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Biomedical subjects

R Bahr

Publications and source records attributed to R Bahr.

90 records · Page 5Linked to original sources
PubMed1988

Motor drive and metabolic responses during repeated submaximal contractions in humans.

Contractile failure during various types of exercise has been attributed to intramuscular metabolic changes. We examined the temporal changes in force-generating capacity and metabolic state during intermittent isometric contractions in humans. One-legged quadriceps contractions at 30% maximum voluntary contraction (MVC) were executed for 6 s, with 4 s of rest between. The decrease in force-generating capacity was tested from brief MVC's and short bursts of 50-Hz stimulation applied at 5-min intervals. After 1 min of exercise, the MVC force declined linearly and in parallel to the 50-Hz stimulation force, indicating that the contractile failure was due to intramuscular processes. After 30 min of exercise the MVC force had declined by approximately 40% compared with the value obtained after 1 min. In separate experiments the same contraction protocol was followed, but two-legged contractions were used. Muscle biopsies taken after 5, 15, and 30 min of exercise showed only minor changes in the concentrations of glycogen, lactate, creatine phosphate (CrP), and ATP. However, at exhaustion, defined as loss of ability to sustain the target force, the concentrations of CrP and glycogen were reduced by 73 and 32%, and muscle lactate concentration had increased to 4.8 mmol/kg wet wt. Thus the gradual decline in force-generating capacity was not due to lactacidosis or lack of substrates for ATP resynthesis and must have resulted from excitation/contraction coupling failure, whereas exhaustion was closely related to phosphagen depletion, without significant lactacidosis.

Adenosine Triphosphate↗
PubMed1987

Effect of duration of exercise on excess postexercise O2 consumption.

This study was undertaken to determine the effect of exercise duration on the time course and magnitude of excess postexercise O2 consumption (EPOC). Six healthy male subjects exercised on separate days for 80, 40, and 20 min at 70% of maximal O2 consumption on a cycle ergometer. A control experiment without exercise was performed. O2 uptake, respiratory exchange ratio (R), and rectal temperature were monitored while the subjects rested in bed 24 h postexercise. An increase in O2 uptake lasting 12 h was observed for all exercise durations, but no increase was seen after 24 h. The magnitude of 12-h EPOC was proportional to exercise duration and equaled 14.4 +/- 1.2, 6.8 +/- 1.7, and 5.1 +/- 1.2% after 80, 40, and 20 min of exercise, respectively. On the average, 12-h EPOC equaled 15.2 +/- 2.0% of total exercise O2 consumption (EOC). There was no difference in EPOC:EOC for different exercise durations. A linear decrease with exercise duration was observed in R between 2 and 24 h postexercise. No change was observed in recovery rectal temperature. It is concluded that EPOC increases linearly with exercise duration at a work intensity of 70% of maximal O2 consumption.

Adult↗
PubMed1986

Functional characterization of preganglionic neurons projecting in the lumbar splanchnic nerves: neurons regulating motility.

Lumbar preganglionic neurons, which projected in the lumbar splanchnic nerves and were probably involved in regulating motility of colon and pelvic organs (motility-regulating, MR neurons), were analyzed for their discharge patterns. The responses of the neurons to the following stimuli were tested: stimulation of arterial baro- and chemoreceptors and of afferents from the urinary bladder, colon, mucosal skin of the anus and perianal hairy skin. The following findings were made: a total of 131 preganglionic neurons were classified as MR neurons; these reacted to natural stimulation of at least one of the afferent inputs from the urinary bladder, colon and anal and perianal skin. The ongoing activity of these neurons did not correlate with the cardiac cycle or the cycle of the artificial ventilation. Most of them did not respond to an increase of blood pressure produced by i.v. injection of adrenaline or noradrenaline; some showed a weak depression or weak excitation which, in the time course, was untypical for visceral vasoconstrictor neurons. Stimulation of arterial chemoreceptors either did not influence MR neurons or produced only a secondary response owing to contraction of the urinary bladder. Ninety-seven preganglionic MR neurons could be subclassified: MR1 neurons were excited by distension and contraction of the urinary bladder and/or inhibited by distension and contraction of the colon (n = 61), a few were excited from both organs (n = 4); MR2 neurons were inhibited by distension and contraction of the urinary bladder and/or excited by distension and contraction of the colon (n = 32). Ninety-five out of 121 MR neurons (78.5%) were excited, 10 (8%) were inhibited and 16 (13%) not influenced by mechanical shearing stimuli applied to the mucosal skin of the anus. Most neurons which were excited by anal stimulation were not influenced by mechanical stimulation of the perianal (perigenital) skin. Twenty-eight per cent of the MR neurons (18 out of 64) were excited or inhibited upon stimulation of perianal skin. A few of these (7 out of 64 neurons, 11%) were involved in reflex responses which were different from those elicited from anal skin. At present no further consistent subclassification of MR1 and MR2 neurons appears possible on the basis of the excitatory and inhibitory anal and perianal reflexes. The results show that the population of visceral preganglionic neurons, which are probably involved in regulation of motility of colon and pelvic organs, is not homogeneous and probably consists of several subpopulations.

Anal Canal↗
PubMed1986

Functional characterization of preganglionic neurons projecting in the lumbar splanchnic nerves: vasoconstrictor neurons.

Lumbar preganglionic neurons, which project in the lumbar splanchnic nerves and which probably have a vasoconstrictor function (visceral vasoconstrictor, VVC neurons), were analyzed for their discharge patterns. The responses of these neurons to the following natural stimuli were tested: stimulation of arterial baroreceptors, arterial chemoreceptors and visceral afferents from the urinary bladder, the colon and the mucosal skin of the anus. Forty-nine preganglionic neurons were classified as VVC neurons. They showed the following characteristics: the ongoing activity of the VVC neurons exhibited pronounced cardiac rhythmicity and correlated with the cycle of the artificial ventilation. Stimulation of arterial baroreceptors, produced by increase of blood pressure or by increase of pressure in an isolated carotid blind sac, led to inhibition of activity in VVC neurons. Unloading of arterial baroreceptors, produced by decrease of blood pressure, led to an increase in VVC neuron activity. Stimulation of arterial chemoreceptors by bolus injections of CO2-enriched saline solution, close to a carotid glomus, led to a weak excitation of VVC neurons. Stimulation of arterial chemoreceptors by systemic hypoxia led to weak excitation and/or to depression of activity in VVC neurons. Stimulation of visceral afferents from urinary bladder and colon by isovolumetric contractions and distensions of the organs had no effect on most VVC neurons. Anal stimulation also did not induce reflexes in the majority of the VVC neurons. Some 14% of the VVC neurons (7 from 49) were excited by at least one of the visceral stimuli in the same manner as the motility-regulating (MR) neurons. This investigation shows that preganglionic neurons, probably involved in regulation of vascular resistance in colon and pelvic organs, are functionally a distinct population of neurons with some interesting functional overlap with the motility-regulating neurons.

Animals↗
PubMed1986

Secondary functional properties of lumbar visceral preganglionic neurons.

Preganglionic visceral vasoconstrictor (VVC) neurons and motility-regulating (MR) neurons and other visceral preganglionic neurons, which project in the lumbar splanchnic nerves, were analyzed for their segmental distribution, the conduction velocity of their axons, ongoing activity and reflexes elicited by electrical stimulation of visceral afferents in white rami and of somatic afferents in spinal nerves. Identified preganglionic neurons and neurons without ongoing and reflex activity were distributed over segments L1-L5. VVC neurons were distributed over segments L1-L4 and MR neurons over segments L3-L5. VVC axons conducted at 2.8 +/- 2.5 m/s (mean +/- 1 S.D., n = 49), MR axons at 8.1 +/- 4.7 m/s (n = 131). The ongoing activity of VVC neurons was 1.6 +/- 0.7 imp/s (n = 46), that of MR neurons 0.8 +/- 0.7 imp/s (n = 91). There was no correlation between the conduction velocity of preganglionic axons and the rate of ongoing activity for VVC and MR neurons. (4) Electrical stimulation of visceral afferents in white rami and of somatic afferents in spinal nerves elicited short-latency (less than 50 ms) and long-latency (greater than 50 ms) reflexes in practically all VVC neurons, but preferentially short-latency reflexes in only 50 to 60% of the MR neurons. These results show that VVC and MR neurons are not only different in their reflex patterns, elicited by stimulation of visceral receptors and of arterial baro- and chemoreceptors, but also in the 4 properties analyzed in this paper.

Animals↗
PubMed1986

Excess post-exercise oxygen consumption. A short review.

Exercise is known to produce an increase in oxygen consumption in the resting post-exercise state. This increase is known as the excess post-exercise oxygen consumption (EPOC). A short review of the literature regarding the magnitude, duration, mechanisms and clinical significance of EPOC is given. It is concluded that a significant contribution of the total oxygen requirement of exercise results from an increase in post-exercise oxygen consumption.

Energy Metabolism↗
PubMed1981

Do dichotomizing afferent fibers exist which supply visceral organs as well as somatic structures? A contribution to the problem or referred pain.

Fibers in the inferior splanchnic nerves were found which could be activated by electrical stimulation of one of the lumbar white rami as well as of the somatic nerve of the same spinal segment at stable latency. The responses of these fibers reliably followed high frequency stimulation (20-100 Hz) of the nerves. The axons were unmyelinated (conduction velocity 1.02 +/- 0.57 m/sec, mean +/- 1 S.D., n = 14), had no ongoing discharges and could not be excited by afferent stimuli via a spinal or supraspinal reflex pathway. Therefore, it is likely that these fibers are afferent. The findings support the hypothesis that referred pain may be produced by dichotomizing sensory fibers, one branch passing to visceral organs and the other branch to the site of reference in muscle or skin.

Afferent Pathways↗
PubMed1981

Eyelid tumors of sweat gland origin.

Tumors of sweat gland origin are not uncommon in the periocular region. These tumors frequently pose diagnostic difficulty due to the wide range of histopathological patterns, and to the fact that they may be infiltrative or have metastatic potential despite their relatively benign appearance. This report discusses the classification and diagnosis of five sweat gland tumors with variable histological appearance, including syringoma, mixed tumors, adenoma of ductal origin, and mucinous adenocarcinoma of sweat gland origin.

Adenocarcinoma, Mucinous↗
PubMed1979

The Clinac-18 linear accelerator. 10 MeV photon beam data.

Measurements were carried out on a Clinac-18 linear accelerator in order to characterize the 10 MeV photon beam. Depth dose data and tissue-maximum-ratios were obtained for field sizes up to 35 x 35 cm2. Using a parabolic expression a least square fit to the tissue-maximum-ratios was performed. The radiation field flatness and the penumbra were found to be in good agreement with the tolerances recommended by the IEC standard (draft). The radiation field and the light field isocentre were determined as suggested by the IEC. The distance between both isocentres was less than 1 mm.

Particle Accelerators↗
PubMed1975

Ischemia of ciliary arterial circulation from ocular compression.

Two patients developed unilateral central retinal artery and posterior ciliary artery occlusions related to ocular compression during general anesthesia. One patient had evidence of extensive choroidal ischemia with diffuse hypopigmentation, pigmentary mottling of the posterior pole, and disc edema. Electroretinography showed diminution of the A and B waves. The other patient showed patchy choroidal ischemia with subsequent development of wedge-shaped areas of pigmentary atrophy and mottling in the midperiphery. Iridocyclitis and prolonged hypotony were also present. Retinal and posterior ciliary artery occlusion (perhaps at the level of the ophthalmic artery) can occur as a result of ocular compression by a face mask or an improperly positioned headrest. Systemic hypotension is a factor in many cases. Proper positioning of the head on an adequate headrest and avoidance of ocular compression will prevent the occurrence of retinal and choroidal occlusion during general anesthesia.

Anesthesia, General↗
PubMed1975

Black hypopyon: report of two cases.

Two patients are described in whom black hypopyon and black keratic precipitates occurred as a result of intraocular melanoma. In one instance the hypopyon was due to a clinically unsuspected primary choroidal melanoma in an eye with opaque media; in the second case the tumor was metastatic to the uvea froma cutaneous melanoma. Histological examination showed the hypopyon to be composed of pigment-laden macrophages and neoplastic melanoma cells.

Anterior Chamber↗
PubMedDate not supplied

[Initial response to therapy as an important prognostic factor in acute lymphoblastic leukemia in childhood. COALL study group].

Prognostic factors to estimate the risk of relapse are crucial for risk-adapted therapy in acute lymphoblastic leukemia (ALL). In a cooperative multicenter treatment study for childhood ALL (COALL-03-85) the prognostic relevance of the bone marrow (BM) blast count at day 28 was evaluated. Treatment was adjusted to the initial risk factors; patients with high risk (white blood count (WBC) greater than or equal to 25/nl, age greater than or equal to 10 years, T- or NULL-ALL) received intensified therapy consisting of rotation of 6 non cross-resistant drug combinations with 12 different agents. After 4 weeks 289/305 (94.8%) children were in complete remission (CR); one child died of infection, and 15 (14 high-risk patients) still had more than 5% blasts in the BM. Twelve of these 15 patients were in remission after 2 to 4 weeks additional treatment. Poor responders often had a high initial WBC, age above 10 years of T- or NULL-ALL. In spite of continuation of intensive therapy all children with more than 10% blasts in the BM on day 28 suffered an early relapse except 2 who were transplanted in first remission. Event-free survival for the poor responders is 0.15 compared to 0.71 (p = 0.0001) for the good responders (median observation time 48 months). In multivariate analysis remission status on day 28 was the only significant prognostic factor in high-risk patients above one year of age; traditional risk factors as initial WBC, age above 10 years, hepatosplenomegaly, and immunological subtype were of no prognostic significance in this study. (ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

Incidence and mechanisms of acute ankle inversion injuries in volleyball. A retrospective cohort study.

In a retrospective cohort study of ankle inversion injuries performed after the 1991-1992 season in the top two divisions of the Norwegian Volleyball Federation, 63 injuries were found among 318 players during 60,612 hours of training and 928 matches. The study was limited to acute ankle inversion injuries that caused an absence of 1 or more days from training or match play. The total injury rate was 0.9 +/- 0.12 per 1000 player hours: 0.7 +/- 0.11 during training and 2.6 +/- 0.56 during match play. The relative risk of injury during match play versus training was 3.9 (P < 0.001). Women had an injury rate of 1.1 +/- 0.18, whereas that of men was 0.7 +/- 0.15 (relative risk = 1.47; not significant). Most of the players (78%) had suffered at least one previous injury of the affected ankle. Most injuries were mild to moderate. The majority of the injuries (86%) occurred at the net, mainly when landing after blocking (63%) or attacking (29%). We suggest that simple measures such as rule changes, technical training, and prophylactic taping or bracing may lead to a significant reduction in the incidence and severity of such injuries.

Acute Disease↗
PubMedDate not supplied

Characteristics of the leg extensors in male volleyball players with jumper's knee.

The aim of the present study was to characterize the performance ability of the leg extensor apparatus in a group of athletes with jumper's knee and to compare the results with those of a matched control group without knee symptoms. Patient and control groups (12 players in each) were selected from a population of 141 well-trained male Norwegian volleyball players, of which 55 (39%) satisfied the diagnostic criteria for jumper's knee. The testing program consisted of a standing jump, a countermovement jump, a 15-second rebound jump test, a standing jump with a 20-kg load, and a standing jump with a load corresponding to one-half of the subject's body weight. Jump height and power were measured using a contact mat connected to an electronic timer. The test results of the patient group were significantly higher than those of the control group for the countermovement jump (15% increase), power during rebound jump (41%), work done in standing jump (12%) and countermovement jump (22%), and the difference between countermovement jump and standing jump (effect of adding eccentric component). Athletes with jumper's knee demonstrated better performance in jump tests than uninjured athletes, particularly in ballistic jumps involving eccentric force generation.

Adult↗
PubMedDate not supplied

Biomechanics of ankle ligament reconstruction. An in vitro comparison of the Broström repair, Watson-Jones reconstruction, and a new anatomic reconstruction technique.

We wanted to use biomechanical testing in a cadaveric model to compare the Broström repair, the Watson-Jones reconstruction, and a new anatomic reconstruction method. Eight specimens were held in a specially designed testing apparatus in which the ankle position (dorsiflexion-plantar flexion and supination-pronation) could be varied in a controlled manner. Testing was done with intact ligaments and was repeated after sectioning of the anterior talofibular ligament and the calcaneofibular ligament and after a Broström repair, a Watson-Jones reconstruction, and a new anatomic reconstruction were performed. An anterior drawer test was performed using an anterior translating force of 10 to 50 N, and a talar tilt test was performed using a supination torque of 1.1 to 3.4 N-m. The forces in the anterior talofibular ligament and calcaneofibular ligament were measured with buckle transducers, and tibiotalar motion and total ankle joint motion were measured with an instrumented spatial linkage. The increase in ankle joint laxity observed after sectioning of both the anterior talofibular and calcaneofibular ligaments was significantly reduced by the three reconstructive techniques, although not always to the level of the intact ankle. Joint motion was restricted after the Watson-Jones procedure compared with that in the intact ankle. Unlike the Watson-Jones procedure, the ligament or graft force patterns observed during loading after the Broström repair and the new anatomic technique resembled those observed in the intact ankle.

Adult↗