Biomedical subjects

E Simon

Publications and source records attributed to E Simon.

At least 73 records · Page 4Linked to original sources

PubMed1997

Temperature sensitivity of neurones in slices of the rat spinal cord.

1. The inherent temperature sensitivity of 343 spontaneously active neurones recorded from rat spinal cord (SC) slices was investigated electrophysiologically. Recordings were made from 321 neurons from transverse and 22 neurons from longitudinal slices and their thermosensitivity was determined by relating changes in firing rate to changes in slice temperature. 2. Of the neurones from transverse slices, 53% were warm sensitive, 2% were cold sensitive and 45% were temperature insensitive. In longitudinal slices, 68% were warm sensitive and the remaining neurones were temperature insensitive. 3. When classified according to their recording sites in transverse slices, warm-sensitive neurones in laminae I and II had the same mean temperature coefficient compared with those recorded from lamina X, despite the fact that the latter had a significantly higher spontaneous activity. 4. The intrinsic temperature sensitivity of the majority of warm-sensitive neurones was confirmed by blocking their synaptic input. 5. A transient overshoot in activity, i.e. a dynamic response characteristic following rapid temperature stimuli (0.4 degree C s-1) was observed in 73% of the warm-sensitive and 59% of the temperature-insensitive neurones in laminae I and II in response to rapid warming, but only rarely (< 10%) in lamina X. 6. Temperature-sensitive SC neurones share response characteristics with temperature-sensitive neurones in the preoptic and anterior hypothalamic (PO/AH) area and with peripheral temperature receptors. Functionally, these neurones may represent the cellular basis for the temperature sensory function of the spinal cord that has been well characterized in vivo in homeothermic species.

Animals↗

PubMed1997

Electrophysiological and immunocytochemical evidence for a cGMP-mediated inhibition of subfornical organ neurons by nitric oxide.

The activation of neurons in the subfornical organ (SFO) by angiotensin II (AngII) is well established and is widely regarded as the basis for the AngII-induced increase in water intake. Application of the nitric oxide (NO) donor sodium nitroprusside (SNP) led to an inhibition of the spontaneous electrical activity in 96% of the neurons sensitive for SNP (n = 50). In addition, the firing rate in 60% of the neurons inhibited by SNP decreased in response to superfusion with the natural substrate of the NO synthase (NOS) L-arginine whereas 70% increased their frequency after application of the NOS blocker NG-monomethyl-L-arginine (L-NMMA; n = 10). The inhibitory effect of SNP could be mimicked by application of membrane-permeable 8-Br-cGMP. The presence of nNOS, the neuronal isoform of NOS, was demonstrated immunocytochemically and using the NADPH-diaphorase technique on SFO slices. Using a highly selective antibody against cGMP in formaldehyde-fixed tissue, the NO donors SNP, 3-morpholinosydnonimine (SIN-1), and S-nitroso-N-acetyl-DL-penicillamine (SNAP) caused a strong increase in cGMP formation when applied under the same conditions as used for the electrophysiological recordings. These electrophysiological results suggest an important role for NO in SFO-mediated responses and offer a plausible explanation for the in vivo-observed opposite effects of AngII and NO on water intake.

Animals↗

PubMed1997

Association between carriage of oral yeasts, malnutrition and HIV-1 infection among Tanzanian children aged 18 months to 5 years.

The objective was to determine whether there is an association between carriage of oral yeasts, malnutrition and HIV-1 infection among Tanzanian children. A case-control study design within a cross-sectional study was used, and the outcome was carriage of oral yeasts. The exposure variables were malnutrition and HIV-1 antibody, and confounders to be adjusted for were age, sex, and breastfeeding. The study was carried out in Dar-es-Salaam, Tanzania, in two maternal and child health (MCH) clinics that offer routine medical checkups to all expectant mothers and children aged between 0 and 5 years in the catchment area. A total of 882 children aged between 18 months and 5 years participated. Smears from the tongue and buccal mucosa were examined for oral yeasts. Malnutrition was categorized according to standards on the MCH chart and World Health Organization/Centers for Disease Control (WHO/CDC) standards as weight-for-height (wasted), weight-for-age (underweight), and height-for-age (stunted). HIV-1 infection was determined by an enzyme-linked immunosorbent assay. Reactive sera were confirmed by Western Blot. About 27% of the children were slightly or severely malnourished according to standards on the MCH chart. According to WHO/CDC standards, 2.6% were wasted, 16.3% were underweight, and 29.6% were stunted. Fourteen (1.6%) were seropositive for HIV-1 antibody. Hyphal forms and blastospores were much more frequent among children infected with HIV-1 with odds ratios ranging from 3.8 (95% CI: 1.3;11.2) to 6.2 (95% CI: 2.1;18.4) depending on categorization of malnutrition. Malnutrition was a risk factor, too, albeit to a much lesser and insignificant degree. The study supports our previous findings that malnutrition may predispose to carriage of oral yeasts and subsequent infection. However, in this study population HIV infection was clearly the predominant risk factor.

AIDS-Related Opportunistic Infections↗

PubMed1997

Heterogeneous actions of vasopressin on ANG II-sensitive neurons in the subfornical organ of rats.

The aim of this study was to investigate the effects of the antidiuretic hormone arginine vasopressin (AVP), which is released in vivo during dehydration and hypovolemia to prevent further water loss, on the activity of neurons in the subfornical organ (SFO). The SFO is a brain structure with an open blood-brain barrier and is critically involved in angiotensin II (ANG II)-dependent water intake. SFO neurons were recorded extracellularly in tissue slices of the rat brain and were tested for responsiveness to AVP and ANG II. About one-half of 159 neurons tested with an AVP concentration of 10(-6) M in the superfusion medium were responsive, and approximately equal proportions were excited and inhibited. Neurons exhibiting the different response types did not differ from each other with respect to spontaneous discharge rate, latency, and duration of the response. Excitatory and inhibitory responses to AVP were dose dependent and reversible, and their threshold concentrations (10(-8) to 10(-9) M) were similar. Superfusion with a medium low in Ca2+ and high in Mg2+ showed that the excitatory effect is most likely direct, whereas the inhibitory effect largely depends on inhibitory synaptic interaction. About one-half of the SFO neurons excited by ANG II (10(-7) M) were responsive to AVP (10(-6) M), and equal proportions were inhibited and excited. Both excitatory and inhibitory AVP actions were blocked by the V1-receptor antagonist, Manning compound, and neurons responsive to AVP did not respond to the V2-receptor agonist [deamino-Cys1,D-Arg8]vasopressin. It is concluded that AVP, probably released from synaptic terminals, may increase or decrease the activity of neurons in the SFO, many of which are activated by ANG II. In contrast to previous experiments on ducks, in which the exclusively excitatory effect of the avian antidiuretic hormone arginine vasotocin on ANG II-sensitive SFO neurons correlates well with the dipsogenic effect of both peptides, a greater functional heterogeneity exists among AVP-responsive neurons in the rat SFO.

Angiotensin II↗

PubMed1997

Plasma and erythrocyte vitamin E content in asymptomatic hypercholesterolemic subjects.

The present study was designed to assess plasma and erythrocyte vitamin E concentrations in 57 asymptomatic hypercholesterolemic (HC) men compared with 56 normocholesterolemic (NC) men. Vitamin E concentrations were determined by using a reversed-phase HPLC method. Compared with NC subjects, HC men had a significantly lower red blood cell (RBC) vitamin E content in spite of their normal plasma vitamin E concentration. This study demonstrates that total plasma vitamin E concentration is not a suitable predictor of cell vitamin E status and suggests an abnormal transfer of tocopherol between plasma and RBCs in HC men. Moreover, the RBCs of HC men were more susceptible to a peroxidative stress. The strong correlation between RBC susceptibility to oxidation and RBC vitamin E content suggests that the low RBC vitamin E content found in HC men has physiological consequences on the RBC oxidation.

Amidines↗

PubMed1997

Transabdominal preperitoneal herniorraphy: technique and results.

As enthusiasm for laparoscopic surgery has grown, laparoscopic approaches to the groin hernia have evolved. The most widely accepted laparoscopic repair employs the placement of a large sheet of mesh in a preperitoneal position to cover potential hernia spaces. Between March 1994 and February 1997 160 inguinal and 3 femoral hernia were operated of an transabdominal preperitoneal (TAPP) polipropylen mesh. 131 patients were operated (128 males and 3 females, ranging in age from 19 to 82 years), 31 (23%) of them had bilateral hernias. Recurrent hernia was the indication in 52 (32%) cases. Average operating time for unilateral repair was 80 minutes and for bilateral repairs was 108 minutes. Postoperative complications included 7 (4.3%) cases of transient neuralgias, 20 (12%) cord/scrotal transient seromas-hematomas and 2 (1.2%) hydrocele. The 5 (3.1%) early recurrences were considered to be caused by technical inexperience and/or too small prosthetic patch. The laparoscopic hernioplasty has definitive advantage: minimal postoperative pain, short hospital stay (average postoperative time of hospitalization 3.1 days) and early restoration of full physical activity (in 1 to 2 weeks). The method should be considered as a potential "best option" in patients with recurrences and bilateral inguinofemoral hernias.

Abdomen↗

PubMed1997

[Medical treatment exclusively for cervical pregnancy with in situ methotrexate].

We present a case report of cervical pregnancy with medical treatment. Medical treatment consisted in injection of methotrexate (50 mg) into the pregnancy, on the first, third and seventh day. Ultrasound and Doppler give important information for follow up. The pregnancy totally resolved and the patient did not need any further treatment.

Adult↗

PubMed1997

Nutritional status of under fives attending maternal and child health clinics in Dar es Salaam, Tanzania.

We designed a study to assess the nutritional status of children under five years of age attending MCH clinics in Dar es Salaam. This was a cross-sectional anthropometric study involving children 6-24 months who from July to August 1993 were attending Magomeni MCH clinic and those aged 18 months to five years who were attending Lugalo and Mwananyamala MCH clinics for routine growth monitoring and for vaccination between May to August 1994. The data collected included age, birthweight, sex, weight, height, breastfeeding status and HIV-1 serostatus. Of the 1854 children enrolled (961 boys and 893 girls) 31.6% were stunted, 14.6% were underweight and 2.9% were wasted. The highest percentage of stunting and wasting was observed between 11 and 25 months and 36 to 40 months. Of the 849 children tested for HIV-1, 14 (1.7%) were seropositive and two out of 770 (0.3%) were born with low weight. HIV seropositivity and low birthweight were both associated with stunting and wasting. We conclude that malnutrition is still a sizeable problem among children attending urban MCH clinics in Dar es Salaam especially among those aged less than three years, to whom special malnutrition control strategies should be targeted. There is also a need to identify factors responsible for the observed decline in MCH attendance with age and correct the situation.

Age Distribution↗

PubMed1996

[New possibility in inguino-femoral hernia repair: laparoscopic herniaplasty].

The development of minimally invasive surgery brought up the challenge: to repair the frequent inguino-femoral hernias laparoscopically. The authors performed 65 laparoscopic hernioplasties in one year: "transabdominal preperitoneal" technique was used in 61 cases und "intraperitoneal onlay mesh" in 4 cases. Fifty-three patients were operated on, 12 of them had bilateral hernias. Recurrent hernia was the indication in 22 patients (34%). The average operating time was 102 and 144 minutes in the unilateral and the bilateral cases, respectively. There was no wound infection, or general complication. Spontaneously dissolving seroma/hematoma of the spermatic cord was noticed and detected by ultrasound in 5 patients (7.7%). The neuralgia caused by the irritation of the nerves of the region in 4 patients (6.1%) disappeared without sequels after treatment with vitamins B. The 2 early recurrences (3.2%), considered to be caused by technical inexperience, these patients were treated successfully with the "intraperitoneal onlay mesh" technique. In the authors' opinion there are definite advantages of laparoscopic hernioplasty, namely the minimal postoperative pain, early mobilization, shorter hospital stay and early restoration of full physical activity (in 1-2 weeks) as well as the known disadvantages of this technique (narcosis, longer operative time, intraperitoneal procedure, higher costs).

Adult↗

PubMed1996

Hormonal secretion patterns but not autonomic effector responses elicited by hypothalamic heating and cooling are altered in febrile rabbits.

The effects of hypothalamic heating and cooling on thermoregulatory effector activities, lipid and carbohydrate metabolism, insulin, glucagon, thyroxine, arginine vasopressin (AVP) and cortisol were investigated in conscious rabbits and compared with those obtained in the febrile state. The study shows that under control conditions hypothalamic heating lowers, and cooling raises core temperature. Core temperature always rose to similar degrees in response to bacterial lipopolysaccharide (LPS) during an observation time of 150 min, but it started to rise from lower and higher levels, respectively, during hypothalamic heating and cooling. The effects of hypothalamic thermal stimulation on specific thermoregulatory effector activities support the conclusion that, within 60 min after LPS, the hypothalamic warm signal input is reduced relative to the cold signal input. The increase of thyroxine levels following LPS suggests that the elevation of the thermoregulatory setpoint was caused by an increased input of hypothalamic TRH neurons, known to induce the full autonomic pattern of cold defense also in response to non-thermal stimuli. With the exception of an increase of glucagon during hypothalamic cooling at control conditions, hypothalamic thermal stimulation alone did not alter lipid and carbohydrate metabolism, insulin, thyroid hormone, AVP and cortisol secretion. A spontaneous heat loss effector response separated the first from the second fever phase 60 min after LPS. Subsequently AVP and cortisol plasma levels rose in febrile animals, irrespective of hypothalamic heating and cooling, presumably as a consequence of pyrogenic activation of corticotropin releasing factor (CRF) producing neurons and their reciprocal interaction with TRH neurons on the one hand, and by a reciprocal interaction of the latter with AVP neurons on the other.

Animals↗

PubMed1996

Angiotensin II receptor subtypes in the duck subfornical organ: an electrophysiological and receptor autoradiographic investigation.

The pharmacology of angiotensin II (AngII) receptors was investigated in the brain of ducks using receptor autoradiographic and electrophysiological methods. Using 125I[Val5]AngII as a ligand, specific binding was observed in sections of the duck adrenal gland and in several brain areas involved in body fluid homeostasis. Displacement studies using the same antagonists as used for classifying mammalian AngII receptor subtypes revealed that the rank order of potencies in competition with AngII receptors in the adrenal gland and in the subfornical organ was: AngII > CGP-42112A > losartan > PD-123319. Electrophysiological recordings from spontaneously active neurons of duck SFO slices revealed that the majority of neurons could be excited by AngII (10(-7) M). The excitatory effect of AngII could be partially inhibited by CGP-42112A (10(-5) M), which proved to be more effective than equimolar losartan and far more effective than PD-123319. These data suggest that the neuronal AngII receptors in the SFO are pharmacologically distinct from the mammalian AT1- and AT2-receptors. Further, central AngII receptors of ducks share common pharmacological characteristics with AngII receptors in the duck adrenal gland and peripheral organs of other bird species.

Angiotensin II↗

PubMed1996

Effects of angiotensin II and its blockers Sar1-Ile8-angiotensin II and DuP 753 on drinking in ducks in relation to properties of subfornical organ neurons.

Properties of systemically applied angiotensin II in stimulating water intake of normally hydrated ducks were studied and the results compared with properties of angiotensin II-responsive neurons of the subfornical organ which are considered as targets for circulating angiotensin II acting as a dipsogen. Following intravenous infusion of hypertonic saline (2000 mosmol.kg-1 at 0.3 ml.min-1 for 1 h), intravenous infusion of 0.3 ml.min-1 isotonic saline with angiotensin II (200 ng.min-1), starting 1 h later, stimulated drinking in each case at an angiotensin II plasma level of about 1400 pg.ml-1. Without hypertonic priming, the same angiotensin II infusion did not stimulate drinking in each experiment; however, if effective, repeated infusions of ANGII induced stable dipsogenic responses. Angiotensin II infusions did not alter plasma levels of antidiuretic hormone. Sar1-Ile8-angiotensin II, a non-selective angiotensin II antagonist, acted weakly as a partial agonist when infused at a dose 200-fold higher than angiotensin II and effectively blocked the dipsogenic action of angiotensin II; this corresponds to the inhibition of angiotensin II-induced excitation by Sar1-Ile8-angiotensin II observed in duck subfornical organ neurons. DuP 753 (losartan), an angiotensin II antagonist specifically blocking AT1 receptors in mammals, had equivocal effects on angiotensin II-induced drinking in ducks at rates 50- and 200-fold higher than angiotensin II, which corresponds to the weak inhibitory action of this compound on angiotensin II-induced neuronal excitation in the duck SFO. Blood pressure was only marginally elevated by the applied angiotensin II dose and Sar1-Ile8-angiotensin II had no effect.

Angiotensin II↗

PubMed1996

Vasotocin acts as a dipsogen in ducks at concentrations stimulating subfornical organ neurons in vitro.

The effects of systemic infusions of the avian antidiuretic hormone arginine vasotocin on water intake of domestic ducks were investigated under steady conditions of water balance in which angiotensin II was effective as a dipsogen. The study proceeded from the consistent stimulatory effect of arginine vasotocin on angiotensin II-responsive neurons found in the subfornical organ of ducks, suggesting brain-intrinsic vasotocinergic control of these neurons which are also accessible to circulating agents because of the lacking blood-brain barrier. Levels of circulating arginine vasotocin of about 2700 pg.ml-1 which were close to the threshold for activation of subfornical organ neurons in vitro, induced weak but significant drinking responses. Even at this high arginine vasotocin level circulatory effects were absent, thereby excluding their interference with water intake. Arginine vasotocin plasma levels of about 60 pg.ml-1 significantly attenuated the dipsogenic action of angiotensin. While drinking in response to high pharmacological levels of arginine vasotocin is assumed to mimic a stimulatory innervation of angiotensin-responsive subfornical organ neurons by brain-intrinsic vasotocinergic axons, attenuation of angiotensin-induced drinking by high physiological arginine vasotocin levels cannot be explained by its action on central neurons, but may be secondary to body fluid retention caused by the antidiuretic action of arginine vasotocin.

Angiotensin II↗

PubMed1996

Opioid receptor imaging and displacement studies with [6-O-[11C] methyl]buprenorphine in baboon brain.

Buprenorphine (BPN) is a mixed opiate agonist-antagonist used as an analgesic and in the treatment of opiate addiction. We have used [6-O-[11C]methyl]buprenorphine ([11C]BPN) to measure the regional distribution in baboon brain, the test-retest stability of repeated studies in the same animal, the displacement of the labeled drug by naloxone in vivo, and the tissue distribution in mice. The regional distribution of radioactivity in baboon brain determined with PET was striatum > thalamus > cingulate gyrus > frontal cortex > parietal cortex > occipital cortex > cerebellum. This distribution corresponded to opiate receptor density and to previously published data (37). The tracer uptake in adult female baboons showed no significant variation in serial scans in the same baboon with no intervention in the same scanning session. HPLC analysis of baboon plasma showed the presence of labeled metabolites with 92% +/- 2.2% and 43% +/- 14.4% of the intact tracer remaining at 5 and 30 min, respectively. Naloxone, an opiate receptor antagonist, administered 30-40 min after tracer injection at a dose of 1.0 mg/kg i.v., reduced [11C]BPN binding in thalamus, striatum, cingulate gyrus, and frontal cortex to values 0.25 to 0.60 of that with no intervention. There were minimal (< 15%) effects on cerebellum. Naloxone treatment significantly reduced the slope of the Patlak plot in receptor-containing regions. These results demonstrate that [11C]BPN can be displaced by naloxone in vivo, and they affirm the feasibility of using this tracer and displacement methodology for short-term kinetics studies with PET. Mouse tissue distribution data were used to estimate the radiation dosimetry to humans. The critical organ was the small intestine, with a radiation dose estimate to humans of 117 nrad/mCi.

Animals↗

PubMed1996

Detection of anti-HIV-1 IgG antibodies in whole saliva by GACELISA and Western blot assays.

The present study, based on 158 HIV seropositives and 167 HIV seronegatives, demonstrates that saliva collected with the Omni-SAL device and tested with GACELISA (an IgG antibody capture ELISA) is an effective non-invasive alternative to serum for anti-HIV IgG antibody screening. The study also shows that a conventional serum Western blot kit can be used, with slight modifications, for confirmatory testing of saliva specimens. Collecting saliva with the Omni-SAL device had a very good acceptance rate among Tanzanian subjects, and although this diagnostic method is not yet known by the general public, 65% of the study participants preferred to give saliva instead of blood for HIV testing.

Adult↗

PubMed1996

Biotypes of oral Candida albicans isolates in a Tanzanian child population.

Although biotypes of Candida albicans from adult populations, especially in the West, have been described, there are no data either from a child population, or from the African continent. Hence a total of 200 oral C. albicans isolates from Tanzanian children aged 6-24 months were biotyped using two commercially available API micromethod kit systems and a boric acid resistance test. The predominant biotypes, which comprised two thirds of the organisms isolated, were J1S (19.5%), A1S (16.0%), J1R (14.5%), A1R (9.5%) and P1R (7.5%). In total, 16 new biotypes comprising 44 (22%) isolates which have not hitherto been described were found in this Tanzanian population and, of these, the P1R biotype predominated with 15 (7.5%) isolates. There was no significant association between predominant biotypes (with clusters > or = 15 isolates) and age, gender, breast feeding and malnutrition. These data indicate that the biotype profile of C. albicans isolates may differ in paediatric and adult populations, and/or global distribution of various subtypes of this common opportunistic pathogen.

Candida albicans↗

PubMed1995

Opposite effects of angiotensin II and nitric oxide on neurons in the duck subfornical organ.

Angiotensin II (ANGII) is known to activate neurons in the subfornical organ (SFO) of mammals and birds and this activation is regarded as the basis for the ANGII induced increase in water intake. Application of the nitric oxide (NO) donor sodium nitroprusside inhibited the activity in 10 out of 12 duck SFO neurons, 8 of which were in addition excited by ANGII. These data, in combination with the histochemical detection of NO synthase in the duck SFO, demonstrate the involvement of NO in SFO mediated responses and might represent the cellular basis for the observed opposite effects of ANGII and NO on water intake.

Angiotensin II↗

PubMed1995

Excitatory action of the bird antidiuretic hormone vasotocin on neurons in the subfornical organ.

The responsiveness of spontaneously active neurons in the subfornical organ (SFO) of adult ducks to angiotensin II (ANGII) and the bird specific antidiuretic hormone, arginine vasotocin (AVT), the analog of the mammalian arginine vasopressin (AVP), were investigated in brain slices with extracellular recording technique. 65% (n = 66) of the neurons increased their activity after superfusion with ANGII, the rest were unresponsive. Application of AVT activated 52% (n = 68) of the investigated neurons and like ANGII never caused an inhibition of the spontaneously active SFO neurons. A close correlation exists between the ANGII and AVT sensitivity of duck SFO neurons, because 29 out of 33 neurons were excited by AVT as well as ANGII. The relatively weak antagonistic effect of the V1-type receptor antagonist Pmp-Tyr (Me)-Arg8-vasopressin on the AVT induced excitation suggests a different pharmacology of the bird AVT receptor as compared to the mammalian AVP receptor. The excitatory response of ANGII and AVT on the very same neurons suggest a similar function of both peptides on SFO mediated effects in vivo, such as an increase in water intake. However, peripheral AVT concentrations, unlike ANGII concentrations in the blood are not high enough to activate SFO neurons from the blood side of the blood brain barrier. Therefore AVT is presumably released from synapses of neurons originating within or projecting to the SFO. The identity of the ANGII and AVT reactive neurons suggests that synaptically released AVT should facilitate SFO mediated drinking.

Angiotensin II↗