Impairment of left ventricular function by acute cardiac lymphatic obstruction.

OBJECTIVES: We performed the following study to define the effects of acute cardiac lymphatic obstruction on left ventricular (LV) systolic and diastolic function. METHODS: Cardiac lymphatic obstruction was created in 8 pentobarbital-anesthetized dogs by identifying (Evans blue) and ligating the right and left epicardial lymphatics, the afferent and efferent lymphatics associated with the pretrachael and cardiac lymph nodes, and the thoracic duct. Left ventricular function was assessed by analysis of micromanometer-conductance catheter-derived LV pressure-volume relationships. Contractility was assessed by preload recruitable stroke work (PRSW). The active and passive phases of LV relaxation were assessed by the time constant o isovolumic relaxation (tau) and the end-diastolic pressure-volume relationship (stiffness), respectively. RESULTS: PRSW decreased significantly and tau increased significantly from baseline at 1, 2, and 3 h after cardiac lymphatic obstruction (n = 8), but stiffness did not change. Cardiac lymphatic obstruction had similar effects on LV function in a group of autonomically blocked dogs (n = 5). Left ventricular function did not change in sham treated controls (n = 8). Cardiac lymphatic obstruction induced a significant increase in LV wet/dry weight ratios (3.58 +/- 0.01) when compared to the control group (3.53 +/- 0.02). Histopathology of the myocardium in the lymphatic obstruction groups revealed significant lymphangiectasis and increased interstitial spacing when compared to controls. CONCLUSIONS: Acute cardiac lymphatic obstruction depresses contractility and active relaxation and causes mild LV myocardial edema, but does not alter diastolic stiffness.

Use of (S)-(trifloxymethyl)oxirane in the synthesis of a chiral beta-adrenoceptor antagonist, (R)- and (S)-9-[[3-(tert-butylamino)-2-hydroxypropyl]oximino]fluorene.

Two synthetic approaches were used to prepare, in chirally pure form, the beta-adrenoceptor antagonist 9-[[3-(tert-butylamino)-2-hydroxypropyl]oximino]fluorene (1a). One of these employed the oxazolidine (S)-6 generated from D-mannitol, while the other utilized (S)-[[(trifluoromethanesulfonyl)oxy]methyl]oxirane (4) as the chiral three-carbon fragment. This latter synthesis was designed to incorporate the amino function in the last step. In vitro, a beta 2 selectivity of only 2.2 was observed for 1a. The example, (S)-9-[[3-(tert-amylamino)-2-hydroxypropyl]oximino]fluorene (1b), was also prepared and found to be selective for the beta 1 receptor by a factor of 2.5. In contrast to other beta-adrenoceptor antagonists, the enantiomers of 1a exhibited no chiral preference; i.e., (S)-1a and (R)-1a possessed a similar order of beta-adrenoceptor antagonistic activity.

Synthesis of 4-substituted 2H-naphth[1,2-b]-1,4-oxazines, a new class of dopamine agonists.

A series of tricyclic oxazines, namely, the 4-substituted 2H-naphth[1,2-b]-1,4-oxazines, have been synthesized and assayed for dopamine agonist activity. One of the members of this series, compound (+)VII-15, was found to be a remarkably potent agonist in vivo when tested in the standard 6-hydroxydopamine lesioned rat assay. The absolute configuration of the compound corresponds to that found in the active isomer of apomorphine. Its activity at the alpha 2 receptor (vs. [3H]clonidine) is relatively low. It also failed to stimulate the synthesis of cAMP in the carp retina assay, thus giving the compound a highly selective profile in favor of the D2 receptor.

Antihypertensive beta-adrenergic blocking agents: N-aralkyl analogues of 2-[3-(tert-butylamino)-2-hydroxypropoxy]-3-cyanopyridine.

An interest in dual-acting antihypertensive agents, specifically those related to (S)-2-[3-(tert-butylamino)-2-hydroxypropoxy]-3-cyanopyridine (1), led us to probe the contribution of the side-chain amino substituent in this series. The ability of 1 and its various analogues to displace radiolabeled alpha 1 (WB-4101 and prazosin) and beta (dihydroalprenolol) adrenergic receptor ligands was assessed by receptor-binding techniques. Most of the compounds exhibited high beta-adrenoceptor binding affinities, but only the N-aralkylamino-substituted compounds showed high alpha 1-adrenoceptor affinities. Therefore, the vasodilation shown by 1 was not due to an interaction with the alpha 1 adrenoceptor. The aralkylamino analogues of 1 in spontaneously hypertensive rats and anesthetized dogs exhibited antihypertensive activity and alpha 1-adrenoceptor blocking properties. Unlike the preference shown by beta-adrenoceptors for S enantiomers in this oxymethylene class of beta blockers, the chirality at the secondary hydroxy center made only a minor contribution to the affinity for the alpha 1-adrenoceptor and even less of a contribution to the observed antihypertensive effects. This lack of chiral influence at the hydroxy center confirmed what had been previously observed in more limited studies with the isomers of both labetalol and medroxalol.

Diethyl 3,6-dihydro-2,4-dimethyl-2,6-methano-1,3-benzothiazocine-5,11- dicarboxylates as calcium entry antagonists: new conformationally restrained analogues of Hantzsch 1,4-dihydropyridines related to nitrendipine as probes for receptor-site conformation.

The pharmacological activity of rigid analogues of 1,4-dihydropyridine calcium entry antagonists 9-16 is demonstrated by dose-dependent inhibition of the calcium contraction in depolarized rat aortic strips and by a [3H]nitrendipine binding assay in using cardiac sarcolemmal membranes. From the results, a model is proposed as the receptor-bound conformation of the dihydropyridine calcium entry antagonists.

Synthesis of (7R)-7H-indolo[3,4-gh][1,4]benzoxazines, a new class of D-heteroergolines with dopamine agonist activity.

Synthesis of several members of the 9-oxaergoline ring system is presented. Both the C/D cis and the C/D trans isomers of 4,6,6a,8,9,10a-hexahydro-7-ethyl-7H-indolo[3,4-gh] [1,4]benzoxazine were prepared, and the C/D trans isomer was resolved into its optical isomers. The enantiomer having the highest affinity for the [3H]apomorphine binding site, (-)-trans-6-ethyl-9-oxaergoline [(-)-6b], was shown to have the same absolute configuration as the natural ergolines, namely, 6aR, 10aR. In vivo and in vitro pharmacological evaluation shows these 9-oxaergolines to possess potent dopamine agonist properties.

Comparison of afferent and efferent lung lymph in the sheep.

Efferent lymph collected from the caudal mediastinal lymph node (CMN) in the sheep lung lymph fistula model has been reported to represent free pulmonary interstitial fluid. Studies that utilize this model assume that nodal transit does not alter the composition of lymph. We collected afferent lymph from the tracheobronchial node (TBN) while simultaneously collecting CMN efferent lymph in acutely prepared sheep. We compared afferent and efferent lymph protein concentrations (CA and CE) and changes in flow rates (QLA and QLE) during base line and periods of elevated left atrial pressure (Pla). As a result of elevated Pla, QLA and QLE increased and the afferent lymph-to-plasma protein concentration ratio (CA/Cp) and the efferent lymph-to-plasma protein concentration ratio (CE/Cp) fell. The CA/Cp was significantly lower than the CE/Cp during base line (0.67 vs. 0.80) and periods of elevated Pla (0.41 vs. 0.61). Although we cannot exclude regional permeability differences, the difference between CA/Cp and CE/Cp is most likely due to the concentration of lymph within the CMN. Our data suggest nodal modification of CA is correlated with the afferent lymph-to-plasma colloid osmotic pressure ratio (pi A/pi p) and further suggest that nodal alteration of lymph during elevated Pla is due to the influence of decreased pi A/pi p at the blood-to-lymph barrier. We conclude that afferent lymph is a more accurate representation of lung free interstitial fluid because collection of pulmonary afferent lymph obviates the complications introduced by the CMN. Studies utilizing efferent lymph may have overestimated lung microvascular permeability in the acute sheep preparation.

Interaction of the component enantiomers of the putative dopamine autoreceptor agonist, TL-99 (6,7-dihydroxy-2-dimethylamino tetralin) with dopaminergic systems in mammalian brain and teleost retina.

The enantiomers of the putative dopamine autoreceptor agonist, TL-99 (6,7-dihydroxy-2-dimethylaminotetralin) were examined in a number of in vivo and in vitro test paradigms to further examine the reported autoreceptor selectivity of this compound. The (+)-isomer of the aminotetralin was more active as a dopamine agonist than either the racemate or the (-)-enantiomer. In addition to this dopaminergic activity, TL-99 was found to be a potent alpha 2-adrenoceptor agonist, this activity being more prominent in the (+)-isomer. The (-)-isomer, however, was a weak alpha 2/DA receptor agonist and unlike the (+)-enantiomer was devoid of activity in the D-1-selective carp retina adenylate cyclase assay. Pharmacological examination of the effects of TL-99 on mouse locomotor activity showed that the effects of the aminotetralin in this dopamine autoreceptor test system were antagonized by either the alpha 2-antagonist, yohimbine or by the dopamine antagonist, sulpiride. TL-99 also produced contralateral turning in 6-OHDA lesioned rats. It is concluded that the apparent dopamine autoreceptor selectivity of TL-99 as assessed by in vivo animal test systems may be due partially to its alpha 2-agonist activity. The sedation and consequent reduction in mouse locomotor activity and in turning in the rat as the dose level is increased undoubtedly occurs via alpha 2-agonist and dopamine autoreceptor activity and cannot be interpreted as selectivity for the dopamine autoreceptor.

Granulomatous pneumonia in the opossum (Didelphis virginiana) associated with an intracellular fungal agent.

BACKGROUND AND PURPOSE: Two of nine female opossums (Didelphis virginiana) in a closed breeding colony were submitted for necropsy due to a history of poor reproductive performance in the absence of overt clinical disease. On histologic examination, marked granulomatous to pyogranulomatous pneumonia was identified in these animals. METHODS: Lung sections were stained with periodic acid-Schiff and Gomori's methenamine silver nitrate. RESULTS: Pulmonary lesions were characterized by large numbers of foamy macrophages within the alveoli and interstitium, prominent subpleural and peribronchiolar aggregates of histiocytes, and a few scattered lymphoid nodules. Numerous fungal organisms were evident within the cytoplasm of macrophages on impregnation of histologic sections with the aforementioned stains. Other inciting agents were not identified. A third opossum lacked pulmonary lesions, but had similar organisms within one auricular sebaceous gland/hair follicle without apparent reaction to the organisms. CONCLUSION: A fungal agent was associated with granulomatous pneumonia in the opossum, and comparison was made with endogenous lipid pneumonia previously described in opossums. These findings stress the importance of use of special stains and additional diagnostic techniques when prominent alveolar macrophage accumulation is present on histologic examination of the opossum lung.

Clinical pathology and sample collection in the laboratory rodent.

Common laboratory rodents have always been a favorite choice as a pet. Although diagnostic clinical pathology has not been viewed as practical for the rodent patient, current advances in technology make processing of small samples possible. Cultivation of the technical skills necessary for rodent sample collection has the potential to improve the standard of rodent veterinary care. This article provides an overview of rodent sample collection techniques, hematology, clinical biochemistry, serology, and clinical pathology of other tissues and fluids for laboratory rodents. General principles of clinical pathology can be applied across species. This article emphasizes the subtleties of the different rodent species which may impact diagnostic interpretation.

A comparison of the effects of aspirin and histamine of fluid balance in the recruited lung.

Salicylate administration has been reported to increase the flow of protein-rich lymph from the lungs of animals, however, the mechanism of this response is unclear. In the present study we measured pulmonary hemodynamics and lung fluid and protein flux in anesthetized sheep, surgically prepared for the collection of lung lymph, in order to examine the possible effect of aspirin (ASP) on lung vascular permeability. ASP was given during recruitment of pulmonary microvascular surface area induced by sustained elevation of left atrial pressure (Pla) (Group 1) or continuous infusion of adenosine triphosphate (ATP) (Group 2). We compared the results of ASP administration to those found in similarly prepared animals given histamine (H) during like periods of increased Pla (Group 3) or ATP infusion (Group 4). ASP administration resulted in increased lymphatic protein clearance (Cp) in both Groups 1 and 2. In Group 1, following the characteristic increase in lung lymph flow (Q1) and fall in the ratio of lung lymph to plasma protein concentration (L/P) produced by Pla elevation, ASP administration resulted in a further increase in Q1 and a significant increase in L/P. The results found in ASP animals are qualitatively similar to those observed in Groups 3 and 4 after H. While we cannot specifically rule out a hemodynamic effect of the drug, our results suggest the increased protein flux observed following ASP administration was mediated at least in part through an increase in lung microvascular permeability.

Assessment of pulmonary microvascular permeability in acutely prepared sheep.

We hypothesized that the apparent difference in base-line lymph-to-plasma protein concentration ratios (L/P) between acutely and chronically prepared sheep is due to an underlying difference in pulmonary microvascular permeability. Therefore, we sought to determine the pulmonary microvascular osmotic reflection coefficient for acutely prepared sheep, in a manner similar to that used by Parker et al. (Circ. Res. 49: 1164-1172, 1981) in chronically prepared animals. In 20 acutely prepared sheep, we evaluated pulmonary lymph flow (QL) and L/P as left atrial pressure was progressively elevated. As a result of the elevated hydrostatic pressure, QL increased by 28 to 773% above base-line flows, accompanied by substantial dilution of lymphatic protein. At high QL, L/P approached a minimal value, (L/P)min, of 0.39. The osmotic reflection coefficient (sigma d), calculated as sigma d = 1 - (L/P)min, was 0.61, substantially lower than the value of 0.74 found by Parker et al. in chronically prepared sheep. We conclude that the higher base-line L/P found in acutely prepared sheep is due to higher pulmonary microvascular permeability, possibly the result of the more immediate surgical trauma.

Effect of histamine on tracheobronchial afferent and caudal mediastinal efferent lymph.

We prepared nine sheep with acute tracheobronchial afferent (TBN) and caudal mediastinal efferent (CMN) lymph fistulas. After a baseline period (B) in 3 sheep, we administered histamine (H) continuously for 4 h. In six sheep, we elevated left atrial pressure (PLA) and reestablished steady-state conditions prior to H administration. The afferent lymph to plasma protein concentration ratio (CA/CP) was significantly lower than the efferent ratio (CE/CP) during periods of B, H, elevated PLA, and elevated PLA with H. H administration increased lymph flow rates (QlA and QlE) and both CA/CP and CE/CP, albeit insignificantly. During elevated PLA, QlA and QlE increased, while CA/CP and CE/CP fell. QlE increased, while QlA did not change during elevated PLA with H. CE/CP increased from its PLA level. CA/CP did not increase. Afferent data suggest that histamine may increase pulmonary microvascular surface area, but does not alter the permeability of the pulmonary circulation. While we cannot exclude the possibility of an increase in pulmonary microvascular permeability from efferent results, the difference between TBN afferent and CMN efferent results likely represent the action of histamine at the CMN.

Effect of acute administration of bleomycin on lung fluid balance in sheep.

This study examined the effects of acute administration of bleomycin (BLM) on lung liquid and protein exchange in anesthetized sheep prepared with caudal mediastinal lung lymph fistulas. Six sheep received BLM (15 U IV) after a baseline period, while seven others were given BLM after a steady state was obtained following elevation of left atrial pressure (PLA), a procedure intended to minimize changes in pulmonary microvascular surface area and produce high lung lymph flow (QL). Plasma and lung lymph angiotensin converting enzyme (ACE) activities were measured in order to independently assess the effects of BLM on pulmonary endothelial integrity. QL rose significantly in all animals following BLM. The ratio of lymph to plasma protein concentration (CL/CP) did not change in the group given BLM alone, and fell continuously during the period of PLA elevation after BLM in that group. Plasma and lung lymph ACE activities were unchanged following BLM administration in either group. The ultrastructure of the gas-exchanging region of lungs from animals in each group was examined by transmission electron microscopy. The data suggest that acute administration of a low dose of BLM does not increase pulmonary microvascular permeability, but may induce an increase in perfused pulmonary microvascular surface area responsible for increased QL.

Effect of extracellular fluid volume expansion on avian lung fluid balance.

We examined the effects of acute expansion of extracellular fluid volume (ECFV) on lung fluid balance and the ultrastructure of the pulmonary air-blood barrier in chickens (Gallus domesticus). We compared changes in extravascular lung water content (EVLW) to the sum of mean pulmonary capillary blood pressure and plasma protein osmotic pressure (tau c), as a measure of net intravascular filtration pressure (NIFP), produced by graded infusion of avian Ringer's solution. NIFP increased with each volume load largely as a result of decreased tau c resulting in progressive increase in EVLW. Progressive interstitial edema occurred with fluid accumulation restricted to the inter air capillary septa, sparing the gas exchanging regions of the air-blood barrier. This was associated with increased thickness of the septa and increased pulmonary capillary endothelial vesiculation. The effect of increased ECFV on pulmonary hemodynamics and lung fluid balance in Gallus is similar to that in mammals.

The effect of indomethacin on plasma and lung lymph angiotensin converting enzyme activity in sheep.

The effect of indomethacin (INDO), an inhibitor of prostaglandin (PG) cyclooxygenase, on pulmonary vascular permeability is unclear. We measured angiotensin converting enzyme (ACE) activity in plasma and lung lymph in order to evaluate pulmonary endothelial integrity. Eighteen sheep, anesthetized and acutely prepared for the collection lung lymph, were used in the study. Four animals (Group I) served as sham controls and were not subjected to experimental intervention. In order to minimize changes in pulmonary microvascular surface area (PMSA), left atrial blood pressure (Pla) was elevated (12-20 Torr) following the baseline period in animals in the three experimental groups. Group II (n = 4) was subjected to increased Pla only in order to assess the effects of that maneuver alone on experimental parameters. Group III (n = 3) received an infusion of buffered vehicle only during a four hour period of elevated Pla, and, thus served as a vehicle control for Group IV (n = 7) which received INDO for the same period of increased Pla. Pulmonary blood pressures, cardiac output (CO), lung lymph flow (Ql) and the ratio of lymph to plasma protein concentration (L/P) were measured in all experiments in order to independently assess changes in lung vascular permeability. While ACE activity in plasma and lymph fell in each experimental group, average ACE experimental values were unchanged from corresponding baseline values. Increased Pla caused a characteristic increase in Ql and fall in L/P in each of the experimental groups. We conclude that INDO does not alter lung fluid and protein balance by a process which involves increased pulmonary vascular permeability secondary to a loss of endothelial integrity.

Mechanical workload-myocardial water content relationship in isolated rat hearts.

We tested the hypothesis that the mechanical workload of the heart inversely determines the rate of myocardial edema formation in an isolated, perfused rat heart preparation. Heart rate (HR) was varied in three groups by pacing at 125 (HR125), 250 (HR250), or 350 beats/min (HR350). Left ventricular pressure (LVP) was varied in two additional groups by pacing at 250 beats/min and with the addition of either epinephrine (Epi) or propranolol (Pro) to the perfusate. In five otherwise identical groups, variation of coronary vascular resistance was minimized by adenosine. Myocardial water content (MWC) varied significantly and inversely with HR in the HR125, HR250, and HR350 groups. MWC of the HR250 group was significantly less than that of the Pro group but did not differ from the Epi group. However, when adenosine was used, MWC had significant inverse relationships with HR and LVP. We concluded that the mechanical workload of the heart inversely determines the rate and degree of myocardial edema formation in this isolated heart preparation, and both HR and LVP are determinants of this relationship.

Acute transient coronary sinus hypertension impairs left ventricular function and induces myocardial edema.

This study was performed to evaluate the direct and indirect effects of acute coronary sinus hypertension (CSH) on systolic and diastolic left ventricular (LV) function. Coronary sinus pressure was elevated to 25 mmHg for 3 h in eight pentobarbital-anesthetized dogs and then relieved. LV contractility was assessed by preload recruitable stroke work (PRSW) and end-systolic elastance (Ees). Diastolic function was assessed by the time constant of isovolumic relaxation (tau) and the end-diastolic pressure volume relationship (EDPVR). PRSW and Ees decreased progressively, and tau and the slope of the EDPVR increased progressively with CSH. These changes persisted after relief of CSH. beta-Adrenergic and cholinergic receptor blockade, performed in six dogs, did not alter the effects of CSH on systolic or diastolic function. The LV wet-to-dry weight ratios of the groups with CSH were significantly greater than those of a control group without CSH. We conclude that CSH results in changes in the left ventricle that depress contractility, prolong active relaxation, and increase diastolic stiffness. The dysfunction was not the direct effect of CSH or autonomic reflex activation, but may have been induced by fluid accumulation within the interstitium.

Effects of hypoproteinemia-induced myocardial edema on left ventricular function.

In previous studies, we observed left ventricular (LV) systolic and diastolic dysfunction in association with interstitial myocardial edema (IME) induced by either coronary venous hypertension (CVH) or lymphatic obstruction. In the present study, we examined the effects of myocardial edema induced by acute hypoproteinemia (HP) on LV systolic and diastolic function. We also combined the methods of HP and CVH (HP-CVH) to determine their combined effects on LV function and myocardial water content (MWC). We used a cell-saving device to lower plasma protein concentration in HP and HP-CVH groups. CVH was induced by inflating the balloon in the coronary sinus. Six control dogs were treated to sham HP. Conductance and micromanometer catheters were used to assess LV function. Contractility, as measured by preload recruitable stroke work, did not change in control or HP groups but declined significantly (14.5%) in the HP-CVH group. The time constant of isovolumic LV pressure decline (tau) increased significantly from baseline by 3 h in the HP (24.8%) and HP-CVH (27.1%) groups. The end-diastolic pressure-volume relationship (stiffness) also increased significantly from baseline by 3 h in the HP (78.6%) and HP-CVH (42.6%) groups. Total plasma protein concentration decreased from 5.2 +/- 0.2 g/dl at baseline to 2.5 +/- 0.0 g/dl by 3 h in the HP and HP-CVH groups. MWC of the HP (79.8 +/- 0.25%) and HP-CVH groups (79.8 +/- 0.2%) were significantly greater than that of the control group (77.8 +/- 0.3%) but not different from one another. In conclusion, hypoproteinemia-induced myocardial edema was associated with diastolic LV dysfunction but not systolic dysfunction. The edema caused by hypoproteinemia was more than twice that produced by our previous models, yet it was not associated with systolic dysfunction. CVH had a negative inotropic effect and no significant influence on MWC. IME may not have the inverse causal relationship with LV contractility that has been previously postulated but appears to have a direct causal association with diastolic stiffness as has been previously demonstrated.