Structure of the human type IV collagen genes.
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Amino Acid Sequence↗
Biomedical subjects
A Ganguly
Publications and source records attributed to A Ganguly.
Structural organization of the gene for the alpha 1 chain of human type IV collagen.
The complete exon size and distribution pattern in the gene for the alpha 1 chain of human type IV collagen was determined. Clones covering 145 kilobases (kb) of genomic DNA including 100 kb of the gene itself as well as 25 kb upstream and 20 kb downstream of the gene sequences, respectively, were isolated from lambda phage and cosmid libraries. The overall gene structure was determined by endonuclease restriction mapping and R-loop analyses and all exon sizes by nucleotide sequencing. The characterized clones contained all the coding sequences except for exon 2 whose sequence was determined after its amplification by the polymerase chain reaction. There were four gaps in the intron sequences; the exact size of the gene is unknown. The entire gene is at least 100 kb in size and contains 52 exons whose size distribution is completely different from that of the genes for fibrillar collagens. In the -Gly-X-Y- coding region there are three exons of 99, 90, and 45 base pairs (bp) each and two exons of 27, 36, 42, 51, 54, 63, and 84 bp each. The rest of the exons have sizes between 71 and 192 bp in the collagenous region. About one-half of the -Gly-X-Y- repeat coding exons start with the second base for the codon of glycine, whereas the other half starts (with two exceptions) with a complete glycine codon. The distribution of split versus unsplit codons is uneven in that the first 19 exons of the gene start with a complete codon. The gene contains repetitive sequences in several regions. A 185-nucleotide segment containing 40 copies of CCT flanked by poly(C) and poly(T) sequences was shown to be located adjacent to an exon. The gene has previously been shown to be located head-to-head to the alpha 2(IV) collagen gene at the distal end of the long arm of chromosome 13, such that the first exons of the two genes are separated by as little as 42 bp (Pöschl, E., Pollner, R., and Kühn, K. (1988) EMBOJ. 7,2687-2695; Soininen, R., Huotari, M., Hostikka, S. L., Prockop, D. J., and Tryggvason, K. (1988) J. Biol. Chem. 263, 17217-17220). The results demonstrate that the human alpha 1(IV) collagen gene has a structure distinctly different from the genes for fibrillar collagens and also that it is considerably larger than any collagen gene characterized to date.
Amino Acid Sequence↗
Atrial natriuretic factor inhibits angiotensin-induced aldosterone secretion: not through cGMP or interference with phospholipase C.
ANF did not prevent the formation of [3H] inositol trisphosphate in response to AII but inhibited aldosterone secretion in calf adrenal glomerulosa cells. 8-bromo cGMP did not affect either inositol phosphate formation or aldosterone secretion. Changes in cytosolic Ca++ concentration induced by AII, as measured by Quin 2 fluorescence, were also unaffected by ANF. No difference in adrenal cell protein phosphorylation with AII or AII + ANF was observed. The results suggest that ANF may inhibit aldosterone secretion through a non-guanyl cyclase linked receptor system not involving the formation of phosphoinositide-derived second messengers. Interference with protein kinase C activity cannot be ruled out.
Aldosterone↗
18-oxocortisol: effect of dexamethasone, ACTH and sodium restriction.
The urinary excretion of 18-oxocortisol in 37 normal subjects consuming a normal sodium diet was 1.2 +/- 0.9(SD) microgram/24 h. Dexamethasone administration to 5 normal individuals suppressed the excretion of 18-oxocortisol from 1.16 +/- 0.5 micrograms/24 h to 0.6 +/- 0.2 micrograms/24 h. While they still received dexamethasone, ACTH administration raised the 18-oxo-cortisol excretion to 3.82 +/- 1.2 micrograms/24 h. Seven normal subjects were placed on a sodium restricted diet, and the urinary excretion of 18-oxocortisol rose from 1.5 +/- 1.21 micrograms/24 h to 8.54 +/- 5.08 micrograms/24 h and aldosterone from 6.6 +/- 2.0 micrograms/24 h to 39.7 +/- 14.6 micrograms/24 h. Two of the seven individuals showed minimal increases in the excretion of 18-oxocortisol, but in all cases aldosterone increased with sodium restriction. The urinary excretion of 18-oxocortisol correlated significantly with the excretion of aldosterone, 18-hydroxycortisol, cortisol, and 19-nordeoxycorticosterone. These studies indicate that 18-oxocortisol secretion is under ACTH regulation, but since sodium restriction also increases the excretion of 18-oxocortisol, the renin-angiotensin system must also participate in its regulation. However, some individuals do not increase their excretion of 18-oxocortisol with sodium restriction, although aldosterone excretion increases as expected, suggesting that additional factors participate in the regulation of 18-oxocortisol production.
Adrenocorticotropic Hormone↗
Proopiomelanocortin-derived peptides, phosphoinositides, cAMP, and aldosterone secretion.
Since the intracellular messengers of various proopiomelanocortin-derived peptides remain ambiguous at best, we have investigated the possible involvement of phosphoinositide metabolism in aldosterone secretion evoked by alpha-MSH, beta-LPH, as well as ACTH in rat and calf adrenal glomerulosa cells. We have also examined the cAMP responses in the adrenal glomerulosa cells to alpha-MSH comparing it with those of ACTH. Our results showed that neither alpha-MSH, beta-LPH, nor ACTH increased inositol triphosphate (IP3) or other inositol phosphates in adrenal glomerulosa cells while increasing aldosterone secretion from the same cells. Angiotensin II, known to cause hydrolysis of the phosphoinositides, increased IP3 in these adrenal cells in a dose-dependent manner. Both ACTH and alpha-MSH raised the cAMP levels in the calf adrenal glomerulosa cells, although the magnitude of the increase of cAMP in response to ACTH was greater. These findings suggest that IP3 as a mediator of alpha-MSH- and beta-LPH-induced aldosterone secretion is not likely and other mediator(s) may be involved.
Adrenocorticotropic Hormone↗
Detection and location of single-base mutations in large DNA fragments by immunomicroscopy.
A technique whereby single-base mutations can be detected by immunomicroscopy of DNA heteroduplexes is described. Four constructs of the filamentous phage M13 were prepared so as to differ by a single base at the same site. Heteroduplexes were prepared and reacted with a water-soluble carbodiimide, with polyclonal antibodies specific for the carbodiimide, and then with a second antibody linked to an electrondense marker. Electron microscopy of the heteroduplexes indicated that the label was located at 4.9 to 5.1 kb in the 7.2-kb phage. The known site of the mismatch was 4.96 kb. Also, plasmids containing inserts of a fragment from the 5' end of hemoglobin A or hemoglobin S were prepared. The median location of the label in heteroduplex molecules was 2.9 kb. The known site of the mismatch was 2.65 kb in the 4.9-kb plasmid. The procedure requires about 10 days to analyze two samples of plasmid or phage DNA.
Anemia, Sickle Cell↗
Aldosterone response to insulin-induced hypoglycemia in hemodialysis patients.
To investigate possible abnormalities of the hypothalamic-pituitary axis in patients with chronic renal failure on dialysis, we have examined the effects of insulin-induced hypoglycemia on the adrenal steroid responses. In normal subjects, plasma aldosterone and cortisol concentrations increase significantly in response to hypoglycemia, with good correlation. In the patients with end-stage renal disease (ESRD) however, insulin-induced hypoglycemia fails to elicit significant increases in the plasma cortisol and aldosterone levels. To test the adrenal responsiveness to adrenocorticotropin (ACTH), we administered ACTH to both groups. Plasma cortisol and aldosterone responses are similar in both groups suggesting that the adrenal responsiveness to ACTH is not impaired. We also investigated the responsiveness of the renin-angiotensin-aldosterone system in response to volume contraction by hemofiltration in patients with ESRD. Neither plasma renin activity nor plasma aldosterone concentration change significantly following such contrived volume contraction. These results reveal several endocrinologic abnormalities in the patients with ESRD on chronic hemodialysis.
Adrenocorticotropic Hormone↗
Counterregulatory hormonal response to insulin-induced hypoglycemia in patients on chronic hemodialysis.
Insulin induced hypoglycemia was produced in 5 chronic hemodialysis patients and 5 normal controls. Normally, several counterregulatory hormones (cortisol, growth hormone, glucagon and epinephrine) are secreted. Although we did not measure glucagon in our study, the other hormones were found to respond normally to the hypoglycemia in the control subjects. In the dialysis patients plasma epinephrine response was normal, but no responses of plasma ACTH, cortisol and growth hormone were found. Failure of the other counterregulatory hormones to respond to hypoglycemia indicates that dialysis patients probably maintain their euglycemic state by increasing plasma glucagon and epinephrine concentrations. We were unable to confirm the expected decrease of catecholamines that has been reported during hemodialysis.
Adrenocorticotropic Hormone↗
Acute effect of captopril on aldosterone secretory responses to endogenous or exogenous adrenocorticotropin.
The aldosterone secretory response to Captopril (12.5 mg, orally) was studied in five normal men. Endogenous ACTH and epinephrine secretion was stimulated by the induction of hypoglycemia. Normally this stimulus increases plasma cortisol, GH, aldosterone, and PRA. Administration of captopril resulted in a blunted plasma aldosterone response to hypoglycemia, but no concomitant blunting of the plasma cortisol response. The responses of other hormones, with the exception of PRA, were not affected. When exogenous ACTH was administered to the same men with and without captopril, the plasma aldosterone response was again blunted by captopril, while the plasma cortisol response was unaffected. We conclude that angiotensin II may be required for ACTH to stimulate aldosterone secretion. Alternatively, the possibility that captopril may selectively inhibit aldosterone secretion at the adrenal cellular level cannot be excluded.
Adrenocorticotropic Hormone↗
Glucocorticoid-suppressible aldosteronism: a disorder of the adrenal transitional zone.
Glucocorticoid-suppressible aldosteronism (GSA) is a rare form of hyperaldosteronism in which the increased secretion of aldosterone and the elevation of blood pressure are corrected when ACTH secretion is suppressed. Two 17-hydroxylated analogs of 18-hydroxycorticosterone and aldosterone, 18-hydroxycortisol and 18-oxocortisol, which had been identified in the urine of patients with hyperaldosteronism due to an adrenal adenoma and in bullfrog adrenal tissue incubated with cortisol, are produced in greater than normal quantities in patients with GSA. The excretion of 18-hydroxycortisol and 18-oxocortisol in nine patients with GSA was 2914 +/- 923 (+/- SD) nmol/day [1108 +/- 351 micrograms/day; normal, 165 +/- 94 nmol/day (63 +/- 36 micrograms/day)] and 141 +/- 77 nmol/day [53 +/- 29 micrograms/day; normal, 3.2 +/- 2.4 nmol/day (1.2 +/- 0.9 micrograms/day)], respectively. The excretion of aldosterone 18-oxoglucuronide was 53 +/- 18 nmold/day [19.4 +/- 6.8 micrograms/day; normal, 16.9 +/- 7.5 nmol/day (6.1 +/- 2.7 micrograms/day)]. Aldosterone excretion was elevated in six patients and within the normal range in three patients. The degree of abnormality in 18-hydroxycortisol and 18-oxocortisol excretion was significantly greater than that in aldosterone. Dexamethasone administration decreased excretion of the three steroids to the normal range. ACTH administration for 3 days resulted in an exaggerated increase in the excretion of these steroids, suggesting ACTH dependence of these steroids in patients with GSA. The excessive production of these steroids, which are 17- and 18-hydroxylated, indicate that they are produced by hybrid-type cells which we have called transitional cells, which are also capable of producing aldosterone. These findings are consistent with the postulate that cytochrome P-450-corticosterone methyl oxidase fails to disappear normally in the zona glomerulosa cells as they migrate to the zona fasciculata and acquire 17-hydroxylase activity. This abnormality explains the supernormal conversion of cortisol to 18-hydroxycortisol and 18-oxocortisol and the ACTH dependence of aldosterone secretion in GSA.
Adolescent↗
Possible involvement of the GABAergic system in dopaminergic-cholinergic interactions in electroacupuncture-induced analgesia.
The involvement of the GABA system in dopamine-acetylcholine interactions in electroacupuncture induced analgesia (EAA), measured in terms of tail flick latency (TFL) test, was studied with administration of the GABA receptor agonist, muscimol (1 mg/kg, i.p.); antagonist, bicuculline (2 mg/kg, i.p.); GABAmimetic drug, ethanolamine-O-sulfate (EOS) (2 mg/kg, s.c.) or the drugs stimulating or inhibiting acetylcholine and dopamine receptors activity to rats exposed to electroacupunture (EA). All the drugs were administered prior to EA (10 Hz, 1 volt) exposure (2-15 min). Results observed under the above conditions suggest that the cholinergic system has a direct inhibitory role on EAA and the dopaminergic system mediates its action via the cholinergic system. A decrease in EAA with both the GABA receptor agonist and antagonist and tremendous increase of EAA with the gabamimetic drug, EOS, showed that GABA receptors may not be directly involved in EAA. Further (a) gradual withdrawal of muscimol, bicuculline or physostigmine induced decrease in EAA with the increase in duration of EA exposure; (b) the characteristic changes in EAA observed with the coadministration of (i) L-DOPA + carbidopa + muscimol (ii) atropine + muscimol; and (c) no significant change in bicuculline + physostigmine induced inhibition of EAA with the increase in duration of EA exposure suggest that some inhibitory substance(s) may be released during EA which may inhibit the GABA system and finally cholinergic activity through the activation of dopaminergic neurone.
Acupuncture Therapy↗
Determination of cyanide through its reaction with gelatin-stabilised gold sol in air.
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Air↗
Testicular defect: the primary abnormality in gonadal dysfunction of uremia.
Gonadal dysfunction is a common problem in end-stage renal disease. We decided to test the ability of the male gonads to respond to exogenous stimuli. The patients receiving chronic hemodialysis showed abnormally low levels of total testosterone and free testosterone in the presence of normal testosterone-binding globulin. Furthermore, the exogenous administration of human chorionic gonadotropin failed to elicit a normal response from the male gonads of hemodialyzed patients. Although basal serum prolactin levels are elevated, we do not believe that elevation is of the magnitude expected to produce testicular failure. Thus we believe that the primary testicular failure is part of the uremic syndrome, and is not corrected by dialysis.
Adult↗
Urinary 18-hydroxycortisol and its relationship to the excretion of other adrenal steroids.
The urinary excretion of 18-hydroxycortisol was recently reported to be increased in patients with primary aldosteronism who have an adrenal adenoma and in those with glucocorticoid-suppressible aldosteronism. A direct RIA for 18-hydroxycortisol in urine and plasma has been described, and we here report our experience using a similar direct RIA and a more elaborate RIA which includes a preliminary high pressure liquid chromatography (HPLC) purification step. The urinary excretion of 18-hydroxycortisol was compared with that of other adrencorticoids. The urinary excretion of 18-hydroxycortisol in 37 normal subjects using the direct RIA was 112 +/- 49 (+/- SD) microgram/24 h, and that with the HPLC-RIA method was 63 +/- 36 micrograms/24 h. The accuracy and specificity of the HPLC-RIA assay method were confirmed by measuring the steroid after the HPLC step as the glycolic acid ester derivative. The urinary excretion of 18-hydroxycortisol correlated with that of cortisol (r = 0.36; P less than 0.01), 18-oxocortisol (r = 0.42; P less than 0.01), and 19-nordeoxycortisosterone (r = 0.71; P less than 0.001), but did not correlate with the excretion of aldosterone 18-oxoglucuronide (r = 0.25; P = 0.15942). Dexamethasone administration to five normal subjects significantly decreased 18-hydroxycortisol excretion from 81 +/- 47 to 23 +/- 8 micrograms/24 h. ACTH infusion in these subjects receiving dexamethasone significantly raised 18-hydroxycortisol excretion to 147 +/- 37 micrograms/24 h. Five days of a sodium-restricted diet (10 mmoles/day) resulted in a significant (P less than 0.02) increase in 18-hydroxycortisol excretion, but two of eight subjects had decreased excretion, although urinary aldosterone excretion increased, as expected. These studies demonstrate that the direct RIA significantly overestimates urinary 18-hydroxycortisol excretion. These studies also demonstrate that the major factor resulting 18-hydroxycortisol excretion is ACTH. However, since 18-hydroxycortisol excretion may increase during sodium depletion, angiotensin or other factors may also regulate its secretion.
Adrenal Cortex Hormones↗
Metoclopramide fails to stimulate aldosterone secretion and inhibits serotonin-mediated aldosterone secretion in the rat.
The acute and chronic effects of metoclopramide on aldosterone secretion in the rat model were examined. Metoclopramide 50 micrograms iv in dexamethasone-treated rats did not increase plasma aldosterone concentration. Chronic infusion of metoclopramide (72 micrograms/hr) over 5 days also did not show any increase in the plasma or urinary aldosterone concentration when compared with control rats. Metoclopramide in vitro showed no effect on aldosterone secretion from rat adrenal capsular cells but it inhibited serotonin-mediated aldosterone secretion from the same cells significantly.
Adrenal Glands↗
Osmoregulation and baroregulation of plasma vasopressin in essential hypertension.
Vasopressin secretion is stimulated by hyperosmolality, hypovolemia, or hypotension and is inhibited by hypoosmolality, hypervolemia, or hypertension. These osmotic and hemodynamic influences are mediated by neuronal afferents that originate in separate osmoreceptors or baroreceptors but ultimately converge to act on the same neurosecretory neurons. Functionally, the two control systems are integrated in such a way that osmoregulation is altered but not disrupted by hemodynamic influences. In patients with uncomplicated essential hypertension, basal as well as osmotically stimulated vasopressin is completely normal. The vasopressin response to an acute reduction in blood pressure is also normal if the values are expressed relative to the change in pressure. However, if the plasma vasopressin response is plotted as a function of absolute blood pressure, the line describing the relationship lies well to the right of normal. Thus, although it is completely intact, the baroregulatory mechanism appears to be reset to a higher level in essential hypertension. These results suggest that increased secretion of vasopressin does not contribute to the genesis or maintenance of uncomplicated, untreated essential hypertension but may antagonize the therapeutic effect of some antihypertensive drugs. If so, antagonists of V1 receptors may be useful as second-line adjunctive therapy for this condition.
Adult↗
Calcium-dependence of serotonin-mediated aldosterone secretion and differential effects of calcium antagonists.
The requirement for calcium in the serotonin-mediated aldosterone secretion was investigated using rat adrenal capsular cells. In the calcium-free medium both basal as well as serotonin-stimulated aldosterone secretion (at concentrations of 10(-7) M and 10(-8) M of serotonin) were significantly impaired. The effects of calcium-channel blockers were then examined. Verapamil (10(-5) M and 10(-6) M markedly inhibited basal and serotonin-evoked aldosterone secretion. In equimolar concentrations nifedipine had much less effect and diltiazem produced no apparent attenuation of either basal or serotonin-stimulated aldosterone secretion. These results indicate the calcium-dependence of serotonin-induced aldosterone secretion. The variable effects of the calcium-channel blockers suggest different or multiple mechanisms of action of these agents.
Adrenal Cortex↗
Alteration of domain architecture of chicken erythrocyte chromatin.
The higher-order organisation of chromatin in chicken erythrocyte nuclei as a function of the ionic strength of the nuclear suspension buffer and also of the time of incubation in this buffer prior to nuclease digestion has been investigated. This organisation is described in terms of a physical parameter called the domain length. The 45-kbp-long domains of control nuclei were unravelled to give rise to domains of length 150 kbp on overnight equilibration at 0 degree C of the nuclei in standard isolation buffer containing 0.135 M NaCl prior to nuclease digestion. However, transition to the equilibrium state was preceded by a metastable and irregular domain architecture when the nuclei were incubated for only 1 h. In contrast, the domain length remained unchanged when nuclei were incubated in the isolation buffer alone for identical periods of time. The proteins dissociated at the higher ionic strength were characterised and their role in stabilising the domain structure is discussed.
Animals↗