Nuclei Of Interstitial Cells Research Articles

Expression of aryl hydrocarbon receptor and aryl hydrocarbon receptor nuclear translocator messenger ribonucleic acids and proteins in rat and human testis.

Dioxins, e.g. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), use the aryl hydrocarbon receptor (AHR)/aryl hydrocarbon receptor nuclear translocator (ARNT) receptor complex to mediate their toxic actions. In addition to interaction with environmental pollutants, several transcription factors, steroid receptors, and growth factors are capable interacting with the AHR/ARNT complex, which suggests a constitutive role for the receptor complex. The testis has been reported to be among the most sensitive organs to TCDD exposure. Our experiments revealed a complex distribution of AHR and ARNT mRNAs and proteins in rat and human testis. AHR and ARNT immunoreactivities could be detected in the nuclei of interstitial and tubular cells. The incubation of seminiferous tubules in a serum-free culture medium resulted in up-regulation of AHR mRNA, which could be depressed by adding FSH to the culture medium. Furthermore, the incubation of tubular segments with a solution of 1 or 100 nM TCDD resulted in a 2- to 3-fold increase in apoptotic cells. Thus, up-regulation of AHR in cultured tubular segments and consecutive depression by FSH suggest a role for AHR in controlled cell death during spermatogenesis. We suggest that AHR and ARNT mediate effects by direct action on testicular cells in the rat and human testis.

5' hox genes and meis 1, a hox-DNA binding cofactor, are expressed in the adult mouse epididymis.

Hox genes determine the formation of segmented structures during development. The epididymis shows a segmented organization in its structure and function beyond embryogenesis. This study examined the adult mouse epididymis and vas deferens for expression of 5' hox genes and a hox-DNA binding cofactor. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed the expression of hoxa-9, hoxa-10, hoxa-11, hoxd-9, and hoxd-10 in all regions including the vas deferens. Semiquantitative RT-PCR revealed highest mRNA levels for hoxa-11 in the distal part of the epididymis and vas deferens, and this was confirmed by Northern blot analysis. To determine protein presence an antibody raised against a peptide N-terminal to the homeodomain of hoxa-11 was produced in rabbits. The antibody recognized a band of approximately 37-39 kDa in Western blot analysis. Immunohistochemistry indicated the presence of hoxa-11 in the nuclei of the epithelial cells with some staining in the cytoplasm. Staining was also detected in nuclei of interstitial cells throughout the entire organ and the vas deferens. A DNA binding cofactor for hoxa-11, Meis 1, was investigated for its presence in the epididymis. Semiquantitative RT-PCR identified both transcripts for Meis 1 (Meis 1a and Meis 1b) in all regions. Protein presence was confirmed by Western blot analysis, and this detected one band of approximately 53-55 kDa. Immunohistochemistry localized Meis 1 in the nuclei of interstitial cells throughout the entire organ and the vas deferens. Our study provides preliminary data from which we suggest the involvement of homeodomain transcription factors in the maintenance of segmental function of the adult epididymis and vas deferens.

Involvement of Pax-2 in the action of activin A on tubular cell regeneration.

It has been recently shown that in ischemic rat kidneys activin A is induced in tubular cells and inhibits their regeneration. The present study was conducted to further investigate the action of activin A in tubular cells during regeneration. Among genes thought to be critical for kidney development, Pax-2 was upregulated in tubular cells during regeneration after renal ischemia. Pax-2 protein was localized in nuclei of tubular and interstitial cells, some of which co-expressed a mesenchymal cell marker, vimentin, suggesting that a population of Pax-2-positive cells have properties of immature progenitor-like tubular cells. The Pax-2-expressing cells co-expressed a cell proliferation marker, BrdU, activin A, and the type II activin receptor. Activin A modulated growth of BrdU/Pax-2 double-positive cells since an administration of follistatin increased; conversely, exogenous activin A decreased the number of BrdU/Pax-2 double-positive cells after renal ischemia. Activin A also reduced the expression of Pax-2 in cultured metanephroi. A proximal tubular cell line, LLC-PK(1) cells, was used to further study the mode of action of activin A. The expression of Pax-2 was not detected in quiescent LLC-PK(1) cells, but it was markedly increased when growth was stimulated. Under this condition, activin A significantly inhibited DNA synthesis and reduced the expression of Pax-2 in LLC-PK(1) cells. In contrast, blockade of the activin signaling by overexpressing dominantly negative mutant receptor enhanced the expression level of Pax-2 in LLC-PK(1) cells and induced an immature phenotype. These results suggest that activin A regulates tubular cell growth and differentiation by modulating the expression of Pax-2 during regeneration.

Immunohistochemical localization of rainbow trout androgen receptors in the testis

SUMMARY: We examined the distribution of two rainbow trout androgen receptors (rtAR: rtAR-α and rtAR-β) in the testis immunohistochemically using a specific antibody to clarify the target cells of androgen in spermatogenesis. Positive rtAR immunoreactivity in paraffin-embedded sections was revealed using microwave treatment, and was detected in the nuclei of Sertoli cells, Leydig cells, and other interstitial cells. The presence of rtAR in Leydig cells suggested that fish androgens regulate Leydig cell activity in an autocrine fashion similar to mammalian androgens. In addition, we found that not all Leydig cells exhibited rtAR immunoreactivity in the mature testis by double staining using anti-3β-hydroxysteroid dehydrogenase (3β-HSD) antibody. Furthermore, rtAR immunoreactivity was also detected in the nuclei of spermatogonia, spermatocytes, and spermatids. The intensity of rtAR immunoreactivity in the nuclei of spermatogonia seemed to be weaker than those of spermatocytes and spermatids. These results suggested that androgens act directly on both germ cells and somatic cells in the regulation of spermatogenesis in the rainbow trout.

Toxicity of chemical components of ambient fine particulate matter (PM 2.5) inhaled by aged rats.

The toxicity of two important chemical components of fine ambient particulate matter (PM 2.5)-ammonium bisulfate (ABS) and elemental carbon (C)-was studied using aged (senescent) rats. The study tested the hypotheses that fine particle exposure can damage lungs and impair host defenses in aged rats and that ozone would potentiate the toxicity of these particles. Ammonium bisulfate aerosols were generated by nebulization of dilute aqueous solutions. Elemental carbon was generated from an aqueous suspension of carbon black. Carbon and ABS mixtures were generated by nebulization of a suspension of carbon black in a dilute aqueous solution of ABS. Rats were exposed, nose-only, for 4 h a day, three consecutive days a week, for 4 weeks. The rats were exposed to one of six atmospheres: (1) purified air; (2) C, 50 microg m(-3), 0.3 microm mass median aerodynamic diameter (MMAD); (3) ABS, 70 microg m(-3), 0.3 microm MMAD; (4) O3, 0.2 ppm; (5) ABS + C, 0.46 microm MMAD; and (6) ABS + C + O3, 0.45 microm MMAD. Data were analyzed using ANOVA and Tukey multiple comparison tests; a two-tailed significance level of 0.05 was used. The nuclei of lung epithelial and interstitial cells were examined to determine the labeling of the DNA of dividing cells by 5-bromo-2-deoxyuridine and to identify the location of injury-repair-related cell replication. Increased labeling of both epithelial and interstitial lung cells occurred following all pollutant exposures. Although epithelial cells are most likely impacted by inhaled particles first, the adjacent interstitial cells were the cells that showed the greatest degree of response. Exposure to the ABS + C + O3 mixture resulted in losses of lung collagen and increases in macrophage respiratory burst and phagocytic activities that were statistically significant. Our results demonstrate that ozone can increase the toxicity of inhaled particles (or vice versa), and suggest that detailed study of mixtures could provide a more comprehensive understanding of the mechanisms by which inhaled pollutants adversely affect human health.

Ovarian steroid protection against coronary artery hyperreactivity in rhesus monkeys.

Our hypothesis was that estrogen and progesterone modulate coronary artery reactivity in rhesus monkeys. Adult ovariectomized (ovx) monkeys were treated for 1, 2, or 4 wk with physiological concentrations of 17 beta-estradiol (E2), natural progesterone (P), and/or therapeutic levels of medroxyprogesterone acetate (MPA). Steroid concentrations in venous blood, coronary artery estrogen receptor (ER) and progesterone receptor (PR) localization, and isolated vascular muscle cell (VMC) Ca2+ and protein kinase C responses to serotonin and U46619 (a thromboxane A2 mimetic) were measured. Ovx monkey VMC responses were hyperreactive, showing prolonged increases in intracellular Ca2+ and protein kinase C that correlated with exaggerated in vivo coronary artery vasoconstrictor responses. The hyperreactive Ca2+ responses were abolished by in vivo treatment with E2 and/or P. However, VMC from ovx monkeys treated with the combination of E2 and MPA or E2, P, and MPA remained hyperreactive to vasoconstrictor stimuli, suggesting that MPA negated the protective effects of E2. ER were detected primarily in interstitial and endothelial cells and a minor fraction of the VMC. PR were localized to coronary artery VMC and interstitial cell nuclei. In vivo treatment of ovx monkeys with E2 tended to up-regulate PR in VMC, but MPA appeared to down-regulate PR expression. These results suggest that E2 and P replacement decreases coronary artery reactivity through direct interactions with ER and PR in coronary artery VMC.

Ontogeny of anti-müllerian hormone, 3 beta-hydroxysteroid dehydrogenase and androgen receptor expression during ovine total gonadal development.

Anti-müllerian hormone (AMH) and androgenic steroids are key factors regulating the masculinisation of the internal and external genitalia during fetal development. AMH is produced in Sertoli cells and causes regression of the müllerian ducts in the male. 3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD) is one of the key steroidogenic enzymes regulating testosterone production in Leydig cells. The objective of this experiment was to elucidate the development of the ovine fetal testes by identifying the spatio-temporal expression of AMH, 3 beta-HSD and androgen receptor expression within them. Fetuses from days 30 and 40 of gestation were fixed intact, while the gonads were dissected from the fetuses on days 70, 100 and 130 of gestation. Tissue was fixed in Bouin's fixative for 6 h, processed into paraffin wax and sections immunostained using rabbit anti-human AMH, 3 beta-HSD or androgen receptor antibodies. While seminiferous cords were absent on day 30 of gestation, pre-cord organisation was apparent and the gonad could be clearly distinguished from surrounding tissue by the presence of AMH and 3 beta-HSD immunopositive cells. Androgen receptor expression was not apparent at this stage. By day 40 of gestation the testis was organised into distinct seminiferous cords and intense immunostaining for AMH and 3 beta-HSD was present in Sertoli cells within the cords and Leydig cells in the interstitium respectively. Androgen receptor immunopositive cells were present in the interstititum but cells destined to develop into rete testis were immunonegative. By day 70 of gestation, the rete testis was organised in the centre of the testis and was strongly androgen receptor immunopositive. AMH and 3 beta-HSD expression was present in Sertoli and Leydig cells respectively. The expression of AMH, 3 beta-HSD and androgen receptor in the 100 and 130 day gestation fetuses was similar to that identified in the 70 day fetuses. In conclusion, Sertoli and Leydig precursor cells are present in the gonad prior to seminiferous cord formation and contain AMH and 3 beta-HSD at all stages of gestation examined. While androgen receptor immunoexpression was present in nuclei of interstitial cells from day 40 of gestation and in the rete testis from day 70 of gestation, Sertoli cells were immunonegative for androgen receptor at all of the stages examined.

Differential patterns of expression of DAX-1 and steroidogenic factor-1 (SF-1) in the fetal rat testis.

Gonadal differentiation is dependent upon a cascade of molecular and morphological events. Steroidogenic factor 1 (SF-1) and DAX-1 have been implicated in this process. A SF-1 binding site has been reported to be present on the DAX-1 gene. We therefore used immunocytochemistry to determine whether these two transcription factors are co-expressed in the fetal testis. DAX-1 was immunolocalised to the cytoplasm of interstitial cells from fetal testis of rat and human from day 15.5 and 16 weeks of gestation respectively. SF-1 was detected in nuclei of fetal Sertoli and interstitial cells. In the fetal rat expression of SF-1 in interstitial cells was not uniform; cells with abundant SF-1 all contained 3-beta HSD and were classified as Leydig cells. DAX-1 expression was not exclusive to cells which contained SF-1 and SF-1/DAX-1 co-expressing cells were not exclusively fetal Leydig cells. We conclude that in the fetal testis expression of the DAX-1 protein is not dependent upon the presence of SF-1 although SF-1 is present at an earlier stage of gestation in the gonad. DAX-1 may therefore play a separate or complementary role to that of SF-1 in the modulation of testicular gene expression and differentiation.

The temporal and cellular expression of c-fos and c-jun in mechanically stimulated rabbit latissimus dorsi muscle

The levels of c-fos and c-jun mRNA were measured by reverse transcription PCR in the rabbit latissimus dorsi muscle following three separate training regimes, i.e. passive stretch, 10 Hz electrical stimulation or a combination of the two. Both c-fos and c-jun mRNA expression peaked at around 1 h after imposing stretch and at around 4.5-6 h after the initiation of electrical stimulation. The combined stretch/electrical stimulation regime induced biphasic expression of both c-fos and c-jun mRNA, with peaks coinciding temporally with those for the individual regimes. Immunostaining with anti-Fos and anti-Jun antibodies revealed the accumulation of these proteins in both myofibre and interstitial cell nuclei following passive stretch. In contrast, following electrical stimulation the localization of immunoreactive c-Fos and c-Jun proteins was predominantly in interstitial cell nuclei. c-Fos and c-Jun immunoreactivity was also clearly colocalized in a proportion of myonuclei from stretched muscle. These findings suggest that the rapid induction of c-fos and c-jun is an early event in response to mechanical stretch and might trigger [via activator protein-1 (AP-1) transcriptional factors] events leading to muscle fibre hypertrophy. However, the involvement of AP-1 in inducing the phenotypic changes in muscle fibres as a result of electrical stimulation appears less clear.

Changes in glucocorticoid receptor immunoreactivity after adrenalectomy and corticosterone treatment in the rat testis.

The distribution of glucocorticoid receptor (GR) in the rat testis was investigated by means of immunocytochemistry (IR) and computer-assisted image analysis. A monoclonal antibody against rat liver GR showed the presence of GR IR selectively in the nuclei of interstitial and tubular cells. The semiquantitative microdensitometry of GR IR revealed that 77% of the specific staining was localized in the tubular compartment of rat testis. After adrenalectomy, GR IR was greatly reduced both in interstitial and tubular cells, roughly at the same degree. Corticosterone treatment (50 mg/kg, for 5 d) of adrenalectomized animals yielded a recovery of nuclear immunopositivity without changing the cellular distribution of GR, as observed in control rats. Nevertheless, the high dose of corticosterone administered produced a significant (p < 0.01) decrease of GR IR with respect to control rats. These results provide evidence for a prevalent nuclear binding of GR in the tubular compartment in basal conditions. On the other hand, adrenalectomy or repeated corticosterone treatment seem to affect GR similarly in all positive cells without changing significantly the proportion of GR IR in the different testicular compartments. This uneven distribution of GR IR suggests that tubular cells can be a major target of corticosterone when affecting directly testicular functions in the rat.

Incorporation of Bromodeoxyuridine as a Method to Quantify Cell Proliferation in Bronchiolar-Alveolar Duct Regions of Asbestos-Exposed Mice

Inhalation of asbestos fibers results in progressive interstitial pulmonary fibrosis in the bronchiolar-alveolar regions of humans and experimental animals. The fibrogenic lesions were described previously by morphometry in a rodent model of asbestos-induced pulmonary fibrosis in our laboratory. Our prior studies also showed that incorporation of tri-tiated thymidine (3H-TdR) into nuclei of epithelial and interstitial cells of bronchiolar-alveolar regions correlates with this histopathologic response. The study presented here describes the early proliferative response in the bronchiolar-alveolar regions in mice after a brief exposure to chrysotile asbestos. Mice exposed to asbestos had significantly increased incorporation of bromodeoxyuridine (BrdU) in interstitial and epithelial cells of first alveolar duct bifurcations and terminal bronchioles at 48 h after exposure. The BrdU incorporation was similar at 24 h after exposure. This study confirms that BrdU provides information on asbestos-induced cell proliferation similar to that of 3H-TdR, but the technology is far safer and less time-consuming.

A role of parathyroid hormone for the activation of cardiac fibroblasts in uremia.

Intermyocardiocytic fibrosis, i.e., nonreparative interstitial fibrosis with collagen fiber deposition, is commonly found in uremic patients and animals. The volume density of interstitial tissue in the left papillary muscle of uremic animals was found to be increased (from 1.9 +/- 0.7 to 4.2 +/- 1.1%; P < 0.001). The nuclei of interstitial cells, but not of endothelial cells, were enlarged, pointing to an activating signal that specifically acts on interstitial cells. Because of the known action of parathyroid hormone (PTH) on the heart, a potential role of PTH in the genesis of fibrosis was explored by comparing subtotally nephrectomized (NX) parathyroidectomized (PTX) rats receiving by osmotic minipump either saline or rat 1,34 PTH (100 ng/kg per hour dissolved in NaCl). Animals were on a standard 0.95% Ca diet. After PTX, they were switched to a high-calcium (3%) diet. At the end of the 14-day experiments, NX-PTX-PTH animals and NX-PTX-solvent animals were comparable with respect to mean body weight (335 versus 338 g), serum creatinine (1.2 versus 1.2 mg/dL), and serum-Ca (2.66 versus 2.63 mmol/L). The volume densities of cardiac interstitium were 4.71 +/- 0.87 versus 1.49 +/- 0.49, and those of capillaries were 8.07 +/- 1.54 versus 7.94 +/- 2.62, respectively (P < 0.001 by analysis of variance). Thus, PTX abolished and PTH restored intermyocardiocytic changes of experimental uremia. These observations argue for a permissive role of PTH for fibroblast activation and the genesis of the cardiac fibrosis of uremia.

Jun, Fos, MyoD1, and Myogenin proteins are increased in skeletal muscle fiber nuclei after denervation

After denervation, mRNA levels of the jun and fos protooncogenes and of the muscular differentiation factors myoD1 and myogenin are increased. Here, immunohistochemistry was used (a) to show that this increase in mRNA is followed by an increase in the transcription factor proteins, and (b) to determine which cell populations in skeletal muscle express these factors after denervation. Rat diaphragms were denervated and analyzed after periods of 90 min-8 days. An increase in Fos and Jun as well as MyoD1 and Myogenin immunoreactivity was found after 2-2.5 days of denervation. Fos, MyoD1, and Myogenin immunoreactivity was mostly confined to muscle cell nuclei, whereas Jun antibodies stained muscle cell and some interstitial cell nuclei. A selective expression of any of the four transcription factors in muscle cell nuclei closely associated with motor endplates could not be detected in either denervated or innervated muscle at any time point examined, indicating that synaptic and extrasynaptic muscle cell nuclei are activated simultaneously after denervation. These results suggest that a genetic program which includes protooncogenes and myogenic differentiation factors is activated in skeletal muscle after denervation.

Intracellular distribution of poly(ADP-ribose) synthetase in rat spermatogenic cells

The highest activity of poly(ADP-ribose) synthetase was found in the testis among several rat tissues tested. Subcellular fractionation of the testis demonstrated that the synthetase was localized primarily in the nucleus and partially in the microsomal-ribosomal fraction. This result was confirmed by immunocytochemical staining with the enzyme-specific antibody. The synthetase was localized in the nuclei of interstitial cells, Sertoli cells, spermatogonia, and spermatocytes. In addition, round spermatids showed a granular staining in the cytoplasm, which was comparable in intensity with that in the nucleus. The cytoplasmic synthetase had a molecular weight of 115,000 and synthesized oligomers of ADP-ribose on itself (automodification). The synthetase activity in the isolated cytoplasmic fraction was stimulated about threefold by the addition of DNA and depressed by treatment with DNase I, suggesting the presence of endogenous activator DNA. A candidate DNA for such an activator was isolated from the microsomal-ribosomal fraction, and identified tentatively as mitochondrial DNA on the basis of its size and restriction fragment patterns.

Lack of association between cytomegalovirus infection of heart and rejection-like inflammation.

Serial myocardial biopsy specimens, taken up to the time of serological evidence of primary cytomegalovirus (CMV) infection in 22 heart transplant patients, were examined and compared with those taken over similar times after transplantation in 21 patients who did not develop CMV infection. None of these 43 patients had serological evidence of CMV infection before their heart transplantation. There was no evidence of an increased cellular infiltrate in the myocardium at the time of the active CMV infection, even though the donor heart is the likeliest source of infection, nor was there any change in myocyte, interstitial cell, or vascular endothelial cell nuclei to identify active CMV infection.

Interactions of cadmium with rat testicular interstitial cell nuclei: Alterations induced by zinc pretreatment and cadmium binding proteins

To help elucidate the mechanism by which zinc prevents cadmium-induced interstitial cell (IC) tumour formation in the rat, the subcellular distribution of cadmium in isolated ICs was studied. In both isolated intact cells and in isolated nuclei, in vivo zinc pretreatment reduced the nuclear uptake of cadmium and resulted in a decreased accumulation of cadmium in subnuclear components, including chromatic and DNA. In intact cells, in vivo zinc pretreatment increased cadmium retention in mitochondria. microsomes and cytosol. An increase in the metal content in three major cytosolic cadmium-binding fractions was also seen, including the low-molecular-weight testicular cadmium-binding protein (TCBP) previously shown to differ from metallothionein. Uptake of cadmium in association with purified TCBP into isolated IC nuclei was about double that of cadmium bound to purified hepatic metallothionein. These data suggest that zinc may prevent IC tumour formation by reducing cadmium accumulation in nuclei and subnuclear components, including chromatin and DNA. This appears to be through a direct inhibition of cadmium uptake by zinc pretreatment at the nuclear membrane and also indirectly by an enhanced retention of cadmium in non-nuclear subcellular components. These data also indicate that the absence of metallothionein in ICs may render this cell population vulnerable to cadmium by allowing increased nuclear uptake.

Regression of cardiac hypertrophy: Morphometric and biochemical studies in rat heart after swimming training

There is currently little information about the morphological changes of the myocardium accompanying the reversal of cardiac hypertrophy. In this study the hypothesis was tested that myocardial alterations induced by exercise will regress within a short interval after the end of training. Rat hearts were examined using morphometric and biochemical methods at the end of a 9-week period of endurance training and also 7, 10 and 14 days after its termination. At the end of the training period the heart weight had increased by 65% but the weight ratio of the right and left ventricular wall remained unchanged. A decline in the DNA content by 27% as well as a decrease in the volume density of the interstitial space by 14% and in the number of interstitial cell nuclei by 32% against controls, are explained by a 30% increase in the width of myofibres. The capillary density was reduced by 22% but the volume density of capillaries remained nearly constant as a result of widening of the capillary diameter by 27%. The surface density of capillaries was diminished by 10%. Ultrastructurally an increase in the ratio of mitochondrial to myofibrillar volume density was observed in the myocytes of hypertrophied hearts as compared to controls (0.54 and 0.63, respectively). Fourteen days after termination of training, 80% of the increment in heart weight had regressed. At this time the width of the myofibres and the volume density of the interstitial space had nearly normalized, while the capillary to fibre ratio had significantly increased. The ratio of mitochondrial and myofibrillar volume density became nearly normal, and a confluence of intermyofibrillar mitochondria resulted in significantly longer organelles. The increased DNA content 10 days after the training, as compared to controls, is attributable to the genesis of non-myocardial cells during the hypertrophic growth and their persistence during regression. The study has shown that cardiac hypertrophy induced by physical training nearly completely regresses within 14 days after termination of conditioning. The increased capillary to fibre ratio indicates neoformation of transversely oriented capillary branches in hypertrophy which particularly becomes apparent in two-dimensional estimation in the regression period. In comparison with myofibres, regression of capillaries seems to be delayed. The decline of heart weight and a significantly diminished RNA content during the regression of hypertrophy suggest that reduced synthesis is responsible for the decrease in heart weight.

Myocardial interstitial fibrosis in experimental uremia—Implications for cardiac compliance

Experimental uremia is known to cause cardiac hypertrophy. In the present study we examined the effect of uremia with or without concomitant treatment of hypertension by the converting enzyme Ramipril (125 micrograms/day) on micromorphometric indices of cardiac interstitium at the light microscopical and ultrastructural level. In male SD rats, 21 days of uremia caused an increase of total heart weight (1040 +/- 73 mg wet wt vs. 871 +/- 81 in controls, P less than 0.05) with an increase of both right and left ventricular weight. This was accompanied by reduction of capillary cross-sectional area despite unchanged capillary length. The volume density (cm3/cm3) of cardiomyocytes was unchanged (0.881 +/- 0.01 vs. 0.871 +/- 0.016 in controls), but volume density of interstitial tissue (excluding capillary lumen) was significantly increased (0.042 +/- 0.011 cm3 interstitial tissue/cm3 total heart tissue vs. 0.019 +/- 0.007 in controls). This was associated with signs of activation of interstitial cells, that is, increased volume of interstitial cell nuclei and interstitial cell cytoplasm. Concomitantly, a significant increase of volume density of non-cellular interstitial ground substance was found which was not normalized by antihypertensive treatment using Ramipril. After three months of uremia, electron microscopy showed collagen fiber deposition in the interstitium. Comparable interstitial fibrosis was not observed in hearts of rats with renovascular (one clip-two kidney) hypertension. It is concluded that uremia increases myocardial interstitial ground substance by mechanisms independent of hypertension. The data may be relevant for recent findings of diastolic heart malfunction secondary to impaired compliance in uremic patients.

Proliferation of cardiomyocytes and interstitial cells in the cardiac muscle of the mouse during pre- and postnatal development.

Proliferation of cardiomyocytes and interstitial cells in the cardiac ventricle of the mouse during pre- and postnatal development was studied. Furthermore, the number of cardiomyocyte and interstitial cell nuclei per unit area was determined on histological sections. The labelling index of cardiomyocytes decreases from 23% on day 14 of gestation to about zero at 3 weeks after birth. The number of cardiomyocyte nuclei per unit area increases up to day 16 of gestation and then continuously declines. This coincides with the concept that the increase in size of the heart during early fetal life is mainly due to hyperplasia, while during late fetal life and after birth it is mainly, and during adult life exclusively, due to hypertrophy of cardiomyocytes. Proliferation of interstitial cells continues up to 5 days after birth and then decreases. The ratio of cardiomyocytes to interstitial cells decreases by a factor of about 10 between day 14 of gestation and 3 weeks after birth.

Do C cells of the thyroid gland of the baboon contain estrogen receptors?

The uptake and retention of radiolabelled estradiol was studied in the thyroid gland of the female baboon. Four baboons were injected intravenously with 1 micron/kg body weight of 3H-estradiol. One animal, which served as a control, received an additional injection of 100 micrograms/kg body weight of unlabelled hormone. One hour after the injections, the animals were killed and the thyroid glands removed and processed for either autoradiography or autoradiography in combination with immunocytochemical staining for C cells. Localization of estradiol was observed in the nuclei of interstitial cells, but not in those of the follicular cells. Nuclei of immunostained calcitonin-containing cells in both the walls of the follicles and the interfollicular compartment were not radiolabelled. This study suggests that estrogen does not regulate calcitonin secretion by the C cells of the thyroid via a classical receptor system.