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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 865 records · Page 48Linked to original sources
PubMed1969

Unusual microtubular patterns and three-dimensional movement of mealybug sperm and sperm bundles.

The spermatozoon of the mealybug Pseudococcus obscurus Essig is a filamentous cell (0.25 micro by 300 micro) which exhibits three-dimensional flagellations throughout most of its length. It has microtubules (200 A diameter) and a threadlike nuclear core (0.07-0.09 micro diameter) which extend almost its entire length, but apparently it has no mitochondria, centrioles, typical flagellum, or acrosome. The microtubules are arranged in two and a half concentric rings and total 56 in the most actively motile region but form two or three concentric rings with totals of 28 or 56 tubules, respectively, in less active regions. The relation of unusual microtubular patterns to the 9 + 2 complex and to flagellar motion is discussed. Mealybug spermatozoa are transmitted to the female in motile bundles which are approximately 1.3 micro by 750 micro and have four regions: (1) an anterior corkscrew region; (2) a region which contains approximately 16 spermatozoa; (3) a region of amorphous content; and (4) an endpiece. Bundle motility originates from the synchronous movements of its spermatozoa which appear to be arranged in two concentric multistranded helices. The spermatozoa provide both forward and gyratory motions of the bundle, and the corkscrew complements bundle propulsion by converting part of the rotation into forward movement.

Cell Movement↗
PubMed1969

Influence of the thyroid state on left ventricular tension-velocity relations in the intact, sedated dog.

The mechanical properties of left ventricular contraction were described in terms of tension, velocity, length, and time in closed-chest, sedated normal, hypothyroid, and hyperthyroid dogs. Heart rate was controlled at 150 beats/min, and instantaneous contractile element velocity was calculated from left ventricular pressure and its first derivative during isovolumic left ventricular contractions, produced by sudden balloon occlusion of the ascending aorta during diastole. Wall tension was derived from ventricular pressure and volume, the latter being obtained from the pressure-volume relation of the arrested ventricle, and tension-velocity relations were analyzed over a range of ventricular endiastolic volumes. At any level of ventricular volume, the hypothyroid state was associated with a displacement of the tension-velocity relation of the left ventricle downwards and to the left, and the time to peak tension was prolonged (154 msec, normal 139 msec). In the hyperthyroid state, the tension-velocity relation of the left ventricle was displaced upwards and to the right, and the time to peak tension was reduced (80 msec). The changes in the tension-velocity relations indicate that the inotropic state of the left ventricle in the intact dog varies directly with the animal's thyroid state. This influence on myocardial contractility necessarily constitutes an important and integral part of the response of the intact circulation to altered thyroid state.

Animals↗