Effects of tacrine on brain muscarinic-receptor-mediated second-messenger signals

The purpose of this study was to investigate the effects of 9-amino-1,2,3,4-tetrahydroacridine (THA; Tacrine) on muscarinic-receptor-linked second-messenger systems in rat brain and to determine the selectivity and mechanisms of these effects. Both competitive and noncompetitive antagonism was revealed in saturation radioligand binding studies performed in cortical and striatal tissue, depending on THA concentration. Micromolar THA concentrations blocked muscarinic-receptor-mediated inhibition of cAMP formation and stimulation of phosphoinositide (PI) hydrolysis with poor selectivity between the two responses. While both responses were blocked in the same concentration range (4-60 mumol/l), non-competitive antagonism of PI hydrolysis occurred at THA concentrations greater than 10 mumol/l while competitive antagonism was displayed for the cAMP response at concentrations of THA up to 40 mumol/l. THA was equally effective at inhibiting PI hydrolysis stimulated by histamine, phenylephrine or oxotremorine-M, when these agonists were employed in concentrations equal to their EC50s for the response. THA did not antagonize PI hydrolysis mediated by the quisqualate receptor at any agonist concentration used. Furthermore, THA blocked carbachol- but not morphine-induced inhibition of forskolin-stimulated cAMP formation in the striatum.

Cross-talk between m1 muscarinic acetylcholine and beta 2-adrenergic receptors. cAMP and the third intracellular loop of m1 muscarinic receptors confer heterologous regulation

Genes encoding the m1 muscarinic (m1 mAChR) and beta 2-adrenergic receptors (beta 2AR) were stably co-expressed into Chinese hamster ovary (CHO) cells to study receptor regulation and cross-talk. Persistent activation of the beta 2AR/adenylate cyclase pathway by isoproterenol leads to heterologous desensitization, internalization, and down-regulation of the m1 mAChR which is comparable, but smaller in magnitude, with that seen with persistent activation of the m1 mAChR by carbachol. This heterologous effect was mimicked by dibutyryl cAMP and forskolin and antagonized by the protein kinase A (PKA) inhibitor H-8. A potential consensus sequence for phosphorylation by PKA (Lys351-Arg-Lys-Thr354) exists on the third intracellular loop of the m1 mAChR, suggesting that receptor phosphorylation by PKA may be involved in heterologous regulation. The loss of m1 mAChRs induced by carbachol was not reversed by H-8, indicating that homologous regulation is not dependent on PKA. Recent evidence suggests that muscarinic agonist-mediated internalization of the m1 mAChR involves the third intracellular loop (i3) (Maeda, S., Lameh, J., Mallet, W. G., Philip, M., Ramachandran, J., and Sadee, W. (1990) FEBS Lett. 269, 386-388). Three deletion mutant receptors were constructed in which the majority, or small regions, of i3 were eliminated but the membrane proximal portions of the loop were left intact. Each of the mutants was co-expressed with the beta 2AR in CHO cells. A small region in i3 was identified which is crucial for carbachol- and isoproterenol-promoted internalization and down-regulation. This region contains a series of 6 serine residues within an 8-amino acid stretch. A similar domain has been identified in the carboxyl tail of the beta 2AR and has been proposed to participate in receptor internalization (Hausdorff, W. P., Campbell, P. T., Ostrowski, J., Yu, S. S., Caron, M. G., and Lefkowitz, R. J. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 2979-2983).

Peak bone mass and affecting factors in Korean women

Maximizing peak bone mass is advocated as a way to prevent osteoporosis. To evaluate the peak bone mass and the affecting factors in Korean women, we analyzed bone stiffness in 116 middle school students, 118 high school students and 115 female college students by using the Achilles densitometer (Lunar Corporation). Peak bone stiffness of Korean women was relatively lower than that of white women (94% of white women) and a rapid rise of bone stiffness was observed in those subjects 3-4 years after menarche. In adolescent females without menstruation, the bone stiffness was lower than that of adolescent girls with menstruation. The factors affecting the peak bone mass was similar to the risk factors of post menopausal osteoporosis: menstruation status, calcium intake and physical activity. The amount of calcium intake in Korean girls at the critical age (3-4 years after menarche) was lower than the RDA (requirement of daily allowance) at this age. To improve any program aimed at maximizing peak bone mass, further intensive study will be required to evaluate some other common factors affecting peak bone mass in Korean.

Impaired beta-adrenergic receptor stimulation of cyclic adenosine monophosphate in human septic shock: association with myocardial hyporesponsiveness to catecholamines

OBJECTIVES

To determine whether myocardial hyporesponsiveness to administered catecholamines occurs in human sepsis and whether this phenomenon is associated with impaired beta-adrenergic receptor stimulation of cyclic adenosine monophosphate.

DESIGN

Prospective study.

SETTING

Medical ICU in a university hospital.

PATIENTS

Normal human volunteers (n = 7), critically ill patients who were not septic (n = 9), septic patients not in shock (n = 16), and septic patients in shock (n = 17).

MEASUREMENTS AND MAIN RESULTS

Pulmonary artery catheter-derived hemodynamic data were obtained in patients with sepsis and septic shock. Isoproterenol and sodium fluoride-stimulated cyclic adenosine monophosphate accumulations were measured in circulating lymphocytes. The hemodynamic response to sequential infusions of dobutamine, 5 and 10 micrograms/kg/min, was obtained in septic and septic shock patients. Baseline hemodynamic values for mean arterial pressure, cardiac index, left ventricular stroke work index, and oxygen delivery index at approximately 2 days after the onset of sepsis were significantly lower in septic shock patients compared with septic (nonshock) patients (p < .01 p < .05, p < .001, p < .01, respectively). Isoproterenol- and sodium fluoride-stimulated cyclic adenosine monophosphate accumulations were significantly reduced in septic shock patients compared with those accumulations observed in septic patients (p < .01 and p < .001, respectively). The heart rate response to 10 micrograms/kg/min of dobutamine was significantly (p < .01) lower in septic shock patients compared with septic patients.

CONCLUSIONS

In patients with septic shock, impaired beta-adrenergic receptor stimulation of cyclic adenosine monophosphate is associated with myocardial hyporesponsiveness to catecholamines, suggesting that beta-adrenergic receptor dysfunction may contribute to the reduced myocardial performance observed in this shock state.

Modulation by certain conserved aspartate residues of the allosteric interaction of gallamine at the m1 muscarinic receptor

Muscarinic acetylcholine receptors belong to a superfamily of G-protein coupled receptors and contain within their structure several conserved aspartate residues. These residues have been implicated to play important roles in the interaction of agonists and their competitive antagonists with the receptor. In the present work, we investigated whether the same residues might also serve as important contact points for allosteric antagonists of muscarinic receptors, because the majority of these compounds are cationic in nature, or if such residues are involved in modification of receptor conformation by these antagonists. Gallamine was used as a prototype for these antagonists. Site-directed mutagenesis of the m1 muscarinic receptor subtype was utilized to define some of the molecular determinants involved in cooperative allosteric interactions. We report that substitution of the aspartate residue at position 71, but not at positions 99 and 122 with asparagine, affected the affinity of gallamine for the unliganded m1 receptor. A similar substitution at positions 71 and 99 decreased the magnitude of its cooperative effects on the binding of [3H]N-methylscopolamine. Our data suggest that these residues are implicated in cooperative interactions. At present, however, we cannot discount a more pivotal role of other residues on the receptor sequence in allosteric interactions. The data also support the notion that different molecular entities are required for the binding of allosteric antagonists as compared to the interaction of agonists and competitive antagonists at the receptor.

Skene's duct cysts in female newborns

The Skene's duct cyst, which presents as a cystic mass just around the urethral meatus, is a rare congenital abnormality in the female newborn. Following a search of available literature we have been able to find Skene's duct cyst reported in only 10 newborns. Herein we report seven cases of Skene's duct cysts in female neonates that were recorded in a 5-year period (June 1984 through May 1989) among 14,518 female births at the Fatima Hospital. In these cases we found that Skene's duct cysts in the female newborn had characteristic morphological and clinical features helpful for diagnosis without a complete urologic evaluation. Needle aspiration of the cyst content provides diagnostic information as well as therapeutic effect. Treatment consisted of partial excision of the cyst wall and needle aspiration. In the initial two cases we performed partial excision of the cystic wall for the purpose of doing tissue examination and drainage of the cyst, but in the following five cases we carried out only needle aspiration. The results of both were excellent without recurrence.

Reproductive outcome after microsurgery for proximal and distal occlusions in the same fallopian tube

The reproductive outcome after microsurgery for both proximal and distal occlusions in the same fallopian tube has been reported in only small numbers of women. Our case series is in agreement with other series and shows that microsurgery for correction of both proximal and distal occlusions in the same fallopian tube yields only modest fertility and may predispose to ectopic tubal pregnancies.

Reproductive outcome after unilateral tubocornual anastomosis and contralateral salpingostomy by microsurgery

A unilateral tubocornual anastomosis and a contralateral salpingostomy for unilateral proximal and contralateral distal occlusive disease yield similar fertility as does pure tubocornual anastomosis for proximal occlusive disease. Ascending inflammation is postulated as the mechanism for tubal occlusion, with distal sparing from disease if the initial insult results in initial occlusion of the proximal portion of the oviduct.

Allosteric interactions at the m1, m2 and m3 muscarinic receptor subtypes

The purpose of our study was to investigate the interactions of allosteric antagonists at the individual m1, m2 and m3 muscarinic receptor subtypes. This was achieved through the use of transformed Chinese hamster ovary cells stably expressing the rat m1 or m3 receptor genes. A homogeneous population of the m2 subtype was obtained from rat heart tissue. Our data indicate that the cardioselective antagonists (gallamine, methoctramine, AF-DX 116 and himbacine) display the following rank order of potency for both displacing ligand binding to the primary site on the receptor and allosterically decelerating ligand dissociation: m2 greater than m1 greater than m3. Schild analysis showed the following rank order of the magnitude of gallamine's cooperative interactions with the three receptor subtypes: m3 greater than m1 greater than m2. By comparison, the ion-channel blockers (verapamil, phencyclidine and quinidine) exhibited a rank order of potency for cooperative effects similar to that of cardioselective antagonists; however, these blockers did not show appreciable specificity in their interaction with the receptor primary binding site. There was a lack of correlation between the displacement of ligand binding and the allosteric potencies of the allosteric antagonists at each of the three muscarinic receptor subtypes, thus revealing the complex nature of interaction (both competitive and allosteric) between many of these compounds with the muscarinic receptor. Despite the fact that the majority of allosteric muscarinic antagonists are also K+ channel blockers, the use of pertussis toxin did not support the notion that this channel represents the allosteric site coupled to the receptor.

Effects of canine endotoxin shock on lymphocytic beta-adrenergic receptors

To determine whether beta-adrenergic receptors on circulating lymphocytes are impaired during endotoxemia and the precise role of catecholamines in this process, we allocated 16 dogs to three groups: I) control-saline vehicle (n = 5), II) endotoxin--Escherichia coli endotoxin 1.0 mg/kg iv bolus (n = 6), and III) endotoxin + propranolol--E. coli endotoxin 1.0 mg/kg after pretreatment with propranolol, 1.5 mg/kg iv bolus followed by a continuous infusion, 30 micrograms/kg per min, (n = 5). Five hours after endotoxin injection, lymphocytic beta-adrenergic receptor number and sodium fluoride (NaF)-stimulated cyclic AMP accumulation were reduced by 41 +/- 6% and 25 +/- 7% of baseline values, respectively, which were significantly different from those observed in the control group (both P less than .01). Propranolol pretreatment prevented the endotoxin-induced reduction in lymphocytic beta-adrenergic receptor number (P less than .02 compared with the endotoxin group), but not the decrease in NaF-stimulated cyclic AMP accumulation (P less than .01 compared with the control group). Myocardial beta-adrenergic receptor number was reduced in the endotoxin group compared with that observed in the control group (P less than .06). These changes were associated with a decreased chronotropic response to isoproterenol in the endotoxin group compared with the control group (P less than .05). We conclude that decreased lymphocytic beta-adrenergic receptor number in endotoxin shock is caused by circulating catecholamines, whereas alterations distal to the receptors may be due to other mechanisms.

[Influence of stress experience on change of attention]

For a man to maintain attention, he needs to keep a certain level of arousal. An inordinate increase or decrease in the level of arousal eventually has a negative influence on attention. Precedent research has shown that the degree of attention changes when an experience of stress is related to anxiety resulting in a rise in arousal. This research was done to examine this hypothesis by looking at the 27 female students, 14 of whom had failed in the annual examination. The results of the investigation are as follows: The stress of failure in the examination was seen to raise the level of physiological arousal. Although pulse and electromyography showed no significant change, further inquiries should be made based on other types of methodology. In spite of the rise of arousal, the performance of selective task was degraded. This suggests those students failed to give moderate attention to given information for that kind of task. But the exact reason of that failure was not identified: that is it was difficult decide whether they gave too much attention to the anxiety brought about by stress. Performance of integral tasks, however, did not show any degradation. Judging from these results, stress seems to exert significant influence on attention in the selection of the appropriate information among the various options given. This offers an important hint in relation to the health care situation where nursing information is offered. Clients who receive nursing information in stressful situations may have difficulty in separating and selecting this helpful information from other options which they have acquired through their life experience. The content and terminology of nursing information may be strange and unintelligible to clients, although they are quite familiar and distinct to nurses. So, it is desirable for nurses to give, in addition and at the same time when nursing information is given, some certain related information as devices for selection, instead of merely giving nursing informations as such. So far it is not clear whether the concepts of information processing theory can be suitably applied to nursing. However, it is obvious, according to this research, that the quality of attention is disturbed in the stress situation. This is why further inquiries should be made into attention in practical nursing situation.

The allosteric binding profile of himbacine: a comparison with other cardioselective muscarinic antagonists

The possibility of an allosteric interaction by himbacine, a cardioselective antagonist, with rat cardiac muscarinic receptors was studied. Himbacine allosterically decelerated the dissociation of bound [3H]N-methylscopolamine [( 3H]NMS) in a concentration-dependent manner with an IC50 value of 103.7 microM. When compared to the IC50 values of other cardioselective antagonists, the rank order of potencies was: methoctramine greater than gallamine greater than himbacine greater than AF-DX 116. In contrast, the potencies of these compounds to displace [3H]NMS binding were: himbacine greater than methoctramine greater than AF-DX 116 greater than gallamine. The allosteric potencies were found not to be correlated with binding potencies (correlation coefficient = -0.15). A striking common feature of the cardioselective antagonists is their ability to bind to an allosteric site on cardiac muscarinic receptors.

Different mechanisms of antagonism by methoctramine of two neuronal muscarinic receptor-mediated second messenger responses

The allosteric effects and subtype selectivity of methoctramine on neuronal muscarinic receptors in N1E-115 cells and two different rat brain regions (cerebral cortex and striatum) were assessed. Saturation isotherms of [3H]N-methylscopolamine binding, performed in N1E-115 cells and dissociated cerebral cortex, showed that methoctramine reduced the Bmax in a concentration-dependent manner. Furthermore, this compound slowed the rate of dissociation of bound [3H]N-methylscopolamine in the same tissue preparations. Low concentrations of methoctramine (less than or equal to 1 microM) antagonized the M1-linked phosphoinositide response in N1E-115 cells and dissociated cerebral cortex in an apparent competitive mechanism. However, methoctramine exhibited noncompetitive effects at higher concentrations in N1E-115 cells. Observation of a similar effect in cerebrocortical cells was precluded since methoctramine by itself, at concentrations higher than 1 microM, stimulated inositol phosphate formation. The stimulatory effect of methoctramine on phosphoinositide hydrolysis was not blocked by atropine. A solely competitive mode of antagonism by methoctramine was observed for the inhibition of cAMP formation (a noncardiac-M2 coupled response) in N1E-115 cells and dissociated striatum. This antagonism was evident even at concentrations of methoctramine that noncompetitively antagonized the M1 response. Anomalously, methoctramine alone inhibited cAMP formation in dissociated striatum at concentrations of greater than or equal to 30 microM. Atropine was ineffective at blocking this effect. Methoctramine failed to demonstrate muscarinic receptor subtype selectively in blocking these two second messenger responses. This nonselectivity was supported by indirect binding experiments involving methoctramine and [3H]N-methylscopolamine. The data presented here demonstrate that methoctramine binds to a secondary site(s) associated with neuronal muscarinic receptors. Furthermore, methoctramine exhibits different mechanisms of antagonism and displays poor selectivity for the M1-linked phosphoinositide and noncardiac-M2 linked cAMP responses.

Mixed competitive and allosteric antagonism by gallamine of muscarinic receptor-mediated second messenger responses in N1E-115 neuroblastoma cells

The antagonistic effects of gallamine on muscarinic receptor-linked responses were investigated in N1E-115 neuroblastoma cells. M1 muscarinic receptor-mediated phosphoinositide hydrolysis induced by carbamylcholine was antagonized by gallamine, with a Ki value of 33 microM. By comparison, gallamine was four- to fivefold less potent in blocking noncardiac M2 muscarinic receptor-mediated inhibition of cyclic AMP formation, with a Ki value of 144 microM. The resulting Arunlakshana-Schild plots of the antagonism of both responses by gallamine were linear and exhibited slopes not differing from 1, a result indicative of a competitive mechanism. To elucidate further the nature of gallamine's inhibitory actions, experiments were performed where the effects of gallamine in combination with the known competitive muscarinic antagonist, N-methylscopolamine (NMS), were studied. In the presence of both antagonists, a supraadditive shift in the carbamylcholine dose-response curve was demonstrated for the two responses, a result suggestive of an allosteric mode of interaction between gallamine and NMS binding sites. Confirmation that gallamine allosterically modifies the muscarinic receptor was provided by radioligand binding studies. Gallamine competition curves with either [N-methyl-3H]scopolamine methyl chloride ([3H]NMS) or [N-methyl-3H]quinuclidinyl benzilate methyl chloride ([3H]NMeQNB) were unusually shallow. Furthermore, gallamine decelerated the rate of dissociation of receptor-bound [3H]NMS greater than [3H]NMeQNB in a dose-dependent manner. The present study demonstrates that whereas gallamine antagonizes carbamylcholine-mediated responses in N1E-115 cells in a competitive manner, an allosteric component of its action is revealed in the presence of muscarinic antagonists such as NMS.

Methoctramine, a cardioselective muscarinic antagonist, stimulates phosphoinositide hydrolysis in rat cerebral cortex

The cardioselective muscarinic antagonist methoctramine antagonized carbamylcholine-mediated phosphoinositide (PI) hydrolysis in a concentration-dependent fashion in dissociated rat cerebrocortical cells. However, as the concentration of methoctramine was increased above 5 microM, there was a reversal of the antagonism of the PI response. In the absence of carbamylcholine, methoctramine by itself significantly increased PI hydrolysis with a maximal effect at 30 microM. Various classes of receptor antagonists, including atropine, and ion-channel blockers were unable to block methoctramine-stimulated PI hydrolysis.

Effects of aging on the interaction of quinuclidinyl benzilate, N-methylscopolamine, pirenzepine, and gallamine with brain muscarinic receptors

The objective of the present study was to investigate the effects of senescence on the binding characteristics of muscarinic receptors by using [3H]quinuclidinyl benzilate ([3H]QNB) and [3H]N-methylscopolamine ([3H]NMS) as ligands in young (3 months), middle-age (10 months) and old (24 months) male Fischer 344 rats. Muscarinic receptor density was found to decrease significantly with aging in certain brain regions, depending on the ligand employed. Moreover, the relative proportions of M1 and M2 muscarinic receptor subtypes was not significantly altered by aging, except in the aged striatum. Furthermore, the dissociation kinetics of [3H]NMS in the cerebral cortex and their allosteric modulation by gallamine were only slightly influenced by age.

Non-selectivity of amitriptyline for subtypes of brain muscarinic receptors demonstrated in binding and functional assays

The characteristics of interaction of amitriptyline, a tricyclic antidepressant, with rat brain muscarinic receptors were assessed using both radioligand binding and functional assays. In competition studies, amitriptyline displaced muscarinic ligand binding from a single high-affinity site in homogenates of various brain regions which have a different distribution of M1 and M2 receptor subtypes. The affinity of amitriptyline for muscarinic receptors was also comparable in all brain regions. Furthermore, amitriptyline identified a single species of muscarinic receptors in intact cells dissociated from the cerebral cortex and in cerebrocortical slices. The non-selectivity of amitriptyline for muscarinic receptor subtypes in these preparations was in contrast to the selectivity exhibited by pirenzepine. This non-selective nature of amitriptyline was also evident in functional assays, since this antidepressant was equipotent at antagonizing M1-mediated increase in phosphoinositide hydrolysis and M2-mediated inhibition of cyclic AMP formation in dissociated cortical cells. Atropine was also equipotent at blocking both responses but was 20- to 30-fold more potent than amitriptyline. These results demonstrate that amitriptyline behaves as a non-selective muscarinic antagonist using both radioligand binding and functional measurements.

Influence of ligand choice on the apparent binding profile of gallamine to cardiac muscarinic receptors. Identification of three main types of gallamine-muscarinic receptor interactions

The binding profile of the positively charged muscarinic antagonist, gallamine, was studied in rat heart homogenates. A proportion of the binding sites labeled by the tertiary muscarinic ligands [( 3H]quinuclidinyl benzilate (QNB) and [3H]atropine) were inaccessible to their quaternary analogs [( 3H]N-methyl-QNB (NMeQNB) and [3H]-N-methylscopolamine (NMS)] or gallamine. Whereas gallamine displaced the binding of [3H]NMeQNB with high affinity, biphasic competition curves were observed using [3H]NMS only at higher ligand concentrations. The rank order of potency of gallamine in allosterically decelerating ligand dissociation kinetics was: [3H]NMS greater than [3H]atropine greater than [3H]NMeQNB greater than [3H]QNB. Our calculations demonstrate that the displayed heterogeneity of gallamine binding sites detected using [3H]NMS, but not the tertiary ligands, might be accounted for by the allosteric modification of the binding of this ligand by gallamine. Based on these findings, the exhibited binding profile of gallamine to muscarinic receptors is influenced strongly by ligand choice, and also by the ligand concentration used in the binding experiment. Furthermore, it is concluded that gallamine binds to three major sites on the muscarinic receptor, thereby revealing an apparent heterogeneity of its binding sites, even in a tissue which presumably possesses one major muscarinic receptor subtype such as the heart. According to several lines of evidence, gallamine binds competitively and with high affinity to NMS-accessible sites on the receptor. Under certain experimental conditions, it also appears to identify another low-affinity site, either due to its binding to NMS-inaccessible sites or through its differential ability to alter the binding of ligands to the main binding domain on the receptor in an allosteric fashion.

Three-year follow-up of risk factors correlated with new atherothrombotic brain infarction in 708 elderly patients

A prospective study correlated cigarette smoking, systolic or diastolic hypertension, diabetes mellitus, hypercholesterolemia, low serum high-density lipoprotein cholesterol, hypertriglyceridemia, and obesity with development of new atherothrombotic brain infarction in 192 elderly men and 516 elderly women. Mean follow-up was 36 +/- 6 months (range 19-39). New atherothrombotic brain infarction occurred in 24 of 192 men (13%) and in 63 of 516 women (12%), difference not significant. Risk factors for atherothrombotic brain infarction in elderly men were cigarette smoking (p less than 0.001), systolic or diastolic hypertension (p less than 0.001), and diabetes mellitus (p less than 0.005). Risk factors for atherothrombotic brain infarction in elderly women were systolic or diastolic hypertension (p less than 0.001), diabetes mellitus (p less than 0.001), and obesity (p less than 0.005).

The effects of intraruminal infusions of urea, casein, glucose syrup and a mixture of casein and glucose syrup on nitrogen digestion in the rumen of cattle receiving grass-silage diets

In an incomplete 5 X 5 Latin square experiment, four cattle were given grass silage in two meals per d to satisfy 1.15 maintenance energy requirements. In addition, water or casein (21 g nitrogen and 0.17 kg organic matter (OM)/d) or urea (U; 28 g N/d) or a glucose syrup (G; 0.87 kg OM/d) or casein and glucose syrup (CG; 17 g N and 0.93 kg OM/d) were infused intraruminally at a constant rate. A 24 h collection of duodenal digesta was made using chromic oxide for flow estimation and 35S as a marker of microbial N entering the small intestine. Samples of rumen fluid were also taken for estimation of rumen pH, and concentrations of ammonia-N and volatile fatty acids. The intraruminal infusions had no significant effects on rumen pH, concentrations of volatile fatty acids or their molar proportions. Infusion of either C or U significantly (P less than 0.05) increased rumen NH3-N concentrations whereas infusions of either G or CG lowered rumen NH3-N concentrations. Infusions of C or U had no significant effect on the quantities of OM, acid-detergent fibre (ADF) or N constituents which entered the small intestine. Infusions of G or CG increased the quantities of OM (G P less than 0.05, CG P less than 0.01), ADF (CG P less than 0.05), non-NH3-N (G P less than 0.05, CG P less than 0.01), amino acid N (G P less than 0.05, CG P less than 0.01) and microbial N (G P less than 0.05, CG P less than 0.01) which entered the small intestine. The efficiency of rumen microbial N synthesis was unchanged by the infusion of C, U or G (P greater than 0.05) but increased significantly (P less than 0.05) when CG were infused.

Risk factors for atherothrombotic brain infarction in persons over 62 years of age in a long-term health care facility

A history of systolic (greater than or equal to 160 mm Hg) or diastolic (greater than or equal to 90 mm Hg) hypertension, diabetes mellitus (fasting venous plasma glucose greater than or equal to 140 mg/dl), a history of cigarette smoking, fasting serum total cholesterol greater than or equal to 200 mg/dl and greater than or equal to 250 mg/dl, and obesity (greater than or equal to 20% above ideal body weight) were examined as risk factors for atherothrombotic brain infarction (ABI) in 144 men, mean age 81 +/- 8 years, and 391 women, mean age 82 +/- 8 years, in a long-term health care facility. ABI occurred in 33 of 144 men (23%) and in 68 of 391 women (17%), P not significant. A history of systolic or diastolic hypertension correlated with ABI in both men and women (P less than 0.001). Diabetes mellitus correlated with ABI in both men and women (P less than 0.001). A history of cigarette smoking correlated with ABI in men (P less than 0.02) but not in women. Serum total cholesterol greater than or equal to 200 mg/dl and greater than or equal to 250 mg/dl did not significantly correlate with ABI in men or in women. Obesity did not significantly correlate with ABI in men or in women. Systolic or diastolic hypertension, diabetes mellitus, and cigarette smoking are risk factors for ABI in elderly men. Systolic or diastolic hypertension and diabetes mellitus are risk factors for ABI in elderly women.

Risk factors for coronary artery disease in persons older than 62 years in a long-term health care facility

A history of smoking 5 to 60 cigarettes per day, hypercholesterolemia (fasting total serum cholesterol 200 mg/dl or more), history of systolic (160 mm Hg or more) or diastolic (90 mm Hg or more) hypertension, diabetes mellitus (fasting venous plasma glucose 140 mg/dl or more) and obesity (at least 20% above ideal body weight) were correlated with coronary artery disease (CAD) in 138 men (mean age 82 +/- 8 years) and 380 women (mean age 82 +/- 8 years) in a long-term health care facility. CAD occurred in 43 of 138 men (31%) and in 103 of 380 women (27%), difference not significant. A history of smoking 5 to 60 cigarettes per day significantly correlated with CAD in men (p less than 0.001) but not in women. Hypercholesterolemia significantly correlated with CAD in both men (p less than 0.001) and women (p less than 0.005). A history of systemic hypertension significantly correlated with CAD in women (p less than 0.001) but not in men. Diabetes mellitus did not significantly correlate with CAD in men or women but weakly correlated with CAD in men plus women (p less than 0.05). Obesity did not significantly correlate with CAD in men or women. Hypercholesterolemia, a history of smoking 5 to 60 cigarettes per day, and a history of systemic hypertension were considered major risk factors. Having 2 or 3 major risk factors correlated with CAD significantly better than having no or 1 major risk factor in both elderly men (p less than 0.001, p less than 0.01) and women (p less than 0.001).

Ca2+ transport by chondrocyte mitochondria of the epiphyseal growth plate

In a study of the Ca2+ kinetics of mitochondria of chick epiphyseal chondrocytes, the rate of Ca2+ uptake was linear up to a medium Ca2+ concentration of 30 mum. The half maximal transport rate occurred at 34 mum Ca2+. The Ca2+ uptake rate, expressed as a function of time, was 35 nmoles/mg protein/min; the presence of Mg2+ had little effect on Ca2+ accumulation. While these kinetic parameters did not differ significantly from mitochondria of cells of nonmineralizing tissues, the respiratory characteristics of the chondrocyte organelles exhibited functional differences. Thus, up to 350 nmoles Ca2+/mg protein, chondrocyte mitochondria performed coupled oxidative phosphorylation. Calcium uptake was energy supported, while Ca2+ binding was low. Addition of respiratory inhibitors and uncouplers to these mitochondria resulted in a rapid loss of more than 80% of the total Ca2+. The Ca/Pi ratio of the extrudate was very similar to the ratio of the ions in cartilage septum fluid. In the most mineralized zones of the epiphyseal plate, there was little change in the state 4 respiratory rate, but nonspecific Ca2+ binding was elevated and a high percentage of the total Ca2+ was in a nonextrudable form. The results indicate that in cells preparing for mineralization, much of the total mitochondrial Ca2+ is in a form that can be transported to the calcification front. In cells close to the calcification front, nonextrudable Ca2+ may form calcium phosphate granules described by other investigators.

Heterogeneity of chondrocyte mitochondria. A study of the Ca2+ concentration and density banding characteristics of normal and rachitic cartilage

Previous morphological studies of the mineralizing epiphysis suggested that some mitochondria were concerned with Ca2+ accumulation while others were associated with cellular energetics and metabolism. To determine if there was mitochondrial heterogeneity in chondrocytes of the epiphyseal growth plate, mitochondria were isolated from four different regions of the plate and subjected to continuous sucrose gradient centrifugation. Centrifugation of the organelles in a narrow density sucrose gradient (1.5--2.0 M) in the presence of inhibitors of Ca2+ transport (ruthenium red and 5,5'-dithiobis-(2-nitrobenzoic acid)) revealed that considerable heterogeneity existed. In the least calcified zone 20% of the mitochondria formed a low density band of low Ca2+ concentration (309 nmol/mg protein). Organelles isolated from more calcified tissue zones showed a concomitant increase in Ca2+ concentration (up to 5700 nmol/mg protein) as well as an increase in the total percentage of mitochondria sedimenting in 2.0 M sucrose. The banding patterns of mitochondria isolated from rachitic and hypertrophic cartilage were similar. In addition, similarities were also noted in the Ca2+ concentration and the cytochrome oxidase activities of mitochondria of these tissues. During recovery from the rachitic condition, there was a change in the density centrifugation characteristics of this tissue and a substantial increase was noted in the proportion of mitochondria sedimenting in 2.0 M sucrose. The Ca2+ concentration of mitochondria of this rapidly calcifying tissue suggested that the critical Ca2+ concentration necessary for initiation of the calcification mechanism was 4 mumol/mg protein.

Calcium accumulation by chondrocyte mitochondria

Chick epiphyseal plate mitochondria observed in vitro suggest that energy dependent Ca++ uptake was maximal in the presence of ATP and a respiratory substrate. However, nucleotides other than ATP had no effect on this type of cation uptake. The observation that Ca++ accumulation was sensitive to the presence of 2,4-DNP and a number of respiratory inhibitors suggested that the mechanism of cation accumulation was similar to that described in tissues that do not undergo biological mineralization. Non-energy supported Ca++ acumulation was studied in the presence of rotenone and antimycin A. Under these conditions, the amount of Ca++ bound by skeletal tissue mitochondria was greater than bound by mitochondria obtained from noncalcifying tissues. Following isopycnic centrifugation, the Ca++ loaded mitochondria banded at different sucrose densties but the Ca++ affinity of mitochondria at each density band was similar. Hence, no particular mitochondrial species seems to be responsible for cation transport.