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Biomedical subjects

J Duchateau

Publications and source records attributed to J Duchateau.

At least 145 records · Page 8Linked to original sources
PubMed1986

Nonlinear summation of contractions in striated muscle. I. Twitch potentiation in human muscle.

The adductor pollicis of intact man was electrically stimulated via its motor nerve, with series of two supramaximal pulses delivered at various intervals. Muscle surface action potential, myogram and corresponding first derivative (dPt/dt) were recorded under isometric conditions. When two stimuli are delivered at intervals shorter than 150 ms a more-than-linear summation, or potentiation, is observed. This potentiation of force production by a second stimulus involves both increased duration and acceleration of contraction. The potentiation is larger in muscles with small twitch-to-tetanus ratio (Pt/Po), and is found to decrease or increase when Pt/Po is respectively augmented (for example in positive staircase and in contractile disuse) or reduced (for example in negative staircase and in dynamic training). No significant modification of muscle surface action potential is observed when these contractile changes are present. Combined prolongation and intensification of intracellular processes, associated with muscle excitation-contraction coupling in a twitch, could account for the potentiation observed in nonlinear summation of contractions.

Action Potentials↗
PubMed1986

Nonlinear summation of contractions in striated muscle. II. Potentiation of intracellular Ca2+ movements in single barnacle muscle fibres.

Nonlinear summation of contractions is studied in single barnacle (Balanus nubilus) muscle fibres, loaded with the photoprotein aequorin. The results indicate that nonlinear summation of aequorin transients is indeed present and for short interpulse intervals (25-250 ms), a more-than-linear summation of transients, which suggest an increase of the cytosolic Ca2+ concentration in the second response, is observed. This augmented Ca2+ concentration is not merely due to summation with the preceding conditioning transient, but to an enlargement of the second transient in its own right. Furthermore, the enlargement of the second Ca2+ response is not the result of prolonged release, or slowing of re-uptake by intracellular organelles. On the contrary, Ca2+ release is found to be enhanced and for short depolarizations (20 ms), its time to half re-uptake is reduced. The intensified Ca2+ release, triggered by the second standard depolarization, is related to the level of cytosolic Ca2+ concentration reached in the conditioning response and, for example, appears to be larger in the presence of Dantrolene-sodium, which is known to reduce Ca2+ movements in a single twitch. It is concluded that contractile potentiation observed during nonlinear summation of contractions, is associated with a potentiation of intracellular Ca2+ movements, which interact to regulate the cytosolic Ca2+ concentration during contraction.

Aequorin↗
PubMed1986

Routine reinsertion of the hump in rhinoplasty.

Reinsertion of the hump as a free graft, a technique based on the rhinoplasty described by Skoog, has been performed for more than 10 years in severely deviated noses to hide residual deformities of the septum after rhinoplasty. The results have been so encouraging that this technique is now routinely used in all rhinoplasties requiring a reduction of the profile. Grafting the hump after remodelling gives a natural aspect to the dorsum, especially in patients with thin skin where irregularities of sharp edges of the cut nasal bones are otherwise often seen. The hump is tailored into a thin composite graft (bone + cartilage) 3-4 cm long and 3-5 mm broad. No major complications have been observed. 32 cases have been reviewed after a mean delay of 24 months. 29 show radiographic evidence of bone graft survival although no fusion with the nasal bones is observed. It is suggested that facial bone grafts survive better in the nose than grafts taken from the iliac crest or the ribs.

Humans↗
PubMed1986

Complement activation in bronchial asthma evaluated by the C3d/C3 index.

In order to demonstrate a suspected complement activation in bronchial asthma, we measured the C3d (split product of C3) and the C3d/C3 ratio in 73 adults. Both are considered to be a sensitive index of complement activation. Compared with the value obtained in 47 normal subjects, the C3d level and the C3d/C3 ratio level were found significantly higher in asthmatic subjects. Fourteen asthmatics presented an increased C3d/C3 above the calculated limit of normality. These 14 subjects differed from the other asthmatics by a significantly lower C4 plasmatic level, suggesting an activation of the classical pathway of the complement system. Nevertheless, the clinical significance of these observations remains difficult to interpret in view of the absence of significant differences of clinical, allergologic and respiratory functional parameters between asthmatics with low or high C3d/C3 index.

Adolescent↗
PubMed1986

[Interaction between asthma and maxillary sinusitis].

We have studied atopic status and respiratory function in 69 asthmatics in relation to possible radiological changes in the sinuses. These alterations were classified under four headings: normal, mucosal thickening (greater than 3 mm), polyp or opaque films. The bronchial obstruction, evaluated by FEV1/FVC ratio was compared in the 4 groups. The reversibility of airflow obstruction by beta-2-sympathomimetics (Fenoterol) was the same with or without changes in the sinuses. The atopic trait (RAST or immediate prick tests) or non-atopic asthma was not associated with any sinus abnormalities. In conclusion, if a close association between asthma and radiological disease of the sinuses exists (60% of cases), it does not seem that chronic sinusitis worsens bronchial obstruction or reduces sensitivity to beta-2-sympathomimetics. The changes in the sinus mucosa may be induced by the same aetiologic agent (allergic or non allergic) as asthma.

Adult↗
PubMed1985

AIDS in two African children--one with fibrosarcoma of the liver.

We report here on two black African girls who developed an acquired immune deficiency syndrome (AIDS). The first patient was a premature girl born to healthy parents. She suffered from interstitial pneumonitis during the first week of life and died of it at the age of 6 months. Her mother, although asymptomatic, had polyclonal hypergammaglobulinaemia, a reversed T-helper/T-suppressor ratio and a decreased lymphocyte response to mitogens. The second patient had the first symptoms at the age of 6 years, developed a primitive malignant fibrosarcoma of the liver at 8 years old and died 1 year later. AIDS can affect black African children who have not been transfused and whose family members are not considered as at a high risk for this disease. In children, AIDS and cancer can be associated. In the second patient, cytotoxic suppressor lymphocytes (OKT8 positive cells) were shown to behave in vitro as precursors of T-killer cells.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Thymopentin treatment in AIDS and pre-AIDS patients.

Three pilot studies testing thymopentin in AIDS patients are presented. One study included 5 patients with the full-blown syndrome, all treated with 50 mg thymopentin 3 times a week by intravenous slow infusion; no immunologically nor clinically positive results were observed, indicating that the T cell pool in such patients is severely depleted. Six other patients with the prodromal stage of AIDS were treated 1 month with 50 mg thymopentin administered as an intravenous bolus injection 3 times weekly and thereafter for another month with same dose regimen as intravenous slow infusions. The patients on infusion therapy experienced statistically significant immunological improvements; these positive findings were paralleled with an improvement of the patients' clinical condition. These positive responses persisted for an average of 8 months. In another group of 5 pre-AIDS patients thymopentin was administered via the subcutaneous route using 15 mg 3 times weekly; only 1 patient revealed immunological and clinical improvement. In summary, only patients with the pre-AIDS syndrome are likely to benefit from immunomodulation therapy with thymopentin, and the mode of administration seems to be crucial.

Acquired Immunodeficiency Syndrome↗
PubMed1985

In vitro influence of thymopentin on proliferative responses and phytohemagglutinin-induced interleukin 2 production in normal human lymphocyte cultures.

Peripheral human blood lymphocytes from healthy blood donors were investigated in vitro to observe the influence of different doses of thymopentin on nonstimulated proliferation, candidin-stimulated proliferation, and phytohemagglutinin (PHA)-induced interleukin 2 (IL2) production. Concentrations of thymopentin ranging from 0.01 to 10,000 ng/ml were used. The proliferation response in non-stimulated cultures was significantly higher in the presence of 0.01, 1, 10, 1,000, and 10,000 ng/ml of thymopentin. There was no significant increase with 0.1 or 100 ng/ml of thymopentin. Thus, three separate peaks were present in these unstimulated cultures: at a concentration of 0.01 ng/ml; between 1 and 10 ng/ml, and between 1,000 and 10,000 ng/ml. These peaks possibly represent three different subpopulations with different sensitivities to different concentrations of thymopentin. Candidin-induced proliferation was significantly higher only at concentrations of 1 and 10 ng/ml of thymopentin, corresponding to the second peak in the unstimulated culture. No other thymopentin concentrations induced significant increase in the candidin-stimulated cultures. No IL2 production was observed in the unstimulated cultures, even in the presence of thymopentin. On the contrary, preincubation with different concentrations of thymopentin influenced PHA-induced IL2 production. A significant increase in the IL2 level was observed in the supernatant of the cultures if 1,000 ng/ml of thymopentin was used in the preculture period. This concentration corresponds to the third peak in the unstimulated cultures. No significant changes were observed with other concentrations of thymopentin. As the measured value of IL2 is a result of a balance between IL2 production and utilization, the above-mentioned findings need further investigation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvants, Immunologic↗
PubMed1985

Effects of surgery and nutritional support on some lymphocyte and PMN leucocyte functions in man.

The purpose of the present study was to evaluate the effect on some leucocyte functions of 1) an elective surgical procedure; 2) nutritional repletion provided by parenteral alimentation (TPN). The rates of cellular proliferation and protein synthesis in lymphocyte cultures were measured by the incorporation of respectively 3H-thymidine and 3H-leucine; both measures were performed without and with additions of mitogenic agents. Random migration and chemotaxis of PMN leucocytes were measured under agarose. In 10 well-nourished patients, both lymphocyte proliferation and protein synthesis in stimulated cultures decreased after elective surgery, respectively by 50% (p < 0.01) and by 32% (p < 0.05) while random migration of PMN leucocytes was increased by 50% (p < 0.02). Stimulated lymphocyte proliferation and protein synthesis measured in 10 nutritionally depleted non-cancer patients prior to TPN were lower in comparison to the values obtained in a control population (respectively p < 0.006 and p < 0.04). These parameters rose progressively during TPN and reached the normal range after 3 weeks. Before TPN, PMN leucocyte random migration was slower in depleted patients than in control subjects; this parameter reached normal values after one week of TPN, while chemotaxis tended to decrease. Both parameters were in the normal range after 3 weeks of TPN. Conclusions 1) an elective operation depresses lymphocyte functions but stimulates PMN leucocyte random migration in well-nourished patients; 2) in depleted patients, previously depressed leucocyte responses are restored within 3 weeks of adequate nutritional support.

Journal Article↗
PubMed1985

False aneurysm of the radial artery.

A 22-year-old man presented a large false aneurysm of the radial artery in the middle third of the forearm. A segment of the artery was resected and replaced with a vein graft. This lesion is uncommon, but should always be treated early because complications can be severe.

Adult↗
PubMed1985

Electrical and mechanical failures during sustained and intermittent contractions in humans.

This paper compares the effects of sustained and intermittent contractions on electrical and mechanical failure during muscle fatigue in the human adductor pollicis electrically stimulated at 30 Hz via its motor nerve. Sixty-second sustained contractions are compared with a series of 60 1-s contractions, separated by 2.0-, 1.0-, and 0.5-s intervals for identical duration of tension development. Sixty-second sustained contractions decrease tetanic force to 60% (P less than 0.05) of initial values. No significant difference (P greater than 0.05) of force reduction was observed during intermittent 1-s contractions separated by 1-s intervals (-40%), but final force reduction was found to be significantly smaller (P less than 0.05) for 2-s intervals (-18%) and larger (P less than 0.05) for 0.5-s intervals (-65%). When identical force reduction is present in both fatigue tests, it appears that concomitant electrical failure is considerably different during sustained and intermittent contractions (P less than 0.05). This electromechanical dissociation suggests that slowing of conduction along nerve and muscle membranes, as well as possible increase of synaptic delay, does not explain the observed mechanical failure. It is therefore suggested that intracellular processes play the major role in contractile failure during sustained and intermittent contractions.

Action Potentials↗
PubMed1985

Stimulation of specific immune response to varicella antigens in the elderly with varicella vaccine.

Ageing is associated with several immune defects that probably lead to the increased incidence of zoster observed after the 5th decade. In a double-blind study to assess an eventual stimulation of the specific immune response against the varicella-zoster virus by vaccination, either the Oka-strain live varicella vaccine or a placebo was administered to 30 healthy volunteers over 70 years of age, after a 4-week pretreatment period with either zinc acetate as an immunostimulant or a placebo. Specific skin delayed hypersensitivity and antibody levels measured by the fluorescent antibody to membrane antigen method were recorded at the start of the pretreatment period, just before vaccination, and two weeks or one month after vaccination. Initially decreased delayed-type responses to varicella antigens were observed when compared with reported values for younger subjects despite normal levels of skin reactivity to common bacterial antigens (Multitest). The varicella-specific responses were markedly boosted in the 3 groups by repeated skin testing. As a result, the effects of zinc pretreatment and vaccination were masked. On the other hand, treatment with zinc acetate was shown to increase tuberculin delayed reactions. Preexisting specific antibody titres were elevated and no significant changes occurred in the 3 study groups. The data suggest that it is not the potential for an immune response that is decreased in the elderly but rather the speed of the response. This might be the defect responsible for the increased incidence of zoster in this age group.

Aged↗
PubMed1985

Modulation of immune response in aged humans through different administration modes of thymopentin.

Thymopentin, a synthetic pentapeptide corresponding to the active site of thymopoietin, has been shown to restore antibody production in old mice. A decrease in immune response can also be observed in elderly humans, which is mainly caused by defective T cell function. The present study shows that the immunomodulating properties of thymopentin involve both specific and nonspecific responses in a population of elderly people vaccinated with keyhole limpet hemocyanin (KLH) antigen. Furthermore, it is demonstrated that these effects depend upon the mode of administration of thymopentin: The specific KLH antibodies (IgM and IgG), measured by solid-phase radioimmunoassay, reach the highest titers after subcutaneous injection. The lowest titers are produced after intravenous injections, whereas the responses to placebo are between these two ranges. The nonspecific immunoglobulin production, measured by nephelometry, does not follow the same pattern, suggesting that different regulatory mechanisms are involved. Future implications of these findings are discussed.

Adjuvants, Immunologic↗
PubMed1984

Oral zinc supplementation improves hepatic encephalopathy. Results of a randomised controlled trial.

22 cirrhotic patients with chronic encephalopathy were given oral zinc supplementation or placebo in a double-blind randomised trial. In the group which received zinc acetate 600 mg a day for 7 days, serum zinc had been restored to normal by day 8. On day 8 hepatic encephalopathy, as assessed by a trailmaking test, was improved in the supplemented group but not in the placebo group. There was also a significant increase in blood urea nitrogen in the supplemented group. Short-term oral zinc supplementation probably improved hepatic encephalopathy by correcting the zinc deficiency that compromises conversion of ammonia to urea. The duration of this improvement requires further investigation.

Acetates↗