3D printed hybrid scaffolds do not induce adverse inflammation in mice and direct human BM-MSC chondrogenesis in vitro

Biomaterials that can improve the healing of articular cartilage lesions are needed. To address this unmet need, we developed novel 3D printed silica/poly(tetrahydrofuran)/poly(ε-caprolactone) (SiO2/PTHF/PCL-diCOOH) hybrid scaffolds. Our aim was to carry out essential studies to advance this medical device towards functional validation in pre-clinical trials. First, we show that the chemical composition, microarchitecture and mechanical properties of these scaffolds were not affected by sterilisation with gamma irradiation. To evaluate the systemic and local immunogenic reactivity of the sterilised 3D printed hybrid scaffolds, they were implanted subcutaneously into Balb/c mice. The scaffolds did not trigger a systemic inflammatory response over one week of implantation. The interaction between the host immune system and the implanted scaffold elicited a local physiological reaction with infiltration of mononuclear cells without any signs of a chronic inflammatory response. Then, we investigated how these 3D printed hybrid scaffolds direct chondrogenesis in vitro. Human bone marrow-derived mesenchymal stem/stromal cells (hBM-MSCs) seeded within the 3D printed hybrid scaffolds were cultured under normoxic or hypoxic conditions, with or without chondrogenic supplements. Chondrogenic differentiation assessed by both gene expression and protein production analyses showed that 3D printed hybrid scaffolds support hBM-MSC chondrogenesis. Articular cartilage-specific extracellular matrix deposition within these scaffolds was enhanced under hypoxic conditions (1.7 or 3.7 fold increase in the median of aggrecan production in basal or chondrogenic differentiation media). Our findings show that 3D printed SiO2/PTHF/PCL-diCOOH hybrid scaffolds have the potential to support the regeneration of cartilage tissue.

Measuring the elastic modulus of soft culture surfaces and three-dimensional hydrogels using atomic force microscopy

Growing interest in exploring mechanically mediated biological phenomena has resulted in cell culture substrates and 3D matrices with variable stiffnesses becoming standard tools in biology labs. However, correlating stiffness with biological outcomes and comparing results between research groups is hampered by variability in the methods used to determine Young's (elastic) modulus, E, and by the inaccessibility of relevant mechanical engineering protocols to most biology labs. Here, we describe a protocol for measuring E of soft 2D surfaces and 3D hydrogels using atomic force microscopy (AFM) force spectroscopy. We provide instructions for preparing hydrogels with and without encapsulated live cells, and provide a method for mounting samples within the AFM. We also provide details on how to calibrate the instrument, and give step-by-step instructions for collecting force-displacement curves in both manual and automatic modes (stiffness mapping). We then provide details on how to apply either the Hertz or the Oliver-Pharr model to calculate E, and give additional instructions to aid the user in plotting data distributions and carrying out statistical analyses. We also provide instructions for inferring differential matrix remodeling activity in hydrogels containing encapsulated single cells or organoids. Our protocol is suitable for probing a range of synthetic and naturally derived polymeric hydrogels such as polyethylene glycol, polyacrylamide, hyaluronic acid, collagen, or Matrigel. Although sample preparation timings will vary, a user with introductory training to AFM will be able to use this protocol to characterize the mechanical properties of two to six soft surfaces or 3D hydrogels in a single day.

Bioglass/carbonate apatite/collagen composite scaffold dissolution products promote human osteoblast differentiation

OssiMend® Bioactive (Collagen Matrix Inc., NJ) is a three-component porous composite bone graft device of 45S5 Bioglass/carbonate apatite/collagen. Our in vitro studies showed that conditioned media of the dissolution products of OssiMend Bioactive stimulated primary human osteoblasts to form mineralized bone-like nodules in vitro in one week, in basal culture media (no osteogenic supplements). Osteoblast differentiation was followed by gene expression analysis and a mineralization assay. In contrast, the dissolution products from commercial OssiMend (Bioglass-free carbonate apatite/collagen scaffolds), or from 45S5 Bioglass particulate alone, did not induce the mineralization of the extracellular matrix, but did induce osteoblast differentiation to mature osteoblasts, evidenced by the strong upregulation of BGLAP and IBSP mRNA levels. The calcium ions and soluble silicon species released from 45S5 Bioglass particles and additional phosphorus release from OssiMend mediated the osteostimulatory effects. Medium conditioned with OssiMend Bioactive dissolution had a much higher concentration of phosphorus and silicon than media conditioned with OssiMend and 45S5 Bioglass alone. While OssiMend and OssiMend Bioactive led to calcium precipitation in cell culture media, OssiMend Bioactive produced a higher concentration of soluble silicon than 45S5 Bioglass and higher dissolution of phosphorus than OssiMend. These in vitro results suggest that adding 45S5 Bioglass to OssiMend produces a synergistic osteostimulation effect on primary human osteoblasts. In summary, dissolution products of a Bioglass/carbonate apatite/collagen composite scaffold (OssiMend® Bioactive) stimulate human osteoblast differentiation and mineralization of extracellular matrix in vitro without any osteogenic supplements. The mineralization was faster than for dissolution products of ordinary Bioglass.

Three-dimensional niche stiffness synergizes with Wnt7a to modulate the extent of satellite cell symmetric self-renewal divisions

Satellite cells (SCs), the resident adult stem cells of skeletal muscle, are required for tissue repair throughout life. While many signaling pathways are known to control SC self-renewal, less is known about the mechanisms underlying the spatiotemporal control of self-renewal during skeletal muscle repair. Here, we measured biomechanical changes that accompany skeletal muscle regeneration and determined the implications on SC fate. Using atomic force microscopy, we quantified a 2.9-fold stiffening of the SC niche at time-points associated with planar-oriented symmetric self-renewal divisions. Immunohistochemical analysis confirms increased extracellular matrix deposition within the basal lamina. To test whether three-dimensional (3D) niche stiffness can alter SC behavior or fate, we embedded isolated SC-associated muscle fibers within biochemically inert agarose gels tuned to mimic native tissue stiffness. Time-lapse microscopy revealed that a stiff 3D niche significantly increased the proportion of planar-oriented divisions, without effecting SC viability, fibronectin deposition, or fate change. We then found that 3D niche stiffness synergizes with WNT7a, a biomolecule shown to control SC symmetric self-renewal divisions via the noncanonical WNT/planar cell polarity pathway, to modify stem cell pool expansion. Our results provide new insights into the role of 3D niche biomechanics in regulating SC fate choice.

Propagation phase-contrast micro-computed tomography allows laboratory-based three-dimensional imaging of articular cartilage down to the cellular level

OBJECTIVE

High-resolution non-invasive three-dimensional (3D) imaging of chondrocytes in articular cartilage remains elusive. The aim of this study was to explore whether laboratory micro-computed tomography (micro-CT) permits imaging cells within articular cartilage.

DESIGN

Bovine osteochondral plugs were prepared four ways: in phosphate-buffered saline (PBS) or 70% ethanol (EtOH), both with or without phosphotungstic acid (PTA) staining. Specimens were imaged with micro-CT following two protocols: 1) absorption contrast (AC) imaging 2) propagation phase-contrast (PPC) imaging. All samples were scanned in liquid. The contrast to noise ratio (C/N) of cellular features quantified scan quality and were statistically analysed. Cellular features resolved by micro-CT were validated by standard histology.

RESULTS

The highest quality images were obtained using propagation phase-contrast imaging and PTA-staining in 70% EtOH. Cellular features were also visualised when stained in PBS and unstained in EtOH. Under all conditions PPC resulted in greater contrast than AC (p < 0.0001 to p = 0.038). Simultaneous imaging of cartilage and subchondral bone did not impede image quality. Corresponding features were located in both histology and micro-CT and followed the same distribution with similar density and roundness values.

CONCLUSIONS

Three-dimensional visualisation and quantification of the chondrocyte population within articular cartilage can be achieved across a field of view of several millimetres using laboratory-based micro-CT. The ability to map chondrocytes in 3D opens possibilities for research in fields from skeletal development through to medical device design and treatment of cartilage degeneration.

Hypoxia impacts human MSC response to substrate stiffness during chondrogenic differentiation

Tissue engineering strategies often aim to direct tissue formation by mimicking conditions progenitor cells experience within native tissues. For example, to create cartilage in vitro, researchers often aim to replicate the biochemical and mechanical milieu cells experience during cartilage formation in the developing limb bud. This includes stimulating progenitors with TGF-β1/3, culturing under hypoxic conditions, and regulating mechanosensory pathways using biomaterials that control substrate stiffness and/or cell shape. However, as progenitors differentiate down the chondrogenic lineage, the pathways that regulate their responses to mechanotransduction, hypoxia and TGF-β may not act independently, but rather also impact one another, influencing overall cell response. Here, to better understand hypoxia's influence on mechanoregulatory-mediated chondrogenesis, we cultured human marrow stromal/mesenchymal stem cells (hMSC) on soft (0.167 kPa) or stiff (49.6 kPa) polyacrylamide hydrogels in chondrogenic medium containing TGF-β3. We then compared cell morphology, phosphorylated myosin light chain 2 staining, and chondrogenic gene expression under normoxic and hypoxic conditions, in the presence and absence of pharmacological inhibition of cytoskeletal tension. We show that on soft compared to stiff substrates, hypoxia prompts hMSC to adopt more spread morphologies, assemble in compact mesenchymal condensation-like colonies, and upregulate NCAM expression, and that inhibition of cytoskeletal tension negates hypoxia-mediated upregulation of molecular markers of chondrogenesis, including COL2A1 and SOX9. Taken together, our findings support a role for hypoxia in regulating hMSC morphology, cytoskeletal tension and chondrogenesis, and that hypoxia's effects are modulated, at least in part, by mechanosensitive pathways. Our insights into how hypoxia impacts mechanoregulation of chondrogenesis in hMSC may improve strategies to develop tissue engineered cartilage. STATEMENT OF SIGNIFICANCE: Cartilage tissue engineering strategies often aim to drive progenitor cell differentiation by replicating the local environment of the native tissue, including by regulating oxygen concentration and mechanical stiffness. However, the pathways that regulate cellular responses to mechanotransduction and hypoxia may not act independently, but rather also impact one another. Here, we show that on soft, but not stiff surfaces, hypoxia impacts human MSC (hMSC) morphology and colony formation, and inhibition of cytoskeletal tension negates the hypoxia-mediated upregulation of molecular markers of chondrogenesis. These observations suggest that hypoxia's effects during hMSC chondrogenesis are modulated, at least in part, by mechanosensitive pathways, and may impact strategies to develop scaffolds for cartilage tissue engineering, as hypoxia's chondrogenic effects may be enhanced on soft materials.

An engineered, quantifiable in vitro model for analysing the effect of proteostasis-targeting drugs on tissue physical properties

Cellular function depends on the maintenance of protein homeostasis (proteostasis) by regulated protein degradation. Chronic dysregulation of proteostasis is associated with neurodegenerative and age-related diseases, and drugs targeting components of the protein degradation apparatus are increasingly used in cancer therapies. However, as chronic imbalances rather than loss of function mediate their pathogenesis, research models that allow for the study of the complex effects of drugs on tissue properties in proteostasis-associated diseases are almost completely lacking. Here, to determine the functional effects of impaired proteostatic fine-tuning, we applied a combination of materials science characterisation techniques to a cell-derived, in vitro model of bone-like tissue formation in which we pharmacologically perturbed protein degradation. We show that low-level inhibition of VCP/p97 and the proteasome, two major components of the degradation machinery, have remarkably different effects on the bone-like material that human bone-marrow derived mesenchymal stromal cells (hMSC) form in vitro. Specifically, whilst proteasome inhibition mildly enhances tissue formation, Raman spectroscopic, atomic force microscopy-based indentation, and electron microscopy imaging reveal that VCP/p97 inhibition induces the formation of bone-like tissue that is softer, contains less protein, appears to have more crystalline mineral, and may involve aberrant micro- and ultra-structural tissue organisation. These observations contrast with findings from conventional osteogenic assays that failed to identify any effect on mineralisation. Taken together, these data suggest that mild proteostatic impairment in hMSC alters the bone-like material they form in ways that could explain some pathologies associated with VCP/p97-related diseases. They also demonstrate the utility of quantitative materials science approaches for tackling long-standing questions in biology and medicine, and could form the basis for preclinical drug testing platforms to develop therapies for diseases stemming from perturbed proteostasis or for cancer therapies targeting protein degradation. Our findings may also have important implications for the field of tissue engineering, as the manufacture of cell-derived biomaterial scaffolds may need to consider proteostasis to effectively replicate native tissues.

Bi-directional cell-pericellular matrix interactions direct stem cell fate

Modifiable hydrogels have revealed tremendous insight into how physical characteristics of cells' 3D environment drive stem cell lineage specification. However, in native tissues, cells do not passively receive signals from their niche. Instead they actively probe and modify their pericellular space to suit their needs, yet the dynamics of cells' reciprocal interactions with their pericellular environment when encapsulated within hydrogels remains relatively unexplored. Here, we show that human bone marrow stromal cells (hMSC) encapsulated within hyaluronic acid-based hydrogels modify their surroundings by synthesizing, secreting and arranging proteins pericellularly or by degrading the hydrogel. hMSC's interactions with this local environment have a role in regulating hMSC fate, with a secreted proteinaceous pericellular matrix associated with adipogenesis, and degradation with osteogenesis. Our observations suggest that hMSC participate in a bi-directional interplay between the properties of their 3D milieu and their own secreted pericellular matrix, and that this combination of interactions drives fate.

Neighboring cells override 3D hydrogel matrix cues to drive human MSC quiescence

Physical properties of modifiable hydrogels can be tuned to direct stem cell differentiation in a role akin to that played by the extracellular matrix in native stem cell niches. However, stem cells do not respond to matrix cues in isolation, but rather integrate soluble and non-soluble signals to balance quiescence, self-renewal and differentiation. Here, we encapsulated single cell suspensions of human mesenchymal stem cells (hMSC) in hyaluronic acid-based hydrogels at high and low densities to unravel the contributions of matrix- and non-matrix-mediated cues in directing stem cell response. We show that in high-density (HD) cultures, hMSC do not rely on hydrogel cues to guide their fate. Instead, they take on characteristics of quiescent cells and secrete a glycoprotein-rich pericellular matrix (PCM) in response to signaling from neighboring cells. Preventing quiescence precluded the formation of a glycoprotein-rich PCM and forced HD cultures to differentiate in response to hydrogel composition. Our observations may have important implications for tissue engineering as neighboring cells may act counter to matrix cues provided by scaffolds. Moreover, as stem cells are most regenerative if activated from a quiescent state, our results suggest that ex vivo native-like niches that incorporate signaling from neighboring cells may enable the production of clinically relevant, highly regenerative cells.

Differential Regulation of Human Bone Marrow Mesenchymal Stromal Cell Chondrogenesis by Hypoxia Inducible Factor-1α Hydroxylase Inhibitors

The transcriptional profile induced by hypoxia plays important roles in the chondrogenic differentiation of marrow stromal/stem cells (MSC) and is mediated by the hypoxia inducible factor (HIF) complex. However, various compounds can also stabilize HIF's oxygen-responsive element, HIF-1α, at normoxia and mimic many hypoxia-induced cellular responses. Such compounds may prove efficacious in cartilage tissue engineering, where microenvironmental cues may mediate functional tissue formation. Here, we investigated three HIF-stabilizing compounds, which each have distinct mechanisms of action, to understand how they differentially influenced the chondrogenesis of human bone marrow-derived MSC (hBM-MSC) in vitro. hBM-MSCs were chondrogenically-induced in transforming growth factor-β3-containing media in the presence of HIF-stabilizing compounds. HIF-1α stabilization was assessed by HIF-1α immunofluorescence staining, expression of HIF target and articular chondrocyte specific genes by quantitative polymerase chain reaction, and cartilage-like extracellular matrix production by immunofluorescence and histochemical staining. We demonstrate that all three compounds induced similar levels of HIF-1α nuclear localization. However, while the 2-oxoglutarate analog dimethyloxalylglycine (DMOG) promoted upregulation of a selection of HIF target genes, desferrioxamine (DFX) and cobalt chloride (CoCl2 ), compounds that chelate or compete with divalent iron (Fe2+ ), respectively, did not. Moreover, DMOG induced a more chondrogenic transcriptional profile, which was abolished by Acriflavine, an inhibitor of HIF-1α-HIF-β binding, while the chondrogenic effects of DFX and CoCl2 were more limited. Together, these data suggest that HIF-1α function during hBM-MSC chondrogenesis may be regulated by mechanisms with a greater dependence on 2-oxoglutarate than Fe2+ availability. These results may have important implications for understanding cartilage disease and developing targeted therapies for cartilage repair. Stem Cells 2018;36:1380-1392.

Expression patterns of α2,3-sialyltransferase I and α2,6-sialyltransferase I in human cutaneous epithelial lesions

Skin tumors have become one of the most common cancers in the world and their carcinogenesis is frequently associated with altered glycosylation patterns. The aberrant sialylation, a type of glycosylation, can mediate pathophysiological key events during various stages of tumor progression, including invasion and metastasis. Sialyltransferases play a key role in a variety of biological processes, including cell-cell communication, cell-matrix interaction, adhesion, and protein targeting. In this study, it was evaluated the expression of ST3Gal I and ST6Gal I in cutaneous epithelial lesions that include actinic keratosis (n=15), keratoacanthoma (n=9), squamous cell carcinoma (n=22) and basal cell carcinoma (n=28) in order to evaluate if sialyltransferases expression is different in premalignant and in malignant tumors. The expression of ST3Gal I was observed in actinic keratosis (53%), keratoacanthoma (78%), squamous cell carcinoma (73%) and basal cell carcinoma (32%) with statistic differences between basal cell carcinoma and keratoacanthoma (P=0.0239) and basal cell carcinoma and squamous cell carcinoma (P=0.0096); for ST6Gal I, cytoplasmic expression was noted in actinic keratosis (40%), heterogeneous and cytoplasmic expression was noted in keratoacanthoma (67%), squamous cell carcinoma (41%) and basal cell carcinoma (7%) with statistic differences between basal cell carcinoma and squamous cell carcinoma (P=0.0061) and basal cell carcinoma and keratoacanthoma (P=0.0008). In summary, our results showed that the high expression of ST3Gal I and ST6Gal I, in skin tumors, is associated with tumors with greater potential for invasion and metastasis, as in the case of squamous cell carcinoma, and this may be related to their behavior.

Detection of oncogenic human papillomavirus in sporadic retinoblastoma

PURPOSE

To investigate the presence of human papillomavirus (HPV) DNA in tumour tissue from patients with unilateral retinoblastoma.

METHODS

Samples of paraffin-embedded tumour tissue from 43 children with unilateral retinoblastoma were collected to investigate the presence of HPV DNA using polymerase chain reaction (PCR) and dot blot hybridization.

RESULTS

Oncogenic HPV DNA types 16 and 35 were detected in 12 (27.9%) of 43 tumour specimens. A higher frequency of differentiated tumours (63.3%) was observed among the HPV-positive tumours.

CONCLUSIONS

Future studies are necessary to demonstrate an association between HPV and sporadic retinoblastoma.

Virus Coat Protein Transgenic Papaya Provides Practical Control of Papaya ringspot virus in Hawaii

Since 1992, Papaya ringspot virus (PRSV) destroyed nearly all of the papaya hectarage in the Puna district of Hawaii, where 95% of Hawaii's papayas are grown. Two field trials to evaluate transgenic resistance (TR) were established in Puna in October 1995. One trial included the following: SunUp, a newly named homozygous transformant of Sunset; Rainbow, a hybrid of SunUp, the nontransgenic Kapoho cultivar widely grown in Puna, and 63-1, another segregating transgenic line of Sunset. The second trial was a 0.4-ha block of Rainbow, simulating a near-commercial planting. Both trials were installed within a matrix of Sunrise, a PRSV-susceptible sibling line of Sunset. The matrix served to contain and trace pollen flow from TR plants, and as a secondary inoculum source. Virus infection was first observed 3.5 months after planting. At a year, 100% of the non-TR control and 91% of the matrix plants were infected, while PRSV infection was not observed on any of the TR plants. Fruit production data of SunUp and Rainbow show that yields were at least three times higher than the industry average, while maintaining percent soluble solids above the minimum of 11% required for commercial fruit. These data suggest that transgenic SunUp and Rainbow, homozygous and hemizygous for the coat protein transgene, respectively, offer a good solution to the PRSV problem in Hawaii.

Effect of infusing gamma-aminobutyric acid receptor agonists and antagonists into the medial preoptic area and ventromedial hypothalamus on prolactin secretion in male sheep

We investigated the effects of gamma-aminobutyric acid (GABA) agonists muscimol and baclofen (GABA(A) and GABA(B) agonists, respectively) and antagonists bicuculline methiodide (BMI, GABA(A) antagonist) or 2-hydroxysaclofen (SAC) and CGP 55845A (GABA(B) antagonists) on prolactin (PRL) secretion in castrated rams. The drugs were applied by microdialysis into either the medial preoptic area (mPOA) or ventromedial hypothalamus (VMH). Dialysis of baclofen into the mPOA significantly increased mean PRL (p < 0.05), whereas SAC caused a small, but significant decrease (p < 0.01). Dialysis of either muscimol or BMI into the mPOA had no effect on prolactin. In the VMH, baclofen significantly increased (p < 0.01) mean PRL but SAC and CGP 55845A were ineffective, whereas dialysis of either muscimol or BMI increased mean prolactin (p < 0.01). These results show that infusion into the mPOA of drugs that affect GABA(B) receptor alter PRL release, whereas infusion of a GABA(A) agonists and antagonist was without effect on PRL release. In contrast, infusion of both GABA(A) and GABA(B) agonists and a GABA(A) antagonist into the VMH altered PRL secretion. This suggest that GABAergic neurons in both regions participate in regulating PRL secretion, but by different receptor systems.

Temporal effects of estradiol (E) on luteinizing hormone-releasing hormone (LHRH) and LH release in castrated male sheep

We tested the hypothesis that rapidly expressed inhibitory effects of estradiol (E) on luteinizing hormone (LH) release in the male are attributable, in part, to suppression of luteinizing hormone-releasing hormone (LHRH) release. Hypophyseal-portal cannulated, castrated male sheep were infused with E (15 ng/kg/hr) or vehicle. Portal and jugular blood samples were collected at 10-min intervals for 4 hr before, and for either 12 hr (E, n = 4; vehicle, n = 4) or 24 hr (E, n = 8; vehicle, n = 3) after the start of infusion. In animals sampled for 16 hr, temporal changes in both LHRH and LH were assessed. In animals sampled for 28 hr, only LH data were analyzed. Before either the 12-hr or 24-hr infusion, LHRH and/or LH mean concentrations, pulse amplitude and interpulse interval (IPI) did not differ between E- and vehicle-infused animals. In animals sampled for 16 hr, no effects of time or steroid x time interactions were detected for mean LHRH and LHRH pulse amplitude; however, both were greater (P < 0.01) in vehicle-infused than in E-infused males. LHRH IPI was unaffected by infusion. In contrast, both mean LH and LH pulse amplitude declined (P < 0.01) within 4-8 hr after the start of E infusion, whereas mean LH IPI was unaffected. In animals sampled for 28 hr, an effect of time (P < 0.01) and a steroid x time interaction (P < 0.01) was detected for mean LH, and there was an effect of time (P < 0.01) on LH pulse amplitude. Mean LH IPI was not affected. Our results show that in male sheep E rapidly reduces LH release in the absence of a detectable change in LHRH release.

Effects of dialyzing gamma-aminobutyric acid receptor antagonists into the medial preoptic and arcuate ventromedial region on luteinizing hormone release in male sheep

We investigated the effects of microdialyzing alpha-aminobutyric acid (GABA) receptor antagonists into either the medial preoptic area (mPOA) or the arcuate-ventromedial region (ARC-VMR) on LH secretion. Bicuculline methiodide (BMI, GABA(A) receptor antagonist), and either 2-hydroxysaclofen (SAC) or CGP 55845A (CGP, GABA(B) receptor antagonists) were used. In experiment 1, castrated rams received 4-h dialysis into either the mPOA (n = 5) or ARC-VMR (n = 4) of artificial cerebrospinal fluid (aCSF) followed by 4 h of either BMI (aCSF-BMI, 375 microM in mPOA, 1 mM in the ARC-VMR for 2-1/2 h), or aCSF-SAC (5 mM). In experiment 2, castrated rams received dialysis only in the ARC-VMR (n = 5) of aCSF-aCSF, aCSF-BMI (375 microM), or aCSF-CGP (50 microM). In experiment 3, untreated or testosterone (T)-treated castrated rams (n = 6/group) received dialysis only in the ARC-VMR of aCSF-aCSF, aCSF-BMI (375 microM), or aCSF-CGP (500 microM). Jugular blood was collected at 10-min intervals. In experiment 1, BMI suppressed mean plasma LH (p < 0.05) and increased interpulse interval (IPI, p < 0.05) at both sites. In experiment 2, BMI significantly reduced mean LH and increased IPI (p < 0.01). In experiment 3, BMI reduced mean LH in both the presence (p < 0.05) and absence of T (p < 0.01) and increased IPI (p < 0.01) in the absence of T. SAC, CGP, and aCSF did not affect LH in any experiment. These results show that dialysis of BMI, into either the mPOA or the ARC-VMR of either castrated or T-treated castrated rams decreased LH release, whereas dialysis of GABA(B) antagonists at these sites was without detectable effect.

Hypothalamic sites of action for testosterone, dihydrotestosterone, and estrogen in the regulation of luteinizing hormone secretion in male sheep

Testosterone (T) inhibits LH secretion partly by acting at unknown sites within the brain to inhibit GnRH secretion. We tested the hypothesis that the preoptic area (POA) and arcuate-ventromedial region (ARC/VMR), areas rich in androgen and estrogen (E) receptors, are neural sites at which T and the T metabolites, dihydrotestosterone (DHT) and estrogen (E), act to suppress LH secretion. Bilateral guide cannulae were surgically implanted into either the POA or ARC/VMR of castrated male sheep. Experiments were conducted under a long day photoperiod to maximize the inhibitory effect of the steroids. In Exp 1, all sheep (n = 6/site) sequentially received bilateral implants of cholesterol (CHOL), T, or E at each site. Jugular blood samples were taken at 10-min intervals for 4 h both immediately before implant insertion and 5 days later. In Exp 2, all sheep (n = 6/site) sequentially received bilateral implants of CHOL, DHT, or E at each site according to a latin square design. Blood samples were taken before and 7 days after implant insertion. In Exp 3, which followed the same design as Exp 2, implants of E, T, or DHT were placed only in the ARC/VMR. In the final experiment, the effects of T and CHOL implants in the ARC/VMR were compared. Neither T, DHT, nor CHOL implants at either site affected LH secretion. In contrast, E treatment in the ARC/VMR suppressed mean plasma LH levels (P < 0.01), primarily due to an increase in interpulse interval (P < 0.01). Estrogen implants in the POA caused a small, but nonsignificant (P > 0.05), decrease in mean LH levels in the first experiment and an increase in LH interpulse interval (P < 0.05) in the second experiment. These results suggest that the ARC/VMR and possibly the POA are sites at which E acts to reduce GnRH secretion in male sheep.

Pharmacokinetics of extracellular melatonin in Siberian hamster forebrain

In vivo brain microdialysis was used to characterize the pharmacokinetics of subcutaneously injected melatonin in the anterior hypothalamic-preoptic area (AH-POA) of the male Siberian hamster. Animals with a microdialysis probe implanted in the AH-POA were treated with a subcutaneous melatonin injection at 0900 h (3 h after lights-on) or 2000 h (2 h prior to lights-off). Treatment with 2.5 or 0.25 mg/kg dosages of melatonin in saline vehicle induced peak concentrations of melatonin in AH-POA microdialysates within 20 min of injection (165 +/- 34 and 18 +/- 8 pg/20 min, respectively). For the 2.5 and 0.25 mg/kg dosages, the half-life of the absorbed melatonin (t 1/2 elimination) was less than 20 min, and the concentrations fell to baseline within 60 min after injection. There were no significant time of day effects on the kinetic profile of extracellular melatonin associated with either of these dosages. These results confirm the rapid accumulation and clearance of extracellular melatonin in the vicinity of its putative target tissues.

Differential regulation of luteinizing hormone release by gamma-aminobutyric acid receptor subtypes in the arcuate-ventromedial region of the castrated ram

We investigated the effects on LH secretion of infusing gamma-aminobutyric acid (GABA) agonists muscimol and baclofen (GABAA and GABAB receptor agonists, respectively) into either the medial preoptic area (mPOA) or the arcuate-ventromedial region (ARC-VMR) of the hypothalamus of castrated rams during the nonbreeding season. Bilateral microdialysis of artificial cerebrospinal fluid for 4 h followed by treatment with artificial cerebrospinal fluid, baclofen (1 mM), or muscimol (1 mM in the ARC-VMR, 250 microM in the mPOA) for 4 h was carried out on three separate occasions in random order. Simultaneously, jugular venous blood was collected at 10-min intervals, and plasma later was assayed for LH. The estimated dose of baclofen delivered to each unilateral microdialysis site was 7.9 micrograms; for muscimol, it was 1.1 micrograms for the mPOA and 4.5 micrograms for the ARC-VMR. In the mPOA, baclofen had no detectable effect, whereas muscimol had a delayed suppressive effect on mean LH (P < 0.01). In the ARC-VMR muscimol rapidly reduced mean LH (P < 0.01). In contrast, baclofen increased mean LH (P = 0.01) and LH pulse amplitude (P = 0.05) without altering the LH interpulse interval (P > 0.10). These results support the involvement of GABAA receptors in the mPOA in regulating LH secretory patterns. More importantly, both GABAA and GABA(B) receptors in the ARC-VMR appear to differentially modulate LH and, presumably, GnRH release. Whether GABA acts directly on the GnRH neuron or indirectly through other neural systems remains to be determined.

Diurnal variation in 5-hydroxyindole-acetic acid output in the suprachiasmatic region of the Siberian hamster assessed by in vivo microdialysis: evidence for nocturnal activation of serotonin release

In vivo brain microdialysis was used to characterize the daily pattern of 5-hydroxyindole-acetic acid (5-HIAA) release in the region of the suprachiasmatic nuclei (SCN) in freely behaving male Siberian hamsters housed under 16L:8D. A marked diurnal variation in the concentration of extracellular 5-HIAA was apparent, with peak levels (147 +/- 5% of the daily mean; p < 0.05) occurring 2-3 h after lights-off. Smaller nocturnal rises in extracellular 5-HIAA were observed in the posterior hypothalamus and preoptic area (128 +/- 4 and 123 +/- 8% of the daily mean, respectively; both p < 0.05 vs. average daytime levels). Tryptophan loading increased 5-HIAA in SCN microdialysates by 44 +/- 6%, and this response was enhanced by localized perfusion with tetrodotoxin (TTX; 5 microM). Localized applications of KCl (150 mM) or veratridine (100 microM) decreased 5-HIAA by 62 +/- 5 or 49 +/- 11%, respectively. The effect of KCl was not significantly affected by specific calcium channel blockers. Perfusion with TTX markedly decreased SCN 5-HIAA during the dark phase, but had little effect during the light phase (42 +/- 8 vs. 12 +/- 5% suppression, respectively; p < 0.01). Addition of serotonin (3 microM) to the perfusate significantly stimulated 5-HIAA output. This treatment increased the release of 5-HIAA more during the dark than during the light phase (61 +/- 8 vs. 25 +/- 5%, respectively; p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

[Mitral valve prolapse in the 8th and 9th decades of life. Anatomo-pathologic study of 3 cases]

Different anatomo-clinic aspects from three mitral valve prolapse cases are compared to those commonly presented in the literature and are also utilized as a basis for a new classification of this disease. The patients are more than 77 years old, what is in contrast with the current concept of MVP as a disease of young-middle aged women. The first case shows marked ostial dilation and many ruptured chordae: as a consequence, this patient showed severe cardiac dysfunction. The anterior, rather than the posterior leaflet, presented intense myxoid degeneration. In the second case, no ruptured chordae were detected and, consequently, the degree of heart failure was lesser than the first one, in spite of the same degree of ostial dilation. Both leaflets showed the same degree of myxoid degeneration. The third patient, who does not have heart failure, showed myxomatous degeneration of both cusps, but no ostial dilation or chordal rupture were present. These aspects reinforce the impression that isolated mixomatous degeneration of the cusps is not so deleterious when compared to those cases where the mitral valvar ring is dilated or its chordae are also involved by that degenerative process. Therefore ostial dimension (normal or enlarged) and the state of the chordae (with or without rupture) appears to be important points to be considered in MVP.

Evidence that short photoperiod-induced gonadal regression in the Mongolian gerbil is mediated by the action of melatonin in the medial hypothalamus

The present study was undertaken to examine the effects of exposure to short photoperiod (SD) and treatment with subcutaneous (s.c.) or intrahypothalamic melatonin-containing beeswax implants on reproduction in the Mongolian gerbil Meriones unguiculatus. Exposure of adult female gerbils to SD (8 h light: 16 h dark) caused a significant decrease in weight of the reproductive tract (ovaries, oviducts, uterus and vagina; RTW) compared to animals maintained under stimulatory photoperiod (12 h light: 12 h dark; 81.4 +/- 8.0 mg vs 151.8 +/- 16.0 mg, respectively (P less than 0.01]. Treatment with two large s.c. implants, each containing 3 mg melatonin, mimicked the antigonadal effect of SD (68.7 +/- 3.9 mg vs 118.1 +/- 19.5 mg for the blank (melatonin-free) implant controls; P less than 0.05). Gerbils with a small melatonin-beeswax pellet (containing 0.2 mg melatonin) in the anterior hypothalamus (AH) underwent a significant reduction in RTW compared to gerbils with a blank intrahypothalamic implant (73.0 +/- 5.7 mg vs 134.6 +/- 14.5 mg, respectively; P less than 0.01). Melatonin pellets in the mediobasal hypothalamus (MBH) also induced gonadal regression, but to a lesser degree (88.7 +/- 12.6 mg; P less than 0.05 vs blank controls). Small melatonin pellets placed elsewhere in the hypothalamus or s.c. had little effect on RTW (143.4 +/- 20.9 mg and 129.2 +/- 19.7 mg, respectively). Only 25% of the gerbils with melatonin pellet in the AH or MBH had a corpus luteum compared to 73% of the blank controls (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

[The mitral valve apparatus: an anatomo-echocardiographic approach]

The shape of the mitral valve ring, the position of its chordae and of its leaflets were studied in 34 normal hearts fixed through intra-ventricular injection of tamponate formalin. As the authors have assumed that the post-rigor left ventricle has an architecture very similar to that seen at to the end of ventricular systole, comparisons were made between the anatomical and the echocardiographic features usually seen at the end of the phase of the cardiac cycle. The mitral ring has the shape of a hyperbolic paraboloid, and this peculiar geometry explains why the "apical-four chambers" view, which explores the most superficial ring segments, is the more appropriate view for detecting mitral valve prolapses. In that incidence the valvar diameter is longer (2.43 +/- 0.45 cm) that in the "parasternal view" (1.99 +/- 0.45 cm) and the angle made by the leaflets is comparatively less acute ("four chambers" = 127.41 +/- 16.45 degrees; "parasternal" = 102.05 +/- 0.17 degrees). In the "four chamber" view the point of coaptation (which represents the vertex of the referred angle) is 0.45 +/- 0.17 cm far from the echographic line usually taken as the valvar plane (EVPL-echocardiographic valvar plane line) whereas in the other view, it is more distant from this line (0.59 +/- 0.16 cm). These two last factors make both leaflets closer to the left atrium and explains why mitral valve prolapse, when present, is more easily seen in that incidence.(ABSTRACT TRUNCATED AT 250 WORDS)