Heart rate variability and apnea during sleep in Down's syndrome

Autonomic system dysfunction has been reported to occur frequently in patients with Down's syndrome (DS) and is constituted mainly by an imbalance between the sympathetic and vagal systems. The analysis of heart rate variability (HRV) during sleep is a quantitative reliable method for studying such a mechanism, but it has not yet been extensively and adequately applied in DS. In this study, HRV during sleep was evaluated in seven DS patients and in six normal controls, by also controlling for the presence of sleep apnea or arousal. The main results were an increased sympathetic function (low-frequency component of HRV) and a decreased vagal activity (high-frequency component of HRV) in DS with respect to normal controls, during apnea-free periods. Moreover, the presence of apnea, in DS, induced a further significant increase in low-frequency and very low-frequency components of HRV during sleep Stage 2. This study provides additional evidence of a brainstem dysfunctioning in DS, responsible for the abnormal imbalance between the sympathetic and vagal systems and confirms the brainstem involvement already suggested in the literature in order to explain brainstem-auditory evoked potential abnormalities and central sleep apnea in these patients.     

The acute cardiovascular actions of intravenous thyrotrophin releasing hormone (TRH) in man are mediated by non-catecholaminergic mechanisms

1. Intravenous bolus doses of thyrotrophin releasing hormone (TRH, 50–1000 μg) caused statistically significant, non-dose dependent and transient rises in blood pressure, heart rate and plasma catecholamines in healthy young males.
2. Mean peak incremental rises in systolic blood pressure (mean ± s.e. mean) following 50, 200 and 500 μg TRH were 14.3 ± 2.9 mmHg, 15.7 ± 3.2 mmHg and 17.1 ± 3.9 mmHg respectively (all P < 0.05 vs placebo). Mean incremental rises in heart rate for the three doses of TRH were 8.2 ± 2.2 beats min⁻¹, 7.1 ± 1.8 beats min⁻¹, and 1O.7 ± 2.9 beats min⁻¹ respectively (all P < 0.05 vs placebo).
3. Following the 50 μg and 1000 μg doses of TRH, plasma noradrenaline and adrenaline rose significantly (P < 0.05) between 4 and 8 min. Mean ± s.e. mean incremental plasma noradrenaline rise following 50, 200 and 1000 μg TRH were 0.4 ± O.13 nmol 1⁻¹, 0.37 ± 0.21 nmol 1⁻¹ and 0.41 ± 0.18 nmol 1⁻¹ respectively. Mean ± s.e. mean incremental rise in adrenaline for the 50, 200 and 1000 μg dose were 0.13 ± 0.04 nmol 1⁻¹, 0.08 ± 0.03 nmol 1⁻¹, and 0.11 ± 0.05 nmol l⁻¹ respectively.
4. Following administration of the ganglion blocking drug pentolinium (5 mg) the incremental systolic blood pressure and heart rate rises following 500 μg TRH alone 16.6 ± 2.8 mmHg and 1O.4 ± 3.1 beats min⁻¹ respectively.
5. The rises in plasma noradrenaline and adrenaline following TRH were attenuated by prior ganglion blockade.
6. α-adrenoceptor blockade with thymoxamine (0.3 mg kg⁻¹ bolus + 0.3 mg kg⁻¹ h⁻¹ infusion), singly and combined with intravenous propranolol (10 mg i.v. over 10 min), did not alter the pressor or tachycardic effects of 500 μg TRH.
7. In conclusion, although plasma noradrenaline rises following i.v. TRH, suggesting activation of the sympathetic nervous system, this effect is not responsible for the pressor response to TRH, which appears to be due to either a direct vasoconstrictive effect on the peripheral resistance vessels or a direct inotropic/chronotropic effect on the heart.

     

Centroblastic transformation of chronic lymphocytic leukaemia with primary skin involvement—cutaneous presentation of Richter's syndrome

The development of a large-cell non-Hodgkin's lymphoma in a patient suffering from chronic lymphocytic leukaemia is known as Richter's syndrome, representing one of the possible anaplastic transformations of the leukaemia. Cutaneous involvement is an extremely rare event. The case of a 45-year-old man with B-cell chronic lymphocytic leukaemia is reported. Five years later multiple cutaneous nodules developed on his extremities. Biopsies of the skin showed a diffuse large-cell lymphoma, bearing the same cell surface immunoglobulin light chain isotype as the leukaemia, suggesting the original relationship between both neoplasms.     

Total serum IgE levels in Venezuelan schoolchildren

Seventy-eight disease-free children were evaluated by PRIST for total serum IgE in order to establish the normal range for this immunoglobulin and assess its utility, in tropical climates, such as Venezuela, as a diagnostic tool for clinical allergy. Seventy-eight normals were selected from a group of 1053 children, aged 7-12 years from fourteen schools in Caracas. Exclusion from the normal pool was based on nationality, and on historical, clinical, and/or laboratory evidence of atopic and/or infectious diseases, particularly with parasites. In addition to a routine CBC and differential, the following studies were performed: a search for stool ova and parasites; in vitro (RAST) and in vivo (skin prick) testing for specific IgE to Dermatophagoides pteronyssinus, Aspergillusfumigatus, and ragweed. Measurement of antibodies against influenza A and B, adenovirus A₂: and B, cytomegalovirus, parainflucnza 1 and 3, herpes simplex, respiratory syncytial virus, Coxsackie B₁ to B₆, Mycoptasma pneumoniae and Rolavirus was also carried out. Normal serum IgE levels for disease-free children in the age group studied ranged from 1.7-255 u/ml. The highest average level (± 74 u/ml) occurred at the age of 9 years. These values differed significantly from age-matched control groups of known atopic and helminth-infected children. Thus, once common causes for elevated IgE levels are eliminated, determination of total serum IgE can be utilized as a valuable tool in diagnosis of clinical allergy in countries with tropical climates.     

Low protein alimentation normalizes renal haemodynamic response to acute protein ingestion in type 1 diabetic children

The effect of an acute protein load (2 g kg-1 bodyweight [BW]) was studied in nine type 1 diabetic children. Patients were maintained on two different dietary regimens. In study one, patients were on a high protein diet providing from 2.7 to 1.8 g of protein/kg of BW per day. In study two, patients were reevaluated after three weeks of a diet providing from 1.0 to 1.2 g kg-1 of BW per day of protein. In study one (High Protein Diet), we failed to observe any rise in GFR and RPF following the protein meal (137 +/- 21 basal vs. 110 +/- 14 and 472 +/- 93 basal vs. 494 +/- 93 ml/1.73 m2 of SA min-1 at 60 min. This is in contrast with results from seven age matched controls consuming a free diet, which showed a significant rise in both GFR and RPF. In study two (low protein diet), basal GFR was significantly reduced. However after the protein load, both GFR (92 +/- 11 vs. 126 +/- 18 ml/1.73 m2 of SA min-1) and RPF (467 +/- 83 vs. 705 +/- 102 ml/1.73 m2 min-1) rose significantly (P less than 0.05 vs. basal). The data indicate that: 1. short term protein restriction reduces significantly GFR in type 1 diabetic children; 2. diabetic children maintained on an high protein intake show an altered haemodynamic response to protein ingestion; 3. a normal response to protein ingestion can be restored by short term dietary protein restriction.