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Biomedical subjects

E Wiedemann

Publications and source records attributed to E Wiedemann.

At least 55 records · Page 3Linked to original sources
PubMed1991

Modulation of endothelin effects on blood pressure and hematocrit by atrial natriuretic peptide.

Infusion of endothelin has been observed to increase hematocrit, and the peptide also stimulates release of atrial natriuretic peptide (ANP) both in vitro and in vivo. We studied the relation of these two actions of endothelin in anesthetized, bilaterally nephrectomized Sprague-Dawley rats. Infusion of endothelin (25 ng/kg/min) for 45 minutes produced a modest increase in blood pressure of 12% from a baseline of 99 +/- 5 mm Hg and an increase in hematocrit of 8.0 +/- 0.6%, reflecting a reduction in plasma volume of 13.1 +/- 0.9%. These changes each exceeded greatly those observed after 45 minutes of vehicle infusion. Plasma protein concentration, however, increased only by 4.2 +/- 0.6%, suggesting protein extravasation, which was confirmed by finding an endothelin-dependent increase in the accumulation of Evans blue dye in heart, skeletal muscle, and intestine, but not liver, lung, brain, or testis. Endothelin infusion increased plasma immunoreactive ANP concentration from 196 +/- 50 to 722 +/- 203 pg/ml (p less than 0.02), and a close correlation existed between the increase in plasma immunoreactive ANP and immunoreactive endothelin concentrations as a result of the infusion (r = 0.84, p less than 0.01). Pretreatment of rats with rabbit anti-rat ANP antiserum did not affect baseline variables but led to an exaggerated increase in blood pressure (25.3 +/- 2.9%, p less than 0.002 versus endothelin alone). No change in hematocrit occurred. Thus, the increase in plasma immunoreactive ANP concentration resulting from endothelin infusion mediates the increase in hematocrit through an increase in vascular permeability to whole plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Mechanism of the natriuretic effect of unilateral carotid artery traction in the rat.

Unilateral traction on a carotid artery is known to activate the carotid baroreceptor reflex. This maneuver increases sodium excretion in a manner not completely dependent on the renal nerves, suggesting that a humoral factor(s) could be involved. We measured sodium excretion before and after unilateral carotid artery traction or sham traction in anesthetized rats and related the results to the plasma concentration of immunoreactive (IR)-gamma-melanocyte stimulating hormone (gamma-MSH), a peptide known to be natriuretic in other circumstances. In 12 rats undergoing sham traction, sodium excretion did not change and plasma IR-gamma-MSH activity at the end of the experiment was 10.5 +/- 5.4 (SD) fmol/mL. Carotid artery fraction in 20 other rats caused a transient dip in mean arterial pressure of 20.1 +/- 13.2 mm Hg, and sodium excretion increased from 746 +/- 431 to 1,739 +/- 1,436 nEq/min (P less than 0.005). Plasma IR-gamma-MSH was increased to 21.1 +/- 7.1 fmol/mL (P less than 0.001 versus sham). Prior ipsilateral carotid sinus denervation markedly attenuated the carotid artery traction-related dip in blood pressure and prevented both the natriuresis and the increase in IR-gamma-MSH activity seen after this maneuver in intact rats. Pretreatment with anti-gamma-MSH antiserum also blocked the natriuretic response to carotid artery traction, despite a similar transient dip in blood pressure of 18.3 +/- 9.9 mm Hg. These observations suggest that activation of the carotid baroreceptor reflex by unilateral carotid artery traction causes natriuresis that is mediated largely by an increase in the plasma concentration of a peptide or peptides closely related to the gamma-MSH sequence.

Animals↗
PubMed1990

[Incisura scapulae syndrome].

The suprascapular nerve may rarely be entrapped in the suprascapular notch. This causes weakness of the supra- and infraspinatus muscles and pain in the glenohumeral and acromioclavicular joints, which are innervated by this nerve. The entrapment syndrome may result from direct or indirect trauma, fracture of the neck of the scapula, kinking or traction on a sling affecting the nerve, from the shape of the notch, compression by a ganglion, or its cause may be idiopathic. Diagnosis of the syndrome is based upon deep unceasing pain reported at the postero-lateral shoulder, atrophy of the supra- and infraspinatus muscles, and impaired shoulder external rotation and a lidocaine test. The final proof is taken from polyphasic EMG potentials which are decreased in amplitude and increased in distal latency. Initially the entrapment neuropathy may be treated by immobilization, analgesics, and physiotherapy. A tear of the rotator cuff as well as a frozen shoulder have to be excluded by arthrography. In persistent cases of pain and pathologic EMG findings surgical decompression of the nerve should be done. The trapezius muscle is approached by a postero-superior incision. Via the suprascapular fossa the notch may be reached. Then the nerve is decompressed by removing the transverse scapular ligament. Reports of the cases operated so far are promising, though their number is small.

Humans↗
PubMed1987

Prevention of reflex natriuresis after acute unilateral nephrectomy by neonatal administration of MSG.

Acute unilateral nephrectomy (AUN) results in natriuresis from the remaining kidney through reflex pathways involving the central nervous system and requiring an intact pituitary gland. The natriuresis is accompanied by an increase in the plasma concentration of a peptide or peptides derived from the N-terminal fragment (NTF) of proopiomelanocortin. We measured plasma immunoreactive NTF-like material (IR-NTF) before and after AUN in control rats and rats treated neonatally with monosodium glutamate (MSG), a procedure that produces neuroendocrine dysfunction by destroying cell bodies in the hypothalamic arcuate nucleus, median eminence, and other brain regions. In control rats, IR-NTF increased from 85.8 +/- 54.9 (SD) to 207 +/- 98.1 fmol/ml after AUN (P less than 0.02) as sodium excretion (UNaV) doubled. In MSG-treated rats, AUN produced no change in plasma IR-NTF concentration (58.8 +/- 21.3 vs. 68.3 +/- 18.5 fmol/ml (P = NS), nor did UNaV increase. Tissue content of IR-NTF was reduced in the arcuate nucleus and anterior lobe of pituitaries from MSG-treated rats compared with controls, but was no different in the neurointermediate lobe. These results indicate that the hypothalamic lesion produced by neonatal administration of MSG prevents both the increase in plasma IR-NTF concentration and the natriuresis after AUN, and therefore lend further support to the concept of a causal relationship between these two consequences of AUN.

Animals↗
PubMed1987

A gamma-melanocyte stimulating hormone-like peptide causes reflex natriuresis after acute unilateral nephrectomy.

Previous studies have shown that acute unilateral nephrectomy stimulates sodium (UNaV) and potassium (UKV) excretion by the remaining kidney through reflex pathways requiring an intact pituitary gland, and the natriuresis is accompanied by an increase in the plasma concentration of a peptide or peptides derived from the adrenocorticotropic hormone-beta-endorphin precursor molecule pro-opiomelanocortin. We tested the hypothesis that gamma-melanocyte stimulating hormone (gamma-MSH) was such a peptide involved in the postnephrectomy natriuresis. In six rats undergoing sham nephrectomy, no change in UNaV or UKV occurred and plasma immunoreactive gamma-MSH-like material was 40 +/- 18 (SD) fmol/ml 2 hours after the sham procedure. In 10 rats undergoing acute unilateral nephrectomy, UNaV and UKV from the remaining kidney increased significantly, and immunoreactive gamma-MSH was 81 +/- 36 fmol/ml (p less than 0.02). In individual studies, the increase in UNaV after nephrectomy correlated with the postnephrectomy concentration of immunoreactive gamma-MSH (r = 0.75, p less than 0.001). In 17 rats injected with serum or globulin from control rabbits, unilateral nephrectomy led to the expected increases in UNaV and UKV. In 23 rats injected with serum or globulin from rabbits immunized against gamma-MSH, no postnephrectomy natriuresis occurred and the kaliuresis was blunted. In hydropenic, mineralocorticoid-treated rats, intravenous infusion of synthetic gamma-MSH led to natriuresis and kaliuresis with no change in inulin clearance; pretreatment with rabbit anti-gamma-MSH antiserum blocked this effect of peptide infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

[Compression syndromes of the shoulder and their differential diagnosis].

Compared to other painful conditions on the shoulder suprascapular nerve entrapment is an obscure and uncommon syndrome causing severe shoulder pain and disability, and is easily cured if only it is recognized. The condition was described by Thompson and Kopell in 1959, Schilf reported a case of isolated suprascapular entrapment in 1952. The nerve passes through the suprascapular notch, the roof of the notch is formed by the transverse scapular ligament. The shape of the suprascapular notch may be guilty for entrapment symptoms. Suprascapular nerve compression may result of acute trauma, of transmitted forces, fracture of collum scapulae, of kinking or traction of the nerve over the edge of the foramen, of sling effect, of compression by ganglia, or its cause may be idiopathic. The hallmark of suprascapular nerve entrapment is a deep and poorly delineated pain, localized to the posterior and lateral aspect of the shoulder. Atrophy and weakness of the supraspinatus and infraspinatus may be noted. Adduction of the extended arm across the body tenses the nerve, increasing the pain. Blocking the nerve by local anesthetic a dramatic, but not long lasting pain relief may be achieved. Electromyographically a decrease in the amplitude or marked polyphasicity of evoked potentials is significant as well as an increased latency time, indicating an impaired conductibility. A surgical release is indicated in case of constant pain and pathological changes of EMG-patterns. From a postero-superior approach decompression of the nerve is performed by simple removal of the transverse scapular ligament.

Diagnosis, Differential↗
PubMed1986

Forearm muscles of man can reverse their function after tendon transfers: an electromyographic study.

In patients suffering from paralysis of a major synergistic muscle group tendon transfers can be considered the therapy of choice in restoring the mobility of the affected joint(s). In order to study the mechanisms underlying the subsequent reversal of function in the transferred muscles, we have recorded the EMG of several forearm muscles in parallel and compared their activation periods with control data from healthy volunteers. Slow and fast extension-flexion movements of the wrist were evaluated. The findings demonstrated a 'new' phasic EMG activity within the transferred muscles, which correlated to their new mechanical function. However, the 'old' EMG pattern was not lost. In some muscles it was present in fast and slow wrist movements, in others only in fast ones. The results indicate that the reversal of function observed in the transferred muscles can be adjusted to meet the specific needs of the movement to be performed.

Adaptation, Physiological↗
PubMed1986

The effect on plasma prolactin levels of interictal epileptiform EEG activity.

Because of the known effects of seizures on plasma prolactin, the plasma prolactin levels were measured before and after generalised interictal epileptiform activity was provoked in the EEG in five epileptic patients. The findings were compared with those obtained in five normal subjects and three epileptic patients who were also exposed to flicker stimulation, but who did not develop a photoconvulsive EEG response. There was no significant difference in baseline prolactin values, and levels did not change with photic stimulation or in response to the presence of generalised epileptiform activity in the EEG.

Adolescent↗
PubMed1985

Role of the pituitary in reflex natriuresis following acute unilateral nephrectomy.

We studied the role of altered pituitary function in the reflex natriuresis that occurs after acute unilateral nephrectomy (AUN). In normal rats, AUN increased both sodium (UNaV) and potassium excretion within 90 min. In hypophysectomized rats, no increase in cation excretion after AUN occurred, results which were duplicated in rats in which pituitary function was altered by prior treatment with dexamethasone (2 mg/kg ip for 3 days). In adrenalectomized rats, AUN led to increases in cation excretion similar to those seen in normal rats, indicating that intact adrenal function was not necessary for this excretory response following AUN. These changes in cation excretion were correlated with measurements in peripheral plasma of two peptides derived from the pituitary precursor molecule pro-opiomelanocortin (POMC). Radioimmunoassayable plasma beta-endorphin failed to change after AUN in any of the conditions studied. However, a sensitive radioimmunoassay for the N-terminal fragment (NTF) of POMC indicated that plasma NTF rose significantly after AUN in normal and adrenalectomized rats but did not change in hypophysectomized, steroid-pretreated, or shamoperated rats. The increase in NTF concentration correlated with the increase in UNaV after AUN. These results demonstrate that the reflex increase in cation excretion after AUN is dependent on an intact pituitary gland and is associated with an increase in peripheral plasma concentration of NTF. NTF, or some other peptide residing in the N-terminal portion of POMC, could promote the natriuresis after AUN; the importance of the pituitary gland in this response could be the secretion of this peptide.

Animals↗
PubMed1985

Reflex responses to reductions in functioning renal mass.

Both acute unilateral nephrectomy (AUN) and unilateral ureteral obstruction (UUO) result in an acute increase in cation excretion from the contralateral kidney. AUN results in reflex changes in systemic hemodynamics owing to an acute and transient increase in arterial pressure that activates carotid sinus baroreceptors and constitutes an afferent limb in the reflex; hemodynamic adjustments and increased cation excretion result. The reflex involves participation of the endogenous opioid system, with receptors located primarily in the central nervous system, and requires intact pituitary function because both hypophysectomy and pretreatment with large doses of dexamethasone prevent the postnephrectomy natriuresis. The natriuresis is closely correlated with an increase in the plasma concentration of the NH2-terminal fragment of the pituitary peptide precursor molecule proopiomelanocortin, which suggests that such a peptide could participate directly or indirectly in the postnephrectomy natriuresis. Surgical denervation of either the ipsilateral or the contralateral kidney markedly alters the response to AUN, which prevents the natriuresis and blunts the kaliuresis, and indicates a role for renal neural reflexes. Renorenal reflex pathways also mediate the response of the contralateral kidney to UUO, because denervation of either the ipsilateral (obstructed) or the contralateral kidney abolishes both the natriuresis and kaliuresis usually seen after UUO. This reflex also involves the endogenous opioid system, for it does not occur in rats receiving an i.v. infusion of the opiate receptor antagonist naloxone.

Adaptation, Physiological↗
PubMed1984

Pyramidal actions in identified radial motornuclei of the cat.

This study aimed to establish the projection from the corticospinal tract (CST) to the motoneurones innervating the deep radial (DR) forelimb muscles. In the anaesthetized cat stimulation of the contralateral pyramid and intracellular recording from identified forelimb motoneurones was used. A train of pyramidal stimuli evoked disynaptic EPSPs in DR motoneurones. The effects were very similar in the different nuclei. Pyramidal IPSPs had a slightly longer latency and occurred in most cases together with disynaptic EPSPs. It is suggested that the inhibitory actions to the distal forelimb are predominantly relayed in a trisynaptic pathway, but that a disynaptic linkage seems possible as well. The disynaptic pyramidal EPSPs remained after CST transection in C5. They were abolished after CST transections in C2. It is concluded that disynaptic corticospinal excitation of distal DR motornuclei is relayed in a short midcervical propriospinal system. Transection experiments at different cervical levels suggest that the majority of the propriospinal neurones is located in C3-C4. The CST facilitated a variety of reflex pathways to motoneurones innervating distal forelimb muscles. Disynaptic excitatory and inhibitory effects from cutaneous and low threshold group I muscle afferents were common. They were present in all investigated nuclei and powerfully facilitated from the CST. It is suggested that this allows the brain to adapt the reflex mechanisms of the distal forelimb to the synergistic-antagonistic relations between the muscles, which are changing according to the performed movement.

Animals↗
PubMed1984

The hormonal responses to generalized tonic-clonic seizures.

We studied the hormonal responses to a generalized tonic-clonic convulsion in 20 patients with idiopathic or posttraumatic epilepsy (6 patients) or alcohol-withdrawal seizures (14 patients). We found an increase shortly after the seizure in plasma levels of ACTH, beta endorphin, beta lipotropin, prolactin, and vasopressin, and a later increase in plasma cortisol. There was no significant change in levels of growth hormone, luteinizing hormone, follicular stimulating hormone, or plasma renin activity. An increase in plasma ACTH level was accompanied by a rise in beta lipotropin and beta endorphin, and followed by a rise in plasma cortisol. In 2 patients there was no postictal increase in plasma prolactin, despite changes in other hormones. There was no difference in the nature or time course of the hormonal changes in patients with alcohol-withdrawal seizures and those with seizures from other causes. The mechanisms subserving these changes are unknown. Nonspecific stress influences the release of certain hormones, but the absence of a significant growth hormone response suggests that this was probably not responsible for our findings. It is possible that the generalized neuronal discharge of a seizure stimulates the hypothalamus either directly, through specific neurotransmitter changes, or through the release of other substances. One possibility that we are investigating in experimental animals is that endogenous opioids are involved, especially in the release of prolactin.

Adrenocorticotropic Hormone↗
PubMed1984

Reagent for the enzymatic determination of serum total triglycerides with improved lipolytic efficiency.

A fully enzymatic assay is described for the determination of triglycerides. The coupled activities of triacylglycerol acylhydrolase and glycerol kinase result in the formation of glycerol-3-phosphate. The system also contains L-alpha-glycerol-phosphate oxidase, which produces hydrogen peroxide from glycerol-3-phosphate, and a sensitive chromogenic indicator system, consisting of peroxidase, 4-chlorophenol and 4-aminophenazone. We evaluated this method with respect to kinetics, linearity, blank rates, precision, accuracy, reagent stability and interfering substances. The accuracy of the triglyceride assay demands that each enzymatic reaction step be complete and homogeneous. We therefore developed HPTLC-1) and HPLC-2) methods to monitor the course and completeness of each step.

Chromatography, Liquid↗