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Biomedical subjects

R Jacobs

Publications and source records attributed to R Jacobs.

At least 37 records · Page 2Linked to original sources
PubMed2001

Diagnostic yield of conventional and digital cephalometric images: a human cadaver study.

OBJECTIVES: To compare the clinical efficacy of digital and conventional cephalometric imaging. METHODS: Conventional and photostimulable phosphor cephalometric radiographs were obtained from three human cadavers at nine different exposure settings. Subjective image quality was assessed by six observers who evaluated six cephalometric landmarks. Organ doses were measured with TLDs and effective doses calculated. RESULTS: Compared with conventional cephalometric images, digital images had a consistently better subjective image quality for all exposure settings which was significant (P<0.05) for all but two. Organ doses were comparable. Higher kV and lower mAs settings yielded the lowest effective dose, which was highly dependent on the position of the thyroid gland in the beam. CONCLUSION: Relatively small variations in exposure settings do not influence subjective diagnostic image quality of digital cephalometric radiographs. Higher kV and lower mAs settings have the lowest effective dose and should therefore be preferred.

Cephalometry↗
PubMed2001

Organ doses and subjective image quality of indirect digital panoramic radiography.

OBJECTIVES: To determine if slight variations in exposure will affect diagnostic image quality and absorbed radiation doses for digital and analogue panoramic radiography. METHODS: Thermoluminescent dosimeters were placed in the thyroid gland, eyes, submandibular glands, parotid glands and skin of two human cadaver heads. Three different exposure settings were used: 70 kV, 120 mAs; 77 kV, 75 mAs; and 81 kV, 60 mAs. Subjective image quality was assessed using a phantom head. Storage phosphor (SP) images were printed on film and both analogue and SP images were assessed for their subjective image quality on a five-point rating scale. The results were statistically analysed using logistic regression analysis and chi(2) tests. RESULTS: Highest organ doses were measured for the submandibular glands, followed by the parotid glands. Salivary gland doses tended to be higher at lower kV settings. Image quality was not statistically different for the different exposure settings. Imaging technique did not seem to influence diagnostic image quality, except for the periapical status of upper premolars where SP was better. The main reason for any differences appeared to be interobserver variation. CONCLUSIONS: Analogue and SP panoramic radiography performed equally well for subjective diagnostic image quality. No significant differences could be found at the exposure settings used in this study. Radiation doses were highest for the salivary glands, especially at lower kV settings.

Eye↗
PubMed2001

Systemic lupus erythematosus and rheumatoid arthritis patients differ from healthy controls in their cytokine pattern after stress exposure.

OBJECTIVE: To study whether patients with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE) differ from healthy individuals in their immune responses to acute psychological stress. METHODS: The phenotype and function of peripheral blood lymphocytes were analysed before and after stress exposure in patients and healthy subjects. RESULTS: Natural killer (NK) cell numbers increased transiently in all groups under stress. NK activity, however, increased in healthy controls only. We observed a stress-induced increase in interleukin (IL)-4-producing (IL-4(+)) cells in SLE patients only, whereas interferon (IFN) gamma(+) cell numbers increased due to stress in all three groups. An analysis of supernatants from phytohaemagglutinin (PHA) cultures revealed increased IFN gamma and IL-10 levels in healthy subjects but not in SLE or RA patients after stress exposure. CONCLUSIONS: These data demonstrate that RA and SLE patients differ in their immune response to stress from healthy controls. Changes in cytokine patterns might be responsible for stress-induced exacerbation of disease activity in RA and SLE patients.

Adult↗
PubMed2001

A comparison of complete blood replacement with varying hematocrit levels on neurological recovery in a porcine model of profound hypothermic (<5 degrees C) circulatory arrest.

Profound hypothermia (<5 degrees C) may afford better neurological protection after circulatory arrest; however, there are theoretical concerns related to microcirculatory sludging of blood components at these ultra-low temperatures. We hypothesized that at temperatures <5 degrees C, complete blood replacement results in superior neurological outcome. Twelve Yorkshire pigs (30 kg) underwent thoracotomy, cardiopulmonary bypass (CPB), and were randomly assigned to one of three target hematocrits during circulatory arrest: 0%, 5%, 15%. Hextend (6% hetastarch in a balanced electrolyte vehicle) was used for the CPB prime and as an exchange fluid. Animals were cooled to a temperature <5 degrees C, underwent 1-h circulatory arrest, and were warmed to 35 degrees C with administration of blood to increase the hematocrit to >25% before separation from CPB. The primary outcome, peak postoperative neurobehavioral score, was compared between groups. The 0% group (mean +/- SD) had significantly (P: < 0.02) better neurobehavioral scores than the 5% and 15% groups (6.0 +/- 2.9 vs 1.3 +/- 1.0 and 1.5 +/- 0.6) respectively. Other variables (e.g., intracranial pressure) were similar between groups. In a porcine model of profound hypothermia (<5 degrees C) and circulatory arrest, complete blood replacement resulted in superior neurological outcome. This finding suggests that at ultralow temperatures, the presence of some blood component (e.g., erythrocytes, leukocytes) may be deleterious.

Animals↗
PubMed2001

Evaluation of factors influencing the marginal bone stability around implants in the treatment of partial edentulism.

BACKGROUND: The original protocol of Brånemark to achieve predictable osseointegration for oral implants has substantially been modified. One may question whether results are influenced by those modifications, especially for the long-term prognosis. PURPOSE: The goal of the present study was to investigate the impact of those parameters that deviate from the original protocol as defined by P-I Brånemark. MATERIALS AND METHODS: In this study, 246 patients with 263 fixed partial prostheses supported by 668 Brånemark implants were followed from 1 to 15 years (mean: 6.3 yr). Radiographs were taken at the time of abutment connection, at 3 to 6 months, at 12 months, and then every 3 years. The bone level was rated mesially and distally from the implants on a total of 2588 radiographs. RESULTS: A positive relation between abutment length and marginal bone level was found (p > .0001). The maxilla (p = .03), porcelain (p = .007), long abutments (p = .008), and regular-sized diameter implants (p = .001) all exhibited more bone loss in the first 6 months. After 6 months, only long implants showed more bone loss (p = .03). CONCLUSIONS: Overall, the marginal bone level remained stable around Brånemark implants, never surpassing 2.2 mm, even after 15 years. Although longer implants lost more bone over time, this has to be interpreted with respect to higher resorption rates in less resorbed jaws.

Adult↗
PubMed2001

Perceptual changes in the anterior maxilla after placement of endosseous implants.

BACKGROUND: The innervation of skin and oral mucosa plays a major physiologic role in exteroception. It is also of interest clinically, as illustrated by sensory changes after neurosurgical procedures. PURPOSE: The goal of this study was to assess the perception of mechanical stimuli applied to the anterior maxilla in denture wearers and subjects rehabilitated with osseointegrated implants compared with that in subjects with a natural dentition. MATERIALS AND METHODS: Five groups of subjects were selected and tested in the maxillary region only. Test groups included patients with a complete denture, an implant-supported fixed prosthesis (full or partial), or a single-tooth replacement. Light-touch sensation and two-point discrimination were performed on the buccal side of the alveolar mucosa and vibrotactile function was determined for natural teeth, full dentures, or implant-supported prostheses. RESULTS: For light-touch sensation, no significant differences could be found between the groups. For two-point discrimination, full-denture patients showed higher threshold levels than the other groups. The threshold levels for vibrotactile function were higher in both full dentures and implant-supported prostheses compared with natural dentitions. CONCLUSION: Natural dentitions offer superior vibrotactile function compared to any other dental status. Full dentures often show a stronger deterioration of the (vibro)tactile function compared with implant-supported prostheses.

Adult↗
PubMed2001

Development of executive functions through late childhood and adolescence in an Australian sample.

Although there have been significant theoretical advances in the field of child neuropsychology, developmental features of adolescence have received less attention. Progress in clinical practice is restricted due to a lack of well-standardized, developmentally appropriate assessment techniques. This article addresses these issues in relation to executive skills. These abilities are targeted for 2 reasons: first, because they are often considered to be mature during late childhood and adolescence, despite limited investigation in this age range; and second, because of their central importance to efficient day-to-day functioning. Using a normative sample of 138 children, aged 11.0 to 17.11 years, this article plots the development of executive skills through late childhood and early adolescence and interprets progress in these skills with reference to current neurological and cognitive theory.

Adolescent↗
PubMed2001

Neuropsychological profiles of children with type 1 diabetes 6 years after disease onset.

OBJECTIVE: To describe neuropsychological profiles and their relationship to metabolic control in children with type 1 diabetes 6 years after the onset of disease. RESEARCH DESIGN AND METHODS: Children with type 1 diabetes (n = 90), aged 6-17 years, who had previously been assessed soon after diagnosis and 2 years later, were reevaluated 6 years after the onset of disease. Their neuropsychological profiles were compared with those of individuals in a community control group (n = 84), who had been assessed at similar intervals. Relationships between illness variables, such as age at the onset of disease and metabolic control history, and neuropsychological status were also examined. RESULTS: Six years after onset of disease, children with type 1 diabetes performed more poorly than control subjects on measures of intelligence, attention, processing speed, long-term memory, and executive skills. Attention, processing speed, and executive skills were particularly affected in children with onset of disease before 4 years of age, whereas severe hypoglycemia was associated with lower verbal and full-scale intelligence quotient scores. CONCLUSIONS: Neuropsychological profiles of children with type 1 diabetes 6 years after the onset of disease are consistent with subtle compromise of anterior and medial temporal brain regions. Severe hypoglycemia, particularly in very young children, is the most plausible explanation for neuropsychological deficits, but the contributory role of chronic hyperglycemia warrants further exploration.

Adolescent↗
PubMed2001

Trigeminal somatosensory evoked potentials in humans.

The recording of somatosensory evoked potentials (SEPs) is a non-invasive routine clinical testing procedure in neurology. For trigeminal nerve stimulation, however, SEPs have not received a widespread clinical attention. A variety of protocols and procedures have been used to record trigeminal SEPs (TSEPs). Differences encountered include the stimulation mode, site and frequency, the recording electrode position and data acquisition parameters. This has resulted in a diversity of recorded TSEP signals, making comparisons almost impossible. The general picture shows a number of short latency waves (within 3 ms) of peripheral origin, followed by at least two longer latency waves (12-15 ms and 19-22 ms). Furthermore, potential waves with a very long latency (> 100 ms) follow when the response is produced by painful stimulation. The origin of the long and very long latency waves is still a matter of debate. In order to allow reliable data interpretation and comparisons between the outcome of different studies, a standardized protocol should be applied for TSEP recordings. By providing an overview, this paper aims to mark a step forward in the harmonization of TSEP protocols with respect to the neural processes of interest. Further studies should also encounter the potential application of other neuroimaging techniques, such as functional magnetic resonance imaging or positron emission tomography, preferably in combination with TSEP recordings.

Adolescent↗
PubMed2001

Treatment of rotator cuff arthropathy with a reversed Delta shoulder prosthesis.

The treatment of rotator cuff arthropathy is still a matter of debate. Up to now a hemiarthroplasty was usually used. We report the results obtained with a reversed shoulder prosthesis (Delta prosthesis, De Puy) in seven patients with severe rotator cuff arthropathy. The mean Constant score increased from 17.9/100 preoperatively to 56.7/100 postoperatively. The mean follow-up was 16 months. Loosening was not observed on follow-up x-rays.

Aged↗
PubMed2000

cis,cis- and trans,trans-ceratospongamide, new bioactive cyclic heptapeptides from the Indonesian red alga Ceratodictyon spongiosum and symbiotic sponge Sigmadocia symbiotica.

Chemical investigation of the marine red alga (Rhodophyta) Ceratodictyon spongiosum containing the symbiotic sponge Sigmadocia symbiotica collected from Biaro Island, Indonesia, yielded two isomers of a new and bioactive thiazole-containing cyclic heptapeptide, cis,cis-ceratospongamide (1) and trans, trans-ceratospongamide (2). Isolation of these peptides was assisted by bioassay-guided fractionation using a brine shrimp toxicity assay (Artemia salina). The structures of the ceratospongamides, which each consist of two L-phenylalanine residues, one (L-isoleucine)-L-methyloxazoline residue, one L-proline residue, and one (L-proline)thiazole residue, were established through extensive NMR spectroscopy, including (1)H-(13)C HMQC-TOCSY, and (1)H-(15)N HMBC experiments, as well as chemical degradation and chiral analysis. cis,cis- and trans,trans-ceratospongamide are stable conformational isomers of the two proline amide bonds. Molecular modeling of these two ceratospongamide isomers showed the trans, trans isomer to be quite planar, whereas the cis,cis isomer has a more puckered overall conformation. trans,trans-Ceratospongamide exhibits potent inhibition of sPLA(2) expression in a cell-based model for antiinflammation (ED(50) 32 nM), whereas the cis,cis isomer is inactive. trans,trans-Ceratospongamide was also shown to inhibit the expression of a human-sPLA(2) promoter-based reporter by 90%.

Animals↗
PubMed2000

Detection and multichannel SVD-based filtering of trigeminal somatosensory evoked potentials.

Very weak and noisy trigeminal somatosensory evoked potentials (TSEPs) are considered, which are successfully evoked by electrical stimulation of the trigeminal nerve of 15 patients with endosseous oral implants. As TSEP analysis provides an objective means of assessing neuronal function, it is considered to be a promising tool for investigating tactile sensation through anchoring implants in bone. For this purpose, a study of TSEP signals acquired from patients with endosseous oral implants has been carried out. Since TSEPs are severely contaminated by background ongoing electrical activities of the brain, a methodology is developed for statistically detecting the transient signal (TSEP) in the biological noise (EEG). For nine out of 15 patients, transient signals are detected in the background EEG activity. The TSEPs of these nine patients are subjected to further analysis. A multichannel singular value decomposition (SVD)-based filtering method is applied which successfully separates out the most energetic TSEPs from the background EEG, thereby increasing significantly the SNR of the recorded signals and improving extraction of the characteristic components of the TSEPs. It is shown that the most prominent feature of the TSEP signals for patients with endosseous oral implants is a wave with peak latency between 9 and 15 ms, generally followed by a wave between 25 and 28 ms or 34 and 38 ms for the specific cortical response areas.

Dental Implantation, Endosseous↗
PubMed2000

The subjective image quality of direct digital and conventional panoramic radiography.

One of the main advantages of digital imaging is the possibility of altering display options for improved image interpretation. The aim of the present study was to evaluate the subjective image quality of direct digital panoramic images and compare the results with those obtained from conventional images. Furthermore, the effect of various filter settings on image interpretation was assessed. Panoramic images were obtained with three different types of panoramic equipment (one direct digital and two conventional units) from three groups of 54 patients with a natural dentition in all quadrants. The first series of panoramic images consisted of 54 unprocessed digital images; conventional film images (n = 108) comprised the second and third series. A final series consisted of the digital images treated with three different filters ("smoothening," "sharpening," and "contrast enhancement"). All images were scored randomly by four experts in oral radiology on a 4-point rating scale. The results showed a statistically significant difference in scorings between the conventional and digital panoramic units. The main reason for poor image quality appeared to be a combination of blurring and overlapping in the panoramic image. The premolar region in the upper jaw was the region where most additional radiographs were needed.

Adolescent↗
PubMed2000

Sensations and trigeminal somatosensory-evoked potentials elicited by electrical stimulation of endosseous oral implants in humans.

The perception of bipolar electrical stimuli through implants was studied. The stimuli were delivered to permucosal oral endosseous implants in 15 individuals, who then reported tapping to beating sensations. In 10 out of the 15, these stimuli evoked clearly distinguishable potentials in the averaged electroencephalograms. The most prominent scalp potential was a positive wave with a latency between 18 and 25 ms, often preceded by a negative wave with a latency around 12-17 ms. In contrast, when a motor response was elicited by stimulation of the lip, a shorter latency wave around 8-11 ms was found additionally, indicating that the former-mentioned waves represent a true sensory response and not an artefact of myogenous origin. Furthermore, topical anaesthesia of the gingiva surrounding the implants in six individuals had little effect on the sensory responses. This evidence excluded peri-implant mucosal innervation as the origin of the perception and of the somatosensory-evoked waves elicited by the electrical stimulation of the oral implants. To the best of our knowledge, for the first time a sensation (osseoperception) has been elicited by electrical stimulation of endosseous oral implants and correlated with simultaneously recorded trigeminal somatosensory-evoked potentials (TSEPs).

Adult↗
PubMed2000

Detecting urethral and prostatic inflammation in patients with chronic prostatitis.

OBJECTIVES: Diagnosis of urethral and prostatic inflammation can represent a challenge. We compare the accuracy of diagnostic methods for detecting inflammation in lower urinary specimens/samples. METHODS: A standardized protocol was used to evaluate urethral smear, first-void urine (VB1), midstream urine (VB2), expressed prostatic secretions (EPS), and postmassage urine (VB3) in urologic patients with no symptoms or signs of urethritis who were attending our prostatitis clinic. RESULTS: Of 235 subjects, 60 (26%) had leukocytes detected by the Gram-stained urethral smear, 44 (18%) by the VB1, and only 14 (6%) by the VB2. Compared with the urethral swab, VB1 had 0% to 22% sensitivity and 81% to 98% specificity, and VB2 had 8% to 11% sensitivity. Of 83 subjects with prostatic inflammation, the EPS detected 63 (76%) and the VB3 detected 68 (82%). CONCLUSIONS: VB1 or VB2 examinations had low sensitivity for detecting urethral inflammation. Examining both the EPS and VB3 proved best for detecting prostatic fluid inflammation. Combining the urethral smear with lower urinary tract localization ("four-glass test") represents an optimal approach for detecting urethral and prostatic inflammation.

Adolescent↗
PubMed2000

Progressive reduction of CMV-specific CD4+ T cells in HIV-1 infected individuals during antiretroviral therapy.

Visualization of antigen-specific T cells has become an important tool in studying immune responses. The aim of this study was to analyze CMV-specific CD4+ T cells in healthy and HIV-infected individuals. Peripheral blood mononuclear cells (PBMC) were examined for antigen-induced intracellular cytokine responses. We found significant numbers of CMV-specific CD4+ T cells detectable in most CMV-IgG+ HIV-1 infected individuals, whereas CMV-specific CD4+ T cells could not be demonstrated in CMV-IgG- patients. Median frequency of CMV-specific CD4+ T cells were lower in HIV-infected subjects who had been treated with highly active antiretroviral therapy (HAART) for more than 1 year than in untreated HIV-infected individuals. In patients under therapy for less than 1 year median CMV-specific CD4+ T cell responder frequency was higher than in subjects treated for more than 1 year but lower than in untreated subjects. HIV suppression with HAART might lead to a progressive reduction of CMV-specific CD4+ T cells indicating an efficient elimination of an opportunistic pathogen.

Adult↗
PubMed2000

Magnetic resonance imaging for the evaluation of a novel metastatic orthotopic model of human neuroblastoma in immunodeficient mice.

Neuroblastoma is the second most common solid tumor in children. So far few tumor models for this cancer have been reported in mice. We have created a murine tumor model for studying human neuroblastoma based on surgical orthotopic implantation in scid mice. Small fragments of subcutaneous tumors of SK-N-BE(2) human neuroblastoma cells expressing enhanced green fluorescent protein were surgically implanted near the left adrenal gland of scid mice. One hundred percent of the animals (n = 21) successfully implanted developed a large retroperitoneal tumor and became moribund between 22 and 57 days after implantation (mean survival time = 41 days). At the time of sacrifice the presence of bone marrow metastasis was detected by RT-PCR for green fluorescent protein in 95% of the cases. The growth of small tumor implants could be easily visualized and quantified by surveillance MR imaging, with a resolution of 117 x 117 x 750 microm in two orthogonal planes allowing accurate volume measurements, as well as assessment of necrosis and tissue invasion. This novel model should be a valuable tool to study the biology and therapeutic approaches to neuroblastoma.

Animals↗