Factor XII Silencing Using siRNA Prevents Thrombus Formation in a Rat Model of Extracorporeal Life Support

Heparin anticoagulation increases the bleeding risk during extracorporeal life support (ECLS). This study determined whether factor XII (FXII) silencing using short interfering RNA (siRNA) can provide ECLS circuit anticoagulation without bleeding. Adult male, Sprague-Dawley rats were randomized to four groups (n = 3 each) based on anticoagulant: (1) no anticoagulant, (2) heparin, (3) FXII siRNA, or (4) nontargeting siRNA. Heparin was administered intravenously before and during ECLS. FXII or nontargeting siRNA were administered intravenously 3 days before the initiation of ECLS via lipidoid nanoparticles. The rats were placed on pumped, arteriovenous ECLS for 8 hours or until the blood flow resistance reached three times its baseline resistance. Without anticoagulant, mock-oxygenator resistance tripled within 7 ± 2 minutes. The resistance in the FXII siRNA group did not increase for 8 hours. There were no significant differences in resistance or mock-oxygenator thrombus volume between the FXII siRNA and the heparin groups. However, the bleeding time in the FXII siRNA group (3.4 ± 0.6 minutes) was significantly shorter than that in the heparin group (5.5 ± 0.5 minutes, p < 0.05). FXII silencing using siRNA provided simpler anticoagulation of ECLS circuits with reduced bleeding time as compared to heparin. http://links.lww.com/ASAIO/A937.

Factors Involved in the onset of infection following bacterially contaminated platelet transfusions

Transfusion of platelet concentrates (PCs) is associated with several adverse patient reactions, the most common of which are febrile non-hemolytic transfusion reactions (FNHTRs) and transfusion-associated bacterial-infection/transfusion-associated sepsis (T-ABI/TA-S). Diagnosis of T-ABI/T-AS requires a positive blood culture (BC) result from the transfusion recipient and also a positive identification of bacterial contamination within a test aliquot of the transfused PC. In a significant number of cases, clinical symptoms post-transfusion are reported by the clinician, yet the BCs from the patient and/or PC are negative. The topic of 'missed bacterial detection' has therefore been the focus of several primary research studies and review articles, suggesting that biofilm formation in the blood bag and the presence of viable but non-culturable (VBNC) pathogens are the major causes of this missed detection. However, platelets are emerging as key players in early host responses to infection and as such, the aforementioned biofilm formation could elicit 'platelet priming', which could lead to significant immunological reactions in the host, in the absence of planktonic bacteria in the host bloodstream. This review reflects on what is known about missed detection and relates this to the emerging understanding of the effect of bacterial contamination on the platelets themselves and the significant role played by platelets in exacerbation of an immune response to infection within the transfusion setting.

Efficient chemical hydrophobization of lactic acid bacteria - One-step formation of double emulsion

A novel concept of stabilizing multiple-phase food structure such as emulsion using solely the constitutional bacteria enables an all-natural food grade formulation and thus a clean label declaration. In this paper, we propose an efficient approach to hydrophobically modifying the surface of lactic acid bacteria Lactobacillus rhamnosus (LGG) using lauroyl ahloride (LC) in non-aqueous media. Compared to the unmodified bacteria, cell hydrophobicity was dramatically altered upon modification, according to the higher percentages of microbial adhesion to hexadecane (MATH) and water contact angles (WCA) of LC-modified bacteria. No evident changes were found in bacterial surface charge before and after LC modification. By using one-step homogenization, all the modified bacteria were able to generate stabile water-in-oil-in-water (W/O/W) double emulsions where bacteria were observed on oil-water interfaces of the primary and secondary droplets. Modification using high LC concentrations (10 and 20 w/w%) led to rapid autoaggregation of bacteria in aqueous solution. A long-term lethal effect of modification primarily came from lyophilization and no apparent impact was detected on the instantaneous culturability of modified bacteria.

Estrogen deficiency - a central paradigm in age-related impaired healing?

Wound healing is a dynamic biological process achieved through four sequential, overlapping phases; hemostasis, inflammation, tissue proliferation and remodeling. For effective wound healing, all four phases must occur in the appropriate order and time frame. It is well accepted that the wound healing process becomes disrupted in the elderly, increasing the propensity of non-healing wound states that can lead to substantial patient morbidity and an enormous financial burden on healthcare systems. Estrogen deprivation in the elderly has been identified as the key driver of age-related delayed wound healing in both genders, with topical and systemic estrogen replacement reversing the detrimental effects of aging on wound repair. Evidence suggests estrogen deprivation may contribute to the development of chronic wound healing states in the elderly but research in this area is somewhat limited, warranting further investigations. Moreover, although the beneficial effects of estrogen on cutaneous healing have been widely explored, the development of estrogen-based treatments to enhance wound repair in the elderly have yet to be widely exploited. This review explores the critical role of estrogen in reversing age-related impaired healing and evaluates the prospect of developing more focused novel therapeutic strategies that enhance wound repair in the elderly via activation of specific estrogen signaling pathways in regenerating tissues, whilst leaving non-target tissues largely unaffected.

Superior Properties and Biomedical Applications of Microorganism-Derived Fluorescent Quantum Dots

Quantum dots (QDs) are fluorescent nanocrystals with superb photo-physical properties. Applications of QDs have been exponentially increased during the past decade. They can be employed in several disciplines, including biological, optical, biomedical, engineering, and energy applications. This review highlights the structural composition and distinctive features of QDs, such as resistance to photo-bleaching, wide range of excitations, and size-dependent light emission features. Physical and chemical preparation of QDs have prominent downsides, including high costs, regeneration of hazardous byproducts, and use of external noxious chemicals for capping and stabilization purposes. To eliminate the demerits of these methods, an emphasis on the latest progress of microbial synthesis of QDs by bacteria, yeast, and fungi is introduced. Some of the biomedical applications of QDs are overviewed as well, such as tumor and microRNA detection, drug delivery, photodynamic therapy, and microbial labeling. Challenges facing the microbial fabrication of QDs are discussed with the future prospects to fully maximize the yield of QDs by elucidating the key enzymes intermediating the nucleation and growth of QDs. Exploration of the distribution and mode of action of QDs is required to promote their biomedical applications.

The Emergence of Hierarchical Somatosensory Processing in Late Prematurity

The somatosensory system has a hierarchical organization. Information processing increases in complexity from the contralateral primary sensory cortex to bilateral association cortices and this is represented by a sequence of somatosensory-evoked potentials recorded with scalp electroencephalographies. The mammalian somatosensory system matures over the early postnatal period in a rostro-caudal progression, but little is known about the development of hierarchical information processing in the human infant brain. To investigate the normal human development of the somatosensory hierarchy, we recorded potentials evoked by mechanical stimulation of hands and feet in 34 infants between 34 and 42 weeks corrected gestational age, with median postnatal age of 3 days. We show that the shortest latency potential was evoked for both hands and feet at all ages with a contralateral somatotopic source in the primary somatosensory cortex (SI). However, the longer latency responses, localized in SI and beyond, matured with age. They gradually emerged for the foot and, although always present for the hand, showed a shift from purely contralateral to bilateral hemispheric activation. These results demonstrate the rostro-caudal development of human somatosensory hierarchy and suggest that the development of its higher tiers is complete only just before the time of normal birth.

'Holiday sickness'-reported exploratory outcome of over 500 United Kingdom holidaymakers with travellers' diarrhoea

AIMS

To ascertain any predictors of potential food poisoning pathogens and development of post-infective irritable bowel syndrome (IBS) in UK travellers. An analysis was undertaken on prospectively collected data on 527 patients reporting symptoms of suspected food poisoning between June 2012 and June 2015.

MAIN OUTCOME MEASURES

Positive stool sample indicative of food poisoning pathogens and diagnosis of post-infective IBS.

RESULTS

Data on 527 patients were examined. The large majority of patients did not provide a stool sample on return from holiday (n = 430, 81.6%) as few visited a Doctor locally or in the UK. Only 18 patients (18.6%, 95% confidence interval [CI] 11.4-27.7) who provided a stool sample were positive for microbiological food poisoning pathogens. Univariate analysis indicated a significant relationship between a positive stool sample and whether the individual sought any medical assistance at the resort (odds ratio [OR] 0.24, 95% CI 0.08-0.70) and whether they took any treatment (including self-medicated), (OR 0.21, 95% CI 0.06-0.67). Of the 527 patients only 30 (5.7%, 95% CI 3.9-8.1) experienced post-infective IBS. Univariate regression indicated a significant relationship between experiencing Per Rectal (PR) bleeding and a diagnosis of post-infective IBS (OR 3.64, 95% CI 1.00-10.49). Univariate regression also indicated an increase in the risk of developing post-infective IBS with increasing duration of symptoms (OR 1.04, 95% CI 1.02-1.05). No significant relationship was found between a positive stool sample and developing post-infective IBS (P = 0.307).

CONCLUSIONS

Very few patients provide a stool sample after experiencing holiday sickness abroad. Of those that do, only a small proportion have a positive stool sample indicative of a food poisoning microorganism. Around 6% of individuals were diagnosed with post-infective IBS. Those individuals with PR bleeding and symptoms persisting for longer durations were significantly more at risk of developing post-infective IBS, whilst medical aid and treatment abroad was found to reduce the odds of a positive stool sample.

Initial adhesion of Listeria monocytogenes to solid surfaces under liquid flow

Some strains of the food borne pathogen Listeria monocytogenes persist in food processing environments. The exact reason behind this phenomenon is not known, but strain differences in the ability to adhere to solid surfaces could offer an explanation. In the present work, initial adhesion of nine strains of L. monocytogenes was investigated under liquid flow at two levels of shear stress on six different surfaces using a flow chamber set-up with microscopy measurements. The surfaces tested were glass and PVC, and glass coated with beef extract, casein, and homogenised and unhomogenised milk. In addition, the effect of prior environmental stress (5% NaCl, low nutrient availability) on initial adhesion was investigated. The hydrophobicity of the investigated surfaces was determined by contact angle measurements and the surface properties of the investigated L. monocytogenes strains were determined using Microbial Adhesion To Solvents (MATS). All surfaces with the exception of PVC were found to be hydrophilic. Strain differences were found to significantly influence the initial adhesion rate (IAR) of all nine strains to all the surfaces (p<0.05) at both low and high shear stress. Furthermore, there was a significant effect of the surfaces tested (p<0.05) in the adhesion ability of almost all strains. The IAR was affected by flow rate (shear stress) as seen by a decrease in adhesion at high shear stress for most strains. A significant effect of interactions between strain-surface and strain-shear stress (p<0.001) was observed but not of interactions between surface-shear stress. No correlation between surface hydrophobicity and IAR was observed. Addition of 5% NaCl during propagation resulted in a decrease in IAR whilst propagation in low nutrient media caused an increase indicating a general change in surface characteristics under these conditions. Known persisting strains did not display general better adherence.

Effect of micronutrients on behavior and mood in adults With ADHD: evidence from an 8-week open label trial with natural extension

OBJECTIVE

To investigate the effect of a 36-ingredient micronutrient formula consisting mainly of minerals and vitamins in the treatment of adults with both ADHD and severe mood dysregulation (SMD).

METHOD

14 medication-free adults (9 men, 5 women; 18-55 years) with ADHD and SMD completed an 8-week open-label trial.

RESULTS

A minority reported transitory mild side effects. Significant improvements were noted across informants (self, observer, clinician) on measures of inattention and hyperactivity/impulsivity, mood, quality of life, anxiety, and stress all with medium to very large effect sizes (all ps < .01); however, the mean of inattention remained in a clinical range whereas the means on measures of mood and hyperactivity/impulsivity were normalized. Follow-up data showed maintenance of changes or further improvement for those who stayed on the micronutrients.

CONCLUSIONS

Although this study, as an open trial, does not in itself prove efficacy, it provides preliminary evidence supporting the need for a randomized clinical trial of micronutrients as treatment for the more complex presentations of ADHD.

160 PREGNANCY RATES AFTER USING THE CIDR-G DEVICE AND FIXED-TIMED ARTIFICIAL INSEMINATION IN WHITE-TAIL DEER

Two synchronization protocols for fixed-timed AI (FTAI) in White-tail deer were evaluated over a 2-year period. InYear 1, White-tail does (n = 38), with a mean body weight of 55 kg and mean age of 2.4 years, were stratified by weight, age, and last fawning date randomly across 2 estrous cycle synchronization treatment groups. Does received either a CIDR-G device for 14 days (CIDR 14) and underwent AI 60 h post-CIDR removal, or received a CIDR-G device for 7 days (CIDR 7) with 1 mg of estradiol benzoate (i.m.) at CIDR insertion (Day 0), 25 mg of prostaglandin F2α (PGF2α; Dinoprost) on Day 6 and 1 mg of estradiol benzoate (i.m.) on Day 7 with AI occurring 52 h post-CIDR removal. In Year 2, White-tail does (n = 36), with a mean body weight of 60 kg and mean age of 3.9 years, were stratified as described for Year 1 and allotted to 2 treatments. Does received a CIDR-G device for 14 days and were inseminated 60 h post-CIDR removal (Treatment A) or were synchronized in the same way as does inTreatment A but also received 200 IU (i.m.) of eCG (Sigma, St. Louis, MO) at CIDR removal (Treatment B). All does received 1 mg of Domosedan (i.v.) before initiating the AI procedure. In both years, electroejaculated semen was collected from a single buck and frozen for AI. In both years, clean-up bucks were introduced into the pen with does for natural cover at no less than 14 days following AI. A gestation length of 195 � 7 days was used to determine whether the fawn(s) resulted from AI or from natural mating. In Year 1, FTAI pregnancy rates were not different between the CIDR 14 (56%) and CIDR 7 (24%) treatment groups. Likewise, pregnancy rates were not different between CIDR 14 FTAI (56%) and clean-up bucks (75%). However, the FTAI pregnancy rate was lower (P < 0.001) for the CIDR 7 treatment group (24%) compared with the clean-up bucks (100%). Treatments did not affect fecundity rates; however, those females pregnant from FTAI had lower (P < 0.001) fecundity rates compared with those females pregnant from natural cover (1.2 v. 1.9 fawns/doe). In Year 2, treatment did not affect FTAI pregnancy rates across treatments (33% for Treatment A and 55% Treatment B); however, fewer (P = 0.024) does in Treatment A were pregnant following FTAI (33%) compared with those pregnant from clean-up bucks (75%). There was no difference in FTAI fecundity rates across treatment groups (1.3 v. 1.7 for Treatments A and B, respectively) or between FTAI treatments and natural cover (1.3, 1.7, and 1.5 for Treatments A, B, and clean-up bucks, respectively). These results indicate that the use of a 14-day CIDR synchronization protocol with FTAI occurring 60 h after CIDR removal yields acceptable pregnancy rates of White-tail does following transcervical AI.

Definition and accountability: a youth perspective

This paper reviews the systemic flaws of residential treatment facilities from a youth perspective concerning the lack of transparency, definition and accountability, and the subsequent mistreatment and human rights violations of youth experiencing emotional, behavioral, and cognitive challenges.

Unlicensed residential programs: the next challenge in protecting youth

Over the past decade in the United States, the number of private residential facilities for youth has grown exponentially, and many are neither licensed as mental health programs by states, nor accredited by respected national accrediting organizations. The Alliance for the Safe, Therapeutic and Appropriate use of Residential Treatment (A START) is a multi-disciplinary group of mental health professionals and advocates that formed in response to rising concerns about reports from youth, families and journalists describing mistreatment in a number of the unregulated programs. This article summarizes the information gathered by A START regarding unregulated facilities. It provides an overview of common program features, marketing strategies and transportation options. It describes the range of mistreatment and abuse experienced by youth and families, including harsh discipline, inappropriate seclusion and restraint, substandard psychotherapeutic interventions, medical and nutritional neglect, rights violations and death. It reviews the licensing, regulatory and accrediting mechanisms associated with the protection of youth in residential programs, or the lack thereof. Finally, it outlines policy implications and provides recommendations for the protection of youth and families who pursue residential treatment.

Factors affecting microbial adhesion to stainless steel and other materials used in medical devices

The role of biofilm in medical device associated infections is well documented. Biofilms are more resistant to antibiotics than planktonic cells, these are extremely difficult to treat. Prevention strategies include efforts to insert implants under stringent aseptic conditions, and also encompass the development of novel materials which interfere with the initial attachment of microorganisms to the surface of the device. Microbial cells also attach onto hygienic surfaces in the hospital setting, and thereby pose a cross-infection problem. In this case, vigorous cleaning and sanitizing regimes may be employed in addition to any surface modifications. Many factors affect the initial attachment of organisms to inert substrata, and their subsequent retention or removal/detachment, including the physical and chemical nature and location of the substratum, the type of organic material and microorganisms potentially fouling the surface, and the nature of the interface (solid-liquid in the body; solid-air on environmental surfaces). Focusing on one factor, surface topography, it is apparent that many further variables need to be defined in order to fully understand the interactions occurring between the cell and surface. It is therefore important when modifying one substratum surface property in order to reduce adhesion, to also consider other potentially confounding factors.

Oral delivery of macromolecules using intestinal patches: applications for insulin delivery

Oral drug delivery, though attractive compared to injections, cannot be utilized for the administration of peptides and proteins due to poor epithelial permeability and proteolytic degradation within the gastrointestinal tract. A novel method is described that utilizes mucoadhesive intestinal patches to deliver therapeutic doses of insulin into systemic circulation. Intestinal patches localize insulin near the mucosa and protect it from proteolytic degradation. In vitro experiments confirmed the secure adhesion of patches to the intestine and the release of insulin from the patches. In vivo experiments performed via jejunal administration showed that intestinal insulin patches with doses in the range of 1-10 U/kg induced dose-dependent hypoglycemia in normal rats with a maximum drop in blood glucose levels of 75% observed at a dose of 10 U/kg. These studies demonstrate that reduction in blood glucose levels comparable to that induced by subcutaneous injections can be achieved via enteral insulin absorption with doses only 2-10-fold higher than subcutaneous doses.

Thermoregulation of transgenic growth hormone mice

Transgenic growth hormone (TG) mice (Mus musculus L., 1758) obtain enhanced growth via compensatory feeding at intermediate sizes and via higher growth efficiency. The latter involves diverting resources from other functions such as locomotion and wakefulness. Thermogenesis is a major expense for small mammals, so we explored whether TG mice express a trade-off between growth and thermoregulation. TG mice are hypothermic and cannot maintain their body temperature under cold stress. TG mice showed initial enlargement of brown adipose tissue and subsequent age-related decreases not seen in controls. Some TG mice became torpid after fasting durations not known to affect other mice. On a high-calorie diet, TG mice had higher body temperatures even though controls did not. Our background strain developed obesity on a high-protein and high-fat diet, and on a diet supplemented with carbohydrates, whereas TG mice never developed obesity. White adipose tissue deposits of TG females were relatively larger, but those of TG males were relatively smaller, than those of controls fed standard food. We also found significant effects of the three experimental diets, as well as gender, age, body mass, ambient temperature, and behavioural activity, on rectal temperatures of TG mice and controls in a large breeding colony. Thermogenesis of TG mice fed standard food appears energetically constrained, likely contributing to enhanced growth efficiency.

Enteral tube feeding training for nurses and care assistants

Increasing numbers of patients are enteral tube-fed in the community, often requiring community nursing support. Appropriate training facilitates effective patient care in this rapidly changing area of practice. The project described involved the development, piloting and evaluation of a validated home enteral tube-feeding training programme for community staff. Following wide consultation, four pilot days were provided (two for registered nurses and two for care assistants) which were positively evaluated. Post-training evaluation suggested the training led to beneficial changes in practice. Additional funding obtained has enabled the basic training to continue on a monthly basis for 2 years with biannual updates. Significant risks are attached to home enteral tube feeding; opportunities to integrate theory and practice in a safe environment should enhance patient care and decrease clinical risk.

Cutaneous histiocytic lymphangitis: an unusual manifestation of rheumatoid arthritis

Two cases are presented of unusual cutaneous lesions associated with rheumatoid arthritis in underlying joints. The lesions were evanescent, erythematous and violaceous partly macular and partly indurated plaques, with a livedo-like pattern of erythema at the edge in one case. Histological changes were identical in the two cases. The major features were dilated, dermal lymphatics containing aggregates of inflammatory cells, mainly histiocytes, with adjacent perivascular lymphoid aggregates. An appropriate name for this reaction would appear to be cutaneous histiocytic lymphangitis.

Heavy metal migration in soils and rocks at historical smelting sites

The vertical migration of metals through soils and rocks was investigated at five historical lead smelting sites ranging in age between 220 and 1900 years. Core samples were taken through metal-contaminated soils and the underlying strata. Concentration profiles of lead and zinc are presented from which values for the distances and rates of migration have been derived. Slag-rich soil horizons contain highly elevated metal concentrations and some contamination of underlying strata has occurred at all sites. However, the amounts of lead and zinc that have migrated from soils and been retained at greater depths are comparatively low. This low metal mobility in contaminated soils is partly attributed to the elevation of soil pH by the presence of calcium and carbonate originating from slag wastes and perhaps gangue minerals. Distances and rates of vertical migration were higher at those sites with soils underlain by sandstone than at those with soils underlain by clay. For sites with the same parent material, metal mobility appears to be increased at lower soil pH. The mean migration rates for lead and zinc reach maxima of 0.75 and 0.46 cm yr(-1) respectively in sandstone at Bole A where the elements have moved mean distances of 4.3 and 2.6 m respectively. There is some evidence that metal transport in the sandstone underlying Bole A and Cupola B occurs preferentially along rock fractures. The migration of lead and zinc is attenuated by subsurface clays leading to relatively low mean migration rates which range from 0.03 to 0.31 cm yr(-1) with many values typical of migration solely by diffusion. However, enhanced metal migration in clays at Cupola A suggest a preferential transport mechanism possibly in cracks or biopores.

Bronchopulmonary atypical carcinoid tumour metastatic to the orbit

BACKGROUND

Bronchopulmonary carcinoid tumours metastatic to the orbit are rare. A case is presented demonstrating presentation, histopathology and treatment.

METHODS

A 64-year-old man with a history of bronchopulmonary atypical carcinoid presented with an orbital mass. The nature of this metastasis was confirmed with histology and it was surgically excised and, in addition, local radiotherapy and chemotherapy were administered.

RESULTS

There was a good response to the treatment for the orbital mass but other metastases developed, causing death.

CONCLUSIONS

In this case of atypical carcinoid, orbital metastasis was the first sign of disease progression. Histological confirmation of the diagnosis was important in this case to allow planning of oncological therapy and for appropriate patient counselling. A good local response was obtained with a combination of surgical excision, local radiotherapy and chemotherapy. The systemic prognosis remains poor in cases of metastatic bronchopulmonary atypical carcinoid tumour, in contrast to typical carcinoid.

Primary extramedullary plasmacytoma of the orbit

BACKGROUND

We report a case of extramedullary plasmacytoma of the orbit. This is a rare tumour which has uncommonly presented in the orbit.

CASE REPORT

A 58-year-old woman presented with painless proptosis, upper lid swelling and ptosis. Incisional biopsy was performed. Clinical findings and investigations were correlated to establish the diagnosis. Treatment consisted of 35 Gy external beam radiotherapy.

CONCLUSIONS

This condition is considered to be of low grade malignancy and as such can be regarded as a separate entity to multiple myeloma involving the orbit or solitary myeloma of bone in terms of treatment and prognosis.

Angiosarcoma of the eyelid

BACKGROUND

Angiosarcomas are uncommon malignant tumours of vascular endothelium. They frequently affect the face and scalp, but to our knowledge there are only three reports of eyelid involvement.

METHODS/RESULTS

We report a case of angiosarcoma arising from the eyelid skin in a 79-year-old woman. Treatment was surgical with wide excision and staged reconstruction of the defect. Systemic oncological work-up for metastatic disease was negative. Adjuvant systemic chemotherapy and radiotherapy were considered but were not felt to be of proven benefit and were not used. The patient died seven months after presentation from a myocardial infarct.

CONCLUSION

Angiosarcoma should be considered in the differential diagnosis of unusual or atypical eyelid lesions. Management is wide surgical excision, although adjuvant systemic therapy should be considered in selected cases in consultation with an oncologist.

Cardiac hypothermia: 31P and 1H NMR spectroscopic studies of the effect of buffer on preservation of human heart atrial appendages

31P and 1H nuclear magnetic resonance spectroscopy has been used to follow noninvasively the time course of energetic metabolite levels in human heart atrial appendages preserved under various temperatures and buffer conditions. From sample harvest up to the normal 5-h time limit for heart preservation, ATP levels in human atrial appendages are much better maintained in 0.9% saline and PIPES-buffered preservation solutions at 12 degrees C than at 4 degrees C. Furthermore, preservation at 12 degrees C can be improved considerably by using high extracellular buffer concentrations. The increased buffer concentration allows better maintenance of the intracellular pH and leads to a faster glycolytic rate as measured by lactate production. At 4 degrees C, ATP levels decline rapidly during the first 5 h but reached a stable plateau, which is well maintained over 15-20 h. At this temperature, the rate of lactate production is similar at all buffer concentrations (20, 60, and 100 mM PIPES). As a consequence of these observations, we postulate that the mechanisms of ATP production and utilization at 4 degrees C and at 12 degrees C are different. At 4 degrees C, the rate of glycolysis is temperature limited whereas at 12 degrees C, low intracellular pH inhibits glycolysis.

Preservation of high-energy phosphates in human myocardium. A phosphorus 31-nuclear magnetic resonance study of the effect of temperature on atrial appendages

After prolonged exposure to low temperatures (1 degree and 4 degrees C), human atrial trabeculae show poor recovery of contraction. At somewhat higher temperatures (12 degrees and 20 degrees C), recovery is much better (Keon and associates. Ann Thorac Surg 1988;46:337-41). Although better preservation of adenosine triphosphate and therefore improved contractile recovery might be expected after exposure to lower temperatures, it remained possible that, below a certain temperature, adenosine triphosphate-generating mechanisms could be slowed more than adenosine triphosphate utilization. To investigate this phenomenon further, we followed the time course of metabolic changes in human atrial appendages, harvested during cardiac bypass operations, at 1 degree, 4 degrees, 12 degrees, and 20 degrees C using high-resolution 31P and 1H nuclear magnetic resonance spectroscopy. The results are quantitated by correlation with data obtained from biochemical assays on quick-frozen tissues. Initial adenosine triphosphate levels in myocytes of human atrial appendages are 3.3 to 4.3 mumol.gm-1 tissue wet weight. At 20 degrees C, adenosine triphosphate disappears after 6 hours; at 12 degrees C, about half the initial adenosine triphosphate is still observable at this time; at 4 degrees C or 1 degree C, the decline is still slower. Only a small contribution toward adenosine triphosphate maintenance comes from creatine phosphate, since creatine phosphate, inorganic phosphate, and total creatine levels in the appendage are low (less than 2 mumol.gm-1 tissue wet weight). Glycolysis is active at all temperatures; the rate of glycolysis correlates positively with increasing temperature. Adenosine triphosphate generated by glycolysis falls just short of demand at all temperatures, but the difference is small at 1 degree and 4 degrees C. These studies lead us to conclude that the relatively poor recovery of contractile response of human atrial trabeculae, together with contracture reported previously at lower temperatures (1 degree and 4 degrees C), is not due to a failure to maintain adenosine triphosphate levels.

The effects of temperature and buffer concentration on the metabolism of human atrial appendages measured by 31P and 1H NMR

In this study we measured changes in intracellular ATP and pH together with lactate production in isolated ischemic human atrial tissue. The measurements were made using 31P and 1H NMR. ATP preservation is improved as temperature is reduced from 20 degrees C to 1 degree C because of a progressive decrease in energy demand. At a constant temperature (12 degrees C), ATP preservation is improved by increasing the extracellular buffer capacity with PIPES buffer at concentrations up to 100 mM. Under these conditions, energy demand appears to increase but the ATP level is kept relatively constant for periods of 10 hours or longer. This appears to be due to a tighter regulation between supply and demand in which glycolysis is driven faster at relatively lower ADP and Pi levels. This tight regulation may be attributed to the better maintenance of intracellular pH.