Distinct role of Rab3A and Rab3B in secretory activity of rat melanotrophs.

Members of the Rab3 (A-D) subfamily of small GTPases are believed to play a key role in regulated exocytosis. These proteins share approximately 80% identity at amino acid level. The question of whether isoforms of Rab3 are functionally redundant was the subject of this study. We used RT-PCR analysis, in situ hybridization histochemistry, and confocal microscope-based analysis of immunocytochemistry to show that rat melanotrophs contain about equal amounts of Rab3A and Rab3B transcripts as well as proteins. Therefore, these cells are a suitable model to study the subcellular distribution and the role of these paralogous isoforms in regulated exocytosis. Secretory activity of single cells was monitored with patch-clamp capacitance measurements, and the cytosol was dialyzed with a high-calcium-containing patch pipette solution. Preinjection of antisense oligodeoxyribonucleotides specific to Rab3A, but not to Rab3B, induced a specific blockage of calcium-dependent secretory responses, indicating an exclusive requirement for Rab3A in melanotroph cell-regulated secretion. Although the injection of purified Rab3B protein was ineffective, the injection of recombinant Rab3A proteins into rat melanotrophs revealed that regulated secretion was stimulated by a GTP-bound Rab3A with an intact COOH terminus and inhibited by Rab3AT36N, impaired in GTP binding. These results indicate that Rab3A, but not Rab3B, enhances secretory output from rat melanotrophs and that their function is not redundant.

Testing of cerebral endothelium function with L-arginine after stroke.

BACKGROUND: Endothelium-dependent vasodilatation could be impaired during hypoperfusion. L-arginine (L-A), a precursor of nitric oxide, is able to elicit endothelium-dependent vasodilatation. To determine cerebral vascular endothelial function in the early stages after ischemic stroke, we studied cerebrovascular reactivity to L-A with transcranial Doppler (TCD). METHODS: The study group consisted of 15 patients with the middle cerebral artery syndrome, aged 57.6+/-9.8 years. They were investigated on days 7 to 10 after ischemic stroke. The control group consisted of 15 healthy volunteers, aged 58+/-10.7 years. All subjects received an intravenous infusion of L-A over 20 min at a rate of 1.5 g/min. The mean arterial velocity (vm) was measured in both middle cerebral arteries by using a bitemporal monitoring system (Multi-Dop X4, DWL). At the same time, the mean arterial pressure (MAP) and heart rate (HR) were measured by Finapres and ECG. The end-tidal CO2 (Et-Co2) was monitored by capnograph. The Vm over 5-min intervals at rest and during the infusion of L-A was determined by using the DWL TCD8 software. RESULTS: The Vm significantly increased in both hemispheres of both groups (p=0.00). Vm differences between rest and L-A stimulation were lower in the ischemic hemispheres compared to the healthy ones (p=0.00), but did not differ between the ischemic hemispheres and hemispheres of the healthy group (p>0.05). MAP, HR and Et-Co2 did not change during the infusion (p>0.05). CONCLUSIONS: Cerebrovascular reactivity to L-A is impaired in patients with recent stroke. The amino acid could thus be useful in testing endothelium function both in healthy persons and in stroke patients since endothelium dysfunction seems to be an important factor in reperfusion injury.

The effect of age on cerebrovascular reactivity to cold pressor test and head-up tilt.

OBJECTIVE: To compare the cold pressor test (CPT) and head-up tilt (HUT) responses of the older and younger healthy individuals by transcranial Doppler. SUBJECTS AND METHODS: Forty healthy volunteers were divided into two age groups (18-39 years, 40-69 years). Mean blood velocity (v(m)) in both middle cerebral arteries was monitored during CPT and HUT. Mean arterial blood pressure, heart rate and end-tidal CO(2) (Et-CO(2)) were measured simultaneously. RESULTS: The v(m) increased by 7.1% during CPT and decreased by 10.1% during HUT. The v(m) responses were significantly lower in the older group (P < 0.01). Linear regression analysis showed a significant effect of age on dv(m) during both CPT (P < 0.01) as well as HUT (P < 0.01). CONCLUSION: The age affected the v(m) responses to CPT and HUT in the group of older subjects.

Influence of the cold pressor test on the middle cerebral artery circulation.

Cold pressor test (CPT) evokes generalized activation of the sympathetic nervous system (SNS). The activity of SNS may be estimated by monitoring the mean blood velocity (v(m)) in the middle cerebral artery (MCA) by using a transcranial Doppler monitoring system (TCD). To determine the response of SNS, we studied the v(m) during CPT. Thirty-four healthy volunteers, 13 female and 21 male (mean age 34 +/- 9.5 years, range 18 to 55 years) participated in our study. The experiment consisted of a 5-min baseline period followed by a 3-min immersion of the right hand in ice water. Blood velocity in both MCA's was monitored by bitemporal 2 MHz probes by using a Multi-Dop X4. MAP and heart rate (HR) were measured simultaneously by a Finapres non-invasive blood pressure monitor and a computerized ECG system. End-tidal CO2 (Et-CO2) was measured with an infrared capnograph. To determine v(m) over a chosen time interval the TCD-8 software was utilized. The results showed that during CPT v(m), MAP, and HR increased significantly (P < 0.01) for 9.8%, 18.5%, and 3.6%, respectively. Et-CO2 did not change significantly (P > 0.05). The increase of v(m) was also significantly higher in the stimulated hemispheres (P = 0.005) regarding to unstimulated ones. The increase of v(m) during CPT was not gender dependent. To establish the association between variables the models of multivariate regression were used. Multiple regression CPT model was significant (P < 0.01) and fitted data moderately well (R2 = 0.28). MAP and Et-CO2 were significant in the model (P < 0.01). It seems that the reactivity of the SNS can be estimated by measuring v(m) with TCD during CPT.

Heart rate variability, norepinephrine and ECG changes in subarachnoid hemorrhage patients.

While electrocardiographic abnormalities in subarachnoid hemorrhage patients have been known since 1947, the provocative mechanism has not yet been satisfactorily explained. The purpose of this study was to evaluate with some tests, the role of autonomic nervous system in provoking the electrocardiographic abnormalities in 22 patients with subarachnoid hemorrhage. The standard electrocardiographic tracings and one-channel computer-based electrocardiographic tracings for spectral analysis of heart rate variability were made. Blood samples for plasma norepinephrine concentrations were taken. Statistically significant parasympathetic hyperactivation between Days 4 and 6 after sudden onset of the disease was found. In standard electrocardiographic tracings in almost all patients transient repolarisation changes and in one patient transient premature ventricular complexes were observed. Plasma norepinephrine concentrations did not parallel electrocardiographic abnormalities. No statistically significant correlation was found among tests of autonomic nervous system activity. Electrocardiographic abnormalities in our group of patients were transient, functional and observed only in the acute phase. They were probably not dependent on elevated plasma norepinephrine concentration. Spectral analysis of heart rate variability failed to explain the role of the autonomic nervous system in provoking the cardiac abnormalities.

Cardiac arrhythmia associated with reversible damage to insula in a patients with subarachnoid hemorrhage.

BACKGROUND: The insular cortex has been shown experimentally to contain an arrhythmogenic center that may play an important role in the genesis of cardiac arrhythmias and electrocardiographic changes in patients with intracranial (eg, cerebrovascular) lesions. The description of our case is intended to substantiate this claim with a clinical observation. CASE DESCRIPTION: A 37-year-old woman with subarachnoid hemorrhage suffered a severe reversible cardiac arrhythmia after neurosurgical clipping of an arterial aneurysm and removal of an intracerebral hematoma from the region of the left insula. CONCLUSIONS: The observed association of a neurosurgical intervention in the region of the left insular cortex with a cardiac arrhythmia supports but does not prove the suggested role of the insulin in the causation of heart rhythm disturbances after stroke.

Autonomic function testing in patients with migraine.

Autonomic nervous system function was studied in 62 patients with migraine. The Valsalva maneuver, deep breathing test, sustained handgrip test, orthostatic test and spectral analysis of heart rate variability in the supine and standing positions were performed in a group of 62 patients of both sexes, aged 21 to 50 years, and in an age-matched control group of 45 healthy volunteers. Heart rate increases during sustained handgrip was significantly reduced in the headache group, when compared to the control group, while the results of the remaining cardiovascular tests did not significantly differ between the control and headache groups. In standing patients, the integrals of middle frequency bands of amplitude spectra were smaller in patients than in controls because the increase induced by standing was smaller in migraine patients. The results in patients with migraine with aura (21 patients) and migraine without aura (41 patients) did not differ significantly from each other. The same was true for the results of the female and male patients. It is concluded that sympathetic function is impaired in migraine patients.

The influence of the type, duration, severity and levodopa treatment of Parkinson's disease on cardiovascular autonomic responses.

The influence of the type, duration, severity and levodopa treatment of Parkinson's disease on autonomic involvement has been assessed. The Valsalva manoeuvre, deep breathing, handgrip and orthostatic tests were performed in 50 patients with Parkinson's disease and in a control group of 30 healthy subjects. No attempt was made to classify further patients with parkinsonian features into groups such as the Shy-Drager syndrome or multiple system atrophy. All test results were significantly smaller in patients than in healthy subjects. The diastolic pressure increase during handgrip was significantly smaller in akinetic-rigid than in tremor-akinetic-rigid type patients. The Valsalva ratio and orthostatic test results were significantly smaller in patients with longer duration than in those with shorter duration of disease. All test results except those of the orthostatic test were significantly smaller in patients with the more severe form than in those with the less severe form of disease. Comparing test results of levodopa-treated and -untreated patients no significant differences were found. Our studies in parkinsonian patients suggest that (1) sympathetic impairment is more pronounced in akinetic-rigid than in tremor-akinetic-rigid type patients; (2) sympathetic impairment occurs early, whereas parasympathetic impairment develops later; (3) sympathetic and parasympathetic impairment parallels the severity of disease; (4) orthostatic parameters are more duration-sensitive than severity-sensitive; (5) chronic levodopa treatment does not markedly influence cardiovascular autonomic responses.

A comparison of cardiovascular reflex tests and spectral analysis of heart rate variability in healthy subjects.

Determination of whether results of cardiovascular reflex tests and spectral analysis of heart rate variability are age dependent and whether there is correlation between results of both, cardiovascular reflex tests (the Valsalva manoeuvre, deep breathing test, handgrip test, cold face stimulus test, orthostatic test) and spectral analysis of heart rate variability were performed on 83 healthy volunteers of both genders, aged 21 to 70 years. We found that results of all heart rate based tests and results of spectral analysis decreased with aging, while results of blood pressure based tests did not. Parasympathetic activity predominated in younger subjects, while in older subjects sympathetic activity was dominant. Valsalva, deep breathing, and orthostatic ratios correlated with integrals of amplitude spectra in the standing posture and deep breathing and cold face stimulus ratios with integrals of amplitude spectra in the supine posture, whereas blood pressure changes during handgrip and orthostatic test did not correlate with integrals of the amplitude spectra. These findings suggest that tests based on heart rate may be more sensitive than tests based on blood pressure changes. This study supports the use of spectral analysis as an additional clinical test of autonomic nervous system function and stresses the importance of age in the evaluation of the results of autonomic nervous system function testing.

Autonomic function testing in patients with tension-type headache.

Autonomic nervous system function was studied in 51 patients with tension-type headache. The Valsalva manoeuvre, deep breathing test, sustained handgrip test, orthostatic test and spectral analysis of heart rate variability in the supine and standing positions were performed in a group of 51 patients of both sexes aged 21 to 50 years and in an age-matched control group of 45 healthy volunteers. Diastolic blood pressure increase and particularly heart rate increase during sustained handgrip were significantly reduced in the headache group, when compared to the control group, while the results of the remaining tests did not significantly differ between the control and headache groups. No significant differences were found between the episodic (19 patients) and chronic (32 patients) tension-type headache subgroups. It is concluded that sympathetic function is impaired in tension-type headache patients.

Effect of elevated plasma norepinephrine on electrocardiographic changes in subarachnoid hemorrhage.

We compared electrocardiographic abnormalities and plasma norepinephrine concentrations in 40 patients with subarachnoid hemorrhage within the first 24 hours, at 72 hours, and after 1 week. In 20 patients with high plasma norepinephrine concentrations within the first 24 hours, sinus tachycardia (p less than 0.02) and negative T waves (p less than 0.01) were more frequent than in the 20 patients with normal plasma norepinephrine concentrations. After 72 hours, only sinus tachycardia (p less than 0.03) was found with increased frequency in the 26 patients with high plasma norepinephrine concentrations. Although 24 patients had high plasma norepinephrine concentrations after 1 week, we found no differences in the frequency of electrocardiographic abnormalities compared to patients with normal plasma norepinephrine. However, QTc prolongation, U waves, ST depression, and arrhythmias were found with similar frequency in patients with both high and normal plasma norepinephrine concentrations. We conclude that, with the exception of sinus tachycardia and negative T waves, electrocardiographic changes in patients with subarachnoid hemorrhage do not depend on elevated plasma norepinephrine concentrations.

Activity, molecular forms, and cytochemistry of cholinesterases in developing rat diaphragm.

Acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) were studied in the diaphragm of early postnatal rats, using radiometric determination of enzyme activities, velocity sedimentation for separation of molecular forms, and electron microscopic cytochemistry to localize enzymes. AChE activity did not change significantly during the first 2 months after birth. The level of 16 S AChE was high at early stages, but decreased to adult levels between days 19 and 32 after birth. In newborn and 8-day-old rats, 16 S and 13 S AChE were present in both endplate and extrajunctional muscle. In newborn muscle, BuChE activity was higher than AChE activity, but decreased 6-fold by day 32. Newborn muscle contained 16 S, 10 S, and 4 S BuChE. The principal form throughout development was 4 S BuChE, but all forms diminished as total BuChE activity decreased with maturation. At early postnatal neuromuscular junctions, end product of both AChE and BuChE was present in the cleft, as well as in Schwann cells. More Schwann cells wee present in early stages than in later stages, and this might account for part of the later decrease of BuChE activity measured biochemically.

Cholinesterases of neuromuscular junction.

The ultrastructural localization of AChE and BuChE was studied in motor endplates of the rat and mouse diaphragms, using the CNS(?) modification of the one-step Cu-thiocholine procedure. AChE activity was observed on pre- and postsynaptic membranes, in the basal lamina and in the Schwann cell-nerve terminal interspace. The localization of BuChE was similar but much less pronounced in the adult muscle, while for the developing muscle, the reverse was true. In developing motor endplates and in endplates of rats after irreversible inhibition of AChE where synthesis de novo is enhanced, AChE activity in the endoplasmic reticulum and perinuclear membrane of the Schwann cell and in the sarcoplasmic reticulum was pronounced, indicating that junctional AChE may be synthesized at these sites. AChE and BuChE have a similar localization, mode of attachment and molecular forms. A possible mechanism underlying these similarities is discussed.