Living in the cold: freeze-induced gene responses in freeze-tolerant vertebrates

1. Winter survival for numerous cold-blooded animals includes freeze tolerance: the ability to endure the conversion of as much as 65% of total body water into extracellular ice. Selected molecular adaptations underlying freeze tolerance (e.g. cryoprotectants, ice nucleating proteins) have been widely studied, but the full range of metabolic adjustments needed for freeze endurance remains unknown. 2. Recent studies using gene screening techniques are providing a different approach to the search for biochemical responses that support freezing survival by identifying genes and proteins that are up-regulated by freezing or thawing in freeze-tolerant amphibians and reptiles. 3. Screening of a cDNA library from wood frog liver revealed the freeze-induced up-regulation of genes coding for the alpha- and gamma-subunits of fibrinogen (a plasma clotting protein), the mitochondrial ADP/ATP translocase and a novel 10 kDa protein containing a nuclear exporting sequence. 4. Northern blotting revealed that these genes were differentially responsive to two of the component stresses of freezing (dehydration and anoxia), indicating that different genes are induced by signals radiating either from cell volume change or oxygen deprivation during freezing. 5. Freeze up-regulation of fibrinogen synthesis in liver and other organs appears to be a damage repair response that anticipates a need for enhanced plasma clotting capacity to deal with ice crystal damage to capillary beds. 6. Up-regulation of ADP/ATP translocase in frog liver is linked with ischaemia resistance and studies with freeze-tolerant turtles have shown that other genes encoding proteins involved in mitochondrial energetics (NADH-ubiquinone oxido-reductase subunit 5, cytochrome C oxidase subunit 1) are also up-regulated by both anoxia and freezing exposures. 7. These studies are making major advances in our understanding of freeze tolerance as a natural phenomenon and also highlight new key areas that can be targeted by applied interventions for the optimization of medical cryopreservation techniques for cells, tissues and organs.     

Effects of upper respiratory tract stimuli on neonatal respiration: reflex and single neuron analyses in the kitten.

Respiratory effects of electrical and chemical stimuli applied to nerves or sites associated with the respiratory tract were tested in kittens aged 6-70 days. Cessation of respiration occurred especially with superior laryngeal nerve stimulation and infusion of water and sodium bicarbonate into the larynx. The apneic reflex was more powerful and prolonged than that previously noted in adult cats and was sometimes irreversible. Brain stem respiratory neurons of the neonate also showed marked susceptibility to these stimuli: the respiratory-related rhythm of 80% could be powerfully suppressed, and only 25% received excitatory inputs. The susceptibility of the neonatal respiratory system to these stimuli may have physiopathological significance in conditions such as the sudden infant (crib) death syndrome.     

P53 polymorphism in codon 72 and risk of human papillomavirus-induced cervical cancer: effect of inter-laboratory variation

An association between codon-72 p53 polymorphism and risk of human papillomavirus (HPV)-induced cervical cancer has been found recently, but it has been difficult to replicate. In this study, we assess the impact of inter-laboratory variation in p53 genotyping on the validity of the proposed association. DNA specimens were randomly selected from 54 invasive, squamous cell carcinoma cases, 52 HPV-negative, and 39 HPV-positive controls from a previous case-control study in Brazil. Codon-72 polymorphism was blindly analyzed in three different laboratories. We calculated age- and race-adjusted odds ratios (OR) and 95% confidence intervals (CI) using logistic regression for gauging the association between p53 polymorphism and cervical cancer risk. The proportions of the Arg/Arg, Arg/Pro, and Pro/Pro genotypes varied substantially among laboratories with Kappa coefficients in the 0.49-0.63 range. When disagreement between labs was allowed, the OR for the Arg/Arg genotype, compared to other forms, was as low as 1.5 (95% CI: 0.5-3. 9). In contrast, the OR increased to 8.0 (95% CI: 2.3-28.5) after exclusion of discordant genotypes. Restricting the comparison to HPV-positive controls increased the magnitude of the relation appreciably. After exclusion of all discordant diagnoses, the OR was 21.5 (95% CI: 3.4-137.8), whereas with disagreed genotypes the association was not significant (OR = 2.9, 95% CI: 0.7-11.9). Homozygous codon-72 p53-Arg apparently confers a higher susceptibility to HPV-associated cervical tumorigenesis. However, exposure misclassification consequent to inter-laboratory variation in protocols may affect the ability to detect the association.     

Hydrogen ion and carbon dioxide content of the oviductal fluid of the rhesus monkey (Macaca mulatta).

The pH in the oviduct lumen of adult female rhesus monkey (Macaca mulatta) during the menstrual cycle was measured by means of miniaturized pH electrodes. Two types were used: one was a flexible electrode 1.4 mm in diameter; the other was a rigid electrode 0.8 mm in diameter. The same results were obtained with both types. For PCO2 measurements, the pH electrodes was converted to a Severinghaus tyep electrode covered with a Teflon membrane. During the follicular phase, the pH remains constant in the range 7.1 to 7.3. In association with ovulation, there is a sudden increase in the pH to the range 7.5 to 7.8. The pH remains high through the luteal phase. The PCO2 values obtained showed no evident changes with day of cycle. The range of values estimated was wide because of drift in electrode calibration, with the average level about 89 Torr, compared with 40 Torr for blood. At the average pH of 7.2 in the follicular phase, this value of PCO2 corresponds to 35 mM HCO3-; at the average pH of 7.6 of the secretory phase, this value corresponds to 90 mM HCO3-. This increase in pH and HCO3- after ovulation would be expected to enhance dispersal of corona cells during fertilization and to provide a favorable environment for the developing embryo.     

Pinhole preparation for self-threading pins

The force required to remove self-threading retention pins from dentin when the holes were drilled with two different methods was determined. The two methods employed to drill the holes were (1) using a conventional slow-speed contra-angle handpiece and (2) using a 10-to-1 gear reduction contra-angle handpiece attached to a conventional slow-speed handpiece. Also determined were the number of drills broken in the process of drilling the holes. Results demonstrated no difference in the retention of pins placed in holes drilled using these two methods. Two drills were broken in the process of drilling well over 100 holes, and both breaks occurred with the gear-reduced handpiece. Either of the two methods tested is acceptable, but we recommended using a conventional slow-speed contra-angle handpiece because of the ease of producing the holes.     

Retaining older nurses in primary care and the community

Title.  Retaining older nurses in primary care and the community.
Aim.  This paper is a report of a study conducted to examine issues associated with the impact of age on the retention of female primary and community care nurses in the National Health Service in England.
Background.  Little is known about why older nurses in the primary and community care workforce leave and what might encourage them to stay.
Methods.  A cross-sectional survey using a semi-structured postal questionnaire was carried out during 2005. Responses were received from 485 (61%) district nurses, health visitors, school nurses and practice nurses in five primary care trusts in England. Data were analysed to test for associations.
Results.  Older nurses were more likely than younger ones to report that their role had lived up to expectations ( P  = 0·001). Issues important for older nurses were feeling valued and being consulted when change was implemented. Important factors encouraging nurses to stay were pension considerations, reduced working hours near retirement, and reduced workload. For those with degree-level qualifications, enhanced pay was a factor encouraging retention ( P  = 0·044). Nurses might leave in response to high administrative workloads, problems in combining work and family commitments ( P ≤  0·001), and lack of workplace support ( P  = 0·029). Retirement and pensions advice was not widely available.
Conclusion.  Since two-thirds of nurses were generally happy in their role, it is important that the conditions necessary to maintain this level of satisfaction are continued throughout a nurse's working life. Nurses may all too easily consider leaving prematurely unless policy makers and managers ensure that their working environment reflects the issues nurses consider to be conducive to retention.     

Occurrennce and impact of community-acquired and nosocomial rotavirus infections — a hospital-based study over 10 y

The need for a rotavirus vaccine in any particular country depends primarily on the number of hospitalized cases. Since only limited data are available for Germany, we undertook a retrospective hospital-based analysis in order to gather further information. From 1987 through 1996, a total of 3618 inpatients were hospitalized with a diagnosis of gastroenteritis (ICD 9). In 892 (25%) of them the causative organism wasa rotavirus. During the same period, 1886 (out of 8383; 22%) stool speciment tested in the hospital laboratory were obtained from rotavirus-positive inpatients. In 49.2% the infection was community-acquired, and in the remainder of nosocomial origin. Infants under 4 months of age(n=709; 38%) predominated among both the nosocomial and community-acquired infections. Premature neonates made up 26% of the nosocomial, but only 2% of the community-acquired cases of diarrhoea. The winter peak (January) was most pronounced in the age group 4-12 months, but in those more than 1 y old the peak came a month later. The median hospitalization time for community-acquired cases was 4 d (mean 5.9 d).The mortality was 0.1%. Rotavirus infection must therefore be regarded as a considerable burden, particularly with regard to infants and young children. Furthermore, the morbidity due to nosocomial infection with the rotavirus, analysed here in a long-term observational study, is unexpectedly high. □ Hospital-based study, nosocomial infection, rotavirus     

Transfer of beta-lactamase-associated cefoxitin resistance in Bacteroides fragilis.

A cefoxitin-resistant Bacteroides fragilis isolate, TAL 4170, which inactivates cefoxitin, was able to transfer beta-lactamase-mediated cefoxitin resistance to a susceptible B. fragilis recipient. Cefoxitin-resistant transconjugants acquired a new beta-lactamase with a pI of 8.1 and were able to inactivate cefoxitin and retransfer cefoxitin resistance. No plasmids were detected in the donor or transconjugants.