Pregnancy and perinatal outcomes of early vs late selective termination in dichorionic twin pregnancy: systematic review and meta-analysis.

OBJECTIVE: To evaluate outcomes of dichorionic twin pregnancies undergoing early vs late selective termination of pregnancy (ST). METHODS: MEDLINE, EMBASE, CINAHL and the Web of Science databases were searched electronically up to March 2022. The primary outcome of this study was pregnancy loss prior to 24 weeks' gestation. The secondary outcomes included preterm birth (PTB) before 37, 34, and 32 weeks, preterm prelabor rupture of membranes (PPROM), gestational age (GA) at delivery, Cesarean delivery, mean birth weight, 5-min Apgar score < 7, overall neonatal morbidity and neonatal survival. Only prospective or retrospective studies reporting data on the outcome of early (before 18 weeks) vs late (at or after 18 weeks) ST in dichorionic twin pregnancies were considered suitable for inclusion. Quality assessment of the included studies was performed using the Newcastle-Ottawa scale for cohort studies. Random-effects head-to-head meta-analysis was used to analyze the data. RESULTS: Seven studies reporting on 649 dichorionic twin pregnancies were included in this systematic review. The risk of pregnancy loss prior to 24 weeks was significantly lower in dichorionic twin pregnancies undergoing early compared with late ST (1% vs 8%; odds ratio (OR), 0.25 (95% CI, 0.10-0.65); P = 0.004). The risk of PTB was significantly lower in dichorionic twin pregnancies undergoing early compared with late ST when considering PTB before 37 weeks (19% vs 45%; OR, 0.36 (95% CI, 0.23-0.57); P < 0.00001), before 34 weeks (4% vs 19%; OR, 0.24 (95% CI, 0.11-0.54); P = 0.0005) and before 32 weeks (4% vs 20%; OR, 0.21 (95% CI, 0.05-0.85); P = 0.03). The mean birth weight was significantly greater in the early-ST group (mean difference (MD), 392.2 g (95% CI, 59.1-726.7 g); P = 0.02), as was the mean GA at delivery (MD, 2.47 weeks (95% CI, 0.04-4.91 weeks); P = 0.049). There was no significant difference between dichorionic twin pregnancies undergoing early compared with late ST in terms of PPROM (P = 0.27), Cesarean delivery (P = 0.38), 5-min Apgar score < 7 (P = 0.35) and neonatal survival of the non-reduced twin (P = 0.54). CONCLUSIONS: The risk of pregnancy loss prior to 24 weeks and the rate of PTB before 37, 34 and 32 weeks were significantly higher in dichorionic twin pregnancies undergoing late vs early ST, thus highlighting the importance of early diagnosis of fetal anomalies in twin pregnancies. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Optimal timing for blastomere biopsy of 8-cell embryos for preimplantation genetic diagnosis.

STUDY QUESTION: What is the optimal timing for blastomere biopsy during the 8-cell stage, at which embryos will have the best implantation potential? SUMMARY ANSWER: Fast-cleaving embryos that are biopsied during the last quarter (Q4) of the 8-cell stage and are less affected by the biopsy procedure, and their implantation potential is better than that of embryos biopsied earlier during the 8-cell stage (Q1-Q3). WHAT IS KNOWN ALREADY: Blastomer biopsy from cleavage-stage embryos is usually performed on the morning of Day 3 when the embryos are at the 6- to 8-cell stage and is still the preferred biopsy method for preimplantation genetic diagnosis (PGD) for monogentic disorders or chromosomal translocations. Human embryos usually remain at the 8-cell stage for a relatively long 'arrest phase' in which cells grow, duplicate their DNA and synthesize various proteins in preparation for the subsequent division. STUDY DESIGN, SIZE, DURATION: This is a retrospective cohort study. The study group (195 embryos) included all 8-cell stage embryos that underwent blastomere biopsy for PGD for monogenetic disorders and chromosomal translocations in our unit between 2012-2014 and cultured in the EmbryoScope until transfer. The control group (115 embryos) included all embryos that underwent intracytoplasmic sperm injection without a biopsy during the same period. PARTICIPANTS/MATERIALS, SETTING, METHODS: The 8-cell stage was divided into four quarters: the first 5 h post-t8 (Q1), 5-10 h post-t8 (Q2), 10-15 h post-t8 (Q3) and at 15-20 h post-t8 (Q4). Non-biopsied control embryos were divided into four equivalent quarters. Embryos were evaluated for timing of developmental events following biopsy including timing of first cleavge after biopsy, timing of comapction (tM) and start of blastulation (tSB). Timing of these events were compared between PGD and control embryos, as well as with 56 PGD implanted embryos with Known Implantation Data (PGD-KID-positive embryos). MAIN RESULTS AND THE ROLE OF CHANCE: Embryos that were biopsied during Q3 (10-15 h from entry into 8-cell stage) were delayed in all three subsequent developmental events, including first cleavage after biopsy, compaction and start of blastulation. In contrast, these events occurred exactly at the same time as in the control group, in embryos that were biopsied during Q1, Q2 or Q4 of the 8-cell stage. The results show also that embryos that were biopsied during Q1, Q2 or Q3 of the 8-cell stage demonstrated a significant delay from the biopsied implanted embryos already in t8 as well as in tM and tSB. However, embryos that were biopsied during Q4 demonstrated dynamics similar to those of the biopsied implanted embryos in t8 and tM, and a delay was noticed only in the last stage of tSB. LIMITATIONS, REASONS FOR CAUTION: This is a retrospective study that is limited to the timing of biopsy that is routinely performed in the IVF lab. A prospective study in which biopsy will be performed at a desired timing is needed in order to differ between the effect of biopsy itself and the cleavage rate of the embryo. WIDER IMPLICATIONS OF THE FINDINGS: Our findings showed that blastomere biopsy can be less harmful to further development if it is carried out during a critical period of embryonic growth, i.e during Q4 of the 8-cell stage. They also demonstrated the added value of time-lapse microscopy for determining the optimal timing for blastomere biopsy. STUDY FUNDING/COMPETING INTEREST(S): The study was funded by the routine budget of our IVF unit. TRIAL REGISTRATION NUMBER: N/A.

Quality of life of immigrant and non-immigrant infertile patients in a publicly funded in vitro fertilisation program: a cross-sectional study.

OBJECTIVE: To investigate whether there are differences in fertility quality of life (FertiQoL) and socio-demographic characteristics between immigrants and non-immigrant patients attending a government-funded fertility program. DESIGN: Cross-sectional study. SETTING: McGill University Reproductive Center in Montreal, Canada, at a time when governmental funding for in vitro fertilisation (IVF) was provided to all residents. POPULATION: All infertile patients, males and females, attending the center between March and July 2015. METHODS: Patients were invited to complete anonymous questionnaires which included socio-demographic items and the validated FertiQoL questionnaire. MAIN OUTCOME MEASURES: Socio-demographic characteristics (age, gender, marital state, infertility type & duration, previous IVF attempts; education, employment, income, ethnicity, spoken languages) and FertiQoL scores. RESULTS: In all, 1020 patients completed the questionnaires; of these, 752 (77.7%) non-immigrant Canadian citizens and 215 (22.3%) resident immigrants were included in the analysis. Median duration in Canada for immigrants was 4 years. Immigrants were more likely to have university/graduate degrees (75% versus 64%), to be unemployed (37% versus 13.1%) and to have lower annual household incomes (72.8% versus 39.5%, all P < 0.05). They also reported poorer QoL and achieved significantly lower scores in the emotional, mind/body, social, treatment and total FertiQoL domains. Multivariate analysis showed male gender, lower education level and Caucasian/European ethnicity to be significantly associated with higher QoL. CONCLUSIONS: Despite governmental funding of IVF, immigrants experience reduced fertility QoL, implying cost is not the only barrier to IVF use. The reduced QoL may stem from cross-cultural differences in infertility perception. This population may be at greater risk for depression and anxiety and should be flagged accordingly. TWEETABLE ABSTRACT: Immigrants' fertility QoL is lower despite publicly funded IVF implying cost is not the only barrier to IVF use.

Timing embryo biopsy for PGD - before or after cryopreservation?

OBJECTIVE: Pre-implantation genetic diagnosis (PGD) is required in order to screen and diagnose embryos of patients at risk of having a genetically affected offspring. A biopsy to diagnose the genetic profile of the embryo may be performed either before or after cryopreservation. The aim of this study was to determine which biopsy timing yields higher embryo survival rates. STUDY DESIGN: Retrospective cohort study of all PGD patients in a public IVF unit between 2010 and 2013. Inclusion criteria were patients with good-quality embryos available for cryopreservation by the slow freezing method. Embryos were divided into two groups: biopsy before and biopsy after cryopreservation. The primary outcome was embryo survival rates post thawing. RESULTS: Sixty-five patients met inclusion criteria. 145 embryos were biopsied before cryopreservation and 228 embryos were cryopreserved and biopsied after thawing. Embryo survival was significantly greater in the latter group (77% vs. 68%, p < 0.0001). CONCLUSION: Cryopreservation preceding biopsy results in better embryo survival compared to biopsy before cryopreservation.

Correlation of cancer risk evaluation and early detection (CADET) scores with abnormal ultrasonographic ovarian findings.

OBJECTIVE: To determine the utility of a modified version of ovarian cancer-focused cancer risk evaluation and early detection (CADET) scores as a screening tool for ultrasonographic ovarian findings. STUDY DESIGN: Prospective pilot study. MAIN OUTCOME MEASURES: CADET scores were compared with abnormal ultrasonographic ovarian findings of peri- and postmenopausal women who attended their gynecologist for a routine check-up. The women filled in the CADET questionnaire before seeing their gynecologists who were blinded to the CADET results. The women whom they referred for pelvic transvaginal ultrasonographic examination comprised the study group. The results of their scans were compared with their CADET scores. RESULTS: Of the 181 peri- and postmenopausal women who were candidates for this study, 154 were referred for ultrasonography, of whom 38 (24%, Group A) had abnormal ovarian scans (30 simple cysts and 8 complex findings). The other 116 (76%) women had normal sonograms (Group B). Demographic characteristics were similar for both groups. Thirteen Group A women (34%) and 52 Group B women (45%) had positive CADET scores (p = NS). The average group CADET scores were also not significantly different (0.8 +/- 1.7 for Group A and 1.7 +/- 2.5 for Group B). CONCLUSION: CADET scores did not correlate with abnormal ultrasonographic ovarian findings.

Risk factors for severe perineal injury during childbirth: a case-control study of 60 consecutive cases.

AIM: The study aimed to evaluate the current risk factors for severe perineal tears in a single university-affiliated maternity hospital. METHOD: An obstetric database of 31 784 consecutive women who delivered from January 2007 to December 2009 was screened for cases of third-degree or fourth-degree perineal tears. Four controls, matched by time of delivery, were selected for each case of third- or fourth-degree perineal tear. Maternal and obstetric parameters were analyzed and compared between the study and control groups. RESULTS: Sixty women (0.25% of all vaginal deliveries) had a third-degree (53 women) or a fourth-degree (seven women) perineal tear. The control group comprised 240 matched vaginal deliveries without severe tears. Primiparity, younger maternal age, Asian ethnicity, longer duration of second stage of labour, vacuum-assisted delivery and heavier newborn birth weight were significantly more common among women who had third- or fourth-degree perineal tears. Of the variables that were found to be statistically significant in the univariate analysis, only primiparity (OR = 2.809, 95% CI: 1.336-5.905), vacuum delivery (OR = 10.104, 95% CI: 3.542-28.827) and heavier newborn birth weight (OR = 1.002, 95% CI: 1.001-1.003) were found to be statistically significant independent risk factors for severe perineal trauma. CONCLUSION: Identification of women at risk may facilitate the use, or avoidance, of certain obstetric interventions to minimize the occurrence of childbirth-associated perineal trauma.

Post-hysterectomy pelvic fluid collection: is it associated with febrile morbidity?

We evaluated the clinical significance and possible association of febrile morbidity with sonographically detected post-hysterectomy fluid collections. Transvaginal ultrasound examinations were performed to assess the presence of fluid collections and correlated to clinical data. Fluid collection was detected in 27 (64%) women at postoperative day 2, in 15 (35%) at postoperative day 7 and in 5 (12%) at the fourth to fifth postoperative week. Febrile morbidity was not related to the presence, location or size of fluid collection. Postoperative pelvic fluid collections are common sonographic findings after hysterectomy and are not associated with postoperative febrile morbidity.

Simian virus 40 illegitimate recombination occurs near short direct repeats.

We have analysed nucleotide sequences at the junction between simian virus 40 (SV40) and cellular DNA in the Fisher rat transformed line tsA30-N2. This line contains a single insertion of one complete SV40 genome with a terminal duplication of 267 nucleotides, the recombination sites being located at nucleotides 439 and 705 in the late region of SV40. These two positions are located within short direct repeats in the virus genome. In order to test the significance of such repeats with respect to illegitimate recombination events, we analysed two series of published sequences of SV40 recombination sites: the first one consists of eight SV40 insertion endpoints derived from four SV40-transformed cell lines; the second one consists of 18 junction points from SV40 evolutionary variants. Our analysis demonstrates that in both cases, recombination preferentially takes place near short direct repeats in the virus genome. A model involving a "slipped mispairing" mechanism is proposed in order to account for this finding.

The use of fibronectin-coated polyvinyl chloride microtest plates to detect monoclonal antibody-binding to adherent tumor cells.

This report describes the use of fibronectin-coated polyvinyl chloride (PVC) plates as a time-saving modification in an assay measuring antibody-binding to live adherent tumor cells. Three cell lines (A-431, Colo 16 and UCLA-SO-P3) derived from human squamous cell carcinomas (SCC) and forming monolayers in cultures were plated onto flexible PVC microtest plates rather than the commonly used rigid polystyrene plates. In PVC plates, two of the three cell lines (A-431 and Colo 16) grew as foci of clumped cells instead of monolayers. Coating of the plates with plasma fibronectin restored the monolayer morphology. [125I]Staphylococcal protein A radioimmunoassays measuring the binding of a monoclonal anti-beta 2 microglobulin antibody to the cells were slightly, but consistently, more sensitive in coated PVC plates than in polystyrene plates. In contrast, the sensitivity of the radioimmunoassay was remarkably constant when the assay was performed on the third cell line (UCLA-SO-P3), which formed monolayers in any of the conditions tested. Preliminary experiments suggested that the inability to form monolayers on uncoated PVC plates correlates with the amount of fibronectin associated with the cell surface.

A computer-controlled ventilator weaning system. A clinical trial.

The purpose of this study was to determine if a computer-directed weaning system could wean patients with complex medical problems from mechanical ventilation and appropriately respond to signs of respiratory failure more effectively than traditional physician-directed weaning methods. In a prospective, randomized, controlled study, we tested the system in 15 patients who had required prolonged mechanical ventilation and met predetermined weaning tests. Patients were randomly assigned to one of two groups: (1) automatic, computer-directed weaning or (2) physician-controlled weaning. The computer-directed system decreased or increased the synchronized intermittent mandatory ventilation rate and pressure support (PS) based on predetermined limits of patient respiratory rate (RR) and tidal volume (TV). Pulse oximeter oxygen saturation was monitored, and alarms were triggered by an oxygen saturation of < 90 percent. In the physician control group, weaning progressed with SIMV rate and PS reduction, as judged appropriate by the physician. Nine patients were assigned to the computer group; six patients were assigned to the control group. The average patient age was 64.8 +/- 14.9 years for the computer group, 65.2 +/- 22.7 years for the control group. The average time on mechanical ventilation prior to weaning was 13.4 +/- 7.8 days for the computer group and 14.5 +/- 11.1 days for the control group. Seven of the nine computer group patients weaned within 48 h of the study, with an average time to wean of 18.7 +/- 5.9 h. All seven were breathing spontaneously 48 h after weaning. Two of the six control group patients weaned within 48 h of the study, with an average time of 25.6 +/- 5.6 h. Both patients who weaned were placed back on mechanical ventilation within 30 h. The number of arterial blood gas samples drawn during the study was 1.4 +/- 0.7 for the computer group, 7.2 +/- 4.3 for the control group. The number of minutes per hour outside acceptable limits of RR > 30, RR < 8, or TV < 5 ml/kg was 3.2 +/- 2.8 min for the computer group and 6.6 +/- 4.1 min for the control group. The study suggests that use of the computer-directed weaning system results in fewer arterial blood gas samples, shorter weaning times, and less time spent outside acceptable RR and TV parameters.

A computer-controlled ventilator weaning system.

Weaning of patients from mechanical ventilation is a time-consuming, labor-intensive process. Because most weaning decisions are based on objective data, we tested a computer-directed weaning system on postoperative patients. We developed an automatic, computer-controlled ventilator weaning system which interfaces a laptop computer to a ventilator and a pulse oximeter. The laptop computer program accesses patient data through the ventilator and pulse oximeter to make weaning decisions. The computer directly controls the ventilator through an interface developed for this system. We tested the system in nine postoperative patients who met the following criteria: negative inspiratory force less than or equal to -20 cm H2O, vital capacity greater than 10 ml/kg, inspired oxygen concentration less than or equal to 40 percent, and satisfactory arterial blood gas parameters (pH between 7.32 and 7.48, PCO2 between 32 and 48, and oxygen saturation greater than or equal to 90 percent). The computer decreased the SIMV rate by 2 breaths/min every 5 min until a rate of 2 breaths/min was reached, then decreased pressure support by 4 cm H2O every 5 min as long as the patient met the following criteria: respiratory rate between 8 and 25 breaths/min, minute ventilation between 6 and 14 L, and pulse oximeter oxygen saturation greater than or equal to 90 percent. If unsatisfactory weaning criteria were noted, the system automatically returned the patient to the previous weaning level. We successfully weaned nine patients using the system. Additional studies are underway to determine if this system can be used in medical patients. We believe this computer-controlled ventilator weaning system can be used successfully in patients requiring mechanical ventilation and may decrease the time and cost associated with the care of these patients.

Treponema pallidum and Helicobacter pylori recovered in a case of chronic active gastritis.

A 49-year-old man complaining of epigastric pain underwent endoscopy, during which thickened stomach folds below the fundus were observed. Microscopic examination of gastric tissue biopsy specimens revealed chronic active gastritis. Dieterle stain revealed overwhelming numbers of "corkscrew-like" spirochetes. These were proved to be consistent with Treponema pallidum. A comprehensive study of the tissue revealed the added presence of Helicobacter pylori. This appears to be the first case report describing the involvement of H. pylori and T. pallidum together in a case of chronic active gastritis.

Human necrotizing splenitis caused by Borrelia burgdorferi.

A 25-year-old Hispanic male presented to the emergency room with complaints of severe left upper quadrant pain. Physicians determined that the patient had an acute inflammatory process with a possible diagnosis of splenic abscess. A splenectomy was performed. Histologic examination of the tissue sections revealed extensive necrosis and inflammation, but no etiologic agent was discernible. Microbiologic cultures of the tissue had negative results. A Dieterle silver stain revealed an overwhelming number of spirochetal bacteria most closely resembling Borrelia spp. The patient's serum was tested for serologic evidence of antibody to Borrelia burgdorferi with the following results; by indirect fluorescent antibody 1:32; by enzyme-linked immunosorbent assay for IgM, 1:320; and Western blotting had positive results for the presence of B. burgdorferi outer-surface protein antibodies. This is the first human case report of an acute necrotizing splenitis resulting from B. burgdorferi.

Lower extremity percutaneous transluminal angioplasty: multifactorial analysis of morbidity and mortality.

We analyzed the outcome of 202 percutaneous transluminal angioplasty (PTA) procedures performed between 1983 and 1989 to quantitate procedural risks and define factors associated with suboptimal results or immediate clinical failure. Premorbid factors studied included age, sex, treatment of single versus multiple lesions, stenoses versus occlusions, premorbid status of the limb (claudication vs limb threat), and most distal level of PTA. Adverse outcomes included complications (hematoma, acute occlusion, or thrombosis of PTA site, distal embolization, failure to dilate or cross, arterial dissection, rupture, and significant systemic derangement), major amputations (below knee and above knee), and deaths. There were 66 complications (32.7%), 22 amputations (10.9%), and 12 deaths (5.9%) in our series. Logistic regression analysis revealed that the major predictive variable for the occurrence of a complication (p = 0.002), and the only predictive variable for the outcomes of amputation and death (p = 0.0001 and p = 0.0139, respectively), was the premorbid clinical status of the limb. Lower extremity PTA is not an intrinsically benign procedure and is associated with a significant risk of complication, amputation, and procedure-associated death. These adverse outcomes cluster in patients with limb threat. Therefore it may be reasonable to restrict the use of PTA to patients with claudication and strictly selected cases of limb threat.

Fatal gastric artery dissection and rupture occurring as a paraesophageal mass: a case report and literature review.

Gastric artery aneurysms are rare, and the majority occur as life-threatening hemorrhage with few premonitory signs or symptoms. We report an unusual hemorrhagic manifestation of a ruptured gastric artery aneurysm, occurring as a pleural effusion and an apparent paraesophageal mass. Acute intraperitoneal and mediastinal bleeding from the extravisceral portion of the left gastric artery resulted in hemorrhagic shock, prompting an emergency laparotomy. Extensive medial degeneration in the gastric artery probably contributed to dissection and rupture.

Migration of adult human vascular endothelial cells: effect of extracellular matrix proteins.

An ideal vascular prosthetic graft should support rapid endothelial coverage and allow maximal rates of endothelial cell migration on its surface. To study this we modified and developed a method to measure rates of migration of adult human vascular endothelial cells (AHVECs) on test surfaces using an O-ring fence technique. We measured the rates of AHVEC migration on a variety of extracellular matrix proteins of interest because of their ability to support cell attachment. AHVECs, initially constrained in rings with an area of 0.62 cm2 (day 0), were allowed to migrate radially, and area coverage was measured after 7 days. The greatest areas of migration were seen on fibronectin (1.20 cm2) and gelatin (1.29 cm2) when compared with control (polystyrene [0.97 cm2]), p less than 0.01, p less than 0.05. Migration on laminin and prepared extracellular matrix from AHVEC was not statistically different from that of controls. Of extracellular matrix proteins studied in our system, a gelatin substrate in the presence of serum resulted in maximal rates of AHVEC migration.

Use of tritiated thymidine as a marker to compare the effects of matrix proteins on adult human vascular endothelial cell attachment: implications for seeding of vascular prostheses.

We have developed a technique to measure attachment of adult human vascular endothelial cells to test surfaces with tritiated thymidine used as a marker. With this technique, we measured attachment of adult human vascular endothelial cells to a series of extracellular matrix proteins, including fibronectin-coated (10 micrograms/cm2), laminin-coated (10 micrograms/cm2), and collagen-coated (1% gelatin) surfaces because of the role of these proteins in promoting cell attachment and growth. For a typical experiment, in the presence of serum, initial attachment (at 1 hour) was greatest on fibronectin-coated (63%) and gelatin-coated (60%) tissue culture plastic (polystyrene) and was least on laminin-coated (28%) or untreated polystyrene (18%). The data suggest that fibronectin, either alone, or with a more complex combination of extracellular components may need to be present on prosthetic surfaces to produce maximal cell attachment and subsequent growth to confluence in vivo. The described method of measuring attachment is independent of surface properties, ensures complete recovery of cells, and will allow systematic exploration of those properties that best support human endothelial cell attachment to vascular prosthetic surfaces.

Postsurgical changes in arterial compliance.

Mismatch in elasticity between artery and graft, a possible contributing factor to graft failure, has traditionally been believed to be caused by the graft. Compliance of the artery and/or graft may change after surgery, resulting in a different compliance mismatch. To study the arterial contribution to compliance mismatch, we measured compliance-pressure (CP) curves noninvasively in the femoral arteries of five dogs. One femoral artery was then simply exposed, and the incision was closed. Repeated CP curves were obtained after 24 hours, and after 1, 2, 3, and 4 weeks. Compliance remained normal after 24 hours, but by one week compliance of the dissected arteries had dropped significantly at all pressures between 70 and 120 mm Hg. Compliance reached a minimum after two weeks and remained low until after four weeks. Postsurgical arterial stiffening causes a significant decrease of arterial-graft compliance mismatch and may suggest an upper limit for synthetic graft compliance.

Adult human vascular endothelial cell attachment and migration on novel bioabsorbable polymers.

We studied the ability of polymers from which vascular prostheses (VPs) are or could be fabricated to support attachment and migration of adult human vascular endothelial cells (AHVECs) in an in vitro system. Polymers included Mylar, Teflon, two novel bioabsorbable polymers with different biologic half-lives (BR1 and BR2), and an elastic nonabsorbable biocompatible polymer (EBN). Both BR1, BR2, and EBN supported AHVEC attachment well (56%, 62%, and 71%, respectively, of plated cells at one hour, respectively) but differed in their ability to support AHVEC migration. The AHVECs attached less well to Mylar and Teflon (39% and 21%), and in no case were AHVECs observed to grow or migrate on either of these polymers. This finding correlates with the clinical observation that VPs fabricated from Mylar and Teflon uniformly fail to develop an endothelial cell lining after implantation in vivo. Future VPs, fabricated from materials chosen for their ability to support AHVEC attachment, growth, and migration in vitro, might better support a spontaneous endothelial cell lining after implantation in humans.

A new RNA-friendly fixative for the preservation of penaeid shrimp samples for virological detection using cDNA genomic probes.

In situ hybridization analysis of shrimp histological sections, utilizing Taura syndrome virus (TSV) specific cDNA probes, is the most sensitive diagnostic technique presently available for the detection of this penaeid shrimp viral disease. However, false negative genomic probe results are obtained frequently from samples of Pacific white shrimp, Penaeus vannamei, that have been preserved with Davidson's AFA (acetic acid, formaldehyde, alcohol) fixative and that, otherwise, demonstrate pathognomonic TSV lesions by routine histology. This problem was linked to prolonged storage of shrimp samples in Davidson's fixative, which is highly acidic (pH approximately 3.5-4). Degradation of TSV genomic RNA was hypothesized to be due to either fixative- induced acid hydrolysis and/or acidophilic endogenous ribonuclease activity. Routine H and E histology and in situ hybridization analyses were conducted on equal numbers of TSV infected P. vannamei juveniles that were preserved for four different time periods (2, 6, 10 and 14 days) with either Davidson's fixative or a new, near neutral (pH approximately 6.0-7.0), RNA-friendly fixative (R-F) that was developed by the authors. In situ hybridization assays were conducted with and without R Nase precautions and all of the samples tested contained moderate to severe TSV lesions by routine histology. Davidson's preserved samples produced weak TSV probe signals after 2 days fixation, but did not react with the probes in those samples that were stored for > 6 days in the fixative. In contrast, TSV was detectable by gene probe in all of the time treatment samples preserved with the new R-F fixative. Equivalent in situ hybridization results were obtained when the same samples were analyzed in the absence of RNase-free conditions. These findings suggest that TSV RNA is degraded when samples are stored in an acidic fixative, such as Davidson's, for more than 2 days and that this problem can be prevented through preservation of shrimp samples with R-F fixative. The efficacy of this new fixative is demonstrated and the results show that RNase-free conditions are not necessary for conducting TSV in situ hybridization analyses.