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Biomedical subjects

B R Johnson

Publications and source records attributed to B R Johnson.

At least 19 recordsLinked to original sources
PubMed2006

Applications and limitations of ADM 1 in municipal wastewater solids treatment.

The ADM 1 model has been implemented in a steady-state whole wastewater plant simulator. The ADM 1 model has been in use with good success for approximately 2 years on a wide range of wastewater treatment facilities. However, a number of modifications were necessary to allow it to be used in the context of municipal wastewater treatment. It was found that the model's use was greatly simplified if used in conjunction with a larger plant simulator to assist in the feed fractionation. It was also found that a better fit to actual operating data was achieved if some of the slowly biodegradable particulate fraction was partitioned into ADM particulate fractions other than the composite fraction. Another significant limitation of the model is in the absence of phosphorus modeling. The ADM model needs to have phosphorus handling for all the relevant fractions, and needs to include the handling of inorganic reactions such as struvite precipitation and metal phosphate/metal hydroxide precipitation. Activity effects on chemical equilibria are significant when considering phosphorus. Also of importance in wastewater treatment is the fate of sulfur compounds. This includes the generation of H2S in the digester gas and the fate of the sulfur species in the digested sludge (as a predictor of odour-generating potential).

Anaerobiosis↗
PubMed2005

Application of the IWA anaerobic digestion model (ADM1) for simulating full-scale anaerobic sewage sludge digestion.

A steady-state implementation of the IWA Anaerobic Digestion Model No. 1 (ADM1) has been applied to the anaerobic digesters in two wastewater treatment plants. The two plants have a wastewater treatment capacity of 76,000 and 820,000 m3/day, respectively, with approximately 12 and 205 dry metric tons sludge fed to digesters per day. The main purpose of this study is to compare the ADM1 model results with full-scale anaerobic digestion performance. For both plants, the prediction of the steady-state ADM1 implementation using the suggested physico-chemical and biochemical parameter values was able to reflect the results from the actual digester operations to a reasonable degree of accuracy on all parameters. The predicted total solids (TS) and volatile solids (VS) concentration in the digested biosolids, as well as the digester volatile solids destruction (VSD), biogas production and biogas yield are within 10% of the actual digester data. This study demonstrated that the ADM1 is a powerful tool for predicting the steady-state behaviour of anaerobic digesters treating sewage sludges. In addition, it showed that the use of a whole wastewater treatment plant simulator for fractionating the digester influent into the ADM1 input parameters was successful.

Bacteria, Anaerobic↗
PubMed2005

A comparison between the theory and reality of full-scale step-feed nutrient removal systems.

Capacity enhancement and volume reduction benefits of step-feeding fully aerobic bioreactors has been well documented. Application of step-feed technology to biological nutrient removal (BNR) systems, particularly those removing nitrogen alone or both nitrogen and phosphorus, is relatively new to the industry. In recent years, a number of full-scale step-feed facilities have been brought into service. This paper reviews nine full-scale step-feed biological nutrient removal systems--both nitrogen removal alone, and nitrogen and phosphorus removal. The objective is to compare the theoretical benefits of such systems with their actual operation. The predicted benefits of reduced bioreactor volume or increased process capacity, reduced energy usage, more robust nitrification performance, and the flexibility to tune (or de-tune) nitrification efficiency were verified in full-scale systems. Equations are also presented that may be used in the prediction of step-feed benefits. There are two primary drivers for considering a step-feed biological reactor system: 1. Reduced bioreactor volume for a defined capacity or performance or increased process capacity given a fixed bioreactor volume. 2. More robust nitrification performance. Full-scale operation of these step-feed nutrient removal systems provides a real world basis for the claimed benefits of step-feed operation. These systems have uniformly shown additional capacity. A number of them have also exhibited more robust performance, especially during storms. Where possible, side-by-side comparisons of full-scale step-feed systems with non-step-feed systems have exhibited greater process reliability and flexibility.

Bioreactors↗
PubMed2001

Tools for physiology labs: an inexpensive high-performance amplifier and electrode for extracellular recording.

The cost of electronic equipment can be a critical barrier to including neurophysiology exercises in biology teaching programs. We describe the construction of a simple and inexpensive AC preamplifier with performance comparable to that of commercial products. The amplifier consists of two integrated circuits in five stages: differential input, fixed gain, variable gain (100 or 1000), low-pass filter (5 or 20 kHz), and 50 or 60 Hz notch filter. We compared our amplifier with two commercial units, the A-M Systems Model 1700 and the Grass P15. The quality of extracellular recording from a typical student preparation (spontaneously active crayfish motor nerve) was the same for all three amplifiers, although our amplifier has slightly higher internal noise than the P15 and slightly lower common-mode rejection than the 1700 and P15. In addition, we describe a simple suction electrode for extracellular nerve recording. It is easily constructed from readily available materials and uses a disposable plastic pipette tip, instead of the traditional glass tip, to contact the nerve. This tip is easily replaced if broken or clogged, and can be adapted to different recording conditions by selecting a different tip size or stretching the plastic. Development of this equipment is part of an ongoing project to promote neuroscience education by expanding the neurophysiology options available to laboratory instructors.

Action Potentials↗
PubMed2000

Guanylyl cyclase-C receptor mRNA distribution along the rat nephron.

Guanylin (GN) and uroguanylin (UGN) are two recently identified peptides that have been shown to affect water and electrolyte transport in both the intestine and the kidney. Mechanistically, the effects of both peptides are thought to be mediated by intracellular cGMP which results from ligand binding to a plasma membrane guanylyl cyclase-C (GC-C) receptor. To date, the specific intrarenal site(s) of GN and UGN action have not been established. To begin to address this issue, the present studies utilized semi-quantitative RT-PCR to assess the distribution of GC-C mRNA in specific microdissected segments of the rat nephron. GC-C mRNA expression was highest in the cortical collecting tubule, followed by the proximal convoluted tubule, medullary thick ascending limb and collecting tubule, and thin limbs of Henle's loop. Expression levels were significantly lower in all other segments tested, including the glomerulus. The renal tubular expression pattern for cGMP-dependent protein kinase II (cGK-II) mRNA, which is activated in response to GN/UGN-dependent cGMP accumulation, was similar to that for GC-C. Notably, both GN and UGN mRNAs were also expressed along the nephron. The highest levels of expression for both peptides were detected in the medullary collecting tubule. Lower, but comparable levels of GN and UGN expression also occurred in the cortical collecting tubule, cortical and medullary thick ascending limb, and thin limbs of Henles loop. In the proximal convoluted tubule, GN mRNA expression was also quite high, while UGN mRNA was almost undetectable. The presence of renal GC-C and cGK-II in the kidney are consistent with a proposed endocrine function for GN and UGN. In addition however, the present data suggest that intrarenally synthesized GN and UGN may also contribute to the regulation of renal tubular transport.

Animals↗
PubMed2000

Assessing the risk for violence.

In addition to taking steps to ensure their own safety, clinicians also have a role in predicting violence. In the past the clinician's ability to accurately assess the risk for violence has been seriously questioned. This chapter provides guidance for making acceptable predictions.

Dangerous Behavior↗
PubMed2000

Sexual violence: the perpetrator.

In addition to assessing and treating victims of sexual violence, mental health professionals are also called upon to provide similar services for sexually violent perpetrators. This chapter addresses these concerns along with the forensic issues surrounding those who commit sexual violence.

Adult↗
PubMed2000

The essential endodontic literature: a survey of postgraduate program directors.

Hundreds of new articles are added to the body of knowledge in endodontics each year. However, a comparatively small number of articles have had a disproportionately large influence on the progress and development of the specialty of endodontics. A survey of postgraduate program directors was conducted to attempt to identify a highly selective short list of articles that program directors felt should be included on every postgraduate reading list. The survey results were then compared with the more objective benchmark of citation indexing. The results of this survey suggest that the collective opinion of the postgraduate program directors correlates well with the results obtained from citation analysis.

Abstracting and Indexing↗
PubMed1999

Comparison of effect of intracanal use of ketorolac tromethamine and dexamethasone with oral ibuprofen on post treatment endodontic pain.

The purpose of this study was to compare the pain-reducing efficacy of dexamethasone and ketorolac tromethamine when used as an intracanal medication, with oral ibuprofen and a placebo. An additional objective was to establish if any relationship exists between the incidence and severity of pretreatment pain and the incidence and severity of postinstrumentation pain. A total of 48 patients who presented to the University of Illinois postgraduate endodontic clinic were invited to participate. Patients were randomly assigned to 1 of 4 groups: oral ibuprofen, placebo, dexamethasone, or ketorolac tromethamine. Patients were asked to evaluate their pretreatment pain when they presented to the clinic with a Visual Analog Scale. The root canal treatment was performed in two appointments. The first appointment consisted of cleansing and shaping of the canal/s and placement of an intracanal medication. All teeth were closed with a sterile cotton pellet and IRM. Each patient was sent home with a Visual Analog Scale to fill out at 6, 12, 24 and 48 h after initiation of therapy. At the 12-h period, both dexamethasone and ketorolac provided statistically significant better pain relief than placebo. At the 24-h period, only ketorolac demonstrated better pain relief than the placebo. There were no statistically significant differences among the groups at 6 and 48 h. Although ibuprofen pain ratings were less than the placebo at all time points, the reduction was not significant. In addition, no significant differences were demonstrated between ibuprofen and either dexamethasone or ketorolac.

Adolescent↗
PubMed1999

In vitro fracture strength of endodontically treated premolars.

The recent introduction of new bonding agents has led some authors to suggest that certain endodontically treated posterior teeth could be restored with a bonded restoration instead of a full-coverage crown or onlay. To test the fracture resistance of endodontically treated premolars restored with and without bonding agents, we randomly divided 56 intact and caries-free maxillary premolars into seven groups as follows: unaltered teeth; access only; MOD prep and RCT; MOD prep, RCT, and amalgam restoration; MOD prep, RCT, and amalgam with 4-META bonding agent; MOD prep, RCT, and composite resin restoration; and MOD prep, RCT, and composite resin with 4-META bonding agent. The teeth were subjected to compressive fracture tests in a Zwick 1435 Universal Testing Machine. Unaltered teeth and those with access only demonstrated similar fracture strengths. Under the conditions of this study, there was no significant difference in fracture strength between the experimental groups.

Acrylic Resins↗
PubMed1999

Considerations in the selection of a root-end filling material.

Surgical root canal treatment often includes the placement of a root-end filling material. New materials have recently emerged to challenge the long-standing position of amalgam as the root-end filling material of choice. This review discusses several of the commonly used root-end filling materials, with emphasis on indications and contraindications for the use of each.

Aluminum Compounds↗
PubMed1999

Diagnosis and treatment of cutaneous facial sinus tracts of dental origin.

BACKGROUND: Cutaneous draining sinus tracts of dental origin often are a diagnostic challenge. A delay in correctly diagnosing these types of lesions can result in ineffective and inappropriate treatment. CASE DESCRIPTION: The authors present five cases of facial lesions that were initially misdiagnosed as lesions of nonodontogenic origin. The correct diagnosis in each case was cutaneous sinus tract secondary to pulpal necrosis and suppurative apical periodontitis. All facial sinus tracts resolved after the patients received nonsurgical root canal therapy. CLINICAL IMPLICATIONS: As patients with cutaneous facial sinus tracts of dental origin often do not have obvious dental symptoms, possible dental etiology may be overlooked. Early correct diagnosis and treatment of these lesions can help prevent unnecessary and ineffective antibiotic therapy or surgical treatment.

Adult↗
PubMed1999

Renal effects of uroguanylin and guanylin in vivo.

Uroguanylin and guanylin are newly discovered endogenous heat-stable peptides that bind to and activate a membrane bound guanylyl cyclase signaling receptor (termed guanylyl cyclase C; GC-C). These peptides are not only found in blood but are secreted into the lumen of the intestine and effect a net secretion of electrolytes (Na+, K+, Cl-, HCO3-) and fluid into the intestine via a cyclic guanosine-3', 5'-monophosphate (cGMP) mechanism. GC-C is also the receptor for Escherichia coli heat-stable enterotoxin (STa) and activation by STa results in a diarrheal illness. Employing mouse renal in vivo models, we have demonstrated that uroguanylin, guanylin, and STa elicit natriuretic, kaliuretic, and diuretic effects. These biological responses are time- and dose-dependent. Maximum natriuretic and kaliuretic effects are observed within 30-40 min following infusion with pharmacological doses of the peptides in a sealed-urethra mouse model. Our mouse renal clearance model confirms these results and shows significant natriuresis following a constant infusion of uroguanylin for 30 min, while the glomerular filtration rate, plasma creatinine, urine osmolality, heart rate, and blood pressure remain constant. These data suggest the peptides act through tubular transport mechanisms. Consistent with a tubular mechanism, messenger RNA-differential display PCR of kidney RNA extracted from vehicle- and uroguanylin-treated mice show the message for the Na+/K+ ATPase gamma-subunit is down-regulated. Interestingly, GC-C knockout mice (Gucy2c -/-) also exhibit significant uroguanylin-induced natriuresis and kaliuresis in vivo, suggesting the presence of an alternate receptor signaling mechanism in the kidney. Thus, uroguanylin and guanylin seem to serve as intestinal and renal natriuretic peptide-hormones influencing salt and water transport in the kidney through GC-C dependent and independent pathways. Furthermore, our recent clinical probe study has revealed a 70-fold increase in levels of urinary uroguanylin in patients with congestive heart failure. In conclusion, our studies support the concept that uroguanylin and guanylin are endogenous effector peptides involved in regulating body salt and water homeostasis.

Animals↗
PubMed1998

Distributed effects of dopamine modulation in the crustacean pyloric network.

It is now clear that neuromodulators can reconfigure a single motor network to allow the generation of a family of related movements. Using dopamine modulation of the 14-neuron pyloric network from the crustacean stomatogastric ganglion as an example, we describe two major mechanisms by which network output is modulated. First, the baseline electrophysiological properties of the network neurons can be altered. Dopamine can affect the activity of each neuron independently. For example, DA modulates IA in nearly every neuron in the pyloric network, but in opposite directions in different cells. Furthermore, DA usually modulates combinations of ionic currents. In some cases, currents with opposing actions on cell excitability are simultaneously affected, and the net response reflects the sum of these opposing effects. Second, neuromodulators can alter the strength of synaptic interactions within the network, quantitatively "rewiring" the network. Every synapse in the network is affected by DA, with some increased and others decreased in strength. DA acts both pre- and postsynaptically to affect transmission: these actions are frequently opposing in sign, and the net response arises as the sum of these opposing actions. Finally, spike-evoked and graded transmission at the same synapse can be oppositely affected by DA. These results emphasize the distributed nature of modulation in motor networks.

Animals↗
PubMed1998

Immunohistochemical demonstration of tissue transglutaminase in amyloid plaques.

The brain of Alzheimer's disease patients contains deposits of the 39-42-amino acid (approximately 4 kDa) amyloid beta-peptide, which is derived from the beta-amyloid precursor protein. These pathological deposits have been shown to consist in part of insoluble 8- and 16-kDa aggregates of the amyloid beta-peptide. This report confirms that the amyloid beta-peptide is a substrate for tissue transglutaminase (TGase) and demonstrates that human brain preparations from Alzheimer's disease patients and control patients form cross-linked dimers from added iodinated amyloid beta-peptide. Immunohistochemical staining for TGase revealed its presence in tissue sections and isolated amyloid plaque cores obtained from brains of patients diagnosed as having Alzheimer's disease. These results provide evidence that the previously described insoluble amyloid deposits in Alzheimer's disease may involve TGase-mediated cross-linked amyloid beta-peptide polymers, and suggest a potential role for TGase in the pathogenesis of this disease.

Aged↗
PubMed1998

Dopamine modulates graded and spike-evoked synaptic inhibition independently at single synapses in pyloric network of lobster.

Bath application of dopamine (DA) modifies the rhythmic motor pattern generated by the pyloric network in the stomatogastric ganglion of the spiny lobster, Panulirus interruptus. Synaptic transmission between network members is an important target of DA action. All pyloric neurons employ both graded transmitter release and action-potential-mediated synaptic inhibition. DA was previously shown to alter the graded synaptic strength of every pyloric synapse. In this study, we compared DA's effects on action-potential-mediated and graded synaptic inhibition at output synapses of the lateral pyloric (LP) neuron. At each synapse the postsynaptic cell tested was isolated from other descending and pyloric synaptic inputs. DA caused a reduction in the size of the LP spike-evoked inhibitory postsynaptic potentials (IPSPs) in the pyloric dilator (PD) neuron. The change in IPSP size was significantly and linearly correlated with DA-induced reduction in the input resistance of the postsynaptic PD neuron. In contrast, graded inhibition, tested in the same preparations after superfusing the stomatogastric ganglion (STG) with tetrodotoxin (TTX), was consistently enhanced by DA. DA shifted the amplitude of spike-evoked IPSPs in the same direction as the alteration of the postsynaptic cell input resistance at two additional synapses tested: DA weakened the LP spike-mediated inhibition of the ventricular dilator (VD) and reduced the VD input resistance, while strengthening the LP --> pyloric constrictor (PY) synapse and increasing PY input resistance. As previously reported, graded inhibition was enhanced at these two LP output synapses. We conclude that DA can differentially modulate the spike-evoked and graded components of synapses between members of a central pattern generator network. At the synapses we studied, actions on the presynaptic cell predominate in the modulation of graded transmission, whereas effects on postsynaptic cells predominate in the regulation of spike-evoked IPSPs.

Action Potentials↗