European Society of Anaesthesiology and Intensive Care consensus document on sustainability: 4 scopes to achieve a more sustainable practice

Climate change is a defining issue for our generation. The carbon footprint of clinical practice accounts for 4.7% of European greenhouse gas emissions, with the European Union ranking as the third largest contributor to the global healthcare industry's carbon footprint, after the United States and China. Recognising the importance of urgent action, the European Society of Anaesthesiology and Intensive Care (ESAIC) adopted the Glasgow Declaration on Environmental Sustainability in June 2023. Building on this initiative, the ESAIC Sustainability Committee now presents a consensus document in perioperative sustainability. Acknowledging wider dimensions of sustainability, beyond the environmental one, the document recognizes healthcare professionals as cornerstones for sustainable care, and puts forward recommendations in four main areas: direct emissions, energy, supply chain and waste management, and psychological and self-care of healthcare professionals. Given the urgent need to cut global carbon emissions, and the scarcity of evidence-based literature on perioperative sustainability, our methodology is based on expert opinion recommendations. A total of 90 recommendations were drafted by 13 sustainability experts in anaesthesia in March 2023, then validated by 36 experts from 24 different countries in a two-step Delphi validation process in May and June 2023. To accommodate different possibilities for action in high- versus middle-income countries, an 80% agreement threshold was set to ease implementation of the recommendations Europe-wide. All recommendations surpassed the 80% agreement threshold in the first Delphi round, and 88 recommendations achieved an agreement >90% in the second round. Recommendations include the use of very low fresh gas flow, choice of anaesthetic drug, energy and water preserving measures, "5R" policies including choice of plastics and their disposal, and recommendations to keep a healthy work environment or on the importance of fatigue in clinical practice. Executive summaries of recommendations in areas 1, 2 and 3 are available as cognitive aids that can be made available for quick reference in the operating room.

Resource allocation

PURPOSE OF REVIEW

The coronavirus disease 2019 pandemic and recent global recessions have brought to the forefront of the medical-political discussion the fact that medical resources are finite and have focused a spotlight on fair allocation and prioritization of healthcare resources describe why this review is timely and relevant.

RECENT FINDINGS

This review presents past and present concepts related to the ethics of resource allocation. Included are discussions regarding the topics of who should determine resource allocation, what types of research require allocation, methods currently in use to determine what resources are appropriate and which should be prioritized.describe the main themes in the literature covered by the article.

SUMMARY

Models for resource allocation must differentiate between different types of resources, some of which may require early preparation or distribution. Local availability of specific resources, supplies and infrastructure must be taken into consideration during preparation. When planning for long durations of limited resource availability, the limitations of human resilience must also be considered. Preparation also requires information regarding the needs of the specific population at hand (e.g. age distributions, disease prevalence) and societal preferences must be acknowledged within possible limits.

Parent and medical team disagreements in the UK: universal lessons in the origins and resolution in conflict

In recent decades, there has been an increase in life expectancy in children with life-limiting conditions. Ideally, parents and clinicians would work together to ensure the best care for these children. Several cases have appeared in the media in recent years where conflict has risen between parents and healthcare professionals acting in the 'best interests' of children, which have resulted in court action. However, the legislation itself promotes conflict. Similar laws exist across Europe based on Article 24 of the UN Convention on the Rights of the Child.The aim of the Children's Act 1989 in the UK was to place the 'child's welfare' as the 'paramount consideration'. It has prevented draconian care and supervision orders, which can only be made if the child is at risk of 'significant harm'. This threshold does not apply to healthcare teams. Healthcare decisions are based on 'best interests', which are not explicitly defined. This sets the threshold for progression to court action much lower, and due to a lack of definitive definition of what 'best interests' are, this has unfortunately escalated conflict rather than resolve it.Healthcare institutions have been criticised for not utilising alternative approaches first, such as mediation. We propose an alternative approach based on collaboration, reasonableness and the threshold of significant harm, which we have explored in this review.Conflict management frameworks are a tool that can be used to recognise early signs of conflict and develop strategies to prevent escalation at ward level. They can be tailored to individual institutions and utilise content-oriented and empathetic communication strategies through designated clinicians. They should offer guidance on when to refer to the courts.Parental wishes should be assessed on whether they represent significant harm or not. If not, they cannot simply be wrong. Acknowledgement of the 'reasonableness' of parental requests can be a key factor which is diffusing conflict. Therefore, setting the threshold for state intervention at 'significant harm' rather than 'best interests' would help to reduce the number of these cases progressing to courts.

Analysis of Anthrax Immune Globulin Intravenous with Antimicrobial Treatment in Injection Drug Users, Scotland, 2009-2010

We studied anthrax immune globulin intravenous (AIG-IV) use from a 2009-2010 outbreak of Bacillus anthracis soft tissue infection in injection drug users in Scotland, UK, and we compared findings from 15 AIG-IV recipients with findings from 28 nonrecipients. Death rates did not differ significantly between recipients and nonrecipients (33% vs. 21%). However, whereas only 8 (27%) of 30 patients at low risk for death (admission sequential organ failure assessment score of 0-5) received AIG-IV, 7 (54%) of the 13 patients at high risk for death (sequential organ failure assessment score of 6-11) received treatment. AIG-IV recipients had surgery more often and, among survivors, had longer hospital stays than did nonrecipients. AIG-IV recipients were sicker than nonrecipients. This difference and the small number of higher risk patients confound assessment of AIG-IV effectiveness in this outbreak.

Information for development: experiences of the International Development Research Centre

The first in a series of articles on the activities of the Information Sciences Division (ISD) of the International Development Research Centre (IDRC) introduces IDRC in general and ISD in particular. It traces the evolution of ISD as a substantive programme devoted to tackling information problems in developing countries, and reviews how the Division has responded to the changing global information environment of the past two decades. Statistics are provided on where and on what activities ISD resources have been directed over the years. General programme areas are described with examples of types of projects supported, including specialized information centres, non-bibliographic systems, networks, information technologies and human resources development, all of which are aimed at contributing to the social and economic advancement of developing countries. Also examined are inhouse information activities, including IDRC's Library and bibliographic services, and the Computer Systems Group responsible for MINISIS software. Concludes with a look at various elements in the current information environment that are influencing the future direction of ISD so that it can remain responsive to the needs of developing countries.

Confirmed Bacillus anthracis infection among persons who inject drugs, Scotland, 2009-2010

Patients who died had an increased sequential organ failure assessment score and need for vasopressors.

Interaction between pre-weaning undernutrition and post-weaning environmental enrichment on somatic development and behaviour in male and female rats

Male and female rats were undernourished from birth to 30 days by restricting access to the lactating mother, and then fed ad libitum. At weaning, underfed and normally suckled controls were permanently housed either in pairs in standard cages or in groups of 10 in 1 m(3) cages containing ladders, ropes etc. Severe undernutrition during suckling followed by 4 months of refeeding, produced some changes in sexual behaviour in adult males (increased ejaculation frequency) but had no effect on behaviour in open field, dark preference or passive avoidance. Differential post-weaning environment produced significant differences in behaviour, irrespective of previous feeding conditions. Enriched animals were more active and exploratory. Females differed from males in the same direction as enriched from standard, and were more responsive to social and housing conditions.

The right inferior phrenic artery: path of its ascending branch at the vena caval foramen

The ascending branch of the right inferior phrenic artery is generally understood to pass to the lateral side of the vena caval foramen, on the inferior surface of the diaphragm. A study of 16 cadavers shows that the artery may pass through the vena caval foramen to run on the superior surface of the diaphragm, before returning to the inferior surface by passing through the muscle of the diaphragm.

Recombinant activated protein C usage in Scotland: a comparison with published guidelines and a survey of attitudes

Severe sepsis is a common cause of admission to the intensive care unit and is associated with a high hospital mortality. This audit explored the current use of, and attitudes towards, recombinant activated protein C therapy across Scotland, and compared these with current guidance. Patients with severe sepsis were followed for three days. Consideration and/or usage of recombinant activated protein C were compared with two different guidelines. Ninety-seven patients were admitted to the intensive care unit over the audit period. Recombinant activated protein C was used in nine of these patients. Depending on the criteria used, between 50% and 81% of the patients who qualified for recombinant activated protein C therapy did not receive it. Subsequent to the audit, a survey was performed to study intensive care unit consultants' attitudes to recombinant activated protein C therapy. A total of 125 consultants responded to the survey (77%). Of these, 104 (83%) stated that they used recombinant activated protein C in their clinical practice, 56 (52%) of whom prescribed it to patients with two-organ failures and an Acute Physiology and Chronic Health Evaluation II score of ≥ 25. Thirty-nine respondents (38%) stated that two-organ failures alone would be an adequate trigger for therapy. We conclude that recombinant activated protein C is potentially under-used to treat severe sepsis. Many consultants seem to reserve the drug for the most severely ill sub group of patients.

Accidental intraventricular administration of phenytoin through an external ventricular drain: case report

A 52-year-old man with an external ventricular drain was transferred from the local neurosurgical intensive care unit to the general intensive care unit for renal replacement therapy. While the patient was in the general intensive care unit, phenytoin was accidentally administered via the external ventricular drain. Tachycardia and hypertension ensued and then seizure activity. The drain was aspirated and then washed out. Propofol was infused for 24 hours and then was stopped to allow continuing neurological assessment. The route of administration of phenytoin was changed from intravenous to oral, and care continued as before. After resolution of the renal failure, the patient was returned to the neurological intensive care unit. He recovered slowly and had no adverse effects due to the error in administration of phenytoin.

Extracorporeal Membrane Oxygenation for Severe Respiratory Failure

Management of severe respiratory failure in a specialist centre which is capable of delivering a complex ‘bundle’ of care including a strict acute respiratory distress syndrome (ARDS) protocol, extracorporeal membrane oxygenation (ECMO), molecular adsorbent recycling system (MARS) and steroids, may improve outcomes when compared with conventional care. It is difficult to comment on the value of ECMO alone based on this study.

Level of evidence: 1+ (RCT with a low risk of bias)

A new method of recording clinical forensic evidence

Digital photography is a practical tool, useful for the recording of clinical forensic evidence.

Three model systems measure oxidation/nitration damage caused by peroxynitrite

Diseases activate the innate immune response which causes ancillary damage to the human body. Peroxynitrite (OONO-) or its carbon dioxide derivatives cause oxidation/nitration and hence mutation to various body polymers e.g. DNA, RNA, protein, lipids and sugars. The control of the ancillary damage can come from antioxidants which inhibit control the amount of peroxynitrite available for damage. In this paper we have developed three different levels of antioxidant screening: (i) Peroxynitrite or SIN-1 reaction with luminol to produce light, and the inhibition of light by substances therefore represents antioxidation. (ii) Nicking of plasmid DNA occurs via oxidants: and is prevented by antioxidants. (iii) Detection of plasmid luciferase activity post-oxidation and infection indicates either prevention or repair of damage: via antioxidants. We found green tea and a number of its polyphenolic constituents effective only at the first level of antioxidation, while extracts of various fruit help at all levels antioxidation. In the final analysis, a combination of green tea extracts and fruits is suggested to produce more complete antioxidant protection.

A framework for integrating the songbird brain

Biological systems by default involve complex components with complex relationships. To decipher how biological systems work, we assume that one needs to integrate information over multiple levels of complexity. The songbird vocal communication system is ideal for such integration due to many years of ethological investigation and a discreet dedicated brain network. Here we announce the beginnings of a songbird brain integrative project that involves high-throughput, molecular, anatomical, electrophysiological and behavioral levels of analysis. We first formed a rationale for inclusion of specific biological levels of analysis, then developed high-throughput molecular technologies on songbird brains, developed technologies for combined analysis of electrophysiological activity and gene regulation in awake behaving animals, and developed bioinformatic tools that predict causal interactions within and between biological levels of organization. This integrative brain project is fitting for the interdisciplinary approaches taken in the current songbird issue of the Journal of Comparative Physiology A and is expected to be conducive to deciphering how brains generate and perceive complex behaviors.

Coronary and myocardial effects of acetaminophen: protection during ischemia-reperfusion

Acetaminophen is a phenol with antioxidant properties, but little is known about its actions on the mammalian myocardium and coronary circulation. We studied isolated, perfused guinea pig hearts, and tested the hypothesis that acetaminophen-treated hearts would be protected during ischemia-reperfusion. Acetaminophen concentrations in the range of 0.3–0.6 mmol/l caused modest but significant ( P< 0.05) coronary vasoconstriction and positive inotropy. The effects were more brisk during constant pressure perfusion than during constant flow. During 20 min of low-flow, global myocardial ischemia and 40 min of reperfusion, hearts treated with acetaminophen retained or recovered a greater percentage of left ventricular function than hearts treated with vehicle. Myofibrillar ultrastructure appeared to be preserved in the reperfused myocardium with acetaminophen. By using chemiluminescence and spin-trap methodologies, we investigated acetaminophen-mediated antioxidant mechanisms to help explain the cardioprotection. The burst of hydroxyl radicals seen between 0 and 10 min of reperfusion was significantly attenuated ( P < 0.05) by acetaminophen but not by vehicle. The 3-morpholinosydnominine (SIN-1) generation of peroxynitrite and its oxidative interaction with luminol to produce blue light during ischemia-reperfusion was also blocked by acetaminophen. Our results show that acetaminophen provides significant functional and structural protection to the ischemic-reperfused myocardium, and the mechanism of cardioprotection seems to involve attenuation of the production of both hydroxyl radicals and peroxynitrite.

Stereoselective binding of an enantiomeric pair of stromelysin-1 inhibitors caused by conformational entropy factors

Isothermal titration calorimetry was used to analyze the binding of an enantiomeric pair of inhibitors to the stromelysin-1 catalytic domain. Differences in binding affinity are attributable to different conformational entropy penalties suffered upon binding. Two possible explanations for these differences are proposed.

Variations in the normal anatomy of the collateral ligaments of the human elbow joint

The variations which occur in the medial and lateral ligament complexes of the elbow were investigated. These occurred frequently with the standard appearances occurring in no more than half the specimens on the medial side and one quarter of those on the lateral side. Surgeons who regularly perform elbow arthroplasty must be aware of these considerations, especially with the introduction of unconstrained prostheses which rely upon the ligament complex for their postoperative stability.

Green tea extract and its polyphenols markedly inhibit luminol-dependent chemiluminescence activated by peroxynitrite or SIN-1

This study is based on a simple chemical interaction of peroxynitrite (OONO-) and luminol, which produces blue light upon oxidation. Since peroxynitrite has a half-life of less than 1 s, a drug known as SIN-1 is used as a peroxynitrite generator. In addition peroxynitrite itself was used directly with a fast injection-mixing system to ascertain whether there are differences between it and the peroxynitrite-generating system (SIN-1) which mimics the natural production of (OONO-). Peroxynitrite is a potent oxidizing compound (1000 times more active than equidose hydrogen peroxide) and it can oxidize carbohydrates, lipids, proteins and nucleic acids. Upon stimulation by inflammation and/or infection, macrophages and neutrophils can be activated to produce large amounts of peroxynitrite. We are interested in simple chemicals that are non-toxic that could inhibit or destroy peroxynitrite, which might otherwise cause inappropriate damage to blood and tissues. Green tea is a complex mixture containing several potent major antioxidant constituents, eg flavins and/or polyphenols. The constituents in green tea may react directly or indirectly with peroxynitrite or its constituents through the process of antioxidation to inhibit light. Alternatively, compounds could produce superoxide which, when reacted with nitric oxide, could produce more peroxynitrite and hence more light with luminol. Therefore, as the tea or antioxidants from tea are diluted, while the peroxynitrite or its precursors are kept at a constant concentration, one can observe unusual behaviour regarding light emission. Initially, at high doses of tea or antioxidant, one observes clear inhibition of the light generated from the reaction of peroxynitrite and luminol. However, at dilute concentrations of antioxidants, one can often observe stimulation of light. Possible reasons for these observations are discussed.

Application of electrospray ionization mass spectrometry for studying human immunodeficiency virus protein complexes

Mass spectrometry (MS) with electrospray ionization (ESI) has shown utility for studying noncovalent protein complexes, as it offers advantages in sensitivity, speed, and mass accuracy. The stoichiometry of the binding partners can be easily deduced from the molecular weight measurement. In many examples of protein complexes, the gas phase-based measurement is consistent with the expected solution phase binding characteristics. This quality suggests the utility of ESI-MS for investigating solution phase molecular interactions. Complexes composed of proteins from the human immunodeficiency virus (HIV) have been studied using ESI-MS. Multiply charged protein dimers from HIV integrase catalytic core (F185K) and HIV protease have been observed. Furthermore, the ternary complex between HIV protease dimer and inhibitor pepstatin A was studied as a function of solution pH. Zinc binding to zinc finger-containing nucleocapsid protein (NCp7) and the NCp7-psi RNA 1:1 stoichiometry complex was also studied by ESI-MS. No protein-RNA complex was observed in the absence of zinc, consistent with the role of the zinc finger motifs for RNA binding.

Blood supply of the Achilles tendon

The Achilles tendon is one of the most common sites of injury and rupture as a result of overuse. Evidence suggests that the pathogenesis of rupture could involve the pattern of its blood supply. With use of angiographic and histological techniques, the blood supply of the Achilles tendon was investigated in 12 human cadaveric specimens. Angiography confirmed Mayer's 1916 finding that the blood supply to the tendon is from three areas: the musculotendinous and osseotendinous junctions and the paratenon, with the posterior tibial artery providing the major contribution. However, qualitative and quantitative histological analyses in this study showed that the Achilles tendon has a poor blood supply throughout its length, as determined by the small number of blood vessels per cross-sectional area, which do not in general vary significantly along its length. In light of these findings, it is suggested that poor vascularity may prevent adequate tissue repair following trauma, leading to further weakening of the tendon.

Design, synthesis, and cocrystal structure of a nonpeptide Src SH2 domain ligand

The specific association of an SH2 domain with a phosphotyrosine (pTyr)-containing sequence of another protein precipitates a cascade of intracellular molecular interactions (signals) which effect a wide range of intracellular processes. The nonreceptor tyrosine kinase Src, which has been associated with breast cancer and osteoporosis, contains an SH2 domain. Inhibition of Src SH2-phosphoprotein interactions by small molecules will aid biological proof-of-concept studies which may lead to the development of novel therapeutic agents. Structure-based design efforts have focused on reducing the size and charge of Src SH2 ligands while increasing their ability to penetrate cells and reach the intracellular Src SH2 domain target. In this report we describe the synthesis, binding affinity, and Src SH2 cocrystal structure of a small, novel, nonpeptide, urea-containing SH2 domain ligand.

Nuclear magnetic resonance solution structure of the growth factor receptor-bound protein 2 Src homology 2 domain

A family of NMR solution structures of the growth factor receptor-bound protein 2 (Grb2) SH2 domain has been determined by heteronuclear multidimensional NMR. Proton, nitrogen, and carbon chemical shift assignments have been made for the SH2 domain of Grb2. Assignments were made from a combination of homonuclear two-dimensional and 15N- and 13C-edited three-dimensional spectra at pH 6.2 and 298 K. Structure-induced proton and carbon secondary shifts were calculated and used to facilitate the spectral assignment process. NOE, scalar coupling, secondary chemical shift, and amide proton exchange data were used to characterize the secondary structural elements and hydrogen-bonding network in the Grb2 SH2 domain. The three-dimensional structure of the Grb2 SH2 domain was calculated using 1112 restraints obtained from NOE, coupling constant, and amide proton exchange data. The rmsd for the 24 calculated structures to the mean structure of the Grb2 SH2 domain was 0.75 A for backbone and 1.28 A for all heavy atoms. The three-dimensional fold of the Grb2 SH2 domain is similar to that observed for other SH2 domains and consists of two alpha-helical segments and eight beta-strands, six strands that make up two contiguous antiparallel beta-sheets, and two strands that form two short parallel beta-sheets. The structure of the phosphotyrosine binding pocket of Grb2 is similar to that observed for other SH2 domains. The hydrophobic binding pocket of Grb2 is similar to that observed for Src with the exception that tryptophan 121 of Grb2 occupies part of the pY+3 binding pocket. Structural implications for the Grb2 SH2 domain selectivity at the pY+2 and pY+3 sites are discussed.

Nurses' compliance with universal precautions before and after implementation of OSHA regulations

The principal objective of this study was to investigate whether or not nurses' compliance with universal precautions procedures improved after the mandatory Occupational Safety and Health Administration regulations were implemented in 1992. Two random samples of registered nurses and licensed practical nurses registered in Tennessee responded to survey questionnaires measuring universal precautions compliance and practice barriers to compliance in 1991 and 1993 (n = 306). The 1993 sample of nurses reported significantly greater compliance with universal precautions (p < 0.001) than the 1991 sample. The most noteworthy improvement between the 1991 and the 1993 groups was a significant increase in compliance for patients described as HIV/HBV-status unknown and HIV/HBV-negative (p < 0.001). Practice barriers hindering compliance with universal precautions decreased significantly (p < 0.001) in the 1991-1993 time frame. Problematic practice barriers identified in both groups were needle recapping, preference for isolation door signs, and concerns about offending patients and visitors.

Development and validation of two solid-phase enzyme immunoassays (ELISA) for quantitation of human epidermal growth factors (hEGFs)

PURPOSE

The purpose of the present investigation was to develop and validate two separate enzyme-linked immunosorbent assays (ELISA) for quantitation of exogenous human epidermal growth factor (hEGF1-53) and its truncated fragment (hEGF1-48) in rat plasma.

METHODS

The present assay systems were based on the sandwiching of the antigen between a monoclonal mouse anti-hEGF1-53 antibody, pre-coated on a 96-well polystyrene plate, and a polyclonal rabbit anti-hEGF1-48 antibody, which is then detected with a peroxidase-labeled goat anti-rabbit antibody.

RESULTS

The calibration curves for hEGF1-48 and hEGF1-53 in plasma were validated over a concentration range of 7.8-250 and 62.5-1000 pg/ml, respectively. Determined from replicate assays of hEGF1-48 quality control samples, the intra-assay precision and accuracy were < or = 8.8% RSD and within +/- 9.8%; and the inter-assay precision and accuracy were < or = 14.8% RSD and within +/- 9.7% RE, respectively. Determined from replicate assays of hEGF1-53 quality control samples, the intra-assay precision and accuracy were < or = 10.0% RSD and within +/- 8.5%; and the inter-assay precision and accuracy were < or = 10.0% RSD and within +/- 5.7% RE, respectively. The limit of quantitation of the hEGF1-48 and hEGF1-53 assay using 200 microliters plasma per well is 7.8 and 62.5 pg/ml, respectively. These two ELISA methods are specific to hEGFs and do not cross-react with mouse EGF or other growth factors (TGF alpha, TGF beta, PDGF, and FGF) or lymphokines (IL1 beta and TNF alpha). These validated methods have been routinely applied to assay of plasma samples from various pharmacokinetic studies in rats receiving intravenous hEGFs. Both assay methods were also adapted to assay endogenous hEGFs in biological fluids of different animal species.

CONCLUSIONS

Two sensitive ELISA methods have been validated for quantitation of hEGF1-53 and hEGF1-48 in rat plasma. Their utility has been demonstrated in the application of assaying immunoreactive concentration of exogenous and endogenous epidermal growth factors.

Applying TQM/CQI principles to information system selection

Faced with the challenge of selecting a new information system, senior management at North Valley Hospital in Whitefish, Montana, decided to employ principles of total quality management and continuous quality improvement to help ensure an efficient process that involved and empowered those who would use the new system. Senior managers set a vision for the process, then assigned responsibility for system selection to a task force representing departments and disciplines that would be most affected by the system. The task force established a systematic process for identifying information system needs, evaluating existing products, and selecting among those products.

Dietitians view the horizon

In honor of the American Dietetic Association's landmark 75th anniversary, FM asked ADA members representing six market sectors to share their perspectives on the opportunities & challenges for dietitians in the '90s. An exciting era lies ahead.

Regeneration of nerve fibres in the anterior medullary velum of neonatal and weanling rats

The responses to injury of myelinated central axons in neonatal (5-day) and weanling (30-day) rats were compared, using the trochlear nerve fibres in the anterior medullary velum (AMV) as an experimental system. In intact animals, fibres of the trochlear nerve decussate completely in the AMV, to enter the contralateral nerve. Sprouting from proximal axon stumps was seen within 36 h after injury in silver-stained, whole mounts of mid-sagittally lesioned AMVs from weanlings. Subsequent growth produced a tangled axon mass which persisted until 15-20 days post-lesion (d.p.l.) but then began to degenerate. By 50 d.p.l., the majority of surviving axons looped within the AMV to enter the ipsilateral trochlear nerve; few axons remained growing randomly within the AMV. Axonal debris persisted within the velum 50 d.p.l. In neonatal rats, lesioned trochlear axons initially developed axon sprouts, but then degenerated with rapid clearance of debris, leaving the AMV devoid of both axons and degeneration products by 6 d.p.l. From 8 d.p.l., the velum became repopulated by axons which either grew randomly or looped to enter the ipsilateral peripheral nerve. Both patterns of axon growth were still observed 50 d.p.l. In both experimental groups, horseradish peroxidase injection to the right superior oblique muscle 40 d.p.l. indicated that at least some of the looping fibres observed within the lesioned AMVs originated in the ipsilateral trochlear nucleus. The origin of those axons growing randomly within the AMVs of neonatally-lesioned animals is unknown. The results are discussed with reference to current ideas concerning regeneration-inhibiting elements in the CNS, and regeneration-promoting factors in the PNS.

The injury response of nerve fibres in the anterior medullary velum of the adult rat

The injury response of myelinated central nervous system (CNS) axons was documented in the anterior medullary velum (AMV) of the adult rat. Study of silver-stained AMV whole-mounts revealed sprouting of injured axons as early as 14 h post-lesion (hpl), with a complex network of fibres formed by 48 hpl. Signs of fibre degeneration were also apparent from 48 hpl, increasing in extent until 15 days post-lesion (dpl). Fragmentation was largely confined to specific fibre bundles, constituted by the distal portions of severed axons. Although some degeneration of regenerated axons was evident from 15-20 dpl, many remained intact beyond this time, particularly in the area adjacent to the exit of the trochlear nerve, where most regenerated fibres penetrated the ipsilateral trochlear nerve. Counts of HRP filled neurons in the trochlear nucleus after injection of the superior oblique muscle showed that axons entering the IVth nerve rootlet were exclusively ipsilateral trochlear fibres. Less than 50% regenerated; most other severed axons degenerated. The few axons remaining in the AMV may have been fibres, undamaged by the original lesion, which normally course longitudinally through the ipsilateral AMV. These results show that IVth nerve fibres preferentially enter IVth nerve rootlets and, in so doing, survive the effects of injury. Most other CNS axons in the AMV which do not enter the trochlear root probably degenerate.

Deposition of scar tissue in the central nervous system

Standard parasagittal lesions were placed stereotactically in the cerebral hemispheres of neonatal and adult rats in order to compare scarring in the immature and mature animal. Lesions were examined by light and electron-microscopy and immunofluorescence to study the astrocyte reaction, collagen deposition, and the formation of the basement membrane of the glia limitans. Normal mature scarring characterized by the deposition of collagen, astrocyte end-feet alignment over a glia limitans, and the permanent presence of mesodermal cells (fibroblasts and macrophages) in the core of the lesion, does not occur in wounds before 8-10 days post-partum (dpp). Instead there is no deposition of collagen, and only a transitory astrocyte response occurs with the formation of an interrupted glia limitans. These latter features disappear with time so that the wound is ultimately obliterated by the growth of axons and dendrites through the lesion. Mature scarring is attained over 8-12 dpp when increasing amounts of collagen are deposited and a continuous permanent glia limitans is formed. The acquisition of the mature response to injury from 8-12 dpp may be correlated with the presence of increasing titres of a fibroblast growth factor (FGF), derived from autolytic digestion of injured brain tissue. We have investigated FGF activity using a 3 T 3 fibroblast tissue culture assay to detect mitogenic activity in brain extracts from rats lesioned at different ages and from leukodystrophic mice which have no myelin. Our results show that high titres of FGF are present in the developing brain long before myelination commences, and that normal levels of FGF are found in the brains of leukodystrophic mice which have no myelin. Scarring in brain lesions in these mutants is quite normal.

Regeneration of ganglion cell axons in the adult mouse retina

The hypothesis that regenerative failure of axons in the adult mammalian CNS is due to release of a growth inhibitor from injured oligodendrocytes and/or myelin2, predicts that regeneration of injured fibers would proceed unchecked in unmyelinated CNS regions. This prediction was borne out by observations on the stratum opticarum of the mouse retina. Axonal sprouts, first seen 14-16 h post-lesion (pl), continued growing until at least 100 days pl, well beyond the time at which regeneration fails in myelinated CNS regions.

Sex differences in effects of environmental stimulation on brain weight of previously undernourished rats

Neonatally undernourished male and female rats were housed under differential (enriched vs standard) environmental conditions during refeeding from 30 days post-partum (dpp). Animals were killed at 170 dpp and whole brain, forebrain and cerebellar weights compared with those of normally-fed, differentially housed control animals. A sex difference was observed in the response to environmental enrichment. Enriched females showed significantly increased brain weights, irrespective of previous nutritional history. Enriched males failed to show any significant alteration in brain weight. Autopsy results indicated that the enriched condition was stressful to males but not to females. The results cast doubt on the notion that infantile undernutrition may limit later effects of differential experience on the brain.

The effects of refeeding after varying periods of neonatal undernutrition on the morphology of Purkinje cells in the cerebellum of the rat

Undernutrition of the rat for the first 30 days of postnatal life is known to permanently alter Purkinje cell (PC) dendritic morphology. The effects of earlier nutritional rehabilitation have not previously been determined. Neonatal rat pups were undernourished by limiting their access to the lactating dam. After 10, 15, or 20 days of food restriction, animals were either killed for histological comparison with normally fed controls, or provided with ad libitum food until 80 dpp, and then killed. Network analysis of Golgi Cox impregnated PCs from the undernourished animals revealed alterations in dendritic length, segment frequency, and branching pattern, which first became apparent at 15 dpp, accompanied by a reduction in the number of granule cells (GCs) per PC. If undernourished animals were refed from 10 or 15 days, however, the total lengths and segment frequencies of their PC trees were indistinguishable from those of controls at 80 dpp, although the 15-day group showed persistent topological alterations. The GC:PC ratios of these refed groups were also found to be similar to those of the controls. In animals refed after 20 days of undernutrition, network size remained reduced, as did the GC:PC ratio. The different degrees of recovery of PC dendritic field parameters recorded in the refed animals could be related either to enhanced GC replication afforded by refeeding, or to the existence of intrinsic mechanisms which limit the growth capacity of the PC dendrites.