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Biomedical subjects

R L Berger

Publications and source records attributed to R L Berger.

At least 55 records · Page 3Linked to original sources
PubMed1984

Iron electronic structure in oxyhemoglobin and carboxypeptidase digested derivatives.

Mössbauer experiments were performed on the oxy- derivatives of human hemoglobin and its products of digestion with carboxypeptidases. The hemoglobins were chemically enriched to 95% in 57Fe, and were free from hemochrome impurities. Spectra were taken at low temperatures in the presence and absence of a 5.0 T magnetic field. It was observed that the enzymatic digestions which remove residues at least 16 A from the iron of the nearest heme appear to modify the electronic environment of the metal.

Carboxypeptidase B↗
PubMed1983

Subzero temperature quenching and electrophoretic methods for the isolation of protein reaction intermediates.

A quenching technique for the study of rapid protein reactions is described which consists of injecting a small volume of aqueous solution of reactants into a large volume (X10) of hydro-organic solvent cooled at subzero temperature and mechanically shaken. The protein reaction intermediates, stabilized at subzero temperature and brought into a hydro-organic solution, can then be separated by subzero temperature electrophoretic methods, such as isoelectric focusing, in the same solvent. The alkaline hydrolysis of 2,4-dinitrophenylacetate was studied by the use of this quenching technique in order to compare the quenching time and the rate constants of the reaction with those obtained by normal rapid quenching methods. It was found that first-order reactions having rate constants up to about 5 s-1 can be satisfactorily studied by this technique. The technique is not suitable for the study of faster reactions because of the high value of the quenching time (40-100 ms). The hybridization reaction of carboxyhemoglobins A and C in aqueous solution at 22 degrees C was studied as an example of the application of this quenching technique and of the isoelectric focusing method at subzero temperature to the isolation of unstable intermediates in a protein reaction.

Carboxyhemoglobin↗
PubMed1983

Dental nerve regeneration in rats. I. Electrophysiological studies of molar sensory deficit and recovery.

Return of sensory nerve function in rat molars following cut or crush injury to the inferior alveolar nerve (IAN) was measured by observing the jaw opening reflex (JOR) response of the digastric muscle to electrical stimulation of individual molars or the gingiva. The IAN was injured from a lateral approach to the mandibular ramus at a site approximately 2 mm proximal to the incisor apex. Following nerve injury, the JOR threshold to stimulation of the first molars increased 6-fold: preoperative threshold mean = 47.4 +/- 21.3 microA (n = 27), postoperative threshold mean = 248.5 +/- 127.1 microA (n = 25). A 4-fold postoperative increase in JOR threshold was found for the second molars, and the thresholds were not significantly affected for third molars or gingiva. These postoperative results indicated that the major pathway of sensory innervation to the first and second molars was affected by the IAN injury, whereas the third molars and gingiva had alternate sources of innervation which remained unaffected by the IAN injury. At 1 week following injury, there was partial return of sensitivity, by 3 weeks there was approximately 50% recovery, and by 6 weeks complete return to normal JOR thresholds was found. The degree of sensory deficit, as reflected in JOR inhibition, and the rate of recovery were not significantly different after cut or crush injury in these experiments; however, there was a tendency for greater sensory loss and for more rapid recovery after crush injury. This study forms the basis for a subsequent autoradiographic analysis of nerve location in rat molars of known sensory deficit, partial recovery, or full sensory recovery.

Alveolar Process↗
PubMed1983

Dental nerve regeneration in rats. II. Autoradiographic studies of nerve regeneration to molar pulp and dentin.

The autoradiographic technique was used to analyze the degeneration and regeneration of sensory nerves to rat molars and gingiva following cut or crush injury to the right inferior alveolar nerve. At 2 days after nerve injury there was almost complete denervation of the first molar, partial denervation of the second molar, and minimal effect on the innervation to the third molar and gingiva. The degree of sensory deficit and recovery for these same rats had been previously determined. Reinnervation of the first molar was analyzed in terms of axon number and location, intensity of axon labeling, and type of nerve injury. At 6 days, neither the cut injury nor crush injury rats had any reinnervation of their first molars. By 7 days, 3 of 4 rats had axons reinnervating first molars; in those teeth there was approximately one-fourth of the normal number of axons in the pulp, and very few axons in the dentin. These rats still had as large a molar sensory deficit as the 7 day rat and 6 day rats that had no reinnervation. By 3 weeks there were one-half to three-fourths of the normal axon numbers in the pulp, one-fourth to one-half of the normal axon numbers in dentin; and sensitivity was at least half-recovered. By 6 weeks, numbers of axons in the pulp and dentin were either normal or slightly less than normal; axons had grown back into dentin to the same depth as in normal teeth; and complete recovery of sensitivity had occurred. The regenerating axons had greater than normal labeling intensity at 1 week and 3 weeks in all rats. Those with the crush nerve injury had somewhat greater numbers of reinnervating axons at 1 week and 3 weeks than the cut injury rats. A structure-function comparison for the molars showed that return of sensitivity correlated with reinnervation of both pulp and dentin.

Alveolar Process↗
PubMed1983

Graft replacement of the thoracic aorta with a sutureless technique.

A sutureless intraluminal graft requiring only ligature fixation was used for replacement of the thoracic aorta in 8 patients. The graft was deployed in the ascending and descending thoracic aorta as well as in the arch. It was used for aortic dissection and atherosclerotic aneurysms. Insertion was easy and relatively quick. Fixation was secure and without serious complications. Seven of the 8 patients became long-term survivors.

Aged↗
PubMed1982

An optimized differential heat conduction solution microcalorimeter for thermal kinetic measurements.

Heat conduction calorimeters are widely used in the biological sciences, but baseline instability, low resolution, electrical noise and motion artifacts have limited their utility. Two main sources of noise, baseline fluctuation or drift and a motion artifact, were traced to amplifier drift, a small (0.015 degrees C) gradient within the constant temperature cylinder, and the method of installing the thermopiles. The addition of heaters to the top and bottom of the cylinder reduced the gradient to approximately 0.003 degrees C and greatly reduced the slow component of the motion artifact. The drift error was reduced by proper mounting of the amplifier and its external components and the enclosure of the calorimeter in a temperature-controlled box. An R-C model of the heat flow in the calorimeter was developed which was employed to discover several means of increasing sensitivity without increasing the rise-time of the calorimeter. Analysis, also based on the model, showed that variations in the air gap between the cell and cell holder can be a major source of error when the calorimeter is used to investigate the kinetics of a chemical reaction. This analysis also showed that the time for the heat to flow through the solution in the cell can be the dominant factor in determining the rise-time of the instrument. The heat conduction calorimeter described here has improved characteristics: a baseline stability of 200 nJ x s-1 (peak-to-peak) over a 48 h period; a resolution of 200 nJ x s-1; a sensitivity of 6.504 +/- 0.045 J x V-1 x s-1 referred to the sensor output; and a rise-time of 122 s for the 10-90% response.

Calorimetry↗
PubMed1982

Computer simulation for deconvolution of a heat conduction batch microcalorimeter by the D-B Finite Element Technique.

The method described here is a general numerical analysis procedure which has been applied to a heat conduction Batch calorimeter for the deconvolution of its thermograms, and is based on a computer simulation of the heat conduction behavior of the instrument with time. We show by means of test signals that the method can deconvolute the signal with a resolving time that is about two orders of magnitude smaller than the time constant of the calorimeter itself. The method can be applied to time signals generally, provided that the instrument producing them can be simulated.

Calorimetry↗
PubMed1982

An observation chamber for a high-pressure stopped-flow apparatus.

A new design of the observation window to observation chamber seal is described for the Berger rapid stopped-flow apparatus. This design permits reliable operation of the apparatus and retains the features of a square non-deviating observation path with flush windows. Incorporation of fiber optic light guides for the observation path has made the apparatus insensitive to vibration artifacts. A demonstration reaction of calcium binding to EGTA is presented; the reaction, which is 90% complete within 2 ms, illustrates the capability of this apparatus for examining fast reactions.

Biochemistry↗
PubMed1982

Surgical therapy for Prinzmetal's variant angina.

Fifty-two patients underwent coronary artery bypass grafting between 1973 and 1979 for variant angina, defined as pain, usually at rest, associated with S-T segment elevation. Only patients with fixed occlusive coronary artery disease, defined as greater than 70% narrowing in diameter, were included. When fixed coronary artery stenosis is present, variant angina--whether presenting as stable, unstable, or postinfarction angina, and regardless of the number of vessels diseased--is effectively treated by myocardial revascularization. Preoperative intraaortic balloon pumping is a useful therapeutic adjunct in the unstable subset refractory to medical therapy. The results of revascularization in patients with Prinzmetal's variant angina and fixed coronary disease were no different from those in patients with classic angina pectoris of comparable clinical categories.

Adult↗
PubMed1982

[Comparison of the cumulative survival among patient groups with a left main coronary artery lesion after surgical and therapeutic treatment].

In order to evaluate survival patterns in patients with left main coronary artery (LMCA) disease, 1492 patients with LMCA disease admitted to the U. S. Collaborative Study on Coronary Artery Surgery (CASS) were followed up. Of the 1492 patients, 1183 (79%) underwent coronary artery bypass (CABG) with an operative mortality of 4.2% and an average of 2.7 grafts/patient inserted. Allocation to surgery was by patient and physician preference and not random. Surgical patients generally had more severe angina, a higher prevalence of beta blocker usage, worse ventricular function and more severe LMCA stenosis than medically treated patients. Overall (4 years) survival of the surgical group was 88% compared to 63% in the medical group (p less than 0.001). Other independent predictors of mortality included angiographic left ventricular (LV) dysfunction score, age, % LMCA stenosis, hypertension, dominance, and presence of significant right coronary artery (RCA) stenosis greater than or equal to 50%. CABG was not shown to significantly improve survival in women, in LMCA patients with left dominant circulation, in LMCA patients with non-diseases dominant or balanced RCA circulation or in LMCA patients with greater than or equal to 50% RCA stenosis but good LV function. These data indicate that CABG prolongs life in most patients with left main coronary artery disease, particularly those with severe LMCA narrowing or severe LV dysfunction, however, subgroups of LMCA patients are identifiable who may fare with medical treatment alone.

Aged↗
PubMed1981

Serial exercise testing after coronary artery bypass surgery.

To determine the duration of functional benefit from coronary bypass surgery, 111 patients with angina pectoris were serially evaluated by standard exercise testing prior to and for up to 4 years after surgery. Exercise testing 6 to 18 months after surgery showed greater heart rate-blood pressure product at peak work load, improved work capacity, and less symptomatic and electrocardiographic evidence of ischemia than was demonstrated preoperatively. Twenty patients were tested 37 to 48 months postoperatively and showed improved exercise performance in comparison with preoperative results, but the frequency of positive tests during this period no longer differed. Thus, improved exercise performance appears to persist for at least 4 years after coronary bypass surgery.

Angina Pectoris↗
PubMed1981

Effect of coronary bypass surgery on survival patterns in subsets of patients with left main coronary artery disease. Report of the Collaborative Study in Coronary Artery Surgery (CASS).

The 3 year cumulative survival rate of 1,492 patients with left main coronary artery disease (50 percent or greater stenosis of luminal diameter) enrolled in the Collaborative Study in Coronary Artery Surgery (CASS) was 91 percent for the surgical group and 69 percent for patients treated medically (p less than 0.0001). Mortality was significantly greater in patients with impaired left ventricular function. The difference between medical and surgical therapy was significant for patients who had normal, moderately abnormal and severely impaired left ventricular function and for patients with stenosis of the left main coronary artery of 50 to 59, 60 to 69, 70 to 79 and 80 percent or greater. Aortocoronary bypass surgery did not significantly improve survival in patient subgroups who had (1) a nonstenotic dominant right or balanced coronary circulation, (2) a stenotic dominant right coronary artery and normal left ventricular function, and (3) left main coronary stenosis of 50 to 59 percent and normal or mildly abnormal left ventricular function. The Cox proportional hazards model was used to select baseline variables that were independent predictors of long-time mortality. The model selected left ventricular score, age, congestive heart failure score, hypertension, percent left main coronary arterial stenosis and coronary arterial dominance as the baseline variables most predictive of long-term survival. A clinical and angiographic prognostic risk index developed from these six baseline variables showed significantly improved survival for the surgical cohort in each of four risk categories. In the best and worst risk category, the 3 year survival rate was 97 and 82 percent, respectively, for the surgical group and 85 and 34 percent, respectively, for the medical group (p less than or equal to 0.0002). The data from this observational study show that coronary bypass surgery prolongs life in most patients with left main coronary artery disease, particularly those who have severe narrowing of the left main coronary artery or impaired left ventricular function. The results permit a better understanding of the natural history of left main coronary artery disease and permit a more accurate estimate of long-term survival for individual patients through the use of a clinical-angiographic risk index.

Cardiac Catheterization↗
PubMed1981

Fast stopped-flow microcalorimeter.

A fast stopped-flow microcalorimeter using a thermistor and an a.c. bridge is described. Time resolution, limited by the response of the thermistor, is 3 ms for t 1/2 while sensitivity is 100 mu degree C in this bandpass. A reaction requires 0.3 ml of each reactant. The microcalorimeter is adiabatic to within 2% for 2 s and mixing may be repeated every 5 min. Computer finite element simulation techniques (FEST) are used to correct for the thermistor response time and heat losses. Results of tests with reactions of NaOH and HCl, NaHCO3, and HCl, and glyclyglycine and CO2 agree with published kinetic and thermodynamic values to within an experimental error of less than 2%.

Bicarbonates↗