bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrogenic and electroneutral components of the sympathetic effect on fluid absorption in the rat jejunum
Authors: HEMLIN M. , BUTCHER P. , SJÖVALL H. 
Published: December 2008

The aim of the study was to test the hypothesis that the sympathetic nerves to the jejunum enhance net fluid absorption rate by inhibiting an electrogenic flux of anions into the lumen. The design of the experiments was based on the observation that the effect of catecholamines on electrogenic transport is abolished by yohimbine, anα2adrenergic antagonist.Net electrogenic transport in jejunal segments of anaesthetized rats was estimated by measurement of the transepithelial potential difference (PD) and short‐circuit current (SCC). Net fluid absorption rate was quantified by a gravimetric technique. The sympathetic nerves to the segment were stimulated electrically, bothin vitroandin vivo. The effect of sympathetic nerve stimulation on SCC and net fluid transport was determined in the absence and presence of theα‐adrenergic antagonists phentolamine (a non‐selectiveα‐adrenergic antagonist), prazosin (a selectiveα1‐antagonist) and yohimbine (a selectiveα2antagonist).Sympathetic nerve stimulation decreased PD and SCC and increased net fluid absorption rate. Phentolamine abolished both the electrogenic response and the effect on net fluid absorption rate, without having any significant intrinsic effects on either parameter. Prazosinper semarkedly increased net fluid absorption rate, but did not significantly influence the sympathetic effect on SCC or net fluid absorption rate. Yohimbine abolished the electrogenic effect of sympathetic stimulation, andper seincreased net fluid absorption rate in innervated but not in denervated segments. In innervated segments, the absorption rate during sympathetic nerve stimulation was similar in controls and yohimbine‐treated animals. In denervated segments, yohimbine significantly attenuated the sympathetic response.The results suggest that the sympathetic nerves enhance fluid absorption rate via effects on both electrogenic and electroneutral epithelial transport. These two components of the sympathetic response seem to be mediated by differentα‐receptor mechanisms.
Transient increase in insulin‐like growth factor I immunoreactivity in rat peripheral nerves exposed to vibrations
Authors: HANSSON H.‐A. , DAHLIN L. B. , LÖWENADLER B. , LUNDBORG G. , PALEUS S. , SKOTTNERU A. 
Published: December 2008

Hind legs of adult rats were exposed to vibrations (81 Hz; amplitude 0.50 mm peak to peak) for 4 h during two consecutive days. The sciatic, tibial and plantar nerves were isolated and processed for immunohistochemical demonstration of IGF‐I (insulin‐like growth factor I; somatomedin C) immunoreactivity at different time intervals after the vibration exposure.In sham‐exposed rats the axons in peripheral nerves showed no or faint IGF‐I immunoreactivity while most Schwann cells were negative. Exposure of the hind legs to vibrations induced increased IGF‐I immunoreactivity in the Schwann cells, demonstrable at the end of the exposure period and reaching maximal intensity 2–3 days after vibration exposure. Several distended axons similarly showed increased staining. The IGF‐I immunoreactivity decreased after 7–10 days to almost the level in the control nerves. The most extensive changes were observed in the plantar nerves. The tibial nerves similarly expressed strongly increased IGF‐I immunoreactivity in their Schwann cells. The sciatic nerve showed, however, only slightly to moderately increased staining. Cells in the epineurium of the plantar and, to a limited extent, of the tibial nerves expressed concomitantly increased IGF‐I immunoreactivity. We conclude that the transiently increased IGF‐I immunoreactivity in peripheral nerves reflects reactive changes caused by vibrations and most prominently expressed by the Schwann cells.
Muscle pathomorphology in m. quadriceps of marathon runners. Early signs of strain disease or functional adaptation?
Authors: SJÖSTRÖM M. , JOHANSSON C. , LORENTZON R. 
Published: December 2008

Muscle biopsies were obtained from m. vastus lateralis of five male marathon runners and five sprinters. The athletes performed their last competition at least 2 weeks prior to the investigation. No clinical signs of discomfort or injury were observed in the runners. The biopsy specimens from the sprinters showed an ordinary overall morphology, although fibre sizes varied considerably within and between the individuals. In contrast, in the marathon runners, structural deviations of pathologic value appeared in four out of five subjects. The fibre shapes were irregular, irrespective of fibre type, and internal architectural changes were common. An increased amount of connective tissue was found. A majority of fibres showed one or more central nuclei. A few fibres were flat and there were also evidence of fibre type grouping.The divergent picture might be an expression of repeated fibre injury with subsequent processes. If so, a peripheral, relative, arterial insufficiency is suggested as a possible aetiology. However, it cannot be ruled out that the deviations express a functional adaptation to the extreme endurance demands.
Insulin‐like growth factor I in the pancreas of normal and diabetic adult rats
Authors: HANSSON H.‐A. , EDWALL D. , LÖWENADLER B. , NORSTEDT G. , PALEUS S. , SKOTTNER A. 
Published: December 2008

Insulin‐like growth factor I (IGF‐I, somatomedin C) was mapped by immuno‐cytochemistry in the pancreas of normal and experimentally influenced rats. The polyclonal IGF‐I antiserum K 37 was characterized and demonstrated to be specific. In the exocrine pancreas some duct cells showed IGF‐I immunoreactivity, other components being negative.The three main endocrine cell types in the islets of Langerhans were IGF‐I immunoreactive, most strikingly the D cells. Hypophysectomy resulted in loss of IGF‐I immunoreactivity in all three endocrine cell types, i.e. D, A and B cells, while the levels of somatostatin, glucagon and insulin, respectively, remained unchanged. Starvation seemed to increase and feeding to decrease the IGF‐I immunoreactivity in the B cells. Cysteamine pre‐treatment reduced the normally intense IGF‐I and somatostatin immunoreactivities in the D cells. In rats made diabetic with alloxan or streptozotocin, the B cells were irreversibly damaged and lost both their insulin and IGF‐I immunoreactivities, while the IGF‐I immunoreactivity was increased in A cells; the D cells remained unchanged. The concentrations of IGF‐I mRNA in the pancreas were almost equal in normal and alloxan diabetic rats as were the concentrations of extractable IGF‐I.We conclude that IGF‐I immunoreactive material can be demonstrated in adult animals in all endocrine islet cells, most prominently in the D cells. The expression of IGF‐I immunoreactivity is in part under pituitary control. In the adult rat only one islet cell type synthesizes IGF‐I immunoreactive material, i.e. the D cells, while, in contrast, the B cells are likely to be a major IGF‐I source in fetal and neonatal islets.
Neurotropism in nerve regeneration: an immunohistochemical study
Authors: NACHEMSON A. K. , HANSSON H.‐A. , LUNDBORG G. 
Published: December 2008

A rectangular pseudomesothelial‐lined chamber was used to elucidate the hypothesis that in adult rats neurotrophic factors are formed after nerve injury and may influence regeneration of peripheral nerves. The proximal end of a cut sciatic nerve was inserted into one corner of the chamber. In one group of animals the distal end of the cut sciatic nerve was implanted in the diagonally opposite corner of the chamber. In another group we just introduced the proximal end of the sciatic nerve; no distal implant was used. The organization, length and direction of the nerve fibres, regenerating from the proximal end of the sciatic nerve, was visualized immunohistochemically with the aid of antibodies against neurofilaments at 2, 3 and 4 weeks after surgery. When a distal sciatic nerve segment was used, nerve fibres regenerating from the proximal cut end of the sciatic nerve showed an organized growth across the chamber, formed bundles and grew into the diagonally implanted nerve piece. If there was no distal implant, the growth of the randomly directed nerve fibres ceased after about two weeks, resulting in formation of a neuroma‐like structure. Increased immunoreactivity of the trophic peptide insulin‐like growth factor I (IGF‐I, somatomedin C) was demonstrated in the regenerating nerve, most evidently in reactive Schwann cells.It is concluded that a positive neurotropic effect is exerted on growing nerve fibres by injured, reactive peripheral nerve tissue. There could tentatively be a relation between nerve regeneration and local formation of trophic factors.
Electric muscle stimulation in the hind leg of the spontaneously hypertensive rat induces a long‐lasting fall in blood pressure
Authors: HOFFMANN P. , THORÉN P. 
Published: December 2008

The influence of prolonged low‐frequency, low‐intensity electric stimulation of the gastrocnemius muscle or of the biceps femoris muscle on blood pressure and heart rate was investigated in unanaesthetized, spontaneously hypertensive rats (SHR). In both groups, elevations of blood pressure and heart rate were elicited during the 60 min of muscle stimulation. After cessation of the stimulation, a depressor response developed within 60 min. Thirty to sixty minutes post‐stimulation the fall in blood pressure was 19 ± 3 and 17 ± 4 mmHg, respectively (mean ± SE) compared with controls. In both groups, the depressor response lasted for over 5 h. In addition, the gastrocnemius‐stimulated animals also developed a post‐stimulatory bradycardia. In one group of SHR the sciatic nerve was anaesthetized with bupivacaine. The arousal response during stimulation was similar to that in the other groups, but after termination of stimulation blood pressure returned to the control level without any further drop.To investigate further the neurotransmitters involved, one group of gastrocnemius‐stimulated SHR was given naloxone by infusion during the stimulation. A modest post‐stimulatory blood pressure fall also occurred in this group, but it lasted only 90 min. Another SHR group was pre‐treated with parachlorophenylalanine, a serotonin synthesis blocker, which completely abolished the post‐stimulatory depressor response. These results indicate that prolonged muscle stimulation gives rise to a post‐stimulatory long‐lasting drop in blood pressure and that this response is mediated by somatic nerve afferents. Involvement of the endorphin and serotonin systems is also suggested.
The calcium entry blocker verapamil increases red cell flux in the vasa recta of the exposed renal papilla
Authors: HANSELL P. , SJÖQUIST M. , ULFENDAHL H. R. 
Published: December 2008

To investigate the vasoreactivity of the vessels of the juxtamedullary vasculature, measurements were made of the red blood cell flux (Qrbe) in the vasa recta of the exposed renal papilla of anaesthetized rats by means of fluorescently labelled erythrocytes. The flux was measured before and after intravenous administration of the calcium entry blocker verapamil, which was infused in two different doses. A control group receiving vehicle was studied in parallel. The lower dose of verapamil (0.6 mg h‐lkg‐1body wt) increasedQrbeby 30 ± 6% (n =9,P <0.05, mean ± I SEM) and reduced the systemic blood pressure by 6% (P <0.05). The osmolality of urine samples from the papillary tip remained statistically unchanged (1199 ± 60vs. 1186 ± 102 mosm kg‐1H2O). In the animals receiving the higher dose of verapamil (2.4 mg h‐1kg‐1body wt), Qrbcincreased by 39 ± 7% (n =10,P0.05) and the blood pressure was reduced by 9% (P <0.05), while urine osmolality was unchanged (1104 ± 110vs. 1264 ± 123 mosm kg‐1H2O). In the time control group there was no statistically significant change in Qrbe(+ 6 ± 8%,n= 10), blood pressure or urine osmolality (1006 ± 61vs. 1091 ± 70 mosm kg‐1H2O).The verapamil‐induced increase inQrbcis probably mainly mediated by a relaxation of the afferent arteriole of the juxtamedullary nephrons. The results confirm our previous indication of a high vasoreactivity in the vessels of the juxtamedullary vasculature. This vasoreactivity is a prerequisite for the large regulatory span of the renal medullary blood flow and consequently for the medullary function.
The importance of the subepithelial resistance for the electrical properties of the rat jejunum in vitro
Authors: HEMLIN M. , JODAL M. , LUNDGREN O. , SJÖVALL H. , STAGE L. 
Published: December 2008

The aim of the study was to evaluate full‐thickness and partially stripped jejunum as a model for neurogenic control of electrogenic ion transport. The electrical properties of full‐thickness and partially stripped segments were studied in Ussing chambers. Using square‐pulse analysis, subepithelial and epithelial resistances (Rs and Rp) were determined, and by compensating for the potential fall across Rs, the current generated by the epithelium could be measured.In full‐thickness tissue, Rs was approximately 80% of total tissue resistance, and the current measured during short‐circuiting of the whole tissue (SCC) was therefore only 20–25 % of the current generated by the epithelium (Im). Surgical stripping of the tissue decreased Rs by 10–20%. This means that in full thickness as well as in stripped tissue, 70–80% of the potential difference across the epithelial layer remains after traditional ‘short circuiting’.Over a 25‐min period, none of the electrical parameters changed significantly in the full‐thickness tissues. In the stripped group PD, SCC and Im fell significantly, and in parallel during the same period of time. Neither glucose, noradrenaline, met‐enkephaline or karbachol had any significant effect on Rs, Rp or the Rs/Rp ratio. The relative effects of these agents on Im and SCC were therefore similar. Substance P and VIP increased the Rs/Rp ratio significantly and, therefore, the effect of these drugs on Im, was significantly more pronounced than the effect on SCC. The results show that the subepithelial resistance must be taken into account when the electrogenic activity in the epithelium is to be determined correctly. Conventionally measured SCC reflects the electrogenic effect of the tested putative neurotransmitters, but the magnitude of the responses is grossly underestimated, particularly for substance P and VIP.
Effects of hypovolaemia or isoprenaline infusion on the sympathetic reflex response to PEEP ventilation in rats
Authors: SELLDÉN H. , RICKSTEN S.‐E. 
Published: December 2008

The aim of this investigation was to study vagally mediated sympathetic reflex responses to mechanical ventilation with positive end‐expiratory pressure (PEEP), during hypovolaemia or during high inotropic stimulation of the heart by isoprenaline infusion. Renal sympathetic nerve activity (RSNA), heart rate and mean arterial pressure were studied during mechanical ventilation with zero end‐expiratory pressure (ZEEP) and 5 and 10 cmH2O PEEP in chloralose anaesthetized Wistar rats.Experiments were performed on two groups of rats: eight animals were subjected to 10% blood volume depletion, and seven animals to infusion of isoprenaline. PEEP ventilation was applied during control conditions and during hypovolaemia or isoprenaline infusion before and after vagotomy. In the intact (control) situation, there was a significant increase in RSNA from ZEEP to 10 PEEP in both groups (+ 75%, + 51%). During hypovolaemia or isoprenaline infusion, PEEP ventilation did not induce any significant increase in RSNA in both groups after vagotomy, 10 PEEP induced a significant increase in both groups (+ 56%, +54%).These results indicated that under conditions of hypovolaemia or increased cardiac inotropism, PEEP ventilation may elicit a vagally mediated reflex with an inhibitory action on sympathetic activity, in turn probably caused by an activation of left ventricular receptors.
Do the fibre‐type proportion and the angular velocity influence the mean power frequency of the electromyogram?
Authors: GERDLE B. , WRETLING M.‐L. , HENRIKSSON‐LARSÉN K. 
Published: December 2008

The dependence of the mean‐power frequency and the signal amplitude of the electromyogram (EMG) on the angular velocity and the fibre‐type proportion were investigated in nine female volunteers. The subjects were required to perform maximum knee extensions using an isokinetic dynamometer at different angular velocities; 0.57, 1.05, 1.57, 2.09 and 3.14 rad S‐1. Electromyographic signals were obtained from the vastus lateralis, vastus medialis and the rectus femoris muscles. The angle and the torque signals were recorded simultaneously with the three EMG signals on a tape‐recorder. From the EMG recordings the mean power frequency (MPF) and the signal amplitude were determined. Muscle biopsies were later obtained from the right vastus lateralis and stained for alkaline and acid mATPase for the determination of fibre‐type proportions and areas.Neither the signal amplitude nor the MPF of the EMG of the three muscles were dependent on the angular velocity. The MPF of the vastus lateralis correlated significantly (r = ‐0.93) with the type 1 fibre proportion at 1.57 rad s‐1. However, there was no significant correlation between the areas of the fibre types, alone or together, and the MPF. In conclusion the fibre‐type proportion was the major factor behind the MPF irrespective of angular velocity.
An intravital microscopic model for mast cell‐dependent inflammation in the hamster cheek pouch
Authors: RAUD J. , DAHLÉN S.‐E. , SMEDEGÅRD G. , HEDQVIST P. 
Published: December 2008

Topical antigen challenge in cheek pouches of immunized hamsters led to an acute inflammatory reaction which was characterized by intravital microscopy. The response consisted of short‐lasting arteriolar spasm, followed by leakage of plasma, vasodilation, and accumulation of leucocytes. Several observations indicated that the reaction was due to mast cell activation. Thus, a very similar inflammatory response was seen after challenge with compound 48/80, and both antigen and compound 48/80 degranulated the numerous mast cells present in the cheek pouch. In addition, fluorescein‐labelled antigen bound specifically to mast cells in cheek pouches of immunized animals, also suggesting the presence of mast cell‐fixed antigen‐specific antibodies, possibly immunoglobulin E. However, although antigen and compound 48/80 caused similar microvascular responses, cross‐desensitization experiments indicated that the two stimuli activated mast cells via different mechanisms.The histamine antagonist mepyramine, which abolished plasma leakage induced by exogenous histamine, substantially inhibited the increase of microvascular permeability evoked by antigen or compound 48/80, but did not appear to affect the vasospasm and leucocyte accumulation.It is concluded that the hamster cheek pouch may be a most useful tool for investigation of dynamic microvascular events during allergic mast cell‐dependent inflammation.
Intrafascicular multi‐unit recordings from the human infra‐orbital nerve
Authors: NORDIN M. , THOMANDER L. 
Published: December 2008

Intrafascicular micro‐electrode recordings were made from the human infra‐orbital nerve close to the infra‐orbital foramen. The fascicular organization was studied and multi‐unit activity from low‐threshold mechanoreceptive afferents was recorded during tactile stimuli, vibration and facial movements. Attempts were also made to record C‐fibre activity.Innervation zones corresponding to 66 fascicles were mapped with tactile stimuli on facial hairy skin and the red zone of the lip. Most of these fields were located on the upper lip, where they overlapped, indicating a high innervation density. The fields had a median size of 3.8 cm2.Skin indentation evoked dynamic on‐ and off‐responses and a much less pronounced static discharge. The afferent double‐peaked responses to an oscillating probe applied to the peri‐oral region induced similar grouping of the EMG activity during sustained lip protrusion. Contraction of facial muscles and stretching of the skin evoked on‐ and off‐responses, whereas the static discharge was less pronounced, especially during sustained stretching. The dynamic sensitivity to minor variations in contraction and stretching was high, and during normal facial movements, as in speech, there was a barrage of impulses originating from mechanoreceptors within large facial areas. Functional implications of these sensorimotor interactions are discussed.Sympathetic C‐fibre activity, frequently seen in recordings from the supra‐orbital nerve, was never encountered in the infra‐orbital nerve recordings, indicating a lack of such fibres. Failure to detect afferent C‐fibre activity could be explained by methodological difficulties.
Some aspects of the communicational and computational organization of the brain
Authors: FUXE K. , AGNATI L.F. , ZOLI M. , BJELKE B. , ZINI I. 
Published: December 2008

Some features of the morphofunctional organization of the CNS have been analysed.Different types of hierarchical organization have been recognized, each of which could deeply affect the circulation (communicational aspect) and elaboration (computational aspect) of information. These two aspects have been discussed on the basis of the existence of two types of electrochemical transmission in the CNS: wiring and volume transmission.By evaluating the CNS operations at different levels of analysis a ‘computational hierarchical organization’ has been delineated.This concept is very relevant to the understanding of the ‘computational power’ of the brain (Agnati & Fuxe 1984, Conrad 1985a).In fact, it leads to the distinction between horizontal and vertical elaboration of information.The hypothesis is introduced that in the vertical elaboration of information a central role may be played by the neuronal membrane. In fact, this structure can not only be influenced by the extra‐ and intracellular signals, but also effectively interconvert the electrical coding into the chemical coding of information. These aspects are discussed in the frame of the possible organization of the membrane into ‘domains’, each domain being a patch of membrane in which pre‐selected molecular movements are possible, resulting in molecular interactions. The movement of a molecule outside its domain is considered energetically unfavourable. The possible formal treatment of this hypothesis is mentioned in Conrad's work (1985b).
Carbachol stimulation of inositol phosphate accumulation in rat submandibular gland fragments is not modified by VIP
Authors: LARSSON O. , FREDHOLM B.B. 
Published: December 2008

Formation of inositol phosphates in response to carbachol, phenylephrine and vasoactive intestinal polypeptide (VIP) was studied after labelling with [3H]myo‐inositol in rat submandibular gland fragments. Carbachol enhanced the accumulation of inositol phosphates in a concentration‐dependent manner. This effect was independent of calcium in the incubation medium and totally antagonized by atropine (IC50= approx.1 nM).Phenylephrine also induced an increase in inositol phosphate accumulation, which was totally antagonized by prazosin but not by atropine. Vasoactive intestinal polypeptide, isoproterenol and forskolin, compounds known to enhance the levels of cAMP in rat salivary gland, or addition of dibutyryl‐cAMP (DB‐cAMP) failed to alter basal or carbachol‐evoked accumulation of inositol phosphates.It is concluded that the formation of inositol phosphates during muscarinic receptor stimulation with carbachol in rat submandibular gland fragments is not affected by adrenoceptor occupation or by cAMP.In particular, addition of VIP, which coexists with acetylcholine, did not alter the muscarinic inositol phosphate response.