Evidence for a direct effect of growth hormone on osteoblasts

In order to determine whether growth hormone (GH) exerts a direct effect on osteoblasts, in vitro and in vivo immunocytological studies were carried out on newborn rat calvaria and a clonal osteoblast-like cell line (MC3T3-E1) isolated from newborn mouse calvaria. After exposure to human growth hormone (hGH) or 1,25 dihydroxyvitamin D3 (1,25(OH)2D3), a significant increase in alkaline phosphatase activity was observed in MC3T3-E1 cells. Simultaneous exposure of MC3T3-E1 cells to hGH and 10 nM 1,25(OH)2D3 showed a synergistic effect of the two hormones on this activity. The optimal dose of hGH was 0.1 nM. An immunocytological procedure was performed on ultrathin frozen sections from 7-day-old rat calvaria and MC3T3-E1 cells cultured with hGH. GH-like immunoreactivity was observed in both cases. In calvaria, endogenous GH-like immunoreactivity was localized at the same ultrastructural level (plasma membrane, cytoplasmic and nuclear matrices) as exogenous GH-like immunoreactivity in MC3T3-E1 cells. Following the initial step of binding to the plasma membrane, GH may be internalized in the cytoplasmic matrix and nucleus. In situ hybridization revealed the presence of mRNA coding for GH receptor in calvaria cells. The density of these receptors seemed to be lower in osteoblasts than in hepatocytes. In MC3T3-E1 cells, hGH induced a dose-dependent secretion of insulin-like growth factor 1. In conclusion, these results indicate that GH may act directly on osteoblasts.

Visualization of gene expression of short and long forms of prolactin receptor in the rat

PRL receptor gene expression was visualized in various tissues by in situ hybridization, using 35S-labeled probes unique to each form of receptor. Tissues were removed rapidly from adult male and female rats and placed in liquid nitrogen. Cryostat sections (10 microns) were prepared, fixed, pretreated, and dehydrated before incubation with the various probes. Hybridization was performed overnight, after which the slides were first exposed to autoradiographic film and then dipped in nuclear emulsion and exposed for 1-2 weeks. The specificity of the signal was studied by competition and using radiolabeled heterologous probes. Some tissues show no expression of either form of receptor mRNA, such as olfactory bulb and penis. Macroautoradiogram signals (optical density) were compared to a standard curve to observe the variation in mRNA expression, which was expressed in arbitrary units. Sex differences in the expression of PRL receptors were seen in a number of tissues, such as adrenal gland and pituitary. Expression of mRNAs specific to the long form of PRL receptor was predominant in adrenal gland, pituitary, thymus, spleen, skin, heart, and skeletal muscle, whereas the short form was expressed to a greater extent in kidney and lung. At the light microscopic level, the silver grains observed by epipolarization or light field were seen in the specific regions or cells that express PRL receptor mRNAs. In conclusion, the long form transcript predominates in most tissues, except kidney and lung. The advantage of in situ hybridization is that it allows the identification of specific regions or cells expressing mRNAs to be identified. The actions of PRL have not been identified in all tissues expressing PRL receptor transcripts, nor has any definitive correlation been made with the expression of short and long forms of PRL receptor and function.

[A single-day survey in pharmacies on the consumption of analgesics and antipyretics]

A one day long survey of antalgics and antipyretics consumption was carried out in 6 pharmacies of a middle-size city. It first shows the majority of medical prescription (62.2%) over self medication (29.4%) and over pharmaceutic advice (8.4%) at the drug delivery. Women are the main consumers, especially in the youngest ones (20-40 years old). Paracetamol is the most used drug; in this indication, the search for the less expensive drug seems usual. Drug abuse cannot be demonstrated in this survey; the consumption of this category of drugs appears as important although for a short duration; and most of the time for pain considered as moderate and trivial. The possibility to carry out such surveys and possibly clinical trials in private pharmacies appears as an opportunity.

[Ultrastructural in situ hybridization. A review]

After the first studies of hybridization in 1961, Jacob et al. developed an ultrastructural in situ hybridization technique in 1971. Advances in molecular biology (preparation of probes, labeling techniques...) allowed to refine this method. The radioisotope-labeled probes used initially required prolonged exposure times to achieve autoradiographic detection. Commercially available nonradioactive antigen-labeled nucleotides decreased revelation time and increased signal resolution. The three currently used methods are respectively performed on non-embedded material, pre-embedded material, and material embedded in a hydrophilic resin. Main applications include detection of viral nucleic acids, studies of ribosome maturation, detection of animal and plant mRNAs, and chromosome mapping studies.

[Ultrastructural in situ hybridization on ultrathin sections of frozen tissues]

In situ hybridization on ultrathin frozen sections can be performed with either complementary DNA or synthetic oligonucleotide probes, labeled with 35S or an antigen (biotin or digoxigenin) respectively revealed by ultrastructural autoradiographic and immunocytological techniques. Using this method, GH mRNA was found in somatotrophs, mainly in the cytoplasm (endoplasmic reticulum and cytoplasmic matrix). Ultrastructural deterioration is the main drawback of this method but is more than outweighed by high sensitivity.

Partial contribution of biliary metabolites to nephrotoxicity, renal content and excretion of [14C]hexachloro-1,3-butadiene in rats

Male Sprague Dawley rats with cannulated bile duct (BDC rats) received 100 or 200 mg kg-1 labelled hexachloro-1,3-butadiene ([14C]HCBD) by gavage 1 h (BDC1 rats) or 24 h (BDC24 rats) after surgical cannula implantation. Twenty-four hours after treatment with HCBD, rats were examined histochemically and biochemically for kidney damage. Urine, faeces, liver and kidney radioactivities were also measured in 24-h samples. Results were compared with those obtained from non-cannulated (NC) rats. Bile-duct cannulation did not completely protect against HCBD-induced kidney damage. The 24-h [14C] urinary excretion and tissue content was 30-50% lower in BDC rats compared to NC rats and correlated well with the toxicity findings. BDC1 rats appeared to be much more resistant to HCBD treatment than BDC24 rats. Since faecal [14C] radioactivity extractable by diethyl ether at neutral pH in BDC1 rats was twice that measured in BDC24 rats, the greater resistance was attributed to a higher deficiency in the gastrointestinal absorption of unchanged HCBD. The present results reveal that the biliary metabolites of HCBD are not solely responsible for kidney toxicity as previously assumed. They suggest a sinusoidal efflux of the HCBD conjugates from the liver.

Rat granulosa cells express the gonadotrophin-releasing hormone gene: evidence from in-situ hybridization histochemistry

There is still debate as to whether natural sequence gonadotrophin-releasing hormone (GnRH) is produced in the mammalian gonads and concerning its potential role as a paracrine modulator of gonadal function. To address this question, we have used in-situ hybridization histochemistry with an oligonucleotide probe complementary to the GnRH decapeptide coding sequence, to determine the cellular site(s) of expression of the GnRH gene in rodent ovaries. GnRH mRNA was detected in granulosa and thecal cells from ovarian follicles at all stages of development (primary-->Graafian), with no significant change in grain density during follicular development. The granulosa cell compartment always contained more mRNA than the thecal cell compartment. Corpora lutea expressed the GnRH gene to the same extent as thecal cells. These results indicate that preproGnRH mRNA is detectable under physiological conditions in the mammalian ovary, though whether this produces authentic GnRH decapeptide or an alternative protein product is not known. The physiological significance of these findings remains to be determined.

Evaluation of the interaction of benzene and toluene on the urinary excretion of t,t-muconic acid in rats

The influence of simultaneous exposure to benzene and toluene on the urine excretion of t,t-muconic acid (t,t-MA) was examined in rats. t,t-MA was measured from 24-h urine of rats subjected to a single 4-h exposure to 5 or 20 ppm benzene and/or 50, 100, 200 or 1000 ppm toluene. Coexposure lowered t,t-MA excretion in a concentration-dependent manner, especially in the 20 ppm benzene group where the decrease averaged 28, 44 and 85% after exposure to 100, 200 and 1000 ppm toluene, respectively, as compared to benzene-exposed groups alone. The data confirm the sensitivity of t,t-MA as an indicator of benzene exposure and point out that measurement of t,t-MA may underestimate the exposure to benzene in the presence of toluene.

Ultrastructural non-radioactive in situ hybridization of GH mRNA in rat pituitary gland: pre-embedding vs ultra-thin frozen sections vs post-embedding

In situ hybridization at the ultrastructural level can be carried out using three different methods: on vibratome sections before embedding in epoxy resin, on ultra-thin frozen sections, or on ultra-thin sections of tissues embedded in hydrophilic resin such as Lowicryl. With the purpose of comparing the sensitivity, resolution, and ultrastructural preservation of these three methods, we examined the expression of the growth hormone (GH) gene in anterior pituitary cells by in situ hybridization at the ultrastructural level, using a synthetic oligonucleotide complementary to the codons of the mRNA from Gln 45 to Ser 54 labeled at the 3' end of biotin-21dUTP. All these methods gave similar results: mRNA was located on the lamellar endoplasmic reticulum of somatotrophs. The pre-embedding method gave the best ultrastructural preservation, with low resolution with the enzymatic detection system and an intermediate sensitivity. A probe concentration of 10 pmol/ml was sufficient to obtain a signal. With this method gold particles could not be used without pre-treatment. The frozen section method gave the best sensitivity (a signal was observed with 4 pmol/ml of probe) but the lowest ultrastructural preservation. On ultra-thin Lowicryl sections, resolution was as high as with the frozen-section method, ultrastructural conservation was intermediate, and sensitivity was low. These results indicate that the last method seems to be a good compromise between sensitivity and ultrastructural preservation.

Immunocytological localization of endogenous calcitonin-like molecules in the crustacean Orchestia

Immunocytological mapping of calcitonin-like molecules (human form) performed in the terrestrial crustacean Orchestia, using PAP procedure on paraffin sections and immunogold method on ultrathin cryosections, reveals two reactive organs: central nervous system and posterior caeca of the midgut. Immunoreactivity within the nervous system is mainly located throughout perikarya and nerve fibers from both dueto- and tritocerebron and ventral nervous chain. Immunolabeling in the posterior caeca is detected on both cell components of the epithelium, with significant quantitative differences between molt and intermolt periods. The role of calcitonin-like substances in these organs is then discussed: at the nervous system level, a neuro transmitter function is suggested; the direct participation of these peptides in the regulation of calcium shifts through the caecal epithelium is hypothesized.

Uptake and ultrastructural localization of a [125I] growth hormone releasing factor agonist in male rat pituitary gland: evidence for internalization

GRF was isolated from a human tumor of the pancreas and characterized. GRF stimulates the in vivo and in vitro secretion of GH. The present study was designed to find out whether human (h) GRF agonist could be internalized and to determine the subcellular localization of internalized peptide in somatotrophs. Autoradiography was performed on rat anterior pituitary glands removed at specific time intervals (2-60 min) after iv injection of monoradioiodinated [125I] (His1,Nle27) hGRF (1-32) NH2. Administration of an excess of unlabeled hGRF agonist along with the radioiodinated hormone prevented the uptake, indicating the specificity of the reaction. At the ultrastructural level only the somatotrophs appeared to contain silver grains. The main effect of hGRF agonist injection on the cytological aspect of the somatotrophs was a decrease in the area occupied by secretory granules, accompanied inversely, by an increase in that of the Golgi complex. The time course study in somatotrophs showed that five compartments (plasma membrane, secretory granules, cytoplasmic matrix, nuclear membrane, and lysosomes) have distinct marked labeling patterns. Plasma membrane, secretory granules, and nuclear membrane were labeled throughout the time course studied (2-60 min after injection). Cytoplasmic matrix was labeled 5 min post injection and lysosomes 15 and 30 min after injection. The Golgi complex, mitochondria, rough endoplasmic reticulum, and nucleus matrix were not labeled. The findings show the cellular specificity of GRF uptake by somatotrophs and the internalization process from the plasma membrane to the intracellular organelles (secretory granules, lysosomes, and nuclear membrane). Labeling of the secretory granule compartment suggests that granules may bind and protect internalized peptide from lysosomal degradation. The appearance of label on the nuclear membrane suggests that GRF may have effects on the translocation of messenger RNA from nucleus to cytoplasm in somatotrophs.

Arginine-vasopressin in anterior pituitary cells: in situ hybridization of mRNA and ultrastructural localization of immunoreactivity

The hypothalamic nonapeptide arginine-vasopressin (AVP) exerts several distinct receptor-mediated actions on pituitary cells. Although hypothalamic AVP reaches the anterior pituitary via well-defined pathways, there is now accumulating evidence that AVP may also be produced endogenously in anterior pituitary cells. Using in situ hybridization, we demonstrate here the presence of AVP mRNA in the anterior pituitary of the rat. The observed grain density over pituitary cells was, however, greater than 10-fold lower than the one observed over AVP producing neurons present in the supraoptic and paraventricular nuclei of the hypothalamus. Immunoelectron microscopic analysis using two different AVP-specific antibodies revealed that the distribution of AVP-like immunoreactivity (AVP-LI) in the anterior pituitary is cell-specific. AVP-LI is most abundant in corticotrophs, followed by lactotrophs, gonadotrophs and thyrotrophs. On the other hand, there is complete absence of AVP-LI from somatotrophs. Interestingly, all pituitary cells in which AVP-LI is detected also represent potential target sites for AVP action. A minor fraction of AVP-LI was found to be membrane-associated and may originate, at least in part, from extrapituitary sources. This fraction likely represents receptor-bound peptide. The bulk of AVP-LI, however, was present in the cellular cytoplasm, not associated with any specific ultracellular structure. Specifically in corticotrophs, AVP-LI was excluded from secretory granules. However, our finding of AVP mRNA in anterior pituitary cells indicates that intracellular AVP-LI includes endogenously produced peptide, suggesting a paracrine and/or autocrine action.

Light and electron microscopic immunocytochemical evidence that delta sleep-inducing peptide and gonadotropin-releasing hormone are coexpressed in the same nerve structures in the guinea pig median eminence

The relationships between delta sleep-inducing peptide (DSIP) and GnRH immunoreactivity within the guinea pig median eminence are investigated by light and electron microscopic immunocytochemistry. Indirect immunofluorescence and elution-restaining experiments show that at the light microscopic level the distribution patterns of DSIP and GnRH immunoreactivity are indistinguishable. This suggested the possible coexistence of both immunoreactivities within the same fibers and neurosecretory endings. At the electron microscopic level, a preembedding double-immunolabeling technique using both indirect immunoperoxidase and immunogold methods, clearly indicate that DSIP and GnRH immunoreactivity are frequently colocalized within single secretory granules. In addition DSIP/GnRH immunoreactive nerve endings were also observed often in close proximity to tanycyte elements. Taken together, the present results provide for the first time ultrastructural evidence for the presence of DSIP immunoreactivity and demonstrate that DSIP and GnRH immunoreactivities may be coexpressed within the same neuronal elements in the median eminence.

Human immunodeficiency virus type 1 infection of U937 cells promotes cell differentiation and a new pathway of viral assembly

The differentiation of U937 monoblastoid cells after human immunodeficiency virus type 1 (HIV-1) infection was studied using the following approaches: reverse transcriptase activity measurement, immunofluorescence labeling, and electron microscopy. For comparison, uninfected U937 cells were induced to differentiate from monocyte to macrophage by phorbol 12-myristate 13-acetate (PMA) or retinoic acid (RA) treatment. Both infected and drug-treated cells showed important and similar ultrastructural cell modifications, with a phenotype that decreased in monocyte specificity and increased in that of macrophages. When U937 cells were induced to differentiate upon HIV-1 infection, a very different pathway of viral production was observed. Production and accumulation of the virus in a vacuolar compartment of intracytoplasmic origin and escape to the antiviral lysosomal activity could explain virus persistence. This makes the cell system a good model with which to study the relationship between HIV-1 production and cell differentiation.

Randomized double-blind trial of injectable heptaminol for controlling spontaneous or bromocriptine-induced orthostatic hypotension in parkinsonians

Heptaminol is a molecule with experimental cardiovascular analeptic properties. In this double-blind vs placebo trial, the potency, so far unproven, of the injectable form of a 626 mg dose of heptaminol chlorhydrate on spontaneous or induced orthostatic hypotension (OH), was assessed. Nineteen patients were included in the study: 7 displayed spontaneous OH, and in the other 12 OH was induced by bromocriptine, as monitored 103 min/after an oral intake of 6.6 mg on average. Neither spontaneous nor induced OH were recorded in 32% of the Parkinsonian population registered, with no obvious distinctive characteristics. Potency tilt-trials, performed 15, 30 and 45 min after parenteral administration of heptaminol, revealed a significant and expressive potency of the molecule on the systolic blood pressure after 15 min (P less than 0.05). Clinical and biological tolerance was excellent. Low plasma renin activity and the absence of response to orthostatism indicated, in this population of Parkinsonian extrapyramidal syndromes, a loss in positive tonus likely to be of sympathetic origin. The anti-hypotensive action of heptaminol does not seem to be related to any renal or even sympathetic interaction.

Localization of endogenous osteocalcin in neonatal rat bone and its absence in articular cartilage: effect of warfarin treatment

Immunocytochemistry after cryoultramicrotomy was used to localize endogenous osteocalcin in bone (calvaria, femoral diaphysis) and epiphyseal femoral cartilage from 8-day-old rats treated (or mot) for 7 days with warfarin. Ultrathin frozen sections were incubated with goat antiserum against rat osteocalcin at high dilutions (2 x 10(-4) to 2 x 10(-6). In calvaria and femur of untreated rats, endogenous osteocalcin was observed in osteoblasts (cytoplasm and nucleus) and in the collagenous matrix. Osteocalcin appeared progressively in osteoblasts and bone matrix in the mineralization front, then increased in the regions of extended calcification. Osteocalcin was also detected in osteocytes but was not as abundant as in osteoblasts. In bone samples of warfarin-treated rats, endogenous osteocalcin was only detected in bone matrix but not in osteoblasts. Furthermore, osteocalcin was only observed if antiserum was not very dilute (2 x 10(-2). In cartilage (hypertrophied and degenerative zones), osteocalcin was not observed in matrix and chondrocytes. However, it was found in the vicinity of matrix vesicles at the initial loci of calcification. Osteocalcin was never detected in the cartilage of warfarin-treated rats. Our results provide ultrastructural immunocytological evidence for the localization of endogenous osteocalcin in osteoblasts, the presence of osteocalcin in bone matrix and a direct gradient between the presence of osteocalcin and the calcification process. Osteocalcin is absent from cartilage, except possibly close to calcifying matrix vesicles. Warfarin inhibits the formation of osteocalcin.

Ultrastructural distribution of somatostatin-14 and -28 in rat adrenal cells

Previous studies have shown that somatostatin modulates angiotensin-induced aldosterone secretion by adrenal glomerulosa cells. This effect is mediated through specific receptors which do not show any preference for somatostatin-14 (S14) or the N-extended form somatostatin-28 (S28). The study of the distribution of 125I-Tyr [Tyr0, DTrp8] S14- and 125I-Tyr [Leu8, DTrp22, Tyr25] S28-binding in frozen sections of the rat adrenal by autoradiography indicated that both peptides bind to similar loci. High concentrations of binding sites were observed in the zona glomerulosa, and low concentrations were detected in the medulla. At the ultrastructural level, immunocytochemistry after cryoultramicrotomy revealed endogenous S14- and S28-like immunoreactive material in zona glomerulosa and in medulla. In glomerulosa cells, immunoreactive material was localized at the plasma membrane level, in the cytoplasmic matrix, in the mitochondria, and in the nucleus. S14- and S28-like materials were detected in both epinephrine and norepinephrine-storing cells of the adrenal medulla. In these cells, the distribution of either immunoreactive product was similar; it was observed in cytoplasmic matrix, secretory granules and nucleus, but not at the plasma membrane level. In situ hybridization does not reveal somatostatin mRNA in zona glomerulosa or medulla. These results demonstrate that S14 and S28 bind to, and are taken up by zona glomerulosa and adrenal medullary cells, but are not produced by these cells.

Assessment of urinary rat beta 2-microglobulin by enzyme immunoassay

An enzyme immunoassay (EIA) was developed using unlabelled and peroxidase-labelled rabbit antibodies to assess urinary rat beta 2-microglobulin (beta 2-m) excretion. It consisted in the adsorption of rabbit anti-rat beta 2-m immunoglobulin to a polystyrene surface, the addition of beta 2-m samples or standard and the addition of peroxidase-labelled rabbit anti-rat beta 2-m immunoglobulin. After addition of hydrogen peroxide and o-phenylenediamine, the enzyme activity of the solid phase was measured photometrically at 490 nm. Analytical recovery of pure beta 2-m in urine was 102%. From determinations made on normal female and male rats, the ranges of 24-h urine beta 2-m individually excreted were found to be 0.84-4.77 and 3.7-17.3 micrograms, respectively. The means +/- SEM were 2.49 +/- 0.17 and 10.2 +/- 0.55 micrograms. EIA was of value in evidencing the tubule-damaging properties of sodium chromate and hexachloro-1,3-butadiene in rats.

[Hydroxylation of debrisoquin in Parkinson's disease]

The accumulation of environmental substances, due to deficiency of liver detoxication processes, is one of the hypotheses put forward in the search of the cause of Parkinson's disease. The debrisoquine test was used to evaluate the capacity for hydroxylation of twenty patients treated for Parkinson's disease. No difference was found with the results obtained in non Parkinsonians: other metabolic pathways, notably S-methylation, should be explored.

Localization of serotonin-like immunoreactivity in the Merkel cells of pig snout skin

The presence of serotonin in the Merkel cells of pig snout epidermis was investigated by the peroxidase-antiperoxidase immunohistochemical technique. Serotonin-like immunoreactive Merkel cells were found in groups located at the base of epidermal rete pegs and in the external root sheath of sinus hair follicles (vibrissae). Immunoreactivity was stronger on the basal side of the Merkel cells, where dense-cored granules are most numerous. Neither the nerve terminal associated with the Merkel cell nor the neighbouring epidermal cells were immunostained. These results are the first evidence of serotonin-like immunoreactivity in mammalian Merkel cells. The fact that immunoreactivity is strongest in those parts of the Merkel cells with the highest granule density suggests that in these cells serotonin is probably localized in the dense-cored granules.

[Effects of Chiari osteotomy on acetabular development in the growing subject. Experimental study in puppies]

A Chiari osteotomy was performed on 10 dogs aged 2 months in order to assess the risks of mechanical or ischaemic loss of growth potential in the peri-acetabular cartilage. The development of the acetabular roof was studied by radiographs, microradiographs and histological assessment between 2 and 12 months. Apart from a few mechanical complications, the principal findings were the absence of any signs of necrosis, persistence of a strongly osteoblastic roof and readaptation of the trabecular pattern with articular remodelling, provided the mechanical conditions were satisfactory. The osteotomy must be sufficiently low, while remaining extra-articular, and adequate medial shift must be obtained. The interposed capsular tissue can then become dense and fibrous, providing a sliding surface.

Ultrastructural distribution of growth hormone (GH) mRNA and GH intron I sequences in rat pituitary gland: effects of GH releasing factor and somatostatin

We have measured the distribution of growth hormone (GH) mRNA or intron I sequences by in situ hybridization on ultrathin frozen sections of pituitaries removed from rats injected with saline, GH-releasing factor (GRF) or somatostatin. A 4-fold increase in labeling of the anterior lobe was observed after GRF, no changes with somatostatin. After ultrastructural in situ hybridization, labeling with the GH cDNA probe was specific to somatotrophs. Two populations of cells containing few or many secretory granules were labeled mainly in the cytoplasm or in both cytoplasm and nucleus. Some cells showed labeling at the perinuclear membrane. Hybridization with the GH intron I probe showed the same cell specificity with silver grains mainly located in the nucleus. After GRF, sequences hybridizing to growth hormone cDNA were increased mainly in the nucleus of somatotrophs when compared to mock-injected rats, indirectly suggesting an increase in the transcriptional activity of the growth hormone gene. After somatostatin, the density of labeling in the nucleus was increased suggesting that somatostatin may prevent the export of growth hormone mRNA molecules from the nucleus to the cytoplasm.