Biomedical subjects

B Ochs

Publications and source records attributed to B Ochs.

8 recordsLinked to original sources

PubMed1990

Temperature as a periodontal diagnostic.

Elevated temperature, normally a characteristic of inflammation, is a potential indicator of periodontal disease. Conversely, local periodontal site temperatures within normal variation could suggest relative periodontal health. To evaluate this potential, a temperature probe was designed with rapid response (less than 1 s), high accuracy and reproducibility (+/- 0.1 degree C), good transducer thermal isolation and physical dimensions approximating those of a conventional periodontal probe. To compensate for subject-to-subject variations in core temperature, site temperatures were measured and expressed as differences relative to the sublingual temperature. A cross sectional study was conducted using this instrument in which pocket temperatures of 14 subjects with advanced adult periodontitis were measured and compared with the sulcus temperatures of 11 healthy subjects. Overall, the mean site temperature of the diseased subjects was 0.65 degree C higher than that of the healthy subjects. A natural posterior-to-anterior temperature gradient was observed with the posterior sites being hotter than the anterior sites. Tooth-by-tooth analysis showed that diseased teeth have higher temperatures than anatomically equivalent healthy teeth (p less than 0.01). Threshold temperatures for differentiating diseased and healthy teeth were determined to optimize sensitivity and specificity. The results suggest that site temperature is a diagnostic of inflammatory activity associated with periodontal disease. The specifically designed instrument detected significant disease-related departures from normality.

Body Temperature↗

PubMed1988

A single amino acid substitution in the human histocompatibility leukocyte antigen DR3 beta chain selectively alters antigen presentation.

Activation of T lymphocytes by immunogenic peptides bound to HLA molecules is a central event in the generation of an immune response. To determine the sites on HLA molecules involved in this process, we isolated mutant EBV-transformed B cell clones that express altered HLA-DR3 molecules. One mutant has lost the ability to stimulate a T cell clone specific for a mycobacterial protein, but retains the ability to stimulate other antigen-specific T cells. The DNA sequence of the complete DR alpha and beta coding regions revealed a single nucleotide change resulting in a glutamic acid to lysine substitution at amino acid 9 in the first hypervariable region of the DR beta chain. These results are discussed in relation to a recently proposed model of class II molecule structure.

Amino Acid Sequence↗

PubMed1988

Tightly regulated tac promoter vectors useful for the expression of unfused and fused proteins in Escherichia coli.

A series of new plasmid expression vectors (the pTrc series) has been constructed for the regulated expression of genes in Escherichia coli. Based on pKK233-2 [Amann and Brosius, Gene 40 (1985) 183-190], the vectors carry a strong hybrid trp/lac promoter, the lacZ ribosome-binding site (RBS), the multiple cloning site of pUC18 and the rrnB transcription terminators. With the aid of synthetic oligodeoxynucleotides, the multiple cloning site has been inserted behind an NcoI site in three reading frames. Thus, the vectors are equally useful for the expression of proteins in their authentic, non-fused form (by using the NcoI site) and for the expression of fusion proteins (by choosing any of the cloning sites in the correct translational frame). To ensure complete repression of the hybrid trp/lac promoter during construction and growth in any host strain, the lacIq allele of the lac repressor gene was added to some of the vectors. The complete vector nucleotide sequence and examples of heterologous gene expression (human coagulation factor XIIIa and human placental anticoagulant protein PP4) with the new vectors are presented.

Bacterial Proteins↗

PubMed1980

Treatment goals of alcohol-dependent and drug-dependent patients.

At the time of admission to treatment, 450 alcohol-dependent patients and 198 drug-dependent patients were asked to complete a brief questionnaire regarding their interest in 26 treatment goals. An analysis of the goal questionnaire data revealed that from the total sample of patients more than 70 percent wanted assistance, in addition to help with substance dependency, with medical problems, psychological problems, school or job counseling, and recreational guidance. Between alcohol- and drug-dependent groups, statistically significant (p less than .05) but small differences were found for numerous goal items, with drug-dependent patients wanting assistance for more goal items than alcohol-dependent patients.

Adult↗

PubMedDate not supplied

A unique left-right flow imbalance compensation scheme for an implantable total artificial heart.

A new method has been developed for accommodating the difference between pulmonary and arterial flows in a totally implantable, hydraulically actuated total artificial heart (TAH). The left and right sides are alternately pumped, with concurrent filling of one pump and ejection from the other. A small hydraulic fluid chamber is used to compensate for the higher left sided flow. This chamber is incorporated into the left inflow of the TAH, with the flexing bladder in contact with atrial blood, and the hydraulic fluid communicates with the right sided hydraulic chamber. The volume of hydraulic fluid that enters and exits the latter chamber constitutes a corresponding reduction in the right sided blood chamber stroke volume. Placement of this compensation chamber in the left side inflow provides a negative feedback of the right sided flow, based on the left atrial pressure (LAP). Higher LAP (indicating too much right sided flow) leads to higher fluid flow to and from the compensation chamber and a lower right sided blood flow and vice versa. The hydraulic flow resistance can be preadjusted to yield a 15% flow difference at an LAP of 15 mmHg.

Animals↗

PubMedDate not supplied

Development of an efficient electrohydraulic total artificial heart.

The efficient use of space and energy is achieved in a new implantable total artificial heart (TAH). To fit the orthotopic thoracic space, toroidal blood pumps encircle an energy converter, consisting of a centrifugal hydraulic fluid pump and a rotary reversing valve. The new centrifugal pump produces cardiac outputs of 6 L/min, with an average hydraulic efficiency of 47%. Toroidal blood pumps encircling the pump deliver a 60 cc stroke with an 85% ejection fraction and have a predictable blood flow pattern with no stagnant regions. Components have been characterized in vitro, and blood contacting elements have been tested in vivo.

Blood Flow Velocity↗

PubMedDate not supplied

An atrial hydraulic shunt in a total artificial heart. A balance mechanism for the bronchial shunt.

An implantable TAH must be able to maintain physiologic atrial pressures over a range of left side shunt flows, which in humans can range up to 5% of the total cardiac output (CO). The authors describe the characteristics of an atrial hydraulic shunt in an electrohydraulic TAH. A small (10 cc stroke) chamber placed in line between the left atrial cuff and the inflow valve is shunted to the right hydraulic chamber. High left atrial pressure increases the volume displaced by this chamber; this concurrently reduces the right chamber stroke volume and flow relative to the left side. For left atrial pressures (LAP) between 0 and 15 mmHg, CO increased from approximately 3 to > 9 L/min (Starling-like behavior). This was attainable with bronchial flow settings between 0.2 to 0.7 L/min, satisfying physiologic needs. Left atrial pressure and RAP (right atrial pressure) tracked each other. The mean difference, LAP-RAP, remained within 5 mmHg at low filling pressures and approached 0 mmHg difference at high filling pressures. The results showed that the atrial hydraulic shunt method can adequately compensate for and manage physiologic left-right flow differences.

Animals↗

PubMedDate not supplied

A compact and noise free electrohydraulic total artificial heart.

The ABIOMED total artificial heart (TAH) is designed for long-term tether-free use in patients with end-stage heart disease. Blood pumping is achieved through hydraulic fluid motion across flexing diaphragms. The hydraulic power is derived from a miniature centrifugal pump (50% efficiency). Flow directional change needed for alternate left and right filling and ejection is achieved with a rotary valve. With no mechanical contact with the flexing membrane, the wedge angle between the two pumps sandwiching the energy convertor can be easily optimized for anatomic fit. The blood pumps (80 ml strokes) are fitted with trileaflet polyetherurethane valves (24 mm). The TAH is implanted using twist-lock stepless quick connectors to the inflow cuffs and outflow grafts. Left-right flow balance is achieved with an atrial hydraulic shunt placed between the left cuff and inflow valve. Animal studies show that the TAH fits very well in Long Horn calves weighing 90 to 100 kg and can provide cardiac output in excess of 10 L/min. A cadaver (85 kg) study showed the TAH fits within the pericardial region.

Adult↗