Biomedical subjects

J Gross

Publications and source records attributed to J Gross.

At least 73 records · Page 4Linked to original sources

PubMed1999

Neurophysiological correlates of the recognition of facial expressions of emotion as revealed by magnetoencephalography.

MEG correlates of the recognition of facial expressions of emotion were studied in four healthy volunteers. Subjects performed a facial emotion recognition task and a control task involving recognition of complex objects including faces. Facial emotion recognition activated inferior frontal cortex, amygdala and different parts of temporal cortex in a relatively consistent time sequence. The characteristics of these activations were clearly different from those recorded during the control task. Most interesting was the fact that faces evoked different MEG responses as a function of task demands, i.e., the activations recorded during facial emotion recognition were different from those recorded during simple face recognition in the control task. These findings support the assumption that MEG is able to specifically identify the activation pattern of the brain when recognition of the emotional expression of a face is performed.

Adult↗

PubMed1999

Validation of an accurate method for three-dimensional reconstruction and quantitative assessment of volumes, lengths and diameters of coronary vascular branches and segments from biplane angiographic projections.

UNLABELLED: The goal of the study was the validation of an accurate method for three-dimensional reconstruction and quantitative assessment of volumes, lengths and diameters of coronary vascular branches and segments from biplane angiographic projections. METHODS: The accuracy was tested in a complex phantom. In vivo, inter- and intraobserver agreement were assessed by analysis of routine angiograms. The sensitivity was evaluated using angiograms of patients having diagnostic vasoactive pharmacological intervention. Two-dimensional quantitative coronary angiography (2-D QCA) and 3-D QCA were compared concerning the accuracy of diameter evaluation. RESULTS: 3-D QCA yields accurate results (< 3% error) even based on nonorthogonal views, provided that projections parallel to the object are avoided. The inter- and intraobserver variability is < or = 5%. Significant (p < 0.01) changes of the volume (36-39%) and the diameter (19-21%) are detected following pharmacological intervention. 2-D QCA and 3-D QCA agree in short matched segments without foreshortening. 2-D QCA is rather sensitive to foreshortening and not suitable for evaluation of diameters of longer branches or total coronaries. CONCLUSION: 3-D QCA permits an accurate, reproducible and sensitive comprehensive three-dimensional geometric analysis of the coronaries and is superior to 2-D QCA with respect to extended diameter evaluation.

Algorithms↗

PubMed1999

Comparative effectiveness of holding therapy with aggressive children.

This study was undertaken to assess the effects of holding therapy on children who have a history of aggressive and delinquent behaviors. The study design was a prospective, pre-post, quasi-experimental controlled study. The subjects were recruited through the Attachment Center at Evergreen, Colorado. Eligible subjects were adopted children between the ages of 5-14 years, living in the present adopted home for at least one year. All children had a history of aggressive and delinquent behaviors, which prompted the contact with Evergreen. Findings resulted in significant decrease in the outcome variable for the treatment group within this study.

Adolescent↗

PubMed1999

SOFIA: spatially optimal fast initial analysis of biomagnetic signals.

A method of analysing biomagnetic signals is presented which focuses attention on activity in a specific region of interest. The method is based on the construction of virtual sensors, corresponding to linear combinations of lead fields that are optimally localized within the region of interest. This method is fast and stable. It is tested against physiologically plausible computer generated signals and also against more elaborate analysis of real data. The results show that the method can be very effective as a fast scanning tool identifying activity from pre-defined regions of interest.

Algorithms↗

PubMed1999

Linear transformations of data space in MEG.

Magnetoencephalography (MEG) is a method which allows the non-invasive measurement of the minute magnetic field which is generated by ion currents in the brain. Due to the complex sensitivity profile of the sensors, the measured data are a non-trivial representation of the currents where information specific to local generators is distributed across many channels and each channel contains a mixture of contributions from many such generators. We propose a framework which generates a new representation of the data through a linear transformation which is designed so that some desired property is optimized in one or more new virtual channel(s). First figures of merit are suggested to describe the relation between the measured data and the underlying currents. Within this context the new framework is established by first showing how the transformation matrix itself is designed and then by its application to real and simulated data. The results demonstrate that the proposed linear transformations of data space provide a computationally efficient tool for analysis and a very much needed dimensional reduction of the data.

Brain↗

PubMed1999

Bone marrow and recombinant human bone morphogenetic protein-2 in osseous repair.

Bone marrow stem cells and recombinant human bone morphogenetic protein-2 each has the capacity to repair osseous defects. Recombinant human bone morphogenetic proteins require the presence of progenitor cells to function. It is hypothesized that a composite graft of recombinant human bone morphogenetic protein-2 and marrow would be synergistic and could result in superior grafting to autogenous bone graft. Syngeneic Lewis rats with a 5-mm critical sized femoral defect were grafted with recombinant human bone morphogenetic protein-2 and marrow, recombinant human bone morphogenetic protein-2, marrow, syngeneic cancellous bone graft, or carrier alone (control). Serial radiographs (3, 6, 9, 12 weeks) and torque testing (12 weeks) were performed. Bone formation and union were determined. The recombinant human bone morphogenetic protein-2 and marrow composite grafts achieved 100% union at 6 weeks. Recombinant human bone morphogenetic protein alone achieved 80% union by week 12. Both groups yielded a higher union rate and superior mechanical properties than did either syngeneic bone graft (38%) or marrow (47%) alone. The superior performance of recombinant human bone morphogenetic protein-2 combined with bone marrow in comparison with each component alone strongly supports a biologic synergism. This experimentation shows the clinical importance of establishing operative site proximity for the osteoinductive factors and responding progenitor cells.

Animals↗

PubMed1999

Pro- and anti-inflammatory cytokine-response in abdominal aortic aneurysm repair: a clinical model of ischemia-reperfusion.

In traumatized and septic patients, excessive cytokine production may lead to organ dysfunction and death. Current understanding of cytokine kinetics with regard to clinical scenarios, however, is still limited by a paucity of studies investigating the cytokine levels in humans with inflammation-reperfusion injury in the absence of infection. Our hypothesis was that endotoxin is introduced into circulation during and after abdominal aortic aneurysm (AAA) repair and is associated with pro- and anti-inflammatory cytokine-response. The purpose of this prospective pilot study in 10 patients who underwent elective AAA repair was to assess organ function and immune response to systemic endotoxemia after the operation by measuring endotoxin, endotoxin neutralizing capacity (ENC), tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10, and TNF-RI and II. Blood samples were obtained from indwelling catheters or direct venipuncture preoperatively, perioperatively (8 time points) until the second postoperative day. Endotoxin and ENC were determined by a special kinetic Limulus amoebocyte lysate (LAL) assay and TNF-alpha, IL-6, IL-10, and TNF-RI and II by commercial ELISA. Endotoxin levels were significantly elevated after declamping and 90 min after clamping of the aorta (2.3 + .9 pg/mL; 5.4+/-3.6 pg/mL). ENC decreased to the lowest levels at 90 min after clamping. TNF-alpha levels were maximal, but not significantly elevated, 120 min after clamping. IL-6 increased significantly during the operation and reached maximum levels (189.8+/-47 pg/mL) at the first postoperative day. Anti-inflammatory IL-10 and TNF-RI and II were elevated early during the operation. The changes in cytokine levels were associated with mild organ dysfunction. We conclude that AAA repair is associated with endotoxin, proinflammatory, and an almost coincidental anti-inflammatory cytokine release, providing baseline data about what constitutes an appropriate immune response. Such responses to trauma and ischemia-reperfusion need to be further investigated before attempting immunomodulation.

Adult↗

PubMed1999

Removal of infected pacemaker leads with deep hypothermic circulatory arrest and open surgical exploration of the superior vena cava and innominate veins.

Despite the use of transvenous methods for extraction of infected leads, failed attempts may result in retained lead fragments. Retained lead fragments may be a focus of continued infection leading to sepsis. We present two patients in which conversion from cardiopulmonary bypass to hypothermic circulatory arrest allowed direct visualization, using venotomies in the superior vena cava and innominate vein to achieve complete removal of retained pacemaker lead fragments. Use of venotomies in the extracardiac venous system is a technical addition to prior descriptions of lead extraction using deep hypothermia and circulatory arrest.

Adult↗

PubMed1998

Apparent caspase independence of programmed cell death in Dictyostelium.

During normal development, cell elimination [1,2] occurs by programmed cell death (PCD) [3], of which apoptosis [4] is the best known morphological type. Activation of cysteine proteases termed caspases [5] is required in many instances of animal PCD [6-9], but its role outside the animal kingdom is as yet unknown. PCD occurs during developmental stages in the slime mold Dictyostelium discoideum [10,11]. Under favorable conditions, Dictyostelium multiplies as a unicellular organism. Upon starvation, a pathway involving aggregation, differentiation and morphogenesis induces the formation of a multicellular fungus-like structure called a sorocarp [12], consisting mainly of spores and stalk cells, the latter being a result of cell death. Dictyostelium cell death is similar to classical apoptosis in that some cytoplasmic and chromatin condensation occurs but differs from apoptosis because it involves massive vacuolisation and, interestingly, lacks DNA fragmentation [11]. We examined whether caspase activity is required for Dictyostelium cell death. We found that caspase inhibitors did not affect cell death, although some caspase inhibitors that did not inhibit cell death impaired other stages in development and could block affinity-labelling of soluble extracts of Dictyostelium cells with an activated caspase-specific reagent. The simplest interpretation of these results is that in Dictyostelium, whether or not caspase-like molecules exist and are required for some developmental steps, caspase activation is not required for cell death itself.

Animals↗

PubMed1998

Quantitation of dopamine D2 receptor mRNA in a mesencephalic cell culture using a nonradioactive competitive reverse transcription polymerase chain reaction method.

Studies on gene expression during differentiation and maturation processes have to cope with determinations of extremely low steady state levels of specific mRNA. Using the experimental model of dopamine D2 receptor (D2R) expression in a primary mesencephalic cell culture we worked out a quantitative reverse transcription polymerase chain reaction method which allows to analyze and quantify mRNA levels of cells present in a few wells of the culture. The method uses an internal cRNA standard which shares both primer binding sites and PCR product length with the target sequence. The amplicons are quantitated in microplates by hybridization with immobilized capture probes that allow for the distinction of internal standard and target sequences followed by the chemiluminescent detection of hybridized DNA. Applying this method the levels of D2 receptor mRNA of the mesencephalic cell culture on day in vitro 1 amounted to about 250 fg/microgram RNA and increased to about 1200 fg/microgram RNA on day in vitro 13-15.

Animals↗

PubMed1998

Dose-dependent cortisol-induced increases in plasma leptin concentration in healthy humans.

BACKGROUND: Leptin is a hormone that regulates fat metabolism and appetite. The secretion of leptin is regulated by adiposity and, in the rodent, by factors such as insulin, beta-adrenergic agonists, and glucocorticoids (GCs). Increased secretion of the endogenous human GC, cortisol, occurs during stress and in disorders such as major depression. Pharmacological GCs can robustly increase plasma leptin concentrations in humans, leading us to hypothesize that cortisol may serve as a physiological regulator of human leptin secretion. METHODS: A randomized double-blind placebo-controlled comparison of 2 fixed oral dosages of cortisol (40 mg/d and 160 mg/d), given for 4 days to matched groups of healthy subjects (n=47). Low-dose treatment approximated GC output during mild stress, while high-dose treatment approximated GC output during maximal stress, spanning a range of GC secretion relevant to physiological stress. RESULTS: Cortisol produced dose-dependent and time-dependent increases in plasma leptin concentrations (time x treatment condition x body mass index; F6,123=10.73; P<.001). Initial treatment-induced increases in plasma leptin concentration returned toward baseline values during 4 treatment days, suggesting tolerance to this GC effect in these healthy subjects. CONCLUSIONS: The results indicate an important role for GCs in the short-term regulation of human leptin secretion. Glucocorticoid-induced increases in leptin secretion suggest a mechanism that may contribute to anorexia and weight loss during stress and disease states such as major depression, if these conditions are associated with sustained increases in plasma leptin concentrations.

Adipose Tissue↗

PubMed1998

Antimicrobial activity of exocrine glandular secretions, hemolymph, and larval regurgitate of the mustard leaf beetle phaedon cochleariae

Larvae and adults of the mustard leaf beetle Phaedon cochleariae (Coleoptera: Chrysomelidae) possess exocrine glands with secretions which are used in defense against predators. This study addressed the question whether these defensive secretions also display antimicrobial activity. Additionally, the effects of larval and adult hemolymph and larval regurgitate toward microorganisms were examined. The larval glandular secretion showed growth-inhibitory activity against the gram-negative bacterium Escherichia coli, but no lytic effect against cell walls of the gram-positive bacterium Micrococcus luteus. Growth of the yeast Saccharomyces cerevisiae and of the entomopathogenic fungus Beauveria bassiana was also inhibited by the larval secretion. The antibacterial and antifungal activity of the larval secretion was found to be due to its main component, the iridoid monoterpene, (epi)chrysomelidial. The mechanism of its antifungal activity was examined by different bioassays and compared to the commercially available fungicide nystatin. The antifungal activity of the larval secretion is not due to a loss of intracellular potassium in treated fungal cells, while high potassium efflux from treated cells is the mode of action of common fungicides. The larval secretion exhibited direct cytotoxicity against both fungal cells and plasmatocytes isolated from the greater wax moth Galleria mellonella. In contrast to the larval secretion, the adult glandular secretion of P. cochleariae showed lytic activity against the cell walls of the gram-positive bacterium M. luteus, but no activity against the gram-negative bacterium E. coli and eukaryotic cells. Hemolymph and larval regurgitate of P. cochleariae displayed the same activity as the tested glandular secretion of adults. Copyright 1998 Academic Press.

Journal Article↗

PubMed1998

The influence of stimulus properties, complexity, and contingency on the stability and variability of ongoing and evoked activity in human auditory cortex.

The real-time, single-trial activity in the human auditory cortex was extracted from magnetoencephalographic signals. A predictor of single-trial activity was defined as the sum of the average response and a mean-free base level computed over a range of base times. For simple stimuli the residual (predicted-actual) activity had a stimulus-independent oscillatory (10 Hz) component. This component was larger and more durable in trained subjects, reaching saturation only in the most trained of the five subjects studied (S1). Changes in variability and associated reduction of the absolute value and duration of the oscillations were evident in experiments with stimuli loaded with information, saliency, or task contingency. Repetition reintroduces stimulus-independent oscillations very slowly. For S1, after training, the stimulus-independent oscillations were reestablished in the auditory cortices to the level seen for simple stimuli, except for the time periods and in the hemisphere associated with the combination of task demands and stimulus processing.

Adult↗

PubMed1998

Investigations of the metastable decay of DNA under ultraviolet matrix-assisted laser desorption/ionization conditions with post-source-decay analysis and hydrogen/deuterium exchange.

The fragmentation of positive ions of DNA under the conditions of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was investigated by post-source decay (PSD) analysis and hydrogen/deuterium (H/D) exchange. Spectra of five different synthetic 4mer oligonucleotides were recorded. As a main result the hypothesis was confirmed that for these ions all fragment ions result from processes, initiated by protonation/deuteration of a suitable base followed by a loss of this base as a neutral or ion and further backbone cleavages. The three bases adenine, guanine, and cytosine all exhibit comparable lability for fragmentation. The spectra show evidence for an interaction of the adenine base with the phosphate backbone. Signals of fragments containing TT- and CT-cycloadducts were observed in the spectra.

Calibration↗

PubMed1998

Magnetic field tomography analysis of continuous speech.

In this article we investigate MEG correlates of syntactic violations in continuous speech. An early left anterior negativity (ELAN) has been reported in previous EEG studies and has been related to syntactic processing. We used Magnetic Field Tomography (MFT) to extract a 3D estimate of the current density distribution J, from MEG data recorded while subjects listened to continuous speech. Separate estimates were obtained from the activity associated with the first word of the sentence, and the last words of the sentence which signified syntactic violation, semantic violation or correct sentences. In each case independent 3D MFT estimates of activity were obtained 2 ms apart. After converting the solutions into a PET-like format we perform a statistical analysis on a voxel-by-voxel basis. Visual inspection of the power of J at the time of the ELAN component and the statistical maps overlaid on the individual anatomical MRI suggests generators in the vicinity of the auditory cortex and in left frontal regions. Directional activation curves are computed to show the variation of activity as a function of time, from well circumscribed areas. The activation curve for the auditory cortex has a characteristic pattern consisting of three peaks, seen in the average time-locked to the onset of the first word, and the critical word of the syntactic violation. The left auditory cortex shows a delay of about 30 ms in the syntactic violation condition compared to the first word condition. No such delay is seen in the right auditory cortex.

Adult↗

PubMed1998

Spontaneous versus extraction related injuries associated with Accufix J-wire atrial pacemaker lead: tracking changes in patient management.

UNLABELLED: To make recommendations for management of potentially fatal failure of the Accufix series of atrial J-wire permanent pacemaker leads, we closely monitored the number of injuries and fatalities resulting either from spontaneous fracture of the J-wire or from attempts to extract the lead. In a population of 30,357 patients, 2,298 patients are enrolled in a prospective follow-up Multicenter Study, the remainder are patients with known clinical status from voluntary reporting, and 2,992 patients died following implant. In the remaining 27,365 patients, 6 deaths have been attributed to J-wire related injury (J-inj) while 13 were complications (E-inj) associated with 4,076 lead extraction procedures (3,974 intravascular (intra)/102 primary thoracotomy (PT). The date of occurrences were from 1994 to November 1997. CONCLUSIONS: (1) Since lead extractions were not conducted in a controlled study, it is not known whether the deaths associated with lead extraction is in excess of what would have occurred if these leads had not been removed in this specific subset. (2) Awareness of the procedure related complication rate appears to have moderated the rate of lead extraction and may ultimately lead to management that reasonably balances the risks of patient injury.

Electrodes, Implanted↗

PubMed1998

Kaplan-Meier analysis of freedom from extraction or death in patients with an Accufix J retention wire atrial permanent pacemaker lead: a potential management tool.

UNLABELLED: Morbidity (36 cases) and mortality (6 cases) have been reported in patients with Accufix J retention wire atrial leads. This has resulted in ongoing patient fluoroscopic monitoring as well as lead extractions. The estimated implanted worldwide population is 40,860. Estimating the size of the remaining population at risk is an important tool for assessing patient management guidelines. RESULTS: The Kaplan-Meier method can be used to calculate the cumulative probability of remaining free of extraction and death for patients based on implant duration. The individual Kaplan-Meier curves for lead extraction and patient survival can also be computed. Based on the Multicenter Study (MCS) population of 2,298 patients, the probability that a patient is alive with the lead still implanted at 5 years implant duration is 52.5%. The event-free survival rate at 5 years implant duration is 81.3%. The corresponding probability of remaining free from injury due to the J-wire is 99.9% at 5 years implant duration. Assuming similar rates of death and extraction, these results can be extrapolated to the world wide population. CONCLUSIONS: The management of Accufix patients must consider patient longevity, the probability of J-wire morbidity/mortality, and the probability of extraction complication morbidity/mortality. The probability of remaining at risk as a function of time from implant can be calculated from the events known in the MCS patient population. These event-free survival estimates can be used to identify subsets of the population at greater or lesser risk based on various clinical parameters.

Disease-Free Survival↗

PubMed1998

Cumulative hazard analysis of J-wire fracture in the Accufix series of atrial permanent pacemaker leads.

UNLABELLED: To permit a more complete analysis of J-wire fracture in the Accufix series of atrial permanent pacemaker leads, the time to occurrence of all known fractures and injuries has been redefined relative to the duration of risk exposure, that is, according to the interval of time between implant and occurrence of the event. This redefinition permits application of a cumulative hazards model to the data, which previously has not been explored. Predictors of J-wire fracture can be tested using this method. This also permits parametric curve-fitting for determination of linearity or constancy of risk of events over time. RESULTS: Among 2,063 Multicenter Study (MCS) leads analyzed, 381 fractures of the J-wire were identified. Stratified analysis based on cumulative hazard curves identified a more open shape of the J-wire as predictive of fracture, which supports the results previously reported based on logistic regression analysis. Fitting a Weibull curve to the cumulative hazard of J-wire fracture gives a shape parameter equal to 0.85. This value indicates that the instantaneous hazard of J-wire fracture decreased over time from implant. CONCLUSIONS: (1) The cumulative hazard function can be used to examine predictors of J-wire fracture and preliminary findings support the previously identified predictor of J shape; (2) Based on these analyses, the rate of J-wire fracture appears to decrease slightly as time from implant increases.

Electrodes, Implanted↗