Machine Learning in Differentiating Gliomas from Primary CNS Lymphomas: A Systematic Review, Reporting Quality, and Risk of Bias Assessment

BACKGROUND

Differentiating gliomas and primary CNS lymphoma represents a diagnostic challenge with important therapeutic ramifications. Biopsy is the preferred method of diagnosis, while MR imaging in conjunction with machine learning has shown promising results in differentiating these tumors.

PURPOSE

Our aim was to evaluate the quality of reporting and risk of bias, assess data bases with which the machine learning classification algorithms were developed, the algorithms themselves, and their performance.

DATA SOURCES

Ovid EMBASE, Ovid MEDLINE, Cochrane Central Register of Controlled Trials, and the Web of Science Core Collection were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

STUDY SELECTION

From 11,727 studies, 23 peer-reviewed studies used machine learning to differentiate primary CNS lymphoma from gliomas in 2276 patients.

DATA ANALYSIS

Characteristics of data sets and machine learning algorithms were extracted. A meta-analysis on a subset of studies was performed. Reporting quality and risk of bias were assessed using the Transparent Reporting of a multivariable prediction model for Individual Prognosis Or Diagnosis (TRIPOD) and Prediction Model Study Risk Of Bias Assessment Tool.

DATA SYNTHESIS

The highest area under the receiver operating characteristic curve (0.961) and accuracy (91.2%) in external validation were achieved by logistic regression and support vector machines models using conventional radiomic features. Meta-analysis of machine learning classifiers using these features yielded a mean area under the receiver operating characteristic curve of 0.944 (95% CI, 0.898-0.99). The median TRIPOD score was 51.7%. The risk of bias was high for 16 studies.

LIMITATIONS

Exclusion of abstracts decreased the sensitivity in evaluating all published studies. Meta-analysis had high heterogeneity.

CONCLUSIONS

Machine learning-based methods of differentiating primary CNS lymphoma from gliomas have shown great potential, but most studies lack large, balanced data sets and external validation. Assessment of the studies identified multiple deficiencies in reporting quality and risk of bias. These factors reduce the generalizability and reproducibility of the findings.

Morphometric profile of large intestinal neuronal plexuses in normal perinatal autopsies and Hirschsprung disease

OBJECTIVES

To derive objective values for the diagnosis of Hirschsprung disease (HSCR) from a comparison of the morphometric profile of large intestinal neuronal plexuses in normal perinatal autopsies and surgical specimens of HSCR.

METHODS

A cross-sectional comparative study with 40 subjects each in (i) non-HSCR perinatal group encompassing neonates and stillborn babies beyond 30 weeks of gestation on whom autopsies were conducted and (ii) HSCR group comprising all patients clinicoradiologically diagnosed as HSCR. The morphometric assessment was done on hematoxylin-and-eosin-stained sections.

KEY RESULTS

The morphometric profile in terms of average number of ganglia/linear mm of colon, interganglion distance, number of ganglion cells/ganglion, average ganglion cell length, ganglion cell nuclear area, ganglion cell nuclear diameter, nerve trunk thickness, and density has been outlined. On comparison with the neuroanatomically normal zone of HSCR, the cut-offs to identify hypertrophic nerve trunks (nerve trunk thickness of >37.85 μm) and reduced number of ganglia (number of ganglia/linear mm of colon <2.05 and interganglion distance of >229 μm) were derived.

CONCLUSIONS & INFERENCES

The determined objective values, after testing on diagnostic rectal biopsies, may serve to formulate a diagnostic algorithm along with immunostaining for diagnosis of HSCR in colorectal specimens.

The Global Relationship between Chromatin Physical Topology, Fractal Structure, and Gene Expression

Most of what we know about gene transcription comes from the view of cells as molecular machines: focusing on the role of molecular modifications to the proteins carrying out transcriptional reactions at a loci-by-loci basis. This view ignores a critical reality: biological reactions do not happen in an empty space, but in a highly complex, interrelated, and dense nanoenvironment that profoundly influences chemical interactions. We explored the relationship between the physical nanoenvironment of chromatin and gene transcription in vitro. We analytically show that changes in the fractal dimension, D, of chromatin correspond to simultaneous increases in chromatin accessibility and compaction heterogeneity. Using these predictions, we demonstrate experimentally that nanoscopic changes to chromatin D within thirty minutes correlate with concomitant enhancement and suppression of transcription. Further, we show that the increased heterogeneity of physical structure of chromatin due to increase in fractal dimension correlates with increased heterogeneity of gene networks. These findings indicate that the higher order folding of chromatin topology may act as a molecular-pathway independent code regulating global patterns of gene expression. Since physical organization of chromatin is frequently altered in oncogenesis, this work provides evidence pairing molecular function to physical structure for processes frequently altered during tumorigenesis.

Procedures for risk-stratification of lung cancer using buccal nanocytology

Lung cancer is the leading cause of cancer deaths in the U.S. with survival dramatically depending on stage at diagnosis. We had earlier reported that nanocytology of buccal cells can accurately risk-stratify smokers for the presence of early and late-stage lung cancer. To translate the technique into clinical practice, standardization of operating procedures is necessary to consistently yield precise and repeatable results. Here, we develop and validate simple, robust, and easily implementable procedures for specimen collection, processing, etc. in addition to a commercially-viable instrument prototype. Results of this work enable translation of the technology from academic lab to physicians' office.

Identification of Dermatophilus congolensis from lower leg dermatitis of cattle in Kerala, India

This study was conducted to identify the aetiological agents associated with a particular type of lower leg dermatitis, locally called pododermatitis, among dairy cattle in Kerala. Skin scabs and scrapings were collected aseptically from 82 naturally occurring cases of lower leg dermatitis in cattle and were subjected to direct microscopical examination and bacterial and fungal culture. Microscopical examination of the skin scrapings with 10% potassium hydroxide revealed fungal spores in hair shafts from only two samples and did not reveal the presence of mites or other parasites. Fungal culture yielded dermatophytes from only five samples; these were identified as Trichophyton mentagrophytes in two cases, T verrucosum in one case, Epidermophyton floccosum in one case and Microsporum nanum in one case. Microscopical examination of Giemsa- and Gram-stained smears of the scab material from the lesions from 72 cases revealed characteristic Gram-positive septate branching filaments with multiple rows of spherical to ovoid cocci, with a typical 'tram-track' appearance suggestive of Dermatophilus congolensis. Culture of the scab materials on sheep blood agar in the presence of 10% carbon dioxide yielded typical beta haemolytic colonies of D. congolensis from 75 samples. The isolates were further confirmed by the macroscopic and microscopic morphology of the colonies, and biochemical test results. This study confirmed the presence of dermatophilosis caused by D. congolensis in cattle in Kerala.

Steady-State Radiolysis of Supercritical Water: Model Predictions and Validation

Chemical kinetic models are being developed for the γ-radiolysis of subcritical and supercritical water (SCW) to estimate the concentrations of radiolytically produced oxidants. Many of the physical properties of water change sharply at the critical point. These properties control the chemical stability and transport behavior of the ions and radicals generated by the radiolysis of SCW. The effects of changes in the solvent properties of water on primary radiolytic processes and the subsequent aqueous reaction kinetics can be quite complicated and are not yet well understood. The approach used in this paper was to adapt an existing liquid water radiolysis model (LRM) that has already been validated for lower temperatures and a water vapor radiolysis model (VRM) validated for higher temperatures, but for lower pressures, to calculate radiolysis product speciation under conditions approaching the supercritical state. The results were then extrapolated to the supercritical regime by doing critical analysis of the input parameters. This exercise found that the vapor-like and liquid-like models make similar predictions under some conditions. This paper presents and discusses the LRM and VRM predictions for the concentrations of molecular radiolysis products, H2, O2, and H2O2 at two different irradiation times, 1 s and 1 hr, as a function of temperature ranging from 25°C to 400°C. The model simulation results are then compared with the concentrations of H2, O2, and H2O2 measured as a function of γ-irradiation time at 250°C. Model predictions on the effect of H2 addition on the radiolysis product concentrations at 400°C are presented and compared with the experimental results from the Beloyarsk Nuclear Power Plant (NPP).

The sGC stimulator riociguat inhibits platelet function in washed platelets but not in whole blood

BACKGROUND AND PURPOSE

Stimulation of soluble guanylyl cyclase (sGC) is a valuable therapeutic strategy for the treatment of several cardiovascular diseases. The sGC stimulator riociguat has been approved for the treatment of two forms of pulmonary hypertension. Platelets contain large amounts of sGC and play a key role in the regulation of haemostasis. Therefore, we investigated the effects of riociguat on platelet function.

EXPERIMENTAL APPROACH

The effect of riociguat treatment on human platelet activation and aggregation was investigated. The sGC-specific effects of riociguat were determined by comparing wild-type and platelet-specific sGC-knockout mice.

KEY RESULTS

Riociguat induced cGMP synthesis and subsequent PKG activation in human platelets, suggesting that the inhibitory effects are mediated by cGMP signalling. This finding was confirmed when sGC-knockout platelets were not inhibited by riociguat. In washed human platelets, 100 nM riociguat reduced ADP-induced GPIIb/IIIa activation, while a 10-fold higher concentration was required to reduce convulxin-stimulated GPIIb/IIIa activation. Riociguat inhibited ADP-induced platelet shape change and aggregation, while ATP-induced shape change remained unaffected. However, in PRP and whole blood, 50-100 μM riociguat was required to inhibit platelet activation and aggregation. Riociguat in combination with iloprost significantly inhibited platelet aggregation, even in whole blood.

CONCLUSIONS AND IMPLICATIONS

Riociguat inhibits platelet activation in whole blood only at concentrations above 50 μM, while the plasma concentrations in riociguat-treated patients are 150 to 500 nM. This finding indicates that riociguat treatment does not affect platelet function in patients. Nevertheless, the possibility that riociguat acts synergistically with iloprost to inhibit platelet activation should be considered.

Anesthetic challenges of decompressive craniotomy for the right frontal lobe abscess in a patient with Ebstein's anomaly: A rare case report

Ebstein's anomaly is a rare congenital heart disease characterized by downward displacement of the tricuspid valve, atrialization of right ventricle, enlarged right atrium with tricuspid regurgitation, or stenosis. It is often associated with atrial septal defect (ASD) or patent foramen ovale with right to left shunt. It has a varied clinical presentation and can manifest as cyanosis, ventricular, or supraventricular arrhythmias and recurrent episodes of congestive heart failure. We describe the anesthetic management of a female patient with Ebstein's anomaly who had right frontal lobe abscess due to paradoxical embolism for decompressive craniotomy.

Orai1-induced store-operated Ca(2+) entry enhances phospholipase activity and modulates canonical transient receptor potential channel 6 function in murine platelets

BACKGROUND

Orai1, the major store-operated Ca(2+) entry (SOCE) channel in platelets, is not only critical for enhancing diverse signaling pathways, but may also regulate receptor-operated Ca(2+) entry (ROCE). Dynamic coupling of the Orai1 signalosome to canonical transient receptor potential channels (TRPCs) has been suggested as an essential step in the activation of SOCE and ROCE. However, the functional significance of the biochemical interaction between Orai and TRPC isoforms remains controversial.

OBJECTIVE

We aimed to elucidate the role of Orai1 in diacylglycerol (DAG)-mediated ROCE.

METHODS

Trpc6(-/-) , Orai1(-/-) and Orai1(-/-) /Trpc6(-/-) mice were generated, and their platelets were analyzed.

RESULTS

Thapsigargin (TG)-induced SOCE was further reduced in Orai1(-/-) /Trpc6(-/-) platelets as compared with Orai1(-/-) platelets, thus revealing that TG-induced signaling pathways can activate TRPC6. Thapsigargin-induced SOCE leads to enhanced phospholipase C and D activity in wild-type platelets. The activity of both enzymes was significantly reduced in Orai1(-/-) platelets upon TG stimulation, whereas receptor-induced phospholipase activity was not affected. Furthermore, TG-induced and glycoprotein VI-mediated thromboxane A2 release was strongly dependent on Orai1-mediated SOCE.

CONCLUSION

The regulation of TRPC6 activity can occur independently of the physical interaction with Orai1. TRPC6 operates in crosstalk with Orai1 through Orai1-induced DAG production via phospholipase activation. Orai1-induced DAG production and thromboxane release amplify the second phase of Ca(2+) signaling in platelets.

Phosphorylation of CalDAG-GEFI by protein kinase A prevents Rap1b activation

BACKGROUND

Signaling via protein kinase A (PKA) and protein kinase G (PKG) is critical for maintaining platelets in the resting state. Both kinases down-regulate the activity of the small GTPase Rap1b, a critical signaling switch for integrin activation and platelet aggregation. However, the mechanism of Rap1b regulation by PKA and PKG is largely unknown.

OBJECTIVE

To identify the PKA phosphorylation sites in calcium and diacylglycerol-regulated guanine nucleotide exchange factor I (CalDAG-GEFI), the main GEF for Rap1b in platelets, and the effect of CalDAG-GEFI phosphorylation in Rap1b activation.

METHODS

The phosphorylation sites in CalDAG-GEFI were identified by radio-active phosphate incorporation assay and mass spectrometry. Phospho-antibody was developed to detect CalDAG-GEFI phosphorylation in Western blots. Rap1b activation was detected by Rap1-GTP pull-down assay.

RESULTS

S587 was identified as the major PKA phosphorylation site in CalDAG-GEFI, while S116/117 was weakly phosphorylated. Phosphorylation of S587 correlated with the inhibitory effect of PKA on Rap1b activation in platelets. In HEK293 cells, expression of a phospho-mimetic mutant of CalDAG-GEFI (S587D) abolished agonist-induced Rap1b activation. Mutation of S587 to alanine partially reversed the inhibitory effect of PKA signaling on Rap1b activation, while mutation of S116, S117 and S587 to alanine completely abolished the inhibitory effect of PKA on Rap1b activation.

CONCLUSION

Our study strongly suggests that phosphorylation of CalDAG-GEFI is a critical mechanism by which PKA controls Rap1b-dependent platelet aggregation.

Interferometric spectroscopy of scattered light can quantify the statistics of subdiffractional refractive-index fluctuations

Despite major importance in physics, biology, and other sciences, the optical sensing of nanoscale structures in the far zone remains an open problem due to the fundamental diffraction limit of resolution. We establish that the expected value of spectral variance (Σ[over ˜](2)) of a far-field, diffraction-limited microscope image can quantify the refractive-index fluctuations of a label-free, weakly scattering sample at subdiffraction length scales. We report the general expression of Σ[over ˜] for an arbitrary refractive-index distribution. For an exponential refractive-index spatial correlation, we obtain a closed-form solution of Σ[over ˜] that is in excellent agreement with three-dimensional finite-difference time-domain solutions of Maxwell's equations. Sensing complex inhomogeneous media at the nanoscale can benefit fields from material science to medical diagnostics.

Molecular characterization of Theileria orientalis causing fatal infection in crossbred adult bovines of South India

The disease condition attributed to have been caused by Theileria orientalis is generally benign. However, it is also thought that the parasite, at least some strains of it, can cause fatal disease. The present communication deals with the clinical signs, postmortem lesions and diagnosis of a fatal disease due to T. orientalis which caused mortality in crossbred adult bovines of South India. High body temperature, lacrimation, nasal discharge, swollen lymph nodes and haemoglobinuria were the symptoms observed. The postmortem lesions observed were punched out ulcers in abomasum, enlargement of spleen, massive pulmonary oedema, frothy exudates in trachea, epicardial and endocardial haemorrhage and haemorrhagic duodenitis. Peripheral blood smear examination revealed rod shaped Theileria sp. organisms. Polymerase chain reaction that amplify the T. orientalis specific P(32/33) gene, followed by cloning and sequencing, revealed maximum homology with Narathiwat (Thailand) and Jingole -1 (Indonesia) isolates which were positioned as isolate type 7 of T. orientalis.

Prevalence of Linguatula serrata in domestic ruminants in South India

Linguatula serrata Frohlich, 1789 is an aberrant endoparasite of occasional zoonotic importance in humans. We report the prevalence of encapsulated nymphal stages of L. serrata in domestic ruminants surveyed in Wayanad, located in Kerala State, South India. Large and small intestine mesentery were examined from 100 goats, cattle and buffaloes each revealing an infection prevalence of 21, 19, and 8%, respectively. The prevalence of L. serrata infection among ruminants is higher than previous reports from India and indicates a strong focus of infection in herbivorous domesticated mammals of South India. The potential importance of these findings to human health is discussed.

Low-coherence enhanced backscattering and its applications

The phenomenon of enhanced backscattering (EBS) of light, also known as coherent backscattering, has been the object of intensive investigation in non-biological media over the last two decades. However, there have been only a few attempts to explore EBS for tissue characterization and diagnosis. We have recently made progress in the EBS measurements in tissue by taking advantage of low spatial coherence illumination, which has led us to the development of low-coherence enhanced backscattering (LEBS) as a technique to characterize living tissue. In this paper, we review the current state of research on LEBS. In particular, we show that LEBS spectroscopy enables detection of early microarchitectural changes in tissue associated with carcinogenesis prior to the development of histologically-detectable alterations as well as any other known markers of neoplasia. Thus, LEBS may offer insights into initial events in carcinogenesis.

Visceral schistosomiasis among domestic ruminants slaughtered in Wayanad, South India

This short communication reports the prevalence of visceral schistosomiasis by worm counts from the mesentery of domestic ruminants of the hilly district of Wayanad, located in Kerala, one of the states in South India. We found 57.3, 50, and 4.7% of cattle, buffaloes and goats, respectively, had visceral schistosomiasis upon slaughter at a municipal slaughter house in Kalpetta. Our findings show that the prevalence of Schistosoma spindale infection is very high in Wayanad in comparison to previous reports from this and neighboring countries.

Phase I/II trial of twice-daily temozolomide and celecoxib for treatment of relapsed malignant glioma: Final data

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Background: Anaplastic astrocytoma (AA) and Glioblastoma multiforme (GBM) overexpress COX-2 enzyme. COX-2 inhibitors demonstrate preclinical efficacy in glioma models and have non-overlapping toxicity with chemotherapy, prompting a phase I/II trial for patients with recurrent/progressive AA or GBM utilizing a regimen of combined temozolomide (TMZ) and celecoxib (CEL). Final survival data is presented. Methods: For phase I, TMZ was given as a fixed loading dose of 200 mg/m2 followed by 9 doses of 90 mg/m2 BID for 5 days. CEL was given in 5 dose levels starting at 60 mg/m2 BID, escalating to 240 mg/m2 BID (maximum 400 mg BID) for 10 days. Cycles were repeated every 28 days until disease progression or toxicity occurred. Results: 46 patients (28 M, 18 F) received 247 cycles of therapy. 37 patients had GBM, 9 AA. Prior treatment was radiation (N=46) and chemotherapy (N=12). No patient received prior TMZ. Median age was 54 years (range 34–74). No dose-limiting toxicity was observed. Hematologic toxicity was mild with Grade 3/4 neutropenia occurring in 3/235 cycles and Grade 3 thrombocytopenia in 3/235 and did not recur following TMZ dose reduction. Grade 1/2 constipation was common, occurring in 28% of patients. No thrombotic events occurred. Overall response rate after 6 cycles was 72%, with 1/18 (5.6%) CR, 7/18 (38.9%) PR, 5/18 (27.8%) SD, and 5/18 (27.8%) PD. Average duration of response was 6 months (range 2–15). Median survival (MS) from time of trial entry for recurrent disease was 8 months (8 months for GBM, 10 months for AA). MS from initial tumor diagnosis was 15 months (15 months GBM, 23 months AA). Conclusion: A regimen of twice-daily TMZ and CEL is safe and potentially effective for the treatment of recurrent/progressive GBM and AA. This combination warrants further study, especially in patients newly diagnosed, given the current use of TMZ in newly diagnosed GBM and the possible value of COX-2 inhibitors in the upfront setting.

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Dirofilariosis in dogs and humans in Kerala

There has been an increased occurrence of filarial worms in the subcutaneous tissues and subconjunctival space of human beings belonging to different areas of the state of Kerala. The present work was carried out to identify the worms recovered from human cases, to study the presence of microfilariae in dogs and to discuss the possible mode of infection in human beings. Twelve worm specimens from human patients received in the Department of Veterinary Parasitology, College of Veterinary and Animal Sciences, Mannuthy from 2002 to 2004 were identified as Dirofilaria repens based on morphology. Out of the 160 blood smears of dogs examined during the same period, microfilariae were detected in 11 samples (7%). With 7 per cent dogs positive for microfilariae of D. repens in Kerala, it is suggested that human beings are at an enhanced risk of acquiring dirofilaria infection.

Age dependence of steady state mitochondrial oxidative metabolism in the in vivo hypoxic dog brain

Mitochondrial bioenergetics were investigated in newborn, neonatal and adult dog brains during normoxia and hypoxia. The ratio of the rate of ATP synthesis to the maximum synthesis rate (V/Vmax), phosphorylation potential, [ADP] and PCr/Pi, were used to evaluate age related mitochondrial hypoxic tolerance. These indicators were calculated from the phosphorus compounds measured by in vivo 31P MRS quantitatively using ATP as an internal reference. Indicators and substrates of mitochondrial function, V/Vmax, ADP, and Pi reached a peak value during the neonatal (3-21 days) period of development, suggesting that the oxidative metabolism of the neonate is more vulnerable to stress when compared to newborns and adults. Distinction among newborns and neonates became apparent during hypoxia. Newborns (0-2 days old) showed substantial tolerance by maintaining V/Vmax until exposure to severe hypoxia. Older neonates (3-21 days old) showed increases in V/Vmax, [Pi] and [ADP] under less than severe conditions of hypoxia. Adults exhibited low V/Vmax values even during exposure to severe hypoxia, further indicating that mitochondrial oxidative processes are more stable in adults than in newborns and neonates. This study provides evidence that newborns and adults are more capable of maintaining mitochondrial function under conditions of minimal to moderate hypoxia than 3-21 day old neonates.

Experimental brain ischaemia: assessment of injury by magnetic resonance spectroscopy and histology

Phosphorus magnetic resonance spectroscopy (31P-MRS) was made to measure changes in brain high energy phosphate compounds, adenosine triphosphate (ATP) and phosphocreatine (PCr), inorganic phosphorus (Pi) and intracellular pH (pHi) during a prolonged period of incomplete brain ischaemia produced, in anaesthetized dogs, by bilateral carotid occlusion together with haemorrhagic hypotension for intervals of up to 300 min. Mean arterial blood pressure (MABP) was lowered in a stepwise fashion, until signs of metabolic decompensation (as estimated by MRS) occurred. At that point MABP was varied against further evidence of metabolic decompensation in an attempt to maintain a more constant degree of insult. At the end of the ischaemic period MABP was restored and the animals observed during a 3 h recovery period. At the end of the recovery period the brains were perfusion-fixed for histological examination. A semi-quantitative method of histological evaluation was used to determine the degree of histological damage. This permitted assignment of an 'ischaemic score' to the tissue sampled from each animal. Comparisons were then made between the magnitude of this 'ischaemic score' and the changes in metabolic and physiological variables (ATP, PCr, pHi and MABP) as well as an estimator of phosphorylation potential (PCr/Pi), which were all measured during the ischaemic insult. Histological examination showed a wide variety of neuronal alterations, including dark and pale type injury, which correlated directly with the metabolic derangements brought about by ischaemia. The degree of damage determined from this histological assessment correlated best with the duration and degree of change in PCr/Pi, supporting the use of this ratio as a critical index of cellular energy state. In particular there was a strong linear relationship between the degree of leucocyte recruitment and changes in PCr/Pi. To summarize, metabolic changes, determined by MRS, correlate with the degree of histological damage, and in turn, the classical descriptions of acute ischaemic neuronal injury appear to be validated by MRS determinations of metabolic changes during ischaemia.

The synthesis of pulse sequences yielding arbitrary magnetization vectors

A new procedure and algorithm are presented to allow the synthesis of a pulse sequence which will generate an arbitrary frequency-dependent spin excitation. This procedure is a generalization of our previous paper, where this was done subject to the restriction that the spin excitation was symmetric about zero offset frequency, and pulses were restricted to being about a fixed axis. The required final z-magnetization vector (Mz) is expressed as a function of the off-resonance frequency as an Nth order complex Fourier series. We then form a consistent Fourier series for (Mxy). As many as 2(2)N different pulse sequences may be directly generated all of which produce a different Mxy(f), but the same Mz(f). A pulse sequence is then generated which will yield the desired Mz(f) and Mxy(f). This is done by an analytic inversion of the Bloch equation, not by the classical Fourier approximation. This technique enables us to generate any Mz which is potentially realizable by a pulse sequence.

Cardiac transfer function relating energy metabolism to workload in different species as studied with 31P NMR

Cardiac metabolism was studied with 31P NMR in 7 dogs and 4 cats to determine whether animals adapted for different life-styles (stalk and sprint vs endurance running) respond to increased work loads (heart rate X blood pressure product) with different high-energy phosphate kinetics. Hearts were exposed via a left lateral thoracotomy under Nembutal anesthesia (40 mg/kg). Two-turned solenoid surface coils were placed on the left ventricles; pacing wires were sutured into the left ventricular apices. The femoral artery and vein were cannulated for blood pressure and arterial blood gas monitoring and fluid and drug infusion, respectively. Animals were placed in a plexiglass holder into a 2.1-T, 31-cm-bore, superconducting magnet. 31P spectra were obtained from the heart using respiratory and electrocardiogram gating. Cardiac work loads were changed by pacing the heart at 4, 4.5, and 5 Hz. Heart rate X blood pressure product "work" was correlated with Pi/PCr ratios. Dog hearts were more resistant than those of cats to changes in Pi/PCr with increasing work load. It is possible that animals adapted to different life-styles may have cardiovascular systems which are metabolically and mechanically adapted for different forms of stress. These differences may be elicited and effectively delineated using in vivo NMR techniques during various physiological interventions, such as pacing. The basis for these differences may be related to cardiac microvasculature or to intrinsic differences in enzyme kinetics. Delineation of these mechanisms may be helpful in the understanding of the physiological basis of cardiac function in health and disease.

Myocardial high energy phosphate metabolism in closed chest dog: creation of an animal model

A chronic closed chest dog model was developed to study myocardial metabolism with NMR spectroscopy. Cardiac windows were surgically created in 10 dogs by removal of two ribs and accompanying skeletal muscle. Marlex mesh was sewn between the two exposed ribs, and fascia and skin were closed. 31P spectra were obtained using a surface coil placed into the surgically created pouch and using routine NMR pulsing techniques.