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Biomedical subjects

N Gruber

Publications and source records attributed to N Gruber.

At least 19 recordsLinked to original sources
PubMed2004

High-latitude controls of thermocline nutrients and low latitude biological productivity.

The ocean's biological pump strips nutrients out of the surface waters and exports them into the thermocline and deep waters. If there were no return path of nutrients from deep waters, the biological pump would eventually deplete the surface waters and thermocline of nutrients; surface biological productivity would plummet. Here we make use of the combined distributions of silicic acid and nitrate to trace the main nutrient return path from deep waters by upwelling in the Southern Ocean and subsequent entrainment into subantarctic mode water. We show that the subantarctic mode water, which spreads throughout the entire Southern Hemisphere and North Atlantic Ocean, is the main source of nutrients for the thermocline. We also find that an additional return path exists in the northwest corner of the Pacific Ocean, where enhanced vertical mixing, perhaps driven by tides, brings abyssal nutrients to the surface and supplies them to the thermocline of the North Pacific. Our analysis has important implications for our understanding of large-scale controls on the nature and magnitude of low-latitude biological productivity and its sensitivity to climate change.

Antarctic Regions↗
PubMed2003

[Evolution of inflammatory parameters after fibroid embolization].

PURPOSE: To describe the rise of classical laboratory tests for inflammation following transarterial uterine fibroid embolization (UFE) in order to monitor the normal course following UFE. MATERIALS AND METHODS: In 20 females, white blood cell (WBC) count and C-reactive protein (CRP) were determined before and up to 5 days after UFE. With the exception of one noninflammatory complication, the post-procedure course was uneventful in all patients. The measured values were correlated with both the total uterine volume and the amount of instilled embolizing agent. RESULTS: Following UFE, an increase in the WBC count to an average maximum of 10.8 +/- 3.5/wL (range 5.9 - 18.6/wL) was found. In 13 of 20 patients, the WBC count was above normal on at least one day following UFE. The increase reached the maximum on the third post-interventional day and subsided within 5 days after the UFE. The CRP values increased significantly to an average maximum of 41.9 +/- 28.8 mg/l. The maximum was found on the 2nd post-interventional day in 8 patients, on the 3rd day in 11 patients and on the 4th day in one patient. No correlation to the total uterine volume or to the amount of the instilled embolizing agents was detected. CONCLUSION: Following uncomplicated UFE, a steep increase in CRP occurs with no or only a mild increase in the WBC count, which does not indicate an infected fibroid. The maximum is reached on the 3rd or 4th post-interventional day, followed by a decline in CRP and normalization of the WBC count.

Adult↗
PubMed2001

Fetal behavioural state changes following maternal fluoxetine infusion in sheep.

Clinical depression is diagnosed in 5-15% of women during pregnancy, increasing the risk of negative outcomes. Fluoxetine (FX), a selective serotonin reuptake inhibitor, is prescribed during pregnancy. In adults, FX alters sleep patterns with single doses decreasing total sleep time and rapid eye movement sleep. The effects of FX on sleep in the fetus are unknown. However, 5-hydroxytryptophan, the precursor of serotonin, has been reported to prolong high-voltage (HV) electrocortical (ECoG) activity and increase the incidence of fetal breathing movements (FBM) in the sheep fetus. We hypothesize that FX exposure will decrease the incidence of LV ECoG in the fetus. Twenty-one pregnant sheep were surgically prepared for chronic study of blood gases, ECoG activity, eye movements and FBM. After 3 days of recovery, ewes received a 70-mg bolus i.v. infusion of FX or sterile water followed by continuous infusion at a rate of 0.036 mg/min for 8 days. The incidence of low-voltage (LV) ECoG decreased from 54+/-4% on the preinfusion day to 45+/-5% on infusion day 1 in the FX group and remained decreased throughout the infusion period. In addition, the incidence of both eye movements and FBM was decreased on infusion day 1 compared to preinfusion day in the FX group. HV ECoG increased from 39+/-3% on preinfusion day to 68+/-14% on FX infusion day 1 and remained elevated throughout the infusion period. These data show that maternal FX administration alters fetal behavioural state.

Animals↗
PubMed2000

The global carbon cycle: a test of our knowledge of earth as a system.

Motivated by the rapid increase in atmospheric CO2 due to human activities since the Industrial Revolution, several international scientific research programs have analyzed the role of individual components of the Earth system in the global carbon cycle. Our knowledge of the carbon cycle within the oceans, terrestrial ecosystems, and the atmosphere is sufficiently extensive to permit us to conclude that although natural processes can potentially slow the rate of increase in atmospheric CO2, there is no natural "savior" waiting to assimilate all the anthropogenically produced CO2 in the coming century. Our knowledge is insufficient to describe the interactions between the components of the Earth system and the relationship between the carbon cycle and other biogeochemical and climatological processes. Overcoming this limitation requires a systems approach.

Animals↗
PubMed1996

Drug treatment of Alzheimer's disease. Effects on caregiver burden and patient quality of life.

Alzheimer's disease is a devastating illness that will become more common as the population ages. Although clinical diagnosis of the illness is not certain without histological examination of the brain, and misdiagnosis may occur, broad working criteria to help diagnose the likely presence of Alzheimer's disease are available. Thoughtful clinical evaluation improves diagnostic accuracy, and appropriately diagnosed patients are critical for involvement in research into new antidementia agents. Essential to the discovery of new drugs is careful measurement of illness response. A variety of scales--some aimed at patients, others at their caregivers, and yet others for clinicians--assess Alzheimer's disease severity, progression, symptom response, and quality of life. Of note, patient response is not the only measurement of treatment benefit today. Growing interest is also being placed on tracking the possible amelioration of caregiver 'burden'. This burden refers to the psychological, physical, and material costs of providing care for an Alzheimer's patient over long periods of time. A number of scales and questionnaires have been developed and are occasionally used. Many drugs have been tried in Alzheimer's disease, but very few have produced any benefit, and this is often modest. Ergoloid mesylates, initially thought to be effective, are now considered of little value. The cholinomimetic drugs, especially the acetylcholinesterase inhibitor tacrine, have provided a very modest benefit, slowing the progression of the illness for a number of months. No cognitive improvement has been noted with the various nootropic agents such as piracetam. Early studies with levacecarnine (acetyl-L-carnitine), a substance that facilitates the use of fatty acids, memantidine, the dimethyl derivative of amantidine, and the calcium channel blocker nimodipine, have shown some promise, but require larger, more rigorous studies. As mentioned above, documenting effects in individual patients is crucial; examining for potential benefit to caregivers is a growing part of research design. Current treatment efforts will become more sophisticated as a deeper understanding of the neurobiology of Alzheimer's disease develops. For the immediate future, the goal is not cure but slowing of the disease process. Achieving this limited goal would have a substantial impact on the financial and human costs of the illness.

Alzheimer Disease↗
PubMed1994

[Comparative evaluation of dipyridamole and dobutamine 2-dimensional echocardiography in ischemic heart disease].

Dipyridamole and dobutamine stress were performed in the same 41 angiographically controlled patients. Both tests were followed by 2 dimensional-echocardiography. The dose of dipyridamole was 0.56 mg/kg/4 min. or 0.84 mg/kg over 10 min., while the dose of dobutamine was 10-20-30-40 and 40 micrograms/kg/min. over 3 min. each step. In addition, to reach the submaximal heart rate 0.25 mg/min Atropine was also injected for 4 minutes in 13 cases. One vessel disease was found in 15 cases, and 2 vessel disease was in 2 cases. The number of coronarography negative cases was 24. The sensitivity, specificity, positive and negative predictive values for both tests were 70%, 91%, 85% and 81%, respectively. False positive results were observed in 2 cases and false negative ones were found in 5 cases, mainly at left anterior descendent stenosis. There was a good agreement between the wall motion abnormality and the anatomic localization of stenoses. Both non-invasive tests are suitable for the diagnosis of ischaemic heart disease.

Adult↗
PubMed1993

Prospective evaluation of thallium-201 reinjection in single-vessel coronary patients undergoing coronary bypass surgery.

Twenty-two patients with single-vessel left anterior descending coronary artery disease were investigated by means of dipyridamole stress thallium-201 myocardial perfusion scintigraphy, using single photon emission tomography (SPET), 1 week before and 2-5 weeks after coronary bypass surgery. The dose of dipyridamole was 0.56 mg/kg, and the injected activity of 201Tl was 74 MBq. Before surgery, and after completion of the redistribution study, a further 37 MBq of 201Tl was injected. Ten minutes and 1 h later, repeated SPET imaging were performed. SPET images were evaluated both subjectively and semiquantitatively, using a five-grade segmental defect score system, with higher scores for more severe perfusion defects. Before surgery, the 3-h redistribution images revealed complete or partial persistence of the perfusion defects in all patients. On the images taken 10 min after reinjection, these defects were completely filled in four cases, and partially filled in ten cases. Further positive changes were observed on the 1-h post-reinjection images in four cases. Three of the 1-h post-reinjection images exhibited a paradox redistribution. The stress images after surgery corresponded well to the 201Tl distribution on the preoperative 1-h post-reinjection images in 11 cases. The average of the segmental defect severity scores was 17.0 after stress, 10.1 at rest, 7.1 10 min after reinjection and 6.4 1 h after reinjection. After surgery, the average of both the post-stress and the 3-h redistribution scores was 3.1.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗
PubMed1992

[False positive results of exercise tests with thallium myocardial scintigraphy].

The authors have examined supposed causes of positive Th-201 stress scintigraphy. Patients were divided into two groups according to the presence of exercise-induced transitory hypoperfusion or in absence of it. In both groups negative coronarograms were verified. Results of two groups were compared according to parameters of the left ventricle function, pulmonary pressure, to the presence of disorder of system stimulus-conduction (LBBB, RBBB), mitral prolapsus, foramen ovale apertum, anomalous coronary anatomy, level of load during exercise, body weight, heart volume-index. Significant difference was found in disorder of left ventricle motion, ejection fraction and in comprehensive value of left ventricle function (F1).

Adult↗
PubMed1992

[Ergometric stress test using Tl-201 myocardial perfusion. Tomographic or planar imaging?].

The clinical performance of the planar vs. tomographic ergometric stress 201-Tl myocard perfusion scintigraphy was compared. The results of the investigations of 80 patients were analysed retrospectively. In 59 patients planar, in 21 tomographic imaging was performed. As a consequence of clinical decision making cardiac catheterization was made in all of the patients, within 3 months after the perfusion scintigraphy. The sensitivity of the planar method was 23/27 (85%), the specificity 18/32 (56%), the accuracy 41/59 (69%). The respective values of the SPECT technique were: Sensitivity: 12/12 (100%), specificity 6/9 (66%), accuracy 18/21 (86%). It is concluded, that in comparison to the planar imaging the SPECT technique is superior in the detection of the perfusion abnormalities of the myocard due to significant coronary narrowings.

Coronary Disease↗
PubMed1991

[The significance of the dipyramidole echocardiography test in ischemic heart disease].

The diagnostic value of the dipyridamole echocardiography test was investigated in 46 patients who underwent coronary angiography due to suspected ischaemic heart disease. Twenty-two of 46 patients were found to have a narrowing of at least 70% one vessel. Twenty-four hour ECG monitoring was also performed on 19 patients on the day of the dipyridamole test. The sensitivity and specificity of the two-dimensional echocardiography test (new wall motion abnormality) were 72.7% and 62.5%. The ECG (V2-5-9) had a low sensitivity during the test (43.8%). Good agreement was found between the localization of the wall motion abnormalities and the site of anatomic narrowing in the ischaemic group. No significant ventricular arrhythmias were detected, and the sensitivity and specificity of ST-T changes were found to be 62.5% and 54.6% by means of Holter monitoring. The dipyridamole echocardiography test proved to be a suitable noninvasive method for the diagnosis of ischaemic heart disease and for the selection of patients for coronary angiography.

Coronary Angiography↗
PubMed1990

[Cardiolite (99m-Tc-isonitrile) SPECT studies in patients prior to coronary bypass surgery].

The authors studied with 99m-Tc Cardiolite (methoxy-isobutyl-isonitrile) SPECT examination the effect of coronary bypass operation on the myocardial perfusion. One week before and 3 weeks after the operation examinations were performed first with dipyridamol loading and 24 hours later in rest. The regional perfusion of the myocardium was studied on the basis of transversal section-pictures of corrected axis position. In the examinations preceding the operation the global sensitivity of the method was found to be 100%. In the demonstration of the structures of the ramus descendens 95%, of the ramus circumflexus and of the right coronary artery 100% sensitivity was reached. In postoperative examinations following the bridging of the ramus descendens anterior the improvement of the perfusion of the corresponding ventricular segment was found in 15/20 during the loading and in 7/8 cases following the bridging of the ramus circumflexus and right coronary artery. Improving perfusion was demonstrated in 17/20 and in 6/8 cases in rest. On the basis of the results the authors consider their method suitable for the study of the regional blood perfusion and for the examination of the changes taking place upon coronary bypass operations.

Aged↗