Incidence of Type 1 diabetes in children in Cáceres, Spain, during 1988-1999.

AIM: To determine the incidence of Type 1 diabetes in Cáceres in children less than 14 years of age. We tested for differences in incidence by age, sex and season at diagnosis. METHODS: All Type 1 diabetes cases with onset <14 years of age between 1988 and 1999 were recorded retrospectively. Pediatric Unit registries provided the primary source of ascertainment. The secondary independent data source was based on the registries of local Diabetic Associations, diabetes camp records and guarantee cards of blood-glucose meters. We used the capture-recapture method for ascertainment. RESULTS: During the 12-year period, 137 new cases of Type 1 diabetes were identified. Completeness of ascertainment was 99.2%. Average annual observed incidence was 16.8/100,000/year (95% C.I. 14.1-19.8). Age-standardised incidence (world population): 16.5/100,000/year (95% C.I. 13.9-19.6). Average annual incidence for 0-4, 5-9 and 10-13-year-old groups: 12.7/100,000 (95% C.I. 8.8-17.9), 18.2/100,000 (95% C.I. 13.7-23.8) and 19.1/100,000 (95% C.I. 14.2-25.1). The highest age-specific annual incidence rate was found in the 10-13-year age group. There was a seasonal onset pattern, with the highest incidence in autumn and winter. November was the month with the highest number of cases (22/137). CONCLUSION: Cáceres has a moderately high incidence of Type 1 diabetes in children less than 14 years of age, similar to that found in other more developed and densely populated regions of Spain, and in the range of other countries of northern Europe. These data do not support the hypothesis of a decrease in the incidence of the disease from north to south over Europe.

Vasopressinergic mechanisms in the nucleus reticularis lateralis in blood pressure control.

We sought to determine whether arginine vasopressin (AVP) modulates arterial pressure (AP) by a receptor-mediated action in the nucleus reticularis rostroventrolateralis (nRVL). Immunocytochemical labeling with an antiserum against a synthetic AVP conjugate revealed a discrete although modest presumptive neuropeptidergic innervation of the nRVL. Electron microscopic analysis of vasopressinergic processes in the nRVL revealed that AVP-like immunoreactivity (AVP-LI) was primarily in axons and axon terminals. Immunoreactive terminals contained numerous small clear vesicles and large dense core vesicles and formed synapses with unlabeled dendrites. In the nRVL, retrograde transport-immunofluorescence data demonstrated close appositions between vasopressinergic beaded processes and a compact subambigual column of reticulospinal neurons labeled by deposits of cholera toxin beta-subunit into the thoracic spinal cord. Similar methods were used to define the origins of the AVP-afferent projection to nRVL. These retrograde transport-immunofluorescence studies demonstrated numerous retrogradely labeled neurons in the hypothalamus, including the paraventricular nucleus (PVN), after injections of a retrograde tracer, Fluoro-Gold into the ventrolateral medulla. However, double-labeled neurons were rare and confirmed a diffuse AVP afferent innervation of the sympathoexcitatory area. Microinjection of AVP into the nRVL in anesthetized rats produced a large dose-related increase in AP different from control at a dose of 1 pmol or higher. AVP injected intravenously elevated AP only at significantly higher doses. Microinjections of AVP into the nucleus tractus solitarii (NTS) had a smaller effect whereas into the caudal ventrolateral medulla exerted no effect on AP. Bilateral microinjections of an AVP antagonist, d(CH2)5[Tyr(Me)2]AVP into the nRVL produced no change in AP but blocked the increase produced by subsequent injections of AVP. An acute hemorrhage produced by withdrawal of 2 ml of blood from the femoral vein did not alter AP. However, bilateral microinjections of the AVP antagonist into the nRVL 5 min after hemorrhage decreased AP. In contrast, the AVP-antagonist injected intravenously after hemorrhage had no effect on AP. Our data suggest that under conditions demanding increased sympathetic drive to maintain AP, such as hemorrhage, a functional AVP receptor mechanism via terminals in the nRVL may be activated to restore normal levels of AP.

Rilmenidine lowers arterial pressure via imidazole receptors in brainstem C1 area.

We sought to determine the site of action and receptor type responsible for the antihypertensive actions of rilmenidine, an oxazoline analogue of clonidine. In anesthetized paralyzed rats decerebration did not alter the dose dependent reductions in arterial pressure and heart rate elicited by i.v. drug. Rilmenidine microinjected bilaterally into the C1 area of the rostral ventrolateral medulla (RVL), but not nucleus tractus solitarii (NTS) nor caudal ventrolateral medulla (CVL), elicited dose-dependent falls in arterial pressure and heart rate at doses an order of magnitude less than required systemically. Prior microinjection into the C1 area of the selective alpha 2-adrenoceptor antagonist SKF-86466, even at high doses, failed to modify the hypotension to i.v. rilmenidine. However, microinjection of 3- to 10-fold lower doses of idazoxan, a ligand for imidazole as well as alpha 2-adrenoceptors, blocked the effects. Rilmenidine also competed with the clonidine analogue [3H]p-aminoclonidine ([3H]PAC) at specific binding sites in membranes of bovine ventrolateral medulla and frontal cortex. In RVL rilmenidine competed with binding to imidazole and alpha 2-adrenergic binding sites with a 30-fold selectivity for the imidazole binding sites. In frontal cortex binding was of lower affinity and restricted to alpha 2-adrenergic sites. We conclude that rilmenidine, like clonidine, acts to lower arterial pressure by an action on imidazole receptors in the C1 area of RVL. The higher selectivity of rilmenidine for imidazole to alpha 2-adrenoceptors as compared to clonidine may explain the lower sedative effects of rilmenidine.

Open field behavior and cardiovascular responses to stress in normal rats.

Experiments were conducted in normal Wistar rats with different patterns of behavior to assess the effects of stress on cardiovascular reactivity. One week after weaning and one month later rats were tested in an open field. Animals that did not cross any square in both open fields were classified as HYPOACTIVE. Those crossing more than 43 squares in the first and any in the second open field were classified as HYPERACTIVE. No difference was found in the basal mean blood pressure (BP) or heart rate (HR) between both groups. After a stress (change of cage, electric shock or immobilization) BP and HR increased. The increase in BP was higher in HYPOACTIVE rats. The HR increase was similar in both groups. Therefore, the ambulatory activity in the open field allowed us to separate groups of rats with different cardiovascular reactivity to stress.

Suprapontine ablation in normal and Doc-salt or one-kidney, one-clip hypertensive rats.

The role of suprapontine areas in the acute maintenance of the hypertension in awake Doc-salt (4 weeks of treatment) or one-kidney, one clip (1K-1C) (4 weeks after clipping) rats was studied. Mean blood pressure (BP) and heart rate (HR) were measured before (15 min) and after (2 hours) removing all brain tissues rostral to the pons. After this procedure no change in BP was found in normal or 1K-1C rats. In Doc-salt rats the BP falls (154 +/- 4 to 110 +/- 5 mmHg; p less than 0.001). HR was increased in normal (351 +/- 10 to 446 +/- 20 beats/min; p less than 0.01) and in 1K-1C rats (350 +/- 10 to 485 +/- 12 beats/min; p less than 0.001). Clonidine injected into the cisterna magna in 1K-1C rats after suprapontine ablation lowered BP (146 +/- 6 to 118 +/- 11 mmHg; p less than 0.05) and HR (515 +/- 17 to 400 +/- 33; p less than 0.05). Pentolinium reduced BP after the suprapontine ablation in normal (116 +/- 4 to 63 +/- 5 mmHg; p less than 0.001), Doc-salt (111 +/- 5 to 53 +/- 3; p less than 0.001) and 1K-1C rats (163 +/- 8 to 59 +/- 6 mmHg; p less than 0.001). These data suggest that suprapontine structures have an important role in the acute maintenance of Doc-salt hypertension. In 1K-1C rats the acute maintenance of hypertension depends on a sympathetic activity originated below the lesion.

Suprapontine ablation in normal and Doc-salt or one-kidney, one-clip hypertensive rats.

The role of suprapontine areas in the acute maintenance of the hypertension in awake Doc-salt (4 weeks of treatment) or one-kidney, one clip (1K-1C) (4 weeks after clipping) rats was studied. Mean blood pressure (BP) and heart rate (HR) were measured before (15 min) and after (2 hours) removing all brain tissues rostral to the pons. After this procedure no change in BP was found in normal or 1K-1C rats. In Doc-salt rats the BP falls (154 +/- 4 to 110 +/- 5 mmHg; p less than 0.001). HR was increased in normal (351 +/- 10 to 446 +/- 20 beats/min; p less than 0.01) and in 1K-1C rats (350 +/- 10 to 485 +/- 12 beats/min; p less than 0.001). Clonidine injected into the cisterna magna in 1K-1C rats after suprapontine ablation lowered BP (146 +/- 6 to 118 +/- 11 mmHg; p less than 0.05) and HR (515 +/- 17 to 400 +/- 33; p less than 0.05). Pentolinium reduced BP after the suprapontine ablation in normal (116 +/- 4 to 63 +/- 5 mmHg; p less than 0.001), Doc-salt (111 +/- 5 to 53 +/- 3; p less than 0.001) and 1K-1C rats (163 +/- 8 to 59 +/- 6 mmHg; p less than 0.001). These data suggest that suprapontine structures have an important role in the acute maintenance of Doc-salt hypertension. In 1K-1C rats the acute maintenance of hypertension depends on a sympathetic activity originated below the lesion.

Effect of transection in the brainstem on short-term maintenance of deoxycorticosterone-salt hypertension.

Sections were made to determine supraspinal areas that participate in the maintenance of deoxycorticosterone (DOC)-salt hypertension. Blood pressure (BP) falls after cuts which severed: (a) the lateral connections between pons and midbrain, (b) the pathways between caudal hypothalamus and midbrain, and (c) parasagittal connections between medial and lateral hypothalamus. No changes in BP were found either after coronal cuts that severed a central area located at: (a) the pons-midbrain edge, (b) above the caudal hypothalamus, and (c) the level of the anterior hypothalamic area, or after parasagittal cuts at the level of the capsula interna or after a hypophysial stalk lesion. These results implicate the hypothalamus in the maintenance of DOC-salt hypertension. The hypothalamus-neural lobe system appears not to be involved in the lowering of BP found.

Further evidence that a beta-adrenergic mechanism regulates water intake: role of the subfornical organ.

The daily water intake was reduced in rats by subcutaneous administration of propranolol. The fluid intake after 24 h of dehydration in nephrectomized animals was decreased by propranolol. In intact rats diazepam did not modify the postdehydration water intake. Propranolol injected into subfornical organ decreased water consumption after 24 h of fluid deprivation but did not change the dipsogenic response to carbachol given in the same structure. These results suggest that a beta-adrenoceptor mechanism participates in the regulation of the daily water intake. After a stimulus such as dehydration, beta-blockade modifies water consumption by a non-renal mechanism. This mechanism involves neither a general depressant nervous activity nor a local anesthetic action and could be located in a periventricular structure, the subfornical organ.

Surface morphology of the subfornical organ: effects of low and high sodium chloride diet.

Ependymal cells found in the subfornical organ of the rat were counted. Cells covered by small microvilli, small protrusions and smooth cells were frequently found. Also present were cells with long or short cilia, cels with large protrusions and supraependymal cells. High and low sodium diets reduced the number of cells with large protrusions. Microvilli-covered cells increased after a low sodium diet.

Effects of propranolol on induced water intake and on the subfornical organ surface.

The chronic effect of propranolol on induced water intake and on the subfornical organ was studied. Propranolol reduced water intake postdehydration. It did not inhibit the increase in plasma renin activity due to dehydration or the dipsogenic response to angiotensin II. Propranolol decreased the subfornical organ large protrusion cells. This result suggests that propranolol impairs the thirst not related to angiotensin II. The subfornical organ changes may indicate that propranolol blocks a beta-adrenergic system originating in ependymal cells.