Evidence of altered fatty acid metabolism in dogs with naturally occurring valvular heart disease and congestive heart failure

INTRODUCTION

Myxomatous mitral valve disease (MMVD) is the most common cardiac condition in adult dogs. The disease progresses over several years and affected dogs may develop congestive heart failure (HF). Research has shown that myocardial metabolism is altered in cardiac disease, leading to a reduction in β-oxidation of fatty acids and an increased dependence upon glycolysis.

OBJECTIVES

This study aimed to evaluate whether a shift in substrate use occurs in canine patients with MMVD; a naturally occurring model of human disease.

METHODS

Client-owned dogs were longitudinally evaluated at a research clinic in London, UK and paired serum samples were selected from visits when patients were in ACVIM stage B1: asymptomatic disease without cardiomegaly, and stage C: HF. Samples were processed using ultra-performance liquid chromatography mass spectrometry and lipid profiles were compared using mixed effects models with false discovery rate adjustment. The effect of disease stage was evaluated with patient breed entered as a confounder. Features that significantly differed were screened for selection for annotation efforts using reference databases.

RESULTS

Dogs in HF had altered concentrations of lipid species belonging to several classes previously associated with cardiovascular disease. Concentrations of certain acylcarnitines, phospholipids and sphingomyelins were increased after individuals had developed HF, whilst some ceramides and lysophosphatidylcholines decreased.

CONCLUSIONS

The canine metabolome appears to change as MMVD progresses. Findings from this study suggest that in HF myocardial metabolism may be characterised by reduced β-oxidation. This proposed explanation warrants further research.

Fractions We Cannot Ignore: The Nonsymbolic Ratio Congruity Effect

Although many researchers theorize that primitive numerosity processing abilities may lay the foundation for whole number concepts, other classes of numbers, like fractions, are sometimes assumed to be inaccessible to primitive architectures. This research presents evidence that the automatic processing of nonsymbolic magnitudes affects processing of symbolic fractions. Participants completed modified Stroop tasks in which they selected the larger of two symbolic fractions while the ratios of the fonts in which the fractions were printed and the overall sizes of the compared fractions were manipulated as irrelevant dimensions. Participants were slower and less accurate when nonsymbolic dimensions of printed fractions were incongruent with the symbolic comparison decision. Results indicated a robust basic sensitivity to nonsymbolic ratios that exceeds prior conceptions about the accessibility of fraction values. Results also indicated a congruity effect for overall fraction size, contrary to findings of prior research. These findings have implications for extending theory about the nature of human number sense and mathematical cognition more generally.

Metabolic Phenotypes of Carotid Atherosclerotic Plaques Relate to Stroke Risk: An Exploratory Study

OBJECTIVE

Stroke is a major cause of death and disability. That three-quarters of stroke patients will never have previously manifested cerebrovascular symptoms demonstrates the unmet clinical need for new biomarkers able to stratify patient risk and elucidation of the biological dysregulations. In this study, the utility of comprehensive metabolic phenotyping is assessed to provide candidate biomarkers that relate to stroke risk in stenosing carotid plaque tissue samples.

METHOD

Carotid plaque tissue samples were obtained from patients with cerebrovascular symptoms of carotid origin (n = 5), and from asymptomatic patients (n = 5). Two adjacent biological replicates were obtained from each tissue. Organic and aqueous metabolite extracts were obtained separately and analysed using two ultra performance liquid chromatography coupled to mass spectrometry metabolic profiling methods. Multivariate and univariate tools were used for statistical analysis.

RESULTS

The two study groups demonstrated distinct plaque phenotypes using multivariate data analysis. Univariate statistics also revealed metabolites that differentiated the two groups with a strong statistical significance (p = 10(-4)-10(-5)). Specifically, metabolites related to the eicosanoid pathway (arachidonic acid and arachidonic acid precursors), and three acylcarnitine species (butyrylcarnitine, hexanoylcarnitine, and palmitoylcarnitine), intermediates of the β-oxidation, were detected in higher intensities in symptomatic patients. However, metabolites implicated in the process of cell death, a process known to be upregulated in the formation of the vulnerable plaque, were unaffected.

CONCLUSIONS

Discrimination between symptomatic and asymptomatic carotid plaque tissue is demonstrated for the first time using metabolic profiling technologies. Two biological pathways (eicosanoid and β-oxidation) were implicated in differentiating symptomatic from asymptomatic patients and will be further investigated. These results indicate that metabolic phenotyping should be further explored to investigate the chemistry of the unstable plaque, in the pursuit of candidate biomarkers for risk-stratification and targets for pharmacotherapeutic intervention.

Chemical mapping of the colorectal cancer microenvironment via MALDI imaging mass spectrometry (MALDI-MSI) reveals novel cancer-associated field effects

Matrix-assisted laser desorption ionisation imaging mass spectrometry (MALDI-MSI) is a rapidly advancing technique for intact tissue analysis that allows simultaneous localisation and quantification of biomolecules in different histological regions of interest. This approach can potentially offer novel insights into tumour microenvironmental (TME) biochemistry. In this study we employed MALDI-MSI to evaluate fresh frozen sections of colorectal cancer (CRC) tissue and adjacent healthy mucosa obtained from 12 consenting patients undergoing surgery for confirmed CRC. Specifically, we sought to address three objectives: (1) To identify biochemical differences between different morphological regions within the CRC TME; (2) To characterise the biochemical differences between cancerous and healthy colorectal tissue using MALDI-MSI; (3) To determine whether MALDI-MSI profiling of tumour-adjacent tissue can identify novel metabolic 'field effects' associated with cancer. Our results demonstrate that CRC tissue harbours characteristic phospholipid signatures compared with healthy tissue and additionally, different tissue regions within the CRC TME reveal distinct biochemical profiles. Furthermore we observed biochemical differences between tumour-adjacent and tumour-remote healthy mucosa. We have referred to this 'field effect', exhibited by the tumour locale, as cancer-adjacent metaboplasia (CAM) and this finding builds on the established concept of field cancerisation.

Comparison of cleaning efficacy between in-use disinfectant and electrolysed water in an English residential care home

BACKGROUND

Infection control in hospitals and care homes remains a key issue. They are regularly inspected regarding standards of hygiene, but visual assessment does not necessarily correlate with microbial cleanliness. Pathogens can persist in the inanimate environment for extended periods of time.

AIM

This prospective study compared the effectiveness of a novel sanitizer containing electrolysed water, in which the active ingredient is stabilized hypochlorous acid (Aqualution™), with the effectiveness of the quaternary ammonium disinfectant in current use for microbial removal from hand-touch surfaces in a care home. The study had a two-period crossover design.

METHODS

Five surfaces were cleaned daily over a four-week period, with screening swabs taken before and after cleaning. Swabs were cultured in order to compare levels of surface microbial contamination [colony-forming units (cfu)/cm(2)] before and after cleaning with each product.

FINDINGS

Cleaning with electrolysed water reduced the mean surface bacterial load from 2.6 [interquartile range (IQR) 0.30-30.40] cfu/cm(2) to 0.10 (IQR 0.10-1.40) cfu/cm(2) [mean log(10) reduction factor 1.042, 95% confidence interval (CI) 0.79-1.30]. Cleaning with the in-use quaternary ammonium disinfectant increased the bacterial load from 0.90 (IQR 0.10-8.50) cfu/cm(2) to 93.30 (IQR 9.85-363.65) cfu/cm(2) (mean log(10) reduction -1.499, 95% CI -1.87 to -1.12) (P < 0.0001). Using two proposed benchmark standards for surface microbial levels in hospitals, electrolysed water resulted in a higher 'pass rate' than the in-use quaternary ammonium disinfectant (80-86% vs 15-21%, P < 0.0001).

CONCLUSION

Electrolysed water exerts a more effective bacterial kill than the in-use quaternary ammonium disinfectant, which suggests that it may be useful as a surface sanitizer in environments such as care homes.

GRANULES IN THE CELLS OF CHICK EMBRYOS PRODUCED BY EGG ALBUMIN IN THE MEDIUM OF TISSUE CULTURES

It is difficult to understand what factors may be concerned in the formation of the al. granules. The phenomenon may be concerned with changes in the cell membrane due to an abnormal environment; that is, material which would otherwise be excluded may be permitted to enter the cell, or, on the other hand, certain substances may be prevented from passing out of the cells. Previous investigators have shown that mesenchyme cells sometimes engulf certain foreign bodies, and it is possible that the solution of white of egg is ingested in the same manner. When a solution of peptone was placed on the cells instead of egg white, the phenomenon did not occur (Fig. 13); the cell remained normal and degenerated in the usual manner (Fig. 14). This would seem to indicate that the al. granules are not formed from peptone. Regardless of the factors involved, it is evident that egg albumin in the medium of tissue cultures of chick embryos causes the formation of numerous large granules in the cytoplasm of the connective tissue cells. This phenomenon is associated with unfavorable conditions for the life of the cells and results in the rapid death of the cultures.

THE ORMATION OF VACUOLES DUE TO BACILLUS TYPHOSUS IN THE CELLS OF TISSUE CULTURES OF THE INTESTINE OF THE CHICK EMBRYO

The introduction of Bacillus typhosus into the hanging drop of a tissue culture of the intestine of a chick embryo leads to the rapid vacuolation of the cells of the tissues which comprise the growth of the cultures. The cells of the connective tissue, the endodermal membrane, the mesothelium, and also the clasmatocytes exhibit the ability to ingest Bacillus typhosus in the cultures.

THE IMPORTANCE OF DEXTROSE IN THE MEDIUM OF TISSUE CULTURES

It is not advisable to enter into a discussion of these findings at the present time, owing to the lack of experimental evidence as to the exact nature of the vacuoles. Regardless of the nature of these bodies or of what factors produce them, they are structures abnormal to the connective tissue cells. The lack of dextrose in the medium of tissue cultures leads to some condition distinctly detrimental to the cells, resulting in their vacuolation and death, even when the medium contains abundant protein material. The addition of small amounts (0.5 to 1 per cent) of dextrose to the medium delays the formation of vacuoles and prolongs the life of the culture. The addition of large amounts (2 to 5 per cent) prevents vacuolation of the cells, but so much dextrose usually leads to a change in the hydrogen ion concentration of the culture resulting in an acid condition which arises coincidentally with the degeneration of the cells.

Development of a two-antibody model for the evaluation of copper-64 radioimmunotherapy

Copper-64 emits beta(+) and beta(-) particles suitable for positron emission tomography and radioimmunotherapy (RIT) of cancer. Copper-64-labelled antibodies have caused complete responses in laboratory animal RIT studies at far lower radiation doses than traditionally prescribed. The intracellular localization of copper radioisotopes may lead to cytotoxic effects by mechanisms beyond ionizing radiation damage. The purpose of this research was to develop a model using both internalizing and non-internalizing antibodies for direct comparison in future RIT studies using the same animal model of cancer. The monoclonal antibodies, cBR96 and cT84.66, were conjugated with N-hydroxysulfosuccinimidyl DOTA. All conjugates retained high immunoreactivity and labelled efficiently with (64)Cu with high specific activity and radiochemical purity. Twenty-four hour biodistributions determined in LS174T tumour-bearing nude mice demonstrated low organ and high tumour uptakes for both monoclonal antibodies. This model constitutes a promising system for elucidating whether internalization of (64)Cu is responsible for an enhanced tumour cytotoxicity in vivo.

In vitro receptor binding assays: general methods and considerations

The development of receptor-targeting radiopharmaceuticals commonly involves the use of peptides, antibodies or small molecules. Resulting from the numerous modifications that can be made to these basic targeting agents, research in this field often generates a series of compounds as potential ligands for in vivo investigation. However, measuring each variant of a series in vivo can be both costly and time-consuming. Therefore, a number of in vitro assays, to study interactions between the targeted receptor and the ligands of interest, are frequently used to quickly and inexpensively narrow the field and identify a lead compound(s) for further investigation. For example, in saturation binding studies, the amount of radioligand required to saturate the receptors is measured and analyzed to determine the radioligand equilibrium dissociation constant (Kd), a useful gauge of the receptor binding affinity of a radioligand. In competitive binding experiments, a ligand of interest competes for available receptor sites with a standard radioligand of known high receptor affinity. Competition data are analyzed to yield another indicator of receptor affinity, called an IC50 value, which can be used to rank the relative receptor binding affinities for a series of ligands. In internalization and efflux studies, the rate and extent of receptor-mediated radioligand taken into and subsequently released from cells is measured, providing insight into cellular uptake and retention of the radioligand. Individually or taken together, these in vitro receptor binding assays are useful tools in radiopharmaceutical development.

Local photodynamic therapy for equine squamous cell carcinoma: evaluation of a novel treatment method in a murine model

The objective of this study was to evaluate the effect of local photodynamic therapy (PDT) with verteporfin on tumor growth inhibition of squamous cell carcinoma (SCC) in a murine model. SCC was implanted in 85 nude mice by subcutaneous injection of A-431 SCC cells. Treatment groups (10 mice/group) received an intra-tumoral injection of verteporfin dissolved in dimethyl sulfoxide (DMSO) or 5% dextrose solution at a dose of 0.01 or 0.1mg/cm3. Controls received only solvent, or no injectate. All groups received identical light illumination (100J/cm2). Relative change in tumor volume (RCTV) at day 30 was compared between groups using the Wilcoxon rank sum test (P< 0.05). Local PDT with verteporfin at a dose of 0.1mg/cm3 resulted in significantly lower RCTV at day 30 compared to controls. Choice of solvent (DMSO versus D5W) did not affect the results. Local PDT may be an effective adjunctive therapy for the treatment of periocular equine SCC.

Xenotransplantation of cryopreserved equine squamous cell carcinoma to athymic nude and SCID mice

Cryopreserved equine ocular squamous cell carcinoma (SCC) was inoculated subcutaneously into 15 athymic nude and 15 SCID mice. Xenotransplantation resulted in tumor growth in two athymic nude mice and 1 SCID mouse. Histological appearance and immunohistochemical characterization using cytokeratin 5/6 markers and p53 markers of the tumor grown in mice was in full accord with the original equine tumors. No evidence of metastasis was noted in any mouse. This model may serve as a relevant in vivo model for studying the biology of equine ocular SCC and for the testing of new therapeutic modalities.

Conjugation of monoclonal antibodies with TETA using activated esters: biological comparison of 64Cu-TETA-1A3 with 64Cu-BAT-2IT-1A3

A simple method for conjugation of monoclonal antibodies (mAbs) with the chelating agent 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA), has been developed using commercially available reagents. This method involved activation of a single carboxyl group of TETA with N-hydroxysulfosuccinimide and 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide. The resulting activated ester of TETA was reacted with the anti-colorectal carcinoma mAb 1A3 at molar ratios ranging from 10:1 to 100:1 to give immunoconjugates modified with an average of 0.4 to 2.0 functional chelators per antibody molecule. The TETA-1A3 conjugate was labeled with 64Cu at specific activities as high as 15.4 microCi/microgram, and the radiolabeled mAb exhibited high in vitro serum stability and minimal loss of immunoreactivity. The biodistribution of 64Cu-labeled TETA-1A3 in hamsters bearing GW39 human colon carcinoma xenografts was compared to that of 64Cu-BAT-2IT-1A3 (BAT = 6-(p-bromoacetamidobenzyl)-1,4,8,11-tetraazacyclotetradecane-1,4,8,11- tetraacetic acid; 2IT = 2-iminothiolane). Both conjugates showed high tumor uptake (6.60-9.05% injected dose/gram) from 24 to 48 h post-injection and generally similar blood clearance and non-target organ uptakes. Human absorbed dose estimates derived from the hamster biodistribution data showed the critical organs for both conjugates to be the large intestine and the red marrow. Our results suggest that the in vitro and in vivo performance characteristics of 64Cu-TETA-1A3 compare favorably with those of 64Cu-BAT-2IT-1A3 and that further evaluation of the diagnostic and therapeutic efficacy of 64Cu-TETA-1A3 is warranted.

Longitudinal stability of coagulation, fibrinolysis, and inflammation factors in stored plasma samples

We sought to assess the longitudinal stability of risk factors for atherosclerosis and thrombosis. including several coagulation. fibrinolysis, and inflammation factors, in frozen plasma samples stored at -70 degrees C for months or years. We reviewed data collected on 29 different control pools over periods ranging from 7 to 59 months for two functional assays (factor VII and fibrinogen) and seven antigen measurements (C-reactive protein. D-dimer, plasmin-alpha2-antiplasmin complex, plasminogen activator inhibitor-1, protein C, protein S, and tissue plasminogen activator), totaling more than 15,000 data points. Screening of the data using least squares regression revealed only sporadic associations between monthly means and time, with no consistent trends. Analysis by repeated measures and summary measure methods revealed no evidence of sample degradation over time for the factors studied. Our finding of longitudinal stability in the biochemical properties of frozen plasma strengthens the presumption of sample stability on which molecular epidemiologic studies are based.

Fibrinogen and preclinical echocardiographic target organ damage: the strong heart study

Relations of fibrinogen to preclinical target organ damage, such as left ventricular hypertrophy, systolic dysfunction, and increased arterial stiffness while accounting for traditional risk factors, are unknown in a population-based sample free of clinically overt coronary heart disease. Therefore, we studied clinical and echocardiographic characteristics of 2709 American Indians participating in the Strong Heart Study without symptomatic atherosclerosis. The study sample was divided into tertiles of fibrinogen (cut-points, 3.24 and 3.83 g/L). Mean age, body mass index, proportion of women, and prevalences of hypertension and diabetes increased from the first to third tertile of fibrinogen. After adjustment for covariates, systolic and pulse pressures did not significantly differ among tertiles of fibrinogen, whereas diastolic pressure was slightly lower in the third than in lower tertiles of fibrinogen. HDL cholesterol was lower and plasma creatinine and urinary albumin/creatinine ratio was higher in the third tertile of fibrinogen. Left ventricular mass index, pulse pressure/stroke index, an estimate of arterial stiffness, and cardiac index were higher and left ventricular systolic function and total peripheral resistance were lower in the third than in two lower tertiles of fibrinogen independent of major covariates. In multiple regression analyses, left ventricular mass and pulse pressure/stroke index were positively associated with, and stress-corrected midwall shortening negatively associated with fibrinogen, independent of major covariates. Participants with fibrinogen >3.83 g/L were more likely to have at least 1 preclinical cardiovascular abnormality such as left ventricular hypertrophy, elevated arterial stiffness, or systolic myocardial dysfunction independent of covariates including renal dysfunction (adjusted odds ratio, 1.38; P<0.001). Thus, in a population sample of adults without clinically overt coronary heart disease, elevated fibrinogen is an independent correlate of prognostically relevant cardiovascular target organ damage.

Remotely sensed biological production in the equatorial Pacific

A combination of ship, buoy, and satellite observations in the tropical Pacific during the period from 1992 to 2000 provides a basin-scale perspective on the net effects of El Niño and La Niña on biogeochemical cycles. New biological production during the 1997-99 El Niño/La Niña period varied by more than a factor of 2. The resulting interannual changes in global carbon sequestration associated with the El Niño/La Niña cycle contributed to the largest known natural perturbation of the global carbon cycle over these time scales.

Complete genome sequence of a virulent isolate of Streptococcus pneumoniae

The 2,160,837-base pair genome sequence of an isolate of Streptococcus pneumoniae, a Gram-positive pathogen that causes pneumonia, bacteremia, meningitis, and otitis media, contains 2236 predicted coding regions; of these, 1440 (64%) were assigned a biological role. Approximately 5% of the genome is composed of insertion sequences that may contribute to genome rearrangements through uptake of foreign DNA. Extracellular enzyme systems for the metabolism of polysaccharides and hexosamines provide a substantial source of carbon and nitrogen for S. pneumoniae and also damage host tissues and facilitate colonization. A motif identified within the signal peptide of proteins is potentially involved in targeting these proteins to the cell surface of low-guanine/cytosine (GC) Gram-positive species. Several surface-exposed proteins that may serve as potential vaccine candidates were identified. Comparative genome hybridization with DNA arrays revealed strain differences in S. pneumoniae that could contribute to differences in virulence and antigenicity.

Ultraviolet-radiation-induced keratinocyte apoptosis in C1q-deficient mice

Exposure to ultraviolet B radiation is an important trigger of both systemic and cutaneous disease flares in individuals with systemic lupus erythematosus. More than 90% of individuals with homozygous C1q deficiency develop a systemic-lupus-erythematosus-like illness, which is typically associated with a severe photosensitive rash. Apoptotic, human keratinocytes have been shown in vitro to bind C1q, in the absence of antibody. These observations, together with the hypothesis that a major source of the autoantigens driving the immune response in systemic lupus erythematosus comes from apoptotic cells, led us to investigate the effects of murine C1q deficiency on ultraviolet-radiation-induced keratinocyte apoptosis in vivo. In this work, we demonstrated C1q binding to apoptotic murine keratinocytes in vitro and showed for the first time that C1q is also present on sunburn cells in vivo. In addition to C1q, we detected C3 deposition on sunburn cells in both wild-type and C1q-deficient mice, suggesting activation of the alternative pathway. Following acute ultraviolet exposure in vivo, no difference in the rate of clearance of sunburn cells was found in C1q-deficient mice from three different genetic backgrounds, compared with strain-matched wild-type controls. Furthermore, chronic ultraviolet exposure did not result in the production of autoantibodies or the development of glomerulonephritis. Our findings suggest that C1q does not play a critical role in the physiologic clearance of apoptotic murine keratinocytes in vivo.

An improved method for conjugating monoclonal antibodies with N-hydroxysulfosuccinimidyl DOTA

A simple, water-soluble procedure for conjugation of monoclonal antibodies to 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) has been improved by optimizing pH, buffer, and temperature conditions for the preparation of N-hydroxysulfosuccinimidyl DOTA and its conjugation to the human/murine chimeric anti-carcinoembryonic antigen antibody cT84.66. This improved method results in a 6-fold increase in conjugation efficiency, a 3-7-fold decrease in antibody cross-linking, a more homogeneous population of conjugate species, and a 5-fold decrease in the quantities of reagents needed for conjugation. The cT84.66-DOTA conjugate was labeled to high specific activity with 111In, 90Y, 88Y, 64Cu, and 67Cu, affording near-quantitative incorporation of the majority of these radiometals. This improved conjugation procedure facilitates large-scale production and radiometal labeling of cT84.66-DOTA for clinical radioimmunotherapy trials.

Comparative dosimetry of copper-64 and yttrium-90-labeled somatostatin analogs in a tumor-bearing rat model

90Y-DOTA-tyrosine3-octreotide (90Y-DOTA-Y3-OC) is currently being evaluated as a radiotherapy agent for trials in patients with somatostatin-receptor positive cancer. In this study, we compared the estimated absorbed doses to human organs, as well as to a CA20948 rat tumor, of 90Y- and 64Cu-labeled DOTA-Y3-OC and DOTA-Y3-octreotate (DOTA-Y3-TATE). Assuming that the radiopharmaceutical biodistributions are the same in rodents and humans, human absorbed dose estimates were obtained from rat biodistribution data. The absorbed doses of 90Y-DOTA-Y3-TATE were determined from the biodistribution of the 88Y-labeled peptide, with and without co-injection of a therapeutic amount of the 90Y-labeled peptide. Additionally, the absorbed doses of 90Y-DOTA-Y3-TATE were determined from data using two different biodistribution endpoints, 48 h and 168 h. Human absorbed dose estimates were calculated using MIRD methodology assuming that rats and humans have the same biodistribution. The biodistribution of the radiolabeled somatostatin analogs was dependent on the peptide and the radiometal. For 90Y-DOTA-Y3-TATE, the tumor dose was dependent on both the administration of therapeutic 90Y-peptide and the biodistribution endpoint. Our data suggested that, for both radionuclides, the TATE derivatives imparted a higher absorbed dose to the tumor than the OC analogs. 90Y-DOTA-Y3-OC and 64Cu-DOTA-Y3-OC were comparable with respect to their tumor-to-normal tissue dose ratios, while 90Y-DOTA-Y3-TATE appeared to have distinct advantages over 64Cu-DOTA-Y3-TATE.

Clustering of procoagulation, inflammation, and fibrinolysis variables with metabolic factors in insulin resistance syndrome

The known metabolic cardiovascular disease risk factors associated with insulin resistance syndrome (IRS) do not adequately explain the excess cardiovascular disease risk attributed to this syndrome, and abnormalities in hemostatic variables may contribute to this excess risk. Using data from 322 nondiabetic elderly men and women (aged 65-100 years) participating in the Cardiovascular Health Study during 1989-1990, the authors performed factor analysis on 10 metabolic risk factors associated with IRS and 11 procoagulation, inflammation, and fibrinolysis variables to examine the clustering of the metabolic and hemostatic risk markers. Factor analysis of the metabolic variables confirmed four uncorrelated factors: body mass, insulin/glucose, lipids, and blood pressure. Adding the hemostatic variables yielded three new factors interpreted as inflammation, vitamin K-dependent proteins, and procoagulant activity. Plasminogen activator inhibitor-1 clustered with the body mass factor, supporting the hypothesis that obesity is related to impaired fibrinolysis. Fibrinogen clustered with the inflammation summary factor rather than procoagulant activity, supporting the position that fibrinogen principally reflects underlying inflammation rather than procoagulant potential. The authors conclude that should hemostatic variables be shown to contribute to IRS-related cardiovascular disease, apart from plasminogen activator inhibitor-1, they may do so independently of the established metabolic abnormalities.

Effect of cholera toxin on rat liver lysosome acidification

We have shown that cholera toxin and cAMP greatly increase both acidification rates of liver endosomes and the liver and endosome content of fluid-phase endocytosis probes. In this study lysosomes were purified from control and cholera toxin-treated livers that were pulsed with fluorescein conjugated dextran and chased overnight. Cholera toxin-treated livers weighed less, contained less protein and exhibited higher contents of lysosomal marker enzymes, consistent with the catabolic effects of this agent. By contrast to its effects on endosomes, cholera toxin had no consistent or significant effect on lysosome acidification rates, steady-state internal pH or potassium content, proton leak rates or fluorescein-dextran content. We conclude that cholera toxin and cAMP predominantly alter earlier steps of endocytosis but may also increase transfer of probes from lysosomes to bile.

Radiotherapy and dosimetry of 64Cu-TETA-Tyr3-octreotate in a somatostatin receptor-positive, tumor-bearing rat model

64Cu [T1/2 = 12.8 h; beta+ = 0.655 MeV (19%); beta- = 0.573 MeV (40%)] has shown promise as a radioisotope for targeted radiotherapy. It has been demonstrated previously that the somatostatin analogue 64Cu-TETA-octreotide (64Cu-TETA-OC, where TETA is 1,4,8,11-tetraazacyclotetradecane-N,N',N",N"'-tetraacetic acid) significantly inhibited the growth of somatostatin receptor-positive CA20948 rat pancreatic tumors in Lewis rats (C. J. Anderson et al., J. Nucl. Med., 39: 1944-1951, 1998). In this study, we evaluated the radiotherapeutic efficacy of a new 64Cu-labeled somatostatin analogue, 64Cu-TETA-Tyr3-octreotate (64Cu-TETA-Y3-TATE), in CA20948 tumor-bearing rats. A single dose of 15 mCi (555 MBq) of 64Cu-TETA-Y3-TATE was shown to be more effective in reducing tumor burden than the same dose of 64Cu-TETA-OC. In multiple dose experiments, tumor-bearing rats were administered three doses of either 10 or 20 mCi (370 or 740 MBq) of 64Cu-TETA-Y3-TATE at 48-h intervals. Rats given 3x10 mCi (3x370 MBq) showed extended mean survival times compared with rats given a single dose; however, no complete regressions occurred. Complete regression of tumors was observed for all rats treated with 3x20 mCi (3x740 MBq), with no palpable tumors for approximately 10 days; moreover, the mean survival time of these rats was nearly twice that of controls. Toxicity was determined by physical appearance and hematological and enzyme analysis, which revealed no overt toxicity and only transient changes in blood and liver chemistry. Absorbed dose estimates showed the dose-limiting organ to be the kidneys. The radiotherapy results, along with absorbed dose estimates to target and clearance organs, confirm that 64Cu-labeled somatostatin analogues warrant continued consideration as agents for targeted radiotherapy.

Antimicrobial activities of amine- and guanidine-functionalized cholic acid derivatives

Compounds in a series of cholic acid derivatives, designed to mimic the activities of polymyxin B and its derivatives, act as both potent antibiotics and effective permeabilizers of the outer membranes of gram-negative bacteria. Some of these compounds rival polymyxin B in antibacterial activity against gram-negative bacteria and are also very active against gram-positive organisms. Other compounds interact synergistically with hydrophobic antibiotics to inhibit bacterial growth.

Comparison of four 64Cu-labeled somatostatin analogues in vitro and in a tumor-bearing rat model: evaluation of new derivatives for positron emission tomography imaging and targeted radiotherapy

Previous studies have shown that modification of the somatostatin analogue octreotide (OC), by substitution of tyrosine for phenylalanine at position 3 and of a C-terminal carboxylic acid for an alcohol, to give Tyr3-octreotate (Y3-TATE) improved uptake of the peptide in somatostatin receptor-positive tissues. To determine which substitution best accounts for increased target tissue uptake, the peptides containing single modifications, Tyr3-octreotide (Y3-OC) and octreotate (TATE), were synthesized. These peptides were conjugated to the macrocyclic chelating agent 1,4,8, 11-tetraazacyclotetradecane-N,N',N",N"'-tetraacetic acid (TETA) and radiolabeled with 64Cu(II). The in vitro receptor binding, in vitro tumor cell uptake, and in vivo distribution properties of 64Cu-labeled TETA-Y3-OC and TETA-TATE were compared to those of [64Cu]TETA-OC and [64Cu]TETA-Y3-TATE. Cu-TETA-TATE (IC50 = 0.297 +/- 0.0055 nM) and Cu-TETA-Y3-TATE (IC50 = 0.308 +/- 0.0375 nM) displayed significantly higher binding affinity to somatostatin receptors on CA20948 rat pancreatic tumor membranes than Cu-TETA-Y3-OC (IC50 = 0.397 +/- 0.0206 nM) and Cu-TETA-OC (IC50 = 0. 498 +/- 0.039 nM). Similarly, the uptakes of [64Cu]TETA-Y3-TATE (60. 75 +/- 1.21%) and [64Cu]TETA-TATE (55.62 +/- 0.16%) into AR42J rat pancreatic tumor cells over a 2-h time period were higher than those of [64Cu]TETA-Y3-OC (47.20 +/- 1.20%) and [64Cu]TETA-OC (34.07 +/- 2. 24%). The in vitro results suggest that the C-terminal carboxylate may contribute more to enhanced receptor binding and tumor cell uptake than the substitution at the 3-position. Biodistributions in CA20948 tumor-bearing rats showed receptor-mediated uptake of the 64Cu-labeled peptides in somatostatin-rich tissues, including the pituitary, adrenals, pancreas, and tumor. The structure-activity relationships of the four 64Cu-labeled peptides did not show consistent trends in all target tissues, but [64Cu]TETA-Y3-TATE exhibited tumor uptake 1.75-3.5 times higher than the other derivatives at 4 h postinjection. The greater tumor retention of [64Cu]TETA-Y3-TATE justifies the selection of this agent for future PET imaging and targeted radiotherapy studies.

Quality assessment of atomic force microscopy probes by scanning electron microscopy: correlation of tip structure with rendered images

While image quality from instruments such as electron microscopes, light microscopes, and confocal laser scanning microscopes is mostly influenced by the alignment of optical train components, the atomic force microscope differs in that image quality is highly dependent upon a consumable component, the scanning probe. Although many types of scanning probes are commercially available, specific configurations and styles are generally recommended for specific applications. For instance, in our area of interest, tapping mode imaging of biological constituents in fluid, double ended, oxide-sharpened pyramidal silicon nitride probes are most often employed. These cantilevers contain four differently sized probes; thick- and thin-legged 100 microm long and thick- and thin-legged 200 microm long, with only one probe used per cantilever. In a recent investigation [Taatjes et al. (1997) Cell Biol. Int. 21:715-726], we used the scanning electron microscope to modify the oxide-sharpened pyramidal probe by creating an electron beam deposited tip with a higher aspect ratio than unmodified tips. Placing the probes in the scanning electron microscope for modification prompted us to begin to examine the probes for defects both before and after use with the atomic force microscope. The most frequently encountered defect was a mis-centered probe, or a probe hanging off the end of the cantilever. If we had difficulty imaging with a probe, we would examine the probe in the scanning electron microscope to determine if any defects were present, or if the tip had become contaminated during scanning. Moreover, we observed that electron beam deposited tips were blunted by the act of scanning a hard specimen, such as colloidal gold with the atomic force microscope. We also present a mathematical geometric model for deducing the interaction between an electron beam deposited tip and either a spherical or elliptical specimen. Examination of probes in the scanning electron microscope may assist in interpreting images generated by the atomic force microscope.

A chimeric anti-CEA antibody with heavy interchain disulfide bonds deleted: molecular characterization and biodistributions in normal and tumor bearing mice

We have deleted the interchain disulfide bonds in a chimeric anti-CEA antibody (chT84.66) by mutating two cysteines in the heavy chain to glycine residues. The resulting antibody delta SSchT84.66 was expressed in high yield in a bioreactor and purified to homogeneity in a single step on an anti-idiotypic antibody affinity column. The molecular size of the antibody was 150 kDa as judged by gel filtration, SDS gel electrophoresis under non-reducing conditions, and MALDI-TOF/MS. The 150 kDa antibody had nearly identical kinetic (Kon = 1.53 x 10(6) M-1 s-1, .koff = 1.14 x 10(-5) s-1) and affinity constants (Kaff = 1.34 x 10(11) M-1) compared to the parent murine (Kaff = 1.25 x 10(11) M-1) and chimeric (Kaff = 1.16 x 10(11) M-1) antibodies when tested on biosensor chips. When delta SSchT84.66 was conjugated to the isothiocynato derivative of DTPA, radiolabeled with 111In, and injected into either normal or nude mice bearing tumor xenografts, it gave nearly identical biodistributions to chT84.66. delta SSchT84.66 and chT84.66 antibodies gave a maximum tumor uptake of 48 and 74% ID/g, and tumor to blood ratios of 5.3 and 6.2 at 48 h, respectively. We conclude that delta SSchT84.66 irreversibly associates into H2L2 dimers after concentration, that the dimers are stable under both the in vitro and in vivo conditions used in this study, and the properties of the antibody are virtually indistinguishable from the parent chT84.66 antibody.

Three-dimensional crystals of Ca2+-ATPase from sarcoplasmic reticulum: merging electron diffraction tilt series and imaging the (h, k, 0) projection

Electron crystallography offers an increasingly viable alternative to X-ray crystallography for structure determination, especially for membrane proteins. The methodology has been developed and successfully applied to 2D crystals; however, well-ordered thin, 3D crystals are often produced during crystallization trials and generally discarded due to complexities in structure analysis. To cope with these complexities, we have developed a general method for determining unit cell geometry and for merging electron diffraction data from tilt series. We have applied this method to thin, monoclinic crystals of Ca2+-ATPase from sarcoplasmic reticulum, thus characterizing the unit cell and generating a 3D set of electron diffraction amplitudes to 8 A resolution with tilt angles up to 30 degrees. The indexing of data from the tilt series has been verified by an analysis of Laue zones near the (h, k, 0) projection and the unit cell geometry is consistent with low-angle X-ray scattering from these crystals. Based on this unit cell geometry, we have systematically tilted crystals to record images of the (h, k, 0) projection. After averaging the corresponding phases to 8 A resolution, an (h, k, 0) projection map has been calculated by combining image phases with electron diffraction amplitudes. This map contains discrete densities that most likely correspond to Ca2+-ATPase dimers, unlike previous maps of untilted crystals in which molecules from successive layers are not aligned. Comparison with a projection structure from tubular crystals reveals differences that are likely due to the conformational change accompanying calcium binding to Ca2+-ATPase.

Zinc gluconate: acute ingestion

CASE REPORT

Despite the popularity of zinc gluconate for use in attenuation of common cold symptoms, there is little information on the effects of acute overdose. A 17-year-old male ingested approximately 85 tablets or 4 g zinc gluconate (570 mg elemental zinc). He experienced severe nausea and vomiting within 30 minutes of the ingestion but had no further sequelae such as diarrhea, gastric erosions, esophageal burns, shock, neurologic dysfunction, symptoms of anemia, or hepatic inflammation. Serum zinc level was 4.97 mg/dL at approximately 5 hours postingestion.

Maleimidocysteineamido-DOTA derivatives: new reagents for radiometal chelate conjugation to antibody sulfhydryl groups undergo pH-dependent cleavage reactions

We have synthesized two bifunctional derivatives of the macrocyclic chelating agent 1,4,7,10-tetraazacyclododecane-N,N',N",N"-tetraacetic acid (DOTA) equipped with maleimide groups for conjugation to reduced disulfide bonds of monoclonal antibodies. Using water-soluble carbodiimide chemistry, DOTA was coupled to L-cysteine to incorporate both a "pendant-type" carboxyl group for metal coordination and an orthogonal thiol group for protein attachment. The homobifunctional reagent 1,6-bis(maleimido)hexane was then used to introduce the maleimide functionality via a sulfide linkage to the macrocycle, and alternatively, the sulfide group was converted to a sulfone side chain. Both maleimide derivatives were conjugated to the anticarcinoembryonic antigen chimeric monoclonal antibody cT84.66 after light reduction of the mAb with dithiothreitol. In this manner, antibody conjugates were prepared which afforded near-quantitative labeling with the radiometals 111In(III) and 90Y(III) as well as quantitative immunoreactivity. Radioimmunoconjugates prepared with the sulfide and sulfone compounds exhibited relatively rapid linker-dependent radiometal loss when incubated in human serum and aqueous solutions at physiological temperature and pH. The unconjugated maleimidocysteineamido-DOTA derivatives and their Y(III) complexes were incubated in aqueous solution at 37 degrees C, and the resulting decomposition products were analyzed by HPLC and mass spectrometry. These studies revealed that the two bifunctional chelating agents underwent linker-specific cleavage reactions which were considerably faster at pH 7.4 than at pH 5.4. The chemically labile linker systems are expected to release chelated radiometal from mAb conjugates in a pH-dependent manner. This property may impart favorable tumor uptake and normal tissue clearance on radioimmunoconjugates prepared with these reagents, on the basis of the observation that many solid tumors are significantly more acidic than normal tissues.

Biodistribution of 111In- and 90Y-labeled DOTA and maleimidocysteineamido-DOTA conjugated to chimeric anticarcinoembryonic antigen antibody in xenograft-bearing nude mice: comparison of stable and chemically labile linker systems

Biodistributions of two radiometal chelate conjugates of the human/murine chimeric anticarcinoembryonic antigen monoclonal antibody cT84.66 were obtained in nude mice bearing LS174T human colorectal carcinoma xenografts. Derivatives of the macrocyclic chelating agent 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) were covalently attached to the antibody by a stable amide linkage and by a maleimidocysteineamido side chain (MC-DOTA) that has been shown to be chemically labile at physiological temperature and pH. Biodistributions of both 111In and 90Y labels were obtained in these studies. At common biodistribution time points, it was found that the 111In label had greater uptake in the liver than 90Y for both conjugates. No significant differences were found with respect to bone uptake of 90Y using either chelate. Blood curves were generally lower at comparable time points for MC-DOTA, indicative of faster clearance as compared to DOTA. Tumor uptake was high for both conjugates (57-68% ID/g at 48 h), with a longer tumor residence time in the case of the DOTA conjugate, probably a result of its longer blood circulation times. We conclude that bone uptake of 90Y would be minimal if either DOTA or MC-DOTA were used as the bifunctional chelator. This would imply preference for these macrocyclic ligands if radiation doses to the bone marrow would be considered to be dominated by skeletal uptakes. Alternatively, if bone marrow radiation dose is dominated by circulating antibody, the chemically labile linker system employed by the MC-DOTA conjugate offers the advantage of enhanced blood clearance.

Variable pitch in frozen-hydrated sickle hemoglobin fibers: an image analysis model study

The intracellular polymerization of deoxyhemoglobin S (HbS) into helical fibers is the primary pathological event which gives rise to sickle cell disease. The structure of these fibers has previously been studied by electron microscopy of negatively stained specimens. We are extending these studies with unstained frozen-hydrated HbS fibers (cryo-EM), which afford better visualization of the internal details of the fiber structure than can be achieved by negative staining, but have lower signal-to-noise ratio images. The pitch of the HbS fiber structure varies locally along any given particle. Because rotation about the particle axis thus is partially decoupled from translation along the axis, the pitch and angular rotation of a fiber unit cell cannot be inferred by symmetry (as is the case with constant pitch helices). Image analysis procedures are presented which are capable of explicitly identifying the pitch and angular rotation of individual HbS fiber unit cells having low signal-to-noise ratios. Fiber images are divided into segments one unit cell long (63 A) which are analyzed in two steps. First each unit cell is aligned with constant pitch electron density reference models by cross-correlation. Correlation coefficients are then used to determine angular rotation and pitch. This procedure was tested, and found to be robust, using model images corrupted to simulate experimental problems normally encountered in the analysis of cryo-electron micrographs. The effects of limited resolution, low signal-to-noise ratio, scaling errors, and rotational and axial misalignment are described.

A facile, water-soluble method for modification of proteins with DOTA. Use of elevated temperature and optimized pH to achieve high specific activity and high chelate stability in radiolabeled immunoconjugates

We have developed a method for attachment of the macrocyclic chelating agent 1,4,7,10-tetraazacyclododecane N,N',N",N"'-tetraacetic acid (DOTA) to proteins by activation of a single carboxyl group with N-hydroxysulfosuccinimide (sulfo-NHS). The sulfo-NHS active ester of DOTA was prepared in a single step using 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC), and DOTA conjugates of cytochrome c and the anti-carcinoembryonic antigen chimeric monoclonal antibody cT84.66 were prepared by adding the DOTA active ester reaction mixture to the proteins at pH 8.5-9.0. Mass spectrometry of the cytochrome c conjugates showed that as the molar ratio of DOTA active ester to protein in the reaction mixture was increased from 10:1 to 100:1, the average number of chelators attached to the protein molecule increased from 2.64 to 8.79. When DOTA active ester reacted with the antibody at a molar ratio of 100:1, the conjugate averaged 3.8 chelates per antibody. Immunoreactivity of the antibody conjugate radiolabeled with 111In(III) and 90Y(III) remained quantitative. Variation of the DOTA:sulfo-NHS:EDC activation stoichiometry from 2:2:1 to 10:10:1 revealed that the kinetic stability of the radioconjugates increased as the molar ratio of carbodiimide, relative to DOTA and sulfo-NHS, was decreased. Radiolabeling of the protein conjugates with 111In(III) and 90Y(III) proved to be sensitive to pH, buffer, and temperature effects. The optimum pH for the labeling reaction was different for each protein and may be related to the isoelectric point of the protein. Radiometal incorporation at high specific activity was accomplished in acetate and Tris buffers, but the presence of citrate inhibited the labeling reaction. Increasing the temperature of the radiolabeling reaction from 25 to 43 degrees C greatly increased both the efficiency of radiometal incorporation and the kinetic stability of the radioconjugates. Stability studies of the conjugates in human serum and in the presence of a 5000- to 250,000-fold excess of diethylenetriaminepentaacetic acid (DTPA) demonstrated that the radiolabeled proteins are kinetically inert under physiological conditions. In serum, the 111In(III)-labeled antibody showed a rate of radiometal loss of approximately 0.08% per day. In the presence of excess DTPA, both conjugates lost 111In(III) at a rate of about 0.3% per day. No loss of 90Y(III) from the conjugates was observed in serum, but in excess DTPA, both 90Y(III) labeled proteins showed a rate of radiometal loss of approximately 0.2% per day. Therefore, kinetic analysis of metal loss from a radiolabeled immunoconjugate in the presence of a vast excess of DTPA may provide a better indication of the in vivo stability of that immunoconjugate than serum stability studies.

Cryo-electron microscopy of deoxy-sickle hemoglobin fibers

Deoxy-sickle hemoglobin (HbS) polymerizes in vivo into long helical fibers which fill the red cell and make it rigid. This impedes red cell passage through the capillaries and is responsible for the clinical manifestations of sickle cell disease. Images of individual and laterally associated HbS fibers were obtained by electron microscopy of frozen hydrated specimens. Each fiber possesses variable pitch, having from 6 degrees to 12 degrees rotation per unit cell. Laterally associated HbS fibers display systematic inter-fiber contacts in spite of their pitch variations, and exhibit better order than isolated fibers. This suggest that inter-fiber contacts can act to couple fibers mechanically and might therefore be a factor in rigidifying red cells in vivo. Fiber variability was attributed to local torsional variations with a standard deviation of 2.5 degrees, but which are weakly coupled over a length of 2.25 unit cells. Variable pitch produces structural changes of as large as 5 A azimuthally and 6 A axially in HbS fiber unit cells.

The hand of the helix of deoxyhemoglobin S fibers

Electron micrographs of deoxyhemoglobin S fiber cross sections provide an end-on view of the fiber whose appearance is sensitive to small changes in orientation. We have developed a procedure to exploit this sensitivity in order to determine the hand of these particles. In a sickle hemoglobin fiber the hemoglobin molecules form long pitch helical strands which twist about the particle axis with a pitch of about 3000 A. Tilting a 400-A-thick cross section by a few degrees aligns one of the long pitch helices so that it is nearly parallel to the direction of view. When a strand of hemoglobin molecules in a fiber is aligned in this manner it appears as a strongly contrasted bright spot. It is this spot, rather than the fiber axis, which appears to be the apparent center of rotation of the cross section. The direction of the displacement of the spot from the particle axis depends upon the particle hand and tilt direction. We have used this property to determine that sickle hemoglobin fibers are right-handed particles. This method may be applicable to other particles with long pitch helices as well.

Primary afferent excitatory transmission recorded intracellularly in vitro from rat medial vestibular neurons

Intracellular recordings were made from rat medial vestibular nucleus (MVN) neurons in transverse brain slices containing the root of the vestibular nerve (N. VIII). Electrical stimuli applied to the N. VIII tract evoked an orthodromic excitatory postsynaptic potential (EPSP) that lasted about 50 ms following a 0.5 to 1.5 ms delay between the stimulus artifact and synaptic potential. These orthodromic EPSPs were insensitive to the following antagonists: atropine, hexamethonium, diphenhydramine, and caffeine. Based on these results we conclude that the primary afferent excitatory transmitter is not acetylcholine, histamine, or adenosine, respectively. However, kynurenic acid, a general excitatory amino acid receptor antagonist, blocked the orthodromic EPSP while having no effect on the resting membrane potential, input resistance, or action potential configuration of MVN neurons. Our data suggest that an excitatory amino acid, or amino acid-like substance, is responsible for primary afferent excitatory transmission in the rat medial vestibular nucleus.

The growth and development status of homeless children entering shelters in Boston

In order to characterize the children who enter emergency shelters in Boston, we reviewed the data collected at intake interviews by the pediatric nurse practitioner visiting 10 family shelters and one hotel in Boston as part of the Boston Health Care for the Homeless Project. Families were interviewed soon after their entry into the shelter. Children were weighed and measured, and the Denver Developmental Screening Test (DDST) was administered. From November 1986 to November 1987, 133 families with 213 children were interviewed. Ninety-four percent of the children were in the care of their mothers, and 92 percent were younger than 5 years of age. Sixty-five percent of the families were black, 20 percent were white, and 11 percent were Hispanic. Eighty-nine percent of the families were receiving Aid to Families with Dependent Children benefits, 90 percent were receiving Medicaid benefits, 72 percent were receiving food stamps, and 52 percent were receiving benefits under the Special Supplement Food Program for Women, Infants, and Children. Eighty-five percent of the children were reported to have a regular source of primary pediatric care, and 23 percent were reported to have medical problems. Weight-for-age, weight-for-height, and height-for-age measurements were similar to those reported for national samples of low income children. Ten children (4.7 percent) were found to have abnormal or questionable DDST examinations.

Studies on Ca(II) binding to gamma-carboxyglutamic acid. Use of thermal decarboxylation to probe metal ion/gamma-carboxyglutamic acid interactions

The thermal decarboxylation of N-benzyloxycarbonyl-L-gamma-carboxyglutamic acid alpha-methyl ester [Z)-L-Gla-OMe) has been studied. In the presence of increasing amounts of calcium or magnesium ions, lyophilized powders of (Z)-L-Gla-OMe exhibit a corresponding increase in thermal stability. Both magnesium and calcium form relatively tight, thermally stable complexes with (Z)-L-Gla-OMe at high metal ion concentrations. Differences between Ca(II) and Mg(II) binding are noted at low metal ion concentrations, where (Z)-L-Gla-OMe is in excess. Under these conditions, complex formation with Mg(II) apparently favors a 2:1 Gla-magnesium ion complex in which both Gla residues are unstable to thermal decarboxylation. Calcium ion complexes, however, are found to favor a 3:1 Gla-calcium ion complex in which 1 of the 3 Gla residues is thermally stable.

Mechanisms underlying the antimotion sickness effects of psychostimulants

The major conclusions of this review are: 1) that selective enhancement of dopaminergic transmission, not noradrenergic, is sufficient to account for amphetamine-induced resistance and perhaps natural resistance to motion sickness; 2) the site of this enhanced dopaminergic transmission is probably within the basal ganglia; and 3) the neuropharmacology of the basal ganglia, but not the brainstem vestibular areas, can account for the therapeutic synergism of scopolamine and amphetamine. The therapeutic actions of psychostimulants may be dissociable from some of their side effects, particularly cardiovascular effects related to peripheral norepinephrine release. Drugs which target specific subtypes of dopaminergic receptors may serve this purpose.

An in vitro brain slice preparation to study the pharmacology of central vestibular neurons

The purpose for development of this preparation was to allow detailed studies of the pharmacological and electrophysiological properties of individual central vestibular neurons. The pharmacology of the central afferent synapses of the vestibular system has not been examined at the level of the neuronal membrane, and as a result few definitive reports are available. The best studies have used in situ extracellular recording techniques that are difficult to interpret. For instance, recent literature still supports the concept that excitatory transmission at the N. VIII to vestibular nuclei synapse is cholinergic. Our data refute this hypothesis and suggest that an excitatory amino acid is the most likely candidate for the eighth nerve to medial vestibular nucleus in the rat. We believe this preparation combined with an intracellular electrophysiological approach will shed information of value to both the basic scientist and the clinician with interest in the vestibular system.

Vertical Nitrate Fluxes in the Oligotrophic Ocean

The vertical flux of nitrate across the thermocline in the upper ocean imposes a rigorous constraint on the rate of export of organic carbon from the surface layer of the sea. This export is the primary means by which the oceans can serve as a sink for atmospheric carbon dioxide. For the oligotrophic open ocean regions, which make up more than 75% of the world's ocean, the rate of export is currently uncertain by an order of magnitude. For most of the year, the vertical flux of nitrate is that due to vertical turbulent transport of deep water rich in nitrate into the relatively impoverished surface layer. Direct measurements of rates of turbulent kinetic energy dissipation, coupled with highly resolved vertical profiles of nitrate and density in the oligotrophic eastern Atlantic showed that the rate of transport, averaged over 2 weeks, was 0.14 (0.002 to 0.89, 95% confidence interval) millimole of nitrate per square meter per day and was statistically no different from the integrated rate of nitrate uptake as measured by incorporation of (15)N-labeled nitrate. The stoichiometrically equivalent loss of carbon from the upper ocean, which is the relevant quantity for the carbon dioxide and climate question, is then fixed at 0.90 (0.01 to 5.70) millimole of carbon per square meter per day. These rates are much lower than recent estimates based on in situ changes in oxygen over annual scales; they are consistent with a biologically unproductive oligotrophic ocean.