PubMed Health⌕ Search

Biomedical subjects

H Stephan

Publications and source records attributed to H Stephan.

At least 19 recordsLinked to original sources
PubMed1992

Acid-base management during hypothermic cardiopulmonary bypass does not affect cerebral metabolism but does affect blood flow and neurological outcome.

In order to compare the effects of blood-gas management on cerebral blood flow, metabolism and neurological outcome after hypothermic cardiopulmonary bypass (CPB) we have studied 65 patients undergoing aorto-coronary bypass surgery allocated randomly to either a pH-stat (temperature-corrected blood-gas management) or an alpha-stat (temperature-uncorrected blood-gas management) group. All patients were examined neurologically on the day before and the 7th day after operation. In 20 patients of the pH-stat group and in 15 patients of the alpha-stat group we measured cerebral blood flow (CBF), using the argon washin technique, and also cerebral oxygen (CMRO2) and glucose (CMRg) uptake. Measurements were performed in awake patients, after induction of anaesthesia with fentanyl, midazolam and pancuronium under normothermic conditions, during CPB at a venous blood temperature of 26 degrees C and at the end of surgery. Compared with postinduction values, hypothermia was associated with an 18% reduction in CBF and decreases in CMRO2 and CMRg of 61% and 60%, respectively, in the alpha-stat group. In the pH-stat group, CMRO2 and CMRg decreased also, by 58% and 74%, respectively, whereas CBF increased by 191%, indicating uncoupling of flow and metabolism. As there were no statistically significant differences between the metabolic variables in both groups, we conclude that acid-base management did not affect cerebral metabolism, despite its influence on blood flow. After rewarming, CBF and cerebral metabolism normalized independently of acid-base management during hypothermia. Nevertheless, neurological dysfunction occurred more often in the pH-stat group (P = 0.036).

Acid-Base Equilibrium↗
PubMed1992

Hepatic disposition of methohexitone in patients undergoing coronary bypass surgery.

In order to clarify the relative contribution of hepatic metabolism to the short term disposition of methohexitone, we have measured hepatic blood flow during induction of anaesthesia with a 1.5-mg kg-1 i.v. bolus dose of methohexitone. Median hepatic clearance was 1.01 litre min-1 and hepatic extraction 87%. As a consequence of the high hepatic extraction, the hepatic clearance of methohexitone was closely dependent on hepatic plasma flow.

Adult↗
PubMed1992

[Cerebral effects of ketanserin. The influence on hemodynamics and brain metabolism].

Ketanserin, a 5HT2- and alpha 1-receptor antagonist, decreases blood pressure by decreasing systemic vascular resistance without causing reflex cardiac stimulation, while cardiac output remains unchanged. To date, little is known about the effects of ketanserin on cerebral haemodynamics and cerebral metabolism. According to a recently published study, ketanserin seems not to impair cerebral blood flow autoregulation in man. The present study was designed to investigate the influence of ketanserin on cerebral circulation and metabolism, and the cerebrovascular response to CO2 in man. METHODS. Twenty male patients between 44 and 67 years of age who were scheduled for coronary artery bypass surgery were randomly allocated to one of two groups. In group 1 measurements were performed after induction of anaesthesia during normocapnia (p(a) CO2 approximately 40 mm Hg) and hypocapnia (p(a) CO2 approximately 30 mm Hg). Then, ketanserin was given at a bolus dose of 0.3 mg.kg-1 followed by an infusion of 0.06 mg.kg-1.h-1 and measurements were repeated under hypocapnic and normocapnic conditions. Patients of group 2 were hyperventilated at first, then normoventilated. Afterwards, ketanserin was administered at the above-mentioned dose and measurements were again performed during normocapnia and hypocapnia. Cerebral blood flow (CBF) was measured using the argon wash-in technique. Cerebral venous blood was obtained from a catheter in the superior bulb of the right internal jugular vein. Cerebral perfusion pressure (CPP) was calculated by subtracting jugular bulb pressure from mean arterial pressure and cerebral vascular resistance (CVR) by dividing CPP by CBF. Cerebral metabolic rates of oxygen, glucose, and lactate were calculated by multiplying the arterial-cerebral venous oxygen and substrate differences by CBF. RESULTS AND DISCUSSION. Ketanserin decreased CPP by 16% to about 60 mm Hg. Cerebral blood flow remained unchanged as a result of an insignificant decline in CVR. Hyperventilation increased CVR by 32%, while CBF decreased by 27% to the same value that had been obtained during hypocapnia without ketanserin. The percentage changes in CBF per mm Hg change in CO2 were 1.45%/mm Hg (group 1 and 2.91%/mm Hg (group 2), respectively, without ketanserin and 1.98%/mm Hg and 2.22%/mm Hg with ketanserin. As CO2-responsiveness with ketanserin was higher in group 1 but lower in group 2 than without ketanserin, the direction in which ventilation was changed rather than ketanserin was responsible for these changes in CO2-responsiveness. Neither during normocapnia nor during hypocapnia did ketanserin have any effects on cerebral metabolic activity. Thus, it can be concluded that ketanserin does not impair CBF regulation and metabolism and that cerebral vascular responsiveness to hypocapnia is preserved.

Aged↗
PubMed1992

[Effects of R80122. The influence of a new phosphodiesterase inhibitor on global and intestinal hemodynamics in coronary surgery patients].

Phosphodiesterase III inhibitors have been established in recent years in the therapy of congestive heart failure. Many disadvantages, such as extensive vasodilation and the lack of proven positive inotropic properties combined with thrombepenia and elevation of transaminases, have complicated the handling of the drug in clinical practice. Enoximone, an imidazole derivative, has been demonstrated to be more cardioselective and vasodilation has been found to be less pronounced than with amrinone. As a consequence, research was performed to enhance the cardioselectivity of phosphodiesterase III inhibitors by reduction of non-specific cross-reactivity with other phosphodiesterases, and R80122 (Janssen Pharmaceutics, Belgium) was introduced into clinical practice. R80122 ((E)-Ncyclohexal-N-methyl-2[[[phenyl (1,2,3,5-tetrahydro-2 oxoimidazo [2,1b]-quinazolin-7-yl)methylene] amino] oxy] acetamide) is a selective inhibitor of phosphodiesterase (PDE) IIIc, which is localized in the myocardium. Thus, its inhibition leads to a positive inotropic effect, whereas phosphodiesterase IIIRo is found in the vessel wall and causes vasodilation. This study was performed to investigate the hemodynamic profile of R80122 under clinical conditions. Additionally, the intestinal hemodynamics were recorded and changes in intestinal perfusion compared with changes in global hemodynamics. METHODS. The study was thoroughly discussed and approved by the local ethics committee; all patients gave written informed consent. The investigation was performed on ten male patients who were about to undergo elective coronary artery bypass surgery. History, physical examination and laboratory results were within the normal limits and revealed no evidence of liver disease. The usual medication was continued until the day before the operation. Premedication consisted of 2 mg flunitrazepam p.o. in the evening before the operation and 1.5 h before induction of anaesthesia. The determination of hepatic plasma flow was performed by the indocyanine green (ICG) infusion extraction technique using liver vein catheterization. After induction of anaesthesia (MP1), after application of a bolus dose of R80122 (0.3 mg/kg BW) (MP2) and at sternotomy (MP3), hemodynamic data (heart rate, arterial pressure, cardiac output) were recorded and blood samples for the determination of hepatic plasma flow by the concentration of ICG were collected. Anaesthesia was induced with a bolus dose of 0.2 mg/kg BW etomidate, 7 micrograms/kgBW fentanyl and 0.1 mg/kgBW pancuronium and maintained with a continuous infusion of 20 micrograms/min fentanyl, 300 micrograms/min midazolam and mechanical ventilation with O2/N2O at an FiO2 of 0.5. Statistical analysis was performed using the Wilcoxon-Mann-Whitney U test comparing the results after induction of anesthesia (MPI) with those after application of R80122 (MPII) and the results of MPII with those at sternotomy (MPIII). Statistical significance was assumed at P less than 0.05. RESULTS. After the induction of anaesthesia, the median heart rate (HR) was 56/min and did not change after administration of R80122. During sternotomy there was a significant increase in the HR from 64 to 78/min (P less than 0.05). Median arterial blood pressure (MAP) tended to decreased from 91 mm Hg after induction of 77 mm Hg after administration of R80122, although there was no statistical significance because of interindividual differences in the tendencies. At sternotomy, MAP remained unchanged. Cardiac output (CO) increased by 60% after administration of R80122 (P less than 0.01) and did not change during sternotomy. As a consequence of the changes in HR and CO, stroke volume (SV) increased by 22% after administration of R80122 (P less than 0.025) and decreased to control values during sternotomy.

Adult↗
PubMed1992

[Hepatic elimination of thiopental in heart surgery patients].

Thiopental is a hypnotic drug that is widely used for the induction of anaesthesia. The mechanism of the short-term action is based on the rapid distribution of the drug, and in contrast to methohexital, the metabolism of thiopental is not relevant in use in conditions of operative anaesthesia. However, in neurotraumatology thiopental is frequently used as continuous infusion for several days to reduce cerebral metabolism. Under these circumstances, the elimination of thiopental becomes the most important factor for the duration of action. In order to clarify the relative contribution of the liver to the disposition of thiopental, hepatic blood flow was measured during the induction of anaesthesia and at sternotomy combined with the determination of plasma concentrations of the drug in arterial and hepatic venous blood, making it possible to calculate the hepatic and total plasma clearance of thiopental. METHOD. The study was thoroughly discussed and approved by the local ethics committee, and all patients gave informed written consent. The investigation was performed in 10 male patients (as detailed in Table 1), who had been referred for elective coronary artery bypass surgery. The determination of hepatic plasma flow was performed by the indocyanine green (ICG) infusion extraction technique using liver vein catheterization. Before induction of anaesthesia (MP1), after induction (MP2) and at sternotomy (MP3), hemodynamic data (heart rate, arterial pressure, cardiac output) were recorded and blood samples for the determination of hepatic plasma flow by the concentration of ICG were collected. Additionally, arterial and hepatic venous plasma concentrations of thiopental were determined by gas chromatography after induction until the extracorporeal circulation was started. Anaesthesia was induced with a bolus dose of thiopental 4 mg/kg body wt, fentanyl 7 micrograms/kg and pancuronium 0.1 mg/kg and maintained with a continuous infusion of fentanyl 20 micrograms/min and mechanical ventilation with O2/N2O at an FiO2 of 0.5. RESULTS. Median arterial pressure (MAP) decreased from 89 mmHg to 74 mmHg after induction and rose again to reach 104 mmHg at sternotomy. Cardiac output (HZV) also decreased from 6.17 l/min to 4.76 l/min after induction, but remained unchanged at sternotomy (Table 2). Hepatic plasma and blood flow showed no significant changes but tended to decrease after the induction of anaesthesia. Hepatic blood flow was constantly 26-28% of cardiac output. In the same way, intestinal oxygen consumption (VO2) did not change significantly, but the tendency was identical to that with hepatic perfusion. Hepatic clearance of thiopental as the product of hepatic extraction of thiopental (with a median value of 0.29) and hepatic plasma flow was 0.21 l/min. CONCLUSIONS. Thiopental is subject to a relatively low hepatic extraction of 0.29. Thus, changes in hepatic perfusion do not influence the elimination of thiopental. The actions of thiopental on global hemodynamics are comparable with the results found in the literature, characterized by a significant reduction in MAP and cardiac output after induction. The hepatic clearance of thiopental found in this study, with an absolute value of 0.21 l/min, is absolutely comparable with the data for total-body clearance reported in the literature. It is concluded that the liver is the only organ responsible for the elimination of thiopental in humans.

Adult↗
PubMed1991

[Coronary circulation and myocardial oxygen balance in anesthesia].

It is generally believed that in patients with impaired coronary reserve an imbalance between myocardial O2-demand and O2-supply is the main cause of myocardial ischaemia. However, clinical experience as well as recent experimental results indicate that this global view may not always explain the occurrence of regional myocardial ischaemia. It was therefore investigated whether in patients before and after induction of anaesthesia as well as during sternotomy metabolic indices of ischaemia, i.e. lactate and/or hypoxanthine release into the coronary sinus, are related to global indices of myocardial O2-balance. It was found that neither myocardial O2-demand or O2-supply nor O2-balance correlated with myocardial ischaemic events. Conversely it was observed that in contrast to expectations lactate and/or hypoxanthine release occurred more often in conjunction with high values of coronary venous oxygen saturation than with low values. Since coronary venous oxygen saturation can be considered as a physiological index of global myocardial O2-balance, the data of the present investigation suggest that during anaesthesia a global imbalance between myocardial oxygen supply and demand is not the main cause of myocardial ischaemia. Thus, regional factors seem to be more important for initiation of myocardial ischaemic events than global O2-balance.

Anesthesia↗
PubMed1991

Priming of cardiopulmonary bypass with human albumin or Ringer lactate: effect on colloid osmotic pressure and extravascular lung water.

We have undertaken a randomized study on 20 patients undergoing coronary artery bypass surgery in order to determine the influence of cardiopulmonary pump prime solutions on colloid osmotic pressure and extravascular lung water. Crystalloid priming with Ringer lactate was compared with an albumin solution of nearly physiological colloid osmotic composition (4%). Measurements of extravascular lung water were performed by a modified, highly sensitive thermal dye technique, with additional detection of tracer signals in the pulmonary artery. In the Ringer lactate group, a significantly greater decrease in colloid osmotic pressure occurred immediately after onset of cardiopulmonary bypass. The more pronounced decrease in colloid osmotic pressure and in transcapillary gradient (difference between colloid osmotic pressure and pulmonary capillary wedge pressure) in the Ringer lactate group was associated with a significant increase in extravascular lung water (by 60%) in the postoperative period; the human albumin group, however, showed only a slight tendency to increased lung water. There were no differences in haemodynamic or respiratory states after operation.

Albumins↗
PubMed1991

Validation of myocardial oxygen demand indices in patients awake and during anesthesia.

An important guideline for anesthesia in patients with ischemic heart disease is the effect on myocardial oxygen demand. Therefore, this investigation evaluated commonly used myocardial oxygen demand formulas for clinical application. The study was performed on patients undergoing coronary bypass surgery (n = 62). Measurements of standard hemodynamics were obtained before and after induction of anesthesia, as well as during sternotomy and after surgery. Coronary blood flow was determined by the argon wash-in technique. In 15 patients, a left ventricular tip manometer was used to accurately assess the first derivative of left ventricular pressure time course. The following indices of left ventricular oxygen demand were calculated: 1) rate pressure product (RPP); 2) tension time index (TTI); 3) pressure work index (PWI) according to the methods of Rooke; and 4) additive parameter (Eg), according to the methods of Bretschneider. All hemodynamic indices of myocardial oxygen demand showed moderate correlation with myocardial oxygen uptake (MVO2) (RPP: r = 0.77; TTI: r = 0.79; PWI: r = 0.79; Eg: r = 0.71). On the average, PWI and Eg led to an underestimation of MVO2 in patients. The constants of the PWI and Eg formulas, which have been developed based on animal experiments, therefore are not directly applicable to clinical conditions. New constants have been derived for PWI by multiple linear regression analysis of the data in the current investigation.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1991

[The effect of acid-base management on the oxygen uptake of the human body during hypothermic extracorporeal circulation].

The effects of two different systems of acid-base management on whole-body oxygen consumption during and following hypothermic cardiopulmonary bypass were investigated in 42 patients undergoing coronary artery bypass grafting or valve replacement surgery. In group I (22 patients) pH-stat management and in group II (20 patients) alpha-stat management was used. METHODS. Anesthesia was performed with fentanyl, midazolam, and pancuronium bromide. Halothane was added whenever MAP exceeded 100 mmHg. Cardiopulmonary bypass was conducted with a membrane oxygenator and a roller pump. Pump flow varied between 2 and 2.5 l/min per m2 body surface area. Once patients had been initially cooled down to a venous blood temperature of 27 degrees C they were kept stable between 28 degrees C and 30 degrees C during the ischemic phase. Measurements were performed after sternotomy during normothermia (control values) and every 15 min from the start until termination of bypass. RESULTS AND DISCUSSION. Neither hemodynamic parameters (MAP, CI, SVR) nor rectal or skin temperatures differed significantly between the two groups during the entire study period. Although at 27 degrees C oxygen availability fell by 43% and 35% in groups I and II, respectively, mixed venous oxygen saturation was significantly elevated compared with the control value, because of a decrease of 60% and 51%, respectively, in the arterio-venous oxygen content difference and of 62% and 55%, respectively, in oxygen consumption. Rewarming led to normalization of the metabolic parameters except for oxygen availability, which was still decreased as a result of low hemoglobin content. After termination of the bypass oxygen consumption increased steadily, which may have been due either to the beginning of shivering or to repayment of an oxygen debt caused by hypothermic bypass. As statistically significant differences were detected between the two groups in metabolic parameters during the course of the investigation, the hypothesis of Rahn and Reeves [2, 3], according to which oxygen consumption must be expected to be higher with alpha-stat than with pH-stat management, could not be verified by this study.

Acid-Base Imbalance↗
PubMed1991

[The effect of sufentanil on cerebral blood flow, cerebral metabolism and the CO2 reactivity of the cerebral vessels in man].

Sufentanil, a synthetic opioid that is 5-10 times as potent as fentanyl, has been suggested for use during neurosurgical procedures because it maintains cardiovascular stability and produces hypnosis without the use of additional anesthetic agents. Doses as low as 2.5 micrograms.kg-1 are reported to create deep levels of anesthesia as demonstrated by EEG changes to high-amplitude delta-waves. However, there are no reports concerning the effects of sufentanil on blood flow and metabolism in the human brain. The present study was designed to investigate the influence of high-dose sufentanil-O2 anesthesia on the cerebral circulation, metabolism, and the cerebrovascular response to CO2 in man. METHODS. Nine male and 2 female patients between 41 and 60 years of age who were scheduled for coronary artery bypass surgery were studied. Premedication consisted of flunitrazepam 2 mg orally and piritramide 15 mg and promethazine 50 mg i.m. 1 h before arrival in the induction room. Measurements were performed with the patients awake (I), after sufentanil 10 micrograms.kg-1 as an induction dose followed by 0.15 micrograms.kg-1.min-1 as an infusion with normocapnia (pa CO2 42.1 +/- 2 mmHg) (II), during hypercapnia (pa CO2 53.7 +/- 3.5 mmHg) (III), and during hypocapnia (pa CO2 31.7 +/- 2 mmHg) (IV). Cerebral blood flow (CBF) was measured using the argon wash-in technique. Cerebral venous blood was obtained from a catheter in the superior bulb of the right internal jugular vein. Cerebral metabolic rates of oxygen (CMRO2) glucose (Mgluc) lactate (CMlac) were calculated by multiplying the arterial-cerebral venous oxygen and substrate differences by CBF. The Anaerobic Index was calculated from the equation avD lactate x 100/2 x avD glucose = ANI (%) Cerebral electrical activity was recorded by aperiodic analysis of the EEG (Lifescan). RESULTS AND DISCUSSION. In the EEG sufentanil anesthesia was characterized by a decrease in the number of high-frequency waves and an increase in the number and amplitude of delta-waves, a pattern that did not change throughout the study period. Concomitantly, under normocapnic conditions high-dose sufentanil led to the significant decrease in CBF by 29% accompanied by an 18% increase in cerebral vascular resistance (CVR). CMRO2 decreased by 22% while CMRgluc and CMRlac changed only insignificantly such that the ANI, which represents the percentage of anaerobically metabolized glucose, essentially remained unchanged. Mean perfusion pressure declined by 18% but stayed within the range of autoregulation. Hypoventilation (III) was followed by an 82% increase in CBF as a result of a 55% reduction in CVR, whereas cerebral metabolic parameters did not show important changes when compared to measurement II. Hyperventilation (IV), on the other hand, produced a distinct fall in CBF by 56% to a value that was 21% below the one obtained under normocapnia. This was due to an increase in CVR of the same magnitude. There was a 31% rise in CMRO2, resulting in a decrease in cerebral venous oxygen tension, but in no case did it fall below the critical value of 20 mmHg at which tissue hypoxia becomes severe. Although CMRlac increased and CMRgluc did not significantly change, the ANI remained essentially unchanged, which suggests a predominantly aerobic metabolism. The increase in metabolic activity with sufentanil during hypocapnia might be caused by an alkalosis-induced stimulation of glycolysis. It might also be related to a reduction in the depth of anesthesia, although neither the EEG nor the hemodynamic parameters indicated this. This study shows that the coupling between CBF and metabolism is well maintained and that the cerebrovascular response to CO2 is unimpaired during high-dose sufentanil anesthesia.

Adult↗
PubMed1990

Cerebral dysfunction following extracorporeal circulation for aortocoronary bypass surgery: no differences in neuropsychological outcome after pulsatile versus nonpulsatile flow.

Nonpulsatile perfusion techniques with extracorporeal circulation for open-heart surgery and aortocoronary bypass grafting are widely used; this treatment is often followed by temporary or permanent neurological deficits. Experimental studies suggest that pulsatile flow may be of greater benefit because of its ability to ameliorate cerebral microcirculation. We therefore investigated 22 men who underwent aortocoronary bypass grafting. Patients were randomly divided into either a group undergoing nonpulsatile (n = 14) or pulsatile flow (n = 8). Neurological examinations were done prior to the operation and on the 7th postoperative day. EEG, cerebral blood flow (CBF), and the metabolic rates of O2 (CMR O2) and glucose (CMR Glucose) were measured before anaesthesia and 30 minutes after the start of extracorporeal circulation, when venous blood temperature was 26 degrees C. Postoperative neurological symptoms consisted of cranial nerve palsies, dysfunctions of the visual cortex, cerebellar symptoms, and slight arm paresis, but no differences between the two treatment groups were detected. Moreover, changes in EEG, CBF, and CMR rates during anaesthesia did not differ between the two groups. Our data suggest that pulsatile flow is not superior to the nonpulsatile perfusion technique, but to confirm this larger patient samples are required.

Adult↗
PubMed1990

Hepatic and extrahepatic disposition of propofol in patients undergoing coronary bypass surgery.

In order to clarify the relative contribution of the liver to the short term disposition of propofol, hepatic blood flow was measured during induction of anaesthesia with an i.v. bolus dose of propofol 2 mg kg-1. Total clearance of the drug was 2390 (SD 340) ml min-1, hepatic extraction 82% and hepatic clearance 1060 (260) ml min-1. During the 60-min period of observation, hepatic extraction of propofol increased from 79% to 92%. It is concluded that, within 1 h, only 44% of the administered dose is removed by the liver. Consequently, drug accumulation may occur with repeated dosing or infusion of propofol. The increase in extraction results presumably from slow release of propofol from the soy-bean emulsion.

Adult↗
PubMed1990

Cardiovascular and renal haemodynamic effects of dopexamine: comparison with dopamine.

We have studied the effects of dopexamine and dopamine on systemic and renal haemodynamics in 20 male patients undergoing elective coronary artery bypass surgery. Patients were allocated randomly to two groups (n = 10) who were treated with incremental doses of either dopexamine 1, 2 and 4 micrograms kg-1 min-1, or dopamine 2.5 and 5 micrograms kg-1 min-1, each dose being maintained for 15 min. Measurements were performed before administration of the drug and at the end of the infusion period at each dose. Fentanyl and midazolam were used as anaesthetic agents. Renal blood flow was measured with the argon washin technique. Dopexamine 4 micrograms kg-1 min-1 produced an increase in cardiac index of 117% caused by a 65% reduction in afterload and an increase in heart rate by 61%. Dopamine 5 micrograms kg-1 min-1 caused a 40% increase in cardiac index as a result of an increase in stroke volume. Renal vascular resistance decreased more than systemic vascular resistance with dopamine. With dopexamine, the increase in renal blood flow (66%) was less than the increase in cardiac index, while renal vascular resistance and systemic vascular resistance declined to almost the same extent. The results show that dopexamine exerts systemic and renal effects mainly via stimulation of beta 2-receptors. An action of dopexamine at renal DA1-receptors could not be demonstrated in this study.

Adrenergic Agonists↗
PubMed1990

The megachiropteran pineal organ: a comparative morphological and volumetric investigation with special emphasis on the remarkably large pineal of Dobsonia praedatrix.

This investigation is based upon the pineal organs of 92 specimens of 36 species of the family Pteropodidae (Mammalia, Chiroptera). The size of the megachiropteran pineal correlates well with body size (r = 0.864), confirming the former conclusions that generally larger bodied bats have larger pineals. The range of the pineal size index in 36 megachiropteran species is from 33 to 4393. In most species the pineal organs are small, deeply recessed under the cerebral hemispheres and of Type A (except in Dobsonia and Pteropus, where they are of Type alpha beta C and AB, respectively). Morphological and volumetric data gathered from serially sectioned brains include body and brain weights, pineal type, dimensions, volume and size index for each species. There are distinct dorsal and ventral subdivisions of the pineal in some species and a clear separation of pineal parenchyma into cortical and medullary regions in others. In several species where overlying ependyma is lacking pinealocyte clusters communicate freely with the CSF. Groups of intrapineal neurons are noted in the connective tissue beside blood vessels. The habenular commissure shows much interspecific variation in its course through the pineal. Detailed examination of pineal-brain relationships clearly suggests that, due to the generally deep location of the pineal in relation to cerebral hemispheres, pinealectomies in the species studied may be extremely difficult, it not entirely impossible. The absolutely and relatively largest pineal organ among bats, and relatively perhaps among all vertebrates, has been discovered in the New Guinean naked-backed bat, Dobsonia praedatrix, with pineal size index of 4393, and a volume of 16.3447 mm3, which is 0.56% of the brain. This alpha beta C-type, mushroom-shaped, solid and compact pineal organ measures 5.33 x 4.51 mm. The cortical and medullary parenchyma are divided into lobes by large calibre blood vessels along which numerous intrapineal neurons are observed. A smaller but similarly shaped pineal is noted in the other three Dobsonia. Data on the largest known pineals in ratitae birds, seals and walruses have been compared with that of D. praedatrix and the human pineal. This study supports the hypothesis that pineal development may reflect dependence on habitat and possibly other related factors.

Animals↗
PubMed1990

Comparison of brain structure volumes in Insectivora and primates. IX. Trigeminal complex.

Volumes of the trigeminal complex (TR) were measured in 30 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of non-human simians and in man. The relative size showed a definite tendency to decrease from 159 in Insectivora to 56 in simians (expressed as size indices). The difference in the development of the TR between Insectivora and Primates is explained by differences in the role of their oro-facial region in exploratory behavior. The largest size was found in semiaquatic Insectivora (average 283). In semiaquatic forms, the reduction of the olfactory centers is compensated by an increase in TR size. The extremely long vibrissae innervated by the trigeminal nerve seem to have a teletactile function in detecting vibrations in the water produced by potential prey.

Animals↗