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Biomedical subjects

T Fritz

Publications and source records attributed to T Fritz.

At least 55 records · Page 3Linked to original sources
PubMed1996

Brachial and digital artery pulse pressures in hypertensive and normotensive subjects.

OBJECTIVES AND PATIENTS: To determine whether or not the pulsatile component of blood pressure (BP) measured centrally and peripherally allows a separation between hypertensive and normal subjects, as well as within hypertensive and normal subjects, as well as within hypertensive patients. We tested the hypothesis that the difference in central and peripheral pulse pressures is increased in hypertensive, compared to normotensive persons, and that this component is influenced by genetic variance. We studied 46 hypertensive patients and 56 age-matched normal subjects, as well as 10 hypertensive families with 74 members of the same age range. DESIGN: Pulse pressure was measured at the brachial artery and the digital artery in the standing and supine position. The difference in the pulse pressures between these sites was calculated. Further, digital volume-pulse amplitude and stroke volume measurements were determined with impedance plethysmography. RESULTS: The differences between central and peripheral pulse pressures were similar in hypertensive patients compared to normal subjects, regardless of posture. However, in the standing position the frequency distribution of this variable in hypertensive patients was bimodal and split into two significantly different distributions (P < 0.05) with peaks at -24 mm Hg and -1 mm Hg, compared to a single peak at -11 mm Hg in normal subjects. Furthermore, these two subgroups of hypertensive patients differed in their brachial systolic BP (127 +/- 10 vs 134 +/- 12 mm Hg; P < 0.05), their brachial pulse pressures (32 +/- 8 vs 42 +/- 8 mm Hg; P < 0.05), and in their peripheral compliance (1.59 +/- 0.92 vs 2.21 +/- 1.00 microliter/mm Hg per 100 ml tissue; P < 0.05). The frequency distribution of pulse pressure differences was also bimodal in members of hypertensive families, even though most (46 out of 74) were normotensive. CONCLUSION: The difference between the digital and brachial pulsatile component may be a useful intermediary phenotype in essential hypertension. Furthermore, the nonuniform decreases in arterial compliance exhibited by our patients may be of pathogenic significance.

Adult↗
PubMed1995

[Experimental studies of the load capacity of DHS osteosyntheses after various kinds of osteotomy in the area of the femoral trochanter].

Standardized osteotomies were performed to mimic fractures classified as (a) stable, (b) partly unstable and (c) complete unstable (according to Evans) in 32 postmortem femoral bones. The stability of all preparations was examined after the performance of an osteosynthesis with a dynamic hip screw. Cycled loadings were increased stepwise every 500 N to the maximum loading capacity (load of fracture). In addition, the distortion at 2000 N was measured. There were no statistically significant differences between the three groups (a), (b), and (c). The average maximum load capacity was significantly lower in group (c) than in groups (a) and (b). Nevertheless, the lowest value (2275 N) recorded for the maximum loading capacity in our study means that in a normal weight person full weight-bearing can be allowed postoperatively.

Aged↗
PubMed1994

[A possible risk for geriatric risk patients caused by intraoperative disorder of cerebral energy utilization?].

OBJECTIVE: This study was carried out on cerebrospinal fluid (CSF) to investigate the perioperative course of certain ischaemic markers, namely neurone-specific enolase (NSE), creatine kinase (CK-BB), hypoxanthine, and lactate in order to identify a disturbed cerebral energy utilisation which could be responsible for the development of temporary mental dysfunctions. Those dysfunctions are characterised by preserved memory content and perception, but the coordination and association of these functions are disturbed. Typical clinical signs are motor restlessness, disordered emotions, and symptoms of dementia. Little is known about the aetiology of those symptoms, but they are most likely due to various events, such as direct drug effects, the extent of surgical trauma, sensorial deprivation, and disturbed perfusion. METHODS: Eight orthopaedic patients (ASA III or IV) scheduled for removal of their total hip replacement were anaesthetised by catheter-spinal anaesthesia (CSA) for pain relief in combination with standardised, modified neuroleptanalgesia (NLA). At six defined times (15 hours preoperatively, immediately before and after surgery and 6, 24, and 36 hours postoperatively) CSF samples were drawn and the ischaemic markers were determined by means of radioimmunoassay (NSE), electrophoresis (CK-BB), photometry (lactate), and high-pressure liquid chromatography (hypoxanthine). The release of ischaemic markers into CSF correlates linear with the extent of ischaemic brain damage. RESULTS: Mean concentrations of the following ischaemic markers increased in all patients intraoperatively: NSE from 12.3 ng/ml to 13.4 ng/ml, hypoxanthine from 1.86 mumol/l to 3.73 mumol/l, and lactate from 1.4 mmol/l to 2.0 mmol/l respectively, all of which returned to normal within 36 hours. The CK-BB concentrations were all within normal values and not affected by the operation during this investigation. CONCLUSION: Although no clinical signs of temporary mental dysfunction have been observed, the results indicate that in CSF ischaemic markers temporarily undergo certain changes in their concentrations during the removal of total hip replacements in elderly patients. These changes are reason for assuming that risk patients may suffer a temporary disturbed cerebral energy utilisation intraoperatively, even if stable clinical and cardiovascular conditions prevail under anaesthesia. Such a temporary ischaemic penumbra might be responsible for the postoperative development of temporary mental dysfunctions.

Aged↗
PubMed1994

Toluene abuse: physical basis for hypointensity of the basal ganglia on T2-weighted MR images.

PURPOSE: To explain the hypointensity in the basal ganglia on T2-weighted magnetic resonance (MR) images of brains of toluene abusers. MATERIALS AND METHODS: Eight patients with histories of toluene abuse underwent MR imaging. A bilayered model of dipalmitoylphosphatidylcholine (DPPC; 100 mmol/L concentration) and varying concentrations of toluene was formed. The DPPC control and toluene-mixed bilayers underwent MR imaging. T1 and T2 were measured as a function of toluene and lipid concentrations. RESULTS: T2-weighted images of patients who had abused toluene showed marked hypointensity in the thalami and moderate hypointensity in the basal ganglia. Measurements of the DPPC-toluene phantom indicated that toluene-tainted lipid bilayers dramatically shortened T2 and had little effect on T1. By comparison, DPPC itself had little discernible effect on either T1 or T2. CONCLUSION: This model suggests that partitioning of toluene into the lipid membranes of cells in cerebral tissue may be responsible for the hypointensity of basal ganglia noted on T2-weighted MR images of brains of toluene abusers.

Adult↗
PubMed1994

[Computerized tomography of kidney tumors].

Among 220 renal tumors which we detected by computed tomography, there were 168 renal cell carcinomas, 24 tumor of the renal pelvis, 16 angiomyolipomas, 6 Wilms tumors, 3 oncocytomas, one liposarcoma, one mesenchymal tumor, and one rhabdomyosarcoma. Computed tomography had the highest accuracy of the diagnostic procedures with a sensitivity of 99.5% and a specificity of 98%. 83% of the renal cell carcinomas showed signs of malignancy in computed tomography; the staging of the renal tumors by computed tomography was correct in 67% of the cases. The diagnostic value of other diagnostic tools (sonography, urography, angiography, cavography) of renal tumors is discussed in terms of our own results.

Adolescent↗
PubMed1994

[PDS cord fixation of sternoclavicular dislocation and para-articular clavicular fractures].

Sternoclavicular joint dislocation and para-articular fractures of the clavicle are rare injuries. Because severe complications of dorsal dislocations have often been seen and because functional impairment has often followed ventral dislocations, we treat most patients with such injuries operatively. Internal fixation with K-wires frequently leads to severe complications. We present our operation techniques with a resorbable 2 mm polydioxanon cord. This pack up technique can be used in both dislocations and para-articular fractures with no risk of implant dislocation.

Clavicle↗
PubMed1993

Blood responses under chronic low daily dose gamma irradiation: II. Differential preclinical responses of irradiated female dogs in progression to either aplastic anemia or myeloproliferative disease.

Female beagle dogs were chronically exposed to low daily doses of 60Co gamma rays (7.5 cGy day-1) and responded in one of three distinct hemopathological patterns. These patterns, reflective of distinct subgroups, were characterized by (a) low radioresistance resulting in progressive hematopoietic suppression, terminal aplastic anemia (AA), and relatively short (< 400 days) survival (-S-AA subgroup); (b) high radioresistance, initially coupled with strong but aberrant regenerative hematopoiesis, and later with the development of myeloproliferative disease (MPD) ((+)-R-MPD subgroup); and (c) high radioresistance, coupled with an early phase of strong regenerative hematopoiesis, but later with no myeloproliferative disease (+R-nonMPD subgroup). In this study, the changes in circulating blood cell levels (granulocytes, monocytes, erythrocytes, lymphocytes and platelets) were sequentially assessed in time and fitted to a flexible, quadratic-linear-type response model previously developed. These analyses provided definition to (a) an initial suppressive, radiotoxic phase and (b) the subsequent recovery phase for each of these subgroups. The magnitude and severity of blood cell loss during the initial suppressive phase was generally greatest in the -S-AA subgroup and lowest in the +R-nonMPD subgroup, with the +R-MPD subgroup showing intermediate level responses. A notable exception included a very high net loss of blood granulocytes by the +R-nonMPD subgroup relative to the other two subgroups. By contrast, the magnitude of blood cell restoration, as well as blood cell maintenance levels during the secondary, recovery phase, was generally highest in the +R-MPD subgroup, of intermediate strength in the +R-nonMPD subgroup, and extremely weak or absent in the -S-AA subgroup. Notable exceptions were in the +R-nonMPD subgroup's high recovery rates of monocyte and lymphocyte blood levels, as well as the high maintenance levels of blood granulocytes during recovery. These results are consistent with our earlier observations of blood responses of chronically irradiated male dogs, in that subgroups of female dogs prone to specific radiogenic hematopathologies (i.e. AA and MPD) can be readily identified and staged in specific preclinical periods by a series of marked differential blood responses.

Anemia, Aplastic↗
PubMed1993

Manganese-based liposomes. Comparative approaches.

RATIONALE AND OBJECTIVES: The purpose of this study was to further develop and compare manganese-based liposomes prepared by two different approaches wherein a manganese ion was entrapped within the internal aqueous space of the vesicles or into the bilayer surface via membrane bound complexes. METHODS: Small unilamellar liposomes (SUVs) were prepared entrapping manganese chloride. Alkylated complexes of manganese were prepared and also incorporated into SUVs. The two different manganese-based liposomes were compared for in-vitro relaxivity, stability, toxicity, and in-vivo imaging in rats with liver tumors. RESULTS: Liposomes entrapping manganese had a concentration-dependent change in relaxivity that was maximal at a several-fold molar excess of phospholipid relative to manganese ion. Liposomes bearing membrane-bound complexes showed relaxivity inversely proportional to vesicle size. In-vivo imaging showed greater and more specific hepatic enhancement with manganese liposomes bearing alkylated complexes than those entrapping manganese ion. CONCLUSIONS: Correlation effects likely explain the increased relaxivity of manganese entrapped in phospholipid vesicles. Greater efficacy, however, is afforded by liposomes bearing alkylated complexes.

Animals↗
PubMed1993

Gas-filled liposomes as echocardiographic contrast agents in rabbits with myocardial infarcts.

RATIONALE AND OBJECTIVES: The authors evaluated gas-filled liposomes as echocardiographic contrast agents in rabbits with myocardial infarcts. METHODS: Ten rabbits underwent ligation of the left anterior descending coronary artery. Five animals underwent echocardiography before and after production of myocardial infarct (MI) and four animals had post-MI imaging only. In either case, images were obtained before and after injection of a single dose of 1 mL of gas-filed liposomes. Three radiologists blinded to clinical information reviewed the pre- and postcontrast images and assessed endomyocardial border definition, wall motion, confidence levels for normal versus abnormal wall motion and visualization of papillary muscle and mitral valve. RESULTS: Postcontrast scans showed significant improvement (P < .05) in endomyocardial border definition, visualization of wall motion, papillary muscle and mitral valve as well as increased reader confidence level. CONCLUSIONS: These results are encouraging and suggest that gas-filled liposomes may be a useful contrast agent for echocardiography.

Animals↗
PubMed1992

[Ultrasound assisted brachial plexus anesthesia].

Plexus brachialis anaesthesia is a common technique for hand and forearm surgery. If the distance between puncture site and plexus brachialis is to long the anaesthesia will be incomplete. If there happens a direct puncture and injection of anaesthetics in the nerves, neurological deficit can occur. Intravascular injection causes cardial complications. This problems can occur mainly in obese patients in whom the brachial artery cannot be identified well by clinical examination. In these patients we perform the plexus brachialis anaesthesia under sonographical control. For the examination we use a linear 7.5-MHz transducer. The technique is presented.

Anesthesia, Conduction↗
PubMed1991

Liposomes as MR contrast agents: pros and cons.

Liposomes are generally thought of as being useful for entrapping drugs within their internal aqueous space. When used with MR contrast agents, this has the drawback that water flux across the membrane bilayer is limiting to contrast enhancement. This can be partially overcome by making the liposomes very small, such that surface area is relatively great compared to internal volume, thereby facilitating water exchange. Alternatively the membranes can be designed to be permeable to water but this may render the vesicles unstable in serum. Another approach is to incorporate the contrast agents into the lipid bilayer. By designing novel complexes of manganese with the ligands incorporated onto dual acyl chains, we have achieved R1 and R2 values of over 20/mmol sec-1 or more than five times higher than Gd-DTPA. Hepatic metastasis detection is significantly improved in rats at doses of only 10 mumol/kg manganese. Membrane-bound manganese complexes function as highly effective liver imaging agents and merit further study for development as agents to undergo human clinical trials.

Animals↗
PubMed1991

Detailed toxicity studies of liposomal gadolinium-DTPA.

Acute, subacute, and delayed toxicity testing was assessed in mice for liposomal gadolinium-DTPA (Gd-DTPA), blank liposomes, and nonliposomal Gd-DTPA. In the subacute experiments mice were injected intravenously (IV) with 0.3 mmol/kg Gd-DTPA per day for 30 days in the form of either free Gd-DTPA, liposomal Gd-DTPA, or an equivalent amount of lipid in blank liposomes without Gd-DTPA. The interpolated acute LD50 of liposomal and nonliposomal Gd-DTPA, estimated as a means of identifying the approximate level, was similar (LD50 = 5.7 mmol/kg Gd-DTPA). In subacute toxicity testing, prolonged high doses of liposomal Gd-DTPA caused splenomegaly, cardiomegaly, lymphocytopenia and hypergammaglobulinemia (P less than .05). Nonliposomal Gd-DTPA caused mild cardiomegaly and altered liver enzymes (P less than .05). Blank liposomes caused relatively mild splenomegaly (P less than .05) but few other changes. Delayed testing three months after the subacute testing showed that most of the changes caused by the liposomal Gd-DTPA were reversible.

Animals↗