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Biomedical subjects

A Martin

Publications and source records attributed to A Martin.

At least 361 records · Page 20Linked to original sources
PubMed1996

Neural correlates of category-specific knowledge.

An intriguing and puzzling consequence of damage to the human brain is selective loss of knowledge about a specific category of objects. One patient may be unable to identify or name living things, whereas another may have selective difficulty identifying man-made objects. To investigate the neural correlates of this remarkable dissociation, we used positron emission tomography to map regions of the normal brain that are associated with naming animals and tools. We found that naming pictures of animals and tools was associated with bilateral activation of the ventral temporal lobes and Broca's area. In addition, naming animals selectively activated the left medial occipital lobe--a region involved in the earliest stages of visual processing. In contrast, naming tools selectively activated a left premotor area also activated by imagined hand movements, and an area in the left middle temporal gyrus also activated by the generation of action words. Thus the brain regions active during object identification are dependent, in part, on the intrinsic properties of the object presented.

Brain↗
PubMed1996

Hypervigilance in patients with obsessive-compulsive disorder.

The hypothesis that patients with obsessive-compulsive disorder (OCD) suffer from hypervigilant attention was investigated via explicit memory (incidental recall and recognition) and priming (reading speed) measures. OCD patients did not differ from normal controls on explicit measures of memory; specifically, recognition of unusual words (experiment 1) and recall and recognition of words and feature-specific information (experiment 2). Although both normal controls and OCD patients showed priming, the pattern of priming differed for the two groups (experiment 2). Specifically, patients with OCD failed to show feature-specific priming, suggesting they may have attended more focally on the priming task than did normal controls. These findings support previous reports of normal performance in OCD on explicit memory tasks, but suggest more sensitive measures may reflect differences in processing information.

Adult↗
PubMed1996

The Duffy antigen receptor for chemokines: structural analysis and expression in the brain.

The Duffy antigen receptor for chemokines (DARC) is expressed in human erythrocytes and on endothelial cells lining postcapillary venules in kidney and spleen. DARC is a promiscuous chemokine receptor and a binding protein for the malarial parasite Plasmodium vivax. The expression of DARC by subsets of endothelial cells and neurons in discrete anatomic sites in the brain suggests that this enigmatic receptor may have multiple roles in normal and pathological physiology. Conservation of this promiscuous chemokine binding function is evident from the similarity in nucleotide sequence of DARC homologues from multiple species, as well as the high-affinity binding of human chemokines to murine and avian erythrocytes. Analysis of the functional domains of DARC using chimeric receptors and and monoclonal antibodies to multiple extracellular domains localized chemokine binding to structures in the amino terminal extracellular domain (E1). Scatchard analysis demonstrated that a chimeric DARC receptor, composed of the E1 domain of DARC and the predicted hydrophobic helices and loops of interleukin-8RB (IL-8RB), bound IL-8, and MGSA with KD values almost identical to the wild type receptors and bound a repertoire of C-X-C and C-C chemokines characteristic of DARC. Although numerous reports have demonstrated that chemokines such as IL-8 are expressed in the brain, presumably by glial cells, little insight into the nature of their role in normal or pathological physiology in the nervous system has developed because the target cells that express the corresponding receptors have not yet been identified. Northern blotting experiments suggest that mRNA encoding DARC are expressed in the central nervous system, however, interpretation of this is unclear because of the ubiquitous expression of DARC lining postcapillary venules. This study provides direct evidence to localize expression of DARC in the central nervous system. Immunohistochemical examination of human archival sections of the brain with monoclonal antibodies specific for DARC localize expression of DARC to cell bodies and processes of Purkinjie cells in the cerebellum. The immunohistochemical findings were supported by analysis of chemokine binding and radioligand crosslinking with membranes made from various brain fractions. The hierarchical expression of DARC in neurons in the cerebellum suggest that chemokines may play an important role in the modulation of neuronal activity by glial cells.

Animals↗
PubMed1996

Co-activation and tension-regulating phenomena during isokinetic knee extension in sedentary and highly skilled humans.

The aim of this study was to examine isokinetic torque produced by highly skilled (HS) and sedentary (S) human subjects, during knee extension, during maximal voluntary and superimposed electrical activation. To verify the level of activation of agonist (vastus lateralis, VL, and vastus medialis, VM) and antagonist muscles (semi-tendineous, ST), during maximal voluntary activation, their myo-electrical activities were detected and quantified as root mean square (rms) amplitude. Ten HS and ten S subjects performed voluntary and superimposed isometric actions and isokinetic knee extensions at 14 angular velocities (from -120 to 300 degrees*s(-1)). The rms amplitude of each muscle was normalized with respect to its rms amplitude when acting as agonist at 15 degrees*s(-1). Whatever the angular velocity considered, peak torque and constant angular torque at 65 degrees of HS were significantly higher (P <0.05) than those of S. Eccentric superimposed torque of S, but not HS, was significantly higher (P <0.05) than voluntary torque at -120, -90, - 60 and - 30 degrees*s(-1) angular velocities. For a given velocity, the rms amplitude of VL and VM were significantly lower (P <0.05), during eccentric than during concentric actions, in S, but not in HS. However, whatever the angular velocity, ST co-activation in HS was significantly lower (P < 0.05) than in S. We concluded that co-activation phenomenon could partly explain differences in isokinetic performances. Differences between voluntary and superimposed eccentric torques as well as lower agonist rms amplitude during eccentric action in S, support the possibility of the presence of a tension-regulating mechanism in sedentary subjects.

Adult↗
PubMed1996

Viscosity of the elbow flexor muscles during maximal eccentric and concentric actions.

The aim of the present study was to estimate the damping coefficient (B factor) of the elbow flexor muscles during both eccentric and concentric muscle actions. We used a muscle model consisting of a viscous damper associated in parallel with a contractile component, both in series with an elastic component. The viscous damper allowed the concentric loss and the eccentric gain of force to be modelled. Eight volunteer subjects performed maximal eccentric and concentric elbow movements on an isokinetic dynamometer at angular velocities of 0.52, 1.04 and 2.09 rad*s(-1). Torques at an elbow joint angle of 90 degrees were recorded. Electromyogram (EMG) signals from the belly of the right elbow flexor and from the long head of the triceps brachia muscles were recorded using two pairs of bipolar surface electrodes. The root mean square (rms) of the EMG was determined. Eccentric and concentric rms were not significantly different (P >0.05). The B factor was higher in the concentric than in the eccentric conditions (P <0.05), and, whatever the muscle action type it decreased as the velocity increased. These results indicated that the concentric loss and the eccentric gain of force were attributable to the behaviour of the contractile machinery. Furthermore, whatever the exact cause of loss and gain of tension, our study showed that the total effect can be modelled by the viscous damper of a three-component muscle model.

Adult↗
PubMed1996

Epidermal growth factor receptor and c-erbB-2 expression in normal breast tissue during the menstrual cycle.

EGF receptor (EGF-R) and c-erbB-2 are homologous tyrosine kinase transmembrane receptors. They are involved in controlling proliferation, and probably differentiation, of normal breast epithelial cells, and their expression has been linked to the prognosis of breast cancer. Their physiological roles in normal breast tissue remain to be elucidated, as most studies to date have involved breast cancer cell lines. We studied the location of EGF-R and c-erbB-2 in 100 samples of normal breast with standard immunohistochemical methods and double-labelling techniques. EGF-R was mainly expressed on the stroma and myoepithelial cells, whereas c-erbB-2 expression was exclusively epithelial. An image analyser was used to quantitate variations in their expression during the menstrual cycle. EGF-R and c-erbB-2 expression on epithelial cells was stronger during the luteal phase than the follicular phase (p < 0.01 for EGF-R). The pattern of expression was also compared with that in 28 breast cancers and 7 fibroadenomas.

Breast↗
PubMed1996

Electrogastroenterographic examination of 22 patients before and after cholecystectomy.

The object of this study was to define the pattern of gastrointestinal myoelectrical activity before and after cholecystectomy. After surgery, on the first postoperative day, the mean and maximal activities of the gastrointestinal tracts decreased significantly, but there was no significant change in the pattern and the duration of the nonreactive period. A dyskinetic effect and/or weakness of electrical activity was observed in all patients before operation, and the same pattern persisted after operation for one month. This suggests the future onset of the so-called postcholecystectomy syndrome, which may result from the fundamental pathological effect of gallstones.

Adult↗
PubMed1996

A double-blind comparison of venlafaxine and fluoxetine for treatment of major depression in outpatients.

1. This was a randomized, double-blind comparison of the efficacy and safety of venlafaxine and fluoxetine in outpatients with major depression. 2. Three hundred fourteen patients were randomly assigned to either venlafaxine 37.5 mg twice daily or fluoxetine 20 mg once daily for a maximum of 8 weeks. 3. If the response was inadequate after two weeks of treatment, the dosage of venlafaxine could be increased to 75 mg twice daily. 4. A clinical response, defined as at least a 50% decrease from baseline in the total HAM-D score, was attained at week 6 in 72% of patients on venlafaxine and 60% of patients on fluoxetine (p = 0.023). 5. Among patients who increased their dose at 2 weeks, venlafaxine was significantly (p < 0.05) superior from week 3 onward on the HAM-D. 6. Venlafaxine 75 mg daily is comparable to fluoxetine, but at 150 mg daily, it may be superior to fluoxetine in outpatients with major depression who do not respond early to treatment.

Adult↗
PubMed1996

Effect of vitamin E on hydrogen peroxide production by human vascular endothelial cells after hypoxia/reoxygenation.

Changes in oxidative stress status play an important role in tissue injury associated with ischemia -- reperfusion events such as those that occur during stroke and myocardial infarction. Endothelial cells (EC) from human saphenous vein and aorta were incubated for 22 h and found to take up vitamin E from media containing 0-60 mM vitamin E in a dose-dependent manner. EC supplemented with 23 or 28 mM vitamin E in the media for 22 h were maintained at normoxia (20% O2, 5% CO2, and balance N2) or exposed to hypoxic conditions (3% O2, 5% CO2, and balance N2) for 12 h, followed by reoxygenation (20% O2) for 30 min. Saphenous EC supplemented with 23 mM vitamin E produced less (p < 0.05) H2O2 than unsupplemented controls, both at normoxic condition (supplemented: 4.9 +/- 0.05 vs. control: 10.9 +/- 1.3 pmol/min/10(6) cells) and following hypoxia/reoxygenation (supplemented: 6.4 +/- 0.78 vs. control: 17.0 +/- 2.7 nmol/min/10(6) cells). In contrast, aortic EC, which were found to have higher superoxide dismutase and catalase activity than EC from saphenous vein, did not produce any detectable levels of H2O2. Following hypoxia/reoxygenation, the concentration of vitamin E in supplemented saphenous EC was 62% lower than cells maintained at normoxia (0.19 +/- 0.03 vs. 0.5 +/- 0.12 nmoles/10(6) cells, p < 0.001); in aortic EC vitamin E content was reduced by 18% following reoxygenation (0.86 +/- 0.16 vs. 0.70 +/- 0.09 nmoles/10(6) cells, p < 0.05). Therefore, enrichment of vitamin E in EC decreases H2O2 production and thus may reduce the injury associated with ischemia-reperfusion events.

Antioxidants↗
PubMed1996

Effect of vitamin E on human aortic endothelial cell responses to oxidative injury.

Reactive oxygen species produced by the cells present in the arterial wall may cause oxidative damage to cellular components altering endothelial cell (EC) function. Changes in the EC function appear to play a key role in the pathogenesis of atherosclerosis. Human aortic endothelial cells (HAEC) were employed to investigate the protective role of vitamin E upon exposure of endothelial cells to oxidative stress in vitro. HAEC assimilate d-alpha-tocopherol from the media in a dose-dependent manner. Exposure of HAEC to 16.5 mM of the free radical generator 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH) for 16 h decreased cell viability (assessed by trypan blue exclusion) from 90 to 28%. HAEC preincubated with vitamin E at 15, 30, and 60 microM prior to the AAPH exposure resulted in a dose-dependent increase in resistance to oxidative stress and increased cell viability by 37, 66, and 85%, respectively. An increase in prostacyclin (PGI2) production by HAEC in response to AAPH exposure was correlated positively with cell damage and negatively with vitamin E concentration. Interleukin (IL)-1 production also increased in parallel with cell damage induced by AAPH. Vitamin E treatment significantly reduced IL-1 production after AAPH exposure. This modulatory role of vitamin E on HAEC function following exposure to an oxidative stress may reflect its antioxidant protection against lipid peroxidation.

Amidines↗
PubMed1996

An evaluation of the Filshie clip for postpartum sterilization in Austria.

Voluntary sterilization is a popular method of family size limitation. Among other techniques for surgical induction of female sterility, the application of various kinds of clips to the Fallopian tubes has been introduced. The Filshie clips consist of rubber-lined titanium and their use for interval sterilization has been repeatedly published. So far, there are only a few reports regarding the use of Filshie clips during the postpartum period, when tubes are edematous and more friable. Therefore, 300 women voluntarily requesting postpartum surgical sterilization for the purpose of family size limitation were enrolled into a prospective trial. Within 72 h of delivery, 282 women were sterilized under general anesthesia using a subumbilical minilaparotomy approach and Filshie clip application. Of these women, 251 were available for follow-up examination at 6 weeks, 240 at 6 months, 234 at 12 months, and 209 at 24 months after the sterilization procedure. Complication rates were low, and there were no pregnancies during the follow-up period. These results indicate that the application of Filshie clips is a safe and efficacious method of surgical female sterilization in the postpartum period.

Adult↗
PubMed1996

Use of the complete genome sequence information of Haemophilus influenzae strain Rd to investigate lipopolysaccharide biosynthesis.

The availability of the complete 1.83-megabase-pair sequence of the Haemophilus influenzae strain Rd genome has facilitated significant progress in investigating the biology of H.influenzae lipopolysaccharide (LPS), a major virulence determinant of this human pathogen. By searching the H. influenzae genomic database, with sequences of known LPS biosynthetic genes from other organisms, we identified and then cloned 25 candidate LPS genes. Construction of mutant strains and characterization of the LPS by reactivity with monoclonal antibodies, PAGE fractionation patterns and electrospray mass spectrometry comparative analysis have confirmed a potential role in LPS biosynthesis for the majority of these candidate genes. Virulence studies in the infant rat have allowed us to estimate the minimal LPS structure required for intravascular dissemination. This study is one of the first to demonstrate the rapidity, economy and completeness with which novel biological information can be accessed once the complete genome sequence of an organism is available.

Animals↗
PubMed1996

Large differences in substitutional pattern and evolutionary rate of 12S ribosomal RNA genes.

We demonstrate using Drosophila, periodical cicadas, and hominid primates, that the molecular clock based on animal mitochondrial small-subunit (12S) rRNA genes ticks at significantly different relative rates depending on which taxa and which region of the gene are examined. Drosophila, which are commonly used as model taxa, are evolving in a highly peculiar manner with the majority of sites in the 3' half of the 12S gene apparently invariant. The analogous 3' half of the mitochondrial large-subunit rRNA gene (16S) appears to be similarly constrained. It is surprising that these regions that are already highly constrained in all animals should be even more constrained in Drosophila, especially when the Drosophila mitochondrial genome as a whole does not display a similar rate slowdown. This extreme 12S rate slowdown is not apparent in periodical cicadas or hominid primates and appears to be related to strong structural and functional constraints rather than a depressed mutation rate. Finally, the slow average rate of evolution in the third domain of Drosophila does not imply that the few variable sites lack multiple hits.

Animals↗
PubMed1996

Meeting the needs of home care patients 24 hours a day.

Meeting the patient care needs after the regular work day requires agencies to have a well-planned, comprehensive extended-hours program. This description of a large agency's approach to providing this service can be helpful to all agencies, regardless of size and location.

Community Health Nursing↗
PubMed1996

Dehydroepiandrosterone does not prevent adrenocorticotrophin-induced hypertension in conscious rats.

1. We tested the hypothesis that dehydroepiandrosterone (DHEA), which prevents dexamethasone-induced hypertension in rats, may block adrenocorticotrophin (ACTH) hypertension, which has been presumed due to corticosterone excess. The blood pressure and metabolic effects of DHEA (18 mg/kg per day) were examined in sham and ACTH-treated (0.5 mg/kg per day) conscious Sprague-Dawley rates (n = 20). 2. ACTH but not sham injection increased blood pressure, water intake and urine output and decreased bodyweight. 3. DHEA administration for 10 days did not alter blood pressure or metabolic effects in either sham or ACTH-treated rats. 4. DHEA, which is known to block dexamethasone-induced hypertension, did not modify ACTH-induced hypertension in the rat. This suggests either that ACTH-induced hypertension is not simply a consequence of glucocorticoid activity or that the action of DHEA in dexamethasone hypertension is not through blocking the glucocorticoid receptor.

Adrenocorticotropic Hormone↗
PubMed1996

The use of antioxidants in healing.

BACKGROUND: Antioxidants enhance the healing of infected and noninfected wounds by reducing the damage caused by oxygen radicals. OBJECTIVE: Studies were conducted to determine if the CTR components (vitamin E, sodium pyruvate, and specific fatty acids) could synergistically enhance healing. METHODS: In vitro and in vivo studies were used to assess the effect of various combinations of CRT components. RESULTS: CTR reduced oxidative damage to keratinocytes and monocytes exposed to ultraviolet light and toxic chemicals and provided protection to human subjects exposed to ultraviolet irradiation. CTR dramatically facilitated healing of infected and noninfected wounds. In herpes-infected guinea pigs, CTR reduced vaginal viral lesion development, severity, and duration, thus facilitated healing of the lesions. CTR also reversed doxorubicin cytotoxicity in monocytes and reversed doxorubicin-impaired wound healing in rats. CONCLUSION: The CTR components worked synergistically to enhancing healing of injuries.

Animals↗