PubMed Health⌕ Search

Biomedical subjects

D Whittlesey

Publications and source records attributed to D Whittlesey.

11 recordsLinked to original sources
PubMed1997

Coronary bypass in vascular patients: a relatively high-risk procedure.

A premise of cardiac risk stratification is that the added risk of coronary artery bypass grafting (CABG) is offset by the improved safety of subsequent vascular reconstruction (VR). We questioned if elective CABG is patients with severe peripheral vascular disease (PVD) is a relatively high-risk procedure. A cohort study of 680 elective CABG patients from January 1993 to December 1994 was performed using three mutually exclusive outcomes of complication-free survival, morbidity, and mortality. Patient characteristic, operative, and outcome data were prospectively collected. Retrospective review determined that 58 patients had either a standard indication for or a history of VR. Overall CABG mortality was 2.5%, with statistically similar but relatively higher rates for PVD as compared to non-PVD patients. In contrast, major morbidity occurred at rates 3.6-fold higher in PVD patients (39.7%) than in disease-free patients (16.7%) after adjustment for the effects of patient and operative variables (odds ratio [OR] 3.67, 95% confidence interval [CI] 1.93-6.99). CABG morbidity in the PVD patient was most likely in those patients with aortoiliac (OR 9.51, CI 3.20-28.27) and aortic aneurysmal (OR 5.24, CI 1.28-21.41) disease types. CABG in PVD patients is associated with significant major morbidity. Such morbidity may preclude or alter the timing of subsequent VR.

Adult↗
PubMed1993

Na+ currents near and away from endplates on human fast and slow twitch muscle fibers.

Fast and slow twitch muscle fibers have distinct contractile properties. Here we determined that membrane excitability also varies with fiber type. Na+ currents (INa) were studied with the loose-patch voltage clamp technique on 29 histochemically classified human intercostal skeletal muscle fibers at the endplate border and > 200 microns from the endplate (extrajunctional). Fast and slow twitch fibers showed slow inactivation of endplate border and extrajunctional INa and had increased INa at the endplate border compared to extrajunctional membrane. The voltage dependencies of INa were similar on the endplate border and extrajunctional membrane, which suggests that both regions have physiologically similar channels. Fast twitch fibers had larger INa on the endplate border and extrajunctional membrane and manifest fast and slow inactivation of INa at more negative potentials than slow twitch fibers. For normal muscle, the differences between INa on fast and slow twitch fibers might: (1) enable fast twitch fibers to operate at high firing frequencies for brief periods; and (2) enable slow twitch fibers to operate at low firing frequencies for prolonged times. Disorders of skeletal membrane excitability, such as the periodic paralyses and myotonias, may impact fast and slow twitch fibers differently due to the distinctive Na+ channel properties of each fiber type.

Aged↗
PubMed1993

Comparison of Na+ currents from type IIa and IIb human intercostal muscle fibers.

The voltage dependence and amplitude of Na+ currents (INa) were studied with the loose-patch voltage-clamp technique on 19 fast-twitch human intercostal skeletal muscle fibers at the endplate border and > 200 microns from the endplate (extrajunctional). The fibers were histochemically classified as fast-twitch oxidative-glycolytic (type IIa, n = 9) or fast-twitch glycolytic (type IIb, n = 10). The voltage dependence of activation and fast and slow inactivation of INa were similar for membrane patches recorded on the endplate border and on extrajunctional membrane for both fiber types. INa was about fivefold larger on the endplate border compared with extrajunctional membrane for both fiber types. Type IIb fibers had larger values of INa and manifest fast inactivation of INa at more negative potentials than type IIa fibers. The difference between type IIa and IIb fibers may enable IIb fibers to operate at higher firing frequencies for brief periods.

Aged↗
PubMed1992

Na+ current densities and voltage dependence in human intercostal muscle fibres.

1. Voltage-clamp Na+ currents (INa) were studied in human intercostal muscle fibres using the loose-patch-clamp technique. 2. The fibres could be divided into two groups based upon the properties of INa. The two groups of fibres were called type 1 and type 2. 3. Both type 1 and type 2 fibres demonstrated fast and slow inactivation of INa. 4. Type 1 fibres had lower INa on the endplate border and extrajunctional membrane than type 2 fibres and required larger membrane depolarizations to inactivate Na+ channels by fast or slow inactivation of INa. 5. Type 2 fibres had a higher ratio of INa at the endplate border compared to extrajunctional membrane than Type 1 fibres. 6. Measurement of membrane capacitance suggested that the increase in INa at the endplate border was due to increased Na+ channel density. 7. Histochemical staining of some fibres suggested that type 1 fibres were slow twitch and type 2 fibres were fast twitch. 8. Differences in the properties of Na+ channels between fast- and slow-twitch fibres may contribute to the ability of fast-twitch fibres to operate at high firing frequencies and slow-twitch fibres to be tonically active.

Electric Stimulation↗
PubMed1991

Ca-, Sr-tension relationships and contraction velocities of human muscle fibers.

Muscle fibers from the lateral gastrocnemius or intercostal muscles of 7 normal adult males were chemically skinned (sarcolemma disrupted) and isolated fibers were divided into two parts for histochemical determination of fiber type and physiologic studies. The Ca- and Sr-induced tension relationships and maximum contraction velocities were measured. Slow twitch fibers developed tension at lower concentrations of Ca or Sr than fast twitch fibers. The difference between fast and slow twitch fibers was greatest when Sr was the activating cation. Fast and slow twitch fibers was greatest when Sr was the activating cation. Fast and slow twitch fibers generated similar maximum tensions. The contraction velocities of fast twitch fibers were more than two-fold greater than slow twitch fibers. Fast-oxidative-glycolytic (FOG, type IIA) and fast-glycolytic (FG, type IIB) fibers had similar Ca- and Sr-tension relationships and contraction velocities.

Adult↗
PubMed1988

Prospective computed tomographic scanning in the staging of bronchogenic cancer.

One hundred eight-five patients with potentially operable lung cancer were prospectively evaluated by computed tomographic scanning of the mediastinum and upper part of the abdomen. Mediastinal lymph node size was correlated with operative and pathologic findings. There was close agreement between computed tomographic estimate of size and operative measurements. Mediastinal lymph nodes that were larger than 2.0 cm were positive for tumor in 69.6%, nodes between 1.1 and 1.9 cm contained metastases in 31.8%, and nodes less than 1.0 cm were positive in only 2.7%. The cell type, T status, and location of the primary tumor did not influence these findings: A node less than 1.0 cm with a T3 lesion had the same probability of being abnormal as with a T1 lesion, although predictably, those patients with T3 and central tumors had a greater likelihood of having nodes larger than 2.0 cm. The presence of pneumonitis did not increase the prevalence of enlarged, histologically normal nodes. Asymptomatic adrenal metastases were present in 3.2% of patients with otherwise operable disease and were suggested only by the computed tomographic scan. Patients with mediastinal nodes less than 1.0 cm probably do not need preresection mediastinal exploration. Those with nodes larger than 2.0 cm should not be considered unresectable without pathologic confirmation, even in large tumors, in view of the 30.4% negativity rate. The computed tomographic scan is useful in depicting and localizing enlarged mediastinal nodes but cannot be used as a substitute for pathologic examination.

Adrenal Gland Neoplasms↗
PubMed1980

Invasive primary cutaneous phycomycosis in diabetic leg ulcers.

Two cases of cutaneous phycomycosis in the form of diabetic leg ulcers were diagnosed by culture and biopsy demonstration of invasive fungal infection. The first patient had an infected vesicular skin lesion. Systemic amphotericin B therapy and repeated debridement were curative. A posttraumatic leg ulcer developed in the second patient in the setting of hyperglycemia and renal insufficiency. Aggressive infection necessitated a curative amputation. Phycomycetes can cause or complicate diabetic leg ulcers and such infections may require biopsy for early recognition and subsequent successful therapy.

Aged↗