The Influence of Pasture and Non-pasture-Based Feeding Systems on the Aroma of Raw Bovine Milk

Aroma-active compounds in raw bovine milk produced from cows fed perennial ryegrass (GRS) or total mixed ration (TMR) consisting of grass silage, maize silage, and concentrates were identified by direct immersion sorptive extraction (DI Hi-Sorb), coupled with gas-chromatography-mass spectrometry and olfactometry using odour intensity (OI) and aroma extraction dilution analysis (AEDA). Ninety-nine volatile organic compounds (VOC) were identified in these raw GRS and TMR milk samples; 33 of which were also present in the feed and rumen samples from these diets. Only the abundance of 13 VOC varied significantly based on diet. However, the odours of both raw milks were quite distinct as aroma perception is not influenced by abundance alone but also by the odour activity of each VOC. Approximately, 30% of the VOC influenced the aroma perception of these raw milks. This study clearly highlighted the significant impact of VOC transferring from the diet that influenced the aroma perception of both raw GRS and TMR milk. The aroma of the raw TMR milk was more complex than that of the raw GRS milk, and many of the key dietary-derived-odour-active VOC likely arose during the production of the TMR feed as most were either derived from Maillard reactions or impacted by heat. Seventeen of the 44 odour activities detected differed between both sample types. This study has clearly demonstrated the impact of diet on the aroma perception of raw bovine milk.

Effect of bovine feeding system (pasture or concentrate) on the oxidative and sensory shelf life of whole milk powder

Correlating volatile compounds with the sensory attributes of whole milk powder (WMP) is fundamental for appreciating the effect of lipid oxidation (LO) on sensory perception. LO compounds can adversely affect the sensory perception of WMP by imparting rancid, metallic, and painty notes. Whole milk powders derived from milk produced by cows maintained on a pasture diet (grass and grass-clover mix) versus a nonpasture diet [total mixed ration (TMR); concentrates and silage] were stored at room temperature 21°C (ambient storage) and 37°C (accelerated storage) and analyzed for volatile compounds and sensory attributes every 2 mo for a total of 6 mo. Thirteen volatile compounds originating from LO were chosen to track the volatile profile of the WMP during storage. Color, composition, total fatty acid, and free fatty acid profiling were also carried out. Significant variations in the concentrations of 14 fatty acids were observed in WMP based on diet. Concentrations of free fatty acids increased in all sample types during storage. Similar trends in sensory attributes were observed with an increase in painty attributes, corresponding to an increase in hexanal. Buttery/toffee attributes were found to be more closely correlated with TMR WMP. Those WMP derived from pasture diets were found to be more susceptible to LO from a volatile perspective, particularly in relation to aldehyde development, which is likely due to increased concentrations of conjugated linoleic acid and α-linolenic acid found in these samples.

Correlating Volatile Lipid Oxidation Compounds with Consumer Sensory Data in Dairy Based Powders During Storage

Lipid oxidation (LO) is a recognised problem in dairy powders due to the formation of volatile odour compounds that can negatively impact sensory perception. Three commercial dairy powders, fat-filled whole milk powder (FFWMP), skim milk powder (SMP), and infant milk formula (IMF), stored under different conditions (21 °C, 37 °C, or 25 °C with 50% humidity), were evaluated by consumer acceptance studies, ranked descriptive sensory analysis, and LO volatile profiling using headspace solid phase microextraction gas chromatography mass spectrometry (HS-SPME GCMS) over 16 weeks. Significant (p = 0.001) differences in the concentration of LO compounds and sensory perception were evident between sample types in the different storage conditions. The sensory acceptance scores for FFWMP and SMP remained stable throughout storage in all conditions, despite the increased perception of some LO products. The IMF sample was perceived negatively in each storage condition and at each time point. Overall increases in hexanal, heptanal, and pentanal correlated with “painty”, “oxidised”, “cooked”, and “caramelised” attributes in all samples. The concentration of some LO volatiles in the IMF was far in excess of those in FFWMP and SMP. High levels of LO volatiles in IMF were presumably due to the addition of polyunsaturated fatty acids (PUFA) in the formulation.

Ultrastructure and intercellular contact-mediated communication in cultured human early stage follicles exposed to mTORC1 inhibitor

The reproductive lifespan of a woman is determined by the gradual recruitment of quiescent follicles into the growing pool. In humans, ovarian tissue removal from its in vivo environment induces spontaneous activation of resting follicles. Similarly, pharmacological activation of the PI3K/Akt pathway leads to accelerated follicle recruitment, but has been associated with follicular damage. Recent findings demonstrate that everolimus (EVE), an mTORC1 inhibitor, limits primordial follicle activation. However, its potential benefit regarding growing follicle integrity remains unexplored. Ovarian cortical fragments were exposed to ± EVE for 24 h and cultured for an additional 5 days. After 0, 1 and 6 days of culture, fragments were either processed for ultrastructural analysis or subjected to follicular isolation for gene expression and immunofluorescence assessments. Data from transmission electron microscopy showed that growing follicles displayed similar ultrastructural features irrespective of the conditions and maintained close contacts between germinal and stromal compartments. Establishment of intra-follicular communication was confirmed by detection of a gap junction component, Cx43, in both groups throughout culture, whereas transzonal projections, which physically link granulosa cells to oocyte, formed later in EVE-treated follicles. Importantly, levels of GJA1 mRNA, encoding for the Cx43 protein, significantly increased from Day 0 to Day 1 in the EVE group, but not in the control group. Given that EVE-treated follicles were smaller than controls, these findings suggest that EVE might facilitate the establishment of appropriate intercellular communications without impairing follicle ultrastructure. Therefore, mTORC1 inhibitors might represent an attractive tool to delay the culture-induced primordial follicle activation while maintaining follicles in a functionally integrated state.

Both in vivo FSH depletion and follicular exposure to Gonadotrophin-releasing hormone analogues in vitro are not effective to prevent follicular depletion during chemotherapy in mice

STUDY QUESTION

Does fertility preservation using gonadotrophin-releasing hormone (GnRH) analogues during chemotherapy act through a direct effect on the ovary or through inhibition of FSH secretion?

SUMMARY ANSWER

The absence of FSH in vivo and the direct exposition of ovarian follicles to GnRH analogues in vitro did not prevent chemotherapy-induced ovarian damage.

WHAT IS KNOWN ALREADY

The potential mechanisms of action of GnRH analogues in protecting ovaries against chemotherapy damage remain poorly understood. We previously showed that GnRH analogues have a limited inhibitory effect on gonadotropin secretion and follicular growth in mice.

STUDY DESIGN SIZE, DURATION

Mouse models were developed to independently evaluate (i) the indirect effect of FSH depletion on chemotherapy-induced ovarian damage using Fshb-deficient (-/-) mice to mimic the profound inhibition of FSH secretion during GnRH analogues treatment and (ii) the direct in vitro effect of GnRH agonist and antagonist in follicles exposed to chemotherapy using a follicular culture system.

PARTICIPANTS/MATERIALS, SETTING, METHODS

To assess the indirect effect of GnRH analogues through FSH inhibition, Fshb-/- mice were treated with 1 IU pregnant mare serum gonadotropin (control group) or saline (study group) for 7 days and with cyclophosphamide (200 mg/kg) on Day 5. Ovaries were collected 48 h post-cyclophosphamide to evaluate ovarian reserve, cellular apoptosis and proliferation. To evaluate the direct effects of GnRH analogues on growing follicles, isolated preantral follicles from prepubertal mice were cultured in vitro for 13 days with 1 μM GnRH analogues and 20 μM of 4-hydroperoxycyclophosphamide or not at Day 4. Oocytes were matured by adding epidermal growth factor (EGF)/hCG on Day 12. Follicular development, follicular survival, oocyte maturation rates, cAMP production, and steroidogenesis were evaluated. To assess the direct GnRH analogues effects on follicular reserve, whole neonatal ovaries were cultured in vitro under the same conditions for 2 days. Ovaries were processed 24 h post-chemotherapy for ovarian reserve, cellular apoptosis and proliferation analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Cyclophosphamide induced a significant follicular loss of more than 50% in Fshb-/- mice regardless of previous treatment with gonadotropins and no difference was observed in cell proliferation or apoptosis. In vitro experiments on growing follicles showed that 4-hydroperoxycyclophosphamide significantly decreased preantral follicle survival and maturation rates (55% and 37%, respectively) and delayed follicular development, regardless of the presence of GnRH analogues. Chemotherapy reduced granulosa cell numbers in all groups, while no change in cAMP production/106 granulosa cells was observed. Similarly, 4-hydroperoxycyclophosphamide induced apoptosis and significant follicular loss in cultured neonatal ovaries irrespective of GnRH analogues exposure.

LIMITATIONS REASONS FOR CAUTION

As ovarian GnRH receptors expression differs in humans and mice, further studies are needed to validate our results in human ovaries.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings demonstrate that ovarian damage occurred even in the absence of FSH, suggesting that inhibition of the pituitary-gonadal axis is not involved in ovarian protection during GnRH analogues treatment. Using in vitro models, no evidence for direct protective effect of GnRH analogues against cyclophosphamide metabolite damage was observed. At present, clinical efficiency of GnRH analogues to prevent chemotherapy-induced ovarian damage remains highly debated and these experimental results reinforced the question as they did not bring evidence of direct or indirect mechanisms of protection.

LARGE SCALE DATA

N/A.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by the Belgian FNRS, 'Le Fonds Emile DEFAY', and 'La Fondation Rose et Jean Hoguet'. Authors have no conflict of interest to declare.

Factors Influencing the Flavour of Bovine Milk and Cheese from Grass Based versus Non-Grass Based Milk Production Systems

There has been a surge in interest in relation to differentiating dairy products derived from pasture versus confined systems. The impact of different forage types on the sensory properties of milk and cheese is complex due to the wide range of on farm and production factors that are potentially involved. The main effect of pasture diet on the sensory properties of bovine milk and cheese is increased yellow intensity correlated to β-carotene content, which is a possible biomarker for pasture derived dairy products. Pasture grazing also influences fat and fatty acid content which has been implicated with texture perception changes in milk and cheese and increased omega-3 fatty acids. Changes in polyunsaturated fatty acids in milk and cheese due to pasture diets has been suggested may increase susceptibility to lipid oxidation but does not seem to be an issue to due increased antioxidants and the reducing environment of cheese. It appears that pasture derived milk and cheese are easier to discern by trained panellists and consumers than milk derived from conserved or concentrate diets. However, milk pasteurization, inclusion of concentrate in pasture diets, cheese ripening time, have all been linked to reducing pasture dietary effects on sensory perception. Sensory evaluation studies of milk and cheese have, in general, found that untrained assessors who best represent consumers appear less able to discriminate sensory differences than trained assessors and that differences in visual and textural attributes are more likely to be realized than flavour attributes. This suggests that sensory differences due to diet are often subtle. Evidence supports the direct transfer of some volatiles via inhalation or ingestion but more so with indirect transfer post rumen metabolism dietary components. The impact of dietary volatiles on sensory perception of milk and dairy products obviously depends upon their concentration and odour activity, however very little quantitative studies have been carried out to date. Some studies have highlighted potential correlation of pasture with enhanced “barny” or “cowy” sensory attributes and subsequently linked these to accumulation of p-cresol from the metabolism of β-carotene and aromatic amino acids or possibly isoflavones in the rumen. p-Cresol has also been suggested as a potential biomarker for pasture derived dairy products. Other studies have linked terpenes to specific sensory properties in milk and cheese but this only appears to be relevant in milk and cheese derived from unseeded wild pasture where high concentrations accumulate, as their odour threshold is quite high. Toluene also a product of β-carotene metabolism has been identified as a potential biomarker for pasture derived dairy products but it has little impact on sensory perception due to its high odour threshold. Dimethyl sulfone has been linked to pasture diets and could influence sensory perception as its odour threshold is low. Other studies have linked the presence of maize and legumes (clover) in silage with adverse sensory impacts in milk and cheese. Considerably more research is required to define key dietary related impacts on the flavour of milk and cheese.

Inhibitory mechanism of an allosteric antibody targeting the glucagon receptor

Elevated glucagon levels and increased hepatic glucagon receptor (GCGR) signaling contribute to hyperglycemia in type 2 diabetes. We have identified a monoclonal antibody that inhibits GCGR, a class B G-protein coupled receptor (GPCR), through a unique allosteric mechanism. Receptor inhibition is mediated by the binding of this antibody to two distinct sites that lie outside of the glucagon binding cleft. One site consists of a patch of residues that are surface-exposed on the face of the extracellular domain (ECD) opposite the ligand-binding cleft, whereas the second binding site consists of residues in the αA helix of the ECD. A docking model suggests that the antibody does not occlude the ligand-binding cleft. We solved the crystal structure of GCGR ECD containing a naturally occurring G40S mutation and found a shift in the register of the αA helix that prevents antibody binding. We also found that alterations in the αA helix impact the normal function of GCGR. We present a model for the allosteric inhibition of GCGR by a monoclonal antibody that may form the basis for the development of allosteric modulators for the treatment of diabetes and other class B GPCR-related diseases.

Temperature dependency of Clostridium botulinum C and D toxin production from anaerobically enriched bovine gastrointestinal samples

AIMS

To determine whether Clostridium botulinum neurotoxin (BoNT) production in anaerobic culture was affected by temperature and could influence the sandwich ELISA (sELISA) detection of group III toxins in pre-enriched gastrointestinal (GI) contents from clinically suspect cattle botulism cases.

METHODS AND RESULTS

Bovine post-mortem GI samples taken from 124 and 96 animals with suspect and nonsuspect botulism, respectively, were pre-enriched anaerobically at 30 and 37°C prior to testing by sELISA. After enrichment at 37°C, BoNT was demonstrated in all clinically suspect bovine botulism cases that had been identified by the mouse bioassay, and enrichment by both temperatures enabled BoNT detection in a number of mouse bioassay-negative suspect cases.

CONCLUSIONS

Culture temperature does influence the production of group III BoNT, and incubation at both 30 and 37°C is required for optimum detection.

SIGNIFICANCE AND IMPACT OF THE STUDY

The in vitro assay defined in this study has the potential of improving the confirmation rate of clinically suspect cattle botulism cases whilst reducing the use of the costly and ethically sensitive mouse bioassay, the current diagnostic gold standard for BoNT testing.

Diagnosis of botulism types C and D in cattle by a monoclonal antibody-based sandwich ELISA

This study was undertaken to evaluate two monoclonal antibody-based sandwich ELISAs (sELISAs) for the detection of Clostridium botulinum neurotoxins (BoNTs) types C and D from culture-enriched intestinal content samples from cattle. To validate the diagnostic significance of the presence of cultivable, toxin-producing C botulinum in the intestines of cattle, samples from both suspect and non-suspect botulism cases were examined. BoNT was detected by both sELISAs in a greater number of suspect animals than by direct testing of uncultured samples by mouse bioassay. One sELISA detected two BoNT C and one BoNT Group III mosaic isoform in three animals that were missed by the other, and both sELISAs failed to identify samples from two mouse bioassay-positive BoNT C animals. BoNT D was also detected in one non-suspect sample by one of the sELISAs.

MBX-102/JNJ39659100, a novel non-TZD selective partial PPAR-γ agonist lowers triglyceride independently of PPAR-α activation

MBX-102/JNJ-39659100 (MBX-102) is a selective, partial PPAR-γ agonist that lowers glucose in the absence of some of the side effects, such as weight gain and edema, that are observed with the TZDs. Interestingly MBX-102 also displays pronounced triglyceride lowering in preclinical rodent models and in humans. Although in vitro reporter gene studies indicated that MBX-102 acid is a highly selective PPAR-γ agonist that lacks PPAR-α activity, we sought to determine if PPAR-α activation in vivo could possibly contribute to the triglyceride lowering abilities of MBX-102. In vivo studies using ZDF and ZF rats demonstrated that MBX-102 lowered plasma triglycerides. However in ZF rats, MBX-102 had no effect on liver weight or on hepatic expression levels of PPAR-α target genes. Further in vitro studies in primary human hepatocytes supported these findings. Finally, the ability of MBX-102 to lower triglycerides was maintained in PPAR-α knockout mice, unambiguously establishing that the triglyceride lowering effect of MBX-102 is PPAR-α independent. The in vivo lipid lowering abilities of MBX-102 are therefore mediated by an alternate mechanism which is yet to be determined.

MBX-102/JNJ39659100, a novel peroxisome proliferator-activated receptor-ligand with weak transactivation activity retains antidiabetic properties in the absence of weight gain and edema

MBX-102/JNJ39659100 (MBX-102) is in clinical development as an oral glucose-lowering agent for the treatment of type 2 diabetes. MBX-102 is a nonthiazolidinedione (TZD) selective partial agonist of peroxisome proliferator-activated receptor (PPAR)-gamma that is differentiated from the TZDs structurally, mechanistically, preclinically and clinically. In diabetic rodent models, MBX-102 has insulin-sensitizing and glucose-lowering properties comparable to TZDs without dose-dependent increases in body weight. In vitro, in contrast with full PPAR-gamma agonist treatment, MBX-102 fails to drive human and murine adipocyte differentiation and selectively modulates the expression of a subset of PPAR-gamma target genes in mature adipocytes. Moreover, MBX-102 does not inhibit osteoblastogenesis of murine mesenchymal cells. Compared with full PPAR-gamma agonists, MBX-102 displays differential interactions with the PPAR-gamma ligand binding domain and possesses reduced ability to recruit coactivators. Interestingly, in primary mouse macrophages, MBX-102 displays enhanced antiinflammatory properties compared with other PPAR-gamma or alpha/gamma agonists, suggesting that MBX-102 has more potent transrepression activity. In summary, MBX-102 is a selective PPAR-gamma modulator with weak transactivation but robust transrepression activity. MBX-102 exhibits full therapeutic activity without the classical PPAR-gamma side effects and may represent the next generation insulin sensitizer.

Incomplete seating of the liner with the Trident acetabular system: a cause for concern?

We reviewed the initial post-operative radiographs of the Trident acetabulum and identified a problem with seating of the metal-backed ceramic liner. We identified 117 hips in 113 patients who had undergone primary total hip replacement using the Trident shell with a metal-backed alumina liner. Of these, 19 (16.4%) were noted to have incomplete seating of the liner, as judged by plain anteroposterior and lateral radiographs. One case of complete liner dissociation necessitating early revision was not included in the prevalence figures. One mis-seated liner was revised in the early post-operative period and two that were initially incompletely seated were found on follow-up radiographs to have become correctly seated. There may be technical issues with regard to the implanting of this prosthesis of which surgeons should be aware. However, there is the distinct possibility that the Trident shell deforms upon implantation, thereby preventing complete seating of the liner.

Impaction bone grafting in revision hip surgery

We retrospectively reviewed the use of impaction bone grafting with cement for the fixation of femoral and acetabular components in revision hip arthroplasty. Seventy hips formed the basis of the study, with a mean follow-up time of 37 months. Sixty-eight percent of the femurs showed severe bone loss (Endoklinik grades 3 and 4). The mean Harris hip and Merle D'Aubigne Postel scores were 84 and 15.4, respectively. Massive subsidence occurred in only one femoral revision (>10 mm) and cup migration >5 mm in 6 cases. Loosening was seen in 1 revision for sepsis but none for aseptic loosening. Five complications were identified that were related to the surgical technique. We therefore support the use of this technique in revision surgery in patients with extensive bone loss.

Development of a sandwich ELISA and comparison with PCR for the detection of F11 and F165 fimbriated Escherichia coli isolates from septicaemic disease in farm animals

The P fimbriae F11 and F165 that have been demonstrated on Escherichia coli septicaemic strains in poultry and calves, respectively, possess a nearly identical major subunit that demonstrates a serological cross-reaction. A polyclonal antibody-based sandwich ELISA (sELISA) that was specific for both F11 and F165 fimbriated strains was compared with a PCR method to detect F11/F165 fimbriated strains, in a collection of E. coli strains isolated from diseased animals. Of 298 isolates tested, 36 were positive by PCR of which only 14 were sELISA positive. There were no sELISA positive but PCR negative results. The 36 PCR positive isolates comprised 11 avian strains of which 10 were sELISA positive, 20 bovine strains of which 4 were sELISA positive and 3 ovine strains, 1 porcine strain and 1 equine strain all of which were sELISA negative. The F11/F165 incidence of 10.7% in 103 poultry and 18.3% in 109 bovine isolates demonstrates a moderate level of these factors in E. coli septicaemic cases in Northern Ireland.

Factors controlling the loss of immunoreactive somatic histone H1 from blastomere nuclei in oocyte cytoplasm: a potential marker of nuclear reprogramming

Nuclei of differentiated cells can acquire totipotency following transfer into the cytoplasm of oocytes. While the molecular basis of this nuclear reprogramming remains unknown, the developmental potential of nuclear-transfer embryos is influenced by the cell-cycle stage of both donor and recipient. As somatic H1 becomes immunologically undetectable on bovine embryonic nuclei following transfer into ooplasm and reappears during development of the reconstructed embryo, suggesting that it may act as a marker of nuclear reprogramming, we investigated the link between cell-cycle state and depletion of immunoreactive H1 following nuclear transplantation. Blastomere nuclei at M-, G1-, or G2-phase were introduced into ooplasts at metaphase II, telophase II, or interphase, and the reconstructed embryos were processed for immunofluorescent detection of somatic histone H1. Immunoreactivity was lost more quickly from donor nuclei at metaphase than at G1 or G2. Regardless of the stage of the donor nucleus, immunoreactivity was lost most rapidly when the recipient cytoplast was at metaphase and most slowly when the recipient was at interphase. When the recipient oocyte was not enucleated, however, immunoreactive H1 remained in the donor nucleus. The phosphorylation inhibitors 6-DMAP, roscovitine, and H89 inhibited the depletion of immunoreactive H1 from G2, but not G1, donor nuclei. In addition, immunoreactive H1 was depleted from mouse blastomere nuclei following transfer into bovine oocytes. Finally, expression of the developmentally regulated gene, eIF-1A, but not of Gapdh, was extinguished in metaphase recipients but not in interphase recipients. These results indicate that evolutionarily conserved cell-cycle-regulated activities, nuclear elements, and phosphorylation-linked events participate in the depletion of immunoreactive histone H1 from blastomere nuclei transferred in oocyte cytoplasm and that this is linked to changes in gene expression in the transferred nucleus.

The treatment of impending and existing pathological femoral fractures using the long gamma nail

The subtrochanteric region of the femur accounts for one-third of all pathological fractures requiring surgical intervention. The large forces occurring in this region and the possible non-occurrence of bony consolidation constitute a difficult problem to the trauma surgeon. The medical records and X-rays of 25 consecutive patients treated with the long gamma nail (LGN) for pathological (impending or existing) fractures of the femur were analysed retrospectively. Our results in the use of the LGN for pathological fractures of the femur have been good. We recommend an aggressive approach to the early stabilisation of impending fractures and the use of distal locking.

High-mobility group proteins 14 and 17 maintain the timing of early embryonic development in the mouse

The high-mobility group (HMG) proteins 14 and 17 are abundant chromosomal proteins that bind to nucleosomes and enhance transcription. We report that both mRNA species and both proteins are present throughout oogenesis and preimplantation development of the mouse. When antisense oligonucleotides targeting each mRNA species are injected into one-cell embryos, the proteins become depleted at the two- and four-cell stages and reaccumulate at the eight-cell stage. One-cell embryos injected with antisense oligonucleotides targeting both HMG-14 and HMG-17 cleave to the two-cell stage. Subsequent cleavages, however, are delayed compared with control-injected embryos. Nevertheless, these embryos ultimately reach the blastocyst stage. Similarly, injection into the nuclei of two-cell embryos of a peptide corresponding to the common nucleosome-binding domain of HMG-14 and HMG-17 delays progression to the four-cell stage. Furthermore, both RNA and protein synthesis is transiently reduced in antisense-injected embryos compared with injected controls. These results identify HMG-14 and HMG-17 as constitutive components of mouse oocyte and embryonic chromatin and establish a link between the structure of embryonic chromatin and the normal progression of embryonic development.

The long gamma nail: a DGH experience

Subtrochanteric fractures constitute a difficult problem for the trauma surgeon. The long Gamma nail (LGN) represents an efficient technique in the management of these fractures. A retrospective analysis of 51 LGN with an average follow up of 16 weeks is presented. The average age of the patients was 72 years and the mean time to union was 11 weeks. The incidence of peroperative, early local and late local complications was 8, 8 and 4%, respectively or 20% in total. The thirty-day mortality was 8%. Our results in the use of the LGN have been good. Its introduction provides the trauma surgeon with a tool for allowing earlier mobilisation, decreasing operative time, surgical trauma, blood loss and wound problems. The LGN is a device by which most complex fractures in the proximal femur can be managed with a single implant.

Linker histone transitions during mammalian oogenesis and embryogenesis

A unique characteristic of the oocyte is that, although it is a differentiated cell, it can to give rise to a population of undifferentiated embryonic cells. This transition from a differentiated to a totipotential condition is thought to be mediated in part by changes in chromatin composition or configuration. In many non-mammalian organisms, oocytes contain unique subtypes of the linker histone H1, which are replaced in early embryos by the so-called somatic histone H1 subtypes. We review evidence that such histone H1 subtype switches also occur in mammals. Immunologically detectable somatic H1 is present in mitotically proliferating oogonia but gradually becomes undetectable after the oocytes enter meiosis. Immunoreactive somatic H1 remains undetectable throughout oogenesis and the early cell cycles after fertilization. Following activation of the embryonic genome, it is assembled onto chromatin. In contrast to the absence of immunoreactive protein, mRNAs encoding each of the five mammalian somatic H1 subtypes are present in growing oocytes and newly fertilized embryos, indicating that post-transcriptional mechanisms regulate expression of these genes. This maternal mRNA is degraded at the late 2-cell stage, and embryonically encoded mRNAs accumulate after embryos reach the 4-cell stage. During the period when somatic H1 is not detectable, oocytes and embryos contain mRNA encoding a sixth subtype, histone H1(0) which accumulates in differentiated somatic cells, and the nuclei can be stained with an H1(0)-specific antibody. We propose that the linker histone composition of the oocyte lineage resembles that of other mammalian cells, namely, that the somatic H1 subtypes predominate in mitotically active oogonia, that histone H1(0) becomes prominent in differentiated oocytes, and that following fertilization and transcriptional activation of the embryonic somatic H1 genes, the somatic H1 subtypes are reassembled onto chromatin of the embryonic cells. Potential functions of these linker histone subtype switches are discussed, including stabilization by H1(0) of the differentiated state of the oocytes, protection of the oocyte chromatin from factors that remodel sperm chromatin after fertilization, and restoration by the incorporation of the somatic H1 subtypes of the totipotential state of embryonic nuclei.

Effects of hydrosalpingeal fluid on murine embryo development and implantation

PURPOSE

Our purpose was to evaluate the effects of various concentrations of hydrosalpingeal fluid (HSF) on the preimplantation development and implantation of murine embryos.

METHODS

One-cell mouse embryos were cultured in KSOM culture medium with 0.1, 1.0, 10, or 50% HSF, without and with lactate supplementation. Late-stage embryos were transferred into the uteri of pseudopregnant CD-1 females to determine implantation rates. The embryo transfer technique used was developed by our group and its effectiveness was evaluated during this experiment.

RESULTS

Blastocyst development in the 0.1, 1.0, 10, and 50% group was 45, 55.0, 12.5, and 17.5%, respectively, with lactate supplementation, and 35.0, 52.5, 12.5, and 5.0%, respectively, without lactate supplementation, while in the KSOM (control) group it was 63.8%. Blastocyst development was reduced compared to controls in the 10% HSF and 50% HSF groups. Implantation rates for the 0.1 and 1.0% groups with lactate supplementation were 43.0 and 25.0%, respectively, and those with lactate supplementation were 50.6 and 61.8%, respectively, while in the KSOM group the implantation rate was 65.5%. None of the implantation rates were significantly different.

CONCLUSIONS

Hydrosalpingeal fluid has a concentration-dependent inhibitory effect on in vitro murine embryo development, but it has minimal effects on implantation rates.

Developmentally regulated loss and reappearance of immunoreactive somatic histone H1 on chromatin of bovine morula-stage nuclei following transplantation into oocytes

One difference between chromatin of bovine oocytes and blastomeres is that somatic subtypes of histone H1 are undetectable in oocytes and are assembled onto embryonic chromatin during the fourth cell cycle. We investigated whether this chromatin modification is reversed when nuclei containing somatic H1 are transplanted into ooplasts. Donor nuclei obtained from morula-stage bovine embryos were fused to ooplasts at different times before and after parthenogenetic activation of the ooplasts. After fusion, immunoreactive H1 became undetectable, and the loss occurred more rapidly when fusion was performed near the time of ooplast activation compared with several hours after activation, when the host oocytes were at a stage corresponding to interphase. Although the loss of immunoreactive H1 occurred independently of DNA replication and transcription, exposure of reconstructed oocytes to cycloheximide or 6-dymethylaminopurine (6-DMAP) delayed the loss of immunoreactive H1 from transplanted nuclei. During further development of nuclear-transplant embryos, somatic H1 remained undetectable at the 2- and 4-cell stages, and it reappeared on the chromatin at the 8- to 16-cell stage, as previously observed in unmanipulated embryos. We conclude that factors in oocyte cytoplasm are able to modify morula chromatin so that somatic H1 becomes undetectable, and that the amount or activity of these factors declines over time in activated ooplasts.

Production of steroids from human cumulus cells treated with different concentrations of gonadotropins during culture in vitro

OBJECTIVE

To evaluate the output of E2 and progesterone produced by cumulus cells, derived from mature and immature oocytes, in culture medium.

DESIGN

Prospective randomized study.

SETTING

McGill Reproductive Center, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.

PATIENT(S)

Twenty-one women, <38 years of age and with normal menstrual cycles, who were undergoing intracytoplasmic sperm injection for assisted reproduction.

INTERVENTION(S)

Culture medium with or without fetal bovine serum (FBS) supplemented with either a physiologic (75 mIU/mL) or a supraphysiologic (7,500 mIU/mL) concentration of gonadotropins.

MAIN OUTCOME MEASURE(S)

Comparison of steroid levels in culture medium.

RESULT(S)

Estradiol secretion was significantly increased in the culture medium with FBS supplemented with both concentrations of FSH alone compared with control. However, E2 secretion was inhibited by both concentrations of FSH with LH. The level of E2 was undetectable in the medium without FBS even after supplementation with both concentrations of FSH alone, hCG alone, and FSH with LH. Progesterone production was increased in the medium with FBS supplemented with FSH alone, hCG alone, and FSH with LH compared with control. There was no difference in progesterone levels in the culture medium without FBS supplemented with both concentrations of FSH alone and hCG alone compared with control. However, progesterone secretion was increased in the medium without FBS supplemented with a physiologic concentration of FSH with LH.

CONCLUSION(S)

Culture medium with FBS supplemented with a physiologic and a supraphysiologic concentration of FSH stimulates E2 secretion from cumulus cells derived from mature and immature oocytes. This suggests that it may be not necessary to add E2 to the culture medium for maturation in vitro of immature human oocytes retrieved from patients undergoing stimulated cycles.

Cytoplasmic factors that control nuclear behavior in mammalian oocytes: a re-evaluation of studies performed as a student of Yoshio Masui

Studies performed by the author in the laboratory of Dr Yoshio Masui are reviewed and interpreted in the light of subsequent findings. The first series of studies indicated that that chromosome condensation during meiotic maturation of mouse oocytes is controlled initially by a stable protein that decays during maturation and subsequently by an unstable protein synthesized after germinal vesicle breakdown. Cyclin B is present in immature oocytes, becomes partially degraded near metaphase I and then re-accumulates, suggesting that this may be protein whose activity was inferred from the original results. The second series of experiments indicated that factors which appear in the oocyte cytoplasm during maturation are able to remodel the sperm into metaphase-like chromosomes, and that the supply of these factors is limited. Recent work indicates that these factors are required for the assembly of histones onto the sperm DNA, and has identified two molecular species, mNAP-1 and NPM-3, known to promote replication-independent chromatin assembly in somatic cells, that are expressed in oocytes.

Inhibitory effect of human hydrosalpingeal fluid on mouse preimplantation embryonic development is significantly reduced by the addition of lactate

Implantation and pregnancy rates following in-vitro fertilization-embryo transfer are reduced in the presence of hydrosalpinges, but the basis of the inhibition is unknown. We examined the effect of hydrosalpingeal fluid on preimplantation development of mouse embryos. Embryos cultured in 100% hydrosalpingeal fluid were significantly inhibited developmentally as compared to embryos cultured in 100% defined medium, which served as controls. In contrast, embryos cultured in 50% hydrosalpingeal fluid/50% defined medium reached the blastocyst stage at the same frequency as the controls. When lactate (final concentration 10 mM) was added to 100% hydrosalpingeal fluid, the percentage of cultured embryos that reached the blastocyst stage was significantly increased as compared to 100% hydrosalpingeal fluid, although the percentage was slightly lower than that observed for embryos cultured in the 100% defined medium. A similar but less pronounced effect occurred when pyruvate was added to hydrosalpingeal fluid. These results do not support the concept that a potent embryotoxic agent is commonly present in hydrosalpingeal fluid. Rather, they are consistent with the notion that the inhibitory effect of hydrosalpingeal fluid on embryonic development is due to the absence of essential factors, and that this deficiency can be largely corrected by the addition of energy sources.

The ability to organize sperm DNA into functional chromatin is acquired during meiotic maturation in murine oocytes

Following fertilization of meiotically mature eggs, the chromatin of the sperm becomes biochemically and structurally remodeled within the egg cytoplasm. Despite the essential role of the paternal genome during embryogenesis, little is known of when the activities that regulate this chromatin remodeling appear during oogenesis. To determine whether these activities were acquired during meiotic maturation, we inseminated maturing oocytes of mice shortly after germinal vesicle breakdown. As previously shown, insemination at this stage did not activate the maturing oocytes, which became arrested at metaphase II. Immunofluorescent analysis revealed that at 1 hr postinsemination the sperm chromatin was dispersed and contained protamines but was devoid of core histones H2B and H3. At 4 hr postinsemination, both protamine and core histones were detectable on the sperm chromatin. By 8 hr postinsemination protamines were absent, and histones stained maximally. The appearance of immunoreactive histones was correlated with a morphological transition of the sperm chromatin from the dispersed to a condensed state, which suggests that the assembly of the histones reflected modification of the chromatin to a somatic-like state in which it was competent to respond to the metaphase-promoting factor activity of the oocyte. Both the assembly of histones and chromatin condensation were reversibly blocked when protein synthesis was inhibited, indicating that the remodeling process required proteins synthesized during maturation. Injection of core histones into protein synthesis-inhibited oocytes failed to induce condensation of the sperm chromatin, which implies that correct remodeling requires synthesis during maturation of nonhistone proteins. To test the functional capacity of remodeled sperm chromatin, maturing oocytes were inseminated, allowed to continue maturation for 17 hr and then parthenogenetically activated. Following activation, the sperm-derived chromatin as well as that of the oocyte became decondensed within pronuclei and underwent DNA replication, indicating that sperm chromatin remodeled in maturing oocyte cytoplasm was functionally normal. When the postinsemination incubation time was reduced to 11 hr; however, neither the female nor the male pronuclei underwent DNA replication, implying that factors synthesized late during maturation are required for DNA replication after activation. Taken together, these results indicate that the ability to organize sperm DNA into functional somatic-like chromatin develops in oocytes during meiotic maturation, requires proteins synthesized during maturation, and can be expressed independently of activation.

Stanmore total hip replacement in younger patients: review of a group of patients under 50 years of age at operation

Fifty-seven Stanmore Total Hip replacements were implanted between 1974 and 1986 in patients under the age of 50 years. We have reviewed the results in terms of survivorship and function, and assessed the reasons for revision. Of the original 57, 22 (39%) have been revised at an average of 12 years from implantation, usually for aseptic loosening. Most of them had originally been implanted for osteoarthritis. Prostheses cemented with second-generation techniques have lasted significantly longer, and acetabular loosening emerged as a continuing problem. The overall survivorship was 90% at 10 years and 68% at 15 years. Cemented hip replacement appears to be a viable option in younger patients and the Stanmore implant is comparable with other cemented prostheses in this age group.

Chromatin modifications during oogenesis in the mouse: removal of somatic subtypes of histone H1 from oocyte chromatin occurs post-natally through a post-transcriptional mechanism

We examined the distribution of the somatic subtypes of histone H1 and the variant subtype, H1(0), and their encoding mRNAs during oogenesis and early embryogenesis in the mouse. As detected using immunocytochemistry, somatic H1 was present in the nuclei of oocytes of 18-day embryos. Following birth, however, somatic H1 became less abundant in both growing and non-growing oocytes, beginning as early as 4 days of age in the growing oocytes, and was scarcely detectable by 19 days. Together with previous results, this defines a period of time when somatic H1 is depleted in oocytes, namely, from shortly after birth when the oocytes are at prophase I until the 4-cell stage following fertilization. At the stages when somatic H1 was undetectable, oocyte nuclei could be stained using an antibody raised against histone H1(0), which suggests that this may be a major linker histone in these cells. In contrast to the post-natal loss of somatic H1 protein, mRNAs encoding four (H1a, H1b, H1d, H1e) of the five somatic subtypes were present, as detected using RT-PCR in growing oocytes of 9-day pups, and all five subtypes including H1c were present in fully grown oocytes of adults. All five subtypes were also present in embryos, both before and after activation of the embryonic genome. mRNA encoding H1(0) was also detected in oocytes and early embryos. Whole-mount in situ hybridization using cloned H1c and H1e cDNAs revealed that the mRNAs were present in the cytoplasm of oocytes and 1-cell embryos, in contrast to the sea urchin early embryo where they are sequestered in the cell nucleus. We suggest that, as in many somatic cell types, the chromatin of mouse oocytes becomes depleted of somatic H1 and relatively enriched in histone H1(0) postnatally, and that somatic H1 is reassembled onto chromatin in cleavage-stage embryos. The post-natal loss of somatic H1 appears to be regulated post-transcriptionally by a mechanism not involving nuclear localization.

Aqueous stability of recombinant human thrombopoietin as a function of processing schemes

Preformulation studies conducted with recombinant human thrombopoietin (rhTPO), a 332 amino acid glycoprotein which stimulates platelet production, show distinctions in degradation profiles as a function of processing schemes. The stability-limiting degradation pathways change as a function of purification stage and method and are dependent upon the presence of contaminating protease. The stability-limiting degradation pathway of affinity-purified and in-process rhTPO preparations is primarily attributed to proteolysis initiated by a protease present as a fermentation contaminant. The proteolysis increases with increasing pH as a function of temperature. The degradation profiles for these preparations show that bioactivity initially increases and then decreases with increasing pH as a function of temperature. This is consistent with proteolysis to active forms which ultimately undergo degradation to less active forms. Similar studies conducted with rhTPO preparations purified by a combination of more conventional chromatographic steps show different stability-limiting degradation pathways and a different pH-stability profile when compared to affinity purified or in-process preparations. In this case, degradation is accompanied by decreases in activity under all conditions, consistent with the conversion to less active forms. These results illustrate the importance of preformulation and stability characterization of protein pharmaceuticals in support of both process and formulation development. Issues related to storage and handling of inprocess preparations differ from those with formulated product since the stability-limiting degradation pathways change as a function of purification stage.

Somatic histone H1 microinjected into fertilized mouse eggs is transported into the pronuclei but does not disrupt subsequent preimplantation development

We injected somatic subtypes of histone H1 into newly fertilized mouse eggs, which do not naturally contain this chromosomal protein, and examined the fate of the injected protein and its effect on preimplantation development of recipient eggs. Rhodamine-labelled H1 injected into the cytoplasm of 53 eggs was transported into the pronuclei in 51 cases, and this nuclear accumulation could be detected within 15 min of injection. Unlabelled histone H1, which was detected using immunofluorescence, was also transported following microinjection to the pronuclei, where it colocalized with the chromatin and remained associated with the nuclei following cleavage to the two-cell stage. Nuclear accumulation of injected H1 was inhibited when injected eggs were incubated in the presence of drugs that prevent mitochondrial electron transport or glycolysis, which indicates that nuclear transport occurs through an energy-dependent process, as previously observed in tissue culture cells. To determine whether the presence of somatic H1 in early embryonic nuclei would influence subsequent development, fertilized eggs were injected with an approximately physiological quantity (1-5 pg) of somatic H1 or, as controls, with another small basic protein, cytochrome c. Fifty-three eggs were injected with cytochrome c, of which 51 divided to the two-cell stage, and 32 (60%) reached the blastocyst stage, after 5 days in culture. One hundred and eleven eggs were injected with somatic H1, of which 95 divided to the two-cell stage, and 53 (48%) reached the blastocyst stage, after 5 days in culture. The two groups did not differ statistically (chi 2, P > 0.1) with respect to the fraction of injected embryos that developed to the blastocyst stage. These results show that, although mouse embryos lack the somatic subtypes of histone H1 until the four-cell stage of development, they are able to progress through preimplantation development when these subtypes are present beginning at the one-cell stage. This may imply that the distinctive chromatin composition that characterizes early embryos of a variety of species is not essential for early development in mammals.

Assembly of somatic histone H1 onto chromatin during bovine early embryogenesis

We have examined the distribution of somatic histone H1 in bovine oocytes and preimplantation embryos, using an antibody that recognizes histone H1 subtypes present in somatic cells. Immunoreactive H1 was not detectable on the chromosomes of metaphase II of meiosis nor in the nuclei of early cleavage-stage embryos. In most embryos, immunoreactive H1 was assembled onto embryonic chromatin during the fourth to sixth cell cycle after fertilization. No immunoreactive somatic histone H1 was detected, however, when embryos were incubated in the presence of alpha-amanitin beginning early during the fourth cell cycle. These results indicate that somatic subtypes of histone H1 are assembled onto embryonic chromatin in a developmentally regulated manner that requires embryonic transcription. Aphidicolin, an inhibitor of DNA replication, also inhibited the assembly of somatic histone H1 onto chromatin when present at early stages of the 4th cell cycle. It is suggested that, because the bulk of histone gene expression in proliferating cells occurs during DNA replication, expression of genes encoding immunoreactive H1 is inhibited in embryos blocked before or soon after entering the S-phase. These findings on the control of somatic histone H1 assembly onto chromatin in cattle show a remarkable similarity to those found in the mouse. Such evolutionary conservation suggests that the somatic histone H1 complement of chromatin may regulate critical aspects of chromatin activity during mammalian oogenesis or early embryogenesis.

Mitogen-activated protein (MAP) kinase during the acquisition of meiotic competence by growing oocytes of the mouse

During the growth phase of oogenesis, oocytes acquire the ability to undergo meiotic maturation. Although the molecular basis of this meiotic competence is unknown, specific differences in microtubular organization exist between incompetent and competent mammalian oocytes. Mitogen-activated protein (MAP) kinase has been implicated in microtubular regulation and is present in fully grown competent oocytes of mice, suggesting a possible role for this protein in the acquisition of meiotic competence. We report that the MAP kinase species, p42ERK2 and p44ERK1, were detectable by immunoblotting in incompetent oocytes at the early stages of oocyte growth and throughout subsequent growth and acquisition of competence. In partially competent oocytes, which can enter metaphase but cannot complete the first meiotic division, both p42ERK2 and p44ERK1 became phosphorylated, as judged by retarded electrophoretic mobility, and a morphologically normal spindle was assembled. In incompetent oocytes, which cannot enter metaphase, p42ERK2 and p44ERK1 remained nonphosphorylated. When these oocytes were treated with okadaic acid, an inhibitor of protein phosphatases 1 and 2A, a portion of them entered metaphase and the slow-migrating phosphorylated forms of p42ERK2 and p44ERK1 were observed. These phosphorylated forms appeared more rapidly, relative to the time of entry into metaphase, than during maturation of fully competent oocytes. The remaining incompetent oocytes, which did not enter metaphase during okadaic acid treatment, also did not generate slow-migrating p42ERK2 and p44ERK1. These results suggest that the acquisition of meiotic competence during oocyte growth is not linked to the de novo appearance of p42ERK2 or p44ERK1, that the failure of partially competent oocytes to complete meiosis I reflects a defect acting downstream or independently of MAP kinase phosphorylation, and that the ability of meiotically incompetent oocytes to generate phosphorylated forms of p42ERK2 and p44ERK1 in response to okadaic acid is linked to the ability to enter metaphase.

Microtubule and chromatin behavior follow MAP kinase activity but not MPF activity during meiosis in mouse oocytes

Oocyte meiotic maturation is triggered by different stimuli (hormones, unknown signals through cell interactions) in different species. These stimuli indirectly lead to the activation of a major cell cycle regulating activity, the maturation promoting factor (MPF). Other factors, such as the product of the proto-oncogene c-mos or enzymes of the MAP kinase family, are also involved in the process of maturation. MAP kinase activation occurs during meiotic maturation in oocytes from different species with different kinetics. The relationships between MPF activation and MAP kinase activation have been well studied in species such as clam and Xenopus. In this paper, we study the precise timing of MAP kinase activation (as measured by phosphorylation of exogenous myelin basic protein and shifts in mobility of ERK 1 and ERK 2) versus MPF activation (as measured by phosphorylation of exogenous histone H1) during mouse oocyte maturation and, in parallel, morphological events such as changes in microtubule organization and chromatin condensation. We observed that MAP kinase activation was delayed after MPF activation and that this activity persisted throughout maturation whereas MPF activity dropped between the two meiotic metaphases. After parthenogenetic activation of ovulated eggs, MAP kinase inactivation was very slow compared to MPF inactivation. During the first mitotic cell cycle, a rise in myelin basic protein kinase activity at M-phase was observed but it was not related to MAP kinase activation. Furthermore, microtubules and chromatin remained in a metaphase-like state during the complete period of maturation (including the period between the two meiotic metaphases) and a few hours after activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental arrest of fertilized eggs from the B6.YDOM sex-reversed female mouse

When the Y chromosome of a Mus musculus domesticus mouse strain is placed onto the C57BL/6J (B6) inbred background, the XY progeny develop ovaries or ovotestes but never normal testes during fetal life. While some of the hermaphroditic males become fertile, none of the XY females produces litters. Here, we examined the fertility and development of oocytes derived from the XY female mouse. With or without preceding injection of gonadotropins, female mice were mated with normal B6 males, and their embryos were recovered at various developmental stages. In vitro fertilization was performed with the eggs recovered from the oviduct after treatment with gonadotropins. Development of embryos was examined by both light and electron microscopy. The results indicate that the oocytes released from the B6.YDOM ovary were efficiently fertilized and often initiated the first cell cleavage, but all embryos died during early preimplantation periods. Even when oocytes were fertilized in vitro, minimizing their exposure to the XY oviduct/uterus environment, most embryos died at the 1- or 2-cell stage. A few exceptional embryos reached the 4- or 8-cell stage, but abnormalities were evident in both nuclear and cytoplasmic structures of all embryos. After cleavage, neighbouring blastomeres were only loosely associated, and microvilli were abundant at the intercellular interfaces. We postulate that oocytes of the B6.YDOM female mouse become defective during XY ovarian differentiation, and, hence, fail to proceed through normal embryonic development.

MAP kinase becomes stably activated at metaphase and is associated with microtubule-organizing centers during meiotic maturation of mouse oocytes

Using antisera generated against sequences conserved between the ERK1- and the ERK2-encoded species of mitogen-activated protein (MAP) kinases of the rat, species of approximate M(r) 42 and 44 kDa were identified in mouse oocytes. When oocytes underwent meiotic maturation, both species displayed a retarded electrophoretic mobility, consistent with modification by phosphorylation. The slow-migrating forms first appeared after the oocytes had entered metaphase, and their appearance was sensitive to inhibitors of protein synthesis or phosphorylation. These forms remained throughout maturation and in oocytes arrested at metaphase II. Following oocyte activation, which induces a transition to interphase, the slow-migrating forms were replaced by the fast-migrating forms observed in prophase oocytes. MAP kinase activity also increased after oocytes entered metaphase, and this increase required protein synthesis and phosphorylation. To investigate the intracellular distribution of the immunoreactive species, spindles were purified from metaphase II eggs. Both the 42- and the 44-kDa species were detected in immunoblots, and bright staining of the spindle poles was observed by immunofluorescence. When intact oocytes undergoing maturation were examined by immunofluorescence, foci of staining were initially detected on opposing sides of the condensing chromosomes and then became congregated at each pole of the first meiotic spindle. No localized staining was observed during the first meiotic division, but stained foci were present at the poles of the second meiotic spindle. In addition, several cytoplasmic foci of staining often could be seen. When oocytes were exposed to taxol, which permits nonspindle microtubule-organizing centers (MTOCs) present in the cytoplasm to nucleate microtubule assembly, the cytoplasmic foci labeled by the MAP kinase antibodies were found to contain tubulin. We conclude that mouse oocytes contain 42- and 44-kDa species of MAP kinase and that, after maturing oocytes enter metaphase, MAP kinase activity is stimulated by means of a process requiring protein synthesis and phosphorylation. MAP kinase is present in the spindle and is specifically associated with the MTOCs present at the spindle poles and in the cytoplasm. Evidence from cell-free systems suggests that the alterations in MTOC activity that normally occur at metaphase in oocytes may be regulated by MAP kinase. The association of MAP kinase with MTOCs provides a potential structural basis for this cell cycle-dependent change in MTOC activity.

Sperm chromatin acquires an activity that induces microtubule assembly during residence in the cytoplasm of metaphase oocytes of the mouse

Evidence from several cell types indicates that chromatin can induce microtubule assembly in its vicinity. To determine whether this activity is present in sperm chromatin, whose biochemical composition differs from somatic chromatin, mouse oocytes that were undergoing meiotic maturation were inseminated. Maturing oocytes are not activated by sperm penetration but remain arrested at metaphase. The sperm chromatin within the oocyte cytoplasm initially became dispersed and later, under the influence of oocyte cytoplasmic factors, recondensed into a small mass or individual chromosomes. When inseminated oocytes were processed for immunofluorescence using an anti-alpha-tubulin antibody, microtubules were never associated with dispersed sperm chromatin, although the chromosomes of the oocyte were arranged on a spindle. In contrast, microtubules were associated with the majority of sperm nuclei that had become recondensed, and were frequently arranged into a spindle-like structure. When oocytes had been penetrated by more than three sperm, most sperm nuclei remained at the dispersed chromatin stage and these were never associated with microtubules. Exposure of polyspermic oocytes to taxol, which promotes microtubule assembly, failed to induce microtubule assembly around dispersed sperm chromatin. Exposure of monospermic oocytes to nocodazole, which inhibits tubulin polymerization, prevented resolution of the recondensed sperm chromatin into individual chromosomes. These results suggest that sperm chromatin lacks an activity that can induce local microtubule assembly, and that it acquires this activity once modified by oocyte cytoplasmic factors.

Nuclear and chromatin composition of mammalian gametes and early embryos

Changes in nuclear structure and chromatin composition regulate gene activity in many cell types and could play a similar role during early mammalian embryogenesis. Oocytes of the mouse contain the three major lamin species present in somatic cells, although lamin A synthesized by oocytes has a higher molecular mass than the somatic species. Oocyte chromatin contains core histones similar to those of somatic cells, as well as elements that are immunologically related to protamines. In contrast, somatic-type histone H1 is not present. DNA topoisomerase II has not yet been identified in mammalian oocytes, but is abundant in frog oocytes. In contrast to oocytes, sperm do not contain a typical nuclear lamina. DNA topoisomerase II is detectable until late spermiogenesis. Although the DNA of sperm is associated mainly with protamines, some histone may be retained. There is also evidence that the arrangement of the DNA in the nucleus is nonrandom. These results demonstrate differences in nuclear and chromatin composition between oocytes and sperm. After fertilization, the nuclei of cleavage-stage blastomeres undergo programmed modifications. Lamin B is synthesized, whereas lamin A is not. In addition, a set of nuclear proteins is transiently synthesized in mice at the two-cell stage. Changes in embryonic chromatin composition also occur. The relative abundance of transcripts from different core histone genes differs between mouse oocytes and blastocysts. Furthermore, somatic histone H1 becomes detectable beginning at the mid-four-cell stage. As well, during early cleavage stages, expression of plasmid-borne genes becomes dependent on enhancers. Thus, developmentally regulated changes in nuclear and chromatin composition occur during early mammalian embryogenesis, and these may be important for the initiation and regulation of embryonic gene activity.

Computerized templating in uncemented total hip arthroplasty to assess component fit and fill

The aim of the uncemented femoral component in total hip arthroplasty is to achieve a stable bone-prosthesis interface without the use of polymethyl methacrylate (PMMA). Maximal fill of the femoral canal by the prosthesis promotes initial stability and long-term optimal stress transfer to the bone. The percentage "fit and fill" of the proximal femur by three prostheses, the porous coated anatomic, anatomic medullary locking, and the Harris-Galante, was compared by use of a computerized templating model to assess preoperative radiographs of 20 patients. Results showed that overall percentage fit and fill was similar and satisfactory (greater than 60%) in 17 of 20 patients. If a satisfactory fill was not achieved with one prosthesis, another prosthesis did not significantly improve fill. Lack of bony contact in the proximomedial femur was the most common deficiency noted.

A biomechanical analysis of solvent-dehydrated and freeze-dried human fascia lata allografts. A preliminary report

This study compares the basic mechanical properties of two groups of commercially available fascia lata allografts processed by different means (solvent-dehydrated and sterilized via gamma radiation, and freeze-dried without secondary sterilization). The results reveal significantly (P less than 0.05) higher stiffness, higher maximum load to failure, and higher maximum load per unit width of graft with the solvent-dried as opposed to the freeze-dried fascia lata. Subsections of individual solvent-dried specimens were also more uniform in their mechanical properties than those of the freeze-dried allografts.

CLINICAL RELEVANCE

Fascia lata is used as a graft material in a variety of orthopaedic procedures. Allograft fascia lata offers an increased cross-sectional area of material and eliminates the morbidity associated with the harvesting of autologous tissues. However, the structural uniformity of such large grafts has been questioned. Processing techniques used in the sterilization and storage of such grafts is varied and represents a potential source of variation in the mechanical properties of allograft specimens. The results of this study suggest that a commercially available solvent-dehydrated form of fascia lata provides a more suitable grafting material than freeze-dried specimens obtained from tissue banks.

Developmental regulation of chromatin composition during mouse embryogenesis: somatic histone H1 is first detectable at the 4-cell stage

We have examined the distribution of histone H1 in oocytes and preimplantation embryos of the mouse, using a polyclonal antibody raised against the histone H1 subtypes present in somatic cells. Immunofluorescence and immunoblotting analyses failed to detect somatic histone H1 in germinal vesicle (GV)-stage oocytes. In contrast, somatic histone H1 was detectable by immunofluorescence in the nuclei of GV oocytes previously injected with histone H1 as well as the nuclei of ovarian granulosa cells, and by immunoblotting in 8-cell embryos. 1- and 2-cell embryos examined by immunofluorescence did not contain detectable somatic histone H1. At the early 4-cell stage (54-56 hours post-hCG), 5 of 52 embryos contained somatic histone H1 in one or more nuclei. By the late 4-cell stage (66-68 hours post-hCG), however, 58 of 62 embryos contained somatic histone H1. In 8-cell embryos, morulae and blastocysts, all nuclei contained somatic histone H1 in every case. When embryos were exposed to the transcriptional inhibitor, alpha-amanitin, beginning at the late 2-cell stage, they cleaved to the 4-cell stage but fewer than 10% developed histone H1 immunoreactivity. When treatment began at the early 4-cell stage, the embryos that remained at the 4-cell stage in the presence of the drug developed histone H1 immunoreactivity in half of the cases. Embryos that reached the 5- to 8-cell stage in the presence of the drug developed histone H1 immunoreactivity in every case.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of acetabular stability in uncemented prostheses

The stability of two commonly used uncemented acetabular prostheses fixed with either pegs or screws has been established by evaluating the torque strengths in ten cadaveric acetabulae. The initial stability of implants to simulated frictional loads was satisfactory compared to previous estimations of the frictional torques in polyethylene-on-metal and metal-on-metal articulations. Testing of the torque required to produce 2 degrees of rotation at the bone-implant interface showed that the peg fixation required significantly greater loads than did the screw fixation (P less than .03). Testing the prostheses to failure gave good results, although lower than previous cemented arthroplasty estimations. The margin of stability over the frictional torques that can be generated is such that it may affect the bony ingrowth into these prostheses. This may account for the common finding of fibrous ingrowth in these prostheses.

Tibio-talar stability in bimalleolar ankle fractures: a dynamic in vitro contact area study

A dynamic weight-bearing model has been developed in a cadaveric ankle model to assess the contact areas of the talus in varying degrees of bimalleolar ankle fractures. A surgically created transverse fibula osteotomy with up to 6 mm of displacement did not cause a significant change in the contact area. Sectioning of the deltoid ligament, regardless of fibular displacement, created a 15% to 20% decrease in the contact area (P less than .001). This model represents a clinically relevant situation, as it examines motion of an unconstrained, axillary loaded ankle. Additional medial side disruption increases ankle instability by allowing anterior and lateral translation of the talus out of the mortise. Isolated lateral malleolar displacement does not appear to cause ankle instability.

Surgical treatment for severe slipping of the upper femoral epiphysis

We have used a modified technique of cervical osteotomy to treat a consecutive series of 23 patients with chronic slip of the upper femoral epiphysis. It has been successful in correcting both moderate and severe deformities with a low incidence of avascular necrosis, comparable to that seen after subtrochanteric osteotomies. We describe the operative details and discuss the features which make cervical osteotomy technically superior to intertrochanteric and subtrochanteric procedures.

Osteointegration of bone graft in porous-coated total hip arthroplasty

Since 1983, 19 patients have had bone grafting of acetabular defects in association with a porous-coated acetabular prosthesis. The defects were defined by anatomic location to assess the rates of incorporation at different sites. The average time to incorporation was 12 months, judged by trabecular continuity. Superolateral grafts showed a greater degree of rarefaction than medial grafts. Nonprogressive migration of the graft was seen in only two cases before full incorporation of the graft. Developing lucency was seen up to 2 mm at the prosthesis-graft interface but not at the graft-ilium level. Roentgenograms suggested that integration of porous acetabular prostheses into bone may improve results of reconstructive surgery of the acetabulum.

Clostridium difficile infection in orthopaedic patients

In a review of the results of toxin assays, twenty-five orthopaedic patients who had a Clostridium difficile infection and associated diarrhea were identified. The infection was due to the use of antibiotics in all but one patient. Seventeen patients had received the antibiotics prophylactically. The two most commonly implicated antibiotics were cefazolin and clindamycin, because those drugs had been commonly used for prophylaxis at the study institutions. However, other antibiotics were implicated. There was a positive correlation between the delay in diagnosis and the severity of the illness. A white blood-cell count of more than 20 x 10(9) per liter indicated severe disease in our survey. The possibility of Clostridium difficile infection should be considered in patients who have signs and symptoms that mimic those of intestinal obstruction. Patients who have an unexplained fever or high white blood-cell count and in whom diarrhea develops in the postoperative period should be treated immediately with metronidazole, and a specimen of stool should be obtained for an assay for Clostridium difficile toxin. If the diagnosis of Clostridium difficile infection is confirmed by the presence of toxin in the stool and the patient has persistent, severe diarrhea, oral administration of vancomycin should be added to the regimen. The duration of antibiotic prophylaxis should be minimized to decrease the risk of Clostridium difficile colitis.

The effect of loading on tibiotalar alignment in cadaver ankles

The tibiotalar movements which occur with axial loading, without applied moment forces were studied in cadaver ankles using a minimally constrained testing apparatus. Lateral translation of the talus measured up to 2 mm, which was associated with increased tibiotalar valgus angulation. Neither displacing the distal fibula laterally, nor sectioning the deltoid ligament, significantly influenced the talar shift. The tibiotalar motion which was observed after simple axial loading in a stable configuration (e.g., fibula and deltoid ligament intact) is of the same magnitude that is usually regarded as signifying an unstable ankle fracture. Consequently, this study suggests that the criteria for an unstable ankle fracture may need closer scrutiny.

Total replacement of the hip for avascular necrosis in sickle cell disease

Total hip replacement was performed in 27 hips of patients who had sickle cell anaemia with avascular necrosis of the femoral head. The disease was bilateral in 11 patients. Considerable medical problems were encountered although most of the patients had exchange transfusion before surgery (86%), which prevented postoperative sickle cell crises in all but two cases. At the primary operation hard sclerotic bone was seen in nine femora with complete obliteration of the femoral canal. There were four femoral fractures, three following perforation of the shaft due to this hard bone. There was a very high morbidity due to loosening in both cemented and uncemented prostheses. With a rate of 59% over a cumulative 5.5 year period, revision was being performed at an average of only 43 months. Surgeons should be aware of these problems.