Biomedical subjects

N Martin

Publications and source records attributed to N Martin.

At least 91 records · Page 5Linked to original sources

PubMed1999

Development of anticipatory postural adjustments in a bimanual load-lifting task in children.

Anticipatory postural adjustments (APA) are needed to perform a movement without perturbing posture. We investigated the development of APA in 3- to 4-year-old children during a bimanual load-lifting task. The task required maintaining a stable elbow position despite imposed or voluntary unloading of the forearm. Although children can compensate the consequences of unloading by using APA, their performance did not reach an adults' level. In addition, children showed high intra-individual variability in the voluntary situation, revealed by the coexistence of both adult-like and immature patterns in kinematic and electromyographic data. In conclusion, the present study reports that APA, associated with a bimanual load-lifting task, are still being set up in 3- to 4-year-old-children. The intra-individual variability should decrease with age and be associated with a progressive mastering of the timing parameters characterizing APA.

Biomechanical Phenomena↗

PubMed1999

Kinematic synergies and equilibrium control during trunk movement under loaded and unloaded conditions.

The aim of the present investigation was to study the adaptation of the kinematic synergy responsible for equilibrium control during upper trunk movements to a 10-kg load added to the subject's shoulders. Five adult subjects were asked to bend their upper trunk forward to an angle of 35 degrees and then to hold the final position for 3 s, first without any load and then with a 10-kg load fixed to their shoulders. The final anteroposterior CM positions 400 ms after the movement offset, the time course of the anteroposterior center of mass (CM) shift during the movement, the EMG pattern of the main muscles involved in the movement and the initial CP shift were studied under both unloaded and loaded conditions. The kinematic synergy was quantified by performing a principal components analysis on the hip, knee and ankle angle changes occurring during the movement. The results indicate that: (1) the final anteroposterior position of the CM changed little if at all in the presence of the additional load, and that the anteroposterior CM shift was minimized throughout the duration of the movement; (2) the kinematic synergy was still characterized, in the presence of the additional load, by a strong coupling between the angle changes, as indicated by the fact that the first principal component (PC1) accounted for more than 99% of the hip, knee and ankle joint movements. A change was observed, however, in the ratio between the angles: the ankle extension increased, thus compensating for the additional theoretical forward CM shift that the additional load could be expected to cause; (3) the lack of change in the initial backward CP shift observed under loaded condition as well as the lack of change of the initial agonist EMG bursts suggest that the initial feedforward control of the kinematic synergy was not affected in the presence of the additional load. An increase in the antagonist bursts, presumably reflecting an adaptation of the kinematic synergy, was observed during the late phase of the movement; and (4) it is concluded that the adaptation of the kinematic synergy to the load was due to a specific change in the feedback control during the braking phase of the movement which presumably increases the ankle joint extension and consequently causes an increased backward shift of the hip which compensates for the forward shift due to the load.

Adult↗

PubMed1999

Clinical performance of CEREC ceramic inlays: a systematic review.

OBJECTIVE: This systematic review of clinical trials seeks to identify the clinical performance of intra-coronal CEREC restorations luted with an adhesive composite technique. The focus of the review is to establish the survival rate of these restorations and to identify the factors that may cause them to fail. METHOD: A comprehensive literature search was undertaken, spanning from the year of introduction of the technology--1986 to 1997. This review identifies universal indicators of the clinical performance of intra-coronal CEREC restorations luted with an adhesive composite technique. Throughout the critical appraisal, each individual study was analysed identifying the aims, the methodology and materials used and the results obtained. RESULTS: 29 clinical reports were identified in the search. The systematic analysis reduced the focus of review to 15 studies. The data available establishes ceramic intra-coronal restorations machined by the CEREC system as a clinically successful restorative method with a mean survival rate of 97.4% over a period of 4.2 years. The review also highlights the reasons and the rates of failure for this type of restoration. The predominant reasons for failures are fracture of the ceramic, fracture of the supporting tooth, postoperative hypersensitivity and wear of the interface lute. SIGNIFICANCE: Machinable ceramics, as used by the CEREC system provide a useful restoration with a high success rate. These restorations are color stable and wear at a clinically acceptable rate. Wear of the luting composite on occlusal surfaces leads to the phenomenon of submargination. Ceramic fracture, wear at the interface and post-operative hypersensitivity remain a problem which require further investigation.

Ceramics↗

PubMed1999

Exposure to N-nitroso compounds in a population of high liver cancer regions in Thailand: volatile nitrosamine (VNA) levels in Thai food.

The recent case-control studies in Thailand indicate that a high incidence of liver cancer in Thailand has not been associated with common risk factors such as hepatitis B infection, aflatoxin intake and alcohol consumption. While the infestation by the liver fluke Opisthorchis viverrini (OV) accounted for the high risk in north-east Thailand, there was no such exposure in the other regions of the country where the incidence of liver cancer is also high. Case-control studies suggest that exposure to exogenous and possibly endogenous nitrosamines in food or tobacco in betel nut and cigarettes may play a role in the development of hepatocellular carcinoma (HCC), while OV infestation and chemical interaction of nitrosamines may also be aetiological factors in the development of cholangiocarcinoma (CCA). Over 1800 samples of fresh and preserved food were systematically collected and tested between 1988 and 1996. All the food items identified by anthropological studies to be consumed frequently in four major regions of Thailand were analysed for volatile nitrosamines using gas chromatography combined with a thermal energy analyser. Relatively high levels of N-nitrosodimethylamine (NDMA), N-nitrosopiperidine (NPIP) and N-nitrosopyrrolidine (NPYR) were detected in fermented fish ("Plasalid"). NDMA was also detected at levels ranging from trace amounts to 66.5 microg/kg in several salted and dried fish ("Larb-pla" and "Pla-siu"). NDMA and NPYR were frequently detected in several vegetables, particularly fermented beans ("Tau-chiau") at levels ranging between 1 and 95.1 microg/kg and 0-146 microg/kg, respectively. The possible role of nitrosamines in Thai food in the aetiology of liver cancer (HCC, CCA) is discussed.

Case-Control Studies↗

PubMed1999

Cuspal deflection during polymerisation of composite lutes of ceramic inlays.

OBJECTIVE: The purpose of this study was to measure the cuspal deflection that occurs in teeth as a result of the dimensional changes of resin-based lutes during polymerisation. METHODS: Standardised MOD cavities were cut in 15 intact human premolar teeth using a custom paralleling device. A ceramic inlay was machined by the CEREC 2 system for each tooth ensuring an interface width of 50 microns (SD = 17.5) at the cavity margin. The 15 teeth were divided into three groups of five according to the cementation system employed: a microfilled hybrid posterior composite; a compomer restorative; a dual-cure luting composite. The inter-cuspal tooth dimension was recorded continuously with a laser micrometer assembly during a 2 min photoactivation period and a further 30 min post-activation period. RESULTS: A clear overall reduction in tooth dimension was detectable for the first 10 min of polymerisation. The mean changes ranged from -0.02% to -0.06% depending on the nature of the luting material. In addition, all samples exhibited a slight expansion of 0.03% during the time of light-activation. CONCLUSIONS: The dimensional changes that teeth experience during the polymerisation of resin-based lutes are clearly detectable. It can be postulated that an increase in the dimensions of the teeth during photoactivation occurs as a result of expansion of the lute due to the thermal energy delivered.

Analysis of Variance↗

PubMed1999

Complex genetic and environmental relationships between psychological distress, fatigue and immune functioning: a twin study.

BACKGROUND: Although there is considerable support for adverse relationships between states of psychological and somatic distress and immune response, there is little evidence in humans of the relative contribution of genetic and environmental factors. METHODS: This study utilized a twin methodology to examine the interplay between psychological distress, fatigue and immune function. We recorded a number of measures of distress, including conventional depression and anxiety as well as the somatic symptom of prolonged fatigue, and immune responsiveness (by delayed-type hypersensitivity skin response) in 124 normal adult twin pairs (79 monozygotic, 45 dizygotic). RESULTS: While there were strong genetic influences on the psychological distress and fatigue factors (only some of which are common to both), familial aggregation of immune responsiveness arose mainly from environmental factors shared by both members of a twin pair. Phenotypic correlations between psychological and immune measures were negligible, but multivariate genetic modelling revealed that these masked larger genetic and environmental correlations of opposite sign. Negative environmental effects of psychological distress and fatigue on immune responsiveness were countered by a positive genetic relationship between psychological distress and immune function. CONCLUSIONS: Our study suggests that current psychoneuroimmunological hypotheses in humans need to be modified to place increasing importance on the individual's genotype. In this cohort immune responsiveness varied in response to a complex interplay of genetic and environmental factors. Additionally, although psychological distress and fatigue had some shared genetic determinants, independent genetic and environmental risk factors for fatigue were also identified.

Adult↗

PubMed1999

Unique genetic and environmental determinants of prolonged fatigue: a twin study.

BACKGROUND: Prolonged fatigue syndromes have been proposed as prevalent and disabling forms of distress that occur independently of conventional notions of anxiety and depression. METHODS: To investigate the genetic and environmental antecedents of common forms of psychological and somatic distress, we measured fatigue, anxiety, depression and psychological distress in 1004 normal adult twin pairs (533 monozygotic (MZ), 471 dizygotic (DZ)) over 50 years of age. RESULTS: Familial aggregation of psychological distress, anxiety and fatigue appeared to be due largely to additive genetic factors (MZ:DZ ratios of 2.12-2.69). The phenotypic correlations between the psychological measures (distress, anxiety and depression) were moderate (0.67-0.79) and higher than that between fatigue and psychological distress (0.38). Multivariate genetic modelling revealed a common genetic factor contributing to the development of all the observed phenotypes (though most strongly for the psychological forms), a second independent genetic factor also influenced anxiety and depression and a third independent genetic factor made a major contribution to fatigue alone. In total, 44% (95% CI 25-60%) of the genetic variance for fatigue was not shared by the other forms of distress. Similarly, the environmental factor determining psychological distress made negligible contributions to fatigue, which was underpinned largely by its own independent environmental factor. CONCLUSION: This study supports the aetiological independence of prolonged fatigue and, therefore, argues strongly for its inclusion in classification systems in psychiatry.

Anxiety Disorders↗

PubMed1999

Is disabling fatigue in childhood influenced by genes?

BACKGROUND: Medically unexplained chronic fatigue in childhood may cause considerable disability and (by definition) its cause remains unclear. A study of fatigue in healthy twins has been undertaken to examine whether or not genetic factors play a part. METHOD: A questionnaire survey of the main carers of an epidemiological population-based sample of 670 twin pairs who were asked about periods of unexplained and disabling fatigue in their twins. Out of 1340 individuals a period of disabling fatigue was reported for 92 (6.9%). Thirty-three (2.5%) reported disabling fatigue for more than 1 month. Zygosity could be confidently assigned in 98% of the sample providing 278 monozygotic (MZ) and 378 dizygotic (DZ) pairs. These data were analysed using a structural equation modelling approach. RESULTS: The results showed that disabling fatigue in childhood is highly familial with an MZ tetrachoric correlation (rMZ) of 0.81 and a DZ tetrachoric correlation (rDZ) of 0.59, for fatigue lasting at least a week. The most acceptable model using Akaike's information criteria, was one containing additive genetic effects (A) and shared environment (C) plus residual (or non-shared) environment (E). For fatigue lasting at least a month rMZ was 0.75 and rDZ 0.47. The most acceptable model included just A and E. However, the role of shared environment could not be conclusively rejected. CONCLUSIONS: Unexplained disabling fatigue in childhood is substantially familial. Both genetic and shared environmental factors are worth further exploration in a search for the causes.

Adolescent↗

PubMed1999

Contribution to the knowledge of malolactic fermentation influence on wine aroma.

In this work, we study two aspects of malolactic fermentation: the use of industrial lactic acid bacteria starter-cultures in a white Sauvignon wine and the effects of the bacterial activity on the composition of wines in terms of volatile substances from oakwood during partial malolactic fermentation in barrels. A sensory evaluation was made by the use of discriminative and descriptive methods. The consequences of bacterial development are thus limited, but it is nevertheless possible to make characteristic observations. The carbonyl substances were formed in connection with a more or less fast bacterial growth and a degradation of the citric acid. However, the influence of the bacterial starter-culture is difficult to establish. The concentration of the compounds resulting from wood was higher in the wines after malolactic fermentation compared to a wine not having undergone bacterial development. Greater complexity was perceived during the sensory analysis, with buttered, spiced, roasted, vanilla, and smoked notes. On the other hand, the intensity of the descriptors characteristic of grape variety decreased.

Analysis of Variance↗

PubMed1999

Combinatorial approach to flavor analysis. 1. Preparation and characterization of a S-methyl thioester library.

A new method for the "one-pot" synthesis of S-methyl thioesters has been developed by reacting methyl chlorothiolformate with carboxylic acids. The resulting "flavor library" contained all the intended thioesters and a single major impurity, identified by GC-MS as S, S-dimethyldithiocarbonate. Quantification of individual compounds present in the library was performed by GC analysis using two independent methods of detection, SCD and FID. It was shown that apart from S-methyl thioacetate (0.8 mol %), molar concentrations of other thioesters varied in a relatively narrow range from 4.2 mol % for S-methyl thiopropionate to 14.1 mol % for S-methyl thiohexanoate. In general, medium chain S-methyl thioesters were present in slightly higher molar concentrations than those prepared from short or long chain carboxylic acids. This variation was attributed to partial loss of the most volatile components during extraction and the lower reactivity of higher homologues. The library was used for the characterization of some physicochemical parameters of thioesters. In particular, lipophilicity coefficients (log k(w)) and thioester retention in 10, 20, and 33% triolein (used as a model lipid phase) were determined directly by reverse-phase HPLC and extrapolated from the respective data. This analysis illustrates that substantial information can be generated using a library containing a relatively large number of compounds in effectively the same way as is necessary for the analysis of a single sample.

Chromatography, Gas↗

PubMed1999

Combinatorial approach to flavor analysis. 2. Olfactory investigation of a library of S-methyl thioesters and sensory evaluation of selected components.

The odor characteristics of individual components present in a library comprised of S-methyl thioesters were determined independently by two laboratories using similar but not identical techniques. The odor potency was assessed by values of best estimate-GC-lower amount detected by sniffing (BE-GC-LOADS). For small and medium chain S-methyl thioesters, these values were found to increase from 6 ng for S-methyl thiobutanoate to 90 ng for S-methyl thiostearate. All assessors detected a "green", "floral", or "pineapple" odor for S-methyl thiohexanoate and described thioesters containing a 2-6 carbon chain length as "cheesy". The results of this preliminary analysis were confirmed by a more extensive study of selected compounds, namely S-methyl thioacetate, S-methyl thiopropionate, S-methyl thiobutanoate, and S-methyl thiohexanoate, using a trained panel of 18 subjects. The subjects confirmed the presence of the "green" and "fruity" notes in the odor of S-methyl thiohexanoate. The analysis also revealed a significant difference in the odor of S-methyl thiopropionate relative to that of S-methyl thioacetate and S-methyl thiobutanoate. When "cheesy" characteristics were mentioned, the majority of panelists clearly associated the flavor of S-methyl thiopropionate with Camembert with almost 20% of all the descriptors given referring specifically to this cheese variety as compared to about 2 and 5% in the case of S-methyl thioacetate and thiobutanoate, respectively. Prompted by this observation, two samples of Camembert prepared from unpasteurized and pasteurized milk were analyzed and relatively large amounts of S-methyl thiopropionate were found in the former but not in the latter cheese. The results obtained in the course of this work suggest that the sensory analysis of combinatorial libraries is a useful new approach in the search for new commercial flavors and/or identification of characteristic flavors in foods.

Chromatography, Gas↗

PubMed1999

Supporting individuals with intellectual disability and challenging behaviour in integrated work settings: an overview and a model for service provision.

An overview of supported employment and its historical context is examined, and supported employment for individuals with both intellectual disability and challenging behaviour is discussed. A proposed model for working with such individuals is briefly outlined. This model is based on previous work in the field, and is characterized by a multi-component approach which addresses the issues of both support and behavioural intervention.

Behavior Therapy↗

PubMed1999

Are doctors still failing to assess and treat asthma attacks? An audit of the management of acute attacks in a health district.

This audit aimed to observe the management of acute asthma by primary and secondary care within a Health District. Asthma attacks occurring during the first 6 weeks of 1996 to patients between the ages of 3 and 74 years in Canterbury and Thanet District were notified by general practitioners, out-of-hours co-operatives and hospitals. Data were obtained retrospectively from the patient records. A total of 378 episodes was registered: 342 (90%) to primary care. Of these 234 (76% of patients aged 6 years or over) had a peak flow recorded; 114 (30%) were given emergency bronchodilation: oxygen was not used in primary care; 204 (54%) were given systemic steroids; and 43 (11%) were referred for hospital care of whom 36 were admitted. Of the attacks, 212 (69% of the patients aged 6 years or over) could be classified by percentage predicted peak flow and management compared to the Guidelines published by the British Thoracic Society. Twenty-eight patients presented with 'life-threatening' asthma: 20 (71%) were given emergency bronchodilation; oxygen was used in only two; 24 (86%) were given systemic steroids; and six (21%) were referred for admission. In their confidential enquiry into the asthma deaths the British Thoracic Society identified a failure to appreciate the severity of the attack, resulting in inadequate emergency treatment and delay in referring to hospital. These data suggest that, 15 years later, these problems may still exist.

Acute Disease↗

PubMed1999

The heat moisture exchange device (HME) in neonatal ventilation.

The objective of this study was to compare the safety and efficacy of the Heat Moisture Exchange (HME) device with conventional humidification in neonates. Sixty-four neonates were randomized at intubation to receive conventional humidification (CH) (n = 34) or HME, via a Neoaid device (n = 30). Groups were compared for intrinsic characteristics and outcome variables. Data were assumed nonparametric and analyzed by Mann-Whitney and Fisher's Exact test. No significant differences were found in group characteristics or outcome variables. Trends were noted for documented patent ductus arteriosus (PDA), endotracheal tube blockage, and positive endotracheal aspirate culture. Rate of pneumothorax 2/34 (CH) versus 4/30 (HME) (p = 0.4); rate of tube blockage 3/34 (CH) versus 2/30 (HME) (p = 1.0); rate of PDA 8/34 (CH) versus 14/30 (HME) (p = 0.093) and rate of endotracheal colonisation 1 7/34 (CH) versus 9/30 (HME) (p = 0.17). No significant difference was found for duration of ventilation or period in greater than 40% oxygen between the two groups. There were no significant outcome differences between CH and HME. The HME device was cost-effective and simple to use. A larger multicenter trial is warranted to confirm the efficacy of HME.

Equipment Design↗

PubMed1999

Volatile nitrosamines and tobacco-specific nitrosamines in the smoke of Thai cigarettes: a risk factor for lung cancer and a suspected risk factor for liver cancer in Thailand.

In Thailand, smoking of commercial cigarettes and of handmade cigarettes has drastically increased in recent decades. Cancer of the lung and of the upper aero-digestive tract have also increased in Thailand as they have in many other countries. It is our working hypothesis that the increase of primary cancer of the liver, especially of cholangiocarcinoma in the north-eastern provinces of Thailand is associated with the use of tobacco in men infested with the liver fluke Opisthorchis viverrini (OV). Bioassays have shown that volatile nitrosamines and tobacco-specific nitrosamines induce cholangiocarcinoma in laboratory animals and that the hepatocarcinogenic action of nitrosodimethylamine in hamsters is significantly increased by infestation with the liver fluke OV. The endogenous formation of nitrosamines is significantly increased by OV infestation. This report presents analytical data on the concentration of volatile nitrosamines and tobacco-specific nitrosamines in mainstream smoke of nine leading brands of commercially produced Thai cigarettes which represent approximately 85% of the market share in Thailand. Observed ranges (ng/cigarette) were 8.5-31.9 for nitrosodimethylamine, 8.8-49.6 for nitrosopyrrolidine and 4.2-18.9 for nitrosodi-n-butylamine. These values are exceptionally high compared with the smoke of light and blended cigarettes from North America and Western Europe. Among the tobacco-specific nitrosamines, the range was 28-730 for nitrosonornicotine and 16-370 for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. There was a correlation between volatile and tobacco-specific nitrosamines, and tar and nicotine deliveries in the mainstream smoke. The analytical data are in line with the rate for lung cancer and support our working hypothesis that nitrosamines, and especially the tobacco-specific nitrosamines, are associated with the increased risk for primary liver cancer among those Thai people who smoke cigarettes and also carry OV infestation.

Bile Duct Neoplasms↗

PubMed1999

Intestinal volvulus in dogs: a study of four clinical cases.

Four cases of intestinal volvulus in German shepherd dogs are described. A definitive diagnosis was achieved by exploratory laparotomy in three cases and after necropsy in the remaining animal. Clinical signs, laboratory investigations and radiological changes are reported for three of the dogs. These dogs were all euthanased. Treatment of complete intestinal volvulus is difficult. By the time the condition is diagnosed, the pathological changes are irreversible, with consequent poor prognosis.

Animals↗

PubMed1999

Comparative in vitro activities of ciprofloxacin, clinafloxacin, gatifloxacin, levofloxacin, moxifloxacin, and trovafloxacin against Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, and Enterobacter aerogenes clinical isolates with alterations in GyrA and ParC proteins.

The in vitro activities of ciprofloxacin, clinafloxacin, gatifloxacin, levofloxacin, moxifloxacin, and trovafloxacin were tested against 72 ciprofloxacin-resistant and 28 ciprofloxacin-susceptible isolates of Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, and Enterobacter aerogenes. Irrespective of the alterations in GyrA and ParC proteins, clinafloxacin exhibited greater activity than all other fluoroquinolones tested against K. pneumoniae and E. aerogenes.

Anti-Infective Agents↗

PubMed1999

Production of sulfur flavors by ten strains of Geotrichum candidum.

Ten strains of Geotrichum candidum were studied on a liquid cheese model medium for the production of sulfur compounds which contribute to the aroma of cheeses. The volatile components produced by each cultured strain were extracted by dynamic headspace extractions, separated and quantified by gas chromatography (GC), and identified by GC-mass spectrometry. It was shown that four strains of this microorganism produced significant quantities of S-methyl thioacetate, S-methyl thiopropionate, S-methyl thiobutanoate, S-methyl thioisobutanoate, S-methyl thioisovalerate, and S-methyl thiohexanoate. This is the first example of the production of these compounds by a fungus. In addition, dimethyldisulfide, dimethyltrisulfide, dimethylsulfide, and methanethiol, which are more commonly associated with the development of cheese flavor in bacterial cultures, were also produced by G. candidum in various yields, depending on the strain selected. The potential application of these strains in cultured microbial associations to produce modified cheeses with more desirable organoleptic properties is discussed.

Cheese↗