Areas of operation of interneurons mediating presynaptic inhibition in sacral spinal segments

Sources of primary afferent depolarization (PAD) of skin afferents in the sural (Sur) nerve and of group-II muscle afferents in the posterior biceps and semitendinosus (PBST) nerve were compared at several sites, about 2 mm apart, within the L7-S2 segments in order to define areas of projection of sacral interneurons mediating PAD of these afferents. Just rostral to the pudendal nucleus, strong PAD of Sur afferents was evoked by stimulation of skin nerves, while stimulation of muscle nerves had only marginal effects. This indicates that sacral PAD interneurons co-excited by skin and muscle afferents operate primarily within the regions overlying the pudendal nucleus. Furthermore, PAD evoked by muscle afferents was weaker over the rostral part of the pudendal nucleus than over the caudal part of this nucleus, where hamstring afferents became its main source, both in Sur and in PBST group-II afferents. By correlating the relative strength of PAD at the levels of the rostral and caudal parts of the pudendal nucleus with the previously established input from muscle and cutaneous afferents to interneurons at these levels, it is therefore proposed that sacral PAD interneurons operate over shorter distances than indicated by previous experiments: over either rostral or caudal parts of the pudendal nucleus, i.e., about 2 mm, rather than over the whole length of this nucleus, i.e., 4-5 mm. Sacral PAD interneurons may, thus, modulate synaptic transmission to even more spatially restricted neuronal populations than previously proposed.

[Bone mineral density of adults living in the city of Wrocław compared with the reference ranges]

Certain elements of lifestyles (distinctive for the particular population) are presumed to influence on bone metabolism. This fact results in considerable differences between various populations, concerning both the occurrence of the normal variability of BMD (bone mineral content) among adult and elderly men and women, and also the prevalence of osteopenia or osteoporosis. The purpose of the study was to evaluate the variability of BMD in a group of healthy and occupationally active inhabitants of the city of Wroclaw, Poland (426 men aged 20-59 and 1218 women aged 20-62) and to compare our results with the reference ranges provided by the producer of the Stratec 960 apparatus. Trabecular and total BMD at the distal radius of the nondominant hand were assessed by peripheral Quantitative Computed Tomography (pQCT) using the Stratec 960 apparatus. BMD of Polish men and women significantly differ from the reference ranges of Stratec 960. The unfavourable phenomenon of the greater BMD decline with age, as compared to the standard values provided by the producer of the device, occurred. It should also be stressed that this reduction is more intense with age and it is marked among men older than 36. Taking into consideration the fact, that our material comprises only occupationally active subjects, the revealed differences would be probably greater, if they were evaluated in Polish population as a whole (our sample does not include persons, who are retired from the healthy conditions). Considering those significant discrepancies between our data and the Stratec reference population, one should be careful when using the normative database provided by Stratec for the densitometric diagnosis of osteoporosis among Polish women and men. Additionally the present study reveals that BMD (and its age-related changes during normal aging) is one of the features characteristic for the particular regional population, which is due to inter-populational differences of those elements of lifestyle, which can influence both general health condition and bone mineral density.

Microsatellite instability in thyroid papillary carcinoma and multinodular hyperplasia

Microsatellite instability (MSI) is a molecular landmark of mutations in DNA mismatch repair genes. The impaired efficiency of DNA repair mechanisms promotes carcinogenesis as well as contributes to tumour progression. Until now, only few studies on MSI in thyroid tumours have been published. Therefore, the aim of the present study was to investigate MSI as a possible characteristic feature of thyroid tumours. The analysis of 12 thyroid papillary carcinomas and 17 multinodular hyperplasias at 13 microsatellite loci showed MSI and loss of heterozygosity (LOH) in both types of lesion, with more alterations noted in the papillary thyroid carcinomas (in 65%) than in multinodular hyperplasia (in 35%). In carcinomas, LOH occurred more frequently than MSI, while in multinodular hyperplasia the LOH/MSI ratio is almost equal.

Serotoninergic and noradrenergic axonal contacts associated with premotor interneurons in spinal pathways from group II muscle afferents

We investigated the possibility that monoaminergic axons make contacts with spinal interneurons which project to motor nuclei and are monosynaptically activated by group II muscle afferents. Interneurons in midlumbar spinal segments of adult cats were characterized electrophysiologically and intracellularly labelled with tetramethylrhodamine dextran. Serotoninergic and noradrenergic axons were identified with immunofluorescence in sections containing labelled cells. Contacts between monoaminergic axons and interneurons were investigated with three-colour confocal laser scanning microscopy and analysed with a computer reconstruction program. Cell bodies and dendritic trees of five cells were reconstructed and putative contacts were plotted. The average number of contacts formed by serotoninergic axons was 140 and the average number of noradrenergic contacts was 38. The majority (95%) of contacts were formed with dendrites; these were distributed over the entire dendritic tree, even on the most distal branches. These findings provide a morphological basis for the modulatory actions of monoamines on premotor spinal interneurons in pathways from group II muscle afferents.

Effects of monoamines on interneurons in four spinal reflex pathways from group I and/or group II muscle afferents

Effects of locally applied serotonin (5-HT) and noradrenaline (NA) were tested on extracellularly recorded responses of single spinal interneurons in deeply anaesthetized cats. These effects were tested on: (i) interneurons mediating reciprocal inhibition from group Ia afferents; (ii) interneurons mediating non-reciprocal inhibition from group Ia and Ib afferents; (iii) intermediate zone interneurons co-excited by group I and II afferents; and (iv) dorsal horn interneurons excited by group II afferents. Effects of monoamines were tested on responses evoked at latencies compatible with monosynaptic coupling. Responses evoked by group Ia and/or Ib muscle afferents were facilitated in all of the tested interneurons both by NA and 5-HT. Responses evoked by group II muscle afferents were depressed in the majority of the interneurons but were facilitated in some of them. 5-HT depressed these responses in all dorsal horn interneurons and in one subpopulation of intermediate zone interneurons, while it facilitated them in another subpopulation of intermediate zone interneurons. NA depressed them in all intermediate zone interneurons and in one subpopulation of dorsal horn interneurons, while it facilitated them in another subpopulation of dorsal horn interneurons. The results of this study lead to the conclusions that: (i) modulation of synaptic actions of muscle spindle and tendon organ afferents on spinal interneurons by 5-HT and NA is related to both the type of the afferent and the functional type of the interneuron; and that (ii) 5-HT and NA counteract each others' actions on some interneuronal types but mutually enhance them on the others.

Filtration properties of nonwovens

This paper presents the results and conclusions from experimental investigations concerning filtration properties of nonwovens. The needled nonwovens were made from polyester fibres (PTE) with average fibre diameter 12 micrometres and polypropylene fibres (PP) with average fibre diameter 32 micrometres. Nonwovens were produced out of each of those fibres or out of a mixture of polyester and polypropylene fibres. This paper also presents investigations of nonwoven fabric made of polypropylene fibres (PP) with average fibre diameter 2.6 micrometres, which was formed according to melt-blown technology. Oil mist, as challenge aerosol, was used to evaluate the performance of filter media at various aerosol velocities. The average oil mist test aerosol particle diameter was 0.3 micrometre. Filter penetration was measured at oil mist concentration 0.24 g/m(3).

Expression of a selenomethionyl derivative and preliminary crystallographic studies of human cystatin C

Human cystatin C, a protein with amyloidogenic properties and a potent inhibitor of papain-like mammalian proteases, has been produced in its full-length form by recombinant techniques and crystallized in two polymorphic forms: cubic and tetragonal. A selenomethionyl derivative of the protein, obtained by Escherichia coli expression and with complete Met-->Se-Met substitution confirmed by mass spectrometry, amino-acid analysis and X-ray absorption spectra, was crystallized in the cubic form. A truncated variant of the protein, lacking ten N-terminal residues, has also been crystallized. The crystals of this variant are tetragonal and, like the two polymorphs of the full-length protein, contain multiple copies of the molecule in the asymmetric unit, suggesting oligomerization of the protein.

[On the healthy male aging: hormonal aspects]

Authors present select problems performed in the "Geneva Manifesto" published by the International Society for the Study of the Aging Male in February 1998 and pay the special attention on the inaccuracy connected with a commonly used name andropause. Additionally they present actual metabolic and clinical aspects resulting from the hormonal disturbances in aging men (hypotestosteronemia, decline in DHEA and hGH).

[Testosterone and atherosclerosis in males during andropause]

Nowadays besides the commonly accepted atherogenic risk factors a special emphasis is laid on the significance of testosterone in atherogenesis in men which physiologic deficit during "andropause" is able to promote this pathology. An elevated estradiol:testosterone ratio seems to be an independent risk factor of atheromatous heart complications. There is a proved positive correlation between free testosterone, total testosterone, dihydrotestosterone and HDL-cholesterol, apoA1 apolipoprotein. The relationship between LDL-cholesterol, VLDL-cholesterol, total cholesterol and total and free testosterone seems to be unanimous, but in certain studies the beneficial influence of testosterone on the mentioned lipids has been observed. The discussed hormone is also functionally connected with coagulation and fibrynolisis; a positive correlation was found between endogenous testosterone and tPA-Fx and a negative correlation between testosterone and PAI-1, fibrinogen, D-dimers, alpha 2-antiplasmin. Testosterone is a functional regulator of the vascular tonus and influences on reological properties of microcirculation (the application of testosterone infusion into canine coronary arteries causes the dilatation of main and the small vessels, through NO syntetase induction and ATP-dependent K(+)- channel activation). A statistically significant positive correlation between testosterone and insulin has been stated (an elevated oestradiol:testosterone ratio is connected with the insulin resistance). Additionally a negative relationship between testosterone and android obesity has been observed. Although nowadays there are more and more facts proving the benefits of the retaining the proper testosterone levels in aging men, the final influence of the testosterone supplementary therapy on atherogenesis is not solved.

[The deterioration of the parameters of the human semen: myth or reality?]

Numerous publications in the world's literature on the base of multiply retrospective analyses suggest a population-wide decline in the quality of human semen over the past 50 years. The average sperm density, the mean sperm volume and the percentage of the typical spermatozoids appear to have decreased. Furthermore, a significant increase in the incidence of both genitourinary abnormalities (hypospadiasis, cryptorchidism) and testicular cancers in the general population has been reported. The data vary among different geographic regions. The possible adverse effect of the environmental pollutants with oestrogenic activity on male reproductive ability has been considered. These chemicals can affect the foetal development of male gonads and also impair testes during maturity, which finally results in disturbances in testicular functions and leads to the reduction of male fertility.

Modulation of information forwarded to feline cerebellum by monoamines

The reported results demonstrate that monoamines modulate activity of three populations of spinocerebellar tract neurons that are rhythmically active during locomotion. However, information on dynamic changes in muscle length and tension (signaled by muscle spindle primary afferents and tendon organs) and on the absolute length of muscles (signaled by muscle spindle secondary afferents) is differently modulated. The transfer of the former is facilitated but that of the latter is either facilitated or depressed; it is facilitated via Clarke's column dorsal spinocerebellar tract neurons and depressed via dorsal horn dorsal spinocerebellar tract neurons. The effects of noradrenaline and serotonin are similar.

Modulation of responses of feline gamma-motoneurones by noradrenaline, tizanidine and clonidine

1. Effects of noradrenaline (NA) and the alpha2 agonists tizanidine and clonidine were tested on extracellularly recorded responses of gamma-motoneurones in deeply anaesthetized cats. Two types of responses were used; firstly, short latency phasic responses evoked by electrical stimulation of group II afferents in a muscle nerve and, secondly, tonic background discharges. 2. Responses evoked by group II muscle afferents were depressed when NA and tizanidine were applied ionophoretically close to a gamma-motoneurone and when clonidine was applied systemically. The number of spike potentials evoked by stimulation of these afferents decreased and their latencies increased. Responses evoked by flexor or extensor afferents in gamma-motoneurones innervating flexors or extensors were similarly depressed. 3. Tonic discharges were inconsistently and/or insignificantly affected by locally applied NA and tizanidine but were depressed by systemically applied clonidine. 4. Control tests indicate specific effects of NA and tizanidine application since similarly ionophoresed H+ ions did not change responses of gamma-motoneurones to stimulation of group II afferents, or only weakly enhanced their background discharges. Furthermore, serotonin ejected from a solution with a similar pH facilitated rather than depressed responses of gamma-motoneurones. 5. The results indicate that some antispastic effects of clonidine and tizanidine may be due to the depression of group II-evoked responses of gamma-motoneurones, resulting in weaker responses of muscle spindles to muscle stretches.

New observations on coupling between group II muscle afferents and feline gamma-motoneurones

1. Extra- or intracellular recordings were made from seventy-six gamma-motoneurones of hindlimb muscles in chloralose anaesthetized cats to re-assess the coupling between secondary muscle spindle afferents (group II muscle afferents) and these neurones. The latencies of a number of responses evoked by group II muscle afferents in gamma-motoneurones were shorter than minimal latencies of responses induced disynaptically in other spinal neurones. These latencies are therefore compatible with monosynaptic coupling between muscle spindle secondaries and gamma-motoneurones. 2. Responses fulfilling criteria for monosynaptically evoked responses were seen in about one third of gamma-motoneurones with input from the group II muscle afferents tested (in 6 of 18 motoneurones recorded intracellularly and in 26 of 74 motoneurones recorded extracellularly). They were usually evoked from only one of the stimulated nerves, stimulation of group II afferents of other nerves being followed by responses at longer latencies. 3. Most gamma-motoneurones were excited by group II afferents from several muscles, both flexors and extensors. However, a comparison of group II input to gamma-motoneurones innervating medial gastrocnemius and four other hindlimb muscles revealed differences in both incidence and sources. 4. This study extends results of previous studies by providing evidence that some synaptic actions of group II afferents, including afferents from the same muscle, are evoked monosynaptically, and may assist in sustaining the activation of gamma-motoneurones by positive feedback.

A leu-enkephalin depresses transmission from muscle and skin non-nociceptors to first-order feline spinal neurones

1. The effects of an opioid (D-Ser-Leu-enkephalin-Thr; DSLET) were tested on synaptic actions of non-nociceptive afferents: group I and II muscle afferents and low-threshold skin afferents. They were tested on population EPSPs (field potentials) evoked in the dorsal horn and the intermediate zone of mid-lumbar segments, and on monosynaptically evoked responses of single interneurones at the same location. DSLET was applied locally (ionophoretically) at locations at which the field potentials were maximal and close to the selected neurones. 2. DSLET potently depressed transmission from group II muscle afferents and from low-threshold skin afferents. Transmission to neurones located in the dorsal horn or in the intermediate zone was depressed to a similar extent. The depression was readily antagonized by naloxone. Transmission from group Ia or Ib muscle afferents to neurones located in the intermediate zone was not affected, or was facilitated by DSLET. 3. The results show that DSLET has similar depressive actions on spinal neurones to monoamines, but its actions are more widespread. Like monoamines it affects transmission from nociceptors and group II muscle afferents, but in addition it gates transmission from low-threshold cutaneous afferents. Furthermore its effects do not appear to be restricted to interneurones at particular locations since it depressed responses of dorsal horn interneurones (gated by serotonin) as well as intermediate zone interneurones (gated by noradrenaline).

Indications for coupling between feline spinocervical tract neurones and midlumbar interneurones

The possibility of collateral segmental actions of spinocervical tract (SCT) neurones upon interneurones with input from cutaneous and group II muscle afferents was investigated in deeply anaesthetized cats. To this end, intracellular and/or extracellular recordings were made from 35 dorsal horn and 15 intermediate zone interneurones in midlumbar segments of the spinal cord and effects of stimulation of the ipsilateral dorso-lateral funiculus (DLF) at C3 and C1 levels, i.e. below and above the lateral cervical nucleus where axons of SCT cells terminate, were compared. The stimuli applied at the C3 segment were within the range of stimuli (50-100 microA) required for antidromic activation of SCT neurones in the same experiment. Those applied at the C segment (200-500 microA) were at least 3 times stronger than C3 stimuli. Under the same experimental conditions, long ascending and descending tract neurones (dorsal spino-cerebellar and rubro-spinal tract neurones) with axons in the DLF were activated at similar thresholds from the C and C3 segments. Intracellular recordings were made from 29 interneurones of which 19 (65%) were dorsal horn and 10 (35%) were intermediate zone interneurones. Excitatory postsynaptic potentials (EPSPs) evoked by single stimuli applied at the C3 segment, but not the C segment, were found in 14 (48%) of those interneurones; their latencies (3.0-5.7 ms) and frequency following with only minimal temporal facilitation were as required for potentials being evoked monosynaptically by the fastest conducting SCT neurones. Extracellular recordings were made from 30 interneurones (24 dorsal horn and 6 intermediate zone interneurones), and in these neurones spike potentials induced from the C3, but not from the C segment, were evoked only by short trains of stimuli. However, their latencies from the first effective stimulus (4.3-5.4 ms) were compatible with mono- or oligosynaptically mediated collateral actions of SCT neurones. They were found in 10 (33%) of the 30 investigated interneurones. Similar effects of C3 stimuli were found in similar proportions of dorsal horn interneurones and intermediate zone interneurones. Indications were also found for synaptic actions evoked by C3 stimuli that could not be attributed to direct collateral actions of SCT neurones. In some intracellularly recorded dorsal horn interneurones, short-latency EPSPs were evoked from the C3 segment by the 2nd or 3rd stimulus in the train, but not by single stimuli. In other dorsal horn and intermediate zone interneurones, inhibitory postsynaptic potentials (IPSPs) were evoked from the C3 segment at minimal latencies (2.7-3.2 ms), which might be too short to allow their mediation via SCT neurones. We conclude that SCT neurones might be used to forward information from muscle group II and cutaneous afferents not only to neurones in the lateral cervical nucleus and via them to thalamus and cerebral cortex but also to interneurones in spinal reflex pathways. Thereby reflex actions evoked from group II and cutaneous afferents might be co-ordinated with responses mediated by supraspinal neurones. We conclude also that dorsal horn and intermediate zone mid-lumbar interneurones might contribute to the previously reported di-and poly-synaptic excitation or inhibition of postsynaptic dorsal column (PSDC), spinothalamic tract (STT) and spinomesencephalic tract (SMT) neurones by collateral actions of SCT cells. Thereby these interneurones might contribute to the co-ordination of responses mediated by various populations of supraspinal neurones.

A confocal and electron microscopic study of contacts between 5-HT fibres and feline dorsal horn interneurons in pathways from muscle afferents

Morphological substrates of actions of serotonin upon dorsal horn interneurons with input from group II muscle afferents were investigated by using two experimental approaches. Twelve interneurons were intracellularly labelled with rhodamine-dextran, and serotoninergic fibres were identified by immunofluorescence. Appositions between the serotoninergic axons and these interneurons were examined with a dual-channel confocal microscope. A further four interneurons were intracellularly labelled with horseradish peroxidase, and serotoninergic axons were identified by immunocytochemistry; these neurons were prepared for combined light and electron microscopy. Confocal microscopy revealed serotoninergic varicosities in apposition to both cell bodies and dendrites. Similar total numbers of appositions were found on the soma, and on dendrites within 100 microm from the soma, on the most completely labelled neurons. The number of appositions on 100-microm segments of dendrites decreased with increasing distances from the soma (from 14.6 within 100 microm, to 3.8 and 2.4 at 100-300 microm, and more than 300 microm distances, respectively). Electron microscopic analysis of two neurons revealed that few of the apparent contacts on cell bodies were synaptic, but, in contrast, many varicosities apposed to proximal dendrites formed synapses. The evidence suggests that serotonin may have more powerful synaptic effects upon the dendrites of this class of dorsal horn interneurons than on their cell bodies.

Modulation of responses of four types of feline ascending tract neurons by serotonin and noradrenaline

Modulation of responses of four types of ascending tract cells by noradrenaline and serotonin was compared in order to investigate how information forwarded by these cells may be gated by monoaminergic tract neurons. Spinocervical tract, postsynaptic dorsal column and dorsal spinocerebellar tract neurons located in Clarke's column and in the dorsal horn were identified by their axonal projections. Noradrenaline and serotonin were applied ionophoretically close to a selected neuron, and their effects were tested on extracellularly recorded responses of this neuron to electrical stimulation of low-threshold skin afferents and group II muscle spindle afferents. The modulatory actions of noradrenaline and serotonin were estimated from changes in the number of responses evoked by 30 successive stimuli, the minimal latencies of these responses, and their firing frequency. All four populations of ascending tract neurons investigated were modulated by serotonin and noradrenaline, but not in the same way. The responses were most often depressed by noradrenaline and facilitated by serotonin, but in some types of neuron they were affected in the same direction. Transmission from low-threshold skin and group II muscle afferents changed in the same direction in some types of neuron but in the opposite direction in other types. The results indicate that transfer of information from skin and group II muscle afferents to supraspinal centres may be gated by descending monoaminergic pathways in a highly differentiated manner, and is adjusted to the requirements of various behavioural situations.

Synaptic connections of dorsal horn group II spinal interneurons: synapses formed with the interneurons and by their axon collaterals

Five dorsal horn interneurons with monosynaptic input from group II primary afferent fibres were physiologically characterized and intracellularly labelled with horseradish peroxidase. The cells were prepared for combined light and electron microscopy, and synaptic arrangements formed by axon collaterals of interneurons and synapses formed with their dendrites and somata were examined with the electron microscope. Immunogold reactions for gamma-aminobutyric acid, glycine and glutamate were performed to determine if these synapses were excitatory or inhibitory. Axon collaterals in lamina VI formed synapses with somata and dendrites of other neurons, and collaterals of one cell also formed axoaxonic synapses. It was concluded that one cell from the sample was inhibitory, whereas the remainder were probably excitatory. Dendrites and cell bodies of interneurons were contacted by several types of synaptic bouton. The first type of bouton displayed immunoreactivity for glutamate, the second type contained both gamma-aminobutyric acid and glycine, the third type contained glycine alone, and the fourth type contained gamma-aminobutyric acid alone. Some large glutamatergic boutons were postsynaptic to other boutons. Presynaptic boutons at these axoaxonic synapses always contained gamma-aminobutyric acid but a minority also contained glycine. The results of this study demonstrate the heterogeneity of dorsal horn group II interneurons and provide evidence that they include inhibitory and probably also excitatory neurons. Boutons originating from several chemically different classes of neuron are responsible for postsynaptic inhibition of these interneurons, and the presence of axoaxonic synapses indicates that their excitatory input is also controlled presynaptically.