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Biomedical subjects

R Jacobs

Publications and source records attributed to R Jacobs.

At least 91 records · Page 5Linked to original sources
PubMed1997

Control model of human stance using fuzzy logic.

A control model of human stance is proposed based on knowledge from behavioral experiments and physiological systems. The proposed model is based on the control of global variables specific to body orientation and alignment, rather than on the control of the body's center of mass within the base of support. Furthermore, the proposed control model is not based on purely inverted pendulum body mechanics where only motion at one joint is controlled, as for instance the ankle. In the proposed model, the degrees of freedom are controlled by using reciprocal and synergistic muscle actions at multiple joints. The control model is based on three sets of different global variables which act in parallel: (1) limb length and its derivative, (2) limb orientation and its derivative, and (3) trunk attitude and its derivative. An important feature of the control model is the use of fuzzy logic, which enables us to model experimental findings and physiological knowledge in a meaningful and explicit way using fuzzy if-then rules. In the control model, 36 fuzzy if-then rules are implemented and applied using a four-linked segment model consisting of a trunk, thigh, shank and foot. Uni- and biarticular limb muscles and trunk muscles are represented as torque actuators at each individual joint. In the model, three sets of global variables act in parallel and make corrective and coordinated responses to internal, self-induced perturbations. The data show that the use of global variables and fuzzy logic successfully enables us to model human standing with sway about a point of equilibrium. Small changes in, for example, total body sway are comparable to those seen during natural sway in human stance. The selected controllers--limb length, limb orientation and trunk attitude--seem to be appropriate for human stance control.

Fuzzy Logic↗
PubMed1997

The stereognostic ability of natural dentitions versus implant-supported fixed prostheses or overdentures.

A stereognostic ability test was performed in 60 patients. Forty patients were rehabilitated by means of osseointegrated implants. One group consisted of 20 patients with fixed prostheses on implants in both the upper and lower jaws. The other 20 patients had a maxillary denture while in the mandible an overdenture was retained by means of two implants connected by a bar. They were compared to a group of 20 subjects (controls) with a non-restored natural dentition. For the stereognostic ability test, subjects had to recognise ten different test pieces by manipulating them with two antagonistic incisor teeth, avoiding any contact with other oral structures. Both response time and percentage accuracy of recognition were evaluated. The present findings indicated that subjects with an overdenture on implants did not score significantly different from those with an implant-supported fixed prosthesis. In contrast, subjects with teeth had a significantly better stereognostic ability. The percentage of correct responses was 52% for overdentures, 56% for fixed prostheses on implants and 75% for natural dentitions. From these results, it could be concluded that the stereognostic ability is impaired in subjects rehabilitated with osseointegrated implants by about one-third to one-quarter compared to subjects with natural teeth.

Adult↗
PubMed1997

Control of a trackball by the chin for communication applications, with and without neck movements.

The overall aim was to evaluate whether a trackball could be used for communication by people who cannot speak due to severe motor impairment. The precision of trackball control by isolated jaw movements or a combination of jaw and head movements was evaluated in 18 healthy physical-education students, free of overt symptoms of craniomandibular dysfunction. The participants were asked to operate a trackball using the chin to type a standard text of four short sentences. There were two experimental situations: nine participants performed the typewriting task with their heads fixed; the other nine performed this task with free head movements. Trackball operation moved to the cursor over an alphabetical keyboard displayed on a computer screen and character selection was made by depression of the left-hand click button using the chin. Participants were asked to perform the task as quickly and accurately as possible. Result showed that those with free head movement typed the test significantly faster than those restricted to using only their jaw muscles. The mean time per character selection was 2.4 s (SD 0.3) for the group with free head movement and 2.7 s (SD 0.3) for the group using only jaw muscles. Group scores were not significantly different with regard to accuracy. It is suggested that a chin-operated trackball could be used for communication applications both with and without neck movements.

Adult↗
PubMed1997

Expression and in-vivo modulation of alpha- and beta-adrenoceptors on human natural killer (CD16+) cells.

Expression and in-vivo modulation of beta- and alpha-adrenoceptors on peripheral human natural killer (CD16+) cells was investigated. Ligand binding studies revealed that CD16+ lymphocytes express beta2, alpha1-, alpha2- but not beta1-adrenoceptors. Infusion of adrenaline, but not noradrenaline, significantly decreased beta2- and alpha1-adrenoceptor numbers on NK cells. Both catecholamines did not appreciably alter alpha2-adrenoceptor numbers. Additional analyses showed that adrenaline administration increases alpha2-adrenoceptor numbers on peripheral mononuclear blood cells (PBMC) and T-cell subsets (CD4+, CD8+) in contrast to decreased receptor numbers on CD16+ cells. These data demonstrate a specific effect of increasing levels of circulating catecholamines on beta2-adrenoceptors on NK cells.

Adrenergic Agonists↗
PubMed1997

Genetic screening--uses, potential abuses and ethical issues.

Potential uses, abuses and control of genetic screening techniques are discussed and the ethical issues arising from their use are compared with those for existing health screening practices. The main emphasis is upon issues affecting employment but more wide ranging implications are also touched upon. Although the current policy of various bodies is described, the views expressed are personal.

Advisory Committees↗
PubMed1997

Chryseobacterium meningosepticum: an emerging pathogen among immunocompromised adults. Report of 6 cases and literature review.

Chryseobacterium meningosepticum is a ubiquitous Gram-negative bacillus historically associated with meningitis in premature neonates. We report 15 positive cultures and 6 cases of infection among immunocompromised adults at our institution over a 10-year period and review the English-language literature on C. meningosepticum. Excluding the present series, there are 308 reports of positive cultures in the literature, of which 59% were determined to represent true infections. Sixty-five percent of those infected were younger than 3 months of age. Meningitis was the most common infectious syndrome among neonates, seen in 84% of cases and associated with a 57% mortality rate. Less commonly reported infections among infants included sepsis (13%) and pneumonia (3%). Pneumonia was the most frequent infection among the postneonatal group, accounting for 40% of cases, followed by sepsis (24%), meningitis (18%), endocarditis (3%), cellulitis (3%), abdominal infections (3%), eye infections (3%), and single case reports of sinusitis, bronchitis, and epididymitis. The 6 cases in our series were all adults, with a mean age of 58.7 years. Sites of C. meningosepticum infection were limited to the lungs, bloodstream, and biliary tree. Infection in our series was associated with prolonged hospitalization, prior exposure to multiple antibiotics, and host immunocompromise, particularly neutropenia. C. meningosepticum is resistant to multiple antibiotics, and disk dilution is notoriously unreliable for antibiotic sensitivity testing. Sensitivity testing on the 15 isolates from our institution revealed the most efficacious antibiotics to be minocycline (100% sensitive), rifampin (93%), trimethoprim-sulfamethoxazole (67%), and ciprofloxacin (53%). In contrast to reports in the literature, the isolates in our series displayed widespread resistance to vancomycin (100% resistant or intermediately sensitive), erythromycin (100%), and clindamycin (86%). These findings have important implications for the clinician when choosing empiric antibiotic regimens for patients with risk factors for C. meningosepticum infection.

Adult↗
PubMed1997

Infusion rates and levels of premedication in tumescent liposuction.

BACKGROUND: Tumescent liposuction has proven to be an extremely safe and effective method of liposuction. However, the infusion of tumescent anesthesia can take 1 hour or more to complete. OBJECTIVE: To document the types, dosages, and routes of administration of premedication utilized by four experienced tumescent liposuction surgeons. To determine if infusion rates for tumescent anesthesia are affected by types of premedication. METHODS: Four experienced liposuction surgeons were asked to review their most recent 100 tumescent liposuction patients with respect to types and dosages of premedication and routes of administration. Data were also provided on corresponding infusion pump settings and infusion rates. Volumes of tumescent anesthesia and corresponding volumes of fat aspirated were also collected on the same 400 patients. RESULTS: Infusion of tumescent anesthesia could be performed more rapidly in patients who were given greater amounts of premedication. Volumes of tumescent anesthesia infused were generally two or more times the volume of fat aspirated. Patients could be infused with less premedication if slow infiltration was employed. CONCLUSION: Infusion rates for tumescent anesthesia can be increased of greater amounts of premedication are given. However, this must be balanced against the safety of the premedication.

Adult↗
PubMed1997

Detection of Pneumocystis carinii DNA in air samples: likely environmental risk to susceptible persons.

The means by which humans acquire Pneumocystis carinii is not well understood. Whether it can be acquired from specific environmental sources or transmitted from person to person has not been determined. This study was designed to detect nucleic acids of P. carinii in air samples from various locations, including P. carinii-infected patients' homes and hospital rooms, non-P. carinii-infected patients' hospital rooms, empty hospital rooms, offices at Indiana University, and other homes in different locations. DNA was extracted from cellulose-ester filters through which air samples had been filtered, and the P. carinii DNA was amplified by PCR with primers specific for the internal transcribed spacer regions of rRNA. P. carinii DNA was found in 17 of 30 air samples (57%) from the rooms of P. carinii-infected patients. It was also found in 6 of the 21 other hospital rooms sampled (29%) but was not found in any of the offices, storage areas, or control homes. Environmental sampling suggests that the airborne presence of P. carinii genetic material and infectious organisms is plausible. The organism was also detected in locations where P. carinii patients were not immediately proximate, such as the hospital rooms of non-P. carinii-infected patients.

Air Microbiology↗
PubMed1997

Postural orientation, equilibrium, and the spinal cord.

In summary, adequate control of postural orientation and equilibrium is a prerequisite for virtually all skilled motor acts, even those apparently simple tasks of standing and walking. In the cat, certain aspects of postural orientation appear to be organized at the spinal level. In contrast, postural equilibrium is not achieved by spinal circuits in isolation, but seems to require input from higher centers. The challenge is to identify those higher centers and the means by which they produce appropriate postural reactions for maintaining balance. If, indeed, postural equilibrium is a function of descending systems, then in the future, the amount of recovery of postural equilibrium after injury and/or treatment could provide a quantitative measure of the degree of sparing and/or re-establishment of functional connections between higher centers and the spinal cord.

Animals↗
PubMed1996

Phenotype and function of hematopoietic-derived cells in the CNS of SCID mouse-Lewis rat bone marrow chimeras.

Severe combined immunodeficient (SCID) mice previously transplanted with Lewis rat hematopoietic cells (SCID mouse-Lewis rat chimeras) developed experimental autoimmune encephalomyelitis (EAE) following injection with myelin basic protein (BP)-specific Lewis rat T lymphocytes. Rat T cells did not cause EAE in non-chimeric SCID mice. Thus, in addition to BP-specific rat T cells, transplanted rat hematopoietic cells were involved in the development of EAE in SCID mice. In order to examine the role of hematopoietic rat cells in the development of EAE, chimeras were constructed in SCID mice by transplanting 40 x 10(6) T cell-depleted adult Lewis rat bone marrow cells. Single cell suspensions of brain, blood and spleen from chimeric mice were phenotyped by monoclonal antibody staining specific for mouse or rat cellular differentiation markers at 2 week intervals. Brain cells from chimeric mice were also evaluated for the presence of rat antigen-presenting cells (APC). Four and six weeks after hematopoietic cell transfer, mouse brain contained rat cells expressing the phenotypic markers (CD45+, CD11b/c+) of CNS antigen-presenting cells (APC). Six weeks after hematopoietic cell transfer, rat cells populating the CNS of chimeras were shown to function as APC, stimulating BP-specific Lewis rat T lymphocytes in vitro.

Animals↗
PubMed1996

Coordinate gene expression of the alpha3, alpha4, and alpha5 chains of collagen type IV. Evidence from a canine model of X-linked nephritis with a COL4A5 gene mutation.

Canine X-linked hereditary nephritis is an animal model for human X-linked hereditary nephritis with a premature stop codon in the alpha5(IV) gene of collagen type IV. We used this model to examine the other alpha(IV) chains at the mRNA and protein level in the kidney, since in human X-linked hereditary nephritis, the alpha3(IV) and alpha4(IV) chains are often absent from the glomerular basement membrane, although both are encoded by autosomal genes. cDNA probes for the alpha1(IV)-alpha6(IV) chains were generated from normal dog kidney using the polymerase chain reaction. Sequences were >/=88% identical at the DNA level and >/=92% identical at the protein level to the respective human alpha(IV) chains. By Northern analysis, transcripts for the alpha1(IV), alpha2(IV), and alpha6(IV) chains were detected at comparable levels in both normal and affected male dog kidney RNA. As previously shown, the transcript for the alpha5(IV) chain was reduced to approximately 10% of normal. Unexpectedly, the alpha3(IV) and alpha4(IV) transcripts were both decreased >/=77% in affected male dog kidney, suggesting a mechanism coordinating the expression of these three basement membrane components. The NC1 domain of collagen type IV isolated from normal dog glomeruli was positive for the alpha3(IV), alpha4(IV), and alpha5(IV) chains by Western blotting. In contrast, in the NC1 domain isolated from affected dog glomeruli, these three chains were not detectable, except for a trace of alpha3(IV) dimer. In X-linked hereditary nephritis, the absence of the alpha3(IV) and alpha4(IV) chains from glomerular basement membrane may reflect factors acting at the transcriptional and/or translational level in addition to the protein assembly level.

Amino Acid Sequence↗
PubMed1996

[10 years transplantation of bone marrow and hematopoietic stem cells in adults at the Hannover Medical School].

PATIENTS AND METHODS: From January 1986 until August 1995 230 adult patients received an allogeneic or autologous transplantation of bone marrow or hematopoietic blood stem cells. The conditioning and myeloablative treatment regimens were chosen according to the underlying disease and type of transplant. RESULTS: The observation period comprises 1 to 115 months after transplantation. After allogeneic transplantation from HLA-identical family donors, the probabilities of disease-free survival were for acute myeloid leukemia in first complete remission (CR) (n = 35) 77%, for acute lymphoid leukemia in 1st CR (n = 7) 72% and in 2nd CR (n = 10) 40%, in first chronic phase of chronic myeloid leukemia (n = 34) 50% and in severe aplastic anemia (n = 7) 100%. Following myeloablative therapy and autologous transplantation the probabilities of disease-free survival were 47% in relapsed Hodgkin's disease (n = 22) and 42% for relapsed high-grade non-Hodgkin's lymphoma (n = 12). Eight of 10 patients with acute myeloid and 7 of 8 with acute lymphoid leukemia suffered a leukemic relapse after autologous bone marrow transplantation. Three of 8 patients with relapsed testicular cancer survived relapse-free. Treatment failures were due to more advanced acute graft versus host disease after allogeneic transplantation and caused by relapse after autologous transplantation. Current protocols evaluate the allogeneic transplantation of enriched CD34+ blood stem cells. In chronic myeloid leukemia the autologous transplantation of blood stem cells after myeloablative therapy is being studied.

Adolescent↗
PubMed1996

Catecholamines modulate human NK cell circulation and function via spleen-independent beta 2-adrenergic mechanisms.

Increases in catecholamines have been shown to induce changes in migration of lymphocytes, in particular NK cells. To analyze the mechanisms of catecholamine-induced NK cell trafficking, normal healthy male human subjects and splenectomized individuals were infused with either adrenaline (0.10 microgram/kg/min), noradrenaline (0.15 microgram/kg/min), or NaCl i.v. for 20 min. Lymphocyte subsets (CD3+, CD4+, CD8+) transiently increased after administration of both catecholamines, with most pronounced increases (up to 600%) in NK cell numbers (CD16+ or CD56+) after infusion of adrenaline. These changes in NK cell numbers and function were accompanied neither by alterations in expression of adhesion molecules (CD11a), CD11b, CD31, CD43, CD44, CD62L) on NK cells nor by changes in plasma concentrations of soluble (s) adhesion molecules (sVCAM-1, sICAM-1, sE-selectin). Comparable increases in lymphocyte subsets were observed in splenectomized subjects, suggesting lymphocyte recruitment from other sources than the spleen. Furthermore, catecholamine-induced increases in lymphocyte subsets could be inhibited by pretreatment with the nonselective beta-adrenoceptor antagonist propranolol, but not by the beta1-selective antagonist bisoprolol. These data demonstrate that adrenaline and noradrenaline modulate the migratory capacity of human NK cells via spleen-independent beta 2-adrenoceptor mechanism.

Adrenergic beta-2 Receptor Antagonists↗
PubMed1996

Mechanical output from individual muscles during explosive leg extensions: the role of biarticular muscles.

The main result of this study is that biarticular leg muscles contribute significantly to the work done at joints, due to transfer of power during explosive leg extensions. In particular, a net power transfer was shown from hip to knee joint during jumping and sprinting. Seven elite athletes performed explosive one legged jump and spring push offs. Kinematics, ground reaction forces and electromyography (EMG) of leg muscles were recorded. The mechanical output of six individual muscle groups was estimated by using Hill-based muscle models. The EMG and kinematics served as input to these models. For jumping as well as for sprinting, the model estimated similar results for the relative work contribution done about a joint due to transfer of power by the biarticular muscles. Rectus femoris showed a power transfer from hip to knee joint, while in contrast hamstrings showed a power transfer from knee to hip joint. Regardless of these opposite directions of power transfer, a net transfer occurred from the hip to the knee joint. The relative work contribution of hamstrings done in hip extension was 7% in jumping and 11% in sprinting. For rectus femoris, the relative work contribution done in knee extension was 21% in jumping and 31% in sprinting. Power transferring actions by gastrocnemius from knee to ankle contributed 25% in jumping and 28% in sprinting to the work done in plantar flexion. These results support the hypothesis that the action of biarticular muscles contributes to a net transfer of power from proximal to distal joints during explosive leg extensions. This action of the biarticular muscles causes an efficient conversion of body segment rotations into the desired translation of the body centre of gravity.

Adult↗
PubMed1996

Chronic pelvic pains represent the most prominent urogenital symptoms of "chronic prostatitis".

OBJECTIVES: To refine and standardize evaluation of current symptoms in men with "chronic prostatitis." METHODS: We reviewed the literature, developed a symptom index, and evaluated the clinical utility of this tool in 50 patients with chronic prostatitis and 75 control patients (25 with benign prostatic hyperplasia [BPH] and 50 with sexual dysfunction). RESULTS: Patients with prostatitis reported more perineal, lower abdominal, testicular, penile, and ejaculatory pain than patients with BPH (P < 0.05 for each symptom) or sexual dysfunction (P < 0.01 for each symptom). Ejaculatory pain was also more common among men with prostatitis than among men with BPH (P = 0.07) or among men with sexual dysfunction (P < 0.01). Although described as characteristic of prostatitis in the literature, low back or rectal pain did not distinguish patients with prostatitis from those with BPH. Patients with prostatitis were intermediate between patients with BPH and sexual dysfunction on the voiding scale and similar to the BPH group on the sexual dysfunction scale. CONCLUSIONS: Pain symptoms were the predominant urologic manifestations of chronic prostatitis. The symptom index may prove valuable for evaluating patients and describing clinical results.

Adult↗
PubMed1996

Modulation of the immunologic response to acute stress in humans by beta-blockade or benzodiazepines.

Acute stress evokes immediate responses in the cardiovascular endocrine, and immune systems. In particular, the number and activity of natural killer (NK) lymphocytes increase after stress. Here, we investigate the possibility to pharmacologically interfere with these stress-induced immunologic changes. Twenty-five healthy males were subjected to an acute stressor, a first-time tandem parachute jump. Subjects were randomly assigned to a beta-adrenoceptor antagonist (propranolol), a benzodiazepine (alprazolam), or placebo group. To analyze the role of the spleen in lymphocyte redistribution, splenectomized subjects performed a parachute jump. Propranolol, but no alprazolam, inhibited the heart rate increase during jumping. Increases in epinephrine and cortisol in the propranolol group were comparable to placebo, but were attenuated by alprazolam. The number and activity of NK cells significantly increased in the placebo group but not in the propranolol group immediately after stress. Alprazolam treatment did not alter the increase in NK cell numbers but did inhibit the increase in NK activity. In splenectomized subjects, NK cell numbers, but not NK activity, increased as in placebo subjects. We conclude that stress-induced changes in the immune system are controlled by beta-adrenergic mechanisms and only partly depend on the spleen; central interference with alprazolam differentially affects stress-induced changes in the NK cell compartment.

Adrenergic beta-Antagonists↗