h after the ischemic episode. There was no significant difference in the resting membrane potential or input resistance between these neurons and those from control slices. Action potentials followed by a fast afterhyperpolarization and spike accommodation were preserved in all post-ischemic neurons. In all neurons investigated, orthodromic stimulation evoked an EPSP followed by a fast- and then a slow-IPSP. One hour after ischemia, the slow-IPSP was reduced. Forty-eight hours after ischemia, the fast-IPSP was significantly increased. The EPSP was markedly attenuated by the non N-methyl-D-aspartate receptor blocker 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM). The residual depolarizing component was amplified by perfusing with Mg(2+)-free medium and blocked by the N-methyl-D-aspartate receptor antagonist DL-2-amino-5-phosphonovaleric acid. Paired-pulse facilitation of the EPSP was also preserved. As in control slices, the slow-IPSP and paired-pulse depression of the fast-IPSP were blocked by 1 microM baclofen. The present experiments provide no evidence that overt alteration of excitatory synaptic transmission or neuronal properties favouring hyperexcitability precede the ischemically induced death of CA1 pyramidal cells.

Inhibition in postischemic rat hippocampus: GABA receptors, GABA release, and inhibitory postsynaptic potentials

We have investigated the GABAergic system in rat hippocampus at 1 hour and up to 21 days following 20 min of global cerebral ischemia. Distribution of 3H-GABA (in excess of unlabeled baclofen) and 3H-Ro-15-1788 (benzodiazepine antagonist) binding sites in hippocampus was studied utilizing quantitative autoradiography. The 3H-GABA binding was unchanged (p greater than 0.01) after ischemia, whereas the 3H-Ro-15-1788 binding decreased significantly (p less than 0.01) in all hippocampal subfields 1-21 days after ischemia. Using microdialysis in CA1, we found that K(+)-stimulated GABA release at 1 hour and 1 day after ischemia was unchanged (p greater than 0.01) in comparison to preischemic controls. Electrophysiological recordings were made from CA1 of hippocampal slices prepared from rats sacrificed 1 hour, 1 day and 2 days after ischemia. Field potentials evoked by stimulation of the Schaffer collaterals showed no differences (p greater than 0.01) from those taken from controls. Postischemic intracellular recordings from the CA1 pyramidal cells showed that fast and slow inhibitory postsynaptic potentials were readily evoked on orthodromic stimulation. Together with our previous morphological results, demonstrating survival of hippocampal interneurons following ischemia, we conclude that hippocampal GABAergic interneurons preserve their inhibitory potential in the period preceding delayed CA1 pyramidal cell death. This conclusion taken together with the observation that postischemic 3H-Ro-15-1788 binding in hippocampus declined, suggest that benzodiazepines (by increasing the receptor affinity), GABA analogs, and GABA uptake inhibitors may be useful in the treatment of ischemic CA1 pyramidal cell death in the rat.

GABAB receptors play a major role in paired-pulse facilitation in area CA1 of the rat hippocampus

Extracellular recordings of field potentials in area CA1 of the rat hippocampal slice have been used to investigate paired-pulse facilitation. Field potentials were evoked by maximal stimulation of the Schaffer collateral/commissural fibres. The height of the population spike (PS) in stratum pyramidale (str. pyr.) and the area under the field excitatory postsynaptic potential (EPSP) following the PS in the stratum radiatum (str. rad.) were quantified. These values were used to describe the time course of paired-pulse facilitation. Facilitation of the PS was maximal 50 ms after the conditioning pulse and was present over a period of about 500 ms. However, facilitation of the late area (LA) of the field EPSP was maximal afer 125 ms and had an overall duration of 1-2 s. The N-methyl-D-aspartate (NMDA) receptor antagonist, 2-amino-5-phosphonovaleric acid (APV), had no effect on paired-pulse facilitation of either the LA or the PS. The gamma-aminobutyric acid-B (GABAB) agonist baclofen increased facilitation of the PS. This was mainly due to a reduction of the unconditioned response. Facilitation of the LA was reduced by both baclofen and the GABAB antagonist, 2-OH-saclofen. Baclofen increased the LA of the unconditioned response, while this was unaffected by 2-OH-saclofen. The LA of facilitated responses was decreased by 2-OH-saclofen while the effect of baclofen on these responses was more complex. Baclofen reduced the LA of maximally facilitated responses, while the LA of slightly facilitated responses was increased. The results show that different mechanisms are involved in the facilitation of the LA and the PS. Furthermore, activation of GABAB receptors makes a large contribution to paired-pulse facilitation of the field EPSP. It is also suggested that recording of extracellular fields in str. rad. in response to paired-pulse stimulation provides a simple electrophysiological model for testing the effect of agents which act at the GABAB receptor.