At least three different biological replicates were performed for

At least three different biological replicates were performed for each condition. Variations in the level of cytoplasmic protein concentrations of B. longum cells grown in the presence of mucus were analysed by a 2DE study. We used a pI range between 4 and 7, which theoretically allows the separation of about c-Met inhibitor two-thirds of the total proteome of B. longum (Sánchez et al., 2008). In all the experiments, cells were collected in the early stationary phase of growth (OD600 nm 0.5–0.9). Cell-free protein extracts were obtained as

described previously (Ruiz et al., 2009a). For 2DE analysis, 500 μg of protein from B. longum NCIMB8809 extracts were loaded onto a strip with an immobilized pH range of 4 to 7 (GE Healthcare) and focused at 65 000 V h−1. Separation in the second dimension was carried out in 12.5% polyacrylamide-sodium dodecyl sulphate gels and protein spots were visualized with colloidal Coomassie staining. Proteins PLX3397 cell line were identified by peptide mass fingerprinting and matrix-assisted laser desorption ionization/time of flight/MS at the Proteomics Unit of

the Parque Científico de Madrid (Cantoblanco, Madrid, Spain). Protein identification was achieved by combining MS data to search a nonredundant protein database (NR; 4.106 entries; National Center for Biotechnology Information) using the mascot software (Matrix Science). Spot detection, volume quantification and statistical analysis were performed using imagemaster platinum software (version 5.00, GE Healthcare). Three protein extracts, coming from three independent GNAT2 cultures, were obtained

for each condition (mucus absence or mucus presence), and at least three independent gels (technical replicates) were performed for each extract. Enzymatic activities were measured for the cytoplasmic fraction and for the secreted fraction. Cell-free protein extracts from the cytoplasmic fraction were obtained as described above. The supernatants were collected by centrifugation from cells grown to the early stationary phase, concentrated 10 times using VivaSpin Columns (cutoff 3000 kDa, Sartorius), and filtered through 0.22-μm sterile filters. Glycosidase activities were measured spectrophotometrically from the release of p-nitrophenol (pNP) produced by the enzymatic hydrolysis of the corresponding pNP-glycoside substrates (Sigma), as described previously (Ruiz et al., 2009b). One unit of enzymatic activity was defined as the amount of protein that releases 1 nmol pNP min−1. Specific activities were determined in duplicate for each culture, and expressed as units per milligram protein. For organic acid determination, Bifidobacterium cultures, grown in the absence or presence of mucus, were collected by centrifugation.

, 2005; Vu-Khac et al, 2007) New primers for STb (F: GGACCTATGT

, 2005; Vu-Khac et al., 2007). New primers for STb (F: GGACCTATGTTCGTTTTTTCTAT, R: ATCTCTAACCCCTAAAAAACCT) were check details designed with an annealing temperature of 52 °C and a product size of 132 bp. The DNA sequences obtained were compared at the GenBank web site using blast ( Clinical isolates confirmed to

be carrying these VGs by DNA sequencing were used as positive controls. PFGE was used to analyze the genomic relatedness among E. coli isolates from diseased piglets. PFGE of chromosomal DNA digested with the restriction enzyme XbaI was carried out according to a standard protocol using a CHEF-MAPPER System (Bio-Rad Laboratories, Hercules, CA). The gels were run at 6.0 V cm−1 with an angle of 120° at 14 °C for 22 h and the results were interpreted according to the criteria of Tenover et al. (1995). Salmonella ser. Braenderup H9812 standards served as size markers. To facilitate our analysis, we grouped the isolates with intermediate susceptibility with the resistant strains. Two-tailed Fisher’s

exact tests (sas, version 8.2; SAS Institute Inc., Cary, NC) were used to analyze the data. P-values of <0.05 were considered significant associations, and in such cases, odds ratios and their 95% confidence intervals (CI) were calculated. According to genotyping, the 167 isolates from diseased piglets were classified as 39 enterotoxigenic E. coli (ETEC) isolates (isolates carrying Apoptosis inhibitor at least one enterotoxin gene and F4 or F18) and 128 non-ETEC isolates (isolates lacking a combination of enterotoxin and fimbrial genes). The frequency of resistance to 12 antimicrobial agents for the whole set of isolates and for the subsets of epidemiologically unrelated isolates is presented in Table 1. Compared with non-ETEC isolates, except for ceftriaxone, kanamycin, streptomycin, and doxycycline, the frequency of resistance to the antimicrobial agents was higher or similar in ETEC isolates. Thirty-one (20%) and 23 (13%) isolates from diseased pigs presented a reduced susceptibility to ceftriaxone and doxycycline, respectively. Resistance to sulfamethoxazole (95%) and

tetracycline (94%) was found to be the most prevalent in epidemiologically unrelated isolates. The majority of isolates from diseased Pembrolizumab mouse pigs were resistant to chloramphenicol (89%) and streptomycin (84%). Resistance to ciprofloxacin was found in 109 strains (72%). The rates of resistance to apramycin, ceftiofur, and florfenicol ranged from 30% to 49%, whereas 25% of the isolates were resistant to amikacin. With regard to multidrug resistance profiles, all isolates were resistant to more than two of the 12 antimicrobials tested, 89% were resistant to more than five, 70% were resistant to more than seven, and 1% were resistant to 12. The most frequently observed pattern of multiresistance in all isolates was sulfamethoxazole/tetracycline/chloramphenicol/streptomycin. According to multi-PCR-based phylotyping, the majority of E.

In addition and again grounded in the current research, there are

In addition and again grounded in the current research, there are three distinct implications for the RPS. In light of the perceived difficulties with understanding the concept, conduct MK0683 purchase and application of CPD, firstly we believe there is scope for further improvements to be made to the process of CPD facilitation. At the time this review was

initiated very little information was available about RPSGB CPD facilitators other than their potential availability as a last resort;[7] this guidance was later transferred to the website of the GPhC. We believe the RPS could offer appropriate CPD facilitation to help improve pharmacy professionals’ understanding, conduct and application of CPD at an early stage. In addition, we believe there must be scope for improving the guidance documents and example cases as well as explanatory courses.

Interestingly, a study investigating satisfaction with RPSGB feedback on CPD submitted by a specific group of pharmacy participants found the feedback report had met or exceeded the expectations of 86% of respondents and 86% stated that they felt fully or mostly able to complete CPD records in the future as a result of receiving feedback.[45] There is some too evidence that RPS has used its new website Ixazomib order to offer further professional support in relation to CPD.[46] But professional support cannot be expected to be delivered in the absence of change at the regulatory level so the direction of flow must be considered. Similarly, work-related aspects can only be addressed following the suggested development of both regulatory and professional support for CPD. Considering the issues related to time, resources and other key factors expressed in the studies examined, we believe a top-down and universal change in ethos is required throughout the pharmacy work environment in GB. The evidence indicates an enhanced role

for employers, who must realise their share of responsibility in helping pharmacy professionals with CPD. The change must look to ways that pharmacy professionals can be supported in their CPD at work by means of protected CPD time, such Branched chain aminotransferase that perhaps in due course ‘CPD time’ will be considered in the same vein as other essential breaks from formal work. The second work-related proposal relates to employer support for educational courses, either in-house or sponsored external training. The third and most pertinent area related to work is of course the opportunity for application of CPD and its integration in the workplace. Only then can pharmacy professionals be completely free of the barriers that have hitherto hindered progress and impeded the universal uptake of a programme designed for the continuous improvement of professional pharmacy practice.

Fresh manure was placed immediately on ice and stored at −80 °C u

Fresh manure was placed immediately on ice and stored at −80 °C until analysis. The four fecal selleckchem samples were individually homogenized with 1% (weight in volume) peptone (Sigma-Aldrich Co., St Louis, MO) (10 g feces: 90 mL of peptone) in a stomacher for 6 min to distribute bacteria throughout the sample (Price et al., 2010). Homogenized samples were centrifuged at 4000× g for 10 min at 4 °C, and pellets were retrieved for microbial DNA extraction. Microbial DNA was extracted from the homogenized fecal pellets using a manual disruption method using the ZR Soil Microbe DNA MiniPrep kit (Zymo Research, Irvine, CA) as per

manufacturer’s instructions (Khafipour et al., 2009; Cuiv et al., 2011). A 270- to 300-bp nucleotide sequence of the V4 region of the 16S rRNA gene was amplified with primers used by Lopez-Velasco et al. (2011) and Jesus et al. (2010). Amplicons were generated as described by Lopez-Velasco et al. (2011). Libraries

were prepared, enrichments titrated, and pyrosequencing performed using a LR70 sequencing kit and 70 × 75 PicoTiterPlates (two samples per plate) performed with a Genome Sequencer FLX System (Roche, Branford, CT) by the core laboratory facility at JAK phosphorylation the Virginia Bioinformatics Institute (Blacksburg, VA). The reads obtained from GS-FLX were preprocessed to identify sequencing errors and trimmed of linker sequences. Unique sequence taxonomic classification and operational taxonomic unit (OTU) assignment were performed

using the those Pyrosequencing pipeline of the Ribosomal Database Project ( (Cole et al., 2009) software tools. Rarefaction indexes were calculated with 3% dissimilarity ( OTU assignments, estimates of richness (Chao1), and diversity (Shannon index [H′]) were calculated at 3% dissimilarity. Evenness was calculated as E =H′/Hmax; Hmax = ln(Chao1) where being S the total number of species in the sample, estimated with Chao1. Relative bacterial phylum abundance was calculated based on the total number of classified reads for each sample using the rdp classifier tool (Fig. 1). Matches with a rdp confidence estimate below 60% were designated as unclassified bacteria. All sequences have been deposited in the GenBank Sequence Read Archive (accession number SRA039855.1). Pyrosequencing of the 16S rRNA gene amplicons was used to characterize the fecal bacteria of healthy adult horses fed a controlled forage diet. Mean length of the pyrosequencing reads and the number of reads per sample were 250 bp and 28458 (range 24802–31164), respectively. Reads meeting the quality parameters (100% match over 25 bases; minimum of two reads) were trimmed. On average, 5898 unique sequences were identified from the four fecal samples.

Our analysis shows that ART was found to be a greater risk factor

Our analysis shows that ART was found to be a greater risk factor among PLHIV compared with treatment-naïve patients and the increased risk was

particularly found for abacavir in the NRTI group among the ART classes. In contrast, a recent meta-analysis of RCT studies (published after our literature search) found that abacavir was not associated with a greater risk of MI or major CVD events, despite the significant impact of abacavir on the risk of CVD in some cohort studies [41]. This meta-analysis included HIV clinical trial data from studies that had a follow-up period of at least 24 weeks, with the check details majority of included studies having approximately 1 year of average follow-up. In contrast, a 96-week RCT follow-up study found that abacavir, compared with tenofovir, was associated with a greater risk for CVD, as discussed above. Of note, it may be that short-term use of abacavir has a low risk for CVD events among PLHIV. More specifically, we found that the annual RR associated with abacavir use was very low (RR 1.09; 95% CI 1.02, 1.16), SCH772984 but that the risk increased with duration of ART. It is important to note that the majority of the cardiovascular events associated with the use of antiretroviral drugs were confined to patients who were already at increased absolute risk of CVD. Study type/design was not found to be a significant predictor of heterogeneity in our

estimates. A longer follow-up RCT measuring the use of abacavir and other antiretrovirals associated with CVD events would assist in ascertaining the role of abacavir among all patients as they continue to use ART long-term. We found that HIV, ART type and duration and CD4 cell count are associated with increased risk of CVD. The risk of CVD is greater in PLHIV than in people PFKL not living with HIV, and higher again for people exposed to ART, and particularly PI-based regimens, and increases with the duration of treatment. Despite being a risk factor for CVD, ART use has increased the quality and

length of life of PLHIV by restoring immune function, reversing AIDS-defining events and reducing AIDS-related mortality rates. It is possible that the use of ART increases life expectancy and hence increases the average age of those taking ART in comparison to the reference group, which may lead to confounding of results. Although the health and survival of PLHIV have improved with effective ARTs, PLHIV are at substantially greater risk of developing other comorbidities, such as CVD, compared with uninfected people. Given that CVD is responsible for a large number of deaths world-wide, this is a significant issue for the population of PLHIV, particularly as they get older and become more treatment-experienced with second-line, third-line or more complex antiretroviral regimens. Increasingly, HIV-positive populations will require long-term clinical management of numerous conditions along with their HIV infection.

(2009) have shown is required for maturation of the S-layer, but

(2009) have shown is required for maturation of the S-layer, but that is not essential for virulence. Of the two proteins classified as ABC transporters, neither conformed to the expected architecture for such a protein, namely, a leader

peptide containing an N- and C-domain completely lacking an intervening hydrophobic domain, in addition to a double-glycine motif N-terminal of the signal peptide cleavage site. All the other ‘transport’ proteins identified contained a significant hydrophobic domain between the N- and the C-domain of the predicted signal peptide, in addition to a number of other motifs usually associated with the twin arginine translocation or Sec secretion pathways. None of the 23 proteins contained any C-terminus cell wall anchor motifs commonly found in Gram-positive bacteria,

such as LPxTG, NPQTN or TLxTC (Dramsi et al., 2005; Desvaux et al., 2006). As in our previous work, we used the pathway reconstruction selleck chemicals llc tool biocyc (Karp click here et al., 2005) to analyse pathways inferred from our proteomics dataset. The snapshot of C. difficile metabolism presented here reflects the nutritional complexity of BHI broth, which contains glucose, proteose peptone and bovine BHI solids. We could, therefore, reconstruct a number of key central metabolic pathways (Djordjevic et al., 2003) that would be expected to be active in clostridial cells including glycolysis, mixed acid fermentation and fermentation of amino acids 3-oxoacyl-(acyl-carrier-protein) reductase (Gottschalk, 1979) (see Figs. S1-S3). The metabolic processes we have identified in C. difficile

are, therefore, broadly similar to those described in a recent proteomic investigation of the Gram-negative gut anaerobe, Fusobacterium varium. Potrykus et al. (2008) report that F. varium may play both beneficial and pathogenic roles in the human gut. While the antics of C. difficile left unchecked have given it a deservedly bad reputation (Heap et al., 2009), its ability to produce butyrate (Fig. S3), as is known to occur in F. varium, could mean that in asymptomatic carriers of C. difficile, the organism has the potential to contribute to colonocyte health. Such a counterintuitive hypothesis highlights the need, not only from a basic science perspective but also from a position of concern for public health, to know the frequency of asymptomatic C. difficile carriers within the general population: therefore, we see an urgent requirement to develop a better understanding of C. difficile biology within the human microbiome. The pathogenicity of C. difficile is dependent on a combination of toxin synthesis, p-cresol production and a diverse range of amino acid fermentations (Kim et al., 2008). Leucine is reported to be indispensible for the growth of this organism and may be metabolized by a reductive pathway, to isocaproate, or by means of an alternative oxidative pathway in which isovalerate and ammonia are produced.

The insertion of a 27-kb sequence in pRE25* might have an impact

The insertion of a 2.7-kb sequence in pRE25* might have an impact on the relative copy number and therefore the copy numbers of pRE25* and pRE25 were determined by qPCR using primer pairs tufA_fw/rv and aph_F/R (Table 2). The tufA gene was used as a chromosomal target gene and aph(3′)-III as the plasmid target SB203580 supplier gene for pRE25 and pRE25*. The copy number of both pRE25* and pRE25 was one to two copies per chromosome, independent of the growth phase (data not shown), indicating that the 2.7-kb insertion in pRE25* had no significant impact on the copy number. This relative low copy number is in agreement with the assumption

that large plasmids are present in the cell at low copy numbers (Dale & Park, 2004). To ensure the genetic stability of the constructed strain, the stable integration of the gfp gene and the stable replication of pRE25* in E. faecalis CG110/gfp/pRE25* was tested. The serial culture test revealed that the integration of gfp was stable for at least 200 generations (data not shown), confirming previously described stability for 30 generations (Scott et al., 2000). Replication

of pRE25* was also stable, which Selumetinib was expected because plasmids of the Inc18 family, including pRE25, replicate unidirectional by a theta (θ) mechanism, which is usually associated with stable plasmids (Jannière et al., 1990; Bruand et al., 1991). Furthermore, stability of low-copy plasmids in prokaryotes is often secured by a toxin–antitoxin system (Magnuson, 2007), such as the ɛ/ζ-system on pSM19035 from Streptococcus pyogenes (Ceglowski et al., 1993). Sequences of the proteins encoded by ORF18 and ORF49 of pRE25 are highly homologous to the ɛ-protein (instable antitoxin), ORF19 and ORF50 to ζ-protein (stable toxin) Mirabegron of pSM19035 (Meinhart et al., 2003), indicating that a toxin–antitoxin

system is present on pRE25 and secures its stability. Although the inserted sequence did not affect copy number and stability of pRE25*, the conjugation potential of pRE25* in E. faecalis CG110/gfp could be altered compared with pRE25 in E. faecalis RE25. Therefore the conjugation potential of both pRE25* in E. faecalis CG110/gfp and pRE25 in RE25 to other Gram-positive bacteria was examined. Similar conjugational transfer of pRE25* and pRE25 was observed to L. monocytogenes strains LM15 and 10403S, and to L. innocua L19 (Table 4). The transfer of pRE25 to L. innocua L19 has already been observed at a frequency of 10−5 per donor (Schwarz et al., 2001), paralleling our results. Transfer rates of pRE25* were only slightly lower compared with pRE25, which is probably due to the different host strain or the slightly increased plasmid size of pRE25* (Table 1). Transfer of both pRE25 and pRE25* to L. monocytogenes LM15 was rather low (Table 4), whereas the transfer frequency of 10−6 for L. monocytogenes 10403S was in the range of conjugative transfer of broad-host range plasmids (Grohmann et al.

The other types of secretion systems use alternative strategies t

The other types of secretion systems use alternative strategies to pass through the outer membrane that do not contain the conserved ‘secretin domain’. Many of these secretory nanomachines are of therapeutic interest owing to their roles in export of virulence factors click here during bacterial infection. Secretins are homo-multimeric complexes that form a gated channel in the outer membrane that open to allow passage of folded proteins,

assembled multi-protein complexes, and DNA. Efforts to determine the structures of secretins by X-ray crystallography and electron microscopy were recently reviewed by Korotkov et al. (2011). The protein that multimerizes to form the secretin is typically comprised of two parts: a conserved C-terminal region containing the ‘secretin domain’ that is embedded into the outer membrane and a variable, system-specific N-terminal region. Both of these regions may interact with other components of the system as well as with the substrates to be secreted or internalized. The N-terminal region contains several different types of subdomains: (1) a N0 domain that resembles the TonB-dependent signaling receptor that may allow signal

transduction between the inner membrane and outer membrane components of the system during secretion or uptake (Larsen et al., 1999; Brillet et al., 2007); (2) up to three heterogeneous nuclear ribonucleoprotein K homology-like domains that may fulfill the DNA binding role of competence SPTLC1 systems (Tarry et al., 2011); and (3) additional elements that have yet to be structurally characterized. Despite the similarities in the overall architecture of the proteins forming secretins, the mechanisms that control secretin assembly vary both between and within systems. This review provides an overview of the differences in the assembly requirements

of secretins. Particular focus will be given to the variability in the structure and function of pilotins and accessory proteins and their role in secretin stabilization, localization and/or assembly, their mode of interaction with the secretin-forming protein, and the effect(s) that the absence of the pilotin or accessory protein has on the secretin. Proteins involved in secretin assembly are diverse in structure, functional role, and genomic context. These differences may reflect the evolutionary divergence from an ancestral secretin by recruitment of a specific set of proteins to optimize the system for a particular function. Generally, there are two classes of ancillary proteins: (1) pilotins and (2) accessory proteins. Localization and/or assembly of secretins is the proposed function of pilotins (Table 1). Pilotins have a type II N-terminal signal sequence followed by a conserved cysteine, which allows the protein to be lipidated and transferred to the inner leaflet of the outer membrane by the Lol system (Okuda & Tokuda, 2010).

Treatment consisted of

aerosolized colistin during 14 day

Treatment consisted of

aerosolized colistin during 14 days and intravenous amikacin for 5 days. On day 18, she was diagnosed with another ventilator-associated pneumonia due to Pseudomonas aeruginosa and Proteus mirabilis. Treatment with piperacillin for 14 days and amikacin for 5 days eliminated the infection. She was discharged from the ICU on day 21 and transferred to our unit. Clinical outcome was favorable, and she was transferred to a rehabilitation unit. Case 2: A 61-year-old man was evacuated from Bangkok in May 2008 after an 8-day hospitalization, suffering from tetraparesia associated with paresthesia buy BMN 673 and loss of balance due to acute myelitis. Clinical status rapidly deteriorated, resulting in neurologically associated respiratory insufficiency, necessitating mechanical ventilation. He was then transferred to another ICU of our hospital. Rectal swabbing was performed on admission and was negative. Five days after repatriation, he was diagnosed with ventilator-associated GDC-0068 pneumonia. Acinetobacter baumannii was isolated from a bronchoalveolar lavage. This strain was only susceptible to amikacin, rifampin, and colistin. He

was successfully treated with aerosolized and intravenous colistin with oral rifampin. He later suffered from septicemia due to P aeruginosa that was successfully treated with appropriate antibiotics. Regarding his neurological symptoms, he was treated with systemic corticosteroids with partial efficacy. He was then transferred to a rehabilitation unit, where he stayed for 4 months without improvement of

his neurological status. The cause of acute myelitis was never established. He was once again transferred to our unit in November 2008 for sepsis secondary to a urinary tract infection. Acinetobacter baumannii was isolated from the urine. This strain was the same MDR strain as that which had been previously attributed to his ventilator-associated pneumonia, NADPH-cytochrome-c2 reductase and was only susceptible to amikacin, rifampin, and colistin. In spite of broad-spectrum antibiotic therapy including amikacin and colistin, he died 8 days later, in the context of unexplained dysautonomia. Case 3: An 81-year-old female patient was repatriated from Turkey in November 2010, after a bus accident (day 1). She suffered from multiple trauma with left arm amputation, deep right arm injuries, right pneumothorax and broken nose, without any hemodynamic distress. Besides amputation, she was hospitalized in an ICU in Turkey and ventilated during 3 days. She was then transferred to the same ICU as for patient 1. On admission (day 5), rectal swabbing showed colonization with MDR A baumannii, and ESBL-producing Citrobacter freundii. The A baumannii strain was only susceptible to tobramycin, colistin, and trimethoprim–sulfamethoxazol.

Small samples of pelleted cysts were placed onto slices of an ald

Small samples of pelleted cysts were placed onto slices of an aldehyde-fixed rabbit lung, which acted as a malleable support during rapid freezing. They

were then impacted onto a liquid helium-cooled copper block of a quick-freezing device (Cryopress, Med-Vac Inc., St. Louis, MO). Next, the frozen specimens were freeze fractured at −115 °C in a Balzer’s BAF 301 freeze-etch unit (BAL-TEC AG, Liechtenstein) and etched for 8 min at −100 °C. Finally, they were rotary replicated by deposition of 2.5 nm of platinum Selleck VX770 from an angle of 24° above the horizontal and backed with 20 nm of pure carbon deposited from 90°. The resulting replicas were cleaned overnight in sodium hypochlorite, washed in distilled water, retrieved on 100-mesh formvar-coated nickel grids and examined using a Phillips CM10 TEM operating at 80 kV. The ability of Acanthamoeba spp. trophozoites to encyst is an important physiological characteristic, relevant for amoebae dispersal and their survival in the environment, as well as for their capacity to resist drug treatments during Acanthamoeba

infections (Kumar & Lloyd, 2002; Johnston et al., 2009). This resistance could be due to the manner in which the cyst components are organized to form a dense, almost impermeable structure (Bowers & Korn, 1969; Khunkiti et al., 1998). Therefore, a better understanding of the cyst wall organization is a relevant element towards the evaluation of cyst resistance to biocides. The mature A. polyphaga cyst Acetophenone processed for conventional ultrathin sectioning TEM presents the classic, previously described (Bowers & Korn, 1969), structural features: i.e. two layers enclosing the encysted form of A. polyphaga (endo- and exocyst), separated from each other by an electron-lucent intercyst space with an average thickness of 840 nm (Fig. 1a), and containing some fuzzy material (Fig. 1c), which is absent at the operculum (Fig. 1b, arrow). Higher magnifications of ultrathin sections of A. polyphaga showed that

the components of the cyst wall appeared as a network of filaments (Fig. 1c). The exocyst layer was approximately twice as thick (650 nm) as the endocyst (290 nm), with a loosen arrangement, while the endocyst layer was thinner and had a finely granular appearance (Fig. 1c). After the observation of a number of cysts by TEM, it was evident that the endocyst was not visible in immature cysts (Fig. 1d), but could be formed after the exocyst is produced by the encysted amoeba, through the secretion of components in large vesicles as observed in Fig. 1e. Previous studies have shown that chemical fixation and dehydration with organic solvents can cause artifacts in TEM samples (Hippe-Sanwald, 1993). The advent of cryofixation resulted in more accurate specimen preservation, leading to more accurate analysis of cells and tissues by electron microscopy (Nicolas, 1991).