Treadmill Assessment of an Activity-Modulated Pacemaker: The Importance of Individual Programming

Maximum benefit from a rate-modulated pacemaker requires individualized programming of rate response settings. We tested an externally strapped activity-sensing pacemaker (Activitrax-Medtronic 8400) in eight healthy volunteers, to assess the pacing responses of the different rate response and activity threshold settings. Five males and three females, aged 20 to 70 years (mean 40), performed a total of 67 treadmill exercise tests, using a specific protocol designed to assess the activity-sensing unit. The external unit was compared to implanted units in four patients, to validate its accuracy. A reproducible sinus response to the treadmill protocol was observed, against which pacing responses were compared. The activity threshold determines the degree of activity required to elicit a pacing rate response, whereas the rate response setting determines the rate attained. Rates of 140 bpm were rarely achieved, despite vigorous exercise. The sensor responds rapidly to activity, not to physiologic demand; to increase in speed, not grade. Four patients performed repeated limited treadmill tests to determine their optimum program setting, with symptomatic status and the healthy volunteer sinus response as guides. These results, and those from the external Activitrax unit, suggest that LOW 6 and MEDIUM 6-10 settings will prove optimum for most patients.     

Parallel and antiparallel aggregation of α-helices

An apolar helical decapeptide with different end groups, Boc- or Ac-, crystallizes in a completely parallel fashion for the Boc-analog and in an antiparallel fashion for the Ac-analog. In both crystals, the packing motif consists of rows of parallel molecules. In the Boc-crystals, adjacent rows assemble with the helix axes pointed in the same direction. In the Ac-crystals, adjacent rows assemble with the helix axes pointed in opposite directions. The conformations of the molecules in both crystals are quite similar, predominantly α-helical, except for the tryptophanyl side chain where χ¹? 60° in the Boc- analog and ? 180° in the Ac-analog. As a result, there is one lateral hydrogen bond between helices, N(lε)…O(7), in the Ac-analog. The structures do not provide a ready rationalization of packing preference in terms of side-chain interactions and do not support a major role for helix dipole interactions in determining helix orientation in crystals. The crystal parameters are as follow. Boc-analog: C₃H₇,N₁₁O₁₃ C₃H₇OH, space group P1 with a = 10.250(3) Å, b = 12.451(4) Å, c = 15.077(6) Å, x= 96.55(3)°, β= 92.31(3)°, y= 106.37(3)°, Z = 1, R = 5.5% for 5581 data (|F| > 3.0a(F)), resolution 0.89 Å. Ac-analog: C₅₇,H₉₁,N₁₁,O₁₂, space group P2₁, with a = 9.965(1) Å, b = 19.707(3) Å, c = 16.648(3) Å, β= 94.08(1), Z = 2, R = 7.2% for 2530 data (|F| > 3.0σ(F)), resolution 1.00 Å.     

Growth and Differentiation of Transplanted W/Wv Marrow

This paper reports new data on the effect of the action of the mutant genesW and W^v on murine hemopoiesis. Our studies demonstrate that the presenceof these mutant genes produces: (1) a macrocytic anemia with neithergranulocytopenia nor thrombocytopenia; (2) a severe defect in the earlystages of hemopoietic repopulation manifested by (a) an apparent block inthe differentiation of immature cells into erythroid precursors, and (b) a greatly reduced rate of proliferation of differentiated hemopoietic elements.

These data demonstrate the existence of genetic influence on repopulationand differentiation of transplanted marrow and suggest that severe anemia mayresult not only from defects in the late stages of erythroid development butalso from abnormalities in the early stages of erythroid maturation andhemopoietic repopulation.

Submitted on February 15, 1967 Accepted on May 5, 1967     

Trisomy 3 in marginal zone B-cell lymphoma: a study based on cytogenetic analysis and fluorescence in situ hybridization

Trisomy 3 represents the most frequent and consistent chromosomal abnormality characterizing the recently defined entity marginal zone B-cell lymphoma (MZBCL). By cytogenetic analysis and/or fluorescence in situ hybridization (FISH) on interphase nuclei we found an increased copy number of chromosome 3 in 22/36 (61%) successfully analysed cases, including 8/12 cases with extranodal MZBCL, 8/13 cases with nodal MZBCL, and 6/11 patients with splenic MZBCL. Sensitivity of interphase cytogenetics was somewhat higher than that of conventional cytogenetic investigation. Structural chromosomal changes involving at least one chromosome 3 were seen in 11/20 cases with an increased copy number of chromosome 3: +del(3)(p13) was demonstrated in three cases, and was the sole chromosomal abnormality in one of them; +i(3)(q10) was seen in two other patients; and rearrangements involving various breakpoints on the long arm of chromosome 3 were found in the remaining cases. FISH on metaphase spreads confirmed these structural abnormalities and additionally showed two unexpected translocations involving chromosome 3. We conclude that: (1) trisomy 3 occurs in a high proportion of extranodal, nodal and splenic MZBCL; (2) FISH on interphase nuclei is an additional and sensitive tool in detecting an increased copy number of chromosome 3 in MZBCL; (3) additional structural abnormalities involving the long arm of chromosome 3 are frequent but non-recurrent and are perhaps secondary changes; and (4) abnormalities such as +del(3)(p13) and +i(3)(q10) suggest that genes located on the long arm of chromosome 3 are of particular importance in the pathogenesis of MZBCL.     

Monitoring Dietary Change in a Low-Fat Diet Intervention Study: Advantages of Using 24-Hour Dietary Recalls vs Food Records

Objective The purpose of the study was to evaluate two methods of dietary assessment for monitoring change in fat intake in a low-fat diet intervention study.Design The two dietary assessment methods were a 4-day food record (4DFR) and an unannounced 24-hour dietary recall conducted by telephone interview (referred to as a telephone recall [TR]). Subjects were assigned randomly to either a low-fat diet intervention group or a control group that received no counseling about fat intake. Dietary data were collected at baseline, 6 months, and 12 months.Subjects Two hundred ninety postmenopausal women with localized breast cancer were recruited at seven clinical centers in the United States.Statistical analysis Analysis of variance was used to test for significant differences in mean fat and energy intakes.Results Three sources of error were identified: (a) an instrument effect, suggesting underreporting at baseline of approximately 8% in mean energy intake and 11% in mean fat intake in the TR group compared with the 4DFR group (P=.0001); (b) a repeated measures effect observed for the 4DFR, suggesting underreporting of approximately 7% for energy intake and 14% for fat intake in the control group at 6 and 12 months compared with baseline values (P<.001); and (c) an adherence effect (or compliance bias), suggesting greater compliance to the low-fat intervention diet when subjects were keeping food records than when estimates were based on the unannounced TR. Compared with the TR, the 4DFR overestimated the extent of fat reduction in the low-fat diet intervention group by 41% (P=.08) and 25% (P=.62) at 6 and 12 months, respectively.Application Multiple days of unannounced 24-hour recalls may be preferable to multiple-day food records for monitoring dietary change in diet intervention studies. J Am Diet Assoc. 1996; 96:574-579.     

Interpersonal versus technological orientations and alcohol abuse in future physicians

Etiologic research on alcohol-related impairment in physicians has elucidated various risk factors including family history of alcoholism, symptomatic distress, personality deficits, and high academic achievement. This study of medical students points to the additional salience of future practice orientations involving technological/status versus interpersonal concerns. A cohort of students was surveyed at medical school entrance and again in the second training year. Alcohol abusers (particularly medical school onset cases) manifested significantly higher technological/status and lower interpersonal concerns compared to non-abusers. Differences across future specialty choices were also found. However, additional longitudinal research is necessary to clarify the causal directionality of these relationships.     

Nutrition and Health Status Assessment of Community-residing Elderly in New York City: A Pilot Study

Ninety-five percent of persons over the age of 65 years live in the community and benefit from community-based health and nutrition services. The purpose of this project was to evaluate diet, function, and mental health in 40 men and women aged 65 years and older who were residing in a large metropolitan community. Nutritional status was assessed using two 24-hour recalls, 5 days of food records, a food frequency, and anthropometric measurements. Participants responded to standardized activities of daily living and instrumental activities of daily living instruments and an investigator-developed, performance-based appraisal of food preparation and management. Cognition and mood were assessed using the Folstein Mini-Mental Examination and the Yesavage Depression Scale. The nutrient intakes for individuals were compared with the Recommended Dietary Allowances (RDAs) and the Food Guide Pyramid. Mean energy intake was 1,625 kcal (range=787 to 2,910 kcal); 7 persons consumed more than 2,000 kcal. The mean vitamin and mineral intake for participants met the RDAs except for calcium, vitamin D, zinc, and magnesium intakes. The average percentages of carbohydrate, protein, and fat were 53%, 16%, and 30%, respectively. Nutritional assessments of subjects with and without congregate meals were contrasted. Six of the 13 congregate-meal participants were at nutritional risk, compared with 6 of 27 not receiving congregate meals. The interrelationships of diet, functional status, and mental health factors were examined along with recommendations for future data collection in similar studies. J Am Diet Assoc. 1998;98:554-558.