The impact of age and frailty on ventricular structure and function in C57BL/6J mice.

KEY POINTS: Heart size increases with age (called hypertrophy), and its ability to contract declines. However, these reflect average changes that may not be present, or present to the same extent, in all older individuals. That aging happens at different rates is well accepted clinically. People who are aging rapidly are frail and frailty is measured with a 'frailty index'. We quantified frailty with a validated mouse frailty index tool and evaluated the impacts of age and frailty on cardiac hypertrophy and contractile dysfunction. Hypertrophy increased with age, while contractions, calcium currents and calcium transients declined; these changes were graded by frailty scores. Overall health status, quantified as frailty, may promote maladaptive changes associated with cardiac aging and facilitate the development of diseases such as heart failure. To understand age-related changes in heart structure and function, it is essential to know both chronological age and the health status of the animal. ABSTRACT: On average, cardiac hypertrophy and contractile dysfunction increase with age. Still, individuals age at different rates and their health status varies from fit to frail. We investigated the influence of frailty on age-dependent ventricular remodelling. Frailty was quantified as deficit accumulation in adult (≈7 months) and aged (≈27 months) C57BL/6J mice by adapting a validated frailty index (FI) tool. Hypertrophy and contractile function were evaluated in Langendorff-perfused hearts; cellular correlates/mechanisms were investigated in ventricular myocytes. FI scores increased with age. Mean cardiac hypertrophy increased with age, but values in the adult and aged groups overlapped. When plotted as a function of frailty, hypertrophy was graded by FI score (r = 0.67-0.55, P < 0.0003). Myocyte area also correlated positively with FI (r = 0.34, P = 0.03). Left ventricular developed pressure (LVDP) plus rates of pressure development (+dP/dt) and decay (-dP/dt) declined with age and this was graded by frailty (r = -0.51, P = 0.0007; r = -0.48, P = 0.002; r = -0.56, P = 0.0002 for LVDP, +dP/dt and -dP/dt). Smaller, slower contractions graded by FI score were also seen in ventricular myocytes. Contractile dysfunction in cardiomyocytes isolated from frail mice was attributable to parallel changes in underlying Ca2+ transients. These changes were not due to reduced sarcoplasmic reticulum stores, but were graded by smaller Ca2+ currents (r = -0.40, P = 0.008), lower gain (r = -0.37, P = 0.02) and reduced expression of Cav1.2 protein (r = -0.68, P = 0.003). These results show that cardiac hypertrophy and contractile dysfunction in naturally aging mice are graded by overall health and suggest that frailty, in addition to chronological age, can help explain heterogeneity in cardiac aging.

A Frailty Index Based On Deficit Accumulation Quantifies Mortality Risk in Humans and in Mice.

Although many common diseases occur mostly in old age, the impact of ageing itself on disease risk and expression often goes unevaluated. To consider the impact of ageing requires some useful means of measuring variability in health in animals of the same age. In humans, this variability has been quantified by counting age-related health deficits in a frailty index. Here we show the results of extending that approach to mice. Across the life course, many important features of deficit accumulation are present in both species. These include gradual rates of deficit accumulation (slope = 0.029 in humans; 0.036 in mice), a submaximal limit (0.54 in humans; 0.44 in mice), and a strong relationship to mortality (1.05 [1.04-1.05] in humans; 1.15 [1.12-1.18] in mice). Quantifying deficit accumulation in individual mice provides a powerful new tool that can facilitate translation of research on ageing, including in relation to disease.

Reaction dynamics of CN radicals with tetrahydrofuran in liquid solutions.

Transient, broadband infra-red absorption spectroscopy with picosecond time resolution has been used to study the dynamics of reactions of CN radicals with tetrahydrofuran (THF) and d(8)-THF in liquid solutions ranging from neat THF to 0.5 M THF in chlorinated solvents (CDCl(3) and CD(2)Cl(2)). HCN and DCN products were monitored via their v(1) (C≡N stretching) and v(3) (C-H(D) stretching) vibrational absorption bands. Transient spectral features indicate formation of vibrationally excited HCN and DCN, and the onsets of absorption via the fundamental bands of HCN and DCN show short (5-15 ps) delays consistent with vibrational relaxation within the nascent reaction products. This interpretation is confirmed by non-equilibrium molecular dynamics simulations employing a newly derived analytic potential energy surface for the reaction in explicit THF solvent. The rate coefficient for reactive formation of HCN (as determined from measurements on both the 1(1)(0) and 3(1)(0) fundamental bands) decreases with increasing dilution of the THF in CDCl(3) or CD(2)Cl(2), showing pseudo-first order kinetic behaviour for THF concentrations in the range 0.5-4.5 M, and a bimolecular rate coefficient of (1.57 ± 0.12) × 10(10) M(-1) s(-1) is derived. Simultaneous analysis of time-dependent HCN 1(1)(0) and 3(1)(0) band intensities following reaction of CN with THF (3.0 M) in CD(2)Cl(2) suggests that C-H stretching mode excitation is favoured, and this deduction is supported by the computer simulations. The results extend our recent demonstration of nascent vibrational excitation of the products of bimolecular reactions in liquid solution to a different, and more strongly interacting class of organic solvents. They serve to reinforce the finding that dynamics (and thus the topology of the reactive potential energy surface) play an important role in determining the nascent product state distributions in condensed phase reactions.

Quasi-classical trajectory study of the dynamics of the Cl + CH4→ HCl + CH3 reaction.

We present an on-the-fly classical trajectory study of the Cl + CH(4)→ HCl + CH(3) reaction using a specific reaction parameter (SRP) AM1 Hamiltonian that was previously optimized for the Cl + ethane reaction [S. J. Greaves et al., J. Phys Chem A, 2008, 112, 9387]. The SRP-AM1 Hamiltonian is shown to be a good model for the potential energy surface of the title reaction. Calculated differential cross sections, obtained from trajectories propagated with the SRP-AM1 Hamiltonian compare favourably with experimental results for this system. Analysis of the vibrational modes of the methyl radical shows different scattering distributions for ground and vibrationally excited products.

Photodissociation dynamics of the A 2Sigma+ state of SH and SD radicals.

Atomic sulfur products from predissociation of the lowest rotational states of SH/SD A (2)Sigma(+) (v(')=0,1,2) are studied using velocity map imaging. The dissociation process, which is slow compared to rotation, is dominated by interference effects due to predissociation of states with low rotation quantum numbers prepared by photoexcitation using overlapping transitions of different parities. The measured product angular distributions can be modeled using the methods presented recently by Kim et al. [J. Chem. Phys. 125, 133316 (2006)]. The S((3)P(J)) (2+1) resonance enhanced multiphoton ionization scheme used in the detection step of the experiment is sensitive to the angular momentum polarization of the atomic fragments. S((3)P(J)), J=2,1,0, fine-structure yields, angular distributions, and atom polarization parameters are reported. Strong polarization of the S((3)P(2,1)) products was observed along with a weak sensitivity of the branching ratio to excess energy and a full insensitivity of the atomic product polarization to excess energy. None of the data fit the predictions of either adiabatic or diabatic photodissociation, emphasizing the need for a fully quantum treatment.

Interactions between oxidative stress and inflammation in salt-sensitive hypertension.

The goal of this study was to test the hypothesis that increases in oxidative stress in Dahl S rats on a high-salt diet help to stimulate renal nuclear factor-kappaB (NF-kappaB), renal proinflammatory cytokines, and chemokines, thus contributing to hypertension, renal damage, and dysfunction. We specifically studied whether antioxidant treatment of Dahl S rats on high Na intake would decrease renal inflammation and thus attenuate the hypertensive and adverse renal responses. Sixty-four 7- to 8-wk-old Dahl S or R/Rapp strain rats were maintained for 5 wk on high Na (8%) or high Na + vitamins C (1 g/l in drinking water) and E (5,000 IU/kg in food). Arterial and venous catheters were implanted at day 21. By day 35 in the high-Na S rats, antioxidant treatment significantly increased the renal reduced-to-oxidized glutathione ratio and decreased renal cortical H(2)O(2) and O(2)(*-) release and renal NF-kappaB. Antioxidant treatment with vitamins C and E in high-Na S rats also decreased renal monocytes/macrophages in the glomeruli, cortex, and medulla, decreased tumor necrosis factor-alpha by 39%, and decreased monocyte chemoattractant protein-1 by 38%. Vitamin-treated, high-Na S rats also experienced decreases in arterial pressure, urinary protein excretion, renal tubulointerstitial damage, and glomerular necrosis and increases in glomerular filtration rate and renal plasma flow. In conclusion, antioxidant treatment of high-Na Dahl S rats decreased renal inflammatory cytokines and chemokines, renal immune cells, NF-kappaB, and arterial pressure and improved renal function and damage.

C-type natriuretic peptide activates a non-selective cation current in acutely isolated rat cardiac fibroblasts via natriuretic peptide C receptor-mediated signalling.

In the heart, fibroblasts play an essential role in the deposition of the extracellular matrix and they also secrete a number of hormonal factors. Although natriuretic peptides, including C-type natriuretic peptide (CNP) and brain natriuretic peptide, have antifibrotic effects on cardiac fibroblasts, the effects of CNP on fibroblast electrophysiology have not been examined. In this study, acutely isolated ventricular fibroblasts from the adult rat were used to measure the effects of CNP (2 x 10(-8) M) under whole-cell voltage-clamp conditions. CNP, as well as the natriuretic peptide C receptor (NPR-C) agonist cANF (2 x 10(-8) M), significantly increased an outwardly rectifying non-selective cation current (NSCC). This current has a reversal potential near 0 mV. Activation of this NSCC by cANF was abolished by pre-treating fibroblasts with pertussis toxin, indicating the involvement of G(i) proteins. The cANF-activated NSCC was inhibited by the compounds Gd(3+), SKF 96365 and 2-aminoethoxydiphenyl borate. Quantitative RT-PCR analysis of mRNA from rat ventricular fibroblasts revealed the expression of several transient receptor potential (TRP) channel transcripts. Additional electrophysiological analysis showed that U73122, a phospholipase C antagonist, inhibited the cANF-activated NSCC. Furthermore, the effects of CNP and cANF were mimicked by the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG), independently of protein kinase C activity. These are defining characteristics of specific TRPC channels. More detailed molecular analysis confirmed the expression of full-length TRPC2, TRPC3 and TRPC5 transcripts. These data indicate that CNP, acting via the NPR-C receptor, activates a NSCC that is at least partially carried by TRPC channels in cardiac fibroblasts.

Immune suppression prevents renal damage and dysfunction and reduces arterial pressure in salt-sensitive hypertension.

The goal of this study was to test the hypothesis that renal infiltration of immune cells in Dahl S rats on increased dietary sodium intake contributes to the progression of renal damage, decreases in renal hemodynamics, and development of hypertension. We specifically studied whether anti-immune therapy, using mycophenolate mofetil (MMF), could help prevent increases in renal NF-kappaB activation, renal infiltration of monocytes/macrophages, renal damage, decreases in glomerular filtration rate (GFR) and renal plasma flow, and increases in arterial pressure. Seventy-four 7-to 8-wk-old Dahl S, Rapp strain rats were maintained on an 8% Na, 8% Na + MMF (20 mg.kg(-1).day(-1)), 0.3% Na, or 0.3% Na + MMF diet for 5 wk. Arterial and venous catheters were implanted at day 21. By day 35, renal NF-kappaB in 8% Na rats was 47% higher than in 0.3% Na rats and renal NF-kappaB was 41% lower in 8% Na + MMF rats compared with the 8% Na group. MMF treatment significantly decreased renal monocyte/macrophage infiltration and renal damage and increased GFR and renal plasma flow. In high-NA Dahl S rats mean arterial pressure increased to 182 +/- 5 mmHg, and MMF reduced this arterial pressure to 124 +/- 3 mmHg. In summary, in Dahl S rats on high sodium intake, treatment with MMF decreases renal NF-kappaB and renal monocyte/macrophage infiltration and improves renal function, lessens renal injury, and decreases arterial pressure. This suggests that renal infiltration of immune cells is associated with increased arterial pressure and renal damage and decreasing GFR and renal plasma flow in Dahl salt-sensitive hypertension.

Inhibition of L-type Ca2+ current by C-type natriuretic peptide in bullfrog atrial myocytes: an NPR-C-mediated effect.

Single atrial myocytes were isolated from the bullfrog heart and studied under current and voltage clamp conditions to determine the electrophysiological effects of the C-type natriuretic peptide (CNP). CNP (10(-8) M) significantly shortened the action potential and reduced its peak amplitude after the application of isoproteronol (10(-7) M). In voltage clamp studies, CNP inhibited isoproteronol-stimulated L-type Ca2+ current (ICa) without any significant effect on the inward rectifier K+ current. The effects of cANF (10(-8) M), a selective agonist of the natriuretic peptide C receptor (NPR-C), were very similar to those of CNP. Moreover, HS-142-1, an antagonist of the guanylyl cyclase-linked NPR-A and NPR-B receptors did not alter the inhibitory effect of CNP on ICa. Inclusion of cAMP in the recording pipette to stimulate ICa at a point downstream from adenylyl cyclase increased ICa, but this effect was not inhibited by cANF. These results provide the first demonstration that CNP can inhibit ICa after binding to NPR-C, and suggest that this inhibition involves a decrease in adenylyl cyclase activity, which leads to reduced intracellular levels of cAMP.

Effects of walking on ventilatory and cardiac function in intact and cardiac-impaired lobsters.

Decapod crustaceans with normal heart function respond to the increased oxygen delivery requirements during walking with a step increase in heart and ventilation rate. In American lobsters, ventilation rate increased by the same amount during exercise at two walking speeds (2.4 and 8 m min(-1)); however, ventilation volume was significantly greater at the fastest walking speed (280 mL min(-1)) compared to animals at rest or walking at the slower speed (180 mL min(-1)). The heart responded in a similar manner to locomotion. Heart rate was elevated to the same level at the two different walking speeds, but cardiac stroke volume was greater, implying increased cardiac output, at the faster walking speed. The communication and compensation between the cardiac and ventilatory systems was revealed when the function of one was impaired. Ventilatory rate was significantly elevated when cardiac output was impaired by sectioning two of the alary ligaments and/or the regulatory nerves to the heart. When cardiac output was more severely impaired, ventilation rate was greater. Despite ventilatory compensation, anaerobic metabolism made a greater contribution to energy production with impaired heart function. Hemolymph lactate concentration was three to five times greater in impaired animals than controls. It is known that the ventilatory and cardiac systems of lobsters are coregulated. These data demonstrate that the performance of one system can respond to compensate for impaired function in the other.

Survival of Escherichia coli O157:H7 in ground beef jerky assessed on two plating media.

Recent outbreaks of food-borne illness due to Salmonella spp. in beef jerky and Escherichia coli O157:H7 in venison jerky, coupled with the fact that a variety of preparation methods and dying procedures abound, raise concern over the safety of processed meat products made in the home. The potential of injured bacterial cells to regain the ability to cause illness is a particular threat with pathogens such as E. coli O157:H7, which is believed to have a low infectious dose. This study examined the efficacy of various methods of jerky preparation in reducing populations of E, coli O157:H7 in ground beef jerky and compared the recovery rate of E. coli O157:H7 on two selective plating media, modified sorbitol MacConkey agar (MSMA) and modified eosin methylene blue agar (MEMB). Populations of E. coli O157:H7 in both heated and unheated samples exhibited a greater decline during drying when a nitrite and salt cure mix was added during jerky preparation. When recovery of E. coli O157:H7 on MSMA and MEMB was compared, a trend toward slightly higher recovery rates with MEMB was observed. On the basis of these results, MEMB is a suitable alternative to MSMA for the recovery of E. coli O157:H7 from heated and dried meat samples similar to beef jerky.

Fungal infections in left ventricular assist device recipients. Incidence, prophylaxis, and treatment.

The authors reviewed the charts of 26 recipients of a left ventricular assist device to determine the incidence of fungal infections and the clinical course of these patients. Nine patients (35%) had positive fungal cultures. Of these, six had clinical infections and three were colonized asymptomatically. Three of the six infected patients (including one with mediastinal sepsis and another requiring left ventricular assist device replacement for intractable fungemia) underwent orthotopic heart transplantation after successful therapy. Of the remaining three, one died of a thromboembolic stroke (probably septic in nature), one died secondary to driveline rupture, and the third succumbed to culture-negative sepsis. Two of the colonized patients underwent transplantation, and the third succumbed to perioperative right sided circulatory failure and hypoxia. Positive fungal cultures were a common finding in our series. Because of a significant incidence of fungal infection-related morbidity, the authors revised their pre operative and post operative protocol to include: 1) 2 weeks of fluconazole therapy (200 mg intravenously daily) for patients receiving broad spectrum antibiotics and for those with evidence of preoperative fungal colonization; 2) daily dressing changes around drivelines; 3) daily nystatin swish and swallow; and 4) empiric fluconazole treatment for culture-negative sepsis. Using this protocol, three left ventricular assist device recipients received prophylactic fluconazole and had no evidence of fungal morbidity or mortality on short-term follow-up.

Ultrasound guided fine needle biopsy of the liver for cytology and histology.

Ultrasound guided fine needle biopsies were performed in 69 patients with space occupying lesions in the liver. Fifty five of these patients had material obtained for both cytology and histology with a 22 gauge modified Menghini needle, while the other 14 were biopsied with a conventional Chiba needle. Results of cytology, histology of Menghini cores, and histology of cell blocks, were reviewed and correlated with the final diagnoses obtained by clinical review and follow-up. Cytology detected 95% of malignant cases, and Menghini core histology detected 89%. A number of factors should determine the choice of fine needle biopsy for cytology or histology or both.

Necator americanus in the DSN hamster: density-dependent expulsion of adult worms during primary infection.

Neonatal hamsters were exposed to varying doses of Necator americanus larvae and changes in the stability of the resulting worm burdens were monitored over a period of 25 weeks. No change in worm burdens was evident for the first 5 weeks of infection, irrespective of the infection intensity, but the more heavily infected groups subsequently lost worms in a density-dependent manner. Male and female hamsters lost comparable proportions of their established parasite burdens indicating that there was no host sex-linked difference in this respect. By week 15 infections had stabilized and the residual worm burdens, usually a maximum of 30 worms survived for a considerably longer period of time. Initially the percentage of male worms varied from 45% to 50% but as infection progressed male worms comprised a significantly increasing proportion of the total worm burden. By week 25 the percentage of male worms was usually in excess of 60%. The growth of infected animals was not severely affected by N. americanus, even when heavy worm burdens established initially, but a significant effect was detected particularly in week 5, prior to worm loss, when the adult worms would have been feeding on intestinal tissues and causing blood loss for a period of about 2 weeks. The most severe depression in the packed cell volume was also recorded in week 5, indicating that anaemia had been initiated in infected hamsters. Whilst, the regulation of parasite burdens in weeks 5-10 post-infection may have resulted from host immunity, the persistence of the residual worm burdens, the marked density-dependent anaemia and the subtle effect on host weight, all reflected well-documented aspects of chronic human necatoriasis.

Acquired immunity to Ancylostoma ceylanicum in hamsters.

A laboratory model of acquired immunity to human hookworm is described. Significant resistance to challenge infection with Ancylostoma ceylanicum was elicited in mature DSN hamsters. The serum and mucosal antibody responses were investigated in both quantitative and qualitative terms and changes associated with immunity were identified. Marked differences in numbers of mast and goblet cells in the small intestine were also recorded and related to the immune status of the host.

The immune response of male DSN hamsters to a primary infection with Ancylostoma ceylanicum.

The immune response of hamsters to a chronic hookworm infection has been investigated. Ancylostoma ceylanicum caused long term infections in hamsters which were associated with prominent changes in secondary lymphoid organs. The mesenteric lymph nodes and spleens increased rapidly in size stabilizing at approximately 3-4 times the weight in control animals by weeks 3-7. Cells from both the mesenteric lymph node and spleen, after an initial period of increased blast cell activity, became less reactive in the latter stages of infection. Serum antibody responses were marked, commencing in weeks 3-4 and increasing in intensity throughout the 10 week period of measurement. The results are discussed in relation to their contribution to the understanding of human hookworm infection.

Ultrasound-guided fine needle aspiration biopsy of the liver.

Our experience with ultrasound-guided fine needle aspiration biopsy in 65 patients suspected of having malignancy of the liver is reviewed. The results of cytology smears were correlated with cell block sections, histology of the liver and/or other relevant sites, and clinical course. Aspiration cytology was positive in 52 of 57 patients (91%) who had a final diagnosis of malignancy, and there were no false positive results. The cell type reported by cytology correlated completely in 23 of 27 cases with histological confirmation, whilst cytology showed better differentiating features in the remaining 4 cases. The microscopic appearances have been described. There was only one significant complication of the procedure.

Evaluation of efficacy of cefoxitin in the prevention of abdominal trauma infections.

Recent studies showed high populations of both aerobes and anaerobes in penetrating abdominal trauma infections. Combined aminoglycoside-clindamycin therapy has resulted in infection rates of 7 to 10 per cent. However, high side-effect incidences of nephrotoxicity and ototoxicity have been attributed to the aminoglycosides. Cefoxitin is reportedly free of these side effects. In our study, 62 penetrating abdominal trauma patients requiring laparotomy were treated with cefoxitin pre- and postoperatively. The majority of the injuries, 75.8 per cent, involved small bowel and large bowel. Infections occurred in four patients of the total 62 (6.5%). Two side effects, a fever and a rash, subsided immediately after discontinuing cefoxitin; no ototoxicity or nephrotoxicity occurred. The safety and efficacy of cefoxitin alone versus aminoglycoside-clindamycin combination therapy was statistically compared in intestinal injuries only among two historical controls and our subgroup. Our infectious rate, 8.5 per cent, was comparable to 7.4 per cent and 10.4 per cent of the historical controls. We concluded that pre- and postoperative use of cefoxitin alone is as effective in the prevention of penetrating abdominal trauma infections as combined aminoglycoside-clindamycin therapy. Experience to date suggests that the use of a beta-lactam antibiotic such as cefoxitin may allow the physician to avoid the more serious side effects associated with the use of aminoglycosides in these patients.