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Biomedical subjects

R Jacobs

Publications and source records attributed to R Jacobs.

At least 55 records · Page 3Linked to original sources
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↗
PubMed2000

A prospective split-mouth comparative study of two screw-shaped self-tapping pure titanium implant systems.

Clinical data indicate different medium and long-term outcomes of endosseous implants for different implant configurations and in particular implant surfaces. The present study compares 2 very similar implant systems but with different surface characteristics in a split-mouth-randomized design. The Astra-Tech (A) system (Astra-Tech AB, Mölndal, Sweden) consisted of selftapping TiO2-blasted screw-shaped implants made of commercially pure titanium, and the Brånemark (B) System (Nobel Biocare, Gothenburg, Sweden) comprised selftapping Mark II implants with machined surface irregularities. Throughout the 2-years' observation period, no significant differences could be found concerning probing depths, presence of plaque or change in marginal bone level. A statistically significant difference in location of the marginal bone level in relation to the shoulder of the implant was found in favor of the A system both at baseline and after 2 years. Cumulative success rates of 100% (A) and 97.7% (B) were not statistically different. From a prosthetic point of view, more soldering points were needed for A compared to B to reach clinical acceptable fit. More years of observation are needed to compare the fate of the soft and hard tissues surrounding two different implant surfaces.

Adult↗
PubMed2000

The clinical use of deproteinized bovine bone mineral on bone regeneration in conjunction with immediate implant installation.

Twenty-one c.p. titanium screw-shaped implants were immediately installed after extraction and thorough curettage of the alveoli in 15 patients. Granules of deproteinized bovine bone of 0.25-1.0 mm diameter were used to fill the remaining defect when the distance of the defect wall to the implant surface was > 3 mm. Dimensional measurements of the defect height and width were made with a pocket probe. Fourteen sites in the upper jaw and 7 sites in the lower jaw were thus treated. The mean defect depth varied between 7 mm vestibularly and 10 mm mesially. The mucoperiosteal flaps were hermetically closed. At re-entry, the particles were packed and firmly attached but still distinguishable from the surrounding bone. Of the 21 sites treated, 5 sites had an exposure of the implant cover screw during the healing period. An exposure of the granular material occurred in 4 sites, but loss of granules in only 3. Even in these sites no signs of infection or inflammation of the soft tissues were observed. At re-entry after 6 months, 10 sites were completely and 9 partially filled. For the partial fills, the mean remaining defect height was 1.6 mm (range: 0.6-3.0 mm). Two sites showed an increased defect of respectively 2.4 and 4.8 mm. No fixtures were lost. The present results indicate that deproteinized bovine bone is a safe filling material to fill remaining defects around implants installed in fresh extraction sockets.

Adolescent↗
PubMed2000

The accuracy of spiral tomography to assess bone quantity for the preoperative planning of implants in the posterior maxilla.

When planning to place implants in the posterior region of the maxilla, the location of the maxillary sinus floor is influencing the available bone height and the implant length chosen. The aim of the present study was to evaluate in vitro the spiral tomographic technique that could be used for pre-operative implant planning. Tomographs were taken of 6 dry human skulls using the Cranex Tome multifunctional unit (Orion Corporation Soredex, Helsinki, Finland). Three sites were selected in the left posterior maxilla and marked with gutta percha meaning a total of 18 sites (6 x 3 = 18) for interpretation. Bone height and width were measured on the tomographs and after sectioning also on the skulls. The values obtained from the measurements on tomographs were divided by an enlargement factor of 1.5 (as defined by the manufacturer) and then compared with those from the real measurements on the skulls. Real measurements were on average 0.24 mm (SD 0.19) lower than the tomographic measurements (P < 0.05). From the present results it could be concluded that spiral tomography using the recently developed Cranex Tome reveals sufficient information and detail for pre-operative planning of a limited edentulous region.

Adult↗
PubMed2000

Evaluation of the psychophysical detection threshold level for vibrotactile and pressure stimulation of prosthetic limbs using bone anchorage or soft tissue support.

In the present study the psychophysical detection threshold levels mechanical stimulation of 32 prosthetic limbs were determined. Prosthetic limbs were anchored to the bone by means of an implant (n=17) or supported by a socket enclosing the amputation stump (n=15). Detection threshold levels were assessed for pressure and vibratory stimulation of the prosthesis and the limb at the contralateral side (control). Following vibratory stimulation, thresholds were increased on an average 20% for socket prostheses. but approached those of the control for bone-anchored prostheses. For pressure stimulation, thresholds were increased up to 60% for socket prostheses and 40% for bone-anchored prostheses compared to the control. While bone-anchored prostheses yielded significantly lower threshold levels than socket prostheses, there was no significant difference between both treatments regarding pressure stimulation. Results were applicable to both upper and lower limb amputees. It could be concluded that detection thresholds for pressure and especially vibratory stimulation of prosthetic limbs were generally higher than for control limbs. The outcome was related to the prosthetic limb design with bone-anchored prostheses yielding better perception than socket prostheses.

Adult↗
PubMed2000

Biologic outcome of single-implant restorations as tooth replacements: a long-term follow-up study.

BACKGROUND: The replacement of a single tooth or several teeth by means of single-implant restorations is an increasingly used method that needs long-term validation. PURPOSE: The goal of this study was to evaluate the outcome of single-implant restorations by means of fixed restorations and to define the prognosis through marginal bone level estimations. MATERIALS AND METHODS: From November 1986 to June 1998, 270 Brånemark implants (215 in the upper jaw) were installed in 219 patients (106 males). Both anterior and posterior sites were involved. Of the 263 single restorations, 28 were placed in private dental offices. The patients were followed until June 1999. RESULTS: Twelve implants failed before or at abutment connection or within 6 months afterward. Only four implants failed later. The cumulative success rates were 93% for the implants and 96.5% for the restorations over a period of 11 years. The marginal bone loss during the first 6 months after abutment connection reached 0.71 mm and then dropped to 0.036 mm annually over a period of 10 years. CONCLUSIONS: Single-implant restorations (Brånemark System) are a reliable treatment with a good long-term prognosis. Failures were concentrated during the healing period and early loading phase.

Adolescent↗
PubMed2000

Lymphocyte subsets and cellular immunity in patients with chronic pancreatitis.

BACKGROUND: An abnormal immune response may play a pathogenetic role in chronic pancreatitis. However, to date characterization of the systemic immunological changes in patients with chronic pancreatitis has not been undertaken. METHODS: Lymphocyte phenotypes and proliferation ((3)H-thymidine) after stimulation with mitogens and interleukin-2 were studied in peripheral mononuclear cells from 11 patients with chronic pancreatitis (alcohol-induced n = 6; idiopathic pancreatitis n = 5). The natural killer cell activity was investigated in a (51)Cr release cytotoxicity assay. In vitro cytokine release of stimulated mononuclear cells was measured. RESULTS: Flow cytometric studies showed a significant decrease in the percentage of circulating CD8+, CD56+ and CD25+ cells in patients with chronic pancreatitis independent of the etiology. Comparing all patients with chronic pancreatitis to controls, the proliferation rate was not significantly increased, but patients with pain (n = 5) showed increased proliferation in comparison to patients without pain (n = 6). No significant difference in natural killer cytotoxicity was observed. The in vitro release of tumor necrosis factor-alpha and interleukin-10 by stimulated mononuclear cells was increased. CONCLUSIONS: Chronic pancreatitis is accompanied by systemic immune dysregulation. The observed changes in peripheral mononuclear cells reveal additional evidence that the cell-mediated immune response may contribute to the development of pain and tissue destruction in chronic pancreatitis.

Adult↗
PubMed2000

Antimicrobial selection for hospitalized patients with presumed community-acquired pneumonia: a survey of nonteaching US community hospitals.

OBJECTIVE: To describe and evaluate empiric antimicrobial regimens chosen for hospitalized patients with presumed community-acquired pneumonia (CAP) in US hospitals, including compliance with the American Thoracic Society (ATS) guidelines. Secondary outcomes included length of stay (LOS) and mortality associated with the choice of therapy. METHODS: A nonrandomized, prospective, observational study was performed in 72 nonteaching hospitals affiliated with a national group purchasing organization. Patients with an admission diagnosis of physician-presumed CAP and an X-ray taken within 72 hours of admission were eligible for the study. Demographic, antibiotic selection, and outcomes data were collected prospectively from patient charts. RESULTS: 3035 patients were enrolled; 2963 were eligible for analysis. Compliance with the ATS guidelines was 81% in patients with nonsevere CAP. The most common antibiotic regimen used for empiric treatment was ceftriaxone alone or in combination with a macrolide (42%). The overall mortality rate was 5.5%. The addition of a macrolide to either a second- or third-generation cephalosporin or a beta-lactam/beta-lactamase inhibitor was associated with decreased mortality and reduced LOS. CONCLUSIONS: Most hospitalized patients with CAP receive antimicrobial therapy consistent with the ATS guidelines. The addition of a macrolide may be associated with improved patient outcomes.

Adolescent↗
PubMed2000

The UNC-119 family of neural proteins is functionally conserved between humans, Drosophila and C. elegans.

C. elegans animals mutant for the unc-119 gene exhibit movement, sensory and behavioral abnormalities. Consistent with a nervous system role, unc-119 reporter genes are expressed throughout the C. elegans nervous system. The UNC-119 protein has strong sequence similarity to the predicted protein from a human gene, HRG4/HsUNC-119, whose transcript is abundant in the retina. Using these similarities, we have identified a Drosphila homolog, DmUNC-119, which is expressed in the Drosophila nervous system. The predicted C. elegans, human and Drosophila gene products are conserved across two domains. Expression of portions of HRG4/HsUNC-119 or DmUNC-119, directed by the unc-119 promoter, can fully rescue the C. elegans unc-119 mutant phenotype. We tested the ability of portions of HRG4/HsUNC-119 to rescue, and found that its function in C. elegans requires the conserved carboxyl terminus, while the dissimilar amino terminus is dispensable. UNC-119, HRG4 and DmUNC-119 constitute members of a new class of neural genes whose common function has been maintained through metazoan evolution.

Adaptor Proteins, Signal Transducing↗
PubMed2000

[Bruxism and overload of periodontium and implants].

Bruxism is responsible for occlusal tooth wear but can not induce nor aggravate gingivitis or periodontitis. Bruxism induces jiggling forces, which cause a clinical tooth hypermobility, radiologically seen as a widened periodontal space. Although there is no direct causal relation between bruxism and implant failure, implant overload may lead to fractures of the components and bone loss.

Bruxism↗
PubMed1999

Immunologic and virologic studies in long-term nonprogressors with HIV-1 infection.

BACKGROUND: It is not known whether clinical latency in long-term nonprogressors (LTNP) with HIV-1 infection is due to a strong HIV-1 specific immune response of the host or to virologic factors. - METHODS: Peripheral blood mononuclear cells (PBMC) of 6 LTNP were analyzed for their phenotype, proliferation rates, natural killer (NK) cell activity, antibody dependent cellular cytotoxicity (ADCC), and CCR5 chemokine receptor genotype. Furthermore sequence analyses of the HIV-1 gene were performed. - RESULTS: Phenotypic analyses of lymphocyte subsets revealed increased CD8+ as well as HLA-DR+ expressing cells in LTNP and patients with progressive disease (PRO). Proliferation assays in LTNP and PRO showed a reduction of stimulation by polyclonal mitogens (PHA, ConA, PWM) of up to 60%. NK activity was within normal ranges in LTNP but reduced in PRO. 1 LTNP exhibited heterozygosity for CCR5-D32. A mutant HIV nef gene was not discovered by PCR in any of the LTNP. HIV-V3 loop PCR in 5 LTNP revealed the HIV-1B (NSI) subtype. In 2 patients further sequence analyses of the HIV-1 genome showed homozygous mutations in the Sp1 and NF-kB binding sites. CONCLUSION: The non-progression of HIV-1 infection in some LTNP seems to be due to single mutations in the viral genome resulting in a less replicative HIV-1 subtype or to a mutant chemokine receptor leading to a reduced HIV-1 entry into CD4+ cells. NK cell activity might be an additional contributing factor in controlling viremia.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Results of a phase II concurrent chemoradiotherapy study using three-dimensional conformal radiotherapy with cisplatin and oral etoposide in stage III nonsmall-cell lung cancer.

This phase II study was designed to utilize conformal radiation therapy with cisplatin and oral etoposide in patients with stage III or locally recurrent non-small-cell lung cancer to determine tolerance and toxicity of therapy. From April 1992-February 1996, 18 patients with pathologically confirmed stage IIIA, IIIB, or locally recurrent non-small-cell lung cancer (NSCLC) were entered on study. Metastatic workup included a CT scan of the thorax and upper abdomen as well as a bone scan. Chemotherapy consisted of IV cisplatin (100 mg/m2) with IV etoposide (25 mg/m2) on day 1; oral etoposide was given (50 mg/m2) days 2-14. Using three-dimensional planning, 40-45 Gy were delivered to the clinical target volume, followed by a boost to the gross tumor volume for a total of 70 Gy. Patients with recurrent disease received 40-50 Gy in total. Eighteen patients were enrolled: 16 patients were treated with curative intent and were evaluable for outcome. Two patients were treated for locally recurrent NSCLC and were not included in the outcome analysis. Stages included IIIA (44%) and stage IIIB (54%). Forty-four percent had T3/4 tumors, and 69% had N2/3 disease. Overall survival at 1 year was 64%, while 2-year overall survival was 50%. Distant metastasis-free survival at 1 year was 67%, and at 2 years 60%. The 1-year chest progression-free survival was 57%, and at 2 years 50%. Sixty-three percent required hospitalization for dehydration or neutropenia. Fifty-six percent developed leukopenia (<1,000 cells/microl) sometime during the therapy. We conclude that concurrent cisplatin and oral etoposide with conformal radiation therapy provide encouraging results in stage III lung cancer. The major toxicities of this therapy included leukopenia, thrombocytopenia, and mucosal esophagitis. Local progression of disease continues to be a problem with the current doses given. Future studies should evaluate dose escalation of radiation therapy with limited volumes, utilizing conformal radiation and chemotherapy to improve local control and potentially impact upon distant metastases.

Administration, Oral↗
PubMed1999

Patients with systemic lupus erythematosus differ from healthy controls in their immunological response to acute psychological stress.

Clinical observations suggest that psychological stress induces exacerbation of disease activity in patients with systemic lupus erythematosus (SLE). In order to determine whether SLE patients differ from healthy controls in their stress response, we analyzed heart rate, blood pressure, catecholamine concentration, lymphocyte subpopulations, natural killer (NK) cell activity, and expression of beta-adrenoceptors on PBMC before, immediately after, and 1 h after a public speaking task in 15 SLE patients and 15 healthy subjects. Both groups demonstrated similar psychological, cardiovascular, and neuroendocrine responses to acute stress. However, natural killer (CD16(+)/CD56(+)) cell numbers transiently increased after stress exposure, with significantly less pronounced changes in SLE patients. In addition, NK activity increased in healthy controls (n = 8) but not in SLE patients (n = 4) after acute stress. Furthermore, the number of beta(2)-adrenoceptors on PBMC significantly increased only in healthy subjects (n = 8) after stress but not in SLE patients (n = 7). These data indicate that SLE patients differ from healthy controls in stress-induced immune responses.

Acute Disease↗
PubMed1999

A multisensory integration model of human stance control.

A model is presented to study and quantify the contribution of all available sensory information to human standing based on optimal estimation theory. In the model, delayed sensory information is integrated in such a way that a best estimate of body orientation is obtained. The model approach agrees with the present theory of the goal of human balance control. The model is not based on purely inverted pendulum body dynamics, but rather on a three-link segment model of a standing human on a movable support base. In addition, the model is non-linear and explicitly addresses the problem of multisensory integration and neural time delays. A predictive element is included in the controller to compensate for time delays, necessary to maintain erect body orientation. Model results of sensory perturbations on total body sway closely resemble experimental results. Despite internal and external perturbations, the controller is able to stabilise the model of an inherently unstable standing human with neural time delays of 100 ms. It is concluded, that the model is capable of studying and quantifying multisensory integration in human stance control. We aim to apply the model in (1) the design and development of prostheses and orthoses and (2) the diagnosis of neurological balance disorders.

Afferent Pathways↗