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R R Jacobs

Publications and source records attributed to R R Jacobs.

At least 19 recordsLinked to original sources
PubMed2000

Observation of a partially opened triple-helix conformation in 1-->3-beta-glucan by fluorescence resonance energy transfer spectroscopy.

This study used fluorescence resonance energy transfer (FRET) spectroscopy as an indirect method to investigate the effect of NaOH treatment on the conformation of a triple-helix (1-->3)-beta-D-glucan and then evaluated the effect of conformation on biological activity. Previous studies have suggested that treatment of the triple-helix glucans with NaOH produces single-helix conformers. FRET spectra of the triple-helix glucan, laminarin, doubly labeled with 1-aminopyrene as donor probe and fluorescein-5-isothiocyanate as acceptor probe attached at the reducing end, showed that a partially opened triple-helix conformer was formed on treatment with NaOH. Increasing degrees of strand opening was associated with increasing concentrations of NaOH. Based on these observations we propose that a partially opened triple-helix rather than a single helix, is formed by treating the triple-helix glucans with NaOH. After neutralizing the NaOH, changes in FRET indicated that the partially opened conformer gradually reverts to the triple-helix over 8 days. Laminarian was stabilized at different degrees of partial opening and its biological activity examined using the Limulus amebocyte lysate assay and nitric oxide production by alveolar macrophage. Both Limulus amebocyte lysate activity and nitric oxide production were related to the degree of opening of the triple-helix. Partially open conformers were more biologically active than the intact triple-helix.

Aniline Compounds↗
PubMed2000

Characterization of an aerosol chamber for human exposures to endotoxin.

The objective of this study was to develop and characterize an exposure chamber in which human subjects could be exposed to low dust concentrations carrying an endotoxin coating. An exposure chamber, dust dispersion method, and endotoxin characterization technique were developed for inhalation exposures. A 6.27 m3 exposure chamber was designed and constructed from cinder block, glass windows, and Plexiglas. Using an acetone adhesion process, Enterobacter agglomerans were adsorbed onto respirable cellulose particles to create the endotoxin aerosol. The size distribution of the endotoxin-treated particles was verified using light microscopy and cascade impactors. A dry powder dust generator was refined to consistently disperse small quantities of the aerosol into the chamber to maintain dust concentrations at approximately 250 micrograms/m3. Dust levels during the chamber exposures were monitored using a portable continuous aerosol monitor (PCAM). During initial exposure runs, PCAM monitoring stations were positioned at different locations within a 0.5-meter matrix to document mixing patterns. Total dust and cascade impactor samples were collected throughout each exposure period to characterize the chamber operating system and insure the mean airborne dust concentration fulfilled target levels. A one-factor analysis of variance at the 95 percent confidence interval illustrated that there was not a statistically significant difference in the mean dust concentration throughout the exposure runs compared to the individual runs. Together the consistency of the total dust filters, endotoxin concentrations, and aerosol-monitoring instrument were adequate to allow use of the chamber for experimental studies involving human volunteers.

Aerosols↗
PubMed2000

Preliminary report on the results of the second phase of a round- robin endotoxin assay study using cotton dust.

In an on-going endotoxin assay study, a two-part interlaboratory endotoxin assay study has been completed. The purpose of the study was to compare the variation in assay results between different laboratories, and, if the variation was high, to see if a common protocol would reduce the variation. In both parts of the study, membrane filters laden with the same approximate amount and type of cotton dust were sent for analysis to laboratories that "routinely" perform endotoxin analyses. First, each of these laboratories performed the analysis using the methodology common to its laboratory. In the second part of the study, membrane filters with cotton dust were again sent to the same laboratories where the analyses were performed as before but with a common extraction protocol. The preliminary results from the first phase of the study have been collected and showed that intra-laboratory variations were small, but large and significant interlaboratory variation was observed. The results were reported elsewhere. The preliminary results from the second part of the study consisting of the data currently collected are presented here. Again, intra-laboratory variations were small, but, also again, large and significant inter-laboratory variation was observed. However, in this part of the study, the range between the highest and lowest average results was narrower than in the first part of the study. Influence of the assay kit type was examined. The variation within assay kit type was small but significant differences in results were observed between assay kit types. The findings suggest that endotoxin concentration in samples can be ranked within laboratories, but not necessarily between laboratories. However, some of the variation between laboratories has been reduced by a common extraction protocol which suggests the possibility of further standardization that may lead to better comparability between laboratories.

Air Pollution, Indoor↗
PubMed2000

Does the chronic prostatitis/pelvic pain syndrome differ from nonbacterial prostatitis and prostatodynia?

PURPOSE: The new consensus classification considers the chronic prostatitis/pelvic pain syndrome (CPPS) based on presence or absence of leukocytes in the expressed prostatic secretions, post-massage urine or seminal fluid analysis. We compared classification based on evaluation of these 3 specimens to the traditional classification based on expressed prostatic secretion examination alone. MATERIALS AND METHODS: A prospective clinical and laboratory protocol was used to evaluate symptomatic patients who had no evidence of urethritis, acute bacterial prostatitis or chronic bacterial prostatitis. RESULTS: Thorough clinical and microbiological evaluation of 310 patients attending our prostatitis clinic was used to select a population of 140 subjects who provided optimal expressed prostatic secretion, post-massage urine and semen specimens. Inflammation was documented in 111 (26%) of 420 samples, including 39 expressed prostatic secretion samples with 500 or greater leukocytes/mm.3, 32 post-massage urine samples with 1 or greater leukocytes/mm.3 and 40 seminal fluid specimens with 1 or greater million leukocytes/mm.3. Of the 140 subjects 73 (52%) had inflammatory chronic prostatitis/pelvic pain according to the consensus criteria but only 39 (28%) had nonbacterial prostatitis according to traditional expressed prostatic secretion criteria (p <0.001). CONCLUSIONS: The new consensus concept of inflammatory chronic prostatitis/pelvic pain includes almost twice as many patients as the traditional category of nonbacterial prostatitis.

Adolescent↗
PubMed1999

Central administration of leptin inhibits food intake and activates the sympathetic nervous system in rhesus macaques.

The present study was performed to determine the effects of central administration of leptin on food intake and sympathetic nervous system activity in a nonrodent species, the rhesus monkey. Peripheral administration of leptin at doses (1 and 3 microg/kg, s.c.) that produced increments of circulating leptin concentrations within a physiological range did not inhibit food intake over the subsequent 3 days. In contrast, leptin (1 microg/kg, intracerebroventricularly) had no acute effect on food intake, but caused a significant and sustained suppression (40-50%) of food intake during the entire following day (P < 0.01). In addition, circulating norepinephrine levels increased by 55 +/- 16% (P < 0.02) 1 h after intracerebroventricular leptin administration, but did not increase after artificial cerebrospinal fluid administration. These results indicate that leptin can provide a signal to the central nervous system that decreases food intake in primates and in addition acutely activates the sympathetic nervous system. However, the results showing an acute increase in circulating leptin concentrations after peripheral administration of human leptin suggest that in primates, increases in circulating leptin within the physiological range do not acutely regulate food intake. Leptin may be more important in regulating food intake when there are sustained changes in circulating concentrations of leptin (e.g. with obesity, prolonged energy restriction, or diabetes).

Animals↗
PubMed1999

Review of methods applicable to the assessment of mold exposure to children.

This article presents discussion of the assessment of the exposure of children to fungi, substances derived from fungi, and the environmental conditions that may lead to exposure. The principles driving investigations of fungal contamination and subsequent exposure are presented as well as guidelines for conducting these investigations. A comprehensive description of available research sampling and analysis techniques is also presented.

Air Pollution, Indoor↗
PubMed1998

An evaluation of the prevalence of latex sensitivity among atopic and non-atopic intensive care workers.

BACKGROUND: Exposure to latex is known to cause an array of symptoms, including pruritus, dermatitis, erythema, and urticaria. Workers at elevated risk for latex exposure include health care personnel whose repeated patient contact or surgical work require extensive use of latex gloves. This study evaluated the prevalence of latex allergies in atopic and non-atopic intensive care workers and sought to determine the impact of risk factors such as frequency of glove use and hand washing on latex sensitization. METHODS: We evaluated the prevalence of latex sensitivity in 122 intensive care unit (ICU) workers using a questionnaire and skin prick test. Atopy and latex sensitivity were determined by skin prick test using a battery of common inhalant allergens and an extract prepared from the gloves used in the ICU. Frequency of glove use and hand washing were determined by questionnaire. RESULTS AND CONCLUSIONS: Forty ICU workers (32.8%) were considered atopic by having at least one positive response to the inhalant allergens. Atopic ICU workers were more likely to have positive latex skin test than non-atopic ICU workers (atopic vs. non-atopic workers: p < 0.001, odds ratio = 14.2). Frequency of current glove use or hand washing frequency were not significant predictors of a positive response to latex; however, a positive history of atopic eczema and family history of allergies, as determined by questionnaire were significant predictors of a positive response to latex antigens.

Adult↗
PubMed1995

Monocyte responsiveness and a T-cell subtype predict the effects induced by cotton dust exposure.

The aim of the study was to evaluate whether peripheral cellular parameters could predict susceptibility to decreased lung function and associated symptoms, in response to a single exposure to cotton dust. Previously nonexposed subjects (n = 42) inhaled an aerosol of cotton dust in a model cardroom during a period of 5 h. The subjects were examined before the exposure for FEV1, procoagulant activity (PCA) in blood mononuclear cells (BMNC), and serum IgE antibodies against a pool of inhalant antigens. Blood lymphocytes were typed into the helper/inducer (CD4+) and cytotoxic/suppressor (CD8+) T cells in combination with surface markers subdividing these populations. A questionnaire was used to identify atopic and nonatopic subjects. Immediately after exposure, the subjects were tested for FEV1 and PCA, and symptoms were recorded with a questionnaire. The dust exposure induced a decrease in FEV1 that was larger for the atopic group, but did not change the PCA in BMNC. The decrease in FEV1 was positively related to the preexposure PCA in both atopics and nonatopics. Symptoms from the airways after the exposure were reported to the same extent in the atopic and nonatopic group, and the subject group reporting chest tightness had a larger preexposure PCA. The atopic group had a larger proportion of blood CD8+ T lymphocytes negative for the monoclonal antibody anti-S6F1 (CD8+S6F1-), and in this group the decrease in FEV1 was significantly related to the proportion of this cell type. Also, in the atopic group, the proportion of CD8+S6F1- cells correlated positively with the preexposure PCA, and a negative correlation was found for this cell and serum levels of IgE.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Sampling environments containing organic dust.

Assessment of airborne organic dust in different environments is necessary to better understand the relationship between exposure and disease. Exposure assessment requires a well-defined sampling strategy which addresses the following questions: Where, how long, who, how many, and when? For assessing exposure to organic dust, the question of "what?" must be included because, in most cases, the specific toxins or appropriate surrogates for exposure have not been identified. For most environments with organic dust, these questions have not been adequately addressed. However, a large database exists for cotton dust. Cotton is used as a model of organic dust to illustrate the application of exposure assessment: 1) to develop a dose-response relationship between aerosolized dust and specific health effects; 2) to evaluate the effects of process change on gravimetric dust levels and for compliance with the cotton dust standard; and 3) to identify specific biologically active components in the dust.

Air Pollutants↗
PubMed1994

Evaluation of the association of acute overshift change in pulmonary function and atopy using OSHA cotton dust surveillance data.

OSHA surveillance data were collected for 769 individuals employed in four different cotton textile mills. Current workers were asked to complete a questionnaire about personal and family history of atopy or asthma. Both surveillance and survey data were available for 502 individuals. The prevalence of atopy in the population as reported by questionnaire was 18%, while asthma was reported by 4%. Dust levels at the four mills were in compliance with the cotton dust standard during the period of surveillance. No relationship was found between a self-reported history of atopy or asthma and the magnitude or frequency of acute overshift declines in forced expiratory volume during 1 second (FEV1). Nonsmokers had annual changes in FEV1 and forced vital capacity (FVC) comparable to nonexposed populations. In one of the four mills surveyed, annual declines in FEV1 and FVC for current smokers were significantly greater than declines for smokers in the other mills or the general smoking population (p < 0.02). This mill effect was also observed for subjects who were categorized as atopic (p < 0.02). For nonsmokers there appears to be no significant adverse health effect from exposure to the levels of cotton dust observed in these mills.

Adult↗
PubMed1993

An in vitro comparison of the permeation of chemicals in vapor and liquid phase through pig skin.

This study used pig skin to compare vapor and liquid permeation of benzene, n-butanol, and toluene in vitro. Vapors of radio-labeled chemicals were generated by passing purified air through two saturators in series containing the labeled chemical. The generated vapor was directed into the donor compartment of a modified liquid permeation cell. For liquid permeation experiments, neat chemicals were dosed directly on the surface of the skin. The variability of the generated concentrations for the vapor phase of each chemical ranged from 3-7%. The mean flux of the liquid chemicals was significantly higher than those of the vapor phase. There was no significant difference in the flux of the individual chemicals in the liquid phase. In the vapor phase test, the flux of toluene and benzene were not significantly different; however, for n-butanol the flux was significantly lower than the for either benzene or toluene.

1-Butanol↗
PubMed1993

Bronchial reactivity, atopy, and airway response to cotton dust.

Studies of cotton textile workers have found an association between atopy and drop in FEV1 over a workshift. We studied the response of previously nonexposed volunteers with and without a history of mild atopy to a 5-h exposure to 1 mg/m3 of respirable cotton dust in a model cardroom. All participants were nonsmokers, had no history of asthma, and had normal spirometry. Twenty atopic subjects gave a personal history of mild respiratory allergy to pollen, dusts, or animals that had been confirmed by a physician. Thirty-two nonatopic subjects had no history of allergy. Spirometry and a methacholine challenge test were performed 1 to 2 days prior to exposure. Spirometry was repeated immediately before exposure to cotton dust; spirometry and a methacholine challenge were performed immediately after exposure. Atopic subjects showed a significantly higher mean serum IgE level to Phadiatop, a screening test to common inhalant allergens, than did nonatopic subjects (mean percent binding, 32.1 versus 1.5; p < 0.001). Atopic subjects had a significantly greater mean fall in FEV1 during exposure (8.3% versus 4.9%, p < 0.05). The difference in FEV1 decline between atopic and nonatopic subjects was similar in magnitude to that reported for workshift FEV1 declines between textile workers with and without mild atopy. Atopic subjects had significantly higher baseline methacholine responsiveness than did nonatopic subjects (26% versus 0% reaching a PD20, p < 0.0005). After cotton dust exposure, there was a significant increase in airway reactivity in both groups (68% versus 20% reaching a PD20, p < 0.0005). For all subjects combined baseline responsiveness was significantly related to the change in FEV1 after exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

The histomorphologic sequence of dural repair. Observations in the canine model.

This study was undertaken to investigate the histopathologic events of the dural reparative process. Uniform 2-mm dural defects were created in adult beagles, repaired, and then examined in a 6-week period. Primary fibroblastic bridging of the durotomy was not seen until Postoperative Day 6, and it was not until Postoperative Day 10 that ablation of this defect was uniformly seen. Cerebrospinal fluid egress through the dural defects was prevented in the vast majority of cases by the formation of an internal patch composed of proliferative elements of pia and arachnoid mater.

Animals↗
PubMed1990

Results of a locking-hook spinal rod for fractures of the thoracic and lumbar spine.

The results of a consecutive series of 110 patients treated with the locking-hook spinal rod are presented. A prospective protocol was completed in 95 patients. Pain was absent or mild in 93%. In those patients with a partial neurologic deficit, there was recovery of at least one Frankel grade in 84%. The overall kyphotic deformity was reduced from 21 to 17 degrees. In those patients in whom no anterior surgery was performed, the deformity improved from 21 to 13 degrees. No rod fractures occurred, and the overall instrument complication rate was 13.7%, of which one was due to infection and four secondary to uncrimped nuts, for a true complication rate of 8.4%. The locking-hook spinal rod has proven to be a satisfactory internal fixation device in the treatment of unstable thoracolumbar fractures.

Adult↗
PubMed1990

Quantification of leakage pressures after durotomy repairs in the canine.

This study was undertaken to investigate the relative strengths of dural repair using standard suture techniques, suture supplemented with tissue adhesive, and tissue adhesive alone. Uniform 2 mm dural defects were created in adult beagles, repaired, and then subjected to pressurization testing. Defects repaired with suture alone initially leaked within the range of physiologic pressurization, while those supplemented with tissue adhesive or repaired with tissue adhesive alone failed at higher pressurization levels. Histologic sections obtained from the dura treated with fibrin adhesive sealant demonstrated minimal inflammatory response not significantly different than those sections examined at sites repaired by suture alone. A new substance, fibrin adhesive sealant, appears to be useful in effecting dural repair due to its ability to withstand pressures greater than those obtained with suture alone.

Animals↗
PubMed1989

Biomechanical analyses of surgical correction techniques in idiopathic scoliosis: significance of bi-planar characteristics of scoliotic spines.

Biomechanical analyses of Harrington distraction, Harrington distraction-compression, Cotrel and Luque correction techniques simulated mechanically on a three-dimensional mathematical model of scoliotic spines are developed and relationships between mechanical forces and achievable corrections are derived in terms of Cobb angle, vertebral inclination from the frontal plane, and bi-plane bending stiffness of motion segments. For all four systems, nomograms between Cobb angles and corrective forces with correction factors as parameters are prepared in terms of given bi-plane characteristics of scoliotic spines. Parametric studies to show the influence of the torsion plane bending stiffness of motion segments and vertebral inclinations from the frontal plane on the mechanical effectiveness of the surgical correction techniques are presented. The mechanical effectiveness of each of the four surgical correction techniques determined with the use of this model compares reasonably well with the clinical findings.

Biomechanical Phenomena↗
PubMed1989

Update-1988. Current status of internal fixation of thoracolumbar fractures.

Rigid internal fixation has become the preferred method of treatment for unstable thoracolumbar fractures in most American spine centers. In most cases, posterior instrumentation alone is adequate, but occasionally an anterior procedure is necessary. A number of internal fixation devices are now available to the orthopaedic surgeon. Controversy exists regarding the number of levels that need to instrumented and the optimal form of internal fixation.

Adult↗