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Biomedical subjects

J Baum

Publications and source records attributed to J Baum.

At least 37 records · Page 2Linked to original sources
PubMed2000

Multicenter evaluation of the Glucometer Elite XL meter, an instrument specifically designed for use with neonates.

OBJECTIVE: To evaluate the clinical performance of the Glucometer Elite XL Diabetes Care System in neonatal settings using a multicenter study RESEARCH DESIGN AND METHODS: A total of 388 blood specimens from 333 neonates were included in the study. A capillary or arterial sample was analyzed for determination of glucose with the Glucometer Elite XL system by an attending trained nurse. Through the same sampling site, a specimen was collected and sent to the laboratory for measurement of plasma glucose, bilirubin, and hematocrit. RESULTS: The regression analysis between the results of the Glucometer Elite XL system and comparative methods resulted in the following: Glucometer Elite XL meter = 1.01 x laboratory method + 0.02 mmol/l (n = 388). For the 1.1-4.0 mmol/l plasma glucose range, the regression was Glucometer Elite XL meter = 1.07 x laboratory method + 0.12 mmol/l (n = 150). A difference plot indicated a mean bias of 0.04 mmol/l (95% CI -0.01 to 0.10). No relationship was found between meter glucose biases and hematocrit levels (r = 0.10, P = 0.14). Although a statistically significant correlation existed between bilirubin levels and the glucose meter biases (r = 0.14, P = 0.005), the predicted mean biases were of little clinical significance. CONCLUSIONS: The Glucometer Elite XL system showed a good performance when used in neonatal settings.

Bilirubin↗
PubMed2000

[Nitrous oxide free low-flow anesthesia].

The routine use of nitrous oxide as a component of the carrier gas has been unanimously called into question in recent surveys, in fact, its use is now recommended in indicated cases only. Whereas a lot of contraindications are listed in the surveys, precise definitions of justified indications are not given. In clinical routine practice, there are absolutely no problems in carrying out inhalational anaesthesia without nitrous oxide. The missing analgetic effect can be compensated for by moderately increasing the additively used amount of opioids, while the missing hypnotic effect can be achieved by raising the expired concentration of the inhalational anaesthetic by not more than 0.2-0.25 x MAC. Thus, when isoflurane is used, an expired concentration of 1.2 vol% is desired, in the case of sevoflurane of 2.2 vol% and with desflurane of 5.0 vol%. In addition, doing without nitrous oxide facilitates the performance of low flow anaesthetic techniques considerably. Since the patient only inhales oxygen and the volatile anaesthetic, the total gas uptake is reduced significantly. Washing out nitrogen is no longer necessary. This means that the initial phase of low flow anaesthesia, during which high fresh gas flows have to be used, can be kept short. Its duration is now determined by the wash-in of the volatile anaesthetic. Since there is no uptake of nitrous oxide, a considerably greater volume of gas is circulating within the breathing system, minimizing the possibility of accidental gas volume deficiency. Thus, if anaesthesia machines with highly gas-tight breathing systems are used, even the performance of non-quantitative closed system anaesthesia becomes possible in routine clinical practice. The carrier gas flow can be reduced to just that amount of oxygen which is really taken up by the patient. This oxygen volume can be roughly calculated by applying the Brody's formula. Using fresh gas flows as low as 0.25 l/min, however, will result in a significant decrease of the output of conventional vaporizers outside the circuit. Thus, it becomes nearly impossible to maintain an expired isoflurane concentration of 1.2 vol%. With respect to their pharmcokinetic properties, the newer low soluble volatile agents sevoflurane and desflurane are better suited for use with flows corresponding to the basal oxygen uptake. Our own clinical experience, gained in the last six months from a trial involving over 1,800 patients, shows that the increase in opioid consumption resulted in additional costs of about 0.25-0.50 DM per patient. The increased concentration of inhalational agents brought additional costs of 3.00 to 5.00 DM for a two-hour anaesthesia. On the other hand, doing without nitrous oxide saved 2.61 DM per one-hour anaesthesia, whereby our consumption of nitrous oxide is extremely low as minimal flow anaesthesia is performed consistently. Furthermore, these calculations disregard the cost of the technical maintenance fo the central gas piping system and of the regular measurement of workplace contamination with nitrous oxide by a certified institute, which in Germany, ad least, is obligatory. The additional costs of nitrous oxide-free inhalational anaesthesia seem to be balanced by the savings. Given the numerous justified arguments against the routine use of nitrous oxide, the lack of precisely-defined indications and the clinical experience showing that doing without nitrous oxide is uncomplicated, self-financing and ecologically beneficial, the use of nitrous oxide should be given up completely.

Anesthesia, Inhalation↗
PubMed1999

Characterization of millisecond time-scale dynamics in the molten globule state of alpha-lactalbumin by NMR.

The motional dynamics of the molten globule (MG) state of alpha-lactalbumin have been characterized using (15)N transverse relaxation rates (R2). A modified version of the Carr-Purcell-Meiboom-Gill (CPMG) R2 pulse sequence is proposed in order to overcome the loss of sensitivity that arises from extreme line broadening due to complex dynamics on the millisecond time-scale. Using this pulse sequence, chemical exchange rates were extracted by examining the (15)N transverse relaxation rates as a function of CPMG delay values. The results clearly illustrate that pervasive conformational exchange of 0.2-0.5 ms in the (15)N backbone resonances of the molten globule state of alpha-lactalbumin. The temperature dependence of the conformational exchange rates display standard Arrhenius kinetic behavior between 10 and 30 degrees C. Estimates of the activation energies range from 0.8 to 4. 4 kcal/mol, indicating a low energetic barrier to conformational fluctuations relative to native state proteins. The fluctuations and low energetic barriers may be critical for directing the search for contacts that will result in the transition from the MG state to the native state.

Lactalbumin↗
PubMed1999

Folding of peptide models of collagen and misfolding in disease.

The misfolding of the triple helix has been shown to play a critical role in collagen diseases. Normal and mutated collagen triple helices can be modeled by short, synthetic peptides of varying design. NMR spectroscopy and circular dichroism studies on the assembly of these peptide models have recently been used to isolate specific steps in the folding pathway and have provided information on the alterations resulting from mutations.

Amino Acid Sequence↗
PubMed1998

Nuclear magnetic resonance shows asymmetric loss of triple helix in peptides modeling a collagen mutation in brittle bone disease.

To investigate a human folding disease, NMR studies were carried out on collagen-like peptides to define the structural consequences of a single amino acid change found in patients with osteogenesis imperfecta (OI), a disease characterized by fragile bones. One peptide included a normal collagen sequence, while a second peptide included a Gly --> Ser substitution as found in a nonlethal case of OI. Residue specific internal dynamics and conformational studies indicate that the normal collagen-like sequence forms a triple helix which is rigid along its entire length. The introduction of a Gly --> Ser substitution induces an asymmetric disruption of the uniform triple helix. While the C-terminal end of the peptide retains the triple helix, the Ser substitution site and residues N-terminal to it exhibit the mobility of a random chain. This equilibrium state indicates that a Gly substitution can terminate the C to N propagation of the triple helix and suggests that renucleation is required for folding to continue. Defective folding has been implicated in brittle bone disease, and these results begin to characterize the folding process in OI collagens. OI collagen studies may also provide insights about defective protein folding, assembly, and aggregation in other human diseases.

Amino Acid Sequence↗
PubMed1998

Electrostatic interactions in the acid denaturation of alpha-lactalbumin determined by NMR.

alpha-Lactalbumin (alpha-LA) undergoes a pH-dependent unfolding from the native state to a partially unfolded state (the molten globule state). To understand the role of electrostatic interactions in protein denaturation, NMR and CD pH titration experiments are performed on guinea pig alpha-LA. Variation of pH over the range of 7.0 to 2.0 simultaneously leads to the acid denaturation of the protein and the titration of individual ionizable groups. The pH titrations are interpreted in the context of these coupled events, and indicate that acid denaturation in alpha-LA is a cooperative event that is triggered by the protonation of two ionizable residues. Our NMR results suggest that the critical electrostatic interactions that contribute to the denaturation of alpha-LA are concentrated in the calcium binding region of the protein.

Animals↗
PubMed1998

[Low-flow and minimal-flow anesthesia with sevoflurane].

Due to its low solubility and the high maximum concentration delivered by the vaporizer sevoflurane is especially suitable for the performance of low flow anaesthetic techniques. High flow phases for wash-in or wash-out of anaesthetic gases can be kept short, the difference between the volatile's concentration in the fresh gas and within the breathing system is comparatively small, and the time constants are short even during low flow anaesthesia. The monitoring, required to sufficiently ensure the safety of the patients, corresponds to the current obliging technical safety standards. As compound A may accumulate in the breathing system, sevoflurane should not be administered with fresh gas flows lower than 1.0 l/min, until the scientific discussion on nephrotoxicity of this substance in humans is solved. Low flow anaesthesia guarantees a sufficient and continuous wash-out of trace gases. Thoroughly the use of sevoflurane with dry soda lime must be avoided, as this volatile in an extreme exothermic reaction is absorbed nearly totally and degraded to a considerable degree by dry carbon dioxide absorbent. The gaseous degradation products are pungent and possibly may be harmful to the patients. Only by low flow anaesthesia the use of sevoflurane will gain an economically and ecologically acceptable range of efficiency.

Anesthesia, Inhalation↗
PubMed1998

Tertiary contacts in alpha-lactalbumin at pH 7 and pH 2: a molecular dynamics study.

Molecular dynamics simulations of alpha-lactalbumin were performed under conditions of neutral pH and low pH in order to study the acid-induced molten globule state. Through the use of experimental techniques such as NMR and CD spectroscopy, molten globules have been characterized as being compact intermediates with secondary structure similar to that of the native protein but with tertiary structure that is disordered. The detailed structure of the molten globule state is unknown, however. Through the use of computer simulations we can study the structural changes which occur upon lowering pH. The simulations presented here differ from previous unfolding simulations in two important ways: the electrostatic interactions are treated more accurately than ever before, and artificially high temperatures are not used to force the protein to unfold. Simulations of 880 psec each were run at pH 7 (control simulation) and pH 2. We concentrate on the interesting changes in the tertiary interactions within the protein with lowering of pH. In particular, there is a loss of native tertiary contacts in the beta domain and interdomain region, and a large decrease in interdomain hydrogen bonds.

Computer Simulation↗
PubMed1998

Bacillus thuringiensis and its pesticidal crystal proteins.

During the past decade the pesticidal bacterium Bacillus thuringiensis has been the subject of intensive research. These efforts have yielded considerable data about the complex relationships between the structure, mechanism of action, and genetics of the organism's pesticidal crystal proteins, and a coherent picture of these relationships is beginning to emerge. Other studies have focused on the ecological role of the B. thuringiensis crystal proteins, their performance in agricultural and other natural settings, and the evolution of resistance mechanisms in target pests. Armed with this knowledge base and with the tools of modern biotechnology, researchers are now reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit.

Amino Acid Sequence↗
PubMed1998

Revision of the nomenclature for the Bacillus thuringiensis pesticidal crystal proteins.

The crystal proteins of Bacillus thuringiensis have been extensively studied because of their pesticidal properties and their high natural levels of production. The increasingly rapid characterization of new crystal protein genes, triggered by an effort to discover proteins with new pesticidal properties, has resulted in a variety of sequences and activities that no longer fit the original nomenclature system proposed in 1989. Bacillus thuringiensis pesticidal crystal protein (Cry and Cyt) nomenclature was initially based on insecticidal activity for the primary ranking criterion. Many exceptions to this systematic arrangement have become apparent, however, making the nomenclature system inconsistent. Additionally, the original nomenclature, with four activity-based primary ranks for 13 genes, did not anticipate the current 73 holotype sequences that form many more than the original four subgroups. A new nomenclature, based on hierarchical clustering using amino acid sequence identity, is proposed. Roman numerals have been exchanged for Arabic numerals in the primary rank (e.g., Cry1Aa) to better accommodate the large number of expected new sequences. In this proposal, 133 crystal proteins comprising 24 primary ranks are systematically arranged.

Bacillus thuringiensis↗
PubMed1998

Fibromyalgia syndrome in children and adolescents: clinical features at presentation and status at follow-up.

OBJECTIVES: To 1) describe the characteristic features of fibromyalgia syndrome (FS) in a pediatric population, 2) note similarities and differences with FS in adults, and 3) determine outcome after treatment. SETTING AND DESIGN: The Pediatric Rheumatology Clinic at the University of Rochester Medical Center is staffed by two pediatric rheumatologists and serves as a regional subspecialty referral service with approximately 450 annual patient visits, of which approximately 120 are initial evaluations. A retrospective medical record review from 1989 to 1995 was used to identify and describe the study population, and a structured telephone interview served to determine current status and response to treatment. RESULTS: A total of 45 subjects were identified (41 female; 42 white; mean age, 13.3 years), of whom 33 were available for telephone interview at a mean of 2.6 years from initial diagnosis (0.1 to 7.6 years). Of a possible 15 symptoms associated with FS, subjects reported a mean of 8, with >90% experiencing diffuse pain and sleep disturbance. Less frequent were headaches (71%), general fatigue (62%), and morning stiffness (53%). The mean cumulative number of tender points summed over all visits was 9.7 (of 18). Telephone interviews showed improvement in most patients, with a mean positive change of 4.8 on a self-rating scale of 1 to 10 comparing current status to worst-ever condition. CONCLUSIONS: FS in patients referred to a pediatric rheumatology clinic is characterized by diffuse pain and sleep disturbance, the latter being more common than that in adults. The mean number of tender points summed over all visits is fewer than the criterion of 11 established for adults at a single visit. The majority of patients improved over 2 to 3 years of follow-up.

Adolescent↗