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Biomedical subjects

R Buck

Publications and source records attributed to R Buck.

At least 19 recordsLinked to original sources
PubMed2006

Bioaccessible arsenic in the home environment in southwest England.

Samples of household dust and garden soil were collected from twenty households in the vicinity of an ex-mining site in southwest England and from nine households in a control village. All samples were analysed by ICP-MS for pseudo-total arsenic (As) concentrations and the results show clearly elevated levels, with maximum As concentrations of 486 microg g(-1) in housedusts and 471 microg g(-1) in garden soils (and mean concentrations of 149 microg g(-1) and 262 microg g(-1), respectively). Arsenic concentrations in all samples from the mining area exceeded the UK Soil Guideline Value (SGV) of 20 microg g(-1). No significant correlation was observed between garden soil and housedust As concentrations. Bioaccessible As concentrations were determined in a small subset of samples using the Physiologically Based Extraction Test (PBET). For the stomach phase of the PBET, bioaccessibility percentages of 10-20% were generally recorded. Higher percentages (generally 30-45%) were recorded in the intestine phases with a maximum value (for one of the housedusts) of 59%. Data from the mining area were used, together with default values for soil ingestion rates and infant body weights from the Contaminated Land Exposure Assessment (CLEA) model, to derive estimates of As intake for infants and small children (0-6 years old). Dose estimates of up to 3.53 microg kg(-1) bw day(-1) for housedusts and 2.43 microg kg(-1) bw day(-1) for garden soils were calculated, compared to the index dose used for the derivation of the SGV of 0.3 microg kg(-1) bw day(-1) (based on health risk assessments). The index dose was exceeded by 75% (18 out of 24) of the estimated As doses that were calculated for children aged 0-6 years, a group which is particularly at risk from exposure via soil and dust ingestion. The results of the present study support the concerns expressed by previous authors about the significant As contamination in southwest England and the potential implications for human health.

Air Pollution, Indoor↗
PubMed2006

Association between concentrations of urinary type II collagen neoepitope (uTIINE) and joint space narrowing in patients with knee osteoarthritis.

OBJECTIVE: To examine whether urine concentrations of type II collagen neoepitope (uTIINE) distinguish subjects with progressive radiographic and/or symptomatic knee osteoarthritis (OA) from those with stable disease. METHODS: Subjects were 120 obese middle-aged women with unilateral knee OA who participated in a 30-month randomized-controlled trial of structure modification with doxycycline, in which a standardized semiflexed anteroposterior view of the knee was obtained at baseline, 16 months and 30 months. Subjects were selected from a larger sample to permit a priori comparisons between 60 OA progressors and 60 nonprogressors, as defined by joint space narrowing (JSN) in the medial tibiofemoral compartment. Each group contained 30 subjects who exhibited clinically significant increases in knee pain over 30 months and 30 who did not. Urine samples were obtained every 6 months for determination of the creatinine (Cr)-adjusted uTIINE concentration. RESULTS: Baseline uTIINE levels were unrelated to JSN in the placebo group. However, among subjects in the active treatment group, a 1-standard deviation increment in baseline uTIINE (68 ng/mM Cr) was associated with a marginally significant, two-fold increase in the odds of progression of JSN (odds ratio 2.04, 95% confidence interval 0.98-4.28). The within-subject mean of uTIINE values at baseline, 6 months and 12 months was associated with concurrent JSN measured at 16 months (0.10mm of JSN per 69 ng/mM Cr, P=0.008). Similar results were seen in the interval between months 16 and 30 and in analyses using the maximum of intercurrent uTIINE levels. CONCLUSION: Baseline uTIINE was not a consistent predictor of JSN in subjects with knee OA. However, serial measurements of uTIINE reflect concurrent JSN.

Anti-Bacterial Agents↗
PubMed2004

The effect of essential oils on methicillin-resistant Staphylococcus aureus using a dressing model.

Patchouli, tea tree, geranium, lavender essential oils and Citricidal (grapefruit seed extract) were used singly and in combination to assess their anti-bacterial activity against three strains of Staphylococcus aureus: Oxford S. aureus NCTC 6571 (Oxford strain), Epidemic methicillin-resistant S. aureus (EMRSA 15) and MRSA (untypable). The individual essential oils, extracts and combinations were impregnated into filter paper discs and placed on the surface of agar plates, pre-seeded with the appropriate strain of Staphylococcus. The effects of the vapours of the oils and oil combinations were also assessed using impregnated filter paper discs that were placed on the underside of the Petri dish lid at a distance of 8mm from the bacteria. The most inhibitory combinations of oils for each strain were used in a dressing model constructed using a four layers of dressings: the primary layer consisted of either Jelonet or TelfaClear with or without Flamazine; the second was a layer of gauze, the third a layer of Gamgee and the final layer was Crepe bandage. The oil combinations were placed in either the gauze or the Gamgee layer. This four-layered dressing was placed over the seeded agar plate, incubated for 24h at 37 degrees C and the zones of inhibition measured. All experiments were repeated on three separate occasions. No anti-bacterial effects were observed when Flamazine was smeared on the gauze in the dressing model. When Telfaclear was used as the primary layer in the dressing model compared to Jelonet, greater zones of inhibition were observed. A combination of Citricidal and geranium oil showed the greatest-anti-bacterial effects against MRSA, whilst a combination of geranium and tea tree oil was most active against the methicillin-sensitive S. aureus (Oxford strain). This study demonstrates the potential of essential oils and essential oil vapours as antibacterial agents and for use in the treatment of MRSA infection.

Anti-Bacterial Agents↗
PubMed2001

Affective-prosodic deficits in schizophrenia: comparison to patients with brain damage and relation to schizophrenic symptoms [corrected].

OBJECTIVE: Although affective prosody seems to be a dominant and lateralised communication function of the right hemisphere, focal lesions of either hemisphere may cause problems with its modulation. When impairment occurs after brain damage, the profiles of affective-prosodic disturbances differ depending on the hemisphere injured. Patients with left brain damage (LBD) improve their performance whereas patients with right brain damage (RBD) do not when the verbal-articulatory demands of the test stimuli are reduced systematically. One of the major arguments for a right hemispheric contribution to schizophrenia has been the documentation of affective prosodic deficits under the assumption that these abnormalities reflect right hemispheric dysfunction. Thus, an essential question to resolve is whether the profile of affective prosodic disturbances in schizophrenia is similar to LBD or RBD, or represents a unique variation. METHODS: Data were collected from four subject groups: 45 chronic, medication-stabilised, schizophrenic patients, 10 patients with focal LBD, nine patients with focal RBD, and 19 controls. All groups were tested on the aprosodia battery, which uses stimuli having incrementally reduced verbal-articulatory demands. Schizophrenic and aphasic symptoms were evaluated using standard assessment tools. RESULTS: For patients with impaired performance on the aprosodia battery, schizophrenic patients were statistically identical to patients with RBD and robustly different from those with LBD. Thirty eight schizophrenic patients (84.4%) were found to have some type of affective prosodic deficit with the predominant pattern indicating, at minimum, right posterior sylvian dysfunction (57.8%). When schizophrenic symptoms and aprosodic deficits were examined using a principal component analysis, affective comprehension and repetition loaded uniquely as separate factors. CONCLUSIONS: The profile of affective-prosodic deficits found in impaired schizophrenic patients is characteristic of RBD, supporting the concept that schizophrenia is a bihemispheric disease process. These deficits may also represent cardinal symptoms of schizophrenia as they are highly prevalent and, except for spontaneous affective prosody, are not associated statistically with traditional clusters of schizophrenic symptoms.

Adult↗
PubMed1999

In vitro disinfection of dentinal tubules by various endodontics irrigants.

Effectiveness of endodontic irrigants within dentinal tubules of human teeth was evaluated. Mid-sections of single-rooted teeth were prepared into dentin wedges. The pulpal sides of the sections were exposed to Micrococcus luteus or Bacillus megaterium that grew into the tubules. Irrigants used in the study included: 0.525% NaOCl, 0.12% chlorhexidine, RC Prep, 0.5% betadine iodine, and sterile H2O (as a control). Pulpal surfaces were exposed to an irrigant and then rinsed in sterile water. The samples were then cracked, exposing a fresh surface. Culture of the exposed dentin surfaces showed that selected irrigants reached to the far ends of the dentinal tubules in a concentration sufficient to kill 100% of the M. luteus. However B. megaterium was neither killed nor apparently inhibited by any irrigant. We conclude that endodontic irrigants permeate throughout dentinal tubules, but their effectiveness is dependent on the type of bacteria found within the tubules.

Adult↗
PubMed1999

The biological affects: a typology.

This typology of biological affects is based on developmental-interactionist theory of motivation, emotion, and cognition. Affects--subjectively experienced feelings and desires--involve interoceptive perceptual systems based on primordial molecules that characterize neurochemicals. Biological affects involve primary motivational-emotional systems (primes) associated with hierarchically organized neurochemical systems in the brain, including subcortical (reptilian) and paleocortical (limbic) brain structures. Affects fulfill individualistic (selfish) functions (arousal, approach-avoidance, agonistic) and prosocial (cooperative) functions. Selfish and cooperative functions are associated respectively with the right and left hemispheres. Biological affects constitute the physiological bases for higher level affects: social affects (e.g., pride, guilt, shame, pity, jealousy), cognitive affects (e.g., curiosity, surprise), and moral affects.

Animals↗
PubMed1995

Free alpha-subunits of human chorionic gonadotropin in preeclampsia.

OBJECTIVE: To investigate free alpha-human chorionic gonadotropin (hCG) as a marker of preeclampsia. METHODS: Four groups of patients were studied: normal pregnancies, preeclampsia, eclampsia and normal pregnant women <20 weeks' gestation. Patients were further divided according to parity and gestational age (< or =20, 21-30, 31-40 weeks). An immunoradiometric assay employing monoclonal antibodies specific for free alpha-hCG was used. RESULTS: A total of 313 patients were analyzed. Thirty-four patients < or =20 weeks' gestation were followed until delivery: five (14.7%) developed preeclampsia; none had abnormal alpha-hCG levels before onset of preeclampsia. Patients with preeclampsia (21-30 weeks' gestation) demonstrated a mean alpha-hCG level greater than that of normotensive controls but this was not statistically significant. Between 31 and 40 weeks' gestation, mean alpha-hCG levels in the hypertensive and control groups were 210.8 ng/ml and 115.8 ng/ml, respectively (P < 0.001). A stronger association was observed between alpha-hCG and preeclampsia with increasing gestational age (relative risk [RR] 2.07, 21-30 weeks; RR 3.02, 31-40 weeks) and severity (RR 4.51, mild; RR 12.15, severe; RR 16.88, eclampsia). CONCLUSION: There is a strong association between alpha-hCG and preeclampsia, nevertheless this test is unsuitable for predicting preeclampsia.

Biomarkers↗
PubMed1995

Is the human chorionic gonadotropin secreted by ectopic trophoblast different from that in normal intrauterine pregnancies?

OBJECTIVE: To determine whether different isoforms of hCG are secreted by trophoblast tissue from ectopic pregnancy (EP). DESIGN: Retrospective study of surgically confirmed EPs compared with normal pregnancies. SETTING: Teaching hospital in South Africa. PATIENTS: One hundred patients with EPs and 120 patients with normal pregnancies. MAIN OUTCOME MEASURES: Isoforms of hCG were measured by specific immunoassays, lectin binding, and examination of disappearance rates of hCG after surgical clearance of EP. RESULTS: There were no obvious differences between the two types of pregnancy apart from a lower binding of beta-subunit immunoactivity to ricin 120. No clinically useful diagnostic measures to distinguish hCG from normal and EPs were found. CONCLUSIONS: No obvious differences were found in the isoforms of hCG between the two types of pregnancy using these methods.

Blood↗
PubMed1995

Effect of maternal glucocorticoid exposure on risk of severe intraventricular hemorrhage in surfactant-treated preterm infants.

OBJECTIVE: To determine whether the reduced risk of severe intraventricular hemorrhage (SIVH) that follows antenatal maternal glucocorticoid (AMG) receipt is mediated by an AMG effect on blood pressure or improved respiratory function in infants who receive artificial surfactant as rescue therapy. DESIGN: Retrospective cohort study. SETTING: Two level III neonatal intensive care units, Boston, Mass. PARTICIPANTS: Two hundred twenty-five infants < or = 32 weeks of gestational age and < or = 1.7 kg birth weight, treated with surfactant. MAIN FINDINGS: SIVH occurred in 10% (10/102) of infants who were exposed to AMG, compared with 23% (25/111) of infants not exposed (odds ratio, 0.4; 95% confidence interval, 0.2 to 0.8). Hypotension and need for colloid or dopamine were associated with both SIVH and the absence of AMG exposure (p < or = 0.03). Logistic regression models of SIVH risk and AMG exposure, with adjustment for antenatal potential confounders, were altered by the addition of measures of hypotension. Most clinical measures of pulmonary function, both before and after surfactant receipt, were not associated with reduced risk of SIVH and did not appear to account for the increased risk of SIVH in babies not exposed to AMG. CONCLUSION: The reduced risk of SIVH in preterm newborn infants whose mothers received AMG was associated with normal blood pressures. The association between AMG and SIVH was not consistently enhanced by respiratory function improvement after surfactant therapy.

Cerebral Hemorrhage↗
PubMed1994

Social and emotional functions in facial expression and communication: the readout hypothesis.

Fridlund (Fridlund, A.J. (1991). Biological Psychology, 32, 3-100) has argued that facial displays are specific to intent and context, rather than being readouts of underlying motivational-emotional states. This paper responds that these views are not incompatible, and that subjective emotional experience functions in part to enhance the learned control of emotional expression and communication. It summarizes the readout position, answers Fridlund's criticisms identifying it with the different notion of "spillover," and contends that the expressive readout functions in spontaneous communication. Fridlund's assertions that the readout is a reflex-like process, and that the readout view has ignored the receiver's coevolutionary role in communication, are addressed. Evidence supporting the readout view is presented, including studies suggesting that there are hierarchically organized neurochemical systems underlying subjective, expressive, and peripheral physiological responses. Such primary motivational-emotional systems (primes) are basic to the readout theory.

Animals↗
PubMed1994

Hyponatremic natriuretic syndrome in tuberculous meningitis: the probable role of atrial natriuretic peptide.

Hyponatremia has been reported in up to one third of patients with intracranial disease and has frequently been associated with tuberculous meningitis, often complicated by hydrocephalus. The lowered plasma sodium levels were previously attributed to the syndrome of inappropriate secretion of antidiuretic hormone. A controlled prospective study of 24 patients with tuberculous meningitis and hydrocephalus was carried out. Analyses of serum electrolytes and cerebrospinal fluid were performed. Plasma and cerebrospinal fluid levels of atrial natriuretic peptide (ANP) and antidiuretic hormone (ADH) were measured by radioimmunoassay. Fifteen patients were found to be hyponatremic (plasma sodium < 130 mmol/L) and ANP levels of 12 to 1,488 pg/ml were present (median, 26 pg/ml). The remaining 9 patients had normal plasma sodium values between 130 and 145 mmol/L, and in these, plasma ANP values varied between 12 and 21.7 pg/ml (median, 12 pg/ml). The difference between these two groups was not statistically significant. (Control values from patients undergoing myelography were established to range between 12 and 40 pg/ml; median, 14.4 pg/ml.) ANP levels were undetectable in the cerebrospinal fluid in all. Plasma ADH levels in the hyponatremic group were between 7 and 159 pg/ml (median, 40 pg/ml). In the normonatremic group, plasma ADH levels of 25 to 250 pg/ml (median, 29 pg/ml) were obtained. (The controls ranged between 3.6 and 35 pg/ml; median, 10.4 pg/ml). In the hyponatremic group, there was a moderate negative correlation (r = -0.683) between plasma ANP and plasma sodium (P = 0.02). No correlation between plasma ADH and plasma sodium was found (r = -0.168; P = 0.62).(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Factor↗
PubMed1994

Pulmonary hemorrhage risk in infants with a clinically diagnosed patent ductus arteriosus: a retrospective cohort study.

OBJECTIVE: To determine if an early, clinically detectable patent ductus arteriosus (PDA) was associated with pulmonary hemorrhage (PH) in infants who received rescue artificial surfactant therapy. METHODS: This retrospective cohort study of 233 low birth weight infants (< or = 1700 g) who received artificial surfactant therapy for respiratory distress syndrome compared antenatal and postnatal characteristics of infants with PH and without PH. Pulmonary hemorrhage was defined by an onset of bright red blood from the endotracheal tube in quantities that resulted in increased ventilatory support and a new infiltrate on a chest radiograph. RESULTS: Pulmonary hemorrhage occurred in 6% (15/233) of the infants. Thirty-three percent (5/15) of the infants with PH died within 14 days of the hemorrhage. Of the 15 PH, 73% occurred within 48 hours of the first surfactant dose. Pulmonary hemorrhage was more common in male infants and infants of mothers who received antibiotic therapy during labor (P < or = .04). Infants with PH received surfactant earlier than those without PH (P = .04). Nursery events or therapies occurring following surfactant therapy that were associated with PH included: little improvement in ventilatory efficiency index (P = .01), dopamine infusion (P = .04), and the presence of a clinically detectable PDA before, or at the time of, the PH [60% (9/15) vs 33% (71/217), P = .03]. After adjusting for severity of illness before surfactant therapy, risk of PH remained greater in infants who developed symptoms of a PDA. Dopamine support appeared to modify the association between PDA and PH. CONCLUSIONS: In this retrospective cohort study, pulmonary hemorrhage, was associated with the presence of a clinically detectable patent ductus arteriosus before, or at the time of, pulmonary hemorrhage.

Cohort Studies↗
PubMed1993

Separation of nicked human chorionic gonadotropin (hCG), intact hCG, and hCG beta fragment from standard reference preparations and raw urine samples.

hCG is found in pregnancy urine and in urine from some cancer patients in a variety of forms whose concentrations have clinical importance. Recently, concerns about accurate measurement of these forms have been raised because of the finding that hCG with peptide bond cleavages within the beta-subunit is not recognized by commonly used antibodies. Such nicked forms of hCG are biologically inactive or of very low activity. They are present in normal pregnancy urine and to varying extents in the urine of patients with trophoblastic disease. International reference preparations of hCG contain nicked forms of hCG. Previously, it was not possible to separate nicked hormone from the intact form of hCG. This was a serious impediment to producing improved reference standards from natural pregnancy hormone. We now report that a simple hydrophobic purification scheme separates intact hCG from nicked hCG as well as from hCG beta core fragment. This scheme is a modification of the method of Hiyama et al. The order of elution from low to high hydrophobicity is hCG beta core fragment, nicked hCG, and lastly, intact hCG. Nicking of the putative amphipathic helix loop, hCG beta 38-57, apparently renders the hormone significantly less hydrophobic despite the equal molar content of sialic acid. The hCG CR 127 nicked preparation was only 10% as potent as the reference preparation in a heterodimer-directed assay. The nicked-depleted hCG CR 127 was 30% more potent in this assay. Improved hCG reference standards should display similar increases in immunopotency (20-30%) with most antiheterodimeric antibodies and similar increases in bio-potency assays. It should now be possible to make reference preparations of these forms of hCG directly from the raw urine of normal pregnant patients and those with trophoblastic disease.

Amino Acid Sequence↗