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Biomedical subjects

L Novak

Publications and source records attributed to L Novak.

At least 19 recordsLinked to original sources
PubMed2005

Spinal extradural arachnoid cyst causing cord compression in a 15-year-old girl: a case report.

The authors describe the case of a fifteen-year-old girl with progressive paraparesis of the lower limbs that was caused by an intraspinal extradural dorsal arachnoid cyst at the level of Th 3-6. Diagnosis was established with MRI and MRI myelography. The latter revealed the CSF-like content of the cyst. The patient underwent laminotomy and en bloc resection of the cyst. Ligation of the pedicle of the cyst was done with laminoplasty. Quick and complete recovery was observed after surgery.

Adolescent↗
PubMed2004

First results from the Cryogenic Dark Matter Search in the Soudan Underground Laboratory.

We report the first results from a search for weakly interacting massive particles (WIMPs) in the Cryogenic Dark Matter Search experiment at the Soudan Underground Laboratory. Four Ge and two Si detectors were operated for 52.6 live days, providing 19.4 kg d of Ge net exposure after cuts for recoil energies between 10 and 100 keV. A blind analysis was performed using only calibration data to define the energy threshold and selection criteria for nuclear-recoil candidates. Using the standard dark-matter halo and nuclear-physics WIMP model, these data set the world's lowest exclusion limits on the coherent WIMP-nucleon scalar cross section for all WIMP masses above 15 GeV/c2, ruling out a significant range of neutralino supersymmetric models. The minimum of this limit curve at the 90% C.L. is 4 x 10(-43) cm2 at a WIMP mass of 60 GeV/c2.

Journal Article↗
PubMed1999

Comparison of standard and alternative prehospital resuscitation in uncontrolled hemorrhagic shock and head injury.

BACKGROUND: Recently acquired data suggest that prehospital fluid resuscitation may worsen outcome of patients with penetrating torso trauma. In patients with head injury, delayed resuscitation (DR) could lead to secondary cerebral ischemia. We hypothesized that standard prehospital resuscitation (SPR) with lactated Ringer's solution or diaspirin cross-linked hemoglobin would reduce secondary cerebral ischemia compared with DR. METHODS: Anesthetized swine were randomized to receive SPR, diaspirin cross-linked hemoglobin, or DR after cryogenic brain injury and uncontrolled hemorrhagic shock and studied for 70 minutes after the combined insults. RESULTS: Hemorrhage volume was lowest in the DR group (p<0.05). There were no significant differences between the groups in systemic or cerebral oxygen delivery. Intracranial pressure was lower and cerebral perfusion pressure higher in the diaspirin cross-linked hemoglobin group compared with SPR (p<0.05). Lesion size was greatest in the SPR group, but the difference was not significant. CONCLUSION: In this model, SPR leads to secondary cerebral ischemia. DR is no worse and may be superior to conventional prehospital resuscitation with lactated Ringer's solution.

Animals↗
PubMed1997

Production of a specific major histocompatibility complex class I-restricted epitope by ubiquitin-dependent degradation of modified ovalbumin in lymphocyte lysate.

Peptide epitopes presented through class I major histocompatability complex (MHC class I) on the cell surface, are generated by proteolytic processing of protein-antigens in the cytoplasm. The length and amino acid sequence determine whether a given peptide can fit into the peptide binding groove of class I heavy chain molecules and subsequently be presented to the immune system. The mode of action of the processing pathway is therefore of great interest. To study the processing mechanism of MHC class I-restricted intracellular antigens, we reconstituted the proteolytic processing of a model antigen in a cell-free system. Incubation of oxidized and urea-treated OVA in lymphocyte lysate resulted in partial degradation of the antigen. Degradation of the antigen depended on the presence of ATP. Addition of methylated ubiquitin abolished the reaction which was then restored by addition of an excess of native ubiquitin, indicating that the breakdown of the antigen in lymphocyte lysate is mediated by the ubiquitin proteolytic system. Upon incubation of modified OVA in lymphocyte lysate, a specific antigenic peptide was generated. The peptide was recognized by cytotoxic T lymphocytes directed against OVA-derived, H-2Kb-restricted peptide (SIINFEKL), and by a monoclonal antibody that recognizes cell-bound Kb-SIINFEKL complexes. Formation of the peptide epitope depended on the presence of ATP and ubiquitin. These results indicate that proteolytic processing of modified OVA is carried out by the ubiquitin-mediated degradation system. The experimental system described provides a tool to analyze the molecular mechanisms underlying the generation of specific, MHC class I-restricted peptide epitopes.

Animals↗
PubMed1997

Metabolism and Energetics of Lactococcus lactis during Growth in Complex or Synthetic Media.

When Lactococcus lactis was grown in various complex or synthetic media, the fermentation of glucose remained homolactic whatever the medium used, with a global carbon balance of about 87%. Moreover, the nitrogen balance was not equilibrated, indicating that some amino acids led to the production of unknown nitrogen-containing carbon compounds while part of the glucose might contribute to anabolic pathways. In minimal medium containing six amino acids, a high concentration of serine was deaminated to pyruvate. This did not occur in more complete media, suggesting the presence of a regulation of this phenomenon by an amino acid. Ammonia produced during serine consumption was partly reconsumed after serine exhaustion. The values for biomass yield and biomass yield relative to ATP (Y(infATP)), the maximal growth rate, the specific rate of glucose consumption, and the corresponding rate of ATP synthesis all increased with the complexity of the medium, amino acid composition having the most pronounced effect. The Y(infATP) values were shown to range from 6.6 to 17.6 g of biomass(middot)mol of ATP(sup-1) on minimal and complex media.

Journal Article↗
PubMed1997

Cerebrovascular reserve capacity many years after vasospasm due to aneurysmal subarachnoid hemorrhage. A transcranial Doppler study with acetazolamide test.

BACKGROUND AND PURPOSE: Vasospasm in aneurysmal subarachnoid hemorrhage results in proliferative vasculopathy. Systemic hypertension also causes vascular hypertrophy. Both of these histological changes can lead to rigidity of the cerebrovascular system, reducing its autoregulatory capacity. METHODS: Blood flow velocity (BFV) in the middle cerebral artery at rest and cerebrovascular reserve capacity (CVRC) (percent rise in BFV after acetazolamide stimulation) measured by means of transcranial Doppler sonography were studied many years after aneurysmal subarachnoid hemorrhage in patients with proven cerebral vasospasm (mean BFV > 160 cm/s). The BFV under resting conditions and the CVRC values of the ipsilateral and the contralateral hemispheres were measured in 29 patients (mean age, 43 years; mean follow-up, 4.6 years) and compared with those of control subjects. RESULTS: Persistent high BFV (> 120 cm/s) was found in three patients in the peripheral branch of the ipsilateral middle cerebral artery. In the main trunks of the arteries of the anterior circle of Willis, BFV was normal in all cases. CVRC was normal in all patients (ipsilateral, 52 +/- 21%; contralateral, 56 +/- 17%); values did not differ significantly from each other or from the control value (45 +/- 18%). The higher value of CVRC on the contralateral side was found to be statistically significant in selected groups (hypertensive patients and patients with residual infarct on late CT). CONCLUSIONS: Proliferative vasculopathy developed at the time of vasospasm must have resolved and did not reduce late vasoreactivity. Comorbidity with hypertension also did not seem to influence the late vasoreactivity toward normalization.

Acetazolamide↗
PubMed1996

Craniospinal irradiation for acute lymphoblastic leukemia with central nervous system disease at diagnosis: a report from the Children's Cancer Group.

PURPOSE: This study attempted to determine if central nervous system (CNS) disease at diagnosis is a poor prognostic factor in children with acute lymphoblastic leukemia (ALL) and whether 6 Gy of spinal irradiation is an adequate dose for these patients. METHODS AND MATERIALS: Previously the Children's Cancer Group (CCG) treated patients with ALL and CNS disease at diagnosis with cranio (24 Gy)-spinal (12 Gy) irradiation, as well as systemic and intrathecal chemotherapy. In a series of CCG trials completed in 1989 the spinal dose was empirically reduced to 6 Gy for patients receiving systemic chemotherapy with an intensive consolidation phase to limit hematopoietic toxicity. The spinal dose was left at 12 Gy for patients treated with a less intensive consolidation phase. RESULTS: With a median follow-up for surviving patients of 74 months, the 5-year event-free survival for 53 patients with CNS disease at diagnosis was 69 +/- 13% (+/- 2 standard deviations), similar to the value obtained for 3364 patients without CNS disease, 67 +/- 2%. Corresponding values for 5-year survival were 77 +/- 12% and 80 +/- 1%, and for freedom from isolated first CNS relapse, were 90 +/- 9% and 94 +/- 1%. Event-free survival, survival, and freedom from isolated first CNS relapse in the 6-Gy group were as good as in the 12-Gy group. CONCLUSION: CNS disease at diagnosis is not a poor prognostic factor for children with ALL who are treated with intensive systemic chemotherapy, craniospinal irradiation, and intrathecal chemotherapy. Six Gy is an adequate dose of spinal irradiation for these patients.

Central Nervous System Neoplasms↗
PubMed1994

Xanthine oxidoreductase. Biochemical, biological and pathogenic functions.

Primary biochemical role of xanthine oxidoreductase (XOR, EC 1.1.1.204 and EC 1.1.3.22.) is the hydroxylation of hypoxathine and xanthine to form uric acid. This enzyme may produce very reactive oxygen forms which can be pathogenic. Although it is one of the longest known and most continuously studied enzymes, its biological function remains unclear. The review of these aspects is discussed in relation to the authors' experimental results.

Animals↗
PubMed1992

Nonoccupational determinants of blood lead concentrations in a general population.

We investigated the influence of various nonoccupational factors on blood lead levels (PbB) in a sample from the general population of southern Germany. Some 1703 men and 1661 women, aged 28-67 years, were examined in the first follow-up examination of the MONICA Augsburg cohort study in 1987-1988. Their mean PbB was 90 micrograms/l (SD:35.9) for men and 65 micrograms/l (26.4) for women. Only 5% of the men and 1% of all women exceeded a PbB level of 150 micrograms/l indicating low-level lead exposure in this population. Blood lead was significantly associated with haematocrit values (P < 0.001) and the shape of this association was curvilinear. Per gram of alcohol consumed, intake of beer had a lower impact on PbB than wine, presumably due to differential lead content in these alcoholic beverages. The alcohol-PbB associations were stronger for women than for men. The impact of smoking was generally moderate but again more prominent in women. In particular, the covariate adjusted odds ratios for women of childbearing age (28-47 years) to have PbB levels above 100 micrograms/l were 2.5 (95% confidence interval (CI): 1.3-4.7) for smoking versus non-smoking females, 2.6 (95% CI: 1.1-6.0) for women drinking up to 40 g alcohol/day compared to abstainers, and 8.9 (95% CI: 3.2-25.1) for those drinking more than 40 g alcohol/day. Other factors like age, body mass, rural place of residence, and education or job position, had only minor influences on PbB. We conclude that haematocrit values should always be considered as potential confounders in low-level lead exposure research. High alcohol consumption and cigarette smoking are strongly related to elevated blood lead concentrations in the general population and may thereby convey additional health hazards such as impaired child development or blood pressure elevations. This deserves proper public health recognition [corrected].

Adult↗
PubMed1991

Our experience in the evaluation of the thermal comfort during the space flight and in the simulated space environment.

The paper presents the results of the mathematical modelling the effects of hypogravity on the heat output by the spontaneous convection. The theoretical considerations were completed by the experiments "HEAT EXCHANGE 1" performed on the biosatellite "KOSMOS 936". In the second experiment "HEAT EXCHANGE 2" accomplished on the board of the space laboratory "SALYUT 6" was studied the effect of the microgravity on the thermal state of a man during the space flight. Direct measurement in weightlessness prowed the capacity of the developed electric dynamic katathermometer to check directly the effect of the microgravity on the heat output by the spontaneous convection. The role of the heat partition impairment's in man as by the microgravity, so by the inadequate forced convection are clearly expressed in changes of the skin temperature and the subjective feeling of the cosmonaut's thermal comfort. The experimental extension of the elaborated methods for the flexible adjustment of the thermal environment to the actual physiological needs of man and suggestions for the further investigation are outlined.

Body Temperature Regulation↗
PubMed1989

Developmental orofacial deficits associated with multimodal cancer therapy: case report.

Multimodal cancer therapy for pediatric head and neck tumors may be associated with significant developmental orofacial morbidity. This report details these effects in a child (C.I.) diagnosed at 2.5 years of age with a rhabdomyosarcoma, primary to the left buccinator. This case is of interest as C.I. has an unaffected identical twin (D.I.) for comparative study. Both were assessed by comparing panoramic radiographs and lateral and frontal tracings of cephalometric radiographs obtained at 8.25 years of age. C.I. had multiple dental anomalies which included agenesis, ectopia, crown malformation, and root malformation. Root malformation, ectopia, and agenesis were restricted to the left dentition, whereas crown malformation was noted bilaterally. C.I. had a generalized craniofacial skeletal hypoplasia relative to D.I. in all three planes, growth defects were greater on the side of the tumor, and the mandible was affected more than the nasomaxillary complex.

Anodontia↗
PubMed1983

Do pressure-demand breathing systems safeguard against inward leakage?

Rescue operations conducted in toxic atmospheres require respiratory protective equipment capable of providing a very high degree of protection. A slight positive pressure in the facepiece throughout the breathing cycle is used in the pressure-demand, compressed-air breathing apparatus to eliminate any inward leakage. In the present work an inward leakage test with sulphur hexafluoride (SF6) was used to measure facepiece penetration in a pressure-demand system at different work loads. During the test, inspiratory-flow pressure variations within the facepiece and heart rate were also measured. Tests were performed on a dummy head and on two subjects. In some tests a poor face seal was introduced by putting an open tubing with an inner diameter of 2 mm and outer diameter of 3 mm under the sealing edge of the mask. It was found that inward leakage was less than 0.0001% under all conditions as long as facepiece pressure was positive. When facepiece pressure fell below zero, which occurred at inhalation peak flows about 300 L/min, an inward leakage was detected. One subject achieved, at extreme work load, an inhalation peak flow around 450 L/min. These results show that pressure-demand systems should be tested with a breathing machine giving peak flows of at least 300 L/min to ascertain the capability of these systems to maintain positive pressure in the facepiece during hard rescue work.

Adult↗