Michael Jacobson

Long‐term effects of streptozotocin‐induced diabetes on the electrocardiogram, physical activity and body temperature in rats

In vivo biotelemetry studies have demonstrated that short‐term streptozotocin (STZ)‐induced diabetes is associated with a reduction in heart rate (HR) and heart rate variability (HRV) and prolongation of QT and QRS intervals. This study investigates the long‐term effects of STZ‐induced diabetes on the electrocardiogram (ECG), physical activity and body temperature. Transmitter devices were surgically implanted in the peritoneal cavity of young adult male Wistar rats. Electrodes from the transmitter were arranged in Einthoven bipolar lead II configuration. ECG, physical activity and body temperature data were continuously recorded with a telemetry system before and following the administration of STZ (60 mg kg−1) for a period of 22 weeks. HR, physical activity and body temperature declined rapidly 3–5 days after the administration of STZ. The effects became conspicuous with time reaching a new steady state approximately 1–2 weeks after STZ treatment. HR at 4 weeks was 268 ± 5 beats min−1 in diabetic rats compared to 347 ± 12 beats min−1 in age‐matched controls. HRV at 4 weeks was also significantly reduced after STZ treatment (18 ± 3 beats min−1) compared to controls (33 ± 3 beats min−1). HR and HRV were not additionally altered in either diabetic rats (266 ± 5 and 20 ± 4 beats min−1) or age‐matched controls (316 ± 6 and 25 ± 4 beats min−1) at 22 weeks. Reduced physical activity and/or body temperature may partly underlie the reductions in HR and HRV. In addition, the increased power spectral low frequency/high frequency ratio from 4 weeks after STZ treatment may indicate an accompanying disturbance in sympathovagal balance.

EFFECTS OF INSULIN TREATMENT ON HEART RHYTHM, BODY TEMPERATURE AND PHYSICAL ACTIVITY IN STREPTOZOTOCIN-INDUCED DIABETIC RAT

1 Streptozotocin (STZ)‐induced diabetic cardiomyopathy is frequently associated with depressed diastolic/systolic function and altered heart rhythm. 2 The effects of insulin treatment on heart rhythm, body temperature and physical activity in STZ‐induced diabetic rats were investigated using biotelemetry techniques. 3 Transmitter devices were surgically implanted in the peritoneal cavity of young adult male Wistar rats. Electrodes from the transmitter were arranged in Einthoven bipolar – Lead II configuration. Electrocardiogram, physical activity and body temperature data were recorded with a telemetry system for 10 days before STZ treatment, for 20 days following administration of STZ (60 mg/kg) and thereafter, for 30 days while rats received daily insulin. 4 Heart rate, physical activity and body temperature declined rapidly 3–5 days after administration of STZ. Pre‐STZ heart rate was 362 ± 7 b.p.m., falling to 266 ± 12 b.p.m. 5–15 days after STZ with significant recovery to 303 ± 14 b.p.m. 10–20 days after commencement of insulin. Pre‐STZ body temperature was 37.5 ± 0.1C, falling to 37.2 ± 0.2C 5–15 days after STZ with significant recovery to 37.5 ± 0.1C 10–20 days after commencement of insulin. Physical activity and heart rate variability were also reduced after STZ but there was no significant recovery during insulin replacement. 5.  Defective autonomic regulation and/or mechanisms of control that are intrinsic to the heart may underlie disturbances in heart rhythm in the STZ‐induced diabetic rat.

Long‐term effects of type 2 diabetes mellitus on heart rhythm in the Goto–Kakizaki rat

In vivo biotelemetry studies have demonstrated a variety of heart rhythm disturbances in type 1 diabetes mellitus. In the streptozotocin (STZ)‐induced diabetic rat, these disturbances have included reductions in heart rate (HR) and heart rate variability (HRV) and an electrocardiogram that displays prolonged QRS duration and Q–T interval. The aim of this study was to investigate the chronic effects of type 2 diabetes mellitus on heart rhythm in the Goto–Kakizaki (GK) rat. Transmitter devices were surgically implanted in the peritoneal cavity of young male GK and age‐matched Wistar control rats. Electrodes from the transmitter were arranged in Einthoven bipolar lead II configuration. Electrocardiogram, physical activity and body temperature data were recorded in rats from age 2 to 15 months. Data were acquired for 2 weeks each month. Non‐fasting blood glucose, glucose tolerance and body weight were measured periodically. In GK rats, growth rate and maximal attained body weight were significantly reduced and non‐fasting blood glucose was progressively increased compared with age‐matched Wistar control animals. Heart rate was significantly lower in GK compared with control rats at 2, 7 and 15 months of age. At 2 months of age, HR was 316 ± 6 beats min−1 in GK rats compared with 370 ± 7 beats min−1 in Wistar control animals. There was a progressive age‐dependent decline in HRV in Wistar control rats; however, HRV in GK rats did not alter significantly with age. Heart rate variability was significantly reduced in GK compared with Wistar control rats at 2 and 7 months. At 2 months of age, HRV was 28 ± 2 beats min−1 in GK rats compared with 38 ± 3 beats min−1 in Wistar control rats. Reduced HR in GK rats may be an inherited characteristic. The absence of age‐dependent reductions in HRV in GK rats may be a consequence of an underlying impairment of autonomic control which manifests at early age.

Short-term effects of streptozotocin-induced diabetes on the electrocardiogram, physical activity and body temperature in rats: STZ effects on HR, activity and temperature

A variety of contractility defects have been reported in the streptozotocin (STZ)‐induced diabetic rat heart including alterations to the amplitude and time course of cardiac muscle contraction. Transmitter devices were surgically implanted in the peritoneal cavity of young adult male Wistar rats. Electrodes from the transmitter were arranged in Einthoven bipolar lead II configuration. Electrocardiogram (ECG), physical activity and body temperature data were continuously recorded with a telemetry system before and following the administration of STZ (60 mg kg−1). Heart rate (HR), physical activity and body temperature declined rapidly 3–5 days after administration of STZ. The effects became more conspicuous with time and reached a new steady state approximately 10 days after STZ treatment when HR was 255 ± 8 beats min−1 in diabetic rats compared to 348 ± 17 beats min−1 in age‐matched controls. Heart rate variability (HRV) was also significantly reduced after STZ treatment (18 ± 3 beats min−1) compared to controls (36 ± 3 beats min−1). Reduced physical activity and/or body temperature may partly underlie the reduction in HR and HRV. Reductions in power spectral density at higher frequencies (2.5–3.5 Hz) suggest that parasympathetic drive to the heart may be altered during the early stages of STZ‐induced diabetes. Short‐term diabetes‐induced changes in vital signs can be effectively tracked by continuous recording using a telemetry system.

Introducing design skills at the freshman level: structured design experience

Development of design skills in engineering students at United Arab Emirates University is achieved using an integrated learning approach which consists of structured, guided, and open-ended design experiences. This paper presents a description of the structured design experience in terms of main objectives, implementation mechanisms, and assessed outcomes as applied to freshman laboratory courses in the College of Engineering. These courses are developed to introduce structured design experience through step-by-step, hands-on procedures which guide students to complete particular learning assignments. The coursework spans a wide range of typical engineering practice, such as measurement, calibration, error and tolerance determination, data acquisition, and control. Finally, the course assessment mechanism is presented as a means of ensuring the successful achievement of Accreditation Board for Engineering and Technology educational outcomes

Heart Rate and QT Interval in Streptozotocin-induced Diabetic Rat

Aim: Prolonged QT interval is a common finding in diabetic patients. The effects of streptozotocin (STZ) – induced diabetes on QT interval has been investigated by application of 4 standard QT correction algorithms. Methods: The electrocardiogram was recorded in STZ-treated (60 mg/kg bodyweight, ip) and agematched control rats with a biotelemetry system for the period of the study. Results: Heart rate (HR) was significantly (P<0.01) reduced and QT interval was signifycantly (P<0.05) prolonged in diabetic rats compared to controls at 8, 10 and 12 weeks after STZ treatment. At 8 weeks HR was 260±16 BPM (n=5) in diabetic rats compared to 333±25 BPM (n=5) in controls and QT interval was 70±7 ms (n=5) in diabetic rats compared to 59±6 ms (n=5) in controls. When QT interval was corrected for HR there was no longer any significant difference in QT interval between diabetic and control rats. The effects of different correction techniques have been compared and the consequences considered. Conclusion: The rapid and dramatic reductions in HR observed after administration of STZ are associated with a prolongation of the QT interval. However, the magnitude of the difference of the QT interval between the STZ and control groups was not significant after QT interval correction for the difference in HR.

Analysis and classification of physiological signals using wavelet transforms

Physiological signals, such as the electrocardiogram (ECG), arterial blood pressure (ABP), and heart rate variability (HRV), have been shown to contain diagnostic information on the condition of the patient cardiac and circulatory systems. Changes in the physiological signal spectrum in response to various stimuli have been shown to be good indicators of the presence of disease, such as coronary heart disease (CHD) and diabetes mellitus (DM). In order to highlight these changes over time, time-frequency analysis is preformed before diagnostic classification. This brief paper focuses on the HRV signal and introduces the wavelet transform decomposition as a means of signal characterization for enhanced classification.

Time-frequency analysis of heart rate variability

The heart rate variability (HRV) is effected by the presence of diabetes mellitus (DM). Specifically, the power spectral density (PSD) of the HRV is perturbed in specific frequency ranges. This study presents the algorithm employed to extract changes in the PSD due to the onset of DM. In particular, streptozotocin (STZ) is administered to test animals in order to impair the insulin producing, pancreatic b-cells and thus model the onset of DM. The treated animals display symptoms of Type 1 DM including hypoinsulinaemia and hyperglycemia. In order to index the progressive effect of DM on the HRV PSD, five minutes of rat (n=12) electrocardiogram (ECG) were acquired hourly for 30 days. At day 10, half the animals were treated with STZ. The HRV signal was extracted from ECG and the short-term frequency transform (STFT) was used to estimate the 24 hr PSD. At 3 days after STZ-treatment, the animals were shown to be diabetic and at 5 days, the HRV PSD displayed a significant depression in the higher frequencies with a 3.3 Hz centered trough.

A laboratory testbed for sensor array processing experiments

An experimental array testbed constructed at the University of Minnesota is described. The system consists of a linear array of eight ultrasonic transducers and several transmitters operating at 40 KHz in air. The characteristics of the system and its calibration are described. Examples of the performances of several high-resolution direction-finding algorithms are shown.<<ETX>>

Non-invasive clinical screening of diabetes and coronary heart disease

A non-invasive, clinical system for low-cost screening of diabetes mellitus (DM) and coronary heart disease (CHD) is introduced and tested on patients with known conditions. In particular, the heart rate variability (HRV) signal is extracted from 30 minutes of lead II electrocardiogram (ECG), during which the patient was requested to perform specific actions. The HRV signal is then characterized using time and frequency domain features which are subsequently used as a basis for classification into normal (N), DM, CHD, and diabetic CHD (CHDD) categories.