Biomedical subjects

D Walmer

Publications and source records attributed to D Walmer.

5 recordsLinked to original sources

PubMed1996

Potentiation of diethylstilbestrol-induced alterations in the female mouse reproductive tract by transforming growth factor-alpha transgene expression.

Neonatal estrogen exposure causes numerous abnormalities in the female reproductive tract, including carcinogenesis. One mechanism by which neonatal estrogen elicits teratogenic and carcinogenic effects is epigenetic and involves the modulation of a number of estrogen-regulated genes including epidermal growth factor (EGF). Because of the evidence that there is an integral relationship between the EGF family, estrogen action, and the regulation of the growth and differentiation of the reproductive tract, we used transforming growth factor-alpha (TGF alpha) transgenic mice to investigate the interaction of constitutive TGF alpha expression with the potent estrogen diethylstilbestrol (DES) in the induction of reproductive-tract alterations. Our study was designed to determine whether TGF alpha expression could modulate DES-induced carcinogenesis of the female mouse reproductive tract. The animals were homozygous TGF alpha transgenic female mice from the MT42 line and the parental CD-1 outbred mice. The presence of the TGF alpha transgene significantly increased the incidence of DES-induced vaginal adenosis, uterine endometrial hyperplasia, uterine polyps, hypospadia, benign ovarian cysts, and pituitary adenomas. However, constitutive TGF alpha expression did not promote reproductive-tract neoplasia. This study demonstrates that TGF alpha participates in the regulation of developmental and morphogenic events in the Müllerian duct and urogenital sinus, suggesting a role for TGF alpha in the pathogenesis of reproductive-tract diseases. Furthermore, we showed that although constitutive expression of the TGF alpha transgene did have an effect on the reproductive tract, TGF alpha overexpression alone could not substitute for DES as a reproductive-tract carcinogen or as a promoter of uterine neoplasia, indicating that DES-induced carcinogenesis requires events in addition to the overexpression of this single peptide growth factor.

Animals↗

PubMed1995

The effect of neonatal exposure to diethylstilbestrol, coumestrol, and beta-sitosterol on pituitary responsiveness and sexually dimorphic nucleus volume in the castrated adult rat.

The neonatal hormone environment influences the sexually differentiated patterns of development. Estrogens, derived from intracerebral aromatization, promote male pattern development of the central nervous system. The purpose of this study was to determine the effects of neonatal exposure to environmental estrogens on luteinizing hormone (LH) secretion and development of the sexually dimorphic nucleus of the medial preoptic area (SDN-POA) in castrated adult rats. Neonatal rats of both sexes received injections of either corn oil, 0.1 microgram diethylstilbestrol (DES), 3 micrograms beta-sitosterol (B1), 30 micrograms beta-sitosterol (B2), 0.1 microgram coumestrol (C1), 1 microgram coumestrol (C2), or 10 micrograms coumestrol (C3) on Day 1-10 of life and were castrated on Day 21. Right heart catheters were placed on Day 42, and GnRH (50 ng/kg) was administered. Blood was sampled for LH at 0-, 5-, 10-, 15-, and 30-min intervals. All doses of beta-sitosterol and coumestrol elicited increased basal levels of LH in females. In males, B1, B2, C2, and C3 increased basal levels of LH. The GnRH-induced LH increase was prevented in females treated with diethylstilbestrol and 10 micrograms of coumestrol. Males in all treatment groups exhibited GnRH-induced LH surges. The animals were sacrificed by decapitation on Day 49. Volumes of the SDN-POA of the groups were compared. Treatment with the agents did not result in significantly increased SDN volume in females; nor was there a difference in SDN size among the male groups. These data show that exposure to environmental estrogens early in development alters both postpubertal pituitary response to GnRH and basal LH secretion in females and alters only basal LH secretion in males. No significant enlargement (i.e., masculinization) of the SDN-POA was exhibited.

Animals↗

PubMed1994

Transforming growth factors beta 1, beta 2, and beta 3 messenger RNA and protein expression in mouse uterus and vagina during estrogen-induced growth: a comparison to other estrogen-regulated genes.

Increasing evidence suggests that the differential regulation of multiple peptide growth factors by steroid hormones contributes significantly to the pleiotropic effects elicited in target tissues. We report here an evaluation of the effects of the potent estrogen, diethylstilbestrol, on the expression of the three mammalian transforming growth factor beta (TGF beta) isoforms, TGF beta 1, TGF beta 2, and TGF beta 3, in both the uterus and the vagina of the prepubescent mouse. Immunohistochemical protein detection, in situ hybridization, and Northern RNA analyses demonstrate overlapping but distinct time-dependent and site-specific induction of all three TGF beta genes in the reproductive tract in response to estrogen. Temporal analysis of steady-state levels of the TGF beta mRNAs in the uterus by Northern blotting clearly demonstrates that diethylstilbestrol significantly but transiently up-regulates TGF beta 3 mRNA within 30 min and TGF beta 1 and TGF beta 2 mRNAs by 3 h with decreases to/or below control levels by 6 h. The vagina also responds to diethylstilbestrol with similar kinetics of induction for TGF beta 2 and TGF beta 3 mRNAs as that observed in the uterus; however, TGF beta 1 mRNA levels increase gradually and peak around 16 h after treatment. Investigation of the steroid specificity demonstrates predominant estrogen specificity in the control of TGF beta expression in the immature mouse reproductive tract. In situ hybridization localizes the mRNAs for all three TGF beta isoforms, primarily to the uterine and vaginal epithelium. Unlike the transient nature of TGF beta mRNA induction elicited by estrogen, immunohistochemistry demonstrates that estrogen treatment results in a more prolonged elevation of the proteins for TGF beta 1, TGF beta 2, and TGF beta 3 in the epithelium of both tissues. Investigation of specific binding of 125I-TGF beta 1 by affinity labeling reveals the existence of the receptor/binding proteins (types I, II, and III) in the uterus. Estrogen treatment significantly reduces binding to each of these components in the uterus, which suggests that estrogen may modulate TGF beta responsiveness at the receptor level. A comparison of TGF beta mRNA expression to the induction of other estrogen-regulated genes, TGF alpha, insulin-like growth factor-1, c-myc, progesterone receptor and lactotransferrin reveals that, in general, the TGF beta transcript levels are regulated in a more transient manner by estrogen.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Differential molecular mechanism of the estrogen action that regulates lactoferrin gene in human and mouse.

The 5'-flanking region of the human lactoferrin gene was isolated from a human placental genomic library. This genomic clone contains a 16-kilobase pair (kbp) insert and produces seven fragments when digested with the SacI restriction enzyme. We sequenced one of the fragments that comprises 1294 bp of the 5'-flanking sequence, 79 bp of the first exon, and 690 bp of the first intron. A major transcription start site was mapped by primer extension. The region immediately upstream from the transcription initiation site following the first exon is abundant in G and C nucleotides. In the promoter and 5'-flanking region within a 300-bp stretch (-465 to -165) of the DNA, we found a noncanonical TATA box (ATAAA), CAAT-like sequence (CAAC) and sequences homologous to the consensus SP1 binding site, Pu.1/Sp.1 binding element (PU box), two half-palindromic estrogen response elements (EREs; GGTCA), an imperfect ERE (GGTCAAGGCGATC), and a sequence resembling the chicken ovalbumin upstream promoter transcription factor (COUP-TF) binding site (GTCTCACAGGTCA). The COUP-TF binding site and the imperfect ERE shared five nucleotides (GGTCA). With the exception of the two half-palindromic EREs, the elements with very well matched sequences were also found in the corresponding positions in the mouse lactoferrin gene. The synthetic oligonucleotide, including the 26 bp of COUP/ERE sequence, was cloned before the SV40 promoter in a chloramphenicol acetyltransferase reporter construct. These chimeric plasmids were transiently transfected into human endometrium carcinoma RL95-2 cells to assess hormone responsiveness. We found that the COUP/ERE element acted as an enhancer in response to estrogen stimulation. In vitro DNase I footprinting analysis showed binding of the estrogen receptor on the imperfect ERE. In contrast to the mouse lactoferrin COUP/ERE element, COUP-TF does not interact with this element, as demonstrated by band shift assay and site-directed mutagenesis. Therefore, the molecular mechanisms of the estrogen action that govern the lactoferrin gene expression differ between mouse and human.

Amino Acid Sequence↗

PubMed1988

Enterococci in post-cesarean endometritis.

Three hundred eleven patients with post-cesarean endometritis were treated with clindamycin and gentamicin. Isolation of enterococci in the endometrium was associated with use of cephalosporin prophylaxis (P less than .001). Other risk factors for enterococcus-associated endometritis included increased numbers of vaginal examinations (P = .018) and increased length of internal monitoring (P = .006). Patients with enterococcus-associated endometritis were less likely to respond to therapy with clindamycin and gentamicin than were patients without enterococci (82.4 versus 92.7%, respectively; P = .015). Patients with enterococcus-associated endometritis also were significantly more likely to have wound infection (15.7 versus 3.2%, respectively; P = .001). In a retrospective survey of 14 patients with postpartum enterococcal bacteremias, four (29%) had a poor response to initial therapy.

Cesarean Section↗