Concentration and mindfulness meditations: unique forms of consciousness?

Electroencephalographic (EEG) recordings from 19 scalp recording sites were used to differentiate among two posited unique forms of mediation, concentration and mindfulness, and a normal relaxation control condition. Analyzes of all traditional frequency bandwidth data (i.e., delta 1-3 Hz; theta, 4-7 Hz; alpha, 8-12 Hz; beta 1, 13-25 Hz; beta 2, 26-32 Hz) showed strong mean amplitude frequency differences between the two meditation conditions and relaxation over numerous cortical sites. Furthermore, significant differences were obtained between concentration and mindfulness states at all bandwidths. Taken together, our results suggest that concentration and mindfulness "meditations" may be unique forms of consciousness and are not merely degrees of a state of relaxation.

The relation of ERP components to complex memory processing.

The relation between various ERP components generated during encoding of a word and its subsequent recall were investigated using a "rote" serial-order and an "elaborative" category memory task. Words (flashed separately) were time-locked to EEG recordings from 21 cortical sites. ERP components from the five subjects having the highest recall scores were compared to the five lowest scoring subjects. Results based on the P200 peak amplitude data as well as the N400 and late positive component peak amplitude and latency data suggest that anterior and posterior distributional differences are elicited during encoding of words for rote and elaborative memory tasks. Furthermore, strong individual differences in these patterns were found as a function of task. A tentative argument was made that the obtained anterior and posterior differences may index different word feature selection and encoding processes, which are differentially utilized by high and low recallers.

Relationship between conjugate lateral eye movements, brain organization, and cognitive style.

The relationship between individual differences in conjugate lateral eye movements (CLEMs) and inferential reasoning was investigated in two experiments. Subjects were given inference tasks in sentence and pictorial form and were later tested for recognition of correct inferences as well as literal recognition of the acquisition items. In Experiment 2, for example, subjects were given logical syllogisms during acquisition. Theoretically, right-eye movement/left-hemispheric (REM/LH) subjects should have excelled at this highly logical task but no significant differences between eye-movement groups were found. However, support for previous research showing the moderating effects of gender on hemispheric activation (measured by CLEMs) and hemispheric competence came from the memory data of Experiment 2. These data indicated that male REM/LH subjects recognized more acquisition sentences than the other eye movement/gender groups. It was suggested CLEMs and other measures of hemispheric activation and competence, coupled with data collected using complex cognitive tasks, can eventually lead to explanatory brain models of cognitive processing.

Atrial natriuretic peptide and furosemide effects on hydraulic pressure in the renal papilla.

Atrial peptides (ANP) have been shown to preferentially increase blood flow to juxtamedullary nephrons and to augment vasa recta blood flow. To determine the effect of this alteration in intrarenal blood flow distribution on pressure relationships in inner medullary structures and their significance as a determinant of ANP-induced natriuresis, we measured hydraulic pressures in vascular and tubule elements of the renal papilla exposed in Munich-Wistar rats in vivo during an euvolemic baseline period and again during an experimental period. Rats in Group 1 received intravenous infusion of rANP administered as a 4 micrograms/kg prime and 0.5 microgram/kg/min continuous infusion, and were maintained euvolemic by plasma replacement. Infusion of ANP resulted in significant natriuresis, diuresis and increase in inulin clearance. Within 90 seconds of initiation of this systemic infusion, vasa recta hydraulic pressures were markedly increased and exceeded the small pressure increment occurring in loops of Henle and collecting ducts. Infusion of furosemide in Group 2 rats at a dosage which reproduced the increase in urine flow in Group 1 was associated with small and equivalent increases in both vascular and tubule elements, indicating that the differential pressure response observed in Group 1 was not due to increased tubule fluid flow rates, but was rather a specific ANP-induced vascular effect. Group 3 rats received an infusion of ANP in a setting where its whole kidney hemodynamic effects were prevented. This resulted in a marked blunting of natriuresis and diuresis, and obliteration of the pressure differential between vasa recta and tubules observed in Group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of the natriuretic response to atrial natriuretic peptide by alterations in peritubular Starling forces in the rat.

The mechanisms underlying the natriuretic response to infusions of atrial natriuretic peptide (ANP) remain incompletely defined. By acting as renal vasodilators, atrial peptides may serve to alter peritubular capillary physical forces and favor a decrease in tubule solute reabsorption. Therefore, we studied the effects of known modifiers of intrarenal Starling forces on the natriuresis induced by infusion of intravenous hANP [4-28] (0.5 microgram/kg/min) in anesthetized, euvolemic Munich-Wistar rats. In the first series of studies, infusion of ANP resulted in a significant natriuresis, diuresis, and increase in inulin clearance and in a slight fall in systemic arterial pressure, as compared to vehicle infusion. Subsequent elevation of renal perfusion pressure by superimposition of angiotensin II infusion (0.1-0.2 microgram/kg/min i.v.) on continued ANP infusion resulted in marked further enhancement of natriuresis, independent of changes in glomerular filtration rate (GFR). In the second set of experiments, in which oncotic pressure in the postglomerular capillaries was elevated by hyperoncotic exchange transfusion, administration of ANP did not result in natriuresis, even though GFR increased by the same magnitude as that seen in isooncotic animals given ANP. These observations are consistent with the view that peritubular capillary hydraulic and oncotic pressures modulate the natriuretic and diuretic effects of ANP.

Prevention of glomerular capillary hypertension in experimental diabetes mellitus obviates functional and structural glomerular injury.

Streptozotocin-diabetic rats kept moderately hyperglycaemic by daily injections of ultralente insulin for 4-6 weeks (group DM) demonstrated a higher glomerular transcapillary hydraulic pressure gradient (delta P), glomerular plasma flow rate and single-nephron glomerular filtration rate (GFR) than was observed in age- and weight-matched non-diabetic controls (group C). This rise in delta P was prevented by therapy with the angiotensin I converting enzyme inhibitor enalapril (15 mg/l drinking water, group DM + E) even though glomerular hyperperfusion and hyperfiltration persisted. Fourteen months after induction of diabetes, animals in group DM displayed high levels of albuminuria and an increased incidence of focal glomerular sclerosis; treatment with enalapril maintained these parameters at levels which did not differ from those observed in group C. We conclude that prevention of glomerular capillary hypertension with enalapril therapy obviates functional and structural glomerular injury in experimental diabetes mellitus.

Renal and systemic hemodynamic effects of synthetic atrial natriuretic peptide in the anesthetized rat.

To characterize the hemodynamic events responsible for alterations in renal function during administration of atrial natriuretic peptide, we studied the systemic, renal, and glomerular circulatory effects of intravenous rANP[126-149], administered as a 4 micrograms/kg prime and 0.5 microgram/kg per minute continuous infusion in anesthetized, euvolemic rats. With this protocol, a small decline in mean systemic arterial blood pressure occurred in the context of markedly enhanced urinary sodium excretion, hemoconcentration, and reduced left ventricular end-diastolic pressure and +dP/dt. However, despite a significant decrement in renal vascular resistance, total peripheral resistance remained constant, thereby denoting a preferential renal vasodilatory effect of this peptide in vivo. Whole kidney and single nephron GFR increased by approximately 20%, while effective renal and glomerular plasma flow rates remained stable, resulting in a substantial rise in filtration fraction. Of all the parameters potentially capable of augmenting single nephron GFR, only glomerular capillary hydraulic pressure increased significantly and therefore accounted entirely for the hyperfiltration observed during ANP infusion. This rise in glomerular capillary pressure, in turn, resulted from afferent arteriolar vasodilatation and concurrent efferent arteriolar vasoconstriction, findings that proved independent of both endogenous angiotensin II activity and ANP-induced reductions in renal perfusion pressure. These renal hemodynamic effects are unique when compared with actions of previously studied renal vasodilatory agents.

Prevention of diabetic glomerulopathy by pharmacological amelioration of glomerular capillary hypertension.

Two groups of adult male Munich-Wistar rats and a third group of nondiabetic age-matched and weight-matched normal control rats underwent micropuncture study 1 mo, and morphologic studies 14 mo, after induction of streptozotocin diabetes or sham treatment. All animals were fed standard rat chow. Diabetic rats received daily ultralente insulin to maintain stable moderate hyperglycemia (approximately 350 mg/dl). In addition, one group of diabetic rats was treated with the angiotensin I converting enzyme inhibitor, enalapril, 15 mg/liter of drinking water. Average kidney weight, whole kidney and single-nephron glomerular filtration rate, and glomerular plasma flow rate were elevated to similar values in both groups of diabetic rats, relative to normal control rats. Non-enalapril-treated diabetic rats exhibited significant elevations in mean glomerular capillary hydraulic pressure and transcapillary hydraulic pressure gradient, compared with the other groups studied, and only this group eventually developed marked and progressive albuminuria. Likewise, histological examination of the kidneys at 14 mo disclosed a high incidence of glomerular structural abnormalities only in non-enalapril-treated diabetic rats. These findings indicate that prevention of glomerular capillary hypertension in rats with diabetes mellitus effectively protects against the subsequent development of glomerular structural injury and proteinuria. This protection is afforded despite pronounced hyperglycemia and elevated levels of glucosylated hemoglobin, further supporting our view that hemodynamic rather than metabolic factors predominate in the pathogenesis of diabetic glomerulopathy.

Acute subdural hematomas with lupus anticoagulant (procoagulant inhibitor).

A patient with systemic lupus erythematosus (SLE) and circulating "lupus anticoagulant" (procoagulant inhibitor) developed both hemorrhagic microinfarction of the brain characteristic of SLE and massive bilateral, fatal, isodense subdural hematomas.