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R P Hoogma

Publications and source records attributed to R P Hoogma.

10 recordsLinked to original sources
PubMed1995

The effect of GHRH on TSH release in rats in vivo and in vitro.

In man, GHRH has been shown to potentiate the TSH-releasing activity of TRH. To study the way by which GHRH affects TRH-stimulated TSH release, we examined the effect of GHRH (1-29)NH2 on basal and stimulated TSH secretion in intact male rats and superfused dispersed rat pituitary cells. In the intact rats, GHRH(1-29)NH2 potentiated TRH-stimulated TSH release in the evening, but potentiation was not observed in the morning and in dispersed pituitary cells. Basal TSH levels were not changed by GHRH(1-29)NH2. It is concluded that GHRH(1-29)NH2 potentiates the TSH-releasing activity of TRH in the evening in rats possibly through suprahypophyseal disinhibition.

Animals↗
PubMed1993

Octreotide scintigraphy for the detection of paragangliomas.

Paragangliomas have neuroendocrine characteristics. We previously described successful in vivo visualization of various tumors of neuroendocrine origin after injection of the radiolabeled somatostatin analogue octreotide. In this study, we report the results of 111In-octreotide scintigraphy in 34 patients referred because of known paragangliomas or in whom a paraganglioma was suspected and compared the results of octreotide scintigraphy with the outcomes of other imaging techniques used in the diagnosis or follow-up of these patients. Fifty of 53 (94%) known localizations in 25 patients with paragangliomas were visualized. In two patients, three localizations were missed during octreotide scintigraphy. Unexpected additional paraganglioma sites, not detected or not investigated with conventional imaging techniques, were found in 9 of 25 patients (36%) with known paragangliomas. In four of them, the supposed tumor localizations were thereafter also demonstrated with other imaging modalities. In eight of nine patients who were referred because of symptoms consistent with paraganglioma or follow-up after surgical removal of a paraganglioma, neither routine imaging nor octreotide scintigraphy revealed any abnormalities indicative of paraganglioma. We conclude that: (1) virtually all paragangliomas can be visualized using in vivo 111In-octreotide scintigraphy and (2) because conventional imaging is usually limited to the site where a paraganglioma is clinically suspected, octreotide scintigraphy, because of the information it provides on potential tumor sites in the whole body, may be useful in detecting multicentricity or metastases in patients with paraganglioma.

Abdominal Neoplasms↗
PubMed1992

MRI screening of kindred at risk of developing paragangliomas: support for genomic imprinting in hereditary glomus tumours.

Paragangliomas of the head and neck (glomus tumours) can occur in a hereditary pattern and may be hormonally active as well as being associated with paragangliomas elsewhere. A number of these tumours may be present without symptoms. To detect the presence of subclinical paragangliomas we screened 83 members of a family at risk of developing hereditary paragangliomas using whole body MRI and urinary catecholamine testing. In eight previously diagnosed members, eight known glomus tumours of which one functioning, and two unknown glomus tumours and one unknown pheochromocytoma were present. Six unsuspected members showed ten glomus tumours and one pheochromocytoma. It has been suggested that the manifestation of hereditary glomus tumours is determined by the sex of the transmitting parent. There were no tumours in the descendants of female gene carriers. Comparing the likelihood of inheritance with genomic imprinting versus inheritance without genomic imprinting we found an odds ratio of 23375 in favour of genomic imprinting.

Carotid Body↗
PubMed1991

MR imaging and MIBG scintigraphy of pheochromocytomas and extraadrenal functioning paragangliomas.

To compare the potential of magnetic resonance (MR) imaging and scintigraphy performed with radiotracer-labeled metaiodobenzyl-guanidine (MIBG) in localization and characterization of functioning paragangliomas, the authors analyzed results of both modalities in 33 patients. Overall sensitivity for detection was 91% for MR imaging and 80% for MIBG scintigraphy. MR imaging demonstrated 100% of adrenal paragangliomas and 75% of extraadrenal paragangliomas, whereas MIBG scintigraphy revealed 75% and 88%, respectively. MIBG scintigraphy was more specific in the characterization of paragangliomas than MR imaging (100% vs 82%). However, MR imaging demonstrated nine other lesions not seen on scintigrams. On the basis of their results and other considerations, the authors believe MR imaging is the preferred initial technique when a functioning paraganglioma is suspected.

3-Iodobenzylguanidine↗
PubMed1990

Iodine-123-metaiodobenzylguanidine scintigraphy in patients with chemodectomas of the head and neck region.

While studying the uptake of iodine-123-metaiodobenzylguanidine ([123I]MIBG) in chemodectomas, we coincidentally detected catecholamine secreting tumors in 5 out of 14 patients. In three of these cases, a norepinephrine secreting abdominal paraganglioma was subsequently removed. One patient had a norepinephrine secreting chemodectoma and one had a dopamine secreting chemodectoma. Prior to [123I]MIBG imaging and urinary catecholamine measurements, endocrine activity was suspected in only one of these five patients. Apart from these five cases, two other patients showed elevated catecholamine secretion and abnormal abdominal [123I]MIBG concentrations. However, these two patients were not surgically explored, because of normal computed tomography (CT) and magnetic resonance (MRI) studies. We suspect that catecholamine-secreting tumors are more common in patients with chemodectomas than is assumed in the literature, and we therefore recommend urinary catecholamine screening for all patients with chemodectomas. In case of elevated catecholamine secretion, MIBG scintigraphy is indicated.

3-Iodobenzylguanidine↗
PubMed1983

Physiological effects of short-term treatment with enalapril in hypertensive patients.

To assess the effects of enalapril eight hospitalized hypertensive patients on constant sodium intake were treated with incremental doses of this angiotensin converting enzyme blocking drug. After four days of placebo treatment enalapril was given in single daily doses, starting with 1.25 mg and increasing until blood pressure was adequately controlled. On the 1.25 mg dose, angiotensin II (AII) and blood pressure did not change significantly, despite a 50% reduction in converting enzyme activity. There were, however, significant increases in noradrenaline, renin and aldosterone. With high doses a more pronounced reduction in converting enzyme activity was found while AII, aldosterone and blood pressure all fell significantly. Renin levels rose, but noradrenaline and adrenaline were reduced. Orthostatic hypotension did not occur. With continued treatment renal vascular resistance decreased concurrently with enhanced natriuresis and a reduction in body weight. Plasma volume rose slightly. The data indicate that enalapril may lower blood pressure by converting enzyme inhibition, but sodium loss and a decrease in sympathetic activity are associated features.

Adult↗
PubMed1981

Neurohumoral response to hospitalization in hypertensive patients.

1. To investigate whether reduced activity of pressor systems could explain the spontaneous drop in pressure upon hospitalization, 51 subjects with uncomplicated essential hypertension were admitted to hospital. Sodium intake was fixed at 55 mmol/day. 2. Blood samples for noradrenaline, adrenaline, active renin, angiotensin II and aldosterone were drawn on each morning of the first 3 days of hospitalization; blood pressure was measured at 2 h intervals and values were averaged for each day. 3. Subjects were divided in two groups depending on whether they became normotensive (group 1; n = 12) or remained hypertensive (group 2; n = 39). This distinction was thought to reflect mild and more severe hypertensive groups respectively. 4. Although both groups showed a comparable fall in blood pressure during hospitalization, noradrenaline levels fell more consistently in group 1, whereas adrenaline levels fell only in group 2. The components of the renin--angiotensin--aldosterone system rose, but more conspicuously in group 1. 5. It is concluded that withdrawal of sympathetic activity can only partly explain the hypotensive response to hospitalization. The renin--angiotensin system behaves only passively and appears to be counterproductive to alterations in blood pressure.

Adult↗
PubMedDate not supplied

Humoral and renal effects of MK-421 (enalapril) in hypertensive subjects.

To assess the effect of MK-421 (enalapril) we treated six hospitalized hypertensive patients receiving constant sodium intake with incremental doses of this new angiotensin-converting enzyme blocking drug. After a few days of placebo treatment, MK-421 was given in single daily doses, starting with 1.25 mg and increasing until blood pressure was adequately controlled. On the lowest dose, converting enzyme activity was reduced by 50%, but angiotensin II and blood pressure did not change significantly. There were, however, significant increases in noradrenaline, renin, and aldosterone. With higher doses there was a more pronounced reduction in converting enzyme activity, while angiotensin II, aldosterone, and blood pressure all fell significantly. Renin levels rose, but noradrenaline and adrenaline were reduced. Orthostatic hypotension was not observed. With continued treatment, renal vasodilatation and enhanced natriuresis occurred together with a 1.2 kg decrement in body weight. Concurrently plasma volume rose, but renal blood flow remained unchanged. The data indicate that MK-421 effectively lowers blood pressure, and it does so by converting enzyme inhibition; sodium loss and a decrease in sympathetic activity are associated features. Since plasma volume increased despite enhanced natriuresis, the drug may act both at the arteriolar and at the venular level.

Adult↗
PubMedDate not supplied

Efficacy and safety of benazepril plus hydrochlorothiazide versus benazepril alone in hypertensive patients unresponsive to benazepril monotherapy.

A combination of benazepril 10 mg plus hydrochlorothiazide 12.5 mg once daily was investigated in the treatment of patients with mild-to-moderate essential hypertension who had not responded to monotherapy with benazepril 10 mg. Patients failing to respond to 4 weeks of benazepril 10 mg/d were randomized to continue with the monotherapy (n = 47) or receive the combination therapy (n = 46). After 4 weeks of double-blind treatment, reductions in blood pressure were significantly greater among patients given the combination than among those receiving benazepril alone: a 4.7 +/- 1.5 mm Hg difference in mean sitting diastolic blood pressure was noted in favor of the combination therapy (P = 0.0037). The incidence of adverse events, particularly cough, was lower with benazepril + hydrochlorothiazide than with benazepril alone; no notable changes in body weight or heart rate were seen in either group.

Administration, Oral↗