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An analysis on the outcome of 124 inseminations monitored using daily milk progesterone concentration data revealed that those cows in which pregnancy did not occur experienced a 1.7day delay in post-ovulatory luteal progesterone rise when compared to the pregnant group (P

1. Transport of l-arginine and the nitric oxide synthase inhibitors NG-monomethyl-l-arginine and NG-nitro-l-arginine was investigated in human erythrocytes from healthy donors and uraemic patients on haemodialysis. 2. Although Km values for total l-arginine influx were not significantly different in erythrocytes freshly isolated from controls or uraemic patients, uraemia was associated with an increase in the Vmax for transport (826 compared with 1176 μmol h−1 l−1 of cells) which was reduced to control values after dialysis. 3. Saturable influx of l-arginine was mediated by the classical cationic amino acid transport system y+ and system y+L, known to transport cationic and neutral amino acids with higher affinity. 4. Under zero-trans conditions, the Vmax for l-arginine transport via system y+ increased from 271 to 700 μmol h−1 l−1 of cells in uraemia, while Km values increased from 44 to 94 μmol/l. Dialysis had no significant effect on the kinetic parameters altered by uraemia. 5. Under zero-trans conditions, and with system y+ inhibited by N-ethylmaleimide (0.2 mmol/l), transport of l-arginine via system y+L was unaffected by uraemia. 6. Saturable influx of NG-monomethyl-l-arginine was also mediated by systems y+ (Km = 56 μmol/l, Vmax = 353 μmol h−1 l−1 of cells) and y+L (Km = 17 μmol/l, Vmax = 51.3 μmol h−1 l−1 of cells) and, as with l-arginine, uraemia increased the transport capacity for NG-monomethyl-l-arginine. 7. Influx of the neutral nitric oxide synthase inhibitor NG-nitro-l-arginine was not readily saturable. 8. Intracellular concentrations of l-arginine and NG-monomethyl-l-arginine were significantly increased in erythrocytes from uraemic patients when compared with controls, consistent with an increased transport capacity for l-arginine and NG-monomethyl-l-arginine. 9. The present study provides evidence that system y+ mediates the increased transport of l-arginine and NG-monomethyl-l-arginine in human erythrocytes from patients with chronic renal failure. Our findings may have implications for the activity of the l-arginine—nitric oxide signalling pathway in vascular endothelial and smooth-muscle cells in uraemia.

The overall effects of oestrogen on the vasculature are beneficial as a result of its antioxidant properties and ability to enhance relaxation by modulating synthesis of endothelium-derived vasodilators and smooth-muscle cell Ca2+ signalling. Although the protective effects of oestrogen are well accepted, only limited and conflicting data are available on the cellular mechanisms mediating steroid action in the vasculature. Discrepancies in cell culture experiments may reflect differences in culture conditions, the origin of cells and/or hormonal status. For example, umbilical vein endothelial cells isolated from gestational diabetic pregnancies exhibit phenotypic changes that are maintained during prolonged cell culture [42,75]. As gender differences in vascular reactivity have long been reported [76-78], gender needs to be taken into account in interpreting vascular responses to oestrogen in animal models. Further research is required to characterize the non-genomic actions of oestrogen in the vasculature. Whether activation of non-genomic receptors by physiologically relevant plasma concentrations of oestrogen modulates the activity of endothelial cell NOS, cyclo-oxygenase and superoxide dismutase and smooth-muscle cell Ca2+ ion channel activity remains to be investigated. Prolonged exposure of the vasculature to circulating steroid hormones may more closely reflect in vivo conditions, since oestrogen is known to enhance endothelium-dependent relaxation in response to some agonists [79].

During the last 10 years, the role of oxidative stress in pancreatitis and the benefits or otherwise of antioxidants has been the subject of numerous research papers. There is general agreement that glutathione and other sulphydryl compounds are depleted while lipid peroxidation is increased in pancreatic tissue during the development of acute pancreatitis. Treatment with antioxidants has been shown to reduce acinar cell injury and oedema in various animal models of pancreatitis, suggesting that the sustained generation of reactive oxygen species depletes cellular antioxidant defences. Evidence for a role for bradykinin and nitric oxide in pancreatitis has been conflicting with some studies suggesting these agents might ameliorate pancreatic dysfunction by enhancing pancreatic blood flow and secretion in response to bradykinin-stimulated generation of nitric oxide from endothelium, while other studies suggest that nitric oxide potentiates pancreatic oxidative stress. Thus, there is clearly a need for well-designed clinical trials to evaluate the protective role of antioxidant therapy in acute pancreatitis.

The effects of exogenous insulin, glucagon and streptozotocin-diabetes on influx (15 s) of L-lysine via a cationic amino acid transporter resembling system y+ were investigated in the isolated perfused rat pancreas. In non-diabetic pancreata, transport of L-lysine was saturable with an apparent Km of 2.11 +/- 0.29 mM and Vmax of 2.21 +/- 0.20 mumol min-1 g-1 (n = 6). Bovine insulin (100 mu u ml-1) increased the maximal transport rate (Vmax = 3.49 +/- 0.30 mumol min-1 g-1, n = 4, P < 0.05) for L-lysine 1.6-fold without altering the Km. L-Lysine transport was not elevated significantly in diabetic pancreata, although insulin (100 mu u ml-1) enhanced transport to values measured in non-diabetic preparations. Human glucagon (1.5 x 10(-9) M) had no stimulatory effect on L-lysine transport. These findings provide the first evidence that exogenous insulin stimulates cationic amino acid transport activity in the exocrine pancreatic epithelium. Activation of the cationic pancreatic amino acid transporter may provide a mechanism to enhance the supply of L-arginine and thus sustain nitric oxide-mediated pancreatic secretion in response to islet hormones and secretagogues.

We have investigated changes in endometrial oxytocin receptor concentrations and prostaglandin F2 alpha release in response to exogenous oxytocin treatment in ovariectomized cows treated with progesterone and oestradiol, and made comparisons with similar treatment in cyclic cows. In long-term ovariectomized cows, endometrial oxytocin receptors were present (300 fmol mg-1 protein), but no prostaglandin F2 alpha was released in response to oxytocin treatment until after the administration of progesterone. Subsequent administration of a concentration of oestradiol sufficient to induce oestrus resulted in the downregulation of these receptors and the loss of oxytocin responsiveness, which did not reappear within 20 days in the absence of further hormone treatment. When induced oestrus was followed by further treatment with luteal phase concentrations of progesterone and oestradiol, both oxytocin receptors and oxytocin-stimulated release of prostaglandin F2 alpha reappeared by day 16 after oestrus, in a pattern similar to that seen during the luteal phase of cyclic cows. These results demonstrate how progesterone and oestradiol control the development and responsiveness of endometrial oxytocin receptors in cows, and provide a valuable model in which to investigate further the precise control of the oxytocin receptor in this species.

Three cases of multiple osteochondromatosis are reported among 843 skeletons excavated from the site of the ancient city of Jericho. Radiocarbon dating and archaeological evidence both suggest that two of the skeletons date from about 1700 BC. These skeletons represent the earliest known cases of diaphyseal aclasis.

Microvascular permeability was studied in the isolated perfused rat pancreas using a rapid multiple indicator-dilution technique. Capillary extractions, permeability-surface area products (PS), and extravascular volumes of distribution (EVV) were determined for 22Na+, 51Cr-labeled EDTA, [57Co]-cyanocobalamin (B12), and 125I-labeled insulin at various perfusion flows. Permeability to albumin was negligible. PS for Na+ and EDTA increased with increasing flow, whereas PS for cyanocobalamin and insulin approached diffusion-limited exchange at flows greater than 3 ml.min-1.g-1. Permeability coefficients for Na+, EDTA, B12, and insulin were 36, 22, 11, and 3.48 x 10(-5) cm/s, respectively, and the permeability ratio for B12/insulin (3.16) indicated restricted diffusion to insulin. In the presence of unlabeled B12 and insulin EVV (0.15-0.19 ml/g) for EDTA, B12 and insulin approximated the interstitial volume. Caerulein-induced pancreatitis or treatment with the synthetic protease inhibitor camostate had no significant effects on permeability. In caerulein-treated rats, EVV for B12 was elevated (0.17 +/- 0.01 vs. 0.28 +/- 0.06; P less than 0.01), reflecting the interstitial edema associated with this model of pancreatitis. Permeability of the rat pancreatic microvasculature is similar to that of other fenestrated tissues, but it is 10- to 20-fold greater than that of continuous capillaries. Contrary to previous assumptions, permeability does not appear to be increased after induction of acute interstitial pancreatitis.

The effects of the oxidant tert-butylhydroperoxide (t-buOOH) on carbachol-stimulated pancreatic secretion in the vascularly perfused rat pancreas have been studied in parallel with [Ca2+]i signalling and amylase output in perifused rat pancreatic acinar cells. Perfusion of the pancreas with t-buOOH (0.1–1 mM) caused a rapid and irreversible inhibition of carbachol-stimulated (3×10−7 M) amylase and fluid secretion. Pre-perfusion of the pancreas with vitamin C and dithiothreitol or a cocktail of GSH and GSH-precursor amino acids provided only marginal protection against the deleterious effects of t-buOOH, even though GSH levels were elevated significantly. In perifused pancreatic acini, repetitive [Ca2+]i spikes evoked by carbachol (3×10−7 M) were sustained for 40 min. t-buOOH (1 mM) acutely increased the amplitude and duration of Ca2+ spikes, then attenuated Ca2+ spiking and subsequently caused a marked and sustained rise in [Ca2+]i. t-buOOH-induced alterations in carbachol-stimulated [Ca2+]i signalling and amylase release in perifused pancreatic acini were prevented by vitamin C. Although vitamin C restored impaired Ca2+ signalling and maintained amylase output in pancreatic acini, it seems likely that oxidative stress inhibits fluid secretion irreversibly in the intact pancreas, resulting in a loss of amylase output. Thus, perturbations in [Ca2+]i signalling may not fully explain the secretory block caused by oxidative stress in acute pancreatitis.

1. Transport of l-arginine was investigated under zero-trans conditions in human erythrocytes from healthy donors and patients with heart failure. 2. Saturable influx of l-arginine was mediated by the classical cationic amino acid transport systems y+ and y+L. 3. The Vmax for l-arginine transport via system y+ increased from 292 to 490 μmol h−-1 l−-1 of cells in heart failure. 4. With system y+ inhibited by N-ethylmaleimide (0.2 mmol/l), the Vmax for the transport of l-arginine via system y+L was unaffected in erythrocytes from patients with heart failure. 5. The inhibition of l-arginine and l-leucine influx by NG-monomethyl-l-arginine was similar in erythrocytes from control and heart failure patients. 6. Plasma l-arginine levels were reduced in patients with heart failure (59 μmol/l) compared with controls (125 μmol/l). Plasma from patients with heart failure also contained the endogenous l-arginine analogue NG-monomethyl-l-arginine, which was undetectable in plasma from controls. 7. Intracellular concentrations of l-arginine and NG-monomethyl-l-arginine were significantly elevated in erythrocytes from patients with heart failure compared with controls, consistent with an increased transport capacity for l-arginine and NG-monomethyl-l-arginine. 8. The present study provides the first evidence that system y+ mediates the increased transport of l-arginine in human erythrocytes from patients with chronic heart failure. These findings are similar to our previous results obtained in patients with chronic renal failure. Since both pathologies seem to present with an increased synthesis of nitric oxide, studies of l-arginine transport in erythrocytes may provide a valuable paradigm to study abnormalities of the l-arginine-nitric oxide signalling pathway.

Vascular endothelial cells synthesize nitric oxide (NO) from the terminal guanidine-nitrogen atom of the cationic amino acid L-arginine (Palmer, R et al, 1988). Although basal NO synthesis is not limited by arginine availability, under conditions of stimulated NO production or following substrate deprivation exogenous L-arginine appears to be rate-limiting (Palmer, R. et al., 1988). We have now investigated whether bradykinin, an agonist which is known to release NO release, modulates the endothelial cell L-arginine transporter.

Amino acid transport in the isolated perfused exocrine pancreas is mediated by at least four parallel transporters, exhibiting differential sensitivity to islet hormones, diabetes, fasting and dietary composition. Insulin and streptozotocin-induced diabetes stimulate amino acid influx via the Na+-independent Systems asc (L-serine) and y+ (L-lysine). Moreover, activation of transport by insulin is dependent upon extracellular Ca2+ and inhibited by somatostatin-14. Elevation of transport induced by diabetes may not be mediated by glucagon, as exogenous glucagon fails to stimulate transport. Although system L (L-phenylalanine) is unaffected by insulin and diabetes, fasting for 72 h activates transport and refeeding for 24 h restores transport to fed levels. Adaptive responses in the activities of systems L and y+ induced by fasting and changes in dietary protein may involve changes in intracellular amino acid levels which are known to influence counter-transport. Elucidating the mechanisms regulating uptake and incorporation of amino acids into pancreatic enzymes is of clinical relevance, since 11 C-labelled amino acids are currently used as PET imaging probes for regional tissue metabolism in pancreatitis.

Transport of short-chain and long-chain neutral amino acids across the basolateral membrane of the epithelium in the perfused cat salivary gland has been studied using a rapid (less than 30 s) single circulation paired-tracer dilution technique. Amino acid uptake was measured by comparing the venous dilution profiles for a tritiated amino acid and D-[14C]mannitol (extracellular reference) following a bolus intra-arterial injection of a mixture containing both molecules. Unidirectional influx (v) was estimated from the maximal tracer uptake (Umax), the perfusate flow (F) and the perfusate amino acid concentration (Ca): v = [-F . ln (1-Umax)] . Ca. L-alanine influx was saturable and apparently mediated by a single entry system (Km = 0.83 +/- 0.11 mM and Vmax = 655 +/- 32 nmol/min . g). These kinetic constants were considerably lower than our previously reported values for L-phenylalanine: Km = 6.4 mM and Vmax = 1719 nmol/min . g. In cross-inhibition experiments performed over a wide range of concentrations (0.05-24 mM), influx of L-alanine and L-phenylalanine could be further discriminated, since both L-phenylalanine (Ki = 22 mM) and L-alanine (Ki = 19 mM) behaved as poor competitors. Removal of Na+ from the perfusate resulted in a selective inhibition of L-alanine and L-serine influx, whereas influx of the long-chain neutral amino acids L-leucine, L-phenylalanine and L-tryptophan remained unaffected. Although prolonged perfusion of glands with dinitrophenol (0.8 mM for 20-30 min) caused a variable but net inhibition of unidirectional uptake, it markedly enhanced the tracer efflux of L-leucine, L-phenylalanine, L-tyrosine and the basic amino acid L-lysine. It appears that at least two separate neutral amino acid transport systems are operative at the blood-tissue interface of the salivary epithelium: (i) a Na+-dependent alanine-serine-cysteine preferring type of carrier exhibiting a high affinity for amino acids with short, polar or linear side chains and (ii) a Na+-independent leucine preferring type of carrier selective for large neutral amino acids.

We have applied the paired-tracer dilution method to the study of transport processes in a mixed mammalian muscle preparation, the perfused rat hindlimb. The method is suitable for the characterization of the kinetic parameters of sugar and amino acid transport and its regulation by hormones, contractile activity, hypoxia, etc. Insulin stimulates sugar transport by increasing the Vmax. of the process 2-3 fold, but its affinity is unchanged. Starvation increases the affinity of sugar transport in perfused skeletal muscle.

Capillary permeability and cellular uptake of noradrenaline by the isolated artificially perfused rabbit heart was measured using rapid (less than 30 s) single-circulation tracer-dilution techniques. In a single coronary circulation capillary extractions of L-[14C]noradrenaline and D-[3H]mannitol (extracellular reference) relative to an intravascular marker, 125I-labelled albumin, were similar and above 60%. The 'apparent' volume of distribution for tracer noradrenaline was 2.5-fold larger than that measured for D-mannitol (0.32 ml g-1) suggesting cellular uptake of the amine. Unidirectional noradrenaline uptake was estimated by directly comparing coronary sinus dilution profiles of L-[3H]noradrenaline and D-[14C]mannitol. Michaelis-Menten saturation kinetics based on a single-entry system were determined (Km = 2.8 +/- 1.5 microM, Vmax = 2.1 +/- 0.5 nmol min-1 g-1, n = 4) by perfusing hearts with varying concentrations of L-noradrenaline (1-10 microM). Various known inhibitors of noradrenaline uptake were investigated to determine whether uptake was mediated by neuronal (uptake1) and/or extraneuronal (uptake2) mechanisms. Desipramine (5 microM), imipramine (5 microM) and metaraminol (2 microM) resulted in a 66-94% inhibition of noradrenaline influx. In comparison, the steroids, 17 beta-oestradiol (1 microM) and corticosterone (10 microM), and the noradrenaline metabolite normetanephrine (5 microM) caused virtually no inhibitory effects. The beta-adrenergic antagonist propranolol (5 microM) was also relatively ineffective. These results together with the kinetic constants estimated suggest that the rapid noradrenaline uptake reflects transport into adrenergic neurones lying in the coronary interstitium. The high resolution of this paired-tracer dilution technique has permitted a 'non-invasive' study of neuronal uptake mechanisms and its application may be of clinical value.

The specificity and kinetics of L-lysine influx across the basolateral surface of the cat salivary epithelium have been investigated in the perfused cat submandibular gland using a high-resolution, paired-tracer dilution technique. L-lysine influx was measured at several different perfusate concentrations (0.05-2.5 mM) and was found to be saturable. A Michaelis-Menten analysis based on a single entry site gave a Km of 0.49 +/- 0.08 mM and a Vmax of 231 +/- 20 nmol/min X g. The uptake of L-lysine was highly stereospecific and markedly inhibited by L-arginine (0.25-2.5 mM). The inhibitor constant (Ki) was 0.23 mM, suggesting that the carrier had a greater affinity for L-arginine than L-lysine. When the inhibitory effects of L-histidine (0.5-10 mM) were examined the Ki, estimated at 10 mM, was 4.6 mM. Nine other neutral amino acids (L-alanine, L-serine, L-cysteine, glycine, L-proline, L-homoserine, L-leucine, L-phenylalanine and L-glutamine), and an acidic amino acid (L-aspartate) were also tested at 10 mM and, although several caused inhibition, the Ki was always at least 20 times higher than the measured Km for L-lysine. It is concluded the carrier is highly specific for the L-form of the basic amino acids. The sodium dependence of L-lysine influx was investigated over a range of L-lysine concentrations (0.05-1 mM), and total removal of sodium from the perfusate had no effect on L-lysine influx. In the presence of sodium, L-homoserine, an amino acid not normally present in animal tissues, inhibited L-lysine influx (Ki = 13 mM). This inhibition was not observed in the absence of sodium, and contrasts with the observation that the inhibitory action of L-histidine was sodium independent. The present data suggest that a specific cationic amino acid transport system is operative in the basolateral membrane of the cat salivary epithelium. The properties of this system appear to be similar to the system y+ which has been described in several other cell types.

On the basis of spectrophotometric data on the characteristic spectral absorptions observed in oxidizing substrates with and without added γ-tocopherol, it has been shown that the red color which develops on accelerated oxidation of fat substrates containing this tocopherol results from its conversion to chroman-5,6-quinone. The chroman-5,6-quinone thus produced possesses relatively little antioxidant activity.

Light-microscopic autoradiography was used to localize the cellular sites for neutral amino acid uptake in submandibular and sublingual salivary gland epithelia. The vasculature of isolated glands was perfused for 3–5 min with either L-(3-3H)serine or L-(4-3H)phenylalanine and then fixed by perfusion with buffered glutaraldehyde. In the submandibular gland the small neutral amino acid L-serine and the aromatic amino acid L-phenylalanine were localized to central acinar cells, demilunar cells and ductal cells. In the sublingual gland silver grains associated with each of these tritiated amino acids were localized to central acinar and ductal cells. Perfusion of both submandibular and sublingual glands with unlabelled L-serine (25 mM) or L-phenylalanine (30 mM) resulted in a significant decrease in the silver grain density associated with each labelled amino acid. The absence of silver grains in the lumina of acinar and ductal cells and the presence of tight junctions near the apical surface of the epithelium strongly suggest that the initial uptake of these amino acids was mediated by basolateral plasma membrane carriers.

1. Capillary permeability-surface area products for 22Na, 51Cr-EDTA (mol. wt. 357), [57Co]cyanocobalamin (mol. wt. 1353) and 125I-labelled insulin (mol. wt. approximately or equal to 6000) were measured using the single-passage, multiple-tracer dilution technique in isolated rabbit hearts perfused at constant flows between 0.2 and 4.7 ml. min-1 . g-1. 2. In hearts perfused with a Krebs-Ringer solution containing bovine albumin (10 g . l . -1), the permeability-surface area products for 51Cr-EDTA and [57Co]cyanocobalamin increased as the perfusion rate increased, but reached constant values at flows above 2 ml . min-1 . g-1. For 125I-labelled insulin a diffusion-limited value of 0.06 +/- 0.02 ml . min-1 . g-1 (mean +/- S.E., n = 10) was measured at significantly lower perfusion rates. As the value for 22Na increased continuously with increments in flow, only a flow-limited value could be estimated. 3. When hearts were initially perfused with albumin (10 g . l . -1) and then with an albumin-free Krebs-Ringer solution, a significant increase in the permeability-surface area for 22Na, 51Cr-EDTA and [57Co]cyanocobalamin was observed. 4. In hearts perfused with albumin capillary permeability coefficients calculated for 22Na, 51Cr-EDTA. [57Co]cyanocobalamin and 125I-labelled insulin were respectively: 10.5, 3.5, 2.1 and 0.21 x 10(-5) cm.sec-1. 5. These findings confirm that bovine albumin reduces the permeability of myocardial capillaries to hydrophilic solutes of varying molecular sizes and this effect may be the result of an interaction of albumin with the pathways for transcapillary exchange.

—The Rhodesian Ridgeback is a modern breed having been standardized in 1922. It originated in South Africa by crossing Hottentot dogs with various European breeds. The breed has one defect, a congenital malformation, generally known as dermoid sinus. The authors have investigated the inheritance of the condition and, contrary to the hypotheses of others, suggest that it is a simple recessive character. The implications of this are discussed. Reslame—Le chien de Rhodesie, denomme Ridgeback, est d'un elevage recent, bien etabli depuis 1922. II est originaire d'Afrique du Sud, resultant d'un croisement de chiens Hottentots et de divers chiens europeens. Cette souche a un defaut, une malformation congenitale generalement designee kyste dermoide. Les auteurs ont recherches l'heredite de cette condition, et contrairement a d'autres hypotheses, ils suggerent qu'il s'agit d'un caractere hereditaire recessif. Les consequences en sont discutees. Zusammenfassung—Der Rhodesische “Ridgeback’ ist eine neuzeitliche Zucht, die im Jahre 1922 standardisiert wurde. Ihr Ursprung ist in Sued Afrika, vollzogen durch Kreuzung von Hottentotten Hunden mit verschiedenen europaeischen Rassen. Der “Ridgeback’ hat einen Fehler: eine congeni-tale Missbildung, die allgemein als “Dermoid Sinus’ bekannt ist. Die Autoren haben die Vererbung dieses Zustandes untersucht und schlagen vor, entgegen den Hypothesen anderer Autoren, sie als ein einfaches, recessives Merkmal zu bezeichnen. Die sich daraus ergebenden Beziehungen werden eroertert.