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Biomedical subjects

J G Collins

Publications and source records attributed to J G Collins.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effect of propofol on spinal dorsal horn neurons. Comparison with lack of ketamine effects.

BACKGROUND: Pentobarbital reduces low-threshold receptive field (RF) size and enhances responses of some spinal dorsal horn neurons to noxious stimulation in cats. To better understand the effects of general anesthetics on spinal sensory processing, this study was designed to determine if intravenous propofol and ketamine have similar effects. METHODS: Spinal dorsal horn neuronal responses to RF stimulation were observed in physiologically intact, awake, drug-free cats. After baseline observations were made, the effects of propofol (7.5 or 10 mg/kg intravenous) or ketamine (10 mg/kg intravenous) on those neuronal responses were observed. RESULTS: Propofol is capable of producing a profound reduction in low-threshold RF size. Propofol also depressed neuronal responses to non-noxious and noxious RF stimulation in many of the neurons tested. Ketamine was not observed to produce any change in either RF size or neuronal response to non-noxious RF stimulation. CONCLUSIONS: General anesthetics that interact with gamma aminobutyric acid receptors may significantly depress low-threshold sensory information within the spinal dorsal horn. This may contribute to anesthetic-induced loss of sensation. Lack of a ketamine effect suggests an absence of n-methyl-d-aspartate receptor involvement in spinal dorsal horn processing of low threshold sensory information.

Action Potentials↗
PubMed1995

Low-threshold neuronal activity of spinal dorsal horn neurons increases during REM sleep in cats: comparison with effects of anesthesia.

1. Cats were prepared for chronic recordings from the lumbar enlargement of the spinal dorsal horn. At the beginning of each recording session, a tungsten microelectrode was advanced through the dura in a physiologically intact, awake, drug-free animal, until amplitude discrimination provided a single neuron with a receptive field on the hindquarters. 2. Extracellular recordings of activity of each neuron were made during receptive field stimulation with tactile and thermal nonnoxious and noxious stimuli. 3. Baseline responses obtained in the awake state were compared with responses of the same neurons during slow-wave or rapid-eye-movement (REM) sleep. In a subpopulation of neurons, the effects of anesthesia (propofol, 7.5 mg/kg iv) were observed after the completion of sleep studies. 4. The low-threshold receptive fields of the seven neurons studied during REM sleep were all increased in size when compared with the baseline value. The average increase was 52.6% (range 26.2-96.7%). 5. The low-threshold receptive fields of the seven neurons studied during REM sleep were reduced by propofol anesthesia by an average of 49.1% (range 29-74%). 6. Neuronal response to receptive field brushing was observed in 15 neurons during REM sleep. The effect of propofol on receptive field brushing was observed in 8 of those neurons. In only one of those eight neurons were the effects of REM sleep and anesthesia in the same direction. 7. Changes in neuronal responses were less consistent during slow-wave sleep but still differed from changes induced by propofol.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1995

[Interaction between opiate subtypes and serotonin in suppressing noxiously evoked activity of WDR neurons].

The present study examined interactions between mu and delta opiate subtypes and serotonin. Noxious activity evoked by radiant heat (51 degrees C, 8 sec) was extracellularly recorded from single discriminated wide dynamic range (WDR) neurons in decerebrate spinally transected cats. DAGO (mu selective opioid agonist) 1 microgram or DPDPE (delta selective opioid agonist) 30 micrograms was combined with serotonin (n = 6 each) 250 micrograms. The dose of each drug by itself when administered intrathecally produced no suppression of noxiously evoked activity. Although the combination of DAGO and serotonin produced no significant suppression of noxiously evoked activity, DPDPE and serotonin produced significant suppression to 72.8 +/- 8.0 % (mean +/- SEM) of control values (P < 0.01). Intravenously administered naloxone 0.1 mg reversed the suppression produced by the DPDPE-serotonin combination. Our results suggest that combinations of serotonin and delta selective opiates may be more effective in suppressing noxiously evoked activity than combinations with mu selective opiates.

Animals↗
PubMed1994

Synergistic antinociceptive interaction after epidural coadministration of morphine and lidocaine in rats.

BACKGROUND: Clinically, epidural coadministration of opioids and local anesthetics has provided excellent analgesia for various types of pain. However, information about the interaction of these drugs when administered epidurally is limited. Therefore, we evaluated the antinociceptive interaction between morphine and lidocaine on both somatic and visceral noxious stimuli in the rat. METHODS: Male Sprague-Dawley rats weighing 300-350 g had epidural catheters implanted at T13-L1. Every rat was tested with both the tail flick test, a somatic noxious stimulus, and the colorectal distension test, a visceral noxious stimulus. In the colorectal distension test, the response threshold was defined by the pressure within the intracolonic balloon required to trigger abdominal contraction. Tail flick latency and colorectal distension threshold were measured before and for 180 min after the administration of morphine, lidocaine, or combinations of those drugs. To characterize the interaction, isobolographic analysis was performed with a fixed morphine: lidocaine dose ratio of 1:1,000. RESULTS: Epidural morphine (0.1-10 micrograms) and lidocaine (100-800 micrograms) increased the tail flick latency and colorectal distension threshold in a dose- and time-dependent fashion. The epidural injection of morphine (0.1-1 microgram) mixed with lidocaine (100 or 200 micrograms) significantly increased the peak effect and prolonged the duration of effects compared with each drug alone in both nociceptive tests. Areas under the curves, calculated to express overall magnitude and duration of antinociceptive effects, were significantly increased by combinations as compared with each drug alone, especially with morphine 0.1 microgram and lidocaine 100 or 200 micrograms, each of which alone produced no change in the area under the curve. Isobolographic analysis revealed that epidural morphine and lidocaine interact synergistically at 10, 20, and 30 min after injection in both somatic and visceral nociception tests. Both potency ratio analysis and fractional analysis confirmed the finding of the isobolographic analysis. Epidural naloxone antagonized the antinociceptive effects produced by the combination. CONCLUSION: These data demonstrate that epidurally coadministered morphine and lidocaine produce synergistic analgesia and prolong the duration of analgesia in tests of somatic and of visceral nociception.

Analgesia↗
PubMed1994

Effects of a Porphyromonas gingivalis infection on inflammatory mediator response and pregnancy outcome in hamsters.

This study examines the effects of various localized, nondissemination challenges of Porphyromonas gingivalis on inflammatory mediator production and pregnancy outcome in the golden hamster. Live or heat-killed (HK) organisms were inoculated into a previously implanted subcutaneous tissue chamber on the 8th day of gestation to determine the effects on fetal weight, viability, and resorption. In one group of animals, HK organisms were inoculated prior to mating to determine the effects of previous exposure on day-8 gestational challenges. Chamber contents were assayed at 1 and 5 days after challenge for prostaglandin E2 (PGE2) and tumor necrosis factor alpha (TNF-alpha). All P. gingivalis challenges caused a significant increase in chamber PGE2 and TNF-alpha at P < 0.01 in the following order of potency: HK < Live < HK+Live. For example, following the HK+Live challenge, PGE2 levels increased from 4.7 pg/ml at baseline to 362 pg/ml at day 5 and TNF-alpha increased from 26.4 pg/ml to 724 pg/ml at day 5. The same order of potency of the various challenges was maintained with regard to the toxic effects of P. gingivalis on pregnancy outcome. For the HK+Live challenge, fetal weight was decreased 24%; embryolethality increased to 26.5% and the percent fetal resorption increased to 10.6% compared with control animal levels. There was a statistically significant association between increasing levels of both PGE2 and TNF-alpha and fetal growth retardation and embryolethality at P < 0.001. These data suggest that infections with gram-negative periodontal pathogens can elicit adverse pregnancy outcomes and that the levels of PGE2 and TNF-alpha produced as a result of challenge are associated with the severity of fetal effect.

Animals↗
PubMed1994

Effects of Escherichia coli and Porphyromonas gingivalis lipopolysaccharide on pregnancy outcome in the golden hamster.

This report describes the effects of two gram-negative bacterial endotoxin (lipopolysaccharide [LPS]) preparations on hamster pregnancy outcome variables. Single intravenous challenges with Escherichia coli and Porphyromonas gingivalis LPS on day 8 of pregnancy produced dose-dependent effects on fetal weight malformation and fetal resorption with E. coli LPS having potent embryolethal effects. Premating maternal exposure to P. gingivalis produced embryolethal effects similar to those of E. coli. These data suggest that maternal exposure to P. gingivalis LPS prior to and during pregnancy can induce deleterious effects on the developing fetus.

Abnormalities, Drug-Induced↗
PubMed1993

A 19F NMR study of the interaction of 3-fluoro-4-demethoxydaunomycin with the hexanucleotide d(TCCGGA)2.

19F NMR spectroscopy has been used to study the binding of the fluorinated anthracycline 3-fluoro-4-demethoxydaunomycin with the hexanucleotide d(TCCGGA)2. In the spectrum of the 1:1 anthracycline-d(TCCGGA)2 complex four resonances of approximately equal intensity were observed. This indicated that 4-demethoxydaunomycin intercalated at all possible sites with similar affinity. This suggests that the specific high affinity binding sites that are observed in anthracycline-DNA footprinting experiments are strongly regulated by the local DNA conformation.

Base Sequence↗
PubMed1993

Exchange reactions catalyzed by group-transferring enzymes oppose the quantitation and the unravelling of the identify of the pentose pathway.

1. The distributions and rates of transfer of carbon isotopes from a selection of specifically labelled ketosugar-phosphate substrates by exchange reactions catalyzed by the pentose and photosynthetic carbon-reduction-pathway group-transferring enzymes transketolase, transaldolase and aldolase have been measured using 13C-NMR spectroscopy. 2. The rates of these exchange reactions were 5, 4 and 1.5 mumol min-1 mg-1 for transketolase exchange, transaldolase exchange and aldolase exchange, respectively. 3. A comparison of the exchange capacities contributed by the activities of these enzymes in three in vitro liver preparations with the maximum non-oxidative pentose pathway flux rates of the preparations shows that transketolase and aldolase exchanges exceeded flux by 9-19 times in liver cytosol and acetone powder enzyme preparations and by 5 times in hepatocytes. Transaldolase was less effective in the comparison of exchange versus flux rates: transaldolase exchange exceeded flux by 1.6 and 5 in catalysis by liver cytosol and acetone powder preparations, respectively, but was only 0.6 times the flux in hepatocytes. 4. Values of group enzyme exchange and pathway flux rates in the above three preparations are important because of the feature role of liver and of these particular preparations in the establishment, elucidation and measurement of a proposed reaction scheme for the fat-cell-type pentose pathway in biochemistry. 5. It is the claim of this paper that the excess of exchange rate activity (particularly transketolase exchange) over pathway flux will overturn attempts to unravel, using isotopically labelled sugar substrates, the identity, reaction sequence and quantitative contribution of the pentose pathway to glucose metabolism. 6. The transketolase exchange reactions relative to the pentose pathway flux rates in normal, regenerating and foetal liver, Morris hepatomas, mammary carcinoma, melanoma, colonic epithelium, spinach chloroplasts and epididymal fat tissue show that transketolase exchange may exceed flux in these tissues by factors ranging over 5-600 times. 7. The confusion of pentose pathway theory by the effects of transketolase exchange action is illustrated by the 13C-NMR spectrum of the hexose 6-phosphate products of ribose 5-phosphate dissimilation, formed after 30 min of liver enzyme action, and shows 13C-labelling in carbons 1 and 3 of glucose 6-phosphate with ratios which range over 2.1-6.4 rather than the mandatory value of 2 which is imposed by the theoretical mechanism of the pathway.

Animals↗
PubMed1993

Trends in medical care and survival from stroke.

Using data from two national surveys in the United States, the National Hospital Discharge Survey and the National Health Interview Survey, we examined whether the incidence of stroke (based on hospitalization rates), the prevalence of stroke, and disability due to stroke had changed. Discharge rates remained virtually constant from 1970 through 1990. At the same time, the proportion of patients who were treated with surgery or other diagnostic procedures increased from 15 to 57% and the proportion who were discharged dead decreased from 20 to 8%. The data suggest that the incidence has not decreased. Hospitalization rates for stroke have changed very little over the past 20 years. Further, neither the prevalence nor the burden of stroke appear to have increased.

Adult↗
PubMed1993

Flurbiprofen in the prevention and treatment of experimental gingivitis.

A clinical trial was undertaken to examine the effects of a potent cyclooxygenase inhibitor, flurbiprofen, on both developing and established gingivitis in humans. 21 subjects with healthy gingiva abstained from all oral hygiene procedures for 21 days. 7 subjects were prescribed flurbiprofen, 50 mg b.d. beginning from baseline and a control group (Cl, n = 14) were given placebo. Gingival redness and bleeding on probing were assessed at baseline, 7, 14 and 21 days. Crevicular fluid (GCF) samples were also taken to determine concentrations of PGE2, TxB2 and LTB4 at baseline and at 21 days. Results show that flurbiprofen significantly inhibited the development of redness and bleeding (p < 0.001) effects which were associated with a significant inhibition of TxB2 (p < 0.05). There were no apparent flurbiprofen effects on GCF-PGE2 or GCF-LTB4 during this 21-day gingivitis, model To assess the effects of flurbiprofen on established experimental gingivitis, the model was extended to 28 days. On day 21, the Cl group was subdivided into 2 groups of 7 subjects. One group was prescribed flurbiprofen (50 mg b.d.) for 7 days and controls (C2) continued to take placebo. All subjects continued to abstain from tooth cleaning. Pretreatment (day 21) and post-treatment (day 28) comparisons showed that flurbiprofen again significantly inhibited bleeding (p < 0.001), but did not affect redness. Control subjects demonstrated a significant elevation in gingival bleeding on day 28, and this was associated with significant rises in GCF-PGE2 (p < 0.001), GCF-TxB2 (p < 0.01) and GCF-LTB4 (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Changes in crevicular fluid levels of interleukin-1 beta, leukotriene B4, prostaglandin E2, thromboxane B2 and tumour necrosis factor alpha in experimental gingivitis in humans.

We conducted a study to determine the sequence of cytokine and lipid mediator activation within the periodontium during the development of experimental gingivitis in humans. Crevicular fluid samples were collected from 7 previously cleaned, healthy patients at baseline, 1, 2, 3 and 4 weeks following the cessation of all oral hygiene measures. Gingival and plaque scores were taken at each visit to follow the development of gingivitis and plaque retention. Crevicular fluid samples were assayed in quadruplicate for prostaglandin E2 (PGE2), thromboxane B2 (TxB2), leukotriene B4, interleukin-1 beta (IL-1 beta) and tumour necrosis factor alpha (TNF alpha) by RIAs or ELISAs, maintaining site pairing to examine temporal changes. Redness scores (expressed as mean percentage of sites with redness present) increased almost linearly from a baseline value of zero to approximately 40% at 1 week, 59% at 2 weeks, 83% at 3 weeks and 100% at 4 weeks. The mean % of sites with bleeding on probing increased gradually from zero at baseline to 5% at 3 weeks and then rose abruptly to 25% at 4 weeks. CF-PGE2 and CF-TxB2 levels remained fairly stable at baseline levels for the first 3 weeks then rose sharply by 2.5- and 2-fold, respectively, at 4 weeks. CF-LTB4 levels increased 2-fold by 1 week and 4-fold by 4 weeks. The CF levels of IL-1 beta increased abruptly from mean baseline values of 16.5 +/- 9.3 ng/ml to 131 +/- 76.0 ng/ml at 1 week and remained at this level for the duration of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

New clinical diagnostic strategies based on pathogenesis of disease.

The pathogenesis of periodontal tissue destruction involves the orchestrated sequential activation of several components of the host response, each of which have the potential for providing diagnostic information regarding the health or disease status of the periodontium. These events include the bacterial triggering of serum components, the release of vasoactive compounds, the recruitment of inflammatory cells, the activation of phagocytes, the local secretion of immunoglobulins and inflammatory mediators, as well as connective tissue remodeling. For purposes of diagnosis, much attention has been directed toward the measurement of local levels of specific byproducts of the pathogenic process either within the tissues or in the adjacent crevicular fluid. These are site-directed assessments of the local concentration of these byproducts, and with the important exception of antibody levels, very few byproducts of the periodontal pathogenic process have been studied on a systemic level. However, since the risk associated with periodontal disease progression is primarily patient-based and secondarily site-based, there is an increasing need to identify patients at risk for intervention strategies. Furthermore, there are substantial data that periodontal diseases are specific infections that occur in an appropriately susceptible host. The expression of periodontal disease has a strong genetic component, which presumably defines the host's response thereby affecting susceptibility. For this reason, there is increased interest in defining those elements of the host response which result in susceptibility to disease. The ultimate objective of a diagnostic strategy is to identify patients who are potentially at risk for acquiring disease to enable preventive measures.

Antibodies, Bacterial↗
PubMed1993

Changes in inflammatory mediators in experimental periodontitis in the rhesus monkey.

Ligature-induced periodontitis was monitored for 6 months in eight Macaca mulatta monkeys to examine clinical status, radiographic bone level, and crevicular fluid (CF) levels of prostaglandin E2 (PGE2), thromboxane B2 (TxB2), interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha, and leukotriene B4 (LTB4). A split-mouth design was used, with eight ligated teeth and eight contralateral nonligated teeth which develop soft-chow-promoted (spontaneous) disease. Ligated sites experienced an average attachment loss of 0.94 mm per site and linear bone loss of 0.88 mm per site, with spontaneous-periodontitis sites experiencing approximately half the loss of ligated sites. The CF mediator levels showed increased levels of PGE2 and TxB2 at the ligated sites, as compared with the spontaneous sites, with no significant contralateral differences in the IL-1 beta or LTB4 responses. The concentrations of LTB4 in CF reached an early threefold peak over the baseline level at 1 month. By 2 months there was a statistically significant threefold elevation in CF-PGE2 in the ligated sites and a twofold elevation in the spontaneous sites as compared to the baseline level (P = 0.041 and 0.008, respectively). The monocyte product IL-1 beta increased sharply at 2 months and returned to the baseline level by 6 months at both ligated and nonligated sites. Tumor necrosis factor alpha in CF was below the limit of detection at all sites throughout the experiment (i.e., < 2 ng/ml). The selective elevation of both PGE2 and TxB2 in ligated sites, compared with levels in spontaneous sites, in the presence of similar levels of LTB4 and IL-1 beta provides further evidence that these molecules regulate the magnitude of the tissue-destructive response in progressive periodontitis.

Animals↗
PubMed1993

Diagnostic potential of host response mediators.

This review summarizes the data which relate the validation and application of host response markers as diagnostic tests for periodontal diseases. Practical considerations regarding the general application and evaluation of a diagnostic test for periodontal disease are presented. Experiments which have documented the performance of host response markers as diagnostic measures of disease activity in terms of sensitivity, specificity, and predictive values are summarized. Particular emphasis is placed on the diagnostic potential of gingival crevicular fluid (GCF) components. The considerable body of evidence supporting the potential application of GCF-PGE2 levels for predicting episodes of disease progression and reflecting disease activity is summarized and placed into perspective for the development of future diagnostic tools.

Biomarkers↗
PubMed1993

Effects of a combination therapy to eliminate Porphyromonas gingivalis in refractory periodontitis.

This report describes the clinical and microbiological features of 30 refractory patients and their response to a combined local and systemic therapy at 6 weeks and 3 years following treatment. The refractory treatment protocol (RefTx) consisted of a 2-week regimen of amoxicillin/clavulanate potassium in conjunction with professional, intrasulcular delivery of povidone iodine, and chlorhexide mouthwash rinses b.i.d. Eighty-seven percent of the patients had favorable clinical responses to the RefTx and could be divided into 3 groups (A, B, C) based upon initial flora patterns and the shifts that occurred following treatment. Pretreatment prevalence of Porphyromonas gingivalis (P.g.) was 36.7%. The RefTx was effective in reducing P.g. below detection levels in 10 of the 11 positive patients at P < 0.01; each of these 10 patients (Group A) demonstrated significant gain in attachment. Other black-pigmented Bacteroides species (OBP) were isolated from 70% of the patients at baseline. Nine of these patients did not harbor P.g., showed clinical improvement upon treatment, and were OBP negative following treatment (Group B). Group C patients (7) demonstrated clinical improvement with therapy and did not fit into either Group A or B based upon microbial patterns. Group D patients (4) did not show clinical improvement with 3 patients harboring either P.g. or OBP after treatment. The RefTx was effective at reducing probing pocket depth with a 56% decrease in the number of pockets greater than 6 mm at 6 weeks. This was accompanied by an overall gain of > or = 1 mm of probable attachment in 45% of all sites. The clinical effects of the RefTx were shown to persist at 34.3 months with an apparent attachment gain of > or = 1 mm in 41.2% of sites. These data suggest that P.g. and OBP are important pathogens in refractory periodontitis and that the RefTx protocol is an acceptable, non-invasive alternative for the management of these patients.

Adult↗
PubMed1993

Modulation of host PGE2 secretion as a determinant of periodontal disease expression.

An increasing body of evidence supports the concept that host-produced PGE2 mediates much of the tissue destruction that occurs in periodontal disease. PGE2 levels within the crevicular fluid can serve as a static assessment of ongoing disease activity; i.e., rate of attachment loss and bone resorption. New insights into the mechanisms that regulate PGE2 synthesis provide an altered paradigm of periodontal disease which places the emphasis on host response, rather than the bacterial etiology, as the principal determinant of disease expression. We described a PGE2 host response model as a hypothetical framework to discuss new, possible explanations for host susceptibility to periodontal disease.

Animals↗
PubMed1993

Health characteristics of large metropolitan statistical areas: United States, 1988-89.

Annual average estimates of rates or percents of limitation of activity, respondent-assessed health status, restricted-activity days, bed-disability days, work-loss days, school-loss days, physician utilization, hospital utilization, incidence of selected acute conditions, and prevalence of selected chronic conditions are shown by geographic region for all large U.S. metropolitan statistical areas combined and for individual metropolitan statistical areas with populations of at least 1.1 million persons.

Absenteeism↗