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M Afework

Publications and source records attributed to M Afework.

16 recordsLinked to original sources
PubMed2000

Age-related changes in the localization of P2X (nucleotide) receptors in the rat adrenal gland.

Observation of the changes in the occurrence and distribution of nucleotide (P2X) receptors in the adrenal gland during development and ageing, and correlation with the changes in adrenal status at similar stages may give morphological insights into the functions of purine nucleotides in the gland. Age-related changes in the localization of all seven subtypes of the P2X receptor in the adrenal gland of rat were therefore investigated immunohistochemically. In the adrenal glands of prenatal rats, immunoreactivity to P2X receptor subtypes was not observed. In glands of the postnatal rat at the developmental stages studied, only immunoreactivity for the P2X(5) receptor subtype was observed. A small number of faintly P2X(5)-immunoreactive chromaffin cells were found in the adrenal glands of 1-day-old rats; the frequency of localization and intensity of staining of immunoreactive cells had increased by day 4 and was further increased at day 7. P2X(5) immunoreactivity was not observed in the adrenal glands from 14- and 21-day-old rats. At 8 weeks of age, immunoreactivity with a specific distribution for each of the seven receptor subtypes was observed. Except for the P2X(4) receptor, adrenal glands at 24 months showed a similar pattern of immunoreactivity for the receptor subtypes as that observed at 8 weeks. Immunoreactivity for P2X(4) was first observed in the adrenal cortical cells of the zona reticularis at 8 weeks, but was absent in 24-month-old rats. However, several P2X(4)-immunoreactive chromaffin cells appeared at 24 months. Such immunoreactive cells were not seen in rats of any of the other ages studied. It was concluded that the greater expression of P2X(5) receptor at an early developmental stage and of P2X(4) in ageing might reflect functional roles for purines in cellular proliferation and/or differentiation, and in cellular degeneration, respectively, in adrenal glands of rat.

Adrenal Glands↗
PubMed2000

Localization of P2X receptors in the guinea pig adrenal gland.

The distribution of each of the seven subtypes of adenosine 5'-triphosphate (ATP)-gated P2X receptors was investigated in the adrenal gland of guinea pig utilizing immunohistochemical techniques. The occurrence of positive immunoreactivity with specific distribution was observed for antibodies against P2X(1), P2X(2), P2X(5) and P2X(6) receptors, whereas no immunoreactivity was found for antibodies against P2X(3), P2X(4) and P2X(7) receptors. Immunoreactivity for P2X(1) occurred in cells of the inner region of the zona reticularis of the cortex, Several P2X(2)-immunoreactive connective tissue-like elements were located between groups of cortical cells of the zona reticularis. Bundles and terminals of nerve fibres as well as intrinsic neurones gave positive immunoreactivity for P2X(5). The immunoreactive nerve fibres appeared to belong to both extrinsic preganglionic sympathetic and intrinsic immunoreactive neurones. Chromaffin cells were immunoreactive for the P2X(6) receptor antibody. The widespread and specific distribution of P2X receptor subtypes in the adrenal gland suggests significant roles for purinergic signalling in the physiology of the guinea pig adrenal gland.

Adrenal Cortex↗
PubMed1999

Distribution of P2X receptors in the rat adrenal gland.

The distribution of each of the seven subtypes of ATP-gated P2X receptors was investigated in the adrenal gland of rat utilizing immunohistochemical techniques with specific polyclonal antibodies to unique peptide sequences of P2X1-7 receptors. A small number of chromaffin cells showed positive immunoreaction for P2X5 and P2X7, with the relative occurrence of P2X7-immunoreactive chromaffin cells exceeding that of P2X5. The preganglionic nerve fibres that form terminal plexuses around some chromaffin cells showed P2X1 immunoreactivity. Intrinsic adrenal neurones were observed to be positively stained for P2X2 and P2X3 receptors. P2X2 immunoreactivity occurred in several neurones found singly or in groups in the medulla, while only a small number of neurones were immunoreactive for P2X3. Adrenal cortical cells were positively immunostained for P2X4-7. Immunoreactivity for P2X4 was confined to the cells of the zona reticularis, while P2X5-7 immunoreactivities occurred in cells of the zona fasciculata. The relative occurrence of immunoreactive cortical cells of the zona fasciculata was highest for P2X6, followed by P2X7 and then P2X5. The smooth muscle of some capsular and subcapsular blood vessels showed P2X2 immunoreactivity. The specific and widespread distribution of P2X receptor subtypes in the adrenal gland suggests a significant role for purine signalling in the physiology of the rat adrenal gland.

Adrenal Cortex↗
PubMed1996

Effect of reserpine treatment and hypophysectomy on the nitric oxide synthase immunoreactivity and NADPH-diaphorase staining in the rat adrenal gland.

BACKGROUND: The presence of nitric-oxide-synthesising neurons in the adrenal gland has recently been described by the immunohistochemical and/or enzyme histochemical demonstration of its synthesising enzyme, nitric oxide synthase (NOS; Afework et al. 1994. Cell Tissue Res,276:133-141). In the present report, these neurons have been examined by studying the changes that occur during conditions known to affect the adrenal gland. METHODS: By using NOS immunohistochemistry and NADPH-diaphorase histochemistry, levels of NOS and/or NADPH-diaphorase containing cellular elements in the adrenal gland were studied in rats subjected to either reserpine treatment or hypophysectomy as compared with the controls. RESULTS: Reserpine treatment caused a significant decrease in immunoreactivity to the neuronal isoform of NOS in the nerve fibres that innervate adrenal medullary cells. Hypophysectomy did not cause any change in the NOS immunoreactivity, although it eliminated most of the NADPH-diaphorase-staining non-NOS-immunoreactive cortical cells. CONCLUSIONS: The reduction in the level of NOS in the reserpine treated rats may indicate a decrease in the production of nitric oxide in the gland; this action may be related to the increase in the biosynthesis and secretion of catecholamine, which follows treatment with the drug. The reduction in the NADPH-diaphorase-positive cells may reflect the elimination of adrenal cortical cells that occurs after hypophysectomy, whereas hypophysectomy by itself appears to have no effect on the level of production of nitric oxide in the gland.

Adrenal Glands↗
PubMed1996

Increase in nitric oxide synthase and NADPH-diaphorase in the adrenal gland of streptozotocin-diabetic Wistar rats and its prevention by ganglioside.

Levels of nitric oxide synthase (NOS) and NADPH-diaphorase in adrenal glands of streptozotocin-diabetic rats of 8 and 12 weeks' duration compared with control rats were assessed with histo-chemical and biochemical techniques. Adrenal glands from streptozotocin-diabetic rats of 8 weeks' duration treated with ganglioside were examined also. In the adrenal medulla of 8-weeks- and 12-weeks-diabetic rats, NOS-immunoreactive nerve fibres were increased and decreased, respectively; additional NOS-immunoreactive and NADPH-diaphorase stained cells, which appeared to be cortical cells, were located in medulla and cortex compared with controls. Increased intensity in NADPH-diaphorase staining of the cortical cells of diabetic rats was observed also. Ganglioside treatment of the 8-weeks-diabetic rats prevented the diabetic-induced increase in NOS-immunoreactive nerve fibres. Also, it reduced most of the increase in the NOS-immunoreactive and NADPH-diaphorase stained cells and the intensity of NADPH-diaphorase staining of cortical cells. With biochemical assay, a significant increase in NOS activity was found in the adrenal glands from 8-weeks-diabetic rats, and this increase was reduced by ganglioside treatment in four out of six diabetic rats. In summary, streptozotocin-induced diabetes causes an initial increase in the levels of NOS and NADPH-diaphorase in the adrenal gland of rat, which was prevented by ganglioside treatment.

Adrenal Cortex↗
PubMed1996

Vasoconstrictor function of the rat isolated perfused mesenteric arterial bed seven days after hypophysectomy.

The effect of removal of the pituitary on mesenteric arterial function was examined in adult male rats that had undergone hypophysectomy 7 days earlier. Sham-operated rats and weight-matched rats served as controls. The body weight of hypophysectomized rats decreased from 220.75 +/- 0.48 g to 188.03 +/- 2.53 g (n = 7). Sham-operated controls gained weight, from 223 +/- 1.47 to 275.85 +/- 3.45 g (n = 8). Frequency-dependent vasoconstriction to electrical field stimulation (2-32 Hz, 90 V, 1 ms, 30 s) was significantly augmented after hypophysectomy. The maximal constrictor response of hypophysectomized preparations, 215.5 +/- 14.9 mm Hg (n = 6), was approximately twice that of the sham-operated controls, 100 +/- 6.1 mm Hg (n = 7) and weight-matched controls 109.8 +/- 5.8 mm Hg (n = 8). Norepinephrine (NE) (0.05-1,500 nmol) elicited dose-dependent vasoconstriction; the maximal response was significantly augmented after hypophysectomy, 221.71 +/- 15.9 (n = 7) as compared with 148.0 +/- 16.0 mm Hg (n = 8) in sham-operated controls and 146.3 +/- 8.7 mm Hg (n = 7) in weight-matched controls. Dose-dependent vasoconstrictor responses to ATP, 5-hydroxytryptamine, vasopressin, and endothelin were similar between the groups. High-performance liquid chromatography analysis showed no difference in NE content of the superior mesenteric artery from hypophysectomized and sham-operated controls. Hypophysectomy of rats caused an increase in sympathetic constrictor function of the mesenteric arterial vasculature that appeared to involve postjunctional adrenoceptors rather than prejunctional mechanisms and was not due to arrested growth or the smaller size of the mesenteric preparations.

Animals↗
PubMed1995

The intra-adrenal distribution of intrinsic and extrinsic nitrergic nerve fibres in the rat.

The intra-adrenal distribution of nitric oxide synthase (NOS)-immunoreactive nerve fibres was studied in rats subjected to various denervations. Splanchnic nerve section eliminated the NOS-immunoreactive nerve fibres which innervate adrenal chromaffin and neuronal cells. It did not affect those innervating blood vessels and zona glomerulosa, which instead were affected by adrenal demedullation. Guanethidine, 6-hydroxydopamine (6-OHDA) and capsaicin treatments, however, did not produce any change. These results suggest that nitrergic nerves which innervate adrenal medullary cells are extrinsic (largely preganglionic sympathetic), whilst those innervating the zona glomerulosa and the majority of adrenal vessels are intrinsic, and that they do not belong to nerves sensitive to the sympathetic nerve neurotoxins, guanethidine and 6-OHDA, or the sensory neurotoxin, capsaicin.

Adrenal Glands↗
PubMed1995

Colocalization of neuropeptides and NADPH-diaphorase in the intra-adrenal neuronal cell bodies and fibres of the rat.

Colocalization of vasoactive intestinal peptide, neuropeptide Y, calcitonin gene-related peptide, substance P, and tyrosine hydroxylase, respectively, with NADPH-diaphorase staining in rat adrenal gland was investigated using the double labelling technique. All vasoactive intestinal peptide- and some neuropeptide Y-immunoreactive intrinsic neuronal cell bodies seen in the gland were double stained with NADPH-diaphorase. Double labelling also occurred in some nerve fibres immunoreactive to vasoactive intestinal peptide and neuropeptide Y in the medulla and cortex. No colocalization of calcitonin gene-related peptide, substance P or tyrosine hydroxylase immunoreactivity with NADPH-diaphorase staining was observed. However, nerve fibres with varicosities immunoreactive for all the neuropeptides examined were closely associated with some of the NADPH-diaphorase-stained neuronal cell bodies. Thus, in rat adrenal gland, nitric oxide is synthesized in all ganglion cells containing vasoactive intestinal peptide and in some containing neuropeptide Y, but not in those containing calcitonin gene-related peptide, substance P or tyrosine hydroxylase.

Adrenal Glands↗
PubMed1995

Calretinin immunoreactivity in adrenal glands of developing, adult and ageing Sprague-Dawley rats.

Localization of calretinin immunoreactivity in the rat adrenal gland was studied using immunohistochemical methods. Calretinin-immunoreactive adrenal chromaffin cells and nerve fibres were found at all of the ages examined from embryonic day 16 up to 2-yr-old. Immunoreactive chromaffin cells showed a decrease in number with increasing age, and in the adult and ageing rats they were found among the adrenaline-storing chromaffin cells. Calretinin immunofluorescence was also observed in a few ganglion cells of the adult and ageing rats, and in most of the cortical cells at embryonic day 16. The density of immunoreactive nerve fibres in the gland showed a progressive increase with age to a peak by day 4 after birth and then a gradual decrease afterwards; they became associated mainly with some of the ganglion cells in the adult rat. As revealed by double labelling of calretinin immunoreactivity in adrenal sections from the adult rat with NADPH-diaphorase histochemistry, no co-localization existed between calretinin and NADPH-diaphorase; however, a small number of neuronal cell bodies which contained nitric oxide synthase were found heavily surrounded with calretinin-immunoreactive nerve fibres. In ageing rats, an increased density of calretinin-immunoreactive nerve fibres was seen associated largely with the chromaffin cells. We conclude from this study that calretinin is found in the rat adrenal gland; the high degree of variability in its expression with age suggests that calretinin may be concerned with age-related activities in the gland.

Adrenal Glands↗
PubMed1994

Distribution and colocalization of nitric oxide synthase and NADPH-diaphorase in adrenal gland of developing, adult and aging Sprague-Dawley rats.

The distribution and colocalization of nitric oxide synthase and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-diaphorase) was investigated in the adrenal gland of developing, adult and aging rats with the use of immunohistochemical and histochemical techniques. Nitric oxide synthase-immunoreactive neurons within the adrenal gland were found from the 20th day of gestation onwards. During early development the neurons were found as small clusters of smaller-size cells compared to those observed in the adult gland. Their number reached that of adult level by the 4th day after birth, and in the glands from aging rats a 28.6% increase was observed. Whilst no immunofluorescence was seen in chromaffin cells during early development, some cells from glands of aging rats showed nitric oxide synthase-immunoreactivity with varying intensity. The immunoreactive neurons from postnatal rat adrenals were also positive for NADPH-diaphorase, whilst those in prenatal rats were negative or lightly stained. Nitric oxide synthase-immunoreactive nerve fibres were present in all adrenal glands examined from the 16th day of gestation onwards. A considerable degree of variation in the distribution of immunoreactive fibres both in medulla and outer region of cortex at the different age groups was observed and described. Most, but not all, nitric oxide synthase-immunoreactive nerve fibres also showed NADPH-diaphorase staining.

Adrenal Glands↗
PubMed1993

The innervation of the mammalian adrenal gland.

Early conflicting reports and the lack of sensitive anatomical methods have led to an oversimplified view of adrenal gland innervation. It was not until the introduction of nerve fibre tracing techniques in the mid-1970s that the true complexity of adrenal innervation began to emerge. The first part of this article comprises a brief review of these and other relevant reports dealing with both medullary and cortical innervation. In the second part a detailed account is given of the work undertaken in Rex Coupland's Department relating to the innervation of the rodent and primate adrenal medulla using a retrograde fluorescent tracer technique. It was concluded that, in all 3 species studied, the adrenal medulla receives a sympathetic and parasympathetic efferent and an afferent innervation. The possible interrelationship between neural control of cortical and medullar secretions is discussed briefly.

Acetylcholinesterase↗
PubMed1992

Colocalization of nitric oxide synthase and NADPH-diaphorase in rat adrenal gland.

The distribution and colocalization of nitric oxide synthase (NOS) and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase was studied in the neuronal elements of the adrenal gland of the rat. Ganglion cells and many nerve fibres in the gland showed both NOS-immunoreactivity and NADPH-diaphorase staining. The adrenal cortical cells showed NADPH-diaphorase staining but were not immunoreactive for NOS. Positive labelling for both NADPH-diaphorase and NOS was found in bundles and in single fibres with varicosities, preferentially located around the noradrenaline (NA)-storing cells. Adrenaline (A)-storing cells and ganglion cells in the medulla, along with the cortical cells and blood vessels in the zona glomerulosa, received relatively fewer positive fibres.

Adrenal Glands↗
PubMed1992

The effects of respiratory training with inspiratory flow resistive loads in premature infants.

Respiratory training of premature infants was performed to determine whether improved respiratory muscle strength and/or endurance would result. Twenty-two premature infants were randomized into control and training groups for 2 wk, using inspiratory flow-resistive loads for training (75 cm H2O.L-1.s in wk 1 and 90 cm H2O.L-1.s in wk 2). Respiratory endurance was assessed by the time interval required for the development of a 5-torr rise in transcutaneous CO2 tension during the hypoventilation induced by loaded breathing, using a moderately severe resistive load (250 cm H2O.L-1.s at 1 L.min-1). Respiratory strength was assessed by the maximum negative airway pressure generated during occluded breaths, a pressure-time integral, and an effort index. Results revealed that respiratory muscle endurance, which was not initially different between control and trained groups, increased significantly after 2 wk in the trained group by 137% (median value, p less than 0.05), whereas it remained unchanged in the control group (-24%). The trained group of infants also showed a significant decrease in baseline breathing frequency between the initial and final measurements taken 2 wk apart when compared with controls (p less than 0.05) and a lesser increase in inspiratory time with loading in the final measurement as compared with the initial value (p less than 0.05). There was no significant difference between the control and trained groups in initial or subsequent measures of respiratory muscle strength. Inspiratory flow-resistive load training appears to improve the respiratory endurance of premature infants in whom respiratory muscle fatigue has been described to play a role in the development of respiratory failure.

Apnea↗