Mimic nets

This paper introduces techniques to train feedforward nets to automate ranking and classification tasks. The techniques are denoted mimic nets since the nets can always mimic self-consistent training data. The mimic nets are constructed not for any neurological analogy, but for computational ease and purposeful utility. Mimic nets are designed for problems requiring sensible extrapolation from noiseless training data, and errorless recall of the training data. Linear programming algorithms are utilized to train the net to exactly mimic the expert in all training situations, to identify efficacious features, and to assess the training data. The number of nodes and the number of connections, the structure of the mimic net, are adapted together with weights in the net. The existence of a mimic net for every consistent set of training data is demonstrated.

Congenital pseudarthrosis

Five cases of congenital pseudarthrosis of the clavicle were treated with open reduction and fixation with appropriate-sized contoured plates and screws. Iliac bone grafts were used to bridge the gap in four patients; local bone graft was used in the fifth patient. Consolidation was noted an average of 3 months postoperatively in all five cases. The plate and screws were removed in all patients at an average of 16 months postoperatively. Average length of follow-up for the five patients is 4 years. Roentgenograms demonstrate that the clavicle has continued to grow normally. All five patients have pain-free full range of motion and are engaged in unrestricted activities.

Proximal femurectomy for decubitus ulceration in the spinal cord injury patient

The results of proximal femoral resections in nine patients were analyzed after an average four year follow-up, together with a retrospective analysis of the patients. The indication for surgery was decubitus ulceration that had failed to respond to multiple previous treatments. The decubitus ulcers were associated with septic arthritis, osteomyelitis, hip dislocation and ankylosis. All patients achieved short term healing with 50% achieving long term healing. The incidence of subsequent surgery for decubitus ulcers decreased significantly. No patient suffered a deterioration in function.

Clinical presentation of spinal cord concussion

Spinal cord concussion is a transient disturbance of spinal cord function, with or without vertebral damage and no demonstrable pathologic changes, that results from a rapid change in velocity following trauma, and resolves within 48 hours. In a retrospective review of patients with spinal injury referred to a tertiary care center, spinal cord concussion was observed in 3.7% of patients. Thirteen cases are presented. A variety of clinical presentations may occur, all of which can be explained on the basis of the magnitude or direction of acceleration of the spinal cord. The cervical cord is most commonly affected, but concussion can occur at any level of the spinal cord. Spinal cord concussion is often associated with pre-existing vertebral abnormalities that result in narrowing of the spinal canal or areas of hypermobility.

Comprehensive functional analysis of shoulders following complete acromioclavicular separation

The purpose of this study was to examine the results of the two major methods of treatment of complete acromioclavicular separation: surgery and nonsurgical techniques. Twenty male patients with complete acromioclavicular separation within the preceding 13 months were retrospectively examined and tested for recovery of shoulder strength and function. Comparisons were conducted between 10 of the patients who had been treated nonsurgically (Group 1), and 10 who had been treated surgically (Group 2). An additional group of 10 uninjured male subjects as controls was also tested for comparison of strength between dominant and nondominant limbs (Group 3). All of the patients were tested for strength of both shoulders using the Kin-Com isokinetic dynamometer, for shoulder flexibility using the Leighton flexometer, and for grip strength using a standard grip dynamometer. A questionnaire concerning patient evaluation of the injury was also administered to all of the subjects. The majority of strength and flexibility tests showed no significant differences between the nonsurgical and surgical groups. The nonsurgical group was statistically superior to the surgical group in the following test scores: eccentric abduction (fast speeds), concentric external rotation (slow speeds), eccentric external rotation (fast), eccentric abduction (slow), and flexibility in external rotation. These findings generally indicated that the nonsurgical treatment of a third-degree acromioclavicular separation is superior in restoring normal shoulder function in the 1st year following injury.

Studies of the hypotensive effect of calcium injected into lateral brain ventricles

Calcium chloride (1-2 mumole) injected into lateral brain ventricles of pentobarbital anesthetized rats markedly decreases blood pressure. The hypotensive response is not affected by vagotomy and is characteristic calcium and barium since other polyvalent cations do not have the same effect. The calcium channel blocker, verapamil given into brain ventricles prevents the depressor effect of calcium suggesting that the hypotensive action of calcium is initiated intracellularly. The well documented lowering of blood pressure by increases in dietary intake of calcium may be mediated by increases in free calcium in cerebrospinal fluid.

Modulation of thiopurine cytotoxicity in the HL-60 cell line by physiological concentrations of hypoxanthine

Thioguanine and mercaptopurine are clinically important agents in widespread use for the treatment of acute leukemia. In this study the effect of low, physiological concentrations of hypoxanthine on thiopurine cytotoxicity was examined in the HL-60 human acute promyelocytic leukemia cell line. Initially the effect of cell concentration on medium hypoxanthine levels was investigated. When 10(5) to 10(6) cells/ml were used, medium hypoxanthine concentrations fell to undetectable (less than 0.1 microM) levels by 24 h, due to cell utilization. However, when the cell density was reduced to 10(3) cells/ml, it was possible to maintain a medium hypoxanthine level as low as 0.5 microM for 24 h without significant hypoxanthine depletion. This allowed for the investigation of the extent to which physiological concentrations of hypoxanthine (1.0 to 10 microM) could modulate thiopurine cytotoxicity. HL-60 cells were incubated in medium containing from 1.0 to 100 microM hypoxanthine concentrations and varying levels of thioguanine or mercaptopurine for 24 h. Cells were then washed and cloned in soft agar. Physiological concentrations of hypoxanthine (1.0 to 10 microM) provided significant protection to HL-60 cells from the cytotoxic effects of both thioguanine and mercaptopurine. An increase in medium hypoxanthine level from 1.0 to 3.0 microM resulted in a 3-fold increase in the thiopurine concentration required to kill 50% of cells. There was a linear relationship between the thiopurine concentration required to reduce clonogenic survival by 50% and medium hypoxanthine level over the hypoxanthine concentrations studied. Although thioguanine was 200-fold more potent than mercaptopurine, and an analogue of guanine rather than hypoxanthine, there was a similar degree of modulation of the cytotoxicity of both agents by hypoxanthine. These results indicate that low, physiological hypoxanthine concentrations can significantly modulate thiopurine cytotoxicity and suggest that endogenous hypoxanthine pools may have an important effect on the clinical activity of thioguanine and mercaptopurine.

Cellular pharmacokinetics of mercaptopurine in human neoplastic cells and cell lines

The accumulation, metabolism, and retention of mercaptopurine (MP) was studied in four human neoplastic cell lines (three acute leukemia lines Molt-4, CCRF-CEM, and HL-60; and one Burkitt's lymphoma line, Wilson), each of which was sensitive to MP. Two cell lines resistant to MP (WilsonR and CCRF-CEMR) were also studied. The cell lines were incubated for 3 h in 10 microM [14C]MP and then placed in drug-free media for an additional 3 h. Cell samples were obtained at regular intervals, and the intracellular MP metabolites were measured in the acid-soluble fractions by anion-exchange high-pressure liquid chromatography. MP accumulated progressively within cells during the 3-h drug exposure period and declined rapidly when the cells were placed in drug-free media. Over 80% of the intracellular MP was present in the form of three nucleotide metabolites, MP ribose monophosphate, thioxanthosine monophosphate, and thioguanosine monophosphate. MP ribose monophosphate was found in greatest amount, accounting for 59-85% of the intracellular metabolite pool. Thioxanthosine monophosphate thioguanosine monophosphate were detected in lesser amounts. Study of leukemic cells obtained from patients demonstrated a similar pattern of MP accumulation, metabolism, and retention, although the overall amounts of the various metabolites formed were less. In contrast, there was essentially no MP nucleotide metabolite formation in the two MP-resistant cell lines. A more complete understanding of the cellular pharmacokinetics of MP in human neoplastic cells is likely to lead to a more rational use of the drug in the clinical setting.

A kinematic model of the human ankle

The spatial gross motion of the foot with respect to the shank is modelled as rotations about two fixed ankle axes: the upper ankle rotation axis (plantar flexion/dorsiflexion) and the subtalar rotation axis (inversion/eversion). The positions of the axes are determined by externally visible bony landmarks of the lower leg, and are measured for a living subject. The model input data are the plantar flexion/dorsiflexion and inversion/eversion rotation angles; the model output is a 4 X 4 transformation matrix which quantitatively describes the relative position of a foot coordinate system with respect to a shank coordinate system.

Muscular synergism--II. A minimum-fatigue criterion for load sharing between synergistic muscles

P6new physiological criterion for muscular load sharing is developed. The criterion is based on the assumption that the endurance time of muscular contractions is maximized, hence muscular fatigue is minimized. The optimization problem is cast in the form of a linearly constrained, non-linear MINIMAX optimization. The new method predicts that: (1) there is synergistic muscle action, (2) muscle force increases non-linearly with external force (load), (3) relatively more force is allocated to muscles that have a large maximum force (large muscles), (4) relatively more force is allocated to muscles with a high percentage of slow-twitch fibers (muscles that are fatigue-resistant), (5) the load sharing does not depend on the moment arm of the muscles (although the absolute force levels do depend on this variable). The predicted load sharing between two cat muscles during standing and walking is in good agreement with direct force measurement data from the literature.

Muscular synergism--I. On criteria for load sharing between synergistic muscles

The use of optimization techniques to predict individual muscle forces in redundant biomechanical systems implies the formulation of a criterion for load sharing between the muscles. In part I of this paper, the characteristics and performance of several linear and non-linear criteria reported in the literature have been compared for static-isometric knee flexion. The results show that linear criteria inherently predict discrete muscle action (orderly recruitment of muscles) whereas non-linear criteria can predict synergistic action. All criteria predict that relatively more force is allocated to muscles with large moment arms. When muscle stresses (or ratios of muscle force to maximum muscle force) are used as the decision variables in the objective function, then relatively more force is allocated to muscles with large maximum possible force as well. Future formulations of the optimization should consider the differences in fiber type composition among the muscles. Such an approach is presented in part II of the paper.

A six-year follow-up study of 155 children with cleft lip and palate

A total of 155 consecutive cases from three "Six-year-old follow-up clinics" have been reviewed to assess the speech results in boys and girls with cleft lip and palate belonging to Group II (complete labio-palatal clefts) and Group III (varying degrees of posterior median clefts of the palate). Clinical examination and assessment of speech was supplemented by X-ray-video assessment and the findings showed a good degree of correlation. The speech results between Group II and III and between the sexes are compared. Finally the extent of bone formation in the alveolar cleft was studied radiologically in 61 children with Group II clefts. Bone formation was present in 43 children, in 38 of whom a tooth had migrated into bone.

Timolol and propranolol: bioavailability, plasma concentrations, and beta blockade

Timolol, like propranolol, is a nonselective beta-adrenergic blocker, but it is much less lipid soluble and is formulated as a single enantiomer rather than a racemic mixture. We examined the effects of such differences on bioavailability, systemic clearance, and pharmacologic response. Ten healthy subjects received placebo, 0.2 mg/kg IV propranolol, 3.2 mg/kg oral propranolol, 0.025 mg/kg IV timolol, and 0.4 mg/kg oral timolol in double-blind, randomized crossover fashion. Plasma concentrations of total drug were monitored up to 8 hr, while responses to submaximal exercise were measured at 0, 2, and 6 hr. Timolol had greater bioavailability (F = 0.61 +/- 0.06(SEM) and 0.32 +/- 0.04) and lower systemic clearance (463 +/- 74 ml kg-1 hr-1 and 1040 +/- 120 ml kg-1 hr-1) than propranolol. Half-lifes were of the same order (2.7 and 2.9 hr). There was a marginal correlation between areas under the intravenous and oral plasma concentration-time curves for timolol (r = 0.66, P = 0.054), but none for propranolol (r = 0.48, P NS). There were also correlations of the response (percent reduction in heart rate) to oral and intravenous timolol at 2 hr (r = 0.72, P less than 0.05) and 6 hr (r = 0.84, P less than 0.01) hr, but none between responses to oral and intravenous propranolol. Finally, the response to oral timolol was related to the area under its plasma concentration-time curve, whereas that to propranolol was not. We conclude that the physicochemical properties of timolol lead to greater bioavailability. Pharmacologic response to an oral dose of timolol, unlike that to propranolol, can be predicted from the response to an intravenous dose and reflects its plasma concentration.

Nonresponsiveness of serum high-density lipoprotein-cholesterol to high dose ascorbic acid administration in normal men

In a prospective, single-blind, 12-wk study, serum lipids were measured serially in nine normal male volunteers before and during oral administration of megadose ascorbic acid (1 g vitamin C/day). Study results revealed no significant effect of vitamin therapy on serum cholesterol, high-density lipoprotein-cholesterol, triglycerides, or calculated low-density lipoprotein-cholesterol. Megadose ascorbic acid therapy is not effective in elevating serum high-density lipoprotein-cholesterol in normal adult men.

Mechanical vibration in neonatal transport

Mechanical vibration encountered in land transports was assessed objectively through measurement of vertical acceleration experienced by neonates in transit. Vibration was most predominant in the hazardous low frequency range of 3 to 18 Hz. The peak acceleration amplitudes (intermittent thrusts) ranged from 5 to 13 m/sq sec. The root mean square acceleration (averaged vibration) ranged from to 6 m/sq sec. These vibration levels are high when compared with adult vibration tolerance limits, and may jeopardize the safety of the transported infants, particularly in long-distance transports. Further research is needed to understand the possible effects of mechanical vibration in neonates and to define safe vibration thresholds in all modes of transport. Careful-evaluation of vibratory stress and its attenuation in newer designs of transport equipment may be desirable to enhance the safety of the transported infants.

Zinc lowers high-density lipoprotein-cholesterol levels

Zinc administration in rats is associated with a rise in serum cholesterol level. This study examined the effect of zinc administration on serum lipoprotein values in man. Twelve healthy adult men ingested 440 mg of zinc sulfate per day for five weeks. High-density lipoprotein-cholesterol concentration decreased 25% below baseline values (40.5 to 30.1 mg/dL). Total cholesterol, triglyceride, and low-density lipoprotein-cholesterol levels did not change throughout the study. The sharp fall of the "antiatherogenic" lipoprotein, high-density lipoprotein, associated with zinc administration supports the concept that zinc ingestion may be atherogenic in man.

Drug prescribing for the elderly in Saskatchewan during 1976

Over 11% of Saskatchewan's population is 65 years of age or older. To study patterns of prescribing for the elderly a computer file of more than 3.6 million prescriptions filled in Saskatchewan in 1976 was reviewed. The elderly population (aged 65 years or more) that year was 102 070, and 77.3% received at least one prescription drug listed in the Saskatchewan Formulary. In comparison with a "middle-aged" group (persons between the ages of 35 and 54 years) the elderly showed moderately higher average numbers of prescriptions filled and drugs used per person that year. However, the prescription of antihypertensive agents and diuretics increased dramatically with age, and barbiturates, in view of their potential toxicity, appeared to be overprescribed for the elderly.

5,7-Dihydroxytryptamine lesions of the ascending 5-hydroxytryptamine pathways: habituation, motor activity and agonistic behavior

Rats were injected stereotactically in mesencephalon with 5,7-dihydroxytryptamine (5,7-DHT) in the medial 5-hydroxytryptamine (5-HT) pathway (n = 8) and in the medial plus the lateral 5-HT pathways (n = 7) or injected with vehicle (n = 8), or sham-operated (n = 8). The 5,7-DHT lesions reduced the in vitro 3H-5-HT uptake in the hypothalamus and the cortex cerebri to 27-51% of control values, 3H-noradrenaline uptake was not significantly changed. 5,7-DHT lesions of the medial, and of the medial plus the lateral, 5-HT induced mouse killing behavior and increased number of boxing positions in the shock elicited fighting test. Both lesions also reduced the rate of habituation to touch, but only the lesion of the medial plus the lateral 5-HT pathway significantly reduced the rate of habituation to acoustic stimulation. Activity in the home cage was not significantly changed by the lesions. It was concluded that selective chemical lesions of the ascending 5-HT pathways result in prolonged habituation of the orienting response and increase in particular components of agonistic behavior. The increase in locomotor activity observed after electrolytic lesions of nucleus raphe medianus seems not to be due only to lesion of the 5-HT neurons ascending from this nucleus.

Popliteal entrapment syndrome

A probable cause of popliteal artery entrapment is proposed. The medial head of the gastrocnemius muscle during its embryological development crosses the popliteal fossa from lateral to medial. It is proposed that the migrating medial head carries the popliteal artery and vein across the fossa and entraps them against the medial condyle of the femur. Dissection of 86 anatomical specimens revealed two cases of unilateral and one case of bilateral entrapment of both popliteal vessels. Two surgical cases of popliteal entrapment are presented. This entrapment syndrome is a remedial cause of claudication and when considered, it is readily diagnosed and surgical correction is effective. Because of distal embolisation and occlusions, early recognition and treatment is desirable. Forty-seven cases from the literature are reviewed as to the entrapment type and the age and sex of the patients.