Osteogenic-angiogenic coupled response of cobalt-containing mesoporous bioactive glasses in vivo

The incorporation of cobalt ions into the composition of bioactive glasses has emerged as a strategy of interest for bone regeneration purposes. In the present work, we have designed a set of bioactive mesoporous glasses SiO2-CaO-P2O5-CoO (Co-MBGs) with different amounts of cobalt. The physicochemical changes introduced by the Co2+ ion, the in vitro effects of Co-MBGs on preosteoblasts and endothelial cells and their in vivo behaviour using them as bone grafts in a sheep model were studied. The results show that Co2+ ions neither destroy mesoporous ordering nor inhibit in vitro bioactive behaviour, exerting a dual role as network former and modifier for CoO concentrations above 3 % mol. On the other hand, the activity of Co-MBGs on MC3T3-E1 preosteoblasts and HUVEC vascular endothelial cells is dependent on the concentration of CoO present in the glass. For low Co-MBGs concentrations (1mg/ml) cell viability is not affected, while the expression of osteogenic (ALP, RUNX2 and OC) and angiogenic (VEGF) genes is stimulated. For Co-MBGs concentration of 5 mg/ml, cell viability decreases as a function of the CoO content. In vivo studies show that the incorporation of Co2+ ions to the MBGs improves the bone regeneration activity of these materials, despite the deleterious effect that this ion has on bone-forming cells for any of the Co-MBG compositions studied. This contradictory effect is explained by the marked increase in angiogenesis that takes place inside the bone defect, leading to an angiogenesis-osteogenesis coupling that compensates for the partial decrease in osteoblast cells. STATEMENT OF SIGNIFICANCE: The development of new bone grafts implies to address the need for osteogenesis-angiogenesis coupling that allows bone regeneration with viable tissue in the long term. In this sense the incorporation of cobalt ions into the composition of bioactive glasses has emerged as a strategy of great interest in this field. Due to the potential cytotoxic effect of cobalt ions, there is an important controversy regarding the suitability of their incorporation in bone grafts. In this work, we address this controversy after the implantation of cobalt-doped mesoporous bioactive glasses in a sheep model. The incorporation of cobalt ions in bioactive glasses improves the bone regeneration ability of these bone grafts, due to enhancement of the angiogenesis-osteogenesis coupling.

Comparative anatomy of the ovine and human pelvis for laparoscopic sacrocolpopexy: evaluating the effectiveness of the ovine model

INTRODUCTION AND HYPOTHESIS

Laparoscopic sacrocolpopexy (LSC) is a functional reconstructive surgery used to treat pelvic organ prolapse (POP) in middle-aged women. Although LSC is widely used, its implementation is hindered by perceived technical difficulties and surgical learning curves. Surgeons require adequate experience with LSC prior to performing the procedure on patients to improve their quality of life. This study is aimed at demonstrating the effectiveness of the ovine model (OM) for training and research in LSC, while also comparing anatomical differences between ovine and human models during the procedure.

METHODS

The animal model and training were provided by the Jesús Usón Minimally Invasive Surgery Centre. Urologists and gynecologists with experience in LSC participated in a course and their findings were recorded and documented.

RESULTS

Differences in patient positioning, trocar placement, and reperitonealization were identified between the ovine and human models. Hysterectomy is always performed in the ovine model, whereas it is not mandatory in humans. There are also differences in the dissection of the levator ani muscle and attachment point of the posterior mesh to the uterus between the two models. Despite differences in some areas, the ovine pelvic structure and vagina are similar in size to those of humans.

CONCLUSIONS

The ovine model is a valuable tool for surgeons in their learning curve for LSC, allowing for safe and effective practice prior to performing the procedure on patients. The use of the OM can help to improve the quality of life for women affected by pelvic organ prolapse.

Injectable Mesoporous Bioactive Nanoparticles Regenerate Bone Tissue under Osteoporosis Conditions

The osteogenic capability of mesoporous bioactive nanoparticles (MBNPs) in the SiO₂-CaO system has been assessed in vivo using an osteoporotic rabbit model. MBNPs have been prepared using a double template method, resulting in spherical nanoparticles with a porous core-shell structure that has a high surface area and the ability to incorporate the anti-osteoporotic drug ipriflavone. In vitro expression of the pro-inflammatory genes NF-κB1, IL-6, TNF-α, P38 and NOS2 in RAW-264.7 macrophages, indicates that these nanoparticles do not show adverse inflammatory effects. An injectable system has been prepared by suspending MBNPs in a hyaluronic acid-based hydrogel, which has been injected intraosseously into cavitary bone defects in osteoporotic rabbits. The histological analyses evidenced that MBNPs promote bone regeneration with a moderate inflammatory response. The incorporation of ipriflavone into these nanoparticles resulted in a higher presence of osteoblasts and enhanced angiogenesis at the defect site, but without showing significant differences in terms of new bone formation. STATEMENT OF SIGNIFICANCE: Mesoporous bioactive glass nanoparticles have emerged as one of the most interesting materials in the field of bone regeneration therapies. For the first time, injectable mesoporous bioactive nanoparticles have been tested in vivo using an osteoporotic animal model. Our findings evidence that MBG nanoparticles can be loaded with an antiosteoporotic drug, ipriflavone, and incorporated in hyaluronic acid to make up an injectable hydrogel. The incorporation of MBG nanoparticles promotes bone regeneration even under osteoporotic conditions, whereas the presence of IP enhances angiogenesis as well as the presence of osteoblast cells lining in the newly formed bone. The injectable device presented in this work opens new possibilities for the intraosseous treatment of osteoporotic bone using minimally invasive surgery.

Development and assessment of an ex-vivo bench model aimed at laparoscopic ureteric reconstructive techniques

INTRODUCTION/BACKGROUND

Reconstructive and ablative urologic techniques require special technical mastery, especially the intracorporeal suturing.

OBJECTIVE

To report the subjective evaluation of a versatile ex-vivo model aimed to practice laparoscopic ureteric reconstructive techniques (LURT) on box-trainer.

STUDY DESIGN

The model is a continuous portion of porcine urinary bladder ("dilated pelvis"), the vesico-ureteral joint ("stenosis") and healthy ureter. All 127 participants (n = 119 urologists and n = 8 paediatric surgeons) performed on the model laparoscopic Anderson-Hynes dismembered pyeloplasty, and then, in the animal model, different LURT procedures (ureteroneocystostomy, ureteric reimplantation and/or dismembered pyeloplasty). The model was subjectively evaluated (face and content validity), through a 12 items questionnaire, based on a Likert scale (1-5 points) and a global question (1-10 points).

RESULTS

The total mean rating for 11/12 items was very high (>4points). Only one was rated under 3 points. The overall total mean rating from 1 to 10 points was very high (9.19 ± 0.82 points). In 10/12 items, expert's feedback (content validity) prevailed over non-experts (face validity).

DISCUSSION/CONCLUSION

The model was highly accepted for the practice of LURT techniques. Additionally, it is cost-effective, easy to assemble, ethically considerate, and realistic.

Silicon substituted hydroxyapatite/VEGF scaffolds stimulate bone regeneration in osteoporotic sheep

Silicon-substituted hydroxyapatite (SiHA) macroporous scaffolds have been prepared by robocasting. In order to optimize their bone regeneration properties, we have manufactured these scaffolds presenting different microstructures: nanocrystalline and crystalline. Moreover, their surfaces have been decorated with vascular endothelial growth factor (VEGF) to evaluate the potential coupling between vascularization and bone regeneration. In vitro cell culture tests evidence that nanocrystalline SiHA hinders pre-osteblast proliferation, whereas the presence of VEGF enhances the biological functions of both endothelial cells and pre-osteoblasts. The bone regeneration capability has been evaluated using an osteoporotic sheep model. In vivo observations strongly correlate with in vitro cell culture tests. Those scaffolds made of nanocrystalline SiHA were colonized by fibrous tissue, promoted inflammatory response and fostered osteoclast recruitment. These observations discard nanocystalline SiHA as a suitable material for bone regeneration purposes. On the contrary, those scaffolds made of crystalline SiHA and decorated with VEGF exhibited bone regeneration properties, with high ossification degree, thicker trabeculae and higher presence of osteoblasts and blood vessels. Considering these results, macroporous scaffolds made of SiHA and decorated with VEGF are suitable bone grafts for regeneration purposes, even in adverse pathological scenarios such as osteoporosis. STATEMENT OF SIGNIFICANCE: For the first time, the in vivo behavior of scaffolds made of silicon substituted hydroxyapatites (SiHA) has been evaluated under osteoporosis conditions. In order to optimize the bone regeneration properties of these bioceramics, 3D macroporous scaffolds have been manufactured by robocasting and implanted in osteoporotic sheep. Our experimental design shed light on the important issue of the biological response of nano-sized bioceramics vs highly crystalline bioceramics, as well as on the importance of coupling vascularization and bone growth processes by decorating SiHA scaffolds with vascular endothelial growth factor.

[Validity studies in laparoscopic simulation. Methodology and design considerations.]

OBJECTIVES

To describe a roadmap of the most representative milestones and considerations in the validation of surgical simulators, especially those of laparoscopic surgery. And additionally, help determine when in this process a simulator can be considered as validated.

METHODS

A non-systematic review was carried out searching terms like simulation, validation, training, assessment, skills and learning curve, as well as providing the experience accumulated by our center.

RESULTS

An ideal classical validation process should consist of the following steps: fidelity, verification/calibration/ reliability, subjective and objective strategies. Baseline tests of fidelity and verification/calibration/ technological reliability are not always detailed in the simulation literature. A simulator can be considered validated if, at least, satisfactorily completed any of the two main objective strategies, that is, constructive and/or criterion validity.

CONCLUSIONS

The methodologies to validate simulators as useful and reliable for the improvement of psychomotor/ technical skills are widely analyzed, although there is a variety of approaches depending on the scientific reference consulted, not being implemented equally in all works. This apparent arbitrariness should be considered in advance because it can lead the researcher to misunderstandings, especially when the simulator will be regarded as valid.

Mesoporous bioactive glass/ɛ-polycaprolactone scaffolds promote bone regeneration in osteoporotic sheep

Macroporous scaffolds made of a SiO2-CaO-P2O5 mesoporous bioactive glass (MBG) and ɛ-polycaprolactone (PCL) have been prepared by robocasting. These scaffolds showed an excellent in vitro biocompatibility in contact with osteoblast like cells (Saos 2) and osteoclasts derived from RAW 264.7 macrophages. In vivo studies were carried out by implantation into cavitary defects drilled in osteoporotic sheep. The scaffolds evidenced excellent bone regeneration properties, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, thick trabeculae, high vascularization and high presence of osteoblasts and osteoclasts. In order to evaluate the effects of the local release of an antiosteoporotic drug, 1% (%wt) of zoledronic acid was incorporated to the scaffolds. The scaffolds loaded with zoledronic acid induced apoptosis in Saos 2 cells, impeded osteoclast differentiation in a time dependent manner and inhibited bone healing, promoting an intense inflammatory response in osteoporotic sheep. STATEMENT OF SIGNIFICANCE: In addition to an increase in bone fragility and susceptibility to fracture, osteoporosis also hinders the clinical success of endosseous implants and grafting materials for the treatment of bone defects. For the first time, macroporous scaffolds made of mesoporous bioactive glass and ε-caprolactone have been evaluated in a sheep model that mimics the osteoporosis conditions in humans. These implants fostered bone regeneration, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, showing thick trabeculae and a high vascularization degree. Our results indicate that macroporous structures containing highly bioactive mesoporous glasses could be excellent candidates for the regenerative treatment of bone defects in osteoporotic patients.

Synergistic effect of Si-hydroxyapatite coating and VEGF adsorption on Ti6Al4V-ELI scaffolds for bone regeneration in an osteoporotic bone environment

The osteogenic and angiogenic responses to metal macroporous scaffolds coated with silicon substituted hydroxyapatite (SiHA) and decorated with vascular endothelial growth factor (VEGF) have been evaluated in vitro and in vivo. Ti6Al4V-ELI scaffolds were prepared by electron beam melting and subsequently coated with Ca₁₀(PO₄)_5.6(SiO₄)_0.4(OH)_1.6 following a dip coating method. In vitro studies demonstrated that SiHA stimulates the proliferation of MC3T3-E1 pre-osteoblastic cells, whereas the adsorption of VEGF stimulates the proliferation of EC₂ mature endothelial cells. In vivo studies were carried out in an osteoporotic sheep model, evidencing that only the simultaneous presence of both components led to a significant increase of new tissue formation in osteoporotic bone. STATEMENT OF SIGNIFICANCE: Reconstruction of bones after severe trauma or tumors extirpation is one of the most challenging tasks in the field of orthopedic surgery. This scenario is even more complicated in the case of osteoporotic patients, since their bone regeneration capability is decreased. In this work we present a porous implant that promotes bone regeneration even in osteoporotic bone. By coating the implant with osteogenic bioceramics such as silicon substituted hydroxyapatite and subsequent adsorption of vascular endothelial growth factor, these implants stimulate the bone ingrowth when they are implanted in osteoporotic sheep.

Interpretation of motion analysis of laparoscopic instruments based on principal component analysis in box trainer settings

BACKGROUND

Motion analysis parameters (MAPs) have been extensively validated for assessment of minimally invasive surgical skills. However, there are discrepancies on how specific MAPs, tasks, and skills match with each other, reflecting that motion analysis cannot be generalized independently of the learning outcomes of a task. Additionally, there is a lack of knowledge on the meaning of motion analysis in terms of surgical skills, making difficult the provision of meaningful, didactic feedback. In this study, new higher significance MAPs (HSMAPs) are proposed, validated, and discussed for the assessment of technical skills in box trainers, based on principal component analysis (PCA).

METHODS

Motion analysis data were collected from 25 volunteers performing three box trainer tasks (peg grasping/PG, pattern cutting/PC, knot suturing/KS) using the EVA tracking system. PCA was applied on 10 MAPs for each task and hand. Principal components were trimmed to those accounting for an explained variance > 80% to define the HSMAPs. Individual contributions of MAPs to HSMAPs were obtained by loading analysis and varimax rotation. Construct validity of the new HSMAPs was carried out at two levels of experience based on number of surgeries.

RESULTS

Three new HSMAPs per hand were defined for PG and PC tasks, and two per hand for KS task. PG presented validity for HSMAPs related to insecurity and economy of space. PC showed validity for HSMAPs related to cutting efficacy, peripheral unawareness, and confidence. Finally, KS presented validity for HSMAPs related with economy of space and knotting security.

CONCLUSIONS

PCA-defined HSMAPs can be used for technical skills' assessment. Construct validation and expert knowledge can be combined to infer how competences are acquired in box trainer tasks. These findings can be exploited to provide residents with meaningful feedback on performance. Future works will compare the new HSMAPs with valid scoring systems such as GOALS.

Initial validation of a training program focused on laparoscopic radical nephrectomy

OBJECTIVE

To assess a training model focused on laparoscopic nephrectomy.

MATERIAL AND METHODS

16 residents participated in the study, who attended a training program with a theoretical session (1hour) and a dry (7hours) and a wet lab (13hours). During animal training, the first and last nephrectomies were assessed through the completion time and the global rating scale "Objective and Structured Assessment of Technical Skills" (OSATS). Before and after the course, they performed 3 tasks on the virtual reality simulator LAPMentor (1) eye-hand coordination; 2) hand-hand coordination; and 3) transference of objects), registering time and movement metrics. All participants completed a questionnaire related to the training components on a 5-point rating scale.

RESULTS

The participants performed the last nephrectomy faster (P<.001) and with higher OSATS scores (P<.001). After the course, they completed the LAPMentor tasks faster (P<.05). The number of movements decreased in all tasks (1) P<.001, 2) P<.05, and 3) P<.05), and the path length in tasks 1 (P<.05) and 2 (P<.05). The movement speeds increased in tasks 2 (P<.001) and 3 (P<.001). With regards to the questionnaire, the usefulness of the animal training and the necessity of training on them prior to their laparoscopic clinical practice were the questions with the highest score (4.92±.28).

CONCLUSIONS

The combination of physical simulation and animal training constitute an effective training model for improving basic and advanced skills for laparoscopic nephrectomy. The component preferred by the urology residents was the animal training.

Assessment of Laparoscopic Skills in Veterinarians Using a Canine Laparoscopic Simulator

The aim of the present study was to assess the content and construct validity of the Canine Laparoscopic Simulator (CLS). Forty-two veterinarians were assigned to experienced (n=12), control (n=15), and training (n=15) groups, which were assessed while performing four laparoscopic tasks on the CLS. The initial and final assessments of all tasks were performed blindly by two experienced surgeons using the Global Operative Assessment of Laparoscopic Skills (GOALS) and a task-specific checklist. At the end of the study, the subjects completed an anonymous survey. The experienced group performed all of the tasks faster, with higher GOALS and checklist scores than the training and control groups (p≤.001). In the second assessment, the training group reduced the time needed to complete all of the tasks and obtained significantly higher GOALS and checklist scores than the control group. The participants perceived the CLS and its training program to be positive or very positive. The CLS and its training program demonstrated content and construct validity, supporting the suitability of the simulator for training and teaching and its ability to distinguish the degree of experience in laparoscopic surgery among veterinarians. In addition, face validity showed that the veterinarians fully accepted the CLS's usefulness for learning basic laparoscopic skills.

Hemostatic sponge effect on adhesion prevention in a porcine model

BACKGROUND

In this work, we aimed to assess the preventive effect of an absorbable hemostatic collagen sponge (HCS) on the reduction of postsurgical gynecological adhesions in a porcine model.

MATERIALS AND METHODS

Forty female pigs were subjected to a right uterine horn myotomy and left uterine horn deserosation. They were randomly divided into two groups, HCS application and control, which were rearranged into laparotomy and laparoscopy groups. Resulting adhesions were macroscopically and microscopically semiquantitatively analyzed after a 5 mo follow-up.

RESULTS

The incidence of adhesion-free animals did not significantly differ between groups, although it increased when the HCS was placed in both laparotomy (from 10%-12.5%) and laparoscopy groups (from 20%-50%). On the contrary, a significant reduction was observed in adhesion severity when the HCS was applied in the laparotomy groups (P < 0.01). Regarding microscopic study, hemostatic sponge application significantly reduced the inflammation score in the laparoscopic approach (P < 0.01). Fibrosis, unlike inflammation, differs between both approaches. In the laparoscopic group, fibrosis was reduced with application of the HCS, whereas in the laparotomy group greater fibrosis was observed within the HCS group.

CONCLUSIONS

HCS has shown to be safe for gynecological use. Although number and extent of adhesions did not decrease with HCS, inflammation and adhesions' severity were reduced in the laparoscopic and laparotomy approaches, respectively.

Validation of a realistic simulator for veterinary gastrointestinal endoscopy training

This article reports on the face, content, and construct validity of a new realistic composite simulator (Simuldog) used to provide training in canine gastrointestinal flexible endoscopy. The basic endoscopic procedures performed on the simulator were esophagogastroduodenoscopy (EGD), gastric biopsy (GB), and gastric foreign body removal (FBR). Construct validity was assessed by comparing the performance of novices (final-year veterinary students and recent graduates without endoscopic experience, n=30) versus experienced subjects (doctors in veterinary medicine who had performed more than 50 clinical upper gastrointestinal endoscopic procedures as a surgeon, n=15). Tasks were scored based on completion time, and specific rating scales were developed to assess performance. Internal consistency and inter-rater agreement were assessed. Face and content validity were determined using a 5-point Likert-type scale questionnaire. The novices needed considerably more time than the experts to perform EGD, GB, and FBR, and their performance scores were significantly lower (p<.010). Inter-rater agreement and the internal validity of the rating scales were good. Face validity was excellent, and both groups agreed that the endoscopy scenarios were very realistic. The experts highly valued the usefulness of Simuldog for veterinary training and as a tool for assessing endoscopic skills. Simuldog is the first validated model specifically developed to be used as a training tool for endoscopy techniques in small animals.

Performance analysis on physical simulator of four different instrument setups in laparo-endoscopic single-site (LESS) surgery

BACKGROUND

Over the past decades, minimally invasive surgery has undergone continuous development due to the demand for scarless results, with laparo-endoscopic single-site (LESS) surgery constituting one of today's most favored alternatives. In this study, we aim to assess the relative technical difficulty and performance benefits of dynamic articulating and pre-bent instruments, either combined with conventional laparoscopic tools or not, during the completion of two basic tasks hands-on simulator.

METHODS

A total of 20 surgeons were included and performed two basic simulator tasks-coordination and cutting-carried out using four different combinations of LESS-designed and straight conventional laparoscopy instruments. Assessment took place before and after the completion of a 14-week training program. Performance data were objectively analyzed over video recordings with an adapted global rating scale (a-GRS) for performance evaluation, combined with a registry of total trial completion time.

RESULTS

In the coordination task, the worst performance scores (p < 0.001) and longest completion times (p < 0.001 on first assessment and p < 0.01 on last assessment) were obtained with the two dynamic articulating tip instruments. On the cut trials, no significant differences between the different setups were found in a-GRS scores. The two dynamic articulating tip instruments also constituted the most time-demanding setup on both assessment trials (p < 0.05). The use of two dynamic articulating tip instruments showed significant improvement with training in all measured parameters except for performance in the cut task, in which the increase in a-GRS score was not significant.

CONCLUSIONS

We conclude that the least adequate instrument set for initiation in LESS surgery is the one that combines two dynamic articulating tip instruments, as this has consistently obtained the worst results in all trials. Further data on more complex tasks and on a complete learning and skills-acquisition program must be obtained to confirm these findings.

Radiologic evaluation of bone loss at implants with biocide coated titanium abutments: a study in the dog

The objective of the present study is to evaluate bone loss at implant abutments coated with a soda-lime glass containing silver nanoparticles subjected to experimental peri-implantitis. Five beagle dogs were used in the experiments, 3 implants were installed in each quadrant of the mandibles. Glass/n-Ag coted abutments were connected to implant platform. Cotton floss ligatures were placed in a submarginal position around the abutment necks and the animals were subject to a diet which allowed plaque accumulation, and after 15 weeks the dogs were sacrificed. Radiographs of all implant sites were obtained at the beginning and at the end of the experimentally induced peri-implantitis. The radiographic examination indicated that significant amounts of additional bone loss occurred in implants without biocide coating, considering both absolute and relative values of bone loss. Percentages of additional bone loss observed in implants dressed with a biocide coated abutment were about 3 times lower (p<0.006 distal aspect; and p<0.031 at mesial aspect) than the control ones. Within the limits of the present study it seems promising the use of soda-lime glass/nAg coatings on abutments to prevent peri-implant diseases.

Relevance of motion-related assessment metrics in laparoscopic surgery

INTRODUCTION

Motion metrics have become an important source of information when addressing the assessment of surgical expertise. However, their direct relationship with the different surgical skills has not been fully explored. The purpose of this study is to investigate the relevance of motion-related metrics in the evaluation processes of basic psychomotor laparoscopic skills and their correlation with the different abilities sought to measure.

METHODS

A framework for task definition and metric analysis is proposed. An explorative survey was first conducted with a board of experts to identify metrics to assess basic psychomotor skills. Based on the output of that survey, 3 novel tasks for surgical assessment were designed. Face and construct validation was performed, with focus on motion-related metrics. Tasks were performed by 42 participants (16 novices, 22 residents, and 4 experts). Movements of the laparoscopic instruments were registered with the TrEndo tracking system and analyzed.

RESULTS

Time, path length, and depth showed construct validity for all 3 tasks. Motion smoothness and idle time also showed validity for tasks involving bimanual coordination and tasks requiring a more tactical approach, respectively. Additionally, motion smoothness and average speed showed a high internal consistency, proving them to be the most task-independent of all the metrics analyzed.

CONCLUSION

Motion metrics are complementary and valid for assessing basic psychomotor skills, and their relevance depends on the skill being evaluated. A larger clinical implementation, combined with quality performance information, will give more insight on the relevance of the results shown in this study.

Cloning and expression of a sorghum gene with homology to maize vp1. Its potential involvement in pre-harvest sprouting resistance

Pre-harvest sprouting (PHS) in sorghum is related to the lack of a normal dormancy level during seed development and maturation. Based on previous evidence that seed dormancy in maize is controlled by the vp1 gene, we used a PCR-based approach to isolate two Sorghum bicolor genomic and cDNA clones from two genotypes exhibiting different PHS behaviour and sensitivity to abscisic acid (ABA). The two 699 amino acid predicted protein sequences differ in two residues at positions 341 (Gly or Cys within the repression domain) and 448 (Pro or Ser) and show over 80, 70 and 60% homology to maize, rice and oat VP1 proteins respectively. Expression analysis of the sorghum vp1 gene in the two lines shows a slightly higher level of vp1 mRNA in the embryos susceptible to PHS than in those resistant to PHS during embryogenesis. However, timing of expression was different between these genotypes during this developmental process. Whereas for the former the main peak of expression was observed at 20 days after pollination (DAP), the peak in the latter was found at later developmental stages when seed maturation was almost complete. Under favourable germination conditions and in the presence of fluridone (an inhibitor of ABA biosynthesis), sorghum vp1 mRNA showed to be consistently correlated with sensitivity to ABA but not with ABA content and dormancy.

Chromosome diversity of the genus Aotus from Colombia

Description of six Colombian karyomorphs is completed through an extensive cytogenetic characterization of 35 Aotus (owl monkeys) specimens. The description of a new karyomorph for Colombian Aotus by chromosome on Q, G, R, and C, sequential banding is included. Pairs of karyomorphs 2 and 3 and 6 and 9 with 2n of 54, and 50, respectively, as well as karyomorphs 7 and 8 with 46 and 58 chromosomes were strongly suspected to represent different species on the grounds of large karyotypic differences. A proposal for a chromosome nomenclature of Aotus karyomorphs that aims to clarify Aotus taxonomy is presented which achieves a precise correspondence of different banding patterns, based on Q, G, R, and C sequential banding and chromosome measurements. Although our contribution is not a universal nomenclature system, unique criteria for chromosome denomination within Aotus karyomorphs are established. Previous systems of chromosome nomenclature have not successfully addressed the nomenclature of chromosomes of the same karyotype.