Nerve growth factor-like immunoreactivities in rodent salivary glands and testis

NGF promotes mitochondrial function by activating PGC-1α in TM4 Sertoli cells

Nerve growth factor (NGF), which is required for the survival and differentiation of the nervous system, has been proved to play important roles in male reproductive physiology. Several studies have focused on the roles of NGF in the testes. However, no study has reported on the mechanism of paracrine and autocrine actions of NGF in Sertoli cells. This study showed that NGF stimulated mitochondrial activity and biogenesis in TM4 Sertoli cells. Moreover, our results demonstrated that peroxisome proliferator-activated receptor-gamma coactivator-1α is a possible downstream key target of the NGF signalling pathway. In a 3-nitropropionic acid cell model, NGF treatment attenuated mitochondrial activity defect and depolarisation. This NGF-triggered signalling may help in discovering new therapeutic targets for certain male infertility disorders.

Immunocytochemical study of granular duct cells with a hormonally enhanced granular cell phenotype in the mouse parotid gland

In the parotid glands (PGs) of intact male mice (12 weeks of age, ICR strain), immunofluorescence labels for a true tissue kallikrein, mK1, and for nerve growth factor (NGF) were recognized through the subluminal edges of the striated duct (SD) segments and interlobular duct segments. Because of their small size, secretory granules were not detectable by light microscopy in any of the duct cells. Full-fledged granular cells, containing large secretory granules that were visible by light microscopy, were induced in the SD segments of male mice after the injection of 5alpha-dehydrotestosterone (DHT) and triiodothyronine (T(3)), given either alone or in combination every other day for 2 weeks. A stronger effect was detected in the mice that were concomitantly injected with DHT and T(3), and more abundant, fully developed granular cells appeared in the SD segments of these mice. These full-fledged granular cells were immunoreactive for mK1, NGF, and epidermal growth factor, but not for renin. The present results indicate that some of the SD cells with small granules in the mouse PG can develop a granular cell phenotype, producing more kinds of growth factors, as a result of the actions of androgen and thyroid hormone.

Initiation of testicular tubulogenesis is controlled by neurotrophic tyrosine receptor kinases in a three-dimensional Sertoli cell aggregation assay

The first morphological sign of testicular differentiation is the formation of testis cords. Prior to cord formation, newly specified Sertoli cells establish adhesive junctions, and condensation of somatic cells along the surface epithelium of the genital ridge occurs. Here, we show that Sertoli cell aggregation is necessary for subsequent testis cord formation, and that neurotrophic tyrosine kinase receptors (NTRKs) regulate this process. In a three-dimensional cell culture assay, immature rat Sertoli cells aggregate to form large spherical aggregates (81.36±7.34 μm in diameter) in a highly organized, hexagonal arrangement (376.95±21.93 μm average distance between spherical aggregates). Exposure to NTRK inhibitors K252a and AG879 significantly disrupted Sertoli cell aggregation in a dose-dependent manner. Sertoli cells were prevented from establishing cell–cell contacts and from forming spherical aggregates.In vitro-derived spherical aggregates were xenografted into immunodeficient nude mice to investigate their developmental potential. In controls, seminiferous tubule-like structures showing polarized single-layered Sertoli cell epithelia, basement membranes, peritubular myoid cells surrounding the tubules, and lumen were observed in histological sections. By contrast, grafts from treatment groups were devoid of tubules and only few single Sertoli cells were present in xenografts after 4 weeks. Furthermore, the grafts were significantly smaller when Sertoli cell aggregation was disrupted by K252ain vitro(20.87 vs 6.63 mg;P<0.05). We conclude from these results that NTRK-regulated Sertoli–Sertoli cell contact is essential to the period of extensive growth and remodeling that occurs during testicular tubulogenesis, and our data indicate its potential function in fetal and prepubertal testis differentiation.

Repeated androgen and thyroid hormone injection modulates the morphology of hormone-responsive duct cells in the mouse parotid gland

When the parotid glands of normal male and female ICR mice (12 weeks of age) were examined under a light microscope, no granular cells were seen in the duct system. However, transmission electron microscopy revealed that, in both sexes, many striated duct cells contained a few electron-dense secretory granules in their subluminal cytoplasm and had formed so-called granular striated tubules (GSTs) in some of the striated duct segments. These secretory granules were not large enough to be visible with a light microscope. Fully fledged granular cells, containing large secretory granules visible with a light microscope, could be induced in the GST segments of the glands of males by injection with 5alpha-dihydrotestosterone (DHT), triiodothyronine (T(3)), and dexamethasone (Dex), given alone or in combination every other day for 2 weeks. Dex alone showed no effect on the GSTs in this study. Both DHT and T(3), either individually or with Dex, were moderately effective, inducing a few scattered fully fledged granular cells. A stronger effect was detected after concomitant injection of DHT and T(3), with or without Dex, with more abundant fully developed granular cells appearing in the GST segments. Electron microscopy revealed that these granular cells had abundant large secretory granules in their apical two-thirds, a basal nucleus, and modest basal infoldings. By contrast, the effect of the same hormones was very weak in the glands of females, and even the concomitant injection of DHT and T(3), with or without Dex, rarely induced fully fledged granular cells. These results indicate a close similarity between the ductal systems of the major salivary glands of the mouse, in terms of some of the striated duct segments containing secretory granules, being under the same multihormonal regulation, and being sexually dimorphic.

Expression of nerve growth factor (NGF), and its receptors TrkA and p75 in the reproductive organs of the adult male rats

Immunolocalization of nerve growth factor (NGF) and its receptors, TrkA and p75 in the reproductive organs of adult male rats was investigated. Sections of the testis, efferent duct, epididymis, deferent duct, seminal vesicle, coagulating gland and prostate of adult male rats were immunostained by the avidin-biotin-peroxidase complex methods (ABC). NGF was expressed in Leydig cells, primary spermatocytes and pachytene spermatocytes in the testis. TrkA only immunoreacted to elongate spermatids and p75 showed positive immunostaining in the Sertoli cells, Leydig cells, the pachytene spermatocytes and elongate spermatids. Immunoreactions for NGF and its two receptors were detected in epithelial cells of efferent duct, deferent duct and epididymis. In addition, immunoreactions for NGF and its two receptors were also observed in columnar secretory epithelium lines of the seminal vesicles, prostate and coagulating gland. These results suggest that NGF is an important growth factor in gonadal function of adult male rats.

The expression of neurotrophins and their receptors in the prenatal and adult human testis: evidence for functions in Leydig cells

Previous studies have demonstrated local functions for neurotrophins in the developing and mature testis of rodents. To examine whether these signaling molecules are present and also potentially active in the human testis, we characterized immunohistochemically the expression and cellular localization of the known neurotrophins and their receptors during prenatal testicular development as well as in the adult human testis. Results obtained revealed the presence of nerve growth factor (NGF), brain-derived neurotrophic factor, neurotrophin-3 and 4, as well as neurotrophin receptors p75(NTR), TrkA, TrkB, and TrkC during testis morphogenesis. These proteins were also detectable in the adult human testis, and their local expression could be confirmed largely by immunoblot and RT-PCR analyses. Remarkably, the Leydig cells were found to represent the predominant neurotrophin/receptor expression sites within both fetal and adult human testes. Functional assays performed with a mouse tumor Leydig cell line revealed that NGF exposure increases cellular steroid production, indicating a role in differentiation processes. These findings support previously-recognized neuronal characteristics of Leydig cells, provide additional evidence for potential roles of neurotrophins during testis morphogenesis and in the mature testis, and demonstrate for the first time a neurotrophin-induced functional activity in Leydig cells.

Localization of NGF and nNOS in varicocele-induced rat testis

Nerve growth factor (NGF) is synthesized in male germ cells. The presence of neuronal nitric oxide synthase (nNOS) in Leydig cells is related to its role in the regulation of testosterone release. Varicocele is often characterized by abnormal sperm quality and influences the fertilizing capacity of the haploid gamete. We investigated the localization of NGF and nNOS in testes of adult Wistar rats with experimentally induced varicocele after 9, 11, and 13 weeks, as well as in sham-operated controls by immunohistochemistry and Western blot. In control testis, we detected NGF in nuclei of Sertoli cells and also as small vesicular-like structures in the cytoplasm of primary spermatocytes, and in round and elongating spermatids. Varicocele-induction revealed a slight decrease of NGF at 13 weeks, especially in Sertoli cells. In control tissue, nNOS protein was present mainly in Leydig cells and in Sertoli cell cytoplasm. Additionally, nNOS immunoreactivity was present in the heads of elongated spermatids. Western blot results revealed that the decrease of NGF was not significant in the 13-week varicocele group, moreover, the amount of nNOS was not altered in any of the varicocele groups. In conclusion, NGF and nNOS have important roles for normal gametogenesis and our data for the first time indicates that varicocele induction does not necessarily affect the expression of NGF and nNOS. Thus, these two molecules do not appear to be related to varicocele induction.

'Mature' nerve growth factor is a minor species in most peripheral tissues

The classic neurotrophin hypothesis is based on the idea that innervating neurons derive 'mature' neurotrophin provided by the target for their survival. Yet large precursor forms of the neurotrophin nerve growth factor (NGF) have been reported in both central and peripheral tissues. In the present study, immunoblotting was used to survey peripheral tissues containing NGF-responsive neurons and to characterize various NGF species. These results demonstrate that 'mature' forms of NGF, i.e., the 13 and 16kDa species, are rare in sympathetic and sensory ganglia and in their peripheral targets, and that large molecular weight NGF precursors are abundant. In addition, certain NGF forms predominate in a given tissue, with each tissue exhibiting a characteristic NGF expression pattern. These findings suggest that NGF processing in peripheral tissues and in NGF-responsive ganglia may involve a variety of NGF species.

Role of thyroid hormone in the initiation of EGF (epidermal growth factor) expression in the sublingual gland of the postnatal mouse

The effect of triiodo-L-thyronine (T3) and propylthiouracil (PTU) on the initiation of epidermal growth factor (EGF) expression in the sublingual glands (SLGs) of postnatal mice was investigated by indirect enzyme-labeled and immunogold antibody methods for light and electron microscopy, respectively. In normal males, EGF immunoreactivity first appeared in a few scattered granular cells of striated ducts (SDs) at 5 weeks of age, and the immunoreactive cells had increased in number at 6 weeks of age. No EGF expression was observed in the glands of females at any ages examined. When T3 (1 mg/kg body weight) was given to males every other day for 2 weeks before examination, EGF expression began earlier; the immunoreactive granular cells were first detected at 4 weeks of age, and at later ages they were markedly increased in number compared to those of normal males. Moreover, T3 was capable of inducing EGF in the female glands. After T3 was administered to females in the same manner as in males, a few immunoreactive cells were first detected at 5 weeks of age, and increased numbers were detected at later ages. By contrast, when PTU (1 mg/kg body weight) was given to male mice every other day for 2 weeks before examination, the EGF-immunoreactive cells were markedly decreased in number compared to those of normal males of the same age. Electron microscopy revealed that many SD cells contained secretory granules, and that these cells constituted the granular striated tubule (GST) in a portion of SDs, but they were undetectable by light microscopy, because their secretory granules were minimal in size and few in number. Gold-labeling of EGF was confined to the secretory granules of scattered granular cells, whose secretory granules were far larger in size and more abundant than those of the GST cells. These results suggest that thyroid hormone is essential to differentiation of the cellular phenotype of GST precursor cells into typical granular cells (detectable by light microscopy) that express EGF in the mouse SLG, showing a close resemblance to the submandibular granular convoluted tubule cells.

Increases in nerve growth factor immunoreactivity in the submandibular gland, but not in the parotid gland, of the rat following sympathetic denervation

The effect of sympathetic denervation on nerve growth factor (NGF) immunoreactivity in the submandibular and parotid glands of adult female rats using a two-site, enzyme-linked immunosorbent assay was investigated. Unilateral sympathetic denervation through the avulsion of the superior cervical ganglion resulted in elevated levels of total amounts (decreased from 40-20%) and concentrations (decreased from 45-32%) of NGF in the submandibular glands, but not in the parotid glands, on the operated side 7-28 days post-operatively. Sympathetic decentralisation had no effect. The present findings support the hypothesis that increased levels of NGF play an important part in the increased activity of the acetylcholine-synthesising enzyme, choline acetyltransferase, in the rat submandibular gland following sympathetic denervation.

Calgizarrin like gene (Cal) deficient mice undergo normal spermatogenesis

The murine calgizzarin like gene (Cal) encodes for a calcium binding protein, which belongs to the S100 family of EF-hand proteins. It is specifically expressed in Sertoli cells in the testis and its expression is down-regulated by unknown factor(s) from spermatocytes/spermatids. In this paper, we show by transfection of a fusion protein of green fluorescent protein and Cal protein into NIH3T3 cells, that the expression of Cal is restricted only in the cytoplasm of the cell. A differentially regulated cytoplasmic expression of the Cal in Sertoli cells during mouse development suggests that Cal might play an important role during spermatogenesis. In order to elucidate the function of the Cal protein in the spermatogenesis, we disrupted the Cal locus in mouse by homologous recombination. In our knockout mouse, we deleted exon 2 and exon 3 of the Cal gene and replaced them with a neomycin cassette, which resulted in a complete loss of the Cal transcript. Male and female Cal4+/- and Cal4-/- mice from genetic backgrounds C57BL/6J x 129X1/SvJ hybrid and 129X1/SvJ inbred exhibited normal phenotype and were fertile. An intensive phenotypic analysis showed no gross abnormalities in testis morphology. The lack of the Cal protein also does not affect the parameters of sperm, as they are able to fertilize the oocytes in a competent manner, which is comparable to wild-type sperm. Collectively our results demonstrate that Cal is a nonessential protein and it does not play an important role in mouse spermatogenesis or in process of fertilization.

Antioxidant superoxide dismutase - a review: its function, regulation in the testis, and role in male fertility

Extracellular superoxide dismutase (SOD(EX)), an antioxidant enzyme, was found to be present in the testis at a relatively high concentration versus other organs. In a more detailed survey of several rat tissues and cells by reverse transcriptase-polymerase chain reaction, it was shown that germ cells expressed approximately one-third that of Sertoli cells, suggesting both cell types are equipped with the machinery needed to defend themselves from radical-induced damage. When we used an in vitro model in which germ cells were co-cultured with Sertoli cells at a Sertoli:germ cell ratio of 1:1, we failed to detect any changes in the mRNA level of SOD(EX). However, the addition of increasing concentrations of germ cell secretory proteins into Sertoli cell cultures resulted in a decrease in Sertoli cell SOD(EX) expression, illustrating that germ cells can indeed regulate Sertoli cell SOD(EX). On the other hand, Sertoli cell SOD(EX) expression was stimulated when human recombinant interleukin-1alpha (IL-1alpha), a germ cell product, was included into Sertoli cells in vitro. These results, taken collectively, suggest SOD(EX) is an important antioxidant molecule in the testis that is under germ cell regulation.

Expression of neurotrophin receptors in rat testis. Upregulation of TrkA mRNA with hCG treatment

We report the expression of TrkA, TrkB and TrkC mRNAs in adult rat testis. With in situ hybridisation a low signal for TrkB and TrkC could be seen in postmeiotic cells of the seminiferous epithelium, whereas no signal for TrkA could be observed in untreated animals. Animals treated with hCG showed an induction of TrkA mRNA in premeiotic cells 12 h after the treatment, whereas an injection with EDS had no effect on the expression of Trk mRNAs. With the RNAse protection assay a low signal for TrkA was seen in whole testis of hCG treated animals. In staged tubules low expression was seen at stages VII-XI of untreated animals. Animals injected with hCG revealed that TrkA induction was highest during stages VIIcd and VIII of the cycle. The distinct expression pattern of these high-affinity neurotrophin receptors suggests different roles for neurotrophins during spermatogenesis. Induction of TrkA mRNA by hCG suggests that high-affinity binding of NGF during stages VIIcd-VIII in premeiotic cells is under control of the hypothalamic-pituitary-testicular axis.

Developmental stage- and germ cell-regulated expression of a calcium-binding protein mRNA in mouse Sertoli cells

There is considerable evidence that germ cells, mainly spermatocytes and spermatids, contribute to the regulation of Sertoli cell activity. We developed an in vitro system to investigate the genes involved in Sertoli cell-germ cell interaction in the mouse by using the differential mRNA display technique. One of the isolated differentially expressed genes, named calgizzarin, belongs to the family of S100 calcium-binding proteins and shows a decreased expression in Sertoli cell-germ cell cocultures compared to cultured Sertoli cells alone. Calgizzarin is expressed in all adult tissues examined, including testis and ovary; however, a high mRNA level for calgizzarin in mouse testis is maintained until day 15 of postnatal development and then declines dramatically, whereas the expression pattern in the ovary remains constantly high. Furthermore, Northern blot studies on testicular RNA from different mouse mutants with defects in spermatogenesis revealed that high levels of calgizzarin transcripts can only be detected in testes of mouse mutants with either no germ cells or primary spermatocytes, but only weak signals for calgizzarin are observed in testes of mutants containing spermatids. In addition, using both RT-PCR analysis and whole-mount in situ hybridization on dissected gonads it was demonstrated that mouse calgizzarin expression starts at 13.5 dpc in the prenatal male gonad and at 16.5 dpc in the embryonic ovary, respectively. The mouse calgizzarin gene was localized on mouse chromosome 5, region E-F. Taken together, our results indicate that calgizzarin expression could be repressed by factors originated from pachytene spermatocytes and/or spermatids.

mRNAs encoding a von Ebner's-like protein and the Huntington disease protein are induced in rat male germ cells by Sertoli cells

The success of spermatogenesis is dependent upon closely coordinated interactions between Sertoli cells and germ cells. To identify specific molecules that mediate interactions between somatic cells and germ cells in the rat testis, Sertoli cell-germ cell co-cultures and mRNA differential display were used. Two cDNAs, clone 1 (660 nucleotides) and clone 2 (390 nucleotides) were up-regulated when Sertoli cells were co-cultured with pachytene spermatocytes or round spermatids. Northern blot analyses confirmed the differential display expression patterns. Sequence analyses indicated that clone 1 was similar to a von Ebner's gland protein (87% at the nucleotide level and 80% at the amino acid level) and clone 2 was identical to a region of the Huntington disease protein. The von Ebner's-like protein mRNA was induced after 4 h of co-culture, while the Huntington disease protein required 18 h of co-culture for expression. The von Ebner's-like protein was induced in germ cells by a secreted Sertoli cell factor(s) smaller than 10 kDa that is sensitive to freezing and thawing or boiling. The Huntington disease protein was induced in germ cells by a Sertoli cell secreted factor(s) larger than 10 kDa which survives freezing and thawing, but is inactivated by boiling.

Regulation of alpha2-macroglobulin expression in rat Sertoli cells and hepatocytes by germ cells in vitro

Germ cells isolated from rat testes by trypsinization have been shown to yield unwanted artifacts in biological assays, since conditioned media derived from these germ cells (germ cell-conditioned media [GCCM]) can modulate Sertoli cell secretory function because of the presence of residual trypsin. To determine whether germ cells themselves can modulate Sertoli cell function, we isolated germ cells from tubules by a mechanical procedure and assessed the effect of these cells on Sertoli cell alpha2-macroglobulin (alpha2-MG) steady-state mRNA level. It was found that germ cells indeed could stimulate Sertoli cell alpha2-MG expression. This effect is probably mediated by a soluble factor(s) released from germ cells, since GCCM fractionated by HPLC contained multiple fractions that can stimulate Sertoli cell alpha2-MG expression dose-dependently. These results illustrate that germ cells play a role in regulating testicular alpha2-MG expression. Since Sertoli cells synthesize and secrete many of the serum proteins behind the blood-testis barrier that are also produced by hepatocytes, we sought to ascertain whether germ cells can affect hepatic alpha2-MG expression. When germ cells were cocultured with hepatocytes isolated from adult rats, the hepatocyte alpha2-MG steady-state mRNA level was shown to be stimulated by germ cells dose-dependently. Using different pools of fractions derived from GCCM after their fractionation by a preparative anion-exchange HPLC column, GCCM was found to contain a factor(s) that stimulated hepatocyte alpha2-MG expression dose-dependently. More importantly, the fractions that stimulated hepatocyte alpha2-MG expression had a retention time different from that of the factor(s) that affected Sertoli cell alpha2-MG expression. These data illustrate that germ cells secrete multiple biological factors capable of regulating alpha2-MG expression in the testis and the liver. In summary, this study reveals a possible physiological link between the testis and the liver in that germ cells may release a factor(s) capable of modulating alpha2-MG expression in both organs.

Localization of nerve growth factor, trkA and P75 immunoreactivity in the hippocampal formation and basal forebrain of adult rats

In the immunohistochemical staining of nerve growth factor, it has been reported that fixation-dependent lability of nerve growth factor hampers its localization. In the present study, we used two different polyclonal antibodies to immunostain nerve growth factor in rat brain tissue. We found that in paraformaldehyde-fixed (immersion- or perfusion-fixed) brains, nerve growth factor-like immunoreactivity was located primarily in the cytoplasmic membrane and fiber tract of hippocampal neurons and was sparse in cortical neurons. When fresh frozen brain sections were fixed in paraformaldehyde solution, nerve-growth factor-like immunoreactivity was distributed evenly in the cell body. However, when fresh frozen brain sections were fixed in acetone, immunoreactivity to nerve growth factor was present as discrete or confluent dense particles in the cell body, especially in the nuclear region. Also, when paraformaldehyde-perfusion-fixed brain sections were heat treated in salt solution before immunostaining, nerve growth factor-like immunoreactivity could be retrieved in the cytoplasmic and nuclear regions. The hippocampal formation, cerebral cortex and basal forebrain expressed nerve growth factor-like immunoreactivity. Double immunostaining in fresh frozen brains showed that the low-affinity nerve growth factor receptor (p75) co-expressed with nerve growth factor and trkA proto-oncogene in basal forebrain neurons. Our study shows that formaldehyde fixation can mask nerve growth factor antigen, and special treatment, such as heating, is needed to retrieve nerve growth factor antigen to permit immunohistochemical detection. For immunohistochemical study of nerve growth factor in rat brain tissue, successful immunostaining can be obtained by using fresh frozen brains to prevent the masking effect of fixatives or by using paraformaldehyde-fixed brains with heat treatment. It is likely that nerve growth factor is synthesized and accumulated mainly in the cell body but not in the fiber tracts, which is similar to the distribution of its messenger RNA. The co-existence of p75 with nerve growth factor and trkA in basal forebrain neurons suggests the role of low- and high-affinity receptors in regulating the trophic effect of nerve growth factor.

Sex-dependent differences in the concentrations of the principal neurotransmitters, noradrenaline and acetylcholine, in the three major salivary glands of mice

The concentrations of principal neurotransmitters in the submandibular, parotid and sublingual glands were compared between two pairs of age-matched male and female ddY mice, one pair consisting of 4-week-old and the other 8-week-old animals. Sex-dependent differences in both noradrenaline and acetylcholine concentrations were observed only in the submandibular gland, although each neurotransmitter showed distinct features. The acetylcholine concentration in the submandibular gland was higher in the female at both ages, whereas the noradrenaline concentration was higher in the female at the age of 4 weeks but became higher in the male by the age of 8 weeks. On the other hand, the total amounts of noradrenaline and acetylcholine per submandibular gland were already greater in the male at 4 weeks, and the male parotid and sublingual glands also had a greater noradrenaline content by 4 weeks and 8 weeks, respectively. Each type of gland had similar growth rates over the 4-week period, and the male submandibular and parotid glands were heavier than the female. In addition, each type of gland had its characteristic ratio of noradrenaline to acetylcholine concentration, which did not differ between the sexes and remained in similar basic patterns during the period examined, except for the submandibular gland of 8-week-old male mice, which developed greater amounts of the sympathetic neurotransmitter noradrenaline.

Characterization of nerve growth factor precursor protein expression in rat round spermatids and the trophic effects of nerve growth factor in the maintenance of Sertoli cell viability

Nerve growth factor (NGF) is expressed by rat round spermatids and is thought to participate in the paracrine regulation of spermatogenesis. In order to elucidate the role of NGF in the rat testis, we further characterized the NGF immunoreactive protein secreted by round spermatids and examined the effect of NGF beta and related neurotrophin family members on the maintenance of Sertoli cell viability. Round spermatids were isolated from rat testes by centrifugal elutriation and the conditioned medium dialyzed/concentrated for the preparation of round spermatid protein (RSP). Immunoblot analysis of RSP with anti-NGF beta antibody identified two immunoreactive bands of 31 and 22 kD, whereas the 13 kD mature form of NGF beta was not observed. Similarly, immunoblot analysis of RSP with an antibody raised against a synthetic peptide (L38) corresponding to the -3 to -40 sequence of proNGF also recognized two immunoreactive bands of 31 and 22 kD. These results are consistent with the identification of two NGF precursors. Interestingly, immunoblot analysis of RSP with an antibody raised against a synthetic peptide (N4) corresponding to the -71 to -46 sequence of proNGF only recognized one immunoreactive band of 31 kD, consistent with the larger NGF precursor observed with the L38 antibody. In a bioactivity test of PC-12 neurite outgrowth, the 31 kD NGF precursor induced flattening and neurite outgrowth of PC-12 cells, consistent with NGF bioactivity. The 22 kD NGF precursor induced modest and inconsistent neurite outgrowth. These results suggest that round spermatids express the 31 and 22 kD precursor forms of the NGF gene product, and that processing of this gene product is incomplete such that the 13 kD mature form of NGF beta is not observed. In view of the role of round spermatids in the paracrine regulation of spermatogenesis, we examined the effect of RSP on the rescue of the viability of Sertoli cells cultured under serum deprived conditions. In the absence of serum, RSP was able to extend the viability of Sertoli cells, and the elimination of this activity by anti-NGF antibody immunoprecipitation of RSP suggests that the NGF precursors in RSP support the maintenance of Sertoli cell viability. In addition, treatment with exogenous NGF beta was able to rescue Sertoli cell viability, whereas L38 peptide, N4 peptide, or the neurotrophins, brain derived neurotrophic factor, neurotrophin-3 and neurotrophin-4/5 were unable to rescue Sertoli cell viability above control levels. Hence, it appears that round spermatids express the precursor forms of the NGF gene product, but not the mature form of NGF beta, and that the NGF beta moiety of the NGF precursor proteins exhibits trophic activity in the rescue of Sertoli cell viability, consistent with the paracrine regulation of spermatogenesis.

Expression of collagen and elastic fibers in duct-ligated submandibular glands of mice

Atrophy of salivary glands may occur by ductal obstruction caused by calculus, infection or neoplastic processes, or as consequence of systemic diseases and aging. In the present work, we have used histochemical methods to study the expression of elastic and collagen fibers during experimental atrophy of the submandibular gland of mice. Glandular atrophy was accompanied by a rapid increase in collagen deposition in both septal and intralobular regions. The expression of elastic fibers was not significantly altered during atrophy: a discrete increase of elastic fibers was noted only around ductal structures. The results showed that experimental ductal obstruction is a useful in vivo model to study molecular events that take part in the remodeling of the extracellular matrix during atrophy of salivary glands.

Expressions of nerve growth factor and p75 low affinity receptor after transient forebrain ischemia in gerbil hippocampal CA1 neurons

Expressions of nerve growth factor (NGF) and low affinity p75 NGF receptor (p75 NGFR) in gerbil hippocampal neurons after 3.5-min transient forebrain ischemia were studied. Most hippocampal CA1 neurons were lost (neuronal density = 44 +/- 12/mm) at 7 days after recirculation, while no cell death was found in the sham-control neurons (220 +/- 27/mm). NGF immunoreactivity was normally present in the sham-control hippocampal neurons. However, it decreased in hippocampal CA1 neurons, and slightly decreased in the neurons of CA3 and dentate gyrus areas from 3 hr after recirculation. By 7 days, NGF immunoreactivity returned almost completely to the sham-control level in the CA3 and dentate gyrus neurons but decreased markedly in the CA1 neurons. In contrast, p75 NGFR immunoreactivity was scarcely present in the sham-control hippocampal neurons but was induced from 1 hr after recirculation in the CA1 and CA3 neurons and from 3 hr in the dentate gyrus. At 7 days, p75 NGFR immunoreactivity was expressed greatly in the surviving CA1 neurons and the reactive astrocytes but was not seen in the other hippocampal neurons. The markedly decreased NGF and greatly induced p75 NGFR immunoreactivity found in the CA1 neurons after transient forebrain ischemia suggests that NGF and p75 NGFR may be involved in the mechanism of delayed neuronal death.

Effects of sialoadenectomy and epidermal growth factor on testicular function of sexually mature male mice

The effect of sialoadenectomy (Sx) and epidermal growth factor (EGF) administration on testicular function was investigated in 8-week old C3H mice. Animals were divided initially into three groups: sham operated controls, Sx, and Sx + EGF treated (100 micrograms./kg./day subcutaneously for 28 days). Sialoadenectomy completely depleted the circulating levels of EGF and reduced body weight and reproductive organ weights. However, kidney weight was not affected. Quantitative analysis of spermatogenesis showed a decrease in preleptotene and pachytene spermatocytes and round spermatids, which resulted in a decrease in sperm counts. Sperm motility and fertility were also significantly decreased. Endocrinologic studies showed a 2- and 6-fold elevation in intratesticular and serum levels of testosterone and a decrease in luteinizing hormone (LH) levels. Follicle stimulating hormone levels were not altered. Administration of EGF to the Sx animals maintained reproductive organ weights, spermatogenesis and levels of LH and testosterone closer to control values; however, sperm motility was not maintained at control value. That sialoadenectomy resulted in a decline in androgen-dependent parameters, in spite of an elevation in testosterone levels, and EGF maintained them closer to the control value suggested that EGF may modulate androgen action. A comparison was therefore carried out between the effects of Sx and administration of flutamide (F), an androgen receptor blocker. Animals were subjected to Sx, F treatment (100 mg./kg./day subcutaneously for 28 days), Sx + F, or Sx + F + EGF. The effects of Sx and F treatment on organ weights, sperm counts and sperm motility were more or less similar. As expected, flutamide treatment increased LH and FSH levels, and testosterone levels were normal. The Sx + F animals showed no further decrease in organ weights, sperm count and motility. Treatment with Sx + F increased intratesticular and serum levels of testosterone by 2- and 10-fold. Circulating levels of LH and FSH were the same as in the flutamide-treated group. Administration of EGF to Sx + F maintained all these parameters, except sperm motility, closer to the control value. These results suggest that EGF either bypasses flutamide effects and acts directly or that EGF modulates androgen action at one or more steps in the signal transduction pathway in the male reproductive organs.

The protective effect of L-threo-3,4-dihydroxyphenylserine on ischemic hippocampal neuronal death in gerbils

BACKGROUND AND PURPOSE

L-Threo-3,4-dihydroxyphenylserine (DOPS) is reported to increase the nerve growth factor (NGF) synthesis in cultured mouse L-M fibroblast and astroglial cells, and this effect is not blocked by treatment with decarboxylase inhibitor. NGF is suggested to play an important role in neuronal survival and regeneration under pathological conditions. We evaluated the possible protective effect of DOPS against hippocampal CA1 cell death after transient forebrain ischemia in gerbils.

METHODS

Male mongolian gerbils were treated with DOPS (30, 100, or 300 mg/kg IP) plus benserazide (10 mg/kg IP) (n = 28) or vehicle (n = 7) before 3.5 minutes of forebrain ischemia. For histopathologic study, the animals were decapitated 7 days after recirculation, and neuronal density of the hippocampal CA1 area was counted after cresyl violet staining. For immunohistochemical study, another group of gerbils (n = 34) was recovered for 1, 3, and 8 hours and 1, 2, and 7 days, when they were decapitated. The brain sections were stained against NGF, NGF receptor, and HSP70 using the avidin-biotin-peroxidase method.

RESULTS

Preservation of the hippocampal CA1 cells was found in the brains treated with 300 mg/kg DOPS plus benserazide (neuronal density, 125 +/- 24 cells per millimeter) compared with the vehicle-treated ones (49 +/- 11 cells per millimeter) (P < .01). The immunoreactive NGF was greatly reduced from 3 hours after recirculation in the vehicle group, but it was much less reduced in the 300-mg/kg-DOPS-plus-benserazide group as compared with the vehicle group. The immunoreactivity for NGF receptor was gradually induced from 1 hour after recirculation with the peak at 1 day in the vehicle group, but it was only slightly induced at 8 hours in the 300-mg/kg-DOPS-plus-benserazide group. HSP70 immunoreactivity was also induced from 3 hours with the peak at 1 day in the vehicle group. However, in the 300-mg/kg-DOPS-plus-benserazide group, the induction of HSP70 was found from 8 hours and was much less intensive.

CONCLUSIONS

Treatment with DOPS is protective to the ischemic hippocampal CA1 cells, and the NGF-receptor system may play a role in this protective effect of DOPS.

The granular convoluted tubule (GCT) cell of rodent submandibular glands

The granular convoluted tubule (GCT) is a segment of the duct system of all rodents, situated between the striated and intercalated ducts. It has the peculiar property of synthesizing a large variety of biologically active polypeptides whose role in saliva remains unknown. The literature on the fine structure of GCT cells is critically reviewed. Some recent developments on endocrine regulation of the structure and contents of rodent GCT cells are summarized, with emphasis on EGF, NGF, renin, and kallikrein proteases. A survey of the distribution of GCT cells in several vertebrate families is presented.

Basic fibroblast growth factor in rat salivary glands

We studied the occurrence and localization of basic fibroblast growth factor (bFGF) in rat salivary glands using a specific monoclonal antibody. It was shown that the extract of rat salivary glands has a pronounced stimulatory activity on the growth of bovine capillary endothelial cells, which is blocked by the addition of an antibody against bFGF. The concentration of bFGF in the submandibular/sublingual gland, as determined by radioimmunoassay, was approximately 80% that in the brain. Immunocytochemistry revealed bFGF-immunoreactivity localized primarily in the epithelial cells lining the striated ducts and excretory ducts of the parotid, sublingual and submandibular glands. In addition, intense bFGF-immunoreactivity was observed in the granular convoluted tubule of the submandibular gland, localized predominantly in the agranular pillar cells, which lay in small numbers among the majority of weakly immunostained cells containing many apical secretory granules. At the electron-microscopic level, the immunoreactive material was distributed diffusely in the cytoplasmic matrix and nuclei of all immunoreactive cells, whereas it was absent from all cytoplasmic organelles including the secretory granules. These results indicate that bFGF is localized in different cellular and subcellular compartments from those of other growth factors in the duct system of rat salivary glands.

An updated role for nerve growth factor in neurobehavioural regulation of adult vertebrates

Increasing attention has been focused on the role(s) of nerve growth factor (NGF) in neurobehavioural regulations of adult vertebrates. This interest springs from the emerging evidence that NGF is a "regulator" of physiological processes belonging to the three main homeostatic systems: the nervous, immune and endocrine systems. In fact, the spectrum of action of the NGF molecule is not restricted to neuronal cell types (central basal forebrain; peripheral sensory and sympathetic neurons) but extends also to nonneuronal cells. In mice intermale aggressive behaviour enhances serum NGF levels and promotes its synthesis in some hypothalamic areas. Other types of social events are able to cause NGF release, particularly under stress conditions. The achievement of a social role (dominant vs subordinate) is due to a functional loop involving salivary NGF release-->enhanced production of adrenal hormones-->submissive behaviour-->NGF release. In humans, plasma platelet-derived growth factor (PDGF) increases following mental stress. The aim of this review is to give an updated survey on NGF roles in neurobehavioural regulations of adult animals.

Function and evolution in the NGF family and its receptors

The gene family of neurotrophins includes nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4). Recently, neurotrophin-5 (NT-5), a possible mammalian homologue to NT-4 described in the frog Xenopus, has been cloned in man and rat. The neurotrophins stimulate survival and differentiation of a range of target neurons by binding to cell surface receptors. The structure of NGF has recently been clarified from crystallographic data. The similarities between the different neurotrophins are substantial with the variable regions, giving specificity to each of the family members, being localized to some exposed loop regions. Low-affinity binding (Kd of 10(-9) M) of all tested neurotrophins is mediated via a 75 K glycoprotein (LNGFR) that has been cloned and characterized. A 140 K tyrosine protein kinase encoded by the proto-oncogene trk has been found to bind NGF with high affinity (Kd of 10(-11) M) and to evoke the cellular neurotrophic responses. In addition, a protein encoded by the trk-related gene trkB has been shown to bind BDNF. Recently, a third member of the trk family, trkC, has been cloned and demonstrated to function as a high-affinity receptor for NT-3. The expression of trk and LNGFR mRNA are co-localized in the rat brain to the medial septal nucleus and the nucleus of Broca's diagonal band containing the NGF-responsive magnocellular cholinergic neurons projecting to hippocampus and cerebral cortex. In sharp contrast, the pattern of expression of trkB is widely spread in many areas of the cortex as well as lateral septum. The trkB protein might serve general functions in large areas of the cortex. Site-directed mutagenesis and expression of recombinant chimaeric neurotrophin proteins have made it possible to localize a likely region for the interaction between NGF and the LNGFR. This region could be altered, resulting in the total loss of LNGFR binding by the mutant NGF protein without affecting the binding to the trk receptor which was sufficient for the full biological activity. Cladistic analysis of likely phylogenies within the neurotrophins shows BDNF and NT-4 to be most closely related whereas NGF may be the sister group to NT-3, BDNF, and NT-4. Neurotrophins offer obvious clinical possibilities for treatment of neurodegenerative diseases.

Expression of beta-nerve growth factor and its receptor in rat seminiferous epithelium: specific function at the onset of meiosis

beta-Nerve growth factor (NGF) is expressed in spermatogenic cells and has testosterone-downregulated low-affinity receptors on Sertoli cells suggesting a paracrine role in the regulation of spermatogenesis. An analysis of the stage-specific expression of NGF and its low affinity receptor during the cycle of the seminiferous epithelium in the rat revealed NGF mRNA and protein at all stages of the cycle. Tyrosine kinase receptor (trk) mRNA encoding an essential component of the high-affinity NGF receptor was also present at all stages. In contrast, expression of low affinity NGF receptor mRNA was only found in stages VIIcd and VIII of the cycle, the sites of onset of meiosis. The low-affinity NGF receptor protein was present in the plasma membrane of the apical Sertoli cell processes as well as in the basal plasma membrane of these cells at stages VIIcd to XI. NGF was shown to stimulate in vitro DNA synthesis of seminiferous tubule segments with preleptotene spermatocytes at the onset of meiosis while other segments remained nonresponsive. We conclude that NGF is a meiotic growth factor that acts through Sertoli cells.

Growth factors as mediators of testicular cell-cell interactions

The development of testicular function may require local cell-cell interactions to regulate tissue growth and differentiation. Locally produced growth factors may mediate the differential growth of mesenchymal, epithelial and germinal cells that occurs during fetal, prepubertal and postpubertal testis development. The complex co-ordination of differential and temporal cellular growth suggests that a variety of locally produced factors may be involved. Presently, a number of growth factors have been identified in the testis, including IGF-I, TGF-alpha, TGF-beta, NGF, IL-1, FGF, SGF and SCSGF. These factors may mediate interactions involving growth stimulation, growth inhibition and differentiation in this tissue (Table 2 and Figure 1). Endocrine agents are also necessary for testis development and function. In many organs, endocrine hormones appear to alter local cell-cell interactions. Similarly, gonadotrophins may modulate growth factor interactions within the testis. Understanding testicular cell-cell interactions involving growth factors requires evaluation of the cellular site of factor expression, production, secretion, target cell action and in vivo significance. Presently, none of the proposed cell-cell interactions involving growth factors have evaluated all these criteria. Further cellular and molecular analysis of these intercellular interactions are necessary to clarify the role of growth factors in the development and maintenance of testicular function.

Germ cell mitogenic activity is associated with nerve growth factor-like protein(s)

The mitogenicity of germ cell proteins released from round spermatids (RS) and pachytene spermatocytes (PS) was investigated. Germ cells were isolated by centrifugal elutriation from 90-day-old rat testes and incubated in a supplement enriched culture media that lacked exogenous proteins. The conditioned culture media of RS and PS were dialysed/concentrated and lyophilized to prepare RS protein (RSP) and PS protein (PSP). Mitogenic activity of RSP and PSP was determined by 3H-thymidine incorporation into Swiss 3T3 fibroblasts. RSP and PSP stimulated 3H-thymidine incorporation by fibroblasts in a dose-dependent manner. At a higher concentration of RSP (300 micrograms/ml), fibroblast proliferation was stimulated from 6- to 20-fold of control cultures, whereas PSP (300 micrograms/ml) stimulated fibroblast proliferation 2.5-fold of control cultures. Since RSP exhibited substantially greater mitogenic activity than PSP we further investigated the RSP mitogenic substance(s) by immunoneutralization with antibodies against several growth factors. The mitogenic activity of RSP was significantly reduced by treatment with nerve growth factor (NGF) antibody, while neither the treatment of RSP with acidic fibroblast growth factor (aFGF) antibody, nor basic fibroblast growth factor (bFGF) antibody significantly modified the mitogenic activity of RSP. Interestingly, murine NGF-beta, recombinant human NGF-beta, and bovine serum albumin (BSA) did not exhibit mitogenic activity on 3T3 fibroblasts. Nevertheless, the presence of a NGF-like protein in RS and PS was confirmed by indirect immunofluorescence staining with a murine NGF antibody. Subsequently, a Western blot analysis with the NGF antibody identified two immunoreactive bands of 41 +/- 2 kDa and 51 +/- 1 kDa in both RSP and PSP under reduced conditions. These germ cell NGF-like proteins were apparently different from similarly prepared murine and human NGFs (13 kDa) in their molecular weight. Furthermore, neurite outgrowth from pheochromocytoma cells (PC-12), a functional bioassay for NGF-like activity, was stimulated by addition of RSP and PSP to the culture media of the PC-12 cells. These results demonstrate mitogenic activity in germ cell proteins (RSP and PSP) and identify a NGF-like protein(s) which is associated with most of this activity.

Evolutionary studies of the nerve growth factor family reveal a novel member abundantly expressed in Xenopus ovary

Evolutionary conservation of members of the NGF family in vertebrates was studied by DNA sequence analysis of PCR fragments for NGF, BDNF, and NT-3 from human, rat, chicken, viper, Xenopus, salmon, and ray. The results showed that the three factors are highly conserved from fishes to mammals. Phylogenetic trees reflecting the evolution and speciation of the members of the NGF family were constructed. In addition, the gene for a fourth member of the family, neurotrophin-4 (NT-4), was isolated from Xenopus and viper. The NT-4 gene encodes a precursor protein of 236 amino acids, which is processed into a 123 amino acid mature NT-4 protein with 50%-60% amino acid identity to NGF, BDNF, and NT-3. The NT-4 protein was shown to interact with the low affinity NGF receptor and elicited neurite outgrowth from explanted dorsal root ganglia with no and lower activity in sympathetic and nodose ganglia, respectively. Northern blot analysis of different tissues from Xenopus showed NT-4 mRNA only in ovary, where it was present at levels over 100-fold higher than those of NGF mRNA in heart.

Expression of the beta-nerve growth factor gene in male sex organs of the mouse, rat, and guinea pig

Steady-state nerve growth factor (NGF) mRNA levels were estimated in male sex organs of the mouse, rat, and guinea pig by RNA blot hybridization analysis. The abundance of NGF mRNAs was in the order vas deferens greater than epididymis greater than or equal to seminal vesicles much greater than testis. NGF mRNA levels in these organs were compared with those estimated for other rat peripheral tissues and were found to correlate with the density of their sympathetic innervation, with the exception of guinea pig prostate. Castration had no significant effect on NGF mRNA levels in the guinea pig prostate, suggesting that NGF synthesis in this tissue is not under direct androgen control. NGF-like and proNGF-like immunoreactivities were localized by immunohistochemical techniques in the secretory cells of the glandular epithelium of the guinea pig prostate and in germ cells in the seminiferous tubules of the mouse testis.

Identification of cells in rat brain and peripheral tissues expressing mRNA for members of the nerve growth factor family

Cells expressing mRNA for hippocampus-derived neurotrophic factor (HDNF/NT-3) or brain-derived neurotrophic factor (BDNF) were identified by in situ hybridization. In the rat brain, HDNF mRNA was predominantly found in pyramidal neurons in CA1 and CA2 of the hippocampus. Lower levels of HDNF mRNA were found in granular neurons of the dentate gyrus and in neurons of the taenia tecta and induseum griseum. BDNF mRNA-expressing cells were more widely distributed in the rat brain, with high levels in neurons of CA2, CA3, and the hilar region of the dentate gyrus, in the external and internal pyramidal layers of the cerebral cortex, in the claustrum, and in one brainstem structure. Lower levels were seen in CA1 and in the granular layer of the hippocampus, in the taenia tecta, and in the mammillary complex. In peripheral tissues, HDNF mRNA was found in glomerular cells in the kidney, secretory cells in the male rat submandibular gland, and epithelial cells in secondary and tertiary follicles in the ovary. Cells expressing BDNF mRNA were found in the dorsal root ganglia, where neurons of various sizes were labeled.

Organ culture of human seminiferous tubules: a useful tool to study the role of nerve growth factor in the testis

Seminiferous tubules from human testes were mechanically isolated, the cut edges were sealed, and the tubules were cultured in medium free of fetal calf serum (FCS). Degeneration of germ cells occurred during the culture period and was paralleled by a disruption of the seminiferous epithelium, a disturbance in morphology and function of Sertoli cells, and a thickening of the lamina propria. However, when tubules were cultured for 5 days in the presence of FCS, degeneration of the spermatogenic tissue was reduced. FCS increased the mitotic activity of germ cells, but did not maintain normal morphology and function of Sertoli cells and cellular elements of the lamina propria. The thickening of the tubular wall concurred with a change in phenotype of lamina-propria cells from myoid to fibroblastic. Addition of nerve growth factor (NGF) to the culture medium (i) maintained the myoid phenotype of lamina-propria cells, (ii) prevented thickening of the tubular wall, and (iii) stabilized Sertoli cell morphology and function. The effects of NGF appeared to depend on the trophic effects of FCS, since NGF alone had no influence on the maintenance of a regular morphology of the spermatogenic epithelium. The present results indicate a decisive role for NGF in stabilizing specific functions of seminiferous tubules.

Evidence for the presence of nerve growth factor (NGF) and NGF receptors in human testis

Nerve growth factor (NGF) affects morphology and function of isolated and cultured seminiferous tubules from human testis. Quantitative determination of this neurotrophic protein revealed an amount of 5.4 ng per g human testis, suggesting a crucial function of NGF in spermatogenic tissue. With the use of immunohistochemical methods target cells for NGF were identified within the lamina propria. NGF receptors were also visualized on sympathetic nerve fibers crossing the interstitial compartment among adjacent tubules and spatially correlated blood vessels. NGF receptors could be demonstrated on isolated lamina-propria cells even after 2 weeks of culture. Most of the NGF receptor-bearing cells differed from myoid cells of the lamina propria expressing desmin, a marker for smooth muscle. However, some NGF receptor-expressing cells were found sharing morphological and structural similarities with myoid cells. The present data indicate the existence of a NGF-responsive lamina-propria cell that influences the tubular wall and also the seminiferous epithelium.

Activation of the immune system in the testis

The present concept for the mechanism of prolonged transplant survival in the testis suggests that lymphocyte activation is inhibited locally in this site by testicular products. As the testis produces several immunoregulatory factors, the behaviour of lymphocytes in the testis may depend on the net effect of all these factors on intralymphocytic events. In the present article, the extra- and intracellular events associated with lymphocyte activation are reviewed and the steps of lymphocyte activation which might be subject to interference by testicular factors are identified.

Testicular immunoregulatory factors

The present data indicate that immune cells are regulated locally in the testis by Leydig cells, Sertoli cells and resident testicular macrophages. The effects of these cells are mediated by several peptide factors, including protectin, a group of high molecular weight testicular immunosuppressive factors, and testicular interleukin-1 alpha-like factor. The testicular interleukin-1 alpha-like factor is produced by Sertoli cells and is under hypophyseal control. Its synthesis starts at puberty concomitantly with the onset of spermatogenesis and it may act as a spermatogonial growth factor. Protectin, which is under hypophyseal control, may be involved in the mechanism of prolonged transplant survival in the testicular interstitial tissue. Its levels increase at puberty. Both the testicular interleukin-1 alpha-like activity and protectin may be important in testicular pathophysiology.

Expression of beta-nerve growth factor receptor mRNA in Sertoli cells downregulated by testosterone

Nerve growth factor (NGF) is synthesized in male germ cells. The NGF receptor (NGFR) mRNA was found in the Sertoli cells of rat testis. Hypophysectomy increased both NGFR mRNA in testis and the number of NGFR hybridizing cells in seminiferous tubules. This was suppressed by treatment with chorionic gonadotropin or testosterone, but not with follicle-stimulating hormone. The NGFR mRNA also increased after destruction of Leydig cells or blocking of the androgen receptor. This suggests that NGF produced by male germ cells regulates testicular function in an androgen-modulated fashion by mediating an interaction germ and Sertoli cells.

Ontogeny of rat testicular mitogenic activity studied with transformed and nontransformed mouse 3T3 fibroblasts

The ontogeny of the testicular mitogenic activity of Sprague Dawley rats was evaluated by stimulation in vitro of [3H]thymidine uptake and cell number in Swiss 3T3 and transformed NIH 3T3 fibroblasts. Addition of various amounts of testicular cytosolic protein resulted in a dose-dependent increase in cell number in both cell lines. The [3H]thymidine responses to testicular cytosolic proteins was also dose dependent but in a nonparametric manner. In addition, the responses of 3T3 cells to testicular cytosol was apparently dependent on the developmental stage of the testis, the time of stimulation, and the proliferative nature of the fibroblast cell line. These results suggest the presence of multiple forms of mitogenic substance in testicular cytosol and imply that the relative amounts of these substances may depend on the age of the donor animal. These substances may be important in the proliferation or differentiation of cell types at various stages of testicular development.

Testicular atrophy and loss of nerve growth factor-immunoreactive germ cell line in rats exposed to n-hexane and a protective effect of simultaneous exposure to toluene or xylene

Testicular and germ cell line morphology in rats were studied 2 weeks, 10 months and 14 months after cessation of a 61-day inhalation exposure to 1000 ppm n-hexane. Androgen biosynthetic capacity of testis, testosterone blood concentration, vas deferens morphology and noradrenaline (NA) concentration, epididymal sperm morphology, and fertility were also studied. Severe testicular atrophy involving the seminiferous tubules with loss of the nerve growth factor (NGF) immunoreactive germ cell line was found. Total loss of the germ cell line was found in a fraction of animals up to 14 months post-exposure, indicating permanent testicular damage. No impairment of androgen synthesis or androgen dependent accessory organs was observed. Simultaneous administration of 1000 ppm n-hexane and 1000 ppm toluene, or 1000 ppm n-hexane and 1000 ppm xylene, did not cause germ cell line alterations or testicular atrophy. Toluene and xylene were thus found to protect from n-hexane induced testicular atrophy.

Characterization of antibodies to synthetic nerve growth factor (NGF) and proNGF peptides

Sequence data for the mature nerve growth factor (NGF) protein and its precursor are available from molecular cloning of the NGF gene in several species, including mice, humans, rats, and chickens. Hydrophilicity analysis of the predicted rat and chicken prepro-NGF was carried out to locate putative antigenic determinants. Eight peptides were selected and synthesized based on hydrophilicity profiles. Two peptides represent sequences in the rat (and mouse) pro-NGF, one peptide (our peptide P3) represents a highly conserved region of the mature NGF protein (identical in humans, mice, rats, and chickens), two peptides are specific for the mature chicken NGF, and the remaining three peptides are specific for the mature rat NGF (each with only one amino acid substitution compared with corresponding segments of the mouse NGF). For immunization, the peptides were conjugated to keyhold limpet hemocyanin and used to produce antisera in rabbits. After bleeding, peptide-specific antibodies were purified on affinity columns prepared by coupling each of the synthetic peptides. The different peptide antisera and affinity-purified antibodies then were characterized by enzyme-linked immunoassay (ELISA) and immunohistochemistry of the male mouse submandibular gland, a rich exocrine source of NGF. ELISA analysis showed that all peptide antisera bound two to four orders of magnitude better than normal rabbit serum to a coat of their proper peptide. The higher binding was retained by the purified peptide antibodies compared with normal rabbit immunoglobulin. Specific tests, in which one peptide antiserum was checked against different peptide coats in the ELISA, also showed two to four orders of magnitude higher binding of antibodies to the proper synthetic peptide. The peptide antibodies also were tested for their ability to bind to native mouse beta NGF coated to the immunoplates. Only antibodies raised to the conserved P3 peptide recognized native NGF to an extent similar to that obtained with polyclonal anti-NGF antibodies. Conversely, P3 was well recognized by several different NGF antisera. Immunohistochemically, both peptide antisera against the pro-NGF stained the perinuclear cytoplasm in the basal part of the cells of the granulated convoluted tubules in the mouse submandibular gland.(ABSTRACT TRUNCATED AT 400 WORDS)

Somatomedin C in the pancreas of young and adult, normal and obese, hyperinsulinemic mice

Immunocytochemical, immunochemical and RNA-hybridization techniques were used to map the distribution of somatomedin C (Sm-C; insulin-like growth factor I; IGF-I) in the pancreas of young and adult lean and obese mice. The D cells in the islets of Langerhans showed intense cytoplasmic Sm-C immunoreactivity, extending into their processes. Only slight Sm-C immunoreactivity was seen in A and B cells, apparently confined to the plasma membranes. In the exocrine pancreas scattered duct cells were immunopositive. Starvation increased, while feeding decreased the Sm-C immunoreactivity in B cells. RNA-hybridization analyses revealed that roughly the same number of Sm-C mRNA molecules, as calculated per DNA amount in the pancreas, could be demonstrated in young and adult, lean and obese mice. Radioimmunoassay (RIA) determinations of total Sm-C showed that there were about equal concentrations in the pancreas of lean and obese mice. There were marked differences between the liver and the pancreas, in that the RIA Sm-C values for the former were twice those in the latter while, in contrast, the corresponding values for the Sm-C mRNA, i.e. the agent determining the synthesis of Sm-C, were about 100 times higher in the liver as compared to that in the pancreas. We interpret our results as follows: The D cells in the islets form and secrete Sm-C in both young and adult, lean and obese mice, while A and B cells bind, but do not necessarily synthesize this peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Polyamines induce precocious development in rats. Possible interaction with growth factors

The study reports the effects of daily subcutaneous injections of the biogenic polyamines putrescine, spermidine and spermine (10 mg/kg each) given for a short postnatal period, on growth and development of rats. Polyamine treatment, while only slightly enhancing normal body weight gain, prevented the weight loss caused by surgical injury of 5-day-old animals. The treatment resulted in earlier eyelid and ear opening and in earlier maturation of righting and gripping responses. Increased number of neurons in the superior cervical ganglion that is caused by polyamine treatment, could not be prevented by castration of newborn rats, thus excluding the testes as a site through which polyamines may exert their action. An apparent increase in immunohistochemically detectable nerve growth factor was evident in iris and submaxillary salivary gland of polyamine-treated animals, but no change in epidermal growth factor immunohistochemistry was detected in the salivary gland. We conclude: (1) treatment of newborn rats with polyamines can accelerate somatic and neurobehavioral development; (2) further studies are required in order to verify and quantitate the effects of polyamines on growth factors, and (3) the results imply that exogenous polyamines may exert their growth-promoting effects on a number of cell types when these cells experience periods of polyamine dependence.

Nerve growth factor can influence growth of cortex cerebri and hippocampus: evidence from intraocular grafts

The effects of nerve growth factor and antiserum against nerve growth factor on cortical cholinergic projection areas in the central nervous system and cerebellum were evaluated using intraocular grafts of cortex cerebri, hippocampus and cerebellum in rat hosts receiving injections into the anterior chamber of the eye of nerve growth factor (at transplantation, 5 and 10 days after transplantation) or antiserum to nerve growth factor (every 5 days). The controls received cytochrome c or preimmune serum. Growth of grafts was followed by repeated observations directly through the cornea of the host using a stereomicroscope. Nerve growth factor-treated grafts of cortex cerebri and hippocampus grew significantly smaller as compared to the corresponding control grafts. In one experiment, growth of cytochrome c and saline-treated cortex cerebri was compared and no difference in growth was found. Growth of nerve growth factor-treated cerebellar grafts did not differ significantly from growth of cytochrome c-treated grafts. Morphological analysis using Nissl-staining, antibodies to glial acidic fibrillary protein to evaluate the degree of gliosis and antiserum to neurofilament as a neuronal marker did not reveal any marked differences between nerve growth factor- and cytochrome c-treated grafts. Cortical grafts receiving anti-nerve growth factor antiserum by injection or by immunizing host rats against nerve growth factor showed similar growth to the controls. Similarly, grafts of fetal hippocampus to rats immunized with nerve growth factor were not significantly different from grafts to host rats immunized with cytochrome c. We conclude that exogenous nerve growth factor affects the development of grafted cortex cerebri and hippocampus. The fact that these cortical areas stop growing earlier in the presence of nerve growth factor without the grafts showing evidence of disturbed glial or neuronal populations compared to control grafts indicates that nerve growth factor acts to induce overall/premature differentiation and maturation. The mechanism for this whether or not it is receptor-mediated and which cells are primarily affected by nerve growth factor is not yet known.