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Biomedical subjects

C Beyer

Publications and source records attributed to C Beyer.

At least 127 records · Page 7Linked to original sources
PubMed1991

Dopamine content and metabolism in mesencephalic and diencephalic cell cultures: sex differences and effects of sex steroids.

Sexual differentiation of dopaminergic neurons was studied in gender-specific cultures. Dissociated cell cultures were prepared from di- or mesencephalon of gestational day 14 rat embryos and raised in the absence or presence of 17 beta-estradiol or testosterone for up to 13 days in vitro (DIV). Developmental profiles of levels of dopamine (DA) and metabolites as well as capacity for vesicular storage of the transmitter were determined by HPLC. Tyrosine hydroxylase-immunoreactive (TH-IR) neurons were counted. Higher levels of DA were measured in female than in male cultures of both brain regions. In mesencephalic cultures, the differences in DA levels were fully accounted for by sex differences in numbers of TH-IR cells, whereas no sex differences in cell numbers were found in diencephalic cultures. Dihydroxyphenylacetic acid (DOPAC) levels and vesicular storage capacity matured faster in mesencephalic than in diencephalic cultures, but no sex differences were observed. Homovanillic acid (HVA) could not be detected except in 13-DIV mesencephalic cultures. Hormonal treatment did not erase sexual differentiation of dopaminergic neurons. Irrespective of the gender, however, both steroids decreased DA and DOPAC contents in diencephalic cultures but not in mesencephalic cultures. It is proposed that sexual differentiation of dopaminergic systems proceeds in a region-specific fashion and that neurogenesis and development of various parameters of dopaminergic activity may be differentially affected. Sexual differentiation of dopaminergic neurons may be initiated independently of the action of gonadal steroid hormones and may subsequently be modified by differences in hormonal environment.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1990

Enhancement of [3H]muscimol binding to brain synaptic membranes by progesterone and related pregnanes.

Progesterone (a delta 4-3 keto-pregnane) as well as a series of pregnanes enhanced [3H]muscimol binding to rat cerebral cortex membranes. This effect was increased by preincubation in the presence of the drugs, progesterone being effective only after a 30 min preincubation. The effect of progesterone was dose-dependent from 1 nM to 100 microM reaching a maximum of 140% over control. Its 20 alpha and 20 beta reduced metabolites (20 alpha- and 20 beta-OH-4-pregnen-3-one) had no effect. Ring A reduction in either the 5 alpha or 5 beta position resulted in steroids (5 alpha- and 5 beta-pregnane-3,20-di-one) producing moderate but consistent facilitation of binding (30-40% increase at 10 microM). The presence of a hydroxyl group in C3 had variable results in the potency of pregnanes to facilitate muscimol binding. Pregnanes with a 3 beta-OH group showed weaker activity than those having a 3 alpha-OH group, 5 alpha-pregnan-3 alpha-ol-20-one being the most potent (100% stimulation). Pregnenolone, a delta 5-3 beta-OH-pregnane, was only effective at low concentrations (10 nM to 10 microM). Scatchard analysis of [3H]muscimol binding in the presence of progesterone and 5 alpha-pregnan-3 alpha-ol-20-one revealed that the observed effect was due to an increase in binding sites rather than to a change in affinity.

Animals↗
PubMed1990

Region- and sex-related differences in maturation of astrocytes in dissociated cell cultures of embryonic rat brain.

Previous studies using dissociated cell cultures of fetal rat brain have revealed considerable regional diversity as well as sex steroid-independent sex differences in developmental schedules of dopaminergic neurons. Because these phenomena might be related to glial heterogeneity, cultures of dissociated male and female diencephalon, mesencephalon, and rhombencephalon of gestational day 14 rats were investigated with respect to the development of astrocytic markers. Cultures were incubated for 3-8 days in vitro (DIV) in serum-supplemented or serum-free medium. Vimentin and glial fibrillary acidic protein (GFAP) were quantified by counting of immunolabeled cells and immunoblotting. Vimentin and GFAP content rose from DIV 3 to 6 in all cultures. Regional variation of vimentin content was low, but large differences occurred in amounts of GFAP. GFAP reached high levels in rhombencephalon, especially when supplemented with serum, but remained very low or not detectable in mesencephalon. Simultaneous immunostaining for both cytoskeletal proteins revealed the presence of large numbers of vimentin single-labeled and small numbers of vimentin/GFAP double-labeled cells. Numbers of cells expressing GFAP showed similar regional variations as GFAP contents in both serum-free and serum-supplemented medium. They rose steeply from DIV 3 to 8 in rhomb- and diencephalon but not in mesencephalon. Transiently, female diencephalic cultures contained slightly more GFAP-immunoreactive cells than male cultures. The results thus demonstrate considerable regional heterogeneity of astrocytic maturation. However, neither the regional nor the sex differences show a consistent correlation with previous data on development of dopaminergic and other monoaminergic neurons in vitro. It seems likely that the dependence of neurons on glial environment for realization of an inherent developmental program varies among neuronal phenotypes.

Animals↗
PubMed1990

Chin marking behavior, sexual receptivity, and pheromone emission in steroid-treated, ovariectomized rabbits.

The effect of daily injections of estradiol benzoate (1 or 10 micrograms) and of progesterone (10 mg) on chin marking activity, sexual receptivity, and emission of nipple-search pheromone in ovariectomized rabbits was investigated. Both estradiol treatments resulted in a significant increase in all three measures over baseline and control group levels within 1-3 days, and withdrawal in a return to pretreatment levels within 2 weeks (Experiment I). In contrast, the administration of progesterone to such estradiol-primed does resulted in an almost immediate suppression of chin marking and lordosis, but in marked enhancement of pheromone emission and aggressive behavior (Experiment II). However, progesterone given alone to nonprimed does had no effect on any of these measure (Experiment III). The response profiles resulting from these treatments correspond well to patterns reported for intact does during estrus (= estradiol alone), pregnancy (= estradiol plus progesterone), and at parturition (= progesterone withdrawal).

Animals↗
PubMed1990

Variations in chin-marking behavior of New Zealand female rabbits throughout the whole reproductive cycle.

Chin-marking (chinning) was measured daily in intact New Zealand female rabbits across their whole reproductive cycle. In Experiment 1 does displayed during estrus (48 days studied) three phases, adaptation, growth and plateau, characterized by progressively higher chinning scores (mean +/- SE = 3.6 +/- 1.1; 17.7 +/- 6.3; 26.6 +/- 4.9 marks/10 min, respectively). Despite great quantitative differences among individuals, these 3 phases and the occurrence of chinning "peaks" at 4-6 day intervals were consistently observed in all subjects (Ss). Mating provoked, within one hour, a dramatic decrease in chinning. Both pregnant and pseudopregnant Ss showed low chinning scores for the first 13 days after mating (combined mean +/- SE = 7.3 +/- 3.8 marks/10 min). From days 14 to 30 postcoitus chinning gradually rose in the pseudopregnant Ss (mean +/- SE = 12.7 +/- 5.4 marks/10 min) while remaining low in the pregnant ones (mean +/- SE = 2.6 +/- 1.9 marks/10 min). Parturition allowed a gradual rise in chinning scores. In Experiment 2 the same Ss were explored across a second reproductive cycle that included lactation. In contrast to Experiment 1, no significant variations in chinning were displayed along estrus, Ss showing high chinning scores already on the first day of observation (mean +/- SE from 12 days = 19.2 +/- 6.7 marks/10 min). In agreement with Experiment 1, mating drastically reduced chinning scores. Low levels were maintained throughout pregnancy (mean +/- SE = 3.4 +/- 2.4 marks/10 min) and lactation (mean +/- SE = 3.3 +/- 4.8 marks/10 min). Weaning allowed a gradual increase in chinning scores.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Modulation by estrogen and progesterone of the effect of muscimol on nociception in the spinal cord.

The GABAA agonist, muscimol, administered intrathecally (IT) to the spinal cord at a dose (1 microgram) that was subthreshold for affecting pain thresholds (vocalization-threshold-to-tail-shock: VTTS, and tail-flick latency: TFL) in ovariectomized, hormonally untreated rats, showed a significant increase in VTTS up to 30 min postinjection in intact females only in proestrus or estrus. This treatment produced no significant effect on TFL at any stage of the estrous cycle. IT muscimol produced a significant increase in VTTS (but not TFL) in ovariectomized rats primed with estradiol benzoate (EB) for 2 days and tested 40 hr after the second injection but had no effect in females primed with a single EB injection and tested 15 min later. By contrast, ovariectomized females primed with progesterone (P) for 15 min exhibited a significant increase in pain thresholds after IT muscimol in both the VTTS and TFL tests. When EB-primed females (2 days) received P 4 hr prior to muscimol there was no analgesia produced by IT muscimol, in contrast to EB-primed females receiving P 15 min prior to IT muscimol in which there was significant analgesia. These results suggest a mechanism for antagonistic effects of estrogen and progesterone.

Animals↗
PubMed1990

Permissivity of primary cultures of human Kupffer cells for HIV-1.

Kupffer cells (liver macrophages) represent the largest reservoir of fixed macrophages in the body. Accordingly, we have undertaken a study to evaluate their susceptibility to human immunodeficiency virus type 1 (HIV-1). Five-day-old primary cultures of Kupffer cells (KC) were infected with HIV-1, and as the infection progressed, syncytia appeared. Within the cells, viral proteins were detected by immunofluorescence using monoclonal antibodies directed against gp120 and p24. Electron microscopic examinations revealed the presence of typical Lentivirinae particles. The particles released from KC in the extracellular medium showed reverse transcriptase activity and p24 antigen; they could infect lymphocytic cells and were neutralized by a HIV+ patient's serum or an anti-gp120 monoclonal antibody. Our results thus demonstrate that the interaction of HIV-1 with KC in vitro leads to a productive infection. They suggest that the KC may be involved in the pathogenesis of HIV-1 infection and may (i) participate in the transmission of the infection to the peripheral blood cells, (ii) play a role in the depletion of uninfected CD4+ cells.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Importance and function of the melanocyte-stimulating hormone in malignant melanoma. Importance of MSH].

According to the present state of findings there are melanocyte-stimulating hormones (MSH) alpha, beta, gamma and delta with hormone alpha-MSH special physiological importance for man. Our study of special literature shows that the secretion of MSH is affected by exogene factors, different biorhythms and some diseases. Numerous investigation with melanocytes and melanoma cell cultures clearly show the impact of MSH on the function, regulation and the proliferation of pigment cells. The results presented contribute to the discussion of possibilities of improving diagnostics or therapy of malignant melanoma.

Biomarkers, Tumor↗
PubMed1990

[Experiments for physiologic improvement of disinfectants].

The use of customary trade disinfectants lead to occupational disease no. 80 in many employers of public health. For that reason our aim is to improve the skin compatibility of this disinfectants. Its possible to achieve a pH-shift to a more physiological level eighter by buffer salt addition or by neutralization. Following this, disinfectants were investigated in a microbiological test.

Dermatitis, Contact↗
PubMed1990

[The effect of disinfectants on epidermal Langerhans cells--possibilities for the improvement of skin tolerance].

The aim of this paper is the characterization of the skin tolerance to several desinfectants. For that reason, guinea pig epidermis was treated for 1, 7 and 14 days with conventional working dilution of peracetic acid-containing and phosphoric acid-containing desinfectants. In addition, buffered desinfectants were applied. In all cases, the exposure to desinfectants causes a disappearance of histochemically detectable Langerhans cells in the treated epidermis. The lowest number of Langerhans cells was encountered after the application of Wofasteril. The buffering of the working dilution causes significantly lower (p = 0.01) damages in the Langerhans cell population. Possibilities for improving the skin tolerance of this desinfectant in normal use could result.

Animals↗
PubMed1989

Somato-motor components of the pelvic and pudendal nerves of the female rat.

The efferent innervation of the pelvic and pudendal nerves was characterized in this study by identifying the muscles activated by electrical stimulation of the nerves distal to the point at which they bifurcate from the L6-S1 trunk. Pelvic nerve electrical stimulation produced EMG-monitored contraction of the ipsilateral ilio- and pubococcygeus muscles, which was abolished by cutting one ('muscular') branch of the bifurcated nerve. (This 'muscular' branch receives proprioceptive input activated by tail displacement, whereas the other, 'viscero-cutaneous' branch receives sensory innervation from the midline perineal region.) Pudendal nerve electrical stimulation produced contraction of the coccygeus, external anal sphincter, and ischiocavernosus muscles. Movements of the orifice and wall of the vagina were directly visualized during electrical stimulation of the two nerves. Intravaginal pressure measured by balloon was increased by pelvic nerve stimulation and decreased by pudendal nerve stimulation. Reflexive contraction of the ilio- en pubococcygeus muscles was produced by mechanostimulation of the perineum, clitoral sheath and distal vagina. This response was abolished by gentle cervical mechanostimulation. One implication of this finding is that passage of the fetuses through the cervix during parturition may relax the ilio- and pubococcygeus muscles, thereby facilitating delivery.

Animals↗
PubMed1989

Intrahypothalamic injection of RU486 antagonizes the lordosis induced by ring A-reduced progestins.

We explored the possibility that ring A-reduced progestins facilitate lordosis in estrogen primed rats through their interaction with an intracellular progestin receptor (PR) by using RU486. This drug binds with high affinity to the PR, thus preventing the action of progesterone (P). Ovariectomized estrogen-primed rats (2 micrograms estradiol benzoate 40 hr earlier) were bilaterally injected into the ventromedial hypothalamic nucleus (VMHN) with 1 microgram of: P, 5 alpha-pregnanedione or 3 beta,5 beta-pregnanolone in 1 microliter oil. All three progestins effectively facilitated lordosis, tested at four and eight hours after intrahypothalamic injections. The ability of RU486 to counteract progestin-induced lordosis was assessed by infusing 10 micrograms of this agent into the VMHN along with any of the progestins. RU486 antagonized the lordosis induced not only by P (67% reduction) but also that induced by 5 alpha-pregnanedione and by 3 beta,5 beta-pregnanolone (47% and 93% reductions, respectively). Results suggest that ring A-reduced progestins may act through the PR mechanism to facilitate lordosis, i.e., in a fashion similar to P.

5-alpha-Dihydroprogesterone↗
PubMed1989

Barbiturate-induced analgesia: permissive role of a GABAA agonist.

Three doses (0.025, 0.25 and 2.5 mg) of the short-acting barbiturate, pentothal, were injected intrathecally at the lumbar level of the spinal cord of female rats and did not produce analgesia in either the tail-flick latency to radiant heat (TFL) or vocalization-threshold-to-tail-shock (VTTS) tests. However, when the high dose of pentothal (2.5 mg) was given in combination with a nonanalgesia producing dose of the GABAA agonist muscimol (1 microgram), a significant and prolonged analgesia was produced in both the VTTS and TFL tests, lasting up to one hour postinjection. Intrathecal injection of the intermediate dose of pentothal (0.25 mg) in combination with 1 microgram muscimol also produced significant analgesia in the TFL but not the VTTS test. We suggest that barbiturates may act on spinal nociceptive pathways to reduce pain thresholds only when sufficient GABAergic activity is present.

Analgesics↗
PubMed1989

Copulatory pelvic thrusting in the male rat is insensitive to the perispinal administration of glycine and GABA antagonists.

The role of the inhibitory neurotransmitters glycine and GABA in the pacing of pelvic thrusting during copulation was assessed in male rats by an accelerometric technique. Either strychnine, an antagonist of glycine (10 micrograms), bicuculline, an antagonist of GABA (1 microgram), or a combination of strychnine (5 micrograms) plus bicuculline (0.3 microgram), and saline as control, were administered intrathecally to sexually active males. Administration of the antagonists either alone or in combination, at these dose levels, produced sensory effects (skin hyperalgesia, scratching or biting the skin) in all rats. Generalized motor seizures occurred in only a few animals. The incidence of ejaculations, but not of mounts, tended to decrease after treatment with the amino acids antagonists. On the other hand, the values of the instantaneous frequency, duration, and rhythmicity of the copulatory thrusting movements performed during mounts, intromissions or ejaculations did not differ significantly from the values obtained under saline treatment. These findings indicate that the duration and rhythmicity of copulatory movements in the male rat are either controlled by synapses that are insensitive or inaccessible to strychnine and bicuculline, or these copulatory components are independent of glycinergic and GABAergic control and are under the control of other neurotransmitter systems.

Animals↗
PubMed1989

Blockage of substance P-induced scratching behavior in rats by the intrathecal administration of inhibitory amino acid agonists.

Intrathecal administration of 20 micrograms of substance P induced scratching behavior in most tested rats (80%). Scratching appeared in bouts of short latency and variable duration, intensity and frequency (range 1-60, mean number of scratching bouts in one hour test: 8.93 +/- 1.86). Intrathecal administration of glycine (400 micrograms but not 66 micrograms) significantly decreased the effect of substance P on this behavior. Taurine, in dosages equimolar to glycine, abolished the response to substance P at the high dose level (700 micrograms), but did not significantly affect it at the lower level (120 micrograms). The GABAA agonist, muscimol, abolished the effect of substance P at the 3 micrograms dose level, but the 0.5 microgram dose did not produce a significant effect. Baclofen, a GABAB agonist, was highly effective in significantly reducing the action of SP at 0.9 and 0.15 microgram; only two of 8 rats receiving the low dose of baclofen (0.15 microgram) exhibited scratching. The results suggest that the spinal inhibitory amino acids modulate nociceptive impulses generated by the action of substance P in dorsal horn neurons of the spinothalamic tract.

Animals↗
PubMed1989

Methodology for a better evaluation of the relation between mechanical strength of solids and polymorphic form.

In order to evaluate the role played by polymorphism in the mechanical strength of solid dosage forms (e.g. compressed tablets) and minimize the influence of other factors (such as compaction force, porosity, particle size, and possibly crystal habit), a melted disc technology was developed. With this technique, tablet-shaped discs of zero porosity were prepared by melting powder and subsequent crystallization in the desired modifications. Taking phenobarbitone as a model drug, different methods were used to get discs of forms I, II and III and the amorphous form. Mechanical properties of the discs were assessed, primarily through their bending strength. The Vickers hardness number was also determined for some specimen discs and monocrystals. Results showed that the amorphous form and form III of phenobarbitone gave the toughest discs and would therefore the most suitable materials to manufacture coherent tablets. Moreover, the various preparation methods used resulted in discs of different internal structures. Both crystal size and crystal habit significantly affected the physical properties of the tested materials.

Chemistry, Pharmaceutical↗
PubMed1989

[Cytochrome P-450 dependent drug metabolism--use of an in vitro test system in multiple chemical exposure].

Investigations of the influence of an actual exposure on the in-vitro-activities and the inducibility of cytochrom P-450 dependent enzymes have not been described in the literature until now. First results gained from mitogen-stimulated lymphocytes of exposed and not-exposed individuals suggest such an influence of the given mixture of noxious agents on the basic deethylational ability of the examined cells acting in the sense of inhibition. Possible causes for this phenomenon are discussed.

Air Pollutants, Occupational↗