PubMed Health⌕ Search

Biomedical subjects

M I Romero

Publications and source records attributed to M I Romero.

At least 19 recordsLinked to original sources
PubMed2003

Growth hormone-releasing hormone-producing and dopaminergic neurones in the mouse arcuate nucleus are independently regulated populations.

Differentiation of hypophysiotropic neurones that regulate the secretion of growth hormone (GH) and prolactin is influenced by GH and prolactin. Genetic GH and prolactin deficiency in mutant rodent models such as the Ames dwarf (df/df) mouse results in an increase in the number of GH-stimulatory GH-releasing hormone (GHRH) neurones and a reduction of prolactin-inhibitory tuberoinfundibular dopaminergic (TIDA) neurones in the arcuate nucleus during postnatal development. The present study tested the hypothesis that these concomitant changes in numbers of tyrosine hydroxylase (TH)- and GHRH-immunoreactive neurones in df/df hypothalamus might represent a neuronal population of fixed number that undergoes a partial change in phenotype during postnatal development. To evaluate this possibility, the postnatal reduction of the df/df TIDA population was prevented by administering prolactin neonatally to preserve TH phenotype; dwarf and normal sibling mice were treated with daily injections of ovine prolactin or vehicle starting at postnatal day 12 and continuing for 30 days. Following this treatment, numbers of arcuate neurones containing GHRH or TH, or both, were quantified using immunocytochemistry. It was hypothesized that prolactin preservation of TH-immunoreactive cell number would be accompanied by either a decrease in the GHRH-producing population or an increase in numbers of cells producing both TH and GHRH. In prolactin-treated normal (DF/df) mice, numbers of arcuate TH-immunoreactive neurones were similar to those in vehicle-treated normals. Numbers of TH-positive neurones in prolactin-treated dwarfs were higher than in vehicle-treated dwarfs, and did not differ from numbers in DF/df. Numbers of GHRH-immunoreactive cells in vehicle-treated df/df were higher than in vehicle-treated DF/df, and were not different in prolactin-treated groups of either dwarf or normal mice. Neurones containing both TH and GHRH constituted 15% of the TH population, and 76% of the GHRH population, in control normal mice; in control dwarfs, double-labelled cells were 9.3% of TH and 9.9% of GHRH. Numbers of cells immunoreactive for both TH and GHRH were not affected by prolactin treatment in either mouse type. These results demonstrate that the increase in number of GHRH-expressing neurones in the df/df arcuate nucleus does not occur at the expense of the TH phenotype, and that this increase is not influenced by prolactin feedback. Although coexpression of TH and GHRH in a subpopulation indicates that TIDA and GHRH populations are not exclusive, they appear to be influenced independently by prolactin and GH signals during development.

Animals↗
PubMed2002

French adolescent attitudes towards informal care for physical and emotional or relational problems.

UNLABELLED: The objective of this study was to determine adolescents' attitudes concerning the use of self-care and traditional medicines. A self-administered anonymous questionnaire with open-ended questions was completed by 543 adolescents aged 15-19 y. The results showed that the most frequent self-care activity for general health problems, in more than three-quarters of them, was self-medication; 14% of them resorted to minor home treatment such as taking care of wounds, bandaging or massages. Instructions for use were mentioned by 69% of adolescents as a way of choosing self-prescribed drugs. Natural medicines were used by 32% of the girls and 23% of the boys, mainly herbal teas or plant-based medicines, followed by homoeopathy. Self-care for emotional and relational problems mainly involved thinking about the problem and questioning themselves about their own behaviour or about the way they are. They also mentioned activities such as sports, going out, listening to music, watching television, and trying to think about something else by keeping themselves occupied. Natural medicines were used by 19% of the girls and 13% of the boys. Plant-based medicines or herbal teas were used most often, followed by drugs or alcohol, with homoeopathy in third place. CONCLUSION: Self-care and alternative medicines were used by adolescents in this study for physical as well as for emotional or relational problems. Their use did not reflect dissatisfaction with physicians and hospital treatment or an objection to formal services, but rather was a choice of these approaches for their own specific characteristics. They were also viewed as being less harmful than conventional treatment.

Adolescent↗
PubMed2002

[Attitudes regarding the delivery of formal and informal care: comparison of French and Chilean adolescents].

The representations that youth have of health professionals and young people's demands in terms of the operation and administration of services create an original and complex problematic. Clearly, this originality implies the important differences from one culture to another. For this very reason, it seemed that a comparative study relating the representations and attitudes confronted when care is sought by young people from countries with different cultural contexts would assist in comprehending why adolescents have such particular ways of using--or not using--formal and self-administered health services. An original open-ended response questionnaire was jointly designed and validated by a French and Chilean team. A mutually agreed upon sample of 957 school children, adolescents aged from 14 to 19, participated in the study in France and in Chili. The following correlations were found. In the event of a sleeping problem (or other general worry that is physically manifested), the mother is the privileged confidant, and in the specific case of a relationship or emotional problem, it is usually one of the adolescents' friends. The general practitioner is the favoured professional person in the event of a purely physical problem. When confronted with an emotional problem, one-third of adolescents say that they would not consider going to a consultation. The expectations of the French toward health professionals are more often within the "emotional" arena than those of the Chileans which generally concern the "medical/technical" field. The practice of self-administered care is qualitatively similar but the French prefer taking medication whereas the Chileans prefer the "little home remedies". The use of natural medicine is more widespread among young Chileans, but the types of medicine used are similar, namely herbal teas and other plant-based remedies and homeopathy. These results have a variety of implications, especially in terms of the need for training health professionals in the consideration of emotional and relationship problems. It is desirable that the official health care sector considers the care delivered outside of it as being complementary resources, which respond to the adolescents' need for autonomy, and then integrate those contributions into its own area of financial responsibility.

Adolescent↗
PubMed2001

Functional regeneration of chronically injured sensory afferents into adult spinal cord after neurotrophin gene therapy.

Lesioned axons within the dorsal roots fail to regenerate through the peripheral nerve transition zone and into the spinal cord. This regenerative failure leads to a persistent loss of sensory function. To induce axonal growth across this barrier, we used recombinant adenovirus to express fibroblast growth factor-2 (FGF2), nerve growth factor (NGF), L1 cell adhesion molecule (L1), or beta-galactosidase (LacZ) within the endogenous glia of the dorsal spinal cord 16 d after injury. Expression of either FGF2 or NGF, but not L1 or LacZ, induced robust axonal regeneration into normal as well as ectopic locations within the dorsal spinal cord. This regeneration led to near-normal recovery of thermal sensory function. Functional recovery and the majority of regenerating axons within the dorsal horn disappeared with recutting of the sensory roots. Injections of adenovirus encoding NGF, but not FGF2, also resulted in extensive sprouting of noninjured sensory axons, which we previously demonstrated could cause hyperalgesia and chronic pain. Thus, neurotrophic factor gene therapy administered as late as 16 d after injury may serve as a useful treatment to elicit recovery after dorsal root avulsion; however, the choice of neurotrophin is important to induce selective regeneration of damaged axons.

Adenoviridae↗
PubMed2001

Ablation of NF1 function in neurons induces abnormal development of cerebral cortex and reactive gliosis in the brain.

Neurofibromatosis type 1 (NF1) is a prevalent genetic disorder that affects growth properties of neural-crest-derived cell populations. In addition, approximately one-half of NF1 patients exhibit learning disabilities. To characterize NF1 function both in vitro and in vivo, we circumvent the embryonic lethality of NF1 null mouse embryos by generating a conditional mutation in the NF1 gene using Cre/loxP technology. Introduction of a Synapsin I promoter driven Cre transgenic mouse strain into the conditional NF1 background has ablated NF1 function in most differentiated neuronal populations. These mice have abnormal development of the cerebral cortex, which suggests that NF1 has an indispensable role in this aspect of CNS development. Furthermore, although they are tumor free, these mice display extensive astrogliosis in the absence of conspicuous neurodegeneration or microgliosis. These results indicate that NF1-deficient neurons are capable of inducing reactive astrogliosis via a non-cell autonomous mechanism.

Alleles↗
PubMed2001

Forward signaling mediated by ephrin-B3 prevents contralateral corticospinal axons from recrossing the spinal cord midline.

To investigate Eph-ephrin bidirectional signaling, a series of mutations were generated in the ephrin-B3 locus. The absence of both forward and reverse signaling resulted in mice with mirror movements as typified by a hopping locomotion. The corticospinal tract was defective as axons failed to respect the midline boundary of the spinal cord and bilaterally innervated both contralateral and ipsilateral motor neuron populations. A second mutation that expresses a truncated ephrin-B3 protein lacking its cytoplasmic domain did not lead to hopping, indicating that reverse signaling is not required for corticospinal innervation. Ephrin-B3 is concentrated at the spinal cord midline, while one of its receptors, EphA4, is expressed in postnatal corticospinal neurons as their fibers pathfind down the contralateral spinal cord. Our data indicate ephrin-B3 functions as a midline-anchored repellent to stimulate forward signaling in EphA4-expressing axons.

Alleles↗
PubMed2000

Extensive sprouting of sensory afferents and hyperalgesia induced by conditional expression of nerve growth factor in the adult spinal cord.

Genetic transfer of growth-promoting molecules was proposed as a potential strategy to modify the nonpermissive nature of the adult CNS to induce axonal regeneration. To evaluate whether overexpression of neurotrophins or cellular adhesion molecules would effect axonal plasticity, adenoviruses encoding fibroblast growth factor-2 (FGF-2/Adts), nerve growth factor (NGF/Adts), neurotrophin-3, and the cell adhesion molecules N-cadherin and L1 were injected into the dorsal horn of the adult spinal cord. Transgene expression was primarily localized to astrocytes in the dorsal horn and motor neurons within the ventral horn. Overexpression of these factors, with the exception of NGF/Adts, failed to increase axonal sprouting. Eight days after NGF/Adts injections, axonal sprouting within the dorsal horn was apparent, and after 4 weeks, extensive spouting was observed throughout the entire dorsal horn, extending into the ventral horn and the white matter of the lateral funiculus. These axons were identified primarily as a subpopulation of nociceptive fibers expressing calcitonin gene-related peptide and substance-P. Behavioral analysis revealed thermal hyperalgesia and perturbation of accurate paw placement on grid-walking tasks for both FGF-2- and NGF-treated animals. These results indicate that the administration of growth-promoting molecules can induce robust axonal plasticity of normal adult primary sensory neurons into areas of transgene expression, causing significant alterations in behavioral responses. This observation also indicates that gene transfer protocols that aim to reconstruct diseased or injured pathways should also be designed to prevent the sprouting of the normal circuitry from adjacent unaffected neurons.

3T3 Cells↗
PubMed2000

[Use of formal and informal health services by adolescents: cross-cultural study technics].

A cross-cultural study, in Chile and in France, has been held in order to compare care utilisation strategies used by teenagers and youths in two different contexts: self-administered cares, family cares, official or non-official professional cares. It has been decided to use a questionnaire with open-answers for collecting data on views and practices. Tool building and validation process, realised with both French and Chilean teams, has enabled to work with an original questionnaire, with good reproducibility of answers and very good acceptability. This tool can be used in other cultural contexts.

Adolescent↗
PubMed1999

Visualization of axonally transported horseradish peroxidase using enhanced immunocytochemical detection: a direct comparison with the tetramethylbenzidine method.

Visualization of the neuronal tract tracer horseradish peroxidase (HRP) is commonly achieved through the histochemical detection of its enzymatic activity using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogen. However, the TMB product is unstable and is incompatible with tissue processing methods that render the enzyme inactive, or when a combination of HRP tract tracing with neuronal phenotype identification is required. In this study we evaluated the applicability of the immunocytochemical detection method for horseradish peroxidase (HRP) visualization using an enhanced detection meth-od based on the Elite ABC peroxidase amplification protocol. The results provide evidence for the immunocytochemical visualization of both anterograde and transganglionic HRP transport in the rat spinal cord. This immunocytochemical method not only showed similar sensitivity to the TMB protocol in detecting HRP-labeled motor neuron perikarya but provided enhanced resolution in the identification of individual neuronal fibers compared to the TMB method. Immunodetection of the HRP tracer also allowed its co-localization with specific neuronal markers using double immunofluorescence techniques. These results offer the first demonstration that sensitive identification of axonally transported HRP can be achieved by immunocytochemistry and provides further support for its use in HRP tract tracing studies.

Animals↗
PubMed1998

Adenoviral gene transfer into the normal and injured spinal cord: enhanced transgene stability by combined administration of temperature-sensitive virus and transient immune blockade.

This study characterized gene transfer into both normal and injured adult rat dorsal spinal cord using first (E1-/E3-) or second (E1-/E2A125/E3-, temperature-sensitive; ts) generation of replication-defective adenoviral (Ad) vectors. A novel immunosuppressive regimen aimed at blocking CD4/CD45 lymphocytic receptors was tested for improving transgene persistence. In addition, the effect of gene transfer on nociception was also evaluated. Seven days after treatment, numerous LacZ-positive cells were observed after transfection with either viral vector. By 21 days after transfection, beta-galactosidase staining was reduced and suggestive of ongoing cytopathology in both Ad-treated groups, despite the fact that the immunogenicity of LacZ/Adts appeared less when compared with that elicited by the LacZ/Ad vector. In contrast, immunosuppressed animals showed a significant (P < or = 0.05) increase in the number of LacZ-positive cells not displaying cytopathology. In these animals, a concomitant reduction in numbers of macrophages/microglia and CD4 and CD8 lymphocytes was observed. Only animals that received LacZ/Adts and immunosuppression showed transgene expression after 60 days. Similar results were observed in animals in which the L4-L5 dorsal roots were lesioned before transfection. Gene transfer into the dorsal spinal cord did not affect nociception, independent of the adenovirus vector. These results indicate that immune blockade of the CD4/CD45 lymphocytic receptors enhanced transgene stability in adult animals with normal or injured spinal cords and that persistent transgene expression in the spinal cord does not interfere with normal neural function.

Adenoviridae↗
PubMed1997

Identification of growth hormone-releasing hormone and somatostatin neurons projecting to the median eminence in normal and growth hormone-deficient Ames dwarf mice.

In the spontaneous mutant Ames dwarf mouse, GH deficiency coincides with a dramatic increase in the expression of both mRNA and peptide for stimulatory GHRH and reduced expression of GH-inhibitory somatostatin (SRIH) mRNA and peptide. However, both GHRH and SRIH are markedly reduced in the dwarf median eminence (ME), suggesting that ME innervation by GHRH and SRIH neurons may be aberrant in the absence of GH. In order to test this hypothesis, the number of GHRH and SRIH ME-projecting neurons was evaluated in normal and dwarf mice using a combination of retrograde tract-tracing and neuron phenotype identification by immunocytochemistry (ICC). Adult animals were injected intraperitoneally with the fluorescent tract-tracer fluorogold (FG), which, in the brain, is taken up only by axons terminating in areas deprived of the blood-brain barrier, such as the ME. Visualization of FG was achieved by either UV illumination or ICC, and was combined as appropriate with fluorescence or bright-field ICC for GHRH or SRIH. Cells immunoreactive for GHRH or SRIH and labeled with FG were quantified at each 180-microns rostral-to-caudal level through the hypothalamus. As reported previously, the total number of hypophysiotropic GHRH neurons was markedly increased in dwarf compared with that in normal mice. However, a similar percentage of ME-innervating GHRH cells was estimated in dwarf (73 +/- 4%) and normal (76 +/- 3%) animals. Such a percentage in dwarfs thus represents a larger population of ME-projecting GHRH cells (749 +/- 53) than in normal mice (128 +/- 15). Increased numbers of FG-labeled GHRH neurons in dwarfs were located at the middle and posterior levels of the arcuate nucleus (2.08, 2.26 and 2.44 mm posterior to bregma). The percentage of FG-labeled SRIH neurons was also similar for dwarf (83 +/- 2%) and normal (87 +/- 2%) mice. Because the total SRIH-immunoreactive neuronal population in dwarfs is significantly reduced compared to that in normal animals, the similar FG-labeled percentage reflects a reduced number of SRIH cells projecting to ME in dwarf (1,376 +/- 104) compared with normal (3,192 +/- 267) mice. Fewer FG-labeled SRIH cells were found in dwarfs at every anterior-to-posterior level of the periventricular nucleus (p < 0.01 for comparisons at 0.28, 0.46, 0.64, and 1.0, and p < 0.05 for comparison at 1.18 mm posterior to the bregma). The present study indicates that the reduction in GHRH and SRIH immunoreactivity in the dwarf ME may result from different phenomena for each neuronal population. The reduction in GHRH immunostaining in the ME, despite a marked increase in the total ME-projecting GHRH neurons, may be interpreted as increased GHRH release, with consequent depletion of the ME stores. In contrast, the deficit in ME SRIH may be proportional to the deficit in the number of detectable SRIH periventricular nucleus neurons.

Animals↗
PubMed1997

[Health promotion in adolescents in Latin America].

The First International Conference on Health Promotion (Ottawa 1996) consolidated and developed the interest of Latin American countries in the amelioration of the health of their populations. Initiatives such as the International Conference for Health Promotion in Columbia in 1992 and the adoption in 1993 of the Caribbean Charter for Health Promotion show the efforts that have been carried out by different American countries to work toward the principles of the Ottawa Charter and to adapt them to their realities. This article focuses on the state of health of adolescents in Latin America as well as different actions that have been, and continue to be, carried out. The authors first discuss the peer approach to health education, which has been used in many health promotion actions throughout Latin America because of its effectiveness. Often in developing countries, the oldest children care for the younger ones. This approach therefore provides a way to reach not only peers of the adolescent involved, but also other youth in his/her entourage. Also, the participation of youth in health education allows them to develop relations with adults outside of their families, to improve their self-perceptions and to acquire a sense of responsibility and belonging within a social group. Examples from several countries are provided by the authors. What the authors call "classic" approaches to health promotion and education are also still used in many countries of Latin America and many of these programmes are concerned with sexual education and managing adolescent parenthood. Also, programmes using in approach specific to problems such as alcoholism, drug abuse, and violence have been developed in many countries. Finally, training programmes for health personnel focusing on the specific health needs of adolescents have been developed in Brazil, Peru, Costa Rica, and Uruguay for a large range of health professionals (psychologists, social workers, etc.). In conclusion, the authors state that although there is an increasing number of health promotion actions for adolescents in Latin America, there is still much work to be done. One of the elements that is priority for managing the health of adolescents is the integral approach of the adolescent, considering the psychological, social, and environmental factors that influence his/her well-being. Multi-disciplinary and intersectoral approaches are also considered as important, as is the participation of adolescents in the development and implementation of actions concerning them.

Adolescent↗
PubMed1997

[Mortality due to traffic accidents in Chile, 1994: an epidemiological approach].

BACKGROUND: Traffic accidents are one of the most important public health problems in the world and produce social, work and human resources losses. AIM: To perform an epidemiological description of traffic accidents occurred in Chile during 1994. MATERIAL AND METHODS: Data were obtained from death certificates in which the cause of death was a traffic accident. All death certificates obtained by the National Institute of Statistics during 1994 were used. Social, demographic and seasonal variables were recorded. RESULTS: During 1994, there were 1679 deaths due to traffic accidents (81% male), with a rate of 19.6 per 100,000 inhabitants. Gender specific risks were 19.62 and 4.48 for men and women, respectively. Mean age at the moment of death was 39 years old. Fifty three percent of deceased people were single, 42% married and 5% widowers. Ten percent had no formal education, 48% had basic education, 23% college education and 6.5% university education. Seventy seven percent of fatalities occurred in urban areas. The risk of death by traffic accidents was 7.02 per 100,000 inhabitants in the metropolitan region. CONCLUSIONS: The information obtained in the present study may help to generate preventive strategies to control deaths caused by traffic accidents.

Accidents, Traffic↗
PubMed1996

Hypophysiotropic somatostatin expression during postnatal development in growth hormone-deficient Ames dwarf mice: peptide immunocytochemistry.

Based on previous findings that the inhibitory hypophysiotropic factor somatostatin (somatotropin-release-inhibiting hormone, SRIH) is markedly reduced in growth hormone (GH)-deficient transgenic or spontaneous Snell dwarf mice, the present study was undertaken to determine whether hypophysiotropic SRIH expression was reduced in a type of dwarf mouse (Ames, df/df) in which SRIH had not been assessed, and whether the supposed reduction was present throughout life or was the result of regression after initial normal differentiation. Brain sections from normal (DF/?) and df/df mice were immunostained for SRIH using both standard and 'Elite' avidin-biotin complex reagents (Vectastain kits, Vector Laboratories, Inc., Burlingame, Calif., USA). Selected adult mice were treated with intracerebroventricular colchicine to maximize SRIH retention in perikarya. The developmental pattern of hypophysiotropic SRIH was assessed in brains of DF/? and df/df mice at 1, 3, 7, 14, 21, 60, and 90 days (d) postnatally. SRIH-immunoreactive neurons in the anterior periventricular nucleus (PeN) were quantified at each age. Although the use of Elite reagents or Elite and colchicine pretreatment increased (p < 0.001) the number of immunoreactive cells that were detectable in adult (60- to 90-day-old) df/df mice, the number of PeN SRIH neurons was reduced to 28% (p < 0.01) in untreated, and to 47% (p < 0.01) in colchicine-treated, df/df compared with DF/?, mice. In other CNS areas, SRIH immunostaining was comparable for df/df and DF/? mice, including neuron numbers in the medial basal hypothalamus of untreated mice. In postnatal development, SRIH was detectable in median eminence (ME) terminals at birth in some mice of both phenotypes, and at 3 d in all DF/? mice; ME SRIH was detectable in all mice by 7 d. In PeN, SRIH cells were first detectable consistently in normals at 3 d, and in dwarfs at 7 d. In DF/? mice, numbers of immunoreactive SRIH perikarya increased from 3 to 21 d, then plateaued. In dwarfs, SRIH cell numbers increased through 14 d. Numbers of SRIH perikarya were lower in df/df than in DF/? at 7, 14, 21, 60, and 90 d (all p < 0.05 or less). Thus, in Ames dwarf mice, as in other GH-deficient models, SRIH is markedly reduced in hypophysiotropic, ME-projecting neurons. The developmental pattern of hypophysiotropic SRIH in Ames dwarf mice is different from that of hypophysiotropic dopaminergic (DA) neurons in these animals, which are also prolactin (PRL)-deficient. Although DA levels and cell numbers are reduced markedly in adult df/df mice, both parameters have been found to be comparable to those of DF/? mice for the first 2-3 weeks postnatally. The consistent PeN SRIH deficit in dwarfs may reflect the importance of GH feedback earlier in development, because GH production in normal mice begins before birth, whereas PRL is not detectable until 7 d postnatally. The findings indicate that absent GH production has a marked negative effect on differentiation and levels of peptide expression in hypophysiotropic SRIH neurons.

Aging↗
PubMed1995

Prolactin replacement in adult dwarf mice does not reverse the deficit in tuberoinfundibular dopaminergic neuron number.

The lack of PRL synthesis in Ames dwarf mice coincides with a marked reduction in dopamine (DA) and in numbers of PRL-inhibiting tuberoinfundibular dopaminergic neurons in the hypothalamus (catecholaminergic area A12), as assessed by tyrosine hydroxylase (TH) immunoreactivity. This DA/TH deficit develops postnatally and can be prevented by PRL replacement initiated at 12 days of age. The present study tested whether a similar PRL treatment in adult dwarfs would reverse the A12 deficit, indicating that these neurons are quiescent due to absent PRL feedback stimulation, or would not reverse the deficit, suggesting that A12 neurons are either absent or refractory to PRL effect. At 60 days of age, Ames dwarf (df/df) mice received renal pituitary allografts from normal (DF/df) donors as a source of mouse PRL. Separate groups of dwarfs were treated sequentially with ovine PRL (50 micrograms/day, ip; 30 days) and vehicle (15 days) to assess whether the putative restorative effect of PRL regressed after hormone withdrawal. Brains were evaluated using DA histofluorescence and TH immunocytochemistry. Total numbers of TH-immunostained cells in A12 and medial zona incerta (area A13) regions were counted, and the intensity of TH immunostaining was assessed by computerized image analysis. The total A12 TH-positive cell number was reduced (P < 0.01) in all PRL-treated dwarfs (1826 +/- 58) compared with that in normal mice (3340 +/- 180), and was not different from that in untreated dwarfs (1953 +/- 304) regardless of the PRL regimen. However, A12 perikarya in all PRL-treated dwarfs showed qualitatively increased histofluorescence and quantitatively increased TH immunostaining (P < 0.01) intensity compared with that in untreated dwarfs, an effect that regressed after ovine PRL withdrawal. Neither cell number nor staining intensity differed by gender. There were no significant differences in A13 cell numbers or staining intensity according to phenotype or PRL treatment. The present results indicate that the tuberoinfundibular dopaminergic neuronal population in adult Ames dwarf mice is permanently reduced, although extant A12 cells in dwarfs are responsive to either homologous or heterologous PRL feedback. Together with the previously reported effect of PRL treatment in neonatal dwarfs, the reduction appears to be the result of absent PRL stimulation during development.

Animals↗
PubMed1994

Postnatal reduction in number of hypothalamic tuberoinfundibular dopaminergic neurons in prolactin-deficient dwarf mice.

Mice homozygous for the recessive 'Ames' dwarf mutation have undetectable serum or pituitary prolactin (PRL). Accompanying this pituitary deficiency is a marked reduction of dopamine (DA) and its rate-limiting synthetic enzyme tyrosine hydroxylase (TH) in PRL-regulating tuberoinfundibular hypothalamic neurons. In order to determine whether this deficit in adult Ames dwarf mice is congenital or arises postnatally, brains of dwarf (df/df) and normal (DF/?) littermate mice were assessed for TH immunoreactivity from 7 days through 2 months of age. Numbers of TH-positive neurons were counted in three hypothalamic DA areas: tuberoinfundibular A12, medial zona incerta A13, and anterior periventricular A14. There was an increase in the number of TH-positive neurons between 7 and 21 days of age in A12 and A14, but not in A13, for both DF/? and df/df mice. Between 21 days and 2 months of age, cell numbers were the same in all three areas in DF/? mice and in A13 and A14 in df/df mice. However, A12 TH-positive cell number in dwarfs decreased significantly (p < 0.01) between 21 days and 2 months, and was markedly lower (p < 0.001) in df/df than in DF/? mice at 2 months of age. The results emphasize the specificity of the dopaminergic neuron reduction in the Ames dwarf, which is restricted to the PRL-regulating tuberoinfundibular region. The data also indicate that the dwarf DA/TH deficit has an onset in late postnatal development, suggesting a response to absence of target PRL, rather than a primary hypothalamic effect of the dwarf mutation.

Animals↗