A summary review of carcass cutability data comparing primal value of immunologically and physically castrated barrows.

The objectives were to 1) assess cutability, quality, and value of carcasses from immunologically castrated (IC) barrows compared with carcasses from physically castrated (PC) barrows and 2) evaluate the effect of hot carcass weight (HCW) on cutability and value of IC barrows summarizing U.S. data. Lean cutting yield (LCY) was defined as: LCY = [(whole ham + trimmed loin + Boston butt + picnic + spareribs)/chilled side wt] x 100. Carcass cutting yield (CCY) was determined using the following equation: CCY = [(lean cutting yield components + natural fall belly)/chilled side wt] x 100. To evaluate the effects of HCW of IC barrows on carcass cutting yields, IC barrows were grouped by HCW: light ( < 90.9 kg), average (90.9-97.7 kg), or heavy ( > 97.7 kg). Differences in the value of the carcass components for IC and PC barrow carcasses were calculated using a 5 yr average of meat prices from the USDA Agriculture Marketing Service and the carcass cutting yield estimates generated from this summary. Data were analyzed using the MIXED procedure of SAS with fixed effects of Improvest treatment or HCW group. Study was included as a random effect. This review allowed for a summarization of the treatment averages of 851 IC and PC barrow carcasses. Lean cutting yield of IC barrows was 1.41 units greater (P < 0.0001) than PC barrows (70.97 vs. 69.56%). Similarly, CCY of IC barrows was 1.29 units greater (P < 0.001) compared with PC barrows (87.27 vs. 85.98%). As HCW of IC barrows increased, both CCY and LCY declined (P < 0.01), with light IC barrow carcasses having a 1.43 unit advantage in CCY compared with heavy IC barrow carcasses (P < 0.01). Natural fall bellies of PC barrows comprised a greater (P < 0.05) percentage of side weight than those from IC barrows (15.81 vs. 15.50%). A reduction in belly primal value was confirmed by a 3.43 unit reduction in the commercial bacon slicing yields of IC barrows. However, belly yield and slicing yield differences were minimized when IC barrows were marketed at a heavier weight. Using carcass cutout estimates determined in the summary as the foundation for value calculations, lean cuts of IC barrow carcasses were worth $2.66 to $3.80 more than PC barrow carcasses. Therefore, after adjustment for the reduction in belly primal value, the primal value of an IC barrow carcass was $2.08 to $3.13 greater than a PC barrow carcass.

Constitutive properties of adult mammalian cardiac muscle cells.

BACKGROUND: The purpose of this study was to determine whether changes in the constitutive properties of the cardiac muscle cell play a causative role in the development of diastolic dysfunction. METHODS AND RESULTS: Cardiocytes from normal and pressure-hypertrophied cats were embedded in an agarose gel, placed on a stretching device, and subjected to a change in stress (sigma), and resultant changes in cell strain (epsilon) were measured. These measurements were used to examine the passive elastic spring, viscous damping, and myofilament activation. The passive elastic spring was assessed in protocol A by increasing the sigma on the agarose gel at a constant rate to define the cardiocyte sigma-versus-epsilon relationship. Viscous damping was assessed in protocol B from the loop area between the cardiocyte sigma-versus-epsilon relationship during an increase and then a decrease in sigma. In both protocols, myofilament activation was minimized by a reduction in [Ca2+]i. Myofilament activation effects were assessed in protocol C by defining cardiocyte sigma versus epsilon during an increase in sigma with physiological [Ca2+]i. In protocol A, the cardiocyte sigma-versus-epsilon relationship was similar in normal and hypertrophied cells. In protocol B, the loop area was greater in hypertrophied than normal cardiocytes. In protocol C, the sigma-versus-epsilon relation in hypertrophied cardiocytes was shifted to the left compared with normal cells. CONCLUSIONS: Changes in viscous damping and myofilament activation in combination may cause pressure-hypertrophied cardiocytes to resist changes in shape during diastole and contribute to diastolic dysfunction.

Gel stretch method: a new method to measure constitutive properties of cardiac muscle cells.

Diastolic dysfunction is an important cause of congestive heart failure; however, the basic mechanisms causing diastolic congestive heart failure are not fully understood, especially the role of the cardiac muscle cell, or cardiocyte, in this process. Before the role of the cardiocyte in this pathophysiology can be defined, methods for measuring cardiocyte constitutive properties must be developed and validated. Thus this study was designed to evaluate a new method to characterize cardiocyte constitutive properties, the gel stretch method. Cardiocytes were isolated enzymatically from normal feline hearts and embedded in a 2% agarose gel containing HEPES-Krebs buffer and laminin. This gel was cast in a shape that allowed it to be placed in a stretching device. The ends of the gel were held between a movable roller and fixed plates that acted as mandibles. Distance between the right and left mandibles was increased using a stepper motor system. The force applied to the gel was measured by a force transducer. The resultant cardiocyte strain was determined by imaging the cells with a microscope, capturing the images with a CCD camera, and measuring cardiocyte and sarcomere length changes. Cardiocyte stress was characterized with a finite-element method. These measurements of cardiocyte stress and strain were used to determine cardiocyte stiffness. Two variables affecting cardiocyte stiffness were measured, the passive elastic spring and viscous damping. The passive spring was assessed by increasing the force on the gel at 1 g/min, modeling the resultant stress vs. strain relationship as an exponential [sigma = A/k(ekepsilon - 1)]. In normal cardiocytes, A = 23.0 kN/m2 and k = 16. Viscous damping was assessed by examining the loop area between the stress vs. strain relationship during 1 g/min increases and decreases in force. Normal cardiocytes had a finite loop area = 1.39 kN/m2, indicating the presence of viscous damping. Thus the gel stretch method provided accurate measurements of cardiocyte constitutive properties. These measurements have allowed the first quantitative assessment of passive elastic spring properties and viscous damping in normal mammalian cardiocytes.

Prolonged bleeding time of Chediak-Higashi cats corrected by platelet transfusion.

Cats with the Chediak-Higashi syndrome (CHS) have a platelet storage pool deficiency (SPD). Ten CHS cats were transfused with a concentrate of 51Cr-labeled platelets prepared from normal donor cats. One hour after transfusion, the donor platelet count in CHS recipient cats was 40,000-60,000/microliters. Bleeding time before transfusion was 9.1 +/- 3.0 min. When donor platelet count in CHS cats was 50,000/microliters, bleeding time was 1.7 +/- 0.2 min. Bleeding time of normal cats was 1.4 +/- 0.3 min. Bleeding time increased to 3.3 +/- 0.2 min and to 5.3 +/- 0.2 min when the platelet count was 30,000/microliters, and 15,000/microliters, respectively. The close inverse relationship between bleeding time and number of donor platelets in CHS cats (r = -0.92), suggests that prolonged bleeding time is due to a platelet abnormality, that platelet transfusion can effectively correct prolonged bleeding time in an animal model of platelet SPD and that CHS cats may be an appropriate animal model to evaluate hemostatic capabilities of transfused platelets.