Clear Sex Difference Research Articles

Sexual dimorphism in the relationship between number of emerged permanent teeth and percentage of adult stature.

The relationship between the number of emerged teeth and statural growth was investigated in a sample of 31 boys and 42 girls followed longitudinally from 6-12 years of age. The number of emerged permanent teeth was counted on the total number of plaster dental casts. Percentage of adult stature attained at a given age was calculated on the basis of predicted adult stature at 25 years of age using the BTT model. Percentage of permanent teeth emerged was based upon 28 teeth, the number of all permanent teeth except for the third molars. Girls attained a greater percentage of adult stature at each age, but there was no clear sex difference in the percentage of emerged teeth. However, when expressed on the basis of %adult stature, there was clear sex difference in %emerged teeth. The results suggest a sex difference in %emerged teeth that is specific to the %adult stature that has been attained. Am. J. Hum. Biol. 11:619-626, 1999. Copyright 1999 Wiley-Liss, Inc.

Bacterial Expression and Functional Characterization of a Rat Thyroid Hormone Sulfotransferase, ST1B1

At least three forms of phenol sulfotransferase (ST) ST1B1, ST1A1 and ST1C1 are contained in rat livers. To identify the form contributing to the metabolism of 3,3',5-triiodothyronine (T3), functional characterization of these forms was performed by expression in Escherichia coli. ST1B1 and ST1C1 were shown to be active on sulfation towards T3 with high affinity (Km: 44.4 and 25.8 [iM, respectively), whereas ST1A1 had low affinity. In Western blotting using antibodies raised against the individual ST, hepatic contents of each ST were quantitatively determined. ST1B1 showed no clear sex-difference, whereas the level of ST1C1 was higher in adult males than adult females. The content of ST1B1 was 1.4, 6.8 and 10 times higher than that of ST1C1 in adult males, adult females and both sexes of immature rats, respectively. The developmental pattern of ST1B1 was similar to that of ST1A1, but differed from that of ST1C1. These results indicate that ST1B1 and ST1C1 are involved in T3 metabolism in rats and ST1B1 is the constitutive form across sexes and ages.

Sex differences in oral asymmetries during wordrepetition

During speech production the right side of the mouth is opened to a larger degree in most people. This facial asymmetry is thought to be related to a left hemisphere dominance in language processing and⧹or motor programming. We investigated asymmetrical lip separations during discrete or serial word productions in right handed persons. The results revealed a right sided lip separation bias in both genders during discrete word production in which the words had to be uttered once. As soon as the words had to be produced continuously, however, a clear sex difference appeared with males having the usual right bias but females now showing no clear asymmetry, with a tendency for larger lip separations on the left side. These results suggest the existence of two separate neural systems from which one controls the discrete task and which is left hemisphere dominant in both genders. The other is probably involved in serial word productions and shows a sex difference with regard to its asymmetry pattern.

Oxidative DNA damage and cell proliferation in kidneys of male and female rats during 13-weeks exposure to potassium bromate (KBrO3).

It has been assumed that oxidative damage, including formation of 8-hydroxydeoxyguanosine (8-OHdG) adducts in kidney DNA due to potassium bromate (KBrO3), a renal carcinogen to both sexes of rats, is involved in its mechanisms of tumor induction. However, despite the presumed existence of a repair enzyme(s) for 8-OHdG, there have been no reports demonstrating the changes in adduct levels during medium- or long-term exposure. To elucidate the actual kinetics regarding this parameter during the early stages of KBrO3 carcinogenesis, we measured 8-OHdG levels in kidney DNA together with cell proliferation in renal tubules in both sexes of rats receiving KBrO3 at a dose of 500 ppm in the drinking water for 1, 2, 3, 4, and 13 weeks. Rapid elevation of 8-OHdG levels was noted in treated male rats which persisted until the end of the experiment. Increased cell proliferation in the proximal convoluted tubules was also observed throughout the experimental period, concomitant with alpha2mu-globulin accumulation. Increase in 8-OHdG levels in treated females first became apparent 3 weeks after the start of exposure, with cell proliferation only elevated at the 13-week time point. The present study, employing the same route and dose of KBrO3 known to cause tumors, strongly suggested the requirement of persistent increase of 8-OHdG for neoplastic conversion. Moreover, a clear sex difference in susceptibility to generation of oxidative stress in kidney DNA was found, in addition to alpha2mu-globulin-dependent variation in cell proliferation in the renal tubules.

Characteristics of young men with clustering risk factors for coronary heart disease: The cardiovascular risk in young finns study.

The majority of coronary heart disease (CHD) arises from a population with only moderately elevated risk factor levels. This study addressed the issue of whether clustering of moderately adverse levels of serum low density lipoprotein cholesterol (LDL-C), serum high density lipoprotein cholesterol (HDL-C), and diastolic blood pressure (DBP) was detectable in children and young adults. Significant clustering of these factors was observed in young men (ages 18-24 years) (Observed/Expected [O/E] ratio = 1.5, p = 0.014), whereas in young women or children no clustering greater than due to chance was found. In males, clustering tended to increase with age. Compared to young women, young men had a higher relative intake of dietary fat, and smoked and used alcohol more often. Compared to men without risk factors, the men at risk were significantly more obese, consumed more dietary fat, and smoked more often. The highest degree of clustering was seen in the highest quartile for the subscapular skinfold thickness (O/E ratio = 2.4). In conclusion, high LDL-C, low HDL-C, and high DBP cluster in young adult males. The clear sex difference observed in clustering may be one of the causes for the susceptibility of adult men to CHD. Am. J. Hum. Biol. 9:565-571, 1997. © 1997 Wiley-Liss, Inc.

Foraging behaviour of wild rats ( Rattus norvegicus) towards new foods and bait containers

Groups of wild rats ( Rattus norvegicus) were housed in large arenas and their foraging behaviour towards unfamiliar food, novel food and novel food containers was monitored using remote sensing equipment. Three main findings resulted from the study. There is a large individual variation in the responses to new foods and food containers placed in the home range. There is a clear sex difference in that, although males and females take approximately the same weight of food over a 24 h period, females forage in many short visits (mean = 28.4, SE = 1.3 per day) whilst males take fewer, longer feeding visits (mean = 15.3, SE = 1.9). The most important findings is that neophobia to new food containers is far stronger than neophobia to new foods. This effect is sufficient to create practical control problems when rodenticide bait is used within bait containers. A possible way to overcome this problem is discussed.

Chromosome sorting of primates: Isolation and identification of Y chromosome in green monkeys

Single laser flow cytometry was applied to the karyotype analysis of green monkeys. Clear sex difference in flow karyotype was recognized in this monkey, because Y chromosome could be identified as a single peak in the histogram of male specimens. We could isolate Y chromosome of this species by the use of a cell sorter, and demonstrate by polymerase chain reaction that the sorted-out chromosomes contained the Y chromosome specific nucleotide sequence (SRY). This chromosome sorting technique provides a powerful strategy for constructing the DNA library specific to Y chromosome in this species.

Regulation of the TRH-like peptide pyroglutamyl-glutamyl-prolineamide in the rat anterior pituitary gland

TRH-like peptides share the N- and C-terminal amino acids with TRH (pGlu-His-Pro-NH2) but differ in the middle amino acid residue. One of them, pGlu-Glu-Pro-NH2 (< EEP-NH2; EEP) is present in the rat pituitary gland, but its biological significance is unknown. We investigated the localization and regulation of this tripeptide in the rat pituitary gland. To distinguish between TRH and EEP two antisera were used for RIA: specificity of antiserum 4319 for the TRH-like peptides pGlu-Phe-Pro-NH2 and EEP was equal to or greater than that for TRH, whereas antiserum 8880 is TRH-specific. Our RIA data showed the presence of a TRH-like peptide in the anterior pituitary gland (AP) and of TRH in the posterior pituitary gland (PP). The TRH-like peptide in the AP was identified on anion-exchange chromatography and subsequent HPLC as EEP. Pathophysiological conditions such as altered thyroid and adrenal status and suckling did not affect pituitary gland levels of EEP. In general, however, there is a clear sex difference: levels of EEP are higher in male than in female rats. In both sexes gonadectomy leads to a substantial two- to threefold rise in EEP levels, abolishing the sex difference. Testosterone administration to gonadectomized male rats normalizes levels of EEP again. Disulfiram, an inhibitor of the enzyme peptidylglycine alpha-amidating monooxygenase, reduced levels of EEP in the AP by approximately 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Sex differences in the distribution of estrogen receptors in the septal area and hypothalamus of the domestic pig (Sus scrofa).

Recently in the pig hypothalamus a vasopressin- and oxytocin-containing nucleus was identified which, like the supraoptic nucleus, becomes sexually dimorphic after puberty. Following the increase in circulating steroids at puberty, the vasopressin- and oxytocin-containing nucleus becomes twice as large in both males and females. In adulthood, the vasopressin- and oxytocin-containing nucleus of females is approximately twice as large as that in males. Because these alterations are possibly due to an influence of gonadal steroids, i.e. estrogens, the vasopressin- and oxytocin-containing nucleus cells were tested for the presence of estrogen receptors. In addition to the area of the vasopressin- and oxytocin-containing nucleus, the present study documented the distribution of estrogen receptors in the septal area and other parts of the hypothalamus of intact post-pubertal male and female pigs, by utilizing immunocytochemical methodology. Intense nuclear estrogen receptor staining was found in a number of areas, i.e. the medial preoptic area, the oxytocin-containing dorsomedial extension of the supraoptic nucleus, a possible homologue of the sexually dimorphic nucleus of the preoptic area, the median preoptic nucleus, the medial and lateral part of the bed nucleus of the stria terminalis, the ventromedial hypothalamus and the arcuate nucleus. In the ventral part of the lateral septum, the septohypothalamic nucleus, the nucleus subfornicalis and the stigmoid nucleus estrogen receptor immunoreactivity was less intense. Dorsolaterally of the vasopressin- and oxytocin-containing nucleus, estrogen receptor positive cells were observed, but the vasopressin- and oxytocin-containing nucleus itself lacked such receptors. In the magnocellular supraoptic nucleus and paraventricular nucleus no nuclear estrogen receptor staining was found. However, a weak cytoplasmic staining was present in all cells. There was a clear sex difference in the estrogen receptor-immunoreactive cell number in a possible homologue of the sexually dimorphic nucleus of the preoptic area. Compared to male pigs, in female pigs the number of cells showing estrogen receptor immunoreactivity in this area, which is known to be sexually dimorphic in various species, was twice as high. In other areas, such as the medial part of the bed nucleus of the stria terminalis, the medial preoptic area, the arcuate and ventromedial hypothalamic nucleus, a similar sex difference was found. In addition estrogen receptor immunoreactivity was generally more intense in females. No sex differences were noted in the overall distribution of estrogen receptor cells in the areas studied.(ABSTRACT TRUNCATED AT 400 WORDS)

Estrogen, not testosterone, creates male predominance of a P4501-related cytochrome in adult guinea pig adrenals.

Guinea pig adrenal microsomes possess a distinctive cytochrome P450 that is immunochemically related to P4501 and correlates with microsomal capacity for xenobiotic metabolism. This 52K protein and the capacity for metabolizing compounds such as ethylmorphine are located in the zona reticularis, are suppressed by ACTH, and are predominant in adult males. The protein is undetectable and the enzyme activity is low in young prepubertal animals. In males, both increase with age. However, in females, the protein remains undetectable, and ethylmorphine demethylase activity remains low into adulthood. Despite this clear sex difference through puberty and into sexual maturity, we recently observed that in female retired breeders, both the 52K cytochrome P450 and the capacity for metabolism of ethylmorphine appear at levels equal to those in males of comparable age. As estrogen levels are low in female retired breeders, we decided to investigate whether estrogen plays a role in maintaining the low levels of this protein and of xenobiotic metabolism seen in younger females. In a series of gonadectomy and hormone replacement experiments, we demonstrated that estrogen suppressed the levels of both protein and enzyme activity in adult guinea pigs. Ovariectomy resulted in the appearance of the 52K cytochrome P450 and of ethylmorphine demethylase in female adrenal microsomes at levels comparable to those seen in adult males. Estrogen replacement suppressed the increase in both protein concentration and enzyme activity. In hemiovariectomized cycling females, compensatory hypertrophy of the remaining ovary occurred, and the characteristic low levels of the 52K P450 and enzyme activity were maintained. Furthermore, estrogen treatment of male guinea pigs suppressed levels of both the 52K P450 and ethylmorphine demethylase activity in male adrenals. These experiments demonstrate that estrogen plays a significant role in the regulation of this protein. Testosterone, on the other hand, was not required to maintain the higher levels of 52K P450 and correlated enzyme activity in adult males. The levels of both were the same in normal, castrated, and sham-operated males, treated with testosterone or vehicle alone or left untreated. In fact, castration of prepubertal males resulted in a rapid rise to adult male levels of both immunodetectable protein and enzyme activity, implying that some suppressive agent of testicular origin effects the gradual increase that normally occurs with age in males.(ABSTRACT TRUNCATED AT 400 WORDS)

Sulfation of carcinogenic aromatic hydroxylamines and hydroxamic acids by rat and human sulfotransferases: substrate specificity, developmental aspects and sex differences

Sulfation of the carcinogen N-hydroxy-2-acetylaminofluorene (N-OH-AAF) and structurally related hydroxamic acids by rat and human sulfotransferases was studied. There was a clear sex and age difference in the sulfation of N-OH-AAF and the other hydroxamic acids by rat liver cytosols: adult male rats had the highest sulfation activity. Experiments with purified aryl sulfotransferase IV (AST IV) indicated that the high expression of this enzyme in male rat liver may be responsible for these differences. No such sex or age difference was found for the sulfation of aromatic hydroxylamines. In cytosols of adult human livers, sulfation activity towards aromatic hydroxamic acids and hydroxylamines was clearly present, but activities were much lower than in rat liver cytosols. Sulfation activity towards these compounds was also found in fetal and neonatal liver and adrenals. These compounds probably are sulfated by several different sulfotransferases in humans

Development of vasoactive intestinal polypeptide neurons in the human suprachiasmatic nucleus in relation to birth and sex

The development of vasoactive intestinal polypeptide (VIP) neurons was determined in the human suprachiasmatic nucleus (SCN) of 43 subjects ranging from 27 weeks of gestation to 30 years of age using immunocytochemistry and morphometry. VIP neurons were first observed at 31 weeks of gestation in the ventrolateral part of the SCN. From 3 months postnatally onwards, VIP positive neurons were observed in some subjects in the centromedial part of the SCN. The centromedial type of VIP staining became a constant finding only at 19 years of age, at term the SCN was still, very immature. Only in a few subjects some VIP neurons stained in the ventrolateral SCN and their number and nuclear diameter was small. Postnatally the number of VIP neurons increased gradually until around 3 years of age adult values were reached. After the age of 10 a clear sex difference in the number of VIP neurons was found: males having on average twice as many VIP neurons in the SCN as females. The adult VIP cell numbers in- the SCN amounted only 35% of those found earlier for vasopressin. The present data do not support a particular role for VIP neurons in those rhythms that are already present in early development, e.g., of the temperature rhythm in prematures of around 30 weeks gestational age. Our observations in this and earlier papers as well as animal studies do suggest though a possible role for VIP neurons in the SCN in sexual dimorphic functions such as reproduction and sexual behavior.

Emergence of permanent teeth among the meiteis of Manipur, India.

To estimate the time and sequence of emergence of the first 28 permanent teeth in rural Meiteis of Manipur, 440 children 5-14 years of age were examined. Median tooth emergence times were earlier in females than males. The first molar was highly variable in its emergence time in both sexes. With the exception of premolars, mandibular teeth emerged earlier than maxillary teeth. Although no definite pattern was found in bilateral differences, left maxillary teeth and right mandibular teeth emerged slightly earlier in females and males, respectively. There was no clear sex difference in the sequence of permanent tooth emergence. The quiescent period between the first and second phases of tooth emergence was more apparent in the mandible than in the maxilla and occurred between the lateral incisor and first premolar in both jaws and sexes. The Meiteis displayed earlier emergence compared to other populations within India. The findings of this study support earlier reports that socioeconomic conditions do not significantly influence permanent tooth emergence; the chief controlling factor is most likely genetic. © 1994 Wiley-Liss, Inc.

Hepatic and lipoprotein lipases selectively assayed in postheparin plasma

Sensitive, reliable procedures are reported for the selective assay of lipoprotein lipase (LPL) and hepatic lipase (HL) in postheparin plasma samples. LPL is inhibited in the HL assay by inclusion of 0.76 mol/L sodium chloride in the substrate. In the LPL assay, specificity is attained by pretreating the sample with sodium dodecyl sulfate, which selectively denatures HL. This LPL method was validated by direct comparison with a procedure in which HL is inactivated by an antiserum to human HL. We used the described assays to quantify LPL and HL activity in 32 normal adults, demonstrating a clear sex difference for both enzymes. On average, the men displayed higher HL and lower LPL activities than did the women.

Annual changes in the binding of follicle-stimulating hormone to gonads and plasma gonadotropin concentrations in Indian weaver birds inhabiting the subtropical zone

In birds, annual changes in gonadal weight are much more pronounced in the male than in the female. To analyze the mechanism inducing such a sex difference in the gonadal responsiveness to natural environmental conditions, we measured annual changes in the binding of follicle-stimulating hormone (FSH) to the gonads and the plasma gonadotropin concentration in adult Indian weaver birds inhabiting the subtropical zone. The binding of FSH was highly specific for mammalian FSHs and located primarily in the gonad. The testicular weight and FSH binding showed marked changes during the annual breeding cycle. The testicular weight was maximal in the breeding phase (June, 1987) and minimal in the nonbreeding phase (December, 1987). FSH binding per unit testicular weight was-greatest in the nonbreeding phase, while the total FSH binding per two testes was maximal in the breeding phase and minimal in the regressive phase (October, 1987). In contrast, the changes in the ovarian weight and FSH binding to the ovary were less pronounced than those in the testis. Although FSH binding per unit ovarian weight showed a peak in the nonbreeding phase; there was no significant change in the total FSH binding per ovary during the year, indicating the presence of a clear sex difference in the total FSH binding. Scatchard plot analyses of the binding suggested that the dissociation constant (Kd) ranged from 0.35 to 1.53 nM regardless of sex and season and that the changes in FSH binding were due to changes in the number of binding sites. Plasma FSH and luteinizing hormone (LH) levels markedly changed during the year in both sexes. Both FSH and LH levels were maximal in the breeding phase and minimal in the nonbreeding phase regardless of sex, although. the rate of change in either hormone tended to be greater in the male than in the female.

Mortality in patients with dependence on prescription drugs

In 1974 we started a follow-up of patients with different psychoactive substance use disorders (PSUD) according to DSM-III; 2082 cases out of 2127 were analyzed; 1370 patients had taken legal drugs (i.e. prescription drugs and/or over-the-counter drugs); 444 patients suffered from abuse or dependence of legal drugs alone; 678 combined legal drugs and ethanol, and 248 cases combined legal and illegal drugs, often together with ethanol. A group of 712 alcoholics were included for comparison. Mean time under observation was 6.5 ± 5.4 years, and 269 patients died. Mortality and survival were calculated and compared with expected survival from the normal population of the former Federal Republic of Germany. Mortality in all subgroups of PSUD was increased, the standardized mortality ratio (SMR) for patients on legal drugs alone being 2.1. Patients with legal plus illegal drugs had a SMR as high as 20.7; those with legal drugs plus ethanol 3.4; and alcoholics 4.2. The increased mortality seemed to be constant over the years. Mortality decreased in patients with stable abstinence. There was no clear sex difference. Abuse had a better prognosis than dependence. An estimation of potential life lost by the different PSUDs was attempted. Patients on legal drugs died from suicides, malignancies or accidents (including intoxication). In alcoholics or patients on legal drugs plus ethanol malignoma, liver cirrhosis, accident and suicide were the most prominent causes of death.

The role of general practice in community mental health: A survey in four districts of Copenhagen

The study describes the activities and referrals of general practitioners (GPs) in relation to patients with mental health problems in the early stage of the establishment of community mental health centres in Copenhagen. During a 2-week period 30 GPs completed a data sheet for each face-to-face contact with patients with mental health problems. Totally, 313 such contacts were reported, involving 271 patients. The commonest problems were neuroses and personality disorders. A clear sex difference was found in diagnosis patterns. One-third of the contacts were initiated by patients with a physical problem - more among the elderly than among younger patients. The duration of the contacts was rather short, but almost half of the contacts included an appointment for a follow-up visit. In more than one-third of the contacts the patients were referred to other services. When asked about unmet needs, the GPs most often mentioned the need for referring to a psychologist, whereas a community mental health centre or...

Acute opiate withdrawal in rats undernourished during infancy: Impact of the undernutrition method

Acute morphine withdrawal was assessed in adult rats following early postnatal undernutrition produced by two different methods (Large Litter procedure—20 pups/litter and Modified Slob procedure—rats cross-fostered on days 2, 4, and 6 to nonlactating dams for 24-hour periods). Response rates were first stabilized on a FR16 operant schedule. A single dose of morphine (20 mg/kg) was then administered, followed 4 h later by a single injection of naloxone (2.5 mg/kg). Males reared in large litters showed little behavioral disruption after morphine, suggesting either insensitivity to the opiate or the rapid development of tolerance. After naloxone, Modified Slob males displayed milder withdrawal than those in the well-nourished control or large litter groups. Thus the method of undernutrition influenced morphine's action and expression of withdrawal. A clear sex difference was also evident, females appearing to be generally less sensitive to the opiate- and naloxone-induced withdrawal than males. Body temperature underwent a characteristic elevation following morphine and a depression following naloxone across all groups, but undernutrition did not affect these responses. Hence, behavior proved to be the more sensitive measure for revealing differences in opiate dependence and withdrawal following early life undernutrition, under the test conditions employed.

Pharmacokinetics of Salazosulfapyridine (Sulfasalazine, SASP). (I). Plasma kinetics and plasma metabolites in the rat after a single intravenous or oral administration.

Salazosulfapyridine (Sulfasalazine, SASP, 2-hydroxy-5-[[4-[(2-pyridinylamino) sulfonyl] phenyl] azo] benzoic acid) labelled with 14C in the carboxyl group and with 3H in chemically as well as metabolically stable positions in the benzenesulfonyl ring was administered either intravenously or orally to male and female rats in order to study the plasma pharmacokinetics of SASP and the plasma profiles of the metabolites. After intravenous administration SASP was eliminated rapidly from plasma with a half-life (t1/2) of 8min. The volume of distribution (Vdss) of SASP was 0.2l/kg and total clearance (CLtot) was 18ml/min × kg. After oral administration, SASP was present in plasma mainly during the first 4 hours. The time for maximal concentration (Tmax) varied for SASP between 1 ?? 3 hours, for 14C, corresponding to 5ASA metabolites, between 3 ?? 10 hours and for 3H, corresponding to sulfapyridine metabolites, between4 ?? 12 hours. The inter-individual variation was considerable. The bioavai lability of SASP was 9% and independent of the dose. The maximal concentration(Cmax) and area under the curve (AUC) increased proportionally with the dose. The absorption of SASP was not influenced by fasting overnight.There was a clear sex difference in the metabolism of SASP. The plasma concentration of sulfapyridine metabolites in female rats was twice that in male rats. No hydroxylated metabolites were found in female rat plasma, whereas in the male rats, the hydroxylated sulfapyridine metabolites were the major metabolites.

Gene expression for estrogen and progesterone receptor mRNAS in rat brain and possible relations to sexually dimorphic functions

A clear neuroendocrine sex difference lies in the ability of the female rat to produce an ovulatory surge of luteinizing hormone. Preoptic neurons, as they respond to estrogen and progesterone, have been proven to be involved in this mechanism, with an emphasis on the possible participation of neurons in the anteroventral periventricular nucleus and the suprachiasmatic portion of the preoptic area (POA). Further, prominent morphological sex differences have been reported in the rat medial POA. To examine expression of the estrogen receptor (ER) and the progesterone receptor (PR) messenger RNAs (mRNAs) in these critical preoptic neurons, we have used in situ hybrization with tritiated single-stranded DNA probes complimentary for ER and PR mRNA. ER mRNA containing cells were found in the periventricular, suprachiasmatic and medical preoptic cell groups, in a manner which agrees with steroid hormone autoradiography. In the female rat, preoptic neurons expressing PR mRNA were distributed very similarly to those for ER mRNA. Moreover, in the male rat brain, all subsets of preoptic neurons which express the PR gene in the female were also detected in the male. Thus, the distribution of PR expressing cells was very similar between females and males. We conclude that the insensivity to the male to progesterone, as regards the hormonal control of ovulation, cannot be due to a total failure of PR gene expression in a specific subset of POA neurons. Instead, male preoptic neurons must be less sensitive to neural or hormonal inducers in the physiological range or perhaps lack sufficient levels of a transcription factor linking progesterone responsive elements to the start sites of hormone-controlled genes.