Adjustment to acute or early HIV-1 infection diagnosis to prompt linkage to care and ART initiation: qualitative insights from coastal Kenya.

Diagnosing and treating patients with acute or early HIV-1 infection (AEHI) is an important strategy to prevent HIV-1 transmission. We used qualitative methods to understand factors that facilitate adjustment to AEHI diagnosis, prompt linkage to care and initiation of antiretroviral treatment (ART). Twenty-three AEHI patients (12 women, 11 men) included 18 participants identified at health facilities, and 5 participants identified in a sex worker cohort. Of these, 17 participants (9 women, 8 men) participated in qualitative interviews about their AEHI status 2 weeks after diagnosis. Thirteen participants (7 women, 6 men) returned for a second interview 12 weeks after diagnosis. Interviews explored participants' experiences at the time of and following their diagnosis, and examined perceptions about ART initiation and behavior change recommendations, including disclosure and partner notification. A grounded theory framework was used for analysis, eliciting three important needs that should be addressed for AEHI patients: 1) the need to better understand AEHI and accept one's status; 2) the need to develop healthy strategies and adjust to the reality of AEHI status; and 3) the need to protect self and others through ART initiation, adherence, safer sex, and disclosure. A preliminary conceptual framework to guide further intervention and research with AEHI populations is proposed.

Pharmacogenetics of antiepileptic drugs: A brief review.

The goal of pharmacogenetic research is to assist clinicians in predicting patient response to medications when genetic variations are identified. The pharmacogenetic variation of antiepileptic drug response and side effects has yielded findings that have been included in drug labeling and guidelines. The goal of this review is to provide a brief overview of the pharmacogenetic research on antiepileptic drugs. It will focus on findings that have been included in drug labeling, guidelines, and candidate pharmacogenetic variation. Overall, several genes have been included in guidelines by national and international organizations; however, much work is needed to implement and evaluate their use in clinical settings.

Extrapituitary production of anterior pituitary hormones: an overview.

Protein hormones from the anterior pituitary gland have well-established endocrine roles in their peripheral target glands. It is, however, now known that these proteins are also produced within many of their target tissues, in which they act as local autocrine or paracrine factors, with physiological and/or pathophysiological significance. This emerging concept is the focus of this brief review.

Screening for genital and anorectal sexually transmitted infections in HIV prevention trials in Africa.

OBJECTIVES: To demonstrate the value of routine, basic sexually transmitted infection (STI) screening at enrolment into an HIV-1 vaccine feasibility cohort study and to highlight the importance of soliciting a history of receptive anal intercourse (RAI) in adults identified as "high risk". METHODS: Routine STI screening was offered to adults at high risk of HIV-1 upon enrolment into a cohort study in preparation for HIV-1 vaccine trials. Risk behaviours and STI prevalence were summarised and the value of microscopy assessed. Associations between prevalent HIV-1 infection and RAI or prevalent STI were evaluated with multiple logistic regression. RESULTS: Participants had a high burden of untreated STI. Symptom-directed management would have missed 67% of urethritis cases in men and 59% of cervicitis cases in women. RAI was reported by 36% of male and 18% of female participants. RAI was strongly associated with HIV-1 in men (adjusted odds ratio (aOR) 3.8; 95% CI 2.0 to 6.9) and independently associated with syphilis in women (aOR 12.9; 95% CI 3.4 to 48.7). CONCLUSIONS: High-risk adults recruited for HIV-1 prevention trials carry a high STI burden. Symptom-directed treatment may miss many cases and simple laboratory-based screening can be done with little cost. Risk assessment should include questions about anal intercourse and whether condoms were used. STI screening, including specific assessment for anorectal disease, should be offered in African research settings recruiting participants at high risk of HIV-1 acquisition.

Sensitivity and specificity of HIV rapid tests used for research and voluntary counselling and testing.

BACKGROUND: HIV rapid tests (RT) are a quick and non-technically demanding means to perform HIV voluntary counselling and testing (VCT) but understanding their limitations is vital to delivering quality VCT. OBJECTIVE: To determine the sensitivity and specificity of HIV rapid tests used for research and voluntary counselling and testing at four sites in East Africa. DESIGN: Cross-sectional study. SETTING: Masaka District, Uganda; a sugar plantation in Kakira, Uganda; Coastal Villages in the Kilifi District of Kenya; and the Urban slum of Kangemi located West of Nairobi, Kenya. SUBJECTS: Six thousands two hundred and fifty five consenting volunteers were enrolled into the study, and 675 prevalent HIV infections were identified. RESULTS: The RT sensitivity tended to be high for all assays at all sites (97.63-100%) with the exception of the Uni-Gold assay (90.24% in Kangemi, 96.58% in Kilifi). Twenty four RT results were recorded as 'weak positives', 22 (92%) of which were negative by ELISA. There was a high rate of RT false positives in Uganda (positive predictive values ranging from 45.70% to 86.62%). CONCLUSIONS: The sensitivity and specificity of the RT varied significantly across sites. The rate of RT misclassification in Uganda suggests that a multiple test algorithm may be preferable to a single test as screener for HIV VCT.

Expression, translation, and localization of a novel, small growth hormone variant.

A novel transcript of the GH gene has been identified in ocular tissues of chick embryos. It is, however, unknown whether this transcript (small chicken GH, scGH) is translated. This possibility was therefore assessed. The expression of scGH mRNA was confirmed by RT-PCR, using primers that amplified a 426-bp cDNA of its coding sequence. This cDNA was inserted into an expression plasmid to transfect HEK 293 cells, and its translation was shown by specific scGH immunoreactivity in extracts of these cells. This immunoreactivity was directed against the unique N terminus of scGH and was associated with a protein of 16 kDa, comparable with its predicted size. Most of the immunoreactivity detected was, however, associated with a 31-kDa moiety, suggesting scGH is normally dimerized. Neither protein was, however, present in media of the transfected HEK cells, consistent with scGH's lack of a signal sequence. Similar moieties of 16 and 31 kDa were also found in proteins extracted from ocular tissues (neural retina, pigmented epithelium, lens, cornea, choroid) of embryos, although they were not consistently present in vitreous humor. Specific scGH immunoreactivity was also detected in these tissues by immunocytochemistry but not in axons in the optic fiber layer or the optic nerve head, which were immunoreactive for full-length GH. In summary, we have established that scGH expression and translation occurs in ocular tissues of chick embryos, in which its localization in the neural retina and the optic nerve head is distinct from that of the full-length protein.

Leptospirosis among patients presenting with dengue-like illness in Puerto Rico.

Leptospirosis is difficult to distinguish from dengue fever without laboratory confirmation. Sporadic cases/clusters of leptospirosis occur in Puerto Rico, but surveillance is passive and laboratory confirmation is rare. We tested for leptospirosis using an IgM ELISA on sera testing negative for dengue virus IgM antibody and conducted a case-control study assessing risk factors for leptospirosis, comparing clinical/laboratory findings between leptospirosis (case-patients) and dengue patients (controls). Among 730 dengue-negative sera, 36 (5%) were positive for leptospirosis. We performed post mortem testing for leptospirosis on 12 available specimens from suspected dengue-related fatalities; 10 (83%) tested positive. Among these 10 fatal cases, pulmonary hemorrhage and renal failure were the most common causes of death. We enrolled 42 case-patients and 84 controls. Jaundice, elevated BUN, hyperbilirubinemia, anemia, and leukocytosis were associated with leptospirosis (p < .01 for all). Male sex, walking in puddles, rural habitation, and owning horses were independently associated with leptospirosis. Epidemiological, clinical, and laboratory criteria may help distinguish leptospirosis from dengue and identify patients who would benefit from early antibiotic treatment.

Determinants of CD4 counts among HIV-negative Ethiopians: role of body mass index, gender, cigarette smoking, khat (Catha Edulis) chewing, and possibly altitude?

To study the determinants of CD4% and CD4 counts among HIV-negative Ethiopians, and to identify factors susceptible to explain the low CD4 counts observed among Ethiopian subjects. Cohort studies among factory workers in Akaki and Wonji, Ethiopia. Clinical and laboratory examinations, including determination of HIV serological status and T-cell subsets, were performed during follow-up visits every six months. In addition, micronutrients (retinol, carotenoids, tocopherol, transferrin receptor, and selenium) plasma concentrations were determined in a subset of 38 HIV-positive and 121 HIV-negative participants. HIV-negative participants with at least one CD4 count measurement were 157 females in Akaki, 203 males in Akaki, and 712 males in Wonji. CD4 counts were independently and positively associated with body mass index (through an increase in lymphocyte counts), female gender (through an increase in CD4%), cigarette smoking (through an increase in CD4%), khat chewing (through an increase in both lymphocyte counts and CD4%), and Akaki study site (through a large increase in lymphocyte counts compensating a decrease in CD4%). Intestinal parasitic infections were not associated with CD4% or CD4 counts. Retinol, carotenoids, and alpha-tocopherol plasma concentrations decreased with HIV infection and advancing immunosuppression, but were not associated with CD4 counts among HIV-negative subjects. Low body mass index among Ethiopians may have contributed to their overall low CD4 counts. Other factors remain to be elucidated.

Growth hormone in the nervous system: autocrine or paracrine roles in retinal function?

Growth hormone (GH) is primarily produced in the pituitary gland, although GH gene expression also occurs in the central and autonomic nervous systems. GH-immunoreactive proteins are abundant in the brain, spinal cord, and peripheral nerves. The appearance of GH in these tissues occurs prior to the ontogenic differentiation of the pituitary gland and prior to the presence of GH in systemic circulation. Neural GH is also present in neonates, juveniles, and adults and is independent of changes in pituitary GH secretion. Neural GH is therefore likely to have local roles in neural development or neural function, especially as GH receptors (GHRs) are widespread in the nervous system. In recent studies, GH mRNA and GH immunoreactive proteins have been identified in the neural retina of embryonic chicks. GH immunoreactivity is present in the optic cup of chick embryos at embryonic day (ED) 3 of the 21-d incubation period. It is widespread in the neural retina by ED 7 but also present in the nonpigmented retina, choroid, sclera, and cornea. This immunoreactivity is associated with proteins in the neural retina comparable in size with those in the adult pituitary gland, although it is primarily associated with 15-16 kDa moieties rather than with the full-length molecule of approximately 22 kDa. These small GH moieties may reflect proteolytic fragments of "monomer" GH and (or) the presence of different GH gene transcripts, since full-length and truncated GH cDNAs are present in retinal tissue extracts. The GH immunoreactivity in the retina persists throughout embryonic development but is not present in juvenile birds (after 6 weeks of age). This immunoreactivity is also associated with the presence of GH receptor (GHR) immunoreactivity and GHR mRNA in ocular tissues of chick embryos. The retina is thus an extrapituitary site of GH gene expression during early development and is probably an autocrine or paracrine site of GH action. The marked ontogenic pattern of GH immunoreactivity in the retina suggests hitherto unsuspected roles for GH in neurogenesis or ocular development.

Role of incidental and/or cured intestinal parasitic infections on profile of CD4+ and CD8+ T cell subsets and activation status in HIV-1 infected and uninfected adult Ethiopians.

Intestinal parasitic infections have been suggested to cause persistent immune activation leading to an unbalanced immune state. Such a state has been proposed to be a major factor in the pathogenesis of AIDS in an African context. The present study investigated the effect of incidental parasitic infection and treatment on the profile of T cell differentiation and activation markers on CD4+ and CD8+ T cells from HIV-1 infected and uninfected adult Ethiopians. Cryopreserved PBMCs from 64 subjects (41 HIV-negative and 23 HIV-positive) with follow-up visits at 6-monthly intervals were used to compare the effect of incidental intestinal parasites and their treatment upon T cell subset profiles and activation status. The samples were stained with antibodies to various T cell differentiation and activation markers allowing naive, memory, effector, memory/effector, activated and resting CD4+ and CD8+ T cell subsets to be quantified by triple-colour FACScan. Incidental intestinal parasitic infections resulted in a significant increase in memory CD4+ T cell numbers both in HIV-negative and HIV-positive subjects (P < 0.05). There was also a significant increase in the percentage of CD8+ HLA-DR+ T cells (P < 0.05) in HIV-positive subjects co-infected with parasites. In HIV-negative subjects, a significant decline in activated cells and a significant increase in resting CD8+ T cells (P < 0.05) was observed after treatment for parasites. These data suggest that intestinal parasitic infections could result in the alteration of T cell subset counts and also in the up-regulation of T cell activation markers in peripheral blood. Treatment of parasitic infections showed a tendency to reduce the activation suggesting that, together with other community based intervention strategies, such treatment could be used to down-regulate immune activation and hence protect the host from being easily attacked by HIV.

The role of mitochondria, cytochrome c and caspase-9 in embryonic lens fibre cell denucleation.

During the differentiation of secondary lens fibre cells from the lens epithelium, the fibre cells lose all of their cytoplasmic organelles as well as their nuclei. The fibre cells, containing crystallins, which confer optical clarity, then persist in the adult lens. The process of denucleation of these cells has been likened to an apoptotic event which is not followed by the plasma membrane changes that are characteristic of apoptosis. We have examined the expression and subcellular translocation of molecules of the apoptotic cascade in differentiating lens epithelial cells in culture. In this culture system, the epithelial cells differentiate into lentoids composed of lens fibre cells. We find that caspase-9, which is expressed and activated before embryonic day 12 in intact lenses, is localized in the cytosol outside mitochondria in non-differentiating cultured cells. In lentoid cells, caspase-9 migrates into mitochondria after the latter undergo a membrane permeability transition that is characteristic of apoptotic cells. At the same time, caspase-9 co-localizes with cytochrome c in the cytosol. The cytochrome c is apparently released from the mitochondria in lentoid cells after the mitochondrial membrane permeability transition and during the period of nuclear shrinkage. Also during this time, the mitochondria aggregate around the degenerating nuclei. Cytochrome c disappears rapidly, while mitochondrial breakdown occurs approximately coincident with the disappearance of the nuclei, but mitochondrial remnants persist together with cytochrome c oxidase, which is a mitochondrial marker protein. Apaf-1, another cytosolic protein of the apoptotic cascade, also migrates to the permeabilized mitochondria and also co-localizes with caspase-9 and cytochrome c in the cytosol or mitochondria of denucleating cells, thus providing evidence for the formation of an 'apoptosome' in these cells, as in apoptotic cells. At no time did we observe the translocation of molecules between cytoplasmic compartments and the nucleus in differentiating lentoid cells. We suggest that the uncoupling of nuclear and membrane apoptotic events in these cells may be due to the early permeability changes in the mitochondria, resulting in the loss of mitochondrial signalling molecules, or to the failure of molecules to migrate to the nucleus in these cells, thus failing to activate nuclear-plasma membrane signalling pathways.

[Results from the 'Ethiopia-Netherlands AIDS Research Project'; 1995-2000]. / Resultaten van het 'Ethiopia-Netherlands aids research project'; 1995-2000.

Since 1995 the 'Ethiopia-Netherlands aids research project' (ENARP) has been up and running in Addis Ababa, Ethiopia. Several surveys point towards an HIV seroprevalence of approximately 15% amongst adult Ethiopians in the capital city. Prospective cohort studies initiated since early 1997 indicate that healthy, HIV negative Ethiopians have lower CD4+ T-cell counts compared to the Dutch population and in addition they have chronically activated immune systems, possibly as a result of the highly prevalent intestinal parasitic infections as well as other infections. HIV positive Ethiopians are mainly infected with HIV-1 subtype C, which can be subdivided in 2 subtypes, both of which entered Ethiopia in the early 1980's. There are considerable differences between Ethiopians and Dutch in terms of biomedical parameters relevant for HIV infection progression; these justify further efforts in future scientific research. The emphasis for this should be on robust and applicable laboratory methods, research in the field of HIV vaccine trials and information transfer to the various partners combating HIV infection/aids in Ethiopia.

[Ethiopia-Netherlands AIDS research project]. / 'Ethiopia-Netherlands AIDS research project'.

The 'Ethiopia-Netherlands AIDS Research Project' (ENARP), started in 1994, is a long-term collaboration between AIDS researchers in Amsterdam and the Ethiopian Health and Nutrition Research Institute in Addis Ababa. The ENARP's primary objectives include conducting studies on HIV and AIDS in Ethiopia, especially by means of some large-scale prospective cohort studies, training Ethiopian scientists in PhD programmes in epidemiology, immunology and virology and establishing a reference laboratory for HIV and AIDS in Ethiopia and neighbouring countries. External funding for ENARP amounts to 32 million Dutch guilders for two periods of four years and is being provided by the Dutch Government. ENARP is the largest third world biomedical project supported by the Dutch Government. In 2000 two Ethiopian students obtained their doctorates from the University of Amsterdam. Five new PhD students commenced their training in 1999. ENARP hopes to set up HIV-1 vaccine phase I and phase II trials in the near future.

Peripheral target contact regulates Ca2+ channels in the cell bodies of bullfrog sympathetic ganglion B-neurons.

Tyrosine-hydroxylase immunohistochemistry demonstrated that a single injection of 120 mg/kg 6-hydroxydopamine (6-OHDA) reversibly disconnected bullfrog sympathetic ganglia from their peripheral targets. This was correlated with a decrease in sympathetic outflow to the eyes and a reversible decrease in pupil diameter. 6-OHDA did not damage the cell bodies of ganglionic neurons. Calcium channel current in ganglionic B-neurons, (measured at -10 mV; holding potential -60 mnV; Ba2+ as charge carrier; IBa) was reduced. It reached a minimum of about 40% of control amplitude 7-14 days after 6-OHDA injection and recovered to 73% of control amplitude after 63 days. 6-OHDA induced loss and recovery of functional sympathetic innervation of peripheral target tissues, as determined by measurement of pupil diameter, occurred at a similar rate. Thus, pupil diameter attained mininum values 7-14 days after 6-OHDA treatment and recovered to 81% of control after 63 days. The properties of Ca2+ channels in sympathetic neurons are, therefore, determined by continuity of contact with peripheral target. 6-OHDA also decreased the peak amplitude and duration of the afterhyperpolarization (a.h.p) that follows the action potential (a.p.). The rate of recovery of a.h.p duration was more rapid than the rate of recovery of peak a.h.p. amplitude. This may reflect known differences in properties of two types of Ca2+-sensitive K currents. IC and IAHP, IC, which is responsible for the peak amplitude of the a.h.p has a low affinity for Ca2+, whereas IAHP, which determines a.h.p. duration, has higher Ca2+ affinity.

Growth hormone in neural tissues of the chick embryo.

Growth hormone (GH) gene expression predominantly occurs in the pituitary gland, although it also occurs in many extrapituitary sites, including the brain. The cellular location and ontogeny of neural GH production is, however, largely unknown. This has therefore been determined during chick embryogenesis. In chicks, the brain develops from the neural tube at embryonic day (ED) 3. At this age, the divisions of the brain (the telencephalon, diencephalon, mesencephalon, metencephalon and myelencephalon) have intense GH immunoreactivity (GH-IR) (detected by two polyclonal antibodies and a monoclonal antibody for chicken GH). The otic and optic vesicles were also strongly GH immunoreactive, as were the Vth (semi-lunar), VIIth (facial), VIIIth (acoustic) and IXth (glossopharyngeal) nerve ganglia. This GH-IR was specific for GH and was lost when the antibodies were preabsorbed with recombinant chicken GH. The widespread distribution of GH-IR in the neural tissues of ED 3 embryos was mirrored by the distribution of GH receptor (GHR) immunoreactivity, detected by an antibody raised against the chicken GHR. In ED 6/ED 7 embryos, the neural retina of the eye and the epithelial and lens fiber cells were intensely stained for GH-IR, as was Rathke's pouch and the wall of the diencephalon. In contrast, only a few scattered cells were immunoreactive in the surrounding mesoderm. At ED 14, the GH-IR in the brain was restricted to specific tissues and cells. For instance, immunoreactive cells were present in the molecular and pyramidal layers of the cerebral cortex, in the gray matter of the cerebellum, in the choroid plexus, and in the walls of the ventricles. In summary, GH- and GHR-like proteins are abundant in neural tissues of the chick during the first third of incubation, becoming discretely localized to specific tissues and cells during later incubation. The localization of GH and GHR in these tissues, prior to the ontogeny of plasma GH, suggests autocrine or paracrine roles for GH during early embryogenesis.

Inhibition of focal adhesion kinase expression correlates with changes in the cytoskeleton but not apoptosis in primary cultures of chick embryo cells.

Cell adhesion to the extracellular matrix through integrin receptors can activate signaling cascades within the cell. Focal adhesion kinase (FAK) is a protein tyrosine kinase activated by integrin adhesion. The role of FAK within the cell is not clear, although evidence suggests roles in cell motility or the regulation of adhesion-dependent cell survival. We have treated primary cultures of chick embryo cells with antisense oligonucleotides to FAK to reduce the level of FAK protein expression. Levels of the related protein, proline-rich tyrosine kinase 2 (Pyk2) and the FAK substrate paxillin, were unaffected by the addition of oligonucleotides, whereas FAK expression was reduced by 70%. Levels of apoptotic cell death did not significantly increase after the addition of oligonucleotides. However, there was a change in the distribution of focal adhesion sites from a uniformly distributed pattern to a mainly peripheral pattern. This was accompanied by a loss of stress fibers and an increase in the peripheral actin cytoskeleton, as the cells became rounded. These results suggest that in these early embryonic cells, FAK expression regulates the arrangement of focal adhesions and the cytoskeleton that result in a motile phenotype, but that FAK does not appear to regulate apoptosis.

Ablation of axial structures activates apoptotic pathways in somite cells of the chick embryo.

It has been known for some time that ablation of the neural tube and/or the notochord in the chick embryo leads to a massive wave of cell death in the adjacent somites. It is postulated that in the normal embryo, survival signals emanate from the neural tube and/or notochord that suppress apoptosis in the cells of the somites, except for a small population of sclerotome cells that are programmed to die naturally. In this study we show that axial ablation results in the death of sclerotome and not somitic neural crest cells, and we have examined the apoptotic response of these cells to the ablation. We show that several elements of the apoptotic cascade become detectable in somite cells in response to the withdrawal of survival signals. We demonstrate the down-regulation of bcl-2 protein in the somites adjacent to, and caudal to, the site of ablation, corresponding to the region that displays an elevated level of cell death. Although caspase-9 appeared to be activated in somites at all levels of the trunk, caspase-2 showed a clear response to the ablation of the axial structures. Removal of the neural tube and notochord produced an up-regulation of caspase-2 activity in somites in the region of the operation. Cleavage of two down-stream substrates of these caspases was examined. The cleavage of poly (ADP-ribose) polymerase (PARP) was apparent in somites at all levels of the trunk, and showed only a modest up-regulation after ablation. By contrast, the cleavage of DNA fragmentation factor (DFF45) showed a marked up-regulation in response to ablation, suggesting that this is a primary substrate for a caspase-dependent apoptotic mechanism. Evidence was also found for a caspase-independent mechanism, since the expression of apoptosis-inducing factor (AIF) was found to be very sensitive to, and up-regulated in somites by, axial ablation. Because the wave of apoptosis that is precipitated in somites by removal of the axial structures may be mediated by BMP-4, we examined the levels of BMP-4 in somites in response to axial ablation. BMP-4 expression was clearly up-regulated in somites adjacent to, or close to, the site of operation.

Comparison between the in vivo and in vitro expression of three adhesion-signaling proteins in embryonic cells.

We have examined the relationship between the in vivo and in vitro expression of three adhesion-signaling proteins (FAK, PYK2 and Paxillin), using cells of the early chick embryo, where pure cell populations may be isolated and cultured, and in which epithelial-to-mesenchymal transformation is occurring. Focal Adhesion Kinase (FAK) and Proline-rich Tyrosine Kinase-2 (PYK2) are related in molecular structure, and may have some overlapping functions in signal transduction associated with cell-substratum adhesion. Paxillin, a cytoskeletal protein, is also localized to focal adhesions. We show that the immunocytochemical detection of these molecules in vivo does not reflect their in vitro localization. Focal Adhesion Kinase showed a developmentally regulated localization to the cytoplasm, but not to sites of adhesion, in epithelial cells in vivo, while Paxillin was associated with migrating mesoderm cells. Proline-rich Tyrosine Kinase-2 was undetectable in vivo. The level of expression of these molecules was compared under in vivo and in vitro conditions. While the expression of Focal Adhesion Kinase showed a tissue-specific regulation of expression with the change to in vitro conditions, Proline-rich Tyrosine Kinase-2 showed a more uniform and less tissue-specific up-regulation. Levels of Paxillin expression also showed an increase with this change in conditions. We conclude that despite the structural and functional relationships between these three molecules in the developing embryo, the expression and localization of each is independently regulated. We suggest that this provides these cells with the adaptability that they require in order to respond to the changing extracellular environment in the early embryo, and to undergo epithelial-to-mesenchymal transformation.

Extra-pituitary growth hormone in peripheral tissues of early chick embryos.

Early embryonic growth is independent of pituitary growth hormone (GH), since it occurs prior to the differentiation of pituitary somatotrophs. Embryogenesis is therefore thought to be regulated by local growth factors. As GH is now known to be produced in many extrapituitary sites, in which it acts in an autocrine or paracrine manner, the possibility that extra-pituitary GH may participate in embryogenesis and organogenesis was assessed by determining the immunocytochemical presence and location of GH- and GH-receptor (GHR)-like proteins in the peripheral tissues of chick embryos during their 21-day incubation period. Immunoreactive (IR)-GH, detectable by a monoclonal and two polyclonal antibodies for chicken GH, was specifically and ubiquitously present in tissues of 3-day-old embryos. At embryonic day (ED) 5, IR-GH was widespread in ectodermal, mesodermal and endodermal tissues, but it was not present in every cell of each tissue. IR-GH was particularly abundant i! n the neural tube, notochord, limb bud, somites, heart, stomach, liver, kidney, Wolffian duct and the amnion. By ED8, IR-GH was still widespread and was now present in limb bud cartilage, although the heart and liver were no longer GH immunoreactive. GH receptor immunoreactivity was also present in most tissues and cells of ED3-ED8 embryos. These results demonstrate that extrapituitary GH is abundantly present during early embryogenesis, prior to the differentiation of pituitary somatotrophs (at ED12). Since GH- and GHR-like proteins are present in most tissues of the chick embryo, it is proposed that extrapituitary GH may act as a local growth factor during embryonic development.