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Biomedical subjects

H Freund

Publications and source records attributed to H Freund.

At least 37 records · Page 2Linked to original sources
PubMed1995

Lactate exchange and removal abilities in sickle cell trait carriers during and after incremental exercise.

Arterial blood lactate concentrations and pH were measured on seven black male sickle cell trait (SCT) carriers before, during and after incremental exhaustive bicycle exercise (25 W increments per minute) and compared with those of six control individuals of the same ethnic origin having a similar physical fitness level. The object of the experiment was to determine if SCT has an effect on lactate kinetics. At volitional exhaustion which was reached at a comparable overall mean absolute work rate for both groups, oxygen consumption expressed per kilogram body mass was significantly lower for the SCT carriers than for the control volunteers. Lactate concentrations were higher for the SCT carriers after the 150 W exercise step but differences reached statistical significance only at exhaustion. Concentrations were distinctly higher for the SCT group during the following 40 minutes of recovery. While there were no observable differences in blood pH between the SCT and control subjects during the exercise, this variable became significantly lower for the SCT than for the control group 8 minutes after the end of exercise. Lactate recovery curves were fitted by a biexponential time function where the two velocity constants inform on the body's overall ability to exchange and remove lactate. The ability to remove lactate was comparable for the two groups. The present results do not warrant drawing a definite conclusion on impairment of the ability to exchange lactate in the presence of SCT. However, SCT carriers are likely to produce more lactate than control subjects reaching exhaustion at similar mean absolute work rate during exhaustive incremental bicycle exercise.

Adult↗
PubMed1994

The role of brachytherapy in the treatment of stage III vaginal cancer. A report of 3 cases.

Advanced vaginal cancer has a grim prognosis: management is complicated. It may include surgery which needs to be exenterative if cure is intended, and/or radiation therapy (RT), the dose of which is limited by the radiosensitivity of adjacent structures. We report on 3 cases, in each of which the tumor was located in different anatomic sites, and we demonstrate how therapy was tailored to each situation. All 3 patients had Stage III, squamous cell carcinoma of the vagina. They received external beam irradiation (EBI) 4000-5000 cGy to the pelvis. This is the maximal tolerable dose by most pelvic organs, but is not curative. Therefore brachytherapy was combined with EBI. In one patient brachytherapy was given intraoperatively, following extensive removal of residual tumor in the pelvis. Two patients are alive and free of disease three and six and a half years later, and one patient died of disease five years following therapy. For eradication of advanced vaginal cancer, treatment includes the combination of EBI and brachytherapy with or without debulking surgery, the role of which was not previously described in this setting. Treatment strategy should be adapted to the anatomic location of the tumor, its intravaginal extension and the age of the patient.

Adult↗
PubMed1993

Heat stress does not modify lactate exchange and removal abilities during recovery from short exercise.

Arterial and femoral venous lactate concentrations were measured before, during, and after short intermittent exercise (55-118% of maximal O2 consumption) in thermoneutral (N, 25 degrees C, 10.5 Torr) and hot (H, 45 degrees C, 17.5 Torr) conditions. The thermal load induced significantly higher heart rate and rectal temperature in H relative to N. All the arterial lactate (La) recovery curves were fitted to an equation containing two exponential time functions of the form La(t) = La(0) + A1a(1 - e-gamma 1at) + A2a(1 - e-gamma 2at) where the velocity constants gamma 1a and gamma 2a are the body's overall ability to exchange and remove lactate after exercise, respectively, and t is time. There was no significant difference in these constants, regardless of thermal conditions. The arterial lactate concentration at the end of exercise, the peak lactate concentration during recovery, the amplitudes A1a and A2a of the biexponential function, and the arteriofemoral venous lactate concentration difference during recovery were not significantly different in H relative to N. However, measured and computed arterial lactate concentrations during recovery, especially at the end of the tests, were higher in H (P < 0.04). The more elevated lactate concentrations in H at rest at the end of recovery denote a higher basal lactate production, and they were not due to muscle hypoxia.

Adult↗
PubMed1992

Lactate exchange and removal abilities in sickle cell patients and in untrained and trained healthy humans.

Arterial blood lactate concentrations obtained on seven black males with hemoglobin sickle cell disease (SC) before, during, and after graded bicycle exercise up to exhaustion were compared with those of seven untrained (HU) and seven trained (HT) healthy males of the same ethnic origin. Lactate recovery curves were fitted by a biexponential time function consisting of a rapidly increasing and a slowly decreasing component. Higher work rates were reached by the HU and HT than by the SC group. Blood lactate rose distinctly over the corresponding preexercise resting values after the 25-, 50-, and 100-W exercise steps for the SC, HU, and HT groups, respectively. The arterial oxygen content was significantly lower for the SC than for the HU group at rest and at the end of exercise. The velocity constants of the slowly decreasing component of the lactate recovery curves were similar for the SC, HU, and HT groups despite the fact that they cycled up to different absolute work rates. The velocity constant of the rapidly increasing component was significantly higher for the HT. In terms of the functional meaning given to these constants and in view of their inverse relationship with absolute work rate (Freund et al. J. Appl. Physiol. 61: 932-939, 1986), these results indicate that, relative to the HU, the HT and the SC display improved and impaired abilities, respectively, to exchange and to remove lactate.

Adult↗
PubMed1992

[Physiologic blood coagulation studies in idiopathic arterial thrombosis].

QUESTIONING: The prevalence of inherited thrombotic syndromes in the general population appears to be higher than that of inherited bleeding disorders. However, the most important candidates for screening are patients with unexplained thromboembolism at ages of less than 40 years: In 19 children suffering from "idiopathic" arterial thrombosis laboratory screening has been performed. METHODS: PT, PTT, TT, platelet count, spontaneous platelet aggregation, von Willebrand-factor, fibrinogen, plasminogen, antithrombin III, protein C, C1-inactivator, alpha-1-antitrypsin, alpha-1-antichymotrypsin, alpha-2-antiplasmin and alpha-2-macroglobulin have been investigated. RESULTS: Compared to an age matched healthy control group we could demonstrate in children with arterial thrombosis in vitro platelet activation with significant enhanced platelet aggregation, elevated levels of von Willebrand-factor and alpha-1-antichymotrypsin at the onset of disease. Protein C and alpha-2-antiplasmin were significantly decreased. These changes turned back to normal in the following 6 to 9 months. PT, PTT, TT, platelet count, plasminogen, alpha-1-antitrypsin, c1-inactivator and alpha-2-macroglobulin showed no alterations compared to controls. CONCLUSIONS: Platelet activation and alteration of platelet function have been shown in vivo and in vitro to initiate thrombosis. The von Willebrand's VIII molecule is involved in this step. The lowering of protein C levels at the onset of thrombotic diseases is discussed to be due to an increased turnover, whereas the decreased levels of alpha-2-antiplasmin might be a counter-regulation to the thrombotic event, showing an "activated" fibrinolytic system.

Adolescent↗
PubMed1991

[The effect of supramaximal exercise on the recovery kinetics of lactate].

Blood lactate recovery curves from muscular exercise can be described by a sum of two exponential terms consisting in a rapidly increasing and a slowly decreasing component. A two-compartment model consisting of the previously working muscles and the remainder of the lactate space furnishes the simplest but nevertheless realistic explanation of this evolution pattern. The velocity constants of the rapidly increasing (gamma 1) and the slowly decreasing (gamma 2) components inform respectively on the abilities of the body to exchange and remove lactate. However the blood lactate recovery curves observed in three untrained subjects after 3-min 107-115% VO2max cycling display a transitory plateauing of the lactate concentration between the increasing and decreasing phases of the curves. This levelling off of the concentrations at their highest value was not observed in an endurance trained subject after a 3-min 107% VO2max exercise. Despite the plateauing and consequent less good fit than to the usual evolution curves, the recovery curves could still be accurately fitted by the biexponential time function. After supramaximal exercise the abilities to exchange and to remove lactate are severely impaired. These impairments in the functional properties of the organism are very likely associated with and/or linked to physico-chemical modifications which have been observed as much at the cellular level as in the body fluids during and after supramaximal exercise.

Acidosis↗
PubMed1990

Blood lactate during constant-load exercise at aerobic and anaerobic thresholds.

Venous blood lactate concentrations [1ab] were measured every 30 s in five athletes performing prolonged exercise at three constant intensities: the aerobic threshold (Thaer), the anaerobic threshold (Than) and at a work rate (IWR) intermediate between Thaer and Than. Measurements of oxygen consumption (VO2) and heart rate (HR) were made every min. Most of the subjects maintained constant intensity exercise for 45 min at Thaer and IWR, but at Than none could exercise for more than 30 min. Relationships between variations in [1ab] and concomitant changes in VO2 or HR were not statistically significant. Depending on the exercise intensity (Thaer, IWR, or Than) several different patterns of change in [1ab] have been identified. Subjects did not necessarily show the same pattern at comparable exercise intensities. Averaging [1ab] as a function of relative exercise intensity masked spatial and temporal characteristics of individual curves so that a common pattern could not be discerned at any of the three exercise levels studied. The differences among the subjects are better described on individual [1ab] curves when sampling has been made at time intervals sufficiently small to resolve individual characteristics.

Aerobiosis↗
PubMed1990

Comparative lactate kinetics after short and prolonged submaximal exercise.

Arterial blood lactate concentrations were determined in two groups of eleven males before, during and after near 2 W.kg body mass-1 bicycle exercise. One group of subjects cycled for 3 min, whereas the second group exercised for 60 min. All the lactate curves during recovery could be fitted to a bi-exponential time function consisting of a rapidly increasing and a slowly decreasing component. This typical evolution pattern indicates that the two-compartment model which has been proposed to represent the movements of lactate after short exercise applies also to recovery from prolonged exercise. Lengthening exercise duration decreased (respectively 10% and 28%) the value of both velocity constants of the fits to the lactate recovery curves, with the difference (28%) being statistically significant for the velocity constant describing the slowly decreasing part of the curves. This result indicates that extending exercise from 3 to 60 min impairs the ability to remove lactate after the exercise.

Adult↗
PubMed1990

Lactate removal ability and graded exercise in humans.

Venous lactate concentrations of nine athletes were recorded every 5 s before, during, and after graded exercise beginning at a work rate of 0 W with an increase of 50 W every 4th min. The continuous model proposed by Hughson et al. (J. Appl. Physiol. 62: 1975-1981, 1987) was well fitted with the individual blood lactate concentration vs. work rate curves obtained during exercise. Time courses of lactate concentrations during recovery were accurately described by a sum of two exponential functions. Significant direct linear relationships were found between the velocity constant (gamma 2 nu) of the slowly decreasing exponential term of the recovery curves and the times into the exercise when a lactate concentration of 2.5 mmol/l was reached. There was a significant inverse correlation between gamma 2 nu and the rate of lactate increase during the last step of the exercise. In terms of the functional meaning given to gamma 2 nu, these relationships indicate that the shift to higher work rates of the increase of the blood lactate concentration during graded exercise in fit or trained athletes, when compared with less fit or untrained ones, is associated with a higher ability to remove lactate during the recovery. The results suggest that the lactate removal ability plays an important role in the evolution pattern of blood lactate concentrations during graded exercise.

Adolescent↗