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Biomedical subjects

R Katz

Publications and source records attributed to R Katz.

At least 235 records · Page 13Linked to original sources
PubMed1984

Labelling of interneurones by retrograde transsynaptic transport of horseradish peroxidase from motoneurones in rats and cats.

Transsynaptic transport of conjugates of wheat germ agglutinin with horseradish peroxidase (WGA-HRP) has been studied in rats and cats. WGA-HRP was injected into a muscle nerve from which it was first transported to motoneurones and along sensory fibres, and secondarily to interneurones. More extensive labelling of interneurones occurred in preparations with only relevant ventral roots intact than in preparations with only dorsal roots intact, which indicates that the transsynaptic transport of WGA-HRP is primarily in the retrograde direction, i.e. from motoneurones to interneurones. Such a transport appeared to be considerably enhanced by neuronal activity.

Animals↗
PubMed1984

Hypothalamic mass and gigantism in neurofibromatosis: treatment with bromocriptine.

A child with neurofibromatosis exhibited gigantism and acromegaly in association with a hypothalamic mass lesion. Bromocriptine, 5 mg daily, reduced somatic growth rate and restored biochemical homeostasis but had no effect on tumor growth. Radiation therapy arrested tumor enlargement and stabilized deteriorating visual function.

Acromegaly↗
PubMed1984

Costs and outcomes in rheumatoid arthritis and osteoarthritis.

A prospective descriptive study was done on the direct and indirect costs to ambulatory patients with rheumatoid arthritis and osteoarthritis, stratified at study entry by level of function. Measures of health status over a 1-year period were taken. On a yearly basis, in 1979 dollars, patients spent an average of $147 for arthritis medications, aids, and devices, and $207 for outpatient visits. A small number were hospitalized and incurred an average charge of $245, and an additional $84 for physician fees. In addition to direct monetary costs, patients averaged 6.8 days of restricted activity costs, patients averaged 6.8 days of restricted activity per month, in some cases so severe as to confine patients to bed for an average of 1.3 days per month. Among students and working patients, 2.5 work-days per month were lost due to arthritis, and 30% reported that they were unemployed or retired because of impaired health. Functional capacity and specific diagnosis on entry to the study were the most important determinants of arthritis-related expenditures. Both direct and indirect costs varied considerably from the observed average. Twenty percent of patients incurred no costs for arthritis-related purchases, 42+ had no costs for outpatient visits, and 93% had no inpatient costs. Yet for some patients, the financial burden was very high.

Arthritis, Rheumatoid↗
PubMed1984

The value of conventional views and radiographic magnification in evaluating early rheumatoid arthritis.

Fifty-four patients with suspected early rheumatoid arthritis had radiographs taken of their hands and wrists in 4 views (posteroanterior [PA], oblique, reverse oblique, and Brewerton) using conventional techniques and, in the PA view, using radiographic magnification. The radiographs were "masked" and presented in random order to 2 radiologists specializing in bone and joint radiology who interpreted them for malalignment, erosions, joint space narrowing, and soft tissue swelling. The PA was the best conventional view for demonstrating malalignment, joint space narrowing, and soft tissue abnormalities; the Brewerton view was better for detecting erosive disease. Radiographic magnification was more sensitive than conventional films for evaluating erosive disease, but otherwise was no better than the conventional PA view. These results help the physician choose the radiologic technique or combination of techniques that is most likely to detect specific abnormalities.

Arthritis, Rheumatoid↗
PubMed1984

A re-evaluation of the pattern of group I fibre projections in the human lower limb on using randomly alternated stimulations.

Changes in amplitude of soleus, quadriceps and biceps femoris monosynaptic reflexes were studied when preceded by conditioning stimulations applied to group I fibres from different muscles of the human lower limb. Control test reflexes and conditioned reflexes were alternated either regularly or randomly. For the most part, the same qualitative pattern of group I fibre projections was found with both modes of alternation, but the amount of facilitation or inhibition induced by group I fibre stimulation was significantly smaller with the random mode. This may be due to an underestimation of randomly-induced effects and/or an overestimation of regularly-induced effects. Because this overestimation can lead to artefactual results, regular mode of alternation should be avoided.

Electric Stimulation↗
PubMed1984

Changes in reciprocal Ia inhibition from wrist extensors to wrist flexors during voluntary movement in man.

Transmission in the Ia inhibitory pathway from wrist extensor muscles onto flexor MNs was studied at various times after the onset of voluntary wrist extension or flexion. At the very onset of wrist movements Ia inhibition was not changed, as compared to at rest, whereas later it progressively increased during wrist extension and decreased during wrist flexion. These results are discussed in relation to the different inputs converging onto Ia interneurones and it is suggested that their inhibition by Renshaw cells might be responsible for the results found at the onset of contraction.

Anterior Horn Cells↗
PubMed1984

Cardiopulmonary abnormalities in severe acute respiratory failure.

Serial cardiopulmonary variables were recorded over 4 days in 23 children with severe acute respiratory failure. In all patients, pulmonary artery catheters were inserted within 24 hours of the diagnosis of respiratory failure, and all required greater than 10 cm H2O positive end-expiratory pressure to achieve adequate oxygenation. Eight patients died (35% mortality). Evaluation of systemic hemodynamic variables indicated that survivors had higher blood pressures than nonsurvivors, although neither group was in the hypotensive range. Systemic vascular resistance was lower in the nonsurvivors. Cardiac function as evaluated by cardiac index, right ventricular stroke work index, and left ventricular stroke work index was similar in both groups. Survivors demonstrated elevations in mean pulmonary artery pressure and pulmonary vascular resistance during the first 36 hours, with gradual improvement thereafter. In contrast, pulmonary artery pressure and resistance increased progressively in patients who died. Intrapulmonary shunt fractions remained high in the nonsurvivors despite the use of up to 25 cm H2O PEEP. Cardiac function and oxygen delivery were well maintained in both groups despite the high levels of PEEP.

Acute Disease↗
PubMed1984

Quantitative gastroesophageal reflux and pulmonary function in asthmatic children and normal adults receiving placebo, theophylline, and metaproterenol sulfate therapy.

There is evidence that theophylline therapy inhibits lower esophageal sphincter pressure and enhances gastroesophageal reflux in normal adults and adult asthmatics. No studies have used intraesophageal pH monitoring to assess the effect of bronchodilators over prolonged periods. With the use of the latter procedure, we studied 10 randomly selected chronic asthmatic children (mean age 10.6 yr) and 10 normal adult subjects; all subjects were without clinical symptoms of GER. In this single-blind study, all subjects were evaluated for GER during three separate 24-hr periods while they were receiving oral doses of placebo, theophylline, and metaproterenol sulfate therapy. No significant increase of GER was found in asthmatic subjects or normal subjects on either drug. No adverse correlation of GER and pulmonary function was noted in either group. Asthmatic subjects and normal subjects had asymptomatic or "silent" physiologic GER during sleep and in the 2-hr postprandial period. This study confirms that in chronic asthmatic children standard oral bronchodilator therapy does not adversely affect "silent" GER or pulmonary functions.

Adolescent↗
PubMed1984

Porokeratosis plantaris discreta.

A 22-year-old black male patient developed discrete, exquisitely painful bilateral plantar lesions. Histologic examination revealed a cutaneous groove filled by a keratin plug (cornoid lamella). There is focal absence of granular layer underlying this defect. The differential diagnosis of this lesion, familiar to podiatrists but relatively unknown to dermatologists, is discussed.

Adult↗
PubMed1984

Blind use of the double-lumen plugged catheter for diagnosis of respiratory tract infections in critically ill children.

Transtracheal aspiration, percutaneous lung biopsy, and tracheal aspiration can be dangerous and/or unreliable methods for obtaining specimens of pulmonary secretions for culture. Using a blind technique, we evaluated the efficacy of a double-lumen catheter (DLC) with a polyethylene glycol plug in obtaining specimens of respiratory tract secretions for culture, and compared these results with simultaneously obtained cultures of tracheal aspirates. Twenty-seven intubated children already receiving antibiotic therapy were studied. Sixteen (59%) DLC specimens were sterile, as opposed to only 6 (22%) tracheal aspirates. Only 2 (8%) of the DLC specimens were contaminated. Two DLC specimens yielded significant bacterial growth (at least 10(5) colony-forming units/ml). Using DLC culture data, there was an 81% success rate in making decisions concerning antibiotic selection. We conclude that blind use of the DLC is a safe and reliable method of obtaining pulmonary secretion specimens for culture.

Adolescent↗
PubMed1984

Some comments on the concepts of dose and dose equivalent.

Although dose is the simplest and most widely used measurement of a radiation field, it does not always lead to an unambiguous estimate of response. This is reflected in the very wide range of relative biologic effectiveness (RBE) values for biological systems. The ambiguity arises from the focus on energy deposition as the source of biological effect, whether in macroscopic or microscopic volumes. The properties of the biological detector play a role equally important to the properties of the radiation field in their interaction. To predict even the most experimentally accessible biological response, cell killing, we must know the probability per unit path length for generating the observed end point. Especially for high LET radiations we need the action across sections and the particle-energy spectrum. No one parameter reduction of a radiation field can predict biological effect. For cell killing such a prediction can be made, however, from a two-parameter reduction of the interaction between the radiation field and a specific cell line and a specific ambience of the survival curve for the specific radiation field. The determination of these two parameters leads to a suggested new procedure for evaluating the dose equivalent.

Cell Survival↗
PubMed1984

Facilitation of soleus-coupled Renshaw cells during voluntary contraction of pretibial flexor muscles in man.

Recurrent inhibition to soleus motoneurones, brought about by a conditioning H-reflex discharge, was estimated in human subjects by a subsequent test H reflex. Changes in recurrent inhibition during voluntary ankle dorsiflexion were evaluated by comparing the amplitude of the test H reflex to a reference H reflex: both reflexes were subjected to the same type of influences which modified soleus monosynaptic reflex excitability during pretibial flexor contraction, but only the test H reflex was subject to the recurrent inhibition evoked by the conditioning H-reflex discharge. During tonic or phasic ramp contractions of the pretibial flexors the inhibition of the test H reflex, as compared to rest, was more marked than that of the reference H reflex. Evidence is presented that this may indicate a facilitation of soleus-coupled Renshaw cells. Since this facilitation of soleus-coupled Renshaw cells was also observed before ramp contraction, it is, at least in part, supraspinal in origin. Within the range of forces studied (8-45% of maximum force) there was no evidence that the facilitation of soleus-coupled Renshaw cells increased along with increased force of the pretibial flexor voluntary contraction. During voluntary phasic ankle dorsiflexion, facilitation of soleus-coupled Renshaw cells was maximum at the moment when soleus motoneurones were most facilitated by the stretch-induced soleus I a discharge. There was no evidence for changes in Renshaw cell excitability during ballistic contractions. It is suggested that this facilitation of soleus-coupled Renshaw cells may be one of the mechanisms preventing the occurrence of a soleus stretch reflex during a voluntary ankle dorsiflexion. Such a mechanism could become important if reciprocal inhibition, via I a inhibitory interneurones, were not strong enough, e.g. because of a weak gamma-drive to the contracting muscles.

Adult↗
PubMed1983

Descending control of reflex pathways in the production of voluntary isolated movements in man.

Transmission in Ib inhibitory spinal pathways from a contracting muscle was studied during a selective voluntary contraction in man. Whereas Ib inhibition to those motoneurons (MNs) responsible for the contraction was depressed, Ib inhibition to those synergistic MNs not directly involved in the contraction was increased. This differential control, supraspinal in origin, helps limit activation to the former MNs and could be important in ensuring the selectivity of skilled movements.

Adult↗
PubMed1983

Determinants of transstenotic gradients observed during angioplasty: an experimental model.

Pressure gradient measurement across a stenosis is used during angioplasty to aid catheter positioning and estimate dilatation efficacy. The angioplasty catheter itself, however, further reduces lumen size, and therefore augments the transstenotic gradient. To more precisely define the catheter influence on gradient, we derived a theoretical expression relating the measured gradient with the angioplasty catheter in situ to the "true" gradient; that is, the gradient in the absence of the angioplasty catheter. We then tested this theoretical construct in a canine femoral artery angioplasty model. Fifty-four measurements were performed using 23 separate, 3-mm-long, 40 to 70% stenoses. As predicted by the theoretic model, "true" gradient is compounded by the angioplasty catheter principally as a function of the angioplasty catheter diameter (Dc) and the stenosis diameter (Ds). The best-fit curve of data points relating "true" and compounded gradients to various Dc and Ds combinations can be expressed as: Measured gradient = K X true gradient, where K = 0.25 (e)4.47 (Dc divided by Ds) and e = 2.718. Thus, the transstenotic gradient measured at angioplasty overestimates "true" resting gradient in a predictable manner, which is dependent on the ratio of Dc to Ds.

Angioplasty, Balloon↗