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M Pierce

Publications and source records attributed to M Pierce.

At least 73 records · Page 4Linked to original sources
PubMed1995

Remodeling of mouse milk glycoconjugates by transgenic expression of a human glycosyltransferase.

The mammary gland is a unique biosynthetic tissue that produces a variety of species-specific glycoconjugates, but the factors regulating the production of specific glycoconjugates are not well understood. To explore the underlying regulation, a fusion gene containing a cDNA encoding the human alpha 1,2-fucosyltransferase (alpha 1,2FT), which generates the H-blood group antigen, flanked by the murine whey acidic protein promoter and a polyadenylation signal, was introduced into mice. Milk samples from transgenic animals contained soluble forms of the alpha 1,2FT, as revealed by Western blots of milk samples using an anti-alpha 1,2FT antiserum and by the demonstration of alpha 1,2FT enzyme activity. Milk from transgenic animals also contained large quantities of 2'-fucosyllactose (Fuc alpha 1-2Gal beta 1-4Glc) and modified glycoproteins containing the H-antigen, whereas milk from control animals lacked these glycoconjugates. Expression levels of 2'-fucosyllactose were high in most animals and represented 1/3 to nearly 1/2 of the total milk oligosaccharides. These results demonstrate that heterologous transgenic expression of a glycosyltransferase can result in the expression of both the transgene and its secondary gene products and that the structures of milk oligosaccharides can be remodeled depending on expression of the appropriate enzyme. Furthermore, these results suggest that the lactating mammary gland may be a unique biosynthetic reactor for the production of biologically active oligosaccharides and glycoconjugates.

ABO Blood-Group System↗
PubMed1995

Effects of 12-O-tetradecanoylphorbol-13-acetate on estrogen receptor activity in MCF-7 cells.

The effects of long term treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) on estrogen receptor (ER) expression in the human breast cancer cell line, MCF-7, were studied. This study demonstrates that treatment of cells with the phorbol ester blocked estrogen receptor activity. Treatment of cells with 100 nM TPA resulted in an 80% decrease in the level of ER protein and a parallel decrease in ER mRNA and binding capacity. Following removal of TPA from the medium, the level of ER protein and mRNA returned to control values; however, the receptor failed to bind estradiol. These cells also failed to induce progesterone receptor in response to estradiol. In addition, TPA treatment blocked transcription from an estrogen response element in transient transfection assays and inhibited ER binding to its response element in a DNA mobility shift assay. The estrogen receptor in treated cells was recognized by two monoclonal anti-ER antibodies and was not quantitatively different from ER in control cells. RNase protection analysis failed to detect any qualitative changes in the ER mRNA transcript. Mixing experiments suggest that TPA induces/activates a factor which interacts with the ER to block binding of estradiol. The effects of TPA on ER levels and binding capacity were concentration-dependent. Low concentrations of TPA inhibited estradiol binding without a decrease in the level of protein, whereas higher concentrations were required to decrease the level of ER protein. The effects of TPA appear to be mediated by activation of protein kinase C since the protein kinase C inhibitors, H-7 and bryostatin, block the effects of TPA on estradiol induction of progesterone receptor. TPA treatment had no effect on the level or binding capacity of the glucocorticoid receptor, indicating that the effects are not universal for steroid receptors. These data demonstrate that activation of the protein kinase C signal transduction pathway modulates the estrogen receptor pathway. The long term effect of protein kinase C activation is to inhibit estrogen receptor function through induction/activation of a factor which interacts with the receptor.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1995

Purification and characterization of human serum N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase.

Many lysosomal enzymes are recognized and selected by a unique marker in the form of mannose 6-phosphate groups which are present exclusively on their N-linked oligosaccharides. Two enzymes act sequentially to catalyze the addition of mannose 6-phosphate groups to the proteins: N-acetylglucosamine phosphotransferase (GlcNAc phosphotransferase) and N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase (phosphodiester alpha-GlcNAcase). We report here the purification and partial characterization of phosphodiester alpha-GlcNAcase from human serum. The enzyme was purified over 600,000-fold by utilizing ammonium sulfate precipitation, fractionation on wheat germ agglutinin-Sepharose, Fe(3+)-chelating Sepharose, and Cu(2+)-chelating Sepharose, and renaturation from gel slices after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The protein observed after renaturation and subsequent SDS-PAGE and silver staining had an apparent molecular mass of 118 kDa, which is slightly smaller than bovine liver phosphodiester alpha-GlcNAcase (Mullis et al. (1994) J. Biol. Chem. 269, 1718-1726). Serum enzyme activity does not require Triton X-100 and is not stimulated by its addition. These results suggest that the enzyme found in serum represents a form secreted after proteolysis in the Golgi of the membrane-bound enzyme. The serum enzyme hydrolyzed UDP-GlcNAc to UDP and GlcNAc and hydrolyzed GlcNAc-P-Man alpha Me into alpha MeMan-P and GlcNAc. The enzyme had no hydrolyzing activity toward UDP-GalNAc, UDP-Glc, [6-3H]GlcNAc beta 1-3Gal beta 1-4Glc, p-nitrophenyl-alpha-N- acetylglucosaminide, p-nitrophenyl-beta-N-acetylglucosaminide, p-nitrophenyl-alpha-N-galactopyranoside, or p-nitrophenyl-beta-N- galactopyranoside. The enzyme activity was strongly inhibited by UDP-GlcNAc and GlcNAc-1-phosphate, had a pH optimum between pH 6.0 and 7.0, and was inhibited by FeCl3, FeSO4, and CuSO4. The Km values for UDP-GlcNAc and GlcNAc-P-Man alpha Me were 0.94 and 0.45 mM, respectively. Over 77% of enzyme activity remained after incubation for 10 min at 70 degrees C, demonstrating an unusual thermostability of the serum enzyme.

Chromatography, High Pressure Liquid↗
PubMed1995

Glycosyltransferase assay system utilizing an acylated glycopeptide acceptor.

A glycosyltransferase assay system was devised utilizing as acceptor a purified glycopeptide which was acylated at its N-terminus using caprylic (C8) anhydride. The glycopeptide contained five amino acids and an N-linked biantennary oligosaccharide, and it was purified from a pronase digest of bovine fibrinogen. Desialylation and beta-galactosidase digestion conditions were developed to produce asialo- and asialo-agalacto glycopeptides. Using fatty acid anhydrides, N-acylation conditions for these glycopeptides were then optimized. The products formed when the appropriate acylated glycopeptide was incubated with either of two N-acetylglucosaminyltransferases and UDP-[3H]N-acetylglucosamine were easily separated from unused sugar nucleotide and breakdown products by exploiting the affinity of the radiolabeled acylated glycopeptide products for pellicular C18 cartridges. The products of the enzymatic reactions bound quantitatively to the cartridges and could be eluted in small amounts of methanol. The Km values for the unacylated and acylated glycopeptide acceptors were similar when measured using either N-acetylglucosaminyltransferase V or the N-acetylglycosaminyltransferase which transfers N-acetylglucosamine in beta(1,3) linkage to N-acetyllactosamine (or lactose). This assay system can be used to measure many glycosyltransferases and other enzymes which transfer to N-linked biantennary oligosaccharides and is applicable to additional glycosyltransferases that transfer to other oligosaccharides which can be prepared as glycopeptides.

Acylation↗
PubMed1995

Preparation of antisera to recombinant, soluble N-acetylglucosaminyltransferase V and its visualization in situ.

N-Acetylglucosaminyltransferase V (GlcNAc-T V) is a glycosyltransferase which transfers N-acetylglucosamine in beta(1,6) linkage to the alpha(1,6)-linked mannose residue of Asn-linked oligosaccharides. This enzyme is characterized by several unusual properties: GlcNAc-T V is the largest lumenal Golgi glycosyltransferase described thus far, and its multiple mRNA transcripts range from 4.5 to about 9.5 kb; GlcNAc-T V mRNA and activity are regulated by the src tyrosine kinase signalling pathway; in brain tissue, large levels of GlcNAc-T V mRNA are present, but only relatively low levels of catalytic activity can be detected; a lectin-resistant cell line, Lec4A, expresses active GlcNAc-T V which is mislocalized intracellularly. In addition, the cell surface oligosaccharide products of this enzyme have been hypothesized to regulate intercellular adhesion. In order to devise specific inhibitors of this enzyme it is necessary to understand its physical structure and how structural changes can influence its activity and localization. We have expressed milligram amounts of a soluble form of recombinant rat GlcNAc-T V, purified it from CHO cell-conditioned media, and used it to prepare specific antisera. This antisera binds selectively to GlcNAc-T V and has been used to visualize B-16 mouse melanoma cell GlcNAc-T V on immunoblots after SDS-PAGE. When the antisera was used in immunofluorescence microscopy experiments on permeabilized B-16 and baby hamster kidney cells, intense, specific staining was observed in intracellular structures which appear to correspond to the Golgi apparatus.

Animals↗
PubMed1995

GlcNAc-transferase V and core 2 GlcNAc-transferase expression in the developing mouse embryo.

UDP-GlcNAc:Manalpha1-6Manbeta-R beta1-6-N-acetylglucosaminyltransferase V (GlcNAc-TV) and UDP-GlcNAc:Galbeta1-3GalNAc-R beta1-6-N-acetylglucosaminyltransferase (core 2 GlcNAc-T) are Golgi enzymes that catalyse the biosynthesis of beta1-6GlcNAc-branched intermediates in the N- and O-linked biosynthesis pathways, respectively. The activities of these enzymes change during haematopoiesis, embryo-carcinoma cell differentiation and following malignant transformation, but little is known about their expression in normal adult tissues and during embryogenesis. We have examined the expression of GlcNAc-TV and core 2 GlcNAc-T in sections of post-implantation mouse embryos by in situ RNA hybridization. The two enzymes showed distinct temporal and spatial patterns of expression. Core 2 GlcNAc-T mRNA was widely expressed at embryonic day (E) 7, and became restricted to a subset of mucin- and cartilage-producing tissues at E11.5 through to E17.5. GlcNAc-TV transcripts were absent at E7, became expressed throughout E9.5 embryos, and then progressively restricted to regions of the developing central nervous system and to specialized epithelia of skin, intestine, kidney, endocrine tissues and respiratory tract. In the adult gonads, GlcNAc-TV transcripts were excluded from germ cells, but were detected in the follicular and testicular cells. Leukoagglutinin (L-PHA)-reactive oligosaccharides co-localized with GlcNAc-TV transcripts in skin, kidney and intestine, but brain showed unexpectedly low overall staining punctuated by bright staining of the vascular endothelium. A common feature of cells in basal epithelia and in the cortical neural epithelium is the capacity to migrate, a cellular function which may require GlcNAc-TV-dependent glycoconjugates.

Animals↗
PubMed1995

Angiomatoid features in fibrohistiocytic sarcomas. Immunohistochemical, ultrastructural, and clinical distinction from vascular neoplasms.

The typical example of malignant fibrous histiocytoma (MFH) or dermatofibrosarcoma protruberans (DFSP) does not require ancillary studies for diagnosis. However, hemorrhage with cystic change consisting of blood-filled spaces may closely mimic a vascular neoplasm. Eight fibrohistiocytic sarcomas exhibiting these angiomatoid features, initially mistaken for vascular neoplasms, were identified from personal consultation files and review of 157 consecutive sarcomas (1985 through 1993) at the University of California-(Davis) Medical Center. They included five MFH giant-cell-type sarcomas, two MFH angiomatoid-type sarcomas, and one DFSP. Immunohistochemical analysis of paraffin-embedded material showed vimentin diffuse positive, CD68 (KP-1) diffuse positive, and factor VIII negative in all eight sarcomas; actin HHF-45 focal positive in six, diffuse positive in one, and negative in one sarcoma; desmin focal positive in two and negative in six sarcomas; and S100 protein, cytokeratin AE1:AE3, cytokeratin 10.11, and EMA negative in all eight sarcomas. Electron microscopy of three tumors exhibited neoplastic cells with fibroblastic, myofibroblastic, and histiocytic features. Weibel-Palade bodies or neolumens diagnostic of vascular differentiation were absent. The clinical characteristics and behavior of these sarcomas reflect entities in the spectrum of fibrohistiocytic lineage (MFH subtypes and DFSP) rather than vascular neoplasms. Patients with deep, large, giant-cell-type MFHs did poorly (two of four patients died from disease at 8 and 25 months). Both patients with angiomatoid MFHs showed local recurrences from large incompletely excised head and neck lesions. One died of disease at 21 months and the other is free of disease 12 months following excision of a local metastasis to the opposite side of the neck. The patient with DFSP had an 18-cm locally recurrent scalp tumor that extended into bone. Immunohistochemical and ultrastructural confirmation of fibroblastic, myofibroblastic, and histiocytic lineage and exclusion of vascular differentiation help to establish the correct diagnosis in these fibrohistiocytic sarcomas with angiomatoid features. The clinicopathologic features of these eight cases reaffirm the practical utility of MFH and DFSP as diagnostic entities in the spectrum of fibrohistiocytic sarcomas.

Adult↗
PubMed1994

Modification of glycoproteins by N-acetylglucosaminyltransferase V is greatly influenced by accessibility of the enzyme to oligosaccharide acceptors.

The formation of tri- and tetraantennary complex-type N-linked oligosaccharides in animal glycoproteins is partly regulated by UDP-N-acetylglucosamine:beta-6-D-mannoside beta-1,6-N-acetylglucosaminyltransferase (EC 2.4.1.155) (GlcNAc-T V), which generates 2,6-branched mannose. In Chinese hamster ovary (CHO) cells we found that 2,6-branched mannosyl structures are preferentially contained on lysosome-associated membrane proteins (LAMPs) and are generally low or absent in other cellular glycoproteins (Do, K.-Y. and Cummings, R.D. (1993) J. Biol. Chem. 268, 22028-22035). To determine the mechanism by which GlcNAc-T V appears to preferentially recognize glycoproteins, we examined the activity of purified GlcNAc-T V toward a variety of glycoprotein acceptors. Because GlcNAc-T V requires as acceptors oligosaccharides lacking outer galactosyl and sialyl residues, we utilized two classes of acceptor preparations. The first class of acceptor was enzymatically desialylated (DS) and degalactosylated (DG) preparations of bovine fetuin, human transferrin, and human fibrinogen. The second class was glycoproteins in extracts of the mutant CHO cell line, Lec8 CHO, which cannot add galactose or sialic acid to N-linked oligosaccharides. GlcNAc-T V was highly active toward DSDG-fetuin, -transferrin, and -fibrinogen (Km values ranged between 30 and 74 microM), and the catalytic efficiencies (Vmax/Km) of the enzyme toward different acceptors were comparable. In the case of fetuin, each of its three sites for attachment of N-linked oligosaccharides were shown to be utilized equally well by GlcNAc-T V. Notably, the enzyme exhibited a 2-3-fold higher rate of transfer toward DSDG-transferrin when it was further denatured by reduction and S-carboxymethylation. When extracts of Lec8 CHO cells were used as acceptors, GlcNAc-T V preferentially transferred to LAMPs, and only low level transfer was observed to other cell-derived glycoproteins, thus demonstrating specificity of GlcNAc-T V toward native glycoprotein acceptors. When the cell-derived glycoproteins were denatured by reduction and S-carboxymethylation prior to use as acceptors for Glc-NAc-T V, significant transfer occurred to other glycoproteins. These results demonstrate that the mechanism of glycoprotein-specific branching by GlcNAc-T V is determined primarily by its accessibility to available bi/triantennary oligosaccharides on glycoproteins and not by its recognition of peptide determinants or conformation-specific determinants.

Animals↗
PubMed1994

Use of polypentapeptides of elastin to prevent postoperative adhesions: efficacy in a contaminated peritoneal model.

We investigated the use of a sheet of polypentapeptide of elastin as a physical barrier to adhesion formation in a contaminated peritoneal wound model. A total of 88 rats were studied with random assignment of animals to three study groups; control (29), polypentapeptide steam sterilized (30), and polypentapeptide gas sterilized (29). Animals were anesthetized and a laparotomy was conducted to reveal the cranial portion of the ileum. The abdominal wall muscle peritoneum was excoriated until hemorrhage was noted. In sham animals, there was no physical barrier placed between bowel loop and the abdominal wall. In two of the study groups, the polypentapeptide sheet was placed directly over the excoriated area. The intestinal loop was then loosely secured to excoriated area with 2-O nylon (stay suture) which was tied subcutaneously in all groups. Four puncture wounds were made with a 20-gauge hypodermic needle in the bowel that was apposed to the excoriated peritoneal musculature which allowed leakage of intestinal contents and contamination. On Day 7 postsurgery, the animals were anesthetized and the stay suture was removed. On Day 14, all animals were sacrificed and adhesions were graded. The incidence of significant adhesions was 28% for the barrier group versus 90% for control animals (P < 0.05). The results of this study indicate that the polypentapeptide of elastin sheet is an effective physical barrier in this surgically induced contaminated wound model.

Animals↗
PubMed1994

Localization of an alpha 1,2 galactosyltransferase activity to the Golgi apparatus of Schizosaccharomyces pombe.

We have cloned a gene encoding an alpha 1,2 galactosyltransferase activity from Schizosaccharomyces pombe. The open reading frame of the gene (gma12 for galactomannan, alpha 1,2), combined with the previous protein purification (Chappell and Warren, 1989), predicts an O-linked glycoprotein with type II transmembrane topology. By homologous gene disruption, we have demonstrated that the gma12 gene product (gma12p) is nonessential. The deletion strain (gma12-D10::ura4) has a significantly reduced level of galactosyltransferase activity relative to the parental strain, but both in situ lectin binding and in vitro biochemical assays demonstrate the presence of further galactosyltransferase activity in addition to gma12p. Although gma12p is not the only galactosyltransferase in S. pombe, it produces a unique carbohydrate structure on the surface of the yeast cells. We have generated a polyclonal antiserum against this carbohydrate epitope and shown that gma12p is capable of synthesizing the epitope both in vitro and in vivo. Electron microscopic localization of the gma12+ specific epitope in gma12+ cells revealed that gma12p synthesizes the carbohydrate structure in the Golgi apparatus, and subsequent intracellular transport distributes the epitope to later stages of the secretory pathway. The immunolocalization studies confirm the presence of one or more galactosyltransferase activities in the Golgi apparatus in fission yeast.

Amino Acid Sequence↗
PubMed1994

Expression of N-acetylglucosaminyltransferase V mRNA in mammalian tissues and cell lines.

The expression of N-acetylglucosaminyltransferase V (Glc-NAc-T V) is increased in many oncogenically transformed cells and in cell lines which are induced to proliferate. In order to characterize the regulation of GlcNAc-T V at the molecular level, we have examined the expression of Glc-NAc-T V mRNAs in a number of mouse tissues and in several human and rodent cell lines. The GlcNAc-T V mRNA is expressed in different amounts in the various mouse tissues, with the greatest amount observed in brain, followed by thymus, kidney, lung, intestine, heart and stomach, and no transcripts detected in liver or skeletal muscle. Measurements of GlcNAc-T V enzymatic activity, by contrast, show brain to have lower levels of activity than several of the other tissues, suggesting possible post-translational regulation. We find that there are two GlcNAc-T V transcripts in most of the RNAs analysed. The rodent cell lines all express both a 7.5 and a 9.5 kb mRNA, with the smaller transcript being more abundant. The human cells have mRNAs of 4.5 and 9.5 kb. Both mRNAs are expressed in HepG2 and MCF-7 cells, while A431 cells express only the 4.5 kb mRNA and HL60 cells express only the 9.5 kb transcript. Furthermore, only the 9.5 kb mRNA appears to be increased, along with activity, when HepG2 cells are stimulated to proliferate, suggesting that the two mRNAs may be under different regulatory controls. Also, a GlcNAc-T V-deficient, mutant lymphoma cell line, PHAR2.1, was found to express mRNAs which are larger than the normal mRNAs, possible due to an insertion or aberrant splicing, resulting in a defective mRNA.

Animals↗
PubMed1993

Isolation, characterization, and expression of a cDNA encoding N-acetylglucosaminyltransferase V.

A cDNA clone for the complete coding sequence for alpha-1,3(6)-mannosylglycoprotein beta-1,6-N-acetylglucosaminyltransferase V (GlcNAc-T V, EC 2.4.1.155) was isolated and expressed in COS-7 cells. Degenerate oligonucleotide primers for polymerase chain reaction were synthesized based on the amino acid sequence of three tryptic peptides isolated from affinity-purified GlcNAc-T V. Polymerase chain reaction amplimers were isolated from rat and mouse mRNA. A cDNA-encoding full-length enzyme was isolated from a rat 1 cell (EJ-ras-transformed) library and sequenced. Transient expression of this clone in COS-7 cells, followed by enzymatic activity assays, demonstrated that this cDNA sequence encodes GlcNAc-T V. Northern analysis of rat kidney mRNA revealed a single band corresponding to a length of about 7 kilobases. Sequence analysis of the cDNA clone demonstrated an open reading frame that encoded a type II membrane protein of 740 amino acids.

Amino Acid Sequence↗
PubMed1992

Novel glycosylation-defective baby hamster kidney cells.

The plant lectin wheat germ agglutinin (WGA) has previously been used to select more than ten different glycosylation-defective phenotypes in a variety of mammalian somatic cells. Three WGA-resistant phenotypes have now been obtained spontaneously from baby hamster kidney (BHK) cells. These mutant BHK cells exhibit a pattern of cross resistance and sensitivity to multiple plant lectins, suggesting that the cell surface carbohydrates of these cells are altered. Two WGA-resistant BHK phenotypes appear similar to WGA-resistant CHO cells that lack terminal sialic acid and galactose residues on their cell surface carbohydrates. The third WGA-resistant BHK cell phenotype has not previously been seen in WGA-resistant mammalian cells.

Animals↗
PubMed1992

Purification and characterization of rat kidney UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,6-N-acetylglucosaminyltransferase.

In order to investigate the molecular mechanism of the specific increase of UDP-N-acetylglucosamine:alpha-6-D-mannoside beta-1,6-N-acetylglucosaminyltransferase (GlcNAcT-V, EC 2.4.1.155) activity after viral or oncogenic transformation, we have purified the enzyme from a Triton X-100 extract of rat kidney acetone powder. GlcNAcT-V was purified by sequential affinity chromatography using first UDP-hexanolamine-agarose and then a synthetic oligosaccharide inhibitor-agarose column. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme revealed two major bands at apparent molecular masses of 69 and 75 kDa. The enzyme was recovered in a 26% final yield with a 450,000-fold increase in specific activity to a Vmax of 18.8 mumols/(mg.min). Enzyme activity was stabilized and enhanced by the addition of 20% glycerol, 0.5 mg/ml IgG, and 0.2 M NaCl. The optimal ranges of pH and Triton X-100 concentrations for enzyme activity were 6.5-7.0 and 1.0-1.5%, respectively. The divalent cations, Mn2+, Ca2+, and Mg2+, were each found to have a negligible (less than 10%) effect on activity; moreover, the enzyme was fully active in the presence of 20 mM EDTA. The Km value of the purified enzyme toward a synthetic trisaccharide acceptor was 90 microM, and the Ki value toward a synthetic active site inhibitor was 140 microM.

Animals↗
PubMed1992

Maturation of the hypothalamo-pituitary-gonadal axis of male Syrian hamsters.

Light-microscope immunocytochemistry (ICC) was used to investigate postnatal changes in the morphology of LHRH neurons in the brains of male Syrian hamsters and to relate these changes to more overt maturational developments within the hypothalamo-pituitary-gonadal axis. The animals were maintained under long-day photoperiods (14L:10D), and groups of 6-7 were killed at 10-day intervals from Day 15 to Day 65. Their brains were fixed with 4% paraformaldehyde, sectioned sagittally with a vibratome (75 microns), and processed for ICC using monoclonal LHRH antibody HU4H. Throughout the study period, the hamsters showed a progressive increase in plasma gonadotropin levels, closely followed by an increase in testicular weight and plasma testosterone levels. Histology of the testes revealed that spermatogenesis was already qualitatively completed by Day 35 and quantitative aspects were established by Day 45. Within the brain, LHRH neuronal perikarya were distributed primarily in the medial septal-preoptic area and the diagonal band of Broca; morphologically, these immunopositive neurons were either monopolar or bipolar. The total number of LHRH neurons detected in the areas examined was approximately 440 throughout the developmental period, and the relative proportions of monopolar and bipolar subtypes (86% and 14%, respectively) remained unchanged. In contrast, the area of the perikarya, as determined by autoimage analysis, showed a highly significant age-related increase, both for the monopolar and bipolar neurons. It is suggested that these developmental changes in the LHRH neurons reflect an increase in LHRH synthesis and may, therefore, provide a neuroendocrine trigger for the onset of puberty.

Animals↗