Effects of endocrine disorders on maxillary and mandibular growth in Colombian children and adolescents: a cross-sectional study

OBJECTIVE

To establish the influence of overweight/obesity, medicated hypothyroidism, and medicated non-syndromic hypogrowth on maxillary and mandibular growth.

MATERIALS AND METHODS

The relation between 10 craniofacial anthropometric measurements and hypothyroidism (n = 216), overweight/obesity (n = 108), and non-syndromic hypogrowth (n = 250) were evaluated in patients aged 1-19 years and a control group of healthy patients (n = 587). A subgroup analysis was performed at the peak growth in all groups.

RESULTS

Patients with overweight/obesity and hypothyroidism showed increased craniofacial growth, while hypogrowth patients showed differences in zygomatic width and nasal base growth. Females with hypothyroidism and non-syndromic hypogrowth showed decreased head circumference at peak growth. Several anthropometric measurements were increased in patients with overweight/obesity, including head circumference. When all age groups were analyzed, overweight/obese and hypothyroidism patients showed increased zygomatic width while decreased hypogrowth. Overall, most craniofacial anthropometric measurements in overweight/obese patients were increased. Finally, the peak growth in males with hypothyroidism and subjects with non-syndromic hypogrowth was delayed compared to the control group (p < 0.05).

CONCLUSIONS

Children and adolescents with overweight/obesity and endocrine disorders showed alterations in craniofacial growth. Clinicians must be aware that the growth peak in these patients may be delayed when planning maxillary and mandibular orthopedic treatment.

Water disinfection by orifice-induced hydrodynamic cavitation

Hydrodynamic Cavitation (HC) is considered as a promising water-disinfection technique. Due to the enormous complexity of the physical and chemical processes at play, research on HC reactors is usually carried out following an empirical approach. Surprisingly, past experimental studies have never been designed on dimensional-analysis principles, which makes it difficult to identify the key processes controlling the problem, isolate their effects and scale up the results from laboratory to full-scale scenarios. The present paper overcomes this issue and applies the principles of dimensional analysis to identify the major non-dimensional parameters controlling disinfection efficacy in classical HC reactors, namely orifice plates. On the basis of this analysis, it presents results from a new set of experiments, which were designed to isolate mainly the effects of the so-called cavitation number (σ_v). Experimental data confirm that the disinfection efficacy of orifice plates increases with decreasing σ_v. Finally, in order to discuss the significance of the results presented herein and frame the scope of future research, the present paper provides an overview of the drawbacks associated with dimensional analysis within the context of HC.

P5249Comprehensive invasive and non-invasive assessment of coronary artery lesions with and without hemodynamic significance

Background

There is limited knowledge about specific morphological parameters beyond the degree of stenosis to further characterize hemodynamically relevant coronary lesions.

Objective

The goal of this study was to identify certain morphological or molecular characteristics that distinguish hemodynamically significant from non-significant coronary lesions using various invasive and non-invasive measures.

Methods

This clinical study included patients with symptoms suggestive of CAD who underwent native T1-weighted CMR and gadofosveset-enhanced CMR as well as invasive coronary angiography between 2015 and 2016. OCT of the culprit vessel to determine the plaque type was performed in a subset of patients. Functional relevance of all lesions was examined using quantitative flow reserve (QFR-Angio). Hemodynamically significant lesions were defined as lesions with a QFR <0.8. Signal intensity (contrast-to-noise ratios; CNRs) on native T1-weighted CMR and gadofosveset-enhanced CMR was defined as a measure for intraplaque hemorrhage and endothelial permeability respectively.

Results

Overall 13 patients (n=28 coronary segments) were included, whose invasive coronary angiograms projections were eligible for QFR analysis. Segments containing lesions with a QFR <0.8 (n=9) were associated with significantly higher signal enhancement on Gadofosveset-enhanced CMR as compared to segments containing a hemodynamically non-relevant lesions (lesion-QFR>0.8; n=19) (7.0±4.9 vs. 3.0±2.6; p=0.02). No differences in signal enhancement were seen on native T1-weighted CMR (2.1±4.3 vs. 3.3±4.1; p=0.24). 66,7% (4 out of 6) of all vulnerable plaque and 33.3% (2 out of 6) of all non-vulnerable plaque (fibroatheroma) as assessed by OCT were hemodynamically significant lesions.

Conclusion

The findings of this small feasibility study suggest that hemodynamically significant lesions are more advanced and associated with a higher grade of endothelial permeability while the presence of intraplaque hemorrhage may not be associated with hemodynamically relevant coronary lesions.

AERMOD as a Gaussian dispersion model for planning tracer gas dispersion tests for landfill methane emission quantification

The measurement of methane emissions from landfills is important to the understanding of landfills' contribution to greenhouse gas emissions. The Tracer Dispersion Method (TDM) is becoming widely accepted as a technique, which allows landfill emissions to be quantified accurately provided that measurements are taken where the plumes of a released tracer-gas and landfill-gas are well-mixed. However, the distance at which full mixing of the gases occurs is generally unknown prior to any experimental campaign. To overcome this problem the present paper demonstrates that, for any specific TDM application, a simple Gaussian dispersion model (AERMOD) can be run beforehand to help determine the distance from the source at which full mixing conditions occur, and the likely associated measurement errors. An AERMOD model was created to simulate a series of TDM trials carried out at a UK landfill, and was benchmarked against the experimental data obtained. The model was used to investigate the impact of different factors (e.g. tracer cylinder placements, wind directions, atmospheric stability parameters) on TDM results to identify appropriate experimental set ups for different conditions. The contribution of incomplete vertical mixing of tracer and landfill gas on TDM measurement error was explored using the model. It was observed that full mixing conditions at ground level do not imply full mixing over the entire plume height. However, when full mixing conditions were satisfied at ground level, then the error introduced by variations in mixing higher up were always less than 10%.

Reducing deposition of encrustation in ureteric stents by changing the stent architecture: A microfluidic-based investigation

Ureteric stents are clinically deployed to retain ureteral patency in the presence of an obstruction of the ureter lumen. Despite the fact that multiple stent designs have been researched in recent years, encrustation and biofilm-associated infections remain significant complications of ureteral stenting, potentially leading to the functional failure of the stent. It has been suggested that "inactive" side-holes of stents may act as anchoring sites for encrusting crystals, as they are associated with low wall shear stress (WSS) levels. Obstruction of side-holes due to encrustation is particularly detrimental to the function of the stent, since holes provide a path for urine to by-pass the occlusion. Therefore, there is an unmet need to develop novel stents to reduce deposition of encrusting particles at side-holes. In this study, we employed a stent-on-chip microfluidic model of the stented and occluded ureter to investigate the effect of stent architecture on WSS distribution and encrustation over its surface. Variations in the stent geometry encompassed (i) the wall thickness and (ii) the shape of side-holes. Stent thickness was varied in the range 0.3-0.7 mm, while streamlined side-holes of triangular shape were evaluated (with a vertex angle in the range 45°-120°). Reducing the thickness of the stent increased WSS and thus reduced the encrustation rate at side-holes. A further improvement in performance was achieved by using side-holes with a triangular shape; notably, a 45° vertex angle showed superior performance compared to other angles investigated, resulting in a significant increase in WSS within "inactive" side-holes. In conclusion, combining the optimal stent thickness (0.3 mm) and hole vertex angle (45°) resulted in a ∼90% reduction in encrustation rate within side-holes, compared to a standard design. If translated to a full-scale ureteric stent, this optimised architecture has the potential for significantly increasing the stent lifetime while reducing clinical complications.

Microbial community analysis of fouled reverse osmosis membranes used in water recycling

Biofouling on RO membranes has major cost implications in water reclamation. In this study membranes and water samples were collected from a RO pilot-plant operated on two sites to study the differences in microbial communities in order to develop a better understanding of the biofouling. For the two sites studied, the examination of the front membrane of the first stage and the tail membrane of the second stage of the RO train using 16S rRNA gene-based molecular technique showed that bacteria were similar on both stages and no significant effect of the membrane location within the RO train on the biofilm development could be discerned. However, the comparison of the identified bacteria from membrane samples between the two sites showed that each site is specific, leading to a different composition of microbial communities. The different nutrient concentrations in the RO feed water due to the different biological pre-treatments are one potential explanation for the observed differences in the microbial communities. Seasonal variations also play a major role in the development of microbial communities as shown by the significant differences observed between the communities measured in the samples in winter and summer on the second site. The results did not show similarity between the species identified on the RO membranes and in the feed water. Hence, the relationship of microbial community between the water generated during the pre-treatment process and RO membranes is not obvious. From this study, results showed that there is an actual need to investigate the development of microbial communities on membrane surface in real conditions in order to suggest tailored solutions for biofouling control and removal.

A simple new non-invasive sweat indicator test for the diagnosis of diabetic neuropathy

A simple non-invasive indicator test (Neuropad(®)) has been developed for the assessment of sweating and, hence, cholinergic innervation in the diabetic foot. The present review summarizes current knowledge on this diagnostic test. The diagnostic ability of this test is based on a colour change from blue to pink at 10 min, with excellent reproducibility, which lends itself to patient self-examination. It has a high sensitivity (65.1-100%) and negative predictive value (63-100%), with moderate specificity (32-78.5%) and positive predictive value (23.3-93.2%) for the diagnosis of diabetic peripheral neuropathy. It also has moderate to high sensitivity (59.1-89%) and negative predictive value (64.7-91%), but low to moderate specificity (27-78%) and positive predictive value (24-48.6%) for the diagnosis of diabetic cardiac autonomic neuropathy. There are some data to suggest that Neuropad can detect early diabetic neuropathy, but this needs further evaluation. It remains to be established whether this test can predict foot ulceration and amputation, thereby contributing to the identification of high-risk patients.

Incretins in type 2 diabetes mellitus: cardiovascular and anti-atherogenic effects beyond glucose lowering

Type 2 diabetes mellitus is the most outspreading disease of the western world and it provides cardiovascular disease. During the past decade new drug categories were added to the already existing ones. Perhaps, the most outstanding, as promising, too, are glucagon-like peptide-1(GLP-1) analogues, which pinpointed at the incretin hormone system, targeting mainly at the postprandial hyperglycemia.It seemed that these novel drugs have beneficial effects on ischemic heart, heart failure,blood pressure, even on lipids and body weight in type 2 diabetics, considering them not only as another glucose lowering agent. A lot of recent studies investigate the potential relationship between GLP-1 and its possible cardioprotective and anti-atherogenic effects in type 2 diabetes and the present review discusses these effects of GLP-1.

Risk factors for ipsilateral reamputation in patients with diabetic foot lesions

This study aimed to examine the rates and risk factors for ipsilateral re-amputation in 121 patients with diabetic foot and prior amputation. Twenty-six (21.5%) patients required re-amputation during a mean follow-up of 18 months. Most re-amputations were performed within the first 6 months of the initial amputation. Re-amputation was more common among patients in whom the initial amputation had only affected one or two toes. Age (hazard ratio: 1.06) and heel lesions (hazard ratio: 2.69) were significantly associated with re-amputation. There is a high risk of re-amputation in the diabetic foot, especially within the first 6 months of the initial amputation, mainly due to poor selection of the original amputation level in an effort to save a greater part of the lower extremity. Patients 70 years and those with heel lesions are at greatest risk of re-amputation.

Radical resection of pancreatic cancer

BACKGROUND

Pancreatic adenocarcinoma (PCa) is a disease with dismal prognosis, and the only possibility of cure, albeit small, is based on the combination of complete resection with negative histopathological margins (R0 resection) with adjuvant treatment. Therefore, a lot of effort has been made during the last decade to assess the role of extensive surgery in both local recurrence and survival of patients with PCa.

DATA SOURCES

Medline search and manual cross-referencing were utilized to identify published evidence-based data for PCa surgery between 1973 and 2006, with emphasis to feasibility, efficacy, long-term survival, disease free survival, recurrence rates, pain relief and quality of life.

RESULTS

Extended surgery is safe and feasible in high volume surgical centers with comparable short-term results. Organ preserving surgery is a main goal because of quality of life reasons and is performed whenever possible from the tumor extent. Concerning long-term survival major vein resection does not adversely affect outcome. To date, there are no changes in long-term survival attributed to the extended lymph node dissection. However, there is a benefit in locoregional control with fewer local recurrences and extended lymphadenectomy allows better staging for the disease.

CONCLUSIONS

Extended PCa surgery is safe and feasible despite the inconclusive results in patient's survival benefit. In the future, appropriately powered randomized trials of standard vs. extended resections may show improved outcomes for PCa patients.

Human placental NAD(P)H oxidase: solubilization and properties

The NAD(P)H oxidase in the syncytiotrophoblast of the term human placenta, which had previously been identified only by cytochemical methods, has been solubilized and a number of its biochemical properties have been defined. It is a protein composed of a 58 kDa and a 33 kDa subunit, with properties that clearly distinguish it from the respiratory burst oxidase of transient neutrophils and macrophages. The enzyme activity is constitutive in the trophoblast and is a source of reactive oxygen species (ROS) at the fetal-maternal interface.

Ultrasonographic features and patterns of regression after conservative treatment of retinoblastoma

The authors analyze the echographic features relative to some cases of retinoblastoma treated with conservative therapy in order to monitor the regression of the tumor consequent to the treatment.

Parental history of hypertension and parental history of diabetes and microvascular complications in insulin-dependent diabetes mellitus: the EURODIAB IDDM Complications Study

Diabetic nephropathy clusters in families, suggesting an inherited predisposition. Parental history of hypertension and of Type 2 diabetes mellitus have been associated with nephropathy in offspring with Type 1 diabetes in some studies but not in others. The associations of parental history of hypertension and of diabetes with both albuminuria and proliferative retinopathy were studied in a large cross-sectional study of 3250 patients with Type 1 diabetes, from 16 European countries. Albuminuria was associated with hypertension in a parent (p < 0.01 in men, p < 0.05 in women), adjusted for age. Patients with a parental history of hypertension had a higher prevalence of hypertension (p < 0.001 in men, p < 0.01 in women) and a higher prevalence of parental diabetes (p < 0.001 in men, p < 0.001 in women). The association of albuminuria with parental hypertension was independent of parental diabetes in men but not women (OR = 1.28 in men p = 0.04, OR = 1.25 in women p = 0.09) and was not independent of hypertension in the patient him/herself in either sex. Albuminuria was associated with parental diabetes in women only (OR = 1.36, p = 0.04). This association was independent of both parental hypertension and hypertension in the patient herself. Proliferative retinopathy was not associated with parental hypertension or diabetes. The implications of these data are that both candidate genes for hypertension and Type 2 diabetes should be considered in the search for the genetic determinants of diabetic nephropathy.

Nonmitochondrial oxygen utilization by rabbit blastocysts and surface production of superoxide radicals

A minimum value for nonmitochondrial oxygen utilization in rabbit blastocysts at day 6 post coitum was determined by measuring oxygen consumption in the presence of cyanide. A microcathode oxygen electrode was used to monitor oxygen concentration continuously during blastocyst incubation in a newly devised culture medium, and the uninhibited blastocyst was found to consume 2.79 +/- 0.09 microliters O2 h-1 cm-2. This rate was reduced by 51% in the presence of 1 mmol KCN l-1. The addition of nitroblue tetrazolium to the cyanide-containing medium reduced net oxygen consumption by an additional 23% as the nitroblue tetrazolium was reduced to formazan. The ability of rabbit blastocysts to reduce nitroblue tetrazolium in the presence of cyanide was investigated using a spectrophotometric assay. Fractionation of blastocyst cells revealed that the enzymatic activity chiefly responsible for formazan production partitioned with the membrane/particulate fraction and could be solubilized by the detergent NP40. The enzyme was NAD(P)H-dependent, did not require divalent cations for activity, and appeared to contain no haeme moiety. The rate of formazan production in the spectrophotometric assay was markedly reduced by the presence of superoxide dismutase. The oxygen electrode and spectrophotometer data indicate that there is a superoxide-generating NAD(P)H oxidase on the blastocyst surface. Calculations based on the average surface area of rabbit blastocysts at day 6 show that these embryos can produce at least 8 nmoles of superoxide per embryo h-1. Potential deciduogenic effects of blastocyst-derived superoxide and its dismutated product, hydrogen peroxide, are discussed.

Epidemiology of diabetes mellitus in the elderly in northern Greece: a population study

This population based study was undertaken to ascertain the overall prevalence of diabetes mellitus (DM) and impaired glucose tolerance (IGT) in the elderly using the WHO criteria. The role of obesity in the development of DM or IGT has been investigated for both sexes per decade of age. Furthermore the potential for DM to increase with age, as has been suggested before, has been evaluated using the IGT as a proportion of total glucose intolerance (IGT/TGI) for the same parts of the tested sample. From the 647 persons registered as elderly people in a small town in northern Greece (total population 5875 people), 66 persons did not participate in this survey. Fifty-six subjects (9.7%) had previously diagnosed DM. The remainder were tested using fasting blood glucose measurements or an oral glucose tolerance test (OGTT). The prevalence of previously undiagnosed DM according to fasting blood glucose values or after 2 h of 75 g load values was 10.1% and 9.3%, respectively. Thus the overall prevalence of DM was 29.1% and of IGT was 15.1%. These data support an increased frequency of DM (65% previously undiagnosed) and IGT in the elderly, whereas this population's susceptibility seems to decline in the older groups for both sexes. Obesity remains a risk factor for DM and IGT particularly among the younger groups although its role has been found to decline with age.

Differences in peripheral and autonomic nerve function measurements in painful and painless neuropathy. A clinical study

OBJECTIVE

To examine the differences in peripheral and autonomic nerve function measurements between diabetic patients without neuropathy (group 1, n = 38, mean age 50.9, range 29-71 years), with painless neuropathy (group 2, n = 32, mean age 49.2, range 30-71 years), and with painful neuropathy (group 3, n = 52, mean age 51.5, range 28-73 years).

RESEARCH DESIGN AND METHODS

The evaluation of neuropathy was based on clinical symptoms, signs, and quantitative sensory testing, including current perception threshold (CPT) with a neurometer and electrophysiology.

RESULTS

The Neuropathy Symptom Score and the Neuropathy Disability Score were higher in patients with painful neuropathy compared with patients with painless neuropathy (6.8 +/- 2.7 vs. 0.5 +/- 0.8 [mean +/- SD], P < 0.0001, and 12.5 +/- 6.2 vs. 8.6 +/- 6.8, P < 0.01, respectively). In contrast, no differences were found in the quantitative sensory testing, including CPT measurements, the electrophysiological measurements, and the autonomic nerve system function tests in the two groups. Significant differences were found in all the above measurements when groups 2 and 3 were compared with diabetic patients without neuropathy (group 1). When all diabetic patients were considered as one group, significant correlations were found between CPT and the other peripheral nerve function assessments. In particular, peroneal nerve motor conduction velocity correlated with CPT at 2 kHz (r = -0.48, P < 0.001) and vibration perception threshold (r = -0.50, P < 0.001).

CONCLUSIONS

We conclude that no difference could be found in the function of small and large nerve fibers between painful and painless diabetic neuropathy using conventional tests currently used. The CPT evaluation failed to quantify painful symptoms, but it compared favorably with other quantitative sensory tests in quantifying peripheral neuropathy.

Comparison of risk factors for foot problems in diabetic patients attending teaching hospital outpatient clinics in four different European states

Although the St Vincent declaration calls for common European action in order to reduce major amputations, the differences in the incidence of foot problems and the prevalence of risk factors has not been fully investigated. We have examined the risk factors for foot ulceration and amputation in 278 consecutive patients (mean age 50.4 years, range 18-79 years) attending outpatient clinics of four teaching hospitals: Athens, Manchester, Rome, and Antwerp. There were no differences in age, weight or sex among the four groups but the percentage of patients with Type 1 diabetes was higher in Rome and Antwerp. Patients in Rome and Antwerp also had a longer duration of diabetes compared to Athens and Manchester. Mean vibration perception threshold was similar in all groups. No differences were found in the number of patients with moderate or severe clinical neuropathy (neuropathy disability score > 5), severe sensory loss (VPT > 25 V), and limited joint mobility. Symptomatic peripheral vascular disease was more frequent in Antwerp (p < 0.05) compared to the other three centres and foot ulceration in Rome compared to Manchester (p < 0.05). The number of smokers or ex-smokers and the average alcohol consumption were similar in all centres. We conclude that, despite a few differences mainly in Type 1 diabetic patients, there are no major differences in the risk factors for foot ulceration and that, therefore, similar strategies for the prevention of foot problems may be equally successful in different European countries.

Painful neuropathy and foot ulceration in diabetic patients

OBJECTIVE

To examine the prevalence of painful symptoms in neuropathic patients with or without foot ulceration. It has been suggested that there are two clinical presentations of sensory diabetic neuropathy with little overlap: painful (acute or chronic) and painless with recurrent foot ulceration.

RESEARCH DESIGN AND METHODS

We examined three groups of diabetic patients matched for age and duration of diabetes--24 without neuropathy on clinical grounds (mean age 56.1 yr [range 38-76 yr], diabetes duration 12.6 yr [0.4-40 yr]), 30 with neuropathy (mean age 55.3 yr [range 21-73 yr], diabetes duration 17.3 yr [range 0.2-61 yr]), and 40 with neuropathic foot ulceration (mean age 58.1 yr [range 41-72 yr], diabetes duration 18.5 yr [range 1-46 yr])--and compared them with 20 healthy subjects (mean age 50 yr [range 37-69 yr]). For evaluation of neuropathy, the neuropathy symptom score, neuropathy disability score, and vibration perception threshold were measured.

RESULTS

No difference existed between the neuropathic and foot ulcer groups in the neuropathy symptom score (4.2 +/- 3.9 [mean +/- SD] vs. 2.5 +/- 2.1, NS) and neuropathy disability score (15.1 +/- 5.7 vs. 16.8 +/- 6.1, NS), but the vibration perception threshold was lower in the neuropathic group (30.1 +/- 13.4 vs. 40.5 +/- 13.8 V, P < 0.001). Painful symptoms (neuropathy symptom score > 3), either in the past or during the time the study was conducted, had been experienced by none of the control subjects, 7 (29%) of the nonneuropathic group, 18 (60%) of the neuropathic group, and 17 (43%) of the foot ulcer group (NS for the last two groups), and were present at the time of examination in 13 (43%) of the neuropathic group and in 13 (33%) of the foot ulcer group (NS in all groups). Duration of symptoms was < 12 mo in 12 (40%) neuropathic and 15 (38%) foot ulcer patients (NS).

CONCLUSIONS

We conclude that painful symptoms are frequent in diabetic neuropathy, irrespective of the presence or absence of foot ulceration and that these symptoms can occur at any stage of the disease. These results suggest that there is a spectrum of neuropathic syndromes from the painful to the patients with foot ulceration, and that much overlap exists.

Cyanide-resistant reduction of nitroblue tetrazolium and hydrogen peroxide production by the rabbit blastocyst

The ability of the rabbit blastocyst to reduce nitroblue tetrazolium (NBT) to formazan in the presence of cyanide was assayed as an indicator of extramitochondrial oxidase activity capable of generating the superoxide radical. A cytochemical method initially developed for the detection and localization of hydrogen peroxide production at the ultrastructural level in phagocytosing leukocytes (Briggs et al.: J Cell Biol 67:566, 1975) was also applied to the blastocyst. The results demonstrate that the rabbit blastocyst acquires the ability to reduce NBT by a cyanide-insensitive process and to generate hydrogen peroxide between the fourth and fifth days postcoitum. The enzymatic activity responsible is apparently an NAD(P)H-dependent oxidase in the outer, microvillous plasma membrane of the trophoblast.

Nucleocytoplasmic translocation of ribosomal RNA in the rabbit blastocyst: participation of sulfhydryl groups

The release of ribosomes from the nucleus in the rabbit blastocyst was investigated by pulse-labeling embryos to within 5 min of the earliest appearance of radiolabeled ribosomal RNA (rRNA) in the cytoplasmic fraction. The accumulation of radiolabeled 4.7 and 1.9 kilobase mature rRNA species in the cytoplasm was then followed during a 2 hour chase period, using polyacrylamide gel electrophoresis to identify the rRNAs. Colchicine, cytochalasin B, KCN, and EDTA were found to have no effect on the release of radiolabeled rRNA from the blastocyst nucleus during the 2 hour chase. Oligomycin, a known inhibitor of the nuclear envelope nucleoside triphosphatase, and the protein synthesis inhibitors puromycin and cycloheximide blocked rRNA release after a short delay. In contrast, actinomycin D and the sulfhydryl-reactive agents N-ethylmaleimide and diamide produced an abrupt and complete block to further rRNA release. The results indicate that ribosomes leave the nuclear compartment by an energy-dependent process. They further underscore the importance of reduced sulfhydryl groups in a rapidly growing blastocyst with a high level of oxidative metabolism.

Polarization of blastomeres in the cleaving rabbit embryo

Cellular polarization is believed to be a crucial event in the differentiative divergence of the two cell lineages leading to the blastocyst in rodent embryos. This study was undertaken to determine if rabbit embryos exhibited cellular polarization prior to blastocyst formation and to define the embryonic stage at which polarization was first apparent. Polarity was assayed by observation of the pattern of binding of FITC-Con A to dissociated blastomeres from three stages of rabbit embryos. Scanning electron microscopy on the dissociated cells confirmed the fluorescence results. Fifty-one percent of blastomeres in 38- to 66-cell rabbit embryos exhibited an intense pole of FITC-Con A binding and a single pole of microvilli. Only 2% of blastomeres at the 17- to 34-cell stage were similarly polarized and none were polarized at the 8- to 16-cell stage. In addition, during attempts to remove the mucin coat and zona pellucida from the rabbit embryos prior to their dissociation, it was found that the protease sensitivity of these coats also changed at the 38- to 66-cell stage. Prior to this time, although the mucin coat disappeared after 30 min in 0.5% pronase, the zona required approximately 1.5-2.5 hr in pronase for even partial removal. At the 38- to 66-cell stage, pronase dissolved the mucin coat within 10 min and the zona pellucida within 20 min. The zona was resistant to 0.1% proteinase K at all stages examined.

Electron microscopic analysis of RNA transcription in preimplantation rabbit embryos

We have examined directly RNA synthesis in several stages of preimplantation rabbit embryos by electron microscopic analysis of chromatin spreads. DNA/chromatin packing ratios were determined for non-transcribing regions (2.0) and for regions active in RNA synthesis (1.1). Significant amounts of RNA transcription were observed in all embryonic stages examined. Lengths of transcribed regions were calculated and range from 1.1 to 10.9 Kb of B-form DNA. The frequency of chromatin-associated ribonucleoprotein (RNP) fibrils was greatly reduced in samples prepared from embryos treated with alpha-amanitin indicating that the RNPs observed were growing chains. The frequency of single and multiple RNP fibrils attached to chromatin is the same at all stages examined implying the absence of extensive modulation of RNA chain initiation. These results are discussed in relation to the biochemical data on RNA synthesis in preimplantation rabbit embryos.

Nucleic acid synthesis in preimplantation rabbit embryos. III. A "dark period" immediately following fertilization, and the early predominance low molecular weight RNA synthesis

This report stems from efforts to characterize the products of transcription during the initial stages of cleavage in the rabbit embryo, since previous studies have suggested that RNA synthesis is required during this period for the continuation of normal development. Early cleaving embryos were exposed to radiolabeled precursors of nucleic acids in vitro and RNA extracted and analyzed by polyacrylamide gel electrophoresis and BD-cellulose chromatography. No unequivocal evidence of RNA synthesis could be obtained during the first three cleavage divisions; all apparent "embryonic" RNA synthesis could be ascribed to contaminating follicle cells. After the fourth cleavage, however, there is readily detectable incorporation of radioisotope into RNA by embryos which have been denuded of follicle cells. Two-thirds of the cytoplasmic RNA labeled during a 4-hour period is 25-30 X 10(3) daltons in size, and some of this low molecular weight RNA can be aminoacylated and shown to be transfer RNA. A low level of ribosomal RNA synthesis is detectable at this stage. The contribution, if any, of the rabbit embryonic genome to development prior to the 16-cell stage remains to be defined.