Pitfalls in the diagnosis and management of papillary muscle rupture: a study of four cases and review of the literature

Four cases of papillary muscle rupture occurring in the setting of acute myocardial infarction are presented, which illustrate the following points: the diagnosis may not be apparent at presentation, a mitral regurgitant murmur may be absent, transesophageal echocardiography may establish the diagnosis when transthoracic echocardiography does not, and appropriate surgical correction can lead to excellent functional recovery.     

Multiple nonanastomotic aneurysms in an external velour ringed Dacron femoropopliteal vascular prosthesis

Nonanastomotic aneurysms of arterial prosthetic grafts are an infrequent but well-documented complication of arterial bypass surgery. Several cases of nonanastomotic aneurysm formation of the external velour-type Dacron graft have been reported. We present a case of an external velour ringed Dacron (Sauvage EXS) femoropopliteal bypass graft with multiple nonanastomotic aneurysms. An extensive review of the English literature shows this to be the first reported case of multiple aneurysms occurring in this type of prosthesis.     

Relationship between sarcomere length and active force in rabbit papillary muscle

Isometric peak twitch force (stimulation frequency 0.5/s; 29.5-30.5 degrees C) was correlated with sarcomere length in isolated papillary muscles of the rabbit. Sarcomere length was measured from photographic recordings (1.5 ms exposure time) performed at rest between contractions and at the time of isometric peak twitch force. The sarcomere length at rest was found to be relatively uniform throughout the preparation and to be linearly related to the overall muscle length within the range Lmax-0.85Lmax. The distribution of sarcomere lengths increased considerably as the muscle went from rest to activity. Studies of surface markers showed different degrees of shortening (or elongation) of individual segments along the length of the preparation. The mean resting sarcomere length at Lmax (the optimum muscle length for force production) was 2.44 +/- 0.01 micron (grand mean +/- S.E., 7 muscles). The means active sarcomere length at Lmax was 2.29 +/- 0.04 micron. Active force declined steeply as the muscle length was reduced below Lmax. At a resting sarcomere length of 2.0 micron, active force was approximately 1/3 of the maximum. The observed differences between the length-tension relat-onships in myocardium (twitch responses) and skeletal muscle (tetanic contractions) are discussed on the basis of a length dependency of the activation process in cardiac muscle.     

Individual growth in stature: a comparison of four growth studies in the U.S.A

Patterns of growth in stature of subjects from the four major U.S. longitudinal growth studies are compared by means of a two-component model for individual growth. Problems inherent in the comparison of data from independent growth studies, such as those arising from different methods of sampling subjects and scheduling measurements and the occurrence of atypical subjects, are considered and solutions are offered. Statistical tests of the individual growth parameters revealed significant, but small, differences among the samples in the magnitude of the contributions of prepubertal and adolescent growth to mature stature and in the velocity of growth. No differences between samples in the timing of the adolescent component were detected.     

In situ morphologies of deep-sea and sediment bacteria

Deep-sea and sediment bacteria at the bottom of an approximately 1200-m water column were sampled by means of pressure vessels attached to a remote underwater manipulator. Cells were immediately fixed in situ with glutaraldehyde, and after processing in the laboratory their morphologies were observed with the scanning electron microscope. Most bacteria were coccoid or rod-lide and less than 0.4 mum in diameter or width. Few filamentous bacteria were observed. Bacteria were in aggregates or free-living. It is concluded that morphologies of deep-sea bacteria collected and fixed at the hydrostatic pressure of their environment are, in general, similar to the observed morphologies of deep-sea bacteria determined at 1 atm pressure after collection and decompression during ascent through the water column.