Advances in transesophageal echocardiographic imaging.

Transesophageal echocardiography (TEE) has emerged as a valuable complement to trans-thoracic echocardiography (TTE) and expanded our ability to visual the heart with ultrasound. TEE provides high resolution imaging with minimal attenuation from non cardiac structures, and allows detailed visualization of cardiac structures and flow disorders not well seen with TTE. While developments in transesophageal imaging over the last 3 decades have led to established clinical indications for TEE, recent advances in TEE including: 1) new applications of trans-thoracic methodologies in TEE; 2) innovations in TEE technology, and 3) advances in clinical care of cardiovascular disease, have all contributed to exciting new clinical applications of TEE. This review provides an overview of the advances in TEE technology and the current and emerging clinical applications of TEE.

Slowing the progression of CHF. Drug therapy to correct neurohormonal abnormalities.

As the population ages, the number of cases of congestive heart failure (CHF) is expected to climb. Primary care physicians will be increasingly called upon to treat patients with this serious cardiac derangement. In this article, Drs Ward and Anderson discuss the latest approaches to treatment, which are based on the current understanding that CHF results from left ventricular dysfunction, which causes a complex activation of multiple neurohormonal reflexes.

Role of adenosine and N-methyl-D-aspartate receptors in mediating haloperidol-induced gene expression and catalepsy.

Acute blockade of dopamine D(2) receptors by the typical antipsychotic drug haloperidol leads to alterations in neuronal gene expression and behavior. In the dorsolateral striatum, the levels of mRNA for the immediate-early gene c-fos and the neuropeptide gene neurotensin/neuromedin N (NT/N) are significantly increased by haloperidol. An acute behavioral response to haloperidol is catalepsy, considered to be a rodent correlate of some of the immediate extrapyramidal motor side effects seen in humans. Several lines of evidence suggest a link between neurotensin induction in the dorsolateral striatum and catalepsy. We hypothesize that both striatal gene induction and catalepsy elicited by haloperidol arise from the combined effect of excitatory adenosinergic and glutamatergic inputs acting at adenosine A(2A) and N-methyl-D-aspartate (NMDA) receptors, respectively. In agreement with our previous reports, adenosine antagonists reduced haloperidol-induced c-fos and neurotensin gene expression as well as catalepsy. In agreement with other reports, the noncompetitive NMDA receptor antagonist MK-801 also reduced gene expression and catalepsy in response to haloperidol. The competitive NMDA receptor antagonist LY235959 decreased haloperidol-induced catalepsy. We show here that blocking both A(2A) and NMDA receptors simultaneously in conjunction with haloperidol resulted in a combined effect on gene expression and behavior that was greater than that for block of either receptor alone. Both c-fos and NT/N mRNA levels were reduced, and catalepsy was completely abolished. These results indicate that the haloperidol-induced increases in c-fos and NT gene expression in the dorsolateral striatum and catalepsy are driven largely by adenosine and glutamatergic inputs acting at A(2A) and NMDA receptors.

Molecular and behavioral effects mediated by Gs-coupled adenosine A2a, but not serotonin 5-Ht4 or 5-Ht6 receptors following antipsychotic administration.

Typical antipsychotic agents are potent antagonists of Gi-coupled dopamine D2 receptors, but their mechanisms of action following this initial blockade remain poorly understood. We hypothesized that in striatal neurons, interruption of this inhibitory dopamine D2 input would unmask endogenous striatal Gs-coupled receptors. An increase in cAMP levels generated by these unopposed receptors would then lead to the well-described behavioral and molecular effects of antipsychotic administration such as catalepsy and striatal c-fos and neurotensin gene transcription. We examined three striatal Gs-coupled receptor systems (serotonin 5-HT4, serotonin 5-HT6 and adenosine A2a) to assess their potential involvement in the mechanism of action of the typical antipsychotic haloperidol. Antagonists of each of these three receptor systems together with a 1 mg/kg dose of haloperidol were co-administered to Sprague-Dawley rats, and both the degree of catalepsy produced in the animals and the induction of striatal c-fos and neurotensin messenger RNAs were measured. Both the specific adenosine A2a antagonist 8-(3-chlorostyryl)-caffeine and the general adenosine antagonist theophylline reduced haloperidol-dependent induction of striatal neurotensin and c-fos messenger RNA. Administration of these agents also greatly reduced the degree of catalepsy induced by haloperidol. Antagonists of the 5-HT6 receptor failed to block the induction of striatal messenger RNAs, but the 5-HT6 antagonist clozapine (an important atypical antipsychotic agent in its own right) was a potent inhibitor of catalepsy. 5-HT4 agents were unable to alter haloperidol's effects on striatal messenger RNA levels or catalepsy. We conclude that the striatal Gs-coupled adenosine A2a receptor is an important mediator of the molecular and behavioral sequelae following haloperidol administration.

Similarity in gallstone formation from 900 kcal/day diets containing 16 g vs 30 g of daily fat: evidence that fat restriction is not the main culprit of cholelithiasis during rapid weight reduction.

Diets containing essentially no fat, 1-2 g fat per day, have resulted in cholesterol gallstones. Greater fat may result in less gallbladder stasis. Do gallstones form with greater fat content? We studied 272 moderately obese subjects who had normal gallbladder ultrasonograms. The 900 kcal/day liquid diets contained either 16 g fat (N = 94) or 30 g fat (N = 178) each day for 13 weeks. A second gallbladder ultrasound was performed. Sixteen of 94 (17.0%) of the 16-g fat group developed stones with a weight loss of 18 (+/- 7) kg and a body mass index (BMI) decrease of 6 (+/- 2) kg/m2. Twenty of 178 (11.2%) of the 30-g fat group developed stones (P = 0.18, no difference in stone formation) with similar weight loss of 20 (+/- 7) kg (P = 0.08) and BMI decrease of 7 (+/- 2) kg/m2 (P = 0.04). Substantial fat for rapid weight-reducing diets resulted in gallstone formation. Since experiments have shown that our higher fat diet, containing 10 g fat per meal, results in maximal gallbladder emptying, cholelithiasis from rapid weight loss may not be solely attributable to gallbladder stasis.

Colocalization of serotonin receptor subtypes 5-HT2A, 5-HT2C, and 5-HT6 with neuropeptides in rat striatum.

There are two primary output pathways from the striatum: a projection to the globus pallidus, and projection to the substantia nigra. Certain striatally expressed neuropeptides are differentially distributed between these two pathways. Specifically, enkephalin is expressed in striatopallidal neurons, whereas substance P and dynorphin are expressed in striatonigral neurons. Several serotonin receptors are also prominently expressed in the striatum, but little is known about how they fit into the molecular neuroanatomy described above. We used double-label in situ hybridization to determine the striatal distribution of the mRNAs of the serotonin2A (5-HT2A), serotonin2C (5-HT2C), and serotonin6 (5-HT6) receptors in relation to enkephalin, substance P, and dynorphin expressing output neurons. Rat brain sections were simultaneously hybridized with an 35S riboprobe for one of the serotonin receptors and a digoxygenin labeled riboprobe for one of the neuropeptides. Sections were examined by using brightfield microscopy, and the degree of colocalization of the two mRNAs determined. All the serotonin receptors colocalized extensively with all three of the neuropeptides examined. None of the serotonin receptors showed preferential colocalization in striatopallidal (enkephalin containing), or striatonigral (substance P or dynorphin containing) cells. The 5-HT2A and 5-HT2C mRNAs displayed a differential distribution with regard to the scattered islands of strongly dynorphin mRNA positive cells, which are thought to reside in the striatal patch compartment. Within these islands, 5-HT2C mRNA expression was much higher than in surrounding areas. 5-HT2A mRNA showed the opposite pattern with decreased expression over dynorphin rich cell clusters.

Assessment of in vivo attachment/phagocytosis by alveolar macrophages.

Alveolar macrophages (AMs) are recognized as an important first line of cellular host defense within the lung. Although mechanisms underlying AM response to microorganisms or particulates are well characterized in vitro, experimental approaches to the study of AMs in vivo are limited. To circumvent these limitations, a new assay was developed using fluorescently labelled liposomes or Pneumocystis carinii (PC) organisms which were administered intratracheally into mechanically ventilated rats. After 30 min, the lungs were lavaged and the percentage of administered liposomes or PC bound to AMs was determined by quantifying fluorescence. Factors known to enhance attachment/phagocytosis by AMs in vitro were assayed to determine their effect in vivo. For example, vitronectin (VN)-coated liposomes increased attachment from 25.2 +/- 2.4% to 47.2 +/- 3.0% (p < 0.001), while addition of VN increased the binding of PC to AMs from 16.5 +/- 1.7% to 24.5 +/- 2.2% (p < 0.05). Confocal laser microscopy of cells obtained by lavage provided morphologic evidence of attachment/phagocytosis by AMs. This model will permit the quantitative assessment of the interaction of fluorescently labelled liposomes or microorganisms with AMs in the lower respiratory tract of living animals.

Localization of serotonin subtype 6 receptor messenger RNA in the rat brain by in situ hybridization histochemistry.

The serotonin receptor subtype 6, which raises intracellular cyclic AMP via stimulatory G-proteins, has recently been cloned and characterized. To determine the distribution of serotonin subtype 6 messenger RNA, in situ hybridization was performed in coronal sections of rat brain. 35S-labeled riboprobe, complementary to the 5' non-coding region of the serotonin subtype 6 messenger RNA, and a 33P-labeled riboprobe complementary to its 3' non-coding region, were used for hybridization. Serotonin subtype 6 receptor message was found in serotonin projection fields, rather than regions of serotonin-containing cell bodies, suggesting that the receptor is mainly postsynaptic. Hybridization signal was highest in olfactory tubercle, as well as prominent in the striatum, nucleus accumbens, dentate gyrus, and CA1, CA2 and CA3 of the hippocampus. Less intense hybridization was observed in cerebellum, some diencephalic nuclei, the amygdala, and layers 2, 3, 4 and 6 of the cortex. This pattern of hybridization was observed with both probes, but not when sense transcripts were used. Because the serotonin subtype 6 receptor has a high affinity for the atypical antipsychotic clozapine, and because striatum and nucleus accumbens are proposed sites of antipsychotic drug effects, the possibility is raised that this receptor may play an important role in mediating the effects of the atypical antipsychotic agents.

Cloning and expression of a novel serotonin receptor with high affinity for tricyclic psychotropic drugs.

We have used the polymerase chain reaction technique to selectively amplify a guanine nucleotide-binding protein-coupled receptor cDNA sequence from rat striatal mRNA that exhibits high homology to previously cloned serotonin receptors. Sequencing of a full length clone isolated from a rat striatal cDNA library revealed an open reading frame of 1311 base pairs, encoding a 437-residue protein with seven hydrophobic regions. Within these hydrophobic regions, this receptor was found to be 41-36% identical to the following serotonin [5-hydroxytryptamine (5-HT)] receptors: 5-HT2 > 5-HT1D > 5-HT1C > 5-HT1B > 5-HT1A > 5-HT1E. Northern blots revealed a approximately 4.2-kilobase transcript localized in various brain regions, with the following rank order of abundance: striatum >> olfactory tubercle > cerebral cortex > hippocampus. Expression of this clone in COS-7 cells resulted in the appearance of high affinity, saturable binding of (+)-[2-125I] iodolysergic acid diethylamide ([125I]LSD) with a Kd of 1.26 nM. Among endogenous biogenic amines, only 5-HT completely inhibited [125I]LSD binding (Ki = 150 nM). The inhibition of [125I]LSD binding by other serotonergic agonists and antagonists revealed a pharmacological profile that does not correlate with that of any previously described serotonin receptor subtype. In addition, this receptor exhibits high affinity for a number of tricyclic antipsychotic and antidepressant drugs, including clozapine, amoxipine, and amitriptyline. In HEK-293 cells stably transfected with this receptor, serotonin elicits a potent stimulation of adenylyl cyclase activity, which is blocked by antipsychotic and antidepressant drugs. The distinct structural and pharmacological properties of this receptor site indicate that it represents a completely novel subtype of serotonin receptor. Based on its affinity for tricyclic psychotropic drugs and its localization to limbic and cortical regions of the brain, it is likely that this receptor may play a role in several neuropsychiatric disorders that involve serotonergic systems.

Effects of repeated gestation and lactation on milk n-6 fatty acid composition in rats fed on a diet rich in 18:2n-6 or 18:3n-6.

The present study examined the effect of repeated gestation and lactation on the levels of long-chain n-6 polyunsaturated fatty acids in rat milk fat, and examined whether such levels might be modulated by supplementing the diet of the lactating dams with either (g/kg) 50 safflower oil (SFO; containing 800 g 18:2n-6/kg), or 50 evening primrose oil (EPO; containing 720 g 18:2n-6 and 90 g 18:3n-6/kg). The milk was collected at three different times (days 1, 8 and 15) in each given lactation period from female Sprague-Dawley rats which were successively bred for four pregnancies and lactations. Results showed that dietary fat and breeding frequency had no significant effects on milk triacylglycerol content, but they modified the pattern of milk fatty acids in both triacylglycerol and phospholipid fractions. After three or four successive breedings rats fed on EPO produced milk containing less saturated but more monounsaturated and polyunsaturated fatty acids compared with those fed on SFO. During the course of lactation the levels of n-6 metabolites, e.g. 18:3n-6, 20:3n-6 and 20:4n-6, in milk fat declined progressively. However, they were consistently higher in the EPO group than in the SFO group. These findings suggest that the levels of long-chain n-6 metabolites in the milk fat may be increased through supplementing the maternal diet with 18:3n-6.

Attenuation of cyclosporine-induced hypertension by dietary fatty acids in the borderline hypertensive rat.

The effects of dietary (10% calories) safflower (SAF), evening primrose (EPO), and fish oil (F) as sources of linoleic acid (control), gamma-linolenic acid, and long-chain n-3 fatty acids, respectively, on cardiovascular and renal responses to chronic (5 weeks) cyclosporine administration were studied in male borderline hypertensive rats. In one experiment (n = 9/group), oral administration of CsA at 0.1 mg/kg.day significantly increased awake systolic blood pressure vs. placebo in SAF-fed rats (P less than 0.01). This increase was prevented by both EPO (P less than 0.001) and F (P less than 0.01), in the absence of group differences in body weight gain or plasma electrolyte levels. In a second experiment, CsA also increased blood pressure vs. placebo in SAF-fed rats (P less than 0.001). While this increase was prevented by EPO (P less than 0.001), F had no significant effect. Differences in group blood pressure responses were not explained by group differences in body weight gain or trough levels of blood CsA. Renal function, assessed in anesthetized rats after week 5, demonstrated a CsA-related (10 mg/kg.day) decrease in whole-kidney GFR in SAF-fed animals vs. placebo (P less than 0.05) that was prevented by EPO and attenuated by F. EPO and F also tended to reduce the CsA-induced elevation in renovascular resistance, but this difference did not reach statistical significance. These findings suggest the potential of dietary EPO and F to offset nephrotoxic effects of CsA administration, and suggest that EPO may also be useful in countering CsA-induced hypertension.

Alteration of baroreflex control of forearm vascular resistance by dietary fatty acids.

The effects of dietary safflower (control, n = 10), borage (n = 9), and fish oil (n = 10), as sources of linoleic, gamma-linolenic, and eicosapentaenoic acid, respectively, at a dose of 4.5 ml/day for 4 wk, on cardiovascular responses to lower body negative pressure (LBNP) were studied in normotensive humans in a randomized, double-blind design. Pre- and postsupplementation, subjects were exposed to 5 min of -10 and -40 mmHg LBNP. Blood pressure (BP), heart rate (HR), forearm blood flow (FBF), forearm vascular resistance (FVR), and plasma norepinephrine (PNE) were measured at each level. Subjects were then exposed to a cold-pressor test, isometric handgrip, and forearm ischemia. At pretest, LBNP reduced BP and FBF and increased HR and FVR in all groups. After diets, the PNE and vasoconstrictor responses to -40 mmHg LBNP, as well as the reflex vasodilation on its cessation, were significantly augmented by borage oil. No diet differences were observed in the HR responses to LBNP or in the responses to the other tasks, with the exception that fish oil increased FBF after forearm ischemia. These data indicate that borage oil augments the arterial baroreflex control of vascular resistance. The vasodilatory effects of fish oil may be mediated via local mechanisms.

Stress modulates cholesterol-induced changes in plasma and liver fatty acid composition in rats fed n-6 fatty acid-rich oils.

The effects of dietary cholesterol (CH) and isolation stress on fatty acid compositions of plasma and liver cholesteryl ester and phospholipids were compared in growing rats fed an 18:2n-6 or an 18:3n-6 enriched semisynthetic diet for 2 weeks. Stress, CH-feeding, and dietary fats had no significant effects on plasma CH level, but CH-feeding alone elevated the liver CH concentrations. CH-feeding also modulated the liver polyunsaturated fatty acid compositions, i.e., increasing 18:2n-6 levels, and reducing 20:4n-6 levels, indicating an inhibition of the enzymes, delta-6 and delta-5-desaturases. The extent of these changes was less in rats fed 18:3n-6 than in those fed 18:2n-6. Stress, which alone had no significant effects on plasma and liver fatty acid compositions, attenuated the CH-induced changes of fatty acid levels.

Effects of prenatal ethanol and long-chain n-3 fatty acid supplementation on development in mice. 2. Fatty acid composition of brain membrane phospholipids.

Pregnant mice were fed equivalent daily amounts of a liquid diet containing 25% (kcal) ethanol, or with maltose dextrin substituted isocalorically for ethanol. The diet also contained 20% oil; this was either of two mixtures, one comprised of predominantly n-6 (18:2n-6) fatty acids, and the other containing an equivalent amount of n-6, but supplemented with a source of long chain n-3 (20:5n-3, 22:6n-3) fatty acids. An additional control group was fed lab chow ad libitum. The treatment was implemented from day 7 to 17 of gestation, whereafter all groups were fed lab chow. Birth occurred on day 19, and the fatty acid composition of the brain membrane phospholipids was determined in the pups 3 days after birth (day 22 postconception) and again, 10 days later (day 32 postconception). On day 22 the polyunsaturated fatty acid (PUFA) composition of the brain phospholipids reflected dietary availability, with the n-3/n-6 ratio higher in the n-3 groups; this was decreased by ethanol in the phosphatidylcholine (PC) fraction. The dietary effect was still apparent on day 32; again ethanol reduced this in both the PC and phosphatidylethanolamine (PE) fractions. The n-3 oil, but not ethanol, increased the 20:3n-6/20:4n-6 ratio, indicative of an inhibition of the activity of delta-5 desaturase. With respect to the 22:C compounds, the n-3 oil decreased the levels of 22:5n-6, while increasing those of 22:6n-3, but generally the sum of these two fatty acids remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prenatal ethanol and long-chain n-3 fatty acid supplementation on development in mice. 1. Body and brain growth, sensorimotor development, and water T-maze reversal learning.

Pregnant mice were fed equivalent daily amounts of a liquid diet containing 25% (kcal) ethanol, or with maltose dextrin substituted isocalorically for ethanol. In addition, the diet contained 20% oil; this was either of two mixtures, one comprised of predominantly n-6 (18:2n-6) fatty acids, and the other containing an equivalent amount of n-6, but supplemented with a source of long chain n-3 (20:5n-3, 22:6n-3) fatty acids. An additional control group was fed lab chow ad libitum. The treatment was implemented from day 7 to 17 of gestation, whereafter all groups were fed lab chow. Ethanol decreased maternal weight gain and pup body and brain weight; it also retarded both sensory and motor development in the pups and impeded reversal learning in a water maze. The n-3 supplementation lowered maternal blood alcohol concentration, but counteracted only some of the effects of ethanol, by increasing maternal weight gain and pup body weight, and also by enhancing sensory development in the pups. Such effects were additive, in that they were also present in the maltose-dextrin control group. These findings suggest that n-3 supplementation may ameliorate some of the effects of ethanol on neurobehavioral development, but the magnitude of the effect appears to be small.

Fatty acid composition of milk from genetically normotensive and hypertensive rats.

To assess milk fatty acid composition in genetically normotensive (Wistar Kyoto, WKY) and spontaneously hypertensive (SH) rats, WKY and SH dams (n = 10/strain) were milked under halothane anesthesia on d 5, 13 and 21 postpartum. Milk samples of 0.5-1.0 mL were then analyzed by gas-liquid chromatography. Additional WKY and SH dams (n = 2/strain) were milked on d 5 and 21 postpartum for assessment of total milk fat. In both WKY and SH strains, the amount of 8:0 and 10:0 fatty acids increased from d 5 to 21 (p less than 0.001), whereas the quantity of 18:3(n-6), 20:3(n-9), 20:3(n-6), 22:4(n-6), 22:5(n-3) and 22:6(n-3) fatty acids declined over the same period (p less than 0.001). Milk from SH rats had higher levels of 10:0 and 20:4(n-6) fatty acids on all sampling days than did milk from WKY rats (p less than 0.001), and milk from SH rats had lower levels of 16:1(n-7), 18:1(n-9) and 18:2(n-6) fatty acids on d 13 and 21 (p less than 0.001). There were no differences in milk fat content between strains. These data suggest that genetically hypertensive rat pups obtain significantly greater amounts of 20:4(n-6) and significantly lower amounts of 18:2(n-6) fatty acids from maternal milk than do their normotensive counterparts.

Interactive effects of prenatal ethanol and N-3 fatty acid supplementation on brain development in mice.

This study assesses the combined effects on brain and behavioral development of ethanol administration and supplementation of the maternal diet with long chain n-3 polyunsaturated fatty acids. From day 7 to 17 of gestation, pregnant mice were fed equivalent daily amounts of isocaloric liquid diets; 20% of the energy was provided by either ethanol or maltose-dextrin, and a further 20% by either safflower oil (rich in linoleic acid, 18:2 n-6), or a combination of safflower oil with a fish oil concentrate (rich in eicosapentaenoic acid, 20:5 n-3, and docosahexaenoic acid, 22:6 n-3). On day 18 the liquid diets were replaced by lab chow; a fifth group was maintained on lab chow throughout the experiment. Measures on the pups included brain weight and the fatty acid composition of the brain phospholipids on days 22 and 32 post-conception (birth = day 19), as well as behavioral development. Maternal weight gain during gestation was decreased by ethanol relative to maltose-dextrin, and increased by fish relative to safflower oil. On day 32, the brain weight of ethanol-treated animals fed fish oil was greater than their safflower oil controls, whereas the reverse was true in the two maltose-dextrin groups; a similar trend was apparent on day 22. The brain phospholipid content of the longer chain fatty acids (20:4 n-6, 22:4 n-6, 22:5 n-6, 20:5 n-3, 22:5 n-3, 22:6 n-3) on day 22 reflected that of the prenatal diet, with the proportion of n-3 compounds being higher and that of n-6 lower in the fish oil than safflower oil groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of essential fatty acid depletion on tissue phospholipid fatty acids in spontaneously hypertensive and normotensive rats.

Weanling male spontaneously hypertensive (SHR) and normotensive (WKY) rats were maintained on a fat-free semisynthetic diet and killed at various intervals. The effects of fat-depletion on the appearance of essential fatty acid (EFA) deficiency symptoms, the progressive changes of major fatty acids in plasma, liver, heart, and kidney phospholipids (PL), and in skin total lipids were compared between these two strains. After five weeks on the diet, the slower growth and the appearance of EFA deficiency symptoms became evident in SHR. In general, fat-depletion reduced the levels of n-6 fatty acids, whereas it increased those of 20:3n-9. However, the fat-depletion induced reduction of 18:2n-6 in heart PL and 20:4n-6 in kidney, while the elevation of 20:3n-9 in plasma, heart, and kidney PL were greater in WKY than in SHR. As a result, the elevation of biochemical EFA deficiency index--20:3n-9/20:4n-6 ratio--was greater in WKY than in SHR. In comparison with WKY, the concentrations of liver triacylglycerols and the weights of adipose tissues in SHR were reduced to a greater extent, indicating an active catabolism of triacylglycerols in SHR. This study suggests that the earlier appearance of morphological symptoms of EFA deficiency in SHR was not associated with the reducing n-6 EFA levels or with an elevation of triene/tetraene ratio, but possibly to a reduced supply of n-6 EFA for skin prostaglandin synthesis.