Subtotal colectomy and ileocolonic anastomosis in a Vietnamese pot-bellied pig with idiopathic megacolon.

A 7-month-old sexually intact female Vietnamese pot-bellied pig was evaluated because of constipation. On abdominal palpation, a hard tubular structure was palpated in the middle of the abdomen. Abdominal radiography revealed loops of intestine that were markedly distended with ingesta, consistent with obstructive intestinal disease. On exploratory celiotomy, a massively distended cecum and spiral colon were found. A subtotal colectomy, with a side-to-side ileocolonic anastomosis, was performed. The cause of the megacolon was not discovered. The pig did well following surgery and eventually defecated normally following an initial period of diarrhea. To our knowledge, this is the first report of therapeutic removal of a substantial portion of the large intestine in swine. Our decisions concerning the pig of this report were based largely on our knowledge of megacolon in cats. The outcome for this pig indicates that subtotal colectomy along with removal of the cecum and ileocecal valve can be used to successfully treat idiopathic megacolon in Vietnamese pot-bellied pigs.

Hypocalcemia and hyperphosphatemia due to primary hypoparathyroidism in a six-month-old kitten.

A six-month-old, intact female Himalayan kitten was presented to the University of Tennessee Veterinary Medical Teaching Hospital for evaluation of chronic lethargy, inappetance, muscle tremors, and seizures. Upon physical examination, the kitten was very small for her age. Bilateral, incipient-to-immature cataracts were seen on ophthalmic examination. Severe hypocalcemia and concurrent hyperphosphatemia were identified on initial diagnostic evaluation. A diagnosis of primary hypoparathyroidism was made by identifying reduced concentrations of parathyroid hormone (PTH). The kitten responded well to treatment with calcium, vitamin D, and aluminum hydroxide and is clinically normal 17 months after initiation of treatment.

Vascularization of the adrenal cortex: its possible involvement in the regulation of steroid hormone release.

This review examines the morphology of the adrenal gland with particular reference to the adrenal vasculature. It examines the possibility that variability in adrenal gland responsiveness may be attributable to neural or hormonal modulation of adrenal blood flow. Changes in the rate of blood flow through the adrenal cortex would be expected to play an important role in the regulation of steroid hormone release. It would affect both the delivery of the major stimulant (ACTH) and the removal of the end product from the steroidogenic cells (the glucocorticoids). In the past, interest in this area has concentrated on the regulation of arterial blood flow, rather than the regulation of venous drainage. The current review examines the concept of vascular damming, and attempts to link the morphological features of the gland with experimental data associated with glucocorticoid release. It is postulated that regulation of venous drainage, via the vascular dam, plays an important role in the storage of the secretory product during the animals' inactive phase, and in the initial rapid rise in plasma levels of the glucocorticoids seen in response to stress or injection of ACTH.

Studies on the role of glycosylation in the origin of the electrophoretic variants for rat corticosteroid-binding globulin.

The glycoprotein corticosteroid-binding globulin (CBG) migrates as doublet bands in PAGE and SDS-PAGE, and as numerous bands in isoelectric focusing (IEF). This study deals with the origin of this heterogeneity. Desialation of rat CBG with neuraminidase does not abolish the doublet in either PAGE or SDS-PAGE, indicating that the doublet does not arise as a result of differences in sialic acid residues. Treatment of the separated upper and lower variants of native CBG with N-glycosidase F (PNGase-F) shows a differential pattern of deglycosylation over time indicating either differences in the number, type, or location of sugars attached to each of the variants. Rate of deglycosylation is quicker and more extensive for the upper variant when compared to the lower variant. PNGase-F treatment of 1% SDS-denatured CBG does not abolish the CBG doublet seen in SDS-PAGE, indicating that there is variation in the protein moiety. Sugars could not be detected on PNGase-F treated CBG using either wheat germ aglutinin horse radish peroxidase conjugate, concavilin-A HRP conjugate, or the digoxigenin glycan detection system. While the results clearly show differences in glycosylation between the CBG variants, differences in the protein moiety may also occur to give rise to the heterogeneity seen in CBG. The latter is supported by the fact that desialated CBG migrates as two bands in IEF. Migration in IEF is based solely on charge, and since only sialic acid residues are charged in N-linked glycosylation, any heterogeneity seen for the desialated glycoprotein must reside within the protein moiety itself. The presence of O-glycosylation containing an N-acetylgalactosamine with a beta 1-3 linkage to galactose could not be demonstrated using O-glycosidase. N-terminal blockage could not account for the variation, as both the upper and lower variants were able to be sequenced resulting in identical sequences for the first 13 amino acids. The data presented supports the hypothesis that the differences in the sugar as well as the protein moiety are responsible for the heterogeneity seen for CBG.

Histological identification of osteocytes in the allegedly acellular bone of the sea breams Acanthopagrus australis, Pagrus auratus and Rhabdosargus sarba (Sparidae, Perciformes, Teleostei).

The bone of advanced teleost fishes such as those of the family Sparidae is said to lack osteocytes or to be acellular. Acellularity has been determined by apparent lack of osteocyte lacunae. This study questions the validity of this criterion. Scanning electron and light microscopy of paraffin and resin sections were used to show that the sides of sea bream mandibles consist of laminar parallel-fibred bone that we call tubular bone, because it contains tubules, and localised regions of Sharpey fibre bone. Osteocytes lie along the walls of tubules that also contain collagen fibril bundles (T-fibres), or in the lumens of tubules that do not contain T-fibres. We show that the osteocytes are derived from osteoblasts. The T-fibre system is different from other fibre systems that have been described. The tubules enclose wide T-fibres (lenticular in cross-section, maximum width about 8 microns) that taper at their ends and continue as thin T-fibres (round in cross-section, about 2 microns wide). The T-fibres originate in the periosteum. In mature tubular bone, spaces of increasing size develop around the osteocytes. Osteocytes are released from the bone matrix and become postosteocytes or bone-lining cells. Secondary bone lines the largest spaces. In Sharpey fibre bone, small osteocytes in small lacunae (about 2 microns wide) are found in columns parallel to the Sharpey fibres. Large osteocytes are found in large round spaces and are much larger than comparable osteocytes in lacunae in the bone of the salmon Salmo salar. We conclude that an absence of visible or conventional osteocyte lacunae does not mean that the cells themselves are absent. There are cells and two types of collagen fibre bundle in the tubules. The cells are osteocytes derived from osteoblasts, and these osteocytes apparently resorb bone with the result that large amounts of bone are destroyed. "Acellular" tubular and Sharpey fibre bone are types of cellular bone that differ from each other and from conventional cellular bone.

Structure and origin of the tooth pedicel (the so-called bone of attachment) and dental-ridge bone in the mandibles of the sea breams Acanthopagrus australis, Pagrus auratus and Rhabdosargus sarba (Sparidae, Perciformes, Teleostei).

Scanning electron and light microscopy were used to show that the pedicels of fish teeth (the so-called "bones of attachment") consist of three types of dentine that lie concentrically around a pulp cavity lined with typical odontoblasts with cytoplasmic processes in dentinal tubules. Circumpulpal canalar dentine forms on a thin layer of orthodentine that is encased in mantle dentine. Canalar dentine is a new name given to a dentine that is similar to vasodentine in canal arrangement, but not apparently in canal content. An inner series of wide, radial canals and an outer series of highly-branched thin canals of two diameters are inhabited by a population of cells, the osteodentocytes, and collagen fibril bundles. The flat, oval osteodentocytes appear to be quiescent cells, lying on the sides of the tubules and covered by a sheath. Plump, intensely metachromatic osteodentocytes appear to be more synthetically active. The canals and the osteodentocytes originate from blood capillaries enclosed in the predentine during dentinogenesis. New teeth begin within the small cavities present in spongy bone that were enlarged by multinucleated osteoclasts during tooth growth. Pedicel formation is initiated by the extension of the crown mantle dentine, forming the outer layer of the crimped ligament and outlining the future length and curvature of the pedicel. Central and inner ligament zones are subsequently formed as orthodentine is secreted in both crown and pedicel, and canalar dentine in the pedicel. Spongy bone osteogenesis begins during stage 1 of pedicel formation with the aggregation of osteoblasts and blood capillaries in the bone cavities and in the dermis between the pedicels. Loose fibrillar osteoid condenses into incomplete thin trabeculae bordered by intensely metachromatic osteoblasts. Osteoblasts become enclosed in the developing trabeculae that thicken to give mature spongy bone with osteocytes throughout. We conclude that the pedicels are the true bases of teeth, that the dental ridge is formed from pedicels and spongy bone, and that sea bream spongy bone is cellular. The term "bone of attachment" is inappropriate for the pedicel. It can be used for the spongy bone between the compact bone of the jaw and between adjacent pedicel.

Diurnal variation in adrenal gland freshweight due to vascular damming: a possible role in corticosterone storage.

Previous in vitro studies have disclosed the existence of a diurnal variation in adrenal gland freshweight in the minimally stressed rat (inactive phase freshweight > active phase freshweight). In the present study this active/inactive phase difference in adrenal weight was examined using light microscopy, transmission electron microscopy (TEM) and backscattered scanning electron microscopy (BSEM). Morphological and stereological examination of the resultant micrographs has shown a significant increase in gland cross-sectional width in the active phase, localised to the zona fasciculata/reticularis region of the cortex. However, TEM examination of cells from this region, comparing volume and surface densities from active and inactive phase glands, has not provided evidence of a diurnal variation in cell size. Analysis of the BSEM investigation of vascular, cellular and interstitial compartments of the glands confirmed the absence of variation in the cellular compartment but showed a diurnal variation in the vascular compartment of the zona fasciculata/reticularis. The circadian related changes in vascular volume density begin at the cortico-medullary border where greatest difference is observed between the active and inactive phases. This difference continues throughout the zona fasciculata/reticularis decreasing in size as it approaches the zona glomerulosa region. These findings are explained in terms of the existence of a cortico-medullary vascular dam that is a possible contributor to the rapid steroidogenic response seen on initial stimulation of the gland by adrenocorticotrophic hormone (ACTH).

The development of corticosteroid binding globulin-like activity in fetal sheep blood.

Parturition in sheep is initiated by the fetus and is preceded by a rise in fetal cortisol and corticosteroid-binding globulin (CBG) late in gestation. In this study plasma cortisol and CBG concentrations were measured in fetal and maternal circulation from 40 days gestation to early post-partum. The fetal cortisol profile was shown to be triphasic in nature; being high in both the first and last trimester but low in the middle period of gestation. In the last trimester, total cortisol increased steadily, reaching it's highest level just prior to parturition (145 days gestation), before falling to maternal levels over the first 10 days post-partum. The changes seen in CBG concentrations throughout gestation and post-partum mirrored the triphasic nature seen in cortisol levels. CBG was significantly higher at 40, 56 and 140 days gestation than at mid-gestation (77 and 90 days). However, at 145 days gestation there was a significant fall in CBG levels. CBG levels were higher at 1 day post-partum when compared to 145 days gestation, the former rapidly falling to maternal levels over the subsequent 9 days. The maximum binding capacity at 40, 56, 70 and 90 days gestation exceeds the total serum cortisol concentration. However at 140 and 145 days gestation and 1 day post-partum the total serum cortisol exceeds the Bmax. The highest cortisol:Bmax ratio is seen at 145 days gestation due to the fall of CBG binding capacity at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Passive immunization with antiserum to adrenocorticotropin increases weight gain in normal female rats.

Passive immunization against ACTH was used to test the hypothesis that growth in female rats is constrained by physiological concentrations of glucocorticoids. When animals were stressed by 15-min exposure to ether before blood sampling by cardiac puncture, serum concentrations of corticosterone were lower (P less than .05) in immunized rats than in stressed controls. The maximum effect was apparent 2 h after injection of ACTH antiserum, and no effect was apparent 6 h after injection. To examine the effects of ACTH immunization on growth, rats received daily injections of either saline, sheep immunoglobulin G, or ACTH antiserum, 2 h before the afternoon peak in plasma concentrations of corticosterone. After 7 d of treatment, rats treated with ACTH antiserum had gained 37% more body weight than saline-injected controls, and this effect was accompanied by a 59% reduction in peak plasma concentrations of corticosterone. Immunoglobulin G purified from normal sheep serum had no effect on weight gain. It is concluded that growth rate in normal female rats can be stimulated through the suppression of adrenal activity.

A circadian rhythm in adrenal responsiveness to ACTH is not confirmed by in vitro studies.

From in vitro studies a circadian variation in adrenal gland response to ACTH was observed. Regulation of this circadian rhythm in adrenal responsiveness was localized to the cellular level; involving variation in either receptor density or affinity. In the present study the circadian variation in adrenal gland responsiveness was studied using an in vitro approach. Levels of corticosterone secretion during the active and inactive phases were determined using incubated rat adrenal slices in the presence and absence of submaximal stimulation by the synthetic ACTH peptide, ACTH(1-24). Initially, a circadian difference in adrenal responsiveness appeared to exist in all groups except the betamethasone pretreated. However, data expressed in terms of corticosterone secretion/mg adrenal weight proved to be misleading due to the presence of an apparent circadian pattern in adrenal gland weight; the adrenal glands from animals in the dark being significantly less in weight than those from animals in the light phase. When the data were expressed in terms of actual gland output, no circadian variation in adrenal response to exogenous ACTH(1-24) stimulation was apparent. In conclusion, the present study does not support the concept of a circadian variation in the adrenal response to ACTH(1-24) stimulation resulting from a variation in the responsiveness of the adrenal cells themselves. However, the present study does not preclude the possibility of a circadian variation due to modulation of adrenal responsiveness by humoral factor(s) other than ACTH.

The release of corticosterone and a corticosterone-binding protein by incubated rat adrenal slices.

Stimulation of incubated rat adrenal slices with ACTH(1-24) resulted in an increase in the release of both corticosterone and specific corticosterone-binding protein into the incubation medium. The release of corticosterone and binding protein was dose and calcium dependent with adrenals from animals pretreated with betamethasone. While the secretion of corticosterone was continuous throughout the incubation period, there appeared to be a limit to the increase in binding capacity. The specificity of steroid binding to the adrenal protein showed a similar profile to that of corticosteroid-binding globulin (CBG) in rat serum. A Western blot analysis using anti-rat CBG as the primary antiserum, showed that the adrenal protein was not CBG. [3H]corticosterone binding with disc electrophoresis, run at 2 degrees C, gave a single peak with approximately the same Rf value for rat serum, purified CBG, and adrenal incubate; at 22 degrees C peaks were only seen for rat serum or purified CBG. The data presented provides further evidence for the existence of a specific corticosterone-binding protein of adrenal origin released in conjunction with corticosterone. The adrenal protein would appear to have a lower affinity for corticosterone than does CBG, and to be functionally more labile. It is possible that the adrenal protein may be CBG that has been internalized, modified and released with corticosterone.

Adrenocorticotropin binding sites in rat cardiac tissue.

Using the ACTH analog [125I-Tyr23,Phe2,Nle4] ACTH(1-24), the existence of specific binding sites for ACTH in atrial membrane preparations was demonstrated. The dissociation constants (Kd), determined by Scatchard analysis were not significantly different for membrane preparations of adrenal gland or atrial tissue (being 6.40 x 10(-12)M and 8.86 x 10(-12)M respectively). No binding was observed to membrane preparations from kidney or lung. While the binding of the ACTH(1-24) analog to atrial membranes was inhibited by ACTH(1-24), it was not affected by norepinephrine or epinephrine. It was proposed that the ACTH(1-24) analog may bind to sites located on the adrenergic nerve endings associated with the cardiac tissue, and that such binding would interfere with the neuronal reuptake of the catecholamines.

Effect of circadian rhythm on the neuronal uptake and sensitivity to the inotropic action of norepinephrine by rat atria.

The circadian rhythm for plasma corticosterone was determined. Animals were then killed at times corresponding to high and low periods of the circadian rhythm in plasma corticosterone. Myocardial sensitivity to norepinephrine was measured at these time periods as the ED50 of the catecholamine, obtained using electrically driven rat atria. The uptake of 3H-norepinephrine by spontaneously beating atria was also measured at both time periods. A circadian variation in the uptake of 3H-norepinephrine by the rat atria was observed. This variation in uptake was associated with a variation in plasma corticosterone, but was not associated with any change in myocardial sensitivity to norepinephrine.

Effect of (1-24)adrenocorticotrophin on the uptake of 3H-norepinephrine by the rat atria.

Spontaneously beating rat atria were incubated with 3H-norepinephrine both in the presence and absence of (1-24)ACTH. A significant reduction in the uptake and retention of radioactivity was found in atria pretreated with (1-24)ACTH. A kinetic study of the uptake process showed similar Km values for both the control (24.1 x 10(-8) M) and (1-24)ACTH pretreated (22.2 x 10(-8) M) groups, but a significantly different Vmax. The Km values were similar to that reported for the neuronal reuptake process (Uptake 1). It was concluded that the ACTH-induced enhanced myocardial sensitivity to catecholamines previously reported, could be explained in part on the basis of an inhibition of neuronal uptake by (1-24)ACTH. The inhibition of neuronal uptake by (1-24)ACTH was dose-dependent.

The physiological measurement of acute stress (public speaking) in bank employees.

An evaluation of a number of non-invasive physiological measures of stress was conducted, using bank employees attending a two-week residential course. The stressor involved was the preparation and delivery of a 15-min public lecture. The physiological parameters measured were urinary excretion rates of noradrenaline (NA), adrenaline (A), dopamine and cortisol, the ratio of NA/A, salivary cortisol levels, heart rate and blood pressure. Measurements were taken at 08.30, 10.30, 12.30, 15.30 and 17.30 h on the day of the public lecture and on the following (control) day. The public lectures were given between 10.30 and 12.30 h. The urinary excretion rates of adrenaline and cortisol were significantly elevated immediately following, but not before, the public lectures. The ratio NA/A was significantly decreased and the salivary cortisol levels were significantly increased both immediately before and after the public lecture. Urinary excretion rates of noradrenaline and dopamine, blood pressure and heart rate were unchanged by the stressor. Measurement of salivary cortisol levels, as well as providing a simple, stress free, non-invasive collection procedure, more closely reflects in time the changes in plasma levels of the hormone, not suffering from the large lag-time involved with urinary hormone measurements. Salivary cortisol measurement would appear to be the measurement of choice in human stress studies where individual stress factors are to be identified and studied. The significance of the stress-induced elevation in cortisol and catecholamine levels in the link between illness and occupational stress is discussed.

Urinary cortisol excretion and mood ratings in aircraft cabin crew during a tour of duty involving a disruption in circadian rhythm.

A psychophysiological study was carried out on 28 cabin crew, comprising two teams, who were to travel from Sydney to Los Angeles and return, with stopovers in Los Angeles of 58 and 82 hr respectively. Every urine sample for a period of nine days, commencing 2 days before the flight, was collected. The volume and time the sample was passed were recorded so that urinary cortisol secretion rates could be calculated. Mood was also rated on a scale scored 0-9 at the same time the urine sample was collected. A control group matched for age, sex ratio, and degree of manual labour involved in their occupation, but not involved with the flights, was included in the study for comparison. On the basis of urinary cortisol excretion rates, the crews in Sydney before the flight and in Los Angeles were more highly stressed than the control group. The urinary cortisol excretion rates were significantly greater than those of the control group in Sydney before the flight, in Los Angeles, and during the return flight, but not on the flight out. The high excretion rates before the flight were attributed to an apprehension factor, whereas the elevated values in Los Angeles and during the flight back were attributed to a disruption in circadian rhythm. A factor analysis of mood ratings showed three major factors assessing vitality, distress, and relaxation. Analysis of variance of the mood ratings showed significant changes over the tour of duty for 13 of the 14 moods.

Enhanced corticosterone-binding capacity in plasma after stimulation of the rat adrenal cortex: the possibility of a simultaneous release of protein and corticosterone.

Exposure of rats to either footshock or handling stress produced a significant increase in both plasma corticosterone concentration and specific binding capacity. Non-specific binding was eliminated using the synthetic glucocorticoid, dexamethasone. The increase in both plasma corticosterone and specific binding capacity was biphasic following exposure to footshock. Adrenalectomy and pretreatment with betamethasone abolished both phases of the enhanced binding capacity and plasma steroid concentration. Intraperitoneal injection of ACTH (1-24) in animals pretreated with betamethasone resulted in a biphasic rise in plasma concentrations of corticosterone but only the initial increase in binding capacity. Dissociation constant (Kd) values, determined by Scatchard analysis, for adrenalectomized and betamethasone-pretreated animals were 546 and 556 pmol/l respectively. These values were significantly different from the Kd in animals with functional adrenals (631 pmol/l). The results are discussed in the light of a possible specific corticosteroid-binding globulin (CBG) like binding protein of adrenal origin released in conjunction with corticosterone. This binding protein has a lower affinity for corticosterone and a shorter half-life than CBG.

Effect of (1-24)adrenocorticotrophin stimulation on the rate of corticosterone synthesis by the rat adrenal cortex.

The rate of corticosterone synthesis by the rat adrenal gland was measured in vitro, using a cell-free system, following the in vivo administration of (1-24)ACTH. The doses of ACTH used were 50, 100 and 250 micrograms ACTH/kg body weight. With all 3 doses of ACTH there was a significant increase in the rate of corticosterone synthesis within the first 5 min; this initial increase in rate did not vary with the dose of ACTH given. With both the 50 and 100 micrograms/kg doses the new rate of synthesis was maintained without further change, up to 30 min post-injection. In the case of the 250 micrograms/kg dose there was a second significant increase in the rate of corticosterone synthesis observed after 20 min. The results are discussed in the light of the hypothesis that the differential response of the adrenal gland represents the binding of ACTH to two receptors; a high affinity receptor of low abundance and a low affinity receptor of greater abundance. The results are consistent with the initial steroidogenic response resulting from binding to the high affinity receptors. Because of their low abundance these receptors may be completely occupied even at low doses of ACTH, thus explaining the dose-independent nature of the initial response to ACTH. Binding to the more abundant low affinity receptors may be associated with the secondary dose-dependent enhanced synthesis rate, a response which may be mediated via c-AMP.

Corticosterone storage within the adrenal cortex: evidence for a sulphate conjugate.

Incubation of homogenized rat adrenal glands with sulphatase for 18 h resulted in a significant increase in the amount of unconjugated corticosterone that could be extracted from the gland and which could not be attributed to de-novo synthesis of corticosterone during the incubation. Therefore corticosterone may be stored within the adrenal gland as a sulphate conjugate rather than as unconjugated hormone. Exposure of animals to footshock stress resulted in an increase in the amount of unconjugated corticosterone in the gland and a disappearance of the conjugate form. The rapid disappearance of the sulphate conjugate may reflect the activation of a steroid sulphatase by ACTH. However, the release of corticosterone from a storage form such as corticosterone sulphate could not explain entirely the initial increase in plasma corticosterone concentration following the stress. It was calculated that a pair of adrenal glands would have to store up to 20 nmole corticosterone in order to account for the initial increase in plasma corticosterone. This level was much greater than that extracted from a pair of glands (4.8 nmol) even after sulphatase pretreatment.