A retrospective observational cohort study on the postoperative respiratory complications and their risk factors in brachycephalic dogs undergoing BOAS surgery: 199 cases (2019-2021)

OBJECTIVES

To observe the occurrence of postanaesthetic respiratory complications and to determine their prevalence and risk factors in dogs undergoing brachycephalic obstructive airway syndrome surgery.

MATERIALS AND METHODS

Data from 199 clinical records were retrospectively analysed. Univariable logistic regression followed by multivariable logistic regression was used to identify associations between the dependent variables (set as the postoperative respiratory complications observed in the study dogs) and various independent covariates. The quality of model-fit was assessed using the likelihood ratio test. P≤0.05 was considered statistically significant.

RESULTS

Four postoperative respiratory complications were observed: hypoxaemia (n=10/199; 5%), dyspnoea requiring tracheal re-intubation (n=13/199, 7%), dyspnoea requiring tracheostomy (n=10/199, 5%) and aspiration pneumonia (n=12/199, 6%). Univariable logistic regression showed an association between postoperative aspiration pneumonia and increasing body condition score and American Society of Anaesthesiology classification; however, when these covariates were evaluated in the multivariable model significance was not maintained. Risk factors for tracheostomy were preoperative and postoperative aspiration pneumonia (odds ratio: 9.52, 95% confidence interval: 1.56 to 57.93) and increasing brachycephalic obstructive airway syndrome grade (odds ratio: 4.65, 95% confidence interval: 0.79 to 27.50).

CLINICAL SIGNIFICANCE

High brachycephalic obstructive airway syndrome grade and aspiration pneumonia, either developing peri-operatively or as pre-existing condition, may represent risk factors for postoperative tracheostomy. Preoperative diagnosis of aspiration pneumonia may further increase the risk of postoperative complications.

Abstract P5-13-32: Mucin 4 expression in high risk breast cancer: Predicting and overcoming resistance to immunotherapy

Background HER2-positive (+) and triple negative breast cancer (TNBC) have the worst survival among BC. BC patients are treated with chemotherapy (CT) and/or radiotherapy (RT), and HER2+ BC patients also receive targeted therapies, such as trastuzumab (Tz). The abundance of tumor infiltrating lymphocytes (TILs), in both HER2+ and TNBC, has a major good prognostic value. Thus, indicating that immunological evasion mechanisms are present in the tumor microenvironment (TME) hampering the efficacy of the treatments. We previously showed that soluble tumor necrosis factor α (sTNF) induces upregulation of mucin 4 (MUC4), which shields Tz epitope on HER2 impairing Tz binding and its effects. In preclinical models of de no5vo Tz-resistant tumors, administration of the sTNF blocking agent INB03 (DN) together with Tz inhibited tumor growth. We proved that MUC4 expression is an independent predictor of poor DFS in patients treated with adjuvant Tz. Our goal is to study whether MUC4 plays a role in tumor immune evasion in HER2+ and TNBC. Methods Untreated primary BC samples were assessed for TILs density (H&E) and MUC4 expression by immunohistochemistry. Tumors with TILs ≥30% and >50%, for TNBC and HER2+ BC respectively, and MUC4 scores 2 and 3 (0-3) were deemed positive. A cohort of 56 TNBC and 90 HER2+BC, stage I-III were retrospectively retrieved from Hospital Fernández and Instituto Henry Moore from 2013-2017, and clinicopathological and treatment characteristics were obtained from electronic records. TNBC were treated with adjuvant (41) or neoadjuvant CT +/- RT (15). HER2+BC patients received adjuvant Tz + CT. The association between MUC4 and OS was assessed by Kaplan Meier and log rank test and between MUC4 and TILs using Chi2. JIMT-1 HER2+ BC, de novo resistant tumors to Tz, containing a doxycycline (Dox)-inducible shRNA MUC4 plasmid (JIMT-1shMUC4) growing in nude mice were treated with IgG, Tz, DN or Tz + DN. Tumor growth was measured and macrophages and NK cells were determined in the TME by flow cytometry. Anti-asialo GM1 and clodronate-encapsulated liposomes were used to deplete NK cells and macrophages, respectively. Results We found an inverse relationship between TILs and MUC4 expression in HER2+ and TNBC (P=0.02 and P= 5 x10-5, respectively). Patients with MUC4+ TNBC have a shorter OS (P=0.03) and MUC4 was an independent predictor of OS [P=0.01; HR 4.9 (95%CI 1.4-17.0)]. To study MUC4 involvement in macrophage and NK cells recruitment in a Tz resistant model, nude mice bearing JIMT-1-shMUC4 tumors were treated or not with Dox to abolish MUC4 expression. Both groups received IgG, Tz, DN or DN + Tz. In control groups (without Dox), only Tz + DN administration was able to inhibit tumor growth (75% inhibition, P<0.0001 vs. IgG), in line with our previous results, and DN treatment reduced MUC4 expression. Knockdown of MUC4 expression by Dox, showed that Tz alone was effective in inhibiting JIMT-shMUC4 tumor growth at similar levels than Tz + DN group. Tumor growth inhibition was accompanied by an increase in NK cells activation and degranulation, and a rise in M1/M2 macrophage ratio. Depletion of macrophages or NK cells totally blunted antitumor effect of Tz + DN in control tumors. In MUC4-silenced tumors only macrophage depletion was able to abolish Tz antitumor effect. Conclusion Our results suggest that i) MUC4 expression is associated with immunologically “cold” HER2+ and TNBC, inducing an immunosuppressive TME that reflects in poor DFS/OS, and it confers resistance to Tz in HER2+ BC; ii) elimination of MUC4 expression reverses resistance to Tz; iii) tumor infiltrating macrophages are critical to the anti-tumor response in HER2+ BC. Patients with MUC4+ HER2+ or MUC4+ TNBC should benefit from sTNF blockade treatment leading to MUC4 downregulation and higher TILs, which would result in a better response to Tz and probably to immune checkpoint inhibitors.

Citation Format: Roxana Schillaci, Sofia Bruni, Florencia Mauro, María F Mercogliano, Agustina Roldan-Deamicis, Cecilia J Proietti, Rosalía Cordo-Russo, Gloria Inurrigarro, Agustina Dupont, Carla Adami, Daniel Lopez Della Vecchia, Sabrina Barchuck, Silvina Figurelli, Ernesto Gil Deza, Sandra Ares, Felipe G Gercovich, Patricia V Elizalde. Mucin 4 expression in high risk breast cancer: Predicting and overcoming resistance to immunotherapy [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-32.

Inadvertent injection of medetomidine in the cerebromedullaris cisterna of a dog during myelographic exam

INTRODUCTION

A mixed breed dog was anesthetized for diagnostic myelography to investigate acute onset neck pain. Instead of contrast medium, 444 μg/kg medetomidine were inadvertently injected into the cerebromedullaris cisterna owing to a human error. Severe bradycardia, undetectable peripheral pulse, respiratory arrest and loss of pupillary, palpebral and corneal reflexes were observed immediately after injection. Profound hypothermia developed and esophageal temperature, measured 20 minutes after medetomidine injection, was 33 °C. Atipamezole at 1 mg/kg im was administered, followed by a second dose of 0,5 mg/kg iv 20 minutes thereafter. In the meantime, cardiorespiratory parameters and body temperature were monitored, and supportive care that included manually assisted pulmonary ventilation, active warming, and administration of 5 μg/kg/min dopamine was initiated. The dog's clinical condition improved within one hour from the beginning of supportive care, at which time ocular reflexes and swallowing returned, spontaneous ventilation was deemed as adequate and the trachea could be extubated. The dog was discharged in good clinical conditions five days later. Human error and distraction led to a potentially life-threatening complication in the dog of this report and could have possibly been prevented with the use of checklists and with a clearer definition of roles and responsibilities of the personnel involved prior to commencing the clinical procedure. Profound cardiovascular, respiratory, and thermoregulatory depression caused by intracisternal injection of medetomidine responded to parenteral administration of its antagonist and supportive care.

Occurrence of pulsus alternans during anaesthesia of two dogs and one cat and its treatment

The authors report the occurrence of pulsus alternans, a condition characterised by the alternance of pulses of higher and lower amplitude, in two dogs and one cat under general anaesthesia. The presence of an underlying cardiac disease was confirmed in the cat but not in either dog, which - based on history and clinical findings - had presumably normal cardiovascular function before the anaesthetic. Possible mechanisms, including negative inotropy and haemodynamic and Frank-Starling effects, as well as the role of general anaesthesia as the potential triggering factor, are discussed in this report. Ephedrine resulted in the successful treatment of pulsus alternans, as demonstrated by the return of normal pulse and synchronisation of heart and pulse rates in the cat and in one dog. In the other dog, pulse pattern and frequency returned to normal once the guidewire for central line placement was withdrawn.

Challenging anaesthetic management of captive reindeer (Rangifer tarandus): Report of 4 cases

INTRODUCTION

Four captive reindeer underwent anaesthesia to allow dehorning or drainage of lymph nodes abscessation. Premedication was based on xylazine (dose range: 0.075- 0.5 mg/kg, IM or IV), with or without ketamine (dose range: 1-2 mg/kg, IM or IV), all of which failed to produce effective sedation without side effects. During anaesthesia, 2 reindeer experienced severe hypoxaemia and hypoventilation. Recovery was smooth in 3 out 4 animals, but delayed in one reindeer sedated with 0.5 mg/kg of xylazine IV; this patient required repeated atipamezole administrations (0.01 mg/kg IM given 3 times) to regain normal locomotion. Anaesthesia of reindeer is challenging and useful dose ranges for safe and effective anaesthesia are mostly unknown.

Etomidate anaesthesia by immersion in oriental fire-bellied toads (Bombina orientalis)

The objective of the present study was to evaluate the efficacy and the safety of etomidate anaesthesia by immersion technique in Bombina orientalis. The study comprised two phases. The first phase was carried out to identify the etomidate concentration capable of producing anaesthetic induction, as well as surgical anaesthesia, in the toads. The second phase was aimed at testing that concentration in eight additional animals. Etomidate administered via immersion at a concentration of 37.5 mg/L produced effective anaesthesia in oriental fire-bellied toads. The average duration of surgical anaesthesia was 20 min. All the toads enrolled in the study survived the anaesthesia and long-term complications did not occur. However, undesired side-effects, namely itching, myoclonus and prolonged recovery, were noticed during the perianaesthetic period. The authors concluded that etomidate anaesthesia by immersion, at a concentration of 37.5 mg/L, is suitable in oriental fire-bellied toads and produces anaesthesia of a depth and duration that is sufficient to allow the completion of various experimental procedures, without resulting in lethal complications. However, the occurrence of undesired side-effects opens a debate on the safety of this anaesthetic technique, and imposes the need for further investigation prior to proposing the latter for routine laboratory practice.

Seizure activity occurring in two dogs after S-ketamine-induction

Two healthy dogs were anaesthetized to undergo elective orthopaedic procedures. After premedication with methadone and acepromazine, general anaesthesia was induced with midazolam and S-ketamine. Immediately after anaesthetic induction, seizures occurred in both dogs. In the first dog the syndrome was characterized by tonic and clonic motor activity, muscular hypertone, hypersalivation, urination, defecation and hyperthermia. In the second dog muscular twitches of the temporal and masseter regions were observed, followed by increased skeletal muscles tone, hypersalivation, spontaneous urination and increase in body temperature. Recoveries from anaesthesia were uneventful and no seizures were observed. Considering the temporal association between anaesthetic induction and occurrence of seizures, and the fact that other causative factors could not be identified, it is hypothesized that S-ketamine played a role in determining the convulsive phenomena observed in these patients. S-ketamine might carry the potential for inducing seizures in otherwise healthy dogs, despite the concomitant use of GABA-ergic drugs.

Anaesthesia with medetomidine-ketamine-isoflurane with and without midazolam, in eight captive chimpanzees (Pan troglodytes) premedicated with oral zuclopenthixol

In 8 captive adult chimpanzees of various ages premedicated with oral zuclopenthixol anaesthesia was induced intramuscularly with a combination of medetomidine and ketamine (40 or 50 µg/kg and 5 mg/kg, IM, respectively), with and without midazolam (0.05 mg/kg), and maintained with isoflurane in oxygen. At the end of the procedure, sedation was reversed with atipamezole (0.25 mg/kg, IM) and sarmazenil (0.005 mg/kg, IM) when midazolam had been administered. Oral zuclopenthixol resulted in tranquillization of the whole group and only one animal required a second dart injection to achieve adequately deep anaesthesia. Effective and reliable anaesthesia was achieved in all apes; the depth of hypnosis was stable and sudden arousal did not occur. Physiological parameters remained within normal ranges in the majority of the animals; however, manageable anaesthesia-related complications, namely apnoea after darting, hypotension, hypoventilation, hypoxemia and prolonged recovery, occurred in 6 out of 8 animals. The use of monitoring devices was essential to guarantee adequate management of these complications.

Preemptive carprofen for peri-operative analgesia in dogs undergoing Tibial Plateau Leveling Osteotomy (TPLO): a prospective, randomized, blinded, placebo controlled clinical trial

Eighteen client-owned dogs undergoing Tibial Plateau Leveling Osteotomy (TPLO) were included in this blinded clinical study and randomly assigned to one of two treatment groups. Group C (carprofen) received intravenous (IV) carprofen, 4 mg/kg, prior to anesthesia, whereas group P (placebo) received IV saline. General anesthesia was maintained with isoflurane in oxygen and a constant rate infusion (CRI) of sufentanyl IV. Intra-operatively, assessment of nociception was based on changes in physiological parameters and on the analgesics requirement, whereas in the post-operative period evaluation of pain was performed by using a Hellyer and Gaynor pain score and by comparing the doses of rescue buprenorphine required by the two treatment groups. Although no statistically significant differences in intra-operative sufentanyl doses were found between treatment groups, group C had superior cardiovascular stability, and lower post-operative pain scores and rescue buprenorphine doses than group P. Our results indicate that administration of carprofen prior to surgery was effective in improving peri-operative analgesia in dogs undergoing TPLO.

Acute pulmonary edema and airway hemorrhage in a goat during sevoflurane anesthesia

A goat was scheduled for experimental surgery under general anesthesia. The first attempt of performing endotracheal intubation failed and provoked laryngeal spasm. After repeated succesful intubation of inhalation anesthesia was delivered in high concentrations of sevoflurane. Suddenly hypertension and tachycardia were observed, followed by foamy airway secretion and then severe airway hemorrhage. The authors hypothesize that laryngeal spasm provoked respiratory distress and pulmonary edema. The delivered high concentrations of sevoflurane probably enhanced a hyperadrenergic response, predisposing to the development of airway hemorrhage.

Exposure setups for laboratory animals and volunteer studies using body-mounted antennas

For two different in vivo exposure setups body-mounted antenna systems have been designed. The first setup is designed for investigation of volunteers during simulated mobile phone usage. The setup consists of a dual-band antenna for GSM/WCDMA with enhanced carrying properties, which enables exposure for at least 8 h a day. The 10 g averaged localised SAR--normalised to an antenna input power of 1 W--measured in the flat phantom area of the SAM phantom amounts to 7.82 mW g(-1) (900 MHz) and 10.98 mW g(-1) (1966 MHz). The second exposure setup is used for a laboratory behavioural study on rats. The design goal was a localised, well-defined SAR distribution inside the animals' heads at 900 MHz. To fulfil the biological requirements, a loop antenna was developed. For tissues around the ears, a localised SAR value of 50.12 W kg(-1) averaged over a mass of 2.2 g for an antenna input power of 1 W is obtained.

A large population of galaxies 9 to 12 billion years back in the history of the Universe

To understand the evolution of galaxies, we need to know as accurately as possible how many galaxies were present in the Universe at different epochs. Galaxies in the young Universe have hitherto mainly been identified using their expected optical colours, but this leaves open the possibility that a significant population remains undetected because their colours are the result of a complex mix of stars, gas, dust or active galactic nuclei. Here we report the results of a flux-limited I-band survey of galaxies at look-back times of 9 to 12 billion years. We find 970 galaxies with spectroscopic redshifts between 1.4 and 5. This population is 1.6 to 6.2 times larger than previous estimates, with the difference increasing towards brighter magnitudes. Strong ultraviolet continua (in the rest frame of the galaxies) indicate vigorous star formation rates of more than 10-100 solar masses per year. As a consequence, the cosmic star formation rate representing the volume-averaged production of stars is higher than previously measured at redshifts of 3 to 4.

Interaction between directional epistasis and average mutational effects

We investigate the relationship between the average fitness decay due to single mutations and the strength of epistatic interactions in genetic sequences. We observe that epistatic interactions between mutations are correlated to the average fitness decay, both in RNA secondary structure prediction as well as in digital organisms replicating in silico. This correlation implies that, during adaptation, epistasis and average mutational effect cannot be optimized independently. In experiments with RNA sequences evolving on a neutral network, the selective pressure to decrease the mutational load then leads to a reduction in the amount of sequences with strong antagonistic interactions between deleterious mutations in the population.

Evolution of digital organisms at high mutation rates leads to survival of the flattest

Darwinian evolution favours genotypes with high replication rates, a process called 'survival of the fittest'. However, knowing the replication rate of each individual genotype may not suffice to predict the eventual survivor, even in an asexual population. According to quasi-species theory, selection favours the cloud of genotypes, interconnected by mutation, whose average replication rate is highest. Here we confirm this prediction using digital organisms that self-replicate, mutate and evolve. Forty pairs of populations were derived from 40 different ancestors in identical selective environments, except that one of each pair experienced a 4-fold higher mutation rate. In 12 cases, the dominant genotype that evolved at the lower mutation rate achieved a replication rate >1.5-fold faster than its counterpart. We allowed each of these disparate pairs to compete across a range of mutation rates. In each case, as mutation rate was increased, the outcome of competition switched to favour the genotype with the lower replication rate. These genotypes, although they occupied lower fitness peaks, were located in flatter regions of the fitness surface and were therefore more robust with respect to mutations.

A comparison between dynamic pelvic magnetic resonance imaging and videoproctography in patients with constipation

PURPOSE

This study attempts to compare the diagnostic efficacy of dynamic pelvic magnetic resonance imaging with that of videoproctography for the presence of rectocele, sigmoidocele, and intussusception as well as the measurement of anorectal angle and perineal descent in constipated patients.

METHODS

Patients volunteering for the study and fulfilling the criteria for videoproctography to evaluate constipation were also scheduled for dynamic pelvic magnetic resonance imaging. Patients undergoing videoproctography were placed in the left lateral decubitus position, after which 50 ml of liquid barium paste was introduced into the rectum. After this, approximately 100 ml of thick barium paste similar to stool in consistency was injected into the rectum, and the patient was instructed to defecate while video images were taken. For dynamic pelvic magnetic resonance imaging, air, to be used as contrast, was allowed to accumulate in the rectum via examination with the patient in the prone position. A capsule was taped to the perineal skin immediately posterior to the anal orifice for marking. Sagittal and axial T1 images were obtained through the pelvis at 8-mm intervals with dynamic breathhold sagittal images of the anorectal region obtained at rest and during strain and squeeze maneuvers. Total acquisition time per maneuver was approximately 19 seconds. The tests were performed by different examiners blinded to the result of the other evaluation. The investigations were independently interpreted, findings compared, and patients questioned regarding their impression of dynamic pelvic magnetic resonance imaging and videoproctography.

RESULTS

From June 1996 to April 1997, 22 patients (15 females) with a mean age of 68 (range, 21-85) years underwent both videoproctography and dynamic pelvic magnetic resonance imaging. Dynamic pelvic magnetic resonance imaging was only able to detect 1 of 12 (8.3 percent) anterior rectoceles and one of two (50 percent) posterior rectoceles identified by videoproctography. It failed to recognize any of the rectoanal intussusception (zero of four) but did show 9 of 12 (75 percent) sigmoidoceles. Significant discrepancy of measurement of the anorectal angle and perineal descent exists between the two studies, and dynamic pelvic magnetic resonance imaging was not able to detect any (0 of 11) of the patients with increased fixed perineal descent and only half (one of two) of the patients with increased dynamic perineal descent noted on videoproctography. All 22 patients preferred dynamic pelvic magnetic resonance imaging over videoproctography because of greater comfort.

CONCLUSION

Occasionally, the increased cost of new technology can be justified by the enhanced diagnostic yield. The ability to avoid unnecessary surgery or, conversely, to continue to search for otherwise occult pathology that can be surgically corrected justifies routine application of these new tools. However, this study has shown that, despite a cost of approximately ten times more for dynamic pelvic magnetic resonance imaging than for videoproctography, no clinical changes were made. Thus, on the basis of this study, we cannot endorse the routine application of dynamic pelvic magnetic resonance imaging for the evaluation of constipated patients. In certain selected individuals, it may play a role, but further study is necessary to clarify its exact role.

S100B expression in and effects on microglia

We evaluated the intracellular and extracellular biological role of S100B protein with respect to microglia. S100B, which belongs to the multigenic family of Ca2+-binding proteins, is abundant in astrocytes where it is found diffusely in the cytoplasm and is associated with membranes and cytoskeleton constituents. S100B protein is also secreted by astrocytes and acts on these cells to stimulate nitric oxide secretion in an autocrine manner. However, little is known about the relationship between S100B and microglia. To address this issue, we used primary microglia from newborn rat cortex and the BV-2 microglial cell line, a well-established cell model for the study of microglial properties. S100B expression was assessed by immunofluorescence in primary microglia and by RT-PCR, Western blotting, and immunofluorescence in BV-2 cells. S100B was found in microglia in the form of a filamentous network as well as diffusely in the cytoplasm and associated with intracellular membranes. S100B relocated around phagosomes during BV-2 phagocytosis of opsonized Cryptococcus neoformans. Furthermore, interferon-gamma (IFN-gamma) treatment caused cell shape changes and redistribution of S100B, and downregulation of S100B mRNA expression in BV-2 cells. Treatment of BV-2 cells with nanomolar to micromolar amounts of S100B resulted in increased IFN-gamma-induced expression of inducible nitric oxide synthase mRNA as well as nitric oxide secretion. Taken together, these data suggest a possible role for S100B in the accomplishment/regulation of microglial cell functions.

Evolution of biological complexity

To make a case for or against a trend in the evolution of complexity in biological evolution, complexity needs to be both rigorously defined and measurable. A recent information-theoretic (but intuitively evident) definition identifies genomic complexity with the amount of information a sequence stores about its environment. We investigate the evolution of genomic complexity in populations of digital organisms and monitor in detail the evolutionary transitions that increase complexity. We show that, because natural selection forces genomes to behave as a natural "Maxwell Demon," within a fixed environment, genomic complexity is forced to increase.

A pilot assessment of whether external coil MRI is useful to assess evacuatory disorders

This study assessed the value of common surface coil magnetic resonance imaging (MRI) in patients with evacuatory disorders including fecal incontinence and constipation. These findings were then compared with those from other standard physiological examinations and/or surgical findings. From July 1996 to June 1997, 14 consecutive patients underwent surface coil MRI for evaluation of either fecal incontinence (n=5) or constipation (n=9). In patients with incontinence we compared the findings from endoanal ultrasound (EAUS), anal MRI, and surgery regarding morphopathological findings of the internal and external anal sphincter components. In constipated patients the findings of videoprography and dynamic pelvic MRI were compared regarding the presence of rectocele, rectoanal intussusception, and sigmoidocele as well as the measurements of anorectal angle and perineal descent. The five incontinent patients were all women, with a median age of 67 years (range 43-77). EAUS revealed an anterior sphincter defect in two patients, a posterior defect in one, and normal anal sphincter images in two. Surgical findings confirmed an anterior external anal sphincter scar in two patients, an internal anal sphincter defect in one, and an anatomically normal anal sphincter in two. In one patient, although anal MRI showed posterior external anal sphincter defect, EAUS and surgery revealed normal external anal sphincter appearance. The accuracy rate between EAUS and anal MRI was only 20%, that between surgery and anal MRI 40%, and that between surgery and EAUS 80%. Thus EAUS was more accurate than anal MRI in incontinent patients. The nine constipated patients were all women, with a mean age of 59 years (range 40-78). Videoproctography revealed an anterior rectocele in six patients, rectoanal intussusception in three, and sigmoidocele in five; no abnormalities were identified in two patients. On dynamic pelvic MRI anterior rectocele was seen in three patients and sigmoidocele in two, and five studies were interpreted as normal. One of the patients underwent sigmoidectomy for sigmoidocele, and five patients were treated by biofeedback. Thus the accuracy rate of dynamic pelvic MRI against videoproctography was 60% for anterior rectocele, 40% for sigmoidocele, and zero for rectoanal intussusception. In conclusion, neither MRI for the evaluation of patients with fecal incontinence nor for the evaluation of patients with constipation added any significant information that would warrant its continued use in these patient groups. Perhaps the more widespread availability of an endoanal coil will alter this conclusion; however, at the present time we cannot routinely endorse the expense, time, or inconvenience of these MRI investigations in patients with these diagnoses. Larger prospective comparative studies are required prior to endorsing the technique.

A developmental model for the evolution of artificial neural networks

We present a model of decentralized growth and development for artificial neural networks (ANNs), inspired by developmental biology and the physiology of nervous systems. In this model, each individual artificial neuron is an autonomous unit whose behavior is determined only by the genetic information it harbors and local concentrations of substrates. The chemicals and substrates, in turn, are modeled by a simple artificial chemistry. While the system is designed to allow for the evolution of complex networks, we demonstrate the power of the artificial chemistry by analyzing engineered (handwritten) genomes that lead to the growth of simple networks with behaviors known from physiology. To evolve more complex structures, a Java-based, platform-independent, asynchronous, distributed genetic algorithm (GA) has been implemented that allows users to participate in evolutionary experiments via the World Wide Web.

Open problems in artificial life

This article lists fourteen open problems in artificial life, each of which is a grand challenge requiring a major advance on a fundamental issue for its solution. Each problem is briefly explained, and, where deemed helpful, some promising paths to its solution are indicated.

A simple explanation for taxon abundance patterns

For taxonomic levels higher than species, the abundance distributions of the number of subtaxa per taxon tend to approximate power laws but often show strong deviations from such laws. Previously, these deviations were attributed to finite-time effects in a continuous-time branching process at the generic level. Instead, we describe herein a simple discrete branching process that generates the observed distributions and find that the distribution's deviation from power law form is not caused by disequilibration, but rather that it is time independent and determined by the evolutionary properties of the taxa of interest. Our model predicts-with no free parameters-the rank-frequency distribution of the number of families in fossil marine animal orders obtained from the fossil record. We find that near power law distributions are statistically almost inevitable for taxa higher than species. The branching model also sheds light on species-abundance patterns, as well as on links between evolutionary processes, self-organized criticality, and fractals.

Genome complexity, robustness and genetic interactions in digital organisms

Digital organisms are computer programs that self-replicate, mutate and adapt by natural selection. They offer an opportunity to test generalizations about living systems that may extend beyond the organic life that biologists usually study. Here we have generated two classes of digital organism: simple programs selected solely for rapid replication, and complex programs selected to perform mathematical operations that accelerate replication through a set of defined 'metabolic' rewards. To examine the differences in their genetic architecture, we introduced millions of single and multiple mutations into each organism and measured the effects on the organism's fitness. The complex organisms are more robust than the simple ones with respect to the average effects of single mutations. Interactions among mutations are common and usually yield higher fitness than predicted from the component mutations assuming multiplicative effects; such interactions are especially important in the complex organisms. Frequent interactions among mutations have also been seen in bacteria, fungi and fruitflies. Our findings support the view that interactions are a general feature of genetic systems.

Tetanus toxin impairs accessory and secretory functions in interferon-gamma-treated murine macrophages

Tetanus neurotoxin (TT), a product of microbial origin, acts as a zinc endopeptidase on vesicle-associated membrane proteins (VAMP). We have demonstrated that TT displays inhibitory effects on secretory and accessory functions in the murine macrophage (Mphi) cell line GG2EE. Nitric oxide (NO) secretion was decreased when interferon (IFN)-gamma-pretreated GG2EE Mphis were coincubated with a fungal costimulus (SMP200) and TT. When heat-inactivated TT was used this effect was not evident. The TT-mediated phenomenon was dose-dependent and specific since, under the same experimental conditions, it did not affect interleukin-6 or tumor necrosis factor-alpha secretion. Furthermore, IFN-gamma-induced major histocompatibility complex class II molecule expression and GG2EE accessory function, assessed by SMP200-stimulated lymphoproliferation, were also inhibited by TT. Such inhibition was incomplete, in line with our previous results showing that TT partially cleaves VAMP proteins in murine Mφ.

A determinant for central nervous system persistence localized in the capsid of Theiler's murine encephalomyelitis virus by using recombinant viruses

The demyelinating process in Theiler's murine encephalomyelitis virus (TMEV) infection in mice requires virus persistence in the central nervous system. Using recombinant TMEV assembled between the virulent GDVII and less virulent BeAn virus cDNAs, we now provide additional evidence supporting the localization of a persistence determinant to the leader P1 (capsid) sequences. Further, recombinant viruses in which BeAn sequences progressively replaced those of GDVII within the capsid starting at the leader NH2 terminus suggest that a conformational determinant requiring homologous sequences in both the VP2 puff and VP1 loop regions, which are in close contact on the virion surface, might underlie persistence.

Evolution of mouse hepatitis virus (MHV) during chronic infection: quasispecies nature of the persisting MHV RNA

Coronavirus infection of mice has been used extensively as a model for the study of acute encephalitis and chronic demyelination. To examine the evolution of coronavirus RNA during chronic demyelinating infection, we isolated RNA from intracerebrally inoculated mice at 4, 6, 8, 13, 20, and 42 days postinfection and used reverse transcription-polymerase chain reaction amplification methods (RT-PCR) to detect viral sequences. RNA sequences from two viral structural genes, the spike gene and the nucleocapsid gene, were detected throughout the chronic infection. In contrast, infectious virus was not detectable from brain homongenates beyond 13 days postinfection. These results indicate that coronavirus RNA persists in the brain at times when infectious virus is not detected. To determine if genetic changes were occurring during viral replication in the host, we cloned and sequenced the RT-PCR products from the spike and nucleocapsid regions and analyzed the sequences for mutations. Sequencing of the cloned products revealed that a variety of mutant forms of viral RNA persisted in the CNS, including point mutants, deletion mutants, and termination mutants. The mutations accumulated during persistent infection in both the spike and the nucleocapsid sequences, with greater than 65% of the mutations encoding amino acid changes. These results show that a diverse population or quasispecies consisting of mutant and deletion variant viral RNAs (which may not be capable of producing infectious virus particles) persists in the central nervous system of mice during chronic demyelinating infection. The implications of these results for the role of persistent viral genetic information in the pathogenesis of chronic demyelination are discussed.

Mutations associated with viral sequences isolated from mice persistently infected with MHV-JHM

Mouse hepatitis virus JHM (JHMV or MHV-4) induces subacute and chronic demyelination in rodents and has been studied as a model human demyelinating diseases, such a multiple sclerosis. However, despite intensive investigation, the state of JHMV during chronic disease is poorly understood. Using reverse transcription-polymerase chain reaction amplification (RT-PCR) to "rescue" viral RNA, we have found that JHMV-specific sequences persist for at least 787 days after intracerebral inoculation of experimental mice. Analysis of persisting viral RNA reveals that it is extensively mutated, and we hypothesize that the mutations observed reflect adaptation of the viral quasispecies to low-level intracellular replication during chronic disease.

Comparative studies on functional and secretory properties of macrophage cell lines derived from different anatomical sites

In the present study, we compared four macrophage (M phi) cell lines from different anatomical origins for functional and secretory activities against the two morphogenetic forms of the fungus Candida albicans. We show that all the cell lines actively phagocytize the yeast and exert antimicrobial activity against both forms of Candida, although M phi of microglial origin are the most effective. When assessed for secretory properties, microglial M phi exhibit a peculiar pattern with respect to other M phi populations under either basal or stimulated conditions. In particular, only microglial M phi fail to respond to the hyphal form of the fungus (H-Candida), which instead acts as a potent tumor necrosis factor inducer in the other M phi cell lines. When exposed to H-Candida, microglial M phi are indistinguishable from other M phi in their ability to modulate specific surface adhesion molecules. In addition to strengthening the knowledge on functional heterogeneity among M phi, our data provide evidence on the peculiar behavior of microglial M phi. To what extent M phi heterogeneity may be related to tissue homeostasis is discussed.

In vivo immortalization of murine peritoneal macrophages: a new rapid and efficient method for obtaining macrophage cell lines

Although several murine macrophage (m phi) cell lines from different sites have previously been obtained by in vitro infection with the J2 murine retrovirus, which carries the v-raf and v-myc oncogenes, it was not possible to immortalize thioglycolate-elicited peritoneal macrophages (Pm phi s) by this in vitro procedure. A technique utilizing in vivo injection of the J2 virus has been developed to overcome this problem. The J2 virus immortalized Pm phi s in a very efficient manner in vivo because no exogenous growth factors were required for the in vitro proliferation of these cells and numerous continuous cloned cell lines were readily established. In contrast, Pm phi s obtained from uninfected mice or Pm phi s infected in vitro with the J2 virus did not proliferate. The in vivo immortalized cells had many of the morphological and functional characteristics of m phi s. Analysis of two of the clones, PMJ2-PC and PMJ2-R, demonstrated intracellular expression of the product of the v-raf gene, presence of m phi-associated cell surface antigens, interleukin-6 secretion induced by lipopolysaccharide, and biological response modifier-induced cytotoxic activity against tumor cells. In addition, one of the clones, PMJ2-PC, constitutively expressed major histocompatibility complex (MHC) class II antigens, and in the other clone, PMJ2-R, MHC class II antigens expression was induced by recombinant murine interferon-gamma. This method of utilizing the J2 virus in vivo represents a novel technique for obtaining hematopoietic cell lines from cells that are difficult to immortalize in vitro.