Biomedical subjects
Publications and source records attributed to J E Alexander.
Scrutinizing the soft tissue as well as the bone is essential when reading bone films. Fat pad signs can be invaluable in the diagnosis of subtle fractures and other injuries. At some sites, such as the elbow and the wrist, these signs can be almost pathognomonic of a fracture, even if radiographic findings are otherwise negative.
Lesions of the patella are relatively rare, although a large variety of etiologies have been reported. To our knowledge this is only the second reported case of a Brodie's abscess of the patella. Its radiologic appearance was identical to that described for the common dorsal defect of the patella.
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Labrador Retrievers with type-II muscle fiber deficiency were examined electrodiagnostically. Electromyographic changes consisted of positive sharp waves, fibrillation potentials, bizarre high-frequency discharges, and, rarely, myotonic-like discharges. Fasciculation potentials were recorded infrequently. Fibrillation potentials and bizarre high-frequency discharges were the most commonly observed electromyographic changes. Bizarre high-frequency discharges were prominent in muscles of the head and neck, proximal muscles of the thoracic limbs, and the thoracolumbar paraspinal musculature. Marked abnormalities were not observed in the motor nerve conduction velocity. Decremental responses of the evoked compound muscle action potential to repetitive nerve stimulation were not observed.
Synovial osteochondromatosis is a benign disorder in which cartilaginous loose bodies develop about the large joints, usually the knee. It is caused by synovial metaplasia of unknown etiology. Symptoms are due either to mechanical problems caused by the loose bodies or to the degenerative arthritis that usually follows in several years. Surgical or arthroscopic removal of the loose bodies appears to be the only effective treatment. Loose bodies may recur, necessitating synovectomy.
Four neonates presented with leg-length discrepancy in the first and second year of life, secondary to physeal growth arrest. All four had stormy postnatal periods, requiring indwelling arterial and/or hyperalimentation catheters. One had documented osteomyelitis. In the last three cases, the growth disturbance may have been secondary to aseptic emboli to the bones from the indwelling catheters. In two cases, there was evidence of other nonseptic embolic phenomena.
Experiments were conducted in open-chest dogs in which ascending aortic blood flow (Q) was measured with an electromagnetic flow probe, and pressure was measured in the left ventricle (LV) and ascending aorta. The aorta just distal to the flow probe was occluded suddenly, causing the aortic bulb (AB) to be the only part of the arterial system to be in communication with the LV during clamped beats. Pressure and flow data from preocclusion, occlusion, and occlusion-release periods were analyzed to assess AB compliance (CAB) and the longitudinal impedance properties of inertance (LVO) and resistance (RVO) in the AB-aortic orifice region. In five dogs (avg wt 24.2 kg), the mean and range of values were as follows: CAB = 45 (31-55) X 10(-4) cm5/dyn; LVO = 1.86 (0.76-2.88) dyn X s2 X cm-5, RVO = 4.07 (0.66-8.55) dyn X s X cm-5. The volume-accommodating actions of CAB caused actual LV outflow to be characteristically different from Q and aortic-clamped beats to be nonisovolumic. Actions of the AB were found to be important in the estimation of arterial characteristic impedance as a component of LV afterload and in the estimation of the LV pump properties of time-varying elastance and internal resistance.
Studies of left ventricle (LV) and systemic arterial (SA) interaction can be grouped into four categories: 1) prediction of pressure and flow waveforms, 2) changes in LV/SA function with changes in SA properties, 3) identification of criteria that reveal matching between LV and SA properties, 4) definition of LV afterload. Whereas results from studies in categories 1, 2, and 3 reveal the consequences of interaction, results from studies in category 4 come closest to revealing the true character of LV/SA interaction. A useful description arising from category 4 is that of a circular feedback path connecting LV outflow, SA input-impedance, LV pressure, and LV pump properties. The identification of a node in this scheme results in the separation of LV functions into active functions and loading functions and the separation of LV/SA load into LV load and SA loading elements. The time-varying LV elastance participates in both LV active functions and LV loading functions, with the former dominating the latter. Total peripheral resistance dominates all other LV and SA loading elements in its loading effects. Although an elastance-resistance LV model coupled with a simple second-order SA load model accounts for many reported observations on LV/SA interaction, data from sudden aortic occlusion studies indicate a need to consider yet another interaction action. Evidence is presented to suggest the existence of an LV pump element that couples ejection events with relaxation and filling events.
To better define beat-to-beat regulation of stroke volume (SV), the several-beat transient response of the left ventricle (LV) to sudden changes in hydraulic loading impedance was studied. Data were collected from eight canine isolated heart-lung preparations with controlled LV loading impedance. At a selected diastolic interval, a sudden increase in hydraulic loading resistance was induced. The resulting transient response in SV, end-diastolic pressure (EDP), and end-systolic pressure (ESP) was analyzed by comparing the relative predictive capability of six competing models, each incorporating different degrees of complexity in the relationship between SV and EDP and ESP. The basic model assumed linear LV pressure-volume relationships at both end diastole and end systole. Incorporation of nonlinear, end-state interaction or coronary perfusion pressure effects into the basic model did not improve predictive performance. Models incorporating SV and ESP of the preceding beat as well as ejecting beat ESP and EDP were consistently superior to all other models. The ranking of the relative influence of the determinants of SV was 1) ejecting beat ESP, 2) preceding beat ESP, 3) ejecting beat EDP, and 4) preceding beat SV.
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The relationship between right ventricle afterloading pressure (P) and outflow (Q) was studied in three isolated canine right ventricle (RV) preparations. Right atrial pressure was held constant while graded elevations in P were induced with stepwise occlusions of the right and left branches of the pulmonary artery. P and Q signals were collected and analyzed using a digital computer system. Data were analyzed by assuming a model structure for the RV and comparing resultant model predictions of Q with actual observations. The model structure was modified in accordance with the discrepancy between prediction and observation to improve the model's predictive capability. The initial model tested was the time-varying linear relationship between ventricular volume and pressure. Utilizing this model, accurate predictions of RV outflow in the face of varying pressure afterloads could not be made. The addition of a series resistance to this elementary model resulted in marked improvement in predictive performance. The addition of greater complexity to the model gave only marginal improvement to the model's predictive capability. It was concluded that a time-varying capacitance and series resistance adequately model internal properties of the RV that relate outflow to afterloading pressure.
The heart rate (HR) response to stepwise changes in mean arterial pressure (MAP) produced by methoxamine and sodium nitroprusside was studied in conscious horses, pigs, and calves. The respective steady-state arterial baroreflex sensitivities (delta HR/delta MAP expressed as beats min-1 . mm of Hg-1) were -1.20, -1.21, and -0.39 for decreasing MAP and -0.08, -0.91, and -0.56 for increasing MAP. After parasympathetic nervous system (PNS) blockade with atropine, the reflex sensitivity to decreasing MAP in horses and the pigs decreased to -0.62 and -0.65, respectively (P less than 0.05), whereas the sensitivity in calves was not significantly different from the calves' base-line sensitivity (P greater than 0.05). In pigs, the sensitivity to increasing MAP decreased to -0.43 after PNS blockade (P less than 0.05). Horses and calves had a response to small increases in MAP similar to that observed in the absence of PNS blockade. There was no additional change in HR with larger increases in MAP in these 2 species. These responses indicate that varying degrees of mixed PNS and sympathetic nervous system activity changes mediate the baroreflex change in HR seen for increasing and decreasing MAP in pigs and for decreasing MAP in horses. Predominantly PNS activity is responsible for the response to increasing MAP in the horses and calves, whereas predominantly sympathetic nervous system activity is responsible for the response to decreasing MAP in calves. Comparisons were made between the observations in these 3 species and other mammalian species.
In a study of 300 Alaskan Malamutes, dwarfism was shown to be an autosomal recessive inherited disease with complete penetrance that resulted in disturbed endochondral bone formation. Osseous growth disturbance was manifest at the metaphyses of tubular bones. Clinical and radiographic changes were very similar to those of rickets, although appositional bone formation rates were normal. Serum calcium, phosphorus, and alkaline phosphatase were within normal limits. Urinary excretion of calcium, phosphate, and amino acids were normal. Excess matrix was formed in the zone of cartilage cell proliferation, and the matrix persisted in the growth plate. Normal stresses resulted in microfractures in the metaphyses with subsequent interference of vascular penetration into the zone of degenerated cartilage cells.
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The acute metabolic responses to metabolic acidosis in the rat include an increase in ammoniagenesis and gluconeogenesis before enzyme adaptations have taken place. In the present studies rats were made acidotic with NH4Cl or HCl. Preincubation of renal cortical slices from normal rats in plasma from acidotic rats produced an increase in ammoniagenic capacity. However, when slices were incubated directly in diluted plasma from acidotic rats, there was also an increase in ammoniagenesis and gluconeogenesis from glutamine. The ammoniagenic factor was detectable within 0.5 h of induction of acidosis, was not detectable in chronic acidosis, was not of adrenal origin, was not a protein, was dialyzable, and acted by an alpha-adrenergic-like mechanism in that its action was blocked by phentolamine but not by propranolol. Phentolamine injected into rats depressed the ammoniagenic response to acidosis. The plasma factor did not show its ammoniagenic effect in a low-sodium buffer and there was no absolute requirement for calcium. The acute response to acidosis is thus mediated by a humoral substance with the above characteristics.
In recent years, there has been considerable discussion and controversy regarding the major vascular supply to the nipple. We report our experience with the use of a long, narrow, glandular pedicle based on the pectoralis major muscle in reduction mammaplasty in 29 breasts in 15 patients. The vascular supply to the nipple-areolar complex in this type of flap is derived from intercostal perforating vessels. Although it may make some contribution, a dermal bridge or flap is not required for the survival of these structures.