Cerebellar nuclei and the nucleocortical projections in the rat: Retrograde tracing coupled to GABA and glutamate immunohistochemistry

The amino acids GABA and glutamate (Glu) are thought to be the principal substances in the central nervous system responsible for neuronal inhibition and excitation. Their distributions among the different neurons in a defined pathway may thus be indicative of the contributions of the cells to pathway function. Examples of such neurons are those of the cerebellar nuclei which, while regulating output from the Purkinje cells of the cerebellar cortex, are also found to project back to the cerebellar cortex. Immunohistochemical experiments were done to identify GABA and glutamate (Glu) containing cells in the adult rat cerebellar nuclei. Consecutive semithin and serial vibratome sections were incubated with antisera raised in rabbit against GABA and Glu. In semithin sections, only small neurons were intensely GABA immunoreactive (GABA-IR) (31.7%), and the majority (80.5%) were Glu immunoreactive (Glu-IR) of different sizes. Consistent with Glu being a metabolic precursor for GABA, 75.4% of the GABA-IR population colocalized Glu. In vibratome sections GABA-IR neurons showed some local differences in number, whereas the Glu-IR were uniformly distributed in the three nuclei studied. Measured mean diameters for these neurons showed a distinct size difference for the GABA- and Glu-IR with little overlap. Cerebellar nuclei neurons projecting to the cortex (nucleocortical neurons, NCN) were identified by locally preinjecting the retrograde transported WGA-apoHRP-colloidal gold complex in the cerebellar cortex. Vibratome sections of these cerebellar were silver intensified for the retrograde tracer and double labeled for GABA and Glu. Of the total number of identified NCN, 8.7% were GABA-IR (10 animals) and 47.7% Glu-IR (5 animals). Many retrograde labeled NCN in the core of the thick sections were immunonegative for both amino acids due to poor antibody penetration, thus underestimating the proportions of cells containing GABA and Glu. The size distributions for the GABA-IR and Glu-IR NCN were similar to those measured in non-retrograde labeled nuclei in thick sections. The conclusions reached are that GABA-IR neurons of the cerebellar nuclei, including the NCN, use GABA as the presumed inhibitory neurotransmitter and that Glu-IR neurons may use Glu or another excitatory neurotransmitter.

Sensitivity of rubrospinal neurons to excitatory amino acids in the rat red nucleus in vivo

Responses of rubrospinal neurons (RSNs) to iontophoretic applications of L-glutamate (L-Glu), L-aspartate (L-Asp), quisqualate (Quis) and N-methyl-D-aspartate (NMDA) have been studied in the rat red nucleus (RN) in vivo. All agonists produced a dose-dependent increase of the firing rate and Quis was found to be the most efficient. The responses to NMDA and to a lesser extent to L-Asp were abolished by steady application of 2-amino-5-phosphonovalerate (2APV) whereas responses to Quis were unaffected and those to L-Glu poorly antagonized. On the other hand, NMDA-mediated excitations were insensitive to steady application of 6,7-dinitroquinoxaline-2,3-dione (DNQX) which abolished responses to Quis and to a lesser extent to L-Glu while those to L-Asp were less affected. These results show the presence of both NMDA and non-NMDA receptors on RSNs in the rat. A specific localization of the NMDA receptors on distal dendrites of these neurons is suggested.

The high and low affinity transport systems for dipeptides in kidney brush border membrane respond differently to alterations in pH gradient and membrane potential

The principal aim of the present study was to investigate the effects of variation in proton gradient and membrane potential on the transport of glycyl-L-glutamine (Gly-Gln) by renal brush border membrane vesicles. Under our conditions of transport assay, Gly-Gln was taken up by brush border membrane vesicles almost entirely as intact dipeptide. This uptake was mediated by two transporters shared by other dipeptides and characterized as the high affinity (Kt = 44.1 +/- 11.2 microM)/low capacity (Vmax = 0.41 +/- 0.03 nmol/mg protein/5 s) and low affinity (Kt = 2.62 +/- 0.50 mM)/high capacity (Vmax 4.04 +/- 0.80 nmol/mg protein/5 s) transporters. In the absence of a pH gradient, only the low affinity system was operational, but with a reduced transport capacity. Imposing a pH gradient of 1.6 pH units increased the Vmax of both transporters. Kinetic analysis of the rates of Gly-Gln uptake as a function of external pH revealed Hill coefficients of close or equal to 1, indicating that transporters contain only one binding site for the interaction with external H+. The effects of membrane potential on Gly-Gln uptake were investigated with valinomycin-induced K+ diffusion potentials. The velocity of the high affinity system but not of the low affinity system increased linearly with increasing inside-negative K+ diffusion potentials (p less than 0.01). The Kt of neither system was affected by alterations in either pH gradient or membrane potential. We conclude that (a) the high affinity transporter is far more sensitive to changes in proton gradient and membrane potential than the low affinity transporter and (b) in the presence of a pH gradient, transport of each dipeptide molecule requires cotransport of one hydrogen ion to serve as the driving force.

Effects of ACPD and AP3 on parallel-fibre-mediated EPSPs of Purkinje cells in cerebellar slices in vitro

The effects of trans-1-amino-cyclopentyl-1,3-dicarboxylate (trans-ACPD) and of DL-2-amino-3-phosphonopropionic acid (AP3), i.e. selective agonist and antagonist of metabotropic quisqualate receptors respectively, on parallel fibre (PF)-mediated EPSPs of Purkinje cells (PCs) were studied in an in vitro slice preparation. Bath application of 500 microM trans-ACPD in conjunction with PF stimulation at 0.2 or 1 Hz depending on the cell always induced a marked depression of PF-mediated EPSPs, which was fully reversible in most cases after wash-out of this compound. Trans-ACPD also often induced a transient depolarization of PCs which induced calcium spike firing in these cells and which again no longer persisted after wash-out of trans-ACPD. Even in cells which were depolarized by trans-ACPD, the decrease in amplitude of PF-mediated EPSPs started before the appearance of calcium spikes, lasted longer than the transient depolarizing effect of trans-ACPD, and was accompanied by no variation in input resistance of the cells when they were manually clamped at their initial resting potential. Bath application of 600 microM DL-AP3 had no effect on PF-mediated EPSPs or the bioelectrical activities of PCs. Moreover, it did not prevent the effects of trans-ACPD mentioned before. The present results are not consistent with the view that coactivation of ionotropic and metabotropic quisqualate receptors of PCs is sufficient to induce a long-term depression of PF-mediated EPSPs.

Transport of pteroylglutamic acid into brush border membrane vesicles from rat small intestine is a partially carrier-mediated process

Intestinal transport of PteGlu was studied using BBMV from rat small intestine. Transport was neither coupled to a specific cation gradient nor was it influenced by variations of the membrane potential. In the presence of a transmembrane pH gradient (pHout less than pHin) initial transport was significantly higher compared to studies without pH gradient. Under these conditions transport could be inhibited by pretreating the vesicles with DIDS, an inhibitor of anion exchange systems. Uptake of PteGlu could not be enhanced by preloading the BBMV with HOP4(2-) and Cl- and was not sensitive to DIDS under these conditions. Uptake studies using different concentrations of PteGlu revealed dual transport kinetics in the presence of a pH gradient and linear uptake in its absence. It could be concluded that uptake is mediated by a PteGlu-/OH(-)-antiporter at low substrate concentrations and occurs by non-ionic diffusion at higher concentrations or in the absence of a pH gradient. In an additional series of experiments it could be shown that about one-third of the substrate is bound to the membrane and is not transported. The biological significance of this binding remains unclear.

We are all people living with AIDS: myths and realities of AIDS in Brazil

Although AIDS was expected in Brazil, no serious efforts were undertaken to prevent AIDS from taking root. Irresponsible press and media coverage highlighted the spread of AIDS within the gay community of the United States, creating an aura of immunity in Brazil to what was characterized as a "foreign" disorder. When AIDS did surface in 1983, the official response was to adopt an abstract, inappropriate, and ideological "Western" model, in which only stigmatized "others" and "minorities" were at risk of HIV infection. Brazilian health authorities subsequently downplayed the significance of the sale of contaminated blood in HIV transmission, and likewise ignored the rising rates of AIDS among Brazil's one unarguable majority group: the poor. An analysis of efforts to force the "facts" of AIDS to fit a false model's predictions leads to a clearer definition of the broader context of the Brazilian epidemic: we all are people living with AIDS, precisely because we live in this age of AIDS; it is sheer folly to discriminate against persons infected by HIV and to obstruct their participation in efforts to curtail the epidemic's spread; and the necessary response to AIDS is solidarity, not because it is poetic, but because no other response will suffice.

In vivo kinetics of intestinal absorption of riboflavin in rats

To investigate absorption kinetics of riboflavin under in vivo conditions, with blood and lymph circulation intact, the small intestine of anesthetized rats was perfused with [14C]riboflavin in a concentration range between 0.31 and 10.00 mumol/L. Apart from the uptake of riboflavin from the perfusate, passage of the vitamin into the portal (vena portae) and peripheral (vena femoralis) blood was determined. The absorption proved to be a dual process: at low substrate concentrations (less than 2 mumol/L) a saturable component predominated; at higher concentrations simple diffusion was found to be the prevailing uptake mechanism. The apparent transport constant of the saturable component was calculated to be 0.38 mumol/L. [14C]flavin concentrations in the portal and peripheral blood were estimated as a function of the riboflavin concentration of the perfusion media. The dual character of the absorption was reflected by the portal blood flavin levels. Due to the high retaining and equalizing capacity of the liver, the [14C]flavin level of the peripheral blood was relatively low and obeyed saturation kinetics. Constants of elimination, determined by pharmacokinetic calculations, were different for the two blood compartments but independent of the concentration of riboflavin in the perfusion media.

Improved xenograft survival with continuous infusion deoxyspergualin and RATG

The critical shortage of available donor organs is the major limit to current allogeneic transplantation. Xenografting has the potential to overcome this difficult problem. Suppressing the vigorous rejection response remains a major obstacle to the clinical application of xenografting, 15-Deoxyspergualin (DOSP), a potent new immunosuppressive agent has been shown to be effective in allogeneic and xenogeneic experimental models. This study tests DOSP in combination with rabbit antithymocyte globulin (RATG) in the hamster-to-rat cardiac xenograft. Results show that combination therapy with DOSP/RATG was superior to treatment with either agent alone (p less than .05). Optimal graft prolongation (20.9 days versus control of 3.1 days, p less than .05) was achieved with combination therapy of RATG and DOSP 2.5 mg/kg day-1 by continuous infusion.

New tetracyclic guanidine derivatives with H1-antihistaminic properties. Chemistry of epinastine

A series of new tetracyclic guanidines were synthesized by various methods. Specific binding of the described compounds to histamine-1 and histamine-2 receptors was determined. The compound 3-amino-9,13b-dihydro-1H-dibenz[c,flimidazo[1,5-a]azepine (epinastine, WAL 801, compound IIIa) combines high selectivity with high affinity for the H1 receptor and was selected from the compounds studied for further pharmacological and clinical investigations. Experimentally determined physicochemical parameters (pka-value, partition coefficient) and the hydrogen-bonding ability of epinastine are indications that this compound will not easily cross the blood-brain barrier. This explains the absence of CNS side-effects of epinastine in pharmacological and clinical studies.

Effect of casein and beta-casomorphins on gastrointestinal motility in rats

The effect of bovine casein and synthetic beta-casomorphins on the motility of rat gastrointestinal tract was studied by noninvasive techniques using the nonabsorbable marker 141Ce. Casein suspensions (CAS) or whey protein suspensions (WPS) were labeled with 141Ce and fed by gastric tube. Gastric emptying rate (GER) as well as gastrointestinal transit time (GITT) of the tracer were significantly longer with feeding CAS compared to WPS. The differences between the CAS and the WPS groups were partly (GER) or completely (GITT) abolished by pretreating the animals with the specific opiate-receptor antagonist naloxone. It is assumed that opioid peptides released from casein during digestion slowed gastrointestinal motility by direct interaction with gut opiate receptors. To prove whether beta-casomorphins, when given by gastric tube, can affect motility, different synthetic beta-casomorphins in doses between 1 and 10 mg were added to the WPS. The beta-casomorphin-4 (Tyr-Pro-Phe-Pro-NH2) showed no effect on GITT. The D-Ala substituted D-Ala-beta-casomorphin-4 (Tyr-D-Ala-Phe-Pro-NH2) and D-Ala-beta-casomorphin-5 (Tyr-D-Ala-Phe-D-Ala-Tyr-NH2), which are more resistant to proteolytic attack and have higher opioid potency than beta-casomorphin-4, slowed GITT in a dose-dependent manner.

Demonstration and modification of intervillous pH profiles in rat small intestine in vitro

The intervillous pH profiles along the crypt villus axis in different regions of the rat small intestine were measured in vitro by using pH-sensitive liquid ion-exchanger microelectrodes. A characteristic pH profile was observed in the duodenum and jejunum. A region of low pH was detected in the upper parts of the villi (pH 6.65 +/- 0.06 to 6.85 +/- 0.07), whereas pH at the villus base was always higher. In the ileum no gradient was observed (pH 7.26 +/- 0.05 to 7.31 +/- 0.05). Preincubation of the tissue in situ with 10 mM theophylline for 1 h caused an increase in the villus base pH in the jejunum (pH 7.24 +/- 0.04) and ileum (7.44 +/- 0.04) followed by a subsequent increase of the pH in the upper part of the villi. These results indicate that the low pH in the upper intervillous space may be related to H+ secretion occurring from the mature enterocytes, whereas the crypt cells may secrete a rather neutral or slightly alkaline fluid. Alkaline secretion from the crypts may be increased by theophylline, which changes the levels of cyclic nucleotides in the mucosa.

Peroxidase activities in the hamster bronchoalveolar lining fluid: modifications induced by exposure to silica dust

The modifications of peroxidase (Po) activity have been studied in bronchoalveolar lavage fluid (BALF) from hamsters exposed to silica dust. In silica-treated animals, the mean total BALF-Po activity was significantly increased compared to control animals. This increased activity was accompanied by an influx of polymorphonuclear neutrophils in airways. HPLC gel filtration of BALF from control animals separated 5 peaks with Po activity. They had an apparent molecular weight of 140, 110, 80, 57, and 42 kDa. In BALF from silica-exposed animals, with the exception of the 57-kDa fraction, the same peaks were found. Additional fractions with an apparent molecular weight of greater than 200, 180, 92, 65, and 20 kDa were detected. All the fractions but those at 57 and 92 kDa were detectable in a whole-blood homogenate. Exposing hamsters to silica induced both quantitative modifications and a different pattern of BALF proteins having Po activity in the alveolar lining fluid.

The GABAergic neurones of the cerebellar nuclei in the rat: projections to the cerebellar cortex

The presence of gamma-aminobutyric acid (GABA) in the neurones of the cerebellar nucleocortical pathway is here reported. The pathway was identified by retrograde tracer and the GABA content was revealed immunohistochemically. It was found that most of the neurones giving rise to the reciprocal, non-reciprocal and symmetrical projections are indeed GABA-immunoreactive. They were observed in all the subdivisions of the nucleus medialis, of the nucleus interpositus and of the nucleus lateralis sending axons respectively to the sagittal zones A, C1-3 and D of the cerebellar cortex. The nucleus vestibularis lateralis and the related sagittal zone B were devoid of such projections.

The effect of Escherichia coli STa enterotoxin and other secretagogues on mucosal surface pH of rat small intestine in vivo

The mucosal surface pH of rat small intestine was measured in vivo. The surface pH in the normal jejunum was 6.20 +/- 0.02 (67) and 7.00 +/- 0.05 (5) in the ileum. Escherichia coli STa toxin induced a rapid and reversible alkalinization of both jejunal and ileal mucosae to a pH of 6.91 +/- 0.08 (10) and 7.67 +/- 0.06 (5) respectively. The synthetic ST analogue, STh-(6-19), had an effect identical to native STa toxin on jejunal surface pH. Theophylline (20 mM) maintained the STa-elevated jejunal surface pH after toxin removal but had no effect on untreated tissue. 8-Bromo cyclic GMP resembled STa by causing similar mucosal alkalinization in the jejunum; 8-bromo cyclic AMP, forskolin and cholera toxin individually had considerably smaller effects on surface pH, although combining forskolin or cholera toxin with theophylline resulted in alkalinization of the jejunal mucosa to a pH of 6.92 +/- 0.03 (5) and 6.76 +/- 0.04 (4). These results indicate that cyclic-GMP-dependent secretory processes are more capable of inducing surface pH changes than those dependent on cyclic AMP. The ability of STa to alter mucosal surface pH makes it a useful tool to investigate the microclimate hypothesis for weak electrolyte absorption.

Persistent reduction of Purkinje cell inhibition on neurones of the cerebellar nuclei after climbing fibre deafferentation

The long lasting effects of inferior olive (IO) destruction were studied in rats treated with 3-acetylpyridine two years before. The activities of the Purkinje cells (PCs) and of their target neurones in the cerebellar nuclei (ECNs), were investigated and compared to those of a group of non-treated rats. Our results show that long-term deafferented PCs recovered a mean firing frequency similar to that of the controls while the ECNs discharge is enhanced. Furthermore, the cryodestruction of the cerebellar cortex produces a significant release of the ECNs firing in the control rats but not in the poisoned animals. Thus, it appears that IO destruction induces a permanent impairment of the inhibitory control exerted by the PCs on the activity of their target neurones.

The red nucleus activity in rats deprived of the inferior olivary complex

The long-term effects of the inferior olive destruction on the red nucleus activity, were studied in the rat following injection of 3-acetylpyridine. As soon as the olivary activity was suppressed, the discharge of the rubral units drastically decreased. Then, they progressively recovered the control frequency during the first month, although a normal rubral activity was not restored up to 8 months. The hypothesis is advanced that the olivocerebellar system is essential to shape the activity of the rubrospinal pathway.

Topographic organization of the interpositorubral connections in the rat. A WGA-HRP study

The projections from the anterior (NIA) and posterior (NIP) interposed nuclei to the magnocellular red nucleus (RNm) have been investigated in the rat, using the retrograde transport of horseradish peroxidase-wheatgerm agglutinin conjugate. Projections from the NIA extend throughout the RNm, whereas those from the NIP only reach its medial aspect. In addition, a topographical organization of the NIA-RNm pathway was found, such that the medial NIA projects ventrally, the lateral NIA projects dorsally.

The interposito-rubrospinal system. Anatomical tracing of a motor control pathway in the rat

The cerebello-rubromotor pathway, impinging on both spinal and facial motor nuclei, has been traced in the rat, using the bidirectional transport of horseradish peroxidase-wheat germ agglutinin conjugate. After injection of the tracer in the red nucleus (NR), retrograde labelling shows a topical arrangement of the cerebellorubral connection. The nucleus lateralis projects to the parvocellular NR (NRp) and the nucleus interpositus to the magnocellular NR (NRm). The nucleus interpositus anterior (NIA) reaches the entire NRm and this projection is topographically arranged: the medial NIA sends fibres ventrally, the lateral NIA dorsally. The medial two-thirds of the nucleus interpositus posterior (NIP) project only to the medial aspect of the NRm, with no apparent organization. No connection has been found between the lateral third of NIP and the NRm. After injection of the tracer in the spinal cord or the nucleus of the facial nerve, retrograde labelling is observed almost throughout the entire caudorostral extent of the NR, although labelling is more scant in NRp than in NRm. Rubrospinal and rubrofacial projections are somatotopically arranged in the dorsoventral direction: ventrolateral regions of NR reach the lumbar cord, medioventral regions the lower cervical levels, intermediary regions the upper cervical levels and finally the dorsalmost part of the NR projects to the nucleus of the facial nerve. After injection of the tracer in the cerebellar nuclei, anterograde labelling in the NR shows that interpositorubral connections determine two subregions in the NR: a lateral one under the exclusive control of the NIA, and a medial one under the control of both NIA-NIP afferents. It confirms in addition the topography of the NIA-NRm projection and shows the preponderant participation of the NIA afferents to the interpositorubral connection. Thus, it appears from our results that the cerebellorubral arrangement matches, to a great extent, the "rubromotor" efferent organization.

[Intestinal liberation and resorption of monosaccharides from carbohydrates of different degrees of polymerization. I. Relation between intestinal hydrolysis of carbohydrates and resorption of monosaccharides]

The study was designed to compare the intestinal absorption of monosaccharides from carbohydrates of different chain length. Furthermore, a correlation between the efficiency of hydrolysis of the polymers and the efficiency of the intestinal absorption was expected to be established. Glucose, the disaccharides maltose and sucrose and the polysaccharides maltodextrin DE 20 , maltodextrin DE 5 and starch were employed as substrates. The whole small intestines of anaesthetized rats were perfused in situ for 60 min with 0.5% solutions of these substrates in an open perfusion system. Initially 3-minute fractions of the perfusion medium, later 10-minute fractions were collected. The parameters determined were: secretion of pancreatic alpha-amylase activity, substrate hydrolysis (by alpha-amylase and by disaccharidases of the brush border membrane), intestinal absorption of the monosaccharides. alpha-amylase activity was significantly higher when the perfusion was carried out with starch solution. The possibility is discussed that this high-polymer substrate might stimulate the pancreas to an elevated alpha-amylase secretion. The highest rate of hydrolysis (45 mumol glucose/min) was determined from maltose as a substrate. The cleavage of the high-polymer substrates was less intensive. The hydrolysis of starch was limited by the capacity of the alpha-amylase, that of the sucrose by low activity of the saccharose. Absorption of glucose was more effective from the maltose solution than from the glucose solution. To understand this phenomenon, an additional "hydrolases-related transport system" could be taken into consideration. Glucose absorption from maltodextrin DE 20 was less effective than might have been expected from the rate of hydrolysis. This fact might possibly be explained by an inhibitory effect of oligosaccharides of chain length 4-10, contained in relatively high amounts in maltodextrin DE 20.

Application of muonic X-rays for elemental analysis

Because of the large μ mass compared to the electron mass, the muonic X-rays have energies very suitable for standard γ-ray spectroscopy (Ge detectors), so every element is easily recognized. By selecting the primary μ energies appropriately any part of the specimen, also well inside, can be nondestructively investigated. On the other hand, surface layers may be analyzed. Accuracies of quantitative analyses are 1% of the atomic abundance of the element in question in favorite cases. Results on applications in nuclear medicine and surface physics are presented, and ways of improving the muon flux density are discussed.

Release of cerebellar inhibitory activity by partial destruction of the inferior olive with kainic acid in rat

Partial destruction of the neurones of the inferior olive was obtained by local ionophoretic injection of kainic acid. Complex spike discharges of the Purkinje cells are suppressed 2-3 h after application of the drug. The metabolic activity increases in the region of the cerebellar nuclei within 2 h and persists for 3 days following the kainic acid injection. The increase is only observed in those parts of the cerebellar nuclei receiving terminals from the Purkinje cells deafferented of the climbing fibres. No changes were detected when the injection affected only the underlying reticular formation.

Comparison of hydrolases, peroxidase and protease inhibitors in bronchoalveolar fluid from Macacus cynomolgus and human controls

1. Serial bronchoalveolar lavages were performed on a subhuman primate (Macacus cynomolgus) in order to give an experimental model for silicosis. 2. We have measured glycosidases, proteases, peroxidase and antiproteases of the BAL fluids from seven normal monkeys. 3. The results obtained were similar to those found in human control BAL fluids. 4. For monkeys, the repetition of the bronchoalveolar procedure does not seem to have an important influence on the values obtained. 5. The present results will now permit sequential follow up studies during the course of experimental silicosis.

[Mechanisms of intestinal absorption of nutrients]

The nutrient uptake from the intestinal lumen into the distributing blood circulation is mediated by the epithelial cell of the small intestine. The transfer process through this distinctly polar cell consists of three partial events: entrance of substances through the brush-border membrane, traversal of a metabolic active intracellular space and exit through the baso-lateral membrane. The fundamental transfer mechanisms--simple diffusion, facilitated diffusion, antiport and symport systems, electroneutral and electrogenic processes--are described. The significance of nutrient metabolization for transport processes is discussed: proton secretion by the epithelial cell coupled to the glucose and lactate metabolization is quoted as an illustration. The "acid microclimate" resulting from this proton secretion on the mucosal surface has a significant influence on weak-electrolyte absorption. This effect was clearly demonstrated for in vitro uptake of nicotinic acid into the intestinal tissue. It can be assumed that--similar to the role of a Na+-gradient--the proton gradient on the surface of absorptive epithelia is highly significant as a driving force of nutrient absorption.

Effect of proteins on availability of zinc. II. Bioavailability of zinc from casein and whey protein--retention study in young rats

The availability of zinc from two semi-synthetic diets with isolated whey protein (Wp D) or with isolated casein (Cas D) as protein component (20% W/W) was compared in a 21-day study with growing male rats (initial weight 40 g; 14 animals/group). Zinc concentration in both diets (18 ppm) was adequate to meet the requirements of the animals fed ad libitum. For radiolabeling approximately 13 micrograms 65Zn (= 4 microCi) was given daily by intragastric intubation to each animal. The investigation was designed primarily as a retention study, but also general parameters like weight development, food and water intake, organ weights etc. were registered and the activity of alkaline phosphatase was determined in serum and femur tissue. A significantly higher percentage of 65Zn was retained in the whole body from the Wp D (36.5%) than from the Cas D (31.6%) during the experimental period. The same is valid for the percentage retention of 65Zn in the femur and for the 65Zn concentration in femur and hair as well as for the total zinc concentration (65Zn and non-labeled zinc) of the femur. The other parameters determined were not unequivocally influenced by the protein component of the diet. The study clearly demonstrated that the availability of zinc by the growing rat was better from a diet with whey protein than from one with casein as the protein component. The reason on this phenomenon has to be elucidated by further investigations.

The cerebellorubral projection in the rat: retrograde anatomical study

The cerebellorubral projections have been studied in the rat using the retrograde transport of horseradish peroxidase-wheat germ agglutinin conjugate. The lateral cerebellar nucleus projects to the parvocellular red nucleus (RN), the anterior (NIA) and posterior (NIP) interposed nuclei project to the magnocellular RN. Whereas the projections from the NIP are limited to the medial aspect of the RN, those from the NIA extend throughout the magnocellular RN. NIA-RN projections are topographically arranged: the medial NIA projects ventrally, the lateral NIA projects dorsally. Functionally, this differential distribution seems to fit the hindlimb-forelimb areas of origin of the rubrospinal tract.

Long term modification of rubral activity after inferior olive destruction

The long term effects of the inferior olive degeneration on red nucleus activity were studied in the rat. The animals were injected with 3-acetylpyridine to produce a pharmacological destruction of the inferior olive and were then used for acute experiments at 1-2, 5-7, 14-18, 29-37, 81-110 and 236-255 days later. After degeneration of the inferior olive, there was an 'initial period' lasting for a few days, characterized by a low discharge frequency of the red nucleus neurones. A 'period of adaptation' followed during the first month, characterized by a slow recovery towards the control firing rates of the rubral units. Nevertheless, the temporal distribution of the discharges was not recovered since the firing became organized in a bursting activity. From 1 up to 8 months, the normal unit activity was not restored. The hypothesis is advanced that the suppression of the inferior olive which increases the cerebellar inhibition, produces a consequent disfacilitation of red nucleus activity which persists for a few days. Then at increasing survival times, a progressive compensation takes place without a real restoration of the initial rubral activity.

Effect of metabolizable sugars on the mucosal surface pH of rat intestine

In a layer juxtaposed to the mucosal surface of distal duodenum and of jejunum, and designated as "acid microclimate," the proton concentration is significantly higher than in the bulk phase of the intestinal lumen. The aim of the present study was to quantify the effect of different sugars on the mucosal surface pH value when these substrates were either added to the in vitro preparation of rat distal duodenal and mid-jejunal segments or administered by intragastric intubation and by i.v. infusion. All pH measurements were carried out in vitro by surface microelectrodes in oxygenated phosphate buffer. Glucose, fructose, mannose, galactose and 3-O-methylglucose were applied in vitro, glucose, maltose, fructose, galactose, 3-O-methylglucose and whey protein for the intragastric intubation and glucose, fructose and galactose for the intravenous infusion. Only substrates that could be metabolized in the intestinal epithelia were able to depress surface pH to a considerable extent. Substrate concentration at which half-maximum decrease of surface pH was obtained (K delta pH) was calculated to be 4.5 mM for glucose, 14.5 mM for fructose and 34.5 mM for mannose. The study was the first to demonstrate that metabolizable sugars are not only able to lower surface pH of intestinal epithelia when they are added in vitro but that they are also effective after intragastric intubation or i.v. infusion. It is plausible that generation of the protons, which are secreted into the acid microclimate zone, is closely related to the intracellular metabolization of glucose. The existence of a high proton concentration on the immediate mucosal surface could be of considerable significance for the absorption of weak electrolytes, a group to which different nutrients belong.

Chemistry of brotizolam and its metabolites

Of a series of azepines annelated with two 5-ring heterocycles, 1, brotizolam (2-bromo-4-(2-chlorophenyl)-9-methyl-6H-thieno[3,2-f]-1,2,4-triazolo [4,3-a]-1,4-diazepine, We 941), 2, was found to possess excellent hypnotic properties. A summary of the two different methods of preparation of 2 (routes A and B) is given. Synthesis of the major metabolites of 2, 6-hydroxy-brotizolam (We 1061), 14, obtained from the intermediates 9 and 10 by method B, 2-bromo-4-(2-chlorophenyl)-9-hydroxymethyl-6H-thieno [3,2-f]-1,2,4-triazolo-[4,3a]-1,4-diazepine (WE 964), 16, and 2-bromo-4-(2-chlorophenyl)-6-hydroxy-9-hydroxymethyl-6H-thieno- [3,2-f]-1,2,4-triazolo-[4,3-a]-1,4-diazepine (We 1073), 17, are described in detail. In contrast to the classical 3-hydroxy-1,4-benzodiazepines, e.g. oxazepam, 14 isomerizes easily in weak alkali. This isomerization is discussed.

Aluminum lactate treatment alters the lung biological activity of quartz

Previous studies of surface modification of quartz particles have suggested that the biological activity of silica is at least in part related to its surface properties. In the present study, we exposed the tracheal lobe of 8 sheep to either 100 ml saline (saline group), 100 mg of quartz (Minusil-5) in 100 ml saline (SI group) or 100 mg of Al lactate treated quartz in 100 ml saline (SI-Al group). The 24 sheep were studied by bronchoalveolar lavage at days 0, 12, 24, 40, 60 and by autopsy at day 60. In the saline group, BAL analyses were as previously reported [1]. In the SI group, we found significant and sustained increases in total BAL cells (x 2, P less than 0.05), macrophages and lymphocytes (x 2, P less than 0.05), neutrophils (x 5-10, P less than 0.01), IgG (x 1.2-1.8, P less than 0.05), fibronectin (x 2-3, P less than 0.05), lactate dehydrogenase (x 3, P less than 0.01) and alkaline phosphatase (x 2, P less than 0.05). Histologically, a macrophagic and lymphocytic alveolitis was observed at day 60. In the SI-Al group, these changes were significantly attenuated and in the above parameters, SI-Al group did not differ from saline group after day 24. These data of BAL and histology of the sheep tracheal lobe model document clearly that aluminum lactate treatment alters the biological activity of quartz.

Effect of proteins on availability of zinc. I. Gastrointestinal transit time of casein and whey protein and zinc absorption in weaned rats

The availability of zinc from isolated casein (CasD) was compared with that from whey protein (WpD) in 23-25 day old rats. The study was designed to show the course of the gastrointestinal transit time of either chyme (radiolabeled by 141Ce as a non-absorbable marker) or zinc (as 65Zn) in groups of 9 to 12 animals each. Animals were killed either 1/4, 1/2, 1, 2, 6, 12 or 24 hours after intragastric intubation of the protein suspensions. Immediately afterwards, intragastric pH was measured and the determination of zinc retention in intestinal tissues and liver as well as in the carcass was performed. 30 and 60 minutes after intubation the intragastric pH of the CasD group was significantly lower than that of the WpD group. The precipitation behaviour of the two protein fractions - compact curd formation by the CasD versus flocculent structure of the WpD - was determining for the pattern of gastric emptying. With the WpD the chyme was emptied according to an exponential function; while the CasD precipitate left the stomach in three distinct phases. With either protein suspension zinc left the stomach ealier than the bulk of the chyme, indicating a partial disintegration of the zinc-protein-complexes. With the WpD, zinc was emptied exponentially, whereas with the CasD a biphasic emptying pattern was found. Ileum was found to be the main zinc absorbing segment, mainly due to the long time of contact with zinc. After 2 and 12 hours zinc retention from the CasD was significantly higher than that from the WpD, however, after 24 hours retention was significantly better from the WpD. From the present study it can be concluded that, for comparison of zinc availability from diets containing different proteins, short-term experiments are not appropriate. Furthermore, it can be supposed that preabsorptive processes in the stomach are crucial for the availability of zinc.

Inferior olive destruction induces dysfacilitation of the red nucleus activity

The spontaneous discharge frequency of the red nucleus neurones was evaluated in rat before and after total destruction of the inferior olive with the 3-acetylpyridine. It was found that the sustained firing recorded in the control animals (33.7 +/- 23.7/s) drastically decreased to a low rate (4.6 +/- 7.1/s) after the intoxication. This effect took place between 2 h 15 min and 2 h 45 min after the injection. which is the critical period corresponding to the inferior olive degeneration and the consequent climbing fiber deafferentation. It lasted at least as long as the acute experiment. The conclusions are reached that the inferior olive destruction leading to an enhanced cerebellar inhibition, produces a dysfacilitatory effect on the red nucleus neurones.

Localization of acid microclimate along intestinal villi of rat jejunum

Considering the significance that pH value could have for digestive and absorptive processes, these investigations were aimed at precisely localizing the position of the acid microclimate, i.e., of proton accumulation along the surface of intestinal villi. The determinations were carried out under microscopic control on jejunal segments of rats incubated at 25 degrees C in O2-saturated phosphate buffer (pH 7.4). Specially manufactured antimony microelectrodes (tip diam 50 microns) and calomel reference electrodes were used for pH registration. Highest proton concentration (214-224 nmol/l not equal to pH 6.67-6.65) was found 10-100 microns below the tip of the villus in the zone of digestive and absorptive epithelial cells. Toward the crypt, a steep decrease of proton concentration was registered with alkaline values 200 microns below the villus tip. Toward the bulk phase, the decrease of the proton concentration was moderate due to the existence of the unstirred water layer as an effective diffusion barrier. The pH value of the bulk phase was reached 440 microns over the villus tip, a distance possibly identical to the thickness of the unstirred water layer.

Long term modification of cerebellar inhibition after inferior olive degeneration

The long term effects of inferior olive destruction on the activities of the Purkinje cells and their target neurones in the cerebellar nuclei were studied in the rat. Careful observations were also made of motor behaviour throughout the study. Albino rats were injected with 3-acetylpyridine to produce a neurotoxic destruction of the inferior olive and then were used for acute recording experiments at 1-2 days, 5-7 days, 12-18 days, 35-38 days, 75-97 days and 230-252 days. After degeneration of the inferior olive, there was an initial period lasting for a few days, characterized by a high firing frequency of Purkinje cells associated with a very low level of activity of the neurones in the cerebellar nuclei. During this period, there was a deep depression of motor activity. A period of adaptation follows during the first month, characterized by a slow recovery of the initial firing frequency of the cerebellar units and a gradual recovery of spontaneous locomotion; nevertheless the firing pattern and motor behaviour remain abnormal. From one month on the unit activities disturbances and the motor deficiencies stabilize. The hypothesis is advanced that Purkinje cell inhibition on their target neurones, which increases during the initial period, gradually diminishes during the adaptation time, and then stabilizes to a subnormal state.

[Effective intraluminal concentration of riboflavin and pyridoxine in various intestinal segments of the rat]

The study was designed to determine the intraluminal concentration of riboflavin and pyridoxine in different gastrointestinal segments of rats as a function of time after intragastric application of the vitamins. A semi-liquid diet with 14C-riboflavin and 3H-pyridoxine was delivered by tube. After a period of 30 minutes, 1, 2, 6, 12 or 24 hours, respectively, concentrations of the vitamins were determined by radio-chemical methods in stomach, duodenum, jejunum and ileum. In the duodenum highest concentration of riboflavin (10.4 nmol/l) was reached 2 hours, that of pyridoxine (5.5 nmol/l) 1.5 hours after intubation. In jejunum maximum concentration of both vitamins--4.1 nmol/l riboflavin and 3.0 nmol/l pyridoxine--was found 1.5 hours after tube feeding. As discussed for riboflavin, precise information about the physiologically relevant intraluminal concentration of micro-nutrients in the absorbing intestinal segments is essential, especially if transport mechanisms have to be elucidated.

Synthesis and antidepressant activity of 4-aryltetrahydrothieno[2,3-c]pyridine derivatives

A series of substituted 4-aryltetrahydrothieno[2,3-c]pyridines was prepared by acid-catalyzed cyclization of 1-aryl-2-[(2-thienylmethyl)amino]ethanol derivatives. The compounds were examined for their antidepressant activity, as demonstrated by their ability to inhibit the uptake of norepinephrine (NE) and serotonin (5-HT) and to prevent tetrabenazine-induced ptosis (TBZ) in mice. Significant inhibition of both neurotransmitters is observed for several of the tested compounds, while some of them are selective inhibitors of either NE or 5-HT uptake. Optimal activity is associated with the introduction of lipophilic substituents into the 4-position of the phenyl ring and less lipophilic substituents into the 2-position of the thiophene ring (11, 23). Compound 33 bearing substituents in positions 2 and 6 of the phenyl ring is inactive. This might be a consequence of an out of plane conformation of this compound.

In vitro kinetics of the intestinal transport of riboflavin in rats

Transmural intestinal transport of riboflavin was studied in a concentration range between 0.033 and 10.0 microM by an in vitro perfusion technique by using everted jejunal segments of rats. The transport was found to have a dual characteristic: at low, i.e., physiologically relevant concentrations, a carrier-mediated saturable component predominated; at higher concentrations this component was increasingly obscured by simple diffusion as the prevailing transport mechanism. The transport constant KT of the saturable component was calculated to be 0.54 microM. The Q10-value was 2.31 for a low concentration (0.322 microM) and 1.44 for a high concentration (10.0 microM) of the substrate. When Na+ was partially replaced by Li+ or choline+ in the media or when ouabain was added to the serosal medium, the saturable component of the transport was completely abolished. The substrate analogue lumiflavin reduced the transport rate of riboflavin at low substrate concentration only. Generally, the results indicate that it is essential to consider the physiologically relevant concentration of micronutrients in studies concerning the mechanism of their intestinal transport.