Rare genetic variation in fibronectin 1 (FN1) protects against APOEε4 in Alzheimer's disease

The risk of developing Alzheimer's disease (AD) significantly increases in individuals carrying the APOEε4 allele. Elderly cognitively healthy individuals with APOEε4 also exist, suggesting the presence of cellular mechanisms that counteract the pathological effects of APOEε4; however, these mechanisms are unknown. We hypothesized that APOEε4 carriers without dementia might carry genetic variations that could protect them from developing APOEε4-mediated AD pathology. To test this, we leveraged whole-genome sequencing (WGS) data in the National Institute on Aging Alzheimer's Disease Family Based Study (NIA-AD FBS), Washington Heights/Inwood Columbia Aging Project (WHICAP), and Estudio Familiar de Influencia Genetica en Alzheimer (EFIGA) cohorts and identified potentially protective variants segregating exclusively among unaffected APOEε4 carriers. In homozygous unaffected carriers above 70 years old, we identified 510 rare coding variants. Pathway analysis of the genes harboring these variants showed significant enrichment in extracellular matrix (ECM)-related processes, suggesting protective effects of functional modifications in ECM proteins. We prioritized two genes that were highly represented in the ECM-related gene ontology terms, (FN1) and collagen type VI alpha 2 chain (COL6A2) and are known to be expressed at the blood-brain barrier (BBB), for postmortem validation and in vivo functional studies. An independent analysis in a large cohort of 7185 APOEε4 homozygous carriers found that rs140926439 variant in FN1 was protective of AD (OR = 0.29; 95% CI [0.11, 0.78], P = 0.014) and delayed age at onset of disease by 3.37 years (95% CI [0.42, 6.32], P = 0.025). The FN1 and COL6A2 protein levels were increased at the BBB in APOEε4 carriers with AD. Brain expression of cognitively unaffected homozygous APOEε4 carriers had significantly lower FN1 deposition and less reactive gliosis compared to homozygous APOEε4 carriers with AD, suggesting that FN1 might be a downstream driver of APOEε4-mediated AD-related pathology and cognitive decline. To validate our findings, we used zebrafish models with loss-of-function (LOF) mutations in fn1b-the ortholog for human FN1. We found that fibronectin LOF reduced gliosis, enhanced gliovascular remodeling, and potentiated the microglial response, suggesting that pathological accumulation of FN1 could impair toxic protein clearance, which is ameliorated with FN1 LOF. Our study suggests that vascular deposition of FN1 is related to the pathogenicity of APOEε4, and LOF variants in FN1 may reduce APOEε4-related AD risk, providing novel clues to potential therapeutic interventions targeting the ECM to mitigate AD risk.

Outcomes following surgical fixation of Gustilo-Anderson IIIb open tibial fractures

There is no consensus as to the optimal skeletal fixation method for Gustilo-Anderson IIIb fractures. External fixation methods have previously shown higher rates of superficial infection, whilst internal fixation has shown higher risk of deep infection, but lower risk of other complications. This paper investigates outcomes in open tibial fractures based on fixation method. A retrospective review was performed for patients presenting to an ortho-plastic unit with GA IIIb tibial fractures between June 2013 and October 2021. 85 patients were identified. The most common implant was an intramedullary nail (IMN), used in 29 patients (34.1%); open reduction and internal fixation (ORIF) was performed in 16 patients (18.8%). 18 patients (21.2%) were definitively managed with a frame alone. Mean follow-up from was 18 months (2-77). Patients with ORIF needed a mean of 3.37 operations; it was 2.48 for IMN which was significantly different from frames at 5.00 (p=0.000). The mean time to bony union after definitive fixation was 11.4 months. This differed depending on the implant used for fixation, with ORIF at 7.1 months, 10.1 for IMN, and frames at 17.2 months; ORIF significantly differed from frames (p=0.009). Superficial infection was common, seen in 38.8% of patients, and only 3 patients (4%) developed deep infections involving metalwork, with no difference in rates of either based on fixation method This study supports that ORIF has faster healing times, with less time to union compared to frames. It also shows that no implant was superior to another in terms of outcomes.

Clonal CD8 T Cells Accumulate in the Leptomeninges and Communicate with Microglia in Human Neurodegeneration

Murine studies have highlighted a crucial role for immune cells in the meninges in surveilling the central nervous system (CNS) and influencing neuroinflammation. However, how meningeal immunity is altered in human neurodegeneration and its effects on CNS inflammation is understudied. We performed the first single-cell analysis of the transcriptomes and T cell receptor (TCR) repertoire of 104,635 immune cells from 55 postmortem human brain and leptomeningeal tissues from donors with neurodegenerative diseases including amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease. RNA and TCR sequencing from paired leptomeninges and brain allowed us to perform lineage tracing to identify the spatial trajectory of clonal T cells in the CNS and its borders. We propose that T cells activated in the brain emigrate to and establish residency in the leptomeninges where they likely contribute to impairments in lymphatic drainage and remotely to CNS inflammation by producing IFNγ and other cytokines. We identified regulatory networks local to the meninges including NK cell-mediated CD8 T cell killing which likely help to control meningeal inflammation. Collectively, these findings provide not only a foundation for future studies into brain border immune surveillance but also highlight important intercellular dynamics that could be leveraged to modulate neuroinflammation.

Rare genetic variation in Fibronectin 1 ( FN1 ) protects against APOEe4 in Alzheimer's disease

The risk of developing Alzheimer's disease (AD) significantly increases in individuals carrying the APOEε4 allele. Elderly cognitively healthy individuals with APOEε4 also exist, suggesting the presence of cellular mechanisms that counteract the pathological effects of APOEε4 ; however, these mechanisms are unknown. We hypothesized that APOEε4 carriers without dementia might carry genetic variations that could protect them from developing APOEε4- mediated AD pathology. To test this, we leveraged whole genome sequencing (WGS) data in National Institute on Aging Alzheimer's Disease Family Based Study (NIA-AD FBS), Washington Heights/Inwood Columbia Aging Project (WHICAP), and Estudio Familiar de Influencia Genetica en Alzheimer (EFIGA) cohorts and identified potentially protective variants segregating exclusively among unaffected APOEε4 carriers. In homozygous unaffected carriers above 70 years old, we identified 510 rare coding variants. Pathway analysis of the genes harboring these variants showed significant enrichment in extracellular matrix (ECM)-related processes, suggesting protective effects of functional modifications in ECM proteins. We prioritized two genes that were highly represented in the ECM-related gene ontology terms, (FN1) and collagen type VI alpha 2 chain ( COL6A2 ) and are known to be expressed at the blood-brain barrier (BBB), for postmortem validation and in vivo functional studies. The FN1 and COL6A2 protein levels were increased at the BBB in APOEε4 carriers with AD. Brain expression of cognitively unaffected homozygous APOEε4 carriers had significantly lower FN1 deposition and less reactive gliosis compared to homozygous APOEε4 carriers with AD, suggesting that FN1 might be a downstream driver of APOEε4 -mediated AD-related pathology and cognitive decline. To validate our findings, we used zebrafish models with loss-of-function (LOF) mutations in fn1b - the ortholog for human FN1 . We found that fibronectin LOF reduced gliosis, enhanced gliovascular remodeling and potentiated the microglial response, suggesting that pathological accumulation of FN1 could impair toxic protein clearance, which is ameliorated with FN1 LOF. Our study suggests vascular deposition of FN1 is related to the pathogenicity of APOEε4 , LOF variants in FN1 may reduce APOEε4 -related AD risk, providing novel clues to potential therapeutic interventions targeting the ECM to mitigate AD risk.

ABCA7-dependent Neuropeptide-Y signalling is a resilience mechanism required for synaptic integrity in Alzheimer's disease

Alzheimer's disease (AD) remains a complex challenge characterized by cognitive decline and memory loss. Genetic variations have emerged as crucial players in the etiology of AD, enabling hope for a better understanding of the disease mechanisms; yet the specific mechanism of action for those genetic variants remain uncertain. Animal models with reminiscent disease pathology could uncover previously uncharacterized roles of these genes. Using CRISPR/Cas9 gene editing, we generated a knockout model for abca7, orthologous to human ABCA7 - an established AD-risk gene. The abca7 +/- zebrafish showed reduced astroglial proliferation, synaptic density, and microglial abundance in response to amyloid beta 42 (Aβ42). Single-cell transcriptomics revealed abca7 -dependent neuronal and glial cellular crosstalk through neuropeptide Y (NPY) signaling. The abca7 knockout reduced the expression of npy, bdnf and ngfra , which are required for synaptic integrity and astroglial proliferation. With clinical data in humans, we showed reduced NPY in AD correlates with elevated Braak stage, predicted regulatory interaction between NPY and BDNF , identified genetic variants in NPY associated with AD, found segregation of variants in ABCA7, BDNF and NGFR in AD families, and discovered epigenetic changes in the promoter regions of NPY, NGFR and BDNF in humans with specific single nucleotide polymorphisms in ABCA7 . These results suggest that ABCA7-dependent NPY signaling is required for synaptic integrity, the impairment of which generates a risk factor for AD through compromised brain resilience.

Abstract Figure

Generalised neuromuscular blockade after intraurethral administration of atracurium besilate in a male cat with urethral obstruction

A 4-year-old, entire, male, domestic long-haired cat was presented with an acute history of stranguria and dysuria and diagnosed with urolithiasis causing urethral obstruction. The patient was induced to general anaesthesia and several unsuccessful attempts to flush the uroliths retrogradely towards the bladder were made. An intraurethral administration of the neuromuscular blocking agent atracurium was performed as it has been reported to facilitate urethral catheterisation without any side effects. Respiratory arrest developed after 15 minutes from atracurium administration, which was promptly recognized and treated with mechanical ventilation. The absence of muscle contraction in response to a nerve stimulation confirmed a generalised muscle blockade. Approximately 35 minutes after, a muscle response to nerve stimulation appeared. Neostigmine combined with glycopyrrolate was administered resulting in complete recovery from neuromuscular blockade. In conclusion, the use of intraurethral atracurium can result in systemic absorption of the drug with subsequent generalised neuromuscular blockade.

Clonal CD8 T cells in the leptomeninges are locally controlled and influence microglia in human neurodegeneration

Recent murine studies have highlighted a crucial role for the meninges in surveilling the central nervous system (CNS) and influencing CNS inflammation. However, how meningeal immunity is altered in human neurodegeneration and its potential effects on neuroinflammation is understudied. In the present study, we performed single-cell analysis of the transcriptomes and T cell receptor repertoire of 72,576 immune cells from 36 postmortem human brain and leptomeninges tissues from donors with neurodegenerative diseases including amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease. We identified the meninges as an important site of antigen presentation and CD8 T cell activation and clonal expansion and found that T cell activation in the meninges is a requirement for infiltration into the CNS. We further found that natural killer cells have the potential to negatively regulate T cell activation locally in the meninges through direct killing and are one of many regulatory mechanisms that work to control excessive neuroinflammation.

Nerve growth factor receptor (Ngfr) induces neurogenic plasticity by suppressing reactive astroglial Lcn2/Slc22a17 signaling in Alzheimer's disease

Neurogenesis, crucial for brain resilience, is reduced in Alzheimer's disease (AD) that induces astroglial reactivity at the expense of the pro-neurogenic potential, and restoring neurogenesis could counteract neurodegenerative pathology. However, the molecular mechanisms promoting pro-neurogenic astroglial fate despite AD pathology are unknown. In this study, we used APP/PS1dE9 mouse model and induced Nerve growth factor receptor (Ngfr) expression in the hippocampus. Ngfr, which promotes neurogenic fate of astroglia during the amyloid pathology-induced neuroregeneration in zebrafish brain, stimulated proliferative and neurogenic outcomes. Histological analyses of the changes in proliferation and neurogenesis, single-cell transcriptomics, spatial proteomics, and functional knockdown studies showed that the induced expression of Ngfr reduced the reactive astrocyte marker Lipocalin-2 (Lcn2), which we found was sufficient to reduce neurogenesis in astroglia. Anti-neurogenic effects of Lcn2 was mediated by Slc22a17, blockage of which recapitulated the pro-neurogenicity by Ngfr. Long-term Ngfr expression reduced amyloid plaques and Tau phosphorylation. Postmortem human AD hippocampi and 3D human astroglial cultures showed elevated LCN2 levels correlate with reactive gliosis and reduced neurogenesis. Comparing transcriptional changes in mouse, zebrafish, and human AD brains for cell intrinsic differential gene expression and weighted gene co-expression networks revealed common altered downstream effectors of NGFR signaling, such as PFKP, which can enhance proliferation and neurogenesis in vitro when blocked. Our study suggests that the reactive non-neurogenic astroglia in AD can be coaxed to a pro-neurogenic fate and AD pathology can be alleviated with Ngfr. We suggest that enhancing pro-neurogenic astroglial fate may have therapeutic ramifications in AD.

Stability of dilutions of methadone alone, and in combination with lidocaine and ketamine

OBJECTIVES

To assess stability and degradation over time, of methadone alone, and mixed with lidocaine and ketamine, using various diluents and storage conditions.

MATERIALS AND METHODS

Solutions of methadone diluted in 0.9% NaCl, and methadone-lidocaine-ketamine diluted in 0.9% NaCl or Hartmann's solution, and stored at room temperature with exposure to light, or refrigerated at 4°C and protected from light, were maintained over 10 days. Chemical stability was determined using liquid chromatography immediately after preparation and following 4, 24, 48, 96 and 240 hours of storage. Physical stability of the solutions was evaluated by visual examination and absorbance of ultraviolet/visible light. A linear model assessed the impact of different diluent solutions and storage conditions on drug degradation over time.

RESULTS

There was no evidence of physicochemical incompatibility for any solution. Methadone concentration, when diluted alone or in methadone-lidocaine-ketamine with Hartmann's solution at 4°C, did not decline over time. Ketamine and lidocaine decreased to a similar extent over time, regardless of the diluent used or storage method, while methadone in methadone-lidocaine-ketamine diluted with 0.9% NaCl or with Hartmann's solution at room temperature exposed to light, also declined over time; however, all three methadone-lidocaine-ketamine components retained acceptable stability (<10% degradation) for at least 48 hours following preparation, irrespective of diluent or storage conditions.

CLINICAL SIGNIFICANCE

Regardless of the diluent or storage method, methadone-lidocaine-ketamine solutions degrade over time, but this only becomes clinically significant after 48 hours. Solutions of 1 mg/ml methadone in 0.9% NaCl are stable for at least 10 days under storage conditions likely to be encountered in general practice.

Racemic ketamine in comparison to S-ketamine in combination with azaperone and butorphanol for castration of pigs

In this prospective blinded randomised study, 28 male 9 week old pigs of bodyweight 25 kg, were anaesthetised for castration using 5 mg/kg azaperone, 0.2 mg/kg butorphanol and 0.4 mg/kg meloxicam, in conjunction with either 15 mg/kg racemic ketamine (Keta-Race) or 9 mg/kg S-ketamine (S-Keta), all drugs being injected intramuscularly. Anaesthesia induction, maintenance and recovery were timed and scored. Insufficient anaesthesia was supplemented with ¼ the initial dose of ketamine or S-ketamine, respectively, administered intravenously. A t-test was utilised for analysis of timings, and, for repeated recovery time data, ANOVA was used. In relation to quantification and timing of supplemental drug doses, a chi square test was used and the scoring was analysed by two sample Wilcoxon rank-sum test. Ketamine re-dosing was required in 23 animals on a total of 46 occasions distributed evenly throughout both groups. The only group differences occurred during recovery, with the S-Keta group showing earlier movements, sternal recumbency and ability to stand. Three pigs in each group showed muscle fasciculations during the recovery period, while an additional two animals of the Keta-Race group exhibited marked and unacceptable paddling in recovery. In conclusion, S-ketamine at a dose rate of 60 % of that of racemic ketamine induced comparable anaesthesia for castration in pigs, but with superior recovery characteristics.

Statistics: general linear models (a flexible approach)

This article moves on to discuss a type of statistical testing different from those we have discussed previously, namely a General Linear Model. This system incorporates a number of other statistical models and is a powerful tool used widely in modern statistics.

Statistics: more regression models

In a previous article, we tackled the question "How are we related?" for the simple case of one explanatory variable or covariate. Now we can move onto a natural extension, with still only one response variable, but more than one explanatory variable.

Statistics: dealing with categorical data

This, the fifth of our series of articles on statistics in veterinary medicine, moves onto modelling categorical data, in particular assessing associations between variables. Some of the questions we shall consider are widely discussed in many clinical research publications, and we will use the ideas of hypothesis tests and confidence intervals to answer those questions.

Statistics: how many?

The fourth in our series of articles on statistics for clinicians focuses on how we determine the appropriate number of subjects to include in an experimental study to provide sufficient statistical "power".

Comparison of the effects of thiopentone and propofol on the electrocardiogram of dogs

Sixty-four dogs were randomly assigned to receive either thiopentone or propofol and their electrocardiograms were recorded immediately before and shortly after they were anaesthetised. Thiopentone caused a marked increase in QT and JT intervals, a flattening of the T-wave and an increase in precordial QT dispersion. Propofol induced a less marked increase in QT and JT intervals, corrected for heart rate. Both agents induced an increase in heart rate and a decrease in heart rate variability, consistent with reduced vagal tone. Shortly after anaesthesia was induced, thiopentone affected ventricular repolarisation to a far greater extent than propofol, changes which suggest that it may be more likely to induce re-entrant ventricular arrhythmogenesis and could be associated with an increase in sympathetic tone. Propofol may therefore be more suitable than thiopentone for dogs with a susceptibility to ventricular arrhythmias or a long QT interval.

Regulation of tau phosphorylation in microtubule fractions by apolipoprotein E

In Alzheimer's disease (AD), a family of proteins collectively named tau are displaced from their normal association with microtubules and are found in in a hyperphosphorylated state deposited into paired helical filaments (PHFs). PHFs are the hallmark cytoskeletal pathology of the disease, and the degree of PHF pathology correlates with the clinical severity of AD. Certain apolipoprotein E (apoE) isoforms have been identified as either risk or protective factors for AD, and one of the proposed mechanisms involves an interaction and potentially modulatory effects on tau hyperphosphorylation by the different apoE isoforms. In these studies, we directly tested the effects of apoE, E2, E3, and E4 on AD-like phosphorylation of tau in brain microtubule fractions. We found that apoE attenuates tau hyperphosphorylation in the fractions, but the pattern was indistinguishable for the different isoforms.

Human endothelial nitric oxide synthase gene transfer inhibits vascular smooth muscle cell proliferation and neointima formation after balloon injury in rats

BACKGROUND

Loss of endothelial NO production after arterial injury may contribute to restenosis, characterized by neointima formation and elastic recoil. Adenovirus-mediated transfer of the gene encoding NO synthase (NOS) in balloon-injured arteries may restore NO production and inhibit neointima formation.

METHODS AND RESULTS

After balloon injury, rat carotid arteries were transduced with 3x10(10) pfu/mL recombinant adenovirus carrying the human endothelial constitutive NOS cDNA (AdCMVceNOS, n=8) or no cDNA (AdRR5, n=8). ceNOS expression was confirmed by immunoblot analysis of vascular extracts and was localized by immunostaining in 30% of medial smooth muscle cells (SMCs) and in the adventitia of AdCMVceNOS-transduced arteries. Vascular cGMP levels were reduced from 3.9 pmol/g wet wt in uninjured arteries to 0.7 pmol cGMP/g after AdRR5 but were restored after ceNOS gene transfer (3.8 pmol cGMP/g wet wt, P<.05 versus AdRR5). Intima-to-media ratio 2 weeks after injury was significantly reduced (0.19+/-0.02 in AdCMVceNOS-infected versus 0.69+/-0.07 in AdRR5-infected arteries, P<.05). In vitro, BrdU incorporation of AdCMVceNOS-infected SMCs was reduced by 28% compared with AdRR5-infected SMCs. Transduced cells from injured carotid arteries subjected to FACS sorting showed a significantly lower BrdU labeling index in ceNOS-infected rats (29+/-6% versus 43+/-5% and 45+/-4% in control, injured, and AdRR5-infected rats, respectively, P<.05).

CONCLUSIONS

AdCMVceNOS gene transfer to balloon-injured rat carotid arteries restores vascular NO production and reduces neointima formation, at least in part because of an antiproliferative effect on medial SMCs. Adenovirus-mediated ceNOS gene transfer might reduce arterial restenosis after balloon angioplasty.

A critique of the World Resources Institute's report "Pesticides and the immune system: the public health risks"

A recent World Resources Institute (WRI) report concluded that pesticides are a likely cause of immune suppression for millions of people throughout the world. The gravity of this conclusion motivated us to review the scientific evidence cited in the report. The predominant human evidence came from cross-sectional studies conducted in the former Soviet Union. These studies were difficult to evaluate due to incomplete reporting and had obvious limitations in terms of subject selection, exposure assessment,lack of quality control, statistical analysis, adequacy of the comparison group, and confounding. The toxicologic evidence was comprised mainly of acute high-dose studies in which the exposure conditions resulted in systemic toxicity. The relevance of these studies to effects at typical human exposure levels is questionable. We did not find consistent, credible evidence to support the conclusion of widespread pesticide-related immune suppression. Nonetheless, the WRI report is an important document because it focuses attention on a potentially important issue for future research and brings a substantial literature of foreign language studies to the attention of Western scientists.

Comparison of three methods used for assessment of pain in dogs

OBJECTIVE

To investigate the reliability of 3 scales used for assessment of pain in dogs.

DESIGN

Prospective study.

ANIMALS

50 dogs that had surgery.

PROCEDURE

Dogs were allocated into 3 groups (group 1, 25 dogs assessed 1 hour after the end of surgery; group 2, 41 dogs assessed between 21 and 27 hours after the end of surgery; group 3, 16 dogs assessed on the day of surgery and on the subsequent day). Each dog was scored for pain 4 times by 3 (groups 1 and 3) or 4 (group 2) veterinarians, using all 3 scales (i.e. simple descriptive, numerical rating, and visual analogue) during each scoring period. Analysis of data was performed using ANOVA, log-linear modeling, calculation of reproducibility coefficients, and Cohen's kappa statistic.

RESULTS

Significant variability existed among observers for use of all 3 scales. Variability among observers and between observers and dogs accounted for 29 to 36% of the total variability (group 1, 36.1 and 32.3% and group 2, 35.1 and 29.7%, for visual analogue scale and numerical rating scale scores, respectively). Kappa statistic values calculated for data obtained by use of the simple descriptive scale indicated that agreement was fair for the observers (group 1, 0.244 to 0.299; group 2, 0.211 to 0.368; group 3, 0.233 to 0.321).

CLINICAL IMPLICATIONS

Analysis of pain score data in dogs must incorporate observer variability when more than 1 observer is used. Comparative analysis of data accrued from pain studies in various hospitals must account for this variability.

A pharmacodynamic study of propofol or propofol and ketamine infusions in ponies undergoing surgery

The pharmacodynamics of infusions of propofol alone (group 1) were compared with the pharmacodynamics of infusions of propofol and ketamine together (group 2) in eight ponies undergoing castration. Anaesthesia was induced with detomidine, 20 micrograms kg-1, followed by ketamine, 2.2 mg kg-1. Subsequently, a bolus dose of propofol, 0.5 mg kg-1, was administered intravenously to both groups, and an infusion of propofol was given for an average of 74 minutes to group 1, and an infusion of propofol and ketamine was given for 60 minutes to group 2. The mean (SD) infusion rates of propofol were 0.330 (0.050) mg kg-1 min-1 in group 1, and 0.124 (0.009) mg kg-1 in group 2, and the ketamine infusion rate was maintained constant at 40 micrograms kg-1 min-1. Arterial hypotension and marked respiratory depression were evident in some of the ponies receiving propofol alone, whereas in the ponies anaesthetised with propofol and ketamine, respiratory and cardiovascular parameters were well maintained. All the ponies in both groups recovered quickly from anaesthesia, with mean times to sternal recumbency and standing of 19.8 (8.0) minutes and 27.2 (7.4) minutes respectively for group 1 and 8.4 (3.2) min and 14.9 (10.1) minutes for group 2.

Simultaneous infusions of propofol and ketamine in ponies premedicated with detomidine: a pharmacokinetic study

The pharmacokinetics of propofol and ketamine administered together by infusion were investigated in four ponies. Blood propofol and plasma ketamine and norketamine concentrations were measured by high performance liquid chromatography. After premedication with detomidine (20 micrograms kg-1) anaesthesia was induced with ketamine (2.2 mg kg-1 intravenously). The trachea was intubated and the ponies were allowed to breathe 100 per cent oxygen. A bolus dose of propofol (0.5 mg kg-1) was then administered intravenously and propofol and ketamine were infused for 60 and 45 minutes, respectively. The average mean infusion rate of propofol was 0.136 mg kg-1 min-1, and the ketamine infusion rate was maintained at 50 micrograms kg-1 min-1. The mean (SD) elimination half-lives of propofol and ketamine were 69.0 (8.0) and 89.8 (26.7) minutes, the mean volumes of distribution at steady state were 0.894 (0.161) litre kg-1 and 1.432 (0.324) litre kg-1; the mean body clearances were 33.1 (4.5) and 23.9 (3.8) ml kg-1 min-1 and the mean residence times for the infusion were 87.1 (4.1) and 110.7 (8.2) minutes, respectively. Norketamine, the main metabolite of ketamine, was detected throughout the sampling period. The mean residence time for norketamine was 144 (16) minutes. All the ponies recovered quickly from the anaesthesia; the mean times to sternal recumbency and standing were 11.1 (5.3) and 30.0 (20.8) minutes, respectively, from the end of the infusion.

Biotransformation of the MPTP analog trans-1-methyl-4-[4-dimethylaminophenylethenyl]-1,2,3,6-tetra- hydropyridine to a fluorescent pyridinium metabolite by intact neuroblastoma cells

The possibility of imaging monoamine oxidase (MAO) containing neurons through the MAO-mediated conversion of the nonfluorescent tetrahydropyridine compound trans-1-methyl-4-[4-dimethylaminophenylethenyl]-1,2,3,6-tetrahydro pyridine (t-THP) to the corresponding fluorescent trans-1-methyl-4-[4-dimethylaminophenylethenyl]pyridinium species (t-P+) was examined with the aid of human neuroblastoma cells (SH-SY5Y). Fluorescence microscopy and fluorescence measurements established the intracellular formation of a fluorescent species with maximal excitation/emission wavelengths of 485/620 and 530/620 nm corresponding to the fluorescence characteristics of synthetic t-P+. An independent assay confirmed the presence of both MAO-A and MAO-B in these cells. As expected, the development of the fluorescence was inhibited by both clorgyline (an MAO-A inhibitor) and deprenyl (an MAO-B inhibitor). Cytotoxic effects, as determined by trypan blue dye exclusion for viability and by the MTT [3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide] assay for mitochondrial integrity, were not observed in cells incubated with concentrations of t-THP as high as 10(-3) M for 4 hr. The results from these studies with a neuronal cell line of human origin suggest: (1) that SH-SY5Y cells metabolize and, therefore, can be used for study of tetrahydropyridine compounds in vitro, and (2) that t-THP may be a useful agent to monitor neurodegenerative processes in MAO-rich neurons, including the dopaminergic nigrostriatal neurons that are damaged by the parkinsonian-inducing tetrahydropyrridine MPTP. The potential advantage of using t-THP over related imaging techniques is the possibility of assessing neuronal function by an in vivo processing of the reporter molecule rather than by postmortem immunofluorescent or formaldehyde-based procedures.

Sequence and genetic analysis of multiple flagellin-encoding genes from Proteus mirabilis

Surface-induced overproduction of flagellin is one of the hallmarks of Proteus mirabilis swarmer cell differentiation. In this study, we analyzed the nucleotide (nt) and amino acid (aa) sequences, and expression of the P. mirabilis flagellin-encoding gene (fliC) region. The nt sequence analysis of a 3567-bp region reveals three ORFs, each with homology to known Escherichia coli flagellar genes. The first ORF corresponds to fliD, the gene encoding the flagellar filament capping protein, FliD (HAP2). The second and third ORFs are highly homologous to each other and to fliC genes from many other Gram- bacteria. To distinguish between the two alleles, we have designated these genes fliC1 and fliC2. Sequences highly homologous to promoter sites for the alternate sigma factor of RNA polymerase, sigma 28, are found 5' to the start of each gene. Additionally, both fliC1 and fliC2 have a conserved direct tandem repeat (DTR) sequence upstream from the sigma 28 promoter that may have functional significance in the transcriptional control of fliC expression during swarmer cell differentiation. Both FliC1 and FliC2 were produced in E. coli, but only FliC1 could complement FliC- mutants of E. coli. Southern hybridization data indicate the presence of fliC1 and fliC2 in six distinct P. mirabilis strains, indicating that multiple flagellin-encoding genes are common in P. mirabilis. Hybridization data also suggest the presence of a third flagellin-encoding gene, fliC3, in all isolates. The possible significance of multiple fliC in swarmer cell differentiation is discussed.

Transposon mutagenesis in Proteus mirabilis

A technique of transposon mutagenesis involving the use of Tn5 on a suicide plasmid was developed for Proteus mirabilis. Analysis of the resulting exconjugants indicated that Tn5 transposed in P. mirabilis at a frequency of ca. 4.5 x 10(-6) per recipient cell. The resulting mutants were stable and retained the transposon-encoded antibiotic resistance when incubated for several generations under nonselective conditions. The frequency of auxotrophic mutants in the population, as well as DNA-DNA hybridizaiton to transposon sequences, confirmed that the insertion of the transposon was random and the Proteus chromosome did not contain significant insertional hot spots of transposition. Approximately 35% of the mutants analyzed possessed plasmid-acquired ampicillin resistance, although no extrachromosomal plasmid DNA was found. In these mutants, insertion of the Tn5 element and a part or all of the plasmid had occurred. Application of this technique to the study of swarmer cell differentiation in P. mirabilis is discussed.

Proteus mirabilis mutants defective in swarmer cell differentiation and multicellular behavior

Proteus mirabilis is a dimorphic bacterium which exists in liquid cultures as a 1.5- to 2.0-microns motile swimmer cell possessing 6 to 10 peritrichous flagella. When swimmer cells are placed on a surface, they differentiate by a combination of events that ultimately produce a swarmer cell. Unlike the swimmer cell, the polyploid swarmer cell is 60 to 80 microns long and possesses hundreds to thousands of surface-induced flagella. These features, combined with multicellular behavior, allow the swarmer cells to move over a surface in a process called swarming. Transposon Tn5 was used to produce P. mirabilis mutants defective in wild-type swarming motility. Two general classes of mutants were found to be defective in swarming. The first class was composed of null mutants that were completely devoid of swarming motility. The majority of nonswarming mutations were the result of defects in the synthesis of flagella or in the ability to rotate the flagella. The remaining nonswarming mutants produced flagella but were defective in surface-induced elongation. Strains in the second general class of mutants, which made up more than 65% of all defects in swarming were motile but were defective in the control and coordination of multicellular swarming. Analysis of consolidation zones produced by such crippled mutants suggested that this pleiotropic phenotype was caused by a defect in the regulation of multicellular behavior. A possible mechanism controlling the cyclic process of differentiation and dediferentiation involved in the swarming behavior of P. mirabilis is discussed.

Stability of positive tuberculin tests: are boosted reactions valid?

To determine the stability and presumed significance of tuberculin skin tests, we followed a cohort of 380 tuberculin-positive patients living in chronic care facilities. Each patient had a positive reaction (greater than or equal to 10 mm induration to 5 tuberculin units of purified protein derivative) to one of three sequential baseline tuberculin tests. One year after the initial series, each patient had a single repeat skin test. Reversion to a negative test occurred in 98 (26%) of the 380 patients. Decreases in induration of 6 mm or more occurred in 88 (90%) of the reverters. Initially positive tests were more likely (p less than 0.001) to remain stable than tests that were "boosted" to positive reactions on the second or third initial administration. Stable responses were found in 96% of those whose tests had greater than or equal to 15 mm induration compared with 61% of those with reactions of 10 to 14 mm induration. Increasing age also was associated with a high rate of reversion. The instability of boosted tuberculin reactions brings into question the clinical significance of these tests. We propose limiting tuberculin testing to two sequential tests.

Conversion and reversion of tuberculin reactions in nursing home residents

To assess the consistency of tuberculin reactions over time, we performed tuberculin tests in a cohort of 495 nursing home residents in both 1982 and 1985. Significant reactions (greater than or equal to 10 mm of induration to 5 TU PPD) were found in 258 (52.1%) and 209 (42.2%) residents in 1982 and 1985, respectively. Males, nonwhites, and persons younger than 80 yr of age had a greater proportion of significant reactions (all, p less than 0.01). Of the 237 persons with nonsignificant reactions in 1982, 15 (6.3%) had a significant reaction in 1985. None of the 15 converters was found to have current tuberculosis. Tuberculin reversions occurred in 64 (24.8%) of 258 persons who had significant reactions in 1982. Of the patients who had a significant reaction only after boosting in 1982, 16 of 21 (76.2%) had nonsignificant reactions with up to 3 tests in 1985. Tuberculin reactions in nursing home residents may vary over time and may not be recalled by boosting, boosted reactions may be transient, and apparent conversions may be due to an extension of the booster phenomenon.

Evaluation of a third sequential tuberculin skin test in a chronic care population

To evaluate factors that might influence the accuracy of tuberculin tests in identifying elderly persons recently infected with Mycobacterium tuberculosis, we performed as many as 3 sequential administrations of 5 tuberculin units of purified protein derivative in 1,726 persons residing in chronic care facilities. Significant reactions (greater than or equal to 10 mm of induration) to 1 of 3 tests were found in 702 (40.7%) persons. Of these, 68% were found with Test 1, 22.5% with Test 2, and 9.5% with Test 3. Of 1,146 persons with nonsignificant reactions to Test 1, 13.8% had significant reactions on Test 2, and of 769 persons with nonsignificant reactions to Tests 1 and 2, 8.7% had significant reactions on Test 3. Males, nonwhites, and persons between 50 and 79 yr of age had a greater proportion of significant reactions for each of the first 2 tests but not for the third test. These data indicate that continued boosting of the tuberculin reaction occurs in a substantial number of persons who receive a third sequential test. Marked increases in the size of reactions caused by boosting may explain high apparent conversion rates found in facilities where the third test is delayed for one year.

Establishing clinical and immunologic criteria for diagnosis of occupational immunologic lung disease with phthalic anhydride and tetrachlorophthalic anhydride exposures as a model

Using a questionnaire and serum antibody studies, we evaluated 13 workers exposed to phthalic anhydride (PA) and tetrachlorophthalic anhydride (TCPA). The questionnaire was designed to identify symptoms compatible with anhydride-induced immunologic or irritant syndromes. Specific IgG and IgE for both PA-human serum albumin (PA-HSA) and TCPA-HSA were determined by enzyme-linked immunosorbent assay in two different laboratories. In addition, 11 workers had cutaneous testing with PA-HSA and TCPA-HSA, and nine workers were interviewed. One worker was found to have PA-associated asthma and rhinitis. We conclude that a questionnaire and serologic assays for specific IgG and IgE are helpful to identify workers who have or are at risk for developing occupational immunologic lung disease such as those induced by anhydrides. However, additional evaluation may be necessary in those workers with such diseases as intrinsic asthma that may be difficult to differentiate from occupational immunologic lung disease.

Cocaine and sudden death

Victims of cocaine are seen increasingly often in physicians' offices and emergency departments. Sudden death in previously healthy individuals may be due to massive overdose. As law enforcement becomes more active in the pursuit of drug dealers, "body stuffing"--the ingestion of large quantities of cocaine or other drugs in a panic situation to avoid arrest--is occurring more frequently.

Somatic evolution of diversity among anti-phosphocholine antibodies induced with Proteus morganii

The variable region sequences of light and heavy chains (VL and VH) were determined for 11 hybridoma antibodies produced in response to the PC moiety on Proteus morganii. These hybridomas were derived from two separate fusions, one obtained from mice early in a secondary response and the other from late in a secondary response. All of these antibodies possessed a cross-reactive idiotype found on anti-PC antibodies in the M603 family, and exhibited preferential specificity for PC in the context of P. morganii. We found that all of the antibodies were derived from a single VH/VL pair. VH was encoded by V1, DFL16.1 and JH1, and VL was encoded by a consensus VK8 gene and JK5. Antibodies differed from each other by somatic point mutations that occurred at a high rate. The mutations in VL were approximately one-third as abundant as those in VH and were randomly distributed throughout the molecule. Mutations in VH were concentrated in CDR 2 and 3 and had a replacement to silent ratio that was three to six times greater than predicted from random accumulation. Based on the sequence data, a single genealogic tree with multiple branches could accommodate all the hybrids from a fusion. We concluded that in both examples the anti-PC response arose by somatic mutation and stepwise selection from a single precursor. Antigen binding studies with these 11 hybridomas and a 12th that had no mutations revealed that the acquisition of preferential specificity for antigen was dependent on somatic mutation of germline genes. Additional binding studies demonstrated that continued selection during clonal expansion was probably antigen driven. An unexpected finding was five independently selected antibodies from one fusion that had identically mutated VH and VL sequences. We suggest that the hypermutation mechanism is not a continuously active process during clonal expansion and that it is regulated, probably during the mid to late phase of the primary response.

Somatic evolution of diversity among anti-phosphocholine antibodies induced with Proteus morganii

The variable region sequences of light and heavy chains (VL and VH) were determined for 11 hybridoma antibodies produced in response to the PC moiety on Proteus morganii. These hybridomas were derived from two separate fusions, one obtained from mice early in a secondary response and the other from late in a secondary response. All of these antibodies possessed a cross-reactive idiotype found on anti-PC antibodies in the M603 family, and exhibited preferential specificity for PC in the context of P. morganii. We found that all of the antibodies were derived from a single VH/VL pair. VH was encoded by V1, DFL16.1 and JH1, and VL was encoded by a consensus VK8 gene and JK5. Antibodies differed from each other by somatic point mutations that occurred at a high rate. The mutations in VL were approximately one-third as abundant as those in VH and were randomly distributed throughout the molecule. Mutations in VH were concentrated in CDR 2 and 3 and had a replacement to silent ratio that was three to six times greater than predicted from random accumulation. Based on the sequence data, a single genealogic tree with multiple branches could accommodate all the hybrids from a fusion. We concluded that in both examples the anti-PC response arose by somatic mutation and stepwise selection from a single precursor. Antigen binding studies with these 11 hybridomas and a 12th that had no mutations revealed that the acquisition of preferential specificity for antigen was dependent on somatic mutation of germline genes. Additional binding studies demonstrated that continued selection during clonal expansion was probably antigen driven. An unexpected finding was five independently selected antibodies from one fusion that had identically mutated VH and VL sequences. We suggest that the hypermutation mechanism is not a continuously active process during clonal expansion and that it is regulated, probably during the mid to late phase of the primary response.

The different types of limb apraxia errors made by patients with left vs. right hemisphere damage

Limb apraxia errors were compared among normal controls and right- or left-hemisphere-damaged patients as they imitated gestures with the ipsilateral hand. Both brain-damaged groups made similar errors on nonrepresentative and representative/intransitive movements. In contrast for pretended object use movements (transitive), the left-hemisphere-damaged group made more arm position and classical body-part-as-object errors while the right hemisphere group made as many partial errors and more less-primitive, body-part-as-object errors than the left-hemisphere-damaged group. These results help explain why a certain percentage of right-hemisphere-damaged patients are labeled apraxic, but also suggest that the left hemisphere is more important for integrating intrapersonal space and the "representation" of extrapersonal space.

Acute effects of grain dust exposure during a work shift

We studied 248 grain handlers and 192 city services workers (control subjects) before and after an 8-h work shift and measured total dust levels using personal samplers. We found that grain workers exposed to a mean total dust level of 3.3 +/- 7.0 mg/m3, when compared with control subjects, had (1) a higher prevalence of work-related respiratory symptoms (p less than 0.05) and significant decrements in forced-expiratory volume in one second (FEV1) and maximal flow rates after exhalation 50 and 75% of forced vital capacity (Vmax50 and Vmax75) during the work shift, and (2) significant differences (p less than 0.05) in preshift/postshift percent changes in forced vital capacity (FVC), Vmax50 and Vmax75. Adjusting for age, height, and smoking habit, grain handling still had a significant negative effect on FVC, Vmax50, and Vmax75. In grain workers, we found a significant (p less than 0.05) negative relationship between total dust levels and the percent change in FVC, Vmax50, and Vmax75 and a positive relationship between dust level and percent change in leukocyte counts. Grain workers' perception of dust level correlated with the measured dust level and the prevalence of symptoms. Occupational exposure to grain dust during a work shift has a dose-related adverse acute respiratory effect regardless of smoking habit, atopic status, or age, and it produces a dose-related leukocyte response at total dust levels below 15 mg/m3.

Grain fever syndrome induced by inhalation of airborne grain dust

To study the clinical and physiologic manifestations of the grain fever syndrome and the potentially pathogenic role of complement activation, 12 subjects (six grain workers and six healthy non-grain workers) underwent inhalation provocations with airborne grain dust. The clinical response was characterized by facial warmth, headache, malaise, myalgias, feverish sensation, chilliness, throat and tracheal burning sensation, chest tightness, dyspnea, cough, and expectoration. Fever developed in four grain workers and two controls. Leukocytosis, ranging between 11,700 and 24,300 leukocytes/mm3 with left shift, developed in five grain workers and five controls. There was no evidence of complement activation by the classical or alternate pathway. None of the subjects had serum precipitins to grain dust. The pulmonary response was characterized by a decrease in FEV1, FVC, MMF, Vmax50, and Vmax75, with significant rise in pulmonary resistance and consistent change in dynamic compliance but without changes in static compliance or diffusing capacity. Hence, grain dust inhalation induced diffuse airways obstruction without detectable parenchymal reaction. The airways response to high concentrations of grain dust inhalation were unrelated to the presence of immediate skin hypersensitivity. Although we cannot exclude the etiopathogenetic role of an immunologic reaction to grain dust, our data do not support the hypothesis that the grain fever syndrome is a precipitin-mediated allergic pneumonitis. More likely, the manifestations of grain fever probably reflect the host reaction to grain dust bacterial endotoxins and/or nonallergic mediator release by grain or grain dust constituents.

Pulmonary reaction to durum wheat; a constituent of grain dust

To identify constituents of grain dust responsible for grain handlers' respiratory symptoms, 11 volunteer grain elevator workers underwent inhalation provocation tests with extracts of durum wheat, durum wheat airborne dust, and grain insects and mites. Factors that might influence the host response to the challenge were assessed. Five of the 11 subjects showed a greater than 20 percent decrement in FEV1 after inhalation of durum wheat extracts (airways reaction). The bronchial reactions were immediate in 1/5 and late in 4/5. These airway reactions were blocked by sodium cromoglycate. Only one subject showed airway reaction to durum wheat dust extract, and none reacted to mites or insect extracts. There was no change in DLCO, temperature, or in total C3 complement blood levels, nor was there evidence of activation of complement by the alternate or classic pathway. The airway response was not always related to the atopic status of the individual. The reaction is more likely to occur in subjects with preexisting airway obstruction and nonspecific bronchial hyperreactivity. Durum wheat has been identified as an inducer of occupational asthma in grain handlers. This reaction is probably due to specific or nonspecific mediator release. There was no apparent parenchymal or systemic reaction or complement activation detectable in the subjects' sera after inhalation of durum wheat extracts.

Relationships between prednisone therapy, disease activity, and the total serum IgE level in allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is an unusual syndrome caused by hypersensitivity to Aspergillus spores growing in the bronchii. Previous investigators have suggested that the IgE levels and precipitating antibodies may vary according to disease activity. We have been able to closely follow 12 out of a group of 40 ABPA patients with IgE and serum precipitating antibody measurements. Our results confirm that both the total serum IgE and the precipitin response vary according to ABPA disease activity. In particular the IgE trend appears to mirror the disease activity in that a rising level may portend a flare, while a stable or declining value implies disease remission.

Effects of experimental rhinovirus 16 infection on airways and leukocyte function in normal subjects

We infected 7 normal volunteers with rhinovirus 16. In general, the symptoms and alterations in airways were minimal although all subjects had upper respiratory symptoms. Three subjects developed in addition lower respiratory and systemic symptoms accompanied by either an increase in the volume of isoflow or a positive methacholine response. Furthermore, these three had a decrease in beta adrenergic and H2 histamine receptor responses of their granulocytes. Since the peripheral airway obstruction and decreased beta adrenergic and H2 histamine responses occurred together, these two phenomenon may have a common cause. All seven subjects had a decrease in number of circulating E rosette-forming lymphocytes, and in 6 of 7, there was a decrease in the antibody-dependent cellular cytotoxicity capacity of mononuclear cell preparations. It is not clear whether these changes reflect redistribution of mononuclear cells or alteration of their function.