Biomedical subjects
Publications and source records attributed to R Norman.
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Echocardiographic dimensions, anthropometric data and maximal oxygen uptake (VO2max) were studied in 26 healthy sedentary male controls (mean age, 22.0 yrs) and 15 male endurance athletes (mean age, 20.3 yrs). Athletes displayed significantly greater mean values for left ventricular internal dimension at end-diastole (LVIDd), end-diastolic volume (LVEDV) and left ventricular mass (LVM). Statistically significant positive correlations were observed within the sedentary control group between left ventricular end-diastolic dimensions (LVIDd, mm and/or LVEDV, cm3) and body height (cm), body weight (kg), chest circumference (cm) and body surface area (m2). Left ventricular mass (LVM, g) correlated significantly with lean body mass (kg). Ectomorphic somatotype rating (Ecto) correlated negatively with LVEDV and LVM. Finally, VO2max (l/min) correlated significantly with LVIDd, LVEDV and LVM. Multiple linear regression analysis indicated that the degree of endomorphy (Endo), LVIDd (mm/m2) and chest circumference accounted for 89% of the variance in VO2max (ml/kg/min) within the athlete group. Endo, Ecto and LVIDd (mm/m2) accounted for 86% of the variance in VO2max (ml/kg/min) in the control group. This study supports the hypothesis that maximal aerobic power can be predicted from cardiac and anthropometric measurements.
Seven previously sedentary women (mean age, 19 yrs) participated in an 11-week running program (4-5 sessions/week) in preparation for a 10 km race. Training intensity was 80-85% of maximum heart rate reserve. Exercise duration began at 20 minutes/session and was lengthened 5 minutes/session every 2 weeks. A control group consisting of 4 women was also evaluated. Maximal oxygen uptake (VO2max, ml/kg/min) increased 11% in the trained group and decreased 6% in the control group during the study (p less than 0.05). Oxygen uptake, cardiac output (Q), and stroke volume (SV) increased significantly (p less than 0.05) in the trained group during each of 3 levels of steady state cycle ergometer exercise (heart rate targets: 115, 135 and 155 beats/min, respectively). Arteriovenous oxygen difference (a-V02 diff) was not increased significantly after training. Resting left ventricular dimensions and performance evaluated by echocardiography also did not change significantly after training. It was concluded that short-term conditioning in this population results in an increased exercise Q without concomitant increases in left ventricular dimensions or arteriovenous oxygen difference.
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Twenty patients from our pacemaker clinic population were assessed clinically and by saline contrast echocardiography (subxiphoid view) to determine the prevalence of tricuspid regurgitation (TR) and, if TR was present, its mechanism. The patients had no known TR before lead placement, a single transvenous right ventricular pacing lead present more than 6 months (mean 52, range 7 to 138), ventricular demand pacing alternating with sinus rhythm and rate programmability. Each patient was studied in sinus rhythm and during ventricular pacing. Using the criterion of inferior vena cava (IVC) contrast reflux during ventricular systole to diagnose TR, no patient had evidence of TR in sinus rhythm, consistent with clinical examination. During ventricular demand pacing, jugular venous pulse cannon A waves developed in 10 patients, and 18 patients (including these 10) had IVC contrast reflux during ventricular systole. Analysis of the timing of IVC reflux revealed its close temporal relation to the timing of atrial systole rather than a fixed timing during ventricular systole. This reflux occurred with loss of normal atrioventricular (AV) synchrony and the underlying mechanism in all cases was shown to be right atrial contraction against a closed tricuspid valve. Two patients who did not have such a pattern with pacing maintained normal AV synchrony. These observations indicate that: TR is an uncommon accompaniment of ventricular demand pacing; the jugular venous pulse and IVC echocardiographic contrast patterns during ventricular demand pacing simulate TR when AV asynchrony [corrected] occurs; and the IVC contrast pattern of pacing induced AV asynchrony [corrected] is best termed the cannon A wave synchronous pattern.
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Radiation-inactivation was used to assess the functional size of the apamin-binding component of the Ca2+-dependent K+ channel. The amount of specific binding of 125I-apamin to receptors in synaptic membranes of rat cortex decayed exponentially with increasing doses of ionizing radiation and target size analysis was consistent with a relative molecular mass of 250 000 +/- 20 000 for the 125I-apamin receptor. Analysis on sodium dodecyl sulfate gels following covalent cross-linking of 125I-apamin to its receptor in a synaptosomal membrane preparation from rat cortex revealed a single labelled polypeptide chain of Mr = 33 000 +/- 2000 in the presence of protease inhibitors. Our results suggest that the Ca2+-dependent K+ channel from rat cortex is an oligomeric structure of Mr = 250 000 +/- 20 000 containing an apamin-binding subunit of Mr = 33 000 +/- 2000. The apamin-binding component of the Ca2+-dependent K+ channel from rat synaptosomes was solubilized using detergents such as sodium cholate or 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate. Phospholipids did not increase the stability of the apamin-binding component during the solubilization. Binding of apamin to its solubilized receptor is reversible and saturable. The dissociation constant of the apamin-receptor complex is 40-150 pM, the rates constants of association and dissociation being 3.2 X 10(6) M-1s-1 and 1.4 X 10(-4)s-1 respectively. These binding characteristics are similar to those found for the membrane-bound apamin receptor.
A relatively rapid, unidimensional method of measuring phosphatidyl glycerol (PG) in amniotic fluid in order to assess pulmonary maturity was compared with measurement of the lecithin/sphingomyelin (L/S) ratio and the bubble test. Measurement of PG alone gave a higher predictive value (95%) than the L/S ratio while maintaining a low ratio rate of false-positive (2,3%) and false-negative results (3,1%).
Amniotic fluid from 19 patients with preeclampsia was compared with samples from normotensive control subjects with respect to the levels of prostaglandin 6-keto prostaglandin F1 alpha, thromboxane B2, and the ratio of 6-keto prostaglandin F1 alpha to thromboxane B2. The study found no significant differences in the levels of these prostanoids or the ratio of 6-keto prostaglandin F1 alpha to thromboxane B2 (study patients, 2.7 +/- 2.1; control patients, 2.8 +/- 1.9) between groups.
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Video monitoring and video recording are useful in ophthalmic microsurgery for self-instruction and improvement, increased interest by operating room personnel, transfer of useful information to other physicians and improvement of technique. Specialized video cameras for such use are expensive. There is, however, a newly-marketed, inexpensive and light-weight video camera, which was designed for electronic newsgathering purposes, and which can be modified for microsurgery application, providing excellent results.
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The development of brain stem auditory evoked responses (BAERs), recorded from a surface electrode as short-latency, volume-conducted potentials, was studied in a series of kittens over a postnatal period ranging from birth to 60 days. Repeated, longitudinal observations on particular kittens were supplemented with observations on additional kittens during the first and second postnatal week to determine age of onset of the BAERs. The position of the animal and sound source within the recording chamber were held constant across recording sessions, as was click intensity except during recordings in which intensity effects were specifically studied. Click rates of 1, 10, 50 and 100/sec were routinely presented. Reference electrodes at the tongue, pinna and neck showed volume-conducted responses to the click stimuli and resulted in considerable distortion of the activity recorded by the vertex electrode; the forepaw, in contrast, showed no activity and a vertex-forepaw electrode configuration provided good resolution of the BAERs across development. A number of new observations were made. BAERs were first observed at 4 days of age, approximately the same age at which depth evoked potentials are first recorded in brain stem auditory nuclei. Initially the BAERs were diffuse, high threshold and fatigued rapidly, characteristics shared with depth evoked potentials in the early postnatal period. Over the first two weeks, the potentials showed marked decrease in threshold, increased resistance to fast click rates, and better definition of wave forms. All BAER components showed exponential decreases in latency. Because all of the brain stem evoked potentials could be recorded concurrently and longitudinally in the same subject a number of developmental comparisons were possible among the BAER components. Wave 1, related to the acoustic nerve in the adult cat, showed a developmental time course and adult latency similar to that reported for N1. Wave 2, related to the cochlear nucleus in the adult, showed a marked bimodality over the first month; wave 2a was a large amplitude clearly separated wave which gradually fused as an inconspicuous leading shoulder on wave 2b. Wave 2b developed with a time course and adult latency similar to that reported for the ventral cochlear nucleus. Wave 3, related to the region of the superior olivary complex in the adult, showed a clear but transient bimodality during the third week of development. Wave 5, related to the inferior colliculus in the adult, appeared later than waves 1-4 and showed a significantly slower rate of development than waves 1-4. These data indicate that differential developmental changes occur within the brain stem auditory pathway and that the BAERs provide a dynamic probe of concurrent maturational interactions.
The auditory brain stem evoked responses (ABRs) of two groups of retarded adults (Down's syndrome and retarded of unknown etiology) were compared with those of a group of non-retarded control subjects as a function of changes in stimulus repetition rate and stimulus intensity. The absence of ABRs at the highest stimulus intensity suggested profound hearing deficits in one or both ears of 4 Down's syndrome and 2 unknown-etiology subjects. Other abnormalities were noted in particular individuals of each group of retarded. In addition, the ABRs of the Down's group as a whole showed a significant pattern of abnormalities. The intervals between peaks I and II and III and IV were shorter than normal white the IV--V interval was prolonged. Wave V also showed abnormally small latency increases at fast click rates. The ABRs of the unknown-etiology group showed a shortened III--IV interval and a prolongation of the IV--V interval, but were otherwise not significantly different from the normal controls. These data suggest a high incidence of hearing loss in both diagnostic categories studies, and abnormal functioning of the auditory brain stem pathway in the Down's syndrome group as a whole.
An experiment was carried out in batteries with raised wire floors to study the protein requirements of guinea keets from one to 56 days of age. Keets were fed protein levels ranging from 18 to 28% using an isocaloric corn-soya diet. Keets in this experiment required a dietary protein level of 24% for optimal growth to eight weeks of age. Feed conversion was slightly better for the keets that received 28% protein; however, this result was not significantly different at the 0.05 level of probability. Feed consumption was generally related to growth rate. Mortality was not influenced by levels of protein.
Ice hockey performance was studied during 10 contests to assess time-motion characteristics and associated physiological changes that occur for each position. Depending on the position played, the actual playing time per game for forwards and defensemen ranged between 20.7 and 28.0 min. The number of shifts ranged from 14 to 21 with an average playing time of 85.4 s/shift. Further analysis of each shift indicated that there was an average of 2.3 play stoppages which averaged 27.1 s, producing a continuous playing time of 39.7 s. Telemetered recordings of heart rate during each shift revealed sustained rates of between 170 and 174 beats/min over the three periods of the game. For both the forwards and defensemen, values for blood lactates were highest during the first and second periods (x = 78.0 and 66.1 mg/100 ml), then declined considerably during the third period (x = 44.5 mg/100 ml). Blood glucose showed a similar tendency (x = 139.3, 133.7, 114.1 mg/100 ml), while hematocrit and total protein showed little tendency to change.
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