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Biomedical subjects

D Martin

Publications and source records attributed to D Martin.

At least 487 records · Page 27Linked to original sources
PubMed1993

The effects of resistance level on muscle coordination patterns and movement profile during trunk extension.

The objective of this research was to investigate the effects of varying resistance level on patterns of muscle activity and trunk motion during the performance of dynamic trunk extension. Twenty-five female subjects were tested at four resistance levels: nominal resistance, and 30%, 50%, and 70% of maximum isometric extension strength. Peak truncal velocity, acceleration, and deceleration decreased with increased resistance, although no difference existed between the nominal and 30% maximum voluntary contraction (MVC) conditions. Coactivation of abdominal muscles was present at all resistance levels, although it was greater for the nominal resistance condition than the other conditions. The timing of EMG activity of the extensor and abdominal muscles was significantly affected by resistance. The amplitude and time course of peak muscle activity are discussed in terms of the implications for spinal loading.

Abdominal Muscles↗
PubMed1993

Risk factors for complications of chronic anticoagulation. A multicenter study. Warfarin Optimized Outpatient Follow-up Study Group.

OBJECTIVE: To define risk factors for complications that occur during warfarin therapy. DESIGN: Retrospective cohort study. SETTING: Five anticoagulation clinics. PATIENTS: Nine hundred twenty-eight consecutive patients receiving 1103 courses of warfarin. MAIN OUTCOME MEASURES: Hemorrhagic and thromboembolic complications. RESULTS: In 1950 patient-years of follow-up, there were 1332 bleeding events (4 were classified as fatal, 31 as life-threatening, 226 as serious, and 1071 as minor). The cumulative incidence of fatal bleeding was 1% at 1 year and 2% at 3 years. The cumulative incidences of first episodes of life-threatening and serious bleeding at 1, 2, 4, and 8 years were 1%, 2%, 5%, and 9% and 12%, 20%, 28%, and 40%, respectively. Of 156 patients who had a serious or life-threatening hemorrhage, 32% suffered a recurrence, typically within 1 year. Independent predictors of a first episode of serious bleeding included a mean prothrombin time ratio (PTR) of 2.0 or more during the course of treatment (relative risk, 3.0; 95% CI, 1.9 to 4.7); recent initiation of warfarin therapy (relative risk during the first 3 months compared with the rest of the first year, the second year, and anytime thereafter, 1.9 [CI, 1.3 to 3.0], 3.0 [CI, 1.8 to 4.8], and 5.9 [CI, 3.8 to 9.3], respectively); variability of the PTR over time (relative risk for the highest compared with the lowest tertile, 1.6 [CI, 1.2 to 2.7]); and the presence of 3 or more comorbid conditions (RR, 1.4 [CI, 1.1 to 2.5]). Age, reason for anticoagulation, use of interfering drugs, and hypertension were not associated with risk for bleeding. The risk for a thromboembolic complication at a PTR of less than 1.3 was 3.6 (CI, 2.1 to 6.4) times higher than at a PTR of 1.3 to 1.5. CONCLUSIONS: The incidence of warfarin-associated bleeding may be reduced by attending to modifiable risk factors (that is, highly variable PTRs and values greater than 2.0), frequent monitoring early in treatment, and careful patient selection. Older age, in and of itself, is not a risk factor.

Adult↗
PubMed1993

Distribution of thyrotropin-releasing hormone binding sites: autoradiographic study in infant and adult human hippocampal formation.

The rostrocaudal distribution of thyrotropin-releasing hormone (TRH) binding sites was studied in the human hippocampus. Cryostat sections of the right and left hippocampi from 6 infants (2 h to 5 months of age) and 11 adults (24 to 92 years) were subjected to in vitro quantitative autoradiography using [3H]MeTRH as a ligand. A single class of high affinity [3H]MeTRH binding sites with an apparent dissociation constant in the nanomolar range has been shown both in the infant and the adult. The maximal number of these sites was higher in the infant. No significant difference was observed between the general patterns of the right and the left hippocampi when taking postmortem delay and age as parameters. The highest concentrations of [3H]MeTRH binding sites were localized in the uncinate gyrus, the uncal subiculum and in the whole length of the molecular layer of the dentate gyrus. The lowest densities were present in the ventral subiculum. The major difference observed between the infant and the adult appeared in the molecular layer of the dentate gyrus where the densities were two-fold higher in infants (189 +/- 6 versus 88 +/- 2 fmol/mg of tissue). The only marked difference in the distribution was localized in the caudal part of the body where no specific labeling was found in the presubiculum of the infant.

Adult↗
PubMed1993

Uridine allows dose escalation of 5-fluorouracil when given with N-phosphonacetyl-L-aspartate, methotrexate, and leucovorin.

BACKGROUND: In a previous trial in which methotrexate and N-phosphonacetyl-L-aspartate (PALA) were used to modulate 5-fluorouracil (5-FU), four of six patients could not tolerate treatment at the 600 mg/m2 5-FU dose level because of mucositis, diarrhea, and a decrease in performance status. The current study examines the ability of uridine rescue to prevent such toxic effects in the same regimen and, thereby, allow additional dose escalation of 5-FU. METHODS: Twenty-nine patients with advanced malignant neoplasms received PALA and MTX, each at 250 mg/m2, followed 24 hours later by increasing bolus doses of 5-FU (600-750 mg/m2) with a leucovorin rescue (10 mg orally every 6 hours for eight doses) and uridine rescue (3 g/m2/hour, for a 72-hour infusion, 3 hours on, 3 hours off). Treatment was repeated weekly with either 2 weeks on, 2 weeks off, or 3 weeks on, 1 week off. RESULTS: Mucositis, which occurred in 4 of 12 patients treated at the 750 mg/m2 5-FU dose level, was the only significant chemotherapy-induced toxic effect. However, uridine-related central venous catheter complications (cellulitis in six patients and superior vena cava syndrome in one patient) precluded additional treatment on this protocol. CONCLUSIONS: In the current regimen, uridine allowed dose escalation of 5-FU to 750 mg/m2, which some patients tolerated on a 3-week on, 1-week off schedule. Because of the vascular toxic effects associated with intravenous uridine, the authors recommend additional studies with oral uridine to determine whether the increase in 5-FU dose that uridine allows is associated with improved response rates.

Adult↗
PubMed1993

Impact of a procedure-specific do not resuscitate order form on documentation of do not resuscitate orders.

BACKGROUND: Serious problems exist with respect to documentation of do not resuscitate (DNR) orders. We studied the impact of a procedure-specific DNR order form on documentation of these orders. METHODS: We prospectively compared DNR chart documentation during a 3-month period before and after implementation of a procedure-specific DNR order form. RESULTS: The order form was used in 41 (93%) of 43 charts after its implementation. Documentation of attending physician agreement with the DNR order form increased from 30 of 34 charts in which the order form was used). The number of orders where it was uncertain whether at least one component of acute cardiopulmonary life support-related procedures was to be performed decreased from 30 (88%) of 34 charts to three (7%) of 43 charts. The order form had no measurable impact on documentation of DNR discussion. Only 25% of the charts had any discussion of the risks and benefits of CPR. CONCLUSIONS: A procedure-specific DNR order form can improve documentation of DNR decisions. The reduction of uncertainty in these orders about the use of specific procedures can prevent errors in patient care.

Advance Directives↗
PubMed1993

Proconvulsant and anticonvulsant properties of ethanol: studies of electrographic seizures in vitro.

Recent studies have demonstrated that ethanol is a potent blocker of N-methyl-D-aspartate (NMDA) receptor mediated responses. It is well known that neuroplasticity processes depend on the activation of the NMDA type of excitatory amino acid receptor. We have used an in vitro model of electrographic seizures (EGS), a neuroplasticity process, to examine the effect of varying ethanol concentrations. In the present experiment, slices of rat hippocampus were electrically stimulated to produce stimulus train-induced epileptiform bursting in area CA3. EGS duration and intensity was enhanced by 10 mM ethanol, whereas increasing the concentration of ethanol (60-300 mM) attenuated established EGSs. Ethanol also raised the threshold to elicit an EGS. Removal of low ethanol concentrations resulted in a hyperexcitable state, with increased EGS duration and intensity. These results reflect acute biphasic effects of ethanol across concentrations, and withdrawal hyperexcitability. The effects of ethanol on EGSs, at concentrations which elicit intoxication but not anesthesia (< 75 mM), resemble the actions produced by NMDA antagonists on EGSs. Therefore the effects of ethanol on stimulus train-induced EGSs may be mediated through an action at the NMDA receptor complex.

2-Amino-5-phosphonovalerate↗
PubMed1993

Effects of aerobic training on bone mineral density of postmenopausal women.

A total of 76 women were enrolled and 55 naturally postmenopausal women completed a 12 month study investigating the effects of aerobic training plus calcium supplementation on lumbar (L2-4) bone mineral density (BMD) and forearm BMD. Training was conducted on treadmills at 70-85% of maximal heart rate for 30 or 45 minutes, three times per week for 12 months. Lumbar BMD was measured with dual-photon absorptiometry and forearm BMD with single-photon absorptiometry. Groups were similar with respect to age, weight, months since menopause, height, maximal oxygen uptake (VO2max), and lumbar and forearm BMD upon entering the study. Following training, percentage changes in VO2max were significantly different between the control and exercise groups but not between exercise groups. ANOVA evaluating lumbar BMD revealed a nonsignificant interaction effect and no significant changes (p > 0.05) between groups or times. The control (N = 19), 30 minute (N = 20), and 45 minute (N = 16) groups percentage lumbar BMD changes (X +/- SD) over 12 months were -0.61 +/- 3.40, -0.48 +/- 3.63, and 0.81 +/- 4.53%, respectively. The 95% confidence limits for percentage changes in lumbar BMD for the control, 30 minute, and 45 minute groups were -2.25 to 1.02, -2.18 to 1.22, and -1.16 to 3.22%, respectively. Forearm BMD changes were also not significant. Improvement in lumbar BMD was weakly but positively correlated with improvements in VO2max, r = 0.28, p < 0.05. Women < or = 6 years of the onset of menopause had an accelerated lumbar BMD loss compared to subjects who were > 6 years postmenopausal, and this subset's BMD changes were examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1993

Transforming growth factor beta as a neuronoglial signal during peripheral nervous system response to injury.

In contrast to the central nervous system (CNS), the peripheral nervous system (PNS) displays an important regenerative ability which is dependent, at least in part, on Schwann cell properties. The mechanisms which stimulate Schwann cells to adapt their behavior after a lesion to generate adequate conditions for PNS regeneration remain unknown. In this work, we report that adult rat dorsal root ganglion (DRG) neurons are able, after a lesion performed in vivo or when they are dissociated and cultured in vitro, to synthesize transforming growth factor beta (TGF beta), a pleiotropic growth factor implicated in wound healing processes and in carcinogenesis. This TGF beta is tentatively identified as the beta-1 isoform. Adult rat DRG neurons release a biologically active form of TGF beta which is able to elicit multiple Schwann cell responses including a stimulation to proliferate. Moreover, purified TGF beta-1 produces a Schwann cell morphology alteration and decreases the secretion of tissue-type plasminogen activator (tPA) and enhances the secretion of plasminogen activator inhibitor (PAI) by Schwann cells. This generates conditions which are thought to favor a successful neuritic regrowth. Furthermore, purified TGF beta-1 stimulates type IV collagen mRNA expression in Schwann cells. This subtype of collagen is associated with the process of myelinization. Finally, TGF beta-1 decreases nerve growth factor (NGF) mRNA expression by Schwann cells, an effect which could participate in the maintenance of a distoproximal NGF gradient during nerve regeneration. We propose that neuronal TGF beta plays an essential role as a neuronoglial signal that modulates the response of Schwann cells to injury and participates in the successful regeneration processes observed in the PNS.

Animals↗
PubMed1993

Plasticity of developing and adult dorsal root ganglion neurons as revealed in vitro.

We review recent data on the plasticity of dorsal root ganglion (DRG) neurons as revealed during cultivation in vitro. Some experiments on cultured developing DRG neurons and on adult DRG neurons in vivo are also mentioned. Cultured developing and adult DRG neurons can be switched from an apolar to a multipolar phenotype by fetal calf serum or fibronectin. The effect is concentration dependent and occurs through an early modification of cell-substratum interaction. Adult DRG neurons synthesize and release within hours after injury TGF beta-1, which is a mitogen and a differentiation factor for Schwann cells. Finally, adult DRG neurons express in vitro neurotransmitters that are not expressed in vivo. This neurotransmitter plasticity can be modulated in vitro by some growth factors and in vivo by distal or proximal axotomy.

Animals↗
PubMed1993

Syngeneic grafting of adult rat DRG-derived Schwann cells to the injured spinal cord.

A subdural inflatable micro-balloon was used to induce closed traumatic contusion to adult rat spinal cord. This spinal cord injury model was associated with reproducible and graded neurological deficits and histopathological alterations. At various delays after injury, transplantations of syngeneic adult cultured dorsal root ganglion-derived Schwann cells were performed into the spinal cord lesion. The transplants were well integrated and reduced the microcystic posttraumatic cavitation as well as the gliosis. Schwann cells transplants were invaded by numerous regenerating neurites most of which, based upon their neurotransmitter contents, seem to originate from the dorsal root ganglion.

Animals↗
PubMed1993

Determinants of stroke volume response to exercise in patients with mitral stenosis: a Doppler echocardiographic study.

OBJECTIVES: The aim of this study was to assess exercise-induced changes in stroke volume and their main determinants in mitral stenosis. BACKGROUND: The mechanisms of the stroke volume response to exercise in mitral stenosis are not clearly established. METHODS: Twenty-seven patients with mitral stenosis, aged 47 +/- 13 years, and 10 healthy control subjects, aged 46 +/- 11 years, were examined by Doppler echocardiography to obtain stroke volume, mitral velocity-time integral and calculated mitral valve area (by continuity equation) at rest and during submaximal supine bicycle exercise. Measured mitral valve area at rest and total mitral score were also obtained. RESULTS: During exercise, stroke volume increased significantly (p < 0.001) in the control subjects (+25 +/- 6%) but remained unchanged in the patients. In 10 patients (Group I), stroke volume increased by > or = 14% (+23 +/- 10%, p < 0.001); in the other 17 (Group II), it decreased or increased by < 14% (-5 +/- 14%, p = NS). Mitral velocity-time integral did not change in the three groups, whereas calculated mitral valve area increased significantly (p < 0.001) and similarly in Group I and the control group but remained unchanged in Group II. The exercise change in calculated mitral valve area correlated significantly with both measured mitral valve area at rest (r = 0.46, p < 0.05) and total mitral score (r - 0.53, p < 0.005). However, at constant mitral score, exercise change in calculated mitral valve area no longer correlated significantly with measured mitral valve area at rest. CONCLUSIONS: In mitral stenosis, the change in stroke volume during exercise depends on the change in mitral valve area, which itself depends on the degree of mitral valve damage.

Blood Flow Velocity↗
PubMed1993

A new mutation within the deoxyribonucleic acid-binding domain of the androgen receptor gene in a family with complete androgen insensitivity syndrome.

OBJECTIVE: To study the androgen receptor gene in a large kindred with complete androgen insensitivity syndrome and positive receptor-binding activity. DESIGN: Enzymatic amplification coupled with single strand conformation polymorphism and DNA sequencing were used. RESULTS: In all the affected members, single strand conformation polymorphism showed a mobility shift in exon 2, suggesting a sequence alteration. Sequencing identified a valine into phenylalanine substitution at position 581 in the first zinc finger of the DNA-binding domain. CONCLUSIONS: This valine 581 is conserved in all nuclear receptors and has an important role for the recognition of the androgen response elements by the activated androgen receptor. This amino acid substitution has not been previously described in the androgen receptor in patients with androgen insensitivity syndrome. Moreover, single strand conformation polymorphism allowed determination of the generation in which the mutation appeared and performance of carrier diagnosis in this family.

Amino Acid Sequence↗
PubMed1993

The osteocutaneous upper arm flap for mandibular reconstruction.

The authors present the osteocutaneous upper arm flap as useful in segmental microsurgical mandibular reconstructions. This flap presents several advantages: easy and rapid dissection; a long and reliable pedicle; excellent segmental blood supply to the bone, allowing multiple osteotomies; remarkable mobility of the skin paddle relating to the underlying bone; and minimal donor-site morbidity. Among its few disadvantages are that the bone is predominantly cortical, and the bone shaft cannot exceed 11 x 2 cm. Nevertheless, this flap is an excellent alternative to conventional procedures, when a segmental reconstruction, requiring short bone segments and skin, is required. Eight consecutive clinical cases have been successfully treated and are reported.

Adult↗
PubMed1993

Effects of acute hypoxia on the VO2 max of trained and untrained subjects.

The purpose of this study was to compare the responses of highly trained (TR) and untrained (UT) subjects' maximal oxygen uptake (VO2 max) while breathing a hypoxic gas mixture. Two groups of healthy volunteers were recruited: (1) trained subjects (n = 8), VO2 max = 67.2 +/- 4.0 ml kg-1 min-1; (2) untrained subjects (n = 8), VO2 max = 45.4 +/- 5.5 ml kg-1 min-1. Both groups were administered maximal cycle ergometer tests under hypoxic (13% O2, 87% N2) and normoxic conditions (21% O2, 79% N2). A pulse oximeter (Ohmeda 3700) was used to estimate arterial haemoglobin saturation (SpO2). The trained group had lower values for SpO2 at maximal exercise (TR = 67.0 +/- 7.1%; UT = 77.5 +/- 9.0%) and greater reductions in VO2 max while breathing the hypoxic gas mixture was linearly correlated with the subjects' normoxic VO2 max (ml kg-1 min-1: r = -0.91). These results indicate that highly trained subjects experience greater percent decrements in SpO2 and VO2 max while breathing a moderately hypoxic gas mixture compared to untrained subjects, and may explain some of the variable decrease observed when VO2 max is measured at simulated altitude.

Adolescent↗