42 Vitrification of invitro-produced feline embryos

Preservation of feline embryos is useful in propagating endangered species, preserving valuable genetics, and supporting biomedical research. Although a wide variety of cryoprotectants (CP) and protocols are successfully used for vitrification of invitro-produced (IVP) embryos, there are often species-specific differences in viability of embryos post-warming. The purpose of this study was to evaluate the viability of IVP feline embryos after vitrification using two common CPs, propanediol (PrOH) or ethylene glycol (EG). Embryos were produced with oocytes and frozen-thawed epididymal sperm collected from local spay-neuter clinics using a published IVP protocol developed for producing domestic feline embryos. Day 7 early blastocysts (stage 5), blastocysts (stage 6), and expanded blastocysts (stage 7) were evaluated for quality (grade 1 or 2) and randomly assigned to one of three treatments: vitrification with PrOH (n=32), vitrification with EG (n=31), or control (n=47), which was allowed to continue in culture until Day 8. The vitrification protocol was as follows. The base medium for all vitrification media was a HEPES-buffered feline optimized culture medium (FOCMH). Embryos were placed in 0.5mL of equilibration medium (7.5% dimethyl sulfoxide, 7.5% PrOH or EG, 0.5M sucrose, 10% Ficoll, and 20% fetal calf serum (FCS)) for 5min at room temperature. Individual embryos were then moved to 20-μL drops of vitrification medium (15% dimethyl sulfoxide, 15% PrOH or EG, 0.5M sucrose, 10% Ficoll, and 20% FCS) at room temperature for 30s before being loaded onto Cryolock devices and plunged into liquid nitrogen. Warming was done using a 3-step process for all vitrified embryos. First, embryos were moved from liquid nitrogen directly to 0.5mL of 1M sucrose, 10% Ficoll, and 20% FCS at 37°C for 1min. Next, embryos were moved to 0.5mL of 0.5M sucrose, 10% Ficoll, and 20% FCS at 20°C for 3min. Finally, embryos were transferred to 0.5mL of FOCMH for 5min at 37°C. All warmed embryos were cultured in medium, optimized for feline embryos, with 5% FCS and evaluated for re-expansion of the blastocoele and progression in development at 24 and 48h. Results are from five replicates. Embryos vitrified in EG exhibited higher percentages of viable embryos 24h after warming (84%) than embryos vitrified in PrOH (59%; P<0.05). The continued embryonic growth of viable embryos after culture for 48h showed equivalent developmental rates, at 87, 96, and 100% for control, EG-treated, and PrOH-treated embryos, respectively (P>0.05). Results indicate EG is a more successful CP treatment for vitrification of feline embryos when evaluating viability 24h post-warming. We report a higher viability of embryos post-thaw than previous studies using the same CPs (Pope et al. 2012 Reprod. Domest. Anim. 47, 125). This may be due to the shorter exposure time to the CPs we used during the vitrification process. We conclude that EG and PrOH are effective CPs for Day 7 feline IVP embryos using this protocol. Further research is needed to increase treatment numbers and evaluate pregnancy rates from embryos transferred post-warming.

Determination of Fat,Moisture, and Protein in Meat and Meat Products by Using the FOSS FoodScan Near-Infrared Spectrophotometer with FOSS Artificial Neural Network Calibration Model and Associated Database: Collaborative Study

A collaborative study was conducted to evaluate the repeatability and reproducibility of the FOSS FoodScan near-infrared spectrophotometer with artificial neural network calibration model and database for the determination of fat, moisture, and protein in meat and meat products. Representative samples were homogenized by grinding according to AOAC Official Method 983.18. Approximately 180 g ground sample was placed in a 140 mm round sample dish, and the dish was placed in the FoodScan. The operator ID was entered, the meat product profile within the software was selected, and the scanning process was initiated by pressing the start button. Results were displayed for percent (g/100 g) fat, moisture, and protein. Ten blind duplicate samples were sent to 15 collaborators in the United States. The within-laboratory (repeatability) relative standard deviation (RSDr) ranged from 0.22 to 2.67% for fat, 0.23 to 0.92% for moisture, and 0.35 to 2.13% for protein. The between-laboratories (reproducibility) relative standard deviation (RSDR) ranged from 0.52 to 6.89% for fat, 0.39 to 1.55% for moisture, and 0.54 to 5.23% for protein. The method is recommended for Official First Action.

95 ROLE OF POLYAMINES IN BOVINE PRE-IMPLANTATION DEVELOPMENT

Polyamines are involved in trophectoderm attachment and outgrowth, but little is known about their role in earlier stages of development. The objective of this study was to evaluate the effects of an inhibitor of polyamine synthesis (difluoromethylornithine, DFMO) on development (blastocyst formation and hatching) and cell allocation to the trophectoderm (TE, CDX2-positive) and inner cell mass (ICM, SOX2-positive) in the bovine embryo. Cumulus-oocyte complexes (COCs) were recovered from slaughterhouse ovaries and matured for 24 h in a defined maturation medium (5.0 mM glucose, 0.6 mM cysteine, 0.5 mM cysteamine, 0.1 IU mL–1 FSH, 50 ng mL–1 EGF, and 2.5 mg mL–1 recombinant human albumin). Frozen-thawed spermatozoa were processed by gradient centrifugation and co-incubated (2 × 106 mL–1) with COC [10 COC/50 µL; 7.5 µg mL–1 heparin, 2 mM caffeine, and 8.0 mg mL–1 fatty-acid free (FAF) BSA] for 20 to 22 h. After removing cumulus cells, zygotes were cultured (10 embryos/20 µL) in a medium for cleavage stage bovine embryos (0.5 mM glucose, 0.3 mM pyruvate, 6.0 mM lactate, 0.25 mM citrate, 1.0 mM alanyl-glutamine, 0.25 × MEM nonessential and essential amino acids, 5 µM EDTA, and 8.0 mg mL–1 FAF BSA). After 72 h, embryos with >4 cells were randomly allocated (5 embryos/20 µL) to a culture medium for compaction and blastocyst formation (3.0 mM fructose, 0.1 mM pyruvate, 6.0 mM lactate, 0.5 mM citrate, 1.0 mM alanyl-glutamine, 1× MEM nonessential amino acids, 0.5× MEM essential amino acids, 0.075 mM myo-inositol, and 8.0 mg mL–1 FAF BSA) containing 0 (control), 5, or 10 mM DFMO. Embryonic development was evaluated at 192 h post-insemination (96 h in the second medium containing DFMO treatments), and hatching or hatched blastocysts were fixed for analysis of cell allocation. All data were analysed by ANOVA and P < 0.05 was considered significant. Blastocyst formation and hatching (% of embryos cultured in the presence of treatments) were both inhibited (P < 0.05) when embryos (n = 157/treatment) were cultured with 5 (39.5 ± 3.9%, 14.6 ± 2.8%) or 10 (39.5 ± 3.9%, 14.0 ± 2.8%) mM DFMO compared with embryos cultured without DFMO (53.5 ± 4.0%, 26.1 ± 3.5%). The number of TE cells was also reduced (P < 0.05) in the presence of 5 (121.4 ± 7.2) and 10 (123.6 ± 6.7) mM DFMO compared with embryos cultured without DFMO (152.4 ± 9.7), but the number of ICM cells (45.2 to 54.0) and the total number of cells (TE+ICM, 168.8 to 201.1) were not affected (P > 0.05). In a second experiment (n = 163 to 165/treatment), the negative effects of DFMO on hatching (17.0 ± 2.9%; P < 0.05, v. control, 30.7 ± 3.6%) could be partially reversed when embryos were cultured with both 10 mM DFMO and an exogenous polyamine (100 µM putrescine, 23.0 ± 3.3% DFMO+Put; P > 0.05 v. control). The number of TE cells for embryos cultured with DFMO+Put (153.9 ± 8.7) was intermediate between embryos cultured with (138.0 ± 6.9) or without DFMO (control, 161.6 ± 8.7), but these differences were not significant (P > 0.05). These results provide the first evidence of a role for polyamines during blastocyst formation and hatching of bovine embryos, with specific effects on trophectoderm proliferation and hatching.

Genetic variation in IGF1, IGFBP3, IRS1, IRS2 and risk of breast cancer in women living in Southwestern United States

BACKGROUND

An insulin-related pathway to breast cancer has been hypothesized.

METHODS

We examine the 19 CA repeat of the IGF1 gene, the -202 C > A IGFBP3, the G972R IRS, and the G1057D IRS2 polymorphisms among 1,175 non-Hispanic white (NHW) and 576 Hispanic newly diagnosed breast cancer cases and 1,330 NHW and 727 Hispanic controls living in Arizona, Colorado, New Mexico, and Utah.

RESULTS

Among post-menopausal women not recently exposed to hormones, not having the 19 CA repeat of IGF1 gene was associated with breast cancer among NHW women [odds ratio (OR) 2.14, 95% confidence interval (CI) 1.21-3.79] and having an R allele of G972R IRS1 increased breast cancer risk among Hispanic women (OR 2.70, 95% CI 1.13-6.46). Among post-menopausal Hispanic women recently exposed to hormones the A allele of the -202 C > A IGFBP3 polymorphism increased risk of breast cancer (OR 1.57, 95% CI 1.06-2.33). The IGF1 19 CA repeat polymorphism interacted with hormone replacement therapy (HRT) among NHW post-menopausal women; women who had the 19/19 IGF1 genotype were at reduced risk of breast cancer (OR 0.64, 95% CI 0.47-0.88) if they did not use HRT. We also observed interaction between body mass index and IGF1 19 CA repeat (p=0.06) and between weight gain and the -202 C > A IGFBP3 polymorphism (p=0.05) in NHW post-menopausal women not recently exposed to hormones.

CONCLUSIONS

Our data suggest that associations between insulin-related genes and breast cancer risk among women living in the Southwestern United States may be dependent on estrogen exposure and may differ by ethnicity.

221 BASAL SEMINAL TRAITS AND IN VITRO FERTILIZATION IN THE SAND CAT (FELIS MARGARITA)

The sand cat (Felis margarita) is one of five small-sized cat species given priority for conservation in North American zoos. An improved understanding of sand cat reproductive biology would benefit captive breeding and facilitate use of assisted reproduction for genetic management. In this study, our objectives were to: (1) characterize basal seminal traits, (2) assess ovarian responses to exogenous gonadotropins, and (3) compare Ham's (HF10) F-10 with 5% fetal bovine serum (FBS) and feline optimized culture medium (FOCM) with 0.4% BSA for supporting gamete function and embryonic development in vitro. Semen was collected by electroejaculation from seven males (n = 10 ejaculates), washed, and resuspended (10 � 106 motile sperm/mL) in HF10 or FOCM for culture (6% CO2 in air at 38.7�C). Sperm motility (% motile and rate of forward progress, 0-5 scale) was evaluated at 0, 1, 3, and 6 h of culture and used to calculate a sperm motility index (SMI; [% + (5 * rate)]/2). Acrosomal integrity was evaluated by staining (fast green FCF-rose bengal) at 0 and 6 h. For IVF, ovarian follicles were aspirated laparoscopically from female sand cats (n = 4) treated at random times of the estrous cycle with 150 IU eCG and 100 IU hCG (84 h post-eCG) prior to oocyte recovery (25 h post-hCG). Grade 1 oocytes were co-incubated with 2 � 105 motile sperm/mL in HF10 (n = 32) or FOCM (n = 33) for 20 h before transfer to fresh medium. Resulting embryos were either cryopreserved (n = 42) at 30 h post-insemination (hpi) or cultured until Day 7 pi after being moved to fresh medium (FOCM with 5% FBS (n = 10) or HF10 (n = 6)) on Day 3 pi. Ejaculates contained (mean � SEM) 43.5 � 11.0 � 106 total spermatozoa, with 77.0 � 2.3% motility, 43.8 � 3.9% normal morphology, and 93.1 � 1.3% intact acrosomes. During 6 h of culture, SMI and % intact acrosomes declined (P < 0.05) slightly (SMI, 73.8-74.8 at 0 h and 68.5-68.8 at 6 h; % intact acrosomes, 87.1-87.6% at 0 h and 69.0-74.2% at 6 h), but similarly (P > 0.05) in both media. Females produced 24.3 � 5.6 follicles, with 19.3 � 5.1 total oocytes and 16.5 � 4.6 Grade 1 oocytes recovered per female. The proportions of oocytes cleaving at 20 and 30 hpi and the quality of the resulting embryos at 30 hpi were higher (P < 0.05) in FOCM (20 hpi, 76.5 � 8.7%; 30 hpi, 92.9 � 7.1%; 89.2 � 7.9% Grade 1) than in HF10 (20 hpi, 29.8 � 11.7%; 30 hpi, 55.9 � 20.6%; 62.9 � 7.2% Grade 1). Two blastocysts developed in FOCM (69.0 � 19.0 cells), but the final cell numbers of all cultured embryos were not different (P > 0.05) between FOCM (26.9 � 8.0 cells) and HF10 (19.3 � 6.4 cells). Compared to other small felid species, sand cats exhibited excellent seminal traits, gonadotropin-induced ovarian responses, and fertilization success in vitro. Although sperm motility and acrosomal integrity were similar in FOCM and HF10, the medium developed specifically for domestic cat embryos (FOCM) better supported IVF and early embryonic development. These results indicate that IVF with fresh spermatozoa could be a valuable tool for genetic management of captive sand cat populations. This work was supported by MAF D04ZO-72.

284 COMPARATIVE FERTILITY OF FRESHLY-COLLECTED VERSUS FROZEN - THAWED SPERMATOZOA FOR IN VITRO FERTILIZATION IN THE FISHING CAT (PRIONAILURUS VIVERRINUS)

Wild populations of fishing cats (Prionailurus viverrinus) in Southeast Asia are in decline, primarily due to habitat loss. Because the fishing cat population in North American zoos is small (n = 69) and inbred (F = 0.17) with relatively low genetic variation (86%), infusion of new founder genes from Asia is a conservation priority. Importation of cryopreserved semen for use with IVF and ET may offer one alternative to the international transport of living animals. In this study, our objectives were to (1) compare motility longevity of fresh vs. frozen-thawed fishing cat spermatozoa in two culture media, (2) evaluate ovarian responses to exogenous gonadotropins, and (3) assess development of IVF embryos produced with fresh vs. frozen-thawed spermatozoa. Raw semen was collected via electroejaculation from male fishing cats (n = 4), divided into groups, and washed. Two sperm pellets were resuspended in either Ham's F10 medium (HF10; with 5% FBS) or our feline optimized culture medium (FOCM; with 0.4% BSA); another pellet was diluted in TEST egg yolk, cooled to 5�C over 3 h, glycerated (4%), and cryopreserved in straws over LN2 vapor. Frozen sperm samples were thawed, washed, and diluted in either HF10 or FOCM. Fresh and frozen-thawed sperm motility (percent motile, rate of forward progress) in each medium (10 � 106 motile sperm/mL) was assessed (at 0, 1, 3, and 6 h) in microdrops under oil during culture (38�C; 6% CO2 in air). Female fishing cats (n = 10) were treated with exogenous gonadotropins (150 IU eCG, 100 IU hCG, 85-h interval) and ovarian follicles were aspirated laparoscopically. Recovered oocytes were inseminated with fresh (2 � 105 motile sperm/mL) or frozen-thawed (5 � 105 motile sperm/mL) spermatozoa in FOCM microdrops; resulting embryos were either cryopreserved or cultured in FOCM (with 5% FBS added at 72 h post-insemination) for 7 days. Sperm motility over time did not differ (P > 0.05) between media for either fresh or frozen-thawed samples; however, across media, frozen-thawed sperm motility was lower (P < 0.05) and declined faster (P < 0.05) compared to fresh spermatozoa. Females produced an average (�SEM) of 9.8 � 2.9 mature ovarian follicles, allowing recovery of 7.3 � 2.6 high-quality oocytes per female. Oocyte cleavage percentage at 42 h p.i. was lower (P < 0.05) with frozen-thawed spermatozoa (38%, 11/29) compared to freshly collected spermatozoa (68%, 17/25). Overall, 35% (6/17) of cultured embryos developed to blastocysts with no difference (P > 0.05) between embryos produced with frozen-thawed (4/11) vs. fresh (2/6) spermatozoa. Although fishing cat sperm motility and fertility appear compromised after cryopreservation, our results demonstrate the ability of frozen-thawed spermatozoa to produce IVF embryos that are capable of developing to blastocyst stage in vitro. This work was supported by (NIH RR015388).

Dementia: the leading predictor of death in a defined elderly population: the Cache County Study

OBJECTIVE

To examine the relative risk and population attributable risk (PAR) of death with dementia of varying type and severity and other risk factors in a population of exceptional longevity.

METHODS

Deaths were monitored over 5 years using vital statistics records and newspaper obituaries in 355 individuals with prevalent dementia and 4,328 without in Cache County, UT. Mean age was 83.3 (SD 7.0) years with dementia and 73.7 (SD 6.8) years without. History of coronary artery disease, hypertension, diabetes, and other life-shortening illness was ascertained from interviews.

RESULTS

Death certificates implicated dementia as an important cause of death, but other data suggested a stronger association. Adjusted Cox relative hazard and PAR of death were higher with dementia than with any other illness studied. Relative hazard of death with dementia was highest at ages 65 to 74, but the high prevalence of dementia after age 85 resulted in 27% PAR among the oldest old. Mortality increased substantially with severity of dementia. Alzheimer disease shortened survival time most dramatically in younger participants, but vascular dementia posed a greater mortality risk among the oldest old.

CONCLUSION

In this population, dementia was the strongest predictor of mortality, with a risk two to three times those of other life-shortening illnesses.

Replication fork density increases during DNA synthesis in X. laevis egg extracts

Duplication of the eukaryotic genome depends on the temporal and spatial organization of DNA replication during the cell cycle. To investigate the genomic organization of DNA replication in a higher eukaryote, multiple origins of replication must be simultaneously analyzed over large regions of the genome as DNA synthesis progresses through S phase of the cell cycle. We have employed a novel technique that allows for the quantitative analysis of DNA replication on a genome wide basis. The technique involves stretching and aligning individual DNA molecules on a glass surface. As a model system, Xenopus laevis egg extract was used to differentially label sperm chromatin at successive time points after the start of DNA synthesis. The differentially labeled DNA allows earlier and later replicating sequences to be distinguished, and hence the sites of DNA synthesis at any given time can be directly visualized. Genomic DNA was extracted, and measurements made on the linearized molecules provided a comprehensive analysis of the spatial and temporal organization of DNA replication in the X. laevis in vitro replication system. It was found that: (i) DNA synthesis initiates asynchronously at irregular intervals but continuously as DNA replication advances; and (ii) that the frequency of initiation (the number of activated origins per kilobase) increases as DNA synthesis nears completion. The implications of these findings for the regulation of DNA replication in early embryos is discussed.

Quantifying single gene copy number by measuring fluorescent probe lengths on combed genomic DNA

An approach was developed for the quantification of subtle gains and losses of genomic DNA. The approach relies on a process called molecular combing. Molecular combing consists of the extension and alignment of purified molecules of genomic DNA on a glass coverslip. It has the advantage that a large number of genomes can be combed per coverslip, which allows for a statistically adequate number of measurements to be made on the combed DNA. Consequently, a high-resolution approach to mapping and quantifying genomic alterations is possible. The approach consists of applying fluorescence hybridization to the combed DNA by using probes to identify the amplified region. Measurements then are made on the linear hybridization signals to ascertain the region's exact size. The reliability of the approach first was tested for low copy number amplifications by determining the copy number of chromosome 21 in a normal and trisomy 21 cell line. It then was tested for high copy number amplifications by quantifying the copy number of an oncogene amplified in the tumor cell line GTL-16. These results demonstrate that a wide range of amplifications can be accurately and reliably quantified. The sensitivity and resolution of the approach likewise was assessed by determining the copy number of a single allele (160 kb) alteration.

Imaging of single DNA molecule: applications to high-resolution genomic studies

Single molecule analysis of DNA has revealed new insights into its structural and physical properties. The application of new methods for manipulating and visualizing DNA has resulted in important advances in high-resolution physical mapping of the genome and quantitative cytogenetic studies of genomic abnormalities (Lichter 1997). Studies of single molecules of DNA have employed a variety of approaches including electron microscopy, atomic force microscopy, scanning-tunneling microscopy and fluorescence microscopy. A number of new technologies have recently been developed to exploit fluorescence microscopy's full potential for genomic analysis and the fine mapping of subtle genetic alterations. In the case of the latter application, particular emphasis has been placed on developing new methods for stretching DNA for high-resolution fluorescence in-situ hybridization studies. We have recently described a process called molecular combing according to which single DNA molecules bound by their extremities to a solid surface are uniformly stretched and aligned by a receding air/water interface (Bensimon et al. 1994). In the following, we will review recent developments concerning molecular combing and discuss its current and potential applications for the high-resolution mapping of the human genome, the detection and quantification of subtle genomic imbalances and the positional cloning of disease-related genes.

Single molecule analysis of DNA replication

We describe here a novel approach for the study of DNA replication. The approach is based on a process called molecular combing and allows for the genome wide analysis of the spatial and temporal organization of replication units and replication origins in a sample of genomic DNA. Molecular combing is a process whereby molecules of DNA are stretched and aligned on a glass surface by the force exerted by a receding air/water interface. Since the stretching occurs in the immediate vicinity of the meniscus, all molecules are identically stretched in a size and sequence independent manner. The application of fluorescence hybridization to combed DNA results in a high resolution (1 to 4 kb) optical mapping that is simple, controlled and reproducible. The ability to comb up to several hundred haploid genomes on a single coverslip allows for a statistically significant number of measurements to be made. Direct labeling of replicating DNA sequences in turn enables origins of DNA replication to be visualized and mapped. These features therefore make molecular combing an attractive tool for genomic studies of DNA replication. In the following, we discuss the application of molecular combing to the study of DNA replication and genome stability.

Sapling biomass allocation and growth in the understory of a deciduous hardwood forest

Above- and belowground tissues of co-occurring saplings (0.1-1 m height) of Acer saccharum Marsh. (very shade tolerant), Acer rubrum L. (shade tolerant), Fraxinus americana L. (intermediate shade tolerant), and Prunus serotina Ehrh. (shade intolerant) were harvested from a forest understory to test the hypothesis that the pattern of biomass allocation varied predictably with shade-tolerance rank. The placement and length of branches along the main axis were consistent with the formation of a monolayer of foliage for the tolerant and intermediate species. Other morphological characteristics did not vary predictably with shade-tolerance rank. The maintenance of high specific leaf area (SLA; leaf area/leaf mass) and leaf area ratio (LAR; leaf area/sapling mass) is considered important for growth under extreme shade, yet these traits were not clearly related to the shade-tolerance rank of these species. Fraxinus americana, an intermediate species, had the highest LAR and growth rate in the understory, and with the exception of P. serotina, the very shade-tolerant A. saccharum had the lowest LAR. Prunus serotina maintained a large starch-rich tap root and shoot dieback was common, yielding the largest root/shoot ratio for these species. The observed allocation patterns were not similar to the long-standing expectation for the phenotypic response of juvenile trees to shade, but were consistent with three hypothetical "growth strategies" in the understory: (1) the low SLA and LAR of A. saccharum may provide a measure of defense against herbivores and pathogens and thus promote persistence in the understory, (2) the high SLA for F. americana and high LAR for F. americana and A. rubrum may enable these species to achieve high growth rates in shade, and (3) the large carbohydrate stores of P. serotina may poise this species for opportunistic growth following disturbance. The relative importance of resistance to herbivores and pathogens vs. the maintenance of high growth rates may be important in evaluating the patterns of biomass allocation in the understory.

The initiation mess?

This review concerns the mechanisms which control initiation of chromosome replication in enterobacteria with respect to cell growth. Initiation control is commonly separated into positive and negative regulatory mechanisms. Four main points are advanced concerning these different aspects of initiation control. (i) The average concentration of the initiator protein DnaA is proportional to the origin concentration, i.e. the origin per cell mass ratio and, thus, inversely proportional to the very often used term of the 'initiation mass'. (ii) The time of initiation of chromosome replication in the cell cycle is set by DnaA protein accumulating to a threshold level, which in concert with a number of other factors allows for a co-operative formation of the initiation complex. (iii) The time of initiation is not determined by the interaction with these other factors or by the transient interaction between newly replicated origins (oriC) and the cell surface. (iv) The aberrant initiation phenotype observed in various mutants, including dnaA (ts) mutants, might be due to a defective preinitiation DnaA-oriC interaction or it might be due to a defect in the protection of newly initiated origins from reinitiation. Many of these points are discussed and evaluated in view of recent developments concerning the regulation of chromosome replication in Escherichia coli.

Parental strand recognition of the DNA replication origin by the outer membrane in Escherichia coli

The outer membrane of Escherichia coli binds the origin of DNA replication (oriC) only when it is hemimethylated. We report here the results of a footprinting analysis with the outer membrane which demonstrate that its interaction with oriC occurs mainly at the left moiety of the minimal oriC, where 10 out of 11 Dam methylation sites are concentrated. Two regions, flanking the Integration Host Factor (IHF) sites, are preferentially recognized at the minimum membrane concentration at which oriC plasmid replication is inhibited in vitro. We have identified the putative proteins involved in hemimethylated oriC binding and cloned one of the corresponding genes (hobH). The purified LacZ-HobH fusion protein specifically binds oriC DNA at the same preferential sites as the membrane. A mutant of the hobH gene reveals partial asynchronous initiation of DNA replication.

Non-attendance at periodontal clinics: forgetting and administrative failure

Using a case-control design, non-attenders and attenders at a periodontal clinic were sent postal questionnaires in order to compare the sociodemographic characteristics of non-attenders and attenders. Non-attenders were also asked why they failed to attend. The main reason given was that they had forgotten about their appointment. Administrative error was the second most frequent category of response explaining non-attendance. Differences in sociodemographic characteristics between attenders and non-attenders did not appear to explain non-attendance, apart from car and telephone ownership. Time between notice of an appointment and the way patients received their appointments was associated with non-attendance. Non-attenders viewed their problem as less serious than attenders.

P59, an hsp 90-binding protein. Cloning and sequencing of its cDNA and preparation of a peptide-directed polyclonal antibody

The primary sequence of the rabbit liver cDNA coding for protein p59 has been determined. The protein binds to the 90-kDa heat shock protein (hsp 90) and is associated with it, including when hsp 90 participates in hetero-oligomeric complexes of untransformed mammalian steroid receptors that sediment at 8-10 S. The cloned cDNA codes for an open reading frame of 458 amino acids defining a yet unknown protein. However, 55% amino acid homology to peptidyl-prolyl isomerase is found between amino acids 41 and 137, suggesting rotamase activity for p59, which speculatively may apply to bound hsp 90 and thus be implied in the intracellular trafficking of hetero-oligomeric forms of steroid hormone receptors. A polyclonal antibody derived from the COOH-terminal peptide 441-458 demonstrates a good affinity for rabbit, rat, and human "p59" protein. It interacts with at least one epitope, available in 8-10 S untransformed steroid receptor complexes and different from that recognized by the monoclonal antibody KN382/EC-1.

Gene regulation under growth conditions. A model for the regulation of initiation of replication in Escherichia coli

A stochastic model is presented to describe gene regulation during growth conditions (non-steady-state), with an emphasis on the distribution of gene activation times. A non-Poissonian distribution, with a smaller variability than in steady-state, is obtained when gene activation by the regulatory protein(s) occurs before the protein(s) reach their saturation concentration. The model is applied to the regulation of initiation of chromosomal replication in Escherichia coli. The rate of initiation is shown to depend linearly on the concentration of the initiator molecule, DnaA, in good agreement with recently published data. It is suggested that the variability of initiation times could be growth rate dependent, with slow growing cells being more synchronized than fast growing ones.

Effects of dnats genes on the replication of plasmids in Bacillus subtilis

An essential region (2.3 kb) for the replication of a low-copy-number plasmid, pBS-2, has been identified and cloned into plasmid pHV60 in Bacillus subtilis. The resultant plasmid, pKW1, and two other plasmids, pC194 (medium copy number) and pTP5 (high copy number), were examined by double radio-labelling and gel electrophoresis to determine which host functions are required for their replication in B. subtilis. Replication of pKW1 requires the functions of most dna genes, in particular dnaB, C, E, F, G and H; pC194 requires only dnaG and H; and pTP5 requires dnaE, F, G and H. Thus dnaG and dnaH are required for the replication of all three plasmids tested, even though each plasmid showed a different spectrum of dependency on other host functions. Because of its greater dependence on host functions and its low copy number, pKW1 should be a useful model with which to investigate the function of host genes in the replication of DNA in B. subtilis. pKW1 should also be a useful shuttle vector for cloning of genes in B. subtilis in cases when high gene dosage might be a problem.