Detection of a knockdown mutation in the voltage-sensitive sodium channel associated with permethrin tolerance in Sarcoptes scabiei var. hominis mites

BACKGROUND

Increasing evidence has sparked a debate on the loss of sensitivity of scabies mites to conventional permethrin therapy. Mutations in the voltage-sensitive sodium channels (VSSC) were associated with knockdown resistance (kdr) in many arthropods, but have never been identified in Sarcoptes scabiei variatio (var.) hominis mites.

OBJECTIVES

To identify factors contributing to therapy failure.

METHODS

Sixty-seven mites were collected from 64 scabies-infested patients in Vienna, Austria, of whom 85.9% were refractory to prior permethrin-based treatments, and genotyped for the presence of nucleotide polymorphisms in Domain II of the VSSC, known to be associated with kdr. Information regarding previous antiscabietic therapies, decontamination procedures and possible re-infestations by contacts as well as the response to re-imposed therapies were obtained.

RESULTS

Sequence alignment comparisons revealed previously unidentified mutations in the coding region of Domain II of the VSSC. A novel A1663T transversion was detected in 97.0% of the mites, resulting in a non-synonymous substitution from methionine to leucine, M918L, a mutation known to confer kdr in other arthropods. In addition, a synonymous G1659A transition was identified in one mite, which otherwise showed a nucleotide sequence identical to the wild-type reference. No major inconsistencies were observed within the previous therapeutic and decontamination procedures, which could have accounted for the observed non-responsiveness to permethrin-based therapies. Subsequent cure of infestation was achieved in 65.6% of the participants, predominantly by combination therapies with topical permethrin and systemic ivermectin. However, in 14.6% of the cured cases, permethrin monotherapy sufficed for eradication of scabies, albeit in some cases prolonged exposure was necessary.

CONCLUSIONS

The kdr-associated M918L mutation in the VSSC gene has now emerged in S. scabiei var. hominis mites. Hence, loss of sensitivity to permethrin due to kdr-type resistance may be more prevalent than anticipated and may be decisive for the therapy responsiveness of scabies-infested patients.

A rapid theta network mechanism for flexible information encoding

Flexible behavior requires gating mechanisms that encode only task-relevant information in working memory. Extant literature supports a theoretical division of labor whereby lateral frontoparietal interactions underlie information maintenance and the striatum enacts the gate. Here, we reveal neocortical gating mechanisms in intracranial EEG patients by identifying rapid, within-trial changes in regional and inter-regional activities that predict subsequent behavioral outputs. Results first demonstrate information accumulation mechanisms that extend prior fMRI (i.e., regional high-frequency activity) and EEG evidence (inter-regional theta synchrony) of distributed neocortical networks in working memory. Second, results demonstrate that rapid changes in theta synchrony, reflected in changing patterns of default mode network connectivity, support filtering. Graph theoretical analyses further linked filtering in task-relevant information and filtering out irrelevant information to dorsal and ventral attention networks, respectively. Results establish a rapid neocortical theta network mechanism for flexible information encoding, a role previously attributed to the striatum.

Left hemisphere dominance for bilateral kinematic encoding in the human brain

Neurophysiological studies in humans and nonhuman primates have revealed movement representations in both the contralateral and ipsilateral hemispheres. Inspired by clinical observations, we ask if this bilateral representation differs for the left and right hemispheres. Electrocorticography was recorded in human participants during an instructed-delay reaching task, with movements produced with either the contralateral or ipsilateral arm. Using a cross-validated kinematic encoding model, we found stronger bilateral encoding in the left hemisphere, an effect that was present during preparation and was amplified during execution. Consistent with this asymmetry, we also observed better across-arm generalization in the left hemisphere, indicating similar neural representations for right and left arm movements. Notably, these left hemisphere electrodes were centered over premotor and parietal regions. The more extensive bilateral encoding in the left hemisphere adds a new perspective to the pervasive neuropsychological finding that the left hemisphere plays a dominant role in praxis.

Intracranial Recordings Demonstrate Both Cortical and Medial Temporal Lobe Engagement in Visual Search in Humans

Visual search is a fundamental human behavior, providing a gateway to understanding other sensory domains as well as the role of search in higher-order cognition. Search has been proposed to include two component processes: inefficient search (Search) and efficient search (Pop-out). According to extant research, these two processes map onto two separable neural systems located in the frontal and parietal association cortices. In this study, we use intracranial recordings from 23 participants to delineate the neural correlates of Search and Pop-out with an unprecedented combination of spatiotemporal resolution and coverage across cortical and subcortical structures. First, we demonstrate a role for the medial temporal lobe in visual search, on par with engagement in frontal and parietal association cortex. Second, we show a gradient of increasing engagement over anatomical space from dorsal to ventral lateral frontal cortex. Third, we confirm previous intracranial work demonstrating nearly complete overlap in neural engagement across cortical regions in Search and Pop-out. We further demonstrate Pop-out selectivity, manifesting as activity increase in Pop-out as compared to Search, in a distributed set of sites including frontal cortex. This result is at odds with the view that Pop-out is implemented in low-level visual cortex or parietal cortex alone. Finally, we affirm a central role for the right lateral frontal cortex in Search.

Nine-year prospective efficacy and safety of brain-responsive neurostimulation for focal epilepsy

OBJECTIVE

To prospectively evaluate safety and efficacy of brain-responsive neurostimulation in adults with medically intractable focal onset seizures (FOS) over 9 years.

METHODS

Adults treated with brain-responsive neurostimulation in 2-year feasibility or randomized controlled trials were enrolled in a long-term prospective open label trial (LTT) to assess safety, efficacy, and quality of life (QOL) over an additional 7 years. Safety was assessed as adverse events (AEs), efficacy as median percent change in seizure frequency and responder rate, and QOL with the Quality of Life in Epilepsy (QOLIE-89) inventory.

RESULTS

Of 256 patients treated in the initial trials, 230 participated in the LTT. At 9 years, the median percent reduction in seizure frequency was 75% (p < 0.0001, Wilcoxon signed rank), responder rate was 73%, and 35% had a ≥90% reduction in seizure frequency. We found that 18.4% (47 of 256) experienced ≥1 year of seizure freedom, with 62% (29 of 47) seizure-free at the last follow-up and an average seizure-free period of 3.2 years (range 1.04-9.6 years). Overall QOL and epilepsy-targeted and cognitive domains of QOLIE-89 remained significantly improved (p < 0.05). There were no serious AEs related to stimulation, and the sudden unexplained death in epilepsy (SUDEP) rate was significantly lower than predefined comparators (p < 0.05, 1-tailed χ2).

CONCLUSIONS

Adjunctive brain-responsive neurostimulation provides significant and sustained reductions in the frequency of FOS with improved QOL. Stimulation was well tolerated; implantation-related AEs were typical of other neurostimulation devices; and SUDEP rates were low.

CLINICALTRIALSGOV IDENTIFIER

NCT00572195.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that brain-responsive neurostimulation significantly reduces focal seizures with acceptable safety over 9 years.

Spectral Imprints of Working Memory for Everyday Associations in the Frontoparietal Network

How does the human brain rapidly process incoming information in working memory? In growing divergence from a single-region focus on the prefrontal cortex (PFC), recent work argues for emphasis on how distributed neural networks are rapidly coordinated in support of this central neurocognitive function. Previously, we showed that working memory for everyday “what,” “where,” and “when” associations depends on multiplexed oscillatory systems, in which signals of different frequencies simultaneously link the PFC to parieto-occipital and medial temporal regions, pointing to a complex web of sub-second, bidirectional interactions. Here, we used direct brain recordings to delineate the frontoparietal oscillatory correlates of working memory with high spatiotemporal precision. Seven intracranial patients with electrodes simultaneously localized to prefrontal and parietal cortices performed a visuospatial working memory task that operationalizes the types of identity and spatiotemporal information we encounter every day. First, task-induced oscillations in the same delta-theta (2–7 Hz) and alpha-beta (9–24 Hz) frequency ranges previously identified using scalp electroencephalography (EEG) carried information about the contents of working memory. Second, maintenance was linked to directional connectivity from the parietal cortex to the PFC. However, presentation of the test prompt to cue identity, spatial, or temporal information changed delta-theta coordination from a unidirectional, parietal-led system to a bidirectional, frontoparietal system. Third, the processing of spatiotemporal information was more bidirectional in the delta-theta range than was the processing of identity information, where alpha-beta connectivity did not exhibit sensitivity to the contents of working memory. These findings implicate a bidirectional delta-theta mechanism for frontoparietal control over the contents of working memory.

Persistent neuronal activity in human prefrontal cortex links perception and action

How do humans flexibly respond to changing environmental demands on a sub-second temporal scale? Extensive research has highlighted the key role of the prefrontal cortex in flexible decision-making and adaptive behavior, yet the core mechanisms that translate sensory information into behavior remain undefined. Utilizing direct human cortical recordings, we investigated the temporal and spatial evolution of neuronal activity, indexed by the broadband gamma signal, while sixteen participants performed a broad range of self-paced cognitive tasks. Here we describe a robust domain- and modality-independent pattern of persistent stimulus-to-response neural activation that encodes stimulus features and predicts motor output on a trial-by-trial basis with near-perfect accuracy. Observed across a distributed network of brain areas, this persistent neural activation is centered in the prefrontal cortex and is required for successful response implementation, providing a functional substrate for domain-general transformation of perception into action, critical for flexible behavior.

Infection and Erosion Rates in Trials of a Cranially Implanted Neurostimulator Do Not Increase with Subsequent Neurostimulator Placements

BACKGROUND/AIMS

The RNS® System utilizes a cranially implanted neurostimulator attached to leads placed at the seizure focus to provide brain responsive stimulation for the treatment of medically intractable partial onset epilepsy. Infection and erosion rates related to the cranial implant site were assessed overall and by neurostimulator procedure to determine whether rates increased with additional procedures.

METHODS

Infection and erosion rates were calculated as (1) chance per neurostimulator procedure, (2) incidence per patient implant year, and (3) rates for initial and each subsequent neurostimulator implant (generalized estimating equation).

RESULTS

In 256 patients followed for an average of 7 years, the infection rate was 3.7% per neurostimulator procedure (n = 31/840), and the rate of erosions was 0.8% per neurostimulator procedure (n = 7/840). Rates did not increase with subsequent neurostimulator procedures (p = 0.66, infection; p = 0.70, erosion). A prior infection or erosion at the implant site did not significantly increase the risk at a later procedure (p ≥ 0.05 for all combinations).

CONCLUSION

These data indicate that the risk for infection compares favorably to other neurostimulation devices and suggest that rates of infection and erosion do not increase with subsequent neurostimulator replacements.

Surface-Guided Formation of an Organocobalt Complex

Organocobalt complexes represent a versatile tool in organic synthesis as they are important intermediates in Pauson-Khand, Friedel-Crafts, and Nicholas reactions. Herein, a single-molecule-level investigation addressing the formation of an organocobalt complex at a solid-vacuum interface is reported. Deposition of 4,4'-(ethyne-1,2-diyl)dibenzonitrile and Co atoms on the Ag(111) surface followed by annealing resulted in genuine complexes in which single Co atoms laterally coordinated to two carbonitrile groups undergo organometallic bonding with the internal alkyne moiety of adjacent molecules. Alternative complexation scenarios involving fragmentation of the precursor were ruled out by complementary X-ray photoelectron spectroscopy. According to density functional theory analysis, the complexation with the alkyne moiety follows the Dewar-Chatt-Duncanson model for a two-electron-donor ligand where an alkyne-to-Co donation occurs together with a strong metal-to-alkyne back-donation.

Lateralization of mesial temporal lobe epilepsy with chronic ambulatory electrocorticography

OBJECTIVE

Patients with suspected mesial temporal lobe (MTL) epilepsy typically undergo inpatient video-electroencephalography (EEG) monitoring with scalp and/or intracranial electrodes for 1 to 2 weeks to localize and lateralize the seizure focus or foci. Chronic ambulatory electrocorticography (ECoG) in patients with MTL epilepsy may provide additional information about seizure lateralization. This analysis describes data obtained from chronic ambulatory ECoG in patients with suspected bilateral MTL epilepsy in order to assess the time required to determine the seizure lateralization and whether this information could influence treatment decisions.

METHODS

Ambulatory ECoG was reviewed in patients with suspected bilateral MTL epilepsy who were among a larger cohort with intractable epilepsy participating in a randomized controlled trial of responsive neurostimulation. Subjects were implanted with bilateral MTL leads and a cranially implanted neurostimulator programmed to detect abnormal interictal and ictal ECoG activity. ECoG data stored by the neurostimulator were reviewed to determine the lateralization of electrographic seizures and the interval of time until independent bilateral MTL electrographic seizures were recorded.

RESULTS

Eighty-two subjects were implanted with bilateral MTL leads and followed for 4.7 years on average (median 4.9 years). Independent bilateral MTL electrographic seizures were recorded in 84%. The average time to record bilateral electrographic seizures in the ambulatory setting was 41.6 days (median 13 days, range 0-376 days). Sixteen percent had only unilateral electrographic seizures after an average of 4.6 years of recording.

SIGNIFICANCE

About one third of the subjects implanted with bilateral MTL electrodes required >1 month of chronic ambulatory ECoG before the first contralateral MTL electrographic seizure was recorded. Some patients with suspected bilateral MTL seizures had only unilateral electrographic seizures. Chronic ambulatory ECoG in patients with suspected bilateral MTL seizures provides data in a naturalistic setting, may complement data from inpatient video-EEG monitoring, and can contribute to treatment decisions.

A direct measure of human lateral temporal lobe neurons responsive to face matching

Do the human cerebral hemispheres process faces differently? Clinical lesion observations and primate studies suggest that the right temporal lobe is critical in face processing. Yet, the nature of this relationship remains unclear. Recording from single neurons during a visuospatial (VS)-matching paradigm, we found that 100% of significantly active neurons discriminated matching from perception, bilaterally. Lateralized differences in the nature and timing of responses revealed that the right hemisphere neurons responded earlier, and with uniform frequency reductions. Additional lateralized differences favoring the right hemisphere neurons were found when subjects matched intact faces compared to scrambled faces or complex objects. We conclude that widely distributed neural ensembles are involved in 'lateralized' behaviors, but cerebral specialization of face processing is as much a function of the nature and timing of neuronal activity as anatomic location.

A role for PKC-epsilon in Fc gammaR-mediated phagocytosis by RAW 264.7 cells

Protein kinase C (PKC) plays a prominent role in immune signaling, and the paradigms for isoform selective signaling are beginning to be elucidated. Real-time microscopy was combined with molecular and biochemical approaches to demonstrate a role for PKC- epsilon in Fc gamma receptor (Fc gammaR)-dependent phagocytosis. RAW 264.7 macrophages were transfected with GFP-conjugated PKC isoforms, and GFP movement was followed during phagocytosis of fluorescent IgG-opsonized beads. PKC- epsilon, but not PKC-delta, concentrated around the beads. PKC- epsilon accumulation was transient; apparent as a "flash" on target ingestion. Similarly, endogenous PKC- epsilon was specifically recruited to the nascent phagosomes in a time-dependent manner. Overexpression of PKC- epsilon, but not PKC-alpha, PKC-delta, or PKC-gamma enhanced bead uptake 1.8-fold. Additionally, the rate of phagocytosis in GFP PKC- epsilon expressors was twice that of cells expressing GFP PKC-delta. Expression of the regulatory domain ( epsilon RD) and the first variable region ( epsilon V1) of PKC- epsilon inhibited uptake, whereas the corresponding PKC-delta region had no effect. Actin polymerization was enhanced on expression of GFP PKC- epsilon and epsilon RD, but decreased in cells expressing epsilon V1, suggesting that the epsilon RD and epsilon V1 inhibition of phagocytosis is not due to effects on actin polymerization. These results demonstrate a role for PKC- epsilon in Fc gammaR-mediated phagocytosis that is independent of its effects on actin assembly.

Mesenchymal proliferation with decidual-like morphology in seminal vesicles of aging mice

Lesions characterized by spindle and epithelioid cells and nuclear progesterone receptors are described in seminal vesicles of four aging mice. The lesions of two mice also contain granular metrial gland (GMG)-like cells. The same cellular details are seen in the uterine decidual reaction and the similar urinary bladder lesion in mice, also called mesenchymal tumor. Therefore, it is hypothesized that these lesions in male accessory sex glands and the urinary bladders of aging male and female mice are of mesenchymal origin with the potential for differentiation along several pathways, leading especially to lesions with decidual-like morphology, but also to lesions which contain only spindle cells. The decidual hypothesis is further supported by the occurrence of round eosinophilic granules and focal necrosis, interpreted as a sign of regression in all these lesion types. The bilateral lesions of a fifth mouse consist of spindle cells and scar-like tissue, the latter suggesting regression, and lack epithelioid and GMG-like cells. In this case, verification of the diagnosis depends on the demonstration of progesterone receptors, absent in normal glands. Uterine decidual reactions during pregnancy are brought about by priming with progesterone/estrogen, initiation through the blastocyst, and maintenance through progesterone. Experiments by others show that priming may also occur through growth factors/growth hormone, initiation through prostaglandins, and maintenance through testosterone in mice. It is hypothesized that upon such stimulation, certain cells in male accessory sex glands and the urinary bladder, possibly derived from the Muellerian ducts or other subperitoneal tissue, appear to have the potential in mice of developing into spindle and epithelioid cells, including decidual-like cells. All published uterine decidual reactions and lesions with decidual-like morphology in other organs of mice stayed within the peritoneal coverage of their respective organ and did not metastasize despite their "anaplastic", tumor-like appearance. Thus, they should be considered non-neoplastic. It is proposed to name above lesions in male accessory sex glands and urinary bladders "mesenchymal proliferation, decidual type" or "mesenchymal proliferation, spindle-cell type", depending on their cellular characteristics.

Reduction of background activity through radiolabeling of antifibrin Fab' with 99mTc-dextran

Scintigraphic detection of occult disease is limited by background activity in the blood and in the extravascular space that reduces target-specific contrast. To lower nonspecific background activity, we have studied the in vivo biodistribution kinetics of a clot-targeting molecule (MH1 Fab') attached to (99m)Tc-dextran. We tested the hypothesis that the complex will have better background clearance than the directly radiolabeled clot-targeting molecule.

METHODS

Fab' fragments of MH1 Fab' antifibrin antibody were coupled to (99m)Tc-sulfhydryl dextran through disulfide exchange, and clot binding bioreactivity was tested in vitro and in vivo in a rabbit jugular vein thrombus model. To assess the background clearance kinetics and extravascular leakage, we studied (99m)Tc-dextran, (99m)Tc-MH1 Fab', and the (99m)Tc-dextran-labeled MH1 Fab' complexes in rats.

RESULTS

(99m)Tc-radiolabeled dextran derivatives were radiochemically stable and retained clot-binding bioreactivity in vivo. In the rat model, blood and tissue clearance of the (99m)Tc-dextran MH1 Fab' constructs was substantially improved relative to directly radiolabeled MH1 Fab'. At 1 h, total and extravascular tracer localizations in lung and muscle were significantly lower for 99mTc-dextranradiolabeled MH1 Fab' than for (99m)Tc-MH1 Fab' (P < 0.05).

CONCLUSION

The study observations suggest that radiolabeling through a (99m)Tc-dextran moiety may improve the detection of pulmonary emboli and other clinically important fixed intravascular targets by lowering nonspecific background activity.

Fucosyltransferase and alpha-L-fucosidase activities and fucose levels in normal and malignant endometrial tissue

Previous immuno- and lectin-histochemical studies using mAbs and Ulex europaeus lectin I, which recognize various fucose-containing blood group antigens, have shown an increased expression of Lewis and H blood group antigens in endometrial carcinoma. We investigated the biochemical basis of aberrant fucose-containing antigen expression by comparing the activity of fucosyltransferases (FTase) and alpha-L-fucosidase in tissue biopsies from normal (n = 18) and malignant (n = 20) endometrium. Alteration of FTase activity in tumor tissue homogenates was evaluated by using a panel of FTase substrates including N-acetyllactosamine (type 2), lacto-N-biose I (type 1), and phenyl-beta-D-galactoside. Based on histological subtyping, the endometrioid group (n = 14) showed a significant (P < 0.05) increase in tumor FTase activity with all three substrates, while no significant increase was detected for the papillary serous group (n = 4). Matched pair analysis of normal and tumor tissue from a subgroup (n = 5) of the patients with increased tumor enzyme activity also showed higher FTase activity (P < 0.05) in the tumor tissue when the type 1 substrate was used. Regression analysis showed a correlation between the FTase activities acting on type 2 or type 1 substrates (r = 0.821 and r = 0.722, respectively) and the endogenous fucose levels in tumor homogenates. Spectrophotometric analysis of alpha-L-fucosidase activity using p-nitrophenyl-alpha-L-fucoside revealed a higher activity in tumor homogenates than in normal homogenates (P < 0.05) and, therefore, could not account for the enhanced expression of fucose-containing antigens. The current study suggests that aberrant expression of fucose-containing antigens, such as the H and the Lewis blood-group antigens, in endometrial carcinoma is consequential to the change in FTase rather than in alpha-L-fucosidase activity. In addition, the investigation suggests that different glycosylation mechanisms are operative in different subtypes of endometrial cancer.

Neuronal recordings in human lateral temporal lobe during verbal paired associate learning

The temporal lobe has a role in memory and learning. The objective of this study was to assess the activity of neurons in the temporal cortex of humans during learning. Single neuron activity was recorded with extracellular microelectrodes in adults undergoing awake craniotomies for resections for medically intractable epilepsy. Participants were administered control tasks of overt reading, silent reading, nonword visual controls and a recent verbal memory task with distracters followed by a verbal paired associates (PA) paradigm. Forty-nine neurons were identified and characterized by their relationship to language and memory. Neurons related to overt speech (Type A neurons) showed increased activity during learning in patients who were good learners compared to patients who were poor learners. Neurons not related to language or to memory (Type D neurons) showed increased activity with exposure to unlearned word pairs in poor learners compared with those who were good learners. Activity in all groups diminished with practice. Levels of activity in specific types of neurons in human temporal lobe differ in patients who learn word pairs rapidly or poorly.

Premortem biodistribution of radioactivity in the rat: measurement of blood and tissue activity of tracers used in clinical imaging studies

Radioactive tracers are used in nuclear medicine imaging studies to detect sites of human disease. Use of animal models helps to establish tracer biodistribution kinetics and, thus, is critical to the early testing of radiopharmaceuticals. We developed a method to characterize the premortem temporal, spatial, and compartmental biodistribution of tracer molecules in the rat and used this method to study three tracers of potential value in detecting thromboembolic disease. Dynamic gamma scintigraphy was used to determine the spatial and temporal distribution of 99mTc-labeled IgG antifibrin antibody, Fab' fragment of antifibrin, and oxidized human serum albumin (OHSA). The blood pool compartment within each tissue was determined from the biodistribution of 131I-labeled bovine serum albumin injected prior to termination. The biodistribution of the blood compartment was maintained by immediately freezing the rat carcass in isotonic saline. Three-dimensional maps of tracer distribution in the tissue and blood compartments were then constructed from cross sections of the frozen tissue. These maps were used to relate necropsy tissue counts to premortem scintigraphic images. Over a 60-min interval after administration of tracer via a tail vein, significant differences in biodistribution were evident. The IgG remained within the blood pool, but there was rapid blood clearance of the OHSA molecules by the kidney and liver. The Fab' molecules were cleared more slowly by the kidney; Fab' molecules were found in the extravascular spaces, whereas IgG and OHSA were not found. The kinetics of OHSA and Fab' in organ regions paralleled changes in the blood compartment.(ABSTRACT TRUNCATED AT 250 WORDS)

Halifax interlaminar clamp for posterior cervical fusion: a long-term follow-up review

Fifty consecutive patients requiring posterior cervical fusion for various pathologies were treated with Halifax interlaminar clamps for internal spinal fixation. Fusion involved the C1-2 level in 17 cases, the C1-3 level in one, and the lower cervical area (C2-7) in 32. No patient was lost to follow-up review, which varied from 6 to 40 months (average 21 months). Fusion failed in five patients, three at the C1-2 level, one at the C1-3 level, and one at the C2-3 level. Screw loosening was the cause of failure in four patients, and in one the arch of C-1 fractured. No other complications occurred. Because of the lack of complications, avoidance of the hazards of sublaminar instrumentation, and an excellent fusion rate, this technique is highly recommended for posterior cervical fusion in the lower cervical spine. Atlantoaxial arthrodesis was achieved in only 14 (82%) of 17 patients, however, which might be due to the higher mobility at this multiaxial level. Improved results in this region may be possible by using a new modified interlaminar clamp, by performing adequate bone fusions, and by postoperative external halo immobilization in high-risk patients.

Use of MR imaging-compatible Halifax interlaminar clamps for posterior cervical fusion

Twenty-one patients requiring posterior cervical fusion were treated with magnetic resonance (MR) imaging-compatible Halifax interlaminar clamps for internal fixation. Various levels were involved: the C1-2 level in eight cases, the C4-5 level in four, the C5-6 level in three, the C6-7 level in three, the C4-6 level in two, and the C5-7 level in one. Bilateral clamps were used in 18 cases and unilateral clamps in three. Autogenous iliac bone grafting was performed in all cases but one. Follow-up periods ranged from 1 to 18 months (average 9.2 months), with no complications or mechanical failures occurring thus far. Follow-up diagnostic studies revealed rigid fixation and fusion in all cases. The MR imaging-compatibility of the clamps allowed excellent follow-up studies with minimal artifact. Because of their ease of use, rigid stabilization, good results, lack of complications, and compatibility with MR imaging, the Halifax interlaminar clamp with bone grafting provides an ideal method for posterior cervical stabilization.

Cleavage of a model peptide at its glycine residue by alkaline mercuric oxycyanide

Treatment of peptides with excess HgO in the presence of alkaline cyanide leads to cleavage of the peptides at glycine residues. The reaction appears to involve both C- and N-mercuration with subsequent release of 2 mol mercury per mol of glycine. An intermediate glyoxylic acid residue in Schiff base linkage is postulated. Treatment of the heptapeptide Phe-Ala-Lys-Gly-Leu-Asp-Val with alkaline HgO and KCN for 6 h at 25 degrees resulted in greater than 90% cleavage, and the resultant reaction products were separated by reverse phase chromatography and identified by amino acid analysis. N-terminal products were approximately equimolar Phe-Ala-Lys, Phe-Ala-Lys-Gly, and Phe-Ala-Lys-amide. C-terminal products were predominantly Leu-Asp-Val (63%), plus Gly-Leu-Asp-Val (9%), and oxalyl-Leu-Asp-Val (8%). This method may be useful for cleavage of peptides or proteins containing glycine residues.

Left ventricular function during lethal and sublethal endotoxemia in swine

Our previous studies suggested that after a median lethal dose (LD50) of endotoxin, cardiac contractility was depressed in nonsurviving dogs. The canine cardiovascular system is unlike humans in that dogs have a hepatic vein sphincter that is susceptible to adrenergic stimulation capable of raising hepatic and splanchnic venous pressures. We retested the hypothesis that lethality after endotoxin administration is associated with cardiac contractile depression in pigs, because the hepatic circulation in this species is similar to that of humans. We compared cardiac mechanical function of pigs administered a high dose (250 micrograms/kg) or a low dose (100 micrograms/kg) endotoxin by use of the slope of the end-systolic pressure-diameter relationship (ESPDR) as well as other measurements of cardiac performance. In all the pigs administered a high dose, ESPDR demonstrated a marked, time-dependent depression, whereas we observed no significant ESPDR changes after low endotoxin doses. The other cardiodynamic variables were uninterpretable, due to the significant changes in heart rate, end-diastolic diameter (preload), and aortic diastolic pressure (afterload). Plasma myocardial depressant factor activity accumulated in all endotoxin-administered animals, tending to be greater in the high-dose group. In this group, both subendocardial blood flow and global function were depressed, whereas pigs administered the low dose of endotoxin demonstrated slight, but nonsignificant, increases in flow and function. These observations indicate that myocardial contractile depression is associated with a lethal outcome to high doses of endotoxin. One possible mechanism for this loss of contractile function may be a relative hypoperfusion of the subendocardium.

Canine left ventricular function during experimental pancreatitis

Left ventricular contractility following induction of experimental pancreatitis (EP) was studied. Contractility was evaluated by analyzing the left ventricular end systolic pressure-diameter relationship (sigma ES). Sigma ES is independent of large changes in preload, afterload, and heart rate, but sensitive to changes in ventricular contractility. Following injection of 100,000 IU trypsin in 4% taurocholate into the pancreas to induce EP, seven of eight dogs survived 5 hr. These dogs exhibited an initial significant reduction in mean arterial pressure (MABP) which stabilized at 90% of control at 3-5 hr post-EP. Cardiac output (CO) dropped slowly after EP induction (from 3.08 +/- 0.43 to 2.22 +/- 0.22 liters/min) associated with no significant change in peripheral resistance. Stroke work and stroke volume were markedly depressed reflecting the changes in MABP and CO. No consistent changes in +dP/dt or -dP/dt were observed. The ratio of endo/epicardial blood flow was unchanged as was blood Ca2+ levels throughout the experiment. Ventricular contractility as reflected by sigma ES tended to improve (from 49.7 to 69.6 mm Hg/mm at 4 hr following EP). Therefore, it was concluded that these animals exhibited no loss of ventricular contractility during EP.

Canine left ventricular performance during LD50 endotoxemia

Previous reports of the effect of endotoxin shock on cardiac performance have not achieved uniform results. These discrepancies have possibly been caused by the use of indices of cardiac performance that may have been sensitive to altered heart rate or preconditions of cardiac contraction as well as altered cardiac performance. We tested the hypothesis that, following a median lethal dose (LD50) of E. coli endotoxin, cardiac performance would be diminished in nonsurviving animals and maintained in surviving animals. We elected to employ the analysis of the end-systolic pressure-diameter relationship (sigma ES) as well as other measurements of cardiac performance to test this hypothesis. We established that the sigma ES measurement was independent of increased and decreased afterload and relatively insensitive to altered heart rate. In the nonsurviving animals, sigma ES exhibited a marked depression following endotoxin a administration. In the surviving animals, sigma ES exhibited a nonsignificant decrease followed by a return toward preendotoxin values. All other cardiodynamic measurements were uninterpretable due to the marked changes in heart rate, peripheral vascular function, aortic pressure, and cardiac output. We conclude that, following endotoxin administration, those animals that exhibited a diminished myocardial contractility failed to survive more than 2.5 h postendotoxin, whereas the surviving animals were able to restore normal cardiac contractility. Thus survival of endotoxin administration is associated with the maintenance of normal cardiac contractility.

Delayed cutaneous hypersensitivity reactions to concanavalin A-binding tumour membrane components

The use of affinity chromatography has permitted the isolation of those tumour membrane fractions possessing affinity for the lectin concanavalin A. That these fractions are rich in tumour-associated antigens is supported by their ability to induce delayed cutaneous hypersensitivity reactions. The tumour extracts possessing concanavalin affinity resulted in skin test reactivity of considerably greater frequency and magnitude than normal tissue fractions, disrupted unfractionated tumour membrane extracts, or tumour membrane fractions not possessing concanavalin A affinity. Although the present data does not permit the correlation of skin reactivity with patient or disease parameters, the isolation of augmented concentrations of tumour-associated antigens may lead to improved diagnostic and prognostic tests and vaccines for patients with cancer.